Liquid spraying device

Abstract

The present invention provides a liquid ejection device, which comprises: an ejection part, which ejects liquid by being driven by a first piezoelectric element and a second piezoelectric element; a path switching circuit, which has a first input part to which a drive signal is input, a second input part to which a constant voltage signal is input, a first output part to output a drive signal, a second output part to output a drive signal or a constant voltage signal, a first switch connected to the second input part and the second output part, and a second switch connected to the first output part and the second output part; a switch control circuit, which controls the first switch and the second switch, and in a first mode in which the drive signal is output from the second output part, the switch control circuit controls the first switch to a non-conducting state and controls the second switch to a conducting state, and in a second mode in which a constant voltage signal is output from the second output part, the switch control circuit controls the first switch to a conducting state and controls the second switch to a non-conducting state.

Description

Technical Field

[0001] The present invention relates to a liquid ejecting device. Background Art

[0002] Among liquid ejection devices that eject liquid onto a medium, there is known a structure that drives a driving element based on a driving signal to change the internal pressure of a cavity filled with liquid, and utilizes this change in internal pressure to eject the liquid. Furthermore, among such liquid ejection devices that eject liquid by changing the internal pressure of the cavity through the driving of a driving element, there is known a liquid ejection device that, for example, ejects a high-viscosity liquid or has a function of circulating liquid supplied to an ejection head, includes a plurality of driving elements corresponding to a single nozzle ejecting liquid for the purpose of stable liquid ejection, and ejects the liquid by driving the plurality of driving elements.

[0003] For example, Patent Document 1 discloses a liquid ejecting device including a plurality of driving elements corresponding to one nozzle that ejects liquid.

[0004] However, the liquid ejection device described in Patent Document 1 still has room for improvement in terms of stable ink ejection and reduction in power consumption.

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2021-119042 Summary of the Invention

[0006] One embodiment of the liquid ejection device according to the present invention includes:

[0007] a discharge portion including a first piezoelectric element and a second piezoelectric element, and discharging liquid by driving at least one of the first piezoelectric element and the second piezoelectric element;

[0008] a drive signal output circuit that outputs a drive signal for driving at least one of the first piezoelectric element and the second piezoelectric element;

[0009] A constant voltage signal output circuit, which outputs a constant voltage signal with a constant voltage value;

[0010] a path switching circuit comprising a first input portion to which the drive signal is input, a second input portion to which the constant voltage signal is input, a first output portion to output the drive signal, a second output portion to output the drive signal or the constant voltage signal, a first switch having one end connected to the second input portion and the other end connected to the second output portion, and a second switch having one end connected to the first output portion and the other end connected to the second output portion;

[0011] a first wiring electrically connecting the first output portion and the first piezoelectric element;

[0012] a second wiring electrically connecting the second output portion and the second piezoelectric element;

[0013] a switch control circuit, which controls the first switch and the second switch,

[0014] In a first mode in which the drive signal is output from the second output unit, the switch control circuit controls the first switch to a non-conductive state and controls the second switch to a conductive state.

[0015] In a second mode in which the constant voltage signal is output from the second output section, the switch control circuit controls the first switch to be in a conducting state and controls the second switch to be in a non-conducting state. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A diagram showing the schematic structure of a liquid ejecting device.

[0017] Figure 2 A diagram showing the functional structure of a liquid ejecting device.

[0018] Figure 3 This is an exploded perspective view of the liquid ejection head.

[0019] Figure 4 for Figure 3 Cross-sectional view along line AA.

[0020] Figure 5 : is a diagram showing an example of the waveform of the driving signal COM.

[0021] Figure 6 1 is a diagram showing an example of the data structure of the discharge control signal DI.

[0022] Figure 7 A diagram showing the structure of a drive signal selection circuit.

[0023] Figure 8 A diagram showing an example of the decoding content of the decoder DC_S.

[0024] Figure 9 A diagram showing an example of the decoding content of the decoder DCa.

[0025] Figure 10 A diagram showing an example of a path switching circuit.

[0026] Figure 11 A diagram showing an example of the configuration of a selection circuit.

[0027] Figure 12 This is a diagram showing an example of the relationship between the drive signals VOUTa and VOUTb, the print data SId, and the output selection data SOd. DETAILED DESCRIPTION

[0028] Below, preferred embodiments of the present invention are described in detail using the accompanying drawings. The accompanying drawings are used for ease of explanation. Furthermore, the embodiments described below are not intended to unduly limit the scope of the present invention as set forth in the claims. Furthermore, not all of the structures described below are necessarily essential components of the present invention.

[0029] 1. Overview of Liquid Dispensing Device

[0030] Figure 1 This figure schematically illustrates the structure of a liquid ejection device 1. The liquid ejection device 1 in this embodiment is a serial printing inkjet printer that forms a desired image on a medium P by reciprocating a carriage 21 equipped with a liquid ejection head 22 that ejects ink, an example of a liquid. The liquid ejection head 22 ejects ink onto a transported medium P, thereby forming a desired image on the medium P. In the following description, the carriage 21 moves in the X direction, the medium P is transported in the Y direction, and the ink is ejected in the Z direction. While the X, Y, and Z directions are described as being orthogonal to each other, the various components of the liquid ejection device 1 are not limited to being arranged so as to be orthogonal.

[0031] Here, in the following description, the direction along the X direction in which the carriage 21 carrying the liquid ejecting head 22 reciprocates may be referred to as the main scanning direction, the direction along the Y direction in which the medium P is transported may be referred to as the transport direction, and the direction along the Z direction in which the liquid ejecting head 22 ejects ink may be referred to as the ejection direction. Furthermore, in the following description, the starting point side of an arrow indicating the X direction may be referred to as the -X side, and the tip side may be referred to as the +X side. The starting point side of an arrow indicating the Y direction may be referred to as the -Y side, and the tip side may be referred to as the +Y side. Furthermore, the starting point side of an arrow indicating the Z direction may be referred to as the -Z side, and the tip side may be referred to as the +Z side.

[0032] like Figure 1 As shown, the liquid ejecting apparatus 1 includes an ink container 2 , a control unit 10 , a head unit 20 , a moving unit 30 , a transport unit 40 , and a circulation mechanism 90 .

[0033] The ink container 2 stores a plurality of types of ink to be ejected onto the medium P. Examples of the colors of the ink stored in the ink container 2 include black, cyan, magenta, yellow, red, and gray. Examples of the ink container 2 storing such ink include ink cartridges, bag-shaped ink packs formed of flexible films, and refillable ink tanks.

[0034] The circulation mechanism 90 supplies ink stored in the ink container 2 to the liquid ejection head 22 based on the control signal CTR1 output by the control unit 10. Furthermore, the circulation mechanism 90 recovers ink stored in the discharge flow path of the liquid ejection head 22 based on the control signal CTR1 output by the control unit 10. In other words, the circulation mechanism 90 refluxes the ink within the liquid ejection device 1.

[0035] The control unit 10 includes, for example, a processing circuit such as a CPU (Central Processing Unit) or an FPGA (Field Programmable Gate Array) and a storage circuit such as a semiconductor memory, and controls each element of the liquid ejection device 1 .

[0036] The head unit 20 includes a carriage 21 and a liquid ejection head 22. The liquid ejection head 22 is mounted on the carriage 21. Furthermore, the carriage 21 is fixed to an endless belt 32 included in a moving unit 30, described later. The liquid ejection head 22 receives input from the control unit 10: an ejection data signal DATA for controlling ink ejection; a drive signal COM for driving the liquid ejection head 22 to eject ink; and a constant voltage signal VCNT having a constant voltage value. Based on the ejection data signal DATA and the drive signal COM, the liquid ejection head 22 ejects ink supplied from the ink container 2 via the circulation mechanism 90 onto the medium P.

[0037] The moving unit 30 includes a carriage motor 31 and an endless belt 32. The carriage motor 31 operates based on a control signal CTR2 input from the control unit 10. The endless belt 32 rotates in accordance with the operation of the carriage motor 31. As a result, the carriage 21, which is fixed to the endless belt 32, reciprocates in the X direction.

[0038] The transport unit 40 includes a transport motor 41 and transport rollers 42. The transport motor 41 operates based on a control signal CTR3 input from the control unit 10. The transport rollers 42 rotate in accordance with the operation of the transport motor 41. The medium P is transported in the Y direction as the transport rollers 42 rotate.

[0039] As described above, the liquid ejection device 1 ejects ink from the liquid ejection head 22 mounted on the slide 21 in conjunction with the transport of the medium P achieved by the transport unit 40 and the reciprocating movement of the slide 21 achieved by the moving unit 30, so that the ink is ejected at any position on the surface of the medium P, thereby forming a desired image on the medium P.

