Pumps – Condition responsive control of drive transmission or pump... – Adjustable cam or linkage
Reexamination Certificate
2002-01-07
2004-02-10
Yu, Justin (Department: 3746)
Pumps
Condition responsive control of drive transmission or pump...
Adjustable cam or linkage
C062S228500, C251S061000
Reexamination Certificate
active
06688853
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a control valve, and more particularly, to a control valve for a variable displacement compressor, such as commonly used in air conditioning systems.
DESCRIPTION OF RELATED ART
FIG. 8
schematically depicts an air conditioning system, such as that used in an automobile to provide passengers a comfortable atmosphere. Air conditioning systems typically include a compressor
100
, a condenser
102
, an expansion device
104
, and an evaporator
106
fluidly connected together by tubes or hoses
108
in which refrigerant flows. In order to condition the air before it is released to the passenger compartment, heat is removed from the air by passing the air through the evaporator
106
. This causes the refrigerant to boil and form a gas, which travels from the evaporator
106
to the compressor
100
. The compressor
100
serves as a pump for circulating the refrigerant through the entire system. In addition, the compressor
100
may increase the temperature and pressure of the refrigerant.
Vehicle air conditioning systems commonly use variable displacement compressors, which allow the adjustment of the refrigerant pumping capacity in response to the air conditioning load. The compressor
100
comprises three main chambers, which include a suction chamber
110
, a crankcase chamber
112
, and a discharge chamber
114
with a valve plate
116
separating the three chambers. This valve plate
116
contains ports fluidly coupling the suction chamber
110
to other areas of the compressor
100
.
Refrigerant flowing from the evaporator
106
enters the compressor
100
through the suction chamber
110
located in the rear head
118
of the compressor
100
. The refrigerant flows into the suction chamber
110
into a cylinder
122
through a port
120
where pistons
124
compress the refrigerant. The compressed refrigerant exits through discharge port
126
into the discharge chamber
128
coupled to the condenser
102
by a tube or hose
108
. The pressure of the refrigerant in the discharge chamber
114
always exceeds both the pressure of the refrigerant in the suction chamber
110
as well as the crankcase chamber
112
.
The pumping capacity of the pistons
124
may be adjusted by changing the inclination angle &thgr; of a swashplate
130
relative to the compressor shaft
132
. The pumping capacity corresponds to the stroke length of the piston
124
. A larger stroke length corresponds to a higher pumping capacity and a higher pressure in the discharge chamber
114
. Similarly, a lessening stroke length corresponds to a decreased pumping capacity and a lower pressure in the discharge chamber
114
. The inclination angle &thgr; of the swashplate
130
relates directly to the piston
124
stroke length.
The swashplate
130
is located in the crankcase chamber
112
and is connected by pivot
134
to the compressor shaft
132
and the pistons
124
. The angle formed between the connection point of the swashplate
130
and the rotation of the swashplate
130
represents the inclination angle &thgr;. The rotational movement of the compressor shaft
132
rotates the swashplate
130
causing the pistons
124
to reciprocate in their cylinders.
122
. The compressor shaft
132
moves responsive to the vehicle engine via a pulley
136
with the compressor shaft
132
being mounted on radial bearings
138
and shoes
140
, which allows the swashplate
130
to rotate.
The crankcase chamber
112
contains refrigerant leaked by the pistons
124
. Variable displacement of the compressor
100
is obtained by varying the crankcase chamber
112
pressure Pc relative to the suction chamber
110
pressure Ps. Changing the pressure differential (Pc−Ps) between the crankcase chamber
112
and the suction chamber
110
causes the inclination angle &thgr; of the swashplate
130
to vary, which regulates the pumping capacity of the pistons
124
.
A small pressure differential (Pc−Ps) corresponds to an increased inclination angle &thgr;. When the inclination angle &thgr; is at its maximum, the pistons
124
reciprocate at the maximum stroke thus highest compression. At this point, the air conditioning system is at its highest cooling capacity. In contrast, an increasing pressure differential (Pc−Ps) corresponds to a decreasing inclination angle &thgr;. Decreasing the inclination angle &thgr; causes the pistons
124
to de-stroke resulting in lower compression. At this point, the air conditioning system is at its lowest cooling capacity.
For example, if the pressure differential Pc−Ps is low, such as 5-15 kPa, the compressor operates at maximum stroke with the swashplate
130
at its maximum inclination angle &thgr;. In contrast, if the pressure differential Pc−Ps is high, such as 100-150 kPa, the compressor operates at minimum stroke with the swashplate
130
at its minimum inclination angle &thgr;. At this point, the swashplate
130
is nearly perpendicular to the compressor shaft
130
. A de-stroke spring
131
in
FIG. 8
is provided to force the swashplate
130
to this position when cooling capacity is not needed.
Reference is made to U.S. Pat. No. 6,146,106 illustrating a control valve consistent with the prior art.
FIG. 9
schematically illustrates the control valve
144
of the '106 patent which may be used with the compressor schematically illustrated in FIG.
8
. The variable displacement compressor
100
uses a control valve
144
to regulate the pressure differential (Pc−Ps). The suction chamber
110
pressure Ps changes as certain parameters in the car change, such as compressor speed. This has a direct effect on the pressure differential (Pc−Ps). The control valve
144
adjusts the pressure Pc in the crankcase chamber
112
relative to the pressure Ps in the suction chamber
110
in order to reach an equilibrium point. The equilibrium point is the set pressure differential (Pc−Ps) value of the control valve. By maintaining a constant pressure differential (equilibrium point), the cooling air entering the passenger compartment stays relatively constant regardless of changing parameters.
The control valve
144
regulates the flow of refrigerant from the discharge chamber
114
having a discharge chamber pressure Pd to the crankcase chamber
112
relative to the pressure of the refrigerant in the suction chamber
110
. The control valve
144
contains a bellows
146
, which compresses or expands as a result of an increase or decrease, respectively, of the fluid in the suction chamber
110
. When there is a high pressure differential Pc−Ps, the control valve
144
allows more refrigerant to flow from the discharge chamber
114
into the crankcase chamber
112
than can escape to the suction chamber
110
through flow passage
148
. The flow passage
148
is sized so that the amount of flow from crankcase chamber
112
to suction chamber
110
is less than the flow from the discharge chamber
114
to the crankcase chamber
112
. As a result, the crankcase chamber pressure Pc increases, causing the compressor
100
to de-stroke. When the compressor
100
de-strokes, the suction chamber pressure Ps increases as a result of reduced refrigerant flow out of the compressor
100
. The bellows
146
of the control valve
144
responds accordingly, reducing the flow into the crankcase chamber
112
until equilibrium is reached.
The bellow
146
connects to a poppet
150
or other type of member for regulating the flow from the discharge chamber
114
to the crankcase chamber
112
. When the compressor
100
begins to de-stroke as the result of a high-pressure differential, the suction chamber
110
pressure increases. The fluid from the suction chamber
110
acts on the exterior of the bellows
146
. An increasing suction chamber
110
pressure causes the bellows
146
to decrease in length. This moves the poppet
150
in a direction to reduce the flow from the discharge chamber
114
to the crankcase chamber
112
until the poppet
150
rests at the equilibrium point. Traditionally, the equi
Burkett Michael J.
Page William
Frederick Kris T.
Honeywell International , Inc.
Rodriguez William H.
Yu Justin
LandOfFree
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