JPH07301180A - Piezoelectric pump - Google Patents

Abstract

PURPOSE:To provide a compact pump by holding a peripheral part of a disc- shaped piezoelectric vibrator with flat casings provided with an intake port and a discharge port for fluid on one side, and setting an electrostatic capacity of the piezoelectric vibrator after installation to indicate a specific value to the electrostatic capacity of the piezoelectric vibrator before installation. CONSTITUTION:A peripheral part of a disc-shaped piezoelectric vibrator 13 is held with flat casings 11a-11c having shield materials of an outer diameter similar to the diameter of the piezoelectric vibrator 13, and an inner diameter of 80% or more of the diameter of the piezoelectric vibrator 13 to be fixed. The casing 11a is provided with an intake port and a discharge port 16, 16' for fluid, and the casing 11b is provided with intake/discharge check valves 12, 12'. In this piezoelectric pump, the piezoelectric vibrator 13 which indicates an electrostatic capacity after installation of 90% or more of the electrostatic capacity of the piezoelectric vibrator 13 before installation in a commertial power supply frequency is used. The pump can thus be formed compact without deteriorating pump characteristics.

Description

Detailed Description of the Invention

[0001]

The present invention relates to medical equipment, industrial equipment,
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric pump used in physics and chemistry equipment and the like, and particularly to a small piezoelectric pump.

[0002]

2. Description of the Related Art A conventional piezoelectric pump will be described with reference to FIG. 1. A peripheral portion of a piezoelectric vibrator 3 is hermetically supported by a fixing shield member 4 provided on an inner peripheral surface of a casing 1.
By applying an AC voltage e to the piezoelectric vibrator 3 to vibrate the piezoelectric vibrator 3, the fluid is sucked into the pump chamber through the suction check valve 2 through the suction port 6, and the fluid sucked into the pump chamber is discharged. The check valve 2'is configured to discharge from the discharge port 6 '.

At present, a piezoelectric pump using a disk-shaped piezoelectric vibrator having a diameter of about 50 mm is mainly used, but there is a strong demand for further miniaturization of the piezoelectric pump. As a means therefor, a disk-shaped piezoelectric vibration is used. The diameter of the child was reduced to 40 mm or less, and the piezoelectric vibrator was mounted in the relatively small casing.

[0004]

However, the design guideline for miniaturization of the piezoelectric pump has not been clarified, and the design guideline is merely a relative miniaturization of the casing of the conventional size piezoelectric pump. There was a problem that sufficient pump performance was not obtained with respect to the expected value, or the piezoelectric vibrator was damaged during driving.

[0005]

In view of the above-mentioned situation, the inventors of the present invention have conducted extensive studies, and as a result, found that the capacitance of the piezoelectric vibrator in the state of being mounted in the casing is static before the mounting. However, it was found that the degree of decrease in such a small pump is an extremely effective index for grasping the mounting state of the piezoelectric vibrator and the performance of the piezoelectric pump, and the present invention has been made. It came to completion.

That is, according to the present invention, a shield material having an outer diameter equal to the diameter of the piezoelectric vibrator and an inner diameter of 80% or more of the diameter of the piezoelectric vibrator is attached to the peripheral portion of the disk-shaped piezoelectric vibrator. A piezoelectric pump that is fixed by sandwiching it with a flat casing, has a fluid suction port and a fluid discharge port on one side of the flat casing, and a suction and discharge check valve for each of these, and is mounted inside the casing. Another feature of the present invention is to provide a small piezoelectric pump characterized in that the electrostatic capacity of the piezoelectric vibrator is 90% or more of the electrostatic capacity of the piezoelectric vibrator before being mounted at a commercial power supply frequency.

The present invention will be described in detail below.

In order to solve the above problems in a small piezoelectric pump, in the present invention, the capacitance of the piezoelectric vibrator mounted in the casing is the capacitance of the piezoelectric vibrator before mounting at the commercial power frequency. Must be 90% or more. When the capacitance is less than 90%, the amplitude of the piezoelectric vibrator is significantly suppressed, and as a result, sufficient pump characteristics cannot be obtained. Furthermore, in extreme cases, the piezoelectric vibrator may be damaged during driving. It is preferable that the capacitance of the piezoelectric vibrator is closer to the value before it is mounted in the casing of the pump. Therefore, the capacitance of the piezoelectric vibrator after mounting in the casing is more preferably 98% or less of the capacitance before mounting.

As the piezoelectric body constituting the piezoelectric vibrator used here, ceramic type or organic type can be used.
Specific examples thereof include lead titanate and lead zirconate titanate for ceramics, and polyvinylidene fluoride for organics. Since these piezoelectric vibrators are electrically insulating, an insulating coating material such as epoxy resin may be applied to the surface thereof.

The check valve is not particularly limited as long as it can be opened when the fluid is sucked in and discharged, but a duck bill type valve, an umbrella type valve or the like can be used.

It is preferable that the piezoelectric material has a dielectric constant of 3000 or more and an electromechanical coupling coefficient Kp of 50% or more. Dielectric constant is 3
If it is less than 000 or the electromechanical coupling coefficient Kp is less than 50%, the displacement amount and the generated force may decrease, and the discharge flow rate and discharge pressure of the pump may decrease.

