Means For Altering The Effective Displacement Of An Axial Vane Compressor

Abstract

In preferred form an axial vane compressor including a housing enclosed by end plates having inner face cam surfaces and rotatably supporting a drive shaft. A rotor is secured to the drive shaft for rotation therewith within the housing between the cam surfaces of the end plates. A specified axial clearance is provided between the rotor and the cam surfaces at their areas of closest proximity. The rotor contains at least one axially extending slot slidably receiving an axially slidable pumping vane. The vane terminates in arcuate edge surfaces in sliding engagement with the end plate cam surfaces and is moved axially by the cam surfaces relative to the rotor during rotation thereof so as to vary the effective volume in fluid working chambers on either side of the rotor as the rotor rotates through inlet and pressurization cycles. In this manner the vane draws in and compresses fluids in the respective work chambers. The rotor is provided with axially aligned cavities in the opposite faces of the rotor having predetermined volumes so that the effective displacement of the rotor in each of the aforementioned work chambers is regulated in accordance with the size of these cavities. This regulation occurs as a result of a predetermined volume of pressurized fluid being carried by the cavities into the intake cycle as the rotor rotates from the pressurization cycle. The clearance between the rotor and the cam surfaces allows this portion of the pressurized fluid to flow against the vanes assisting rotation of the rotor. Therefore, the provision of the rotor cavities and the clearance between the rotor and the cam surfaces results in recapturing some of the work used to pressurize the portion of the fluid carried forwardly into the intake cycle. By providing cavities of a predetermined size in the rotor surfaces an axial vane compressor can be suited to a range of applications such as occurs in air conditioning systems in compact vehicles as compared to similar systems in large vehicles.

Description

This invention relates to rotary axial vane compressors and more specifically to means for varying the effective displacement of such compressors.

In general rotary axial vane compressors include a housing enclosed by end plates having inner cam surfaces. A rotor is mounted on a drive shaft and is positioned between the cam surfaces. Axially movable vanes are mounted in the rotor and move relative to the rotor as they engage and follow the cam surfaces. In so doing, they vary the volume on either side of the rotor between an inlet maximum volume and a compressing or pressurizing minimum volume. It is obvious that the same results can be obtained by fixing the shaft and rotating the housing relative thereto. While the subject invention is described in association with an axial vane compressor having fluid working chambers on each side of the rotor, it is also apparent the machine can be readily designed to pump fluid on one side of the rotor only.

Rotary axial vane compressors, by virtue of their inherent design characteristics including that of not being adjustable, provide a substantially constant effective fluid displacement resulting from one complete revolution of the rotor within the housing. Consequently, a machine of a predetermined size has a constant capacity and therefore is not normally suitable for a range of work loads. Of course, on the other hand, production efficiency is enhanced and costs are reduced when a relative large number of compressors of uniform size are produced. For these reasons, it is a purpose of this invention to provide a means for simply and economically adapting a standard compressor assembly to a range of operating capacities. By practicing my invention a quantity of compressor rotors can be produced and then be machined to provide oppositely axially aligned cavities in the rotor radially extending faces to adjust the effective displacement of the machine to suit a particular use. If, for example, the compressor assembly is to be used with an air conditioning system in a large vehicle, the rotor can be assembled in the compressor without cavities so that a maximum effective fluid displacement is obtained. In such installation, a compressor having a displacement of approximately 12.6 cubic inches is desirable. In vehicles of medium size, the air conditioning system requires a lesser effective displacement of approximately 10.8 cubic inches. In a compact vehicle, an air conditioning system may require as low as 7.5 cubic inches effective displacement. By providing an air conditioning compressor capable of adaptation to an entire line of vehicles it is obvious that production of the resulting large quantities of components creates a manufacturing situation wherein maximum efficiency can be obtained and large quantities of materials can be purchased at minimum cost.

Accordingly, it is a primary object of my invention to provide a basic rotary fluid compressor assembly capable of slight modification so as to adapt the compressor to a range of load applications.

Another object of my invention is the provision of a standard rotary axial vane compressor wherein cavities of specified size are formed in rotor surfaces, the cavities carrying a quantity of pressurized fluid into the intake cycle so as to prevent discharge thereof thereby varying the effective displacement of the standard machine.

A further object of my invention is the provision of a specific clearance between the rotor and end plate cam surfaces at their areas of closest proximity so that the pressurized fluid in the rotor cavities is carried into the intake cycle of the machine and applied against the axial vanes aiding rotation of the rotor.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its organization and method of operation, may best be understood by reference to the following description taken in connection with the accompanying drawings in which:

FIG. 1 is an elevational view of a rotary axial vane compressor, partly in section, illustrating the assembled relationship of a rotor incorporating features of my invention.

