CN111032360A

CN111032360A - Liquid coating device

Info

Publication number: CN111032360A
Application number: CN201880053399.6A
Authority: CN
Inventors: 前田贤司; 中谷政次
Original assignee: Nidec Corp
Current assignee: Nidec Corp
Priority date: 2017-09-28
Filing date: 2018-06-28
Publication date: 2020-04-17
Also published as: JPWO2019064770A1; WO2019064770A1

Abstract

The invention provides a liquid application device capable of inhibiting damage of a piezoelectric element. A liquid application device (10) is provided with a diaphragm (12) that changes the internal volume of a liquid storage unit (11), a piezoelectric element (13) that is positioned above the diaphragm (12), and a preload spring (14) that is positioned above the piezoelectric element (13).

Description

Liquid coating device

Technical Field

The present invention relates to a liquid agent application device.

Background

Piezoelectric elements are used in liquid application apparatuses for ejecting liquid onto the surface of an object in a wide range of fields such as semiconductors, printing, and chemicals because they convert energy from electric energy to mechanical energy by utilizing a piezoelectric effect and have excellent responsiveness.

A liquid application apparatus generally includes a liquid storage portion having an ejection port, a diaphragm for changing a volume in the liquid storage portion, and a piezoelectric element for vibrating the diaphragm by applying pressure thereto (see, for example, patent document 1).

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2007-160701

Disclosure of Invention

Problems to be solved by the invention

However, when the piezoelectric element that has been extended contracts, the contraction rate of the piezoelectric element is faster than the restoration rate of the diaphragm, and therefore the piezoelectric element may be damaged.

Specifically, when the piezoelectric element is connected to the diaphragm (that is, when the piezoelectric element is fixed to the diaphragm), a tensile force may be applied to the piezoelectric element from the diaphragm, and the piezoelectric element may be peeled off from the diaphragm, or damage may occur in the piezoelectric element.

In addition, when the piezoelectric element is in contact with the diaphragm (that is, when the piezoelectric element is not fixed to the diaphragm), a tensile force may be generated inside the piezoelectric element by the weight of the piezoelectric element, and the inside of the piezoelectric element may be damaged.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a liquid application apparatus capable of suppressing damage to a piezoelectric element.

Means for solving the problems

A liquid application device according to one aspect of the present invention includes a liquid storage unit, a diaphragm, a driving unit, and a pressurizing mechanism. The liquid storage portion has a liquid outlet. The diaphragm changes the internal volume of the liquid agent storage portion. The driving portion is located above the diaphragm. The pre-pressing mechanism is positioned above the driving part.

ADVANTAGEOUS EFFECTS OF INVENTION

According to an aspect of the present invention, a liquid application apparatus capable of suppressing damage to a piezoelectric element can be provided.

Drawings

Fig. 1 is a schematic diagram showing a configuration of a liquid agent application device according to an embodiment.

Fig. 2 is a schematic diagram showing another configuration of the liquid agent application device according to the embodiment.

Fig. 3 is a schematic diagram for explaining an operation in a case where the piezoelectric element of the embodiment is in contact with the diaphragm.

Fig. 4 is a schematic diagram for explaining an operation in a case where the piezoelectric element of the embodiment is connected to the diaphragm.

Detailed Description

Hereinafter, a liquid application apparatus according to an embodiment of the present invention will be described with reference to the drawings. However, the scope of the present invention is not limited to the following embodiments, and can be arbitrarily changed within the scope of the technical idea of the present invention. In the drawings below, in order to easily distinguish the respective structures, the scale, the number of the structures, and the like may be different from those of the actual structures.

In the present specification, "connected" means a state in which two members are fixed or connected to each other. Therefore, when two members are connected, both always operate together. Further, "contact" means a state in which two members are in direct contact with each other but the two members are not fixed or coupled to each other. When two members are in contact with each other, there are cases where both members operate together and where both members operate not together.

