U.S. patent application number 09/925681 was filed with the patent office on 2002-02-28 for thermal expansion valve.
Invention is credited to Minowa, Masakatsu, Watanabe, Kazuhiko.
Application Number | 20020023460 09/925681 |
Document ID | / |
Family ID | 18733314 |
Filed Date | 2002-02-28 |
United States Patent
Application |
20020023460 |
Kind Code |
A1 |
Minowa, Masakatsu ; et
al. |
February 28, 2002 |
Thermal expansion valve
Abstract
A heat transmission retardant member 140 is formed of a cup-like
shaped resin material utilizing nylon or polyacetals, comprising a
collar 141 formed to the outside of the upper end thereof, and a
thick-walled cylinder portion 143 having at the lower end thereof a
tapered portion 142. Said retardant member 140 is positioned so
that the upper end contacts a support member 82', said collar 141
is supported by the inner surface of a housing 81, the outer
surface of said cylinder portion 143 contacts the inner surface of
said housing 81, and the end of said tapered portion 142 is
inserted to a second hole 72 and contacting the outer surface of a
heat-sensing driven member 100 and further positioned within a
lower chamber 85 defined by a diaphragm 82. Said retardant member
140 is mounted to said driven member 100 so as to cover the outer
surface thereof and being mounted outside the second refrigerant
passage 63, said tapered portion 143 defining a space 144 between
the exterior of the driven member 100 and the interior of said
cylinder portion 142. Not only is the hunting phenomenon suppressed
by the existence of the activated carbon, but the invasion of the
refrigerant to the lower chamber 85 is prevented, and the heat from
the heat transmission retardant member 140 is transmitted to the
heat-sensing driven member 100 via space 144 which enables to
provide a further retardation to the response of the valve to the
temperature change of the refrigerant exiting the evaporator. The
hunting is further suppressed effectively.
Inventors: |
Minowa, Masakatsu; (Tokyo,
JP) ; Watanabe, Kazuhiko; (Tokyo, JP) |
Correspondence
Address: |
RADER FISHMAN & GRAUER PLLC
LION BUILDING
1233 20TH STREET N.W., SUITE 501
WASHINGTON
DC
20036
US
|
Family ID: |
18733314 |
Appl. No.: |
09/925681 |
Filed: |
August 10, 2001 |
Current U.S.
Class: |
62/527 ;
62/222 |
Current CPC
Class: |
F25B 2341/0683 20130101;
F25B 2341/0682 20130101; F25B 41/335 20210101 |
Class at
Publication: |
62/527 ;
62/222 |
International
Class: |
F25B 041/04; F25B
041/06 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 10, 2000 |
JP |
2000-242271 |
Claims
We claim:
1. A thermal expansion valve including a refrigerant passage
extending from an evaporator to a compressor, and a heat-sensing
driven member with a hollow portion formed to the interior thereof
and having a heat sensing function that is positioned within said
refrigerant passage; wherein the end of said hollow portion of said
heat-sensing driven member is fixed to the center opening portion
of a diaphragm constituting a power element portion that drives
said driven member, thereby communicating said hollow portion with
an upper pressure chamber defined by said diaphragm within said
power element portion and forming a sealed space filled with
working fluid, said hollow portion storing a time constant
retardant material; and a heat transmission retardant member is
mounted outside said refrigerant passage covering and forming a
space between the outer circumferential surface of said
heat-sensing driven member.
2. A thermal expansion valve including a refrigerant passage
extending from an evaporator to a compressor, and a heat-sensing
driven member with a hollow portion formed to the interior thereof
and having a heat sensing function that is positioned within said
refrigerant passage; wherein the end of said hollow portion of said
heat-sensing driven member is fixed to the center opening portion
of a diaphragm constituting a power element portion that drives
said driven member, thereby communicating said hollow portion with
an upper pressure chamber defined by said diaphragm within said
power element portion and forming a sealed space filled with
working fluid, said hollow portion storing a time constant
retardant material; and a heat transmission retardant member
including a thick-wall portion and a thin-wall portion is mounted
to and covers the outer circumferential surface of said
heat-sensing driven member, said thick-wall portion mounted outside
said refrigerant passage and forming a space between said outer
circumferential surface, and said thin-wall portion mounted within
said refrigerant passage.
