JP4583888B2 - Droplet discharge head, head driving device, liquid cartridge, and image forming apparatus - Google Patents

Description

  The present invention relates to a droplet discharge head, a head driving device, a liquid cartridge, and an image forming apparatus.

  For example, as an ink jet recording apparatus used as an image forming apparatus such as a printer, a facsimile machine, a copying apparatus, a composite apparatus of these, a plotter, etc., a nozzle for ejecting recording liquid (ink) droplets and a liquid chamber (ejection) connected to the nozzle A chamber, a pressure chamber, a pressurized liquid chamber, and an ink flow path), a diaphragm that forms the wall surface of the liquid chamber, and an electrode that faces the diaphragm through a gap (gap), Some of them include an electrostatic droplet discharge head that deforms a diaphragm with an electrostatic force and applies pressure to a recording liquid in a liquid chamber with its mechanical restoring force to discharge droplets from a nozzle.

In such an electrostatic droplet discharge head, the electrostatic force increases in inverse proportion to the square of the effective gap length between the diaphragm electrode and the fixed electrode, whereas the restoring force of the diaphragm is the amount of displacement. Since it is almost proportional to the first power, the diaphragm is placed on the fixed electrode side (stopper provided on the fixed electrode or fixed electrode) in order to efficiently eject droplets using a large electrostatic force in the minute gap region. (It is natural that an insulating film or the like is provided between the two). The droplet discharge is performed by the contact driving method.
JP-A-7-214769 JP 2001-260346 A JP 2001-287357 A

  When driving by such a contact driving method, the amount of displacement of the diaphragm is determined by the gap length, so it is not possible to change the droplet discharge amount discharged at one time while maintaining the desired droplet discharge speed. Have difficulty. In other words, it is possible to change the drive voltage and pulse width to some extent if only the discharge amount is used, but in this case, the droplet discharge speed will change greatly, and the drive method for changing the drive voltage is costly. There is also a disadvantage that it becomes high.

Therefore, as described in Patent Document 4, the gap formed between the diaphragm of the droplet discharge head and the electrode is, for example, stepped like a large gap, an intermediate gap, and a small gap. A method is known in which the droplet discharge amount is controlled by the magnitude of the drive voltage.
JP-A-9-39235

Further, as described in Patent Document 5, by changing the width or thickness of the vibration plate of the droplet discharge head depending on the region, a plurality of vibration regions having different displacement characteristics are formed, and depending on the magnitude of the driving voltage. A method for controlling the droplet discharge amount is known.
JP 2001-10036 A

Further, Patent Documents 6 and 7 describe a method of changing the droplet amount at the landing position by combining the discharged droplets during flight.
JP 2002-96488 A JP 2002-113863 A

In addition, as described in Patent Documents 8 to 10, there are known ones in which a plurality of fixed electrodes per nozzle of a droplet discharge head are provided.
JP-A-8-72240 JP 11-309855 A JP 2000-15801 A

  However, in the droplet discharge heads described in Patent Documents 4 and 5, the drive voltage has to be multi-valued, so that the drive circuit is complicated, and a high voltage is required when a large droplet is blown. Therefore, there is a problem that the cost of the drive circuit becomes high.

  In addition, in the driving method of the droplet discharge head described in Patent Documents 6 and 7, it is possible to control the discharge amount over a relatively wide range, for example, several times. On the other hand, the discharge amount can be controlled. However, there are problems that it is limited to approximately an integral multiple of the single discharge amount, and that a plurality of droplets need to be discharged in order to produce a final drop, so that the drive frequency is lowered accordingly.

  Further, in the droplet discharge heads described in Patent Documents 8 to 10, although fine droplet discharge amount control for each nozzle is possible, the number of electrodes increases, so that the cost of a drive circuit such as a driver IC is increased. Will increase. For example, in the case of having three electrodes for each nozzle, the number of channels of the driver IC is also required three times, and the cost of the driver IC is also tripled. In addition, since the number of electrode extractions is tripled, there is a problem that the mounting cost increases.

  The present invention has been made in view of the above problems, and a droplet discharge head capable of varying the droplet discharge amount with a simple configuration, a liquid cartridge integrated with the droplet discharge head, and the droplet discharge head. It is an object of the present invention to provide a head driving device for driving, and an image forming apparatus including these droplet discharge heads and a head driving device.

  In order to solve the above-described problems, the droplet discharge head according to the present invention has a configuration in which a plurality of common electrodes capable of applying a voltage independently are provided corresponding to each individual electrode.

  The head drive device according to the present invention is configured to include means for changing the discharge amount of the liquid droplets by varying the drive voltage applied to the plurality of common electrodes of the liquid droplet discharge head according to the present invention. .

  Here, when discharging a droplet with a discharge amount smaller than the maximum discharge amount, a driving voltage that reduces the maximum potential difference between the individual electrodes when discharging a droplet with the maximum discharge amount is reduced for some common electrodes. When applying or discharging droplets with a discharge amount smaller than the maximum discharge amount, a drive voltage having the same polarity as the drive voltage applied to the individual electrodes and a small voltage value is applied to some common electrodes. It has a means to apply, or when discharging droplets with a discharge amount smaller than the maximum discharge amount, for some common electrodes, the same polarity as the drive voltage applied to the individual electrodes and the same application width When applying a drive voltage that is wide or small and has a small voltage value, or when discharging a droplet with the maximum discharge amount, the polarity of the drive voltage applied to the individual electrodes is reversed for all of the plurality of common electrodes. Apply drive voltage, maximum When ejecting a small discharge amount of the droplet than volume, it is preferable not to apply a driving voltage to a portion of the common electrode.

  In addition, it is preferable that the maximum potential difference between the common electrode and the individual electrode when discharging a droplet having a discharge amount smaller than the maximum discharge amount is smaller than the contact voltage when the diaphragm contacts the fixed electrode side.

  The head driving device according to the present invention is a head driving device for driving the liquid droplet ejection head according to the present invention, and is configured to eject a plurality of regions of a plurality of common electrodes when ejecting a liquid droplet having a smaller ejection amount than the maximum ejection amount. Then, after applying a driving voltage whose maximum potential difference with the individual electrode is equal to or higher than the contact voltage when the diaphragm is in contact with the fixed electrode side, and the diaphragm is in contact with the fixed electrode side, In some areas, the potentials of the individual electrode and common electrode are made equal, and in the remaining areas, the potential difference between the individual electrode and common electrode is kept above the potential at which the diaphragm does not move away from the fixed electrode side. The apparatus includes a means for applying a driving voltage for causing droplets to be ejected by restoring the plate and maintaining the diaphragm in contact with the fixed electrode in the remaining region.

  Here, after droplet discharge is performed by restoring the diaphragm in a part of the area, a driving voltage is applied to restore the diaphragm in the remaining area from the fixed electrode side when the liquid chamber is at negative pressure. It is preferable to do.

  The liquid cartridge according to the present invention is obtained by integrating a liquid droplet ejection head according to the present invention that ejects liquid droplets and an ink tank that supplies recording liquid to the liquid droplet ejection head.

