Abstract:
A compressor having a device for recovering lubricating oil. The compressor includes a discharge chamber and a muffler, which attenuates the pressure pulsation of refrigerant gas sent out from the discharge chamber. The muffler is defined by a muffler base, which is formed on the cylinder block, and a muffler cover, which is attached to the muffler base. The muffler includes a first muffler chamber and a second muffler chamber, which are connected by an opening. The muffler cover has a gas outlet for sending the refrigerant gas out of the compressor from the second muffler chamber. Lubricating oil separated from the refrigerant gas in the first muffler chamber is sent to the crank chamber through a recovery passage. The location of the gas outlet can be easily changed by replacing the muffler cover. Thus, the compressor can be easily adapted to different engine compartments.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to compressors that may be applied to, for example, automotive air-conditioning systems. More particularly, the present invention pertains to mechanisms for separating and recovering lubricating oil from refrigerant gas in compressors. 
     Japanese Unexamined Patent Publication No. 5-240158 and Japanese Unexamined Patent Publication No. 8-35485 describe compressors that incorporate oil recovery devices. Each of these compressors has a housing, which houses a discharge chamber, a crank chamber, and cylinder bores. A rotatable drive shaft is supported in the housing such that it extends through the crank chamber. A swash plate is supported in the crank chamber and supported by the drive shaft such that it rotates integrally with the drive shaft. A piston is accommodated in each cylinder bore and coupled to the swash plate. When the drive shaft is rotated by an external drive source, such as an automotive engine, the swash plate converts the rotation of the drive shaft to linear reciprocation of each piston in the associated cylinder bore. The reciprocation of each piston draws refrigerant gas into the cylinder bore, compresses the gas, and discharges the gas into the discharge chamber. 
     A typical compressor has a muffler located downstream of the discharge chamber. The muffler has a gas outlet that is connected with an external refrigerant circuit. Accordingly, the refrigerant gas in the discharge chamber is sent to the external refrigerant circuit by way of the muffler. The muffler attenuates the pressure pulsation of the refrigerant gas. This reduces vibrations and noise, which result from pressure pulsation of the refrigerant gas. 
     Atomized lubricating oil is suspended in the refrigerant gas to lubricate moving parts in the compressor as the refrigerant gas flows through the compressor. However, the lubricating oil that travels through the compressor is sent to the external refrigerant circuit together with the refrigerant gas. If a large amount of lubricating oil is discharged from the compressor, the amount of lubricating oil in the compressor decreases. This may lead to insufficient lubrication. Accordingly, the mufflers of the compressors described in the above publications incorporate a device for separating and recovering the lubricating oil from the refrigerant gas. The oil recovery device includes an oil separating chamber, which is arranged in the muffler, and a cylindrical tube, which is secured to the gas outlet such that the tube projects into the oil separating compartment. Further, a recovery passage connects the oil separating chamber to the crank chamber. 
     As the refrigerant gas flows from the muffler toward the external refrigerant circuit, the refrigerant gas swirls about the tube in the oil separating chamber. The refrigerant gas then enters the tube and flows through the gas outlet into the external refrigerant circuit. Centrifugal force acts on the refrigerant gas swirling about the tube. The centrifugal force separates the lubricating oil from the refrigerant gas. The separated lubricating oil is then sent to the crank chamber through the recovery passage. This maintains satisfactory lubrication in the compressor. 
     The location of the gas outlet is normally changed in accordance with the type of vehicle in which the compressor is installed. The layout of various equipment in the engine compartment differs in each type of vehicle. Thus, the arrangement of the compressor and the external refrigerant circuit depends on the spatial limitations resulting from the layout of the engine compartment. There are cases in which the location of the gas outlet on the compressor must be changed because of the engine compartment layout. As a result, the structure of the oil recovery device must also be changed. Such changes decrease production efficiency and increases costs. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an objective of the present invention to provide a compressor having an oil recovery device that permits the location of the gas outlet to be easily changed without making changes to the oil recovery device. 
