JPH07148934A - Maintenance method of ink-jet print head - Google Patents

Abstract

PURPOSE: To prevent the generation of clogging after a long-time non-use state by providing a step for detecting the elapse of a predetermined period after an ink jet printing head is used finally and a step for preparing the ink jet printing head after the elapse of the predetermined period is detected. CONSTITUTION: When the printing head already ejects ink, a timer is set to zero (58, 60). When the printing head is capped, the timer is reset from zero (60, 61). It is judged whether the elapse time after the timer is finally set exceeds a first predetermined period T1 and, if the elapse time exceeds, a low power mode excepting the unnecessary power of a fan, a heater or the like is confirmed (64). Next, it is judged whether the elapse time after the timer is reset exceeds a predetermined period T2 (62, 64) and, if exceeds, a command is issued to a carriage motor to move the printing head to a proper preparation station and ink is ejected to a spittoon or the printing head is wipen by a wiper (67).

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to ink jet printing systems. More particularly, the present invention relates to methods and apparatus for servicing inkjet printheads or nozzles after a predetermined period of inactivity.

[0002]

Inkjet printing systems typically operate by ejecting ink from a plurality of small, closely spaced nozzles located on a printhead. Inkjet printheads must be serviced regularly to function properly.

During printing, floating ink droplets can accumulate on the nozzle plate around the nozzles and interfere with the trajectory of the ejected ink droplets to affect print quality. To minimize this, the inkjet printhead can be serviced by occasionally wiping the nozzle plate to remove accumulated ink.

During periods of inactivity, the ink in the nozzle may dry or harden and clog the nozzle. Therefore, it is possible to delay the occurrence of clogging by attaching a cap to the inkjet print head to keep the periphery of the nozzle in an appropriate state. This capping can be done automatically after a short period of inactivity, even in the middle of printing a page when the printer is waiting for more data to print. “Spitting” the inkjet print head to a “spittoon” to minimize nozzle clogging
That is, the ink jet print head can be maintained by ejecting the ink from the nozzle and forcibly discharging the clogging of the hardened ink. A spittoon is usually a container provided with an absorbent material that holds the ejected ink while it dries. Preferably, spitting occurs before the nozzle is clogged. Maintenance can be accomplished by spitting out the wiper and then wiping the nozzle plate with this wet wiper to combine spitting and wiping. The wet wiper serves to melt and remove the dried ink that has accumulated on or in the nozzle plate.

The occurrence of various events has been used to initiate the maintenance of inkjet printheads. Such events can be broadly divided into three groups. (1) When the printer is turned on or off,
(2) Immediately before the print job, and (3) in the middle of the print job.

When the inkjet printer is turned on, the printhead can be serviced as part of the printer initialization procedure. This initialization procedure requires the printer to be "reset" after it has been turned on for some time.
It can also be done by sending a command or signal. Some printers that have a "soft" power switch receive a "off" command to service the printhead in case of a potentially unused state. "Soft" power switching is the actuation or deactivation of most of the circuitry, motors, etc. in the printer with the power supply continuously connected to the mains. This allows some devices, such as clocks and timers, to remain active when other functions are down.

Some printers service inkjet printheads upon receipt of a print job after a period of non-use. In the case of a certain printer, a timer determines the time the print head has been capped, and if this elapsed time is less than one hour, spit each nozzle a certain number of times, and if more than one hour, Repeat the above spitting. When the maintenance is complete, the printer executes the print job.

Some printers count the number of ink drops ejected since the printhead was last serviced. When the count value exceeds a predetermined amount, the printer cleans the nozzle plate by wiping the nozzle plate.

All of the above-mentioned events that initiate servicing occur during normal use of the printer. No one starts servicing the printhead after a long period of inactivity unless an additional command is sent. Unfortunately, nozzles in inkjet printheads can also become clogged when the printhead is capped. What is needed is a method and apparatus that allows an inkjet printhead to be serviced during periods of non-use.

[0010]

SUMMARY OF THE INVENTION It is a primary object of the present invention to provide a method and apparatus for preventing nozzle clogging of ink jet print heads from occurring after extended periods of non-use. Another object of the present invention is to provide a method and apparatus for servicing an inkjet printhead after a period of inactivity.

[0011]

SUMMARY OF THE INVENTION The present invention detects the time elapsed since the print head was last used. If the elapsed time exceeds a predetermined time, the inkjet print head is serviced. Since maintenance of the printhead involves ejection of ink, it may be that the last use was maintenance, during a long period of non-use.

