JP4342744B2 - Head drive device and ink jet recording apparatus - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a head drive device and an ink jet recording apparatus, and more particularly to a head drive device that drives an electrostatic droplet discharge head and an ink jet recording apparatus that mounts the electrostatic ink jet head.
[0002]
[Prior art]
As an ink jet recording apparatus used as an image recording apparatus or an image forming apparatus such as a printer, a facsimile machine, a copying apparatus, etc., a nozzle for ejecting ink droplets and an ejection chamber (an ink channel, an ink chamber, a pressure chamber, a liquid chamber) communicating with the nozzle , A pressurizing chamber, a pressurized liquid chamber, etc.), a diaphragm that forms the wall surface of the discharge chamber, and an electrode facing the diaphragm, and the diaphragm is deformed by an electrostatic force. There is known one equipped with an electrostatic ink jet head that discharges ink droplets from nozzles by changing the pressure / volume in the discharge chamber.
[0003]
By the way, in the inkjet head, if the nozzle density is increased in order to perform high-density and high-quality recording, mutual interference occurs between adjacent pressurized liquid chambers (discharge chambers), resulting in deterioration of image quality. This mutual interference is caused when the pressure is applied to the pressurized liquid chamber of the drive bit (the bit that ejects ink droplets) by the diaphragm, through the common liquid chamber or the partition between the pressurized liquid chambers. The pressure is transmitted to the non-driving bit (bit that does not eject ink droplets), and the pressure fluctuation is caused in the non-driving bit that does not originally operate.
[0004]
In particular, in an electrostatic ink jet head, a diaphragm is not fixed to a piezoelectric element as in, for example, a piezo ink jet head, and the diaphragm can freely vibrate without applying a driving waveform. There is a feature that the diaphragm easily vibrates when receiving pressure propagation from an adjacent bit.
[0005]
Therefore, as a conventional head driving method or apparatus, as disclosed in Japanese Patent Laid-Open No. 06-143562, the diaphragm of the non-driving bit is deformed in the direction opposite to the vibration caused by the pressure wave propagation from the driving bit side. Some drive waveforms are applied to hold the diaphragm of the non-driven bit in a fixed state.
[0006]
Further, as disclosed in JP-A-6-191030, JP-A-9-141864, and JP-A-11-192699, an attempt is made to suppress mutual interference by the structure of the head itself. Some provide a region for buffering pressure in the vicinity of the chamber.
[0007]
[Problems to be solved by the invention]
However, as in the conventional head driving apparatus or method described above, the non-driving bit of the non-driving bit is applied by applying a driving waveform that deforms the diaphragm of the non-driving bit in the direction opposite to the vibration caused by the pressure wave propagation from the driving bit side. In order to hold the diaphragm in a fixed state, a driving waveform having a very complicated waveform pattern must be applied, and there is a problem that it is difficult to strictly fix and hold a diaphragm that generates free vibration. .
[0008]
In addition, in the case of the conventional head itself that attempts to suppress mutual interference, an increase in the process of creating a pressure buffer layer that buffers pressure near the common liquid chamber increases yield and costs. There is a problem of being connected. In addition, there is a problem that the pressure buffer layer must be redesigned even if the head becomes larger and the design changes slightly.
[0009]
The present invention has been made in view of the above points, and an object thereof is to provide a head drive device that suppresses mutual interference with a simple configuration and an inkjet recording device capable of high-quality recording.
[0010]
[Means for Solving the Problems]
  In order to solve the above problems, a head driving device according to the present invention is provided.Is
  A first drive waveform that deforms with a deformation amount that drops when the diaphragm is restored to the driving bit is applied, and at the same time, a deformation that does not cause droplet ejection when the diaphragm is restored to the non-driving bit is deformed. Means for applying a second drive waveform;
  When the vibration width direction of the diaphragm is the Z direction, and the Z direction coordinate at the center of the diaphragm when the diaphragm is stationary is zero, the Z direction coordinate at the center of the diaphragm of the non-driving bit is the vibration bit. Application of the second drive waveform is canceled when it is equal to the Z-direction coordinate at the center of the diaphragm
The configuration.
[0011]
  According to the present inventionThe head drive device
  A first drive waveform that deforms with a deformation amount that drops when the diaphragm is restored to the driving bit is applied, and at the same time, a deformation that does not cause droplet ejection when the diaphragm is restored to the non-driving bit is deformed. Means for applying a second drive waveform;
  The pressure P1 at the nozzle tip of the non-driving bit when a voltage is applied to the diaphragm of the non-driving bit, and the pressure at the nozzle tip of the non-driving bit when no voltage is applied to the diaphragm of the non-driving bit When the ratio P1 / P2 to the maximum pressure value P2 becomes approximately 0.8, the application of the second drive waveform is canceled.
The configuration.
