JP2024053370A - HEAD UNIT, LIQUID EJECTION DEVICE, APPLICATION DEVICE, DRIVE DEVICE, AND DRIVE METHOD - Google Patents

Abstract

A liquid ejection failure caused by air bubbles being caught in a nozzle hole that ejects the liquid is reduced.
SOLUTION
A head unit comprising: a liquid ejection head having a liquid chamber for containing pressurized liquid, a nozzle hole for ejecting the liquid, a valve body provided within the liquid chamber, and a driver for moving the valve body to a position where the valve body closes the nozzle hole and a position where the valve body opens the nozzle hole, and a drive control unit for applying to the driver an opening voltage for moving the valve body to a position where the nozzle hole is opened and a closing voltage for moving the valve body to a position where the nozzle hole is closed, wherein a signal waveform of the opening voltage has a first period in which a first voltage is applied, and a second period in which a second voltage different from the first voltage is applied after the first period.
[Selected Figure] Figure 6

Description

The present invention relates to a head unit, a liquid ejection device, a coating device, a driving device, and a driving method.

Patent Document 1 describes a paint injection nozzle that includes a nozzle hole from which paint is injected, a paint chamber that supplies paint to the nozzle hole, a needle valve located in the paint chamber and that closes or opens the nozzle hole at its tip, and a drive mechanism that moves the needle valve forward and backward, in which, when the needle valve opens the nozzle hole, the needle valve is retracted at a speed faster than the deformation return speed of the synthetic resin layer formed at the tip of the needle valve.

JP 2022-064482 A

However, increasing the retraction speed of the needle valve increases the vibration of the needle valve when it opens, and this vibration causes air bubbles to be drawn in from the nozzle hole, resulting in poor liquid ejection.

The present invention is a head unit including a liquid ejection head having a liquid chamber that contains pressurized liquid, a nozzle hole that ejects the liquid, a valve body provided in the liquid chamber, and a driver that moves the valve body to a position where the valve body closes the nozzle hole and a position where the valve body opens the nozzle hole, and a drive control unit that applies to the driver an opening voltage that moves the valve body to a position where the nozzle hole is opened and a closing voltage that moves the valve body to a position where the nozzle hole is closed, and is characterized in that the signal waveform of the opening voltage has a first period in which a first voltage is applied and a second period in which a second voltage different from the first voltage is applied after the first period.

The present invention can reduce poor liquid ejection caused by air bubbles being entrained in the nozzle hole through which the liquid is ejected.

FIG. 2 is a cross-sectional view showing an example of a head unit according to the embodiment. FIG. 4 is an explanatory diagram showing an example of a pressure mechanism and a movement mechanism. FIG. 4 is a block diagram showing an example of a control system for the head unit, the pressure mechanism, and the movement mechanism. 5A to 5C are explanatory diagrams of the opening and closing operation of a nozzle hole. FIG. 11 is an explanatory diagram showing the relationship between a drive signal and a displacement of a needle in a comparative example. FIG. 4 is an explanatory diagram showing the relationship between a drive signal and a displacement of a needle in the first embodiment. FIG. 11 is an explanatory diagram showing the relationship between a drive signal and a displacement of a needle in a second embodiment. FIG. 13 is an explanatory diagram showing the relationship between a drive signal and a displacement of a needle in the third embodiment. FIG. 13 is an explanatory diagram showing the relationship between a drive signal and a displacement of a needle in the fourth embodiment. FIG. 13 is an explanatory diagram showing the relationship between a drive signal and a displacement of a needle in the fifth embodiment. FIG. 11 is a cross-sectional view showing another configuration example of the head unit according to the embodiment. FIG. 4 is an explanatory diagram showing an example of a method for measuring a natural vibration period. FIG. 2 is an explanatory diagram showing an example of a coating device. FIG. 4 is an explanatory diagram showing an example of use of the coating device. FIG. 2 is an explanatory diagram showing an example of an electrode manufacturing apparatus. FIG.

Below, we will explain the mode for implementing the invention with reference to the drawings. Note that in the explanation of the drawings, the same elements are given the same reference numerals, and duplicate explanations will be omitted.

[Head unit configuration]
First, the configuration of a head unit according to an embodiment will be described with reference to Fig. 1. Fig. 1 is a cross-sectional view showing an example of a head unit according to an embodiment.

The head unit illustrated in FIG. 1 is an inkjet head unit that ejects ink, which is an example of a liquid. The inkjet head unit HU (hereinafter referred to as the head unit) is composed of an inkjet head 100 (hereinafter referred to as the head), which is an example of a liquid ejection head, and a drive control unit 500 that controls the driving of the head 100. The drive control unit 500 is also an example of a drive device. The head 100 includes a housing 110 formed in a hollow shape, and a nozzle plate 101 provided at one end of the housing 110. The nozzle plate 101 is a plate-shaped member in which nozzle holes 102 that eject ink 10 are formed.

The housing 110 has an inlet 113 for injecting the ink 10 on the side close to the nozzle hole 102. The ink 10 injected from the inlet 113 is contained in a liquid chamber 114 inside the housing 110. The liquid chamber 114 is roughly formed by the space formed between the nozzle plate 101 and a sealing member 135 provided inside the housing 110.

A needle 131, which is an example of a valve body, is provided in the liquid chamber 114. A valve member 130 is joined to the tip of the needle 131 on the side where the nozzle plate 101 is located, so as to face the nozzle hole 102. The valve member 130 is made of an elastic body such as rubber. By providing the valve member 130 at the tip of the needle 131, the needle 131 adheres better to the nozzle hole 102, and the nozzle hole 102 can be closed more reliably. Note that the configuration of the needle 131 is not limited to the above. For example, the needle 131 may be configured to directly close the nozzle hole 102 at the tip of the needle 131 without providing the valve member 130.

The sealing member 135 is made of an elastic material such as rubber. In this embodiment, a rubber O-ring is used as the sealing member 135, and the O-ring is fitted onto the needle 131 so as to seal the gap between the inner surface of the housing 110 and the outer circumferential surface of the needle 131. In this way, the sealing member 135 prevents the ink 10 in the liquid chamber 114 from flowing into the piezoelectric element 132.

The piezoelectric element 132, which is an example of a driver, is provided in a space formed next to the liquid chamber 114 (above in FIG. 1) with the sealing member 135 as the boundary. The piezoelectric element 132 moves the needle 131 between a position for closing the nozzle hole 102 and a position for opening the nozzle hole 102 in response to a drive signal from the drive control unit 500. At the position for closing the nozzle hole 102, the valve member 130 is in contact with the nozzle plate 101, and at the position for opening the nozzle hole 102, the valve member 130 is separated from the nozzle plate 101. Note that in the case of a configuration without the valve member 130, the needle 131 is in contact with the nozzle plate 101 at the position for closing the nozzle hole 102, and the needle 131 is separated from the nozzle plate 101 at the position for opening the nozzle hole 102.

The piezoelectric element 132 is a piezoelectric element formed using zirconia ceramics or the like, and the shape of the piezoelectric element 132 is appropriately set according to the amount of ink droplets to be ejected, etc.

The drive control unit 500 is electrically connected to the piezoelectric element 132 and controls the drive of the piezoelectric element 132.

[Configuration of the pressure mechanism and the movement mechanism]
Next, a pressurizing mechanism that pressurizes and supplies the ink 10 to the head 100, and a moving mechanism that moves the head 100 relative to an object will be described with reference to Figures 2 and 3. Figure 2 is an explanatory diagram showing an example of the pressurizing mechanism and the moving mechanism, and Figure 3 is a block diagram showing an example of a control system for the head unit, the pressurizing mechanism, and the moving mechanism.

In FIG. 2, the ink 10 ejected from the head 100 is contained in a sealed ink tank 202. The ink tank 202 and the injection port 113 of the head 100 are connected by a tube 201.

