Liquid ejection device and printing device

A liquid ejection device includes a switching circuit. The switching circuit includes: a multilayer wiring board including a first wiring layer and a second wiring layer; a first transistor and a second transistor mounted on the first wiring layer side of the multilayer wiring board; and a capacitor mounted on the second wiring layer side of the multilayer wiring board. When the multilayer wiring board is viewed in a plan view, a third via conductor is arranged in an area not overlapping a straight-line path connecting a source electrode of the first transistor with a drain electrode of the second transistor in a second wire.

This application claims the benefit of Japanese Patent Application No. 2013-62926, filed on Mar. 25, 2013. The content of the aforementioned application is incorporated herein by reference in its entirety.

BACKGROUND

1. Technical Field

The present invention relates to a liquid ejection device, a printing device, and the like.

2. Related Art

Like an ejection head mounted on an inkjet printer, there are many actuators composed of a capacitive load such as a piezoelectric element. For driving the actuator as a capacitive load, a drive signal at a certain level of power is needed. Therefore, the drive signal is generated by power-amplifying a drive waveform signal as the source of the drive signal. In this case, when an analog drive waveform signal is power-amplified in an analog manner to directly generate an analog drive signal, power efficiency is reduced because a large power loss occurs. Therefore, a technique of performing power amplification using a so-called class-D amplifier has been proposed.

When using a switching circuit such as a class-D amplifier, a bypass capacitor is generally arranged between a power supply potential and a ground potential for suppressing the ringing of output voltage (for example, JP-A-2011-187809 (Patent Document 1)). In inkjet printers, the occurrence of ringing leads to the occurrence of EMI noise. As a result, the discharge amount of ink varies, which is obstructive to an improvement in print quality.

It is important for suppressing the ringing to reduce the wire impedance of a loop formed of two transistors and a bypass capacitor that constitute a switching circuit. In a multilayer wiring board shown in FIGS. 1 and 2 of Patent Document 1, a wire has to be routed around via conductors, which is a cause of increasing the wire impedance of the loop formed of the two transistors and the bypass capacitor that constitute the switching circuit. For this reason, when the multilayer wiring board disclosed in Patent Document 1 is used for a printing device or the like, there are limitations to suppress ringing, that is, to improve print quality.

SUMMARY

An advantage of some aspects of the invention is to provide a liquid ejection device that can accurately discharge a liquid, a printing device, and the like.

Application Example 1

This application example is directed to a liquid ejection device including a switching circuit, the switching circuit including: a multilayer wiring board including a first wiring layer and a second wiring layer; a first transistor and a second transistor mounted on the first wiring layer side of the multilayer wiring board; and a capacitor mounted on the second wiring layer side of the multilayer wiring board, wherein the multilayer wiring board includes a first wire, a second wire, and a third wire formed in the first wiring layer, a fourth wire, a fifth wire, and a sixth wire formed in the second wiring layer, a first via conductor electrically connecting the first wire with the fourth wire, a second via conductor electrically connecting the third wire with the fifth wire, and a third via conductor electrically connecting the second wire with the sixth wire, a drain electrode of the first transistor is electrically connected with the first wire, a source electrode of the first transistor is electrically connected with the second wire, a drain electrode of the second transistor is electrically connected with the second wire, a source electrode of the second transistor is electrically connected with the third wire, a first electrode of the capacitor is electrically connected with the fourth wire, a second electrode of the capacitor is electrically connected with the fifth wire, and when the multilayer wiring board is viewed in a plan view, the third via conductor is arranged in an area not overlapping a straight-line path connecting the source electrode of the first transistor with the drain electrode of the second transistor in the second wire.

According to this application example, since the third via conductor is arranged in the area not overlapping the straight-line path connecting the source electrode of the first transistor with the drain electrode of the second transistor in the second wire, the fourth wire or the fifth wire electrically connected with the capacitor does not have to be routed around the third via conductor. Hence, it is possible to reduce the wire impedance of a loop formed of the first transistor, the second transistor, and the capacitor. Due to this, the ringing of the output voltage of the switching circuit can be suppressed. Hence, it is possible to realize the liquid ejection device that can accurately discharge a liquid.

Application Example 2

In the liquid ejection device according to the application example described above, it is preferable that when the multilayer wiring board is viewed in the plan view, at least a portion of the fourth wire or the fifth wire is arranged so as to overlap the straight-line path connecting the source electrode of the first transistor with the drain electrode of the second transistor in the second wire.

According to this application example, currents in opposite directions generally flow in the area where the second wire and the fourth wire or the fifth wire overlap each other. Hence, due to the effect of mutual inductance, the parasitic inductance becomes small. Due to this, the ringing of the output voltage of the switching circuit can be suppressed. Hence, it is possible to realize the liquid ejection device that can accurately discharge a liquid.

