Rotary compressor

Abstract

A rotary gas compressor of the sliding vane type having a rotor positioned eccentrically within a working chamber provided by a cylinder in the stator housing which is closed by end plates secured to the housing. The rotor carries blades or vanes slidable within slots formed in the rotor to engage the cylinder and sweep the working chamber to compress gas introduced therein. The end plates are formed with arcuate, gas discharge slots connecting the outlet port of the housing with circumferentially-spaced discharge slots in the rotor in a manner to provide an alternate, low resistance path for gas flow at a point located a substantial distance from the outlet port. This arrangement is effective to reduce the extremely high pressure which is normally generated in the discharge zone as the vanes approach the main outlet port and valve assembly.

Parent Case Text

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of my copending application Ser. No. 261,846, filed June 12, 1972, now abandoned.

Description

BACKGROUND AND SUMMARY OF THE INVENTION

This invention relates to gas compressors and more particularly to gas discharge arrangements for compressors.

One common type of rotary gas compressor comprises a bladed or vaned rotor eccentrically mounted in a cylindrical stator housing to provide a crescent-shaped working chamber between the rotor and housing. The chamber communicates with an inlet or suction port and an outlet or discharge port. During rotation of the rotor, gas flows through the suction port and into the chamber and is then compressed by the vanes between the converging walls of the rotor and the cylinder. As the blades approach the discharge port, the distance between the cylinder wall and the rotor surface is very small; and, as a result, gas is under extremely high pressure in the zone adjacent to the discharge port. When the compressor is operating with high discharge pressure, this restriction adjacent the discharge port becomes even more troublesome, resulting in extreme overcompression of the gas and concommitant loss of efficiency.

There are numerous examples in the prior art of discharge arrangements which provide a continuous flow path for discharge gas after suction is closed. In U.S. Pat. No. 1,949,723 (Kotelevtseff) issued Mar. 6, 1934, a rotor sweeps the compression chamber in such a way that discharge gas is continuously directed through a passage in one end wall during the final 90.degree. of rotation. Such a device is mechanically fixed as to discharge and provides only a single path for discharge gas flow.

In U.S. Pat. No. 2,674,953 (Conde), issued Apr. 13, 1954, the compression chamber is defined in part by an end wall having an elongated, arcuate discharge port formed therein. This has the disadvantage that the gas, which is in the final stage of compression before the vane passes into the area of the port, will blow-back (short circuit) into the pocket defined between the leading and trailing vanes. This could cause a serious loss in capacity, because it would perform a considerable part of its work forcing the gas from a leading pocket to a trailing pocket.

The rotary gas compressor of the present invention is characterized by the provision of an improved gas discharge arrangement featuring a housing having a discharge port, which is covered by a discharge valve, and arcuate slots in its end faces communicating with said outlet port and cooperating with fluid passages in the rotor adjacent each vane to provide a secondary, low pressure drop path for gas flow at a point located at a substantial distance from the outlet port in the housing. In this arrangement, the gas may begin to flow to the outlet port as soon as the rotor ports are in communication with the distal ends of the slots in the housing, provided there is sufficient pressure to overcome the opening force on the discharge valve. This alternate, low resistance path is effective in reducing the extremely high pressures otherwise normally generated in the discharge zone of a conventional gas compressor as the vanes approach the discharge port.

Another aspect of the invention relates to the location of the arcuate slots in the end faces. Except for the outlet end of the slots, they are completely covered by the side faces of the rotor. This prevents gas from blowing back through the slot to the trailing, lower pressure pocket. Thus the only blow-back that can occur is over the tip of the vane in the outlet zone (inherent in all sliding vane compressors) and some small carryover of high pressure gas from the pockets in the rotor side faces.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a rotary gas compressor having an improved gas discharge arrangement;

FIG. 2 is a cross-sectional view taken along the plane of line 2--2 of FIG. 1;

FIG. 3 is a cross-sectional view taken along the plane of line 3--3 of FIG. 1; and

FIG. 4 is a cross-sectional view taken along the plane of line 4--4 of FIG. 1, but with the valve stop removed.

BRIEF DESCRIPTION OF THE INVENTION

Referring to FIGS. 1 and 2, the gas compressor 10 comprises a rotor assembly 11 rotatable within a stator assembly 12 and which serves as a housing for the rotor assembly. More particularly, the stator assembly 12 comprises a cylinder housing 13 and end plates 14 and 15 held in engagement with housing 13 by bolts 16. The plates 14 and 15 are bored as at 17 and 18 to provide bearings for rotatably mounting the rotor assembly 11 within the stator assembly 12.

The rotor assembly 11 comprises a cylindrical rotor 19 having a plurality of equidistantly-spaced slots 20 receiving vanes 21 slidably reciprocable therein. Rotor 19 is keyed at 22 to a drive shaft 23 journalled in the bearings 17 and 18 and is adapted to be driven by a pulley 24 connected to a motor (not shown) or other suitable drive means. In the case of an automotive application, the compressor is usually driven from the engine through an accessory drive system.

As shown in FIG. 1, the substantially cylindrical inner surface 25 of the cylinder housing 13 has a contact area 26 engaging the outer cylindrical surface 19b of the rotor. Since the rotor is rotatably mounted on an axis 27 offset from the center line of the cylinder wall, the rotor is substantially in sliding contact with the contact area 26, leaving a generally crescent-shaped working chamber 28 extending over a substantial portion of the inner periphery of the cylinder housing 13.

As best shown in FIGS. 1 and 4, a suction port 29 and a discharge passage 30 are provided in the cylinder housing 13, both of which communicate with the working chamber 28. A discharge gas plenum 40 is located between discharge passage 30 and a series of ports 41 which communicate directly with the discharge gas zone 42 adjacent the contact area 26. Ports 41 are drilled through a valve plate 43 to which is secured a valve 44 and valve stop 45 in a conventional manner. For clarity, the valve stop is not shown in FIG. 4. Valve 44 is biased to a closed position and requires a predetermined opening force to build up in the discharge zone 42 before gas may flow into plenum 40 and discharge passage 30.

The improved gas discharge system comprises a plurality of substantially arcuate gas discharge slots 31 and 32 in the end faces of the housing plates 14 and 15, respectively, the slots communicating with discharge passage 30 in the cylinder housing through the valve 44. The end faces 19a and 19b of rotor 19 are provided with circumferentially-spaced fluid passages 33, 34 located on opposite faces 19a and 19b of the rotor immediately ahead of each vane 21, in terms of the direction of rotation 25 shown by the arrow, FIG. 1. The passages 33 and 34 cooperate with the slots 31 and 32 in a manner that the respective sets of the passages 33 and 34 are successively placed in communication with the slots 31 and 32 in the end plates 14 and 15 during rotation of the rotor in the direction indicated by the arrow in FIG. 1.

In the operation of the compressor, the discharge slots 31 and 32 in the housing plates 14 and 15 are effective to provide an alternate, low resistance path for gas flow at a point located a substantial distance from the outlet port 30 of the stator housing. As shown in FIG. 1, the passage 33, which would be located directly across from passage 34, as illustrated, is just beginning communication with the entrance end 31b of slot 31. It will be noted that the passage is defined by the slot 31 and the side face 19a of rotor 19 as the vane sweeps along. Accordingly, the gas may not flow back to the trailing pocket, as would be case if the slot 31 were located radially outwardly of the peripheral surface 19b of rotor 19.

At the same time, gas may also be discharged through the primary passage defined between the cylindrical surface 19b of rotor 19, end plates 14 and 15, and surface 25 of the cylinder, as in a conventional rotary sliding vane compressor. It will be apparent from the foregoing description that there is provided an improved arrangement for discharging high pressure gas from a compressor which effectively reduces the extremely high pressures normally generated in the outlet area as the vanes approach the same. The system also provides minimum flow resistance by avoidance of flow restriction to thereby insure proper compression at the outlet of the compressor.

Claims

What is claimed is:

1. A rotary gas compressor comprising a housing having a substantially cylindrical interior surface and opposed end plates defining a closed chamber;

a rotor having a cylindrical peripheral surface and opposed side faces, said rotor being mounted in said chamber and rotatable about an axis which is offset with respect to the axis of said cylindrical interior surface, said rotor and said housing defining a generally crescent shaped compression cavity;

a gas inlet port and a gas discharge port communicating with said compression cavity;

a valve associated with said gas discharge port;

a plurality of vanes slidably supported in said rotor and engaging said cylindrical interior surface;

means defining an elongated slot in at least one of said end plates having an exit end located in communication with said discharge port and an entrance end located at a point circumferentially spaced in a direction toward said inlet port and inwardly spaced from said cylindrical peripheral surface, the entire slot being substantially covered by one of the side faces of said rotor; and

means defining a passage immediately adjacent each vane in said one rotor end surface extending away from the cylindrical surface and providing a first flow path for gas which intermittently connects that portion of the compression cavity ahead of the vane with the entrance end of said elongated slot, a second flow path, communicating with said discharge port, for gas being provided between the cylindrical surface on said rotor, the cylindrical interior surface of said housing and said end plates within said housing.