JP2009281300A - Liquid circulation system including piezoelectric pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a liquid circulation system including a thin-shaped piezoelectric pump having a long service life in which cracks are hardly caused in a piezoelectric body layer of a piezoelectric vibrator or the deterioration of polarization is suppressed. <P>SOLUTION: The liquid circulation system includes the piezoelectric pump 20 having a pump chamber P and an atmospheric chamber A formed on front and rear sides of the piezoelectric vibrator 10 with its edge kept liquid-tight to obtain a pumping function by vibrating the piezoelectric vibrator 10, a circulation flow path 60 extending from a discharge port 25 to a suction port 14 of the pump chamber P, and a suction fluid resistance regulating pipe 70 and a discharge fluid resistance regulating pipe 80 arranged on the circulation flow path 60 in the vicinity of the suction port 24 and the discharge port 25. The fluid resistance of the suction fluid resistance regulating pipe 70 is set larger than that of the discharge fluid resistance regulating pipe 80. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a liquid circulation system including a piezoelectric pump that obtains a pump action by a vibrating piezoelectric vibrator.

  Conventionally, various liquid cooling devices for circulating a liquid have been proposed as cooling devices for electronic components (Patent Documents 1 to 6). In recent years, piezoelectric pumps that are excellent in miniaturization and thinning have attracted attention as pumps for liquid cooling devices such as liquid crystal TVs and notebook personal computers. A piezoelectric pump forms a pump chamber and an air chamber on the front and back sides of a piezoelectric vibrator whose periphery is held liquid-tight, and a pair of check valves (to the pump chamber) having different flow directions are formed in a pair of flow paths connected to the pump chamber. And a check valve that allows fluid outflow from the pump chamber). When the piezoelectric vibrator is vibrated, the volume of the pump chamber changes, and a pump action is obtained because one of the pair of check valves closes and the other opens in accordance with the volume change (Patent Document 6). .

As the piezoelectric vibrator used in this piezoelectric pump, 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 are known. Both types of piezoelectric vibrators are common in that they have an alternately laminated structure of at least one shim made of a conductive metal thin plate and at least one piezoelectric layer polarized in the layer thickness direction. 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.
JP-A-5-160310 JP 2005-79066 A Japanese Patent No. 2661265 JP-A-11-89213 Japanese Patent Laid-Open No. 2002-268038 Japanese Patent Laid-Open No. 2003-75037

  However, a piezoelectric vibrator provided with a piezoelectric layer on the atmosphere chamber side may crack in the piezoelectric layer on the atmosphere chamber side or be polarized in the thickness direction of the piezoelectric layer (polling) when used for a long time. ), It has been found that there is a possibility that a predetermined displacement may not occur even if a predetermined voltage is applied to the piezoelectric vibration by releasing the polarization.

  In the liquid cooling devices described in the cited documents 1 to 5, the flow rate is adjusted by inserting a resistance element into the flow path, changing the diameter and length of the flow path, etc., but the pump is not specified. Even if a piezoelectric pump is used in these conventional liquid cooling devices, problems such as the occurrence of cracks in the piezoelectric layer cannot be solved.

  Accordingly, an object of the present invention is to provide a liquid circulation system including a long-life piezoelectric pump that is thin, hardly cracks in a piezoelectric layer of a piezoelectric vibrator, and is difficult to unpolarize.

  As a result of researches on the cause of cracks in the piezoelectric layer on the atmosphere chamber side and the cause of the unraveling of polarization, the piezoelectric vibrator is always projected to the atmosphere chamber side during operation by receiving liquid pressure on the pump chamber side. To the conclusion that the generation of cracks is caused by the application of tensile stress in the in-plane direction to the thin piezoelectric layer having a thickness of 100 to 300 μm on the atmosphere chamber side. Reached. Also, when a tensile stress is applied in the in-plane direction of the piezoelectric layer, at the same time, a compressive stress is applied in the thickness direction of the piezoelectric layer, and it is discovered that the polarization is released by this compressive stress, The present invention has been made. That is, the piezoelectric layer made of ceramic is strong against compressive force but weak against tensile force. Therefore, the tensile force acting on the piezoelectric layer may be reduced, and polarization can be prevented from being released. As long as the compression stress in the direction parallel or antiparallel to the polarization should not be applied, it is based on the point of view.

