JP2016052792A - Liquid discharge device and control method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress complication and an increase in size of a circuit generating a driving signal in a liquid discharge device provided with a liquid discharge head having actuators driven in accordance with the driving signal.SOLUTION: A liquid discharge device comprises: a liquid discharge head having a plurality of nozzles discharging liquid and a plurality of actuators being provided corresponding to the plurality of nozzles and being driven in accordance with a driving signal; a main drive circuit generating the driving signal by using a first transistor pair driven by an analog signal and supplying the driving signal generated to the liquid discharge head; and an auxiliary drive circuit generating one auxiliary driving signal by using a second transistor pair driven by a pulse signal and supplying the auxiliary driving signal generated to collectors of the individual transistors constituting the first transistor pair.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a liquid ejection apparatus and a control method for the liquid ejection apparatus.

  Ink jet printers that record images and documents by ejecting ink onto a print medium from a plurality of nozzles provided in a print head are widely used. In such an ink jet printer, an actuator provided corresponding to each nozzle of the print head is driven according to a drive signal supplied from a drive circuit, whereby a predetermined amount of ink is ejected from the nozzle at a predetermined timing. .

  A drive circuit for driving the print head generates a drive signal to be supplied to the print head using, for example, a transistor pair driven by an analog signal. At this time, the power consumption of each transistor constituting the transistor pair is a value obtained by multiplying the potential difference between the collector and the emitter by the current.

  Two auxiliary drives using a transistor pair (hereinafter referred to as “auxiliary transistor pair”) driven by a pulse signal separately from a transistor pair for generating a drive signal (hereinafter referred to as “main transistor pair”) There is known a drive circuit configured to generate a signal, supply one auxiliary drive signal to the collector of one transistor of the main transistor pair, and supply the other auxiliary drive signal to the collector of the other transistor ( For example, see Patent Document 1). In this driving circuit, since the auxiliary transistor pair is driven by a pulse signal, the power consumption is extremely small, and the potential difference between the collector and the emitter of each transistor constituting the main transistor pair is reduced. Power consumption is reduced, and as a result, power consumption for generating a drive signal can be reduced.

JP 2006-272907 A

  In the above conventional technique, the auxiliary transistor pair generates two auxiliary drive signals, and each auxiliary drive signal needs to be supplied to each transistor constituting the main transistor pair, so that the circuit tends to be complicated and large in size. It was in.

  Such a problem is not limited to a print head in an ink jet printer, but a liquid discharge head having a plurality of nozzles that discharge liquid and a plurality of actuators that are provided corresponding to the plurality of nozzles and that are driven according to a drive signal. This is a problem common to the liquid ejection devices provided.

  SUMMARY An advantage of some aspects of the invention is that a circuit for generating a drive signal is complicated in a liquid discharge apparatus including a liquid discharge head having an actuator driven in accordance with a drive signal.・ The purpose is to suppress the increase in size.

  In order to solve at least a part of the above problems, the present invention can be realized as the following forms or application examples.

Application Example 1 A liquid discharge apparatus,
A liquid discharge head having a plurality of nozzles for discharging liquid, and a plurality of actuators provided corresponding to the plurality of nozzles and driven according to a drive signal;
A main drive circuit that generates the drive signal using a first transistor pair driven by an analog signal, and supplies the generated drive signal to the liquid ejection head;
An auxiliary drive circuit that generates one auxiliary drive signal using a second transistor pair driven by a pulse signal and supplies the generated auxiliary drive signal to the collectors of the transistors that constitute the first transistor pair And a liquid ejection device.

  In this liquid ejecting apparatus, the second transistor pair is driven by a pulse signal, so that the power consumption is extremely small, and the potential difference between the collector and the emitter of each transistor constituting the first transistor pair is reduced. In addition, the power consumption in the first transistor pair is reduced, and as a result, the power consumption for generating the drive signal can be reduced. Further, in this liquid ejection apparatus, since one auxiliary drive signal generated by the auxiliary drive circuit is supplied to the collector of each transistor constituting the first transistor pair, two auxiliary drives are performed by the second transistor pair. Compared with the case where a signal is generated and each auxiliary drive signal is supplied to each of the transistors constituting the first transistor pair, it is possible to suppress the complexity and increase in size of the circuit that generates the drive signal.

[Application Example 2] The liquid ejection apparatus according to Application Example 1,
The liquid ejection apparatus, wherein the auxiliary drive circuit includes a pulse signal generation circuit that generates the pulse signal, and a feedback signal line that feeds back the auxiliary drive signal to the pulse signal generation circuit.

  In this liquid ejecting apparatus, the pulse signal generation circuit performs feedback control, so that the auxiliary drive signal can be supplied with the potential difference between the collector and the emitter of each transistor constituting the first transistor pair regardless of the fluctuation of the actuator load. It is possible to maintain the optimum signal as reduced, and the power consumption for generating the drive signal can be sufficiently reduced.

