JP2009062947A - Liquid diaphragm pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid diaphragm pump without receiving (or reducing) unbalance pressure to the obverse-reverse of a diaphragm, in the diaphragm pump for forming a pump room for receiving liquid pressure in any one of the obverse-reverse of the diaphragm. <P>SOLUTION: In this liquid diaphragm pump, a liquid chamber is formed by being positioned on the opposite side of the pump room between an upper housing for sandwiching the diaphragm and the diaphragm, and is straddled over the upper housing and a lower housing, and a free liquid flow passage is arranged for communicating this liquid chamber with at least one of a suction port and a delivery port, and liquid can be freely moved between the inside or the suction port or the delivery port and the liquid chamber. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a liquid diaphragm pump that obtains a pumping action by a vibrating diaphragm.

The liquid diaphragm pump has a pump chamber formed on one of the front and back sides of the diaphragm whose periphery is liquid-tight, and a pair of flow paths (suction port and discharge port) connected to the pump chamber have a pair of different flow directions. A check valve (a check valve that allows fluid flow to the pump chamber and a check valve that allows fluid flow from the pump chamber) is provided. When the diaphragm is vibrated, the volume of the pump chamber changes, and as the volume changes, one of the pair of check valves closes and the other opens repeatedly, so that a pump action is obtained. Since such a liquid diaphragm pump can be reduced in size when a piezoelectric vibrator is used as the diaphragm, the present applicant is developing a piezoelectric pump used as a cooling water circulation pump of a water-cooled notebook type personal computer.
JP2003-013861 Japanese Unexamined Patent Publication No. 2006-132477 JP 2006-161674 A

  Conventionally, in this liquid diaphragm pump, the chamber opposite to the pump chamber across the diaphragm is an atmospheric chamber (air chamber). However, when the opposite side of the pump chamber is the atmospheric chamber, it has been found that there are the following problems.

  That is, the diaphragm always receives the liquid pressure on the pump chamber side during operation and receives a force in the direction of projecting to the atmosphere chamber side, whereas the liquid pressure does not act on the atmosphere chamber. For this reason, the way in which force is applied to the diaphragm becomes excessively uneven, which causes damage to the diaphragm or shortens its life.

  Further, it has been clarified that the piezoelectric vibrator generally used as a diaphragm has the following problems. Piezoelectric vibrators are known as a unimorph type in which a piezoelectric layer is provided on one surface of a metal shim made of a conductive metal plate, and a bimorph type in which a piezoelectric layer is provided on both sides. A multimorph type has been proposed (Japanese Patent Application No. 2007-35879) in which a plurality of piezoelectric layers are electrically connected in parallel or in series (Japanese Patent Application No. 2007-35879). At least one type of piezoelectric vibrator is made of a conductive metal thin plate. This is common in that it has an alternately laminated structure of one shim and at least one piezoelectric layer. Then, no matter what type of piezoelectric vibrator is used, conventionally, a metal shim is positioned on the side of the pump chamber that comes into contact with the liquid, and a piezoelectric layer is positioned on the side of the atmospheric chamber. However, it has been found that a piezoelectric vibrator provided with a piezoelectric layer on the atmosphere chamber side may cause cracks in the piezoelectric layer on the atmosphere chamber side when used for a long period of time.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a diaphragm pump in which a pump chamber that receives liquid pressure is formed on either one of the front and back sides of the diaphragm, so that the diaphragm does not receive unbalanced pressure on the front and back sides. And
Another object of the present invention is to obtain a piezoelectric pump in which cracks are unlikely to occur in a piezoelectric layer of a piezoelectric vibrator in a liquid piezoelectric pump using a piezoelectric vibrator as a diaphragm.
Further, according to the present invention, when the upper housing and the lower housing that form the pump chamber by sandwiching the diaphragm are made of a synthetic resin, it is easy to form a flow path around the housing, and a structure for preventing the diaphragm from being damaged can be easily configured. The object is to obtain a liquid diaphragm pump.

