JPS61123782A - Piezoelectric type pump - Google Patents

Abstract

PURPOSE:To prevent the flow rate of a pump from lowering, by forming a container for confining the outer periphery of a piezoelectric element from a material having a greater thermal expansion coefficient so that the lowering of amplitude characteristic of the piezoelectric element may be compensated when the temperature of the atmospheric temperature is lowered. CONSTITUTION:An asymmtric type BIMORPH 3 is disposed in a container 1 for a piezoelectric pump, through the intermediary of a seal member 4. This container 1 is arranged to confine the outer periphery of the asymmtric type BIMORPH 3, and is made of a material having a greater thermal expansion coefficient. Therefore, even if the atmospheric temperature lowers and the amplitude characteristic of the asymmetric type BIMORPH 3 is lowered, the container itself contracts to curve the asymmetric type BIMOPRH 3 so that the operating area thereof is increased, thereby it is possible to prevent the flow rate of the pump from lowering.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF THE INVENTION The present invention relates to a fluid pump using a piezoelectric ceramic as a driving source for pressurizing and transporting fluid.

2. Description of the Related Art Conventionally, in this type of pump, as shown in FIG. Room 5 was configured. According to this configuration, when the environmental temperature decreases, the amplitude becomes smaller and the amount of expansion and contraction of the pump chamber 5 decreases due to the temperature characteristics of the piezoelectric element 3, even though the same AC drive voltage is applied. As a result, it was not possible to prevent the phenomenon in which the flow rate of the pump decreased significantly. Since the pump is used, it is not desirable for the pump flow rate to vary widely depending on the environmental temperature.

Problems to be Solved by Chimei The present invention provides a piezoelectric pump with stable performance, in which the pump flow rate does not decrease much even when the environmental temperature decreases.

Means for Solving the Problems In order to achieve this object, the present invention provides the following features:
The piezoelectric element is made of a material that fits dimensionally, and the material of the container has a large coefficient of thermal expansion for the piezoelectric element, and the piezoelectric element is configured to be able to move in the axial direction. “It connects elements.

Operation With this configuration, when the environmental temperature decreases, the container having a large coefficient of thermal expansion contracts more than the piezoelectric element. Then, since the piezoelectric element is constrained and fitted at its outer periphery, it receives a force in the radial direction, and as a result, it generates displacement in the axial direction. Since the piezoelectric element is movable in the axial direction, the piezoelectric element is distorted in the axial direction.As a result, the operating area for expansion and contraction of the piezoelectric element increases, and the piezoelectric element expands and contracts due to temperature. It is possible to compensate for the decrease in amplitude and reduce the decrease in pump flow.

EXAMPLE Hereinafter, an example of the present invention will be explained using FIGS. 1 to 5.

In FIG. 1, the container 1, the inflow channel 6, and the outlet channel 7 are integrally formed, and each communicates with the pump chamber 5. The inflow channel 6 is provided with a check valve 8 that extends in the forward direction toward the outlet channel 7 , and the outlet channel 7 is provided with a check valve 9 that extends in the reverse direction toward the inflow channel 6 . When the volume of the pump chamber 5 increases, fluid is sucked in from the inflow channel 6, and when the volume of the pump chamber 5 decreases, fluid is discharged from the outlet flow path 7. As shown in FIGS. 2a and 2b, the piezoelectric element 3 has a structure in which a metal disk 10 and a piezoelectric ceramic 11 are bonded together with an adhesive, and electrodes are printed on the surface of the piezoelectric ceramic 11. (not shown) This is typically what is available on the market as a piezoelectric buzzer. This piezoelectric element 3 is fitted into the container 1 with its outer periphery 12 restrained, and a sealing material 4 for sealing between the container 'a1 and the piezoelectric element 3 is pressed and positioned by a sealing material holding fitting 13. It is fixed by a lid 14. Seal material holding fitting 1
3 is not in contact with the piezoelectric element 3, leaving a gap, and the sealing material 4 is made of an elastic polymer such as rubber, and when the piezoelectric element 3 receives a force outward from the pump chamber 5, the sealing material It is possible to displace within the elastic range of 40.

