[0001] The present invention relates to an expansion valve, and more particularly to a thermostatic
expansion valve suitable for use in a refrigeration cycle.
[0002] A refrigeration cycle in an automotive air conditioner typically includes a compressor
for compressing a circulating refrigerant, a condenser for condensing the compressed
refrigerant, an expansion valve for throttling and expanding the condensed refrigerant,
and an evaporator for cooling the air in a vehicle interior using evaporative latent
heat of the refrigerant. The expansion valve is, for example, a thermostatic expansion
valve that senses the temperature and the pressure of the refrigerant on the outlet
side of the evaporator and adjusts the valve opening degree so that the refrigerant
delivered from the evaporator has a predetermined degree of superheat, to control
the flow rate of the refrigerant to be delivered to the evaporator (refer, for example,
to Japanese Patent Application Publication No.
2013-242129).
[0003] Such an expansion valve has a body in which a first passage, through which the refrigerant
flowing from the condenser toward the evaporator passes, and a second passage, through
which the refrigerant having returned from the evaporator passes, are formed. The
first passage includes a valve hole, and a valve element disposed facing the valve
hole. The valve element moves toward and away from the valve hole to regulate the
flow rate of the refrigerant flowing toward the evaporator. The body has a mounting
hole formed at one end thereof, which communicates with the second passage via a communication
hole. A power element is mounted on the mounting hole. The power element senses the
temperature and the pressure of the refrigerant flowing through the second passage
and operates in response to the sensed temperature and pressure. The drive force of
the power element is transmitted to the valve element via a shaft. The shaft extends
through a partition between the first passage and the second passage. One end of the
shaft is connected to the power element, and the other end thereof is connected to
the valve element.
[0004] The power element has a housing mounted on the body, a diaphragm that partitions
the housing into a closed space and an open space, and a disc disposed in the open
space. A gas for sensing temperature is sealed in the closed space. The open space
communicates with the second passage. Part of the refrigerant flowing through the
second passage flows into and out from the open space. Expansion or contraction of
the closed space depending on the temperature and the pressure of the refrigerant
displaces the diaphragm, and the drive force caused by the displacement is transmitted
to the shaft via the disc. When the refrigerant temperature at the outlet of the evaporator
becomes lower, the closed space contracts, and the valve section thus operates in
the closing direction. Conversely, when the refrigerant temperature becomes higher,
the closed space expands, and the valve section thus operates in the opening direction.
Such autonomous operation of the power element adjusts the opening degree of the valve
section and thus properly controls the degree of superheat of the refrigerant at the
evaporator outlet. A material having a high thermal conductivity is typically used
for the disc so that the temperature of the refrigerant introduced into the open space
is efficiently transmitted to the diaphragm.
[0005] Note that, during low-load operation of the refrigeration cycle, the proportion of
liquid-phase components in the refrigerant delivered from the evaporator outlet may
increase, and the liquid refrigerant (droplets) may be directed into the open space
of the power element and adhere to the disc. Since liquid refrigerant (liquid phase)
has a smaller heat transfer time constant (hereinafter also simply referred to as
"time constant") than gas refrigerant (gas phase), the liquid refrigerant adhering
to the disc having a high thermal conductivity may cause hunting, which is frequent
opening and closing of the valve section.
[0006] Thus, in order to prevent or minimize the hunting, a technique of regulating the
flow of the liquid refrigerant into the open space by providing a closing plate in
a communication passage through which the open space of the power element and the
second passage communicate with each other and permitting flow of the refrigerant
only through a pressure equalizing hole formed in the closing plate is also proposed
(refer, for example, to Japanese Patent Application Publication No.
2013-245921). In this structure, the closing plate has a stepped disc-like shape, and has an
insertion hole for the shaft at the center and the pressure equalizing hole having
a small diameter at a position offset from the insertion hole. The pressure equalizing
hole is positioned in the closing plate to open at the downstream of the shaft in
the second passage. In addition, a small-diameter part of the closing plate is fitted
into the communication passage, which results in no step at the position of the communication
passage in the second passage, so as to reduce the noise caused by the refrigerant
passing therethrough.
Related Art List
[0007]
- (1) Japanese Patent Application Publication No. 2013-242129
- (2) Japanese Patent Application Publication No. 2013-245921
[0008] With the structure disclosed in Japanese Patent Application Publication No.
