JP3721876B2 - Inkjet recording device - Google Patents

Description

[0001]
BACKGROUND 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]
[Prior art]
In a recording head of an ink jet recording apparatus used as an ink jet printer or an ink jet plotter, a pressure generating chamber in which pressure generating elements such as a plurality of piezoelectric vibrators (for example, piezo elements) corresponding to the plurality of nozzle openings communicate with the nozzle openings Ink droplets are ejected from the nozzle openings by pressurizing the ink. In the ink jet recording apparatus, as shown in FIG. 7, the drive signal generation circuit that generates a drive signal for driving the recording head generates a signal that outputs a charge / discharge pulse 80 that defines the timing of charge / discharge of the pressure generating element 17. The circuit 81, the voltage amplification circuit 82 for the charge / discharge pulse 80, and the NPN transistor Q1 and the PNP transistor Q2 that are push-pull connected based on the charge / discharge pulse 80 perform a switching operation and are amplified to the pressure generating element 17 The current amplification circuit 83 that outputs the drive signal COM is configured.
[0003]
Here, since the pressure generating element 17 is represented as the capacitive load C1, for example, when the driving signal COM as shown in FIG. 8 is applied, the pressure generating element 17 is discharged and charged based on the driving signal COM. And repeat. That is, in the drive amplifier circuit 83, the NPN transistor Q1 is turned on at time T1 to charge the pressure generating element 17, and instead of turning off the NPN transistor Q1 at time T2, the PNP transistor Q2 is turned on. Discharge from the generating element 17 to the ground potential GND is performed. Accordingly, charging current I1 and discharging current I2 flow through NPN transistor Q1 and PNP transistor Q2.
[0004]
[Problems to be solved by the invention]
However, in the current amplifying circuit 83 shown in FIG. 7, during charging or discharging, the potential V0 corresponding to the potential difference between the driving potential Vcc or the ground potential GND and the driving signal COM remains as it is as the emitter of the NPN transistor Q1 or PNP transistor Q2. Since the voltage is applied between the collectors, the amount of heat generated by the NPN transistor Q1 and the PNP transistor Q2 is large. For this reason, since the reliability of the NPN transistor Q1 and the PNP transistor Q2 is likely to deteriorate, 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]
[Means for Solving the Problems]
In order to solve the above problems, in the present invention, a pressure generating element that discharges 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 In the ink jet recording apparatus, the drive signal generation means generates a signal that defines a waveform of the drive signal, and amplifies the output from the waveform generation circuit. The current amplifier circuit includes a transistor having a push-pull connection between a high-potential side power source and a low-potential side power source, and an output signal from the waveform generation circuit is connected to each base of the transistor. A push-pull circuit to be applied; a first coil electrically connected between the push-pull circuit and the high-potential side power supply; and the push-pull circuit. And a second coil electrically connected between the low potential side power source 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 source. It is characterized by being connected.
[0007]
In the present invention, since the output signal from the waveform generation circuit is applied to each base of the NPN transistor and the PNP transistor that are push-pull connected between the high potential side power source and the low potential side power source in the current amplifier circuit, As the potential of the output signal changes, charging of the pressure generating element from the high potential side power source via the NPN transistor and discharging from the pressure generating element to the low potential side power source via the PNP transistor occur. Here, since the first coil is electrically connected between the NPN transistor of the push-pull circuit and the high-potential side power supply, an induced electromotive force is generated in the first coil due to the charging current, The collector potential of the NPN transistor is lowered. Therefore, the voltage between the emitter and the collector of the NPN transistor decreases during charging. In addition, 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 due to the discharge current, and the PNP Increase the collector potential of the transistor. Therefore, the voltage between the emitter and the collector of the PNP transistor is reduced during discharge. Therefore, the emitter-collector voltages of the NPN transistor and the PNP transistor can be lowered at the time of charging and at the time of discharging, respectively, and heat generation at these transistors can be prevented.