3. A thermal expansion valve according to claim 2, wherein said
thin-film portion is positioned within said refrigerant passage so
as to form a space between said outer circumferential surface of
said heat-sensing driven member.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a thermal expansion valve
used in a refrigeration cycle.
DESCRIPTION OF THE RELATED ART
[0002] Conventionally, a thermal expansion valve shown in FIG. 5 is
used in a refrigeration cycle in order to control the flow rate of
the refrigerant being supplied to an evaporator and to decompress
the refrigerant.
[0003] In FIG. 5, a prism-shaped aluminum valve body 510 comprises
a first refrigerant passage 514 including an orifice 516, and a
second refrigerant passage 519, the two passages formed 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 520a in the
power element 520 defined by the diaphragm 522 is maintained
airtight, and it is filled with temperature-corresponding working
fluid.
[0004] A small pipe 521 extending out from the upper chamber 520a
of the power element 520 is used to degasify the upper chamber 520a
and to fill the temperature-corresponding working fluid to the
upper chamber 520a, before the end of the pipe is sealed. The
extended end of a valve drive member 523 functioning as the
heat-sensing/transmitting 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
520b of the power element 520, contacting the diaphragm 522. The
valve drive member 523 is made of a material having a large thermal
capacity, and it 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 520a of the power element 520,
which generates a working gas having a pressure corresponding to
the transmitted temperature. The lower chamber 520b is communicated
to the second refrigerant passage 519 through the space formed
around the valve drive member 523 within the valve body 510.
[0005] 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
520a and the pressure of the refrigerant vapor exiting the
evaporator 515 in the lower chamber 520b, under the influence of
the biasing force of the bias means 517 provided to the valve means
518.
[0006] 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
520a receives influence not only from the temperature of the
refrigerant exiting the evaporator and transmitted by the valve
drive member 423 but also from the external atmosphere, especially
the engine room temperature. Moreover, the above conventional 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.
[0007] Conventionally, a time constant retardant such as an
absorbent or a thermal ballast is utilized to prevent such hunting
phenomenon. FIG. 6 is a cross-sectional view showing the
conventional thermal expansion valve utilizing an activated carbon
as 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 a heat-sensing driven 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 toward an evaporator 515, an entrance port 60 of a
second passage 63 through which the gas-phase refrigerant exiting
the evaporator returns, and an exit port 64 through which the
refrigerant exits toward the compressor 511.
[0008] 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 for the
refrigerant is adjusted by varying the gap 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.
[0009] 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
made of stainless steel or aluminum is welded onto a round hole or
opening formed to the center area of the diaphragm 82 together with
a diaphragm support member 82'. The diaphragm support member 82' is
supported by the housing 81.
[0010] An inert gas 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 forming an upper chamber 83 and
a lower chamber 85.
[0011] The heat-sensing driven member 100 is constituted of a
hollow pipe-like member exposed to the second passage 63, with
activated carbon 40 stored to the interior thereof. The upper end
of the heat-sensing/pressure transmitting member 100 is
communicated to the upper chamber 83, defining a pressure space 83a
by the upper chamber 83 and the hollow portion 84 of the
heat-sensing driven member 100. The pipe-like heat-sensing driven
member 100 penetrates through a second hole 72 formed on the axis
of the valve body 50, and is inserted to a third hole 74. A gap is
formed between the second hole 72 and the heat-sensing driven
member 100, through which the refrigerant within the passage 63 is
introduced to the lower chamber 85 of the diaphragm.