2013-245921, however, the pressure equalizing hole needs to be formed in addition to the insertion
hole in the closing plate. In addition, coaxial alignment of the outer shape of the
closing plate and the insertion hole needs to be ensured so that the operation of
the shaft will not be inhibited, which requires high processing accuracy of the closing
plate. Furthermore, since the pressure equalizing hole being offset from the center
makes the closing plate directional, the pressure equalizing hole needs to be precisely
positioned in mounting of the closing plate. This leads to an increase in the numbers
of processes and manhours, and constitutes a factor in rising manufacturing cost.
As a result of verification conducted by the inventors, however, no advantage is found
in forming the pressure equalizing hole at a position downstream of the shaft in terms
of reducing the liquid refrigerant entering the power element. Document
US2009/045264 discloses an expansion valve according to the preamble of claim 1.
[0009] In view of the above and other circumstances, one purpose of an embodiment of the
present invention is to provide an expansion valve that favorably functions at low
cost while preventing control hunting.
[0010] An expansion valve according to the invention, is defined by the features of claim
1. The expansion valve includes: a body having a first passage through which the refrigerant
flowing from the upstream side toward the evaporator passes, a second passage through
which the refrigerant returning from the evaporator passes, a valve hole formed in
the first passage, and a mounting hole communicating with the second passage; a valve
element that moves toward and away from the valve hole to adjust an opening degree
of the valve section; a power element having a housing mounted on the body in such
a manner as to close the mounting hole, a diaphragm partitioning an inside of the
housing into a closed space in which a temperature sensing medium is sealed and an
open space communicating with the second passage, and a disc located in the open space
in contact with the diaphragm; a shaft extending through a partition between the first
passage and the second passage, having a first end connected to the diaphragm through
the disc and a second end connected to the valve element, and being configured to
transmit a drive force in an axial direction to the valve element, the drive force
being generated by displacement of the diaphragm; and an inflow regulating part that
separates the open space from the second passage, has an insertion hole, through which
the shaft extends, coaxially along a central axis of the inflow regulating part, and
limits a flow of the refrigerant from the second passage into the open space to a
flow through a clearance between the shaft and the insertion hole.
[0011] The insertion hole is formed such that an opening area of the clearance between the
shaft and the insertion hole is 7.0 mm
2 or smaller, and the inflow regulating part is constituted by a shield member located
between the body and the housing and prevented from dropping off from the mounting
hole.
[0012] According to the invention, the inflow regulating part permits the flow of the refrigerant
from the second passage into the open space but limits the flow to a proper amount.
In particular, since the opening area of the insertion hole is set as above, occurrence
of control hunting is prevented or minimized as will be explained in the embodiment
described below. In addition, the insertion hole has both of the function of allowing
the shaft to pass and the function of properly limiting the inflow of the refrigerant.
Furthermore, since the clearance is formed between the insertion hole and the shaft,
the need for strict control of the dimensional accuracy of the inflow regulating part
is reduced. Thus, the number of processes required for the inflow regulating part
is reduced, and the expansion valve can be provided at low cost.
[0013]
- FIG. 1
- is a cross-sectional view of an expansion valve according to an embodiment;
- FIGS. 2A and 2B
- illustrate a power element and a structure around the power element;
- FIGS. 3A and 3B
- illustrate temperature sensing operation of the expansion valve;
- FIGS. 4A and 4B
- show a result of a hunting verification test;
- FIGS. 5A and 5B
- show a result of the hunting verification test;
- FIG. 6
- is a graph showing the relation between the opening degree of an insertion hole and
the amount of hunting; and
- FIGS. 7A and 7B
- Fig. 7a illustrates a structure of a main part of an expansion valve which does not
belong to the invention, Fig. 7b each illustrates a structure of a main part of an
expansion valve according to the invention.
[0014] Certain embodiments of the invention will now be described. The description does
not intend to limit the scope of the present invention, but to exemplify the invention.
[0015] An embodiment of the present invention will now be described in detail with reference
to the drawings. In the description below, for convenience of description, the positional
relationship in each structure may be expressed with reference to how the structure
is depicted in the drawings. In the following embodiment and its modifications, components
that are substantially the same will be designated by the same reference numerals
and redundant description thereof may be omitted as appropriate.