[0008]
In another embodiment of the present invention, a pressure generating element that ejects ink droplets from the nozzle opening and a drive signal to be applied to the pressure generating element are generated by pressurizing ink in a pressure generating chamber communicating with the nozzle opening. In the ink jet recording apparatus having the drive signal generation unit, the drive signal generation unit includes a waveform generation circuit that generates a signal that defines a waveform of the drive signal, and current amplification for amplifying the output from the waveform generation circuit The transistor is push-pull connected between the high potential side power source and the low potential side power source, and the output signal from the waveform generation circuit is applied to each base of the transistor. A transistor is push-pull connected between the first push-pull circuit and the high-potential side power source and the low-potential side power source, and the waveform is connected to each base of the transistor. A primary side coil is electrically connected between the second push-pull circuit to which the inverted output signal from the circuit is applied, and the first push-pull circuit and the high-potential side power source, A first transformer in which a secondary coil is electrically connected between a push-pull circuit and the low-potential side power source, and a primary-side coil between the first push-pull circuit and the low-potential side power source And a second transformer in which a secondary coil is electrically connected between the second push-pull circuit and the high-potential-side power supply. The pressure generating element is electrically connected between the connection points of the transistors in the push-pull circuit and the second push-pull circuit.
[0009]
Also in the present invention, in the current amplifier circuit, the output signal from the waveform generation circuit and the inverted output signal are respectively connected to the bases of the two sets of NPN transistors and PNP transistors that are push-pull connected between the high potential side power source and the low potential side power source Is applied, charging and discharging occur as the potential of the output signal changes. That is, during charging, a charging current flows from the high potential side power source to the pressure generating element via the NPN transistor of the first push-pull circuit.
[0010]
Here, since the primary coil of the first transformer is electrically connected between the NPN transistor of the first push-pull circuit and the high-potential side power supply, the primary coil of the first transformer is connected to the primary coil of the first transformer. Causes an induced electromotive force due to the charging current, which lowers the collector potential of the NPN transistor. In the first transformer, secondary induction occurs in the secondary coil, and electromotive force is generated between the coil terminals. This electromotive force raises the collector potential of the PNP transistor of the second push-pull circuit. Let Accordingly, during charging, the voltage between the emitter and the collector of the NPN transistor of the first push-pull circuit and the PNP transistor of the second push-pull circuit is lowered, so that heat generation in these transistors can be suppressed.
[0011]
On the other hand, during discharging, a charging current flows from the pressure generating element via the PNP transistor of the first push-pull circuit. Here, since the primary coil of the second transformer is electrically connected between the PNP transistor of the first push-pull circuit and the low-potential side power supply, the primary coil of the second transformer is connected to the primary coil of the second transformer. Causes an induced electromotive force due to the discharge current, and raises the collector potential of the PNP transistor. In the second transformer, secondary induction occurs in the secondary coil, and an electromotive force is generated between the coil terminals. This electromotive force lowers the collector potential of the NPN transistor of the second push-pull circuit. Let Accordingly, during discharge, the voltage between the emitter and the collector of the PNP transistor of the first push-pull circuit and the NPN transistor of the second push-pull circuit is lowered, so that heat generation in these transistors can be suppressed.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the drawings. Note that any form described below basically corresponds to the drive signal generation circuit described with reference to FIG. 7 because the push-pull circuit is used in the current amplification circuit of the drive signal generation circuit. The parts having the function will be described with the same reference numerals. In addition, since Embodiments 1 and 2 described below have the same overall configuration as an ink jet recording apparatus, before describing the characteristic configuration of each mode, a configuration common to each mode is described. This will be described with reference to FIGS.
[Overall configuration of inkjet recording apparatus]
FIG. 1 is a perspective view showing a configuration of an ink jet recording apparatus to which the present invention is applied. In FIG. 1, an ink jet recording apparatus 1 of this embodiment is used by being connected to a computer (not shown) together with a scanner (not shown). By loading and executing a predetermined program on this computer, these devices as a whole function as a recording device. In the computer, an application program operates under a predetermined operating system, and displays an image on a CRT display (not shown) while performing predetermined processing on an image read from the scanner. Further, when the application program issues a print command, the computer converts image data read via the scanner, character data input via the keyboard, and the like into data used by the inkjet recording apparatus 1, and the inkjet recording apparatus 1. Output to.
