Abstract:
A variable displacement swash plate type compressor which incorporates a lubrication passage formed in the drive shaft, wherein the lubrication passage provides fluid communication between a discharge chamber and a crank chamber. The lubrication passage maximizes the low of refrigerant gas and lubricating oil to the crank chamber under all operating conditions providing cooling and lubrication to the internal moving components in the crank chamber. The lubrication passage facilitates the efficient flow of lubricating oil from the discharge chamber to the crank chamber.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a variable displacement swash plate type compressor adapted for use in an air conditioning system for a vehicle, and more particularly to a compressor having a passage in a drive shaft for providing lubricating oil to the crankcase. 
     BACKGROUND OF THE INVENTION 
     A typical conventional variable displacement swash plate type compressor includes a cylinder block provided with a number of cylinders, a piston disposed in each of the cylinder of the cylinder block, a crankcase sealingly disposed on one end of the cylinder block, a cylinder head sealingly disposed on the other end of the cylinder block, a rotatably supported drive shaft, and a swash plate. The swash plate is adapted to be rotated by the drive shaft. Rotation of the swash plate is effective to reciprocatively drive the pistons. The length of the stroke of the pistons is varied by the inclination of the swash plate. Inclination of the swash plate is varied by controlling the pressure differential between a suction chamber and a crank chamber. The pressure differential is typically controlled using a control valve and a conduit formed within the cylinder block which provides fluid communication between a discharge chamber and the crank chamber to convey compressed gases from the discharge chamber to the crank chamber based on the pressure in the suction chamber. The conduit also typically provides communication for lubricating oil between the discharge chamber and the crank chamber to achieve lubrication of the moving components within the crank chamber. 
     Another conventional lubricating system disclosed in the prior art employs a forced lubrication system including an oil pump provided at one end of the drive shaft and driven by the drive shaft to lubricate the moving components within the crank chamber. The forced lubrication system typically causes lubricating oil to be pumped from an oil sump, through a pump chamber, a lubrication passage and radial branch passageways within the drive shaft, to the crank chamber. 
     The compressor arrangements in the prior art described above have several disadvantages. First, when a compressor having a conduit within the cylinder block is operating at minimum capacity, ineffective lubrication of the close tolerance moving parts within the crank chamber occurs due to the lack of consistent flow of refrigerant gas from the discharge chamber to the crank chamber. Second, in a compressor having a forced lubrication system, the compressor may include an oil sump, a pump chamber, and an oil pump operatively connected to the drive shaft adding expense. 
     An object of the present invention is to produce a swash plate type compressor wherein oil flow to the crankcase during both minimum and maximum operating conditions is improved to result in efficient lubrication of the compressor components. 
     Another object of the present invention is to produce a swash plate type compressor wherein the oil sump, the pump chamber, and the drive shaft driven oil pump of the prior art can be eliminated. 
     SUMMARY OF THE INVENTION 
     The above, as well as other objects of the invention, may be readily achieved by a variable displacement swash plate type compressor comprising: a cylinder block having a plurality of cylinders arranged radially therein; a piston reciprocatively disposed in each of the cylinders of the cylinder block; a cylinder head attached to said cylinder block and having a discharge chamber formed therein; a crankcase attached to the cylinder block to define a crank chamber; a drive shaft rotatably supported by the crankcase and the cylinder block; a swash plate adapted to be driven by the drive shaft and having a central aperture for receiving the drive shaft, radially outwardly extending side walls, and a peripheral edge; and a lubrication passage formed within the drive shaft providing fluid communication between the discharge chamber and the crank chamber. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above, as well as other objects, features, and advantages of the present invention will be understood from the following detailed description of the preferred embodiment of the present invention with reference to the accompanying drawings, in which: 
