Image forming apparatus, inkjet head unit, and head control device

Abstract

To provide an image forming apparatus, an inkjet head unit, and a head control device capable of suppressing the degradation of piezoelectric elements in actuators of specific channels. [Solution] According to the embodiment, the image forming apparatus comprises an inkjet head unit and a control means. The inkjet head unit has an effective pixel channel including actuators for a specified number of pixels for ink ejection operation, and a spare channel including one or more actuators located at at least one end of the effective pixel channel. The control means switches the range of actuators to be used for image formation from among all actuators in the effective pixel channel and the spare channel each time that an image is formed on a specified number of media by the inkjet head unit.

Description

Technical Field

[0001] Embodiments of the present invention relate to an image forming apparatus, an inkjet head unit, and a head control device.

Background Art

[0002] Generally, an inkjet head unit of an inkjet printer has a plurality of channels for ejecting ink. Each channel includes a nozzle for ejecting ink, a pressure chamber communicating with the nozzle, and an actuator for changing the volume of the pressure chamber. The inkjet head unit further includes a head drive circuit that selects a channel for ejecting ink from among the plurality of channels and applies a drive waveform to the actuator to drive it. When the actuator is driven, the volume of the pressure chamber filled with ink changes, and ink is ejected from the nozzle.

[0003] The actuator of the inkjet head unit uses a piezoelectric element. The piezoelectric element expands and contracts in response to an input waveform in order to eject ink. That is, the piezoelectric element repeats mechanical operations of expansion and contraction. Therefore, due to long-term use, the piezoelectric element itself may become fatigued and deteriorate.

[0004] Therefore, Patent Document 1 proposes generating a drive waveform composed of a curve waveform without sharp edges. By eliminating sharp edges from the drive waveform in this way, the mechanical operation of the piezoelectric element is softened, and deterioration of the piezoelectric element is suppressed.

[0005] Also, Patent Document 2 proposes a duty ratio of the voltage application time within one cycle of pulse voltage driving that can drive the piezoelectric element without suppressing its deterioration.

[0006] The conventional methods disclosed in Patent Documents 1 and 2 are methods that have an equal effect on all channels of the piezoelectric element. On the other hand, one use case for inkjet printers is to print a large number of the same print image. In such use cases, depending on the image, the piezoelectric element of a particular channel may be driven more frequently, concentrating the load and causing the piezoelectric element to deteriorate and shorten its lifespan. Therefore, conventional methods such as those disclosed in Patent Documents 1 and 2 cannot suppress the deterioration of the piezoelectric element when the load on a particular channel becomes high. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2004-122744 [Patent Document 2] Japanese Patent Application Publication No. 07-066464 [Overview of the project] [Problems that the invention aims to solve]

[0008] The problem that the embodiments of the present invention aim to solve is to provide an image forming apparatus, an inkjet head unit, and a head control device that can suppress the degradation of the piezoelectric element of an actuator in a specific channel. [Means for solving the problem]

[0009] According to one embodiment, the image forming apparatus comprises an inkjet head unit and a control means. The inkjet head unit has an effective pixel channel containing actuators for a predetermined number of pixels for ink ejection, and a spare channel containing one or more actuators located at least one end of the effective pixel channel. The control means switches the range of actuators used for image formation from among all actuators in the effective pixel channel and the spare channel each time that an image is formed on a predetermined number of sheets of media by the inkjet head unit. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a block diagram showing the configuration of an inkjet printer as an image forming apparatus according to the first embodiment. [Figure 2] Figure 2 shows the data format of a data signal containing print data for one line, which is input to the inkjet head unit according to the first embodiment. [Figure 3] Figure 3 is a schematic diagram showing an example of the arrangement of actuators in an inkjet head unit. [Figure 4] Figure 4 is a schematic diagram showing another example of the actuator arrangement in an inkjet head unit. [Figure 5] Figure 5 is a block diagram showing an example of the circuit configuration of the head drive circuit included in an inkjet head unit. [Figure 6] Figure 6 is a schematic diagram showing an example of the contents held in the setting data register included in the head drive circuit. [Figure 7] Figure 7 shows an example of the configuration of the print data registers included in the head drive circuit. [Figure 8] Figure 8 is a schematic diagram showing an example of the shift of printable pixel data stored in the print data register. [Figure 9] Figure 9 is a schematic diagram showing another example of the shift of print-effective pixel data stored in the print data register. [Figure 10] Figure 10 is a block diagram showing the configuration of an inkjet printer as an image forming apparatus according to the second embodiment. [Figure 11] Figure 11 is a block diagram showing an example of the circuit configuration of the head drive circuit included in the inkjet head unit in the second embodiment. [Figure 12] Figure 12 is a flowchart showing an example of the printing process in an image forming apparatus. [Figure 13]FIG. 13 is a diagram showing the data format of a data signal including print data for one line output to the inkjet head unit when the shift amount is "0". [Figure 14] FIG. 14 is a diagram showing the data format of a data signal including print data for one line output to the inkjet head unit when the shift amount is "2" and the shift direction is "right". [Figure 15] FIG. 15 is a diagram showing the data format of a data signal including print data for one line output to the inkjet head unit when the shift amount is "2" and the shift direction is "left". [Figure 16] FIG. 16 is a flowchart showing an example of the printing process in an inkjet printer as an image forming apparatus according to the third embodiment.

