JP5028802B2 - Piezoelectric liquid transporter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric type liquid conveyer which is reliable, can be miniaturized and thinned, and has large flow rate characteristics while having a structure to prevent a piezoelectric vibration element from being exposed to high humidity. <P>SOLUTION: Water contact resin sheet 10 composed of resin sheet having metal foil 11 stuck on one surface is fixed on a water contact part which is a pump chamber 9 side of a bimorph type piezoelectric vibration element 12 with the resin sheet facing to water contact side, the water contact sheet 10 covers the pump chamber 9 including a side wall upper end part of a pump casing part 1, and is put between the pump casing body 1 and a pump lid part 15. A humidity resistant sheet rubber 13 of low moisture permeability is put between the pump lid part 15 and the water contact resin sheet 10. An outer circumference of an electrode of the piezoelectric vibration element is constructed inside of an outer circumference of the pump chamber 9 which is a support of vibration. <P>COPYRIGHT: (C)2007,JPO&amp;INPIT

Description

  The present invention relates to a small and thin piezoelectric liquid transporter that constitutes a cooling device for cooling a heating element such as an electric device and an electronic component.

  Conventionally, a piezoelectric pump that sucks and conveys liquid by vibration of a piezoelectric vibrator generally has a structure as shown in FIG. As shown in FIG. 5, in the conventional piezoelectric pump, an inner plate 30 is fitted into a pump housing portion 26 in which a fluid inlet 27 and an outlet 28 are formed, and along the periphery of the inner plate 30. A pump chamber hermetic seal 23 is arranged, a bimorph type piezoelectric vibrator 22 is placed with the pump chamber hermetic seal 23 as a support, and a pump lid 21 is further installed on the bimorph piezoelectric vibrator 22. The housing part 26 is sealed.

  The space surrounded by the lower surface of the bimorph piezoelectric vibrator 22, the upper surface of the inner plate, and the pump chamber sealing seal 23 and sealed by the pump chamber sealing seal 23 forms a pump chamber 29. The inner plate 30 is provided with an inflow valve 24 and an outflow valve 25 so that the liquid flowing in from the inflow port 27 flows out of the outflow port 28 through the pump chamber. The piezoelectric vibrator is a bimorph type in which two piezoelectric ceramics 22a are fixed to the upper and lower surfaces of an elastic plate 22b, and is configured to cover a water contact mold 22c.

  Next, the operation of the conventional piezoelectric pump will be described. When a voltage is applied, the bimorph type piezoelectric vibrator 22 vibrates in the vertical direction, so that the inside of the pump chamber 29 is continuously depressurized and pressurized alternately, and the inflow valve 24 and the outflow valve 25 are alternately opened and closed. The fluid flows from the inlet 27 into the pump chamber 29 and flows out from the pump chamber 29 to the outlet 28.

  In the conventional example shown in FIG. 5, a sealing seal (for example, an O-ring rubber) that supports the piezoelectric vibrator and serves as a leakage seal to the outside against a liquid leak entering the pump chamber is provided between the lid and the casing. It arrange | positions between, and it is given so that it may not leak by crushing with the fastening force of a lid | cover and a housing | casing. Also, as conventional techniques, in Patent Documents 1 to 3, the discharge pressure is increased and measures against insulation deterioration of the piezoelectric body are taken with respect to the basic piezoelectric pump shown in FIG.

  In Patent Document 1, when attaching the diaphragm to which the piezoelectric vibrator is attached to the pump housing, by sealing and fixing by welding, a strong measure against liquid leakage is performed, and by such a fixing, It is described that the vibration support point of the diaphragm is firmly fixed, and as a result, the displacement of the central portion of the diaphragm is increased, and the discharge flow rate can be increased.

