JPH03225086A - Micropump - Google Patents

Abstract

PURPOSE:To bond a driving piezoelectric element on a diaphragm uniformly and easily in a micropump formed of a base plate, a diaphragm, and the like by providing the diaphragm center part with a supporting part with the tip thereof in contact with the base plate. CONSTITUTION:A diaphragm 6 is supported not only at its peripheral part by the engagement with a surface plate 3 but also at its center part by a protrusion 81. Accordingly, at the time of bonding a driving piezoelectric element 7 on the diaphragm 6, because of the protrusion 81 becoming a support and a stopper to oppose the pressing force to the piezoelectric element 7, the surface of the diaphragm 6 is hardly curved, and its flatness is maintained. The piezoelectric element 7 can be therefore bonded uniformly and stably, and even if the piezoelectric element 7 is pressed rather hard at the time of bonding, there is no fear of damaging peripheral joints, thus facilitating bonding work.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a micropump to which micromachining technology is applied, and particularly to a mounting structure between a piezoelectric element for driving a micropump and a diaphragm.

[Prior art] Regarding the micropump applying St micromachining technology, for example, Nikkei Electronics Nα480
．． It is described on pages 135 to 139 (published August 21, 1989). The configuration of the micropump is as follows:
There are two-valve types (two inlet and outlet valves) and three-valve types (three intermediate valves in addition to the inlet and outlet valves), and each type has its advantages and disadvantages. I will not specifically discuss the advantages and disadvantages of each here.

Now, to explain the two-valve type, it is constructed as shown in Fig. 12. Two bulbs 202 and 203 and a diaphragm 204 are formed and bonded between them using a Si thin film plate 201 on a glass substrate 200, and the S
A glass plate 205 is bonded onto a thin film plate 201, and a diaphragm 204 is driven by a heat generating resistor 207 via an air layer 206. A bulb 202 is provided on the glass substrate 200.
An inlet port 208 and an outlet port 209 are provided, which respectively communicate with the pump. The pressure fluid in the chamber 210 is discharged to the outlet port 209, and when the diaphragm 204 returns to its original position due to the contraction of the air layer 206, the valves 202,
203 operate in opposite directions, drawing in fluid from the inlet port 208 and discharging it to the outlet port 209 via valve 2.
It is cut off by closing 03.

Since such micropumps are capable of precisely controlling minute amounts of flow, this suggests that they can be applied to medical applications (such as insulin administration for diabetic patients) and chemical analysis.

[Problems to be Solved by the Invention] By the way, using a piezoelectric element to drive the diaphragm of a micropump is advantageous because of good controllability of the piezoelectric element, and this fact itself is known. However, in order to fully utilize the piezoelectric effect of the piezoelectric element, it is necessary to bond it to the diaphragm evenly.
Adhesion of extremely thin membranes onto diaphragms was very difficult. In other words, in conventional micropumps, a thin film diaphragm is supported at its periphery, and the piezoelectric element is pressed onto the diaphragm while being bonded. Therefore, when the piezoelectric element is bonded, the diaphragm may bend and the surface may be damaged. In some cases, the flatness was not maintained at 11#, and adhesion was not performed well. Furthermore, if the pressing force applied to the piezoelectric element is excessive, the surrounding joints may be damaged, making it difficult to adjust the pressing force and making the bonding work extremely difficult.

The present invention has been made in order to solve such problems, and an object thereof is to provide a micropump in which a wire tube can be uniformly and stably attached to a diaphragm of a piezoelectric element for driving a micropump, and in which bonding work is easy. purpose.

[Means for Solving the Problems] In order to achieve the above object, the micropump according to the present invention has a sandwich structure of a substrate, a thin film plate, and a surface plate, and has a drive plate on a diaphragm formed on the thin film plate. In a two-valve or three-valve micropump in which a piezoelectric element is fixed and the peripheral part of the diaphragm is bonded to a surface plate, a support part is provided to support the center part of the diaphragm,
The tip of the support portion is provided so as to be in contact with the substrate.

