Head unit and liquid discharge apparatus

There is provided a head unit including: a discharge section that includes a piezoelectric element driven by a first driving signal and discharges a liquid; a switching circuit that switches whether or not to supply the first driving signal; a first substrate that propagates the first driving signal and the discharge control signal to the switching circuit; a second substrate to which the first driving signal and the discharge control signal are supplied and which propagates the first driving signal and the discharge control signal to the first substrate; a first coupling member including a first conductive section that electrically couples the first substrate and the second substrate; and a second coupling member including a second conductive section that electrically couples the first substrate and the second substrate, in which a cross-sectional area of the first conductive section is larger than a cross-sectional area of the second conductive section.

The present application is based on, and claims priority from JP Application Serial Number 2021-077540, filed Apr. 30, 2021, the disclosure of which is hereby incorporated by reference herein in its entirety.

BACKGROUND

1. Technical Field

The present disclosure relates to a head unit and a liquid discharge apparatus.

2. Related Art

A liquid discharge apparatus that discharges a liquid to a medium has a driving element such as a piezoelectric element that drives based on a driving signal, controls the supply of the driving signal to the driving element to control the drive of the driving element, and controls the amount of liquid discharged in response to the drive of the driving element to form a desired dot on the medium.

For example, JP-A-2016-179586 discloses a liquid discharge apparatus that propagates a driving signal having a plurality of serial trapezoidal waveforms to a liquid discharge unit via a flexible flat cable (FFC), controls a driving amount of the piezoelectric element, which is a driving element, by switching whether or not to supply the trapezoidal waveform included in the driving signal to the piezoelectric element, and controls the amount of ink discharged from the nozzle.

In recent years, in liquid discharge apparatuses, there is an increasing demand for a high image formation speed on a medium, and therefore, a fast dot formation cycle for forming dots having a desired size on a medium by discharging a liquid is required. However, in order to increase the speed of the dot formation cycle, it is necessary to increase the driving amount of the driving element per unit time, and therefore, the amount of current generated by the driving signal for driving the driving element increases. The increase in the amount of current generated by such a driving signal causes the increase in size of the wiring, cable, and connector through which the driving signal propagates, and therefore, there is a concern that the size of the head unit that discharges the medium becomes large. JP-A-2016-179586 does not describe the problem at all that there is a concern about the increase in the amount of current generated by the driving signal due to such an increase in the image formation speed, and an increase in the size of the head unit due to the increase in the amount of current. From this point of view, the liquid discharge apparatus described in JP-A-2016-179586 has room for improvement.

SUMMARY

According to an aspect of the present disclosure, there is provided a head unit including: a discharge section that includes a piezoelectric element driven by a first driving signal and discharges a liquid in response to drive of the piezoelectric element; a switching circuit that switches whether or not to supply the first driving signal to the piezoelectric element based on a discharge control signal; a first substrate that propagates the first driving signal and the discharge control signal to the switching circuit; a second substrate to which the first driving signal and the discharge control signal are supplied and which propagates the first driving signal and the discharge control signal to the first substrate; a first coupling member including a first conductive section that electrically couples the first substrate and the second substrate to each other; and a second coupling member including a second conductive section that electrically couples the first substrate and the second substrate to each other, in which a cross-sectional area of the first conductive section is larger than a cross-sectional area of the second conductive section.

According to another aspect of the present disclosure, there is provided a liquid discharge apparatus including: a driving circuit unit having a first driving signal output circuit that outputs a first driving signal; a discharge control unit that outputs a discharge control signal; and a head unit that discharges a liquid based on the first driving signal and the discharge control signal, in which the head unit includes a discharge section that includes a piezoelectric element driven by the first driving signal and discharges the liquid in response to drive of the piezoelectric element, a switching circuit that switches whether or not to supply the first driving signal to the piezoelectric element based on the discharge control signal, a first substrate that propagates the first driving signal and the discharge control signal to the switching circuit, a second substrate to which the first driving signal and the discharge control signal are supplied and which propagates the first driving signal and the discharge control signal to the first substrate, a first coupling member including a first conductive section that electrically couples the first substrate and the second substrate to each other, and a second coupling member including a second conductive section that electrically couples the first substrate and the second substrate to each other, and a cross-sectional area of the first conductive section is larger than a cross-sectional area of the second conductive section.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, appropriate embodiments of the present disclosure will be described with reference to the drawings. The drawing to be used is for convenience of description. In addition, the embodiments which will be described below do not inappropriately limit the contents of the present disclosure described in the claims. Moreover, not all of the configurations which will be described below are necessarily essential components of the present disclosure.

1. Configuration of Liquid Discharge Apparatus

FIG.1is a view illustrating a schematic configuration of a liquid discharge apparatus1. As illustrated inFIG.1, the liquid discharge apparatus1in the present embodiment is a line type ink jet printer that forms a desired image on a medium P by discharging ink, which is an example of a liquid, to the medium P transported by a medium transport unit40, at a desired timing. Here, in the following description, the width direction of the medium P to be transported may be referred to as a main scanning direction, and the direction in which the medium P is transported may be referred to as a transport direction.

As illustrated inFIG.1, the liquid discharge apparatus1includes a liquid container2, a control unit10, a liquid discharge unit20, and a medium transport unit40.

The ink supplied to the liquid discharge unit20is stored in the liquid container2. Specifically, the liquid container2stores inks of a plurality of colors, such as black, cyan, magenta, yellow, red, and gray, which are discharged to the medium P. As the liquid container2, an ink cartridge, a bag-shaped ink pack made of a flexible film, an ink tank capable of replenishing ink, and the like can be used.

The control unit10includes a processing circuit such as a central processing unit (CPU) or a field programmable gate array (FPGA), and a storage circuit such as a semiconductor memory. In addition, the control unit10outputs a control signal for controlling each element of the liquid discharge apparatus1.

The liquid discharge unit20has a plurality of head modules21. In the liquid discharge unit20, the plurality of head modules21are arranged side by side along the main scanning direction so as to be equal to or larger than the width of the medium P. In other words, the liquid discharge apparatus1includes the plurality of head modules21, and the plurality of head modules21are arranged side by side along the main scanning direction intersecting the transport direction in which the medium P to which ink, which is as an example of the liquid, is discharged is transported.

A data signal DATA for controlling the operation of the plurality of head modules21and a driving signal COM for driving the head module21such that the ink is discharged from each of the plurality of head modules21are input from the control unit10to each of the plurality of head modules21included in the liquid discharge unit20. Further, the ink stored in the liquid container2is supplied to each of the plurality of head modules21via a tube (not illustrated) or the like. Then, each of the plurality of head modules21discharges the ink supplied from the liquid container2based on the input data signal DATA and the driving signal COM.

The medium transport unit40includes a transport motor41and a transport roller42. The transport motor41operates based on a transport control signal Ctrl-T input from the control unit10. The transport roller42is rotationally driven by the operation of the transport motor41. Then, the medium P is transported along the transport direction by the rotational drive of the transport roller42.

In the liquid discharge apparatus1configured as described above, the control unit10interlocks with the transport of the medium P by the medium transport unit40, and discharges ink from the plurality of head modules21included in the liquid discharge unit20. Accordingly, the liquid discharge apparatus1makes the ink land at a desired position on the medium P, and forms a desired image on the medium P.

Here, a specific example of control of the liquid discharge unit20by the control unit10will be described.FIG.2is a view illustrating a functional configuration of the liquid discharge apparatus1. InFIG.2, only the electrical coupling between the control unit10and the liquid discharge unit20is illustrated, and the medium transport unit40and the liquid container2are not illustrated.

As illustrated inFIG.2, the liquid discharge apparatus1includes the control unit10and the liquid discharge unit20. The control unit10includes a control circuit100, a driving circuit unit50, and a converter circuit120. Further, the driving circuit unit50includes driving circuits51-1to51-m. The liquid discharge unit20includes the plurality of head modules21. The control unit10and each of the plurality of head modules21included in the liquid discharge unit20are electrically coupled to each other by a cable (not illustrated).

Here, the plurality of head modules21all have the same configuration. Therefore,FIG.2illustrates only the circuit configuration included in one head module21, and the circuit configurations included in other head modules21is not illustrated. Further, in the following description, only the operation and functional configuration of one head module21will be described, and the description of the operations and functional configurations of other head modules21will be omitted or simplified.

The control circuit100includes an integrated circuit such as a CPU and an FPGA. A signal such as image data formed on the medium P is input to the control circuit100from an external device such as a host computer (not illustrated). The control circuit100outputs a control signal for controlling each element of the liquid discharge apparatus1based on the signal such as the input image data.

The control circuit100generates a reference data signal dDATA which is a reference of a data signal DATA to be output to the liquid discharge unit20based on the signal such as the input image data, and outputs the generated signal to the converter circuit120. The converter circuit120converts the reference data signal dDATA into the data signal DATA of a differential signal such as a low voltage differential signaling (LVDS), and outputs the converted data to the head module21included in the liquid discharge unit20. The converter circuit120may generate the data signal DATA obtained by converting the reference data signal dDATA into various high-speed transfer type differential signals such as a low voltage positive emitter coupled logic (LVPECL) and a current mode logic (CML) other than LVDS, and output the generated signal to the head module21. In addition, the converter circuit120may convert a part or the entirety of the input reference data signal dDATA into the single-ended data signal DATA, and output the converted signal to the head module21.

Further, the control circuit100outputs reference driving signals dA1, dB1, and dC1to the driving circuit51-1included in the driving circuit unit50. The driving circuit51-1includes driving signal output circuits52a,52b, and52chaving the same circuit configuration.

The reference driving signal dA1is input to the driving signal output circuit52aincluded in the driving circuit51-1. The driving signal output circuit52agenerates a driving signal COMA1by digital-to-analog converting the input reference driving signal dA1and then applying class D amplification to the analog signal, and outputs the generated driving signal COMA1to the head module21. The reference driving signal dB1is input to the driving signal output circuit52bincluded in the driving circuit51-1. The driving signal output circuit52bgenerates a driving signal COMB1by digital-to-analog converting the input reference driving signal dB1and then applying class D amplification to the analog signal, and outputs the generated driving signal COMB1to the head module21. The reference driving signal dC1is input to the driving signal output circuit52cincluded in the driving circuit51-1. The driving signal output circuit52cgenerates a driving signal COMC1by digital-to-analog converting the input reference driving signal dC1and then applying class D amplification to the analog signal, and outputs the generated driving signal COMC1to the head module21.

Here, each of the driving signal output circuits52a,52b, and52cmay be configured to include a class A amplifier circuit, a class B amplifier circuit, a class AB amplifier circuit or the like instead of the class D amplifier circuit or in addition to the class D amplifier circuit as long as the driving signals COMA1, COMB1, and COMC1can be generated by amplifying the waveforms regulated by each of the reference driving signals dA1, dB1, and dC1, which are the input digital signals. Further, each of the reference driving signals dA1, dB1and dC1may be a signal that can regulate the waveforms of the corresponding driving signals COMA1, COMB1and COMC1, or may be an analog signal.

Further, the driving circuit51-1has a reference voltage output circuit53. The reference voltage output circuit53generates a constant potential reference voltage signal VBS1indicating a reference potential of the piezoelectric element60(which will be described later) included in the head module21by boosting or stepping down the power supply voltage (not illustrated) used in the liquid discharge apparatus1, and outputs the generated signal to the head module21. The reference voltage signal VBS1output by the reference voltage output circuit53may be a constant signal at a ground potential, or may be a constant signal at a potential such as 5.5 V or 6 V. In addition, a case where the potential is constant includes a case where the potential is substantially constant when errors such as potential fluctuations caused by the operation of peripheral circuits, potential fluctuations caused by variations in circuit elements, and potential fluctuations caused by temperature characteristics are taken into consideration.

Here, the driving circuits51-1to51-mincluded in the driving circuit unit50differ only in the input signal and the output signal, and both have the same configuration. Specifically, the driving circuit51-mincludes a circuit corresponding to the driving signal output circuits52a,52b, and52cand a circuit corresponding to the reference voltage output circuit53, generates driving signals COMAm, COMBm, and COMCm and a reference voltage signal VBSm based on the reference driving signals dAm, dBm, and dCm, which are input from the control circuit100, and outputs the generated signals to the head module21. Similarly, the driving circuit51-j(j is any number of 1 to m) includes a circuit corresponding to the driving signal output circuits52a,52b, and52cand a circuit corresponding to the reference voltage output circuit53, generates driving signals COMAj, COMBj, and COMCj and a reference voltage signal VBSj based on the reference driving signals dAj, dBj, and dCj, which are input from the control circuit100, and outputs the generated signals to the head module21.

