JP2011079220A - Inkjet recorder and image processor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correct variations in the amount of ink droplet ejected from an ink ejecting section even using a memory of small storage capacity. <P>SOLUTION: A reference value storage section 711 stores a reference value for a drive waveform according to a gradation. A correction value storage section 712 stores a correction value for each piezoelectric element 80, the correction value being used for correcting a drive waveform supplied to the piezoelectric element 80 by a drive waveform generating circuit 77 according to the characteristics of the piezoelectric element 80 and the characteristics of a recording head 18. A register 73 captures the correction value and gradation data. A selector 76 selects a reference value corresponding to each nozzle, from reference values corresponding to gradations temporarily stored in the register 75 based on the gradation data held by a buffer 74. A drive waveform generating circuit 77 generates a drive waveform parameter by making a correction following the content of the correction value for the reference value selected by the selector 76. Following this drive waveform parameter, the circuit 77 generates a drive waveform and outputs it to a compression element 80. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an ink jet recording apparatus and an image processing apparatus that form an image on a sheet with ink droplets ejected from a nozzle.

  In recent years, many inkjet printers that form images by ejecting ink onto paper have become widespread. In such an ink jet printer, the sheets stored in the sheet cassette are fed out one by one, and the sheets are transported to a position facing the recording head for ejecting ink by a transport belt. When the paper reaches a position facing the recording head, ink droplets are ejected from the recording head toward the paper, and images are sequentially formed on the paper.

  The recording head has a configuration in which a plurality of ink ejection units having a pressurizing chamber communicating with a nozzle that is an ejection port for ejecting ink droplets and a piezoelectric element (piezo element) disposed on a wall surface of the pressurizing chamber are arranged. Is done. The piezoelectric element operates according to the supplied driving waveform, and the pressurizing chamber is always filled with ink. The ink filled in the pressurizing chamber is ejected as ink droplets from the nozzle in accordance with the operation of the piezoelectric element.

  In order to obtain high image quality in an image formed on paper, common conditions such as appropriate timing, the same discharge speed, and the same amount of ink droplets are required from all nozzles. However, in practice, it is difficult to make the ink droplets ejected from all the nozzles the same due to variations in accuracy of the piezoelectric elements, variations in the configuration of the ink ejection unit, and the like.

  Therefore, in Patent Document 1, drive data corresponding to the characteristics of the ink discharge unit (nozzle or piezoelectric element) is stored as compressed data for each ink discharge unit, and this compressed data is expanded during printing to generate a drive waveform. A method of correcting variations in the amount of ink droplets ejected from each ink ejection unit by supplying the piezoelectric element to the piezoelectric element is described.

JP 2006-218766 A

  However, in the method described in Patent Document 1, although the drive data is compressed and stored, in the case of a recording head having a large number of nozzles, the number of data increases correspondingly and a large memory capacity is required. Since such a memory is generally mounted on a recording head, it is desirable that the memory be a small memory with a small capacity. The method described in Patent Document 1 reduces the memory size (integrated circuit size). It was difficult.

  The present invention has been made to solve the above-described problem, and an ink jet recording apparatus and image processing capable of correcting variations in the amount of ink droplets ejected from an ink ejecting section even using a memory having a small storage capacity The object is to provide an apparatus.

  An ink jet recording apparatus according to a first aspect of the present invention includes a pressurizing chamber for storing ink, and a piezoelectric element disposed on a wall surface of the pressurizing chamber, and the piezoelectric element according to a supplied driving waveform. Operates, an ink discharge means for discharging ink droplets from nozzles communicating with the pressurizing chamber, a recording head having a plurality of the ink discharge means, and gradation data based on input image data Is supplied to the ink discharge means, the reference value storage means for storing the reference value of the drive waveform supplied to the ink discharge means for each gradation indicated by the gradation data, and the ink discharge means. Correction value storage means for storing a correction value preset for correcting the drive waveform for each ink discharge means, and each ink discharge means generated by the gradation data generation means The reference value for each of the ink ejection units is selected from the reference value storage unit according to the gradation data, and the drive is performed using the selected reference value and the correction value set for each of the ink ejection units. A drive waveform generation unit that generates a waveform and outputs the waveform to each of the ink discharge units; and a transfer unit that transfers a sheet to a position opposite to a nozzle of the ink discharge unit, and is discharged from the ink discharge unit An image is formed on the paper by ink droplets.