     To achieve the above objective, the present invention provides a compressor for compressing gas that contains atomized oil. The compressor includes a housing, a gas compression mechanism located within the housing, and a discharge chamber into which the gas compressed by the compression mechanism is discharged. A muffler base is arranged on the housing. A muffler cover is attached to the muffler base such that a muffler is enclosed by the muffler base and the muffler cover. A partition separates the muffler into a first muffler chamber and a second muffler chamber. The first muffler chamber is defined by the muffler base and the partition. The second muffler chamber is defined by the muffler cover and the partition. The partition has an opening for connecting the first muffler chamber with the second muffler chamber. The muffler cover has a gas outlet connected with the second muffler chamber. A discharge passage connects the discharge chamber to the first muffler chamber. Compressed gas is sent out of the compressor by way of the discharge chamber, the discharge passage, the first muffler chamber, the partition opening, the second muffler chamber, and the gas outlet. Pressure pulsation of the compressed gas is attenuated by the first and second muffler chambers. The atomized oil is separated from the compressed gas when passing through the first muffler chamber. A recovery passage is connected to the first muffler chamber to drain the separated oil in the first muffler chamber to portions of the compressor requiring lubrication. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features of the present invention that are believed to be novel are set forth with particularity in the appended claims. 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 in which: 
     FIG. 1 is a cross-sectional view showing a first embodiment of a variable displacement compressor according to the present invention; 
     FIG. 1A is an enlarged view showing the encircled portion of FIG. 1; 
     FIG. 2 is a cross-sectional view taken along line  2 — 2  in FIG. 1; 
     FIG. 3 is a cross-sectional view showing a second embodiment of a variable displacement compressor according to the present invention; 
     FIG. 3A is an enlarged view showing the encircled portion of FIG. 3; 
     FIG. 4 is a cross-sectional view taken along line  4 — 4  in FIG. 3; and 
     FIG. 5 is a partial cross-sectional view showing an oil recovery device employed in a further embodiment according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A first embodiment of a variable displacement compressor according to the present invention will now be described with reference to FIGS. 1 and 2. As shown in FIG. 1, the compressor has a front housing  11 , which is coupled to the front end of a cylinder block  12 . A rear housing  13  is coupled to the rear end of the cylinder block  12  with a valve plate  14  arranged in between. The front housing  11 , the cylinder block  12 , and the rear housing  13  define a compressor housing. 
     A crank chamber  15  is defined in the front housing  11  in front of the cylinder block  12 . A drive shaft  16  extends through the crank chamber  15  and is rotatably supported by the front housing  11  and the cylinder block  12 . The drive shaft  16  is connected to an external drive source, or an engine, by a clutch mechanism such as an electromagnetic clutch. During operation of the engine, the drive shaft  16  is rotated when the clutch connects the engine to the drive shaft  16 . 
     A rotor  22  is fixed to the drive shaft  16  in the crank chamber  15 . A drive plate, or swash plate  23 , is supported inclinably on the drive shaft  16 . A hinge mechanism  24  connects the swash plate  23  to the rotor  22 . The hinge mechanism  24  rotates the swash plate  23  integrally with the drive shaft  16  while permitting inclination of the swash plate  23  with respect to the drive shaft  16 . 
     Cylinder bores  12   a  (only one shown) extend through the cylinder block  12 . A single-headed piston  25  is accommodated in each cylinder bore  12   a . Each piston  25  is coupled to the peripheral portion of the swash plate  23  by a pair of shoes  26 . The swash plate  23  and the shoes  26  convert the rotation of the drive shaft  16  to reciprocation of each piston  25  in the associated cylinder bore  12   a.    
     A suction chamber  27  and a discharge chamber  28  are defined in the rear housing  13 . A suction port  29  and a suction flap  30 , which opens and closes the suction port  29  are formed in the valve plate  14  in association with each cylinder bore  12   a . A discharge port  31  and a discharge flap  32 , which opens and closes the discharge port  31 , are also formed in the valve plate  14  in association with each cylinder bore  12   a . When each piston  25  moves from its top dead center position to its bottom dead center position, the refrigerant gas in the suction chamber  27  opens the suction flap  30  and enters the associated cylinder bore  12   a  through the suction port  29 . When the piston  25  moves from the bottom dead center position to the top dead center position, the refrigerant gas in the cylinder bore  12   a  is first compressed. The compressed gas then opens the discharge flap  32  and enters the discharge chamber  28  through the discharge port  31 . The drive shaft  16 , the swash plate  23 , and the pistons  25  define a compression mechanism for compressing the refrigerant gas. 
