JP3743301B2 - Ink jet printer head drive apparatus and drive method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a head driving technique for an ink jet printer in which the ground side of a piezoelectric element provided corresponding to a nozzle for ejecting ink droplets in the head of an ink jet printer is held at an intermediate potential. is there.
[0002]
[Prior art]
Conventionally, ink jet color printers that eject several colors of ink from a recording head have become widespread as computer output devices, and are widely used to print images processed by computers and the like in multi-color and multi-tone. It has been.
[0003]
For example, in an ink jet printer using a piezoelectric element as a drive element for ejecting ink, each piezoelectric element is selectively driven by driving a plurality of piezoelectric elements respectively corresponding to a plurality of nozzles of a print head. The ink droplets are ejected from the nozzles based on the dynamic pressure of the element, and the ink droplets are adhered to the printing paper, whereby dots are formed on the printing paper and printing is performed.
[0004]
Here, each piezoelectric element is provided corresponding to a nozzle for ejecting ink droplets, and is driven by a drive signal supplied from a driver IC (head drive circuit) mounted in the print head. Drops are ejected.
[0005]
By the way, in such a piezoelectric element, when it is not driven (that is, when printing is not performed), the electric charge accumulated by charging is discharged by the insulation resistance, and the voltage decreases, so that May affect discharge.
[0006]
For this reason, in Japanese Patent No. 3097155 by the present applicant, there is provided a head driving apparatus and driving method in which a charging voltage is applied to a piezoelectric element at a timing different from the driving timing to maintain the charging voltage. It is disclosed.
[0007]
[Problems to be solved by the invention]
However, in such an ink jet printer head drive, the drive signal applied to each piezoelectric element is set to a high voltage when not driven, for example, and the voltage is lowered when driven. In this case, the power consumption increases and the voltage applied to the piezoelectric element becomes relatively high. Therefore, the voltage drop due to the above-described discharge is large and the power loss is large.
[0008]
Also, when trying to increase the density of printed dots in order to improve the print quality, the gap between the electrodes of the adjacent piezoelectric elements becomes narrower, but there is a difference between the driven piezoelectric element and the non-driven piezoelectric element. When the voltage between the electrodes increases, a discharge may occur between the electrodes of these piezoelectric elements. For this reason, an insulation process is required between the electrodes of the piezoelectric element.
[0009]
On the other hand, there is also a head drive system in which the ground side of each piezoelectric element is held at an intermediate potential of the drive signal. According to such a head driving method, it is possible to prevent the discharge between the piezoelectric element electrodes at the time of increasing the density described above, but the voltage is changed in accordance with the fluctuation of the driving signal, and the charging and discharging are performed. Therefore, a bidirectional variable power supply is necessary.
[0010]
Furthermore, since the operating characteristics of the piezoelectric element change depending on the temperature, it is necessary to change the power supply in order to correct the intermediate potential depending on the temperature.
[0011]
Accordingly, an object of the present invention is to provide a head driving device and a head driving method for an ink jet printer that can easily hold an intermediate potential of each piezoelectric element with a simple configuration.
[0012]
[Means for Solving the Problems]
In order to solve the above problems, in the present invention, the reference voltage from the reference voltage generation circuit is applied to the ground-side electrode of each piezoelectric element so that the ground side of each piezoelectric element is held at an intermediate potential.
[0013]
That is, in the head drive device for an ink jet printer according to claim 1, piezoelectric elements that apply pressure to ink respectively provided corresponding to a plurality of nozzles are selectively supplied from the drive waveform generation circuit at a predetermined print timing. A head drive device for an ink jet printer that performs recording by ejecting ink droplets from corresponding nozzles driven by a drive signal, and includes a reference voltage generation circuit that applies an intermediate potential to the ground-side electrode of each piezoelectric element. Preparation The piezoelectric element is applied in the same direction as the direction in which the polarization voltage is generated during charging, and is applied in the direction opposite to the direction in which the polarization voltage is generated during discharging. It is characterized by that.
