Liquid dispensing head and liquid dispensing device

Abstract

Conventionally, in liquid ejection heads that have a piezoelectric pump for circulating ink, the current flowing through the piezoelectric pump was measured by adding a shunt resistor or current detection circuit to determine the normal operation of the piezoelectric pump. However, this configuration resulted in a large circuit size, which hindered the miniaturization of liquid ejection heads. [Solution] A liquid discharge head having a piezoelectric pump for circulating ink, comprising: a boost circuit that generates a boosted voltage for driving the piezoelectric pump in response to a drive signal; a drive circuit that generates a pump drive signal for driving the piezoelectric pump based on the boosted voltage; and a monitoring circuit that monitors the displacement of the boosted voltage output from the boost circuit, wherein the monitoring circuit holds the results of monitoring the boosted voltage in a readable format.

Description

Technical Field

[0001] The present invention relates to a liquid ejection device that stirs ink using a piezoelectric pump.

Background Art

[0002] In recent inkjet printers, ink circulation type liquid ejection devices are often used to record images at high speed using high-concentration ink. In such a device, an ink supply path and an ink recovery path are provided for ink circulation, and a configuration is adopted in which a differential pressure is generated between the ink supply path and the ink recovery path to obtain a circulating flow of ink.

[0003] Patent Document 1 describes an ink circulation device having two storage parts for supplying and refluxing ink to a liquid ejection head, a circulation pump for transporting ink between the storage parts, a pressure sensor, and a drive circuit for driving the circulation pump according to the output of the pressure sensor.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the technology described in Patent Document 1 above, a piezoelectric pump having a piezoelectric element is provided in the liquid ejection head to circulate high-concentration ink.

[0006] In addition to the piezoelectric pump, a drive circuit for the piezoelectric pump, an ink storage part, etc. are mounted on the liquid ejection head, but miniaturization of the liquid ejection head is desired in order to miniaturize the printer.

[0007] Furthermore, during operation of the piezoelectric pump, malfunctions such as electrode detachment or cracking of the piezoelectric element may occur, preventing it from performing as intended. Patent document 2 describes an abnormality detection circuit that determines the normality of the piezoelectric element by measuring the current flowing to the piezoelectric element by adding a shunt resistor and a current detection circuit. However, such a circuit configuration increases the circuit size, which has been an obstacle to miniaturizing the liquid discharge head, including the piezoelectric pump.

[0008] The object of the present invention is to solve at least one of the problems of the prior art described above.

[0009] The objective of the present invention is, [Means for solving the problem]

[0010] To achieve the above objective, a liquid dispensing head according to one aspect of the present invention has the following configuration. That is, A liquid dispensing head having a piezoelectric pump for circulating ink, A boosting means that generates a boosted voltage for driving the piezoelectric pump in response to a drive signal, A driving means that generates a pump drive signal to drive the piezoelectric pump based on the boosted voltage, The system includes a monitoring means for monitoring the displacement of the boosted voltage output from the boosting means, The monitoring means is characterized by storing the results of monitoring the boosted voltage in a readable format. [Effects of the Invention]

[0011] The present invention has the effect of providing a liquid dispensing head that incorporates a circuit capable of detecting whether or not the piezoelectric pump is malfunctioning.

[0012] Other features and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings. In the accompanying drawings, the same or similar components are given the same reference numeral. [Brief explanation of the drawing]

[0013] The accompanying drawings are included in the specification, form a part thereof, show embodiments of the present invention, and are used to explain the principles of the present invention together with the description. [Figure 1] (a) A schematic perspective view of a configuration example of a liquid ejection device using the liquid ejection head 1 according to an embodiment, and (b) a block diagram for explaining an outline of a configuration controlled by a control unit that controls the liquid ejection device. [Figure 2] An exploded perspective view for explaining the configuration of the liquid ejection head according to an embodiment. [Figure 3] An external schematic view of one of the ink circulation units applied to the inkjet recording device according to an embodiment. [Figure 4] A schematic diagram showing a circulation path of ink of one color applied to the inkjet recording device according to an embodiment. [Figure 5] A schematic diagram of an electrical connection configuration for driving a circulation pump (piezoelectric pump) used for ink circulation. [Figure 6] A diagram for explaining the operation of the circulation pump according to an embodiment. [Figure 7] A diagram showing a configuration example of an ink circulation circuit when monochrome printing is performed in the inkjet recording device according to an embodiment. [Figure 8] An overview diagram of an example of the ink circulation circuit of the present invention (color) [Figure 9] A diagram showing a specific circuit example of a booster circuit according to an embodiment. [Figure 10] A diagram showing a circuit example of a driver circuit according to an embodiment. [Figure 11] A diagram showing an example of displacement of a pump drive voltage during printing in the inkjet recording device according to an embodiment. [Figure 12] A diagram showing an example of displacement of a pump drive voltage during diagnosis in the inkjet recording device which is a feature of an embodiment. [Figure 13] A flowchart for explaining the flow of processing when performing a diagnosis process of a circulation pump in the inkjet recording device according to an embodiment. [Figure 14]A diagram showing a circuit example for checking the operation of each circulation pump when using a plurality of circulation pumps.

Embodiment for Carrying Out the Invention

[0014] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the invention according to the claims. Although a plurality of features are described in the embodiments, not all of these plurality of features are essential for the invention, and the plurality of features may be arbitrarily combined. Further, in the accompanying drawings, the same or similar configurations are given the same reference numerals, and duplicate explanations are omitted.

