U.S. patent application number 13/411937 was filed with the patent office on 2012-09-20 for expansion valve.
This patent application is currently assigned to TGK CO., LTD.. Invention is credited to Hisatoshi Hirota, Takeshi Kaneko, Takanao Kumakura, Shinji Saeki.
Application Number | 20120234931 13/411937 |
Document ID | / |
Family ID | 46811940 |
Filed Date | 2012-09-20 |
United States Patent
Application |
20120234931 |
Kind Code |
A1 |
Hirota; Hisatoshi ; et
al. |
September 20, 2012 |
EXPANSION VALVE
Abstract
An expansion valve is configured such that a shaft, a first
valve, a second valve, a compression coil spring, and an adjustment
screw are coaxially arranged within a body exactly below a power
element, and the first valve and the second valve control the flow
rate in an interlocked manner. A second valve seat of the second
valve is press-fitted into the body, and an amount of press-fitting
of the second valve seat into the body is adjusted such that when
the first valve is in a closed state in which a first valve element
is seated on a first valve seat, the second valve is in a closed
state in which a second valve element is seated on the second valve
seat.
Inventors: |
Hirota; Hisatoshi; (Tokyo,
JP) ; Saeki; Shinji; (Tokyo, JP) ; Kaneko;
Takeshi; (Tokyo, JP) ; Kumakura; Takanao;
(Tokyo, JP) |
Assignee: |
TGK CO., LTD.
Tokyo
JP
|
Family ID: |
46811940 |
Appl. No.: |
13/411937 |
Filed: |
March 5, 2012 |
Current U.S.
Class: |
236/92B |
Current CPC
Class: |
F25B 41/062 20130101;
F25B 5/02 20130101; F25B 2341/0683 20130101; F25B 2341/0661
20130101 |
Class at
Publication: |
236/92.B |
International
Class: |
F25B 41/04 20060101
F25B041/04 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 14, 2011 |
JP |
2011-055616 |
Claims
1. An expansion valve comprising a first valve having a first valve
element and a first valve seat, a second valve having a second
valve element and a second valve seat, and a power element
configured to control lifts of the first valve element and the
second valve element in an interlocked manner, wherein the second
valve seat of the second valve is a movable valve seat which is
adjustable in a direction toward or away from the second valve
element.
2. The expansion valve according to claim 1, wherein the power
element, the first valve, the second valve, and a spring which
urges the first valve element and the second valve element toward
the power element are coaxially arranged, wherein a high pressure
inlet port for introducing high-pressure liquid refrigerant is
communicated with a flow passage between the first valve and the
second valve, wherein a first low-pressure outlet port for
delivering low-pressure vapor refrigerant is communicated with a
downstream side of the first valve, wherein a second low-pressure
outlet port for delivering low-pressure vapor refrigerant is
communicated with a downstream side of the second valve, wherein
the second valve seat is press-fitted into a body forming the first
valve seat, and wherein an amount of press-fitting of the second
valve seat is adjusted such that the first valve and the second
valve are simultaneously closed.
3. The expansion valve according to claim 2, wherein the first
valve element is axially movably disposed in a valve chamber into
which high-pressure liquid refrigerant is introduced, such that a
front end of a shaft for transmitting a driving force of the power
element is in contact therewith through a first valve hole of the
first valve seat, and that an axially extending portion of the
second valve element is contact therewith through a second valve
hole of the second valve seat.
4. The expansion valve according to claim 3, wherein guides which
slide along an inner wall of the valve chamber are integrally
formed on respective portions of the first valve element toward the
first valve seat and the second valve seat, and the guides have
respective communication passages formed therethrough for
introducing liquid refrigerant into the first valve hole and the
second valve hole.
5. The expansion valve according to claim 4, wherein the first
valve element is configured such that a ratio between an axial
length of a guide toward the first valve seat and an axial length
of a guide toward the second valve seat is made equal to a ratio
between a flow rate of the second valve and a flow rate of the
first valve.