The support portion is usually a bar-shaped projection, but it may also be a cylindrical projection or a protrusion provided in the diameter direction of the diaphragm, or the diaphragm itself may be brought into direct contact with the substrate instead of a protrusion-like support portion. You can also.

In addition, the diaphragm is formed not on the thin film plate but on the surface plate bonded on top of it, and on the other hand, the thin film plate is provided with a cylindrical protrusion whose bottom part is bonded to the substrate and whose tip touches the center of the diaphragm, allowing the fluid to flow into the substrate. The device is configured to inhale from the artificial port of the protrusion and discharge from the outlet port of the substrate through the central hole of the protrusion.

[Function] In the micropump of the present invention, the peripheral part of the diaphragm is bonded and supported by the surface plate, and the central part is supported by the support part whose tip (lower end) contacts the substrate. When bonding the piezoelectric element for use, the support part acts as a stopper and, together with the joint part around the diaphragm, sufficiently counters the pressing force against the piezoelectric element, so that the flatness of the diaphragm surface can be maintained. Therefore, piezoelectric elements can be bonded uniformly and stably, and bonding work is also easy.

The support of the diaphragm is further stabilized by forming the support portion as a cylindrical protrusion or a convex protrusion provided in the diametrical direction of the diaphragm. Furthermore, the same effect can be obtained by supporting the diaphragm itself in direct contact with the substrate instead of using the protruding support portion.

In addition, since the support part functions as a stopper in the operation of the diaphragm by the drive piezoelectric element, the amplitude is always constant, and stable quantitative discharge is possible. Note that since the amplitude is only on one side, the amount of ejection per time is reduced, but there is no practical problem because the total amount of ejection can be increased by increasing the number of ejections or increasing the drive voltage.

In addition, when the support part and the diaphragm are separated, the support part is formed as a cylindrical projection on a thin film plate, the bottom of the projection is joined to the substrate, and the tip is brought into contact with the center of the diaphragm. In addition to the above-mentioned stopper function, the protrusion also functions as a flow rate control valve, such as discharging a fixed amount of fluid to the output side through the central hole of the protrusion.

[Example] FIG. 1 is a sectional view showing an example of a micropump according to the present invention, and shows a case of two valves.

Figures 2 and 3 are lines A-A and B-B in Figure 1, respectively.
FIG.

The micropump designated by the general reference numeral 10 has a sandwich structure of a substrate 1, a thin film plate 2, and a surface plate 3.

The substrate 1 is made of, for example, a glass substrate with a thickness of about 1 am, and is provided with an artificial port 11 and an exit port 12. Tubes 13 and 14 are respectively connected to these ports with adhesive 15 to prevent liquid leakage.
For example, the proximal end of the tube 1 is connected to a chemical tank (not shown).
The tip of 4 is connected to, for example, an injection needle (not shown).

The thin film plate 2 is made of, for example, an St substrate with a thickness of about 0.31 cm, and is formed by etching an inlet valve 4° and an outlet valve 5.
．． A diaphragm 6 is formed between both valves, and a support portion 8 consisting of a rod-shaped protrusion 81 whose tip (lower end) 82 contacts the surface of the substrate 1 is formed at the center of the diaphragm 6.
In addition, the necessary flow paths (see Figures 2 and 3) are provided, and the substrate l
It is bonded on top by anodic bonding method. The joining point is number 16a
.

These are the parts indicated by 16b, 16c, and 16d.

Note that the cross-sectional shape of the support portion 8 is arbitrary, and may be any shape such as circular or square.

As seen in FIGS. 2 and 3, an input flow path 111 is provided which is connected to the inlet port 11, and the input flow path 111 communicates with a chamber 113 provided above the outlet valve 5 through a through hole 112. Furthermore, it communicates via a through hole 114 and a communication channel 115 with a chamber 116 of the inlet valve 4 . The inlet valve 4 is formed by a valve body 41 and has a through hole 117 in its center, which communicates with an upper chamber 118 . Furthermore, the chamber 118 communicates via a through hole 119 and a communication channel 120 with a pump chamber 121 below the diaphragm 6, and the pressure fluid flows via an output channel 122 into a chamber 123 of the outlet valve 5. The outlet valve 5 is formed of a cap-shaped valve body 51 that covers the inlet 12a of the outlet port 12.