  An image forming apparatus according to the present invention includes the droplet discharge head or the liquid cartridge according to the present invention and the head driving device according to the present invention.

  According to the droplet discharge head according to the present invention, since a plurality of common electrodes capable of independently applying a voltage is provided corresponding to each individual electrode, a driving voltage is independently applied to each common electrode. By applying this, the droplet discharge amount can be varied, and the droplet discharge amount can be changed without significantly increasing the number of extraction electrodes.

  According to the head driving device of the present invention, there is provided a configuration including means for changing the discharge amount of the liquid droplet by changing the drive voltage applied to the plurality of common electrodes of the liquid droplet discharge head of the present invention. Therefore, the droplet discharge amount can be changed without increasing the number of channels of the drive circuit.

  According to the head driving device of the present invention, the head driving device drives the droplet discharge head according to the present invention, and when discharging droplets having a discharge amount smaller than the maximum discharge amount, In a plurality of regions, after applying a driving voltage whose maximum potential difference with the individual electrode is equal to or higher than the contact voltage when the diaphragm abuts on the fixed electrode side, and after the diaphragm abuts on the fixed electrode side, In some of the regions, the potentials of the individual electrode and the common electrode are made equal, and in the remaining regions, the potential difference between the individual electrode and the common electrode is maintained at a potential that does not leave the diaphragm from the fixed electrode side, and some regions In the configuration, the liquid crystal is discharged by restoring the vibration plate, and in the remaining area, the driving circuit is provided with means for applying a driving voltage to keep the vibration plate in contact with the fixed electrode side. More channels It is possible to change the ejection amount without enables high-speed driving at the time of drop ejection. .

  According to the liquid cartridge according to the present invention, the liquid droplet ejection head according to the present invention and the liquid tank that supplies the liquid to the liquid droplet ejection head are integrated. A liquid tank integrated head) can be obtained.

  The image forming apparatus according to the present invention includes the droplet discharge head or the liquid cartridge according to the present invention and the head driving device according to the present invention, so that gradation recording can be performed.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
First, a first embodiment of a droplet discharge head according to the present invention will be described with reference to FIGS. 1 is an exploded perspective view of the head, FIG. 2 is an explanatory plan view showing the head viewed from the nozzle plate side, and FIG. 3 is an explanatory plan view in which patterns of respective parts in FIG. 2 are extracted. 2 is a cross-sectional explanatory view taken along line X1-X1 in FIG. 2, FIG. 5 is a cross-sectional explanatory view taken along line X2-X2 in FIG. 2, FIG. 6 is a cross-sectional explanatory view taken along line Y1-Y1 in FIG. 2 is a cross-sectional explanatory view taken along line Y2-Y2.

  This ink jet head is of a side shooter type that discharges liquid droplets from nozzle holes provided in the surface portion of a substrate, and is an actuator substrate 1 that is a first substrate and a flow path substrate (liquid chamber substrate) that is a second substrate. 2) and the nozzle substrate 3 which is the third substrate are sequentially laminated, and the three substrates 1, 2, and 3 are joined together so that the nozzle 4 for ejecting droplets passes through the nozzle communication path 5. A fluid chamber (discharge chamber) 6 communicating with the fluid chamber 6, a fluid resistance portion 7 for supplying liquid (ink) to the fluid chamber 6, and a common liquid chamber 10 are formed. Each liquid chamber 6 is partitioned by a liquid chamber interval wall 9.

  The actuator substrate 1 includes a diaphragm 12 that forms a diaphragm region (deformable region) 12A that forms a part of the wall surface of the liquid chamber 6, and a gap formed by sacrificial layer etching in the diaphragm region 12A of the diaphragm 12. A counter electrode 14 that is a fixed electrode facing through a (gap) 13 is provided, and the diaphragm 12 and the counter electrode 14 constitute an electrostatic actuator that is a pressure generating means corresponding to each liquid chamber 6. .

  The actuator substrate 1 is provided with a liquid supply port 15 for supplying ink as a recording liquid to the common liquid chamber 10 from outside the back side of the head.

  Here, as shown in FIGS. 4 to 7, the actuator substrate 1 is formed by patterning an electrode forming layer 24 through an insulating film 22 on a silicon substrate 21 having a crystal plane orientation (110), for example. The counter electrode 14 to be an individual electrode is formed, an insulating film 25 is formed on the individual electrode (counter electrode) 14, and a sacrificial layer 27 for forming a gap (gap) 13 on the insulating film 25 is formed. The insulating film 28, the diaphragm electrode layer 30, the stress adjusting film 31 for protecting the diaphragm, and the diaphragm crack preventing film 32 are sequentially laminated.

  Sacrificial layer etching is performed in which a sacrificial layer removal hole 29 leading to the sacrificial layer 27 is formed in the diaphragm 12 before the diaphragm crack prevention film 32 is formed, and the sacrificial layer 27 is removed through the sacrificial layer removal hole 29. Thus, a gap (air gap) 13 corresponding to the counter electrode 14 is formed, and then a diaphragm crack prevention film 32 is formed to seal the sacrificial layer removal hole 29.

Specifically, for example, a thermal oxide film (silicon oxide film) is formed as an insulating film 22 on a silicon substrate 21 having a crystal plane orientation (110), and LP-CVD is formed on the insulating film 22 (thermal oxide film). A polysilicon film is formed and phosphorus-doped to form an electrode formation layer 24 (phosphorus-doped polysilicon film) that can be etched, and a separation groove 24a is formed in the electrode formation layer 24 by lithoetching to correspond to each nozzle. Each individual electrode (counter electrode) 14 is divided. Thereafter, an HTO film is formed as the insulating film 25 by LP-CVD using SiH ₄ + N ₂ O gas.

  Then, a polysilicon film is formed as a sacrificial layer 27 for forming a gap (gap) 13 on the insulating film 25, and an HTO film is further formed as an insulating film 28 on the diaphragm 12 side by the same method as described above. Then, a diaphragm electrode layer 30 made of phosphorus-doped polysilicon is formed on the insulating film 28 by LP-CVD, and as will be described in detail later, the diaphragm electrode layer 30 is separated into a plurality of common electrodes 30A by separation grooves 40 and the like. After being divided into 30B, a silicon nitride film is formed on the diaphragm electrode layer 30 as a stress adjusting film 31 for adjusting the rigidity of the diaphragm by LP-CVD.

  Next, a sacrificial layer removal hole 29 that penetrates the insulating film 28, the diaphragm electrode layer 30, and the stress adjustment film 31 that are sequentially stacked is formed, and the sacrificial layer 27 is removed through the sacrificial layer removal hole 29. After the gap (air gap) 13 is formed, an HTO film is formed as the diaphragm crack preventing film 32 by the same method as described above, and at the same time, the sacrificial layer removal hole 29 is sealed with the diaphragm crack preventing film 32.

