JP2006116705A - Liquid droplet discharging apparatus and liquid droplet discharging control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To carry out image formation of many gradations by securing a stable liquid droplet discharging amount according to an ink viscosity change while wasting of a recording medium is surely prevented. <P>SOLUTION: A driving control means which controls discharging of ink droplets by supplying a drive signal to an actuator is equipped with a drive signal generating circuit 70 which serves both as a drive signal generating means for outputting a drive signal for discharging control of liquid droplets to the actuator, and as a residual vibration generating means for outputting a drive signal for residual vibration generation to generate residual vibration in a pressure chamber to the actuator; a residual vibration detecting means 150 which detects a residual vibration waveform generated at the residual vibration generating means; and a signal compensating means 80 for compensating the drive signal for discharging control on the basis of a deviation between a peak value of the residual vibration waveform detected at the residual vibration detecting means and a target peak value. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a droplet discharge device such as an ink jet printer and a droplet discharge control method.

An ink jet printer, which is one of droplet discharge devices, forms an image on a predetermined recording medium by discharging ink droplets (droplets) from a plurality of nozzles formed on a recording head. As this recording head, there is known a recording head in which pressure fluctuation is generated in a pressure chamber communicating with a nozzle by an actuator, and ink droplets are ejected from a nozzle opening.
Various systems have been proposed as such a recording head. These methods are roughly classified into a piezo method and a film boiling ink jet method.

In the piezo method, a driving signal is given to a piezo element which is an actuator, so that a vibration plate in the cavity serving as a pressure chamber is displaced to cause a pressure change in the cavity, and the ink change is ejected from the nozzle by the pressure change. I have to.
On the other hand, in the film boiling ink jet system, a micro heater is provided in the cavity, and the ink in the cavity is instantaneously heated to 300 ° C. or more by the micro heater to generate bubbles in a film boiling state. The ink droplets are ejected from the nozzles by the change.

  In such a recording head, printing is performed by forming dots by ink droplets ejected from each nozzle landing on the recording medium. In order to improve gradation expression of one pixel, it is necessary to record one pixel with a plurality of different types of dots. In multi-tone printing, one pixel is formed by selecting from a plurality of types of ink droplets of small ink droplets in large steps. In order to form such a plurality of types of ink droplets, control can be performed by changing the waveform of the drive signal of the piezo element that is the actuator of the recording head. However, it can be controlled by changing the ink drop and at the same time changing the ejection speed of the ink drop. However, since the ejection speed of the ink drops changes at the same time, the ejection speed of each size changes due to the manufacturing variation of the recording head and the change in the ambient temperature of the printer. There is an unsolved problem that the dot positions do not match in each element.

In order to solve this unresolved problem, pre-discharge printing is performed on a test chart, and this is read automatically by an image scanner and driven automatically so that the gradation dots match the ink droplet landing on the recording paper. An ink jet apparatus that adjusts signal timing is known (see, for example, Patent Document 1).
JP-A-9-109395 (first page, FIG. 1)

However, in the conventional example described in Patent Document 1, preliminary discharge printing on a test chart is necessary, and there is an unsolved problem that recording paper is wasted.
Therefore, the present invention has been made paying attention to the unsolved problems of the above-described conventional example, and ensures a stable droplet discharge amount according to changes in ink viscosity while reliably preventing waste of the recording medium. It is an object of the present invention to provide a droplet discharge apparatus and a droplet discharge control method capable of forming a multi-tone image.

  According to a first aspect of the present invention, a plurality of pressure chambers filled with a liquid therein, a plurality of nozzles that individually communicate with the pressure chamber and discharge the liquid as droplets, and a pressure signal input to the pressure chamber. A droplet discharge device comprising a droplet discharge head having an actuator for changing the pressure to discharge a droplet from the nozzle to a recording medium, and a drive control means for controlling the drive by supplying a drive signal to the actuator The drive control means outputs a drive signal generation means for outputting a droplet discharge control drive signal to the actuator, and a residual vibration generation drive signal for generating residual vibration in the pressure chamber to the actuator. Residual vibration generating means, residual vibration detecting means for detecting the residual vibration waveform generated by the residual vibration generating means, and the height of the residual vibration waveform detected by the residual vibration detecting means It is characterized in that it comprises a signal compensation means for compensating the ejection control drive signal based on the deviation between the target peak value and.

  In the first aspect of the invention, a residual vibration generating drive signal is output to an actuator that discharges droplets by the residual vibration generating means to generate the residual vibration in the pressure chamber, and the peak value of the residual vibration is determined as the residual vibration. Since the discharge control drive signal is compensated by the signal compensation means based on the deviation between the detected peak value and the target peak value detected by the detection means, the peak value of the residual vibration is proportional to the temperature change, Since it is proportional to the ink viscosity, it is possible to compensate for the drive signal in consideration of the ink viscosity to ensure a stable droplet discharge amount and to form a multi-tone image.

In a second aspect based on the first aspect, the residual vibration generating means is configured such that the residual vibration generating drive signal is set to a voltage that generates residual vibration in a non-ejection state of droplets from the nozzle. It is characterized by that.
In the second aspect of the invention, since the residual vibration generating drive signal is set to a voltage that generates residual vibration in a non-ejection state of the liquid droplets from the nozzle, the image forming process using ink droplets is not affected. A compensation value for compensating the ejection control drive signal can be set.

The third invention is characterized in that, in the first or second invention, the residual vibration generating drive signal also serves as a fine vibration drive signal for a nozzle that does not eject droplets.
In the third aspect of the invention, since the residual vibration generation drive signal also serves as the fine vibration drive signal for the nozzles that do not eject droplets, it is possible to prevent the ink from solidifying in the nozzles that are not ejecting droplets. .

  According to a fourth invention, in any one of the first to third inventions, the ejection control drive signal is a plurality of drive signals capable of forming a plurality of gradation dots in time series for one pixel. The drive signals are arranged in time sequence in order of decreasing discharge speed, and the crest values of the drive signals are set so that the discharge speeds corresponding to the landing times of the respective gradation dots on the recording medium are the same. It is characterized by being.

  In the fourth aspect of the invention, the plurality of drive signals for forming a plurality of gradation dots for one pixel by the ejection control drive signal are sequentially arranged in order from the lowest discharge speed, and the gradation dots are recorded on the recording medium. Since the crest values of the respective drive signals are set so that the ejection speeds coincide with the landing times, multi-tone dots can be formed on the recording medium by selecting the drive signals for forming the respective gray-scale dots.

  According to a fifth invention, in any one of the first to fourth inventions, the residual vibration detection means is generated when the ground end of the actuator is opened and closed with respect to a ground, and the ground end is released. AC amplification means for amplifying the AC component of the residual vibration, peak hold means for holding the peak wave height value of the residual vibration amplified by the AC amplification means, and converting the peak wave value held by the peak hold means to digital data And an A / D conversion means.

  In the fifth aspect of the invention, the residual vibration detecting means is provided with a switch for opening and closing the ground end of the actuator with respect to the ground, and the AC component of the residual vibration generated when the ground end is opened by the switch is the AC amplifying means. The peak value of the AC amplification output is held by the peak hold means, and the held peak peak value is converted to digital data by the A / D conversion means, so that the residual vibration peak value is accurately determined. Can be detected.

  In a sixth aspect based on any one of the first to fifth aspects, the signal compensation means compares the target peak value with the detected residual vibration peak value, and calculates a deviation amount between them. A calculation means, a compensation calculation means for outputting a compensation value by performing at least a proportional and integral calculation on the deviation amount calculated by the deviation calculation means, and a sign of the compensation value calculated by the compensation calculation means is determined. And a code determination unit that outputs the determination result, and the determination result of the code determination unit is output to the ejection control drive signal generation unit.

  In the sixth aspect of the invention, the signal compensation means is a deviation calculating means, which compares the peak value of the residual vibration detected by the residual vibration detecting means with the target peak value to calculate a deviation amount between them, and calculates the calculated deviation. Compensation value is calculated by performing at least proportional and integral calculation with respect to the quantity by the compensation calculation means, the sign of the calculated compensation value is determined by the sign determination means, and the determination result and the compensation value are driven for discharge control By outputting to the signal generating means, the ejection control drive signal can be easily compensated by adding / subtracting with the compensation value.

  In a seventh aspect based on the sixth aspect, the ejection control drive signal generation means controls the offset value and the amplitude change of the drive signal from the waveform data of the reference control drive signal at the waveform data selection section. The drive signal is accurately and easily compensated by adding and subtracting the compensation value based on the sign determination result input from the signal compensation means to the separated waveform part by separating the waveform portion from the waveform portion. it can.

An eighth invention is characterized in that in any one of the first to seventh inventions, it is constituted by a piezoelectric actuator.
In the eighth aspect of the invention, since the actuator is composed of a piezoelectric actuator, the crest value of the residual vibration can be easily detected by detecting the electromotive voltage of the piezoelectric actuator.

According to a ninth invention, in any one of the first to seventh inventions, the invention is constituted by an electrostatic actuator.
In the ninth aspect of the invention, since the actuator is composed of an electrostatic actuator, the crest value of the residual vibration is determined by causing the applied voltage of the drive vibration to remain in the electrostatic actuator and between the electrodes of the electrostatic actuator. By detecting the displacement as a voltage change, the peak value of the residual vibration can be easily detected.

