JP3024424B2 - Driving device for ink ejection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving device for an ink ejecting apparatus.

[0002]

2. Description of the Related Art The non-impact type printing apparatus which has been replacing the conventional impact type printing apparatus and is now expanding its market greatly is the simplest in principle and has a multi-gradation and color printing. For example, an ink-jet type printing apparatus can be used. Above all, a drop that ejects only ink drops used for printing
The on-demand type is rapidly spreading due to its good injection efficiency and low running cost.

The Kaiser type disclosed in Japanese Patent Publication No. 53-12138 as a drop-on-demand type,
Alternatively, a thermal jet type disclosed in Japanese Patent Publication No. 61-59914 is a typical method.
Among them, the former is difficult to miniaturize, and the latter requires a heat resistance of the ink in order to apply high heat to the ink, and each has a very difficult problem.

Japanese Patent Laid-Open No. 63-252750 proposes a new method for simultaneously solving the above-mentioned defects.
This is a shear mode type disclosed in Japanese Patent Application Laid-Open Publication No. HEI 10-303, 1988. Less than,
The schematic configuration will be described with reference to the drawings.

[0005] As shown in FIG. 9, the above-described shear mode type ink ejecting apparatus 1 includes a piezoelectric ceramic plate 2, a cover plate 10, a nozzle plate 14, and a substrate 41.

The piezoelectric ceramic plate 2 is cut by a diamond blade or the like to form a plurality of grooves 3.
Are formed. Also, a side wall 6 serving as a side surface of the groove 3
Is polarized in the direction of arrow 5. The grooves 3 are of the same depth and are parallel. The depth of each of the grooves 3 gradually decreases as approaching one end face 15 of the piezoelectric ceramic plate 2, and a shallow groove 7 is formed near the one end face 15. On the inner surface of the groove 3, metal electrodes 8 are formed on the upper halves of both sides by sputtering or the like. On the inner surface of the shallow groove 7, a metal electrode 9 is formed on the side and bottom surfaces thereof by sputtering or the like. Thereby, the metal electrodes 8 formed on both side surfaces of the groove 3 are formed.
Are electrically connected by a metal electrode 9 formed in the shallow groove 7.

Next, the cover plate 10 is made of a ceramic material or a resin material. And
The cover plate 10 has an ink inlet 16 and a manifold 18 formed by grinding or cutting. Then, the surface of the piezoelectric ceramic plate 2 on the processing side of the groove 3 and the surface of the cover plate 10 on the processing side of the manifold 18 are bonded by an epoxy adhesive 20 (see FIG. 11). Accordingly, the ink ejecting apparatus 1 has an ink chamber 4 (see FIG. 11), which is a plurality of ink flow paths that cover the upper surface of the groove 3 and have the same interval in the horizontal direction. As shown in FIG. 11, the ink chamber 4 has an elongated shape with a rectangular cross section, and all the ink chambers 4 are filled with ink.

As shown in FIG. 9, the ink chambers 4 are provided on the end faces of the piezoelectric ceramic plate 2 and the cover plate 10.
The nozzle plate 14 provided with the nozzles 12 is bonded at a position corresponding to the position. This nozzle plate 1
4 is formed of a plastic such as polyalkylene (eg, ethylene), terephthalate, polyimide, polyetherimide, polyetherketone, polyethersulfone, polycarbonate, or cellulose acetate.

A substrate 41 is bonded to the surface of the piezoelectric ceramic plate 2 opposite to the processing side of the groove 3 with an epoxy-based adhesive or the like. The substrate 41
Has a conductive layer pattern 42 formed at a position corresponding to the position of each ink chamber 4. The pattern 42 of the conductive layer
The metal electrode 9 on the bottom surface of the shallow groove 7 is connected by a conductive wire 43 by wire bonding.

