COMPRESSOR WITH AN OIL MANAGEMENT SYSTEM

Abstract

A compressor (10) containing a hollow casing (12) having a suction chamber (20), a discharge chamber (30), and a crank chamber (38) formed therein. A first fluid flow path (22, 54, 55, 56) provided in the compressor facilitates the flow of the working fluid from the crank chamber to the suction chamber. A second fluid flow path (22, 80) provided in the compressor facilitates the flow of a mixture of the working fluid and a lubricating fluid from the crank chamber to the suction chamber, the second fluid flow path being open or closed as selected by an annular sleeve (58).

Description

The present invention relates to a compressor. More particularly, this invention relates to an oil management system for a compressor. Known compressors used in refrigeration and air conditioning systems, such as variable displacement flat cam compressors, for example, typically include a lubricating mist suspended in a refrigerant gas medium. These compressors also include a first path that allows refrigerant communication between a crank chamber and a discharge chamber, and a second path that allows refrigerant communication between the crank chamber and a suction chamber. During operation of the compressor, the oil mist lubricates the moving parts of the compressor. However, the oil remains suspended in the refrigerant as it moves during refrigeration, and the air conditioning system may limit the performance and efficiency of the refrigeration and air conditioning system. To address these issues, an oil separator is added to the refrigeration and air conditioning system. One type of oil separator is usually found in the refrigeration and air conditioning system, between the compressor and a condenser. The oil separator works to separate suspended oil from the gaseous refrigerant, so the oil is retained within the compressor and introduced into the suction chamber. This type of oil separator requires additional containment space in the discharge chamber or a separate external component attached to the compressor. A second type of oil separator uses the crank chamber to store the oil, so that the oil is kept in the compressor and not introduced into the suction chamber. Adding this type of oil management system to the refrigeration and air conditioning system, however, does not address other compressor operating conditions that can lead to performance and durability issues such as fluid fill start-up, high temperature operations, or inadequate lubrication of the -2-piston at high speeds caused by oil jamming in the compressor crank chamber, for example. It would be desirable to produce a variable displacement compressor where the performance, efficiency and durability of the compressor are maximized, and the manufacturing cost, weight, packaging size and assembly time are as low as possible. In accordance and in accordance with the present invention, a variable displacement compressor has been surprisingly discovered in which the performance, efficiency and durability of the compressor are maximized and the manufacturing cost, weight, package size and assembly time are as low as possible. According to one embodiment, the compressor comprises: a hollow housing comprising a cylinder head having a suction chamber and a fluid passage formed therein, a cylinder block having at least one cylindrical bore formed therein and a casing, in which a substantially sealed crank chamber is located between the cylinder head and the casing; a freely rotatable drive shaft disposed in the casing and configured to extend therethrough to the cylinder block, the drive shaft comprising at least one fluid passage formed therein; a first fluid flow path fluidly connecting the crank chamber to the suction chamber to facilitate a flow of the working fluid from the crank chamber to the suction chamber, the first fluid flow path comprising at least one fluid passage formed in the drive shaft;a second fluid flow path fluidly connecting the crank chamber to the suction chamber to facilitate flow of a mixture of the working fluid and a lubricating fluid from the crank chamber to the suction chamber, the second fluid flow path including the fluid passage formed in the cylinder head; and an annular sleeve slidably disposed between the drive shaft and the cylinder block, the annular sleeve being selectably positionable to open and close the second fluid flow path. ; According to another embodiment, the compressor comprises: a hollow housing containing a cylinder head having a suction chamber and a fluid passage formed therein, a cylinder block having at least one cylindrical hole formed therein and a casing, wherein a substantially sealed crank chamber is formed between the cylinder head and the crankcase, a freely rotatable drive shaft disposed in the crankcase and adapted to extend therethrough to the cylinder block, the drive shaft containing at least one fluid passage formed therein; a rotor fixedly coupled to the drive shaft, wherein rotational movement of the drive shaft causes rotational movement of the rotor; a drive plate assembly