Embodiments for Carrying Out the Invention

[0011] Hereinafter, an image forming apparatus according to an embodiment will be described in detail with reference to the accompanying drawings. In each figure, the same components are denoted by the same reference numerals.

[0012] [First Embodiment] FIG. 1 is a block diagram showing the configuration of an inkjet printer 1 as an image forming apparatus according to the first embodiment. The inkjet printer 1 forms an image on a printing medium while conveying the printing medium which is a recording medium.

[0013] As shown in FIG. 1, the inkjet printer 1 includes a processor 11, a ROM (Read Only Memory) 12, a RAM (Random Access Memory) 13, a page memory 14, an operation panel 15, a communication interface 16, a conveyance motor 17, a motor drive circuit 18, a pump 19, a pump drive circuit 20, and an inkjet head unit 21 according to the first embodiment. Further, the inkjet printer 1 has bus lines 22 such as an address bus and a data bus. The processor 11, ROM 12, RAM 13, page memory 14, operation panel 15, communication interface 16, motor drive circuit 18, pump drive circuit 20, and head drive circuit 23 are connected directly or via an input / output circuit to the bus line 22 and can transmit and receive data to and from each other. Furthermore, the inkjet printer 1 includes a conveyance mechanism, a paper feed cassette, a paper discharge tray, a power supply, etc. not shown in the drawings. In the drawings, the interface is abbreviated as "IF".

[0014] The processor 11 corresponds to the central part of the computer. The processor 11 controls each part in order to realize various functions as the inkjet printer 1 according to an operating system and an application program. The processor 11 is, for example, a CPU (Central Processing Unit).

[0015] The ROM 12 corresponds to the read-only main memory part of the computer. The ROM 12 stores the above-mentioned operating system and application program. The ROM 12 may also store data necessary for the processor 11 to execute processes for controlling each part.

[0016] The RAM 13 corresponds to the rewritable main memory part of the computer. The RAM 13 stores data necessary for the processor 11 to execute processes. Also, the RAM 13 is used as a work area where information is appropriately rewritten by the processor 11.

[0017] The page memory 14 is an image memory in which print data is expanded as print data for each page. The page memory 14 can store print data for multiple pages.

[0018] The control panel 15 has a display unit and an operation unit. The display unit is, for example, a display device such as a liquid crystal display. The display unit displays images indicating various states of the inkjet printer 1 in response to video signals input from the processor 11 or a graphics controller (not shown) for image processing. The operation unit generates operation signals based on user operations. The operation unit includes, for example, a touch sensor, a numeric keypad, a power key, a paper feed key, an error release key, and various function keys, or a keyboard. The touch sensor is, for example, a resistive touch sensor or a capacitive touch sensor. The touch sensor acquires information indicating a specified position within a certain area. Alternatively, the touch sensor may be arranged on the top surface of the display unit and used as an integrated touch panel. In this case, the touch sensor generates a signal indicating the touched position on the screen displayed on the display unit.

[0019] The communication interface 16 is an interface for communicating with external devices. In this embodiment, the communication interface 16 is used, for example, for communication between a host PC 2 that sends various setting values ​​to the inkjet printer 1 and at least one client terminal 3 that sends print data to the inkjet printer 1. The communication interface 16 communicates with the host PC 2 and the client terminals 3 via a wired or wireless network 4, such as a LAN (Local Area Network). One of the client terminals 3 may function as the host PC 2. Conversely, the host PC 2 may function as a client terminal 3 and send print data to the inkjet printer 1. Furthermore, the communication interface 16 sends an error notification signal from the processor 11 to the host PC 2 when an error occurs in the inkjet printer 1.

[0020] The transport motor 17 rotates to drive a transport mechanism (not shown) for transporting printing media such as printing paper. The transport mechanism consists of a transport belt for transporting the printing media, a plurality of rollers (drive rollers and driven rollers) on which the transport belt is stretched, guides, etc. The transport motor 17 rotates the drive rollers to move the transport belt. The printing media moves along a transport path defined by guides placed near the transport belt.

[0021] The motor drive circuit 18 drives the transport motor 17 according to the transport control signal input from the processor 11. The motor drive circuit 18, the transport motor 17, and the transport mechanism transport the printing medium taken out of the paper feed cassette (not shown) to the output tray (not shown) via the inkjet head unit 21. The paper feed cassette is a cassette that contains multiple printing media. The output tray is a tray that contains the printing media discharged from the inkjet printer 1.

[0022] Pump 19 supplies ink from an ink tank (not shown) to the inkjet head unit 21.

[0023] The pump drive circuit 20 drives the pump 19 according to the ink supply control signal input from the processor 11.

[0024] The inkjet head unit 21 ejects ink onto the printing medium to form an image. As shown in Figure 1, the inkjet head unit 21 includes a head drive circuit 23 and an actuator unit 24.

[0025] The actuator unit 24 has multiple actuators. Each actuator is a driving element that expands and contracts the pressure chamber containing the ink and ejects ink droplets from a nozzle communicating with the pressure chamber. For example, each actuator uses a piezoelectric element made of PZT (lead zirconate titanate). Each actuator of the actuator unit 24 operates according to the drive waveform supplied from the head drive circuit 23 to expand and contract the pressure chamber and eject ink droplets from the nozzle.

[0026] The head drive circuit 23 is a circuit that generates drive waveforms for the actuator unit 24. The head drive circuit 23 receives print data transmitted from the page memory 14 one line at a time, and generates drive waveforms for each actuator of the actuator unit 24 based on this print data. Driven by these drive waveforms, the actuators eject ink droplets from the corresponding nozzles. As a result, the inkjet head unit 21 ejects ink onto the printing medium transported by the transport mechanism, printing images and other data onto the printing medium.

