U.S. patent application number 11/711683 was filed with the patent office on 2007-09-13 for expansion valve.
This patent application is currently assigned to TGK CO., LTD.. Invention is credited to Hisatoshi Hirota.
Application Number | 20070209387 11/711683 |
Document ID | / |
Family ID | 38121651 |
Filed Date | 2007-09-13 |
United States Patent
Application |
20070209387 |
Kind Code |
A1 |
Hirota; Hisatoshi |
September 13, 2007 |
Expansion valve
Abstract
To provide an expansion valve which is capable of preventing the
temperature of refrigerant compressed by a compressor from becoming
too high, when a refrigeration load on a refrigeration cycle using
an internal heat exchanger is high. A thermostatic expansion valve
is applied to a refrigeration cycle provided with an internal heat
exchanger that performs heat exchange between high-temperature
refrigerant flowing from a condenser to the expansion valve and
low-temperature refrigerant flowing from an evaporator to a
compressor via the expansion valve. The expansion valve comprises a
bypass passage or for causing refrigerant in a high-pressure
refrigerant inlet or a low-pressure refrigerant outlet to flow to
the downstream side of a temperature-sensing section, such that
moist refrigerant is mixed with refrigerant whose degree of
superheat is controlled by the expansion valve. This lowers the
temperature of refrigerant that is drawn into the compressor when
refrigeration load is high is lowered, to thereby prevent the
temperature of refrigerant compressed by the compressor from
becoming too high.
Inventors: |
Hirota; Hisatoshi; (Tokyo,
JP) |
Correspondence
Address: |
WESTERMAN, HATTORI, DANIELS & ADRIAN, LLP
1250 CONNECTICUT AVENUE, NW, SUITE 700
WASHINGTON
DC
20036
US
|
Assignee: |
TGK CO., LTD.
Hachioji-shi
JP
|
Family ID: |
38121651 |
Appl. No.: |
11/711683 |
Filed: |
February 28, 2007 |
Current U.S.
Class: |
62/527 ;
62/222 |
Current CPC
Class: |
F25B 2400/0411 20130101;
F25B 2400/0409 20130101; F25B 41/31 20210101; F25B 2500/06
20130101; F25B 2341/0683 20130101; F25B 40/00 20130101; F25B
2500/08 20130101 |
Class at
Publication: |
62/527 ;
62/222 |
International
Class: |
F25B 41/06 20060101
F25B041/06; F25B 41/04 20060101 F25B041/04 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 7, 2006 |
JP |
2006-060813 |
Claims
1. A thermostatic expansion valve that is configured to control a
flow rate of refrigerant to be delivered to an evaporator by
causing a temperature-sensing section to sense a temperature and a
pressure of refrigerant having flowed out from an evaporator,
comprising: a bypass passage formed between a high-pressure
refrigerant inlet to which high-pressure refrigerant is supplied or
a low-pressure refrigerant outlet from which low-pressure
refrigerant is delivered to the evaporator, and a refrigerant
passage that passes the refrigerant having flowed out from the
evaporator, for passing high-pressure liquid refrigerant or
low-pressure gas-liquid mixed refrigerant to a downstream side of
said temperature-sensing section.
2. The expansion valve according to claim 1, wherein said bypass
passage is an orifice formed through a body between said
high-pressure refrigerant inlet and said refrigerant passage.
3. The expansion valve according to claim 1, wherein said bypass
passage has a differential pressure control valve that opens when a
differential pressure thereacross becomes not lower than a
predetermined value, in a passage formed through a body between
said high-pressure refrigerant inlet and said refrigerant
passage.
4. The expansion valve according to claim 1, wherein said bypass
passage is an orifice formed through a body between said
low-pressure refrigerant outlet and said refrigerant passage.
5. The expansion valve according to claim 1, wherein said bypass
passage has a differential pressure control valve that opens when a
differential pressure thereacross becomes not lower than a
predetermined value, in a passage formed through a body between
said low-pressure refrigerant outlet and said refrigerant
passage.
6. The expansion valve according to claim 1, wherein said bypass
passage is a through hole formed through a body such that a shaft
is inserted therethrough, said shaft being disposed between said
temperature-sensing section and a valve element that controls the
flow rate of refrigerant delivered to the evaporator.