Next, the configuration of the control unit will be described with reference to FIG. 10 which shows a block diagram of the control unit. The conductive layer patterns 42 formed on the substrate 41 are individually LSI chips 51
It is connected to the. Further, the clock line 52, the data line 53, the voltage line 54 and the ground line 55
It is connected to the SI chip 51. LSI chip 51
Determines which nozzle 12 should eject ink droplets according to data appearing on the data line 53, based on continuous clock pulses supplied from the clock line 52. Then, the voltage V of the voltage line 54 is applied to the conductive layer pattern 42 connected to the metal electrode 8 in the ink chamber 4 to be driven. Further, the ink chamber 4 to be driven
A voltage of 0 V of the ground line 55 is applied to the conductive layer pattern 42 that is electrically connected to the other metal electrodes 8.

Next, the operation of the ink ejecting apparatus 1 will be described with reference to FIGS. It is determined that the LSI chip 51 ejects ink from the ink chamber 4b of the ink ejecting apparatus 1 according to required data. Then, a positive drive voltage V is applied to the metal electrodes 8e and 8f,
d and 8g are grounded. Then, as shown in FIG. 12, a driving electric field in the direction of arrow 13b is generated on the side wall 6b, and a driving electric field in the direction of arrow 13c is generated on the side wall 6c. Then, since the drive electric field directions 13b and 13c are orthogonal to the polarization direction 5, the side walls 6b and 6c are rapidly deformed in the ink chamber 4b in this case due to the piezoelectric thickness-shear effect. Due to this deformation, the volume of the ink chamber 4b decreases, the ink pressure increases rapidly, a pressure wave is generated, and ink droplets are ejected from the nozzles 12 (see FIG. 9) communicating with the ink chamber 4b.

When the application of the driving voltage V is stopped,
Since the side walls 6b and 6c return to the positions before deformation (see FIG. 11), the ink pressure in the ink chamber 4b gradually decreases. Then, the ink supply port 16 is moved from an ink tank (not shown).
The ink is supplied into the ink chamber 4b through the manifold (FIG. 9) and the manifold 18 (FIG. 9).

The side walls 6b and 6c are deformed so that the polarity of the driving voltage is reversed and the side walls 6b and 6c are deformed so as to separate from each other by applying a voltage, and then the application of the voltage is stopped. It is also possible to return to the previous position (see FIG. 11) and eject ink droplets.

However, the ink ejecting apparatus 1 having the above-described configuration
When image information is formed on a recording medium by using the ink chambers 4, at least the adjacent ink chamber 4
Cannot be ejected at the same time. Therefore, as described in, for example, Japanese Patent Application Laid-Open No. 2-150355, a method is used in which the ink chambers 4 are divided into two groups, odd and even, and are alternately ejected. Further, in the above-mentioned publication, when mutual interference between the ink chambers 4, so-called crosstalk, is large, as a method for improving the interference, three or more groups (for example, in the case of three groups, the ink chambers in FIG. 4a and the ink chamber 4d, the ink chamber 4b and the ink chamber 4e
It is also proposed that the ink chamber 4c and the ink chamber 4f are members of the same group, respectively, and the groups are sequentially rotated and driven for each group.

[0015] However, the following inconvenience occurs even when the driving is performed sequentially in the three or more groups. That is, in FIG. 12, for example, when ink is ejected from the ink chamber 4b, the side walls 6b and 6c of the ink chamber 4b naturally deform, but the side wall 6b is also the side wall 6 of the ink chamber 4a, and the side wall 6c is simultaneously Room 4
The pressure wave also occurs in the ink in the ink chambers 4a and 4c because it is also the side wall 6 of the ink chamber 4c. Here, the magnitude of the pressure wave generated in the ink chambers 4a and 4c is a size that does not eject ink from the ink chambers 4a and 4c. The pressure wave in each ink chamber 4 propagates in the ink chamber 4 using ink as a medium, is reflected on a wall surface or the like, and attenuates while reciprocating in the ink chamber 4 many times.