[0027] The print data stored in the page memory 14 is transmitted to the inkjet head unit 21 based on the synchronization signal of the transport mechanism. Specifically, a data signal containing print data and setting data for one line is transmitted at intervals of once per line. Figure 2 shows the data format of the data signal containing print data for one line transmitted to the inkjet head unit 21. In the drawing, channels are abbreviated as "ch". One channel corresponds to one pixel to be printed. The data signal includes an 8-bit start byte, followed by 8 bits of setting data and other commands, 320 bits of print data for one line of channel to be printed by the actuator unit 24 (hereinafter referred to as "print-enabled channel data"), and 8 bits of NOP (Not Operation).

[0028] Although Figure 1 shows only one inkjet head unit 21, the inkjet printer 1 can be equipped with multiple inkjet head units 21, each corresponding to a different ink color, such as cyan, magenta, yellow, and black.

[0029] Next, the configuration of the actuator section 24 of the inkjet head unit 21 according to this embodiment will be described. Figure 3 is a schematic diagram showing an example of the arrangement of actuators 25 in the actuator section 24. As shown in Figure 3, the actuator section 24 can be configured by arranging a total of 328 channels of actuators 25 in a single line. Of these 328 channels, 320 channels from channel 5 to channel 324 are effective pixel channels 26 corresponding to 320 bits of print-effective channel data (hereinafter referred to as "print-effective pixel data"). In the actuator section of a typical inkjet head unit, the number of actuators corresponds to the number of bits in the print-effective channel.

[0030] In contrast, the actuator unit 24 in this embodiment has four actuators 25 each positioned as spare channels 27 at both ends of the actuator 25 of the effective pixel channel 26. Specifically, channels 1 to 4 of the spare channel 27 are positioned before channels 5 to 324 of the effective pixel channel 26 (on the right in the figure), and channels 324 to 328 of the spare channel 27 are positioned after channels 5 to 324 of the effective pixel channel 26 (on the left in the figure). In this embodiment, these spare channels 27 are used to shift the driven channels, thereby distributing the load and controlling the system so that the piezoelectric elements of a particular channel are not driven excessively.

[0031] It should be noted that this embodiment is an example where the data length of the print data for one line is 320 bits, and it goes without saying that the number of channels in the effective pixel channel 26 will vary depending on the data length of the print data for one line. Furthermore, the number of channels in the spare channel 27 is not limited to four. Moreover, the spare channel 27 does not necessarily have to be provided at both ends of the effective pixel channel 26, but may be provided at least at one end.

[0032] Furthermore, the arrangement of the actuators 25 in the actuator unit 24 is not necessarily limited to a single row, as shown in Figure 3. Figure 4 is a schematic diagram showing an example of the arrangement of actuators 25 in the actuator unit 24. As shown in Figure 4, the actuator unit 24 may have actuators 25 arranged in multiple rows.

[0033] Next, the head drive circuit 23 will be described with reference to Figure 5. Figure 5 is a block diagram showing an example of the circuit configuration of the head drive circuit 23 provided in the inkjet head unit 21.

[0034] The head drive circuit 23 includes an I / O section 28, a logic section 29, and an analog section 30.

[0035] The I / O unit 28 includes a comparator 31 and a serial-to-parallel conversion unit 32. In the drawings, the "serial-to-parallel conversion unit" is abbreviated as "conversion unit".

[0036] The comparator 31 receives the clock signal CLK for Low Voltage Differential Signaling (LVDS) and the data signal DI as shown in Figure 2. The comparator 31 outputs the data of the clock signal CLK and the data of the data signal DI to the serial-to-parallel converter 32.

[0037] The serial-to-parallel conversion unit 32 converts the serial data input from the comparator 31 into parallel data. It acquires the data of the data signal DI at the rising edge of the clock signal CLK. More specifically, it acquires the value (0 or 1) of the data contained in the data signal DI at the timing when the clock signal CLK changes from 0 to 1. The serial-to-parallel conversion unit 32 outputs the data of the parallel data signal DI to the logic unit 29. The serial-to-parallel conversion unit 32 also outputs the data of the clock signal CLK to the logic unit 29 and the analog unit 30.

[0038] The logic unit 29 includes a start byte / command recognition unit 33, a setting data register 34, a print data register 35, and a waveform pattern generation unit 36.

[0039] The start byte / command recognition unit 33 recognizes the start byte from the parallel data signal DI input from the serial-to-parallel conversion unit 32 and determines whether to input one line of print data. The start byte / command recognition unit 33 then separates the command and print data following the start byte and recognizes the command content. If the command is an instruction to rewrite setting data, the start byte / command recognition unit 33 outputs the setting data instructed by the command to the setting data register 34. The start byte / command recognition unit 33 also outputs the print data to the print data register 35. At this time, the start byte / command recognition unit 33 adjusts the storage position of the printable pixel data based on the setting data held in the setting data register 34, as described later, and outputs it to the print data register 35.

[0040] Furthermore, the start byte / command recognition unit 33 may also have a counter 37. If the recognized command content is a count-up instruction given when printing the final line on a single print medium, the start byte / command recognition unit 33 increments the counter 37. That is, the counter 37 counts the number of printed sheets, i.e., the number of pages.

