Liquid droplet discharge head and liquid droplet discharge apparatus

Abstract

A droplet discharge head has an actuator (Ac) that is driven in accordance with a voltage supplied thereto, and imparts a pressure variation to a liquid to discharge a droplet, and a power supply circuit to the actuator (Ac). The power supply circuit has an input path (101c) to supply power at a voltage (VLb), and an input path (102) to supply power at a voltage (VH) greater than the voltage (VLb). The input path (101c) has a reverse flow prevention element (DI1) to prevent application of the voltage (VH), and an element (C1) having no voltage resistance performance to the voltage (VH) located on a side opposite to the reverse flow prevention element (DI1) from a connection point (P) of the input path (101c) and the input path (102).

Description

Technical Field

[0001] This invention relates to a droplet ejector head and a droplet ejection device. Background Technology

[0002] A droplet ejector is provided as follows: by supplying electricity to a drive element arranged along the flow path of a liquid such as ink, the liquid is activated, causing a pressure change in the liquid, and droplets are ejected from a nozzle connected to the flow path according to the pressure change.

[0003] In such a droplet ejector, voltage and current (electricity) are output from the drive circuit in a predetermined pattern to uniformly drive the drive element. Patent Document 1 illustrates a technique for uniformly driving the piezoelectric element by applying a voltage supplied from a predetermined power source different from the power source used for printing, thereby adjusting its polarization.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 9-300636 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] In droplet ejectors capable of selectively applying multiple types of driving voltages, mechanically switching circuits require significant time and resources, or result in larger scale. On the other hand, if the design allows for easy input of any voltage without mechanical switching, all circuits and electronic components must be matched to the maximum output voltage, leading to issues such as increased size or higher costs.

[0009] The purpose of this invention is to provide a droplet ejector and a droplet ejection device that can selectively input multiple voltages with a simpler structure.

[0010] Methods for solving problems

[0011] To achieve the above objectives, the invention described in claim 1 is a droplet ejector head, comprising:

[0012] A driving element, driven by a supplied voltage, imparts pressure variations to the liquid, causing droplets to be ejected; and

[0013] The power supply circuit to the driving element,

[0014] The power supply circuit has the following features:

[0015] The first power supply circuit supplies power at the first voltage; and

[0016] The second power supply circuit supplies power at a second voltage that is greater than the first voltage.

[0017] The first supply circuit has:

[0018] A reverse current prevention element to prevent the application of the second voltage; and

[0019] An element located on the side opposite to the contacts of the first and second supply circuits, which is further away from the reverse current prevention element, and which does not have the voltage withstand capability for the second voltage.

[0020] Furthermore, the invention described in claim 2 incorporates the droplet ejector head described in claim 1.

[0021] The backflow prevention element includes a diode.

[0022] Furthermore, the invention described in claim 3 incorporates the droplet ejector head described in claim 1.

[0023] The backflow prevention element includes an ideal diode.

[0024] Furthermore, the invention described in claim 4 incorporates the droplet ejector head described in claim 3.

[0025] In the first supply circuit, the voltage difference between the first voltage supplied to the first supply circuit and the voltage applied to the driving element is less than 0.1V.

[0026] Furthermore, the invention described in claim 5 is incorporated in the droplet ejector head described in claim 3 or 4.

[0027] The current flowing through the ideal diode is greater than 0.1mA and less than 10A.

[0028] Furthermore, the invention described in claim 6 is incorporated in the droplet ejector head described in any one of claims 1 to 5.

[0029] The power supply circuit has a third supply circuit that supplies power at a third voltage.

[0030] Power is supplied to the first terminal of the driving element from either the first supply circuit or the second supply circuit.

[0031] Power is supplied from the third supply circuit to the second terminal of the driving element on the side opposite to the first terminal.

[0032] Furthermore, the invention described in claim 7 is incorporated in the droplet ejector head described in any one of claims 1 to 5.

[0033] The power supply circuit supplies power to the first terminal of the driving element.

[0034] The second terminal of the driving element, on the side opposite to the first terminal, is grounded.

[0035] Additionally, the invention described in claim 8 is a droplet ejection device.

[0036] It has a droplet ejector head as described in any one of claims 1 to 7.

[0037] Additionally, the invention described in claim 9 is a droplet ejection device comprising:

[0038] A driving element, driven by a supplied voltage, imparts pressure variations to the liquid, causing droplets to be ejected; and

[0039] The power supply circuit to the driving element,

[0040] The power supply circuit has the following features:

[0041] The first power supply circuit supplies power at the first voltage; and

[0042] The second power supply circuit supplies power at a second voltage that is greater than the first voltage.

[0043] The first supply circuit has:

[0044] A reverse current prevention element to prevent the application of the second voltage; and

[0045] An element located on the side opposite to the contacts of the first and second supply circuits, which is further away from the reverse current prevention element, and which does not have the voltage withstand capability for the second voltage.

[0046] Furthermore, the invention described in claim 10, in the droplet ejection device described in claim 8 or 9,

[0047] Equipped with a control unit,

[0048] The control unit determines the ejection speed of the droplet based on the image data of the droplet being ejected and flying according to the drive element.