[0012] The heat-sensing driven member 100 is slidably inserted to
the third hole 74, and the end thereof is connected to one end of
the shaft 114. The shaft 114 is slidably inserted to a fourth hole
76 formed to the valve body 50, and the other end thereof is
connected to the valve means 120.
[0013] According to this structure, the adsorbent 40 functioning as
a time constant retardant works as follows. When a granular
activated carbon is used as the adsorbent 40, the combination of
the temperature-correspondin- g working fluid and the adsorbent 40
is an absorption-equilibrium type, where the pressure can be
approximated by a linear expression of the temperature within a
considerably wide temperature range, and the coefficient of the
linear expression can be set freely according to the amount of
granular activated carbon used as the adsorbent. Therefore, the
characteristic of the thermal expansion valve can be set at
will.
[0014] Accordingly, it takes a relatively long time to set the
adsorption-equilibrium-type pressure-temperature equilibrium state
when the temperature of the refrigerant vapor flowing out from the
exit of the evaporator 515 is either rising or falling. In other
words, by increasing the time constant, the work efficiency of the
air conditioning device is improved, stabilizing the performance of
the air conditioning device capable of suppressing the sensitive
operation of the thermal expansion valve caused by the influence of
disturbance which may lead to the hunting phenomenon.
SUMMARY OF THE INVENTION
[0015] However, the hunting phenomenon differs according to the
work characteristic of each individual refrigeration cycle.
Especially when a fine temperature variation occurs to the
low-pressure refrigerant exiting the evaporator, the small
fluctuation or pulsation of the refrigerant temperature is
transmitted directly to the opening/closing movement of the valve
means, which causes unstable valve movement, and the use of a
thermal ballast material or an adsorbent can no longer suppress
hunting.
[0016] Therefore, the present invention aims at providing a thermal
expansion valve that enables to control stably the amount of
low-pressure refrigerant sent out towards the evaporator, and that
enables to further suppress the hunting phenomenon by providing an
appropriate delay to the response of the valve to temperature
change, even when small temperature variation occurs to the
low-pressure refrigerant transmitted from the evaporator. This is
realized without changing the basic design of the conventional
thermal expansion valve, maintaining the conventional operation of
the valve.
[0017] In order to achieve the above objects, the present invention
provides a thermal expansion valve including a refrigerant passage
extending from an evaporator to a compressor, and a heat-sensing
driven member with a hollow portion formed to the interior thereof
and having a heat sensing function that is positioned within the
refrigerant passage; wherein the end of the hollow portion of the
heat-sensing driven member is fixed to the center opening portion
of a diaphragm constituting a power element portion that drives the
driven member, thereby communicating the hollow portion with an
upper pressure chamber defined by the diaphragm within the power
element portion and forming a sealed space filled with working
fluid, the hollow portion storing a time constant retardant
material; and a heat transmission retardant member is mounted
outside the refrigerant passage covering and forming a space
between the outer circumferential surface of said heat-sensing
driven member.
[0018] The thermal expansion valve of the present invention having
the above-explained structure is realized without changing the
basic structure of the conventional thermal expansion valve, but by
providing a heat transmission retardant material to the outer
circumferential surface of the heat-sensing driven member. The
present invention not only delays the temperature transmission from
the heat-sensing driven member to the time constant retardant
material and thereby enables to further increase the time constant
compared to the valve where only the time constant retardant is
utilized, but also forms a space between the heat-sensing driven
member and the heat transmission retardant member which provides a
double effect of delaying the transmission of temperature variation
of the refrigerant to the heat-sensing driven member. Therefore,
the present invention enables to further effectively suppress
hunting of the valve means.
