WO2021141823A1

WO2021141823A1 - Imaging system with length determination of toner image

Info

Publication number: WO2021141823A1
Application number: PCT/US2020/067652
Authority: WO
Inventors: Shinya Nakasha; Koji Yamaguchi; Naoyuki Iwata
Original assignee: Hewlett Packard Development Co LP
Current assignee: Hewlett Packard Development Co LP
Priority date: 2020-01-08
Filing date: 2020-12-31
Publication date: 2021-07-15
Anticipated expiration: 2022-07-08
Also published as: JP2021110797A

Abstract

An imaging system includes an imaging apparatus to form a toner image to be analyzed and a controller. The imaging apparatus has a plurality of rotation members that include a conveyance member to convey the toner image in a conveyance direction. The controller receives a selection of a target member among the plurality of rotation members, and determines a length, in the conveyance direction, of the toner image to be formed based on the target member selected. The controller outputs length information to the imaging apparatus, to control the imaging apparatus to form the toner image according to the length determined.

Description

IMAGING SYSTEM WITH LENGTH DETERMINATION OF TONER IMAGE

BACKGROUND

[0001] Some imaging apparatuses include a conveying device which conveys a sheet, an image carrier which forms an electrostatic latent image, a developing device which develops the electrostatic latent image, a transfer device which secondarily transfers a toner image to a sheet, a fixing device which fixes the toner image to the sheet, and a discharge device which discharges the sheet.

BRIEF DESCRIPTION OF DRAWINGS

[0002] FIG. 1 is a schematic diagram illustrating a configuration of an example imaging apparatus.

[0003] FIG. 2 is a diagram schematically illustrating an example imaging device.

[0004] FIG. 3 is another diagram schematically illustrating the example imaging device.

[0005] FIG. 4 is a diagram illustrating an example screen display of a user interface for operating an example imaging device.

[0006] FIG. 5 is a table showing example rotation frequencies of rotation members of an imaging device.

[0007] FIG. 6 is an example table of numbers of samples, frequency resolutions, detection times, and lengths of a toner image.

[0008] FIG. 7 is a flowchart illustrating an example operation of deriving a length of a toner image in an example imaging system.

[0009] FIG. 8 is a flowchart illustrating an example operation of deriving a length of a toner image in an example imaging system.

[0010] FIG. 9 is a diagram schematically illustrating an example toner image formed on a conveyance member.

[0011] FIG. 10 is an example table of numbers of samples, frequency resolutions, detection times, and lengths of toner images. DETAILED DESCRIPTION

[0012] In the following description, with reference to the drawings, the same reference numbers are assigned to the same components or to similar components having the same function, and overlapping description is omitted. Hereinafter, an example imaging system will be described with reference to the drawings. The imaging system may be an imaging apparatus such as a printer in some examples, a part of an imaging apparatus, such as, a developing device or the like, according to other examples, or a system including the imaging apparatus in yet other examples.

[0013] With reference to FIG. 1 , an example imaging apparatus 1 forms a color image with colors of cyan, magenta, yellow, and black. The imaging apparatus 1 may include a conveying unit (or conveying device) 10 which conveys a sheet P corresponding to a printing medium, a transfer unit (or transfer device) 20 which transfers a developed toner to the sheet P, a photoconductor unit (or photoconductor device) 30 which includes a photoconductor drum 31 having a surface (a peripheral surface) to form an electrostatic latent image, a developing unit (or developing device) 100 which develops an electrostatic latent image with toner, and a fixing unit (or fixing device) 40 which fixes the toner to the sheet P. In the present description, the developing device 100 may refer to one or more developing devices associated with respective toners of the colors of cyan, magenta, yellow, and black, and the photoconductor unit 30 and corresponding photoconductor drum 31 may refer one or more photoconductors and photoconductor drums, associated with the cyan, magenta, yellow, and black toners. In addition, four toner tanks 36 are filled with the cyan, magenta, yellow and black toners, respectively, to supply the four developing devices 100, respectively.

[0014] The conveying unit 10 conveys the sheet P on which an image is to be formed, along a conveyance path. The sheet P is stacked in a cassette. The conveying unit 10 directs the sheet P to reach a secondary transfer region R at a timing when a composite toner image conveyed by the transfer unit 20 reaches the secondary transfer region R. [0015] The transfer unit 20 conveys the toner image formed by the respective photoconductor units 30, to the secondary transfer region R. The transfer unit 20 includes, for example, a transfer belt 21 , a drive roller 21 d, a tension roller 21a, guide rollers 21b and 21c, four primary transfer rollers 22, and a secondary transfer roller 24. The transfer belt 21 is supported by the drive roller 21 d, the tension roller 21a, and the guide rollers 21b and 21c. The transfer belt 21 is an endless belt which is driven to rotate by the drive roller 21 d. Each of the primary transfer rollers 22 presses the transfer belt 21 against an adjacent one of the photoconductor drums 31 from the inner peripheral side of the transfer belt 21 . The secondary transfer roller 24 presses the transfer belt 21 against the drive roller 21 d from the outer peripheral side of the transfer belt 21. Further, the transfer unit 20 includes a belt cleaning device or the like which removes residual toner adhered to the transfer belt 21 .

