JP5849516B2 - Liquid ejecting apparatus, printing apparatus, and medical device - Google Patents

Description

  The present invention relates to a technique for driving a capacitive load such as a piezoelectric element using a drive signal.

  There are many actuators that are configured by a capacitive load such as a piezoelectric element and operate when a drive signal is applied, such as an ejection head mounted on an inkjet printer. If an attempt is made to generate this drive signal using an analog amplifier circuit, a large current flows through the analog amplifier circuit, so that a large amount of power is consumed. As a result, not only does the power efficiency decrease, but the circuit board becomes larger, and further, since the consumed power changes to heat, a large heat sink is required, and the board becomes larger.

  Therefore, instead of directly amplifying the analog drive signal, the drive waveform signal serving as a reference for the drive signal is pulse-modulated and converted into a modulation signal, and the obtained modulation signal is amplified and then passed through a smoothing filter. A technique for obtaining an amplified drive signal has been proposed (see, for example, Patent Document 1). Amplification of the modulation signal can be realized simply by switching on / off of the switch. Furthermore, since the smoothing filter can be realized by using an LC circuit in which a coil and a capacitor are combined, in principle, power is not consumed. For this reason, according to the proposed technique, it is possible to generate a drive signal without consuming a large amount of power, and it is possible to reduce the size of the circuit board.

  In the proposed technique, a smoothing filter is configured by the LC circuit, and therefore a peak appears in the gain at the resonance frequency of the LC circuit. Normally, the output peak is suppressed by the resistance value of the electric load or by separately inserting a damping resistor. However, in this method, power is consumed by the resistor. Therefore, it has been proposed to suppress the output peak by performing feedback from the output stage (see, for example, Patent Document 2). Further, since the signal passing through the smoothing filter is delayed in phase by 180 degrees at the maximum, there is a possibility that the output oscillates if feedback is applied as it is with the signal of the output stage. Therefore, feedback is performed after phase lead compensation is applied to the signal of the output stage.

  In addition, when feeding back the signal from the output stage, the wiring resistance is taken into consideration in order to suppress the unstable operation of the drive circuit due to the resistance of the wiring from the smoothing filter to the capacitive load. A technique for applying feedback (for example, see Patent Document 3) and a technique for switching a carrier frequency in accordance with the waveform of a drive signal (for example, see Patent Document 4) for the purpose of suppressing power consumption are also proposed. Has been.

  Furthermore, a technique for cutting or excising an object by ejecting fluid in a pulse shape is known. For example, in the medical field, a fluid ejecting apparatus as a surgical instrument for incising or excising a living tissue includes a fluid chamber whose volume is changed by driving a volume changing unit, and a nozzle communicated with the fluid chamber, It is known that a fluid is supplied to a chamber and a volume changing means is driven to convert the fluid into a pulsating flow so that the fluid is jetted at high speed from a nozzle.

JP 2007-168172 A JP 2009-153272 A JP 2005-329710 A JP 2007-190708 A

  However, the conventional techniques such as Patent Document 1 to Patent Document 4 described above have a problem that the ripple (carrier ripple) of the carrier frequency that is removed by the smoothing filter may be superimposed on the drive signal. It was. As a result, the actuator, which is a capacitive load, cannot be driven properly. Especially in the medical field, adjustment of the depth and direction of the incision is extremely required, so a minute ripple (carrier ripple) of the carrier frequency is superimposed on the drive signal. It is not allowed to do.

  The present invention has been made to solve at least a part of the above-described problems of the prior art, and provides a technique capable of avoiding a carrier frequency ripple from being superimposed on a drive signal after a smoothing filter. For the purpose.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

  Application Example 1 A liquid ejecting apparatus according to this application example includes a nozzle, a liquid chamber that is connected to the nozzle and whose volume can be changed, and a liquid passage pipe that communicates the nozzle and the liquid chamber. A unit, a capacitive load that extends the capacitive load by applying a drive signal to the capacitive load, and changes the volume of the liquid chamber; and applying the drive signal to the capacitive load A capacitive load drive circuit that drives the capacitive load, and changes the volume of the liquid chamber, thereby ejecting the liquid that has flowed into the liquid chamber from the nozzle, The capacitive load drive circuit includes a drive waveform signal generation circuit that generates a drive waveform signal serving as a reference for the drive signal, a modulation circuit that generates a modulation signal by pulse-modulating the drive waveform signal, and the modulation signal. A digital power amplifier that amplifies the power to generate a pulsed power amplification modulation signal, a smoothing filter that generates the drive signal by smoothing the pulsed power amplification modulation signal, the smoothing filter, and the capacitance And a wiring cable provided to connect at least one of the smoothing filter and the capacitive load, and a capacitor is provided in the wiring cable.

  According to this application example, a modulation signal is generated by pulse-modulating a drive waveform signal that is a reference of a drive signal to be applied to a capacitive load, and the obtained modulation signal is amplified after power and smoothed. To generate a drive signal. In this way, phase lead compensation is performed on the drive signal applied to the capacitive load to generate a feedback signal, and negative feedback to the drive waveform signal. The drive signal output from the smoothing filter is applied to the capacitive load via the wiring cable. Here, the wiring cable is provided with an auxiliary capacitor for suppressing the amplitude of the carrier ripple of the drive signal to a predetermined value or less.