6. The expansion valve according to claim 1, wherein there are
provided high-pressure-dependent characteristics that the expansion
valve is operated in a valve-closing direction according to a
balance between a port diameter of the first valve through which
high-pressure liquid refrigerant acts in the valve-closing
direction, and a port diameter of the second valve through which
high-pressure liquid refrigerant acts in a valve-opening
direction.
7. The expansion valve according to claim 1, wherein a shaft which
transmits a driving force of the power element to the first valve,
the first valve, and a first spring which urges the first valve
element toward the shaft are coaxially arranged, wherein the second
valve is disposed in a direction orthogonal to the axial direction
of the shaft, wherein a valve shaft of the second valve element is
brought into contact with a tapered surface having a frustoconical
shape and formed on an intermediate portion of the shaft, by an
urging force of a second spring, to thereby cause a lift of the
second valve element to be interlocked with a lift of the first
valve element, wherein a high pressure inlet port for introducing
high-pressure liquid refrigerant is communicated with a flow
passage between the first valve and the second valve, wherein a
first low-pressure outlet port for delivering low-pressure vapor
refrigerant is communicated with a downstream side of the first
valve, wherein a second low-pressure outlet port for delivering
low-pressure vapor refrigerant is communicated with a downstream
side of the second valve, wherein the second valve seat is screwed
into a body forming the first valve seat, and wherein a screwing
amount of the second valve seat is adjusted such that the first
valve and the second valve are simultaneously closed.
8. The expansion valve according to claim 7, wherein the first
valve element is brought into contact with or is welded to a front
end of the shaft extended through a first valve hole of the first
valve seat.
9. The expansion valve according to claim 7, wherein there are
provided high-pressure-dependent characteristics that the expansion
valve is operated in the valve-closing direction according to a
balance between a port diameter of the first valve through which
high-pressure liquid refrigerant acts in the valve-opening
direction, and a sealing diameter of an O ring disposed around the
shaft at a location where the shaft is supported by the body, via
which high-pressure liquid refrigerant acts on the shaft in the
valve-closing direction.
10. The expansion valve according to claim 1, further comprising a
throttle passage member disposed on a downstream side of at least
one of the first valve and the second valve, for preventing bubbles
from being generated in refrigerant having passed through the first
valve and the second valve.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority of the prior Japanese Patent Application No. 2011-055616,
filed on Mar. 14, 2011, the entire contents of which are
incorporated herein by reference.
FIELD
[0002] The embodiments discussed herein are related to an expansion
valve.
BACKGROUND
[0003] In an automotive air conditioning system, a refrigeration
cycle is formed by piping between a compressor that compresses
refrigerant, a condenser that condenses refrigerant, a receiver
that separates gas-liquid mixture refrigerant, an expansion valve
that adiabatically expands refrigerant, and an evaporator that
evaporates refrigerant, into a loop. The expansion valve that
expands refrigerant is generally implemented e.g. by a thermostatic
expansion valve configured to control a flow rate of refrigerant to
be supplied to the evaporator according to the temperature and
pressure of refrigerant at an outlet of the evaporator.
[0004] The evaporator that performs heat exchange between
refrigerant and air in a vehicle compartment is installed in the
vehicle compartment, and hence the evaporator is demanded to be
compact. For this reason, an evaporator has been generally used
which is formed by disposing two heat exchangers each having a
reduced thickness in an air passing direction in a laminated manner
and allows refrigerant to serially flow through these heat
exchangers.
[0005] In the evaporator described above, respective passages of
the heat exchangers through which refrigerant flows are narrowed
due to the reduced thickness of each heat exchanger, and what is
more, the total length of the passages is made longer due to serial
connection of the passages of the heat exchanges. For this reason,
in the evaporator having the above-described arrangement, a
pressure loss generated in the passages through which refrigerant
flows increases, which lowers the efficiency of the refrigeration
cycle.
