Liquid dispensing device and head unit

Abstract

The drive circuit can be cooled using a simple configuration. [Solution] A liquid dispensing device comprising: a dispensing unit that is driven by a drive signal to dispense liquid; a circuit board on which a drive circuit that generates a drive signal is arranged; and a clay-like heat conductive member having electrical insulating properties, wherein the drive circuit comprises an electronic component that generates heat in conjunction with the generation of the drive signal and an electrolytic capacitor, and the heat conductive member is in contact with the electronic component and the electrolytic capacitor.

Description

Technical Field

[0001] The present invention relates to a liquid ejection device and a head unit.

Background Art

[0002] There is known a liquid ejection device including a drive circuit that generates a drive signal and a ejection unit that is driven by the drive signal to eject a liquid. In such a liquid ejection device, since the drive signal for driving the ejection unit is a signal with a large amplitude, the drive circuit generates heat when generating the drive signal, and the drive circuit becomes hot. For this reason, various configurations for cooling the drive circuit have been proposed conventionally. For example, Patent Document 1 discloses a configuration in which heat generated from the drive circuit is radiated by a heat sink having a shape corresponding to the height of electronic components included in the drive circuit.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, according to the conventional technology, in order to efficiently cool the drive circuit, the shape of the heat sink may become complicated. For this reason, according to the conventional technology, for example, the manufacturing load of the configuration for cooling the drive circuit may increase, or the manufacturing cost of the configuration for cooling the drive circuit may increase.

Means for Solving the Problems

[0005] To solve the above problems, the liquid dispensing device according to the present invention comprises a dispensing unit that is driven by a drive signal to dispense liquid, a circuit board on which a drive circuit that generates the drive signal is arranged, and a clay-like heat conductive member having electrical insulating properties, wherein the drive circuit comprises an electronic component that generates heat in conjunction with the generation of the drive signal and an electrolytic capacitor, and the heat conductive member is in contact with the electronic component and the electrolytic capacitor.

[0006] Furthermore, the head unit according to the present invention comprises a discharge unit that discharges liquid when driven by a drive signal, a circuit board on which a drive circuit that generates the drive signal is arranged, and a clay-like heat conductive member having electrical insulating properties, wherein the drive circuit comprises an electronic component that generates heat in conjunction with the generation of the drive signal and an electrolytic capacitor, and the heat conductive member is in contact with the electronic component and the electrolytic capacitor. [Brief explanation of the drawing]

[0007] [Figure 1] This block diagram shows an example of the configuration of an inkjet printer 1 according to an embodiment of the present invention. [Figure 2] This is a perspective view showing an example of the general internal structure of inkjet printer 1. [Figure 3] This is a cross-sectional view showing an example of the structure of the discharge section D[m]. [Figure 4] This block diagram shows an example of the configuration of head unit 3. [Figure 5] This is a timing chart showing an example of the signals supplied to head unit 3. [Figure 6] This is an explanatory diagram showing an example of an individual designation signal Sd[m]. [Figure 7] This is a block diagram showing an example of the configuration of the drive signal generation circuit 40. [Figure 8] This is a plan view showing an example of the configuration of the drive signal generation circuit 40. [Figure 9] This is a cross-sectional view showing an example of the structure of the drive signal generation unit 4. [Figure 10]It is a plan view showing an example of the structure of the drive signal generation unit 4. [Figure 11] It is a schematic diagram showing an example of the outline of the heat conductive clay CY. [Figure 12] It is a cross-sectional view showing an example of the structure of the drive signal generation unit 4B according to Modification 1 of the present invention. [Figure 13] It is a cross-sectional view showing an example of the structure of the drive signal generation unit 4C according to Modification 2 of the present invention. [Figure 14] It is a cross-sectional view showing an example of the structure of the drive signal generation unit 4D according to Modification 3 of the present invention. [Figure 15] It is a block diagram showing an example of the configuration of the drive signal generation circuit 40E according to Modification 4 of the present invention. [Figure 16] It is a cross-sectional view showing an example of the structure of the drive signal generation unit 4E according to Modification 4 of the present invention. [Figure 17] It is a plan view showing an example of the structure of the inkjet printer 1F according to Modification 5 of the present invention. [Figure 18] It is a block diagram showing an example of the structure of the inkjet printer 1G according to Modification 6 of the present invention.

Embodiments of the Invention

[0008] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, in each figure, the dimensions and scales of each part are appropriately different from the actual ones. In addition, the embodiments described below are preferred specific examples of the present invention, and thus various technically preferable limitations are imposed. However, the scope of the present invention is not limited to these embodiments unless there is a description specifically limiting the present invention in the following description.

[0009] <<A. Embodiment>> Hereinafter, a liquid ejection device will be described by exemplifying an inkjet printer 1 that ejects ink to form an image on a recording paper PP.

[0010] <<A.1. Outline of the Inkjet Printer 1>> Hereinafter, an example of the configuration of the inkjet printer 1 according to the present embodiment will be described while referring to FIGS. 1 to 3.

[0011] FIG. 1 is a functional block diagram showing an example of the configuration of the inkjet printer 1.

[0012] As shown in FIG. 1, print data Img indicating an image to be formed by the inkjet printer 1 is supplied to the inkjet printer 1 from a host computer such as a personal computer or a digital camera. The inkjet printer 1 executes a printing process for forming an image indicated by the print data Img supplied from the host computer on a recording sheet PP.

[0013] As shown in FIG. 1, the inkjet printer 1 includes a control unit 2 that controls each part of the inkjet printer 1, a head unit 3 provided with a discharge unit D that discharges ink onto the recording sheet PP, a drive signal generation unit 4 provided with a drive signal generation circuit 40 that generates a drive signal Com for driving the discharge unit D, and a conveyance unit 9 for conveying the head unit 3 and the recording sheet PP. In the present embodiment, the inkjet printer 1 is an example of a "liquid discharge device", the ink is an example of a "liquid", and the drive signal generation circuit 40 is an example of a "drive circuit".

[0014] In the present embodiment, it is assumed that the inkjet printer 1 includes one or a plurality of head units 3. Specifically, in the present embodiment, as an example, it is assumed that the inkjet printer 1 includes four head units 3. Hereinafter, for convenience of explanation, as shown in FIG. 1, there may be cases where an explanation is made by focusing on one of the four head units 3.

[0015] Furthermore, in this embodiment, as an example, we assume that the inkjet printer 1 is equipped with one or more drive signal generation units 4 corresponding to one head unit 3. Specifically, in this embodiment, we assume that the inkjet printer 1 is equipped with one drive signal generation unit 4 corresponding to one head unit 3. That is, in this embodiment, we assume that the inkjet printer 1 is equipped with four drive signal generation units 4 corresponding to four head units 3. However, the present invention is not limited to these embodiments. The inkjet printer 1 may be equipped with two drive signal generation units 4 corresponding to one head unit 3, or with three or more drive signal generation units 4 corresponding to one head unit 3. For the sake of explanation, in the following, we may focus on one of the four drive signal generation units 4, as shown in Figure 1.

[0016] The control unit 2 is comprised of a control circuit (not shown) and a memory circuit (not shown). The memory circuit is composed of volatile memory such as RAM (Random Access Memory) and non-volatile memory such as ROM (Read Only Memory), EEPROM (Electrically Erasable Programmable Read-Only Memory), or PROM (Programmable ROM), and stores various information such as the control program for the inkjet printer 1. The control circuit consists of one or more CPUs (Central Processing Units). However, the control circuit may include a programmable logic device such as an FPGA (field-programmable gate array) instead of a CPU, or in addition to a CPU. The control circuit executes the control program for the inkjet printer 1 stored in the memory circuit and controls each part of the inkjet printer 1 by operating according to the control program. Specifically, the control circuit generates signals for controlling the operation of each part of the inkjet printer 1, such as a designation signal SI, a waveform designation signal dCom, and a carrier control signal SH.

[0017] Here, the waveform specification signal dCom is a digital signal that defines the waveform of the drive signal Com. The drive signal Com is an analog signal for driving the ejection unit D. The specification signal SI is a digital signal that specifies the type of operation of the ejection unit D. Specifically, the specification signal SI specifies whether or not to supply the drive signal Com to the ejection unit D, thereby specifying the type of operation of the ejection unit D, such as whether or not ink is ejected from the ejection unit D. The transport control signal SH is a signal for controlling the transport unit 9.

[0018] When printing is performed, the control unit 2 generates signals to control the head unit 3, such as a specified signal SI, based on the print data Img. The control unit 2 also generates signals to control the drive signal generation unit 4, such as a waveform specified signal dCom, when printing is performed. Furthermore, the control unit 2 generates signals to control the transport unit 9, such as a transport control signal SH, when printing is performed. In this way, during printing, the control unit 2 controls the transport unit 9 to move the head unit 3 and the recording paper PP, while adjusting the presence or absence of ink ejection from the ejection unit D, the ink ejection timing, etc., thereby controlling each part of the inkjet printer 1 so that an image corresponding to the print data Img is formed on the recording paper PP.