  When the vibration plate 12 is formed in a three-layer structure including a silicon nitride film (stress adjusting film) 31, a polysilicon film (vibration plate electrode layer) 30, and a silicon oxide film (insulating film) 28, Although the diaphragm 12 is easily cracked, as described above, in addition to this, the diaphragm 12 is hardly cracked by forming a silicon oxide film (HTO film) as the diaphragm crack preventing film 32 to form a four-layer structure. It was confirmed experimentally.

  The flow path substrate 2 bonded onto the actuator substrate 1 is, for example, a silicon substrate having a crystal plane orientation (110), a liquid chamber (discharge chamber) 6, and each liquid chamber 6 via a fluid resistance portion 7. A common liquid chamber 10 that communicates is provided. Furthermore, a silicon oxide film for improving the liquid resistance of the liquid contact surface of a member (not shown) is formed on the surface of the flow path substrate 2 by thermal oxidation.

  For example, a polyimide film is used as the nozzle substrate 3 bonded on the flow path substrate 2, and the nozzles 4 communicating with the liquid chambers via the nozzle communication passages 5 are formed by laser processing.

  In FIG. 2, only two nozzles 4 are shown for convenience, but in reality, a larger number of nozzles are arranged. Further, although only five sacrificial layer removal holes 29 are drawn per wall surface of the liquid chamber 6, the number is not limited to this number. The same applies to the following figures.

  Next, the electrode configuration in this droplet discharge head will be described. In this droplet discharge head, the diaphragm 12 side is a common electrode corresponding to all the nozzles, and the counter electrode 14 side is an individual electrode divided corresponding to each nozzle.

  Therefore, the common electrode formed by the diaphragm electrode layer 30 provided on the diaphragm 12 is separated into two (here, two) first and second common electrodes by separating the diaphragm electrode layer 30 by the separation groove 40. The drive voltage can be applied independently by dividing into 30A and 30B (see also FIGS. 2 and 3E). The widths of the first and second common electrodes 30A and 30B (the width in the longitudinal direction of the liquid chamber) can be the same or different. In this example, the width of the first common electrode 30A is different. Is formed wider than the width of the second common electrode 30B.

  Then, an electrode extraction pad 17 provided on the outer surface is connected to each counter electrode 14 which is an individual electrode via an electrode connecting portion 16, and a driving voltage is applied to the first and second common electrodes 30A and 30B. In order to apply independently, it connects to the electrode extraction pads 19A and 19B provided on the outer surface via the electrode connecting portion 18, respectively.

  Therefore, an electrostatic force is generated between the counter electrode 14 that is an individual electrode by selectively applying a driving voltage to the first and second common electrodes 30A and 30B or by making the applied driving voltage different. Since the regions can be made different, and the region to be deformed in the vibration plate region 12A of the vibration plate 12 can be made different, the amount of liquid droplets to be ejected can be varied. A head driving device for this droplet discharge head will be described later.

  As described above, in this droplet discharge head, a plurality of common electrodes can be provided and a drive voltage can be applied independently for each common electrode, so the number of extraction electrodes and the number of channels of the driver IC (drive circuit) can be greatly increased. The droplet discharge amount can be varied without increasing.

  Next, a second embodiment of the droplet discharge head according to the present invention will be described with reference to FIGS. 8 is a cross-sectional explanatory view similar to FIG. 6, and FIG. 9 is a cross-sectional explanatory view similar to FIG.

  In the present embodiment, a partition wall 41 is formed in the gap 13 to divide the gap 13 into a gap 13A corresponding to the first common electrode 30A and a gap 13B corresponding to the second common electrode 30B. Thereby, the deformable diaphragm region 12A facing each individual electrode (counter electrode) 14 of the diaphragm 12 has the first vibration region 12A1 facing the individual electrode 14 via the gap portion 13A and the gap portion 13B. And the second vibration region 12A2 facing the individual electrode 14 completely.

  The partition wall 41 is formed by forming a separation groove for dividing the gap 13 into the gap 13A and the gap 13B in the polysilicon film as the sacrificial layer 27 described in the manufacturing process of the first embodiment. The inside can also be formed by embedding with an insulating film 28 made of HTO.

  Thus, by separating the diaphragm region 12A of the diaphragm 12 into the first and second diaphragm regions 12A1 and 12A2 by providing the partition wall portion 41, the first and second diaphragm regions 12A1, When only one diaphragm region of 12A2 is deformed, it is possible to prevent the other diaphragm region from being affected via the diaphragm 12 itself.

  In each of the above embodiments, the configuration is described in which the diaphragm side is a common electrode and the counter electrode side is an individual electrode, but the counter electrode side is a common electrode and the diaphragm side is an individual electrode. The same can be applied.

Next, a liquid cartridge according to the present invention will be described with reference to FIG.
The liquid cartridge integrated head 90 includes an ink jet head 92 which is a droplet discharge head according to the present invention having nozzle holes 91 and the like, and an ink tank (liquid tank) for supplying a recording liquid (ink) to the ink jet head 92. ) 93 is integrated.

  As described above, by integrating the ink tank (liquid tank) for supplying the recording liquid (ink) to the liquid droplet ejection head according to the present invention, the liquid cartridge capable of changing the liquid droplet ejection amount with a simple configuration. (Ink tank integrated head) can be obtained.

  Next, an example of an image forming apparatus according to the present invention provided with a liquid droplet ejection head according to the present invention and a head driving device according to the present invention for driving the liquid droplet ejection head will be described with reference to FIGS. To do. FIG. 11 is an explanatory side view for explaining the overall configuration of the image forming apparatus, and FIG. 12 is an explanatory plan view of a main part of the apparatus.

  In this image forming apparatus, a carriage 103 is slidably held in a main scanning direction by a guide rod 101 and a guide rail 102 that are horizontally mounted on left and right side plates (not shown), and a driving pulley 106A is driven by a main scanning motor 104. 12 and the driven pulley 106B, the moving scanning is performed in the direction indicated by the arrow (main scanning direction) in FIG.

  For example, four independent liquid discharge heads that discharge recording liquid droplets (ink droplets) of black (K), cyan (C), magenta (M), and yellow (Y) are provided on the carriage 103. A recording head 107 composed of 107k, 107c, 107m, and 107y is arranged in a direction along the main scanning direction, and is mounted with the droplet discharge direction facing downward. In addition, although the independent liquid discharge head is used here, it is also possible to employ a configuration in which one or a plurality of heads having a plurality of nozzle rows for discharging recording liquid droplets of each color are used. Further, the number of colors and the arrangement order are not limited to this.

  As the liquid ejection head constituting the recording head 107, a diaphragm that forms the wall surface of the ink flow path is deformed by using an electromechanical conversion element such as a piezoelectric element as pressure generating means for pressurizing ink in the pressurized liquid chamber. A so-called piezo type that discharges ink droplets by changing the volume of the ink flow path, a so-called thermal type that utilizes film boiling of the recording liquid using an electrothermal transducer such as a heating resistor, The diaphragm and the electrode forming the wall surface are arranged opposite to each other, and the diaphragm is deformed by an electrostatic force generated between the diaphragm and the electrode, thereby changing the volume of the ink flow path and discharging the ink droplets. An electric type, a shape memory alloy actuator using a metal phase change due to a temperature change, or the like can be used.