[0041] The setting data register 34 holds the setting data input from the start byte / command recognition unit 33. Figure 6 is a schematic diagram showing an example of the contents held in the setting data register 34. As shown in Figure 6, the setting data register 34 stores, for example, the shift amount, the shift direction, and the number of pages to switch. The shift amount is an integer value indicating the number of spare channels 27 used. This shift amount may include "0", i.e., no shift. The maximum value of the shift amount is the number of channels in the spare channels 27, which in this embodiment is "4". The shift direction indicates which of the spare channels 27 at both ends of the effective pixel channel 26 is used. If the spare channels 27 exist at only one end of the effective pixel channel 26, this shift direction is a fixed value. The number of pages to switch indicates the number of print pages for which the switching of the spare channels 27 to be used is performed, and is an integer value of "1" or more.

[0042] The shift amount, shift direction, and number of pages to switch, held in the setting data register 34, are updated by the setting values ​​output from the start byte / command recognition unit 33 in response to the command included in the data signal DI. For example, the processor 11 sets a command to update the setting value in response to a rewrite command to an arbitrary value transmitted from the host PC 2 at any time, or instructed by the operation of the operation panel 15 at any time. In other words, the administrator managing the inkjet printer 1 can manually set the shift amount, shift direction, and number of pages to switch using the host PC 2 or the operation panel 15. In this case, the shift amount, shift direction, and number of pages to switch may all be updated at once, or only one of the setting values ​​may be updated. Furthermore, it is not necessarily required that the shift amount, shift direction, and number of pages to switch all be updatable. That is, any one of the shift amount, shift direction, or number of pages to switch may be set as a fixed value. Furthermore, the shift direction can be set to an initial value by a command, and the start byte / command recognition unit 33 can update it alternately each time it recognizes that the number of pages set in the switching page count has been printed. In addition, the shift amount, shift direction, and switching page count may be set randomly by the start byte / command recognition unit 33 each time the switching page count is printed. In this case, the shift amount and switching page count are set randomly within a predetermined range, that is, they do not exceed their respective maximum values.

[0043] The setting data register 34 may either non-volatilely store the set value or volatilely store it. In the latter case, when the inkjet printer 1 is powered on, the processor 11 sets a predetermined setting value as the initial setting.

[0044] The print data register 35 stores the print data input from the start byte / command recognition unit 33. Figure 7 shows an example of the configuration of the print data register 35. The print data register 35 is a register with a number of bits corresponding to the number of channels in the actuator unit 24, and in this embodiment, it is a 328-bit register.

[0045] Figure 8 is a schematic diagram showing an example of a shift in printable effective pixel data stored in the print data register 35. The start byte / command recognition unit 33 determines the bits of the print data register 35 to be used to store the 320 bits of printable effective pixel data, which are the print data included in the data signal DI, based on the shift amount and shift direction held by the setting data register 34. For example, if the shift amount is "0", the start byte / command recognition unit 33 determines that bits 5 to 324 of the print data register 35 corresponding to the effective pixel channel 26 are the bits to store the printable effective pixel data, as shown in the upper part of Figure 8. The start byte / command recognition unit 33 then generates 328 bits of print data by placing the printable effective pixel data in bits 5 to 324 and outputs it to the print data register 35. In this case, the start byte / command recognition unit 33 may add invalid data to the bits in the generated print data that do not store printable pixel data in the print data register 35, in this example, bits 1 to 4 and bits 325 to 328, which will not perform the ink ejection operation.

[0046] Furthermore, for example, if the shift amount is "2" and the shift direction is "right", the start byte / command recognition unit 33 generates 328 bits of print data by placing printable effective pixel data in bits 3 to 322 of the print data register 35, as shown in the lower part of Figure 8, and outputs it to the print data register 35. At this time, the start byte / command recognition unit 33 can add invalid data to bits 1 to 2 and bits 323 to 328 of the print data register 35 in the generated print data where printable effective pixel data is not stored.

[0047] Figure 9 is a schematic diagram showing another example of the shift of print-effective pixel data stored in the print data register 35. For example, if the shift amount is "2" and the shift direction is "left", the start byte / command recognition unit 33 generates 328 bits of print data, with the print-effective pixel data placed in bits 7 to 327 of the print data register 35, as shown in the lower part of Figure 9, and outputs it to the print data register 35. At this time, the start byte / command recognition unit 33 can add invalid data to bits 1 to 6 and bits 327 to 328 of the print data that are not stored in the print data register 35.

[0048] The waveform pattern generation unit 36 ​​acquires print data from the print data register 35 and generates a waveform pattern based on that print data. The waveform pattern generation unit 36 ​​outputs the generated waveform pattern to the analog unit 30.

[0049] The analog section 30 is a drive waveform generation unit that generates a drive waveform based on a waveform pattern. The analog section 30 includes a level shifter 38, a prebuffer 39, and a gate driver 40.

[0050] The level shifter 38 converts the waveform pattern input from the waveform pattern generation unit 36 ​​into a high voltage. The level shifter 38 outputs the waveform pattern converted to a high voltage to the pre-buffer 39.

[0051] The pre-buffer 39 appropriately amplifies and shapes the waveform pattern input from the level shifter 38. The pre-buffer 39 outputs the appropriately amplified and shaped waveform pattern to the gate driver 40.

