Abstract:
A valve device having a novel vale seat plate is provided. The valve seat plate has an inlet opening, an outlet opening, a front side and a back side. A sealing case covers the front side and inlet and outlet pipes are attached to the back side to communicate respectively with the inlet and outlet openings. A valve element moves to cover the outlet opening on the front side to close the outlet opening. The novel valve seat plate includes at least two plates that are joined to each other. One plate forms the area around the outlet opening and the other plate forms other areas of the valve seat plate.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of Invention  
           [0002]    The present invention relates to a valve device. More specifically, it relates to configuration of a valve seat plate which is used in the valve device.  
           [0003]    2. Description of Related Art  
           [0004]    In refrigerators, a valve device is used to distribute a common refrigerant (fluid) to a plurality of compartments to cool them. As illustrated in FIGS.  6 (A) and (B), such a valve device comprises a valve seat plate  13 ′ having a refrigerant inlet opening  13   c  and refrigerant outlet openings  13   a  and  13   b  through which a refrigerant flows in the thickness direction, a sealing case (not illustrated) which covers a front surface of the valve seat plate  13 ′, and a valve element (not illustrated) which rotates on the front surface of the valve seat plate  13 ′ to open and close the refrigerant outlets  13   a  and  13   b . Also, a rotor support shaft  18  and a valve element support shaft  35  are fixed to the valve seat plate  13 ′.  
           [0005]    In the valve seat plate  13 ′, the inlet opening  13   c  and outlet openings  13   a  and  13   b  are formed as holes, each of which has a small diameter portion on the front side and a large diameter portion on the back side. The portions of different diameters are connected by a step. The large diameter portions of the inlet opening  13   c  and outlet openings  13   a  and  13   b  on the back surface side are the holes for inserting pipes. Inlet pipe  28   c  and outlet pipes  28   a  and  28   b  are brazed to the respective pipe-inserting holes with the incoming ends thereof in contact with the steps.  
           [0006]    In a valve device having such a configuration, the area of the outlet openings  13   a  and  13   b  in the front surface of the valve seat plate  13 ′ is the surface on which the valve element rotates. Therefore, this area of the front surface of the valve seat plate  13 ′ is required to have high surface precision so that the flow of the refrigerant is completely cut off. Also, the valve seat plate  13 ′ needs to have a thickness such that the surface on which the valve element rotates does not warp even when heated to the temperature of 1000° C. or above for fixing the pipes  28   a ,  28   b  and  28   c  by brazing. Further, the valve seat plate  13 ′ needs to be composed of a ferrous material so that it can be brazed, and SUS is used because of its excellent corrosion resistance.  
           [0007]    For these reasons, when the valve seat plate  13 ′ is manufactured conventionally, a thick SUS needs to be lathed, which increases the cost of the valve seat plate  13 ′.  
           [0008]    Although forging may be considered in place of lathing, as a manufacturing method for a valve seat plate, it is also an expensive method though not as costly as lathing. In addition, when it is a sintered body, a hole-sealing process is required. Also, it is difficult to obtain precise dimensions and positions of the holes. Also, forging creates a great residual stress on the surface; therefore, when brazed, the surface which requires high precision is warped due to the heat of the brazing.  
           [0009]    A sinter molding may also be considered in place of lathing as a manufacturing method for a valve seat plate. However, this method is also expensive though not as costly as lathing. In addition, when a sintered body is used, a hole-sealing process is required. However, resin-impregnation, a common hole-sealing process, is problematic because the resin cannot resist the brazing temperature. Further, since a sintered body is low in surface hardness, its resistance against the rotation of the valve element is also poor. Furthermore, sintering restricts the smallest formable hole diameter. For example, to form a hole with a diameter of 1.5φ by sintering, a lathing process is required as a secondary process.  
           [0010]    Considering the above problems, an object of the present invention is to provide a valve device in which pipes can be installed without causing warping on the area of the surface on which a valve element rotates, and which can reduce the manufacturing cost of a valve seat plate.  