7. The expansion valve according to claim 1, wherein said bypass
passage has a differential pressure control valve that opens when a
differential pressure thereacross becomes not lower than a
predetermined value, in a through hole formed through a body such
that a shaft is inserted therethrough, said shaft being disposed
between said temperature-sensing section and a valve element that
controls the flow rate of refrigerant delivered to the
evaporator.
8. The expansion valve according to claim 1, which is applied to a
refrigeration cycle provided with an internal heat exchanger that
performs heat exchange between refrigerant having flowed out from a
condenser and refrigerant being drawn into a compressor.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority of Japanese Application No.
2006-060813 filed on Mar. 7, 2006 and entitled "Expansion
Valve".
BACKGROUND OF THE INVENTION
[0002] (1) Field of the Invention
[0003] The present invention relates to an expansion valve, and
more particularly to a thermostatic expansion valve that controls
the flow rate of refrigerant to be supplied to an evaporator,
according to a temperature and a pressure at an outlet of the
evaporator in a refrigeration cycle of an automotive air
conditioner.
[0004] (2) Description of the Related Art
[0005] From the viewpoint of environmental problems concerning
global warming, it is proposed to use carbon dioxide in place of a
CFC substitute (HFC-134a), as refrigerant in a refrigeration cycle
for an automotive air conditioner. In the system of the
refrigeration cycle using carbon dioxide as refrigerant, to enhance
efficiency, an internal heat exchanger is generally used (see e.g.
Japanese Unexamined Patent Publication No. 2001-108308).
[0006] The internal heat exchanger is configured such that heat
exchange is performed between refrigerant flowing through a path
extending from a gas cooler that cools high-temperature,
high-pressure refrigerant compressed by a compressor, to an
expansion valve, and refrigerant flowing through a path extending
from an accumulator to the compressor. With this configuration,
gaseous-phase refrigerant drawn from the accumulator is superheated
by the refrigerant flowing through the path on the high-pressure
side of the internal heat exchanger, and then is delivered to the
compressor. This enables the compressor to draw in dry refrigerant,
and hence operate efficiently.
[0007] In contrast, also in a refrigeration cycle using HFC-134a as
refrigerant, it is contemplated to employ a system incorporating
the internal heat exchanger. Improved efficiency is expected from
such a system as well.
[0008] However, in the refrigeration cycle using HFC-134a as
refrigerant, a thermostatic expansion valve is generally used as an
expansion valve. The thermostatic expansion valve controls
refrigerant at the outlet of an evaporator such that it has a
predetermined degree of superheat. As a result, in a refrigeration
cycle provided with an internal heat exchanger such that heat
exchange is performed between refrigerant flowing through a path
extending from a condenser to the expansion valve, and refrigerant
flowing through a path extending from the evaporator to the
compressor, refrigerant already superheated at the outlet of the
evaporator is further superheated by the internal heat exchanger
and then is delivered to the compressor, so that particularly when
the refrigeration cycle is being operated in a state of the
refrigeration load being high, there arises a problem of the
temperature of refrigerant compressed by the compressor becoming
too high to causes deterioration of lubricating oil in the
compressor by the high temperature.
SUMMARY OF THE INVENTION
[0009] The present invention has been made in view of the problem,
and an object thereof is to provide an expansion valve which is
capable of preventing the temperature of refrigerant compressed by
a compressor from becoming too high, when a refrigeration load on a
refrigeration cycle using an internal heat exchanger is high.
[0010] To solve the above problem, according to the present
invention, there is provided a thermostatic expansion valve that is
configured to control a flow rate of refrigerant delivered to an
evaporator by causing a temperature-sensing section to sense a
temperature and a pressure of refrigerant having flowed out from an
evaporator, comprising a bypass passage formed between a
high-pressure refrigerant inlet to which high-pressure refrigerant
is supplied or a low-pressure refrigerant outlet from which
low-pressure refrigerant is delivered to the evaporator, and a
refrigerant passage that passes the refrigerant having flowed out
from the evaporator, for passing high-pressure liquid refrigerant
or low-pressure gas-liquid mixed refrigerant to a downstream side
of the temperature-sensing section.