[0049] Furthermore, the invention described in claim 11, in the droplet ejection device described in claim 10,

[0050] It has a camera unit that can capture images of the ejected droplets and output the captured data.

[0051] The effects of the invention

[0052] According to the present invention, it has the effect of selectively inputting multiple voltages in a droplet ejector head with a simpler structure. Attached Figure Description

[0053] Figure 1 This is a block diagram showing the functional structure of the droplet ejection device.

[0054] Figure 2 This is a circuit diagram illustrating the head drive unit of the first embodiment.

[0055] Figure 3 This is a circuit diagram illustrating other examples of the head drive unit.

[0056] Figure 4 This is a graph illustrating the voltage drop of a diode.

[0057] Figure 5 This is a flowchart illustrating the control process of concentration adjustment performed by the droplet ejection device.

[0058] Figure 6 This is a circuit diagram illustrating the head drive unit of the second embodiment.

[0059] Figure 7 This is a circuit diagram illustrating a modified example of the head drive unit.

[0060] Figure 8 This is a block diagram showing the functional structure of the droplet ejection device according to the third embodiment. Detailed Implementation

[0061] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0062] [First Implementation]

[0063] Figure 1 This is a block diagram showing the functional structure of the droplet ejection device 1.

[0064] The droplet ejection device 1 of the first embodiment is, for example, an inkjet recording device that ejects ink (here, colored ink). The droplet ejection device 1 includes a control unit 41, a storage unit 42, a conveying unit 51, a head drive control unit 52, a droplet ejection head 53, a communication unit 6, a display unit 7, an operation receiving unit 8, an imaging unit 9 (sensor), and a power supply unit E, etc.

[0065] The control unit 41 includes a CPU 411 (hardware processor) for performing calculations and a RAM 412 for providing memory space for the CPU 411 and storing temporary data, and performs overall control over the operation of the droplet ejection device 1.

[0066] The storage unit 42 stores programs and setting data related to motion control. The storage unit 42 may include non-volatile memory and / or an HDD (Hard Disk Drive). Additionally, the storage unit 42 may store image data 421 of a recording object acquired from an external source via the communication unit 6, along with its processing data. The image data 421 may also include pre-set test image data, which will be described later. For storing this data, the storage unit 42 may also include volatile memory such as DRAM.

[0067] The conveying unit 51 moves the medium (mainly paper) that is the object of recording images, etc., by the droplet ejection device 1 relative to the ink ejection surface of the droplet ejection head 53 while facing the ink ejection surface. The conveying unit 51 has a conveying drive unit 511. The conveying drive unit 511 has, for example, a roller on which an endless belt carrying the medium is mounted, and by rotating the roller at a predetermined speed, the endless belt and the medium on the belt are rotated and moved at a predetermined speed.

[0068] The head drive control unit 52 outputs a control signal for obtaining a drive signal to drive the actuator Ac of the droplet ejection head 53 at an appropriate timing based on the pixel data of the image of the recording object. The head drive control unit 52 can be centrally mounted on a substrate or distributed among various parts of the droplet ejection device 1. Furthermore, part or all of the structure of the head drive control unit 52 can be included in the droplet ejection head 53. The head drive control unit 52 includes a head control unit 521, etc.

[0069] The head control unit 521 includes a CPU and a storage unit, and controls the operation of the head drive control unit 52 based on image data of whether or not an object is being recorded and the content of the image data. The storage unit stores in advance data such as waveform patterns of drive signals used to eject ink from the nozzle N or to vibrate the surface (squirm) of the ink within the nozzle N, or timing data for switching output voltages. The head control unit 521 outputs the aforementioned control signals to the head drive unit 531 at an appropriate timing corresponding to a clock signal (synchronization signal) omitted from the illustration.

[0070] The droplet ejector head 53 ejects ink from a medium to record and form images. The droplet ejector head 53 includes a head drive unit 531 and a nozzle N.

[0071] The head drive unit 531 performs an operation that dispenses ink in a timing match with the ink ejected from each nozzle N. The head drive unit 531 includes an input unit 100 (power supply circuit), a drive circuit 110, and an actuator Ac (drive element). The actuator Ac is, for example, a piezoelectric element that deforms according to the applied voltage. The actuator Ac is disposed along the ink flow path communicating with the nozzle N, and imparts pressure variations to the ink (liquid) in the ink flow path corresponding to the deformation.

[0072] Input unit 100 receives voltages VH, VLa, and VLb (described later) from power supply unit E (see reference). Figure 2 , Figure 3 The input of the circuit is sent to the drive circuit 110 to supply power.

[0073] The drive circuit 110 switches between outputting a voltage input from the input unit 100 to each actuator Ac according to a control signal input from the head control unit 521 based on image data of the recording object. The drive circuit 110 is not particularly limited; for example, it is a CMOS sensor, and it selectively outputs either the input voltage from the input unit 100 or a ground voltage according to the control signal. By switching the output voltage to the actuator Ac, the actuator Ac is driven to deform, imparting pressure variations to the ink within the nozzle N, causing ink droplets to be ejected from the nozzle N or vibrating within the nozzle N. Alternatively, the drive circuit 110 may also include the power supply circuit of this embodiment in addition to the input unit 100.

