JPH05172060A - Micropump - Google Patents

Abstract

PURPOSE:To provide a micropump which can continuously feed liquids without stopping its functions as a pump as air bubbles enter it, even if the whole pump is miniaturized. CONSTITUTION:A micropump 10 comprises a check valve 4 installed within a pump room 11 which is divided into two parts, with the direction of flow in the check valve 4 being parallel to the direction in which a piezoelectric element 1 is deformed by vibration. Also, a small space is provided between a valve seat 2 and a valve body 3 to allow easier passage of air bubbles 5. In this case, the valve body 3 is manufactured by a thin film of silicone rubber which can be elastically deformed by a large amount, and is coated at its surface with Teflon.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a micro-pump using a laminated or bimorph type piezoelectric element, and more particularly to a bubble removing device when bubbles are mixed in a pump chamber.

[0002]

2. Description of the Related Art A pump to which a laminated or bimorph type piezoelectric element is applied is generally used as a small flow rate pump. This is because the vibration deformation amount of the piezoelectric element is several tens of μm.
This is because it is small and it is difficult to deliver a large flow rate with the amount of deformation of only the element. Usually, in such a piezoelectric pump, a part of the casing of the pump chamber is composed of a piezoelectric element, and the flow passages near the inlet and outlet of the fluid are formed, as disclosed in, for example, JP-A-61-28776. It has a structure in which a check valve is attached to the. In the pump configured as described above, when an AC voltage is applied to the piezoelectric element, the element vibrates and deforms, the fluid in the pump chamber is pushed out, and the pump can function as a pump.

FIG. 2 shows an example of the structure of a micro-pump 10 to which a conventional piezoelectric element is applied. here,
Two bimorph type piezoelectric elements 1 above and below the pump chamber 11.
And a check valve 4 in the flow path near the suction port 20 and the discharge port 21 to suppress the return to the upstream side. As the check valve 4 used in such a pump, for example, a structure as shown in FIGS. 3 (a) and 3 (b) can be considered. Both of the check valves 4 are provided with a valve seat 2 which is a fixed component and an elastically deformable valve body 3 to control the flow. The fluid that has flowed into the pump chamber 11 flows forward (rightward in the drawing), and the central portion of the valve body 3 is elastically deformed in the flow direction by the fluid force and flows out from the slit portion of the valve body 3. On the other hand, in the flow in the reverse direction (leftward in the figure), the valve body 3 blocks the flow to prevent the reverse flow to the upstream side. If the piezoelectric pump 10 is downsized, the check valve 4 itself must be downsized. For example, when the outer diameters of the suction port 20 and the discharge port 21 are set to about 1 mm, it is necessary to fabricate each flow path portion of the check valve in a size of about 0.2 to 0.3 mm. When a fluid containing bubbles 5 (generally having a size of 1 to 2 mm) flows into such a pump 10, as shown in FIG. 4, the bubbles 5 stay in the narrow flow passage of the check valve 4, It is expected that the pump 10 cannot be discharged to the outside of the pump 10, and as a result, the function as the pump cannot be achieved.

Further, as the size of the pump 10 is reduced, the movable portion of the valve body 3 becomes very small, so that a relatively large force is required to deform the valve body 3, and the repulsive force of the piezoelectric element 1 causes the valve to move. There is a problem that the body 3 cannot be deformed sufficiently.

[0005]

Since a pump used for medical or pharmaceutical equipment requires a micro-pump for transferring a flow rate of several cc or less, it has excellent controllability and can easily be adapted to miniaturization. It can be said that the piezoelectric pump is one of the effective methods. However, in order to reduce the size of the pump, it is necessary to reduce the size of the check valve mounted on the pump body.
The cross-sectional area of the flow passage in the check valve becomes very narrow. Therefore, when a fluid mixed with bubbles flows into the pump, the bubbles may not be able to pass through the narrow passage portion of the check valve and may remain inside the pump chamber. Due to the influence of the surface tension, the bubbles that remain once cannot be discharged to the outside of the pump by the force of the pump itself, the bubbles gradually accumulate, and finally there is a problem that the function of the pump cannot be fulfilled.

As a countermeasure, it is conceivable to attach a dedicated pressurizing means for forcibly eliminating air bubbles, but if air bubbles are removed each time, the usability is poor and the size of the entire pump becomes large. There is a problem. Also, as another means, in order to increase the flow passage cross-sectional area of the check valve, it is conceivable that the check valve is not mounted on the pump body but is arranged outside.
This leads to an increase in the size of the entire pump, making it unsuitable as a pump for trace amounts.

An object of the present invention is to provide a piezoelectric element application pump that handles a small amount of fluid of about several cc, and even if bubbles are mixed inside the pump, the bubbles are discharged by the pump's own force without stopping the pump function. It is to provide a micro pump capable of continuous liquid feeding.

[0008]

In order to achieve the above object, a check valve is installed inside a pump chamber so that a size for allowing passage of bubbles can be obtained without upsizing the device. did.

