Liquid dispensing device

Abstract

To provide a liquid dispensing device that can perform higher-resolution printing while being miniaturized. [Solution] A liquid dispensing device comprising a print head and a drive circuit provided outside the print head that outputs a drive signal, the drive circuit comprising a plurality of drive signal output circuits, each of the plurality of drive signal output circuits associated with one of the plurality of drive signals, each of the plurality of drive signal output circuits having the associated drive signal as the target drive signal, a P-channel type MOSFET that switches whether or not to output the target drive signal, and a first comparator, the upper limit of the dynamic range of the plurality of drive signals exceeds the dynamic range of the source-gate voltage of the MOSFET, and the first comparator switches the voltage value of the gate voltage of the MOSFET according to the voltage value of the target drive signal so that the source-gate voltage of the MOSFET does not exceed the dynamic range of the source-gate voltage of the MOSFET.

Description

Technical Field

[0001] This disclosure relates to a liquid ejection device.

Background Art

[0002] Research and development have been carried out on liquid ejection devices that eject liquid onto a printing medium such as printing paper to form an image.

[0003] Regarding this, there is known a liquid ejection device that includes a print head having a large number of drive elements, uses ink droplets of various sizes from small to large, and can perform high-definition gradation reproduction printing by driving the large number of drive elements of the print head (see Patent Document 1). Note that the liquid ejection device in this specification may also be referred to as a printing device.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] On the other hand, there is a demand in the market for a smaller liquid ejection device and a liquid ejection device that can perform higher-definition printing. Here, the larger the size of the ink droplets that can be used in the liquid ejection device, the higher-definition printing can be performed. However, in the liquid ejection device described in Patent Document 1, increasing the size of the ink droplets that can be used sometimes leads to an increase in the size of the print head. Therefore, in the liquid ejection device described in Patent Document 1, it may be difficult to perform higher-definition printing while achieving miniaturization.

Means for Solving the Problems

[0006] To solve the above problems, one aspect of the present disclosure is a liquid dispensing device comprising: a print head for printing an image onto a printing medium; a drive circuit provided outside the print head for outputting at least one of a plurality of drive signals to the print head, wherein the drive circuit comprises a plurality of drive signal output circuits, each of the plurality of drive signal output circuits associated with one of the plurality of drive signals, each of the plurality of drive signal output circuits uses the associated drive signal as the target drive signal and switches whether or not to output the target drive signal to the print head; and a first comparator, wherein the upper limit of the dynamic range of each of the plurality of drive signals exceeds the dynamic range of the source-gate voltage of the MOSFET, and the first comparator switches the voltage value of the gate voltage of the MOSFET according to the voltage value of the target drive signal so that the source-gate voltage of the MOSFET does not exceed the dynamic range of the source-gate voltage of the MOSFET.

[0007] To solve the above problems, one aspect of the present disclosure is a liquid dispensing device comprising: a print head for printing an image onto a printing medium; and a drive circuit provided outside the print head for outputting at least one of a plurality of drive signals to the print head, wherein the drive circuit comprises a plurality of drive signal output circuits, each of the plurality of drive signal output circuits is associated with one of the plurality of drive signals, each of the plurality of drive signal output circuits includes a P-channel type MOSFET that switches whether or not to output the associated drive signal to the print head, with the assigned drive signal being the target drive signal, the upper limit of the dynamic range of each of the plurality of drive signals exceeds the dynamic range of the source-gate voltage of the MOSFET, and each of the plurality of drive signal output circuits outputs a voltage as the gate voltage of the MOSFET by a wired OR so that the dynamic range of the source-gate voltage of the MOSFET does not exceed the dynamic range of the source-gate voltage of the MOSFET, according to the voltage value of the target drive signal. [Brief explanation of the drawing]

[0008] [Figure 1] This figure shows a schematic example of the internal configuration of the liquid dispensing device 1 according to the embodiment. [Figure 2] This figure shows an example of the functional configuration of the liquid dispensing device 1. [Figure 3] This figure shows an example of the functional configuration of the drive circuit 50. [Figure 4] This figure shows an example of the functional configuration of the drive signal output unit SOX. [Figure 5] This figure shows an example of a specific circuit configuration for realizing a drive signal output unit SOX equipped with a drive signal output switching unit OCX, as shown by the equivalent circuit in Figure 4. [Modes for carrying out the invention]

[0009] <Embodiment> Embodiments of this disclosure will be described below with reference to the drawings. In this specification, forming an image on a print medium will be referred to as printing an image on a print medium.

[0010] <Overview of the liquid dispensing device according to this embodiment> First, an overview of the liquid dispensing device according to the embodiment will be described.

[0011] The liquid ejection device according to this embodiment includes a print head and a drive circuit. The print head prints an image onto a printing medium. The drive circuit is provided outside the print head and outputs at least one of a plurality of drive signals to the print head. The drive circuit also includes a plurality of drive signal output circuits. Each of the plurality of drive signal output circuits is associated with one of the plurality of drive signals. Each of the plurality of drive signal output circuits includes a P-channel type MOSFET (Metal Oxide Semiconductor Field Effect Transistor) and a first comparator. The MOSFET uses the associated drive signal from the plurality of drive signals as the target drive signal and switches whether or not to output the target drive signal to the print head. Here, the upper limit of the dynamic range of each of the plurality of drive signals exceeds the dynamic range of the source-gate voltage of the MOSFET. Therefore, the first comparator switches the gate voltage value of the MOSFET according to the voltage value of the target drive signal so that the source-gate voltage of the MOSFET does not exceed the dynamic range of the source-gate voltage of the MOSFET. This allows the liquid ejection system to be miniaturized, and the size of the drive circuit can be suppressed compared to cases where the drive signal output circuit is equipped with an N-channel MOSFET. Furthermore, because the size of the drive circuit can be suppressed, the number of drive signal output circuits can be increased while the liquid ejection system itself is miniaturized. This leads to an increase in the size of the droplets that the print head can use in printing, and as a result, leads to the realization of high-resolution printing by the liquid ejection system. Therefore, the liquid ejection system can achieve higher resolution printing while being miniaturized.

[0012] The configuration of the liquid dispensing device according to the embodiment will be described in detail below.

[0013] <Configuration of the liquid dispensing device according to this embodiment> The configuration of the liquid dispensing device according to the embodiment will be described below, using liquid dispensing device 1 as an example.

[0014] Figure 1 is a diagram showing a schematic example of the internal configuration of a liquid ejection device 1 according to an embodiment. Image data is supplied to the liquid ejection device 1 from an externally located host computer. The liquid ejection device 1 forms dots by ejecting liquid onto the printing medium P according to the image data supplied from the host computer. In this way, the liquid ejection device 1 can print an image corresponding to the supplied image data onto the printing medium P. For example, the liquid ejection device 1 is an inkjet printer, but any other type of printer that can form dots by ejecting liquid onto the printing medium P may be used. Here, the printing medium P may be any sheet-like medium such as printing paper. In the following, as an example, the case where the printing medium P is printing paper will be described. Note that in Figure 1, some of the components of the liquid ejection device 1, such as the housing and cover, have been omitted in order to simplify the diagram. Also, the liquid ejected by the liquid ejection device 1 may be any liquid that can form dots on the printing medium P. In the following, as an example, the case where the liquid ejected by the liquid ejection device 1 is ink will be described.