  According to a fourth aspect of the present invention, there is provided an image processing apparatus according to a fourth aspect, wherein gradation data generating means for generating gradation data based on input image data, a pressurizing chamber containing ink, A piezoelectric element disposed on the wall surface, and the piezoelectric element is operated in accordance with the supplied driving waveform to supply ink droplets to an ink ejection unit that ejects ink droplets from a nozzle communicating with the pressurizing chamber. A reference value storage means for storing a reference value of the drive waveform for each gradation indicated by the gradation data, and a correction value set in advance for correcting the drive waveform supplied to the ink ejection means. A correction value storage means for storing each ink discharge means, and a reference value storage means for each ink discharge means according to the gradation data for each ink discharge means generated by the gradation data generation means. Generating a drive waveform using the selected reference value and the correction value set for each of the ink ejection means, and outputting the drive waveform to each of the ink ejection means Means.

  According to these configurations, the number of reference value data only needs to be the number of gradations, and the correction value is a value for correcting the reference value. The numerical value to be stored can be reduced as compared with the method of storing the drive waveform data corrected in advance according to the accuracy of the recording head for each nozzle. Therefore, regarding the correction value, the number of bits can be reduced, and the capacity of the memory for storing these values can be reduced. If the memory capacity can be reduced, the cost of the memory can be reduced and the integrated circuit mounted on the recording head can be reduced in size.

  A second aspect of the present invention is the ink jet recording apparatus according to the first aspect, wherein the recording means detects the temperature of the recording head, and the reference value storage means stores the detection value according to the detected temperature. Change means for changing a reference value for each gradation.

  When the ink jet recording apparatus performs continuous printing, the temperature of the recording head rises and the amount of ink discharged from the nozzles may change. When the ink discharge amount changes, the image quality changes, which reduces the reliability of the ink jet recording apparatus. Therefore, by changing the reference value according to the temperature of the recording head, the ink discharge amount can be kept constant even when the temperature of the recording head changes, and the image quality can be maintained.

  A third aspect of the present invention is the ink jet recording apparatus according to the second aspect, wherein the changing unit performs the following after the ink ejection related to the image formation for the one sheet by the ink ejection unit is completed. The reference value for each gradation is changed until the ink ejection related to the image formation on the sheet conveyed to the beginning is started.

  If the reference value is changed during page printing, the image quality changes within the page. Therefore, by changing the reference value between print pages, it is possible to avoid a change in image quality (in one image) within the page.

  According to the present invention, since the number of reference value data is only the number of gradations, and the correction value is a value for correcting the reference value, the characteristics of ink ejection means such as piezoelectric elements and nozzles, and recording are conventionally used. The numerical value to be stored can be made smaller than the method of storing the drive waveform data corrected in advance according to the accuracy of the head for each nozzle. Therefore, regarding the correction value, the number of bits can be reduced, and the capacity of the memory for storing these values can be reduced. If the memory capacity can be reduced, the cost of the memory can be reduced and the integrated circuit mounted on the recording head can be reduced in size.

1 is a schematic sectional view of an ink jet printer. FIG. 3 is a plan view when the recording head and the belt unit are viewed from above. 1 is a block diagram showing an electrical configuration of an ink jet printer. The block diagram which showed the electric constitution of the drive control circuit. The figure for demonstrating the relationship between a reference value and a correction value, and the drive waveform produced | generated by the drive waveform production | generation circuit. The flowchart which showed the flow of the drive waveform production | generation process. The flowchart which showed the flow of the modification of a drive waveform production | generation process.

  Hereinafter, embodiments of an ink jet recording apparatus and an image processing apparatus according to the present invention will be described with reference to the drawings. In the following embodiments, an inkjet printer alone will be described as an example of an inkjet recording apparatus. However, the inkjet recording apparatus according to the present invention can be applied to a copying machine, a facsimile, or an electronic apparatus such as a multifunction machine having these functions. . An ink jet printer that performs color printing using a plurality of recording heads will be described as an example, but an ink jet printer for monochromatic printing may be used.

