Pumps – Condition responsive control of drive transmission or pump... – Adjustable cam or linkage
Reexamination Certificate
2000-05-31
2002-03-12
Koczo, Michael (Department: 3746)
Pumps
Condition responsive control of drive transmission or pump...
Adjustable cam or linkage
C137S469000, C137S538000
Reexamination Certificate
active
06354810
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a check valve. The check valve is suitable for use in a refrigerating circuit having a variable capacity type compressor or in the compressor itself. In particular, the check valve is useful to realize a discharge capacity of substantially 0%, in the case where the compressor is operatively coupled to an external drive source in a clutchless manner.
2. Description of the Related Art
A compressor is incorporated in, for example, a refrigerating circuit used for a car air-conditioning system to compress the coolant gas. Such a compressor is usually operatively coupled to a car engine, as an external drive source, via a magnetic clutch by which the compressor is connected to the engine only when a refrigerating load occurs to effect a compressing operation. However, if the magnetic clutch is provided in the compressor, problems arise in that a total weight increases, a production cost increases, and a power is consumed for operating the magnetic clutch. To eliminate such a drawback, there has recently been a proposal of a so-called clutchless swash plate type variable capacity type compressor which is directly coupled to an external drive source without a magnetic clutch interposed between the engine and the compressor, so that the compressor is normally driven while the external drive source is operating (for example, refer to Japanese Unexamined Patent Publication (Kokai) No. 10-205446).
In the compressor disclosed in the above-described publication, a swash plate is arranged so that it is tiltable with respect to a drive shaft directly coupled to the external drive source, and a minimum tilting angle of the swash plate is maintained to provide a discharge capacity which is not zero %. Therefore, in this compressor, it is possible to realize reduction of weight as well as to minimize power consumption of the external drive source, by directly coupling the compressor to the drive source without a magnetic clutch.
Also, a check valve is arranged in this compressor, as shown in
FIG. 14
of the attached drawings. That is, a housing
90
has a discharge chamber
91
, an accommodation chamber
92
adjacent to the discharge chamber
91
and an outer discharge passage
93
for fluid communication between the accommodation chamber
92
and a condenser (not shown) of a refrigerating circuit, and a check valve
94
together with an O-ring
95
and a circlip
96
is arranged in the accommodation chamber
92
to prevent a coolant gas from reversely flowing into the accommodation chamber
92
. More specifically, the check valve
94
comprises a valve seat member
81
, a case
82
fitted to the valve seat member
81
, a valve element
83
axially slidably arranged in the case
82
, and a spring
84
for biasing the valve element
83
toward the valve seat member
81
in the case
82
, as shown in
FIGS. 15 and 16
.
A flow passage
81
a
is formed through the valve seat member
81
in communication, on one hand, with the discharge chamber
91
and, on the other hand, with the interior of the case
82
, and a valve seat
81
b
is formed in the valve seat member
81
around the outlet of the flow passage
81
a
. Also, an annular groove
81
c
is provided in the outer peripheral surface of the valve seat member
81
around the valve seat
81
b.
Projections
82
a
are formed in the inner wall of the open-side end of the case
82
to fit in the annular groove
81
c
, and communication holes
82
b
are formed in the outer peripheral wall of the case
82
on the axially opposite side of beyond the valve seat
81
b.
The valve element
83
has a seal surface
83
a
, which is in contact with the valve seat
81
b
when the valve element
83
slides in one direction toward the valve seat
81
b
and leaves the valve seat
81
b
when it slides in the other direction, and an outer peripheral surface
83
b
perpendicular to the seal surface
83
a.
As shown in
FIG. 15
, in this check valve
94
, when the compressor is stopped due to the stopping of the external drive source, a high pressure coolant gas on the side of the condenser and the biasing force of the spring
84
are applied to the valve element
83
to cause the latter to slide in the one direction. Thus, the seal surface
83
a
is seated on the valve seat
81
b
of the valve seat member
81
to disconnect the flow passage
81
a
from the communication holes
82
b
. Accordingly, the high pressure coolant gas on the side of the condenser is prevented from reversely flowing into the discharge chamber
91
.
On the other hand, as shown in
FIG. 16
, during the operation of the compressor, the high pressure coolant gas in the discharge chamber
91
pushes the valve element
83
through the flow passage
81
a
, and overcomes the biasing force of the spring
84
to cause the valve element
83
to slide in the other direction. Accordingly, the seal surface
83
a
leaves the valve seat
81
a
of the valve seat member
81
to allow the flow passage
82
b
to be connected to the communication holes
82
b
. Thus, the high pressure coolant gas in the discharge chamber
91
is delivered to the condenser.
Therefore, in the compressor with such a check valve
94
, it is possible to prevent the coolant gas from reversely flowing when the compressor is stopped, so it is possible to prevent the liquid coolant from being held in the compressor and to avoid an excessive temperature or pressure rise in the compressor, as well as to improve durability of the compressor.
Also, in the compressor having a flow passage extending from the discharge chamber
91
to the crank chamber (not shown), it is possible to suppress the pressure rise in the crank chamber when the compressor is stopped, which allows a quick increase in the tilting angle of the swash plate and a quick recovery of the high capacity condition upon starting the operation of the compressor, resulting in a rapid appearance of the refrigerating effect.
However, according to the experimental result considered by the inventors of the present case, it has been found that a pressure loss is apt to occur soon after the check valve is opened by the movement of the valve element
83
away from the valve seat
81
b
and the flow passage
81
a
starts to communicate with the communication holes
82
b
, since in this check valve
94
, the case
82
and the valve element
83
are made as plastic molded products to reduce the manufacturing cost and the weight, and the outer peripheral surface
83
b
of the valve element
83
perpendicularly extending from the seal surface
83
a
thereof is formed in a simple cylindrical shape.
That is, the case
82
and the valve element
83
as resin molded products form a relatively large clearance between them since tolerances are required. As shown in
FIG. 17A
, when the valve, in which the valve element
83
is seated on the valve seat
81
b
, is fully closed, a fluid such as a coolant gas will not leak from the flow passage
81
a
even if the outer peripheral surface
83
b
of the valve element
83
is formed in a simple cylindrical shape, since the outlet opening of the flow passage
81
a
is closed by the seal surface
83
a
. Also, as shown in
FIG. 17C
, when the valve, in which the valve element
83
is lifted to the top dead center, is fully opened, there is no problem occurring due to an increase in the back pressure behind the valve element
83
, since the fluid flows out from the flow passage
81
a
to the exterior of the case
82
via the largely opened communication hole
82
b
rather flowing into a gap between the inner peripheral surface of the case
82
and the outer peripheral surface
83
b
of the valve element
83
. However, as shown in
FIG. 17B
, when the valve is at an initial stage of opening in which the valve element
83
slightly leaves the valve seat
81
b
, the fluid which flows out from the flow passage
81
a
passes through the clearance between the inner peripheral surface of the case
82
and the outer peripheral surface
83
b
of the valve element
83
to the back s
Imanishi Takeshi
Kaneshige Yuji
Kayukawa Hiroaki
Kimura Kazuya
Minami Kazuhiko
Kabushiki Kaisha Toyoda Jidoshokki Seisakusho
Koczo Michael
Woodcock & Washburn LLP
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