[0015] The liquid dispensing device 1 includes a moving mechanism 3. The moving mechanism 3 moves the carriage 24, on which the head unit 2 is mounted, in the main scanning direction. The moving mechanism 3 includes a carriage motor 31, a carriage guide shaft 32, and a timing belt 33. The carriage motor 31 is the drive source for the head unit 2. The carriage guide shaft 32 is a shaft body with both ends fixed. The timing belt 33 is a belt that extends almost parallel to the carriage guide shaft 32 and is driven by the carriage motor 31. The moving mechanism 3 also includes a linear encoder 90. The linear encoder 90 detects the position of the head unit 2 in the main scanning direction.

[0016] The head unit 2 is mounted on the carriage 24. The carriage 24 is configured to accommodate a predetermined number of ink cartridges 22. The carriage 24 is supported on the carriage guide shaft 32 so as to be able to reciprocate, and is also fixed to a part of the timing belt 33. Therefore, by causing the timing belt 33 to move in the forward and reverse directions by the carriage motor 31, the carriage 24 is guided by the carriage guide shaft 32 and moves back and forth along the main scanning direction. In other words, the carriage motor 31 moves the carriage 24 in the main scanning direction. A print head 20 is attached to the part of the carriage 24 that faces the printing medium P. The print head 20 has multiple nozzles, and a drive signal is input to drive the print head 20. In response to the input drive signal, a predetermined amount of ink is ejected from these multiple nozzles at a predetermined timing. Here, the predetermined amount is an amount that changes according to the waveform of the drive signal. In other words, when the print head 20 receives any of several drive signals with different waveforms, it sets a predetermined amount corresponding to the waveform of the input drive signal and ejects a predetermined amount of ink from these nozzles at a predetermined timing. Various signals are supplied to the head unit 2, which operates as described above, via a cable 190 such as a flexible flat cable. These various signals include, for example, the aforementioned drive signals.

[0017] Further, the liquid ejection device 1 includes a conveyance mechanism 4. The conveyance mechanism 4 conveys the printing medium P along a sub-scanning direction intersecting the main scanning direction. The conveyance mechanism 4 includes a platen 43, a conveyance motor 41, and conveyance rollers 42. The platen 43 faces the print head 20 and supports the printing medium P on which an image is printed by the print head 20. The conveyance motor 41 is a drive source that drives the conveyance rollers 42. The conveyance rollers 42 are rollers that convey the printing medium P in the sub-scanning direction by being rotated by the conveyance motor 41. The liquid ejection device 1 ejects ink from the print head 20 to the printing medium P at a necessary timing and prints a desired image in the process where the printing medium P conveyed by the conveyance mechanism 4 passes between the print head 20 and the platen 43. Here, the sub-scanning direction in which the printing medium P is conveyed may be referred to as the conveyance direction in which the printing medium P is conveyed.

[0018] Also, a home position serving as a base point for the movement of the carriage 24 is set in one of the regions at both ends of the movement range of the carriage 24. In the home position, a capping member 70 that seals the nozzle forming surface of the print head 20 and a wiper member 71 for wiping the nozzle forming surface are arranged. The liquid ejection device 1 prints an image on the surface of the printing medium P in both the forward movement when the carriage 24 moves from this home position toward the other of the both ends and the reverse movement when the carriage 24 moves from the other toward the home position side.

[0019] A flushing box 72 for collecting the ink ejected from the print head 20 during the flushing operation is arranged at an end of the platen 43 on the main scanning direction side and on the opposite side of the end from the home position where the carriage 24 moves. The flushing operation is an operation of forcibly ejecting ink from each nozzle regardless of the image data in order to prevent the nozzle from being clogged due to thickening of the ink near the nozzle, air bubbles entering the nozzle, etc., which would cause an inappropriate amount of ink to be ejected. Note that the flushing box 72 may be configured to be provided at both ends of the platen 43 in the main scanning direction.

[0020] As described above, in the liquid ejection device 1 according to the present embodiment, the conveyance mechanism 4 conveys the print medium P along the sub-scanning direction, and reciprocates the carriage 24 mounted with the head unit 2 along the main scanning direction intersecting the sub-scanning direction. Then, the print head 20 included in the head unit 2 mounted on the carriage 24 ejects ink onto the print medium P in synchronization with the conveyance of the print medium P and the reciprocating movement of the carriage 24, so that the ink can land at a desired position on the print medium P. As a result, a desired image is printed on the print medium P.

[0021] <Functional Configuration of Liquid Ejection Device> Hereinafter, referring to FIG. 2, the functional configuration of the liquid ejection device 1 will be described. FIG. 2 is a diagram showing an example of the functional configuration of the liquid ejection device 1. As shown in FIG. 2, the liquid ejection device 1 includes a control unit 10 and a head unit 2. The control unit 10 and the head unit 2 are electrically connected via a cable 190.

[0022] The control unit 10 includes a control circuit 100, a carriage motor driver 35, a conveyance motor driver 45, a voltage output circuit 110, and a drive circuit 50. That is, the drive circuit 50 is provided outside the print head 20. More specifically, the drive circuit 50 is provided outside the head unit 2. The control circuit 100 is supplied with image data from a host computer. The control circuit 100 generates various signals according to the image data supplied from the host computer. After generating any one of the various signals, the control circuit 100 outputs the signal to the functional unit corresponding to the generated signal.

[0023] Specifically, the control circuit 100 determines the current scanning position of the head unit 2 based on the detection signal output from the linear encoder 90. The control circuit 100 then generates control signals CTR1 and CTR2 according to the current scanning position of the head unit 2. Control signal CTR1 is a signal supplied to the carriage motor driver 35. The control circuit 100 outputs the generated control signal CTR1 to the carriage motor driver 35. The carriage motor driver 35, having received control signal CTR1 in this way, drives the carriage motor 31 according to the input control signal CTR1. Control signal CTR2 is a signal supplied to the transport motor driver 45. The control circuit 100 outputs the refined control signal CTR2 to the transport motor driver 45. The transport motor driver 45, having received control signal CTR2 in this way, drives the transport motor 41 according to the input control signal CTR2. Through these actions, the control circuit 100 controls the reciprocating movement of the carriage 24 in the main scanning direction and the transport of the printing medium P in the sub-scanning direction.

[0024] Furthermore, the control circuit 100 generates a signal corresponding to the current scanning position of the head unit 2 based on image data supplied from an externally located host computer and a detection signal output from the linear encoder 90. Specifically, the control circuit 100 generates the following signals: a clock signal SCK, a print data signal SI, a latch signal LAT, a change signal CH, and N base drive signals. The control circuit 100 then outputs the generated clock signal SCK, print data signal SI, latch signal LAT, change signal CH, and N base drive signals to the head unit 2. Here, a base drive signal is a signal that serves as the basis for generating the drive signals. As an example, the case where N is 14 will be described below. Note that N may be an integer smaller than 14 or an integer larger than 14, as long as N is an integer greater than or equal to 1. For convenience of explanation, each of these 14 base drive signals will be referred to as base drive signal dA, base drive signal dB, ..., base drive signal dN below.

[0025] Furthermore, the control circuit 100 causes the maintenance unit 80 to perform maintenance processing to restore the ink ejection state of the ejection unit 600 to normal. The maintenance unit 80 has a cleaning mechanism 81 and a wiping mechanism 82. The cleaning mechanism 81 performs pumping processing as part of the maintenance processing, sucking out the thickened ink, air bubbles, etc., accumulated inside the ejection unit 600 using a tube pump (not shown). The wiping mechanism 82 also performs wiping processing as part of the maintenance processing, wiping off foreign matter such as paper dust attached near the nozzle of the ejection unit 600 with a wiper member 71. The control circuit 100 may also be configured to perform the flushing operation described above as maintenance processing to restore the ink ejection state of the ejection unit 600 to normal.