[0021]
In the ink jet recording apparatus according to the present invention, a head driving apparatus that drives an electrostatic ink jet head that records an image by ejecting ink droplets is the head driving apparatus according to any one of claims 1 to 17.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic perspective explanatory view of a mechanism part of an ink jet recording apparatus according to the present invention, and FIG. 2 is a side explanatory view of a main part of the recording apparatus.
[0023]
In this ink jet recording apparatus, a main guide rod 2 and a sub guide rod 3 are horizontally mounted on a frame 1 in a substantially horizontal positional relationship, and the carriage 5 is slid in the main scanning direction by the main guide rod 2 and the sub guide rod 3. Supports freely.
[0024]
The carriage 5 has four heads 6 for ejecting yellow (Y) ink, magenta (M) ink, cyan (C) ink, and black (Bk) ink, respectively (the heads of the respective colors are denoted by “6y”, "6m", "6c", and "6k" are used), and four ink cartridges 7 for supplying each color ink to the head 6 are provided on the carriage 5. "7y", "7m", "7c", and "7k" are used).
[0025]
As the head 6, an electrostatic ink jet head that discharges ink droplets by deforming and displacing the diaphragm with an electrostatic force using a diaphragm (or an electrode integrated with the diaphragm) that forms the wall surface of the ejection chamber and a counter electrode is used. ing. Further, the head 6 can be composed of a seven-color head in which three colors of light cyan, light magenta, and light yellow are added to the above four colors. Furthermore, as the head 6, a multi-nozzle head having nozzles that eject ink droplets of each color with one head can be used instead of an independent head for each color.
[0026]
The ink cartridge 7 has an air port that communicates with the atmosphere upward, a supply port that supplies ink to the individual inkjet heads of the head 6, and a porous body filled with ink inside. The ink supplied to the inkjet head is maintained at a slight negative pressure by the capillary force of the material. Ink is supplied from the ink cartridge 7 into each inkjet head of the head 6.
[0027]
The carriage 5 is connected to a timing belt stretched between a drive pulley (drive timing pulley) rotated by a main scanning motor (not shown) and a driven pulley (idler pulley) to drive and control the main scanning motor. Thus, the carriage 5 is moved and scanned in the main scanning direction.
[0028]
Further, the sheet 10 set on the guide plate 8 is taken in by a platen roller 13 rotated via a drive gear 11 and a sprocket gear 12 by a drive source (not shown), and the peripheral surface of the platen roller 13 is brought into pressure contact with the guide. The roller 14 and the pressure roller 15 can convey in the arrow B direction. A knob 13 a is attached to the platen roller 13.
[0029]
In this inkjet recording apparatus, ink droplets are ejected from each head of the recording head 6 while the carriage 5 is moved and scanned in the main scanning direction (arrow A direction), and an image for one line is printed on the paper 10. The image is recorded on the paper 10 while repeating the operation of conveying the paper 10 for one line in the sub-scanning direction (arrow B direction).
[0030]
Further, although not shown, a recovery device for recovering defective ejection of the head 14 is disposed at a position outside the recording area on the right end side in the movement direction of the carriage 5. The recovery device includes a cap unit, a suction unit, and a cleaning unit. The carriage 5 is moved to the recovery device side during printing standby, and the head 6 is capped by the capping means, and the ejection port portion (nozzle hole) is kept in a wet state to prevent ejection failure due to ink drying. Further, by ejecting (purging) ink not related to recording during recording or the like, the ink viscosity of all the ejection ports is made constant and stable ejection performance is maintained.
[0031]
When a discharge failure occurs, the discharge port (nozzle) of the head 6 is sealed with a capping unit, and bubbles and the like are sucked out from the discharge port with the suction unit through the tube. Is removed by the cleaning means to recover the ejection failure. The sucked ink is discharged to a waste ink reservoir (not shown) installed at the lower part of the main body, and is absorbed and held by an ink absorber inside the waste ink reservoir.
[0032]
Next, an ink jet head constituting the head 6 of the ink jet recording apparatus will be described with reference to FIGS. 3 is a sectional explanatory view of the head in the longitudinal direction of the diaphragm, FIG. 4 is a sectional explanatory view of the head in the lateral direction of the diaphragm, and FIG. 5 is an explanatory plan view of the head excluding the lid member.
[0033]
This inkjet head is a flow path substrate 41 as a first substrate, an electrode substrate 43 as a second substrate provided below the flow path substrate 41, and a third substrate provided above the flow path substrate 41. It is a laminated structure in which a lid member 44 is overlapped and joined. With these, a plurality of nozzles 45, a discharge chamber 46 that is an ink flow path that communicates with each nozzle 45, and a discharge chamber 46 communicate with each other via a fluid resistance portion 7. A common ink chamber 48 is formed.
[0034]
In the flow path substrate 41, a silicon substrate is used to form a nozzle groove that becomes the nozzle 45, a discharge chamber 46, a diaphragm 50 that forms a wall surface that forms the bottom of the discharge chamber 46, and a partition that separates the discharge chambers 46. A concave portion, a groove portion that forms the fluid resistance portion 47, a concave portion that forms the common liquid chamber 48, and the like are formed.