  The present invention for solving the above-mentioned problems is a piezoelectric pump in which a pump chamber and an air chamber are formed on the front and back of a piezoelectric vibrator having a liquid-tight peripheral edge, and the piezoelectric vibrator vibrates to obtain a pump action; Piezoelectric pumps in which a pump chamber and an air chamber are formed on the front and back surfaces of the closely-maintained piezoelectric vibrator to obtain a pump action by vibrating the piezoelectric vibrator; a circulation flow path from the discharge port of the pump chamber to the suction port; And a fluid resistance adjusting member that is formed separately from the piezoelectric pump and is provided in the middle of the circulation flow path and in the vicinity of at least one of the discharge port and the suction port. The fluid resistance on the suction port side is formed to be larger than the fluid resistance on the discharge port side.

  The fluid resistance adjusting member is preferably provided in the vicinity of both the suction port and the discharge port. By providing both, the adjustment range is widened and versatility is enhanced.

  The fluid resistance adjusting member is tubular, and the fluid resistance can be adjusted by changing the inner diameter thereof. Easy to manufacture and adjust.

In the present invention, as the piezoelectric pump, the piezoelectric vibrator of the piezoelectric pump has an alternately laminated structure of at least one shim made of a conductive metal thin plate and at least one piezoelectric layer, and It can also be used for the shim facing the pump chamber.
As the piezoelectric pump, a unimorph type in which a single piezoelectric layer is formed only on the surface of the shim on the atmosphere chamber side, or a bimorph type in which a plurality of piezoelectric layers are formed can be used. The piezoelectric pump is provided with check valves between the suction port and the pump chamber, and between the discharge port and the air chamber, and these check valves are used with the same specifications. it can.

  In the liquid circulation system including the piezoelectric pump according to the present invention, the piezoelectric vibrator is disposed so that the shim faces the pump chamber side, and circulation in the vicinity of the suction port to the pump chamber or the fluid discharge port from the pump chamber is performed. Since a fluid resistance adjusting member is provided in the middle of the flow path so that the fluid resistance on the suction port side is increased by the fluid resistance adjusting member, the tensile stress in the in-plane direction and the thickness direction (polarization) It is possible to relieve the compressive stress (in the direction parallel or antiparallel to the direction) and to extend the life. Furthermore, since the fluid resistance can be adjusted by the fluid resistance adjusting member, it is possible to easily provide a liquid circulation system that can obtain desired characteristics by using the piezoelectric pump of the same standard.

  Hereinafter, the best embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an embodiment in which a liquid circulation system having a piezoelectric pump of the present invention is applied to a liquid cooling system for a personal computer. This embodiment includes a piezoelectric pump 20, a heat receiving unit 40 having a first heat source (CPU) 40A and a second heat source (GPU) 40B, and a heat radiating unit 50.

  2 and 3 show the basic structure of the piezoelectric pump used in the liquid circulation system of the present invention. The piezoelectric pump 20 has a lower housing 21, a middle housing 22, and an upper housing 23 that are stacked in order from the bottom of the figure.

  In the lower housing 21, a suction port 24 and a discharge port 25 for cooling water (fluid, liquid) are opened. Between the middle housing 22 and the upper housing 23, an annular electrode terminal 29 disposed on the front side (atmosphere chamber A side) of the piezoelectric vibrator 10 via a pair of annular narrowing members (O-ring 27, guide 28) A main shim 11 disposed on the back side (pump chamber P side) of the piezoelectric vibrator 10 is supported in a liquid-tight manner with the piezoelectric vibrator 10 interposed therebetween, and is interposed between the piezoelectric vibrator 10 and the middle housing 22. A pump chamber P is configured. An atmospheric chamber A is formed between the piezoelectric vibrator 10 and the upper housing 23. The atmosphere chamber A may be opened or sealed.

