Printing device and head

Abstract

To provide a printing device which can measure electrostatic capacities and a head.SOLUTION: A printing device comprises: a piezoelectric body that is deformed by an applied voltage in order to make a nozzle discharge liquid; an individual electrode formed on the piezoelectric body; a first common electrode formed in the piezoelectric body to oppose to the individual electrode; a second common electrode applied with a voltage which is different from a voltage applied to the first common electrode and formed in the piezoelectric body to oppose to the individual electrode; and a detection circuit that detects electrostatic capacities in a first capacitor constituted of the piezoelectric body, the individual electrode and the first common electrode and in a second capacitor constituted of the piezoelectric body, the individual electrode and the second common electrode, where the detection circuit includes an oscillation circuit connected to the individual electrode.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present technology relates to a printing device and a head that prints by ejecting liquid from nozzles. [Background technology]

[0002] A liquid ejection head has been proposed that includes an actuator having two common electrode layers, one individual electrode layer, a piezoelectric element, and a piezoelectric layer, and ejects liquid from a nozzle by vibration of the actuator. The capacitance of the piezoelectric layer of the liquid ejection head is measured in an inspection process (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2004-96070 A Summary of the Invention [Problem to be solved by the invention]

[0004] In a printing device, it is important to measure the capacitance of the piezoelectric layer for purposes such as estimating the temperature of the head.

[0005] The present disclosure has been made in consideration of the above circumstances, and has an object to provide a printing device and a head capable of measuring capacitance. [Means for solving the problem]

[0006] A printing device according to one embodiment of the present disclosure comprises a piezoelectric body that deforms when a voltage is applied to it in order to eject liquid from a nozzle, an individual electrode formed on the piezoelectric body, a first common electrode formed on the piezoelectric body so as to face the individual electrode, a second common electrode that is applied with a voltage different from that of the first common electrode and is formed on the piezoelectric body so as to face the individual electrode, a first capacitor formed by the piezoelectric body, the individual electrode, and the first common electrode, and a detection circuit that detects the electrostatic capacitance of a second capacitor formed by the piezoelectric body, the individual electrode, and the second common electrode, and the detection circuit includes an oscillator circuit connected to the individual electrode.

[0007] A head according to one embodiment of the present disclosure comprises a piezoelectric body that deforms when a voltage is applied to it in order to eject liquid from a nozzle, an individual electrode formed on the piezoelectric body, a first common electrode formed on the piezoelectric body opposite the individual electrode, a second common electrode formed on the piezoelectric body opposite the individual electrode and to which a voltage different from that of the first common electrode is applied, a first capacitor formed by the piezoelectric body, the individual electrode, and the first common electrode, and a detection circuit that detects the capacitance of a second capacitor formed by the piezoelectric body, the individual electrode, and the second common electrode, and the detection circuit includes an oscillator circuit connected to the individual electrode. Effect of the Invention

[0008] In the printing device and head according to an embodiment of the present disclosure, the capacitance of the first capacitor and the second capacitor can be detected by using an oscillator circuit. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a plan view illustrating a printing device according to a first embodiment. [Diagram 2] FIG. 4 is an explanatory diagram illustrating the flow of ink between a subtank and an inkjet head. [Diagram 3] FIG. 2 is a simplified partial enlarged cross-sectional view of an ink-jet head. [Figure 4] FIG. 2 is a block diagram of a printing device. [Diagram 5] FIG. 2 is a circuit diagram of a detection circuit. [Figure 6] 10 is a flowchart illustrating a printing process performed by the control device. [Figure 7] FIG. 11 is a block diagram of a control device according to a second embodiment. [Figure 8] 10 is a timing chart showing an example of the on / off timing of a first detection switch and the on / off timing of a second detection switch. [Figure 9] 4 is a timing chart showing an example of voltage waveforms from a first capacitor and a second capacitor of a first actuator and a second actuator, which are input to a detection circuit. [Figure 10] FIG. 11 is a block diagram of a control device according to a third embodiment. [Figure 11] FIG. 11 is a circuit diagram of a detection circuit according to a fourth embodiment. [Figure 12] 10 is a flowchart illustrating a printing process performed by the control device. [Figure 13] FIG. 13 is a circuit diagram of a detection circuit according to a fifth embodiment. [Figure 14] 10 is a flowchart illustrating a printing process performed by the control device. [Figure 15] FIG. 13 is a schematic plan view of a printing device according to a sixth embodiment. [Figure 16] 10 is a flowchart illustrating a printing process performed by the control device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] (Embodiment 1) The present invention will be described below with reference to the drawings showing a printing device according to a first embodiment. Fig. 1 is a plan view showing the printing device, and Fig. 2 is an explanatory diagram showing the flow of ink between a sub-tank and an inkjet head. In the following description, the front, back, left and right directions shown in Fig. 1 will be used. The front and back directions correspond to the transport direction, and the left and right directions correspond to the scanning direction. The front side of Fig. 1 corresponds to the top, and the back side corresponds to the bottom, and up and down will also be used.

[0011] 1, the printing device 1 includes a platen 2, an ink ejection device 3, and transport rollers 4 and 5. A recording medium, that is, a recording paper 200, is placed on the upper surface of the platen 2. The ink ejection device 3 ejects ink onto the recording paper 200 placed on the platen 2 to record an image. The ink ejection device 3 includes a carriage 6, a sub-tank 7, four inkjet heads 8, a circulation pump 10, and the like.

[0012] Two guide rails 11 and 12 extending to the left and right are provided above the platen 2 to guide the carriage 6. An endless belt 13 extending to the left and right is connected to the carriage 6. The endless belt 13 is driven by a carriage drive motor 14. By driving the endless belt 13, the carriage 6 is guided by the guide rails 11 and 12 and reciprocates in the scanning direction in an area facing the platen 2. More specifically, while supporting four inkjet heads 8, the carriage 6 performs a first movement in which the heads are moved from one position to another position from left to right in the scanning direction, and a second movement in which the heads are moved from another position to one position from right to left in the scanning direction.

