Abstract:
A diaphragm pump includes a duct structure capable of connecting an inlet port and an outlet port without using a tube. In the diaphragm pump, each of an inlet channel hole and an outlet channel hole is formed as a depression without the provision of inlet and outlet ports each formed as a protrusion on a housing, and a tubular protrusion provided on a plate forming a channel is fit in the depression.

Description:
[0001]    This application claims benefit of the Japanese Patent Application No. 2006-285842 filed on Oct. 20, 2006, which is hereby incorporated by reference. 
       BACKGROUND 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a diaphragm pump using a vibrating diaphragm to produce a pumping action, and in particular, to a diaphragm pump and a thin channel structure that can be reduced in size and thickness. 
         [0004]    2. Description of the Related Art 
         [0005]    The applicant is developing a diaphragm pump (piezoelectric pump) for use as, for example, a cooling-water circulating pump for a water-cooled notebook personal computer (PC). A notebook PC has a limited space for storing parts, so a smaller and thinner pump is increasingly demanded. A technique for providing such a pump is disclosed in, for example, U.S. Patent Application Publication No. 2005-0231914 A1 and Japanese Unexamined Patent Application Publication Nos. 2005-229038 and 2005-282386. 
         [0006]    However, according to typical known techniques, an inlet port and an outlet port for a piezoelectric pump are each formed as a protrusion protruding from a housing, and a flexible tube is used as a duct connected to both ports. The inlet and outlet ports as a protrusion and the structure of connection including the tube connected to both ports and its surroundings prevent size and thickness reduction in the entire system, even when the piezoelectric pump is reduced in size and thickness in itself. 
       SUMMARY 
       [0007]    The present invention provides a diaphragm pump that has a duct structure capable of connecting a duct to an inlet port and an outlet port without using a tube. 
         [0008]    According to a first aspect, a diaphragm pump includes a vibrating diaphragm, an inlet channel hole in which an inlet check valve is disposed, an outlet channel hole in which an outlet check valve is disposed, an inlet channel, and an outlet channel. The diaphragm is supported between a pair of housings, has a sealed edge to prevent leakage of liquid, and forms a pump chamber. The inlet channel hole and the outlet channel hole are formed through at least a first housing of the pair of housings so as to communicate with the pump chamber. The inlet channel has a first inlet channel plate and a second inlet channel plate laminated together with the first inlet channel plate. The first inlet channel plate includes a tubular protrusion communicating with the inlet channel hole. The second inlet channel plate forms an inlet channel communicating with the tubular protrusion. The outlet channel has a first outlet channel plate and a second outlet channel plate laminated together with the first outlet channel plate. The first outlet channel plate includes a tubular protrusion communicating with the outlet channel hole. The second outlet channel plate forms an outlet channel communicating with the tubular protrusion. 
         [0009]    In one embodiment, the inlet channel hole and the outlet channel hole may be substantially parallel to each other. 
         [0010]    In one embodiment, the first inlet channel plate and the first outlet channel plate may be made of a single plate material, and the second inlet channel plate and the second outlet channel plate may be made of a single plate material. Therefore, the number of parts can be reduced, and assembly can be facilitated. 
         [0011]    According to a second aspect of the present invention, a thin channel structure includes a channel block in which a channel hole is formed, a first plate having a tubular protrusion communicating with the channel hole of the channel block, and a second plate laminated together with the first plate and forming a liquid channel communicating with the tubular protrusion. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a plan view of a piezoelectric pump to which the disclosed structure is applied, with a part of the surface being removed to show the inside thereof. 
           [0013]      FIG. 2  is a cross-sectional view taken along the line II-II in  FIG. 1 . 
           [0014]      FIG. 3  is an exploded perspective view of the piezoelectric pump. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0015]    According to the present embodiment, the disclosed pump is applied to a two-valve piezoelectric pump  20 . As illustrated in  FIGS. 1 to 3 , the piezoelectric pump  20  includes a lower housing  21  and an upper housing  22  in sequence from the bottom. 