  FIG. 1 is a schematic cross-sectional view of an inkjet printer 1 according to the present embodiment. The ink jet printer 1 includes a paper cassette 11, a pickup roller 12, a transport roller pair 13, a suction roller 14, a transport belt 15, a recording head 18, a cleaning device 21, a discharge roller pair 25, and a discharge tray 26.

  In the paper cassette 11, paper P before printing is stacked and stored. The paper P is picked up one by one by driving the pickup roller 12 and sent out to the conveyance path 31. The transport roller pair 13 transports the paper P that has passed through the transport path 31 to the transport path 32.

  The sheet P that has passed through the conveyance path 32 is conveyed to a position facing the ink discharge port of the recording head 18 via the nip portion between the suction roller 14 and the conveyance belt 15. The surface of the suction roller 14 is in contact with the transport belt 15, and the paper P is pressed against the transport belt 15 and sucked.

  For example, a dielectric resin sheet is used as the transport belt 15, and a (seamless) belt having no seam is mainly used. The conveyor belt 15 is stretched over a paper feed side (upstream side) driven roller 22, a paper discharge side (downstream side) drive roller 20, and a tension roller 19, and the drive roller 20 is counterclockwise on the paper surface. When rotating around, the conveyor belt 15 rotates in the direction of arrow Y, and the driven roller 22 and the tension roller 19 are driven by the conveyor belt 15 to rotate. The tension roller 19 is a roller for applying tension so that the conveying belt 15 does not sag between the driving roller 20 and the driven roller 22. Hereinafter, a portion constituted by the conveyor belt 15, the driven roller 22, the tension roller 19, the driving roller 20, the cleaning device 21, and the like is referred to as a “belt unit 100”.

  The recording head 18 includes, for example, a yellow recording head 18Y, a magenta recording head 18M, a cyan recording head 18C, and a black recording head 18K. Then, cyan, magenta, yellow, and black inks are ejected toward the paper P to sequentially form images. The ink ejection method of the recording head 18 in the present embodiment uses a piezo method in which ink is ejected from a nozzle using a piezoelectric element such as a piezo element.

  The cleaning device 21 is for removing ink adhering to the surface of the transport belt 15. The sheet P on which the image has been formed passes through the discharge conveyance path 24 and is discharged to the discharge tray 26 by the discharge roller pair 25.

  FIG. 2 is a plan view of the recording head 18 and the belt unit 100 as viewed from above. The recording head 18 is disposed from the upstream side toward the downstream side in the rotation direction along the circumferential direction (paper conveyance direction) of the conveyance belt 15. Each recording head 18 has a line head 51 extending in a direction perpendicular to the paper transport direction (paper width direction), and a plurality of nozzles for ejecting ink droplets on the lower surface of the line head 51. Is provided.

  Each nozzle provided in the line head 51 communicates with the pressurizing chamber, and a piezoelectric element (piezo element) is disposed on the wall surface of the pressurizing chamber. The piezoelectric element operates according to the supplied driving waveform, and the pressurizing chamber is always filled with ink. Therefore, the ink filled in the pressurizing chamber is ejected as ink droplets from the nozzle in accordance with the operation of the piezoelectric element. Each recording head 18 is equipped with a drive control circuit that selects a nozzle for ejecting ink droplets and supplies a drive waveform to a piezoelectric element corresponding to the selected nozzle.

  Here, in order to form an image with good image quality on the paper P, appropriate timing, the same ejection speed, and the same amount of ink droplets are ejected from all the nozzles provided in the line head 51. Common conditions are required. However, in practice, it is difficult to make the amount of ink droplets ejected from all the nozzles constant due to variations in accuracy of the piezoelectric elements and variations in the configuration of the recording head 18.