  In this way, the drive signal applied to the capacitive load is negatively fed back with respect to the drive waveform signal serving as a reference for the drive signal, so that the drive signal is prevented from being distorted due to the resonance of the smoothing filter. Can do. Further, when negatively feeding back the drive signal, since the negative feedback is performed after the phase advance compensation (phase advance compensation), the drive signal whose phase is delayed by the smoothing filter is negatively fed back. The output does not become unstable. Further, as will be described in detail later, the phenomenon in which carrier ripple is superimposed on the drive signal after passing through the smoothing filter is that the resonance frequency between the inductance component of the wiring cable and the capacitive load approaches the carrier frequency (or This is due to the fact that Therefore, if an auxiliary capacitor is provided in the wiring cable, the resonance frequency between the inductance component of the wiring cable and the capacitive load can be shifted from the carrier frequency, so that carrier ripple is not superimposed on the drive signal. It becomes possible.

  In addition, since the wiring cable is provided so that at least one of the smoothing filter and the capacitive load can be replaced, the length of the wiring cable can be set to a desired length.

  Application Example 2 In the liquid ejecting apparatus according to the application example, the capacitor provided in the wiring cable is a capacitor having a capacity corresponding to an inductance value or an impedance value of the wiring cable.

  According to this application example, it is possible to avoid the carrier ripple from being superimposed on the drive signal after passing through the smoothing filter.

  Application Example 3 In the liquid ejecting apparatus according to the application example described above, the capacitor provided in the wiring cable is a capacitor having a capacity corresponding to the length of the wiring cable.

  According to this application example, it is possible to avoid the carrier ripple from being superimposed on the drive signal after passing through the smoothing filter.

  Application Example 4 In the liquid ejecting apparatus according to the application example described above, the wiring cable connects the first terminal and the second terminal connected to the smoothing filter side, the capacitive load, and the first terminal. And a fourth terminal for connecting the capacitive load and the second terminal, and the capacitor is connected between the third terminal and the fourth terminal. It is characterized by.

  According to this application example, the size of the capacitive component of the capacitive load can be made the same as if it was increased by the amount of the auxiliary capacitor. As a result, the resonance frequency between the inductance component of the wiring cable and the capacitive load can be shifted from the carrier frequency, and it is possible to avoid the carrier ripple from being superimposed on the drive signal.

  Application Example 5 In the liquid ejecting apparatus according to the application example described above, the wiring cable connects the first terminal and the second terminal connected to the smoothing filter side, the capacitive load, and the first terminal. A third terminal that connects the capacitive load and the second terminal, and the capacitor is between the first terminal and the third terminal, or the second terminal. And at least one of the fourth terminal and the fourth terminal.

  According to this application example, the resonance frequency between the inductance component of the wiring cable and the capacitive load can be shifted from the carrier frequency. As a result, it is possible to avoid the carrier ripple from being superimposed on the drive signal.

  Application Example 6 A printing apparatus according to this application example uses the liquid ejecting apparatus described in the application example.

  According to this application example, even in a cable having a different length, the resonance frequency between the inductance component of the wiring cable and the capacitive load can be shifted from the carrier frequency, so that the carrier ripple can be prevented from being superimposed. A plurality of actuators can be driven with an intended drive signal.

  Application Example 7 A medical device according to this application example uses the liquid ejecting apparatus described in the application example.

  According to this application example, by using the above-described fluid ejection device as a medical device, it is possible to provide more excellent characteristics as a surgical instrument as a more effective device.

An explanatory view showing a configuration of a liquid ejecting apparatus equipped with a capacitive load driving circuit according to the present embodiment. Explanatory drawing which showed the circuit structure of the capacitive load drive circuit concerning this embodiment. Explanatory drawing which showed the circuit structure of the digital power amplifier concerning this embodiment. Explanatory drawing which showed the circuit model containing the inductance component and resistance component concerning this embodiment. Explanatory drawing about the transfer function H1. Explanatory drawing which showed the mechanism in which a carrier ripple generate | occur | produces under the influence of the inductance component (and resistance component) which a wiring cable has. Explanatory drawing which showed the mechanism in which a carrier ripple generate | occur | produces under the influence of the inductance component (and resistance component) which a wiring cable has. The circuit diagram which showed a part of capacitive load drive circuit of 1st Example. Explanatory drawing which shows the reason which can suppress the carrier ripple which a drive signal overlaps with the capacitive load drive circuit of 1st Example. The circuit diagram which showed a part of capacitive load drive circuit of 2nd Example. Explanatory drawing which shows the reason which can suppress the carrier ripple which a drive signal overlaps with the capacitive load drive circuit of 2nd Example. 1 is a schematic diagram showing an embodiment of a liquid jet printing apparatus using a capacitive load driving circuit.

Hereinafter, in order to clarify the contents of the present invention described above, examples will be described in the following order.
A. Device configuration:
B. Circuit configuration of capacitive load drive circuit:
C. Mechanism for generating carrier ripple:
D. Capacitive load driving circuit of the first embodiment:
E. Capacitive load driving circuit of the second embodiment:
F. Liquid jet printer (printer):

A. Device configuration:
FIG. 1 is an explanatory diagram showing a configuration of a liquid ejecting apparatus equipped with a capacitive load driving circuit according to the present embodiment. As shown in the figure, the liquid ejecting apparatus 100 is roughly divided into an ejecting unit 110 that ejects liquid, a supply pump 120 that supplies the liquid ejected from the ejecting unit 110 toward the ejecting unit 110, and the ejecting unit 110. And a control unit 130 for controlling the operation of the supply pump 120. The liquid ejecting apparatus 100 is an example of a water jet knife as a surgical tool used for excising or incising a living tissue by ejecting pulsed liquid from the ejecting unit 110.

