JPH10213073A - Piezoelectric pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve durability without reducing secular pump performance by forming at least a part of a casing of a piezoelectric pump out of a resin material having specified flexural rigidity and a temperature change ratio, and specifying a piezoelectric strain constant in the horizontal direction having a specified permittivity in a piezoelectric body. SOLUTION: When AC power is applied between electric poles 13a, 13b of a piezoelectric body 15 so as to vibrate the piezoelectric body 15, the inside of a pump chamber 16 becomes negative pressure, and thereby, a carries fluid is absorbed through a suction side check valve 9a. When the inside of a pump chamber 16 becomes positive pressure, a delivery side check valve 9b is opened so as to deliver the carried fluid. A pump actuator unit 3 for composing a casing of a piezoelectric pump, a pump sucking and delivering unit 1, and a pump valve seat unit 2 are formed of a thermoplastic resin and the like. In a range in which a flexural rigidity ratio is set to 1GPA or more at a normal temperature and temperature change is set to 20 deg.C to 50 deg.C, it is formed of a resin having the change ratio of the flexural rigidity ratio of 15% and less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric pump driven by vibration of a piezoelectric body, and more particularly to a piezoelectric pump having a temperature higher than room temperature.
For example, the present invention relates to a piezoelectric pump having improved driving performance at 40 to 50 ° C.

[0002]

2. Description of the Related Art As a conventional technique of this kind, there is, for example, a piezoelectric pump disclosed in Japanese Utility Model Application Laid-Open No. 64-15789. As the material of the casing used in the conventional piezoelectric pump,
Resins such as polypropylene (PP) and polyacetal (POM) have been used. In such a piezoelectric pump, a ceramic or polymer-based piezoelectric material is provided on one or both sides of a shim made of, for example, phosphor bronze in a casing.
A set (single-layer type; unimorph) or a plurality of sets (multi-layer type; bimorph) are stacked, and the periphery of a piezoelectric body having thin-film electrodes provided on both surfaces thereof is fixed, and a voltage is applied between the thin-film electrodes of the piezoelectric body. Then, by vibrating the piezoelectric body, a fluid such as liquid or air is sucked through the suction-side check valve and discharged through the discharge-side check valve.
It has been used to flow fluids in a temperature range around 0 ° C.

[0003] In a piezoelectric pump, it is preferable that the piezoelectric material used has a large piezoelectric strain constant.
Conventionally, for example, the horizontal piezoelectric strain constant d ₃₁ is 200 × 10
So-called soft PZT exceeding ^-12 m / v
System ceramics and the like have been generally used. It is d
_This is because a material whose ₃₁ is smaller than 200 × 10 ⁻¹² m / v has a small deformation amount and is not preferable for a piezoelectric pump.

However, in a conventional piezoelectric pump using a casing member made of a resin such as polypropylene (PP) or polyacetal (POM), the temperature is higher than normal temperature.
For example, when a fluid is transported for a long time in an environment at a temperature of 40 to 50 ° C., there is a problem that pump performance such as a flow rate and a discharge pressure is reduced. The cause is due to the heat generation of the element when the piezoelectric element is AC driven,
The calorific value W is represented by the following relationship: W = 2π × F × C × voltage × tan δ (where F is frequency, C is electric capacity, and tan δ is dielectric loss coefficient). Generally, a material having a large piezoelectric strain constant has a property of having a large dielectric constant.
When a piezoelectric element having a large dielectric constant is used in order to obtain a larger piezoelectric strain, even when the pump performance such as the flow rate and the discharge pressure is not reduced during normal temperature driving, it is 40 to 50 higher than normal temperature.
When driven at a temperature of ° C., the dielectric constant further increases and the heat generation increases, and the temperature inside the casing further increases.
The casing material is deformed by the heat, and the pump performance decreases with driving.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a piezoelectric pump which is excellent in durability without deterioration of pump performance over time even when operated at a temperature higher than room temperature.

