JP2001063040A - Ink jet recording apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet recording apparatus capable of reducing the heat value in a transistor by putting the characteristics of an inductor to practical use. SOLUTION: A push/pull circuit 830 equipped with an NPN transistor Q1 and a PNP transistor Q2 both of which are subjected to push/pull connection is formed to the current amplifying circuit 83 of the drive signal forming circuit 8 of an ink jet recording apparatus. Since the primary coil L1 of a transformer 90 is electrically connected across the collector of the NPN transistor Q1 of the push/pull circuit 830 and drive potential Vcc, and the secondary coil L2 of the transformer 90 is electrically connected across the collector of the PNP transistor Q2 and ground potential GND, the voltage across the emitter-collector of the NPN transistor Q1 and the PNP transistor Q2 can be suppressed low at times of charge and discharge.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus used as an ink jet printer or the like. More specifically, the present invention relates to a circuit technique for driving a pressure generating element.

[0002]

2. Description of the Related Art In a recording head of an ink jet recording apparatus used as an ink jet printer or an ink jet plotter, pressure generating elements such as a plurality of piezoelectric vibrators (for example, piezo elements) corresponding to a plurality of nozzle openings are provided in the nozzle openings. An ink droplet is ejected from the nozzle opening by pressurizing the ink in the communicating pressure generating chamber. In the ink jet recording apparatus, a driving signal generating circuit for generating a driving signal for driving the recording head includes a driving signal generating circuit shown in FIG.
As shown in FIG. 7, a signal generation circuit 8 for outputting a charge / discharge pulse 80 for defining a charge / discharge timing of the pressure generating element 17.
1 and a voltage amplifying circuit 82 for the charge / discharge pulse 80
And a current amplifier circuit 8 that performs a switching operation on the push-pull connected NPN transistor Q1 and PNP transistor Q2 based on the charge / discharge pulse 80 and outputs the amplified common drive signal COM to the pressure generating element 17.
3 are constituted.

Here, the pressure generating element 17 has a capacitive load C
For example, when a drive signal COM as shown in FIG. 8 is applied, the pressure generating element 17 repeats discharge and charge based on the drive signal COM. That is, in the drive amplifying circuit 83, at time T1, NPN
When the transistor Q1 is turned on, the pressure generating element 1
7, and at time T2, instead of turning off the NPN transistor Q1, the PNP transistor Q2 is turned on to discharge the pressure generating element 17 to the ground potential GND. Therefore, the charging current I1 and the discharging current I2 flow through the NPN transistor Q1 and the PNP transistor Q2.

[0004]

However, in the current amplifying circuit 83 shown in FIG. 7, the potential V0 corresponding to the potential difference between the drive potential Vcc or the ground potential GND and the drive signal COM remains unchanged during charging or discharging. NP
Since the voltage is applied between the emitter and the collector of the N transistor Q1 or the PNP transistor Q2, the heat generated by the NPN transistor Q1 and the PNP transistor Q2 is large. Therefore, the NPN transistor Q1 and the PNP
Since the reliability is likely to decrease in the transistor Q2,
There is a problem that a large-scale heat dissipation device is required.

[0005] In view of the above problems, an object of the present invention is to provide an ink jet recording apparatus capable of reducing the amount of heat generated in a transistor by utilizing the characteristics of an inductor.

[0006]

According to the present invention, there is provided a pressure generating element for discharging ink droplets from a nozzle opening by pressurizing ink in a pressure generating chamber communicating with the nozzle opening. In an ink jet recording apparatus having a drive signal generation unit for generating a drive signal to be applied to a pressure generating element, the drive signal generation unit includes a waveform generation circuit for generating a signal defining a waveform of the drive signal; A current amplifying circuit for amplifying an output from the generation circuit, wherein the current amplifying circuit has a transistor which is push-pull connected between a high potential side power supply and a low potential side power supply, and is connected to each base of the transistor. A push-pull circuit to which an output signal from the waveform generation circuit is applied;
A first coil electrically connected between the push-pull circuit and the high-potential-side power supply, and a second coil electrically connected between the push-pull circuit and the low-potential-side power supply And the pressure generating element is electrically connected between the connection point of the transistor in the push-pull circuit and the low potential side power supply.