[0016] The embodiment embodies an expansion valve of the present invention in a form of
a thermostatic expansion valve applicable to a refrigeration cycle in an automotive
air conditioner. The refrigeration cycle includes a compressor for compressing a circulating
refrigerant, a condenser (external heat exchanger) for condensing the compressed refrigerant,
a receiver for separating the condensed refrigerant into gas and liquid, an expansion
valve for throttling and expanding the separated refrigerant and delivering the expanded
refrigerant, and an evaporator (internal heat exchanger) for evaporating the misty
refrigerant to cool the air in a vehicle interior by evaporative latent heat. For
convenience of description, detailed description of components other than the expansion
valve will be omitted herein.
[0017] FIG. 1 is a cross-sectional view of the expansion valve according to the embodiment.
[0018] The expansion valve 1 has a body 2 formed by extrusion molding of a material made
of an aluminum alloy and performing predetermined cutting on the member obtained by
the extrusion molding. The body 2 has a prism shape, and a valve section for throttling
and expanding the refrigerant is provided inside the body 2. A power element 3 is
disposed at an end in the longitudinal direction of the body 2.
[0019] The body 2 has, on lateral sides thereof, an inlet port 6 through which a high-temperature
and high-pressure refrigerant is introduced from the receiver side (condenser side),
an outlet port 7 through which the low-temperature and low-pressure refrigerant resulting
from the throttling expansion through the expansion valve 1 is delivered toward the
evaporator, an inlet port 8 through which the refrigerant evaporated by the evaporator
is introduced, and an outlet port 9 through which the refrigerant having passed through
the expansion valve 1 is delivered to the compressor side. In the embodiment, the
inlet port 6 and the outlet port 9 are open in a first side face of the body 2. The
outlet port 7 and the inlet port 8 are open in a second side face opposite to the
first side face. In a modification, the first side face and the second side face may
be adjacent to each other at the right angle. A screw hole 10 for mounting a pipe,
which is not illustrated, is formed between the inlet port 6 and the outlet port 9.
Each of the ports is connected with a pipe joint.
[0020] In the expansion valve 1, the inlet port 6, the outlet port 7, and a refrigerant
passage connecting these ports constitute a first passage 13. A valve section is formed
in an intermediate portion of the first passage 13. The refrigerant introduced through
the inlet port 6 is throttled and expanded into a spray through the valve section,
and delivered toward the evaporator through the outlet port 7. In addition, the inlet
port 8, the outlet port 9, and a refrigerant passage connecting these ports constitute
a second passage 14. The second passage 14 extends straight and an intermediate portion
thereof communicates with the inside of the power element 3. Part of the refrigerant
introduced through the inlet port 8 is supplied to the power element 3, which senses
the temperature of the refrigerant. The refrigerant having passed through the second
passage 14 is delivered toward the compressor through the outlet port 9.
[0021] A valve hole 16 is formed at the intermediate portion of the first passage 13. An
open end edge of the valve hole 16 on the side of the inlet port 6 is a valve seat
17. A valve element 18 is disposed facing the valve seat 17 from the side of the inlet
port 6. The valve element 18 has a spherical ball valve element 41 for opening and
closing the valve section by leaving and touching the valve seat 17, and a valve element
support 43 for supporting the ball valve element 41 from below, which are joined together.
[0022] A communication hole 19 connecting the inside and the outside of the body 2 is formed
in the lower part of the body 2. The upper half of the communication hole 19 forms
a valve chamber 40, in which the valve element 18 is accommodated. The valve chamber
40 communicates with the valve hole 16, and is formed coaxially with the valve hole
16. The valve chamber 40 also communicates with the inlet port 6 at a lateral side
thereof via an upstream-side passage 37. The upstream-side passage 37 includes a small
hole 42 that is open toward the valve chamber 40. The small hole 42 is a portion of
the first passage 13 where the cross-section of the first passage 13 is locally made
small.
[0023] The valve hole 16 communicates with the outlet port 7 via a downstream-side passage
39. Thus, the upstream-side passage 37, the valve chamber 40, the valve hole 16, and
the downstream-side passage 39 constitute the first passage 13. The upstream-side
passage 37 and the downstream-side passage 39 are parallel to each other and each
extend in a direction perpendicular to the axis of the valve hole 16. In a modification,
the inlet port 6 or the outlet port 7 may be positioned so that projections of the
upstream-side passage 37 and the downstream-side passage 39 are perpendicular to each
other (so that the upstream-side passage 37 and the downstream-side passage 39 are
skew with respect to each other).