According to a tenth aspect of the present invention, a plurality of pressure chambers filled with a liquid therein, a plurality of nozzles individually communicating with the pressure chamber and ejecting the liquid as droplets, and a pressure signal input to the pressure chamber. An actuator that discharges droplets from the nozzles to the recording medium by changing the pressure; and a drive control unit that drives and controls the actuators, and the actuators are driven and controlled by the drive control unit. A droplet discharge control method for discharging droplets, wherein a reference signal for residual vibration generation is output to the actuator, the generated residual vibration is detected by a residual vibration detection means, and the detected residual vibration wave is detected. It is characterized in that the ejection control drive signal for controlling the ejection of droplets is compensated based on the deviation between the high value and the target peak value.
In the tenth aspect of the invention, similar to the first embodiment described above, since the peak value of the residual vibration is proportional to the temperature change and proportional to the ink viscosity, the drive signal is compensated in consideration of the ink viscosity. In addition, it is possible to form a multi-tone image while securing a stable droplet discharge amount.

An eleventh invention is characterized in that, in the tenth invention, the residual vibration detection timing by the residual vibration detection means is executed at a timing different from a normal droplet discharge timing.
In the eleventh aspect of the invention, since the residual vibration is detected at a timing different from the normal droplet ejection timing at which the ink droplets from the nozzles are not ejected, the compensation value setting process for the ejection control drive signal is performed. This can be performed without affecting the image forming process by ejection.

In a twelfth aspect based on the tenth aspect, the residual vibration is detected by the residual vibration detecting means at the time of turning on the power, at the elapse of a fixed time after the power is turned on, and completion of image formation on a predetermined number of recording media. It is characterized by being implemented in any one of each.
In the twelfth aspect of the invention, the residual vibration detection timing is set at least one of when the power is turned on, after every elapse of a certain time after the power is turned on, and every time when the image formation on a certain number of recording media is completed. Therefore, the compensation value setting process for the ejection control drive signal can be reliably performed without affecting the image forming process, and image formation on a certain number of recording media can be performed at every elapse of a certain time after the power is turned on. When it is performed every time it is completed, compensation value setting processing can be performed periodically, and accurate compensation control that follows changes in ink viscosity due to temperature changes can be performed.

Hereinafter, embodiments of a droplet discharge apparatus and a droplet discharge control method of the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view showing a schematic configuration when the liquid droplet ejection apparatus according to the first embodiment of the present invention is applied to an ink jet printer.
In the drawing, reference numeral 1 denotes an ink jet printer. The ink jet printer 1 includes an apparatus main body 2, and a tray 21 on which a recording paper P as a recording medium is placed on the upper rear side, and the recording paper P is ejected on the lower front side. A discharge port 22 is provided, and an operation panel 7 is provided on the upper surface.

The operation panel 7 is composed of, for example, a liquid crystal display, an organic EL display, an LED lamp, etc., and a display unit (not shown) for displaying a liquid crystal message and the like, and an operation unit (not shown) composed of various switches and the like. And.
Further, inside the apparatus main body 2, mainly, a printing apparatus 4 including a reciprocating printing unit 3, a paper feeding apparatus 5 that feeds recording paper P one by one to the printing apparatus 4, the printing apparatus 4, and paper feeding And a control device 6 for controlling the device 5.

  Under control of the control device 6, the paper feeding device 5 intermittently feeds the recording paper P one by one. The recording paper P passes near the lower part of the printing unit 3. At this time, the printing unit 3 reciprocates in a direction substantially orthogonal to the feeding direction of the recording paper P, and printing on the recording paper P is performed. That is, the reciprocation of the printing unit 3 and the intermittent feeding of the recording paper P become the main operation direction and the sub operation direction in printing, and ink jet printing is performed.

The printing apparatus 4 includes a printing unit 3, a carriage motor 41 that serves as a driving mechanism for moving the printing unit 3 in the main scanning direction, and a reciprocating mechanism 42 that reciprocates the printing unit 3 in response to the rotation of the carriage motor 41. It has.
The printing unit 3 includes a plurality of head units 35 corresponding to the type of ink having a plurality of nozzles 110 at a lower portion thereof, a plurality of ink cartridges 31 that supply ink to each head unit 35, and each head unit 35 and ink. And a carriage 32 on which the cartridge 31 is mounted.

Further, the head unit 35 includes a large number of ink jet recording heads (droplet discharge heads) 100 as shown in FIG.
As shown in FIG. 2, the inkjet head 100 includes a vibration plate 121, a piezoelectric actuator 122 that displaces the vibration plate 121, and a liquid ink inside, and the internal pressure is reduced by the displacement of the vibration plate 121. A cavity (pressure chamber) 123 that is increased or decreased, and a nozzle 124 that communicates with the cavity 123 and discharges ink as droplets by increasing or decreasing the pressure in the cavity 123 are provided.

More specifically, the inkjet head 100 includes a nozzle substrate 125 on which nozzles 124 are formed, a cavity substrate 126, a vibration plate 121, and a stacked piezoelectric actuator 122 in which a plurality of piezoelectric elements 127 are stacked. Yes.
The cavity substrate 126 is formed in a predetermined shape as shown in the figure, whereby a cavity 123 and a reservoir 128 communicating with the cavity 123 are formed. The reservoir 128 is connected to the ink cartridge 31 via the ink supply tube 129.

The piezoelectric actuator 122 includes comb-shaped electrodes 131 and 132 arranged opposite to each other, and piezoelectric elements 127 arranged alternately with the comb teeth of the electrodes 131 and 132. Further, one end of the piezoelectric actuator 122 is joined to the diaphragm 121 via the intermediate layer 130 as shown in FIG.
In the piezoelectric actuator 122 having such a configuration, a mode in which the actuator is extended or contracted in the vertical direction as shown in FIG. 2 by a drive signal from a drive signal source applied between the first electrode 131 and the second electrode 132. Is used. The piezoelectric actuator 122 is characterized in that a large driving force can be obtained because the piezoelectric elements 127 are laminated.

Therefore, in the piezoelectric actuator 122, when a drive signal as shown in FIG. 2 is applied, the diaphragm 121 is displaced, the pressure in the cavity 123 changes, and an ink droplet is ejected from the nozzle 124. .
The nozzles 124 for each inkjet head 100 formed on the nozzle substrate 126 shown in FIG. 2 are arranged, for example, as shown in FIG. In the example of FIG. 3, the arrangement pattern of the nozzles 124 when applied to four colors of ink (yellow Y, magenta M, cyan C, black K) is shown.

  The head unit 35 is shown in FIG. 1 as including the ink cartridge 31, but is not limited to such a configuration. For example, the ink cartridge 31 may be separately fixed and supplied to the head unit 35 by a tube or the like. Accordingly, in the following description, a unit provided with a plurality of inkjet heads 100 each including a diaphragm 121, an electrostatic actuator 122, a cavity 123, a nozzle 124, and the like separately from the printing unit 3 will be referred to as a head unit. .

  Note that full-color printing can be performed by using an ink cartridge 31 filled with ink of four colors, yellow, magenta, cyan, and black. In this case, the print unit 3 is provided with a head unit 35 corresponding to each color. Here, FIG. 1 shows four cartridges 31 corresponding to four colors of ink, but the printing unit 3 is further provided with ink cartridges 31 of other colors such as light cyan, light magenta, and dark yellow. It may be configured.

The reciprocating mechanism 42 includes a carriage guide shaft 422 supported at both ends by a frame (not shown), and a timing belt 421 extending in parallel with the carriage guide shaft 422.
The carriage 32 is supported by the carriage guide shaft 422 of the reciprocating mechanism 42 so as to be reciprocally movable, and is fixed to a part of the timing belt 421.

  When the timing belt 421 travels forward and backward via a pulley by the operation of the carriage motor 41, the printing unit 3 is reciprocated by being guided by the carriage guide shaft 422. During this reciprocation, ink is appropriately discharged from the nozzles 124 of the plurality of inkjet heads 100 in the head unit 35 corresponding to the image data to be printed (print data, droplet discharge control information), and recording is performed. Printing on the paper P is performed.

The sheet feeding device 5 includes a sheet feeding motor 51 serving as a driving source thereof, and a sheet feeding roller 52 that is rotated by the operation of the sheet feeding motor 51.
The paper feed roller 52 includes a driven roller 52 a and a drive roller 52 b that are vertically opposed to each other with the recording paper P sandwiched by the recording paper P feed path. The drive roller 52 b is connected to the paper feed motor 51. As a result, the paper feed roller 52 can feed a large number of recording sheets P set on the tray 21 one by one toward the printing apparatus 4. Instead of the tray 21, a configuration may be adopted in which a paper feed cassette that stores the recording paper P can be detachably mounted.

The control device 6 performs a printing process on the recording paper P by controlling the printing device 4, the paper feeding device 5, and the like based on print data input from a host computer 60 such as a personal computer or a digital camera. It is.
As shown in FIG. 4, the control device 6 receives the print data input from the host computer 60 and executes print processing based on the print data input from the input interface unit 61. For example, a control unit 62 configured by a microcomputer, a carriage motor driver 63 that drives and controls the carriage motor 41, a paper feed motor driver 64 that drives and controls the paper feed motor 51, and a head driver 65 that drives and controls the head unit 35. The output signals of the drivers 63, 64, and 65 are converted into control signals used by the external carriage motor 41, the paper feed motor 51, and the head unit 35, and the residual vibration waveform of the head unit 35 is detected. The peak value detected by the residual vibration detection circuit 150 is used as a control unit. And an output interface unit 67 to be input to 2.

