JP2007301757A - Driving circuit and liquid delivering head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a driving circuit capable of suppressing variation of driving electric voltage and performing a stable liquid delivering operation, and a liquid delivering head. <P>SOLUTION: In the driving circuit 3 applying the driving electric voltage on a piezoelectric means 2 as a volumetric loading, a plurality of electric voltage generating means 4a, 4b-4n for generating the different driving electric voltages, a plurality of electric voltage stabilizing means 5a, 5b-5n provided by corresponding to each of a plurality of the electric voltage generating means 4a, 4b-4n and for stabilizing the driving electric voltages, and a plurality of electric voltage switching means 8a, 8b-8n electrically connected with each of a plurality of the electric voltage stabilizing means 5a, 5b-5n and capable of switching on/off of the driving electric voltages, are provided. In addition, a switching controlling means 12 for forming a required driving waveform by controlling selectively on/off of a plurality of the electric voltage switching means 8a, 8b-8n, is provided. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a drive circuit and a liquid discharge head, and more particularly to a drive circuit that applies a drive voltage to piezoelectric means and a liquid discharge head including the drive circuit.

  2. Description of the Related Art Conventionally, in a liquid ejection apparatus such as an ink jet recording apparatus, a driving circuit that ejects liquid by switching the potential (applied potential) of a driving power source applied to piezoelectric means included in a liquid ejection head in multiple stages is used.

For example, as shown in FIG. 8, Patent Document 1 includes a drive voltage source including a plurality of resistors connected in series and a plurality of capacitors connected in parallel, and each of a plurality of power supplies having different potentials. A drive circuit is described in which one of a plurality of power supplies is selected by a switching element connected to, and an applied potential to a load (piezoelectric means) is switched in a plurality of stages.
JP 2004-153411 A

  However, in the driving circuit described in Patent Document 1, when a driving voltage is continuously applied to the piezoelectric means during the liquid discharge operation, a part of the capacitor charge of the driving voltage source moves to the piezoelectric means that is a capacitive load. A voltage drop occurs on the drive voltage source side. In addition, since recharging the capacitor of the driving voltage source is performed via a resistor, it takes time and charging cannot be performed in time.

9A shows a positive drive voltage output from the drive voltage source, FIG. 9B shows a negative drive voltage, and FIG. 9C shows an example of a drive waveform generated by the drive circuit 3. Is. In the drive voltage source composed of a combination of a resistance matrix and a capacitor as shown in FIG. 8, the drive voltage changes to a stepped waveform in which the drive voltage gradually decreases, as shown in FIGS. 9A and 9B. However, there has been a problem that a stable liquid discharge operation cannot be performed due to a change in the ink discharge speed and liquid amount. The voltage V appearing in the capacitor of the RC circuit is represented by V = V ₁ (1−e ^{−t / RC} ) where V ₁ is a set drive voltage and t is time, and the larger the resistance R or the capacitance C, the larger the resistance V is. It will take time to recharge.

  On the other hand, when the capacitor capacity of the drive voltage source is increased in order to reduce the influence of the voltage drop due to the movement of the capacitor charge in the drive voltage source, there is a problem that the charging time is further increased. Further, if the resistance value of the drive voltage source is lowered in order to shorten the recharging time, there is a problem that the current flowing through the drive voltage source increases and power saving is not achieved.

  Furthermore, in the drive voltage source described above, since the power source is divided by a fixed resistor, there is a problem that the output voltage value is fixed and cannot be applied to each of the liquid ejection heads having various characteristics. .

  SUMMARY An advantage of some aspects of the invention is that it provides a drive circuit and a liquid discharge head that enable a stable liquid discharge operation to be performed while suppressing fluctuations in drive voltage. .

  In order to solve the above-mentioned problem, the invention described in claim 1 is a drive circuit for applying a drive voltage to piezoelectric means as a capacitive load, and a plurality of voltage generation means for generating different types of drive voltages; A plurality of voltage stabilizing means provided corresponding to each of the plurality of voltage generating means, and electrically connected to each of the plurality of voltage stabilizing means, for turning on and off the driving voltage. A plurality of voltage switching means capable of switching, and a switching control means for generating a desired drive waveform by selectively controlling on / off of the plurality of voltage switching means.