According to the present invention, in the current amplifying circuit, the output signal from the waveform generating circuit is applied to each base of the NPN transistor and the PNP transistor which are push-pull connected between the high potential side power source and the low potential side power source. So
With the potential change of this output signal, N
Charging of the pressure generating element via the PN transistor and discharging from the pressure generating element to the lower potential side power supply via the PNP transistor occur. Here, NP of the push-pull circuit
Since the first coil is electrically connected between the N-transistor and the high-potential-side power supply, an induced electromotive force is generated in the first coil by the charging current to lower the collector potential of the NPN transistor. Let it. Therefore, when charging, N
The emitter-collector voltage of the PN transistor decreases. Further, since the second coil is electrically connected between the PNP transistor of the push-pull circuit and the low-potential-side power supply, an induced electromotive force is generated in the second coil by the discharge current, and the PNP Increase the collector potential of the transistor. Therefore, the emitter-collector voltage of the PNP transistor decreases during discharging. Accordingly, the voltage between the emitter and the collector of the NPN transistor and the PNP transistor can be reduced at the time of charging and at the time of discharging, respectively, so that heat generation in these transistors can be prevented.

In another aspect of the present invention, a pressure generating element for discharging ink droplets from the nozzle opening by pressurizing ink in a pressure generating chamber communicating with the nozzle opening, and a drive signal to be applied to the pressure generating element And a drive signal generation unit for generating a waveform of the drive signal, wherein the drive signal generation unit generates a signal defining a waveform of the drive signal, and amplifies an output from the waveform generation circuit. A current amplifying circuit, wherein the current amplifying circuit includes a transistor having a push-pull connection between a high-potential-side power supply and a low-potential-side power supply, and an output signal from the waveform generation circuit being connected to each base of the transistor. A transistor is push-pull connected between the applied first push-pull circuit and the high-potential-side power supply and the low-potential-side power supply. A second push-pull circuit the inverted output signal is applied from the waveform generating circuit, the first
A primary coil is electrically connected between the push-pull circuit and the high-potential power supply, and a secondary coil is electrically connected between the second push-pull circuit and the low-potential power supply. A primary coil is electrically connected between the first transformer, the first push-pull circuit, and the low-potential-side power supply, and the primary coil is electrically connected between the second push-pull circuit and the high-potential-side power supply. The secondary coil is electrically connected between the second
And the pressure generating element is electrically connected between the connection points of the transistors in the first push-pull circuit and the second push-pull circuit. .

According to the present invention, in the current amplifying circuit, the output signal from the waveform generating circuit and the base of each of the two sets of NPN transistors and PNP transistors which are push-pull connected between the high potential side power supply and the low potential side power supply. Since the inverted output signal is applied, charging and discharging occur as the output signal changes in potential. That is, at the time of charging, a charging current flows from the high potential side power supply to the pressure generating element via the NPN transistor of the first push-pull circuit.

Here, the NPN of the first push-pull circuit
Since the primary coil of the first transformer is electrically connected between the transistor and the high-potential power supply, an induced electromotive force is generated in the primary coil of the first transformer by a charging current, The collector potential of the NPN transistor is lowered. In the first transformer, secondary induction occurs in the secondary coil, and an electromotive force is also generated between the coil terminals. The electromotive force is generated by the PNP of the second push-pull circuit.
Increase the collector potential of the transistor. Therefore, during charging, the voltage between the emitter and the collector of the NPN transistor of the first push-pull circuit and the voltage of the emitter-collector of the PNP transistor of the second push-pull circuit are reduced.
Heat generation in these transistors can be suppressed.

On the other hand, during discharge, the first
Charging current flows through the PNP transistor of the push-pull circuit of FIG. Here, the PN of the first push-pull circuit
Since the primary coil of the second transformer is electrically connected between the P transistor and the low potential side power supply, an induced electromotive force is generated in the primary coil of the second transformer by the discharge current. , The collector potential of the PNP transistor is increased. In the second transformer, secondary induction occurs in the secondary coil, and an electromotive force is also generated between the coil terminals. This electromotive force is generated by the NP of the second push-pull circuit.
The collector potential of the N transistor is lowered. Therefore,
At the time of discharging, the voltage between the emitter and the collector of the PNP transistor of the first push-pull circuit and the voltage of the emitter-collector of the NPN transistor of the second push-pull circuit are reduced, so that heat generation in these transistors can be suppressed.