[0014]
According to a seventh aspect of the present invention, there is provided a head driving method for an ink jet printer, wherein a piezoelectric element that applies pressure to the ink provided corresponding to each of the plurality of nozzles is selectively supplied from the driving waveform generation circuit at a predetermined printing timing. A method of driving a head of an ink jet printer that is driven by a drive signal and performs recording by ejecting ink droplets from corresponding nozzles, and a reference voltage generation circuit Is Apply intermediate potential to the ground side electrode of each piezoelectric element The piezoelectric element is applied in the same direction as the direction in which the polarization voltage is generated during charging, and is applied in the direction opposite to the direction in which the polarization voltage is generated during discharging. It is characterized by that.
[0015]
According to this configuration, the ground potential of the piezoelectric element is held at the intermediate potential by supplying the intermediate potential directly from the reference voltage generating circuit to the electrode on the ground side of the piezoelectric element. Therefore, since the voltage applied between both electrodes of the piezoelectric element is relatively low, power consumption is reduced, voltage drop due to spontaneous discharge of the piezoelectric element is small, and power loss is reduced.
[0016]
In addition, since the voltage applied to the piezoelectric element becomes relatively low, the occurrence of discharge due to the voltage difference between the driven piezoelectric element and the non-driven piezoelectric element is reduced, and the insulation treatment between the electrodes of the piezoelectric element is reduced. Without increasing the density of the head, the density of the head can be easily increased.
[0017]
Furthermore, since the heat generation of the piezoelectric element is reduced, the change in the characteristic of the piezoelectric element due to the temperature change is reduced, and even if the operation characteristic of the piezoelectric element is changed due to the temperature, the reference voltage generating circuit is always Since the ground side is held at the intermediate potential, temperature correction becomes unnecessary.
[0018]
3. The head driving device according to claim 2, wherein the reference voltage generation circuit applies a charging voltage to each piezoelectric element at a timing different from the printing timing of each piezoelectric element to correct a decrease in charge due to the discharge of the piezoelectric element. A voltage hold circuit that latches an arbitrary voltage of the drive signal from the drive waveform generation circuit based on a charge signal from the piezoelectric element charging means; and a current amplification circuit that amplifies the output of the voltage hold circuit. It is characterized by that.
[0019]
9. The head driving method according to claim 8, wherein the reference voltage generation circuit applies a charging voltage to each piezoelectric element at a timing different from the printing timing of each piezoelectric element to correct a decrease in charge due to discharge of the piezoelectric element. Based on the charge signal from the piezoelectric element charging means, the voltage hold circuit latches an arbitrary voltage of the drive signal from the drive waveform generation circuit, and the output of the voltage hold circuit is current amplified by the current amplification circuit. To do.
[0020]
According to this configuration, the voltage hold circuit of the reference voltage generation circuit latches an arbitrary voltage of the drive signal on the basis of the charge signal from the piezoelectric element charging means for holding the charging voltage of the piezoelectric element. The reference voltage is generated by the current amplification circuit based on the reference voltage, so that the electrode on the ground side of the piezoelectric element is charged with a relatively large current. The electrode can be held at an intermediate potential. Therefore, there is no need to vary the charging voltage as in the prior art, and a variable power supply is not necessary.
[0021]
Also, since the reference voltage is generated by current amplification based on the drive signal from the drive waveform generation circuit, it is necessary to route another power supply line by using a constant voltage power supply used for current amplification of the drive signal Therefore, the conventional circuit can be used as it is.
[0022]
4. The head driving device according to claim 3, wherein the reference voltage generating circuit discharges the piezoelectric element when the driving signal is higher than the intermediate potential, and charges the piezoelectric element when the driving signal is lower than the intermediate potential. Features.
[0023]
10. The head driving method according to claim 9, wherein the reference voltage generating circuit discharges the piezoelectric element when the driving signal is higher than the intermediate potential, and charges the piezoelectric element when the driving signal is lower than the intermediate potential. Features.
[0024]
According to this configuration, the reference voltage generating circuit discharges and charges the piezoelectric element based on the drive signal, thereby holding the electrode on the ground side of the piezoelectric element at an intermediate potential. It becomes unnecessary.
[0025]
5. The head driving device according to claim 4, wherein the reference voltage generating circuit outputs a reference voltage when charging each piezoelectric element by the piezoelectric element charging means based on the output of the voltage hold circuit. To do.
[0026]
11. The head driving method according to claim 10, wherein the reference voltage generation circuit outputs a reference voltage when charging each piezoelectric element by the piezoelectric element charging means based on the output of the voltage hold circuit. To do.