  According to Patent Document 2, with respect to a piezoelectric vibrator coated with an elastic shield material, the insulation deterioration of the piezoelectric body occurs due to water gradually penetrating into the elastic shield material from the liquid contact surface in contact with the fluid. As a countermeasure against this problem, there is a structure in which an insulating film in which a metal film is formed on the liquid contact surface side that is the pump chamber side is attached to the piezoelectric vibrator, and a piezoelectric body on the liquid contact side opposite to the liquid contact surface The thing of the structure which covered the whole with the insulating film is disclosed.

  In Patent Document 3, due to the brittleness of the hermetic seal of the pump chamber in the prior art, the liquid in the pump chamber wraps around the diaphragm and leaks to the opposite side of the pump chamber, and the piezoelectric vibrator touches the liquid. To solve the problem of insulation deterioration and breakdown, the inner plate equipped with a check valve and the cartridge with the piezoelectric vibrator attached are firmly tightened with an O-ring rubber to completely prevent liquid leakage in the pump chamber. The thing of the structure aiming at making it seal is disclosed.

JP 2003-028068 A JP 2001-323879 A JP 2002-130137 A

  However, the conventional techniques described above have the following problems.

  If an attempt is made to increase the flow rate and thickness of the piezoelectric pump, the electric field applied to the piezoelectric vibrator becomes very large. When a large electric field continues to be applied in a state where the piezoelectric vibrator is exposed to moisture, electrode migration occurs, insulation deterioration of the vibrator occurs, and short-circuit breakdown eventually occurs. In the piezoelectric pump, since the piezoelectric vibrator is disposed above or below the pump chamber, liquid is present in the immediate vicinity of the piezoelectric vibrator, but the piezoelectric vibrator is easily exposed to moisture.

  In addition, the temperature of the liquid in the pump chamber may increase in the cooling device, which is the technical application range of the present invention, and the water in the liquid vaporizes due to this temperature increase. The vaporized water vapor passes through the hermetic seal portion of the pump chamber or the water contact portion of the piezoelectric vibrator, and has a problem that it touches the ceramic portion of the piezoelectric vibrator. Therefore, moisture-resistant separation between the piezoelectric vibrator and water vapor from the liquid in the pump chamber, and further moisture-resistant separation structure from the outside air are important for increasing the flow rate and reducing the thickness of the piezoelectric pump.

  As a technique for moisture-proof separation of water vapor from a liquid in a pump chamber and a piezoelectric vibrator, there is a technique disclosed in Patent Document 1, which describes a piezoelectric pump in which a metal plate is arranged as a diaphragm in a water contact portion. However, since the rigidity of the metal plate is too great, displacement restraint of the piezoelectric vibrator becomes strong, and the flow rate as a pump is about several tens of cc at most, and it is difficult to increase the flow rate.

  In Patent Document 2, an insulating film in which a metal film is formed on the wetted surface side is fixed to a piezoelectric vibrator, and a piezoelectric vibrator is covered with the insulating film. In this case, since the metal film is in contact with water, there are problems in reliability, such as corrosion of the metal film or the possibility of electrical leakage, and the pump life is only about 2 to 3 years. There was a problem.

  Further, Patent Document 3 discloses a device that has improved sealing performance by bonding a piezoelectric vibrator to a rigid cartridge and firmly crushing an O-ring that is a sealing seal of the pump chamber with the cartridge and the inner plate. Has been. However, with this structure, the thickness increases in order to ensure the rigidity of the cartridge, and there is a limit to the reduction in thickness.

  Therefore, in order to improve the reliability of the piezoelectric pump and realize a long life of about 5 to 10 years, it is required to develop a structure in which the piezoelectric vibrator in the piezoelectric pump is not exposed to high humidity.

  The present invention has been made in view of such problems, and has a structure in which a piezoelectric vibrator is not exposed to high humidity, is highly reliable, can be reduced in size and thickness, and has a large flow rate characteristic. An object is to provide a liquid transporter.