[0024] An adjusting screw 20 is screwed into a lower half of the communication hole 19 in
such a manner as to seal the communication hole 19 from outside. A spring 23 for biasing
the valve element 18 in a valve closing direction is disposed between the valve element
18 (more specifically, the valve element support 43) and the adjusting screw 20. The
load of the spring 23 can be adjusted by adjustment of the insertion amount of the
adjusting screw 20 into the body 2. An O-ring 24 for preventing leakage of the refrigerant
is disposed between the adjusting screw 20 and the body 2.
[0025] A support portion 60, which is raised in an embossed manner, is formed on the middle
of an upper face of the body 2, and a mounting hole 50 having a recessed shape (a
bottomed, circular hole shape) is formed in the middle of the support portion 60.
A communication hole 52 is formed through a partition 51 between the mounting hole
50 and the second passage 14. The communication hole 52 is coaxial with the center
of a bottom portion of the mounting hole 50. The power element 3 has a lower part
screwed into the mounting hole 50 and is mounted on the body 2 in such a manner as
to seal an upper end opening of the body 2. An O-ring 30 for preventing leakage of
refrigerant is disposed between the power element 3 and the body 2.
[0026] The power element 3 has a housing 25 mounted on the body 2 in such a manner as to
close the mounting hole 50, and a diaphragm 28 disposed in such a manner as to partition
the inside of the housing 25 in the axial direction. The housing 25 includes an upper
housing 26 and a lower housing 27 attached to each other in the axial direction. The
upper housing 26 functions as a "first housing" and the lower housing 27 functions
as a "second housing."
[0027] Specifically, the power element 3 includes the diaphragm 28 between the upper housing
26 and the lower housing 27, and a disc 29 disposed on the lower housing 27 side of
the diaphragm 28. The upper housing 26 is formed by press-forming a stainless steel
material into a lidded shape. The lower housing 27 is formed by press-forming a stainless
steel material into a stepped cylindrical shape. The disc 29 is made of aluminum or
an aluminum alloy, for example, and has a higher thermal conductivity than the upper
and lower housings.
[0028] The power element 3 is formed in a shape of a container by making the upper housing
26 and the lower housing 27 in contact with each other at the openings thereof, mounting
the diaphragm 28 so that an outer edge of the diaphragm 28 is placed between outer
edges of the upper housing 26 and the lower housing 27, and welding along a circumferential
joint of the upper and lower housings. The inside of the power element 3 is partitioned
into a closed space S1 and an open space S2 by the diaphragm 28. A gas for sensing
temperature (which functions as a "temperature sensing medium") is sealed in the closed
space S1. The disc 29 is located in the open space S2.
[0029] A disc-like plate 31 is provided at the bottom portion of the mounting hole 50. The
plate 31 separates the open space of the power element 3 from the second passage 14,
and has an insertion hole 36 through which the shaft 33 extends in the middle. The
plate 31 functions as an "inflow regulating part" that limits the flow of the refrigerant
from the second passage 14 into the open space S2 to a flow through a clearance between
the shaft 33 and the insertion hole 36. Part of the refrigerant passing through the
second passage 14 is directed to the open space S2 via the communication hole 52 and
the insertion hole 36. The power element 3 senses the pressure and the temperature
of the refrigerant and generates a drive force in the opening or closing direction
of the valve section. A temperature sensing structure of the power element 3 will
be described later in detail.
[0030] An insertion hole 34 is formed through a partition 35 that separates the first passage
13 from the second passage 14 at a middle part of the body 2. The insertion hole 34
is a stepped hole having a small-diameter part 44 and a large-diameter part 46, which
are coaxial with each other. A lower end of the small-diameter part 44 is open toward
the first passage 13, while an upper end of the large-diameter part 46 is open toward
the second passage 14. An elongated shaft 33 extends through the small-diameter part
44 slidably in the axial direction. The large-diameter part 46 constitutes a mounting
hole in which a vibration-proof spring 48, which will be described below, is contained
in a coaxial manner.