  The lower housing 21 and the middle housing 22 are respectively formed with a suction channel 30 for communicating the suction port 24 and the pump chamber P and a discharge channel 31 for communicating the pump chamber P and the discharge port 25. Are provided with check valves (umbrellas) 32 and 33 in the suction flow path 30 and the discharge flow path 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 umbrellas 32b and 33b made of an elastic material are mounted on perforated substrates 32a and 33a that are bonded or welded and fixed to the flow path. A plurality of communication holes 32c and 33c are formed in the perforated substrates 32a and 33b, respectively.

  The lower housing 21 is formed with a rectangular storage recess 21 a at a position separated from the suction flow path 30 and the discharge flow path 31, and the piezoelectric vibrator is interposed between the storage recess 21 a and the middle housing 22. A driver circuit board 26 for driving and controlling the liquid crystal 10 is stored in a liquid-tight manner.

  When the piezoelectric vibrator 10 is elastically deformed (vibrated) in the forward / reverse direction (projecting into the air chamber A and projecting into the pump chamber P), the piezoelectric pump 20 is operated on the suction side in the process of expanding the volume of the pump chamber P. Since the check valve 32 is opened and the discharge side check valve 33 is closed, 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 discharge port 25 and the suction port 24 of the piezoelectric pump 20 are connected to a series of circulation channels 60, and a heat receiving unit having a first heat source 40 </ b> A and a second heat source 40 </ b> B on the circulation channel 60. The part 40 and the heat radiating part 50 are installed. Further, a discharge fluid resistance adjusting pipe 80 is provided as a fluid resistance adjusting member in the vicinity of the discharge port 25, that is, in the middle of the circulation flow path 60 between the discharge port 25 and the first heat source 40A. That is, the suction fluid resistance adjusting pipe 70 is provided as a fluid resistance adjusting member in the middle of the circulation flow path 60 between the suction port 24 and the heat radiating portion 50. The longitudinal sections of the discharge fluid resistance adjusting pipe 80 and the suction fluid resistance adjusting pipe 70 are shown in FIG. In this embodiment, the smallest inner diameter Inφ of the suction fluid resistance adjusting pipe 70 is formed to be thinner than the smallest inner diameter Outφ of the discharge fluid resistance adjusting pipe 80 (FIGS. 5A and 5B). .

  In the piezoelectric pump 20 described above, as described above, the piezoelectric vibrator 10 (and the annular electrode terminal 29) is interposed between the middle housing 22 and the upper housing 23 via the pair of annular narrowing members (O-ring 27, guide 28). It is supported tightly in a liquid-tight manner.

  FIG. 4 is an enlarged cross-sectional view showing the piezoelectric vibrator 10 and its narrow support structure according to the embodiment of the present invention in an enlarged manner.

  The piezoelectric vibrator 10 is a piezoelectric vibrator having a circular main shim 11 and a circular piezoelectric layer 12 formed on the surface of the main shim 11.

  The main shim 11 is a conductive metal thin plate made of stainless steel or 42 alloy having a thickness of about 30 to 300 μm, and has rigidity to support the piezoelectric layer 12. The main shim 11 has a wiring projection 11a for connecting the wiring at the peripheral portion, the back surface (one surface) 11b faces the pump chamber P side, and the piezoelectric layer 12 is formed on the front surface (the other surface) 11c. It is. In the middle housing 22, a protruding recess 22 a corresponding to the wiring protrusion 11 a is formed continuously to the pump chamber P.

  The piezoelectric layer 12 is configured on the surface 11c of the main shim 11 and faces the atmosphere chamber A side. The diameter of the piezoelectric layer 12 is equal to or slightly smaller than the diameter of the circular portion of the main shim 11.