coupled to the rotor, the drive plate assembly having an angle of inclination relative to a plane perpendicular to a longitudinal axis of the drive shaft;a first fluid flow path fluidly connecting the crank chamber to the suction chamber to facilitate a flow of working fluid from the crank chamber to the suction chamber, the first fluid flow path containing at least one fluid passage formed in the drive shaft; a second fluid flow path fluidly connecting the crank chamber to the suction chamber to facilitate the flow of a mixture of working fluid and a lubricating fluid from the crank chamber to the suction chamber, the second fluid flow path containing the fluid passage formed in the cylinder head;and an annular sleeve slidably disposed between the drive shaft and the cylinder block, the annular sleeve being selectably positionable to open and close the second fluid flow path, wherein the annular sleeve is operatively coupled to the drive plate to slide from a first annular sleeve position to a second annular sleeve position in response to a decrease in the tilt angle of the drive plate assembly from a maximum to a minimum, and to slide from the second annular sleeve position to the first annular sleeve position in response to an increase in the tilt angle of the drive plate assembly from a minimum to a maximum. ; According to another embodiment, the compressor comprises: a hollow housing containing a cylinder head having a suction chamber and a fluid passage formed therein, a cylinder block having at least one cylindrical bore formed therein, and a casing, in which a substantially fluid-tight crank chamber is -4- formed between the cylinder head and the crankcase; a freely rotatable drive shaft disposed in the crankcase and adapted to extend therethrough to the cylinder block, the drive shaft containing at least one fluid passage formed therein; a rotor fixedly coupled to the drive shaft, wherein rotational movement of the drive shaft causes rotational movement of the rotor; a drive plate assembly coupled to the rotor, the drive plate assembly having an angle of inclination relative to a plane perpendicular to a longitudinal axis of the drive shaft; a first fluid flow path connecting the crank chamber to the suction chamber to facilitate flow of working fluid from the crank chamber to the suction chamber,the first fluid flow path containing at least one fluid passage formed in the drive shaft; a second fluid flow path fluidly connecting the crank chamber to the suction chamber to facilitate the flow of a mixture of the working fluid and a lubricating fluid from the crank chamber to the suction chamber, the second fluid flow path containing the fluid passage formed in the cylinder head; an annular sleeve slidably disposed between the drive shaft and the cylinder block, the annular sleeve being selectably positionable to open and close the second fluid flow path,wherein the annular sleeve is operatively coupled to the drive plate assembly to slide from a first annular sleeve position to a second annular sleeve position in response to a decrease in the tilt angle of the drive plate assembly from a maximum to a minimum, and to slide from the second annular sleeve position to the first annular sleeve position in response to an increase in the tilt angle of the drive plate assembly from the minimum to the maximum,wherein the second fluid flow path is closed when the annular sleeve is in the first position and open when the annular sleeve is in the second position; a constant flow member fluidly connecting the crank chamber to the suction chamber to facilitate a constant flow of the mixture of working fluid and lubricating fluid from the crank chamber to the suction chamber; and a bearing lubricating member, - 5 - serving to facilitate a flow of the mixture of the working fluid and the lubricating fluid around at least one bearing arranged in the cylinder block. The foregoing, as well as other advantages of the present invention, will be clearly understood by those skilled in the art from the following detailed description of the preferred embodiment considered in light of the following accompanying drawings. Figure 1 is a sectional and elevational view of a compressor including an oil management system according to one embodiment of the present invention, showing an annular sleeve of the oil management system in a first position. Figure 2 is a sectional and elevational view of the compressor shown in Figure 1, showing the annular sleeve of the oil management system in a second position. Figure 3 is a sectional and elevational view of the compressor shown in Figure 1, including a constant flow element and a bearing lubrication element of the oil management system. Figure 4 is an enlarged, side perspective view of the annular sleeve of the oil management system shown in Figures 1-3. The following detailed description and accompanying drawings describe and illustrate an exemplary embodiment of the invention. The description and drawings are intended to enable a person skilled in the art to make and use the invention, and are not intended to limit the