[0026] The voltage output circuit 110 generates a DC voltage VHV, for example, 42V, and outputs it to the head unit 2. This voltage VHV is used as the power supply voltage for various functional parts of the head unit 2. Alternatively, the voltage VHV generated by the voltage output circuit 110 may be used as the power supply voltage for various functional parts of the control unit 10. Furthermore, the voltage output circuit 110 may be configured to generate multiple DC voltage signals with voltage values ​​different from the voltage value of VHV and supply them to the various functional parts included in the control unit 10 and the head unit 2.

[0027] The drive circuit 50 has N drive signal output circuits, from drive signal output circuits 50A to drive signal output circuits 50N. Each of these N drive signal output circuits is associated with one of the N drive signals. Some or all of these N drive signals have different waveforms. However, all of these N drive signals may have the same waveform. Below, as an example, we will describe the case where some of these N drive signals have different waveforms and the other parts of these N drive signals have the same waveform. Here, for the sake of explanation, the Xth drive signal output circuit among the N drive signal output circuits 50A to drive signal output circuits 50N will be referred to as drive signal output circuit 50X. Here, X represents one of A to N. Also, for the sake of explanation, the Xth base drive signal among the N base drive signals dA to base drive signals dN will be referred to as base drive signal dX. Furthermore, for the sake of explanation, in the following, among the N drive signals mentioned above, the drive signal generated by the drive signal output circuit 50X based on the base drive signal dX will be referred to as the drive signal COMX. For example, the drive signal COMA is the drive signal generated by the drive signal output circuit 50A based on the base drive signal dA.

[0028] The drive signal output circuit 50X receives a digital base drive signal dX and a voltage VHV as inputs. The drive signal output circuit 50X then converts the input base drive signal dX from digital to analog and generates a drive signal COMX by class D amplification of the converted analog signal to a voltage value corresponding to the voltage VHV. The drive signal output circuit 50X then outputs the generated drive signal COMX to the print head 20. For example, the drive signal output circuit 50B converts the input base drive signal dB from digital to analog and generates a drive signal COMB by class D amplification of the converted analog signal to a voltage value corresponding to the voltage VHV. The drive signal output circuit 50B then outputs the generated drive signal COMB to the print head 20. Also, for example, the drive signal output circuit 50N converts the input base drive signal dN from digital to analog and generates a drive signal COMN by class D amplification of the converted analog signal to a voltage value corresponding to the voltage VHV. The drive signal output circuit 50N then outputs the generated drive signal COMN to the print head 20.

[0029] Thus, the base drive signal dX is a signal that defines the waveform of the drive signal COMX. For this reason, the base drive signal dX can be any signal that can define the waveform of the drive signal COMX, for example, an analog signal. Details of the drive signal output circuit 50X will be described later.

[0030] Furthermore, the drive circuit 50 generates a constant reference voltage signal VBS with a voltage value of 5.5V, 6V, etc., and supplies it to the print head 20. Here, the reference voltage signal VBS is a signal that indicates the potential that serves as the reference for driving the piezoelectric element 60, and is, for example, the ground potential, but is not limited to this.

[0031] The head unit 2 has a print head 20.

[0032] The print head 20 is composed of a selection control circuit 210, a plurality of selection circuits 230, and a plurality of ejection units 600 corresponding to each of the plurality of selection circuits 230. The selection control circuit 210 generates selection signals to select or deselect the waveforms of each of the drive signals COMA to COMN based on the clock signal SCK, print data signal SI, latch signal LAT, and change signal CH supplied from the control circuit 100, and outputs these to the selection circuits 230 corresponding to each of the plurality of ejection units 600.

[0033] Each selection circuit 230 receives the drive signals COMA to COMN and the selection signal output by the selection control circuit 210. Therefore, each selection circuit 230 is electrically connected to the integrated wiring LA to LN. Integrated wiring LX is electrically connected to the source terminal of the MOSFET 52X provided in the drive signal output circuit 50X, which will be described later. Based on the input selection signal, the selection circuit 230 generates the drive signal VOUT by selecting or deselecting the waveforms of the drive signals COMA to COMN and outputs it to the corresponding output unit 600.

[0034] Each ejection unit 600 includes one or more piezoelectric elements 60. A drive signal VOUT, output from a selection circuit 230 corresponding to the ejection unit 600 including the piezoelectric element 60, is supplied to one end of a piezoelectric element 60. A reference voltage signal VBS is supplied to the other end of the piezoelectric element 60. The piezoelectric element 60 is driven according to the potential difference between the drive signal VOUT supplied to one end of the piezoelectric element 60 and the reference voltage signal VBS supplied to the other end of the piezoelectric element 60. As a result, an amount of ink corresponding to the drive of the piezoelectric element 60 is ejected from the ejection unit 600. The piezoelectric element 60 may be any other type of drive element capable of ejecting an amount of ink corresponding to the drive from the ejection unit 600. The piezoelectric element 60 is, for example, a piezo element, but is not limited to this.

[0035] As described above, the liquid ejection device 1 in this embodiment includes a drive signal output circuit 50X that outputs a drive signal COMX, and an ejection unit 600 that includes a piezoelectric element 60 that is driven based on a drive signal VOUT based on the drive signal COMX, and ejects ink by driving the piezoelectric element 60. The drive signal output circuit 50X is provided outside the head unit 2. This allows the liquid ejection device 1 to be miniaturized. The head unit 2, including the ejection unit 600, is mounted on the carriage 24.

[0036] <Functional configuration of the drive circuit> The functional configuration of the drive circuit 50 will be described below with reference to Figure 3. Figure 3 is a diagram showing an example of the functional configuration of the drive circuit 50.

[0037] As described above, the drive circuit 50 includes N drive signal output circuits, from drive signal output circuit 50A to drive signal output circuit 50N. The drive circuit 50 also includes a first drive signal output terminal 51.

[0038] Here, the drive signal output circuit 50X comprises a drive signal generation unit SG and a drive signal output unit SO. For the sake of explanation, the drive signal generation unit SG of the drive signal output circuit 50X will be referred to as the drive signal generation unit SGX below. In this case, for example, the drive signal generation unit SGA is the drive signal generation unit SG of the drive signal output circuit 50A. Also, for example, the drive signal generation unit SGC is the drive signal generation unit SG of the drive signal output circuit 50C. Furthermore, for the sake of explanation, the drive signal output unit SO of the drive signal output circuit 50X will be referred to as the drive signal output unit SOX below. In this case, for example, the drive signal output unit SOB is the drive signal output unit SO of the drive signal output circuit 50B. Also, for example, the drive signal output unit SOD is the drive signal output unit SO of the drive signal output circuit 50D.

[0039] The drive signal generation unit SGX has a Class D amplification circuit. The drive signal generation unit SGX can be any circuit that is capable of generating the drive signal COMX by digital-to-analog conversion of the base drive signal dX and Class D amplification of the converted base drive signal dX using a Class D amplification circuit. For this reason, the base drive signal dX is input to the drive signal generation unit SGX from the control circuit 100. The drive signal generation unit SGX then generates the drive signal COMX by digital-to-analog conversion of the input base drive signal dX and Class D amplification of the converted base drive signal dX. After generating the drive signal COMX, the drive signal generation unit SGX outputs the generated drive signal COMX to the drive signal output unit SOX.

