U.S. patent application number 11/955869 was filed with the patent office on 2008-06-19 for automotive air conditioner.
This patent application is currently assigned to TGK CO., LTD.. Invention is credited to Hisatoshi HIROTA.
Application Number | 20080141691 11/955869 |
Document ID | / |
Family ID | 39027080 |
Filed Date | 2008-06-19 |
United States Patent
Application |
20080141691 |
Kind Code |
A1 |
HIROTA; Hisatoshi |
June 19, 2008 |
AUTOMOTIVE AIR CONDITIONER
Abstract
An automotive air conditioner which is capable of efficiently
disposing an internal heat exchanger, and enabling the air
conditioner to perform an efficient operation. A thermostatic
expansion valve is accommodated in a casing directly connected to
the refrigerant outlet of an evaporator. The inlet of the expansion
valve and a pipe for receiving high-pressure liquid refrigerant are
connected to each other within the casing. The outlet of the
expansion valve and the refrigerant inlet of the evaporator are
connected to each other within the casing. The internal heat
exchanger for performing heat exchange between high-pressure
refrigerant delivered to the inlet of the expansion valve and
low-pressure refrigerant returning to a compressor is connected
between the casing and a pipe joint disposed in a firewall.
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.
Tokyo
JP
|
Family ID: |
39027080 |
Appl. No.: |
11/955869 |
Filed: |
December 13, 2007 |
Current U.S.
Class: |
62/190 ;
62/515 |
Current CPC
Class: |
F25B 40/00 20130101;
B60H 2001/00957 20130101; F25B 2341/0683 20130101; B60H 1/00571
20130101; F25B 41/31 20210101; F25B 2500/18 20130101; F25B
2400/0409 20130101 |
Class at
Publication: |
62/190 ;
62/515 |
International
Class: |
F25B 1/00 20060101
F25B001/00; F25B 9/00 20060101 F25B009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 15, 2006 |
JP |
2006-338152 |
Claims
1. An automotive air conditioner wherein a thermostatic expansion
valve having an inlet to which is connected a pipe for receiving
high-pressure refrigerant and an outlet to which is connected a
refrigerant inlet pipe of an evaporator is accommodated in a casing
directly connected to a refrigerant outlet of said evaporator,
wherein an internal heat exchanger for performing heat exchange
between the high-pressure refrigerant and low-pressure refrigerant
returning from said casing to a compressor is connected to said
casing, and wherein a pipe joint for connecting a high-pressure
pipe extending from a receiver and a low-pressure pipe extending to
said compressor independently of each other is connected to an end
of said internal heat exchanger on the side opposite to the side
where the casing is connected.
2. The automotive air conditioner according to claim 1, wherein
said internal heat exchanger is formed by a double pipe in which a
low-pressure return pipe for allowing low-pressure refrigerant to
flow to said compressor is coaxially disposed outside a
high-pressure forward pipe for allowing the high-pressure
refrigerant to flow therethrough.
3. The automotive air conditioner according to claim 2, wherein in
the double pipe, heat transfer baffles are arranged between the
high-pressure forward pipe and the low-pressure return pipe,
whereby the state of the low-pressure return pipe and the
high-pressure forward pipe being coaxial with each other is
held.
4. The automotive air conditioner according to claim 1, wherein
said expansion valve has a back pressure cancelling structure in
which an area for a valve element to receive pressure of the
high-pressure refrigerant introduced into the inlet of said
expansion valve in a valve-opening direction and an area for a
shaft operating in unison with the valve element to receive the
pressure of the high-pressure refrigerant in a valve-closing
direction are made substantially equal to each other, the valve
element being provided with a guide for guiding the valve element
such that the valve element moves along a valve hole during opening
and closing operations of said expansion valve.
5. The automotive air conditioner according to claim 1, wherein
said expansion valve is provided with a differential pressure valve
for causing refrigerant having been just expanded to bypass to the
low-pressure return pipe of said internal heat exchanger when a
differential pressure between pressure at the refrigerant inlet of
said evaporator and pressure at the refrigerant outlet of said
evaporator exceeds a predetermined value.
6. The automotive air conditioner according to claim 5, wherein
said differential pressure valve includes a diaphragm for sensing
the differential pressure, a hollow cylindrical valve element held
in a center of said diaphragm, a spring for urging the hollow
cylindrical valve element such that the hollow cylindrical valve
element is seated on a valve seat having a flat surface, and an
orifice disposed in a refrigerant passage within the hollow
cylindrical valve element.
7. The automotive air conditioner according to claim 2, wherein the
pipe joint has one end face formed with a first connecting hole in
which the low-pressure return pipe of the double pipe is fitted,
and a second connecting hole which is coaxially disposed in the
first connecting hole, for having the high-pressure forward pipe
fitted therein, and another end face having a third connecting hole
and a fourth connecting hole arranged in parallel for communication
with the first connecting hole and the second connecting hole,
respectively.
8. The automotive air conditioner according to claim 1, wherein the
pipe joint is disposed in a firewall separating an engine room from
a vehicle compartment.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS, IF ANY
[0001] This application claims priority of Japanese Application No.
2006-338152 filed on Dec. 15, 2006, entitled "AUTOMOTIVE AIR
CONDITIONER".
