JP2020151943A - Liquid discharge device and liquid discharge head drive control method - Google Patents

Abstract

To provide a liquid discharge head for supplying heat to a necessary point by a necessary amount according to a droplet size at each nozzle during a discharge operation, and maintaining a proper temperature state.SOLUTION: A liquid discharge head comprises a control signal creation part for creating a binary control signal for cutting out a drive waveform at each droplet size by selecting a period including one or a plurality of pulses from a fundamental drive waveform; and a switch control part for controlling the switching of the control signal. Each of a plurality of switching elements switches on/off-states in response to the switching of the control signal, applies the cutout drive waveform at each droplet size to each piezoelectric element during a period in which the control signal is one value, and also during a period in which the switching element is in an on-state, and the switching control part increases and decreases the number of times of the switching of the control signal correlated with a magnitude relationship of the droplet size discharged by the drive waveform according to a detected temperature in the liquid discharge head.SELECTED DRAWING: Figure 12

Description

The present invention relates to a liquid discharge device and a drive control method for a liquid discharge head.

In order to eject a high-viscosity liquid such as UV ink in an inkjet head, there is a technique of heating the liquid to reduce the viscosity and ejecting the liquid. In order to heat efficiently, it is advantageous to heat at a position close to the discharge, so there is already a technology to control the temperature inside the head with a temperature control mechanism represented by a heater and discharge the liquid with low viscosity. It is known (for example, Patent Document 1).

However, the temperature control mechanism provided in the head can heat the head in the discharge stopped state and set an appropriate temperature environment, but during the discharge operation, heat energy is sent to the outside of the head according to the volume of the discharged droplets. In the escaping situation, the temperature followability is poor, so it is difficult to supply the required amount of heat to the required location and maintain an appropriate temperature state. This is because it is necessary to divide the temperature control mechanism in the head in order to perform local heating, but the division requires extra space and increases the size. Further, since the temperature control mechanism is thermally connected to the entire frame of the head, the temperature change is inevitably slowed down far from the nozzle from which the droplets are ejected.

Therefore, in Patent Document 2, the temperature difference of the temperature distribution in the flow path between the plurality of nozzles caused by the discharge of the recording liquid discharged from the liquid discharge head during the image forming process is eliminated so as to eliminate the temperature difference of the recording liquid. A control for adjusting a drive waveform at the time of discharge is disclosed according to the distance from the inlet of the nozzle based on the discharge amount.

Further, in Patent Document 3, a resistor that generates heat when a drive waveform is supplied to the piezoelectric element at the time of droplet ejection is provided in the drive unit so as to eliminate the temperature difference between the pressurizing chambers corresponding to a plurality of nozzles. It has been proposed to switch the calorific value by changing the electric resistance value of the resistor.

However, in Patent Document 2, since the voltage and waveform shape of the drive waveform for ejection are changed for each section in which a plurality of nozzles are grouped, the amount of heat radiated differs due to the difference in drop size for each nozzle. However, the correspondence for each nozzle was not considered.

Further, in Patent Document 3, since the pressurizing chambers are grouped and controlled so as to make the temperature of the entire pressurizing chamber uniform, the response to the temperature change for each nozzle is not considered. ..

Therefore, in view of the above circumstances, in view of the above circumstances, the present invention supplies heat to a necessary place in the liquid discharge head in a necessary amount according to the drop size for each nozzle to maintain an appropriate temperature state. The purpose is to provide a liquid discharge device capable of producing a liquid.

In order to solve the above problems, in one aspect of the present invention,
A plurality of nozzles for discharging a liquid, a plurality of pressure chambers corresponding to the plurality of nozzles, a plurality of piezoelectric elements for applying pressure to the plurality of pressure chambers, and a plurality of switching elements provided corresponding to the plurality of piezoelectric elements. , And a liquid discharge head provided with a temperature detection unit that detects the temperature inside the liquid discharge head.
A basic drive waveform generator that generates a basic drive waveform that includes multiple pulses,
A control signal generation unit that generates a binary control signal by selecting a period including one or more pulses from the basic drive waveform and cutting out a drive waveform for each droplet size.
A switching control unit that controls switching of the control signal is provided.
Each switching element of the plurality of switching elements performs ON / OFF switching in response to the switching of the control signal, and during the period when the control signal has one value and each switching element is ON. , The driving waveform for each of the cut out droplet sizes is applied to each piezoelectric element.
The switching control unit increases or decreases the number of times of switching of the control signal, which has a correspondence relationship with the size of the droplet size discharged by the drive waveform, according to the detected temperature in the liquid discharge head. The device, provided.

According to one aspect, in the liquid discharge device, during the discharge operation, heat is supplied to a necessary place in the liquid discharge head in a necessary amount according to the drop size for each nozzle to maintain an appropriate temperature state. Can be done.

The side schematic which shows the whole structure of the inkjet recording apparatus (image forming apparatus) which concerns on one Embodiment of this invention. The plan view of the mechanical part of the inkjet recording apparatus of FIG. The exploded perspective view of the liquid discharge head of 1st Embodiment. An exploded plan view showing each plate-shaped member of the liquid discharge head from the nozzle side. The exploded plan view which shows each plate-shaped member of a liquid discharge head from the laminated piezoelectric element side. FIG. 3 is a cross-sectional view showing an AA'cross section of the liquid discharge head of FIG. The figure which shows the positional relationship between the common liquid chamber of the liquid discharge head of 2nd Embodiment, and a temperature adjustment flow path. 7 is an exploded view of FIG. 7, where FIG. 7A shows a common liquid chamber and FIG. 7B shows a temperature control flow path. The control block diagram of the inkjet recording apparatus of this invention. A detailed block diagram of an example of the print control unit and the head driver of FIG. The figure which shows the reference drive waveform, the control signal and the drive waveform used for the control of this invention. The figure which shows the reference drive waveform, the control signal and the drive waveform used for the control of the comparative example. A graph showing the drive signal ratio for each density gradation when a liquid is discharged to form an image. The graph which shows the heat dissipation amount for each density gradation in the comparative example. The graph which shows the heat generation amount by switching for every density gradation when the drive control of this invention is carried out. A graph showing a comparative example and heat transfer for each density gradation when the drive control of the present invention is carried out. An example of a flowchart showing signal processing according to the temperature inside the head of the present invention. FIG. 5 is a cross-sectional view showing an AA'cross section of the liquid discharge head of the third embodiment. The schematic view of the ink heating part included in the liquid ejection head of 4th Embodiment. The plan view which shows the nozzle arrangement image on the nozzle surface of the liquid discharge head of 4th Embodiment.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In each drawing, the same components may be designated by the same reference numerals and duplicate description may be omitted.

<Inkjet recording device (image forming device)>
First, the overall configuration of the inkjet recording apparatus according to the first embodiment will be described. FIG. 1 is a configuration diagram of an inkjet recording device 100 according to a first embodiment of the present invention. FIG. 2 is a plan view showing a main configuration of the inkjet recording device of FIG. The inkjet recording device 100 is an example of a liquid ejection device and an image forming device.

The inkjet recording device 100 according to the present embodiment is a serial type inkjet recording device, and the carriage 433 is reciprocated in the main scanning direction (arrow direction) by master-slave guide rods 431 and 432 laid horizontally on the left and right side plates 421A and 421B. It is held movable. The carriage 433 has two liquid discharge units 430A and 430B in which a liquid discharge head 434 as a liquid discharge member and a head tank 435 which is a sub tank for supplying liquid ink to the liquid discharge head 434 are integrated. It is installed.