Application Example 3

In the liquid ejection device according to the application example described above, it is preferable that when the multilayer wiring board is viewed in the plan view, the capacitor is arranged at a position closer to the second transistor than the first transistor.

In many cases, the drain electrode of a transistor is formed to be larger in size than the source electrode. Therefore, heat generated by the transistor is released to the multilayer wiring board mainly via the drain electrode. According to this application example, the capacitor is arranged at the position closer to the second transistor than the first transistor, and therefore arranged at a position far from the drain electrode of the first transistor. Hence, the capacitor is less susceptible to the influence of heat generation of the first transistor.

Application Example 4

In the liquid ejection device according to the application example described above, it is preferable that the multilayer wiring board further includes a seventh wire formed in the first wiring layer, that a gate electrode of the first transistor is electrically connected with the seventh wire, and that when the multilayer wiring board is viewed in the plan view, the sixth wire and the seventh wire are formed at positions where at least a portion of the sixth wire and at least a portion of the seventh wire overlap each other.

In the area where the sixth wire and the seventh wire overlap each other, currents in opposite directions generally flow. According to this application example, the sixth wire and the seventh wire are formed at the positions where at least a portion of the sixth wire and at least a portion of the seventh wire overlap each other. Therefore, due to the effect of mutual inductance, the parasitic inductance becomes small. Due to this, the ringing of the output voltage of the switching circuit can be suppressed. Hence, it is possible to realize the liquid ejection device that can accurately discharge a liquid.

Application Example 5

In the liquid ejection device according to the application example described above, it is preferable that the multilayer wiring board further includes an eighth wire formed in the first wiring layer, that a gate electrode of the second transistor is electrically connected with the eighth wire, and that when the multilayer wiring board is viewed in the plan view, the fifth wire and the eighth wire are formed at positions where at least a portion of the fifth wire and at least a portion of the eighth wire overlap each other.

In the area where the fifth wire and the eighth wire overlap each other, currents in opposite directions generally flow. According to this application example, the fifth wire and the eighth wire are formed at the positions where at least a portion of the fifth wire and at least a portion of the eighth wire overlap each other. Therefore, due to the effect of mutual inductance, the parasitic inductance becomes small. Due to this, the ringing of the output voltage of the switching circuit can be suppressed. Hence, it is possible to realize the liquid ejection device that can accurately discharge a liquid.

Application Example 6

This application example is directed to a printing device including any of the liquid ejection devices described above.

According to this application example, since the liquid ejection device that can accurately discharge a liquid is included, it is possible to realize the printing device with good print quality.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, a preferred embodiment of the invention will be described in detail with reference to the drawings. The drawings used herein are for purposes of description. The embodiment described below does not unduly limit the contents of the invention set forth in the appended claims. Moreover, not all of the configurations described below are essential components of the invention.

The embodiment of the invention will be described below in the following order.

1. Configuration example of printing device and liquid ejection device

2. Circuit configuration of capacitive load drive circuit

3. Arrangement example of switching circuit

4. Modified example of arrangement example of switching circuit

5. Medical device

1. Configuration Example of Printing Device and Liquid Ejection Device

FIG. 1is an explanatory view showing a configuration example of an inkjet printer10as an example of a printing device. The inkjet printer10shown inFIG. 1includes a carriage23that forms an ink dot on a print medium3while reciprocating in a main scanning direction, a drive mechanism33that makes the carriage23reciprocate, and a platen roller36for feeding the print medium3. The carriage23is provided with an ink cartridge16that contains ink, a carriage case22into which the ink cartridge16is loaded, an ejection head24that is mounted on the bottom surface side (side facing the print medium3) of the carriage case22to eject ink, and the like. The ink in the ink cartridge16is guided to the ejection head24, and ejected from the ejection head24onto the print medium3, so that an image is printed.

The drive mechanism33that makes the carriage23reciprocate includes a timing belt35that is stretched by a pulley, and a step motor34that drives the timing belt35via the pulley. A portion of the timing belt35is fixed to the carriage case22. By driving the timing belt35, the carriage case22can be reciprocated. The platen roller36constitutes, together with a not-shown drive motor or gear mechanism, a sheet feeding mechanism that feeds the print medium3, and can feed the print medium3in a sub-scanning direction by a predetermined amount.

On the inkjet printer10, a printer control circuit50that controls the overall operation, and a capacitive load drive circuit200for driving the ejection head24are also mounted. The printer control circuit50controls the overall operation of the capacitive load drive circuit200, the drive mechanism33, the sheet feeding mechanism, and the like to drive the ejection head24to eject ink while feeding the print medium3.