  In order to solve this problem, conventionally, a drive waveform that has been corrected in advance according to the characteristics of the piezoelectric element, the recording head 18 and the like is stored in a memory for each nozzle, so that the ink droplets discharged from the nozzles are stored. A method of correcting variation in quantity was used. However, in the case of a print head with a large number of nozzles, the number of drive waveform data to be stored increases accordingly, so a memory with a large storage capacity is required, and the drive control circuit mounted on the print head 18 can be reduced in size and cost. There was a problem in terms of

  Therefore, the present invention proposes a method capable of correcting the variation in the amount of ink droplets ejected from the nozzles even using a memory having a small storage capacity.

  FIG. 3 is a block diagram showing an electrical configuration of the ink jet printer 1. The inkjet printer 1 includes a control unit 60, a storage unit 61, a paper transport unit 62, an image memory 63, an image processing unit 64, an image forming unit 65, an input operation unit 66, and a network I / F unit 67. . Note that the constituent elements indicated by dotted lines are elements used in other embodiments and will be described later.

  The control unit 60 is configured by a CPU (Central Processing Unit) or the like, reads a program stored in the storage unit 61 and executes processing, and outputs an instruction signal to each functional unit, data transfer, and the like. The overall control of the ink jet printer 1 is performed.

  The storage unit 61 stores programs, data, and the like for realizing various functions provided in the inkjet printer 1. The paper transport unit 62 includes the belt unit 100 and various rollers. The image memory 63 temporarily stores image data transmitted from an external device via the network I / F unit 67. The image processing unit 64 performs image processing such as image correction and enlargement / reduction on the image data stored in the image memory 63. The image forming unit 65 includes the recording head 18 and forms an image indicated by the image data on the sheet conveyed by the sheet conveying unit 62. The recording head 18 includes a drive control circuit 181 that supplies a drive waveform to the piezoelectric element to control ink droplets ejected from each nozzle. The drive control circuit 181 corresponds to the image processing apparatus of the present invention, and will be described in detail later.

  The input operation unit 66 includes a display panel for displaying various messages and operation buttons for inputting various operation commands such as a power key and a reset key. The network I / F unit 67 includes a communication module such as a LAN board, and transmits / receives various data to / from an external device via a network (not shown) connected to the network I / F unit 67.

  FIG. 4 is a block diagram showing an electrical configuration of the drive control circuit 181. The drive control circuit 181 includes a memory 71, a gradation data generation unit 72, registers 73 and 75, a buffer 74, a selector 76, a drive waveform generation circuit 77, and a control unit 78. The piezoelectric elements 80 are arranged on the wall surface of the pressurizing chamber communicating with the nozzles provided in the recording head 18, and the number of piezoelectric elements 80 is N (N Is an integer equal to or greater than 1. The piezoelectric element 80 operates according to the drive waveform supplied from the drive waveform generation circuit 77.

  The memory 71 includes a reference value storage unit 711 and a correction value storage unit 712. The reference value storage unit 711 stores, for each gradation, a reference value indicating a value related to a waveform that serves as a reference when the drive waveform generation circuit 77 generates a drive waveform supplied to the piezoelectric element 80. The reference value for each gradation is a value common to each piezoelectric element 80. For example, if the number of gradations is G (G is an integer of 1 or more), the reference value storage unit 711 stores G reference values for each gradation. Remember.

  The correction value storage unit 712 stores a correction value for correcting the drive waveform supplied to the piezoelectric element 80 by the drive waveform generation circuit 77 according to the characteristics of the piezoelectric element 80 and the recording head 18 for each piezoelectric element 80. The correction value storage unit 712 stores N correction values for each piezoelectric element 80. Here, the correction value storage unit 712 does not store drive waveform data for each piezoelectric element 80, but stores a correction value for correcting a reference drive waveform. Compared to the case where the drive waveform data itself is stored for each piezoelectric element 80 as in the prior art, the stored numerical value can be reduced when the correction value for the reference value is stored, so the number of bits can be reduced. . Therefore, the memory capacity of the memory 71 can be reduced.

  The gradation data generation unit 72 generates gradation data for instructing each nozzle whether or not an ink droplet is discharged and the amount (gradation) of the droplet based on the image data received from the image memory 63. The gradation data generation unit 72 outputs N pieces of data that are the number of nozzles, that is, the number of piezoelectric elements 80.