The liquid discharge head 434 sets the nozzle arrangement direction (longitudinal direction of the nozzle row) of the nozzle row composed of a plurality of nozzles (discharge holes) to the sub-scanning direction (longitudinal direction of the liquid discharge head) orthogonal to the main scanning direction, and discharges the liquid. It is mounted with the direction facing downward in the vertical direction.

Each of the two liquid discharge units 430A and 430B has two nozzle rows. The liquid discharge head 434 of one liquid discharge unit 430A discharges black (K) ink droplets at each nozzle in one nozzle row and cyan (C) ink droplets at each nozzle in the other nozzle row. Discharge. Further, the liquid discharge head 434 of the other liquid discharge unit 430B discharges magenta (M) ink droplets at each nozzle in one nozzle row, and yellow (Y) ink at each nozzle in the other nozzle row. Discharge drops. Although FIG. 1 shows an example of ejecting four colors of ink, the liquid ejection unit also includes inks of orange (O), green (G), clear (Cl), white (W), and the like. May be discharged.

The inkjet recording device 100 uses two liquid ejection heads to eject ink droplets of four colors. Four nozzle rows are arranged on one liquid ejection head, and one liquid ejection head is used for ejecting ink droplets. It is also possible to eject four colors of ink. Further, "integration" in the liquid discharge units 430A and 430B means that the liquid discharge head 434 and the head tank 435 are directly fixed to each other by a fastening member or an adhesive through a filter member or the like. To do. Alternatively, it means that the liquid discharge head 434 and the head tank 435 are connected to each other by a tube or the like.

The main tanks 410k, 410c, 410m, 410y, which are liquid cartridges of each color, are detachably attached to the cartridge holder 404 on the apparatus main body side. Then, the head tanks 435 of the liquid discharge units 430A and 430B are filled with inks of each color from the main tank 410 of each color by the liquid feed unit 424 including the liquid feed pump 423 (see FIG. 9) via the supply tubes 436 of each color. Is pumped.

The inkjet recording device 100 includes a paper feed unit for feeding the recording sheet 442 as a recording material loaded on the sheet loading unit 441 of the paper feed tray 402. The paper feeding unit includes a paper feeding roller 443 that separates and feeds the recording sheets 442 from the sheet loading unit 441 one by one, a separation pad 444 facing the paper feeding roller 443, and the like.

The inkjet recording device 100 also includes a guide 445 that conveys and guides the fed recording sheet 442, a counter roller 446, a transfer guide member 447, and a pressing member 448 having a tip pressure roller 449. Further, it also includes a transport belt 451 which is a transport means for sucking the transported recording sheet 442 and transporting it at a position facing the liquid discharge head 434 of the liquid discharge unit 430.

The transport belt 451 is an endless belt, is hung between the transport roller 452 and the tension roller 453, and is configured to circulate in the belt transport direction (sub-scanning direction). As the transport belt 451, an electrostatic transport belt charged by a charging roller 456, which is a charging means, is used. However, the transport belt 451 may be a transport belt that is adsorbed by air suction. Further, as the conveying means, the conveying means may be one that is conveyed by a roller without using a conveying belt.

On the downstream side of the tension roller 453 around which the transport belt 451 is hung, a separation claw 461 for separating the recording sheet 442 from the transport belt 451, a paper ejection roller 462 and a paper ejection roller 463 are provided, and a paper ejection roller 462 is provided. A paper ejection tray 403 is provided below the paper output tray 403.

Further, a double-sided unit 471 is detachably attached to the back surface of the apparatus main body. The double-sided unit 471 takes in the recording sheet 442 returned by the reverse rotation of the transport belt 451, reverses it, and feeds the paper again between the counter roller 446 and the transport belt 451. Further, the upper surface of the double-sided unit 471 is a manual feed tray 472.

Further, in the non-printing area on one side of the carriage 433 in the scanning direction, a maintenance / recovery mechanism 481 for maintaining and recovering the state of the nozzle of the liquid discharge head 434 in the liquid discharge units 430A and 430B is arranged.

The maintenance / recovery mechanism 481 includes caps 482a and 482b for capping the nozzle surface of the liquid discharge head 434. Further, the maintenance / recovery mechanism 481 includes a blade member 483 for wiping the nozzle surface. Further, the maintenance / recovery mechanism 481 includes an empty ejection receiver 484 that receives ink when performing blank ejection to eject ink that does not contribute to image formation in order to eject thickened ink. Further, in the non-printing area on the other side of the carriage 433 in the scanning direction, an empty ejection receiver 488 that receives ink when blank ejection is performed during image formation or the like is arranged. The empty discharge receiver 488 is provided with an opening 489 or the like along the nozzle arrangement direction of the liquid discharge head 434.

In the inkjet recording apparatus 100 according to the present embodiment, the recording sheets 442 are separately fed from the paper feed tray 402 one by one, and the recording sheet 442 fed substantially vertically upward is guided by the guide 445 and is guided by the transport belt. It is sandwiched between 451 and the counter roller 446 and conveyed. Further, the tip of the recording sheet 442 is guided by the transport guide 437 and pressed against the transport belt 451 by the tip pressurizing roller 449, and the transport direction is changed by approximately 90 °. Then, when the recording sheet 442 is fed onto the charged transfer belt 451, the recording sheet 442 is attracted to the transfer belt 451 and the recording sheet 442 is conveyed in the sub-scanning direction by the orbital movement of the transfer belt 451.

Therefore, by driving the liquid discharge heads 434 of the liquid discharge units 430A and 430B in response to the image signal while moving the carriage 433, ink is discharged to the stopped recording sheet 442 and an image for one line is recorded. To do. Then, after transporting a predetermined amount of the recording sheet 442, the image of the next row is formed. When the recording end signal or the signal that the rear end of the recording sheet 442 reaches the recording area is received, the recording operation is ended and the recording sheet 442 is ejected to the output tray 403.

<Head of the first embodiment>
FIG. 3 is an exploded perspective view simply showing the configuration of the liquid discharge head 434 according to the first embodiment of the present invention. FIG. 4 is an exploded plan view showing each plate-shaped member of the liquid discharge head 434 from the nozzle side. FIG. 5 is an exploded plan view showing each plate-shaped member of the liquid discharge head 434 from the laminated piezoelectric element side. FIG. 6 is a cross-sectional view showing a cross section taken along the line AA'in FIG. 3 of the liquid discharge head 434.

It should be noted that FIGS. 3 to 6 show only one of the two nozzle rows provided on the liquid discharge head 434, excluding the piezoelectric actuator 21 at the bottom of FIG.

In these figures, the nozzle 1 which is a plurality of discharge holes is formed in the nozzle plate 2 as a discharge hole forming member, and is formed as a slit hole in the nozzle plate 2 made of a stainless plate or the like.

The side surfaces of the pressure generating chamber 3 which is a plurality of individual liquid chambers and the plurality of individual supply passages 4 which communicate with each other individually are formed by slits provided in the flow path plate 5. Each of the plurality of individual supply paths 4 individually communicates the common liquid chamber 10 and the plurality of pressure generating chambers 3, which will be described later, with a large diameter portion having a relatively large size in the plate surface direction (reference numeral 4a in FIG. 6). ) And a relatively small diameter portion (reference numeral 4b in FIG. 6). Then, the amount of ink flowing from the common liquid chamber 10 to the pressure generating chamber 3 is controlled by the flow path resistance in the small diameter portion 4b.