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates to an automotive air conditioner, and
more particularly to an automotive air conditioner which is capable
of performing an efficient operation with component elements on a
vehicle compartment side in compact arrangement.
[0004] 2. Description of the Related Art
[0005] In general, an automotive air conditioner comprises a
compressor driven by an automotive engine, a condenser for
condensing refrigerant compressed by the compressor, a receiver for
separating the condensed refrigerant into gas and liquid phases and
storing the liquid refrigerant, an expansion valve for throttling
and expanding high-temperature, high-pressure refrigerant into
atomized low-temperature, low-pressure refrigerant, and an
evaporator for evaporating the atomized refrigerant by heat
exchange between the atomized refrigerant and air in the vehicle
compartment and then returning the evaporated refrigerant to the
compressor. As the expansion valve, there is widely used a
thermostatic expansion valve which controls the flow rate of
refrigerant delivered into the evaporator by sensing the
temperature and pressure of refrigerant at the refrigerant outlet
of the evaporator.
[0006] In the automotive air conditioner constructed as above, the
compressor, the condenser, and the receiver are arranged in an
engine room which accommodates the automotive engine, while the
evaporator is disposed in the vehicle compartment. Further, the
expansion valve is disposed between the evaporator and the
compressor and between the evaporator and the receiver. It is also
known to dispose the expansion valve in a firewall separating the
engine room from the vehicle compartment such that the body block
of the expansion valve is also used as a pipe joint for connecting
between the evaporator in the vehicle compartment and the
compressor and the receiver in the engine room (see e.g. Japanese
Unexamined Patent Publication No. 2001-235259 (FIGS. 11, 17 and
18)). To configure the expansion valve such that the body block
thereof also plays the role of the pipe joint can be said to be
very rational from the viewpoint of construction since operations
for assembling component elements to the automotive vehicle are
performed separately for those in the engine room and those in the
vehicle compartment, and finally it is necessary to install piping
in the firewall for connection via the expansion valve between the
compressor and the receiver in the engine room and the evaporator
in the vehicle compartment.
[0007] Further, in a supercritical refrigeration cycle using carbon
dioxide as refrigerant, for improvement of efficiency, that is, the
coefficient of performance and the cooling power thereof, it is
known to provide an internal heat exchanger and cause heat to be
exchanged between refrigerant flowing from a gas cooler to an
expansion device and refrigerant returning from an evaporator to a
compressor (see e.g. Japanese Unexamined Patent Publication No.
2001-108308).
[0008] The above idea is expected to be also applicable to a
refrigeration cycle which uses chlorofluorocarbon (HFC-134a),
generally used as refrigerant, or a gas having a physical property
equivalent or similar to that of chlorofluorocarbon, to improve the
efficiency thereof.
[0009] However, the idea suffers from the problem that when the
internal heat exchanger is disposed in the refrigeration cycle, it
is necessary to newly install piping to the refrigerant inlet and
outlet of the heat exchanger, which makes the construction of the
refrigeration cycle complicated, thereby making it difficult to
perform operations for assembling the component elements to the
automotive vehicle. Further, the internal heat exchanger returns
refrigerant leaving the evaporator to the compressor after
superheating the refrigerant by refrigerant sent from the condenser
to the expansion valve, and hence when refrigeration load is low,
the efficiency of the refrigeration cycle can be improved, whereas
when the refrigeration load is high, the temperature of refrigerant
returned to the compressor tends to become too high, which makes
lubricating oil for the compressor liable to undergo thermal
deterioration.
SUMMARY OF THE INVENTION
[0010] The present invention has been made in view of the above
points, and an object thereof is to provide an automotive air
conditioner which is capable of efficiently disposing an internal
heat exchanger, and enabling the air conditioner to perform an
efficient operation.
[0011] To attain the above object, the present invention provides
an automotive air conditioner. The automotive air conditioner is
characterized in that a thermostatic expansion valve having an
inlet to which is connected a pipe for receiving high-pressure
refrigerant and an outlet to which is connected a refrigerant inlet
pipe of an evaporator is accommodated in a casing directly
connected to a refrigerant outlet of the evaporator, an internal
heat exchanger for performing heat exchange between the
high-pressure refrigerant and low-pressure refrigerant returning
from the casing to a compressor is connected to the casing, and a
pipe joint for connecting a high-pressure pipe extending from a
receiver and a low-pressure pipe extending to the compressor
independently of each other is connected to an end of the internal
heat exchanger on the side opposite to the side where the casing is
connected.
[0012] 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
[0013] FIG. 1 is a system diagram of a refrigeration cycle for an
automotive air conditioner according to the present invention.
[0014] FIG. 2 is a cross-sectional view of a first embodiment of a
unit disposed in a vehicle compartment.
[0015] FIG. 3A is an enlarged cross-sectional view of essential
parts of an expansion valve.
[0016] FIG. 3B is a cross-sectional view taken on line a-a of FIG.
3A.
[0017] FIG. 4 is a cross-sectional view of a pipe connected to an
inlet of the expansion valve, taken along a plane passing through a
center line of the pipe.
[0018] FIG. 5 is an end view of a pipe joint.
[0019] FIG. 6A is an enlarged cross-sectional view of essential
parts of an expansion valve according to a second embodiment of the
present invention.