[0031] The shaft 33 is a rod made of metal such as stainless steel, and disposed between
the disc 29 and the valve element 18. This enables the drive force generated by displacement
of the diaphragm 28 to be transmitted to the valve element 18 via the disc 29 and
the shaft 33 to open or close the valve section. One end side of the shaft 33 extends
across the second passage 14 and through the plate 31, and is connected with the disc
29. The other end side of the shaft 33 extends across the downstream-side passage
39 of the first passage 13 and through the valve hole 16, and is connected with the
valve element 18.
[0032] The large-diameter part 46 contains the vibration-proof spring 48 for applying biasing
force in a direction perpendicular to the axial direction of the shaft 33, that is,
a lateral load (sliding load) onto the shaft 33. The shaft 33 is subjected to the
lateral load of the vibration-proof spring 48, which suppresses vibration of the shaft
33 and the valve element 18 due to refrigerant pressure fluctuation.
[0033] The vibration-proof spring 48 is fixed coaxially with the small-diameter part 44,
and supports the shaft 33 with the shaft 33 coaxially extending through the vibration-proof
spring 48. The vibration-proof spring 48 biases the shaft 33 radially inward to apply
sliding resistance (friction) to the shaft 33. Note that a structure disclosed in
Japanese Patent Application Publication No.
2013-242129 can be used for the vibration-proof spring 48. Detailed description of a specific
structure of the vibration-proof spring 48 will thus be omitted.
[0034] In the present embodiment, a clearance between the insertion hole 34 and the shaft
33 is sufficiently small to achieve clearance seal to prevent or minimize leakage
of refrigerant from the first passage 13 into the second passage 14. In a modification,
a seal ring such as an O-ring may be disposed between the insertion hole 34 and the
shaft 33 to prevent leakage of refrigerant from the first passage 13 into the second
passage 14.
[0035] In the expansion valve 1 having the structure as described above, the power element
3 senses the pressure and the temperature of refrigerant having returned from the
evaporator via the inlet port 8, and the diaphragm 28 displaces. This displacement
of the diaphragm 28 results in the drive force, which is transmitted to the valve
element 18 via the disc 29 and the shaft 33 so as to open and close the valve section.
In the meantime, a liquid refrigerant supplied from a receiver is introduced through
the inlet port 6, throttled and expanded while passing through the valve section to
be turned into a low-temperature and low-pressure spray of refrigerant. The refrigerant
is then delivered through the outlet port 7 toward the evaporator.
[0036] Next, a temperature sensing structure of the power element will be described in detail.
[0037] FIGS. 2A and 2B illustrate the power element and the structure around the power element.
FIG. 2A is an enlarged view of part A in FIG. 1, and FIG. 2B is a plan view of the
plate 31.
[0038] As illustrated in FIG. 2A, an internal thread portion 62 is formed on an inner surface
of the mounting hole 50. The communication hole 52 mentioned above is formed in the
middle of the bottom portion (partition 51) of the mounting hole 50. A stopper surface
64 is formed on the upper face of the body 2, and an O-ring 30 is fitted into a fitting
groove 65 formed in the stopper surface 64.
[0039] The lower housing 27 has a stepped cylindrical shape with the diameter gradually
decreasing downward in a stepwise manner. A lower half part of the lower housing 27
constitutes a connection part 66. An external thread portion 68 (which functions as
a "screw portion") to be screwed into the thread portion 62 is formed on an outer
surface of the connection part 66. The lower housing 27 is mounted on the body 2 in
such a manner that the connection part 66 is screwed into the mounting hole 50. A
base end (which functions as a "stopper") of the connection part 66 of the lower housing
27 has a stopper surface 70 perpendicular to the axis, and is to come in contact with
the stopper surface 64 of the body 2.
[0040] The disc 29 has a disc-shaped body 72, and a heat transfer promoting part 74 extending
downward from a middle of a lower face of the disc body 72. As illustrated, the heat
transfer promoting part 74 has a large side face, which allows efficient transfer
of the temperature of the refrigerant introduced into the open space S2. The heat
transfer promoting part 74 has an outer diameter slightly smaller than the inner diameter
of the connection part 66. A recess 76 having a diameter increasing downward in a
tapered manner is formed in the middle of a lower face of the heat transfer promoting
part 74. A groove 53 is formed in a lower face of the disc body 72. Refrigerant having
flowed into the open space S2 is directed to a lower face of the diaphragm 28 via
the groove 53.