[0027]
According to this configuration, when the piezoelectric element charging unit charges the piezoelectric element before printing, the reference voltage generating circuit outputs the reference voltage to the ground-side electrode of the piezoelectric element. Since both of the electrodes are charged with almost no voltage difference between them, malfunction of the piezoelectric element is prevented. Accordingly, it becomes possible to quickly charge the piezoelectric element by the piezoelectric element charging means before printing in a shorter time.
[0028]
The head driving device according to claim 5 is characterized in that the reference voltage generating device includes a discharging means for discharging the piezoelectric element.
[0029]
According to this configuration, when the ground side of the piezoelectric element has a voltage higher than the intermediate potential, the ground side of the piezoelectric element can be held at the intermediate potential by discharging through the discharging means.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
A head driving device according to an embodiment of the present invention will be described with reference to the drawings. The embodiments described below are preferable specific examples of the present invention, and thus various technically preferable limitations are given. However, the scope of the present invention particularly limits the present invention in the following description. As long as there is no description of the effect, it is not restricted to these aspects.
[0031]
FIG. 1 shows the configuration of an embodiment of a head driving device according to the present invention. In FIG. 1, a head driving device 10 supplies a driving signal to a piezoelectric element 11 provided corresponding to each of a plurality of nozzles of an ink jet printer and one electrode 11 a of each piezoelectric element 11. A predetermined voltage is applied to the generation circuit 12, the current amplification circuit 13 and the switch circuit 14 provided between the drive waveform generation circuit 12 and each piezoelectric element 11, and the other ground-side electrode 11b of the piezoelectric element 11. And a reference voltage generation circuit 20 to be applied. Among the elements constituting the head drive device 10, the drive waveform generation circuit 12, the reference voltage generation circuit 20, and the current amplification circuit 13 are provided in the printer main body portion 100 in the present embodiment, while the piezoelectric element 11. The switch circuit 14 is provided in the head portion 200. Here, in FIG. 1, only one piezoelectric element 11 is shown, but actually, the head of the ink jet printer is provided with a plurality of nozzles, and each of the nozzles is provided for each nozzle. One piezoelectric element is provided. Then, as shown in FIG. 1, when the control signal CS is input, the switch circuit 14 is turned on at the drive timing of the corresponding piezoelectric element 11 among the plurality of piezoelectric elements, and a drive signal COM described later is sent to the piezoelectric element 11. To output. Note that the drive signal COM from the drive waveform generation circuit 12 is actually output sequentially to each piezoelectric element 11 via a shift register or the like.
[0032]
The piezoelectric element 11 is, for example, a piezo element, and is configured to be displaced by a voltage applied between both electrodes 11a and 11b. The piezoelectric element 11 is always charged near the intermediate potential, and by applying pressure to the ink in the corresponding nozzle when discharging based on the drive signal COM from the drive waveform generation circuit 12, the piezoelectric element 11 is discharged from this nozzle. An ink droplet is ejected.
[0033]
The drive waveform generation circuit 12 generates a drive signal COM to the head of the ink jet printer. As described above, the drive waveform generation circuit 12 is disposed in the printer main body portion 100 in the present embodiment.
[0034]
The current amplifier circuit 13 includes two transistors 15 and 16. Among these transistors, the first transistor 15 has a collector connected to a constant voltage power source (not shown), a base connected to the output of the drive waveform generating circuit 12, and an emitter connected to the input side of the switch circuit 14. As a result, conduction is made based on the drive signal from the drive waveform generation circuit 12, and the VH voltage is supplied to the piezoelectric element 11 via the switch circuit 14.
[0035]
The second transistor 16 has an emitter connected to the input side of the switch circuit 14, a base connected to the output of the drive waveform generating circuit 12, and a collector connected to the ground. As a result, conduction is made based on the drive signal from the drive waveform generation circuit 12, and the piezoelectric element 11 is discharged via the switch circuit 14.
[0036]
When the control signal CS is input, the switch circuit 14 is turned on at the drive timing of the corresponding piezoelectric element 11 and outputs the drive signal COM to the piezoelectric element 11.