[0012]

Embodiments of the present invention will be described with reference to the drawings. In any of the embodiments described below, basically, a push-pull circuit is used for the current amplifier circuit of the drive signal generation circuit, similarly to the drive signal generation circuit described with reference to FIG. Parts having functions will be described with the same reference numerals. In addition, the first and second embodiments described below have the same overall configuration as an ink jet recording apparatus. Therefore, before describing the characteristic configuration of each embodiment, the common configuration in each embodiment will be described. This will be described with reference to FIGS. [Overall Configuration of Inkjet Recording Apparatus] FIG. 1 is a perspective view showing the configuration of an inkjet recording apparatus to which the present invention is applied. In FIG. 1, an ink jet recording apparatus 1 of the present embodiment is used by being connected to a computer (not shown) together with a scanner (not shown) and the like. A predetermined program is loaded on this computer,
When executed, these devices as a whole function as a recording device. In a computer, an application program operates under a predetermined operating system, and performs a predetermined process on an image or the like read from a scanner while displaying a CRT (not shown).
To display the image. When the application program issues a print command, the computer converts image data read via a scanner, character data input via a keyboard, and the like into data used by the inkjet printing apparatus 1. Output to

In the ink jet recording apparatus 1, a carriage 101 is connected to a carriage motor 103 of a carriage mechanism 12 via a timing belt 102, and is guided by a guide member 104 to reciprocate in the paper width direction of a recording paper 105 (medium). Is configured. The inkjet recording apparatus 1 is also provided with a paper feed mechanism 11 using a paper feed roller 106. An ink jet type recording head 10 is attached to a surface of the carriage 101 facing the recording paper 105, in the example shown in FIG. The recording head 10 receives the supply of ink from the ink cartridge 107 mounted on the upper part of the carriage 101, and moves the recording paper 1 according to the movement of the carriage 101.
05 to form dots by ejecting ink droplets on recording paper 1
Print images and characters on 05.

A capping device 108 is provided in a non-printing area (non-recording area) of the ink jet recording apparatus 1, and seals a nozzle opening of the recording head 10 during a pause of printing. Therefore, it is possible to suppress the ink from thickening or forming an ink film due to the solvent being scattered from the ink during the suspension of printing. Therefore, it is possible to prevent the nozzle from being clogged while the printing is stopped. Further, the capping device 108 receives ink droplets from the recording head 10 due to a flushing operation performed during a printing operation. A wiping device 109 is disposed near the capping device 108.
Is configured to wipe off the ink residue and paper powder adhering thereto by wiping the surface of the recording head 10 with a blade or the like.

FIG. 2 is a functional block diagram of the ink jet recording apparatus 1 of the present embodiment.

In FIG. 2, an ink jet recording apparatus 1
Has a print controller 40 and a print engine 5. The print controller 40 includes an interface 43 for receiving print data including multi-level hierarchical information from a computer (not shown), a RAM 44 for storing various data such as print data including multi-level hierarchical information, A ROM 45 storing a routine for performing data processing, a control unit 6 including a CPU, an oscillation circuit 47, and a drive signal C to the recording head 10.
A drive signal generation circuit 8 for generating OM; and an interface 49 for transmitting print data and drive signals developed into dot pattern data to the print engine 5.
And

The recording data including the multi-level hierarchical information sent from the computer 90 or the like is held in the receiving buffer 44A inside the recording device via the interface 43. The recording data held in the reception buffer 44A is sent to the intermediate buffer 44B after the command analysis. In the intermediate buffer 44B, recording data as an intermediate format converted into an intermediate code by the control unit 6 is held,
The control unit 6 executes a process of adding a print position, a type of modification, a size, a font address, and the like of each character. Next, the control unit 6 analyzes the recording data in the intermediate buffer 44B, and develops and stores the binarized dot pattern data obtained by decoding the hierarchical data in the output buffer 44C as described later.

When dot pattern data corresponding to one scan of the recording head 10 is obtained, the dot pattern data is serially transferred to the recording head 10 via the interface 49 and the flexible wiring board 110. When dot pattern data corresponding to one scan is output from the output buffer 44C, the contents of the intermediate buffer 44B are erased, and the next intermediate code conversion is performed.

The print engine 5 includes the paper feed mechanism 11, the carriage mechanism 12, and the recording head 10.
And The paper feed mechanism 11 sequentially feeds a recording medium such as recording paper to perform sub-scanning, and the carriage mechanism 12 causes the recording head 10 to perform main scanning.