[0040] The drive signal output unit SOX outputs the drive signal associated with the drive signal output circuit 50X to the print head 20 as a drive signal COMX via the first drive signal output terminal 51. Here, the first drive signal output terminal 51 is an output terminal of the drive signal output circuit 50X and is electrically connected to the print head 20 of the head unit 2. More specifically, the first drive signal output terminal 51 is electrically connected to the integrated wiring LX and outputs the drive signal COMX output from the drive signal output circuit 50X to each selection circuit 230. This allows each selection circuit 230 to select whether or not to output the drive signal output from at least one of the N drive signal output circuits to one or more piezoelectric elements 60 included in the corresponding ejection unit 600. All N drive signal output circuits are connected to the first drive signal output terminal 51. Therefore, the drive circuit 50 can also output a signal obtained by superimposing two or more drive signals from the N drive signals to the print head 20 as a new drive signal. However, it is desirable that the two or more drive signals to be superimposed are signals with the same waveform. In other words, it is desirable that the two or more drive signals to be superimposed are signals whose phase and amplitude are synchronized with each other. In this case, the two or more superimposed drive signals are superimposed as a single amplified drive signal.

[0041] The drive signal output unit SOX has, for example, a drive signal input terminal IX, a drive signal output switching unit OCX, and a second drive signal output terminal OX, as shown in Figure 4. Figure 4 is a diagram showing an example of the functional configuration of the drive signal output unit SOX. Note that the drive signal output unit SOX may have other configurations as long as it is capable of outputting the drive signal associated with the drive signal output circuit 50X as a drive signal COMX to the print head 20.

[0042] The drive signal input terminal IX is connected to the drive signal generation unit SGX. The drive signal COMX generated by the drive signal generation unit SGX is input to the drive signal input terminal IX. The drive signal COMX input to the drive signal input terminal IX is an example of a target drive signal.

[0043] The drive signal output switching unit OCX is equipped with a P-channel type MOSFET 52X that switches whether or not to output the drive signal COM to the print head 20, and outputs one of several different voltage values ​​as the gate voltage of the MOSFET 52X. As a result, the liquid ejection device 1 can suppress the enlargement of the drive circuit 50 compared to when the drive signal output switching unit OCX is equipped with an N-channel type MOSFET. Furthermore, if the enlargement of the drive circuit 50 can be suppressed, the liquid ejection device 1 can be miniaturized while increasing the number of drive signal output circuits 50X. This leads to an increase in the size of ink droplets that can be used by the print head 20 during printing, and as a result, it leads to the realization of high-definition printing by the liquid ejection device 1, which is useful. In addition, this means that the size of the ink droplets can be increased without the ink droplets merging together, and as a result, it leads to faster printing by the liquid ejection device 1, which is also useful. Furthermore, by including a MOSFET 52X in the drive signal output switching unit OCX, the liquid dispensing device 1 can prevent the application of a voltage value exceeding the dynamic range of the source-gate voltage of the MOSFET 52X between the source and gate terminals of the MOSFET 52X. The reason for this will be explained later. Although the MOSFET 52X is made of silicon, it may be made of other types of semiconductors. In addition, as an example, the case in which the MOSFET 52X is an enhancement type MOSFET will be described below.

[0044] Here, as an example, we will explain the case where the upper limit of the dynamic range of the drive signal COM exceeds the dynamic range of the source-gate voltage of the MOSFET52X. This is because increasing the upper limit of the dynamic range of the drive signal COMX increases the number of types of drive signal waveforms that can be used by the liquid ejection device 1. Increasing the types of drive signal waveforms means that the liquid ejection device 1 can increase the size of ink droplets without causing them to merge, which in turn leads to faster printing by the liquid ejection device 1 and is therefore useful. On the other hand, the dynamic range of the source-gate voltage of the MOSFET52X is often in the range of -20V or more and +20V or less. This is because we want to keep the on-resistance of the MOSFET52X low. For this reason, the higher the resolution of the printing, the more likely the upper limit of the dynamic range of the drive signal COM will exceed the dynamic range of the source-gate voltage of the MOSFET52X. For these reasons, the drive signal output circuit 50X outputs one of several different voltage values ​​as the gate voltage of MOSFET 52X, according to the voltage value of the drive signal COMX, so that the source-gate voltage of MOSFET 52X does not exceed the dynamic range of MOSFET 52X. In the following, as an example, the case where the dynamic range of the drive signal COMX is between 0V and +42V is described. Also, in the following, as an example, the case where the dynamic range of the source-gate voltage of MOSFET 52X is between -20V and +20V is described.

[0045] In Figure 4, the circuit diagram drawn within the frame showing the drive signal output switching unit OCX is an equivalent circuit diagram of the specific circuit for realizing the drive signal output switching unit OCX. The drive signal output switching unit OCX includes a MOSFET 52X, a first output voltage output unit OC1, a second output voltage output unit OC2, a third output voltage output unit OC3, and wiring LX.

[0046] The source terminal of MOSFET52X is electrically connected to the drive signal input terminal IX. Therefore, the drive signal COMX is input to the source terminal of MOSFET52X. The drain terminal of MOSFET52X is electrically connected to the second drive signal output terminal OX. Therefore, the voltage value applied to the drain terminal of MOSFET52X matches the voltage value of the drive signal COMX input to the source terminal of MOSFET52X, provided that there is electrical conduction between the drain terminal and the source terminal of MOSFET52X. The gate terminal of MOSFET52X is electrically connected to wiring LX.

[0047] The first output voltage output unit OC1 is electrically connected to the wiring LX, and outputs a first output voltage OV1 with a predetermined first voltage value to the wiring LX when the voltage value of the drive signal COMX input to the drive signal input terminal IX exceeds a first threshold. In other words, the switch in the first output voltage output unit OC1 shown in Figure 4 is a switch that switches whether or not to output the first output voltage OV1 to the wiring LX depending on whether or not the voltage value of the drive signal COMX input to the drive signal input terminal IX exceeds a first threshold. Here, the first threshold is a voltage value higher than 0V and less than or equal to the upper limit of the dynamic range of the source-gate voltage of the MOSFET52X. However, a higher first threshold is desirable. For this reason, if the device margin is not considered, the first threshold is 20V, which is the upper limit. On the other hand, if the device margin is considered, the first threshold is, for example, 16.1V, which is lower than the upper limit. On the other hand, the first voltage value is a voltage value below the first threshold, and is determined so that the source-gate voltage of the MOSFET52X does not exceed the dynamic range of the source-gate voltage of the MOSFET52X when the voltage value of the drive signal COMX is within the range from the first threshold to a second threshold higher than the first threshold. Similar to the first threshold, a higher first voltage value is desirable. For this reason, if the device margin is not considered, the first voltage value is 20V, the same as the first threshold of 20V. On the other hand, if the device margin is considered, the first voltage value is, for example, 10.2V, which is lower than the first threshold of 16.1V. The second threshold is a voltage value higher than the first threshold, and lower than the voltage value obtained by adding the first threshold to the upper limit of the dynamic range of the source-gate voltage of the MOSFET52X. However, a higher second threshold is desirable. For this reason, if the device margin is not considered, the second threshold is 40V, which is the upper limit plus the first threshold. On the other hand, when considering the device margin, the second threshold is, for example, 25.9V, which is lower than 40V.Therefore, when the voltage value of the drive signal COMX is within the range from the first threshold to the second threshold, the liquid dispensing device 1 can prevent the application of a voltage value exceeding the dynamic range of the source-gate voltage of the MOSFET 52X between the source terminal and the gate terminal of the MOSFET 52X, as described above. Furthermore, the lower the first voltage value, the lower the on-resistance of the MOSFET 52X can be. This is useful because it helps to suppress the increase in power consumption of the drive circuit 50.

