Reciprocating pistons of piston-type compressor

Abstract: A piston type fluid displacement apparatus includes a plurality of pistons having a cylindrical body and an arm portion axially extending from a first axial end of the cylindrical body and a pair of engaging portions formed the first axial end of the cylindrical body and the arm portion. The cylindrical body of the pistons includes an hollow portion therein. A plurality of apertures are formed on the first axial end of the cylindrical body of the piston and fluidly communicated with the hollow portion of the piston. At least two of the apertures have respectively a rectangular shape. Thereby, a piston type compressor has lightweight pistons while simultaneously maintain a strength of the pistons.

Description: BACKGROUND OF THE INVENTION Field of Invention The present invention relates to a piston type compressor, in which fluid is compressed by means of reciprocating pistons connected to a swash plate. More particularly, it relates to a configuration of reciprocating pistons, which reduces the weight of the pistons in the refrigerant compressor for an automotive air conditioning system. Description of the Prior Art A conventional piston type refrigerant compressor is used in an air conditioning apparatus for an automobile. The conventional piston type refrigerant compressor disclosed in US5,174,728 to Kimura et al (Japanese unexamined publication No.H9-105380). The description will be made as regards a swash plate type compressor as a reciprocating compressor according to a first embodiment of this invention. In the following description, the left side of Figure 1 will represent the front side of the compressor while the right side thereof will represent the rear side of the compressor, which is only for the sake of convenience of description and is not intended to limit the invention is any way. Referring to Figure 1, the compressor, which is generally designated by reference number 100, includes a closed cylinder housing assembly formed by annular casing 10 provided with a cylinder block 22 at one of its sides, a hollow portion, such as a crank chamber 31, a front end plate 13, and a rear end plate 26. Cylinder block 22 is accommodated in cylinder housing 10 of a compressor. Piston 11 are accommodated in cylinder bore 21 and are reciprocatedly moved therein A drive shaft 15, which is driven by an engine(not shown), is rotatably supported by means of the central portion of cylinder block 22 and a front end plate 13. Rotor plate 14 is mounted on drive shaft 15, and synchronously rotates with drive shaft 15. Further, a swash plate 20 is tiltably mounted on drive shaft 15 and is reciprocally slidable together with special sleeve 17 paralleled to the axis of drive shaft 15. Rotor plate 14 and swash plate 20 are connected to each other by means of a hinge mechanism. Swash plate 20 engages the interior portion of the associate piston 11 along its circumference. Cylinder block 22 is provided with a communication passages 23 which is communicated crank chamber 31 with suction chamber 42. Communication passages 23 includes a bellows 28 which open and close communication passage 23 according to the differential pressure and suction pressure. Control of displacement of this compressor is achieved by varying the stroke of piston 11. The stroke of piston 11 varies depending on the difference between pressure which are acting on the opposing sides of swash plate 20. The difference is generated by balancing the pressure in a crank chamber acting on the rear surface of piston 11. Consequently, such the suction pressure in cylinder bore 21 acting on the front surface of piston 11, which suction pressure acts on swash plate 20, through piston 11. According to the above described compressor, when drive shaft 15 is rotated, rotor plate 14 rotates together with drive shaft 15. The rotation of rotor plate 14 is transferred to swash plate 20 through the hinge mechanism. Rotor plate 20 is rotated with a surface inclined with respect to drive shaft 15, so that piston 11 reciprocate in cylinder bores 21, respectively. Therefore, refrigerant gas is drawn into suction chamber 42 and compressed and discharged from the inlet chamber into an associated discharge chamber 44. Thus, the volume of compressed refrigerant gas discharged into discharge chamber 44 is regulated according as the pressure in crank chamber 31 is controlled so as to open and close communication passage 23 relation to the differential pressure between suction pressure and the design pressure of bellows 28. Namely, when suction pressure is higher than the design pressure of bellows 28, the communication passage 23 opens, the pressure in crank chamber 31 decreases, rotor