[0009]

By configuring as described above, the check valve can be manufactured with a size approximately the same as the diameter of the piezoelectric element even when the entire pump is downsized, so that the flow path of the check valve is blocked. A sufficient size can be ensured so that bubbles can pass through the area. With this, it is possible to eliminate a portion where bubbles easily remain from each flow passage of the pump, that is, a narrow flow passage of the check valve. Therefore, even if air bubbles are mixed in the pump, they can be smoothly discharged to the outside of the pump, so that the function of the pump is not impaired.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of a micro pump 10 of the present invention. Here, the check valve 4 is connected to the pump chamber 1
The pump chamber 11 is divided into two parts, and the flow direction of the check valve 4 and the vibration deformation direction of the piezoelectric element 1 are parallel to each other. Further, a slight gap is provided between the valve seat 2 and the valve body 3 so that the bubbles 5 can easily pass through.
In this case, the valve body 3 is made of thin-film silicon rubber or the like having a large amount of elastic deformation, and its surface is coated with Teflon to improve water repellency. With this configuration, the check valve 4 can be manufactured to have a size substantially the same as the diameter of the piezoelectric element 1 even when the entire pump 10 is downsized, so that the flow passage cross-sectional area of the check valve 4 can be reduced. It can be set large enough. Therefore, there is no place where the bubbles 5 are likely to stay inside the pump 10, and the bubbles 5
Even if is mixed, it is quickly discharged to the outside, so the pump function is not impaired. Further, since the single check valve 4 can prevent the backflow, the number of parts can be reduced to achieve high reliability and the manufacturing can be performed at low cost.

Next, FIG. 5 shows an example of a modified application of the present invention. In this, the valve seat 2 part of the check valve 4 is configured as one part of the pump 10 main body. That is, this is an example in which the pump body is configured to have a part of the function of the check valve. As is clear from the figure, since the valve seat 2 portion can be omitted, leakage from the joint between the valve seat 2 and the pump 10 can be prevented, so that a highly reliable pump can be realized. Further, since the number of parts constituting the pump 10 is reduced, the manufacturing cost can be further reduced.

The structure of the check valve 4 attached to the present pump may be configured such that the valve seat 2 and the valve body 3 are separated from each other by a constant distance T, as shown in FIG. 6, for example. is there.
With this structure, the discharge side flow path diameter Do of the valve can be set to be as large as the valve suction side flow path diameter Di, so that the bubbles 5 are more easily discharged.

Further, as shown in FIG. 7, it is possible to provide the check valve 4 with a plurality of suction ports 20. As a result, the plurality of bubbles 5 that have entered the pump chamber 11 are not
Since it flows dispersedly in each of the suction ports 20, the gas is promptly discharged to the outside of the pump 10. Therefore, the flow rate reduction time due to the inclusion of the bubbles 5 can be shortened. The shape of the suction port 20 is not limited to the straight shape.
For example, as shown in FIG. 8, the shape of the suction port 20 may be tapered. As a result, the bubbles 5 inside the pump chamber 11 can be smoothly guided to the suction port 20 of the check valve 4, so that the flow rate reduction time due to the inclusion of the bubbles 5 can be further shortened.

[0015]

As described above, according to the present invention, it is possible to realize a small amount pump capable of continuous liquid feeding without stopping the pump function due to bubbles mixed in the pump even when the entire pump is downsized.

Further, since a single check valve can prevent the backflow, the number of parts can be reduced to improve the reliability and the manufacturing cost can be reduced.

[Brief description of drawings]

FIG. 1 is a top view (a) and a cross-sectional view (b) of a micropump showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a structural example of a conventional piezoelectric element-applied pump.

FIG. 3 is a cross-sectional view of an example of a check valve used in a conventional piezoelectric pump.

FIG. 4 is a cross-sectional view showing a state of retention when bubbles are mixed in a check valve used for a conventional piezoelectric pump.

FIG. 5 is a cross-sectional view of a micro pump in which the valve seat component of the check valve is configured as one component of the pump body.

FIG. 6 is a cross-sectional view of a micro-pump configured so that a space between a valve seat and a valve body of a check valve is separated by a certain amount.

FIG. 7 is a cross-sectional view of a micro pump having a plurality of check valves as suction ports.

FIG. 8 is a cross-sectional view of a micro pump having a tapered suction port shape.

[Explanation of symbols]

1 ... Piezoelectric element, 2 ... Valve seat, 3 ... Valve body, 4 ... Check valve, 5 ...
Bubbles, 10 ... Pump, 11 ... Pump chamber, 20 ... Suction port,
21 ... Discharge port.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yusuke Takagi 4-6, Surugadai Kanda, Chiyoda-ku, Tokyo Hitachi, Ltd.

Claims (3)

[Claims] 1. A pump comprising a piezoelectric element and a control device for driving and controlling the piezoelectric element, wherein a check valve or a one-way fluid resistance is installed inside the pump chamber, and the pump chamber is divided into two parts. Characteristic micro pump. 2. A pump including a piezoelectric element and a control device for driving and controlling the piezoelectric element, wherein a part of a function of a check valve or a one-way fluid resistance is attached to the pump body. A small amount of pump. 3. A pump including a piezoelectric element and a control device for driving and controlling the piezoelectric element, wherein a check valve or a one-way fluid resistance is installed inside the pump chamber, and the pump chamber is divided into two parts. A method for removing bubbles from a micro-pump.