[0048] The second output voltage output unit OC2 is electrically connected to the wiring LX, and outputs a second output voltage OV2 with a predetermined second voltage value to the wiring LX when the voltage value of the drive signal COMX input to the drive signal input terminal IX exceeds the second threshold. In other words, the switch in the second output voltage output unit OC2 shown in Figure 4 is a switch that switches whether or not to output the second output voltage OV2 to the wiring LX depending on whether or not the voltage value of the drive signal COMX input to the drive signal input terminal IX exceeds the second threshold. Here, the second voltage value is a voltage value less than or equal to the second threshold, and is a voltage value determined so that the source-gate voltage of MOSFET52X does not exceed the dynamic range of the source-gate voltage of MOSFET52X when the voltage value of the drive signal COMX is within the range from the second threshold to less than the third threshold which is higher than the second threshold. This is because when the source voltage and gate voltage of MOSFET52X are the same, the drain terminal and source terminal of MOSFET52X are electrically isolated as in the conventional case. Similar to the second threshold, a higher second voltage value is desirable. Therefore, if the device margin is not considered, the second voltage value is 40V, the same as the second threshold of 40V. On the other hand, if the device margin is considered, the second voltage value is 21.5V, which is lower than the second threshold of 25.9V, for example. The third threshold is a voltage value less than or equal to the upper limit of the voltage value of the drive signal COMX. For example, the third threshold is a voltage value less than or equal to the upper limit of the voltage value of the drive signal COMX, which is 42V. Below, as an example, the case where the third threshold is 42V, which is the upper limit of the voltage value of the drive signal COMX, will be described. Therefore, as described above, when the voltage value of the drive signal COMX is within the range from the second threshold to less than the third threshold, the liquid dispensing device 1 can suppress the application of a voltage value exceeding the dynamic range of the source-gate voltage of the MOSFET 52X between the source terminal and the gate terminal of the MOSFET 52X. Note that the lower the second voltage value, the smaller the on-resistance of the MOSFET 52X can be. This is useful as it leads to suppression of the increase in power consumption of the drive circuit 50.

[0049] The third output voltage output unit OC3 is electrically connected to the wiring LX and outputs a third output voltage OV3 with a predetermined third voltage value to the wiring LX when predetermined conditions are met. In other words, the switch in the third output voltage output unit OC3 shown in Figure 4 is a switch that switches whether or not to output the third output voltage OV3 to the wiring LX depending on whether or not predetermined conditions are met. Here, the predetermined conditions include, for example, the following two conditions: Condition 1 and Condition 2.

[0050] Condition 1: A control signal is input from the host computer to stop the output of the drive signal COMX from the drive signal output unit SOX to the print head 20. Condition 2: The voltage value of the drive signal COMX is the third threshold.

[0051] Furthermore, the predetermined conditions may include either condition 1 or condition 2 above, or they may include other conditions in place of at least one of condition 1 or condition 2, or in addition to at least one of condition 1 or condition 2.

[0052] When at least one of the above conditions 1 and condition 2 is satisfied, the third output voltage output unit OC3 determines that a predetermined condition is satisfied, and outputs a third output voltage OV3 of a predetermined third voltage value to the wiring LX. The third voltage value is a voltage value determined such that when the voltage value of the drive signal COMX is the third threshold value, the voltage between the source and gate of the MOSFET 52X becomes the lower limit value of the dynamic range of the voltage between the source and gate of the MOSFET 52X (-20V < VGS ≤ 0). In other words, the third voltage value is a voltage value determined to electrically insulate between the drain terminal and the source terminal of the MOSFET 52X. For example, the third voltage value is 42V, but it may be a voltage higher than 42V. Therefore, when the third output voltage OV3 is input to the gate terminal of the MOSFET 52X, the MOSFET 52X electrically insulates between the drain terminal and the source terminal. That is, in this case, the MOSFET 52X stops the output of the drive signal COMX from the drive signal output unit SOX to the print head 20.

[0053] Thus, the third output voltage output section OC3 is a circuit that switches whether or not to stop the output of the drive signal COMX from the drive signal output section SOX to the print head 20. For this reason, in the equivalent circuit shown in Figure 4, when the switch of the third output voltage output section OC3 is on, the voltage applied to the gate terminal of the MOSFET 52X via the wiring LX is the third output voltage OV3, regardless of whether the switches of the first output voltage output section OC1 and the second output voltage output section OC2 are on or off. On the other hand, the equivalent circuit shown in Figure 4 can also be interpreted as a wired OR being formed by the two output voltage output sections, the first output voltage output section OC1 and the second output voltage output section OC2, when the switch of the third output voltage output section OC3 is on. A wired OR is an OR logic created by connecting multiple output signals. For example, by connecting multiple open collector outputs, etc., whose output values ​​are low or high impedance (Hi-z), and connecting pull-up resistors, a negative logic OR is formed. This configured negative logic OR is an example of a wired OR. However, the wired OR shown in Figure 4 is different from a normal wired OR. In Figure 4, the circuit constituting the wired OR is enclosed by a dotted frame WOR. The circuit shown in Figure 4 is a circuit in which two open collector outputs with low or high impedance (Hi-z) output values ​​are connected and a pull-up resistor is connected. In the wired OR shown in Figure 4, when the switch of the first output voltage output section OC1 is on and the switch of the second output voltage output section OC2 is off, the voltage applied to the gate terminal of MOSFET 52X via the wiring LX is the first output voltage OV1. Also, in the wired OR shown in Figure 4, when the switch of the first output voltage output section OC1 is on and the switch of the second output voltage output section OC2 is on, the voltage applied to the gate terminal of MOSFET 52X via the wiring LX is the second output voltage OV2. Furthermore, in the wired OR shown in Figure 4, even when the switch for the first output voltage output section OC1 is off and the switch for the second output voltage output section OC2 is on, the voltage applied to the gate terminal of MOSFET 52X via the wiring LX is the second output voltage OV2.Furthermore, in the wired OR shown in Figure 4, when the switch of the first output voltage output section OC1 is off and the switch of the second output voltage output section OC2 is off, the voltage applied to the gate terminal of MOSFET 52X via the wiring LX is 0V. Therefore, the two output voltage output sections, the first output voltage output section OC1 and the second output voltage output section OC2, can be interpreted as a circuit that performs wired OR-like operation. For these reasons, the wired OR shown in Figure 4 may also be called an extended wired OR.

[0054] The drive signal output unit SOX, which includes a drive signal output switching unit OCX as shown by the equivalent circuit in Figure 4, can be realized, for example, by a circuit configuration as shown in Figure 5. Figure 5 is a diagram showing an example of a specific circuit configuration for realizing the drive signal output unit SOX, which includes a drive signal output switching unit OCX as shown by the equivalent circuit in Figure 4.

