Abstract:
A compressor includes a cylinder block and a housing connected to the ends of the cylinder block. A suction chamber and a discharge chamber are defined in the housing, respectively, and the chambers are divided by a bulkhead, or wall. A valve plate, which has a discharge port for connecting the cylinder bores with the discharge chamber, is positioned between the cylinder block and the housing. A discharge valve is provided for selectively opening and closing the discharge port. A gasket is positioned between the housing and the valve plate, and the gasket is held to the bulkhead. The gasket has a bulkhead seal portion, which is between the bulkhead and the valve plate for sealing between the discharge chamber and the suction chamber, and a protruding portion, which protrudes radially beyond the bulkhead, extending along and contacting the valve plate.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to compressors, and more particularly, to an improved gasket for sealing between compression and suction chambers in a compressor. 
     2. Description of the Related Art 
     Typical compressors include a cylinder block having a plurality of cylinder bores defined therein. A piston is accommodated in and reciprocates with respect to each cylinder bore. Front and rear housings are secured to the front and rear end faces of the cylinder block with a valve plate in between, respectively. Each housing includes a bulkhead formed therein. Each housing, the associated valve plate and the cylinder block define suction and discharge chambers. Suction and discharge valve mechanisms are formed on both sides of the valve plate. The suction and discharge mechanisms correspond to the suction and discharge chamber, respectively. 
     A compressor of the above structure includes, for example, a discharge valve mechanism as illustrated in FIG. 6. A first plate  43  and a gasket  44  are located between a valve plate  41  and a housing  42 . A plurality of discharge port  45  (only one is shown) are formed in the valve plate  41 , each corresponding to one of the cylinder bores. A plurality of discharge valve flaps  43   a  are formed on the first plate  43 . Each flap  43   a  corresponds to one of the valve port  45 . Each flap  43   a  selectively opens and closes the corresponding port  45 . 
     The gasket  44  includes an annular seal  44   a  (see FIGS. 5 and 6) the width of which is substantially the same as that of a bulkhead  42   a  of the housing  42 . The seal  44   a  is held between the distal end of the bulkhead  42   a  and the valve plate  41  thereby sealing a suction chamber  46  defined in the housing  42  from a discharge chamber  47  defined in the housing  42 . 
     The gasket  44  also includes retainers  44   b  integrally formed with the seal  44   a.  Each retainer  44   b  defines the opening amount of the corresponding discharge valve flap  43   a . When highly pressurized refrigerant gas is discharge to the discharge chamber  47 , the gas causes the associated discharge valve flap  43   a  to flex to an open position, which is defined by the retainer  44   b . The force of the refrigerant gas pushes the inner wall of the discharge chamber  47  in a direction away from the valve plate  41 . If the contact pressure of the valve plate  41  and the distal end face of the bulkhead  42   a  with the seal  44   a  in between is not great enough, the force of the gas partly separates the seal  44   a  from the valve plate  41 . This deteriorates the sealing between the suction chamber  46  and the discharge chamber  47  and causes compressed gas in the discharge chamber  47  to leak into the suction chamber  46 . The compression efficiency of the compressor in thus reduced. 
     Since the retainer  44   b  and the seal  44   a  are integrally formed, refrigerant gas discharged to the discharge chamber  47  presses each discharge valve flap  43   a  against the corresponding retainer  44   b  with a great force. As shown in FIG. 7, a force f 1  acting on the retainer  44   b  generates an angular moment M 0  the center of which is a contact point A 0  of the inner edge of the bulkhead  42   a  and the seal  44   a  of the gasket  44 . A reactive force f 0  is generated at the contact point B 0  of the valve plate  41  and the outer edge of the seal  44   a  in accordance with the angular moment M 0 . A resultant force f 1 +f 0  is generated at the contact point A 0 . The force f 1 +f 0  pushes the bulkhead  42   a  away from the valve plate  41 . 
     Since the width of the seal  44   a  is substantially the same an that of the bulkhead  42   a,  the center A 0  of the angular moment M 0  is relatively close to the point of application B 0  or the reactive force f 0 . The shorter the distance between the center A 0  of the moment and the reactive force f 0 , the greater the magnitude of the reactive force f 0  becomes. If the reactive force f 0  is increased, the force f 1 +f 0 , which pushes the housing  42  away from the valve plate  41 , is increased, accordingly. Thus the housing  42  becomes more likely to separate from the valve plate  41 . 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an objective of the present invention to provide a compressor that improves sealing between chambers having different pressures. 
