Liquid dispensing device

Abstract

To provide a liquid discharge device which can stably discharge an ink and reduce consumption power.SOLUTION: A liquid discharge device comprises: a discharge part which discharges a liquid by drive of a first piezoelectric element and a second piezoelectric element; a route changeover circuit having a first input part to which a driving signal is inputted, a second input part to which a constant voltage signal is inputted, a first output part which outputs the driving signal, a second output part which outputs the driving signal or the 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; and a switch control circuit which controls the first switch and the second switch. In a first mode that the driving signal is outputted from the second output part, the switch control circuit so controls the first switch as to be non-conductive and so controls the second switch as to be conductive. In a second mode that the constant voltage signal is outputted from the second output part, the switch control circuit so controls the first switch as to be conductive and so controls the second switch as to be non-conductive.SELECTED DRAWING: Figure 7

Description

Technical Field

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

Background Art

[0002] In a liquid ejection device that ejects liquid onto a medium, there is known a configuration in which the internal pressure of a cavity filled with liquid is changed by driving a driving element based on a drive signal, and the liquid is ejected by the change in the internal pressure. Further, among liquid ejection devices that eject liquid by changing the internal pressure of a cavity by driving such a driving element, in the case of a liquid ejection device that ejects a highly viscous liquid or a liquid ejection device having a function of circulating the liquid supplied to a discharge head, for the purpose of stable ejection of the liquid, a plurality of driving elements are provided corresponding to one nozzle from which the liquid is ejected, and a liquid ejection device that ejects the liquid by driving the plurality of driving elements is known.

[0003] For example, Patent Document 1 discloses a liquid ejection device provided with a plurality of driving elements corresponding to one nozzle from which liquid is ejected.

Prior Art Documents

Patent Documents

[0004] <(

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the liquid ejection device described in Patent Document 1 had room for improvement from the viewpoints of stable ink ejection and reduction of power consumption.

Means for Solving the Problems

[0006] One aspect of the liquid ejection device according to the present invention is ​A discharge unit comprising a first piezoelectric element and a second piezoelectric element, wherein at least one of the first piezoelectric element and the second piezoelectric element is driven to discharge liquid, A drive signal output circuit that outputs a drive signal to drive at least one of the first piezoelectric element and the second piezoelectric element, A constant voltage output circuit that outputs a constant voltage signal with a constant voltage value, A path switching circuit comprising: a first input unit into which the drive signal is input; a second input unit into which the constant voltage signal is input; a first output unit that outputs the drive signal; a second output unit that outputs the drive signal or the constant voltage signal; a first switch with one end connected to the second input unit and the other end connected to the second output unit; and a second switch with one end connected to the first output unit and the other end connected to the second output unit. A first wiring that electrically connects the first output unit and the first piezoelectric element, A second wiring that electrically connects the second output section and the second piezoelectric element, A switch control circuit that controls the first switch and the second switch, Equipped with, In the first mode in which the drive signal is output from the second output unit, the switch control circuit controls the first switch to be non-conductive and the second switch to be conductive. In the second mode in which the constant voltage signal is output from the second output unit, the switch control circuit controls the first switch to conduct and the second switch to deconduct. [Brief explanation of the drawing]

[0007] [Figure 1] This is a diagram showing the schematic configuration of a liquid dispensing device. [Figure 2] This diagram shows the functional configuration of a liquid dispensing device. [Figure 3] This is a disassembled perspective view of the liquid dispensing head. [Figure 4] Figure 3 is a cross-sectional view of line AA. [Figure 5] This figure shows an example of the waveform of the drive signal COM. [Figure 6] This figure shows an example of the data structure of the discharge control signal DI. [Figure 7] This diagram shows the configuration of the drive signal selection circuit. [Figure 8] This figure shows an example of the decoded contents of decoder DC_S. [Figure 9] This figure shows an example of the decoding content of the decoder DCa. [Figure 10] This is a diagram showing an example of a route switching circuit. [Figure 11] This is a diagram showing an example of a selection circuit configuration. [Figure 12] This figure shows an example of the relationship between the drive signals VOUTa and VOUTb, the print data Sid, and the output selection data SOd. [Modes for carrying out the invention]

[0008] Preferred embodiments of the present invention will be described below with reference to the drawings. The drawings used are for illustrative purposes only. The embodiments described below are not intended to unduly limit the scope of the present invention as described in the claims. Furthermore, not all of the configurations described below are essential components of the present invention.

[0009] 1. Overview of the liquid dispensing device Figure 1 shows a schematic configuration of the liquid ejection device 1. In this embodiment, the liquid ejection device 1 is a serial printing inkjet printer in which a carriage 21 equipped with a liquid ejection head 22 that ejects ink as an example of a liquid moves back and forth, and the liquid ejection head 22 ejects ink onto the transported medium P, thereby forming a desired image on the medium P. In the following description, the direction in which the carriage 21 moves will be described as the X direction, the direction in which the medium P is transported will be described as the Y direction, and the direction in which the ink is ejected will be described as the Z direction. Note that the X, Y, and Z directions will be described as being orthogonal to each other, but this does not mean that the various components of the liquid ejection device 1 are not arranged orthogonally.

[0010] Here, in the following description, the direction along the X direction in which the carriage 21 equipped with the liquid ejection head 22 reciprocates is referred to as the main scanning direction, the direction along the Y direction in which the medium P is conveyed is referred to as the conveyance direction, and the direction along the Z direction in which the liquid ejection head 22 ejects ink may be referred to as the ejection direction. Also, in the following description, the starting point side of the arrow indicating the X direction may be referred to as the -X side, the tip side 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 side 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 side may be referred to as the +Z side.

[0011] As shown in FIG. 1, the liquid ejection device 1 includes an ink container ②, a control unit 10, a head unit 20, a moving unit 30, a conveyance unit 40, and a circulation mechanism 90. [[ID=⑤]] [[ID=⑥]]

[0012] [[ID=⑦]] [[ID=⑧]]A plurality of types of inks to be ejected onto the medium P are stored in the ink container ②. Examples of the colors of the inks stored in the ink container ② include black, cyan, magenta, yellow, red, gray, etc. As the ink container ② in which such inks are stored, an ink cartridge, a bag-shaped ink pack formed of a flexible film, an ink tank capable of replenishing ink, etc. can be used. [[ID=⑨]] [[ID=⑩]]

[0013] [[ID=⑪]] [[ID=⑫]]The circulation mechanism 90 supplies the 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. Also, the circulation mechanism 90 recovers the 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. That is, the circulation mechanism 90 recirculates the ink in the liquid ejection device 1. [[ID=⑬]] [[ID=⑭]]

[0014] [[ID=⑮]] [[ID=⑯]]The control unit 10 includes 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. [[ID=⑰]] [[ID=⑱]]

[0015] [[ID=⑲]] Note: There seems to be some inconsistent numbering in the original text (e.g., ② instead of a proper ID). I've translated it as is while maintaining the integrity of the text. If this is a formatting error in the original, it might need to be corrected for a more accurate translation process in the future.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. The carriage 21 is fixed to an endless belt 32 included in the moving unit 30, which will be described later. The liquid ejection head 22 receives an ejection data signal DATA, which is output by the control unit 10 to control the ejection of ink, a drive signal COM, which drives the liquid ejection head 22 to eject ink, and a constant voltage signal VCNT, which has 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.

[0016] 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. This causes the carriage 21, which is fixed to the endless belt 32, to reciprocate along the X direction.

[0017] 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. As the transport rollers 42 rotate, the medium P is transported along the Y direction.

[0018] As described above, the liquid dispensing device 1 works in conjunction with the transport of the medium P by the transport unit 40 and the reciprocating movement of the carriage 21 by the moving unit 30. Ink is dispensed from the liquid dispensing head 22 mounted on the carriage 21, causing the ink to land at any desired position on the surface of the medium P and forming a desired image on the medium P.