As a driving means for the diaphragm 6, a piezoelectric element 7 of a piezo disk is bonded onto the diaphragm 6 via a thin film electrode plate 71. The support portion 8 described above serves as a support when the piezoelectric element 7 is bonded. In the figure, 72 and 73 are lead wires for applying voltage to the piezoelectric element 7.

On the thin film plate 2, a surface plate 3 made of a glass substrate similar to the substrate 1 is bonded by an anodic bonding method with an insertion opening 31 for the piezoelectric element 7, thereby establishing the above-mentioned pump flow path system. A peripheral portion 61 of the diaphragm 6 is also joined around the insertion opening 31 of the surface plate 3.

The thickness of the top plate 3 is approximately 0.5-cm.

According to the configuration of this embodiment, the diaphragm 6 is connected to the surface plate 3.
In addition to being supported at the periphery by joining with , the center part is supported by the protrusion 81 . Therefore, when bonding the driving piezoelectric element 7 onto the diaphragm 6, the protrusion 81 acts as a support or a stopper and sufficiently opposes the pressing force against the piezoelectric element 7.
Since the surface of the diaphragm 6 is less likely to curve, in other words the flatness of the surface of the diaphragm 6 is maintained, the piezoelectric element 7 can be bonded uniformly and stably. Also,
Even if the piezoelectric element 7 is pressed with some force during adhesion, there is no risk of damaging the surrounding joints, so the adhesion work is easy.

Next, the pump operation of this embodiment will be explained.

FIG. 4 is a block diagram showing a drive circuit for the driving piezoelectric element 7, and FIG. 5 is an explanatory diagram of the operation of this embodiment.

In FIG. 4, 701 is a power source such as a lithium battery, and 70
2 is a booster circuit, 703 is a CPU, 704 is a level shifter that converts a low voltage signal into a high voltage signal, 705 is a driver that drives the piezoelectric element 7 706 is a display device that displays the pump flow rate, 707 is a flow rate selection It's a switch.

First, a flow rate is selected using the switch 707, and a pump drive signal is output from the CPU 703. The signal of the CPU 703 is generally operated at a voltage of 3 to 5V, and the piezoelectric element 7 is operated at an alternating voltage such as 50V. Then, the booster circuit 702 boosts the voltage of 3V to 50V, and the level shifter 704 converts the signal from the CPU 703 into a 50V signal.

In this way, an alternating voltage of 50 V is periodically applied to the piezoelectric element 7 to give vibrations of IHz to several Hz.

When the diaphragm 6 deflects upward due to the piezo effect as shown in FIG. The septum 42 at 118 is deflected upwardly, opening the inlet valve 4 and thus sucking in a fixed amount of fluid from the chamber 116 communicating with the inlet port 11 through the through hole 117 .

On the contrary, the diaphragm 6 is shown in FIG. 5(b) as shown in FIG.
When trying to return to the original state from a), the pressure in the pump chamber 121 increases, and this pressure increases through the flow paths 120 and 122, respectively.
The air is simultaneously transmitted to the chambers 118 and 123 through the air, increasing the internal pressure thereof. Due to the increase in the internal pressure of the chamber 118, the partition wall 42 provided with the inlet valve 4 is pushed downward, and the valve element 4 of the artificial valve 4 is pushed downward.
1 is pressed against the substrate 1, the artificial valve 4 is closed. At the same time, the increase in the internal pressure of the chamber 123 pushes up the partition wall 52, so the valve element 51 of the outlet valve 5 separates from the substrate 1, the outlet valve 5 opens, and a fixed amount of pressure fluid is discharged to the outlet port 12.