[0019] Moreover, the present invention further provides a thermal
expansion valve including a refrigerant passage extending from an
evaporator to a compressor, and a heat-sensing driven member with a
hollow portion formed to the interior thereof and having a heat
sensing function that is positioned within the refrigerant passage;
wherein the end of the hollow portion of the heat-sensing driven
member is fixed to the center opening portion of a diaphragm
constituting a power element portion that drives the driven member,
thereby communicating the hollow portion with an upper pressure
chamber defined by the diaphragm within said power element portion
and forming a sealed space filled with working fluid, the hollow
portion storing a time constant retardant material; and a heat
transmission retardant member including a thick-wall portion and a
thin-wall portion is mounted to and covers the outer
circumferential surface of the heat-sensing driven member, the
thick-wall portion mounted outside the refrigerant passage and
forming a space between the outer circumferential surface, and the
thin-wall portion mounted within said refrigerant passage.
[0020] The above-explained structure does not change the basic
structure of the conventional thermal expansion valve, but instead,
provides a heat transmission delay member having a thick-wall
portion and a thin-wall portion mounted to cover the outer
circumferential surface of the heat-sensing driven member. Here,
the thick-wall portion is mounted to the outside of a refrigerant
passage so as to form a space between the outer circumferential
surface thereby delaying the transmission of temperature variation
of the refrigerant to the heat-sensing driven member, and the
thin-wall portion provides delay while transmitting the temperature
change of the refrigerant to the heat-sensing driven member without
blocking the flow of refrigerant traveling through the refrigerant
passage. Therefore, the present invention suppresses the hunting of
the valve means even more effectively.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is a vertical cross-sectional view showing one
embodiment of the thermal expansion valve according to the present
invention;
[0022] FIG. 2 is an exploded view of the main portion explaining
the embodiment shown in FIG. 1;
[0023] FIG. 3 is a vertical cross-sectional view showing another
embodiment of the thermal expansion valve according to the present
invention;
[0024] FIG. 4 is a vertical cross-sectional view showing yet
another embodiment of the thermal expansion valve according to the
present invention;
[0025] FIG. 5 is a vertical cross-sectional view showing the
thermal expansion valve of the prior art; and
[0026] FIG. 6 is a vertical cross-sectional view showing another
thermal expansion valve of the prior art.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0027] Now, the embodiments of the present invention will be
explained with reference to the drawings.
[0028] FIG. 1 is a vertical cross-sectional view showing the
structure according to one embodiment of the thermal expansion
valve of the present invention, and FIG. 2 is a cross-sectional
view showing the main portion thereof. In the embodiment shown in
FIG. 1, the basic structure of the present valve is the same as
that of the conventional thermal expansion valve, so the identical
or equivalent portions of the present valve are provided with the
same reference numbers as those of the conventional valve, and the
explanations thereof are omitted. Only the portions that differ
from the conventional valve are explained here.
[0029] In FIG. 1, 140 refers to a heat transmission retardant
member, which is a cup-like member made of resin utilizing nylon or
polyacetals and the like. The retardant member 140 comprises a
collar 141 formed to the outside of the upper end thereof and a
large-diameter cylinder portion 143 having thick walls which is
tapered at the lower end forming a tapered portion 142. The upper
end of the member 140 contacts a support member 82' explained
later, the collar 141 is supported by the inner surface of a
housing 81, and the outer surface of the cylinder portion 143
contacts the inner surface of the housing 81. The tip of the
tapered portion 142 of the member 140 is inserted to the interior
of a second hole 72 and contacts the outer surface of the
heat-sensing driven member 100, positioned within a lower chamber
85 defined by a diaphragm 82. Accordingly, when the heat
transmission retardant member 140 is mounted to the heat-sensing
driven member 100, the retardant member 140 covers the external
surface of the heat-sensing driven member 100 and is mounted to the
exterior of the refrigerant passage of the second passage 63.
Further, the tapered portion 142 defines a space 144 between the
external surface of the heat-sensing driven member 100 and the
inner surface of the cylinder portion 143.