Each of the plurality of pressure generating chambers (example of the pressure chamber) 3 of the flow path plate 5 communicates with any one of the plurality of nozzles 1 provided on the nozzle plate 2. Slits are also provided in the individual liquid chamber forming member and the flow path plate 5 as the individual supply path forming member in order to form the individual supply path 4 and the pressure generating chamber 3.

Further, the flow path plate 5 is formed with a sensor accommodating hole 27 for accommodating a temperature sensor (an example of a temperature detecting unit) 28 composed of a thermistor or the like. The temperature sensor 28 (see FIG. 6) measures the head temperature around the nozzle inside the flow path plate 5.

The diaphragm plate 8 has a diaphragm film 7 which is a displaceable portion for efficiently transmitting the displacement of the piezoelectric actuator 21 to the pressure generating chamber 3, and exists at the boundary between the common liquid chamber 10 and the plurality of individual supply paths 4. Individual supply openings 6 and the like are formed. The diaphragm film 7 is formed of a solid region in the base material plate of the diaphragm plate 8, and has the same thickness as the base material plate. In the diaphragm plate 8, the portion thicker than the diaphragm film 7 is composed of a base plate and a portion electrodeposited on the base plate by electroplating. The individual supply opening 6 is a through opening, and communicates the inside of the individual supply path 4 with the inside of the common liquid chamber 10.

The frame 11, which is a common liquid chamber forming member, is formed with a large rectangular through opening for forming an actuator insertion portion 9 for inserting the piezoelectric actuator 21, which will be described later. In addition, a large rectangular opening for forming the common liquid chamber 10 is also formed. Further, on the side of the frame 11 opposite to the side where the common liquid chamber 10 is opened, a large rectangular opening for forming the temperature adjusting flow path 12 which is a refrigerant flow path is also formed. The temperature adjusting flow path 12 is formed so as to be adjacent to the common liquid chamber 10, and is located on the opposite side of the common liquid chamber 10 from the flow path plate 5 in which the pressure generating chamber 3 is formed. In the present embodiment, the temperature adjusting flow path 12 is arranged above the common liquid chamber 10 in the vertical direction.

The partition plate 13 is for sealing the temperature control flow path 12 by covering the opening of the temperature control flow path 12 in the frame 11. The partition plate 13 guides the ink sent from the head tank 435 to the common liquid chamber 10, and also discharges the ink that has passed through the common liquid chamber 10 from the common liquid chamber 10. A through hole is formed to form the ink. Further, the partition plate 13 is also formed with a through hole for forming a temperature control liquid introduction / discharge flow path 15 for introducing and discharging the temperature control liquid which is a refrigerant into the temperature control flow path 12.

The rectangular through-opening for forming the actuator insertion portion 9 is formed so as to accommodate the entire piezoelectric actuator 21, but a plurality of partition walls so as to individually accommodate the plurality of piezoelectric elements 19 of the piezoelectric actuator 21. May be provided to increase the rigidity.

The piezoelectric actuator 21 has a plurality of piezoelectric elements 19 individually corresponding to each of the plurality of nozzles 1, and a fixing member 20 for fixing the piezoelectric elements 19. One end surface of the piezoelectric element 19 is fixed to one end surface of the fixing member 20 using an adhesive, and the other end surface of the piezoelectric element 19 is joined to the diaphragm film 7. Each piezoelectric element 19 is connected to an individual electrode individually provided for each element and a common electrode common to each element, and each of the plurality of individual electrodes is individually used to individually control power on / off. An analog switch 715 (see FIG. 10), which is a switching element of the above, is connected.

The head driver 509 including the analog switches 715 is arranged on the flexible printed circuit board 22. With such an electrode configuration, it is possible to drive (displace) each of the plurality of piezoelectric elements 19 individually, and the ink pressures in the plurality of pressure generating chambers 3 are individually driven by the individual driving. Can be changed. Ink droplets are ejected from the nozzle 1 leading to the pressure generating chamber 3 in which the ink pressure is increased by the displacement of the piezoelectric element 19.

The cross section of the liquid discharge head 434 shown in FIG. 6 shows the cross section of one channel. Further, the portion shown as a cross section of each component in FIGS. 4 and 5 corresponds to a portion broken along the AA'line.

The ink introduced from the head tank 435 flows into the common liquid chamber 10 through the ink introduction / out flow path 14. In the common liquid chamber 10, each large diameter portion 4a in the individual supply passage 4 of each channel is communicated through the individual supply opening 6. The ink that has entered the large diameter portion 4a of the individual supply path 4 from the common liquid chamber 10 enters the small diameter portion 4b and heads for the pressure generating chamber 3 while being imparted with flow path resistance.

Further, in the liquid discharge head 434 of the present embodiment, in order to make the ink temperature uniform, as shown in FIG. 6, the temperature adjustment flow path 12 which is the refrigerant flow path is provided in the liquid discharge direction (vertical direction in FIG. 6). , It is arranged adjacent to the common liquid chamber 10 on the side opposite to the side where the pressure generating chamber 3 is located. As a result, the temperature adjusting flow path 12 does not have an individual supply path 4 that communicates the common liquid chamber 10 and each pressure generating chamber 3, and is located between the individual supply paths 4 in order to secure the flow of the refrigerant. Since it is not necessary to increase the interval (the interval in the nozzle arrangement direction; the direction perpendicular to the paper surface in FIG. 6) and the interval between the pressure generating chambers 3, it is possible to keep the interval between the plurality of nozzles 1 in the nozzle row narrow. it can.

Further, when the liquid discharge head 434 of the present embodiment includes two nozzle rows, the distance between these nozzle rows can also be maintained narrow because the individual supply paths 4 do not exist between them. If the spacing (arrangement pitch) of the nozzle rows is maintained narrow, the liquid discharge head can be miniaturized, and the landing position error between the nozzle rows due to the uneven movement speed of the liquid discharge head 434 can be reduced.

Here, the heat generated by the piezoelectric element 19 is transmitted from the pressure generation chamber 3 and the individual supply passages 4 to the common liquid chamber 10, and the ink in the common liquid chamber 10 is heated. In the heat distribution of the entire ink in the liquid ejection head 434, the ink temperature tends to increase in the vertical direction above the common liquid chamber 10 due to the occurrence of heat convection. The liquid discharge head 434 in the present embodiment is mounted so that the nozzle plate 2 faces downward in the vertical direction, and the liquid discharge direction is directed downward in the vertical direction.

Therefore, the temperature control flow path 12 of the present embodiment is arranged vertically upward with respect to the common liquid chamber 10. Therefore, the heat above the common liquid chamber 10 in the vertical direction can be exchanged with the refrigerant in the temperature adjusting flow path 12, and the liquid discharge head 434 with good cooling efficiency can be realized.

<Head of the second embodiment>
Next, a second embodiment of another embodiment in which the present invention is applied to a liquid discharge head used in an inkjet recording device which is a device for discharging a liquid will be described.

The inkjet recording device of the second embodiment includes four nozzle rows for one liquid ejection head, and ejects ink of the same color from all the nozzle rows. However, since the basic configuration and operation thereof are the same as those in the first embodiment described above, the temperature adjustment configuration of the liquid discharge head will be mainly described below.

FIG. 7 is an explanatory diagram showing the positional relationship between the common liquid chamber 10α of the liquid discharge head 434 and the temperature adjusting flow path 12α in the second embodiment. FIG. 8 is an explanatory view showing the common liquid chamber 10α of FIG. 7 and the temperature adjusting flow path 12α separately.