According to the first aspect of the present invention, when the driving voltage is continuously applied to the piezoelectric means, the driving voltage gradually drops due to the movement of the capacitor charge, but the voltage stabilizing means corresponds to each of the voltage generating means. By providing this, it becomes possible to stabilize the drive voltage applied to the piezoelectric means without changing the resistance value or the like in the voltage generating means.
In addition, by controlling the on / off of the voltage switching means connected to each of the voltage stabilizing means by the switching control means, it becomes possible to generate a desired drive waveform.

  A second aspect of the present invention is the drive circuit according to the first aspect, wherein the voltage stabilizing means is connected in parallel to a buffer circuit that performs an impedance conversion function and a preceding stage of the capacitive load, and A capacitor having a capacity of 50 times or more is provided.

According to the second aspect of the present invention, it is possible to increase the voltage supply capability of the drive circuit by providing the buffer circuit that performs the function of impedance conversion. In addition, a capacitor having a capacity of 50 times or more that of the capacitive load is connected in parallel to the previous stage of the capacitive load, and the driving voltage supplied from the voltage generating means is once accumulated in the capacitor, and then the piezoelectric means as the capacitive load As a result, the rising characteristics and falling characteristics of the driving waveform can be improved compared to the case where the driving voltage supplied from the voltage generating means is directly applied to the piezoelectric means.
Further, by using a buffer circuit and a capacitor as voltage stabilizing means, it is possible to reduce the size of the drive circuit as compared with the case where a conventional high power transistor circuit is used.

  According to a third aspect of the present invention, in the driving circuit according to the first or second aspect, the voltage generation unit includes a DA converter, and the digital data relating to the voltage value of the driving waveform is converted into an arbitrary voltage waveform by analog conversion. Output.

  According to the third aspect of the present invention, it is possible to output an arbitrary voltage waveform in an analog-converted form simply by setting the voltage value of the drive waveform as digital data, so that components such as resistors on the circuit are removed. It is possible to easily change the driving voltage corresponding to the liquid ejection heads having various characteristics without performing the work.

  A fourth aspect of the present invention is the drive circuit according to any one of the first to third aspects, wherein the voltage switching means is an analog switch composed of a field effect transistor. .

  According to the fourth aspect of the present invention, it is possible to perform on / off control of the drive voltage at high speed.

  A fifth aspect of the present invention is a liquid ejection head, comprising the drive circuit according to any one of the first to fourth aspects.

  According to the fifth aspect of the present invention, the same action as described above can be obtained in the liquid discharge head.

  A sixth aspect of the present invention is the liquid ejection head according to the fifth aspect, wherein a plurality of the piezoelectric means corresponding to a plurality of nozzles and a plurality of the drives provided corresponding to the plurality of piezoelectric means. And a switching control unit that is electrically connected to each of the plurality of driving circuits and generates a desired driving waveform for each of the plurality of driving circuits.

According to the sixth aspect of the invention, it is possible to control the drive waveform more precisely by changing the liquid discharge timing for each nozzle.
In addition, by configuring the voltage stabilizing means with a buffer circuit and a capacitor, the entire liquid discharge head can be reduced in size even when a drive circuit is arranged for each nozzle, as compared with the case where a conventional high power transistor circuit is used. It becomes possible.

  A seventh aspect of the present invention is the liquid ejection head according to the sixth aspect, further comprising drive voltage setting means for setting different types of drive voltages for each of the plurality of drive circuits.

  According to the seventh aspect of the present invention, it is possible to set the drive voltage for each nozzle and control the drive waveform more precisely.

  According to the first aspect of the present invention, it is possible to stabilize the drive voltage applied to the piezoelectric means without changing the resistance value or the like in the voltage generating means. In addition, a desired drive waveform can be generated by the switching control means.

  According to the second aspect of the present invention, it is possible to improve the rising characteristics and the falling characteristics of the driving waveform as compared with the case where the driving voltage supplied from the voltage generating means is directly applied to the piezoelectric means. . In addition, the drive circuit can be reduced in size.