[0030] According to the present invention, not only is the hunting
phenomenon suppressed by the existence of the activated carbon 40,
but the invasion of the refrigerant to the lower chamber 85 is
prevented, and the heat from the heat transmission retardant member
140 is transmitted to the heat-sensing driven member 100 via space
144, the existence of which enables to provide a further
retardation to the response of the valve against the temperature
change of the refrigerant exiting the evaporator. Therefore, the
hunting phenomenon is even more suppressed effectively. Moreover,
the present thermal expansion valve can be formed without changing
the basic structure of the conventional thermal expansion valve, so
an appropriate delay can be provided to the temperature variation
of the refrigerant by setting the thickness of the cylinder portion
143 of the heat transmission retardant 140 and the area of the
space 144.
[0031] In the embodiment shown in FIG. 1, the evaporator, the
compressor, the condenser and the receiver constituting the
refrigeration cycle are omitted from the drawing. Reference 21' is
a stainless steel plug body for sealing into the upper chamber 83 a
predetermined refrigerant working as a temperature working fluid
that drives the diaphragm 82, and it is welded so as to plug the
hole 91a formed to the housing 91. Reference 74a refers to an
o-ring mounted to a shaft 114 within a third hole 74, and 74b is a
push nut preventing movement of the o-ring. Reference 79 is a lid
having a protrusion for pushing down the adsorbent, for example an
activated carbon, arranged inside the hollow portion of the
heat-sensing driven member 100, and it is press-fit to the hollow
portion.
[0032] Further, according to the embodiment of FIG. 1, a granular
activated carbon is filled as the activated carbon 40 to the
heat-sensing driven member 100, and the member 100 filled with
granular activated carbon and the diaphragm 82 is welded together
as explained in FIG. 2 to form an integral space 84 by the power
element portion 80 and the heat-sensing driven member 100. A plug
body 21' is used to seal the temperature-corresponding working
fluid to the housing 91 defining the space 84. In another example,
a small pipe as shown in FIG. 6 can be used instead of the plug 21'
to degasify the housing, to fill the working fluid thereto, before
sealing the end of the pipe.
[0033] FIG. 2 is a drawing showing the structure of the
heat-sensing driven member 100, the diaphragm 82 and the support
member 82' according to the embodiment of FIG. 1.
[0034] As shown in FIG. 2(a), a collar 100a is formed to the
exterior of the opening 100b of the heat-sensing driven member 100,
and a protrusion 100c and a groove 100d are formed to the collar
100a toward the downward direction in the drawing. The protrusion
100c and the groove 100d are formed to the whole perimeter of the
collar 100a.
[0035] Moreover, a diaphragm 82 made of stainless steel material
and the like having an opening 82a formed to the center area
thereof is inserted to the heat-sensing driven member 100 through
the opening, and it is moved toward the direction of the arrow in
FIG. 2(a) until the diaphragm contacts the protrusion 100c, and
there the diaphragm 82 is fixed to the heat-sensing driven member
100.
[0036] A support member 82 made of stainless steel material and the
like for supporting the diaphragm 82 and having an opening 82' a
formed concentrically with the opening 82a of the diaphragm 82 is
inserted to the heat-sensing driven member 100 through the opening,
and it is moved toward the direction of the arrow in FIG. 2(a)
until the support member contacts the diaphragm 82. The protrusion
100c and the support member 82' are pressed against each other at
upper and lower electrodes (not shown) so that the support member
is concentrical with the protrusion 100c, and current is applied to
these electrodes to perform a so-called projection welding, thereby
welding together the collar 100a, the diaphragm 82 and the support
member 82' as shown in FIG. 2(b).
[0037] As a result, the diaphragm 82 is welded to position between
the collar 100a and the support member 82' by protrusion 100c. The
end portion of the diaphragm 82 is sandwiched between the housing
81 and 91, and welded thereto.
[0038] In the above embodiment, the heat transmission retardant
member 140 that covers the external surface of the heat-sensing
driven member 100 is mounted outside the second passage 63, thereby
delaying further the response to the temperature variation of the
refrigerant. However, the present invention is not limited to such
example, but in another example, the tapered portion of the
cup-like heat transmission retardant member can further be
connected to a thin-walled cylinder extension portion constituting
a heat transmission retardant member covering the heat-sensing
driven member, and the cylinder extension portion can be positioned
within the second passage.
