Liquid dispensing device

Abstract

To provide a liquid discharge device that can discharge liquid accurately, even in discharging the liquid from a plurality of liquid discharge ports simultaneously.SOLUTION: The liquid discharge device comprises: a liquid discharge body that comprises a plurality of liquid discharge ports for discharging liquid, a plurality of valve bodies provided to correspond to the liquid discharge ports, and a plurality of driving bodies that drive the valve bodies so that the liquid discharge ports are opened and closed; liquid supply means that pressurizes and supplies the liquid to the liquid discharge body; and control means that controls applied voltages to the driving bodies in accordance with the number of the valve bodies that are driven simultaneously of the plurality of valve bodies.SELECTED DRAWING: Figure 8

Description

[Technical Field]

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

[0002] Patent Document 1 discloses a droplet ejection head in which ejection liquid is pressurized and supplied to a cavity 23 communicating with a nozzle 22, the nozzle 22 can be blocked by a pin 24, the pin 24 can be moved toward and away from the nozzle 22 by an actuator 25, and the actuator 25 is controlled by a control device 12, so that the pressurized and supplied ejection liquid is ejected as droplets from the nozzle 22 only while the pin 24 is away from the nozzle 22. Summary of the Invention [Problem to be solved by the invention]

[0003] An object of the present invention is to provide a liquid ejection device that can eject liquid accurately even when ejecting liquid from a plurality of liquid ejection ports simultaneously. [Means for solving the problem]

[0004] The present invention provides a liquid ejection head including: a plurality of liquid ejection ports for ejecting liquid; so as to approach and separate from the liquid ejection port a plurality of valve bodies provided corresponding to the liquid discharge ports; The amount of separation of the valve body from the liquid discharge port is changed in response to an applied voltage. a liquid ejection body including a plurality of driving bodies that drive the valve body to open and close the liquid ejection port; Pressurized to a specified pressure The liquid Provide the number of valve bodies to be simultaneously driven among the plurality of valve bodies; and the predetermined pressure The applied voltage of the driver is Size and a control means for controlling the above. [Effects of the Invention]

[0005] According to the present invention, it is possible to provide a liquid ejection device that can eject liquid accurately even when ejecting liquid from a plurality of liquid ejection ports simultaneously. [Brief explanation of the drawings]

[0006] [Figure 1] 1 is an overall perspective view showing an example of a liquid ejection apparatus according to the present invention. [Figure 2] FIG. 2 is an overall perspective view of a carriage of the liquid ejection device. [Figure 3] FIG. 2 is an overall perspective view of a liquid ejection head alone. [Figure 4] FIG. 2 is an overall cross-sectional view of a liquid ejection head alone. [Figure 5] FIG. 3 is an explanatory diagram of a liquid ejection module alone. [Figure 6] FIG. 2 is a schematic diagram showing an example of a liquid supply unit. [Figure 7] FIG. [Figure 8] FIG. 4 is an explanatory diagram of control of applied voltage to a piezoelectric element. [Figure 9] FIG. 2 is a block diagram of a control system of the liquid ejection device. [Figure 10] FIG. 10 is a configuration diagram showing another embodiment of the drive waveform generating unit. [Figure 11] FIG. 4 is an explanatory diagram of a drive waveform table. [Figure 12] FIG. 10 is an explanatory diagram of an example of liquid ejection head installation that enables reduction in simultaneous driving. [Figure 13] FIG. [Figure 14] 10A and 10B are explanatory diagrams illustrating a liquid ejection operation by a liquid ejection head according to Modification 1. [Figure 15] FIG. 10 is an explanatory diagram of a liquid ejection head according to a second modified example. DETAILED DESCRIPTION OF THE INVENTION

[0007] An embodiment of the present invention will be described with reference to the drawings.

[0008] FIG. 1 is an overall perspective view showing an example of a liquid ejection device of the present invention.

[0009] The liquid ejection device 1000 is installed facing a drawing target 100, which is an example of an object. The liquid ejection device 1000 includes an X-axis rail 101, a Y-axis rail 102 that intersects with the X-axis rail 101, and a Z-axis rail 103 that intersects with the X-axis rail 101 and the Y-axis rail 102.

[0010] The Y-axis rail 102 holds the X-axis rail 101 so that the X-axis rail 101 can move in the Y direction. The X-axis rail 101 also holds the Z-axis rail 103 so that the Z-axis rail 103 can move in the X direction. The Z-axis rail 103 then holds the carriage 1 so that the carriage 1 can move in the Z direction. Here, the carriage 1 is an example of a liquid ejection unit.

[0011] The liquid ejection device 1000 includes a first Z-direction drive unit 92 that moves the carriage 1 in the Z direction along the Z-axis rail 103, and an X-direction drive unit 72 that moves the Z-axis rail 103 in the X direction along the X-axis rail 101. The liquid ejection device 1000 also includes a Y-direction drive unit 82 that moves the X-axis rail 101 in the Y direction along the Y-axis rail 102. The liquid ejection device 1000 also includes a second Z-direction drive unit 93 that moves the head holder 70 in the Z direction relative to the carriage 1. Here, the head holder 70 is an example of a holder.

[0012] The liquid ejection device 1000 configured as described above ejects ink, an example of a liquid, from a head provided on the head holder 70 while moving the carriage 1 in the X-axis, Y-axis, and Z-axis directions, to draw on the drawing target 100. Here, the movement of the carriage 1 and head holder 70 in the Z direction does not need to be parallel to the Z direction, and may be oblique movement as long as it includes at least a component in the Z direction.

[0013] In Figure 1, the surface shape of the object to be drawn 100 is shown as a flat surface, but the surface shape of the object to be drawn 100 may also be a nearly vertical surface, such as the body of a car or truck, or the body of an airplane, or a surface with a large radius of curvature.

[0014] Next, the configuration of the carriage 1 will be described.

[0015] FIG. 2 is an overall perspective view of a carriage of the liquid ejection device.

[0016] The carriage 1 includes a head holder 70. The carriage 1 is movable in the Z direction along a Z-axis rail 103 by power from a first Z-direction drive unit 92 shown in Fig. 1. The head holder 70 is movable in the Z direction relative to the carriage 1 by power from a second Z-direction drive unit 93 shown in Fig. 1.

