Pumps – Condition responsive control of drive transmission or pump... – Adjustable cam or linkage
Reexamination Certificate
1999-03-04
2001-08-28
Freay, Charles G. (Department: 3746)
Pumps
Condition responsive control of drive transmission or pump...
Adjustable cam or linkage
C417S269000
Reexamination Certificate
active
06280151
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a single-ended swash plate compressor for use in automotive vehicles and the like.
2. Description of the Related Art
Swash plate compressors, in which a plurality of cylinder bores are disposed parallel to a drive shaft in a peripheral portion of a cylinder block, with piston assemblies housed in the cylinder bores, the piston assemblies being reciprocated by a swash plate which rotates together with the drive shaft so as to compress a refrigerant gas, are in general use as compressors for conventional automotive air-conditioners. Moreover, double-ended swash plate compressors, which include double-headed piston assemblies in which compression pistons are formed on both ends of piston rods and a compression action is performed at both the front end and the rear end of the piston bores, are often used. However, when using carbon dioxide (C
0
2) as a refrigerant as an alternative to chloro fluorocarbons, there are cases where single-ended swash plate compressors are used.
Generally-known conventional single-ended swash plate compressors include single-headed piston assemblies in which compression pistons are formed on one end of the piston rods only and the compression action is performed at one end of the piston bores, for example, the rear end only.
The fixed-capacity single-ended swash plate compressor shown in
FIG. 13
is a known example of such a swash plate compressor.
In the figure, the outer shell
201
of the compressor is formed by joining a front housing
201
b
to the front end of a cylinder block
201
a
, forming a swash plate chamber
202
within. A cylinder cover
203
functioning as a rear housing having a discharge chamber
203
a
and an intake chamber
203
b
therein is joined to the rear end of the cylinder block
201
a
by means of a valve plate
204
. An intake port
205
for receiving intake gas from an external refrigerant circuit (not shown) is disposed in a side wall of the cylinder cover
203
and is connected to the intake chamber
203
b
. A drive shaft
206
is disposed in a central portion of the outer shell
201
of the compressor and is rotatably supported by radial bearings
207
. A plurality of cylinder bores
208
are formed in the cylinder block
201
a
parallel to the drive shaft
206
and equidistantly spaced in a circle of fixed circumference centered on the drive shaft
206
. Consequently, a cylinder assembly is formed by the cylinder block
201
a
. Piston assemblies
209
each comprise a piston rod
209
b
and a single-headed piston
209
a
formed on the rear end of the piston rod
209
b
. A single-headed piston
209
a
is housed within each of the cylinder bores
208
so as to be free to slide and reciprocate.
A swash plate
210
is secured to the drive shaft
206
within the swash plate chamber
202
so as to rotate together with the drive shaft
206
, the pistons
209
a
being engaged by the swash plate
210
by means of shoes
211
. Furthermore, a thrust bearing
214
is disposed at the front end of a boss portion
210
a
of the swash plate
210
, that is to say, between the boss portion
210
a
and the front housing
201
b
, thrust loads acting on the swash plate
210
being supported by the thrust bearing
214
.
Discharge holes
204
a
connecting each of the cylinder bores
208
to the discharge chamber
203
a
and intake holes
204
b
connecting each of the cylinder bores
208
to the intake chamber
203
b
are disposed in the valve plate
204
. An intake valve-forming plate
212
integrally formed with a plurality of intake valves
212
a
for controlling the opening and closing of each of the intake holes
204
b
is interposed between the valve plate
204
and the cylinder block
201
a
, and a discharge valve-forming plate
213
integrally formed with a plurality of discharge valves
213
a
for controlling the opening and closing of each of the discharge holes
204
a
is interposed between the valve plate
204
and the cylinder cover
203
.
Gas passages
215
are disposed in the cylinder block
201
a
in the spaces between the plurality of cylinder bores
208
, the swash chamber
202
being connected to the intake chamber
203
b
by means of the gas passages
215
, so that blowback gas flowing into the swash chamber
202
during the process of compression by the pistons
209
a
is expelled to the intake chamber
203
b.
Moreover,
216
is a retainer,
217
is a discharge port, and
218
is a bolt joining the cylinder block
201
a
, the front housing
201
b
, and the cylinder cover
203
together.
When a single-ended swash plate compressor constructed in the above manner is activated, intake gas is directed from the external refrigerant circuit through the intake port
205
into the intake chamber
203
b
. Then, the refrigerant gas is taken from the intake chamber
203
b
through the intake holes
204
b
and intake valves
212
a
into the cylinder bores
208
and is compressed by the pistons
209
a
. The compressed refrigerant gas is expelled through the discharge holes
204
a
and the discharge valves
213
a
to the discharge chamber
203
a
and is discharged through the discharge port
217
to the external refrigerant circuit.
In a single-ended swash plate compressor constructed in the above manner, the front ends of the pistons
209
a
(left side in figure) are exposed to the swash chamber which is at intake pressure, and at the same time the rear ends of the pistons
209
a
are exposed to the cylinder bores
208
which are filled with compressed refrigerant gas, Thus, the internal pressure (intake pressure) of the swash chamber
202
acts on the front end surface of each of the pistons
209
a
, and the internal pressure of the cylinder bores
208
acts on the rear end surface of each of the pistons
209
a
.
FIG. 14
is a graph explaining the conditions in one piston and shows the changes in the internal pressure Pc in the swash plate chamber
202
and the changes in the internal pressure Pb in the cylinder bore
208
relative to the rotational angle of the swash plate
210
(in degrees). As shown in this diagram, the internal pressure Pc in the swash plate chamber
202
always remains at a practically constant low pressure, that is at the intake pressure, but the internal pressure Pb in the cylinder bore
208
fluctuates periodically between a low intake pressure and a high discharge pressure depending on the rotational angle of the swash plate
210
.
Now, thrust loads from the front end towards the rear end act on the front end surfaces of the pistons
209
a
, and thrust loads from the rear end towards the front end act on the rear end surfaces of the pistons
209
a
. Thus, the thrust load acting on the thrust bearing
214
is given by the sum of these loads acting on the pistons
209
a.
FIG. 15
is a graph explaining the axial load, and the vertical axis shows the thrust load, the direction from the rear end towards the front end being taken as positive. The number of pistons
209
a
has been taken to be six and the loads acting on all six pistons have been totalled. In
FIG. 15
, Ff indicates the thrust load acting from the front end towards the rear end due to the internal pressure in the swash chamber
202
. Fr indicates the thrust load acting from the rear end towards the front end due to the internal pressure in the cylinder bores
208
. Ft indicates the total load resulting from Ff and Fr. Since Ft is the sum of all of the loads acting on a plurality of pistons (in this case six), the amplitudes and periods of the fluctuations are small compared to those of the internal pressure in the single cylinder bore
208
shown in FIG.
14
.
Now, as can be understood from
FIGS. 14 and 15
, because the difference between the internal pressure Pb in the cylinder bores
208
and the internal pressure Pc in the swash plate chamber
202
is great, the difference between the thrust load Ff acting from the front end towards the rear end and the thrust load Fr acting from the rear end towards the front end is great, making the overall total thrust
Fujii Toshiro
Imai Takayuki
Koide Tatsuya
Murakami Kazuo
Yokomachi Naoya
Freay Charles G.
Kabushiki Kaisha Toyoda Jidoshokki Seisakusho
Morgan & Finnegan L.L.P.
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