Fig. 1 is a schematic diagram showing the configuration of a liquid agent application device 10 according to a first embodiment.

The liquid application device 10 includes a liquid storage portion 11, a diaphragm 12, a piezoelectric element 13, a preload spring 14 (an example of a preload mechanism), a fixing member 15, and a control portion 16. The liquid storage portion 11, the diaphragm 12, the piezoelectric element 13, and the fixing member 15 constitute a head portion 17.

(1) The liquid storage portion 11 includes a housing 11a and a nozzle 11 b.

The housing 11a is formed in a hollow shape. In the present embodiment, the housing 11a is formed in a cylindrical shape, but is not limited thereto. The housing 11a can be made of, for example, an alloy material, a ceramic material, a synthetic resin material, or the like.

A pressure chamber 11c is formed inside the housing 11 a. The liquid agent is stored in the pressure chamber 11 c. Examples of the liquid agent include, but are not limited to, a coating liquid for forming solder, a thermosetting resin, ink, and a functional film (an alignment film, a protective film, a color filter, organic electroluminescence, and the like).

A liquid agent supply port 11d is formed in a side wall of the housing 11 a. The liquid agent supplied from the liquid agent supply device 30 through the liquid agent supply pipe 31 is replenished into the pressure chamber 11c through the liquid agent supply port 11 d.

The nozzle 11b is formed in a plate shape. The nozzle 11b is disposed to close one end opening of the housing 11 a. The nozzle 11b has an ejection port 11 e. The liquid agent in the pressure chamber 11c is discharged to the outside from the discharge port 11e as droplets.

(2) The diaphragm 12 and the diaphragm 12 are arranged to close the other end opening of the housing 11 a. When the diaphragm 12 is subjected to pressure vibration from the piezoelectric element 13 described below, the diaphragm 12 elastically vibrates. Thereby, the diaphragm 12 changes the volume of the pressure chamber 11c formed in the liquid storage portion 11.

When the diaphragm 12 is curved convexly toward the inside of the pressure chamber 11c, the volume of the pressure chamber 11c becomes smaller. Thereby, the liquid agent is ejected from the ejection port 11 e. After that, when the diaphragm 12 returns to the steady state due to its own elasticity, the volume of the pressure chamber 11c also returns. At this time, the liquid agent is replenished from the liquid agent supply port 11d to the pressure chamber 11 c.

The material of the diaphragm 12 is not particularly limited, and an alloy material, a ceramic material, a synthetic resin material, or the like can be used, for example.

(3) Piezoelectric element 13 the piezoelectric element 13 is an example of a "driving section" that drives the diaphragm 12 to vibrate. The piezoelectric element 13 is located above the diaphragm 12. The piezoelectric element 13 is disposed between the diaphragm 12 and the pre-pressure spring 14. The piezoelectric element 13 is sandwiched by the diaphragm 12 and the pre-pressure spring 14.

The first end 13p of the piezoelectric element 13 abuts on the diaphragm 12. The first end 13p of the piezoelectric element 13 may be in contact with only the diaphragm 12, or may be connected to the diaphragm 12. That is, the first end 13p of the piezoelectric element 13 may be fixed to the diaphragm 12 or may not be fixed. When the first end 13p of the piezoelectric element 13 is connected to the diaphragm 12, an adhesive such as an epoxy resin can be used. The first end 13p of the piezoelectric element 13 is an end of the piezoelectric element 13 on the diaphragm 12 side in the expansion and contraction direction.

The second end portion 13q of the piezoelectric element 13 is connected to the pre-compression spring 14. That is, the second end 13q of the piezoelectric element 13 is fixed to the preload spring 14. The preload spring 14 may be directly fastened to the second end 13q of the piezoelectric element 13, or may be connected via an adhesive such as epoxy resin.