[0011] The above and other objects, features and advantages of the
present invention will become apparent from the following
description when taken in conjunction with the accompanying
drawings which illustrate preferred embodiments of the present
invention by way of example.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a system diagram of a refrigeration cycle to which
is applied an expansion valve according to the present
invention.
[0013] FIG. 2 is a central longitudinal cross-sectional view of the
construction of an expansion valve according to a first
embodiment.
[0014] FIG. 3 is a central longitudinal cross-sectional view of the
construction of an expansion valve according to a second
embodiment.
[0015] FIG. 4 is a central longitudinal cross-sectional view of the
construction of an expansion valve according to a third
embodiment.
[0016] FIG. 5 is a central longitudinal cross-sectional view of the
construction of an expansion valve according to a fourth
embodiment.
[0017] FIG. 6 is a central longitudinal cross-sectional view of the
construction of an expansion valve according to a fifth
embodiment.
[0018] FIG. 7 is a central longitudinal cross-sectional view of the
construction of an expansion valve according to a sixth
embodiment.
[0019] FIG. 8 is a central longitudinal cross-sectional view of the
construction of an expansion valve according to a seventh
embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0020] Hereinafter, embodiments of the present invention will be
described in detail based on examples in which they are applied to
a refrigeration cycle using HFC-134a as refrigerant and including
an internal heat exchanger.
[0021] FIG. 1 is a system diagram showing a refrigeration cycle to
which an expansion valve according to the present invention is
applied.
[0022] The refrigeration cycle comprises a compressor 1 that
compresses refrigerant, a condenser 2 that condenses the compressed
refrigerant, an expansion valve 3 that throttles and expands cooled
refrigerant, and an evaporator 4 that evaporates the expanded
refrigerant. Further, the refrigeration cycle includes an internal
heat exchanger 5 that performs heat exchange between refrigerant
flowing from the condenser 2 to the expansion valve 3 and
refrigerant flowing from the evaporator 4 to the compressor 1 via
the expansion valve 3.
[0023] The expansion valve 3 is a so-called thermostatic expansion
valve that has a temperature-sensing section for sensing the
temperature and pressure of refrigerant having flowed out from the
evaporator 4, and is configured to control the flow rate of
refrigerant delivered to the evaporator 4 according to the
temperature and pressure of refrigerant, sensed by the
temperature-sensing section. The expansion valve 3 according to the
present invention internally includes a bypass passage 3a
(indicated by arrows of solid lines) for causing high-pressure
liquid refrigerant delivered from the internal heat exchanger 5 to
flow to a downstream side of the temperature-sensing section, or a
bypass passage 3b (indicated by a arrow of a broken line) for
causing low-pressure gas-liquid mixed refrigerant delivered to the
evaporator 4 to flow to the downstream of the temperature-sensing
section. Next, a description will be given of details of the
construction of the expansion valve 3.
[0024] FIG. 2 is a central longitudinal cross-sectional view of the
construction of the expansion valve according to a first
embodiment.
[0025] The expansion valve 10 according to the first embodiment has
a body 11 a side of which is formed with a high-pressure
refrigerant inlet 12 into which high-temperature, high-pressure
liquid refrigerant is delivered from the internal heat exchanger 5,
a low-pressure refrigerant outlet 13 from which low-temperature,
low-pressure liquid throttled and expanded by the expansion valve
10 is delivered to the evaporator 4, a refrigerant passage inlet 14
for receiving evaporated refrigerant from the evaporator 4, and a
refrigerant passage outlet 15 for delivering refrigerant having
passed through the expansion valve 10 to the internal heat
exchanger 5.
[0026] A valve seat 16 is integrally formed with the body 11 in a
passage communicating between the high-pressure refrigerant inlet
12 and the low-pressure refrigerant outlet 13, and a ball-shaped
valve element 17 is disposed on the upstream side of the valve seat
16. A valve element receiver 18 for receiving the valve element 17,
and a compression coil spring 19 that urges the valve element 17
via the valve element receiver 18 in a direction in which the valve
element 17 is seated on the valve seat 16 are arranged in a space
accommodating the valve element 17. A lower end, as viewed in FIG.