[0040] Figure 2 1 is a diagram showing the functional structure of the liquid ejection device 1. Figure 2 As shown, the liquid ejecting apparatus 1 includes a control unit 10 and a head unit 20. The control unit 10 and the head unit 20 are electrically connected via a slidable cable 190 such as a flexible flat cable.

[0041] The control unit 10 includes a control circuit 100 , a drive signal output circuit 50 , and a constant voltage signal output circuit 52 .

[0042] The control circuit 100 receives input of an image information signal IMG, which is output from an external device such as a host computer and contains information about an image to be formed on the medium P. Furthermore, based on the image information signal IMG, the control circuit 100 outputs a discharge control signal DI, a latch signal LAT, a switching signal CH, and a clock signal SCK to the head unit 20 as a discharge data signal DATA for controlling various components of the liquid discharge device 1.

[0043] Specifically, the control circuit 100 generates a control signal CTR1 and outputs it to the circulation mechanism 90. Based on the input control signal CTR1, the circulation mechanism 90 supplies ink stored in the ink container 2 to the liquid ejection head 22 and recovers ink stored in the discharge flow path of the liquid ejection head 22. Furthermore, the control circuit 100 generates a control signal CTR2 and outputs it to the carriage motor 31. This drives the carriage motor 31. Furthermore, the control circuit 100 generates a control signal CTR3 and outputs it to the transport motor 41. This controls the reciprocating movement of the carriage 21 in the X direction and the transport of the medium P in the Y direction. Furthermore, the control signals CTR1, CTR2, and CTR3 can also be input to the corresponding components via a driver circuit (not shown).

[0044] Furthermore, the control circuit 100 generates a base drive signal dA and outputs it to the drive signal output circuit 50. The drive signal output circuit 50 generates a drive signal COM based on the input base drive signal dA and outputs it to the head unit 20. Specifically, the drive signal output circuit 50 performs digital-to-analog conversion on the input base drive signal dA and performs D-class amplification on the converted analog signal to generate the drive signal COM and output it to the head unit 20.

[0045] Furthermore, the constant voltage signal output circuit 52 included in the control unit 10 generates a constant voltage signal VCNT having a constant voltage value based on the commercial voltage supplied to the liquid ejection device 1 or various power supply voltages used within the liquid ejection device 1, and outputs the constant voltage signal VCNT to the head unit 20. The constant voltage signal output circuit 52 may be an AC-DC converter that converts the commercial voltage supplied to the liquid ejection device 1 into a DC voltage, or a DC-DC converter that converts various power supply voltages used within the liquid ejection device 1 into a DC voltage.

[0046] The head unit 20 includes a plurality of liquid ejecting heads 22. Each of the plurality of liquid ejecting heads 22 includes a drive signal selection circuit 200 and a plurality of ejecting portions 600.

[0047] The drive signal selection circuit 200 receives inputs from the ejection control signal DI, latch signal LAT, exchange signal CH, and clock signal SCK output by the control circuit 100, the drive signal COM output by the drive signal output circuit 50, and the constant voltage signal VCNT output by the constant voltage signal output circuit 52. The drive signal selection circuit 200 switches whether to supply the drive signal COM to the ejection unit 600 and whether to supply the constant voltage signal VCNT to the ejection unit 600 based on the input ejection control signal DI, latch signal LAT, exchange signal CH, and clock signal SCK.

[0048] Each of the plurality of ejection units 600 includes a piezoelectric element 60a and a piezoelectric element 60b. One end of the piezoelectric element 60a is supplied with a drive signal VOUTa, which is generated by the drive signal selection circuit 200 based on whether the ejection unit 600 is supplied with the drive signal COM and the constant voltage signal VCNT. Furthermore, one end of the piezoelectric element 60b is supplied with a drive signal VOUTb, which is generated by the drive signal selection circuit 200 based on whether the ejection unit 600 is supplied with the drive signal COM and the constant voltage signal VCNT. Furthermore, the other ends of the piezoelectric elements 60a and 60b are commonly supplied with a reference voltage signal VBS.

[0049] The piezoelectric element 60a is driven based on the potential difference between a drive signal VOUTa supplied to one end thereof and a reference voltage signal VBS supplied to the other end thereof, while the piezoelectric element 60b is driven based on the potential difference between a drive signal VOUTb supplied to one end thereof and a reference voltage signal VBS supplied to the other end thereof. The reference voltage signal VBS supplied to the other ends of the piezoelectric elements 60a and 60b is a DC voltage signal that serves as a reference for driving the piezoelectric elements 60a and 60b. For example, it can be a constant potential signal such as DC 5.5V or DC 6V, or it can be a signal at ground potential.

[0050] Then, by driving the piezoelectric elements 60a and 60b, ink is ejected from the corresponding ejection portion 600. The ink ejected from the ejection portion 600 lands on the medium P, whereby characters and images are formed on the medium P.

[0051] As described above, the liquid ejection device 1 of this embodiment includes: an ejection portion 600, which includes a piezoelectric element 60a and a piezoelectric element 60b, and ejects ink by driving at least one of the piezoelectric element 60a and the piezoelectric element 60b; a drive signal output circuit 50, whose output becomes a drive signal COM based on the drive signal VOUTa for driving the piezoelectric element 60a and the drive signal VOUTb for driving the piezoelectric element 60b; a constant voltage signal output circuit 52, which outputs a constant voltage signal VCNT with a constant voltage value.

[0052] 2. Structure of the liquid ejection head

[0053] Next, the structure of the liquid ejection head 22 provided with the drive signal selection circuit 200 will be described. Figure 3 It is an exploded perspective view of the liquid ejection head 22. Figure 4 for Figure 3 Cross-sectional view along line AA.

[0054] like Figure 3 as well as Figure 4 As shown, the liquid ejection head 22 includes a nozzle substrate 360 , compliance sheets 361 and 362 , a communication plate 302 , a pressure chamber substrate 303 , a vibration plate 304 , a storage chamber forming substrate 305 , and a wiring substrate 308 .

[0055] The nozzle substrate 360 is a plate-shaped component that is elongated in the Y direction and extends approximately parallel to the XY plane. M nozzles N are formed on the nozzle substrate 360. The nozzles N are through-holes provided in the nozzle substrate 360. Furthermore, the M nozzles N are arranged side by side along the Y direction on the nozzle substrate 360. In the following description, the row of nozzles N arranged side by side along the Y direction may be referred to as nozzle row Ln. Here, "approximately parallel" includes not only completely parallel but also situations that can be considered parallel after accounting for errors.

[0056] The communication plate 302 is located at the -Z side of the nozzle substrate 360. The communication plate 302 is a plate-shaped member that is elongated in the Y direction and extends substantially parallel to the XY plane, and has an ink flow path formed therein.

[0057] Specifically, a supply flow channel RA1 and a discharge flow channel RA2 are formed in the connecting plate 302. The supply flow channel RA1 is located on the +X side of the connecting plate 302 and extends along the Y direction. The discharge flow channel RA2 is located on the -X side of the connecting plate 302 and extends along the Y direction.

[0058] In addition, on the connecting plate 302, there are formed M connecting flow channels RK1 corresponding one-to-one to the M nozzles N, M connecting flow channels RK2 corresponding one-to-one to the M nozzles N, M connecting flow channels RR1 corresponding one-to-one to the M nozzles N, M connecting flow channels RR2 corresponding one-to-one to the M nozzles N, and M nozzle flow channels RN corresponding one-to-one to the M nozzles N.

[0059] The M connecting flow channels RK1 are arranged in parallel along the Y direction on the -X side of the supply flow channel RA1. The M connecting flow channels RR1 are arranged in parallel along the Y direction on the -X side of the M connecting flow channels RK1 arranged in parallel along the Y direction. In addition, the M connecting flow channels RK2 are arranged in parallel along the Y direction on the +X side of the discharge flow channel RA2 and on the -X side of the M connecting flow channels RR1 arranged in parallel along the Y direction. The M connecting flow channels RR2 are arranged in parallel along the Y direction on the +X side of the M connecting flow channels RK2 arranged in parallel along the Y direction and on the -X side of the M connecting flow channels RR1 arranged in parallel along the Y direction. The nozzle flow channel NR connects the connecting flow channel RR1 and the connecting flow channel RR2 corresponding to the common nozzle N. Moreover, when observing the connecting plate 302 from the Z direction, the corresponding nozzle N is located approximately in the center of the nozzle flow channel NR in the X direction. Here, “approximately the center” includes not only the case where it is strictly the center but also the case where it can be regarded as the center by taking errors into account.

[0060] The pressure chamber substrate 303 is located on the -Z side of the communication plate 302. The pressure chamber substrate 303 is a plate-shaped member that is elongated in the Y-axis direction and extends substantially parallel to the XY plane, and has an ink flow path formed thereon.