  According to the third aspect of the present invention, it is possible to easily change the drive voltage corresponding to the liquid discharge heads having various characteristics.

  According to the fourth aspect of the present invention, it is possible to perform on / off control of the drive voltage at high speed.

  According to the fifth aspect of the present invention, the same effect as described above can be obtained in the liquid discharge head.

  According to the sixth aspect of the present invention, it is possible to control the drive waveform more precisely.

  According to the seventh aspect of the present invention, it is possible to control the drive waveform more precisely.

[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 shows a schematic configuration of a liquid discharge head 1 according to the present embodiment. The liquid discharge head 1 includes a plurality of piezoelectric means 2 provided corresponding to a plurality of nozzles. Each piezoelectric means 2 is electrically connected to a drive circuit 3 that generates and stabilizes a drive voltage and applies the drive voltage to the piezoelectric means 2.

  The piezoelectric means 2 is a piezoelectric element as a capacitive load, and is a piezoelectric element that is deformed by application of a voltage and discharges liquid from a nozzle of a liquid discharge head.

  The drive circuit 3 includes a voltage generating unit 4 and a voltage stabilizing unit 5. As shown in FIG. 1, the drive circuit 3 of this embodiment includes a plurality of voltage generating means 4a, 4b,..., 4n, and each of the voltage generating means 4a, 4b,. 5a, 5b... 5n are electrically connected to each other.

  FIG. 2 shows the configuration of the voltage generating means 4 and the voltage stabilizing means 5. FIG. 2 shows the configuration of the voltage generating means 4a and 4b and the voltage stabilizing means 5a and 5b among the voltage generating means 4 and the voltage stabilizing means 5.

  The voltage generating means 4 is a voltage source comprising a plurality of resistors connected in series and a plurality of capacitors connected in parallel. Of these, the voltage generating means 4a is a positive voltage source, and the voltage generating means 4b is a negative voltage. Is the source. The voltage generating means 4a and 4b generate positive or negative driving voltages and supply them to the voltage stabilizing means 5a and 5b, respectively. The configuration of the voltage generating means 4 is not limited to this, and other known voltage generating means can also be used.

  The voltage stabilizing means 5a and 5b are configured to include buffer circuits 6a and 6b and capacitors 7a and 7b, respectively, and are used for the positive or negative driving voltage supplied from the voltage generating means 4a and 4b. Each is to be stabilized.

  The buffer circuits 6a and 6b are buffer amplifiers having a gain of 1. The buffer amplifier performs the function of impedance conversion. Since the output impedance is so small that the output impedance is negligible and the voltage supply capability is high, the recharge time of the capacitive load can be shortened. In addition, when the capacity of the capacitive load is increased, the recharge time becomes longer. In this case as well, the drive voltage can be stabilized at an early stage.

  Further, as shown in FIG. 2, when capacitors 7a and 7b are connected to the drive circuit 3, it becomes the same as the RC integration circuit configured with the resistors of the voltage generating means 4a and 4b. However, by connecting the buffer circuits 6a and 6b, it is possible to increase the voltage supply capability and suppress the influence of the resistance of the voltage generating means 4a and 4b.

  The capacitors 7a and 7b are connected corresponding to the buffer circuits 6a and 6b, respectively, and are grounded so as to be connected in parallel to the piezoelectric means 2 as a capacitive load. The capacitors 7a and 7b have a capacity 50 times or more that of the piezoelectric means 2 as a capacitive load.

  With this configuration, the capacitors 7a and 7b accumulate the drive voltage supplied from the buffer circuits 6a and 6b, and the drive voltage accumulated in the capacitors 7a and 7b is applied to the piezoelectric means 2 as a capacitive load, thereby Compared with the case where the drive voltage supplied from the circuits 6a and 6b is directly applied to the piezoelectric means 2, the rising and falling characteristics of the drive waveform can be improved.