         SUMMARY OF THE INVENTION  
         [0011]    To achieve the above object, the present invention comprises a valve seat plate having an inlet opening and an outlet opening through which a fluid flows in the thickness direction, a sealing case which covers a front surface of the valve seat plate, an inlet pipe and an outlet pipe which are fixed on a back surface of the valve seat plate to respectively communicate with the inlet opening and the outlet opening, and a valve element which rotates on the area of the outlet opening in the front surface of the valve seat plate to open and close the outlet opening; wherein the valve seat plate has a first plate member, which forms the area of the outlet opening, and a second plate member, to which the first plate member is joined.  
           [0012]    In one embodiment, the valve seat plate consists of a first plate member and a second plate member to meet the property requirements of the plate. For example, the second plate member is composed of a press product and the first plate member is composed of a lathe product which has a thickness greater than that of the second plate member. Thus, the first plate member composed of a lathe product is used to form the area of the surface of the valve seat plate in which the outlet openings are formed and on which the valve element rotates. Therefore, this area can be formed with high surface precision. Since the first plate member is a lathe product, it is thick enough to endure the temperature of brazing. Even when the outlet pipe is brazed into the first plate member, brazing does not cause warping on the surface on which the valve element rotates. Although a lathe product is relatively high in the process cost, the present invention in the embodiment shown uses a lathe product only for the first plate member. Therefore, only a limited surface area needs to be lathed. For this reason, the manufacturing costs can be kept to a minimum. As for the second plate member, an inexpensive press product is used. Although high surface precision cannot be obtained with a press product, it is not necessary for the second plate member since the valve element does not rotate on it. In other words, according to the present invention, a thick lathe product is used only for a minimal portion of the valve seat plate; therefore, pipes can be fixed without warping the surface portion on which the valve element rotates, and the manufacturing costs of the valve seat plate can be reduced.  
           [0013]    In the present invention, it is preferable that the first plate member be large enough to form the entire area on which the valve element rotates to open and close the outlet opening.  
           [0014]    In the present invention, it is preferable that the second plate member have a through hole which is used for attaching the first plate member, and that the first plate member have a small diameter portion which is inserted into the through hole, an annular step portion which comes into contact with the opening edge of the through hole when the small diameter portion is inserted into the through hole, and a large diameter portion which is to be outside the through hole. With this configuration, when the pipes are brazed from the side of the large diameter portion, the brazing material spreads in the gap between the first plate member and the second plate member. Thus, the members are joined together in a highly airtight manner.  
           [0015]    In this present invention, it is preferable that the first plate member have a large diameter portion on the back surface side of the valve seat plate, and the first plate member and the second plate member be joined together by brazing from the back surface side. This configuration can prevent the surface precision of the valve seat plate, on which the valve element rotates, from being degraded due to the brazing material.  
           [0016]    In the present invention, it is preferable that the thickness of the first plate member be 2.1 mm or more, and more suitably 2.4 mm or more. When the outlet pipes are first inserted into the pipe-inserting holes in the first plate member and then brazed to the first plate member, stress is applied to the first plate member during press-fitting and heat stress during brazing. However, by forming the first plate member with a thickness of 2.1 mm or more, change in the planarity of the first plate member, which may caused during press-fitting and brazing, can be limited to 1.0 μm or less. By forming the first plate member with a thickness of 2.4 mm or more, change in the planarity can be completely prevented. Therefore, the valve element moves on the surface of the first plate member with excellent planarity, and consequently the outlet openings are tightly closed.  
           [0017]    An embodiment of a refrigerant distribution device of a refrigerator to which the present invention is applied, is described hereinafter referring to the drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]    [0018]FIG. 1 is a vertical cross-sectional view of a refrigerant distribution device in a refrigerator to which the present invention is applied.  
         [0019]    FIGS.  2 (A), (B) and (C) are respectively a plan view, a vertical cross-sectional view, and a bottom view of a valve seat plate of a valve device which is used for the refrigerant distribution device of FIG. 1.  
         [0020]    FIGS.  3 (A) through (F) are diagrams of the modes of the refrigerant distribution device of FIG. 1.  
         [0021]    [0021]FIG. 4 is a vertical cross-sectional view of the disassembly of the valve seat plate of FIG. 2.  
         [0022]    [0022]FIG. 5 is a graph showing the relationship between the thickness of the first plate member and the change of the planarity of the first plate member after press-fitting and brazing of the outlet pipes into the pipe-inserting holes in the refrigerant distribution device of FIG. 1.  