As described above, the liquid discharge head 434α mounted on the inkjet recording device of the present embodiment includes four nozzle rows, and one common liquid chamber 10α is provided corresponding to each nozzle row. .. In the present embodiment, since ink of the same color is ejected from all four nozzle rows, ink of the same color is supplied to a total of four common liquid chambers 10α connected to each nozzle row.

In the second embodiment, the four common liquid chambers 10α are communicated with each other by the liquid communication passage 23A at one end in the nozzle alignment direction, and the common liquid passage 24A connected to the head tank 435 is connected to the liquid communication passage 23A. ing. Further, the four common liquid chambers 10α are communicated with each other by the liquid communication passage 23B even at the other end in the nozzle alignment direction, and the liquid communication passage 23B is common for discharging the ink discharged from the common liquid chamber 10α. The liquid passage 24B is connected.

Further, in the present embodiment, four refrigerant flow paths 12α are arranged corresponding to the four common liquid chambers 10α. The temperature adjusting passages 12α are communicated with each other by the refrigerant communication passage 25A at one end in the nozzle arrangement direction, and the common refrigerant passage 26A connected to the refrigerant supply source is connected to the refrigerant communication passage 25A. Further, the four temperature control flow paths 12 are communicated with each other by the refrigerant communication passage 25B even at the other end in the nozzle arrangement direction, and the refrigerant (temperature control liquid) discharged from the temperature control flow path 12α is connected to the refrigerant communication passage 25B. ) Is connected to the common refrigerant passage 26B.

Also in this embodiment, in the liquid discharge direction (vertical direction in FIG. 7), the four temperature control flow paths 12α are opposite to the side where the pressure generating chamber 3 is located with respect to each of the four common liquid chambers 10α. It is placed adjacent to. Therefore, the same effect as that of the first embodiment described above can be exhibited, such that the interval between the nozzles 1 can be kept narrow.

Further, the four temperature control flow paths 12α are also arranged vertically upward with respect to each of the four common liquid chambers 10α. Therefore, in the second embodiment as well as in the first embodiment, the heat above the vertical direction of each common liquid chamber 10α can be exchanged with the refrigerant in each temperature adjusting flow path 12α, and the liquid discharge head having good cooling efficiency. 434 can be realized.

Further, in the present embodiment, as shown in FIG. 7, the common liquid passages 24A and 24B and the common refrigerant passages 26A and 26B are arranged at different positions from each other. Specifically, the common liquid passages 24A and 24B are arranged closer to one end side of the nozzle row arrangement direction (main scanning direction) at each end of the nozzle arrangement direction (secondary scanning direction), and are arranged closer to one end side of the nozzle arrangement direction (main scanning direction). , 26B are arranged closer to the other end side of the row arrangement direction (main scanning direction) of the nozzle rows at each end in the nozzle arrangement direction (secondary scanning direction).

With such an arrangement, the common liquid passages 24A and 24B and the common refrigerant passages 26A and 26B can be arranged at the same position in the nozzle arrangement direction (secondary scanning direction), and it is possible to suppress an increase in size in the nozzle arrangement direction.

In particular, in the present embodiment, the common refrigerant passages 26A and 26B are arranged diagonally when viewed from above in the vertical direction. As a result, it becomes easy to make the flow path lengths from the common refrigerant passage 26A on the inlet side to the common refrigerant passage 26B on the outlet side passing through each of the four temperature adjusting passages 12α substantially the same. Therefore, the fluid resistance of the four temperature adjusting flow paths 12α can be substantially made uniform, the flow rate of the refrigerant (temperature control liquid) can be made uniform, and the variation in the cooling effect with respect to the four common liquid chambers 10α can be eliminated.

Moreover, in the present embodiment, the common liquid passages 24A and 24B are arranged diagonally when viewed from above in the vertical direction. As a result, it becomes easy to make the flow path lengths from the common liquid passage 24A on the inlet side to the common liquid passage 24B on the outlet side, which pass through each of the four common liquid chambers 10α, substantially the same as each other. Therefore, the fluid resistance of the four common liquid chambers 10α can be substantially made uniform, the flow rate of the ink can be made uniform, and the variation in the cooling effect of the ink can be eliminated among the four common liquid chambers 10.

Further, in the present embodiment, the four common liquid chambers 10 and the four temperature control flow paths 12α are communicated by the liquid communication passages 23A and 23B and the refrigerant communication passages 25A and 25B at both ends in the nozzle arrangement direction, respectively. Road control is not complicated and easy.

<Control configuration>
Next, the outline of the control unit of the inkjet recording device 100 will be described with reference to FIG. Note that FIG. 9 is a control block diagram of the inkjet recording device 100.

The control unit 500 includes a CPU 501 that controls the entire device, a ROM 502 that stores fixed data such as various programs including a program executed by the CPU 501, and a RAM 503 that temporarily stores image data and the like. In addition, a rewritable non-volatile memory 504 for holding data even while the power of the device is cut off, image processing for performing various signal processing and sorting on image data, and other control for the entire device. It includes an ASIC 505 that processes input / output signals.

Further, a print control unit 508 including a data transfer means for driving and controlling the liquid discharge head (recording head) 434 and a drive signal generating means, and a head for driving the liquid and liquid discharge head 434 provided on the carriage 433 side. It includes a driver (driver IC) 509. In addition, the main scanning motor 554 that moves and scans the carriage 433, the sub-scanning motor 555 that orbits the transport belt 451, the cap 82 and wiper member 83 of the maintenance and recovery mechanism 481, and the maintenance and recovery motor 556 that moves the suction pump 812 and the like. The motor drive unit 510 for driving the motor drive unit 510 is provided. Further, it includes an AC bias supply unit 511 that supplies AC bias to the charging roller 456, a supply system drive unit 512 that drives the liquid feed pump 423, and the like.

Further, an operation panel 514 for inputting and displaying information necessary for the device is connected to the control unit 500.

The control unit 500 has an I / F 506 for sending and receiving data and signals to and from the host side, and is connected to a cable or a cable from the host PC 600 side such as an information processing device such as a personal computer, an image reading device, or an imaging device. Received by I / F 506 via the network.

Then, the CPU 501 of the control unit 500 reads out the print data in the reception buffer included in the I / F 506, analyzes the print data, performs necessary image processing, data rearrangement processing, and the like on the ASIC 505, and print-controls this image data. Transfer from unit 508 to head driver 509. In order to output an image, the dot pattern data can be generated by the printer driver 601 on the host PC 600 side or by the control unit 500.

The print control unit 508 transfers the above-mentioned image data as serial data, and outputs a transfer clock, a latch signal, a control signal, and the like necessary for transferring the image data and confirming the transfer to the head driver 509. It also includes a drive signal generator including a D / A converter that D / A-converts the pattern data of the drive pulse stored in the ROM 502, a voltage amplifier, a current amplifier, and the like. Then, a drive waveform composed of one drive pulse or a plurality of drive pulses is generated and output to the head driver 509.

The head driver 509 selects a drive pulse that constitutes a drive waveform given by the print control unit 508 based on image data corresponding to one line of the liquid discharge head 434 that is serially input, and selects a drive pulse that constitutes a drive waveform, and the pressure of the liquid discharge head 434. It is given to the piezoelectric element 19 as a generating means. This drives the liquid discharge head 434. At this time, by selecting a part or all of the pulses constituting the drive waveform or all or a part of the waveform elements forming the pulse, dots having different sizes such as large droplets, medium droplets, and small droplets are selected. Can be separated.