[0039] FIG. 3 shows an embodiment of the present invention where a
heat transmission retardant member 140' comprises a cup-like
thick-wall portion and an integrally formed thin-wall portion, and
the structure of the present embodiment is identical to that shown
in FIG. 1 except for the heat transmission retardant member 140',
so the equivalent members are provided with the same reference
numbers and the explanations thereof are omitted.
[0040] In FIG. 3, the heat transmission retardant member 140'
comprises a cup-like thick-wall portion and a thin-wall portion
formed integrally thereto, wherein the structure of the cup-like
thick-wall portion 140'a is identical to that of the heat
transmission retardant member 140 shown in FIG. 1 with a collar
141' formed to the exterior of the upper end surface, and a
large-diameter cylinder portion 143' having a tapered portion 142'
formed to the lower end thereof. The thin-wall portion comprises a
cylinder extended portion 140'b extended downward from the tapered
portion 142', and the thin-wall cylinder extended portion 140'b is
arranged within the second passage 63, and the end of the cylinder
extended portion 140'b is bent inward to form a contact portion 145
that mounts the retardant member 140' to the external surface of
the heat-sensing driven member 100.
[0041] According to this structure, the area of the heat-sensing
driven member 100 positioned within the second passage 63 is
covered by the thin-wall cylinder extended portion 140'b, so that
the thin-wall portion is also positioned within the passage 63,
which delays the transmission of temperature variation of the
refrigerant and further delays the response of the valve to the
refrigerant temperature variation. Moreover, since the cylindrical
extended portion 140'b has a thin wall, it allows to sense the
refrigerant temperature without blocking the refrigerant flow, and
to transmit the temperature change.
[0042] FIG. 4 is a vertical cross-sectional view showing yet
another embodiment of the thermal expansion valve according to the
present invention. The embodiment shown in FIG. 4 is identical to
that of FIG. 3 except that according to FIG. 4, a space is formed
between the inner surface of the thin-wall cylindrical extended
portion 140'b and the outer surface of the heat-sensing driven
member 100, so the equivalent members are provided with the same
reference numbers, and the explanations thereof are omitted.
According to the embodiment of FIG. 4, the contact portion 145 is
formed longer than the embodiment of FIG. 3, thereby creating a
space 146 between the outer surface of the heat-sensing driven
member 100 and the thin-wall cylindrical extended portion 140'b.
According to such structure, the temperature variation of the
refrigerant is transmitted from the heat transmission retardant
member 140' via space 146 to the heat-sensing driven member 100, so
the transmission of temperature change is even further delayed, and
the response of the valve to the temperature variation of the
refrigerant is thereby effectively delayed. The present embodiment
suppresses the generation of hunting phenomenon even further.
[0043] The above embodiments utilize a separately formed support
member and a heat transmission retardant member, but the present
invention is also capable of utilizing a support member and a heat
transmission retardant member integrally formed using a resin
material. In this case, the collar 100a of the heat-sensing driven
member and the diaphragm 82a are welded together as shown in FIG.
2.
[0044] As explained above, the thermal expansion valve according to
the present invention includes a heat transmission retardant member
mounted to the outer surface of the heat-sensing driven member with
a space formed between the outer surface of the driven member and
the inner surface of the retardant member, so that the temperature
variation of the refrigerant is even further delayed while being
transmitted to the heat-sensing driven member. This transmission
delay realizes a further delay in the response of the valve to
refrigerant temperature changes, thus effectively suppressing the
hunting phenomenon. Moreover, the present invention achieves the
above effects without changing the basic structure of the
conventional thermal expansion valve but by applying a heat
transmission retardant member thereto, enabling to provide an
advantageous thermal expansion valve at low assembly cost and low
manufacturing cost.
* * * * *