[0017] The head holder 70 also includes a head fixing plate 70a for mounting the liquid ejection head 300. Here, the liquid ejection head 300 is an example of a liquid ejection body.

[0018] In this embodiment, six liquid ejection heads 300a to 300f are arranged in a stack on a head fixing plate 70a. In the following description, these liquid ejection heads will be collectively referred to as liquid ejection heads 300.

[0019] Each of the liquid ejection heads 300a to 300f is equipped with a plurality of nozzles 302. The color of ink used by the liquid ejection heads 300a to 300f may be different for each head, or may all be the same color. The number of heads constituting the liquid ejection head 300 is not limited to six. It may be more or less than six.

[0020] As shown in the figure, the liquid ejection heads 300 are fixed to the head fixing plate 70a with the nozzle rows of each head intersecting a horizontal plane (XZ plane) and the arrangement direction of the multiple nozzles 302 tilted with respect to the X axis. In this state, the nozzles 302 eject ink in a direction intersecting the direction of gravity (Z direction). Here, the nozzles 302 are an example of liquid ejection ports.

[0021] FIG. 3 is an overall perspective view of the liquid ejection head alone.

[0022] Each of the liquid ejection heads 300a to 300f shown in Fig. 2 includes a housing 310 as shown in Fig. 3. The housing 310 is made of metal or resin. The housing 310 also includes a connector 350 at its top for communicating electrical signals. The housing 310 also includes a supply port 311 on the left and right sides for supplying ink into the head, and a recovery port 313 for discharging ink from the head.

[0023] FIG. 4 is an overall cross-sectional view of the liquid ejection head alone (a cross-sectional view taken along the line AA in FIG. 3).

[0024] The housing 310 holds a nozzle plate 301 equipped with nozzles 302 for ejecting ink. The housing 310 also includes a flow path 312 that sends ink from a supply port 311 side through the nozzle plate 301 to a recovery port 313 side.

[0025] Between the supply port 311 and the recovery port 313, a liquid ejection module 330 is arranged to eject ink in the flow path 312 from the nozzles 302. The number of liquid ejection modules 330 corresponds to the number of nozzles 302, and in this example, a configuration is shown in which eight liquid ejection modules 330 corresponding to eight nozzles 302 arranged in a row are provided. Note that the number and arrangement of the nozzles 302 and liquid ejection modules 330 are not limited to those described above. For example, the number of nozzles 302 and liquid ejection modules 330 may be one instead of multiple. Furthermore, the nozzles 302 and liquid ejection modules 330 may be arranged in multiple rows instead of a single row.

[0026] With the above configuration, supply port 311 takes in pressurized ink from the outside, sends the ink in the direction of arrow a1, and supplies the ink to flow path 312. Flow path 312 sends the ink from supply port 311 in the direction of arrow a2. Then, recovery port 313 discharges ink that has not been ejected from nozzles 302 arranged along flow path 312 in the direction of arrow a3.

[0027] The liquid ejection module 330 includes a needle valve 331 that opens and closes the nozzle 302 , and a piezoelectric element 332 that drives the needle valve 331 .

[0028] The housing 310 is provided with a restricting member 314 at a position facing the upper end of the piezoelectric element 332. The restricting member 314 abuts against the upper end of the piezoelectric element 332 and serves as a fixing point for the piezoelectric element 332. Here, the needle valve 331 is an example of a valve body, and the piezoelectric element 332 is an example of a driver.

[0029] In the above configuration, when the piezoelectric element 332 is actuated to move the needle valve 331 upward, the nozzle 302 that was closed by the needle valve 331 opens, and ink is ejected from the nozzle 302. When the piezoelectric element 332 is actuated to move the needle valve 331 downward, the tip of the needle valve 331 abuts against the nozzle 302, closing the nozzle 302 and preventing ink from being ejected from the nozzle 302. Note that while ink is being ejected onto the drawing object 100 (see FIG. 1), the ejection of ink from the recovery port 313 may be temporarily suspended in order to prevent a decrease in the efficiency of ink ejection from the nozzle 302.

[0030] 5A and 5B are explanatory diagrams of a single liquid ejection module that constitutes a liquid ejection head, in which Fig. 5A is an overall cross-sectional view of the liquid ejection module, and Fig. 5B is an enlarged view of part B in Fig. 5A.

[0031] The liquid ejection module 330 includes a needle valve 331 that opens and closes the nozzle 302, and a piezoelectric element 332 that drives the needle valve 331. The nozzle plate 301 is joined to the housing 310. The flow path 312 is a common flow path for the plurality of liquid ejection modules 330 provided in the housing 310.

[0032] The tip of needle valve 331 is provided with elastic member 331a, which ensures that nozzle 302 is closed reliably when the tip of needle valve 331 is pressed against nozzle plate 301. In addition, bearing 321 is provided between needle valve 331 and housing 310, and sealing member 315 such as an O-ring is provided between bearing 321 and needle valve 331.

[0033] A piezoelectric element 332 is accommodated within space 322 of housing 310. A central space 333a of holding member 333 holds the piezoelectric element 332, and the piezoelectric element 332 and needle valve 331 are coaxially connected via tip 333b of holding member 333. That is, holding member 333 has central space 333a that accommodates piezoelectric element 332, tip 333b is connected to needle valve 331, and rear end 333c is fixed by regulating member 314 attached to housing 310.

[0034] Here, when a voltage is applied by the voltage application means 200, the piezoelectric element 332 drives the needle valve 331 in a direction that opens the nozzle 302. Therefore, when no voltage is applied to the piezoelectric element 332, the needle valve 331 closes the nozzle 302, so that ink is not ejected from the nozzle 302 even if ink is supplied under pressure to the flow path 312. When a voltage is applied to the piezoelectric element 332, the piezoelectric element 332 contracts and pulls the needle valve 331 via the holding member 333, causing the needle valve 331 to move away from the nozzle 302 and open the nozzle 302. As a result, ink supplied under pressure to the flow path 312 is ejected from the nozzle 302.

[0035] FIG. 6 is a schematic diagram showing an example of the liquid supply means.

[0036] The liquid ejection device 1000 includes tanks 105a to 105d as sealed containers that contain inks 30a to 30d to be ejected from the liquid ejection heads 300a to 300d, respectively. In the following description, these inks will be collectively referred to as ink 30. Furthermore, the tanks will be collectively referred to as tank 105.