[0019] Figure 2 shows the functional configuration of the liquid dispensing device 1. As shown in Figure 2, the liquid dispensing device 1 comprises a control unit 10 and a head unit 20. The control unit 10 and the head unit 20 are electrically connected by a sliding cable 190, such as a flexible flat cable.

[0020] The control unit 10 includes a control circuit 100, a drive signal output circuit 50, and a constant voltage output circuit 52.

[0021] The control circuit 100 receives an image information signal IMG, which contains image information formed on a medium P output by an external device such as a host computer. Based on the image information signal IMG, the control circuit 100 outputs a discharge control signal DI, a latch signal LAT, a change signal CH, and a clock signal SCK to the head unit 20 as discharge data signals DATA for controlling each part of the liquid discharge device 1.

[0022] Specifically, the control circuit 100 generates a control signal CTR1 and outputs it to the circulation mechanism 90. The circulation mechanism 90 supplies the ink stored in the ink container 2 to the liquid discharge head 22 according to the input control signal CTR1, and also recovers the ink stored in the discharge channel of the liquid discharge head 22. The control circuit 100 also generates a control signal CTR2 and outputs it to the carriage motor 31. This drives the carriage motor 31. The control circuit 100 also generates a control signal CTR3 and outputs it to the transport motor 41. This controls the reciprocating movement of the carriage 21 along the X direction and the transport of the medium P along the Y direction. The control signals CTR1, CTR2, and CTR3 may be input to the corresponding configuration via a driver circuit (not shown).

[0023] 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 converts the input base drive signal dA from digital to analog, and generates the drive signal COM by class D amplification of the converted analog signal, which is then output to the head unit 20.

[0024] Furthermore, the constant voltage output circuit 52 of the control unit 10 generates a constant voltage signal VCNT with a constant voltage value based on the commercial voltage supplied to the liquid dispensing device 1 or the various power supply voltages used inside the liquid dispensing device 1, and outputs it to the head unit 20. Such a constant voltage output circuit 52 may be an AC-DC converter that converts the commercial voltage supplied to the liquid dispensing device 1 into a DC voltage, or a DC-DC converter that converts the various power supply voltages used inside the liquid dispensing device 1 into a DC voltage.

[0025] The head unit 20 has a plurality of liquid discharge heads 22. Each of the plurality of liquid discharge heads 22 includes a drive signal selection circuit 200 and a plurality of discharge sections 600.

[0026] The drive signal selection circuit 200 receives the discharge control signal DI, latch signal LAT, change 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 output circuit 52. Based on the input discharge control signal DI, latch signal LAT, change signal CH, and clock signal SCK, the drive signal selection circuit 200 switches whether or not to supply the drive signal COM to the discharge unit 600 and whether or not to supply the constant voltage signal VCNT to the discharge unit 600.

[0027] Each of the multiple discharge units 600 has a piezoelectric element 60a, 60b. One end of piezoelectric element 60a is supplied with a drive signal VOUTa, which is generated by the drive signal selection circuit 200 deciding whether or not to supply a drive signal COM to the discharge unit 600 and whether or not to supply a constant voltage signal VCNT to the discharge unit 600. Similarly, one end of piezoelectric element 60b is supplied with a drive signal VOUTb, which is generated by the drive signal selection circuit 200 deciding whether or not to supply a drive signal COM to the discharge unit 600 and whether or not to supply a constant voltage signal VCNT to the discharge unit 600. The other end of piezoelectric elements 60a and 60b is supplied with a common reference voltage signal VBS.

[0028] The piezoelectric element 60a is driven according to the potential difference between the drive signal VOUTa supplied to one end and the reference voltage signal VBS supplied to the other end, and the piezoelectric element 60b is driven according to the potential difference between the drive signal VOUTb supplied to one end and the reference voltage signal VBS supplied to the other end. Here, the reference voltage signal VBS supplied to the other end 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, and may be a signal of a constant potential such as DC 5.5V or DC 6V, or it may be a signal of ground potential.

[0029] Then, when the piezoelectric elements 60a and 60b are driven, ink is ejected from the corresponding ejection unit 600. When the ink ejected from this ejection unit 600 lands on the medium P, characters or images are formed on the medium P.

[0030] As described above, the liquid dispensing device 1 of this embodiment includes a dispensing unit 600 that includes a piezoelectric element 60a and a piezoelectric element 60b and dispensing ink when at least one of the piezoelectric elements 60a and 60b is driven, a drive signal output circuit 50 that outputs a drive signal COM which is the basis for a drive signal VOUTa that drives the piezoelectric element 60a and a drive signal VOUTb that drives the piezoelectric element 60b, and a constant voltage output circuit 52 that outputs a constant voltage signal VCNT which has a constant voltage value.

[0031] 2. Configuration of the liquid dispensing head Next, the configuration of the liquid discharge head 22, which is equipped with a drive signal selection circuit 200, will be described. Figure 3 is an exploded perspective view of the liquid discharge head 22. Figure 4 is a cross-sectional view taken along line AA in Figure 3.

[0032] As shown in Figures 3 and 4, the liquid discharge head 22 comprises a nozzle substrate 360, compliance sheets 361 and 362, a communication plate 302, a pressure chamber substrate 303, a vibrating plate 304, a storage chamber forming substrate 305, and a wiring substrate 308.

[0033] The nozzle substrate 360 ​​is a plate-shaped member that is elongated in the Y direction and extends substantially parallel to the XY plane. M nozzles N are formed on the nozzle substrate 360. A nozzle N is a through hole provided in the nozzle substrate 360. 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 the nozzle row Ln. Here, "substantially parallel" includes not only cases where they are perfectly parallel, but also cases where they can be considered parallel when errors are taken into account.

[0034] The communication plate 302 is located on 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 an ink flow path is formed therein.

[0035] Specifically, the connecting plate 302 has a supply channel RA1 and a discharge channel RA2. The supply channel RA1 is located on the +X side of the connecting plate 302 and extends along the Y direction. The discharge channel RA2 is located on the -X side of the connecting plate 302 and extends along the Y direction.

[0036] Furthermore, the communication plate 302 has M connection channels RK1 that correspond one-to-one with M nozzles N, M connection channels RK2 that correspond one-to-one with M nozzles N, M communication channels RR1 that correspond one-to-one with M nozzles N, M communication channels RR2 that correspond one-to-one with M nozzles N, and M nozzle channels RN that correspond one-to-one with M nozzles N.

[0037] M connection channels RK1 are arranged side by side along the Y direction on the -X side of the supply channel RA1. M communication channels RR1 are arranged side by side along the Y direction on the -X side of the M connection channels RK1 which are arranged side by side along the Y direction. M connection channels RK2 are on the +X side of the discharge channel RA2, and are arranged side by side along the Y direction on the -X side of the M communication channels RR1 which are arranged side by side along the Y direction. M communication channels RR2 are on the +X side of the M connection channels RK2 which are arranged side by side along the Y direction, and are arranged side by side along the Y direction on the -X side of the M communication channels RR1 which are arranged side by side along the Y direction. The nozzle channel NR connects the communication channels RR1 and RR2 corresponding to a common nozzle N. When the communication plate 302 is viewed from the Z direction, the nozzle N corresponding to the approximate center in the X direction of the nozzle channel NR is located there. Here, "approximately center" includes not only cases where it is exactly in the center, but also cases where it can be considered to be in the center considering the error.

[0038] 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 within it.