[0015] Also, in the embodiment, as an ejection element for ejecting a liquid, an example using a thermal method in which bubbles are generated by an electrothermal conversion element to eject the liquid will be described, but the present invention is not limited to this. The present invention can also be applied to a liquid ejection head that employs a piezoelectric element (piezo) to eject a liquid or another ejection method. Further, the pumps, pressure adjustment means, etc. described below are also not limited to the configurations themselves described in the embodiments and the drawings.

[0016] First, the terms used in this embodiment are defined as follows in advance. · "Recording" In this specification, "recording" not only refers to the case of forming significant information such as characters and figures. Regardless of whether it is significant or not, and regardless of whether it is made manifest so that it can be perceived visually by humans. It also represents the case of forming an image, pattern, pattern, etc. on a recording medium widely, or performing processing on the medium. · "Recording medium" The recording medium not only refers to paper used in general recording devices, but also widely represents materials such as cloth, plastic film, metal plate, glass, ceramics, wood, leather, etc. that can receive ink. · "Ink" Ink, as with the definition of "record" above, should be interpreted broadly and refers to a medium containing recording material that, when applied to a recording medium, can be used to form images, patterns, designs, etc., or to process the recording medium, or to treat the ink. Physically, it is a liquid. The ink treatment mentioned above refers, for example, to the coagulation or insolubilization of the colorant in the ink applied to the recording medium. ·"nozzle" Unless otherwise specified, the term "nozzle" refers to the discharge port. Inside the nozzle are interconnected liquid channels and an element that generates energy used for ink ejection. ·"scanning" To record data onto a recording medium, the recording head scans the recording medium and performs the recording. Here, scanning refers to the movement of the head during acceleration and deceleration for the purpose of recording or related to recording.

[0017] [Embodiment] Figure 1(a) is a schematic perspective view showing an example of the configuration of a liquid dispensing device using the liquid dispensing head 1 according to the embodiment, and Figure 1(b) is a block diagram illustrating the control unit that controls the liquid dispensing device and the configuration controlled by the control unit.

[0018] The liquid ejection device according to this embodiment is a serial scan type inkjet recording device 50 that ejects ink from a liquid ejection head 1 to record (print) an image on a recording medium P. The liquid ejection head 1, as an inkjet liquid ejection head, is mounted on a carriage 53, and the carriage 53 can reciprocate along a guide axis 51 in the main scanning direction indicated by arrow X. The recording medium P is transported by transport rollers 55, 56, 57, 58 in the sub-scanning direction indicated by arrow Y, which intersects (in this example, is perpendicular to) the main scanning direction. An ink circulation unit 54 is mounted on the liquid ejection head 1, and ink circulation is performed by the ejection unit 300 (Figure 2), which will be described later. The ejection energy generating element in the ejection unit 300 is driven by a head driver 1A (Figure 1(b)) in response to an input signal from an electrical connection board. Electrical wiring, ink, and air piping necessary for ejection are supplied to the carriage 53 by a guide 59.

[0019] The CPU (control unit) 400 controls the inkjet recording device 50 based on a program containing code describing processing procedures stored in the ROM 401, and the RAM 402 is used as a work area for executing these processes. When the CPU 400 receives a job containing image data from an external host device 500, it drives and controls the head driver 1A according to the job to record the image. In addition, during recording, the CPU 400 controls the drive of the carriage motor 403 for moving the carriage 53 via the motor driver 403A, and controls the drive of the transport motor 404 for transporting the recording medium P via the motor driver 404A.

[0020] The liquid ejection head 1 is capable of full-color printing using CMYK (cyan, magenta, yellow, black) inks for color printing. In configurations for monochrome printing, recording is performed using only the K ink for monochrome printing, or in recording device configurations, only the K ink ejection head is provided. A cap member (not shown) is positioned away from the transport path of the recording medium P, and when recording is not being performed, the cap member moves relatively to a position that covers the face surface of the liquid ejection head 1 to prevent drying of the ejection port. Furthermore, with the cap member covering the face surface of the liquid ejection head 1, suction operations can be performed to refill the ink or recover from ink ejection failures.

[0021] Figure 2 is an exploded perspective view illustrating the configuration of the liquid dispensing head 1 according to this embodiment.

[0022] As shown in Figure 2, the liquid ejection head 1 has an ink circulation unit 54. The circulation unit 54 has circulation units 54m, 54y, 54k, and 54c, each corresponding to a different ink, and each circulation unit 54 is connected to a flow channel member 110. Here, m, y, k, and c correspond to the colors of the inks mentioned above. The method of connecting the circulation unit 54 and the flow channel member 110 may be a screw-fastening method with a sealing member sandwiched in between, or a connection by welding. The flow channel member 110 has a joint 200 for receiving ink from the main body of the inkjet recording device 50, and the joint 200 is connected to each circulation unit 54m, 54y, 54k, and 54c.

[0023] When the liquid ejection head 1 is mounted on the main body of the inkjet recording device 50, supply tubes (not shown) corresponding to each ink are connected from the main body of the recording device to each joint 200. The ink supplied from these supply tubes is then supplied to the respective circulation units 54m, 54y, 54k, and 54c via the joints 200 of the flow channel member 110. An ejection unit 300 is connected to the bottom surface of the flow channel member 110, and the ink supplied to the circulation unit 54 is supplied to the ejection unit 300 via the flow channel member 110.

