Pumps – Condition responsive control of drive transmission or pump... – Adjustable cam or linkage
Reexamination Certificate
1998-01-21
2001-03-13
Kamen, Noah P. (Department: 3747)
Pumps
Condition responsive control of drive transmission or pump...
Adjustable cam or linkage
C417S213000
Reexamination Certificate
active
06200105
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a displacement control valve incorporated in variable displacement compressors that are used in vehicle air conditioners and to a method of manufacture. More particularly, the present invention relates to a displacement control valve that controls the difference between the pressure in a crank chamber and the pressure in cylinder bores, and includes a mechanism for changing a target suction pressure of the compressor.
A typical variable displacement compressor has a supply passage for connecting a discharge chamber with a crank chamber and a displacement control valve located in the supply passage. The displacement control valve controls the opening amount of the supply passage for adjusting the amount of highly pressurized refrigerant gas that is supplied to the crank chamber from the discharge chamber. The pressure in the crank chamber is changed, accordingly. This alters the difference between the pressure in the crank chamber and the pressure in cylinder bores. Changes in the pressure difference adjust the inclination of a swash plate of the compressor and ultimately change the displacement of the compressor.
Japanese Unexamined Patent Publication No 3-23385discloses such a displacement control valve
101
as illustrated in FIG.
7
. The control valve
101
includes a housing
102
and a solenoid
111
, which is secured to the bottom of the housing
102
. The housing
102
, together with an inner wall of the compressor, defines a high pressure chamber
109
. The housing
102
also includes a low pressure chamber
107
defined in its lower portion and an intermediate pressure chamber
110
located between the chambers
109
and
107
. The low pressure chamber
107
accommodates a bellows
108
. A valve seat
103
is located between the high pressure chamber
109
and the intermediate chamber
110
. The valve seat
103
has a valve hole
104
. The upper end of the bellows
108
is coupled to a rod
106
, which extends through the valve hole
104
. The distal end of the rod
106
is coupled to a valve body
105
, which faces the valve seat
103
to open and close the valve hole
104
. In other words, the rod
106
connects the valve body
105
with the bellows
108
. The low pressure chamber
107
communicates with suction pressure Ps of the compressor. The suction pressure Ps therefore expands or collapses the bellows
108
. The high pressure chamber
109
communicates with a discharge chamber of the compressor by the upstream portion of the supply passage. Therefore, the discharge pressure Pd is introduced to the high pressure chamber
109
. The intermediate pressure chamber
110
communicates with the high pressure chamber
109
by the valve hole
104
and is connected to the crank chamber by the down stream portion of the supply passage.
A solenoid
111
is secured to the bottom of the housing
102
. A fixed steel core
113
is provided at the upper portion of the solenoid
111
. A steel plunger
112
is arranged in the solenoid
111
and moves along the axis of the plunger
112
. A rod
112
a
is coupled to the plunger
112
and extends through the core
113
. A coil
114
is wound about the plunger
112
and the fixed core
113
. The top end of the rod
112
a
is attached to the inner wall of the bellows
108
. A spring
115
extends between the bottom end of the plunger
112
and the bottom of the solenoid
111
. The spring
115
urges the plunger
112
upward. That is, the spring
115
urges the valve body
105
in a direction separating the valve body
105
from the valve seat
103
to open the valve hole
104
.
An external control unit (not shown) sends electric current to the coil
114
. The magnetic attractive force produced between the plunger
112
and the fixed core
113
is varied by the magnitude of the current from the control unit. The magnitude of the force that pushes the plunger
112
upward, or the force for separating the valve body
105
from the valve seat
103
, corresponds to the magnitude of the attraction force. When the solenoid
111
is excited, increasing the suction pressure Ps contracts the bellows
108
and lowers the plunger
112
. This causes the valve body
105
and ultimately closes the valve hole
104
. Contrarily, lowering the suction pressure Ps expands the bellows
108
and lifts the valve body
105
. This opens the valve hole
104
. In this manner, the opening area between the valve body
105
and the valve hole
104
is adjusted in accordance with the suction pressure Ps. The level of the suction pressure Ps required for lowering the valve body
105
, that is, for moving the valve body
105
toward the valve seat
103
, is varied in accordance with the attraction force produced between the armature
112
and the retainer
113
.
The above described prior art control valve
101
has the following disadvantages.
If a vehicle having the above compressor, which is connected to an external refrigerant circuit, is caught in a traffic jam in summer, the heat exchange capacity of the condenser in the circuit is significantly lowered. In this case, the valve body
105
closes the valve hole
104
and the compressor operates at the maximum displacement. This results in an extremely high discharge pressure Pd and causes the pressure Pc in the crank chamber to approach the lower suction pressure Ps. In this state, the upper surface of the valve body
105
receives the high discharge pressure Pd and the lower surface of the valve body
105
receives the pressure in the intermediate pressure chamber
110
, or the pressure Pc in the crank chamber. A force based on the difference between the pressures Pd and Pc strongly presses the valve body
105
against the valve seat
103
. The valve body
105
is therefore not easily moved in a direction to open the valve hole
104
and the responsiveness of the valve body
105
to the suction pressure Ps is degraded In other words, the valve body
105
does not respond to subtle changes in the auction pressure Pa.
If the cooling load falls when the compressor is operating at the maximum displacement, the displacement must be decreased. In order to decrease the displacement, the opening area between the valve body
105
and the valve hole
104
must be enlarged. The valve body
105
thus must be moved by a force that is greater than the force resulting from the difference between the discharge pressure Pd and the crank chamber pressure Pc. That is, the attractive force between the plunger
112
and the fixed core
113
must be increased for enlarging the opening area between the valve body
105
and the valve hole
104
. In order to increase the attractive force, the solenoid
111
must be larger. A large solenoid
111
consumes a relatively large amount of electric power and thus increases the load on the alternator.
SUMMARY OF THE INVENTION
Accordingly, it is an objective of the present invention to provide a variable displacement compressor control valve that accurately controls the opening of a valve hole by a valve body and a method of manufacture.
Another objective of the present invention is to provide a variable displacement compressor control valve that has a compact solenoid and a method of manufacture.
To achieve the foregoing and other objectives and in accordance with the purpose of the present invention, a control valve for adjusting the amount of gas flowing in a gas passage in accordance with an operating pressure applied to the control valve is proposed. The control valve includes a housing, a movable valve body, a reacting member, a first rod, a solenoid and a second rod. The housing includes a valve hole and a valve chamber located in the gas passage. The valve hole communicates with the valve chamber. The movable valve body is located in the valve chamber in close proximity to the valve hole. The valve body restricts the valve hole. The reacting member reacts to the operating pressure. The first rod is located between the reacting member and the valve body to transmit the reaction of the reacting member to the valve body. The so
Kawaguchi Masahiro
Kubo Hiroshi
Murase Masakazu
Suitou Ken
Gimie Mahmoud M
Kabushiki Kaisha Toyoda Jidoshokki Seisakusho
Kamen Noah P.
Morgan & Finnegan L.L.P.
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