1, of the compression coil spring 19 is received by a spring
receiver 20 which is fitted into an adjustment screw 21 screwed
into a lower end of the body 11. The adjustment screw 21 has a
function of adjustmenting the load of the compression coil spring
19 by adjusting the amount of screwing itself into the body 11.
[0027] Further, the expansion valve 10 has a temperature-sensing
section provided in an upper end of the body 11. The
temperature-sensing section comprises an upper housing 22, a lower
housing 23, a diaphragm 24 disposed in a manner dividing a space
enclosed by the housings, and a disk 25 disposed below the
diaphragm 24.
[0028] A shaft 26 is disposed below the disk 25 for transmitting
the displacement of the diaphragm 24 to the valve element 17. An
upper portion of the shaft 26 is held by a holder 28 disposed
extending across a refrigerant passage 27 communicating between the
refrigerant passage inlet 14 and the refrigerant passage outlet 15.
A compression coil spring 29 giving lateral load to an upper end of
the shaft 26 is disposed in the holder 28 so as to suppress the
vibration of the shaft 26 in the longitudinal direction thereof,
caused by fluctuations in the pressure of high-pressure
refrigerant.
[0029] The body 11 is formed with a bypass passage 30 through which
the high-pressure refrigerant delivered into the body 11 bypasses
the expansion valve 10. The bypass passage 30 is formed between the
high-pressure refrigerant inlet 12 into which the high-pressure
liquid refrigerant is delivered, and the refrigerant passage 27,
and has a differential pressure control valve inserted in an
intermediate portion thereof. The differential pressure control
valve comprises a valve seat 31, a valve element 32 disposed on the
downstream side of the valve seat 31 in opposed relation thereto in
a manner movable to and away therefrom, a compression coil spring
33 urging the valve element 32 in the valve-closing direction, and
a spring receiver 34 press-fitted into the bypass passage 30 for
receiving the compression coil spring 33. The bar-shaped valve
element 32 has a plurality of communication grooves formed in an
outer periphery thereof such that they extend in the longitudinal
direction, and when the differential pressure control valve is
opened, the high-pressure liquid refrigerant flows through the
communication grooves.
[0030] The expansion valve 10 configured as above senses the
pressure and temperature of refrigerant returning from the
evaporator 4 to the refrigerant passage inlet 14. When the
temperature of the refrigerant is high or the pressure thereof is
low, the diaphragm 24 is displaced downward, as viewed in FIG. 2,
and the displacement is transmitted to the valve element 17 via the
shaft 26 to thereby move the valve element 17 in the valve-opening
direction, whereas when the temperature of the refrigerant is low
or the pressure thereof is high, the valve element 17 is caused to
move in the valve-closing direction, whereby the opening degree of
the expansion valve 10 is controlled to control the flow rate of
refrigerant to be delivered to the evaporator 4. The expansion
valve 10 controls the flow rate of refrigerant to be delivered to
the evaporator 4 by sensing the temperature of refrigerant in the
outlet of the evaporator 4, to thereby control refrigerant flowing
from the evaporator 4 into the refrigerant passage inlet 14 such
that it has a predetermined degree of superheat.
[0031] On the other hand, liquid refrigerant delivered from the
evaporator 4 into the refrigerant passage inlet 14 is mixed with
superheated refrigerant passing through the refrigerant passage 27,
via the bypass passage 30. The bypassing amount of the liquid
refrigerant is controlled according to the differential pressure
between pressure in the high-pressure refrigerant inlet 12 and
pressure in the refrigerant passage 27. When the refrigeration load
is low, the differential pressure between discharge pressure and
suction pressure in the compressor 1 is low, and hence the
differential pressure between the pressure in the high-pressure
refrigerant inlet 12 and the pressure in the refrigerant passage 27
is also low, whereby the differential pressure control valve
inserted in the bypass passage 30 is closed. In such a case, the
liquid refrigerant is inhibited from directly flowing into the
downstream side of the temperature-sensing section. This is because
when the refrigeration load is low, the temperature of refrigerant
compressed by the compressor 1 is not very high.