[0024] The ejection unit 300 includes an ejection element 310 equipped with an actuator for ejecting ink, a support member 320, an electrical wiring board 330 on an ejection element substrate 350 for sending electrical signals to the ejection element 310, and a cover member 340 covering the electrical wiring board. The ejection element 310 and the electrical wiring board 330 are adhesively fixed to the support member 320, and the cover member 340 is further adhesively bonded to cover the surface. The ejection element 310 and the electrical wiring board 330 are electrically connected by wire bonding. Here, the electrical connection method may be flying lead bonding or the like. The part of the cover member 340 corresponding to the ejection element 310 is open. The method of connecting the ejection unit 300 to the flow path member 110 may be bonding using adhesive, or fixing by screw fastening with a sealing member sandwiched in between.

[0025] The opposite side of the joint 200 of the flow channel member 110 is a contact surface, and a head board 210 that receives electrical signals from the main body is connected to this contact surface. From this head board 210, electrical signals are sent to the discharge element 310 via the electrical wiring board 330 of the discharge unit 300. At this time, the connection between the head board 210 and the flow channel member 110 may be fixed by crimping, adhesive, or double-sided tape. The electrical connection between the head board 210 and the electrical wiring board 330 is formed, for example, by electrical connection processing using ACF (anisotropic conductive film) and ACF crimping.

[0026] Figure 3 is a schematic view of one of the ink circulation units 54 applied to the inkjet recording device 50 according to this embodiment.

[0027] Each ink circulation unit 54 is provided with one unit per color and includes a first pressure control mechanism 24, a second pressure control mechanism 28, a filter 23, and a circulation pump 27 (piezoelectric pump) used for circulating the ink.

[0028] Figure 4 is a schematic diagram showing the circulation path of one color of ink applied to the inkjet recording device 50 according to this embodiment.

[0029] Ink is supplied under pressure from the ink tank 2 to the liquid ejection head 1 by the pump 21. After the supplied ink has been cleaned of debris by the filter 23, it is supplied to the first valve chamber 25 of the first pressure control mechanism 24. Subsequently, the pressure is adjusted as it flows into the first pressure control chamber 26, which is connected to the first valve chamber 25 via a valve. Driven by the circulation pump 27, the pressure-adjusted ink in the first pressure control chamber 26 is supplied to the supply channel 75 and the bypass channel 79. The supply channel 75 is a channel composed of channel members 110 and is connected to the ejection unit 300 of the liquid ejection head 1. Similarly, the recovery channel 76 is also a channel composed of channel members 110 and is connected to the ejection unit 300. The ink supplied to the supply channel 75 passes through the ejection element 310 formed on the ejection element substrate 350 of the ejection unit 300 and is ejected onto the recording medium P to form an image. The excess ink is then discharged from the channel members 110 into the recovery channel 76 and finally supplied to the second pressure control chamber 30 of the second pressure control mechanism 28. In the second pressure control mechanism 28, the ink supplied to the second valve chamber 29 is supplied to the second pressure control chamber 30, which is connected to the second valve chamber 29 via a valve. The ink supplied to the second pressure control chamber 30 is supplied to the pump inlet passage 77, passes through the circulation pump 27, and is then supplied to the pump outlet passage 78. After that, it is supplied to the first pressure control chamber 26. By configuring the circulation pump 27 to circulate the ink that has passed through the ejection element 310 in this way, it is possible to suppress the thickening of the ink in the ejection element 310. This circulation path is not limited to a configuration that passes through the ejection element 310, but is sufficient as long as it is configured to circulate the ink within the ejection unit 300 within a range that has the effect of suppressing the thickening of the ink in the ejection element 310.

[0030] Figure 5 is a schematic diagram of the electrical connection configuration that drives the circulation pump 27 used for circulating the ink.

[0031] A drive signal is sent from the CPU 400 mounted on the main board 230 within the inkjet recording device 50 to the carriage board 220 via cable 213. Furthermore, a drive signal is sent from the carriage board 220 to the head electrical board 210 via an electrical connection section 212 with contact connections. The head board 210 is equipped with a control chip, a boost circuit, a voltage divider circuit, etc. When the control chip receives the drive signal from the carriage board 220, it drives the boost circuit by outputting a PWM waveform. Here, the boost circuit boosts the input voltage, for example, from 5V to about 70V. The boosted voltage is controlled by the drive circuit 413 (Figure 7) on the head board 210 and output to the circulation pump 27 via harness wiring 211 (including 608a, 608b in Figure 7 and 609a, 609b in Figure 8, etc.), and the circulation pump 27 operates to circulate the ink.

[0032] Figure 6 is a diagram illustrating the operation of the circulation pump 27 according to the embodiment.

[0033] Figure 6(a) shows the configuration of a piezoelectric pump 54, which is an example of a circulation pump 27 according to the embodiment. The circulation pump 27 changes the shape of the ink chamber 903, which is a diaphragm, according to the deformation of the piezoelectric element 904. The circulation pump 27 has an upper electrode 905 and a lower electrode 906 arranged to sandwich the piezoelectric element 904, and a check valve 900 that prevents backflow to the pump outlet channel 78 when ink is taken into the ink chamber 903 from the pump inlet channel 77. The circulation pump 27 further includes an intake check valve 901, etc., which prevents ink from flowing out into the pump inlet channel 77 when ink is sent to the pump outlet channel 78. Due to the deformation of the piezoelectric element 904, ink is taken in from the pump inlet channel 77 and sent to the pump outlet channel 78. This is repeated alternately to transport the ink.