The ink tank 202 is connected to the compressor 205 via a pipe 203 including an air regulator 204. The air regulator 204 adjusts the pressure of the compressed air created by the compressor 205 to the required air pressure, and supplies the pressurized air from the compressor 205 to the ink tank 202. As a result, pressurized ink 10 is supplied to the liquid chamber 114 of the head 100, and the valve member 130 is separated from the nozzle plate 101, so that the liquid chamber 114 and the nozzle hole 102 communicate with each other, and the ink 10 is ejected from the nozzle hole 102. Here, the tube 201, the ink tank 202, the pipe 203, the air regulator 204, and the compressor 205 constitute a pressurizing mechanism 200 for supplying pressurized ink 10 to the liquid chamber 114 of the head 100. The pressurizing mechanism 200 is an example of a pressurizing means.

A part of the housing 110 of the head 100 (the upper part in FIG. 2) is held by a head holding member 301. The head holding member 301 is connected to a driving device 302, and by driving the driving device 302, the head holding member 301 can move in the directions of arrows A and B along a rail member 303. As a result, the head 100 held by the head holding member 301 also moves in the directions of arrows A and B along the rail member 303. Here, the head holding member 301, the driving device 302, and the rail member 303 constitute a head moving mechanism 300 for moving the head 100 relative to the object. The head moving mechanism 300 is an example of a moving means.

The drive device 302 and rail member 303 may be appropriately configured using known mechanisms, such as a feed screw mechanism using a ball screw, a feed mechanism using a rack and pinion, or a feed mechanism using a power transmission belt and pulleys.

Here, the head unit HU (head 100, drive control unit 500) connected to the pressure mechanism 200 and head movement mechanism 300 is an example of a liquid ejection device.

As shown in FIG. 3, the head unit HU, the pressure mechanism 200, and the head movement mechanism 300 are electrically connected to a control unit 600. The control unit 600 may, for example, control the overall operation of the coating device described below, and components other than those shown in FIG. 3 may be added as necessary.

The control unit 600 transmits, for example, an ink ejection period signal based on image data to the drive control unit 500 of the head unit HU. The control unit 600 receives status information of the head 100 and the like via the drive control unit 500. The control unit 600 also transmits a switching signal to the pressure mechanism 200 to switch pressure on and off. Furthermore, the control unit 600 transmits a movement signal to the head movement mechanism 300 to move the head 100.

The drive control unit 500 of the head unit HU includes an input unit 501, a drive voltage generating unit 502, an amplifier unit 503, and an output unit 504.

The input unit 501 receives an ink ejection period signal based on image data from the control unit 600.

The drive voltage generation unit 502 generates a drive voltage for driving the piezoelectric element 132 of the head 100 in response to information such as the ink ejection period signal received by the input unit 501.

The amplifier unit 503 amplifies the drive voltage generated by the drive voltage generator unit 502 and outputs the amplified signal to the output unit 504.

The output unit 504 applies a drive voltage to the piezoelectric element 132 based on the signal amplified by the amplifier unit 503.

The functions of the input unit 501, drive voltage generating unit 502, amplifier unit 503, output unit 504, etc. can be realized by electrical circuits, and some of these functions can also be realized by software (CPU: Central Processing Unit). Furthermore, each of the above functions may be realized by multiple circuits or multiple pieces of software.

As described above, the drive control unit 500 generates a drive signal based on the ink ejection periodic signal received from the control unit 600, and drives the head 100 using the generated drive signal. The head 100 opens and closes the nozzle holes 102 in response to the drive signal from the drive control unit 500, and ejects ink.

Based on a switching signal received from the control unit 600, the pressurizing mechanism 200 switches the compressor 205 (or the air regulator 204) on and off, switching the ink 10 sent to the liquid chamber 114 between a pressurized state and a non-pressurized state.

Based on the movement signal received from the control unit 600, the head movement mechanism 300 drives the drive device 302 a predetermined distance in a predetermined direction, and moves the head 100 to the desired position via the head holding member 301.

[Opening and closing of nozzle holes]
Next, the opening and closing operation of the nozzle holes will be described with reference to FIG.

When a drive voltage is applied from the drive control unit 500 to the piezoelectric element 132, as shown in FIG. 4A, when a closing voltage is applied to the piezoelectric element 132, the valve member 130 is in a position in contact with the nozzle plate 101, and the valve member 130 closes the nozzle hole 102. As a result, the ink 10 in the liquid chamber 114 is not ejected from the nozzle hole 102.

When an open voltage is applied to the piezoelectric element 132, as shown in FIG. 4B, the piezoelectric element 132 contracts and moves the needle 131 upward in the figure. This movement of the needle 131 causes the valve member 130 joined to the needle 131 to move to a position away from the nozzle plate 101, and a gap G is formed between the tip of the valve member 130 and the nozzle hole 102. Since the ink 10 in the liquid chamber 114 is pressurized and supplied at a predetermined pressure by the pressurizing mechanism 200, the ink 10 in the liquid chamber 114 is ejected from the nozzle hole 102 as an ink droplet 10' as the gap G is formed.

In this way, when a drive voltage (close voltage, open voltage) is applied to the piezoelectric element 132, the valve member 130 moves between a position in contact with the nozzle plate 101 and a position away from it (in the direction of arrow C in Figure 4(b)), and the valve member 130 opens and closes the nozzle hole 102.

[Drive signal]
The relationship between the drive signal output from the drive control unit 500 and the operation of the needle 131 of the head 100 will be described below with reference to Figures 5 to 10. Figures 5 to 10 are explanatory diagrams showing the relationship between the drive signal and the displacement of the needle, with Figure 5 being a comparative example and Figures 6 to 10 being an embodiment based on the present invention.

Comparative Example
5A, the drive signal is a square wave defined by a closing voltage E1 and an opening voltage E2. Here, the closing voltage refers to the drive voltage applied to the piezoelectric element 132 when the needle 131 is moved to a position where the nozzle hole 102 is closed. The opening voltage refers to the drive voltage applied to the piezoelectric element 132 when the needle 131 is moved to a position where the nozzle hole 102 is opened.

When an open voltage E2 is applied to the piezoelectric element 132, the piezoelectric element 132 contracts, and the needle 131 is displaced from position P1 to position P2 as shown in FIG. 5B. That is, the needle 131 moves in a direction that separates the valve member 130 from the nozzle plate 101 based on the drive signal. When the valve member 130 separates from the nozzle plate 101 and a gap G is formed between the valve member 130 and the nozzle hole 102 as shown in FIG. 4B, the ink 10 in the liquid chamber 114 becomes capable of being ejected from the nozzle hole 102. However, in reality, as shown in FIG. 5, when an open voltage E2 is applied to the piezoelectric element 132, the needle 131 vibrates with its own natural vibration period T, resulting in the following ejection failure.

In other words, because the needle 131 is displaced steeply from position P1 to position P2 based on the application of the release voltage E2 to the piezoelectric element 132, if the pressure mechanism 200 is unable to apply pressure to the liquid chamber 114 in time, the pressure in the liquid chamber 114 will fluctuate as the needle 131 displaces. As a result, air bubbles are drawn in (sucked in) from the nozzle hole 102 into the liquid chamber 114 during the process in which the needle 131 moves from position P1 to position P2 (the "air bubble entrainment 1" section in FIG. 5B).

The air bubbles caught in the liquid chamber 114 are pushed out when the pressure mechanism 200 starts applying pressure to the liquid chamber 114, and are gradually discharged from the nozzle hole 102 to the outside of the liquid chamber 114 (corresponding to the "air bubble discharge" section in Figure 5 (b)).

However, during the period t1 when the open voltage E2 is applied to the piezoelectric element 132, the needle 131 vibrates with its own natural vibration period T, and the pressure in the liquid chamber 114 fluctuates in tune with the natural vibration period T of the needle 131. Therefore, as shown in the "Air bubble entrainment 2" section in Figure 5(b) , when the needle 131 is displaced again toward position P2, an air bubble is entrained again from the nozzle hole 102 into the liquid chamber 114.

After time t1, when a closing voltage E1 is applied to the piezoelectric element 132, the piezoelectric element 132 expands, and as the needle 131 expands, it displaces to position P1, as shown in the "droplet ejection" section of FIG. 5(b). That is, the needle 131 moves in a direction that brings the valve member 130 into contact with the nozzle plate 101 based on the drive signal. Then, in the process until the needle 131 reaches position P1 (the "droplet ejection" section of FIG. 5(b)), the ink 10 in the liquid chamber 114 is ejected from the nozzle hole 102 as an ink droplet 10'.