A piezoelectric liquid transporter according to a first aspect of the present invention includes a pump housing having an opening, a water contact sheet disposed so as to cover the opening, the water contact sheet, and an inner wall of the pump housing. And a pump chamber formed as a space surrounded by the water contact sheet, a piezoelectric vibrator fixed on the water contact sheet, an inlet provided in the pump housing and into which the fluid flows into the pump chamber, and the pump chamber An outlet through which fluid flows out, and a pump lid fixed to the pump housing and disposed on the top of the piezoelectric vibrator, the volume of the pump chamber being variable by bending vibration of the piezoelectric vibrator The fluid contact sheet has a pump function of sucking fluid from the inlet and discharging from the outlet, the water contact sheet is made of a resin sheet having a metal foil formed on one side, and the water contact sheet is water contact Front so that the side is the resin sheet It is arranged so as to cover up to the upper end of the side wall of the pump casing, and on the water contact sheet at the upper end of the side wall of the pump casing, a moisture-resistant sheet having low moisture permeability is further provided, the resin sheet, The metal foil and the moisture-resistant sheet having low moisture permeability are sandwiched between the pump casing and the pump lid .

  In the present invention, a water contact sheet made of a resin sheet having a metal foil formed on one side is disposed between the piezoelectric vibrator and the pump chamber so that the water contact surface becomes a resin sheet. Blocks the permeation of water vapor generated from the liquid in the pump chamber, and the piezoelectric vibrator and the pump chamber have a moisture-resistant separation structure, so that the water vapor does not affect the piezoelectric vibrator.

  The inlet and outlet respectively have a check valve that allows fluid to flow into the pump from the inlet and not vice versa, and allows the fluid to flow out of the pump and vice versa. A check valve can be provided that does not allow fluid flow.

  A side surface of the pump chamber is formed of a hermetic seal, and the hermetic seal can support the piezoelectric vibrator and seal the pump chamber.

  The water contact sheet is preferably larger than the opening of the pump chamber.

  The piezoelectric vibrator is provided with an electrode for applying a voltage to vibrate, and the outer circumference of the electrode is located inside the outer circumference of the pump chamber with respect to the outer circumference of the pump chamber which is a support portion of the piezoelectric vibrator. Also good. Thereby, since the application part of the stress applied to the piezoelectric vibrator via the support part and the application part of the electric field do not concentrate, the progress of electrode migration is suppressed.

  In the water contact sheet, the thickness of the metal foil is 0.3 to 3% of the thickness of the piezoelectric vibrator, and the thickness of the resin sheet is 5 to 15% of the thickness of the piezoelectric vibrator. it can. As a result, it is possible to achieve an extremely thin pump overall thickness without drastically reducing the performance such as the flow rate of the pump.

  According to the present invention, a water contact sheet made of a resin sheet with a metal foil attached on one side is disposed between the piezoelectric vibrator and the pump chamber so that the water contact surface becomes a resin sheet. Since the water sheet blocks the permeation of water vapor generated from the liquid in the pump chamber and the piezoelectric vibrator and the pump chamber have a moisture-resistant separation structure, the water vapor does not affect the piezoelectric vibrator. As a result, a long life of about 5 to 10 years can be realized as the life of the piezoelectric vibrator, that is, the life of the piezoelectric liquid transporter.

  Next, embodiments of the present invention will be specifically described with reference to the accompanying drawings. FIG. 1 is a sectional view of a piezoelectric liquid transporter according to an embodiment of the present invention, and FIG. 2 is a partially enlarged view thereof. 3A and 3B are a top view and a cross-sectional configuration diagram of the piezoelectric vibrator according to the present embodiment, respectively, and FIG. 4 is a diagram illustrating electrode positions of the piezoelectric vibrator.