The recording head 10 discharges ink droplets from each nozzle opening at a predetermined timing. The driving signal COM output from the driving signal generation circuit 8 is recorded via the interface 49 and the flexible wiring board 110. Output to the head 10.

The recording head 10 has, for example, 64 nozzles in the sub-scanning direction, and discharges ink droplets from each nozzle opening 111 at a predetermined timing. In the print controller 40, the print data SI developed into dot pattern data is serially output to the print head 10 via the interface 49 and the flexible wiring board 110 in synchronization with the clock signal CLK from the oscillation circuit 7, and the print head 10 Shift register 13
Is serially transferred to The serially transferred recording data SI is temporarily latched by the latch circuit 14. The latched print data SI is boosted by the level shifter 15 as a voltage amplifier to a voltage that can drive the nozzle selection circuit 16 (head selection means), for example, a predetermined voltage of about several tens of volts. The print data boosted to a predetermined voltage is supplied to the nozzle selection circuit 16.
The input side of the nozzle selection circuit 16 includes a drive signal generation circuit 8
And a piezoelectric vibrator as a pressure generating element 17 is connected to the output side of the nozzle selection circuit 16. The pressure generating elements 17 are also formed in the same number as the nozzle openings 111 (for example, 64) in a one-to-one relationship with the nozzle openings 111.

Here, the print data SI controls the operation of the nozzle selection circuit 16. For example, nozzle selection circuit 1
During a period in which the recording data SI applied to 6 is "1", the drive signal COM is applied to the pressure generating element 17, and the pressure generating element 17 expands and contracts in response to this signal. As a result, the pressure generating element 17 pressurizes the ink in the pressure generating chamber 113 communicating with the nozzle opening 111, and causes the ink droplet to be ejected from the nozzle opening 111. On the other hand, while the print data SI applied to the nozzle selection circuit 16 is “0”, the supply of the drive signal COM to the pressure generating element 17 is cut off. [Embodiment 1] FIG. 3 is a circuit diagram showing a connection relationship between a drive signal generating circuit 8 and a pressure generating element 17 in an ink jet recording apparatus according to Embodiment 1 of the present invention. FIGS. 4A and 4B are waveform diagrams showing potential changes such as terminal voltages of the pressure generating element when the drive signal generating circuit 8 is used, and waveforms applied from the waveform generating circuit to the bases of the transistors. It is a waveform diagram of a charge / discharge pulse.

In FIG. 3, the driving signal generating circuit 8 provided in the ink jet recording apparatus of the present embodiment also includes a signal generating circuit 81 for outputting a charging / discharging pulse 80 for defining the charging / discharging timing of the pressure generating element 17. A voltage amplifying circuit 82 for the charge / discharge pulse 80 and a charge / discharge pulse 8
0, a current amplifier circuit 83 that outputs a common drive signal COM amplified to the pressure generating element 17 is configured,
This current amplifying circuit 83 has a push-pull connected N
A push-pull circuit 830 including a PN transistor Q1 and a PNP transistor Q2 is formed.

In the push-pull circuit 830, the charge / discharge pulse 80 output from the signal generation circuit 81 is amplified by the voltage amplification circuit 82, and then the input resistances R1, R
2 is applied to each base of the NPN transistor Q1 and the PNP transistor Q2. In the push-pull circuit 830, the collector of the NPN transistor Q1 is electrically connected to the drive potential Vcc, which is a high-potential power supply, and the collector of the PNP transistor Q2 is
It is electrically connected to the side of the ground potential GND which is a low potential side power supply. Further, the NPN transistors Q1 and P
With respect to a connection point P1 between the emitters of the NP transistor Q2, the pressure generating element
Are electrically connected. This pressure generating element 17
It is represented as a capacitive load C1 and has an internal resistance R10.

In this embodiment, N of the push-pull circuit 830
The primary coil L1 of the transformer 90 is electrically connected between the collector of the PN transistor Q1 and the driving potential Vcc, and the secondary coil L2 of the transformer 90 is connected between the collector of the PNP transistor Q2 and the ground potential GND. Are electrically connected. In this transformer 90,
A diode D17 is electrically connected to the closed circuit including the secondary coil L2. When a discharge occurs from the PNP transistor Q2 to the ground potential GND, the secondary coil L2
Is applied to the collector of the PNP transistor Q2. In the present embodiment, as for the transformer 90, from the viewpoint of suppressing heat loss, a ferrite or amorphous material is more suitable than a core material having a small hysteresis loss, such as a silicon steel plate.