As described above, in the comparative example, the air bubbles once discharged from the liquid chamber are re-entered into the liquid chamber, and the liquid droplets are ejected from the nozzle hole while still containing the air bubbles, making it impossible to achieve the desired liquid ejection.

First Embodiment
Next, the first embodiment will be described with reference to Fig. 6. Fig. 6 is an explanatory diagram showing the relationship between the drive signal and the displacement of the needle in the first embodiment.

The drive signal in the first embodiment is a step-shaped waveform defined by a closing voltage E1 and two types of opening voltages E2 and E3 as shown in FIG. 6(a). The closing voltage refers to the drive voltage applied to the piezoelectric element 132 when the needle 131 is moved to a position where the nozzle hole 102 is closed. The opening voltage refers to the drive voltage applied to the piezoelectric element 132 when the needle 131 is moved to a position where the nozzle hole 102 is opened.

The open-circuit voltage E2 is set to a different value from the open-circuit voltage E3 (a value smaller than the open-circuit voltage E3 in this embodiment), and the open-circuit voltage E3 is first applied to the piezoelectric element 132 for a period of time t1, and then the open-circuit voltage E2 is applied to the piezoelectric element 132 for a period of time t2. In the first embodiment, the open-circuit voltage E3 is an example of a "first voltage", and the open-circuit voltage E2 is an example of a "second voltage". Furthermore, the period of time t1 during which the open-circuit voltage E3 is applied is an example of a "first period", and the period of time t2 during which the open-circuit voltage E2 is applied is an example of a "second period".

In the first embodiment, when the first voltage, the release voltage E3, is applied to the piezoelectric element 132, the piezoelectric element 132 contracts, and the needle 131 is displaced from position P1 to position P2 as shown in FIG. 6B in accordance with the contraction. That is, the needle 131 moves in a direction that separates the valve member 130 from the nozzle plate 101 based on the drive signal. As in the comparative example, the displacement of the needle 131 from position P1 to position P2 at this time is steep, so that in cases where the pressure mechanism 200 is unable to apply pressure to the liquid chamber 114 in time, the pressure in the liquid chamber 114 fluctuates with the displacement of the needle 131. As a result, in the process in which the needle 131 reaches position P2 from position P1 (the "air bubble entrainment" section in FIG. 6B), air bubbles are entrained (sucked) from the nozzle hole 102 into the liquid chamber 114.

The air bubbles caught in the liquid chamber 114 are pushed out when the pressure mechanism 200 starts applying pressure to the liquid chamber 114, and are gradually discharged from the nozzle hole 102 to the outside of the liquid chamber 114 (corresponding to the section "air bubble discharge 1" in Figure 6 (b)).

Next, at the timing when the needle 131 starts to displace again toward position P2 due to its own natural vibration period T, the drive control unit 500 applies a second voltage, an opening voltage E2, to the piezoelectric element 132. The application of the opening voltage E2 causes the piezoelectric element 132 to expand, and as the needle 131 expands, it moves in a direction that moves the valve member 130 toward the nozzle plate 101, and the displacement of the needle 131 toward position P2 is suppressed, as shown in the "Bubble Discharge 2" section in Figure 6(b).

After time t2, when a closing voltage E1 is applied to the piezoelectric element 132, the piezoelectric element 132 expands, and as the needle 131 expands, it displaces to position P1, as shown in the "droplet ejection" section of FIG. 6(b). That is, the needle 131 moves in a direction that brings the valve member 130 into contact with the nozzle plate 101 based on the drive signal. Then, in the process until the needle 131 reaches position P1 (the "droplet ejection" section of FIG. 6(b)), the ink 10 in the liquid chamber 114 is ejected from the nozzle hole 102 as an ink droplet 10'.

As described above, according to the first embodiment, it is possible to prevent air bubbles from being re-entered from the nozzle hole. In the case of the first embodiment, as shown in FIG. 6(b), the crest value after "air bubble discharge 2" is kept low, and the needle 131 (valve member 130) is positioned closer to the nozzle plate 101, but the amount of liquid discharged can be secured since there are no air bubbles in the liquid chamber 114.

As an example of the first embodiment, if the natural vibration period of the needle 131 is T, time t1 is specified to satisfy the relationship T<t1<3/2T, and time t2 is specified to satisfy the relationship t2<1/2T. This makes it possible to efficiently suppress the vibration of the needle 131 at a timing slightly delayed from the start of the transition from "air bubble discharge 1" to "air bubble discharge 2" in FIG. 6(b), and to efficiently eject liquid at the timing when "air bubble discharge 2" ends. Furthermore, the opening voltage E2 is specified to satisfy the relationship 1/2E3<E2<E3 with respect to the opening voltage E3.

As described above, this embodiment is a head unit HU including a liquid chamber 114 that contains pressurized ink 10, a nozzle hole 102 that ejects ink 10, a needle 131 provided in the liquid chamber 114, a piezoelectric element 132 that moves the needle 131 to a position where the needle 131 closes the nozzle hole 102 and a position where the needle 131 opens the nozzle hole 102, and a drive control unit 500 that applies to the piezoelectric element 132 an opening voltage that moves the needle 131 to a position where the nozzle hole 102 is opened and a closing voltage that moves the needle 131 to a position where the nozzle hole 102 is closed, and the signal waveform of the opening voltage has a time t1 at which an opening voltage E3 is applied, and a time t2 at which an opening voltage E2 different from the opening voltage E3 is applied after the time t1.

Also, as described above, the open voltage E2 is set to be a voltage between the close voltage E1 and the open voltage E3.

As described above, when the needle 131 is in the position where the nozzle hole 102 is open, it vibrates with a natural vibration period T in the direction in which the needle 131 moves, and the time t2 is shorter than half of the natural vibration period T.

Furthermore, when the needle 131 is in the position where the nozzle hole 102 is open, it vibrates with a natural vibration period T in the direction in which the needle 131 moves, and the time t1 is longer than the natural vibration period T and shorter than 3/2 of the natural vibration period T.

As a result, when the open voltage E2 is applied to the piezoelectric element 132, air bubbles are not entrapped and unintended ejection is prevented.

Second Embodiment
Next, a second embodiment will be described with reference to Fig. 7. Fig. 7 is an explanatory diagram showing the relationship between the drive signal and the displacement of the needle in the second embodiment.

The drive signal in the second embodiment is a step-shaped waveform defined by a closing voltage E1 and two types of opening voltages E2 and E3, as shown in FIG. 7(a). The definitions of the closing voltage and the opening voltage are the same as in the first embodiment.

The open-circuit voltage E2 is set to a different value from the open-circuit voltage E3 (a value smaller than the open-circuit voltage E3 in this embodiment), and the open-circuit voltage E2 is first applied to the piezoelectric element 132 for a period of time t1, and then the open-circuit voltage E3 is applied to the piezoelectric element 132 for a period of time t2. In the second embodiment, the open-circuit voltage E2 is an example of a "first voltage", and the open-circuit voltage E3 is an example of a "second voltage". Furthermore, the period of time t1 during which the open-circuit voltage E2 is applied is an example of a "first period", and the period of time t2 during which the open-circuit voltage E3 is applied is an example of a "second period".

In the second embodiment, when a first voltage, an open voltage E2, is applied to the piezoelectric element 132, the piezoelectric element 132 contracts, and the needle 131 is displaced from position P1 to position P2 as shown in FIG. 7B in accordance with the contraction. That is, the needle 131 moves in a direction that moves the valve member 130 away from the nozzle plate 101 based on the drive signal. For the same reasons as in the comparative example and the first embodiment, air bubbles are entrained from the nozzle hole 102 into the liquid chamber 114 during the process in which the needle 131 moves from position P1 to position P2 (the "air bubble entrainment" section in FIG. 7B).

