JP2600180B2 - Piezoelectric micro pump - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a piezoelectric micropump.

(Prior art) A plate having a piezoelectric bimorph structure bonded so that electric fields are applied in directions opposite to each other with respect to the polarization direction is easily curved due to the fact that one plate expands and the other contracts when an electric field is applied. It can be deformed to a state in which If the electric field applied at this time is given by an AC voltage, the bending direction changes alternately, and if this is partially supported, it becomes a sounding body. If such a deformation is used, not only a sounding body but also a relay or an actuator by moving a contact can be considered, and many devices relating to these have been devised.

One of these applications is to attach an electro-piezoelectric bimorph diaphragm to a part of the outer wall of the fluid path, and install a check valve near the fluid supply port and fluid discharge port at both ends of the flow path to make the motor etc. The result is a micropump that has no mechanical parts as used.

(Problems to be Solved by the Invention) In such a micropump, even if a diaphragm is simply formed on one surface of the fluid path, the volume change of the fluid path caused by the deformation of the diaphragm is at the center of the diaphragm. In this case, the fluid in the fluid path can move evenly. For this reason, as shown in FIG. 6, the fluid discharged by the deformation of the diaphragm 61 also comes out of the supply port. Furthermore, when the deformation of the diaphragm returns to its original state, it returns not only from the supply port but also from the discharge port. In order to eliminate such a defect, a backflow preventing valve 71 is provided at each of the supply port and the discharge port as shown in FIG.
Need to be installed. However, such a check valve must be configured to flow only in one direction. For this reason, there is a limit to miniaturization, and it becomes difficult to mount the check valve in a fluid path of, for example, several millimeters or less. Further, even if ceramic integration is considered for miniaturization, such a check valve cannot be formed.

An object of the present invention is to provide a piezoelectric micropump which solves these conventional problems.

(Means for Solving the Problems) That is, according to the present invention, there are at least one or more fluid supply ports and fluid discharge ports in which a fluid path is formed, and the side near the fluid supply port is free in this fluid path. A first bimorph forming portion provided in parallel with the fluid path such that a side which is an end and is far from the fluid supply port is a fixed end, and a side near the fluid discharge port is a free end and a side far from the fluid discharge port is a fixed end. There is at least two or more bimorph forming portions of a second bimorph forming portion provided in parallel with the fluid path, and the bimorph forming portion is sintered with a material that becomes a piezoelectric body and a material that is sintered and becomes a conductor. Is made by the laminate.

(Function) The piezoelectric micropump according to the present invention is configured as a bimorph-type laminate in which two vibrating portions that move independently in the fluid path are formed with three electrode layers, and a part thereof is formed as a fluid path wall. And has a fluid path and two independent bimorph portions so that a fluid supply port and a fluid discharge port are formed at positions on the displaced side of the bimorph portion, respectively. Therefore, the bimorph on the supply port side and the bimorph on the discharge port side can be driven independently, and a time difference can be provided between them.
Then, if the bimorph is first deformed on the fluid supply port side in the fluid path, the fluid is pushed out from the fluid discharge port, and then the bimorph on the fluid discharge port side is deformed while the bimorph on the fluid supply port side is deformed. If deformed, the fluid discharge port is blocked, and at this time, if the fluid supply port side is returned to the original position, the fluid is supplied from the fluid supply port. Further, even when the bimorph on the fluid discharge port side is returned, the direction of the fluid is deformed in the direction in which the fluid is supplied from the fluid supply port, so that the fluid flows backward during one cycle from discharge to supply. That is, a ceramic-integrated piezoelectric micropump can be obtained.

Example Next, a piezoelectric micropump according to the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of a piezoelectric micropump showing one embodiment of the present invention.