The present inventor has completed the present invention by reaching the knowledge that the pressure balance applied to the front and back of the diaphragm can be improved only by guiding the liquid in the suction port or the discharge port in a free state to a chamber that has been conventionally used as an atmospheric chamber. is there.
That is, the present invention relates to a diaphragm sandwiched between an upper housing and a lower housing and forming a pump chamber between the lower housing; a suction port formed in the lower housing and connected to the pump chamber, and a discharge A check valve between the suction port and the pump chamber that allows fluid flow from the suction port to the pump chamber and prevents the reverse flow; and between the discharge port and the pump chamber to the discharge port In a liquid diaphragm pump that obtains a pumping action by vibrating the diaphragm, it is opposite to the pump chamber between the upper housing and the diaphragm. Forming a liquid chamber on the side, straddling the upper housing and the lower housing, and at least one of the liquid chamber, the suction port and the discharge port The free liquid flow path communicating provided, said through free liquid passage is characterized in that a freely movable liquid between the suction inlet port or discharge port and the liquid chamber.

  In mass-produced products, both the upper housing and the lower housing are preferably formed from a molded product of a synthetic resin material. In this case, the upper housing includes the liquid chamber, an external opening hole that opens to the outer surface of the upper housing, and a connection hole that opens to the lower housing side. The lower housing is provided with a flow passage protrusion to be inserted into the connection hole, and an internal passage for communicating either the suction port or the discharge port with the external opening hole of the upper housing is provided in the flow passage protrusion. It is preferable to form the free liquid flow path by the internal passage and the external opening hole.

  In this aspect, the flow projection of the lower housing includes the large-diameter portion and the large-diameter portion so that the liquid-tight free liquid flow channel is configured simply by inserting the flow projection of the lower housing into the connection hole of the upper housing. A narrow-diameter portion located at the upper portion of the large-diameter portion and an annular inclined surface that is not orthogonal to the axis that divides the large-diameter portion and the thin-diameter portion are provided, and the outer opening hole of the upper housing has A large-diameter hole that opens, a small-diameter hole located inside the large-diameter hole, and an annular slope that is not orthogonal to the axis corresponding to the annular slope of the channel protrusion located at the boundary between the large-diameter hole and the small-diameter hole; And an O-ring fitted to the narrow diameter portion of the channel protrusion is compressed and sandwiched between the two annular inclined surfaces to maintain liquid tightness.

  Specifically, the diaphragm is composed of a piezoelectric vibrator having an alternately laminated structure of at least one shim made of a conductive metal thin plate and at least one piezoelectric layer, and the shim is disposed on the liquid chamber side. It is good to be located. Between the shim and the piezoelectric layer, or on the front and back of the piezoelectric layer, there is an adhesive layer for bonding the shim and the piezoelectric layer, or an electrode layer for energizing the piezoelectric layer. The electrode layer is not included as an element of the laminated structure. Each piezoelectric layer may have a single layer structure or a multiple layer structure in which a plurality of layers are electrically connected in series or in parallel.

  In a preferred aspect of the piezoelectric vibrator, the shim includes a main shim having piezoelectric layers on the front and back sides thereof, and a protective shim laminated on the piezoelectric layer on the liquid chamber side of the piezoelectric layers on the front and back sides of the main shim. is doing.

  The protective shim preferably has a large diameter covering the entire liquid chamber side piezoelectric layer, but the tensile stress received by the flat circular liquid chamber side piezoelectric material is the largest at the center and decreases as it goes to the periphery. In consideration of the above, it is possible to make the diameter small so as to expose the peripheral edge portion of the liquid chamber side piezoelectric layer.

  Specifically, the protective shim is preferably composed of a conductive metal thin plate having a thickness of 5 to 500 μm, such as stainless steel or 42 alloy.

  The present invention provides a liquid diaphragm pump that forms a pump chamber that receives liquid pressure on one of the front and back sides of a diaphragm, and a liquid chamber is formed on the opposite side of the diaphragm from the pump chamber. Since the liquid in the discharge port is guided in a free state, the pressure balance applied to the front and back of the diaphragm can be improved, the diaphragm can be prevented from being damaged, and a longer life can be achieved.

  The present embodiment is an embodiment in which the present invention is applied to a piezoelectric liquid pump using a piezoelectric vibrator as a diaphragm. As shown in FIGS. 1 to 3, the piezoelectric liquid pump 20 has a lower housing 21 and an upper housing 22 made of a synthetic resin material, and the lower housing 21 has a lower divided lower housing 21D and an upper portion. The divided lower housing (middle housing) 21U. The divided lower housing 21D and the divided lower housing 21U may be integrally formed.