Next, when the needle 131 begins to displace from position P2 toward position P1 due to its own natural vibration period T, the drive control unit 500 applies a second voltage, an open voltage E3, to the piezoelectric element 132. The application of the open voltage E3 to the piezoelectric element 132 causes the piezoelectric element 132 to contract further, and as a result of this contraction, the needle 131 also moves to position P3, which is further away from the nozzle plate 101. This makes it possible to increase the volume of the ejected droplet.

As described above, in the second embodiment, when the needle 131 starts to displace from position P2 toward position P1, the needle 131 can be moved further away from the nozzle plate 101, thereby maintaining the needle 131 at approximately the position P2. During the "air bubble discharge" section in FIG. 7(b), the needle 131 is substantially stationary near position P3, so that the air bubbles entrained in the liquid chamber 114 are gradually discharged by the pressure applied to the liquid chamber 114 by the pressure mechanism 200.

In addition, in the second embodiment, the displacement of the needle 131 immediately before droplet ejection is large, so the volume of the droplet can be increased.

As an example of the second embodiment, if the natural vibration period of the needle 131 is T, time t1 is specified to satisfy the relationship 1/2T<t1<T, and time t2 is specified to satisfy the relationship 1/2T<t2<T. This makes it possible to efficiently suppress the vibration of the needle 131 when it starts to move from position P2 toward position P1, and to efficiently eject liquid when "bubble ejection" ends. Furthermore, the release voltage E3 is specified to satisfy the relationship E2<E3<4/3E2 with respect to the release voltage E2. This makes it possible to increase the volume of the droplet when the release voltage E3 is applied to the piezoelectric element 132 without entraining air bubbles and preventing unintended ejection.

As described above, in this embodiment, the open voltage E2 is a voltage between the closed voltage E1 and the open voltage E3.

As described above, when the needle 131 is in the position where the nozzle hole 102 is open, it vibrates with a natural vibration period T in the direction in which the needle 131 moves, and time t1 is longer than half the natural vibration period T and shorter than the natural vibration period T.

As a result, when the open voltage E3 is applied to the piezoelectric element 132, air bubbles are not entrapped and unintended ejection is prevented.

Third Embodiment
Next, a third embodiment will be described with reference to Fig. 8. Fig. 8 is an explanatory diagram showing the relationship between the drive signal and the displacement of the needle in the third embodiment.

The drive signal in the third embodiment is a step-shaped waveform defined by a closing voltage E1 and two types of opening voltages E2 and E3, as shown in FIG. 8(a). The definitions of the closing voltage and the opening voltage are the same as in the first embodiment.

The open-circuit voltage E2 is set to a different value from the open-circuit voltage E3 (a value smaller than the open-circuit voltage E3 in this embodiment), and the open-circuit voltage E2 is first applied to the piezoelectric element 132 for a period of time t1, and then the open-circuit voltage E3 is applied to the piezoelectric element 132 for a period of time t2. In the third embodiment, the open-circuit voltage E2 is an example of a "first voltage", and the open-circuit voltage E3 is an example of a "second voltage". Furthermore, the period of time t1 during which the open-circuit voltage E2 is applied is an example of a "first period", and the period of time t2 during which the open-circuit voltage E3 is applied is an example of a "second period".

In the third embodiment, when a first voltage, an opening voltage E2, is applied to the piezoelectric element 132, the piezoelectric element 132 contracts, and the needle 131 is displaced from position P1 to position P2 as shown in FIG. 8B in accordance with the contraction. That is, the needle 131 moves in a direction that moves the valve member 130 away from the nozzle plate 101 based on the drive signal. For the same reasons as in the comparative example and the first embodiment, air bubbles are entrained from the nozzle hole 102 into the liquid chamber 114 during the process in which the needle 131 moves from position P1 to position P2 (the "air bubble entrainment 1" section in FIG. 8B).

Next, at the timing when the needle 131 starts to move from position P2 towards position P1 (the timing when the needle starts to transition to the "Bubble Discharge 1" section in FIG. 8(b)), a second voltage, an open voltage E3, is applied to the piezoelectric element 132. Since the open voltage E3 is a larger value than the open voltage E3 in the second embodiment, the needle 131 is moved to position P3, which is farther away from the nozzle plate 101. This makes it possible to increase the volume of the ejected droplet compared to the second embodiment.

In the process in which the needle 131 moves from position P2 to position P3 (the "air bubble entrainment 2" section in FIG. 8B), air bubbles are entrained from the nozzle hole 102 into the liquid chamber 114, but the air bubbles are discharged in the next "air bubble discharge 2" section. Time t2 is set to a time sufficient for the air bubbles to be discharged from the liquid chamber 114 by the pressure applied by the pressure mechanism 200.

As an example of the third embodiment, if the natural vibration period of the needle 131 is T, time t1 is specified to satisfy the relationship 1/2T<t1<T, and time t2 is specified to satisfy the relationship T<t2. This makes it possible to efficiently suppress the vibration of the needle 131 when it starts to displace from position P2 toward position P1, and allows liquid to be ejected with bubbles ejected when "bubble ejection 2" ends. Furthermore, the opening voltage E3 is specified to satisfy the relationship 4/3E2<E3<3/2E2 with respect to the opening voltage E2. This makes it possible to further increase the volume of the droplet while preventing unintended ejection.

In the above, the first to third embodiments have described a configuration in which the vibration of the needle 131 is suppressed or amplified at the timing when the needle 131, which has been displaced to position P2 based on the open voltage, begins to displace toward position P1 due to its own natural vibration period, thereby discharging air bubbles.

The fourth and fifth embodiments described below aim to suppress the vibration of the needle 131 when it rises when an open voltage is applied to the piezoelectric element 132, and to reduce the intake of air bubbles when it rises.

Fourth Embodiment
The fourth embodiment will be described with reference to Fig. 9. Fig. 9 is an explanatory diagram showing the relationship between the drive signal and the displacement of the needle in the fourth embodiment.

The drive signal in the fourth embodiment is a step-shaped waveform defined by a closing voltage E1 and two types of opening voltages Em and E2, as shown in FIG. 9(a). The definitions of the closing voltage and the opening voltage are the same as in the above-mentioned embodiments.

The open-circuit voltage Em is set to a value different from the open-circuit voltage E2 (a value smaller than the open-circuit voltage E2 in this embodiment), and the open-circuit voltage Em is first applied to the piezoelectric element 132 for a period of time t1, and then the open-circuit voltage E2 is applied to the piezoelectric element 132 for a period of time t2. In the fourth embodiment, the open-circuit voltage Em is an example of a "first voltage", and the open-circuit voltage E2 is an example of a "second voltage". Furthermore, the period of time t1 during which the open-circuit voltage Em is applied is an example of a "first period", and the period of time t2 during which the open-circuit voltage E2 is applied is an example of a "second period".

In the fourth embodiment, the needle 131 is not displaced from position P1 to position P2 in one go, but rather a period is provided during which the needle 131 maintains position Pm as shown in FIG. 9(b). This makes it possible to suppress sudden pressure fluctuations within the liquid chamber 114. In addition, since the needle 131 vibrates more slowly, it is possible to reduce the entrainment of air bubbles into the liquid chamber 114 and to reduce heat generation from the piezoelectric element 132.

After reaching position P2, the needle 131 may re-enter air bubbles due to vibrations with the natural vibration period T of the needle 131. However, if a needle with a small amplitude of free vibration is used, the amount of re-entered air bubbles is small, and this configuration is effective.

As an example of the fourth embodiment, if the natural vibration period of the needle 131 is T, time t1 is specified to satisfy the relationship t1<1/2T, and time t2 is specified to satisfy the relationship T<t2<3/2T. This allows the needle 131 to temporarily stagnate near position Pm while being displaced toward position P2, suppressing the entrainment of air bubbles, and at the timing when "air bubble discharge 2" ends, liquid can be ejected with air bubbles discharged. Furthermore, the opening voltage Em is specified to satisfy the relationship 2/3E2<Em<E2 with respect to the opening voltage E2.

As described above, in this embodiment, the needle 131 vibrates with a natural vibration period T in the direction in which the needle 131 moves when the nozzle hole 102 is in an open position, and the time t1 is shorter than half of the natural vibration period T.