The piezoelectric element 13 includes a plurality of piezoelectric bodies 13a, a plurality of internal electrodes 13b, and a pair of

side surface electrodes

13c and 13 c. The piezoelectric bodies 13a and the internal electrodes 13b are alternately stacked. Each piezoelectric body 13a is made of piezoelectric ceramics such as lead zirconate titanate (PZT). Each internal electrode 13b is electrically connected to one of the pair of

side electrodes

13c, 13 c. That is, the internal electrode 13b electrically connected to one side electrode 13c is electrically insulated from the other side electrode 13 c. Such a configuration is generally referred to as a local electrode configuration. However, the piezoelectric element 13 may include at least one piezoelectric body and a pair of electrodes, and various known piezoelectric elements may be used as the piezoelectric element 13.

The piezoelectric element 13 vibrates in accordance with a drive voltage signal (i.e., a drive pulse) applied from a control unit 16 described below. Specifically, when a drive voltage signal is applied from the control unit 16 to the pair of

side electrodes

13c and 13c, each piezoelectric body 13a expands and contracts. The diaphragm 12 is vibrated by being pressed with the expansion and contraction of the piezoelectric bodies 13 a.

(4) The pre-pressing spring 14 is located above the piezoelectric element 13. The pre-compression spring 14 is configured to be sandwiched between the piezoelectric element 13 and the fixing member 15.

A first end portion 14p of the preload spring 14 on the opposite side to the piezoelectric element 13 is connected to the fixed member 15. That is, the first end portion 14p of the pre-compression spring 14 is fixed to the fixed member 15. Therefore, the first end portion 14p of the pre-pressing spring 14 is a fixed end. The first end portion 14p of the preload spring 14 may be directly fastened to the fixing member 15, or may be connected to the fixing member 15 via an adhesive such as epoxy resin, for example. The first end 14p of the preload spring 14 is an end opposite to the piezoelectric element 13 in the expansion and contraction direction of the piezoelectric element 13.

A second end portion 14q of the preload spring 14 on the piezoelectric element 13 side is connected to the first end portion 13p of the piezoelectric element 13. That is, the second end portion 14q of the pre-compression spring 14 is fixed to the first end portion 13p of the piezoelectric element 13. Therefore, in the present embodiment, the first end portion 13p of the piezoelectric element 13 is not a fixed end. The second end 14q of the preload spring 14 may be directly fastened to the piezoelectric element 13, or may be connected to the piezoelectric element 13 via an adhesive such as epoxy resin, for example. The second end 14q of the preload spring 14 is an end closer to the piezoelectric element 13 in the expansion and contraction direction of the piezoelectric element 13.

Fig. 1 shows a case where a coil spring is used as the preload spring 14, but the present invention is not limited to this. As the preload spring 14, a known spring such as a disc spring, a leaf spring, or a coil spring can be used.

The fixing member 15 may be formed of an elastic member to function as the preload spring 14. In this case, the component of the preload spring 14 is not required, and the fixing member 15 functions as a preload mechanism, so that the number of components can be reduced and the size can be reduced.

Fig. 2 shows this configuration example. In fig. 2, the fixing member 18 has an elastic structure, and the second end portion 13q of the piezoelectric element 13 on the opposite side of the diaphragm 12 is fixed to the fixing member 18, whereby the piezoelectric element 13 is held by applying a preload. The fixing member 18 in fig. 2 has a desired spring constant by locally reducing the thickness of the piezoelectric element 13 in the expansion and contraction direction. Of course, it is also effective to use a material having appropriate elasticity. In fig. 2, the fixing member 18 is supported by the support portion 19 located above the liquid agent storage portion 11, but the method of supporting the fixing member 18 is not limited to this.