[0032] When the refrigeration load is high, the differential
pressure between the discharge pressure and the suction pressure in
the compressor 1 increases and the differential pressure between
the pressure in the high-pressure refrigerant inlet 12 and the
pressure in the refrigerant passage 27 also increase, so that when
the differential pressure across the differential pressure control
valve becomes equal to a predetermined value (e.g. 1.3 MPa) or
higher, the differential pressure control valve opens against the
urging force of the compression coil spring 33 to cause the liquid
refrigerant to flow into the downstream side of the
temperature-sensing section and get mixed with the liquid
refrigerant in the superheated state. This lowers the temperature
of the refrigerant in the superheated state to thereby change the
mixture into moist refrigerant. The internal heat exchanger 5
causes such refrigerant to exchange heat with lowered-temperature
refrigerant from the condenser 2, whereby the refrigerant undergoes
evaporation and is superheated, and the superheated refrigerant is
drawn into the compressor 1. Therefore, the temperature of
refrigerant drawn into the compressor 1 is prevented from becoming
too high, which prevents the temperature of refrigerant compressed
by the compressor 1 from becoming too high. This prevents thermal
deterioration of lubricating oil in the compressor 1, which
circulates together with refrigerant through the refrigeration
cycle.
[0033] FIG. 3 is a central longitudinal cross-sectional view of the
construction of an expansion valve according to a second
embodiment. In FIG. 3, component elements identical to those shown
in FIG. 2 are designated by identical reference numerals, and
detailed description thereof is omitted.
[0034] As is distinct from the expansion valve 10 according to the
first embodiment in which the differential pressure control valve
is inserted in the bypass passage 30, the expansion valve 40
according to the second embodiment is characterized in that the
bypass passage 30 is provided with an orifice 35 having a very
small degree of opening. According to the expansion valve 40
configured as above, liquid refrigerant always flows though the
bypass passage 30. Therefore, although the temperature of
refrigerant delivered to the internal heat exchanger 5 can be too
low when the refrigeration load is low, it is possible to reduce
costs compared with the expansion valve 10 according to the first
embodiment.
[0035] FIG. 4 is a central longitudinal cross-sectional view of the
construction of an expansion valve according to a third embodiment.
In FIG. 4, component elements identical to those shown in FIG. 2
are designated by identical reference numerals, and detailed
description thereof is omitted.
[0036] As is distinct from the expansion valve 10 according to the
first embodiment in which the bypass passage 30 is formed between
the high-pressure refrigerant inlet 12 and the refrigerant passage
27, the expansion valve 50 according to the third embodiment is
characterized in that the bypass passage 30 is formed through the
body 11 between the low-pressure refrigerant outlet 13 and the
refrigerant passage 27.
[0037] In the expansion valve 50, although the differential
pressure control valve is inserted in the bypass passage 30, the
spring load of the compression coil spring 33 is set such that the
differential pressure control valve is opened when the differential
pressure thereacross is not lower than a predetermined value of
e.g. 0.03 MPa. With this configuration, when the refrigeration load
is low, the flow rate of refrigerant flowing through the evaporator
4 is low, and hence the differential pressure between pressure in
the inlet of the evaporator 4 and pressure in the outlet thereof is
also low, and moreover the differential pressure is approximately
equal to the differential pressure across the differential pressure
control valve inserted in the bypass passage 30, so that the
differential pressure control valve is closed. As a result, when
high-pressure liquid refrigerant passes through a clearance between
the valve element 17 and the valve seat 16, all the gas-liquid
mixed refrigerant expanded at the low-pressure refrigerant outlet
13 is delivered to the evaporator 4, and is inhibited from directly
flowing into the downstream side of the temperature-sensing
section.
[0038] When the refrigeration load is high, the flow rate of
refrigerant flowing through the evaporator 4 is high, and hence the
differential pressure between the pressure in the inlet of the
evaporator 4 and the pressure in the outlet thereof becomes high,
that is, the differential pressure across the differential pressure
control valve is increased. When the differential pressure becomes
equal to the predetermined value or higher, the differential
pressure control valve opens against the urging force of the
compression coil spring 33 to cause the liquid refrigerant to flow
into the downstream side of the temperature-sensing section and get
mixed with the refrigerant in the superheated state. As a result,
the temperature of refrigerant drawn into the compressor 1 is
prevented from becoming too high, which also prevents the
temperature of refrigerant compressed by the compressor 1 from
becoming too high. This also prevents thermal deterioration of
lubricating oil in the compressor 1.
