VARIABLE DISPLACEMENT COMPRESSOR
A variable displacement compressor comprising a cylinder block having a plurality of cylinder bores. The cylinder block has an extension which extends from an outer periphery of an end surface of the cylinder block which faces a swash plate. The extension has an extension surface which forms a part of a bore surface of each cylinder bore and first and second wall surfaces which extend continuously from opposite ends of the extension surface in a circumferential direction of the extension surface. A part of each extension surface which is connected to the first wall surface which is located on a preceding side of rotation of the swash plate corresponds to a high-load area which is locally subjected to loads from a single-headed piston during a compression stroke. The high-load area has a chamfered region which is formed into a curved surface by chamfering.
The present invention relates to a variable displacement compressor, and more particularly to a variable displacement compressor having a single-headed piston.
Japanese Patent Application Publication No. 2000-120533 discloses a swash plate type variable displacement compressor which includes a cylinder block having formed therein a plurality of cylinder bores, a rotary shaft rotatably supported by the cylinder block at its center, a swash plate provided on the rotary shaft for rotation therewith and single-headed pistons engaged with the swash plate for reciprocation in the respective cylinder bores, wherein the openings of the cylinder bores which face the swash plate are chamfered so as to extend the diameter of the openings. A front housing is joined to the front of the cylinder block, and a rear housing is joined to the rear of the cylinder block through a valve plate.
In such a variable displacement compressor, the end surface of the cylinder block on the side of the swash plate is a plane which extends perpendicularly to the axial direction of the rotary shaft without any step. The chamfered surface is formed into a curved surface at the opening of the cylinder bore on the side of the swash plate for facilitating insertion of a piston into the cylinder bore. It is noted that the chamfered surface is formed along the entire circumference of the cylinder bore or along a part of the circumference of the cylinder bore.
According to the variable displacement compressor having the chamfered surface, a pressing force of a piston in radial direction which is generated when the piston moves from its bottom dead center toward its top dead center is reduced, so that the coating of the piston is prevented from a damage.
There has existed another variable displacement compressor having a cylinder block which has formed in the end surface thereof a step which faces the swash plate. For example, as shown in
As compared with the cylinder block disclosed in Japanese Patent Application Publication No. 2000-120533, the cylinder block 61 of
When the chamfered surface of cylinder bore of Japanese Patent Application Publication No. 2000-120533 is applied to the variable displacement compressor of Japanese Patent Application Publication No. 7-180658, however, the coating of the piston is not necessarily prevented from being damaged. This is because the contact surface pressure between the edge and the piston is excessively large due to the presence of the edge between the extension surface and the beveled surface in the variable displacement compressor of Japanese Patent Application Publication No. 7-180658. Especially, the piston during its compression stroke receives a pressure in the cylinder bore and the extension receives a high load from the piston. Therefore, part of the extension tends to receive a large contact surface pressure. In addition, since the swash plate is rotated in one direction, a pressing force of the piston which is caused by the rotation of the swash plate is applied to the edge between the extension surface and the wall surface. Therefore, there is a fear that the contact surface pressure at the edge in the extension is significantly large.
The present invention which has been made in view of the above problems is directed to a variable displacement compressor having an extension which extends from the end surface of the cylinder block on the side adjacent to the swash plate, which prevents generation of an excessive contact surface pressure at a part of the extension surface of the extension.
SUMMARY OF THE INVENTIONIn one aspect of the present invention, there is provided a variable displacement compressor comprising a cylinder block, a rotary shaft, a swash plate and a plurality of pistons. The cylinder block has a plurality of cylinder bores. The rotary shaft is rotatably supported by the cylinder block. The swash plate is provided on the rotary shaft for rotation therewith. The plurality of single-headed pistons are engaged with the swash plate for reciprocation in the cylinder bores. A diameter expansion surface is formed at an edge of a bore surface of each cylinder bore which faces the swash plate so that a diameter of an opening of the cylinder bore are extended. The cylinder block has an extension which extends from an outer periphery of an end surface of the cylinder block which faces the swash plate. The extension has an extension surface which forms a part of the bore surface of each cylinder bore and first and second wall surfaces which extend continuously from opposite ends of the extension surface in a circumferential direction of the extension surface. A part of each extension surface which is connected to the first wall surface which is located on a preceding side of rotation of the swash plate corresponds to a high-load area which is locally subjected to loads from the piston during a compression stroke. The high-load area has a chamfered region which is formed into a curved surface by chamfering.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.
The features of the present invention that are believed to be novel are set forth with particularity in the appended claims. The invention together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:
The following will describe a variable displacement compressor of a preferred embodiment according to the present invention with reference to
Referring to
A rotary shaft 15 which extends through the crank chamber 14 is rotatably supported by the cylinder block 11 and the front housing 12 through radial bearings 16 and 17. The front end of the rotary shaft 15 extends out of the front housing 12 and is connected to a mechanism (not shown) which receives power from an engine or a motor of vehicle (not shown).