[0074] The nozzle N ejects ink according to the pressure variation imparted by the deformation action of each actuator Ac. The openings of the nozzle N are arranged in a predetermined pattern on the side (nozzle surface) facing the medium (the transport surface of the medium). The arrangement pattern is not particularly limited; for example, multiple nozzle openings arranged at intervals corresponding to the image resolution in a direction perpendicular to the transport direction of the transport unit 51 are set at one or more locations relative to the transport direction. Alternatively, it may be a two-dimensional head where the nozzle openings are also distributed to a large number of locations relative to the transport direction.

[0075] The droplet ejection device 1 is, for example, a linear head that records images by ejecting ink from a fixed droplet ejection head 53 onto a transported medium in a single-pass manner. However, it is not particularly limited as long as it is a device that allows the droplet ejection head 53 and the medium to move relative to each other at a certain speed during the ink ejection operation. For example, it could also be a device with a movable droplet ejection head 53 (scanning head). Alternatively, it could be a droplet ejection device 1 that records images in a multi-pass manner instead of a single-pass manner. When the opening of the nozzle N is arranged in two dimensions, the timing of ink ejection from the nozzle N at different positions relative to the direction of relative movement is shifted according to the relative movement speed.

[0076] The communication unit 6 controls communication with external devices to send and receive data. The communication unit 6 includes, for example, a network card, and controls data communication according to communication specifications such as TCP / IP using a LAN. Connected external devices include various computer terminals that output image recording commands and record object data. Furthermore, as described later, detection results from the detector that detects the flight speed of the ink can be obtained directly or via a computer terminal.

[0077] The display unit 7 performs various displays on the display screen under the control of the control unit 41. For example, a liquid crystal display (LCD) can be used as the display screen. The display screen may include, for example, displays of conditions related to image recording operations and settings selection screens. Furthermore, the display unit 7 may include LED lights, and may be able to report whether there is power supply from the mains power source and / or any abnormal conditions.

[0078] The operation receiving unit 8 receives input operations from external sources, such as users, and outputs them as input signals to the control unit 41. For example, the operation receiving unit 8 can be a touch panel superimposed on a display screen. Alternatively, the operation receiving unit 8 may also include push-button switches and / or rotary switches.

[0079] The imaging unit 9 captures images of the ink ejected from the droplet ejector head 53 and alighting from a direction perpendicular to the direction of flight. The imaging unit 9 is equipped with multiple imaging elements to acquire images with temporal resolution, determining the distance traveled by the ink ejected from each nozzle N. The imaging unit 9 can detect changes in brightness across multiple wavelength bands (RGB, etc.) based on the color (CMYK, etc.) of the ejected ink, or it can capture images of ink droplets with a single wavelength band for identifiable imaging.

[0080] The power supply unit E supplies power to the droplet ejector head 53 and other components to operate them. The power supply unit E outputs power to the head drive unit 531 using the three voltages VH, VLa, and VLb described later. The supplied power is sufficient for driving the ink ejection from the maximum number of nozzles N capable of simultaneous ejection. The power supply unit E can be capable of converting power obtained from an external power source (e.g., AC power from a commercial source) into the aforementioned DC voltage for output, or it can be a component that accepts the necessary DC voltage input and outputs it unchanged.

[0081] Next, the head drive unit 531 in the droplet ejection head 53 of the first embodiment will be described.

[0082] Figure 2 This is a circuit diagram illustrating the head drive unit 531. Furthermore, only the parts necessary for illustrating the invention are shown here; the head drive unit 531 may also include other electronic components and circuits besides the illustrated structure.

[0083] The head drive unit 531 has two input units 100a and 100b and two drive circuits 110a and 110b. Input unit 100a has an input path 101a (third supply circuit) for receiving an input voltage VLa (third voltage), and switches whether the drive circuit 110a supplies power at voltage VLa to one end (second end) of actuator Ac (either the output voltage VLa or the ground voltage). Input unit 100b has an input path 101b (first supply circuit) for receiving an input voltage VLb (first voltage) and an input path 102 (second supply circuit) for receiving an input voltage VH (second voltage), and the input paths 101b and 102 merge at connection point P (the junction of the first and second supply circuits). The drive circuit 110b switches whether to supply power (output voltage VH or VLb or ground voltage) to the end (first end) of the actuator Ac opposite to the aforementioned end, at the voltage input from the input section 100b (either input path 101b or input path 102).

[0084] Voltages VLa and VLb are voltages corresponding to the drive waveform of actuator Ac, and their magnitudes are not particularly limited. Input section 100 can selectively supply power by outputting voltage VLb and a voltage VH larger than VLb. The magnitude of the voltage referred to here is an absolute value; voltages VLb and VH are not limited to positive voltages and can be negative voltages. For example, voltage VH can also be the voltage used when performing polarization adjustment as described later. Voltages VLb and VH can be exclusively input to input section 100b from power supply section E, or they can be switched within input section 100b by means of FETs (not shown in the figure). Furthermore, FETs can switch between input to and / or output from input section 100b, but reverse current is allowed by the operation of the body diode, so they are not equivalent to the reverse current prevention element described later.

