JP2014177045A - Droplet discharge device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a droplet discharge device capable of heating liquid of respective pressure liquid chambers using a drive waveform supplied to a piezoelectric element to reduce the temperature distribution in the whole head.SOLUTION: The droplet discharge device includes: a droplet discharge head comprising a plurality of nozzle holes for discharging droplets, a plurality of pressure liquid chambers with which the nozzle holes communicate, and a plurality of piezoelectric elements for applying the pressure change to the pressure liquid chambers via diaphragms constituting a part of the pressure liquid chambers; and a drive section for supplying the drive waveform to the piezoelectric elements. The electric resistance value of the resistor on a circuit for supplying the drive waveform to the piezoelectric elements from the drive section can be changed.

Description

  The present invention relates to a droplet discharge device including a droplet discharge head that discharges droplets from nozzle holes, and an image forming apparatus that forms an image by discharging a recording liquid agent onto a medium from the droplet discharge head. .

  This type of droplet discharge apparatus is used as an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a plotter. The image forming apparatus here forms an image on a recording material, but the material of the recording material is not limited to paper, and is a thread, fiber, fabric, leather, metal, plastic, glass, It means an apparatus for forming an image by discharging a liquid onto any recording material such as wood or ceramics. Image formation not only applies an image having a meaning such as a character or a figure to a recording material, but also applies an image having no meaning such as a pattern to the recording material (simply ejects a droplet). ) Also means. The liquid ejected as droplets is not limited to so-called ink, and is not particularly limited as long as it becomes liquid when ejected, and includes, for example, DNA samples, resists, pattern materials, and the like. It is.

  As a driving method of the droplet discharge head in such an image forming apparatus, an electromechanical conversion method using a piezoelectric element composed of a common electrode, a piezoelectric layer, and an individual electrode is mainly used at present. In this droplet discharge head, the deformation of the piezoelectric element is converted into a pressure change in each pressure liquid chamber via a vibration plate that constitutes a ceiling portion of the plurality of pressure liquid chambers communicating with each of the plurality of nozzle holes. Thereby, a droplet is discharged from each nozzle hole provided in the nozzle plate constituting the bottom portion of each pressurized liquid chamber. At this time, a driving waveform for each droplet size is supplied from the driver IC to each piezoelectric element. In this way, the supply of the drive waveform causes heat generation of the driver IC and heat generation due to the electrical resistance of the wiring that is electrically connected to the individual electrodes of the driver IC. In order to meet the demand for high-speed printing, high-speed processing of driver ICs and increase in nozzle holes have been promoted, or in order to meet the demand for miniaturization, the density of nozzle holes has been increased. When the speed of the driver IC is increased, the amount of heat generated from the driver IC tends to further increase. When the nozzle holes are increased and the density is increased, the power supply terminals are increased and the density is increased in parallel with the increase in the number of wirings to the driver IC. As a result, the temperature in the head rises further, the temperature of the ink in the pressurized liquid chamber rises, and the ink viscosity falls below the desired viscosity. As a result, the ejection characteristics when the drive waveform is supplied change before and after the temperature rise, and the print quality is not stable. In order to prevent this, the head temperature is detected by a temperature sensor, or the temperature inside the device is detected and the head temperature is estimated from the driving history of the droplet discharge head to obtain the target discharge characteristics. Select a drive waveform that matches the head temperature. By using this drive waveform selection method, the droplet discharge head can be driven with a target discharge characteristic regardless of the head temperature.