The plurality of head modules21included in the liquid discharge unit20each includes a restoration circuit220and discharge modules23-1to23-m.

The restoration circuit220restores the data signal DATA of the differential signal output by the control unit10to a single-ended signal, separates the restored signal into signals corresponding to each of the discharge modules23-1to23-m, and outputs the separated signals to the corresponding discharge modules23-1to23-m.

Specifically, the restoration circuit220restores and separates the data signal DATA of the differential signal output by the control unit10to generate a clock signal SCK1, a print data signal SI1, and a latch signal LAT1corresponding to the discharge module23-1. Then, the restoration circuit220outputs the generated clock signal SCK1, the print data signal SI1, and the latch signal LAT1to the discharge module23-1. Further, the restoration circuit220restores and separates the data signal DATA of the differential signal output by the control unit10to generate a clock signal SCKm, a print data signal SIm, and a latch signal LATm corresponding to the discharge module23-m, and output the generated signals to the discharge module23-m. Further, the restoration circuit220restores and separates the data signal DATA of the differential signal output by the control unit10to generate a clock signal SCKj, a print data signal SIj, and a latch signal LATj corresponding to the discharge module23-j, and output the generated signals to the discharge module23-j. The clock signal SCK1corresponding to the discharge module23-1output by the restoration circuit220, the clock signal SCKj corresponding to the discharge module23-j, and the clock signal SCKm corresponding to the discharge module23-mmay be common signals.

As described above, the restoration circuit220restores the data signal DATA of the differential signal output by the control unit10and separates the restored signal into signals corresponding to the discharge modules23-1to23-m. Accordingly, the restoration circuit220generates the clock signals SCK1to SCKm, the print data signals SI1to SIm, and the latch signals LAT1to LATm corresponding to each of the discharge modules23-1to23-mincluded in the head module21, and outputs the generated signals to the corresponding discharge modules23-1to23-m.

Here, in view of the fact that the restoration circuit220restores and separates the data signal DATA of the differential signal to generate the clock signals SCK1to SCKm, the print data signals SI1to SIm, and the latch signals LAT1to LATm, the reference data signal dDATA, which is the reference of the data signal DATA output by the control circuit100includes signals corresponding to each of the clock signals SCK1to SCKm, the print data signals SI1to SIm, and the latch signals LAT1to LATm, and the data signal DATA output by the converter circuit120includes differential signals corresponding to the clock signals SCK1to SCKm, differential signals corresponding to the print data signals SI1to SIm, and differential signals corresponding to the latch signals LAT1to LATm.

The converter circuit120may output the differential signals corresponding to the clock signals SCK1to SCKm, the differential signals corresponding to the print data signals SI1to SIm, and the differential signals corresponding to the latch signals LAT1to LATm, as differential signals which are different from each other. Further, without converting any of the clock signals SCK1to SCKm, the print data signals SI1to SIm, and the latch signals LAT1to LATm, which are included in the reference data signal dDATA, into a differential signal, the converter circuit120may output the signals as single-ended signals.

The discharge module23-1includes a driving signal selection control circuit200and a plurality of discharge sections600. Further, each of the plurality of discharge sections600includes a piezoelectric element60. The driving signals COMA1, COMB1, and COMC1, the reference voltage signal VBS1, the clock signal SCK1, the print data signal SI1, and the latch signal LAT1are input to the discharge module23-1.

Among the signals input to the discharge module23-1, the driving signals COMA1, COMB1, and COMC1, the clock signal SCK1, the print data signal SI1, and the latch signal LAT1are input to the driving signal selection control circuit200included in the discharge module23-1. The driving signal selection control circuit200selects or deselects each of the driving signals COMA1, COMB1, and COMC1based on the input clock signal SCK1, the print data signal SI1, and the latch signal LAT1to generate the driving signal VOUT, and supply the generated driving signal VOUT to one end of the piezoelectric element60included in the corresponding discharge section600. At this time, the reference voltage signal VBS1is supplied to the other end of the piezoelectric element60. Then, the piezoelectric element60included in the plurality of discharge sections600is driven by the potential difference between the driving signal VOUT supplied to one end and the reference voltage signal VBS1supplied to the other end.

Similarly, the discharge module23-mincludes the driving signal selection control circuit200and the plurality of discharge sections600. Further, each of the plurality of discharge sections600includes a piezoelectric element60. The driving signals COMAm, COMBm, and COMCm, the reference voltage signal VBSm, the clock signal SCKm, the print data signal SIm, and the latch signal LATm are input to the discharge module23-m. Among these, the driving signals COMAm, COMBm, and COMCm, the clock signal SCKm, the print data signal SIm, and the latch signal LATm are input to the driving signal selection control circuit200included in the discharge module23-m. The driving signal selection control circuit200selects or deselects each of the driving signals COMAm, COMBm, and COMCm based on the input clock signal SCKm, the print data signal SIm, and the latch signal LATm to generate the driving signal VOUT, and supply the generated driving signal VOUT to one end of the piezoelectric element60included in the corresponding discharge section600. Further, the reference voltage signal VBSm is commonly supplied to the other end of the piezoelectric element60included in the plurality of discharge sections600. As a result, the piezoelectric element60included in the plurality of discharge sections600is driven by the potential difference between the driving signal VOUT supplied to one end and the reference voltage signal VBSm supplied to the other end.

Similarly, the discharge module23-jincludes the driving signal selection control circuit200and the plurality of discharge sections600. Further, each of the plurality of discharge sections600includes a piezoelectric element60. The driving signals COMAj, COMBj, and COMCj, the reference voltage signal VBSj, the clock signal SCKj, the print data signal SIj, and the latch signal LATj are input to the discharge module23-j. Among these, the driving signals COMAj, COMBj, and COMCj, the clock signal SCKj, the print data signal SIj, and the latch signal LATj are input to the driving signal selection control circuit200included in the discharge module23-j. The driving signal selection control circuit200selects or deselects each of the driving signals COMAj, COMBj, and COMCj based on the input clock signal SCKj, the print data signal SIj, and the latch signal LATj to generate the driving signal VOUT, and supply the generated driving signal VOUT to one end of the piezoelectric element60included in the corresponding discharge section600. Further, the reference voltage signal VBSj is commonly supplied to the other end of the piezoelectric element60included in the plurality of discharge sections600. As a result, the piezoelectric element60included in the plurality of discharge sections600is driven by the potential difference between the driving signal VOUT supplied to one end and the reference voltage signal VBSj supplied to the other end.

Then, the discharge modules23-1to23-mare driven by the piezoelectric element60to discharge an amount of ink corresponding to the drive of the piezoelectric element60.

In the liquid discharge apparatus1configured as described above, the driving circuit unit50including the driving signal output circuit52athat outputs the driving signals COMA1to COMAm, the driving signal output circuit52bthat outputs the driving signals COMB1to COMBm, and the driving signal output circuit52cthat outputs the driving signals COMC1to COMCm is an example of a driving circuit unit, the control circuit100that outputs the reference data signal dDATA which is a reference of the clock signals SCK1to SCKm, the print data signals SI1to SIm, and the latch signals LAT1to LATm is an example of a discharge control unit, and the head module21that discharges the ink based on the driving signals COMA1to COMAm, COMB1to COMBm, and COMC1to COMCm, the clock signals SCK1to SCKm based on the reference data signal dDATA, the print data signals SI1to SIm, and the latch signals LAT1to LATm is an example of a head unit.

2. Functional Configuration of Driving Signal Selection Control Circuit

Next, the operation of the driving signal selection control circuit200included in the discharge modules23-1to23-mwill be described. Here, the discharge modules23-1to23-mdiffer from each other only in the input signals, and all have the same configuration. Therefore, in the following description, when it is not necessary to distinguish the discharge modules23-1to23-mfrom each other, there is a case of being simply referred to as a discharge module23. Further, in this case, the driving signals COMA1to COMAm input to the discharge module23are referred to as driving signals COMA, the driving signals COMB1to COMBm are referred to as driving signals COMB, the driving signals COMC1to COMCm are referred to as driving signals COMC, the clock signals SCK1to SCKm are referred to as clock signals SCK, the print data signals SI1to SIm are referred to as print data signals SI, and the latch signals LAT1to LATm are referred to as latch signals LAT.

In describing the functional configuration of the driving signal selection control circuit200included in the discharge module23, first, an example of signal waveforms included in the driving signals COMA, COMB, and COMC input to the driving signal selection control circuit200will be described.

FIG.3is a view illustrating an example of signal waveforms of the driving signals COMA, COMB, and COMC. As illustrated inFIG.3, the driving signal COMA includes a trapezoidal waveform Adp arranged in a cycle T from the rise of the latch signal LAT to the next rise of the latch signal LAT, the driving signal COMB includes a trapezoidal waveform Bdp arranged in the cycle T, and the driving signal COMC includes a trapezoidal waveform Cdp arranged in the cycle T. Here, the cycle T from the rise of the latch signal LAT to the next rise of the latch signal LAT corresponds to the dot formation cycle for forming dots having a desired size on the medium P.

The trapezoidal waveform Adp is a waveform that is supplied to one end of the piezoelectric element60to discharge a predetermined amount of ink from the discharge section600corresponding to the piezoelectric element60. Further, the trapezoidal waveform Bdp is a waveform of which a voltage amplitude is smaller than that of the trapezoidal waveform Adp. When the trapezoidal waveform Bdp is supplied to one end of the piezoelectric element60, a smaller amount of ink than a predetermined amount is discharged from the discharge section600corresponding to the piezoelectric element60. The trapezoidal waveform Cdp is a waveform of which a voltage amplitude is smaller than those of the trapezoidal waveforms Adp and Bdp. When this trapezoidal waveform Cdp is supplied to one end of the piezoelectric element60, the ink in the vicinity of the nozzle opening portion is vibrated to the extent that the ink is not discharged from the discharge section600corresponding to the piezoelectric element60. Accordingly, the concern that the viscosity of the ink in the vicinity of the nozzle opening portion increases is reduced.

The voltages at the start timing and the end timing of each of the trapezoidal waveforms Adp, Bdp, and Cdp are a voltage Vc which is a common voltage. In other words, each of the trapezoidal waveforms Adp, Bdp, and Cdp is a waveform that starts at the voltage Vc and ends at the voltage Vc.

Here, in the following description, when the trapezoidal waveform Adp is supplied to one end of the piezoelectric element60, the amount of ink discharged from the discharge section600corresponding to the piezoelectric element60may be referred to as a large amount, and when the trapezoidal waveform Bdp is supplied to one end of the piezoelectric element60, the amount of ink discharged from the discharge section600corresponding to the piezoelectric element60may be referred to as a small amount. Further, vibrating the ink in the vicinity of the nozzle opening portion to the extent that the ink is not discharged from the discharge section600corresponding to the piezoelectric element60may be referred to as micro-vibration.

The driving signals COMA, COMB, and COMC may be signals having a continuous waveform of two or more trapezoidal waveforms in the cycle T. In this case, a signal for regulating the boundary between two or more trapezoidal waveforms, that is, a signal for regulating the switching timing of the two or more trapezoidal waveforms, may be input to the driving signal selection control circuit200. In this case, in the cycle T corresponding to the dot formation cycle, the discharge section600may discharge the ink plural times, and the ink discharged in plural times lands on the medium P and is combined to form one dot. On the other hand, in the present embodiment, the driving signals COMA, COMB, and COMC will be described as signals including one trapezoidal waveform in the cycle T. Accordingly, regarding the cycle T, compared to a case where the driving signals COMA, COMB, and COMC include a plurality of trapezoidal waveforms, the cycle T corresponding to the dot formation cycle can be shortened, and a high image formation speed on the medium P can be achieved.

Next, the functional configuration and operation of the driving signal selection control circuit200will be described with reference toFIGS.4to7.FIG.4is a view illustrating a functional configuration of the driving signal selection control circuit200. As illustrated inFIG.4, the driving signal selection control circuit200includes a selection control circuit210and a plurality of selection circuits230.