[0085] The power supply to both ends of the actuator Ac based on the drive circuit 110 is switched according to image data, etc. In addition, the output of voltage VLa and voltage VLb or voltage VH can be applied to multiple actuators Ac respectively from the common input sections 100a, 100b via multiple drive circuits 110.

[0086] Diode D1 and capacitor C1 are located in input path 101b with voltage VLb. Diode D1 is a reverse current prevention element to prevent a large output voltage VH from being applied to input path 101b. When both voltage VH and voltage VLb are negative, diode D1 is oriented in the opposite direction. Therefore, no voltage VH is applied to capacitor C1, which is located upstream of diode D1 (opposite to connection point P) within input path 101b.

[0087] Capacitor C1 is a component used to stabilize the output voltage VLb. Capacitor C1 may not be a component with withstand capability (voltage withstand performance) to voltage VH.

[0088] As described above, no voltage VH is input to the input section 100a of the drive circuit 110a, so the input path 101a has a capacitor C0 to stabilize the output voltage VLa, but does not need to have a diode (reverse current prevention element).

[0089] Figure 3 This is a circuit diagram illustrating other examples of the head drive unit 531.

[0090] In this example, the input section 100c has an input path 101c with an ideal diode DI1 as a reverse current prevention element instead of diode D1 in the input path 101b.

[0091] As described above, when diode D1 is used to prevent reverse current (application) to the large voltage VH in the input path 101b, a voltage drop occurs due to diode D1 when the output voltage VLb is obtained from the input path 101b. The voltage drop caused by diode D1 is on average about 0.6V in silicon diodes and about 0.3V in Schottky diodes. When the number of driving elements is large, the total current increases and the power consumption cannot be ignored.

[0092] Figure 4 This is a graph illustrating the voltage drop in a diode.

[0093] In a diode, the magnitude of the drop voltage shown on the horizontal axis varies in relation to the magnitude of the current shown on the vertical axis (logarithmic) and the temperature represented by the lines.

[0094] In the droplet ejection device 1, the current flowing through it varies greatly depending on the number of actuators Ac with applied voltage, i.e., the number of drive circuits 110 that switch in the manner of output voltages VLa, VLb, etc. For example, when the number of actuators Ac is set to four digits (1000 or more, for example, around 1800 to 2000), the current varies by three to four digits. The current conceived for driving each actuator Ac is, for example, around 0.1mA to 1.0mA, and the current four digits higher is around 1A to 10A. That is, the range of current conceived in the input section 100 is between 0.1mA to 1A and between 1mA and 10A, and the overall range is around 0.1mA to 10A. Such a current range is as follows: Figure 4 The range shown is mainly from 1 mA to 1 A, where the voltage drop caused by the magnitude of the current is particularly significant. Since the voltage drop is so large as to be non-negligible, the ink ejection volume and ejection speed change accordingly, resulting in a decrease in image quality. Furthermore, due to seasonal changes in ambient temperature and the continuous operation of the droplet ejection device 1, the ink temperature changes, which in turn can also cause variations in the ink ejection volume and ejection speed.

[0095] Input path 101c incorporates an ideal diode DI1 as a reverse current prevention element, thereby reducing voltage drop and its amplitude. The ideal diode DI1 is not particularly limited; for example, it may include a transistor Tr and a controller Ct. The ideal diode DI1 can also be a modular element integrating these components and circuitry. The reverse current prevention element referred to herein is not limited to a single electronic component but can also be a structure combining multiple components (reverse current prevention circuit). The transistor Tr is a MOSFET, and its voltage drop during operation is sufficiently small, for example, suppressed to the level of 25mV. Furthermore, the controller Ct is a conventionally known circuit structure, such as a circuit with an op-amp, which operates such that even when the input-output voltage difference, i.e., the voltage difference between voltage VLb and the actuator Ac, is small, it causes a current proportional to that small voltage difference to flow through input path 101c. In fact, considering the voltage drop caused by parasitic resistance in the input section 100c and the drive circuit 110b, the voltage difference (voltage drop magnitude) between the overall output voltage VLb and the voltage applied to the actuator Ac is suppressed to less than 0.1V. If the voltage drop magnitude is less than 0.1V, the effect of the drop position caused by the change in ink ejection speed is negligible and will not significantly degrade the image quality.

[0096] With this circuit structure, in the head drive unit 531, it is not necessary for the components and circuits constituting the input path 101c to be resistant to a voltage VH (electricity) that is larger than the voltage VLb, and it is possible to stably apply the same voltage VLb to one end of each actuator Ac. Such components are not limited to the capacitor C1 mentioned above; for example, passive components such as resistors, integrated circuit components (ICs), voltage conversion circuits (DC / DC conversion components), and active components, as well as various other components, can be used.