plate 14 become to be rotated with a greater angle with respect to drive shaft 15 and the stroke of piston 11 increases. As a result, the compression capacity of the compressor increases. The other hand, when suction pressure is lower than the design pressure of bellows 28, the communication passage 23 closes, the pressure in crank chamber 31 increases, rotor plate 14 become to be rotated with a smaller angle with respect to drive shaft 15 and the stroke of piston 11 increases. As a result, the compression capacity of the compressor decreases. Further, a part of refrigerant gas remained in cylinder bore 21 is used as lubricating oil which leaks into crank chamber 31 so as to lubricate the surface between rotor plate 14 and sleeves 17. Referring to Figure 2 and 3, piston 11 includes a cylindrical main body 12 which is sealingly formed with an open space 11a therein. Cylindrical main body 12 is provided with an annular groove 13 on the peripheral surface thereof for receiving a lubricating oil. Annular groove 13 is formed so as to never enter the crankchamber when piston 11 stays in a lower dead center. Annular groove 13 includes three apertures 24, which are fluidly communicated with open space 11a, at equal interval. Referring to Figure 3 and 4, piston 11 includes three second apertures 25, which are fluidly communicated with open space 11a, at equal interval, Piston 11 includes first arm portion 16 axially extending from the one end of cylindrical main body 12, integrally connected to the part of the peripheral surface of piston 11 and a second arm portion 17 radially extending from one end of first arm portion 16. Piston 11 includes a first sleeve supporting portions 18 thereof. First sleeve supporting portion 18 is formed on one axial end 11b of cylindrical main body 12. A second sleeve supporting portion 19 is formed on one axial end of a second arm portion 17 so as to face first shoe supporting portion 18. Each piston 11, which are manufactured as above mentioned, is slidably supported by sleeves 17, which are disposed in first shoe supporting portion 18 and second shoe supporting portion 19, and is inserted into and slidably disposed in cylinder bore 21. When the compressor provided with the above piston 11 is activated, a rotary motion of drive shaft 15 is transmute to swash plate 20 via rotor plate 14 and guide pins. Thus, each piston 11 reciprocates within the corresponding bore 21 so that the suction gas is introduced into corresponding bore 21, then compressed and discharged as discharge gas into discharge chamber 44. Depending on a pressure differential between pressure in crank chamber 31 and suction chamber 42, the inclination of swash plate 20 and thus the stroke of piston 10 are changed to control the capacity of the compressor in the manner known in the art. The pressure in the crank chamber 31 is controlled by a control valve mechanism (not shown ) provided in cylinder block 22 depending on the heat load. According to the operation of the compressor, cylinder bore 21 as assume high pressure and low pressure conditions, alternately. There are breathing operation between cylinder bore 21 and open space 11a of piston 11 through aperture 24. In accordance with the breathing operation, the breathing operation occurs smoothly between crank chamber 31 and open space 11a of piston 11 through apertures 25. Lubricating oil included in refrigerant gas adheres to inner surface of cylinder bore 21. lubricating oil is scratched by annular groove 13 when piston reciprocates in cylinder bore 21. Therefore, high condense refrigerant gas flow into open space 11a and crank chamber 31. Apart of the refrigerant gas is effectively used as lubricating oil which lubricates the sliding surface between rotor plate 14 and sleeves 17 in crank chamber 31. Thus, piston 11, which has completely sealed open space 11a therein, is manufactured such that at least one pair of material members for a piston are connected each other by welding in vacuum. Although piston 11 needs to have open space 11a therein and thin thickness cylindrical main body 12 in order to reduce the weight of the piston, it is desirable to be provided with more light weight piston in the compressor used in an automobile. Generally, a pair of members for piston are assembled to a piston by welding in vacuum. According to this manufacturing process, piston have to be manufactured with complex operation in vacuums since a pair of members are welded after coupling each other. Further, open space 11a should be maintained vacuums. SUMMARY OF THE INVENTION It is an object of the present invention to provide a piston type compressor which has lightweight pistons while simultaneously maintaining a strength of the