Fixed displacement compressors

Abstract

A fixed displacement compressor includes a cylinder block having a plurality of cylinder bores formed therethrough, a drive shaft rotatably supported by the cylinder block, and a plate rotatably mounted on the drive shaft. Moreover, an inclination angle of the plate varies relative to a radial line perpendicular to the drive shaft. The compressor also includes a spring positioned adjacent to the plate. The spring is adapted to urge the plate in a direction which reduces the inclination angle of the plate. In an embodiment, the plate is a swash plate. In another embodiment, the compressor further includes a cam rotor fixed to the drive shaft. In this latter embodiment, the spring is positioned between the cam rotor the plate.

Description

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The invention relates generally to fixed displacement compressors used in automotive air conditioning systems. More particularly, the invention relates to swash plate-type, fixed displacement compressors used in automotive air conditioning systems.

[0003] 2. Description of Related Art

[0004] A known swash plate-type, fixed displacement compressor may comprise a cylinder block, a front housing, a valve plate, and a cylinder head. The cylinder block may be substantially cylindrical and also may be enclosed by the front housing and the cylinder head. A crank chamber may be formed between the cylinder block and the front housing. Moreover, a suction chamber and a discharge chamber may be formed within the cylinder head and adjacent to the valve plate. An inlet port and an outlet port may communicate with the suction chamber and the discharge chamber, respectively, and the inlet port and the outlet port may be connected to a refrigerant circuit of an air conditioning system of a vehicle. The cylinder block, the front housing, the valve plate, and the cylinder head may be fixably attached to each other by a plurality of bolts. Such known compressors also may comprise a plurality of cylinder bores formed in the cylinder block. The cylinder bores may be arranged radially with respect to a central axis of the cylinder block.

[0005] Such known compressors further may comprise a drive shaft, a cam rotor, a swash plate, a plurality of shoes, and a plurality of pistons. The drive shaft may extend along a central axis of such known compressors through the crank chamber, and also may be rotatably supported by the front housing and the cylinder block via a pair of bearings mounted in the front housing and the cylinder block, respectively. Such known compressors also may comprise an electromagnetic clutch. A drive belt may be used to engage the electromagnetic clutch by transmitting a driving force from a crankshaft of an engine of a vehicle to the electromagnetic clutch. When the electromagnetic clutch is engaged, the driving force also is transmitted from the electromagnetic clutch to the drive shaft. Moreover, the cam rotor may be fixed to the drive shaft and may be positioned within the crank chamber, and a slot may be formed through the cam rotor. The swash plate also may be positioned within the crank chamber and may be fixably mounted on the drive shaft. The swash plate may comprise a pin member which may extend toward the cam rotor. The pin member may be inserted into the slot of the cam rotor.

[0006] Moreover, each piston may be positioned within a corresponding cylinder bore, and the pistons may reciprocate independently within their corresponding cylinder bore. Each of the pistons also may be connected to the swash plate via a pair of shoes. Specifically, each shoe may comprise a substantially flat surface and a substantially semispherical portion. The flat surface may be in slidable contact with the swash plate, and the semispherical portion may rotatably engage a substantially semispherical cavity of the piston. A plurality of suction ports and a plurality of discharge ports may be formed through the valve plate for each of the cylinder bores. A suction reed valve may be positioned between the cylinder block and the valve plate. The suction reed valve may open and may close the suction port in order to control a flow of a refrigerant from the suction chamber to the cylinder bores. A discharge reed valve may be positioned between the valve plate and the cylinder head. The discharge reed valve may open and may close the discharge port in order to control a flow of the refrigerant from the cylinder bores to the discharge chamber.

[0007] In operation, when the electromagnetic clutch and the drive shaft are engaged, the driving force from the engine of the vehicle is transmitted to the drive shaft, such that the drive shaft, the cam rotor, and the swash plate rotate substantially simultaneously about an axis of the drive shaft. Specifically, the rotational movement of the drive shaft is transmitted to the cam rotor, and the rotational movement of the cam rotor is transmitted to the swash plate via a coupling mechanism comprising the slot and the pin member, such that the swash plate moves back and forth in a wobbling motion. Consequently, each piston reciprocates within its corresponding bore. When the pistons reciprocate within their corresponding cylinder bore, refrigerant gas introduced into the suction chamber via the inlet port may be drawn into each cylinder bore and subsequently may be compressed. When the refrigerant gas is compressed, the discharge reed valve opens and the refrigerant gas is discharged from the cylinder bores into the discharge chamber. Moreover, the refrigerant gas is discharged from the discharge chamber into the refrigerant circuit via the outlet port.

[0008] In such known compressors, the electromagnetic clutch and the drive shaft may be engaged or disengaged in order to control the air conditioning system of the vehicle. Nevertheless, when the operation of such known compressors begins, frictional forces may exist between the swash plate and the shoes. Moreover, an initial torque of the compressor may be such that the vehicle's speed may decrease when the operation of such known compressors begins. Other known compressors may include an electromagnetic clutch adapted to absorb a greater initial torque than the known compressors described above. However, such an electromagnetic clutch may increase the weight of the vehicle, and also may increase the manufacturing cost of the vehicle.

SUMMARY OF THE INVENTION

[0009] Therefore, a need has arisen for fixed displacement compressors which overcome these and other shortcomings of the related art. A technical advantage of the present invention is that when a drive shaft is engaged, an inclination angle of a swash plate initially may be at a minimum inclination angle, and may increase to a maximum inclination angle. Consequently, an initial frictional force between a swash plate and a shoe and an initial torque of the compressor may be reduced relative to that of known swash plate-type, fixed displacement compressors, as described above. As such, a vehicle's speed may not decrease when the drive shaft is engaged.

[0010] According to an embodiment of the present invention, a fixed displacement compressor is described. The compressor comprises a cylinder block having a plurality of cylinder bores formed therethrough, a drive shaft rotatably supported by the cylinder block, and a plate rotatably mounted on the drive shaft. Moreover, an inclination angle of the plate varies relative to a radial line perpendicular to the drive shaft. The compressor also comprises at least one spring positioned adjacent to the plate. The at least one spring is adapted to urge the plate in a direction which reduces the inclination angle of the plate. In an embodiment, the plate is a swash plate. In another embodiment, the compressor further comprises a cam rotor fixed to the drive shaft. In this latter embodiment, the at least one spring is positioned between the cam rotor and the plate.

[0011] Other objects, features, and advantages of the present invention will be apparent to persons of ordinary skill in the art in view of the following detailed description of the invention and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] For a more complete understanding of the present invention, the needs satisfied thereby, and the objects, features, and advantages thereof, reference now is made to the following descriptions taken in connection with the accompanying drawings.

[0013] FIG. 1 is a cross-sectional view of a swash plate-type, fixed displacement compressor according to an embodiment of the invention when a drive shaft is engaged.

[0014] FIG. 2 is a cross-sectional view of the swash plate-type, fixed displacement compressor of FIG. 1 according to an embodiment of the invention when the drive shaft is disengaged.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0015] Preferred embodiments of the present invention and their advantages may be understood by referring to FIGS. 1 and 2, like numerals being used for like corresponding parts in the various drawings.

[0016] Referring to FIGS. 1 and 2, a swash plate-type, fixed displacement compressor 100 according to an embodiment of the present invention is depicted. Although the present invention is described with respect to a swash plate-type, fixed displacement compressor, it will be understood by those of ordinary skill in the art that the present invention may be applied to swash plate-type, fixed displacement compressors, wobble plate-type, fixed displacement compressors, or the like. Compressor 100 may comprise a cylinder block 2, a front housing 4, a valve plate 5, and a cylinder head 8. Cylinder block 2 may be substantially cylindrical, and also may be enclosed by front housing 4 and cylinder head 8. A crank chamber 3 may be formed between cylinder block 2 and front housing 4. Moreover, a suction chamber 6 and a discharge chamber 7 may be formed within cylinder head 8 and adjacent to valve plate 5. An inlet port (not shown) and an outlet port (not shown) may communicate with suction chamber 6 and discharge chamber 7, respectively, and the inlet port and the outlet port may be connected to a refrigerant circuit (not shown) of an air conditioning system of a vehicle. Cylinder block 2, front housing 4, valve plate 5, and cylinder head 8 may be fixably attached to each other by a plurality of bolts 50. Compressor 100 also may comprise a plurality of cylinder bores 1 formed in cylinder block 2. Cylinder bores 1 may be arranged radially with respect to a central axis of cylinder block 2.

[0017] Compressor 100 further may comprise a drive shaft 9, a cam rotor 10, a swash plate 11, a plurality of shoes 13, and a plurality of pistons 14. Drive shaft 9 may extend along a central axis of compressor 100 through crank chamber 3 and also may be rotatably supported by front housing 4 and cylinder block 2 via a pair of bearings 20a and 20b mounted in front housing 4 and cylinder block 2, respectively. Compressor 100 also may comprise an electromagnetic clutch (not shown). A drive belt (not shown) may be used to engage the electromagnetic clutch by transmitting a driving force from a crankshaft of an engine of a vehicle (not shown) to the electromagnetic clutch. When the electromagnetic clutch is engaged, the driving force also is transmitted from the electromagnetic clutch to drive shaft 9. Moreover, cam rotor 10 may be fixed to drive shaft 9 and may be positioned within crank chamber 3, and a slot 10a may be formed through cam rotor 10. Swash plate 11 also may be positioned within crank chamber 3, and may be slidably mounted on drive shaft 9, such that an inclination angle &thgr; of swash plate 11 may vary relative to a line which is perpendicular to drive shaft 9. Swash plate 11 may comprise a pin member 11a which may extend toward cam rotor 10. Pin member 11a may be inserted into slot 10a of cam rotor 10, and a coil spring 12 may urge swash plate 11 away from cam rotor 10. Specifically, coil spring 12 may engage drive shaft 9 and may be positioned between cam rotor 10 and swash plate 11, such that coil spring 12 urges swash plate 11 to move in a direction which reduces inclination angle &thgr; of swash plate 11.