[0035]
The diaphragm 50 is formed by utilizing the fact that the etching rate is very small in the high-concentration P-type impurity region in alkali Si etching. That is, a high-concentration boron-doped silicon layer, which is a high-concentration P-type impurity layer serving as a vibration plate, is formed on the silicon substrate serving as the flow path substrate 1 at a position where a desired vibration plate thickness can be produced. By forming the discharge chamber 46, the common liquid chamber 48, etc. by the isotropic etching, the etching rate becomes extremely small when the high-concentration boron-doped silicon layer (high-concentration P-type impurity layer) is exposed. The diaphragm 50 whose plate thickness is controlled with high accuracy can be formed. As the high-concentration P-type impurity, gallium, aluminum, or the like can be used in addition to boron.
[0036]
As the electrode substrate 43, a silicon substrate is used to form a silicon oxide film 52 having a thickness by a thermal oxidation method or the like, a recess 54 is formed in the silicon oxide film 52, and the diaphragm 50 is formed on the bottom surface of the recess 54. An opposing electrode 55 is formed with a predetermined gap 56, and the electrode 55 and the diaphragm 50 constitute an electrostatic actuator unit that changes the inner volume of the discharge chamber 46 by displacing the diaphragm 55 with an electrostatic force. ing.
[0037]
Here, the electrode 55 is formed by sputtering titanium nitride in the recess 54 to a thickness of 0.1 μm and patterning this titanium nitride into an electrode shape. Therefore, in this head, the length of the gap 56 (interval between the diaphragm 50 and the electrode 55) after the electrode substrate 43 and the flow path substrate 41 are joined is 0.3 μm. The electrode 55 may be made of a refractory metal such as doped polysilicon or tungsten instead of titanium nitride. Further, the electrode 55 extends to the vicinity of the end portion of the electrode substrate 43 to form an electrode pad portion 55a for connection with a driving device (driving circuit) via a connecting means.
[0038]
Further, the surface of the electrode 55 is coated with a silicon oxide film or the like except for the electrode pad portion 55a to form an insulating layer 57 so as to prevent dielectric breakdown or short-circuit when the inkjet head is driven. The electrode substrate 43 may be a glass substrate such as borosilicate glass or a glass electrode substrate on which an electrode using a material such as nickel and an alloy thereof is formed.
[0039]
Further, the lid member 44 is formed with a recess for forming the common liquid chamber 48 and an ink supply port 49 for supplying ink from the ink cartridge 15 described above.
[0040]
In this inkjet head, when a pulse potential of 0 V to 35 V is applied to the electrode 55 by a drive circuit (driver IC) and the surface of the electrode 55 is positively charged, the lower surface of the corresponding diaphragm 50 is charged to a negative potential. Therefore, the diaphragm 50 bends downward due to electrostatic attraction. Next, when the potential of the electrode 55 is turned off, the diaphragm 50 is restored. As a result, the pressure in the pressurizing chamber 46 increases rapidly, and ink droplets are ejected from the nozzle 45. Next, the vibration plate 50 is bent again toward the electrode 55, whereby ink is supplied from the common liquid chamber 48 into the discharge 46 through the fluid resistance portion 47.
[0041]
As examples of head dimensions of this head, the following were produced. Nozzle inner diameter: 20 μm, nozzle length: 50 μm, diaphragm length: 2500 μm, diaphragm thickness: 3 μm, pressurized liquid chamber length: 3000 μm, pressurized liquid chamber width: 130 μm, pressurized liquid chamber height: 400 μm, Fluid resistance path length: 500 μm, fluid resistance path height: 50 μm, fluid resistance path width: 70 μm, common liquid chamber length: 1000 μm, common liquid chamber height: 550 μm, 1-bit pitch: 169 μm.
[0042]
Next, an outline of the control unit of the ink jet recording apparatus will be described with reference to FIG.
The control unit includes a microcomputer (hereinafter referred to as “CPU”) 60 that controls the entire recording apparatus, a ROM 61 that stores required fixed information such as driving waveform parameters and a control program, a working memory, and the like. A RAM 62, an image memory 63 for storing data processed from image data transferred from the host, a parallel input / output (PIO) port 64, an input buffer 65, a parallel input / output (PIO) port 66, , A waveform generation circuit 67 for generating and outputting a drive waveform, a head drive circuit 68, a driver 69, and the like.
[0043]
Here, the PIO port 84 has various information such as image data from the host side, various instruction information from an operation panel (not shown), a detection signal from a paper presence / absence sensor that detects the start and end of the paper, and the home position of the carriage 5 ( Signals from various sensors such as a home position sensor for detecting a reference position) are input, and necessary information is sent to the host side and the operation panel side via the PIO port 64.