  A cooling water (liquid) suction port 24 and a discharge port 25 are opened in the divided lower housing 21D. Between the divided lower housing 21U and the upper housing 22, the piezoelectric vibrator 10 is liquid-tightly supported and supported via a pair of annular narrowing members (O-ring 27, guide 28). 10 and the divided lower housing 21 </ b> U constitute a pump chamber P, and a liquid chamber A constitutes between the piezoelectric vibrator 10 and the upper housing 22. An annular electrode terminal 29 is in close contact with the pump chamber P side of the piezoelectric vibrator 10.

  The divided lower housing 21D and the divided lower housing 21U are formed with a suction flow path 30 for communicating the suction port 24 and the pump chamber P, and a discharge path 31 for communicating the pump chamber P and the discharge port 25, respectively. In the housing 21U, check valves (umbrellas) 32 and 33 are provided in the suction passage 30 and the discharge passage 31, respectively. The check valve 32 is a suction-side check valve that allows a fluid flow from the suction port 24 to the pump chamber P and does not allow the reverse fluid flow. The check valve 33 transfers from the pump chamber P to the discharge port 25. This is a discharge-side check valve that allows the fluid flow of the fluid but does not permit the reverse fluid flow. The check valves 32 and 33 in the illustrated embodiment have the same configuration, and are provided with umbrellas 32b and 33b made of an elastic material on perforated substrates 32a and 33a that are bonded or welded and fixed to the flow path. .

  The divided lower housing 21D has a rectangular storage recess 21a formed at a position separated from the suction flow path 30 and the discharge path 31, and a piezoelectric vibration is provided between the storage recess 21a and the split lower housing 21U. A driver circuit board 26 that drives and controls the child 10 is stored in a liquid-tight manner. When the divided lower housing 21D and the divided lower housing 21U are integrally formed, the driver circuit board 26 is accommodated from the back side of the lower housing and appropriately covered.

  When the piezoelectric vibrator 10 is elastically deformed (vibrated) in the forward and reverse directions, the piezoelectric pump 20 opens the suction side check valve 32 and closes the discharge side check valve 33 in the stroke in which the volume of the pump chamber P increases. The liquid flows into the pump chamber P from the suction port 24. On the other hand, in the stroke in which the volume of the pump chamber P decreases, the discharge side check valve 33 opens and the suction side check valve 32 closes, so that the liquid flows out from the pump chamber P to the discharge port 25. Accordingly, the pump action can be obtained by elastically deforming (vibrating) the piezoelectric vibrator 10 continuously in the forward and reverse directions.

  The piezoelectric vibrator (diaphragm) 10 having a planar circular shape has a structure in which piezoelectric layers 12f and 12r are laminated and bonded to the front and back of the main shim 11, as shown in FIGS. A protective shim 13 is laminated and adhered on the piezoelectric layer 12f facing the A side, and a cover film 14 is laminated and adhered on the piezoelectric layer 12r facing the pump chamber P side. The piezoelectric layer 12f on the front side (liquid chamber A side) is formed smaller than the diameter of the main shim 11, and the guide 28 is located on the outer portion of the outer portion of the piezoelectric layer 12f on the front side (liquid chamber A side) of the main shim 11. The main shim 11 is supported tightly. In FIG. 2, the piezoelectric layers 12f and 12r, the main shim 11, and the cover film 14 of the piezoelectric vibrator 10 are omitted.

  The main shim 11 is a conductive metal thin plate made of stainless steel or 42 alloy having a thickness of about 30 to 500 μm, and has rigidity for supporting the piezoelectric layers 12f and 12r.

The piezoelectric layers 12f and 12r on the front and back of the main shim 11 are made of a piezoelectric material such as PZT (Pb (Zr, Ti) O ₃ ) having a thickness of about 50 to 500 μm, for example, and are subjected to polarization treatment in the front and back directions. Has been. The polarization directions of the piezoelectric layers 12f and 12r on the front and back sides are the same direction. Such a piezoelectric vibrator is known as a bimorph type (parallel connection). When the same alternating electric field is applied to the front and back of each of the piezoelectric layers 12f and 12r, a cycle in which one of the front and back of the piezoelectric layers 12f and 12r extends and the other contracts is repeated, and the shim 11 (piezoelectric vibrator 10) is centered. It vibrates so that the amplitude of the part becomes the largest.

