JP7013692B2 - Inkjet recording device and operation abnormality detection method - Google Patents

Description

The present invention relates to an inkjet recording device and an operation abnormality detecting method.

There is an inkjet recording device that records an image or structure by ejecting ink from a nozzle and landing it on a medium. In an inkjet recording device, a large number of nozzles are usually used, and there is a problem that the quality of recording deteriorates when ejection defects occur in these nozzles or uneven ejection occurs between the nozzles.

One of the causes of ejection failure and uneven ejection state is a defect or deterioration of a pressure generating element for applying pressure to ink and a drive circuit of the element. As a technique for detecting these, a technique for detecting an abnormality in the resistance of the drive circuit and the capacitance of the piezoelectric element has been proposed from the rising speed of the voltage when a voltage is applied to the piezoelectric element as the pressure generating element. Patent Document 1). Further, in Patent Document 2, the natural vibration generated in the vibrating plate forming the wall surface of the ink flow path due to the deformation of the piezoelectric element causes residual vibration in the piezoelectric element, and the electromotive force corresponding to the residual vibration is utilized. Disclosed is a technique for detecting whether or not the piezoelectric element is operating properly by detecting the vibration of the above.

Japanese Unexamined Patent Publication No. 2008-62513 Japanese Patent Application Laid-Open No. 2015-51606

However, when a piezoelectric element is used for ink ejection operation, the capacitance of the piezoelectric element is very small, so it is necessary to obtain changes in voltage and current when a voltage is applied to each piezoelectric element with sufficient resolution. The time and effort required for configuration, adjustment, and detection will be excessive compared to the conventional method. As a result, there is a problem that it is difficult to easily identify an abnormality in the drive operation related to ink ejection from the nozzle.

An object of the present invention is to provide an inkjet recording apparatus and an operation abnormality detection method capable of more easily identifying an abnormality in a driving operation related to ink ejection.

In order to achieve the above object, the invention according to claim 1 is
A nozzle that ejects ink and
A piezoelectric element that deforms according to the applied voltage and gives a pressure change to the ink supplied to the nozzle.
A power supply unit that supplies power related to the application of a drive voltage to the piezoelectric element, and
A drive voltage is periodically applied to the piezoelectric element according to a predetermined drive voltage pattern, and a representative value corresponding to a fluctuation component in a predetermined low frequency band among the power supplied by the power supply unit related to the application of the drive voltage. And an abnormality detection unit that detects an abnormality in the capacitance of the piezoelectric element, which is obtained according to the representative value.
Equipped with
The power supply unit
A drive voltage output unit that receives power and outputs a predetermined drive voltage,
A capacitor that can supply electric power corresponding to the predetermined drive voltage to the piezoelectric element based on the predetermined drive voltage output by the drive voltage output unit.
Equipped with
It is an inkjet recording device characterized by this.

The invention according to claim 2 is the inkjet recording apparatus according to claim 1.
The predetermined drive voltage pattern is characterized by a non-ejection waveform in which ink is not ejected from the nozzle.

The invention according to claim 3 is the inkjet recording apparatus according to claim 1 or 2.
A connection switching unit for switching the state of connection between the capacitor and the piezoelectric element is provided.
The capacity of the capacitor is larger than the capacity of the piezoelectric element .

The invention according to claim 4 is the inkjet recording apparatus according to claim 3.
The power supply unit
It is provided with a current measuring unit that measures the output current from the driving voltage output unit as the representative value based on the voltage drop by the resistance element having a predetermined resistance value.
One end of the capacitor is connected between one end of the resistance element and the connection switching portion.
The current measuring unit is characterized in that it measures voltage fluctuations in the predetermined low frequency band according to the resistance value of the resistance element and the electric capacity of the capacitor.

The invention according to claim 5 is the inkjet recording apparatus according to claim 3.
The power supply unit
A current measuring unit that measures the input current to the drive voltage output unit as the representative value based on the voltage drop by the resistance element having a predetermined resistance value is provided.
One end of the capacitor is connected between the resistance element and the drive voltage output unit.
The current measuring unit is characterized in that it measures voltage fluctuations in the predetermined low frequency band according to the resistance value of the resistance element and the electric capacity of the capacitor.

The invention according to claim 6 is the inkjet recording apparatus according to claim 4 or 5.
The power supply unit
A short circuit circuit provided in parallel with the resistance element and
A circuit switching unit that switches between the measurement circuit that passes through the current measurement unit and the short-circuit circuit, and
Equipped with
The circuit switching unit is characterized in that it can be switched to the short-circuit circuit when the abnormality of the capacitance is not detected.

The invention according to claim 7 is
A nozzle that ejects ink and
A piezoelectric element that deforms according to the applied voltage and gives a pressure change to the ink supplied to the nozzle.
A power supply unit that supplies power related to the application of a drive voltage to the piezoelectric element, and
A drive voltage is periodically applied to the piezoelectric element according to a predetermined drive voltage pattern, and a representative value corresponding to a fluctuation component in a predetermined low frequency band among the power supplied by the power supply unit related to the application of the drive voltage. And an abnormality detection unit that detects an abnormality in the capacitance of the piezoelectric element, which is obtained according to the representative value.
Equipped with
The power supply unit
A first drive voltage output unit and a second drive voltage output unit that receive power supply and output a predetermined drive voltage, respectively.
A current measuring unit that measures the output current from the first drive voltage output unit as the representative value based on the voltage drop by the resistance element having a predetermined resistance value, and the current measuring unit.
An input switching unit that selects and outputs one of the drive voltage output by the first drive voltage output unit and the drive voltage output by the second drive voltage output unit.
A capacitor that can supply electric power corresponding to the predetermined drive voltage to the piezoelectric element based on the predetermined drive voltage output by the input switching unit.
Equipped with
It is an inkjet recording apparatus characterized by measuring voltage fluctuations in the predetermined low frequency band according to the resistance value of the resistance element and the electric capacity of the capacitor.

The invention according to claim 8 is the inkjet recording apparatus according to claim 5.
A plurality of piezoelectric elements and a plurality of nozzles classified into a group of piezoelectric elements having a predetermined number of two or more groups,
A short circuit circuit provided in parallel with the resistance element and
A circuit switching unit that switches between the measurement circuit that passes through the current measurement unit and the short-circuit circuit, and
Equipped with
The power supply unit includes the drive voltage output units in the predetermined number of groups, and outputs the predetermined drive voltage related to the different piezoelectric element groups.
The circuit switching unit is characterized in that, for each of the drive voltage output units of the predetermined number of groups, which of the measurement circuit and the short-circuit circuit is used to supply power is switched.

The invention according to claim 9 is the inkjet recording apparatus according to claim 5.
A plurality of piezoelectric elements and a plurality of nozzles classified into a group of piezoelectric elements having a predetermined number of two or more groups,
A short circuit circuit provided in parallel with the resistance element and
A circuit switching unit that switches between the measurement circuit that passes through the current measurement unit and the short-circuit circuit, and
Equipped with
The power supply unit includes the drive voltage output units in the predetermined number of groups, and outputs the predetermined drive voltage related to the different piezoelectric element groups.
The drive voltage output unit having the predetermined number of groups is characterized in that the presence / absence of output of the predetermined drive voltage related to the piezoelectric element group can be switched.

The invention according to claim 10 is the inkjet recording apparatus according to any one of claims 1 to 9.
The abnormality detection unit is characterized in that the representative value is acquired after a predetermined standby time has elapsed after the periodic application of the drive voltage is started.

The invention according to claim 11 is the inkjet recording apparatus according to any one of claims 4 to 6, 8 and 9.
After the abnormality detection unit starts the periodic application of the drive voltage, a predetermined standby time determined based on the capacity of the capacitor and the resistance value of the resistance element of the current measurement unit elapses. It is characterized by acquiring the representative value.

The invention according to claim 12 is the inkjet recording apparatus according to any one of claims 4 to 6, 8 and 9.
At the time of the predetermined initial setting, after the periodic application of the drive voltage is started, the time until the fluctuation of the measured value of the current measuring unit falls within the predetermined reference range is measured and used as the predetermined standby time. Equipped with an initial setting unit to be determined
The abnormality detection unit is characterized in that the representative value is acquired after the predetermined standby time has elapsed after the periodic application of the drive voltage is started.

The invention according to claim 13 is the inkjet recording apparatus according to any one of claims 10 to 12.
A storage unit for storing the standby time data is provided.
The abnormality detection unit is characterized in that it refers to the data of the standby time at the time of the operation of detecting the abnormality of the capacity.

The invention according to claim 14 is the inkjet recording apparatus according to any one of claims 4 to 6, 8 and 9.
After starting the periodic application of the drive voltage, the abnormality detecting unit acquires the representative value based on the measured value in which the fluctuation of the measured value of the current measuring unit is within a predetermined reference range. It is characterized by that.

The invention according to claim 15 is
A nozzle that ejects ink, a piezoelectric element that deforms according to the applied voltage and gives a pressure change to the ink supplied to the nozzle, and a power supply that supplies power related to the application of a drive voltage to the piezoelectric element. The power supply unit is provided with a unit, and the power supply unit is based on a drive voltage output unit that receives power supply and outputs a predetermined drive voltage and the predetermined drive voltage output by the drive voltage output unit. A method for detecting an operation abnormality of an inkjet recording device including a capacitor that can supply power according to a drive voltage to the piezoelectric element .
A drive voltage is periodically applied to the piezoelectric element according to a predetermined drive voltage pattern, and a representative value corresponding to a fluctuation component in a predetermined low frequency band of the power supplied by the power supply unit related to the application of the drive voltage. Is included, and the abnormality detection step of detecting the abnormality of the capacitance of the piezoelectric element obtained according to the representative value is included.