[0041] As also illustrated in FIG. 2B, the plate 31 has a disc-like shape having flat upper
and lower faces. The insertion hole 36 is formed in the plate 31 coaxially with the
central axis of the plate 31. The plate 31 is coaxially supported at the bottom portion
of the mounting hole 50, and the shaft 33 extends coaxially through the plate 31.
Note that "coaxially" used herein includes cases where the axes are substantially
in alignment as well as cases where the axes are exactly in alignment. The plate 31
has an outer diameter approximately equal to but slightly smaller than the inner diameter
of the mounting hole 50. This facilitates mounting of the plate 31. The plate 31 has
a thickness slightly smaller than a distance L between the bottom portion of the mounting
hole 50 and a lower end of the lower housing 27. The lower end of the lower housing
27 faces an upper face around a circumferential edge of the plate 31. The gap between
the lower housing 27 and the plate 31 is smaller than the thickness of the plate 31.
[0042] As a result of allowing for play (looseness) between the plate 31 and the lower housing
27 in this manner, the lower housing 27 is securely fastened to the body 2 and the
sealing function of the O-ring 30 is ensured. In addition, as a result of making the
gap between the lower end of the lower housing 27 and the plate 31 small, flapping
of the plate 31, if any, is suppressed.
[0043] An upper part of the shaft 33 extends through the insertion hole 36 into the open
space S2, and a leading end thereof is inserted in the recess 76 and in contact with
a lower face of the disc 29.
[0044] The plate 31 is made of resin (or plastic) having a lower hardness and a lower thermal
conductivity than the housing 25. The clearance between the insertion hole 36 and
the shaft 33 has a cross-sectional area (referred to as "an opening area of the insertion
hole 36"; see the dotted region) limits the flow of refrigerant from the second passage
14 into the open space S2. The opening area is set to such a size that passage of
gas refrigerant (gas-phase components) is promoted while passage of liquid refrigerant
(liquid-phase components) is reduced (such a size that inflow of droplets is reduced
or prevented). In the present embodiment, the opening area is about 5 mm
2.
[0045] For mounting the power element 3 onto the body 2, the plate 31 is inserted in the
mounting hole 50, the O-ring 30 is then fitted into the fitting groove 65, and in
this state, the lower housing 27 is screwed into the mounting hole 50.
[0046] In this manner, the O-ring 30 is pressed in close contact with both of the power
element 3 and the body 2, which achieves good sealing performance. As the lower housing
27 is screwed in this manner, the stopper surface 70 of the lower housing 27 is stopped
by the stopper surface 64 of the body 2, and the mounting of the power element 3 is
thus completed.
[0047] Next, operations and advantageous effects of the present embodiment will be explained
in detail.
[0048] FIGS. 3A and 3B illustrate temperature sensing operation of the expansion valve.
FIG. 3A illustrates the temperature sensing operation of the expansion valve 1 according
to the present embodiment, and FIG. 3B illustrates the temperature sensing operation
of an expansion valve 101 according to a comparative example, which does not form
part of the invention. The difference between the expansion valve 1 and the expansion
valve 101 is that the expansion valve 1 includes the plate 31 while the expansion
valve 101 has no plate 31. In FIGS. 3A and 3B, two-dot chain arrows indicate the flow
of refrigerant. In FIGS. 3A and 3B, components similar to each other are designated
by the same reference numerals.
[0049] As illustrated in FIG. 3A, the inlet port 8 is connected with an end portion (joint)
of a pipe 80 connecting an outlet of the evaporator with the expansion valve 1. An
O-ring 82 for sealing is fitted around an outer surface of the end portion of the
pipe 80, so as to prevent leakage of refrigerant to the outside. In addition, a flange
portion 84 protruding radially outward is formed in the vicinity of the end portion
of the pipe 80. The flange portion 84 is stopped by a side face of the body 2, so
that the length to which the pipe 80 is inserted into the second passage 14 is restricted.
[0050] The outlet port 9 is connected with an end portion (joint) of a pipe 90 connecting
an inlet of the compressor with the expansion valve 1. An O-ring 92 for sealing is
fitted around an outer surface of the end portion of the pipe 90, so as to prevent
leakage of refrigerant to the outside. In addition, a flange portion 94 protruding
radially outward is formed in the vicinity of the end portion of the pipe 90. The
flange portion 94 is stopped by the side face of the body 2, so that the length to
which the pipe 90 is inserted into the second passage 14 is restricted. Although these
pipes 80 and 90 are fixed to the body 2 with respective pipe fixing plates, which
are not illustrated, the description thereof is omitted herein.