     To achieve the above objective, the present invention provides a compressor. The compressor includes a cylinder block and a housing connected to the ends of the cylinder block. A first gas chamber and a second gas chamber are defined in the housing, respectively, and the chambers are divided by a bulkhead. A valve plate, which has a first port for connecting the cylinder bores with the discharge chamber, is positioned between the cylinder block and the housing. A valve is provided for selectively opening and closing the first port. A gasket is positioned between the housing and the valve plate, and the gasket is held to the bulkhead. The gasket has a bulkhead seal portion, which is between the bulkhead and the valve plate for sealing between the first gas chamber and the second gas chamber, and a protruding portion, which protrudes radially beyond the bulkhead, extending along and contacting the valve plate. 
     Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principals of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings. 
     FIG. 1 is a plan view illustrating a gasket according to the present invention, which also functions an a retainer plate; 
     FIG. 2 is a cross-sectional view illustrating a compressor; 
     FIG. 3 is an enlarged partial cross-sectional view illustrating a portion of the compressor of FIG. 2; 
     FIG. 4 is an enlarged partial cross-sectional view illustrating a portion of the compressor of FIG. 2 when a discharge port is open; 
     FIG. 5 is a plan view illustrating a prior art gasket; 
     FIG. 6 is an enlarged partial cross-sectional view illustrating a prior art compressor; and 
     FIG. 7 is an enlarged partial cross-sectional view illustrating the compressor of FIG. 6 when a discharge valve is open. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A swash plate type compressor having double-headed pistons according to the present invention will now be described with reference to FIGS. 1 to  4 . 
     As shown in FIG. 2, a pair of cylinder blocks  11  are secured to each other at their ends. A front housing  12  is secured to the front end face of the front cylinder block  11  with a valve plate  13  in between. A rear housing  14  is secured to the rear end face of the rear cylinder block  11  with a valve plate  13  in between. The cylinder blocks  11  and the front and rear housings  12 ,  14  are made of aluminum or aluminum alloy. 
     A plurality of bolts  15  extend through the front housing  12 , cylinder blocks  11  and the valve plates  13  and are threaded in screw holes  16  formed in the rear housing  14 . The bolts  15  secure the front and rear housings  12 ,  14  to the front and rear faces of the cylinder blocks  11  with a metal valve plate  13  in between, respectively. 
     A rotary shaft  17  is rotatably supported in the center of the cylinder blocks  11  and the front housing  12  with a pair of radial bearings  18 . A lip seal  19  is located between the rotary shaft  17  and the front housing  12 . The rotary shaft  17  is connected to and rotated by an external power source such as a vehicle engine (not shown). 
     A plurality of aligned pairs of cylinder bores  20  are defined in the cylinder blocks  11  such that the rotary shaft  17  is located centrally with respect to the bores  20 . A double-headed piston  21  is housed in and reciprocates with respect to each pair of cylinder bores  20 . Compression chambers  22  are defined by the heads of a set of pistons  21  and the associated valve plate  13  in each cylinder bore  20 . 
     A crank chamber  23  is defined between the cylinder blocks  11 . A swash plate  24  is fixed to the rotary shaft  17  and is located in the crank chamber  23 . The swash plate  24  is also coupled to the central part of each piston  21  with a pair of semispherical shoes  25 . The swash plate  24  is rotated by the rotary shaft  17 . The rotation of the swash plate  24  is then transmitted to the pistons  21  through the shoes  25  and is converted into linear reciprocation of each piston  21 . A pair of thrust bearings  26  are located between an inner wall of each cylinder block  11  and the swash plate  24 , respectively. 
     Bulkheads  12   a  and  14   a  are formed in the housings  12  and  14 , respectively. A suction chamber  27  and a discharge chamber  28  are defined by the bulkheads  12   a ,  14   a  in the radially outer portion and inner portions of the housings  12 ,  14 , respectively. The suction chambers  27  are communicated with the crank chamber  23  via suction passages  11   a  defined in the cylinder blocks  11  and the valve plates  13 . The crank chamber  23  is connected to an external refrigerant circuit via an inlet port (not shown). The discharge chambers  28  are connected to the refrigerant circuit via a discharge muffler and an outlet (both not shown). 