         [0023]    FIGS.  6 (A) and (B) are respectively a vertical cross-sectional view and a bottom view of a valve seat plate of a conventional valve device. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0024]    [0024]FIG. 1 is a vertical cross-sectional view of a refrigerant distribution device of a refrigerator, to which the present invention is applied. FIGS.  2 (A), (B), and (C) are respectively a plan view, a vertical cross-sectional view, and a bottom view of a valve seat plate of a valve device which is used in the refrigerant distribution device illustrated in FIG. 1. FIG. 2(B) is a cross-section of the valve seat plate along the A-A′ line of FIGS.  2 (A) and (C). FIGS.  3 (A) through (F) are respectively diagrams for the modes of the refrigerant distribution device illustrated in FIG. 1.  
         [0025]    In FIG. 1, a refrigerant distribution device  1  of this embodiment has a valve device  1   a  equipped with a valve seat plate  13  and a sealing case  19  which covers the front side of the valve seat plate.  
         [0026]    In the valve device  1   a , a stepping motor  10  is configured inside and outside of the sealing case  19  as a valve drive device to drive a valve element. In the stepping motor  10 , a rotor  15  is positioned inside the sealing case  19  and a stator  16  is positioned around the outer circumference of the sealing case  19 . A conductor  16   b  is pulled out from a fixed coil  16   a  of the stator  16 ; a drive signal is sent from a controller (not  
         [0027]    illustrated) which is composed of a micro-computer to the conductor  16   b  to rotate and stop the rotor  15 .  
         [0028]    The rotor  15  has a magnet  15   a  integral with the outer circumference thereof and also has a pinion  17  formed at the end portion thereof on the side of the valve seat plate  13 . The pinion  17  is rotatably supported with respect to a rotor support shaft  18  (center axis for rotation).  
         [0029]    The bottom end of the sealing case  19  is widened to form a step on which the stator  16  is mounted, and is tightly fitted to a step 135 which is formed around the outer circumferential edge of the valve seat plate  13 .  
         [0030]    As illustrated in FIGS. 1 and 2 (A), (B), and (C), in the valve device  1   a , the valve seat plate  13  has a front surface side and a back surface side. A fluid inlet  13   c  opens to the front surface, which is on the same side as the sealing case  19 . A first fluid outlet  13   a  and a second fluid outlet  13   b  open to the area in the front surface of the valve seat plate  13 , opposite the fluid inlet  13   c  with respect to the pinion  17 .  
         [0031]    The opposite side (the back surface side) of the valve seat plate  13  from the fluid outlet openings  13   a  and  13   b  and the fluid inlet opening  13   c  provides holes  14   a ,  14   b  and  14   c  for inserting pipes. The pipe-inserting holes  14   a  and  14   b  are formed with a diameter larger than those of the fluid outlet openings  13   a  and  13   b . While each of the pipe-inserting holes  14   a  and  14   b  is formed with a step, the pipe-inserting hole  14   c  is a straight hole.  
         [0032]    To the pipe-inserting hole  14   c  having such a configuration, a fluid inlet pipe  28   c , through which a refrigerant is supplied, is inserted from the back and brazed so that the inlet pipe  28   c  and the inlet opening  13   c  are connected to each other. Also, to the pipe-inserting holes  14   a  and  14   b , the first outlet pipe  28   a  and the second outlet pipe  28   b , which send refrigerant to each compartment of the refrigerator, are inserted from the back and brazed so that the first outlet pipe  28   a  and the second outlet pipe  28   b  are connected respectively with the first outlet opening  13   a  and the second outlet opening  13   b.    
         [0033]    In the valve seat plate  13 , shaft holes  13   d  and  13   e  are formed as straight holes in the vicinity of the outlet openings  13   a  and  13   b . The base end of the rotor support shaft  18  and the base end of the valve element support shaft  35  are respectively brazed to the shaft holes  13   d  and  13   e.    
         [0034]    Also, a shaft hole  13   f  is formed as a straight hole in the valve seat plate  13 . The base end of a positioning shaft  191  is brazed to the shaft hole  13   f . Further, a bag hole  13   g  is formed in the valve seat plate  13  for positioning a jig, and a protrusion  192  is created on the opposite side from the bag hole  13   g  when the bag hole  13   g  is formed by pressing.  