FIG. 1A is an enlarged fragmentary view illustrating the detailed structure of a vane assembly used in an axial vane compressor in association with my invention.

FIG. 2 is an unfolded geometrically developed view of the path of a vane as it traverses one complete revolution within the compressor housing.

FIG. 3 is a fragmentary view, partly in section, of a rotor removed from the compressor and including cavities in accordance with my invention.

Referring now to the drawings, a rotary axial vane compressor assembly 10 having particular application in vehicle air conditioning systems has a central cylindrical housing 12 enclosed by end plates 14 and 16 as shown in FIG. 1. The end plates 14 and 16 have bearing surfaces 18 and 20 rotatably supporting like surfaces 22 and 24 on a drive shaft 26 which can be rotated by a vehicle engine through a pulley and clutch assembly not shown. The end plates 14 and 16 have cam inner faces 28 and 30 which cooperate with cylindrical housing 12 defining a generally cylindrical fluid chamber 32. A circular rotor 34, attached to the shaft 26, is adapted to rotate with the shaft in chamber 32. While the rotor 34 may be formed to support any number of vanes 36, in preferred form it contains three equally circumferentially spaced slots 38, each axially slidably supporting a vane 36. In one form, the vanes 36 are longitudinally split into halves 40 and 42, as best shown in FIG. 1a,and contain a centrally disposed spring 44 positioned within a chamber 45 formed by cavities 45a and 45b molded in the vane halves 40 and 42, respectively. The spring 44 engages respective edges of the cavities 45a and 45b biasing the vane halves 40 and 42 to the exaggerated position shown in FIG. 1a and in this manner maintains positive engagement with cam faces 28 and 30. The vane halves 40 and 42, respectively, include upwardly extending arcuate end surfaces 41 and 43 which engage the cam faces 28 and 30. These vane halves 40 and 42 terminate in rectangular shoulders 40a and 42a which support the vane halves in the compressor assembly. As can be seen in FIG. 1A, the contour of the cams 28 and 30 forces the vane halves 40 and 42 axially relative to one another against the force of spring 45 so as to insure a sealed engagement with the cam surfaces biases their edges into engagement with cam faces 28 and 30.

Rotation of the shaft 26 rotates rotor 34 and the vanes 36 within the fluid chamber 32 causing the vanes to slide axially as they engage the cam faces 28 and 30. Since an oil film on the outer periphery of the rotor provides a seal between it and inner surface 46 of cylindrical housing 12, the fluid chamber 32 is divided by rotor 34 into separate working chambers 48 and 50 so that each vane 36 is effective to compress fluid in both chambers as the shaft 26 is rotated. The end plate 14 has affixed an inlet fluid fitting 52 which directs the fluid to passages in both end plates 14 and 16, not shown, which connect with fluid inlet ports 54 illustrated in FIG. 2. Likewise, the end plates contain discharge ports 56 controlled by spring biased ball check valves 58 which regulate flow of pressurized fluid from both fluid chambers 48 and 50 to a combining discharge passage 60 from which the fluid exits the compressor. With reference to the developed view in FIG. 2, it can be seen that during a fluid inlet cycle, the fluid is drawn through port 54 into a maximum volume chamber 62 defined by vanes 36, cam face 28 and the rotor 34. Continued rotation of rotor 34 moves the fluid toward a minimum volume chamber 64 during a fluid pressurizing cycle whereupon the fluid is sufficiently pressurized moving the ball valve 58 against its spring discharging the fluid through passage 60. As shown, the compressor 10 is double acting because of the vanes 36 engaging both of the cam faces 28 and 30 on the opposite side of the rotor.

It is readily apparent from the developed view is FIG. 2, a compressor of this type does not lend itself to adjustments for varying its effective capacity. The rotor 34 is of a fixed size and the housing 12 along with end plates 14 and 16 are not easily adjustable. As a result the usual rotary axial vane compressor has a fixed predetermined effective fluid displacement. In accordance with my invention, cavities 66 of a predetermined size are machined in axial alignment in opposing rotor faces as best illustrated in FIG. 3. These cavities 66 are filled with pressurized fluid during the compression cycle and contain the fluid as they move with the rotor 34 into the inlet cycle where the fluid is re-expanded into maximum volume chambers 62. The quantity of pressurized fluid carried over decreases the effective displacement of the compressor to the extent of the volume of cavities 66. Obviously, in accordance with my invention a basic machine can be designed to provide a predetermined displacement which can readily be modified by the cavities 66 so that the unit is capable of being used in a range of load applications. Furthermore, the quantity of fluid re-expanding into the maximum volume chamber 62 from the cavities 66 can perform useful work. The provision of a clearance 68 in the range of 0.010 to 0.020 inches between the rotor faces 70 and the cam faces 28 and 30 at their areas of closest proximity, which occurs at the conclusion of the pressurizing cycle, permits application of the re-expanding fluid against the vanes 36 thereby assisting rotation of the rotor 34. Use of these clearances 68 provides for recovery of approximately 93 percent of the work used to pressurize the fluid in the cavities 66.

