JPWO2015111451A1 - Image forming apparatus - Google Patents

Abstract

Provided is an image forming apparatus capable of outputting a driving voltage more stably with a simple configuration against a change in load accompanying the start of operation of a recording element. A recording head in which a plurality of recording elements are arranged, a driving unit that supplies a driving voltage to a load element of the recording element based on the formed image data, and a driving unit that operates each of the load elements, and a variation in the driving voltage that is supplied to the driving unit A voltage control unit that performs control to suppress, a resistance element that is connected to the voltage control unit and is provided corresponding to the load element of the recording element, and switching that switches whether to supply a drive voltage to the resistance element The drive voltage is supplied to the resistance element in at least a part of the period before the supply start timing for supplying the drive voltage to the element and the load element of the recording element, and to the load element of the print element. And a load control unit for controlling the switching element.

Description

  The present invention relates to an image forming apparatus.

  There is an ink jet type image forming apparatus (ink jet recording apparatus) that forms an image on a recording medium by ejecting ink by controlling timing from openings of a plurality of nozzles arranged in a predetermined pattern. In this ink jet recording apparatus, ink is ejected from the nozzles at high speed by abruptly applying pressure to the ink in the ink flow paths communicating with the respective nozzles, thereby ejecting and flying ink droplets.

  As a method for ejecting ink droplets, the ink chamber is heated by energizing a heater provided at the nozzle end, and a piezo type that pushes ink by compressing and deforming an ink chamber communicating with the nozzle by a piezoelectric element or the like. The thermal type that pushes out ink by generating bubbles in the ink flow path is mainly used. In these driving methods, load elements such as piezoelectric elements and heaters are individually provided for each nozzle. Since a predetermined voltage is applied to the load element corresponding to the nozzle that ejects ink, the total load, that is, the power consumption increases as the number of nozzles that eject ink simultaneously increases.

  In electrical equipment that does not have a sufficient capacity for the power supply with respect to the maximum load, the supply voltage decreases or rises when a large load is suddenly applied or removed. The amount of ink discharged from each nozzle is closely related to the drive voltage applied to the load element corresponding to each nozzle. Therefore, when the drive voltage fluctuates, the ink density becomes uneven and the image quality of the formed image decreases. The problem arises. Therefore, conventionally, as a circuit for supplying a stable voltage, a technique for suppressing a change in output voltage using a feedback circuit is used.

  In Patent Document 1, a pre-pulse that does not eject ink is output before outputting a drive pulse that ejects ink, and the length of this pre-pulse is changed to compensate for the power consumption of the nozzle that does not eject ink. A technique for suppressing power fluctuations is disclosed.

  In recent years, however, the number of nozzles provided in an ink jet recording apparatus has increased with the increase in accuracy and speed of images formed by the ink jet recording apparatus. As a result, in the technique described in Patent Document 1, even if an attempt is made to correct the drive voltage fluctuation by increasing the control width of the pre-pulse width, the ejection may become unstable, and the drive voltage fluctuation may not be fully corrected. is there. On the other hand, in Patent Document 2, a plurality of dummy resistors and switches are provided in parallel with the nozzles, the number of ink ejection nozzles is counted, and the power corresponding to the reduction in power consumption of the nozzles is obtained by the combination of the resistors. A technique is disclosed that suppresses fluctuations in power consumption by consuming power and prevents variations in voltage drop between lines during image formation.

JP 2003-237056 A JP 2002-254648 A

However, in the drive voltage output circuit, the response time of the feedback circuit for suppressing the fluctuation of the drive voltage with respect to the change in power consumption is determined depending on constants such as a coil and a capacitor used in the feedback circuit. Accordingly, when the load is switched at high speed, the response time becomes longer than the output time of the drive voltage. In such a situation, large drive voltage fluctuations cannot be suppressed immediately.
In particular, driving in which an operation relating to voltage application is performed from a non-driving state in which no voltage is applied to the load element of each element related to image formation, such as at the start of image formation (including restarting from interruption due to a blank space or the like). When the drive voltage is first applied after the transition to the state and the operation of the recording element is started, a clear and sudden change in power consumption occurs. There is a problem that it is impossible to avoid the occurrence of this. Moreover, there is a problem that the improvement of the hardware configuration for shortening the response time leads to a complicated circuit and an increased size.

  An object of the present invention is to provide an image forming apparatus capable of outputting a driving voltage more stably with a simple configuration against a change in load accompanying the start of operation of a recording element.

In order to achieve the above object, the present invention described in claim 1
A recording head in which a plurality of recording elements are arranged;
A driving unit for supplying a driving voltage to the load element of the recording element based on the formed image data and operating the load element;
A voltage control unit that performs control so as to suppress fluctuations in the drive voltage supplied to the drive unit;
A resistance element connected to the voltage control unit and provided corresponding to a load element of the recording element;
A switching element for switching whether to supply the drive voltage to the resistance element;
Before the supply start timing for supplying the drive voltage to the load element of the recording element and at least part of a period in which the drive voltage is not supplied to any of the load elements of the recording element, A load controller that controls the switching element to supply a driving voltage;
An image forming apparatus comprising:

According to a second aspect of the present invention, in the image forming apparatus of the first aspect,
The supply of the drive voltage to the load element of the recording element is started in a state where the drive voltage is lowered by the supply of the drive voltage to the resistance element.

According to a third aspect of the present invention, in the image forming apparatus of the first aspect,
The amount of decrease in the drive voltage at the start of supplying the drive voltage to the load element of the recording element is equal to or less than the amount of decrease in the drive voltage at the start of supplying the drive voltage to the resistance element. It is a feature.

According to a fourth aspect of the present invention, in the image forming apparatus according to the first or second aspect,
The amount of decrease in the driving voltage at the start of supplying the driving voltage to the load element of the recording element supplies the driving voltage to the load element of the recording element without supplying the driving voltage to the resistance element. It is smaller than the amount of decrease in the drive voltage at the start of virtual supply.

According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects,
When the response time is the time from the fluctuation of the driving voltage when the driving voltage is supplied to the resistance element until it converges to a predetermined driving voltage,
The switching element is configured to supply the drive voltage to the resistance element from the response start time before supply start timing for supplying the drive voltage to the load element of the recording element until the supply start timing. It is characterized by controlling.

According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects,
The supply start timing includes a timing at which the drive voltage is supplied to a load element of the recording element at the start of image formation for one page.