FIG. 2is an explanatory view showing a configuration example of a liquid ejection device100included in the inkjet printer10.FIG. 2shows a state where the capacitive load drive circuit200drives the ejection head24under the control of the printer control circuit50. First of all, the internal structure of the ejection head24will be briefly described. As shown in the drawing, a plurality of ejection ports101for ejecting ink drops are provided in the bottom surface of the ejection head24facing the print medium3. The ejection ports101are connected respectively to ink chambers102. The ink chamber102is filled with ink supplied from the ink cartridge16. A piezo element104is provided above each of the ink chambers102. When a voltage is applied to the piezo element104, the piezo element104is deformed to pressurize the ink chamber102, so that the ink is ejected through the ejection port101. The deformation amount of the piezo element104varies depending on the voltage value to be applied to the piezo element104. A proper voltage waveform is applied to the piezo element104to control the deformation amount or timing of the ink chamber102, so that a proper amount of ink can be ejected at proper timing.

A drive signal408as a voltage to be applied to the piezo element104is generated by the capacitive load drive circuit200based on a control signal400from the printer control circuit50. The generated drive signal408is supplied to the piezo element104via a gate unit300. The gate unit300is a circuit unit including a plurality of gate elements302connected in parallel. The gate elements302can be individually brought into a conductive state or a cut-off state under the control from the printer control circuit50. Hence, the drive signal408output from the capacitive load drive circuit200transmits through the gate element302previously set by the printer control circuit50into the conductive state, and is applied to the corresponding piezo element104, so that the ink is ejected through the ejection port101corresponding to the piezo element104.

2. Circuit Configuration of Capacitive Load Drive Circuit

FIG. 3is an explanatory view showing the detailed configuration of the capacitive load drive circuit200of the embodiment. As shown in the drawing, the capacitive load drive circuit200is configured to include a drive waveform generator210that generates a drive waveform signal402, a modulator220that pulse-modulates the drive waveform signal402to generate a modulated signal GH and a modulated signal GL, a switching circuit230that accepts the modulated signal GH and the modulated signal GL to generate an amplified digital signal406as a signal obtained by power-amplifying the modulated signal GH and the modulated signal GL, and a low pass filter240that smoothes the amplified digital signal406to generate the drive signal408. A capacitive load Z1to which the drive signal408is applied corresponds to the piezo element104shown inFIG. 2.

The drive waveform generator210generates, based on the control signal400, the drive waveform signal402as a reference of the drive signal408.

The modulator220is configured to include a PWM modulator221that performs PWM-modulation (pulse-width modulation) on the drive waveform signal402to generate a PWM modulated signal404, and a gate driver circuit222that generates the modulated signal GH and the modulated signal GL based on the PWM modulated signal404.

The gate driver circuit222is configured to include a level shifter224that adjusts the level of the PWM modulated signal404, a high-side driver228H that switches ON/OFF of a first transistor M1based on the PWM modulated signal404via the level shifter224, and a low-side driver228L that switches ON/OFF of a second transistor M2based on the PWM modulated signal404via the level shifter224.

A signal output from the high-side driver228H to switch ON/OFF of the first transistor M1is the modulated signal GH, while a signal output from the low-side driver228L to switch ON/OFF of the second transistor M2is the modulated signal GL.

The switching circuit230is configured as a digital power amplifier including the first transistor M1and the second transistor M2that generate the amplified digital signal406, and a capacitor C1that functions as a bypass capacitor. In the capacitive load drive circuit200of the embodiment, the first transistor M1and the second transistor M2are each an N-type MOSFET. However, another kind of element such as an insulated gate bipolar transistor (IGBT) may be used. Examples of switching circuits to which the invention is applied include various kinds of switching circuits including a switching amplifier circuit, a switching power supply circuit, a motor drive circuit, and an inverter circuit.

As shown inFIG. 3, the first transistor M1and the second transistor M2are connected between a potential VDD (hereinafter referred to simply as VDD) supplied from a power supply and a ground potential GND (hereinafter referred to simply as GND). By switching ON/OFF of the first transistor M1and the second transistor M2, the amplified digital signal406is generated. A contact point (node) where the first transistor M1and the second transistor M2are connected together is a first node N1. The first node N1is located on a wire through which the amplified digital signal406passes. The capacitor C1is connected between VDD and GND.

The low pass filter240removes a high-frequency component of the amplified digital signal406to generate the drive signal408. In the example shown inFIG. 3, the low pass filter240is configured as a low-pass filter including a coil LF and a capacitor CF.

FIG. 4is an explanatory view showing the outline of operation of the capacitive load drive circuit200to generate the drive signal408. The drive waveform generator210generates, for example, the drive waveform signal402shown inFIG. 4based on the control signal400. The drive waveform signal402is not limited to an analog signal shown in FIG.4, and may be, for example, a signal output at DC level or a multibit digital signal.