First, there are two independent bimorphs 13 and 14 in which three layers of electrodes 12 are formed in the fluid path 11, and a fluid supply port 15 and a fluid discharge port 16 are provided on the displaceable side of the bimorph. Furthermore, the two bimorphs 13 and 14 are fixed at one end to the wall of the fluid path. At this time, the positional relationship between the fixed bimorph and the fluid supply port and the fluid discharge port is such that when no voltage is applied to the bimorph (that is, the bimorph is not deformed), the fluid supply port and the fluid discharge port are not connected. It is configured to have the upper height. Further, a fluid supply path 17 and a fluid discharge path 18 are connected to the fluid supply port and the fluid discharge port.

FIG. 2 is a plan view showing an example of a pattern and an example of a perforated state formed on a piezoelectric green sheet for obtaining a piezoelectric micropump according to the present invention, wherein each shape and pattern of (a) to (j) are ( a) is stacked as the uppermost layer.

In the configuration shown in FIG. 2, (a) is a green sheet forming the uppermost fluid path wall surface, and (b) is a green sheet having a cut portion 21 forming a space above the bimorph forming portion. . Next, (c) is a green sheet for insulating the uppermost layer electrode from the fluid, which has a cut portion 22 having a shape conforming to the bimorph formation portion, and below this a cut portion 22 and an electrode 23 forming a bimorph. There are green sheets (d), (e), and (f) of a bimorph forming portion having a cut portion 24 for setting the bimorph portion in a free state and an extraction electrode 25 for extracting each electrode to the outside. Further, (g) is a green sheet having a cut portion 26 for forming a space for allowing a bimorph to be deformable, and (h) is a green sheet for forming a supply path and a discharge port of the fluid path. (I) is a green sheet having a cut portion 28 for forming a fluid path, and finally (j) is a green sheet having a lowermost fluid path wall surface. Be composed. The description in FIG. 2 shows the pattern and the shape of one piezoelectric micropump. For this reason, although the green sheet shown in FIG. A single green sheet is formed as a pattern, and a pattern per one layer is obtained by cutting after lamination. In addition, the cut portion in each green sheet in FIG. 2 will be crushed if the lamination press is performed as it is, so the carbon green sheet or carbon paste matched to the pattern of the cut portion at the stage when the cutting of each sheet is completed. It is only necessary to embed a material that burns and gasifies in the sintering process such as that described above to form a cavity.

The thus obtained ten green sheets of piezoelectric material are stacked in a press die, and pressed at a pressure of about 250 kg / cm ² while heating at a temperature of about 100 ° C. to obtain a laminate.
Next, the laminate is fired through a binder removal process to obtain a piezoelectric micropump having a cross-sectional structure shown in FIG.

In the laminated configuration shown in this example, the sheets forming the upper and lower fluid passage walls are shown as one layer, but when reinforcement is necessary in relation to the thickness of the green sheet, each green sheet is provided in a plurality. It is obvious that the above configuration can provide reinforcement and protect the internal bimorph forming portion. Further, the type of the bimorph forming portion is not limited to this type, but can be freely designed according to the shape of the fluid path, and the number and size of the fluid supply port and the fluid discharge port are not limited. On the other hand, the fluid supply port and the fluid discharge port are configured to be opposed to the two bimorph forming portions, but if the fluid supply port and the fluid discharge port are provided in the displaceable portion of the bimorph, the third As shown in the figure, the pattern of each green sheet may be configured such that two bimorph forming parts 31 are arranged in the same direction, and a partition part 32 and a fluid path 33 are formed between them.

Here piezoelectric material green using sheet, dispersed powder of electrostrictive material mainly containing lead magnesium niobate Pb (Mg1 / 3 · Nb2 / 3) O 3 in a solvent together with an organic binder,
Slurry. The thickness was 20 μm to 200 μm by slip casting using a doctor blade.
Of a raw ceramic sheet having a uniform thickness.

