JPH10235863A - Ink-jet head driving circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make an IC utilizable as a switch means by applying a driving signal changing with a voltage of a specific value or larger to one electrode of an electrostriction element, impressing a voltage of a specific value or larger to the other electrode, applying a voltage in a forward, rearward direction to a polarization direction by a potential difference, and expanding, compressing the electrostriction element. SOLUTION: A positive voltage not smaller than 0V output from a driving waveform generation circuit 11 is input to input terminals of a plurality of transfer gates(TG) 14 through a common line 13. The other terminals of the TG 14 are connected to an electrostriction element 15. A driving waveform is controlled to be applied and not to be applied to the electrostriction element 15 by switching ON/OFF the TG 14. The other electrode of the electrostriction element 15 is a common electrode 16 connected to electrodes of a plurality of the other electrostriction elements. The common electrode 16 is connected to a DC power source 12 outputting 0V or more. When a potential of the driving waveform is higher than a potential Vcom of the common electrode 16 of the electrostricion element 15, the voltage is applied in a forward direction to a polarization direction. When the potential of the common electrode is higher, the voltage is applied in a rearward to the polarization direction. As a result, the electrostriction element 15 is expanded or compressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an ink jet head driving circuit.

[0002]

2. Description of the Related Art First, an ink jet head will be briefly described. FIG. 5 shows an example of the structure of the inkjet head. The diaphragm 54 is bonded to one surface of the pressure chamber 51 filled with ink, and the electrostrictive element 15 is bonded to the surface opposite to the pressure chamber. As shown in the figure, when the electrostrictive element is applied with a drive waveform in the polarization direction as shown in FIG. 6B, the electrostrictive element extends in a direction perpendicular to the electrode,
The volume of the pressure chamber is contracted, and the ink is ejected. Also,
When the voltage is applied in the opposite direction as shown in FIG. 6c, the pressure chamber contracts, the pressure chamber contracts, and ink is injected.

Conventionally, as shown in FIG. 7, ink is ejected and injected by applying a positive voltage to the electrostrictive element and extending it to eject (a). Then, the voltage is set to 0 V, and the ink is injected (b) when the electrostrictive element is returned to a non-distorted state.

In comparison with this, when a negative voltage is applied to the electrostrictive element as shown in FIG. 8 to distort the element in the contracting direction (b), the positive voltage can be reduced accordingly. In the conventional case, the positive voltage was too large, and when the electrostrictive element tried to expand, the diaphragm could not fully expand, it was restrained, the ideal distortion could not be obtained, and there was a loss for ink ejection. . By applying a negative voltage and shrinking the electrostrictive element,
By reducing the amount of extension and the amount of distortion from 0 V, ink can be ejected without being restricted by the diaphragm. The following data shows the difference in the ink ejection characteristics when the same voltage is applied in the positive and negative directions as compared with the conventional driving. It can be seen that the ejection speed and the droplet diameter are different even at the same voltage.

[0005]

[Table 1]

As described above, when a voltage is applied to the electrostrictive element in a direction opposite to the positive direction with respect to the polarization direction, the electrostrictive element is distorted in both directions of expansion and contraction, and the diaphragm moves up and down. Distortion only in the direction of extension does not restrict the diaphragm, so that efficient discharge can be achieved. To realize the driving of the above-described electrostrictive element,
FIG. 9 shows a drive circuit of a conventional inkjet head.
One electrode of the electrostrictive element 15 is connected to GND (0 V), and the other electrode is connected to a waveform generation circuit 91 that generates a drive waveform. As shown in FIG. 10, the driving waveform changes from a positive potential to a negative potential with respect to 0 V (GND). When the driving waveform has a positive potential, a voltage in the positive direction with respect to the polarization direction is applied, so the electrostrictive element expands. When the driving waveform has a negative potential, a voltage in the reverse direction is applied. The electrostrictive element shrinks. For example, JP-A-56-11347
The same applies to the circuit described in No. 3.

As a first method, the waveform generating circuit 91 comprises a DA converter 21, an operational amplifier 22, and a transistor 23 as shown in FIG. 11. A driving waveform is generated from the DA converter, and the operational amplifier amplifies the driving voltage to an actual driving voltage. The current is amplified by the emitter follower output of the transistor.