  When the droplet discharge head has a plurality of nozzle holes, the temperature rise is not the same across the entire nozzle array. Depending on the print data, the current flowing through the wiring electrically connected to the individual electrodes of the piezoelectric elements corresponding to the nozzle holes with high discharge frequency is concentrated in the pressurized liquid chamber communicating with the nozzle holes with high discharge frequency. As a result, an ink temperature difference may occur between the pressurized liquid chambers. The head temperature when the above drive waveform selection method is used is the temperature detected or estimated for the entire head, and is different from the temperature of each pressurizing fluid chamber, so pressurization at a temperature different from the detected or estimated temperature is used. For the liquid chamber, the target ejection characteristics cannot be obtained, and the print quality may become unstable. In contrast, a heating means such as a heater is provided for each pressurized liquid chamber, and the pressure liquid chamber is individually heated by applying a heating voltage to the heating means, thereby adjusting the temperature between the pressurized liquid chambers. There is a method to make it substantially uniform. However, when a heater is mounted for each pressurized liquid chamber as in this method, there are problems that the cost is increased and the head is enlarged.

  As a droplet discharge device that reduces a temperature difference of ink between pressurized liquid chambers without mounting a heater, a device described in Patent Document 1 is known. In the droplet discharge device of Patent Document 1, the ink temperature in each pressurized liquid chamber is detected, and any one of a plurality of fine driving waveforms selected according to the detected ink temperature is supplied to each piezoelectric element. . The fine drive waveform is a drive waveform in which liquid is not discharged from the nozzle holes. In addition, each piezoelectric element provided corresponding to each pressurized liquid chamber is switched between supplying and not supplying a selected fine driving waveform, and a switching element having a predetermined electric resistance value is electrically connected. Has been. Controls on / off switching of the switching element. For example, the switching element corresponding to the pressurized liquid chamber in which the detected ink temperature is low is turned on, and the fine driving waveform selected according to the ink temperature is supplied to the piezoelectric element via the switching element. At that time, the switching element generates heat due to the electric resistance of the element itself, and this heat is transmitted to the corresponding pressurized liquid chamber, and the temperature of the ink in the pressurized liquid chamber rises. Accordingly, the ink in the low-temperature pressurized liquid chamber can be heated while preventing the droplets from being discharged without using a heater. Therefore, the temperature between the pressurized liquid chambers can be made substantially uniform, and the viscosity of the ink in all the pressurized liquid chambers can be made substantially uniform to a desired viscosity without increasing the cost and increasing the size of the head.

  However, since the voltage value of the fine driving waveform is smaller than the voltage value of the driving waveform for discharging droplets in the droplet discharge device of Patent Document 1, the amount of heat generated by the resistance of the switching element is small. For this reason, when the temperature difference of the ink between the pressurizing liquid chambers is large, there is a possibility that the ink cannot be heated only by stirring the ink in the pressurizing liquid chamber using the fine driving waveform. Therefore, there is a problem that the temperature distribution in the entire head cannot be reduced.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a droplet discharge device and an image forming apparatus that can reduce the temperature distribution in the entire head better than in the past. Is to provide.

  In order to achieve the above object, the invention of claim 1 comprises a plurality of nozzle holes for discharging droplets, a plurality of pressurized liquid chambers in communication with the nozzle holes, and a part of the pressurized liquid chamber. In a droplet discharge device including a droplet discharge head including a plurality of piezoelectric elements that apply a pressure change to the pressurized liquid chamber via a vibrating plate, and a drive unit that supplies a drive waveform to the piezoelectric element. The electrical resistance value of the resistor on the circuit that supplies the drive waveform from the drive unit to the piezoelectric element is configured to be switchable.

