Pumps – Condition responsive control of drive transmission or pump... – Adjustable cam or linkage
Reexamination Certificate
2000-02-28
2001-07-03
Thorpe, Timothy S. (Department: 3746)
Pumps
Condition responsive control of drive transmission or pump...
Adjustable cam or linkage
C417S454000, C137S454600, C137S625650
Reexamination Certificate
active
06254356
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a fitting structure for a control valve for controlling a discharge capacity in a variable capacity compressor used for a car air conditioner, for example.
2. Description of the Related Art
The following construction is known for a variable capacity compressor (hereinafter called merely the “compressor”) of the kind described above. A crank chamber is defined and partitioned inside a housing, and a drive shaft is rotatably supported by the housing in such a fashion as to cross, transversely, the crank chamber. A swash plate is supported by the drive shaft through a rotary support member inside the crank chamber in such a fashion as to be capable of integrally rotating and rocking. A plurality of pistons are engaged with to the outer peripheral portion of the swash plate. Cylinder bores are formed in a cylinder block, that constitutes a part of the housing, equiangularly arranged around the drive shaft. The head of each piston is fitted into each cylinder bore and is allowed to reciprocate.
When the drive shaft is driven for rotation by driving force transmitted thereto from an external driving source such as a car engine through a belt, or the like, the swash plate is rotated through the rotary support. The rotary motion of this swash plate is converted to the reciprocating motion of each piston. In consequence, a series of compression cycles such as suction of a refrigerant gas into the cylinder bores, compression of the refrigerant gas so sucked and discharge of the compressed refrigerant gas from the cylinder bores are repeated.
In the compressor described above, a discharge pressure region, in which the compressed refrigerant gas stays temporarily, and the crank chamber are connected through an supply passage having a control valve. The control valve is fitted into a fitting hole formed in a rear housing that constitutes a part of the housing of the compressor. This control valve plays the roles of changing an open area in the supply passage and regulating the feeding amount of the high-pressure discharge refrigerant gas into the crank chamber. When the feeding amount of the discharge refrigerant gas is adjusted, the internal pressure of the crank chamber is varied, and the pressure difference between the pressure of the crank chamber piston and the pressure of the cylinder bores through the piston is varied, too. As the pressure difference is varied, the tilt angle of the swash plate is varied, and the stroke of each piston, that is, the discharge capacity, is regulated.
The control valve shown in
FIG. 7
is known as a control valve
200
of this kind. The control valve
200
includes a valve body
202
for opening and closing the supply passage
201
described above, an electromagnetic driving portion
203
for changing the load applied to the valve body
202
in accordance with an input current value, and a pressure-sensitive mechanism
205
for changing the load applied to the valve body
202
in accordance with the pressure of the suction pressure region of the compressor. In this control valve, the overall force of the impressed load from the pressure-sensitive mechanism
205
and the impressed load from the electromagnetic driving portion
203
operates the valve body
202
, and the open area of the supply passage
201
is decided.
Gas chambers such as a valve chest
207
for storing the valve body
202
and a pressure-sensitive chamber
208
for storing the pressure-sensitive mechanism
205
are defined and partitioned inside the valve housing
206
of the control valve
200
. A plurality of step portions
209
a
to
209
c
are defined in the valve housing
206
. A pressure-sensitive hole
210
that communicates with the pressure-sensitive chamber
208
is open to the first step portion
209
a
. A valve port
211
that can be connected and disconnected to the valve chest
207
by the valve body
202
is open to the second step portion
209
b
. An inlet port
212
that communicates with the valve chest
207
is open to the third step portion
209
c.
Each of these step portions
209
a
to
209
c
is partitioned hermetically by an O-ring
214
while the control valve
200
is fitted to the fitting hole
213
of the compressor. This is because different pressures are guided to the pressure-sensitive hole
210
, the valve port
211
and the inlet port
212
, respectively.
A taper surface
216
the diameter of which decreases progressively towards the bottom of the fitting hole
213
is formed in the fitting hole
213
in such a fashion as to correspond to a holding portion
215
of the O-ring
214
as shown in
FIGS. 5B and 7
. As the O-ring
214
passes over the taper surface
216
during the fitting operation of the control valve, it is compressed in a predetermined quantity.
Incidentally, the compressor is mounted in the proximity of the engine inside the car engine room. The mounting space of the compressor inside the engine room is limited, and there has been a strong requirement for reducing the size of the compressor, particularly the requirement for reducing its projecting distance from the outer periphery in the diametric direction of the housing
217
.
In the compressor having the conventional construction described above, its control valve
200
includes the electromagnetic driving portion
203
and the pressure-sensitive mechanism
205
. Therefore, it is elongated in the axial direction. As indicated by two-dot-chain line in
FIG. 3
, the control valve
200
is fitted while its proximal end portion protrudes from the outer periphery of the housing
217
of the compressor. When this protruding distance is great, the control valve
200
interferes with the car engine or other auxiliary machinery, and mountability of the compressor to the car is poor.
To cope with this problem, the full length of the control valve
200
in the axial direction may be reduced. In this case, the reduction of the length in the axial direction is limited because the electromagnetic driving portion
203
and the pressure-sensitive mechanism
205
have to apply predetermined impressed loads to the valve body
202
inside the control valve
200
. In other words, if the length of electromagnetic driving portion
203
and the pressure-sensitive mechanism
205
are greatly decreased in the axial direction, the predetermined impressed loads are likely to be insufficient, and the regulation capability of the valve body
202
of adjusting the open area to the supply passage
201
may drop. In consequence, stability of discharge capacity control in the compressor may drop.
Therefore, the length in the axial direction must be reduced at the intermediate portion between the electromagnetic driving portion
203
and the pressure-sensitive mechanism
205
in the valve housings
206
. In this case, the width of the second and third step portions
209
b
and
209
c
becomes small. Consequently, the distances between the O-rings
214
that separate them and the distances between the pressure-sensitive hole
210
, the valve port
211
and the inlet port
212
opening to the step portions
209
a
to
209
c
become short, too. The distances between the taper surfaces
216
inside the fitting hole
213
become short, as well. The requirement for machining accuracy of the pressure detecting passage
218
and the supply passage
201
that open to oppose the pressure-sensitive hole
210
, the valve port
211
and the inlet port
212
on the inner peripheral surface of the fitting hole
213
, becomes higher with the result that the production cost of the compressor becomes higher.
A predetermined open area must be secured, in some cases, in each of the supply passage
201
and the pressure detecting passage
218
in order to restrict an excessive pressure loss. In such a case, a part of each passage extends over the taper surface
216
. When a part of the pressure detecting passage
218
or the supply passage
201
is open over the taper surface
216
, the O-ring
214
is damaged when it passes over the taper surface
216
wh
Kawaguchi Masahiro
Kumazawa Shingo
Nakaima Hiroyuki
Yamada Kiyohiro
Hayes E D
Kabushiki Kaisha Toyoda Jidoshokki Seisakusho
Thorpe Timothy S.
Woodcock Washburn Kurtz Mackiewicz & Norris LLP
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