Returning to FIG. 1, a voltage switching means 8 is electrically connected to the voltage stabilizing means 5. In the present embodiment, a plurality of voltage switching means 8a, 8b... 8n are provided so as to correspond to each of the plurality of voltage stabilization means 5a, 5b. The voltage switching means 8a, 8b ... 8n has a FET (field effect _transistor) 1, _FET 2 ... _{FET n} as a switching element.

Further, a switching control unit 9 for controlling ON / OFF of the switching element is electrically connected to each of the voltage switching means 8a, 8b... 8n. In FIG. 3, the example of the switching control by the switching control part 9 and a drive waveform is shown. As shown in FIG. 3, the switching control unit 9 controls ON / OFF of FET ₁ , FET ₂ ... FET _n , and changes the drive voltage from V _{1 to} V ₃ to generate a desired drive waveform. Can be done.

  4A is a positive drive voltage output from the voltage stabilization means 5a, 5b... 5n, FIG. 4B is a negative drive voltage, and FIG. The example of a drive waveform is shown. As shown in FIGS. 4A and 4B, in the drive circuit 3, the voltage supply capability is enhanced by impedance conversion of the buffer circuits 6a, 6b... 6n, and the piezoelectric means 2 as a capacitive load is quickly charged. Therefore, the drive voltage does not change to a stepped waveform that gradually decreases, but is maintained at a voltage value within a certain range. Thereby, the amplitude value of the drive waveform shown in FIG. 4C is also kept substantially constant, and the drive voltage applied to the piezoelectric means 2 is stabilized.

  Further, in the drive circuit 3, since the drive voltage is once accumulated by the capacitors 7a, 7b... 7n and then applied to the piezoelectric means 2, the rising and falling characteristics of the drive waveform are as shown in FIG. improves.

  Next, the operation of the liquid discharge head 1 will be described.

  First, the voltage generators 4a, 4b,... 4n generate positive and negative drive voltages, respectively, and supply them to the voltage stabilizers 5a, 5b,.

  Subsequently, the voltage stabilization means 5a, 5b,... 5n stabilizes the positive and negative drive voltages supplied from the voltage generation means 4a, 4b,. Specifically, the voltage supply capability is enhanced by impedance conversion of the buffer circuits 6a, 6b... 6n, and the drive voltage is temporarily stored in the capacitors 7a, 7b,. Let

  Next, the switching control unit 9 generates a desired drive waveform by controlling ON / OFF of the switching elements as the voltage switching units 8a, 8b... 8n, and applies them to the piezoelectric unit 2 as a capacitive load.

  As described above, according to the drive circuit 3 and the liquid discharge head 1 of the present embodiment, when the drive voltage is continuously applied to the piezoelectric means 2, the drive voltage gradually drops due to the movement of the capacitor charge, but the voltage generating means 4a. , 4b... 4n are provided in correspondence with the voltage stabilizing means 5a, 5b... 5n, so that the drive voltage applied to the piezoelectric means 2 without changing the resistance values of the voltage generating means 4a, 4b. Can be stabilized.

  Further, the switching control means 9 can control the on / off of the voltage switching means 8a, 8b... 8n connected to each of the voltage stabilization means 5a, 5b. Become.

  Further, by providing the buffer circuits 6a, 6b,... 6n that perform the function of impedance conversion, the voltage supply capability of the drive circuit 3 can be increased. Further, capacitors 7a, 7b,..., 7n having a capacity 50 times or more that of the piezoelectric means 2 as a capacitive load are connected in parallel to the previous stage of the piezoelectric means 2, thereby being supplied from the voltage generating means 4a, 4b,. Compared with the case where the driving voltage supplied from the voltage generating means 4a, 4b,..., 4n is directly applied to the piezoelectric means 2 by temporarily storing the driving voltage in the capacitors 7a, 7b,. Thus, it is possible to improve the rising characteristics and falling characteristics of the drive waveform.

  Further, by using the buffer circuits 6a, 6b... 6n and the capacitors 7a, 7b... 7n as the voltage stabilizing means 5a, 5b... 5n, the drive circuit 3 can be compared with the case where the conventional high power transistor circuit is used. It becomes possible to reduce the size.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIG. In addition, the same code | symbol is attached | subjected to the same part as 1st Embodiment, the description is abbreviate | omitted, and a different part from 1st Embodiment is demonstrated.