[0013]
In the inkjet recording apparatus 1, the carriage 101 is connected to the carriage motor 103 of the carriage mechanism 12 via the timing belt 102, and is guided by the guide member 104 to reciprocate in the paper width direction of the recording paper 105 (medium). ing. In the ink jet recording apparatus 1, a paper feed mechanism 11 using a paper feed roller 106 is also formed. An ink jet recording head 10 is attached to the carriage 101 on the surface facing the recording paper 105, and in the example shown in the drawing, the lower surface. The recording head 10 receives ink replenishment from the ink cartridge 107 placed on the upper part of the carriage 101, ejects ink droplets onto the recording paper 105 in accordance with the movement of the carriage 101, and forms dots. Print images and text on
[0014]
Further, a capping device 108 is configured in the non-printing area (non-recording area) of the inkjet recording apparatus 1 and seals the nozzle openings of the recording head 10 during printing pause. Therefore, it is possible to prevent the ink from thickening or forming an ink film due to the solvent scattering from the ink during the suspension of printing. Therefore, it is possible to prevent the nozzles from being clogged during the suspension of printing. The capping device 108 receives ink droplets from the recording head 10 by a flushing operation performed during a printing operation. A wiping device 109 is arranged in the vicinity of the capping device 108. The wiping device 109 is configured to wipe the ink fountain and paper dust adhering thereto by wiping the surface of the recording head 10 with a blade or the like. Yes.
[0015]
FIG. 2 is a functional block diagram of the inkjet recording apparatus 1 of the present embodiment.
[0016]
In FIG. 2, the inkjet recording apparatus 1 includes a print controller 40 and a print engine 5. The print controller 40 includes an interface 43 that receives recording data including multilevel hierarchical information from a computer (not shown), a RAM 44 that stores various data such as recording data including multilevel hierarchical information, and various types of data. ROM 45 storing a routine for performing data processing, a control unit 6 including a CPU, an oscillation circuit 47, a drive signal generation circuit 8 for generating a drive signal COM to the recording head 10, and dot pattern data And an interface 49 for transmitting the developed print data and drive signal to the print engine 5.
[0017]
The recording data including the multilevel hierarchy information sent from the computer 90 or the like is held in the reception buffer 44A inside the recording apparatus via the interface 43. The recording data held in the reception buffer 44A is sent to the intermediate buffer 44B after command analysis is performed. In the intermediate buffer 44B, recording data in an intermediate format converted into an intermediate code by the control unit 6 is held, and processing for adding the print position, modification type, size, font address, etc. of each character is controlled. This is executed by the unit 6. Next, the control unit 6 analyzes the recording data in the intermediate buffer 44B, and develops and stores the binarized dot pattern data after decoding the hierarchical data as will be described later in the output buffer 44C.
[0018]
When dot pattern data corresponding to one scan of the recording head 10 is obtained, this 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.
[0019]
The print engine 5 includes the paper feeding mechanism 11, the carriage mechanism 12, and the recording head 10. 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.
[0020]
The recording head 10 ejects ink droplets from each nozzle opening at a predetermined timing, and the drive signal COM output from the drive signal generation circuit 8 is sent to the recording head 10 via the interface 49 and the flexible wiring board 110. Is output.
[0021]
The recording head 10 has, for example, 64 nozzles in the sub-scanning direction, and ejects ink droplets from the nozzle openings 111 at a predetermined timing. In the print controller 40, the recording data SI developed into dot pattern data is serially output to the recording head 10 via the interface 49 and the flexible wiring board 110 in synchronization with the clock signal CLK from the oscillation circuit 7. Serially transferred to the shift register 13. The serially transferred recording data SI is once latched by the latch circuit 14. The latched recording data SI is boosted 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, by a level shifter 15 that is a voltage amplifier. The recording data boosted to a predetermined voltage is given to the nozzle selection circuit 16. A drive signal COM from the drive signal generation circuit 8 is applied to the input side of the nozzle selection circuit 16, 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 formed in the same number (for example, 64) as the nozzle openings 111 having a one-to-one relationship with the nozzle openings 111.
[0022]
Here, the recording data SI controls the operation of the nozzle selection circuit 16. For example, during a period in which the recording data SI applied to the nozzle selection circuit 16 is “1”, the drive signal COM is applied to the pressure generating element 17, and the pressure generating element 17 expands and contracts according to this signal. As a result, the pressure generating element 17 pressurizes the ink in the pressure generating chamber 113 that communicates with the nozzle opening 111 and discharges ink droplets from the nozzle opening 111. On the other hand, during the period in which the recording 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 interrupted.
[Embodiment 1]
FIG. 3 is a circuit diagram showing a connection relationship between the drive signal generation circuit 8 and the pressure generation element 17 in the ink jet recording apparatus according to Embodiment 1 of the present invention. 4A and 4B are waveform diagrams showing potential changes such as the terminal voltage of the pressure generating element when the drive signal generating circuit 8 is used, respectively, and the waveform generating circuit is applied to the base of the transistor. It is a wave form diagram of a charge / discharge pulse.