  The piezoelectric layer 12 is made of piezoelectric ceramics such as PZT having a thickness of 200 μm and a diameter of about 28 mm. When the positive and negative voltages are applied in the thickness direction as is well known, the piezoelectric layer 12 is elastic in the direction in which the surface area expands or contracts. Deform. The piezoelectric layer 12 has a surface on the main shim 11 side that is electrically connected to one of the pair of power supply lines via the shim side electrode layer 13b and the main shim 11, and a surface on the atmosphere chamber A side that connects the surface electrode layer 13c and the annular electrode terminal 29. Through the other power supply line.

  The annular electrode terminal 29 is an annular conductive metal thin plate that does not hinder the displacement of the piezoelectric layer 12 and can be stably connected to the surface electrode layer 13c, and is annularly bonded to the peripheral portion of the surface electrode layer 13c. It has the part 29b and the wiring protrusion 29a for wiring connection extended from the cyclic | annular part 29b, and is electrically connected to the electric power feeding line by the wiring protrusion 29a. The wiring protrusion 29a is paired with the wiring protrusion 11a of the main shim 11, and is housed in the protruding recess 22a of the middle housing 22 together with the wiring protrusion 11a. The annular electrode terminal 29 is formed of 42 alloy having a thickness of about 30 μm, for example.

  As shown in FIG. 4, the piezoelectric vibrator 10 is tightly supported at the peripheral portion of the piezoelectric layer 12 by a pair of elastic narrowing members (O-ring 27 and guide 28) having elasticity. The O-ring 27 is disposed between the middle housing 22 and the piezoelectric vibrator 10 and abuts on the peripheral edge portion of the back surface 11b of the main shim 11 to give an upward pressing force in the drawing. On the other hand, the guide 28 is disposed between the upper housing 23 and the piezoelectric vibrator 10, abuts on the annular electrode terminal 29 bonded to the surface electrode layer 13 c of the piezoelectric body layer 12, and the piezoelectric body is interposed via the annular electrode terminal 29. The peripheral edge of the layer 12 is pressed from the upward direction in the figure to the downward direction in the figure.

  In the piezoelectric pump 20 having the narrow attachment support structure, when an alternating voltage is applied between a pair of power supply lines, the surface area of the piezoelectric layer 12 is instantaneous when one power supply line is positive and the other power supply line is negative. Shrinks. Then, as a whole, the piezoelectric layer 12 deforms the piezoelectric vibrator 10 in a direction that protrudes toward the pump chamber P side. On the other hand, when the positive and negative of the pair of power supply lines are reversed, the surface area of the piezoelectric layer 12 is increased contrary to the above, and the piezoelectric vibrator 10 is deformed in a direction convex toward the atmosphere chamber A as a whole. . By repeating this, the piezoelectric vibrator 10 as a whole vibrates toward the pump chamber P side and the atmosphere chamber A side, and a pump action is obtained.

  During this pumping action, liquid pressure is constantly applied to the piezoelectric vibrator 10 from the pump chamber P side, and as a result, tensile stress is applied to the piezoelectric layer 12 on the atmosphere chamber A side. This tensile stress increases as the liquid temperature increases. In this embodiment, the inner diameter Inφ of the suction fluid resistance adjusting tube 70 is made thinner than the inner diameter Outφ of the discharge fluid resistance adjusting tube 80 (FIG. 5), and the fluid resistance flowing into the pump chamber P is changed to the pump chamber. It is larger than the fluid resistance flowing out from P. With this configuration, during the pump operation, the fluid pressure that causes the piezoelectric vibrator 10 to project and displace toward the atmosphere chamber A side becomes low, and the displacement that the piezoelectric vibrator 10 projects to the atmosphere chamber A side becomes small. The tensile stress in the in-plane direction generated in the piezoelectric layer 12 constituting the structure is reduced. Therefore, even if the piezoelectric layer 12 is provided on the atmosphere chamber A side, cracks are unlikely to occur in the piezoelectric layer 12 and the life is extended. Further, the compressive stress parallel to the thickness direction generated simultaneously in the piezoelectric layer 12 is relieved, so that the polarization polarized in the thickness direction is difficult to be solved, and characteristic deterioration due to a decrease in displacement can be prevented.