  The injection unit 110 has a structure in which a metal rear block 114 is overlapped on a metal front block 113 and screwed, and a circular liquid passage pipe 112 is erected on the front surface of the front block 113. An injection nozzle 111 is inserted at the tip of the liquid passage tube 112. A thin disk-shaped liquid chamber 115 is formed on the mating surface of the front block 113 and the rear block 114, and the liquid chamber 115 is connected to the ejection nozzle 111 via the liquid passage tube 112. In addition, an actuator 116 composed of a laminated piezoelectric element is provided inside the rear block 114. The ejection unit 110 and the control unit 130 are connected by a wiring cable 150, and a drive signal is supplied from the capacitive load driving circuit 200 in the control unit 130 to the actuator 116 via the wiring cable 150. Further, one end side of the wiring cable 150 is attached to the injection unit 110 by a connector 152, and the other end side of the wiring cable 150 is attached to the control unit 130 by a connector 154. For this reason, the distribution cable 150 can be replaced with various distribution cables 150 having different lengths and characteristics. The actuator 116 corresponds to the “capacitive load” in the present invention.

  The supply pump 120 sucks up the liquid through the tube 121 from the liquid tank 123 in which the liquid to be ejected (water, physiological saline, chemical liquid, etc.) is stored, and then the liquid in the ejection unit 110 through the tube 122. Supply into the chamber 115. For this reason, the liquid chamber 115 is filled with the liquid.

  When a drive signal is applied from the control unit 130 to the actuator 116, the actuator 116 extends and the liquid chamber 115 is compressed, and as a result, the liquid filled in the liquid chamber 115 is pulsed from the ejection nozzle 111. Is injected into. The extension amount of the actuator 116 depends on the voltage applied as the drive signal. Therefore, in order to eject a pulsed liquid having a desired characteristic, it is necessary to apply an accurate drive signal to the actuator 116. Therefore, in order to generate such a drive signal, a capacitive load drive circuit 200 as described below is mounted in the control unit 130.

B. Circuit configuration of capacitive load drive circuit:
FIG. 2 is an explanatory diagram showing a circuit configuration of the capacitive load driving circuit 200 according to the present embodiment. As shown in the figure, the capacitive load drive circuit 200 pulses a drive waveform signal generation circuit 210 that outputs a drive waveform signal (hereinafter referred to as WCOM) serving as a reference for the drive signal, and pulses WCOM from the drive waveform signal generation circuit 210. A modulation circuit 230 that modulates and converts it into a modulated signal (hereinafter referred to as MCOM); a digital power amplifier 240 that digitally amplifies the power of MCOM from the modulation circuit 230 to generate a power amplified modulated signal (hereinafter referred to as ACOM); A smoothing filter 250 that receives the ACOM from the digital power amplifier 240 and removes the modulation component, and then supplies it to the actuator 116 of the injection unit 110 as a drive signal (hereinafter referred to as COM).

  Of these, the drive waveform signal generation circuit 210 includes a waveform memory storing WCOM data and a D / A converter, and converts data read from the waveform memory into an analog signal by the D / A converter. To generate a WCOM (drive waveform signal). Conversely, the modulation circuit 230 is constituted by a digital circuit using a signal processing circuit so that the WCOM (drive waveform signal) read from the waveform memory of the drive waveform signal generation circuit 210 is handled as digital data. Good.

  The modulation circuit 230 generates (pulse modulation) a pulse wave-like MCOM (modulation signal) by comparing the WCOM with a triangular wave having a fixed period. The reciprocal of the above-described triangular wave period, that is, the frequency is called a carrier frequency fc. The MCOM generated by the modulation circuit 230 is input to the digital power amplifier 240. As shown in FIG. 3, the digital power amplifier 240 includes two switch elements (such as MOSFETs) that are push-pull connected, a power source, and a gate driver that drives these switch elements. In this embodiment, it is assumed that the voltage of the power source described above is Vdd [V]. When MCOM is in the high state, the high-side switch element is turned on, the low-side switch element is turned off, and the power supply voltage Vdd is output as ACOM. When the MCOM is in the Low state, the high-side switch element is turned off, the low-side switch element is turned on, and the ground voltage is output as ACOM. As a result, the MCOM that changes in a pulse waveform between the operating voltage of the modulation circuit 230 and the ground is amplified to an ACOM that changes in a pulse waveform between the power supply voltage Vdd and the ground. In this amplification, since only the ON / OFF of the two switch elements connected in a push-pull manner is switched, it is possible to greatly suppress the power loss as compared with the case where the analog waveform is amplified. As a result, not only can the power efficiency be improved, but there is no need to provide a large heat sink for heat dissipation, and the circuit can be miniaturized.

  The power-amplified ACOM (power amplification modulation signal) is converted into COM (drive signal) by passing through a smoothing filter 250 constituted by an LC circuit, and is applied to the actuator 116 via the wiring cable 150.

  Here, the wiring cable 150 described above also has an impedance including an inductance component and a resistance component. Therefore, it is considered that a signal (hereinafter referred to as RCOM) applied to the actuator 116 changes in some way when the wiring cable 150 is replaced with various wiring cables 150 having different lengths and characteristics. When actually examined, depending on the length and type of the connected wiring cable 150 or the size of the inductance component (and resistance component) of the wiring cable 150 determined by them, the carrier ripple is applied to the RCOM applied to the actuator 116. Has been found to be superimposable. Here, the carrier ripple means a signal component of the carrier frequency included in the RCOM applied to the actuator 116. Hereinafter, this point will be described in detail.