[0037] The tank 105 and the inlet (supply port 311 shown in FIGS. 3 and 4) of the liquid ejection head 300 are connected via a tube 311a. Meanwhile, the tank 105 is connected to a compressor 108 via a pipe 107 including an air regulator 106, and the compressor 108 supplies pressurized air. As a result, the ink 30 inside the liquid ejection head 300 is pressurized, so that when the needle valve described above is opened, the ink 30 is ejected from the nozzle 302. Here, the compressor 108, the pipe 107 including the air regulator 106, the tank 105, and the tube 311a are an example of a liquid supply means that supplies pressurized ink 30 to the liquid ejection head 300.

[0038] 7A and 7B are explanatory diagrams of the liquid ejection operation, where Fig. 7A is an explanatory diagram showing the schematic configuration during ejection and the voltage applied to the piezoelectric element at that time, and Fig. 7B is an explanatory diagram showing the schematic configuration during non-ejection and the voltage applied to the piezoelectric element at that time.

[0039] 7(a), the piezoelectric element 332 contracts in the longitudinal direction when a predetermined voltage Vh is applied (i.e., when a relatively large voltage is applied), and moves the needle valve 331 to the right in the figure, thereby opening the nozzle 302 and ejecting the ink 30 from the nozzle 302.

[0040] 7(b), when the voltage applied to the piezoelectric element 332 is set to 0 V (i.e., when a relatively small voltage is applied), the piezoelectric element 332 expands and returns to its original position, moving the needle valve 331 to the left in the figure. This closes the nozzle 302, preventing the ejection of ink 30 from the nozzle 302. Note that in this embodiment, the voltage is set to 0 V when the nozzle 302 is closed, but it may be set to a value other than 0 V as long as it is smaller than the predetermined voltage Vh.

[0041] FIG. 8 is an explanatory diagram of the control of the voltage applied to the piezoelectric element.

[0042] 4 and other figures, the liquid ejection head 300 in the liquid ejection device of the present invention is configured so that ink 30 flowing in a flow path 312 connecting a supply port 311 and a recovery port 313 is used by a plurality of liquid ejection modules 330. For this reason, for example, when ink is ejected from one nozzle out of eight nozzles 302 arranged in a row, the total area of ​​the nozzles from which ink flows changes, and therefore the pressure applied to each nozzle changes.

[0043] That is, the pressure applied to each nozzle varies depending on the number of simultaneously actuated needle valves 331 among the multiple needle valves 331, resulting in variations in ejection characteristics such as the ejection volume and ejection speed of the ink 30. This is because, while the flow rate and flow speed of ink supplied from the supply port 311 to the flow path 312 are approximately constant regardless of the number of simultaneously actuated needle valves 331, the flow rate and ejection speed of ink ejected from each nozzle 302 decrease as the number of simultaneously actuated needle valves 331, i.e., the total cross-sectional area of ​​the simultaneously opened nozzles 302, increases. This problem is particularly pronounced in a structure in which individual liquid chambers are connected to each other by a flow path (a structure in which the nozzles are connected in series). That is, among multiple nozzles 302 fluidly connected in series, the flow rate and ejection speed of ink ejected from the nozzle 302 located downstream in the flow path 312 in the ink flow direction decreases significantly.

[0044] Therefore, in the present invention, as shown in FIG. 8 , the applied voltage to the piezoelectric element 332 is controlled to increase in accordance with the number of simultaneously driven needle valves 331 among the multiple needle valves 331. The larger the number of simultaneously driven needle valves 331, the larger the correction amount (i.e., increase amount) ΔVh added to the reference drive voltage Vh. The applied voltage VH to the piezoelectric element 332 is controlled to increase as the number of simultaneously driven needle valves 331 increases. This causes the piezoelectric element 332 to displace more, increasing the amount of movement of the needle valve 331. As the amount of movement of the needle valve 331 increases and its displacement increases, the needle valve 331 retracts further from the nozzle 302 within the flow path 312. This reduces pressure loss caused by the needle valve 331 obstructing the flow near the nozzle 302 during the time it takes for the ink 30 to flow from the supply port 311 to the nozzle 302. This prevents a decrease in the flow rate and discharge flow velocity of the ink 30 ejected from each nozzle 302. As a result, the fluid resistance between the nozzle 302 and the needle valve 331 is reduced, and the ejection characteristics of the ink 30 are improved.

[0045] FIG. 9 is a block diagram showing an example of a control configuration of the liquid ejection device.

[0046] The liquid ejection device 1000 includes a controller 901, a head drive control unit 902, and the like. The controller 901 is connected to a computer 903. The computer 903 includes a RIP (Routing Information Protocol) unit 9031, a rendering unit 9032, and the like. The RIP unit 9031 has a function of performing image processing according to a color profile and user settings. The rendering unit 9032 has a function of decomposing image data to be drawn on the drawing target 100 (see FIG. 1) into image data for each scan (for example, each unit of drawing performed by one movement of the carriage 1 in the X direction). The computer 903 is also connected to an input device 9033. The input device 9033 includes a keyboard, a mouse, a touch panel, and the like, and receives input from the user, such as image data to be drawn on the drawing target 100, coordinate data settings, and drawing mode selection.

[0047] The controller 901 includes a system control unit 9011, an image data storage unit 9012, a memory control unit 9013, an ejection period signal generation unit 9014, and a carriage control unit 9015. The system control unit 9011 receives image data and commands from the computer 903 and controls the overall operation of the liquid ejection device 1000. The image data storage unit 9012 includes memory such as a ROM (Read Only Memory), a RAM (Random Access Memory), and an HDD (Hard Disk Drive), and stores image data and the like received from the computer 903. The memory control unit 9013 writes image data and the like to the image data storage unit 9012 and reads image data and the like from the image data storage unit 9012 based on commands from the system control unit 9011.

[0048] The ejection period signal generating unit 9014 generates an ink ejection period signal based on the output signal of the encoder sensor 109 and information indicating the resolution of the image data received from the computer 903 .

[0049] Here, the encoder sensor 109 optically detects the slits of a linear encoder installed along the X-axis rail 101 of the liquid ejection device 1000, for example, and generates the output signal described above. Note that the encoder sensor 109 is not limited to a linear encoder system, as long as it is capable of detecting the position of the carriage 1 in the X direction. Instead of the linear encoder system, it may be replaced with a system that counts the rotations of the drive motor of the X-direction drive unit 72, for example.