[0044]
Further, the waveform generation circuit 67 is a first drive waveform (discharging) between the vibrating plate 50 of the head 6 and the electrode 55 that displaces the vibrating plate 50 toward the electrode 55 at a displacement amount and timing sufficient for discharging ink droplets. Pulse) and a second drive waveform (non-ejection pulse) that causes the diaphragm 50 to be displaced toward the electrode 55 side at a displacement amount and timing not to eject the ink droplet. As the waveform generation circuit 67, a D / A converter that D / A converts drive waveform data from the CPU 60 can be used to generate and output a plurality of required drive waveforms with a simple configuration.
[0045]
The head drive circuit (head driver) 68 is first connected to each actuator (the diaphragm 50 and the electrode 55) corresponding to each nozzle 45 of the head 6 based on various data and signals given through the PIO port 66. A drive waveform or a second drive waveform is selected and applied.
[0046]
As shown in FIG. 7, the head drive circuit 68 inputs the ejection pulse P1 and the non-ejection pulse P2 generated and output from the waveform generation circuit 67 to the terminals a and b, respectively, and is switched to 3 terminals according to the print data. A switch 70 is included, and the ejection pulse P1 or the non-ejection pulse P2 is applied to the individual electrode 55 of the head, or neither the ejection pulse P1 nor the non-ejection pulse P2 is applied to the individual electrode 55 of the head.
[0047]
Further, the driver 69 drives and controls the main scanning motor 71 that moves the carriage 5 in the main scanning direction and the sub-scanning motor 72 that rotates the platen 13 in accordance with driving data given through the PIO port 66. The carriage 5 is moved and scanned in the main scanning direction, the platen 13 is rotated, and the paper 10 is conveyed by a predetermined amount.
[0048]
Next, head drive control in this ink jet recording apparatus will be described with reference to FIG.
First, the first drive waveform (discharge pulse) PV1 and the second drive waveform (non-discharge pulse) PV2 applied to the head will be described with reference to FIG.
[0049]
The ejection pulse PV1 is a pulse having a pulse voltage value Pv1 and a voltage application time width (pulse width) Pw1. When the ejection pulse PV1 is applied, the vibration plate 50 is deformed more than the ink droplet can be ejected (in this case, for example, until it contacts the electrode 55), and the application of the ejection pulse PV1 is canceled and the vibration plate 50 is released. When the ink is restored to the initial position (position where no voltage is applied), ink droplets are ejected.
[0050]
The non-ejection pulse PV2 is a pulse having a pulse voltage value Pv2 and a voltage application time width (pulse width) Pw2, having a polarity opposite to that of the ejection pulse PV1, and the pulse voltage value Pv2 being smaller than the pulse voltage value Pv1 of the ejection pulse PV1 ( Pv2 <Pv1) and the pulse width Pw2 are pulses longer than the pulse width Pw1 of the ejection pulse PV1 by the time ΔTa (Pw2> Pw1). When this non-ejection pulse PV2 is applied, the diaphragm 50 is deformed to such an extent that no ink droplets are ejected at the time of restoration, and the application of the non-ejection pulse PV2 is canceled and the diaphragm 50 is moved to the initial position (position where no voltage is applied). Ink droplets are not ejected even when restored to (1).
[0051]
Therefore, in this ink jet recording apparatus, when the ink jet head is driven, an ejection pulse PV1 is applied to a bit that ejects ink droplets according to print data (referred to as a drive bit), and a bit that does not eject ink droplets (non-discharged). The non-ejection pulse P2 is applied simultaneously (at time T0 in FIG. 8) to the driving bit.
[0052]
Therefore, the diaphragm 50 of the driving bit is deformed to the extent that ink droplets can be ejected to the electrode side by application of the ejection pulse PV1, and the diaphragm 50 of the non-driving bit is similarly restored to the electrode side by application of the non-ejection pulse PV2. Sometimes it deforms so as not to eject ink droplets. Although the ejection pulse PV1 and the non-ejection pulse PV2 have different polarities, the generated electrostatic force is an electrostatic attractive force between the diaphragm 50 and the electrode 55 and does not generate a repulsive force. The diaphragm 50 is deformed in the same direction (electrode side).
[0053]
Then, at time T2 in FIG. 8 when the application of the ejection pulse PV1 is canceled, the driving bit diaphragm 50 starts to be restored, and ink droplets are ejected from the nozzle 45 of the driving bit. Further, at the time T3 when ΔTa has elapsed from the time T2 in FIG. 8 where the application of the ejection pulse PV1 is released, the application of the non-ejection pulse PV2 to the non-drive bit is released, and the diaphragm 50 of the non-drive bit is restored. The ink droplets are not ejected from the nozzles 45 of the non-driving bits depending on the restoration of the diaphragm 50.
[0054]
Therefore, details of the relationship between the timing for releasing the force applied to the diaphragm of the driving bit and the timing for releasing the force applied to the diaphragm of the non-driving bit for the ejection pulse PV1 and the non-ejection pulse PV2 as drive waveforms will be described.