[0006] To solve this problem, there has been proposed an evaporator
configured such that two heat exchangers are independently
provided, and refrigerant is supplied in parallel to the heat
exchangers (see e.g. Japanese Laid-Open Patent Publication No.
2010-38455 (FIGS. 5 and 6) and International Publication Pamphlet
NO. WO2010/131918 (FIG. 3)). According to this evaporator, a
pressure loss generated when refrigerant flows through the heat
exchangers is reduced, and a net loss is reduced which is caused
when the whole refrigeration cycle is considered, whereby it is
possible to improve cooling power.
[0007] An expansion valve used in such an evaporator described
above has also been proposed in Japanese Laid-Open Patent
Publication No. 2010-38455 and International Publication Pamphlet
NO. WO2010/131918. This expansion valve includes two valves each
capable of adiabatically expanding refrigerant independently of
each other, and is configured to control the two valves in an
interlocked manner according to temperature and pressure of
refrigerant joined after flowing out of the heat exchangers, which
are detected at an outlet of the evaporator.
[0008] However, both of the configurations of the disclosed
expansion valves are theoretical ones, and are not specifically
illustrated. If refrigerant leakage flow through the expansion
valve occurs when the automotive air conditioning system is
stopped, this generates a considerably large noise of flow of the
refrigerant, which is perceived as a untoward noise by the sense of
hearing of occupants, and hence it is necessary to close the
expansion valve. The expansion valve having two valves also has the
same problem, and in this case, it is important to simultaneously
close the two valves.
SUMMARY
[0009] According to an aspect of the invention, there is provided
an expansion valve including a first valve having a first valve
element and a first valve seat, a second valve having a second
valve element and a second valve seat, and a power element
configured to control lifts of the first valve element and the
second valve element in an interlocked manner, wherein the second
valve seat of the second valve is a movable valve seat which is
adjustable in a direction toward or away from the second valve
element.
[0010] The object and advantages of the invention will be realized
and attained by means of the elements and combinations particularly
pointed out in the claims.
[0011] It is to be understood that both the foregoing general
description and the following detailed description are exemplary
and explanatory and are not restrictive of the invention, as
claimed.
BRIEF DESCRIPTION OF DRAWINGS
[0012] FIG. 1 illustrates a refrigeration cycle to which an
expansion valve according to embodiments is applied;
[0013] FIG. 2 is a central vertical cross-sectional view of an
expansion valve according to a first embodiment;
[0014] FIG. 3 is a central vertical cross-sectional view of the
expansion valve according to the first embodiment, as viewed at
right angles to a plane of FIG. 2; and
[0015] FIG. 4 is a central vertical cross-sectional view of an
expansion valve according to a second embodiment.
DESCRIPTION OF EMBODIMENTS
[0016] Embodiments of the present invention will be explained below
with reference to the accompanying drawings, wherein like reference
numerals refer to like elements throughout.
[0017] FIG. 1 illustrates a refrigeration cycle to which an
expansion valve according to the present embodiments is
applied.
[0018] A refrigeration cycle of an automotive air conditioning
system comprises a compressor 1, a condenser 2, an expansion valve
3, and an evaporator 4, which are connected by piping between them
into a loop. The compressor 1 compresses refrigerant circulating
through the refrigeration cycle and delivers the compressed
refrigerant to the condenser 2. The condenser 2 is configured such
that a cooling fan 5 causes outside air to pass through the
condenser 2, and condenses high-temperature, high-pressure
refrigerant compressed by the compressor 1 by performing heat
exchange with outside air. A receiver (not illustrated) that
temporarily stores the condensed refrigerant is disposed at an
outlet of the condenser 2, and liquid refrigerant obtained by
gas/liquid separation performed in the receiver is supplied to the
expansion valve 3.