  3A is a top view and FIG. 3B is a cross-sectional configuration diagram of the bimorph piezoelectric vibrator 12 to which the water contact resin sheet 10 is bonded and integrated. As shown in FIG. 3, a metal foil having a thickness of, for example, about 10 to 20 μm is formed on the non-water-contact side surface that is the upper surface of the square water-contact resin sheet 10 so as to cover the water-contact resin sheet 10. 11 is affixed, and a disk-shaped bimorph piezoelectric vibrator 12 is adhered to the upper surface of the water-contacting resin sheet 10 on which the metal foil 11 is formed with a strong adhesive. The water contact resin sheet 10 is made of, for example, a fluororesin (Teflon (registered trademark)) sheet. The metal foil 11 is, for example, Al (aluminum) or Cu (copper) foil. The bimorph type piezoelectric vibrator 12 is configured by adhering piezoelectric ceramics 22a to the upper and lower surfaces of an elastic plate 22b, and further, the water contact resin sheet 10 is bonded so as to cover the upper surface. Further, the area of the water contact resin sheet 10 provided below the bimorph type piezoelectric vibrator 12 is larger than the horizontal cross-sectional area of the bimorph type piezoelectric vibrator 12, and as shown in FIG. A disc-shaped bimorph piezoelectric vibrator 12 is provided inside the sheet 10. Further, in FIG. 3, the water contact resin sheet 10 is also bonded to the upper side of the bimorph type piezoelectric vibrator 12, but this is formed in consideration of the symmetry of vibration, and this is not necessary. Although the symmetry is lost, the pump characteristics are not greatly affected.

  As shown in FIG. 1, in the piezoelectric liquid transporter according to the embodiment of the present invention, a pump bottom liquid leakage seal 2 is provided on the inner bottom surface of the pump housing portion 1 having a concave shape as a seal seal of the pump bottom portion. The valve hole penetrating plate 3 is arranged so as to overlap the upper part. A fluid inlet 6 and an outlet 7 are formed on the bottom surface of the pump casing 1, and these vertically penetrate the pump bottom liquid leakage seal 2 and the valve hole penetrating plate 3. In addition, an inflow valve 4 and an outflow valve 5 provided in the valve hole penetrating plate 3 are respectively disposed at predetermined locations communicating with the outflow port 7. The inflow valve 4 allows the inflow of fluid from the inlet 6 to the inside of the pump and does not allow the reverse fluid flow, and the outflow valve 5 permits the outflow of fluid to the outside of the pump and allows the reverse fluid flow. A check valve that does not allow.

  On the outer periphery of the valve hole penetrating plate 3, a pump chamber sealing seal 8 that forms a support portion of the piezoelectric vibrator together with the side wall of the pump housing portion 1 is disposed. A bimorph piezoelectric vibrator 12 to which a water resin sheet 10 is bonded and integrated is placed. The water contact resin sheet 10 is, for example, a fluororesin (Teflon (registered trademark)) sheet. At this time, the water contact resin sheet 10 formed at the lower part of the bimorph type piezoelectric vibrator 12 is arranged so as to cover the upper end of the side wall of the pump casing 1 so as to seal the pump casing 1 from above. Has been. The space surrounded by the upper surface of the valve hole penetrating plate 3, the water contact resin sheet 10 formed under the bimorph type piezoelectric vibrator 12, and the pump chamber sealing seal 8 is sealed by the pump chamber sealing seal 8. A pump chamber 9 is formed.

  Further, a pump lid 15 is disposed on the upper part of the bimorph type piezoelectric vibrator 12 to which the water contact resin sheet 10 is bonded and integrated, and is fastened and fixed to the pump casing 1 by screwing. In addition, as shown in an enlarged view in FIG. 2, a vibration damper made of, for example, silicon rubber or fluorine rubber is provided between the water-contacting resin sheet 10 provided on the bimorph type piezoelectric vibrator 12 and the pump lid portion 15. Between the water-contacting resin sheet 10 provided at the lower part of the bimorph type piezoelectric vibrator 12 and the pump lid 15 via the material 14, for example, fluorine rubber is provided at the upper end of the side wall of the pump casing 1. Alternatively, it is fixed via a moisture-resistant sheet rubber 13 made of ethylene propylene rubber or the like having a low moisture permeability. For the moisture-resistant sheet rubber 13, for example, 0.4 mm-thick fluororubber is used.