According to the present invention, there is an effect that an abnormality in the driving operation related to ink ejection can be more easily identified.

It is a figure which shows the whole structure of the inkjet recording apparatus of embodiment of this invention. It is a figure which shows typically the nozzle surface of a head unit. It is a block diagram which shows the functional structure of an inkjet recording apparatus. It is a schematic diagram explaining the power supply circuit of the power supply unit and the image recording unit. It is a figure explaining the change of a current and a voltage. It is a figure explaining the image recording position on a recording medium when it is performed during execution of an image recording operation. It is a flowchart which shows the control procedure of operation abnormality detection processing. It is a figure explaining the modification of the power supply part. It is a figure explaining the modification of the power supply part. It is a figure explaining the modification of the power supply part.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an overall perspective view showing the inkjet recording apparatus 1 according to the embodiment of the present invention.

The inkjet recording device 1 includes a transport unit 10, an image recording unit 20, a cleaning unit 30, a control unit 40 (abnormality detection unit, initial setting unit), a reading unit 60, and the like.

The transport unit 10 includes a drive roller 11, a transport belt 12, a driven roller 13, a transport motor 14, a pressing roller 15, a peeling roller 16, and the like. The endless transfer belt 12 is bridged between the drive roller 11 and the driven roller 13, and rotates orbits as the drive roller 11 rotates by the drive of the transfer motor 14. By using the outer peripheral surface of the transport belt 12 as a transport surface and relatively moving the image recording unit 20 in a predetermined transport direction, a transport operation for moving the recording medium P mounted on the transport surface in the transport direction is performed. conduct. As the transport belt 12, a material that flexibly bends at the contact surface with the drive roller 11 and the driven roller 13 and reliably supports the recording medium P is used. For example, a resin belt such as rubber or a belt made of resin such as rubber is used. Examples include steel belts. Since the transport belt 12 has a material and / or a configuration in which the recording medium P is adsorbed, the recording medium P can be more stably mounted on the transport belt 12. In this case, a configuration for peeling the recording medium P from the transport belt 12 may be further provided on the downstream side of the image recording unit 20 in the transport direction.

The driven roller 13 rotates with the movement of the transport belt 12.
The recording medium P is not particularly limited, but here, a cloth or the like continuous in the transport direction is used, and a plurality of images recorded on the recording medium P at appropriate intervals are obtained by a post-processing device (not shown). It is dried, rolled up or shaken off, and / or cut.

The conveyor motor 14 rotates the drive roller 11 at a rotation speed according to a control signal from the control unit 40. The transport motor 14 can also rotate the drive roller 11 in the direction opposite to the normal transport direction. As a result, the transport belt 12 transports the recording medium P at a transport speed corresponding to the rotation speed of the drive roller 11.

The pressing roller 15 presses the recording medium P supplied to the mounting surface of the transport belt 12 against the mounting surface to remove floating from the mounting surface such as wrinkles.
The peeling roller 16 pulls the recording medium P, which has been transported while being attracted to the transport belt 12, with a predetermined pressure, thereby peeling the recording medium P from the transport surface and sending it to the post-processing apparatus.

The cleaning unit 30 is placed on a surface (nozzle surface 210; see FIG. 2, here, a transport surface) provided with a nozzle 27 (see FIG. 3) and a nozzle opening 27a (see FIG. 2) of the image recording unit 20. Cleaning (cleaning) of the surface facing the recording medium P is performed. The cleaning unit 30 has, for example, a non-woven fabric, a blade member, or the like, and wipes off ink, foreign matter, and the like adhering to and solidifying on the nozzle surface 210. If necessary, a cleaning liquid or the like may be contained or adhered to the non-woven fabric or the blade member. Further, the cleaning unit 30 may have an ink tray or the like for collecting the ink ejected at the time of performing cleaning for removing foreign substances and air bubbles in the nozzle by ejecting the ink in the nozzle 27. .. The cleaning unit 30 is moved relative to the image recording unit 20 and is arranged to face the nozzle surface when the cleaning operation is performed.

The control unit 40 controls the operation of each unit of the inkjet recording device 1 in an integrated manner.

The reading unit 60 includes an image pickup sensor and the like, and performs an operation of capturing and reading the surface of the recording medium P (particularly, the recorded image to be recorded). The reading unit 60 captures an image of the surface of the recording medium P on the downstream side in the transport direction of the image recording unit 20 and on the upstream side of the position where the recording medium P is peeled off from the transport belt 12 by the peeling roller 16. It is possible to read the image recorded by.

The image recording unit 20 records (forms) an image by ejecting ink from a nozzle 27 (see FIG. 3) and landing (imparting) it on the upper surface of the recording medium P (the surface opposite to the side in contact with the transport surface). ) Perform the recording operation. The image recording unit 20 has a plurality of head units 21Y, 21M, 21C, 21K (hereinafter, a part or all of them are collectively referred to as a head unit 21). From these head units 21, inks of different colors supplied from ink storage portions (not shown), for example, inks of each color of yellow, magenta, cyan, and black are ejected. The head unit 21 has a recordable width of a recording medium P having a predetermined size (maximum width size described above) in a width direction intersecting (here, orthogonal to) the transport direction of the recording medium P in a plane parallel to the transport surface. A nozzle 27 (see FIG. 3) is provided over the nozzle 27 so that ink can be ejected.

FIG. 2 is a diagram schematically showing a nozzle surface of the head unit 21K.
Since the head units 21C, 21M, and 21Y also have the same configuration, the description thereof will be omitted.

The head unit 21K has nozzle openings 27a (only one code is specified here) on the bottom surface at predetermined intervals (nozzle intervals), here, for example, at intervals of about 70.6 μm corresponding to 360 dpi (dot per inch). A plurality of (16 in this case) discharge heads 211 arranged are provided. The two ejection heads 211 are paired, and the nozzle openings 27a of each ejection head 211 are arranged alternately in the width direction, so that an image recording with a total recording resolution of 720 dpi (nozzle spacing of about 35.3 μm) can be recorded. It is possible. By further arranging the set of the discharge heads 211 in a houndstooth pattern, the line heads in which the nozzle openings 27a are arranged over the above-mentioned recordable width at uniform intervals in the width direction are formed.

During the image recording operation, the head unit 21K is fixed so that the nozzle surface faces the transport surface, and ink is sequentially ejected at predetermined intervals at different positions in the transport direction according to the transport of the recording medium P. Then, the image is recorded by the one-pass method. The recording resolution in the transport direction is determined by the ejection frequency from the nozzle 27, the transport speed, and the like, but may be equal to or different from the above-mentioned 720 dpi.

FIG. 3 is a block diagram showing a functional configuration of the inkjet recording device 1 of the present embodiment.

In addition to the above-mentioned transport unit 10, image recording unit 20, cleaning unit 30, control unit 40, and reading unit 60, the inkjet recording device 1 includes a storage unit 50, a communication unit 70, an operation display unit 80, and power supply. A unit 90 or the like is provided.

The control unit 40 controls the overall operation of the inkjet recording device 1 in an integrated manner. The control unit 40 includes a CPU 41, a RAM 42, and the like. The CPU 41 performs various arithmetic processes and executes various instructions of the control program related to the control operation. The control operation includes a process of controlling the operation of the transport unit 10 and the image recording unit 20 (application of a drive voltage to each piezoelectric element 26) according to the image data of the image to be recorded to record the image on the recording medium. It includes a process of detecting an operation abnormality of each piezoelectric element 26 and / or a nozzle 27, a process of operating the cleaning unit 30 based on the detection result, and the like. The RAM 42 provides a working memory space to the CPU 41 and stores primary data. The RAM 42 may include a write-renewable non-volatile memory such as a flash memory.

The storage unit 50 stores various control programs, setting data, image data to be recorded, and image recording processing data of the image data. Various control programs and setting data are preferably stored in a non-volatile memory such as a flash memory or an HDD (Hard Disk Drive), and the data related to the image to be recorded can be processed at a large capacity and high speed by a DRAM or the like. It is preferably stored in a volatile memory or the like. The storage unit 50 has these non-volatile memories and DRAM. The control program includes a malfunction nozzle detection program 51. The setting data includes a defective nozzle list 52 in which a malfunctioning nozzle is associated with or classified as a defect cause described later, a missing complement setting 53 for a malfunctioning nozzle, a capacitance history data 54 of each piezoelectric element 26, and an operation. The standby time setting 55 used at the time of defect detection is included.

The transport unit 10 supplies a recording medium for recording an image to an image recording position by the image recording unit 20, and discharges the recording medium on which the image is recorded. The transport unit 10 moves and holds the recording medium in an appropriate positional relationship with respect to the image recording unit 20 at the image recording position. As described above, the transport unit 10 has a transport motor 14 and rotates the drive roller 11 at a predetermined speed to move the recording medium on the transport belt 12.