[0020] FIG. 6B is a cross-sectional view taken on line b-b of FIG.
6A.
[0021] FIG. 7 is a view of a differential pressure valve according
to a third embodiment of the present invention.
[0022] FIG. 8A is a partial perspective view of an end of an
example of the internal heat exchanger.
[0023] FIG. 8B is a partial cross-sectional perspective view of an
example of a high-pressure forward pipe.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0024] The invention will now be described in detail with reference
to the drawings showing a preferred embodiment thereof.
[0025] FIG. 1 is a system diagram of a refrigeration cycle for an
automotive air conditioner according to the present invention.
[0026] In the automotive air conditioner, a compressor 1 for
compressing refrigerant, a condenser 2 for condensing the
compressed refrigerant by heat exchange between the refrigerant and
the outside air, and a receiver 3 for separating the condensed
refrigerant into gas and liquid phases and storing surplus
refrigerant within the refrigeration cycle are arranged in an
engine room. On the other hand, an internal heat exchanger 4 for
performing heat exchange between high-temperature, high-pressure
refrigerant flowing from the receiver 3 and low-temperature,
low-pressure refrigerant returning to the compressor 1 are disposed
in a vehicle compartment. The outlet of the internal heat exchanger
4 on the high-pressure side is connected to the inlet of a
thermostatic expansion valve 5, and the outlet of the thermostatic
expansion valve 5 is connected to the refrigerant inlet of an
evaporator 6. The refrigerant outlet of the evaporator 6 opens into
a casing 7 accommodating the thermostatic expansion valve 5. The
casing 7 is connected to the inlet of the compressor 1 via the
internal heat exchanger 4. Further, disposed within the casing 7 is
a differential pressure valve 8 connecting the outlet of the
expansion valve 5 and the inlet of the internal heat exchanger 4 on
the low-pressure side. Furthermore, a pipe joint 9 is disposed in a
firewall 10 separating the engine room from the vehicle
compartment, for connecting between pipes to the compressor 1 and
the receiver 3 in the engine room and the internal heat exchanger 4
in the vehicle compartment.
[0027] The expansion valve 5 includes a temperature-sensing section
for sensing the temperature and pressure of refrigerant leaving the
evaporator 6, and controls the flow rate of refrigerant sent to the
evaporator 6 according to the temperature and pressure of the
refrigerant, sensed by the temperature-sensing section. The whole
expansion valve 5 is accommodated in the casing 7 directly
connected to the refrigerant outlet of the evaporator 6. Therefore,
connection between the inlet of the expansion valve 5 and a pipe
for receiving liquid refrigerant from the internal heat exchanger
4, and connection between the outlet of the expansion valve 5 and a
pipe to the refrigerant inlet of the evaporator 6 are both
performed within the casing 7, and moreover the casing 7 forms part
of a low-pressure return pipe for returning refrigerant from the
evaporator 6 to the compressor 1. For this reason, even when a
minute amount of refrigerant leaks from the sealing portions of the
inlet and outlet of the expansion valve 5, the refrigerant leaks
only into the casing 7, i.e. only into the low-pressure return
pipe, and hence is prevented from leaking to the outside of the
refrigeration cycle.
[0028] The internal heat exchanger 4 includes a high-pressure
forward pipe 4a for allowing high-temperature, high-pressure
refrigerant to flow to the expansion valve 5, and a low-pressure
return pipe 4b for allowing low-temperature, low-pressure
refrigerant to flow to the compressor 1, and performs heat exchange
between the high-temperature, high-pressure refrigerant flowing
through the high-pressure forward pipe 4a and the low-temperature,
low-pressure refrigerant flowing through the low-pressure return
pipe 4b.
[0029] In the automotive air conditioner configured as above, the
compressor 1 is driven by an automotive engine, for sucking and
compressing refrigerant to discharge the same. In doing this, the
displacement of the compressor 1 is controlled such that
refrigerant is discharged at a predetermined flow rate,
irrespective of the rotational speed of the engine. Refrigerant
compressed by the compressor 1 into high-temperature, high-pressure
refrigerant is sent to the condenser 2, in which the refrigerant is
condensed by heat exchange with the outside air to be sent to the
receiver 3. Liquid refrigerant obtained by gas/liquid separation in
the receiver 3 is sent via the internal heat exchanger 4 to the
expansion valve 5, where the liquid refrigerant is throttled and
expanded into atomized low-temperature, low-pressure refrigerant.
The atomized refrigerant is sent to the evaporator 6, where the
refrigerant exchanges heat with air in the vehicle compartment to
evaporate. As the atomized refrigerant evaporates in the evaporator
6, it cools air in the vehicle compartment by depriving the air of
latent heat of vaporization.
[0030] The refrigerant evaporated in the evaporator 6 returns to
the compressor 1 via the casing 7 and the internal heat exchanger
4. At this time, in the casing 7, the temperature-sensing section
of the expansion valve 5 accommodated in the casing 7 senses the
temperature and pressure of the refrigerant leaving the evaporator
6, and the expansion valve 5 controls the flow rate of refrigerant
supplied to the evaporator 6 such that the refrigerant leaving the
evaporator 6 has a predetermined degree of superheat. In the
internal heat exchanger 4, when the refrigerant leaving the
evaporator 6 returns to the compressor 1 via the low-pressure
return pipe 4b, the refrigerant is further superheated by
high-temperature, high-pressure refrigerant flowing through the
high-pressure forward pipe 4a toward the expansion valve 5, whereby
it is possible to enhance the efficiency of the refrigeration
cycle.