This ceramic raw sheet is punched to the specified size,
Holes for forming each cut portion are formed by a punch and a die. Next, an electrode paste is printed on the processed green sheet including the perforations by using a screen printer. Furthermore, these green sheets are set in a press die, and at the same time, each green sheet is stacked while being filled with carbon green sheets corresponding to each cut portion, and heated at a temperature of about 100 ° C., and is heated to 250 kg / cm ²
The laminated body is obtained by pressure bonding at a moderate pressure. Next, the laminate is cut into predetermined dimensions as required, and first, organic substances present in the cavity pattern and the ceramic green sheet are slowly heated in an oxidizing atmosphere in a debinding step to decompose and disappear. Usually these organics are 500 ° C
It decomposes and oxidizes completely up to 600 ° C, but if the temperature is rapidly raised to the decomposition temperature, the laminate will be damaged.
The organic material is completely eliminated by raising the temperature for a time or at a slower temperature rising speed and maintaining the temperature at 500 ° C. to 600 ° C. for a sufficiently long time.

Thereafter, by firing at a temperature of 900 ° C. to 1200 ° C., the piezoelectric micropump described above is obtained. In addition,
Since the electrode pattern as an extraction terminal extends to the end face of the laminate, a silver paste or the like may be baked here as an external electrode.

In the piezoelectric micropump obtained as described above, first, in order to perform a polarization process, 10 μm is applied to the electrode of the bimorph forming portion.
A voltage of about 0 to 200 V is applied for about 1 minute.

Next, the electrodes of these two bimorph forming portions are connected in parallel so that they are connected in opposite directions with respect to the polarization direction, and are taken out as terminals of bimorph 1 and bimorph 2.

In this manner, two drive circuits having a voltage waveform as shown in FIG. 4 are connected to the extracted terminals. FIGS. 5A to 5E are sectional views showing the operation of the piezoelectric micropump of the present invention when driven by the drive waveform.

First, (a) shows a state in which no voltage is applied to either bimorph, and a state in which fluid is filled in the fluid path. (B) is a state in which a voltage is applied to the bimorph on the fluid supply port side and the bimorph is deformed. The fluid moves in the direction of the fluid discharge port, and at the same time, the fluid comes out of the fluid discharge port. (C) is a state in which a voltage is also applied to the bimorph on the other fluid discharge port and the bimorph is deformed. At this time, the fluid discharge is cut off from the fluid discharge port. (D) is a state where the voltage of the bimorph on the fluid supply port side is cut off and the circuit returns to the original state by the operation of the discharge circuit. At this time, the fluid is supplied from the fluid supply port into the fluid path. (E) is a state in which the voltage of the bimorph on the fluid discharge side is cut off, and the state returns to the original state by the operation of the discharge circuit. At this time, the fluid is supplied from the fluid supply port into the fluid path, and the state shown in (a). You have returned to. Hereinafter, similarly, (b) to (e) are repeated to form a pump in which the fluid flows continuously. At this time, the bimorphs that deform independently on the fluid supply port side and the fluid discharge port side operate with a time lag, and this operation itself exerts the effect of the check valve.

(Effects of the Invention) As is clear from the above description, according to the present invention, the independent bimorphs that are respectively deformed on the fluid supply port side and the fluid discharge port side are formed in the fluid path, so that the independent bimorphs are formed. Is a pump that enables the fluid to flow in a fixed direction by driving the pump with a staggered time relationship, and the two bimorphs that operate at this time work so as to prevent backflow. Therefore, a valve for preventing backflow is not required at all, and it is sufficient if two bimorphs can be formed in the fluid path regardless of the size of the fluid path, and a microminiature pump can be obtained. Further, the piezoelectric micropump of the present invention is obtained only by laminating and sintering the piezoelectric ceramics and does not require any external parts or other assemblies, so that the piezoelectric micropump can be reduced in cost.