C. Mechanism for generating carrier ripple:
In explaining the reason why the carrier ripple described above can be superimposed, first, it is necessary to explain a transfer function (hereinafter referred to as H1) when ACOM is an input signal and RCOM is an output signal.
Examples of components of the transfer function H1 include a smoothing filter 250, a wiring cable 150, and an actuator 116 that is a capacitive load. Various circuit models can be considered for the wiring cable 150. In this embodiment, as shown in FIG. 4, a circuit model including an inductance component and a resistance component will be described as an example.
For convenience, regarding the four terminals of the wiring cable 150 shown in FIG. 4, a terminal connected to the COM output side of the smoothing filter 250 is a first terminal, and a terminal connected to the ground (GND) side of the smoothing filter 250 is a second terminal. Call it. A terminal connected to the side to which the RCOM is applied of the actuator 116 is called a third terminal, and a terminal connected to the side opposite to the side where the RCOM of the actuator 116 is applied is called a fourth terminal.
As shown in FIG. 4, the inductance component per unit length is Lc [H] and the resistance per unit length in each of the wiring cable 150 from the first terminal to the third terminal and from the second terminal to the fourth terminal. It is assumed that the component is Rc [Ω]. FIG. 5 is an explanatory diagram of the transfer function H1 described above. In the present embodiment, as shown in FIG. 5, the inductance of the coil of the smoothing filter 250 is Llpf [H], and the capacitance of the capacitance component of the smoothing filter 250 is Clpf [F]. Further, the capacitance of the capacitive load is Cload [F].

For convenience, as shown in FIG. 5, the impedance of the coil of the smoothing filter 250 is set as Z1, the impedance between the first terminal and the third terminal of the wiring cable 150 is set as Za, and the actuator 116 is connected to the wiring cable 150. Assuming that the impedance of the portion from the fourth terminal to the second terminal is Zb, Z1, Za, and Zb are respectively given by the following equations.
Z1 = jω · Llpf
Za = Rc + jω · Lc
Zb = 1 / (jω · Cload) + (Rc + jω · Lc)
Further, in the circuit configuration shown in FIG. 5A, the impedance of the transmission element (the reciprocating portion of the wiring cable 150 and the capacitive component of the actuator 116 and the smoothing filter 250) connected in series to the coil of the smoothing filter 250 is set. If Z2 is set, Z2 is given by the following equation.
Z2 = {1 / (jω · Clpf)} // {2 (Rc + jω · Lc) + 1 / (jω · Cload)}
Here, ω is an angular frequency, which is obtained by multiplying the frequency f by a double circumferential ratio π. j is an imaginary unit. // is a parallel composite symbol representing the composite impedance of parallel connection.
Then, the transfer function H1 described above is given by the equation (1) in FIG. In the equation (1) of FIG. 5B, the transfer function H1 is represented by impedances Z1, Z2, and Za, Zb in order to avoid complicating the notation of the equation. However, as described above, the impedances Z1 and Z2, and Za and Zb are represented by the angular frequency ω (or frequency f), the inductance component Lc of the wiring cable 150, and the like.
Therefore, when the transfer function H1 shown in the equation (1) is expanded, the equation A including the angular frequency ω (or the frequency f), the inductance component Lc, the resistance component Rc, and the like of the wiring cable 150 is finally included. , B can be expressed in the form of equation (2) in FIG.
Further, the gain | H1 | [dB] of the transfer function H1 is expressed by Expression (3) in FIG. Similar to Expression (2), since Expression (3) includes the angular frequency ω (or frequency f), the gain | H1 | of the transfer function H1 is a parameter that varies depending on the frequency.

The transfer function H1 has been described above. Next, in order to explain the reason why the above-described carrier ripple can be superimposed, the relationship between the gain | H1 | −frequency characteristic of the transfer function H1 and the carrier ripple will be described.
FIG. 6 shows an example of the gain-frequency characteristic of the transfer function H1 when there is no wiring cable 150 (when the cable length is 0 m). As described above, the carrier frequency fc is a fixed and constant frequency.
In FIG. 6, when there is no wiring cable 150, the gain at the carrier frequency fc is assumed to be y [dB]. When the power supply voltage of the digital power amplifier 240 described above is Vdd [V], the carrier ripple Vrpp [Vpp] superimposed on RCOM is expressed by Expression (4) in FIG. However, Formula (4) is a carrier ripple when the duty ratio of the above-described pulse modulation signal is 50%.
From equation (4), for example, assuming that the power supply voltage of the digital power amplifier 240 is 100 V and the gain y shown in FIG. 6 is −40 [dB], the carrier ripple superimposed on RCOM is calculated as 1 Vpp.
On the other hand, consider the case where there is a wiring cable 150.
Similar to Equation (2) described above, Equation (3) includes the inductance component Lc, resistance component Rc, and the like of the wiring cable 150. Therefore, when the wiring cable 150 is present and the wiring cable 150 is replaced with a wiring cable 150 having a different length or type, the inductance component Lc and the resistance component Rc of the wiring cable 150 change, and therefore the gain | H1 | −frequency of the transmission coefficient H1. The characteristics will change.
FIG. 7 shows an example of the gain | H1 | −frequency characteristic of the transfer function H1. In FIG. 7, assuming that the resistance component Rc per unit length of the wiring cable 150 is about several hundred milliohms and the inductance component Lc per unit length is about several μH, gains obtained with various wiring lengths— The frequency characteristic is illustrated.