[0016] The example imaging apparatus 1 includes four photoconductor units 30 for the cyan, magenta, yellow, and black toners, respectively. Each of the photoconductor units 30 may include the corresponding photoconductor drum 31 , a charging roller 32, the developing unit (or developing device) 100, and a cleaning unit (cleaning device) 38. An exposure unit (or exposure device) 34 is provided adjacent the four photoconductor units 30. The photoconductor drum 31 is an electrostatic latent image carrier which forms an image on a peripheral surface thereof. The photoconductor drum 31 may be, for example, an Organic PhotoConductor (OPC). The example imaging apparatus 1 includes the four photoconductor drums 31 which correspond to the respective colors of cyan, magenta, yellow, and black toners. The four photoconductor drums 31 are provided in the movement direction of the transfer belt 21 . Adjacent each of the photoconductor drums 31 , are provided the corresponding charging roller 32, the corresponding developing unit 100, and the corresponding cleaning unit 38. In the present description, the charging roller 32 may refer to one or more charging rollers, and the cleaning unit 38 may refer to one or more cleaning units. For example, with reference to FIG. 1 , the imaging apparatus 1 includes the four charging rollers 32, and the four cleaning devices 38, in addition to the four primary transfer rollers 22, that are associated with the cyan, magenta, yellow, and black toners, respectively.

[0017] For each of the photoconductor drums 31 , the corresponding charging roller 32 charges the surface of the photoconductor drum 31 to a predetermined potential. The exposure unit 34 exposes the surface of the photoconductor drum 31 charged by the charging roller 32 according to an image (an electrostatic latent image) to be formed. The example exposure unit 34 exposes the surface of the photoconductor drum 31 by irradiating the surface with a laser beam. A potential of a portion exposed by the exposure unit 34 in the surface of the photoconductor drum 31 changes. With this change, an electrostatic latent image is formed on the surface of the photoconductor drum 31.

[0018] For each of the photoconductor drum 31 , the corresponding cleaning unit 38 collects the toner remaining on the photoconductor drum 31 after the associated toner image on the photoconductor drum 31 is primarily transferred to the transfer belt 21. For example, the cleaning unit 38 may include a cleaning blade to contact the peripheral surface of the photoconductor drum 31 , in order to remove the remaining toner. Additionally, a static elimination lamp which resets a potential of the photoconductor drum 31 may be disposed adjacent the photoconductor drum 31 , between the cleaning unit 38 and the charging roller 32 in a circumferential direction of the photoconductor drum 31 .

[0019] Toners are supplied from the toner tanks 36 respectively corresponding to the four developing units 100. Four toner tanks 36 are respectively filled with, for example, a yellow replenishment developer (or yellow supply developer) obtained by mixing a yellow toner with a carrier, a magenta replenishment developer (or magenta supply developer) obtained by mixing a magenta toner with a carrier, a cyan replenishment developer (or cyan supply developer) obtained by mixing a cyan toner with a carrier, and a black replenishment developer (or black supply developer) obtained by mixing a black toner with a carrier. Each of the developing units 100 develops the electrostatic latent image formed on the associated photoconductor drum 31 by the associated toner. When the electrostatic latent image is developed, the toner image is generated on the photoconductor drum 31 . [0020] Each developing unit 100 may include, for example, a developing roller 110, a supply auger 120, and a stirring auger 130. In the present description, the developing roller 110 may refer to one or more developing roller associated with the cyan, magenta, yellow and black toners. The supply auger 120 may refer to one or more supply augers associated with the cyan, magenta, yellow and black toners. The stirring auger 130 may refer to one or more stirring augers associated with the cyan, magenta, yellow and black toners. In each of the developing units 100, the developing roller 110 is a developer carrier that carries a developer containing toner, and supplies the toner to the electrostatic latent image formed on the peripheral surface of the photoconductor drum 31 . The developing roller 110 receives the developer from the supply auger 120 by a magnetic force and conveys the developer such that the toner in the developer is transferred to the photoconductor drum 31 .

[0021] In each of the developing units 100, the supply auger 120 and the stirring auger 130 stir a magnetic carrier and a non-magnetic toner constituting the developer so as to frictionally charge the carrier and the toner. The stirring auger 130 conveys the charged developer to the supply auger 120. In some examples, the stirring auger 130 may be disposed below the supply auger 120, for example, in the direction of gravity. The supply auger 120 supplies the mixed and stirred developer to the developing roller 110. In some examples, the supply auger 120 may be disposed below the developing roller 110, for example, in the direction of gravity. Each of the supply auger 120 and the stirring auger 130 has a spiral conveying surface disposed along a longitudinal direction (e.g., a direction parallel to a rotation axis of the developing roller 110).

[0022] The fixing unit 40 fixes the toner image secondarily transferred from the transfer belt 21 to the sheet P. The fixing unit 40 may include a heating roller 42 and a pressing roller 44, for example. The heating roller 42 is rotatable around a rotation axis. In some examples, a heat source such as a halogen lamp is provided inside the heating roller 42. The pressing roller 44 is rotatable around a rotation axis. The pressing roller 44 is provided so as to press against the heating roller 42. The outer peripheral surfaces of the heating roller 42 and the pressing roller 44 may each be provided with a heat-resistant elastic layer such as silicon rubber. When the sheet P is conveyed to pass through a fixing nip portion corresponding to a contact region between the heating roller 42 and the pressing roller 44, the toner image is melted and fixed to the sheet P.

