Expansible chamber devices – Relatively movable working members – Interconnected with common rotatable shaft
Reexamination Certificate
2002-02-13
2004-02-24
Look, Edward K. (Department: 3745)
Expansible chamber devices
Relatively movable working members
Interconnected with common rotatable shaft
C092S169100
Reexamination Certificate
active
06694863
ABSTRACT:
TECHNICAL FIELD
This invention relates to a swash plate compressor, and more particularly to a swash plate compressor suitable for use as a compressor for an automotive vehicle, which uses CO
2
(carbon dioxide) as a refrigerant.
BACKGROUND ART
FIG. 7
is a longitudinal cross-sectional view of a conventional swash plate compressor.
The swash plate 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
which rotates along with rotation of the shaft
105
, a crankcase
108
in which the swash plate
110
is received, and pistons
107
each of which is connected to the swash plate
108
via a pair of shoes
160
,
161
and slides in a corresponding one of the cylinder bores
106
along with rotation of the swash plate
110
.
The piston
107
is comprised of a hollow cylindrical portion
107
a
for sliding in the cylinder bore
106
, and a bridge
107
b
rollably supporting the pair of shoes
160
,
161
.
The bridge
107
b
projects radially outward with respect to the hollow cylindrical portion
107
a
by a connecting portion
107
c
extending from a bottom portion
107
e
of the hollow cylindrical portion
107
a
in a radially outward direction of the cylinder block
101
.
As the shaft
105
rotates, the swash plate
110
rotates along with rotation of the shaft
105
. The rotation of the swash plate
110
causes relative rotation of the shoes
160
,
161
on sliding surfaces
110
a
,
110
b
of the swash plate
110
, which converts rotation of the swash plate
110
into reciprocating motion of each piston
7
.
As a result, the volume of a compression chamber
122
within the cylinder bore
106
changes, which causes suction, compression and delivery of refrigerant gas to be sequentially carried out, whereby refrigerant gas is delivered from the compression chamber
122
in an amount corresponding to the angle of inclination of the swash plate
110
.
During this operation, the compression reaction force from refrigerant gas compressed by the reciprocating motion of the piston
107
is received by the inclined swash plate
110
, so that tilting loads R
1
, R
2
are applied on the piston
107
as shown in the figure.
The tilting loads R
1
, R
2
are dependent on dimensions L
1
, L
2
shown in the figure, such that the loads R
1
, R
2
become smaller as the length L
1
is longer (i.e. the length L
2
is shorter). Here, L
1
represents the distance between the point of application of the tilting load R
1
on a top side of the piston
107
and the point of application of the tilting load R
2
on a bottom side of the same, while L
2
represents the distance between the point of application of the tilting load R
2
and the point of application of the compression reaction force from the swash plate
110
.
It should be noted that in a compressor using CO
2
as a refrigerant, the difference between high pressure and low pressure is so large (approximately 15 MPa at the maximum) that the compression reaction force generated during a compression stroke of a piston is larger than in a conventional compressor using chlorofluorocarbon as a refrigerant.
Further, the delivery quantity of the compressor using CO
2
is ⅙ to {fraction (1/10)} of that of the conventional compressor using chlorofluorocarbon, and the diameter of each cylinder bore
106
of the former is as small as ⅓ to ½ of that of the latter, so that surface pressure becomes much higher.
Moreover, the pistons
107
and the cylinder bores
106
are abraded due to sliding frictions between the pistons
107
and the respective cylinder bores
106
, which are caused by the tilting loads R
1
, R
2
.
Furthermore, the edge (peripheral edge of the top surface) of each piston
7
removes lubricating oil attached to the corresponding cylinder bore
106
, so that the breaking of oil film can cause seizure of the piston
107
.
It is an object of the invention to reduce tilting load acting on each piston to thereby provide a highly durable and reliable swash plate compressor.
DISCLOSURE OF INVENTION
To achieve the above object, the present invention provides a swash plate compressor including a cylinder block having a plurality of cylinder bores formed therein, a rotational shaft rotatably supported in a central portion of the cylinder block, a swash plate which rotates along with rotation of the rotational shaft, a crankcase in which the swash plate is received, and pistons each connected to the swash plate via a pair of shoes and sliding in a corresponding one of the cylinder bores along with rotation of the swash plate, and wherein each of the pistons comprises a hollow cylindrical portion for sliding in the cylinder bore, and a bridge for rollably supporting the pair of shoes, the bridge projecting radially outward with respect to the hollow cylindrical portion by a connecting portion extending from a bottom portion of the cylindrical portion in a radially outward direction of the cylinder block, characterized in that the cylinder block is formed with a projecting portion projecting from a central portion of a front end face thereof toward the crankcase, within a range limited such that the projecting portion does not interfere with the connecting portion.
Since the cylinder block is formed with the projecting portion projecting from the central portion of the front end face thereof toward the crankcase, within the range limited such that the projecting portion does not interfere with the connecting portion, a point of application of a tilting load on the bottom side of the piston for tilting the piston is shifted toward the front head side of the same, whereby the distance between the point of application of the tilting load on the top side of the piston and the point of application of the tilting load on the bottom side of the same is increased. Consequently, the tilting load is reduced, whereby abrasion between the piston and the cylinder block is decreased, which enhances durability. Further, friction loss is reduced, and slidability of each piston is improved, which makes it possible to reduce the driving force of the compressor, thereby enhancing performance and reliability of the same.
Preferably, the projecting portion has a generally hollow cylindrical shape in side view.
Since the projecting portion is has a generally hollow cylindrical shape in side view, it is easy to machine the same.
Preferably, the projecting portion has a generally hollow truncated cone shape in side view.
Since the projecting portion is generally conical in shape in side view, it is easy to remove burrs produced when the projecting portion is machined, which improves machining efficiency.
Preferably, the hollow cylindrical portion has a portion of a bottom-side end thereof extended to a location radially opposed to the connecting portion.
Since the portion of the bottom-side end of the cylindrical portion is extended to the location radially opposed to the connecting portion, the bottom-side end portion of the piston is not completely received in the cylinder bore even when the piston is close to its top dead center position. Therefore, the tilting load is progressively reduced as the piston becomes close to its top dead center position.
Preferably, the projecting portion has a generally hollow cylindrical shape in side view, and the hollow cylindrical portion has a portion of a bottom-side end thereof extended to a location radially opposed to the connecting portion.
Preferably, the projecting portion has a generally truncated cone shape in side view, and the hollow cylindrical portion has a portion of a bottom-side end thereof extended to a location radially opposed to the connecting portion.
Preferably, the cylindrical portion of the piston is formed with an annular groove always radially opposed to an inner peripheral surface of the cylinder bore.
Since the cylindrical portion of the piston is formed with the annular groove always radially opposed to the inner peripheral surface of th
Furuya Shunichi
Kanai Hiroshi
Frishauf Holtz Goodman & Chick P.C.
Kershteyn Igor
Look Edward K.
Zexel Valeo Climate Control Corporation
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