[0050] The carriage control unit 9015 calculates position information of the carriage 1 based on the output signal of the encoder sensor 109, and controls the speed of the X-direction drive unit 72. In this example, the system control unit 9011 calculates the amount of change in the movement speed of the carriage 1. The system control unit 9011 then controls the speed of the carriage 1 based on this amount of change.

[0051] As described above, the controller 901 includes a system control unit 9011, an image data storage unit 9012, a memory control unit 9013, an ejection period signal generation unit 9014, and a carriage control unit 9015. The controller 901 has an arithmetic processing unit and a storage device, and realizes each of these functional units by having the arithmetic processing unit execute a program pre-recorded in the storage device.

[0052] Next, we will explain the head drive control unit 902. The head drive control unit 902, which controls the driving of the liquid ejection head 300, includes a drive waveform data storage unit 9021, a drive waveform generation unit 9022, a D / A converter 9023, a voltage amplifier 9024, and a current amplifier 9025. The drive waveform data storage unit 9021 stores drive waveforms for driving the liquid ejection head 300.

[0053] The drive waveform generation unit 9022 outputs the drive waveform data read out from the drive waveform data storage unit 9021 to the D / A converter 9023 in response to an ejection period signal from the ejection period signal generation unit 9014. The D / A converter 9023 converts the drive waveform data received from the drive waveform generation unit 9022 into analog data and outputs the analog data to a voltage amplification unit 9024. The voltage amplification unit 9024 amplifies the voltage of the analog data received from the D / A converter 9023. Furthermore, the current amplification unit 9025 amplifies the current of the analog data received from the voltage amplification unit 9024.

[0054] As described above, the head drive control unit 902 includes a drive waveform data storage unit 9021, a drive waveform generation unit 9022, a D / A converter 9023, a voltage amplifier 9024, and a current amplifier 9025. The drive waveforms generated by the head drive control unit 902 are used to realize drive control for each nozzle of the liquid ejection head 300.

[0055] 9 is an example, and is not limited to this. For example, the RIP unit 9031 and the rendering unit 9032 may be provided in the system control unit 9011 of the controller 901, rather than in the computer 903.

[0056] As described above, this embodiment includes a liquid ejection head 300 having a plurality of nozzles 302 that eject ink 30, a plurality of needle valves 331 provided corresponding to the nozzles 302, and a plurality of piezoelectric elements 332 that drive the needle valves 331 to open and close the nozzles 302, a liquid supply means (compressor 108, pipe 107 including air regulator 106, tank 105, and tube 311a) that pressurizes and supplies ink 30 to the liquid ejection head 300, and a control means (controller 901, head drive control unit 902, and computer 903) that controls the applied voltage Vh of the piezoelectric elements 332 depending on the number of needle valves 331 that are driven simultaneously out of the plurality of needle valves 331.

[0057] This makes it possible to provide a liquid ejection device that can eject liquid accurately even when ejecting liquid from a plurality of liquid ejection ports simultaneously.

[0058] FIG. 10 is a diagram showing the configuration of another embodiment of the drive waveform generating section.

[0059] In the head drive control unit 902 of Fig. 9, the drive waveform generation unit 9022 may be configured as the drive waveform generation unit 9026 of Fig. 10. The drive waveform generation unit 9026 includes an image data output unit 9026a, a pixel count unit 9026b, a drive waveform correction value calculation unit 9026c, a drive waveform table 9026d, and a drive waveform correction unit 9026e.

[0060] The image data output unit 9026a identifies image data for ejecting ink in the next cycle based on the image data received from the controller 901. The image data output unit 9026a then outputs the identified image data to the pixel count unit 9026b. The image data output unit 9026a outputs image data at a predetermined cycle, for example, for each scan.

[0061] Based on the image data received from the image data output unit 9026a, the pixel counting unit 9026b counts the number of nozzles that are driven simultaneously in the liquid ejection head 300. After counting the number of nozzles that are driven simultaneously, the pixel counting unit 9026b outputs the number of nozzles to the drive waveform correction value calculation unit 9026c.

[0062] The drive waveform table 9026d stores in advance a table showing the relationship between the number of driven nozzles and the amount of drive voltage correction (details will be described later). The drive waveform correction value calculation unit 9026c obtains a drive waveform correction value based on the information indicating the number of driven nozzles received from the pixel count unit 9026b and the table information in the drive waveform table 9026d. The drive waveform correction value calculation unit 9026c calculates the amount of change in head drive voltage (ΔVh in FIG. 8) and further corrects the obtained drive waveform correction value.

[0063] The drive waveform correction unit 9026e performs correction processing based on the correction value received from the drive waveform correction value calculation unit 9026c and the drive waveform stored in the drive waveform table 9026d. By outputting the drive waveform corrected by the drive waveform correction unit 9026e to the liquid ejection head 300, drive control for each nozzle of the liquid ejection head 300 is achieved.

[0064] FIG. 11 is an explanatory diagram showing an example of the drive waveform table 9026d.

[0065] This example shows a table that associates air pressure setting values, the number of simultaneously driven nozzles, and the drive voltage correction amount. As shown in the figure, multiple air pressure setting values ​​can be prepared, and different air pressures can be used depending on the ink characteristics, such as setting it to 0.45 for color inks (C, M, Y, K, etc.) and 0.3 for white ink. When the number of simultaneously driven nozzles is 1, the drive voltage correction amounts A1 and A2 are zero volts. The drive voltage correction amount increases as you move from A1 to H1, and from A2 to H2.

[0066] Using this drive waveform table, the drive voltage VH is derived by adding a correction amount ΔVh to the reference drive voltage Vh.

[0067] As described above, in the liquid ejection head 300, the needle valve 331 is closed when no voltage is applied to the piezoelectric element 332, and when a voltage is applied to the piezoelectric element 332, the needle valve 331 opens and ejects ink 30 from the nozzle 302.

[0068] As a result, even if the power supply is cut off due to an emergency or the like, the needle valve 331 closes the nozzle 302, and the ejection of the ink 30 from the nozzle 302 can be reliably stopped.