         [0016]    The lower housing  21  has an inlet channel hole  24  and an outlet channel hole  25  for allowing cooling water (liquid) to pass therethrough. The inlet channel hole  24  and the outlet channel hole  25  are substantially perpendicular to the through-thickness plane of the lower housing  21  and are preferably substantially parallel to each other. A piezoelectric vibrator (diaphragm)  28  is supported between the lower housing  21  and the upper housing  22  via an O ring  29  so as to be sealed against leakage of liquid. A pump chamber P is formed between the piezoelectric vibrator  28  and the lower housing  21 . An air chamber A is formed between the piezoelectric vibrator  28  and the upper housing  22 . According to the present embodiment, the axis of the inlet channel hole  24  and that of the outlet channel hole  25  are preferably substantially perpendicular to the piezoelectric vibrator  28 . 
         [0017]    The piezoelectric vibrator  28  may be of a unimorph type and may have a central shim  28   a  and a piezoelectric element  28   b  laminated on one of both sides of the shim  28   a  (in  FIG. 2 , on the upper surface). The shim  28   a  is made of a conductive metal sheet, for example, a metal sheet having a thickness of approximately about 50 μm to about 300 μm made of stainless steel, 42 alloy, or other materials. The piezoelectric element  28   b  is made of lead zirconate titanate (PZT) (Pb(Zr,Ti)O 3 ) and has a thickness of the order of about 300 μm. The piezoelectric element  28   b  is poled in the direction of both sides thereof. Such a piezoelectric vibrator is well known. 
         [0018]    The inlet channel hole  24  and the outlet channel hole  25  of the lower housing  21  are provided with (umbrella) check valves  32  and  33 , respectively. The check valve  32  is disposed adjacent to the pump chamber P and is an inlet check valve for permitting a fluid to flow from the inlet channel hole  24  to the pump chamber P and preventing reverse flow of the fluid. The check valve  33  is disposed adjacent to the outlet channel and is an outlet check valve for permitting a fluid to flow from the pump chamber P to the outlet channel hole  25  and preventing reverse flow of the fluid. 
         [0019]    The check valves  32  and  33  have the same form. The check valves  32  and  33  have perforated substrates  32   a  and  33   a  and elastic umbrellas  32   b  and  33   b  attached thereto, respectively. Such umbrella check valves are well known. In the present embodiment, the perforated substrates  32   a  and  33   a  are separated from the lower housing  21 . However, they may be integrally molded with the lower housing  21 . 
         [0020]    According to the present embodiment, the lower housing  21  has the inlet channel hole  24  and the outlet channel hole  25 , as described above. In addition, the inlet channel hole  24  and the outlet channel hole  25  are connected to an inlet channel  26  and an outlet channel  27 , respectively. Both the inlet channel  26  and the outlet channel  27  are formed by a first channel plate  40  and a second channel plate  50 . The lower housing  21  includes annular grooves  24   a  and  25   a  whose outer surfaces are opened (see  FIG. 2 ). The annular grooves  24   a  and  25   a  are concentric with the inlet channel hole  24  and the outlet channel hole  25 , respectively. The annular grooves  24   a  and  25   a  may be eccentric as needed. The first channel plate  40  serves as both a first channel plate for the inlet side and that for the outlet side and is formed as a plate in which both the first channel plates are integrated with each other. The first channel plate  40  includes an inlet tubular protrusion  41  to be fit in the annular groove  24   a , an outlet tubular protrusion  42  to be fit in the annular groove  25   a , an inlet channel recess  43  communicating with the inlet tubular protrusion  41 , an outlet channel recess  44  communicating with the outlet tubular protrusion  42 , and a partition  45  separating the inlet channel recess  43  and the outlet channel recess  44 . 
         [0021]    The second channel plate  50  serves as both a second channel plate for the inlet side and that for the outlet side and is formed as a plate in which both the second channel plates are integral with each other, as in the case of the first channel plate  40 . The second channel plate  50  includes an inlet channel recess  53  (which corresponds to the inlet channel recess  43  in the first channel plate  40 ), an outlet channel recess  54  (which corresponds to the outlet channel recess  44 ), and a partition  55  (which corresponds to the partition  45 ). The first channel plate  40  and the second channel plate  50  are joined together by joining of a joint surface  46  including the partition  45  and a joint surface  56  including the partition  55  by, for example, brazing using solder, thereby forming the inlet channel  26  extending to the inlet tubular protrusion  41  and the outlet channel  27  extending to the outlet tubular protrusion  42 . Each of the first channel plate  40  and the second channel plate  50  is constructed of a sheet made of, for example, aluminum, copper, or stainless steel and having a thickness of approximately 0.1 mm to 0.3 mm, and the thickness of the channel is equal to or smaller than 1 mm. Therefore, the thickness of the entire pump can be reduced. The inlet channel  26  and the outlet channel  27  are noncircular in cross section. The inlet channel  26  has a flat shape that has a greater width in a direction substantially perpendicular to the protruding direction of the inlet tubular protrusion  41 . Similarly, the outlet channel  27  has flat shape that has a greater width in a direction substantially perpendicular to the protruding direction of the outlet tubular protrusion  42 . One of the outlet channel recesses  44  and  54  may be omitted such that only one of the first channel plate  40  and the second channel plate  50  has an outlet channel recess. 