  The carriage 103 is equipped with a sub tank 108 for each color for supplying each color ink to the recording head 107. Ink is supplied to the sub tank 108 from a main tank (ink cartridge) (not shown) via an ink supply tube 109.

  On the other hand, as a sheet feeding unit for feeding a recording medium (sheet) 112 loaded on a sheet stacking unit (pressure plate) 111 such as a sheet feeding cassette 110, the sheets 112 are separated and fed from the sheet stacking unit 111 one by one. Opposite to the half-moon roller (feed roller) 113 and the feed roller 113 to be fed, a separation pad 114 made of a material having a large friction coefficient is provided, and this separation pad 114 is urged toward the feed roller 113 side.

  As a transport unit for transporting the paper 112 fed from the paper feed unit below the recording head 107, a transport belt 121 for electrostatically attracting and transporting the paper 112, and a paper feed unit A counter roller 122 for transporting the paper 112 fed through the guide 115 while sandwiching it between the transport belt 121 and the paper 112 fed substantially vertically upward is changed by about 90 ° and copied on the transport belt 121. A conveying guide 123 for adjusting the pressure and a tip pressure roller 125 urged toward the conveying belt 121 by a pressing member 124. In addition, a charging roller 126 that is a charging unit for charging the surface of the conveyance belt 121 is provided.

  Here, the conveyance belt 121 is an endless belt, is stretched between the conveyance roller 127 and the tension roller 128, and the conveyance roller 127 is rotated from the sub-scanning motor 131 via the timing belt 132 and the timing roller 133. By doing so, it is configured to circulate in the belt conveyance direction (sub-scanning direction) of FIG. A guide member 129 is disposed on the back side of the conveyance belt 121 in correspondence with the image forming area formed by the recording head 107.

  As shown in FIG. 2, a slit disk 134 is attached to the shaft of the transport roller 127, and a sensor 135 for detecting the slit of the slit disk 134 is provided. An encoder 136 is configured.

  The charging roller 126 is arranged so as to contact the surface layer of the conveyor belt 121 and rotate following the rotation of the conveyor belt 121, and applies 2.5N to both ends of the shaft as a pressing force.

  Further, as shown in FIG. 1, an encoder scale 142 having slits is provided on the front side of the carriage 103, and an encoder sensor comprising a transmissive photosensor for detecting the slits of the encoder scale 142 on the front side of the carriage 103. The encoder 144 for detecting the position of the carriage 103 in the main scanning direction is configured by these.

  Further, as a paper discharge unit for discharging the paper 112 recorded by the recording head 107, a separation unit for separating the paper 112 from the conveying belt 121, a paper discharge roller 152 and a paper discharge roller 153, and paper discharge A paper discharge tray 154 for stocking the paper 112 to be printed.

  A double-sided paper feeding unit 155 is detachably mounted on the back. The double-sided paper feeding unit 155 takes in the paper 112 returned by the reverse rotation of the transport belt 121, reverses it, and feeds it again between the counter roller 122 and the transport belt 121.

  Furthermore, as shown in FIG. 12, a maintenance / recovery mechanism 156 for maintaining and recovering the state of the nozzles of the recording head 107 is disposed in the non-printing area on one side of the carriage 103 in the scanning direction.

  The maintenance / recovery machine 156 includes a cap 157 for capping each nozzle surface of the recording head 107, a wiper blade 158 which is a blade member for wiping the nozzle surface, and a discharge unit for discharging the thickened recording liquid. An empty discharge receiver 159 for receiving droplets when performing empty discharge for discharging droplets that do not contribute to recording is provided.

  In the image forming apparatus configured as described above, the sheets 112 are separated and fed one by one from the sheet feeding unit, and the sheet 112 fed substantially vertically upward is guided by the guide 115, and includes the conveyance belt 121 and the counter roller 122. The leading end is guided by the conveying guide 123 and pressed against the conveying belt 121 by the leading end pressure roller 125, and the conveying direction is changed by approximately 90 °.

  At this time, a positive voltage output and a negative output are alternately repeated from the high voltage power supply to the charging roller 126 by a control circuit (not shown), that is, an alternating voltage is applied, and a charging voltage pattern in which the conveying belt 121 alternates, that is, In the sub-scanning direction, which is the circumferential direction, plus and minus are alternately charged in a band shape with a predetermined width. When the paper 112 is fed onto the conveyance belt 121 charged alternately with plus and minus, the paper 112 is attracted to the conveyance belt 121 by electrostatic force, and the paper 112 is conveyed in the sub-scanning direction by the circular movement of the conveyance belt 121. Is done.

  Therefore, by driving the recording head 107 according to the image signal while moving the carriage 103 in the forward and backward directions, ink droplets are ejected onto the stopped paper 112 to record one line, and the paper 112 is After transporting a predetermined amount, the next line is recorded. Upon receiving a recording end signal or a signal that the trailing edge of the paper 112 has reached the recording area, the recording operation is finished and the paper 112 is discharged onto the paper discharge tray 54.

  In the case of double-sided printing, when recording on the front surface (surface to be printed first) is completed, the recording belt 112 is fed into the double-sided paper feeding unit 155 by rotating the conveyor belt 121 in the reverse direction. The paper 112 is reversed (with the back surface being the printing surface), and is fed again between the counter roller 122 and the conveyor belt 121. The timing is controlled, and the sheet is conveyed onto the conveyor bell 121 as described above. After recording on the back side, the sheet is discharged to the discharge tray 154.

  Further, during printing (recording) standby, the carriage 103 is moved to the maintenance / recovery mechanism 155 side, and the nozzle surface of the recording head 107 is capped by the cap 157 so that the nozzles are kept in a wet state. To prevent. In addition, the recording liquid is sucked from the nozzle in a state where the recording head 107 is capped by the cap 157 (referred to as “nozzle suction” or “head suction”), and a recovery operation is performed to discharge the thickened recording liquid or bubbles. Wiping is performed by the wiper blade 158 in order to clean and remove ink adhering to the nozzle surface of the recording head 107 by this recovery operation. In addition, an idle ejection operation for ejecting ink not related to recording is performed before the start of recording or during recording. Thereby, the stable ejection performance of the recording head 107 is maintained.

Next, an outline of a control unit including the head driving device according to the present invention of the image forming apparatus will be described with reference to FIG. This figure is an overall block diagram of the control unit.
The control unit 200 includes a CPU 201 that controls the entire apparatus, a ROM 202 that stores programs executed by the CPU 201 and other fixed data, a RAM 203 that temporarily stores image data, and the like, while the apparatus is powered off. 1 includes a non-volatile memory (NVRAM) 204 for holding data, an image processing for performing various signal processing and rearrangement on image data, and an ASIC 205 for processing input / output signals for controlling the entire apparatus. Yes.