     A pressurizing passage  33  extends through the rear housing  13 , the valve plate  14 , and the cylinder block  12  to connect the discharge chamber  28  to the crank chamber  15 . A bleeding passage  34  extends through the center of the valve plate  14 . The rear end of the drive shaft  16  is inserted into a shaft bore  12   b , which extends through the center of the cylinder block  12 , and is supported by a bearing. The refrigerant gas in the crank chamber  15  flows toward the suction chamber  27  by way of the shaft bore  12   b , the space between the bearing and the drive shaft  16 , and the bleeding passage  34 . 
     A displacement control valve  35  is installed in the rear housing  13  and arranged in the pressurizing passage  33 . A communication passage  36  extends through the rear housing  13  to communicate the pressure of the suction chamber  27  to the control valve  35 . The control valve  35  includes a diaphragm  35   a , which serves as a pressure sensing member, and a valve body  35   b , which is operably connected to the diaphragm  35   a  by a rod. 
     The diaphragm  35   a  moves the valve body  35   b  in accordance with the pressure of the suction chamber  27  (suction pressure) communicated to the control valve  35  through the communication passage  36 . The movement of the valve body  35   b  alters the opened amount of the pressurizing passage  33 . The amount of refrigerant gas that flows into the crank chamber  15  from the discharge chamber  28  relies on the opened amount of the pressurizing passage  33  and determines the pressure of the crank chamber  15 . Therefore, the control valve  35  changes the difference between the pressure of the crank chamber  15 , which acts on one side of the pistons  25 , and the pressure of the cylinder bores  12   a , which acts on the other side of the pistons  25 . Changes in the pressure difference alters the inclination of the swash plate  23 . This, in turn, changes the stroke of the pistons  25  and varies the displacement of the compressor. 
     As shown in FIGS. 1 and 2, a muffler base  41  projects integrally from the outer surface of the cylinder block  12 . 
     A muffler cover  42  is fixed to the top of the muffler base  41 . A muffler  43  is housed by the muffler base  41  and the muffler cover  42 . A gasket  44 , which serves as a partition, is arranged between the muffler base  41  and the muffler cover  42  to define a first muffler chamber  43 A, which is encompassed by the muffler base  41 , and a second muffler chamber  43 B, which is encompassed by the muffler cover  42 . As shown in FIG. 1A, the gasket  44  includes a flat metal base plate  44   a  and a synthetic resin rubber coating  44   b , which is applied to the surface of the base plate  44   a . The gasket  44  has a rim  45 , which seals the space between the muffler base  41  and the muffler cover  42 . The coating  44   b  has superior adhesion properties and securely seals the space between the muffler base  41  and the muffler cover  42 . 
     A discharge passage  47  connects the discharge chamber  28  to the first muffler chamber  43 A. The discharge passage  47  has an outlet  47   a , which extends through the wall of the muffler base  41  to connect the discharge passage  47  with the first muffler chamber  43 A. An opening  46  extends through the gasket  44  to connect the first muffler chamber  43 A with the second muffler chamber  43 B. The opening  46  does not face and is misaligned with the discharge passage outlet  47   a . A cylindrical separating tube  51  is formed integrally with the gasket  44  about the opening  46  projecting into the first muffler chamber  43 A. A gas outlet  48  extends through the top surface of the muffler cover  42 . The gas outlet  48  connects the second muffler chamber  43 B to an external refrigerant circuit. 
     A cylindrical wall  41   a , which encompasses the separating tube  51 , projects from the bottom surface of the first muffler chamber  43 A. The top of the cylindrical wall  41   a  contacts the gasket  44 . The space between the inner side of the cylindrical wall  41   a  and the gasket  44  defines a swirling chamber  49  in the first muffler chamber  43 A. The separating tube  51  is arranged in the swirling chamber  49  such that its axis coincides with the axis of the swirling chamber  49 . An intake passage  50  extends through the cylindrical wall  41   a  to connect the first muffler chamber  43 A with the swirling chamber  49 . The intake passage  50  does not face and is misaligned with the discharge passage outlet  47   a . The axis of the inlet passage  50  is tangential to the inner surface of the wall  41   a , as shown in FIG.  2 . 