The apparatus according to the present invention starts maintenance of the ink jet print head according to a timer, a circuit for resetting the timer according to the usage state of the ink jet print head, and a predetermined time after the timer is last reset. It has a circuit to do.

The circuit for resetting the timer can reset the timer in response to the printhead being capped, ejecting ink, or one or more nozzles of the printhead ejecting ink. The principles of the present invention can be applied to printing systems having more than one printhead, including multicolor printing systems.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a printing apparatus capable of carrying out the present invention is a timer 12 and an ink jet print head 1.
8 and print head maintenance equipment such as spitoons and wipers 22. A central processing unit (CPU) 14 controls the operation of this printing device.

The inkjet printhead 18 has nozzles 19 and is mounted in a carriage (not shown) that moves across the page. Carriage motor 16
Is for moving this carriage and is controlled by the CPU 14. In addition to traversing the page, the inkjet print head 18 moves to the capping station 24 during non-use times to delay the occurrence of nozzle 19 blockages due to ink curing in the nozzles.

During maintenance, the ink jet print head 18 can be moved to the wiper 22 to wipe off the accumulated ink from the nozzle plate. The inkjet print head 18 can also be moved to the spittoon 20. This is the nozzle 19 during maintenance of the print head 18.
It is a device that collects the ink ejected from. The spittoon holds the ejected ink while it dries or cures to prevent the ink from hitting the printing mechanism.

The timer 12 can be read and reset by the CPU 14. The timer 12 can be a conventional hardware timer or a memory register that is periodically updated by the CPU 14 to indicate the passage of time. The control panel 17 allows the user to control the operation of the printing device, such as ejecting paper, changing fonts, initiating maintenance of the inkjet printhead 18, and the like. The control panel 17 may also include a lamp or other status display device (not shown) for displaying the current status of the printer.

FIG. 2 shows a flow chart of an embodiment of the present invention. As shown in block 50, the timer 12 is initialized. That is, the timer is reset to zero and started. When the printing device receives data, as detected at decision block 52, the printer determines that it is in standard power mode (block 54) and processes this data (block 56). The method is performed from block 58 after decision block 52 or block 56.

If the printhead is already ejecting ink, the timer is reset to zero as shown in blocks 58 and 59. This execution process continues at block 60.
Also, when the printhead is capped, the timer is reset to zero as shown in blocks 60 and 61. This execution process continues at block 62.

At block 62, the timer 12 is checked to determine if the time elapsed since the timer was last reset exceeds the first predetermined time period T1. If so, the printer verifies that it is in low power mode, as shown in block 64. Removing power from circuits in the printer not required for the functionality of the present invention, such as fans, heaters, or other similar environmental control elements in the paper path (not shown), lamps in carriage motor 16 and control panel 17. Therefore, the low power mode is preferable.

After decision block 62 (and block 64 depending on the result of block 62), timer 12 is checked, as shown in decision block 66, and the time elapsed since the timer was last reset is determined by a second predetermined value. It is determined whether the period T2 is exceeded. If so, CPU 14 commands carriage motor 16 to move inkjet printhead 18 to the appropriate service station. As mentioned in the description of the prior art, the printhead is spit on the spittoon 20 or wiped by a wiper 22. Or both are done. It is also possible to issue a command from the CPU 14 to the print head 18 to cause the wiper 22 to eject ink, and then wipe the print head with the wiper so that the wiper can be wiped with a wet wiper.

Other maintenance methods are possible, depending on the combination of printhead and ink preparation. Evaporation of the ink component from the tip of the nozzle causes the ink to chemically and physically change gradually from the tip toward the ink reservoir. This can be solved by warming the ink to make it less viscous, and stimulating convection to homogenize the ink,
This can delay clogging. In thermal inkjet printheads, such warming can be simply accomplished by supplying the bubble-forming resistor with a power level that is lower than the power level causing ink ejection. This maintenance procedure is called "pulse warming".

After the print head has been serviced at block 67,
The timer is reset at block 68 and the main loop continues. The period T2 is preferably chosen short to prevent clogging of the nozzle 19. Therefore, if clogging may occur after 4 weeks of non-use, the period T2
2 weeks is appropriate.

The timer is reset at two different events: block 59 and block 61 as a result of ink ejection by the nozzle and capping of the printhead. However, the printhead is preferably capped after a short period of non-use. Therefore, when the period T2 is relatively long, the elapsed time after the ink is ejected from the nozzle and the elapsed time from the capping of the print head are almost the same.
Therefore, the timer does not have to be reset for both of these events. Depending on the implementation of timer 12,
Either event will be the better trigger event.