[0013] A cap 20 and a flushing receiver 21 are provided between the guide rails 11 and 12. The cap 20 and the flushing receiver 21 are disposed below the ink ejection device 3. The cap 20 is disposed at the right end of the guide rails 11 and 12, and the flushing receiver 21 is disposed at the left end of the guide rails 11 and 12. The cap 20 and the flushing receiver 21 may be disposed left and right reversed.

[0014] The sub-tank 7 and the four inkjet heads 8 are mounted on a carriage 6 and move back and forth in the scanning direction together with the carriage 6. The sub-tank 7 is connected to a cartridge holder 15 via a tube 17. Ink cartridges 16 of one or more colors (four colors in this embodiment) are attached to the cartridge holder 15. Examples of the four colors include black, yellow, cyan, and magenta.

[0015] Four ink chambers 19 are formed inside the subtank 7. The four ink chambers 19 store four colors of ink supplied from the four ink cartridges 16, respectively.

[0016] The four inkjet heads 8 are aligned in the scanning direction below the subtank 7. A plurality of nozzles 80 are formed on the bottom surface of each inkjet head 8. As shown in Fig. 2, one inkjet head 8 corresponds to one color of ink and is connected to one ink chamber 19. That is, the four inkjet heads 8 correspond to four colors of ink, respectively, and are connected to four ink chambers 19, respectively.

[0017] An ink supply port 8a and an ink discharge port 8b are provided on the top surface of the inkjet head 8. The ink supply port 8a and the ink discharge port 8b are connected to an ink chamber 19 via a tube or the like. A circulation pump 10 is interposed between the ink supply port 8a and the ink chamber 19.

[0018] The circulation pump 10 is a tube pump that pushes out the liquid in a tube by, for example, squeezing the tube with a rotor. The circulation pump 10 sends the ink in the ink chamber 19 to the inkjet head 8.

[0019] Ink sent from the ink chamber 19 by the circulation pump 10 flows into the inkjet head 8 through the ink supply port 8a and is ejected from the nozzle 80. Ink that is not ejected from the nozzle 80 returns to the ink chamber 19 through the ink discharge port 8b. The ink circulates between the ink chamber 19 and the inkjet head 8. Note that instead of the circulation pump 10, another power source for circulation, such as a device that sends compressed air into the subtank 7 to send the ink to the inkjet head 8, may be used. The four inkjet heads 8 eject the four colors of ink supplied from the subtank 7 onto the recording paper 200 while moving in the scanning direction together with the carriage.

[0020] As shown in FIG. 1, the transport roller 4 is disposed upstream (rear) of the platen 2 in the transport direction. The transport roller 5 is disposed downstream (front) of the platen 2 in the transport direction. The two transport rollers 4, 5 are driven synchronously by a motor (not shown). The two transport rollers 4, 5 transport the recording paper 200 placed on the platen 2 in a transport direction perpendicular to the scanning direction. The printing device 1 includes a control device 50. The control device 50 includes a CPU or logic circuit (e.g., FPGA), a storage unit 50a such as a non-volatile memory and a RAM, and the like. The control device 50 receives a print job from the external device 100 and stores it in the storage unit 50a. The control device 50 controls the driving of the ink ejection device 3 and the transport roller 4 based on the print job, and executes the print process.

[0021] 3 is a simplified partial enlarged cross-sectional view of the inkjet head 8. The inkjet head 8 includes a plurality of pressure chambers 81. The plurality of pressure chambers 81 form a plurality of pressure chamber rows. A vibration plate 82 is formed above the pressure chambers 81. A layered piezoelectric body 83 is formed above the vibration plate 82. A first common electrode 84 is formed above each pressure chamber 81, between the piezoelectric body 83 and the vibration plate 82.

[0022] A second common electrode 86 is provided inside the piezoelectric body 83. The second common electrode 86 is disposed above each pressure chamber 81 and above the first common electrode 84. The second common electrode 86 is disposed at a position not facing the first common electrode 84. An individual electrode 85 is formed on the upper surface of the piezoelectric body 83 above each pressure chamber 81. The individual electrode 85 faces the first common electrode 84 and the second common electrode 86 vertically with the piezoelectric body 83 in between. In other words, the inkjet head 8 includes the piezoelectric body 83, the individual electrode 85, the first common electrode 84, and the second common electrode 86. The inkjet head 8 also includes a detection circuit 65, which will be described later.

[0023] A nozzle plate 87 is provided below each pressure chamber 81. A plurality of nozzles 80 penetrating vertically are formed in the nozzle plate 87. Each nozzle 80 is disposed below each pressure chamber 81. The plurality of nozzles 80 form a plurality of nozzle rows extending along the rows of pressure chambers.

[0024] The multiple nozzles 80 include a first nozzle 80a and a second nozzle 80b. A portion of the piezoelectric body 83 arranged above the first nozzle 80a is also referred to as a first piezoelectric body 83a, and an individual electrode 85 arranged above the first nozzle 80a is also referred to as a first individual electrode 85a. A portion of the piezoelectric body 83 arranged above the second nozzle 80b is also referred to as a second piezoelectric body 83b, and an individual electrode 85 arranged above the second nozzle 80b is also referred to as a second individual electrode 85b.

[0025] The first common electrode 84 is connected to a COM terminal, which is ground in this embodiment, and the second common electrode 86 is connected to a VCOM terminal. The VCOM voltage is higher than the COM voltage. The individual electrode 85 is connected to a switch control unit 67 (see FIG. 4). When a high or low voltage is applied to the individual electrode 85, the piezoelectric body 83 deforms and the diaphragm 82 vibrates. The vibration of the diaphragm 82 causes ink to be ejected from the pressure chamber 81 through the nozzle 80.