While I have shown and described a particular embodiment of my invention it will, of course, be understood that various modifications and alternative constructions thereof may be made without departing from the true spirit and scope of my invention and that I intend by the appended claims to cover all such modifications and alternative constructions as fall within the true spirit and scope of my invention.

Claims

I claim:

1. In an axial vane compressor of the type including a housing, said housing being enclosed by end plates, at least one of said end plates having a cam surface on its inner face; a drive shaft rotatably mounted in said end plates; a rotor secured to said shaft for rotation therewith through fluid inlet and fluid pressurization cycles within said housing between said end plates; said rotor being in sealing engagement with the inner peripheral surface of said housing and having a face defining at least one fluid pressurizing chamber in association with said end plate cam surface; at lease one axially extending slot formed in said rotor; a compressor vane slidably received in said slot; inlet and outlet ports connecting with said fluid pressurizing chamber; rotation of said drive shaft axially moving said vane in said slot as the said vane slidably engages the end plate cam surface whereby the volume in said fluid chamber is varied during rotation of the shaft to sequentially draw fluid into said chamber during an inlet cycle and subsequent discharge through said outlet ports upon completion of a pressurizing cycle; the improvement comprising: the provision of a cavity of predetermined volume in the fluid chamber defining face of said rotor whereby a portion of the fluid pressurized during the pressurization cycle is carried into the inlet cycle thereby decreasing the effective displacement of the compressor, the pressurized fluid in the inlet cycle assisting rotation of the rotor by virtue of application of the pressurized gas on one side of said vane; said cavity being formed of a specific volume sufficient to provide a predetermined desired output of pressurized fluid from said compressor.

2. In an axial vane compressor of the type including a housing; said housing being enclosed by a pair of end plates having a cam surface on their inner faces; a drive shaft rotatably mounted in said end plates; a rotor secured to said shaft for rotation within said housing dividing the interior thereof into separate fluid working chambers; opposite radially extending faces of said rotor partially defining said working chambers; said rotor faces being spaced from said cam surfaces providing a specified clearance therebetween at the area of closest proximity, a plurality of axially extending slots in said rotor; a pumping vane slidably mounted in each of said slots; said vane moving through fluid inlet and fluid pressurization cycles as said rotor rotates moving said vanes axially thereof as they engage said cam surfaces; the improvement comprising: axially aligned oppositely facing cavities of a predetermined volume in the radially extending faces of said rotor; said cavities capturing a portion of the fluid pressurized during the pressurization cycle and carrying it into the fluid inlet cycle where it acts against a pumping vane aiding rotation of said rotor as it flows through the clearance provided between said rotor and said cam surfaces; the predetermined volume of said cavities decreasing the effective displacement of said compressor thereby varying it for a particular work application.

3. In an axial vane compressor of the type including a cylindrical housing; end plates having matched cam surfaces on their inner faces enclosing said housing; a drive shaft rotatably journaled in said end plates; a rotor secured to said drive shaft being positioned within said housing between said cam surfaces for rotation relative thereto; said rotor including radially extending faces partially defining fluid chambers on either side thereof in association with said cam surfaces; an inlet passage connecting with each of the fluid chambers on either side of said rotor; an inlet valve in each of said passages; a discharge passage connecting with each of said fluid chambers on either side of said rotor; a discharge valve in each of said passages; a plurality of equiangular circumferentially spaced axially extending slots formed in said rotor and said drive shaft; a compressor vane slidably received in each of said slots and having edges in rubbing contact with each of the end plate cam surfaces; said rotor having an outer peripheral surface in sealing engagement with an inner peripheral surface of said housing dividing the housing into the aforementioned separate fluid chambers on either side of said rotor; rotation of said drive shaft causing said compressor vanes to move axially within their respective slots as their edges engage the end plate cam surfaces so as to vary the volume of the respective fluid chambers on either side of said rotor so that the volume in each of said chambers sequentially changes from a maximum fluid inlet volume to a minimum fluid compressing volume as said rotor rotates and said vanes move axially in response to engagement with said cam surfaces; the improvement comprising the provision of preformed cavities of a specific volume less than the fluid chamber volumes in axial alignment in the opposite radial surfaces of said rotor whereby the effective displacement of said compressor is regulated discharging a predetermined volume of pressurized fluid; the pressurized fluid remaining in said rotor cavities applying a pressure against said vanes aiding rotation of said rotor.