[0019] As shown in Figure 1, the head unit 3 comprises a supply circuit 31 and a head unit 32.

[0020] The print head 32 is equipped with M ejection units D. Here, the value M is a natural number satisfying "M≧1". In the following, the m-th ejection unit D among the M ejection units D provided in the print head 32 may be referred to as ejection unit D[m]. Here, the variable m is a natural number satisfying "1≦m≦M". Furthermore, in the following, if a component or signal of the inkjet printer 1 corresponds to ejection unit D[m] among the M ejection units D, the subscript [m] may be added to the code used to represent that component or signal. The supply circuit 31 switches whether or not to supply the drive signal Com to the discharge unit D[m] based on the specified signal SI. Hereinafter, the drive signal Com supplied to the discharge unit D[m] may be referred to as the supply drive signal Vin[m].

[0021] Figure 2 is a perspective view showing an example of the schematic internal structure of inkjet printer 1.

[0022] As shown in Figure 2, in this embodiment, we assume that the inkjet printer 1 is a serial printer. Specifically, when the inkjet printer 1 performs a printing process, it transports the recording paper PP in the X1 direction, and while moving the head unit 3 in the Y1 direction which intersects the X1 direction, or in the Y2 direction which is opposite to the Y1 direction, it ejects ink from the head unit 3 to form an image on the recording paper PP according to the print data Img.

[0023] In the following, the X1 direction and its opposite direction, the X2 direction, will be collectively referred to as the "X-axis direction," the Y1 direction intersecting the X-axis direction and its opposite direction, the Y2 direction, will be collectively referred to as the "Y-axis direction," and the Z1 direction intersecting the X-axis and Y-axis directions and its opposite direction, the Z2 direction, will be collectively referred to as the "Z-axis direction." In this embodiment, as an example, the case in which the X-axis direction, Y-axis direction, and Z-axis direction are mutually orthogonal will be described. However, the present invention is not limited to this embodiment. The X-axis direction, Y-axis direction, and Z-axis direction only need to intersect each other. In this embodiment, the Z1 direction is the direction in which ink is ejected from the ejection unit D.

[0024] As shown in Figure 2, the inkjet printer 1 according to this embodiment comprises a housing 100 and a carriage 110 that can reciprocate within the housing 100 in the Y-axis direction.

[0025] As shown in Figure 2, this embodiment assumes that the carriage 110 is equipped with four ink cartridges 120, each corresponding one-to-one with four inks: cyan, magenta, yellow, and black. Furthermore, this embodiment assumes that the carriage 110 is equipped with four head units 3, each corresponding one-to-one with the four ink cartridges 120. Each ejection unit D[m] receives ink from the ink cartridge 120 corresponding to the head unit 3 on which the ejection unit D[m] is provided. As a result, each ejection unit D[m] fills itself with the supplied ink, and the ink filled inside the ejection unit D[m] can be ejected from the nozzle N provided in the ejection unit D[m]. Note that the ink cartridges 120 may be provided outside the carriage 110.

[0026] As described above, the inkjet printer 1 according to this embodiment includes a transport unit 9. As shown in Figure 2, the transport unit 9 includes a carriage transport motor 91, a media transport motor 92, a media transport mechanism 93, a platen 95, a carriage guide shaft 96, and a belt 97. The carriage transport motor 91 drives the belt 97 based on a transport control signal SH. The belt 97 transports the carriage 110 in the Y-axis direction based on the drive of the carriage transport motor 91. The carriage guide shaft 96 supports the carriage 110 so that it can reciprocate in the Y-axis direction. The media transport motor 92 drives the media transport mechanism 93 based on a transport control signal SH. The media transport mechanism 93 transports the recording paper PP in the X1 direction by rotating based on the drive of the media transport motor 92. The platen 95 is provided in the Z1 direction of the carriage 110 and supports the recording paper PP being transported by the media transport mechanism 93. In this way, when printing is performed, the transport unit 9 uses the carriage transport motor 91 to reciprocate the head unit 3 and the carriage 110 together along the carriage guide axis 96 in the Y-axis direction, and the media transport motor 92 transports the recording paper PP on the platen 95 in the X1 direction, thereby changing the relative position of the recording paper PP with respect to the head unit 3 and enabling ink to land on the entire surface of the recording paper PP.

[0027] Figure 3 is a schematic partial cross-sectional view of the head portion 32, which is cut to include the discharge portion D[m].

[0028] As shown in FIG. 3, the ejection unit D[m] includes a piezoelectric element PZ[m], a cavity CV[m] filled with ink inside, a nozzle N[m] communicating with the cavity CV[m], and a diaphragm 321. When the piezoelectric element PZ[m] is driven by a supply drive signal Vin[m], the ink in the cavity CV[m] is ejected from the nozzle N[m]. The cavity CV[m] is a space partitioned by a cavity plate 324, a nozzle plate 323 in which the nozzle N[m] is formed, and the diaphragm 321. The cavity CV[m] communicates with a reservoir 325 via an ink supply port 326. The reservoir 325 communicates with an ink cartridge 120 corresponding to the ejection unit D[m] via an ink inlet 327. The piezoelectric element PZ[m] has an upper electrode Zu[m], a lower electrode Zd[m], and a piezoelectric body Zm[m] provided between the upper electrode Zu[m] and the lower electrode Zd[m]. The lower electrode Zd[m] is electrically connected to a power supply line LD set to a predetermined potential VBS. When a supply drive signal Vin[m] is supplied to the upper electrode Zu[m] and a voltage is applied between the upper electrode Zu[m] and the lower electrode Zd[m], the piezoelectric element PZ[m] is displaced in the Z1 direction and the Z2 direction according to the applied voltage, and as a result, the piezoelectric element PZ[m] vibrates. The lower electrode Zd[m] is joined to the diaphragm 321. Therefore, when the piezoelectric element PZ[m] is driven by the supply drive signal Vin[m] and vibrates, the diaphragm 321 also vibrates. Then, due to the vibration of the diaphragm 321, the volume of the cavity CV[m] and the pressure inside the cavity CV[m] change, and the ink filled in the cavity CV[m] is ejected from the nozzle N[m].

[0029] <<A.2. Configuration and Operation of Head Unit 3>> Hereinafter, an example of the configuration and operation of the head unit 3 will be described while referring to FIGS. 4 to 6.

[0030] FIG. 4 is a block diagram showing an example of the configuration of the head unit 3.

[0031] As shown in Figure 4, the head unit 3 comprises a supply circuit 31 and a head unit 32. The head unit 3 also includes wiring LC to which the drive signal Com is supplied from the drive signal generation unit 4.

[0032] As shown in Figure 4, the supply circuit 31 comprises M switches WS[1] to WS[M] that correspond one-to-one with M discharge units D[1] to D[M], and a connection state specification circuit 310 that specifies the connection state of each switch. The connection status specification circuit 310 generates a connection status specification signal QS[m] that specifies whether the switch WS[m] is on or off, based on at least some of the signals supplied from the control unit 2: the specification signal SI, the latch signal LAT, the change signal CH, and the clock signal CLK. The switch WS[m] switches between conductivity and non-conductivity between the wiring LC and the upper electrode Zu[m] of the piezoelectric element PZ[m] provided in the discharge section D[m], based on the connection status specification signal QS[m]. In this embodiment, the switch WS[m] is turned on when the connection status specification signal QS[m] is high level and turned off when it is low level. When the switch WS[m] is turned on, the drive signal Com supplied to the wiring LC is supplied to the upper electrode Zu[m] of the discharge section D[m] as the supply drive signal Vin[m].

[0033] Figure 5 is a timing chart showing an example of various signals, such as the drive signal Com, supplied to the head unit 3.

[0034] As shown in Figure 5, when the inkjet printer 1 performs a printing process, one or more unit periods TP are set as the operating period of the inkjet printer 1. In this embodiment, the inkjet printer 1 can drive each ejection unit D[m] for the printing process during each unit period TP.

[0035] As shown in Figure 5, the control unit 2 outputs a latch signal LAT which has a pulse PLL. This allows the control unit 2 to define a unit period TP as the period from the rising edge of one pulse PLL to the rising edge of the next pulse PLL. The control unit 2 also outputs a change signal CH which has a pulse PLC during the unit period TP. The control unit 2 then divides the unit period TP into a drive period TQ1, from the rising edge of the pulse PLL to the rising edge of the pulse PLC, and a drive period TQ2, from the rising edge of the pulse PLC to the rising edge of the pulse PLL.

[0036] As shown in Figure 5, the designation signal SI includes M individual designation signals Sd[1] to Sd[M] that correspond one-to-one with M ejection units D[1] to D[M]. The individual designation signals Sd[m] specify the mode of operation of the ejection units D[m] in each unit period TP when the inkjet printer 1 performs printing. Prior to each unit period TP, the control unit 2 supplies the designation signal SI, which includes the M individual designation signals Sd[1] to Sd[M], to the connection state designation circuit 310 in synchronization with the clock signal CLK. The connection state designation circuit 310 then generates a connection state designation signal QS[m] based on the individual designation signals Sd[m] in the unit period TP.