[0034] Figure 6(b) shows the state when the circulation pump 27 is drawing in ink.

[0035] Ink is drawn in by applying a voltage to the upper electrode 905 and the lower electrode 906 so that the piezoelectric element 904 contracts. This causes the ink chamber 903 to expand, increasing its volume. As a result, the ink chamber 903 is filled with ink via the check valve 901.

[0036] Figure 6(c) shows the state when the circulation pump 27 is dispensing ink.

[0037] By applying a voltage to cause the piezoelectric element 904 to expand, the ink chamber 903 contracts, and the ink in the ink chamber 903 is sent from the discharge valve 900 to the pump outlet passage 78.

[0038] Figure 7 shows an example of the configuration of an ink circulation circuit when performing monochrome printing with the inkjet recording device 50 according to this embodiment.

[0039] The CPU 400 controls the entire device and issues voltage boosting instructions to the drive voltage generation circuit 410 and operation instructions to the drive circuit 413 via the setting bus 424.

[0040] The drive voltage generation circuit 410 generates a high voltage to drive the circulation pump 27. The PWM waveform generation circuit 411 generates a PWM waveform signal with a specified period and duty cycle according to the instructions of the CPU 400 and inputs it to the boost circuit 412 as a PWM signal 606.

[0041] Figure 9 shows a specific circuit example of the boost circuit 412 according to the embodiment.

[0042] The power supply voltage input from the pump drive power supply 604 is input to the inductor 701, and the switching element 702 connected to another terminal of the inductor 701 is turned ON / OFF according to the PWM signal 606. Energy is stored in the inductor 701 when the switching element 702 is ON, and when the switching element 702 is OFF, the voltage boosted by the diode 703 is output to the capacitor 704 and the pump drive voltage 607.

[0043] The Zener diode 706 is connected to prevent the pump drive voltage 607 from exceeding a predetermined voltage. For example, if four 18V Zener diodes are connected in series, when the pump drive voltage 607 exceeds 72V, current flows to GND, preventing the pump drive voltage 607 from exceeding 72V. The bypass capacitor 705 suppresses switching noise generated by the inductor 701.

[0044] Thus, in this boost circuit 412, the higher the repetition frequency of the PWM signal 606 and the larger the duty cycle of the PWM signal 606, the greater the power generated for driving the pump.

[0045] Returning to Figure 7, the drive circuit 413 includes a drive pulse generation circuit 414 and a driver circuit 415. The drive pulse generation circuit 414 outputs the pulse signal necessary for driving the piezoelectric pump 54, and the pulse signal with its polarity reversed, to the driver circuit 415 as pump control signals 605a and 605b, according to the settings from the CPU 400. The pump control signals 605a and 605b repeatedly transition between, for example, 3.3V and GND voltage according to a period specified by the CPU 400.

[0046] Figure 10 shows an example of a driver circuit 415 according to the embodiment.

[0047] The pump drive voltage 607 is connected to the collectors of resistors 801a and 801b, and transistors 802a and 802b. In this embodiment, transistors 802a and 802b are NPN transistors. The emitters of transistors 803a and 803b are connected to the emitters of transistors 802a and 802b, respectively. Transistors 803a and 803b are PNP transistors. The pump drive signal 608a is connected to the emitters of transistor 802a and transistor 803a. The pump drive signal 608b is connected to the emitters of transistor 802b and transistor 803b.

[0048] Resistor 801a is connected to the base of transistor 802a, the base of transistor 803a, the collector of transistor 805a, and capacitor 806a. Resistor 801b is connected to the base of transistor 802b, the base of transistor 803b, the collector of transistor 805b, and capacitor 806b. Transistors 805a and 805b are NPN transistors.

[0049] The pump control signal 605a output from the drive pulse generation circuit 414 is connected to the base of transistor 805a. When the pump control signal 605a is at a low potential while the pump drive voltage 607 is input, the potential of the bases of transistors 802a and 803a becomes the pump drive voltage 607 via resistor 801a. As a result, transistor 802a turns on (active) and transistor 803a turns off (inactive). Consequently, current flows from the pump drive voltage 607 to the pump drive signal 608a.

[0050] On the other hand, the pump control signal 605b is in the opposite phase to the pump control signal 605a, and becomes high when the pump control signal 605a is low. Therefore, at this time, transistor 805b becomes active, and the bases of transistor 802b and transistor 803b become ground voltage. As a result, transistor 802b becomes inactive and transistor 803b becomes active, so the pump drive signal 608b is drawn to ground potential. Since transistors 802a and 802b, 803a and 803b, and 805a and 805b are symmetrical, the pump control signals 605a and 605b alternately change between the pump drive voltage 607 and the ground level.

[0051] As a result, at the point where the pump drive signals 608a and 608b change between the pump control signals 605a and 605b, the voltage rises to the pump drive voltage 607 and the voltage drops to the ground level simultaneously.

[0052] At this time, the circulating pump 27, which is the load for these pump drive signals 608a and 608b, has the voltage of the change in the pump drive signals 608a and 608b applied to it, resulting in a voltage twice the width of the pump drive voltage 607.