[0023] In addition, the imaging apparatus 1 may be provided with discharge rollers 52 and 54 which discharge the sheet P having the toner image fixed thereto by the fixing unit 40 to the outside of the imaging apparatus 1 . [0024] An example of an operation of the example imaging apparatus 1 will be described. When an image signal of a recording target image is input to the imaging apparatus 1 , the controller of the imaging apparatus 1 causes the charging roller 32 to charge the surface of the photoconductor drum 31 to a predetermined potential. Then, the controller causes the exposure unit 34 to form an electrostatic latent image on the surface of the photoconductor drum 31 based on the received image signal.

[0025] Each of the developing units 100 mixes and stirs the associated toner and carrier while adjusting a mixing ratio of the toner and the carrier within a targeted range. The developing unit 100 adjusts the developer by dispersing the toner so as to apply a suitable charge amount. The adjusted developer is carried (held) by the developing roller 110. Then, when the developer is conveyed to a region (supply position) facing the photoconductor drum 31 with the rotation of the developing roller 110, the toner of the developer carried by the developing roller 110 moves to the electrostatic latent image formed on the peripheral surface of the associated photoconductor drum 31 so as to develop the corresponding electrostatic latent image. Accordingly, the corresponding toner image is formed on the peripheral surface of the photoconductor drum 31 . The formed toner image is primarily transferred from the photoconductor drum 31 to the transfer belt 21 in a region in which the photoconductor drum 31 faces the transfer belt 21 . The toner images formed on the four photoconductor drums 31 are sequentially layered on the transfer belt 21 so that a composite toner image is formed. The composite toner image is secondarily transferred to the sheet P conveyed from the conveying unit 10 in the secondary transfer region R where the drive roller 21 d faces the secondary transfer roller 24. In some examples, the belt cleaning device is provided to remove the toner remaining on the transfer belt 21 after the composite toner image is secondarily transferred to the sheet P.

[0026] The sheet P having the composite toner image is conveyed to the fixing unit 40. When the sheet P is conveyed to the fixing unit 40, the heating roller 42 and the pressing roller 44 apply heat and pressure to the sheet P, so as to melt and fix the composite toner image to the sheet P. Then, the sheet P is discharged to the outside of the imaging apparatus 1 by the discharge rollers 52 and 54.

[0027] With reference to FIG. 2, the imaging apparatus 1 may include an analysis system. The analysis system can detect or identify a member causing an image defect generated in the imaging apparatus 1 . The analysis target may be a rotation member of the imaging apparatus 1.

[0028] FIG. 2 is a schematic diagram illustrating an imaging system including an analysis system. An example imaging device S includes the imaging apparatus 1 and a controller C. The imaging apparatus 1 includes a plurality of rotation members RM including a conveyance member CM that conveys a toner image E in a conveying direction D. Examples of the rotation members RM and of the conveyance member CM will be described further below, with reference to FIG. 3. The toner image E is used to identify a member causing an image defect. The controller C receives a selection of a target member among the plurality of rotation members RM. The controller C determines the length of the toner image E in the conveying direction D according to the selection result of the target member. The controller C outputs length information to the imaging apparatus 1 in order to control the imaging apparatus 1 so that the toner image E is formed in accordance with the determined length.

[0029] According to examples, one among the plurality of rotation members RM of the imaging apparatus 1 can be identified as a member that causes an image defect. The controller C receives the selection of the target member, and determines the length of the toner image E. For example, the controller C may vary the length of the toner image E based on the selected target member. Then, the imaging apparatus 1 forms the toner image E of the length determined by the controller C. In this case, the length of the toner image E used for the analysis can be set to an optimal or suitable length adapted to the selected target member, in that the length is sufficient for the analysis and also inhibits consumption of the toner in excess and the wearing of the rotation member RM. [0030] FIG. 3 is a schematic diagram illustrating an example imaging device S including the analysis system. The example imaging device S includes the imaging apparatus 1 , the controller C, and a toner density sensor 29. The imaging apparatus 1 includes, as the rotation members RM that may be an analysis target, a conveyance member (e.g., conveyance member CM in FIG. 2) that is common to a plurality of colors, and a plurality of color-specific rotation members respectively corresponding to a plurality of colors of toner. For example, the rotation members RM may include the photoconductor drum 31 and the charging roller 32 in the photoconductor unit 30 (cf. FIG. 1), the developing roller 110 and the supply auger 120 in the developing unit 100 (cf. FIG. 1), and the transfer belt (the conveyance member) 21 , the drive roller 21 d, the tension roller 21a, the guide roller 21c, and the primary transfer roller 22 in the transfer unit 20 (cf. FIG. 1 ). The example analysis system analyzes the state of one or more rotation members selected among these rotation members RM. The transfer belt 21 is an example conveyance member CM (cf. FIG. 2).

[0031] The toner density sensor 29 includes, for example, a light emitting element and a light receiving element. The toner density sensor 29 detects the adhering amount (or adherence amount) e.g., the toner density, of the toner in the toner image transferred to the transfer belt 21 by receiving reflected light at the light receiving element, from the light emitted from the light emitting element toward the transfer belt 21 . The toner density sensor 29 can output data obtained by the detection to the controller C. In an example, the toner density sensor 29 may also output an output voltage of the light receiving element to the controller C. The toner density sensor 29 can be disposed at a position facing the transfer belt 21 and adjacent to the transfer belt 21.