[0037] In this embodiment, it is assumed that during a unit period TP in which the printing process is performed, the ejection unit D[m] is capable of forming any of the following dots: a large dot made of ink with an ink amount ξ1, a medium dot made of ink with an ink amount ξ2 less than ξ1, and a small dot made of ink with an ink amount ξ3 less than ξ2.

[0038] Figure 6 is an explanatory diagram illustrating an example of an individualized signal Sd[m].

[0039] As shown in Figure 6, in this embodiment, the individual designation signal Sd[m] can take any one of four values ​​during the unit period TP in which the printing process is performed: a value of "1" which designates the ejection unit D[m] as the large dot forming ejection unit DP-1, a value of "2" which designates the ejection unit D[m] as the medium dot forming ejection unit DP-2, a value of "3" which designates the ejection unit D[m] as the small dot forming ejection unit DP-3, and a value of "4" which designates the ejection unit D[m] as the non-dot forming ejection unit DP-4. Here, the large dot-forming discharge section DP-1 is the discharge section D that forms large dots in a unit period TP. The medium dot-forming discharge section DP-2 is the discharge section D that forms medium dots in a unit period TP. The small dot-forming discharge section DP-3 is the discharge section D that forms small dots in a unit period TP. The non-dot-forming discharge section DP-4 is the discharge section D that does not form dots in a unit period TP.

[0040] Return to Figure 5 for the explanation. As shown in Figure 5, in this embodiment, the drive signal Com has a waveform PA1 provided during the drive period TQ1 and a waveform PA2 provided during the drive period TQ2. Of these, waveform PA1 is a waveform that returns to potential V0, passing through potential VL1 which is lower than potential V0, and potential VH1 which is higher than potential V0. When a supply drive signal Vin[m] having waveform PA1 is supplied to the ejection unit D[m], waveform PA1 is defined so that ink equivalent to ink amount φ1 is ejected from the ejection unit D[m]. Waveform PA2 is a waveform that returns to potential V0, passing through potential VL2 which is lower than potential V0, and potential VH2 which is higher than potential V0. When a supply drive signal Vin[m] having waveform PA2 is supplied to the ejection unit D[m], waveform PA2 is defined so that ink equivalent to ink amount φ2 is ejected from the ejection unit D[m]. In this embodiment, it is assumed that ink quantity ξ1 corresponds to the sum of ink quantity φ1 and ink quantity φ2, ink quantity ξ2 corresponds to ink quantity φ1, and ink quantity ξ3 corresponds to ink quantity φ2.

[0041] Furthermore, in this embodiment, as an example, we assume that when the potential of the supply drive signal Vin[m] supplied to the ejection unit D[m] is high, the volume of the cavity CV[m] in the ejection unit D[m] becomes smaller compared to when the potential is low. Therefore, when the ejection unit D[m] is driven by a supply drive signal Vin[m] having a waveform PA1 or the like, the ink in the ejection unit D[m] is ejected from the nozzle N[m] as the potential of the supply drive signal Vin[m] changes from low to high.

[0042] As shown in Figure 6, when the individual designation signal Sd[m] indicates a value of "1" which designates the ejection unit D[m] as the large dot forming ejection unit DP-1 during the unit period TP, the connection state designation circuit 310 sets the connection state designation signal QS[m] to a high level during the drive period TQ1 and the drive period TQ2. In this case, the switch WS[m] is turned on during the drive period TQ1 and the drive period TQ2. Therefore, during the unit period TP, the ejection unit D[m] is driven by the supply drive signal Vin[m] which has waveforms PA1 and PA2, and ejects ink with an ink amount ξ1 corresponding to a large dot. Furthermore, if the individual designation signal Sd[m] indicates a value of "2" which designates the ejection unit D[m] as the medium dot forming ejection unit DP-2 during the unit period TP, the connection state designation circuit 310 sets the connection state designation signal QS[m] to a high level during the drive period TQ1. In this case, the switch WS[m] is turned on during the drive period TQ1. Therefore, during the unit period TP, the ejection unit D[m] is driven by the supply drive signal Vin[m] having waveform PA1 and ejects ink with an ink amount ξ2 corresponding to the medium dot. Furthermore, if the individual designation signal Sd[m] indicates a value of "3" which designates the ejection unit D[m] as the small dot forming ejection unit DP-3 during the unit period TP, the connection state designation circuit 310 sets the connection state designation signal QS[m] to a high level during the drive period TQ2. In this case, the switch WS[m] is turned on during the drive period TQ2. Therefore, during the unit period TP, the ejection unit D[m] is driven by the supply drive signal Vin[m] having waveform PA2 and ejects ink with an ink amount ξ3 corresponding to a small dot. Also, when the individual specification signal Sd[m] indicates the value "4" that specifies the ejection unit D[m] as the dot non-formation ejection unit DP-4 in the unit period TP, the connection state specification circuit 310 sets the connection state specification signal QS[m] to the low level over the unit period TP. In this case, the switch WS[m] turns off over the unit period TP. Therefore, the ejection unit D[m] is not driven by the supply drive signal Vin[m] and does not eject ink in the unit period TP.

[0043] <<A.3. Configuration of Drive Signal Generation Circuit 40>> Hereinafter, an example of the configuration of the drive signal generation circuit 40 provided in the drive signal generation unit 4 will be described with reference to FIGS. 7 and 8.

[0044] FIG. 7 is a block diagram showing an example of the circuit configuration of the drive signal generation circuit 40.

[0045] As shown in FIG. 7, the drive signal generation circuit 40 is a class D amplifier circuit that includes an integrated circuit 41, an amplifier circuit 43, a smoothing circuit 44, a pull-up circuit 45, and a filter circuit 46, and generates a drive signal Com based on the waveform specification signal dCom.

[0046] The integrated circuit 41 is, for example, an LSI (Large Scale Integration), and generates a gate signal SGH and a gate signal SGL based on the waveform specification signal dCom supplied to the terminal tIN via the node nIN. The integrated circuit 41 includes an analog conversion circuit 412, a subtractor 414, an adder 416, an attenuator 418, an integral attenuator 422, a comparator 424, and a gate driver 426.

[0047] The analog conversion circuit 412 is a DAC (digital to analog converter) that converts the digital waveform specification signal dCom into an analog signal Aa. The voltage amplitude of the signal Aa is, for example, about 0 to 2 volts, and the drive signal Com is obtained by amplifying this voltage by about 20 times. That is, the signal Aa is the signal before amplification of the drive signal Com. The integrating attenuator 422 outputs a signal Ax obtained by attenuating the signal SN1 input to terminal t1 (described later) and then integrating it. The subtractor 414 outputs a signal Ab, which represents the potential obtained by subtracting the potential of signal Aa from the potential of signal Ax. The attenuator 418 outputs a signal Ay, which is the signal SN2 input to terminal t2 (described later) with its high-frequency components attenuated. The adder 416 outputs a signal As, which represents the potential obtained by adding the potentials of signal Ab and signal Ay. Comparator 424 outputs a modulated signal Ms obtained by pulse-modulating signal As. Specifically, comparator 424 outputs a modulated signal Ms that becomes high level when signal As's voltage rises above threshold voltage Vth1, and low level when signal As's voltage falls below threshold voltage Vth2. The threshold voltages Vth1 and Vth2 are set to the relationship 'Vth1 > Vth2'.

[0048] The power supply voltage for the circuit from the analog conversion circuit 412 to the comparator 424 is a low voltage, such as 3.3 volts. In contrast, the drive signal Com has a large amplitude, sometimes exceeding 40 volts. Therefore, the integrating attenuator 422 attenuates the signal SN1, which has an amplitude corresponding to the drive signal Com, to match the amplitude range of the signal Ax to the amplitude range of the signal in the circuit from the analog conversion circuit 412 to the comparator 424. Furthermore, although a digital signal is used as an example to describe the waveform specification signal dCom in this embodiment, the waveform specification signal dCom can be any signal that defines the target value for generating the drive signal Com. For example, an analog signal Aa may be used as the waveform specification signal dCom. If signal Aa is the waveform specification signal dCom, the integrated circuit 41 may be configured without including the analog conversion circuit 412.

[0049] The gate driver 426 outputs a gate signal SGH, which is obtained by converting the modulated signal Ms to a specific amplitude, to node nH via terminal tH. The gate driver 426 also outputs a gate signal SGL, which is obtained by converting the inverted logic level of the modulated signal Ms to a specific amplitude, to node nL via terminal tL.

[0050] The amplification circuit 43 includes, for example, transistors TrH and TrL, and generates an amplified signal Az, which is a signal obtained by amplifying the modulated signal Ms, based on the gate signals SGH and SGL output from the integrated circuit 41. In this embodiment, as an example, it is assumed that transistors TrH and TrL are field-effect transistors. More specifically, in this embodiment, it is assumed that N-channel type metal-oxide-semiconductor field-effect transistors (MOSFETs) are used as transistors TrH and TrL.