[0026] 4 is a block diagram of the printing device 1. The printing device 1 includes an AC / DC converter 62 connected to an AC power source 61. The AC / DC converter 62 converts AC voltage into DC voltage and outputs it to a DC / DC converter 63. The DC / DC converter 63 changes the voltage and outputs it to a switch control unit (SW control unit) 67.

[0027] The switch control unit 67 includes a plurality of n-th switches 67(n) (n=1, 2,...) and a detection switch 67a. The switch control unit 67 configures a switching circuit. The n-th switch 67(n) and the detection switch 67a are configured by, for example, an analog switch IC. One end of each of the n-th switches 67(n) and one end of the detection switch 67a are connected to an individual electrode 85 via a common bus.

[0028] The other ends of the multiple nth switches 67(n) are connected to multiple nth waveform generating units 66(n) (n = 1, 2, ...), respectively. That is, the first switch 67(1) is connected to the first waveform generating unit 66(1), the second switch 67(2) is connected to the second waveform generating unit 66(2), and the nth switch 67(n) is connected to the nth waveform generating unit 66(n). The AC / DC converter 62 converts the AC voltage into a DC voltage and outputs it to the second DC / DC converter 68. The second DC / DC converter 68 outputs a VCOM voltage to each of the n-th waveform generating units 66(n), and also outputs the VCOM voltage to the second common electrode 86.

[0029] A first capacitor 89a is formed by the individual electrode 85, the first common electrode 84, and the piezoelectric body 83. A second capacitor 89b is formed by the individual electrode 85, the second common electrode 86, and the piezoelectric body 83.

[0030] The other end of the detection switch 67a is connected to a terminal 31 (see FIG. 5) of the detection circuit 65. The detection circuit 65 detects the capacitance of the actuator 88, in other words, the capacitance of the first capacitor 89a and the second capacitor 89b. The printing device 1 includes a control circuit 64. The control circuit 64 includes a CPU, a non-volatile memory, a RAM, a logic circuit (e.g., FPGA), or the like. The control circuit 64 causes the switch control unit 67 to connect or disconnect the n-th switch 67(n) and the detection switch 67a. The control circuit 64 causes each n-th waveform generating unit 66(n) to output a drive waveform. Each n-th waveform generating unit 66(n) outputs a different waveform. The control circuit 64 causes the detection circuit 65 to detect the capacitance. The control circuit 64 instructs the second DC / DC converter 68 to specify a voltage value. The second DC / DC converter 68 outputs a voltage corresponding to the specified voltage value.

[0031] A case where the actuator 88 is driven will be described. For example, when the actuator 88 is driven by a drive waveform generated by the first waveform generating unit 66(1), the control circuit 64 causes the switch control unit 67 to connect only the first switch 67(1) and output a drive waveform from the first waveform generating unit 66(1) to the actuator 88. At this time, all other switches, that is, the second switch 67(2), the third switch 67(3), ..., the nth switch 67(n), and the detection switch 67a, are disconnected. The same process is performed when the actuator 88 is driven by a drive waveform generated by the second waveform generating unit 66(2), the third waveform generating unit 66(3), ..., or the nth waveform generating unit 66(n).

[0032] The circuit operation for detecting the capacitance will be described. The control circuit 64 connects only the detection switch 67a to the switch control section 67. The detection circuit 65, for example, charges and discharges the capacitance to measure the capacitance. At this time, all of the n-th switches 67(n), i.e., the first switch 67(1), the second switch 67(2), ..., the n-th switch 67(n), are disconnected.

[0033] 5 is a circuit diagram of the detection circuit 65. The detection circuit 65 includes a clap-type oscillation circuit 30. The clap-type oscillation circuit 30 includes an inductor 32. One end of the inductor 32 is connected to a terminal 31. The terminal 31 is connected to the other end of a detection switch 67a. The other end of the inductor 32 is connected to the gate of an FET 33. The drain of the FET 33 is connected to the positive electrode of a power supply 37. The source of the FET 33 is connected to ground via a resistor 36. The negative electrode of the power supply 37 is connected to ground. The FET 33 performs a switching function. Instead of the FET, an element having a switching function, such as a bipolar transistor, may be used.

[0034] The clap-type oscillator circuit 30 includes two capacitors 34 and 35. The two capacitors 34 and 35 are connected in series. One capacitor 34 is connected to the gate of the FET 33. The other capacitor 35 is connected to ground. The clap-type oscillator circuit 30 includes a resistor 38. One end of the resistor 38 is connected to the gate of the FET 33, and the other end is connected to ground. A waveform signal is output from the connection point between the FET 33, the resistor 36, and the capacitors 34 and 35.

[0035] The detection circuit 65 includes a waveform shaping circuit 40, an AND gate 41, a reference oscillation circuit 42, a frequency divider circuit 43, a counter circuit 44, and a memory unit 45. The waveform shaping circuit 40, the AND gate 41, the reference oscillation circuit 42, the frequency divider circuit 43, and the counter circuit 44 form a direct count type frequency counter. The waveform shaping circuit 40 is connected to the output of the clap type oscillation circuit 30, and the waveform signal is input to the waveform shaping circuit 40.