In the crank chamber 14, a lug plate 18 is secured on the rotary shaft 15, and a swash plate 19 is provided on the rotary shaft 15. The swash plate 19 has at the center thereof a hole 19a through which the rotary shaft 15 is inserted. The swash plate 19 has guide pins 20 which are slidably inserted in guide holes 21 formed in the lug plate 18 so that the swash plate 19 is connected to the lug plate 18 for rotation with the rotary shaft 15.
Sliding motion of the guide pins 20 in the guide holes 21 allows the swash plate 19 to slide in the axial direction of the rotary shaft 15 and to be inclined relative to the rotary shaft 15. A thrust bearing 22 is provided between the lug plate 18 and the front inner wall of the front housing 12, thus the lug plate 18 being rotatable relative to the front housing 12 through the thrust bearing 22.
The cylinder block 11 has formed therein a plurality of cylinder bores 28 (only one cylinder bore being shown in
A suction chamber 26 is defined in the center region of the rear housing 13 in facing relation to the valve forming assembly 25. A discharge chamber 27 is defined in the rear housing 13 radially outward of the suction chamber 26. As shown in
The following will describe more in detail the cylinder block 11 of the compressor with reference to
The cylinder block 11 has the front end surface 32 from which an annular extension 33 extends toward the swash plate 19, so that a step is formed in axial direction of the cylinder block 11 between the end surface 34 of the extension 33 which faces the swash plate 19 and the front end surface 32.
The extension 33 of the cylinder block 11 is formed such that it has on the inner side thereof an extension surface 36 which forms a part of the bore surface of each cylinder bore 28, as best seen in
In the preferred embodiment, a chamfered surface 44 is formed between the extension surface 36 and the first wall surface 37 so as to be inclined relative to the extension surface 36. The chamfered surface 44 are contiguous with the end surface 34, the extension surface 36, the first wall surface 37, the beveled surface 40, and the beveled surface 42.
Of the first and second wall surfaces 37 and 38 located on opposite sides of the cylinder bore 28, the first wall surface 37 is located on the preceding side of the rotation of the swash plate 19 with respect to the cylinder bore 28. The first wall surface 37 and a part of the extension surface 36 adjacent to the chamfered surface 44 provide a high-load area S indicated by shaded area in
Referring to
The first through fourth regions D1 through D4 are indicated by the hatching in
As mentioned earlier, the chamfered region D in the high-load area S is formed by removing or chamfering edges which had been present between the surfaces 36, 37, 40, 40 and 44 before the chamfering. Thus, the high-load area S receiving a high load from the piston 23 is not subjected an excessively high contact surface pressure.
It can be verified by a calculation method for contact surface pressure using Herz formula that an excessively high contact surface pressure is not generated at the high-load area S having the chamfered region D in comparison with the case where the aforementioned edges in a high-load area are not chamfered. Using the calculation method for the contact surface pressure, the radius of curvature of the curved surface for each of the regions D1 through D4 in the chamfered region D may be determined so as to prevent the piston coating from being damaged. Generally, the contact surface pressure in the high-load area S is decreased with an increase of the radius of curvature.
The following will describe a procedure of forming the chamfered region D in the high-load area S in the cylinder block 11 of the preferred embodiment.
The chamfered surface 44 is formed with a grinding tool 51 as shown in
Such edges in the high-load area S are chamfered with a polishing brush 54, as shown in
The polishing brush 54 being driven to rotate is inserted into the cylinder bore 28 from the side of the end surface 34 in facing relation to the high-load area S. The polishing brush 54 is brought into contact with the cylinder block 11 to chamfer the edges in the high-load area S. With the polishing brush 54 kept in contact with the cylinder block 11, the polishing brush 54 is moved relative to the cylinder bore 28 reciprocally in the vertical direction in
The chamfered region D shown in
According to the variable displacement compressor of the preferred embodiment of the present invention, the following advantageous effects are obtained.
(1) In the cylinder bore 28, the high-load area S includes the chamfered region D which is chamfered into curved surfaces. Thus, the contact surface pressure between the piston 23 and the cylinder block 11 in the high-load area S is reduced in comparison with the case where a high-load area does not include a chamfered region, so that the coating of the piston is substantially prevented from being damaged.
(2) The edges in the region other than the high-load area S remains between the extension surface 36 and the beveled surface 40, so that the length of the extension surface 36 as a guide surface is not shortened in comparison with the case where the chamfered region is formed along the entire circumference of the cylinder bore 28, thus the piston 23 being stably supported in the cylinder bore 28.
(3) In the high-load area S, the chamfered surface 44 is formed before the formation of the chamfered region D. Thus, the radius of curvature of the curved surface for the chamfered region D may be easily set larger in comparison with the case where the chamfered surface 44 is not formed in the high-load area S. Larger radius of curvature contributes to reduction of the contact surface pressure in the high-load area S.