First, assuming that the vibration period of the diaphragm 50 is T, non-drive is performed by the force applied to the diaphragm 50 of the non-drive bit when 0.31 T has elapsed since the force applied to the diaphragm 50 of the drive bit was removed. How the pressure at the nozzle tip of the bit changes will be described.
[0055]
Here, the force applied to the diaphragm of the non-driving bit is F1, the force applied to the diaphragm of the driving bit is F2, and the ratio of F1 and F2, that is, the absolute value of F1 / F2, is F (F = | F1 / F2 | ). That is, F is a relative value of the force applied to the diaphragm of the non-driven bit with respect to the force applied to the diaphragm of the driving bit.
[0056]
In the general case where no force is applied to the diaphragm of the non-driving bit, the pressure at the nozzle tip of the non-driving bit is P1, and the non-driving when the force is also applied to the diaphragm of the non-driving bit. The pressure at the nozzle tip of the bit is P2, and the ratio of P1 and P2, that is, P1 / P2 is P (P = P1 / P2). That is, P applies the present invention to the pressure at the nozzle tip of the non-driving bit in the case where no force is applied to the diaphragm of the conventional non-driving bit (that is, the force is also exerted on the diaphragm of the non-driving bit. ) In this case, the relative value of the pressure at the nozzle tip of the non-driven bit.
[0057]
Based on the above, the relationship between the defined F and P is shown in FIG. According to the figure, it is understood that P can be made smaller than “1” if the previously defined F is “0.3 or more and 1 or less”. The fact that P is smaller than “1” means that the increase in the nozzle tip pressure of the non-driven bit is suppressed as compared with the case where no force is applied to the diaphragm of the non-driven bit. That is, mutual interference is suppressed.
[0058]
Further, in more detail, it can be seen from FIG. 10 in which FIG. 9 is enlarged that P can be minimized especially by setting F (= F1 / F2) to “0.5”.
[0059]
Therefore, next, when F is 0.5, the time when the force applied to the diaphragm of the drive bit is removed is T1 (time T1 in FIG. 8), and the time when the force applied to the diaphragm of the non-drive bit is released. When the time difference ΔT (here, ΔT = ΔTa) between T2 and T1 is changed to T2 (time T2 in FIG. 8), how P changes as described above is summarized as shown in FIG. In FIG. 11, the horizontal axis is normalized by the above-described ΔT with the vibration period T of the diaphragm.
[0060]
As can be seen from FIG. 11, by setting (time difference ΔT) / (vibration period T of the diaphragm) to “0.33 or more and 0.44 or less”, P can be made “1 or less”. It can also be seen from the figure that P can be minimized by setting (time difference ΔT) / (vibration period T) to “0.41”.
[0061]
Next, the relationship between the pulse widths Pw1 and Pw2 of the ejection pulse PV1 and the non-ejection pulse PV2 is examined in relation to the diaphragm position.
The deflection width direction of the diaphragm 50 is defined as the Z direction, and the position in the Z direction of the diaphragm central portion when the diaphragm is stationary is defined as zero. The time when the diaphragm of the non-driving bit and the diaphragm of the driving bit are in the same position in the Z direction is t1, and the time when the force applied to the diaphragm of the non-driving bit is zero is t2, and is applied to the diaphragm of the non-driving bit. When the ratio F1 / F2 between the force F1 and the force F2 applied to the drive bit diaphragm is -0.3, (t2-t1) / (vibration period T of the diaphragm) and the nozzle tip pressure ratio P described above. This relationship is shown in FIG.
[0062]
From FIG. 12, by removing the force applied to the diaphragm of the non-driving bit at the time (time point) when the diaphragms of both the non-driving bit and the driving bit are substantially at the same position in the Z direction (release the non-ejection pulse PV2). That is, it can be seen that the nozzle tip pressure ratio P can be reduced by setting the pulse width Pw2 of the non-ejection pulse PV2.
[0063]
Here, the “substantially the same position in the Z direction” will be specifically described.
The Z-direction coordinate of the diaphragm of the non-driving bit is Z1, the Z-direction coordinate of the diaphragm of the driving bit is Z2, and the relationship of P defined above with respect to the ratio Z1 / Z2 is as shown in FIG. From FIG. 13, it can be seen that in order to reduce P, the Z-direction coordinate Z2 of the diaphragm of the non-driving bit may be 80% to 110% of the Z-direction coordinate Z1 of the diaphragm of the driving bit. Furthermore, it can be seen that P can be minimized when the Z-direction coordinate Z2 of the diaphragm of the non-driving bit is 100% of the Z-direction coordinate Z1 of the diaphragm of the driving bit.
[0064]
Next, the relationship between the pulse widths Pw1 and Pw2 of the ejection pulse PV1 and the non-ejection pulse PV2 is examined in relation to the nozzle tip pressure.