[Application Example 3] The liquid ejection apparatus according to Application Example 1 or Application Example 2,
The auxiliary drive circuit is configured such that the potential difference between the collector and the emitter of one of the transistors operating in the first transistor pair becomes a preset potential difference when the potential of the drive signal increases and decreases. A liquid ejection device that generates a signal.

  In this liquid ejection device, the potential difference between the collector and the emitter of each transistor constituting the first transistor pair is maintained at a preset potential difference, so that the power consumption for generating the drive signal can be sufficiently reduced. it can.

Application Example 4 The liquid ejection apparatus according to Application Example 3,
In the auxiliary drive circuit, when the potential rise rate during the potential rise period of the drive signal is equal to or greater than a threshold value, the potential difference between the collector and the emitter of the one transistor over the whole potential rise period is the preset potential difference. As described above, the liquid ejection apparatus that raises the potential of the auxiliary drive signal from before the start of the potential rise period.

  In this liquid ejection apparatus, even when the potential rise rate during the potential rise period of the drive signal is equal to or higher than the threshold value, the potential difference between the collector and the emitter of the operating transistor can be reduced while ensuring the normal operation of the transistor. The power consumption for generating the drive signal can be reduced.

[Application Example 5] The liquid ejection device according to Application Example 3,
In the auxiliary drive circuit, when the potential drop rate during the potential fall period of the drive signal is equal to or greater than a threshold value, the potential difference between the collector and the emitter of the one transistor over the whole potential drop period is the preset potential difference. As described above, the liquid ejection device that lowers the potential of the auxiliary drive signal from before the start of the potential drop period.

  In this liquid ejecting apparatus, even when the potential decrease rate during the potential decrease period of the drive signal is equal to or higher than the threshold value, the potential difference between the collector and the emitter of the operating transistor can be reduced while ensuring the normal operation of the transistor. The power consumption for generating the drive signal can be reduced.

  The present invention can be realized in various modes. For example, a drive circuit and a drive method for driving a liquid discharge head, a liquid discharge apparatus having such a liquid discharge head and a drive circuit, and the same Control method, printing apparatus having such a liquid discharge head and drive circuit, and printing by discharging ink as liquid, a printing method, a computer program for realizing the function of these method or apparatus, and the computer program Can be realized in the form of a recording medium on which is recorded.

It is explanatory drawing which shows schematic structure of the printing system in the Example of this invention. 2 is an explanatory diagram showing a schematic configuration centering on a control unit 40 of the printer 100. FIG. FIG. 6 is an explanatory diagram illustrating an example of various signals supplied to the print head 60. 4 is an explanatory diagram illustrating a configuration of a switching controller 61 of a print head 60. FIG. 2 is an explanatory diagram showing a schematic configuration of a drive circuit 80 for driving a print head 60. FIG. 6 is an explanatory diagram illustrating an example of auxiliary drive signals COMs generated by an auxiliary drive circuit 210. FIG. It is explanatory drawing which shows the modification of auxiliary drive signal COMs.

  Next, embodiments of the present invention will be described based on examples.

A. Example:
FIG. 1 is an explanatory diagram showing a schematic configuration of a printing system according to an embodiment of the present invention. The printing system of the present embodiment includes a printer 100 and a host computer 90 that supplies print data PD to the printer 100. The printer 100 is connected to the host computer 90 via the connector 12.

  The printer 100 of this embodiment is an ink jet printer that is one of liquid ejecting apparatuses that eject liquid. The printer 100 forms ink dots on a print medium by ejecting ink as a liquid, thereby recording characters, figures, images, and the like according to the print data PD.

  As shown in FIG. 1, the printer 100 includes a carriage 30 on which a print head 60 is mounted, a moving mechanism that performs main scanning for reciprocating the carriage 30 along a direction parallel to the axis of the platen 26, and a print medium. A transport mechanism that performs sub-scanning to transport the paper P in a direction intersecting the main scanning direction (sub-scanning direction), an operation panel 14 for performing various instruction / setting operations related to printing, and each unit of the printer 100 are controlled. And a control unit 40. The carriage 30 is connected to the control unit 40 via a flexible cable (FFC) (not shown).

  The transport mechanism that transports the paper P has a paper feed motor 22. The rotation of the paper feed motor 22 is transmitted to the paper transport roller (same) via a gear train (not shown), and the paper P is transported along the sub-scanning direction by the rotation of the paper transport roller.

  The moving mechanism for reciprocating the carriage 30 includes an endless drive belt between the carriage motor 32, a slide shaft 34 that is laid in parallel to the axis of the platen 26, and slidably holds the carriage 30, and the carriage motor 32. And a pulley 38 for tensioning 36. The rotation of the carriage motor 32 is transmitted to the carriage 30 via the drive belt 36, whereby the carriage 30 reciprocates along the slide shaft 34. The printer 100 detects an position of the carriage 30 (print head 60) along the main scanning direction, and an encoder (not shown) that outputs a pulse signal to the control unit 40 as the carriage motor 32 rotates. It has. Based on the pulse signal output from the encoder, the control unit 40 generates a timing signal PTS that defines the input timing of the drive signal selection signal SI & SP to the shift register 63 described later.