[0061] Specifically, on the pressure chamber substrate 303, M pressure chambers CB1, corresponding one-to-one to the M nozzles N, and M pressure chambers CB2, corresponding one-to-one to the M nozzles N, are arranged along the Y-axis direction. Furthermore, the pressure chambers CB1 communicate with the connecting flow channel RK1 and the communication flow channel RR1 corresponding to the common nozzle N. Specifically, when viewed from the Z direction, the pressure chambers CB1 communicate with the connecting flow channel RK1 at the +X side of the pressure chamber CB1 and with the communication flow channel RR1 at the -X side. This allows the connecting flow channel RK1 and the communication flow channel RR1 corresponding to the common nozzle N to communicate. Furthermore, the pressure chambers CB2 communicate with the connecting flow channel RK2 and the communication flow channel RR2 corresponding to the common nozzle N. In detail, the pressure chamber CB2 connects the connecting flow channel RK2 and the connecting flow channel RR2 corresponding to the common nozzle N by connecting the end of the pressure chamber CB2 on the -X side and the connecting flow channel RK2 when viewed from the Z direction, and connecting the end of the pressure chamber CB2 on the +X side and the connecting flow channel RR2.

[0062] The vibration plate 304 is located on the -Z side of the pressure chamber substrate 303. The vibration plate 304 is a plate-shaped member that is elongated in the Y direction and extends substantially parallel to the XY plane, and is a member that can elastically vibrate.

[0063] On the -Z side of the vibration plate 304, M piezoelectric elements 60a, corresponding one-to-one to the M pressure chambers CB1 among the plurality of piezoelectric elements 60 included in the liquid ejection head 22, and M piezoelectric elements 60b, corresponding one-to-one to the M pressure chambers CB2 among the plurality of piezoelectric elements 60 included in the liquid ejection head 22, are arranged side by side along the Y direction. In other words, 2M piezoelectric elements 60 are arranged side by side in two rows on the -Z side of the vibration plate 304.

[0064] Piezoelectric element 60a is driven by changes in the potential of the supplied drive signal VOUTa, while piezoelectric element 60b is driven by changes in the potential of the supplied drive signal VOUTb. Furthermore, vibration plate 304 displaces in conjunction with the driving of piezoelectric elements 60a and 60b. As a result, the internal pressures of pressure chambers CB1 and CB2 change. Furthermore, this change in internal pressure causes the ink filling pressure chambers CB1 and CB2 to be ejected from nozzle N via connecting flow passages RR1 and RR2 and nozzle flow passage RN.

[0065] The wiring substrate 308 is connected to the surface on the -Z side of the vibration plate 304. The wiring substrate 308 transmits various signals including the ejection data signal DATA and the drive signal COM to the inside of the liquid ejection head 22. As such a wiring substrate 308, for example, a flexible structure such as a flexible wiring substrate (FPC: Flexible Printed Circuit) can be used. In addition, an integrated circuit 201 is mounted on the wiring substrate 308 in a COF (Chip On Film) manner. The drive signal selection circuit 200 described above is mounted on the integrated circuit 201. That is, the wiring substrate 308 transmits various signals including the ejection data signal DATA and the drive signal COM to the integrated circuit 201, and transmits the drive signals VOUTa and VOUTb output by the drive signal selection circuit 200 included in the integrated circuit 201 to the corresponding piezoelectric elements 60a and 60b.

[0066] The reservoir forming substrate 305 is located at the -Z side of the communicating plate 302. The reservoir forming substrate 5 is a member that is long and narrow in the Y direction, and has an ink flow path formed thereon.

[0067] Specifically, the reservoir forming substrate 305 is formed with a supply channel RB1 and a discharge channel RB2. The supply channel RB1 communicates with the supply channel RA1. The discharge channel RB2 communicates with the discharge channel RA2. Furthermore, the reservoir forming substrate 305 is provided with an inlet 351 communicating with the supply channel RB1 and a discharge channel 352 communicating with the discharge channel RB2. Ink is supplied from the ink container 2 to the inlet 351. Thus, ink is supplied from the ink container 2 to the supply channel RB1 via the inlet 351. Furthermore, ink stored in the discharge channel RB2 is recovered via the discharge channel 352. Ink recovered from the discharge channel 352 returns to the ink container 2. Furthermore, an opening 350 is formed in the reservoir forming substrate 305. Inside the opening 350, the pressure chamber substrate 303, the vibration plate 304, and the wiring substrate 308 are provided.

[0068] In the liquid ejection head 22 configured as described above, ink supplied from the ink container 2 to the inlet 351 flows through the supply flow path RB1 into the supply flow path RA1. The ink flowing into the supply flow path RA1 then branches off in the connecting flow path RK1 for each nozzle N and flows into the pressure chamber CB1. A portion of the ink flowing into the pressure chamber CB1 flows through the connecting flow path RR1, the nozzle flow path RN, and the connecting flow path RR2 into the pressure chamber CB2. Furthermore, a portion of the ink flowing into the pressure chamber CB2 flows through the connecting flow path RK2, the discharge flow path RA2, and the discharge flow path RB2, and is discharged from the discharge port 352.

[0069] When the piezoelectric element 60a is driven by the drive signal VOUTa, a portion of the ink filling the interior of the pressure chamber CB1 is ejected from the nozzle N via the communication flow path RR1 and the nozzle flow path RN. Furthermore, when the piezoelectric element 60b is driven by the drive signal VOUTb, a portion of the ink filling the interior of the pressure chamber CB2 is ejected from the nozzle N via the communication flow path RR2 and the nozzle flow path RN.

[0070] The plastic sheet 361 is located on the +Z side of the connecting plate 302 and seals the supply channel RA1 and the connecting channel RK1 formed on the connecting plate 302. The plastic sheet 361 is formed of an elastic material and absorbs pressure fluctuations of the ink generated in the supply channel RA1 and the connecting channel RK1. Furthermore, the plastic sheet 362 is located on the +Z side of the connecting plate 302 and seals the discharge channel RA2 and the connecting channel RK2 formed on the connecting plate 302. The plastic sheet 362 is formed of an elastic material and absorbs pressure fluctuations of the ink generated in the discharge channel RA2 and the connecting channel RK2.

[0071] As described above, the liquid ejection head 22 of the liquid ejection device 1 according to this embodiment includes a pressure chamber CB1, a pressure chamber CB2, and a nozzle N. The pressure chamber CB1 changes its internal pressure when the piezoelectric element 60a is driven, and the pressure chamber CB2 changes its internal pressure when the piezoelectric element 60b is driven. The nozzle N communicates with the pressure chambers CB1 and CB2 and ejects ink. The changes in the internal pressure of the pressure chamber CB1 caused by the driving of the piezoelectric element 60a and the changes in the internal pressure of the pressure chamber CB2 caused by the driving of the piezoelectric element 60b cause the ink filled in the pressure chambers CB1 and CB2 to be ejected from the nozzles N. This improves the driving capability compared to a case where a single piezoelectric element 60 is used to eject ink from a single pressure chamber, and achieves stable ejection characteristics even when using ink with high viscosity.

[0072] Here, the structure including the piezoelectric elements 60a and 60b, the pressure chambers CB1 and CB2, the communication channels RR1 and RR2, and the nozzle N corresponds to the discharge unit 600 that discharges ink by driving at least one of the piezoelectric elements 60a and 60b.

[0073] 3. An example of a driving signal waveform

[0074] Here, an example of the waveform of the drive signal COM output by the drive signal output circuit 50 will be described. Figure 5 FIG. 1 is a diagram showing an example of the waveform of the driving signal COM. Figure 5 As shown, the drive signal COM includes a signal waveform that is a continuous combination of a trapezoidal waveform Adp1, which is arranged in the period T1 from the rise of the latch signal LAT to the rise of the switching signal CH, and a trapezoidal waveform Adp2, which is arranged in the subsequent period T2 until the rise of the latch signal LAT. In other words, the drive signal output circuit 50 outputs the drive signal COM, which is a signal waveform that is a continuous combination of the trapezoidal waveform Adp1 and the trapezoidal waveform Adp2, for each period Ta specified by the latch signal LAT. In other words, the latch signal LAT corresponds to the starting point of the period Ta of the drive signal COM.

[0075] The trapezoidal waveform Adp1 includes a period during which voltage Vc is constant, a period following the period during which voltage Vc is constant and voltage Vb, which is lower than voltage Vc, is constant, a period following the period during which voltage Vb, which is higher than voltage Vc, is constant, and a period following the period during which voltage Vt is constant. That is, the drive signal COM includes a trapezoidal waveform Adp whose voltage value starts at voltage Vc, changes to voltages Vb and Vt, and then ends at voltage Vc.