As described above, when the needle 131 is in the position where the nozzle hole 102 is open, it vibrates with a natural vibration period T in the direction in which the needle 131 moves, and the time t2 is longer than half of the natural vibration period T.

Also, as described above, the open voltage Em is set to be a voltage between the closed voltage E1 and the open voltage E2.

This allows the needle 131 to be displaced and the bubbles to be entrained almost completely in a short initial period, suppressing subsequent entrainment of bubbles. It also suppresses heat generation from the piezoelectric element 132.

Fifth Embodiment
Next, a fifth embodiment will be described with reference to Fig. 10. Fig. 10 is an explanatory diagram showing the relationship between the drive signal and the displacement of the needle in the fifth embodiment.

The drive signal in the fifth embodiment is a step-shaped waveform defined by a closing voltage E1 and two types of opening voltages Em and E2, as shown in FIG. 10(a). The definitions of the closing voltage and the opening voltage are the same as in the above-mentioned embodiments.

The open-circuit voltage Em is set to a value different from the open-circuit voltage E2 (a value smaller than the open-circuit voltage E2 in this embodiment), and the open-circuit voltage Em is first applied to the piezoelectric element 132 for a period of time t1, and then the open-circuit voltage E2 is applied to the piezoelectric element 132 for a period of time t2. In the fifth embodiment, the open-circuit voltage Em is an example of a "first voltage", and the open-circuit voltage E2 is an example of a "second voltage". Furthermore, the period of time t1 during which the open-circuit voltage Em is applied is an example of a "first period", and the period of time t2 during which the open-circuit voltage E2 is applied is an example of a "second period".

In the fifth embodiment, as in the fourth embodiment, the needle 131 is not displaced from position P1 to position P2 in one go, but rather a period is provided during which the needle 131 maintains position Pm as shown in FIG. 10(b). This makes it possible to suppress sudden pressure fluctuations in the liquid chamber 114. In addition, since the vibration of the needle 131 becomes gentler, it is possible to reduce the entrainment of air bubbles into the liquid chamber 114 and to reduce heat generation from the piezoelectric element 132.

When droplets are ejected at a high speed, the time taken for ejection can be one peak of the amplitude of the needle 131. In this case, as shown in FIG. 10(b), the steepness (slope of the curve) from position P1 to position P2 can be reduced to reduce the entrainment of air bubbles.

As an example of the fifth embodiment, when the natural vibration period of the needle 131 is T, the time t1 is specified to satisfy the relationship t1<1/2T, and the time t2 is specified to satisfy the relationship t2<1/2T. As a result, the needle 131 is temporarily stopped near the position Pm while being displaced toward the position P2, and the entrainment of air bubbles can be suppressed, and at the timing when the "air bubble discharge" ends, the liquid can be discharged with the air bubbles discharged. In addition, the open voltage Em is specified to satisfy the relationship 2/3E2<Em<E2 with respect to the open voltage E2. It is desirable for the voltage slew rate to set the rise time of the waveform to 1/8T or less. For example, if the waveform of the drive signal is a drive waveform as shown in FIG. 10, two rises occur in the process of passing the time of 1/2T, so each rise is assigned 1/4T, which is a division of two. Furthermore, considering that each time is not equal, it is desirable to set it to 1/8T.

As described above, in this embodiment, the needle 131 vibrates with a natural vibration period T in the direction in which the needle 131 moves when the nozzle hole 102 is in an open position, and the time t1 is shorter than half of the natural vibration period T.

Also, as mentioned above, time t2 is shorter than half the natural vibration period T.

This prevents air bubbles from being drawn in and allows the liquid to be ejected with the air bubbles expelled.

The drive signals shown in the first to fifth embodiments may be waveforms having transitions (slew rates) with a predetermined inclination, rather than being perfect square waves. In other words, the closing voltage, the first voltage, and the second voltage may be switched between at a predetermined slew rate. In this case, it is preferable that the slew rate is sufficiently short with respect to the natural vibration period T of the needle 131, for example, 1/8T or less.

[Another example of a head unit configuration]
Another configuration example of the head unit will be described with reference to Fig. 11. Fig. 11 is a cross-sectional view showing another configuration example of the head unit according to the embodiment, Fig. 11(a) is a cross-sectional view showing a state in which the nozzle holes are closed, and Fig. 11(b) is a cross-sectional view showing a state in which the nozzle holes are open.

This configuration example differs from the configuration of the head unit shown in FIG. 1 etc. in that it includes an inverse spring mechanism 134 as an example of a transmission mechanism between the needle 131 and the piezoelectric element 132. Therefore, the configuration and operation of the inverse spring mechanism 134 will be mainly described here, and members having the same configuration and function as those in the head unit of FIG. 1 will be given the same reference numerals and will not be described. Note that in this configuration example, the piezoelectric element 132 used has an expansion and contraction characteristic that expands toward the nozzle plate 101 when a voltage is applied.

The reverse spring mechanism 134 is an elastic member formed by molding a suitably deformable material such as rubber, soft resin, or a thin metal plate. The reverse spring mechanism 134 includes a deformation portion 134a, a fixed portion 134b, a guide portion 134c, and a bent edge 134d.

The deformation portion 134a has a generally trapezoidal cross section formed so as to abut against the base end surface of the needle 131 (the upper end surface of the needle 131 in FIG. 11(a)).

The fixed portion 134b is fixed to the deformation portion 134a and the inner wall surface of the housing 110.

The guide portion 134c connects the fixed portion 134b and the piezoelectric element 132.

The bent side 134d connects the long side of the trapezoidal deformation part 134a (corresponding to the bottom base of the trapezoid) to the fixed part 134b.

When a predetermined voltage is applied to the piezoelectric element 132 of the inverse spring mechanism 134 configured as described above, the piezoelectric element 132 expands, and the expansion of the piezoelectric element 132 pushes the guide portion 134c toward the nozzle hole 102 (in the direction of the arrow a in Figure 11 (b)).

This pushing force retracts the deformation portion 134a in a direction away from the nozzle hole 102 (the direction of arrow b in FIG. 11(b)). In other words, the inverse spring mechanism 134 converts the expanding force of the piezoelectric element 132 into a force that retracts the needle 131, and then transmits it to the needle 131.

In the head 100 according to this configuration example, when a voltage is applied to the piezoelectric element 132, the piezoelectric element 132 expands, causing the valve member 130 to open the nozzle hole 102 and eject a droplet 10' from the nozzle hole 102.

As described above, this configuration example includes an inverse spring mechanism 134 between the needle 131 and the piezoelectric element 132, which converts the expanding force of the piezoelectric element 132 into a force that retracts the needle 131, i.e., a force opposite to the expanding force of the piezoelectric element 132, and then transmits the force to the needle 131.

In the head unit HU of this configuration example, by using the drive signals described in the first to fifth embodiments, it is possible to reduce liquid ejection defects caused by air bubbles being drawn into the nozzle hole 102. However, in the case of the head unit shown in FIG. 4, the nozzle hole 102 closes when the piezoelectric element 132 expands, and the nozzle hole 102 opens when the piezoelectric element 132 contracts, but in the case of a head unit equipped with a reverse spring mechanism 134, this relationship is reversed.

In other words, in the case of a head unit equipped with an inverse spring mechanism 134, when the piezoelectric element 132 expands, the nozzle hole 102 opens as shown in FIG. 11(b), and when the piezoelectric element 132 contracts, the nozzle hole 102 closes as shown in FIG. 11(a). Therefore, in a head unit equipped with an inverse spring mechanism 134, the drive signals shown in the first to fifth embodiments can be used, taking into account that the relationship between the expansion and contraction of the piezoelectric element 132 and the opening and closing of the nozzle hole 102 is reversed.

The head 100 equipped with the inverse spring mechanism 134 is able to obtain a large displacement with a small displacement of the piezoelectric element 132 compared to a head without the inverse spring mechanism. In addition, by providing the inverse spring mechanism 134 between the needle 131 and the piezoelectric element 132, the natural vibration period can be lengthened, so that the natural vibration speed of the needle 131 in the first period or the second period can be suppressed, and the entrainment of air bubbles can be reduced.