[0036] The waveform shaping circuit 40 shapes the input waveform signal and outputs it to the AND gate 41. For example, it outputs it as a rectangular pulse wave. The reference oscillation circuit 42 generates a clock signal and outputs it to the frequency division circuit 43. The frequency division circuit 43 divides the input clock signal and outputs it to the AND gate 41. For example, the High time of the frequency-divided clock signal becomes the measurement time. The AND gate 41 outputs the pulse wave input from the waveform shaping circuit 40 during the measurement time to the counter circuit 44. The counter circuit 44 counts the number of pulses of the input pulse wave and divides the number of pulse waves by the measurement time to derive the frequency F1 of the waveform signal output from the clap-type oscillation circuit 30. For example, if the number of pulses input to the counter circuit 44 is 10,000 and the measurement time is 1 ms, a frequency of 10,000 / 0.001=10 MHz is derived. That is, the frequency F1 of the waveform signal is derived based on the following formula 1. In the following formula 1, C1 represents the capacitance of the capacitor 34, C2 represents the capacitance of the capacitor 35, C3 represents the combined capacitance of the first capacitor 89a and the second capacitor 89b, and L1 represents the inductance of the inductor 32.

number

[0037] The storage unit 45 stores a reference frequency F0 of the waveform signal from the first capacitor 89a and the second capacitor 89b and a reference combined capacitance C0 of the first capacitor 89a and the second capacitor 89b in correspondence with each other. The counter circuit 44 calculates the difference between the frequency F1 and the reference frequency F0. The counter circuit 44 calculates a difference C3-C0 between the combined capacitance C3 of the first capacitor 89a and the second capacitor 89b and the reference combined capacitance C0 from the frequency difference F1-F0, and adds the difference C3-C0 and the reference combined capacitance C0 to find the combined capacitance C3.

[0038] The frequency difference F1-F0 corresponds to the capacitance difference C3-C0, and the temperature change amount of the actuator 88 corresponds to the capacitance difference C3-C0. That is, the frequency difference F1-F0 corresponds to the temperature change amount of the actuator 88. Therefore, the temperature change amount of the actuator 88 can be obtained from the frequency difference F1-F0.

[0039] 6 is a flowchart explaining the printing process by the control device 50. The control device 50 determines whether or not a print job has been received from the external device 100 (S1). If a print job has not been received (S1: NO), the control device 50 returns the process to step S1. If a print job has been received (S1: YES), the control device 50 executes a flushing process (S2). The flushing process is a process in which ink is ejected from the nozzles 80 for purposes other than printing.

[0040] Next, the control device 50 executes a capacitance detection process (S3). The capacitance detection process is executed periodically, for example, to detect the temperature of the inkjet head 8. The control device 50 outputs a detection execution command to the control circuit 64, and the control circuit 64 causes the detection circuit 65 to detect the capacitance of the first capacitor 89a and the second capacitor 89b. Next, the control device 50 executes one print task (S4). A print task is a unit that constitutes a print job. Specifically, it is a liquid ejection process performed while the inkjet head 8 moves rightward or leftward by the left-right width of the recording paper 200. Next, the control device 50 determines whether or not one print task has been completed (S5). Note that in one print task, the carriage 6 performs one scan. If one print task has not been completed (S5: NO), the process returns to step S5. If one print task has been completed (S5: YES), the control device 50 determines whether or not the print job has been completed (S6).

[0041] If the print job is completed (S6: YES), the control device 50 ends the print process. If the print job is not completed (S6: NO), the control device 50 determines whether or not the second print task is completed (S7). If the second print task is completed (S7: YES), the control device 50 determines whether or not it is time to perform a flushing process (S8). The flushing process is performed periodically for maintenance of the nozzle 80. If it is time to perform a flushing process (S8: YES), the control device 50 performs a flushing process (S9), performs a capacitance detection process (S10), and returns the process to step S4. Note that the control device 50 may determine whether or not one print task is completed in step S7. Also, the flushing process may be performed after performing the capacitance detection process.

[0042] In step S8, if it is not the timing to perform the flushing process (S8: NO), the control device 50 executes a capacitance detection process (S15) and returns the process to step S4.

[0043] In step S7, if the three print tasks are not completed (S7: NO), the control device 50 determines whether it is time to perform flushing processing (S11). If it is time to perform flushing processing (S11: YES), the control device 50 executes the flushing processing (S12) and returns the process to step S4.

[0044] In step S11, if it is not the timing to perform the flushing process (S11: NO), the control device 50 judges whether it is the timing to perform the non-ejection flushing process (S13). The non-ejection flushing process is a process for preventing the nozzle 80 from drying without discharging liquid, and more specifically, it is a process for slightly deforming the piezoelectric body 83 to vibrate the surface (meniscus) of the liquid. The non-ejection flushing process is periodically performed. If it is the timing to perform the non-ejection flushing process (S13: YES), the control device 50 performs the non-ejection flushing process (S14) and returns the process to step S4. In step S14, the control device 50 outputs a command to the control circuit 64 to perform the non-ejection flushing process, and the control circuit 64 causes the n-th waveform generating unit 66(n) to generate a drive waveform corresponding to the non-ejection flushing process and supply it to the individual electrode 85. If it is not the timing to perform the non-ejection flushing process (S13: NO), the control device 50 returns the process to step S4.

[0045] In steps S10 and S15, the detection switch 67a is connected in a state where a voltage is applied to the first common electrode 84 (COM) and the second common electrode 86 (VCOM) by the execution of the flushing process or the print task, that is, in a live line state, and the capacitance detection process is executed. When the detection switch 67a is connected in a live line state, a voltage divided by the first capacitor 89a and the second capacitor 89b is input to the clap-type oscillation circuit 30. The parallel resistance values ​​of the first capacitor 89a and the second capacitor 89b are sufficiently large. Therefore, even if the detection switch 67a is connected in a live line state, the clap-type oscillation circuit 30 is not destroyed and the capacitance detection process can be executed.

[0046] In order to prevent the destruction of the detection circuit 65, the voltage of VCOM may be turned on and then turned off, and the detection switch 67a may be connected while waiting for the voltage of VCOM to stabilize. However, the waiting time increases the time required for the capacitance detection process. As described above, in the first embodiment, the control device 50 can perform the capacitance detection process when it is in a live line state, for example, during printing, and therefore the time required for detecting the capacitance can be shortened.

[0047] In the first embodiment, by using an oscillator circuit, for example the clap-type oscillator circuit 30, in the detection circuit 65, it is possible to detect the capacitances of the first capacitor 89a and the second capacitor 89b.