The I / O unit 513 acquires information from various sensor groups 515 mounted on the device, extracts information necessary for printer control, and print control unit 508, motor drive unit 510, and AC bias supply unit. Used for controlling 511. The sensor group 515 includes an optical sensor for detecting the position of the paper, a thermistor for monitoring the temperature inside the machine, a sensor for monitoring the voltage of the charging belt, an interlock switch for detecting the opening / closing of the cover, and the like. .. The I / O unit 513 can process various sensor information.

Next, an example of the print control unit 508 and the head driver 509 will be described with reference to the block explanatory diagram of FIG. The head driver 509 is provided on the flexible printed circuit board 22 shown in FIG.

The print control unit 508 includes a drive waveform generation unit (an example of a basic drive waveform generation unit) 701 and a data transfer unit (an example of a control signal generation unit) 702. The drive waveform generation unit 701 generates and outputs a drive waveform (common drive waveform) composed of a plurality of pulses (drive signals) within one print cycle (one drive cycle) at the time of image formation. The data transfer unit 702 outputs 2-bit image data (gradation signals 0, 1) corresponding to the printed image, a clock signal, a latch signal (LAT), and control signals a to d.

The control signal (also referred to as a drop control signal, a selection signal, or a mask signal) is a 2-bit signal that instructs each drop to open / close (ON / OFF) the analog switch 715, which is an example of the switching element of the head driver 509. is there. Then, the control signal transitions to the H level (ON) at the pulse or waveform element to be selected according to the printing cycle of the common drive waveform, and transitions to the L level (OFF) when not selected.

The head driver 509 includes a shift register 711 for inputting a transfer clock (shift clock) and serial image data (gradation data: 2 bits / 1 channel (1 nozzle)) from the data transfer unit 702, and each registration value of the shift register 711. Is provided with a latch circuit 712 for latching by a latch signal.

Further, the head driver 509 has a decoder 713 that decodes the gradation data and control signals M0 to M3 and outputs the result, and a level shifter that converts the logic level voltage signal of the decoder 713 into a level at which the analog switch 715 can operate. It is equipped with 714.

The head driver 509 includes an analog switch 715 that is turned ON / OFF (opened / closed) by the output of the decoder 713 given via the level shifter 714.

The analog switch 715 is connected to a selection electrode (individual electrode) of each piezoelectric element 19, and a common drive waveform Pv from the drive waveform generation unit 701 is input. Therefore, the common drive waveform Pv is configured by turning on the analog switch 715 according to the result of decoding the serially transferred image data (gradation data) and the control signals M0 to M3 (a to d) by the decoder 713. The required pulse (or corrugated element) to be applied passes (selected) to the piezoelectric element 19.

<Cut out the reference drive waveform by the control signal>
Next, the basic drive waveform, the control signal, and the discharge waveform used in FIG. 10 will be described with reference to FIG. FIG. 11 is a diagram showing a reference drive waveform, a control signal, and a discharge waveform used for the control of the present invention. First, the definition of each signal (waveform) will be described.

The reference drive waveform (also referred to as a common drive waveform) is a waveform obtained by D / A conversion of waveform data stored in ROM 502 or the like, and is a waveform corresponding to one print cycle (one drive cycle).

The pulse represents a unit pulse constituting the basic drive waveform, and is a pulse including one drop discharge (expansion → retention → contraction). A plurality of drive pulses are included in the basic drive waveform.

The control signal (also referred to as a mask signal, a drop control signal, or a selection signal) is a 2-bit (binary value) signal that instructs the opening / closing of the analog switch 715 for inputting the drive waveform for each drop size. Here, when the control signals a to d are H (one value), the drive pulse or waveform element of the basic drive waveform passes through, and the waveform is given to the piezoelectric element 19.

The analog switch (switching element) 715 is turned on so that the control signal applies the basic drive waveform to the piezoelectric element during the H (High) period, and the basic drive waveform is applied to the piezoelectric element during the L (Low) period. The analog switch 715 is turned off so as to mask without applying to. In this example, the control signal shows an example in which the H period corresponds to the ON period of the analog switch 715 and the L period corresponds to the OFF period of the analog switch 715, but the control signal is L and the switch. Control may be performed so that the switch is turned off when the switch is turned ON or H. Alternatively, ON / OFF control of the analog switch 715 may be performed by turning the control signal itself ON / OFF.

It is a waveform composed of a series of drive pulses or waveform elements cut out from the drive waveform by switching the discharge waveform and the control signals a to d, and is a waveform given to the piezoelectric element 19 within one printing cycle.

The discharge pulse indicates a unit pulse constituting the discharge waveform, and means a unit discharge waveform including one drop discharge (expansion → holding → contraction).

Further, the fine drive pulse is an example of a non-ejection pulse, which is a pulse applied to the piezoelectric element 19 but does not eject drops (flows ink in the nozzle). When the fine drive pulse is selected, the droplet is not ejected from the nozzle, but the waveform is also treated as one of the ejection waveforms for convenience.

FIG. 11 shows an example of a reference drive waveform for ejecting droplets (large droplet, medium droplet, and small droplet) having three types of droplet sizes. The drive waveform generation unit 701 outputs a reference drive waveform (common drive waveform) Vcom as shown in FIG. 11A. This drive waveform Vcom is a waveform in which a fine drive pulse P0 and drive pulses P1, P2, and P3 which are discharge pulses for ejecting droplets are generated in time series within one print cycle (one drive cycle). ..

Here, focusing on the control signal, the control signals a, b, and c, except for the fine drive, have the potential of the basic drive waveform at the reference potential after the final pulse P3 of a plurality of pulses within the period of the basic drive waveform. The period includes a waveform that becomes H for a predetermined period. By the control signal L → H → L during this period, the analog switch 715 is switched from OFF to OFF for a short period of time.

Further, in the waveform control shown in FIG. 11, in the control signal a for large droplets, continuous pulses included in the basic drive waveform are continuously selected, and between continuous pulses (P1⇒P2, P2⇒P3). ) Has a portion that becomes L for a predetermined period. By H → L → H of the control signal during this period, each analog switch 715 is switched from ON to ON for a short period of time.

Therefore, in the present invention, assuming that the switching of H → L and the switching of L → H in the control signal are combined as the number of switchings, in FIG. 12, in one drive cycle, 8 times for large droplets and 6 times for medium droplets. Switching is performed 4 times for small drops and 2 times for fine drive.

Therefore, in the control waveform that cuts out the pulse elements required to eject different droplet sizes from the basic drive signal that includes a plurality of pulses, the number of ON / OFF times of the signal that cuts out the waveform is large. It is increasing as it becomes. That is, the number of times of switching correlates with the size of the discharge size.

As described above, since the control signal is switched between H and L according to the timing of the latch signal, switching can be performed when selecting a discharge pulse in which the control signal for large droplets is continuous in the drive cycle. At the joints of the discharge pulses P1, P2, and P3, there is at least one latch that maintains the reference voltage. It is preferable that it is provided. Further, since the control signals a, b, and c for the droplets are switched from L to H to L after the final pulse, it is preferable that at least three latches are provided to maintain the reference potential.