[0019] The expansion valve 3 is a thermostatic expansion valve
including a first valve 3a and a second valve 3b, which
adiabatically expands liquid refrigerant. The evaporator 4 includes
a first heat exchanger 4a and a second heat exchanger 4b, which are
disposed in a laminated manner within an air blowing passage on a
downstream side of a fan 6. Adiabatically expanded vapor
refrigerant is supplied from the first valve 3a of the expansion
valve 3 to the first heat exchanger 4a disposed on a side toward
the fan 6, and adiabatically expanded vapor refrigerant is supplied
from the second valve 3b to the second heat exchanger 4b disposed
on an air outlet port side. The refrigerant is evaporated by heat
exchange with air blown by the fan 6. Refrigerant flowing out of
the first heat exchanger 4a and refrigerant flowing out of the
second heat exchanger 4b are joined and the joined refrigerant is
returned to the compressor 1 through the expansion valve 3. When
the refrigerant returning from the evaporator 4 passes through the
expansion valve 3, the expansion valve 3 monitors the temperature
and pressure of the refrigerant, i.e. a degree of superheat of the
refrigerant at the outlet of the evaporator, and controls the flow
rate of refrigerant supplied from the first valve 3a and the second
valve 3b according to the degree of superheat.
[0020] In the evaporator 4, the first heat exchanger 4a disposed on
the side toward the fan 6 performs heat exchange with
higher-temperature air, and the second heat exchanger 4b disposed
on the air outlet port side performs heat exchange with air cooled
by the first heat exchanger 4a. Therefore, the flow rate of
refrigerant supplied from the first valve 3a to the first heat
exchanger 4a is set to be higher than the flow rate of refrigerant
supplied from the second valve 3b to the second heat exchanger 4b,
and in the present embodiment, the flow rate ratio between the
first valve 3a and the second valve 3b is set to 2:1.
[0021] FIG. 2 is a central vertical cross-sectional view of an
expansion valve according to a first embodiment, and FIG. 3 is a
central vertical cross-sectional view of the expansion valve
according to the first embodiment, as viewed at right angles to a
plane of FIG. 2.
[0022] The expansion valve according to the first embodiment
includes a rectangular parallelepiped body 11 having a high
pressure inlet port 12 formed in a lower portion, as viewed in FIG.
3, of one side surface thereof (right side surface, as viewed in
FIG. 3). High-pressure liquid refrigerant is supplied to the high
pressure inlet port 12. The body 11 has a first low-pressure outlet
port formed in a central portion of a side surface (left side
surface, as viewed in FIG. 2) adjacent to the one side surface
formed with the high pressure inlet port 12. The first low-pressure
outlet port 13 is connected to the first heat exchanger 4a disposed
on the side toward the fan 6. Further, the body 11 has a second
low-pressure outlet port 14 formed in a lower portion than the
central portion where the first low-pressure outlet port 13 is
formed, as viewed in FIG. 2. The second low-pressure outlet port 14
is connected to the second heat exchanger 4b disposed on the air
outlet port side. Also, the body 11 has a returning refrigerant
inlet port 15 formed in an upper portion than the central portion
where the first low-pressure outlet port 13 is formed, as viewed in
FIG. 2. Further, the body 11 has a returning refrigerant outlet
port 16 formed in an upper portion of the one side surface formed
with the high pressure inlet port 12 as viewed in FIG. 3.
[0023] A power element 17 that senses a degree of superheat of
refrigerant returning from the evaporator 4 is screwed into an
upper end surface of the body 11. A shaft 18, the first valve 3a,
the second valve 3b, a compression coil spring 19, and an
adjustment screw 20 are coaxially arranged within the body 11
exactly below the power element 17. The shaft 18, the first valve
3a, and the second valve 3b are separately disposed such that they
operate independently of each other, and are configured to be
capable of smoothly operating in an axial direction even when they
are disposed with the center of the axis slightly displaced.