A capacitor C22 is connected between the driving potential Vcc and the transformer 90 and between the driving potential Vcc and the ground potential GND.

In the driving signal generating circuit 8 having the above-described configuration, as shown in FIG. 4B, the charging / discharging pulse 80 generated by the waveform generating circuit 81 changes from time T11 to time T11.
After the voltage rises linearly during the period from T12 to T12, the potential is kept constant from the time T12 to the time T13, and thereafter, the potential decreases linearly from the time T13 to the time T14.

Therefore, at time T11, when the base potential of the NPN transistor Q1 becomes higher than the emitter potential, the NPN transistor Q1 turns on and the driving potential Vcc
From the side through the NPN transistor Q1 to the pressure generating element 17 occurs. At this time, the transformer 9 is connected between the collector of the NPN transistor Q1 and the drive potential Vc.
0, since the primary coil L1 is electrically connected,
An induced electromotive force (back electromotive force) is generated in the primary coil L1 by the charging current, and as shown in FIG.
The collector potential of N transistor Q1 is lowered. Therefore, at the time of charging, the voltage between the emitter and the collector of the NPN transistor Q1 is reduced by the induced electromotive force of the primary coil L1, compared with the potential difference between the potential of the pressure generating element 17 and the drive potential Vcc. The potential is represented by V1.
During this time, the PNP transistor Q2 is off.

On the other hand, at time T13, when the potential of the charge / discharge pulse 80 decreases and the base potential of the PNP transistor Q2 becomes lower than the emitter potential, the PNP transistor Q2 turns on and the PNP transistor Q2 is turned on by the pressure generating element 17. Discharge to the ground potential GND occurs. At this time, since the secondary coil L2 of the transformer 90 is electrically connected between the collector of the PNP transistor Q2 and the ground GND, the induced electromotive force ( Back electromotive force) is generated, and as shown in FIG. 4A, the collector potential of the PNP transistor Q2 is increased. Therefore, at the time of discharging, the voltage between the emitter and the collector of the PNP transistor Q2 is reduced by the amount of the induced electromotive force of the secondary coil L2 as compared with the potential difference between the potential of the pressure generating element 17 and the ground GND. The potential is represented by V2. During this time, NP
N transistor Q1 is off.

As described above, in the present embodiment, the pressure generating element 1
7, the voltage between the emitter and collector of the NPN transistor Q1 and the PNP transistor Q2 is reduced by the induced electromotive force in the primary coil L1 and the secondary coil L2 of the transformer 90 at the time of charging and discharging.
NPN transistor Q1 and PNP transistor Q2
Heat generation can be suppressed. Therefore, in the inkjet recording apparatus 1, the NPN transistors Q1 and P
A large cooling device is not required for the NP transistor Q2. [Second Embodiment] FIG. 5 is a circuit diagram showing a connection relationship between a drive signal generating circuit 8 and a pressure generating element 17 in an ink jet recording apparatus according to a first embodiment of the present invention. FIGS. 6A, 6B, and 6C are waveform diagrams showing potential changes such as terminal voltages of pressure generating elements when the drive signal generation circuit 8 is used, and FIGS. FIG. 3 is a waveform diagram of a charging / discharging pulse applied to the power supply of FIG.

In FIG. 5, the driving signal generating circuit 8 provided in the ink jet recording apparatus of the present embodiment also includes a signal generating circuit 81 for outputting a charging / discharging pulse 80 for defining the timing of charging / discharging of the pressure generating element 17. A voltage amplifying circuit 82 for the charge / discharge pulse 80 and a charge / discharge pulse 8
A current amplifier circuit 83 that outputs the common drive signal COM amplified to the pressure generating element 17 based on the value 0.

In the present embodiment, the current amplifying circuit 83 includes:
A first push-pull circuit 831 in which an NPN transistor Q11 and a PNP transistor Q12 are push-pull connected between a driving potential Vcc as a high potential power source and a ground potential GND as a low potential power source; An NPN transistor Q13 and a PN
A second transistor in which the P transistor Q14 is push-pull connected.
And a push-pull circuit 832.