scope of the invention in any way. Figure 1 shows a variable displacement flat cam type compressor 10 according to the present invention. The compressor 10 includes a cylindrical housing 12 containing a cylinder head 14, a cylinder block 16 and a crankcase 18. The cylinder head 14 contains a suction chamber 20 formed therein. An inlet port (not shown) and an associated inlet conduit (not shown) provide fluid communication between the suction chamber 20 and an external component (not shown), such as an evaporator of a heating, ventilation and air conditioning system, for example. A fluid passage 22 is formed in the cylinder head 14. The fluid passage 22 is in fluid communication with a central hole 27 formed in the cylinder block 16, via an opening 24 formed in a valve plate 25 and -6- of a cavity 26 formed in the cylinder block 16. This fluid passage 22, the opening 24 and the cavity 26 fluidly connect the central hole 27 to the suction chamber 20 to facilitate the flow of a working fluid (a refrigerant for example) from the central hole 27 to the suction chamber 20. The suction chamber 20 is also in fluid communication with a set of cylindrical holes 28 formed in the cylinder block 16 through a set of valved suction ports (not shown) formed in the valve plate 25. Each of the cylindrical holes 28 is formed in the cylindrical block 16 at a predetermined interval and peripherally disposed about a longitudinal axis A of the compressor 10. Each of the cylindrical holes 28 is also in fluid communication with a discharge chamber 30 through a set of valved discharge ports 32 formed in the valve plate. An outlet port (not shown) and an associated outlet conduit (not shown) provide fluid communication between the discharge chamber 30 and an external component (not shown) such as a heating, ventilation, and air conditioning system condenser, for example.A piston 34 is slidably received in each of the cylindrical holes 28. As seen, the pistons 34 are coupled to a drive plate assembly 36 by means of shoes 37. It will be understood that the drive plate assembly 36 may correspond to any desired drive plate assembly, such as a flat cam or a cylindrical plate, for example. As seen, the drive plate assembly 36 has a generally circular shape and is located in a sealed crank chamber 38 formed by the cylinder block 16 and the crankcase 18. The drive plate assembly 36 contains an annular plate 39 and a hub member 40 having a central opening 41 formed therein. It will be understood that the annular plate 39 and the hub member 40 may be formed separately or as an integrated structure if desired.The annular plate 39 contains a pair of opposed, substantially planar surfaces 42 and a central opening 43 formed therein. At least a portion of the hub-forming member 40 is received in the central opening 43 of the plate. -7 -annular 39 and mechanically coupled thereto to form the assembly 36 forming a drive plate. The drive plate assembly 36 is mechanically coupled to a rotor 44. The rotor 44 is configured to vary an angle of inclination of the drive plate assembly 36 relative to a plane perpendicular to the longitudinal axis A of the compressor 10. The rotor 44 includes an outwardly extending shaft portion 45 having an opening 46 formed therein. As can be seen, a guide pin 47 formed on the drive plate assembly 36 slidably engages walls forming the opening 46 formed in the shaft portion 45 of the rotor 44. The rotor 44 is fixedly coupled to a freely rotatable drive shaft 48. The drive shaft 48 is centrally disposed in the housing 18 and adapted to extend therethrough to the cylinder block 16 of the compressor 10. The illustrated drive shaft 48 is rotatably supported by a roller bearing 50 at a first end thereof and by stops 52 at a second end thereof. The drive shaft 48 is mechanically coupled to a power source (e.g., a motor) via a pulley (not shown) which causes the drive shaft 48 to rotate. An axially extending fluid passage 54 and a radially outwardly extending fluid passage 55 are formed in the drive shaft 48. It will be appreciated that additional radially outwardly extending passages (not shown) may be formed in the drive shaft 48 and connected to the axially extending passage 54 as desired.The passages 54, 55 of the drive shaft 48 are in fluid communication with a fluid passage 56 formed in the rotor 44. It will be understood that additional fluid passages (not shown) may be provided in the rotor 44 if desired. The fluid passage 56 extends from a central opening (not shown) formed in the rotor 44 to an outer radial surface 57 thereof. The fluid passages 54, 55, 56 cooperate to provide a flow path between the crank chamber 38 and the central hole 27 formed in the cylinder block 16. Accordingly, a first fluid flow path between the crank chamber 38 and the suction chamber 20 is provided through the fluid passages 22, 54, 55 and 56, the opening 24 of the valve plate 25 and the cavity 26 of the block. - 8 -cylinder 16, in order to facilitate the flow of the working fluid from the crank chamber 38 to the suction chamber 20. A freely rotatable annular sleeve 58 having