[0031] Further, the differential pressure valve 8 operates by
sensing the differential pressure between the pressure at the
refrigerant inlet and the pressure at the refrigerant outlet of the
evaporator 6. When pressure loss in the evaporator 6 increases, the
differential pressure valve 8 opens to cause refrigerant at the
outlet of the expansion valve 5 to bypass to the low-pressure
return pipe 4b of the internal heat exchanger 4. This increases
refrigeration load to increase the flow rate of refrigerant
circulating through the refrigeration cycle, and when the pressure
loss of the evaporator 6 exceeds a predetermined value, the
differential pressure valve 8 opens to supply refrigerant which is
throttled and expanded by the expansion valve 5 into atomized
low-temperature, low-pressure refrigerant. As described above, when
refrigeration load is high, moist refrigerant is supplied to the
low-pressure return pipe 4b of the internal heat exchanger 4, to
thereby prevent the temperature of refrigerant returned to the
compressor 1 from becoming too high, for preventing thermal
deterioration of lubricating oil for the compressor 1.
[0032] Next, a description will be given of examples of the
constructions of the internal heat exchanger 4, the expansion valve
5, the evaporator 6, and the pipe joint 9.
[0033] FIG. 2 is a cross-sectional view of a first embodiment of a
unit disposed in the vehicle compartment. FIG. 3A is an enlarged
cross-sectional view of essential parts of the expansion valve, and
FIG. 3B is a cross-sectional view taken on line a-a of FIG. 3A.
FIG. 4 is a cross-sectional view of a pipe connected to the inlet
of the expansion valve, taken along a plane passing through the
center line of the pipe. FIG. 5 is an end view of the pipe joint.
It should be noted that component elements in FIGS. 2 to 5
identical or similar to those shown in FIG. 1 are designated by
identical reference numerals.
[0034] The evaporator 6 has a refrigerant inlet 11 and a
refrigerant outlet 12 formed in the same end face thereof, for
introducing refrigerant and for discharging refrigerant,
respectively. An inlet pipe 13 is joined to the refrigerant inlet
11, and a hollow cylindrical connecting part 14 is joined to an end
face of the evaporator 6 in a manner enclosing the refrigerant
inlet 11 and the refrigerant outlet 12. Preferably, the inlet pipe
13 and the connecting part 14 are integrally formed with the
evaporator 6 by being welding to the evaporator 6 together when the
evaporator 6 is formed by furnace brazing.
[0035] A hollow cylindrical casing 7 having a closed end is
hermetically joined to the connecting part 14 via an O ring, and
accommodates the expansion valve 5. The expansion valve 5 has a
body 18 made e.g. of a resin material. The body 18 is integrally
formed with an inlet port 16 for introducing high-pressure
refrigerant and an outlet port 17 for discharging low-pressure
refrigerant. The body 18 has a passage formed therethrough for
communication between the inlet port 16 and the outlet port 17, and
a valve seat 19 is inserted in an intermediate portion of the
passage.
[0036] A valve element 20 is disposed on the downstream side of the
valve seat 19 in a manner movable to and away from the valve seat
19. The valve element 20 is disposed in a state urged by a spring
21 in the valve-closing direction. The spring 21 is received by an
adjustment screw 22 screwed into the outlet port 17, and the load
of the spring 21 is adjusted by the screwing amount of the
adjustment screw 22 into the body 18, whereby the set point of the
expansion valve 5 is adjusted.
[0037] The valve element 20 is rigidly fixed to a shaft 23. As
shown in detail in FIG. 3, the shaft 23 includes a large-diameter
portion 23a which is supported by the body 18 in a manner movable
in the opening and closing directions of the valve element 20, and
a small-diameter portion 23b which extends through a valve hole of
the valve seat 19. The shaft 23 has the valve element 20 fixed to
the small-diameter portion 23b thereof. The large-diameter portion
23a of the shaft 23 has a groove circumferentially formed in the
periphery thereof. An O ring 24 is fitted in the groove to thereby
prevent high-pressure refrigerant introduced into the inlet port 16
from leaking into the casing 7 through a clearance between the body
18 and the large-diameter portion 23a of the shaft 23.
[0038] Here, the large-diameter portion 23a of the shaft 23 is
configured to have a back pressure cancelling structure in which
the large-diameter portion 23a has an outer diameter equal to the
inner diameter of the valve hole of the valve seat 19 such that the
force of high pressure introduced into the inlet port 16 acting on
the valve element 20 in the valve-opening direction and the force
of the high pressure acting on the large-diameter portion 23a in
the valve-closing direction are set to be substantially equal to
each other to prevent the valve element 20 from being adversely
affected by the high pressure introduced into the inlet port 16.