[0032] The controller C may control the operation for forming an image in the imaging apparatus 1. According to examples, the controller C may be included in the imaging apparatus 1 . In other examples, the controller C may be externally connected to or in communication with the imaging apparatus 1. The controller C may be configured as a computer including, for example, a processor such as a Central Processing Unit (CPU) and a storage device such as a Read- Only Memory (ROM) and a Random Access Memory (RAM). The storage device is, for example, a non-temporary computer-readable storage device (recording medium) storing a program in the form of data and/or instructions for controlling the imaging apparatus 1 . The controller C may read and execute the data and/or instructions to control the imaging apparatus 1 to carry out the control of the imaging apparatus 1 .

[0033] According to examples, the controller C may read and/or execute the data/instructions via functional units which may include a selection receiving unit C1 , a length determining unit C2, an information output unit C3, and an evaluation unit C4.

[0034] Via the selection receiving unit C1 , the controller receives the selection of the target member among the plurality of rotation members RM included in the imaging apparatus 1 . In an example, a user interface 9 such as a touch panel is connected to or in communication with the controller C. In some examples, the user interface 9 may be provided on the imaging apparatus 1. The information relating to the selection of the target member input from the user is received via the user interface 9. In an example, the user interface 9 receives the input of the user when the target member is selected. The user interface 9 may display a plurality of identifiers or pieces of identification information (for example, the name of the rotation member RM) associated with the plurality of rotation members RM. When the user selects a rotation member RM, the identification information of the selected member may be displayed to indicate the selection. [0035] FIG. 4 illustrates an example of a screen display of the user interface 9. As illustrated in FIG. 4, the imaging apparatus 1 is operable in a "periodic unevenness detection mode" as an example of an operation mode. For example, when a defect such as unevenness occurs in an image formed by the imaging apparatus 1 , the user may activate the "periodic unevenness detection mode". In the example illustrated in FIG. 4, a prompt "Please select a member to be detected" is displayed to remind the user to select a target member.

[0036] In the example illustrated in the drawings, the user can select any one or more target members among the photoconductor drum 31 and the charging roller 32 of the photoconductor unit 30, the developing roller 110 and the supply auger 120 of the developing unit 100, and the transfer belt 21 , the drive roller 21 d, the tension roller 21a, the guide roller 21c, and the primary transfer roller 22 of the transfer unit 20. Accordingly, the identification information (e.g., name) of each rotation member is displayed together with a check box for allowing selection of the rotation member. FIG. 4 illustrates an example state in which the supply auger 120 and the guide roller 21c are selected by the user. In this example, the check boxes corresponding to the supply auger 120 and the guide roller 21c are checked to indicate that they have been selected by the user. [0037] Via the length determining unit C2, the controller C determines the length of the toner image E formed by the imaging apparatus 1 in response to the target member selected. In an example, each of the plurality of rotation members RM rotates according to an associated rotation characteristic. The rotation characteristic may be, for example, a rotation speed. The rotation speed is, for example, the number of rotations of the rotation member per unit time and is indicated as the rotation frequency (Hz) which is the number of rotations per second. FIG. 5 illustrates a table indicating the rotation frequencies of the respective rotation members. The rotation frequency of the rotation members RM may be stored as, for example, a look-up table in the storage device of the controller C. The length of the toner image E is determined based on the rotation characteristic (for example, the rotation frequency) of at least one of the target members. The controller C determines the length of the toner image E necessary for the analysis based on a minimum difference among frequency differences between the rotation frequency(ies) of each selected target member with the rotation frequencies of the rotation members RM (other than the subject selected target member). Accordingly, the minimum difference reflects the rotation frequency that is closest to the rotation frequency of any one of the target member(s) relative to the other selectable rotation members. Accordingly, the length of the toner image E is determined based on the minimum difference among the frequency differences between the rotation frequency of each target member with each of the rotation frequencies of the plurality of rotation members RM. [0038] Via the information output unit C3, the controller C outputs the length information to the imaging apparatus 1 in order to control the imaging apparatus 1 so that the toner image E is formed according to the determined length. The length information output to the imaging apparatus 1 may be information for forming the toner image E of the determined length by the imaging apparatus 1 . The imaging apparatus 1 forms the toner image E having a size of a length L in the conveying direction on the transfer belt 21 based on the information of the length L. In an example, the toner image E of the length L for each color of magenta, yellow, cyan, and black is formed on the transfer belt 21 . For example, four toner images of the respective colors may be formed sequentially in the conveying direction, either continuously or separately from one another.

[0039] Via the evaluation unit C4, the controller C analyzes the state of the selected target member from the toner image E formed by the imaging apparatus 1 . The controller C acquires sampling data based on data from the toner density sensor 29 according to a sampling frequency, and analyzes the state of the selected target member based on the frequency analysis of the data. For example, the state of the selected target member may be analyzed based on Fourier-transformed data (frequency spectrum) of sampling data (density time waveform). In an example, the controller C acquires a frequency spectrum by a calculation based on the Cooley-Tukey type fast Fourier transform (Cooley-Tukey FFT) on the acquired sampling data. Additionally, the controller C acquires the spectrum intensity of the frequency corresponding to the rotation frequency of the target member from the acquired frequency spectrum. When the spectrum intensity is equal to or greater than a predetermined value, the controller C determines that the corresponding target member has a defect.

[0040] An operation of the controller, that may be carried out by the length determining unit C2 for example, will be described. As described above, in the example analysis system, the time waveform of the density data may be converted into a frequency spectrum by a fast Fourier transform to identify the rotation member that is causing a failure based on a frequency component included in the frequency spectrum. In order to determine which frequency component of the frequency spectrum corresponds to which of the selected target members, a frequency peak(s) appearing in the frequency spectrum may be considered.