     A recovery passage  52  extends through the cylinder block  12  to connect the first muffler chamber  43 A, and particularly the swirling chamber  49 , to the crank chamber  15 . The recovery passage  52  has an inlet, which is located in the bottom surface of the swirling chamber  49 . The inlet of the recovery passage  52  is misaligned with both the discharge passage outlet  47   a  and the intake passage  50 . A filter  53  is arranged in the inlet. A throttle  52   a  is provided in the recovery passage  52 . 
     The refrigerant gas discharged into the discharge chamber  28  is sent to the external refrigerant circuit by way of the discharge passage  47 , the first muffler chamber  43 A, the intake passage  50 , the swirling chamber  49 , the opening  46 , the second muffler chamber  43 B, and the gas outlet  48 . The first and second muffler chambers  43 A,  43 B attenuate the pressure pulsation of the refrigerant gas. This reduces vibrations and noise, which result from pressure pulsation of the refrigerant gas. 
     Atomized lubricating oil is suspended in the refrigerant gas. The refrigerant gas thus lubricates the parts that move and contact other parts in the compressor, such as the swash plate  23  and the shoes  26 . The lubricating oil travels through the discharge chamber  28  and the discharge passage  47  and enters the first muffler chamber  43 A together with the refrigerant gas. When the stream of refrigerant gas collides against the inner surface of the muffler chamber  43 A and changes directions, some of the lubricating oil suspended in the refrigerant gas is separated from the gas and collected on the inner surface of the first muffler chamber  43 A. The separated lubricating oil then enters the swirling chamber  49  through the intake passage  50  together with the refrigerant gas. 
     The intake passage  50  is tangential to the inner surface of the swirling chamber  49 . Thus, the refrigerant gas that enters the swirling chamber  49  through the intake passage  50  swirls about the separating tube  51 . Centrifugal force acts on the refrigerant gas swirling about the separating tube  51  and effectively separates lubricating oil from the refrigerant gas. The refrigerant gas then flows into the second muffler chamber  43 B through the opening  46  and enters the external refrigerant circuit through the gas outlet  48 . 
     The lubricating oil separated from the refrigerant gas is collected in the swirling chamber  49 . The pressure in the swirling chamber  49  is higher than that in the crank chamber  15 . Therefore, the lubricating oil in the swirling chamber  49  is sent to the crank chamber  15  through the recovery passage  52 . Accordingly, satisfactory lubrication continues in the compressor. 
     The control valve  35  adjusts the amount of refrigerant gas that flows into the crank chamber  15  from the discharge chamber  28 . However, if a large amount of refrigerant gas flows from the swirling chamber  49  into the crank chamber  15  though the recovery passage  52 , this would interfere with the functions of the control valve  35 . In such case, the control valve  35  would not be able to properly control the compressor displacement. However, the throttle  52   a  in the recovery passage  52  limits the amount of refrigerant gas flowing into the crank chamber  15  from the swirling chamber  49 . Thus, the pressure in the crank chamber  15  is not significantly affected by the refrigerant gas from the swirling chamber  49 . Accordingly, the compressor displacement is not influenced by the refrigerant gas from the swirling chamber  49 . 
     Foreign matter in the lubricating oil may clog the recovery passage  52 , especially at the throttle  52   a . However, the filter  53 , which is arranged at the inlet of the recovery passage  52  prevents foreign matter from entering the recovery passage  52 . Thus, the recovery passage  52  is kept open. 
     The gasket  44  divides the muffler  43  into two parts, the first muffler chamber  43 A and the second muffler chamber  43 B. The swirling chamber  49  and the separating tube  51 , which serve to separate lubricating oil from the refrigerant gas and recover the oil, are arranged in the first muffler chamber  43 A in association with the opening  46  of the gasket  44 . The recovery passage  52  connects the swirling chamber  49  to the crank chamber  15 . The gas outlet  48 , which is provided in the muffler cover  42 , is connected with the second muffler chamber  43 B. 