The drive waveform generator210may include, for example, an operator, and generate the drive waveform signal402through arithmetic operation based on the control signal400. Moreover, the drive waveform generator210may include, for example, a waveform memory that stores waveforms, and generate the drive waveform signal402corresponding to the control signal400with reference to the waveform memory.

When accepting the drive waveform signal402from the drive waveform generator210, the modulator220performs predetermined modulation to generate the modulated signal GH and the modulated signal GL. The predetermined modulation is pulse-width modulation (PWM) in the embodiment. However, another modulation method such as pulse-density modulation (PDM) may be used.

The switching circuit230accepts the modulated signal GH and the modulated signal GL and performs power amplification. As shown inFIG. 3, the switching circuit230amplifies power using the first transistor M1and the second transistor M2. In the example shown inFIG. 4, the switching circuit230generates the amplified digital signal406that is obtained by amplifying the voltage of the PWM modulated signal404to VDD.

Then, the low pass filter240smoothes the amplified digital signal406to generate the drive signal408in an analog form where a portion modulated into a wide pulse width has a high voltage value and a portion modulated into a narrow pulse width has a low voltage value. As shown inFIG. 3, the low pass filter240can be easily realized by combining the coil LF and the capacitor CF.

In the capacitive load drive circuit200of the embodiment, since power is amplified by switching ON/OFF of the first transistor M1and the second transistor M2in the switching circuit230, unnecessary power is not consumed. Moreover, the low pass filter240can be composed of components with less power consumption such as the coil LF and the capacitor CF. For this reason, power loss can be greatly reduced compared to the case where the drive waveform signal402in an analog form is power-amplified as analog like a so-called analog amplifier circuit. Therefore, power loss when generating the drive signal408can be greatly reduced.

In the switching circuit230described above, the ringing of output voltage is a problem in some cases. The occurrence of ringing causes EMI noise, which is obstructive to the operation of the device itself or peripheral equipment. When the rise time of a switching waveform is increased for suppressing the ringing, power efficiency is reduced, or the accuracy of fluid control is reduced. Moreover, the occurrence of ringing increases a voltage to be applied to the first transistor M1and the second transistor M2, which causes an element breakdown or malfunction.

Factors causing the ringing include the resonance phenomenon due to the parasitic resistance and parasitic inductance of an electrical loop including the first transistor M1, the second transistor M2, and the capacitor C1and the parasitic capacitance between the drain and source of the first transistor M1or the second transistor M2, the resonance phenomenon due to the parasitic inductance of an electrical loop including the high-side driver228H and the first transistor M1and the gate capacitance of the first transistor M1, and the resonance phenomenon due to the parasitic inductance of an electrical loop including the low-side driver228L and the second transistor M2and the gate capacitance of the second transistor M2.

Hence, when arranging elements or wires constituting the switching circuit230, it is especially important to reduce the wire impedance (parasitic resistance and parasitic inductance) of an electrical loop.

3. Arrangement Example of Switching Circuit

The switching circuit230in the embodiment is configured to include a multilayer wiring board1000including a first wiring layer and a second wiring layer, the first transistor M1and the second transistor M2mounted on the first wiring layer side of the multilayer wiring board1000, and the capacitor C1mounted on the second wiring layer side of the multilayer wiring board1000.

FIGS. 5A and 5Bare plan views showing an arrangement example of the switching circuit230.FIG. 5Amainly shows the configuration of the first wiring layer.FIG. 5Bmainly shows the configuration of the second wiring layer. InFIGS. 5A and 5B, the solid-line polygons indicate wires formed in the first wiring layer or the second wiring layer, while the solid-line circles indicate the positions of via conductors that electrically connect the wires of the first wiring layer with the wires of the second wiring layer. Also inFIGS. 5A and 5B, the dash-dotted lines indicate the mounting positions of the transistors, capacitors, and coil, while the dashed lines indicate the positions of electrodes of the transistors, capacitors, and coil.

FIG. 6is a cross-sectional view taken along the line A-A inFIGS. 5A and 5B. As shown inFIG. 6, an insulating layer is provided between the first wiring layer and the second wiring layer of the multilayer wiring board1000. That is, the wires formed in the first wiring layer and the wires formed in the second wiring layer are insulated from each other, excepting the case where the wires are connected by means of the via conductor. In general, the thickness of the insulating layer is sufficiently smaller than the wire width. The multilayer wiring board1000may include three or more wiring layers, and any two wiring layers selected from the three or more wiring layers may be used as the first wiring layer and the second wiring layer. The first wiring layer and the second wiring layer are preferably closest to each other. The multilayer wiring board1000may include a protective layer that protects the wiring layer.