In addition, since the protrusion 81 functions as a stopper in the operation of the diaphragm 6, the amplitude becomes constant as shown in FIG. 5(C), and stable quantitative discharge becomes possible. Note that since the amplitude is only on one side, the amount of discharge per discharge will decrease, but
There is no practical problem because the total amount of ejection can be increased by increasing the number of ejections or increasing the drive voltage.

By vibrating the diaphragm 6 using the piezoelectric element 7 in this manner, the suction and discharge described above are performed continuously, and by increasing the vibration frequency, a pump with less pulsation can be obtained. Note that since the outlet valve 5 is formed of a cap-shaped valve body 51 that covers the port 12a of the outlet port 12, the direction of action of the lifting force (opening force of the outlet valve 5) on the partition wall 52 due to the back pressure of the outlet port 12 is is the same as the upward direction of the pressure in the pump chamber 121 against the partition wall 52, and the back pressure always acts on the outlet valve 5 in the direction of opening. In other words, until the back pressure overcomes the elastic force of the outlet valve 5 and the pressing force based on the external force exerted on the partition wall 52, a substantially constant flow rate is discharged within the required range of use of the pump.

By the way, the flow rate performance of this micro pump is 11th.
As shown in the figure, the pressure with differential pressure P is approximately 4001IH2
A substantially constant flow ff1Q is discharged until 0.

Next, FIG. 6 shows another embodiment of the present invention, in which the support portion 8 is formed as a cylindrical projection 83 coaxial with the diaphragm 6.

This cylindrical protrusion 83 makes the support of the diaphragm 6 more stable, so that the work of bonding the driving piezoelectric element 7 can be performed more easily and reliably. Further, the operation of this embodiment is similar to that of the embodiment shown in FIG. Although not shown, a combination with the embodiment shown in FIG. 1 is also possible.

FIG. 7 shows another embodiment of the present invention, in which the support portion 8 is a protrusion 84 extending in the diameter direction of the diaphragm 6. Although a plurality of bar-shaped protrusions 81 shown in FIG. 1 may be arranged in a row in the diametrical direction of the diaphragm 6, they are formed in the form of convex strips for ease of manufacture. In this case as well, substantially the same effects as in the embodiment shown in FIG. 1 can be achieved. Moreover, even when unexpected pressure is applied from the input side, the protrusion can suppress the movement of fluid toward the outlet side, and can also suppress backflow from the outlet valve side.

In the embodiments described above, the protrusions 81, 83, 84 are provided at the center of the diaphragm 6 so that their tips are in contact with the substrate 1. Therefore, in the end, the protrusion can be eliminated and the diaphragm 6 itself can be formed so as to be in direct contact with the substrate 1. The configuration of this embodiment is shown in FIG.

In the embodiment shown in FIG. 8, since the entire surface of the diaphragm 6 is in contact with the substrate 1, the piezoelectric element 7 can be bonded more easily. Further, in order for the entire diaphragm 6 to perform a pumping action, it must vibrate in the upper region as shown by the broken line in the figure. Further, a groove 62 is provided in a portion of the diaphragm 6 that connects to the communication channel 120 and the output channel 122, so that the structure allows liquid to flow from the substrate 1. In this case as well, the same effect as explained in FIG. 7 is achieved.

Next, FIG. 9 is a sectional view showing still another embodiment of the present invention, and FIG. 10 is a cross-sectional plan view taken along the line CC in FIG. 9.

In this embodiment, the diaphragm 6A is not a thin film plate as in the above embodiment (it is formed integrally with a thin film surface plate 3A made of Si or glass, and the central part of the diaphragm 6A is A cylindrical protrusion 85 is provided to support the protrusion 85, an output channel 122 is communicated with the center hole 124 of the protrusion 85, and a portion other than the output channel 122 at the bottom of the protrusion 85 is bonded to the substrate 1. Note that the joints between the thin film plate 2A and the substrate 1 are 16a, 16b, 16c, and 16d, similar to the embodiment shown in FIG.
This is the location indicated by h.

In this embodiment, the tip of the protrusion 85 is located at the surface 11 [Z
3A, that is, contacts the lower surface of the diaphragm 6A, and acts as a stopper for the diaphragm 6A.
Vibration of the diaphragm 6A allows a constant flow rate to flow through the center hole 12.
4 acts as a flow rate control valve for discharging to the output side.