Changes the ratio between the nozzle tip pressure P3 of the non-driven bit at the moment when the force applied to the diaphragm of the non-driven bit is removed and the maximum value P4 of the nozzle tip pressure when no force is applied to the diaphragm of the non-driven bit FIG. 14 shows the change in the nozzle tip pressure ratio P defined as the ratio P1 / P2 between the nozzle tip pressure P1 and the nozzle tip pressure P2 according to the conventional technique in which the non-ejection pulse P2 is not applied to the non-driving bit. Show.
[0065]
From FIG. 14, at the time (time point) when P3 / P4 becomes approximately “0.8”, the force applied to the diaphragm of the non-driving bit is released (the non-ejection pulse P2 is released, that is, the non-ejection pulse It can be seen that the nozzle tip pressure of the non-driven bit can be minimized by setting the pulse width Pw2 of P2.
[0066]
By applying the first drive waveform and the second drive waveform as described above, it is possible to obtain a high-quality recording apparatus with little mutual interference.
[0067]
Next, a second embodiment of the present invention will be described.
In this embodiment, as shown in FIG. 15, the first drive waveform (ejection pulse) PV11 is a pulse having a pulse voltage value Pv11 and a voltage application time width (pulse width) Pw11. When this ejection pulse PV11 is applied, the vibration plate 50 is deformed more than the ink droplet can be ejected (here, for example, until it abuts on the electrode 55 side), and the application of the ejection pulse PV11 is canceled and the vibration plate 50 is released. When the ink is restored to the initial position (position where no voltage is applied), ink droplets are ejected.
[0068]
The non-ejection pulse PV12 is a pulse having a pulse voltage value Pv12 and a voltage application time width (pulse width) Pw12, which has the same polarity as the ejection pulse PV1, and the pulse voltage value Pv12 is smaller than the pulse voltage value Pv1 of the ejection pulse PV1 ( Pv2 <Pv1), the pulse width Pw2 is a pulse shorter than the pulse width Pw1 of the ejection pulse PV1 by the time ΔT (Pw2 <Pw1). When this non-ejection pulse PV2 is applied, the diaphragm 50 is deformed to such an extent that no ink droplets are ejected at the time of restoration, and the application of the non-ejection pulse PV2 is canceled and the diaphragm 50 is moved to the initial position (position where no voltage is applied). Ink droplets are not ejected even when restored to (1).
[0069]
Therefore, in this ink jet recording apparatus, when the ink jet head is driven, a discharge pulse PV11 is applied to a bit (referred to as a drive bit) that discharges ink droplets according to print data, and a bit that does not discharge ink droplets (non-discharged). A non-ejection pulse P12 is applied simultaneously (at time T0 in FIG. 15).
[0070]
Therefore, the diaphragm 50 of the driving bit is deformed to the extent that ink droplets can be ejected to the electrode side by application of the ejection pulse PV1, and the diaphragm 50 of the non-driving bit is similarly restored to the electrode side by application of the non-ejection pulse PV2. Sometimes it deforms so as not to eject ink droplets.
[0071]
At time T1, the application of the non-ejection pulse PV12 to the non-driving bit is released, and the diaphragm 50 of the non-driving bit starts to be restored. Depending on the restoration of the diaphragm 50, an ink droplet from the nozzle 45 of the non-driving bit. Is not discharged. Then, the application of the ejection pulse PV11 is canceled at time T2 when ΔTb has elapsed from time T1, the drive bit diaphragm 50 starts to be restored, and ink droplets are ejected from the nozzle 45 of the drive bit.
[0072]
Therefore, details of the relationship between the timing for releasing the force applied to the diaphragm of the driving bit and the timing for releasing the force applied to the diaphragm of the non-driving bit for the ejection pulse PV11 and the non-ejection pulse PV12 as the drive waveform will be described.
First, in FIGS. 16 to 18, when the force applied to the diaphragm of the non-driving bit is constant for each figure, the force applied to the diaphragm of the non-driving bit is removed (the application of the non-ejection pulse PV12 is canceled). ) And the time ΔT (here, ΔT = ΔTb) from when the force applied to the diaphragm of the driving bit is removed (application of the discharge pulse PV11 is released), how the nozzle tip pressure P of the non-driving bit is changed. Shows how it will change.
[0073]
Again, the force applied to the diaphragm of the non-driving bit is F1, the force applied to the diaphragm of the driving bit is F2, and the ratio of F1 and F2, that is, F1 / F2 is F. That is, F is a relative value of the force applied to the diaphragm of the non-driven bit with respect to the force applied to the diaphragm of the driving bit.
[0074]
When this ratio F is F = 0.3, as shown in FIG. 15, when F = 0.5, as shown in FIG. 16, when F = 0.7, As shown in FIG.
[0075]
Further, as shown in FIG. 19, even in a general case where no force is applied to the diaphragm of the non-driving bit, the pressure on the driving bit side is transmitted, the diaphragm of the non-driving bit also moves, The nozzle tip pressure also changes (as shown by the solid line in the figure). Similarly, when a force is applied to the diaphragm of the non-driving bit, the pressure on the driving bit side is transmitted, and the nozzle tip pressure of the non-driving bit also changes (as shown by the broken line in the figure).