[0053] As shown in Figure 7, the pump drive voltage 607 is connected to the capacitor 704 and charges the capacitor 704. When the circulating pump 27 is operated and a change in the pump terminal voltage occurs, the polarity of the charge between the upper electrode 905 and the lower electrode 906 is reversed. This causes current to flow through the driver circuit 415, and the pump drive voltage 607 temporarily drops (Figures 11-A~B, D~E). If the power sent from the power supply to the capacitor 704 by the PWM waveform is sufficient charge for driving, the drop in the drive voltage 607 will be small. Also, the amount of voltage drop is proportional to the capacitance of the circulating pump 27, and the larger the capacitance, the larger the current that flows when the polarity of the pump terminal voltage changes, so the pump drive voltage 607 will drop more significantly. The pump terminal voltage continues to receive charge from the boost circuit 412 even after the polarity to the circulating pump 27 changes, so after the terminal voltage drops once, it recovers to the original pump drive voltage (Figures 11-B~C, E~F).

[0054] Figure 11 shows an example of the displacement of the pump drive voltage 607 during printing in the inkjet recording device 50 according to the embodiment.

[0055] As mentioned above, the boost circuit 412 generates a pump drive voltage 607 corresponding to the repetition frequency and duty cycle of the powered PWM signal 606. Then, based on the pump control signals 605a and 605b output from the drive circuit 413, the driver circuit 415 outputs pump drive signals 608a and 608b, which increase the voltage up to the pump drive voltage 607 and then drop to ground level at the point where the pump control signals 605a and 605b change. In this way, the terminals of the circulating pump 27 are subjected to the voltage changes of the pump drive signals 608a and 608b, resulting in a voltage twice the width of the pump drive voltage 607.

[0056] The states shown at A-B and D-E of the pump drive voltage 607 in Figure 11, as described above, indicate a state in which the circulating pump 27 operates, the polarity of the terminal voltage changes, current flows to the driver circuit 415, and the pump drive voltage 607 temporarily drops. Furthermore, states B-C and E-F in Figure 11 indicate a state in which the terminal voltage drops once due to the change in polarity to the circulating pump 27, and then recovers to the original pump drive voltage. The upper limit voltage Vh and lower limit voltage Vl of the pump drive voltage 607 are reference voltages used to determine whether a fault, described later, has occurred.

[0057] The drive power supply monitoring circuit 416 in Figure 7 is a monitoring circuit for the pump drive voltage 607, and is a circuit for checking whether the pump drive voltage 607 is at the set voltage. The pump drive voltage 607 is divided by the voltage divider circuits 417H and 417L, respectively, and converted to lower voltages for discrimination by comparators 419 and 420. Comparators 419 and 420 compare the divided pump drive voltage with a reference voltage 425 supplied from the reference voltage source 418, respectively. The reference voltage source 418 supplies a first reference voltage 425H and a second reference voltage 425L, which are at different potentials, to comparators 419 and 420, respectively, according to instructions from the CPU 400. Comparator 419 raises its output to a high level and sets latch 421H when the output voltage of the voltage divider circuit 417H is greater than the first reference voltage. Meanwhile, when the output voltage of the voltage divider circuit 417L falls below the second reference voltage, the comparator 420 goes high and sets latch 421L. The latch data of latches 421H and 421L is read from the CPU 400 via the read bus 422. It is also cleared by the latch clear 423 from the CPU 400. In this way, the system monitors whether the pump drive voltage 607 falls below the set voltage on the falling edge or rises above it on the rising edge over a predetermined period, and the CPU 400 can read and retain the result.

[0058] During operation, comparator 419 is set to detect a voltage slightly above the pump drive voltage 607, for example, set to the upper limit voltage Vh (corresponding to the first reference voltage) in Figure 11. Comparator 420 is set to detect a voltage a certain amount below the pump drive voltage 607, for example, the lower limit voltage Vl (corresponding to the second reference voltage) in Figure 11. This allows the system to monitor whether the circulation pump 27 is operating normally by detecting whether the pump drive voltage 607 is within the set voltage range when the circulation pump 27 is running. A fault that can be detected with this configuration is, for example, if the Zener diode 706 in the boost circuit 412 in Figure 9 fails and becomes open, the pump drive voltage 607 will exceed the first set voltage. Comparator 419 detects this and sets latch 421H. The CPU 400 can then read latch 421H and detect this fault. In another example, if the inductor 701 in the boost circuit 412 in Figure 9 is broken, the pump drive voltage 607 will not rise above ground potential and will not reach the set second voltage, causing the comparator 420 to set latch 421L. The CPU 400 can then read latch 421L to detect the fault.

[0059] As explained in Figure 6, the circulation pump 27 uses the deformation of the piezoelectric element 904 to deliver ink. Failures of the piezoelectric pump 27 due to cracking of the piezoelectric element 904 itself, cracking or deformation of the upper electrode 905 or lower electrode 906, or disconnection of the wiring for the pump drive signals 608a and 608b from the drive circuit 413 are anticipated due to prolonged use.

[0060] By detecting these malfunctions during the preparation period after powering on the inkjet recording device 50, and before starting printing, and by taking appropriate measures such as replacing the liquid ejection head to ensure normal printing, reliability can be improved.

[0061] Figure 12 shows an example of the displacement of the pump drive voltage 607 during diagnosis in an inkjet recording device 50, which is a characteristic of an embodiment of the present invention.

[0062] In the detection of a suspected failure of the circulation pump 27, the CPU 400 sets the PWM signal 606 to a waveform different from the PWM waveform used during printing shown in Figure 11. In Figure 12, for example, the PWM generation circuit 411 is set so that the duty cycle of the PWM signal 606 is lower than in Figure 11. Then, the boost circuit 412 is driven to generate the pump drive voltage 607. Subsequently, the drive pulse generation circuit 414 is operated to output operation signals 605a and 605b to the driver circuit 415.