[0097] Even if a stable voltage can be output, if the characteristics and sensitivity (referring to the ejection speed of the droplet relative to the applied voltage (driving voltage)) of the actuator Ac are inconsistent, the actuator Ac will not produce a uniform deformation for the same applied voltage, and will not eject ink at all. In a droplet ejection head 53 with multiple, especially a large number of, actuator Acs, it is difficult to manufacture all actuator Acs with completely consistent characteristics, and a small degree of deviation is unavoidable. In addition, when there is a deviation in the number of ink ejections corresponding to the position of the nozzle N, deviations may also occur as the sensitivity decreases over time. Therefore, in the droplet ejection device 1, a polarization adjustment process is performed to match the sensitivity of the actuator Ac during post-manufacturing inspection, initial setting after sale, and at appropriate intervals after the start of use, for example, to match the sensitivity of the relatively high-sensitivity actuator Ac with the sensitivity of the relatively low-sensitivity actuator Ac by reducing the sensitivity. Alternatively, if the sensitivity of the relatively low-sensitivity actuator Ac can be increased, a polarization adjustment process can be performed to match the sensitivity of the relatively high-sensitivity actuator Ac.

[0098] Sensitivity is measured by measuring the ejection speed of the ink when the same voltage is applied to the actuator Ac. In the initial state where the droplet ejection head 53 is not inserted into the droplet ejection device 1, the measurement is performed by mounting the droplet ejection head 53 on a dedicated adjustment device or similar device that has a camera section for capturing images of the ejected ink droplets. After the droplet ejection head 53 is inserted into the droplet ejection device 1, the camera section 9 can capture images.

[0099] Ink is ejected from each nozzle N separately. However, if the adjustment device and the imaging unit 9 can simultaneously identify and photograph the ink ejected from multiple nozzles N, ink can also be ejected from the number of nozzles N that can be photographed at the same time.

[0100] The polarization adjustment of actuator Ac can be performed, for example, by continuously applying a predetermined voltage to actuator Ac for a period of time corresponding to the reduced sensitivity amplitude. The predetermined voltage can be, for example, voltage VH as described above. The correspondence between the reduced sensitivity amplitude and the voltage application time may not be proportional. In this case, the adjustment device and the droplet ejection device 1 can store the conversion formula or table data used to convert the sensitivity amplitude into voltage application time in the storage unit (storage unit 42). By switching each drive circuit 110 in such a way that the output of voltage VH is stopped after the voltage application time set for nozzle N (actuator Ac), the duration of voltage application (i.e., the reduced sensitivity amplitude) is determined for each nozzle N (actuator Ac), so that the sensitivity of each actuator Ac is nearly uniform.

[0101] Figure 5 This is a flowchart illustrating the control process performed by the CPU for the concentration adjustment process executed by the aforementioned adjustment device. This concentration adjustment process begins, for example, during post-manufacturing inspection of the droplet ejector 53, based on a predetermined input operation made to the adjustment device by the inspection personnel.

[0102] After the concentration adjustment process begins, the CPU outputs driving signals of voltages VLa and VLb to each actuator Ac via the input unit 100 based on the test image data, causing ink to be ejected from the corresponding nozzle N (step S101). The CPU then uses the imaging unit to capture images of the ejected ink as it flies through the air (step S102).

[0103] Based on the imaging results, the CPU determines the ink ejection speed from each nozzle N (step S103). The CPU sets the voltage application time corresponding to the relatively high ejection speed for the actuator Ac corresponding to the nozzle N with the high ejection speed (step S104).

[0104] The CPU activates the drive circuit 110 corresponding to the actuator Ac to which the voltage is applied, and begins to continuously output a predetermined voltage (voltage VH) (step S105). The CPU then activates the drive circuits 110 corresponding to the actuator Ac after the voltage application time has elapsed in sequence, stopping the output of the predetermined voltage (step S106). After the output of the predetermined voltage has been stopped in all drive circuits 110, the CPU ends the output of voltage VH and the concentration adjustment process ends.

[0105] Furthermore, as described above, when inspecting the ink droplets after embedding the droplet ejector head 53 into the droplet ejector device 1, the imaging unit 9 can also capture images of the ejected ink droplets. The CPU 411 of the control unit 41 determines the ejection speed based on the imaging data and applies a voltage VH to the actuator Ac corresponding to each nozzle N according to the time corresponding to the ejection speed. Alternatively, if an external device is available that allows the droplet ejector head 53 to be embedded in the droplet ejector device 1 as is, enabling the imaging of flying droplets, this external device can also be used to capture images of flying ink droplets, and the imaging data can be transmitted from the external device to the control unit 41 via the communication unit 6.

[0106] [Second Implementation]

[0107] Next, the droplet ejection head 53 of the droplet ejection device of the second embodiment will be described.

[0108] The functional structure of the droplet ejection device 1 having the droplet ejection head 53 of the second embodiment is the same as that of the droplet ejection device 1. Figure 1 The structures shown are identical, so the explanation is omitted.