[0051] The gate signal SGH, output from gate driver 426 to terminal tH, is input to the gate gate gt of transistor TrH via node nH and resistor RGH. Similarly, the gate signal SGL, output from gate driver 426 to terminal tL, is input to the gate gate gt of transistor TrL via node nL and resistor RGL. The logic levels of gate signals SGH and SGL are mutually exclusive. Here, "mutually exclusive" means that the signal level of gate signal SGH supplied to the gate gate gt of transistor TrH and the signal level of gate signal SGL supplied to the gate gate gt of transistor TrL can never be high at the same time; in other words, transistors TrH and TrL can never be turned on at the same time. Transistor TrH turns on when the potential of its gate gate gt is high, and turns off when the potential of its gate gate gt is low. The transistor TrL turns on when the potential of its gate electrode gt is high, and turns off when the potential of its gate electrode gt is low.

[0052] The drain electrode dt of transistor TrH is electrically connected to node nV, which is set to the high-potential power supply potential VHV, and the source electrode st is electrically connected to node nD. Similarly, the source electrode st of transistor TrL is electrically connected to node nG, which is set to ground potential, and the drain electrode dt is electrically connected to node nD. Alternatively, the source electrode of transistor TrL may be electrically connected to the power supply line LD, which is set to potential VBS.

[0053] As described above, transistor TrH turns on when the gate signal SGH supplied to the gate electrode gt is high level and turns off when it is low level. Transistor TrL turns on when the gate signal SGL supplied to the gate electrode gt is high level and turns off when it is low level. Therefore, the node nD that electrically connects the source electrode st of transistor TrH and the drain electrode dt of transistor TrL outputs an amplified signal Az, which is the modulated signal Ms amplified.

[0054] An electrolytic capacitor Cd is connected to node nV, to which the power supply potential VHV is supplied. One end (terminal tD1) of the electrolytic capacitor Cd is electrically connected to node nV, and the other end (terminal tD2) is electrically connected to node nG, which is set to ground potential. In this embodiment, the electrolytic capacitor Cd is, for example, a large-capacity aluminum electrolytic capacitor, which suppresses potential fluctuations at node nV and stabilizes the power supply potential VHV. Terminals tD1 and tD2 will be described later in Figure 8.

[0055] The smoothing circuit 44 is an LPF (Low Pass Filter) that smooths the amplified signal Az to generate the drive signal Com. The smoothing circuit 44 includes an inductor L0 and a capacitor C0. One end (terminal tL1) of the inductor L0 (an example of a "coil") is electrically connected to node nD, and the other end (terminal tL2) is electrically connected to node nX. One end (terminal tC1) of the capacitor C0 is electrically connected to node nX, and the other end (terminal tC2) is electrically connected to node nG, which is set to ground potential. Terminals tL1 and tL2, and terminals tC1 and tC2 will be described later in Figure 8.

[0056] The pull-up circuit 45 feeds back the signal SN1, which is the drive signal Com output to node nX, to terminal t1. The pull-up circuit 45 includes a resistor R1, one end of which is electrically connected to node nX and the other end of which is electrically connected to terminal t1, and a resistor R2, one end of which is electrically connected to terminal t1 and the other end of which is electrically connected to node nV, which is set to the power supply potential VHV.

[0057] The filter circuit 46 is a Band Pass Filter (BPF) and feeds back a signal SN2, which is obtained by cutting the DC component from the frequency components of a predetermined band of the drive signal Com, to terminal t2. The filter circuit 46 comprises a resistor R3, a capacitor C1 with one end electrically connected to node nX and the other end electrically connected to one end of resistor R3, a resistor R4 with one end electrically connected to one end of resistor R3 and the other end electrically connected to node nG which is set to ground potential, a capacitor C2 with one end electrically connected to the other end of resistor R3 and the other end electrically connected to node nG which is set to ground potential, and a capacitor C3 with one end electrically connected to the other end of resistor R3 and the other end electrically connected to terminal t2. Of these, capacitor C1 and resistor R4 function as a High Pass Filter (HPF) that allows high-frequency components of the drive signal Com above the cutoff frequency to pass through. Furthermore, resistor R3 and capacitor C2 function as an LPF (Low Pass Filter) that allows low-frequency components of the drive signal Com below the cutoff frequency to pass through. In this embodiment, the cutoff frequency of the HPF is set lower than the cutoff frequency of the LPF in the filter circuit 46. Therefore, the filter circuit 46 allows frequency components of the drive signal Com that are above the cutoff frequency of the HPF and below the cutoff frequency of the LPF to pass through. In addition, because the filter circuit 46 is equipped with capacitor C3, the signal from which the DC component has been cut off from the frequency components of the drive signal Com that have passed through the HPF and LPF is fed back to terminal t2.

[0058] Thus, the drive signal generation circuit 40 generates a drive signal Com by smoothing the amplified signal Az at node nD using the smoothing circuit 44. The drive signal Com is integrated and subtracted by the integrating attenuator 422 and then fed back to the subtractor 414. Therefore, it self-oscillates at a frequency determined by the delay in the smoothing circuit 44, the delay in the integrating attenuator 422, and the feedback transfer function. However, because the delay amount of the feedback path via terminal t1 is large, the self-oscillation frequency cannot be increased to a level that sufficiently ensures the accuracy of the waveform of the drive signal Com with only feedback via terminal t1. In contrast, in this embodiment, a path is provided via terminal t2 to feed back the high-frequency component of the drive signal Com, separate from the path via terminal t1, so that the overall feedback delay of the drive signal generation circuit 40 can be reduced. That is, in this embodiment, the frequency of signal As, obtained by adding signal Ay, which is the high-frequency component of the drive signal Com, to signal Ab can be increased compared to the case where there is no path via terminal t2, so that the accuracy of the drive signal Com can be sufficiently ensured.

[0059] Note that transistors TrH and TrL, and inductor L0 are examples of "electronic components" that generate heat when the drive signal generation circuit 40 generates the drive signal Com.

[0060] Figure 8 is a plan view showing an example of the wiring pattern of the drive signal generation circuit 40 in a plan view of the drive circuit board 400 on which the drive signal generation circuit 40 is provided. Note that in Figure 8, some electronic components of the drive signal generation circuit 40 are omitted from the description. Also, although Figure 8 illustrates and explains the case in which the drive circuit board 400 is provided on a plane with the Z1 direction as the normal direction, the present invention is not limited to this embodiment. The normal direction of the drive circuit board 400 may be any direction. Note that the drive circuit board 400 is an example of a "circuit board".

[0061] As shown in FIG. 8, the terminal tIN of the integrated circuit 41 is connected to the node nIN. The terminal tH of the integrated circuit 41 is electrically connected to the gate electrode gt of the transistor TrH via the node nH, and the terminal tL of the integrated circuit 41 is electrically connected to the gate electrode gt of the transistor TrL via the node nL. Also, the source electrode st of the transistor TrL is electrically connected to the node nG. The drain electrode dt of the transistor TrL is electrically connected to the source electrode st of the transistor TrH and the terminal tL1 of the inductor L0 via the node nD. The terminal tL2 of the inductor L0 is electrically connected to the terminal tC1 of the capacitor C0 via the node nX. The terminal tC2 of the capacitor C0 is electrically connected to the node nG. Also, the drain electrode dt of the transistor TrH is electrically connected to the terminal tD1 of the electrolytic capacitor Cd via the node nV. The terminal tD2 of the electrolytic capacitor Cd is electrically connected to the node nG.

[0062] In this embodiment, when the drive circuit board 400 is viewed in the Z1 direction, a non-coating region HK is provided, which is a region on the wiring pattern of the drive signal generation circuit 40 where no resist is coated, and the electronic components of the drive signal generation circuit 40 are not arranged and the wiring pattern is exposed. Specifically, in this embodiment, it is assumed that non-coating regions HK1 and HK2 where the node nG is exposed and non-coating regions HK3, HK4, HK5, and HK6 where the node nV is exposed are provided.

[0063] <<A.4. Configuration of the drive signal generation unit 4>> Hereinafter, the configuration of the drive signal generation unit 4 will be described while referring to FIGS. 9 to 11.

[0064] Figure 9 is a cross-sectional view showing an example of a drive signal generation unit 4. Specifically, Figure 9 is a cross-sectional view of the drive signal generation unit 4 when viewed in the Z1 direction, with the cross section including a broken line passing through the integrated circuit 41, transistors TrH and TrL, inductor L0, capacitor C0 and electrolytic capacitor Cd.

[0065] As shown in Figure 9, the drive signal generation unit 4 comprises a drive circuit board 400, a drive signal generation circuit 40, a thermal conductive clay CY, and a heat sink 5.