  The voltage generating means 4a, 4b,... 4n included in the drive circuit 3 of the present embodiment includes a CPU 10 and DA converters 11a, 11b,. The CPU 10 is electrically connected to input means (not shown).

  The input means (not shown) is a liquid crystal display panel or the like, and the voltage value of the drive waveform can be set as digital data.

  The CPU 10 outputs an arbitrary voltage waveform from the DA converters 11a, 11b,... 11n in an analog-converted form in accordance with digital data input from an input means (not shown).

  The DA converters 11a, 11b... 11n convert digital data into analog data under the control of the CPU 11.

  In this way, based on the voltage value set as digital data, an arbitrary voltage waveform is output in the form of analog conversion, so that it is compatible with liquid discharge heads with various characteristics without removing the resistance on the circuit. Thus, the drive voltage can be easily changed.

The voltage switching unit 8a of this embodiment, 8b ... 8n _may use the _FET 1, FET 2 ... FET _n as a switching element is configured as an analog switch that can handle analog signals.

  Next, points of the operation of the liquid discharge head 1 that are different from the above-described embodiment will be described.

  The user sets the voltage value of the drive waveform as digital data using an input means (not shown).

  Subsequently, the CPU 10 outputs an arbitrary voltage waveform from the DA converters 11a, 11b,..., 11n in an analog-converted form in accordance with digital data input from an input unit (not shown). The drive waveform generated in this way is supplied to the voltage stabilization means 5a, 5b... 5n.

  Thus, according to the drive circuit 3 and the liquid ejection head 1 of the present embodiment, an arbitrary voltage waveform can be output in an analog-converted form simply by setting the voltage value of the drive waveform as digital data. It is possible to easily change the drive voltage corresponding to the liquid ejection head 1 having various characteristics without performing an operation of removing a component such as a resistor.

  In addition, the on / off control of the driving voltage can be performed at high speed by the analog switch.

[Third Embodiment]
Next, a third embodiment of the present invention will be described with reference to FIGS. In addition, the same code | symbol is attached | subjected to the same part as 1st Embodiment, the description is abbreviate | omitted, and a different part from 1st Embodiment is demonstrated.

  As shown in FIG. 6, the liquid ejection head 1 of the present embodiment is provided with a plurality of drive circuits 3a, 3b... 3n so as to correspond to the plurality of piezoelectric means 2a, 2b.

  In addition, the liquid discharge head 1 of the present embodiment includes a switching control unit 12 that is electrically connected to each of the plurality of drive circuits 3a, 3b,. The switching control unit 12 controls the voltage switching means 8a, 8b,... 8n included in each of the drive circuits 3a, 3b,... 3n so that a desired drive waveform can be generated for each of the drive circuits 3a, 3b,. It has become.

In FIG. 7, the example of the switching control by the switching control part 9 of this embodiment is shown. As shown in FIG. 7, the switching control unit 9 controls ON / OFF of the FET ₁ , FET ₂ ... FET _n for each of the voltage switching means 8 a, 8 b... 8 _n , and drives the drive voltages to V _{1a to} V _3a , V by varying the respective _1b ~V _3b or _V 1c _{~V 3c,} the drive circuit 3a, and is capable of generating a desired driving waveform every 3b ... 3n.

  In addition, the liquid ejection head 1 of the present embodiment includes a drive voltage setting unit 13. The drive voltage setting unit 13 is electrically connected to each of the plurality of drive circuits 3a, 3b... 3n, and can set different drive voltage values for each of the drive circuits 3a, 3b. Yes. The drive voltage setting unit 13 is electrically connected to input means (not shown).

  Next, points of the operation of the liquid discharge head 1 that are different from the above-described embodiment will be described.

  First, the drive voltage setting unit 13 sets a different drive voltage value for each of the drive circuits 3a, 3b,... 3n in accordance with an input signal from an input means (not shown).

  Subsequently, for each of the plurality of drive circuits 3a, 3b,... 3n provided so as to correspond to the plurality of piezoelectric means 2a, 2b... 2n, the voltage generating means 4a, 4b. Each is generated and supplied to voltage stabilizing means 5a, 5b... 5n.