In the present invention, a heating means such as a heater to which a heating voltage is applied is not provided for each pressurized liquid chamber, and a fine driving waveform is not supplied to the piezoelectric element. A resistor capable of switching the electric resistance value when supplied to the piezoelectric element was constructed. Since the electrical resistance value of the resistor can be switched, the amount of heat generated by the resistor that generates heat by supplying the drive waveform can be switched to control the liquid temperature in the pressurized liquid chamber. For example, the liquid temperature in the pressurized liquid chamber is measured by a temperature sensor provided for each pressurized liquid chamber, or the liquid temperature in the pressurized liquid chamber is determined from the driving history of the droplet discharge head by detecting the temperature inside the apparatus. Or estimate. Based on the detected or estimated liquid temperature of the pressurized fluid chamber, the electrical resistance value of the resistor corresponding to the pressurized fluid chamber at a low temperature is switched to a higher value to increase the heat generation of the resistor, thereby increasing the fluid in the pressurized fluid chamber. Is increased as compared with the case of a lower electric resistance value. The drive waveform from the drive unit is supplied to the piezoelectric element through the resistor. However, even if the electric resistance value of the resistor changes, the voltage value and current value in the piezoelectric element do not substantially change. Experiments have shown that there is a range of change. If the electric resistance value is switched within this change range, the deformation of the piezoelectric element is hardly affected, and the ejection characteristics of the droplet are hardly affected.
As described above, according to the present invention, the temperature of the liquid in each pressurized liquid chamber can be controlled using a driving waveform having a voltage value larger than that of the conventional fine driving waveform, and the temperature distribution in the entire head can be compared with the conventional one. Thus, a unique effect that it can be satisfactorily reduced is obtained.

1 is a perspective view illustrating a configuration of an ink jet recording apparatus according to an embodiment. It is a side view of the mechanism part of the inkjet recording device of this embodiment. It is a schematic diagram which shows the heat_generation | fever location of a droplet discharge head. It is a figure which shows the mode of the change of the ink temperature for every group. It is an example of the drive circuit in a droplet discharge head. It is a wave form diagram which shows an example of a drive waveform. It is a figure which shows the voltage waveform applied to a piezoelectric element when the synthetic resistance value of an analog switch is 100 [Ω] and 200 [Ω]. It is a figure which shows the electric current waveform which flows per piezoelectric element 1ch. It is a figure which shows the power consumption waveform per drive IC when the synthetic resistance value of an analog switch is 100 [Ω] and 200 [Ω].

First, the configuration of an ink jet recording apparatus equipped with an ink jet recording head which is an example of a liquid droplet ejection head according to the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing a configuration of an ink jet recording apparatus according to the present embodiment, and FIG. 2 is a side view of a mechanism portion of the ink jet recording apparatus according to the present embodiment.
The ink jet recording apparatus 100 of this embodiment shown in FIGS. 1 and 2 includes a carriage 101 that can move in the main scanning direction inside the apparatus main body. A droplet discharge head 1 mounted on the carriage 101 and a print mechanism 103 including an ink cartridge 102 for supplying ink to the droplet discharge head 1 are accommodated. A paper feed cassette (or a paper feed tray) 104 capable of stacking a large number of recording materials 30 from the front side is detachably attached to the lower part of the apparatus main body. In addition, a manual feed tray 105 that is opened to manually feed the recording material 30 is provided. The recording material 30 fed from the paper feed cassette 104 or the manual feed tray 105 is taken in, a required image is recorded by the printing mechanism unit 103, and then discharged to a paper discharge tray 106 mounted on the rear side. The recording material 30 includes a medium made of a material such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics.

  The print mechanism 103 holds a carriage 101 slidably in the main scanning direction by a main guide rod 107 and a sub guide rod 108 which are guide members horizontally mounted on left and right side plates (not shown). (Y), cyan (C), magenta (M), and black (Bk) droplet ejection heads 1 that eject ink droplets of each color are arranged in a sub-scanning direction in which a plurality of ink ejection ports (nozzles) are orthogonal to the main scanning direction. And are mounted with the ink droplet ejection direction facing downward. In addition, each ink cartridge 102 for supplying ink of each color to the droplet discharge head 1 is replaceably mounted on the carriage 101.

  The ink cartridge 102 is provided with an atmosphere port communicating with the atmosphere above and a supply port for supplying ink to the droplet discharge head 1 below. A porous body filled with ink is contained inside, and the ink supplied to the droplet discharge head 1 is maintained at a slight negative pressure by the capillary force of the porous body. Further, although the droplet discharge head is used for each color as the droplet discharge head 1, one droplet discharge head having nozzles for discharging ink droplets of each color may be used.