     FIG. 1 is a cross sectional elevational view of a variable displacement swash plate type compressor incorporating the features of the invention, schematically showing a lubrication passage in the drive shaft in fluid communication with the discharge chamber and the crank chamber; 
     FIG. 2 is a cross-sectional view of the compressor illustrated in FIG. 1 taken along line  2 — 2  thereof, showing a first radial bore of the lubrication passage, and an orifice tube in the cylinder block in fluid communication with the crank chamber and the suction chamber; 
     FIG. 3 is a cross sectional elevational view of the compressor illustrated in FIGS. 1 and 2 taken along line  3 — 3  of FIG. 2, schematically showing a lubrication passage in the drive shaft in fluid communication with the discharge chamber and the crank chamber, and an orifice tube in the cylinder block in fluid communication with the crank chamber and the suction chamber; 
     FIG. 4 is a cross-sectional view of the compressor illustrated in FIG. 3 taken along line  4 — 4  thereof, showing an additional radial bore of the lubrication passage; and 
     FIG. 5 is a elevational view of the hub of the swash plate illustrated in FIGS. 1 and 3 showing the features thereof. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings, and particularly FIGS. 1 and 3, there is shown generally at  10  a variable displacement swash plate type compressor incorporating the features of the invention. The compressor  10  includes a cylinder block  12  having a plurality of cylinders  14 . A cylinder head  16  is disposed adjacent one end of the cylinder block  12  and sealingly closes the end of the cylinder block  12 . A valve plate  18  is disposed between the cylinder block  12  and the cylinder head  16 . A crankcase  20  is sealingly disposed at the other end of the cylinder block  12 . The crankcase  20  and cylinder block  12  cooperate to form an airtight crank chamber  22 . 
     The cylinder head  16  includes a suction chamber  24  and a discharge chamber  26 . An orifice tube  28  is disposed to provide fluid communication between the crank chamber  22  and the suction chamber  24 . A shut-off valve  30  provides selective fluid communication between an evaporator (not shown) of the cooling portion of the air conditioning system for a vehicle and the suction chamber  24 . An outlet port  34  provides fluid communication between the discharge chamber  26  and the cooling portion of the air conditioning system for a vehicle. Suction ports  38  provide fluid communication between the suction chamber  24  and each cylinder  14 . Each suction port  38  is opened and closed by a flap valve  40  which may be formed as an integral part of the valve plate  18 . Discharge ports  42  provide fluid communication between each cylinder  14  and the discharge chamber  26 . Each discharge port  42  is opened and closed by a discharge valve  44 . A retainer  46  restricts the opening of the discharge valve  44 . 
     An electronic control valve  48  is disposed in the discharge chamber  26  and arranged to monitor the discharge pressure of the compressor  10 , the RPM of the vehicle engine, the humidity in the vicinity of the evaporator, and the like, to control the flow of refrigerant gas from the discharge chamber  26  to the crank chamber  22 . The shut-off valve  30  is arranged to be actuated by the electronic control valve  48  through a fluid pressure channel (not shown), for example. In the embodiment shown, a mechanical shut-off valve is illustrated, but it is understood that other types of valves can be used. 
     A drive shaft  52  is centrally disposed in and arranged to extend through the crankcase  20  to the cylinder block  12 . One end of the drive shaft  52  is rotatably supported by a bearing  54  mounted in the crankcase  20 , and the other end of the drive shaft  52  is rotatably supported in a bearing  56  mounted in the cylinder block  12 . Longitudinal movement of the drive shaft  52  is restricted by a thrust bearing  58  mounted in the cylinder block  12 . 
     A longitudinally extending lubrication passage or bore  62  is formed within the drive shaft  52 . The bore  62  communicates with a plurality of spaced apart radially extending bores  64 . The lubrication passage  62  and the bores  64  provide fluid communication between the discharge chamber  26  and the crank chamber  22 . 
     A rotor  66  is fixedly mounted on an outer surface of the drive shaft  52  adjacent one end of the crankcase  20  within the crank chamber  22 . An arm  68  extends outwardly from a surface of the rotor  66  opposite the surface of the rotor  66  that is adjacent the end of the crankcase  20 . A slot  70  is formed in the distal end of the arm  68 . A pin  72  has one end slidingly disposed in the slot  70  of the arm  68  of the rotor  66 . 