[0039] Specifically, the pressure chamber substrate 303 has M pressure chambers CB1 and M pressure chambers CB2, each corresponding to one-to-one with M nozzles N, arranged along the Y-axis. Pressure chamber CB1 connects a common nozzle N to a connecting channel RK1 and a communication channel RR1. More specifically, when viewed from the Z direction, the +X end of pressure chamber CB1 connects to the connecting channel RK1, and the -X end of pressure chamber CB1 connects to the communication channel RR1, thereby connecting the common nozzle N to the connecting channel RK1 and the communication channel RR1. Pressure chamber CB2 connects a common nozzle N to a connecting channel RK2 and a communication channel RR2. In detail, when viewed from the Z direction, the -X end of the pressure chamber CB2 is in communication with the connecting channel RK2, and the +X end of the pressure chamber CB2 is in communication with the connecting channel RR2, thereby connecting the connecting channel RK2 and the connecting channel RR2 that correspond to the common nozzle N.

[0040] The diaphragm 304 is located on the -Z side of the pressure chamber substrate 303. The diaphragm 304 is a plate-shaped member that is elongated in the Y direction and extends substantially parallel to the XY plane, and is an elastically vibrating member.

[0041] On the -Z side of the diaphragm 304, M piezoelectric elements 60a, which correspond one-to-one with the M pressure chambers CB1 of the liquid discharge head 22, and M piezoelectric elements 60b, which correspond one-to-one with the M pressure chambers CB2 of the liquid discharge head 22, are arranged side by side along the Y direction. In other words, 2M piezoelectric elements 60 are arranged in two rows on the -Z side of the diaphragm 304.

[0042] Piezoelectric element 60a is driven in response to changes in the potential of the supplied drive signal VOUTa, and piezoelectric element 60b is driven in response to changes in the potential of the supplied drive signal VOUTb. The diaphragm 304 is displaced in conjunction with the driving of piezoelectric elements 60a and 60b. As a result, the internal pressure of pressure chambers CB1 and CB2 changes. Due to the change in internal pressure of pressure chambers CB1 and CB2, the ink filled inside pressure chambers CB1 and CB2 is ejected from nozzle N via the communication channels RR1 and RR2 and nozzle channel RN.

[0043] The wiring board 308 is connected to the -Z side of the diaphragm 304. The wiring board 308 propagates various signals, including the discharge data signal DATA and the drive signal COM, into the liquid discharge head 22. As such a wiring board 308, a flexible configuration such as a flexible printed circuit board (FPC) is used. An integrated circuit 201 is mounted on the wiring board 308 using COF (Chip On Film). The aforementioned drive signal selection circuit 200 is mounted on this integrated circuit 201. In other words, the wiring board 308 propagates various signals, including the discharge data signal DATA and the drive signal COM, to the integrated circuit 201, and also propagates the drive signals VOUTa and VOUTb output by the drive signal selection circuit 200 contained in the integrated circuit 201 to the corresponding piezoelectric elements 60a and 60b.

[0044] The storage chamber forming substrate 305 is located on the -Z side of the communication plate 302. The storage chamber forming substrate 5 is an elongated member in the Y direction and has an ink flow path formed within it.

[0045] Specifically, the storage chamber forming substrate 305 has 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. The storage chamber forming substrate 305 is also provided with an inlet 351 that communicates with the supply channel RB1 and an outlet 352 that communicates with the discharge channel RB2. Ink is supplied from the ink container 2 to the inlet 351. As a result, ink is supplied to the supply channel RB1 from the ink container 2 via the inlet 351. The ink stored in the discharge channel RB2 is recovered via the outlet 352. The ink recovered from the outlet 352 is returned to the ink container 2. The storage chamber forming substrate 305 also has an opening 350. Inside the opening 350 are a pressure chamber substrate 303, a diaphragm 304, and a wiring substrate 308.

[0046] In the liquid ejection head 22 configured as described above, the ink supplied from the ink container 2 to the inlet 351 flows into the supply channel RA1 via the supply channel RB1. The ink that flows into the supply channel RA1 then branches off for each nozzle N in the connecting channel RK1 and flows into the pressure chamber CB1. A portion of the ink that flows into the pressure chamber CB1 flows into the pressure chamber CB2 via the communication channel RR1, the nozzle channel RN, and the communication channel RR2. A portion of the ink that flows into the pressure chamber CB2 is then discharged from the outlet 352 via the connecting channel RK2, the discharge channel RA2, and the discharge channel RB2.

[0047] When the piezoelectric element 60a is driven by the drive signal VOUTa, a portion of the ink filling the pressure chamber CB1 is discharged from the nozzle N via the communication channel RR1 and the nozzle channel RN. Similarly, when the piezoelectric element 60b is driven by the drive signal VOUTb, a portion of the ink filling the pressure chamber CB2 is discharged from the nozzle N via the communication channel RR2 and the nozzle channel RN.

[0048] Compliance sheet 361 is located on the +Z side of the communication plate 302 and blocks the supply channel RA1 and the connecting channel RK1 formed in the communication plate 302. This compliance sheet 361 is made of an elastic material and absorbs pressure fluctuations of the ink that occur in the supply channel RA1 and the connecting channel RK1. Compliance sheet 362 is also located on the +Z side of the communication plate 302 and blocks the discharge channel RA2 and the connecting channel RK2 formed in the communication plate 302. This compliance sheet 362 is made of an elastic material and absorbs pressure fluctuations of the ink that occur in the discharge channel RA2 and the connecting channel RK2.

[0049] As described above, the liquid discharge head 22 of the liquid discharge device 1 according to this embodiment includes a pressure chamber CB1 whose internal pressure changes when driven by a piezoelectric element 60a, a pressure chamber CB2 whose internal pressure changes when driven by a piezoelectric element 60b, and a nozzle N that communicates with pressure chambers CB1 and CB2 and discharges ink. The change in internal pressure of pressure chamber CB1 due to the driving of piezoelectric element 60a and the change in internal pressure of pressure chamber CB2 due to the driving of piezoelectric element 60b cause the ink filled inside pressure chamber CB1 and the ink filled inside pressure chamber CB2 to be discharged from the nozzle N. This makes it possible to increase the driving capacity compared to the case in which ink filled inside one pressure chamber is discharged using one piezoelectric element 60, and stable discharge characteristics can be achieved even when high viscosity ink is used.

[0050] Here, the configuration including piezoelectric elements 60a, 60b, pressure chambers CB1, CB2, communication channels RR1, RR2, and nozzle N corresponds to the ejection unit 600 that ejects ink by driving at least one of the piezoelectric elements 60a, 60b.

[0051] 3. Example of a drive signal waveform Here, we will describe an example of the waveform of the drive signal COM output by the drive signal output circuit 50. Figure 5 shows an example of the waveform of the drive signal COM. As shown in Figure 5, the drive signal COM includes a signal waveform consisting of a trapezoidal waveform Adp1, which is placed during the period T1 from when the latch signal LAT rises until when the change signal CH rises, and a trapezoidal waveform Adp2, which is placed during the period T2 until the next latch signal LAT rises. In other words, the drive signal output circuit 50 outputs a drive signal COM with a signal waveform consisting of trapezoidal waveform Adp1 and trapezoidal waveform Adp2 in succession at each period Ta defined 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.

[0052] The trapezoidal waveform Adp1 includes a period of constant voltage Vc, a period of constant voltage Vb which is lower in potential than the voltage Vc located after the period of constant voltage Vc, a period of constant voltage Vt which is higher in potential than the voltage Vc located after the period of constant voltage Vb, and a period of constant voltage Vc located after the period of constant voltage Vt. In other words, the drive signal COM includes a trapezoidal waveform Adp whose voltage value starts at voltage Vc, changes to voltage Vb and voltage Vt, and ends at voltage Vc.