  The control unit 200 also has an I / F 206 for transmitting and receiving data and signals to and from the host, which is an image processing apparatus (or data processing apparatus) such as a personal computer, and a drive for driving the recording head 107. A drive waveform generation unit 207 that generates a waveform; a head driver 208 that controls the drive of the recording head 107 that is a droplet discharge head according to the present invention; a main scanning motor drive unit 211 that drives the main scanning motor 104; A sub-scanning motor driving unit 213 for driving the scanning motor 131, an AC bias supply unit 114 for supplying an AC bias voltage to the charging roller 126, an environmental sensor 218 for detecting environmental temperature and / or environmental humidity, I / O 216 for inputting detection signals from various sensors that are not connected.

  The control unit 200 is connected to an operation panel 217 for inputting and displaying information necessary for the apparatus.

  Here, the control unit 200 transmits print data (print data) including image data from the host side such as an image processing apparatus such as a personal computer, an image reading apparatus such as an image scanner, an imaging apparatus such as a digital camera, or the like. The data is received by the I / F 206 via the net.

  The CPU 201 reads and analyzes the print data in the reception buffer included in the I / F 206, performs necessary image processing, data rearrangement processing, and the like in the ASIC 205, and transfers the image data to the head driver 208. The dot pattern data for image output may be generated by storing font data in the ROM 202, for example, or the image data is developed into bitmap data by a host-side printer driver and transferred to this apparatus. You may do it.

  The drive waveform generation unit 207 includes a D / A converter that performs D / A conversion on the pattern data of the drive signal, and outputs a drive waveform including one or a plurality of drive signals to the head driver 208.

  The head driver 208 selectively records a drive signal constituting a drive waveform supplied from the drive waveform generation unit 207 based on image data (dot pattern data) corresponding to one line of the recording head 107 input serially. The recording head 107 is driven by applying between the common electrode and the individual electrodes of the head 107.

  The drive waveform generator 207 and the head driver 208 apply a drive voltage to the common electrode and the individual electrode of each electrostatic actuator of the recording head 107 which is a droplet discharge head according to the present invention. The head driving device according to the present invention is provided with means for applying different voltages to the common electrode.

  Therefore, application of the head driving voltage by this head driving device will be described with reference to FIG. Hereinafter, a nozzle that discharges a droplet is referred to as a “discharge nozzle”, and a nozzle that does not discharge a droplet is referred to as a “non-discharge nozzle”. The “common electrode 30A” is referred to as “common electrode 1”, the “common electrode 30B” is referred to as “common electrode 2”, and the “vibrating plate region 12A of the common electrode 30A (common electrode 1)” is referred to as the “vibrating plate region”. 1 ”,“ the diaphragm region 12A of the common electrode 30B (common electrode 2) ”and“ the diaphragm region 2 ”.

  First, the relationship between the displacement amount of the electrostatic actuator and the voltage characteristic will be described with reference to FIG. In the electrostatic actuator, when the voltage is increased from the initial state (the state in which the potential difference between the diaphragm electrode and the fixed electrode is zero), the displacement of the diaphragm gradually increases as the voltage increases. To go. At this point, the electrostatic force and the repulsive force of the diaphragm are balanced. When the voltage is further increased, at a certain voltage Vth1, the diaphragm is immediately moved to the fixed electrode side (since immediately before, there is an effective gap length of about 2/3 of the initial state between the diaphragm and the fixed electrode). The diaphragm is brought into contact with the fixed electrode side (actually, the surface of an insulating film or a stopper). In such a phenomenon, when the voltage is increased, the repulsive force of the diaphragm increases in proportion to the amount of displacement, whereas the electrostatic force increases rapidly in inverse proportion to the square of the effective gap length. It depends. The voltage Vth1 when the diaphragm abuts on the fixed electrode side is referred to as “abutment voltage Vth1”.

  On the other hand, depending on the design of the effective gap length and maximum displacement (depending on the insulation film thickness and stopper height), the effective gap length can be reduced when the voltage is lowered from the state where the diaphragm is in contact with the fixed electrode. Is extremely small and a larger electrostatic force is working, so that the diaphragm does not move away from the fixed electrode side just below the contact voltage Vth1, and when the voltage is further lowered to a voltage Vth2 (Vth2 <Vth1), the diaphragm Is away from the fixed electrode side. The voltage Vth2 when the diaphragm in contact is separated from the fixed electrode side is referred to as “separation voltage Vth2”.

  Therefore, a first embodiment of the head driving device will be described with reference to FIG. Since this figure is shown in a table format, each column is referred to as column (a) to (l) (the same applies to FIG. 19 below).

<When discharging large droplets>
At this time, as shown in the columns (a) and (b), the common electrode 1 and the common electrode 2 are both fixed to the reference voltage (0 V), and the individual electrodes are the ejection nozzles that eject droplets. As shown in the column (a), a pulse voltage Va larger than the contact voltage Vth1 is applied (the voltage value is also “Va”, Va> Vth1). For the non-ejection nozzles, the column (b) No pulse voltage is applied as shown in (reference voltage: leave 0V).

  As a result, the potential difference between the individual electrode and the common electrode 1 and 2 becomes a pulse voltage larger than the contact voltage Vth1 as shown in the column (c) for the discharge nozzle, and therefore, as shown in the column (e). In addition, in both the diaphragm region 1 corresponding to the common electrode 1 and the diaphragm region 2 corresponding to the common electrode 2, the diaphragm 12 is greatly deformed and abuts on the fixed electrode side. Thereafter, when the potential difference returns to 0 V, the diaphragm 12 returns to the original position, and droplets are ejected. At this time, for example, as described in Japanese Patent Application Laid-Open No. 2002-113863, the pulse width is set so that the diaphragm is restored at the timing when the pressure in the liquid chamber is positive in order to discharge efficiently. It is preferable to do.

  On the other hand, in the non-ejection nozzle, the potential difference between the individual electrode and the common electrode 1 and 2 remains 0 V as shown in the column (d), so that the diaphragm regions 1 and 2 are deformed as shown in the column (f). No droplets are ejected.

<During droplet ejection>
At this time, as shown in the columns (g) and (h), the common electrode 1 is fixed to the reference voltage (0 V), and the common electrode 2 has a drop discharge pulse voltage Va applied to the individual electrodes of the discharge nozzle and A pulse voltage Vb (Vb <Va) having the same polarity and the same phase and a voltage of about ½ is applied. The pulse width (application width, application time width) of the pulse voltage Vb is the same as the pulse width of the pulse voltage Va. For the individual electrodes, the discharge nozzle applies the same pulse voltage Va as in the large droplet discharge as shown in the (g) column, and the non-discharge nozzle does not apply the pulse voltage as shown in the (h) column (reference voltage: 0V)

  At this time, if each voltage is set appropriately in advance, in the discharge nozzle, as shown in the column (i), the potential difference between the individual electrode and the common electrode 1 becomes larger than the contact voltage Vth1, and the individual electrode- The potential difference between the common electrodes 2 is smaller than the contact voltage Vth1 (Va−Vb <Vth1). Thereby, as shown in the column (k), in the diaphragm region 1, the diaphragm 12 is greatly deformed and abuts on the fixed electrode side, and in the diaphragm region 2, the diaphragm 12 is only slightly deformed. Thereafter, when the potential difference returns to 0 V, the diaphragm 12 returns to the original position, and droplets are discharged. At this time, since the vibration plate 12 is deformed and restored almost only in the vibration plate region 1, smaller droplets are ejected than when large droplets are ejected.