[0006]

To achieve the above object, a piezoelectric pump according to the present invention is a piezoelectric pump in which a piezoelectric material, which is a drive source of a transported object, is loaded in a casing. Some have a flexural rigidity of 1 GPA or more at room temperature and a temperature change of 20 ° C. or more.
In a temperature range of 50 ° C., the piezoelectric body (1) is made of a resin whose bending rigidity has a temperature change rate of 15% or less.
5) having a dielectric constant of 5000 or less and a horizontal piezoelectric strain constant d
₃₁ is 200 × 10 ⁻¹² m / v or more.

The inventor of the present invention has found that the performance of a piezoelectric pump when it is used at a temperature higher than room temperature largely depends on the material of the casing used for the piezoelectric pump and the dielectric constant and the piezoelectric coefficient of the piezoelectric material constituting the piezoelectric element. In particular, it has been found that there is a correlation between the rigidity of the material used for the pump casing and its temperature characteristics and the pump performance at high temperatures, and the pump suction / discharge constituting the pump casing At least one of the unit for use (1), the pump valve seat unit (2) and the pump actuator unit (3) has a flexural rigidity of 1 GPA or more at room temperature and a temperature range of 20 ° C. to 50 ° C. in temperature change. , By using a resin whose temperature change rate of the bending rigidity is 15% or less, the change rate of the pump flow rate and the discharge pressure change rate over time It can be a good piezoelectric pump less pump performance. The dielectric constant of the piezoelectric body (15) is 5,000 or less, and the horizontal piezoelectric strain constant d ₃₁ is 200.
With a configuration of × 10 ⁻¹² m / v or more, the heat generation from the piezoelectric body itself is further suppressed, and since the amount of distortion of the element is larger, the temperature dependence of the pump performance is small, and the change in the pump performance is more reduced. It is possible to provide a piezoelectric pump having excellent durability such that little deformation of the casing does not occur.

According to a second aspect of the present invention, in the piezoelectric pump according to the first aspect, the casing is detachably attached to the pump actuator unit (3) and the pump actuator unit (3), and the suction port (8) is provided.
a) a pump suction / discharge unit (1) having a discharge port (8b) and a pump suction / discharge unit (1) and a pump actuator unit (3), and the suction side and the discharge side are reversed. Stop valve (9a, 9
b) and a pump valve seat unit (2) having a piezoelectric body (15) in a pump actuator unit (3).
Is fixed, and the electrodes (13a, 13a) of the piezoelectric body (15) are fixed.
By applying a voltage during b) to vibrate the piezoelectric body (15), fluid is sucked through the suction-side check valve (9a) and discharged through the discharge-side check valve (9b).

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a piezoelectric pump according to the present invention will be described in detail with reference to FIGS. FIG. 1 is a longitudinal sectional view showing an embodiment of a piezoelectric pump according to the present invention, and FIG.
FIG. 2 is an exploded sectional view of FIG. First, as shown in FIG. 1, a piezoelectric pump of the present invention basically includes, for example, a pump suction / discharge unit 1 and a pump valve seat unit 2.
And a casing comprising the pump actuator unit 3 and the piezoelectric body 15, the electrodes 13a and 13
b, a piezoelectric element portion composed of the piezoelectric vibrator 12 and the coating material 11, the pump actuator unit 3, and the pump valve seat unit 2 are arranged so as to constitute the pump chamber 6.

The pump suction / discharge unit 1 is detachably attached to the pump actuator unit 3 and has suction ports and discharge ports 8a and 8b formed on the upper surface thereof. Here, 8a is a suction flow path into which the carrier fluid flows when the pump operates, and 8b is a discharge flow path from which the carrier fluid flows out when the pump operates. The pump valve seat unit 2 is a pump suction / discharge unit 1
And the pump actuator unit 3 and have check valves 9a and 9b corresponding to the suction side and the discharge side.