[0053] Here, the voltage Vc functions as a reference potential that serves as the basis for the displacement of the piezoelectric element 60. When this voltage Vc is supplied to the piezoelectric elements 60a and 60b, the piezoelectric elements 60a and 60b are held at a constant displacement. Then, as the voltage value of the trapezoidal waveform Adp1 supplied to the piezoelectric elements 60a and 60b changes from voltage Vc to voltage Vb, the piezoelectric elements 60a and 60b bend upward as shown in Figure 4. This expands the internal volume of pressure chambers CB1 and CB2. Consequently, ink is drawn into pressure chambers CB1 and CB2. Subsequently, as the voltage value of the trapezoidal waveform Adp1 supplied to the piezoelectric elements 60a and 60b changes from voltage Vb to voltage Vt, the piezoelectric elements 60a and 60b bend downward as shown in Figure 4. As a result, the internal volume of pressure chambers CB1 and CB2 decreases. Consequently, the ink stored in pressure chambers CB1 and CB2 is ejected from nozzle N. In other words, the trapezoidal waveform Adp1 is a signal waveform for ejecting ink from the ejection unit 600.

[0054] The trapezoidal waveform Adp2 is a signal waveform with a smaller voltage amplitude than the trapezoidal waveform Adp1. It is a signal waveform that drives the piezoelectric elements 60a and 60b to the extent that ink is not ejected from the ejection unit 600, thereby vibrating the ink near the nozzle N. This reduces the risk of an increase in the viscosity of the ink near the nozzle N and stabilizes the ink ejection characteristics from the ejection unit 600. In other words, the trapezoidal waveform Adp2 is a signal waveform that prevents ink from being ejected from the ejection unit 600. Hereinafter, in the following explanation, the trapezoidal waveform Adp2 will be referred to as a micro-vibration waveform, and the operation by which the piezoelectric elements 60a and 60b are driven to the extent that the ink near the nozzle N vibrates when the trapezoidal waveform Adp2 is supplied will be referred to as micro-vibration.

[0055] As described above, the drive signal COM includes, in period Ta, a trapezoidal waveform Adp1 for ejecting ink from the ejection unit 600, and a trapezoidal waveform Adp2 for preventing ink ejection from the ejection unit 600 and reducing the increase in ink viscosity near the nozzle N. However, the signal waveforms included in the drive signal COM are not limited to these, and 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, etc.

[0056] 4. Configuration and operation of the drive signal selection circuit Next, the configuration and operation of the drive signal selection circuit 200 will be described. The drive signal selection circuit 200 receives the discharge control signal DI, latch signal LAT, change 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 output circuit 52 as inputs. Based on the input discharge control signal DI, latch signal LAT, change signal CH, and clock signal SCK, the drive signal selection circuit 200 switches whether or not to supply the drive signal COM to the discharge unit 600 and whether or not to supply the constant voltage signal VCNT to the discharge unit 600.

[0057] To explain the configuration of the drive signal selection circuit 200, we will first describe the data structure of the ejection control signal DI input to the drive signal selection circuit 200. Figure 6 shows an example of the data structure of the ejection control signal DI. As shown in Figure 6, the ejection control signal DI includes a print data signal SI and an output selection control signal SO that follows the print data signal SI.

[0058] The print data signal SI corresponds to each of the M ejection units 600 of the liquid ejection head 22 and includes a 1-bit print data SId for selecting whether or not to eject ink from the corresponding ejection unit 600. In other words, the print data signal SI is a total of M bits of signal that controls the ejection of ink from the M ejection units 600.

[0059] The output selection control signal SO includes a 1-bit output selection data SOd for selecting whether to supply a drive signal VOUTb based on a drive signal COM or a drive signal VOUTb based on a constant voltage signal VCNT to each of the M discharge units 600's piezoelectric elements 60b. In other words, the output selection control signal SO is a 1-bit signal common to each of the M discharge units 600.

[0060] As described above, the ejection control signal DI in this embodiment is a signal totaling M+1 bits, including an M-bit print data signal SI and a 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.

[0061] Here, the print data signal SI included in the ejection control signal DI is not limited to M bits. For example, if the liquid ejection head 22 forms four-tone dots, including non-ejected dots, on the medium P, the print data SId included in the print data signal SI may contain 2 bits of information to represent the four tones. In this case, the print data signal SI becomes a 2M-bit signal that controls the ejection of ink from the M ejection units 600.

[0062] Furthermore, the output selection control signal SO included in the discharge control signal DI is not limited to 1 bit. For example, in a liquid discharge head 22, when selecting whether to supply a drive signal VOUTb based on a drive signal COM or a drive signal VOUTb based on a constant voltage signal VCNT to each of the M discharge units 600 piezoelectric elements 60b, the output selection control signal SO may include 1 bit of information to select whether to supply a drive signal VOUTb based on a drive signal COM or a drive signal VOUTb based on a constant voltage signal VCNT during period T1, and 1 bit of information to select whether to supply a drive signal VOUTb based on a drive signal COM or a drive signal VOUTb based on a constant voltage signal VCNT during period T2. In this case, the output selection control signal SO becomes a 2-bit signal.

[0063] In addition to the print data signal SI and the output selection control signal SO, the ejection control signal DI may also include information indicating the driving conditions of the piezoelectric elements 60a and 60b, such as signals that define waveform selection in the decoder DC described later.

[0064] Next, the configuration and operation of the drive signal selection circuit 200 will be described. Figure 7 shows the configuration of the drive signal selection circuit 200. Here, 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 ejection unit 600[i] (where i is one of 1 to M) may be referred to as piezoelectric element 60a[i], and the piezoelectric element 60b of ejection unit 600[i] may be referred to as piezoelectric element 60b[i]. Furthermore, among the print data SId corresponding to the M ejection units 600 included in the print data signal SI, the print data SId corresponding to ejection unit 600[i] may be referred to as print data SId[i].

[0065] As shown in Figure 7, the drive signal selection circuit 200 includes a selection control circuit 210, a path switching circuit 230, and selection circuits TGa[1]~TGa[M] and TGb[1]~TGb[M]. Here, in the following description, when it is not necessary to distinguish between selection circuits TGa[1]~TGa[M], they may simply be referred to as selection circuit TGa, and when it is not necessary to distinguish between selection circuits TGb[1]~TGb[M], they may simply be referred to as selection circuit TGb. Furthermore, when it is not necessary to distinguish between selection circuit TGa and selection circuit TGb, they may simply be referred to as selection circuit TG.

[0066] The selection control circuit 210 includes a shift register 220, latch circuits LTa_S, LTb_S, LTa[1]~LTa[M], LTb[1]~LTb[M], and decoders DC_S, DCa[1]~DCa[M], DCb[1]~DCb[M]. Here, in the following description, when it is not necessary to distinguish between latch circuits LTa[1]~LTa[M], they may simply be referred to as latch circuit LTa, and when it is not necessary to distinguish between latch circuits LTb[1]~LTb[M], they may simply be referred to as latch circuit LTb. Furthermore, when it is not necessary to distinguish between latch circuit LTa and latch circuit LTb, they may simply be referred to as latch circuit LT. Similarly, when it is not necessary to distinguish between decoders DCa[1]~DCa[M], they may simply be referred to as decoder DCa, and when it is not necessary to distinguish between decoders DCb[1]~DCb[M], they may simply be referred to as decoder DCb. Furthermore, when there is no need to distinguish between decoder DCa and decoder DCb, they are sometimes simply referred to as decoder DC.

[0067] The shift register 220 includes a first shift register 221 and a second shift register 222.

[0068] The first shift register 221 receives the discharge control signal DI and a signal obtained by inverting the logic level of the clock signal SCK by an inverter. The first shift register 221 also includes registers RGa_S, RGa[1] to RGa[M]. In the first shift register 221, registers RGa_S, RGa[1] to RGa[M] are connected in series from the upstream side where the discharge control signal DI is input to the downstream side, in the order of registers RGa_S, RGa[1], RGa[2], ..., RGa[M].