The diameter of the piezoelectric vibrator is preferably 50 mm or less, and more preferably 40 mm or less from the viewpoint of miniaturization of the piezoelectric pump. However, if the diameter is too small, the device characteristics may be deteriorated, which may lead to the deterioration of pump characteristics. Since this tendency begins to appear when the diameter becomes smaller than 20 mm, 20 mm or more is preferable.

The thickness of the piezoelectric vibrator is 0.8 to 1.5 mm
In the range, it is preferable that the capacitance is selected in consideration of the above-mentioned diameter so that the electrostatic capacity at the commercial power frequency before mounting the piezoelectric pump is 70 to 180 nF. If the electrostatic capacitance is out of this range, the element characteristics may be deteriorated and the pump characteristics may be deteriorated.

The material of the casing on which the piezoelectric vibrator is mounted is not particularly limited and may be appropriately selected depending on the purpose of use of the pump, but polypropylene, polyacetal or the like can be used in terms of chemical resistance and the like.

The material of the shield material is not particularly limited as long as the adhesiveness with the piezoelectric vibrator is maintained, and examples thereof include silicon rubber. The upper limit of the inner diameter of the shield material must be smaller than the diameter of the piezoelectric vibrator. However, if the inner diameter is too close to the diameter of the piezoelectric vibrator, the adhesion with the piezoelectric vibrator may not be maintained in some cases.
95%.

The thickness of the shield material is preferably 0.1 to 1.0 mm, and when the thickness is less than 0.1 mm, the piezoelectric vibrator after being mounted in the casing is kept at a commercial power frequency. There is a case where a decrease in the electric capacity occurs, and if it is attempted to suppress this decrease, the adhesion between the piezoelectric vibrator and the shield material deteriorates, which is not preferable. On the other hand, if the thickness exceeds 1.0 mm, the element characteristics of the piezoelectric vibrator may be deteriorated and the pump characteristics may be deteriorated, which is not preferable.

[0017]

EXAMPLES The present invention will be described below with reference to examples.
The present invention is not limited to these.

A vector impedance meter was used to measure the capacitance, dielectric constant and electromechanical coupling coefficient shown in the present invention.

FIG. 2 is a vertical sectional view showing an embodiment of the small piezoelectric pump of the present invention, and FIG. 3 is a top view thereof. 2 and 3
11a, 11b, 11c are casings, and the casing 11a is provided with a suction port 16 and a discharge port 16 ', and the casing 11b is provided with a suction check valve 12 and a discharge check valve 12'. The check valve used was an umbrella type. The piezoelectric vibrator 13 is hermetically supported via a fixing shield material 14 provided on the inner peripheral portion between the casings 11b and 11c. The size of the assembled casing, excluding the nozzle, is 40 x 36 x 2
0 mm, the nozzle has an inner diameter of 4 mmφ and a length of 10 mm,
The material is polyacetal.

The fixing shield material is a ring made of silicon rubber having a flat cross section in the radial direction, and has an inner diameter of 26 mm and an outer diameter of 30.
mm and thickness 0.3 mm.

The element is fixed in this casing by fastening the four corners of the casing with M3 fixing screws 17.

The piezoelectric vibrator of this embodiment is composed of Pb, Z
Dielectric constant 3900, electromechanical coupling coefficient 64 obtained by sintering and machining a complex oxide composed of r, Ti and La
%, Two piezoelectric plates adhered via a phosphor bronze plate are used, and the capacitance is 84 nF at a diameter of 30 mm, a thickness of 1.0 mm and 50 Hz.

Adjusting the tightening force of the fixing screw when mounting the piezoelectric vibrator in the casing of FIG.
A small piezoelectric pump in which the capacitance of the piezoelectric vibrator at z is 80 nF (95% before mounting, the same applies to the following, Example 1), 78 nF (93%, Example 2), 72 nF (86%, Comparative Example 1). 2V by applying AC voltage of 200V, 50Hz to
Water at 5 ° C was circulated. The pump characteristics obtained at this time are shown in Table 1.

[0024]

[Table 1]

[0025]

As described above, according to the piezoelectric pump of the present invention, the size can be reduced without impairing the pump characteristics.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing the structure of a conventional piezoelectric pump.

FIG. 2 is a vertical sectional view showing an embodiment of the present invention.

FIG. 3 is a top view showing an embodiment of the present invention.

[Explanation of symbols]

 1, 11a, 11b, 11c: Casing 2, 12: Suction check valve 2 ', 12': Discharge check valve 3, 13: Piezoelectric element 4, 14: Fixing shield material 5, 15: Lead wire 6, 16 : Suction port 6 ', 16': Discharge port 17: Fixing screw

Claims (1)

[Claims] 1. A flat casing in which a shield member having an outer diameter that matches the diameter of the piezoelectric vibrator and an inner diameter that is 80% or more of the diameter of the piezoelectric vibrator is attached to the peripheral portion of the disk-shaped piezoelectric vibrator. In a piezoelectric pump in which a fluid suction port and a fluid discharge port are provided on one side of the flat plate-like casing, and a suction and discharge check valve is provided for each of them, A small-sized piezoelectric pump having a capacitance of 90% or more of the capacitance of the piezoelectric vibrator before mounting.