According to a seventh aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects,
The supply start timing is when forming the image by repeatedly moving the recording head along the recording medium to form a one-band image and transporting the recording medium to form the next one-band image. It includes a timing for supplying the drive voltage to the load element of the recording element at the start of image formation of one band.

An invention according to claim 8 is the image forming apparatus according to any one of claims 1 to 5,
A transport unit that transports a recording medium on which an image is formed by the recording head;
The transport unit includes a first measurement unit that measures positions of the recording medium with respect to the plurality of recording elements in a transport direction of the recording medium,
The supply start timing is determined based on the position of the recording medium relative to the plurality of recording elements in the conveyance direction of the recording medium set for the recording medium and the operation related to the start of printing on the recording medium. Is a timing at which the recording unit is transported to a position where it overlaps with a position where the recording element is started.

The invention according to claim 9 is the image forming apparatus according to any one of claims 1 to 5,
A transport unit for transporting a recording medium on which an image is formed by the recording head;
A power source for reciprocating the recording head in a direction orthogonal to the conveyance direction of the recording medium;
With
The transport unit includes a first measurement unit that measures positions of the recording medium with respect to the plurality of recording elements in a transport direction of the recording medium,
The power source has a second measurement unit that measures positions of the recording medium with respect to the plurality of recording elements in a direction in which the recording head reciprocates.
The supply start timing is determined by the position of the recording medium relative to the plurality of recording elements in the conveyance direction of the recording medium set for the recording medium and the start of printing on the recording medium. The recording element is transported to the position where it overlaps the position in the transport direction of the recording medium that causes the recording element to start operation, and the recording head set for the recording medium is reciprocated. A timing at which the power source moves to a position where a position of the recording medium with respect to the plurality of recording elements in a direction to overlap and a position at which the recording element starts the operation related to the start of printing. .

The invention according to claim 10 is the image forming apparatus according to any one of claims 1 to 9,
The load control unit is 50% of a load amount applied to the voltage control unit when supplying the drive voltage to all of the load elements of the plurality of recording elements as a magnitude of a load amount by the resistance element. It is characterized by setting the load amount.

The invention according to claim 11 is the image forming apparatus according to claim 10.
The load control unit adjusts a period during which the drive voltage is supplied to the resistance element by PWM control so that a load amount by the resistance element becomes the set magnitude.

According to a twelfth aspect of the present invention, in the image forming apparatus of the first aspect,
The load control unit
A buffer storage unit for sequentially storing the formed image data;
Output discriminating means for discriminating whether or not to operate at least one load element of the recording element in each block in which image formation is performed simultaneously with the stored formation image data;
When data of a block for operating the load element of the recording element is acquired by the output determining means, the resistance element is used until before the load element is operated by the drive unit based on the data of the block. The drive voltage is supplied to the circuit.

According to a thirteenth aspect of the present invention, in the image forming apparatus of the twelfth aspect,
The output determination means counts the number of operations of the load element of the recording element operated in each block,
The load control unit determines a magnitude of a load amount by the resistance element based on the number of operations in an initial predetermined number of blocks in which the driving unit shifts from a non-driving state to a driving state.

According to a fourteenth aspect of the present invention, in the image forming apparatus according to the thirteenth aspect,
The load control unit adjusts a period during which the drive voltage is supplied to the resistance element by PWM control so that a load amount by the resistance element becomes the set magnitude.

The invention according to claim 15 is the image forming apparatus according to any one of claims 12 to 14,
When the response time is the time from the fluctuation of the driving voltage when the driving voltage is supplied to the resistance element until it converges to a predetermined driving voltage,
The switching element is configured to supply the drive voltage to the resistance element from the response start time before supply start timing for supplying the drive voltage to the load element of the recording element until the supply start timing. It is characterized by controlling.

According to a sixteenth aspect of the present invention, in the image forming apparatus according to the fifteenth aspect,
The response time is longer than the time required for image formation for two blocks.

The invention according to claim 17 is the image forming apparatus according to any one of claims 1 to 16, wherein the recording head is an ink jet head.
The recording element is a nozzle and an ink ejection mechanism that ejects ink from the nozzle.

The invention according to claim 18 is the image forming apparatus according to any one of claims 1 to 17,
The load element of the recording element is a piezoelectric element.

  According to the present invention, in the image forming apparatus, there is an effect that a driving voltage can be more stably output with a simple configuration with respect to a change in load accompanying the start of operation of the recording element.

It is a block diagram which shows the internal structure of an inkjet recording device. It is a figure explaining the circuit structure which concerns on the electric power supply to an inkjet head. It is a schematic diagram which shows the relationship between the output voltage of a DC / DC conversion part, and head load. FIG. 4 is a schematic diagram illustrating a relationship among an output voltage, a resistance load, and a head load of a DC / DC conversion unit in the inkjet recording apparatus of the present embodiment. It is a schematic diagram which shows the load pattern in the case of carrying out PWM control of the resistance load. It is a flowchart which shows the control procedure of a load control process.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing an internal configuration of an ink jet recording apparatus 1 which is an embodiment of an image forming apparatus of the present invention.

The ink jet recording apparatus 1 has a line head in which a plurality of nozzles are arranged in a width direction perpendicular to a conveyance direction of a recording medium on which an image is formed, over a width capable of forming an image on the recording medium, and is fixed. Further, the image forming is performed for each row (line) extending in the width direction by controlling the ink ejection timing from each nozzle of the line head and transporting the recording medium. The line head includes a plurality of inkjet heads 70 (recording heads) arranged in parallel. In each of the inkjet heads 70, a predetermined number, for example, 1024 nozzles are arranged alternately in two rows extending in parallel in the width direction, and an ink flow path that supplies ink to each nozzle, and A pressurizing mechanism 72 (see FIG. 2) is provided for pressurizing the ink in the ink flow path and discharging the ink from the nozzle. Here, as the pressurizing mechanism 72, a piezoelectric element that deforms the ink flow path (pressure chamber) is used.
A recording element is constituted by a combination of these nozzles and the corresponding ink flow path and the pressurizing mechanism 72 (ink ejection mechanism). Of these, the pressurizing mechanism 72 is a load element.

  The inkjet recording apparatus 1 includes a control unit 10, a storage unit 20, a voltage control unit 30 of a power supply unit 90, a load control unit 35, a communication unit 40, an operation display unit 50, a transport unit 60, and an inkjet. A head driving unit 71 (driving unit) of the head 70 is provided.