[0109] Figure 6 as well as Figure 7 These are diagrams illustrating the circuit structure of the head drive unit 531 in the droplet ejection head 53 of the second embodiment and its variations.

[0110] In the first embodiment described above, it is explained that the actuator Ac is driven by applying voltages to both ends of the actuator Ac, but the driving voltage can also be applied to one end of the actuator Ac while the other end is grounded.

[0111] exist Figure 6 In the example shown, the voltage VL or voltage VH input to the input section 100d is input to one end of the actuator Ac via the drive circuit 110, and the other end of the actuator Ac is grounded. In the input path 101d of the input section 100d, the diode D1 is located closest to the connection point P, and the voltage VH is not reversed and applied to the capacitor C1, etc., which is closer to the input side of the voltage VL than the diode D1.

[0112] exist Figure 7 In the example shown, in input section 100e, the diode D1 of input section 100d is replaced with an ideal diode DI1. This prevents the application of voltage VH to input path 101e and steadily reduces the drop in input voltage VL within the reverse current prevention element.

[0113] [Third Implementation]

[0114] Next, the droplet ejection device 1a of the third embodiment will be described.

[0115] Figure 8This is a block diagram showing the functional structure of the droplet ejection device 1a according to the third embodiment.

[0116] In this droplet ejection device 1a, the input section 100 of the head drive section 531 and the drive circuit 110 of the droplet ejection head 53 are located on the drive substrate 54 outside the droplet ejection head 53. The drive waveform signal output from the drive circuit 110 of the drive substrate 54 is input to each actuator Ac of the droplet ejection head 53 to activate the actuator Ac. Other structures are the same as those in the droplet ejection device 1 of the first and second embodiments described above, and the same reference numerals are used to represent the same structures, so the description is omitted.

[0117] In this way, the driving waveform does not need to be generated inside the droplet ejector 53. In addition, the backflow prevention element of the input voltage VLb and the input paths 101b to 101e of VL can also be located outside the droplet ejector 53.

[0118] As described above, the droplet ejector head 53 of this embodiment includes: an actuator Ac, which is driven according to a supplied voltage to impart pressure variation to the liquid and eject droplets; and an input section 100b to 100e for power to the actuator Ac. The input section 100b to 100e has an input path 101b to 101e for supplying power with voltages VLb and VL, and an input path 102 for supplying power with a voltage VH that is larger than voltages VLb and VL. The input path 101b to 101e includes: a diode D1 or an ideal diode DI1 as a reverse current prevention element to prevent the application of voltage VH; and a capacitor C1 located on the side opposite to the connection point P, which is closer to the diode D1 or the ideal diode DI1, and does not have withstand capability (voltage withstand performance) to voltage VH.

[0119] Thus, in the droplet ejector head 53, in the input paths 101b-101e and 102 where low voltages VLb and VL are input but not mechanically or physically separated, a voltage greater than the voltage VLb and VL of the power input to the input paths 101b-101e themselves is not applied. Therefore, in the input sections 100b-100e, which can be easily formed on the drive substrate, the components and circuits within the input paths 101b-101e do not need to withstand voltages greater than VLb and VL. Consequently, power supply operations can be performed easily and safely without unnecessarily increasing the size and cost of these components and circuits, enabling the operation and adjustment of the actuator Ac.

[0120] Furthermore, the droplet ejector 53 can also utilize diode D1 to prevent reverse current flow and the application of voltage VH. Reverse current can be prevented with the simplest structure, thus minimizing cost and effort.

[0121] Alternatively, the droplet ejector 53 can also utilize an ideal diode DI1 to prevent reverse current flow and the application of voltage VH. In a typical diode D1, in a droplet ejector 53 that can operate a large number of actuators Ac, voltage drops and their fluctuations are not negligible, leading to image quality degradation associated with increased power consumption, deviations in ejection speed and ejection volume. By using an ideal diode to prevent reverse current flow, it is possible to prevent the application of voltage VH to the input paths 101c and 101e, supply power to the actuators Ac with a stable voltage, and suppress unnecessary power consumption increases.

[0122] Furthermore, in input paths 101c and 101e, the voltage difference between the voltages VLb and VL supplied to these input paths and the voltage applied to the actuator Ac should be less than 0.1V. This suppresses variations in the droplet ejection speed in the droplet ejection head 53, reducing image quality degradation.

[0123] Furthermore, the current flowing through the ideal diode DI1 can be between 0.1mA and 10A. In the droplet ejector 53, where the current dependence of voltage drop in diode D1 is large (below 1A) and the current consumption amplitude is close to four digits, using the ideal diode DI1 instead of diode D1 to prevent reverse current can suppress voltage drop fluctuations very little and stabilize them. Therefore, in the droplet ejector 53, it is possible to prevent the application of voltage VH to the input paths 101c and 101e and minimize the adverse effects on image quality.

[0124] Additionally, the input unit 100 has an input path 101a that supplies power at voltage VLa. Power is supplied to the first terminal of the actuator Ac from any one of the input paths 101b, 101c, and 102, and power is supplied to the second terminal of the actuator Ac on the side opposite to the first terminal from the input path 101a.