The spring constant of the pre-pressure spring 14 is preferably larger than the spring constant of the diaphragm 12. This can suppress transmission of the expansion/contraction force of the piezoelectric element 13 to the preload spring 14 side (i.e., the upward direction in fig. 1), and can efficiently transmit the expansion/contraction force of the piezoelectric element 13 to the diaphragm 12. Specifically, the piezoelectric element 13 sandwiched between the pre-compression spring 14 and the diaphragm 12 is compressed by the two springs and is restricted to a position where the two springs are balanced, the diaphragm 12 is in a state of being slightly deflected toward the pressure chamber 11c side, and the pre-compression spring 14 is in a state of being compressed compared to the initial state. When the piezoelectric element 13 is extended in this state, the spring constant of the pre-compression spring 14 is larger than the spring constant of the diaphragm 12, so that the displacement on the diaphragm 12 side becomes large, the pressurizing force applied to the pressure chamber 11c can be increased, and the driving efficiency can be improved.

The preload spring 14 presses the piezoelectric element 13 to the diaphragm 12 side. The preload spring 14 presses the piezoelectric element 13 to the diaphragm 12 side regardless of whether the piezoelectric element 13 is in an extended state or a contracted state. However, when the second end 13q of the piezoelectric element 13 is connected to the diaphragm 12, the pressing force applied from the preload spring 14 to the piezoelectric element 13 may be "0" when the piezoelectric element 13 is in the contracted state.

Here, as shown in fig. 3, when the first end 13p of the piezoelectric element 13 is in contact with the diaphragm 12, when the piezoelectric element 13 that is elongated contracts, not only a tensile force due to the elongation is generated inside the piezoelectric element 13, but also the piezoelectric element 13 itself may damp oscillation. However, in the present embodiment, as described above, the piezoelectric element 13 can be pressed against the diaphragm 12 in advance by the pressing force of the pre-compression spring 14. Therefore, the tensile force generated by the piezoelectric element 13 can be suppressed, and the ringing of the piezoelectric element 13 can be suppressed.

When the first end portion 13p of the piezoelectric element 13 is in contact with the diaphragm 12, if the contracted piezoelectric element 13 is extended and the piezoelectric element 13 is separated from the diaphragm 12, the inside of the piezoelectric element 13 may be damaged by the extension force of the piezoelectric element 13 itself. Specifically, peeling of the laminated portion, breakage of the electrode and the wiring, and the like may occur. However, in the present embodiment, as described above, the piezoelectric element 13 can be pressed against the diaphragm 12 in advance by the pressing force of the pre-compression spring 14. Therefore, the occurrence of damage inside the piezoelectric element 13 can be suppressed.

On the other hand, as shown in fig. 4, when the second end 13q of the piezoelectric element 13 is connected to the diaphragm 12, when the piezoelectric element 13 that has been extended contracts, the contraction rate of the piezoelectric element 13 becomes faster than the restoration rate of the diaphragm 12, and therefore a tensile force is applied from the diaphragm 12 to the piezoelectric element 13. As a result, the piezoelectric element 13 may be peeled off from the diaphragm 12 or the piezoelectric element 13 may be damaged. However, in the present embodiment, as described above, the piezoelectric element 13 can be always pressed against the diaphragm 12 by the pressing force of the pre-compression spring 14. Therefore, peeling of the piezoelectric element 13 or damage to the inside of the piezoelectric element 13 can be suppressed.

(5) The fixing member 15 is a member that fixes the first end portion 14p of the pre-compression spring 14. The fixing member 15 is located above the liquid agent storage portion 11. However, the fixing member 15 may be configured to fix the first end portion 14p of the preload spring 14, or may be spaced apart from the liquid agent storage portion 11. The shape of the fixing member 15 is not limited to the shape shown in fig. 1, and may be appropriately changed in consideration of the arrangement relationship with the peripheral members.

As described above, the fixing member 15 may be formed of an elastic member to function as the preload spring 14 (see the fixing member 18 in fig. 2).

(6) The control Unit 16 is realized by the control Unit 16 including a microprocessor such as a CPU (Central Processing Unit) or a DSP (Digital Signal Processor), an arithmetic device such as an ASIC (application specific Integrated Circuit), and a power amplifier including a power MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor).