  The control unit 10 controls various operations of the inkjet recording apparatus 1. The control unit 10 includes a CPU (Central Processing Unit) 101 and a RAM (Random Access Memory) 102. The CPU 101 performs arithmetic processing and outputs a control signal related to operation control to each unit. The RAM 102 is a volatile memory, provides a working memory space to the CPU 101, and stores temporary data.

  The storage unit 20 stores the acquired image data to be formed, intermediate data processed for image formation, raster image data, and the like, and stores various setting data. The storage unit 20 includes a volatile memory such as a DRAM, a non-volatile memory such as a flash memory, and an HDD (Hard Disk Drive) each with an appropriate capacity.

  In the power supply unit 90, the voltage control unit 30 outputs a drive voltage supplied from the power supply unit 37 (see FIG. 2) to the nozzle pressurizing mechanism 72 of the inkjet head 70, and also supplies the power supplied as the nozzle drive voltage. The load is adjusted (see FIG. 2). The voltage control unit 30 may be provided separately for each of the plurality of inkjet heads 70 and may be controlled independently. When the number of nozzles is larger than the power capacity of the voltage control unit 30, a plurality of voltage control units 30 may be provided for one inkjet head 70 and used in parallel.

The load control unit 35 calculates a change in the load amount in the inkjet head 70 in advance, and performs control for applying a load amount corresponding to the load amount to a dummy resistance element 33 described later.
The voltage control unit 30 and the load control unit 35 will be described in detail later.

  The communication unit 40 is an interface for performing communication with a print server and an external computer terminal, and includes, for example, a network card and a wireless LAN control module. The control unit 10 receives the image data to be formed and the print job related to the image formation and transmits the status data via the communication unit 40.

The operation display unit 50 includes a display screen that displays an operation menu and a status, and an operation unit that receives an operation from the user. Although the display screen is not particularly limited, for example, a liquid crystal screen (LCD) is used, and various displays are performed by a drive signal generated by a liquid crystal driver based on a control signal output from the control unit 10.
As the operation unit, a touch panel using a touch sensor provided on the LCD is used. Further, the operation unit may be provided with a push button switch related to power-on or reset. When the operation unit detects a user operation, the operation unit converts the operation information into an electric signal and outputs the electric signal to the control unit 10.

  The conveyance unit 60 moves a recording medium on which an image is formed to an image forming position facing the inkjet head 70, and discharges the recording medium from the image forming position after the image is formed. As the transport unit 60, a transport base that rotates a ring-shaped belt by a motor, a transport drum that rotates a cylindrical drum by a motor, or a linear stage that linearly operates the transport base is used. The transport unit 60 includes an encoder 61 (first measurement unit), and can measure the distance transported by the transport unit 60, for example, by setting the value of the transport start position by the transport unit 60 to “0”.

  In the inkjet head 70, the head drive unit 71 sends a drive voltage signal for causing each nozzle to perform an ink ejection operation at an appropriate timing according to the input raster image data to the pressurizing mechanism 72 corresponding to the nozzle. Output.

FIG. 2 is a diagram illustrating a circuit configuration relating to power supply to the inkjet head 70.
In the inkjet head 70, the head driving unit 71 decodes input image data and outputs a driving signal in accordance with the driving pulse, and a ground voltage or voltage control based on the output driving signal. And a driver circuit 712 that outputs any one of the driving voltages input from the unit 30 to the pressurizing mechanism 72 of each nozzle. Here, only one pressure mechanism 72 and a circuit configuration relating to a drive voltage output to the pressure mechanism 72 are shown, but these numbers are provided in electrical parallel with each other. ing. In addition, the decoder circuit 711 separately performs switching for switching whether or not to apply a driving pulse to the pressurizing mechanism 72, and in a situation where the ink ejection operation is not performed, the switching can switch the non-driving state and the driving state. It has become.

  The voltage control unit 30 converts a predetermined input voltage signal output from the power supply unit 37 into a drive voltage suitable for driving each nozzle, and outputs the converted drive voltage to the inkjet head 70 (head drive unit 71). The voltage control unit 30 includes a DC / DC conversion unit 31, a compensation circuit 32, and the like.

  The DC / DC converter 31 is a circuit that converts a predetermined DC voltage input using PWM (Pulse Width Modulation) control into a drive voltage. As the detailed circuit configuration of the DC / DC conversion unit 31, any one of well-known configurations can be used. Here, for example, a switching element for switching presence or absence of input of a DC voltage, and in series with the switching element. It includes a connected coil, a diode provided between the coil and the ground on the upstream side, and a smoothing capacitor provided between the coil and the ground on the downstream side of the coil. The switching element is controlled to be opened / closed so that a set voltage (in this case, a driving voltage) is output, and is also opened / closed by the compensation circuit 32 based on a change in the feedback voltage.

  The compensation circuit 32 feeds back the output voltage of the DC / DC converter 31 and switches the switching element so as to change the operation of the DC / DC converter 31 in a direction to suppress the change when the output voltage changes. Operate.

  A plurality of voltage control units 30 may be provided. For example, a configuration may be adopted in which a DC / DC converter 31 having an output voltage of 9V and a DC / DC converter having an output voltage of 18V are provided, and the drive voltage output is switched as appropriate.

  The resistance element 33 has one end connected to the output of the DC / DC converter 31 and the other end connected to the switching element 34. The resistance value of the resistance element 33 is set so that the current flowing through the resistance element 33 and the switching element 34 does not become unnecessarily large when the switching element 34 is turned on.

  The switching element 34 is a switch for switching whether or not the resistance element 33 is energized. One end of the switching element 34 is connected to the resistance element 33 and the other is grounded. On / off of the switching element 34 is controlled based on a control signal from the load control unit 35. That is, when the switching element 34 is turned on, the output voltage of the DC / DC conversion unit 31 is applied to both ends of the resistance element 33 and a current flows to the ground plane. At this time, the output element of the DC / DC converter 31 is not applied to the pressurizing mechanism 72 of the inkjet head 70 by opening the switching element of the head drive unit 71 and bringing the inkjet head 70 into a non-driven state. On the other hand, when the switching element 34 is turned off, the resistance element 33 is in a floating state. When the ink jet head 70 is in a driving state in this state, the output voltage of the DC / DC conversion unit 31 is The pressure is applied to the pressure mechanism 72) corresponding to the nozzle to be discharged.

  The switching element 34 is an FET (Field Effect Transistor), for example, an n-channel MOSFET. Although it is desirable that this FET has a low resistance, an appropriate one is selected according to the assumed load range. Alternatively, the switching element 34 may be a bipolar transistor, and a control signal from the load control unit 35 may be applied to the base terminal.