     A suction valve mechanism  29  is formed on the cylinder block side of each valve plate  13 . The mechanism  29  allows the reciprocation of each piston  21  to draw refrigerant gas from the suction chamber  27  into each compression chamber  22 . A discharge valve mechanism  30  is formed on an outer side of each valve plate  13 . The mechanism  30  allows the reciprocation of each piston  21  to discharge refrigerant gas that is compressed in the corresponding compression chamber  22  to the discharge chamber  28 . 
     The construction of the suction valve mechanisms  29  and the discharge valve mechanisms  30  will hereafter be described with reference to FIGS. 1 to  3 . Each valve plate  13  has a plurality of suction ports  31  and discharge ports  32 . Each suction port  31  and each discharge port  32  correspond to one of the cylinder bores  20 . A first metal plate  33  and a metal gasket  34  are located between each valve plate  13  and the corresponding cylinder block  11 . Both sides of the gasket  34  are coated with rubber. Each first plate  33  has a plurality of suction valve flaps  33   a . Each flap  33   a  selectively opens and closes the corresponding suction port  31 . 
     A second metal plate  35  and a metal gasket  36 , which also functions as a retainer, are located between the housings  12 ,  14  and the corresponding valve plate  13 . Both sides of the gasket  36  are coated with rubber. Each second plate  35  has a plurality of discharge valve flaps  35   a . Each flap  35   a  selectively opens and closes the corresponding discharge port  32 . 
     As shown in FIG. 1, the gasket  36  includes an annular outer seal  36   a , an annular inner seal  36   b , a plurality of retainers  36   c . Each retainer  36   c  defines the opening of one of discharge valve flaps  35   a . A plurality of hole portions  36   d , through which the bolts  15  are inserted, are formed between the outer seal  36   a  and the inner seals  36   b . The inner seal  36   b  is connected to the hole portions  36   d  and the outer seal  36   a  by a plurality of connectors  36   e.    
     The width of the inner seal  36   b  is substantially the same as that of the bulkheads  12   a ,  14   a  of the housing  12 ,  14 . The inner seal  36   b  of each gasket  36  is located between the bulkheads  12   a ,  14   a  and the corresponding valve plate  13 . Each inner seal  36   b  seals between the corresponding suction chamber  27  and the discharge chamber  28 . 
     The gasket  36  has a plurality of protrusions  36   f , each of which radially protrudes outward from the inner seal  36   b . As shown in FIGS. 3 and 4, the protrusions  36   f  protrude from the edge of the bulkheads  12   a ,  14   a  into the suction chamber  27 . In this embodiment, the gasket  36  is 0.8 mm thick end the inner seal  36   b  is 4 mm wide. In a gasket of this size, the width of the protrusion  36   f  is preferably at least 0.5 mm. In this embodiment, the protrusions  36   f  are 2 mm wide. 
     The operation of the compressor of FIG. 2 will hereafter be described. 
     When rotated by an external power source such as an engine, the rotary shaft  17  causes the swash plate  24  to rotate together. The rotation of the swash plate  24  is converted into linear reciprocation of each piston  21  in the associated cylinder bore  20  by the shoes  25 . The reciprocation of each piston  21  causes refrigerant gas in an external refrigerant circuit to be drawn into the crank chamber  23  and then drawn into the suction chambers  27  through the suction passages  11   a . As each piston  21  moves from the top dead center to the bottom dead center, refrigerant gas in the suction chamber  27  is drawn into each cylinder bore  20  while causing the associated suction valve flap  33   a  to flex to an open position. As each piston  21  moves from the bottom dead center to the top dead center, refrigerant gas is compressed in the cylinder bore  20  until it reaches a certain pressure level. The compressed gas is then discharged to the discharge chamber  28  while causing the associated discharge valve flap  35   a  to flex to an open position. Refrigerant gas in the discharge chambers  28  is supplied to the external refrigerant circuit via a discharge muffler and a outlet part (both not shown). 
     A high pressure in the suction chamber  28  pushes the inner wall of the discharge chambers  28  in the front housing  12  and the rear housing  14  in a direction illustrated by an arrow in FIG. 3, or away from the valve plate  13 . 
     Highly pressurized refrigerant gas that is compressed in each cylinder bore  20  is quickly discharged to the discharge chamber  28  through the discharge ports  32  when the valve flap  35   a  are opened. The discharged gas is sprayed on the inner wall of the discharge chamber  28  near the discharge port  32  and deforms the bulkheads  12   a ,  14   a  of the discharge ports  32 . 