At the image recording position, the image recording unit 20 ejects inks of each color of CMYK onto the recording medium supplied by the transport unit 10 to record an image. Each ejection head 211 of the image recording unit 20 communicates with a plurality of nozzles 27 for ejecting ink and a plurality of arranged nozzles 27, respectively, and is in the middle of an ink flow path for supplying ink to the plurality of nozzles 27. It has a plurality of piezoelectric elements 26 that deform the pressure chamber) to change the pressure of the ink, and a head drive unit 25 that applies a voltage to deform the piezoelectric element 26 by the applied voltage. A well-known material such as lead zirconate titanate (PZT) is used for the piezoelectric element 26, and the deformation mode is not particularly limited.

As described above, the cleaning unit 30 has a non-woven fabric, a blade, and the like, and has a driving unit that moves them relative to the nozzle surface 210. Further, it has a mechanism for moving the cleaning unit 30 in the transport direction, and can make the non-woven fabric, the blade, and the ink tray commonly available for the nozzle surfaces 210 of the plurality of head units 21.

The reading unit 60 has an image pickup sensor, images the surface of the recording medium P at an appropriate timing under the control of the control unit 40, and outputs the image pickup data to the control unit 40. As the image pickup sensor, for example, a line sensor capable of capturing images in three colors of RGB is used, and it is possible to acquire a two-dimensional image by repeating imaging according to the transport of the recording medium P.

The communication unit 70 controls the transmission / reception of data between the inkjet recording device 1 and the outside according to a predetermined communication standard. The communication unit 70 includes, for example, a network card that controls a TCP / IP connection via a LAN. Examples of the external device that communicates with the inkjet recording device 1 via the communication unit 70 include a print server, various PCs, and a computer such as a mobile terminal.

The operation display unit 80 receives an input operation from the outside such as a user and outputs the received operation content as an electric signal to the control unit 40, and the status of the inkjet recording device 1 based on the control of the control unit 40. , It has a display unit for displaying a warning display and a menu related to a user's input operation. The display unit includes, for example, a liquid crystal display, and a touch sensor is provided on the liquid crystal display so as to operate as a touch panel, thereby receiving an input operation from the outside as an operation reception unit. The operation display unit 80 may be provided with other configurations, such as an LED lamp and a push button switch, and these may be used in combination. Further, the operation display unit 80 may be able to generate a beep sound and output a voice at the same time when a warning display is performed by the display unit.

The power supply unit 90 supplies the necessary power to each unit of the inkjet recording device 1. The power supply unit 90 receives power supply from the outside, and each unit converts it into a required DC voltage and outputs it by the DC power conversion unit 95. As the DC power conversion unit 95, various well-known DC / DC conversion units, LDOs (Low Dropouts), and the like can be used.

As will be described later, the power supply unit 90 outputs (supplies) power to the head drive unit 25 of the image recording unit 20 with two types of voltages VH1 and VH2 (DC voltage) related to the application of the drive voltage of the piezoelectric element. It is possible. The power supply unit 90 has a current detection unit 91 (current measurement unit) that measures the current in the supply path of the voltage VH2. As the current detection unit 91, a system in which a resistance element having a predetermined resistance value is inserted in series in the circuit and the current value (output current) is measured based on the voltage drop in the resistance element is used.

Next, a circuit configuration related to voltage application to the piezoelectric element 26 in the inkjet recording device 1 of the present embodiment will be described.
FIG. 4 is a schematic diagram illustrating a power supply circuit of the power supply unit 90 and the image recording unit 20 in the inkjet recording device 1 of the present embodiment. Here, the configuration related to the power supply to the piezoelectric element 26 corresponding to one nozzle 27 and the head drive unit 25 is shown, but it is common to the plurality of piezoelectric elements 26 and the head drive unit 25 corresponding to the plurality of nozzles 27. It is possible to supply electric power to the piezoelectric element 26 and switch the supply voltage to the piezoelectric element 26 individually in each head drive unit 25.

In the power supply unit 90, the power input from the outside (here, DC voltage such as 24V) is converted into voltages VH1 and VH2 (for example, 15V) by the DC power conversion unit 95 (drive voltage output unit). Is output respectively. The outputs of the voltage VH2 are provided in parallel in two systems, one is directly input to the switching element 92 (circuit switching unit) (in a short circuit circuit that does not pass through the resistance element of the current detecting unit 91), and the other is the current detecting unit 91. It is input to the switching element 92 via a measurement circuit including (the resistance element). One of these is output to the head drive unit 25 according to the switching state of the switching element 92. It should be noted that the output of the voltage VH2 from the DC power supply conversion unit 95 may be one, and the output of the single output may be branched into a short circuit circuit and a measurement circuit. Further, in this case, the switching element 92 may be provided in the separation portion, and the short-circuit circuit and the measurement circuit may simply merge in the portion where the switching element 92 is provided in FIG.

The voltage VH2 is input from the switching element 92 to the first switch 251 (connection switching unit) of the head drive unit 25. One end of the first stabilized capacitor 93 (capacitor) is connected between the switching element 92 (one end of the resistance element of the current detection unit 91) and the first switch 251 and the other end is grounded. The voltage VH1 is input to the second switch 252 of the head drive unit 25. A second stabilizing capacitor 94 is provided between the connection end with the second switch 252 and the ground plane. Further, one end of the third switch 253 of the head drive unit 25 is grounded. The capacities of the first stabilized capacitor 93 and the second stabilized capacitor 94 can supply power to all the piezoelectric elements 26, that is, even if the power is supplied, the first stabilized capacitor 93 and the second stabilized capacitor 93 can be supplied. The voltage of 94 is sufficiently larger than the capacity of the piezoelectric element 26 to the extent that the voltage does not drop so as to cause a problem in the drive operation.

An image data signal, a control signal of a drive voltage pattern described later, and a predetermined clock signal are input to the driver circuit 254, and any of the first switch 251 and the second switch 252 and the third switch 253 respond to these signals. When one of them is turned on (it can be configured so that a period in which none of them is turned on is inserted in the switching period), one of the voltages is supplied to one end of the piezoelectric element 26 (the third switch 253 is turned on). If so, the electric charge stored in the piezoelectric element 26 is discharged). The other end of the piezoelectric element 26 is grounded, so that the supplied voltage is applied to the piezoelectric element 26. Here, the voltage VH1 is a voltage (discharge voltage) for ejecting ink from the nozzle 27, and the voltage VH2 is a voltage (non-existence) to the extent that ink is not ejected from the nozzle 27 (the ink liquid level vibrates in the nozzle 27). Discharge voltage).

FIG. 5 is a diagram illustrating changes in current and voltage in each part.
It should be noted that here, for qualitative explanation, the transient situation of current and voltage is exaggerated, and the waveform corresponding to a specific representative value quantitatively is not intended.

Since the piezoelectric element 26 is a capacitive element, when the first switch 251 or the second switch 252 is turned on, one end of the piezoelectric element 26 is sent from the DC power conversion unit 95 according to the supplied voltage and the capacity of the piezoelectric element 26. A current Ia (> 0) temporarily flows to one end of the piezoelectric element 26 according to the potential difference, that is, until the voltage Va at one end of the piezoelectric element 26 becomes equal to the voltage Vb output by the DC power conversion unit 95. .. Further, when the third switch 253 is turned on, a temporary current Ia (that is, until one end of the piezoelectric element 26 reaches the ground voltage) corresponding to the potential of the one end from one end of the piezoelectric element 26 to the ground surface. <0) flows.

When the first switch 251 or the second switch 252 is turned on (connected), a current flows from the first stabilized capacitor 93 or the second stabilized capacitor 94 and the DC power conversion unit 95 to the piezoelectric element 26. The magnitude of the current is the first stabilized capacitor 93, the voltage difference between the second stabilized capacitor 94 and the piezoelectric element 26, and the first stabilized capacitor 93 such as the on-resistance of the first switch 251 or the second switch 252. 2 The size corresponds to the circuit resistance from the stabilizing capacitor 94 to the piezoelectric element 26 (that is, these are set as time constants). An output current corresponding to the output impedance is generated from the DC power conversion unit 95, and the remaining current is from the first stabilized capacitor 93 and the second stabilized capacitor 94. Since the circuit resistance is sufficiently small compared to the output impedance, most of the large current Ia immediately after the first switch 251 or the second switch 252 is turned on is the first stabilized capacitor 93 and the second stabilized capacitor. It becomes the current flowing from 94. When the discharge from the first stabilized capacitor 93 and the second stabilized capacitor 94 is performed, the voltage of the first stabilized capacitor 93 and the second stabilized capacitor 94 slightly decreases according to the amount of discharge.

When the first switch 251 and the second switch 252 are turned off (when the connection is disconnected) after the drive voltage is applied to the piezoelectric element 26, the first stabilized capacitor 93 and the second stabilized capacitor 94 The electric charge for the discharge is recharged by the DC power conversion unit 95. In particular, when the first stabilized capacitor 93 is charged via the current detection unit 91, the resistance element of the current detection unit 91 is larger than that of other circuit resistances, so that the time constant corresponding to these ( The output current Ib detected by the current detection unit 91 at the time of recharging (larger than the time constant related to the discharge to the piezoelectric element 26 described above) is smaller and continues for a longer time.
That is, the first switch 251 switches the connection state between the first stabilizing capacitor 93 and the piezoelectric element 26. Of the variable components (including the DC component) of the power supplied by the DC power conversion unit 95 due to the charging / discharging of the first stabilized capacitor 93 being switched according to the on / off of the first switch 251, the first stabilized capacitor 93 A predetermined low frequency band (including a DC component) determined according to the electric capacity of the current detection unit 91 and the resistance value of the resistance element of the current detection unit 91 is detected by the current detection unit 91.