For this reason, even after the ink ejection, the pressure fluctuation caused by the pressure wave remains in each ink chamber 4 for a while. This is a so-called residual pressure fluctuation. here,
If the next ink ejection is performed in the ink chamber 4c, the pressure in the ink chamber 4c is added to the above-mentioned residual pressure fluctuation in addition to the pressure for the ink ejection, and the characteristics of the ejected ink droplet (for example, the flying speed) And volume) are different from the case where there is no fluctuation of the residual pressure. On the other hand, the presence / absence of a pressure wave due to ink ejection in the ink chamber 4b differs depending on the printing pattern. If the ink chamber 4b is not ejected immediately before ejection from the ink chamber 4c, the above-described residual pressure fluctuation does not exist. Therefore, in this case, the characteristics of the ink droplet ejected from the ink chamber 4c change depending on the ink pattern,
Stable injection is not performed. Further, since the ink is sequentially ejected from the ink chambers 4 of each group, the above-described disadvantage occurs in all the ink chambers 4 except the ink chambers 4 on both sides of the ink ejecting apparatus 1.

On the other hand, for example, Japanese Patent Application Laid-Open No. 61-3752
It has been proposed to reduce the residual pressure fluctuation in the ink chamber 4 by applying a cancel pulse subsequent to a print pulse for performing ink ejection, as disclosed in Japanese Patent Application Laid-Open Publication No. H10-163,088. That is, after a certain period of time after the ink is ejected, a cancel pulse for generating a pressure wave whose phase is opposite to the residual pressure fluctuation in the ink chamber 4 is applied. Using this method, the ink chamber 4
By applying a print pulse and a cancel pulse to b, fluctuations in the residual pressure in the ink chambers 4a, 4b and 4c can be canceled at the same time.

Next, the behavior of the pressure wave at the time of ink ejection in each ink chamber 4 and the process of cancellation will be described with reference to FIG.
This will be specifically described with reference to a timing chart of FIG. 3 and a sectional view of the ink ejecting apparatus of FIG.

First, in order to eject ink from the ink chamber 4b of FIG. 2, an ejection voltage pulse B shown in FIG. Applying a voltage refers to applying a voltage to the electrode facing the ink chamber 4). Then, at the first rise, the side walls 6b and 6c move away from each other (see FIG. 2), the volume of the ink chamber 4b increases, and the pressure in the ink chamber 4b including the vicinity of the nozzle 12 decreases (FIG. 1).
3 (d)). This state is maintained only while indicated by AL in FIG. In the meantime, ink is supplied from the manifold 18 (FIG. 9).

The above AL is the time required for the pressure wave in the ink chamber 4 to propagate one way in the longitudinal direction of the ink chamber 4 (from the manifold 18 to the nozzle plate 14 or vice versa). It is determined by the length of the chamber 4 and the speed of sound in the ink.

According to the pressure wave propagation theory, the pressure in the ink chamber 4b reverses and changes to a positive pressure when the time AL has just started from the rise of the pressure wave. The applied voltage is returned to 0 V (FIG. 13A). Then, the side walls 6b and 6c return to the state before deformation, and pressure is applied to the ink. At this time, the pressure that has turned positive and the pressure generated when the side walls 6b and 6c return to the state before deformation are added together, and FIG.
The relatively high pressure Pb as shown in FIG.
Is supplied to the ink inside, and the ink is ejected from the nozzle 12.

After the ink is ejected, if the ink chamber 4b
If no new voltage pulse is given to the ink chamber 4
As shown by the solid line in FIG. 13D, the pressure b near the nozzle 12 continues to fluctuate for a period of 2AL (residual pressure fluctuation). On the other hand, when the above series of operations is viewed from the ink chamber 4c adjacent to the ink chamber 4b, only one side wall 6c moves in the opposite direction as viewed from the ink chamber 4b. As shown by the solid line in FIG. 13 (e), the phase changes from that in FIG. The same applies to the ink chamber 4a (not shown).

Next, it is assumed that, after the ink is ejected from the ink chamber 4b, for example, an ejection voltage pulse C shown in FIG. 13B is applied to the ink chamber 4c to eject the ink. At the time when the pulse C is applied, the residual pressure fluctuation still remains in the ink chamber 4c as shown in FIG. 13E, so that the pressure in the ink chamber 4c differs from the case where there is no residual pressure fluctuation (Pc ), The ejected ink droplets are also different from those in the case where there is no residual pressure fluctuation.