Since the outer diameter of the large-diameter portion 23a and the
inner diameter of the valve hole of the valve seat 19 are set to be
equal to each other, the shaft 23 cannot be incorporated in the
expansion valve 5 via the valve hole of the valve seat 19 from the
outlet port side, with the O ring 24 fitted on the large-diameter
portion 23a. Therefore, the shaft 23 is inserted from a side
opposite to the outlet port 17, and the valve element 20 is fitted
from the outlet port side onto the small-diameter portion 23b of
the shaft 23 extending through the valve hole of the valve seat 19,
whereby the shaft 23 and the valve element 20 are assembled with
each other.
[0039] Further, the valve element 20 has a tapered portion 20a
which can be seated on a tapered portion 19a formed on the inner
periphery of the valve seat 19 on the downstream side thereof.
Further, a portion inward of the tapered portion 20a is integrally
formed with three guides 20b which are arranged at
circumferentially equal intervals and projecting radially outward.
The guides 20b move in the opening or closing direction of the
valve element 20 while sliding along the inner wall of the valve
hole, whereby it is possible to secure passages through which
refrigerant passes, between adjacent ones of the guides 20b, and
guide the opening or closing operation of the valve along the valve
hole while positioning the valve element 20 in the center of the
valve hole. This prevents the valve element 20 from rolling in
which the valve element 20 radially vibrates.
[0040] The body 18 has a power element 25 mounted on an end thereof
opposite from the outlet port 17. The power element 25 comprises an
upper housing and a lower housing, each made of thick metal, a
diaphragm 26 made of a flexible thin metal plate and disposed in a
manner partitioning a space enclosed by the upper and lower
housings, and a center disk 27 for transmitting the displacement of
the diaphragm 26 to the shaft 23. The space enclosed by the upper
housing and the diaphragm 26 forms a temperature-sensing chamber,
which is filled with refrigerant gas and the like. The lower
housing has several gas-passing holes formed so as to introduce
refrigerant passing through the casing 7 into space on the center
disk side. The amount of refrigerant to be introduced is adjusted
by changing the size or number of the gas-passing holes. Further, a
heat-insulating cover 28 made e.g. of resin is attached to the
power element 25 in a manner covering the same. The heat-insulating
cover 28 also serves as a fixing element for fixing the power
element 25 to the body 18.
[0041] The expansion valve 5 has the differential pressure valve 8
provided in the body 18 thereof. The differential pressure valve 8
is configured such that a passage for causing a space accommodating
the spring 21 to communicate with the outside of the expansion
valve 5 is formed through the body 18, and a valve element for
opening and closing the passage is urged by a spring from the
outside of the expansion valve 5 such that the valve element closes
the passage. As a result, when the pressure at the outlet port 17
of the expansion valve 5 becomes higher than the pressure outside
the expansion valve 5 (i.e. the interior of the casing 7) by a
value exceeding a predetermined value, the differential pressure
valve 8 acts to open. The predetermined value is set by adjusting
the load of the spring urging the valve element in the
valve-closing direction.
[0042] The outlet port 17 of the expansion valve 5 is fitted on the
inlet pipe 13 of the evaporator 6 and is sealed by an O ring 29. On
the other hand, the inlet port 16 of the expansion valve 5 and the
casing 7 are directly connected to the internal heat exchanger 4.
The internal heat exchanger 4 is formed as a double pipe in which
the low-pressure return pipe 4b is disposed outside the
high-pressure forward pipe 4a in coaxial relation thereto, so that
one end of the high-pressure forward pipe 4a and one end of the
low-pressure return pipe 4b are connected to the inlet port 16 of
the expansion valve 5 and the casing 7, respectively. More
specifically, the high-pressure forward pipe 4a is fitted in the
inlet port 16 of the expansion valve 5 and is sealed by an O ring
30. As to the casing 7, as shown in FIG. 4, a hollow cylindrical
connecting pipe 31 is brazed to a side surface thereof, and the
low-pressure return pipe 4b is fitted in the connecting pipe 31 and
is sealed by an O ring 32.
[0043] As described above, the expansion valve 5, the casing 7
accommodating the expansion valve 5, and the high-pressure forward
pipe 4a and the low-pressure return pipe 4b of the internal heat
exchanger 4 are connected to each other by a clamp device 33. As
clearly shown in FIG. 4, the clamp device 33 includes a first
holding member 33a formed in a manner covering a half of a side
surface of the casing 7, a second holding member 33b formed in a
manner covering the remaining half of the side surface of the
casing 7 including the connecting pipe 31, and fixing pins 33c for
connecting the first holding member 33a and the second holding
member 33b. The first holding member 33a and the second holding
member 33b have restricting portions for covering respective
fitting portions of the connecting part 14 and the casing 7 where
they are fitted to each other, from outside along the whole
circumference thereof, such that the restricting portions restrict
the motions of the connecting part 14 and the casing 7 in the
fitting direction. The second holding member 33b has an engaging
portion engaged with a rib formed in the vicinity of a foremost end
of the low-pressure return pipe 4b of the internal heat exchanger
4, in addition to the restricting portion, such that when the first
holding member 33a and the second holding member 33b are connected
to each other by the fixing pins 33c, a state of the rib of the
low-pressure return pipe 4b being pressed against the connecting
pipe 31 is maintained. At this time, since the high-pressure
forward pipe 4a and the low-pressure return pipe 4b are connected
to each other such that they maintain the coaxial arrangement
thereof, the connected state of the high-pressure forward pipe 4a
and the inlet port 16 of the expansion valve 5 is also maintained.