Of these push-pull circuits, in the first push-pull circuit 831, the charge / discharge pulse 80 output from the signal generating circuit 81 is supplied to the voltage amplifying circuit 82 as shown in FIG. After being amplified, the NPN signal is input through the input resistors R12 and R13 with the same waveform.
The voltage is applied to each base of the transistor Q11 and the PNP transistor Q12. On the other hand, in the second push-pull circuit 832, the charge / discharge pulse 80 output from the signal generation circuit 81 is inverted as the inverted output signal 80 'as shown in FIG. , After the voltage is amplified by the voltage amplifying circuit 82, the input resistors R13, R1
4 is applied to the bases of an NPN transistor Q13 and a PNP transistor Q14.

In the first push-pull circuit 831, the collector of the NPN transistor Q11 is electrically connected to the drive potential Vcc, which is a high-potential power supply.
The collector of the NP transistor Q12 is electrically connected to a ground potential GND which is a low-potential-side power supply. In the second push-pull circuit 832, the NPN
The collector of the transistor Q13 is electrically connected to the drive potential Vcc, which is a high-potential power supply, and the collector of the PNP transistor Q14 is electrically connected to the ground potential GND, which is a low-potential power supply. .

Here, the NPN transistor Q11 and the PNP transistor Q12 of the first push-pull circuit 831
The pressure generating element 17 is electrically connected between a connection point P11 between the emitters of the second push-pull circuit 832 and a connection point P12 between the emitters of the NPN transistor Q13 and the PNP transistor Q14 of the second push-pull circuit 832. This pressure generating element 17 is also represented as a capacitive load C1, and has an internal resistance R10.

Further, in this embodiment, the primary coil L11 of the first transformer 91 is electrically connected between the collector of the NPN transistor Q11 of the first push-pull circuit 831 and the driving potential Vcc, Between the collector of the PNP transistor Q14 of the push-pull circuit 832 and the ground potential GND.
The secondary coil L12 of the transformer 91 is electrically connected. In the first transformer 91, the primary coil L11 includes a diode D18 and a capacitive element C23.
Are electrically connected. In the first transformer 91, a diode D19 is electrically connected to the secondary coil L12.

Similarly, the collector of the PNP transistor Q12 of the first push-pull circuit 831 and the ground potential G
The diode D4 and the primary coil L13 of the second transformer 92 are electrically connected to the driving potential Vcc between the collector of the NPN transistor Q13 of the second push-pull circuit 832 and the driving potential Vcc. Transformer 9 of 2
The two secondary coils L14 are electrically connected. In the second transformer 92, a diode D15 is electrically connected to the primary coil L13. In the second transformer 92, a diode D16 and a capacitive element C25 are electrically connected to the secondary coil L14. In the present embodiment, the first transformer 91 and the second transformer 92 have a core material having a small hysteresis loss from the viewpoint of suppressing heat loss.
For example, ferrite or amorphous materials are more suitable than materials such as silicon steel plates. Note that a ground potential GN is provided between the drive potential Vcc and the second transformer 92.
A capacitor C26 is electrically connected between the capacitor D and the capacitor D.
In the drive signal generation circuit 8 configured as described above, FIG.
As shown in (B), the charge / discharge pulse 80 generated by the waveform generation circuit 81 linearly rises in voltage from time T21 to time T22, and then rises from time T22 to time T23.
Until the time T23.
The potential drops linearly from to T24. On the other hand, as shown in FIG.
1. An inverted output signal 80 'of the charge / discharge pulse 80 generated in step 1.
Is, after a linear voltage drop from time T21 to time T22, is kept at a constant potential from time T22 to time T23, and thereafter, from time T23 to time T24.
The potential rises linearly during the period.

Therefore, at time T21, the base potential of the NPN transistor Q11 in the first push-pull circuit 831 becomes higher than the emitter potential, and the base potential of the PNP transistor Q14 in the second push-pull circuit 832 increases. When the potential becomes lower than the potential, the NPN transistor Q11 and the PNP transistor Q14 are turned on.