  The load control unit 35 reads raster image data for image formation, detects in advance the start timing of ink discharge, and switches the switching element 34 based on the ink discharge amount for a predetermined row (predetermined block) after the start of the ink discharge. And the load of the pressure mechanism 72 necessary for the discharge operation of the ink amount discharged in the predetermined row to the DC / DC converter 31 before the ink discharge is actually started by the resistance element 33. And corresponding load.

The load control unit 35 includes a CPU 351 (output determination unit) and a RAM 352 (buffer storage unit). The RAM 352 can store a predetermined number of rows of image data before being output to the inkjet head 70. Here, the RAM 352 can store raster image data for “N + X” rows, and when raster image data for the next row is input, the data of the oldest acquired row is output to the inkjet head 70. Functioning as a buffer.
The number of rows “N” corresponds to the response time of the DC / DC converter 31 with respect to a change in load. The number of rows “X” (predetermined number of blocks) is the number of rows used when acquiring the ink discharge amount in order to determine the magnitude of the load applied to the DC / DC converter 31 by the load controller 35. . The CPU 351 performs switching control of the switching element 34 based on the raster image data stored in the RAM 352.

  As described above, when a plurality of voltage control units 30 are provided, the resistance element 33 and the switching element 34 respectively corresponding to the voltage control unit 30 are provided, and the load control unit 35 is used in common, and the power supply unit The DC / DC conversion unit 31 for inputting a voltage from 37 is selected, and the switching element 34 for switching on / off the voltage supply to the resistance element 33 is collectively controlled to be switched by one load control unit 35. A plurality of voltage control units 30 can be controlled.

Next, a method for controlling the output voltage of the DC / DC converter 31 will be described.
FIG. 3A is a schematic diagram illustrating the relationship between the output voltage of the DC / DC converter and the head load.

  When the power consumption is larger than the power capacity of the DC / DC conversion unit 31, the output voltage of the DC / DC conversion unit 31 decreases from a preset voltage according to the magnitude of the power consumption. In a state where the switching element 34 is open (off) and the inkjet head 70 is in a non-driven state, that is, when no load is applied, the power consumption is almost negligible, and the voltage drop is No (period p1).

  Subsequently, when the driving of the inkjet head 70 is started at a time of 0.4 ms (supply start timing), a driving voltage is applied to the pressure mechanism 72 (piezoelectric element) that discharges ink from the nozzle, and a load is generated, DC The voltage output from the / DC converter 31 drops and fluctuates (period p2). The amount of decrease is determined according to the power capacity of the DC / DC converter 31 and the magnitude of power consumption. The duration (response period) of this fluctuation is relative to the damped vibration that occurs in accordance with the inductance of the coil used in the DC / DC converter 31 and the capacitance of the capacitor and the load associated with driving the inkjet head 70. The time constant is determined based on the effect of the operation (such as the PWM pulse frequency and pulse variable width) performed by the compensation circuit 32 to stabilize the voltage. Here, as described above, a voltage drop appears over a length corresponding to N times in the drive pulse indicating the ejection timing of the ink. This voltage drop is accompanied by an overshoot. Thereafter, the output voltage is stabilized at a voltage drop width corresponding to the load (period p3).

  This response time (time constant) can be determined using a calculated value of voltage change obtained by numerical simulation of the voltage control unit 30. For example, the moving average of voltage values within a predetermined time width (for example, the average value of the voltage value of the target time and the voltage value before the predetermined time), the integrated value of the absolute value of the voltage change amount, etc. The change level sufficiently attenuates the timing when the amount or the latter value is below a predetermined level (for example, ± 1.0% or less of the initial fluctuation amplitude (the difference in drive voltage before and after the change)), and the drive voltage after the change By setting the timing as converged to, the response time can be obtained while eliminating the influence of the maximum and minimum of the voltage due to ON / OFF of the resistance element 33 or the like.

  Here, when calculating the response time related to the voltage control unit 30, it is not necessary to actually perform numerical calculation including the circuits related to the head drive unit 71 and the inkjet head 70, and when the switching element 34 is turned on. In addition, the resistance value of the resistance element 33 may be determined to perform numerical calculation so that a load corresponding to the load generated in the inkjet head 70 is generated in the resistance element 33. The load corresponding to the load generated in the inkjet head 70 is, for example, a resistance value such that a total current consumption flows to the resistance element 33 when a predetermined drive voltage is applied to the pressurizing mechanisms 72 of all the nozzles of the inkjet head 70. Can be set. For example, in a case where a consumption current of 0.5 A in total flows by applying a driving voltage to all of the nozzles of the inkjet head 70 having 512 nozzles, the resistance value for flowing the consumption current is 30.4Ω. . In the same simulation as the pattern shown in FIG. 3A, the drive voltage is supplied to the resistance element 33 in a pulse form at a cycle of 20 ms from the timing of 0.4 ms. As a result, the drive voltage of 15.2V is about 15.05V. And converges to a fluctuation amplitude of ± 1.5 μV or less after 300 μs (15 cycles).

  FIG. 3B is a schematic diagram illustrating the relationship between the output voltage of the DC / DC conversion unit, the resistance load, and the head load in the inkjet recording apparatus of the present embodiment. FIG. 3C is a schematic diagram showing a load pattern when the resistive load is subjected to PWM control.

  In the ink jet recording apparatus 1 according to the present invention, as shown in FIG. 3B, before the ink jet head 70 is driven at time = 0.4 ms and the supply of the drive voltage to the pressurizing mechanism 72 is started. In the period when the driving voltage is not supplied to the pressurizing mechanism 72 of any nozzle, that is, the period when the head load is zero (period q1), the switching element 34 is turned on and the resistance element 33 performs DC in advance. A load is applied to the DC converter 31. Here, the driving state is started N times before the supply start timing (15 times in the above simulation example) (predetermined time), that is, before the response time of the supply start timing of the drive voltage. Until just before the switching, the switching element 34 is turned on, and the output voltage of the DC / DC converter 31 is supplied to the resistance element 33. As a result, the driving operation related to ink ejection is already started in a stable state with the output voltage from the DC / DC converter 31 decreasing (period q2).