[0041] When a plurality of target members is selected, the targeted resolution (e.g., required resolution) for identifying the peaks of the target members in the frequency spectrum corresponds to the minimum difference, among the frequency differences between the rotation frequency of each target member with the rotation frequency of each of the rotation members. Accordingly, the targeted resolution corresponds to a difference between a first rotation frequency which is the rotation frequency of the target member, and a second rotation frequency corresponding to the rotation frequency of the rotation member having the closest rotation frequency to the first rotation frequency. Meanwhile, the frequency resolution Af of the frequency spectrum acquired from the toner image E formed by the imaging apparatus 1 is expressed by the formula below, in which the sampling frequency is denoted by fs, the number of samples is denoted by N, the detection time is denoted by T, the toner image conveying speed of the transfer belt 21 is denoted by PS, and the length of the toner image is denoted by L. When the length L of the toner image E is set so that the frequency resolution Af has a resolution greater than the targeted resolution, the spectrums corresponding to the plurality of target members can be suitably identified by the length determining unit C2. Additionally, a sampling frequency fs is the number of toner density data acquired in one second, the number N of samples is the total number of toner density data acquired from the formed toner image E, and the detection time is the time for the toner density sensor 29 to detect the toner image E. As shown in the following formula, since the frequency resolution Af is a value based on the detection time T, it can be said that the relationship between the target member and the length L is also based on the detection time T.

[0042] Af = 1/T = fs/N = PS/L

[0043] In the Cooley-Tukey type fast Fourier transform (FFT) calculation, the number N of samples to be acquired are powers of 2, satisfying 2 to the n-th power, where n is a natural number, in order to increase the calculation efficiency. In an example, the length L of the toner image can be determined so that the number of samples corresponds to a power of 2 (e.g., 2n). As an example, when the conveyance speed of the toner image E using the transfer belt 21 is 280 mm/s and the sampling frequency fs is 100 Hz, a relationship of the number N of samples satisfying 2n, the frequency resolution Af, the detection time T, and the length L of the toner image is shown in the table of FIG. 6. The example controller C may store the relationship shown in FIG. 6 as a look-up table.

[0044] Via the length determining unit C2, the controller C derives the targeted resolution based on the rotation frequency (Hz) of the selected target member. In an example, the frequency differences between the rotation frequency of each of the selected target member(s) and the rotation frequencies of each of the rotation members are considered, and a minimum difference is derived among the frequency differences, as the targeted resolution.

[0045] Via the length determining unit C2, the controller C derives the length L which corresponds to the maximum frequency resolution Af satisfying the targeted resolution by accessing a look-up table. For example, with reference to FIG. 5, in a case where the selected target members are the photoconductor drum 31 having a rotation frequency of 2.96 Hz and the drive roller 21 d having a rotation frequency of 3.57 Hz, a frequency difference of 0.18 Hz is identified as the minimum difference, e.g., a difference between the rotation frequency of the drive roller 21 d and the rotation frequency of the tension roller 21a, and the minimum difference of 0.18 Hz is derived as the targeted resolution. With reference to the look-up table of FIG. 6, the minimum frequency resolution that satisfies 0.18 Hz is 0.098 Hz, and the associated length L is 2867 mm. Accordingly, the length L (that is, 2867 mm) of the toner image that satisfies the minimum frequency resolution Af (that is, 0.098 Hz) that satisfies 0.18 Hz is derived.

[0046] In addition, as an example, when the rotation member constituting the developing unit 100 is selected as the target member, the controller C may change, via the length determining unit C2, the rotation speed of the developing unit 100 so that the targeted resolution decreases (and accordingly, the value of the targeted resolution increases). Accordingly, the rotation frequency of the rotation member may be adjusted so that a difference in the rotation frequency increases. FIG. 7 is a flowchart illustrating an operation of the controller C via the example length determining unit C2. At operation S11 , the information of the target member selected by the user is first acquired by the selection receiving unit C1.

[0047] At operation S12, the value of the frequency resolution is initialized. The frequency resolution with the greatest value among the settable values is set as the initial value. At operation S13, a frequency change rate is initialized. The frequency change rate is a change rate of the rotation frequency of the developing unit 100 changed in the imaging apparatus 1 according to the determination of the length determining unit C2. The frequency change rate is set as "1" by the initialization so that the rotation frequency is not changed.

[0048] At operation S14, the targeted resolution is derived. For example, a difference is calculated between the value of the rotation frequency of each selected target member and the rotation frequency of the rotation member closest to each rotation frequency, and a minimum difference is derived as the targeted resolution.

[0049] Operation S15 determines whether the value of the derived targeted resolution is equal to or greater than the value of the frequency resolution. When the value of the targeted resolution is equal to or greater than the value of the frequency resolution, for example, the set frequency resolution is equal to or greater than the targeted resolution, the length of the toner image corresponding to the frequency resolution is derived at operation S16.

[0050] Referring back to operation S15, when the value of the targeted resolution is less than the value of the frequency resolution, for example, the set frequency resolution is lower than the targeted resolution, operation S17 determines whether a relationship according to which the targeted resolution is equal to or greater than the frequency resolution (which may be represented as “targeted resolution > frequency resolution”), is established in the frequency change range. The frequency change range may be, for example, a range (upper limit and lower limit) of the rotation frequency that can be set in the developing unit 100 and is set in advance under conditions that do not apply an excessive load to the developing unit. The length determining unit C2 determines whether the relationship of targeted resolution > frequency resolution is established when the rotation frequency of the rotation member RM constituting the developing unit 100 is changed to an upper limit and a lower limit that can be set.

