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  Diaphragm pump and cooling system with the diaphragm pumpUSPTO Application #: 20070065308Title: Diaphragm pump and cooling system with the diaphragm pump Abstract: A diaphragm pump enabling an increase in pump efficiency by reducing the pressure loss of liquid and reduction in thickness. The flow passage in piezoelectric pump (1) includes a pressure chamber (50) formed into a flat shape in cross section and a suction side flow passage (70a) and discharge side flow passage (70b). The suction side flow passage (70a) and the discharge side flow passage (70b) are disposed at both ends of the pressure chamber (50) so that the axes thereof are aligned with each other. The check valves (20a, 20b) are respectively disposed on the suction side flow passage (70a) and the discharge side flow passage (70b), and are tilted relative to the flow direction of the liquid. (end of abstract) Agent: Sughrue Mion, PLLC - Washington, DC, US Inventors: Mitsuru Yamamoto, Yasuhiro Sasaki, Atsushi Ochi, Sakae Kitajo USPTO Applicaton #: 20070065308 - Class: 417413100 (USPTO) Related Patent Categories: Pumps, Motor Driven, Electric Or Magnetic Motor, Collapsible Wall Pump, Diaphragm Type The Patent Description & Claims data below is from USPTO Patent Application 20070065308. Brief Patent Description - Full Patent Description - Patent Application Claims
TECHNICAL FIELD [0001] The present invention relates to a diaphragm pump used for a cooling system or the like, and in particular, relates to a slim diaphragm pump capable of discharging liquid efficiently. Further, the present invention relates to a cooling system with the diaphragm pump used for cooling electronic equipment or the like. BACKGROUND ART [0002] As the performance of electronic equipment becomes higher and processing speed is enhanced, power consumption for electronic parts such as CPU increases. As a result, the heating value in the electronic parts becomes high, and it is absolutely necessary to have a technology that can efficiently dissipate heat generated from the electronic parts and that remains inside the electronic equipment in terms of ensuring reliable operation of the electronic equipment. [0003] As a cooling technique for a portable personal computer such as a notebook personal computer, instead of an air-cooled cooing system, there is proposed a water-cooled cooling system that can provide cooling by circulating liquid by a pump (for example, refer to Japanese Patent Laid-Open No. 2002-232174). The water-cooled cooling system is provided with a closed-structure flow passage to be in thermally contact with heating parts, such as electronic parts, and a pump to circulate the liquid inside the flow passage. The cooling system dissipates heat by circulating the liquid that is heated by the heated parts with the pump, so as to provide cooling for the heated parts. [0004] As the pump for the cooling system, a piezoelectric pump, a kind of diaphragm pump, which is compact and capable of generating a high discharge pressure, is often used. The piezoelectric pump is usually provided with a pressure chamber with a suction port and a discharge port, a piezoelectric oscillator disposed on a wall of the pressure chamber, and a flow passage that is connected with the suction port and the discharge port. In the piezoelectric pump, the piezoelectric oscillator functions as a diaphragm in the diaphragm pump. The piezoelectric oscillator is provided with an elastic plate made of metal and the like and a piezoelectric element bonded to the elastic plate. When a voltage is applied to the piezoelectric element, the elastic plate (piezoelectric oscillator itself) is bent and displaced. In the piezoelectric pump, by oscillating the piezoelectric oscillator, pressure operating on the liquid is generated in the pressure chamber. Further, the suction port and the discharge port are provided with check valves to prevent backflow of the liquid so as to restrict the flow direction of the liquid from the suction port to the discharge port. [0005] FIG. 10 shows an example of a conventional piezoelectric pump. The piezoelectric pump shown in FIG. 10 is provided with piezoelectric oscillator 130 arranged to form an upper surface of pressure chamber 150. On the lower surface of pressure chamber 150, suction port 121a is provided for ingesting the liquid and discharge port 121 b is provided for discharging the liquid. Suction side flow passage 170a for supplying the liquid to suction port 121a is formed under pressure chamber 150, and is connected with suction port 121a. Discharge side flow passage 170b, a flow passage for the liquid discharged from discharge port 121b, is formed under the pressure chamber 150, and is connected with discharge port 121b. With this arrangement, the flow passage of the liquid in piezoelectric pump 100 is formed from suction side flow passage 170a to discharge side flow passage 170b through suction port 121a, pressure chamber 150, and discharge port 121b in order. [0006] Suction port 121a and discharge port 121b are respectively provided with suction valve 120a and discharge valve 120b. Suction valve 120a and discharge valve 120b are made from elastic members, such as silicon rubber, and respectively control the