     Accordingly, the location of the gas outlet  48  does not affect the arrangement of the swirling chamber  49 , the separating tube  51 , and the recovery passage  52 . Thus, the compressor of the preferred embodiment may be applied to different types of vehicles merely by preparing muffler covers  42  having gas outlets  48  located at different positions. Other changes are not necessary. Since the structural changes to the compressor are minimal when adapting to different types of vehicles, the production of the compressor is simplified and productions costs are reduced. 
     The flow path of the refrigerant gas is complicated due to the two muffler chambers  43 A,  43 B, which are separated from each other. The intake passage  50 , the swirling chamber  49 , and the separating tube  51  further complicate the flow path of the refrigerant gas. This effectively attenuates the pressure pulsation of the refrigerant gas. 
     The gasket  44  not only seals the space between the muffler base  41  and the muffler cover  42  but also serves to partition the muffler  43  into two chambers. In addition, the separating tube  51  is formed integrally with the gasket  44 . This reduces the number of parts and provides a simplified structure in comparison to a compressor employing a gasket, a partition, and a separating tube that are formed independently from one another. 
     The intake passage  50  does not face and is misaligned with the outlet  47   a  of the discharge passage  47  in the first muffler chamber  43 A. Thus, the refrigerant gas that flows into the first muffler chamber  43 A through the discharge passage outlet  47   a  generally flows through the entire first muffler chamber  43 A before entering the swirling chamber  49  through the intake passage  50 . Accordingly, the lubricating oil separated from the refrigerant gas in the first muffler chamber  43 A is forced into the swirling chamber  49  by the stream of the refrigerant gas in the muffler chamber  43 A. In other words, all of the lubricating oil in the first muffler chamber  43 A is sent toward the swirling chamber  49 . This increases the recovery rate of the lubricating oil. 
     A second embodiment according to the present invention will now be described with reference to FIGS. 3 and 4. The description will center on parts differing the first embodiment. The swirling chamber  49  and the separating tube  51  of the first embodiment are not employed in this embodiment. Furthermore, the displacement control valve  35  is installed in the muffler base  41  and arranged midway in the recovery passage  52 . The recovery passage  52  functions not only to send lubricating oil to the crank chamber  15  but also as a pressurizing passage (corresponding to the pressurizing passage  33  employed in the embodiment of FIG.  1 ). The recovery passage  52  does not have a throttle. 
     The recovery passage  52  has an inlet located in the bottom surface of the first muffler chamber  43 A directly below the opening  46  of the gasket  44  (FIG.  4 ). An oil sink  55  is formed in the bottom surface of the first muffler chamber  43 A in association with the inlet of the recovery passage  52 . As shown in FIG. 3A, the structure of the gasket  44  is similar to that of the gasket  44  employed in the embodiment illustrated in FIG.  1 A. 
     Refrigerant gas flows into the first muffler chamber  43 A through the outlet  47   a  of the discharge passage  47 . When the stream of refrigerant gas contacts the inner surface of the muffler chamber  43 A and changes directions, some of the lubricating oil suspended in the refrigerant gas is separated from the gas and collected on the inner surface of the first muffler chamber  43 A. The separated lubricating oil is moved toward the opening  46  by the stream of refrigerant gas and collected in the oil sink  55 . When the control valve  35  opens the recovery passage  52 , the lubricating oil in the oil sink  55  is sent to the crank chamber  15  through the recovery passage  52  together with the refrigerant gas in the first muffler chamber  43 A. Accordingly, the second embodiment has the same advantages as the first embodiment. 
     The amount of lubricating oil supplied to the crank chamber  15  is varied in accordance with the opened amount of the recovery passage  52 , which is controlled by the control valve  35 . For example, if the displacement of the compressor is small, the amount of lubricating gas that flows into the compressor is small. This may lead to insufficient lubrication in the compressor. However, the control valve  35  increases the opened amount of the recovery passage  52  when decreasing the displacement of the compressor. In other words, the amount of lubricating oil supplied to the crank chamber  15  increases when the displacement of the compressor is small. This prevents insufficient lubrication. 