[0069] As described above, the first shift register 221 transfers the input discharge control signal DI to the registers RGa_S, RGa[1], RGa[2], ..., RGa[M] in the order of RGa_S, RGa[1], RGa[2], ..., RGa[M] on the falling edge of the clock signal SCK. When the input of the discharge control signal DI to the first shift register 221 is complete and the supply of the clock signal SCK is stopped, the output selection data SOd is held in the register RGa_S, and the corresponding print data Sid[1] to Sid[M] are held in each of the registers RGa[1] to RGa[M].

[0070] The second shift register 222 receives the discharge control signal DI and the clock signal SCK as inputs. The second shift register 222 also contains the registers RGb_S, RGb[1] to RGb[M]. In the second shift register 222, the registers RGb_S, RGb[1] to RGb[M] are connected in series from the upstream side where the discharge control signal DI is input to the downstream side, in the order of registers RGb_S, RGb[1], RGb[2], ..., RGb[M].

[0071] As described above, the second shift register 222 transfers the input discharge control signal DI to the registers RGb_S, RGb[1], RGb[2], ..., RGb[M] in the order of rising edge of the clock signal SCK. When the input of the discharge control signal DI to the second shift register 222 is complete and the supply of the clock signal SCK is stopped, the output selection data SOd is held in register RGb_S, and the corresponding print data Sid[1] to Sid[M] are held in each of the registers RGb[1] to RGb[M].

[0072] The latch circuit LTa_S is provided in correspondence with register RGa_S. At the rising edge of the latch signal LAT, the latch circuit LTa_S latches the output selection data SOd held in register RGa_S as latch data LtaS. Similarly, the latch circuit LTb_S is provided in correspondence with register RGb_S. At the rising edge of the latch signal LAT, the latch circuit LTb_S latches the output selection data SOd held in register RGb_S as latch data LtbS.

[0073] The latch data LtaS latched by latch circuit LTa_S and the latch data LtbS latched by latch circuit LTb_S are input to decoder DC_S. The latch signal LAT and the change signal CH are also input to decoder DC_S. Then, for each of the periods T1 and T2 defined by the latch signal LAT and the change signal CH, decoder DC_S generates a selection signal Sc with a logic level defined by the latch data LtaS and latch data LtbS, and outputs it from the selection control circuit 210.

[0074] Figure 8 shows an example of the decoding contents of decoder DC_S. As shown in Figure 8, when latch data LtaS=1 and latch data LtbS=1 are input to decoder DC, it generates an H-level selection signal Sc for both periods T1 and T2 and outputs it from the selection control circuit 210. When latch data LtaS=0 and latch data LtbS=0 are input to decoder DC, it generates an L-level selection signal Sc for both periods T1 and T2 and outputs it from the selection control circuit 210.

[0075] Here, when the latch circuit LTa_S latches the information held in register RGa_S as latch data LtaS, and the latch circuit LTb_S latches the information held in register RGb_S as latch data LtbS, the output selection data SOd is held in registers RGa_S and RGb_S. In light of this, the logic level of the latch data LtaS latched by the latch circuit LTa_S is equal to the logic level of the latch data LtbS latched by the latch circuit LTb_S. Therefore, when the decoder DC_S receives latch data LtaS=0 and latch data LtbS=1, or latch data LtaS=1 and latch data LtbS=0, the decoder DC_S may determine that the input latch data LtaS or latch data LtbS is not normal and may not change the logic level of the output selection signal Sc, but instead retain the output at the most recent logic level.

[0076] Returning to Figure 7, the latch circuits LTa[1] to LTa[M] are provided in correspondence with the registers RGa[1] to RGa[M]. Then, at the rising edge of the latch signal LAT, the latch circuits LTa[1] to LTa[M] simultaneously latch the print data Sid[1] to Sid[M] held in each of the registers RGa[1] to RGa[M] as latch data Lta[1] to LTa[M]. Specifically, at the rising edge of the latch signal LAT, the latch circuit LTa[1] latches the print data Sid[1] held in register RGa[1] as latch data Lta[1], and at the rising edge of the latch signal LAT, the latch circuit LTa[i] latches the print data Sid[i] held in register RGa[i] as latch data Lta[i]. Here, in the following explanation, when it is not necessary to distinguish between the latch data Lta[1] to LTa[M], they may be referred to as latch data Lta. In other words, the latch circuit LTa will be described as latching the print data Sid, held in register RGa, as the latch data Lta on the rising edge of the latch signal LAT.

[0077] Similarly, latch circuits LTb[1] to LTb[M] are provided in correspondence with registers RGb[1] to RGb[M]. Then, at the rising edge of the latch signal LAT, latch circuits LTb[1] to LTb[M] simultaneously latch the print data Sid[1] to Sid[M] held in each of the registers RGb[1] to RGb[M] as latch data Ltb[1] to LTb[M]. Specifically, at the rising edge of the latch signal LAT, latch circuit LTb[1] latches the print data Sid[1] held in register RGb[1] as latch data Ltb[1], and latch circuit LTb[i] latches the print data Sid[i] held in register RGb[i] as latch data Ltb[i] at the rising edge of the latch signal LAT. Here, in the following explanation, when it is not necessary to distinguish between latch data Ltb[1] to LTb[M], they may be referred to as latch data Ltb. In other words, the latch circuit LTb latches the print data Sid, held in register RGb, as the latch data Ltb on the rising edge of the latch signal LAT.

[0078] The latch data Lta[1] to Lta[M] latched by each of the latch circuits LTa[1] to LTa[M] is input to the corresponding decoders DCa[1] to DCa[M]. The latch signal LAT and the change signal CH are also input to the decoders DCa[1] to DCa[M]. The decoders DCa[1] to DCa[M] then generate a selection signal S of a logic level defined by the latch data Lta[1] to LTa[M] during periods T1 and T2 defined by the latch signal LAT and the change signal CH, respectively, and output it from the selection control circuit 210.

[0079] Similarly, the latch data Ltb[1] to LTb[M] latched by each of the latch circuits LTb[1] to LTb[M] is input to the corresponding decoders DCb[1] to DCb[M]. The latch signal LAT and the change signal CH are also input to the decoders DCb[1] to DCb[M]. The decoders DCb[1] to DCb[M] then generate a selection signal S of a logic level defined by the latch data Ltb[1] to LTb[M] during periods T1 and T2 defined by the latch signal LAT and the change signal CH, respectively, and output it from the selection control circuit 210.

[0080] Figure 9 shows an example of the decoding contents of decoders DCa[1] to DCa[M]. The same applies to decoders DCb[1] to DCb[M]. Therefore, in Figure 9, the decoding contents of decoders DCa[1] to DCa[M] are explained, and the explanation of decoders DCb[1] to DCb[M] is omitted. In addition, the configurations corresponding to some of decoders DCb[1] to DCb[M] are shown in parentheses in Figure 9.

[0081] As shown in Figure 9, when the latch data Lta=0 is input, decoder DCa generates a selection signal S that is L level during period T1 and H level during period T2, and outputs it from the selection control circuit 210. Also, when the latch data Lta=1 is input, decoder DC generates a selection signal S that is H level during period T1 and L level during period T2, and outputs it from the selection control circuit 210.

[0082] Here, when the latch circuit LTa[i] latches the information held in register RGa[i] as latch data Lta[i], and the latch circuit LTb[i] latches the information held in register RGb[i] as latch data Ltb[i], registers RGa[i] and RGb[i] hold the print data SId[i] included in the print data signal SI. That is, the logic level of the latch data Lta[i] latched by the latch circuit LTa[i] is equal to the logic level of the latch data Ltb[i] latched by the latch circuit LTb[i]. Therefore, the logic level of the selection signal S output by decoder DCa[i] is equal to the logic level of the selection signal S output by decoder DCb[i]. In other words, decoders DCa[i] and DCb[i] corresponding to the output unit 600[i] output selection signals S at the same logic level.