  The broken line shown in FIG. 7 is the gain-frequency characteristic when the length of the wiring cable 150 is 2 [m (meter)], and the alternate long and short dash line is the gain-frequency characteristic when the length is 1 [m]. The two-dot chain line is a gain-frequency characteristic in the case of 0.5 [m]. A solid line represents a gain-frequency characteristic when the wiring cable 150 is not provided. As shown in the figure, when the actuator 116 (capacitive load) is connected via the wiring cable 150, the resonance frequency f0 of the smoothing filter 250 is higher than the relationship of the equation (3) (transfer function gain | H1 |). On the frequency side, resonance of frequency fx occurs. Further, when the wiring cable 150 is replaced with a longer one, the inductance value of the wiring cable 150 becomes larger, and therefore the above-described resonance frequency fx becomes lower from the relationship of the expression (3). Therefore, as in the case where the length of the wiring cable 150 shown in FIG. 7 is 1 m, depending on the length of the wiring cable 150 to be connected (or the inductance determined by the length), the resonance peak of the frequency fx has a carrier frequency fc. Approaches or matches. As a result, the gain at the carrier frequency fc becomes large, and a very large carrier ripple may remain in the drive signal applied to the actuator 116 from the relationship shown in the equation (3).

With reference to FIG. 7, how much the carrier ripple changes depending on the presence / absence of the wiring cable 150 and the length of the connected wiring cable 150 will be described. Here, the power supply voltage Vdd of the digital power amplifier 240 is assumed to be 100V. In addition, the wiring cable 150 that connects the smoothing filter 250 and the actuator 116 is connected to cables of various lengths between 0.5 [m] and 2 [m].
From FIG. 7, the carrier is shown when there is no wiring cable 150 (0 [m]), when the cable length of the wiring cable 150 is 0.5 [m], 1 [m], and 2 [m]. Gains at the frequency fc are -40db, -38db, -20db, and -45db, respectively. The carrier ripples remaining in the drive signal from Expression (4) are 1 Vpp, 1.25 Vpp, 10 Vpp, and 0.56 Vpp, respectively. Therefore, in the case of this embodiment, when the wiring cable 150 having a length of 1 [m] is replaced, the gain at the carrier frequency fc increases, and the drive signal applied to the actuator 116 has a very large carrier of 10 Vpp. It may happen that ripple remains. Although the ACOM amplified by the digital power amplifier 240 is smoothed through the smoothing filter 250, the carrier ripple may be superimposed on the drive signal due to the mechanism described above.

  If the carrier ripple is superimposed, the actuator 116 cannot be driven appropriately. Particularly in the medical field, such a phenomenon is not allowed because it is directly related to the difficulty in adjusting the depth and direction of the incision. However, if a damping resistor is inserted in the wiring, power is consumed by the resistor, so that power efficiency is lowered. Further, if the characteristics of the smoothing filter 250 are changed so that the frequency component of the carrier ripple is further suppressed, the resonance frequency f0 of the smoothing filter 250 is lowered, so that the signal frequency band cannot be secured. On the contrary, if the carrier frequency at the time of pulse modulation is increased, carrier ripple can be suppressed, but this causes an increase in switching loss at the time of pulse modulation or at the time of amplification of the modulation signal. Therefore, in order to apply a drive signal without carrier ripple to the actuator 116 without such problems, the following method is employed.

D. Capacitive load driving circuit of the first embodiment:
FIG. 8 is a circuit diagram showing a part of the capacitive load driving circuit 200 of this embodiment. In this embodiment, as shown in FIG. 4, the wiring cable 150 has two wire cores, and each wire core has a resistance component (Rc) and an inductance (Lc). Yes. In FIG. 8, only the resistance component (Rc) and the inductance (Lc) for one wire core are denoted by the reference numerals, and the symbols for the resistance components and inductances of the other wire cores are omitted. As shown in FIG. 8, the names of the terminals of the wiring cable 150 are referred to as the first terminal to the fourth terminal as described above.

  In the present embodiment, an auxiliary capacitor Cas is provided on the wiring cable 150 that connects the smoothing filter 250 and the actuator 116 so as to be in parallel with the actuator 116. That is, Cas is provided between the third terminal and the fourth terminal of the wiring cable 150. An auxiliary capacitor Cas is provided according to the cable length of the wiring cable 150, and the capacitance of the auxiliary capacitor Cas is adjusted. This makes it possible to avoid the carrier ripple from being superimposed on the drive signal after passing through the smoothing filter 250 for the following reason.

FIG. 9 is an explanatory diagram showing the reason why the carrier ripple superimposed with the drive signal can be suppressed in the capacitive load drive circuit 200 of the present embodiment. FIG. 9A shows a circuit configuration from ACOM to RCOM in the case where the auxiliary capacitor Cas is provided in the wiring cable 150. As illustrated, the auxiliary capacitor Cas is connected in parallel to the actuator 116. 9A, the impedance of the coil of the smoothing filter 250 is set as Z1, and the impedance between the first terminal and the third terminal of the wiring cable 150 is set as Za. Further, the impedance of the portion obtained by adding the space from the fourth terminal to the second terminal of the wiring cable 150 to the actuator 116 and the auxiliary capacitor Cas is set as Zb ′. Then, Z1, Za and Zb ′ are given by the following equations, respectively.
Z1 = jω · Llpf
Za = Rc + jω · Lc
Zb ′ = 1 / (jω · (Cload + Cas)) + (Rc + jω · Lc)
In addition, in the circuit configuration shown in FIG. 9A, the transmission elements connected in series to the coil of the smoothing filter 250 (the reciprocating portion of the wiring cable 150, the actuator 116, the auxiliary capacitor Cas, and the capacitance component of the smoothing filter 250 are included. ) Is given by the following equation.
Z2 ′ = {1 / (jω · Clpf)} // {2 (Rc + jω · Lc) + 1 / (jω · (Cload + Cas))}
Here, ω is an angular frequency, which is obtained by multiplying the frequency f by a double circumferential ratio π. j is an imaginary unit. // is a parallel composite symbol representing the composite impedance of parallel connection.
Then, the transfer function H2 between ACOM and RCOM is given by equation (5) in FIG. 9B.