[0051] When the relationship of targeted resolution > frequency resolution is not established as a determination result, operation S18 sets the value of the frequency resolution is to be decreased (so as to increase the frequency resolution). Referring to the table of FIG. 6, when the frequency resolution before the determination is, for example, 1.563 Hz, the next lowest value, 0.781 Hz, is set as the value of the frequency resolution, which corresponds to an increase in the resolution. In this case, the process returns to operation S15.

[0052] When the relationship of targeted resolution > frequency resolution is established as a result of operation S17, operation S19 adjusts the frequency change rate. In an example, the adjusted frequency change rate may be the lowest value which satisfies the relationship of targeted resolution > frequency resolution. For example, the frequency change rate may be adjusted so that the targeted resolution is the same as the frequency resolution.

[0053] When the frequency change rate is adjusted, operation S20 acquires the rotation frequency of the target member. For example, the rotation frequency of the target member constituting the developing unit 100 among the target members is changed by the frequency adjustment rate and the changed rotation frequency is acquired. At operation S16, the length L of the toner image corresponding to the frequency resolution is derived. In addition, the rotation frequency adjusted based on the frequency adjustment rate is output to the imaging apparatus 1. Accordingly, the imaging apparatus 1 operates the developing unit 100 at the changed rotation frequency when forming the toner image.

[0054] The above-described operations can determine the length L for analysis of the toner image to be shorter while reducing a load on the developing roller 110. An example will be described, in which the selected target members are the photoconductor drum 31 having a rotation frequency of 2.96 Hz and the supply auger 120 having a rotation frequency of 7.61 Hz. In this case, a difference between 7.61 Hz corresponding to the frequency of the supply auger 120, and 7.43 Hz corresponding to the frequency of the guide roller 21c which is not a target member, is the smallest difference in frequencies. When the rotation frequency is not adjusted, the targeted resolution is 0.18 Hz. For that reason, 2867 mm corresponding to the frequency resolution Af of 0.098 Hz which is less than 0.18 Hz, is derived as the length L of the toner image (cf. FIG. 6). Meanwhile, when the rotation frequency of the supply auger 120 reaches 7.625 Hz (100.2%), that is, the frequency adjustment rate reaches +0.2%, the targeted resolution decreases to 0.195 Hz. In this case, 1434 mm corresponding to the frequency resolution of 0.195 Hz is derives as the length L of the toner image. This example corresponds to a case in which the flow of operations S15, S17, and S18 is repeated until the frequency resolution reaches 0.195 Hz in operation S15 in the flowchart of FIG. 7.

[0055] The above-described rotation members RM may be categorized as common members that are common to a plurality of colors such as the transfer belt (the conveyance member) 21 , the drive roller 21 d, the tension roller 21 a, and the guide roller 21 c of the transfer unit 20 (see FIG. 1 ), and as color members (or color-specific members) that are each associated with one of a plurality of colors. Examples of color-specific members include the photoconductor drum 31 , the charging roller 32, the developing roller 110, the supply auger 120, and the primary transfer roller 22. For example, the controller C may determine the length L of the toner image E so that the sum of the lengths of the toner images (toner- image components) corresponding to any two or more colors is no less than the circumference length (circumferential length) of the common member when the common member is included in the plurality of selected target members. The circumference length (or circumferential length) of the transfer belt 21 may be defined as the length of the loop of the belt in the rotational direction of the transfer belt 21.

[0056] As an example, the controller C may perform, via the length determining unit C2, an operation illustrated in the flowchart of FIG. 8 when the transfer belt 21 is selected as the target member. In some cases, the transfer belt 21 has a longer circumference length than other rotation members RM. For example, when the length L of the toner image determined is less than the length of the transfer belt 21 , it may be more difficult to analyze the transfer belt 21 by the formed toner image. Here, when the transfer belt 21 is selected as the target member, four toner images corresponding to respective colors of magenta, yellow, cyan, and black may be used in the analysis of the transfer belt 21 as one continuous toner image.

[0057] When the transfer belt 21 is selected as the target member, operation S31 determines the length L of the toner image based on the processes of operations S11 to S20 (of. FIG. 7). Then, operation S32 determines whether the length (circumference length) of the transfer belt 21 is longer than four times the determined length of the toner image. When the length of the transfer belt 21 is four times or less the determined length L of the toner image as a determination result, the determined length L of the toner image is output to the imaging apparatus 1 along with the value of the rotation frequency of the target member. Meanwhile, when it is determined that the length of the transfer belt 21 is greater than four times the length L of the toner image, operation S33 sets a new length L of the toner image, to twice the determined length L of the toner image and the process returns to operation S32. That is, the frequency resolution Af is set to be further increased.