In addition, even when the switching element 34 is turned on after the drive pulse is input N times before or when the switching element 34 is turned off before the drive voltage supply start timing, The output voltage from the DC / DC converter 31 is not completely reduced to a value corresponding to the load of the resistance element 33 unless the voltage once reduced and the voltage once reduced completely returns to the original output voltage. Although it is in a state, the amount of decrease in the drive voltage after the drive voltage supply start timing is smaller than the amount of decrease in the case shown in FIG. 3A, and the drive voltage quickly corresponds to the load of the pressurizing mechanism 72. It becomes. That is, the switching element 34 has a predetermined period (at least a part of the period) before the supply start timing so that the drive voltage of the pressurizing mechanism 72 is lower than the initial state at the drive voltage supply start timing. When turned on, a load is generated by the resistance element 33.
In this case, the amount of decrease in the output voltage at the start of supply of the drive voltage (rather than the amount of decrease in the output voltage in the period q1 (when supply of the output voltage to the resistance element 33 is started) due to the switching element 34 being turned on. It is preferable to set and control the period during which the switching element 34 is turned on so that the amount of drop that occurs temporarily only near the top in the period q2 is small.

  As shown in FIG. 3B, the load applied to the DC / DC converter 31 by the resistance element 33 enters the driving state as shown in FIG. 3C in addition to the case where it is set continuously. The duty ratio may be intermittently determined by PWM control in accordance with the size of a load assumed later. In this case, the switching element 34 is switched on and off at a time ratio corresponding to the duty ratio. Each timing at which the switching element 34 is turned on can be synchronized with the drive pulse. In this case, the drive pulse is also input to the load control unit 35.

  As described above, the voltage after the drop can be set by adjusting the magnitude of the load more finely by the PWM control. Therefore, the voltage value after the voltage drop due to the nozzle operation can be stabilized more promptly after the ink jet head 70 starts to be driven.

Next, the switching operation of the switching element 34 will be described.
FIG. 4 is a flowchart showing a control procedure of the load control process executed by the load control unit 35.

This load control process is started as part of the image formation process when an image formation command and image formation target image data are received from an external print server or the like. The image data in this case may be a single recording medium (one page) to be output, or may be image data of each page of image data over a plurality of pages. Further, in a later-described scanning inkjet recording apparatus or the like, a recorded image is formed in band units within the same page or the like, and the recording medium is sequentially transferred by the transport unit 60 each time the band unit image formation is intermittently performed. It may be started according to data input for each band or processing start timing in the case of conveyance.
When the load control process is started, the CPU 351 first activates and initializes the DC / DC converter 31 and the compensation circuit 32 (step S201). In this state, after the drive voltage is output to the inkjet head 70, the drive voltage is not applied to the load element (piezoelectric element) of each nozzle.

The CPU 351 permits reading of raster image data to be image formed from the control unit 10, and starts reading data of each row of the raster image data (step S202).
The CPU 351 determines whether or not ink is ejected from each nozzle of the read line, and counts the number of nozzles (number of operations) from which ink is ejected (step S203).

  The CPU 351 determines whether or not the counted number of ink ejection nozzles is “0” (step S204). If it is determined that the value is “0” (“YES” in step S204), the processing of the CPU 351 proceeds to step S207. At this time, the CPU 351 counts the number of rows determined to be “0” continuously.

  If it is determined that the number of ink ejection nozzles is not “0” (“NO” in step S204), the CPU 351 continues for “N + X” rows or more until the previous row, and the number of ink ejection nozzles is “0”. It is determined whether or not (step S205). If it is determined that it is not “0” after the “N + X” line (“NO” in step S205), the processing of the CPU 351 proceeds to step S207. When it is determined that “0” continues for “N + X” rows or more (“YES” in step S205), the CPU 351 sets a flag indicating that ink ejection is started or resumed from a state where there is no ink ejection. Turn on (set) (step S206). Then, the process of the CPU 351 proceeds to step S207.

  In step S207, the CPU 351 determines whether or not the flag is on (step S207). If it is determined that the flag is not on (“NO” in step S207), the processing of the CPU 351 proceeds to step S211. If it is determined that the flag is on (“YES” in step S207), the CPU 351 subsequently obtains the value of the number of ink ejection nozzles for “X” rows after the flag is turned on. Is determined (step S208). If it is determined that it has not been acquired (“NO” in step S208), the processing of the CPU 351 proceeds to step S211.

  If it is determined that the value of the number of ink ejection nozzles for “X” rows has been acquired (“YES” in step S208), the CPU 351 determines whether the value of DC / DC is based on the acquired value of the number of ink ejection nozzles. The output voltage control level from the converter 31 is determined (step S209). The CPU 351 starts driving voltage control according to the determined output voltage control level (step S210). Then, the process of the CPU 351 proceeds to step S211.

  When the process proceeds from the process of steps S207, S208, and S210 to the process of step S211, the CPU 351 is in the flag-on state, and whether or not the drive voltage is controlled while the raster image data for N rows is input / output. Is determined (step S211). If it is determined that the drive voltage is controlled while the flag is on and the raster image data for N rows is input / output (“YES” in step S211), the CPU 351 And the flag is turned off (reset) (step S212). Then, the process of the CPU 351 proceeds to step S213. If it is determined that the flag is not in the ON state, or that the drive voltage is not controlled while the raster image data for N rows is input / output (“NO” in step S211), the CPU 351 The process proceeds to step S213 as it is.

  When the process proceeds to step S213, the CPU 351 outputs the oldest row data currently stored in the RAM 352 to the inkjet head 70 (step S213). At this time, in the process of step S212, the CPU 351 cancels the drive voltage control, and simultaneously instructs the inkjet head 70 to shift to the drive state, thereby maintaining the non-drive state until immediately before starting the drive operation.

  The CPU 351 determines whether or not all rows of data related to the output image have been output (step S214). If it is determined that all rows of data have not been output (there is data that has not been output) ("NO" in step S214), the processing of the CPU 351 returns to step S203. If it is determined that all the rows of data have been output (“YES” in step S214), the CPU 351 performs settings related to the end of drive voltage output (step S215). The CPU 351 can shift the inkjet head 70 to a non-driven state after the inkjet head 70 has been driven according to the last output row data. Then, the load control process is terminated.

  Here, as a case of shifting to “YES” in the determination processing in step S205, a case where a blank portion is included in the middle of the image formation in addition to the case of shifting from the margin at the top of the page at the start of image formation to the image formation range. In some cases, the process proceeds from the blank portion to the image forming portion. In consideration of such a case, if the process of step S204 continues (N + X) lines and branches to “YES”, it can be temporarily shifted to the non-driven state. Thereby, the operation of each nozzle is not performed in the head drive unit 71 in the blank portion.