  Subsequently, the voltage stabilizing means 5a, 5b... 5n stabilize the drive voltage and output it to the voltage switching means 8a, 8b.

  Next, as shown in FIG. 7, the switching control unit 12 controls the voltage stabilizing means 5a, 5b... 5n for each of the drive circuits 3a, 3b... 3n to generate a desired drive waveform, and a plurality of piezoelectric means 2a. , 2b... 2n.

  Thus, according to the drive circuit 3 and the liquid discharge head 1 of the present embodiment, it is possible to control the drive waveform more precisely by changing the liquid discharge timing for each nozzle of the liquid discharge head 1. .

Further, the voltage stabilizing means 5a, 5b... 5n are constituted by buffer circuits 6a, 6b... 6n and capacitors 7a, 7b... 7n, so that each nozzle can be compared with a case where a conventional high power transistor circuit is used. Even when the drive circuit is arranged, the liquid discharge head 1 can be downsized.

  In addition, the drive voltage setting unit 13 can set the drive voltage for each nozzle to control the drive waveform more precisely.

  As described above, according to the drive circuit and the liquid discharge head of the present invention, it is possible to perform a stable liquid discharge operation while suppressing fluctuations in the drive voltage.

1 is a circuit diagram illustrating an overall configuration of a liquid ejection apparatus according to a first embodiment. 1 is a circuit diagram illustrating a configuration of a drive circuit according to a first embodiment. It is a time chart which shows the sequence of switch control. 4 is a graph showing an output voltage and a drive waveform of the drive circuit according to the first embodiment. It is a circuit diagram which shows the whole structure of the liquid discharge apparatus which concerns on 2nd Embodiment. It is a circuit diagram which shows the whole structure of the liquid discharge apparatus which concerns on 3rd Embodiment. It is a time chart which shows the sequence of switch control. It is a circuit diagram which shows the structure of the conventional drive circuit. It is a graph which shows the output voltage of the conventional drive circuit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid discharge head 2 Piezoelectric means 3 Drive circuit 4a, 4b ... 4n Voltage generation means 5a, 5b ... 5n Voltage stabilization means 6a, 6b ... 6n Buffer circuit 7a, 7b ... 7n Capacitors 8a, 8b ... 8n Voltage switching means 9 Switching Control unit 10 CPU
11a, 11b... 11n Converter 12 Switching control unit 13 Drive voltage setting unit

Claims (7)

A drive circuit for applying a drive voltage to piezoelectric means as a capacitive load,
A plurality of voltage generating means for generating different types of driving voltages;
A plurality of voltage stabilizing means provided corresponding to each of the plurality of voltage generating means to stabilize the drive voltage;
A plurality of voltage switching means electrically connected to each of the plurality of voltage stabilizing means and capable of switching on and off the driving voltage;
Switching control means for generating a desired drive waveform by selectively controlling on / off of the plurality of voltage switching means;
A drive circuit comprising:   2. The voltage stabilization means includes a buffer circuit that performs an impedance conversion function, and a capacitor that is connected in parallel to a preceding stage of the capacitive load and has a capacity that is 50 times or more that of the capacitive load. Driving circuit.   3. The drive circuit according to claim 1, wherein the voltage generation unit includes a DA converter, and converts the digital data relating to the voltage value of the drive waveform into an arbitrary voltage waveform and outputs the analog data.   The drive circuit according to claim 1, wherein the voltage switching unit is an analog switch configured by a field effect transistor.   A liquid discharge head comprising the drive circuit according to claim 1. A plurality of piezoelectric means corresponding to a plurality of nozzles;
A plurality of the drive circuits provided corresponding to the plurality of piezoelectric means;
The liquid ejection head according to claim 5, further comprising a switching control unit that is electrically connected to each of the plurality of drive circuits and generates a desired drive waveform for each of the plurality of drive circuits.   7. The liquid ejection head according to claim 6, further comprising drive voltage setting means for setting different types of drive voltages for each of the plurality of drive circuits.

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