  The register 73 captures the gradation data from the gradation data generation unit 72 according to the print cycle signal output from the control unit 78, and further captures the correction value from the correction value storage unit 712 and temporarily stores it. Further, the register 73 outputs the temporarily stored gradation data and the correction value to the buffer 74, and the buffer 74 temporarily stores these data. The print cycle signal is intermittently output at predetermined intervals in consideration of the time required for ink ejection for one line.

  The register 75 takes in the reference value from the reference value storage unit 711 and temporarily stores it.

  The selector 76 takes in the gradation data for each nozzle temporarily stored in the buffer 74, and selects a reference value for each nozzle from the reference values for each gradation temporarily stored in the register 75 based on this gradation data. To do. The selector 76 is composed of N selectors, which is the number of nozzles, that is, the number of piezoelectric elements 80, and each selector and nozzle (piezoelectric element 80) have a one-to-one correspondence. In the present embodiment, the N selectors are collectively referred to as “selector 76”.

  The drive waveform generation circuit 77 takes in the input of the correction value temporarily stored in the buffer 74 and supplies the drive waveform to each piezoelectric element 80 using the two values of the reference value selected by the selector 76 and the taken correction value. Is generated. Similarly to the selector 76, the drive waveform generation circuit 77 is composed of N generation circuits, which is the number of compression elements 80, and each generation circuit and the piezoelectric element 80 are in one-to-one correspondence. In the present embodiment, the N drive waveform generation circuits are collectively referred to as “drive waveform generation circuit 77”.

  The control unit 78 performs overall control of the drive control circuit 181 by transferring data, outputting instruction signals, and the like to the respective functional units constituting the drive control circuit 181.

  FIG. 5 is a diagram for explaining the relationship between the reference value and the correction value and the drive waveform generated by the drive waveform generation circuit 77. First, the values in the row (1) in the table shown at the bottom of FIG. 5 will be described in order.

  Each selector 76 selects one reference value from the reference values for each gradation stored in the register 75 based on the gradation data for each nozzle fetched from the buffer 74. For example, the reference value selected by the selector 76m (m is an integer not less than 1 and not more than N) is Toff1 = 10 [μs] (off time of the piezoelectric element 80m) shown in the row (1) in the table of FIG. = 8 [μs] (the ON time of the piezoelectric element 80m). The amount of ink droplets ejected from the nozzle is determined by the voltage value applied to the piezoelectric element 80 and the on / off time of the drive waveform. Therefore, the reference value indicates the on / off time of the drive waveform supplied to the piezoelectric element 80 for each gradation. Note that if the drive waveform generation circuit 77 sets the on-off and off-time voltage values (voltages V1 and V2 in FIG. 5) (in this embodiment, V1 = off-time voltage = 15 [V V2 = voltage at ON = 0 (set as 0 [V]), and it is not necessary to include a voltage value as a reference value.

  Then, the drive waveform generation circuit 77m takes a correction value corresponding to the piezoelectric element 80m out of the reference value selected by the selector 76m and the correction value temporarily stored in the buffer 74, and generates a drive waveform. At this time, the correction values temporarily stored in the buffer 74 are Toff1 = 0 [μs], V1 = 0 [V], Ton1 = 0.2 [μs] shown in the row (1) in the table of FIG. It is assumed that V2 = 1 [V]. In this case, the drive waveform generation circuit 77m calculates a drive waveform parameter by combining the reference value shown above and the correction value. That is, as shown in the row (1) in the table of FIG. 5, Toff1 is 10 [μs] unchanged from the reference value, V1 is 15 [V] unchanged from the reference value, and Ton1 is 0 with respect to the reference value. .2 [μs] Long 8.2 [μs], V2 = 1 [V]. When the drive waveform generation circuit 77m generates a drive waveform to be supplied to the piezoelectric element 80m in accordance with this parameter, the waveform of the period Toff1 and Ton1 shown by the drive waveform in FIG. 5 is obtained. Note that when the reference waveform in FIG. 5 is corrected according to the content of the correction value, a drive waveform is obtained.