  Here, the control unit 62 includes a CPU (Central Processing Unit) 62a that executes various processes such as a print process, and a data storage area (not shown) that includes print data input from the host computer 60 via the input interface unit 61. EEPROM (Electrically Erasable Programmable Read-Only Memory) 62b which is a kind of non-volatile semiconductor memory stored in the memory and various data temporarily when executing print data print processing or the like, or an application program such as print processing At least a RAM (Random Access Memory) 62c and a ROM (Read-Only Memory) 62d composed of a nonvolatile semiconductor memory for storing a control program executed by the CPU 62a.

Although not shown, the control unit 62 is electrically connected with various sensors capable of detecting, for example, the remaining amount of ink in the ink cartridge 31, the position of the printing unit 3, the printing environment such as temperature, humidity, and the like. Yes.
When the control unit 62 obtains print data from the host computer 60 via the input interface unit 61, the control unit 62 stores the print data in the EEPROM 62b. The CPU 62a executes predetermined processing on the print data, and outputs control signals to the drivers 63 to 65 based on the processing data and input data from various sensors. When the control signals are output from the drivers 63, 64, and 65, these are converted into drive signals by the input / output interface unit 67, and the piezoelectric actuators 122 corresponding to the plurality of inkjet heads 100 of the head unit 35 and the printing device 4. The carriage motor 41 and the paper feeding device 5 are operated, and the printing process is executed on the recording paper P.

  Further, the control unit 62 writes a write enable signal DEN and a write clock signal WCLK in order to write waveform forming data DATA for forming a reference drive signal and a gradation signal to be described later into a waveform memory 701 to be described later. And write address data A0 to A3 of the waveform memory 701 are output to write, for example, 16-bit waveform forming data DATA into the waveform memory 701 and read out the waveform forming data DATA stored in the waveform memory 701. Read address data A0 to A3 for output, a first clock signal ACLK for setting the timing for latching the waveform forming data read from the waveform memory 701, and a second for setting the timing for adding the latched waveform data The clock signal CLK and the clear signal CLER for clearing the latch data are And outputs it to the bus 65.

  The head driver 65 includes a drive signal generating means 70 that forms a drive signal COM including a discharge control drive signal and a residual vibration generating drive signal, and a reference drive signal generating circuit 70 that also serves as a residual vibration generating means, and a residual vibration detection that will be described later. The signal compensation circuit 80 as signal compensation means for compensating the ejection control drive signal COM based on the deviation between the peak value PDATA of the residual vibration waveform detected by the means and the target peak value, and the ejection control drive signal COM are selected. And an oscillation circuit 90 that outputs a clock signal SCK for this purpose.

  As shown in FIG. 5, the drive signal generation circuit 70 generates a plurality of, for example, four ejection control drive signals and one residual vibration generation drive signal corresponding to the gradation dots input from the control unit 62. A waveform memory 701 for storing waveform forming data DATA for storage in a storage element corresponding to a predetermined address, an absolute value circuit 702 for converting the waveform forming data WD read from the waveform memory 701 into an absolute value, and a waveform memory Based on the waveform forming data WD read from 701, a waveform data selection unit 703 that determines to separate into an offset unit and a waveform unit, and any state of the offset unit and the waveform unit output from the waveform data selection unit 703 An AND gate 704 to which a selection data signal Ds indicating whether or not and a compensation value CDATA supplied from the signal compensation circuit 80 are input, and an absolute value count Based on the sign determination signal ASSEL supplied compensation value CDATA from the signal compensation circuit 80 and a subtractor 705 for subtraction with respect to the absolute value of the waveform forming data WD outputted from the 702.

Further, the drive signal generation circuit 70 determines whether the waveform forming data WD output from the waveform memory 701 is positive or negative, and the adder / subtractor 705 based on the sign determination result of the sign determiner 706. The sign adder 707 for adding the sign by multiplying the output addition / subtraction value by, for example, +1 or −1 and outputting the waveform compensation data WDc, and the waveform compensation data WDc output from the sign adder 707 are described above. A latch circuit 708 latched by the first clock signal ACLK, an adder 709 for adding an output of the latch circuit 708 and waveform generation data WDATA output from a latch circuit 710 described later, and an addition output of the adder 709 Is latched by the above-mentioned second clock signal CLK, and the latch circuit 7 A D / A converter 711 that converts the waveform generation data WDATA output from 0 into an analog signal, a voltage amplifier 712 that amplifies the analog signal output from the D / A converter 711, and the voltage amplifier A current amplifying unit 713 that amplifies the output signal 712 and outputs a reference drive signal COM;
Here, the clear signal CLER output from the control unit 62 is input to the latch circuits 708 and 710, and the latch data is cleared when the clear signal CLER is turned off.

  Further, as shown in FIG. 6, the waveform data selection unit 703 detects the coincidence between the read address numbers A0 to A3 from the waveform memory 701 and the address numbers A0 to A3 representing the desired waveform set by the control unit 62. When the two match, for example, coincidence comparators 721a to 721d that output a comparison signal of logical value “1”, an OR gate 722 to which the comparison signal output from these coincidence comparators 721a to 721d is input, An output signal of the OR gate 722 is input to one input side, an AND gate 724 to which the first clock signal BCLK is inverted by the inverter 723 and input to the other input side, and an output signal of the OR gate 722 is input to one input side. OR gate 725 in which the output signal of inverter 723 is input to the other input side, and the output signal of this OR gate 725. AND gate 726 with clear signal CLER input to one input terminal and the output signal of AND gate 724 are input to clock input terminal CK, and the output signal of AND gate 726 is input to the reset terminal And a latch circuit 727 composed of a D-type flip-flop. Then, the selection data signal Ds indicating which state is the offset portion or the waveform portion is output from the output terminal Q of the latch circuit 727 to the AND gate 704.

  As shown in FIG. 7, the signal compensation circuit 80 receives a target peak value TDATA input from the control unit 62 and a residual vibration peak value PDATA input from a residual vibration detection circuit 150 to be described later, and their deviations. a comparison deviation calculator 81 that outputs ε, a PID calculator 82 that receives the deviation ε output from the comparison deviation calculator 81, and a sign of the compensation value CDATA output from the PID calculator A code determination unit 83 that outputs a code determination signal ASSEL.

The PID computing unit 82 includes a proportional computing unit 82a that performs proportional computation, to which a deviation ε is input, an integration computing unit 82b that performs integral computing, a differential computing unit 82c that performs differential computing, and each of these computing units 82a, 82b, A compensation value CDATA is obtained by adding the multipliers 82d, 82e and 82e, which multiply the calculation output of 82c individually by the proportional gain Kp, the integral gain Ki and the differential gain Kd, and the multiplication outputs output from the multipliers 82d to 82e. And an adder 82f for calculation. The compensation value CDATA output from the adder 82f is expressed by the following equation (1).
CDATA = Kp · ε + (Ki / Ti) ∫εdt + Kd · Td (dε / dt) (1)
Here, Ti is an integration time, and Tp is a differentiation time.

  The input / output interface unit 67 outputs the ejection control drive signal COM output from the reference drive signal generation circuit 70 and the clock signal SCLK output from the oscillation circuit 90 to the head unit 35 as they are, and from the control unit 62. A drive signal selection signal SI for each nozzle with respect to the ejection control drive signal COM output in accordance with the print data, and a latch signal LAT for latching the drive signal selection signal SI are output to the head unit 35, and a residual which will be described later. The peak value PDATA of the residual vibration detection signal output from the vibration detection circuit 150 is output to the signal compensation circuit 80.

  Further, as shown in FIG. 8, the head unit 35 selects whether to supply the drive signal COM to the first electrode 131 of the piezoelectric actuator 122 corresponding to each nozzle 124 in units of a predetermined number of nozzles. It has a switch 201 and a drive signal selection control circuit 210 that selectively controls the selection switch 201. Here, the second electrode 132 of the piezoelectric actuator 122 is connected to a residual vibration detection circuit 150 described later.

  As shown in FIG. 8, the drive signal selection control circuit 210 is supplied with drive signal selection signals SI for a predetermined number of piezoelectric actuators 122 from the input / output interface unit 67 as serial data, and sequentially shifts in response to the clock signal SCK. A latch circuit 212 that latches the drive signal selection signal SLb stored in the shift register 211 as a parallel signal by the latch signal LAT, and a latch output of the latch circuit 212 is set to a voltage required by the first selection switch 201. And a level shifter 213 for conversion.

  On the other hand, as described above, when the piezoelectric actuator 122 is applied as an actuator that ejects ink droplets from the inkjet head 100, the drive signal source applied between the first electrode 131 and the second electrode 132. When a drive signal as shown in FIG. 2 is applied by using a mode that expands and contracts in the vertical direction as shown in FIG. 2 by the drive signal from FIG. 2, the diaphragm 121 is displaced and the pressure in the cavity 123 is increased. Changes, and ink droplets are ejected from the nozzle 124. Residual vibration is generated in the vibration plate 121 by the drive signal at this time, and this residual vibration causes the piezoelectric actuator 122 to respond to the residual vibration. Voltage is generated.

  An electromotive voltage corresponding to the generated residual vibration generated by the piezoelectric actuator 122 is detected by a residual vibration detection circuit 150 serving as a residual vibration detection means. As shown in FIG. 8, in the residual vibration detection circuit 150, the second electrode 132 of each piezoelectric actuator 122 is connected to the collector, the emitter is grounded to the ground end, and the selection is supplied from the control unit 62 to the base. A switching element 151 constituting an open / close switch to which the signal DSEL is input, an AC amplifier 152 connected to the collector of the switching element 151, and a peak hold circuit that holds the peak value PV of the AC amplified output of the AC amplifier 152 153, and an A / D converter 154 that converts the peak peak value PV held in the peak hold circuit 153 into digital data and outputs the peak peak value data PDATA.