With such a configuration, a temporary decrease in voltage Vb due to the inrush current to the piezoelectric element 26, that is, a decrease in voltage Va applied to the piezoelectric element 26 is reduced, and the current value from the DC power conversion unit 95 is reduced. An output current Ib (average current value Ir) with a small time change is generated. The capacities of the first stabilized capacitor 93 and the second stabilized capacitor 94 required for such an application usually cause a problem in ink ejection performance when a drive voltage is applied to all the piezoelectric elements 26 at the same time. It is a value that does not cause a decrease in the voltage Vb to such an extent that the voltage Vb is caused, that is, a value that is one to two orders of magnitude or more larger than the product of the capacity of the piezoelectric element 26 and the number of the piezoelectric elements 26.

When the driving voltage VH2 related to the ink ejection operation is to be output to a large number of piezoelectric elements 26 at once through the resistance element of the current detection unit 91 during the image recording operation, the resistance element is increased according to the number of the piezoelectric elements 26. In addition, the amount of heat generated in the first stabilizing capacitor 93 needs to be further increased in order to reduce the influence of the voltage drop. Therefore, when it is not necessary to measure the current by providing the switching element 92, it is preferable to switch to a path that bypasses the current detection unit 91 and output the drive voltage.

Next, the operation of detecting a malfunctioning nozzle related to ink ejection in the inkjet recording apparatus 1 of the present embodiment will be described.
Malfunctioning nozzles include those that cannot individually recover ink ejection from the nozzle 27, such as deterioration of the piezoelectric element 26 and disconnection of the drive circuit, and those that are clogged with the nozzle 27 and have air bubbles or foreign matter mixed in the ink flow path. Some ink ejection can be recovered by cleaning operation and recovery operation.

In the inkjet recording device 1, by outputting image data of a predetermined test image (ejection defect inspection image) to the driver circuit 254, the ejection defect inspection image is periodically recorded in a margin or the like on the recording medium P, and a reading unit is used. By detecting the abnormality of the test image read by 60, it is determined (detected) whether or not there is an ink ejection defect from each nozzle 27. As a predetermined test chart, a ladder chart or the like in which a separate line segment is recorded by each nozzle 27 so that it can be identified from which nozzle 27 the ink is ejected is widely used. In this case, the nozzle 27 having an ink ejection defect is uniformly detected regardless of the cause of the above-mentioned malfunction.

On the other hand, in the inkjet recording device 1 of the present embodiment, the piezoelectric element 26 is measured (acquired) by the current detection unit 91 of the power supply unit 90 described above to measure (acquire) the output current Ib (representative value according to the power supply). And it detects whether or not there is an abnormality in the drive circuit (electrical system). When detecting an abnormality in the piezoelectric element 26 and the drive circuit, the first switch has a predetermined switching cycle according to the drive voltage pattern control signal with the second switch 252 turned off for the selected piezoelectric element 26. The 251 and the third switch 253 are alternately turned on to periodically switch whether or not the drive voltage of the voltage VH2, which is a non-discharge voltage, is applied to each nozzle 27. As a result, charging / discharging of the selected piezoelectric element 26 is repeated (a predetermined drive voltage pattern having a non-discharge waveform). The on / off switching cycle is set to be longer than the time during which the piezoelectric element 26 is sufficiently charged and discharged, that is, the lower limit time depends on the circuit resistance such as the on-resistance of the first switch 251 and the third switch 253 and the capacity of the piezoelectric element 26. It will be decided. The circuit resistance is configured so that the dullness of the waveform applied to the piezoelectric element 26 does not cause a problem in the operation of the piezoelectric element 26. On the other hand, in the on / off switching cycle, it is preferable that the charging of the first stabilized capacitor 93 is not completed and an appropriate charging current continuously flows in balance with the amount of discharge to the piezoelectric element 26. For example, when a voltage of about 15 V is applied to the piezoelectric element 26 of about 0.1 nF to 1.0 nF, the on / off switching frequency f appropriate for obtaining the current value of the measurable output current Ib is about 10 kHz. Is determined.

Specifically, the work from charging the voltage "0" to the voltage V1 with respect to the capacitance Cp of the piezoelectric element 26 (that is, the electrostatic energy at the voltage V1 of the piezoelectric element 26) E = Cp · V1 ^2/2 . Since the on / off switching frequency f of the first switch 251 is executed a number of times per second, the amount of work per second, that is, the amount of power supplied by the DC power conversion unit 95 is E · f = ∫ (Ib · Vb) dt to Ir.・ It becomes V1. Therefore, the capacitance Cp of the piezoelectric element 26 is 2 · Ir / (V1 · f) to 2 · Ir / (V0 · f), and the capacitance Cp is the known applied voltage V0 (that is, voltage VH2) and the on / off switching frequency. It is obtained according to f and the average current value Ir of the measured output current Ib. In the case of a configuration in which the two piezoelectric elements 26 are simultaneously deformed in the shear mode, the capacitance may be calculated assuming that the capacitance Cp of the piezoelectric elements is doubled.

Actually, the current value of the measured output current Ib fluctuates slightly (± ε) under the influence of ripple (± ε here does not mean that the fluctuation ranges are the same positively and negatively). The average current value Ir can be obtained by measuring and averaging the output currents Ib a plurality of times. When the voltage VH2 and the switching frequency f are fixed values, the average current value Ir becomes a value corresponding to the capacitance Cp without actually calculating the capacitance Cp.

Here, when the voltage Vb of the first stabilized capacitor 93 changes, the charge / discharge rate (current) of the first stabilized capacitor 93 also changes. The charging speed of the first stabilized capacitor 93 is affected by the capacity of the first stabilized capacitor 93 and the circuit resistance such as the internal resistance of the current detection unit 91 (resistance value of the resistance element). Further, the discharge of the first stabilized capacitor 93 is affected by each configuration related to the charging of the above-mentioned piezoelectric element 26. If the voltage Vb is too high, the charging speed becomes slower than the discharging speed, and the voltage Vb gradually decreases. If the voltage Vb is too low, the charging speed becomes faster than the discharging speed, and the voltage Vb gradually increases. When the on / off operation at the switching frequency f is continuously performed, the voltage Vb of the first stabilized capacitor 93 is slightly lower than the set applied voltage V0, and the value at which the discharge and charge speeds are balanced (equilibrium). It stabilizes in a form that periodically fluctuates up and down with the value voltage V1). The amount of decrease from the applied voltage V0 to the voltage V1 makes it possible to ignore the influence on the applied voltage (that is, deformation operation) to the piezoelectric element 26 according to the capacities of the first stabilized capacitor 93 and the second stabilized capacitor 94. While it can be made smaller, the influence on the charge / discharge speed of the first stabilized capacitor 93 becomes larger due to a slight decrease depending on the capacity. Therefore, when measuring the average current value Ir of the charging current, the voltage Vb is the equilibrium value voltage V1 after the voltage application to the piezoelectric element 26 to be inspected via the current detection unit 91 at the switching frequency f is started. The measurement accuracy is improved by performing the measurement after waiting (the predetermined standby time has elapsed) until the voltage is sufficiently close to (the discharge speed and the charge speed are equal to or less than the reference difference).

Regarding the time required for waiting before the inspection of each nozzle (predetermined standby time trms), the voltage Vb actually approaches the voltage V1 sufficiently each time and the fluctuation is within the predetermined reference range (for example, about several%). It may wait until it becomes, or it may be calculated based on the value of each parameter set in advance (that is, the product of the above capacitance and the resistance value by the RC circuit). Alternatively, the measured value related to the waiting time trms can be written and held. The standby time trms is generally determined according to the response speed related to the charge / discharge of the first stabilized capacitor 93, that is, the product of the capacity of the first stabilized capacitor 93 that determines the time constant and the resistance element of the current detection unit 91. It is a fixed value. Therefore, the above-mentioned periodic drive voltage waveform is supplied at the time of initial setting performed according to pre-shipment inspection, replacement and mounting of the head unit 21, etc., and after the start of the supply, until the fluctuation becomes within a predetermined reference range. The time may be actually measured and stored in the storage unit 50 or the like as the standby time setting 55. It is also possible to change the time constant by using the first stabilized capacitor 93 as a variable capacitance, but if the capacitance is lowered to lower the time constant, the variation from the average current value Ir when measuring the output current Ib ± Since ε also becomes large, in this case, it is desirable to increase the number of measurements of the output current Ib to improve the accuracy of the average value. Further, although the resistance value of the resistance element of the current detection unit 91 can be made variable, it is necessary not to reduce the detection accuracy of the current detection unit 91. In this case, if it is possible to make the resistance value sufficiently close to "0" or "0", a short-circuit circuit can be substantially obtained by changing the resistance value instead of providing the above-mentioned short-circuit circuit.

If the first stabilized capacitor 93 is not stored at the time of starting the inkjet recording device 1, it takes an extra time for the voltage of the first stabilized capacitor 93 to rise to about the voltage VH2. Since the standby time trms is significantly different from the above case, the standby time trms in this case may be held separately, or the measured values may be periodically acquired to determine the voltage fluctuation of the first stabilized capacitor 93. It may be possible to wait until it is within the reference range of.

When the capacitance Cp (that is, the average current value Ir) of the piezoelectric element 26 calculated in this way is very small (including "0") compared to the reference range, the DC power conversion unit 95 to the piezoelectric element 26 It can be seen that there is a defect such as disconnection in (including both ends). On the other hand, when the capacitance Cp (average current value Ir) is very large compared to the reference range, a short circuit occurs from the DC power conversion unit 95 to the piezoelectric element 26 (for example, due to the influence of deformation or heat generation). It can be seen that there is a poor energization state (due to deterioration of the protective film of the electrode, etc.).

Further, the calculated capacitance Cp of the piezoelectric element 26 is compared with the past initial value and the calculated history (timekeeping change) stored in the capacitance history data 54, and if it deviates from a predetermined reference range, the piezoelectric element is concerned. It is determined that deterioration or the like has occurred in 26 (deterioration information is determined). The reference range may be the initial range measured and held in advance by pre-shipment inspection or the like, or the value obtained based on the average current value Ir of the first predetermined number of times may be averaged. can. The reference range data is stored in the storage unit 50 or the like. Further, even before the deviation from the predetermined reference range, if it is expected that the reference range will be deviated soon (for example, within the predetermined reference days) based on the history, a caution display or the like may be displayed.

Electrical system abnormalities (operation abnormalities) such as disconnection, short circuit, and deterioration detected from these capacitance Cp abnormalities are individually unrecoverable abnormalities and are stored as unrecoverable abnormal nozzles in the defective nozzle list 52. To. Alternatively, when the plurality of nozzles 27 commonly driven by the head drive unit 25 are similarly deteriorated, the entire adjustment may be made by setting the applied voltage V0 to be changed. If there is an abnormal nozzle that cannot be recovered individually, and if a new one occurs, in the inkjet recording device 1, the piezoelectric element 26 having an operation abnormality of the electrical system ejects ink due to the deformation of the nozzle 27 (abnormal nozzle). The drive is stopped, and the ejection setting of each nozzle 27 is performed so that the ink ejection amount of the nozzle 27 is complementarily performed by the nozzles 27 (adjacent nozzles) arranged adjacent to the nozzle 27. It is stored as a missing completion setting 53. In the inkjet recording apparatus 1 of the present embodiment, the nozzle openings 27a are two-dimensionally arranged, and there are 3 to 4 nozzles 27 adjacent to a certain nozzle except for both ends in the width direction, but they are not complemented. It is not always necessary for all of these adjacent nozzles 27 to perform the complementary ink ejection operation according to the above, and it is sufficient that the missing complement is set by at least a part of the adjacent nozzles 27.

On the other hand, among the nozzles 27 (nozzles with defective ejection) in which ejection defects are detected using the above test chart, those that are not unrecoverable (abnormal nozzles) are judged to be recoverable. When a recoverable nozzle 27 is generated, while the number of the recoverable nozzles 27 is small, the above-mentioned missing complement is set, and the number of recoverable nozzles 27 increases to some extent, or the missing complement is generated. When a predetermined condition such as difficulty (for example, when a plurality of nozzles 27 arranged adjacent to each other have a ejection failure) is satisfied, the cleaning unit 30 is operated to operate the nozzle surface 210. Perform cleaning. Alternatively, when even one recoverable nozzle 27 is generated, the nozzle surface 210 may be immediately cleaned without setting the missing complement.

The processing related to these abnormality detection operations is periodically performed at the time of starting the inkjet recording device 1 (at the time of starting power supply) or during the execution of the image recording operation. Further, it may be performed while the image recording operation is interrupted due to switching of print jobs or the like.
FIG. 6 is a diagram illustrating an image recording position on the recording medium P when the image recording operation is performed.

When the recording target images F1 and F2 are continuously recorded on the continuous recording medium P (the recording operation is repeated), the test charts C1 and C2 are YMCK 4 colors on the downstream side in the transport direction of the recording target images F1 and F2. It is formed in a band shape for each of the above. These test charts C1 and C2 do not necessarily have to be able to detect ejection defects for all nozzles every time, and ejection defects for all nozzles can be detected by combining a plurality of test charts C1 and C2. May be.

On the downstream side of the test chart C2 in the transport direction, a slight gap M1 is provided between the test chart C2 and the previous recording target image F1. The current measurement operation related to the capacity calculation of each piezoelectric element 26 can be performed without ejecting ink between the gaps M1. In this current measurement operation, it is not always necessary to measure the capacitances of all the piezoelectric elements 26 in one gap M1, but it is a combination of a plurality of current measurement operations executed between a plurality of gaps, that is, a plurality of times. The capacitance of all the piezoelectric elements 26 may be calculated by being divided between the recording operations of.

Further, it is not possible to identify the ink ejection failure of all the nozzles 27 and the operation abnormality of the piezoelectric element 26 every time, and it is possible to detect whether or not there is an ink ejection failure or an operation abnormality in a group of a plurality of nozzles 27 or the piezoelectric element 26. May be. When it is detected that there is an ink ejection failure or an operation abnormality in the group, each of the plurality of nozzles 27 and the piezoelectric element 26 belonging to the group is inspected, and the nozzle 27 or the operation abnormality causing the ink ejection failure occurs. The piezoelectric element 26 may be identified.

FIG. 7 is a flowchart showing a control procedure by the control unit 40 of the operation abnormality detection process executed by the inkjet recording apparatus 1 of the present embodiment.
This operation abnormality detection process, which is an operation abnormality detection method in the inkjet recording device 1 of the present embodiment, is performed, for example, at the time of starting the inkjet recording device 1, at predetermined intervals, during the recording operation at the time of recording an image, and / or. It is executed when the print job related to image recording is completed and the state shifts to the standby state. Further, this operation abnormality detection process may be called and executed in combination with the process related to the detection of the ejection failure nozzle described above.

When the operation abnormality detection process is started, the control unit 40 acquires the waiting time trms with reference to the waiting time setting 55 (step S101). The control unit 40 switches the switching element 92 to the measurement circuit side and receives power supply via the current detection unit 91 (step S102).

The control unit 40 selects the piezoelectric element 26 to be inspected (step S103). The control unit 40 starts outputting the voltage of the periodic drive voltage pattern for inspection to the selected piezoelectric element 26 (step S104). The control unit 40 determines whether or not the waiting time trms has elapsed from the start of the output (step S105). If it is determined that the process has not elapsed (“NO” in step S105), the control unit 40 repeats the process of step S105.

When it is determined that the standby time trms has elapsed (“YES” in step S105), the control unit 40 acquires the output current Ib measured from the current detection unit 91 (step S106). When the output current Ib is used a plurality of times to acquire the average current value Ir, the control unit 40 acquires the output current Ib a plurality of times at a set interval.

The control unit 40 acquires the average current value Ir based on the output current Ib and compares it with the reference value to determine whether or not the average current value Ir is abnormal (step S107). The control unit 40 determines whether or not the inspection (determination of the presence or absence of abnormality) has been completed for all the piezoelectric elements 26 to be inspected (step S108). If it is determined that the process has not been completed (“NO” in step S108), the process of the control unit 40 returns to step S103. If it is determined that the operation has been completed (“YES” in step S108), the control unit 40 ends the operation abnormality detection process. The control unit 40 switches the switching element 92 and the control signal related to the output of the drive voltage as necessary.

By setting the number of the piezoelectric elements 26 selected at one time to one in the process of step S103, an abnormality (operation abnormality) in the capacitance Cp of the piezoelectric element 26 can be immediately determined. On the other hand, when there is no time between a plurality of image recording operations, it is only necessary to select a plurality of piezoelectric elements 26 at a time and check whether or not the piezoelectric elements 26 include those having an abnormality in the capacitance Cp. If it is determined and it is determined that the piezoelectric element 26 is included, the plurality of piezoelectric elements 26 may be further selected one by one to identify the piezoelectric element 26 having an abnormal operation.

[Modification example]
Next, a modified example of the power supply unit 90 of the inkjet recording device 1 will be described.
8 to 10 are views for explaining a modification of the power supply unit 90.

In the modification 1 shown in FIG. 8A, a plurality of (predetermined number of groups) of head drive units 25 are provided for the piezoelectric elements 26, and the corresponding (divided) predetermined number of piezoelectric elements 26 (divided) are provided. The drive voltage (voltage VH2) related to the piezoelectric element group) is output. Separate DC power conversion units 95a and 95b (first drive voltage output unit and second drive voltage output unit, respectively) are provided for the head drive units 25 of the predetermined number of groups (two in this case). , The voltage VH2 is output to the switching elements 92a and 92b (input switching unit), respectively. On the other hand, the DC power conversion unit 95c outputs the voltage VH2 to the switching elements 92a and 92b via the current detection unit 91. In the following, the description of the configuration related to the output of the voltage VH1 will be omitted.

The switching elements 92a and 92b can be switched by independent control signals, and for each of the head drive units 25, the DC power conversion unit (which one supplies power) that is the supply source of the voltage VH2 is selected. Switch to. Therefore, the current of the voltage VH2 output to a part (particularly one) head drive unit 25 can be measured by the current detection unit 91 to inspect the capacitance Cp of the corresponding piezoelectric element 26.

In the modification 2 shown in FIG. 8B, the control signal related to the switching of the switching elements 92a and 92b is common to the modification 1, while the power supply operation of the DC power conversion units 95a and 95b is controlled on and off, respectively. can do. In this way, it is possible to easily switch between the normal drive signal input and the inspection signal input for the plurality of head drive units 25. In the piezoelectric element 26 that is actually inspected, the first switch 251 and the third switch 253 are selectively operated by the driver circuit 254 as in the above embodiment.