  Subsequently, it is assumed that the reference values selected by the selector 76m are Toff2 = 5 [μs] and Ton2 = 11 [μs] shown in the row (2) in the table of FIG. The correction values corresponding to the piezoelectric element 80m fetched from the buffer 74 are Toff2 = 0.5 [μs] and Ton2 = −0.5 [μ] shown in the row (2) in the table of FIG. To do. In such a case, the drive waveform parameters are Toff2 = 5.5 [μs], V1 = 15 [V], Ton2 = 10.5 [μs], and V2 = 0 [V], and the drive waveform generation circuit according to these parameters When 77m generates a drive waveform, the waveform shown in the period of Toff2 and Ton2 shown in the drive waveform in FIG. 5 is obtained.

  FIG. 6 is a flowchart showing the flow of drive waveform generation processing in the present embodiment. When the register 73 fetches the correction value and gradation data for each nozzle in accordance with the print cycle signal output from the control unit 78 (step S11; YES), the register 73 fetches the correction value and the level stored in the buffer 74. Output key data. The buffer 74 fetches the correction value and gradation data from the register 73 and temporarily stores (latches) it (step S12). Subsequently, the selector 76 fetches the gradation data from the buffer 74, and selects a reference value corresponding to each nozzle from the reference values for each gradation temporarily stored in the register 75 based on the gradation data (step S13). .

  Then, the drive waveform generation circuit 77 fetches the correction value from the buffer 74, corrects the reference value selected by the selector 76 according to the content of the correction value, and generates a drive waveform parameter (step S14). A drive waveform is generated according to the drive waveform parameter and output to the piezoelectric element 80 (step S15).

  As described above, the drive waveform data itself corrected in advance according to the characteristics of the piezoelectric element 80 and the recording head 18 is not stored for each nozzle, but the reference value for each gradation and the correction value for each nozzle. Since the numerical value to be stored can be reduced, the number of bits can be reduced, and the memory capacity of the memory 71 can be reduced. When the memory capacity of the memory 71 is reduced, the integrated circuit mounted on the recording head 18 can be reduced in size and cost.

  The present invention is not limited to the configuration of the above embodiment, and various modifications can be made. For example, when the inkjet printer 1 performs continuous printing, the temperature of the recording head 18 may rise and the amount of ink discharged from the nozzles may change. When the ink discharge amount changes, the image quality changes, and the reliability of the inkjet printer 1 is reduced. Therefore, the temperature of the recording head 18 may be measured, and the reference value may be changed according to the measured temperature.

  This will be specifically described. As shown in FIG. 3, the temperature sensor 182 is disposed in the recording head 18. The temperature sensor 182 measures the temperature of the recording head 18 and outputs temperature data to the control unit 78 of the drive control circuit 181.

  This will be described with reference to FIG. The control unit 78 takes in the temperature data from the temperature sensor 182 and changes the reference value temporarily stored in the register 75 according to the temperature data. For example, the control unit 78 calculates the parameter 78 according to the temperature data and the reference value of the register 75 by substituting it into a predetermined calculation formula, and stores the calculation result in the register 75 as a new reference value.

  If the reference value is changed during printing of one page, the image quality changes in the image of the same page. Therefore, it is preferable that the reference value is changed between pages. (However, since the temperature of the recording head 18 rises and the image quality changes when continuous printing is performed, the reference value may be changed during printing in such a case.) That is, the control unit 78 is one page. Whether the reference value is changed by fetching the temperature data from the temperature sensor 182 after the ink ejection relating to the image formation for the minute is finished and before the ink ejection relating to the image formation of the next conveyed paper is started. It is determined whether or not the reference value is changed.

  FIG. 7 is a flowchart showing a flow of a modified example of the drive waveform generation processing. When the register 75 takes in the reference value from the reference value storage unit 711 (step S21) and the print processing of the recording head 18 is between pages (step S22; YES), the control unit 78 detects the reference value from the temperature sensor 182. Temperature data indicating the temperature of the recording head 18 is captured (step S23). And the control part 78 judges whether a reference value is changed based on temperature data (step S24). When changing the reference value (step S24; YES), the control unit 78 changes the reference value temporarily stored in the register 75 (step S25). When the printing process of the recording head 18 is not between pages (step S22; NO), when the control unit 78 determines not to change the reference value (step S24; NO), the control unit 78 proceeds to step S11. Transition.