     In the second embodiment, the recovery passage  52  also serves as a pressurizing passage. Therefore, separate passages for each purpose need not be provided. This simplifies production of the compressor. Furthermore, the recovery passage  52  does not include a throttle. Thus, the diameter of the recovery passage  52  can be enlarged. This prevents foreign matter from clogging the recovery passage  52 . Accordingly, a filter for removing foreign matter need not be provided. This decreases the number of components. If necessary, however, a filter may be located in the oil sink  55 . 
     The opening  46  does not face and is misaligned with the outlet  47   a  of the discharge passage  47 . Also, the inlet of the recovery passage  52  is misaligned with the discharge passage outlet  47   a  as seen in FIG.  4 . Thus, the refrigerant gas that flows into the first muffler chamber  43 A though the discharge passage outlet  47   a  generally flows through the entire first muffler chamber  43 A before entering the second muffler chamber  43 B through the opening  46 . Accordingly, the lubricating oil separated from the refrigerant gas in the first muffler chamber  43 A is forced toward the opening  46  by the stream of the refrigerant gas in the muffler chamber  43 A. In other words, all of the lubricating oil in the first muffler chamber  43 A is collected in the oil sink  55 , which is located directly below the opening  46 . This increases the recovery rate of the lubricating oil. 
     The control valve  35  extends perpendicular to the axis of the drive shaft  16  in the muffler base  41 . This allows the dimensions of the compressor to be decreased in the axial direction. 
     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. More specifically, the present invention may be embodied as described below. 
     As shown in FIG. 5, the separating tube  51  of the first embodiment may be replaced by a cylindrical separating pillar  61 , which projects from the bottom surface of the swirling chamber  49 . The separating pillar  61  is located directly below the connecting bore  46  such that the separating pillar  61  and the connecting bore  46  are coaxial. The refrigerant gas drawn into the swirling chamber  49  is swirled about the separating pillar  61  before flowing through the connecting bore  46  and into the second muffler chamber  43 B. 
     In the first embodiment, the outlet of the recovery passage  52  may be connected with the suction chamber  27  instead of the crank chamber  15 . The difference between the pressure of the swirling chamber  49  and the pressure of the suction chamber  27  is greater than the difference between the pressure of the swirling chamber  49  and the pressure of the crank chamber  15 . Accordingly, the lubricating oil collected in the swirling chamber  49  would be readily drawn into the suction chamber  27  through the recovery passage  52 . 
     In the first embodiment, the separating tube  51  and the gasket  44  may be formed separately. The separating pillar  61  of the embodiment illustrated in FIG. 5 may be formed separately from the bottom surface of the swirling chamber  49 . 
     In the first embodiment, the displacement control valve  35  may be arranged in a bleeding passage that connects the crank chamber  15  to the suction chamber  27 . In this case, the control valve  35  adjusts the amount of refrigerant gas released into the suction chamber  27  from the crank chamber  15  to control the pressure of the crank chamber  15 . 
     In the above embodiments, the muffler base  41  may be formed integrally with the cylinder block  12  such that the opening of the muffler base  41  faces toward the front or toward the rear. In this case, a muffler cover  42  is formed integrally with either the front housing  11  or the rear housing  13  depending on which way the opening of the muffler base  41  faces. By coupling the cylinder block  12  to the front housing  11  or the rear housing  13 , a muffler  43  is formed between the muffler base  41  and the muffler cover  42 . On the other hand, the muffler base  41  may be formed on the front housing  11  or the rear housing  13  and the muffler cover  42  may be formed on the cylinder block  12 . Although not shown in FIG. 1, a gasket is arranged between the cylinder block  12  and each housing  11 ,  13  to seal the space in between. Accordingly, the gasket may also serve to partition the muffler  43  into two chambers. 
     The present invention is not limited to variable displacement compressors such as that shown in FIG.  1  and may be applied to a fixed displacement type compressor. Additionally, the present invention is not limited to swash plate type compressors. For example, the present invention may be applied to vane type compressors, scroll type compressors, and wave cam 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.