As shown inFIGS. 5A and 5B, the multilayer wiring board1000in the embodiment is configured to include a first wire1001, a second wire1002, and a third wire1003that are formed in the first wiring layer, a fourth wire1004, a fifth wire1005, and a sixth wire1006that are formed in the second wiring layer, first via conductors2001that electrically connect the first wire1001with the fourth wire1004, second via conductors2002that electrically connect the third wire1003with the fifth wire1005, and third via conductors2003that electrically connect the second wire1002with the sixth wire1006.

A drain electrode D of the first transistor M1is electrically connected with the first wire1001. A source electrode S of the first transistor M1is electrically connected with the second wire1002. A drain electrode D of the second transistor M2is electrically connected with the second wire1002. A source electrode S of the second transistor M2is electrically connected with the third wire1003. A first electrode +C1of the capacitor C1is electrically connected with the fourth wire1004. A second electrode −C1of the capacitor C1is electrically connected with the fifth wire1005.

That is, a portion of a wiring path from the drain electrode D of the first transistor M1to the first electrode +C1of the capacitor C1is formed as the fourth wire1004of the second wiring layer. Moreover, a portion of a wiring path from the source electrode S of the second transistor M2to the second electrode −C1of the capacitor C1is formed as the fifth wire1005of the second wiring layer.

When the multilayer wiring board1000is viewed in a plan view, the third via conductors2003are arranged in an area not overlapping a straight-line path connecting the source electrode S of the first transistor M1with the drain electrode D of the second transistor M2in the second wire1002. The straight-line path connecting the source electrode S of the first transistor M1with the drain electrode D of the second transistor M2in the second wire1002is a dominant path as the path of current flowing between the source electrode S of the first transistor M1and the drain electrode D of the second transistor M2.

According to the embodiment, since the third via conductors2003are arranged in the area not overlapping the straight-line path connecting the source electrode S of the first transistor M1with the drain electrode D of the second transistor M2in the second wire1002, the fourth wire1004or the fifth wire1005that is electrically connected with the capacitor C1does not have to be routed around the third via conductors2003. Hence, the wire impedance of the loop formed of the first transistor M1, the second transistor M2, and the capacitor C1can be reduced. Due to this, the ringing of the output voltage of the switching circuit230can be suppressed. Hence, it is possible to realize the liquid ejection device100that can accurately discharge a liquid.

In the example shown inFIGS. 5A and 5B, when the multilayer wiring board1000is viewed in the plan view, at least a portion of the fourth wire1004or the fifth wire1005is arranged so as to overlap the straight-line path connecting the source electrode S of the first transistor M1with the drain electrode D of the second transistor M2in the second wire1002. In the example shown inFIGS. 5A and 5B, when the multilayer wiring board1000is viewed in the plan view, especially a portion of the fourth wire1004is arranged so as to overlap the straight-line path connecting the source electrode S of the first transistor M1with the drain electrode D of the second transistor M2in the second wire1002.

FIG. 7explains a parasitic inductance. InFIG. 7, two wires provided spaced apart from each other are illustrated. When current flows through one of the wires, a counter-electromotive force is generated in a direction of cancelling a magnetic field produced by the current itself. When the two wires are provided in proximity to each other, a counter-electromotive force is generated also in the other wire in the direction of cancelling the magnetic field produced by the current flowing through the one wire (effect of mutual inductance). Hence, by wiring the two wires such that the currents flowing through the two wires flow in opposite directions, the parasitic inductance of the wire can be reduced.

According to the embodiment, in the area where the second wire1002overlaps the fourth wire1004or the fifth wire1005, currents in opposite directions generally flow. Hence, due to the effect of mutual inductance, the parasitic inductance becomes small. Due to this, the ringing of the output voltage of the switching circuit230can be suppressed. Hence, it is possible to realize the liquid ejection device100that can accurately discharge a liquid.

In general, the thickness of the insulating layer is sufficiently smaller than the wire width. Therefore, even compared to the case where all wires are formed in the same wiring layer, it is possible to suppress an increase in the area of the electrical loop including the first transistor M1, the second transistor M2, and the capacitor C1. That is, an increase in parasitic inductance can be suppressed. Due to this, the ringing of the output voltage of the switching circuit230can be suppressed. Hence, it is possible to realize the liquid ejection device100that can accurately discharge a liquid.

In the example shown inFIGS. 5A and 5B, when the multilayer wiring board1000is viewed in the plan view, the capacitor C1is arranged at a position closer to the second transistor M2than the first transistor M1.

In many cases, the drain electrode of a transistor is formed to be larger in size than the source electrode. Therefore, heat generated by the transistor is released to the multilayer wiring board1000mainly via the drain electrode. According to the embodiment, the capacitor C1is arranged at the position closer to the second transistor M2than the first transistor M1, and therefore arranged at a position far from the drain electrode D of the first transistor M1. Hence, the capacitor C1is less susceptible to the influence of heat generation of the first transistor M1.