The control signal itself that cuts out the waveform element is not intended to directly drive the piezoelectric element, but a minute current is generated by the switching resistance of the analog switch 715, which is the resistor of the head driver 509 (drive IC) on the flexible printed circuit board 22. Heat is generated by contracting and expanding to the extent that the piezoelectric element does not discharge.
Due to the heat generated by this switching, heating can be performed using a control signal without the need for an additional mechanism.

Therefore, in the control of the present invention, since the heat generated by the piezoelectric element is generated in the immediate vicinity of the nozzle, the ink in the pressure chamber communicating with the nozzle can be directly heated by the temperature control mechanism such as a heater, and the liquid is liquid. By changing the number of switchings according to the drop size, it is possible to improve the time responsiveness as compared with the temperature control mechanism.

These controls do not require a special mechanism, and details such as time response and heat generation amount can be determined only by changing H and L of the control signals for waveform extraction.

The number of switchings in the control signals a, b, and c in FIG. 11 is an example, and the number of switchings in one cycle can be changed according to the head temperature. The setting of the number of switching times according to the temperature will be described in detail together with FIG. When the number of times of switching of the control signal can be adjusted, the control signal shown in FIG. 11 is taken as an example of the reference value.

<Waveform of comparative example>
FIG. 12 is a diagram showing a reference drive waveform, a control signal, and a discharge waveform used for controlling a comparative example. Compared with the present invention shown in FIG. 11, in the comparative example shown in FIG. 12, the point where switching after the final pulse is not provided, and when selecting a large drop, the control signal is finally selected once the selection is started. The difference is that the H state is maintained without switching to the pulse.

In the comparative example, in the control of a large drop, once the selection is started, it is until the end of the final pulse. In order to maintain the H state, the mask signal is 2 times for a large drop, 4 times for a medium drop, 2 times for a small drop, and 2 times for a fine drive in one drive cycle.

Therefore, in the comparative example, the number of times of switching does not correlate with the drop size, and especially for large drops, the number of times of switching is different from that of the present invention, so that the amount of heat generated by switching is smaller than that of the present invention.

<Drive signal ratio for each general density gradation>
FIG. 13 is a graph showing the drive signal ratio for each density gradation when the liquid is discharged to form an image. As shown in FIG. 13, as the concentration increases, the proportion of droplets having a large droplet size to be ejected increases.

<Temperature according to density gradation in comparative example>
FIG. 14 is a graph showing the amount of heat released for each density gradation when the control of the comparative example is used. In general, the larger the volume of liquid discharged, the greater the heat transfer, that is, the heat dissipation. Therefore, if no measures are taken against heat dissipation, the temperature tends to decrease as the density gradation increases, as shown in FIG.

In particular, in the comparative example, the temperature of the large droplet is significantly reduced because the number of switching times of the analog switch is smaller than that of the medium droplet and the heat generation effect is low with respect to the amount of heat radiation.

<Amount of heat generated under the control of the present invention>
FIG. 15 is a graph showing the amount of heat generated by switching for each density gradation when the drive control of the present invention is carried out.

The amount of heat generated by the drive control of the present invention is the heat generated by the contraction / expansion of the piezoelectric element 19 due to the discharge waveform, and the heat generated by the switching resistance when the analog switch 715 is turned ON / OFF according to the control signal. The total is the calorific value shown in FIG.

In the present invention, the number of times the control signal is switched increases as the droplet size increases, so that ON / OFF switching increases in the analog switch 715, and the higher the density gradation, the more heat is generated.

<Temperature according to the density gradation in the comparative example and the present invention>
FIG. 16 is a graph showing a comparative example and thermal fluctuations for each density gradation when the drive control of the present invention is carried out.

In the control of the present invention, by supplementing the amount of heat radiated by the discharge with the heat generated by the analog switch 715 (switching element) according to the switching of the control signal, even if the density gradation fluctuates, the control of the comparative example is performed. It is difficult for the temperature to drop. As a result, fluctuations in image quality can be prevented.

<Example of control according to temperature in the present invention>
In the present invention, the number of times the control signal is switched is adjusted according to the temperature detected by the temperature sensor 28 in order to realize an appropriate temperature inside the head according to the situation.

FIG. 17 is an example of a flowchart showing signal processing according to the temperature inside the head of the present invention.

First, the image data is read in S1.

In S2, the temperature sensor 28 detects the temperature inside the head.

In S3 to S9, switching of the control signal is set according to the detected temperature. Table 1 shows an example of setting the number of switching times. Table 1 is an example of a drop type / switching number correspondence table when the switching number is set according to the detection temperature.

詳しくは、Ｓ３で検知された温度が、所定範囲内（Ｔｂ〜Ｔｃ）の場合は（Ｙｅｓ）、Ｓ６で制御信号のスイッチング回数を基準値に設定する。

Specifically, when the temperature detected in S3 is within a predetermined range (Tb to Tc) (Yes), the number of times the control signal is switched is set as a reference value in S6.

If the detected temperature is higher than the predetermined range (Yes in S4), the number of times the control signal is switched is set less than the reference value in S7.

When the temperature in the detected liquid discharge head is higher than the predetermined range, the number of times of switching of the control signal after the final pulse in the drive cycle is reduced, or the switching of the control signal after the final pulse is deleted.

If the detected temperature is below the predetermined range and is equal to or higher than the lower threshold value (Yes in S4 and Yes in S5), the number of times the control signal is switched in S8 is set one step more than the reference value.

For example, as an example of increasing the switching of the control signal when the temperature in the detected liquid discharge head is lower than the predetermined range, the number of times of switching of the control signal after the final pulse is increased. Alternatively, the control signal may be switched so as to be performed before the head pulse P0 in the drive cycle.

If the detected temperature is less than the lower threshold below the predetermined range (Yes in S4 and No in S5), the number of times the control signal is switched in S9 is set two steps more than the reference value.

For example, the number of times the control signal is switched after the final pulse may be increased, or the control signal may be switched before the first pulse P0 of the drive cycle.

Then, in S10, the control unit outputs a reference drive waveform for each drive cycle.

In S11, the control signal is set in any of S6, S7, S8, and S9 based on the droplet size which is the pixel information included in the image data at the printing timing, and the control signal is switched between H and L (switching control). do.

In S12, when the control signal becomes H during the drive pulse period of the reference drive waveform, the analog switch 715 is turned on during the H period, and the drive waveform is applied to each piezoelectric element 19. At this time, in each drive cycle, the control signal is switched at the number of switching times set in the order of large drop> medium drop> small drop, and the analog switch 715 is switched ON / OFF.

After the end of the final pulse period of the reference drive waveform in S13, the control signal is switched to H for a predetermined period as necessary, and the analog switch 715 is turned OFF⇒ON⇒OFF. When the switching after the final pulse is deleted in S7, the switching in S13 is unnecessary.

When the next detection temperature detection time is reached in S14, the temperature in the head is detected by returning to S2, and the number of times of switching of the control signal is reset in S3 to S9.

Then, in S15, the process returns to S10 until the end of the image data is reached (No), processing is continued for each drive cycle, and when the end of the image data is reached, the processing ends.

In the present invention, by such control, the heat radiated by the ejection can be compensated only by changing the switching of the control signal for cutting out without changing the driving portion related to the ejection of the liquid drops. In the first place, it is possible to suppress the temperature change of the head.

Since the temperature change width is small, (1) the discharge liquid can be discharged in a stable region of the physical property value, (2) the correction of the drive waveform for discharge can be minimized, and (3) the print quality. It has the effect of being able to increase the temperature.