[0076] Here, the voltage Vc functions as a reference potential that serves as a reference for the displacement of the piezoelectric element 60. When the voltage Vc is supplied to the piezoelectric elements 60a and 60b, the piezoelectric elements 60a and 60b are maintained at a certain displacement. Furthermore, by changing the voltage value of the trapezoidal waveform Adp1 supplied to the piezoelectric elements 60a and 60b from the voltage Vc to the voltage Vb, the piezoelectric elements 60a and 60b are displaced. Figure 4 The pressure chamber CB1 and the pressure chamber CB2 are bent upward. As a result, the internal volume of the pressure chamber CB1 and the pressure chamber CB2 is expanded. Therefore, the ink is drawn into the pressure chamber CB1 and the pressure chamber CB2. Thereafter, by changing the voltage value of the trapezoidal waveform Adp1 supplied to the piezoelectric elements 60a and 60b from the voltage Vb to the voltage Vt, the piezoelectric elements 60a and 60b are moved to the Figure 4 The lower portion shown in FIG. 1 is bent. As a result, the internal volumes of pressure chambers CB1 and CB2 decrease. Consequently, the ink stored in pressure chambers CB1 and CB2 is ejected from nozzles N. In other words, trapezoidal waveform Adp1 is the signal waveform for ejecting ink from ejection unit 600.

[0077] The trapezoidal waveform Adp2 is a signal waveform with a smaller voltage amplitude than the trapezoidal waveform Adp1. It is used to vibrate the ink near the nozzle N by driving the piezoelectric elements 60a and 60b to such an extent that the ink is prevented from being ejected from the ejection unit 600. This reduces the likelihood of an increase in the viscosity of the ink near the nozzle N, thereby stabilizing the ink ejection characteristics from the ejection unit 600. In other words, the trapezoidal waveform Adp2 is a signal waveform used to prevent ink from being ejected from the ejection unit 600. In the following description, the trapezoidal waveform Adp2 may be referred to as a microvibration waveform, and the action of driving the piezoelectric elements 60a and 60b to such an extent that the ink near the nozzle N is vibrated when the trapezoidal waveform Adp2 is supplied is referred to as microvibration.

[0078] As described above, the driving signal COM includes, within the period Ta, a trapezoidal waveform Adp1 for causing ink to be ejected from the ejection portion 600, and a trapezoidal waveform Adp2 for reducing the increase in ink viscosity near the nozzle N without causing ink to be ejected from the ejection portion 600. The signal waveform included in the driving signal COM is not limited to this; various signal waveforms may be used depending on the viscosity of the ejected ink, the transport speed of the medium P, the movement speed of the carriage 21, and the like.

[0079] 4. Structure and Operation of the Drive Signal Selection Circuit

[0080] Next, the structure and operation of the drive signal selection circuit 200 will be described. The drive signal selection circuit 200 receives inputs from the control circuit 100: the ejection control signal DI, latch signal LAT, exchange signal CH, and clock signal SCK; the drive signal COM from the drive signal output circuit 50; and the constant voltage signal VCNT from the constant voltage signal output circuit 52. Based on the input ejection control signal DI, latch signal LAT, exchange signal CH, and clock signal SCK, the drive signal selection circuit 200 switches between supplying the drive signal COM to the ejection unit 600 and supplying the constant voltage signal VCNT to the ejection unit 600.

[0081] When describing the configuration of the drive signal selection circuit 200 , first, the data structure of the discharge control signal DI input to the drive signal selection circuit 200 will be described. Figure 6 FIG. 1 is a diagram showing an example of the data structure of the ejection control signal DI. Figure 6 As shown, the ejection control signal DI includes a printing data signal SI and an output selection control signal SO following the printing data signal SI.

[0082] The print data signal SI includes 1-bit print data SId corresponding to each of the M ejection units 600 included in the liquid ejection head 22 and used to select whether to eject ink from the corresponding ejection unit 600. In other words, the print data signal SI is a total of M bits that controls the ejection of ink from the M ejection units 600.

[0083] The output selection control signal SO includes 1-bit output selection data SOd for selecting whether to supply the drive signal VOUTb obtained based on the drive signal COM or the drive signal VOUTb obtained based on the constant voltage signal VCNT to the piezoelectric element 60b included in each of the M ejection units 600. In other words, the output selection control signal SO is a 1-bit signal common to each of the M ejection units 600.

[0084] As described above, the ejection control signal DI in this embodiment is a signal consisting of a total of M+1 bits, including the M-bit print data signal SI and the 1-bit output selection control signal SO. This M+1-bit ejection control signal DI is input to the drive signal selection circuit 200 in synchronization with the clock signal SCK.

[0085] The print data signal SI included in the ejection control signal DI is not limited to M bits. For example, when the liquid ejection head 22 forms dots on the medium P, including four grayscales that are not ejected, the print data SId included in the print data signal SI may include 2 bits of information to represent these four grayscales. In this case, the print data signal SI becomes a 2M-bit signal totaling 2M bits that controls the ejection of ink from the M ejection units 600.

[0086] Furthermore, the output selection control signal SO included in the discharge control signal DI is not limited to a single bit. For example, in the liquid discharge head 22, when selecting whether to supply the drive signal VOUTb derived from the drive signal COM or the drive signal VOUTb derived from the constant voltage signal VCNT to the piezoelectric element 60b of each of the M discharge units 600 during periods T1 and T2, respectively, as defined by the latch signal LAT and the exchange signal CH, the output selection control signal SO may include a single bit of information selecting whether to supply the drive signal VOUTb derived from the drive signal COM or the drive signal VOUTb derived from the constant voltage signal VCNT during period T1, and a single bit of information selecting whether to supply the drive signal VOUTb derived from the drive signal COM or the drive signal VOUTb derived from the constant voltage signal VCNT during period T2. In this case, the output selection control signal SO becomes a two-bit signal.

[0087] In addition, the ejection control signal DI may include, in addition to the print data signal SI and the output selection control signal SO, information indicating the driving conditions of the piezoelectric elements 60a and 60b, such as a signal that specifies the waveform selection in the decoder DC described later.

[0088] Next, the configuration and operation of the drive signal selection circuit 200 will be described. Figure 7 is a diagram showing the structure of the drive signal selection circuit 200. In the following description, when distinguishing between the M ejection units 600, they may be referred to as ejection units 600[1] to 600[M]. In this case, the piezoelectric element 60a of the ejection unit 600[i] (i is any one of 1 to M) may be referred to as the piezoelectric element 60a[i], and the piezoelectric element 60b of the ejection unit 600[i] may be referred to as the piezoelectric element 60b[i]. Furthermore, the print data SId corresponding to the ejection unit 600[i] within the print data SId corresponding to the M ejection units 600 included in the print data signal SI may be referred to as the print data SId[i].

[0089] like Figure 7 As shown, the drive signal selection circuit 200 includes a selection control circuit 210, a path switching circuit 230, and selection circuits TGa[1] to TGa[M] and TGb[1] to TGb[M]. In the following description, when there is no need to distinguish between the selection circuits TGa[1] to TGa[M], they may be referred to simply as the selection circuit TGa, and when there is no need to distinguish between the selection circuits TGb[1] to TGb[M], they may be referred to simply as the selection circuit TGb. Furthermore, when there is no need to distinguish between the selection circuits TGa and TGb, they may be referred to simply as the selection circuit TG.

[0090] The selection control circuit 210 includes a shift register 220, latch circuits LTa_S, LTb_S, LTa[1] to LTa[M], LTb[1] to LTb[M], and decoders DC_S, DCa[1] to DCa[M], and DCb[1] to DCb[M]. In the following description, when there is no need to distinguish between latch circuits LTa[1] to LTa[M], they may be referred to simply as latch circuit LTa, and when there is no need to distinguish between latch circuits LTb[1] to LTb[M], they may be referred to simply as latch circuit LTb. Also, when there is no need to distinguish between latch circuits LTa and LTb, they may be referred to simply as latch circuit LT. Similarly, when there is no need to distinguish between decoders DCa[1] to DCa[M], they may be referred to simply as decoder DCa, and when there is no need to distinguish between decoders DCb[1] to DCb[M], they may be referred to simply as decoder DCb. Furthermore, when there is no need to distinguish between the decoder DCa and the decoder DCb, they may be simply referred to as the decoder DC.

[0091] The shift register 220 includes a first shift register 221 and a second shift register 222 .

[0092] The first shift register 221 receives the ejection control signal DI and the clock signal SCK, whose logic levels are inverted by an inverter. Furthermore, the first shift register 221 includes registers RGa_S and RGa[1] to RGa[M]. In the first shift register 221, the registers RGa_S, RGa[1] to RGa[M] are connected in series in the order of registers RGa_S, RGa[1], RGa[2], ..., RGa[M], from the upstream side of the input ejection control signal DI toward the downstream side.