In addition to heads equipped with an inverse spring mechanism, the present invention can also be applied to heads with low rigidity and heads that are prone to picking up vibrations from the liquid ejection device.

In addition, the above explanation is based on the assumption that the piezoelectric element has an expansion and contraction characteristic in which it expands when voltage E1 is applied and contracts when a voltage greater than voltage E1 is applied, but the present invention is not limited to this. For example, a piezoelectric element may be used that has an expansion and contraction characteristic in which it contracts when voltage E1 is applied and expands when a voltage greater than voltage E1 is applied.

[Method for measuring natural vibration period]
FIG. 12 is an explanatory diagram illustrating an example of a method for measuring the natural vibration period.

The natural vibration period T of the needle 131 is determined by measuring the surface of the needle 131 that abuts against the nozzle plate 101' (in this embodiment, the end surface of the valve member 130 joined to the needle 131).

A laser Doppler displacement meter 901 is used for the measurement. Laser light 902 emitted from the laser Doppler displacement meter 901 is irradiated onto the end face of the valve member 130, which is the object of measurement. The natural vibration period T can be obtained by Fourier analysis of the obtained measurement value.

It is desirable to carry out measurements under the same driving conditions as the actual liquid ejection operation, and the actual driving waveform is continuously applied to the head. If the head is configured so that ink is supplied to the liquid chamber under pressure, it is desirable to carry out measurements while supplying ink under pressure.

When the laser light 902 is irradiated toward the nozzle hole 102', it may be blocked by the ink droplets 10A' ejected from the nozzle hole 102' during measurement, and the measurement target may not be measured correctly. For this reason, the laser light 902 is irradiated toward a position away from the position of the nozzle hole 102'. Here, the nozzle plate 101 actually used is not made of a material that allows the laser light 902 to pass through. For this reason, if the laser light 902 is irradiated toward a position away from the position of the nozzle hole 102' as described above, a problem occurs in that the laser light 902 does not reach the measurement target.

Therefore, in this embodiment, during measurement, the nozzle plate 101' is replaced with one made of a material that is transparent to the laser light 902, so that the laser light 902 reaches the measurement target. The nozzle plate 101' may be made of any material that is transparent to the laser light 902, and although there are no particular limitations on the material, glass is preferable from the standpoint of the transparency of the laser light 902 and the rigidity of the parts.

The ink 10A used for the measurement is a transparent ink because, if the ink 10 were the actual ink 10, the filler components contained in the ink 10 would prevent the laser light 902 from passing through. However, it is preferable to use an ink 10A for the measurement that has the same dynamic viscosity characteristics as the actual ink 10.

A deflection device 903 for changing the direction of the ink droplets 10A' may be installed between the laser Doppler displacement meter 901 and the head 100. The deflection device 903 may be, for example, a blower fan, which blows air toward the ink droplets 10A' in a direction that moves the ink droplets 10A' away from the optical path of the laser light 902. This makes it possible to avoid the ink droplets 10A' from interfering with the measurement and to prevent contamination of the laser Doppler displacement meter 901.

[Coating device]
Next, a coating device to which the above-mentioned head unit is applied will be described.

<Application example to car body painting system>
As an example of the coating device, an application example to a vehicle body coating system will be described with reference to Fig. 13 and Fig. 14. Fig. 13 is an explanatory diagram showing an example of the coating device. Fig. 14 is an explanatory diagram showing an example of use of the coating device, with Fig. 14(a) being a diagram showing a first example of the arrangement of the coating device on an object, and Fig. 14(b) being a diagram showing a second example of the arrangement of the coating device on an object.

The coating device 1001 includes at least one head 100, a camera 1004 disposed near the head 100, an X-Y table 1003 for moving the head 100 and the camera 1004 in the X and Y directions, image editing software S for editing images captured by the camera 1004, a monitor 1010 for displaying the images to be edited, and a control unit 600. The control unit 600 operates the X-Y table 1003 and ejects liquid from the head 100 based on a predetermined control program.

The application device 1001 can apply liquid (e.g., ink 10) ejected by the head 100 to an object U.

The head 100 ejects ink 10 from the nozzle hole 102 toward the surface of the object U to be coated. The ink 10 ejected from the nozzle hole 102 is ejected in a direction approximately perpendicular to the X-Y plane. The distance between the nozzle hole 102 and the surface of the object U to be coated is, for example, about 20 cm.

The X-Y table 1003 has an X-axis 1005 formed with a linear movement mechanism, and a Y-axis 1006 that moves the X-axis 1005 in the Y direction while holding the X-axis 1005 with two arms. The X-axis 1005 corresponds to the rail member 303 in FIG. 2, and the head 100 and camera 1004 are attached to the head holding member 301 in FIG. 2. A shaft 1007 is provided on the Y-axis 1006. By holding this shaft 1007 with a robot arm 1008, the head 100 and camera 1004 can be freely positioned with respect to the object U.

For example, if the object U is an automobile, the robot arm 1008 can be placed above the object U as shown in FIG. 14(a) or to the side of the object U as shown in FIG. 14(b). The control unit 600 controls the operation of the robot arm 1008 based on a predetermined program.

The camera 1004 moves in the X-Y directions together with the head 100 and captures images of a predetermined range of the surface of the object U at constant, minute intervals. The camera 1004 is, for example, a digital camera. The specifications of the lens or resolution, etc., that enable the camera 1004 to capture multiple subdivision images that divide the predetermined range of the surface to be coated are appropriately selected. The camera 1004 captures the multiple subdivision images of the surface to be coated continuously and automatically according to a program pre-installed in the control unit 600.

As described above, the applicator 1001 has the head 100, and thus can apply ink 10 to a desired position on the target U with high precision, even when the distance between the target U and the nozzle hole 102 is long. In addition, the head 100 can stably eject ink 10, so the applicator 1001 can apply ink 10 to the target U with high precision.

<Application example to electrode manufacturing equipment>
Next, as another example of the coating device, an application example to an electrode manufacturing device will be described with reference to Fig. 15. Fig. 15 is an explanatory diagram showing an example of the electrode manufacturing device.

The electrode manufacturing apparatus 800 is an apparatus that manufactures an electrode having a layer containing an electrode material by ejecting a liquid composition using the head 100 described above.

By ejecting the liquid composition from the head 100, the liquid composition can be applied onto the target to form a liquid composition layer. In this case, the target is not particularly limited as long as it is an object on which a layer having an electrode material is to be formed, and can be appropriately selected according to the purpose, and examples include an electrode substrate (current collector), an active material layer, and a layer having a solid electrode material. In addition, the application of the liquid composition to the target may be a configuration in which the liquid composition is directly ejected to form a layer having an electrode material, or a configuration in which the liquid composition is indirectly ejected to form a layer having an electrode material, as long as it is possible to form a layer having an electrode material on the target.

Other components of the electrode manufacturing device can be appropriately selected depending on the purpose, and examples include a heating means. The heating means is a means for heating the liquid composition ejected by the head 100. The liquid composition layer can be dried by heating.

Figure 15 shows an example of an electrode manufacturing device that forms an electrode mixture layer containing an active material on an electrode substrate (current collector).

The electrode manufacturing device 800 includes a discharge process section 801 that includes a process of applying a liquid composition to a printing substrate W having an object to form a liquid composition layer, and a heating process section 802 that includes a heating process of heating the liquid composition layer to obtain an electrode mixture layer.

The electrode manufacturing apparatus 800 includes conveying sections 803 and 804 that convey the printing substrate W, and the conveying sections 803 and 804 convey the printing substrate W at a preset speed in the order of the ejection process section 801 and the heating process section 802. There are no particular limitations on the method for manufacturing the printing substrate W having an object such as an active material layer, and any known method can be appropriately selected.

The ejection process section 801 includes a printing device 811 that performs an application process of applying a liquid composition onto a printing substrate W, a storage container 812 that stores the liquid composition, and a supply tube 813 that supplies the liquid composition stored in the storage container 812 to the printing device 811. The printing device 811 includes at least one head 100 described above.

