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Variable displacement type compressorRelated Patent Categories: Pumps, Three Or More Cylinders Arranged In Parallel, Radial, Or Conical Relationship With Rotary Transmission AxisVariable displacement type compressor description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070081904, Variable displacement type compressor. Brief Patent Description - Full Patent Description - Patent Application Claims
TECHNICAL FIELD [0001] The present invention relates to a variable displacement swash plate type compressor that forms, for example, part of a refrigeration circuit and compresses refrigerant gas. BACKGROUND ART [0002] As shown in FIG. 9, such a swash plate type compressor includes a swash plate 92, which is coupled to a drive shaft 91 to be rotatable integrally with the drive shaft 91. Single head pistons 94 are coupled to the outer circumferential portion of the swash plate 92 with pairs of semispherical shoes 93A, 93B. Therefore, when the swash plate 92 is rotated by rotation of the drive shaft 91, the swash plate 92 slides with respect to the shoes 93A, 93B causing the pistons 94 to reciprocate, thereby compressing refrigerant gas. [0003] Each pair of shoes 93A, 93B rotates about an axis S (a line that passes through the center of curvature P of the spherical surface and is perpendicular to sliding surfaces with respect to the swash plate 92) as the shoes 93A, 93B rotate relative to the swash plate 92. The rotation of the shoes 93A, 93B about the axis S is caused because a rotational force is applied to the shoes 93A, 93B in one direction about the axis S due to the difference between the circumferential velocities of the inner and outer circumferences of the swash plate 92. More specifically, the circumferential velocity of the outer circumference of the swash plate 92 is greater than that of the inner circumference of the swash plate 92. [0004] That is, the swash plate type compressor shown in FIG. 9 is configured such that the shoes 93A, 93B directly slide against the swash plate 92. Therefore, the shoes 93A, 93B are unnecessarily rotated about the axis S due to the sliding motion caused as the shoes 93A, 93B rotate relative to the swash plate 92. This increases the mechanical loss particularly at the sliding portion between each piston 94 and the corresponding shoe 93B that receives reactive force of compression, and causes problems such as seizure at the sliding portions. [0005] To solve such problems, for example, a technique shown in FIG. 10 has been proposed (for example, patent document 1). That is, an annular step 90a is provided at the center of a rear surface (a surface facing rightward in FIG. 10) of a swash plate (hereinafter, referred to as a first swash plate 90). An annular sliding plate (hereinafter, referred to as a second swash plate 95) is arranged outward of the step 90a of the first swash plate 90. The second swash plate 95 is supported to be coaxial with and rotatable relative to the first swash plate 90. The outer circumferential portion of the second swash plate 95 is arranged between the first swash plate 90 and the second shoes 93B to be slidable with respect to the first swash plate 90 and the second shoes 93B. [0006] Therefore, when the first swash plate 90 is rotated, the first swash plate 90 slides relative to the second swash plate 95, which reduces the rotation speed of the second swash plate 95 as compared to the rotation speed of the first swash plate 90. This reduces the relative rotation speed of the second swash plate 95 and the second shoes 93B as compared to the relative rotation speed of the second shoes 93B and the first swash plate 90. As a result, the rotation of each second shoe 93B about the axis S caused by the relative rotation of the second swash plate 95 and the second shoes 93B is suppressed, which suppresses mechanical loss and occurrence of problems. [0007] A configuration has also been proposed in which rolling elements are provided between the first shoes 93A and the second shoes 93B and between the first swash plate 90 and the second swash plate 95 (for example, patent document 2). In the patent document 2, a race of a thrust bearing arranged toward the second shoe 93B can be considered as the second swash plate 95. With this configuration, the first swash plate 90 reliably slides with respect to the second swash plate 95, which significantly reduces the relative rotation speed of the second swash plate 95 and the second shoes 93B as compared to the relative rotation speed of the second shoes 93B and the first swash plate 90. [0008] However, according to the swash plate configuration including the second swash plate 95 and the rolling element in addition to the first swash plate 90, the thickness between the first shoes 93A and the second shoes 93B is increased. The first swash plate 90, which tilts with respect to the drive shaft 91, has a salient corner 90b at the outer circumferential edge portion corresponding to the vicinity of the piston 94 located at the top dead center position (the state shown in FIG. 10). The salient corner 90b is provided at the outer circumferential edge portion opposite to the second swash plate 95 and significantly protrudes in the radial direction (upward in the drawing) of the drive shaft 91. Furthermore, the second swash plate 95, which tilts with respect to the drive shaft 91, has a salient corner 95b at the outer circumferential edge portion corresponding to the vicinity of the piston 94 located at the bottom dead center position (not shown). The salient corner 95b is provided at the outer circumferential edge portion opposite to the first swash plate 90 and significantly protrudes in the radial direction of the drive shaft 91. [0009] When the salient corner 90b of the first swash plate 90 and the salient corner 95b of the second swash plate 95 significantly protrude in the radial direction of the drive shaft 91, part of each piston 94 corresponding to the protruding portions needs to be made thin, or the pistons 94 need to be enlarged in the radial direction to avoid interference with the protruding portions. Reducing the thickness of the pistons 94 leads to reduction in the durability, and enlargement of the pistons 94 leads to