  Here, for the diaphragm region 2, various design values and physical property values (diaphragm rigidity / area ratio of the diaphragm region 1 and the diaphragm region 2, volume of the pressurized liquid chamber, fluid resistance value of the nozzle / fluid resistance unit, Depending on the viscosity of liquid droplets, elastic modulus, etc., it may be affected more by the pressure of the liquid chamber than by the electrostatic force, and may move like a wavy line. .

  On the other hand, in the non-ejection nozzle, as shown in the column (l), since the diaphragm 12 is not deformed and restored in the diaphragm area 1, and the diaphragm area 2 is only slightly deformed and restored, the droplets are ejected. Not.

  Such a phenomenon is due to the aforementioned “diaphragm displacement amount-voltage characteristic” of the electrostatic actuator. That is, as shown in FIG. 14, the “vibration plate displacement amount-voltage” characteristic of the electrostatic actuator shows that the displacement amount of the vibration plate starts to increase slightly with a change in voltage at a small voltage, and gradually increases as the voltage increases. The displacement amount increases at a stroke at a certain contact voltage Vth1, and is due to the property of contacting the fixed electrode.

  Although the case where the common electrode is divided into two has been described here, the same applies to the case where the common electrode is divided into three or more (the same applies to the following embodiments). In the configuration of the first and second embodiments of the droplet discharge head described above, for example, as disclosed in JP-A-7-214769, when the diaphragm abuts on the fixed electrode side, Electric charges are generated in the insulating film between the electrodes, but it is possible to obtain certain characteristics by appropriately changing the polarity of the pulse. Further, although illustration in the case of reverse polarity is omitted, the same is true except that the illustrated voltage is reversed.

  As described above, the channel of the drive circuit (driver) is provided by including means for changing the discharge amount of the droplet by changing the drive voltage applied to the plurality of common electrodes of the droplet discharge head according to the present invention. Without greatly increasing the number, it is possible to change the droplet discharge amount discharged at one time with a simple configuration.

  Here, when discharging a droplet with a discharge amount smaller than the maximum discharge amount, the maximum potential difference from the individual electrode when discharging a droplet (large droplet) with the maximum discharge amount is small with respect to some common electrodes. By applying the drive voltage, a part of the common electrode does not deform the corresponding diaphragm region (including deformation not accompanied by droplet ejection; the same applies hereinafter), so a small droplet (a droplet with a small ejection amount) ) Can be discharged.

  Also, when discharging droplets with a discharge amount smaller than the maximum discharge amount, a drive voltage having the same polarity as the drive voltage applied to the individual electrodes and a small voltage value is applied to some common electrodes. Since a part of the common electrode does not deform the corresponding diaphragm region, it is possible to discharge a small droplet (a droplet with a small discharge amount).

  Furthermore, when discharging droplets with a discharge amount smaller than the maximum discharge amount, a drive with the same polarity as the drive voltage applied to the individual electrodes, the same application width, and a small voltage value is applied to some common electrodes. By applying the voltage, the diaphragm region corresponding to some of the common electrodes is not deformed, so that a small droplet (a droplet with a small discharge amount) can be discharged.

Next, a second embodiment of the head driving device will be described with reference to FIG.
<When discharging large droplets>
At this time, the voltages applied to the common electrodes 1 and 2 and the individual electrodes and the operation of the head due thereto are the same as those in the first embodiment, and the description thereof is omitted.

<During droplet ejection>
At this time, as shown in columns (g) and (h), the common electrode 1 is fixed to the reference voltage (0 V), and the common electrode 2 has the same pulse voltage as the pulse voltage PW1 applied to the individual electrodes of the ejection nozzle. A pulse voltage Vc having a polarity of about ½ and a wide pulse width PW2 (PW2> PW1) is applied. For the individual electrodes, the discharge nozzle applies the same pulse voltage Va as in the large droplet discharge as shown in the (g) column, and the non-discharge nozzle does not apply the pulse voltage as shown in the (h) column (reference voltage: Leave at 0V).

  At this time, if the respective voltages are appropriately set for the discharge nozzles in advance, the potential difference between the individual electrode and the common electrode 1 becomes a potential exceeding the contact voltage Vth1 as shown in the column (i), and the common electrode 2 Even if the pulse width PW2 of the pulse voltage Vc applied to is wider than the pulse width PW1 of the pulse voltage Va applied to the fixed electrode, the timing shown in the column (g) (within the time during which the pulse voltage Vc is applied) If the pulse voltage Va is applied), the potential difference between the individual electrode and the common electrode 2 can be made smaller than the contact voltage Vth1, and as shown in the column (k), the diaphragm region 1 vibrates. Since the plate 12 is greatly deformed and restored, and the diaphragm 12 is only slightly deformed in the diaphragm region 2, a small droplet is ejected.

  As for the non-ejection nozzle, as in the first embodiment, the diaphragm 12 in the diaphragm region 2 only vibrates slightly, so that no droplet is ejected.

  Note that, depending on the configuration, it is possible to apply a forward / reverse polarity pulse as a countermeasure against residual charges.

  Furthermore, when discharging droplets with a discharge amount smaller than the maximum discharge amount, a drive voltage with the same polarity as the drive voltage applied to the individual electrodes, a wide application width, and a small voltage value is applied to some common electrodes. By applying the, the diaphragm region corresponding to some of the common electrodes is not deformed, so that a small droplet (a small discharge amount) can be discharged.

Next, a third embodiment of head drive will be described with reference to FIG.
<When discharging large droplets>
At this time, the voltages applied to the common electrodes 1 and 2 and the individual electrodes and the operation of the head due thereto are the same as those in the first embodiment, and the description thereof is omitted.

<During droplet ejection>
At this time, as shown in the columns (g) and (h), the common electrode 1 is fixed at the reference voltage (0 V), and the common electrode 2 has a voltage having the same polarity as the pulse voltage Va applied to the individual electrodes of the ejection nozzle. A constant voltage Vd of about 1/2 is applied. For the individual electrodes, the discharge nozzle applies the same pulse voltage Va as in the large droplet discharge as shown in the (g) column, and the non-discharge nozzle does not apply the pulse voltage as shown in the (h) column (reference voltage: Leave at 0V).

  At this time, as described above, with regard to the discharge nozzle, as shown in the columns (i) and (k), the potential difference between the individual electrode and the common electrode 1 is greater than Vth1, and in the diaphragm region 1, the diaphragm 12 Is greatly deformed and restored, and the potential difference between the individual electrode and the common electrode 2 is smaller than Vth1, and the diaphragm 12 slightly vibrates in the diaphragm region 2 to eject a small droplet.

