A wobble plate type compressor with a variable displacement mechanism

Abstract: A wobble plate type compressor with a variable displacement mechanism is disclosed which includes a compressor housing (3) which has a crank chamber (32). A rotatable drive shaft (7) is rotatably supported and axially fixed in the compressor housing (3). A rotor (10) is fixed on the drive shaft (7). A cylindrical member (12) is hingedly connected to the rotor (10) so that the angle of the cylindrical member (12) can be varied. A central hole is formed through the cylindrical member (12) for receiving the drive shaft (7). The central hole has an annular edge portion at its inner surface which contacts the outer peripheral surface of the drive shaft (7) to restrict radial movement of the cylindrical member (12) while permitting the angle of the cylindrical member (12) to be varied. The annular edge portion is defined by intersecting a first inner surface at one end of the cylindrical member (12) and a second inner surface at the other end of the cylindrical member (12) along with a central axis of a circle which is defined by the annular edge portion. The first inner surface corresponds to the extended lines of the inclined surfaces of a first right circular cone which has an apex and a center of the bottom surface of the first right circular cone on the central axis. The first right circular cone is spread at the one end. The second inner surface corresponds to the extended lines of the inclined surfaces of a second right circular cone which has an apex and a center of the bottom surface of the second right circular cone on the central axis. The second right circular cone is spread at the other end. Thus, the above shape of the central hole is very simple, and can be more easily formed while maintaining its accuracy.

Description: The present invention relates to a wobble plate type compressor with a variable displacement mechanism, and more particularly to a support mechanism for a variable displacement mechanism of which the cylindrical member is provided with a central hole to enable to be easily formed therethrough. A wobble plate type compressor which reciprocates pistons by converting the rotational movement of a cam rotor into nutational movement of a wobble plate is well known in the art. Changing the inclined angle of the wobble plate changes the stroke of the pistons and therefore changes the displacement volume of the cylinder. In U.S. Pat. No. 4,846,049, forming the generic portion of claim 1, a wobble plate is proximately disposed on a variable angle rotating cylindrical member. The cylindrical member is hingedly connected to a rotor which is fixed on the drive shaft and has a central hole which is formed therethrough to extend a drive shaft through the central hole. The rotor permits varying the inclined angle of the cylindrical member Movement of the cylindrical member is controlled by the pressure difference between the crank chamber and the suction chamber. In this structure, since the inclined angle of the cylindrical member is required to be easily varied in response to changing of the pressure difference therebetween, the shape of the central hole is elongate, and its form is complicated to maintain accuracy of its shape. A working tool is used when the central hole is formed. Since the shape of the central hole is elongate, the inclined angle of the rotational axis of the working tool is necessary to be continuously and steplessly changed within the certain range of angles to complete its shape while working. However, since the working tool has to work while moving its rotational central axis, it is necessary to control complicatedly the movement of the rotational central axis of the work tool to attain the desired accuracy at the shape of the central hole. Thus, the manufacturing of the central hole which has such a complicated shape is at very high cost. Various additional advantages and features of novelty which charactetize the invention are further pointed out in the claims that follow. However, for a better understanding of the invention and its advantages reference should be made to the accompanying drawings and descriptive matter which illustrate and describe preferred embodiments of the invention. It is a primary object of this invention to provide a wobble plate type compressor with a variable displacement mechanism which is manufactured at low cost. It is another object of this invention to provide a wobble plate type compressor with a variable displacement mechanism which has a cylindrical member including a central hole manufactured very easily. A wobble plate type compressor with a variable displacement mechanism according to the present invention includes a compressor housing which has a crank chamber. A cylinder block is disposed in the compressor housing. A plurality of cylinders are disposed therein. A plurality of pistons, each of said pistons are reciprocatingly disposed in a respective one of the cylinders. A rotatable drive shaft is rotatably supported and axially fixed in the compressor housing. A rotor is fixed on the drive shaft. A cylindrical member is hingedly connected to the rotor so that