[0083] As described above, the selection control circuit 210 generates and outputs a selection signal Sc and 2M selection signals S corresponding to each of the piezoelectric elements 60a and 60b of the M discharge units 600, based on the discharge control signal DI, latch signal LAT, change signal CH, and clock signal SCK output by the control circuit 100.

[0084] The selection signal Sc output by the selection control circuit 210 is input to the path switching circuit 230. The drive signal COM is input to input In1 of the path switching circuit 230, and the constant voltage signal VCNT is input to input In2. The path switching circuit 230 then 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 voltage signal V1 from output Out1 and as voltage signal V2 from output Out2.

[0085] Figure 10 shows an example of a route switching circuit 230. As shown in Figure 10, the route switching circuit 230 has switches SW1 and SW2. One end of switch SW1 is connected to the input unit In2, and the other end of switch SW1 is connected to the output unit Out2. One end of switch SW2 is connected to the output unit Out1, and the other end of switch SW2 is connected to the output unit Out2.

[0086] When a high-level selection signal Sc is input to the path switching circuit 230, one end and the other end of switch SW1 are controlled to be non-conductive, and one end and the other end of switch SW2 are controlled to be conductive. As a result, in the path switching circuit 230, the input section In1 and the output section Out1 are controlled to be conductive, and the input section In1 and the output section Out2 are controlled to be conductive.

[0087] On the other hand, when a low-level selection signal Sc is input to the path switching circuit 230, one end of switch SW1 and the other end are controlled to conduct, and one end of switch SW2 and the other end are controlled to not conduct. As a result, in the path switching circuit 230, the input section In1 and the output section Out1 are controlled to conduct, and the input section In2 and the output section Out2 are controlled to conduct.

[0088] In other words, the path switching circuit 230 has an input section In1 to which a drive signal COM is input, an input section In2 to which a constant voltage signal VCNT is input, an output section Out1 that outputs the drive signal COM as a voltage signal V1, an output section Out2 that outputs the drive signal COM or the constant voltage signal VCNT as a voltage signal V2, a switch SW1 with one end connected to the input section In2 and the other end connected to the output section Out2, and a switch SW2 with one end connected to the output section Out1 and the other end connected to the output section Out2, and when a selection signal Sc of the high level is input from the selection control circuit 210, one end and the other end of switch SW1 are controlled to be non-conductive, and the switch When one end and the other end of SW2 are controlled to conduct, the drive signal COM input to input In1 is output as a voltage signal V1 from output Out1, and the drive signal COM input to input In1 is output as a voltage signal V2 from output Out2. When a low-level selection signal Sc is input from the selection control circuit 210, one end and the other end of switch SW1 are controlled to be non-conductive, and one end and the other end of switch SW2 are controlled to conduct, so that the drive signal COM input to input In1 is output as a voltage signal V1 from output Out1, and the constant voltage signal VCNT input to input In2 is output as a voltage signal V2 from output Out2.

[0089] In other words, in the operating mode in which the path switching circuit 230 outputs a drive signal COM from the output unit Out2, the selection control circuit 210 controls switch SW1 to be non-conductive and switch SW2 to be conductive, and in the operating mode in which the path switching circuit 230 outputs a constant voltage signal VCNT from the output unit Out2, the selection control circuit 210 controls switch SW1 to be conductive and switch SW2 to be non-conductive. That is, the selection control circuit 210 controls switch SW1 and switch SW2. Such switches SW1 and SW2 can be configured, for example, by one or more transistors.

[0090] Returning to Figure 7, the voltage signal V1 output from the output unit Out1 of the path switching circuit 230 propagates through the wiring W1 and is input to the selection circuits TGa[1]~TGa[M]. The selection signals S output by the decoders DCa[1]~DCa[M] are also input to the selection circuits TGa[1]~TGa[M]. The selection circuits TGa[1]~TGa[M] then control whether or not to supply the voltage signal V1 to the piezoelectric element 60a as a drive signal VOUTa, according to the logic level of the selection signal S. In other words, the wiring W1 electrically connects the output unit Out1 and the piezoelectric element 60a via the selection circuits TGa[1]~TGa[M].

[0091] 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]~TGb[M]. The selection signals S output by the decoders DCb[1]~DCb[M] are also input to the selection circuits TGb[1]~TGb[M]. The selection circuits TGb[1]~TGb[M] then control whether or not to supply the voltage signal V2 to the piezoelectric element 60b as a drive signal VOUTb according to 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]~TGb[M].

[0092] Here, we will describe an example of the configuration of the selection circuit TG. Figure 11 is a diagram showing an example of the configuration of the selection circuit TG. In Figure 11, 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 shown in parentheses.

[0093] As shown in Figure 11, the selection circuit TG includes an inverter 232, which is a NOT gate, and a transfer gate 234. The selection signal S is input to the positive control terminal of the transfer gate 234 (which is not marked with a circle), while it is logically inverted by the inverter 232 and input to the negative control terminal of the transfer gate 234 (which is marked with a circle). A voltage signal V1 is supplied to the input terminal of the transfer gate 234. The drive signal VOUTa is output from the output terminal of the transfer gate 234.

[0094] Specifically, when the selection signal S is at a high level, the input and output terminals of the transfer gate 234 become conductive, and when the selection signal S is at a low level, the input and output terminals of the transfer gate 234 become non-conductive. In other words, the selection circuit TG selects or deselects the voltage signal V1 supplied to the input terminal of the transfer gate 234 by switching the conduction state between the input and output terminals of the transfer gate 234 based on the logic level of the selection signal S. As a result, the drive signal VOUTa generated by selecting or deselecting the voltage signal V1 is output to the output terminal of the transfer gate 234.

[0095] As mentioned above, decoders DCa[i] and DCb[i], which correspond to the output unit 600[i], output selection signals S at the same logic level. Therefore, when selection circuit TGa[i] outputs voltage signal V1 as drive signal VOUTa, selection circuit TGb[i] outputs voltage signal V2 as drive signal VOUTa, and when selection circuit TGa[i] does not output voltage signal V1 as drive signal VOUTa, selection circuit TGb[i] does not output voltage signal V2 as drive signal VOUTa. In other words, the selection control circuit 210 controls selection circuits TGa and TGb based on the same print data Sid.

[0096] Here, we will explain 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.

[0097] Figure 12 shows an example of the relationship between the drive signals VOUTa and VOUTb, the print data Sid, and the output selection data SOd.

[0098] If the discharge control signal DI input to the drive signal selection circuit 200 includes the 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 discharge unit 600, and the drive signal COM is supplied as voltage signal V2 to the selection circuit TGb corresponding to the discharge unit 600.

[0099] When the ejection control signal DI input to the drive signal selection circuit 200 at this time includes the 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, and 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 a drive signal VOUTa including the trapezoidal waveform Adp1 during period Ta, and the piezoelectric element 60b is supplied with a drive signal VOUTb including the trapezoidal waveform Adp1 during period Ta. That is, during period Ta, both the piezoelectric elements 60a and 60b included in the ejection unit 600 are driven to eject ink from the nozzle N. This enables stable ink ejection even when the viscosity of the ink stored in the pressure chambers CB1 and CB2 is high.

[0100] If the discharge control signal DI input to the drive signal selection circuit 200 includes the 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 discharge unit 600, and the drive signal COM is supplied as voltage signal V2 to the selection circuit TGb corresponding to the discharge unit 600.