  Like the main shim 11, the protective shim 13 is a conductive metal thin plate made of stainless steel having a thickness of about 5 to 500 μm, 42 alloy, or the like. The protective shim 13 has a diameter that covers the entire piezoelectric layer 12f on the liquid chamber A side. By providing this protective shim 13, the tensile stress applied to the piezoelectric layer 12f on the liquid chamber A side can be relaxed, and the occurrence of cracks can be prevented. As described above, in the piezoelectric vibrator 10, the front side (liquid chamber A side) piezoelectric layer 12f is formed smaller than the diameter of the main shim 11, and the guide 28 is a front side (liquid chamber A side) piezoelectric body of the main shim 11. The main shim 11 is tightly supported on the outer part of the outer shape of the layer 12f, but the front side (liquid chamber A side) piezoelectric layer 12f has the same diameter as the main shim 11, and the guide 28 is on the front side (liquid chamber A side). ) It may be a structure in contact with the piezoelectric layer 12f.

  The cover film 14 is laminated and bonded onto the piezoelectric layer 12r located on the pump chamber P side, and protects the piezoelectric layer 12r from the fluid entering and leaving the pump chamber P. The cover film 14 is made of a synthetic resin film having a thickness of about 10 to 100 μm, for example, PPS (polyphenylene sulfide).

  The annular electrode terminal 29 located on the back side of the piezoelectric vibrator 10 is in electrical contact with the exposed surface of the piezoelectric layer 12r on the back side of the main shim 11 in an annular shape. Further, the protective shim 13 positioned on the front surface of the piezoelectric vibrator 10 is in electrical contact with the exposed surface of the piezoelectric layer 12 on the front surface of the main shim 11 in a concentric manner. The main shim 11, the protective shim 13, and the annular electrode terminal 29 have wiring projections 11a, 13a, and 29a for connecting wires at their peripheral portions, respectively, and the divided lower housing 21U corresponds to the wiring projections 11a, 13a, and 29a. A protruding recess 22 a is formed continuously with the pump chamber P.

  The diameter of the annular electrode terminal 29 is substantially the same as the diameter of the O-ring 27, and they do not cross each other when seen in a plan view. That is, the annular electrode terminal 29 and the O-ring 27 have a relationship in which at least a part thereof overlaps along the entire circumference, or the relationship in which the O-ring 27 can press the annular electrode terminal 29 over the entire circumference. It is. Therefore, when the O-ring 27 and the annular electrode terminal 29 overlap with each other, the O-ring 27 is positioned in one plane, and no minute unevenness is generated, and the minute unevenness generated in the O-ring 27 adversely affects the liquid tightness. There is nothing.

  In the present embodiment, the discharge port 25 and the liquid chamber A communicate with each other via a free liquid channel 40 formed across the lower housing 21 and the upper housing 22. The free liquid flow path 40 will be described with reference to FIGS. 1, 2, 5 and 6. The upper housing 22 is formed with a recess 22a that forms the liquid chamber A, and an external opening 41 that extends in parallel with the recess 22a and whose inner end communicates with the recess 22a via the communication path 22b. The external opening hole 41 is located at the boundary between the large-diameter hole 41a that opens to the outer surface of the upper housing 22, the small-diameter hole 41b that is located inside the large-diameter hole 41a, and the large-diameter hole 41a and the small-diameter hole 41b. It has an annular slope 41c that is not orthogonal to the axis. Further, the upper housing 22 is formed with a connection hole 42 that is positioned on the annular inclined surface 41c portion of the outer opening hole 41 and communicates perpendicularly to the outer opening hole 41 and opens to the lower housing 21 side. . The external opening hole 41 and the connection hole 42 can be formed integrally with the upper housing 22 by a forming die (cutting die).

  The lower housing 21 is formed with a channel protrusion 43 that fits into the connection hole 42 of the upper housing 22. FIG. 6 shows the shape of the channel protrusion 43. Specifically, the channel protrusion 43 is formed integrally with the divided lower housing 21D, and includes a large diameter portion 43a, a small diameter portion 43b positioned above the large diameter portion 43a, and the large diameter portion 43a. It has an annular slope 43c that is not orthogonal to the axis that divides (determines the boundary of) the small-diameter portion 43b, and an internal flow path 44 that communicates with the discharge port 25 is formed in the shaft portion. The divided lower housing 21U is formed with an insertion hole 45 through which the large diameter portion 43a of the flow path projection 43 is inserted. The channel protrusion 43 can also be formed integrally with the divided lower housing 21D by a forming die (cutting die).