the angle of the cylindrical member can be varied. A central hole is formed through the cylindrical member for receiving the drive shaft. The cylindrical member is nonfixedly disposed on the drive shaft. The central hole has an annular edge portion at its inner surface which contacts the outer peripheral surface of the drive shaft to restrict radial movement of the cylindrical member while permitting the angle of the cylindrical member to be varied. The annular edge portion is defined by intersecting a first inner surface at one end of the cylindrical member and a second inner surface at the other end of the cylindrical member along with a central axis of a circle which is defined by the annular edge portion. The first inner surface corresponds to the extended lines of the inclined surfaces of a first right circular cone which has an apex and a center of the bottom surface of the first right circular cone on the central axis. The first right circular cone is spread at the one end. The second inner surface corresponds to the extended lines of the inclined surfaces of a second right circular cone which has an apex and a center of the bottom surface of the second right circular cone on the central axis. The second right circular cone is spread at the other end. A wobble plate is proximate the cylindrical member and coupled to the pistons. Figure 1 is a cross-sectional view of a wobble plate type compressor with a variable displacement mechanism in accordance with this invention. Figure 2 is an illustrative view of manufacturing a cylindrical member used in a wobble plate type compressor with a variable displacement mechanism as shown in Figure 1. Figure 3 is a front view of a cylindrical member as shown in Figure 2. Figure 4 is a rear view of a cylindrical member as shown in Figure 2. Referring to Figure 1 , wobble plate type compressor 1 includes front end plate 2, cylinder casing 3 having cylinder block 31, valve plate 4, and cylinder head 5. Front end plate 2 is fixed on one end of cylinder casing 3 by securing bolts 6. Axial hole 21, which is formed through the centre of front end plate 2, receives drive shaft 7. Radial bearing 8 is disposed in axial hole 21 to rotatably support drive shaft 7. Annular sleeve portion 22 projects from end plate 2 and surrounds drive shaft 7, defining seal cavity 23. Cylinder casing 3 is provided with cylinder block 31 and crank chamber 32. Cylinder block 31 has a plurality of equiangularly spaced cylinders 33 formed therein. Cam rotor 10 is fixed on drive shaft 7 by pin 103. Thrust needle bearing 11 is disposed between the inner wall surface of front end plate 2 and the adjacent axial end surface of cam rotor 10. Arm portion 101 of cam rotor 10 extends in the direction of cylinder block 31. Hole 102 is formed on arm portion 101. Cylindrical member 12, provided with flange portion 121, is disposed around drive shaft 7. Second arm portion 122 is formed on the outer surface of flange portion 121 of cylindrical member 12 and faces arm portion 101 of cam rotor 10. Elongated holes 123 are respectively formed on second arm portions 122. Hole 102, formed in arm portion 101, is aligned with elongated holes 123. Pin 14, inserted through hole 102, is slidably moveable within elongated holes 123. Ring-shaped wobble plate 15 is rotatably mounted on the outer surface of cylindrical member 12 through radial needle bearing 30 and is prevented from axial movement by flange portion 121 and snap ring 16 disposed on cylindrical member 12. Thrust needle bearing 17 is disposed in a gap between flange portion 121 and wobble plate 15. The other end of drive shaft 7 is rotatably supported through radial bearing 18 in the central bore of cylinder block 31. Sliding member 151 is attached on the outer peripheral portion of wobble plate 15 and projects toword the bottom surface of cylinder casing 3. The end of sliding shaft 151 is slidably disposed on the outer surface of guide bar 321 to prevent the rotation of wobble plate 15. Two second arm portions 123 are used to prevent cylindrical member 12 from inclining perpendicular to the direction of the inclination of the cylindrical member which is allowed to vary the compression volume. One end of piston rod 19 is rotatably connected to receiving surface 152 of wobble plate 15. The other end of piston rod 19 is rotatably connected to piston 20 which is slidably disposed in cylinder 33. Suction ports 41 and discharge ports 42 are formed in valve plate 4. A suction reed valve (not shown) is disposed on valve plate 4. A discharge reed valve (not shown) is disposed on valve plate 4 opposite the suction reed valve. Cylinder head 5 is connected to cylinder casing 3 through gaskets 34 and 35 and valve plate 4. Partition wall 51 expends axially from the inner surface of cylinder head 5 and divides the interior of cylinder head 5 into suction chamber 52 and discharge chamber 53. Suction chamber 52 is connected to the external fluid circuit through fluid inlet port 60 formed in cylinder head 5. Discharge chamber 53 is connected to the external fluid circuit through a fluid outlet port (not shown) formed in cylinder head 5. Crank chamber 32 of cylinder casing 3 and suction