[0039] FIG. 5 is a central longitudinal cross-sectional view of the
construction of an expansion valve according to a fourth
embodiment. In FIG. 5, component elements identical to those shown
in FIG. 3 are designated by identical reference numerals, and
detailed description thereof is omitted.
[0040] Similarly to the expansion valve 40 according to the second
embodiment, the expansion valve 60 according to the fourth
embodiment has the orifice 35 formed in the bypass passage 30.
According to the expansion valve 60 configured as above, gas-liquid
mixed refrigerant is always allowed to flow though the bypass
passage 30. As described above, gas-liquid mixed refrigerant is
mixed with refrigerant flowing through the refrigerant passage,
thereby lowering the temperature of refrigerant delivered to the
internal heat exchanger 5, which prevents the temperature of
refrigerant compressed by the compressor 1 from becoming too
high.
[0041] FIG. 6 is a central longitudinal cross-sectional view of the
construction of an expansion valve according to a fifth embodiment.
In FIG. 6, component elements identical to those shown in FIG. 2
are designated by identical reference numerals, and detailed
description thereof is omitted.
[0042] In the expansion valve 70 according to the fifth embodiment,
the bypass passage 30 is formed by a through hole which is formed
through the body 11 such that the shaft 26 disposed between the
temperature-sensing section and the valve element 17 is inserted
therethrough. In the bypass passage 30, the valve element 32 of the
differential pressure control valve is axially movably disposed as
a guide for the shaft 26, and the compression coil spring 33 is
disposed between the valve element 32 and the holder 28, for urging
the valve element 32 in a direction in which the valve element 32
is seated on the valve seat 31 formed by a stepped portion in the
bypass passage 30.
[0043] When compared to the expansion valve 50 of FIG. 4 according
to the third embodiment, the expansion valve 70 is different
therefrom only in the location of the bypass passage 30 and has the
differential pressure control valve disposed in the bypass passage
30, which opens when the differential pressure thereacross becomes
equal to the predetermined value or higher. Therefore, the
expansion valve 70 operates in quite the same manner.
[0044] Further, although an opening, through which refrigerant is
supplied from the bypass passage 30 to the refrigerant passage 27,
is disposed at a location of the refrigerant passage 27, opposed to
the temperature-sensing section, low-temperature gas-liquid mixed
refrigerant that has been supplied from the bypass passage 30 to
the refrigerant passage 27 through the differential pressure
control valve is immediately carried away toward the refrigerant
passage outlet 15 by refrigerant from the evaporator 4, so that the
gas-liquid mixed refrigerant is mixed with refrigerant returning
from the evaporator 4 on the downstream side of the
temperature-sensing section, without the temperature thereof being
sensed by the temperature-sensing section.
[0045] FIG. 7 is a central longitudinal cross-sectional view of the
construction of an expansion valve according to a sixth embodiment.
In FIG. 7, component elements identical to those shown in FIG. 3
are designated by identical reference numerals, and detailed
description thereof is omitted.
[0046] In the expansion valve 80 according to the sixth embodiment,
the bypass passage 30 is formed by a through hole formed through
the body 11 such that the shaft 26 disposed between the
temperature-sensing section and the valve element 17 is inserted
therethrough, and has the orifice 35 formed in an intermediate
portion thereof. The expansion valve 80 is substantially identical
with the expansion valve 60 of FIG. 5 according to the fourth
embodiment, in respect of construction in which moist refrigerant
is always mixed with superheated refrigerant that is delivered from
the evaporator 4, by utilizing the differential pressure between
the pressure in the inlet of the evaporator 4 and the pressure in
the outlet thereof, and therefore the expansion valve 80 operates
in the same manner as the expansion valve 60.
[0047] FIG. 8 is a central longitudinal cross-sectional view of the
construction of an expansion valve according to a seventh
embodiment. In FIG. 8, component elements identical to those shown
in FIG. 4 are designated by identical reference numerals, and
detailed description thereof is omitted.