The print data signal SI, the latch signal LAT, and the clock signal SCK are input to the selection control circuit210. In the selection control circuit210, sets of a shift register (S/R)212, a latch circuit214, and a decoder216are provided corresponding to each of n discharge sections600. In other words, the driving signal selection control circuit200includes n (the same number as the total number of discharge sections600) sets of the shift register212, the latch circuit214, and the decoder216.

Specifically, the print data signal SI is a signal synchronized with the clock signal SCK, and is a signal of a total of 2n bits including 2-bit print data [SIH, SIL] for selecting any one of “large dot LD”, “small dot SD”, “Non-discharge ND”, and “Micro-vibration BSD” with respect to each of n discharge sections600. The print data signal SI is held in the shift register212for each of the two bits of print data [SIH, SIL] included in the print data signal SI, corresponding to discharge sections600. Specifically, n stages of shift register212corresponding to the discharge sections600are continuously coupled to each other, and the serially input print data signal SI is sequentially transferred to the subsequent stage in accordance with the clock signal SCK. InFIG.4, in order to distinguish the shift registers212from each other, the shift register212is denoted as 1-stage, 2-stage, . . . , and n-stage in order from the upstream to which the print data signal SI is input.

Each of n latch circuits214latches the 2-bit print data [SIH, SIL] held by each of n shift registers212all at once at the rise of the latch signal LAT.

Each of the n decoders216decodes the 2-bit print data [SIH, SIL] latched by each of the n latch circuits214. Further, the decoder216outputs selection signals S1, S2, and S3for each cycle T regulated by the latch signal LAT.

FIG.5is a view illustrating the decoding contents in the decoder216. The decoder216outputs the selection signals S1, S2, and S3according to the latched 2-bit print data [SIH, SIL]. For example, when the 2-bit print data [SIH, SIL] is [1, 0], the decoder216outputs the logic levels of the selection signals S1, S2, and S3as L, H, and L levels to the selection circuit230in the cycle T.

The selection circuit230is provided corresponding to each of the discharge sections600. In other words, the number of selection circuits230of the driving signal selection control circuit200is n, which is the same as the total number of the corresponding discharge sections600.

FIG.6is a view illustrating a configuration of the selection circuit230that corresponds to one discharge section600. As illustrated inFIG.6, the selection circuit230has inverters232a,232b, and232cwhich are NOT circuits, and transfer gates234a,234b, and234c.

While the selection signal S1is input to a positive control end, which is not marked with a circle, at the transfer gate234a, the selection signal S1is logically inverted by the inverter232aand is input to a negative control end marked with a circle at the transfer gate234a. The driving signal COMA is supplied to the input end of the transfer gate234a. In addition, the transfer gate234aconducts the input end and the output end to each other when the input selection signal S1is the H level, and does not conduct the input end and the output end to each other when the input selection signal S1is the L level.

While the selection signal S2is input to a positive control end, which is not marked with a circle, at the transfer gate234b, the selection signal S2is logically inverted by the inverter232band is input to a negative control end marked with a circle at the transfer gate234b. The driving signal COMB is supplied to the input end of the transfer gate234b. In addition, the transfer gate234bconducts the input end and the output end to each other when the input selection signal S2is the H level, and does not conduct the input end and the output end to each other when the input selection signal S2is the L level.

While the selection signal S3is input to a positive control end, which is not marked with a circle, at the transfer gate234c, the selection signal S3is logically inverted by the inverter232cand is input to a negative control end marked with a circle at the transfer gate234c. The driving signal COMC is supplied to the input end of the transfer gate234c. In addition, the transfer gate234cconducts the input end and the output end to each other when the input selection signal S3is the H level, and does not conduct the input end and the output end to each other when the input selection signal S3is the L level.

The output ends of the transfer gates234a,234b, and234care commonly coupled to each other. Accordingly, as the transfer gates234a,234b, and234care switched between conduction and non-conduction, signals obtained by selecting or deselecting the driving signals COMA, COMB, and COMC are supplied to the output ends of the commonly coupled transfer gates234a,234b, and234c. The signals supplied to the output ends of the commonly coupled transfer gates234a,234b, and234ccorrespond to the driving signal VOUT.

The operation of the driving signal selection control circuit200will be described with reference toFIG.7.FIG.7is a view for describing the operation of the driving signal selection control circuit200. The print data signals SI are serially input in synchronization with the clock signal SCK and sequentially transferred in the shift register212that corresponds to the discharge section600. Then, when the input of the clock signal SCK is stopped, the 2-bit print data [SIH, SIL] that corresponds to each of the discharge sections600is held in each of the shift registers212. The print data signal SI is input in order corresponding to the n-stage, . . . , 2-stage, and 1-stage discharge sections600of the shift register212.

When the latch signal LAT rises, each of the latch circuits214latches the 2-bit print data [SIH, SIL] held in the shift register212all at once. InFIG.7, LT1, LT2, . . . , and LTn indicate the 2-bit print data [SIH, SIL] latched by the latch circuit214corresponding to the 1-stage, 2-stage, . . . , and the n-stage shift registers212.

The decoder216outputs the logic levels of the selection signals S1, S2, and S3in the cycle T with the contents illustrated inFIG.5, corresponding to the size of the dot regulated by the latched 2-bit print data [SIH, SIL].

Specifically, when the print data [SIH, SIL] is [1, 1], the decoder216sets the selection signal S1to the H level, the selection signal S2to the L level, and the selection signal S3to the L level in the cycle T. In this case, the selection circuit230selects the trapezoidal waveform Adp in the cycle T, and as a result, the driving signal VOUT corresponding to the “large dot LD” is output.

Further, when the print data [SIH, SIL] is [1, 0], the decoder216sets the selection signal S1to the L level, the selection signal S2to the H level, and the selection signal S3to the L level in the cycle T. In this case, the selection circuit230selects the trapezoidal waveform Bdp in the cycle T, and as a result, the driving signal VOUT corresponding to the “small dot SD” is output.

Further, when the print data [SIH, SIL] is [0, 1], the decoder216sets the selection signal S1to the L level, the selection signal S2to the L level, and the selection signal S3to the L level in the cycle T. In this case, the selection circuit230does not perform any of the trapezoidal waveforms Adp, Bdp, and Cdp in the cycle T, and as a result, the driving signal VOUT corresponding to the “non-discharge ND” is output. Here, the driving signal VOUT corresponding to the non-discharge ND has a constant voltage waveform at a voltage Vc. When none of the trapezoidal waveforms Adp, Bdp, and Cdp is selected as the driving signal VOUT, the voltage Vc immediately before is held by the capacity component of the piezoelectric element60. Therefore, when the selection circuit230does not select any of the trapezoidal waveforms Adp, Bdp, and Cdp, this voltage Vc is supplied to the piezoelectric element60as the driving signal VOUT.

Further, when the print data [SIH, SIL] is [0, 0], the decoder216sets the selection signal S1to the L level, the selection signal S2to the L level, and the selection signal S3to the H level in the cycle T. In this case, the selection circuit230selects the trapezoidal waveform Cdp in the cycle T, and as a result, the driving signal VOUT corresponding to the “Micro-vibration BSD” is output.

As described above, the driving signal selection control circuit200selects or deselects the driving signals COMA, COMB, and COMC based on the print data signal SI, the latch signal LAT, and the clock signal SCK, to generate the driving signal VOUT corresponding to each of the plurality of discharge sections600and output the generated signal to the corresponding discharge section600. In other words, the driving signal selection control circuit200switches whether or not to supply the driving signals COMA, COMB, and COMC as the driving signal VOUT to the piezoelectric element60based on the print data signal SI, the latch signal LAT, and the clock signal SCK. The driving signal selection control circuit200is an example of a switching circuit, and any one of the print data signal SI, the latch signal LAT, and the clock signal SCK for regulating the operation of the driving signal selection control circuit200is an example of a discharge control signal. Further, at least one of the driving signals COMA and COMB for driving the piezoelectric element60included in the discharge section600such that the ink is discharged from the discharge section600is an example of a first driving signal, and the driving signal COMC for driving the piezoelectric element60included in the discharge section600such that the ink is not discharged from the discharge section600is an example of a second driving signal.

Further, as illustrated inFIG.2, the driving signal COMA is output by the driving signal output circuit52aincluded in the driving circuit unit50, the driving signal COMB is output by the driving signal output circuit52bincluded in the driving circuit unit50, and the driving signal COMC is output by the driving signal output circuit52cincluded in the driving circuit unit50. At least one of the driving signal output circuit52athat outputs the driving signal COMA and the driving signal output circuit52bthat outputs the driving signal COMB is an example of a first driving signal output circuit, and the driving signal output circuit52cthat outputs the driving signal COMC is an example of a second driving signal output circuit.

3. Structure of Liquid Discharge Head

Next, the structure of the head module21will be described.FIG.8is an exploded perspective view of the head module21.FIG.8illustrates arrows indicating the X, Y, and Z directions that are orthogonal to each other. Further, in the following description, the starting point side of the arrow indicating the X direction may be referred to as the −X side, and the tip end side thereof may be referred to as the +X side. The starting point side of the arrow indicating the Y direction may be referred to as the −Y side, the tip end side thereof may be referred to as the +Y side. The starting point side of the arrow indicating the Z direction may be referred to as the −Z side, and the tip end side thereof may be referred to as the +Z side.

As illustrated inFIG.8, the head module21includes a housing31, an aggregate substrate33, a flow path structure34, a head substrate35, a flow path distribution section37, and a fixing plate39. Then, the head module21is configured such that the flow path structure34, the head substrate35, the flow path distribution section37, and the fixing plate39are positioned in a state where the fixing plate39, the flow path distribution section37, the head substrate35, and the flow path structure34are stacked in this order from the −Z side to the +Z side in the direction along the Z direction, the housing31is positioned around the flow path structure34, the head substrate35, the flow path distribution section37, and the fixing plate39so as to support the flow path structure34, the head substrate35, the flow path distribution section37, and the fixing plate39, and the aggregate substrate33is erected on the +Z side of the housing31in a state of being held by the housing31.

Further, as illustrated inFIG.8, the head module21has the plurality of discharge modules23. The plurality of discharge modules23are positioned between the flow path distribution section37and the fixing plate39, and are partially positioned so as to be exposed to the outside of the head module21.FIG.8illustrates a case where the head module21has six discharge modules23. In the following description, when it is necessary to distinguish each of the six discharge modules23, the six discharge modules23may be referred to as discharge modules23-1to23-6. The number of discharge modules23included in the head module21is not limited to six.

In describing the details of the configuration of the head module21in the present embodiment, first, a specific example of the configuration of the discharge module23included in the head module21will be described.FIG.9is an exploded perspective view of the discharge module23, andFIG.10is a sectional view of the discharge module23illustrated inFIG.9when the discharge module23is taken along the line X-X. Here, the line X-X illustrated inFIG.9is a virtual line segment that passes through an introduction path661included in the discharge module23and passes through a nozzle N1and a nozzle N2.

As illustrated inFIGS.9and10, the discharge module23has the plurality of nozzles N1arranged side by side and the plurality of nozzles N2arranged side by side. The total number of the plurality of nozzles N1and the plurality of nozzles N2included in the discharge module23is n, which is the same as the number of discharge sections600included in the discharge module23. In the present embodiment, the description will be made while the number of nozzles N1and the number of nozzles N2included in the discharge module23are the same. In other words, the discharge module23has n/2 nozzles N1and n/2 nozzles N2. In the following description, when it is not necessary to distinguish the nozzle N1and the nozzle N2from each other, the nozzle N1and the nozzle N2may be simply referred to as a nozzle N.

As illustrated inFIGS.9and10, the discharge module23includes a wiring member388, a case660, a protective substrate641, a flow path forming substrate642, a communication plate630, a compliance substrate620, and a nozzle plate623. Each member included in the discharge module23is laminated along the Z direction and is joined by an adhesive or the like.

