Expansible chamber devices – Displacement control of plural cylinders arranged in... – Parallel cylinders
Reexamination Certificate
2001-11-08
2003-06-17
Look, Edward K. (Department: 3745)
Expansible chamber devices
Displacement control of plural cylinders arranged in...
Parallel cylinders
C074S060000
Reexamination Certificate
active
06578465
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 a vehicle air conditioning apparatus. More particularly, this invention relates to a swash plate-type, variable displacement compressor that effectively reduces piston top clearance for a range of oblique angles of the swash plate, and thereby reduces the compressor's vibration, while improving volumetric efficiency.
2. Description of Related Art
In
FIG. 1
, a known swash plate-type, variable displacement compressor
100
used in a vehicle air conditioning apparatus is shown. The casing of compressor
100
comprises a front housing
101
, a cylinder block
102
, and a rear housing
103
. A drive shaft
104
is provided to pass through the center of front housing
101
and cylinder block
102
. Drive shaft
104
is rotatably supported by front housing
101
and cylinder block
102
, via bearings
105
,
106
. In cylinder block
102
, a plurality of cylinder bores
107
are arranged equiangularly around an axis
108
of drive shaft
104
. In each of cylinder bores
107
, a piston
109
is slidably disposed. Pistons
109
reciprocate along a direction parallel to drive shaft axis
108
.
A rotor
110
is fixed to drive shaft
104
, so that rotor
110
may rotate together with drive shaft
104
. Rotor
110
has an arm
110
a,
through a terminal part of which is provided an oblong hole
110
h.
Front housing
101
and cylinder block
102
cooperatively define a crank chamber
111
. A swash plate
112
having a penetration hole
112
c
at its center portion is accommodated within crank chamber
111
, through which drive shaft
104
penetrates. Penetration hole
112
c
of swash plate
112
has a complex shape that enables changes of oblique angle of the swash plate
112
with respect to the axis
108
. An arm
112
a
is provided on a front housing side surface of swash plate
112
. A pin
112
p
projects at a terminal part of arm
112
a.
The terminal part of arm
112
a
draws a circular locus when arm
112
a
rotates around axis
108
(i.e., perpendicular to the plane of FIG.
1
). Pin
112
p
projects in a direction tangential to that circular locus. Pin
112
p
is slidably fitted into oblong hole
110
h.
Because pin
112
p
moves within oblong hole
110
h,
the oblique angle of swash plate
112
with respect to axis
108
varies. Hereinafter, the connection mechanism comprising arm
110
a
of rotor
110
, oblong hole
110
h
of arm
110
a,
pin
112
p,
and arm
112
a
of swash plate
112
, is referred to as C
1
. The circumferential portion of swash plate
112
has the shape of a planar ring, and is connected slidably to a tail portion of each of pistons
109
via pairs of shoes
113
.
When drive shaft
104
is driven by an external power source (not shown), rotor
110
rotates around axis
108
together with drive shaft
104
. Swash plate
112
also is made to rotate by rotor
110
, via the connection mechanism C
1
. Simultaneously with the rotation of swash plate
112
, the circumferential portion of swash plate
112
exhibits a wobbling motion. A component of movement in the axial direction parallel to axis
108
of the wobbling circumferential portion of swash plate
112
is transferred to pistons
109
via sliding shoes
113
. As a result, pistons
109
reciprocate within cylinder bores
107
. Finally, in refrigeration circuit operation, a refrigerant may be repeatedly introduced from an external refrigeration circuit (not shown) into a compression chamber
115
, which is defined by the piston top of piston
109
, cylinder bore
107
, and a valve plate
114
, to compress the refrigerant by the reciprocation of each piston
109
, and to then discharge the refrigerant to the external refrigeration circuit (not shown).
However, such known compressors may exhibit the following limitations. First, in compressor
100
, the vertex of the oblique angle is designed to be located at a point
116
at the intersection of a center line
117
of swash plate
112
and axis
108
, as shown in FIG.
1
. Thus, the position of the vertex of the oblique angle of swash plate
112
depends on the shape of penetration hole
112
c
of swash plate
112
. On the other hand, a center of gravity
118
of swash plate
112
is located at a point relatively far offset above axis
108
, as shown in FIG.
1
. Because center of gravity
118
of swash plate
112
is relatively far offset from axis
108
of rotation of drive shaft
104
, compressor
100
is unbalanced. When drive shaft
104
rotates, this offset generates a vibration in compressor
100
. Second, in actual manufacture, connection mechanism C
1
may be difficult to make with a low tolerance (i.e., a reduced dimensional variance among the components) because of its complicated shape. As a result, it is difficult to suppress the occurrence of a high tolerance (i.e., increased dimensional variance among the components) between oblong hole
110
h
and pin
112
p.
The existence of a high tolerance adversely affects the durability of compressor
100
. Third, there may be a problem of controlling piston top clearance. The piston top clearance is a distance between the piston top of piston
109
and valve plate
114
when piston
109
is in a top dead center position.
SUMMARY OF THE INVENTION
A need has arisen to reduce compressor vibration, while improving the volumetric efficiency of the compressor. The present invention provides a swash plate-type, compressor having a connection mechanism for the rotor and the swash plate that eliminates or reduces the size of tolerances between compressor components and thereby improves volumetric efficiency. According to the present invention, the compressor may have a connection mechanism between the rotor and the swash plate comprising a link arm having two pivots. This link arm mechanism provides in practice a connection mechanism of the rotor and the swash plate that has a low tolerance. Another need has arisen to locate the vertex of the oblique angle of the swash plate at an improved or optimum position, so that the variation of the piston top clearance as a function of the oblique angle of the swash plate is improved. By making the variation of the piston top clearance as a function of the oblique angle of the swash plate optimum, it is possible to suppress the dead volume and improve the volumetric efficiency of the compressor for the required range of the oblique angle of the swash plate.
In an embodiment of this invention, a swash plate-type compressor includes a front housing, a cylinder block, and a rear housing. A drive shaft is supported rotatably by the front housing and cylinder block. A rotor is fixed to, and rotatable with, the drive shaft. Cylinder bores are arranged around the axis of the drive shaft. Each cylinder bore houses a piston that reciprocates therein. A swash plate is mounted movably on the drive shaft. The pistons are connected to the swash plate by shoes. A connection mechanism links the rotor and swash plate such that the swash plate changes its oblique angle with respect to the drive shaft axis. The connection mechanism includes a first arm that projects from the rotor, a second arm that projects from the swash plate, and a link arm that connects the first and second arms. The first arm and a terminal end of the link arm are connected rotatably by a first pin. The second arm and the other terminal end of the link arm are connected rotatably by a second pin. The first pin extends in a direction tangential to a circular locus formed by a terminal part of the first arm as it rotates around the axis of the drive shaft. The second pin extends in a direction parallel to the first pin.
In another embodiment of this inventions a method is provided for adjusting the location of the vertex of an oblique angle of a swash plate-type compressor. First, a central portion of a swash plate is drilled to form an opening through the central portion of the swash plate. Then, the location of the vertex of the oblique angle is offset from the g
Baker & Botts L.L.P.
Lazo Thomas E.
Look Edward K.
Sanden Corporation
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