  FIG. 9C shows the gain | H2 | -frequency characteristic of the transfer function H2. The solid line in the figure is the gain-frequency characteristic when there is no auxiliary capacitor Cas, and the broken line is the gain-frequency characteristic when there is an auxiliary capacitor Cas. Here, when the auxiliary capacitor is not provided, it is considered that the frequency fx of the resonance peak that appears due to the inductance (Lc) of the wiring cable 150 matches (or approaches) the carrier frequency fc. Further, as an example, when no auxiliary capacitor is provided, it is assumed that the gain at the carrier frequency fc is −20 db. As described above, according to the equation (4), in this case, a very large carrier ripple of 10 Vpp is obtained. However, even when such a length or type of wiring cable 150 is connected, the resonance frequency can be lowered from fx to df by providing the auxiliary capacitor Cas in the wiring cable 150. However, df is a value determined according to the magnitude of the capacitance value of Cas from the relationship of Expression (5). As a result, as shown in FIG. 9C, assuming that the gain at the carrier frequency fc is −40 db as an example, the carrier ripple can be reduced to 1 Vpp from the equation (4). The capacitance value of the auxiliary capacitor Cas may be a small capacitance value that shifts the resonance peak frequency fx from the carrier frequency fc. For this reason, the power consumption is almost the same as when a damping resistance of about several Ω is inserted. In addition, whether or not it is necessary to shift the frequency fx of the resonance peak and how much to shift it is determined for each wiring cable 150. For the auxiliary capacitor Cas, the capacitance value is finally selected by using the equations (4) and (5) so that the carrier ripple, that is, the gain | H2 | at the carrier frequency fc is within the target value. It is incorporated in the cable 150.

  Therefore, an auxiliary capacitor Cas having an appropriate capacitance value is provided for each wiring cable 150 in an integrated state with the wiring cable 150. Of course, it is not necessary to provide the auxiliary capacitor Cas for the wiring cable 150 in which the resonance peak frequency fx is sufficiently away from the carrier frequency fc. In this way, it is possible to avoid the carrier ripple from being superimposed on the drive signal applied to the actuator 116 no matter what wiring cable 150 is connected.

E. Capacitive load driving circuit of the second embodiment:
In the first embodiment described above, the auxiliary capacitor Cas is provided in parallel with the actuator 116. However, an auxiliary capacitor may be provided in parallel with the wiring cable 150. The second embodiment will be described below. In the description of the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  FIG. 10 is a circuit diagram showing a part of the capacitive load driving circuit 200 of the present embodiment. In this embodiment, an auxiliary capacitor Cas <b> 2 is provided in parallel with the wiring cable 150. Here, as shown in FIG. 10, the names of the terminals of the wiring cable 150 are referred to as the first terminal to the fourth terminal, as described above. The wiring cable 150 of the present embodiment is composed of four wire cores. The first terminal connects the first terminal and the third terminal, and the second terminal connects the first terminal and the third terminal via the auxiliary capacitor Cas2. Further, the third terminal connects the second terminal and the fourth terminal, and the fourth terminal connects the second terminal and the fourth terminal via the auxiliary capacitor Cas2. Each of these four wire cores has a resistance component (Rc) and an inductance (Lc). In FIG. 10, only the resistance component (Rc) and the inductance (Lc) for one wire core are denoted by the reference numerals, and the symbols for the resistance components and inductances of the other wire cores are omitted.

  FIG. 11 is an explanatory diagram illustrating the reason why the carrier ripple superimposed on the drive signal can be suppressed in the capacitive load drive circuit 200 of the present embodiment. FIG. 11A is an explanatory diagram showing a circuit configuration from ACOM to RCOM in the capacitive load driving circuit 200 of the present embodiment. Also in the present embodiment, the inductance of the coil of the smoothing filter 250 is Llpf, the capacitance of the capacitance component of the smoothing filter 250 is Clpf, the resistance value and inductance of the wiring cable 150 are Rc and Lc, The capacitance of the capacitive load is Cload.

Also in FIG. 11A, the impedance of the coil of the smoothing filter 250 is set to Z1. Also, the impedance of the two wire cores between the first terminal and the third terminal of the distribution cable 150 is set to Za ″. Further, the actuator 116 has a distance between the fourth terminal and the second terminal of the distribution cable 150. The impedance of the added portion is set as Zb ″. Then, Z1, Za ″, and Zb ″ are respectively given by the following equations.
Z1 = jω · Llpf
Za ″ = (Rc + jω · Lc) // (Rc + jω · Lc + 1 / (jω · Cas2))
Zb ″ = 1 / (jω · Cload) + (Rc + jω · Lc) // {(Rc + jω · Lc + 1 / (jω · Cas2))}
In addition, in the circuit configuration shown in FIG. 11A, the transmission elements connected in series to the coil of the smoothing filter 250 (the four wire core portions of the wiring cable 150, the actuator 116, and the capacitance component of the smoothing filter 250). ) Is given by the following equation.
Z2 = {1 / (jω · Clpf)} // {2 [(Rc + jω · Lc) // (Rc + jω · Lc + 1 / (jω · Cas2))] + 1 / (jω · Cload)}
Here, ω is an angular frequency, which is obtained by multiplying the frequency f by a double circumferential ratio π. j is an imaginary unit. Then, the transfer function H3 between ACOM and RCOM is given by equation (6) in FIG.