[0125] In this way, the droplet ejector 53 of actuator Ac can also be driven by the voltage difference applied to both ends of actuator Ac. Therefore, the drive waveform under digital drive, which switches between two values ​​of supply voltage and ground voltage, can be applied to actuator Ac more appropriately. Furthermore, for droplet ejectors that operate by applying a drive voltage to adjacent actuator Ac, the need for high-voltage withstand components can be reduced, and their proper operation can be ensured.

[0126] Alternatively, the input sections 100d and 100e can supply power to the first terminal of the actuator Ac with the output voltage, and the second terminal of the actuator Ac can be grounded.

[0127] In this way, even if the head drive unit 531 is a component that changes the voltage relative to the ground plane, it can safely operate the input paths 101d and 101e that have components that do not have the ability to withstand voltage VH.

[0128] Furthermore, the droplet ejection device 1 of this embodiment includes the aforementioned droplet ejection head 53. With this droplet ejection device 1, the droplet ejection head 53 can be operated appropriately while suppressing size and cost.

[0129] Furthermore, the droplet ejection device 1a of the third embodiment includes the aforementioned actuator Ac and an input section 100 for supplying power to the actuator Ac. This input section 100 may also be located outside the droplet ejection head 53. Such a droplet ejection device 1a can also ensure proper operation of the droplet ejection head 53 while minimizing size and cost.

[0130] Furthermore, the droplet ejection device 1 includes a control unit 41 (CPU 411). The control unit 41 determines the ejection speed of the droplets based on the imaging data of the droplets ejected and flying according to the drive of the actuator Ac. For uniform ink ejection, not only the applied voltage but also the consistency of the sensitivity of the actuator Ac (the ejection speed obtained based on the applied voltage) is important. In the droplet ejection device 1, by determining the ejection speed of the ink droplets, deviations in the sensitivity of the actuator Ac can be determined. In the droplet ejection device 1, a voltage VH can be applied to each actuator Ac without causing adverse effects on other parts, etc. Therefore, by continuously applying voltage VH to each actuator Ac for an appropriate time according to the determination result, image quality degradation caused by sensitivity deviations can be reduced.

[0131] Furthermore, the droplet ejection device 1 includes an imaging unit 9 that captures images of the ejected droplets and outputs the captured data. Therefore, even after the droplet ejection head 53 is inserted into the droplet ejection device 1, since processing related to determining the ejection speed and adjusting polarization can be consistently performed within the droplet ejection device 1, the degradation of sensitivity over time caused by the use of the droplet ejection device 1 can be addressed in a way that reduces the effort and time required by users and managers and facilitates uniform ink ejection.

[0132] Furthermore, the present invention is not limited to the above-described embodiments and various modifications can be made.

[0133] For example, in the above embodiment, voltages VL, VLa, and VLb are described as fixed, but multiple input paths 101b to 101e supplying lower voltages may exist for the input path 102 (second supply circuit) that receives the highest input voltage. In this case, each of the multiple input paths (first supply circuit) has a reverse current prevention element.

[0134] Alternatively, the structure can output multiple or consecutive voltages smaller than voltage VH from input paths 101b to 101e. For example, the drive waveforms supplied from the outside from input paths 101b to 101e can be trapezoidal waveforms with peak voltages VL and VLb, or stepped waveforms with peak voltages VL, VLb, and combinations of voltages smaller than them. In this case, the drive circuit 110 has a current outflow path when the output voltage from input paths 101b to 101e decreases. Even with such a structure, reverse current from voltage VH from input path 102 is suppressed.

[0135] Furthermore, in the above embodiment, the voltage VH is described as a voltage used for polarization adjustment, but it is not limited to this. It can also be a voltage for other purposes, and there can be various voltages for ink ejection.

[0136] Furthermore, not all parts and components located within input paths 101b to 101e need to be components that are not resistant to voltage VH. For example, components that are resistant to voltage VH can be used to complete the supply of parts that do not differ significantly in cost or size, and for which cost is reduced when the same part is procured together.

[0137] Furthermore, the current flowing through input paths 101b to 101e is not limited to the range of large voltage drops caused by diode D1. Larger currents can also flow. Additionally, if the effect voltage variation is small, using an ideal diode DI1 is also possible.

[0138] In addition, diode D1 is not limited to a typical rectifier diode.

[0139] Furthermore, the specific shape of the ideal diode DI1 is not particularly limited. It only needs to be able to produce a current corresponding to the applied voltage. Also, if the voltage drop is kept constant, it does not necessarily have to be less than 0.1V.

[0140] Alternatively, in the first embodiment, the input path 101a may be a voltage to a common electrode connected to the second terminal of the plurality of actuators Ac. In this case, the number of drive circuits 110a may be less than the number of actuators Ac, or it may be a single circuit.

[0141] Furthermore, in the above embodiment, an inkjet recording apparatus that ejects colored ink was described as an example of the droplet ejection device 1, but it is not limited to this. It may also be able to eject transparent ink, or liquids other than inks used for image recording, such as liquids used for coating, liquid metals used for circuit formation, liquids used for forming three-dimensional structures, etc.