[0055] In the example shown in Figure 5, the first output voltage output section OC1 of the drive signal output section SOX includes a first comparator IC1, and outputs a first output voltage OV1 according to the signal output from the first comparator IC1. More specifically, in the first output voltage output section OC1, the first comparator IC1 compares the voltage value of the drive signal COMX input to the drive signal input terminal IX with a first threshold, and if the voltage value of the drive signal COMX input to the drive signal input terminal IX exceeds the first threshold, it outputs a signal indicating that the voltage value of the drive signal COMX has exceeded the first threshold as a first excess signal. Here, the output terminal of the first comparator IC1 is electrically connected to the wiring LX via a first current limiting element D1. The first current limiting element D1 is provided between the first output voltage output section OC1 and the wiring LX, and is an element that allows current to pass from the first output voltage output section OC1 to the wiring LX, but does not allow current to pass from the wiring LX to the first output voltage output section OC1, for example, a diode. In this example, the voltage value of the first excess signal is 11.2V, which is determined considering the voltage drop when the first voltage value is 10.2V as in this embodiment, so that the voltage applied to the anode of the first current limiting element D1 becomes 11.2V. The first current limiting element D1 is provided between the output terminal of the first comparator IC1 and the wiring LX so that it can continue to maintain the output of the first excess signal from the output terminal of the first comparator IC1, regardless of whether the second output voltage is output from the second output voltage output unit OC2 to the wiring LX, or whether the third output voltage is output from the third output voltage output unit OC3 to the wiring LX. For this reason, the first current limiting element D1 is an essential component for configuring a wired OR gate between the first output voltage output unit OC1 and the second output voltage output unit OC2. However, it is not necessary to configure a wired OR gate between the first output voltage output unit OC1 and the second output voltage output unit OC2 in the liquid dispensing device 1. Therefore, if the output of the first excess signal from the first comparator IC1 is to be stopped in either case—when the second output voltage is output from the second output voltage output unit OC2 to the wiring LX, or when the third output voltage is output from the third output voltage output unit OC3 to the wiring LX—then the drive signal output unit SOX may be configured without the first current limiting element D1.In this case, the method for stopping the output of the first excess signal from the first comparator IC1 may be a known method or a method to be developed in the future.

[0056] Furthermore, in the example shown in Figure 5, the second output voltage output section OC2 of the drive signal output section SOX includes a second comparator IC2, and outputs a second output voltage OV2 according to the signal output from the second comparator IC2. More specifically, in the second output voltage output section OC2, the second comparator IC2 compares the voltage value of the drive signal COMX input to the drive signal input terminal IX with a second threshold, and if the voltage value of the drive signal COMX input to the drive signal input terminal IX exceeds the second threshold, it outputs a signal indicating that the voltage value of the drive signal COMX has exceeded the second threshold as a second excess signal. Here, the output terminal of the second comparator IC2 is electrically connected to the wiring LX via a second current limiting element D2. The second current limiting element D2 is provided between the second output voltage output section OC2 and the wiring LX, and is an element that allows current from the second output voltage output section OC2 to flow toward the wiring LX, but does not allow current from the wiring LX to flow toward the second output voltage output section OC2, for example, a diode. In this example, the voltage value of the second excess signal is 22.5V, which is determined considering the voltage drop when the second voltage value is 21.5V as in this embodiment, so that the voltage applied to the anode of the second current limiting element D2 becomes 22.5V. The second current limiting element D2 is provided between the output terminal of the second comparator IC2 and the wiring LX so that even when the third output voltage is output from the third output voltage output unit OC3 to the wiring LX, the output of the second excess signal from the output terminal of the second comparator IC2 can be maintained. For this reason, the second current limiting element D2 is an essential component for configuring a wired OR gate between the first output voltage output unit OC1 and the second output voltage output unit OC2. However, as mentioned above, in the liquid dispensing device 1, it is not necessary to configure a wired OR gate between the first output voltage output unit OC1 and the second output voltage output unit OC2. Therefore, if the output of the second excess signal from the second comparator IC2 is stopped even when the third output voltage is output from the third output voltage output section OC3 to the wiring LX, the drive signal output section SOX may be configured without the second current limiting element D2. In this case, the method for stopping the output of the second excess signal from the second comparator IC2 may be a known method or a method to be developed in the future.

[0057] Furthermore, in the example shown in Figure 5, the third output voltage output section OC3 of the drive signal output section SOX is electrically connected to the wiring LX and includes a third comparator IC3, which outputs a third output voltage OV3 in accordance with the signal output from the third comparator IC3. More specifically, in the third output voltage output section OC3 of this example, the control signal input terminal IE is connected to the non-inverting input terminal of the third comparator IC3. When a control signal to stop the output of the drive signal COMX from the drive signal output section SOX to the print head 20 is input from the host computer via the control signal input terminal IE, that is, when predetermined conditions are met, the third comparator IC3 outputs a signal as a third excess signal indicating that a voltage exceeding the reference voltage of the third comparator IC3 has been input to the third comparator IC3. Here, in this example, the reference voltage is about 2V, but it is not limited to this. When the third excess signal is output from the third comparator IC3, the third output voltage output section OC3 outputs the third output voltage to the wiring LX. Here, the third output voltage output section OC3 is electrically connected to the wiring LX via the third current limiting element D3. The third current limiting element D3 is provided between the third output voltage output section OC3 and the wiring LX, and is an element that allows current to pass from the third output voltage output section OC3 to the wiring LX, but does not allow current to pass from the wiring LX to the third output voltage output section OC3; for example, it is a diode.

[0058] With the above configuration, the drive signal output circuit 50X, which includes the drive signal output unit SOX shown in Figure 5, switches the gate voltage value of MOSFET 52X in accordance with the voltage value of the drive signal COMX, so that the source-gate voltage of MOSFET 52X does not exceed the dynamic range of the source-gate voltage of MOSFET 52X. As a result, the liquid dispensing device 1 can, for example, lower the on-resistance of MOSFET 52X and suppress an increase in the power consumption of the drive circuit 50. The drive signal output circuit 50X may also be configured to include one or more output voltage output units, such as the first output voltage output unit OC1 and the second output voltage output unit OC2, along with the first output voltage output unit OC1, the second output voltage output unit OC2, and the third output voltage output unit OC3. In this case, when the third output voltage is not output from the third output voltage output unit OC3, the liquid dispensing device 1 can switch the gate voltage of MOSFET 52X in four or more stages instead of switching it in three stages as described above. Furthermore, the drive signal output circuit 50X may be configured to include only one of the first output voltage output section OC1 and the second output voltage output section OC2, along with the third output voltage output section OC3. Even in this case, the liquid dispensing device 1 can switch the gate voltage of the MOSFET 52X in two stages when the third output voltage is not output from the third output voltage output section OC3.

[0059] As described above, the liquid ejection device 1 comprises a print head 20 and a drive circuit 50. The drive circuit 50 is located outside the print head 20 and comprises N drive signal output circuits. One of the N drive signals is associated with each drive signal output circuit 50X. The drive signal output circuit 50X comprises a MOSFET 52X and a first comparator IC 1. The first comparator IC 1 switches the gate voltage value of the MOSFET 52X according to the voltage value of the drive signal COMX, so that the source-gate voltage of the MOSFET 52X does not exceed the dynamic range of the source-gate voltage of the MOSFET 52X. In other words, the liquid ejection device 1 comprises a print head 20 and a drive circuit 50. The drive circuit 50 is located outside the print head 20 and includes N drive signal output circuits. One of the N drive signals is associated with each drive signal output circuit 50X. The drive signal output circuit 50X includes a MOSFET 52X. The drive signal output circuit 50X outputs one of several different voltage values ​​as the gate voltage of the MOSFET 52X using a wired OR, so that the dynamic range of the source-gate voltage of the MOSFET 52X is not exceeded by the voltage value of the drive signal COMX. As a result, the liquid ejection device 1 can be miniaturized while performing higher-resolution printing.