[0037]
The reference voltage generation circuit 20 is configured to apply a predetermined voltage to the other electrode 11 b of the piezoelectric element 11. Here, this predetermined voltage can be set to a voltage substantially equal to the intermediate potential by the drive signal COM of the piezoelectric element 11, for example. Such a configuration example will be described with reference to FIG.
[0038]
In the example shown in FIG. 2, the reference voltage generation circuit 20 is configured as an intermediate voltage generation circuit 20 </ b> A, and the output side of the intermediate voltage generation circuit 20 </ b> A is connected to the other electrode 11 b of the piezoelectric element 11. The input side of the intermediate voltage generation circuit 20A is connected to the output side of the drive waveform COM of the drive waveform generation circuit 12, and the drive signal COM is input from the drive waveform generation circuit 12.
[0039]
Here, specifically, the intermediate voltage generation circuit 20A includes, for example, a voltage hold circuit 21 and a current amplification circuit 22, as shown in FIG.
[0040]
The voltage hold circuit 21 is configured to be charged by the drive signal COM from the drive waveform generation circuit 12 at the timing of charging the piezoelectric element 11 based on the charge signal NCHG for the piezoelectric element 11. The current amplifier circuit 22 includes two transistors 23 and 24.
[0041]
One third transistor 23 has a collector connected to a constant voltage power supply (not shown), a base connected to the output of the voltage hold circuit 21, and an emitter connected to the ground side of the piezoelectric element 11 via a forward diode 23a. To the electrode (common terminal). Thus, conduction is made based on the signal from the voltage hold circuit 21, and the VH voltage is applied to the ground-side electrode 11 b of the piezoelectric element 11.
[0042]
The other fourth transistor 24 has an emitter connected to the ground side electrode (common terminal) of the piezoelectric element 11 via a diode 24a in the reverse direction, and a base connected to the output of the voltage hold circuit 21. The emitter is grounded to ground. As a result, conduction is made based on the signal from the voltage hold circuit 21, and the ground-side electrode 11 b of the piezoelectric element 11 is discharged.
[0043]
FIG. 4 shows a specific configuration example of the voltage hold circuit 21. In FIG. 4, the voltage hold circuit 21 includes an analog switch 25, a charging capacitor 26, a hold reset circuit 29, and an analog amplifier 27.
[0044]
The analog switch 25 has a known configuration, and is composed of two opposingly connected FETs 25a and 25b and an inverter 25c. The gate electrode of one FET 25a is connected to the gate electrode via the inverter 25c. The charge signal NCHG is directly input to the gate electrode of the other FET 25b, and the drive signal COM from the drive waveform generating circuit 12 is input to the source electrodes of both FETs 25a and 25b. It is like that.
[0045]
The charging capacitor 26 has one electrode connected to the drain electrodes of both FETs 25a and 25b and the other electrode connected to the ground. Note that the capacitance of the charging capacitor 26 is appropriately selected so as to correspond to the self-discharge due to the input impedance of the analog amplifier 27 and to have a time constant that does not affect the cycle of the charge signal. The hold reset circuit 29 includes a fifth transistor 30. When a hold reset signal is input to the base of the fifth transistor 30, the collector and the emitter are brought into conduction so that the charging capacitor 26 Discharge the remaining voltage.
[0046]
The analog amplifier 27 has one input terminal connected to one electrode of the charging capacitor 26 and two output terminals connected to the bases of the two transistors 23 and 24 of the current amplifier circuit 22, respectively. Further, the other input terminal of the analog amplifier 27 is fed back with the output of the current amplifier circuit 22.
[0047]
Here, the current from the constant voltage power supply of the current amplifier circuit 22 is the current flowing through the piezoelectric element 11 via the first transistor 15 and the piezoelectric element 11 via the fourth transistor 24 when the piezoelectric element is charged. The current discharged from the piezoelectric element 11 via the second transistor 16 and the piezoelectric element 11 via the third transistor 23 so that the discharged current has the same peak current. Is selected as appropriate so that the current flowing in the current has the same peak current.
[0048]
The head driving device 10 according to the embodiment of the present invention is configured as described above, and operates as follows based on the head driving method according to the present invention. Hereinafter, the head driving method according to the embodiment of the present invention will be described in detail with reference to the timing chart of FIG. 5 and the flowchart of FIG.