The pump actuator unit 3 supports an outer peripheral portion of a piezoelectric vibrator 12 composed of a piezoelectric body 15 inside the envelope 10, and the electrodes 13 a, 1
The lead wires 14a, 14b connected to the
Pull out and configure. The electrodes 13a and 13b are laminated on both surfaces of the piezoelectric bodies 15 and 15, respectively. The piezoelectric vibrator 12 is covered with an elastic elastomer mold as the covering material 11. The piezoelectric vibrator 12 is a bimol element in which two flat piezoelectric members 15 are laminated on both surfaces of a shim material (not shown).

The piezoelectric pump according to this embodiment has a lead wire 14
a, 14b, the electrodes 13a, 1
The piezoelectric body 15 is vibrated by applying an AC power source e between the electrodes 3b, that is, the piezoelectric body 15 vibrates and bends in one direction, and the inside of the pump chamber 16 becomes a negative pressure. The carrier fluid is sucked through the stop valve 9a, flows into the pump chamber 16 formed between the pump valve seat unit 2 and the piezoelectric body 15 in the envelope, and then the piezoelectric body 15 is moved to the previous position. The pump chamber 16 vibrates and curves in a direction opposite to the direction, and the inside of the pump chamber 16 becomes a positive pressure, so that the discharge-side check valve 9b is opened, and the driving operation is performed by discharging the carrier fluid through the discharge-side check valve 9b.

The piezoelectric pump of this embodiment has a pump suction / discharge unit 1 and a pump valve seat unit 2.
And the piezoelectric pump in which the casing is constituted by the pump actuator unit 3, the piezoelectric pump of the present invention is not limited to the structure exemplified here. Next, the material and physical properties of the unit and the piezoelectric body that constitute the piezoelectric pump will be described.

The pump actuator unit 3, the pump suction / discharge unit 1 and the pump valve seat unit 2 constituting the casing are made of polyphenylene sulfide (PPS), polysulfone (PSF), polyetheretherketone (PEEK), polyetherketone. (P
An EK) -based thermoplastic resin or the like having a flexural rigidity of 1 GPA or more at room temperature and a temperature change of 20 ° C.
In a temperature range of 50 ° C., a resin having a change rate of the flexural rigidity of 15% or less is preferable.

As long as the flexural rigidity and the rate of change of the flexural rigidity are in the above-mentioned range (temperature change of 20 ° C. to 50 ° C.), resin containing a filler such as pigment or fiber may be used. The above resin having a flexural rigidity of 1 GPA at room temperature and a rate of change of the flexural rigidity of 10% or less in a temperature range of 20 ° C. to 50 ° C. is more preferable.

In particular, among the members constituting the casing, the pump actuator unit 3 and the pump valve seat unit 2, that is, the members that directly form the pump chamber have a bending rigidity at room temperature as described above of 1 GPA, And,
It is preferable to use a resin having a rate of change in flexural rigidity of 15% or less in a temperature range of 20 ° C to 50 ° C.

The piezoelectric body 15 used as a driving source of the piezoelectric pump of the present invention is made of a ceramic material such as barium titanate, lead titanate, or lead zirconate titanate, or a mixture of polyfukkavinylidene, fukkavinylidene and trifukkavinylidene. An organic piezoelectric element such as a copolymer is used.
Formed into a 2-3mm flat plate, metal deposition on both sides,
The electrodes 13a and 13b are formed by laminating metals by baking, bonding a metal foil, applying a metal coating agent, or the like.

The piezoelectric body 15 constituting the piezoelectric vibrator 12 used in the piezoelectric pump of the present invention has a dielectric constant of 5%.
000 or less, and the piezoelectric strain constant d ₃₁ is 200 × 10 ^−12.
Those having m / v or more are preferred. In the piezoelectric pump of the present invention, a piezoelectric body 15 having such a dielectric constant and a piezoelectric distortion constant is used, and a material surrounding the piezoelectric body 15 has a large flexural rigidity and a material having a small temperature dependence of flexural rigidity. Therefore, even when used at a temperature higher than the normal temperature of 40 ° C. to 50 ° C., the bending rigidity of the casing does not significantly decrease, so that the casing does not deform like a conventional pump, and the pump flow rate and pump discharge pressure do not change. And a piezoelectric pump excellent in durability with little change with time can be obtained.