[0051] In the present embodiment, most of the refrigerant delivered from the evaporator
flows straight from an outlet of the pipe 80 through the second passage 14, enters
an inlet of the pipe 90, and is directed to the compressor. In contrast, part of the
refrigerant flows in such a manner as to spread from the outlet of the pipe 80, reaches
an end face 96 of the pipe 90 or an inner side face on a downstream side of the communication
hole 52, changes its flowing direction, and flows toward the power element 3. Most
of the refrigerant that has changed its direction, however, reaches the plate 31,
is returned to the second passage 14, and is directed to the inlet of the pipe 90.
Part of the refrigerant having changed its direction is directed to the open space
S2 through the insertion hole 36.
[0052] The refrigerant in the open space S2 is delivered to the second passage 14 via the
insertion hole 36 and the communication hole 52, and directed to the inlet of the
pipe 90. In this manner, a proper amount of refrigerant enters and exits the open
space S2. This allows the power element 3 to sense the temperature and the pressure
at the outlet of the evaporator stably and in real time. Liquid refrigerant delivered
into the communication hole 52, if any, is actively received by the plate 31, which
minimizes liquid refrigerant being introduced into the open space S2. As a result,
the control hunting is prevented or minimized.
[0053] In contrast, in the comparative example illustrated in FIG. 3B, liquid refrigerant
delivered into the communication hole 52 is then delivered into the open space S2.
This is likely to cause the control hunting. In other words, according to the present
embodiment, the control hunting is effectively prevented or minimized only by providing
the plate 31 of a simple structure in the mounting hole 50.
[0054] FIGS. 4A, 4B, 5A, and 5B show results of a hunting verification test. In this test,
a test product in which the body and the housing are made of transparent resin is
used to visualize the flow of refrigerant during operation of the refrigeration cycle.
FIGS. 4A and 4B show a result of experiments according to the present embodiment,
and FIGS. 5A and 5B show a result of experiments according to a comparative example.
In the comparative example, the plate 31 of the present embodiment is not provided.
FIGS. 4A and 5A each show the flow of refrigerant in the vicinity of a temperature
sensing part when the degree of superheat is zero, and FIGS. 4B and 5B each show a
result of measurement of hunting when the refrigeration cycle is switched from operation
with a minimum capacity to normal operation. In FIGS. 4B and 5B, the horizontal axis
represents time (seconds) elapsed from the switching of operation of the refrigeration
cycle, and the vertical axis represents the degree of superheat (°C) of refrigerant
at the evaporator outlet. FIG. 6 is a graph showing the relation between the opening
degree of the insertion hole 36 and the amount of hunting. In FIG. 6, the horizontal
axis represents the opening area (mm
2) of the insertion hole 36, and the vertical axis represents the amount (°C) of fluctuation
in the degree of superheat.
[0055] FIG. 4B shows that, according to the present embodiment, the degree of superheat
becomes substantially constant and thus stable after about 200 seconds have elapsed
from the operation switching. In addition, FIG. 4A shows that, when the degree of
superheat zero, that is, when the refrigerant is in a gas-liquid two-phases state,
the gas-phase components of the refrigerant are stably introduced into the open space
S2. In contrast, FIG. 5B shows that, according to the comparative example, the degree
of superheat fluctuates significantly independently of the elapsed time. In addition,
FIG. 5A shows that, when the degree of superheat is zero, refrigerant in a gas-liquid
two-phase state flows rapidly into the open space S2 (see the bubbling state). Note
that about 200 second from the operation switching is the time taken for the refrigeration
cycle to be stabilized after transition to steady operation. Thus, comparison in the
steady operation state of the refrigeration cycle shows that control hunting notably
appears in the comparative example while control hunting is reduced in the present
embodiment.
[0056] In addition, FIG. 6 shows that the effect of reducing hunting according to the present
embodiment is increased by setting the opening area of the insertion hole 36 to 7.0
mm
2 or smaller while permitting flow of refrigerant through the insertion hole 36.