On the flow path forming substrate642, pressure chambers CB1partitioned by a plurality of partition walls by anisotropic etching from one surface side are arranged side by side corresponding to the nozzles N1, and pressure chambers CB2partitioned by a plurality of partition walls by anisotropic etching from one surface side are arranged side by side corresponding to the nozzles N2. In other words, on the flow path forming substrate642, a row of pressure chambers CB1arranged side by side corresponding to n/2 nozzles N1and a row of pressure chambers CB2arranged side by side corresponding to n/2 nozzles N2are provided. Here, in the following description, when it is not necessary to distinguish the pressure chamber CB1and the pressure chamber CB2from each other, the pressure chamber CB1and the pressure chamber CB2may be simply referred to as a pressure chamber CB. Further, the flow path forming substrate642may be provided with a supply path or the like on one end portion side of the pressure chamber CB such that the opening area is narrower than that of the pressure chamber CB and the flow path resistance of the ink flowing into the pressure chamber CB is imparted.

The nozzle plate623is positioned on the −Z side of the flow path forming substrate642. The nozzle plate623is provided with a nozzle row Ln1formed by n/2 nozzles N1and a nozzle row Ln2formed by n/2 nozzles N2. Here, in the following description, the −Z side surface of the nozzle plate623where the nozzles N are open may be referred to as a liquid ejection surface623a.

The communication plate630is positioned on the −Z side of the flow path forming substrate642and on the +Z side of the nozzle plate623. The communication plate630is provided with a nozzle communication path RR1that makes the pressure chamber CB1and the nozzle N1communicate with each other, and a nozzle communication path RR2that makes the pressure chamber CB2and the nozzle N2communicate with each other. Further, on the communication plate630, a pressure chamber communication path RK1that makes the end portion of the pressure chamber CB1and a manifold MN1(which will be described later) communicate with each other, and a pressure chamber communication path RK2that makes the end portion of the pressure chamber CB2and a manifold MN2(which will be described later) communicate with each other, are provided independently corresponding to each of the pressure chambers CB1and CB2. In other words, on the communication plate630, a row of the nozzle communication paths RR1corresponding to n/2 nozzles N1arranged side by side and the pressure chamber CB1, a row of the pressure chamber communication paths RK1, a row of nozzle communication paths RR2corresponding to n/2 nozzles N2arranged side by side and the pressure chamber CB2, and a row of pressure chamber communication paths RK2are provided.

Further, the communication plate630includes the manifolds MN1and MN2. The manifold MN1includes a supply communication path RA1and a coupling communication path RX1. The supply communication path RA1is provided so as to penetrate the communication plate630in the Z direction, and the coupling communication path RX1is provided to be open on the nozzle plate623side of the communication plate630in the middle of the Z direction without penetrating the communication plate630in the Z direction. Similarly, the manifold MN2includes a supply communication path RA2and a coupling communication path RX2. The supply communication path RA2is provided so as to penetrate the communication plate630in the Z direction, and the coupling communication path RX2is provided to be open on the nozzle plate623side of the communication plate630in the middle of the Z direction without penetrating the communication plate630in the Z direction. Then, the coupling communication path RX1included in the manifold MN1is communicated with the corresponding pressure chamber CB1by the pressure chamber communication path RK1, and the coupling communication path RX2included in the manifold MN2is communicated with the corresponding pressure chamber CB2by the pressure chamber communication path RK2.

Here, in the following description, when it is not necessary to distinguish the nozzle communication path RR1and the nozzle communication path RR2from each other, the nozzle communication path RR1and the nozzle communication path RR2may be simply referred to as a nozzle communication path RR. When it is not necessary to distinguish the manifold MN1and the manifold MN2from each other, the manifold MN1and the manifold MN2may be simply referred to as a manifold MN, and when it is not necessary to distinguish the supply communication path RA1and the supply communication path RA2from each other, the supply communication path RA1and the supply communication path RA2may be simply referred to as a supply communication path RA, and when it is not necessary to distinguish the coupling communication path RX1and the coupling communication path RX2from each other, the coupling communication path RX1and the coupling communication path RX2may be simply referred to as the coupling communication path RX.

A vibrating plate610is positioned on the +Z side surface of the flow path forming substrate642. Further, on the +Z side surface of the vibrating plate610, the piezoelectric elements60are formed in two rows corresponding to the nozzles N1and N2. One electrode of the piezoelectric element60and the piezoelectric layer are formed for each pressure chamber CB, and the other electrode is configured as a common electrode common to the pressure chamber CB. Then, the driving signal VOUT is supplied from the driving signal selection control circuit200to one electrode of the piezoelectric element60, and the reference voltage signal VBS is supplied to the common electrode which is the other electrode.

Further, the protective substrate641having substantially the same size as that of the flow path forming substrate642is joined to the +Z side surface of the flow path forming substrate642. The protective substrate641forms a holding section644which is a space for protecting the piezoelectric element60. Further, the protective substrate641is provided with a through-hole643that penetrates along the Z direction. The end portion of a lead electrode611drawn out of the electrode of the piezoelectric element60is extended so as to be exposed in the through-hole643. A wiring member388is electrically coupled to the end portion of the lead electrode611exposed in the through-hole643.

Further, a case660defining a part of the manifold MN that communicates with the plurality of pressure chambers CB is fixed to the protective substrate641and the communication plate630. The case660has substantially the same shape as that of the communication plate630in a plan view, and is joined to the protective substrate641and also to the communication plate630. Specifically, the case660has a recess portion665having a depth for accommodating the flow path forming substrate642and the protective substrate641on the −Z side surface. The recess portion665has a wider opening area than that of the surface on which the protective substrate641is joined to the flow path forming substrate642. Then, in a state where the flow path forming substrate642or the like is accommodated in the recess portion665, the opening surface of the recess portion665on the −Z side is sealed by the communication plate630. Accordingly, the supply communication path RB1and the supply communication path RB2are defined by the case660, the flow path forming substrate642, and the protective substrate641on the outer peripheral portion of the flow path forming substrate642. Here, when it is not necessary to distinguish the supply communication path RB1and the supply communication path RB2from each other, the supply communication path RB1and the supply communication path RB2may be simply referred to as a supply communication path RB.

Further, the compliance substrate620is provided on the surface of the communication plate630where the supply communication path RA and the coupling communication path RX are open. The compliance substrate620seals the openings of the supply communication path RA and the coupling communication path RX. The compliance substrate620has a sealing film621and a fixed substrate622. The sealing film621is formed of a flexible thin film or the like, and the fixed substrate622is formed of a hard material such as a metal such as stainless steel.

Further, the case660is provided with the introduction path661for supplying ink to the manifold MN. In addition, the case660is provided with a coupling port662in which the wiring member388is inserted so as to communicate with the through-hole643of the protective substrate641. The coupling port662is an opening that penetrates along the Z direction.

The wiring member388is a flexible substrate for electrically coupling the discharge module23and the head substrate35(which will be described later) to each other, and is, for example, a flexible substrate such as a flexible printed circuits (FPC). The driving signal selection control circuit200configured with, for example, an integrated circuit, is mounted on the wiring member388by chip on film (COF).

In the discharge module23configured as described above, the driving signal VOUT output by the driving signal selection control circuit200and the reference voltage signal VBS are supplied to the piezoelectric element60via the wiring member388. The piezoelectric element60is driven by a change in the potential of the driving signal VOUT. Then, as the piezoelectric element60is driven, the vibrating plate610is deformed in the up-down direction, and the internal pressure of the pressure chamber CB changes. Due to the change in the internal pressure of the pressure chamber CB, the ink stored inside the pressure chamber CB is discharged from the corresponding nozzle N. In the discharge module23configured as described above, the configuration including the nozzle N, the nozzle communication path RR, the pressure chamber CB, the piezoelectric element60, and the vibrating plate610corresponds to the discharge section600. In other words, the discharge section600includes the piezoelectric element60driven by the driving signal VOUT based on the driving signals COMA and COMB, and discharges ink in response to the drive of the piezoelectric element60.

Returning toFIG.8, the fixing plate39is positioned on the −Z side of the discharge module23. The fixing plate39has six exposed opening portions391penetrating the fixing plate39in the Z direction. Then, the six discharge modules23are fixed to the fixing plate39such that the liquid ejection surface623aincluded in the six discharge modules23is exposed from each of the corresponding six exposed opening portions391.

The flow path distribution section37is positioned on the +Z side of the discharge module23. Four introduction coupling sections373are provided on the +Z side surface of the flow path distribution section37. The four introduction coupling sections373are flow path pipes that protrude from the +Z side surface of the flow path distribution section37toward the +Z side along the Z direction, and communicate with a flow path holes (not illustrated) formed on the −Z side surface of the flow path structure34(which will be described later). Further, on the −Z side surface of the flow path distribution section37, a flow path pipe (not illustrated) that communicates with the corresponding introduction coupling section373among the four introduction coupling sections373is positioned. A flow path pipe (not illustrated) positioned on the −Z side surface of the flow path distribution section37is coupled to the introduction path661included in each of the six discharge modules23. Further, the flow path distribution section37has six opening portions371that penetrate in the Z direction. The wiring member388included in each of the six discharge modules23is inserted through the six opening portions371.

The head substrate35is positioned on the +Z side of the flow path distribution section37. The head substrate35is provided with the connector CN1that is electrically coupled to the aggregate substrate33(which will be described later) and a cable FC. Further, on the head substrate35, four opening portions351and two notch sections353are formed. The wiring member388of the discharge modules23-2to23-5is inserted through the four opening portions351. Then, each of the wiring members388of the discharge modules23-2to23-5through which the four opening portions351are inserted is electrically coupled to the head substrate35by solder or the like. Further, the wiring member388included in the discharge module23-1passes through one of the two notch sections353, and the wiring member388included in the discharge module23-6passes through the other one of the two notch sections353. Then, the wiring member388included in each of the discharge modules23-1and23-6, through which each of the two notch sections353pass, is electrically coupled to the head substrate35by solder or the like. In other words, the head substrate35branches the signal input via the connector CN1and the cable FC corresponding to each of the discharge modules23-1to23-6, and signals output by each of the discharge modules23-1to23-6are output to the aggregate substrate33(which will be described later) via the connector CN1and the cable FC.

Further, four notch sections355are formed at the four corners of the head substrate35. The four introduction coupling sections373included in the flow path distribution section37positioned on the −Z side of the head substrate35pass through the four notch sections355. Then, the four introduction coupling sections373that passed through the notch section355are coupled to the flow path structure34positioned on the +Z side of the head substrate35.

The flow path structure34is positioned on the +Z side of the head substrate35. The flow path structure34has a flow path plate Su1and a flow path plate Su2laminated along the Z direction. The flow path plate Su1and the flow path plate Su2are joined to each other by an adhesive or the like in a state where the flow path plate Su1is positioned on the +Z side and the flow path plate Su2is positioned on the −Z side. The flow path plate Su1and the flow path plate Su2are formed, for example, by injection molding of a resin.

Further, the flow path structure34has four supply coupling sections341which are flow path pipes protruding toward the +Z side along the Z direction on the +Z side surface. The four supply coupling sections341communicate with the flow path holes (not illustrated) formed on the −Z side surface of the flow path structure34via the ink flow path formed inside the flow path structure34. Further, the flow path structure34is formed with a through-hole343that penetrates along the Z direction. The connector CN1and the cable FC provided on the head substrate35are inserted through the through-hole343. Inside the flow path structure34, in addition to the ink flow path that makes the supply coupling section341and the flow path hole (not illustrated) formed on the −Z side surface communicate with each other, a filter or the like for capturing foreign matter included in the ink may be provided.

The housing31is positioned so as to cover the periphery of the flow path structure34, the head substrate35, the flow path distribution section37, and the fixing plate39, and supports the flow path structure34, the head substrate35, the flow path distribution section37, and the fixing plate39. The housing31has four supply holes311and an aggregate substrate insertion section313, and holding members315and317.

The four supply coupling sections341included in the flow path structure34are inserted through each of the four supply holes311. Then, ink is supplied from the liquid container2to the four supply coupling sections341through which the four supply holes311are inserted, via a tube (not illustrated) or the like.

The holding members315and317sandwich and hold the aggregate substrate33in a state where a part of the aggregate substrate33is inserted through the aggregate substrate insertion section313. The aggregate substrate33is provided with the connectors CN1and330. Various signals such as the data signal DATA, the driving signals COMA, COMB, and COMC, the reference voltage signal VBS, and other power supply voltages, which are output by the control unit10, are input to the connector330. The connector CN1is inserted through the aggregate substrate insertion section313of the housing31together with the aggregate substrate33, and is electrically coupled to the connector CN2included in the head substrate35. Further, the cable FC included in the head substrate35is electrically coupled to the aggregate substrate33. Accordingly, the aggregate substrate33and the head substrate35are electrically coupled to each other. The details of the electrical coupling between the aggregate substrate33and the head substrate35will be described later.