The combination of the inner diameter Inφ (mm) of the suction fluid resistance adjustment pipe 70 and the inner diameter Outφ (mm) of the discharge fluid resistance adjustment pipe 80, the displacement of the piezoelectric vibrator 10 on the pump chamber P side, and the displacement (μm) on the atmosphere chamber A side. Results obtained by experiments are shown in Table 1 as a table and FIG. 6 as a graph. In the graph of FIG. 6, the vertical axis represents the displacement (μm) of the piezoelectric vibrator 10, and the horizontal axis represents the combination of the inner diameters Inφ and Outφ (mm) of the suction fluid resistance adjustment tube 70 and the discharge fluid resistance adjustment tube 80.
<Table 1>

  Condition number (1) indicates that the inner diameters Inφ and Outφ of the suction fluid resistance adjustment pipe 70 and the discharge fluid resistance adjustment pipe 80 are equal. Condition number (8) indicates that the discharge fluid is larger than the inner diameter Inφ of the suction fluid resistance adjustment pipe 70. This is a comparative example when the inner diameter Outφ of the resistance adjusting tube 80 is reduced. In condition numbers (2), (3), (4), (5), (6), and (7), the inner diameter Inφ of the suction fluid resistance adjustment pipe 70 is set smaller than the inner diameter Outφ of the discharge fluid resistance adjustment pipe 80. It is an example of different combinations. From the above experimental results, in the conditions (2) to (7), the displacement on the atmosphere chamber A side becomes smaller than the condition (1). In particular, in the conditions (2) and (5) to (7), the atmosphere chamber side Is smaller than the displacement on the pump chamber side. Further, in the conditions (2) to (5) in which the value of (suction fluid resistance adjusting pipe inner diameter) / (discharge fluid resistance adjusting pipe inner diameter) is 0.56 to 0.89, the atmospheric chamber is more than the condition (1). It can be seen that the life of the piezoelectric layer 12 and the flow rate of the pump can be compatible since the displacement on the side is small and the overall displacement is not so small as compared with the condition (1). When the displacement on the atmosphere chamber A side is reduced, the tensile stress generated in the piezoelectric layer 12 is also reduced, the occurrence of cracks is prevented, and the life is extended. Under this condition, if the overall displacement is not reduced, it is possible to achieve both the flow rate of the pump. If the inner diameter Inφ of the suction fluid resistance adjusting pipe 70 is made thicker than the inner diameter Outφ of the discharge fluid resistance adjusting pipe 80 as in condition (8), the displacement on the atmosphere chamber side becomes smaller than in condition (1). However, it can be seen that the overall displacement is rather small, which is undesirable in this liquid circulation system.

  In the above embodiment, the fluid resistance to the pump chamber P is adjusted by making the inner diameters of the suction fluid resistance adjustment pipe 70 and the discharge fluid resistance adjustment pipe 80 different from each other. However, the fluid resistance may be adjusted by crushing a plastic pipe. Alternatively, the circulation channel 60 is formed of a tube made of rubber, synthetic resin or the like, and the tube is crushed by fitting a tubular fluid resistance adjusting member into the tube and crushing the fluid resistance adjusting member, thereby adjusting the cross-sectional area. The fluid resistance may be adjusted by the above. Furthermore, it is good also as a structure which adjusts fluid resistance by making the internal diameter of the fluid resistance adjustment pipes 70 and 80 the same, and varying length.

  In the illustrated embodiment, the suction and discharge fluid resistance adjusting pipes 70 and 80 are provided in the middle of the circulation flow path 60, but the circulation flow path 60 is formed so as to be used also as a connection pipe connected to the suction port 24 and the discharge port 25. May be. In short, in the present invention, the fluid adjustment member may be formed separately from the piezoelectric pump.