[0093] The first shift register 221 configured as described above forwards the input ejection control signal DI in the order of registers RGa_S, RGa[1], RGa[2], ..., RGa[M] at the falling edge of the clock signal SCK. Furthermore, by completing the input of the ejection control signal DI to the first shift register 221 and stopping the supply of the clock signal SCK, the output selection data SOd is retained in register RGa_S, and the corresponding print data SId[1] to SId[M] are retained in registers RGa[1] to RGa[M], respectively.

[0094] The second shift register 222 receives the ejection control signal DI and the clock signal SCK. Furthermore, the second shift register 222 includes registers RGb_S and RGb[1] to RGb[M]. In the second shift register 222, the registers RGb_S, RGb[1] to RGb[M] are connected in series in the order of registers RGb_S, RGb[1], RGb[2], ..., RGb[M], from the upstream side of the input ejection control signal DI toward the downstream side.

[0095] The second shift register 222 configured as described above forwards the ejection control signal DI inputted to the registers RGb_S, RGb[1], RGb[2], ..., RGb[M] in the order of the rising edge of the clock signal SCK. Furthermore, by completing the input of the ejection control signal DI to the second shift register 222 and stopping the supply of the clock signal SCK, the output selection data SOd is retained in the register RGb_S, and the corresponding print data SId[1] to SId[M] are retained in the registers RGb[1] to RGb[M], respectively.

[0096] Latch circuit LTa_S is configured to correspond to register RGa_S. At the rising edge of latch signal LAT, latch circuit LTa_S latches output selection data Sod held by register RGa_S as latch data LtaS. Furthermore, latch circuit LTb_S is configured to correspond to register RGb_S. At the rising edge of latch signal LAT, latch circuit LTb_S latches output selection data SOd held by register RGb_S as latch data LtbS.

[0097] The latch data LtaS latched by the latch circuit LTa_S and the latch data LtbS latched by the latch circuit LTb_S are input to the decoder DC_S. Furthermore, the decoder DC_S receives inputs of the latch signal LAT and the exchange signal CH. Furthermore, during periods T1 and T2 defined by the latch signal LAT and the exchange signal CH, the decoder DC_S generates a selection signal Sc having a logic level defined by the latch data LtaS and the latch data LtbS, respectively, and outputs the selected signal Sc from the selection control circuit 210.

[0098] Figure 8 FIG. 1 is a diagram showing an example of the decoding content of the decoder DC_S. Figure 8 As shown, when the decoder DC is input with latch data LtaS=1 and latch data LtbS=1, it generates an H-level selection signal Sc during both periods T1 and T2, and outputs it from the selection control circuit 210. When the decoder DC is input with latch data LtaS=0 and latch data LtbS=0, it generates an L-level selection signal Sc during both periods T1 and T2, and outputs it from the selection control circuit 210.

[0099] Here, when latch circuit LTa_S latches the information held by register RGa_S as latch data LtaS, and latch circuit LTb_S latches the information held by register RGb_S as latch data LtbS, output select data SOd is held in registers RGa_S and RGb_S. Given this, the logic level of latch data LtaS latched by latch circuit LTa_S and the logic level of latch data LtbS latched by latch circuit LTb_S are equal. Therefore, when decoder DC_S receives inputs of latch data LtaS = 0 and latch data LtbS = 1, or when decoder DC_S receives inputs of latch data LtaS = 1 and latch data LtbS = 0, decoder DC_S can determine that the input latch data LtaS or latch data LtbS is not normal, and thus maintains the output at the most recent logic level without changing the logic level of the output select signal Sc.

[0100] Back to Figure 7, latch circuits LTa[1]~LTa[M] are provided in a manner corresponding to registers RGa[1]~RGa[M]. Moreover, latch circuits LTa[1]~LTa[M] latch the printing data SId[1]~SId[M] held by registers RGa[1]~RGa[M] as latch data Lta[1]~LTa[M] at the rising edge of latch signal LAT. Specifically, latch circuit LTa[1] latches the printing data SId[1] held by register RGa[1] as latch data Lta[1] at the rising edge of latch signal LAT, and latch circuit LTa[i] latches the printing data SId[i] held by register RGa[i] as latch data Lta[i] at the rising edge of latch signal LAT. In the following description, latch data Lta[1] to LTa[M] may be referred to as latch data Lta when it is not necessary to distinguish between them. Specifically, the description assumes that latch circuit LTa latches print data SId held by register RGa as latch data Lta at the rising edge of latch signal LAT.

[0101] Similarly, latch circuits LTb[1] to LTb[M] are provided in a manner corresponding to registers RGb[1] to RGb[M]. Furthermore, latch circuits LTb[1] to LTb[M] latch the print data SId[1] to SId[M] held by registers RGb[1] to RGb[M] as latch data Ltb[1] to LTb[M] at the rising edge of latch signal LAT. Specifically, latch circuit LTb[1] latches the print data SId[1] held by register RGb[1] as latch data Ltb[1] at the rising edge of latch signal LAT, and latch circuit LTb[i] latches the print data SIb[i] held by register RGb[i] as latch data Ltb[i] at the rising edge of latch signal LAT. In the following description, latch data Ltb[1] to LTb[M] may be referred to as latch data Ltb unless they need to be distinguished. Specifically, latch circuit LTb latches print data SId held by register RGb as latch data Ltb at the rising edge of latch signal LAT.

[0102] The latch data Lta[1]-LTa[M] latched by the latch circuits LTa[1]-LTa[M] are input to the corresponding decoders DCa[1]-DCa[M]. Furthermore, the decoders DCa[1]-DCa[M] are also input with the latch signal LAT and the exchange signal CH. Furthermore, during the periods T1 and T2 specified by the latch signal LAT and the exchange signal CH, the decoders DCa[1]-DCa[M] generate the selection signal S of the logic level specified by the latch data Lta[1]-LTa[M], and output it from the selection control circuit 210.

[0103] Similarly, the latch data Ltb[1]-LTb[M] latched by the latch circuits LTb[1]-LTb[M] are input to the corresponding decoders DCb[1]-DCb[M]. Furthermore, the latch signal LAT and the exchange signal CH are also input to the decoders DCb[1]-DCb[M]. Furthermore, during the periods T1 and T2 specified by the latch signal LAT and the exchange signal CH, the decoders DCb[1]-DCb[M] generate the selection signal S of the logic level specified by the latch data Ltb[1]-LTb[M], and output it from the selection control circuit 210.

[0104] Figure 9 This is a diagram showing an example of the decoding content of decoders DCa[1]~DCa[M]. In addition, the same is true for decoders DCb[1]~DCb[M]. Therefore, in Figure 9 In the decoder, the decoding contents of the decoders DCa[1] to DCa[M] are described, while the description of the decoders DCb[1] to DCb[M] is omitted, and the structure corresponding to a part of the decoders DCb[1] to DCb[M] is recorded in the form of brackets. Figure 9 middle.

[0105] like Figure 9 As shown, when the latch data Lta=0 is input, the decoder DCa generates a selection signal S that is at an L level during a period T1 and at an H level during a period T2, and outputs the selection signal from the selection control circuit 210. Furthermore, when the latch data Lta=1 is input, the decoder DC generates a selection signal S that is at an H level during a period T1 and at an L level during a period T2, and outputs the selection signal from the selection control circuit 210.

[0106] Here, when latch circuit LTa[i] latches the information held by register RGa[i] as latch data Lta[i], and latch circuit LTb[i] latches the information held by register RGb[i] as latch data Ltb[i], registers RGa[i] and RGb[i] hold print data SId[i] included in print data signal SI. That is, the logic level of latch data Lta[i] latched by latch circuit LTa[i] and the logic level of latch data Ltb[i] latched by latch circuit LTb[i] are equal. Therefore, the logic level of select signal S output by decoder DCa[i] and the logic level of select signal S output by decoder DCb[i] are equal. In other words, decoder DCa[i] and decoder DCb[i] corresponding to ejection unit 600[i] output select signal S of the same logic level.

[0107] As described above, the selection control circuit 210 generates a selection signal Sc and 2M selection signals S corresponding to the piezoelectric elements 60a and 60b of the M ejection parts 600 based on the ejection control signal DI, latch signal LAT, exchange signal CH and clock signal SCK output by the control circuit 100, and outputs them.

[0108] The selection signal Sc output by the selection control circuit 210 is input to the path switching circuit 230. Furthermore, the drive signal COM is input to the input portion In1 of the path switching circuit 230, and the constant voltage signal VCNT is input to the input portion In2. The path switching circuit 230 selects either the drive signal COM or the constant voltage signal VCNT based on the logic level of the selection signal Sc, and outputs the selected signal as the voltage signal V1 from the output portion Out1 and as the voltage signal V2 from the output portion Out2.