opening and closing of suction port 121 a and discharge port 121b. [0007] Piezoelectric pump 100, arranged as described above, operates as follows. When piezoelectric oscillator 130 is displaced upward and the volume in pressure chamber 150 is increased, there is a negative pressure in pressure chamber 150. With this operation, suction valve 120a is opened and the liquid is supplied from suction side flow passage 170a into pressure chamber 150. At this time, by the action of discharge valve 120b, there is no backflow of the liquid from discharge side flow passage 170b to pressure chamber 150. Then, piezoelectric oscillator 130 is displaced in the opposite direction, and the volume of pressure chamber 150 is reduced. Then, since the pressure in pressure chamber 150 is raised, discharge valve 120b is opened and the liquid is discharged toward discharge side flow passage 170b. At this time, since suction valve 120a operates, there is no backflow of the liquid from pressure chamber 150 to suction side flow passage 170a. Piezoelectric pump 100 functions as a pump by repeating the above-mentioned operations, and the liquid can flow in one direction. [0008] However, in conventional pumps, the flow passage from the suction side flow passage to the discharge side flow passage via the pressure chamber is formed in being bent. For example, in piezoelectric pump 100 shown in FIG. 10, suction side flow passage 170a and discharge side flow passage 170b are formed under pressure chamber 150, and are each connected with suction port 121 a and discharge part 120b arranged on the lower surface of pressure chamber 150. Accordingly, when piezoelectric pump 100 operates and the liquid flows along the flow passage, the flow direction of the liquid is bent at a point where the liquid flows from suction side flow passage 170a into pressure chamber 150. The flow direction of the liquid which has passed through pressure chamber 150 is bent once again where the liquid flows from pressure chamber 150 to discharge side flow passage 170b. In this way, when the flow of the liquid is changed rapidly, the pressure of the liquid is largely lost. As a result, the amount of flow of the liquid passing through the flow passage is reduced, and therefore the pump efficiency is decreased. The decrease in pump efficiency indicates a decrease in the cooling efficiency of the cooling system. [0009] Further, in piezoelectric pump 100, suction port 121a, discharge port 121 b, and respective flow passages 170a, 170b are positioned on/under the lower surface of pressure chamber 150. Accordingly, the thickness obtained by adding the thickness of pressure chamber 150 and the thickness of flow passages 170a, 170b means that the pump has a substantial thickness. The pump is incorporated in electronic equipment such as portable personal computers, and therefore it is desirable to make the pump thinner in order to reduce the thickness of electronic equipment. DISCLOSURE OF INVENTION [0010] The present invention has its object to provide a diaphragm pump that enables an increase in pump efficiency by reducing the pressure loss of liquid and that enables reduction in thickness. Also, the present invention has its object to provide a cooling system that enables an increase in cooling efficiency by being provided with the diaphragm pump. [0011] To achieve the above-mentioned object, a diaphragm pump according to the present invention includes: [0012] a pressure chamber formed into a flat shape and is filled up with liquid; [0013] a suction side flow passage and a discharge side flow passage disposed at both ends of the pressure chamber so that axes thereof are aligned with each other and are connected with the pressure chamber; [0014] check valves, respectively disposed on the suction side flow passage and the discharge side flow passage, at least one of the check valves being tilted relative to the direction of the axes; and [0015] at least one diaphragm disposed on at least one of an upper surface and a lower surface of the pressure chamber and for oscillation to make a volume of the pressure chamber variable. [0016] According to the present invention, the suction side flow passage and the discharge side flow passage are disposed at both ends of the pressure chamber so that the pressure chamber is sandwiched between the flow passages and the flow passages are connected with the pressure chamber. The suction side flow passage and the discharge side flow passage are extended in the same direction so that axes thereof are aligned with each other. Therefore, the flow passage for the pump, including the respective flow passages and the pressure chamber, is formed in a straight line without being bent, and thus the pressure loss of the liquid is reduced and the liquid flows efficiently. Also, check valves respectively disposed in the flow passages are tilted relative to the axial direction of these flow passages, namely, the flow direction of the liquid, and thus the pressure loss of the liquid is further reduced. Additionally, since the pressure chamber is formed into a flat shape and, since the suction side flow passage and the discharge side flow passage are disposed at both ends of the pressure chamber, the whole of the pump is reduced in thickness. The diaphragm is