<Head of the third embodiment>
In the drive control for the first and second embodiments described above, an example in which the temperature is heated and controlled only by the analog switch 715 has been described.

However, in the present invention, in addition to the heat generation control by the switching resistance by the analog switch 715, a heater for adjusting the temperature in the head may be further provided.

FIG. 18 is a cross-sectional view showing an AA'cross section of the liquid discharge head 434β of the third embodiment.

In the present embodiment, the heater 29 is provided in the vicinity of the common liquid chamber 10 and the temperature control flow path 12 of the first embodiment. In this embodiment, the heater 29 and the temperature control flow path 12 function as a temperature control mechanism.

For example, in the above-mentioned first and second temperature control mechanisms, the refrigerant is circulated in the temperature adjusting flow path 12, but even if the temperature is made uniform as a whole by the refrigerant, when the outside air temperature is low, the ink is used. The viscosity will decrease. Therefore, in the present embodiment, by mounting the heater 29 on the wall constituting the common liquid chamber 10 and the temperature adjusting flow path 12, the refrigerant in the temperature adjusting flow path 12 can be heated and the ink in the common liquid chamber 10 can be heated. it can.

In the present embodiment, the heater control unit is provided in the control unit 500 (see FIG. 9), and the heater control unit controls the heater 29 according to the detection result of the temperature sensor 28 and passes through the temperature adjustment flow path 12. The temperature of the refrigerant and the ink in the common liquid chamber 10 is adjusted so as to be a predetermined set temperature.

In the present embodiment, for example, the heater 29 adjusts the temperature for each section so as to eliminate the variation for each nozzle due to the length of the flow path. Alternatively, the heater 29 may be operated only when it is necessary, such as when the outside air temperature is cold and the temperature inside the head detected by the temperature sensor 28 is low.

Therefore, in the present embodiment, by adjusting the temperature by the heater in addition to the temperature adjustment by switching the control signal described above, the physical property value of the discharged liquid is more stable while eliminating the temperature difference between the nozzles. It is possible to improve the print quality by ejecting in a wide area.

<Ink heating unit of the head of the fourth embodiment>
In the third embodiment, an example in which a heater is provided in the vicinity of the common liquid chamber is shown, but in addition to switching, an ink heating unit may be provided in the vicinity of the nozzle as a configuration for adjusting the temperature by heating.

FIG. 19 is a schematic view of the ink heating unit 64 of the liquid ejection head (recording head) 434γ. FIG. 20 is a plan view showing a nozzle arrangement image on the nozzle surface of the liquid discharge head 434γ.

The ink heating unit 64 includes a housing 132 as shown in FIG. In the case of the present embodiment, as shown in FIG. 20, the housing 132 has a liquid discharge head 535γ, so as to expose the nozzle surface 134 in which a plurality of nozzles 106 are arranged on one surface side (the back surface side of the housing 132). Alternatively, a part of the liquid discharge head 434γ can be stored.

In the case of the present embodiment, as an example, a plurality of rows, for example, two rows of A nozzle rows 134a and B nozzle rows 134b are formed on the nozzle surface 134. The A nozzle row 134a and the B nozzle row 134b are connected to separate common liquid chambers 10, and are configured so that different inks can be ejected from each nozzle row.

For example, the A nozzle row 134a and the B nozzle row 134b may eject inks of the same color (recording liquid), or inks of different colors may be ejected. The number of nozzles 106 in the A nozzle row 134a and the B nozzle row 134b is the same, and the nozzles 106 are provided at the same positions in the longitudinal direction of the liquid discharge head 434γ.

As an example, the housing 132 has groove-shaped nozzle storage portions 132a and 132b corresponding to the liquid discharge head 434γ. That is, the flow path corresponding to the A nozzle row 134a is stored in the nozzle storage portion 132a, and the flow path corresponding to the B nozzle row 134b is stored in the nozzle storage portion 132b. Ink heaters 66a and 66b for adjusting the temperature (heating adjustment) of the ink passing through the stored flow path are mounted on the inner walls of the nozzle storage portions 132a and 132b. Further, a concave sensor storage portion 132c is formed at a position between a part of the housing 132, for example, the nozzle storage portion 132a and the nozzle storage portion 132b, so that the temperature sensor (an example of the temperature detection unit) 68 can be stored. There is. The temperature sensor 68 composed of a thermistor or the like detects (estimates) the temperature of the ink flowing in the flow path stored in the nozzle housing portions 132a and 132b via the housing 132.

In the present embodiment, a heater control unit is provided in the control unit 500 (see FIG. 9), and the heater control unit controls the ink heaters 66 (66a, 66b) according to the detection result of the temperature sensor 68 to obtain ink. The temperature of the ink passing through the heating unit 64 is adjusted to a predetermined set temperature.

Although FIG. 19 shows a configuration in which the flow path is surrounded by a sheet-shaped heater, a rod-shaped heater may be inserted into the housing 132 to heat the entire housing 132, and the same control and effect can be obtained. ..

The arrangement of the heater 29 in FIG. 18 and the ink heater 66 in FIG. 19 as the heating unit of the temperature adjusting mechanism is an example, and other arrangements can be used as long as the ink temperature can be adjusted to a desired temperature. Good.

Therefore, in the present embodiment, as in the third embodiment, in addition to the temperature adjustment by switching the control signal described above, the temperature is adjusted by the heater to eliminate the temperature difference between the nozzles and discharge the liquid. It is possible to improve the print quality by ejecting in a more stable region of the physical property value of.

Although the preferred embodiment has been described in detail above, it is not limited to the above-described embodiment, and various modifications and substitutions are made to the above-described embodiment without departing from the scope of claims. Can be added.

Further, in the above example, the liquid discharge device of the present invention is an image forming apparatus using a serial type liquid discharge head that discharges liquid over the entire area in the direction orthogonal to the transport direction in which the carriage moves in the direction orthogonal to the transport direction. Although an example of applying the device has been described, the liquid discharge device of the present invention and the drive waveform control of the liquid discharge head are applied to the line type image forming device that discharges liquid over the entire area perpendicular to the transport direction. For example, in the above-described embodiment, the image forming apparatus including the conveying device according to the present invention has been described, but the conveying device according to the present invention is widely applied to an apparatus for discharging a liquid including the image forming apparatus. be able to.

Here, the "liquid discharge device" is a device provided with a liquid discharge head or a liquid discharge unit which is a liquid discharge unit, and drives the liquid discharge unit to discharge the liquid. The device for discharging the liquid includes not only a device capable of discharging the liquid to a device to which the liquid can adhere, but also a device for discharging the liquid into the air or the liquid.

This "liquid discharge device" can also include means related to feeding, transporting, and discharging paper to which a liquid can adhere, as well as a pretreatment device, a posttreatment device, and the like.

Further, the "liquid discharge device" is not limited to a device in which significant images such as characters and figures are visualized by the discharged liquid. For example, those that form patterns that have no meaning in themselves and those that form a three-dimensional image are also included.

The above-mentioned "material to which a liquid can adhere" means a material to which a liquid can adhere at least temporarily, such as one that adheres and adheres, one that adheres and permeates. Specific examples include media such as paper, recording paper, recording paper, film, cloth and other recording media, electronic substrates, electronic components such as piezoelectric elements, powder layers (powder layers), organ models, and inspection cells. Yes, and unless otherwise specified, includes anything to which the liquid adheres.

The material of the above-mentioned "material to which liquid can be attached" may be paper, thread, fiber, cloth, leather, metal, plastic, glass, wood, ceramics or the like as long as the liquid can be attached even temporarily.