[0024] The first valve 3a includes a first valve element 21 and a
first valve seat 22 formed in the body 11, and the first valve seat
22 is formed with a first valve hole 23 communicating with the
first low-pressure outlet port 13. The second valve 3b includes a
second valve element 24 and a second valve seat 25 press-fitted
into the body 11, and the second valve seat 25 is formed with a
second valve hole 26 having a smaller port diameter than that of
the first valve hole 23.
[0025] The first valve element 21 of the first valve 3a is disposed
in a valve chamber 27 communicating with the high pressure inlet
port 12, in a manner movable to and away from the first valve seat
22. For this purpose, the first valve element 21 is integrally
formed with two guides 28 which slide along an inner wall of the
valve chamber 27, on respective sides toward the first valve seat
22 and the second valve 3b.
[0026] The guides 28 are each formed with a plurality of
communication passages 29 for guiding liquid refrigerant introduced
into the valve chamber 27 toward the first valve seat 22 and toward
the second valve 3b. The communication passages 29 may be three
arc-shaped openings formed through each guide 28 in a concentric
arrangement at equally-spaced intervals. The guides 28 on the
respective sides toward the first valve seat 22 and the second
valve 3b have different axial lengths such that when liquid
refrigerant flows through the communication passages 29, respective
forces are cancelled out by which the first valve element 21 is
pulled toward the first valve seat 22 and the second valve 3b, due
to viscosity of refrigerant. In the present embodiment, the
distribution ratio between the flow rate of refrigerant supplied
from the first valve 3a and the flow rate of refrigerant supplied
from the second valve 3b is set to 2:1, and hence a ratio between
the axial length of the guide 28 toward the first valve seat 22 and
that of the guide 28 toward the second valve 3b is set to 1:2.
[0027] Further, the first valve 3a has a structure in which the
first valve element 21 is disposed on a upstream side of the first
valve seat 22, whereby high-pressure liquid refrigerant acts on the
first valve element 21 in a valve-closing direction. With this
structure, the first valve 3a has high-pressure-dependent
characteristics that although there is a proportional relationship
between pressure of liquid refrigerant on a primary side and
pressure of vapor refrigerant of a secondary side when the first
valve 3a is fully open, when the valve opening becomes smaller than
a predetermined opening, as the pressure on primary side increases,
the pressure on the secondary side decreases.
[0028] The second valve 3b is disposed in a space formed within the
body 11, which communicates between the valve chamber 27 and the
second low-pressure outlet port 14 and is formed coaxially with the
valve chamber 27. The second valve seat 25 is fixed to the body 11
by press fitting, and the second valve element 24 is disposed in a
manner movable to and away from the second valve seat 25. The
second valve element 24 has an axially extending portion 30
integrally formed thereon such that the axially extending portion
30 extends through the second valve hole 26 of the second valve
seat 25 toward the first valve 3a. An end face of the axially
extending portion 30 is constantly brought into contact with the
first valve element 21 by an urging force of the compression coil
spring 19.
[0029] Further, the second valve 3b has a structure in which the
second valve element 24 is disposed on a downstream side of the
second valve seat 25, and high-pressure liquid refrigerant acts on
the second valve element 24 in a valve-opening direction.
Therefore, the present expansion valve is configured to have
high-pressure-dependent characteristics that the expansion valve is
operated in the valve-closing direction according to a balance
between the port diameter of the first valve hole 23 and the port
diameter of the second valve hole 26.
[0030] The compression coil spring 19 is received by the adjustment
screw 20 screwed into the body 11. Load of the compression coil
spring 19 is adjusted by adjusting a screwing amount of the
adjustment screw 20. This adjustment corresponds to the setting of
the superheat degree to be controlled by the expansion valve. A
portion where the adjustment screw 20 is screwed into the body 11
is hermetically sealed by an O ring 31.