[0063] Here, as with A and D in Figure 11, the pump drive voltage 607 temporarily decreases when the signal applied to the circulation pump 27 is switched, as shown in B and E in Figure 12. In Figure 12, the waveform of the PWM signal 606 is different from that during operation shown in Figure 11, and the voltage temporarily drops more significantly, as shown in A-C and D-F in Figure 12. If the capacitance of the circulation pump 27 is large, the pump drive voltage 607 will fall below the lower limit voltage (Vl), which the comparator 420 detects and sets the latch 421L. The CPU 400 can then read the latch 421L to detect that the circulation pump 27 has normal capacitance. Conversely, if the pump drive voltage 607 does not fall below the lower limit voltage (Vl), it can be determined that the circulation pump 27 is faulty, as described above.

[0064] Figure 13 is a flowchart illustrating the process flow when performing a diagnostic process on the circulation pump 27 in the inkjet recording apparatus 50 according to this embodiment. This process is achieved by the CPU 400 of the control unit executing a program stored in the ROM 401.

[0065] First, in S1301, the CPU 400 sets the frequency and duty cycle of the diagnostic PWM signal 606 to the PWM generation circuit 411 and generates the PWM signal 606, thereby starting the boost circuit 412 to boost the voltage. Next, in S1302, the CPU 400 waits until the boosted voltage output from the boost circuit 412 reaches the target value. Once the boosted voltage reaches the target value, in S1303, the CPU 400 outputs a latch clear 423 to clear latches 421H and 421L of the drive voltage monitoring circuit 416. Next, in S1304, the CPU 400 activates the drive circuit 413 to start the drive pump 27. Then, in S1305, it waits until the polarity of the pump drive signals 608a and 608b applied to the drive pump 27 is determined a predetermined number of times.

[0066] Then, proceeding to S1306, the CPU 400 reads the values ​​of latches 421H and 421L via the read bus 422 and proceeds to S1307. In S1307, if the CPU 400 determines that latch 421H is set and the boost voltage exceeds the normal upper limit, it proceeds to S1315, determines that there is an abnormality in the boost circuit 412, and proceeds to error processing in S1313. In S1315, the CPU 400 stops the operation of the boost circuit 412 and the drive circuit 413, ends the diagnosis, and proceeds to error processing in S1314.

[0067] On the other hand, if the CPU 400 determines in S1307 that the boosted voltage does not exceed the normal upper limit, it proceeds to S1308. In S1308, the CPU 400 diagnoses the circulation pump 27. Here, it determines, based on the latch data of latch 421L, whether the circulation pump 27 has the target capacitance and whether the drop in the boosted voltage during polarity reversal is below the expected level. If latch 421L is not set, that is, if there is no evidence that the voltage has dropped to the set voltage, it proceeds to S1312. In S1312, the CPU 400 determines that the circulation pump 27 is abnormal and proceeds to S1313 to perform the same processing as described above.

[0068] On the other hand, in S1308, if the CPU 400 determines that the latch 421L is set, it proceeds to S1309 and determines that the circulation pump 27 is functioning normally. In this way, the CPU 400 determines that the capacitance of the circulation pump 27 is as expected and normal because a normal voltage is applied to the electrodes of the circulation pump 27, and when the polarity is reversed for driving, the boosted voltage drops to a voltage lower than the reference value. Then, proceeding to S1310, the CPU 400 sets the frequency and duty cycle of the PWM signal 606 for printing in the PWM generation circuit 411 and generates the PWM signal 606 in preparation for printing. Then, proceeding to S1311, it enters a print standby state, waiting to start printing.

[0069] As explained above, this process changes the PWM waveform used for boosting the voltage from the one used for printing to one used for diagnosis, thereby increasing the drop in the boosted voltage when the polarity of the drive voltage applied to the electrodes of the circulation pump is switched. Then, by constructing a simple circuit including a comparator to detect this drop, it is possible to determine whether the capacitance of the circulation pump is normal, that is, whether the circulation pump is functioning correctly.

[0070] Figure 8 shows an example of the configuration of the ink circulation circuit when performing color printing with the inkjet recording device 50 according to the embodiment. Parts shared with Figure 7 are given the same reference numerals, and their explanations are omitted. In Figure 8, the circulation pumps 27y, 27m, and 27c are driven by two drive circuits 413K and 413YMC, respectively, using a common drive voltage generation circuit 410 for K and YMC. The basic operation of this circuit is basically the same as that described with reference to Figure 7. In Figure 8, each of the three circulation pumps 27y, 27m, and 27c is driven by pump drive signals 609a and 609b output from the YMC drive circuit 413. The circulation pump 27k for black ink is driven by pump drive signals 608a and 608b output from the drive circuit 413K. The configuration and operation of the YMC drive circuit 413 and drive circuit 413K are the same as those of the drive circuit 413 described above.

[0071] For monochrome printing, only the circulating pump 27k is driven, while for color printing, three circulating pumps 27y, 27m, and 27c are driven by a single drive circuit 413YMC, enabling both monochrome and color printing with fewer components.

[0072] Furthermore, when using the same specifications of circulation pumps with ink circulation units 54K and 54YMC, the capacitance of the circulation pump is 1 / 3 when using only circulation pump 27k for monochrome printing compared to printing with YMC using all three circulation pumps 27y, 27m, and 27c. Therefore, when measuring with only circulation pump 27k, the capacitance is lower than when printing with YMC, so the duty cycle of the PWM signal 606 should be made even smaller than in the case of YMC for measurement.