enlargement of the swash plate type compressor. Therefore, in the prior art, when the thickness of the swash plate configuration needs to be increased, the radii of the first swash plate 90 and the second swash plate 95 are reduced to avoid interference of the salient corners 90b, 95b with the pistons 94. [0010] However, when the radii of the first swash plate 90 and the second swash plate 95 are reduced, particularly the piston 94 located in the vicinity of the top dead center position (in a compression stroke) has a reduced contact area between the second shoe 93B, which receives a significant reaction force of compression, and the second swash plate 95. This undesirably reduces the durability of the second swash plate 95 and the second shoe 93B. [0011] It has become a common practice to use carbon dioxide as refrigerant of the refrigeration circuit. When carbon dioxide refrigerant is used, the pressure in the refrigeration circuit becomes extremely high as compared to a case where chlorofluorocarbon refrigerant (for example, R134a) is used. Therefore, the reaction force of compression applied to the pistons 94 is increased in the swash plate type compressor, and the aforementioned problem (reduction in the durability of the second swash plate 95 and the second shoes 93B) has become a significant matter of concern. [0012] Patent Document 1: Japanese Laid-Open Patent Publication No. 8-338363 (page 4, FIG. 1) [0013] Patent Document 2: Japanese Laid-Open Patent Publication No. 8-28447 (page 3, FIG. 1) SUMMARY OF THE INVENTION [0014] Accordingly, it is an objective of the present invention to provide a variable displacement swash plate type compressor that improves the durability of a swash plate and shoes while suppressing reduction in the durability of pistons and enlargement of the pistons. [0015] To achieve the above objective, the present invention provides a variable displacement swash plate type compressor. A swash plate is coupled to a drive shaft to be rotatable integrally with the drive shaft. Pistons are coupled to the swash plate via shoes. Rotation of the drive shaft rotates the swash plate, which causes the pistons to reciprocate and compress gas. The displacement is changed by varying the inclination angle of the swash plate. An inclined surface is provided at part of the entire outer circumferential edge portion of the swash plate. [0016] Providing the inclined surface at a projecting salient corner of the outer circumferential edge portion of the swash plate, which inclines with respect to the drive shaft, permits the diameter of the swash plate to be increased while suppressing decrease of the durability and enlargement of the pistons. Therefore, a significant reaction force of compression applied to the swash plate via the shoes is received in a suitable manner. This improves the durability of the swash plate and the shoes. [0017] In a preferred embodiment, part of the outer circumferential edge portion of the swash plate corresponding to the piston located at the top dead center position is provided with the inclined surface on a salient corner opposite to the piston. That is, part of the outer circumferential edge portion of the swash plate corresponding to a circumferential range of the swash plate that arranges any of the pistons at the top dead center position is provided with the inclined surface on the salient corner opposite to the piston. [0018] At the outer circumferential edge portion of the swash plate that corresponds to the piston located at the top dead center position, the salient corner opposite to the piston significantly projects in the radial direction of the drive shaft when the swash plate tilts with respect to the drive shaft. Therefore, a significant reaction force of compression applied to the swash plate via the shoe of the piston located in the vicinity of the top dead center position is received in a suitable manner. This improves the durability of the swash plate and the shoes. [0019] In a preferred embodiment, part of the outer circumferential edge portion of the swash plate corresponding to the piston located at the bottom dead center position is provided with the inclined surface on a salient corner toward the piston. That is, part of the outer circumferential edge portion of the swash plate corresponding to a circumferential range of the swash plate that arranges any of the pistons at the bottom dead center position is provided with the inclined surface on the salient corner toward the piston. [0020] At the outer circumferential edge portion of the swash plate corresponding to the piston located at the bottom dead center position, the salient corner toward the piston significantly projects in the radial direction of the drive shaft. Therefore, chamfering the projecting portion of the swash plate permits the diameter of the first swash plate to be increased while suppressing decrease of the durability and enlargement of the pistons. [0021] In the preferred embodiment, the swash plate includes a first swash plate, which is coupled to the drive shaft to be rotatable integrally with the drive shaft, and a second swash plate, which is supported by the first swash plate. The pistons are coupled to the first and second swash plates via first shoes, which abut against the first swash plate, and second shoes, which abut against the second swash plate and receive a reaction force of compression. Part of the outer circumferential edge of the first swash plate corresponding to the piston located at the top dead center position is provided with the inclined surface on a salient corner opposite to the second swash plate. That is, part of the outer circumferential edge portion of the first swash plate corresponding to a circumferential range of the first swash plate that arranges any of the pistons at the top dead center position is provided with the inclined surface on the salient corner opposite to the first swash plate. Continue reading about Variable displacement type compressor... Full patent description for Variable displacement type compressor Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Variable displacement type compressor patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. 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