Here, the AC amplifier 152 includes an operational amplifier OP including a DC component removing capacitor C that removes a DC component of the electromotive voltage of the piezoelectric actuator 122, a DC resistor DC that provides an input resistor R1, a feedback resistor R2, and a reference voltage. It consists of and.
In a state where a drive signal COM including a discharge control drive signal for discharging ink droplets based on print data and a residual vibration generation drive signal is applied to the first electrode 131 of the piezoelectric actuator 122, The selection signal DSEL output from the control unit 62 is controlled to a high level, the switching element 151 is turned on, and the second electrode 132 of each piezoelectric actuator 122 is connected to the ground end via the switch element 151. The For this reason, during ink droplet ejection control, the vibration plate 121 vibrates up and down in accordance with the voltage applied to the piezoelectric actuator 122 for ejection control drive signals, and ink droplets are ejected from the nozzles 124 due to the volume change of the cavity 123. When residual vibration is detected, the residual vibration generation drive signal is set to a voltage that does not cause ink droplets to be ejected from the nozzles 124, thereby causing a pressure change in the cavity 123.

  Then, immediately after the application of the residual vibration generating drive signal to the piezoelectric actuator 122 is completed, the selection signal DSEL is inverted to a low level by the control unit 62, whereby the switching element 151 is turned off, and the residual vibration generating The electromotive voltage of the piezoelectric actuator 122 due to the residual vibration generated by the drive signal is supplied to the AC amplifier 152, amplified by the AC amplifier 152, and supplied to the peak hold circuit 153, and the peak peak value PV is output from the peak hold circuit 153. Is held, and the held peak peak value PV is converted into digital data by the A / D converter 154 and supplied to the signal compensation circuit 80 via the input / output interface unit 67 as peak peak value data PDATA.

  Here, the electromotive voltage based on the residual vibration output from the piezoelectric actuator 122 shows a waveform depending on the ink temperature, as shown in FIG. 9, and the peak peak value is, for example, when the ink temperature is 5 ° C. As the ink temperature increases to 20 ° C., 30 ° C., and 45 ° C., the peak wave height value gradually increases. Therefore, the ink temperature, that is, the ink viscosity can be detected by detecting the residual vibration, and the peak value data PDATA output from the residual vibration detection circuit 150 represents the ink viscosity. At this time, when the ink temperature is low, the ink viscosity is high, the discharge speed of the ink droplets discharged from the nozzle 124 is slow, and when the reverse ink temperature is high, the ink viscosity is low, and the ink liquid discharged from the nozzle 124 Drop ejection speed increases.

Incidentally, as shown in FIG. 10, the relationship between the drive voltage applied to the piezoelectric actuator 122 and the ink discharge weight is such that the ink discharge weight is light when the drive voltage is low, and the ink discharge weight increases as the drive voltage increases. Proportional relationship.
Further, as shown in FIG. 11, the relationship between the drive voltage applied to the piezoelectric actuator 122 and the ink discharge initial speed is low when the drive voltage is low, and the ink discharge initial speed increases as the drive voltage increases. There is an increasing proportional relationship.
Further, as shown in FIG. 12, when the drive voltage is low, the peak voltage value of the residual vibration is low and the drive voltage is low. As the value increases, the peak value of the residual vibration also increases.

  Therefore, in order to form multi-tone dots with the ink discharge weight, for example, as shown in FIG. 13, four tone drive signals whose drive voltage gradually increases are set, and these tone drive signals are respectively driven. Since the ink discharge initial speed is also different because the voltage is different, in order to match the landing positions on the recording paper P, as shown in FIG. 13, in order of decreasing ink discharge initial speed in the section constituting one pixel. In other words, 8 to 9 gradation dots can be formed on the recording paper P by arranging them in time series in ascending order of drive voltage and selecting one or more of these four gradation drive signals. it can. Further, We is set as a detection signal for residual vibration detection. We is a drive waveform for detection that generates residual vibration that can be detected in the cavity. In some cases, a drive waveform that does not eject ink may be used, or a drive waveform for fine vibration that slightly vibrates the inside of the cavity may be used in order to prevent ink thickening and drying of the nozzle.

As shown in FIG. 13, the gradation drive signals are arranged at an equal arrangement interval Tw (sec), the droplet discharge initial velocity of the first initial drive waveform W0 is V0 (m / s), the nozzle 124 and the recording paper P. When the gap between them is g (m), the ink discharge initial speed Vn of the drive waveform Wn (n: an integer from 1 to k) for generating each gradation dot can be expressed by the following equation (2).
Vn = g / {(g / V0) − (n × Tw)} (2)
Therefore, the ink discharge initial speeds V1 to V3 of the drive waveforms W1 to W3 are calculated based on the above equation (2), and the voltage (amplitude) of the gradation drive signal is calculated according to these ink discharge initial speeds V1 to V3. Set.

  Then, when the power of the inkjet printer 1 is turned on, the control unit 62 executes a print control process shown in FIG. In this print control process, first, in step S1, the compensation process start flag FS indicating that it is the timing to start the compensation process for calculating the compensation value of the drive signal in the compensation process timing monitoring process described later is set to “1”. If the compensation process start flag FS is reset to “0”, the process jumps to step S5, which will be described later. If the compensation process start flag FS is set to “1”, the process proceeds to step S2. It is determined whether there is print data input from the host computer 60. If there is no print data, the process proceeds to step S10 described later, and if there is print data, the process proceeds to step S3. .

  In this step S3, it is determined whether or not printing of one printing paper P is completed. When printing is completed, the process proceeds to step S10 to be described later, and the printing paper P is being printed. Sometimes, the process proceeds to step S4, where it is determined whether or not the output of the drive signal in the dot formation cycle of one pixel is completed. When the output of the drive signal is completed, the process proceeds to step S10 to be described later. If it is not when the output is completed, the process proceeds to step S6.

On the other hand, if the determination result in step S1 is that the compensation processing start flag FS is reset to “0”, the process proceeds to step S5, where it is determined whether print data input from the host computer 60 exists, If the print data does not exist, the process returns to step S1, and if the print data exists, the process proceeds to step S6.
In step S6, the selection signal DSEL for the switching element 151 of the residual vibration detection circuit 150 is set to the high level, and then the process proceeds to step S7 to execute the printing process. This print processing shows a series of operations for controlling the head, paper feed, and the like based on the image data. Here, the print processing is performed based on the image data.

  Next, the process proceeds to step S8, where it is determined whether or not the printing process has been completed. If the printing process has not been completed, the process returns to step S1. If the printing process has been completed, the process proceeds to step S9 and the power is turned on. It is determined whether or not the printer has been turned off. When the power source is kept on, the process returns to step S1, and when the power source is off, the printing process is terminated.

  On the other hand, when the determination result of step S2 is that there is no print data, the determination result of step S3 is when printing of one printing paper is completed, the determination result of step S4 is when output of the drive signal is completed. In some cases, the process proceeds to step S10 to output a high-level selection signal DSEL to the switching element 151, and then the process proceeds to step S11 to select a nozzle for generating residual vibration, and a serial data selection signal SI. Is input to the drive signal selection control circuit 210 in synchronization with the clock SCK, and then the process proceeds to step 12.

  In step 12, a drive signal for generating residual vibration is generated, and a drive waveform We for residual vibration detection is selected and output, and the process proceeds to step 13. In step 13, it is determined when the output of the detection signal We is completed. When the output is completed, the process proceeds to step 14, where the low level selection signal DSEL is output to the switching element 151 of the residual vibration detection circuit 150, and then in step S 15. Then, the residual vibration waveform is detected by the residual vibration detection circuit 150, the peak value of the residual vibration waveform is converted into digital data and output as PDATA, and the process proceeds to step 16.

  In step S16, the read peak peak value PDATA calculates a deviation ε from the target peak peak value TDATA, and then the process proceeds to step S17 to determine whether or not the calculated deviation ε is within a predetermined settling range. If it is within the settling range, the process returns to step S1, and if it is outside the settling range, the process proceeds to step S18. In step S18, the deviation ε is calculated by the PID calculator, and the compensation value CDATA, CDATA positive / negative determination result is output as AS_SEL as the calculation result, and the process returns to step S10. Note that CDATA and AS_SEL are fed back to the drive signal generation in step S12 and used for drive signal compensation processing.

  In the drive signal generation process of FIG. 15, first, in step S61, the waveform data WD is read from the waveform memory 701 in synchronization with the clock signal CLK, and then the process proceeds to step S22, where the address of the waveform data WD is the address of the waveform portion. 25. If it is not the address of the waveform part but the address of the offset part, the process jumps to step S66, which will be described later, and if it is the address of the waveform part, the process proceeds to step S63, and the signal compensation of FIG. It is determined whether or not the sign determination flag FC of the compensation value data CDATA calculated in the process is set to “1”. When the sign determination flag FC is set to “1”, the sign is positive. The process proceeds to step S64 and the waveform data is added to the value obtained by adding the absolute value of the compensation value data CDATA to the absolute value of the waveform data WD. After calculating the compensation waveform data WDc to which the sign of the data WD is added, the process proceeds to step S66, and when the sign determination flag FC of the compensation value data CDATA is reset to “0”, it is determined that the sign is negative. Then, the process proceeds to step S65, and after calculating the compensation waveform data WDc obtained by adding the sign of the waveform data WD to the value obtained by adding the absolute value of the compensation value data CDATA to the absolute value of the waveform data WD, the process proceeds to step S66. In step S66, the offset data or compensation waveform data WDc is D / A converted into an analog drive signal, which is output to the voltage amplifier 712, and then the process proceeds to step S67 to determine whether all waveform generation has been completed. If not completed, the process returns to step S61. When all waveform generation is completed, generation of the drive signal for one pixel is terminated.