pistons. It is a still another object of the present invention to provide a piston type compressor which is simple to manufacture. According to the present invention, a piston type fluid displacement apparatus includes a housing enclosing a crank chamber, a suction chamber, and a discharge chamber The housing includes a cylinder block wherein a plurality of cylinder bores formed, a drive shaft rotatably supported in the cylinder block and a plurality of pistons each of which is slidably disposed within one of the cylinder bores. Each of the pistons includes a cylindrical body and an arm portion axially extending from a first axial end of the cylindrical body and a pair of engaging portions formed the first axial end of the cylindrical body and the arm portion. The cylindrical body of the pistons includes an hollow portion therein. The housing further includes a plate having an angle of tilt and tiltably connected to the drive shaft and bearing coupling devices coupling the plate to each of the pistons, so that the pistons reciprocates within the cylinder bores upon rotation of the plate. A plurality of apertures are formed on the first axial end of the cylindrical body of the piston and fluidly communicated with the hollow portion of the piston. At least two of the apertures have respectively a rectangular shape. Further objects, features and advantages of this invention will be understood from the following detailed description of preferred embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a longitudinal cross-sectional view of a swash plate type refrigerant compressor with a variable displacement mechanism in accordance with a prior art embodiment. Figure 2 is a side view of a piston in accordance with the prior art embodiment. Figure 3 is a cross-sectional view of a piston taken along lines 3-3 in accordance with the prior art embodiment. Figure 4 is a cross-sectional view of the piston in Figure 2 according to the prior art embodiment. Figure 5 is a cross-sectional view of the swash plate type refrigerant compressor in Figure 1 according to the prior art embodiment. Figure 6 is a side view of a piston in accordance with a first embodiment of the present invention. Figure 7 is a cross-sectional view of the piston taken along lines 8-8 in accordance with the first embodiment of the present invention. Figure 8 is a cross-sectional view of the piston of Figure 6 in accordance with the first embodiment of the present invention. Figure 9 is a cross-sectional view of the swash plate type refrigerant compressor in accordance with the first embodiment of the present invention. Figure 10 is a side view of a piston in accordance with a second embodiment of the present invention. Figure 11 is a cross-sectional view of the piston taken along lines 12-12 in accordance with the second embodiment of the present invention. Figure 12 is a cross-sectional view of the piston in accordance with the second embodiment of the present invention. Figure 13 is a cross-sectional view of the swash plate type refrigerant compressor in accordance with the second embodiment of the present invention. Figure 14 is a side view of a piston in accordance with a third embodiment of the present invention. Figure 15 is a cross-sectional view of the piston taken along lines 16-16 in accordance with the third embodiment of the present invention. Figure 16 is a cross-sectional view of the piston in accordance with the third embodiment of the present invention. Figure 17 is a cross-sectional view of the swash plate type refrigerant compressor in accordance with the third embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention are illustrated in figures 6 -17 in which the same numerals are used to denote elements which correspond to similar elements depicted in Figures 1-5 of the prior art. US5,174,728, which is herein incorporated by reference, forms the starting material for the device of this specification. A detail explanations of several elements and characteristics of the prior art compressor is provided above and is, therefore, omitted from this section. Referring to Figure 6-9, piston 111 includes a cylindrical main body 112 which is sealingly formed with an open space 111a therein. Piston 111 includes first arm portion 116 axially extending from the one end of cylindrical main body 112, integrally connected to the part of the peripheral surface of piston 111 and a second arm portion 117 radially extending from one end of first arm portion 116. Piston 111 includes a pair of shoe supporting portions 118 thereof A first shoe supporting portion 118 is formed on one axial end 111b of cylindrical main body 112. A second shoe supporting portion 119 is formed on one axial end of a second arm