[0073] Figure 14 shows an example in which switches 609y, 609m, and 609c are added to the three pump drive signals 609a during the diagnosis of a YMC that drives three circulation pumps 27y, 27m, and 27c with a single drive circuit 413YMC, allowing for independent connection / disconnection of each. These switches 609y, 609m, and 609c can be turned on / off in response to control signals (not shown) from the CPU 400, allowing selection of the circulation pump to be diagnosed. This allows for further identification of which circulation pump is faulty within the YMC by connecting one switch to each of the circulation pumps 27y, 27m, and 27c during diagnosis.

[0074] With this configuration, in a liquid discharge head having multiple circulation pumps, each circulation pump can be diagnosed independently.

[0075] (Other embodiments) The present invention can also be realized by supplying a program that implements one or more of the functions of the above-described embodiments to a system or device via a network or storage medium, and by having one or more processors in the computer of that system or device read and execute the program. It can also be realized by a circuit (e.g., an ASIC) that implements one or more functions.

[0076] This specification and drawings disclose the following liquid dispensing heads and liquid dispensing devices.

[0077] <Item 1> A liquid dispensing head having a piezoelectric pump for circulating ink, A boosting means that generates a boosted voltage for driving the piezoelectric pump in response to a drive signal, A driving means that generates a pump drive signal to drive the piezoelectric pump based on the boosted voltage, The system includes a monitoring means for monitoring the displacement of the boosted voltage output from the boosting means, The liquid dispensing head is characterized in that the monitoring means holds the results of monitoring the boosted voltage in a readable format.

[0078] <Item 2> The monitoring means includes a detection means for detecting whether the boosted voltage has become higher than a first predetermined voltage and whether the boosted voltage has become lower than a second predetermined voltage, A holding means for holding the results detected by the detection means, A liquid dispensing head according to item 1, characterized by having the following features.

[0079] <Item 3> The aforementioned drive signal is a pulse signal, The system further includes a generating means that outputs the pulse signal by changing at least one of the period and duty cycle of the pulse signal according to the settings, The liquid discharge head according to item 1 or 2, characterized in that the boosting means generates the boosted voltage with power corresponding to the pulse signal.

[0080] <Item 4> A liquid dispensing head according to any one of items 1 to 3, further comprising a capacitor connected to the output of the voltage boosting means for charging the voltage boosted by the voltage boosted.

[0081] <Item 5> It further comprises a liquid ejection head for monochrome printing and multiple liquid ejection heads for color printing, The liquid discharge head according to any one of items 1 to 4, characterized in that the driving means comprises a first driving means for driving a piezoelectric pump of the liquid discharge head for monochrome printing, and a second driving means for driving a plurality of piezoelectric pumps of the plurality of liquid discharge heads.

[0082] <Item 6> A liquid dispensing device having a liquid dispensing head with a piezoelectric pump for circulating ink, The aforementioned liquid dispensing head is A boosting means that generates a boosted voltage for driving the piezoelectric pump in response to a drive signal, A driving means that generates a pump drive signal to drive the piezoelectric pump based on the boosted voltage, The system includes monitoring means that monitors the displacement of the boosted voltage output from the boosting means and holds the results of the monitoring, The aforementioned liquid discharge device is During diagnosis of the liquid discharge head, the control means controls the drive signal to reduce the power of the boosted voltage generated by the boosting means, and determines whether the liquid discharge head is normal based on the result held by the monitoring means, A liquid dispensing device characterized by having the following features.

[0083] <Item 7> The monitoring means includes a detection means for detecting whether the boosted voltage has become higher than a first predetermined voltage and whether the boosted voltage has become lower than a second predetermined voltage, A holding means for holding the results detected by the detection means, A liquid dispensing device according to item 6, characterized by having the following features.

[0084] <Item 8> The liquid dispensing head further, The system has a generating means that outputs a pulse signal which is the drive signal, The control means sets the generating means to shorten or reduce the period and duty cycle of the pulse signal when diagnosing the liquid ejection head, compared to when printing. The liquid dispensing device according to item 6 or 7, characterized in that the boosting means generates the boosted voltage with power corresponding to the pulse signal.

[0085] <Item 9> The liquid discharge device according to item 7, characterized in that the control means determines that the piezoelectric pump is not functioning correctly if the result held by the holding means indicates that the boosted voltage is not lower than the second predetermined voltage.

[0086] <Item 10> The liquid dispensing device according to item 7, characterized in that the control means determines that the boosting means is not functioning correctly if the result held by the holding means indicates that the boosted voltage has become higher than the first predetermined voltage.

[0087] <Item 11> The liquid dispensing device according to any one of items 7, 9, and 10, characterized in that the control means can set a first predetermined voltage and a second predetermined voltage.

[0088] <Item 12> The aforementioned liquid dispensing head is It includes a liquid ejection head for monochrome printing and multiple liquid ejection heads for color printing. The driving means comprises a first driving means for driving the piezoelectric pump of the liquid discharge head for monochrome printing, and a second driving means for driving the plurality of piezoelectric pumps of the plurality of liquid discharge heads. The liquid ejection apparatus according to item 8, characterized in that the control means sets the generating means to shorten or reduce at least one of the period and duty cycle of the pulse signal when diagnosing the liquid ejection head for monochrome printing, compared to when diagnosing the plurality of liquid ejection heads.