[0058] Accordingly, when the transfer belt 21 is selected as the target member, the derived length L of the toner image corresponds to the frequency resolution Af which is greater than the targeted resolution and satisfies that the size four times the length L is longer than the length of the transfer belt 21 . In this case, as illustrated in FIG. 9, in the imaging apparatus 1 , four colors of toner images E1 , E2, E3, and E4 are continuously formed so as to have the determined length L. In this case, in the evaluation unit C4, the determination of the target member (that is, a member other than the transfer belt) corresponding to each color is performed based on the toner density data acquired from the toner images E1 , E2, E3, and E4 of the respective colors. Further, the determination of the transfer belt 21 is performed based on toner density data of a toner image ET having a length 4L obtained by continuously forming four colors of the toner images (or toner-image components) E1 , E2, E3, and E4. Additionally, although the length of the transfer belt 21 is shorter than 4L, the transfer belt 21 is expressed as an infinite length for ease of understanding. Further, although an example is illustrated in which the toner image ET obtained by connecting all four toner images E1 , E2, E3, and E4 is used for analyzing a common member, a toner image obtained by adding any two or more toner images corresponding the plurality of toner colors, may be used for analyzing the common member, without connecting all the toner images together.

[0059] As described above, the sampling data acquired by the toner density sensor 29 is frequency-analyzed, in order to identify a member that causes an image defect, among the plurality of rotation members RM. The length L of the toner image E detected by the toner density sensor 29 is determined based on the target member selected by the user. Accordingly, the controller C can vary the length of the toner image E according to the target member selected. [0060] In some examples, an example imaging system that does not include a function for selecting the target member. In such a case, all rotation members are analysis targets. In this case, a toner image having a predetermined length is formed so that the two rotation members having the lowest difference in rotation frequency can be distinguished from each other. In this case, since the toner image having an unnecessarily long length is formed, toner may be consumed in excess, or the rotation member may be used in excess. As described above, in the example imaging system, the length of the toner image E used for analysis can be set to an optimal length according to the selected target member. In an example, the length of the toner image is determined to be the minimum length among the lengths suitable for the frequency analysis, in order to reduce consumption of the toner and the consumption or use/wear of the rotation member RM.

[0061] A relationship between the selected target member and the length L of the formed toner image E is based on a frequency resolution Af. The frequency resolution Af is a value based on the detection time (time window length) of the toner image E. For that reason, the length L of the toner image E formed for the analysis can be determined based on detection time in order to inhibit excess consumption or deficiencies.

[0062] Each of the plurality of rotation members RM rotates according to the rotation characteristic (e.g., the rotation frequency) and the controller C determines the length L of the toner image E based on the minimum difference between the rotation frequency of each target member selected by the user and the rotation frequency of the rotation member. The minimum difference between the rotation frequencies corresponds to the resolution targeted for distinguishing the target member and the rotation member having the rotation frequency closest to the rotation frequency of the target member by frequency analysis. Consequently, the length L is determined based on the minimum difference between the rotation frequencies, in order to more reliably identify the spectrum of the target member.

[0063] The controller C may adjust the rotation frequency of the rotation member so that the minimum difference between the rotation frequencies increases. In this example, the targeted resolution can be decreased, in order to decrease the length L of the toner image E for analysis.

[0064] When the rotation frequency is adjusted, the controller C outputs the adjusted rotation frequency of the target member to the imaging apparatus 1 along with the information of the length L of the toner image E. Accordingly, the imaging apparatus 1 can form the toner image E while reflecting the adjusted rotation frequency.

[0065] The imaging device S includes the user interface 9 that receives the input of the user when selecting the target member. For example, the user interface 9 outputs for user selection, a plurality of pieces of identification information (member names) respectively associated with a plurality of rotation members. Accordingly, the user can input the section of the target member. [0066] In the user interface 9, the display of the identification information corresponding to the target member selected by the user is changed. The user can confirm or modify the target member selected using the display of the user interface 9.

[0067] In an example, the length L of the toner image E is determined by accessing the look-up table, to reduce the load of the calculation process on the controller C. Additionally, although an example is described in which the length L is derived by referring to the look-up table shown in FIG. 6, in other examples, the controller C may derive the length L using a calculation based on various parameters such as a rotation frequency, the number of samples, and a conveyance speed. In other examples, the controller C may access a look-up table which illustrates a relationship between the combination of the selected target members and the length L of the toner image E, so as to derive the length L by accessing the look-up table.

[0068] It is to be understood that not all aspects, advantages and features described herein may necessarily be achieved by, or included in, any one particular example. Indeed, having described and illustrated various examples herein, it should be apparent that other examples may be modified in arrangement and detail is omitted.

[0069] For example, a color sensor capable of identifying a plurality of colors used in the imaging process may be used as the toner density sensor. In this case, for example, the toner images of magenta, yellow, and cyan may be formed in an overlapping state (or layered). A sample data can be acquired for each color from the toner image in which the color toners are layered, to analyze the target member corresponding to each color.

[0070] In other examples, the rotation frequencies of the four developing units corresponding to the color toners may be adjusted to be different from one another. In this case, the peak frequencies corresponding to respective developing units can be different from each other. Accordingly, even when the four color toner images are formed so as to overlap each other, peaks corresponding to the respective colors can be identified in the acquired frequency spectrum.