Further, in the above-mentioned first method, the cost of parts such as a DA converter and an OP amplifier is increased. Therefore, as a second method, a circuit for charging and discharging a capacitor as shown in FIG. 12 can be considered. The drive waveform is formed in the capacitor 35 by the charge / discharge circuits 33 and 34, and the current is amplified by the transistor 23. However, the signals for controlling the charge / discharge circuit are CMOS or TTL for 31, 32.
Since the input is performed at the level, a voltage converter such as the level shifter 121 is required, which leads to an increase in cost.

In either of the first and second methods, since the drive voltage changes from negative to positive, it is possible to apply both forward and reverse voltages to the electrostrictive element in the polarization direction.

[0010]

However, in the above-described conventional drive circuit, since a drive waveform has a negative potential state, there is no problem in the case of a single electrostrictive element. To control the application and non-application of the drive waveform to the electrostrictive element by using multiple electrostrictive elements as described above, when printing characters, etc., switching means for applying and not applying the drive voltage to the electrostrictive element is required become. As a switching means, a semiconductor switch is preferable in consideration of cost, switching speed, and the like. For example, it is easily conceivable to configure the switching means with the TG 14 as shown in FIG.
A configuration of C (Integrated-Circuit) is conceivable. Since the IC is controlled by a CPU, a gate array, or the like, it basically operates at 0 V or more. However, since the driving waveform has a state of a negative potential, a negative voltage is naturally applied to the input terminal of the IC.
There is a possibility that a large current flows from the input terminal and the IC is broken. In this case, ICs cannot be used, and discrete components must be used, resulting in a large increase in cost.

[0011]

In order to solve the above-mentioned problems, a drive circuit for an ink jet head according to the present invention provides a drive signal which changes at a voltage of 0 V or more to one electrode of an electrostrictive element and applies the drive signal to the other electrode. In addition, a voltage of 0 V or more is applied, and a voltage is applied in a direction opposite to the polarization direction by the potential difference between the electrodes to expand and contract the electrostrictive element.

According to the drive circuit of the ink jet head of the present invention, the drive waveform has a negative potential with respect to 0 V regardless of whether a positive or negative voltage is applied to the polarization direction of the electrostrictive element. Since it does not become a state, an IC can be used as a conventional switch means for controlling application and non-application to the electrostrictive element, the ink ejection efficiency is increased, and the polarization direction of the electrostrictive element is increased. The application in the opposite direction can be realized by a cheap ink jet head drive circuit.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a driving circuit for an ink jet head according to the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing an embodiment of a driving circuit of an ink jet head according to the present invention. Is a circuit for generating a drive waveform applied to the electrostrictive element, and generates a drive waveform at the maximum printing frequency. The output of the drive waveform generation circuit is connected to input terminals of a plurality of TGs 14 through a common line. The other terminal of each TG 14 is an electrostrictive element 1
5 is connected to the electrode 5 and the TG is turned ON / OFF,
The application and non-application of the drive waveform to the electrostrictive element are controlled. TG
The serial print data 20a is input to the shift register 18 at the CMOS or TTL level in synchronization with the data transfer clock 20b. The print data output from the shift register is input to the latch circuit 17 and stored in the latch circuit by the latch signal 19. Each output of the latch circuit is connected to the gate input of TG14.

The other electrode of the electrostrictive element is a common electrode 16 connected to the electrodes of a plurality of other electrostrictive elements.
The common electrode 16 is connected to the DC power supply 12 that outputs 0 V or more. The relationship between the common electrode 16 and the potential of the drive waveform is as shown in FIG.
When the potential of the driving waveform is higher than that of the common electrode (A), the voltage is applied in the positive direction in the polarization direction, and when the potential of the common electrode is higher (B), the voltage is applied in the opposite direction to the polarization direction.

Drive waveform generating circuit 11 and common electrode 1
Since the output Vcom of the DC power supply 12 is a positive voltage of 0 V or more, no negative voltage is input to the TG 14. Except for the necessity of a DC power supply for the common electrode, there is no need for a device such as a negative voltage converter, so that no extra cost is required.

FIGS. 2 and 3 show a waveform generating circuit 1 of the circuit of FIG.
FIG. 2 is a detailed view of a first example and a second example of FIG. It is basically the same as the waveform generation circuit 91 shown in the conventional example, except that a negative voltage is not used.

FIG. 2 shows a system using a DA converter.
And the voltage is amplified by the OP amplifier 22 to the actual drive waveform. Push for output current amplification
-Pull emitter follower circuit 23 is connected. The driving waveform is displaced in the range of 0 to Vh.