[0049]
First, at the start of printing (start-up) of the ink jet printer, the drive signal COM from the drive waveform generation circuit 12 is inverted to the low level for a time of, for example, 100 μs as shown in FIG. In FIG. 6, step S1), the voltage is raised to the intermediate potential (FIG. 6, step S2). As a result, a current flows from the first transistor 15 of the current amplification circuit 13 to the one electrode 11a of the piezoelectric element 11 via the switch circuit 14 and charges the drive signal COM, whereby one electrode 11a of the piezoelectric element 11 is charged. As shown by the solid line in FIG. 5 (B), it rises to an intermediate potential.
[0050]
At this time, the charging capacitor 26 of the voltage hold circuit 21 is charged via the analog switch 25 by inversion of the charge signal NCHG, whereby an arbitrary voltage of the drive signal COM is latched and output from the analog amplifier 27. . As a result, the third transistor 23 of the current amplification circuit 22 becomes conductive, and a current flows from the constant voltage power supply (not shown) to the ground-side electrode 11b of the piezoelectric element 11 through the diode 23a. As a result, as indicated by a dotted line in FIG. 5B, the potential of the electrode 11b on the ground side of the piezoelectric element 11 also gradually increases and reaches an intermediate potential (FIG. 6, step S3).
[0051]
Here, as shown in FIG. 5B, the potential of the electrode 11b on the ground side of the piezoelectric element 11 reaches an intermediate potential with substantially the same gradient as that of the drive signal COM. The potential difference between 11b is held at almost zero. Therefore, the time to the intermediate potential between the electrodes 11a and 11b of the piezoelectric element 11 at the start-up need not be 100 μs, for example, as in the prior art, and even if it is set to a shorter time, for example, about 20 μs or 10 μs, There is no case where the piezoelectric element 11 malfunctions and ejects ink droplets.
[0052]
During printing, the drive signal COM is output to the voltage hold circuit 21 (FIG. 6, step S4). When the drive signal COM is higher than the intermediate potential based on the fluctuation of the drive signal COM, the current amplification circuit When one of the electrodes 11a of the piezoelectric element 11 is charged via the 13 first transistor 15 and the drive signal COM is lower than the intermediate potential, via the second transistor 16 of the current amplifying circuit 13. One electrode 11a of the piezoelectric element 11 is discharged (No in step S5 in FIG. 6). As a result, the piezoelectric element 11 operates based on the drive signal COM and ejects ink droplets.
[0053]
Here, as indicated by a symbol X in FIG. 5B, the charge signal NCHG is output in order to prevent the charging capacitor 26 from causing a voltage drop due to self-discharge and lowering below the intermediate potential. (FIG. 6, step S6). That is, the charge signal NCHG generates an L-level pulse at a constant cycle of the drive signal COM, that is, at each timing when the drive signal COM does not fluctuate, as indicated by symbol Y in FIG. Thereby, one electrode 11a of the piezoelectric element 11 is charged via the first transistor 15 of the current amplification circuit 13 based on the drive signal COM from the drive waveform generation circuit 12, and is boosted to an intermediate potential each time. It has become so.
[0054]
At the same time, a predetermined voltage is applied to the ground-side electrode 11b of the piezoelectric element 11 through the third transistor 23 of the current amplification circuit 22 of the reference voltage generation circuit 20 by the L level pulse of the charge signal NCHG. As a result, the electrode 11b on the ground side of the piezoelectric element 11 is charged and similarly held at an intermediate potential.
[0055]
As a result, even if the charging capacitor 26 is self-discharged, the electrodes 11a and 11b of the piezoelectric element 11 are charged to the intermediate potential based on the L level pulse Y of the charge signal NCHG. Can be retained. The above operations in steps S4 to S6 are repeated until the end of printing (No in step S7 in FIG. 6).
[0056]
Further, at the end of printing (Yes in FIG. 6, step S7), a predetermined stop-end operation is performed (FIG. 6, step S8). That is, the drive signal COM from the drive waveform generation circuit 12 is discharged from the one electrode 11a of the piezoelectric element 11 through the second transistor 16 of the current amplification circuit 13 as shown in FIG. As a result, the level drops to the Low level. At the same time, the fourth transistor 24 of the current amplifying circuit 22 of the reference voltage generating circuit 20 is turned on, and the ground-side electrode 11b of the piezoelectric element 11 is discharged through the fourth transistor 24 to become a low level. . Here, as shown in FIG. 5B, the potential of the electrode 11b on the ground side of the piezoelectric element 11 reaches the Low level with a gradient almost the same as that of the drive signal COM. The potential difference is held at almost zero.