  FIG. 11C shows the gain | H3 | -frequency characteristic of the transfer function H3. The solid line in the figure is the gain-frequency characteristic when there is no auxiliary capacitor Cas2, and the broken line is the gain-frequency characteristic when there is the auxiliary capacitor Cas2. Also in this embodiment, when no auxiliary capacitor is provided, it is considered that the frequency fx of the resonance peak that appears due to the inductance (Lc) of the wiring cable 150 coincides (or approaches) the carrier frequency fc. Similarly to the example described above, when the auxiliary capacitor is not provided, it is assumed that the gain at the carrier frequency fc is −20 db, that is, the carrier ripple is 10 Vpp. As shown in the figure, the resonance frequency can be lowered from fx by df by using the wiring cable 150 provided with the auxiliary capacitor Cas2. However, df is a value determined according to the magnitude of the capacitance value of Cas2 from the relationship of Expression (6). Also in the second embodiment, as in the first embodiment, whether or not the resonance peak needs to be shifted and how much it is shifted in the case of shifting is determined for each wiring cable 150. For the auxiliary capacitor Cas2, the capacitance value is finally selected using the equations (4) and (6) so that the carrier ripple, that is, the gain | H3 | at the carrier frequency fc is within the target value. It is incorporated in the cable 150. Of course, also in the second embodiment, it is not necessary to provide the auxiliary capacitor Cas2 for the wiring cable 150 whose resonance peak is sufficiently away from the carrier frequency fc.

  In this way, it is possible to avoid the carrier ripple from being superimposed on the drive signal applied to the actuator 116 no matter what wiring cable 150 is connected.

F. Liquid jet printer (printer):
FIG. 12 is a schematic diagram illustrating an embodiment of a liquid jet printing apparatus using the capacitive load driving circuit of the present embodiment. FIG. 12A is a schematic configuration front view. FIG. 12B is a plan view of the vicinity of the liquid jet head.

  The liquid jet printing apparatus according to this embodiment includes a capacitive load driving circuit (not shown) described in the above embodiment, a liquid tank (not shown) for supplying liquid via a liquid supply tube, and a liquid tank. A plurality of liquid ejecting heads having a liquid chamber (not shown) into which the liquid supplied from the liquid flows in, an actuator (not shown) as a capacitive load, and an ejection nozzle that ejects the liquid that has flowed into the liquid chamber (Injection unit) 2. The liquid ejection type printing apparatus ejects the liquid that has flowed into the liquid chamber from the ejection nozzles when a drive signal is applied to the actuator.

  Among the liquid ejecting printing apparatuses, those that place the liquid ejecting head 2 on which the liquid ejecting nozzles are formed on a moving body called a carriage and move it in a direction intersecting the transport direction of the print medium are generally “multi-pass printing apparatuses”. It is called. On the other hand, what is capable of printing in a so-called one pass by arranging a long liquid jet head in a direction crossing the conveyance direction of the printing medium is generally called a “line head type printing apparatus”.

  Reference numeral 2 in FIG. 12A denotes a plurality of liquid ejecting heads provided above the conveyance line of the print medium 1, and a direction so as to form two rows in the print medium conveyance direction and intersect the print medium conveyance direction. Are arranged side by side and fixed to the head fixing plate 11, respectively. A large number of nozzles are formed on the lowermost surface of each liquid jet head 2, and this surface is called a nozzle surface. As shown in FIG. 12 (b), the nozzles are arranged in a row in the direction intersecting the print medium transport direction for each color of the liquid to be ejected. The nozzle row direction. A line head that extends over the entire length in the direction intersecting the transport direction of the print medium 1 is formed by the nozzle rows of all the liquid jet heads 2 arranged in the direction intersecting the print medium transport direction. When the print medium 1 passes below the nozzle surfaces of these liquid ejecting heads 2, printing is performed by ejecting liquid from a large number of nozzles formed on the nozzle surfaces.

  For example, liquids such as yellow (Y), magenta (M), cyan (C), and black (K) inks are supplied to the liquid ejecting head 2 from liquid tanks of respective colors (not shown) through liquid supply tubes. Supplied. Then, a small amount of liquid is output onto the print medium 1 by ejecting a necessary amount of liquid from a nozzle formed in each liquid ejecting head 2 to a necessary portion at the same time. By performing this for each color, it is possible to perform printing in a so-called one pass only by passing the print medium 1 conveyed by the conveyance unit once.

  As a method of ejecting liquid from each nozzle of the liquid ejecting head, there are an electrostatic method, a piezo method, a film boiling liquid ejecting method, and the like. In this embodiment, the piezo method is used. In the piezo method, when a drive signal is given to a piezoelectric element that is a nozzle actuator, the diaphragm in the cavity is displaced to cause a pressure change in the cavity, and a droplet is ejected from the nozzle by the pressure change. . The droplet ejection amount can be adjusted by adjusting the peak value of the drive signal and the voltage increase / decrease slope.