portion 117 so as to face first shoe supporting portion 118. Cylindrical main body 112 includes a pair of apertures 51a and 51b formed respectively on the edge portion of second shoe supporting portion 119. Open space 111a of cylindrical main body 112 is formed of the purpose of reducing the weight of piston 111. A pair of apertures 51a and 51b are formed oppositely along the circumference surface of cylindrical main body 112 so as to fluidly communicate open space 111a with the out side of piston 111. The pair of apertures 51a and 51b radially extends from the bottom side of cylindrical main body 112 to neighbor of first arm portion 116. The pair of apertures 51a and 51b have respectively rectangular shape in order to prompt to reduce the weight of piston 111. Further, the pair of apertures 51a and 51b includes the part of peripheral surface of cylindrical main body 112 of piston 111. A second aperture 52 is formed on one axial end 111b of cylindrical main body 112 so as to communicated open space 111a with the outside of piston 111, fluidly. Small aperture 52 extends from one of the corner of open space 111a to radial outer side surface of first arm portion 116. Thus, piston 111, which has completedly sealed open space 111a therein, is manufactured such that a pair of members for piston 111 are connected each other by welding. Namely, a pair of members are welded so as to be attached a welding machine. According to this manufacturing process, open space 111 of piston 100 is easily worked by cutting process and cylindrical main body 112 easily performs to have thin thickens. For example, a pair of members for piston 100 may be manufactured by forging and then a pair of apertures 51a and 51b are simultaneously formed. A small aperture 52 is formed by machine process after forging of piston 100. Each piston 100, which are manufactured as above mentioned, is slidably supported by shoes 117, which are disposed in first shoe supporting portion 118 and second shoe supporting portion 119, and is inserted into and slidably disposed in cylinder bore 21. When the compressor provided with the above piston 111 is activated, a rotary motion of drive shaft 15 is transmitted to swash plate 20 via rotor plate 14 and guide pins. Thus, each piston 111 reciprocates within the corresponding bore 21 so that the suction gas is introduced into corresponding bore 21, then compressed and discharged as discharge gas into discahrge chamber 44. Depending on a pressure differential between pressure in crank chamber 31 and suction chamber 42, the inclination of swash plate 20 and thus the stroke of piston 111 are changed to control the capacity of the compressor in the manner known in the art. The pressure in the crank chamber 31 is controlled by a control valve mechanism (not shown ) provided in cylinder block 22 depending on the heat load. Referring to Figure 9, a refrigerant gas stayed in cylinder bore 21 is easily discharged to the outside of cylinder bore 21 because small aperture 52 is positioned apart from drive shaft 5 and at the bottom of the compressor. In other word, a refrigerant gas and a lubricating oil, which are accumulated in cylinder bore 21 by the gravity and reciprocating movement of piston, is easily discharged to the outside of cylinder bore 21 because a pair of apertures 51a and 51b and small aperture 52 are positioned at top dead center of the piston regardless of the mounted position of the compressor. Thereby, open space 111a of the piston store no refrigerant gas therein, the piston does not increase its weight, substantially. Further, a pair of apertures 51a and 51b and small aperture 52 contribute to reduce the weight of the piston. Furthermore, since a pair of apertures 51a and 51b and small aperture 52 are oppositely along the circumference surface of cylindrical main body 112 different from the piston of the prior art which includes the aperture formed on the peripheral surface of the cylindrical body of the piston, the peripheral of cylindrical main body 112 could have more thin thickness in comparison to the piston of the prior art while simultaneously first arm portion 116 of piston maintains its strength. Figure 10-13 illustrates a second embodiment of the present invention. Elements in Figure 10-13 similar to those in Figure 6-9 are designated with the same reference numerals. A detail explanations of several elements and characteristics of the first embodiment is provided above and is, therefore, omitted from this embodiment. A pair of apertures 61a and 61b are formed on one axial end 111b of cylindrical main body 112 so as to fluidly communicate open space 111a with the out side of piston 111. A pair of apertures 61a and 61b radially extends from the bottom