In the modification 3 shown in FIG. 9A, two inputs from an external power source (DC 24V or the like) to the DC power conversion unit 95 are provided, and a current detection unit 91 is provided in one of them, and this current is also provided. A capacitor 93a is provided in which one end is connected between the resistance element of the detection unit 91 and the DC power conversion unit 95 and the other end is grounded. Then, the switching element 92 (input switching unit) can switch whether or not the power supply to the DC power conversion unit 95 passes through the current detection unit 91. Similarly, by measuring the input current to the DC power conversion unit 95 in this way, and here, by performing the measurement based on the voltage drop by the resistance element of the current detection unit 91, the resistance value of the resistance element and the electric capacity of the capacitor 93a are also measured. The current (that is, the voltage fluctuation in the low frequency band) to the smoothed (passing through the low frequency band) the piezoelectric element 26 can be measured, and the capacitance Cp of the piezoelectric element 26 can be calculated more easily.

In this case, the current consumption related to the operation of the DC power conversion unit 95 itself is added as an offset value, so the offset value is subtracted for calculation. Since no change is expected in the operation (power consumption) of the DC power conversion unit 95 during the inspection of the piezoelectric element 26, this offset value may be a fixed value.

In the modified example 4 shown in FIG. 9B, when a plurality of DC power conversion units 95a and 95b corresponding to the plurality of head drive units 25 are provided, a common input current to the DC power conversion units 95a and 95b is provided. Is measured by the current detection unit 91. The supply power input to the DC power conversion units 95a and 95b is independently switched by the switching elements 92a and 92b by independent control signals whether or not they pass through the current detection unit 91. Therefore, only the current (smoothed by the capacitors 93a and 93b) corresponding to the electric power supplied from the head drive unit 25 of any one (particularly one) to the piezoelectric element 26 is detected by the current detection unit 91, and the others. The piezoelectric element 26 of the above is supplied with electric power without going through the current detection unit 91.

In the modified example 5 shown in FIG. 9 (c), whether or not the power supplied from the outside is input via the current detection unit 91 is switched by the single switching element 92 with respect to the modified example 4. One of the switches is commonly input to the DC power conversion units 95a and 95b. Further, signals for controlling on / off of voltage output (switching of output presence / absence) are input to the DC power supply conversion units 95a and 95b, respectively.

That is, when inspecting the capacitance Cp only for the piezoelectric element 26 to which power is supplied from one head drive unit 25, the input via the current detection unit 91 is selected by the switching element 92, and the piezoelectric element 26 to be inspected is selected. The voltage output from the head drive unit 25 other than the head drive unit 25 according to the above is turned off. As a result, simple on / off control is sufficient without increasing the number of switching control signals according to the number of DC power conversion units 95 (the presence or absence of output can be switched), and wiring related to switching control becomes easy.

In the modified examples 6 and 7 shown in FIGS. 10 (a) and 10 (b), contrary to the above-described embodiment and the modified examples 1 to 5, a bypass path that does not pass through the current detection unit 91 is not provided. That is, in the modification 6 shown in FIG. 10A, the voltage VH2 output from the DC power conversion unit 95 is always applied to the first stabilized capacitor 93 and the head drive unit 25 via the current detection unit 91. To. Further, in the modification 7 shown in FIG. 10B, the power supplied from the external power source input to the DC power conversion unit 95 always passes through the current detection unit 91.

In this case, if a large current is passed while driving the normal piezoelectric element 26, the voltage drop due to the resistance element of the current detection unit 91 becomes large, so the number of nozzles (the number of piezoelectric elements 26) in which such a voltage drop does not become so large. It may be used in the inkjet recording apparatus 1 having a small amount of current, or the voltage drop may be appropriately adjusted by the DC power conversion unit 95.

As described above, the inkjet recording device 1 of the present embodiment includes a nozzle 27 that ejects ink, a piezoelectric element 26 that deforms according to an applied voltage and gives a pressure change to the ink supplied to the nozzle 27. The power supply unit 90 that supplies the power related to the application of the drive voltage to the piezoelectric element 26 and the power supply unit 26 that periodically applies the drive voltage according to a predetermined drive voltage pattern and the power related to the application of the drive voltage. A representative value corresponding to a fluctuation component (including a DC component) in a predetermined low frequency band among the power supplied by the supply unit 90 is acquired, and an abnormality in the capacitance Cp of the piezoelectric element 26 obtained according to the representative value is detected. A control unit 40 as an abnormality detection unit is provided.
In this way, detection is performed by applying a periodic inspection drive voltage pattern and acquiring a representative value of the power supplied by the power supply unit 90 without measuring changes in the applied voltage or current of the piezoelectric element 26 itself. The required level of accuracy can be reduced. Therefore, it is possible to easily identify an abnormality in the driving operation related to ink ejection from the nozzle without requiring a high-performance configuration or requiring a high degree and / or complicated labor.

Further, the predetermined drive voltage pattern is a non-ejection waveform that does not eject ink from the nozzle 27. Therefore, even if the voltage is applied in the drive voltage pattern for periodic inspection, the ink is not consumed during the application of the voltage, so that the cost and the labor related to the processing of the discharged ink can be reduced. Further, since the voltage VH2 is only used as such a non-discharge waveform, fine control of the voltage or the like is not required, and complicated labor is not required.

Further, the power supply unit 90 receives the power supply and outputs a predetermined drive voltage (voltage VH2), and the DC power supply conversion unit 90 outputs the predetermined drive voltage based on the DC power supply conversion unit 95 and the predetermined drive voltage output by the DC power supply conversion unit 95. It includes a first stabilized capacitor 93 that can supply and store electric power corresponding to the drive voltage to the piezoelectric element 26. Further, the head drive unit includes a first switch 251 that switches the state of connection between the first stabilizing capacitor 93 and the piezoelectric element 26. Then, when the control unit 40 detects an abnormality in the capacitance Cp as an abnormality detection unit, the DC power conversion unit 95 charges the first stabilized capacitor 93 when the connection is disconnected by the first switch 251. The time constant is larger than the time constant related to the charging of the piezoelectric element 26 by the first stabilizing capacitor 93 when the connection is made by the first switch 251.
That is, since the charging speed of the first stabilized capacitor 93 at the time of charging is slower than the charging speed of the piezoelectric element 26 at the time of charging, the power supply unit 90 converts the DC power supply to be related to the charging of the first stabilized capacitor 93. By measuring the power supply from the unit 95, the measurement accuracy can be easily improved. Further, at this time, since the power is supplied periodically, it is easy to obtain the average power supply. In particular, the time constant related to the charging of the first stabilized capacitor 93 in which the drive voltage can be applied to the plurality of piezoelectric elements 26 (the voltage drop of the first stabilized capacitor 93 is very small even if applied) is determined. Since it is much larger than the time constant related to the charging of the piezoelectric element 26, the output current of the DC power conversion unit 95 becomes almost the steady current by outputting the drive voltage waveform at an appropriate frequency, so that it is from once to several degrees. It is possible to easily estimate the capacitance Cp by measuring the representative value (output current Ib) of the degree.

Further, the power supply unit 90 includes a current detection unit 91 that measures the output current from the DC power conversion unit 95 as a representative value based on the voltage drop due to the resistance element having a predetermined resistance value, and the first stabilized capacitor 93. One end is connected between one end of the resistance element of the current detection unit 91 and the switching element 92, and the current detection unit 91 has the predetermined value according to the resistance value of the resistance element and the electric capacity of the first stabilizing capacitor 93. Measure the voltage fluctuation in the low frequency band.
The normal current detection unit 91 measures the voltage drop in the resistance element, and when this resistance element is inserted into the circuit, the resistance value of the resistance element and the electric capacity of the first stabilized capacitor 93 are combined. As a result, the time constant related to the charging of the first stabilized capacitor 93 is further significantly increased, so that the low-frequency voltage fluctuation with smoother fluctuation is measured, and the average is easier and more accurate. The current value Ir can be acquired. That is, the inkjet recording device 1 can easily and more reliably detect an abnormality in the piezoelectric element 26.

Further, the power supply unit 90 shown in the modifications 3 to 5 includes a current detection unit 91 for measuring the input current to the DC power conversion unit 95, and one end of the capacitor 93a is a resistance element of the current detection unit 91 and a DC power supply. Connected to the conversion unit 95, the current detection unit 91 measures voltage fluctuations in a predetermined low frequency band according to the resistance value of the resistance element and the electric capacity of the capacitor 93a.
In this way, even when the input current to the DC power conversion unit 95 is detected, the average current value Ir corresponding to the power supplied to the piezoelectric element 26 can be easily obtained by the current detection unit 91, and therefore, the above-mentioned As in the embodiment, the abnormality of the piezoelectric element 26 can be easily and appropriately detected.

In the inkjet recording device 1, a short-circuit circuit provided in parallel with the current detection unit 91 (resistance element) is provided in the power supply unit 90, and the inkjet recording device 1 has a current detection unit 91. A switching element 92 for switching between the measuring circuit via the circuit and the short-circuit circuit is provided, and the switching element 92 is switched to the short-circuit circuit when an abnormality in the capacitance Cp is not detected. As described above, when a large amount of current flows through the resistance element, the voltage drop becomes large, and if a current is passed through the current detection unit 91 when the normal piezoelectric element 26 is driven, the drive voltage may be adversely affected. Further, the increase in the current may increase the amount of heat generated and affect each part, or may shorten the life of the image recording unit 20. Therefore, when a short-circuit circuit that supplies electric power without passing through the current detection unit 91 is provided in parallel and the piezoelectric element 26 is not inspected, the short-circuit circuit is switched to be used by the switching element 92, thereby causing the above-mentioned adverse effect. Can be avoided.

