Patent Application
20060285981
1. Technical Field of the Invention
The present invention generally relates to a variable displacement compressor having a swash ring construction. More specifically, the present invention relates to a variable displacement swash-ring compressor having spherical bearing.
2. Description of the Prior Art
In an automotive vehicle equipped with air conditioning, a compressor is used to pump coolant through the air conditioning system to cool the vehicle. Most often, the compressor is driven by a serpentine belt of the vehicle and, hence, the speed of the compressor is controlled by the speed of the vehicle. In order to provide consistent operation of the air conditioning system, variable displacement compressors have been developed to allow the compressor to provide constant performance at all vehicle speeds. In a variable displacement compressor, higher displacement is necessary when the vehicle is idling or running at low speeds. When the vehicle is running at high speeds, the compressor is cycling much more rapidly, and therefore can provide equivalent performance at a lower displacement.
The typical automotive air conditioning compressor uses multiple pistons to pump the coolant through the system. The pistons are driven back and forth within the compressor by a plate or ring that is attached to a rotating shaft. The plate or ring is mounted at an angle relative to the shaft and engages each of the pistons. Due to the angle of the ring, radial positions around a periphery of the ring have varying axial positions within the compressor. The pistons are fixed radially within the compressor housing, so that as the shaft and ring rotate the pistons slide along the periphery of the ring and are thereby moved axially back and forth with rotations of the shaft and ring. Variable displacement is achieved by limiting the stroke of the pistons. Variable displacement compressors are available in three basic types: 1) wobble plate compressors, 2) swash-plate compressors, or 3) swash ring compressors. The present invention is related to a swash ring compressor.
In a swash ring compressor, the pistons within the compressor are driven by a swash ring. Variable displacement, by limiting the stroke of the pistons, is achieved by varying the angle of the swash ring relative to the rotating shaft. U.S. Pat. No. 6,164,252 describes the construction of a variable displacement swash ring compressor and is hereby incorporated by reference into the present application.
In the '252 patent, a sleeve is slidably mounted for limited axial movement along the compressor's shaft and a swash ring is pivotally mounted onto the sleeve. A pin, rigidly mounted within and extending from the shaft, engages the swash ring at an axial distance from the pivotal connection between the swash ring and the sleeve. As the sleeve slides along the shaft, the swash ring moves axially with the sleeve at the pivotal connection, but cannot move axially at the point where the pin engages the swashring. This causes the swash ring to pivot about the point where the pin engages the swash ring, thereby changing the angle of the swash ring relative to the shaft.
As a result of the pin transferring rotation to the swash ring, the pin undergoes very high stresses and is therefore made from very hard materials. The contact between the pin and a pocket formed within the swash ring is generally a point contact, causing very high stress at that point, leading to accelerated wear.
As seen from the above, there is a need to improve the design of the pin/swash ring interface for a compressor so that the compressor can be made more robust.
The disadvantages of the prior art are overcome by providing a variable displacement swash ring compressor with a spherical bearing insert that couples the pin to the swash ring. Use of the spherical bearing insert spreads the loads out over a larger area of the pocket within the swash ring, thereby reducing the point loads and stresses.
In one aspect, the present invention is a compressor that includes a shaft rotatably mounted within the compressor. A sleeve is slidably supported on the shaft. A swash ring is pivotally mounted onto the sleeve such that the swash ring is angularly adjustable with respect to the shaft. A pin is fixedly mounted to and extends from the shaft and has a cylindrical distal end. The swash ring includes a radially inwardly open spherical pocket. A spherical bearing insert is positioned within the pocket and the cylindrical distal end of the pin slidably engages the spherical bearing insert such that the distal end of the pin is pivotally coupled to the swash ring. The connection between the swash ring and the pin forces the swash ring to rotate with the shaft, while allowing the swash ring to be angularly adjusted relative to the shaft. The sleeve is further biased along the shaft by a spring whose position may be varied.
In another aspect of the present invention, the spherical bearing insert includes a cylindrical orifice extending therethrough, the cylindrical distal end of the pin being received within the cylindrical orifice of the spherical bearing insert.
The above, as well as other advantages of the present invention, will become readily apparent to those skilled in the art from the following detailed description of a preferred embodiment when considered in the light of the accompanying drawings in which:
A complete description of a variable displacement swash-ring compressor is found in U.S. Pat. No. 6,164,252 which has been incorporated by reference into the present application.
Referring now to
Referring now also to
The spring 28 can be positioned between one of the collar portions 24, 26 of the sleeve 22 and a structural portion of the compressor 10. As shown in
Referring to
Referring again to
The distal end 40 of the pin 42 slidingly engages the orifice 48 within the spherical bearing insert 46. The spherical bearing insert 46 allows pivotal movement of the pin relative to the swash ring such that the swash ring 30 is allowed to pivot about the distal end 42 of the pin 40. However, the connection between the distal end 42 of the pin 40 and the swash ring 30 forces the swash ring 30 to rotate with the shaft 12.
Because the shape of the pocket 44 and the spherical bearing insert 46 are both generally spherical, the engagement between the pocket 44 and the spherical bearing insert 46 is over a large portion of the surface area of the pocket. This larger area of engagement spreads the loads transferred between the pin 40 and the swash ring 30 over the contact area, thereby reducing the point loads that are experienced by the pin 40, the bearing insert 46, and the swash ring 30. Because the loads experienced are low, the spherical bearing insert 46 can be formed of a softer alloy, such as copper alloys. The use of the spherical bearing insert 46 will reduce the overall wear and tear experienced by the swash ring 30 and the pin 40, thereby increasing the life of the compressor 10.
The foregoing discussion discloses and describes the preferred embodiment, and variations thereof, of the present invention. One skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims, that changes and modifications can be made to the invention without departing from the true spirit and fair scope of the invention as defined in the following claims. The invention has been described in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation.