[0076]
In a general case where no force is applied to the diaphragm of the non-driving bit, the peak value of the pressure at the nozzle tip of the non-driving bit at the first round of the vibration period of the diaphragm is P11, and the vibration of the non-driving bit is When a force is also applied to the plate, the peak value of the pressure at the nozzle tip of the non-driven bit at the first round of the vibration period of the diaphragm is P12, the peak value at the second round is P13, and P12 or P13 and P11 , That is, P12 / P11 or P13 / P11 is P.
[0077]
That is, P applies force to the diaphragm of the non-driven bit as in the present invention against the pressure at the nozzle tip of the non-driven bit when no force is applied to the diaphragm of the conventional non-driven bit. In this case, it is the relative value of the pressure at the nozzle tip of the non-driven bit.
[0078]
Further, when the time (time point) at which the force applied to the diaphragm of the non-driving bit is removed is T11, the time (time point) at which the force applied to the diaphragm of the driving bit is removed is T12, and the time difference ΔT between T12 and T11 is changed. FIG. 16 to FIG. 18 summarize how the above-described P12 / P11 or P13 / P11 changes. In each figure, the above ΔT is normalized by the vibration period T of the diaphragm.
[0079]
Here, FIGS. 16 to 18 show the result of the nozzle tip pressure ratio in the first and second rounds of the vibration period of the diaphragm in the non-driven bit. In each figure, the solid line is the peak of the nozzle tip pressure ratio in the first round of the vibration period of the diaphragm in the non-driven bit, and the broken line is the nozzle tip in the second round of the vibration period of the diaphragm in the non-driven bit. It is the peak of the pressure ratio.
[0080]
As can be seen from these figures, in each F, in the second round, ΔT / T is the minimum around 0.065, and it can be said that the tendency of the graph is almost the same (the tendency of the first round is also the same). It can be said that it is almost the same.) The effect of suppressing the pressure rise at the nozzle tip of the non-driving bit is larger as F is larger. However, when F is 0.7, there is a possibility that ink may be ejected from the nozzle tip of the non-driving bit. .5 or less is preferable. As F is larger, the effect of suppressing the pressure rise at the nozzle tip of the non-driven bit is larger, so the following description will be made on the case where F is 0.5.
[0081]
First, from FIG. 17, it can be said that the effect of the present invention is not effective unless P in at least the second round is smaller than when ΔT / T is 0. Therefore, ΔT / T should be 0.15 or less. It ’s fine.
[0082]
FIG. 20 shows how P13 / P12 changes depending on ΔT / T. P13 / P12 is a numerical value indicating the ratio of the nozzle tip pressure ratio of the non-driven bit to the peak of the second round compared to the peak of the first round, that is, an attenuation factor. When this attenuation factor is low, the nozzle tip pressure that has once increased is unlikely to return to the initial state, and the possibility of stable ejection during the next ejection increases.
[0083]
First, from FIG. 17, the nozzle tip pressure ratio in the second round is minimized when ΔT / T is 0.065. Further, from FIG. 20, P13 / P12 is small when ΔT / T is larger than 0.065, but P13 / P12 is large where ΔT / T is smaller than 0.065. Therefore, even if the value of the second round is large, if P13 / P12 is small, the pressure at the nozzle tip is attenuated before the next ink discharge, and therefore ΔT / T is preferably 0.065 or more.
[0084]
For example, in an inkjet printer, when the driving speed is 10 KHz and P13 / P12 is 0.93 (when ΔT / T = 0), the nozzle tip pressure ratio until the next ink droplet discharge is attenuated with respect to the first round. The rate is 0.80, whereas when P13 / P12 is 0.87 (when ΔT / T = 0.065), 0.66 and P13 / P12 is 0.85 (P13 / P12). Was the minimum value) was 0.61. Thus, it can be seen that if ΔT / T is 0.065 or more, it is sufficiently attenuated. In the case of the conventional technique in which no force is applied to the diaphragm of the non-driven bit, P13 / P12 is 0.94, and the attenuation rate of the nozzle tip pressure ratio is 0.83 at 10 KHz.
[0085]
By applying the first and second driving waveforms described above, it is possible to obtain a high-quality recording apparatus with little mutual interference.
[0086]
【The invention's effect】
  As described above, the head driving device according to the present invention isIn placeAccording to,A first drive waveform that deforms with a deformation amount that drops when the diaphragm is restored to the driving bit is applied, and at the same time, a deformation that does not cause droplet ejection when the diaphragm is restored to the non-driving bit is deformed. Means for applying a second drive waveform;When the vibration width direction of the diaphragm is the Z direction, and the Z direction coordinate at the center of the diaphragm when the diaphragm is stationary is zero, the Z direction coordinate at the center of the diaphragm of the non-driving bit is the vibration bit. The application of the second drive waveform is canceled when it is equal to the Z-direction coordinate at the center of the diaphragm.Therefore, it is possible to reduce mutual interference with non-driving bits.