[0052] The gate driver 40 outputs a drive waveform that drives each actuator 25 of the actuator section 24 of the inkjet head unit 21 by controlling the ON / OFF state of multiple switch elements within the gate driver 40 based on the waveform pattern input from the prebuffer 39. In other words, the gate driver 40 is a drive waveform output unit that outputs a drive waveform based on a waveform pattern. For example, the switch element is a MOSFET, and the gate driver 40 controls the ON / OFF state of the MOSFET by applying a control signal (gate voltage) to the gate of the MOSFET.

[0053] The inkjet printer 1 as an image forming apparatus according to the first embodiment has an inkjet head unit 21 according to the first embodiment, which has an actuator section 24 that includes an effective pixel channel 26 containing 320 actuators 25 for a predetermined number of pixels for ink ejection operation, and a spare channel 27 containing one or more actuators 25 located at at least one end of the effective pixel channel 26. The inkjet head unit 21 has a head drive circuit 23 as a control means that switches the range of actuators 25 used for image formation from all actuators 25 in the effective pixel channel 26 and spare channel 27 each time an image is formed on a predetermined number of print media.

[0054] Therefore, according to the inkjet printer 1 as an image forming apparatus according to the first embodiment, the inkjet head unit 21 according to the first embodiment, which has actuators 25 of spare channels 27 at both ends of the effective pixel channel 26, is controlled to distribute the load by switching the range of actuators 25 used for image formation every predetermined number of prints, i.e., pages, so that the actuator of a particular channel does not continue to be driven. This makes it possible to suppress the deterioration of the piezoelectric element of the actuator of a particular channel, and has the effect of extending the life of the piezoelectric element and, consequently, the inkjet head unit 21.

[0055] Here, the head drive circuit 23 in the inkjet head unit 21 of the first embodiment of the inkjet printer 1, which is an image forming apparatus according to the first embodiment, can input drive waveforms to the actuators 25 of the effective pixel channel 26 and the spare channel 27. The head drive circuit 23 includes a shifting means for shifting printable effective pixel data, which is image forming data indicating the image to be formed, so that the range of the actuators 25 to which the drive waveform is input shifts, and a waveform generation unit that generates a drive waveform according to the print data including the printable effective pixel data shifted by the shifting means. The waveform pattern generation unit 36 ​​and the analog unit 30 are examples of the waveform generation unit.

[0056] Therefore, according to the inkjet printer 1 as an image forming apparatus according to the first embodiment, the load is distributed by shifting the printable effective pixel data, that is, by shifting the drive channel, so that the actuator of a specific channel does not continue to drive, thereby suppressing the deterioration of the piezoelectric element of the actuator of a specific channel.

[0057] While shifting the drive channels can cause a side effect of shifting the main scanning and printing position on the printing medium, a shift of a few channels is usually within the margin of error and does not pose a problem.

[0058] Furthermore, in the inkjet head unit 21 of the inkjet printer 1, which is an image forming apparatus according to the first embodiment, the shift means includes a setting data register 34 as a holding unit that holds at least one of the shift direction and shift amount of the shift of the printable effective pixel data, and a start byte / command recognition unit 33 that shifts the printable effective pixel data according to at least one of the shift direction and shift amount held in the setting data register 34.

[0059] Therefore, according to the inkjet printer 1 as an image forming apparatus according to the first embodiment, the printable effective pixel data can be shifted according to at least one of an arbitrary shift direction and an arbitrary shift amount held in the setting data register 34.

[0060] Here, the inkjet printer 1 as an image forming apparatus according to the first embodiment further includes a processor 11 as a control circuit that inputs printable effective pixel data, which is image forming data indicating the image to be formed, and a command including a setting value for at least one of the shift direction and shift amount, to the head drive circuit 23. The start byte / command recognition unit 33 of the inkjet head unit 21 according to the first embodiment functions as a rewrite unit that receives the setting value included in the command from the processor 11 and rewrites the contents held in the setting data register 34.

[0061] Therefore, according to the inkjet printer 1 as an image forming apparatus according to the first embodiment, the direction of shift and the amount of shift can be set arbitrarily.

[0062] Furthermore, the inkjet head unit 21 according to the first embodiment also holds a switching page number, which is a predetermined number of pages for which the printable effective pixel data is further shifted in the setting data register 34, and the start byte / command recognition unit 33 rewrites this switching page number in accordance with the command from the processor 11.

[0063] Therefore, according to the inkjet printer 1 as an image forming apparatus of the first embodiment, it is possible to shift the drive channel for any number of printed sheets, i.e., every page.

[0064] [Second Embodiment] Figure 10 is a block diagram showing the configuration of an inkjet printer 1 as an image forming apparatus according to the second embodiment. In this embodiment, the inkjet printer 1 includes, in addition to the configuration of the first embodiment, a data / setting value storage memory 41 and a printed page counter 42.

[0065] The data / settings storage memory 41 non-volatilely stores print data from the client terminal 3. That is, even if the inkjet printer 1 is turned off in the middle of printing, it retains the unprinted print data, and when the inkjet printer 1 is turned on again, it is possible to continue printing the unprinted data.

[0066] Furthermore, the data / setting value storage memory 41 stores the shift amount, shift direction, and number of pages to switch, similar to the setting data register 34 of the inkjet head unit 21 in the first embodiment. The data / setting value storage memory 41 stores these shift amount, shift direction, and number of pages to switch non-volatilely. The shift amount, shift direction, and number of pages to switch stored in the data / setting value storage memory 41 may be set manually from the host PC 2 or the operation panel 15, as described in the first embodiment, or they may be pre-set to predetermined values ​​at the time of factory shipment, etc.