[0089] <Item 13> The aforementioned liquid dispensing head is The system further includes a selection means for selecting one of the plurality of piezoelectric pumps driven by the second driving means, The liquid dispensing device according to item 12, characterized in that the control means selects the piezoelectric pump to be diagnosed from among the plurality of piezoelectric pumps by the selection means.

[0090] <Item 14> The liquid dispensing apparatus according to any one of items 8 to 13, characterized in that the pulse signal is a PWM signal.

[0091] The present invention is not limited to the embodiments described above, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, the following claims are attached to make the scope of the invention public. [Explanation of Symbols]

[0092] 1…Liquid discharge head, 24…First pressure control mechanism, 28…Second pressure control mechanism, 27…Circulation pump (piezoelectric pump), 50…Inkjet recording device, 54, 54YMC…Circulation unit, 400…CPU, 401…ROM, 402…RAM, 410…Drive voltage generation circuit, 411…PWM generation circuit, 412…Boost circuit, 413, 413K, 413YMC…Drive circuit, 416…Drive voltage monitoring circuit, 418…Reference voltage source, 419, 420…Comparator, 421H, 421L…Latch

Claims

1. A liquid dispensing head having a piezoelectric pump for circulating ink, A boosting means that generates a boosted voltage for driving the piezoelectric pump in response to a drive signal, A driving means that generates a pump drive signal to drive the piezoelectric pump based on the boosted voltage, The system includes a monitoring means for monitoring the displacement of the boosted voltage output from the boosting means, The liquid dispensing head is characterized in that the monitoring means holds the results of monitoring the boosted voltage in a readable format.

2. The monitoring means includes a detection means for detecting whether the boosted voltage has become higher than a first predetermined voltage and whether the boosted voltage has become lower than a second predetermined voltage. A holding means for holding the results detected by the detection means, A liquid dispensing head according to claim 1, characterized by having the following features.

3. The aforementioned drive signal is a pulse signal, The system further includes a generating means that outputs the pulse signal by changing at least one of the period and duty cycle of the pulse signal according to the settings, The liquid discharge head according to claim 1 or 2, characterized in that the boosting means generates the boosted voltage with power corresponding to the pulse signal.

4. The liquid dispensing head according to claim 1, further comprising a capacitor connected to the output of the voltage boosting means for charging the voltage boosted by the voltage boosted.

5. It further comprises a liquid ejection head for monochrome printing and multiple liquid ejection heads for color printing, The liquid discharge head according to claim 1, characterized in that the driving means comprises a first driving means for driving a piezoelectric pump of the liquid discharge head for monochrome printing, and a second driving means for driving a plurality of piezoelectric pumps of the plurality of liquid discharge heads.

6. A liquid dispensing device having a liquid dispensing head with a piezoelectric pump for circulating ink, The aforementioned liquid dispensing head is A boosting means that generates a boosted voltage for driving the piezoelectric pump in response to a drive signal, A driving means that generates a pump drive signal to drive the piezoelectric pump based on the boosted voltage, The system includes a monitoring means that monitors the displacement of the boosted voltage output from the boosting means and stores the results of the monitoring, The aforementioned liquid discharge device is During the diagnosis of the liquid discharge head, the control means controls the drive signal to reduce the power of the boosted voltage generated by the boosting means, and determines whether the liquid discharge head is normal based on the result held by the monitoring means, A liquid dispensing device characterized by having the following features.

7. The monitoring means includes a detection means for detecting whether the boosted voltage has become higher than a first predetermined voltage and whether the boosted voltage has become lower than a second predetermined voltage. A holding means for holding the results detected by the detection means, The liquid dispensing device according to claim 6, characterized by having the following features.

8. The liquid dispensing head further, The system has a generating means that outputs a pulse signal which is the drive signal, The control means sets the generating means to shorten or reduce the period and duty cycle of the pulse signal when diagnosing the liquid ejection head, compared to when printing. The liquid dispensing apparatus according to claim 6, characterized in that the boosting means generates the boosted voltage with power corresponding to the pulse signal.

9. The liquid discharge device according to claim 7, characterized in that the control means determines that the piezoelectric pump is not functioning correctly if the result held by the holding means indicates that the boosted voltage is not lower than the second predetermined voltage.

10. The liquid dispensing apparatus according to claim 7, characterized in that the control means determines that the boosting means is not functioning correctly if the result held by the holding means indicates that the boosted voltage has become higher than the first predetermined voltage.

11. The liquid dispensing device according to claim 7, characterized in that the control means can set the first predetermined voltage and the second predetermined voltage.

12. The aforementioned liquid dispensing head is It includes a liquid ejection head for monochrome printing and multiple liquid ejection heads for color printing. The driving means includes a first driving means for driving the piezoelectric pump of the liquid discharge head for monochrome printing, and a second driving means for driving the plurality of piezoelectric pumps of the plurality of liquid discharge heads. The liquid ejection apparatus according to claim 8, characterized in that the control means sets the generating means to shorten or reduce at least one of the period and duty cycle of the pulse signal when diagnosing the liquid ejection head for monochrome printing, compared to when diagnosing the plurality of liquid ejection heads.

13. The aforementioned liquid dispensing head is The system further includes a selection means for selecting one of the plurality of piezoelectric pumps driven by the second driving means, The liquid dispensing device according to claim 12, characterized in that the control means selects the piezoelectric pump to be diagnosed from among the plurality of piezoelectric pumps using the selection means.

14. The liquid dispensing apparatus according to claim 8, characterized in that the pulse signal is a PWM signal.

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