[0066] The drive circuit board 400 has an upper substrate surface 4001 on which the drive signal generation circuit 40 is provided, and a lower substrate surface 4002 which is the surface opposite to the upper substrate surface 4001. In this embodiment, it is assumed that the drive circuit board 400 is a multilayer substrate. Specifically, in this embodiment, the drive circuit board 400 has multiple layers between the upper substrate surface 4001 and the lower substrate surface 4002, including a surface layer 401, an insulating layer 402, a wiring layer 403, and a protective layer 404.

[0067] The surface layer 401 is a layer that includes the upper substrate surface 4001 and is provided with wiring 401L. The wiring 401L is made of a conductive material. The portion of the surface layer 401 other than the wiring 401L is coated with an insulating resist member 401R. Furthermore, as described above, the surface layer 401 is provided with an uncoated region HK, which is a region where electronic components such as transistors TrH are not provided, where the wiring 401L is exposed, and where the resist member 401R is not provided.

[0068] The insulating layer 402 is a layer on which the wiring 402L is provided, and is located between the surface layer 401 and the lower substrate surface 4002. The wiring 402L is made of a conductive material. The portion of the insulating layer 402 other than the wiring 402L is made of an insulating material. The wiring layer 403 is a layer on which wiring 403L is provided, and is located between the insulating layer 402 and the lower substrate surface 4002. The wiring 403L is made of a conductive material. The portion of the wiring layer 403 other than the wiring 403L is made of an insulating material. The protective layer 404 is a layer that includes the lower substrate surface 4002 and is made of an insulating material.

[0069] In this embodiment, it is assumed that the wiring pattern of the drive signal generation circuit 40 described in Figure 8 consists of wiring 401L, wiring 402L, and wiring 403L.

[0070] The thermal conductive clay CY (an example of a "thermal conductive member") is a clay-like material having electrical insulating and thermal conductive properties, and is provided on the upper substrate surface 4001 so as to cover at least a portion of the drive signal generation circuit 40. Specifically, in this embodiment, the thermal conductive clay CY is provided so as to cover a portion of the electrolytic capacitor Cd, transistor TrH, transistor TrL, and inductor L0. However, the present invention is not limited to this embodiment. The thermal conductive clay CY may be provided so as to cover electronic components other than transistor TrH, transistor TrL, inductor L0, and electrolytic capacitor Cd, such as capacitor C0 or integrated circuit 41. Alternatively, the thermal conductive clay CY may be provided so as not to cover some of the electronic components among transistor TrH, transistor TrL, and inductor L0.

[0071] Furthermore, in this embodiment, we assume that the height HCY of the thermal conductive clay CY in the Z-axis direction is higher than the height HCd of the electrolytic capacitor Cd in the Z-axis direction, the height Ht1 of the transistor TrH in the Z-axis direction, the height Ht2 of the transistor TrL in the Z-axis direction, and the height HL of the inductor L0 in the Z-axis direction. In addition, in this embodiment, we assume as an example that heights Ht1 and Ht2 are the same, height HCd is higher than height Ht1, and height HL is higher than height Ht1.

[0072] Furthermore, in the following description, when the drive circuit board 400 is viewed in plan in the Z1 direction, the region of the drive circuit board 400 covered by the thermal conductive clay CY will be referred to as the clay-placed region AR1, and the region of the drive circuit board 400 not covered by the thermal conductive clay CY will be referred to as the clay-free region AR2. As described above, in this embodiment, the thermal conductive clay CY is provided so as to cover the non-coated region HK. That is, in this embodiment, the clay-placed region AR1 encompasses the non-coated region HK.

[0073] The heat sink 5 is made of a thermally conductive material such as aluminum and has a flat plate portion 51 and a heat dissipation portion 52. The flat plate portion 51 is a flat plate-shaped component extending in the XY plane and has a planar portion 5000. The planar portion 5000 is a plane with the Z1 direction as its normal direction and is in contact with the thermally conductive clay CY. The heat dissipation portion 52 is made up of a plurality of fins and dissipates the heat transferred from the flat plate portion 51.

[0074] Figure 10 is a plan view of the drive signal generation unit 4 as seen in the Z1 direction.

[0075] As shown in Figure 10, in this embodiment, when the drive signal generation unit 4 is viewed in plan in the Z1 direction, the thermal conductive clay CY is provided so as to cover a part of the electrolytic capacitor Cd, transistors TrH and TrL, and inductor L0. In this embodiment, it is assumed that the thermal conductive clay CY is provided so as to cover only a part of the electrolytic capacitor Cd and not the other part. Furthermore, the thermal conductive clay CY is provided so as to cover the uncoated areas HK1 and HK2 and the uncoated areas HK3, HK4, HK5, and HK6.

[0076] Figure 11 is a schematic diagram illustrating the overview of the thermally conductive clay CY.

[0077] As shown in FIG. 11, for example, the thermal conduction clay CY includes silicone clay SL and thermal conduction particles PT. The silicone clay SL is a clay-like substance made of silicone and serves as a base material for the thermal conduction clay CY. The thermal conduction particles PT are particles made of substances with high thermal conductivity such as diamond, gold, silver, and copper, and are dispersed in the silicone clay SL.

[0078] In addition, when conductive substances such as gold, silver, and copper are adopted as the thermal conduction particles PT, the diameter rrP of the thermal conduction particles PT is provided to be sufficiently smaller than the minimum distance rr1 between two adjacent wirings 401L in the surface layer 401 and the minimum distance rr3 between two adjacent wirings 403L in the wiring layer 403. Therefore, in this embodiment, even when the thermal conduction clay CY is provided to contact two adjacent wirings 401L or two adjacent wirings 403L, it is possible to suppress the two wirings from being electrically connected by the thermal conduction clay CY, and ensure the electrical insulation of the thermal conduction clay CY in the drive signal generation unit 4. Also, in this embodiment, since the thermal conduction clay CY contains the thermal conduction particles PT, the thermal conductivity of the thermal conduction clay CY can be increased as compared with the aspect where the thermal conduction clay CY does not contain the thermal conduction particles PT.

[0079] <<A.5. Summary of the Embodiment>> As described above, according to this embodiment, the clay-like thermal conduction clay CY contacts the transistor TrH, the transistor TrL, and the inductor L0. Therefore, according to this embodiment, for example, even when the heights of the transistor TrH, the transistor TrL, and the inductor L0 are different, the thermal conduction clay CY can be in close contact with the transistor TrH, the transistor TrL, and the inductor L0, and the heat generated from the drive signal generation circuit 40 can be efficiently dissipated through the thermal conduction clay CY.

[0080] Also, according to the present embodiment, the thermal conductive clay CY contacts the transistor TrH, the transistor TrL, and the inductor L0, and the thermal conductive clay CY contacts the planar portion 5000 of the heat sink 5. Therefore, according to the present embodiment, for example, compared with an aspect of using a heat sink having a plurality of protruding portions having heights corresponding to the heights of each of a plurality of electronic components constituting the drive signal generation circuit 40, it is possible to simplify the configuration of the heat sink 5, reduce the manufacturing load of the configuration for cooling the drive signal generation circuit 40, or reduce the manufacturing cost of the configuration for cooling the drive signal generation circuit 40.

[0081] Also, according to the present embodiment, the thermal conductive clay CY contacts the transistor TrH, the transistor TrL, and the inductor L0, and the thermal conductive clay CY contacts the electrolytic capacitor Cd. In the present embodiment, the thermal conductive clay CY is a large-capacity aluminum electrolytic capacitor and has a large surface area and high thermal conductivity. Therefore, according to the present embodiment, for example, compared with an aspect in which the thermal conductive clay CY does not contact the electrolytic capacitor Cd, it is possible to efficiently dissipate heat generated from the drive signal generation circuit 40 through the thermal conductive clay CY.

[0082] Also, according to the present embodiment, the thermal conductive clay CY contacts the transistor TrH, the transistor TrL, and the inductor L0, and the thermal conductive clay CY contacts the non-coating region HK. Therefore, according to the present embodiment, for example, compared with an aspect in which the thermal conductive clay CY does not contact the non-coating region HK, it is possible to efficiently dissipate heat generated from the drive signal generation circuit 40 through the thermal conductive clay CY.

[0083] <<B. Modified Example>> Each of the above embodiments can be variously modified. Specific modification aspects are exemplified below. Two or more aspects arbitrarily selected from the following examples can be appropriately combined within a range not conflicting with each other. Note that for elements whose actions and functions are equivalent to those of the embodiment in the modified examples exemplified below, the reference numerals referred to in the above description are reused, and the detailed description of each is appropriately omitted.

[0084] <<B.1. Variant Example 1>> In the above-described embodiment, the case where the thermal conductive clay CY contacts the non-coating region HK and the heat sink 5 has been illustrated and described. However, the present invention is not limited to such a mode. For example, the thermal conductive clay CY may not contact one or both of the non-coating region HK and the heat sink 5.

[0085] FIG. 12 is a cross-sectional view showing an example of the drive signal generation unit 4B according to this variant example.