[0067] Furthermore, the printed page counter 42 corresponds to the counter 37 of the inkjet head unit 21 in the first embodiment.

[0068] When the processor 11 expands the print data into page memory 14 as print data for each page, it adds invalid data before and after the printable pixel data to prevent ink ejection for the spare channel 27, thereby preparing data for all channels. According to the shift amount and shift direction stored in the data / setting value storage memory 41, the processor 11 adjusts the amount of invalid data before and after the printable pixel data for each page. Then, the processor 11 sends the print data for each page stored in the page memory 14 to the inkjet head unit 21 as data signals DI, one line at a time.

[0069] Figure 11 is a block diagram showing an example of the circuit configuration of the head drive circuit 23 included in the inkjet head unit 21 in the second embodiment. In this embodiment, the head drive circuit 23 has a logic unit 29 which includes a start byte recognition unit 43 instead of the start byte / command recognition unit 33 of the first embodiment. Also, the logic unit 29 does not have a setting data register 34. The start byte recognition unit 43 recognizes the start byte from the data of the parallel format data signal DI input from the serial-to-parallel conversion unit 32, determines the input of one line of print data, and outputs the print data to the print data register 35. The data signal DI includes print data in which the printable pixel data has been shifted. Therefore, the start byte recognition unit 43 separates the print data from the data signal DI and stores it as is in the print data register 35.

[0070] Figure 12 is a flowchart showing an example of printing processing in an inkjet printer 1 as an image forming apparatus according to the second embodiment. The processor 11 can perform this printing processing by executing a program stored in the ROM 12. This printing processing can be started, for example, in response to the acquisition of a print job from a client terminal 3. The print job includes print data such as image data that will be used to form an image on the printing paper. The print data may be data for forming an image on one sheet of printing paper, or data for forming an image on multiple sheets of printing paper. The number of pixels per line in the print data is defined according to the number of channels in the effective pixel channel 26 of the actuator unit 24. Furthermore, the print job may include printing options such as the number of copies to print (number of page sets) and the number of pages per copy as supplementary information. Unless otherwise specified, the processing operation of the processor 11 shown in the flowchart is assumed to transition from ACTn (where n is a natural number) to ACT(n+1). Also, the procedure shown in Figure 12 is just one example. The procedure is not particularly limited as long as similar results can be obtained.

[0071] When a print job is acquired, in ACT11, the processor 11 temporarily stores the print data in the data / settings storage memory 41.

[0072] In ACT12, the processor 11 reads the shift amount, shift direction, and number of pages to be switched from the data / settings storage memory 41 and temporarily stores them in RAM 13.

[0073] In ACT13, the processor 11 creates print data for each line of one page in RAM 13 from the print data stored in the data / settings storage memory 41.

[0074] In ACT14, the processor 11 shifts the print data for each line created in RAM 13 according to the shift amount and shift direction stored in RAM 13.

[0075] In ACT15, the processor 11 adds invalid data for bits that do not have a value set to both ends of the shifted print data for each line created in RAM13.

[0076] In ACT16, the processor 11 saves the print data for each shifted line, each with invalid data added, which was created in RAM 13, to page memory 14.

[0077] In ACT17, the processor 11 outputs the print data for one page stored in the page memory 14 as data signals DI to the inkjet head unit 21, one line at a time.

[0078] Figure 13 shows the data format of the data signal DI, which contains print data for one line output to the inkjet head unit 21 when the shift amount is "0". The print data consists of 328 bits of print-enabled channel data, plus 4 bits of invalid data for channels 1 to 4 and 4 bits of invalid data for channels 325 to 328. All 328 channels of print data are stored in the print data register 35, which drives all actuators 25 of the effective pixel channel 26.

[0079] Figure 14 shows the data format of the data signal containing one line of print data output to the inkjet head unit 21 when the shift amount is "2" and the shift direction is "right". In this case, the 328 bits of print-enabled channel data from channels 3 to 322 are supplemented with 2 bits of invalid data from channels 1 to 2 and 6 bits of invalid data from channels 323 to 328. All of this 328 channels of print data is stored in the print data register 35. That is, the print data with the print-enabled pixel data shifted, as shown in the lower part of Figure 8, is input to and stored in the print data register 35. As a result, the actuators 25 for channels 5 to 322 of the effective pixel channels 26 from channels 5 to 324, and the actuators 25 for channels 3 to 4 of channels 1 to 4 are driven.

[0080] Figure 15 shows the data format of the data signal containing one line of print data output to the inkjet head unit 21 when the shift amount is "2" and the shift direction is "left". In this case, the 328 bits of print-enabled channel data from channels 7 to 327 are supplemented with 6 bits of invalid data from channels 1 to 6 and 2 bits of invalid data from channels 327 to 328. All of this 328 channels of print data is stored in the print data register 35. That is, the print data with the print-enabled pixel data shifted as shown in the lower part of Figure 9 is input to and stored in the print data register 35. As a result, the actuators 25 for channels 7 to 324 and the actuators 25 for channels 325 to 326 of the effective pixel channels 26 from channels 5 to 324 are driven.

[0081] In ACT18 of Figure 12, the processor 11 determines whether it has finished outputting the print data for one page stored in the page memory 14. If there is still print data for lines that have not yet been output, the processor 11 determines NO in ACT18 and returns to the process of ACT17. If it has finished outputting the print data for one page, the processor 11 determines YES in ACT18 and proceeds to the process of ACT19.