On the other hand, the presence or absence of the residual pressure fluctuation is determined by the injection pulse B
Cannot be made constant because it is determined by the presence or absence, that is, the printing pattern. In order to alleviate this, various driving methods for eliminating the residual pressure fluctuation after ink ejection, so-called cancel waveforms, have been proposed. Explaining an example, a cancel pulse K indicated by a broken line in FIG. 13A is applied AL after the fall of the ejection pulse B, and its width is equal to AL, and the polarity is opposite to B. Further, the voltage value is set according to the amplitude of the residual pressure fluctuation so as to just cancel the fluctuation. By giving the cancel pulse K, the side walls 6b and 6c move in the opposite direction to that at the time of ink ejection, and apply a pressure wave whose phase is opposite to that of the residual pressure fluctuation, thereby eliminating the residual pressure fluctuation. That is, as shown by the broken lines in FIGS. 13D and 13E, the pressure of the ink in the ink chamber 4c is set to 0 before the voltage pulse C is applied.

[0025]

However, when ink is ejected using the above-described driving method, a pressure wave is generated in the ink chamber 4 after at least an ink ejection pulse is applied in order to cancel the residual pressure fluctuation. After propagation and one round trip, a cancel pulse must be given. Furthermore, considering the pulse width of the cancel pulse itself,
A longer time is required to cancel the residual pressure fluctuation. For example, when the ink is ejected by deforming the side walls 6b and 6c of the ink chamber 4b to cancel the residual pressure fluctuation, the ink ejection from the ink chamber 4a or 4c is performed until the cancel pulse is completely completed. Can not. This is because the side walls 6b and 6c need to be deformed in order to eject ink from the ink chamber 4a or 4c. Therefore, there is a disadvantage that printing cannot be performed at high speed.

The above-described method of canceling the fluctuation of the residual pressure can be said to be an inefficient method of erasing existing energy before ink ejection. There is a drawback that the applied voltage required for ejecting ink is substantially increased, and the cost of the driving circuit including the power supply is increased.

Further, since the applied voltage required for printing is relatively high as described above,
It adversely affects both electrical (polarization) and mechanical (displacement)
There is a drawback that deterioration is promoted and the life of the injection device is shortened.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has no need to use a cancel pulse, eliminates a change in ink droplet characteristics due to a print pattern, and provides a high-speed ink with high print quality. The injection device,
It is an object of the present invention to provide a driving device that drives without using a complicated driving circuit.

[0029]

Means for Solving the Problems The present invention to achieve this purpose, a plurality of ink chambers separated by partition walls of the piezoelectric elements, giving a pressure to the ink chamber by deformation of the partition wall Using an ink ejection device that ejects ink,
All the ink chambers are divided into three or more groups that straddle each other, and ink is sequentially ejected for each group. Thus, when forming recording information on a recording medium , adjacent inks are ejected before ejecting ink in each ink chamber. Other groups to do
If ink is not ejected from the ink chamber of
A drive pulse smaller than the drive pulse
A driving device of an ink jet apparatus Ru applied to the ink in the ink chamber includes a power source and a drive circuit operated by a single voltage supplied from the power source, a driving circuit, a plurality of single voltage And a voltage dividing circuit for dividing the voltage into different voltage levels.

[0030]

In the driving device according to the present invention, the driving circuit operated by a single voltage supplied from the power supply includes a voltage dividing circuit for dividing the single voltage into a plurality of different voltage levels,
The divided voltage is applied to an ink chamber that generates a pseudo pressure. Further, in the ink ejecting apparatus using this driving device, the ink pressure state in each ink chamber is almost the same immediately before ejecting ink regardless of whether or not ink is ejected from an ink chamber of another adjacent group. In addition, it is not necessary to cancel a pressure wave generated when ink is ejected from another adjacent group of ink chambers, and energy can be effectively used.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. The same parts as in the prior art are denoted by the same reference numerals, and description thereof will be omitted. Further, the same ink jetting device as that shown in FIGS. 9 to 11 is used. First, FIG. 1 and FIG. 2 show the operation of the ejecting device when the driving method of the present invention is used when the ink ejecting devices are divided into three groups and sequentially driven.
This will be described with reference to FIG. FIG. 1 is a timing chart showing a driving waveform and a pressure fluctuation waveform.
2 and 3 show the movement of the side wall 6 when ink is ejected from the ink chamber 4b and when ink is not ejected, respectively. The symbol G in the figure is connected to the ground, and V is connected to the voltage level of the ejection pulse.