FIG. 3 shows a system using a capacitor for the purpose of cost reduction. It comprises a capacitor 35, charge / discharge circuits 33 and 34, and a current amplification transistor 23. The capacitor is charged and discharged in the range of 0 to Vh.

The drive circuit according to the present invention basically includes only a DC power supply for a common electrode added to a drive circuit for realizing a drive method for applying a voltage only in the positive direction to the polarization direction of the electrostrictive element. Driving in both forward and reverse directions with respect to the polarization direction is enabled, and efficient ink ejection is enabled.

[0020]

According to the ink jet head drive circuit of the present invention, as described above, the drive waveform is 0 V with respect to the polarization direction of the electrostrictive element regardless of whether the voltage is applied in the forward or reverse direction. Since there is no negative potential, an IC can be used in the same manner as in the prior art for the switch means for controlling application and non-application to the electrostrictive element, and the ink ejection efficiency is increased. Can be realized by the inexpensive inkjet head drive circuit.

[Brief description of the drawings]

FIG. 1 is a driving circuit of an inkjet head according to an embodiment of the present invention.

FIG. 2 is a first example of a waveform generation circuit of a drive circuit of an ink jet head according to an embodiment of the present invention.

FIG. 3 is a second example of the waveform generating circuit of the driving circuit of the inkjet head according to the embodiment of the present invention.

FIG. 4 shows an example of a drive waveform of a drive circuit of an inkjet head according to an embodiment of the present invention.

FIG. 5 is a structural diagram of a conventional inkjet head.

FIG. 6 shows a state of distortion when a voltage is applied in a direction opposite to the positive direction with respect to the polarization direction of the electrostrictive element.

FIG. 7 shows a case in which a voltage is applied only in a positive direction with respect to a polarization direction of an electrostrictive element to perform ejection and injection of ink.

FIG. 8 shows a case in which a voltage is applied in a direction opposite to a positive direction with respect to a polarization direction of an electrostrictive element, and ink is ejected and injected.

FIG. 9 illustrates a conventional ink jet head driving circuit that applies a voltage in a direction opposite to the direction of polarization of an electrostrictive element.

FIG. 10 is a driving waveform of a driving circuit of an ink jet head that applies a voltage in a direction opposite to a direction of polarization of a conventional electrostrictive element.

FIG. 11 is a first example of a conventional waveform generation circuit of a drive circuit of an ink jet head that applies a voltage in a direction opposite to a polarization direction of an electrostrictive element.

FIG. 12 is a second example of a waveform generation circuit of a driving circuit of an ink jet head which applies a voltage in a direction opposite to the direction of polarization of a conventional electrostrictive element.

FIG. 13 is an example of a conventional circuit for controlling the driving of a plurality of electrostrictive elements by a driving circuit of an ink jet head which applies a voltage in a direction opposite to the polarization direction of the electrostrictive elements.

[Explanation of symbols]

 11 Waveform generation circuit of drive circuit of the present invention 12 DC power supply for common electrode 13 Drive waveform common line 14 TG (transfer gate) 15 Electrostrictive element 16 Common electrode 17 Latch circuit 18 Shift register 19 Latch signal 20a Serial print data 20b Transfer clock Reference Signs List 21 DA converter 22 OP amplifier 23 Current amplification transistor 24 Waveform generation circuit output terminal 31 Charge circuit input 32 Discharge circuit input 33 Charge circuit 34 Discharge circuit 35 Capacitor 51 Pressure chamber 52 Ink 53 Nozzle plate 54 Diaphragm 55 Electrode of electrostrictive element 56 Electrode Electrode of strain element 57 Base 91 Waveform generation circuit of conventional drive circuit 121 Level shifter (voltage converter)

Claims (1)

[Claims] A voltage applied to an electrostrictive element in an ink jet head driving circuit for printing ink characters and graphics by pressing ink with the electrostrictive element and discharging the ink from nozzles is positive with respect to the polarization direction of the electrostrictive element. An ink jet head drive circuit that applies a drive signal that changes at a voltage of 0 V or more to one electrode of an electrostrictive element and applies a voltage of 0 V or more to the other electrode, An ink jet head driving circuit characterized in that a voltage is applied in a direction opposite to the polarization direction by a potential difference between the electrodes to expand and contract the electrostrictive element.