The present invention can also be applied to printheads that experience premature ink clogging when used with inks of some formulation. If nozzle clogging can occur after a very short period of inactivity,
The timer period T2 must be correspondingly short.

In FIG. 3, a separate timer is used for each nozzle on printhead 18 in one embodiment of the invention. Also, there is no low power mode in this aspect.
Although the low power mode has advantages, the present invention does not necessarily require it. In addition, the method shown in FIG. 2 eliminates blocks 52, 54, 56, 62 and 64 and blocks 50.
Can be modified to eliminate the low power mode by following the direct decision block 58 followed by the block 60 followed by the direct decision block 66.

As shown in block 70, all timers are reset to zero and started. If the nozzle ejects ink (determined at block 72), the timer corresponding to that nozzle is reset to zero at block 76. When ink is ejected from a plurality of nozzles at the same time, a plurality of corresponding timers are reset to zero.

After blocks 72 and 80, as shown in block 86, the respective timers have a predetermined time T3.
Compared to. If the timer value is above T3, the printhead is serviced at block 88. In order to save ink, ejection is done only at the nozzles corresponding to timers above T3. Alternatively, the ejection may be performed from all the nozzles. Next, the timer corresponding to the serviced nozzle is reset at block 90. After block 86 or block 90,
Control returns to decision block 72. In this way, nozzles that have not ejected ink for a predetermined period of time are serviced even when the print head is printing.

Although the embodiments of the present invention have been described in detail above, the respective embodiments of the present invention will be listed below.

Example 1 A method of servicing an inkjet printhead having nozzles for ejecting ink in an inkjet printing system, which comprises (a) detecting the passage of a predetermined period from the last use of the printhead. And (b) servicing the inkjet printhead after detecting elapse of the predetermined period of time since the printhead was last used.

Example 2 The method of Example 1 wherein the detecting step comprises detecting the passage of a predetermined period of time since the inkjet printhead was last capped.

Third Embodiment The method according to the first embodiment, wherein the detecting step includes detecting a lapse of a predetermined period of time since the ink jet print head last ejected ink.

Fourth Embodiment The method according to the first embodiment, wherein the detecting step includes detecting a lapse of a predetermined period since the nozzle of the ink jet print head last ejected ink.

Fifth Embodiment The method according to the first embodiment, wherein the detecting step includes detecting the passage of a predetermined period of time since the print head was last serviced.

EXAMPLE 6 The method of Example 1 wherein said servicing step comprises causing said printhead to expel ink.

EXAMPLE 7 The method of Example 1 wherein the servicing step includes pulse warming the ink.

[Embodiment 8] In an inkjet printing system having at least one print head and means for servicing the print head, (a) a timer, (b) resetting the timer according to the usage status of the inkjet print head. And (c) means for starting maintenance of the inkjet print head in response to a timer indication indicating that at least a predetermined time has elapsed since the timer was last reset.

[Embodiment 9] An improvement according to Embodiment 8 wherein the reset means resets the timer in response to the print head being capped.

[Embodiment 10] An improvement described in Embodiment 8 in which the reset means resets the timer in response to the print head ejecting ink.

[Embodiment 11] An improvement according to embodiment 8 wherein the reset means resets the timer in response to maintenance of the print head.

[0030]

As described above, by using the present invention, it is possible to prevent the nozzles of the ink jet print head from being clogged after being unused for a long time.

[Brief description of drawings]

FIG. 1 is a block diagram of a printing device capable of performing the method of the present invention.

2 is a flow diagram of one aspect of the present invention implemented by the apparatus of FIG.

FIG. 3 is a flow chart of one embodiment of the present invention capable of timing the unused state of each nozzle.

[Explanation of symbols]

12: Timer 14: Central processing unit (CPU) 16: Carriage motor 17: Control panel 18: Inkjet print head 19: Nozzle 20: Spitoun 22: Wiper 24: Capping station 50, 52, 54, 56, 58, 59, 60 , 61, 62, 64, 66, 67, 6
8, 70, 72, 76, 80, 86, 88, 90: Block T1, T2, T3: Period

Claims (1)

[Claims] 1. A method comprising: detecting a lapse of a predetermined period of time since the inkjet print head was last used; and servicing the inkjet print head after detecting the lapse of the predetermined period of time. Method of servicing an inkjet print head.