As shown in FIG. 4, an electrode 20 of a piezoelectric vibrator for applying a voltage to the piezoelectric vibrator is formed below the bimorph piezoelectric vibrator 12. In the present embodiment, the support portion is a contact point between the pump chamber closure seal 8 and wetted the resin sheet 10, the electrode 20 of the piezoelectric vibrator at dimensioned as to be located outside the outer periphery of the electrode 20 of the piezoelectric vibrator Is formed. That is, the outer circumference of the electrode of the piezoelectric vibrator is located inside the outer circumference of the pump chamber that supports vibration.

  In the present embodiment, as the thickness of the water contact resin sheet disposed in the piezoelectric vibrator water contact portion, the thickness of the metal foil is 0.3 to 3% of the total thickness of the piezoelectric vibrator, and the thickness of the resin portion. The thickness is about 5 to 15%. Specifically, a 0.2 mm-thick fluororesin (Teflon (registered trademark)) sheet is used for the water-contact resin sheet 10 and a 12 μm-thick Al foil is formed on the metal foil 11 to achieve piezoelectric vibration. The displacement of the child is 120 μmp-p (micrometer peak-to-peak), the flow rate of the pump exceeds 200 cc / min, and the displacement constraint of the piezoelectric vibrator is relatively small.

  Next, the operation of the piezoelectric liquid transporter according to this embodiment configured as described above will be described. By applying an alternating electric field to the bimorph type piezoelectric vibrator 12, the piezoelectric vibrator is bent and vibrated, and when the volume of the pump chamber 9 increases based on the bending vibration, the fluid is introduced from the inlet 6 into the inflow valve. When the volume of the pump chamber 9 decreases after that, the fluid flows out from the outflow port 7 through the outflow valve 5, and thus the inflow valve 4 and the outflow valve 5 are alternately arranged. By operating, suction and discharge are performed, and the liquid is transported. Further, even if water vapor generated from the liquid in the pump chamber 9 permeates the water-contact resin sheet 10 above the pump chamber 9, the metal foil 11 is attached to the piezoelectric vibrator side of the water-contact resin sheet 10. Therefore, it does not enter the piezoelectric vibrator side.

  Next, the effect of this embodiment will be described. The piezoelectric liquid transporter of the present invention is assumed to be incorporated in a cooling device for electronic equipment. In this case, the temperature of the liquid in the pump chamber 9 may be close to 80 ° C. When the temperature rises, the water in the liquid is turned into water vapor, and the water vapor is transmitted from the resin portion forming the pump chamber 9. At this time, the metal foil 11 has an effect of moisture-resistant separation so that water vapor transmitted through the water-contacting resin sheet 10 does not touch the bimorph type piezoelectric vibrator 12. Further, since the water contact resin sheet 10 is less rigid than the metal, there is an effect that the displacement of the piezoelectric vibrator is not constrained so much. Although it is possible to obtain the same effect by arranging the metal foil 11 on the wetted surface, in this case, the metal foil comes into contact with the liquid, and the reliability such as corrosion of the metal foil is impaired. Since a problem arises, in this embodiment, the side opposite to the water contact side is used.

  In the present embodiment, the moisture-resistant sheet rubber 13 is disposed between the water-contact resin sheet 10 and the pump lid portion 15, and the pump lid portion 15 and the pump housing portion 1 are fixed by screwing. This is intended to prevent the bimorph piezoelectric vibrator 12 from entering moisture from the outside air. The moisture-resistant short life of the bimorph type piezoelectric vibrator 12 changes depending on the presence or absence of the moisture-resistant sheet rubber 13, and when the moisture-resistant sheet rubber 13 is not present, it is about 2 to 3 years. A dramatic improvement in service life of 10 years will be made.

  In addition, the pressure that crushes the pump chamber hermetic seal 8 is applied as stress to the outer peripheral portion of the piezoelectric vibrator due to the vibration of the piezoelectric vibrator. Since the outer circumference of the electrode of the piezoelectric vibrator is located, the stress concentration portion and the electric field application portion do not overlap each other, and there is an effect of suppressing the migration of the electrode.