  The annular inclined surface 41c of the external opening hole 41 and the annular inclined surface 43c of the flow passage protrusion 43 are in a corresponding relationship. In the illustrated example, the annular inclined surface 41c (annular inclined surface 43c) is the axis of the external opening hole 41 (flow passage protrusion 43). The angle is 45 °. This angle can be changed within a range of about 30 ° to 60 °. An O-ring 46 is fitted around the small-diameter portion 43 b of the channel protrusion 43 (on the annular slope 43 c), and when the channel protrusion 43 is fitted into the connection hole 42, the annular slope 41 c of the external opening hole 41. And an annular slope 43c of the channel protrusion 43, an O-ring 46 is sandwiched and compressed, and a liquid-tight free liquid channel 40 is formed by the internal channel 44 and the small diameter hole 41b.

  The piezoelectric pump 20 configured as described above has a wiring between the wiring protrusion 11a of the main shim 11 and the wiring protrusion 13a of the protective shim 13 (between the front and back surfaces of the front piezoelectric layer 12f) and between the wiring protrusion 11a of the main shim 11 and the annular electrode terminal 29. When an alternating electric field is applied between the protrusions 29a (between the front and back surfaces of the back-side piezoelectric layer 12r), the piezoelectric vibrator 10 is elastically deformed (vibrated) in the forward and reverse directions. Then, as described above, the liquid is sucked from the suction port 24 into the pump chamber P, and then the pumping action of discharging from the pump chamber P to the discharge port 25 is repeated. In this pumping operation, the liquid chamber A communicates with the discharge port 25 via the free liquid flow path 40. Therefore, in the process of increasing the volume of the pump chamber P, the liquid flows from the liquid chamber A to the discharge port 25. In the process of reducing the volume of the pump chamber P, the liquid flows from the discharge port 25 to the liquid chamber A. In any state, since the liquid pressure of the discharge port P is exerted on the liquid chamber A in a free state, the unbalance of the pressure applied to the front and back of the piezoelectric vibrator 10 is improved. This effect is apparent when compared with the conventional product in which the liquid chamber A is an air chamber.

  In addition, liquid pressure is constantly applied to the piezoelectric vibrator 10 from the pump chamber P side. As a result, tensile stress is applied to the piezoelectric layer 12f on the liquid chamber A side. The present embodiment in which the free liquid pressure of the discharge port 25 is guided to the liquid chamber A can be expected to relax the tensile stress applied to the piezoelectric layer 12f on the liquid chamber A side. Further, according to the present embodiment, the liquid chamber The protective shim 13 laminated and adhered to the piezoelectric layer 12f on the A side resists this tensile stress well. That is, the tensile stress applied to the piezoelectric body layer 12f is relaxed by the protective shim 13, and cracks can be prevented from occurring in the piezoelectric body layer 12f, or the life of the piezoelectric body layer 12f can be extended.

  In the above embodiment, the free liquid flow path 40 connected to the liquid chamber A is communicated with the discharge port 25, but may be communicated with the suction port 24.

  Further, according to the illustrated embodiment, by combining the divided lower housings 21U and 21D and fitting the flow path protrusion 43 of the divided lower housing 21D into the connection hole 42 of the upper housing 22, the annular inclined surface 41c of the external opening hole 41 and the flow path There is an advantage that the O-ring 46 is compressed between the annular inclined surface 43c of the protrusion 43 and the liquid-tight free liquid flow path 40 is formed by the internal flow path 44 and the small diameter hole 41b. However, for example, the liquid tightness can be maintained by closing the opening end of the external opening hole 41 with another member.

  In the above embodiment, the piezoelectric vibrator is exemplified as the diaphragm. However, the present invention can be widely applied to liquid pumps using other vibrating diaphragms.

  In the above embodiment, the names “upper” and “lower” are given to the housing for the sake of convenience. However, it is obvious that the housing is not limited thereto.