The storage container 812 stores the liquid composition 10B, and the ejection process unit 801 ejects the liquid composition 7 from the head 100 provided in the printing device 811 to apply the liquid composition 10B onto the printing substrate W to form a thin film of the liquid composition layer. The storage container 812 may be integrated with the electrode manufacturing device 800, or may be removable from the electrode manufacturing device 800. It may also be a container used for adding to the storage container 812 integrated with the electrode manufacturing device 800 or the storage container 812 removable from the electrode manufacturing device 800.

The storage container 812 and the supply tube 813 can be selected arbitrarily as long as they can stably store and supply the liquid composition 10B.

The heating process section 802 includes a heating device 821 and includes a solvent removal process in which the solvent remaining in the liquid composition layer is heated and dried by the heating device 821 to remove the solvent. This allows the electrode mixture layer to be formed. The heating process section 802 may perform the solvent removal process under reduced pressure.

The heating device 821 is not particularly limited and can be appropriately selected depending on the purpose. For example, a substrate heater, an IR heater, a hot air heater, etc. can be used, and these can be combined. The heating temperature and time can be appropriately selected depending on the boiling point of the solvent contained in the liquid composition 10B and the thickness of the formed film.

The electrode mixture layer formed as described above can be suitably used, for example, as part of the configuration of an electrochemical element. The components other than the electrode mixture layer in the electrochemical element are not particularly limited and can be appropriately selected from known components, such as a positive electrode, a negative electrode, and a separator.

The head unit according to the embodiment is not limited to a vehicle body painting system or an electrode manufacturing device, but may be an image forming device that forms an image on a recording medium such as paper.

[Application example]
Next, an application example will be described with reference to Fig. 16. Fig. 16 is an explanatory diagram showing an application example.

As shown in FIG. 16, the head module 700 has multiple heads 100 (eight in the example of FIG. 16) in a housing 710. The housing 710 has a supply port 711 that supplies ink 10 into the housing 710, a supply path 712 that connects the supply port 711 and an inlet 713, and an outlet 715 provided on the opposite side of the inlet 713 across the liquid chamber 714. The housing 710 also has a recovery port 717 that recovers ink 10 in the housing 710, and a recovery path 716 that connects the recovery port 717 and the outlet 715.

The basic configuration of the multiple heads 100 is similar to that described in Figures 1 and 4, and in Figure 16, corresponding elements are designated by reference numbers in the 700s. In addition, the multiple heads 100 may be configured using a head equipped with a reverse spring mechanism as shown in Figure 11.

In this application example, eight heads 100 are provided so that their nozzle holes 702 are arranged at approximately equal intervals in one direction (the left-right direction in FIG. 16). Each head 100 is provided extending in the vertical direction so that ink 10 is ejected downward from the nozzle hole 702 at the bottom in the figure.

The liquid chamber 714 of each head 100 is provided through the head 100 so that the ink 10 flows from one side (the left side in FIG. 16) to the other side (the right side in FIG. 16) in the arrangement direction of the eight heads 100. In other words, the configuration differs from the above-described embodiment in that each head 100 has an outlet 715 on the opposite side of the inlet 713.

In the above configuration, by applying the drive signals described in the first to fifth embodiments to the piezoelectric elements 732 of each head 100, it is possible to reduce liquid ejection defects caused by air bubbles being entrained in each nozzle hole 702.

In the present invention, examples of liquids include solutions, suspensions, emulsions, etc., containing solvents such as water and organic solvents, colorants such as dyes and pigments, functional materials such as polymerizable compounds, resins, and surfactants, biocompatible materials such as DNA, amino acids, proteins, and calcium, and edible materials such as natural pigments.

These can be used, for example, in inkjet inks, coating materials, surface treatment liquids, components of electronic elements and light-emitting elements, liquids for forming electronic circuit resist patterns, and material liquids for three-dimensional modeling.

The above is just one example, and the present invention provides unique effects for each of the following aspects:

[First aspect]
The first aspect is a liquid ejection head (e.g., head 100) having a liquid chamber (e.g., liquid chamber 114) that contains pressurized liquid (e.g., ink 10), a nozzle hole (e.g., nozzle hole 102) that ejects the liquid, a valve body (e.g., needle 131) provided in the liquid chamber, and a driver (e.g., piezoelectric element 132) that moves the valve body to a position where the valve body closes the nozzle hole and a position where the valve body opens the nozzle hole, and an opening device that controls the driver to move the valve body to a position where the nozzle hole is opened. a drive control unit (e.g., drive control unit 500) that applies a voltage and a closing voltage that moves the valve body to a position that closes the nozzle hole, and the signal waveform of the opening voltage is characterized in having a first period (e.g., time t1 in Figure 6) during which a first voltage (e.g., opening voltage E3 in Figure 6) is applied, and a second period (e.g., time t2 in Figure 6) during which a second voltage different from the first voltage (e.g., opening voltage E2 in Figure 6) is applied after the first period.

[Second aspect]
A second aspect is characterized in that, in the first aspect, the second voltage (e.g., the open circuit voltage E2 in FIG. 6) is a voltage between the closing voltage (e.g., the closing voltage E1 in FIG. 6) and the first voltage (e.g., the open circuit voltage E3 in FIG. 6).

[Third aspect]
A third aspect is characterized in that in the second aspect, the valve body (e.g., needle 131) vibrates with a natural vibration period (e.g., natural vibration period T in Figure 6) in the direction in which the valve body moves when the nozzle hole (e.g., nozzle hole 102) is in an open position, and the second period (e.g., time t2 in Figure 6) is shorter than half of the natural vibration period.

[Fourth aspect]
A fourth aspect is characterized in that, in the second aspect, the valve body (e.g., needle 131) vibrates with a natural vibration period (e.g., natural vibration period T in Figure 6) in the direction in which the valve body moves when the nozzle hole (e.g., nozzle hole 102) is in an open position, and the first period (e.g., time t1 in Figure 6) is longer than the natural vibration period and shorter than 3/2 of the natural vibration period.

[Fifth aspect]
A fifth aspect is characterized in that, in the first aspect, the first voltage (e.g., the open circuit voltage E2 in Figures 7 and 8, and the open circuit voltage Em in Figures 9 and 10) is a voltage between the closing voltage (e.g., the closing voltage E1 in Figures 7, 8, 9 and 10) and the second voltage (e.g., the open circuit voltage E3 in Figures 7 and 8, and the open circuit voltage E2 in Figures 9 and 10).

[Sixth aspect]
A sixth aspect is characterized in that, in the first or fifth aspect, the valve body (e.g., needle 131) vibrates with a natural vibration period (e.g., natural vibration period T in Figures 7 and 8) in the direction in which the valve body moves when the nozzle hole (e.g., nozzle hole 102) is in an open position, and the first period (e.g., time t1 in Figures 7 and 8) is longer than half the natural vibration period and shorter than the natural vibration period.

[Seventh aspect]
A seventh aspect is characterized in that, in the first, fifth or sixth aspect, the valve body (e.g., needle 131) vibrates with a natural vibration period (e.g., natural vibration period T in Figures 9 and 10) in the direction in which the valve body moves when the nozzle hole (e.g., nozzle hole 102) is in an open position, and the first period (e.g., time t1 in Figures 9 and 10) is shorter than half of the natural vibration period.

[Eighth aspect]
An eighth aspect is the seventh aspect, characterized in that the second period (for example, time t2 in FIG. 10) is shorter than half of the natural vibration period (for example, natural vibration period T in FIG. 10).

[Ninth aspect]
A ninth aspect is characterized in that, in any of the first to eighth aspects, the liquid ejection head (e.g., head 100) is provided with a nozzle plate (e.g., nozzle plate 101) in which the nozzle hole (e.g., nozzle hole 102) is formed, and the valve body (e.g., needle 131) closes the nozzle hole by abutting against the nozzle plate and opens the nozzle by moving away from the nozzle plate.

[Tenth aspect]
The tenth aspect is characterized in that, in any of the first to ninth aspects, a transmission mechanism (e.g., a reverse spring mechanism 134) is provided between the valve body (e.g., needle 131) and the driver (e.g., piezoelectric element 132) for converting the extending force of the driver into a force that retracts the valve body and transmitting the force to the valve body.