[0086] As shown in FIG. 12, the drive signal generation unit 4B is different from the drive signal generation unit 4 according to the embodiment in that it does not have the heat sink 5 and the non-coating region HK. In this variant example, the thermal conductive clay CY is provided so as to cover a part of the electrolytic capacitor Cd, the transistor TrH, the transistor TrL, and the inductor L0. However, in this variant example, the thermal conductive clay CY may be provided so as to cover electronic components other than the transistor TrH, the transistor TrL, the inductor L0, and the electrolytic capacitor Cd, such as the capacitor C0 or the integrated circuit 41. Also, in this variant example, the thermal conductive clay CY may be provided so as not to cover some of the electronic components among the transistor TrH, the transistor TrL, and the inductor L0.

[0087] Note that in this variant example, it is assumed that the height HCY of the thermal conductive clay CY in the Z-axis direction is higher than the height HCd of the electrolytic capacitor Cd in the Z-axis direction, the height Ht1 of the transistor TrH in the Z-axis direction, the height Ht2 of the transistor TrL in the Z-axis direction, and the height HL of the inductor L0 in the Z-axis direction. However, in this variant example, the height HCY of the thermal conductive clay CY in the Z-axis direction may be lower than some or all of the height HCd, the height Ht1, the height Ht2, and the height HL.

[0088] As described above, according to this modified example, the thermal conductive clay CY contacts the transistor TrH, the transistor TrL, and the inductor L0, and the thermal conductive clay CY contacts the electrolytic capacitor Cd. Therefore, according to this modified example, for example, compared with a mode in which the thermal conductive clay CY does not contact the electrolytic capacitor Cd, heat generated from the drive signal generation circuit 40 can be efficiently radiated through the thermal conductive clay CY.

[0089] <<B.2. Modified Example 2>> In the above-described embodiment, the case where the thermal conductive clay CY contacts the non-coating region HK and the electrolytic capacitor Cd has been exemplified and described, but the present invention is not limited to such a mode. For example, the thermal conductive clay CY may not contact one or both of the non-coating region HK and the electrolytic capacitor Cd.

[0090] FIG. 13 is a cross-sectional view showing an example of the drive signal generation unit 4C according to this modified example.

[0091] As shown in FIG. 13, the drive signal generation unit 4C is different from the drive signal generation unit 4 according to the embodiment in that it does not have the non-coating region HK and the thermal conductive clay CY does not contact the electrolytic capacitor Cd. In this modified example, the thermal conductive clay CY is provided so as to cover the transistor TrH, the transistor TrL, and the inductor L0 and contact the planar portion 5000 of the heat sink 5. However, in this modified example, the thermal conductive clay CY may be provided so as to cover electronic components other than the transistor TrH, the transistor TrL, the inductor L0, and the electrolytic capacitor Cd, such as the capacitor C0 or the integrated circuit 41. Also, in this modified example, the thermal conductive clay CY may be provided so as not to cover some of the electronic components among the transistor TrH, the transistor TrL, and the inductor L0.

[0092] In addition, in this modified example, it is assumed that the height HCY of the thermal conduction clay CY in the Z-axis direction is higher than the height HCd of the electrolytic capacitor Cd in the Z-axis direction, the height Ht1 of the transistor TrH in the Z-axis direction, the height Ht2 of the transistor TrL in the Z-axis direction, and the height HL of the inductor L0 in the Z-axis direction.

[0093] As described above, according to this modified example, the thermal conduction clay CY contacts the transistor TrH, the transistor TrL, and the inductor L0, and the thermal conduction clay CY contacts the planar portion 5000 of the heat sink 5. Therefore, according to this modified example, for example, compared with the aspect of using a heat sink having a plurality of protruding portions having heights corresponding to the heights of each of the plurality of electronic components constituting the drive signal generation circuit 40, it is possible to simplify the configuration of the heat sink 5.

[0094] <<B.3. Modified Example 3>> In the above-described embodiment, the case where the thermal conduction clay CY contacts the electrolytic capacitor Cd and the heat sink 5 has been exemplified and described, but the present invention is not limited to such an aspect. For example, the thermal conduction clay CY may not contact one or both of the electrolytic capacitor Cd and the heat sink 5.

[0095] FIG. 14 is a cross-sectional view showing an example of the drive signal generation unit 4D according to this modified example.

[0096] As shown in FIG. 14, the drive signal generation unit 4D is different from the drive signal generation unit 4 according to the embodiment in that it does not have a heat sink 5 and the thermal conduction clay CY does not contact the electrolytic capacitor Cd. In this modified example, the thermal conduction clay CY is provided so as to cover the non-coating region HK, the transistor TrH, the transistor TrL, and the inductor L0. However, in this modified example, the thermal conduction clay CY may be provided so as to cover electronic components other than the transistor TrH, the transistor TrL, the inductor L0, and the electrolytic capacitor Cd, such as the capacitor C0 or the integrated circuit 41. Also, in this modified example, the thermal conduction clay CY may be provided so as not to cover some of the electronic components among the transistor TrH, the transistor TrL, and the inductor L0.

[0097] Note that in this modified example, it is assumed that the height HCY of the thermal conduction clay CY in the Z-axis direction is higher than the height Ht1 of the transistor TrH in the Z-axis direction, the height Ht2 of the transistor TrL in the Z-axis direction, and the height HL of the inductor L0 in the Z-axis direction. However, in this modified example, the height HCY of the thermal conduction clay CY in the Z-axis direction may be lower than some or all of the height Ht1, the height Ht2, and the height HL.

[0098] As described above, according to this modified example, the thermal conduction clay CY contacts the transistor TrH, the transistor TrL, and the inductor L0, and the thermal conduction clay CY contacts the non-coating region HK. Therefore, according to this modified example, for example, it is possible to efficiently dissipate the heat generated from the drive signal generation circuit 40 through the thermal conduction clay CY as compared with a mode in which the thermal conduction clay CY does not contact the non-coating region HK.

[0099] <<B.4. Modified Example 4>> In the embodiments and modifications 1 to 3 described above, the case in which the drive signal generation circuit 40 is a Class D amplifier circuit was used as an example, but the present invention is not limited to such embodiments. The drive signal generation circuit 40 may be an amplifier circuit other than a Class D amplifier circuit, for example, a Class AB amplifier circuit.

[0100] Figure 15 is a block diagram showing an example of the circuit configuration of the drive signal generation circuit 40E according to this modified example. Figure 16 is a cross-sectional view showing an example of the drive signal generation unit 4E according to this modified example. Note that the inkjet printer according to this modified example differs from the inkjet printer 1 according to the embodiment in that it is equipped with a drive signal generation unit 4E instead of a drive signal generation unit 4. Furthermore, the drive signal generation unit 4E according to this modified example differs from the drive signal generation unit 4 according to the embodiment in that it is equipped with a drive signal generation circuit 40E instead of a drive signal generation circuit 40.

[0101] As shown in Figure 15, the drive signal generation circuit 40E comprises an analog conversion circuit 41E, a transistor pair 43E, and an electrolytic capacitor Cd, and generates a drive signal Com based on a waveform specification signal dCom. Specifically, the drive signal generation circuit 40E generates the drive signal Com by, for example, class-AB amplification of the input signal obtained by analog conversion of the waveform specification signal dCom.

[0102] The analog conversion circuit 41E outputs a waveform specification signal QB, which includes a base supply signal QB1 and a base supply signal QB2, based on a digital waveform specification signal dCom. Specifically, the analog conversion circuit 41E converts the waveform specification signal dCom into an analog input signal and generates a base supply signal QB1, which is an analog signal indicating a potential based on the potential of the input signal, and a base supply signal QB2, which is an analog signal indicating a potential based on the potential of the input signal but lower than the base supply signal QB1. The analog conversion circuit 41E then outputs the base supply signal QB1 from output terminal Tn1 and the base supply signal QB2 from output terminal Tn2.

[0103] The transistor pair 43E is a so-called push-pull circuit comprising an NPN bipolar transistor TB1 and a PNP bipolar transistor TB2, which generates a drive signal Com based on base supply signals QB1 and QB2.

[0104] The bipolar transistor TB1 has its base electrode (B) electrically connected to the output terminal Tn1, from which the base supply signal QB1 is supplied. The collector electrode (C) of the bipolar transistor TB1 is electrically connected to node nV, which is set to the power supply potential VHV, and the emitter electrode (E) is electrically connected to node nD, which supplies the drive signal Com. The bipolar transistor TB1 turns on, for example, when the potential of the base supply signal QB1 rises, thereby increasing the potential of the drive signal Com. The bipolar transistor TB1 turns off, for example, when the potential of the base supply signal QB1 is constant, and when the potential of the base supply signal QB1 falls.

[0105] The bipolar transistor TB2 has its base electrode (B) electrically connected to the output terminal Tn2, from which the base supply signal QB2 is supplied. The collector electrode (C) of the bipolar transistor TB2 is electrically connected to node nG, which is set to ground potential, and the emitter electrode (E) is electrically connected to node nD, which supplies the drive signal Com. The bipolar transistor TB2 turns on, for example, when the potential of the base supply signal QB2 decreases, thereby decreasing the potential of the drive signal Com. The bipolar transistor TB2 turns off, for example, when the potential of the base supply signal QB2 is constant, and when the potential of the base supply signal QB2 increases.