[0048] Furthermore, for example, during printing, an oscillator circuit is connected to the individual electrodes 85 to detect the capacitances of the first capacitor 89a and the second capacitor 89b while a voltage is applied between the first common electrode 84 and the second common electrode 86. There is no need to turn on and off the voltage application to the second common electrode 86 and wait until the voltage stabilizes, and the time required for capacitance detection can be shortened.

[0049] Furthermore, by measuring the frequency every time the carriage 6 performs one or two scans a predetermined number of times, the number of times the capacitance detection process is performed can be reduced.

[0050] (Embodiment 2) The present invention will be described below with reference to the drawings showing a printer 1 according to a second embodiment. Among the configurations according to the second embodiment, the same configurations as those in the first embodiment are given the same reference numerals, and detailed description thereof will be omitted. Fig. 7 is a block diagram of the control device 50. Note that in Fig. 7, the AC power supply 61 and the DC / DC converter 63 are omitted.

[0051] The control device 50 includes a plurality of actuators 88 including a first actuator 88a and a second actuator 88b. The first actuator 88a and the second actuator 88b are each provided with a switch control section 67. The nth waveform generating section 66(n) is connected to the nth switch 67(n) of each switch control section 67. That is, one nth waveform generating section 66(n) is connected to the plurality of nth switches 67(n). The detection circuit 65 is connected to the detection switch 67a of each switch control section 67. That is, one detection circuit 65 is connected to the plurality of detection switches 67a. Here, the detection switch 67a connected to the first actuator 88a is referred to as a first detection switch 67a1, and the detection switch 67a connected to the second actuator 88b is referred to as a second detection switch 67a2.

[0052] For example, when detecting the capacitance of the first actuator 88a and the second actuator 88b, the first detection switch 67a1 is first connected and the second detection switch 67a2 is disconnected to detect the capacitance of the first actuator 88a. Next, the first detection switch 67a1 is disconnected and the second detection switch 67a2 is connected to detect the capacitance of the second actuator 88b. As in the first embodiment, the capacitances of the first actuator 88a and the second actuator 88b are detected with a voltage applied between the first common electrode 84 and the second common electrode 86.

[0053] Fig. 8 is a timing chart showing an example of the on / off timing of the first detection switch 67a1 and the on / off timing of the second detection switch 67a2. In Fig. 8, W1 indicates the on / off timing of the first detection switch 67a1, and W2 indicates the on / off timing of the second detection switch 67a2. On means that the switch is connected, and off means that the switch is disconnected.

[0054] As shown in FIG. 8, in the case where "waiting time exists," there is a waiting time from when the first detection switch 67a1 is turned off until the second detection switch 67a2 is turned on, and there is a waiting time from when the second detection switch 67a2 is turned off until the first detection switch 67a1 is turned on. In the case of "simultaneous", the first detection switch 67a1 and the second detection switch 67a2 are turned on and off at the same time. In the case of "overlap", while the first detection switch 67a1 is on, the second detection switch 67a2 is on, and after a predetermined time has passed, the first detection switch 67a1 is off, while the second detection switch 67a2 is on, the first detection switch 67a1 is on, and after a predetermined time has passed, the first detection switch 67a1 is off. That is, when the first detection switch 67a1 and the second detection switch 67a2 are switched on and off, there is a time when both the first detection switch 67a1 and the second detection switch 67a2 are on.

[0055] Fig. 9 is a timing chart showing an example of voltage waveforms from the first capacitor 89a and the second capacitor 89b of the first actuator 88a and the second actuator 88b, which are input to the detection circuit 65. In Fig. 9, "with wait time", "simultaneous", and "with overlap" correspond to "with wait time", "simultaneous", and "with overlap" in Fig. 8, respectively.

[0056] When there is a standby time, the voltage waveforms from the first capacitor 89a and the second capacitor 89b input to the detection circuit 65 become unstable for time T1 during the standby time. When they are simultaneous, the voltage waveform becomes unstable for time T2. When there is an overlap, when the first detection switch 67a1 and the second detection switch 67a2 are switched on and off, the voltage waveform becomes unstable for time T3. However, time T3 is only the time for a few waves, which is shorter than times T1 and T2.

[0057] In embodiment 2, when the first detection switch 67a1 and the second detection switch 67a2 are switched on and off, a time is provided during which both the first detection switch 67a1 and the second detection switch 67a2 are on, thereby stabilizing the voltage waveforms from the first capacitor 89a and the second capacitor 89b input to the detection circuit 65 in a short period of time.

[0058] (Embodiment 3) The present invention will be described below with reference to the drawings showing a printing device 1 according to a third embodiment. Among the components according to the third embodiment, the same components as those in the first or second embodiment are given the same reference numerals, and detailed description thereof will be omitted. Fig. 10 is a block diagram of a control device 50.

[0059] As shown in FIG. 10, the printing device 1 includes a first detection circuit 65(1) corresponding to the first actuator 88a and a second detection circuit 65(2) corresponding to the second actuator 88b. The first actuator 88a includes a first piezoelectric body 83a (see FIG. 3), and the second actuator 88b includes a second piezoelectric body 83b (see FIG. 3). That is, the detection circuit 65(1) corresponds to the first piezoelectric body 83a, and the second detection circuit 65(2) corresponds to the second piezoelectric body 83b. The first detection circuit 65(1) and the second detection circuit 65(2) each include a clap-type oscillation circuit 30. Hereinafter, the clap-type oscillation circuit 30 of the first detection circuit 65(1) is referred to as the first oscillation circuit, and the clap-type oscillation circuit 30 of the second detection circuit 65(2) is referred to as the second oscillation circuit.