[0069] Furthermore, as described above, when the number of valve bodies to be simultaneously driven among the multiple needle valves 331 is large, the voltage applied to the piezoelectric element 332 is increased (corrected from voltage Vh to voltage VH) compared to when the number of valve bodies to be simultaneously driven among the multiple needle valves 331 is small. Furthermore, when the number of valve bodies to be simultaneously driven among the multiple needle valves 331 is large, the amount of movement of the needle valve 331 is increased compared to when the number of valve bodies to be simultaneously driven is small.

[0070] Furthermore, as described above, the voltage applied to the piezoelectric element 332 is controlled according to the drive waveform table 9026d that associates the number of needle valves 331 to be simultaneously driven out of the plurality of needle valves 331 with the amount of correction for the voltage applied to the piezoelectric element 332.

[0071] This reduces the fluid resistance between the nozzle 302 and the needle valve 331, improving the ejection characteristics of the ink 30.

[0072] In addition, when the number of nozzles driven simultaneously is two or more, the drive voltage correction amounts B1 to H1 and B2 to H2 may be set such that the drive voltage correction amount of the nozzle 302 located on the downstream side in the ink flow direction in the flow path 312 among the plurality of nozzles 302 fluidly connected in series is larger than the drive voltage correction amount of the nozzle 302 located on the upstream side. For example, when the drive voltage correction amounts of the eight nozzles 302 shown in FIG. 4 when the number of nozzles driven simultaneously is two are B1(1), B1(2),..., B1(8) in order from the upstream side (left side in the figure), B1(1) < B1(2) <... < B1(8). As the drive voltage correction amounts of the two nozzles driven among the eight nozzles 302, two corresponding correction amounts among the eight correction amounts are used.

[0073] Among the plurality of nozzles 302 connected in series, the nozzle 302 located on the downstream side has its ink flow obstructed by the needle valve 331 located upstream of the nozzle 302 before the ink flows from the supply port 311 to the nozzle 302, increasing the pressure loss. As a result, the ink flow rate and ejection flow velocity ejected from the nozzle 302 located on the downstream side are significantly reduced compared to the nozzle 302 located on the upstream side. Therefore, by making the drive voltage correction amount of the nozzle 302 located on the downstream side larger than the drive voltage correction amount of the nozzle 302 located on the upstream side, it is possible to prevent the ink flow rate and ejection flow velocity ejected from the nozzle 302 on the downstream side from decreasing.

[0074] FIG. 12 is an explanatory diagram of an installation example of a liquid ejection head that enables reduction of simultaneous driving. Here, for simplicity of explanation, the case where the number of nozzles of the liquid ejection head 300 is four is described.

[0075] When the dot pitch is X (mm), the liquid ejection head 300 is provided at an angle θ such that the displacement amount in the X direction of the nozzles 302-2, 302-3, and 302-4 with respect to the nozzle 302-1 becomes 1 / 4 of the dot pitch X. The dot pitch X is a value determined by the resolution (dpi) in the X direction.

[0076] That is, if the nozzle spacing of the liquid ejection head 300 is NP, then L=1 / 4·X=NP·sinθ (mm), and if the number of nozzles is N, then L=1 / N·X=NP·sinθ (where 0°<θ<90°).

[0077] If the moving speed of the liquid ejection head 300 in the X direction is V (mm / s), one drive period T (s) is T=X / V (s).

[0078] By mounting the liquid ejection head 300 as described above, the head drive period (ejection period) of each nozzle is shifted by 1 / 4 T (s) from adjacent nozzles, which distributes the nozzle drive timing and makes it possible to reduce the number of nozzles that are driven simultaneously.

[0079] Furthermore, there is not just one angle θ, but multiple angles that satisfy the following formula: L=(1 / 4+M)·X=NPsinθ(mm)(0°<θ<90°) However, M is a positive integer, and when the number of nozzles is N, (1 / 4+M) in the above equation becomes (1 / N+M).

[0080] As described above, the liquid ejection head 300 is tilted at an angle determined from the resolution (dpi) in the X direction and the interval NP between the nozzles 302.

[0081] This distributes the drive timings of the multiple nozzles 302, making it possible to reduce the number of nozzles 302 that are driven simultaneously, that is, the number of needle valves 331 that are driven simultaneously.

[0082] Figure 13 is an explanatory diagram of the nozzle opening and closing operation, where Figure 13(a) shows the state when the nozzle open time is 25% of the discharge cycle T, i.e., 1 / 4T, and Figure 13(b) shows the state when the nozzle open time is 50% of the discharge cycle T, i.e., 1 / 2T.

[0083] 13(a), although all four nozzles 302-1 to 302-4 are driven, the nozzles are not driven simultaneously. Therefore, when combined with the above-mentioned embodiment, there is no need to correct the voltage applied to the piezoelectric element 332.

[0084] 13(b), even though all four nozzles 302-1 to 302-4 are driven, the number of simultaneously driven nozzles can be reduced to 2. Therefore, when combined with the above-described embodiment, the applied voltage to the piezoelectric element 332 is corrected with the number of simultaneously driven nozzles set to 2.

[0085] Figure 14 is an explanatory diagram of the liquid ejection operation by the liquid ejection head according to Modification 1. Figure 14(a) is an explanatory diagram showing the schematic configuration during ejection and the voltage applied to the piezoelectric element at that time, Figure 14(b) is an explanatory diagram showing the schematic configuration during non-ejection and the voltage applied to the piezoelectric element at that time, and Figure 14(c) is an explanatory diagram of the control of the voltage applied to the piezoelectric element.

[0086] The liquid ejection heads according to the above-described embodiments use piezoelectric elements having a characteristic that the total length in the longitudinal direction contracts as the applied voltage increases, whereas the liquid ejection head according to Modification 1 uses piezoelectric elements having a characteristic that the total length in the longitudinal direction expands as the applied voltage increases. As shown in Figure 14(a), when a small voltage Vl (i.e., a relatively small voltage) is applied as the applied voltage, the piezoelectric element 332 contracts in the longitudinal direction, moving the needle valve 331 to the right in the figure. This opens the nozzle 302, and ink 30 is ejected from the nozzle 302.

[0087] 14(b), when a voltage Vh greater than the above-mentioned voltage Vl (i.e., a relatively large voltage) is applied as the applied voltage, the piezoelectric element 332 expands in the longitudinal direction, moving the needle valve 331 to the left in the figure, which closes the nozzle 302 and prevents the ink 30 from being ejected from the nozzle 302.