[0071] In the above-described imaging systems, the sampling frequency fs is set to 100 Hz in advance. In this case, a maximum value fm of the frequency of the frequency spectrum obtained by the FFT is 50 Hz which is a half of the sampling frequency fs. Namely, when the sampling frequency fs is 100 Hz, the rotation frequency of the rotation target member may not exceed 50 Hz. Since the rotation frequency of each member illustrated in FIG. 4 is 50 Hz or less, the rotation frequency does not exceed the maximum value fm of the frequency. When a member having a rotation frequency of 50 Hz or more is selected as the target member, the sampling frequency fs may be set to be greater than 100 Hz. As an example, FIG. 10 is a table showing a relationship of the number N of samples, the frequency resolution Af, the detection time T, and the length L of the toner image when the sampling frequency fs is 200 Hz. As shown in FIG. 10, when the sampling frequency fs is 200 Hz, the number N of samples is twice as much, as compared with a case in which the sampling frequency fs is 100 Hz (for example, as compared with the case of FIG. 6). Since the maximum value fm of the frequency subjected to the FFT is 100 Hz when the sampling frequency fs is set to 200 Hz, a member having a greater rotation frequency can be an analysis target as compared with a case in which the sampling frequency fs is 100 Hz. The example imaging system may include a plurality of look-up tables corresponding to the plurality of sampling frequencies fs. Further, the sampling frequency fs may be automatically selected so that a relationship of fm > fr is established when the greatest rotation frequency among the rotation frequencies of the plurality of target members is set to fr, in order to select the sampling frequency fs having a sufficient height. Accordingly, an optimal or suitable sampling frequency fs may be selected, to reduce a calculation load in the FFT. [0072] As a further example, immediately after a rotation member RM (or a part thereof) is replaced with a new one, there is a lower possibility that the replaced rotation member RM have a defect. Consequently, the user may be prompted to select a member other than the replaced rotation member as the target member. In this case, there is a likelihood that a frequency spectrum does not appear in the rotation frequency of the non-selected rotation member. Accordingly, the length of the toner image E for analysis may be determined based on a difference between the rotation frequencies of the selected target members. Accordingly, the length of the toner image E for analysis may be determined without considering the rotation frequency of the non-selected rotation member, which may decrease the length of the toner image as the minimum difference between the rotation frequencies increases.

[0073] In addition, although an example in which the frequency analysis is performed using the FFT has been described, the frequency analysis is not limited to the FFT and the frequency analysis may be performed using another Fourier transform.

[0074] In addition, although the rotation frequency has been exemplified as the rotation characteristic of the rotation member, the rotation characteristic may be a rotation cycle that is a time for the member to make a complete rotation, a rotation angular velocity that is an angle at which the member rotates in a unit time, or the like.

Claims

1. An imaging system comprising: an imaging apparatus to form a toner image to be analyzed, wherein the imaging apparatus includes a plurality of rotation members, wherein the plurality of rotation members includes a conveyance member to convey the toner image in a conveyance direction; and a controller to: receive a selection of a target member among the plurality of rotation members, determine a length, in the conveyance direction, of the toner image to be formed based on the target member selected, and output length information to the imaging apparatus to control the imaging apparatus to form the toner image according to the length determined.

2. The imaging system according to claim 1 , the controller to receive the selection of a plurality of target members including the target member, and to determine the length of the toner image in response to the selection received.

3. The imaging system according to claim 2, wherein the plurality of rotation members includes a common member that is associated with a plurality of colors to form respective toner-image components of the toner image and color-specific members that are each associated with one color among the plurality of colors, and wherein the common member has a circumferential length in a rotational direction of the common member, the controller to determine the length of the toner image when the common member is included in the selection of the plurality of target members, so that a sum of the lengths of the toner-image components corresponding to any two or more of the plurality of colors, is no less than the circumferential length of the common member.

4. The imaging system according to claim 1 , wherein each of the plurality of rotation members is associated with a rotation characteristic, the controller to receive a selection of a plurality of target members including the selection of the target member, and to determine the length of the toner image based on the rotation characteristic that is associated with at least one target member among the plurality of target members selected.

5. The imaging system according to claim 4, wherein the rotation characteristic includes any one of a rotation frequency, a rotation cycle, and a rotation angular velocity.

6. The imaging system according to claim 4, wherein the rotation characteristic includes a rotation frequency, the controller to determine the length of the toner image based on a minimum difference among a plurality of frequency differences obtained between the rotation frequency of each target member among the selection of the plurality of target members, and the rotation frequency of each of the plurality of rotation members.

7. The imaging system according to claim 6, the controller to adjust a rotation frequency of one of the plurality of rotation members to an adjusted rotation frequency, so that the minimum difference between the rotation frequencies increases.

8. The imaging system according to claim 7, the controller to output the adjusted rotation frequency of the rotation member with the length information of the toner image.

9. The imaging system according to claim 1 , comprising a user interface to receive a user input associated with the selection of the target member.

10. The imaging system according to claim 9, wherein the user interface displays a plurality of identifiers respectively associated with the plurality of rotation members selectable by a user.

11. The imaging system according to claim 4, wherein the rotation characteristic includes a rotation frequency, the controller to receive a selection of the plurality of target members and to determine the length of the toner image based on a difference between rotation frequencies of the selected target members.

12. The imaging system according to claim 1 , comprising: a sensor to detect a density of the toner image conveyed in the conveyance direction, the controller to acquire data of the density detected by the sensor and to analyze a state of the selected target member based on the data of the density.

13. The imaging system according to claim 12, the controller to analyze the state of the selected target member based on data obtained by performing a Fourier transform on the data of the density.

14. A non-transitory computer-readable recording medium for an imaging apparatus including a plurality of rotation members, the recording medium comprising data and instructions to receive a selection of a target member among the plurality of rotation members of the imaging apparatus, to determine a length of a toner image to be formed by the imaging apparatus, in response to the received selection of the target member, and to output length information to the imaging apparatus in order to control the imaging apparatus to form the toner image according to the length determined.

15. The recording medium according to claim 14, the data and instructions to determine the length of the toner image based on a look-up table.