     Further, in the embodiment of FIG. 1, the fastening force of the bolts  15  is weakest at points along the inner seal  36  that are located about midway between each adjacent pair of the bolts  15 . At these points, the bulkheads  12   a ,  14   a  of the housings  12 ,  14  are also relatively flexible. 
     Because of the above listed factors, a higher pressure in the discharge chamber  28  lowers the contact pressure between the distal ends of the bulkheads  12   a ,  14   a  and the inner seals  36   b  and the contact pressure between the valve plates  13  and the inner seals  36   b . In these low contact pressure areas, some part of each inner seal  36   b  is separated from the valve plate  13 . This reduces the contact area between the inner seal  36   b  and the valve plate  13 . This deteriorates the sealing between the suction chambers  27  and the discharge chambers  28 . 
     However, in this embodiment, the protrusions  36   f  are formed on the inner seal  36   b . This improves the rigidity in the radial direction of the parts of the inner seal  36   b  having the protrusions  36   f . Thus, deformation of the inner seal  36   b  is reduced and the contact pressure between the inner seal  36   b  and the valve plate  13  is improved. 
     When the pressure in the discharge chambers  28  is high, the high pressure expands the entire discharge chamber  28 . The bulkheads  12   a ,  14   a  are deformed outward. In this embodiment, however, the contact area between the gasket  36  and the valve plate  13  is enlarged by the protrusions  36   f . Thus, the protrusions  36   f  maintain contact with the valve plate  13  and the sealing between the suction chambers  27  and the discharge chambers  28  is improved. 
     Also, as shown in FIG. 4, when the valve flap  35   a  is opened, discharged refrigerant gas applies a force f 1  to the retainer  36   c . Since the retainer  36   c  is integrally formed with the inner seal  36   b , the force f 1  acts on the inner seal  36   b  and the protrusion  36   f . The force f 1  generates an angular moment M 1 , the center of which is a contact point A 1  of the inner edge of the bulkheads  12   a ,  14   a  and the inner seal  36   b . In accordance with the angular moment M 1 , a reactive force f 2  is generated at the contact point B 1  of the valve plate  13  and the outer edge of the protrusions  36   f . The resultant force f 1 +f 2  pushes the bulkhead  12   a ,  14   a  away from the valve plate  13 . 
     However, the protrusion  36   f  increases the distance between the point M 1 , which is the center of the angular moment M 1 , and the point B 1 , at which the force f 2  is produced by the angular moment M 1 , by the width of the protrusion  36   f.  According to the principles of the leverage, if the force f 1  is constant, the longer the distance between the fulcrum B 1  and the point of application A 1  is, the weaker the force f 2  becomes. Thus, a longer distance between the points A 1  and B 1  decreases the magnitude of the resultant force f 1 +f 2 . Accordingly, the contact area between the bulkheads  12   a ,  14   a  and the inner seal  36   b  and the contact area between inner seal  36   b  and the valve plate  13  are enlarged. This improves the sealing between the suction chambers  27  and the discharge chambers  28 . 
     The protrusions  36   f  are formed on the inner seal  36   b  midway between the adjacent bolts  15 . In other words the protrusions  36   f  correspond to parts of the bulkheads  12   a ,  14   a  that are relatively flexible and more likely to separate from the valve plate  13 . Thus, the protrusions  36   f  improve the sealing between the suction chambers  27  and the discharge chambers  28 . 
     Although only one embodiment of the present invention has been described so far, it should be apparent to those skilled in the art that the present invention may be embodied in many other specific forms without departing from the spirit or scope of the invention. Particularly, it should be understood that the invention may be embodied in the following forms. 
     (1) The protrusions  36   f  may be formed along the whole inner seal  36   b . This structure further improves the sealing between the suction chamber  27  and the discharge chamber  28 . 
     (2) Unlike the above embodiments, the suction chamber  27  may be formed in the radially inner portion of the housings  12 ,  14 , and the discharge chamber  28  may be formed in the radially outer portion of the housings  12 ,  14 . 
     (3) The present invention may be embodied in other types of compressors such an wave cam plate type compressors employing double-headed pistons, single headed-piston type compressors, and vane-type compressors. 
     Therefore, the present examples and embodiments are to be considered as illustrative and not restrictive and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims.