Refrigeration – Automatic control – Refrigeration producer
Reexamination Certificate
2002-07-11
2003-04-22
Tapolcai, William E. (Department: 3744)
Refrigeration
Automatic control
Refrigeration producer
C236S09200D, C137S901000
Reexamination Certificate
active
06550262
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
This invention relates to an expansion valve unit, and more particularly to an expansion valve unit which controls the quantity of refrigerant flowing into an evaporator in a refrigeration cycle according to the temperature and pressure of refrigerant sent out from the evaporator to a compressor in the refrigeration cycle.
(2) Description of the Related Art
In an air conditioning system installed on an automotive vehicle, a refrigeration cycle is constructed in which high-temperature and high-pressure gaseous refrigerant compressed by a compressor is condensed by a radiator, and a high-pressure liquid refrigerant is adiabatically expanded by an expansion valve to obtain a low-temperature and low-pressure refrigerant, which is evaporated in an evaporator, and then returned to the compressor. The evaporator which is supplied with the low-temperature refrigerant exchanges heat with air in the compartment of the vehicle, thereby performing a cooling operation.
The expansion valve is comprised of a temperature-sensing chamber which senses temperature changes of the refrigerant in a low-temperature refrigerant passage on the outlet side of the evaporator, to have the pressure therein increased and decreased, and a valve mechanism which is actuated by the pressure increased and decreased in the temperature-sensing chamber for control of the flow rate of the refrigerant supplied to the inlet of the evaporator. The temperature-sensing chamber is connected to a temperature-sensing tube whose distal end portion is fixed to a refrigerant piping on the outlet side of the evaporator in a manner brought into intimate contact therewith, for sensing the temperature of the refrigerant at the outlet of the evaporator.
It should be noted that an expansion valve originally detects not only the temperature but also the pressure of the refrigerant at the outlet of an evaporator so that the valve mechanism may be controlled also in response to changes in the pressure. There is a demand for reducing of the manufacturing costs of such an expansion valve. To meet the demand, the expansion valve capable of sensing only the temperature of the refrigerant at the outlet of the evaporator has been developed, as described hereinabove. The expansion valve dispenses with a connecting portion for connecting a refrigerant piping on the outlet side of the evaporator to a refrigerant piping extending to the compressor, thereby reducing the manufacturing costs of the expansion valve. This configuration is based on the fact that when the refrigerant delivered from the expansion valve passes through the evaporator, its pressure loss in the evaporator is approximately constant, so that a pressure obtained by subtracting the pressure loss from the pressure of refrigerant at the outlet of the expansion valve can be regarded as the pressure of the refrigerant at the outlet of the evaporator.
Even in the temperature-sensing type expansion valve which dispenses with connection between the refrigerant piping on the outlet side of the evaporator and the refrigerant piping to the compressor, described above, it is desired to further reduce both the assembling cost and parts cost. The present applicant already proposed in Japanese Patent Application No. 2000-353672 an expansion valve configured such that a valve casing is formed by expanding a portion of piping, and an expansion valve unit comprised of a temperature-sensing chamber and a valve mechanism which provide minimum functions of the expansion valve is mounted in the valve casing, thereby reducing assembling cost and parts cost. After that, the present assignee proposed in Japanese Patent Application No. 2001-119686 an expansion valve configured to suppress flowing noises generated by expansion of the refrigerant, as an improvement over the above type of expansion valve. In the following, description will be given of an example of the construction of the expansion valve of a low noise type.
FIG. 6
is a longitudinal sectional view showing an example of the construction of the conventional expansion valve.
FIG. 7
is a cross-sectional view taken on line a—a of FIG.
6
.
The expansion valve is comprised of a valve casing
103
which is formed by enlarging an end portion of a low-pressure refrigerant piping
101
connected to the refrigerant inlet of an evaporator and joining integrally a high-pressure refrigerant piping
102
connected to a receiver to a side portion of the enlarged end portion by aluminum welding and an expansion valve unit
104
inserted into the valve casing
103
from an open end thereof. Although not particularly shown, the expansion valve unit
104
is fixed to the open end portion of the valve casing
103
such that the expansion valve unit
104
is inhibited from being drawn out from the valve casing
103
.
The expansion valve unit
104
is comprised of a temperature-sensing chamber
105
and a valve mechanism integrally formed with the temperature-sensing chamber
105
actuated by internal pressure increased and decreased in the temperature-sensing chamber
105
, for opening and closing a high-pressure refrigerant passage. The temperature-sensing chamber
105
has an inside thereof partitioned by a diaphragm
106
to fill the inside with the refrigerant gas therein, and a top thereof connected to a temperature-sensing tube
107
such that the temperature-sensing chamber
105
and the temperature-sensing tube
107
portion are communicated with each other. The temperature-sensing tube
107
has an end in contact with an outlet pipe of the evaporator, for sensing the temperature of the refrigerant at the outlet of the evaporator.
The valve mechanism of the expansion valve unit
104
has a high-pressure refrigerant passage
109
formed in a body
108
in a manner such that the passage
109
extends from a longitudinally approximately central side portion toward the center of the body
108
. The expansion valve unit
104
has a low-pressure refrigerant passage
110
axially formed in a lower end portion thereof. Along the axis of the body
108
, a hole serving as a valve hole is formed between the high-pressure refrigerant passage
109
and the low-pressure refrigerant passage
110
, for communication between the high-pressure refrigerant passage
109
and the low-pressure refrigerant passage
110
. An end of the hole on a low-pressure refrigerant passage side serves as a valve seat
111
. Arranged in a manner opposed to the valve seat
111
is a spherical valve element
112
which is urged toward the valve seat
111
by a conical spring
113
. The conical spring
113
has a base portion supported by an adjusting screw
114
screwed to be fitted in an inner wall of the low-pressure refrigerant passage
110
. The adjusting screw
114
is used for adjusting a set value allowing the valve element
112
to start to be opened.
A shaft
115
is axially movably inserted along the axis of the body
108
at a location below the temperature-sensing chamber
105
. The shaft
115
has one end thereof brought into abutment with or welded to the valve element
112
, and the other end thereof brought into abutment with a lower surface of the diaphragm
106
via a disc
116
. The shaft
115
has an upper end portion thereof positioned on the axis of the body
108
by a holder
117
.
Further, the body
108
has a communication passage
118
formed therein for equalizing the pressure in a space below the diaphragm
106
of the temperature-sensing chamber
105
with the pressure in the low-pressure refrigerant passage
110
. The space below the diaphragm
106
is sealed from the high-pressure refrigerant passage
109
by an O ring
119
arranged on the shaft
115
.
In the expansion valve constructed as above, when refrigerant is supplied from the high-pressure refrigerant piping
102
, the refrigerant passes through a gap formed between the valve seat
111
and the valve element
112
, thereby undergoing adiabatic expansion, and is delivered through the low-pressure refrigerant passage
110
to the evaporator by
Patterson, Thuente, Skaar & Christensen LLC
TGK Co. Ltd.
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