[0109] Figure 10 FIG. 2 is a diagram showing an example of the path switching circuit 230. Figure 10 As shown, the path switching circuit 230 includes switches SW1 and SW2. One end of the switch SW1 is connected to the input portion In2, and the other end of the switch SW1 is connected to the output portion Out2. One end of the switch SW2 is connected to the output portion Out1, and the other end of the switch SW2 is connected to the output portion Out2.

[0110] When an H-level selection signal Sc is input to path switching circuit 230, one end and the other end of switch SW1 are controlled to a non-conductive state, while one end and the other end of switch SW2 are controlled to a conductive state. As a result, in path switching circuit 230, input portion In1 and output portion Out1 are controlled to a conductive state, and input portion In1 and output portion Out2 are controlled to a conductive state.

[0111] On the other hand, when an L-level selection signal Sc is input to path switching circuit 230, one end and the other end of switch SW1 are controlled to be conductive, while one end and the other end of switch SW2 are controlled to be non-conductive. As a result, in path switching circuit 230, input portion In1 and output portion Out1 are controlled to be conductive, and input portion In2 and output portion Out2 are controlled to be conductive.

[0112] That is, the path switching circuit 230 includes an input portion In1 to which the drive signal COM is input, an input portion In2 to which the constant voltage signal VCNT is input, an output portion Out1 that outputs the drive signal COM as a voltage signal V1, an output portion Out2 that outputs the drive signal COM or the constant voltage signal VCNT as a voltage signal V2, a switch SW1 having one end connected to the input portion In2 and the other end connected to the output portion Out2, and a switch SW2 having one end connected to the output portion Out1 and the other end connected to the output portion Out2. When the selection signal Sc at an H level is input from the selection control circuit 210, one end and the other end of the switch SW1 are controlled to be in a non-conductive state, and the switch SW2 is closed. One end and the other end are controlled to be in a conductive state, so that the drive signal COM input to the input part In1 is output from the output part Out1 as a voltage signal V1, and the drive signal COM input to the input part In1 is output from the output part Out2 as a voltage signal V2. When an L-level selection signal Sc is input from the selection control circuit 210, one end and the other end of the switch SW1 are controlled to be in a non-conductive state, and one end and the other end of the switch SW2 are controlled to be in a conductive state, so that the drive signal COM input to the input part In1 is output from the output part Out1 as a voltage signal V1, and the constant voltage signal VCNT input to the input part In2 is output from the output part Out2 as a voltage signal V2.

[0113] In other words, in an operation mode where the path switching circuit 230 outputs the drive signal COM from the output portion Out2, the selection control circuit 210 controls the switch SW1 to a non-conducting state and the switch SW2 to a conducting state. In an operation mode where the path switching circuit 230 outputs the constant voltage signal VCNT from the output portion Out2, the selection control circuit 210 controls the switch SW1 to a conducting state and the switch SW2 to a non-conducting state. In other words, the selection control circuit 210 controls both the switch SW1 and the switch SW2. These switches SW1 and SW2 can be formed, for example, from one or more transistors.

[0114] Back to Figure 7 The voltage signal V1 output from the output unit Out1 by the path switching circuit 230 is propagated through the wiring W1 and input to the selection circuits TGa[1] to TGa[M]. In addition, the selection signal S output from the decoders DCa[1] to DCa[M] is also input to the selection circuits TGa[1] to TGa[M]. Moreover, the selection circuits TGa[1] to TGa[M] control whether to supply the voltage signal V1 as the drive signal VOUTa to the piezoelectric element 60a based on the logic level of the selection signal S. That is, the wiring W1 electrically connects the output unit Out1 and the piezoelectric element 60a via the selection circuits TGa[1] to TGa[M].

[0115] Similarly, the voltage signal V2 output from the output unit Out2 of the path switching circuit 230 propagates through the wiring W2 and is input to the selection circuits TGb[1] to TGb[M]. In addition, the selection signal S output by the decoders DCb[1] to DCb[M] is also input to the selection circuits TGb[1] to TGb[M]. Moreover, the selection circuits TGb[1] to TGb[M] control whether to supply the voltage signal V2 as the drive signal VOUTb to the piezoelectric element 60b based on the logic level of the selection signal S. In other words, the wiring W2 electrically connects the output unit Out2 and the piezoelectric element 60a via the selection circuits TGb[1] to TGb[M].

[0116] Here, an example of the configuration of the selection circuit TG will be described. Figure 11 FIG. 1 is a diagram showing an example of the structure of the selection circuit TG. Figure 11 In FIG. 1 , the selection circuit TGa to which the voltage signal V1 is input is illustrated as an example, and the configuration related to the selection circuit TGb to which the voltage signal V2 is input is illustrated with parentheses.

[0117] like Figure 11As shown, the selection circuit TG includes an inverter 232 serving as a NOT circuit and a transmission gate 234. The selection signal S is input to the positive control terminal (not marked with a circle) of the transmission gate 234, is logically inverted by the inverter 232, and is input to the negative control terminal (marked with a circle) of the transmission gate 234. Furthermore, the voltage signal V1 is supplied to the input terminal of the transmission gate 234. Furthermore, the drive signal VOUTa is output from the output terminal of the transmission gate 234.

[0118] Specifically, when the select signal S is at an H level, the connection between the input and output terminals of transmission gate 234 is established, while when the select signal S is at an L level, the connection between the input and output terminals of transmission gate 234 is established. In other words, selection circuit TG switches the connection between the input and output terminals of transmission gate 234 based on the logic level of select signal S, thereby selecting or deselecting the voltage signal V1 supplied to the input terminal of transmission gate 234. Consequently, the drive signal VOUTa generated by selecting or deselecting the voltage signal V1 is output to the output terminal of transmission gate 234.

[0119] As described above, the decoders DCa[i] and DCb[i] corresponding to the ejection units 600[i] output the selection signal S at the same logic level. Therefore, when the selection circuit TGa[i] outputs the voltage signal V1 as the drive signal VOUTa, the selection circuit TGb[i] outputs the voltage signal V2 as the drive signal VOUTa. When the selection circuit TGa[i] does not output the voltage signal V1 as the drive signal VOUTa, the selection circuit TGb[i] does not output the voltage signal V2 as the drive signal VOUTa. In other words, the selection control circuit 210 controls the selection circuits TGa and TGb based on the same print data SId.

[0120] Here, the relationship between the drive signals VOUTa and VOUTb output by the drive signal selection circuit 200, the print data SId of the print data signal SI included in the ejection control signal DI input to the drive signal selection circuit 200, and the output selection data SOd of the output selection control signal SO is described.

[0121] Figure 12 This is a diagram showing an example of the relationship between the drive signals VOUTa and VOUTb, the print data SId, and the output selection data SOd.

[0122] When the ejection control signal DI input to the drive signal selection circuit 200 includes output selection data SOd=1, the path switching circuit 230 outputs the drive signal COM as voltage signals V1 and V2. Therefore, the drive signal COM is supplied as voltage signal V1 to the selection circuit TGa corresponding to the ejection unit 600, and as voltage signal V2 to the selection circuit TGb corresponding to the ejection unit 600.

[0123] At this time, when the ejection control signal DI input to the drive signal selection circuit 200 includes print data SId = 1 corresponding to the ejection unit 600, the selection circuit TGa corresponding to the ejection unit 600 selects the trapezoidal waveform Adp1 during period T1 and does not select the trapezoidal waveform Adp2 during period T2. The selection circuit TGb corresponding to the ejection unit 600 selects the trapezoidal waveform Adp1 during period T1 and does not select the trapezoidal waveform Adp2 during period T2. As a result, the piezoelectric element 60a of the ejection unit 600 is supplied with the drive signal VOUTa including the trapezoidal waveform Adp1 during period Ta, and the piezoelectric element 60b is supplied with the drive signal VOUTb including the trapezoidal waveform Adp1 during period Ta. That is, during period Ta, the piezoelectric elements 60a and 60b of the ejection unit 600 are driven to eject ink from the nozzles N together. Thus, even when the viscosity of the ink stored in the pressure chambers CB1 and CB2 is high, stable ink discharge can be achieved.

[0124] When the ejection control signal DI input to the drive signal selection circuit 200 includes output selection data SOd=1, the path switching circuit 230 outputs the drive signal COM as voltage signals V1 and V2. Therefore, the drive signal COM is supplied as voltage signal V1 to the selection circuit TGa corresponding to the ejection unit 600, and as voltage signal V2 to the selection circuit TGb corresponding to the ejection unit 600.