[0057]
Further, when the drive signal COM becomes Low level, a hold reset signal is output to the above-described hold reset circuit 29 (FIG. 6, step S9). That is, when a hold reset signal is input to the base of the fifth transistor 30 of the hold reset circuit 29, the collector-emitter of the fifth transistor 30 becomes conductive, and the remaining voltage of the charging capacitor 26 is discharged. Thereby, the sequence of the head driving method according to the present embodiment is completed.
[0058]
In this way, the output of the reference voltage generation circuit 20, that is, the potential of the electrode 11b on the ground side of the piezoelectric element 11, is the drive waveform generation circuit 12 except for the pulse waveform at the print timing from the start of printing to the end of printing. Therefore, the potential difference between the electrodes 11a and 11b of the piezoelectric element 11 is maintained at substantially zero.
[0059]
Therefore, even when the rise time to the intermediate potential of the piezoelectric element 11 at the start of printing is shortened from the conventional 100 μs to a shorter time, the piezoelectric element 11 does not malfunction, and the time from the start of printing to the end of printing is not increased. Printing time can be shortened.
[0060]
Further, since the reference voltage generation circuit 20 charges and discharges the electrode 11b on the ground side of the piezoelectric element 11, it is compared with the case where the ground side of the piezoelectric element 11 is held at an intermediate potential using a conventional power supply circuit. This eliminates the need for a bidirectional variable power supply.
[0061]
Furthermore, since the current during charging and discharging of the piezoelectric element 11 may be the maximum value of the peak current during charging and discharging of one electrode of the piezoelectric element 11 by the drive signal COM, it is necessary to route another power supply line. Absent. Therefore, when the head driving device 10 is mounted on the print head, the number of power supply lines can be reduced, and the same FFC (Flexible Flat Cable) can be used to connect the head driving device 10 and the printer body. , The occurrence of L minutes can be reduced.
[0062]
Further, since the voltage hold circuit 21 of the reference voltage generation circuit 20 operates based on the drive signal COM from the drive waveform generation circuit 12, adjustment is easy.
[0063]
Furthermore, since the electrode 11b on the ground side of the piezoelectric element 11 is always held at an intermediate potential, the drive voltage applied between the electrodes 11a and 11b of the piezoelectric element 11 is lowered. Therefore, power consumption in the piezoelectric element 11 is reduced, voltage drop due to self-discharge of the piezoelectric element 11 is small, and power loss is reduced. In addition, since the potential difference between the driven piezoelectric element and the non-driven piezoelectric element becomes low, even when such a piezoelectric element is adjacent, the occurrence of discharge between the piezoelectric elements is reduced. It is possible to easily realize high-density heads without performing insulation treatment between the piezoelectric elements.
[0064]
Furthermore, since the heat generation of the piezoelectric element is reduced, the change in the characteristic of the piezoelectric element due to the temperature change is reduced, and even if the operation characteristic of the piezoelectric element is changed due to the temperature, the reference voltage generating circuit is always Since the ground side is held at the intermediate potential, temperature correction as in the case where the reference voltage is a variable power supply is not required.
[0065]
In the above-described embodiment, for example, a piezoelectric element is used as the piezoelectric element 11, but not limited to this, other piezoelectric elements such as an electrostrictive element, a magnetostrictive element, and the like may be used.
[0066]
【The invention's effect】
As described above, according to the present invention, by supplying the intermediate potential directly from the reference voltage generation circuit to the electrode on the ground side of the piezoelectric element, the ground side of the piezoelectric element is held at the intermediate potential. Therefore, since the voltage applied between both electrodes of the piezoelectric element is relatively low, power consumption is reduced, voltage drop due to spontaneous discharge of the piezoelectric element is small, and power loss is reduced.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of an embodiment of a head driving device according to the present invention.
2 is a block diagram showing a configuration example in which the reference voltage generation circuit in the head driving device of FIG. 1 is an intermediate voltage generation circuit.