It should be noted that the closed end of the casing 7 is
configured to hold the power element 25 when the casing 7 is fitted
in the connecting part 14, which causes the connection between the
outlet port 17 of the expansion valve 5 and the inlet pipe 13 of
the evaporator 6 to be also maintained.
[0044] As described above, the expansion valve 5 is accommodated in
the low-pressure return pipe of the evaporator 6, and the expansion
valve 5 and the internal heat exchanger 4 are connected to each
other in the low-pressure return pipe, and hence the connecting
portion connecting between the inlet port 16 and the high-pressure
forward pipe 4a is the only connecting portion of a high-pressure
system in the vehicle compartment, from which refrigerant can leak
out. Moreover, since the connecting portion is within the
low-pressure return pipe, even if a minute amount of high-pressure
refrigerant leaks via the O ring 30, the refrigerant remains in the
low-pressure return pipe without leaking out into the
atmosphere.
[0045] The pipe joint 9 is disposed on a side of the internal heat
exchanger 4, opposite from the side where the casing 7 is disposed.
The pipe joint 9 has a first connecting hole 9a in which the
low-pressure return pipe 4b is fitted, and a second connecting hole
9b which is disposed in the first connecting hole 9a coaxially
therewith, for having the high-pressure forward pipe 4a fitted
therein, on an end face thereof on the internal heat exchanger
side. The low-pressure return pipe 4b fitted in the first
connecting hole 9a is fixed to the pipe joint 9 by inwardly swaging
the outer periphery of the first connecting hole 9a such that it is
entirely circumferentially engaged with a rib formed in the
vicinity of the foremost end of the low-pressure return pipe
4b.
[0046] Further, as shown in FIG. 5, the pipe joint 9 has a third
connecting hole 9c and a fourth connecting hole 9d formed in
parallel in an end face thereof on the engine room side, for
communication with the first connecting hole 9a and the second
connecting hole 9b, respectively. It should be noted that in the
present embodiment, the pipe joint 9 has an expanding hole 9e
formed in the end face, for expanding a passage between the first
connecting hole 9a and the third connecting hole 9c. Furthermore,
screw holes 9f and 9g are formed adjacent to the third connecting
hole 9c and the fourth connecting hole 9d in the end face of the
pipe joint 9, respectively. The screw hole 9f is provided for
screwing a fixing plate provided in the vicinity of the foremost
end of a low-pressure pipe after the low-pressure pipe extending to
the refrigerant inlet of the compressor 1 is fitted in the third
connecting hole 9c from the engine room side. The screw hole 9g is
provided for screwing a fixing plate provided in the vicinity of
the foremost end of a high-pressure pipe after the high-pressure
pipe extending from the receiver 3 is fitted in the fourth
connecting hole 9d from the engine room side.
[0047] Next, a description will be given of the operation of the
unit which is constructed as described above, and is disposed in
the vehicle compartment. First, when the automotive air conditioner
is not in operation, gas filling the temperature-sensing chamber of
the power element 25 is condensed, so that the pressure of the gas
is low. Therefore, as shown in FIG. 2, the diaphragm 26 is
displaced toward the temperature-sensing chamber, and the
displacement of the diaphragm 26 is transmitted to the valve
element 20 via the shaft 23, whereby the expansion valve 5 is
placed in the fully closed state.
[0048] When the automotive air conditioner is started in this
state, refrigerant is sucked by the compressor 1, and hence
pressure within the low-pressure return pipe 4b of the internal
heat exchanger 4 drops. The power element 25 senses this, so that
the diaphragm 26 is displaced outward to lift the valve element 20
via the shaft 23. On the other hand, refrigerant compressed by the
compressor 1 is condensed by the condenser 2, and liquid
refrigerant obtained by gas/liquid separation in the receiver 3 is
supplied to the inlet port 16 of the expansion valve 5 through the
high-pressure forward pipe 4a of the internal heat exchanger 4.
[0049] The high-temperature, high-pressure liquid refrigerant
supplied to the inlet port 16 is throttled and expanded while
passing through the expansion valve 5 and flows out as
low-temperature, low-pressure gas-liquid mixture refrigerant from
the outlet port 17. The refrigerant is supplied to the evaporator 6
through the inlet pipe 13, and is evaporated in the evaporator 6 to
flow out from the refrigerant outlet 12. The refrigerant having
returned from the evaporator 6 returns to the compressor 1 via the
casing 7, the low-pressure return pipe 4b of the internal heat
exchanger 4, the pipe joint 9, and the low-pressure pipe.
[0050] The space enclosed by the diaphragm 26 of the power element
25 and the lower housing of the same communicates with the inside
of the casing 7 via the gas-passing holes, so that while
refrigerant having returned from the evaporator 6 is passing
through the casing 7, some of the refrigerant is introduced into
the space within the power element 25, and the temperature of the
introduced refrigerant is detected by the power element 25. In the
early stage of the start of the automotive air conditioner, the
temperature of the refrigerant returning from the evaporator 6 is
high due to heat exchange with high-temperature air in the
compartment, and the power element 25 senses the temperature of the
refrigerant, so that the pressure within the temperature-sensing
chamber becomes high. This causes the diaphragm 26 to be largely
displaced toward the valve element 20, and this displacement is
transmitted to the valve element 20 via the shaft 23, whereby the
expansion valve 5 is fully opened.