  The thickness of the metal foil 11 is 0.3 to 3% of the total thickness of the piezoelectric vibrator, and the thickness of the water-saving resin sheet is about 5 to 15%. The pump can be made extremely thin without being dropped.

  In addition, as a method for blocking moisture from the piezoelectric vibrator, in the joining of the pump lid portion and the pump housing portion, for example, the humidity around the installation location of the piezoelectric vibrator by welding, winding fastening, caulking joining, or the like. It is clear that the blocking is further strengthened, which makes the present invention more effective.

  According to the present invention, it can be suitably used as a cooling device for electronic devices such as notebook computers and electronic components.

It is sectional drawing which shows the piezoelectric type liquid conveying device which concerns on embodiment of this invention. It is the elements on larger scale of FIG. It is (a) top view and (b) cross-sectional block diagram of the piezoelectric vibrator in this embodiment. It is the figure which showed the electrode position of the piezoelectric vibrator in this embodiment. It is sectional drawing which showed an example of the conventional piezoelectric liquid transporter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1; Pump housing | casing part 2; Pump bottom liquid leak seal 3; Valve hole penetration plate 4; Inflow valve 5; Outflow valve 6; Inlet 7; Outlet 8; Sheet 11; Metal foil 12; Bimorph type piezoelectric vibrator 12a; Piezoelectric ceramic 12b; Elastic plate 13; Moisture resistant sheet rubber 14; Vibrator damper material 15; Pump lid portion 20; Electrode 21 of piezoelectric vibrator; Bimorph type piezoelectric vibrator 22a; piezoelectric ceramic 22b; elastic plate 22c; water contact mold 23; pump chamber hermetic seal 24; inlet valve 25; outlet valve 26; pump casing 27; inlet 28; outlet 29; 30; Inner plate

Claims (6)

A pump housing having an opening, a water contact sheet disposed so as to cover the opening, a pump chamber formed as a space surrounded by the water contact sheet and an inner wall of the pump housing, and the contact A piezoelectric vibrator fixed on a water sheet, an inlet provided in the pump housing and into which the fluid flows into the pump chamber, an outlet through which the fluid flows out of the pump chamber, and the pump housing. A pump lid portion disposed on an upper portion of the piezoelectric vibrator, and by making the volume of the pump chamber variable by bending vibration of the piezoelectric vibrator, fluid is sucked from the inlet and from the outlet. The drainage sheet has a pumping function, and the water contact sheet is made of a resin sheet having a metal foil formed on one side, and the water contact sheet has an upper end on the side wall of the pump housing such that the water contact side becomes the resin sheet. Arranged to cover up Further, on the water contact sheet at the upper end of the side wall of the pump casing, a moisture resistant sheet having low moisture permeability is further provided, and the resin sheet, the metal foil, and the moisture resistant sheet having low moisture permeability are A piezoelectric liquid transporter sandwiched between a pump housing and the pump lid. The piezoelectric liquid transporter according to claim 1, wherein a check valve is provided at the inlet and the outlet. 3. The piezoelectric liquid transporter according to claim 1, wherein a side surface of the pump chamber includes a hermetic seal, and the hermetic seal supports the piezoelectric vibrator and seals the pump chamber. The piezoelectric liquid transporter according to any one of claims 1 to 3 , wherein the water contact sheet is larger than an opening of the pump chamber. The piezoelectric vibrator is provided with an electrode that vibrates by applying a voltage. The outer periphery of the electrode is on the inner side of the outer periphery of the pump chamber with respect to the outer periphery of the pump chamber that is a support portion of the piezoelectric vibrator. The piezoelectric liquid transporter according to claim 1, wherein the piezoelectric liquid transporter is located at a position. In the water contact sheet, the thickness of the metal foil is 0.3 to 3% of the thickness of the piezoelectric vibrator, and the thickness of the resin sheet is 5 to 15% of the thickness of the piezoelectric vibrator. The piezoelectric liquid transporter according to any one of claims 1 to 5 , wherein:

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