[0060] The control circuit 64 connects the first detection switch 67a1 to cause the first detection circuit 65(1) to detect the capacitance of the first piezoelectric body 83a. The control circuit 64 connects the second detection switch 67a2 to cause the second detection circuit 65(2) to detect the capacitance of the first piezoelectric body 83a. The first oscillation circuit and the second oscillation circuit detect the capacitance of the first piezoelectric body 83a and the second piezoelectric body 83b approximately simultaneously. In other words, the first oscillation circuit and the second oscillation circuit may partially overlap the time when they detect the capacitance of the first piezoelectric body 83a and the second piezoelectric body 83b, or may coincide the start of the time when they detect the capacitance of the first piezoelectric body 83a and the second piezoelectric body 83b. Furthermore, the first oscillation circuit and the second oscillation circuit may coincide the start of the time when they detect the capacitance of the first piezoelectric body 83a and the second piezoelectric body 83b, and may also coincide the cycle of the time when they detect the capacitance of the first piezoelectric body 83a and the second piezoelectric body 83b. As in the first embodiment, when a voltage is applied between the first common electrode 84 and the second common electrode 86, the electrostatic capacitance of each of the first actuator 88a and the second actuator 88b is detected.

[0061] In embodiment 3, the first oscillator circuit and the second oscillator circuit simultaneously detect the capacitance of the first piezoelectric body 83a and the second piezoelectric body 83b, thereby reducing the capacitance detection time compared to when the capacitance of each piezoelectric body is detected in sequence.

[0062] (Embodiment 4) The present invention will be described below with reference to the drawings showing a printing device 1 according to a fourth embodiment. Among the components according to the fourth embodiment, the same components as those in the first to third embodiments are given the same reference numerals, and detailed description thereof will be omitted. FIG. 11 is a circuit diagram of a detection circuit 65A. The detection circuit 65A includes a waveform shaping circuit 40, an AND gate 41, a reference oscillation circuit 42, a frequency dividing circuit 43, a counting circuit 44, a storage unit 45, and an arithmetic circuit 46. The waveform shaping circuit 40, the AND gate 41, the reference oscillation circuit 42, the frequency dividing circuit 43, the counting circuit 44, and the arithmetic circuit 46 constitute a frequency counter of a reciprocal counting type.

[0063] The waveform shaping circuit 40 shapes the input waveform signal and outputs it to the frequency dividing circuit 43. The frequency dividing circuit 43 divides the input waveform signal and outputs it to the AND gate 41. The reference oscillation circuit 42 generates a clock signal and outputs it to the AND gate 41. The AND gate 41 outputs a pulse wave of the clock signal input from the reference oscillation circuit 42 during one period of the divided waveform signal. The counter circuit 44 counts the number of pulses of the input pulse wave and outputs it to the calculation circuit 46. The calculation circuit 46 calculates the inverse of the counted number of pulses, that is, the period of the frequency-divided waveform signal, and multiplies the period by the frequency division ratio to calculate the period of the waveform signal. Then, the calculation circuit 46 multiplies the period of the waveform signal by the frequency of the clock signal to derive the frequency F1 of the waveform signal from the clap-type oscillation circuit 30 including the first capacitor 89a and the second capacitor 89b. For example, when the frequency division ratio is 4, the frequency of the clock signal is 20 MHz, and the number of counted pulses is 1000, a frequency of 80 kHz is derived. It should be noted that frequency divider circuit 43 does not have to be provided, and in the case where frequency divider circuit 43 is not provided, calculation circuit 46 calculates the period of the waveform signal.

[0064] Fig. 12 is a flowchart illustrating the printing process by the control device 50. Steps S21 to S25 in Fig. 12 are similar to steps S1 to S5 (see Fig. 6) in the first embodiment, and therefore detailed description thereof will be omitted.

[0065] In step S25, if one print task is completed (S25: YES), the control device 50 determines whether or not printing of one page is completed (S26). If printing of one page is not completed (S26: NO), the control device 50 returns the process to step S24. If printing of one page is completed (S26: YES), the control device 50 determines whether or not the print job is completed (S27). If the print job is completed (S27: YES), the control device 50 ends the print process. If the print job is not completed (S27: NO), the control device 50 performs paper feed processing (S28).

[0066] Here, the recording paper 200 includes a first recording medium and a second recording medium. The first recording medium and the second recording medium each correspond to one page. For example, when printing of the first recording medium is completed and the print job is not completed, in the paper feeding process, the second recording medium is conveyed to the platen 2 through a state in which only the conveying roller 5 conveys the first recording medium, a state in which only the conveying roller 5 conveys the first recording medium and a state in which only the conveying roller 5 conveys the second recording medium. That is, the first recording medium and the second recording medium are conveyed toward the nozzle 80. Note that, when the second recording medium reaches the platen 2, the first recording medium leaves the conveying roller 5, and the conveyance of the first recording medium ends.

[0067] After the paper feed process starts, the control device 50 executes a capacitance detection process (S29) in parallel with the paper feed process, and returns to S24. The control device 50 outputs a detection execution command to the detection circuit 65A, and the control circuit 64 causes the detection circuit 65A to detect the capacitances of the first capacitor 89a and the second capacitor 89b. That is, after printing on the first recording medium is completed and before printing on the second recording medium is started, the detection circuit 65A measures the period of the waveform signal output from the clap-type oscillation circuit 30 and detects the capacitance.

[0068] The time between the end of printing on the first recording medium and the start of printing on the second recording medium is shorter than the time between print tasks. A frequency counter using a reciprocal counting method can measure the frequency in a shorter time than a frequency counter using a direct counting method. Therefore, the detection circuit 65A measures the frequency after the end of printing on the first recording medium and before the start of printing on the second recording medium.

[0069] In the fourth embodiment, the frequency is measured after printing on the first recording medium is completed and before printing on the second recording medium is started, thereby making it possible to shorten the time required for measuring the frequency.

[0070] In addition, by using a frequency counter that uses a reciprocal counting method, frequency measurement can be achieved in a short period of time.