As a result, the pressure generating element 17 is charged from the drive potential Vcc side via the NPN transistor Q11. At this time, since the primary coil L11 of the first transformer 91 is electrically connected between the collector of the NPN transistor Q11 and the driving potential Vc, the primary coil L11 is induced by a charging current. Electric power (back electromotive force) is generated to lower the collector potential of NPN transistor Q11. Therefore, as shown in FIG. 6A, at the time of charging, the voltage between the emitter and the collector of the NPN transistor Q11 is compared with the potential difference between the potential of the pressure generating element 17 and the drive potential Vcc.
Only the induced electromotive force of the primary coil L11 decreases,
The potential is represented by V11. Also, the first transformer 9
When the charging current flows through the primary coil L11, the first
In the transformer 91, a secondary induced electromotive force is generated in the secondary coil L12 to raise the collector potential of the PNP transistor Q14.

For example, when the winding ratio between the primary coil L11 and the secondary coil L12 is 1: 1 in the first transformer 91, the secondary coil L12 has a voltage substantially equal to that of the primary coil L12. Occurs. Therefore, as shown in FIG. 6A, during charging, the voltage between the emitter and the collector of the PNPN transistor Q14 does not add the potential difference between the potential of the pressure generating element 17 and the ground potential GND, but the first voltage. Only the electromotive force of the secondary coil L12 of the transformer 91 decreases, and its potential is represented by V12.

On the other hand, at time T23, the potential of the charging / discharging pulse 80 decreases and the first push-pull circuit 831
As a result, the base potential of the PNP transistor Q12 becomes lower than the emitter potential, and the inverted output signal 80 'of the charging / discharging pulse 80 rises, so that the second push-pull circuit 83
2, when the base potential becomes higher than the emitter potential in the NPN transistor Q13 and the PNP transistor Q12 and the NPN transistor Q13 are turned on, discharge from the pressure generating element 17 to the ground potential GND via the PNP transistor Q12 occurs. At this time, between the collector of the PNP transistor Q12 and the ground GND,
Since the primary coil L13 of the second transformer 92 is electrically connected, an induced electromotive force is generated in the primary coil L13 by the discharge current, and as shown in FIG. Raise the collector potential of. Therefore, at the time of discharging, the PNP transistor Q
The voltage between the emitter and the collector of the pressure generating element 17 is
Compared with the potential difference between the potential of the second transformer and the ground GND, only the induced electromotive force of the primary coil L13 of the second transformer decreases, and the potential is represented by V21.

When a discharge current flows through the primary coil L13 of the second transformer 92, a secondary induced electromotive force is generated in the secondary coil L14 of the second transformer 92.
As shown in FIG. 6A, the collector potential of the NPN transistor Q13 is reduced. For example, when the turn ratio between the primary coil L13 and the secondary coil L14 is 1: 1 in the second transformer 92, a voltage substantially equal to that of the primary coil L13 is generated in the secondary coil L14. . Therefore, at the time of discharging, the voltage between the emitter and the collector of the NPN transistor Q13 does not add the potential difference between the potential of the pressure generating element 17 and the drive Vcc as it is, but generates the electromotive force of the secondary coil L14 of the second transformer 92. Only a minute drops, and its potential is represented by V22.

As described above, in this embodiment, the pressure generating element 1
7 during charging and discharging, the voltage between the emitter and collector of the NPN transistor Q11 and the PNP transistor Q12 is changed by the induced electromotive force in the primary coil L11 of the first transformer 91 and the primary coil L13 of the second transformer 92. As a result, heat generation of the NPN transistor Q11 and the PNP transistor Q12 can be suppressed. Further, when charging and discharging the pressure generating element 17, a current also flows through the PNP transistor Q 14 and the NPN transistor Q 13. The emitter-collector voltage of the PNP transistor Q 14 and the NPN transistor Q 13 Secondary coil L12 and second transformer 9
Since it is reduced by the electromotive force in the secondary coil L14, heat generation of the PNP transistor Q14 and the NPN transistor can be suppressed. Therefore, no device is required in the inkjet recording device 1.

During charging and discharging, NPN transistors Q11 and Q13 and PNP transistor Q1
2. Since heat generation in Q14 is small and heat generation occurs in these transistors in a dispersed manner, there is an advantage that each transistor is small and can be selected with priority given to frequency characteristics.

Further, the first and second transformers 91,
Even when the induced electromotive force at the terminal 92 is used, when the charging current or the discharging current does not flow, the induced electromotive force is not generated in the first and second transformers 91 and 92. Has no effect.

[0046]

As described above, in the ink jet recording apparatus according to the present invention, the voltage between the emitter and collector of the push-pull connected transistor is reduced by the induced electromotive force of the inductor in the current amplifying circuit of the drive signal generating circuit. Therefore, power loss which causes heat generation in the transistor can be reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a main part of an ink jet recording apparatus.