First, an ink ejection pulse B shown by a solid line is applied to the ink chamber 4b (see FIG. 2) with the driving voltage waveform shown in FIG. 1A, and the ink in the ink chamber 4b is ejected. Is done. At this time, when viewed from the ink chamber 4c, the side wall 6c on one side is once deformed inward as shown by the solid line in FIG. 1C (see FIG. 2), and returns to the original position after AL. In this case, since no voltage pulse is applied to the ink chamber 4c, the side wall 6a2 is not deformed and the nozzle 12 of the ink chamber 4c is not deformed.
The pressure in the vicinity fluctuates as shown in FIG. Here, the ink chamber 4c generated by the ejection of the ink chamber 4b
The magnitude of the pressure wave at is such that the ink is not ejected from the ink chamber 4c. Subsequently, if ink is ejected from the ink chamber 4c, the ejection voltage pulse C shown in FIG.
After that, the ink is applied to the ink chamber 4c. As a result, the side walls 6c and 6a2 are deformed, and pressure is applied to the ink in the ink chamber 4c. At this time, a pressure wave P generated by the ejection of the ink chamber 4b and a so-called residual pressure fluctuation are generated in the ink chamber 4c, and the ink is ejected.

Next, in FIG. 1, before the ejection pulse C is applied to the ink chamber 4c, a printing pattern
If the ejection pulse B is not applied to the ink chamber 4b as shown by the dotted line in FIG.
Is applied to the ink chamber 4c as indicated by a broken line in FIG. The polarity of the excitation pulse Q is opposite to the ejection pulse B or the ejection pulse C, and the voltage value is half of the ejection pulse B or the ejection pulse C. Thereby, the side wall 6c
And 6a2 are deformed as shown by broken lines in FIGS. 1 (c) and 1 (d) (see FIG. 3).

The volume reduction of the ink chamber 4c caused by this deformation is caused by the one side wall 6 when the ejection pulse B is given.
Since this is the same as that due to the deformation of c (see FIG. 2), the same pressure fluctuation (pseudo pressure) as described above occurs in the ink chamber 4c, and the same residual pressure fluctuation occurs. Here, the magnitude of the pseudo pressure is such that the ink is not ejected from the ink chamber 4c. Thereafter, when the ejection voltage pulse C is applied to the ink chamber 4c, the state of the pressure wave in the ink chamber 4c becomes exactly the same as when ink is ejected from the ink chamber 4b. Therefore, ink droplets having the same characteristics are ejected from the ink chamber 4c regardless of whether or not the ink chamber 4b is ejected.

The above description is based on the viewpoint of the ink chamber 4c. When comparing FIGS. 2 and 3, for example, the movement of the side wall 6a2 is different,
The pressure wave in a2 is not the same. However, the timing at which ink is ejected from the ink chamber 4a2 is further after t of the pulse C in FIG. 1 (not shown), and is separated from the pulse B or Q by 2t, during which the pressure wave by the pulse B or Q is considerably large. Attenuation, the effect of which is almost negligible compared to that by pulse C.

When the other ink chambers 4 are driven in the same manner as described above, the characteristics of the ink droplets ejected from all the ink chambers 4 can be made substantially the same regardless of the print pattern.

Next, optimization of the ink ejection pulse when the driving method of the present invention is used will be described.

As described above, when the driving method of the present invention is used, ink is ejected by a pressure wave obtained by synthesizing a pressure generated by an ejection pulse and a residual pressure fluctuation.
When the injection pulse is applied in phase with the residual pressure fluctuation, a relatively high injection pressure can be obtained even if the voltage of the injection pulse is low. Therefore, as can be seen from the waveform of FIG. 1, the period of the pressure fluctuation in the ink chamber 4 is 2AL, and taking the initial phase into account, when the timing t in the figure is an odd multiple of AL, both pressures are changed. The phases of the waves are perfectly matched. Note that the residual pressure fluctuation attenuates over time,
If only energy efficiency is emphasized, it is advantageous that t is an odd multiple of AL and shorter.