[0142] Furthermore, if it is difficult to determine the sensitivity of actuator Ac by measuring the ejection speed performed by imaging unit 9, various other parameters can be read using a brightness sensor, such as the ink dripping onto the medium. For each dripping range of ink corresponding to nozzle N, the correspondence between nozzle N and concentration can be determined based on the brightness data. As for concentration, the brightness value can be used as is, or it can be converted from the brightness value to a concentration grayscale based on a conversion formula or table data stored in the storage unit 42. Alternatively, sensitivity can be determined by measuring the thickness on the medium, the spread on the medium surface, the surface reflection state, etc.

[0143] Alternatively, the droplet ejector head 53 can be sold separately from the droplet ejector device 1. It can also be used in the droplet ejector device 1 by simply replacing the droplet ejector head 53.

[0144] Furthermore, the specific structures, processing actions, and procedures described in the above embodiments can be appropriately modified without departing from the spirit of the invention. The scope of the invention includes the scope of the invention as set forth in the claims and its equivalents.

[0145] Industrial availability

[0146] This invention can be used in droplet ejection heads and droplet ejection devices.

[0147] Symbol Explanation

[0148] 1.1a Droplet ejection device

[0149] 6 Ministry of Communications

[0150] 7 Display Section

[0151] 8. Operations and Acceptance Department

[0152] 9. Filming Department

[0153] 41 Control Department

[0154] 411 CPU

[0155] 412 RAM

[0156] 42 Storage Section

[0157] 421 Image Data

[0158] 51 Transport Department

[0159] 511 Conveying Drive Department

[0160] 52-head drive control unit

[0161] 521 Head Control Unit

[0162] 53 Droplet ejection head

[0163] 531 Head Drive Unit

[0164] 54 Driver substrate

[0165] Input sections 100, 100a~100e

[0166] Input paths 101a~101e, 102

[0167] 110, 110a, 110b drive circuits

[0168] Ac actuator

[0169] C0 and C1 capacitors

[0170] Ct controller

[0171] D1 diode

[0172] DI1 Ideal Diode

[0173] E Power Supply Section

[0174] N nozzle

[0175] P Connection point

[0176] Tr transistor

[0177] VL, VLa, VLb, VH voltages

Claims

1. A droplet ejector head, comprising: A driving element, driven by a supplied voltage, imparts pressure variations to the liquid, causing droplets to be ejected; and A power supply circuit that supplies power to the driving element. The power supply circuit has: The first power supply circuit supplies power at the first voltage; and The second power supply circuit supplies power at a second voltage that is greater than the first voltage. The first supply circuit has: A reverse current prevention element to prevent the application of the second voltage; and An element located on the side opposite to the contacts of the first and second supply circuits, which is further away from the reverse current prevention element, and which does not have the voltage withstand capability for the second voltage.

2. The droplet ejector according to claim 1, wherein, The backflow prevention element includes a diode.

3. The droplet ejector according to claim 1, wherein, The backflow prevention element includes an ideal diode.

4. The droplet ejector according to claim 3, wherein, In the first supply circuit, the voltage difference between the first voltage supplied to the first supply circuit and the voltage applied to the driving element is less than 0.1V.

5. The droplet ejector according to claim 3, wherein, The current flowing through the ideal diode is greater than 0.1mA and less than 10A.

6. The droplet ejector according to claim 4, wherein, The current flowing through the ideal diode is greater than 0.1mA and less than 10A.

7. The droplet ejector according to any one of claims 1 to 6, wherein, The power supply circuit has a third supply circuit that supplies power at a third voltage. Power is supplied to the first terminal of the driving element from either the first supply circuit or the second supply circuit. Power is supplied from the third supply circuit to the second terminal of the driving element on the side opposite to the first terminal.

8. The droplet ejector according to any one of claims 1 to 6, wherein, The power supply circuit supplies power to the first terminal of the driving element. The second terminal of the driving element, on the side opposite to the first terminal, is grounded.

9. A droplet ejection device, It has a droplet ejector as described in any one of claims 1 to 8.

10. A droplet ejection device, comprising: A driving element, driven by a supplied voltage, imparts pressure variations to the liquid, causing droplets to be ejected; and A power supply circuit that supplies power to the driving element. The power supply circuit has: The first power supply circuit supplies power at the first voltage; and The second power supply circuit supplies power at a second voltage that is greater than the first voltage. The first supply circuit has: A reverse current prevention element to prevent the application of the second voltage; and An element located on the side opposite to the contacts of the first and second supply circuits, which is further away from the reverse current prevention element, and which does not have the voltage withstand capability for the second voltage.

11. The droplet ejection device according to claim 9 or 10, wherein, Equipped with a control unit, The control unit determines the ejection speed of the droplet based on the image data of the droplet being ejected and flying according to the drive element.

12. The droplet ejection device according to claim 11, wherein, It has a camera unit that can capture images of the ejected droplets and output the captured data.

Images