As described above, the inkjet recording apparatus 1 supplies a driving voltage to the inkjet head 70 in which a plurality of nozzles are arranged and the pressurizing mechanism 72 (piezoelectric element) of each nozzle based on the formed image data. The pressure driving mechanism 72 is connected to the head driving unit 71 that operates the pressure mechanism 72, the voltage control unit 30 that performs a control operation so as to suppress fluctuations in the driving voltage supplied to the head driving unit 71, and the pressure control unit 72. (Resistive element 33 provided corresponding to (piezoelectric element)), switching element 34 for switching whether to supply the output voltage from the DC / DC converter 31 to the resistive element 33, and the pressurizing mechanism 72 Before the supply start timing for starting the supply of the output voltage, and at least part of the period in which the drive voltage is not supplied to any of the pressurizing mechanisms 72, the resistance element 33 is supplied with DC It includes a load control unit 35 for controlling the switching element 34 to provide an output voltage from the DC converter unit 31, a.
As described above, before the supply of the drive voltage to each pressurizing mechanism 72 of the inkjet recording apparatus 1 is started and the operation of ejecting ink to each nozzle is started, the DC / DC conversion unit 31 applies the resistance element 33 in advance. By supplying the output voltage, a load corresponding to the load related to the ink discharge operation is applied to the DC / DC converter 31. At the time when the ink discharge operation is started, the output voltage from the DC / DC converter 31 (that is, the output voltage) , The driving voltage of the pressurizing mechanism 72) can be reduced. Therefore, the fluctuation of the driving voltage that occurs when the supply of the driving voltage to the pressurizing mechanism 72 is started can be reduced more easily than in the past, thereby reducing the ink density and unevenness in the vicinity of the head of the formed image. An image having a stable density can be formed while being suppressed.

  In addition, since ink density lowering and unevenness can be suppressed by simple software control, the capacity of the smoothing capacitor is increased to increase the size in order to shorten the response time to voltage fluctuation in the voltage control unit 30, There is no need to complicate the hardware configuration.

  In addition, in the state where the output voltage from the DC / DC converter 31 is lowered by the supply of the output voltage (drive voltage) to the resistance element 33, the drive voltage is supplied from the DC / DC converter 31 to the pressurizing mechanism 72. Since the process is started, the magnitude and length of the rapid fluctuation of the drive voltage that occurs at the time of transition from the non-drive state to the drive state can be reduced.

  Further, the amount of decrease in the drive voltage at the start of supplying the drive voltage to the pressurizing mechanism 72 is equal to or less than the amount of decrease in the output voltage at the start of supplying the output voltage from the DC / DC converter 31 to the resistance element 33. Therefore, it is possible to more effectively suppress fluctuations in the drive voltage at the start (resumption) of image formation and reduce the occurrence of ink density unevenness.

  In addition, the amount of decrease in the driving voltage at the start of supplying the driving voltage to the nozzle pressing mechanism 72 is such that the driving voltage is supplied to the pressing mechanism 72 without supplying the output voltage to the resistance element 33 as shown in FIG. 3A. Is controlled so as to be smaller than the amount of decrease in the drive voltage at the start of the virtual supply, that is, by appropriately determining the supply period of the output voltage to the resistance element 33, and thereafter to the pressurizing mechanism 72. It is possible to easily reduce the occurrence of ink density unevenness due to the drive voltage fluctuation at the drive voltage supply start timing.

  In addition, when the response time is defined as the time from when the output voltage is supplied to the resistance element 33 from the DC / DC conversion unit 31 until it converges to a predetermined output voltage (drive voltage), the load control unit 35 Controls the switching element 34 so as to supply the output voltage to the resistance element 33 from before the supply start timing response time for supplying the drive voltage to the nozzle pressurizing mechanism 72 until the supply start timing. That is, the output voltage is supplied to the resistance element 33 for a suitable time until the drive voltage decreases and stabilizes according to the load of the resistance element 33, whereby the fluctuation of the drive voltage at the start of supply of the drive voltage. Can be suppressed more effectively. Moreover, since it is not necessary to flow current through the resistance element 33 more than necessary, an increase in unnecessary power consumption can be suppressed.

  The drive voltage supply start timing includes a timing at which the drive voltage is supplied to the pressure mechanism 72 of the nozzle at the start of image formation for one page. That is, when image formation is performed in units of pages, fluctuations in drive voltage due to interruption of driving of the pressurizing mechanism 72 between pages are effectively suppressed every time, so that density unevenness of ink or the like occurs near the top of each page. Can be suppressed.

  In addition, a transport unit 60 that transports the recording medium P on which an image is formed by the inkjet head 70 is provided, and the transport unit 60 includes an encoder 61. The position of the recording medium P with respect to the nozzle is acquired by measuring the moving distance of the recording medium P from the start of conveyance with the encoder 61. The drive voltage supply start timing is such that the recording medium P transported by the transport unit 60 corresponds to the plurality of nozzles set for the recording medium P in the transport direction of the recording medium P by the transport unit 60. The timing at which the position of the recording medium P (print start position) and the position at which the nozzle starts discharging ink is overlapped by the transport unit 60 is set. Therefore, since the moving distance of the recording medium P until the drive voltage supply start timing corresponding to the response time is calculated backward from the conveyance speed of the recording medium P by the encoder 61, the switching element is appropriately started from the time corresponding to the response time. The drive voltage can be supplied to the resistance element 33 by turning on 34.

Note that when the scanning method is used instead of the one-pass method using the line head as the image forming apparatus, the width of the recording medium P in which the inkjet head is in a direction perpendicular to the conveyance direction along the guide rail by a power source (for example, a motor). An image (one band image) is formed on the recording medium P in units of bands having a predetermined length in the transport direction while reciprocating along the direction and extending across the width of the recording medium P in the width direction. The transport unit 60 forms the entire image by repeating the operation of moving the recording medium P by the predetermined length every time the band-unit image is formed. In the case of using such a scan type image forming apparatus, for example, in addition to the encoder 61 described above, a second encoder (second measuring unit) is further provided on the rotating shaft of a motor for reciprocating the recording head, and the recording head is reciprocated. It is preferable that one end in the width direction to be moved is “0” and the moving distance in the width direction of the recording head is measured. In the case described above, the drive voltage supply start timing is set for the recording medium P while the recording medium P transported by the transport unit 60 reaches the print start position set for the recording medium P. This is when the recording head moves to the position of the recording medium with respect to the plurality of recording elements in the direction in which the recording head is reciprocated. Therefore, when using the scan type image forming apparatus, the moving distance of the recording medium P by the transport unit 60 and the moving distance of the recording head that is reciprocated by the power source are set as the print start position.
In the above description, the second encoder is provided on the rotating shaft of the motor for reciprocating the recording head, and one end in the width direction for reciprocating the recording head is set to “0”, and the moving distance of the recording head is measured. As shown, for example, a separate linear scale may be provided on the guide rail, and the moving distance of the recording head may be measured by reading the linear scale with an optical sensor such as a CCD camera or a magnetic sensor.
Even with such a configuration, similarly to the one-pass ink jet recording apparatus, the drive voltage supply start timing is appropriately acquired in advance, and the output voltage is applied to the resistance element 33 in an appropriate period. Thus, fluctuations in the driving voltage at the start of supplying the driving voltage can be reduced.