  As shown in FIG. 16, the compensation process timing monitoring process is started when the power is turned on. First, in step S41, the compensation process start flag FS is set to “1”, and then in step S42. It is determined whether or not the compensation value CDATA is output from the signal compensation circuit 80. If the compensation value CDATA is not output, the process waits until it is output. If the compensation value CDATA is output, the process proceeds to step S43. To do.

In step S43, the compensation process start flag FS is reset to “0” and then the process proceeds to step S44. A timer preset with a set time until the start of the next compensation process is started, and then the process proceeds to step S45. After the number of prints is preset and a counter that counts down every time one sheet of recording paper is printed is started, the process proceeds to step S46.
In this step S46, it is determined whether or not the timer has expired. When the timer has not expired, the process proceeds to step S47, where it is determined whether or not the count value of the counter has become “0”. If it is “over”, the process returns to step S46.

  On the other hand, if the determination result in step S46 is that the timer has timed up, the process proceeds to step S48, the compensation process start flag FS is set to “1”, then the process proceeds to step S49, and the signal compensation circuit 80 Whether or not the compensation value CDATA has been output. If the compensation value CDATA has not been output, the process waits until it is output. If the compensation value CDATA has been output, the process proceeds to step S50, and a compensation processing start flag is displayed. After resetting FS to "0", the process proceeds to step S51, the timer is restarted, and then the process returns to step S46.

  If the determination result in step S47 is that the counter value is "0", the process proceeds to step S52, the compensation process start flag FS is set to "1", and then the process proceeds to step S53. Then, it is determined whether or not the compensation value CDATA is output from the signal compensation circuit 80. If the compensation value CDATA is not output, the process waits until it is output. If the compensation value CDATA is output, the process proceeds to step S54. Then, after resetting the compensation processing start flag FS to “0”, the process proceeds to step S55, and after the counter is restarted, the process proceeds to step S46.

In the correction of the drive signal due to the temperature change of the ink, the residual vibration detection result is fed back to the generation of the drive signal until the desired settling range is entered at the timing of the non-printing process as shown in FIG. The compensation result at the time of settling is stored in the integrator of the PID computing unit in FIG. 7 and output as CDATA. Therefore, in the ink ejection operation of the printing process in step S7 after settling, a drive waveform is generated at any time with the compensated value after settling and printing is performed.
In the processing of FIG. 14, the processing of steps S5 to S9 and the processing of FIG. 15 and the drive signal generating circuit 70 correspond to the drive signal generating means, and the processing of steps S10 to S13 of FIG. This corresponds to the residual vibration generating means. The processing in steps S15 to S17 in FIG. 14, the processing in FIG. 16, and the signal processing circuit 80 correspond to signal compensation means.

Next, the operation of the first embodiment will be described.
Now, when the power of the inkjet printer 1 is turned on, first, initialization processing is performed by the CPU 62a of the control unit 62, and drive signal waveform data is written into the waveform memory 701 of the drive signal generation circuit 70. As shown in FIG. 17, the drive signal waveform data is written by outputting 16-bit waveform data DATA in the state of specifying an address, and simultaneously outputting the write clock signal WCLK to generate the enable signal DEN. Thus, the waveform data is stored in the memory elements corresponding to the addresses A0 to A3 of the waveform memory 701, respectively. At this time, the most significant bit MSB of the waveform data is used as a sign bit representing a positive / negative sign. In this embodiment, waveform data of “0” is stored at address A0 of the waveform memory 701, + ΔV1 for setting the initial increase amount of the ejection control drive signal is set at address A1, and ejection control is performed at address A2. -ΔV2 is set to set the amount of decrease after the initial increase of the drive signal is completed, and + ΔV3 is set to the address A3 to set the amount of increase in the initial state after the decrease of the discharge control drive signal. ΔV1 | = | ΔV2 | and + ΔV1> + ΔV3. Also, waveform data of “0” is stored at address E0, + ΔVE1 is set to address E1 to set the initial increase amount of the residual vibration generating drive signal, and the initial increase of the residual vibration generating drive signal is ended at address E2. -ΔVE2 is set to set the initial state return decrease amount after this, and these are set to a relationship of | ΔVE1 | = | ΔVE2 |.

After the initialization process is completed, the CPU 62a of the control unit 62 starts to execute the print control process of FIG. 14 and the compensation process timing monitoring process of FIG.
At this time, in the compensation process timing monitoring process, the compensation process monitoring flag FS is set to “1” in step S41, and in the print control process of FIG. 14, the process proceeds from step S1 to step S2 to step S10. Compensation value calculation processing is started.

In this compensation value calculation process, first, a high-level selection signal DSEL is output to the switching element 151 of the signal compensation circuit 80, and the switching element 151 is turned on to turn on the second electrode 132 of each piezoelectric actuator 122. Is connected to the ground end (step S10).
In this state, the nozzle that generates the residual vibration for calculating the compensation value is selected, and the selection signal SI is output to the shift register 211 of the drive signal selection control circuit 210 in synchronization with the clock signal SCK. When the writing is completed, the latch signal LAT is output, and the necessary selection switch 201 is turned on (step S11).

  Next, read addresses A0 to A3 for outputting the waveform data of the residual vibration generating drive signal to the waveform memory 701 of the drive signal generating circuit 70 after outputting the clear signal CLER to the drive signal generating circuit 70 as necessary. The clock signal CLK and the first clock signal ACLK are sequentially output so as to form a predetermined drive signal waveform, and the drive signal generation circuit 70 outputs the signal from the nozzle 124 of the inkjet head 100. A drive signal (detection signal) for generating a residual vibration having a maximum voltage at which ink droplets are not ejected is output to the selection switch 201 (step S12).

In the waveform data reading process at this time, first, as shown in FIG. 18A, the clear signal CLER is output from the control unit 62 to the drive signal generation circuit 70 at time t1, and the drive signal generation circuit 70 After the latch data of the latch circuits 708 and 710 are cleared, predetermined addressing is performed and the desired offset voltage V _0FF of the drive signal COM is set. Next, at time t2, as shown in FIG. 18D, the second clock signal CLK is supplied to the latch circuit 710 of the drive signal generation circuit 70, but at this time, new addressing is not performed. Therefore, the drive signal COM output from the current amplifying unit 713 maintains the offset voltage V _OFF as shown in FIG.

Next, when the address E1 is designated by the control unit 62 at time t3, and then the first clock signal ACLK rises as shown in FIG. 18C at time t4, the address A1 read from the waveform memory 701 is read. The absolute value of the waveform data + ΔV1 and the compensation value CDATA indicating “0” in the initial state are added by the adder / subtractor 705, and the sign of the waveform forming data WD read by the waveform memory 701 by the sign adder 707 is added to the added value. The drive compensation waveform data WDc is latched by the latch circuit 708 and supplied to the adder 709. The latch output of the latch circuit 710 input to the adder 709 is the offset voltage V. since maintaining _OFF, addition value of the adder 709 becomes a value obtained by adding + [Delta] V1 to the offset voltage V _OFF, Sum of is latched by the latch circuit 710 at the time t5 when the second clock signal CLK rises, the drive signal waveform data WDATA of V _OFF + [Delta] V1 from the latch circuit 710 is outputted.

For this reason, the drive signal waveform data WDATA is converted into an analog signal by the D / A converter 711, amplified by the voltage amplifier 712, and then amplified by the current amplifier 713 and output as a drive signal for generating residual vibration. This is supplied to the first electrode 131 as one input end of the actuator 122.
Thereafter, at time t6, the address of the waveform memory 701 is changed to A0. However, since the first clock signal ACLK does not rise, the latch circuit 708 maintains the previous latch signal, so that the above-described time t5 is reached. When the reference drive signal waveform data becomes V _OFF + ΔV1 when the latch circuit 710 is latched, the added value of the adder 708 is V _OFF + 2ΔV1, which is latched at time t7 when the second clock signal CLK rises. Latched by the circuit 710, drive signal waveform data WDATA of V _OFF + 2ΔV1 is output from the latch circuit 710 as shown in FIG.

Thereafter, the latch circuit 710 latches at time t8 when the second clock signal CLK rises, so that the drive signal waveform data WDATA becomes V _OFF + 3ΔV1 as shown in FIG. 18E, and then the first clock at time t9. When the signal ACLK rises, the waveform data “0” at the address E0 is latched by the latch circuit 708. However, since the waveform data is “0”, the addition value of the adder 709 is not changed.

After that, the address data E2 is output at time t10, the waveform data of -ΔV2 is read from the waveform memory 701, and this is latched in the latch circuit 708 when the first clock signal ACLK rises at time t11.
Therefore, the output of the adder 709 becomes V _OFF + 3ΔV1−ΔV2, which is latched by the latch circuit 710 at the time t12 when the second clock signal CLK rises, so that the drive signal waveform data WDATA is as shown in FIG. Start decreasing as shown.

Thereafter, the reference drive signal waveform data WDATA and the residual vibration generation drive signal continue to decrease until time t15, and the output of the adder 709 becomes V _OFF + 3ΔV1-3ΔV2, which is the same offset voltage V _OFF between time t1 and t4. Return to.
At this time t15, the address of the waveform memory 701 is changed to A0, and at time t16, the first clock signal ACLK rises. However, since the waveform data is “0”, the offset voltage V _OFF is maintained.
Thus, since the residual vibration generating drive signal We is output from the drive signal generating circuit 70, the residual vibration generating drive signal We is supplied to the piezoelectric actuator 122 through the selection switch 201 in which the residual vibration generating drive signal We is controlled to be on (FIG. 19). supplied as shown in a).