(4) In the extension surface 36 of the cylinder bore 28, there exist both chamfered and non-chamfered regions. The use of the polishing brush 54 makes possible chamfering only those portions which need to be chamfered. This method of chamfering in the preferred embodiment increases reliability and reduces the time of chamfering operation, as compared with chamfering by other methods such as shot blasting.
The present invention is not limited to the above-described preferred embodiment and may be practiced in various other ways as exemplified below.
One example of the chamfered surface 44 is shown in the above-described preferred embodiment, but the configuration of the chamfered surface 44 is not limited to that of the above-described preferred embodiment. The chamfered surface 44 may be formed in such a range that adjoins with the extension surface 36, the first wall surface 37, the beveled surface 40, and the beveled surface 42 so that it does not exist in the bore surface other than the extension surface 36.
In the above-described preferred embodiment, the chamfered surface 44 is formed before the formation of the chamfered region D. However, the chamfered region D may be formed without forming the chamfered surface 44. In this case, it is preferable that the edges in the high-load area S should be chamfered or beveled to form curved surfaces with a large radius of curvature, and the procedure of forming the chamfered surface 44 can be omitted.
In the above-described preferred embodiment, the grinding tool 51 and the polishing brush 54 are used to form the chamfered surface 44 and the chamfered region D in the high-load area S. Other means for chamfering may be used as required instead of the combination of the grinding tool 51 and the polishing brush 54.
In the above-described preferred embodiment, the beveled surface 40 is formed along the front end of the extension surface 36 so as to extend the diameter of the opening of the cylinder bore 28, and the beveled surface 41 is formed between the front end surface 32 and the bore surface along the front end of the bore surface. However, any surface may be formed as long as it extends the diameter of the opening of the cylinder bore 28. For example, chamfering for a curved surface may be done as in the chamfered for the region D.
Therefore, the present examples and embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein but may be modified within the scope of the appended claims.
Claims
1. A variable displacement compressor comprising:
- a cylinder block having a plurality of cylinder bores;
- a rotary shaft rotatably supported by the cylinder block;
- a swash plate provided on the rotary shaft for rotation therewith;
- a plurality of single-headed pistons engaged with the swash plate for reciprocation in the cylinder bores; and
- a diameter expansion surface formed at an edge of a bore surface of each cylinder bore which faces the swash plate so that a diameter of an opening of the cylinder bore are extended,
- wherein the cylinder block has an extension which extends from an outer periphery of an end surface of the cylinder block which faces the swash plate,
- wherein the extension has an extension surface which forms a part of the bore surface of each cylinder bore and first and second wall surfaces which extend continuously from opposite ends of the extension surface in a circumferential direction of the extension surface,
- wherein a part of each extension surface which is connected to the first wall surface which is located on a preceding side of rotation of the swash plate corresponds to a high-load area which is locally subjected to loads from the piston during a compression stroke, and
- wherein the high-load area has a chamfered region which is formed into a curved surface by chamfering.
2. The variable displacement compressor according to claim 1, wherein the chamfered region has a curved surface which is formed in a circumferential direction and a longitudinal direction of the cylinder bore.
3. The variable displacement compressor according to claim 1, wherein the chamfered region has a part of the diameter expansion surface which is located in the high-load area.
4. The variable displacement compressor according to claim 1, wherein the chamfered region includes a first region which is formed an edge between the extension surface and the diameter expansion surface in the high-load area into a curved surface by chamfering.
5. The variable displacement compressor according to claim 1, wherein a chamfered surface is formed between the extension surface and the first wall surface so as to be inclined relative to the extension surface.
6. The variable displacement compressor according to claim 5, wherein the chamfered region includes a second region which is formed an edge between the diameter expansion surface and the chamfered surface into a curved surface by chamfering.
7. The variable displacement compressor according to claim 5, wherein the chamfered region includes a third region which is formed an edge between the extension surface and the chamfered surface into a curved surface by chamfering.
8. The variable displacement compressor according to claim 1, wherein the chamfered region includes a fourth region which is formed an edge between the extension surface and the first wall surface into a curved surface by chamfering.
9. The variable displacement compressor according to claim 1, wherein a beveled surface is formed between the first wall surface and an end surface of the extension which faces the swash plate.
10. The variable displacement compressor according to claim 1, wherein a beveled surface is formed between the second wall surface and an end surface of the extension which faces the swash plate.
11. The variable displacement compressor according to claim 1, wherein the diameter expansion surface includes a beveled surface which is formed between the extension surface and an end surface of the extension which faces the swash plate.
12. The variable displacement compressor according to claim 11, wherein the diameter expansion surface includes a beveled surface which is formed between the end surface of the cylinder block and the bore surface of the cylinder bore.
Type: Application
Filed: Aug 23, 2007
Publication Date: Feb 28, 2008
Inventors: Suguru Hirota (Kariya-shi), Hiroshi Uneyama (Kariya-shi), Junya Yano (Kariya-shi), Hiroaki Kayukawa (Kariya-shi)
Application Number: 11/843,986
International Classification: F01B 7/04 (20060101);