[0125] At this time, when the ejection control signal DI input to the drive signal selection circuit 200 includes print data SId = 0 corresponding to the ejection unit 600, the selection circuit TGa corresponding to the ejection unit 600 does not select the trapezoidal waveform Adp1 during period T1 and selects the trapezoidal waveform Adp2 during period T2. The selection circuit TGb corresponding to the ejection unit 600 does not select the trapezoidal waveform Adp1 during period T1 and selects the trapezoidal waveform Adp2 during period T2. As a result, the piezoelectric element 60a of the ejection unit 600 is supplied with the drive signal VOUTa including the trapezoidal waveform Adp2 during period Ta, and the piezoelectric element 60b is supplied with the drive signal VOUTb including the trapezoidal waveform Adp2 during period Ta. That is, during period Ta, the piezoelectric elements 60a and 60b of the ejection unit 600 microvibrate. This can reduce the possibility that the viscosity of the ink stored in the pressure chambers CB1 and CB2 increases and the ink adheres near the nozzle N.

[0126] When the ejection control signal DI input to the drive signal selection circuit 200 includes output selection data SOd = 0, the path switching circuit 230 outputs the drive signal COM as the voltage signal V1 and the constant voltage signal VCNT as the voltage signal V2. Therefore, the drive signal COM is supplied as the voltage signal V1 to the selection circuit TGa corresponding to the ejection unit 600, while the constant voltage signal VCNT is supplied as the voltage signal V2 to the selection circuit TGb corresponding to the ejection unit 600.

[0127] At this time, when the ejection control signal DI input to the drive signal selection circuit 200 includes print data SId = 1 corresponding to the ejection unit 600, the selection circuit TGa corresponding to the ejection unit 600 selects the trapezoidal waveform Adp1 during period T1 and does not select the trapezoidal waveform Adp2 during period T2. The selection circuit TGb corresponding to the ejection unit 600 selects the constant voltage signal VCNT during period T1 and does not select the constant voltage signal VCNT during period T2. As a result, the piezoelectric element 60a of the ejection unit 600 is supplied with the drive signal VOUTa including the trapezoidal waveform Adp1 during period Ta, while the piezoelectric element 60b is supplied with the drive signal VOUTb including the constant voltage signal VCNT during period Ta. Specifically, during period Ta, the piezoelectric element 60a of the ejection unit 600 is driven to eject ink from the nozzle N, while the piezoelectric element 60b of the ejection unit 600 is not driven, maintaining a constant displacement. Thus, even when the viscosity of the ink stored in the pressure chambers CB1 and CB2 is softened due to the ambient temperature or the like, stable ink discharge can be achieved.

[0128] When the ejection control signal DI input to the drive signal selection circuit 200 includes output selection data SOd = 0, the path switching circuit 230 outputs the drive signal COM as the voltage signal V1 and the constant voltage signal VCNT as the voltage signal V2. Therefore, the drive signal COM is supplied as the voltage signal V1 to the selection circuit TGa corresponding to the ejection unit 600, while the constant voltage signal VCNT is supplied as the voltage signal V2 to the selection circuit TGb corresponding to the ejection unit 600.

[0129] At this time, when the ejection control signal DI input to the drive signal selection circuit 200 includes print data SId = 0 corresponding to the ejection unit 600, the selection circuit TGa corresponding to the ejection unit 600 does not select the trapezoidal waveform Adp1 during period T1 and selects the trapezoidal waveform Adp2 during period T2. The selection circuit TGb corresponding to the ejection unit 600 does not select the constant voltage signal VCNT during period T1 and selects the constant voltage signal VCNT during period T2. As a result, the piezoelectric element 60a of the ejection unit 600 is supplied with the drive signal VOUTa including the trapezoidal waveform Adp2 during period Ta, while the piezoelectric element 60b is supplied with the drive signal VOUTb including the constant voltage signal VCNT during period Ta. Specifically, during period Ta, the piezoelectric element 60a of the ejection unit 600 microvibrates, while the piezoelectric element 60b maintains a constant displacement and is not driven. Thus, even when the viscosity of the ink stored in the pressure chambers CB1 and CB2 is softened due to the ambient temperature or the like, the possibility of the ink being discharged can be reduced by the microvibration.

[0130] Here, when the selection circuit TGa does not select the voltage signal V1, the voltage value immediately before being supplied to the piezoelectric element 60, specifically, the voltage Vc, is retained in the piezoelectric element 60a by the capacitance component of the piezoelectric element 60a. Furthermore, when the selection circuit TGb does not select the voltage signal V2, the voltage value immediately before being supplied to the piezoelectric element 60, specifically, the voltage Vc, is retained in the piezoelectric element 60b by the capacitance component of the piezoelectric element 60b.

[0131] Therefore, the voltage value of the constant voltage signal VCNT is preferably voltage Vc. Thus, when the operation of the selection circuits TGa and TGb controls whether the constant voltage signal VCNT is supplied to the piezoelectric elements 60a and 60b, the voltage value supplied to the piezoelectric elements 60a and 60b is varied, thereby reducing the possibility of unintended driving of the piezoelectric elements 60a and 60b. Specifically, the voltage value of the constant voltage signal VCNT is preferably equal to voltage Vc, the voltage value of the drive signal COM at the timing of the rising edge of the latch signal LAT, which determines the supply cycle of the drive signal COM to the piezoelectric elements 60a and 60b, which is the timing of the rising edge of the latch signal LAT, which corresponds to the start of the supply cycle of the drive signal COM.

[0132] Therefore, when the path switching circuit 230 outputs the constant voltage signal VCNT as the voltage signal V2, even when the conduction state of the selection circuit TGb is switched, the possibility of the output voltage of the drive signal VOUTb being deformed unexpectedly can be reduced. As a result, the possibility of the piezoelectric element 60b being displaced unexpectedly can be reduced.

[0133] In this liquid ejection device 1, the output selection data SOd included in the output selection control signal SO for switching the operation of the path switching circuit 230 can be selected by the control circuit 100 based on the temperature of the ink detected by the temperature detection circuit not shown in the figure, and output as the output selection control signal SO, or can be selected by the control circuit 100 based on the ejection state of the ink detected by the ejection state detection circuit not shown in the figure, and output as the output selection control signal SO, or can be selected by the user's operation.

[0134] Here, piezoelectric element 60a is an example of a first piezoelectric element, piezoelectric element 60b is an example of a second piezoelectric element, and drive signal COM is an example of a drive signal. Furthermore, considering that drive signals VOUTa and VOUTb are generated by setting the signal waveform of drive signal COM to a selected or non-selected state, drive signals VOUTa and VOUTb are also examples of drive signals. Furthermore, input portion In1 of path switching circuit 230 is an example of a first input portion, input portion In2 is an example of a second input portion, output portion Out1 is an example of a first output portion, output portion Out2 is an example of a second output portion, switch SW1 is an example of a first switch, and switch SW2 is an example of a second switch. Furthermore, selection control circuit 210 is an example of a switch control circuit, wiring W1 is an example of a first wiring, and wiring W2 is an example of a second wiring. The operation mode in which path switching circuit 230 outputs drive signal COM as voltage signal V2 is an example of a first mode, and the operation mode in which path switching circuit 230 outputs constant voltage signal VCNT as voltage signal V2 is an example of a second mode. In addition, the selection circuit TGa is an example of a third switch, the selection circuit TGb is an example of a fourth switch, the printing data SId of the printing data signal SI included in the ejection control signal DI is an example of drive data, the latch signal LAT is an example of a periodic signal, the period Ta specified by the latch signal LAT is an example of a supply period, the control circuit 100 that outputs the latch signal LAT is an example of a periodic control circuit, the pressure chamber CB1 is an example of a first pressure chamber, and the pressure chamber CB2 is an example of a second pressure chamber.

[0135] 4. Effects

[0136] In the liquid ejection device 1 configured as described above, when the selection control circuit 210 controls switch SW1 of the path switching circuit 230 to a non-conductive state and switch SW2 to a conductive state, thereby establishing an operating mode in which the drive signal COM is output from the output unit Out2 of the path switching circuit 230, the piezoelectric element 60a is supplied with the drive signal COM via the selection circuit TGa, and the piezoelectric element 60b is supplied with the drive signal COM via the selection circuit TGb. Consequently, both the piezoelectric elements 60a and 60b are driven by the drive signal COM. As a result, a large driving force can be applied by the ejection unit 600, enabling stable ink ejection even when using ink with a high viscosity. On the other hand, when the selection control circuit 210 controls the switch SW1 of the path switching circuit 230 to the conductive state and the switch SW2 to the non-conductive state, thereby establishing an operating mode in which the output portion Out of the path switching circuit 230 outputs a constant voltage signal VCNT, the piezoelectric element 60a is supplied with the drive signal COM via the selection circuit TGa, and the piezoelectric element 60b is supplied with the constant voltage signal VCNT via the selection circuit TGb. Consequently, the piezoelectric element 60a is driven by the drive signal COM. The piezoelectric element 60b is maintained at a constant displacement by the constant voltage signal VCNT. As a result, the driving force applied to the ejection unit 600 can be reduced, enabling stable ink ejection even when the ink viscosity varies.