The control unit 16 generates a drive voltage signal for driving the piezoelectric element 13. The control unit 16 transmits the generated drive voltage signal to the power amplifier to amplify the power, and applies the amplified power to the pair of

side electrodes

13c and 13c of the piezoelectric element 13, thereby vibrating the piezoelectric element 13.

(other embodiments) the present invention is described by the above-described embodiments, but the discussion and drawings constituting a part of the present disclosure should not be construed as limiting the present invention. Various alternative embodiments, examples, and application techniques will be apparent to those skilled in the art in light of this disclosure.

In the above-described embodiment, the piezoelectric element 13 is described as an example of the "driving unit" for driving the diaphragm 12 to vibrate, but the "driving unit" may include a member other than the piezoelectric element 13.

For example, the "driving section" may include a horn for amplifying the vibration amplitude of the piezoelectric element 13. For the horn, a cylindrical metal rod can be used, for example. The vibration amplitude of the piezoelectric element 13 can be increased by setting the natural frequency of the horn to be equal to or lower than the drive limit frequency of the piezoelectric element 13 and multiplying the natural frequency by the frequency of the drive voltage signal. The natural frequency is a frequency at which the horn vibrates freely. The drive limit frequency is the maximum value of the limit frequency at which the piezoelectric element 13 can be driven with a stable amplitude.

The "driving unit" may include a piezoelectric element for vibration for vibrating the diaphragm 12 at a high frequency. The piezoelectric element for vibration vibrates based on a high-frequency signal having a frequency higher than a driving voltage signal applied to the piezoelectric element 13. By applying a minute pressure vibration to the diaphragm 12 to such an extent that the liquid agent is not ejected from the ejection port 11e, the fluidity of the liquid agent stored in the liquid agent storage portion 11 can be improved, and the breaking property of the liquid agent after ejected from the ejection port 11e can be improved.

In the above embodiment, the first end 13p of the piezoelectric element 13 is directly in contact with or connected to the diaphragm 12, but an intermediate member that is in surface contact with the piezoelectric element 13 and in point contact with the diaphragm 12 may be interposed between the first end 13p and the diaphragm 12. The intermediate member is fixed to the first end 13p of the piezoelectric element 13, and the diaphragm 12 is freely moved toward and away from the first end. By sandwiching such an intermediate member, the pressurizing force can be suppressed from concentrating on a part of the first end portion 13p of the piezoelectric element 13, and the piezoelectric element 13 can be further suppressed from being damaged.

Description of the symbols

10-liquid agent application device, 11-liquid agent reservoir, 11 a-housing, 11 b-nozzle, 11 c-pressure chamber, 11 d-liquid agent supply port, 11 e-ejection port, 12-diaphragm, 13-piezoelectric element, 14-pre-compression spring, 15-fixed member, 16-control portion.

Claims

1. A liquid agent application device is characterized by comprising:

a liquid storage portion having a liquid outlet;

a diaphragm for changing the internal volume of the liquid agent storage part;

a driving part located above the diaphragm; and

and a pre-pressing mechanism located on the driving part.

2. The liquid application device of claim 1,

the end of the pre-pressing mechanism opposite to the driving part is a fixed end.

3. The liquid application device according to claim 1 or 2,

the driving part is in contact with the diaphragm.

4. The liquid application device according to any one of claims 1 to 3,

the driving part is connected with the diaphragm.

5. The liquid application device according to any one of claims 1 to 4,

the spring constant of the preload mechanism is larger than the spring constant of the diaphragm.

6. The liquid application device according to any one of claims 1 to 5,

a fixing member for fixing an end portion of the pre-pressing mechanism on the side opposite to the driving portion,

the pre-pressing mechanism is a pre-pressing spring.

7. The liquid application device according to any one of claims 1 to 5,

the pre-pressing mechanism is a fixing member for fixing an end portion of the driving portion opposite to the diaphragm,

the fixing member is formed of an elastic member.