[0106] The electrolytic capacitor Cd is a capacitor that supplies current to the transistor pair 43E. Specifically, of the two electrodes of the electrolytic capacitor Cd, one electrode is electrically connected to node nV, which is set to the power supply potential VHV, and to the collector electrode of the bipolar transistor TB1, while the other electrode is electrically connected to node nG, which is set to the ground potential.

[0107] Figure 16 is a cross-sectional view showing an example of a drive signal generation unit 4E according to this modified example.

[0108] As shown in Figure 16, the drive signal generation unit 4E differs from the drive signal generation unit 4 in that it has a drive signal generation circuit 40E instead of a drive signal generation circuit 40. In this modified example, the thermal conductive clay CY is provided so as to cover a part of the electrolytic capacitor Cd, the uncoated area HK, the bipolar transistor TB1, and the bipolar transistor TB2. In this modified example, the thermal conductive clay CY is provided so as to contact the planar portion 5000 of the heat sink 5. However, in this modified example, the thermal conductive clay CY may be provided so as to cover electronic components other than the bipolar transistor TB1, the bipolar transistor TB2, and the electrolytic capacitor Cd, such as the analog conversion circuit 41E. In this modified example, the thermal conductive clay CY may be provided so as not to cover some of the electronic components among the bipolar transistor TB1, the bipolar transistor TB2, and the electrolytic capacitor Cd.

[0109] In this modified example, it is assumed that the height HCY of the thermal conductive clay CY in the Z-axis direction is higher than the height Ht1 of the bipolar transistor TB1 in the Z-axis direction and the height Ht2 of the bipolar transistor TB2 in the Z-axis direction. In this modified example, the bipolar transistors TB1 and TB2 are examples of "electronic components" that generate heat when the drive signal generation circuit 40E generates the drive signal Com.

[0110] As described above, according to this modification example, the thermal conduction clay CY contacts the bipolar transistor TB1 and the bipolar transistor TB2, and the thermal conduction clay CY contacts a part of the electrolytic capacitor Cd, the heat sink 5, and the non - coating region HK. Therefore, according to this modification example, for example, compared with an aspect where the thermal conduction clay CY is not provided, it becomes possible to efficiently radiate the heat generated from the drive signal generation circuit 40E through the thermal conduction clay CY.

[0111] <<B.5. Modification Example 5>> In the above - described embodiments and modification examples 1 to 4, an aspect in which the thermal conduction clay CY is provided individually in each of the plurality of drive signal generation units 4 provided in the inkjet printer 1 has been illustrated and described. However, the present invention is not limited to such an aspect. The thermal conduction clay CY may be provided so as to be common to the plurality of drive signal generation units 4 provided in the inkjet printer 1.

[0112] FIG. 17 is a plan view when looking at the four drive signal generation units 4F included in the inkjet printer 1F according to this modification example in the Z1 direction. In this modification example, the inkjet printer 1F is different from the inkjet printer 1 according to the embodiment in that it includes the drive signal generation unit 4F instead of the drive signal generation unit 4. Hereinafter, among the four drive signal generation units 4F included in the inkjet printer 1F, the q - th drive signal generation unit 4F is referred to as the drive signal generation unit 4F[q]. Here, the variable q is a natural number satisfying "1≦q≦4".

[0113] As shown in Figure 17, the drive signal generation unit 4F differs from the drive signal generation unit 4 according to the embodiment in that it is provided on a drive circuit board 400 common to the other drive signal generation units 4F, and that it is equipped with a heat conductive clay CY common to the other drive signal generation units 4F. In other words, the inkjet printer 1F in this modified example differs from the inkjet printer 1 according to the embodiment in that the heat conductive clay CY is provided in common to the four drive signal generation units 4F[1] to 4F[4], and the drive circuit board 400 is provided in common to the four drive signal generation units 4F[1] to 4F[4].

[0114] In this modified example, the drive signal generation circuit 40 provided in the drive signal generation unit 4F[q] is referred to as the drive signal generation circuit 40[q]. Also in this modified example, each electronic component provided in the drive signal generation circuit 40[q] is represented by the symbol [q]. In this case, the thermal conductive clay CY is provided so as to cover the electrolytic capacitors Cd[1] to Cd[4], the transistors TrH[1] to TrH[4], the transistors TrL[1] to TrL[4], and the inductors L0[1] to L0[4].

[0115] In this modified example, the thermal conductive clay CY is provided so as to cover one or more uncoated areas HK provided on the drive circuit board 400. In this modified example, the thermal conductive clay CY is provided so as to be in contact with one or more heat sinks 5.

[0116] As described above, according to this modified configuration, the thermal conductive clay CY is in contact with the transistors TrH[1]~TrH[4], the transistors TrL[1]~TrL[4], and the inductors L0[1]~L0[4], while the thermal conductive clay CY is also in contact with the electrolytic capacitors Cd[1]~Cd[4], the heat sink 5, and the uncoated region HK. Therefore, according to this modified configuration, for example, compared to a configuration in which the thermal conductive clay CY is not provided, it is possible to efficiently dissipate the heat generated from the drive signal generation circuits 40[1]~40[4] via the thermal conductive clay CY.

[0117] <<B.6. Modification Example 6>> In the above-described embodiments and Modification Examples 1 to 5, the driving signal generation unit 4 is illustrated and described in a mode provided separately from the head unit 3. However, the present invention is not limited to such a mode. The driving signal generation unit 4 may be mounted on the head unit 3.

[0118] FIG. 18 is a functional block diagram showing an example of the configuration of the inkjet printer 1G according to this modification example.

[0119] As shown in FIG. 18, the inkjet printer 1G differs from the inkjet printer 1 according to the embodiment in that it includes a head unit 3G instead of the head unit 3 and a conveyance unit 9G instead of the conveyance unit 9. The head unit 3G differs from the head unit 3 according to the embodiment in that it includes a driving signal generation unit 4 in addition to the supply circuit 31 and the head unit 32. The conveyance unit 9G differs from the conveyance unit 9 according to the embodiment in that it conveys the recording paper PP but does not have the function of conveying the carriage 110 on which the head unit 3 is mounted. Specifically, the conveyance unit 9G differs from the conveyance unit 9 according to the embodiment in that it does not include a carriage conveyance motor 91, a carriage guide shaft 96, and a belt 97.

[0120] Also in this modification example, as in the embodiment, heat generated from the driving signal generation circuit 40 can be efficiently dissipated through the heat conductive clay CY.

[0121] <<B.7. Modification Example 7>> In the above-described embodiments and modification examples 1 to 6, it is assumed that the inkjet printer 1 is a serial printer, but the present invention is not limited to such an aspect. The inkjet printer 1 may be a so-called line printer in which a plurality of nozzles N are provided in the head unit 3 so as to extend wider than the width of the recording paper PP. In this case, the head unit 3 does not reciprocate inside the housing 100, and the relative positional relationship between the head unit 3 and the housing 100 does not change.

[0122] <<C. Supplementary Note>> Aspects related to the above description are appended below. For the sake of easy understanding of each aspect, hereinafter, the reference numerals in the drawings are appended in parentheses for convenience, but this is not intended to limit the present invention to the illustrated aspects.

[0123] <<C.1. Supplementary Note 1>> Hereinafter, the inkjet printer 1 according to Supplementary Note 1 will be described.

[0124] <<Supplementary Note 1-1>> The inkjet printer 1 according to Supplementary Note 1-1 includes a discharge unit D that is driven by a drive signal Com to discharge ink, a drive circuit board 400 on which a drive signal generation circuit 40 that generates the drive signal Com is disposed, and a clay-like heat-conductive clay CY having electrical insulation. The drive signal generation circuit 40 includes an electronic component that generates heat when generating the drive signal Com and an electrolytic capacitor Cd. The heat-conductive clay CY contacts the electronic component and the electrolytic capacitor Cd.

[0125] According to Supplementary Note 1-1, it is possible to simplify the configuration for cooling the electronic component as compared with the aspect of cooling the drive signal generation circuit 40 using a heat sink designed according to the height of the electronic component.

[0126] <<Supplementary Note 1-2>> The inkjet printer 1 according to Supplementary Note 1-2 is the inkjet printer 1 according to Supplementary Note 1-1, wherein the drive signal generation circuit 40 includes an AB class amplifier circuit, and the thermal conduction clay CY contacts the bipolar transistor TB1 and the electrolytic capacitor Cd included in the AB class amplifier circuit.

[0127] <<Supplementary Note 1-3>> The inkjet printer 1 according to Supplementary Note 1-3 is the inkjet printer 1 according to Supplementary Note 1-1, wherein the drive signal generation circuit 40 includes a D class amplifier circuit, and the thermal conduction clay CY contacts the transistor TrH and the electrolytic capacitor Cd included in the D class amplifier circuit.