In the example shown inFIGS. 5A and 5B, the multilayer wiring board1000further includes a seventh wire1007formed in the first wiring layer. A gate electrode G of the first transistor M1is electrically connected with the seventh wire1007. When the multilayer wiring board1000is viewed in the plan view, the sixth wire1006and the seventh wire1007are formed at positions where at least a portion of the sixth wire1006and at least a portion of the seventh wire1007overlap each other.

In the area where the sixth wire1006and the seventh wire1007overlap each other, currents in opposite directions generally flow. According to the embodiment, since the sixth wire1006and the seventh wire1007are formed at the positions where at least a portion of the sixth wire1006and at least a portion of the seventh wire1007overlap each other, the parasitic inductance becomes small due to the effect of mutual inductance. Due to this, the ringing of the output voltage of the switching circuit230can be suppressed. Hence, it is possible to realize the liquid ejection device100that can accurately discharge a liquid.

In the example shown inFIGS. 5A and 5B, the multilayer wiring board1000further includes an eighth wire1008formed in the first wiring layer. A gate electrode G of the second transistor M2is electrically connected with the eighth wire1008. When the multilayer wiring board1000is viewed in the plan view, the fifth wire1005and the eighth wire1008are formed at positions where at least a portion of the fifth wire1005and at least a portion of the eighth wire1008overlap each other.

In the area where the fifth wire1005and the eighth wire1008overlap each other, currents in opposite directions generally flow. According to the embodiment, since the fifth wire1005and the eighth wire1008are formed at the positions where at least a portion of the fifth wire1005and at least a portion of the eighth wire1008overlap each other, the parasitic inductance becomes small due to the effect of mutual inductance. Due to this, the ringing of the output voltage of the switching circuit230can be suppressed. Hence, it is possible to realize the liquid ejection device100that can accurately discharge a liquid.

In the example shown inFIGS. 5A and 5B, the multilayer wiring board1000further includes a ninth wire1009formed in a wiring layer other than the first wiring layer, and fourth via conductors2004that electrically connect the second wire1002with the ninth wire1009.

According to the embodiment, since the ninth wire1009that is electrically connected with the second wire1002is formed in the wiring layer (for example, the second wiring layer) other than the first wiring layer, the ninth wire1009functions as a heat sink. Hence, the heat dissipation efficiency of the second transistor M2can be improved.

In the example shown inFIGS. 5A and 5B, the multilayer wiring board1000further includes a tenth wire1010that is formed in the first wiring layer and electrically connected with a first electrode +CF (electrode on the positive potential side) of the capacitor CF. The fifth wire1005and the tenth wire1010are formed at positions where at least a portion of the fifth wire1005and at least a portion of the tenth wire1010overlap each other when the multilayer wiring board1000is viewed in the plan view.

When common mode noise is superimposed on an output signal of the capacitive load drive circuit200, the component of common mode noise appears as current components in the same direction in the fifth wire1005and the tenth wire1010. According to the embodiment, the fifth wire1005and the tenth wire1010are formed at the positions where at least a portion of the fifth wire1005and at least a portion of the tenth wire1010overlap each other. Therefore, due to the effect of mutual inductance described with reference toFIG. 7, the wire impedance with respect to the current components in the same direction that flow in the fifth wire1005and the tenth wire1010is increased, which acts so as to cancel the common mode noise. Hence, the common mode noise can be suppressed. Moreover, EMI noise caused by the common mode noise can be suppressed.

FIG. 8Ais a graph showing an output voltage waveform example of the switching circuit230of the embodiment.FIG. 8Bis a graph showing an output voltage waveform example of a switching circuit of a comparative example. The switching circuit of the comparative example is a circuit in which all wires constituting the electrical loop including the first transistor M1, the second transistor M2, and the capacitor C1are formed in the first wiring layer. The electrical connections of the switching circuit are the same as those of the circuit diagram shown inFIG. 3. The output voltage waveform is a voltage waveform measured at anode corresponding to the first node N1.

In the output voltage waveform example of the comparative example shown inFIG. 8B, large ringing occurs at the rising and falling edges of the voltage waveform. On the other hand, in the output voltage waveform example of the embodiment shown inFIG. 8A, the occurrence of ringing is reduced due to the various actions described above.

When the liquid ejection device100that can accurately discharge a liquid is applied to a printing device (the inkjet printer10) as in the embodiment, a printing device with good print quality can be realized.

4. Modified Example of Arrangement Example of Switching Circuit

The same configurations as those of the embodiment described above are denoted by the same reference numerals and signs, and the detailed description is omitted. The circuit configuration of the capacitive load drive circuit200in the modified example is the configuration shown inFIG. 3.