  The carriage 30 stores a plurality of inks each having a predetermined color (for example, cyan (C), light cyan (Lc), magenta (M), light magenta (Lm), yellow (Y), and black (K)). Ink cartridge 70 is mounted. The ink stored in the ink cartridge 70 mounted on the carriage 30 is supplied to the print head 60. The print head 60 includes a plurality of nozzles that eject ink and actuators (nozzle actuators) that are provided corresponding to the nozzles. In this embodiment, a piezoelectric element (piezoelectric element) that is a capacitive load is used as the nozzle actuator. When the nozzle actuator is driven by a drive signal to be described later, the vibration plate in the cavity (pressure chamber) communicating with the nozzle is displaced to cause a pressure change in the cavity, and the ink from the corresponding nozzle is changed by the pressure change. Is discharged. By adjusting the peak value of the drive signal used for driving the nozzle actuator and the voltage increase / decrease slope, the ink ejection amount (that is, the size of the dots to be formed) can be adjusted.

  FIG. 2 is an explanatory diagram showing a schematic configuration centering on the control unit 40 of the printer 100. The control unit 40 includes an interface 41 for inputting print data PD and the like input from the host computer 90, and a control unit 42 that executes predetermined arithmetic processing based on the print data PD input via the interface 41. , A paper feed motor driver 43 for driving and controlling the paper feed motor 22, a head driver 45 for driving and controlling the print head 60, a carriage motor driver 46 for driving and controlling the carriage motor 32, the drivers 43, 45 and 46, and the paper And an interface 47 for connecting the feed motor 22, the print head 60, and the carriage motor 32.

  The control unit 42 includes a CPU 51 that executes various arithmetic processes, a RAM 52 that temporarily stores and expands programs and data, and a ROM 53 that stores programs executed by the CPU 51. Various functions by the control unit 42 are realized by the CPU 51 operating based on a program stored in the ROM 53. Note that at least a part of the functions of the control unit 42 may be realized by operating an electric circuit included in the control unit 42 based on the circuit configuration.

  When the control unit 42 obtains the print data PD from the host computer 90 via the interface 41, the control unit 42 executes a predetermined process on the print data PD to eject ink from which nozzle of the print head 60, or which Generates nozzle selection data (drive signal selection data) that defines whether or not a certain amount of ink is to be ejected, and outputs control signals to the drivers 43, 45, and 46 based on the print data PD, drive signal selection data, etc. To do. The drivers 43, 45, and 46 output drive signals for driving the paper feed motor 22, the print head 60, and the carriage motor 32, respectively. For example, the head driver 45 supplies the print head 60 with a reference clock signal SCK, a latch signal LAT, a drive signal selection signal SI & SP, a channel signal CH, and a drive signal COM. The paper feed motor 22, the print head 60, and the carriage motor 32 operate according to the drive signal, whereby the printing process on the paper P is executed.

  FIG. 3 is an explanatory diagram illustrating an example of various signals supplied to the print head 60. The drive signal COM is a signal for driving a nozzle actuator provided in the print head 60. The drive signal COM is a signal in which drive pulses PCOM (drive pulses PCOM1 to PCOM4) as a minimum unit (unit drive signal) of the drive signal for driving the nozzle actuator are continuous in time series. A set of four drive pulses PCOM of the drive pulses PCOM1 to PCOM4 corresponds to one pixel (print pixel).

  Each drive pulse PCOM is composed of a voltage trapezoidal wave. The rising portion of each drive pulse PCOM is a portion for enlarging the volume of the cavity communicating with the nozzle and drawing ink (which can be said to draw a meniscus in terms of the ink ejection surface), and the falling edge of the drive pulse PCOM. The portion is a portion for reducing the volume of the cavity and pushing out the ink (which can be said to push out the meniscus in terms of the ink ejection surface). Therefore, ink is ejected from the nozzles by driving the nozzle actuator according to the drive pulse PCOM.

  In the drive signal COM, the waveforms (voltage increase / decrease slope and peak value) of the drive pulses PCOM2 to PCOM4 are different from each other. When the waveform of the drive pulse PCOM supplied to the nozzle actuator is different, the ink drawing amount and drawing speed, the ink pushing amount and the pushing speed are different, and the ink discharge amount (that is, the ink dot size) is different. It becomes. By selecting one or a plurality of drive pulses PCOM from the drive pulses PCOM2 to PCOM4 and supplying them to the nozzle actuator, ink dots of various sizes can be formed. In this embodiment, the drive signal COM includes a drive pulse PCOM1 called micro vibration. The drive pulse PCOM1 is used when only ink is drawn and no extrusion is performed, for example, when the viscosity increase of the nozzle is suppressed.