[0031] The power element 17 is screwed into a fitting hole formed
in an upper surface of the body 11, as viewed in FIGS. 2 and 3. The
fitting hole for fitting the power element 17 communicates with a
refrigerant returning passage 32 formed between the returning
refrigerant inlet port 15 and the returning refrigerant outlet port
16, and enables refrigerant flowing through the refrigerant
returning passage 32 to be introduced into the power element
17.
[0032] The power element 17 is formed by sandwiching a diaphragm 33
between an upper housing 34 and a lower housing 35, and welding
together the outer peripheries of these. A hermetically sealed
space enclosed by the diaphragm 33 and the upper housing 34 is
filled with gas having characteristics similar to refrigerant, and
forms a temperature sensing chamber. The lower housing 35 is
provided with a disk 36 which transmits the displacement of the
diaphragm 33 to the first valve 3a and the second valve 3b. The
disk 36 is fitted on an upper end of the shaft 18 held by a holder
37, and has its center positioned by the shaft 18 within the lower
housing 35.
[0033] The holder 37 has an upper portion disposed in the fitting
hole of the power element 17, and accommodates a compression coil
spring 38 in the upper portion thereof so as to apply a lateral
load to the shaft 18, as illustrated in FIG. 3. The shaft 18 is
limited in axial motion by having the lateral load applied thereto,
and hence even when liquid refrigerant introduced into the high
pressure inlet port 12 fluctuates in pressure, the first valve
element 21 is prevented from vibrating in the axial direction to
generate untoward noise. Further, the holder 37 hangs down through
the refrigerant returning passage 32, and a lower end of the holder
37 retains an O ring 39 disposed around the shaft 18 between the
first low-pressure outlet port 13 and the refrigerant returning
passage 32. The O ring 39 blocks refrigerant from leaking from the
first low-pressure outlet port 13 into the refrigerant returning
passage 32 without flowing toward the first heat exchanger 4a of
the evaporator 4.
[0034] The power element 17 is covered with a cap 40, and is
thereby thermally insulated from the environment so as not to be
affected by the temperature of the environment in which the
expansion valve is disposed. Further, a throttle passage member 41
having an annular shape is fitted in the first low-pressure outlet
port 13. The throttle passage member 41 has a through hole formed
through a central portion thereof, which has a predetermined
opening area, and throttles the flow of refrigerant flowing from
the first low-pressure outlet port 13 to thereby prevent bubbles
from being generated and reduce noise generated when refrigerant
passes through the expansion valve.
[0035] According to the expansion valve constructed as above,
during the stoppage or the minimum capacity operation of the
compressor 1, the pressure in the refrigerant returning passage 32
is high, and in the power element 17 which has sensed the high
pressure, the diaphragm 33 is displaced toward the temperature
sensing chamber. As a result, since the first valve element 21 and
the second valve element 24 are urged by the compression coil
spring 19 in the valve-closing direction, the first valve 3a and
the second valve 3b are in a closed state.
[0036] When the compressor 1 starts compression of refrigerant, the
pressure in the refrigerant returning passage 32 decreases, whereby
the diaphragm 33 of the power element 17 is displaced toward the
first valve 3a and the second valve 3b, and high-pressure
refrigerant is introduced into the high pressure inlet port 12.
Before long, the first valve 3a and the second valve 3b are opened
by the power element 17, whereby the liquid refrigerant condensed
by the condenser 2 is introduced into the high pressure inlet port
12. The liquid refrigerant introduced into the valve chamber 27 is
adiabatically expanded by the first valve 3a to form
low-temperature, low-pressure vapor refrigerant, and is delivered
from the first low-pressure outlet port 13 to the first heat
exchanger 4a of the evaporator 4. Further, the liquid refrigerant
in the valve chamber 27 is adiabatically expanded by the second
valve 3b to form low-temperature, low-pressure vapor refrigerant,
and is delivered from the second low-pressure outlet port 14 to the
second heat exchanger 4b of the evaporator 4.