  When the output of the residual vibration generating drive signal We is completed, the selection signal DSEL is inverted to a low level as shown in FIG. 19B (step S14). For this reason, the switching element 151 is turned off, and the electromotive voltage generated in the piezoelectric actuator 122 according to the residual vibration generated by the residual vibration generating drive signal We is supplied to the AC amplifier 152 and amplified. The amplified signal VOUT of the residual vibration detection signal is output from the amplifier 152 as shown in FIG. The amplified signal VOUT is supplied to the peak hold circuit 153, whereby the peak hold circuit 153 holds the peak peak value PV of the amplified signal VOUT, and the held peak peak value PV is sent to the A / D converter 154. By supplying, the peak value data PDATA is outputted from the A / D converter 154 (step S15).

  The peak value data PDATA output from the A / D changer 154 is input to the signal compensation circuit 80 via the input / output interface unit 67. Therefore, in the signal compensation circuit 80, the comparison deviation calculator 81 subtracts the peak peak value data PDATA from the target peak value data TDATA to calculate the deviation ε (step S16), and the calculated deviation ε is assumed to be the ink temperature. If the deviation ε is a positive value and a relatively large value, the set value is out of the set range. In this case, since the drive signal needs to be corrected, the calculated deviation ε is supplied to the PID calculator 82 to The compensation value CDATA is calculated by performing the PID calculation represented by the equation (1).

  As described above, when the ink temperature is low, the peak peak value data PDATA detected by the residual vibration detection circuit 150 is smaller than the target peak value data TDATA, and the deviation ε between them is a relatively large positive value. Become. Therefore, for example, a sign determination signal AS_SEL having a logical value “1” representing a positive value is supplied from the sign determination unit 83 to the adder / subtractor 705 of the drive signal generation circuit 70 as an addition command, and the adder / subtractor 705 is set to the addition process. The The absolute value of the compensation value CDATA output from the signal compensation circuit 80 is supplied to the AND gate 704 of the drive signal generation circuit 70. Until the optimum compensation value is obtained in this manner, the process returns to step S10 until the deviation ε enters the settling range.

  At this time, when the read addresses A0 to A3 are supplied to the waveform memory 701 in a predetermined order and the waveform data WD is read out, the selection data signal Ds output from the waveform data selection unit 703 becomes high level. 704 opens, and the compensation value data CDATA calculated by the signal compensation circuit 80 is supplied to the adder / subtractor 705 and added to the waveform data We read from the waveform memory 701. For this reason, as shown in FIG. 18 (f), the residual vibration generation drive signal We is increased by the compensation value CDATA with respect to the residual vibration generation drive signal We immediately after the power is turned on. Therefore, the amount of expansion / contraction of the piezoelectric actuator 122 increases, and the displacement of the diaphragm 121 increases, thereby increasing residual vibration.

For this reason, when the peak peak value data PDATA detected by the residual vibration detection circuit 150 increases and approaches the target peak value data TDATA, and the deviation ε of both falls within the settling range, the print control process of FIG. Returning from step S14 to step S1, the compensation value calculation process is terminated.
As described above, when the compensation value calculation process is completed, the compensation process start flag FS is set to “0” when the compensation value CDATA is output from the signal compensation circuit 80 in the compensation value process timing monitoring process shown in FIG. Since it is reset (step S43), in the print control process shown in FIG. 14, the process proceeds from step S1 to step S2, it is determined whether print data is input from the host computer 60, and the print data is input. If not, the process returns to step S1.

In this state, when print data including gradation data is input from the host computer 60 to the control unit 62 via the input inkjet circuit 61, the print data is stored in the EEPROM 62b.
As described above, when the print data is stored in the EEPROM 62b, the process proceeds from step S2 to step S3 in the print control process of FIG. 14 to start the print process. In this printing process, first, a paper feed command is output to the paper feed motor driver 64 by a paper feed process (not shown).

As a result, the paper feed motor 51 is driven to rotate to start feeding only one sheet of the recording paper P placed on the tray 21 to the printing unit 3. When the print start area of the recording paper P reaches the nozzle position of the head unit 35, ink is ejected from the nozzle and a printing operation is executed.
Therefore, the drive signal selection control circuit 210 sequentially converts the drive signal selection signal SI for selecting the ejection control drive signal necessary for the actuator 122 that ejects ink droplets based on the gradation data included in the print data as serial data for each nozzle. And the clock signal SCK is output to the reference drive signal selection control circuit 210.

  Therefore, when the drive signal selection signal SI is sequentially stored in the shift register 211 of the reference drive signal selection control circuit 210 and the drive signal selection signals SI for all the nozzles 124 are stored, the latch signal LAT is output and latched. The drive signal selection signal SI is latched in the circuit 212, and the latched reference drive signal selection signal SI is converted into a voltage necessary for operating the first selection switch 201 with a level shifter. Therefore, the first selection switch 201 corresponding to the nozzle 124 that ejects ink droplets is controlled to be in the ON state based on the print data. Further, the first selection switch 201 simultaneously selects a necessary drive waveform. As the drive signal selection signal SI, several bits of data are transmitted with respect to the number of nozzles, and a plurality of drives connected in time series as shown in FIG. 13 by the bit data of SI transmitted for each nozzle. A necessary drive waveform is selected from the drive signal including the waveform, and the drive signal of each gradation is output to the head actuator.

Thus, when the setting of the drive signal selection signal SI to the drive signal selection control circuit 210 is completed, a signal output command for outputting the ejection control drive signal is output to the head driver 65.
When this signal output command is input to the head driver 65, the drive signal generation circuit 70 performs reading processing of the first gradation drive signal waveform data stored in the waveform memory 701. The first gradation drive signal waveform data is read from the waveform memory 701 in the same manner as the above-described residual vibration detection waveform data, but only the value is different from the residual vibration detection waveform data. In order to simplify the description, the same addresses A0 to A3 will be used.

Here, the ejection control drive signal W0 output from the drive signal generation circuit 70 outputs the clear signal CLER from the control unit 62 to the drive signal generation circuit 70 at time t1, as shown in FIG. Then, after the latch data of the latch circuits 708 and 710 of the drive signal generation circuit 70 is cleared, predetermined address designation is performed and the desired offset voltage V _0FF of the ejection control drive signal W0 is set. Next, at time t2, as shown in FIG. 20D, the second clock signal CLK is supplied to the latch circuit 710 of the drive signal generation circuit 70, but at this time, new addressing is not performed. Therefore, the first gradation drive signal W0 output from the current amplifying unit 713 maintains the offset voltage V _OFF as shown in FIGS.

Next, when the address A1 is designated by the control unit 62 at time t3, and then the first clock signal ACLK rises as shown in FIG. 20C at time t4, the address A1 read from the waveform memory 701 is read. The waveform data + ΔV1 is output to the adder / subtractor 705 and the waveform data selection unit 703.
In this waveform data selection unit 703, since the address A1 of the waveform data WD read from the waveform memory 701 and the address data A0 to A3 of the input waveform data match, the latch circuit 727 is set, and this latch circuit 727 As shown in FIG. 20 (h), a selection signal Ds that is at a high level is output from the output terminal Q of the output terminal Q and supplied to the AND gate 704.

  Since the compensation value CDATA is input from the signal compensation circuit 80 to the AND gate 704 as described above, the compensation value CDATA is input to the adder / subtractor 705. Since the adder / subtractor 705 also receives the selection signal AS_SEL having the logical value “1” as an addition command from the signal compensation circuit 80 as described above, the adder / subtractor 705 reads out the waveform memory 701 from FIG. The compensation value CDATA is added to the waveform data ΔV1 shown in e), the sign of the waveform data + ΔV1 is added to the added value by the sign adder 707, and the ink viscosity is compensated as shown in FIG. 20 (f). Compensation waveform data WDc (= + ΔV1 + CDATA) corresponding to the drive signal is output.

The waveform data WDc is latched by the latch circuit 708, which is supplied to the adder 709. Since the latch output of the latch circuit 710 input to the adder 709 maintains the offset voltage V _OFF , the adder 709. Is a value V _OFF + ΔV1 + CDATA obtained by adding the compensation waveform data WDc (= + ΔV1 + CDATA) to the offset voltage V _OFF , and this added value is latched by the latch circuit 710 at the time t5 when the second clock signal CLK rises.

Further, at time t7, the waveform data + ΔV1 + CDATA is added to obtain V _OFF +2 (ΔV1 + CDATA), and at time t8, the waveform data + ΔV1 + CDATA is added to obtain V _OFF +3 (ΔV1 + CDATA). This state continues until time t14. By subtracting waveform data − (ΔV2 + CDATA) at address A2 at t15 to obtain V _OFF +3 (ΔV1 + CDATA) − (ΔV2 + CDATA), and thereafter subtracting waveform data − (ΔV2 + CDATA) sequentially at time t17, time t18, and time t19. At time t19, V _OFF +3 (ΔV1 + CDATA) −4 (ΔV2 + CDATA), which is the minimum value. This state is continued until time t24, and then waveform data + ΔV3 of address A3 is added at time t25 to obtain V _OFF +3 (ΔV1 + CDATA ) −4 (ΔV2 + CDATA) + (ΔV3 + CDATA), and then at time t27, the waveform data + (ΔV3 + CDATA) is added to obtain V _OFF +3 (ΔV1 + CDATA) −4 (ΔV2 + CDATA) +2 (ΔV3 + CDATA). Return to V _OFF .

