Axial compressor

Abstract

This invention relates to fluid compression and fluid transfer mechanisms for an axial fluid displacement apparatus. More particularly, it relates to a configuration of a bearing supported wobble plate plus intake and discharge valve mechanisms for a reciprocating piston wobble plate-type refrigerant compressor suitable for use with high pressure CO2 as a working refrigerant.

Description

This invention claims benefit of Provisional Application No. 60/830,374, filed Jul. 12, 2006.

GOVERNMENT RIGHTS

This invention was made with Government support under Contract No. DAAB15-02-C-0006 awarded by USA CECOM Acquisition Ctr-Washington. The Government has certain rights in the invention.

I. BACKGROUND OF THE INVENTION

This invention relates to fluid compression and fluid transfer mechanisms for an axial fluid displacement apparatus. More particularly, it relates to a configuration of a bearing supported wobble plate plus intake and discharge valve mechanisms for a reciprocating piston, wobble plate-type refrigerant compressor suitable for use with high pressure CO₂ as a working refrigerant.

Piston-type compressors, such as swash plate-type compressors and wobble plate-type compressors are known in the art.

The challenges of lubricating piston-type compressors which utilize carbon dioxide as a refrigerant are known in the art.

The use of higher pressures in both the high pressure output side and low pressure input side sections of a refrigeration system that utilizes carbon dioxide as the refrigerant are known in the art.

II. SUMMARY OF THE INVENTION

With reference to FIG. 1, a wobble plate-type compressor is shown comprising a compressor housing 01 having a cylinder block 02 fixed at the rear end of compressor housing 01. A cylinder head 03, defining a discharge chamber 04 and intake chamber 05 is mounted on the rear end opening of compressor housing 01 behind a valve plate 06. In the instant invention, the motor 07, drive shaft 08, wobble plate 09, cylinder barrel 10 and pistons 11 are hermetically sealed in compressor housing 01. It will be obvious to one skilled in the art to separate the motor 07 and the compressor housing 01.

A discharge valve assembly is mounted on a rear end surface of valve plate 06. Valve plate 06 has a discharge hole 12 extending there through to allow communication between the compression chamber 13 and discharge chamber 04. The discharge valve assembly comprises a discharge valve 14 and a valve retainer 15, which is secured to a rear end surface of valve plate 06. In the instant invention, discharge valve 14 is fabricated from a single sheet of material. It will be obvious to one skilled in the art, that other means of fabricating discharge valves and securing their position over cylindrical bore 16 are possible.

Referring to FIG. 1, valve retainer 15 limits the bending movement of discharge reed valve 14 in the direction in which the refrigerant gas exits a cylindrical bore 16 and enters discharge chamber 13 through discharge hole 12. Discharge reed valve 14 has a modulus of elasticity which keeps discharge hole 12 closed until the pressure in cylinder bore 16 reaches a predetermined value.

Referring to FIG. 1, intake port 17 in the side of cylindrical bore 16 allows communication between the compression chamber 13 and the intake chamber 05. At or about bottom-dead-center of piston 11 stroke, intake port 17 is open to the intake chamber 05. When refrigerant pressure in the intake chamber 05 exceeds the pressure within the compression chamber 13, refrigerant is injected into the compression chamber 13 through intake port 17. As piston 11 begins its travel to the top of compression chamber 13, it covers intake port 17 and seals the compression chamber 13. It will be obvious to one skilled in the art to change the location distance of the intake port from top-dead-center of the cylindrical bore, the size of the intake port or both to optimize the efficiency of the refrigerant compressor.

Compressor housing 01 defines a center bearing crank chamber 18 that is adjacent to cylinder block 02. Cylinder block 02 is provided with a plurality of equi-angularly spaced cylindrical bores 16. A drive shaft 08 is rotatably supported at its rear end by compressor housing end block 19 and bearing 20, and at its front end through a wobble plate 09 which is itself captured by a thrust bearing 21 and a tapered roller bearing 22 while being driven by the motor shaft 08 to which it is keyed. Wobble plate 09 is prevented from axial and longitudinal movement by use of roller bearings 21 and 22 while permitting free rotational movement of the wobble plate. A reciprocating piston 11 is received in each of cylindrical bores 16. Each piston 11 is held in contact to a slipper plate 30 with piston shoe 23. A retainer ring 24 is loaded against the shoe 23 flange by spring 25 and spherical ball seat 26 thus holding the pistons against the slipper plate 30. The slipper plate 30 is separated from the wobble plate 09 by a thrust bearing 29; thus, the slipper plate 30 wobbles but does not rotate even as the wobble plate 09 spins rapidly under it. This precludes the piston shoes 23 having to slide frictionally over the face of a spinning wobble plate 09. It will be obvious to one skilled in the art that the load spring assembly can be replaced by gas springs to maintain proper piston shoe contact with the wobble plate.

It will be obvious to one skilled in the art that the use of roller bearings, ball bearings or both to support the wobble plate will enhance lubrication of rotating surfaces in the presence of carbon dioxide which is known to dilute compressor lubricants over time until too thin to sustain plain bearing loads.

III. OBJECTS AND ADVANTAGES

It is an object of the present invention to provide a piston-type fluid displacement apparatus which prevents the problem of lubrication of piston compressors for carbon dioxide refrigerant caused by dilution of lubricant by the refrigerant.

It is another object of the present invention to provide a piston-type fluid displacement apparatus which utilizes roller bearings, ball bearings or both to prevent axial and longitudinal movement of the wobble plate while permitting free rotational movement of the wobble plate.

It is another object of the present invention to provide a piston-type fluid displacement apparatus which utilizes the high pressure refrigerant in the suction side to inject refrigerant into the cylinder bore through a side intake port at or about bottom-dead-center position of the piston.

It is another object of the present invention to provide a piston-type fluid displacement apparatus which utilizes a common discharge reed valve plate to control discharge of refrigerant from the cylinder bore.

It is a further object of the present invention to provide a piston-type fluid displacement apparatus which comprises roller bearings, ball bearings, or both to prevent axial and longitudinal movement of the wobble plate while permitting free rotational movement of the wobble plate, a common discharge reed valve plate to control discharge of refrigerant from the cylinder bore and an intake port in the side of the cylinder bore to allow injection of refrigerant into the cylinder bore at or about bottom-dead-center position of the piston.

Further objects, features, and advantages of this invention will be understood from the attached drawings.

IV. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a wobble plate-type refrigerant compressor in accordance with a known embodiment.

FIG. 2 is a schematic diagram of an output valve plate in accordance with a known embodiment.

FIG. 3 is a schematic diagram of an output reed valve in accordance with a known embodiment.

V. DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, there is illustrated a hermetically sealed, multi-cylinder axial refrigerant compressor. The compressor is contained within a main housing or case 01 having a top or front end 19 and a rear end 27. Case bolts 28 extend through the main housing 01 to secure the housing and its components yet allow access to the components when required. A drive shaft 08 spins a wobble plate 09. The cylinder barrel 02 contains at least one compression cylinder 10. The cylinder 10 has a head end 03 adjacent to the rear end 27. There is a piston foot 23 at one end of each of the pistons opposite the head end 03 with the other end of each piston extending into each of the cylinders 10. The pistons 11 cycle as the wobble plate 09 is spun by the drive shaft 08. Near the rear end 03 of the cylinder 10 is a fixed valve plate 06.

The compression cycle operates as in a conventional axial compressor. The cylinders 10 and pistons 11 are disposed circumferentially about the drive shaft 08 within the cylinder barrel 02. There are piston cylinder discharge ports 12 in the head end 03 of the cylinder 10 that are open to and communicate with the discharge chamber 04. During operation of the compressor, an intake charge is injected through the intake port 17 and a high pressure charge is delivered at the discharge port 12. Movement of the piston 11 opens and closes communication between the compression chamber 13 and the intake chamber 05. Communication between the compression chamber 13 and the discharge chamber 04 is controlled by valve plate 06 and valve 14.

Thus there has been provided a reciprocating piston, wobble plate-type refrigerant compressor that fully satisfies the objects set forth above. While the invention has been described in conjunction with a specific embodiment, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications and variations as fall within the spirit and scope of the appended claims.

Claims

1. A refrigerant compressor comprising:

a compressor housing,

a centrally mounted drive shaft,

a wobble plate mounted on the drive shaft, the wobble plate and the drive shaft rotating about a common axis of rotation,

a plurality of bearings to control axial and longitudinal movement of the wobble plate,

a plurality of cylinders disposed in a cylinder barrel,

a piston disposed in each of the cylinders, the piston defining a piston stroke as it reciprocates in the cylinder,

an intake port, and

an output valve.

2. The compressor of claim 1 and further comprising a motor hermetically sealed within the compressor housing.

3. The compressor of claim 1 further comprising a ball thrust bearing to prevent longitudinal movement of the wobble plate on the shaft, one end of which it supports.

4. The compressor of claim 1 further comprising a taper roller bearing to prevent longitudinal movement of the wobble plate on the shaft and axial movement of the wobble plate about the shaft for precision control of piston clearance volume.

5. The compressor of claim 1 further comprising a ball thrust bearing between the wobble plate and the slipper plate to eliminate piston shoe sliding friction on the slipper plate.

6. The compressor of claim 1 further comprising an intake port in each cylinder.

7. The compressor of claim 1 further comprising an output valve that covers each cylinder output port.

8. The compressor of claim 1 wherein the refrigerant is carbon dioxide.