[0037] In the evaporator 4, the vapor refrigerant introduced into
the first heat exchanger 4a and the vapor refrigerant introduced
into the second heat exchanger 4b are evaporated by heat exchange
with air blown by the fan 6, and then are joined together to be
returned to the returning refrigerant inlet port 15. The air having
passed through the evaporator 4 is dehumidified and cooled, and is
then blown out into the vehicle compartment after being adjusted to
appropriate temperature.
[0038] The refrigerant introduced into the returning refrigerant
inlet port 15 flows through the refrigerant returning passage 32,
and is then returned from the returning refrigerant outlet port 16
to the compressor 1. When the refrigerant returning from the
evaporator 4 flows through the refrigerant returning passage 32,
the degree of superheat of the refrigerant is sensed by the power
element 17, and valve lifts of the first valve 3a and the second
valve 3b are controlled according to the degree of superheat. This
controls the flow rate of refrigerant flowing through the first
valve 3a and that of refrigerant flowing through the second valve
3b, whereby refrigerant is supplied to the first heat exchanger 4a
and the second heat exchanger 4b of the evaporator 4 at a
predetermined distribution ratio. The first valve 3a and the second
valve 3b are thus feedback-controlled according to the degree of
superheat of the refrigerant detected at the outlet of the
evaporator 4, and hence the present expansion valve controls the
flow rate of vapor refrigerant to be delivered to the evaporator 4
such that the refrigerant at the outlet of the evaporator maintains
the degree of superheat set by the compression coil spring 19.
[0039] FIG. 4 is a central vertical cross-sectional view of an
expansion valve according to a second embodiment. Component
elements illustrated in FIG. 4 identical or equivalent to those
illustrated in FIG. 2 are designated by identical reference
numerals, and detailed description thereof is omitted.
[0040] The expansion valve according to the second embodiment
includes the shaft 18, the first valve 3a, the compression coil
spring 19, and the adjustment screw 20, coaxially arranged within
the body 11 exactly below the power element 17. The second valve 3b
is arranged such that the valve is lifted in a direction orthogonal
to an axial direction of the shaft 18, and is screwed into an inner
wall of a refrigerant passage 42 formed in a manner extending from
the second low-pressure outlet port 14 across the shaft 18. The
shaft 18 has a tapered surface 43 having a frustoconical shape
formed on an intermediate portion thereof, and the second valve 3b
is in constant contact with the tapered surface 43. The O ring 39
fitted around the shaft 18 prevents the high-pressure refrigerant
introduced into the high pressure inlet port 12 from leaking into
the refrigerant returning passage 32 through a clearance between
the shaft 18 and the body 11.
[0041] The first valve 3a includes the first valve element 21,
which is ball-shaped, and the first valve element 21 is urged by
the compression coil spring 19 disposed between a valve
element-supporting portion 44 which receives the first valve
element 21 and the adjustment screw 20, in the valve-closing
direction. With this arrangement, the first valve element 21 is
brought into contact with a front end of the shaft 18 extended
through the first valve hole 23 of the first valve seat 22. Since
the first valve element 21 is ball-shaped, it is preferable to
spot-weld the first valve element 21 to the front end of the shaft
18, so as to improve the assembly properties. The valve chamber 27
which accommodates the first valve element 21 communicates with the
first low-pressure outlet port 13, and the throttle passage member
41 is fitted in an intermediate portion of the passage
communicating between the valve chamber 27 and the first
low-pressure outlet port 13.
[0042] Further, the first valve 3a has a structure in which that
the first valve element 21 is disposed on the 12 downstream side of
the first valve seat 22 and is operated by high-pressure liquid
refrigerant in the valve-opening direction, whereas the O ring 39
sealing the shaft 18 receives high pressure refrigerant through the
clearance between the shaft 18 and the body 11 to thereby operate
the shaft 18 in the valve-closing direction. Therefore, the
expansion valve is configured to have high-pressure-dependent
characteristics that the expansion valve is operated in the
valve-closing direction according to a balance between the port
diameter of the first valve hole 23 and the sealing diameter of the
O ring 39.
