Thermal expansion valve

Details Thermal expansion valve Thermal expansion valve

2001-07-10

2002-11-05

Tapolcai, William E. (Department: 3744)

Automatic temperature and humidity regulation

Thermostatic

With pressure control

C062S225000

Reexamination Certificate

active

06474560

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a thermal expansion valve used in a refrigeration cycle.
DESCRIPTION OF THE RELATED ART
The example of a thermal expansion valve conventionally used in a refrigeration cycle is disclosed in Japanese Patent Laid-Open Publication No. 5-322380.
In
FIG. 5
, a prism-shaped valve body
510
comprises a first refrigerant passage
514
including an orifice
516
, and a second refrigerant passage
519
, mutually independent from one another. One end of the first refrigerant passage
514
is communicated to the entrance of an evaporator
515
, and the exit of the evaporator
515
is communicated through the second refrigerant passage
519
, a compressor
511
, a condenser
512
and a receiver
513
to the other end of the first refrigerant passage
514
. A bias means
517
which is a bias spring biasing a sphere-shaped valve means
518
is formed to a valve chamber
524
communicated to the first refrigerant passage
514
, and the valve means
518
is driven toward or away from the orifice
516
. Further, the valve chamber
524
is sealed by a plug
525
, and the valve means
518
is biased through a support member
526
. A power element
520
including a diaphragm
522
is fixed to the valve body
510
adjacent to the second refrigerant passage
519
. An upper chamber
520
a
formed to the power element
520
defined by the diaphragm
522
is maintained airtight, with temperature-corresponding working fluid filled thereto.
A small pipe
521
extending out from the upper chamber
520
a
of the power element
520
is used to degasify the upper chamber
520
a
and to fill the temperature-corresponding working fluid to the upper chamber
520
a
, before the end of the pipe is sealed. One large-diameter end of a valve drive member
523
functioning as the heat-sensing driven member positioned within the valve body
510
extending from the valve means
518
and penetrating through the second refrigerant passage
519
is positioned in the lower chamber
520
b
of the power element
520
, contacting the diaphragm
522
. The valve drive member
523
transmits the temperature of the refrigerant vapor exiting the evaporator
515
and flowing through the second refrigerant passage
519
to the temperature-corresponding working fluid filled to the upper chamber
520
a
of the power element
520
, which generates a working gas with a pressure corresponding to the transmitted temperature. The lower chamber
520
b
is communicated to the second refrigerant passage
519
through the space formed around the valve drive member
523
within the valve body
510
.
Accordingly, the diaphragm
522
of the power element
520
uses the valve drive member
523
to adjust the valve opening of the valve means
518
against the orifice
516
(that is, the amount of flow of liquid-phase refrigerant entering the evaporator) according to the difference in pressure of the working gas of the temperature-corresponding working fluid filling the upper chamber
520
a
and the pressure of the refrigerant vapor exiting the evaporator
515
within the lower chamber
520
b
, under the influence of the biasing force of the bias means
517
provided to the valve means
518
.
Moreover, the other end of the valve drive member
523
contacts the shaft
114
, and thereby drives the valve means
518
via the shaft
114
.
According to the above-mentioned prior-art thermal expansion valve, the power element
520
is exposed to external atmosphere, and the temperature-corresponding driving fluid in the upper chamber
520
a
receives influence not only from the temperature of the refrigerant exiting the evaporator and transmitted by the valve drive member
523
but also from the external atmosphere, especially the engine room temperature. Moreover, the above valve structure often caused a so-called hunting phenomenon where the valve responds too sensitively to the refrigerant temperature at the exit of the evaporator and repeats the opening and closing movement of the valve means
518
. The hunting phenomenon is caused for example by the structure of the evaporator, the method of positioning the pipes of the refrigeration cycle, the method of using the expansion valve, and the balance with the heat load.
Conventionally, an adsorbent such as an activated carbon is utilized as means for preventing such hunting phenomenon.
FIG. 6
is a cross-sectional view showing the thermal expansion valve disclosed in the above prior-art publication utilizing an adsorbent, the structure of which is basically similar to the prior-art thermal expansion valve of
FIG. 5
, except for the structure of the diaphragm and the structure of the valve drive member that functions as temperature sensing/pressure transmitting member. According to
FIG. 6
, the thermal expansion valve comprises a prism-shaped valve body
50
, and the valve body
50
comprises a port
52
through which the liquid-phase refrigerant flowing through a condenser
512
and entering from a receiver tank
513
travels into a first passage
62
, a port
58
sending the refrigerant traveling through the first passage
62
out towards an evaporator
515
, an entrance port
60
of a second passage
63
through which the gas-phase refrigerant exiting the evaporator enters, and an exit port
64
through which the refrigerant exits toward the compressor
511
.
The port
52
through which the refrigerant is introduced is communicated to a valve chamber
54
positioned on the center axis of the valve body
50
, and the valve chamber
54
is sealed by a nut-type plug
130
. The valve chamber
54
is communicated through an orifice
78
to a port
58
through which the refrigerant exits toward the evaporator
515
. A sphere-shaped valve means
120
is mounted to the end of a small-diameter shaft
114
that penetrates the orifice
78
, and the valve means
120
is supported by a support member
122
. The support member
122
biases the valve means
120
toward the orifice
78
using a bias spring
124
. The area of the flow path of the refrigerant is adjusted by varying the space formed between the valve means
120
and the orifice
78
. The refrigerant sent out from the receiver
514
expands while passing through the orifice
78
, and travels through the first passage
62
and exits from the port
58
toward the evaporator. The refrigerant exiting the evaporator enters from the port
60
, and travels through the second passage
63
and exits from the port
64
toward the compressor.
The valve body
50
is equipped with a first hole
70
formed from the upper end portion along the axis, and a power element portion
80
is mounted to the first hole using a screw portion and the like. The power element portion
80
includes housings
81
and
91
that constitute the heat sensing portion, and a diaphragm
82
that is sandwiched between these housings and fixed thereto through welding. The upper end portion of a heat-sensing driven member
100
is welded onto a round hole or opening formed to the center area of the diaphragm
82
together with a diaphragm support member
82
′, as shown in FIG.
7
. The diaphragm support member
82
′ is supported by the housing
81
.
A two-phase refrigerant of gas and liquid that is either identical to the refrigerant flowing within passage
62
or having similar characters thereto is sealed inside the housing
81
,
91
as a temperature-corresponding working fluid, which is sealed thereto by the small tube
21
. Further, a plug body welded to the housing
91
can be used instead of the small tube
21
. The diaphragm
82
divides the space within the housing
81
,
91
and defines an upper chamber
83
and a lower chamber
85
.
The heat-sensing/pressure transmitting member
100
is constituted of a hollow pipe-like member exposed to the second passage
63
, with an adsorbent stored to the interior thereof. The upper end of the heat-sensing driven member
100
is communicated to the upper chamber
83
, defining a pressure space
83
a
by the upper chamber
83
and the hollow portion
84
of the heat-sensing d

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