chamber 52 of cylinder head 5 are connected to one another to control the angle of cylindrical member 12 and wobble plate 15. The structure of the connecting means and the control method for varying the inclined angle of cylindrical member 12 and wobble plate 15 may be of the form disclosed in U.S. Pat. No. 4,846,049. Referring to Figures 2-4, the construction of a cylindrical member in acccordance with one embodiment or the present invention is shown. Central hole 124 is formed through cylindrical member 12 and has annular edge portion 124a. Annular edge portion 124a is defined by intersecting first inner surface 124b at one end of cylinder member 12 and second inner surface 124c at the other end of cylindrical member 12. Central axis a1 passes through the central point of a circle which is defined by annular edge portion 124a and is perpendicular to one end surface of flange portion 121. Central axis a2 also passes through the central point of the above circle and inclines about 14 degrees from central axis a1 round the central point. First inner surfaces 124b correspond to extended lines 901 and 902 of the inclined surfaces of first right circular cone 125. The apex and the center of the bottom surface of first right circular cone 125 are on the line of central axis a2. First right circular cone 125 is spread to one end of cylindrical member 12. Second inner surfaces 124c correspond to extended lines 903 and 904 of the inclined surfaces of second right circular cone 126. The apex and the center of the bottom surface of second right circular cone 126 are on the line of central axis a2. Second right circular cone 126 is spread to the other end of cylindrical member 12. In this embodiment, the angle of the apex of respective first and second right circular cones 125 and 126 is about 39.8 degrees. The value of the angle of the apex is changed in accordance with the design choice of cylindrical member 12. With respect to forming central hole 124 of cylindrical member 12, cylindrical member 12 which has a hole pre-formed therethrough is retained at its boss portion 127 by chuck 71 through jig 70. Chuck 71 is rotated round central axis a2 and work tool 80 is axially moved along with one of extended lines 901 and 902. After first inner surface 124b of central hole 124 is formed, the inclined angle of work tool 80 is changed so as to be aligned with one of extended lines 903 and 904 and work tool 80 is thereafter axially moved to form second inner surface 124c. In the above embodiment, it is not necessary to change the central axis of a wook tool when only one of first and second inner surfaces 124b and 124c is formed. Thus, central hole 124 of cylindrical member 12 can be more easily formed by a simpler work tool. This invention has been described in detail in connection with the preferred embodiments. These embodiments, however, are merely for example only and the invention is not restricted thereto. It will be understood by those skilled in the art that other variations and modifications can easily be made within the scope of this invention as defined by the claims.

Claims: A wobble plate type compressor with a variable displacement mechanism comprising: a compressor housing having a crank chamber; a cylinder block disposed in said compressor housing and having a plurality of cylinders disposed therein; a plurality of pistons, each of said pistons being reciprocatingly disposed in a respective one of said cylinders; a rotatable drive shaft rotatably supported and axially fixed in said compressor housing; a rotor fixed on said drive shaft; a cylindrical member hingedly connected to said rotor so that the angle of said cylindrical member can be varied; a central hole formed through said cylindrical member for receiving said drive shaft, said cylindrical member being non-fixedly disposed on said drive shaft, said central hole having an annular edge portion at its inner surface which contacts the outer peripheral surface of said drive shaft to restrict radial movement of said cylindrical member while permitting the angle of said cylindrical member to be varied, characterised in that said annular edge portion are defined by intersecting a first inner surface at one end of laid cylindrical member and a second inner surface at the other end of said cylindrical member along with a central axis of a circle defined by said annular edge portions, said first inner surface corresponding to a portion of the surface of a first right circular cone, said second inner surface corresponding to a portion of the surface of a second right circular cone both cones including said same central axis; and a wobble plate proximate said cylindrical member and coupled to said pistons. The wobble plate type compressor with a variable displacement mechanism of claim 1 wherein said central axis intersects the central axis of said drive shaft. The wobble plate type compressor with a variable displacement mechanism of claims 1 and 2 wherein said cylindrical member includes at least two arm portions.

Inventors: TERAUCHI KIYOSHI, TERAUCHI, KIYOSHI
Applicants: SANDEN CORP, SANDEN CORPORATION
Application year: 1991
Main classification: F04B27
IPC codes: F04B27