[0088] In Modification 1, as shown in FIG. 14(c), the applied voltage to the piezoelectric element 332 is controlled to decrease as the number of simultaneously driven needle valves 331 increases among the multiple needle valves 331. The greater the number of simultaneously driven needle valves 331, the greater the correction amount (i.e., reduction amount) ΔVl to be subtracted from the reference drive voltage Vl. The applied voltage VL to the piezoelectric element 332 is controlled to decrease as the number of simultaneously driven needle valves 331 increases. This causes the piezoelectric element 332 to displace more, increasing the amount of movement of the needle valve 331.

[0089] The amount of movement of the needle valve 331 increases, and as a result of this increased displacement, the needle valve 331 retracts further from the nozzle 302 within the flow path 312. This reduces the pressure loss that occurs when the needle valve 331 obstructs the flow of ink near the nozzle 302 from the supply port 311 to the nozzle 302. This prevents a decrease in the flow rate and ejection flow velocity of ink ejected from each nozzle 302. As a result, the fluid resistance between the nozzle 302 and the needle valve 331 decreases, improving the ejection characteristics of the ink 30.

[0090] According to the first modification, as in the above-described embodiment, it is possible to provide a liquid ejection device that can eject liquid accurately even when ejecting liquid from a plurality of liquid ejection ports simultaneously.

[0091] Fig. 15 is an explanatory diagram of a liquid ejection head according to Modification 2. Fig. 15(a) is a cross-sectional view showing an embodiment of a valve-type liquid ejection head according to Modification 2 in a state where the ejection ports are closed, and Fig. 15(b) is a cross-sectional view showing an embodiment of a valve-type liquid ejection head according to Modification 2 in a state where the ejection ports are open.

[0092] The illustrated valve-type liquid ejection head 500 generally includes a hollow housing 510 having a nozzle 502 at its tip for ejecting ink (an example of a liquid) and an inlet 512 for injecting ink near the nozzle 502, a piezoelectric element 532 built into the housing 510 that expands and contracts (expands and contracts in the left-right direction in FIGS. 15(a) and 15(b)) in response to the application of an external voltage, a needle valve 531 that opens and closes the nozzle 502, a reverse spring mechanism 533 (an example of a movement mechanism) disposed between the needle valve 531 and the piezoelectric element 532, a sealing member 515 fitted around the needle valve 531 to prevent ink from flowing into the piezoelectric element 532, and a pair of lead wires 200a and 200b for applying voltage connected to electrodes of the piezoelectric element 532. Similar to the piezoelectric element 332 used in the first modification, the piezoelectric element 532 has the characteristic that its overall length expands as the applied voltage increases.

[0093] The housing 510 is formed into a cylindrical or rectangular tubular shape overall, and is closed except for the nozzle 502 and the inlet 512. The nozzle 502 is a small opening drilled at the tip of the housing 510, through which ink D2 is ejected. The inlet 512 is provided on the side of the housing 510 near the nozzle 502. It is connected to an ink tank and is configured to continuously supply ink (or paint) to the valve-type liquid ejection head 500 by a pressurizing means. The piezoelectric element 532 is formed using zirconia ceramics or the like, and is formed with an appropriate outer shape and thickness depending on the amount of ink D2 to be ejected, etc. In addition, a voltage output from a head drive control unit 902 controlled by a controller 901 is continuously applied to the piezoelectric element 532. The sealing member 515 is, for example, a packing or an O-ring. By fitting the sealing member 515 around the needle valve 531, it prevents ink from flowing from the inlet 512 side to the piezoelectric element 532 side. A coating device equipped with the valve type liquid ejection head 500 is constructed by arranging a plurality of valve type liquid ejection heads 500, each of which ejects ink of a different color, in parallel.

[0094] The reverse spring mechanism 533 is an elastic member formed by molding suitably deformable rubber, soft resin, or a thin metal plate, and is provided with a deformation portion 533a having an approximately trapezoidal cross section formed so as to abut against the base end surface of the needle valve 531 (the right end surface of the needle valve 531 in Figure 15(a)), a fixed portion 533b fixed to the inner wall surface of the housing 510, and a guide portion 533c connected to the end surface of the piezoelectric element 532, and the long side of the trapezoidal deformation portion 533a (corresponding to the lower base of the trapezoid) is a bent side 533d connected to the fixed portion 533b. In the reverse spring mechanism 533 having such a structure, when a predetermined voltage is applied to the piezoelectric element 532 via the head drive control unit 902, the piezoelectric element 532 expands, causing the guide portion 533c to move toward the nozzle 502 and press against the central portion of the curved edge 533d of the deformation portion 533a, while the peripheral edge side of the curved edge 533d is deformed so as to be drawn toward the piezoelectric element 532.

[0095] As a result, the apex of the deformation portion 533a connected to the needle valve 531 (corresponding to the upper base of the trapezoid) moves toward the piezoelectric element 532 (see FIG. 15(b)). This causes the needle valve 531 to be drawn toward the piezoelectric element 532 by a distance d shown in FIG. 15, thereby opening the nozzle 502. By appropriately adjusting the distance between the apex, which is the connection portion of the deformation portion 533a of the inverse spring mechanism 533 connecting the needle valve 531, and the curved edge 533d, as well as the length of the curved edge 533d, it is possible to make the travel distance of the needle valve 531 longer than the extension distance of the piezoelectric element 532. In other words, the inverse spring mechanism 533 can amplify the slight extension of the piezoelectric element 532. For example, if the travel distance of the needle valve 531 is double the travel distance of the end face of the piezoelectric element 532, the length of the piezoelectric element 532 can be reduced to approximately half of the conventional length.

[0096] In this way, when the voltage applied to the piezoelectric element 532 is 0 V (i.e., when a relatively small voltage is applied), the piezoelectric element 532 returns to its original shape, so that no external force is applied to the inverse spring mechanism 533, and no deformation occurs as shown in Fig. 15(a). On the other hand, when a voltage of +Vh is applied to the piezoelectric element 532 (i.e., when a relatively large voltage is applied), the piezoelectric element 532 expands, and in response, the guide portion 533c of the inverse spring mechanism 533 moves toward the nozzle 502 (axial direction), so that the deformation portion 533a is deformed in the axial direction and deforms as if being crushed, as shown in Fig. 15(b).