The operation will be explained using the above configuration. When an AC driving voltage (not shown) is applied to the piezoelectric element 3, the piezoelectric element 3 is deformed into irregularities. Due to the change in the volume of the pump chamber 5 due to the deformation of the irregularities, a fluid flow from the inlet channel 6 to the outlet channel 7 is generated. Now, consider a case where the piezoelectric element 3 and the container 1 are fitted together as shown in FIG. 3 at an environmental temperature of 20°C. When a voltage is applied to push out the fluid in the pump chamber 5, the piezoelectric element 3 moves ΔL1 as shown by the dotted line.
Just make a bend. The operating area at this time is displayed as A1. When the environmental temperature decreases from this state, the container 1 contracts and the piezoelectric element 3 bends outward from the pump chamber 5 as shown in FIG. This is because the volume 17's 1 and the end 15 of the outer periphery of the piezoelectric element 3 contract.As a result, the operating area A2 of the piezoelectric element 3 moves outward from the outer periphery 16 of the pump chamber 5. Therefore, AI < A2
becomes. When a voltage is applied to the piezoelectric element 3, it bends by ΔL2. The curve values △L1 and △L2 are determined by the voltage applied to the piezoelectric element 3 and the environmental temperature, and △L1〉△L2
However, since AI < A2, the volume change △v of the pump chamber 5 is △V1 oc △r, 1- AI , △
Since there is a relationship between V20c△L2 and A2, △v1 and △v can be obtained by optimizing the fitting dimensions and the dimensions of the piezoelectric element 3.
2. As shown in Fig. 4, piezoelectric element 3
The reason for the bending is that the sealing material 4 is an elastic body. To explain the pump characteristics using Figure 5, as the environmental temperature changes, it becomes a straight line! It changes like this. This is a characteristic of conventional products, and in the case of the present invention, when assembled and fitted to a metal plate at 20°C, when the environmental temperature becomes 20°C or lower, the line becomes like a straight line (■), and the flow rate decreases due to the temperature drop. will be improved. This is because this was compensated for by increasing the operating area A2.

Effects of the invention Attach a piezoelectric element. The thermal expansion coefficient of the container is increased, the outer periphery of the piezoelectric element is fitted, and the piezoelectric element is forcibly bent due to the difference in the amount of thermal contraction between the container and the piezoelectric element, and as a result, the operating area for expansion and contraction is increased. Due to this, the expansion of the piezoelectric element due to a drop in the environmental temperature
It is possible to compensate for the decrease in contraction amplitude and minimize the decrease in pump flow rate.

[Brief explanation of the drawing]

, FIG. 1 is a side sectional view of a piezoelectric pump according to an embodiment of the present invention, FIG. 2 a is a front view of an asymmetric bimorph, and FIG. Figure 3 is a partial side sectional view of the asymmetric bimorph part at different assembly temperatures;
The figure is a side sectional view of the asymmetric bimorph part when the temperature decreases, FIG. 5 is a graph explaining the correlation between environmental temperature and pump flow rate, and FIG. 6 is a partial side sectional view of a conventional piezoelectric pump. 1...-container, 3-... asymmetric bimorph, 4...
... Seal material, 5 ... Pump chamber, 6 ...
- Inflow channel, 7-... Outlet channel, 8... Check valve, 9... Check valve, 10... Metal disk, 11- ...Piezoelectric ceramic. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 (1! II

Claims (1)

[Claims] An asymmetrical bimorph consisting of a disk-shaped piezoelectric ceramic attached to a metal disk is restrained in the radial direction in a container having an inlet flow path and an outlet flow path to form an attached pump chamber, Each is provided with a check valve, and an AC drive voltage is applied to the asymmetric bimorph to inflate and inflate the pump chamber.
and causing a fluid flow from the inlet channel to the outlet channel, and the container is made of a material with a larger thermal expansion coefficient than metal, and as the environmental temperature decreases, the difference in shrinkage between the container and the metal disc A piezoelectric pump in which the operating area for expansion and contraction of the asymmetric bimorph is increased by the force of.