In the head module21configured as described above, the liquid container2and the supply coupling section341communicate with each other via a tube or the like (not illustrated), and accordingly, the ink stored in the liquid container2is supplied to the head module21. The ink supplied to the head module21is guided to the flow path hole (not illustrated) formed on the −Z side surface of the flow path structure34via the ink flow path formed inside the flow path structure34. The ink guided to the flow path hole (not illustrated) formed on the −Z side surface of the flow path structure34is supplied to the four introduction coupling sections373included in the flow path distribution section37.

The ink supplied to the flow path distribution section37via the four introduction coupling sections373is supplied to the introduction path661included in the corresponding discharge module23after the ink is distributed corresponding to each of the six discharge modules23in the ink flow path (not illustrated) formed inside the flow path distribution section37. Then, the ink supplied to the discharge module23via the introduction path661is stored in the pressure chamber CB included in the discharge section600.

Further, the control unit10and the head module21are electrically coupled to each other by a cable (not illustrated). Then, various signals including the driving signals COMA, COMB, and COMC, the reference voltage signal VBS, and the data signal DATA are input from the control unit10to the head module21via the cable. Various signals including the driving signals COMA, COMB, and COMC, the reference voltage signal VBS, and the data signal DATA input to the head module21propagate through the aggregate substrate33and the head substrate35, and are supplied to the discharge module23. Then, in the discharge module23, the driving signals COMA, COMB, and COMC corresponding to each of the n discharge sections600and the driving signal VOUT based on the data signal DATA are generated, and are supplied to the piezoelectric element60included in the corresponding discharge section600. Accordingly, the piezoelectric element60is driven based on the driving signal VOUT. Then, in response to the drive of the piezoelectric element60, the ink stored in the pressure chamber CB included in the discharge section600is discharged.

4. Electrical Coupling Between Aggregate Substrate and Head Substrate

Here, in the head module21, a specific example of the electrical coupling between the aggregate substrate33and the head substrate35, and a propagation path for propagating various signals including the clock signal SCK, the print data signal SI, the latch signal LAT, and the driving signals COMA, COMB, and COMC will be described.FIG.11is a view illustrating an example of the electrical coupling between the aggregate substrate33and the head substrate35when the head module21is viewed from the direction along the Z direction,FIG.12is a view illustrating an example of the electrical coupling between the aggregate substrate33and the head substrate35when the head module21is viewed from the direction along the Y direction, andFIG.13is a view illustrating an example of the electrical coupling between the aggregate substrate33and the head substrate35when the head module21is viewed from the direction along the X direction.

As illustrated inFIGS.11to13, the head substrate35has a surface35aand a surface35b. The head substrate35is positioned such that the surface35aand the surface35bextend along a plane formed by the X direction and the Y direction, the surface35ais on the +Z side, and the surface35bis on the −Z side. At the center portion of the head substrate35, four opening portions351penetrating the surface35aand the surface35bare formed side by side along the X direction. Further, a notch section353is formed on each of the +X side of the four opening portions351formed side by side and the −X side of the four opening portions351formed side by side. In other words, on the head substrate35, four opening portions351are formed between the two notch sections353in the direction in which the two notch sections353and the four opening portions351are along the X direction.

Then, as described above, the head substrate35is electrically coupled to the six discharge modules23via the wiring member388through which the two notch sections353and the four opening portions351which are formed on the head substrate35are inserted. In other words, the head substrate35propagates the driving signals COMA, COMB, and COMC, the print data signal SI, the latch signal LAT, and the clock signal SCK to the driving signal selection control circuit200mounted on the wiring member388included in the discharge module23by COF. This head substrate35is an example of a first substrate.

Further, the connectors CN1and CN2, the cable FC, and the aggregate substrate33are positioned on the −Y side of the four opening portions351arranged side by side along the X direction.

The aggregate substrate33has a surface33aand a surface33b. In addition, the aggregate substrate33is positioned such that the surface33aand the surface33bextend along a plane formed by the X direction and the Z direction, the surface33ais on the +Y side, and the surface33bis on the −Y side. In other words, the aggregate substrate33and the head substrate35are positioned such that the surface33aof the aggregate substrate33and the surface35aof the head substrate35intersect with each other. The aggregate substrate33is provided with two connectors330. In the two connectors330, one connector330is provided on the surface33aand the other connector330is provided on the surface33balong the side of the aggregate substrate33on the +Z side. A cable (not illustrated) electrically coupled to the control unit10is attached to the two connectors330. Here, as the cable attached to the connector330, for example, a flexible flat cable (FFC) is used.

The cable FC and the connectors CN1and CN2electrically couples the aggregate substrate33and the head substrate35to each other.

One end of the cable FC is electrically coupled to the surface35aof the head substrate35, and the other end is electrically coupled to the surface33aof the aggregate substrate33. Then, the cable FC supplies the signal propagating through the aggregate substrate33to the head substrate35. As the cable FC, for example, a flexible printed circuit (FPC) on which a plurality of propagation wirings is formed is used. Generally, in FPC, a copper foil having a thickness of 10 μm to 20 μm is formed on a base such as a PET film or a polyimide film having a thickness of 10 μm to 50 μm, and by performing etching with respect to the copper foil or the like, a wiring pattern having a thickness of 30 μm to 150 μm is formed on the base. The FPC is configured by protecting the wiring pattern formed on the substrate with a film such as a polyimide film or a solder resist having a thickness of 10 μm to 50 μm. In other words, in FPC, fine wiring patterns having a cross-sectional area of 0.0003 to 0.0025 mm2are formed at high density.

In addition to the base, the wiring pattern, and the film which are described above, the thickness including an adhesive that adheres the base, the wiring pattern, and the film is an extremely thin thickness of generally 100 μm or less, and thus, the FPC can be bent, and can electrically couple the substrate to be coupled with a high degree of freedom. Furthermore, the FPC can form a high-density wiring pattern as described above, and even when the FPC is bent, the rate of change in the electrical characteristics of the wiring pattern is small, and thus, it is possible to propagate many signals with high reliability.

As described above, the cable FC includes a wiring pattern that electrically couples the aggregate substrate33and the head substrate35to each other. Here, the cable FC may electrically couple the head substrate35and the aggregate substrate33to each other by coupling the head substrate35and the aggregate substrate33to each other by, for example, soldering, and may electrically couple the head substrate35and the aggregate substrate33to each other by electrically coupling the head substrate35and the aggregate substrate33to each other via the connector (not illustrated). Here, the cable FC that electrically couples the aggregate substrate33and the head substrate35to each other is an example of a second coupling member, and the wiring pattern included in the cable FC is an example of a second conductive section.

The connector CN1is electrically coupled to the surface33bof the aggregate substrate33. Further, the connector CN2is positioned on the −Y side of the aggregate substrate33and is electrically coupled to the surface35aof the head substrate35. Then, when the connector CN1and the connector CN2are fitted to each other, the connector CN1and the connector CN2are electrically coupled to each other, and the aggregate substrate33provided with the connector CN1and the head substrate35provided with the connector CN2are electrically coupled to each other. In other words, the connectors CN1and CN2are directly fitted without a cable or the like to electrically couple the aggregate substrate33and the head substrate35to each other.

Here, a specific example of the structure of the connectors CN1and CN2will be described. In the present embodiment, in the description, the connector CN1is a right angle type male connector and the connector CN2is a straight type female connector. However, the connector CN1may be a female connector and the connector CN2may be a male connector. Further, the connector CN1may be a straight type and the connector CN2may be a right angle type. Furthermore, the aggregate substrate33and the head substrate35may be coupled to each other in a stack, and in this case, both the connectors CN1and CN2may be a straight type.

An example of the structure of the connector CN1will be described with reference toFIGS.14to16. In order to describe the structure of the connector CN1with reference toFIGS.14to16, inFIGS.14to16, arrows indicating the P1 direction, the Q1 direction, and the R1 direction, which are orthogonal to each other, are illustrated. Further, in the following description, the starting point side of the arrow indicating the P1 direction may be referred to as the −P1 side, and the tip end side thereof may be referred to as the +P1 side. The starting point side of the arrow indicating the Q1 direction may be referred to as the −Q1 side, the tip end side thereof may be referred to as the +Q1 side. The starting point side of the arrow indicating the R1 direction may be referred to as the −R1 side, and the tip end side thereof may be referred to as the +R1 side.

FIG.14is a view illustrating an example of the structure of the connector CN1when the connector CN1is viewed from the direction along the Q1 direction,FIG.15is a view illustrating an example of the structure of the connector CN1when the connector CN1is viewed from the direction along the R1 direction, andFIG.16is a view illustrating an example of the structure of the connector CN1when the connector CN1is viewed from the direction along the P1 direction.

As illustrated inFIGS.14to16, the connector CN1includes insertion pins410a-1to410a-pand410b-1to410b-p, substrate coupling terminals411a-1to411a-pand411b-1to411b-p, and a holding member420.

The insertion pins410a-1to410a-pand410b-1to410b-pare rectangular coupling pins having conductivity having a width pw on one side, and each of the insertion pins extends to the −R1 side from the −R1 side surface of the connector CN1. The insertion pins410a-1to410a-pand410b-1to410b-pmay be conductive coupling pins on a cylinder of which the diameter has the width pw.

The insertion pins410a-1to410a-pare arranged side by side at equal intervals to be separated from each other with an inter-pitch distance ph1, from the −P1 side to the +P1 side in the order of the insertion pins410a-1,410a-2, . . . , and410a-p, in the direction along the P1 direction. The insertion pins410b-1to410b-pare arranged side by side at equal intervals to be separated from each other with the inter-pitch distance ph1, from the −P1 side to the +P1 side in the order of the insertion pins410b-1,410b-2, . . . , and410b-p, in the direction along the P1 direction, on the −Q1 side of the insertion pins410a-1to410a-p, which are arranged side by side along the P1 direction. Here, the fact that the insertion pins are arranged side by side at equal intervals to be separated from each other with the inter-pitch distance ph1includes a case of being arranged at equal intervals including variations and the like.

Further, the insertion pin410a-1and the insertion pin410b-1are arranged side by side to be separated from each other with an inter-pitch distance ph2in the direction along the Q1 direction, the insertion pin410a-pand the insertion pin410b-pare arranged side by side to be separated from each other with the inter-pitch distance ph2in the direction along the Q1 direction, and an insertion pin410a-i(i is any of 1 to p) and an insertion pin410b-iare arranged side by side to be separated from each other with the inter-pitch distance ph2in the direction along the Q1 direction.

Here, in the connector CN1of the present embodiment, the shortest distance between the insertion pin410a-iand the insertion pin410a-i+1 positioned adjacent to the insertion pin410a-iis preferably 1 mm or more, and the cross-sectional area of the insertion pin410a-iand the insertion pin410a-i+1 is preferably 0.1 mm2or more. Furthermore, the insertion pin410a-iand the insertion pin410a-i+1 are preferably positioned such that the shortest distance between the insertion pin410a-iand the insertion pin410a-i+1 is three times or more the width pw of the insertion pin410a-iand the insertion pin410a-i+1.

In the connector CN1, as an example in which the arrangement and dimensions of the insertion pins410a-1to410a-pand410b-1to410b-psatisfy the above-described conditions, a case where the inter-pitch distance ph1and the inter-pitch distance ph2are 2.54 mm and the width pw of the insertion pins410a-1to410a-pand410b-1to410b-pis 0.635 mm. In this case, the shortest distance between the insertion pin410a-iand the insertion pin410a-i+1 positioned adjacent to the insertion pin410a-iis “2.54 mm−0.635 mm=1.905 mm”, and the cross-sectional areas of the insertion pins410a-1to410a-pand410b-1to410b-pare “0.635 mm×0.635 mm=0.403 mm2”. The inter-pitch distance ph1and the inter-pitch distance ph2are not limited to 2.54 mm, and the width pw of the insertion pins410a-1to410a-pand410b-1to410b-pis not limited to 0.635 mm.