In the embodiment of the present invention, the piezoelectric ceramic green sheets are formed by the lamination technology. However, when miniaturization is not particularly required, only the bimorph plate is obtained by the ceramic lamination technology, and this is made of stainless steel. It is clear that the same effect can be obtained by assembling in a fluid passage having a fluid supply port and a fluid discharge port made of such materials. Further, if the fluid supply port and the fluid discharge port are adjusted to, for example, the diameter of a hose for transporting the fluid, the installation place of the pump can be completely eliminated. Further, if the fluid path, the fluid supply port, and the fluid discharge port are also formed on the upper side of the bimorph forming portion, and the drive voltage is set to the AC voltage and the phase is similar to the drive waveform shown in FIG. 4, the amount of deformation of the bimorph portion increases. Since the fluids in the upper and lower fluid paths can be moved alternately, the flow rate of the fluid as a pump and the force for transporting the fluid are increased, and a high-performance piezoelectric micropump can be obtained.

On the other hand, the method of forming pores inside is not limited to carbon green sheets and carbon pastes, but also Japanese Patent Application No. 60-243218,
Exposure to the photosensitive resin described in JP-A-60-243219, and the development of the phenomenon, the pressure-bonding of the patterned film to the green sheet at the time of lamination results in a piezoelectric micropump having the same effect.

In the piezoelectric micropump of the present invention, if the fluid discharge port is formed in a nozzle shape, and is driven by a pulse-shaped waveform (not a continuous wave), a suitable fluid is ejected from the nozzle, and for example, the ink jet of a dot printer is used. Obviously, it can be used for a head or the like.In this case, even if the fluid discharge port is not directly a nozzle, a thin fluid path can be formed ahead of the fluid discharge port, and can be adjusted to the dot pitch of the dot printer. This can be easily performed by forming a pattern with a substance that is burned off in the firing process.

[Brief description of the drawings]

1 is a cross-sectional view of one embodiment of the present invention, FIG. 2 is a green sheet shape and pattern diagram showing one embodiment of the present invention, and FIG. 3 is an internal bimorph showing another embodiment of the present invention. FIG. 4 is a drive waveform diagram for driving two bimorphs and a drive circuit diagram thereof, FIG. 5 is a cross-sectional view of the structure of FIG. 1 when driven in the state of FIG. 4, and FIG. FIG. 1 is a sectional view of a conventional piezoelectric pump, and FIG. 7 is a sectional view of a piezoelectric pump provided with a check valve. In the drawing, 11: fluid path, 12: electrode, 13: bimorph on the fluid supply side, 14: bimorph on the fluid outlet side,
15 fluid supply port, 16 fluid outlet, 17 fluid supply path, 18 fluid discharge path, 21 cut section forming a space above the bimorph formation section, 22 bimorph formation section A cut portion having a shape of a bimorph forming portion for insulating the uppermost layer electrode, 23... An electrode forming a bimorph, 24... A cut portion for setting the bimorph portion to a free state, 25. 26 ... cut section that forms a space to allow the bimorph to deform, 27
... cut portion for forming a fluid path and a fluid supply port and a fluid discharge port, 28 ... cut portion for forming a fluid path, 31 ...
Bimorph forming part, 32: Partition wall, 33: Fluid path, V ₁ ...
... drive waveform of the fluid supply port side, V ₂ ...... fluid outlet side of the drive waveform, 61 ...... diaphragm, 71 ...... check valve is.

Claims (2)

(57) [Claims] 1. A piezoelectric micropump having at least one fluid supply port and a fluid discharge port having a fluid path formed therein, wherein a side near the fluid supply port is a free end in the fluid path. A first bimorph forming portion provided in parallel with the fluid path so that the side farthest from the fluid outlet is a fixed end; and a first bimorph forming portion parallel to the fluid path such that the side near the fluid outlet is a free end and the side far from the fluid outlet is a fixed end. A piezoelectric micropump having at least two or more bimorph forming portions of the second bimorph forming portion provided in the piezoelectric micropump. 2. The piezoelectric micropump according to claim 1, wherein the bimorph forming portion is a laminate of a material that becomes a piezoelectric body by sintering and a material that becomes a conductor by sintering.