Therefore, the waveform data latched by the latch circuit 710 is converted into an analog signal by the D / A converter 711, amplified by the voltage amplifying unit 712, and then amplified by the current amplifying unit 713, and recorded in each recording of the head unit 35. The piezoelectric actuator 122 of the head 100 is applied to the first selection switch 201.
For this reason, in the piezoelectric actuator 122 of the recording head 100 that ejects ink droplets by the first gradation drive signal based on the gradation data of the print data, the first selection switch 201 is controlled to be in the on state. The ejection control drive signal W 0 is supplied to the first electrode 131 of the piezoelectric actuator 122.

Therefore, as shown in FIG. 13, the drive signal W0 applied to the piezoelectric actuator 122 has a pull-push-pull drive waveform provided with an intermediate potential assuming the inkjet head 100 using a piezoelectric element.
The relationship between the voltage of the drive signal of the actuator 122 and the discharge weight of the ink droplets discharged from the nozzle 124 is that the ink droplet discharge weight increases as the drive voltage increases, as shown in FIG. Therefore, the ink droplet having the minimum discharge weight is discharged from the nozzle 124.

  After that, when the cycle Tw of the first gradation driving signal W0 has elapsed, the second gradation driving signal W1 has an absolute value from the waveform data read from the waveform memory 701 in the first gradation driving signal W0. 13 is output from the drive signal generation circuit 70 except that large waveform data is read out, and this is selected by the selection switch 201. Ink droplets that are applied to the piezoelectric actuator 122 and have increased discharge weight are discharged from the nozzle 124.

After that, the third gradation drive signal W2 and the fourth gradation drive signal W3 whose amplitudes are sequentially increased are output from the sequential drive signal generation circuit 70, and these are output to the piezoelectric actuator 122 selected by the selection switch 201. The ink droplets that have been applied and have an increased discharge weight are discharged from the nozzle 124.
At this time, since the initial ejection speed of the ink droplets ejected by the first to fourth gradation drive signals W0 to W3 is set by the equation (2), all the ejected ink droplets are simultaneously recorded on the recording paper. By reaching P, 8 to 9 gradation dots can be formed by the combination of the selected gradation drive signals W0 to W3.

The above printing operation is continued until there is no print data input from the host computer 60.
During this printing operation or when printing of print data is finished, the set timer is timed up or the count value of the subtraction counter in which the predetermined number of prints is set becomes “0” by the compensation process timing monitoring process. Thus, when the compensation processing start flag FS is set to “1”, when printing is being performed, the fourth time at the time when the printing of one print sheet P is completed or the drive signal output cycle for one pixel is completed. When the output of the gray scale driving signal W3 is completed, the process proceeds to step S10 in FIG.

  At this time, when the ink viscosity decreases to an appropriate viscosity due to the increase in the ambient temperature of the head unit 35 due to the printing operation on the recording paper P or the temperature increase in the space where the inkjet printer 1 is installed, the signal compensation circuit 80 calculates. Since the compensated compensation value data CDATA has not been changed, the drive signal generation circuit 70 adds the compensation value CDATA to the appropriate residual vibration generation waveform data We shown in FIG. 18 (f). The residual vibration generation drive signal is supplied to the piezoelectric actuator 122 via the selection switch 201, so that a relatively large residual vibration is generated in the piezoelectric actuator 122. This residual vibration is detected by the residual vibration detection circuit 150. And the peak peak value data PDATA is output to the signal compensation circuit 80.

  At this time, since the ink viscosity is lowered, the peak value PDATA of the residual vibration becomes larger than the target peak value TDATA, and the deviation ε calculated by the comparison deviation calculator 81 is, for example, a negative value. A relatively large value. For this reason, the absolute value of the compensation value CDATA output from the PID calculator 82 is increased and supplied to the AND gate 704 of the drive signal generation circuit 70, and the logical value “ 0 ", which is supplied to the adder / subtractor 705 of the drive signal generation circuit 70.

  At this time, since the residual vibration is generated based on the compensation value CDATA in a state where the ink viscosity is high and does not correspond to the decrease in the ink viscosity, the peak peak value PDATA in which the residual vibration is detected by the residual vibration detection circuit 150 becomes too high. Since the deviation ε from the target peak peak value TDATA is a large negative value and is outside the settling range, the process returns to step S7 in the process of FIG. 14, and the compensation process is executed again.

  Therefore, the compensation value CDATA is subtracted from the residual vibration generation waveform data We read from the waveform memory 701, and the waveform data with a small amplitude shown in FIG. 18 (g), for example, is output from the latch circuit 710. The analog signal is converted by the D converter 711, the voltage is amplified by the voltage amplifying unit 712, the current is further amplified by the current amplifying unit 713, and is supplied to the piezoelectric actuator 122 via the selection switch 201 as a residual signal generating drive signal. Is done.

  For this reason, the piezoelectric actuator 122 is driven to the extent that it does not eject ink droplets, and residual vibration is generated after the driving, and the peak value data PDATA of this residual vibration is detected again by the residual vibration detection circuit 150. The compensation process is repeated until the deviation ε between the peak peak value data PDATA and the target peak peak value data TDATA falls within the settling range, and the compensation value data CDATA and its sign when the deviation ε falls within the settling range. Thus, the waveform data of the first to fourth gradation drive signals constituting the discharge control drive signal during the printing operation can be added or subtracted to form an appropriate discharge control drive signal corresponding to the ink viscosity.

  As described above, according to the above-described embodiment, the residual vibration generation drive signal that does not eject ink droplets is supplied to the piezoelectric actuator 122 to generate the residual vibration, and the peak value is obtained by the residual vibration detection circuit 150. The detected peak value data PDATA is subjected to feedback processing in which a PID operation is performed by the signal compensation circuit 80 to calculate compensation value data CDATA, and the discharge generated by the drive signal generation circuit 70 based on the compensation value data CDATA. Since the control waveform data W0 to W3 are compensated, accurate compensation value data CDATA corresponding to the actual ink viscosity can be obtained without providing a separate temperature sensor and without forming an image on the recording paper P. Can be calculated.

Since the waveform data of the ejection control drive signal is compensated based on the compensation value data CDATA, accurate ink droplet ejection control corresponding to the ink viscosity can be performed, and the print quality can be improved.
Furthermore, the preset value of the timer started in step S44 in the compensation process timing monitoring process of FIG. 16 is set to a value corresponding to the time required to prevent ink drying at the nozzles that are not ejecting ink. By doing so, it is possible to generate micro vibrations that do not eject ink droplets from nozzles that do not eject ink liquid or all nozzles, and it is possible to suppress solidification of ink.

  In the above embodiment, the first to fourth gradation drive signals are generated by the drive signal generation circuit 70 and these first to fourth gradation drive signals are combined, so that the eighth to ninth gradations are combined. However, the present invention is not limited to this, but by setting the number of gradation drive signals constituting one pixel to an arbitrary number, the number of permutation combinations is one or more according to an arbitrary number Gradation dots can be formed.

  In the above embodiment, the case where the drive signal generation circuit 70 generates a plurality of gradation drive signals has been described. However, the present invention is not limited to this, and the drive signal generation circuit 70 generates one reference drive signal. Is generated and supplied to the first electrode 131 of the piezoelectric actuator 122 via the selection switch 201, and the gradation signal is supplied to the second electrode 132 of the piezoelectric actuator 122 so that the reference drive signal A gradation dot corresponding to gradation data may be formed by driving the piezoelectric actuator 122 with a difference from the tone signal.

  Furthermore, in the above-described embodiment, the case where the drive signal selection signal SI is supplied as serial data to the drive signal selection control circuit 210 has been described. However, the present invention is not limited to this, and parallel transmission may be performed. In this case, the shift register for serial / parallel conversion can be omitted.

  Further, in the above-described embodiment, the case where the inkjet head 100 having the piezoelectric (piezo-electric) type multilayer actuator 127 is applied has been described. However, the present invention is not limited to this, and as shown in FIG. A piezoelectric unimorph actuator 304 using a mode in which the diaphragm 121 is vibrated by using an actuator having a simple structure in which a 301 is sandwiched between upper and lower electrodes 302 and 303 and is bent in the vertical direction in FIG. As shown in FIG. 22, electrodes 312 are provided at both ends of the piezoelectric material 311 and pressure chambers 313 are formed. The actuator drives every other nozzle, and when a drive signal is given, a broken line is shown in FIG. In this way, the pressure in the pressure chamber 313 is changed and the ink liquid is discharged from the nozzle 314. If the ESO type shear mode 1 actuator 315 is applied, or electrodes 322 and 323 are alternately provided on the surface of the piezoelectric material 321 as shown in FIG. Then, a 4-piezo type air mode 2 actuator in which the pressure in the pressure chamber 324 changes and ink droplets are ejected from the nozzles 325 can be applied.

  In addition to the piezo method, as shown in FIG. 24, ink that has flowed from the ink intake port 350 enters the reservoir 351, and enters the cavity 353 from the reservoir 351 through the narrow flow path 352. The cavity 353 includes a conductive diaphragm 355 connected to the common electrode 354, and an individual electrode 356 disposed through the diaphragm 355 and a gap, and the common electrode 354, the individual electrode 356, and the like. Alternatively, an electrostatic actuator 357 having a capacitance between the two may be applied. In this electrostatic actuator 357, when a drive signal is given between the common electrode and the individual electrode 356, the diaphragm 355 is attracted to the individual electrode side by electrostatic adsorption force, elastic energy is stored in the diaphragm 355, and the drive signal When the supply is stopped, the elastic energy is released, the diaphragm 355 is returned to the opposite side of the individual electrode, and the pressure in the cavity 353 increases and then decreases, whereby ink droplets are ejected from the nozzle holes 358. The Also in this electrostatic actuator 357, the vibration plate 355 generates residual vibration after ejecting ink droplets, and this residual vibration causes the displacement between the common electrode 254 and the individual electrode 356 as a voltage change by the electric charge remaining in the electrostatic actuator. The peak vibration value may be obtained by detecting with a residual vibration detection circuit.