side of cylindrical main body 112 to neighbor of first arm portion 116. A pair of apertures 61a and 61b have respectively rectangular shape in order to prompt to reduce the weight of piston 111. However, a pair of apertures 61a and 61b does not include the part of peripheral surface of cylindrical main body 112 of piston 111 different from the first embodiment of the present invention. A small aperture 52 is formed on one axial end 111b of cylindrical main body 112 so as to communicate open space 111a with the out side of piston 111, fluidly. Small aperture 52 extends from one of the corner of open space 111a to radial outer side surface of first arm portion 116. Substantially the same advantages as those achieved in the first embodiment is realized in the present embodiment. Figure 14-17 illustrates a third embodiment of the present invention. Elements in Figure 14-17 similar to those in Figure 6-9 of the first embodiment are designated with the same reference numerals. A detail explanations of several elements and characteristics of the first embodiment is provided above and is, therefore, omitted from this embodiment. A pair of first apertures 51a and 51b and second aperture 52 are entirely formed as same as the first embodiment of the present invention. A third aperture 71 is formed between first apertures 51a and 51b so as to be communicated open space 111a with the out side of piston 111, fluidly. Substantially the same advantages as those achieved in the first embodiment is realized in the present embodiment. Furthermore, a refrigerant gas and a lubricating oil accumulated in cylinder bore 21 is more easily discharged to the outside of cylinder bore 21 Although the present invention has been described in connection with the preferred embodiments, the invention is not limited thereto. Specifically, while the preferred embodiments illustrate the invention in a swash plate type compressor, this invention is not restricted to swash plate type refrigerant compressors, but may be employed in other piston type compressor or a piston type fluid displacement apparatus. Accordingly, the embodiments and features disclosed herein are provided by way of example only. It will be easily understood by those of ordinary skill in the art that variations and modifications can be easily made within the scope of this invention as defined by the following claims.

Claims: A piston type fluid displacement apparatus comprising: a housing enclosing a crank chamber a suction chamber, and a discharge chamber, said housing including a cylinder block wherein a plurality of cylinder bores formed: a drive shaft rotatably supported in said cylinder block; a plurality of pistons each of which is slidably disposed within one of said cylinder bores, each of said pistons including a cylindrical body and an arm portion axially extending from a first axial end of said cylindrical body and a pair of engaging portions formed on said first axial end of said cylindrical body and said arm portion, said cylindrical body of said pistons including a hollow portion therein; a plate having an angle of tilt and tiltably connected to said drive shaft; a bearing coupling said plate to each of said pistons, so that said pistons reciprocates within said cylinder bores upon rotation of said plate; characterized by, a plurality of apertures formed on said first axial end of said cylindrical body of said piston and fluidly communicated with said hollow portion of said piston, at least two of said apertures having respectively a rectangular shape. The piston type fluid displacement apparatus of claim 1, wherein at least two of said apertures are oppositely located on said first axial end of said cylindrical body of said piston so as to be along an edge surface of said first axial end of said cylindrical body. The piston type fluid displacement apparatus of claim 1 or 2, wherein each of said aperture extends to a radial peripheral surface of said cylindrical body of said piston. The piston type fluid displacement apparatus of claim 2, wherein at least one aperture is formed between at least two of said apertures. The piston type fluid displacement apparatus of one of claims 1 to 4, wherein said rectangular shape of said aperture extends from said arm portion to a bottom of said first axial end of said cylindrical body. The piston type fluid displacement apparatus of one of claims 1 to 5, wherein at least one aperture is fluidly communicated from an outer surface of said arm portion to said hollow portion of said piston.

Inventors: FUKUSHIMA EIJI, FUKUSHIMA, EIJI, Fukushima, Eiji c/o SANDEN CORPORATION
Applicants: SANDEN CORP, SANDEN CORPORATION
Application year: 1998
Main classification: F04B27
IPC codes: F04B27