[0051] As the temperature of refrigerant from the evaporator 6
becomes lower, the pressure within the temperature-sensing chamber
also becomes lower. Accordingly, the diaphragm 26 is displaced in a
direction away from the valve element 20, whereby the expansion
valve 5 moves in the valve-closing direction to control the flow
rate of refrigerant passing therethrough. At this time, the
expansion valve 5 operates to detect the temperature of refrigerant
having flowed from the evaporator 6, and controls the flow rate of
refrigerant supplied to the evaporator 6 such that the refrigerant
maintains a predetermined degree of superheat. As a consequence,
refrigerant in a superheated state is always returned to the
compressor 1, which enables the compressor 1 to perform an
efficient operation.
[0052] When refrigeration load is high as when the outside air
temperature is very high, the expansion valve 5 continues to allow
refrigerant to flow at a large flow rate. At this time, the
temperature of refrigerant having passed through the expansion
valve 5 is not lowered, and the evaporation temperature of the
refrigerant in the evaporator 6 is high. Moreover, the refrigerant
is further superheated in the internal heat exchanger 4 while the
refrigerant is returning from the evaporator 6 to the compressor 1.
When the flow rate of refrigerant is large as described above, the
differential pressure between the pressure at the inlet and the
pressure at the outlet of the evaporator 6 becomes large, and hence
the differential pressure valve 8 detects the differential pressure
to open itself. As a result, part of the atomized refrigerant
expanded into low-temperature refrigerant is mixed with superheated
refrigerant flowing out from the evaporator 6 and flowing into the
low-pressure return pipe 4b of the internal heat exchanger 4. This
causes the temperature of the superheated refrigerant to become
lower, and the refrigerant lowered in temperature comes to contain
moisture. Such refrigerant is evaporated and superheated by heat
exchange with high-temperature refrigerant flowing from the
receiver 3 in the internal heat exchanger 4, and is then sucked by
the compressor 1. This prevents the temperature of refrigerant
sucked by the compressor 1 from becoming too high, and therefore
the temperature of refrigerant compressed by the compressor 1 is
also prevented from becoming too high, which prevents thermal
deterioration of lubricating oil for the compressor 1, circulating
through the refrigeration cycle together with refrigerant.
[0053] FIG. 6A is an enlarged cross-sectional view of essential
parts of an expansion valve according to a second embodiment of the
present invention, and FIG. 6B is a cross-sectional view taken on
line b-b of FIG. 6A. It should be noted that component elements in
FIGS. 6A and 6B identical or similar to those shown in FIGS. 3A and
3B are designated by identical reference numerals.
[0054] The expansion valve 5a according to the present embodiment
is modified in valve structure thereof, and further the shape of
the guides 20b integrally formed with the valve element 20, for
preventing rolling of the valve element 20, is changed. More
specifically, in the expansion valve 5a, a guide for the O ring 24
is formed by fitting two rings 34a and 34b axially away from each
other onto the shaft 23 having a straight shape. Further, the valve
seat 19 of the expansion valve 5a includes the tapered portion 19a
which forms a seating surface where the valve element 20 is seated,
a valve hole 19b which forms an annular space between the same and
the tapered portion 20a of the valve element 20, and a
guide-holding portion which has an inner diameter smaller than that
of the valve hole 19b, and has an inner wall surface forming a
sliding surface along which the guides of the valve element 20
slide.
[0055] Here, the inner diameter of a cylinder 18a of the body 18
for holding the rings 34a and 34b of the shaft 23 in a manner
movable in the valve opening and closing directions is set to be
approximately equal to the diameter of a circle forming a boundary
between the tapered portion 19a of the valve seat 19 and an end
face thereof toward the outlet port 17, and the outer diameter of
the rings 34a and 34b on the shaft 23 is set to be approximately
equal to the diameter of a circle forming a boundary between the
tapered portion 19a and the valve hole 19b of the valve seat 19.
Thus, the effective pressure-receiving area of the valve element 20
for receiving high pressure in the valve-opening direction, and the
effective pressure-receiving area of the ring 34a (O ring 24) on
the shaft 23 for receiving high pressure in the valve-closing
direction can be made substantially equal to each other. This
enables even the power element 25 which operates with a small power
and is made compact in size so as to be accommodated in the casing
7 to accurately control the valve element 20 without being
adversely affected by the high pressure.
[0056] Further, as shown in FIG. 6B, in the present embodiment,
four guides 20b integrally formed with the valve element 20 are
circumferentially arranged for guiding the valve element 20 in the
valve opening and closing directions while positioning the valve
element 20 in the center of the guide-holding portion of the valve
seat 19.
[0057] FIG. 7 is a view of a differential pressure valve according
to a third embodiment of the present embodiment. It should be noted
that component elements in FIG. 7 identical or similar to those
shown in FIG. 2 are designated by identical reference numerals.