[0060] In the liquid ejection device 1 described above, each of the N drive signal output circuits is electrically connected to the print head 20 via the first drive signal output terminal 51. Therefore, in the liquid ejection device 1, the interface electrically connecting the drive circuit 50 and the head unit 2 is a single cable 190. This remains unchanged even if the number of drive signal output circuits in the drive circuit 50 exceeds N. In other words, the liquid ejection device 1 can increase the types of drive signals that can be output to the print head 20 while suppressing an increase in the size of the print head 20. In this sense as well, the liquid ejection device 1 can achieve higher resolution printing while being miniaturized.

[0061] Furthermore, the matters described above may be combined in any way.

[0062] <Note> [1] A liquid dispensing device comprising: a print head for printing an image onto a printing medium; a drive circuit provided outside the print head for outputting at least one of a plurality of drive signals to the print head, wherein the drive circuit comprises a plurality of drive signal output circuits, each of the plurality of drive signal output circuits associated with one of the plurality of drive signals, each of the plurality of drive signal output circuits uses the associated drive signal as the target drive signal and switches whether or not to output the target drive signal to the print head; and a first comparator, wherein the upper limit of the dynamic range of each of the plurality of drive signals exceeds the dynamic range of the source-gate voltage of the MOSFET, and the first comparator switches the voltage value of the gate voltage of the MOSFET according to the voltage value of the target drive signal so that the source-gate voltage of the MOSFET does not exceed the dynamic range of the source-gate voltage of the MOSFET. [2] Each of the plurality of drive signal output circuits comprises a drive signal output unit, the drive signal output unit comprising a drive signal input terminal into which the target drive signal is input, a drive signal output terminal electrically connected to the print head and outputting the target drive signal to the print head, a first output voltage output unit including a first comparator and outputting a first output voltage of a first voltage value according to the signal output from the first comparator, and wiring electrically connected to the first output voltage output unit and from which the first output voltage is output, the MOSFET comprising a drain terminal electrically connected to the drive signal input terminal, a source terminal electrically connected to the drive signal output terminal, and the wiring and electrical The liquid dispensing device according to [1], having a gate terminal that is directly connected, wherein the first comparator compares the voltage value of the target drive signal input to the drive signal input terminal with a first threshold, and outputs a signal indicating that the voltage value of the target drive signal input to the drive signal input terminal exceeds the first threshold as a first excess signal, the first threshold is a voltage value less than or equal to the upper limit of the dynamic range of the source-gate voltage of the MOSFET, the first voltage value is a voltage value less than or equal to the first threshold, and the first output voltage output unit outputs the first output voltage to the wiring when the first excess signal is output from the first comparator. [3] The drive signal output unit includes a second comparator, which is electrically connected to the wiring, and a second output voltage output unit that outputs a second output voltage of a second voltage value to the wiring in accordance with the signal output from the second comparator; a first current limiting element provided between the first output voltage output unit and the wiring, which allows current to pass from the first output voltage output unit to the wiring but prevents current from passing from the wiring to the first output voltage output unit; and a second current limiting element provided between the second output voltage output unit and the wiring, which allows current to pass from the second output voltage output unit to the wiring but prevents current from passing from the wiring to the second output voltage output unit. The second comparator is input to the drive signal input terminal. The liquid dispensing device according to [2], wherein the voltage value of the target drive signal is compared with a second threshold, and if the voltage value of the target drive signal input to the drive signal input terminal exceeds the second threshold, a signal indicating that the voltage value of the target drive signal exceeds the second threshold is output as a second excess signal, and the second output voltage output unit outputs the second output voltage to the wiring when the second excess signal is output from the second comparator, the second threshold is a voltage value less than or equal to the voltage value obtained by adding the first threshold to the upper limit of the dynamic range of the source-gate voltage of the MOSFET, the second voltage value is a voltage value less than or equal to the second threshold, and the third threshold is a voltage value less than or equal to the upper limit of the voltage value of the target drive signal. [4] The drive signal output unit further comprises a third output voltage output unit which includes a third comparator and is electrically connected to the wiring, and outputs a third output voltage of a third voltage value in accordance with the signal output from the third comparator, and a third current limiting element provided between the third output voltage output unit and the wiring, which allows current to pass from the third output voltage output unit toward the wiring but prevents current from passing from the wiring toward the third output voltage output unit, wherein the third threshold is the upper limit of the voltage value of the target drive signal, and the third comparator, when predetermined conditions are met, the reference voltage of the third comparator The liquid dispensing device according to [3], wherein a voltage exceeding a certain value is input, and a signal indicating that a voltage exceeding the reference voltage of the third comparator has been input to the third comparator is output as a third excess signal, and the third output voltage output unit outputs the third output voltage to the wiring when the third excess signal is output from the third comparator, the third voltage value is the upper limit of the voltage value of the target drive signal and is a voltage value higher than the second voltage value, and the MOSFET electrically insulates the drain terminal and the source terminal when the third output voltage is input to the gate terminal. [5] The liquid ejection device according to any one of [2] to [4], wherein the print head comprises one or more drive elements, an integrated wiring electrically connected to the source terminal of the MOSFET provided in each of the plurality of drive signal output circuits, and a plurality of selection circuits, each of the plurality of selection circuits being electrically connected to the integrated wiring and selecting whether or not to output the target drive signal output from at least one of the plurality of drive signal output circuits to the one or more drive elements. [6] The liquid dispensing device according to [5], wherein each of the one or more drive elements is a piezoelectric element. [7] The liquid dispensing device according to any one of [2] to [6], wherein each of the plurality of drive signal output circuits comprises a drive signal generation unit that generates the target drive signal, the drive signal generation unit has a Class D amplifier circuit that generates the target drive signal by Class D amplification, and outputs the generated target drive signal to the drive signal output unit. [8] The MOSFET is made of silicon, and the liquid dispensing device is as described in any one of [1] to [7]. [9] A liquid dispensing device according to any one of [1] to [8], wherein some or all of the aforementioned multiple drive signals have different waveforms from each other.

[10] A liquid dispensing device comprising: a print head for printing an image onto a printing medium; a drive circuit provided outside the print head for outputting at least one of a plurality of drive signals to the print head, wherein the drive circuit comprises a plurality of drive signal output circuits, each of the plurality of drive signal output circuits associated with one of the plurality of drive signals, each of the plurality of drive signal output circuits comprises a P-channel type MOSFET (Metal Oxide Semiconductor Field Effect Transistor) that switches whether or not to output the associated drive signal to the print head, with the assigned drive signal being the target drive signal, the upper limit of the dynamic range of each of the plurality of drive signals exceeds the dynamic range of the source-gate voltage of the MOSFET, and each of the plurality of drive signal output circuits outputs a voltage as the gate voltage of the MOSFET by a wired OR, such that the dynamic range of the source-gate voltage of the MOSFET does not exceed the dynamic range of the source-gate voltage of the MOSFET, according to the voltage value of the target drive signal.