[0023]
In FIG. 3, the drive signal generation circuit 8 configured in the ink jet recording apparatus of the present embodiment also includes a signal generation circuit 81 that outputs a charge / discharge pulse 80 that defines the charge / discharge timing of the pressure generating element 17, and the charge / discharge pulse 80. A voltage amplification circuit 82 for the discharge pulse 80 and a current amplification circuit 83 that outputs a common drive signal COM amplified to the pressure generating element 17 based on the charge / discharge pulse 80 are configured. A push-pull circuit 830 including an NPN transistor Q1 and a PNP transistor Q2 that are push-pull connected is formed.
[0024]
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 each of the NPN transistor Q1 and the PNP transistor Q2 via the input resistors R1 and R2. Applied to the base. In the push-pull circuit 830, the collector of the NPN transistor Q1 is electrically connected to the drive potential Vcc side which is the high potential side power supply, and the collector of the PNP transistor Q2 is the ground potential GND which is the low potential side power supply. Is electrically connected to the side. Further, the pressure generating element 17 is electrically connected to the ground potential GND with respect to the connection point P1 between the emitters of the NPN transistor Q1 and the PNP transistor Q2. This pressure generating element 17 is represented as a capacitive load C1 and has an internal resistance R10.
[0025]
In this embodiment, the primary coil L1 of the transformer 90 is electrically connected between the collector of the NPN transistor Q1 of the push-pull circuit 830 and the drive potential Vcc, and between the collector of the PNP transistor Q2 and the ground potential GND. The secondary coil L2 of the transformer 90 is electrically connected. In this transformer 90, a diode D17 is electrically connected to the closed circuit including the secondary coil L2, and an electromotive force generated in the secondary coil L2 when a discharge occurs from the PNP transistor Q2 to the ground potential GND. Is applied to the collector of the PNP transistor Q2. In the present embodiment, for the transformer 90, from the viewpoint of suppressing heat loss, ferrite or amorphous type is more suitable than a core material such as a silicon steel plate that has less hysteresis loss.
[0026]
A capacitive element C22 is connected between the drive potential Vcc and the transformer 90 between the ground potential GND.
[0027]
In the drive signal generation circuit 8 configured as described above, as shown in FIG. 4B, the charge / discharge pulse 80 generated by the waveform generation circuit 81 rises linearly from time T11 to time T12. After that, the voltage is held at a constant potential from time T12 to time T13, and then the potential decreases linearly from time T13 to time T14.
[0028]
Therefore, when the base potential becomes higher than the emitter potential in the NPN transistor Q1 at time T11, the NPN transistor Q1 is turned on, and the pressure generating element 17 is charged via the NPN transistor Q1 from the drive potential Vcc side. At this time, since the primary coil L1 of the transformer 90 is electrically connected between the collector of the NPN transistor Q1 and the drive potential Vc, an induced electromotive force (reverse voltage) is applied to the primary coil L1 by a charging current. Electromotive force) is generated and the collector potential of the NPN transistor Q1 is lowered as shown in FIG. Therefore, at the time of charging, the emitter-collector voltage of the NPN transistor Q1 is reduced by the induced electromotive force of the primary coil L1 as compared with the potential difference between the potential of the pressure generating element 17 and the driving potential Vcc. The potential is represented by V1. During this time, the PNP transistor Q2 is in an off state.
[0029]
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 is turned on, and the pressure generating element 17 passes through the PNP transistor Q2 to the ground. A discharge to the potential GND occurs. At this time, since the secondary side coil L2 of the transformer 90 is electrically connected between the collector of the PNP transistor Q2 and the ground GND, an induced electromotive force (induced electromotive force ( As shown in FIG. 4A, the collector potential of the PNP transistor Q2 is raised. Therefore, at the time of discharge, the emitter-collector voltage of the PNP transistor Q2 is reduced by 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, the NPN transistor Q1 is in an off state.
[0030]
Thus, in the present embodiment, between the emitter and collector of the NPN transistor Q1 and the PNP transistor Q2 due to the induced electromotive force in the primary side coil L1 and the secondary side coil L2 of the transformer 90 during charging and discharging of the pressure generating element 17 Since the voltage is lowered, heat generation of the NPN transistor Q1 and the PNP transistor Q2 can be suppressed. Therefore, the inkjet recording apparatus 1 does not require a large cooling device for the NPN transistor Q1 and the PNP transistor Q2.