[0071] (Embodiment 5) The present invention will be described below with reference to the drawings showing a printing device 1 according to a fifth embodiment. Among the components according to the fifth embodiment, the same components as those in the first to fourth embodiments are given the same reference numerals, and detailed description thereof will be omitted. FIG. 13 is a circuit diagram of a detection circuit 65B. The detection circuit 65B includes a waveform shaping circuit 40, an AND gate 41, a reference oscillation circuit 42, a frequency divider circuit 43, a counter circuit 44, a memory unit 45, an arithmetic circuit 46, and a multiplication circuit 47. The waveform shaping circuit 40, the AND gate 41, the reference oscillation circuit 42, the frequency divider circuit 43, the counter circuit 44, and the arithmetic circuit 46 constitute a frequency counter using a multiplication circuit.

[0072] The waveform signal output from the clap-type oscillator circuit 30 is input to the multiplier circuit 47. The multiplier circuit 47 increases the frequency of the waveform signal, for example by 10 times, and outputs the increased frequency to the waveform shaping circuit 40. The waveform shaping circuit 40, the divider circuit 43, the AND gate 41, the reference oscillator circuit 42, the counter circuit 44, and the arithmetic circuit 46 calculate the period of the waveform signal in the same manner as in the reciprocal counting method of the fourth embodiment, multiply the period by the frequency of the clock signal, and derive the frequency F1 of the waveform signal from the clap-type oscillator circuit 30 including the first capacitor 89a and the second capacitor 89b. The multiplier circuit 47 may be incorporated into the frequency counter of the direct counting method of the first embodiment to derive the frequency F1.

[0073] Fig. 14 is a flow chart for explaining the printing process by the control device 50. Steps S41 to S46 in Fig. 14 are similar to steps S21 to S26 (see Fig. 12) in the fourth embodiment, and therefore detailed explanations thereof will be omitted.

[0074] In step S46, if printing of one page is completed (S46: YES), the control device 50 determines whether the print job is completed or not (S47). If the print job is not completed (S47: NO), the control device 50 returns the process to step S44. If the print job is completed (S47: YES), that is, if the print job is not stored in the storage unit 50a, the control device 50 executes a flushing process (S48), executes a capacitance detection process (S49), and ends the printing process. That is, the control device 50 executes the flushing process and the capacitance detection process in parallel, and ends the printing process.

[0075] In the fifth embodiment, the control device 50 executes the capacitance detection process after all printing based on the print job is completed. When the multiplication circuit 47 is incorporated into a direct count type frequency counter to derive the frequency F1, it may take a long time to derive the frequency. Therefore, by executing the capacitance detection process after all printing based on the print job is completed, printing can be executed smoothly.

[0076] In addition, the control device 50 executes the flushing process and the capacitance detection process in parallel after all printing based on the print job is completed. The time required for the flushing process is longer than the time between print tasks. By executing the capacitance detection process during the flushing process, the capacitance detection process by the detection circuit 65B can be realized. Also, by executing them in parallel, the time required for the entire print process can be reduced.

[0077] When the suction process is performed from the nozzle 80, the suction process requires a time equal to or longer than that of the flushing process. Therefore, the capacitance detection process may be performed during the suction process. The flushing process and the suction process are included in the maintenance process.

[0078] (Embodiment 6) The present invention will be described below with reference to the drawings of a printing device 1A according to a sixth embodiment. Among the components according to the sixth embodiment, the same components as those according to the first to fifth embodiments are given the same reference numerals, and detailed description thereof will be omitted. FIG. 15 is a schematic plan view of the printing device 1A. As shown in FIG. 15, the printing device 1A includes a platen 2, four inkjet heads 8A, two transport rollers 4 and 5, a control device 50, and the like. The printing device 1A is a line head type printing device, and the inkjet heads 8A are fixed at predetermined positions.

[0079] Labels 201 are placed on the upper surface of the platen 2. The labels 201 include a first label and a second label. The four inkjet heads 8A are lined up in the transport direction (front-rear direction) above the platen 2. Each inkjet head 8A is a so-called line-type head. For example, each inkjet head 8A has a plurality of inkjet heads 8 of the first embodiment, and the inkjet heads 8 of the first embodiment are arranged in a staggered manner. Ink is supplied to the inkjet heads 8A from an ink tank. Inks of different colors are supplied to the four inkjet heads 8A.

[0080] As shown in Fig. 1, the two transport rollers 4, 5 are disposed on the rear and front sides, respectively, of the platen 2. The two transport rollers 4, 5 are each driven by a motor (not shown) and transport the label 201 on the platen 2 forward. For example, after transporting the first label, they transport the second label. The control device 50 controls each part of the printer 1A based on the print data sent from the external device 100. The printer 1A is equipped with a detection circuit 65 (see Fig. 5).

[0081] Fig. 16 is a flow chart for explaining the printing process by the control device 50. In Fig. 16, steps S61 to S63 are similar to steps S1 to S3 (see Fig. 6) in the first embodiment, and therefore detailed explanations thereof will be omitted.

[0082] After executing the capacitance detection process (S63), the control device 50 executes printing of one label (S64) and determines whether printing of one label is complete (S65). If printing of one label is not complete (S65: NO), the control device 50 returns the process to step S65. If printing of one label is complete (S65: YES), the control device 50 determines whether the print job is complete (S66). If the print job is complete (S66: YES), the control device 50 ends the print process.

[0083] If the print job is not complete (S66: NO), the control device 50 conveys the label (S67), executes the capacitance detection process (S68), and returns to step S64. That is, after the control device 50 finishes printing on the first label and before it starts printing on the second label, the detection circuit 65 measures the period of the waveform signal output from the clap-type oscillation circuit 30 and detects the capacitance.

[0084] In the sixth embodiment, the detection circuit 65 measures the frequency after printing of the first label is finished and before printing of the second label starts. If a frequency counter using a direct count method is used to derive the frequency F1, it may take a long time to derive the frequency. The time between the end of printing of the first label and the start of printing of the second label is equal to or longer than the time between print tasks, so it is possible to derive the frequency F1 using the direct count method.