[0018] Moreover, each piston 14 may be positioned within a corresponding cylinder bore 1, and pistons 14 may reciprocate independently within a corresponding cylinder bore 1. Each piston 14 also may be connected to swash plate 11 via a pair of shoes 13. Specifically, each shoe 13 may comprise a substantially flat surface and a substantially semispherical portion. The flat surface may be in slidable contact with swash plate 11, and the semispherical portion may rotatably engage a substantially semispherical cavity of piston 14.

[0019] A plurality of suction ports 15 and plurality of discharge ports 16 may be formed through valve plate 5 for each cylinder bore 1. A suction reed valve 15a may be positioned between cylinder block 2 and valve plate 5. Suction reed valve 15a may open and may close suction port 15 in order to control a flow of a refrigerant from suction chamber 6 to cylinder bores 1. A discharge reed valve 16a may be positioned between valve plate 5 and cylinder head 8. Discharge reed valve 16a may open and may close discharge port 16 in order to control a flow of the refrigerant from cylinder bores 1 to discharge chamber 7.

[0020] In operation, when the electromagnetic clutch and drive shaft 9 are engaged, the driving force from the engine of the vehicle is transmitted to drive shaft 9, such that drive shaft 9, cam rotor 10, and swash plate 11 rotate substantially simultaneously about an axis of drive shaft 9. Specifically, the rotational movement of drive shaft 9 is transmitted to cam rotor 10, and the rotational movement of cam rotor 10 is transmitted to swash plate 11 via a coupling mechanism comprising slot 10a and pin member 11a, such that swash plate 11 moves back and forth in a wobbling motion. Consequently, each piston 14 reciprocates within its corresponding bore 1. When pistons 14 reciprocate within their corresponding cylinder bore 1, refrigerant gas introduced into suction chamber 6 via the inlet port may be drawn into each cylinder bore 1 and subsequently is compressed. When the refrigerant gas is compressed, discharge reed valve 16a opens and the refrigerant gas is discharged from cylinder bores 1 into discharge chamber 7. Moreover, the refrigerant gas then is discharged from discharge chamber 7 into the refrigerant circuit via the outlet port.

[0021] During operation, a compressive force is applied to pistons 14, and pistons 14 may apply a first force M1 on swash plate 11. First force M1 may be a force which is adapted to turn pin member 11a in a clockwise direction, such that first force M1 may urge swash plate 11 in a direction, which increases inclination angle &thgr; of swash plate 11. Moreover, coil spring 12 may apply a second force M2 on swash plate 11. Second force M2 may be a force which is adapted to turn pin member 11a in a counterclockwise direction, such that second force M2 may urge swash plate 11 in a direction which decreases inclination angle &thgr; of swash plate 11. Nevertheless, during operation of compressor 100, first force M1 may be greater than second force M2. Consequently, as shown in FIG. 1, during operation, inclination angle &thgr; of swash plate 11 may increase to a maximum inclination angle, and a stroke of each piston 14 also may increase to a maximum piston stroke. In contrast, as shown in FIG. 2, when compressor 100 is not in operation, first force M1 may be zero, such that only second force M2 may act on swash plate 11. Consequently, inclination angle &thgr; of swash plate 11 may decrease to a minimum inclination angle, and the stroke of each piston 14 may decrease to a minimum piston stroke.

[0022] When drive shaft 9 is engaged, because inclination angle &thgr; of swash plate 11 initially may be at the minimum inclination angle, an initial frictional force between swash plate 11 and shoes 13 and an initial torque of compressor 100 each may be reduced relative to known swash plate-type, fixed displacement compressors. As such, the vehicle's speed may not decrease when drive shaft 9 is engaged. Moreover, after drive shaft 9 is engaged, first force M1 may increase and may become greater than second force M2, such that inclination angle &thgr; of swash plate 11 increases until inclination angle &thgr; of swash plate 11 reaches the maximum inclination angle.

[0023] While the invention has been described in connection with preferred embodiments, it will be understood by those of ordinary skill in the art that other variations and modifications of the preferred embodiments described above may be made without departing from the scope of the invention. Other embodiments will be apparent to those of ordinary skill in the art from a consideration of the specification or practice of the invention disclosed herein.

Claims

1. A fixed displacement compressor comprising:

a cylinder block having a plurality of cylinder bores formed therethrough;

a drive shaft rotatably supported by said cylinder block;

a plate rotatably mounted on said drive shaft, wherein an inclination angle of said plate varies relative to a radial line perpendicular to said drive shaft; and

at least one spring positioned adjacent to said plate, wherein said spring is adapted to urge said plate in a direction which reduces said inclination angle of said plate.

2. The compressor of claim 1, wherein said plate is a swash plate.

3. The compressor of claim 1, wherein when said drive shaft is engaged, said inclination angle increases from a minimum inclination angle to a maximum inclination angle.

4. The compressor of claim 1, wherein when said drive shaft is disengaged, said inclination angle deceases from a maximum inclination angle to a minimum inclination angle.

5. The compressor of claim 1, further comprising a cam rotor fixed to said drive shaft, wherein said at least one spring is positioned between said cam rotor and said plate.

6. The compressor of claim 5, wherein said plate is a swash plate.