[0019]

Table 1 shows an example in which Examples 1 and 2 of the piezoelectric pump of the present invention are compared with Comparative Examples 1 to 3 of the conventional piezoelectric pump. As a casing material, Example 1 is a PPS resin, Example 2 is a PSF resin, Comparative Example 1 is a PP resin, Comparative Example 2 is a POM resin, and Comparative Example 3 is a PSF resin. used. The structures and materials used other than the casing material are the same in Examples and Comparative Examples. The bending stiffness of the casing is set to 1 GPA or more in both the example and the comparative example. The change rate of the bending stiffness due to the temperature is set to 15% or less in Examples 1 and 2 and Comparative Example 3, Comparative Examples 1 and 2 are 15% or more, and Comparative Example 3 is an example using a piezoelectric body having a dielectric constant of 5000 or more and a temperature change rate of a flexural rigidity of 15% or less. .

The piezoelectric vibrator 12 has a dielectric constant and a lateral piezoelectric strain constant (d ₃₁ ) shown in Table 1 on both sides of a phosphor bronze having a diameter of 50 mm and a thickness of 50 μm.
A bimorph-type piezoelectric body formed by bonding two PZT-based piezoelectric ceramics having a thickness of 0.65 mm was used. Also,
The outside of each piezoelectric body was molded with a silicon-based elastic elastomer, which was used as a piezoelectric vibrator 12.

As the suction side and discharge side valves 9a and 9b, dimethyl silicone rubber bulky type valves are used, and five types of piezoelectric pumps having the structure shown in FIG. 1 (Examples 1 and 2 and Comparative Examples 1 and 2) are used. 3) Made. The following durability tests were performed on these five types of piezoelectric pumps. At room temperature, an alternating current of 200 V and 50 Hz was applied to drive the pump to convey water, and the amount of water flowing per minute (flow rate W _{0 at the} beginning of operation) was measured. Further, the pressure at the outlet side when the flow rate was set to zero by closing the outlet of the pump was measured, and this was also defined as the initial discharge pressure V ₀ . After that, the water was discharged, and the pump was placed in a thermostat at 45 ° C., and while the pump was driven by applying an alternating current of 200 V and 50 Hz, air was conveyed for 1000 hours. extraction, under the same driving conditions, at room temperature again, water was allowed to transport, to measure the flow rate W _t between the discharge pressure V _t at that time, the flow rate change rate of the pump {(1-W _t
/ W ₀ ) × 100} and the rate of change in discharge pressure {(1-V _t /
V ₀ ) × 100 °, and the results are shown in Table 1.

In the case of an ideal pump without deterioration, these rates of change are zero. The smaller the value, the smaller the change in the flow rate of the pump and the change in the discharge pressure, which means that the performance of the pump is good. I do. In addition, the above-mentioned 5
1000 kinds of deformation of the casing of the piezoelectric pump
Comparison was made before and after the time drive, and the results are also shown in Table 1.

[0023]

[Table 1]

As can be seen from Table 1, the pumps of Comparative Examples 1 and 2 using a material having low temperature dependence of bending stiffness as a casing, when used at a temperature higher than room temperature (45 ° C.), have both a flow rate and a discharge pressure. On the other hand, the pump performance of the pumps according to the first and second embodiments of the present invention is small, and the pump performance is remarkably improved. Was.