Next, the printing speed of the present invention will be described. The printing speed mainly depends on the frequency of the voltage pulse for ink ejection. In the driving method of the present invention for the ink ejecting apparatus, the printing speed is determined by the ejection pulse B in FIG.
And C by the time difference t. In order to increase the printing speed, it is necessary to reduce the time difference t. However, in the driving method of the present invention, since there is no cancel waveform as in the related art, the time difference t is reduced to such an extent that the ejection pulses B and C do not overlap. Therefore, very high-speed printing is possible. When the time difference t is changed in accordance with the required printing speed, the pressure state in the ink chamber 4 at the time of ink ejection naturally changes, but the change is the same in all the ink chambers 4. There is no loss of uniformity of the drop characteristics.

Next, an embodiment of a driving circuit for realizing the driving method of the present invention will be described.

FIG. 4A is a block diagram showing a control unit for generating a drive waveform, and FIG. 4B is an explanatory diagram showing a logic for generating a drive waveform.
The signal input to 1 is converted according to the logic table and output. Here, the symbols of each signal line will be described.
Subscript n-1, n, n + 1 attached to each symbol
Represents a signal for the (n−1), n, and (n + 1) th ink chambers 4, respectively, and the description thereof is omitted in the description unless necessary. Also, the signal state H in the logic table
And L denote on and off of the signal, respectively.

First, among the input signals, the scanning signal S is a signal for giving the timing of ink ejection. The image signal I indicates the presence or absence of ink ejection according to the print pattern. Therefore, ink is ejected from the corresponding ink chamber 4 only when the scanning signal S and the image signal I are simultaneously turned on. The signal d is the ink ejection device 1 for printing.
(See FIG. 9). This is to set the ink chamber 4 to 3
In the case where ink is ejected by rotating the ink jetting device in order into two groups, if the direction of movement of the ink ejecting device is reversed, the direction of rotation must be reversed. You need to know if it will come around.

The output signals X, Y, and Z are signals for setting the voltages applied to the electrodes 8 of the ink chamber 4 to V, 0, and -V / 2, respectively. As can be seen from the logic table, the scanning signal S
When the image signal I and the image signal I are simultaneously turned on, X is turned on, and a voltage pulse (C in FIG. 1) is used to eject ink.
Generate. When the image signal I does not turn on in accordance with the printing pattern in the adjacent ink chamber 4 determined by the moving direction of the ejecting device despite the printing timing S, the output signal Z turns on and the pseudo A voltage pulse (Q in FIG. 1) for causing pressure fluctuation is generated. In other cases, the output signal Y is turned on, and the output voltage is set to zero.

FIG. 5 shows an example of a circuit for generating a drive waveform in accordance with the output of the control section. The input signals X, Y, and Z in FIG. 5 correspond to the output signals X, Y, and Z in FIG. The condenser 91 is constituted by the side wall 6 of the ink chamber 4 and the electrodes 8 formed on both sides thereof.

The entire circuit is composed of three blocks surrounded by broken lines, each of which is an injection charging circuit 82, a discharging circuit 84 and a pseudo pressure generating circuit 86. When only the input signal X is turned on, the transistor Tc is turned on, and a potential of V is applied to the electrode E of the capacitor 91 via the resistor R12. When only the input signal Y is turned on, the transistor Tg is turned on, and a potential of 0 V is applied to the electrode E of the capacitor 91 via the resistor R12. When only the input signal Z is turned on, the transistor Ts is turned on, and the electrode E of the capacitor 91 is connected to the electrode E via the resistor R12.
A potential of V / 2 is applied.

Next, another embodiment of the driving circuit for realizing the driving method of the present invention will be described. However, the same members as those in FIGS. 4 and 6 are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 6A is a block diagram showing a control unit for generating a drive waveform, and FIG. 6B is an explanatory diagram showing a logic for generating a drive waveform.
The signal input to 1 is converted according to the logic table and output. The output signals are two of X and Y, and the driving waveform circuit is controlled by a combination of the two signals.