[0087]
  According to the present inventionAccording to the head driving device, the first driving waveform that is deformed by the deformation amount that is ejected when the diaphragm is restored to the driving bit is applied, and at the same time the droplet is restored when the diaphragm is restored to the non-driving bit. Means for applying a second drive waveform to be deformed with a deformation amount that does not discharge;The pressure P1 at the nozzle tip of the non-driving bit when a voltage is applied to the diaphragm of the non-driving bit, and the pressure at the nozzle tip of the non-driving bit when no voltage is applied to the diaphragm of the non-driving bit When the ratio P1 / P2 to the maximum pressure value P2 becomes approximately 0.8, the application of the second drive waveform is canceled.Therefore, it is possible to reduce mutual interference with non-driving bits.
[0098]
  According to the ink jet recording apparatus of the present invention, there is provided a head driving device that drives an electrostatic ink jet head that records an image by ejecting ink droplets.According to the present inventionSince it is a head drive device, stable ink droplet ejection characteristics can be obtained, and high-quality and high-quality recording can be performed.
[Brief description of the drawings]
FIG. 1 is a schematic perspective explanatory view of a mechanism part of an ink jet recording apparatus according to the present invention;
FIG. 2 is a schematic side view of FIG.
FIG. 3 is an explanatory cross-sectional view along the longitudinal direction of a diaphragm showing an example of an inkjet head of the recording apparatus.
FIG. 4 is an explanatory cross-sectional view of the head along the transversal direction of the diaphragm.
FIG. 5 is an explanatory plan view of the flow path portion of the head.
FIG. 6 is a schematic block diagram of a control unit of the recording apparatus.
FIG. 7 is an explanatory diagram of a main part of a head drive circuit of the control unit.
FIG. 8 is an explanatory diagram of a first drive waveform and a second drive waveform used in the first embodiment of the present invention.
FIG. 9 is an explanatory diagram for explaining the embodiment;
FIG. 10 is an explanatory diagram for explaining the embodiment;
FIG. 11 is an explanatory diagram for explaining the embodiment;
FIG. 12 is an explanatory diagram for explaining the embodiment;
FIG. 13 is an explanatory diagram for explaining the embodiment;
FIG. 14 is an explanatory diagram for explaining the embodiment;
FIG. 15 is an explanatory diagram of a first drive waveform and a second drive waveform used in the second embodiment of the present invention.
FIG. 16 is an explanatory diagram for explaining the embodiment;
FIG. 17 is an explanatory diagram for explaining the embodiment;
FIG. 18 is an explanatory diagram for explaining the embodiment;
FIG. 19 is an explanatory diagram for explaining the embodiment;
FIG. 20 is an explanatory diagram for explaining the embodiment;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 5 ... Carriage, 6 ... Head, 10 ... Paper, 13 ... Platen roller, 45 ... Nozzle, 46 ... Discharge chamber, 50 ... Diaphragm, 55 ... Electrode, 68 ... Head drive circuit.

Claims (3)

In a head drive device for driving an electrostatic droplet discharge head that discharges droplets by deforming a diaphragm with an electrostatic force,
A first driving waveform that is deformed with a deformation amount that drops when the diaphragm is restored to the driving bit is applied, and at the same time, a deformation that does not cause droplet ejection when the diaphragm is restored with respect to the non-driving bit is deformed. Means for applying a second drive waveform;
When the vibration width direction of the diaphragm is the Z direction and the Z direction coordinate at the center of the diaphragm when the diaphragm is stationary is zero, the Z direction coordinate at the center of the diaphragm of the non-driven bit is in a vibration state. The head driving device according to claim 1, wherein the application of the second driving waveform is canceled when the bit is equal to the Z-direction coordinate at the center of the diaphragm. In a head drive device for driving an electrostatic droplet discharge head that discharges droplets by deforming a diaphragm with an electrostatic force,
A first driving waveform that is deformed with a deformation amount that drops when the diaphragm is restored to the driving bit is applied, and at the same time, a deformation that does not cause droplet ejection when the diaphragm is restored with respect to the non-driving bit is deformed. Means for applying a second drive waveform;
The pressure P1 at the nozzle tip of the non-driving bit when a voltage is applied to the diaphragm of the non-driving bit, and the pressure at the nozzle tip of the non-driving bit when no voltage is applied to the diaphragm of the non-driving bit The head drive device according to claim 1, wherein the application of the second drive waveform is canceled when the ratio P1 / P2 to the maximum pressure value P2 becomes approximately 0.8. 3. An ink jet recording apparatus equipped with an electrostatic ink jet head for recording an image by ejecting ink droplets, wherein the head driving apparatus for driving the electrostatic ink jet head is the head driving apparatus according to claim 1 or 2. An ink jet recording apparatus.

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