[0085] The embodiments disclosed herein are illustrative in all respects and should not be considered as limiting. The technical features described in each embodiment can be combined with each other, and the scope of the present invention is intended to include all modifications within the scope of the claims and the scope equivalent to the claims. [Explanation of symbols]

[0086] 1, 1A printing device 4, 5 Conveyor roller (conveyor section) 6 Carriage 8, 8A Inkjet Head 30 Clapp-type oscillator circuit 50 Control device 64 Control circuit 65, 65A, 65B Detection circuit 67 Switch control section (switching circuit) 80 Nozzles 80a No. 1 nozzle 80b No. 2 nozzle 83 Piezoelectric 84 1st common electrode 85a 1st individual electrode 85b 2nd individual electrode 86 2nd common electrode 89a First capacitor 89b Second capacitor

Claims

1. a piezoelectric body that deforms when a voltage is applied to it in order to eject liquid from a nozzle; An individual electrode formed on the piezoelectric body; a first common electrode formed on the piezoelectric body so as to face the individual electrodes; a second common electrode to which a voltage different from that of the first common electrode is applied and which is formed on the piezoelectric body so as to face the individual electrodes; a detection circuit that detects the capacitance of a first capacitor formed by the piezoelectric body, the individual electrode, and the first common electrode, and a second capacitor formed by the piezoelectric body, the individual electrode, and the second common electrode; Equipped with the detection circuit includes an oscillation circuit connected to the individual electrode; a switching circuit for switching between connection and disconnection of the individual electrodes and the oscillation circuit, The detection circuit is connected to the individual electrodes via the switching circuit. Printing device.

2. When detecting the capacitance of the piezoelectric body, the switching circuit connects the oscillator circuit to the individual electrodes while a voltage is applied between the first common electrode and the second common electrode. The printing device of claim 1 .

3. the nozzles include a first nozzle and a second nozzle; The printing device includes: A first piezoelectric element corresponding to the first nozzle; a second piezoelectric element corresponding to the second nozzle; Equipped with the individual electrodes include a first individual electrode formed on the first piezoelectric body and a second individual electrode formed on the second piezoelectric body; When the detection of the capacitance of the first piezoelectric body is terminated and the detection of the capacitance of the second piezoelectric body is started, the first individual electrode and the second individual electrode are connected to the oscillation circuit for a predetermined time, and then the connection between the first individual electrode and the oscillation circuit is cut. The printing device according to claim 2 .

4. The nozzles include a first nozzle and a second nozzle, the piezoelectric element includes a first piezoelectric element and a second piezoelectric element corresponding to the first nozzle and the second nozzle, respectively; the oscillation circuit includes a first oscillation circuit and a second oscillation circuit corresponding to the first piezoelectric body and the second piezoelectric body, respectively; The first oscillator circuit and the second oscillator circuit simultaneously detect the capacitances of the first piezoelectric body and the second piezoelectric body, respectively. The printing device according to claim 2 .

5. the detection circuit includes a measurement circuit that measures a frequency output from the oscillation circuit; The measurement circuit measures the frequency each time a predetermined number of processes constituting a printing process are completed.

5. The printing device according to claim 1.

6. The measurement circuit measures the frequency output from the oscillation circuit by a direct count frequency counter. The printing device according to claim 5 .

7. a head including the piezoelectric body, the individual electrodes, the first common electrode, the second common electrode, and the detection circuit; a carriage that supports the head and performs a first movement to move the head from a first position to a second position in a scanning direction and a second movement to move the head from the second position to the first position in the scanning direction; In the case of printing during the first movement or the second movement, The measurement circuit measures the frequency every time the carriage makes one or two scans during the printing process.

7. The printing device according to claim 5 or 6.

8. When the first label and the second label are printed by a line head method, the measurement circuit measures the frequency during the printing process after the printing of the first label is completed and before the printing of the second label is started.

7. The printing device according to claim 5 or 6.

9. The detection circuit detects the capacitances of the first capacitor and the second capacitor before or after a flushing process in which liquid is ejected from the nozzle.

9. The printing device according to claim 5,

10. a conveying unit that conveys a first recording medium and a second recording medium toward the nozzle; the detection circuit includes a second measurement circuit that measures a period of the signal output from the oscillation circuit; After printing on the first recording medium is completed and before printing on the second recording medium is started, the second measurement circuit measures the period.

5. The printing device according to claim 1.

11. the second measurement circuit measures the period of the signal output from the oscillation circuit by a frequency counter of a reciprocal counting type; The printing device of claim 10.

12. A memory unit is provided, The storage unit stores a print job, the detection circuit includes a third measurement circuit that measures the frequency output from the oscillation circuit by a frequency counter using a multiplication circuit; After all printing based on the print job stored in the storage unit is completed, the third measurement circuit measures the frequency.

5. The printing device according to claim 1.

13. The third measurement circuit measures the frequency when a maintenance process is performed after all printing based on the print job is completed. The printing device of claim 12.

14. a piezoelectric body that deforms when a voltage is applied to it in order to eject liquid from a nozzle; An individual electrode formed on the piezoelectric body; a first common electrode formed on the piezoelectric body so as to face the individual electrodes; a second common electrode to which a voltage different from that of the first common electrode is applied and which is formed on the piezoelectric body so as to face the individual electrodes; a detection circuit that detects the capacitance of a first capacitor formed by the piezoelectric body, the individual electrode, and the first common electrode, and a second capacitor formed by the piezoelectric body, the individual electrode, and the second common electrode; Equipped with the detection circuit includes an oscillation circuit connected to the individual electrode; a switching circuit for switching between connection and disconnection of the individual electrodes and the oscillation circuit, The detection circuit is connected to the individual electrodes via the switching circuit. head.

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