[0082] In ACT19, the processor 11 increments the print page counter 42.

[0083] In ACT20, the processor 11 determines whether or not it has printed the number of pages corresponding to the number of switching pages stored in RAM 13. This determination can be made by comparing the number of switching pages stored in RAM 13 with the count value of the printed page counter 42. If the number of switching pages has been printed, the processor 11 determines YES in ACT20 and proceeds to the process of ACT22 described later. If the number of switching pages has not yet been printed, the processor 11 determines NO in ACT20 and proceeds to the process of ACT21.

[0084] In ACT21, the processor 11 determines whether or not to terminate printing. This determination is made by determining whether or not all of the print data stored in the data / settings memory 41 has been printed. If printing is not yet terminated, the processor 11 proceeds to the process of ACT13 described above and prints the next page. If printing is terminated, the processor 11 terminates the printing process shown in this flowchart.

[0085] In ACT22, the processor 11 updates the shift direction stored in the data / settings storage memory 41 and the shift direction stored in the RAM 13 in opposite directions.

[0086] In ACT23, the processor 11 resets the print page counter 42 so that it can count the updated number of print pages in the shift direction. After that, the processor 11 proceeds to the processing of ACT21.

[0087] The inkjet printer 1 as an image forming apparatus according to the second embodiment has an inkjet head unit 21 according to the second embodiment, which has an actuator section 24 that includes an effective pixel channel 26 containing 320 actuators 25 for a predetermined number of pixels for ink ejection operation, and a spare channel 27 containing one or more actuators 25 located at at least one end of the effective pixel channel 26. The inkjet printer 1, under the control of the processor 11, switches the range of actuators 25 used for image formation from all actuators 25 in the effective pixel channel 26 and spare channel 27 each time an image is formed on a predetermined number of print media.

[0088] Therefore, in the inkjet printer 1 as an image forming apparatus according to the second embodiment, similar to the inkjet printer 1 as an image forming apparatus according to the first embodiment, the load can be distributed and controlled so that the actuator of a specific channel does not continue to operate by switching the range of the actuator 25 used for image formation for each predetermined number of prints, i.e., number of pages.

[0089] Here, the head drive circuit 23 in the inkjet head unit 21 of the second embodiment of the inkjet printer 1, which is an image forming apparatus according to the second embodiment, can input drive waveforms to the actuators 25 of the effective pixel channel 26 and the spare channel 27, respectively. The processor 11, which is a control circuit that controls the overall operation of the inkjet printer 1, which is an image forming apparatus according to the second embodiment, and generates print data, which is image forming data indicating the image to be formed, generates print data such that the range of the actuators 25 to which the drive waveforms are input shifts. The head drive circuit 23 includes a waveform generation unit that generates drive waveforms according to such print data. The waveform pattern generation unit 36 ​​and the analog unit 30 are examples of the waveform generation unit.

[0090] Therefore, according to the inkjet printer 1 as an image forming apparatus according to the second embodiment, the drive channel can be shifted by inputting print data, in which the printable effective pixel data has been shifted to use the actuator 25 of the spare channel 27, into the inkjet head unit 21. This distributes the load and allows control so that the actuator of a specific channel does not continue to drive, thereby suppressing the deterioration of the piezoelectric element of the actuator of a specific channel.

[0091] Furthermore, the inkjet printer 1 as an image forming apparatus according to the second embodiment includes a data / setting value storage memory 41 as a holding unit that holds at least one of the shift direction and shift amount of the shift.

[0092] Therefore, according to the inkjet printer 1 as an image forming apparatus according to the second embodiment, printable effective pixel data can be shifted according to at least one of an arbitrary shift direction and an arbitrary shift amount held in the data / setting value storage memory 41.

[0093] Here, the processor 11 of the inkjet printer 1, which is an image forming apparatus according to the second embodiment, functions as a rewriting unit that rewrites at least one of the shift direction and shift amount held in the data / setting value storage memory 41 according to instructions from the host PC 2 or the operation panel 15.

[0094] Therefore, according to the inkjet printer 1 as an image forming apparatus of the second embodiment, the direction of the shift and the amount of the shift can be arbitrarily set by specifying at least one of the shift direction and the data length.

[0095] Furthermore, the processor 11, which is a head control device according to the second embodiment, generates print data, which is image formation data, that shifts the range of actuators 25 to which the drive waveform is input each time an image is formed on a predetermined number of print media, thereby switching the range of actuators used for image formation from among all actuators 25 of the effective pixel channel 26 and the spare channel 27.

[0096] Therefore, in the processor 11 as a head control device according to the second embodiment, the load can be distributed by switching the range of actuators 25 used for image formation for each predetermined number of printed sheets, i.e., pages, thereby preventing the actuator of a particular channel from continuing to operate.

[0097] [Third Embodiment] Figure 16 is a flowchart showing an example of the printing process in an inkjet printer 1 as an image forming apparatus according to the third embodiment. In the third embodiment, instead of the processes ACT14 to ACT16 in the second embodiment, the processes ACT31 and ACT32 are performed.

[0098] In ACT31, the processor 11 stores invalid data in each area of ​​the page memory 14 reserved for the print data of each line for one page, according to the shift amount and shift direction stored in RAM 13. In other words, in the second embodiment, invalid data was added to the print data of each line before it was stored in the page memory 14, but in this embodiment, only the invalid data is set in the page memory 14 before the print data.