3 is a block diagram illustrating a configuration example of a voltage hold circuit of the intermediate voltage generation circuit of FIG. 2;
4 is a block diagram illustrating a specific configuration example of the voltage hold circuit of FIG. 3;
5 is a time chart showing fluctuations of (A) drive signal, (B) electrode voltages of the piezoelectric elements, and (C) charge signal in the head drive device of FIG. 1. FIG.
6 is a flowchart for explaining the operation of the driving method of the head driving device of FIG. 1;
[Explanation of symbols]
10 Head drive device
11 Piezoelectric elements
11a One electrode
11b Ground side electrode
12 Drive waveform generation circuit
13 Current amplifier circuit
14 Switch circuit
15 First transistor
16 Second transistor
20 Reference voltage generator
21 Voltage hold circuit
22 Current amplifier circuit
23 Third transistor
24 Fourth transistor
25 Analog switch
26 Capacitor for charging
27 Analog amplifier

Claims (10)

Piezoelectric elements that apply pressure to the ink chambers provided corresponding to the plurality of nozzles are selectively driven at a predetermined printing timing by a drive signal from the drive waveform generation circuit, and ink droplets are ejected from the ink chambers of the corresponding nozzles. A head driving device for an ink jet printer that performs recording by discharging
Provided with a reference voltage generating circuit for applying an intermediate potential to the ground side electrode of each piezoelectric element ,
The piezoelectric element is applied in the same direction as a direction in which a polarization voltage is generated during charging, and is applied in a direction opposite to the direction in which the polarization voltage is generated during discharge. apparatus.  The reference voltage generation circuit applies a charging voltage to each piezoelectric element at a timing different from the printing timing of each piezoelectric element, and corrects a decrease in charge due to discharge of the piezoelectric element, based on a charge signal from a piezoelectric element charging unit. 2. A voltage hold circuit that latches an arbitrary voltage of a drive signal from the drive waveform generation circuit, and a current amplification circuit that amplifies the output of the voltage hold circuit. Inkjet printer head drive device.  3. The reference voltage generating circuit according to claim 1, wherein the piezoelectric element is discharged when the driving signal is higher than the intermediate potential, and the piezoelectric element is charged when the driving signal is lower than the intermediate potential. A head driving device of the ink jet printer described above.  4. The reference voltage generation circuit according to claim 1, wherein the reference voltage generation circuit outputs a reference voltage when charging each piezoelectric element by the piezoelectric element charging means based on the output of the voltage hold circuit. A head driving device of the ink jet printer described above.  5. The head driving device for an ink jet printer according to claim 3, wherein the reference voltage generating device includes a discharging means for discharging the piezoelectric element.  An ink jet printer comprising the head driving device according to claim 1. Piezoelectric elements that apply pressure to the ink chambers provided corresponding to the plurality of nozzles are selectively driven at a predetermined printing timing by a drive signal from the drive waveform generation circuit, and ink droplets are ejected from the ink chambers of the corresponding nozzles. Ink jet printer head driving method for recording by discharging
Reference voltage generating circuit, an intermediate potential is applied to the ground-side electrode of the piezoelectric elements,
The piezoelectric element is applied in the same direction as a direction in which a polarization voltage is generated during charging, and is applied in a direction opposite to the direction in which the polarization voltage is generated during discharge. Method.  Based on the charge signal from the piezoelectric element charging means that applies a charging voltage to each piezoelectric element at a timing different from the printing timing of each piezoelectric element in the reference voltage generation circuit to correct the decrease in charge due to the discharge of the piezoelectric element. 8. The ink jet printer according to claim 7, wherein an arbitrary voltage of the drive signal from the drive waveform generation circuit is latched by the voltage hold circuit, and the output of the voltage hold circuit is current amplified by the current amplification circuit. Head drive method.  9. The reference voltage generation circuit according to claim 7 or 8, wherein when the drive signal is higher than the intermediate potential, the piezoelectric element is discharged, and when the drive signal is lower than the intermediate potential, the piezoelectric element is charged. A method for driving a head of the ink jet printer described above.  10. The reference voltage generation circuit according to claim 7, wherein the reference voltage generation circuit outputs a reference voltage when charging each piezoelectric element by the piezoelectric element charging means based on the output of the voltage hold circuit. A method for driving a head of the ink jet printer described above.

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