         [0035]    The brazing material, which is used for the brazing processes, provides airtightness to the shaft holes  13   d ,  13   e  and  13   f.    
         [0036]    Referring back to FIG. 1, the valve element  30  is formed integral with a gear  36  at the valve element support shaft  35 . In this embodiment, the valve element  30  rotates over the area of the first outlet opening  13   a  and the second outlet opening  13   b  in the front surface of the valve seat plate  36  to open and close both first and second outlet openings  13   a  and  13   b.    
         [0037]    The gear  36  is meshed with the pinion  17  and driven by the stepping motor  10  to rotate about the valve element support shaft  35 . Accordingly, the valve element  10  is also rotated by the stepping motor  10 .  
         [0038]    The close-close mode is where both the first and second outlet openings  13   a  and  13   b  are closed; the close-open mode is where the first outlet opening  13   a  is closed and the second outlet opening  13   b  is open; the open-open mode is where both the first and second outlet openings  13   a  and  13   b  are open; and the open-close mode is where the first outlet opening  13   a  is open and the second outlet opening  13   b  is closed. By changing the angular position of the valve element  30  (the area indicated by oblique lines in FIG. 3), the four modes of the outlet openings can be switched in the following order: the original position in close-close as illustrated in FIG. 3(A) (0th step); the close-close mode as illustrated in FIG. 3(B) (34th step); the close-open mode as illustrated in FIG. 3(C) (100th step); the open-open mode as illustrated in FIG. 3(D) (154th step); the open-close mode as illustrated in FIG. 3(E) (195th step); and the final position in open-close as illustrated in FIG. 3(F) (200th step).  
         [0039]    [0039]FIG. 4 is a vertical cross-sectional view of the disassembly of the valve seat plate as illustrated in FIG. 2.  
         [0040]    As illustrated in FIGS.  1 ,  2 (A),  2 (B),  2 (C) and  4 , in the valve device  1   a  of this embodiment, the valve plate  13  consists of a first annular plate member  11 , in which the outlet openings  13   a  and  13   b  are formed, and a second annular plate member  12 , to which the first plate member  11  is joined. The first plate member  11  is large enough to form the entire area on which the valve element  30  rotates to open and close the outlet openings  13   a  and  13   b.    
         [0041]    In this embodiment, the second plate member  12  is composed of a press product and the first plate member  11  is composed of an SUS lathe product which has a thickness greater than that of the second plate member  12 , for example, a thickness of 4 mm.  
         [0042]    In the second plate member  12 , a through hole  120  is formed to attach the first plate member  11 .  
         [0043]    In the first plate member  11 , a small diameter portion  111 , an annular step portion  112  and a large diameter portion  113  are formed. The small diameter portion  111  is inserted into the through hole  120  from the back surface side. When the small diameter portion  111  is inserted into the through hole  120 , the annular step portion  112  comes into contact with the opening edge of the through hole  111 . The large diameter portion  113  is positioned outside the through hole  120 .  
         [0044]    With this configuration, the small diameter portion  111  is press-fitted into the through hole  120  from the back so that the large diameter portion  113  is positioned on the back surface side and temporarily fixed as the annular step portion  112  comes into contact with the opening edge of the through hole  120 . Then, the gap between the large diameter portion  113  and the second plate member  11  is brazed, and the brazing material spreads well in the gap between the first and second plate members  11  and  12 . Thus, an excellent airtightness can be obtained in the gap. Since brazing is performed from the back surface of the valve seat plate  13 , the surface precision of the front surface of the valve seat plate  13  is protected from degradation, which normally is affected by brazing.  
         [0045]    The inlet pipe  28   c  and outlet pipes  28   a  and  28   b  are connected to the valve seat plate  13 , which is configured as above, in the following manner. The inlet pipe  28   c  is inserted from the back surface into the pipe-inserting hole  14   c  that is connected to the inlet opening  13   c , and the outlet pipes  28   a  and  28   b  are inserted from the back surface into the pipe-inserting holes  14   a  and  14   b  that are connected to the outlet openings  13   a  and  13   b ; then, each joint is brazed from the back surface side.  