[0097] [Operation of the valve-type liquid ejection head 500] Next, we will explain the operation of the above-mentioned valve-type liquid ejection head 500. When no voltage is applied to the piezoelectric element 532, that is, when the applied voltage is 0 V (i.e., when a relatively small voltage is applied), the deformation portion 533a of the inverse spring mechanism 533 is in a bulged state (normal state), the needle valve 531 is urged toward the nozzle 502 by the elastic force of the deformation portion 533a, and the nozzle 502 is blocked by the end face of the needle valve 531, as shown in Figure 15(a). Therefore, ink D2 is not ejected from the nozzle 502.

[0098] When a voltage (+Vh) is applied to the piezoelectric element 532 (i.e., when a relatively large voltage is applied), the tip (left end in FIG. 15) of the piezoelectric element 532 extends in the axial direction shown in FIG. 15(b), and the guide portion 533c moves toward (axially) the nozzle 502. Accordingly, the vicinity of the center of the bent edge 533d of the deformation portion 533a is pressed toward the nozzle 502 (in the direction of arrow a in FIG. 15(b)), and the peripheral portion of the bent edge 533d near the inner wall of the housing 510 retreats toward the piezoelectric element 532 (in the direction of arrow b in FIG. 15(b)), so that the deformation portion 533a is compressed, the length from the bent edge 533d of the deformation portion 533a to the connection surface between the bent edge 533d and the needle valve 531 is shortened, and the needle valve 531 is drawn toward the piezoelectric element 532 by the distance d shown in FIG. 15. 15B, a gap is created between the tip surface of the needle valve 531 and the nozzle 502, opening the nozzle 502. This connects the injection port 512 and the nozzle 502, allowing ink D2 to be ejected from the nozzle 502.

[0099] The valve-type liquid ejection head 500 according to the second modification uses a piezoelectric element 532 that has the property of expanding longitudinally as the voltage applied thereto increases. A movement mechanism is interposed between the piezoelectric element and the needle valve, and a relatively large voltage is applied to the piezoelectric element, causing the movement mechanism to move the needle valve to open the ejection port (nozzle), thereby ejecting ink from the ejection port. The movement mechanism also closes the ejection port by applying a relatively small voltage to the piezoelectric element. Similar to the above-described embodiment, i.e., in the same manner as shown in FIGS. 7 and 8, the voltage applied to the piezoelectric element is controlled according to the number of needle valves to be simultaneously driven.

[0100] In Modification 2, the voltage applied to the piezoelectric element 532 is controlled to increase in accordance with the number of simultaneously driven needle valves 531 among the multiple needle valves 531. The larger the number of simultaneously driven needle valves 531, the larger the correction amount (i.e., increase amount) ΔVh added to the reference drive voltage Vh. The voltage VH applied to the piezoelectric element 532 is controlled to increase as the number of simultaneously driven needle valves 531 increases. This causes the piezoelectric element 532 to displace more, increasing the amount of movement of the needle valve 531. As the amount of movement of the needle valve 531 increases and its displacement increases, the needle valve 531 retracts further from the nozzle 502 within the inlet 512. This reduces pressure loss caused by the needle valve 531 obstructing the flow near the nozzle 502 during the time it takes for ink to flow from the supply port to the nozzle 502. This prevents a decrease in the flow rate and ejection flow velocity of ink ejected from each nozzle 502. As a result, the fluid resistance between the nozzle 502 and the needle valve 531 is reduced, improving the ejection characteristics of the ink D2.

[0101] In addition, in variant example 2, a liquid ejection head according to variant example 1, i.e., a liquid ejection head having a piezoelectric element with a characteristic that the total length in the longitudinal direction increases as the applied voltage increases, is combined with a moving mechanism. However, instead of this, a liquid ejection head having a piezoelectric element with a characteristic that the total length in the longitudinal direction decreases as the applied voltage increases may be combined with a moving mechanism.

[0102] In the present invention, the liquid may be a solution, suspension, emulsion, or the like containing a solvent such as water or an organic solvent, a colorant such as a dye or a pigment, a polymerizable compound, a resin, a surfactant, or the like, a functional material such as DNA, an amino acid, a protein, or calcium, an edible material such as a natural colorant, etc. These can be used, for example, as inkjet ink, a surface treatment liquid, a liquid for forming components of electronic elements or light-emitting elements, or an electronic circuit resist pattern, a material liquid for 3D modeling, etc.

[0103] The above description is merely an example, and the present invention provides unique effects for each of the following aspects.

[0104] (Aspect 1) Aspect 1 is characterized by comprising a liquid ejection body (e.g., liquid ejection head 300) having a plurality of liquid ejection ports (e.g., nozzles 302) that eject liquid (e.g., ink 30), a plurality of valve bodies (e.g., needle valves 331) provided corresponding to the liquid ejection ports, and a plurality of driving bodies (e.g., piezoelectric elements 332) that drive the valve bodies to open and close the liquid ejection ports, liquid supply means (e.g., compressor 108, pipe 107 including air regulator 106, tank 105, and tube 311a) that pressurizes and supplies the liquid to the liquid ejection body, and control means (e.g., controller 901, head drive control unit 902, and computer 903) that controls the applied voltage (e.g., applied voltage Vh) to the driving bodies depending on the number of valve bodies that are driven simultaneously out of the plurality of valve bodies.

[0105] According to the first aspect, it is possible to provide a liquid ejection device that can eject liquid accurately even when ejecting liquid from a plurality of liquid ejection ports simultaneously.

[0106] (Aspect 2) Aspect 2 is characterized in that, in Aspect 1, the liquid ejection body (e.g., liquid ejection head 300, 500) has the valve body (e.g., needle valve 331, 531) closed when the applied voltage applied to the driving body (e.g., piezoelectric element 332, 532) is relatively small, and the valve body opens when the applied voltage applied to the driving body is relatively large, thereby ejecting the liquid (e.g., ink 30, D2) from the liquid ejection port (e.g., nozzle 302, 502).

[0107] According to the second aspect, even if the power supply is cut off due to an emergency or the like, the valve body closes the liquid discharge port, and the discharge of liquid from the liquid discharge port can be reliably stopped.