[0101] When the ejection control signal DI input to the drive signal selection circuit 200 at this time includes the 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, but selects the trapezoidal waveform Adp2 during period T2, and the selection circuit TGb corresponding to the ejection unit 600 does not select the trapezoidal waveform Adp1 during period T1, but selects the trapezoidal waveform Adp2 during period T2. As a result, the piezoelectric element 60a of the ejection unit 600 is supplied with a drive signal VOUTa including the trapezoidal waveform Adp2 during period Ta, and the piezoelectric element 60b is supplied with a drive signal VOUTb including the trapezoidal waveform Adp2 during period Ta. That is, during period Ta, the piezoelectric elements 60a and 60b included in the ejection unit 600 perform micro-vibrations. This increases the viscosity of the ink stored in the pressure chambers CB1 and CB2, reducing the risk of it sticking near the nozzle N.

[0102] If the discharge control signal DI input to the drive signal selection circuit 200 includes the output selection data SOd=0, the path switching circuit 230 outputs the drive signal COM as voltage signal V1 and the constant voltage signal VCNT as voltage signal V2. Therefore, the drive signal COM is supplied as voltage signal V1 to the selection circuit TGa corresponding to the discharge unit 600, and the constant voltage signal VCNT is supplied as voltage signal V2 to the selection circuit TGb corresponding to the discharge unit 600.

[0103] When the ejection control signal DI input to the drive signal selection circuit 200 at this time includes the 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, and 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 a drive signal VOUTa including the trapezoidal waveform Adp1 during period Ta, and the piezoelectric element 60b is supplied with a drive signal VOUTb of the constant voltage signal VCNT during period Ta. That is, during period Ta, both piezoelectric elements 60a included in the ejection unit 600 are driven to eject ink from the nozzle N, while the piezoelectric element 60b included in the ejection unit 600 remains at a constant displacement and is not driven. This ensures stable ink ejection even if the viscosity of the ink stored in pressure chambers CB1 and CB2 softens due to ambient temperature or other factors.

[0104] If the discharge control signal DI input to the drive signal selection circuit 200 includes the output selection data SOd=0, the path switching circuit 230 outputs the drive signal COM as voltage signal V1 and the constant voltage signal VCNT as voltage signal V2. Therefore, the drive signal COM is supplied as voltage signal V1 to the selection circuit TGa corresponding to the discharge unit 600, and the constant voltage signal VCNT is supplied as voltage signal V2 to the selection circuit TGb corresponding to the discharge unit 600.

[0105] When the ejection control signal DI input to the drive signal selection circuit 200 at this time 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, but selects the trapezoidal waveform Adp2 during period T2, and the selection circuit TGb corresponding to the ejection unit 600 does not select the constant voltage signal VCNT during period T1, but selects the constant voltage signal VCNT during period T2. As a result, the piezoelectric element 60a of the ejection unit 600 is supplied with a drive signal VOUTa including the trapezoidal waveform Adp2 during period Ta, and the piezoelectric element 60b is supplied with a drive signal VOUTb of the constant voltage signal VCNT during period Ta. That is, during period Ta, the piezoelectric element 60a included in the ejection unit 600 performs micro-vibrations, while the piezoelectric element 60b included in the ejection unit 600 remains at a constant displacement and does not move. This reduces the risk of ink being ejected due to micro-vibrations, even if the viscosity of the ink stored in the pressure chambers CB1 and CB2 softens due to ambient temperature, etc.

[0106] Here, if the selection circuit TGa does not select the voltage signal V1, the piezoelectric element 60a holds the voltage value that was supplied to the piezoelectric element 60 immediately before, specifically the voltage Vc, due to the capacitance component of the piezoelectric element 60a. Also, if the selection circuit TGb does not select the voltage signal V2, the piezoelectric element 60b holds the voltage value that was supplied to the piezoelectric element 60 immediately before, specifically the voltage Vc, due to the capacitance component of the piezoelectric element 60b.

[0107] Therefore, it is preferable that the voltage value of the constant voltage signal VCNT is voltage Vc. This reduces the risk that the piezoelectric elements 60a and 60b may be unintentionally driven due to fluctuations in the voltage value supplied to the piezoelectric elements 60a and 60b when the operation of the selection circuits TGa and TGb controls whether or not the constant voltage signal VCNT is supplied to the piezoelectric elements 60a and 60b. In other words, it is preferable that the voltage value of the constant voltage signal VCNT is equal to voltage Vc, which is the voltage at the rising edge timing of the latch signal LAT that defines the supply cycle of the drive signal COM to the piezoelectric elements 60a and 60b, and is the voltage value of the drive signal COM at the rising edge timing corresponding to the starting point of the supply cycle of the drive signal COM of the latch signal LAT.

[0108] As a result, when the path switching circuit 230 outputs a constant voltage signal VCNT as a voltage signal V2, even if the conduction state of the selection circuit TGb is switched, the risk of unintended distortion occurring in the output voltage of the drive signal VOUTb is reduced, and consequently, the risk of unintended displacement occurring in the piezoelectric element 60b is reduced.

[0109] In such a liquid dispensing device 1, the output selection data SOd included in the output selection control signal SO that switches the operation of the path switching circuit 230 may be selected by the control circuit 100 based on the ink temperature detected by a temperature detection circuit (not shown) and output as the output selection control signal SO, or selected by the control circuit 100 based on the ink dispensing state detected by a dispensing state detection circuit (not shown) and output as the output selection control signal SO, or further, selected by the user's operation.

[0110] 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 selecting or deselecting the signal waveform of drive signal COM, drive signals VOUTa and VOUTb are also examples of drive signals. Additionally, input section In1 of the path switching circuit 230 is an example of a first input section, input section In2 is an example of a second input section, output section Out1 is an example of a first output section, output section Out2 is an example of a second output section, switch SW1 is an example of a first switch, and switch SW2 is an example of a second switch. Furthermore, the selection control circuit 210 is an example of a switch control circuit, wiring W1 is an example of a first wiring, wiring W2 is an example of a second wiring, the operation mode in which the path switching circuit 230 outputs the drive signal COM as a voltage signal V2 is an example of a first mode, and the operation mode in which the path switching circuit 230 outputs a constant voltage signal VCNT as a voltage signal V2 is an example of a second mode. Furthermore, the selection circuit TGa is an example of a third switch, the selection circuit TGb is an example of a fourth switch, the print data SId of the print data signal SI included in the discharge control signal DI is an example of drive data, the latch signal LAT is an example of a periodic signal, the period Ta defined 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.

[0111] 4. Effects In the liquid dispensing device 1 configured as described above, when the selection control circuit 210 controls switch SW1 of the path switching circuit 230 to be non-conductive and switch SW2 to be conductive, thereby entering an operating mode in which a drive signal COM is output from the output section Out2 of the path switching circuit 230, the drive signal COM is supplied to piezoelectric element 60a via the selection circuit TGa, and the drive signal COM is supplied to piezoelectric element 60b via the selection circuit TGb. As a result, both piezoelectric elements 60a and 60b are driven according to the drive signal COM. Consequently, it becomes possible to apply a greater driving force to the dispensing section 600, enabling stable ink dispensing even when high-viscosity ink is used. On the other hand, when the selection control circuit 210 controls switch SW1 of the path switching circuit 230 to conduct and switch SW2 to deconduct, resulting in an operating mode where a constant voltage signal VCNT is output from the output section Out of the path switching circuit 230, the piezoelectric element 60a is supplied with a drive signal COM via the selection circuit TGa, and the piezoelectric element 60b is supplied with a constant voltage signal VCNT via the selection circuit TGb. As a result, the piezoelectric element 60a is driven according to the drive signal COM, and the piezoelectric element 60b is held at a constant displacement according to the constant voltage signal VCNT. Consequently, the driving force applied to the ejection section 600 can be reduced, enabling stable ink ejection even when the viscosity of the ink changes.

[0112] In other words, the liquid dispensing device 1 of this embodiment can reduce the power consumption of the ink viscosity adjustment mechanism, such as a heater, and can also achieve stable ink dispensing even with a liquid dispensing device 1 that requires a large driving force, such as for high-viscosity inks.

