Expansible chamber devices – Displacement control of plural cylinders arranged in... – Parallel cylinders
Reexamination Certificate
2001-10-22
2003-08-12
Look, Edward K. (Department: 3745)
Expansible chamber devices
Displacement control of plural cylinders arranged in...
Parallel cylinders
C092S071000
Reexamination Certificate
active
06604447
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a swash plate-type, variable displacement compressor for use in vehicular air conditioning apparatus. More particularly, this invention relates to a swash plate-type, variable displacement compressor that maintains piston top clearance at substantially zero over a whole range of oblique angles of swash plate.
2. Description of Related Art
In
FIG. 1
, a known swash plate-type, variable displacement compressor
100
used in vehicular air conditioning apparatus is shown. A cashing of the compressor
100
includes a front housing
102
, a cylinder block
101
and a cylinder head
103
. A drive shaft
106
is provided which passes through the center of front housing
102
and cylinder block
101
. Drive shaft
106
is rotatably supported by front housing
102
and cylinder block
101
via bearings
107
a
and
107
b
. In cylinder block
101
, a plurality of cylinder bores
108
are provided equiangularly around an axis XO of drive shaft
106
. In each of cylinder bores
108
, a piston
109
is slidably disposed. Pistons
109
are capable of reciprocation along axes parallel to the axis X
0
.
A rotor
110
is fixed to drive shaft
106
, so that rotor
110
and drive shaft
106
may rotate together. Rotor
110
has an arm
117
, and a hole
117
a
having an axis oblique to the axis X
0
is provided in a terminal portion of arm
117
. Front housing
102
and cylinder block
101
cooperatively define a crank chamber
105
. Within crank chamber
105
, a swash plate
111
having a penetration hole
120
at its center portion is accommodated, and drive shaft
106
penetrates through swash plate
111
. Penetration hole
120
of swash plate
111
has a complex shape so as to enable changes in the oblique angle of swash plate
111
with respect to the axis X
0
. A bracket
115
is provided on the front housing-side surface of swash plate
111
, and a guide pin
116
is fixed to a terminal portion of bracket
115
. A spherical part
116
a
provided on the top of guide pin
116
is slidably fitted into hole
117
a
. Because spherical part
116
a
moves within hole
117
a
, the oblique angle of swash plate
111
may vary with respect to the axis XO. Hereafter, this connection mechanism including arm
117
of rotor
110
, hole
117
a
, and guide pin
116
, is labeled K. The circumferential portion of swash plate
111
has a shape of plane ring and is connected slidably to tail portions of pistons
109
via pairs of shoes
114
.
When drive shaft
106
is driven by an external power source (not shown), rotor
110
also rotates around the axis XO together with drive shaft
106
. Swash plate
111
also is made to rotate by rotor
110
via connection mechanism K. Simultaneously with the rotation of swash plate
111
, the circumferential portion of swash plate
111
exhibits a wobbling motion. Only a component of the movement of the wobbling, circumferential portion of swash plate
111
in the axial direction parallel to the axis XO is transferred to pistons
109
via sliding shoes
114
. As a result, pistons
109
are made to reciprocate within cylinder bores
108
. Finally, in the operation of a refrigeration circuit, the refrigerant may be introduced repeatedly from an external refrigeration circuit (not shown) into a compression chamber, which is defined by the piston top of piston
109
, cylinder bore
108
, and valve plate
104
, via suction chamber
130
. The refrigerant then may be compressed by reciprocating piston
109
, and the refrigerant subsequently may be discharged to the external refrigeration circuit via discharge chamber
131
.
However, known compressors, such as that shown in
FIG. 1
, may exhibit several deficiencies. First, there may be a problem of controlling piston top clearance. Second, in such known compressors, because the frictional resistance against the inclining movement of swash plate
111
is large, changes in the oblique angel of the swash plate are not smooth. Third, there may be a problem with vibration of the compressor.
With reference to
FIG. 1
, the center of changes in the oblique angle of swash plate
111
is located at point Z. When the oblique angle of swash plate
111
changes, a resistant force is created due to frictional contact of spherical part
116
a
and the inner surface of hole
117
a
. The distance between the contact point of spherical part
116
a
and the inner surface of hole
117
a
and the center of changes in the oblique angle of the swash plate is relatively large. As a result, the resistant force due to the frictional contact of spherical part
116
a
and hole
117
a
impedes smooth changes to the oblique angle of swash plate
111
.
With further reference to
FIG. 1
, the swash plate may be designed so as to have a center of gravity located on the axis XO when the oblique angle of the swash plate is minimized. The center of gravity of the swash plate deviates from the axis XO as the oblique angle of the swash plate increases. As the oblique angle of the swash plate increases, the distance between the center of gravity of the swash plate and the axis increase monotonically. Thus, as the oblique angle of the swash plate increases, the degree of unbalance due to the shift in the center of gravity of the swash plate also increases monotonically. As a result, a vibration of the whole compressor occurs during operation due to that unbalance.
SUMMARY OF THE INVENTION
A need has arisen to provide a swash plate-type, variable displacement compressor having a connection mechanism between the rotor and the swash plate that keeps the piston top clearance substantially zero over a whole range of oblique angles of the swash plate. It is a technical advantage of the present invention that the compressor may maintain the dead volume at substantially zero by keeping the piston top clearance at about zero over the range of oblique angles of the swash plate. Thus, the volumetric efficiency of the compressor is improved. A further need has arisen to provide a connection mechanism between the rotor and the swash plate, such that the impeding, frictional force acting against the inclining movement of the swash plate is suppressed. It is a further technical advantage of the compressor that the inclining movement of the swash plate becomes smooth, and the responsiveness of the compressor to changes in demanded capacity improves. An additional need has arisen to provide a swash plate, the center of gravity of which shifts less from the axis of the drive shaft than that of known compressors, when the oblique angle of the swash plate is changed. It is an additional technical advantage of such compressors that the vibration of the whole compressor due to an unbalanced center of gravity of the swash plate with regard to the axis of the drive shaft, may be reduced.
In an embodiment of the invention, a swash plate-type, variable displacement compressor comprises a front housing, a cylinder block, and a cylinder head. A drive shaft is supported rotatably by the front housing, and the cylinder block. A rotor is fixed to the drive shaft so as to be rotatable with the drive shaft. A plurality of pistons are accommodated slidably in a corresponding plurality of cylinder bores which are provided and arranged through an end surface of the cylinder block, and axes of the cylinder bores are arranged about a virtual cylinder having a radius R and formed around an axis X of the drive shaft. A central portion the drive shaft penetrates through a swash plate, and each of the pistons is connected to the swash plate via a pair of shoes. A connection mechanism is operably connected between the rotor and the swash plate, and the connection mechanism enables the swash plate to change its oblique angle with respect to the axis X of the drive shaft. The swash plate comprises a flat ring and a second ring, and the pistons are connected to the flat ring from inside. The connection mechanism further comprises a first arm and a second arm provided on the rotor, a pin, and a third arm formed on the swash p
Iizuka Jiro
Morita Yuujirou
Baker & Botts L.L.P.
Leslie Michael
Look Edward K.
Sanden Corporation
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