[0048] The expansion valve 90 according to the seventh embodiment
is applied to a refrigeration cycle that employs a double tube 36
as a pipe on the side toward the compressor 1 and the condenser 2.
The double tube 36 is formed by coaxially arranging an outer tube
36a and an inner tube 36b, and since refrigerant flowing through
the outer tube 36a and refrigerant flowing through the inner tube
36b are separated by the inner tube 36b, the double tube 36 has the
function of the internal heat exchanger 5.
[0049] The expansion valve 90 has the high-pressure refrigerant
inlet 12, into which high-temperature, high-pressure liquid
refrigerant is delivered from the condenser 2, disposed on a side
from which the valve element 17 is opened, and the compression coil
spring 19 and the spring receiver 20 disposed on the downstream
side of the valve element 17. The bypass passage 30 is formed
between a low-temperature, low-pressure chamber where the valve
element 17 is disposed, and the refrigerant passage 27 through
which refrigerant returning from the evaporator 4 passes. The valve
element 32 held on the shaft 26 in a manner movable in the
directions of opening and closing the bypass passage 30 is disposed
at an open end of the bypass passage 30 opening into the
refrigerant passage 27. The valve element 32 is urged by the
compression coil spring 33 in the direction in which the valve
element 32 is seated on the valve seat 31, to thereby form a
differential pressure control valve.
[0050] The high-temperature, high-pressure liquid refrigerant
delivered from the outer tube 36a of the double tube 36 into the
high-pressure refrigerant inlet 12 is throttled and expanded into
low-temperature, low-pressure refrigerant when passing through the
clearance between the valve element 17 and the valve seat 16, and
is delivered from the low-pressure refrigerant outlet 13 to the
evaporator 4. Refrigerant returning from the evaporator 4 is
received by the refrigerant passage inlet 14, and passes through
the refrigerant passage 27 to be delivered from the refrigerant
passage outlet 15 to the inner tube 36b of the double tube 36. At
this time, the temperature-sensing section senses the temperature
and pressure of the refrigerant passing through the refrigerant
passage 27, to control the flow rate of refrigerant to be delivered
to the evaporator 4.
[0051] Further, the differential pressure control valve disposed in
the bypass passage 30 senses the differential pressure between the
pressure of refrigerant in the low-pressure refrigerant outlet 13
and the pressure of refrigerant in the refrigerant passage 27, to
control the flow rate of refrigerant passing from the low-pressure
refrigerant outlet 13 to the refrigerant passage 27. Although an
opening, through which refrigerant is supplied from the bypass
passage 30 to the refrigerant passage 27, is formed at a location
of the refrigerant passage 27, opposed to the temperature-sensing
section, low-temperature gas-liquid mixed refrigerant that has been
supplied from the bypass passage 30 to the refrigerant passage 27
through the differential pressure control valve is carried away
toward the refrigerant passage outlet 15 by refrigerant evaporated
by the evaporator 4, so that the temperature of the gas-liquid
mixed refrigerant is not sensed by the temperature-sensing
section.
[0052] Although in the above-described embodiments, the
descriptions have been given of the examples in which they are
applied to the refrigeration cycle having the internal heat
exchanger and using HFC-134a as refrigerant, the present invention
can also be applied to a refrigeration cycle that uses another
refrigerant with a small global warming coefficient and similar
physical properties.
[0053] The expansion valve according to the present invention is
configured such that moist refrigerant is caused to flow through
the bypass passage to a downstream side of the temperature-sensing
section. Therefore, when the present invention is applied to the
refrigeration cycle employing the internal heat exchanger, it is
possible to lower the temperature of refrigerant to be delivered to
the compressor via the heat exchanger. This makes it possible to
prevent the temperature of refrigerant compressed by the compressor
under a high refrigeration load condition from becoming too high to
thereby prevent thermal deterioration of the lubricating oil in the
compressor.
[0054] The foregoing is considered as illustrative only of the
principles of the present invention. Further, since numerous
modifications and change will readily occur to those skilled in the
art, it is not desired to limit the invention to the exact
construction and applications shown and described, and accordingly,
all suitable modifications and equivalents may be regarded as
falling within the scope of the invention in the appended claims
and their equivalents.
* * * * *