  Here, the carriage 101 is slidably fitted to the main guide rod 107 on the rear side (downstream side in the paper conveyance direction), and is slidably mounted on the secondary guide rod 108 on the front side (upstream side in the paper conveyance direction). doing. In order to move and scan the carriage 101 in the main scanning direction, a timing belt 112 is stretched between a driving pulley 110 and a driven pulley 111 that are rotationally driven by a main scanning motor 109a. The timing belt 112 is fixed to the carriage 101, and the carriage 101 is reciprocally scanned by forward and reverse rotation of the main scanning motor 109a.

  On the other hand, the recording material 30 set in the paper feed cassette 104 is conveyed to the lower side of the droplet discharge head 1. For this purpose, the feeding roller 113 and the friction pad 114 for separating and feeding the recording material 30 from the paper feeding cassette 104, the guide member 115 for guiding the recording material 30, and the fed recording material 30 are reversed and conveyed. And a conveying roller 116 to be provided. Further, a conveyance roller 117 pressed against the peripheral surface of the conveyance roller 116 and a leading end roller 118 that defines a feeding angle of the recording material 30 from the conveyance roller 116 are provided. The conveyance roller 116 is rotationally driven via a gear train by the sub-scanning motor 109b.

  In addition, a printing receiving member 119 that is a paper guide member is provided to guide the recording material 30 fed from the conveying roller 116 below the droplet discharge head 1 in accordance with the moving range of the carriage 101 in the main scanning direction. ing. A conveyance roller 120 and a spur 121 which are rotationally driven to send the recording material 30 in the paper discharge direction are provided on the downstream side of the printing receiving member 119 in the paper conveyance direction, and the recording material 30 is further sent to the paper discharge tray 106. A paper discharge roller 123, a spur 124, and guide members 125 and 126 that form a paper discharge path are disposed.

  When recording with the ink jet recording apparatus 100, the droplet discharge head 1 is driven in accordance with the image signal while moving the carriage 101, thereby ejecting ink onto the recording material 30 that has stopped to record one line. Thereafter, after the recording material 30 is conveyed by a predetermined amount, the next line is recorded. Upon receiving a recording end signal or a signal that the trailing edge of the recording material 30 has reached the recording area, the recording operation is terminated and the recording material 30 is discharged.

  A recovery device 127 for recovering the ejection failure of the droplet ejection head 1 is disposed at a position outside the recording area on the right end side in the movement direction of the carriage 101. Each of the recovery devices 127 includes a cap unit, a suction unit, and a cleaning unit (not shown). During printing standby, the carriage 101 is moved to the recovery device 127 side and capping the droplet discharge head 1 with a capping unit to keep the discharge port portion in a wet state, thereby preventing discharge failure due to ink drying. Further, by discharging ink that is not related to recording during recording or the like, the viscosity of ink at all of the discharge ports is made constant, and stable discharge performance is maintained.

  Further, when a discharge failure occurs, the discharge port (nozzle) of the droplet discharge head 1 is sealed with a capping unit, and bubbles and the like are sucked out from the discharge port through the tube with a suction unit. As a result, the ink, dust, etc. adhering to the ejection port surface are removed by the cleaning means, and the ejection failure is recovered. Further, the sucked ink is discharged to a waste ink reservoir (not shown) installed at the lower part of the main body and absorbed and held by an ink absorber inside the waste ink reservoir.

  As described above, since the ink jet recording apparatus 100 includes the ink jet recording head having the actuator unit, stable ink droplet ejection characteristics can be obtained and the image quality can be improved.