         [0022]    The inlet tubular protrusion  41  is fit into the annular groove  24   a  such that an O ring  47  is disposed between the outer surface of the inlet tubular protrusion  41  and the inner surface of the annular groove  24   a . Similarly, the outlet tubular protrusion  42  is fit into the annular groove  25   a  such that an O ring  57  is disposed between the outer surfaces of the outlet tubular protrusion  42  and the inner surface of the annular groove  25   a . This maintains sealing to prevent leakage of liquid. The inlet tubular protrusion  41  and the outlet tubular protrusion  42  include internal flanges  41   a  and  42   a  at the respective ends such that the inlet tubular protrusion  41  and the outlet tubular protrusion  42  are mechanically strengthened to avoid both protrusions from becoming flattened easily. In the present embodiment, the internal flanges  41   a  and  42   a  project toward the inside of the end of the inlet tubular protrusion  41  and that of the outlet tubular protrusion  42 , respectively. However, the internal flanges  41   a  and  42   a  may outwardly project. In this case, the O rings  47  and  57  are prevented from falling when the lower housing  21  and the first channel plate  40  are attached or detached from each other. 
         [0023]    For the piezoelectric pump  20  having the above described structure, when the piezoelectric vibrator  28  is elastically deformed (vibrated) in forward and reverse directions, on a stroke for increasing the volume of the pump chamber P, because the inlet check valve  32  is opened and the outlet check valve  33  is closed, liquid flows from the inlet channel  26  and the inlet channel hole  24  into the pump chamber P; on a stroke for reducing the volume of the pump chamber P, because the outlet check valve  33  is opened and the inlet check valve  32  is closed, the liquid flows from the pump chamber P to the outlet channel hole  25  and the outlet channel  27 . Therefore, a pumping action is produced by continuously causing the piezoelectric vibrator  28  to be elastically deformed (vibrated) in forward and reverse directions. 
         [0024]    In the present embodiment, both the channel from the inlet channel  26  to the pump chamber P and the channel from the pump chamber P to the outlet channel  27  are formed by the first channel plate  40  and the second channel plate  50 , and the first channel plate  40  includes the inlet tubular protrusion  41  and the outlet tubular protrusion  42 , which are fit in the annular grooves  24   a  and  25   a  being concentric with the inlet channel hole  24  and the outlet channel hole  25 , respectively. As a result, the size and the thickness of the entire system can be reduced. That is, the lower housing  21  and the upper housing  22  do not have a protrusion for connecting the pump chamber P to the inlet channel  26  and the outlet channel  27 , and a flexible tube also is not present. 
         [0025]    In the embodiment described above, the first channel plate  40  and the second channel plate  50  form both the inlet and outlet channels. However, the first channel plate and the second channel plate can be provided for each of the inlet channels and the outlet channels, i.e., the first channel plate  40  and the second channel plate  50  can be separated by the partition  45  and the partition  55 , respectively, into different portions. In this case, the arrangement of the inlet channel hole  24  and the outlet channel hole  25  and the orientations thereof can be designed more flexibly. 
         [0026]    In the embodiment described above, the unimorph piezoelectric vibrator  28  is illustrated as a diaphragm. However, a bimorph piezoelectric vibrator can also be used. In the embodiment described above, the present invention is applied to a two-valve diaphragm pump in which the pump chamber P is disposed on only one side of the piezoelectric vibrator  28 . However, the present invention is applicable to a diaphragm pump in which a pump chamber is disposed on each of both sides of a piezoelectric vibrator. In addition, the present invention is applicable to general diaphragm pumps, which produce a pumping action by causing the volume of a pump chamber to increase and decrease in cycles.