The substrate coupling terminals411a-1to411a-pand411b-1to411b-pare conductive members which are respectively provided on the +Q1 side surface of the connector CN1, and extend to protrude to the +Q1 side along the Q1 direction. The substrate coupling terminals411a-1to411a-pand411b-1to411b-pare inserted through the aggregate substrate33and coupled to the aggregate substrate33by soldering or the like, and accordingly, the connector CN1is electrically coupled to the aggregate substrate33.

The substrate coupling terminals411a-1to411a-pare provided corresponding to each of the insertion pins410a-1to410a-p. Each of the substrate coupling terminals411a-1to411a-pand each of the insertion pins410a-1to410a-pare electrically coupled to each other via internal electrodes413a-1to413a-p. Specifically, the substrate coupling terminal411a-1is electrically coupled to the insertion pin410a-1via the internal electrode413a-1, the substrate coupling terminal411a-pis electrically coupled to the insertion pin410a-pvia the internal electrode413a-p, and the substrate coupling terminal411a-iis electrically coupled to the insertion pin410a-ivia the internal electrode413a-i.

The substrate coupling terminals411b-1to411b-pare provided corresponding to each of the insertion pins410b-1to410b-p. Each of the substrate coupling terminals411b-1to411b-pand each of the insertion pins410b-1to410b-pare electrically coupled to each other via internal electrodes413b-1to413b-p. Specifically, the substrate coupling terminal411b-1is electrically coupled to the insertion pin410b-1via the internal electrode413b-1, the substrate coupling terminal411b-pis electrically coupled to the insertion pin410b-pvia the internal electrode413b-p, and a substrate coupling terminal411b-iis electrically coupled to the insertion pin410b-ivia the internal electrode413b-i.

Further, the substrate coupling terminals411a-1to411a-pare arranged side by side in the order of the substrate coupling terminals411a-1,411a-2, . . . , and411a-pfrom the −P1 side to the +P1 side in the direction along the P1 direction, and the substrate coupling terminals411b-1to411b-pare arranged side by side in the order of the substrate coupling terminals411b-1,411b-2, . . . , and411b-pfrom the −P1 side to the +P1 side in the direction along the P1 direction, on the +R1 side of the substrate coupling terminals411a-1,411a-2, . . . , and411a-pwhich are arranged side by side in the direction along the P1 direction. The substrate coupling terminal411a-1and the substrate coupling terminal411b-1are arranged side by side in the direction along the R1 direction, the substrate coupling terminal411a-pand the substrate coupling terminal411b-pare arranged side by side in the direction along the R1 direction, and the substrate coupling terminal411a-iand the substrate coupling terminal411b-iare arranged side by side in the direction along the R1 direction.

The holding member420also functions as an insulating member that holds the insertion pins410a-1to410a-pand410b-1to410b-pand the substrate coupling terminals411a-1to411a-pand411b-1to411b-pand insulates the insertion pins410a-1to410a-pand410b-1to410b-pfrom each other and the substrate coupling terminals411a-1to411a-pand411b-1to411b-pfrom each other.

As the holding member420, polybutylene terephthalate (PBT) resin is preferably used. In the liquid discharge apparatus1, a part of the ink discharged from the discharge section600may become mist before landing on the medium P and float as ink mist inside the liquid discharge apparatus1. Since the ink mist floating inside the liquid discharge apparatus1is extremely small, charging is performed by the Lenard effect. Therefore, there is a high concern that ink mist floating inside the liquid discharge apparatus1adheres in the vicinity of the discharge section600from which the ink is discharged and in the vicinity of the connector included in the head module21through which various signals propagate.

In particular, in the liquid discharge apparatus1, inks having various physical properties can be used depending on the type and application of the medium P. Therefore, it is required that the connector included in the head module21is unlikely to change in characteristics even when various types of solvents adhere thereto. As the holding member420of the connector CN1included in the head module21, a PBT resin having excellent insulation performance, low water absorption rate, and excellent oil resistance and solvent resistance is used, and accordingly, even when the ink used in the liquid discharge apparatus1adheres to the connector CN1, the concern that the characteristics of the holding member420change is reduced. Therefore, the concern about the change in characteristics of the insertion pins410a-1to410a-pand410b-1to410b-pand the substrate coupling terminals411a-1to411a-pand411b-1to411b-p, which are held by the holding member420, is reduced. As a result, the stability of various signals propagating through the insertion pins410a-1to410a-pand410b-1to410b-pand the substrate coupling terminals411a-1to411a-pand411b-1to411b-pis improved. In other words, when the holding member420of the connector CN1contains the PBT resin, the reliability of various signals propagating through the insertion pins410a-1to410a-pand410b-1to410b-pand the substrate coupling terminals411a-1to411a-pand411b-1to411b-pis improved.

The connector CN1configured as described above is a so-called pin header including the insertion pins410a-1to410a-pand410b-1to410b-pincluding the insertion pins410a-iand the insertion pins410a-i+1, and the holding member420that holds the insertion pins410a-1to410a-pand410b-1to410b-pin a state of being insulated from each other. The connector CN1is provided on the aggregate substrate33such that the P1 direction, the Q1 direction, and the R1 direction illustrated inFIGS.14to16are respectively directions along each of the X direction, the Y direction, and the Z direction illustrated inFIGS.11to13.

Next, an example of the structure of the connector CN2will be described with reference toFIGS.17to19. In order to describe the structure of the connector CN2with reference toFIGS.17to19, inFIGS.17to19, arrows indicating the P2 direction, the Q2 direction, and the R2 direction, which are orthogonal to each other, are illustrated. Further, in the following description, the starting point side of the arrow indicating the P2 direction may be referred to as the −P2 side, and the tip end side thereof may be referred to as the +P2 side. The starting point side of the arrow indicating the Q2 direction may be referred to as the −Q2 side, the tip end side thereof may be referred to as the +Q2 side. The starting point side of the arrow indicating the R2 direction may be referred to as the −R2 side, and the tip end side thereof may be referred to as the +R2 side.

FIG.17is a view illustrating an example of the structure of the connector CN2when the connector CN2is viewed from the direction along the Q2 direction,FIG.18is a view illustrating an example of the structure of the connector CN2when the connector CN2is viewed from the direction along the R2 direction, andFIG.19is a view illustrating an example of the structure of the connector CN2when the connector CN2is viewed from the direction along the P2 direction.

As illustrated inFIGS.17to19, the connector CN2includes insertion holes450a-1to450a-pand450b-1to450b-p, substrate coupling terminals451a-1to451a-pand451b-1to451b-p, and a holding member460.

The insertion holes450a-1to450a-pand450b-1to450b-pare recess portions which are respectively open on the +R2 side surface of the connector CN2and formed from the opening to the −R1 side along the R2 direction. A conductive member (not illustrated) is provided inside each of the recess portions formed as the insertion holes450a-1to450a-pand450b-1to450b-p.

The insertion holes450a-1to450a-pare arranged side by side at equal intervals to be separated from each other with an inter-pitch distance ps1, from the −P2 side to the +P2 side in the order of the insertion holes450a-1,450a-2, . . . , and450a-p, in the direction along the P2 direction. The insertion holes450b-1to450b-pare arranged side by side at equal intervals to be separated from each other with the inter-pitch distance ps1, from the −P2 side to the +P2 side in the order of the insertion holes450b-1,450b-2, . . . , and450b-p, in the direction along the P2 direction, on the −Q2 side of the insertion holes450a-1to450a-p, which are arranged side by side along the P2 direction. Here, the fact that the insertion holes are arranged side by side at equal intervals to be separated from each other with the inter-pitch distance ps1includes a case of being arranged at equal intervals including variations and the like.

Further, the insertion hole450a-1and the insertion hole450b-1are arranged side by side to be separated from each other with an inter-pitch distance ps2in the direction along the Q2 direction, the insertion hole450a-pand the insertion hole450b-pare arranged side by side to be separated from each other with the inter-pitch distance ps2in the direction along the Q2 direction, and an insertion hole450a-iand an insertion hole450b-iare arranged side by side to be separated from each other with the inter-pitch distance ps2in the direction along the Q2 direction.

The substrate coupling terminals451a-1to451a-pand451b-1to451b-pare conductive members which are respectively provided on the −R2 side surface of the connector CN2, and extend to protrude to the −R2 side along the R2 direction. The substrate coupling terminals451a-1to451a-pand451b-1to451b-pare inserted through the head substrate35and coupled to the head substrate35by soldering or the like, and accordingly, the connector CN2is electrically coupled to the head substrate35.

The substrate coupling terminals451a-1to451a-pare provided corresponding to each of the insertion holes450a-1to450a-p, and are electrically coupled to the conductive section (not illustrated) provided inside each of the insertion holes450a-1to450a-p. Specifically, the substrate coupling terminal451a-1is electrically coupled to the conductive section (not illustrated) provided inside the insertion hole450a-1, the substrate coupling terminal451a-pis electrically coupled to the conductive section (not illustrated) provided inside the insertion hole450a-p, and the substrate coupling terminal451a-iis electrically coupled to the conductive section (not illustrated) provided inside the insertion hole450a-i.

Further, the substrate coupling terminals451b-1to451b-pare provided corresponding to each of the insertion holes450b-1to450b-p, and are electrically coupled to the conductive section (not illustrated) provided inside each of the insertion holes450b-1to450b-p. Specifically, the substrate coupling terminal451b-1is electrically coupled to the conductive section (not illustrated) provided inside the insertion hole450b-1, the substrate coupling terminal451b-pis electrically coupled to the conductive section (not illustrated) provided inside the insertion hole450b-p, and a substrate coupling terminal451b-iis electrically coupled to the conductive section (not illustrated) provided inside the insertion hole450b-i.

Further, the substrate coupling terminals451a-1to451a-pare arranged side by side in the order of the substrate coupling terminals451a-1,451a-2, . . . , and451a-pfrom the −P2 side to the +P2 side in the direction along the P2 direction, and the substrate coupling terminals451b-1to451b-pare arranged side by side in the order of the substrate coupling terminals451b-1,451b-2, . . . , and451b-pfrom the −P2 side to the +P2 side in the direction along the P2 direction. The substrate coupling terminal451a-1and the substrate coupling terminal451b-1are arranged side by side in the direction along the Q2 direction, the substrate coupling terminal451a-pand the substrate coupling terminal451b-pare arranged side by side in the direction along the Q2 direction, and the substrate coupling terminal451a-iand the substrate coupling terminal451b-iare arranged side by side in the direction along the Q2 direction.

The holding member460also functions as an insulating member that holds the insertion holes450a-1to450a-pand450b-1to450b-pand the substrate coupling terminals451a-1to451a-pand451b-1to451b-pand insulates the conductive members provided inside each of the insertion holes450a-1to450a-pand450b-1to450b-pfrom each other and the substrate coupling terminals451a-1to451a-pand451b-1to451b-pfrom each other.

It is preferable that the holding member460also contain the PBT resin similar to the holding member420included in the connector CN1. Accordingly, even when ink adheres to the connector CN2, the concern that the characteristics of the holding member460change, is reduced and the concern that the characteristics of the insertion holes450a-1to540a-pand450b-1to450b-p, which are held by the holding member460, and the substrate coupling terminals451a-1to451a-pand451b-1to451b-pchange, is also reduced. As a result, the stability of various signals propagating through the conductive members formed inside the insertion holes450a-1to450a-pand450b-1to450b-pand the substrate coupling terminals451a-1to451a-pand451b-1to451b-pis improved. In other words, by using the PBT resin as the holding member460of the connector CN2, the reliability of the signals propagating through the conductive members formed inside the insertion holes450a-1to450a-pand450b-1to450b-pand the substrate coupling terminals451a-1to451a-pand451b-1to451b-pis improved.

The connector CN2configured as described above is a so-called pin socket having 2p (the same number as that of the insertion pins410a-1to410a-pand410b-1to410b-pincluded in the connector CN1) insertion holes450a-1to450a-pand450b-1to450b-pprovided corresponding to the insertion pins410a-1to410a-pand410b-1to410b-pincluded in the connector CN1. The connector CN2is provided on the head substrate35such that the P2 direction, the Q2 direction, and the R2 direction illustrated inFIGS.17to19are respectively directions along each of the X direction, the Y direction, and the Z direction illustrated inFIGS.11to13.

