Expansible chamber devices – Relatively movable working members – Interconnected with common rotatable shaft
Reexamination Certificate
1999-09-07
2001-06-19
Ryznic, John E. (Department: 3745)
Expansible chamber devices
Relatively movable working members
Interconnected with common rotatable shaft
Reexamination Certificate
active
06247391
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a coil spring positioner. The present invention also pertains to a compressor for vehicle air-conditioning systems having the spring positioner.
Generally, existing structures for positioning spring ends include an annular groove. A stopper ring is fixed in the annular groove to project inward. One end of a coil spring abuts against the projecting part of the stopper ring, which positions the coil spring.
In a compressor having the above-described structure, as shown in
FIG. 12
, a crank chamber
203
is formed between a front housing member
201
and a cylinder block
202
. In the crank chamber
203
, a drive shaft
204
is supported by the front housing member
201
and the cylinder block
202
. The cylinder block
202
, which constitutes part of the housing, includes a plurality of cylinder bores
202
a
. A piston
206
is accommodated in each cylinder bore
202
a.
In the crank chamber
203
, a swash plate
205
, which serves as a drive plate, is supported by the drive shaft
204
to integrally rotate and to incline with respect to the drive shaft. The swash plate
205
is coupled to a lug plate
217
through a hinge mechanism
216
, and the lug plate
217
is fixed to the drive shaft
204
. Each piston
206
is coupled to the swash plate
205
through a pair of shoes
222
. A valve plate
207
is located between the cylinder block
202
and a rear housing member
208
.
The rotation of the swash plate
205
is converted into reciprocation of each piston
204
through the corresponding pair of shoes
222
. The reciprocation compresses refrigerant gas that is drawn to each cylinder bore
202
a
from a suction chamber
209
through the valve plate
207
and discharges compressed refrigerant gas to a discharge chamber
210
.
A bleed passage
224
connects the crank chamber
203
to the discharge chamber
210
. A control valve
218
is located in the bleed passage
224
and adjusts the flow rate of refrigerant gas. The difference between the pressure in the crank chamber
203
and the pressure in the cylinder bore
202
a
is varied by the control valve
218
. The inclination angle of the swash plate
205
is varied in accordance with the pressure difference, which controls the displacement of the compressor.
The variable displacement compressor of this kind is coupled to an external drive source Eg such as vehicle engines through an electromagnetic clutch
223
.
A support spring
212
abuts against the rear end of the drive shaft
204
through a thrust bearing
211
. The support spring
212
is a cylindrical coil spring. The support spring
212
urges the drive shaft
204
axially. The support spring
212
prevents chattering of the drive shaft
204
in the axial direction due to measurement error of the parts. The force of the support spring
212
causes the drive shaft
204
to contact the thrust bearing
211
.
A center bore
213
is formed substantially in the center of the cylinder block
202
. A first annular groove
214
is formed in the center bore
213
, and a stopper ring
215
is fitted in the annular groove
214
. The support spring
212
engages and is located between the rear surface of a race
211
a
of the thrust bearing
211
and the stopper ring
215
. In other words, the rear end
212
a
of the support spring
212
is positioned with respect to the cylinder block
202
by abutting against the stopper ring
215
.
A second annular groove
220
is formed in the drive shaft
204
between the swash plate
205
and the cylinder block
202
. A stopper ring
221
is fitted in the second annular groove
220
. A limit spring
219
engages and is located between the rear surface
205
a
of the swash plate
205
and the stopper ring
221
. The limit spring
219
is a cylindrical coil spring. The limit spring
219
resists a force that urges the swash plate
205
toward the rear housing member
202
. When the limit spring
219
is compressed to its minimum length, the swash plate
205
is positioned at its minimum inclination angle. The rear end
219
a
of the limit spring
219
is positioned with respect to the drive shaft
204
by the stopper ring
221
.
In the prior art spring positioners of
FIG. 12
, the position of each spring end is determined by a stopper ring. Accordingly, annular grooves for securing the stopper rings are required.
In the compressor of
FIG. 12
, spaces for the annular grooves
214
,
220
for installing the support spring
212
, the limit spring
219
, and the stopper rings
215
,
221
are limited. That is, large spaces are not provided between the race
211
a
and the stopper ring
215
or between the swash plate
205
and the stopper ring
221
. To fully meet the force requirements of each spring
212
,
219
, the springs
212
,
219
must be made of wires having a relatively large diameter. However, since the spaces for the springs
212
,
219
are relatively small, springs made of relatively small-radius wires are actually used. Therefore, the springs
212
,
219
may not have the desired operating characteristics.
A compression load in the direction of the axis of the drive shaft
204
is continually applied to the springs
212
,
219
. The support spring
212
is supported and compressed between the race
211
a
and the stopper ring
215
. The limit spring
219
is supported and compressed between the swash plate and the stopper ring
221
. Therefore, radial movement of each spring
212
,
219
is limited.
If the compression load is reduced, each spring
212
,
219
radially moves as the drive shaft
204
rotates. As a result, each spring
212
repeatedly contacts the inner surface of the center bore
213
and peripheral surface of the drive shaft
204
. This generates noise and vibration and wears the springs
212
,
219
, which shortens the life of the compressor.
SUMMARY OF THE INVENTION
An objective of the present invention is to provide a structure for positioning springs that have enough strength to prevent the noise and vibration of a compressor. Another objective of the present invention is to provide a more durable compressor that includes the spring positioning structure.
To achieve the above objectives, the present invention provides a positioning structure for determining the position of one of two ends of a coil spring relative to a support. The coil spring has a large-diameter end and a small-diameter end. The small-diameter end is opposite to the large-diameter end. Either the large-diameter end or the small-diameter end serves as a positioning end. The support has an annular groove, which is substantially coaxial to the coil spring. The positioning end engages the annular groove, which fixes the position of the positioning end. The positioning end is elastically urged toward the annular groove.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.
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Enokijima Fuminobu
Murao Kazushige
Kabushiki Kaisha Toyoda Jidoshokki Seisakusho
Morgan & Finnegan , LLP
Ryznic John E.
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