     A swash plate  74  is formed to include a hub  76  and an annular plate  78 . Referring now to FIG. 5, the hub  76  includes a centrally disposed aperture formed therein and an arm  86  that extends outwardly and perpendicularly from the surface of the hub  76 . An aperture  88  is formed in the distal end of the arm  86  of the hub  76 . One end of the pin  72  is slidingly disposed in the slot  70  of the arm  68  of the rotor  66 , while the other end is fixedly disposed in the aperture  88  of the arm  86 . 
     A pair of spaced apart holes  92 ,  94  are formed in the hub  76  and are adapted to receive pins  96 ,  98 , respectively which are typically press fit therein. The outer surfaces of the pins  96 ,  98  are formed to extend inwardly within the hub  76 . 
     The hub  76  is press fit in a suitable central aperture of the annular plate  78 . In the assembled form the drive shaft  52  is adapted to extend through the central aperture of hub  76 . 
     A helical compression spring  102  is disposed to extend around the outer surface of the drive shaft  52 . One end of the spring  102  abuts the rotor  66 , while the opposite end abuts the hub  76  of the swash plate  74 . The spring tends to urge the swash plate  74  away from the rotor  66 . 
     A piston  104  is slidably disposed in each of the cylinders  14  in the cylinder block  12 . Each piston  104  includes a head  106 , a middle portion  108 , and a bridge portion  110 . A circumferential groove  112  is formed in an outer cylindrical wall of the head  106  to receive piston rings (not shown). The middle portion  108  terminates in the bridge portion  110  defining an interior space  114  for receiving the annular plate  78 . Spaced apart concave pockets  116  are formed in the interior space  114  of the bridge portion  110  for rotatably containing a pair of semi-spherical shoes  118 . The spherical surfaces of the shoes  118  are disposed in the shoe pockets  116  with a flat bearing surface disposed opposite the spherical surface for slidable engagement with the opposing sides of the annular plate  78 . 
     In operation, the compressor  10  is actuated by the rotation of the drive shaft  52  which is typically an associated internal combustion engine of a vehicle. Rotation of the drive shaft  52  causes the simultaneous rotation of the rotor  66 . The swash plate  74  is connected to the rotor  66  by a hinge mechanism formed by the pin  72  slidingly disposed in the slot  70  of the arm  68  of the rotor  66  and fixedly disposed in the aperture  88  of the arm  86  of the hub  76 . As the rotor  66  rotates, the swash plate  74  is caused to rotate. During rotation, the swash plate  74  is disposed at an inclination. The rotation of the swash plate  74  is effective to reciprocatively drive the pistons  104 . The rotation of the swash plate  74  further causes a sliding engagement between the annular plate  78  and the cooperating spaced apart shoes  118 . 
     The reciprocation of the pistons  104  causes refrigerant gas and lubricating oil to be introduced from the suction chamber  22  into the respective cylinders  14  of the cylinder head  16 . The reciprocating motion of the pistons  104  then compresses the refrigerant gas within each cylinder  14 . When the pressure within each cylinder  14  reaches the pressure within the discharge chamber  26 , the compressed refrigerant gas is discharged into the discharge chamber  26 . 
     The capacity of the compressor  10  can be changed by changing the inclination of the swash plate  74  and thereby changing the length of the stroke for the pistons  104 . The inclination of the swash plate  74  is changed by controlling the pressure differential between the crank chamber  22  and the suction chamber  24 . The pressure differential is controlled by controlling the net flow of refrigerant gas from the discharge chamber  26  to the crank chamber  22  through the lubrication passage  62 . As the piston  104  is caused to move toward a bottom dead center position, the pressure within the cylinder  14  is less than the pressure within the suction chamber  24 . The suction valve  40  is opened causing refrigerant gas to flow into the cylinder  14  through the suction port  38 . As the piston  104  is moved toward a top dead center position, the refrigerant gas within the cylinder  14  is compressed until the pressure within the cylinder  14  exceeds the pressure within the discharge chamber  26 . The discharge valve  44  is then opened and refrigerant gas flows through the discharge port  42  to the discharge chamber  26 . 