  FIG. 3 is a schematic view showing a heat generation portion of the droplet discharge head. In the liquid droplet ejection head 300 shown in the figure, a drive signal is supplied from the control device 400 to the drive IC 302 via the drive signal wiring 301. The drive IC 302 supplies a drive waveform to the piezoelectric element 304 via the analog switch 303 as a resistor based on the drive signal. The piezoelectric element 304 is electrically connected to the control device 400 via the common electrode wiring 305. The drive IC 302 selects a drive signal so that a drive waveform is supplied only to the piezoelectric element 304 to be driven. As shown in FIG. 3, the nozzle hole rows (not shown) of the droplet discharge head 300 are divided into, for example, three groups A, B, and C. A temperature sensor 306 as temperature detecting means is provided at an arbitrary position in each group. A temperature sensor may be provided for each pressurized liquid chamber. The temperature sensor 306 detects the temperature of ink in a pressurized liquid chamber (not shown) in each group. For example, the temperature detection for each group is performed as follows. As one method, as shown in FIG. 3, the temperature of the ink for each pressurized liquid chamber in which the temperature sensors 306 are mounted is detected. Based on the temperature of each ink in each pressurized liquid chamber, the average temperature of the ink in the group is calculated. As another method, there is a method of obtaining by calculating from the driving history of the group with respect to the environmental temperature, but it is not necessary to limit to this. The difference between the highest temperature of the detected ink temperatures and the temperature of the other group is obtained. In a group other than the temperature group having the highest ink temperature, an on-resistance value of an analog switch (to be described later) of a driving IC that drives the piezoelectric elements of the group is largely changed according to the obtained temperature difference. This increases the heat generation of the analog switch. The temperature of the ink in the pressurized liquid chamber in the group is increased. Therefore, it is possible to bring the temperature of the other group closer to the temperature of the group having the highest ink temperature, and to minimize the temperature difference of the ink in the pressurized liquid chamber between the groups.

  Here, as an example of how to divide into a plurality of groups over the entire nozzle hole row, as shown in FIG. As shown in FIG. 4, in the group A, the temperature of the ink in the pressurized liquid chamber corresponding to almost all the nozzle holes in the group is outside the target range of the ink temperature. In the group B, the portion of the pressurized liquid chamber corresponding to the nozzle hole in which the temperature of the ink in the pressurized liquid chamber is within the target range of the ink temperature, and the nozzle that is outside the target range of the ink temperature The portion of the pressurized liquid chamber corresponding to the hole is almost halved. In the group C, the temperature of the ink in the pressurized liquid chamber corresponding to almost all the nozzle holes in the group is within the ink temperature target range. As described above, the heat generation of the piezoelectric element and the drive IC is transmitted to a wide range by heat conduction, and therefore, the temperature rises not only in a specific nozzle hole but in a certain range. At this time, the temperature range in which the temperature gradient of the ink temperature between the nozzle holes in the head substrate can be driven without affecting the print quality is grouped as the maximum range. Therefore, in the example shown in FIG. 4, heat generation by the analog switch in the group C is unnecessary, and heat generation by the analog switch in the groups A and B is increased to reduce the ink temperature gradient indicated by the dotted line shown in FIG. To do. Although the heat is generated by the resistance of the analog switch, it may be a terminal or wiring to which a drive waveform is supplied and the electrical resistance value can be switched. That is, any resistor that can switch the electric resistance value when the drive waveform is supplied to the piezoelectric element may be used. Further, the resistor may be installed in the vicinity of the pressurized liquid chamber heated by the resistor, and the installation location is not limited as long as it is an installation position capable of heating the liquid temperature of the pressurized liquid chamber.

  Next, the temperature detection of the ink will be described. The temperature detection wiring 307 electrically connected to the temperature sensor of FIG. 3 is a wiring configured using a platinum thin film used for the piezoelectric element wiring. Yes, the resistance value changes according to the temperature change of the head substrate (not shown). When the platinum thin film is used, the resistance value of the temperature detection wiring 307 is configured to be 100 [Ω] when the wiring pattern is 0 [° C.]. In the operating environment temperature of 0 [° C.] to 40 [° C.] in which the droplet discharge head is normally used, assuming that the operating environment temperature is T [° C.] and the wiring resistance value is R [Ω], R = 100 + 0.3908 · It can be expressed by an approximate expression T. By measuring the resistance value of the temperature detection wiring 307 by the device controller of the droplet discharge device, the temperature of the head substrate in the groups A, B, and C in FIG. 3 can be detected. Since the temperature detection wiring 307 is on the head substrate, the temperature of the head substrate is substantially equal to the ink temperature in the pressurized liquid chamber. By detecting the temperature of the head substrate, the temperature of the ink in the pressurized liquid chamber is detected.

  In addition, when the resistance value of the switching element is changed, a driving waveform in which deformation of the driving waveform caused by passing through a low-pass filter composed of the capacitance of the piezoelectric element and the resistance value of the switching element is applied to the switching element in advance. Let me lick. Thereby, the change of the ejection characteristic due to the change of the resistance value of the switching element can be minimized. By changing the number of nozzle holes in the group that increases the resistance value of the switching element due to the temperature difference between the groups, by controlling the number of nozzles that raise the resistance value instead of all the nozzle holes in the low temperature group, Fine heating control is possible. By increasing the resistance value of the switching element corresponding to the piezoelectric element to which the fine driving waveform for stirring the liquid in the pressurized liquid chamber is applied, the switching element generates heat by the fine driving waveform, thereby enabling fine heating control.

  FIG. 5 shows an example of a drive circuit in the droplet discharge head. In the figure, C1 to CN (N is a positive integer) are piezoelectric elements to which the drive waveform selected by the analog switch 311 is applied. Analog switches SW1 and SW2 are connected in parallel to the 1ch piezoelectric element. At the time of printing, both the switches SW1 and SW2 are turned on via the AND circuit and the amplifier circuit by the data signals DATA1 and DATA2, and the switch-on signals of SWON1 and SWON2, and the piezoelectric element is driven. The data signals DATA1 and DATA2 are signals synchronized with the reference clocks from the switch control units 312 and 313. When increasing the heat generation of the driving IC (not shown), the logical product circuit and the amplification circuit are generated by the data signal of either DATA1 or DATA2 from the switch control units 312, 313, or the switch-on signal of either SWON1 or SWON2. Then, either the switch SW1 or the switch SW2 is turned on to increase the combined resistance value. For example, when the resistance value of the switch SW1 and the resistance value of the switch SW2 are both 200 [Ω], the combined resistance value is 100 [Ω] when the switch SW1 is on and the switch SW2 is on. When the switch SW1 is on and the switch SW2 is off, the combined resistance value is 200 [Ω].

  FIG. 6 is a waveform diagram showing an example of a drive waveform. The drive waveform shown in FIG. 6 is applied to the piezoelectric element as a signal of the drive waveform of FIG. FIG. 7 is a diagram showing a voltage waveform applied to the piezoelectric element when the combined resistance value of the analog switch is 100 [Ω] and 200 [Ω], and FIG. 8 is a diagram showing a waveform of a current flowing per 1 ch of the piezoelectric element. . When the combined resistance value is 100 [Ω] and 200 [Ω], there is almost no difference in the voltage waveform and the current waveform applied to the piezoelectric element. Thus, it can be seen that even if a difference in the combined resistance value of the analog switch occurs, the ink ejection characteristics are not affected.

FIG. 9 is a diagram showing a power consumption waveform per channel of the driving IC when the combined resistance value of the analog switch is 100 [Ω] and 200 [Ω]. The power consumption P of the analog switch is P = R × I ^{2 where} R is the combined resistance value and I is the current, and is proportional to the combined resistance value. The power consumption when the combined resistance value is 200 [Ω] is about twice that when the combined resistance value is 100 [Ω]. That is, by changing the combined resistance value of the analog switch from 100 [Ω] to 200 [Ω], the power consumption of the driving IC can be doubled without affecting ink ejection. Since the heat generation of the drive IC is proportional to the power consumption, the heat generation is also doubled. The ink can be heated by conducting this heat to the ink in the pressurized liquid chamber.

What has been described above is merely an example, and the present invention has a specific effect for each of the following modes.
(Aspect 1)
The electrical resistance value of the resistor such as the analog switch 303 on the circuit for supplying the drive waveform to the piezoelectric element 304 from the drive unit such as the drive IC 302 can be switched. According to this, as described in the above embodiment, a heating means such as a heater to which a heating voltage is applied is not provided for each pressurized liquid chamber, but a fine driving waveform is supplied to the piezoelectric element. In addition, a resistor capable of switching the electric resistance value when the drive waveform is supplied to the piezoelectric element during droplet discharge is configured. Since the electrical resistance value of the resistor can be switched, the amount of heat generated by the resistor that generates heat by supplying the drive waveform can be switched to control the liquid temperature in the pressurized liquid chamber. For example, the liquid temperature in the pressurized liquid chamber is measured by a temperature sensor provided for each pressurized liquid chamber, or the liquid temperature in the pressurized liquid chamber is determined from the driving history of the droplet discharge head by detecting the temperature inside the apparatus. Or estimate. Based on the detected or estimated liquid temperature of the pressurized fluid chamber, the electrical resistance value of the resistor corresponding to the pressurized fluid chamber at a low temperature is switched to a higher value to increase the heat generation of the resistor, thereby increasing the fluid in the pressurized fluid chamber. Is increased as compared with the case of a lower electric resistance value. The drive waveform from the drive unit is supplied to the piezoelectric element through the resistor. However, even if the electric resistance value of the resistor changes, the voltage value and current value in the piezoelectric element do not substantially change. Experiments have shown that there is a range of change. If the electric resistance value is switched within this change range, the deformation of the piezoelectric element is hardly affected, and the ejection characteristics of the droplet are hardly affected. As described above, according to the present invention, the temperature of the liquid in each pressurized liquid chamber can be controlled using a driving waveform having a voltage value larger than that of the conventional fine driving waveform, and the temperature distribution in the entire head can be compared with the conventional one. And can be reduced satisfactorily.
(Aspect 2)
In (Aspect 1), the resistor is a switching means capable of switching an electric resistance value. According to this, as described in the above embodiment, the electric resistance value when the driving waveform is supplied to the piezoelectric element when the droplet is discharged can be switched.
(Aspect 3)
In (Aspect 2), the switching means includes a plurality of switching elements, and supplies a drive waveform from the drive unit to the piezoelectric elements via at least one of the switching elements. According to this, as described in the above embodiment, the electrical resistance value when the drive waveform is supplied to the piezoelectric element at the time of droplet discharge can be switched by switching a plurality of switching elements.
(Aspect 4)
In (Aspect 3), the switching elements are connected in parallel. According to this, as described in the above embodiment, the electric resistance value when the drive waveform is supplied to the piezoelectric element when the droplet is discharged can be switched with a simple configuration.
(Aspect 5)
In (Aspect 1), temperature detecting means for detecting the liquid temperature in the pressurized liquid chamber is provided, and the temperature difference from the highest liquid temperature among the liquid temperatures in the pressurized liquid chambers detected by the temperature detecting means is reduced. Thus, the electrical resistance value of the resistor corresponding to the pressurized liquid chamber to be heated is switched. According to this, as described in the above embodiment, the liquid for each pressurized liquid chamber can be heated using the drive waveform supplied to the piezoelectric element, and the temperature distribution in the entire head can be reduced.
(Aspect 6)
In (Aspect 5), the temperature detection means divides each pressurizing liquid chamber into a plurality of groups to detect the liquid temperature in the pressurizing liquid chamber for each group. Switches the electrical resistance value. According to this, as described in the above embodiment, the number of temperature detecting means can be reduced.
(Aspect 7)
In (Aspect 6), the electrical resistance value of the resistor in the group other than the group having the high liquid temperature is switched to be larger than the electrical resistance value of the resistor in the group having the high liquid temperature. According to this, as described in the above embodiment, the temperature detecting means and the control circuit can be reduced.
(Aspect 8)
In (Aspect 6) or (Aspect 7), the number of nozzle holes in the group in which the electrical resistance value of the resistor is increased by the temperature difference between the groups is changed. According to this, as described in the above embodiment, according to this, as described in the above embodiment, not all the nozzles of the low temperature group, but the pressurizing corresponding to the resistor that increases the electric resistance value. By controlling the number of nozzle holes in the liquid chamber, finer heating control can be performed.
(Aspect 9)
In (Aspect 1), the drive waveform is supplied to the resistor so as to have substantially the same shape as that of the drive waveform when the drive waveform is passed through a low-pass filter composed of the capacitance component of the piezoelectric element and the resistance component of the resistor. The drive waveform to be smoothed in advance. According to this, as described in the above embodiment, it is possible to minimize the change in the ejection characteristics due to the change in the electrical resistance value of the resistor.
(Aspect 10)
An image is formed by discharging a recording liquid onto a medium by a droplet discharge head provided in any of the droplet discharge apparatuses according to (Aspect 1) to (Aspect 9). According to this, as described in the above-described embodiment, according to this, as described in the above-described embodiment, it is possible to perform stable image formation with excellent ejection characteristics.

300 Liquid droplet ejection head 301 Drive signal wiring 302 Drive IC
303 Analog switch 304 Piezoelectric element 305 Common electrode wiring 306 Temperature sensor 307 Temperature detection wiring 311 Analog switch 312 Switch control unit 313 Switch control unit 400 Controller

JP 2008-143023 A

Claims (10)

A plurality of nozzle holes for discharging droplets, a plurality of pressurized liquid chambers communicating with the nozzle holes, and a pressure change in the pressurized liquid chamber via a vibration plate constituting a part of the pressurized liquid chamber. In a droplet discharge apparatus including a droplet discharge head including a plurality of piezoelectric elements to be applied and a drive unit that supplies a drive waveform to the piezoelectric elements,
A droplet discharge device characterized in that the electrical resistance value of a resistor on a circuit for supplying a drive waveform from the drive unit to the piezoelectric element can be switched. The droplet discharge device according to claim 1,
The droplet discharge apparatus according to claim 1, wherein the resistor is a switching means capable of switching an electric resistance value. The droplet discharge device according to claim 2,
The liquid droplet ejection apparatus, wherein the switching unit includes a plurality of switching elements, and supplies a driving waveform from the driving unit to the piezoelectric elements via at least one of the switching elements. The droplet discharge device according to claim 3.
Each of the switching elements is connected in parallel. The droplet discharge device according to claim 1,
Temperature detection means for detecting the liquid temperature in the pressurized liquid chamber is provided, and the temperature difference between the liquid temperature in the pressurized liquid chamber detected by the temperature detection means and the highest liquid temperature is reduced. A droplet discharge device characterized by switching an electric resistance value of the resistor corresponding to a pressurized liquid chamber to be heated. The droplet discharge device according to claim 5,
The temperature detecting means divides each of the pressurized liquid chambers into a plurality of groups, detects the liquid temperature of the pressurized liquid chamber for each group, and the electrical resistance value of the resistor in the group where the detected liquid temperature is low A droplet discharge device characterized by switching between. The droplet discharge device according to claim 6.
A droplet discharge device, wherein the electrical resistance value of the resistor in a group other than the group having a high liquid temperature is switched to be larger than the electrical resistance value of the resistor in a group having a high liquid temperature. In the droplet discharge device according to claim 6 or 7,
The droplet discharge device according to claim 1, wherein the number of nozzle holes in the group in which the electric resistance value of the resistor is increased is changed according to a temperature difference between the groups. The droplet discharge device according to claim 1,
A drive waveform supplied to the resistor so as to have substantially the same shape as the deformation of the drive waveform when the drive waveform is passed through a low-pass filter composed of a capacitance component of the piezoelectric element and a resistance component of the resistor. A droplet discharge device characterized by being smoothed in advance.   An image forming apparatus, wherein a recording liquid agent is ejected onto a medium by a liquid droplet ejection head provided in the liquid droplet ejection apparatus according to claim 1.

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