[0099] In ACT32, the processor 11 saves the print data for each line created in RAM 13 between the invalid data for each line set in page memory 14. As a result, the page memory 14 stores the same data as after processing in ACT16 of the second embodiment.

[0100] Thus, the processor 11 of the inkjet printer 1 as an image forming apparatus according to the third embodiment can shift the drive channels by setting invalid data in the page memory 14 according to at least one of the position and data length of invalid data that does not perform ink ejection operations, which is added to the printable effective pixel data, which is image forming data based on the image to be formed. This distributes the load and allows control so that the actuator of a particular channel does not continue to drive, thereby suppressing the deterioration of the piezoelectric element of the actuator of a particular channel.

[0101] Although the first to third embodiments have been described above, the embodiments are not limited to those described above.

[0102] For example, in the second and third embodiments, the page memory 14 is allocated an area for both the effective pixel channel 26 and the spare channel 27 for storing the print data for each line, and the print data is shifted when the print data is stored in the page memory 14. However, the page memory 14 may be allocated an area for the effective pixel channel 26, similar to the first embodiment, and the shift may be performed by creating the shifted data signal DI when sending a data signal DI containing the print data for one line to the inkjet head unit 21.

[0103] Additionally, the system may be given a function to create shifted print data for client terminal 3.

[0104] The embodiments of the present invention are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be carried out in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents. [Explanation of Symbols]

[0105] 1…Inkjet printer, 2…Host PC, 3…Client terminal, 4…Network, 11…Processor, 12…ROM, 13…RAM, 14…Page memory, 15…Operation panel, 16…Communication interface, 17…Transport motor, 18…Motor drive circuit, 19…Pump, 20…Pump drive circuit, 21…Inkjet head unit, 22…Bus line, 23…Head drive circuit, 24…Actuator section, 25…Actuator, 26…Effective pixel channel, 27…Spare channel, 28…I / O section, 29…Logic section, 30…Analog section, 31…Comparator, 32…Serial-to-parallel conversion section, 33…Start byte / command recognition section, 34…Setting data register, 35…Print data register, 36…Waveform pattern generation section, 37…Counter, 38…Level shifter, 39…Pre-buffer 40...Gate driver, 41...Data / settings storage memory, 42...Print page counter, 43...Start byte recognition unit.

Claims

1. An inkjet head unit having an effective pixel channel including actuators for a specified number of pixels for ink ejection operation, and a spare channel including one or more actuators located at at least one end of the effective pixel channel, Each time an image is formed on a specified number of media by the inkjet head unit, a control means is provided to switch the range of actuators used for image formation from among all the actuators in the effective pixel channel and the spare channel. An image forming apparatus comprising:

2. The inkjet head unit further includes a drive circuit capable of inputting a drive waveform to each of the actuators of the effective pixel channel and the spare channel. The control means is mounted on the drive circuit and includes a shifting means for shifting image forming data indicating the image to be formed so that the range of the actuator to which the drive waveform is input shifts. The drive circuit includes a waveform generation unit that generates a drive waveform according to the shifted image forming data. The image forming apparatus according to claim 1.

3. The image forming apparatus according to claim 2, wherein the shifting means includes a holding portion that holds at least one of the shift direction and the shift amount of the shift.

4. The system further includes a control circuit that inputs the image forming data and at least one of the set values ​​for the shift direction and shift amount to the drive circuit. The image forming apparatus according to claim 3, wherein the control means further includes a rewriting unit that receives the set value from the control circuit and rewrites the contents held by the holding unit.

5. The image forming apparatus further includes a control circuit that controls the overall operation of the image forming apparatus and generates image forming data indicating the image to be formed. The inkjet head unit further includes a drive circuit capable of inputting a drive waveform to each of the actuators of the effective pixel channel and the spare channel. The control means is mounted in the control circuit and generates image forming data such that the range of the actuator to which the drive waveform is input shifts. The drive circuit has a waveform generation unit that generates the drive waveform according to the image forming data generated by the control circuit. The image forming apparatus according to claim 1.

6. The image forming apparatus according to claim 5, wherein the control means further includes a holding unit that holds at least one of the shift direction and the shift amount of the shift.

7. The image forming apparatus according to claim 6, wherein the control circuit determines at least one of the shift direction and shift amount by adjusting at least one of the addition position and data length of invalid data that does not perform the ink ejection operation, which is added to the image forming data based on the image to be formed.

8. An effective pixel channel including actuators for a specified number of pixels for ink ejection operation, A spare channel including one or more actuators located at at least one end of the effective pixel channel, A drive circuit capable of inputting a drive waveform to each of the actuators of the effective pixel channel and the auxiliary channel, wherein, each time an image is formed on a predetermined number of media, the drive circuit generates a drive waveform corresponding to image formation data indicating the image to be formed, such that the range of actuators to which the drive waveform is input shifts from among all the actuators of the effective pixel channel and the auxiliary channel, An inkjet head unit equipped with the following features.

9. A head control device for controlling an inkjet head unit having an effective pixel channel including actuators for a specified number of pixels for ink ejection operation, a spare channel including one or more actuators located at at least one end of the effective pixel channel, and a drive circuit capable of inputting drive waveforms to each of the actuators in the effective pixel channel and the spare channel, A head control device comprising a control circuit that switches the range of actuators used for image formation from among all the actuators in the effective pixel channel and the spare channel, by generating image formation data such that the range of the actuator to which the drive waveform is input shifts each time an image is formed on a specified number of media.

Images