Further, the power supply units 90 of Modifications 1 and 2 are outputs from the DC power conversion units 95c and the DC power conversion units 95a and 95b, which receive the power supply and output a predetermined drive voltage, respectively, and the DC power conversion units 95c. The current detection unit 91 that measures the current, and the switching elements 92a and 92b that select and output either the drive voltage output by the DC power conversion unit 95c or the drive voltage output by the DC power conversion units 95a and 95b. A first stabilizing capacitor 93 that can supply and store power corresponding to the voltage based on the voltage output by the switching elements 92a and 92b to the piezoelectric element 26, and a resistance element of the current detection unit 91. The voltage fluctuation in the above-mentioned predetermined low frequency band according to the resistance value of the first stabilized capacitor 93 and the electric capacity of the first stabilized capacitor 93 is measured.
In this way, by appropriately switching and outputting using different DC power conversion units during inspection of the capacitance Cp and during normal driving, it is possible to handle the load appropriate for each operation, and it is possible to operate more appropriately. can. Further, in particular, when a plurality of DC power conversion units are used to perform a normal drive operation for a plurality (many) piezoelectric elements 26, a DC power supply commonly used for each piezoelectric element 26 for inspection is used. By combining with the conversion unit, it is possible to achieve both more efficient drive operation and inspection.

Further, the inkjet recording device 1 provided with the power supply unit 90 of the modification 4 has a plurality of piezoelectric elements 26 and a plurality of nozzles 27 classified into two or more predetermined groups of piezoelectric element groups, and a current detection unit 91 (its). The power supply unit 90 includes a short-circuit circuit provided in parallel with the resistance element), switching elements 92a and 92b for switching between the measurement circuit passing through the current detection unit 91 and the short-circuit circuit, and the power supply unit 90. The DC power conversion units 95a and 95b are provided with a predetermined number of groups to output a predetermined drive voltage for different piezoelectric element groups, and the switching elements 92a and 92b are a plurality of DC power conversion units 95a and 95b having a predetermined number of groups. For each of the above, the power is switched from the measurement circuit or the short-circuit circuit.
In this way, when a plurality of DC power conversion units are used corresponding to a plurality of piezoelectric element groups, a short-circuit circuit and a measurement circuit are provided in parallel, and DC power conversion is performed from either of them by the switching elements 92a and 92b. By enabling power to be supplied to the unit, when inspecting the capacitance Cp of the piezoelectric element 26 to be supplied with power from any of the DC power conversion units, DC power conversion according to the piezoelectric element 26 to be inspected can be easily performed. Appropriate power can be supplied to the unit and other DC power conversion units. In addition, the amount of heat generated by the current detection unit 91 is not increased more than necessary. Therefore, it is possible to easily inspect the piezoelectric element 26 to be inspected by applying an appropriate voltage to each piezoelectric element 26 while avoiding unnecessary power consumption and heat generation.

Further, the inkjet recording device 1 provided with the power supply unit 90 of the modification 5 includes a plurality of piezoelectric elements 26 and a plurality of nozzles 27 classified into two or more predetermined groups of piezoelectric element groups, and a current detection unit 91 (its). A short-circuit circuit provided in parallel with the resistor element), a switching element 92 for switching between the measurement circuit passing through the current detection unit 91 and this short-circuit circuit, and the power supply unit 90 are DC. The power conversion units 95a and 95b are provided with a predetermined number of groups to output a predetermined drive voltage related to different piezoelectric element groups, and the DC power conversion units 95a and 95b having a predetermined number of groups have a predetermined drive voltage related to the piezoelectric element group. It is possible to switch the presence or absence of output.
In this way, the switching element 92 collectively switches whether to supply the power supplied via the short-circuit circuit or the measurement circuit to the plurality of piezoelectric element groups, so that the wiring and output of the control signal are easy. become. On the other hand, the number of the piezoelectric elements 26 to be inspected at one time is limited to one or a small number, and the electric power (current) simultaneously supplied to all the DC power conversion units 95a and 95b is supplied by the current detection unit 91. There is not much merit to detect. Therefore, by making it possible to turn off the output of the drive voltage from other than the DC power conversion unit that supplies power to the piezoelectric element 26 to be inspected, unnecessary power supply can be suppressed. Further, as compared with the wiring for switching the connection source (power supply source) by the control signal, the wiring for simply switching the output on / off is easier and the control signal is also simple, so that the configuration and structure of the power supply unit 90 are simple. Can be facilitated.

Further, the control unit 40 acquires a representative value as an abnormality detection unit after the predetermined standby time trms has elapsed after starting the application of the periodic drive voltage.
As described above, the change in the drive voltage itself due to the periodic application of the drive voltage is insignificant, but in particular, the charging speed to the first stabilized capacitor 93, that is, the output current Ib is relative. Can change significantly. Therefore, by waiting until the charging speed is balanced with the discharging speed from the first stabilizing capacitor 93 to the piezoelectric element 26, the output current Ib can be obtained more easily and accurately, and the capacitance Cp is abnormal. The accuracy can be improved.

Further, since the predetermined standby time trms is determined based on the capacity of the first stabilized capacitor 93 and the resistance value of the resistance element of the current detection unit 91, it can be appropriately determined in advance based on these information. .. This makes it possible to easily measure and acquire the output current Ib more accurately.

Further, the control unit 40 has started to apply a periodic drive voltage for inspection as an initial setting unit at the time of initial setting performed at the time of pre-shipment inspection of the inkjet recording device 1 or at the time of replacement of the head unit 21. After that, the time until the fluctuation of the measured value of the current detection unit 91 becomes within a predetermined reference range is measured and determined as the standby time trms. As a result, it is possible to easily determine an appropriate measurement timing of the output current Ib at the time of actual inspection, and it is possible to reliably detect an abnormality in the capacitance Cp.

Further, the inkjet recording device 1 includes a storage unit 50 that stores data of the standby time trms as the standby time setting 55, and the control unit 40 sets the standby time setting 55 as the abnormality detection unit during the operation of detecting an abnormality in the capacitance Cp. refer. As a result, the measurement timing of the output current Ib can be easily and appropriately determined at the time of inspection, and the abnormality of the capacitance Cp can be reliably detected.

Further, the control unit 40, as an abnormality detection unit, determines the output current Ib in which the fluctuation of the measured value of the current detection unit 91 falls within a predetermined reference range after starting the application of the periodic drive voltage for inspection. get. In this way, even if the standby time trms is not inspected and held in advance, an appropriate output current Ib can be obtained by determining an appropriate timing by actual measurement, whereby an abnormality in the capacitance Cp can be appropriately detected. ..

Further, in the operation abnormality detection method of the present embodiment, a drive voltage is periodically applied to the piezoelectric element 26 according to a predetermined drive voltage pattern, and among the power supplied by the power supply unit 90 related to the application of the drive voltage, a predetermined value is obtained. Abnormality detection step of acquiring the average current value Ir which is a representative value corresponding to the fluctuation component (including the DC component) of the low frequency band of the above and detecting the abnormality of the capacitance Cp of the piezoelectric element 26 obtained according to the representative value. including.
By such an operation abnormality detection method, the required level of detection accuracy related to the detection of the abnormality of the capacitance Cp can be lowered. Therefore, it is possible to easily identify the abnormality of the drive operation related to the ink ejection from the nozzle without requiring a high-performance configuration and requiring a high-level and / or complicated plan.

The present invention is not limited to the above embodiment, and various modifications can be made.
For example, in the above embodiment, the input / output current to the DC power conversion unit 95 is measured by the current detection unit 91, but the voltage value may be measured if the supply power can be calculated.

Further, in the above embodiment, a rectangular wave-shaped drive voltage pattern that simply repeats on / off of the drive voltage is used as a waveform for inspection, but the present invention is also applied to a trapezoidal waveform or the like to apply the present invention to the capacitance Cp of the piezoelectric element. Can be inspected.

Further, in the above embodiment, it is decided to detect the abnormality of the capacitance Cp (without ejection) by the voltage VH2 to the extent that the ink is not ejected, but the ink is ejected in the normal drive operation. Even if the voltage is about to be ejected (voltage VH1, etc.), the drive frequency is switched, for example, the deformation of the piezoelectric element 26 does not follow, and / or the ink in the ink flow path is deformed (pressure change) in the pressure chamber. By setting the frequency so high that it does not follow, a non-discharge waveform can be obtained, and it becomes possible to detect an abnormality in the circuit related to the supply of the voltage (voltage VH1 or the like). At such a high frequency, the frequency of output of the current Ia to the piezoelectric element 26 increases, and the average current value Ir also increases accordingly, so that measurement becomes easy. Alternatively, when detecting an abnormality in the circuit related to the supply of such an ejection voltage, ink may be ejected to detect the abnormality in the capacitance Cp.