  When the register 73 fetches the correction value and gradation data for each nozzle in accordance with the print cycle signal output from the control unit 78 (step S11; YES), the register 73 fetches the correction value and the level stored in the buffer 74. Output key data. The buffer 74 fetches the correction value and gradation data from the register 73 and temporarily stores (latches) it (step S12). Subsequently, the selector 76 fetches the gradation data from the buffer 74, and selects a reference value corresponding to each nozzle from the reference values for each gradation temporarily stored in the register 75 based on the gradation data (step S13). .

  Then, the drive waveform generation circuit 77 fetches the correction value from the buffer 74, corrects the reference value selected by the selector 76 according to the content of the correction value, and generates a drive waveform parameter (step S14). A drive waveform is generated according to the drive waveform parameter and output to the piezoelectric element 80 (step S15).

1 Inkjet printer 15 Conveying belt (conveying means)
18 Recording head 181 Drive control circuit (image processing apparatus)
182 Temperature sensor (detection means)
65 Image forming unit 71 Memory 711 Reference value storage unit (reference value storage means)
712 Correction value storage unit (correction value storage means)
72 gradation data generation unit (gradation data generation means)
73, 75 Register 74 Buffer 76 Selector 77 Drive waveform generation circuit (drive waveform generation means)
78 Control unit (changing means)
80 Piezoelectric elements (ink ejection means)

Claims (4)

A pressure chamber containing ink; and a piezoelectric element disposed on a wall surface of the pressure chamber. The piezoelectric element is operated according to a supplied driving waveform to communicate with the pressure chamber. Ink ejection means for ejecting ink droplets from the nozzles,
A recording head having a plurality of ink ejection means;
Gradation data generating means for generating gradation data based on the input image data;
Reference value storage means for storing a reference value of a drive waveform supplied to the ink ejection means for each gradation indicated by the gradation data;
Correction value storage means for storing a correction value set in advance for correcting the drive waveform supplied to the ink discharge means for each ink discharge means;
The reference value for each ink ejection means is selected from the reference value storage means according to the gradation data for each ink ejection means generated by the gradation data generation means, and the selected reference value and the ink ejection are selected. Drive waveform generation means for generating the drive waveform using the correction value set for each means and outputting the generated drive waveform to the ink ejection means;
Transport means for transporting paper to a position facing the nozzles of the ink ejection means;
And an ink jet recording apparatus that forms an image on the paper with ink droplets ejected from the ink ejection means. Detecting means for detecting the temperature of the recording head;
Changing means for changing the reference value for each gradation stored in the reference value storage means according to the detected temperature;
The inkjet recording apparatus according to claim 1, further comprising:   The changing unit is configured to change the gradation for each gradation after the ink ejection related to the image formation for the one sheet by the ink ejection unit is finished and the ink ejection related to the image formation on the next transported paper is started. The inkjet recording apparatus according to claim 2, wherein the reference value is changed. Gradation data generating means for generating gradation data based on the input image data;
A pressure chamber containing ink; and a piezoelectric element disposed on a wall surface of the pressure chamber. The piezoelectric element is operated according to a supplied driving waveform to communicate with the pressure chamber. Reference value storage means for storing a reference value of a drive waveform supplied to the ink discharge means for discharging ink droplets from the nozzles, for each gradation indicated by the gradation data;
Correction value storage means for storing a correction value set in advance for correcting the drive waveform supplied to the ink discharge means for each ink discharge means;
The reference value for each ink ejection means is selected from the reference value storage means according to the gradation data for each ink ejection means generated by the gradation data generation means, and the selected reference value and the ink ejection are selected. Drive waveform generation means for generating the drive waveform using the correction value set for each means and outputting the generated drive waveform to the ink ejection means;
An image processing apparatus.

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