[Embodiment 2]
FIG. 5 is a circuit diagram showing a connection relationship between the drive signal generation circuit 8 and the pressure generation element 17 in the ink jet recording apparatus according to Embodiment 1 of the present invention. 6A, 6B, and 6C are waveform diagrams showing potential changes such as the terminal voltage of the pressure generating element when the drive signal generating circuit 8 is used, and the base of the transistor from the waveform generating circuit. FIG. 3 is a waveform diagram of a charge / discharge pulse applied to the, and a waveform diagram of an inverted output signal of the charge / discharge pulse.
[0031]
In FIG. 5, the drive signal generation circuit 8 configured in the ink jet recording apparatus of this embodiment also includes a signal generation circuit 81 that outputs a charge / discharge pulse 80 that defines the charge / discharge timing of the pressure generating element 17, and the charge / discharge pulse 80. A voltage amplification circuit 82 for the discharge pulse 80 and a current amplification circuit 83 for outputting a common drive signal COM amplified to the pressure generating element 17 based on the charge / discharge pulse 80 are configured.
[0032]
In this embodiment, the current amplifying circuit 83 includes a first transistor in which an NPN transistor Q11 and a PNP transistor Q12 are push-pull connected between a drive potential Vcc that is a high potential power source and a ground potential GND that is a low potential power source. The push-pull circuit 831 and the second push-pull circuit 832 in which the NPN transistor Q13 and the PNP transistor Q14 are push-pull connected between the drive potential Vcc and the ground potential GND are configured.
[0033]
Among these push-pull circuits, in the first push-pull circuit 831, the charge / discharge pulse 80 output from the signal generation circuit 81 is voltage amplified by the voltage amplification circuit 82 as shown in FIG. Thereafter, the waveform is applied as it is to the bases of the NPN transistor Q11 and the PNP transistor Q12 via the input resistors R12 and R13. In contrast, in the second push-pull circuit 832, the charge / discharge pulse 80 output from the signal generation circuit 81 is in a state where the waveform is inverted as an inverted output signal 80 ′, as shown in FIG. The voltage is amplified by the voltage amplification circuit 82 and then applied to the bases of the NPN transistor Q13 and the PNP transistor Q14 via the input resistors R13 and R14.
[0034]
In the first push-pull circuit 831, the collector of the NPN transistor Q11 is electrically connected to the drive potential Vcc side that is the high potential side power supply, and the collector of the PNP transistor Q12 is the ground that is the low potential side power supply. It is electrically connected to the potential GND side. In the second push-pull circuit 832, the collector of the NPN transistor Q13 is electrically connected to the drive potential Vcc side which is the high potential side power supply, and the collector of the PNP transistor Q14 is the ground potential which is the low potential side power supply. It is electrically connected to the GND side.
[0035]
Here, the connection point P11 between the emitters of the NPN transistor Q11 and the PNP transistor Q12 of the first push-pull circuit 831 and the connection point P12 between the emitters of the NPN transistor Q13 and the PNP transistor Q14 of the second push-pull circuit 832 In between, the pressure generating element 17 is electrically connected. This pressure generating element 17 is also represented as a capacitive load C1 and has an internal resistance R10.
[0036]
Furthermore, 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 drive potential Vcc, and the second push-pull circuit The diode D3 and the secondary coil L12 of the first transformer 91 are electrically connected between the collector of the PNP transistor Q14 of the circuit 832 and the ground potential GND. In the first transformer 91, a diode D18 and a capacitive element C23 are electrically connected to the primary coil L11. In the first transformer 91, a diode D19 is electrically connected to the secondary coil L12.
[0037]
Similarly, a primary coil L13 of the diode D4 and the second transformer 92 is electrically connected between the collector of the PNP transistor Q12 of the first push-pull circuit 831 and the ground potential GND, and the second push-pull circuit 831 The secondary coil L14 of the second transformer 92 is electrically connected between the collector of the NPN transistor Q13 of the pull circuit 832 and the drive potential Vcc. 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 this embodiment, with respect to the first transformer 91 and the second transformer 92, from the viewpoint of suppressing heat loss, the ferrite material or the amorphous material is less than the core material, for example, a silicon steel plate or the like, which has less hysteresis loss. Is suitable.