Returning toFIGS.11to13, regarding the connector CN1provided on the aggregate substrate33and the connector CN2provided on the head substrate35, the connector CN1is positioned on the +Z side and the connector CN2is positioned on the −Z side along the Z direction. Then, the insertion pins410a-1to410a-pand410b-1to410b-pof the connector CN1are inserted into the insertion holes450a-1to450a-pand450b-1to450b-pof the connector CN2such that the connector CN1and the connector CN2are electrically coupled to each other. As a result, the aggregate substrate33provided with the connector CN1and the head substrate35provided with the connector CN2are electrically coupled to each other.

Specifically, the insertion pin410a-1included in the connector CN1is inserted into the insertion hole450a-1included in the connector CN2. Accordingly, the insertion pin410a-1and the conductive member formed inside the insertion hole450a-1are electrically coupled to each other. Therefore, the substrate coupling terminal411a-1that is electrically coupled to the insertion pin410a-1is electrically coupled to the substrate coupling terminal451a-1that is electrically coupled to the conductive member formed inside the insertion hole450a-1. As a result, the aggregate substrate33electrically coupled via the substrate coupling terminal411a-1and the head substrate35electrically coupled via the substrate coupling terminal451a-1are electrically coupled to each other.

Similarly, the insertion pin410a-iincluded in the connector CN1is inserted into the insertion hole450a-iincluded in the connector CN2. Accordingly, the insertion pin410a-iand the conductive member formed inside the insertion hole450a-iare electrically coupled to each other. Therefore, the substrate coupling terminal411a-ithat is electrically coupled to the insertion pin410a-iis electrically coupled to the substrate coupling terminal451a-ithat is electrically coupled to the conductive member formed inside the insertion hole450a-i. As a result, the aggregate substrate33electrically coupled via the substrate coupling terminal411a-iand the head substrate35electrically coupled via the substrate coupling terminal451a-iare electrically coupled to each other.

Further, the insertion pin410b-iincluded in the connector CN1is inserted into the insertion hole450b-iincluded in the connector CN2. Accordingly, the insertion pin410b-iand the conductive member formed inside the insertion hole450b-iare electrically coupled to each other. Therefore, the substrate coupling terminal411b-ithat is electrically coupled to the insertion pin410b-iis electrically coupled to the substrate coupling terminal451b-ithat is electrically coupled to the conductive member formed inside the insertion hole450b-i. As a result, the aggregate substrate33electrically coupled via the substrate coupling terminal411b-iand the head substrate35electrically coupled via the substrate coupling terminal451b-iare electrically coupled to each other.

Here, the connectors CN1and CN2that electrically couple the head substrate35and the aggregate substrate33to each other are examples of a first coupling member, and the insertion pin410b-iincluded in the connector CN1is an example of a first conductive section.

Next, a propagation path through which various signals propagate in the aggregate substrate33and the head substrate35, which are electrically coupled to each other, as described above will be described. Various signals including the driving signals COMA, COMB, and COMC and the data signal DATA output by the control unit10propagate through a cable (not illustrated) coupled to the connector330included in the aggregate substrate33and are supplied to the aggregate substrate33.

Among the driving signals COMA, COMB, and COMC and the data signal DATA input to the aggregate substrate33, the data signal DATA propagates through the aggregate substrate33and is input to the restoration circuit220provided on the aggregate substrate33. The restoration circuit220generates and outputs the plurality of clock signals SCK, the plurality of print data signals SI, and the plurality of latch signals LAT corresponding to the plurality of discharge modules23by restoring the input data signal DATA. The aggregate substrate33propagates the clock signal SCK, the print data signal SI, and the latch signal LAT, which are generated by the restoration circuit220, and the driving signals COMA, COMB, and COMC input via the connector330, to the head substrate35.

The aggregate substrate33and the head substrate35are electrically coupled to each other by connectors CN1and CN2and the cable FC. Specifically, the connector CN1is fitted to the connector CN2which is electrically coupled to the surface33bof the aggregate substrate33and is electrically coupled to the surface35aof the head substrate35such that the aggregate substrate33and the head substrate35are electrically coupled to each other. The cable FC is electrically coupled to the surface33aof the aggregate substrate33at one end and is electrically coupled to the surface35aof the head substrate35at the other end such that the aggregate substrate33and the head substrate35are electrically coupled to each other. In other words, the connectors CN1and CN2and the cable FC are electrically coupled to each other on different surfaces of the aggregate substrate33.

A large number of signals are included in the clock signal SCK, the print data signal SI, and the latch signal LAT, which are propagated through the aggregate substrate33, and the driving signals COMA, COMB, and COMC. Therefore, the voltage values of the clock signal SCK, the print data signal SI, and the latch signal LAT, which are propagated through multiple signal lines, are smaller than those of the driving signals COMA, COMB, and COMC, and thus, the amount of current generated when propagating is also small. The clock signal SCK, the print data signal SI, and the latch signal LAT, which have a small amount of current and are propagated through multiple signal lines, are propagated from the aggregate substrate33to the head substrate35through the cable FC in which the wiring pattern is formed at high density. In other words, the clock signal SCK, the print data signal SI, and the latch signal LAT, which have a small maximum current value, propagate from the aggregate substrate33to the head substrate35through the wiring pattern included in the cable FC.

Further, the driving signals COMA and COMB, in which a voltage value is large and thus a large current can be generated, are propagated from the aggregate substrate33to the head substrate35through the insertion pins410a-1to410a-pand410b-1to410b-pin which the cross-sectional area of the propagation path is larger than that of the plurality of wiring patterns included in the cable FC. In other words, the maximum value of the current flowing through the insertion pins410a-1to410a-pand410b-1to410b-pis larger than the maximum value of the current flowing through the plurality of wiring patterns included in the cable FC.

Specifically, the driving signal COMA in which a large current can be generated is propagated from the aggregate substrate33to the head substrate35through any of the insertion pins410a-1to410a-pand410b-1to410b-pincluded in the connector CN1, and the driving signal COMB in which a large current can be generated is propagated from the aggregate substrate33to the head substrate35through the insertion pins410a-1to410a-pand410b-1to410b-pwhich are different from the insertion pins410a-1to410a-pand410b-1to410b-pto which the driving signal COMA propagates among the insertion pins410a-1to410a-pand410b-1to410b-pincluded in the connector CN1.

Here, since the driving signal COMC supplied to the aggregate substrate33drives the piezoelectric element60such that the ink is not discharged from the discharge section600, the voltage amplitude is small compared to the driving signals COMA and COMB for driving the piezoelectric element60such that the ink is discharged from the discharge section600. Therefore, the amount of current generated when the driving signal COMC is propagated is smaller than the amount of current generated when the driving signals COMA and COMB are propagated. It is preferable that the driving signal COMC having such a small amount of current be propagated by the wiring pattern included in the cable FC. In other words, among the driving signals COMA, COMB, and COMC output by the driving circuit unit50, it is preferable that the driving signals COMA and COMB having a large amount of current generated when propagating propagate through the insertion pins410a-1to410a-pand410b-1to410b-phaving a large cross-sectional area, and do not propagate by the wiring pattern included in the cable FC having a small cross-sectional area, and the driving signal COMC having a small amount of current generated when propagating propagate by the wiring pattern included in the cable FC having a small cross-sectional area, and do not propagate through the insertion pins410a-1to410a-pand410b-1to410b-phaving a large cross-sectional area.

Since the insertion pins410a-1to410a-pand410b-1to410b-phave a large cross-sectional area, when a signal having a small amount of current propagates using the insertion pins410a-1to410a-pand410b-1to410b-p, there is a concern that the specifications become excessive. As a result, there is a concern that the miniaturization of the connectors CN1and CN2and the miniaturization of the head module21is hindered. Therefore, by propagating the driving signal COMC having a small amount of current by the wiring pattern included in the cable FC having a small cross-sectional area, the concern that the connectors CN1and CN2become large is reduced, and as a result, the head module21can be miniaturized.

Here, whether the driving signal COMC propagates by the wiring pattern included in the cable FC having a small cross-sectional area or propagates through the insertion pins410a-1to410a-pand410b-1to410b-phaving a large cross-sectional area may be appropriately changed depending on the amount of current generated when the driving signal COMC is propagated. Specifically, when the number of discharge sections600included in the discharge module23is a predetermined number or more, it is estimated that the amount of current generated when the driving signal COMC is propagated increases. In such a case, when the driving signal COMC is propagated by the wiring pattern included in the cable FC having a small cross-sectional area, it becomes necessary to propagate the driving signal COMC by using many wiring patterns included in the cable FC, and as a result, the cable FC becomes large. Therefore, when the number of discharge sections600included in the discharge module23is a predetermined number or more, it is preferable that the driving signal COMC be propagated by the insertion pins410a-1to410a-pand410b-1to410b-phaving a large cross-sectional area.

Meanwhile, when the number of discharge sections600included in the discharge module23is less than a predetermined number, it is estimated that the amount of current generated when the driving signal COMC is propagated decreases. In such a case, when the driving signal COMC propagates through the insertion pins410a-1to410a-pand410b-1to410b-phaving a large cross-sectional area, there is a concern that the specifications become excessive. Therefore, when the number of discharge sections600included in the discharge module23is less than a predetermined number, it is preferable that the driving signal COMC be propagated by the wiring pattern included in the cable FC having a small cross-sectional area.

Then, the clock signal SCK, the print data signal SI, and the latch signal LAT, which are propagated to the head substrate35through the connectors CN1and CN2and the cable FC, and the driving signals COMA, COMB, and COMC are input to each of the plurality of discharge modules23through the wiring member388after being branched so as to correspond to the plurality of discharge modules23, on the head substrate35. Then, the driving signal selection control circuit200mounted on the wiring member388by COF generates the driving signal VOUT corresponding to the plurality of discharge sections600, and the generated driving signal VOUT is supplied to the piezoelectric element60included in the corresponding discharge section600. Accordingly, the piezoelectric element60is driven, and the ink having an amount that corresponds to the drive of the piezoelectric element60is discharged from the nozzle N.

Here, the aggregate substrate33is an example of a second substrate, the surface33bof the aggregate substrate33is an example of a first surface, and the surface33aof the aggregate substrate33is an example of a second surface.

5. Operational Effect

In recent years, in the liquid discharge apparatus1, there is an increasing demand for a high image formation speed, which is the speed at which a desired image is formed on the medium P. As one method for achieving a high image formation speed, as illustrated inFIG.3or the like of the present embodiment, a method is considered in which the driving circuit unit50included in the control unit10simultaneously transfers the driving signal COMA having only the trapezoidal waveform Adp for discharging a large amount of ink and the driving signal COMB having only the trapezoidal waveform Bdp for discharging a small amount of ink to the head module21, and switches whether to supply the driving signal COMA to the piezoelectric element60or the driving signal COMB to the piezoelectric element60in the cycle T in the discharge module23included in the head module21to control the dot size formed on the medium P. Accordingly, compared to a method for forming the dots on the medium P by selecting the trapezoidal waveform supplied to the piezoelectric element from the driving signal having the plurality of trapezoidal waveforms in order as described in JP-A-2016-179586, and discharging the ink in plural times based on the selected trapezoidal waveform, it become possible to shorten the time required for propagating the trapezoidal waveform, and as a result, the cycle T regulated by the driving signal can be shortened, and it is possible to achieve a high image formation speed in the liquid discharge apparatus1.

However, when achieving a high image formation speed by using the method of simultaneously transferring the driving signal COMA having only the trapezoidal waveform Adp for discharging a large amount of ink and the driving signal COMB having only the trapezoidal waveform Bdp for discharging a small amount of ink, to the head module21, the driving signal COMA preferably drives the piezoelectric element60such that a large amount of ink can be discharged with a small trapezoidal waveform Adp, and the driving signal COMB preferably drives the piezoelectric element60such that a small amount of ink can be discharged with a small trapezoidal waveform Bdp. Therefore, it becomes necessary to increase the voltage values of the trapezoidal waveforms Adp and Bdp, and as a result, the amount of current generated when the trapezoidal waveforms Adp and Bdp are propagated also increases.