[0063] Although embodiments of this disclosure have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments and may be modified, replaced, deleted, etc., as long as it does not deviate from the gist of this disclosure. [Explanation of Symbols]

[0064] 1…Liquid dispensing device, 2…Head unit, 3…Moving mechanism, 4…Conveying mechanism, 10…Control unit, 20…Print head, 22…Ink cartridge, 24…Carriage, 31…Carriage motor, 32…Carriage guide shaft, 33…Timing belt, 35…Carriage motor driver, 41…Conveyor motor, 42…Conveyor roller, 43…Platen, 45…Conveyor motor driver, 50…Drive circuit, 50A~50N, 50X…Drive signal output circuit, 51…First drive signal output terminal, 52X…MOSFET, 60…Piezoelectric element, 70…Capping member, 71…Wiper member, 72…Flushing box, 80…Maintenance unit, 81…Cleaning mechanism, 82…Wiping pin 90…Linear encoder, 100…Control circuit, 110…Voltage output circuit, 190…Cable, 210…Selection control circuit, 230…Selection circuit, 600…Discharge unit, D1…First current limiting element, D2…Second current limiting element, D3…Third current limiting element, IC1…First comparator, IC2…Second comparator, IC3…Third comparator, IE…Control signal input terminal, IX…Drive signal input terminal, LX…Wiring, OC1…First output voltage output unit, OC2…Second output voltage output unit, OC3…Third output voltage output unit, OCX…Drive signal output switching unit, OX…Second drive signal output terminal, P…Printing medium, SG, SGA, SGC, SGX…Drive signal generation unit, SO, SOB, SOD, SOX…Drive signal output unit

Claims

1. A print head that prints images onto a print medium, A drive circuit provided outside the print head, which outputs at least one of a plurality of drive signals to the print head, Equipped with, The aforementioned drive circuit includes a plurality of drive signal output circuits, Each of the aforementioned plurality of drive signal output circuits is associated with one of the aforementioned plurality of drive signals. Each of the aforementioned plurality of drive signal output circuits is A P-channel type MOSFET (Metal Oxide Semiconductor Field Effect Transistor) is used to select a target drive signal from among the multiple drive signals mentioned above, and to switch whether or not to output the target drive signal to the print head. The first comparator, Equipped with, The upper limit of the dynamic range of each of the aforementioned multiple drive signals exceeds the dynamic range of the source-gate voltage of the MOSFET. The first comparator switches the gate voltage value of the MOSFET so that the source-gate voltage of the MOSFET does not exceed the dynamic range of the source-gate voltage of the MOSFET, according to the voltage value of the target drive signal. Liquid discharge device.

2. Each of the aforementioned plurality of drive signal output circuits includes a drive signal output section, The aforementioned drive signal output unit is A drive signal input terminal to which the target drive signal is input, A drive signal output terminal that is electrically connected to the print head and outputs the target drive signal to the print head, A first output voltage output unit that includes the first comparator and outputs a first output voltage of a first voltage value in accordance with the signal output from the first comparator, A wiring that is electrically connected to the first output voltage output unit and from which the first output voltage is output from the first output voltage output unit, Equipped with, The MOSFET has a drain terminal electrically connected to the drive signal input terminal, a source terminal electrically connected to the drive signal output terminal, and a gate terminal electrically connected to the wiring. The first comparator compares the voltage value of the target drive signal input to the drive signal input terminal with a first threshold, and if the voltage value of the target drive signal input to the drive signal input terminal exceeds the first threshold, it outputs a signal indicating that the voltage value of the target drive signal exceeds the first threshold as a first excess signal. The first threshold is a voltage value that is less than or equal to the upper limit of the dynamic range of the source-gate voltage of the MOSFET. The first voltage value is a voltage value less than or equal to the first threshold value. The first output voltage output unit outputs the first output voltage to the wiring when the first excess signal is output from the first comparator. The liquid dispensing device according to claim 1.

3. The aforementioned drive signal output unit is A second output voltage output unit includes a second comparator, is electrically connected to the wiring, and outputs a second output voltage of a second voltage value to the wiring in accordance with the signal output from the second comparator, A first current limiting element is provided between the first output voltage output unit and the wiring, which allows current to pass from the first output voltage output unit to the wiring but prevents current from passing from the wiring to the first output voltage output unit. A second current limiting element is provided between the second output voltage output unit and the wiring, which allows current to pass from the second output voltage output unit to the wiring but prevents current from passing from the wiring to the second output voltage output unit. Equipped with, The second comparator compares the voltage value of the target drive signal input to the drive signal input terminal with a second threshold, and if the voltage value of the target drive signal input to the drive signal input terminal exceeds the second threshold, it outputs a signal indicating that the voltage value of the target drive signal exceeds the second threshold as a second excess signal. The second output voltage output unit outputs the second output voltage to the wiring when the second excess signal is output from the second comparator. The second threshold is a voltage value less than or equal to the voltage value obtained by adding the first threshold to the upper limit of the dynamic range of the source-gate voltage of the MOSFET. The second voltage value is a voltage value less than or equal to the second threshold value. The third threshold is a voltage value that is less than or equal to the upper limit of the voltage value of the target drive signal. The liquid dispensing device according to claim 2.

4. The aforementioned drive signal output unit is A third output voltage output unit is provided, which includes a third comparator, is electrically connected to the wiring, and outputs a third output voltage of a third voltage value in accordance with the signal output from the third comparator. A third current limiting element is provided between the third output voltage output unit and the wiring, which allows current to pass from the third output voltage output unit to the wiring but prevents current from passing from the wiring to the third output voltage output unit. Furthermore, The third threshold is the upper limit of the voltage value of the target drive signal, When a predetermined condition is met, the third comparator receives a voltage exceeding its reference voltage and outputs a signal as a third excess signal indicating that a voltage exceeding its reference voltage has been input to the third comparator. The third output voltage output unit outputs the third output voltage to the wiring when the third comparator outputs the third excess signal. The third voltage value is the upper limit of the voltage value of the target drive signal and is a voltage value higher than the second voltage value. The MOSFET electrically isolates the drain terminal and the source terminal when the third output voltage is input to the gate terminal. The liquid dispensing device according to claim 3.

5. The aforementioned print head is One or more drive elements, Each of the plurality of drive signal output circuits has an integrated wiring that is electrically connected to the source terminal of the MOSFET, Multiple selection circuits, Equipped with, Each of the plurality of selection circuits is electrically connected to the integrated wiring and selects whether or not to output the target drive signal output from at least one of the plurality of drive signal output circuits to one or more drive elements. The liquid dispensing device according to claim 2.

6. Each of the one or more driving elements is a piezoelectric element. The liquid dispensing device according to claim 5.

7. Each of the plurality of drive signal output circuits includes a drive signal generation unit that generates the target drive signal, The drive signal generation unit has a Class D amplification circuit and generates the target drive signal by performing Class D amplification, and outputs the generated target drive signal to the drive signal output unit. The liquid dispensing device according to claim 2.

8. The above-mentioned MOSFET is made of silicon. The liquid dispensing device according to claim 1.

9. Some or all of the aforementioned multiple drive signals have waveforms that are different from each other. The liquid dispensing device according to claim 1.

10. A print head that prints images onto a print medium, A drive circuit provided outside the print head, which outputs at least one of a plurality of drive signals to the print head, Equipped with, The aforementioned drive circuit includes a plurality of drive signal output circuits, Each of the aforementioned plurality of drive signal output circuits is associated with one of the aforementioned plurality of drive signals. Each of the aforementioned plurality of drive signal output circuits includes a P-channel type MOSFET (Metal Oxide Semiconductor Field Effect Transistor) that selects the corresponding drive signal from the plurality of drive signals as the target drive signal and switches whether or not to output the target drive signal to the print head. The upper limit of the dynamic range of each of the aforementioned multiple drive signals exceeds the dynamic range of the source-gate voltage of the MOSFET. Each of the aforementioned multiple drive signal output circuits outputs one of several different voltage values ​​as the gate voltage of the MOSFET using a wired OR, so as to ensure that the source-gate voltage of the MOSFET does not exceed the dynamic range of the source-gate voltage of the MOSFET, according to the voltage value of the target drive signal. Liquid discharge device.

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