In the illustrated embodiment, the suction and discharge fluid resistance adjusting pipes 70 and 80 are provided in the vicinity of both the suction port 24 and the discharge port 25, but only one of them may be provided. In that case, it is preferable to provide the suction fluid resistance adjusting pipe 70.
In the present embodiment, the piezoelectric layer 12 is a unimorph, but an effect can be obtained even if it is a bimorph or a laminated type.

It is a system connection top view which shows one Embodiment of the liquid circulation system by this invention. It is a disassembled perspective view which shows the basic structure of the Example of the piezoelectric pump used for the embodiment. It is sectional drawing which follows the cutting line III-III of FIG. 1 of the piezoelectric pump. It is a partial expanded sectional view of sectional drawing of FIG. In the embodiment, (A) is a longitudinal sectional view of the suction fluid resistance adjusting pipe, and (B) is a longitudinal sectional view of the discharge fluid resistance adjusting pipe. FIG. 5 is a graph showing displacements of the piezoelectric vibrator on the atmosphere chamber side and the pump chamber side in different combinations of the inner diameter of the suction port and the inner diameter of the discharge port in the piezoelectric pump.

Explanation of symbols

10 Piezoelectric vibrator 11 Main shim 11a Wiring protrusion 12 Multilayer piezoelectric body 13b Shim side electrode layer 13c Surface electrode layer 20 Piezoelectric pump 21 Lower housing 22 Middle housing 23 Upper housing 24 Suction port 25 Discharge port 26 Driver circuit board 27 O-ring (narrow ring) Landing member)
28 Guide (annular constriction member)
29 annular electrode terminal 30 suction flow path 31 discharge flow path 32, 33 check valve 50 heat radiating section 60 circulation flow path 7070 suction fluid resistance adjustment pipe 8080 discharge fluid resistance adjustment pipe A atmosphere chamber P pump chamber

Claims (6)

A piezoelectric pump in which a pump chamber and an air chamber are formed on the front and back of the piezoelectric vibrator having a liquid-tight peripheral edge, and the piezoelectric vibrator is vibrated to obtain a pump action;
A circulation flow path from the discharge port of the pump chamber to the suction port; and formed separately from the piezoelectric pump, provided in the middle of the circulation flow path and in the vicinity of at least one of the discharge port and the suction port A fluid resistance adjusting member;
A fluid circulation system comprising a piezoelectric pump, wherein the fluid resistance adjusting member is formed such that a fluid resistance on the suction port side is larger than a fluid resistance on the discharge port side. 2. A liquid circulation system comprising the piezoelectric pump according to claim 1, wherein the fluid resistance adjusting member comprises a piezoelectric pump provided in the vicinity of both the suction port and the discharge port. 3. The liquid circulation system including the piezoelectric pump according to claim 1, wherein the fluid resistance adjusting member includes a piezoelectric pump that adjusts fluid resistance by changing an inner diameter. 4. The liquid circulation system including the piezoelectric pump according to claim 1, wherein the piezoelectric vibrator of the piezoelectric pump includes at least one shim made of a conductive metal thin plate and at least one piezoelectric layer. A liquid circulation system comprising a piezoelectric pump having an alternating laminated structure with the shim facing the pump chamber. 5. The liquid circulation system including the piezoelectric pump according to claim 4, wherein the piezoelectric vibrator is a unimorph type in which the single piezoelectric layer is formed only on the surface of the shim on the atmosphere chamber side, or a plurality of the piezoelectric vibrators. A liquid circulation system including a bimorph type piezoelectric pump in which a body layer is formed. 6. The liquid circulation system comprising the piezoelectric pump according to claim 4 or 5, wherein the piezoelectric pump has check valves between the suction port and the pump chamber, and between the discharge port and the air chamber, respectively. A liquid circulation system provided with a piezoelectric pump that is provided and these check valves have the same specifications.

Images