  Further, in the above embodiment, the case where the drive signal generation circuit 70 generates the ejection control drive signals W0 to W3 and the residual vibration generation drive signal We has been described. However, the present invention is not limited to this, and the drive signal generation is performed. The circuit 70 may be a discharge control drive signal generation circuit that generates the discharge control drive signals W0 to W3, and a residual vibration generation drive circuit having the same configuration as the drive signal generation circuit 70 may be provided separately.

Furthermore, in the above embodiment, the case where the signal compensation circuit 80 includes the PID calculator 82 has been described. However, the present invention is not limited to this, and the differential calculator 82c and the gain multiplier 82f are omitted. It is also possible to use a PI calculator or a proportional calculator including only the proportional calculator 82a and the gain multiplier 82d.
Furthermore, in the above embodiment, the case where the signal compensation means is configured by the hardware signal compensation circuit 80 has been described. However, the present invention is not limited to this, and the CPU 62a of the control unit 62 performs the signal compensation shown in FIG. You may make it perform a process.

  That is, the signal compensation process of FIG. 25 is executed when the compensation process start flag FS is set to “1” in the compensation process timing monitoring process of FIG. 16, and is first output from the residual vibration detection circuit 150 in step S71. The peak wave height value data PDATA is read, then the process proceeds to step S72, the peak wave height PDATA read from the target peak wave height value TDATA is subtracted to calculate the deviation ε, and then the process proceeds to step S73, as described above ( 1) The compensation value data CDATA is calculated by performing the calculation of equation (1), and then the process proceeds to step S74, the sign of the compensation value data CDATA is judged and the sign judgment flag FC is set to “1” or “0”. Next, the process proceeds to step S75, where the compensation value data CDATA and the sign determination flag FC are output to the drive signal generation process of FIG. The process is terminated.

1 is a perspective view illustrating a schematic configuration of an inkjet printer according to a first embodiment of the present invention. It is sectional drawing which shows the structure of the inkjet head of the inkjet printer shown in FIG. It is a top view which shows the structure of the nozzle substrate of the head shown in FIG. It is a block which shows an example of the control apparatus which can be applied to 1st Embodiment. It is a block diagram which shows an example of a drive signal generation circuit. It is a block diagram which shows an example of a waveform data selection part. It is a block diagram which shows an example of a signal compensation circuit. It is a block diagram which shows a drive signal selection control circuit and a residual vibration detection circuit. FIG. 6 is a characteristic diagram showing the relationship between ink temperature and residual vibration waveform. FIG. 6 is a characteristic diagram showing a relationship between drive voltage and ink discharge weight. FIG. 6 is a characteristic diagram showing a relationship between drive voltage and ink discharge speed. It is a characteristic diagram which shows the relationship between a drive voltage and a residual vibration peak wave height value. It is a time chart which shows the time series of the drive signal for 1 pixel. 6 is a flowchart illustrating an example of a print control processing procedure executed by a control unit. It is a flowchart which shows an example of the drive signal generation process procedure of FIG. It is a flowchart which shows an example of a compensation process timing monitoring process procedure. It is a time chart with which it uses for description of the data writing procedure to the waveform memory. It is a time chart with which it uses for description of the generation | occurrence | production operation | movement of the drive signal for residual vibration generation. It is a time chart used for description of residual vibration detection operation. 6 is a time chart for explaining an operation of generating a discharge control drive signal. It is sectional drawing which shows the unimorph actuator in a piezo type. It is sectional drawing which shows the shear mode 1 actuator in a piezo type. It is sectional drawing which shows the share mode 2 actuator in a piezo system. It is sectional drawing which shows an electrostatic actuator. It is a flowchart which shows an example of the signal compensation process sequence performed with a control part.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Inkjet printer, 3 ... Printing part, 4 ... Printing apparatus, 5 ... Paper feeding apparatus, 6 ... Control apparatus, 31 ... Ink cartridge, 32 ... Carriage, 35 ... Head unit, 62 ... Control part, 65 ... Head driver, DESCRIPTION OF SYMBOLS 70 ... Drive signal generation circuit, 701 ... Waveform memory, 702 ... Absolute value circuit, 703 ... Waveform data selection part, 704 ... AND gate, 705 ... Adder / subtractor, 706 ... Sign judgment unit, 707 ... Sign adder, 708, 710 ... Latch circuit, 709 ... Adder, 711 ... D / A converter, 712 ... Voltage amplifier, 713 ... Current amplifier, 80 ... Signal compensation circuit, 81 ... Comparison deviation calculator, 82 ... PID calculator, 83 ... Sign determining unit, 90... Oscillating circuit, 100... Inkjet head, 120 .. electrostatic actuator, 121. Cavity (pressure chamber), 124 ... nozzle, 150 ... residual vibration detection circuit, 151 ... switching element, 152 ... AC amplifier, 153 ... peak hold circuit, 154 ... A / D converter, 201 ... first selection switch, 210 ... Drive signal selection control circuit

Claims (12)

A plurality of pressure chambers filled with liquid therein, a plurality of nozzles individually communicating with the pressure chambers to discharge the liquid as droplets, and a pressure of the pressure chamber being changed by input of a drive signal; A droplet discharge device comprising a droplet discharge head having an actuator for discharging a droplet from a nozzle to a recording medium, and a drive control means for controlling the drive by supplying a drive signal to the actuator,
The drive control means outputs a drive signal for controlling droplet discharge to the actuator, and generates a residual vibration to output a residual vibration generation drive signal for generating residual vibration in the pressure chamber. A residual vibration detecting means for detecting a residual vibration waveform generated by the residual vibration generating means, and the discharge based on a deviation between a peak value of the residual vibration waveform detected by the residual vibration detecting means and a target peak value. A droplet discharge apparatus comprising: a signal compensation unit that compensates a control drive signal.   2. The liquid according to claim 1, wherein the residual vibration generating means is configured such that the drive signal for generating the residual vibration is set to a voltage that generates residual vibration in a non-ejection state of the droplet from the nozzle. Drop ejection device.   The droplet ejection apparatus according to claim 1, wherein the residual vibration generation drive signal also serves as a fine vibration drive signal for a nozzle that does not eject droplets.   The ejection control drive signal is formed of a plurality of drive signals capable of forming a plurality of gradation dots in time series for one pixel, and each drive signal is arranged in time sequence in order of decreasing ejection speed, respectively. 4. The crest value of each drive signal is set so that the ejection speeds of the gradation dots on the recording medium coincide with each other at discharge speeds. 5. Droplet discharge device.   The residual vibration detecting means includes a switch means for opening and closing the ground end of the actuator with respect to the ground, an AC amplifying means for amplifying an alternating current component of residual vibration generated when the ground end is released, and amplifying by the AC amplifying means. 2. A peak hold means for holding the peak value of the residual vibration, and an A / D conversion means for converting the peak value held by the peak hold means into digital data. 5. The droplet discharge device according to any one of items 4 to 4.   The signal compensation means compares the target peak value with the detected residual vibration peak value, and calculates a deviation amount between them, and at least proportional to the deviation amount calculated by the deviation calculation means, and Compensation computing means for performing an integral computation and outputting a compensation value; and a sign judging means for judging the sign of the compensation value calculated by the compensation computing means and outputting the judgment result. 6. The droplet discharge device according to claim 1, wherein the determination result is output to a discharge control drive signal generating means.   The ejection control drive signal generation means includes a waveform data selection section that separates the waveform data of a reference ejection control drive signal into an offset value and a waveform portion that controls an amplitude change of the drive signal, and the signal compensation means The liquid droplet ejection apparatus according to claim 6, further comprising: addition / subtraction means for adding / subtracting the compensation value to / from the waveform portion separated based on the sign determination result input from.   The liquid droplet ejection apparatus according to claim 1, wherein the actuator is a piezoelectric actuator.   The liquid droplet ejection apparatus according to claim 1, wherein the actuator is an electrostatic actuator. A plurality of pressure chambers filled with liquid therein, a plurality of nozzles individually communicating with the pressure chambers to discharge the liquid as droplets, and a pressure of the pressure chamber being changed by input of a drive signal; An actuator for discharging droplets from a nozzle onto a recording medium; and a drive control unit for driving and controlling the actuator. The actuator is driven and controlled by the drive control unit so that droplets are discharged from the plurality of nozzles. A droplet discharge control method,
A residual vibration generating reference signal is output to the actuator, the generated residual vibration is detected by the residual vibration detecting means, and droplet discharge is controlled based on the deviation between the detected peak value of the residual vibration and the target peak value. A droplet discharge control method characterized in that a discharge control drive signal is compensated.   11. The droplet discharge control method according to claim 10, wherein the residual vibration detection timing by the residual vibration detection means is executed at a timing different from a normal droplet discharge timing.   The residual vibration detection means by the residual vibration detection means is implemented at least one time when the power is turned on, every time a certain time has elapsed after the power is turned on, and every time image formation on a certain number of recording media is completed. The droplet discharge control method according to claim 10.

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