FIGS. 9A and 9Bare plan views showing the modified example of the arrangement example of the switching circuit230.FIG. 9Ashows mainly the configuration of the first wiring layer.FIG. 9Bshows mainly the configuration of the second wiring layer. InFIGS. 9A and 9B, the solid-line polygons indicate wires formed in the first wiring layer or the second wiring layer, while the solid-line circles indicate the positions of via conductors that electrically connect the wires of the first wiring layer with the wires of the second wiring layer. Also inFIGS. 9A and 9B, the dash-dotted lines indicate the mounting positions of the transistors, capacitors, and coil, while the dashed lines indicate the positions of electrodes of the transistors, capacitors, and coil.

Comparing the embodiment with the modified example, the arrangement of the electrodes of the first transistor M1and the second transistor M2is different, but the other configurations are the same.

Also in the configuration described above, similar advantageous effects are provided for reasons similar to those of the embodiment described above.

5. Medical Device

The capacitive load drive circuit200using the switching circuit230can be mounted on various medical devices to enhance the reliability of the medical devices. Both of a fluid ejection device1and a fluid transport device20described later are configuration examples included in the liquid ejection device.

For example, the capacitive load drive circuit200can be applied as the fluid ejection device1.FIG. 10is an explanatory view illustrating the fluid ejection device1. The fluid ejection device1can be adopted in various applications such as cleaning of minute objects and structures, or surgical scalpel. However, the invention will be described herein as the fluid ejection device1that is suitable for operation or treatment of living tissues. Hence, a fluid herein is a liquid such as water or physiological saline.

InFIG. 10, the fluid ejection device1includes a fluid supply container2that contains a fluid, a pump14as a fluid supplying unit, a pulsed flow generator21that converts the fluid supplied from the pump14into pulsed flow (hereinafter referred to also as pulse flow), a drive control unit15that controls driving of the pump14and the pulsed flow generator21. The pump14and the pulsed flow generator21are connected by means of a fluid supply tube4.

A connection channel tube90having a narrow pipe shape is connected to the pulsed flow generator21. A nozzle95having a fluid ejection opening96with a reduced channel diameter is inserted in the connection channel tube90at the distal end. The connection channel tube90has a predetermined rigidity when ejecting a fluid.

The pulsed flow generator21includes an ejection command switching unit25. In the embodiment, a pulse flow command switch26for selecting pulse flow ejection, a continuous flow command switch27for selecting continuous flow ejection, and an OFF switch28for stopping fluid ejection are provided as the ejection command switching unit25.

The flow of fluid in the fluid ejection device1configured as described above will be briefly described. The fluid contained in the fluid supply container2is sucked by the pump14and supplied at a constant pressure to the pulsed flow generator21via the fluid supply tube4. The pulsed flow generator21includes a fluid chamber80(refer toFIG. 11described later), and a piezoelectric element30and a diaphragm40as a volume varying unit that varies the volume of the fluid chamber80. The pulsed flow generator21drives the piezoelectric element30to generate pulsed flow in the fluid chamber80, and ejects the fluid at a high speed in, for example, a pulsed manner from the fluid ejection opening96via the connection channel tube90and the nozzle95.

When the pulsed flow generator21stops driving, the fluid supplied from the pump14passes through the fluid chamber80and is ejected as continuous flow from the fluid ejection opening96.

The “pulsed flow” herein means the flow of fluid flowing in the constant direction and being associated with periodic or irregular variations in the flow rate or flow velocity of the fluid. The pulsed flow includes intermittent flow in which the flow and stop of the fluid are repeated, but does not necessarily have to be the intermittent flow because it is sufficient that the flow rate or flow velocity of the fluid varies periodically or irregularly.

In the same manner, “ejecting the fluid in a pulsed manner” means the ejection of fluid in which the flow rate or moving velocity of the fluid to be ejected varies periodically or irregularly. Examples of the ejection in a pulsed manner include intermittent ejection in which the ejection and non-ejection of the fluid are repeated. However, it does not have to be necessarily the intermittent ejection because it is sufficient that the flow rate or moving velocity of the fluid to be ejected varies periodically or irregularly.

FIG. 11is a cross-sectional view showing a cross section of the pulsed flow generator21according to the embodiment taken along the ejection direction of fluid.FIG. 11is a schematic view in which vertical and lateral reduction scales of members or portions are different from actual ones for convenience sake. The pulsed flow generator21is configured to include an inlet channel81for supplying a fluid from the pump14to the fluid chamber80via the fluid supply tube4, the piezoelectric element30and the diaphragm40as the volume varying unit that varies the volume of the fluid chamber80, and an outlet channel82in communication with the fluid chamber80. The fluid supply tube4is connected to the inlet channel81.

The diaphragm40is formed of, for example, a disk-shaped metal thin plate. The diaphragm40is in tight contact between a case52and a case70. The piezoelectric element30illustrated in the embodiment is a stacked piezoelectric element, and one of the both ends thereof is secured to the diaphragm40and the other end is secured to a bottom plate60.