[Eleventh aspect]
The eleventh aspect is a liquid ejection device characterized by comprising a head unit (e.g., head unit HU) of any of the first to tenth aspects, and a pressure applying means (e.g., pressure applying mechanism 200) that supplies pressurized liquid to a liquid ejection head (e.g., head 100) provided in the head unit.

[Twelfth aspect]
A twelfth aspect is the eleventh aspect, characterized in that the liquid ejection head (for example, the head 100) is further provided with a moving means (for example, the head moving mechanism 300) for moving the liquid ejection head (for example, the head 100) relative to an object.

[Thirteenth aspect]
A thirteenth aspect is an application device comprising a liquid ejection device of the eleventh or twelfth aspect, and characterized in that the liquid is applied to an object (e.g., object U in FIG. 14 or printing substrate W in FIG. 15).

[14th aspect]
A fourteenth aspect is a drive device (e.g., drive control unit 500) that drives a liquid ejection head (e.g., head 100) having a liquid chamber (e.g., liquid chamber 114) that contains pressurized liquid (e.g., ink 10), a nozzle hole (e.g., nozzle hole 102) that ejects the liquid, a valve body (e.g., needle 131) provided in the liquid chamber, and a driver (e.g., piezoelectric element 132) that moves the valve body to a position where the valve body closes the nozzle hole and a position where the valve body opens the nozzle hole, and the drive device controls the driver to move the valve body to a position where the nozzle hole is opened. an opening voltage for moving the valve body to a position where the nozzle hole is closed is applied to the driver, and the liquid is controlled to be ejected from the nozzle hole; a closing voltage for moving the valve body to a position where the nozzle hole is closed is applied to the driver, and the liquid is controlled not to be ejected from the nozzle hole; and a signal waveform of the opening voltage has a first period (e.g., time t1 in FIG. 6 ) during which a first voltage (e.g., opening voltage E3 in FIG. 6 ) is applied, and a second period (e.g., time t2 in FIG. 6 ) during which a second voltage different from the first voltage (e.g., opening voltage E2 in FIG. 6 ) is applied after the first period.

[Fifteenth aspect]
A fifteenth aspect is a driving method for driving a liquid ejection head (e.g., head 100) having a liquid chamber (e.g., liquid chamber 114) that contains pressurized liquid (e.g., ink 10), a nozzle hole (e.g., nozzle hole 102) that ejects the liquid, a valve body (e.g., needle 131) provided in the liquid chamber, and a driver (e.g., piezoelectric element 132) that moves the valve body to a position where the valve body closes the nozzle hole and a position where the valve body opens the nozzle hole, the fifteenth aspect is a driving method for driving a liquid ejection head (e.g., head 100) having a liquid chamber (e.g., liquid chamber 114) that contains pressurized liquid (e.g., ink 10), a nozzle hole (e.g., nozzle hole 102) that ejects the liquid, a valve body (e.g., needle 131) provided in the liquid chamber, and a driver (e.g., piezoelectric element 132) that moves the valve body to a position where the valve body closes the nozzle hole and a position where the valve body opens the nozzle hole, The method is characterized by comprising: a first step of applying a first voltage (e.g., opening voltage E3 in FIG. 6 ) to move the valve body; a second step, subsequent to the first step, of applying a second voltage (e.g., opening voltage E2 in FIG. 6 ) to the driver to move the valve body to a position to open the nozzle hole, the second voltage being different from the first voltage; and a third step, subsequent to the second step, of applying a closing voltage (e.g., closing voltage E1 in FIG. 6 ) to the driver to move the valve body to a position to close the nozzle hole.

REFERENCE SIGNS LIST 10 Ink 100 Head 101 Nozzle plate 102 Nozzle hole 113 Inlet 114 Liquid chamber 130 Valve member 131 Needle (an example of a valve body)
132 Piezoelectric element (an example of a driver)
134 Reverse spring mechanism (an example of a transmission mechanism)
500 Drive control unit (an example of a drive device)
200 Pressurizing mechanism (an example of a pressurizing means)
300 Head moving mechanism (an example of a moving means)
600 Control unit HU Head unit

Claims (15)

a liquid ejection head including a liquid chamber for storing pressurized liquid, a nozzle hole for ejecting the liquid, a valve body provided in the liquid chamber, and a drive body for moving the valve body to a position where the valve body closes the nozzle hole and a position where the valve body opens the nozzle hole;
a drive control unit that applies to the drive body an opening voltage for moving the valve body to a position that opens the nozzle hole and a closing voltage for moving the valve body to a position that closes the nozzle hole;
A head unit comprising:
The signal waveform of the open circuit voltage is
a first period during which a first voltage is applied;
a second period in which a second voltage different from the first voltage is applied after the first period;
A head unit comprising: The head unit of claim 1, wherein the second voltage is a voltage between the closing voltage and the first voltage. The head unit according to claim 2, characterized in that the valve body vibrates with a natural vibration period in the direction in which the valve body moves when the nozzle hole is in an open position, and the second period is shorter than half of the natural vibration period. The head unit according to claim 2, characterized in that the valve body vibrates with a natural vibration period in the direction in which the valve body moves when the nozzle hole is in an open position, and the first period is longer than the natural vibration period and shorter than 3/2 of the natural vibration period. The head unit of claim 1, wherein the first voltage is a voltage between the closing voltage and the second voltage. The head unit according to claim 5, characterized in that the valve body vibrates with a natural vibration period in the direction in which the valve body moves when the nozzle hole is in an open position, and the first period is longer than half the natural vibration period and shorter than the natural vibration period. The head unit according to claim 5, characterized in that the valve body vibrates with a natural vibration period in the direction in which the valve body moves when the nozzle hole is in an open position, and the first period is shorter than half of the natural vibration period. The head unit according to claim 7, characterized in that the second period is shorter than half the natural vibration period. The head unit according to claim 1, characterized in that the liquid ejection head includes a nozzle plate in which the nozzle holes are formed, and the valve body closes the nozzle holes by contacting the nozzle plate and opens the nozzles by moving away from the nozzle plate. The head unit according to claim 1, characterized in that a transmission mechanism is provided between the valve body and the driver, which converts the force of the driver body to expand into a force that retracts the valve body and transmits the force to the valve body. A head unit according to any one of claims 1 to 10,
a pressurizing unit for supplying pressurized liquid to a liquid ejection head of the head unit;
A liquid ejection device comprising: The liquid ejection device according to claim 11, further comprising a moving means for moving the liquid ejection head relative to the target object. An application device comprising the liquid ejection device according to claim 11, and configured to apply the liquid to an object. A drive device for driving a liquid ejection head having a liquid chamber for storing pressurized liquid, a nozzle hole for ejecting the liquid, a valve body provided in the liquid chamber, and a drive body for moving the valve body to a position where the valve body closes the nozzle hole and a position where the valve body opens the nozzle hole,
The drive device is
applying an opening voltage to the driving body to move the valve body to a position to open the nozzle hole, and controlling so that the liquid is ejected from the nozzle hole;
applying a closing voltage to the driving body to move the valve body to a position where the nozzle hole is closed, thereby controlling so that the liquid is not discharged from the nozzle hole;
A driving device characterized in that the signal waveform of the open circuit voltage has a first period in which a first voltage is applied, and a second period after the first period in which a second voltage different from the first voltage is applied. A method for driving a liquid ejection head having a liquid chamber that contains pressurized liquid, a nozzle hole that ejects the liquid, a valve body provided in the liquid chamber, and a driver that moves the valve body to a position where the valve body closes the nozzle hole and a position where the valve body opens the nozzle hole, comprising:
a first step of applying a first voltage to the driver to move the valve body to a position to open the nozzle hole;
a second step of applying to the driving body, after the first step, a second voltage that moves the valve body to a position that opens the nozzle hole and is different from the first voltage;
a third step of applying a closing voltage to the driver to move the valve body to a position where the valve body closes the nozzle hole after the second step;
A driving method comprising the steps of: