Rotary compressor - Patent Review 4403929

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BACKGROUND OF THE INVENTION

(1) Field of the Invention

This invention relates to rotary compressors, and more particularly to a rotary compressor of the type suitable for use as a compressor for compressing a refrigerant for an air conditioning system of a motor vehicle, for example.

(2) Description of the Prior Art

In rotary compressors for compressing a refrigerant, it is necessary that back pressure be applied to the vanes to prevent chattering of the vanes during operation, as is disclosed in Japanese Patent Laid-Open Nos. 10411/76 and 133811/76. However, in case the back pressure applied to the vanes is too high, a loss of power would be great and the load applied to the prime mover would be increased. Moreover, a reduction in the service life of the compressors would result.

SUMMARY OF THE INVENTION

Accordingly, an object of this invention is to provide a rotary compressor in which chattering of the vanes can be avoided to ensure that the compressor can be operated without making noise.

Another object is to rpovide a rotary compressor of simple construction and low cost which eliminates the need to use a separate device for introducing oil into oil grooves.

Still another object is to provide a rotary compressor in which the oil intoroduced into the oil grooves is under a pressure which is suitably reduced, to minimize power loss and increase the durability of the vanes and housing.

According to the invention, there is provided a rotary compressor comprising a housing having therethrough a cylindrical bore; cover plates attached to the axial ends of the housing to close the open axial ends of the cylindrical bore, respectively; a shaft extending within the cylindrical bore in the housing and rotatably supported by the end plates, the shaft having an axis thereof extending in eccentric relation to the axis of the cylindrical bore in the housing; a rotor mounted on the shaft for rotation therewith and having a plurality of circumferentially spaced vane grooves, the rotor having axial end faces opposite to inner surfaces of the end plates, respectively; a vane slidably received in each of the vane grooves, each of the vanes cooperating with the adjacent vane, the wall surface of the cylindrical bore in the housing, the inner surfaces of the end plates and the outer periphery of the rotor to define a working chamber; one revolution of the rotor including a suction stroke section and a compression stroke section, the working chambers having their volumes increased during the suction stroke ssection and decreased during the compression stroke section; an oil groove formed in a portion, opposite to at least a portion of the suction stroke section, of the inner surface of at least one of the end plates, and located opposite to a path along which the bottoms of the vane grooves pass; a cover attached to the one end plate to define therebetween a discharge chamber having defined at the bottom thereof an oil reservoir; passage means for communicating the oil reservoir and the axial end face of the shaft opposite to the one end plate; and the oil in the oil reservoir being introduced into the oil groove through the passage means, along the outer periphery of the shaft, and through a gap between the rotor and the one end plate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of the rotary compressor comprising one embodiment of the invention, taken along the line I--I in FIG. 2;

FIG. 2 is a sectional view taken along the line II--II in FIG. 1;

FIG. 3 is a sectional view taken along the line III--III in FIG. 2;

FIG. 4 is a sectional view of the essential portions of a modification of the embodiment shown in FIG. 1;

FIG. 5 is a sectional view of the essential portions of another modificatin of the embodiment shown in FIG. 1; and

FIG. 6 is a sectional view of the essential portions of still another modification of the embodiment shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 1-3, the rotary compressor according to the inventin comprises a housing 1 having therethrough a cylindrical bore 1a, and a cylindrical rotor 2 mounted eccentrically within the bore 1a of the housing 1. A rotary shaft 3 is force fitted in the rotor 2 and secured thereto for rotation therewith as a unit. The rotor 2 is formed with a plurality (four in number in this embodiment) of vane grooves 2a equidistantly spaced apart from one another circumferentially of the rotor 2. The vane grooves 2a each support a vane 4 for sliding movement.

End plates 6 and 7 are secured, through O-rings 8, to axial opposite ends of the housing 1, and the rotary shaft 3 is rotatably supported by the end plates 6 and 7 through bearings 9.

The end plates 6 and 7 cooperate with the adjacent two vanes 4, the wall surfaces of the cylindrical bore 1a and the outer circumferential surface of the rotor 2 to define a working chamber R. The housing 1 is formed with a discharge port 10 including a plurality of bores, the discharge port 10 having one end 10a successively communicating with the working chambers R and another end 10b communicating, through a discharge valve 11, with a first discharge chamber 23. The movement of the discharge valve 11 is regulated by a stopper 12.

First and second oil grooves 7b and 7c are formed on the end plate 7 disposed on the rear end (hereinafter referred to as rear end plate 7) of the housing 1 and located in positions in which they face the working chambers R and are juxtaposed against a path along which bottoms 2a' of the vane grooves 2a pass. The oil groove 7b is disposed in a suction stroke section extending from a position in which the vane 4 is slidably withdrawn to the lowermost position in the vane groove 2a after passing by the discharge port 10 to a postion in which the vane 4 is slidably extended to the uppermost portion in the vane groove 2a as the working chamber R has its volume maximized. Stated differently, the first oil groove 7b extends along substantially the entire length of the suction stroke section in which the working chamber R has its volume increased. The second oil groove 7c is located between predetermined angular positions of an intermediate section of a compression stroke section in which the working chamber R has its volume reduced.

An annular front cover 14 is intimately secured to the end plate 6 on the front end of the housing 1 (hereinafter referred to as front end plate 6). The front cover 14 is formed with a not shown suction port for drawing a refrigerant from an evaporator, not shown. The refrigerant is introduced into a suction chamber 5 formed in the front cover 14, and then led into the working chambers R through a suction port 13 formed in the front end plate 6.

A seal assembly 15 is mounted between the front cover 14 and the rotary shaft 5 for providing a seal to the latter to avoid leakage of the refrigerant and lubricant along the rotary shaft 3 to outside.

A rear cover 16 is in the form of a cylinder with a closed bottom is attached to the rear end plate 7 to define therebetween a second discharge chamber 16a, and has a filter element 17 formed of a porous plate secured by a bolt 18 to the closed bottom portion thereof. An oil separator 19 formed of unwoven metal cloth and arranged in a complex three-dimensional structure is stuffed between the filter element 17 and the bottom of the rear cover 16.

A keep plate 20 is secured by bolts 21 to an end face of the rear end plate 7 facing the rear cover 16 and formed therein with an oil feeding passage 20a communicating an oil reservoir 16b formed in the bottom of the second discharge chamber 16a with an oil feeding port 7d formed in the rear end plate 7, so that the lubricant in the reservoir 16b can be drawn by differential pressure through the oil feeding passage 20a and the oil feeding port 7d to the end face of the rotary shaft 3. To avoid drawing of no more lubricant than is necessary, the oil feeding port 7d has a diameter of 1-3 mm to offer resistance to the flow of the lubricant or to restrict the flow of the lubricant therethrough. The lubricant supplied to the end face of the rotary shaft 3 flows from the circumferential surface thereof to between the end faces of the end plates 6 and 7 and the rotary 2, to feed the lubricant to the bearings 9 and the end faces of the rotor 2.

The rear end plate 7 and the keep plate 20 are formed with communicating ducts 7e and 20b respectively for communicating the vicinity of the trailing end of the first oil groove 7b with the second discharge chamber 16a in the rear cover 16.

The front cover 14, end plates 6 and 7, housing 1 and rear cover 16 are all formed of an aluminum alloy, and tightly secured together by bolts 26 and 28. The housing 1 is formed with bolt receiving openings designated by the numerals a1-a6 in FIG. 1.

The rear end plate 7 is formed with a communicating port 22 in a position in which the working chamber R begins to have its volume reduced and the working chamber R is not yet brought into communication with the discharge port 10 or, stated differently, a position in which a compression stroke is initiated, for communicating the working chamber R with the second discharge chamber 16a in the rear cover 16. The communicating port 22 has mounted therein a check valve assembly 24 for opening the communicating port 22 only when the internal pressure of the working chamber R has risen a predetermined amount (between 1 and 5 atmospheric pressures, for example, and preferably 1 atmospheric pressure) above the pressure in the second discharge chamber 16a, to allow the refrigerant in the working chamber R to escape to the second discharge chamber 16a.

As shown in FIG. 2, the check valve assembly 24 comprises a valve body 25 operative to abut against a tapering surface 22a of the communicating port 22 to block the port 22, and a spring 27 urging by its biasing force the valve body 25 to move in a direction in which the valve body 25 closes the port 22. The spring 27 is secured to the keep plate 20. The valve body 25 is in the form of a ball made of steel.

