Pumps – Three or more cylinders arranged in parallel – radial – or...
Reexamination Certificate
2002-04-04
2003-11-11
Koczo, Michael (Department: 3746)
Pumps
Three or more cylinders arranged in parallel, radial, or...
C092S158000, C417S222200
Reexamination Certificate
active
06644936
ABSTRACT:
This application is a U.S. National Phase Application under 35 USC 371 of International Application PCT/JP00/07021 (not published in English) filed Oct. 10, 2000.
TECHNICAL FIELD
This invention relates to a swash plate refrigerant compressor, and more particularly to a swash plate refrigerant compressor suitable for use as a refrigerant compressor for an automotive vehicle, using CO
2
(carbon dioxide) as a refrigerant.
BACKGROUND ART
FIG. 6
is a longitudinal cross-sectional view of a conventional swash plate refrigerant compressor, and
FIG. 7
is an enlarged partial view of FIG.
6
.
The swash plate refrigerant compressor includes a cylinder block
101
having a plurality of cylinder bores
106
formed therein, a shaft
105
rotatably supported in a central portion of the cylinder block
101
, a swash plate
110
tiltably and slidably fitted on the shaft
105
and connected to a thrust flange
140
via a linkage
141
, a crankcase
108
in which the swash plate
110
and the thrust flange
140
are received, and pistons
107
each of which is connected to the swash plate
110
via a shoe
150
which can perform relative rotation on a sliding surface
110
a
of the swash plate
110
, the pistons
107
each reciprocating within a corresponding one of the cylinder bores
106
as the swash plate
110
rotates.
The inclination of the sliding surface
110
a
of the swash plate
110
with respect to an imaginary plane, not shown, orthogonal to the shaft
105
varies with pressure within the crankcase
108
.
The shoe
150
is comprised of a dish-shaped shoe body
151
for relatively rollably supporting a forward end face of a ball
111
a
formed on one end of a connecting rod
111
and an annular washer
152
for relatively rollably supporting a rearward end face of the ball
111
a.
A retainer
153
for retaining the washer
152
of the shoe
150
is mounted on a boss
110
b
of the swash plate
110
via a radial bearing
155
. The retainer
153
is relatively rotatable with respect to the swash plate
110
. The radial bearing
155
is prevented from falling off by a stopper
154
. The connecting rod
111
has another end
111
b
thereof secured to a corresponding one of the pistons
107
.
As the shaft
105
rotates, the swash plate
110
also rotates in a state inclined with respect to the imaginary plane orthogonal to the shaft
105
. The rotation of the swash plate
110
causes relative rotation of the shoe
150
on the sliding surface
110
a
of the swash plate
110
with respect to the swash plate
110
, whereby rotation of the swash plate
110
is converted into linear reciprocating motion of the piston
107
.
As a result, the volume of a compression chamber
122
within the cylinder bore
6
changes, whereby suction, compression, and delivery of refrigerant gas are sequentially carried out to deliver an amount of refrigerant gas corresponding to an inclination angle of the swash plate.
It should be noted that since the swash plate
110
is inclined with respect to the imaginary plane orthogonal to the shaft
105
, when the swash plate
110
receives a compression reaction force from the refrigerant gas, tilt loads R
1
, R
2
of the piston
107
are generated as shown in FIG.
7
.
In the case of the swash plate refrigerant compressor using CO
2
as the refrigerant, the difference (approximately 15 MPa at the maximum) between high pressure and low pressure is extremely large, so that a compression reaction force generated during compression of the refrigerant is larger than in a conventional swash plate refrigerant compressor using chlorofluorocarbon as the refrigerant. This results in increased tilt loads R
1
, R
2
of the piston
107
.
Further, in the case of the swash plate refrigerant compressor using CO
2
as the refrigerant, lubricating oil separated by an oil separator, not shown, arranged in an intermediate portion of a path from a discharge chamber
112
to a discharge port
103
a
is returned into the crankcase
108
, and attached to an outer peripheral surface of a bottom face-side end portion of the piston
107
when the piston
107
is close to its bottom dead center position, whereby the lubricating oil is supplied into a corresponding one of the cylinder bores
106
. However, since a piston clearance (i.e. a gap between the outer peripheral surface of a piston and the inner peripheral surface of a cylinder bore) is not large, the amount of lubricating oil supplied to a top face-side end portion of the piston
107
is small.
Moreover, the lubricating oil circulates within the compressor without flowing out into a refrigerating cycle, so that refrigerant gas drawn into a compression chamber
122
contains very little lubricating oil, and hence only a small amount of lubricating oil is supplied to the top face-side end portion of the piston
107
, which increases a sliding frictional force between the top face-side end portion of the piston
107
and the cylinder bore
106
.
Therefore, the cylinder bore
106
is prone to abrasion (biased abrasion), and a coating film on the outer peripheral surface of the piston
107
is prone to peel-off.
It is an object of the invention to provide a swash plate refrigerant compressor which is capable of dividing and distributing tilt loads of pistons as well as enhancing lubricating oil-holding capability of the pistons.
DISCLOSURE OF INVENTION
To achieve the above object, the present invention provides a swash plate refrigerant compressor including a cylinder block having a plurality of cylinder bores formed therein, a drive shaft rotatably supported in a central portion of the cylinder block, pistons slidably inserted in the cylinder bores, respectively, a swash plate for transmitting a driving force to the pistons, and a crankcase in which the swash plate is received, and wherein an outer diameter of a top face-side end portion of the pistons is slightly smaller than an outer diameter of a hollow cylindrical portion of the pistons other than the top face-side end portion.
The outer diameter of the top face-side end portion of each piston is slightly smaller than that of the hollow cylindrical portion of the piston other than the top face-side end portion, as described above. Therefore, the tilt load of the top face-side end portion of the piston is divided and distributed onto two points, and at the same time, lubricating oil is held on the top face-side end portion of the piston. This ensures high lubricating oil-holding capability of the top face-side end portion of the piston, and hence it is possible to enhance slidability of the piston without increasing the clearance between the outer peripheral surface of the piston (hollow cylindrical portion) and the inner peripheral surface of the corresponding cylinder bore (i.e. without degrading volumetric efficiency). As a result, wear of the cylinder bore is reduced, and a coating film on the outer peripheral surface of the piston is made more peel-proof.
Preferably, inclination of the swash plate varies with pressure within the crankcase to thereby change a stroke length of the pistons.
As the inclination of the swash plate (with respect to an imaginary plane orthogonal to the drive shaft) increases, the tilt load of the piston also increases. However, since the outer diameter of the top face-side end portion of the piston is slightly smaller than that of the hollow cylindrical portion of the piston other than the top face-side end portion, the tilt load of the top face-side end portion of the piston is divided and distributed onto two points, and at the same time, lubricating oil is held on the top face-side end portion of the piston, thereby maintaining slidability of the piston.
Preferably, the top face-side end portion of the pistons is tapered.
The top face-side end portion of the each of the pistons is tapered, as described above, and hence the amount of lubricating oil held on the top face-side end portion of the piston is increased, which further enhances the slidability of the piston.
Preferably, inclination of the swash plate varies with pressure within the crankcas
Frishauf Holtz Goodman & Chick P.C.
Koczo Michael
Zexel Valeo Climate Control Corporation
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