[0043] The second valve 3b includes a screwing portion 25a by which
the second valve seat 25 is screwed into the inner wall of the
refrigerant passage 42, and a valve shaft-supporting portion 25b
which supports a valve shaft 24a of the second valve element 24,
and the valve shaft-supporting portion 25b has a groove
communicating with the second valve hole 26, formed in a supporting
hole within which the valve shaft 24a is supported. A spring
receiver is fitted on the valve shaft 24a, and a compression coil
spring 45 is disposed between the spring receiver 50 and the
screwing portion 25a of the second valve seat 25, for urging the
second valve element 24 in the valve-closing direction, and
constantly bringing the front end of the valve shaft 24a into
contact with the tapered surface 43 of the shaft 18. With this
arrangement, the second valve seat 25 forms a movable valve seat
adjustable in a direction toward or away from the second valve
element 24 having the valve shaft 24a in contact with the tapered
surface 43. This makes it possible to match timing for closing the
first valve 3a with timing for closing the second valve 3b by
adjusting a screwing amount of the second valve seat 25. A
downstream side of the second valve 3b communicates with the second
low-pressure outlet port 14, and a throttle passage member 46 is
fitted in an intermediate portion of a passage communicating
between the second valve 3b and the second low-pressure outlet port
14. Similarly to the throttle passage member 41 of the first valve
3a, the throttle passage member 46 throttles the flow of
refrigerant flowing from the second low-pressure outlet port 14 to
thereby prevent bubbles from being generated, and reduce noise
generated when refrigerant passes through the expansion valve.
[0044] According to the expansion valve configured as above, when
the first valve 3a is in a closed state, the shaft 18 is at rest in
a position in which the valve shaft 24a of the second valve element
24 seated on the second valve seat 25 is just in contact with the
tapered surface 43.
[0045] When the power element 17 is driven in a direction of
lifting the first valve element 21 of the first valve 3a, the
tapered surface 43 of the shaft 18 is moved toward the first valve
3a. As a result, the direction of lifting the first valve element
21 is converted into a direction orthogonal thereto by the tapered
surface 43, which causes the second valve element 24 to be lifted
in a manner interlocked with the lift of the first valve element
21. Therefore, the operation of the present expansion valve is the
same as the above-described operation of the expansion valve
according to the first embodiment, and hence detailed description
of the operation is omitted.
[0046] Also in the present expansion valve according to the second
embodiment, similarly to the expansion valve according to the first
embodiment, the flow rate of vapor refrigerant to be fed to the
evaporator 4 is controlled such that the refrigerant at the outlet
of the evaporator maintains the degree of superheat set by the
compression coil spring 19. Further, the first valve 3a and the
second valve 3b operating in an interlocked manner are
simultaneously closed, and refrigerant does not leak during valve
closing, and hence it is possible to completely prevent flowing
noise of refrigerant from being generated by the leakage of
refrigerant.
[0047] The expansion valve configured as above is capable of
simultaneously closing the first valve and the second valve
operating in an interlocked manner, and hence leakage of
refrigerant during valve closing does not occur, which is
advantageous in positively preventing noise caused by the leakage
of refrigerant.
[0048] All examples and conditional language recited herein are
intended for pedagogical purposes to aid the reader in
understanding the invention and the concepts contributed by the
inventor to furthering the art, and are to be construed as being
without limitation to such specifically recited examples and
conditions, nor does the organization of such examples in the
specification relate to a showing of the superiority and
inferiority of the invention. Although the embodiments of the
present invention have been described in detail, it should be
understood that various changes, substitutions, and alterations
could be made hereto without departing from the spirit and scope of
the invention.
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