[0137] That is, in the liquid ejection device 1 of this embodiment, the power consumption in the ink viscosity adjustment mechanism such as the heater can be reduced, and stable ink ejection can be achieved even in the liquid ejection device 1 using ink with high viscosity and requiring a large driving force.

[0138] Although the embodiments and modifications have been described above, the present invention is not limited to these embodiments, but can be implemented in various forms within the scope of the present invention. For example, the above-described embodiments can be appropriately combined.

[0139] The present invention includes structures that are substantially the same as the structures described in the embodiments (for example, structures with the same functions, methods, and results, or structures with the same purposes and effects). In addition, the present invention includes structures in which non-essential parts of the structures described in the embodiments are replaced. In addition, the present invention includes structures that can have the same effects as the structures described in the embodiments, or structures that can achieve the same purposes. In addition, the present invention includes structures to which known technologies are added to the structures described in the embodiments.

[0140] The following can be derived from the above-mentioned embodiments.

[0141] One embodiment of a liquid ejection device comprises:

[0142] a discharge portion including a first piezoelectric element and a second piezoelectric element, and discharging liquid by driving at least one of the first piezoelectric element and the second piezoelectric element;

[0143] a drive signal output circuit that outputs a drive signal for driving at least one of the first piezoelectric element and the second piezoelectric element;

[0144] A constant voltage signal output circuit, which outputs a constant voltage signal with a constant voltage value;

[0145] a path switching circuit comprising a first input portion to which the drive signal is input, a second input portion to which the constant voltage signal is input, a first output portion to output the drive signal, a second output portion to output the drive signal or the constant voltage signal, a first switch having one end connected to the second input portion and the other end connected to the second output portion, and a second switch having one end connected to the first output portion and the other end connected to the second output portion;

[0146] a first wiring electrically connecting the first output portion and the first piezoelectric element;

[0147] a second wiring electrically connecting the second output portion and the second piezoelectric element;

[0148] a switch control circuit, which controls the first switch and the second switch,

[0149] In a first mode in which the drive signal is output from the second output unit, the switch control circuit controls the first switch to a non-conductive state and controls the second switch to a conductive state.

[0150] In a second mode in which the constant voltage signal is output from the second output section, the switch control circuit controls the first switch to be in a conducting state and controls the second switch to be in a non-conducting state.

[0151] According to the liquid ejection device, by setting it to be in a first mode where a driving signal is output from the second output part, the switch control circuit controls the first switch to a non-conducting state and the second switch to a conducting state, and in a second mode where a constant voltage signal is output from the second output part, the switch control circuit controls the first switch to a conducting state and the second switch to a non-conducting state, the driving state of the first piezoelectric element and the second piezoelectric element can be changed according to the viscosity of the liquid, thereby achieving stable liquid ejection and reduced power consumption.

[0152] In one embodiment of the liquid ejection device, the following embodiment may be adopted, namely,

[0153] The first wiring is electrically connected to the first piezoelectric element via a third switch.

[0154] The second wiring is electrically connected to the second piezoelectric element via a fourth switch.

[0155] The third switch and the fourth switch are controlled by the switch control circuit.

[0156] According to the liquid ejection device, by utilizing a common switch control circuit to control the first switch and the second switch of the supply switching circuit, the third switch for switching the electrical connection between the first output part and the first piezoelectric element, and the fourth switch for switching the electrical connection between the second output part and the second piezoelectric element, the control signals for controlling the first switch, the second switch, the third switch, and the fourth switch can be aggregated into one signal for forwarding.

[0157] In one embodiment of the liquid ejection device, the following embodiment may be adopted, namely,

[0158] The switch control circuit controls the third switch and the fourth switch based on driving data.

[0159] According to this liquid ejection device, by controlling the third switch and the fourth switch based on the same drive data, the amount of drive data for driving the third switch and the fourth switch can be reduced.

[0160] In one embodiment of the liquid ejection device, the following embodiment may be adopted, namely,

[0161] A period control circuit is provided for outputting a period signal that defines a supply period of the drive signal to at least one of the first piezoelectric element and the second piezoelectric element.

[0162] A voltage value of the constant voltage signal is equal to a voltage value of the drive signal at a start point of the supply period of the periodic signal.

[0163] According to this liquid ejection device, the possibility of unintended displacement of the first and second piezoelectric elements when switching from the first mode to the second mode and when switching from the second mode to the first mode can be reduced.

[0164] In one embodiment of the liquid ejection device, the following embodiment may be adopted, namely,

[0165] The ejection part includes a first pressure chamber, a second pressure chamber and a nozzle. The first pressure chamber converts the internal pressure by driving the first piezoelectric element, and the second pressure chamber converts the internal pressure by driving the second piezoelectric element. The nozzle is connected to the first pressure chamber and the second pressure chamber and ejects liquid.

[0166] According to this liquid ejection device, the liquid supplied to the ejection portion can be circulated, and the viscosity of the liquid can be adjusted more finely.

[0167] Explanation of symbols

[0168] 1…Liquid ejecting device; 2…Ink container; 5…Reservoir chamber forming substrate; 10…Control unit; 20…Head unit; 21…Slide; 22…Liquid ejecting head; 30…Moving unit; 31…Slide motor; 32…Endless belt; 40…Conveying unit; 41…Conveying motor; 42…Conveying roller; 50…Drive signal output circuit; 52…Constant voltage signal output circuit; 60, 60a, 60b…Piezoelectric element; 90…Circulation mechanism; 100…Control circuit; 190…Cable; 200…Drive signal selection circuit; 201…Integrated circuit; 210…Selection control circuit; 220…Shift register; 221…First shift register; 222…Second shift register; 230…Path switching circuit; 232…Inverter; 234…Transmission gate; 302…Connecting plate; 303…Pressure chamber substrate; 304…Vibration plate; 305…Reservoir forming Substrate; 308…wiring substrate; 350…opening; 351…inlet; 352…exhaust outlet; 360…nozzle substrate; 361, 362…plastic sheet; 600…ejection portion; CB1, CB2…pressure chamber; DC, DC_S, DCa, DCb…decoder; In1, In2…input portion; LT, LTa, LTa_S, LTb, LTb_S…latch circuit; Ln…nozzle array; N…nozzle; NR…nozzle channel; Out1, Out2…output portion; P…medium; RA1…supply channel; RA2…exhaust channel; RB1…supply channel; RB2…exhaust channel; RGa, RGa_S, RGb, RGb_S…register; RK1, RK2…connection channel; RN…nozzle channel; RR1, RR2…connection channel; SW1, SW2…switch; TG, TGa, TGb…selection circuit.

Claims

1. A liquid ejection device, characterized in that: have: a discharge portion including a first piezoelectric element and a second piezoelectric element, and discharging liquid by driving at least one of the first piezoelectric element and the second piezoelectric element; a drive signal output circuit that outputs a drive signal for driving at least one of the first piezoelectric element and the second piezoelectric element; A constant voltage signal output circuit, which outputs a constant voltage signal with a constant voltage value; a path switching circuit comprising a first input portion to which the drive signal is input, a second input portion to which the constant voltage signal is input, a first output portion to output the drive signal, a second output portion to output the drive signal or the constant voltage signal, a first switch having one end connected to the second input portion and the other end connected to the second output portion, and a second switch having one end connected to the first output portion and the other end connected to the second output portion; a first wiring electrically connecting the first output portion and the first piezoelectric element; a second wiring electrically connecting the second output portion and the second piezoelectric element; a switch control circuit, which controls the first switch and the second switch, In a first mode in which the drive signal is output from the second output unit, the switch control circuit controls the first switch to a non-conductive state and controls the second switch to a conductive state. In a second mode in which the constant voltage signal is output from the second output section, the switch control circuit controls the first switch to be in a conducting state and controls the second switch to be in a non-conducting state.

2. The liquid ejection device according to claim 1, wherein The first wiring is electrically connected to the first piezoelectric element via a third switch. The second wiring is electrically connected to the second piezoelectric element via a fourth switch. The third switch and the fourth switch are controlled by the switch control circuit.

3. The liquid ejection device according to claim 2, wherein: The switch control circuit controls the third switch and the fourth switch based on driving data.

4. The liquid ejection device according to any one of claims 1 to 3, wherein: A period control circuit is provided for outputting a period signal that defines a supply period of the drive signal to at least one of the first piezoelectric element and the second piezoelectric element. A voltage value of the constant voltage signal is equal to a voltage value of the drive signal at a start point of the supply period of the periodic signal.

5. The liquid ejecting device according to claim 1, wherein The ejection part includes a first pressure chamber, a second pressure chamber and a nozzle. The first pressure chamber converts the internal pressure by driving the first piezoelectric element, and the second pressure chamber converts the internal pressure by driving the second piezoelectric element. The nozzle is connected to the first pressure chamber and the second pressure chamber and ejects liquid.

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