The fluid chamber80is a space formed by a recess formed in a surface of the case70facing the diaphragm40and the diaphragm40. The outlet channel82is opened substantially at the center portion of the fluid chamber80.

The case70and the case52are integrally joined at respective surfaces facing each other. The connection channel tube90having a connection channel91in communication with the outlet channel82is fitted to the case70, and the nozzle95is inserted in the connection channel tube90at the distal end. The fluid ejection opening96having a reduced channel diameter is opened in the nozzle95.

The piezoelectric element30corresponds to the capacitive load Z1inFIG. 1. The deformation amount or deformation timing thereof is controlled by the drive signal408(refer toFIG. 10) from the capacitive load drive circuit200. By pressing the fluid chamber80as indicated by the arrow A inFIG. 11, a fluid can be ejected in a pulsed manner from the nozzle95at the distal end. The fluid ejection device1is used as, for example, a device for medical purposes. Specifically, the fluid ejection device1can be used as a surgical device as follows: a liquid is supplied at a high pressure from the pump14to the fluid supply tube4introduced into a body cavity, and the liquid is ejected from the nozzle95at the distal end to excise tissues in the body cavity by a fluid pressure.

Moreover, the capacitive load drive circuit200can be applied as the fluid transport device20that transports a liquid at a stable flow rate.

FIG. 12is a perspective view showing the appearance of a fluid transporter1A including the fluid transport device20of the embodiment. InFIG. 12, the fluid transporter1A includes the fluid transport device20that transports a fluid by peristaltic action, and a pack-shaped fluid containing container94that contains the fluid. The fluid transport device20and the fluid containing container94are in communication with each other by means of a tube4A.

The fluid containing container94is made of a synthetic resin having flexibility, and formed of, for example, a silicone-based resin. A tube holding portion92is provided at one end of the fluid containing container94, and the tube4A is hermetically fixed by means of pressure bonding, heat welding, adhesion, or the like so that the fluid does not leak.

The tube4A is in communication at one end with the interior of the fluid containing container94, passes through the fluid transport device20, and is extended to the outside of the fluid transport device20. The tube4A transports the fluid contained in the fluid containing container94to the outside with the fluid transport device20.

The fluid transport device20is formed by successively stacking a lower lid84, a pump unit frame31, a tube frame32, and an upper lid83and integrating them using fixing screws97(upper lid fixing screws are shown in the drawing) or the like. In the interior of the fluid transport device20, a push mechanism for transporting the fluid is stored.

When the fluid transporter1A is mounted on a living body, a highly biocompatible material, for example, a synthetic resin such as polysulfone or urethane is preferably adopted for the lower lid84, the pump unit frame31, the tube frame32, the upper lid83, and the fluid containing container94.

FIG. 13explains the mechanism of fluid transportation of the fluid transport device20. The drive signal408as a voltage to be applied to the piezo element104is generated by the capacitive load drive circuit200based on the control signal400from a push control circuit50A (not shown inFIG. 12). The generated drive signal408is supplied to the piezo element104via the gate unit300. The gate unit300is a circuit unit having the plurality of gate elements302connected in parallel. The gate elements302can be individually brought into the conductive state or the cut-off state under the control from the push control circuit50A. Hence, the drive signal408output from the capacitive load drive circuit200is caused, by the push control circuit50A, to successively pass through the gate elements302to be applied to the corresponding piezo element104, so that a corresponding pressing shaft106is pushed. The pressing shaft106is arranged in a direction substantially at right angle to a direction in which the fluid in the tube4A flows. Then, the tube4A is pressed successively by a plurality of pressing shafts106. Therefore, the fluid transport device20can transport the fluid in the tube4A by peristaltic action.

As fluids used in the invention, liquids having fluidity such as water, a salt solution, a medicinal solution, an oil, an aromatic solution, and ink, or gases can be used. For example, when a medicinal solution is used, the fluid transport device20can be used as a dosing pump.

According to the medical device of the embodiment described above, the switching circuit230in which the occurrence of ringing is suppressed is included, and therefore, it is possible to realize a medical device with which a fluid can be stably handled.

The embodiment and modified example described above are illustrative only, and the invention is not limited to them. For example, the embodiment and modified example can be appropriately combined.

The invention is not limited to the embodiment and modified example described above, and more various modifications are possible. For example, the invention includes configurations (for example, configurations having the same functions, methods, and results, or configurations having the same advantages and advantageous effects) that are substantially the same as those described in the embodiment. Moreover, the invention includes configurations in which a non-essential portion of the configurations described in the embodiment is replaced. Moreover, the invention includes configurations providing the same operational effects as those described in the embodiment, or configurations capable of achieving the same advantages. Moreover, the invention includes configurations in which a publicly known technique is added to the configurations described in the embodiment.