         [0046]    As mentioned, the valve seat plate  13  consists of the first plate member  11  and the second plate member  12 . The second plate member  12  is composed of a press product; the first plate member  11  is composed of a lathe product with a thickness greater than that of the second plate member  12 . The area of the outlet openings  13   a  and  13   b  in the front surface of the valve seat plate  13  is the surface on which the valve element  30  rotates. Since the first plate member  11  composed of a lathe product is used to form this area, surface precision is high. Also, since the first plate member  11  is thick, even when the outlet pipes  28   a  and  28   b  are press-fitted into the holes and brazed, the press-fitting stress or heat stress does not warp the surface on which the valve element  30  rotates.  
         [0047]    As described in this embodiment, although a lathe product is costly, the first plate member  11  composed of a lathe product is used only for the area which requires high surface precision with no warping. Therefore, high quality is obtained for the valve seat plate  13 . Also, since the first plate member  11  composed of a lathe product is used only for the limited area requiring high-quality, it can be polished efficiently. Further, since a lathe product is used for the first plate member  11  which has a smaller outer diameter, only a shorter lathe processing time is required. Consequently the manufacturing cost can be kept to a minimum.  
         [0048]    Additionally, an inexpensive press product is used for the second plate member  12 . Although high surface precision may not be obtained and the heat from brazing may warp the surface, the area that is brazed is not the surface on which the valve element  30  will rotate. Therefore, although an inexpensive press product is used, the quality of the valve seat plate  13  is not degraded.  
         [0049]    In the present invention, a thick lathe product is used for only a minimal portion; thus, the pipes can be attached without warping the surface on which the valve element  30  rotates, and also the manufacturing cost of the valve seat plate  13  can be reduced.  
         [0050]    [0050]FIG. 5 is a graph that shows the changes in the planarity of the first plate ember  11  when the outlet pipes  28   a  and  28   b  are inserted into and then brazed to the pipe-inserting holes  14   a  and  14   b  of the first plate member  11 .  
         [0051]    When the outlet pipes  28   a  and  28   b  are first press-fitted into and then brazed to the pipe-inserting holes  14   a  and  14   b  in the first plate member  11 , the change in the planarity of the first plate member  11  after press-fitting and brazing depends on the thickness of the first plate member  11 , as illustrated in FIG. 5.  
         [0052]    The front surface of the first plate member  11 , that is, the surface on which the valve element  30  rotates, is polished in advance to increase planarity. The first plate member  11  needs to be given a thickness that can maintain the planarity thereof even after the outlet pipes  28   a  and  28   b  are press-fitted into the pipe-inserting holes  14   a  and  14   b  and brazed.  
         [0053]    In this embodiment, the thickness of the first member  11  is determined in the following manner, based on the result shown in FIG. 5: when the amount of the change in the planarity must be limited to 1.0 μm or less, the first plate member  11  is given a thickness of 2.1 mm or more; when the planarity must be completely protected from degradation, the first plate member is given a thickness of 2.4 mm or more.  
         [0054]    In the present invention, the valve seat plate consists of the first plate member and the second plate member, and a suitable material is used for each member according to the function of the member. Therefore, either a sintered product or a forged product can be used as the material for the first and the second plate member, depending on the type of valve device and valve seat plate that needs to be manufactured.  
         [0055]    As described above, in the present invention, the valve seat plate consists of the first plate member and the second plate member. The second plate member is composed of a press product and the first plate member is composed of a lathe product which has a thickness greater than that of the second plate member. In this manner, the valve seat plate is configured to meet the required properties of each member. The area of the outlet opening in the front surface of the valve seat plate is also the surface on which the valve element rotates. Since the first plate member composed of a lathe product is used for this area, high surface precision can be obtained. The first plate member is composed of a lathe product; therefore, it can be formed with a thickness that can endure the temperature of the heat when the outlet pipe is brazed. Consequently the brazing does not warp the surface on which the valve element rotates. The manufacturing cost for a lathe product is high; however, since a lathe product is used only for the first plate member, which is a limited area, the increase in the manufacturing cost can be kept to a minimum. On the other hand, since the second plate member is not used for the area on which the valve element rotates, an inexpensive press product can be used for the second plate member, reducing the manufacturing cost of the valve seat plate.