[0058] In the third embodiment, there is modified the construction
of the differential pressure valve 8 for delivering moist
refrigerant at the outlet of the expansion valve 5 to the
low-pressure return pipe 4b of the internal heat exchanger 4 by
bypassing the evaporator 6. More specifically, in this differential
pressure valve 8, a hollow cylindrical portion 35 is connected to a
position away from the power element 25 but close to the inlet of
the low-pressure return pipe 4b, that is, the outside of the body
18 of the expansion valve 5 in the vicinity of a position where the
adjustment screw 22 is screwed, and an opening 36 is formed in the
body 18 located at a position eccentric from the center line of the
hollow cylindrical portion 35. A portion of the body 18 located on
the center line of the hollow cylindrical portion 35 is formed with
a valve seat 37 having a flat surface, and a hollow cylindrical
valve element 38 is disposed in a manner movable to and away from
the valve seat 37. The valve element 38 is supported by a central
portion of a diaphragm 39 disposed in a manner partitioning the
interior of the hollow cylindrical portion 35, and is urged by a
spring 40 in the direction in which the valve element 38 is seated
on the valve seat 37. Further, an orifice 41 for limiting the flow
rate of refrigerant is formed within the hollow cylindrical valve
element 38.
[0059] According to the differential pressure valve 8 configured as
above, the differential pressure between the pressure at the
refrigerant inlet 11 of the evaporator 6 and the pressure at the
refrigerant outlet 12 of the same is sensed by the diaphragm 39
having a large pressure-receiving area. As a result, even with the
evaporator 6 which is small in pressure loss and hence generates
only a small differential pressure, the diaphragm 39 having a large
pressure-receiving area senses the small differential pressure,
whereby it is possible to obtain a sufficient actuating force to
open and close the valve element 38.
[0060] When the automotive air conditioner is not in operation, or
when it is operating with low refrigeration load, the valve element
38 is seated on the valve seat 37 by the urging force of the spring
40 in the valve-closing direction to close the differential valve
8. When the automotive air conditioner is operating with high
refrigeration load, refrigerant flows through the evaporator 6 at a
large flow rate, and hence the differential pressure between the
pressure at the refrigerant inlet 11 and the pressure at the
refrigerant outlet 12 is increased, and when the differential
pressure becomes larger than a predetermined value, the
differential pressure valve 8 is opened. As a consequence,
low-temperature moist refrigerant having been just throttled and
expanded flows via the hollow cylindrical valve element 38 to flow
into the low-pressure return pipe 4b of the internal heat exchanger
4, and is mixed with refrigerant from the evaporator 6. At this
time, the flow rate of the refrigerant is limited by the orifice 41
formed in the valve element 38. The moist refrigerant is completely
evaporated by the internal heat exchanger 4, and is then sucked by
the compressor 1. Since the temperature of the refrigerant becomes
lower during evaporation thereof, the refrigerant from the
evaporator 6 is cooled, whereby the temperature of refrigerant
compressed by the compressor 1 and discharged is prevented from
becoming too high, to prevent thermal deterioration of lubricating
oil.
[0061] FIG. 8A is a partial perspective view of an end of an
example of the internal heat exchanger. FIG. 8B is a partial
cross-sectional perspective view of an example of the high-pressure
forward pipe.
[0062] The internal heat exchanger 4 is formed by inserting the
high-pressure forward pipe 4a into the low-pressure return pipe 4b.
The high-pressure forward pipe 4a has a plurality of baffles 4c
radially formed on the outer periphery thereof, and a plurality of
protrusions 4d radially formed on inner periphery thereof. The
high-pressure forward pipe 4a configured as above is formed by
working on a pipe material having the baffles 4c and the
protrusions 4d, which is formed by drawing, such that the outer
edges of the baffles 4c are bent into wavy shapes along the
direction of the length thereof. Further, the foremost end of the
high-pressure forward pipe 4a is subjected to rib processing for
disposing the O ring 30 after eliminating the protrusions 4d within
the foremost end. The rib processing is similarly performed on the
foremost end of the low-pressure return pipe 4b so as to dispose
the O ring 32.
[0063] By arranging the baffles 4c between the high-pressure
forward pipe 4a and the low-pressure return pipe 4b, the
low-pressure return pipe 4b and the high-pressure forward pipe 4a
is held in the coaxial state, and by bending the baffles 4c into
the form of a wave, contact areas between refrigerant flowing
through the low-pressure return pipe 4b and the baffles 4c are
increased to enhance heat transfer efficiency from high-temperature
refrigerant flowing through the high-pressure forward pipe 4a to
low-temperature refrigerant flowing through the low-pressure return
pipe 4b.
[0064] The automotive air conditioner according to the present
invention is configured such that the evaporator, the expansion
valve, and the pipe joint are connected by the internal heat
exchanger, whereby improvement of the efficiency of the
refrigeration cycle by the installation of the internal heat
exchanger is made possible, while dispensing with a special space
for disposing the internal heat exchanger. Further, although in the
refrigeration cycle having the internal heat exchanger, the
temperature of refrigerant discharged from the compressor during
high load tends to become too high, refrigerant having been just
expanded is mixed in refrigerant returning from the evaporator to
the compressor to thereby lower the temperature of the returning
refrigerant, which makes it possible to lower the temperature of
the discharged refrigerant, thereby making it possible to prevent
thermal deterioration of lubricating oil for the compressor.
[0065] The foregoing is considered as illustrative only of the
principles of the present invention. Further, since numerous
modifications and changes 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.
* * * * *