It is a disassembled perspective view which shows embodiment which applied the diaphragm pump by this invention to the piezoelectric pump. It is sectional drawing which follows the II-II line in the assembly state of the piezoelectric pump of FIG. It is sectional drawing which shows the detail of a structure around the piezoelectric vibrator of the piezoelectric pump of FIG. FIG. 3 is a schematic exploded perspective view of the same piezoelectric vibrator. It is the V section expanded sectional view of FIG. (A), (B) is the perspective view which changed the view direction which shows the example of the shape of the flow-path protrusion protruded from the lower housing, and an O-ring.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Piezoelectric vibrator 11 Main shim 11a Wiring protrusion 12 12f 12r Piezoelectric layer 13 Protection shim 13a Wiring protrusion 14 Cover film 20 Piezoelectric pump 21 Lower housing 21D Split lower housing 21U Split lower housing (middle housing)
22 Upper housing 22a Recess 22b Communication path 24 Suction port 25 Discharge port 29 Annular electrode terminal 29a Wiring projection 30 Suction flow path 31 Discharge flow path 32 33 Check valve 40 Free liquid flow path 40 External opening hole 41a Large diameter hole 41b Small diameter hole 41c Annular slope 42 Connection hole 43 Channel protrusion 43a Large diameter part 43b Small diameter part 43c Annular slope 44 Internal channel 45 Insertion hole 46 O-ring A Liquid chamber P Pump chamber

Claims (6)

A diaphragm sandwiched between the upper housing and the lower housing and forming a pump chamber between the lower housing;
A suction port and a discharge port formed in the lower housing and connected to the pump chamber;
A check valve between the suction port and the pump chamber that allows fluid flow from the suction port to the pump chamber and prevents reverse fluid flow; and between the discharge port and the pump chamber to the discharge port A check valve that allows fluid flow of the fluid and prevents reverse fluid flow;
In a liquid diaphragm pump that obtains a pump action by vibrating the diaphragm,
A liquid chamber is formed between the upper housing and the diaphragm on the opposite side of the pump chamber,
A free liquid channel that communicates the liquid chamber and at least one of the suction port and the discharge port is provided across the upper housing and the lower housing, and the suction port or the discharge port is provided via the free liquid channel. A liquid diaphragm pump characterized in that liquid can freely move between a port and a liquid chamber. 2. The liquid diaphragm pump according to claim 1, wherein the upper housing and the lower housing are both formed of a synthetic resin material,
The upper housing has the liquid chamber, an external opening hole that opens to the outer surface of the upper housing, and a connection hole that opens to the lower housing side and communicates with the external opening hole.
The lower housing has a flow path protrusion inserted into the connection hole, and an internal passage that communicates either the suction port or the discharge port with the external opening hole of the upper housing is formed in the flow path protrusion. Formed,
A liquid diaphragm pump in which the internal passage and the external opening constitute the free liquid flow path. 3. The liquid diaphragm pump according to claim 2, wherein the flow path protrusion of the lower housing has a large diameter portion, a small diameter portion located above the large diameter portion, and an axis that divides the large diameter portion and the small diameter portion. An annular slope that is not orthogonal to the
The outer opening hole of the upper housing includes a large-diameter hole that opens to the outer surface of the upper housing, a small-diameter hole that is located inside the large-diameter hole, and the flow path protrusion that is located at the boundary between the large-diameter hole and the small-diameter hole. An annular slope that is not orthogonal to the axis corresponding to the annular slope,
A liquid diaphragm pump in which an O-ring fitted to a narrow diameter portion of the flow path protrusion is compressed and sandwiched between both annular inclined surfaces to maintain liquid tightness. 4. The liquid diaphragm pump according to claim 1, wherein the diaphragm comprises a piezoelectric vibrator having an alternately laminated structure of at least one shim made of a conductive metal thin plate and at least one piezoelectric layer. And a liquid diaphragm pump in which the shim is positioned on the liquid chamber side. 5. The liquid diaphragm pump according to claim 4, wherein the shim includes a main shim having piezoelectric layers on both sides thereof, and a protective shim laminated on the piezoelectric layer on the liquid chamber side of the piezoelectric layers on the front and back sides of the main shim. Liquid diaphragm pump having. 6. The liquid diaphragm pump according to claim 4, wherein the protective shim is a conductive metal thin plate having a thickness of 5 to 500 [mu] m.

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