arranged on at least one upper surface and one the down surface of the pressure chamber so as to operate on a surface having a large area in the flat-shaped pressure chamber, and thus oscillation by the diaphragm is transmitted to the pressure chamber efficiently. Therefore, the driving source is reduced in size, work is saved, and the size of the pump is also reduced. [0017] Each of the flow passages may be formed so that the axes thereof are positioned at the center of a cross-sectional shape of the pressure chamber on a surface orthogonal to the axes. Accordingly, the flow of the liquid in the pressure chamber is even around the axes. With this arrangement, since the axes of the respective flow passages approximately pass through the center of the pressure chamber, the space in the pressure chamber is approximately symmetric relative to the axes. Accordingly, the flow passage of the liquid is approximately symmetric relative to the axes, and thus the pressure loss of the liquid in the pressure chamber is reduced. [0018] Each cross-sectional shape of flow passages and the pressure chamber is formed in an approximate rectangle in cross section. In this case, these can be formed by a cutting process or the like, and thus manufacturing is easy. In particular, when the lower surfaces of the flow passages and the pressure chamber are formed on the same surface, manufacturing is easy. Further, since the flow passage is made flatly, the liquid is circulated efficiently. In order to further reduce the pressure loss of the liquid, the length of the pressure chamber, viewed from an upper surface in a direction orthogonal to the axes, may be continuously shortened toward the suction side flow passage or toward the discharge side flow passage. Also, a height of the pressure chamber may be continuously lowered toward the suction side flow passage or the discharge side flow passage. In both cases, the section of the pressure chamber is made smaller continuously toward the respective flow passages, and thus the pressure loss of the liquid in the pressure chamber is reduced. [0019] In the diaphragm pump according to the present invention, at least one groove may be formed in a peripheral wall of the pressure chamber and can accelerate the flow of the liquid downstream in a flow direction. The groove may have a part with an opening opened to the pressure chamber, into which the liquid flows, and a side part with an opening opened to a peripheral wall surface of the pressure chamber, from which the liquid is discharged downstream in the flow direction. The groove may be extended in a radial direction while a point in the vicinity of the entrance of the discharge side flow passage is set as a center. By arranging the groove, when pressure is applied to the pressure chamber by the diaphragm, the liquid is discharged from the side part with an opening downstream and the flow of liquid is accelerated. [0020] The diaphragm pump may include: at least one intake opened to an upper surface of the suction side flow passage and is used to introduce bubbles mixed in the liquid; and a sealed space connected with the intake and is used to collect the introduced bubbles. The intake may be positioned in the suction side flow passage upstream relative to the check valve. Bubble collection means like this are arranged in this way, and thus the bubbles mixed in the liquid are collected and are prevented from entering the pressure chamber. In this way, by removing bubbles from the flow passages and the pressure chamber, the pressure loss of the liquid is further reduced. The intake is positioned in the suction side flow passage upstream relative to the check valve, and thus the bubbles are efficiently prevented from entering the pressure chamber. [0021] The diaphragm pump is a so-called piezoelectric pump in which the driving source is a piezoelectric element. The piezoelectric element enables a reduction in the size and thickness of the pump. [0022] Further, the above-mentioned diaphragm pump is available for a cooling system that has a closed-structure flow passage for circulating liquid discharged from the discharge side flow passage in the diaphragm pump and for returning the liquid to the suction side flow passage. The cooling system cools electric equipment efficiently. In particular, the cooling system having a pump with the bubble collection means circulates the liquid efficiently for a long period because the bubbles in the flow passage are collected. [0023] Additionally, in this description, a "flat" pressure chamber is a pressure chamber in which a length of the pressure chamber in the height direction is shorter than one-half of the maximum length of the pressure chamber viewed from the upper surface in the axial direction, and than one-half of the maximum length in the direction orthogonal to the axis. [0024] According to the present invention, by adding ideas to the structure of the diaphragm pump, the pressure loss of the liquid is reduced and the pump is improved in pump efficiency and is reduced in thickness. Also, the cooling system is provided with the diaphragm pump, and thus the cooling system is improved in cooling efficiency and is reduced in thickness. Continue reading... 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