  For the non-ejection nozzles, as shown in columns (j) and (l), the potential difference between the individual electrode and the common electrode 1 remains 0V, and the diaphragm 12 is not deformed in the diaphragm region 1, and 0 < Since the potential difference between the individual electrode 2 and the common electrode 2 (constant voltage Vd) <Vth1, and the diaphragm 12 does not move in the diaphragm region 2 (it remains slightly deformed), droplet discharge is not performed.

  In this way, droplets can be ejected by applying a constant voltage lower than the contact voltage vth1 to any one of the common electrodes. However, in this case, since the polarity of the pulse is limited to one pole, the influence of the residual charge cannot be eliminated by applying the pulse of both poles. For example, JP 2001-260346 A and JP 2001-2001 A. It is preferable that a residual charge is not generated even in the case of a unipolar pulse, as in 287357.

Next, a fourth embodiment of head drive will be described with reference to FIG.
<When discharging large droplets>
At this time, as shown in the columns (a) and (b), both the common electrode 1 and the common electrode 2 have a pulse voltage Vf having a voltage substantially equal to the reverse polarity to the pulse voltage Ve applied to the individual electrode corresponding to the ejection nozzle. Apply. In this case, the pulse voltage Ve and the pulse voltage Vf are each smaller than the contact voltage Vth1 (Ve <Vth1, Vf <Vth1), and the total value of the pulse voltage Ve and the pulse voltage Vf is larger than the contact voltage Vth1 (Ve + Vf>). Vth1) is set. In the non-ejection nozzle, the voltage of the individual electrode is fixed to the reference voltage (0 V).

  At this time, as shown in the columns (c) and (e), for the discharge nozzle, the potential difference between the individual electrode and the common electrode 1> Vth1, and the diaphragm region 1 is greatly deformed and restored, and similarly, Since the potential difference between the electrode and the common electrode 2 is greater than Vth1, and the diaphragm region 2 is also greatly deformed and restored, large droplets are ejected.

  On the other hand, as shown in the columns (d) and (f) for the non-ejection nozzle, 0 <the potential difference between the individual electrode and the common electrode 1 <Vth1, and the diaphragm region 1 vibrates slightly. Since the potential difference between the individual electrode and the common electrode 2 is smaller than Vth1, the diaphragm region 2 vibrates slightly, and no droplet is ejected.

<During droplet ejection>
At this time, as shown in the columns (g) and (h), the common electrode 1 is a pulse having a polarity opposite to that of the pulse voltage Ve applied to the individual electrode corresponding to the discharge nozzle and substantially the same fall timing. A voltage Vf is applied, and the common electrode 2 is fixed to a reference voltage (0 V).

  At this time, for the discharge nozzle, as shown in columns (i) and (k), the potential difference between the individual electrode and the common electrode 1> Vth1, and the diaphragm region 1 is greatly deformed and restored, but 0 <individual electrode -Since the potential difference between the common electrodes 2 <Vth1 and the diaphragm region 2 vibrates only slightly, a small droplet is ejected.

  On the other hand, for the non-ejection nozzles, as shown in the columns (j) and (l), 0 <the potential difference between the individual electrode and the common electrode 1 <Vth1, and the diaphragm region 1 vibrates slightly, Since the potential difference between the individual electrode and the common electrode 2 is 0, the diaphragm region 2 does not vibrate, and thus no liquid droplet is ejected.

  As described above, when a voltage having a polarity opposite to that of the individual electrode is applied to the common electrode, the voltage of the individual electrode can be substantially halved as compared with the first to third embodiments. The cost of a circuit or the like can be reduced.

Next, a fifth embodiment of head drive will be described with reference to FIG.
<When discharging large droplets>
At this time, since it is the same as the fourth embodiment, the description thereof is omitted.

<During droplet ejection>
At this time, as shown in the columns (g) and (h), the common electrode 1 is a pulse voltage having a polarity opposite to that of the pulse voltage Ve applied to the individual electrode corresponding to the discharge nozzle and substantially the same fall timing. Vg is applied. The common electrode 2 is applied with a pulse voltage Vi having a polarity almost the same as that of the pulse voltage Ve applied to the individual electrode corresponding to the ejection nozzle and having a falling timing slower than the pulse voltage Ve.

  By appropriately setting each voltage at this time, a pulse voltage in which the potential difference between the individual electrode and the common electrode 1 is larger than the contact voltage Vth1 is applied to the ejection nozzle as shown in the column (i). Thus, as shown in the column (k), the diaphragm region 1 is deformed and restored, and droplets are ejected.

  On the other hand, as shown in the column (i), the potential difference between the individual electrode and the common electrode 2 once exceeds the contact voltage Vth1, and then when the pulse voltage Ve of the individual electrode falls, the separation voltage Vth2 And a contact voltage Vth1 (voltage value Vg), and then returns to 0 V at a certain timing. At this time, as shown in FIG. 14 described above, the vibration plate returns from the contact state to the non-contact state after the contact at the timing when the potential difference becomes smaller than the separation voltage Vth2. Compared with a predetermined timing, the diaphragm in the diaphragm region 2 is restored. In this case, after the liquid droplets are discharged by the restoration of the diaphragm region 1, the diaphragm in the diaphragm region 2 is restored at the timing when the pressure of the pressurized liquid chamber is negative, so that the (k) column As shown in the drawing, it is possible to prevent droplet discharge from occurring when the diaphragm in the diaphragm region 2 is restored. That is, since droplets are ejected by restoring the diaphragm of only the diaphragm region 1, small droplets are ejected.

  On the other hand, as shown in the columns (j) and (l) for the non-ejection nozzle, 0 <the potential difference between the individual electrode and the common electrode 1 <Vth1, and the diaphragm region 1 only vibrates slightly. Further, since 0 <potential difference between the individual electrode and the common electrode 2 <Vth1 and the diaphragm region 2 only vibrates slightly, no liquid droplet is ejected.

  In this manner, by keeping the diaphragm in the diaphragm region 2 in contact with the fixed electrode side when ejecting a small droplet, the compliance of the flow path system is reduced, so that faster driving is possible. Of course, the effect depends on the ratio of the diaphragm region 2 to the overall compliance. Therefore, various design values / physical values (diaphragm rigidity / area ratio between the diaphragm region 1 and the diaphragm region 2, the volume of the pressurized liquid chamber, The driving method may be selected depending on the fluid resistance value of the nozzle / fluid resistance portion, the viscosity of the droplet, the elastic modulus, etc.

  In other words, when discharging a droplet with a discharge amount smaller than the maximum discharge amount, the maximum potential difference with the individual electrode is greater than or equal to the contact voltage when the diaphragm contacts the fixed electrode side in multiple regions of the multiple common electrodes. After applying the drive voltage, and the diaphragm abuts on the fixed electrode side, the potentials of the individual electrode and the common electrode are made equal in some areas of the plural areas, and the same for the individual electrodes in the remaining areas The potential difference between the electrodes is kept above the potential at which the diaphragm does not move away from the fixed electrode side. In some areas, droplets are ejected by restoring the diaphragm, and in the remaining areas, the diaphragm is in contact with the fixed electrode side. By applying a driving voltage that maintains the flow rate, it is possible to keep a part of the diaphragm area in contact with the fixed electrode side when ejecting a small droplet, thereby reducing the compliance of the flow path system. , Improve responsiveness more It can be.