On the other hand, FIG. 7 shows a drive waveform generation circuit controlled by output signals X and Y of the control section 71. The input signals X and Y in FIG. 7 are the same as the output signals X and Y in FIG. The entire circuit is composed of two blocks surrounded by a broken line, each of which is a charging circuit 87 and a discharging circuit 88, which are connected to each other via voltage dividing resistors Rc and Rg. When only the input signal X is turned on, the transistor Tc
Becomes conductive and gives a potential of 3 V / 2 to the electrode E of the capacitor 91 via the resistor Rc. When only the input signal Y is turned on, the transistor Tg is turned on, and a potential of 0 V is applied to the electrode E of the capacitor 91 via the resistor Rg.

Here, if the input signals X and Y are turned on at the same time, the transistors Tc and Tg naturally conduct at the same time, but the on-resistance of the transistors Tc and Tg is reduced by the voltage dividing resistors Rc and Rg. Since it is sufficiently smaller than the resistance, the potential of the electrode E is determined by the ratio between the voltage dividing resistors Rc and Rg, that is, Rc / Rg. That is, since the voltage dividing resistors Rc and Rg are connected in series, the voltage applied to both ends of each resistor is proportional to their resistance value, so that the ratio Rc / Rg between the voltage dividing resistors Rc and Rg is calculated as follows. If it is set to about 2, when the input signals X and Y are simultaneously turned on, both the transistors Tc and Tg become conductive, and R
The voltage across c is V, the voltage across Rg is V / 2,
The potential of the electrode E is about V / 2 with respect to the ground.

Therefore, based on this V / 2,
When only the input signal X is turned on, the potential is set to V, and when only the input signal Y is turned on, the potential of -V / 2 is set to a capacitor 91, respectively.
Is output to the electrode E. The drive waveform circuit shown in FIG. 7 is considerably simpler than the circuit shown in FIG. 5, not only the number of input signals and the number of amplifier circuits are reduced by one, but also can be operated with a single power supply without requiring a negative power supply.

However, when the side wall 6 having a relatively large capacitance is to be driven by using the circuit of FIG. 7, in order to keep the charging / discharging time short and maintain the responsiveness of the deformation of the side wall 6. Inevitably, it is necessary to reduce the resistance values of the resistors Rc and Rg. Then, while the input signals X and Y are both turned on and the potential of the electrode E is maintained at V / 2, a large current continues to flow from the transistors Tc to Tg.
This may cause abnormal heating of the drive circuit. In order to solve this, for example, a switch signal SW shown by a broken line is added to the control unit 71 of FIG. 6 and the switch is turned off except for charging and discharging the side wall 6 irrespective of other input signals. The output signals X and Y are simultaneously turned off. Meanwhile, in the drive circuit of FIG. 7, both the input signals X and Y are turned off,
Since the transistors Tc and Tg are both turned off, the current does not flow. Specifically, the switch signal SW may have a pulse waveform as shown in FIG.

Further, the timing for generating the above-mentioned pseudo pressure need not necessarily be the position of the pulse Q in FIG. The cycle of the pressure fluctuation in the ink chamber 4 is 2A as described above.
For example, as shown in FIG. 8, if the position of the pulse Q is delayed by AL and its polarity is made positive, as shown in FIG.
By properly adjusting the voltage level of, a similar pseudo pressure is obtained. In this case, the pulse interval t
Cannot be made shorter than 2AL, and a delay circuit for delaying the pulse Q is newly required. However, when the voltage dividing drive circuit of FIG. 7 is used, the pulse Q is generated. Since the output signals X and Y are not turned on at the same time except at the time, even if the switch signal SW is omitted, the current flowing from the transistor Tc to the transistor Tg does not continue to flow, and abnormal heating of the drive circuit can be avoided. In addition, since the polarity of the voltage pulse for generating the pseudo pressure matches the polarity of the ejection pulse, the total maximum voltage difference is only 2/3 of the case of using the waveform of FIG. Therefore, the power supply voltage can be substantially reduced to 2/3, and operation can be performed with a single power supply.

In this embodiment, the resistor Rc and the resistor Rg are used.

Next, another embodiment of the driving method of the present invention will be described.

When the method of the above embodiment is used, a constant pressure fluctuation always exists in each ink chamber 4 irrespective of the presence or absence of printing, but ink is not ejected at a predetermined ejection timing depending on a printing pattern. For the ink chamber 4,
It is not always necessary to generate the pseudo pressure. In other words, if the presence or absence of the pulse C can be predicted in addition to the presence or absence of the ejection pulse B in the drive waveform of FIG.
Not be given. By doing so, it is possible to avoid giving extra energy and suppress heat generation of the drive circuit.

The description of the above embodiment has been made in all of the ink chambers 4.
Is divided into three groups. However, even when the ink chambers 4 are divided into four or more groups, the same driving method and driving circuit as described above can be used. Further, the present invention is not limited to the embodiment described in detail above, and a change in a range without departing from the gist of the present invention is possible.

[0057]

According to the driving apparatus of the present invention, the driving circuit operated by the single voltage supplied from the power supply includes the voltage dividing circuit for dividing the single voltage into a plurality of different voltage levels. In addition, the circuit configuration can be simplified, and the drive circuit can be reduced in size and cost. Further, according to the ink ejecting apparatus using the driving circuit, the state of the ink in each ink chamber is almost the same immediately before ejecting the ink, irrespective of the presence or absence of the ink ejection from the ink chamber of another adjacent group. It is. Therefore, characteristics such as the volume and the flying speed of the ejected ink droplet are uniform, and the printing quality is good. Further, there is no need to cancel a pressure wave generated when ink is ejected from another adjacent group of ink chambers, energy can be effectively used, and running costs can be reduced. By eliminating the cancel pulse, a high-frequency ejection pulse can be given, and high-speed printing can be performed.

[Brief description of the drawings]

FIG. 1 is a timing chart showing a driving method according to an embodiment of the present invention.

FIG. 2 is a sectional view of an ink ejecting apparatus showing an operation method of the embodiment.

FIG. 3 is a sectional view of an ink ejecting apparatus showing an operation method of the embodiment.

FIG. 4A is an explanatory diagram showing a control unit of the embodiment. (B) is an explanatory view showing the logic of the embodiment.

FIG. 5 is a circuit diagram showing a driving circuit of the embodiment.

FIG. 6A is an explanatory diagram showing another control unit of the embodiment. (B) is an explanatory view showing another logic of the embodiment.

FIG. 7 is a circuit diagram showing another driving circuit of the embodiment.

FIG. 8 is a timing chart showing a driving method according to another embodiment of the present invention.

FIG. 9 is a perspective view showing a conventional shear mode type ink ejecting apparatus.

FIG. 10 is an explanatory diagram illustrating a control unit according to the related art.

FIG. 11 is a cross-sectional view showing a conventional shear mode type ink ejecting apparatus.

FIG. 12 is an explanatory view showing the operation of a conventional shear mode type ink ejecting apparatus.

FIG. 13 is a timing chart showing a conventional driving method.

[Explanation of symbols]

 2 Piezoelectric ceramic plate 4 Ink chamber 6 Side wall Q Pseudo pressure generation pulse Rc Divided resistance Rg Divided resistance

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) B41J 2/045 B41J 2/055

Claims (2)

(57) [Claims] [Claim 1 further comprising a plurality of ink chambers separated by partition walls of the piezoelectric element, using an ink jet apparatus for ejecting ink by applying pressure to the ink chamber by deformation of the partition wall, the entire ink chamber By dividing the ink into three or more groups that straddle each other and sequentially ejecting ink for each group, when forming recording information on a recording medium, another group adjacent to each other is ejected before ejecting ink in each ink chamber.
If ink is not ejected from the ink chamber of the
Drive pulse smaller than the drive pulse for injecting
And a driving device of an ink jet apparatus Ru applied to the ink in the ink chamber includes a power source and a drive circuit operated by a single voltage supplied from the power source, a driving circuit, a single voltage And a voltage dividing circuit that divides the voltage into a plurality of different voltage levels. 2. The driving device for an ink ejecting apparatus according to claim 1, wherein an output terminal of the driving circuit has a high impedance except when charging and discharging the piezoelectric element.