a hole 60 formed therein surrounds and provides support to the drive shaft 48 along a longitudinal axis thereof. It will be understood that the annular sleeve 58 may have any shape and size as desired, for example having a bore diameter close to 26 mm. The annular sleeve 58 is coupled to the hub member 40 of the drive plate assembly 36. In particular, the shown annular sleeve 58 is pivotally coupled to the drive plate assembly 36 by a set of pins 66 indicated by broken lines in Figures 1-3. The pins 66 are received in respective openings 68, shown in Figure 4, formed opposite the first end of the annular sleeve 58 and aligned openings (not shown) formed in the hub member 40 of the drive plate assembly 36.A spring 62 is positioned around an outer surface of the drive shaft 48, between a first end of the annular sleeve 58 and the rotor 44. An annular recess 70 is formed in the annular sleeve 58 to receive a lubricant such as a lubricating fluid (e.g., oil) disposed in the crank chamber 38 of the compressor 10, for example, to provide lubrication therein and to limit friction between the annular sleeve 58 and the drive shaft 48. In a non-limiting example, the lubricating fluid disposed in the crank chamber 38 flows along an outer surface of the drive shaft 48, between the annular sleeve 58 and the drive shaft 48, and is received in the annular recess 70.An outer surface 72 of the annular sleeve 58 includes a surface treatment such as a coating 73, as shown in FIGS. 1-3, a mechanical treatment or a chemical treatment, for example, to limit friction between the annular sleeve 58 and the cylinder block 16. As a non-limiting example, the coating 73 is a layer of material such as Teflon®, for example. It will be understood, however, that any suitable material may be employed for the coating 73, as desired. The annular sleeve 58 can slide axially along the drive shaft 48 to be received reciprocally in the central hole -9- 27 of the cylinder block 16. A position of the annular sleeve 58 along the drive shaft 48 corresponds to the tilt angle of the drive plate assembly 36. In particular, when the tilt angle of the drive plate assembly 36 is maximized as shown in FIG. 1, the annular sleeve 58 is in a first position. Conversely, when the tilt angle of the drive plate assembly 36 is at a minimum as shown in FIG. 2, the annular sleeve 58 is in a second position. A second end of the annular sleeve 58 abuts against one of the thrust bearings 52 when the annular sleeve 58 is in the second position. When the angle of inclination of the assembly 36 forming a drive plate is between the maximum and the minimum, the annular sleeve 58 is in an intermediate position between the first position and the second position. A fluid passage 80 formed in the cylinder block 16 is provided with a bypass to facilitate the flow of a mixture of the working fluid and the lubricating fluid between the crank chamber 38 and the suction chamber 20. Accordingly, a second fluid flow path between the crank chamber 38 and the suction chamber 20 is created by the fluid passages 22 and 80, the opening 24 in the valve plate 25, and the cavity 26 in the cylinder block 16 to facilitate a flow of the working fluid from the crank chamber 38 to the suction chamber 20. The fluid passage 80, and thus the second fluid flow path, is selectively opened and closed by the annular sleeve 58 sliding axially along the drive shaft 48. In particular, when the annular sleeve 58 is in the first position shown in Figure 1, an inlet of the passage 80 is fully closed.Conversely, when the annular sleeve 58 is in the second position shown in Figure 2, the inlet of the passage 80 is fully open. When the annular sleeve 58 is in the intermediate position, the inlet of the passage 80 is fully open, fully closed or at least partially open. In the compressor 10, a constant flow element 88 shown in Figure 3 may serve to facilitate a constant flow of the mixture of working fluid and lubricating fluid from the crank chamber 38 to the suction chamber 20. In the illustrated embodiment, the constant flow element 88 corresponds to a - 10- recess in the cylinder block 16, forming a hollow between the annular sleeve 58 and the cylinder block 16. It will be understood that the constant flow element 88 may correspond to a recess in the annular sleeve 58 forming the hollow between the annular sleeve 58 and the cylinder block 16 if desired. The hollow facilitates a constant flow of the mixture of working fluid and lubricating fluid from the crank chamber 38 to the fluid passage 80 and the suction chamber 20. It will be understood that the recess may be formed in the cylinder block 16 or the annular sleeve 58 by any desired means, for example by casting into the cylinder block 16 or the annular sleeve 58 and then machining into the cylinder block 16 or the annular sleeve 58 after casting thereof, for example.In the compressor 10, a bearing lubrication element 86 shown in Figure 3 may serve to facilitate the flow of the mixture of working fluid and lubricating fluid around the thrust bearings 52 for their lubrication. In the illustrated embodiment, the bearing lubrication element 86 corresponds to a recess formed in the cylinder block 16. It will be understood that the recess may be formed by any desired means such as by casting into the cylinder block 16 or machining into the cylinder block after pre-casting, for example. During operation of the compressor 10, the external power source rotates the drive shaft 48. Rotation of the drive shaft 48 consequently causes the rotor 44 to rotate with the drive shaft 48. As the rotor 44 rotates, the connection between the drive plate assembly 36 and the rotor 44 causes the drive plate assembly 36 to rotate. Rotation of the drive plate assembly 36 causes the pistons 34 to reciprocate within the cylindrical bores 28. As the pistons 34 are moved to a lower dead center position, the pressure within the cylindrical bores 28 is lower than the pressure within the suction chamber 20.As a result, the valved suction ports are caused to open, causing the working fluid to flow from the suction chamber 20 through the valved suction ports, and to the cylindrical holes 28. When the pistons 34 are caused to move to a high dead center position, the working fluid within the cylindrical holes 28 is compressed. When the pressure in the cylindrical holes 28 is . - 11 -caused to exceed the pressure in the discharge chamber 30, the valved discharge ports 32 are caused to open and the compressed working fluid is caused to flow through the valved discharge ports 32 to the discharge chamber 30. In addition, when the pistons 34 are moved to the upper dead center position, the pressure within the cylindrical holes 28 is caused to exceed a pressure in the crank chamber 38. When the pistons 34 are moved to the lower dead center position, the pressure within the cylindrical holes 28 is lower than the pressure in the crank chamber 38. Accordingly, when the pistons 34 reciprocate, the pressure in the discharge chamber 30 is higher than the pressure in the crank chamber 38, which is higher than the pressure in the suction chamber 20. These pressure differences between the discharge chamber 30, the crank chamber 38 and the suction chamber 20 cause the working fluid and the lubricating fluid to flow into the crank chamber 38 and mix therein. The pressure difference between the crank chamber 38 and the suction chamber 20 causes the mixture to flow into the passage 56 formed in the rotor 44. The rotation of the rotor 44 produces a centrifugal force exerted on the mixture. The density of the lubricating fluid is greater than that of the working fluid. The differences in physical characteristics between the working fluid and the lubricating fluid, and the centrifugal force exerted on the mixture cause the lubricating fluid to separate from the working fluid. Since the lubricating fluid has a greater density than the working fluid, the lubricating fluid is caused to flow back into the crank chamber 38. Simultaneously, the working fluid continues to flow through the first fluid flow path to the suction chamber 20. When operation of the compressor 10 is initiated by rotation of the drive shaft 48, the pressure in the suction chamber 20 drops temporarily and rapidly. As a result, the pressure within the crank chamber 38 is greater than the pressure in the suction chamber 20, causing the angle of inclination of the drive plate assembly 36 and the stroke length of the pistons 34 to decrease. As the angle of inclination of the drive plate assembly 36 decreases, the sleeve - 12-annular 58 is positioned in the second position, as shown in Figure 2, which fully opens the inlet of the fluid passage 80. As a result, a maximum amount of the mixture of the working fluid and the lubricating fluid flows from the crank chamber 38, to and through the second fluid flow path, and then into the suction chamber 20. When the pistons 34 are moved to the lower dead center position, the mixture of the working fluid and the lubricating fluid is received in the cylindrical holes 28. The mixture of the working fluid and the lubricating fluid lubricates the pistons 34 by facilitating a sealing effect between the pistons 34 and the cylindrical holes 28. The sealing effect restricts the flow of the mixture from the cylindrical holes 28 to the crank chamber 38. As the operation of the compressor 10 continues and the mixture of the working fluid and the lubricating fluid flows from the crank chamber 38 to the suction chamber 20, the pressure difference between the pressure in the crank chamber 38 and the pressure within the suction chamber 20 gradually decreases. Thus, the angle of inclination of the drive plate assembly 36 and the stroke length of the pistons 34 gradually increases. When the angle of inclination of the drive plate assembly 36 increases from the minimum to the maximum (i.e., during the full displacement operation of the compressor 10), the annular sleeve 58 is caused to move from the second position to the intermediate position, and then to the first position shown in FIG. 1.Accordingly, the annular sleeve 58 slides from the second position which fully opens the inlet of the fluid passage 80, to the intermediate position, and then to the first position which fully closes the inlet of the fluid passage 80 by restricting the flow of the mixture of the working fluid and the lubricating fluid from the crank chamber 38, to the second fluid flow path and through it, to the suction chamber 20. During the increase of the inclination angle of the drive plate assembly 36 from the minimum to the maximum, a first predetermined inclination angle of the drive plate assembly 36 and a second predetermined inclination angle of the drive plate assembly 36 are reached. At the first predetermined inclination angle of the drive plate assembly - 13 -drive 36, the annular sleeve 58 is caused to move from fully opening the inlet of the liquid passage 80 to partially opening the inlet of the fluid passage 80. As a result, a reduced amount of the working fluid and lubricating fluid mixture flows from the crank chamber 38 into and through the second fluid flow path and then into the suction chamber 20. For the second predetermined angle of inclination of the drive plate assembly 36, the annular sleeve 58 is caused to move from a partial opening of the inlet of the fluid passage 80 to a complete closure of the inlet of the fluid passage 80, and to restrict the flow of the mixture of the working fluid and the lubricating fluid flowing from the crank chamber 38, to and through the second fluid flow path, and then to the suction chamber 20. After the compressor 10 has operated at full displacement for an appropriate period of time, a load applied to the compressor 10 is reduced. The reduction in the load applied to the compressor 10 causes the pressure in the suction chamber 20 to decrease. The decrease in the pressure within the suction chamber 20 causes the pressure differential between the pressure in the crank chamber 38 and the pressure within the suction chamber 20 to increase. As a result, the inclination angle of the drive plate assembly 36 and the stroke length of the pistons 34 are caused to decrease from maximum to minimum (i.e., a small displacement operation of the compressor 10).As already described, when the angle of inclination of the drive plate assembly 36 is at a minimum, the annular sleeve 58 is in the second position illustrated in FIG. 2, fully opening the inlet of the fluid passage 80. As a result, the maximum amount of the working fluid and lubricating fluid mixture flows from the crank chamber 38 to and through the second fluid flow path and then to the suction chamber 20. During the decrease of the inclination angle of the drive plate assembly 36 from the maximum to the minimum, the second predetermined inclination angle of the drive plate assembly 36 and the first predetermined inclination angle of the drive plate assembly 36 are reached. For the - 14- second predetermined angle of inclination of the drive plate assembly 36, the annular sleeve 58 is caused to move from a complete closure of the inlet of the fluid passage 80 to a partial opening of the inlet of the fluid passage 80. As a result, an increased amount of the mixture of the working fluid and the lubricating fluid flows into the crank chamber 38, to and through the second fluid flow passage, and then to the suction chamber 20. For the first predetermined angle of inclination of the drive plate assembly 36, the annular sleeve 58 is caused to move from a partial opening of the inlet of the fluid passage 80 to a complete opening of the inlet of the fluid passage 80.As a result, the maximum amount of the mixture of the working fluid and the lubricating fluid flows from the crank chamber 38 to and through the second fluid flow path and then into the suction chamber 20. When the compressor 10 is operated between the full displacement operation and the small displacement operation, the inclination angle of the drive plate assembly 36 and the stroke length of the pistons 34 are between the maximum and the minimum. Accordingly, the annular sleeve 58 is at an intermediate position between the first position and the second position. Depending on the inclination angle of the drive plate assembly 36 between the maximum and the minimum, the first predetermined inclination angle and the second predetermined inclination angle, the inlet of the fluid passage 80 is fully open, fully closed or partially open. Optionally, the mixture of working fluid and lubricating fluid may be caused to flow from the crank chamber 38 through the constant flow member 88 to the suction chamber 20 regardless of the angle of inclination of the drive plate assembly 36. In addition, the mixture of working fluid and lubricating fluid may be caused to flow from the cavity 26 formed in the cylinder block 16 to and through the bearing lubricating member 86, and around the thrust bearings 52, to provide lubrication thereto. From the above description, a person skilled in the art can easily discern the essential characteristics of this - 15 - invention and without departing from the spirit and scope thereof, make numerous variations and modifications of the invention to adapt it to various uses and conditions.

Claims

CLAIMS 1. Compressor (10) comprising: a hollow housing (12) containing a cylinder head (14) having a suction chamber (20) and a fluid passage formed therein, a cylinder block (16) having at least one cylindrical bore (27) formed therein and a crankcase (18), in which a substantially sealed crank chamber (38) is formed between the cylinder head and the crankcase; a freely rotatable drive shaft (48) disposed in the housing (18) and adapted to extend therethrough to the cylinder block (16), the drive shaft containing at least one fluid passage (54, 55) formed therein; a first fluid flow path (22, 54, 55, 56) connecting the crank chamber (38) to the suction chamber (20) to facilitate the flow of working fluid from the crank chamber to the suction chamber, the first fluid flow path containing the at least one fluid passage (54, 55) formed in the drive shaft (48); a second fluid flow path (22, 80) connecting the crank chamber (38) to the suction chamber (20) to facilitate the flow of a mixture of the working fluid and the lubricating fluid from the crank chamber to the suction chamber, the second fluid flow path containing the fluid passage (22) formed in the cylinder head; and an annular sleeve (58), slidably disposed between the drive shaft (48) and the cylinder block (16), the annular sleeve being positionable in a selectable manner to open and close the second fluid flow path compressor (10) characterized in that it further comprises an assembly forming a drive plate having an angle of inclination relative to a plane substantially perpendicular to a longitudinal axis of the drive shaft and in that the second fluid flow path is partially open when the annular sleeve is in an intermediate position and the angle - 17-inclination of the assembly forming a drive plate is between a minimum and a maximum.

2. Compressor according to claim 1, characterized in that the second fluid flow path is closed when the annular sleeve is in a first position and the angle of inclination of the assembly forming a drive plate is maximized.

3. Compressor according to claim 2, characterized in that the second fluid flow path is open when the annular sleeve is in a second position and the angle of inclination of the assembly forming a drive plate is reduced to its minimum.

4. A compressor according to claim 1, characterized in that the annular sleeve is operatively coupled to the drive plate assembly for sliding from a first position of the annular sleeve to a second position of the annular sleeve in response to a decrease in the angle of inclination of the drive plate assembly, and from the second position of the annular sleeve to the first position of the annular sleeve in response to an increase in the angle of inclination of the drive plate assembly.

5. Compressor according to claim 1, characterized in that the annular sleeve contains an annular recess formed in an inner surface thereof, for receiving a lubricant therein, this lubricant providing lubrication to the annular sleeve and to the drive shaft and limiting the friction between them.

6. Compressor according to claim 1, characterized in that the annular sleeve contains a surface treatment serving to limit the friction between the annular sleeve and the cylinder block.

7. A compressor according to claim 1, characterized in that it further comprises a constant flow element serving to facilitate a constant flow of the mixture of the working fluid and the lubricating fluid from the crank chamber to the suction chamber.

8. A compressor according to claim 1, characterized in that it further comprises a bearing lubricating element serving to facilitate a flow of the mixture of the working fluid and the lubricating fluid around at least one bearing disposed in the cylinder block.

9. Compressor (10) comprising: a hollow housing (12) containing a cylinder head (14) having a suction chamber (20) and a fluid passage formed therein, a cylinder block (16) having at least one cylindrical bore (27) formed therein and a crankcase (18), in which a substantially sealed crank chamber (38) is formed between the cylinder head and the crankcase; a freely rotatable drive shaft (48) disposed in the housing (18) and adapted to extend therethrough to the cylinder block (16), the drive shaft containing at least one fluid passage (54, 55) formed therein; a rotor fixedly coupled to the drive shaft (48), wherein rotational movement of the drive shaft causes rotational movement of the rotor; a drive plate assembly (36) coupled to the rotor, the drive plate assembly having an angle of inclination relative to a plane perpendicular to a longitudinal axis of the drive shaft; a first fluid flow path (22, 54, 55, 56) fluidly connecting the crank chamber (38) to the suction chamber (20) to facilitate the flow of working fluid from the crank chamber to the suction chamber, the first fluid flow path containing the at least one formed fluid passage (54, 55) in the drive shaft (48); a second fluid flow path (22, 80) fluidly connecting the crank chamber (38) to the suction chamber (20) to facilitate flow of a mixture of the working fluid and the lubricating fluid from the crank chamber to the suction chamber, the second fluid flow path containing the fluid passage (22) formed in the cylinder head; and an annular sleeve (58), slidably disposed between the drive shaft (48) and the cylinder block (16), the annular sleeve being selectably positionable to open and close the second fluid flow path, the annular sleeve being operatively coupled to the drive plate assembly to slide from a first position of the annular sleeve to a second position of the annular sleeve in response to a decrease in the tilt angle of the drive plate assembly by a maximum to a minimum, and to slide from the second position of the annular sleeve to the first position of the annular sleeve in response to an increase in the angle of inclination of the assembly forming a drive plate from the minimum to the maximum, compressor (10) characterized in that the second fluid flow path is partially open when the annular sleeve is in an intermediate position and the angle of inclination of the assembly forming a drive plate is between the minimum and the maximum.