FIG. 2 is a block diagram illustrating an overall configuration of the inkjet recording apparatus.

FIG. 3 is a circuit diagram showing a connection relationship between a drive signal generation circuit and a pressure generation element in the inkjet recording apparatus according to the first embodiment of the present invention.

4A and 4B are waveform diagrams showing potential changes such as terminal voltage of a pressure generating element when the drive signal generation circuit shown in FIG. 3 is used, and FIGS. FIG. 4 is a waveform diagram of a charge / discharge pulse applied to the pulsating circuit.

FIG. 5 is a circuit diagram showing a connection relationship between a drive signal generation circuit and a pressure generation element in an ink jet recording apparatus according to Embodiment 2 of the present invention.

FIGS. 6A, 6B, and 6C are waveform diagrams showing potential changes such as terminal voltages of pressure generating elements when the drive signal generation circuit shown in FIG. 5 is used, and FIG. FIG. 3 is a waveform diagram of a charge / discharge pulse applied to a base of a transistor and a waveform diagram of an inverted signal thereof.

FIG. 7 is a circuit diagram showing a connection relationship between a driving signal generation circuit and a pressure generating element in a conventional ink jet recording apparatus.

8 is a waveform diagram showing a potential change such as a terminal voltage of a pressure generating element when the drive signal generation circuit shown in FIG. 7 is used.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 inkjet recording device 5 print engine 6 control unit 8 drive signal generation circuit 17 pressure generating element 40 print controller 80 charge / discharge pulse 80 ′ inverted output signal of charge / discharge pulse 81 signal generation circuit 82 voltage amplification circuit 83 current amplification circuit 90 transformer 91 First transformer 92 Second transformer 111 Nozzle opening 113 Pressure generating chamber 830 Push-pull circuit 831 First push-pull circuit 832 Second push-pull circuit COM Drive signal L1, L11, L13 Primary coil L2, L12, L14 Primary coil Q1, Q11, Q13 NPN transistor Q2, Q12, Q14 PNP transistor

Claims (2)

[Claims] 1. A pressure generating element for discharging ink droplets from a nozzle opening by pressurizing ink in a pressure generating chamber communicating with a nozzle opening, and a driving signal generation for generating a driving signal to be applied to the pressure generating element. Means, the drive signal generating means includes: a waveform generating circuit that generates a signal that defines a waveform of the drive signal; and a current amplifying circuit that amplifies an output from the waveform generating circuit. A push-pull circuit in which a transistor is push-pull connected between a high-potential power supply and a low-potential power supply, and an output signal from the waveform generation circuit is applied to each base of the transistor; A first coil electrically connected between the push-pull circuit and the high-potential-side power supply, the push-pull circuit and the low-potential-side power supply, A second coil electrically connected therebetween, wherein the pressure generating element is electrically connected between a connection point of a transistor in the push-pull circuit and the low potential side power supply. Characteristic inkjet recording device. 2. A pressure generating element for discharging ink droplets from the nozzle opening by pressurizing ink in a pressure generating chamber communicating with the nozzle opening, and a drive signal generating for generating a driving signal to be applied to the pressure generating element. Means, the drive signal generating means includes: a waveform generating circuit that generates a signal that defines a waveform of the drive signal; and a current amplifying circuit that amplifies an output from the waveform generating circuit. The current amplification circuit has a first transistor in which a transistor is push-pull connected between a high-potential-side power supply and a low-potential-side power supply, and an output signal from the waveform generation circuit is applied to each base of the transistor. A push-pull circuit, a transistor being push-pull connected between a high-potential-side power supply and a low-potential-side power supply, and a waveform generation circuit provided at each base of the transistor; A second push-pull circuit to which the inverted output signal is applied, a primary coil electrically connected between the first push-pull circuit and the high-potential-side power supply, A first transformer having a secondary coil electrically connected between a circuit and the low-potential-side power supply; and a primary coil electrically connected between the first push-pull circuit and the low-potential-side power supply. A second transformer having a secondary coil electrically connected between the second push-pull circuit and the high-potential-side power supply, wherein the first push-pull circuit and An ink jet recording apparatus, wherein the pressure generating element is electrically connected between connection points of transistors in the second push-pull circuit.