The "liquid" also includes inks, treatment liquids, DNA samples, resists, pattern materials, binders, modeling liquids, solutions containing amino acids, proteins and calcium, and dispersion liquids.

In addition, as a "liquid discharge device", a treatment liquid coating device that discharges a treatment liquid onto a paper in order to apply the treatment liquid to the surface of the paper for the purpose of modifying the surface of the paper, and a solution of raw materials. There are injection granulators and the like that atomize fine particles of raw materials by injecting a composition liquid dispersed therein through a nozzle.

The "liquid discharge unit" is a liquid discharge head such as an inkjet head in which functional parts and a mechanism are integrated, and is an assembly of parts related to liquid discharge. For example, the "liquid discharge unit" includes a head tank, a carriage, a supply mechanism, a maintenance / recovery mechanism, a main scanning movement mechanism in which at least one of the configurations is combined with a liquid discharge head, and the like.

Here, "integration" means, for example, a liquid discharge head and a functional component, a mechanism fixed to each other by fastening, adhesion, engagement, etc., or one in which one is movably held with respect to the other. Including. Further, the liquid discharge head and the functional parts and the mechanism may be detachably attached to each other.

Further, the pressure generating means used for the "liquid discharge head" is not limited. For example, a piezoelectric actuator (which may use a laminated piezoelectric element), a thermal actuator using an electrothermal conversion element such as a heat generating resistor, an electrostatic actuator composed of a diaphragm and a counter electrode, or the like can be used.

In addition, image formation, recording, printing, printing, printing, modeling, etc. in the terms of the present application are all synonymous.

1,106 Nozzle 2 Nozzle plate 3 Pressure generation chamber (pressure chamber)
4 Individual supply path 5 Flow path plate 6 Individual supply opening 7 Diaphragm film 8 Diaphragm plate 9 Actuator insertion part 10, 10α Common liquid chamber 11 Frame 12, 10 α Temperature control flow path (temperature control mechanism)
13 Partition plate 14 Ink introduction / output flow path 15 Temperature control liquid introduction / output flow path 19 Piezoelectric element 20 Fixing member 21 Piezoelectric actuator 22 Flexible printed substrate 23A, 23B Liquid communication passage 24A, 24B Common liquid passage 25A, 25B Refrigerant communication passage 26A, 26B Common refrigerant passage 27 Sensor accommodating holes 28,68 Temperature sensor (temperature detector)
29 Heater (temperature control mechanism)
66a, 66b Ink heater (temperature control mechanism)
100 Inkjet recording device (image forming device, liquid ejection device)
410 Main tank 430A, 430B Liquid discharge unit 433 Carriage 434, 434α, 434β, 434γ Liquid discharge head (recording head)
435 Head tank 436 Supply tube 442 Recording sheet 481 Maintenance / recovery mechanism 701 Drive waveform generator (basic drive waveform generator)
702 Data transfer unit (control signal generation unit)
715 Analog switch (switching element)
a, b, c, d control signal Vcom basic drive waveform

Japanese Unexamined Patent Publication No. 2000-289204 Japanese Unexamined Patent Publication No. 2016-175183 Japanese Patent No. 6135993

Claims (8)

A plurality of nozzles for discharging a liquid, a plurality of pressure chambers corresponding to the plurality of nozzles, a plurality of piezoelectric elements for applying pressure to the plurality of pressure chambers, and a plurality of switching elements provided corresponding to the plurality of piezoelectric elements. , And a liquid discharge head provided with a temperature detection unit that detects the temperature inside the liquid discharge head.
A basic drive waveform generator that generates a basic drive waveform that includes multiple pulses,
A control signal generation unit that generates a binary control signal by selecting a period including one or a plurality of pulses from the basic drive waveform and cutting out a discharge waveform for each droplet size.
A switching control unit that controls switching of the control signal is provided.
Each switching element of the plurality of switching elements performs ON / OFF switching in response to the switching of the control signal, and during the period when the control signal has one value and each switching element is ON. , The ejection waveform for each of the cut droplet sizes is applied to each piezoelectric element,
The switching control unit increases or decreases the number of times of switching of the control signal, which has a correspondence relationship with the size of the droplet size discharged by the discharge waveform, according to the detected temperature in the liquid discharge head. apparatus. One side of the wall facing each nozzle in each pressure chamber is composed of a partially displaceable diaphragm.
The plurality of piezoelectric elements apply pressure to the pressure chamber by displacement in a state where the end face is in contact with the displaceable portion of the diaphragm.
A flexible printed circuit board provided with each of the switching elements associated with the control signal is contacted and connected to the side surface of each of the piezoelectric elements.
When the liquid is discharged from each of the nozzles, the temperature of each of the pressure chambers is lowered due to heat dissipation by the discharge.
The switching control unit switches ON / OFF of each switching element by switching the control signal while the basic drive waveform is at a reference potential other than the pulse.
When switching ON / OFF of each of the switching elements, a minute current is generated by the switching resistance of each of the switching elements, and the piezoelectric element contracts and expands to such an extent that the piezoelectric element is not discharged by the minute current, so that each of the piezoelectric elements The liquid discharge device according to claim 1, wherein the heat is generated and transmitted to each of the pressure chambers. After the final pulse of the plurality of pulses in the period of the basic drive waveform, the control signal is switched during the period when the potential of the basic drive waveform is at the reference potential, and each switching element is turned off for a short period of time. The liquid discharge device according to claim 1 or 2, wherein the switching of turning on and off is performed. The liquid discharge device according to claim 3, wherein when the detected temperature in the liquid discharge head is lower than a predetermined range, the number of times of switching of the control signal after the final pulse is increased. If the detected temperature in the liquid discharge head is higher than a predetermined range, the number of times the control signal is switched after the final pulse is reduced, or the switching of the control signal after the final pulse is deleted. Item 3. The liquid discharge device according to item 3. When the control signal continuously selects continuous pulses included in the basic drive waveform, the control signal is switched between the continuous pulses, and each switching element is turned from ON to OFF for a short period of time. The liquid discharge device according to any one of claims 1 to 5, wherein the switching is performed. The invention according to any one of claims 1 to 6, wherein a temperature control mechanism for adjusting the temperature of the liquid discharge head so as to reduce a temperature difference between a plurality of nozzles is provided inside the liquid discharge head. Liquid discharge device. It is a drive control method for the liquid discharge head.
The liquid discharge head is provided corresponding to a plurality of nozzles for discharging liquid, a plurality of pressure chambers corresponding to the plurality of nozzles, a plurality of piezoelectric elements for applying pressure to the plurality of pressure chambers, and the plurality of piezoelectric elements. It has a plurality of switching elements, and a temperature detection unit that detects the temperature inside the liquid discharge head.
A basic drive waveform generation step that generates a basic drive waveform containing multiple pulses,
A control signal generation step of selecting a period including one or more pulses from the basic drive waveform, cutting out a discharge waveform for each droplet size, and generating a binary control signal.
It has a switching control step that controls switching of the control signal.
Each switching element of the plurality of switching elements performs ON / OFF switching in response to the control signal, and the ejection waveform for each of the droplet sizes cut out during the period of one value of the control signal is displayed. Apply to each piezoelectric element,
In the switching control step, the number of times the control signal is switched, which has a correspondence relationship with the size of the droplet size discharged by the discharge waveform, is increased or decreased according to the detected temperature in the liquid discharge head. Head drive control method.

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