  Further, in such a scanning type ink jet recording apparatus, the driving of the pressurizing mechanism 72 is interrupted every time one band image is formed, so that the drive voltage supply start timing related to the start of image formation of each band is reached. Accordingly, by applying the output voltage to the resistance element 33 in advance, it is possible to reduce fluctuations in the drive voltage at the start of image formation for each band and the resulting ink density unevenness.

  Further, as the magnitude of the load amount generated in the inkjet head 70, 50% of the load amount applied to the voltage control unit 30 (DC / DC conversion unit 31) when supplying the drive voltage to all nozzles of the inkjet head 70. By setting the load amount, the control becomes easier and the magnitude of the deviation from the actual load amount can be reduced to half of the conventional load amount.

  Further, the load control unit 35 adjusts the period during which the output voltage (driving voltage) is applied to the resistance element 33 by PWM control so that the load by the resistance element 33 has a predetermined magnitude. It is possible to apply an appropriate load to the DC / DC converter 31 with easy control without increasing the number of components by the element 33 more than necessary.

The load control unit 35 includes a RAM 352 that sequentially stores the formed image data and a CPU 351. The CPU 351 serving as an output determination unit at least in each row in which image formation is simultaneously performed on the stored formed image data. It is determined whether or not to operate the pressurizing mechanism 72 of one nozzle. When data of a row that operates the pressurizing mechanism 72 of at least one nozzle is acquired, the head drive is performed based on the data of the row. The drive voltage is applied to the resistance element 33 until the drive voltage is applied to the pressure mechanism 72 by the unit 71 and before the pressure mechanism 72 operates.
Therefore, it is possible to easily detect the start timing of the nozzle operation in advance and to energize the resistance element 33 at an appropriate timing.
Here, “simultaneous” refers to a range in which the output periods of the drive voltage pulses partially or entirely overlap.

  Further, the CPU 351 serving as an output determination unit counts the number (the number of operations) of the pressure mechanisms 72 operated in each row based on the data of each row stored in the RAM 352. Based on the number of nozzle operations in the first X rows that have shifted from the driving state to the driving state, the magnitude of the load by the resistance element 33 is determined. That is, since the output voltage of the DC / DC converter 31 is changed to a corresponding drop voltage according to the magnitude of the voltage drop from the non-drive state to the drive state, the voltage fluctuation after the actual operation of the pressurizing mechanism 72 starts. Can be suppressed more effectively.

  In addition, since the voltage is supplied to the resistance element 33 before the response time longer than the time required to output data of two or more rows, the raster data of the formed image stored in the RAM 352 is effectively used and supplied in advance. The voltage can be stabilized at a level corresponding to the number of nozzle operations.

  In particular, by applying the present invention to an ink jet recording apparatus having an ink jet head 70 that forms an image by ejecting ink with a plurality of nozzles arranged, the ink concentration that reacts sensitively to the drive voltage is further stabilized. To form an image.

  In addition, since the voltage supplied to the piezoelectric element that is the load element is stably controlled, the deformation amount of the piezoelectric element can be accurately controlled to prevent occurrence of unevenness in the formed image.

The present invention is not limited to the above-described embodiment, and various modifications can be made.
For example, in the above embodiment, the image data is actually acquired and the presence / absence of driving by the head driving unit 71 is determined in advance, but more simply, when performing image output without providing a margin on the recording medium, In the case of an image in which the head is always driven within the margin, image data may be output to the inkjet head 70 after a load is simply applied by the resistance element 33 for a response time. Alternatively, instead of performing control in real time, when generating raster image data for image formation, information is generated in advance regarding the lines in which the nozzles are not continuously operated, and the load control unit 35 includes the information. Based on this, the switching element 34 may be operated.

  Although the DC / DC converter and the compensation circuit are used for the output of the drive voltage, the drive voltage may be configured using another DC voltage control such as a three-terminal regulator.

  The resistance element 33 is not limited to a single resistor. A plurality of resistors may be arranged in series or in parallel, and switching control may be performed collectively or individually. The resistance element 33 may be an element that limits current, such as a constant current diode.

  In the above embodiment, the CPU 351 counts the number of ink ejection nozzles, but it may be a flag for simply determining whether or not ink is ejected. In this case, the load by the resistance element 33 is set to a fixed value regardless of the number of ink ejection nozzles. The fixed value may be an average value or may correspond to a load when one half of all the central nozzles is driven (ink is ejected). Thereby, it is possible to at least halve the voltage change amount while further simplifying the processing with the simple circuit configuration shown in FIG.

  Moreover, although the said embodiment demonstrated the case where an ink was discharged from the nozzle for one line at a time, it is not restricted to this. For example, when nozzles arranged in a pattern across multiple rows are made into one block and ink is ejected all at the same time, or in a single row or multiple rows of nozzle arrangement, divided into multiple blocks for each predetermined row and / or column When ink is ejected for each block, control related to a decrease in drive voltage can be performed in units of blocks to which the drive voltage is applied simultaneously.

  In the above-described embodiment, the configuration having the head drive unit 71 inside the inkjet head 70 is described as an example. However, the head drive unit 71 may be provided outside the inkjet head 70. In this case, for example, a head drive unit that generates only a drive waveform based on the drive voltage and the drive pulse is provided outside the inkjet head 70, and the drive waveform is added in the inkjet head 70 based on a signal obtained by decoding the image data. Whether to output to the pressure mechanism 72 can be switched.

In the above embodiment, the inkjet recording apparatus has been described as an example. However, the present invention is also applied to other apparatuses that form an image by combining pixel points from a plurality of output elements, for example, LED printers. I can do it.
In addition to the piezo ink jet recording apparatus, these image forming apparatuses also apply the present invention to the suppression of fluctuations in the voltage applied to the heater resistor, which is a load element in the thermal ink jet recording apparatus. I can do it.
In addition, specific details such as the configuration, control procedure, and numerical values shown in the above embodiment can be changed as appropriate without departing from the spirit of the present invention.