Note that a capacitive element C26 is electrically connected between the drive potential Vcc and the second transformer 92 and the ground potential GND.
In the drive signal generation circuit 8 configured as described above, as shown in FIG. 6B, the charge / discharge pulse 80 generated by the waveform generation circuit 81 rises linearly from time T21 to time T22. After that, the voltage is maintained at a constant potential from time T22 to time T23, and then the potential decreases linearly from time T23 to time T24. On the other hand, as shown in FIG. 6C, the inverted output signal 80 ′ of the charge / discharge pulse 80 generated by the waveform generation circuit 81 linearly drops from time T21 to time T22. Thereafter, the voltage is held at a constant potential from time T22 to time T23, and thereafter, the potential rises linearly from time T23 to time T24.
[0038]
Therefore, at time T21, the base potential is higher than the emitter potential in the NPN transistor Q11 in the first push-pull circuit 831, and the base potential is higher than the emitter potential in the PNP transistor Q14 in the second push-pull circuit 832. When low, the NPN transistor Q11 and the PNP transistor Q14 are turned on.
[0039]
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 side coil L11 of the first transformer 91 is electrically connected between the collector of the NPN transistor Q11 and the drive potential Vc, the primary side coil L11 is induced by the charging current. Electric power (back electromotive force) is generated, and the collector potential of the NPN transistor Q11 is lowered. Accordingly, as shown in FIG. 6A, during charging, the emitter-collector voltage 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, so that the first transformer 91 The primary electromotive force of the primary side coil L11 is reduced, and the potential is represented by V11. Further, when a charging current flows through the primary side coil L11 of the first transformer 91, a secondary induced electromotive force is generated in the secondary side coil L12 of the first transformer 91, and the collector potential of the PNP transistor Q14 is increased. Raise.
[0040]
For example, when the turns ratio of the primary side coil L11 and the secondary side coil L12 is 1: 1 in the first transformer 91, a voltage substantially equal to the primary side coil L12 is generated in the secondary side coil L12. . Therefore, as shown in FIG. 6A, during charging, the voltage between the emitter and the collector of the PNPN transistor Q14 is not the same as the potential difference between the potential of the pressure generating element 17 and the ground potential GND. Only the electromotive force of the secondary side coil L12 of the transformer 91 is lowered, and the potential is represented by V12.
[0041]
On the other hand, at time T23, the potential of the charge / discharge pulse 80 decreases, the base potential becomes lower than the emitter potential in the PNP transistor Q12 in the first push-pull circuit 831, and the inverted output signal 80 ′ of the charge / discharge pulse 80 When the base potential becomes higher than the emitter potential in the NPN transistor Q13 in the second push-pull circuit 832 and the PNP transistor Q12 and the NPN transistor Q13 are turned on, the pressure generation element 17 passes through the PNP transistor Q12. Discharging to the ground potential GND occurs. At this time, since the primary side coil L13 of the second transformer 92 is electrically connected between the collector of the PNP transistor Q12 and the ground GND, an induced electromotive force is generated in the primary side coil L13 by the discharge current. As shown in FIG. 6A, the collector potential of the PNP transistor Q12 is raised. Therefore, at the time of discharge, the emitter-collector voltage of the PNP transistor Q12 is equal to the induced electromotive force of the primary coil L13 of the second transformer as compared with the potential difference between the potential of the pressure generating element 17 and the ground GND. The potential decreases and is represented by V21.
[0042]
When a discharge current flows through the primary coil L13 of the second transformer 92, secondary induced electromotive force is generated in the secondary coil L14 of the second transformer 92, as shown in FIG. Thus, the collector potential of the NPN transistor Q13 is lowered. For example, when the turn ratio of the primary side coil L13 and the secondary side coil L14 is 1: 1 in the second transformer 92, a voltage substantially equal to the primary side coil L13 is generated in the secondary side coil L14. . Therefore, at the time of discharging, the emitter-collector voltage of the NPN transistor Q13 is not the same as the potential difference between the potential of the pressure generating element 17 and the drive Vcc, but the electromotive force of the secondary coil L14 of the second transformer 92. The voltage drops by the minute, and the potential is represented by V22.
[0043]
As described above, in this embodiment, the NPN transistor Q11 is generated 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 during charging and discharging of the pressure generating element 17. Since the emitter-collector voltage of the PNP transistor Q12 is lowered, heat generation of the NPN transistor Q11 and the PNP transistor Q12 can be suppressed. In addition, when the pressure generating element 17 is charged and discharged, a current also flows through the PNP transistor Q14 and the NPN transistor Q13. The voltage between the emitter and the collector of the PNP transistor Q14 and the NPN transistor Q13 is Since it is lowered by the electromotive force in the secondary side coil L12 and the secondary side coil L14 of the second transformer 92, heat generation of the PNP transistor Q14 and the NPN transistor can be suppressed. Therefore, the inkjet recording apparatus 1 does not require a device.
[0044]
Further, since the heat generation in the NPN transistors Q11 and Q13 and the PNP transistors Q12 and Q14 is small during charging and discharging, and the heat generation is dispersed in these transistors, each transistor is small and has a frequency characteristic. There is also an advantage that selection can be made with priority given to.
[0045]
Furthermore, even if the induced electromotive force in the first and second transformers 91 and 92 is used, when the charging current or the discharge current does not flow, the first and second transformers 91 and 92 have induced electromotive force. Since it does not occur, the peak voltage of the drive signal COM is not affected.
[0046]
【The invention's effect】
As described above, in the ink jet recording apparatus according to the present invention, in the current amplification circuit of the drive signal generation circuit, the voltage between the emitter and the collector of the push-pull connected transistor is reduced by the induced electromotive force of the inductor. The power loss that causes heat generation can be kept low.
[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 ink jet 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 ink jet recording apparatus according to Embodiment 1 of the present invention.
4A and 4B are a waveform diagram showing a potential change such as a terminal voltage of a pressure generating element when the drive signal generating circuit shown in FIG. 3 is used, and a base of a transistor from the waveform generating circuit. It is a wave form diagram of the charge / discharge pulse applied to.
FIG. 5 is a circuit diagram showing a connection relationship between a drive signal generation circuit and a pressure generation element in an inkjet recording apparatus according to Embodiment 2 of the present invention.
FIGS. 6A, 6B, and 6C are a waveform diagram showing a potential change such as a terminal voltage of a pressure generating element when the drive signal generating circuit shown in FIG. 5 is used; FIG. 4 is a waveform diagram of charge / discharge pulses applied to the 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 drive signal generation circuit and a pressure generation element in a conventional inkjet recording apparatus.
8 is a waveform diagram showing a potential change such as a terminal voltage of the pressure generating element when the drive signal generating circuit shown in FIG. 7 is used.
[Explanation of symbols]
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 amplifier circuit
90 transformer
91 1st transformer
92 Second transformer
111 Nozzle opening
113 Pressure generation 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 transistors

Claims (2)

In an ink jet recording apparatus comprising a drive signal generating means for generating a drive signal to be applied to a pressure generating element for ejecting ink droplets,
The drive signal generation means includes
A current amplification circuit for amplifying a signal defining the drive signal waveform;
The current amplifier circuit is:
A pair of push-pull connected transistors connected between a high potential and a low potential, to which a signal defining the waveform of the drive signal is applied;
A first coil connected to the high potential side of the pair of push-pull connected transistors;
A second coil connected to the low potential side of the pair of push-pull transistors;
Have
The first coil and the second coil constitute one transformer,
A capacitive element connected between the high potential and the transformer and the low potential;
The pressure generating element includes a connection point, which is a push-pull connection of said pair of transistors, the ink jet recording apparatus which is connected between the low potential. In an ink jet recording apparatus comprising a drive signal generating means for generating a drive signal to be applied to a pressure generating element for ejecting ink droplets,
The drive signal generation means includes
A current amplification circuit for amplifying a signal defining the drive signal waveform;
The current amplifier circuit is:
A first push-pull circuit comprising a pair of push-pull transistors to which a signal defining a waveform of the drive signal is applied;
A second push-pull circuit comprising a pair of push-pull connected transistors to which a signal obtained by inverting the signal defining the waveform of the drive signal is applied;
A first transformer in which a primary coil is connected to the high potential side of the first push-pull circuit, and a secondary coil is connected to the low potential side of the second push-pull circuit;
A primary transformer having a second transformer connected to a low potential side of the first push-pull circuit and a secondary coil connected to a high potential side of the second push-pull circuit, respectively;
The ink jet recording apparatus, wherein the pressure generating element is connected between connection points of transistors in the first push-pull circuit and the second push-pull circuit.

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