  As described above, the drive signal COM of this embodiment is maintained at a predetermined intermediate level for a certain period except for the portion of the drive pulse PCOM1 for fine vibration, and then gradually increases from the intermediate level toward a predetermined high level. A series of signals that maintain the high level for a certain period, gradually decrease from the high level toward a predetermined low level, maintain the low level for a certain period, and gradually increase from the low level toward the intermediate level, It is a repeated signal. In the present specification, maintaining a signal at a certain level means that the signal does not substantially (significantly) vary from a certain level, although fine variations due to noise and errors are allowed.

  The drive signal selection signal SI & SP is a signal that selects a nozzle that ejects ink based on the print data PD and determines the connection timing of the nozzle actuator to the drive signal COM. The latch signal LAT and the channel signal CH are signals for connecting the drive signal COM and the nozzle actuator of the print head 60 based on the drive signal selection signal SI & SP after the nozzle selection data for all the nozzles is input. As shown in FIG. 3, the latch signal LAT and the channel signal CH are signals synchronized with the drive signal COM. That is, the latch signal LAT is a signal that becomes a high level corresponding to the start timing of the drive signal COM, and the channel signal CH is a high level that corresponds to the start timing of each drive pulse PCOM constituting the drive signal COM. Is a signal. Output of a series of drive signals COM is started according to the latch signal LAT, and each drive pulse PCOM is output according to the channel signal CH. The reference clock signal SCK is a signal for transmitting the drive signal selection signal SI & SP to the print head 60 as a serial signal. That is, the reference clock signal SCK is a signal used for determining the timing for ejecting ink from the nozzles of the print head 60.

  FIG. 4 is an explanatory diagram showing the configuration of the switching controller 61 of the print head 60. The switching controller 61 is constructed in the print head 60 in order to supply a drive signal COM (drive pulse PCOM) to the nozzle actuator 67. The switching controller 61 has a shift register 63 that stores the drive signal selection signal SI & SP, a latch circuit 64 that temporarily stores the data of the shift register 63, and level-converts the output of the latch circuit 64 and supplies it to the selection switch 66. A level shifter 65 and a selection switch 66 for connecting the drive signal COM to the nozzle actuator 67 are provided.

  The drive signal selection signal SI & SP is sequentially input to the shift register 63, and the area stored in accordance with the input pulse of the reference clock signal SCK is sequentially shifted to the subsequent stage. Note that the input of the drive signal selection signal SI & SP to the shift register 63 is executed according to the timing signal PTS described above. The latch circuit 64 latches the output signals of the shift register 63 according to the input latch signal LAT after the drive signal selection signals SI & SP for the number of nozzles are stored in the shift register 63. The signal stored in the latch circuit 64 is converted by the level shifter 65 into a voltage level at which the selection switch 66 at the next stage can be switched (ON / OFF). The nozzle actuator 67 corresponding to the selection switch 66 that is closed (becomes connected) by the output signal of the level shifter 65 is connected to the drive signal COM (drive pulse PCOM) at the connection timing of the drive signal selection signal SI & SP. Further, after the drive signal selection signal SI & SP input to the shift register 63 is latched by the latch circuit 64, the next drive signal selection signal SI & SP is input to the shift register 63, and the latch circuit 64 receives the ink discharge timing. Update stored data sequentially. According to the selection switch 66, even after the nozzle actuator 67 is disconnected from the drive signal COM (drive pulse PCOM), the input voltage of the nozzle actuator 67 is maintained at the voltage just before the disconnection. In addition, the symbol HGND in FIG. 4 is the ground end of the nozzle actuator 67.

  FIG. 5 is an explanatory diagram showing a schematic configuration of a drive circuit 80 for driving the print head 60. The drive circuit 80 is a circuit that generates the drive signal COM described above and supplies it to the nozzle actuator 67 of the print head 60, and is constructed in the control unit 42 and the head driver 45 (see FIG. 2) in the control unit 40. ing.

  The drive circuit 80 includes a main drive circuit 230 and an auxiliary drive circuit 210. The main drive circuit 230 is a circuit that generates a drive signal COM, and the auxiliary drive circuit 210 is a circuit that generates auxiliary drive signals COMs described later.

  The main drive circuit 230 includes a DAC circuit 231 and a main transistor pair 234. The DAC circuit 231 receives from the CPU 51 (FIG. 2) a DAC value DV that is updated at predetermined intervals as information for generating the drive signal COM. The DAC circuit 231 generates an analog signal ANG having a potential corresponding to the input DAC value DV. The DAC value DV is, for example, information representing the output potential as a 10-bit digital value.

  The main transistor pair 234 includes a charging transistor 232 and a discharging transistor 233 that are complementarily connected (complementarily connected). In this embodiment, the charging transistor 232 is an NPN bipolar transistor, and the discharging transistor 233 is a PNP bipolar transistor. The emitters of the charging transistor 232 and the discharging transistor 233 are connected to each other, and further connected to a signal line 235 for outputting a drive signal COM. The collectors of the charging transistor 232 and the discharging transistor 233 are respectively connected to signal lines 222 and 223 for supplying auxiliary driving signals COMs from an auxiliary driving circuit 210 described later. The analog signal ANG is input from the DAC circuit 231 to the bases of the charging transistor 232 and the discharging transistor 233. The main transistor pair 234 corresponds to the first transistor pair in the present invention.