  The present invention can be used in an image forming apparatus.

1 Inkjet recording apparatus 10 Control unit 101 CPU
102 RAM
20 Storage Unit 30 Voltage Control Unit 31 DC / DC Conversion Unit 32 Compensation Circuit 33 Resistance Element 34 Switching Element 35 Load Control Unit 351 CPU
352 RAM
37 Power supply unit 40 Communication unit 50 Operation display unit 60 Transport unit 61 Encoder 70 Inkjet head 71 Head drive unit 711 Decoder circuit 712 Driver circuit 72 Pressure mechanism 90 Power supply unit

Claims (18)

A recording head in which a plurality of recording elements are arranged;
A driving unit for supplying a driving voltage to the load element of the recording element based on the formed image data and operating the load element;
A voltage control unit that performs control so as to suppress fluctuations in the drive voltage supplied to the drive unit;
A resistance element connected to the voltage control unit and provided corresponding to a load element of the recording element;
A switching element for switching whether to supply the drive voltage to the resistance element;
Before the supply start timing for supplying the drive voltage to the load element of the recording element and at least part of a period in which the drive voltage is not supplied to any of the load elements of the recording element, A load controller that controls the switching element to supply a driving voltage;
An image forming apparatus comprising:   2. The image forming apparatus according to claim 1, wherein supply of the drive voltage to a load element of the recording element is started in a state where the drive voltage is lowered by supply of the drive voltage to the resistance element. .   The amount of decrease in the drive voltage at the start of supplying the drive voltage to the load element of the recording element is equal to or less than the amount of decrease in the drive voltage at the start of supplying the drive voltage to the resistance element. The image forming apparatus according to claim 1, wherein:   The amount of decrease in the driving voltage at the start of supplying the driving voltage to the load element of the recording element supplies the driving voltage to the load element of the recording element without supplying the driving voltage to the resistance element. The image forming apparatus according to claim 1, wherein the image forming apparatus is smaller than a decrease amount of the drive voltage at the start of virtual supply. When the response time is the time from the fluctuation of the driving voltage when the driving voltage is supplied to the resistance element until it converges to a predetermined driving voltage,
The switching element is configured to supply the drive voltage to the resistance element from the response start time before supply start timing for supplying the drive voltage to the load element of the recording element until the supply start timing. The image forming apparatus according to claim 1, wherein the image forming apparatus is controlled.   6. The image formation according to claim 1, wherein the supply start timing includes a timing at which the drive voltage is supplied to a load element of the recording element at the start of image formation of one page. apparatus.   The supply start timing is when forming the image by repeatedly moving the recording head along the recording medium to form a one-band image and transporting the recording medium to form the next one-band image. 6. The image forming apparatus according to claim 1, further comprising a timing for supplying the drive voltage to a load element of the recording element at the start of image formation of one band. A transport unit that transports a recording medium on which an image is formed by the recording head;
The transport unit includes a first measurement unit that measures positions of the recording medium with respect to the plurality of recording elements in a transport direction of the recording medium,
The supply start timing is determined based on the position of the recording medium relative to the plurality of recording elements in the conveyance direction of the recording medium set for the recording medium and the operation related to the start of printing on the recording medium. The image forming apparatus according to claim 1, wherein the image forming apparatus is a timing at which the recording unit is transported to a position where the recording element overlaps a position where the recording element is started. A transport unit for transporting a recording medium on which an image is formed by the recording head;
A power source for reciprocating the recording head in a direction orthogonal to the conveyance direction of the recording medium;
With
The transport unit includes a first measurement unit that measures positions of the recording medium with respect to the plurality of recording elements in a transport direction of the recording medium,
The power source has a second measurement unit that measures positions of the recording medium with respect to the plurality of recording elements in a direction in which the recording head reciprocates.
The supply start timing is determined by the position of the recording medium relative to the plurality of recording elements in the conveyance direction of the recording medium set for the recording medium and the start of printing on the recording medium. The recording element is transported to the position where it overlaps the position in the transport direction of the recording medium that causes the recording element to start operation, and the recording head set for the recording medium is reciprocated. A timing at which the power source moves to a position where a position of the recording medium with respect to the plurality of recording elements in a direction to be overlapped with a position at which the recording element starts the operation related to the start of printing. The image forming apparatus according to claim 1.   The load control unit is 50% of a load amount applied to the voltage control unit when supplying the drive voltage to all of the load elements of the plurality of recording elements as a magnitude of a load amount by the resistance element. The image forming apparatus according to claim 1, wherein a load amount is set.   The load control unit adjusts a period during which the drive voltage is supplied to the resistance element by PWM control so that a load amount by the resistance element becomes the set size. Image forming apparatus. The load control unit
A buffer storage unit for sequentially storing the formed image data;
Output discriminating means for discriminating whether or not to operate at least one load element of the recording element in each block in which image formation is performed simultaneously with the stored formation image data;
When data of a block for operating the load element of the recording element is acquired by the output determining means, the resistance element is used until before the load element is operated by the drive unit based on the data of the block. The image forming apparatus according to claim 1, wherein the driving voltage is supplied to the image forming apparatus. The output determination means counts the number of operations of the load element of the recording element operated in each block,
The load control unit determines a magnitude of a load amount by the resistance element based on the number of operations in an initial predetermined number of blocks in which the driving unit shifts from a non-driving state to a driving state. Item 13. The image forming apparatus according to Item 12.   8. The load control unit according to claim 7, wherein a period during which the drive voltage is supplied to the resistance element is adjusted by PWM control so that a load amount by the resistance element becomes the set magnitude. Image forming apparatus. When the response time is the time from the fluctuation of the driving voltage when the driving voltage is supplied to the resistance element until it converges to a predetermined driving voltage,
The switching element is configured to supply the drive voltage to the resistance element from the response start time before supply start timing for supplying the drive voltage to the load element of the recording element until the supply start timing. The image forming apparatus according to any one of claims 12 to 14, wherein the image forming apparatus is controlled.   16. The image forming apparatus according to claim 15, wherein the response time is equal to or longer than a time required for image formation for two blocks. The recording head is an inkjet head;
The image forming apparatus according to claim 1, wherein the recording element is a nozzle and an ink ejection mechanism that ejects ink from the nozzle.   The image forming apparatus according to claim 1, wherein the load element of the recording element is a piezoelectric element.

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