[0128] <<Supplementary Note 1-4>> The inkjet printer 1 according to Supplementary Note 1-4 is the inkjet printer 1 according to Supplementary Note 1-1, wherein the drive signal generation circuit 40 includes a D class amplifier circuit and a smoothing circuit, and the thermal conduction clay CY contacts the inductor L0 and the electrolytic capacitor Cd included in the smoothing circuit.

[0129] <<Supplementary Note 1-5>> The inkjet printer 1 according to Supplementary Note 1-5 is the inkjet printer 1 according to Supplementary Notes 1-1 to 1-4, wherein the electronic component contacted by the thermal conduction clay CY and the electrolytic capacitor Cd have different heights.

[0130] According to Supplementary Note 1-5, since heat is propagated from the electronic component to the electrolytic capacitor Cd using the clay-like thermal conduction clay CY, even when the heights of the electronic component and the electrolytic capacitor Cd are different, the electronic component can be cooled with a simple configuration.

[0131] <<C.2. Supplementary Note 1>> Hereinafter, the inkjet printer 1 according to Supplementary Note 2 will be described.

[0132] <<Supplementary Note 2-1>> The inkjet printer 1 according to Appendix 2-1 comprises an ejection unit D that ejects ink driven by a drive signal Com, a drive circuit board 400 on which a drive signal generation circuit 40 that generates the drive signal Com is arranged, a heat sink 5 for cooling the drive signal generation circuit 40, and an electrically insulating clay-like thermal conductive clay CY, wherein the thermal conductive clay CY comprises a base material made of silicone clay SL and thermal conductive particles PT added to the base material, and is in contact with the drive signal generation circuit 40 and the heat sink 5.

[0133] According to Appendix 2-1, since the thermal conductive clay CY comes into contact with the drive signal generation circuit 40, the drive signal generation circuit 40 can be cooled by a simpler heat sink 5 compared to a configuration in which the drive signal generation circuit 40 is cooled using a heat sink designed according to the height of the drive signal generation circuit 40.

[0134] <<Note 2-2>> The inkjet printer 1 according to Appendix 2-2 is the same as the inkjet printer 1 according to Appendix 2-1, wherein the drive circuit board 400 comprises a clay-placed region AR1 whose surface is covered with thermal conductive clay CY, and a clay-free region AR2 whose surface is not covered with thermal conductive clay CY, wherein the surface of the clay-placed region AR1 includes a non-coated region HK that is not coated with an insulating resist member 401R, and the surface of the clay-free region AR2 is coated with an insulating resist member 401R.

[0135] According to Appendix 2-2, since the thermal conductive clay CY is clay-like, high adhesion between the thermal conductive clay CY and the drive circuit board 400 can be achieved, so the drive circuit board 400 can be protected by the thermal conductive clay CY even without protection by the resist member 401R in the non-coated area HK. Furthermore, according to Appendix 2-2, since the thermal conductive clay CY is in contact with the non-coated area HK, heat from the drive signal generation circuit 40 can be dissipated through the drive circuit board 400.

[0136] <<Note 2-3>> The inkjet printer 1 according to Appendix 2-3 is the inkjet printer 1 according to Appendix 2-2, characterized in that in the non-coated area HK, the wiring 401L provided on the surface layer 401 of the drive circuit board 400 and the thermal conductive clay CY are in contact.

[0137] According to Appendix 2-3, since the thermal conductive clay CY is in contact with the uncoated region HK, heat from the drive signal generation circuit 40 can be dissipated through the drive circuit board 400.

[0138] <<Note 2-4>> The inkjet printer 1 described in Appendix 2-4 is the same as the inkjet printer 1 described in Appendix 2-3, characterized in that a plurality of wirings 401L are provided on the surface layer 401, and the diameter of the heat-conducting particles PT is smaller than the distance between two adjacent wirings 401L among the plurality of wirings 401L.

[0139] According to Appendix 2-4, it is possible to suppress the electrical connection between two adjacent wires 401L by the heat-conducting particles PT in the heat-conducting clay CY, thereby ensuring the electrical insulation of the heat-conducting clay CY in the drive signal generation circuit 40.

[0140] <<Note 2-5>> The inkjet printer 1 described in Appendix 2-5 is the inkjet printer 1 described in Appendix 2-1 to Appendix 2-4, characterized in that a plurality of drive signal generation circuits 40 are arranged on the drive circuit board 400, and the thermal conductive clay CY is provided so as to cover the plurality of drive signal generation circuits 40.

[0141] According to Appendix 2-5, compared to the configuration in which heat conductive clay CY is provided for each of the multiple drive signal generation circuits 40, it is possible to simplify the configuration for cooling the drive signal generation circuits 40.

[0142] <<Note 2-6>> The inkjet printer 1 described in Appendix 2-6 is the inkjet printer 1 described in Appendix 2-1 to Appendix 2-5, characterized in that the drive signal generation circuit 40 includes a plurality of electronic components of different heights, and the thermal conductive clay CY covers the plurality of electronic components.

[0143] According to Appendix 2-6, since the clay-like thermal conductive clay CY can cool multiple electronic components that are at different heights by coming into contact with them, it is possible to cool the drive signal generation circuit 40 with a simpler configuration compared to a method of cooling the drive signal generation circuit 40 using a heat sink designed according to the height of the drive signal generation circuit 40.

[0144] <<Note 2-7>> The inkjet printer 1 described in Appendix 2-7 is the inkjet printer 1 described in Appendix 2-1 to Appendix 2-6, characterized in that the heat sink 5 has a flat portion 5000, and the thermal conductive clay CY is in contact with the heat sink 5 at the flat portion 5000.

[0145] According to Appendix 2-7, compared to a configuration in which the drive signal generation circuit 40 is cooled using a heat sink designed according to the height of the drive signal generation circuit 40, this configuration allows for cooling of the drive signal generation circuit 40 with a simpler setup. [Explanation of Symbols]

[0146] 1...Inkjet printer, 2...Control unit, 3...Head unit, 4...Drive signal generation unit, 5...Heat sink, 9...Transport unit, 31...Supply circuit, 32...Head section, 40...Drive signal generation circuit, 41...Integrated circuit, 51...Platform section, 52...Heat dissipation section, 400...Drive circuit board, 401...Surface layer, 402...Insulating layer, 403...Wiring layer, 404...Protective layer, 5000...Planar section, CY...Thermal conductive clay, C0...Capacitor, Cd...Electrolytic capacitor, D...Ejection section, HK...Uncoated area, L0...Inductor, TrH...Transistor, TrL...Transistor.

Claims

1. A dispensing unit that is driven by a drive signal to dispense liquid, A circuit board on which a drive circuit that generates the aforementioned drive signal is arranged, A clay-like heat-conducting member having electrical insulating properties is provided, The aforementioned drive circuit comprises an electronic component that generates heat in conjunction with the generation of the drive signal, and an electrolytic capacitor. The heat conductive member is in contact with the electronic component and the electrolytic capacitor. A liquid dispensing device characterized by the following features.

2. The aforementioned drive circuit includes a Class AB amplifier circuit. The aforementioned electronic component is a bipolar transistor included in the Class AB amplifier circuit. The liquid dispensing device according to claim 1, characterized in that...

3. The aforementioned drive circuit includes a Class D amplifier circuit, The aforementioned electronic component is a field-effect transistor included in the Class D amplifier circuit. The liquid dispensing device according to claim 1, characterized in that...

4. The drive circuit includes a Class D amplifier circuit and a smoothing circuit. The aforementioned electronic component is a coil included in the smoothing circuit. The liquid dispensing device according to claim 1, characterized in that...

5. The aforementioned electronic component and the aforementioned electrolytic capacitor have different heights. A liquid dispensing device according to any one of claims 1 to 4, characterized in that

6. A dispensing unit that is driven by a drive signal to dispense liquid, A circuit board on which a drive circuit that generates the aforementioned drive signal is arranged, A clay-like heat-conducting member having electrical insulating properties is provided, The aforementioned drive circuit comprises an electronic component that generates heat in conjunction with the generation of the drive signal, and an electrolytic capacitor. The heat conductive member is in contact with the electronic component and the electrolytic capacitor. A head unit characterized by the following features.

7. The aforementioned drive circuit includes a Class AB amplifier circuit. The aforementioned electronic component is a bipolar transistor included in the Class AB amplifier circuit. The head unit according to claim 6, characterized in that...

8. The aforementioned drive circuit includes a Class D amplifier circuit, The aforementioned electronic component is a field-effect transistor included in the Class D amplifier circuit. The head unit according to claim 6, characterized in that...

9. The drive circuit includes a Class D amplifier circuit and a smoothing circuit. The aforementioned electronic component is a coil included in the smoothing circuit. The head unit according to claim 6, characterized in that...

10. The aforementioned electronic component and the aforementioned electrolytic capacitor have different heights. A head unit according to any one of claims 6 to 9, characterized in that...

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