  In this case, after droplet discharge is performed by restoring the diaphragm in a part of the area, a driving voltage is applied to restore the diaphragm in the remaining area from the fixed electrode side when the liquid chamber is at negative pressure. By doing so, it is possible to reliably prevent droplet discharge by restoring the diaphragm in the remaining area.

1 is an exploded perspective view of a droplet discharge head according to a first embodiment of the present invention. It is a plane explanatory view showing the head in the transmission state seen from the nozzle plate side. FIG. 3 is an explanatory plan view in which patterns of respective parts in FIG. 2 are extracted. FIG. 3 is a cross-sectional explanatory view taken along line X1-X1 in FIG. FIG. 3 is a cross-sectional explanatory view taken along line X2-X2 of FIG. FIG. 3 is a cross-sectional explanatory view taken along line Y1-Y1 of FIG. FIG. 3 is a cross-sectional explanatory view taken along line Y2-Y2 of FIG. FIG. 3 is an explanatory cross-sectional view corresponding to a cross section taken along line Y1-Y1 of FIG. 2 of the droplet discharge head according to the first embodiment of the present invention. It is a section explanatory view equivalent to the section which meets the Y2-Y2 line. FIG. 3 is a perspective explanatory view of a liquid cartridge according to the present invention. 1 is an explanatory side view illustrating an overall configuration of an image forming apparatus according to the present invention. It is principal part plane explanatory drawing of the apparatus. It is a block diagram which shows the outline | summary of the control part of the apparatus. It is explanatory drawing with which it uses for description of the diaphragm displacement amount-voltage characteristic in an electrostatic actuator. It is explanatory drawing with which it uses for description of the application method of the drive voltage in 1st Embodiment of the head drive device which concerns on this invention. It is explanatory drawing with which it uses for description of the application method of the drive voltage in 2nd Embodiment of the head drive device which concerns on this invention. It is explanatory drawing with which it uses for description of the application method of the drive voltage in 3rd Embodiment of the head drive device which concerns on this invention. It is explanatory drawing with which it uses for description of the application method of the drive voltage in 4th Embodiment of the head drive device which concerns on this invention. It is explanatory drawing with which it uses for description of the application method of the drive voltage in 5th Embodiment of the head drive device which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Actuator board | substrate 2 ... Flow path board | substrate 3 ... Nozzle board | substrate 4 ... Nozzle hole 6 ... Liquid chamber (discharge chamber)
DESCRIPTION OF SYMBOLS 10 ... Common liquid chamber 12 ... Diaphragm 12A ... Diaphragm area | region 12A1 ... Diaphragm area | region corresponding to 1st common electrode 12A2 ... Diaphragm area | region corresponding to 2nd common electrode 13 ... Air gap 14 ... Fixed electrode (individual electrode)
15 ... Liquid supply port 30 ... Common electrode (diaphragm electrode)
30A ... 1st common electrode 30B ... 2nd common electrode 90 ... Liquid cartridge 200 ... Control part

Claims (11)

  A diaphragm that forms at least one wall surface of a liquid chamber that communicates with a plurality of nozzles that discharge droplets, and at least a part of which is a diaphragm electrode; and a fixed electrode that faces the diaphragm through a gap, And using either one of the diaphragm electrode and the fixed electrode as a common electrode and the other as an individual electrode, applying a voltage between the two electrodes to deform the diaphragm by electrostatic force, thereby causing droplets from the nozzle. In the liquid droplet discharge head for discharging liquid, a plurality of common electrodes capable of applying a voltage independently are provided corresponding to each individual electrode.   2. The head driving apparatus for driving a droplet discharge head according to claim 1, further comprising means for changing the discharge amount of the droplet by varying a drive voltage applied to the plurality of common electrodes. A head drive device characterized by the above.   3. The head driving device according to claim 2, wherein when a droplet having a discharge amount smaller than the maximum discharge amount is discharged, a part of the common electrode is connected to an individual electrode when discharging a droplet having the maximum discharge amount. A head driving device characterized by applying a driving voltage that reduces a maximum potential difference.   3. The head drive device according to claim 2, wherein when a droplet having a discharge amount smaller than the maximum discharge amount is discharged, a voltage value having the same polarity as that of a drive voltage applied to each individual electrode with respect to some common electrodes Applies a small driving voltage.   3. The head drive device according to claim 2, wherein when a droplet having a discharge amount smaller than the maximum discharge amount is discharged, a part of the common electrode has the same polarity as the drive voltage applied to the individual electrode and the same application width. A head driving device characterized by applying a driving voltage which is wide or wide and has a small voltage value.   3. The head drive device according to claim 2, wherein when a maximum discharge amount of liquid droplets is discharged, a drive voltage having a polarity opposite to the drive voltage applied to the individual electrodes is applied to all of the plurality of common electrodes. A head driving device characterized by not applying a driving voltage to some of the common electrodes when ejecting droplets having an ejection amount smaller than the amount.   7. The head driving apparatus according to claim 2, wherein the maximum potential difference between the common electrode and the individual electrode when discharging a droplet having a discharge amount smaller than the maximum discharge amount is such that the diaphragm is the fixed electrode. A head driving device characterized in that the head driving device is smaller than a contact voltage when contacting the side.   2. The head driving apparatus for driving a droplet discharge head according to claim 1, wherein when a droplet having a discharge amount smaller than the maximum discharge amount is discharged, the maximum number of the plurality of common electrodes and the individual electrode is maximized. After applying a driving voltage having a potential difference equal to or higher than a contact voltage when the diaphragm contacts the fixed electrode, and after the diaphragm contacts the fixed electrode, a part of the plurality of regions In the region, the potentials of the individual electrode and the common electrode are made equal, and in the remaining region, the potential difference between the individual electrode and the common electrode is kept higher than the potential at which the vibration plate is not separated from the fixed electrode side, A head driving device comprising: means for applying a driving voltage for causing droplets to be discharged by restoring the plate and maintaining the diaphragm in contact with the fixed electrode in the remaining region.   9. The head driving device according to claim 8, wherein after the liquid droplets are ejected by restoring the diaphragm in the partial area, the remaining area of the remaining area is in a negative pressure. A head driving apparatus characterized by applying a driving voltage for restoring the diaphragm from the fixed electrode side.   The liquid droplet ejection head according to claim 1, wherein the liquid droplet ejection head for ejecting liquid droplets and an ink tank for supplying a recording liquid to the liquid droplet ejection head are integrated. A liquid cartridge characterized by.   An image forming apparatus equipped with a droplet discharge head for discharging droplets, wherein the droplet discharge head according to claim 1 or the droplet discharge head of a liquid cartridge according to claim 10 and any one of claims 2 to 9. An image forming apparatus comprising the head driving device according to claim 1.

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