The operation of the rotary compressor of the aforesaid construction will now be described. As the rotary shaft 3 is rotated by the motive force produced by a drive source, such as an automatic vehicle engine, not shown, the rotor 2 and the vanes 4 are rotated as a unit and the working chambers 4 show changes in volume. When the working chamber R is disposed in a position in which its volume increases, a refrigerant introduced into the suction chamber 5 in the front cover 14 from the refrigeration cycle is drawn by suction into the working chamber R through the suction port 13. The refrigerant in a gaseous state drawn into the working chamber R is cut off the suction port 13 as the working chamber R rotates and then compressed as the volume of the working chamber R is reduced until the volume is minimized, when the working chamber R is brought into communication with the discharge port 10. Thus the compressed refrigerant is discharged from the working chamber R through the discharge valve 11 into the first discharge chamber 23.

From the first discharge chamber 23, the gaseous refrigerant flows through an outlet duct 7a formed in the rear end plate 7 into the second discharge chamber 16a in the rear cover 16, from which the gaseous refrigerant is discharged, after having the lubricant separated therefrom by the oil separator 19, into the condenser of the refrigeration cycle.

During operation, the vanes 4 are withdrawn from the vane grooves 2a largely by centrifugal forces into sliding contact with the inner wall surface of the housing 1 defining the bore 1a. In the rotary compressor of this constructional form, the oil grooves 7b and 7c communicating with the bottom portions 2a' of the vane grooves 2a are formed in the rear end plate 7. By this arrangement, the vane 4 being withdrawn from the vane groove 2a in the suction stroke section is under the influence of the pressure in the first oil groove 7b, so that the vane 4 can be pressed with increased force against the inner wall surface of the housing.

More specifically, in the rotary compressor of this constructional form, the oil reservoir 16b is maintained in communication with the end face of the rotary shaft 3 through the oil feeding port 7d and the oil feeding passage 20a, and the pressure (about 16-18 atmospheric pressures) of the gaseous refrigerant compressed in the working chamber R is applied to the second discharge chamber 16a, so that the lubricant in the oil reservoir 16b is urged by the pressure of the gaseous refrigerant to flow upwardly to the end face of the rotary shaft 3, from which the lubricant flows along the outer circumferential surface of the rotary shaft 3 and through the bearing 9 into a gap (which is about 0.02 mm in dimension) between the rotor 2 and the rear end plate 7. The lubricant flowing into the gap then flows on the end face of the rotor 2 in a direction in which the working chamber R has its volume increased, so that the pressure of the lubricant is applied to the first oil groove 7b to aid the vane 4 in being withdrawn from the vane groove 2a in the suction stroke section. The vane 4 is withdrawn from the vane groove 2a by centrifugal forces combined with the pressure of the lubricant in the first oil groove 7b, so that the forward end of the vane 4 is positively brought into sliding contact with the inner wall surface of the housing 1 defining the bore 1a and chattering of the vanes 4 in the vane grooves 2a can be avoided during operation.

In the rotary compressor of this constructional form, the pressure of the lubricant in the oil reservoir 16b is not applied to the first oil groove 7b as it is. Instead, the pressure of the lubricant is greatly reduced when applied to the first oil groove 7b, due to the throttling of the lubricant flow at the oil feeding port 7d and the resistance offered to the flow of the lubricant through the clearance between the end face of the rotor 2 and the rear end plate 7. Thus the pressure in the first oil groove 7b is not much higher than the pressure (about 2-3 atmospheric pressures) of the refrigerant in the working chamber R in the suction stroke section.

By virtue of the aforesaid features, the vanes 4 of the compressor according to the invention are forced out of the vane grooves 2a with enough force to positively bring the vanes 4 into sliding contact with the inner wall surface of the housing 1 but the force is not too high and causes to disadvantage. Thus there are no risks of the surface pressure between the forward ends of the vanes 4 and the inner wall surface of the housing 1 becoming higher than is necessary, the loss of power becoming too great and the durability of the compressor being reduced.

In the compression stroke section in which the vane 4 is forced into the vane groove 2a, the vane groove 2a communicates with the second oil groove 7c which is filled with the lubricant that has flowed through the clearance between the end face of the rotor 2 and the rear end plate 7, to feed the lubricant to the bottom portion 2a' of the vane groove 2a. Thus, after passing by the second oil groove 7c, the vane 4 is forced into the vane groove 2a while compressing the lubricant fed into the vane groove 2a from the second oil groove 7c, so that a sufficiently high surface pressure can be maintained between the forward end of the vane 4 and the inner wall surface of the housing 1 by the reaction of the lubricant compressed by the vane 4 in the vane groove 2a.

The provision of the first and second oil grooves 7b and 7c according to the invention enables an optimum surface pressure to be maintained between the forward end of the vane 4 and the inner wall surface of the housing 1 both in the suction stroke section and the compression stroke section. As a result, both chattering and leaping of the vanes 4 in the vane grooves 2a can be avoided, thereby ensuring that the rotary compressor operates quietly without making any noise.

The rotary compressor of the aforesaid constructional form might be faced with the difficulty with which the compressor performs its function due to the first oil groove 7b being sealed at startup. If this phenomenon occurs, the vanes 4 could not be withdrawn readily and the performance of the compressor would be impaired. To avoid this trouble, the first oil groove 7b formed in the rear end plate 7 is maintained in communication with the second discharge chamber 16a in the rear cover 16 through the communicating duct 7e and the communicating duct 20b formed in the keep plate 20, to avoid sealing of the first oil groove 7b at startup. This eliminates the risk that the pressure at the back of the vanes 4 is reduced, and enables the vanes 4 to be smoothly withdrawn from the vane grooves 2a by centrifugal forces, to thereby permit the compressor to initiate compression of the refrigerant without any trouble.

The invention has been shown and described by referring to a preferred embodiment. However, the invention is not limited to the specific form of the embodiment and many changes and modifications may be made therein.

For example, the oil feeding passage 20a is shown in the embodiment of FIGS. 1-3 as being formed in the keep plate 20. However, the same results can be achieved by forming an oil feeding passage 120a in the rear end plate 7 in place of the oil feeding passage 20a formed in the keep plate 20, as shwon in FIG. 4. In this case, the oil feeding port 7d juxtaposed against the end face of the rotary shaft 3 has a diameter of 1-3 mm to offer resistance to the flow of the lubricant therethrough, as is the case with the embodiment shown in FIGS. 1-3.

To offer resistance to the flow of the lubricant, a projection 203a may be formed integrally with the rotary shaft 203 at its end face and loosely inserted in the oil feeding port 207d formed in the rear end plate 207, as shown in FIG. 5, so as to throttle the flow of the lubricant by a clearance between the inner surface of the oil feeding port 207d and the outer circumferential surface of the projection 203a. In this case, the need to reduce the diameter of the oil feeding port 207d can be eliminated, thereby facilitating the application of pressure.

Alternatively, as shown in FIG. 6, a rotary disk 303b may be attached to the projection 303a of the rotary shaft 303, and a recess 307d' for receiving the rotary disk 303b may be formed in the oil feeding port 307d formed in the rear end plate 307, to throttle the flow of the lubricant by a clearance between the bottom surface of the recess 307d' and the rotary disk 303b. In this case, the rotation of the rotary disk 303b with the rotary shaft 303 as a unit permits any foreign matter incorporated in the lubricant flowing from the oil feeding passage 20a to be flipped by the rotary disk 303b, with a result that the amount of the foreign matter flowing through the clearance between the recess 307d' and the rotary disk 303b to the end face of the rotary shaft 303 can be greatly reduced. In the compressor of this modified constructional form, obturation of the oil feeding port 307d by foreign matter can be avoided and the compressor can continue its satisfactory performance over a prolonged period of time.

From the foregoing description, it will be appreciated that the novel features of the invention described hereinabove enable satisfactory operation of the compressor to be obtained. The provision of the first oil groove in the rear end plate in a position corresponding to the position of the vane groove for the vane in the suction stroke section enables the vane in the suction stroke section to be withdrawn from the associated vane groove by the pressure of the lubricant in the first oil groove. By this feature, the vanes can be kept in firm sliding contact with the inner wall surface of the housing at all times and chattering can be avoided, to enable the compressor to operate quietly at all times.

The lubricant introduced into the first oil groove in the compressor according to the invention is fed thereinto by differential pressure, so that an additional device for feeding oil, such as an oil pump, can be eliminated. This is conducive to simplification of the construction of the compressor and a reduction in cost.

The lubricant introduced into the first oil groove is subjected to a resistance offered to its flow as it flows through the oil feeding port, etc., before being fed into the oil groove. Because of this arrangement, the pressure of the lubricant in the first oil groove is suitably reduced and prevented from becoming higher than is necessary for forcing the vanes against the inner wall surface of the housing. Thus a loss of power can be minimized, sealing of the working chambers can be effected satisfactorily and the service life of the compressor can be prolonged.

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