In the above embodiments, a two-valve type micropump has been described, but a three-valve type micropump is also applicable.

[Effects of the Invention] As explained above, according to the present invention, the following effects can be obtained.

(1) In a 2-valve or 3-valve micropump, the diaphragm is supported by a surface plate that connects and supports the diaphragm around the diaphragm, and in addition, the central part is supported by a protruding support part, so that the drive piezoelectric element Adhesion to the diaphragm can be done with uniform force and stability, making the adhesion work easy.

(2) By configuring the support section to bring the diaphragm itself into contact with the substrate, it not only simplifies the bonding work but also prevents the fluid from moving toward the outlet side in response to unexpected pressure from the input side. It is expected to prevent backflow from occurring, and improve pump performance.

(3) Also, the support part and the diaphragm are separated, and the diaphragm is formed on the surface plate, while a cylindrical protrusion that supports the center of the diaphragm is formed on the thin film plate, and the bottom of the protrusion is bonded to the substrate. By making the tip contact the diaphragm, the protrusion not only acts as a stopper for the diaphragm, but also acts as a flow rate control valve that discharges a fixed amount of flow to the pressure side through the center hole of the protrusion. Performance can be improved.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of the micropump according to the present invention, and FIGS. 2 and 3 are respectively taken along the line A-A in FIG.
A cross-sectional plan view taken along the line B-B, FIG. 4 is a block diagram showing an example of the drive circuit configuration of the drive piezoelectric element, and FIGS.
c) is an operational diagram of the embodiment shown in Fig. 1, Fig. 6 is a cross-sectional view showing another embodiment in which the support part is a cylindrical projection, and Fig. 7 is a diagram showing another embodiment in which the support part is a convex projection. Cross-sectional plan view showing the embodiment, No. 8
The figure is a sectional view showing another embodiment in which the diaphragm itself is used as a support part, FIG. 9 is a sectional view showing still another embodiment of the present invention, and FIG. A cross-sectional plan view, FIG. 11 is a characteristic diagram showing the pump performance of the embodiment shown in FIG. 1, and FIG. 12 is a cross-sectional view of a conventional two-valve type microbomb. 1...Substrate 2.2A...Thin film plate 3.3A...Surface plate 4...Inlet valve 5...Outlet valve 6.6A...Diaphragm 7...Piezoelectric element 8... Support part 10...Micro pump 11...Inlet port 12...Outlet port 81...Bar-shaped projection 83...Cylindrical projection 84...Convex projection 85...Cylindrical projection

Claims (1)

Scope of Claims: (1) A substrate, a thin film plate bonded on the substrate, a diaphragm formed on the thin film plate, and at least two valves, a thin film plate bonded on the thin film plate, and a diaphragm formed on the thin film plate, A micropump comprising a surface plate having a peripheral portion joined to the diaphragm and a driving piezoelectric element fixed on the diaphragm, the micropump sucking in fluid from an inlet port of the substrate and discharging it from an outlet port of the substrate. . A micropump, characterized in that a support portion whose tip contacts the substrate is provided in the center of the diaphragm. (2) The micropump according to claim 1, wherein the support portion is a cylindrical projection. (3) The micropump according to claim 1, wherein the support portion is a protrusion provided in a diametrical direction of the diaphragm. (4) The micropump according to claim 1, wherein the support portion is the diaphragm itself that contacts the substrate. (5) a substrate, a thin film plate bonded onto the substrate, at least two valves formed on the thin film plate, a surface plate bonded onto the thin film plate and provided with a diaphragm, and a surface plate bonded onto the thin film plate and provided with a diaphragm; a piezoelectric element for driving fixed to the diaphragm; and a cylindrical protrusion formed on the thin film plate, the bottom of which is joined to the substrate and the tip of which contacts the center of the diaphragm; A micropump that sucks in fluid and discharges it from an outlet port of the substrate through a central hole of the protrusion.