10. Compressor according to claim 9, characterized in that the second fluid flow path is closed when the annular sleeve is in the first position.

11. Compressor according to claim 10, characterized in that the second fluid flow path is open when the annular sleeve is in the second position.

12. Compressor according to claim 9, characterized in that the annular sleeve contains an annular recess formed in an inner surface thereof, for receiving a lubricant therein, this lubricant allowing the lubrication of the annular sleeve and the drive shaft and limiting the friction between them.

13. Compressor according to claim 9, characterized in that the annular sleeve contains a surface treatment serving to limit the friction between the annular sleeve and the cylinder block.

14. A compressor according to claim 9, characterized in that it further comprises a constant flow element serving to facilitate a constant flow of the mixture of the working fluid and the lubricating fluid from the crank chamber to the suction chamber.

15. A compressor according to claim 9, characterized in that it further comprises a bearing lubrication element serving to facilitate the flow of the mixture of the working fluid and the lubricating fluid around at least one bearing disposed in the cylinder block.

16. Compressor (10) comprising: a hollow housing (12) containing a cylinder head (14) having a suction chamber (20) and a fluid passage formed therein, a cylinder block (16) having at least one cylindrical bore (27) formed therein and a crankcase (18), in which a substantially sealed crank chamber (38) is formed between the cylinder head and the crankcase; a freely rotatable drive shaft (48) disposed in the housing (18) and adapted to extend therethrough to the cylinder block (16), the drive shaft containing at least one fluid passage (54, 55) formed therein; a rotor fixedly coupled to the drive shaft (48), wherein rotational movement of the drive shaft causes rotational movement of the rotor; a drive plate assembly (36) coupled to the rotor, the drive plate assembly having an angle of inclination relative to a plane perpendicular to a longitudinal axis of the drive shaft; a first fluid flow path (22, 54, 55, 56) fluidly connecting the crank chamber (38) to the suction chamber (20) to facilitate the flow of working fluid from the crank chamber to the suction chamber, the first fluid flow path containing at least one fluid passage (54, 55) formed in the drive shaft (48); a second fluid flow path (22, 80) fluidly connecting the crank chamber (38) to the suction chamber (20) to facilitate flow of a mixture of the working fluid and the lubricating fluid from the crank chamber to the suction chamber, the second fluid flow path containing the fluid passage (22) formed in the cylinder head; an annular sleeve (58), slidably disposed between the drive shaft (48) and the cylinder block (16), the annular sleeve being selectably positionable to open and close the second fluid flow path, the annular sleeve being operatively coupled to the drive plate assembly to slide from a first annular sleeve position to a second annular sleeve position in response to a decrease in the tilt angle of the drive plate assembly from a maximum to a minimum, and to slide from the second annular sleeve position to the first annular sleeve position in response to an increase in the tilt angle of the drive plate assembly from a minimum to a maximum, the second fluid path being closed when the annular sleeve is in the first position and open when the annular sleeve is in the second position; a constant flow element (88) connecting the crank chamber (38) to the suction chamber (20), for facilitating a constant flow of the mixture of working fluid and lubricating fluid from the crank chamber to the suction chamber; and a bearing lubricating element (86) for facilitating flow of the mixture of working fluid and lubricating fluid around at least one bearing disposed in the cylinder block. 10 17. Compressor according to claim 16, characterized in that that the annular sleeve contains an annular recess formed in an inner surface thereof for receiving a lubricant therein, this lubricant allowing the lubrication of the annular sleeve and the drive shaft and limiting the friction between them, and a surface treatment serving to limit the friction between the annular sleeve and the cylinder block.

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