With the increase in the amount of current generated when the trapezoidal waveforms Adp and Bdp are propagated, it is required that the driving signals COMA and COMB having the trapezoidal waveforms Adp and Bdp propagate through the propagation path having a sufficient cross-sectional area in terms of current density. In particular, in the coupling member that couples the substrates to each other in the head module21, unlike the wiring pattern formed on the substrate, it is difficult to individually form the cross-sectional area corresponding to the amount of current of the propagated signal. Therefore, the driving signals COMA and COMB having a large amount of current may be propagated through a plurality of propagation paths from the viewpoint of ensuring a sufficient cross-sectional area, and as a result, there is a problem that the coupling member that couples the substrates to each other large becomes large in the head module21.

In response to such a problem, in the liquid discharge apparatus1of the present embodiment, the head module21includes the cable FC including the wiring pattern for electrically coupling the aggregate substrate33and the head substrate35to each other, and the connectors CN1and CN2that electrically couple the aggregate substrate33to the head substrate35to each other and have the insertion pins410a-1to410a-pand410b-1to410b-phaving a larger cross-sectional area than that of the wiring pattern included in the cable FC. In other words, in the head module21, the aggregate substrate33and the head substrate35are electrically coupled to each other by a plurality of coupling methods having different cross-sectional areas of the conductive sections through which signals propagate. Accordingly, the voltage value of the signal propagating between the aggregate substrate33and the head substrate35or the current value generated when the signal propagates can be selected corresponding to the cross-sectional area of the propagation path through which the signal propagates. Accordingly, when the current value generated when the signal propagates between the aggregate substrate33and the head substrate35is small, the signal propagates with a plurality of wiring patterns included in the cable FC having a small cross-sectional area, and thus the number of wiring patterns included in the cable FC significantly increases, and the concern that the cable FC becomes large can be reduced. Therefore, the amount of current generated by the driving signal increases due to the increase in the image formation speed, and the concern that the head unit becomes large due to the increase in the amount of current can be reduced.

Further, in the liquid discharge apparatus1of the present embodiment, the head module21propagates the driving signals COMA and COMB having a large voltage value through the insertion pins410a-1to410a-pand410b-1to410b-phaving a large cross-sectional area, and propagates the clock signal SCK, the print data signal SI, and the latch signal LAT, which have a small voltage value, by the wiring pattern included in the cable FC. The liquid discharge apparatus1has thousands of discharge sections600, and therefore, the clock signal SCK, the print data signal SI, and the latch signal LAT contain a large amount of information. By propagating the clock signal SCK, the print data signal SI, and the latch signal LAT containing such a large amount of information by the wiring pattern included in the cable FC capable of forming a high-density wiring pattern, it becomes possible to propagate the clock signal SCK, the print data signal SI, and the latch signal LAT in parallel without increasing the size of the cable FC, and a higher image formation speed becomes possible.

Above, the embodiments have been described, but the present disclosure is not limited to the embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the above-described embodiments can also be appropriately combined with each other.

The present disclosure includes substantially the same configurations (for example, configurations having the same functions, methods, and results, or configurations having the same objects and effects) as the configurations described in the embodiments. Further, the present disclosure includes configurations in which non-essential parts of the configuration described in the embodiments are replaced. In addition, the present disclosure includes configurations that achieve the same operational effects or configurations that can achieve the same objects as those of the configurations described in the embodiment. Further, the present disclosure includes configurations in which a known technology is added to the configurations described in the embodiments.

The following contents are derived from the above-described embodiments.

According to an aspect, there is provided a head unit including: a discharge section that includes a piezoelectric element driven by a first driving signal and discharges a liquid in response to drive of the piezoelectric element; a switching circuit that switches whether or not to supply the first driving signal to the piezoelectric element based on a discharge control signal; a first substrate that propagates the first driving signal and the discharge control signal to the switching circuit; a second substrate to which the first driving signal and the discharge control signal are supplied and which propagates the first driving signal and the discharge control signal to the first substrate; a first coupling member including a first conductive section that electrically couples the first substrate and the second substrate to each other; and a second coupling member including a second conductive section that electrically couples the first substrate and the second substrate to each other, in which a cross-sectional area of the first conductive section is larger than a cross-sectional area of the second conductive section.

According to this head unit, the first coupling member including the first conductive section that electrically couples the first substrate and the second substrate to each other, and the second coupling member including the second conductive section that electrically couples the first substrate and the second substrate to each other are provided, and the cross-sectional area of the first conductive section is larger than the cross-sectional area of the second conductive section. In other words, in the head unit, the first substrate and the second substrate are electrically coupled to each other by a plurality of methods for coupling the conductive sections having different cross-sectional areas to each other. Accordingly, corresponding to the voltage value of the signal propagating between the first substrate and the second substrate or the current value generated when the signal propagates, it becomes possible to select the propagation path through which the signal propagates corresponding to the cross-sectional area. Accordingly, when the current value generated when the signal propagates between the first substrate and the second substrate is large, by propagating the signal by using a plurality of second conductive sections having a small cross-sectional area, the concern that the second coupling section including the second conductive section becomes large can be reduced. Accordingly, even when the amount of current generated by the driving signal increases due to the increase in the image formation speed, the concern that the head unit becomes large due to the increase in the amount of current can be reduced.

In the head unit according to the aspect, the first driving signal may be propagated from the second substrate to the first substrate through the first conductive section, and the discharge control signal may be propagated from the second substrate to the first substrate through the second conductive section.

According to this head unit, by propagating the first driving signal having a large voltage value from the second substrate to the first substrate through the first conductive section having a large cross-sectional area, the size of the second conductive section included in the second coupling section does not significantly increase, and accordingly, the concern that the second coupling section including the second conductive section becomes large is reduced. Furthermore, by propagating the discharge control signal having a small voltage value from the second substrate to the first substrate through the second conductive section having a small cross-sectional area, the concern that the first coupling section including the first conductive section becomes large due to excessive specifications caused by propagation of the discharge control signal having a small voltage from the second substrate to the first substrate through the first conductive section having a large cross-sectional area, is reduced. Accordingly, the concern that the head unit becomes large is further reduced.

In the head unit according to the aspect, a maximum value of a current flowing through the first conductive section may be larger than a maximum value of a current flowing through the second conductive section.

According to this head unit, by propagating the signal having a large current value to the first conductive section having a large cross-sectional area, and by propagating the signal having a small current value to the second conductive section having a small cross-sectional area, the size of the second conductive section included in the second coupling section does not significantly increase. Accordingly, the concern that the second coupling section including the second conductive section becomes large is reduced, and thus, the concern that the first coupling section including the first conductive section due to excessive specifications becomes large is also reduced. Accordingly, the concern that the head unit becomes large is further reduced.

In the head unit according to the aspect, a second driving signal for driving the piezoelectric element may be supplied to the second substrate such that the liquid is not discharged from the discharge section.

In the head unit according to the aspect, the first driving signal may propagate through the first conductive section and may not propagate through the second conductive section, and the second driving signal may propagate through the second conductive section and may not propagate through the first conductive section.

In the head unit according to the aspect, the first coupling member may be coupled to a first surface of the second substrate, and the second coupling member may be coupled to a second surface different from the first surface of the second substrate.

According to this head unit, as the second substrate is positioned between the first coupling member and the second coupling member, the concern that the signal that propagates from the second substrate to the first substrate through the first coupling member and the signal that propagates from the second substrate to the first substrate through the second coupling member interfere with each other is reduced. Accordingly, the stability of the operation of the head unit is improved.

According to another aspect, there is provided a liquid discharge apparatus including: a driving circuit unit having a first driving signal output circuit that outputs a first driving signal; a discharge control unit that outputs a discharge control signal; and a head unit that discharges a liquid based on the first driving signal and the discharge control signal, in which the head unit includes a discharge section that includes a piezoelectric element driven by the first driving signal and discharges the liquid in response to drive of the piezoelectric element, a switching circuit that switches whether or not to supply the first driving signal to the piezoelectric element based on the discharge control signal, a first substrate that propagates the first driving signal and the discharge control signal to the switching circuit, a second substrate to which the first driving signal and the discharge control signal are supplied and which propagates the first driving signal and the discharge control signal to the first substrate, a first coupling member including a first conductive section that electrically couples the first substrate and the second substrate to each other, and a second coupling member including a second conductive section that electrically couples the first substrate and the second substrate to each other, and a cross-sectional area of the first conductive section is larger than a cross-sectional area of the second conductive section.

According to this liquid discharge apparatus, the head unit includes the first coupling member including the first conductive section that electrically couples the first substrate and the second substrate to each other, and the second coupling member including the second conductive section that electrically couples the first substrate and the second substrate to each other are provided, and the cross-sectional area of the first conductive section is larger than the cross-sectional area of the second conductive section. In other words, in the head unit, the first substrate and the second substrate are electrically coupled to each other by a plurality of methods for coupling the conductive sections having different cross-sectional areas to each other. Accordingly, corresponding to the voltage value of the signal propagating between the first substrate and the second substrate or the current value generated when the signal propagates, it becomes possible to select the propagation path through which the signal propagates corresponding to the cross-sectional area. Accordingly, when the current value generated when the signal propagates between the first substrate and the second substrate is large, by propagating the signal by using a plurality of second conductive sections having a small cross-sectional area, the concern that the second coupling section including the second conductive section becomes large can be reduced. Accordingly, even when the amount of current generated by the driving signal increases due to the increase in the image formation speed, the concern that the head unit becomes large due to the increase in the amount of current can be reduced.

In the liquid discharge apparatus according to the aspect, the first driving signal may be propagated from the second substrate to the first substrate through the first conductive section, and the discharge control signal may be propagated from the second substrate to the first substrate through the second conductive section.

According to this liquid discharge apparatus, by propagating the first driving signal having a large voltage value from the second substrate to the first substrate through the first conductive section having a large cross-sectional area, the size of the second conductive section included in the second coupling section does not significantly increase, and accordingly, the concern that the second coupling section including the second conductive section becomes large is reduced. Furthermore, by propagating the discharge control signal having a small voltage value from the second substrate to the first substrate through the second conductive section having a small cross-sectional area, the concern that the first coupling section including the first conductive section becomes large due to excessive specifications caused by propagation of the discharge control signal having a small voltage from the second substrate to the first substrate through the first conductive section having a large cross-sectional area, is reduced. Accordingly, the concern that the head unit becomes large is further reduced.

In the liquid discharge apparatus according to the aspect, a maximum value of a current flowing through the first conductive section may be larger than a maximum value of a current flowing through the second conductive section.

According to this liquid discharge apparatus, by propagating the signal having a large current value to the first conductive section having a large cross-sectional area, and by propagating the signal having a small current value to the second conductive section having a small cross-sectional area, the size of the second conductive section included in the second coupling section does not significantly increase. Accordingly, the concern that the second coupling section including the second conductive section becomes large is reduced, and thus, the concern that the first coupling section including the first conductive section due to excessive specifications becomes large is also reduced. Accordingly, the concern that the head unit becomes large is further reduced.

In the liquid discharge apparatus according to the aspect, the driving circuit unit may have a second driving signal output circuit that outputs a second driving signal for driving the piezoelectric element such that the liquid is not discharged from the discharge section, and the second driving signal may be supplied to the second substrate.

In the liquid discharge apparatus according to the aspect, the first driving signal may propagate through the first conductive section and may not propagate through the second conductive section, and the second driving signal may propagate through the second conductive section and may not propagate through the first conductive section.

In the liquid discharge apparatus according to the aspect, the first driving signal output circuit and the second driving signal output circuit may have the same circuit configuration.

According to this liquid discharge apparatus, in the driving circuit unit, by making the first driving signal output circuit and the second driving signal output circuit have the same circuit configuration, the circuit layout in the driving circuit unit becomes easy.

In the liquid discharge apparatus according to the aspect, the first coupling member may be coupled to a first surface of the second substrate, and the second coupling member may be coupled to a second surface different from the first surface of the second substrate.

According to this liquid discharge apparatus, as the second substrate is positioned between the first coupling member and the second coupling member, the concern that the signal that propagates from the second substrate to the first substrate through the first coupling member and the signal that propagates from the second substrate to the first substrate through the second coupling member interfere with each other is reduced. Accordingly, the stability of the operation of the head unit is improved.

In the liquid discharge apparatus according to the aspect, a plurality of the head units may further be provided, and the plurality of the head units may be provided side by side along a direction intersecting a transport direction in which a medium to which a liquid is discharged is transported.