  As shown in FIG. 12B, the line head type printing apparatus is provided with a plurality of liquid jet heads. The capacitive load driving circuit and the plurality of liquid jet heads are connected to each other by the wiring cable 150 described above. However, since the plurality of liquid ejecting heads are long in the direction intersecting with the conveyance direction of the print medium, each wiring cable 150 connecting the capacitive load driving circuit and the plurality of liquid ejecting heads is liquid. Depending on the positional relationship between the ejection head and the capacitive load drive circuit, a suitable length is prepared.

  Then, for the reasons described above, at least some of the plurality of liquid ejecting heads may possibly have a large carrier ripple depending on the length of the cable. As a result, in the liquid jet printing apparatus, appropriate droplet discharge control becomes difficult, and the image quality of the printed matter may be deteriorated.

  Even in such a case, according to the present embodiment, the resonance frequency between the inductance component of the wiring cable and the capacitive load (liquid ejecting head) is shifted from the carrier frequency to avoid the carrier ripple from being superimposed. Therefore, a plurality of actuators can be driven with an intended drive signal. As a result, it is possible to avoid a decrease in the image quality of the printed material. This embodiment can also be applied to an electrostatic system.

  Although the capacitive load drive circuits of various embodiments have been described above, the present invention is not limited to all the embodiments described above, and can be implemented in various modes without departing from the scope of the invention. For example, by applying the capacitive load driving circuit of this embodiment to various electronic devices including medical devices such as a fluid ejection device used for forming a microcapsule containing a medicine or a nutrient, power efficiency is improved. A miniaturized electronic device can be provided. The present invention can also be suitably applied to a capacitive load driving circuit that is mounted on an ink jet printer and drives an ejection nozzle that ejects ink.

  DESCRIPTION OF SYMBOLS 100 ... Liquid injection apparatus 110 ... Injection unit 111 ... Injection nozzle 112 ... Liquid passage pipe 113 ... Front block 114 ... Rear block 115 ... Liquid chamber 116 ... Actuator (capacitive load) 120 ... Supply pump 121 ... Tube 122 ... Tube 123 ... Liquid tank 130 ... Control unit 150 ... Wiring cable 152 ... Connector 154 ... Connector 200 ... Capacitive load drive circuit 210 ... Drive waveform signal generation circuit 230 ... Modulation circuit 240 ... Digital power amplifier 250 ... Smooth filter.

Claims (5)

A capacitive load to change the volume of the liquid chamber connected to the nozzle;
And the capacitive load driving circuit for generating drive signals for driving the pre-Symbol capacitive load,
A wiring cable for connecting the capacitive load and the capacitive load drive circuit;
A capacitor provided in parallel with the wiring cable ,
Before Symbol capacitive load driving circuit,
A drive waveform signal generating circuit for generating a drive waveform signal which is a reference of the drive signal;
A modulation circuit that generates a modulation signal by pulse-modulating the drive waveform signal;
A digital power amplifier that amplifies the modulated signal to generate a pulsed power amplified modulated signal;
A smoothing filter that generates the drive signal by smoothing the pulse-wave-shaped power amplification modulation signal ;
The wiring cable can connect the smoothing filter and the capacitive load,
A first terminal and a second terminal connected to the smoothing filter side;
A third terminal connecting the capacitive load and the first terminal;
A fourth terminal connecting the capacitive load and the second terminal;
The capacitor is a liquid ejecting apparatus provided between at least one of the first terminal and the third terminal or between the second terminal and the fourth terminal . A capacitive load to change the volume of the liquid chamber connected to the nozzle;
A capacitive load drive circuit for generating a drive signal for driving the capacitive load;
A capacitor having a capacitor, and a wiring cable for connecting the capacitive load and the capacitive load driving circuit,
The capacitive load driving circuit includes:
A drive waveform signal generating circuit for generating a drive waveform signal which is a reference of the drive signal;
A modulation circuit that generates a modulation signal by pulse-modulating the drive waveform signal;
A digital power amplifier that amplifies the modulated signal to generate a pulsed power amplified modulated signal;
A smoothing filter that generates the drive signal by smoothing the pulse-wave-shaped power amplification modulation signal;
The wiring cable can connect the smoothing filter and the capacitive load,
Condenser provided before Symbol wiring cables, Ru condenser der of capacity according to the inductance value or the impedance value of the wiring cable, a liquid ejecting apparatus. A capacitive load to change the volume of the liquid chamber connected to the nozzle;
A capacitive load drive circuit for generating a drive signal for driving the capacitive load;
A capacitor having a capacitor, and a wiring cable for connecting the capacitive load and the capacitive load driving circuit,
The capacitive load driving circuit includes:
A drive waveform signal generating circuit for generating a drive waveform signal which is a reference of the drive signal;
A modulation circuit that generates a modulation signal by pulse-modulating the drive waveform signal;
A digital power amplifier that amplifies the modulated signal to generate a pulsed power amplified modulated signal;
A smoothing filter that generates the drive signal by smoothing the pulse-wave-shaped power amplification modulation signal;
The wiring cable can connect the smoothing filter and the capacitive load,
Condenser provided before Symbol wire cable is a condenser capacity corresponding to the length of the connection cable, the liquid ejecting apparatus. The printing apparatus which has a liquid ejecting apparatus as described in any one of Claims 1-3 . A medical device comprising the liquid ejecting apparatus according to any one of claims 1 to 3 .