[0113] Although embodiments and modified examples have been described above, the present invention is not limited to these embodiments and can be implemented in various forms without departing from its spirit. For example, the above embodiments can be combined as appropriate.

[0114] The present invention includes configurations that are substantially identical to those described in the embodiments (for example, configurations with the same function, method, and result, or configurations with the same purpose and effect). Furthermore, the present invention includes configurations in which non-essential parts of the configurations described in the embodiments are replaced. Furthermore, the present invention includes configurations that produce the same effects or achieve the same purpose as those described in the embodiments. Furthermore, the present invention includes configurations that add known technology to the configurations described in the embodiments.

[0115] The following conclusions can be drawn from the embodiments described above.

[0116] One embodiment of a liquid dispensing device is: A discharge unit comprising a first piezoelectric element and a second piezoelectric element, wherein at least one of the first piezoelectric element and the second piezoelectric element is driven to discharge liquid, A drive signal output circuit that outputs a drive signal to drive at least one of the first piezoelectric element and the second piezoelectric element, A constant voltage output circuit that outputs a constant voltage signal with a constant voltage value, A path switching circuit comprising: a first input unit into which the drive signal is input; a second input unit into which the constant voltage signal is input; a first output unit that outputs the drive signal; a second output unit that outputs the drive signal or the constant voltage signal; a first switch with one end connected to the second input unit and the other end connected to the second output unit; and a second switch with one end connected to the first output unit and the other end connected to the second output unit. A first wiring that electrically connects the first output unit and the first piezoelectric element, A second wiring that electrically connects the second output section and the second piezoelectric element, A switch control circuit that controls the first switch and the second switch, Equipped with, In the first mode in which the drive signal is output from the second output unit, the switch control circuit controls the first switch to be non-conductive and the second switch to be conductive. In the second mode in which the constant voltage signal is output from the second output unit, the switch control circuit controls the first switch to conduct and the second switch to deconduct.

[0117] In this liquid dispensing device, in the first mode in which a drive signal is output from the second output unit, the switch control circuit controls the first switch to be non-conductive and the second switch to be conductive, and in the second mode in which a constant voltage signal is output from the second output unit, the switch control circuit controls the first switch to be conductive and the second switch to be non-conductive. By doing so, the drive 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 dispensing and reduced power consumption.

[0118] In one embodiment of the liquid dispensing device, The first wiring is electrically connected to the first piezoelectric element via the third switch. The second wiring is electrically connected to the second piezoelectric element via the fourth switch. The third switch and the fourth switch may be controlled by the switch control circuit.

[0119] In this liquid dispensing device, the first and second switches in the supply switching circuit, the third switch that switches the electrical connection between the first output unit and the first piezoelectric element, and the fourth switch that switches the electrical connection between the second output unit and the second piezoelectric element are all controlled by a common switch control circuit. This allows the control signals for controlling the first, second, third, and fourth switches to be transmitted together as a single signal.

[0120] In one embodiment of the liquid dispensing device, The switch control circuit may control the third switch and the fourth switch based on the drive data.

[0121] This liquid dispensing device allows for the control of the third and fourth switches based on the same drive data, thereby reducing the amount of drive data required to drive the third and fourth switches.

[0122] In one embodiment of the liquid dispensing device, The system includes a periodic control circuit that outputs a periodic signal that defines the period for supplying the drive signal to at least one of the first piezoelectric element and the second piezoelectric element, The voltage value of the constant voltage signal may be equal to the voltage value of the drive signal at the starting point of the supply cycle of the periodic signal.

[0123] This liquid dispensing device reduces the risk of unintended displacement occurring in the first piezoelectric element and the second piezoelectric element when switching from the first mode to the second mode, and when switching from the second mode to the first mode.

[0124] In one embodiment of the liquid dispensing device, The discharge unit may include a first pressure chamber whose internal pressure is converted by driving the first piezoelectric element, a second pressure chamber whose internal pressure is converted by driving the second piezoelectric element, and a nozzle that communicates with the first and second pressure chambers and discharges liquid.

[0125] This liquid dispensing device allows for the circulation of the liquid supplied to the dispensing section, enabling more precise control of the liquid's viscosity. [Explanation of symbols]

[0126] 1…Liquid dispensing device, 2…Ink container, 5…Storage chamber forming substrate, 10…Control unit, 20…Head unit, 21…Carriage, 22…Liquid dispensing head, 30…Movement unit, 31…Carriage motor, 32…Endless belt, 40…Conveying unit, 41…Conveying motor, 42…Conveying roller, 50…Drive signal output circuit, 52…Constant voltage 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…Transfer gate, 302…Communication plate, 303…Pressure chamber substrate, 30 4…Diaphragm, 305…Storage chamber forming substrate, 308…Wiring board, 350…Opening, 351…Inlet, 352…Outlet, 360…Nozzle substrate, 361,362…Compliance sheet, 600…Discharge section, CB1,CB2…Pressure chamber, DC,DC_S,DCa,DCb…Decoder, In1,In2…Input section, LT,LTa,LTa_S,LTb,LTb_S…Latch circuit, Ln…Nozzle row, N…Nozzle, NR…Nozzle flow path, Out1,Out2…Output section, P…Medium, RA1…Supply flow path, RA2…Discharge flow path, RB1…Supply flow path, RB2…Discharge flow path, RGa,RGa_S,RGb,RGb_S…Register, RK1,RK2…Connection flow path, RN…Nozzle flow path, RR1,RR2…Communication flow path, SW1,SW2…Switch, TG,TGa,TGb…Selection circuit

Claims

1. A discharge unit comprising a first piezoelectric element and a second piezoelectric element, wherein at least one of the first piezoelectric element and the second piezoelectric element is driven to discharge liquid, A drive signal output circuit that outputs a drive signal to drive at least one of the first piezoelectric element and the second piezoelectric element, A constant voltage output circuit that outputs a constant voltage signal with a constant voltage value, A path switching circuit comprising: a first input unit into which the drive signal is input; a second input unit into which the constant voltage signal is input; a first output unit that outputs the drive signal; a second output unit that outputs the drive signal or the constant voltage signal; a first switch with one end connected to the second input unit and the other end connected to the second output unit; and a second switch with one end connected to the first output unit and the other end connected to the second output unit. A first wiring that electrically connects the first output unit and the first piezoelectric element, A second wiring that electrically connects the second output unit and the second piezoelectric element, A switch control circuit that controls the first switch and the second switch, Equipped with, In the first mode in which the drive signal is output from the second output unit, the switch control circuit controls the first switch to be non-conductive and the second switch to be conductive. In the second mode in which the constant voltage signal is output from the second output unit, the switch control circuit controls the first switch to conduct and the second switch to deconduct. A liquid dispensing device characterized by the following features.

2. The first wiring is electrically connected to the first piezoelectric element via the third switch. The second wiring is electrically connected to the second piezoelectric element via the fourth switch. The third switch and the fourth switch are controlled by the switch control circuit. The liquid dispensing device according to feature 1.

3. The switch control circuit controls the third switch and the fourth switch based on the drive data. The liquid dispensing device according to feature 2.

4. The system includes a periodic control circuit that outputs a periodic signal that defines the period for supplying the drive signal to at least one of the first piezoelectric element and the second piezoelectric element, The voltage value of the constant voltage signal is equal to the voltage value of the drive signal at the starting point of the supply cycle of the periodic signal. A liquid dispensing device according to any one of claims 1 to 3.

5. The discharge unit includes a first pressure chamber whose internal pressure is converted by the driving of the first piezoelectric element, a second pressure chamber whose internal pressure is converted by the driving of the second piezoelectric element, and a nozzle that communicates with the first and second pressure chambers and discharges liquid. A liquid dispensing device according to any one of claims 1 to 4.

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