Further, in the above embodiment, the capacity of the first stabilizing capacitor 93 of the power supply unit 90 is used, and the smoothing of the supply power due to the influence of the resistance element of the current detection unit 91 or the resistance in the circuit is used. However, an inductive component such as a DC power conversion unit 95 may be included and used. Further, if the resistance value in the circuit is sufficient, the current detection unit 91 does not have to be provided with a resistance element in series with the measurement circuit.

Further, in the above embodiment, an inkjet recording apparatus having a line head and performing image recording on a continuous recording medium with one pass has been described as an example, but the present invention is not limited to this. Scan-type inkjet recording that repeats the operation of transporting the recording medium P and the operation of ejecting ink onto the recording medium P while moving the ejection head 211 with respect to the stopped recording medium P with respect to the recording medium P. It may be a device. Further, the recording medium is not limited to a continuous one, and may be one or a predetermined number of images to be recorded, such as a sheet of paper. In this case, the operation of detecting an abnormal operation that does not eject ink may be performed between a plurality of recording media.
In addition, specific details such as the configuration, circuit arrangement, processing contents and procedures thereof shown in the above-described embodiment can be appropriately changed without departing from the spirit of the present invention.

1 Inkjet recording device 10 Conveying unit 11 Driving roller 12 Conveying belt 13 Driven roller 14 Conveying motor 15 Pressing roller 16 Peeling roller 20 Image recording unit 21, 21C, 21M, 21Y, 21K Head unit 25 Head drive unit 26 Piezoelectric element 27 Nozzle 27a Nozzle opening 30 Cleaning unit 40 Control unit 41 CPU
42 RAM
50 Storage unit 51 Detection program 52 Defective nozzle list 53 Missing complement setting 54 Capacity history data 60 Reading unit 70 Communication unit 80 Operation display unit 90 Power supply unit 91 Current detection unit 92, 92a, 92b Switching element 93 First stabilizing capacitor 93a , 93b Capacitor 94 2nd stabilized capacitor 95, 95a, 95b, 95c DC power conversion unit 210 Nozzle surface 211 Discharge head 251 1st switch 252 2nd switch 253 3rd switch 254 Driver circuit Cp Capacity f Switching frequency Ib Output current Ir Average current value P Recording medium trms Standby time Vb, VH2 Voltage

Claims (15)

A nozzle that ejects ink and
A piezoelectric element that deforms according to the applied voltage and gives a pressure change to the ink supplied to the nozzle.
A power supply unit that supplies power related to the application of a drive voltage to the piezoelectric element, and
A drive voltage is periodically applied to the piezoelectric element according to a predetermined drive voltage pattern, and a representative value corresponding to a fluctuation component in a predetermined low frequency band among the power supplied by the power supply unit related to the application of the drive voltage. And an abnormality detection unit that detects an abnormality in the capacitance of the piezoelectric element, which is obtained according to the representative value.
Equipped with
The power supply unit
A drive voltage output unit that receives power and outputs a predetermined drive voltage,
A capacitor that can supply electric power corresponding to the predetermined drive voltage to the piezoelectric element based on the predetermined drive voltage output by the drive voltage output unit.
Equipped with
An inkjet recording device characterized by this. The inkjet recording apparatus according to claim 1, wherein the predetermined drive voltage pattern is a non-ejection waveform in which ink is not ejected from the nozzle. A connection switching unit for switching the state of connection between the capacitor and the piezoelectric element is provided.
The inkjet recording apparatus according to claim 1 or 2, wherein the capacity of the capacitor is larger than the capacity of the piezoelectric element . The power supply unit
It is provided with a current measuring unit that measures the output current from the driving voltage output unit as the representative value based on the voltage drop by the resistance element having a predetermined resistance value.
One end of the capacitor is connected between one end of the resistance element and the connection switching portion.
The inkjet recording apparatus according to claim 3, wherein the current measuring unit measures voltage fluctuations in the predetermined low frequency band according to the resistance value of the resistance element and the electric capacity of the capacitor. The power supply unit
A current measuring unit that measures the input current to the drive voltage output unit as the representative value based on the voltage drop by the resistance element having a predetermined resistance value is provided.
One end of the capacitor is connected between the resistance element and the drive voltage output unit.
The inkjet recording apparatus according to claim 3, wherein the current measuring unit measures voltage fluctuations in the predetermined low frequency band according to the resistance value of the resistance element and the electric capacity of the capacitor. The power supply unit
A short circuit circuit provided in parallel with the resistance element and
A circuit switching unit that switches between the measurement circuit that passes through the current measurement unit and the short-circuit circuit, and
Equipped with
The inkjet recording apparatus according to claim 4 or 5, wherein the circuit switching unit is switched to the short-circuit circuit when the abnormality of the capacitance is not detected. A nozzle that ejects ink and
A piezoelectric element that deforms according to the applied voltage and gives a pressure change to the ink supplied to the nozzle.
A power supply unit that supplies power related to the application of a drive voltage to the piezoelectric element, and
A drive voltage is periodically applied to the piezoelectric element according to a predetermined drive voltage pattern, and a representative value corresponding to a fluctuation component in a predetermined low frequency band among the power supplied by the power supply unit related to the application of the drive voltage. And an abnormality detection unit that detects an abnormality in the capacitance of the piezoelectric element, which is obtained according to the representative value.
Equipped with
The power supply unit
A first drive voltage output unit and a second drive voltage output unit that receive power supply and output a predetermined drive voltage, respectively.
A current measuring unit that measures the output current from the first drive voltage output unit as the representative value based on the voltage drop by the resistance element having a predetermined resistance value, and the current measuring unit.
An input switching unit that selects and outputs one of the drive voltage output by the first drive voltage output unit and the drive voltage output by the second drive voltage output unit.
A capacitor that can supply electric power corresponding to the predetermined drive voltage to the piezoelectric element based on the predetermined drive voltage output by the input switching unit.
Equipped with
An inkjet recording apparatus characterized by measuring voltage fluctuations in the predetermined low frequency band according to the resistance value of the resistance element and the electric capacity of the capacitor. A plurality of piezoelectric elements and a plurality of nozzles classified into a group of piezoelectric elements having a predetermined number of two or more groups,
A short circuit circuit provided in parallel with the resistance element and
A circuit switching unit that switches between the measurement circuit that passes through the current measurement unit and the short-circuit circuit, and
Equipped with
The power supply unit includes the drive voltage output units in the predetermined number of groups, and outputs the predetermined drive voltage related to the different piezoelectric element groups.
The inkjet according to claim 5, wherein the circuit switching unit switches whether to supply power from the measurement circuit or the short-circuit circuit for each of the drive voltage output units of the predetermined group number. Recording device. A plurality of piezoelectric elements and a plurality of nozzles classified into a group of piezoelectric elements having a predetermined number of two or more groups,
A short circuit circuit provided in parallel with the resistance element and
A circuit switching unit that switches between the measurement circuit that passes through the current measurement unit and the short-circuit circuit, and
Equipped with
The power supply unit includes the drive voltage output units in the predetermined number of groups, and outputs the predetermined drive voltage related to the different piezoelectric element groups.
The inkjet recording apparatus according to claim 5, wherein the drive voltage output units having a predetermined number of groups can switch between the presence and absence of output of the predetermined drive voltage related to the piezoelectric element group. One of claims 1 to 9, wherein the abnormality detecting unit acquires the representative value after a predetermined standby time has elapsed after starting the periodic application of the driving voltage. The inkjet recording device according to the section. After the abnormality detection unit starts the periodic application of the drive voltage, a predetermined standby time determined based on the capacity of the capacitor and the resistance value of the resistance element of the current measurement unit elapses. The inkjet recording apparatus according to any one of claims 4 to 6, 8 and 9, wherein the representative value is acquired. At the time of the predetermined initial setting, after the periodic application of the drive voltage is started, the time until the fluctuation of the measured value of the current measuring unit falls within the predetermined reference range is measured and used as the predetermined standby time. Equipped with an initial setting unit to be determined
Claims 4 to 6, 8, wherein the abnormality detecting unit acquires the representative value after the predetermined standby time has elapsed after starting the periodic application of the driving voltage. 9. The inkjet recording apparatus according to any one of 9. A storage unit for storing the standby time data is provided.
The inkjet recording apparatus according to any one of claims 10 to 12, wherein the abnormality detecting unit refers to the data of the waiting time at the time of the operation of detecting the abnormality of the capacity. After starting the periodic application of the drive voltage, the abnormality detecting unit acquires the representative value based on the measured value in which the fluctuation of the measured value of the current measuring unit is within a predetermined reference range. The inkjet recording apparatus according to any one of claims 4 to 6, 8 and 9. A nozzle that ejects ink, a piezoelectric element that deforms according to the applied voltage and gives a pressure change to the ink supplied to the nozzle, and a power supply that supplies power related to the application of a drive voltage to the piezoelectric element. The power supply unit is provided with a unit, and the power supply unit is based on a drive voltage output unit that receives power supply and outputs a predetermined drive voltage and the predetermined drive voltage output by the drive voltage output unit. A method for detecting an operation abnormality of an inkjet recording device including a capacitor that can supply power according to a drive voltage to the piezoelectric element .
A drive voltage is periodically applied to the piezoelectric element according to a predetermined drive voltage pattern, and a representative value corresponding to a fluctuation component in a predetermined low frequency band of the power supplied by the power supply unit related to the application of the drive voltage. A method for detecting an operation abnormality, which comprises an abnormality detection step for detecting an abnormality in the capacitance of the piezoelectric element, which is obtained according to the representative value.

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