     The valve  48  controls the capacity of the compressor  10  by adjustably changing the flow of refrigerant gas and lubricating oil from the discharge chamber  26  to the crank chamber  22  through the lubrication passage  62  in the drive shaft  52 . When an increase in thermal load occurs, the shut-off valve  30  is caused to open and the flow of refrigerant gas to the suction chamber  24  is increased, increasing the pressure therein. The pressure differential between the crank chamber  22  and the suction chamber  24  is therefore increased and the backpressure acting on the pistons  104  in the crank chamber  22  is decreased by bleeding refrigerant gas through the orifice tube  28 . As a result of the decreased backpressure in the crank chamber  22 , the pin  72  connecting the rotor  66  and the swash plate  74  is caused to move slidably and outwardly within the slot  70 . The swash plate  74  is moved against the force of the spring  102 , increasing the inclination of the swash plate  74 , which increases the length of the stroke of each piston  104  and the compressor  10  is caused to operate at a maximum capacity. 
     Conversely, when a decrease in thermal load occurs, the shut-off valve  30  is caused to close and the flow of refrigerant gas to the suction chamber  24  is decreased, decreasing the pressure therein. The valve  48  is opened, causing refrigerant gas to flow from the discharge chamber  26  to the crank chamber  22  through the lubrication passage  62 . The pressure differential between the crank chamber  22  and the suction chamber  24  is decreased, and the backpressure acting on the pistons  104  in the crank chamber  22  is increased. As a result of the increased backpressure in the crank chamber  22 , the pin  72  is moved slidably and inwardly within the slot  70 . The swash plate  74  yields to the force of the spring  102 , the inclination of the swash plate  74  is decreased, and as a result, the length of the stroke of each piston  104  is reduced. 
     When the length of the stroke of each piston  104  is reduced, the compressor  10  is caused to operate at a minimum capacity. When operating at a minimum capacity and with the shut-off valve  30  closed, an internal refrigeration circuit is formed. Within the internal refrigeration circuit, refrigerant gas and lubricating oil are caused to flow serially from the suction chamber  24  to the cylinder  14 , the discharge chamber  26 , the valve  48 , the lubrication passage  62 , and the crank chamber  22 , thus lubricating the component parts within the crank chamber  22 . The refrigerant gas and lubricating oil in the crank chamber  22  is then caused to flow through the orifice tube  28  to the suction chamber  24 , thereby completing the internal refrigeration circuit. 
     By introducing the refrigerant gas and lubricating oil from the discharge chamber  26  into the crank chamber  22  through the lubrication passage  62 , instead of introducing the refrigerant gas from the discharge chamber  26  into the crank chamber  22  through the conduit of prior art, several benefits are achieved. The lubricating efficiency of the compressor  10  is maximized. The conduit within the cylinder block of prior art compressors causes the discharge chamber  26  to be in continuous fluid communication with the crank chamber  22 . In the preferred embodiment of the invention, the flow of refrigerant gas and lubricating oil between the discharge chamber  26  and the crank chamber  22 , through the lubrication passage  62 , is controlled by the electronic control valve  48 . The use of the electronic control valve  48  efficiently controls the flow of refrigerant gas and lubricating oil from the discharge chamber  26  into the crank chamber  22 . The lubricating oil introduced into the crank chamber  22  through the plurality of spaced apart radial bores  64  provides lubrication to the components within the crank chamber  22 . Further, when the compressor  10  is operating at a minimum capacity, it is not necessary to circulate the refrigerant gas through an external refrigeration circuit such as the air conditioning system for a vehicle. At such a minimum capacity, the electronic control valve  48  is caused to open and the shut-off valve  30  is caused to close, causing the refrigerant gas and lubrication oil to flow within the internal refrigeration circuit, thereby efficiently lubricating moving components such as bearings  54 ,  56 ,  58 , and the swash plate  74 . The introduction of lubricating oil to the crank chamber  22  improves the durability of the compressor  10 . 
     Additionally, by introducing the refrigerant gas to the crank chamber  22  through the lubrication passage  62 , as described above, the requirement an oil sump, a pump chamber, and a drive shaft driven oil pump is eliminated, thereby reducing manufacturing and operating costs. 
     From the foregoing description, one ordinarily skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications to the invention to adapt it to various usages and conditions.