  In the main transistor pair 234, when the analog signal ANG rises and the base potential in the charging transistor 232 becomes higher than the emitter potential by a predetermined value or more (for example, 0.6 volts or more), the charging transistor 232 is turned on, and the drive signal COM The potential increases. On the other hand, when the analog signal ANG falls and the base potential in the discharge transistor 233 becomes lower than the emitter potential by a predetermined value or more, the discharge transistor 233 is turned on, and the potential of the drive signal COM falls. When the analog signal ANG is constant, both the charging transistor 232 and the discharging transistor 233 are turned off. As described above, the operation of the main transistor pair 234 is controlled by the analog signal ANG, whereby the analog signal ANG is current-amplified to generate the drive signal COM. The generated drive signal COM is supplied to the print head 60 via the signal line 235.

  The auxiliary drive circuit 210 includes a pulse generation circuit 211, an auxiliary transistor pair 214, and a smoothing filter 219. A pulse modulation control signal MS is input to the pulse generation circuit 211 from the CPU 51 (FIG. 2). The pulse modulation control signal MS is a signal that serves as a reference for the auxiliary drive signal COMs. The pulse generation circuit 211 modulates the pulse modulation control signal MS by a predetermined pulse modulation method (for example, pulse width modulation or pulse density modulation) to generate a control pulse signal PWS. The control pulse signal PWS is a rectangular pulse signal that represents the level of the pulse modulation control signal MS by the pulse duty.

  The auxiliary transistor pair 214 includes a power supply side transistor 212 and a ground side transistor 213 that are complementarily connected (complementarily connected). In this embodiment, the power supply side transistor 212 is a P-channel MOSFET, and the ground side transistor 213 is an N-channel MOSFET. The drains of the power supply side transistor 212 and the ground side transistor 213 are connected to each other, and further connected to the input end of the smoothing filter 219. The source of the power supply side transistor 212 is connected to the power supply VH, and the source of the ground side transistor 213 is grounded. A control pulse signal PWS is input from the pulse generation circuit 211 to the gates of the power supply side transistor 212 and the ground side transistor 213.

  Diodes 215 and 216 are respectively provided in parallel with the power supply side transistor 212 and the ground side transistor 213 constituting the auxiliary transistor pair 214. The auxiliary transistor pair 214 corresponds to the second transistor pair in the present invention.

  In the auxiliary transistor pair 214, when the control pulse signal PWS is at a high level, the power supply side transistor 212 is turned on and the ground side transistor 213 is turned off. As a result, the output of the auxiliary transistor pair 214 becomes the potential of the power supply VH. On the other hand, when the control pulse signal PWS is at a low level, the power supply side transistor 212 is turned off and the ground side transistor 213 is turned on. As a result, the output of the auxiliary transistor pair 214 becomes the ground potential. As described above, the operation of the auxiliary transistor pair 214 is controlled by the control pulse signal PWS, whereby the pulse modulation control signal MS is current-amplified.

  The smoothing filter 219 smoothes the signal output from the auxiliary transistor pair 214 and generates the auxiliary drive signal COMs. In this embodiment, as the smoothing filter 219, a low-pass filter (low-pass filter) configured by a combination of a capacitor 218 and a coil 217 is used. The smoothing filter 219 attenuates and removes the modulation frequency component generated by the pulse generation circuit 211 and outputs the auxiliary drive signal COMs via the signal line 221.

  Thus, the pulse generation circuit 211, the auxiliary transistor pair 214, and the smoothing filter 219 in the auxiliary drive circuit 210 function as a circuit (so-called class D amplifier) that amplifies the pulse modulation control signal MS using the pulse signal. The auxiliary drive signal COMs output from the smoothing filter 219 via the signal line 221 is input to the collectors of the charging transistor 232 and the discharging transistor 233 via the two signal lines 222 and 223 branched from the signal line 221. The

  Note that a diode 225 is provided on the signal line 222 connecting the smoothing filter 219 and the collector of the charging transistor 232 with the charging transistor 232 side as the cathode side. A diode 226 is provided on the signal line 223 connecting the smoothing filter 219 and the collector of the discharging transistor 233 with the charging transistor 232 side as the anode side.

  FIG. 6 is an explanatory diagram illustrating an example of the auxiliary drive signal COMs generated by the auxiliary drive circuit 210. FIG. 6 illustrates a part of the drive signal COM (FIG. 3) and a part of the auxiliary drive signal COMs corresponding to the drive signal COM. As shown in FIG. 6, the auxiliary drive signal COMs has a predetermined potential difference ΔVs (for example, 1 to 3 volts) from the drive signal COM during the rising period (for example, the period from ta to tb) of the drive signal COM in which the charging transistor 232 operates. ) And is lower than the drive signal COM by a predetermined potential difference ΔVs during the falling period of the drive signal COM in which the discharge transistor 233 operates (for example, the period from tc to td). In addition, the auxiliary drive signal COMs gradually increases from a state higher than the drive signal COM by a predetermined potential difference ΔVs during a constant potential period (for example, a period from tb to tc) between the rising period and the subsequent falling period of the drive signal COM. It is a signal that goes down and becomes lower by a predetermined potential difference ΔVs than the drive signal COM at the end of the period. In addition, the auxiliary drive signal COMs gradually decreases from a state lower than the drive signal COM by a predetermined potential difference ΔVs during a constant potential period (for example, a period from td to te) between the falling period of the drive signal COM and the subsequent rising period. It is a signal that rises and becomes higher by a predetermined potential difference ΔVs than the drive signal COM at the end of the period.

  In the present embodiment, the auxiliary drive signal COMs as shown in FIG. 6 is generated and supplied to the collectors of the charging transistor 232 and the discharging transistor 233 constituting the main transistor pair 234, and therefore the collector of the charging transistor 232 Compared to the case where the collector of the discharging transistor 233 is grounded, the potential difference between the collector and the emitter during the operation of the charging transistor 232 or the discharging transistor 233 can be reduced. Power consumption in the pair 234 can be reduced. In addition, the auxiliary transistor pair 214 that operates to generate the auxiliary drive signal COMs operates based on the pulse signal, and thus consumes very little power. Therefore, in the drive circuit 80 of the present embodiment, it is possible to reduce power consumption for generating the drive signal COM.

  Here, the load of the nozzle actuator 67 driven according to the drive signal COM may vary. When the load of the nozzle actuator 67 is different, even if the auxiliary transistor pair 214 is driven based on the same control pulse signal PWS, the auxiliary drive signal COMs becomes a different signal. For example, in the rising period of the drive signal COM (for example, the period from ta to tb), the potential difference between the auxiliary drive signal COMs and the drive signal COM becomes considerably larger than the predetermined potential difference ΔVs, or conversely, considerably higher than the predetermined potential difference ΔVs. It may become smaller. In such a case, the potential difference between the collector and the emitter during the operation of the charging transistor 232 or the discharging transistor 233 cannot be sufficiently reduced, and the power consumption in the main transistor pair 234 can be sufficiently reduced. Can not.

  In the drive circuit 80 of this embodiment, as shown in FIG. 5, the auxiliary drive circuit 210 includes a feedback signal line 224 that feeds back the auxiliary drive signal COMs output from the signal line 221 to the pulse generation circuit 211. In other words, the pulse generation circuit 211 detects that the auxiliary drive signal COMs is a signal as shown in FIG. 6 regardless of the load variation of the nozzle actuator 67 (that is, when the potential of the drive signal COM increases and decreases, the main transistor pair 234 The feedback control is performed so that the potential difference between the collector and the emitter of one of the transistors (charging transistor 232 or discharging transistor 233) is the predetermined potential difference ΔVs. Therefore, in the drive circuit 80 of the present embodiment, the potential difference between the collector and the emitter during the operation of the charging transistor 232 or the discharging transistor 233 can always be sufficiently reduced, and the power consumption in the main transistor pair 234 can be sufficiently reduced. Can be reduced.

  In the drive circuit 80 of the present embodiment, one auxiliary drive signal COMs generated by the auxiliary drive circuit 210 is supplied to both collectors of the charge transistor 232 and the discharge transistor 233 constituting the main transistor pair 234. Therefore, the circuit is simplified and miniaturized as compared with the case where two auxiliary drive signals COMs are generated by the auxiliary transistor pair 214 and each auxiliary drive signal COMs is supplied to each transistor constituting the main transistor pair 234. Cost reduction can be achieved. For example, in the driving circuit 80 of the present embodiment, it is not necessary to provide two smoothing filters, and only one smoothing filter 219 may be provided.

  Further, in the driving circuit 80 of this embodiment, the diode 225 is provided on the signal line 222 and the diode 226 is provided on the signal line 223, so that the generation of reverse current can be prevented. For example, even when the collector potential of the charging transistor 232 is lower than the base potential at the timing before and after tc in FIG. 6, the reverse current is prevented from flowing through the charging transistor 232 due to the presence of the diode 225.

  Further, in the drive circuit 80 of the present embodiment, the diodes 215 and 216 are provided in parallel with the power supply side transistor 212 and the ground side transistor 213, respectively, and therefore, using the back electromotive force of the coil 217 of the smoothing filter 219, Power can be saved by flowing a current from the ground to the capacitor 218 of the smoothing filter 219 or by flowing a current from the ground side transistor 213 to the power source.

B. Variations:
The present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.

B1. Modification 1:
The configuration of the printer 100 in the above embodiment is merely an example and can be variously modified. For example, in the above embodiment, a piezo element (piezoelectric element) is used as the nozzle actuator 67, but other nozzle actuators may be used. The elements constituting the smoothing filter 219, the main transistor pair 234, and the auxiliary transistor pair 214 in the above embodiment can be variously modified.

  In the above embodiment, the printer 100 receives the print data PD from the host computer 90 and performs the printing process. Instead, the printer 100, for example, receives image data acquired from a memory card or a predetermined value. The print data PD may be generated based on the image data acquired from the digital camera via the interface, the image data acquired by the scanner, and the like to perform the printing process.

  In the above embodiment, the printer 100 moves the print head 60 back and forth in a predetermined direction (main scanning direction) with respect to the continuous paper P positioned in the print area, and the paper P is used as the main paper P. Although it is assumed that the printer performs printing while repeating the operation (sub-scanning) for conveying in the conveying direction that intersects the scanning direction, the present invention is a so-called impact printer that performs printing on cut paper, and the lower surface of the print head. The present invention can also be applied to a so-called line printer that performs printing while transporting a sheet in a direction intersecting the sheet width direction under a nozzle row arranged side by side over the sheet width.

  The present invention can also be applied to apparatuses other than ink jet printers as long as the apparatus discharges a liquid (including a liquid material in which particles of functional material are dispersed and a fluid such as a gel). Examples of such liquid ejection devices include electrode materials and color materials used in the manufacture of textile printing devices for applying patterns to fabrics, liquid crystal displays, EL (electroluminescence) displays, surface-emitting displays, color filters, and the like. Such as a device that discharges a liquid material containing the above material in a dispersed or dissolved form, a device that discharges bioorganic materials used in biochip manufacturing, a device that discharges a liquid used as a precision pipette, a watch, a camera, etc. A device that ejects lubricating oil pinpoint to a precision machine, a device that ejects a transparent resin liquid such as an ultraviolet curable resin to form a micro hemispherical lens (optical lens) used in optical communication elements, etc., a substrate For example, an apparatus for discharging an etching solution such as an acid or an alkali in order to etch the above may be used.

  In the above embodiment, a part of the configuration realized by hardware may be replaced by software, and conversely, a part of the configuration realized by software may be replaced by hardware. Good.

  In addition, when part or all of the functions of the present invention are realized by software, the software (computer program) can be provided in a form stored in a computer-readable recording medium. In the present invention, the “computer-readable recording medium” is not limited to a portable recording medium such as a flexible disk or a CD-ROM, but an internal storage device in a computer such as various RAMs and ROMs, a hard disk, etc. It also includes an external storage device fixed to the computer.

B2. Modification 2:
The aspect of the auxiliary drive signal COMs generated in the above embodiment is merely an example and can be variously modified. FIG. 7 is an explanatory diagram showing a modification of the auxiliary drive signal COMs. In FIG. 7, the potential of the drive signal COM rises during the period from te to tf, but the potential rise speed during this period is equal to or greater than a predetermined threshold. This threshold is set based on, for example, the maximum throughput of the auxiliary drive circuit 210, that is, the maximum value of the potential increase (or decrease) speed of the auxiliary drive signal COMs. If the potential of the auxiliary drive signal COMs is increased from the start timing te of the potential increase period when the potential increase rate of the drive signal COM is equal to or higher than the threshold, the auxiliary drive signal COMs and the drive signal COM are changed during the potential increase period. In some cases, the potential difference cannot be ensured by a predetermined potential difference ΔVs, and normal operation of the charging transistor 232 may be hindered. In this modification, the potential of the auxiliary drive signal COMs is increased from the timing tx before the start timing te of the potential increase period, and the potential difference between the auxiliary drive signal COMs and the drive signal COM is set to a predetermined value throughout the potential increase period. The potential difference is ΔVs or more. As a result, even when the potential rise rate of the drive signal COM is equal to or higher than the threshold value, the potential difference between the collector and the emitter during the operation of the charging transistor 232 can be reduced while ensuring the normal operation of the charging transistor 232. it can. Similarly, when the potential drop speed of the drive signal COM is equal to or higher than the threshold value, the potential of the auxiliary drive signal COMs is lowered from the timing before the start timing of the potential drop period, and the auxiliary drive signal is over the entire potential drop period. The potential difference between COMs and the drive signal COM may be greater than or equal to a predetermined potential difference ΔVs. As a result, even when the potential drop rate of the drive signal COM is equal to or higher than the threshold value, the potential difference between the collector and the emitter during the operation of the discharge transistor 233 can be reduced while ensuring the normal operation of the discharge transistor 233. it can.

B3. Modification 3:
In the above embodiment, one auxiliary drive signal COMs is generated by one auxiliary drive circuit 210, and the generated auxiliary drive signal COMs is supplied to the respective collectors of the charging transistor 232 and the discharging transistor 233. Instead, a set of a pulse generation circuit 211, an auxiliary transistor pair 214, and a smoothing filter 219 for generating an auxiliary drive signal COMs to be supplied to the charging transistor 232 is supplied to the auxiliary drive circuit 210, and supplied to the discharge transistor 233. Alternatively, a pulse generation circuit 211 for generating another auxiliary drive signal COMs, an auxiliary transistor pair 214, and another set of a smoothing filter 219 may be provided. In this case, the auxiliary drive signal COMs to be supplied to the charging transistor 232 is always a signal higher than the drive signal COM by a predetermined potential difference ΔVs, and another auxiliary drive signal COMs to be supplied to the discharge transistor 233 is If the signal is always lower than the drive signal COM by the predetermined potential difference ΔVs, the potential difference between the collector and the emitter during the operation of the charging transistor 232 or the discharging transistor 233 can always be made sufficiently small. Electric power can be sufficiently reduced.

B4. Modification 4:
Of the constituent elements in the above-described embodiments, examples, and modifications, elements other than those described in the independent claims are additional elements, and can be omitted or combined as appropriate.

DESCRIPTION OF SYMBOLS 12 ... Connector 14 ... Operation panel 22 ... Paper feed motor 26 ... Platen 30 ... Carriage 32 ... Carriage motor 34 ... Sliding shaft 36 ... Drive belt 38 ... Pulley 40 ... Control unit 41 ... Interface 42 ... Control part 43 ... Paper feed motor Driver 45 ... Head driver 46 ... Carriage motor driver 47 ... Interface 51 ... CPU
52 ... RAM
53 ... ROM
DESCRIPTION OF SYMBOLS 60 ... Print head 61 ... Switching controller 63 ... Shift register 64 ... Latch circuit 65 ... Level shifter 66 ... Selection switch 67 ... Nozzle actuator 70 ... Ink cartridge 80 ... Drive circuit 90 ... Host computer 100 ... Printer 210 ... Auxiliary drive circuit 211 ... Pulse generation circuit 212 ... Power source side transistor 213 ... Ground side transistor 214 ... Auxiliary transistor pair 215 ... Diode 217 ... Coil 218 ... Capacitor 219 ... Smoothing filter 221 ... Signal line 222 ... Signal line 223 ... Signal line 224 ... Feedback signal line 225 ... Diode 226 ... Diode 230 ... Main drive circuit 231 ... DAC circuit 232 ... Charging transistor 233 ... Discharging transistor 234 ... Main transistor pair 2 35 ... Signal line COMs ... Auxiliary drive signal PD ... Print data CH ... Channel signal VH ... Power supply SI ... Drive signal selection signal PCOM ... Drive pulse MS ... Pulse modulation control signal SCK ... Reference clock signal LAT ... Latch signal ANG ... Analog signal COM ... Drive signal PTS ... Timing signal PWS ... Control pulse signal

Claims (6)

A liquid ejection device comprising:
A liquid discharge head having a plurality of nozzles for discharging liquid, and a plurality of actuators provided corresponding to the plurality of nozzles and driven according to a drive signal;
A main drive circuit that generates the drive signal using a first transistor pair driven by an analog signal, and supplies the generated drive signal to the liquid ejection head;
An auxiliary drive circuit that generates one auxiliary drive signal using a second transistor pair driven by a pulse signal and supplies the generated auxiliary drive signal to the collectors of the transistors that constitute the first transistor pair And a liquid ejection device. The liquid ejection device according to claim 1,
The liquid ejection apparatus, wherein the auxiliary drive circuit includes a pulse signal generation circuit that generates the pulse signal, and a feedback signal line that feeds back the auxiliary drive signal to the pulse signal generation circuit. The liquid ejection device according to claim 1 or 2, wherein
The auxiliary drive circuit is configured such that the potential difference between the collector and the emitter of one of the transistors operating in the first transistor pair becomes a preset potential difference when the potential of the drive signal increases and decreases. A liquid ejection device that generates a signal. The liquid ejection device according to claim 3,
In the auxiliary drive circuit, when the potential rise rate during the potential rise period of the drive signal is equal to or greater than a threshold value, the potential difference between the collector and the emitter of the one transistor over the whole potential rise period is the preset potential difference. As described above, the liquid ejection apparatus that raises the potential of the auxiliary drive signal from before the start of the potential rise period. The liquid ejection device according to claim 3,
In the auxiliary drive circuit, when the potential drop rate during the potential fall period of the drive signal is equal to or greater than a threshold value, the potential difference between the collector and the emitter of the one transistor over the whole potential drop period is the preset potential difference. As described above, the liquid ejection device that lowers the potential of the auxiliary drive signal from before the start of the potential drop period. A control method of a liquid discharge apparatus comprising a liquid discharge head having a plurality of nozzles for discharging liquid, and a plurality of actuators provided corresponding to the plurality of nozzles and driven according to a drive signal,
Generating the drive signal using a first transistor pair driven by an analog signal, and supplying the generated drive signal to the liquid ejection head;
Generating one auxiliary drive signal using a second transistor pair driven by a pulse signal, and supplying the generated auxiliary drive signal to a collector of each transistor constituting the first transistor pair; A method comprising:

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