[0108] (Aspect 3) Aspect 3 is characterized in that, in aspect 2, when the number of valve bodies (e.g., needle valves 331, 531) to be simultaneously driven is large, the applied voltage (e.g., applied voltage Vh) is made larger than when the number is small. (Aspect 4) Aspect 4 is characterized in that in Aspect 1, the liquid ejection body (e.g., liquid ejection head 300) has a valve body (e.g., needle valve 331) that is closed when the applied voltage applied to the driving body (e.g., piezoelectric element 332) is relatively large, and when the applied voltage applied to the driving body is relatively small, the valve body is open and ejects the liquid (e.g., ink 30) from the liquid ejection port (e.g., nozzle 302).

[0109] (Aspect 5) Aspect 5 is characterized in that, in aspect 4, when the number of valve bodies (e.g., needle valves 331) to be simultaneously driven is large, the applied voltage (e.g., applied voltage Vh) is made smaller than when the number is small.

[0110] (Aspect 6) Aspect 6 is characterized in that, in any of aspects 1 to 5, when the number of valve bodies (e.g., needle valves 331, 531) that are simultaneously driven is large, the amount of movement of the valve bodies is made larger than when the number is small.

[0111] (Aspect 7) Aspect 7 is characterized in that in any of aspects 1 to 6, the applied voltage (e.g., applied voltage Vh) is controlled in accordance with a control table (e.g., drive waveform table 9026d) that associates the number of valve bodies (e.g., needle valves 331, 531) that are simultaneously driven with the applied voltage correction amount (e.g., applied voltage correction amount ΔVh) of the drive body (e.g., piezoelectric element 332, 532).

[0112] According to the third to seventh aspects, the fluid resistance between the liquid ejection port and the valve body is reduced, and the ejection characteristics of the liquid can be improved.

[0113] (Aspect 8) Aspect 8 is characterized in that, in any of Aspects 1 to 7, the liquid ejection body (e.g., liquid ejection head 300, 500) is tilted at an angle determined from the resolution (e.g., resolution in the X direction (dpi)) and the spacing between each liquid ejection outlet (e.g., nozzle spacing NP).

[0114] According to the eighth aspect, the drive timing of a plurality of liquid ejection ports is dispersed, and the number of liquid ejection ports that are driven simultaneously, that is, the number of valve bodies that are driven simultaneously, can be reduced. [Explanation of symbols]

[0115] 30 Ink (liquid) 105 Tank 106 Air regulator 107 Pipe 108 Compressor 300 Liquid ejection head (liquid ejection body) 302 Nozzle (liquid outlet) 311a Tube 331 Needle valve (valve body) 332 Piezoelectric element (driver) 901 Controller 902 Head drive control unit 903 Computer 1000 liquid dispensing device [Prior art documents] [Patent documents]

[0116] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-241003

Claims

1. a liquid ejection body including a plurality of liquid ejection ports for ejecting liquid, a plurality of valve bodies provided corresponding to the liquid ejection ports so as to move toward and away from the liquid ejection ports, and a plurality of drivers that drive the valve bodies so that the amount of separation of the valve bodies from the liquid ejection ports changes in response to an applied voltage, thereby opening and closing the liquid ejection ports; a liquid supply means for supplying the liquid pressurized to a predetermined pressure to the liquid ejection body; A liquid ejection device comprising a control means for controlling the number of valve bodies to be simultaneously driven among the plurality of valve bodies and the magnitude of the voltage applied to the drive bodies in accordance with the predetermined pressure.

2. The liquid ejection device according to claim 1, characterized in that when the applied voltage applied to the driving body is relatively small, the valve body contacts the liquid ejection port to close the liquid ejection port, and when the applied voltage applied to the driving body is relatively large, the valve body moves away from the liquid ejection port to open the liquid ejection port and eject the liquid from the liquid ejection port.

3. 3. The liquid ejection device according to claim 2, wherein when the number of valve elements to be simultaneously driven is large among the plurality of valve elements, the applied voltage is made larger than when the number is small.

4. The liquid ejection device according to claim 1, characterized in that when the applied voltage applied to the driving body is relatively large, the valve body contacts the liquid ejection port to close the liquid ejection port, and when the applied voltage applied to the driving body is relatively small, the valve body moves away from the liquid ejection port to open the liquid ejection port and eject the liquid from the liquid ejection port.

5. 5. The liquid ejection device according to claim 4, wherein when the number of valve elements to be simultaneously driven is large among the plurality of valve elements, the applied voltage is made smaller than when the number is small.

6. 6. The liquid ejection device according to claim 1, wherein when a large number of the plurality of valve bodies are driven simultaneously, the amount of movement of the valve bodies is made larger than when a small number of the valve bodies are driven simultaneously.

7. A liquid ejection device according to any one of claims 1 to 6, characterized in that the applied voltage is controlled according to a control table that correlates the number of valve bodies among the plurality of valve bodies that are driven simultaneously, the specified pressure, and the applied voltage correction amount of the driving body.

8. 8. The liquid ejection device according to claim 1, wherein the liquid ejection body is provided tilted at an angle determined from a resolution and an interval between the liquid ejection ports.

9. A liquid ejection body comprising: a plurality of liquid ejection ports for ejecting liquid; a plurality of individual liquid chambers provided corresponding to the liquid ejection ports and communicating with the liquid ejection ports; a common flow path connecting the plurality of individual liquid chambers; a supply port communicating with the common flow path; a plurality of valve bodies provided corresponding to the liquid ejection ports so as to move toward and away from the liquid ejection ports; and a plurality of driving bodies that drive the valve bodies so that the amount of separation of the valve bodies from the liquid ejection ports changes in accordance with an applied voltage, thereby opening and closing the liquid ejection ports. a liquid supply means for supplying the liquid pressurized to a predetermined pressure to the supply port of the liquid ejection body; a control means for controlling the magnitude of the applied voltage to the driver in accordance with the number of valve bodies to be simultaneously driven among the plurality of valve bodies, A liquid ejection device characterized in that the control means controls the applied voltage of the driver corresponding to the individual liquid chamber based on the position of the supply port in the common flow path and the position where the individual liquid chamber connects to the common flow path.

10. The liquid ejection device described in Claim 9, characterized in that the control means controls the applied voltage of the driver corresponding to the individual liquid chamber connected downstream in the common flow path so that the valve body is further away from the liquid ejection port than the applied voltage of the driver corresponding to the individual liquid chamber connected upstream in the common flow path.

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