Further, in the pumps of Comparative Examples 1 and 2, the rigidity of the material forming the casing is insufficient, and the pump is clearly driven around the pump chamber by the long-term driving at 45 ° C. for 1000 hours. Deformation was confirmed by the shape sensor. On the other hand, in the pumps of Examples 1 and 2, such deformation was not observed. Furthermore, in the case of the pump of Comparative Example 3 using a piezoelectric element having a dielectric constant of more than 5000, when the air is conveyed at 45 ° C., the dielectric constant which is originally large even at room temperature is further increased due to a rise in temperature. Despite the use of a casing made of a material having a small rate of change in rigidity due to temperature, although not as large as the pumps of Comparative Examples 1 and 2, deformation of the casing was slightly observed, and the pump performance also deteriorated. I was

[0026]

According to the piezoelectric pump of the present invention, at least a part of the casing has a bending rigidity of 1 GPA or more at room temperature in a piezoelectric pump in which a piezoelectric body which is a driving source of a transported object is loaded in a casing. Yes and temperature change is 2
In a temperature range of 0 to 50 ° C., the piezoelectric body (15) is made of a resin having a temperature change rate of the flexural rigidity of 15% or less, the dielectric constant of the piezoelectric body (15) is 5000 or less, and the lateral piezoelectric strain constant d ₃₁ is By setting the pressure to 200 × 10 ⁻¹² m / v or more, even when the pump is driven for a long time at a temperature of 40 ° C. to 50 ° C. which is higher than the normal temperature, the pump performance such as the flow rate and discharge pressure of the carrier fluid with time. It is possible to provide a piezoelectric pump that is less subject to change and has excellent durability.

Further, the piezoelectric pump of the present invention according to claim 2 is
2. The pump according to claim 1, wherein the casing is detachably attached to the pump actuator unit (3) and the pump actuator unit (3), and has a suction port (8a) and a discharge port (8b). Valve unit (1) provided between the pump suction / discharge unit (1) and the pump actuator unit (3), and having a suction side and a discharge side check valve (9a, 9b). 2), the periphery of the piezoelectric body (15) is fixed in the pump actuator unit (3), and the electrodes (1) of the piezoelectric body (15) are fixed.
By applying a voltage between 3a and 13b) to vibrate the piezoelectric body (15), the fluid is sucked through the suction-side check valve (9a) and discharged through the discharge-side check valve (9b). In this way, 40 ° C to 5
Even when driven at a temperature of 0 ° C. for a long time, there is little change over time in pump performance such as flow rate and discharge pressure of a carrier fluid,
A piezoelectric pump having excellent durability can be provided.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of a piezoelectric pump according to the present invention.

FIG. 2 is an exploded sectional view of FIG.

[Explanation of symbols]

 Reference Signs List 1 pump suction / discharge unit 2 pump valve seat unit 3 pump actuator unit 8a suction port, 8b discharge port 9a suction-side check valve 9b discharge-side check valve 10 envelope 11 coating material 12 piezoelectric vibrator 13a, 13b film Electrode 14a, 14b Lead wire 15 Piezoelectric body 16 Pump chamber 17 O-ring

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Katsuhiro Mizuno 1060 Narita, Odawara-shi, Kanagawa Kasei Optonics Co., Ltd. Odawara Plant

Claims (2)

[Claims] 1. A piezoelectric body (15) which is a driving source of a body to be conveyed.
A piezoelectric pump in which at least a part of the casing has a flexural rigidity of 1 GPA or more at room temperature and a temperature change of 20 to 50 ° C. in a temperature range of 20 to 50 ° C. Change rate is 15
% Or less, the dielectric constant of the piezoelectric body (15) is 5000 or less, and the horizontal piezoelectric strain constant d ₃₁ is 200 or less.
A piezoelectric pump characterized by being at least 10 ^-12 m / v. 2. The piezoelectric pump according to claim 1, wherein the casing is detachably attached to the pump actuator unit (3) and the pump actuator unit (3), and has a suction port (8a) and a discharge port (8b). Pump suction / discharge unit (1) and the pump suction / discharge unit (1) and the pump actuator unit (3), and have suction side and discharge side check valves (9a, 9b). The pump actuator unit (3) includes a piezoelectric body (1).
5) is fixed, and the electrodes (13a,
A piezoelectric element is characterized in that a fluid is sucked through a suction-side check valve (9a) by applying a voltage during 13b) to vibrate the piezoelectric body (15), and is discharged through a discharge-side check valve (9b). pump.