[0057] As described above, according to the present embodiment, the plate 31 separating
the open space S2 of the power element 3 from the second passage 14 and the opening
area of the insertion hole 36 in the plate 31 is set to 7.0 mm
2 or smaller, which effectively reduces occurrence of control hunting. In addition,
the plate 31 has such a simple shape in which the insertion hole 36 is formed at the
center of a flat disc, which can be achieved at low cost in such a manner that the
plate 31 is easily obtained by punching a sheet material into this shape, for example.
Since the shape of the plate 31 is centrally symmetric and nondirectional, the plate
31 is easily mounted on the body 2. Since the clearance of such a suitable size that
promotes passage of gas refrigerant is formed between the insertion hole 36 and the
shaft 33, error in the dimensional accuracy of the plate 31, if any, does not interfere
with the shaft 33. In other words, the need for strict control of the dimensional
accuracy of the plate 31 is reduced. Thus, the number of manhours required for fabrication
and mounting of the plate 31 is reduced, which achieves the expansion valve 1 at low
cost.
[Modifications]
[0058] FIGS. 7A and 7B each illustrate a structure of a main part of an expansion valve.
FIG. 7A illustrates a first modification which does not belong to the invention, and
FIG. 7B illustrates a second modification which belongs to the invention.
[0059] As illustrated in FIG. 7A, the "inflow regulating part" is integrated with a "power
element 203" in the first modification. Specifically, a plate 231 is fixed to an open
end of the lower housing 27. The method for fixing the plate 231 may be press-fitting,
welding, swaging, fastening (screwing), or other fixing means. The plate 231 has an
insertion hole 36 in the middle, and limits the flow of refrigerant from the second
passage 14 to the open space S2. With such a structure, control hunting is prevented
or minimized similarly to the embodiment described above. Note that the plate 231
may be made of resin or may be made of metal. In the latter case, the plate 231 may
be made of metal having a higher thermal conductivity than the housing 25, such as
aluminum or an aluminum alloy.
[0060] As illustrated in FIG. 7B, the "inflow regulating part" is constituted by a plate
331 of a stepped disc-like shape in the second modification. The plate 331 has a plate
body 310 supported by the bottom portion of the mounting hole 50, and a fitted portion
312 to be partially inserted in the communication hole 52. An insertion hole 36 is
formed through the middle of the plate 331 in the axial direction. With such a structure,
control hunting is prevented or minimized similarly to the embodiment described above.
In addition, the state in which the plate 331 is mounted on the body 2 is stable without
press-fitting of the plate 331 into the body 2.
[0061] The description of the present invention given above is based upon a certain embodiment.
The embodiment is intended to be illustrative only and it will be obvious to those
skilled in the art that various modifications could be further developed within the
scope of the appended claims.
[0062] In the embodiment described above, the plate 31 has an outer diameter slightly smaller
than the inner diameter of the mounting hole 50, which achieves easier mounting of
the plate 31. In addition, even if this structure results in misalignment of the axes
of the plate 31 and the shaft 33, the size (opening area) of the insertion hole 36
is set such that the plate 31 does not interfere with the shaft 33. Specifically,
the size (opening area) of the insertion hole 36 is set so that the clearance between
the insertion hole 36 and the shaft 33 is larger than the clearance between the plate
31 and the mounting hole 50. In a modification, the plate 31 may have a press-fit
allowance for being press-fitting into the mounting hole 50.
[0063] In the embodiment described above, the plate 31 has a thickness slightly smaller
than the distance L between the bottom portion of the mounting hole 50 and the lower
end of the lower housing 27, and play (looseness) is provided between the plate 31
and the lower housing 27. In a modification, the plate 31 may be held between the
body 2 and the lower housing 27 without such play. This allows the plate 31 to be
stably supported. In this case, the plate 31 is preferably made of a material having
lower hardness than the lower housing 27, such as a resin material.
[0064] In the embodiment described above, an example in which the power element 3 (the housing
25) is mounted on the body 2 by screwing of the screw portion has been presented.
In a modification, the power element (housing) and the body may be assembled by press-fitting
or swaging.
[0065] While the expansion valve of the embodiment described above is suitably applicable
to a refrigeration cycle using an alternative for chlorofluorocarbon (HFC-134a) or
the like as the refrigerant, the expansion valve of the present invention can also
be applied to a refrigeration cycle using a refrigerant such as carbon dioxide with
high working pressure. In this case, an external heat exchanger such as a gas cooler
is provided instead of the condenser in the refrigeration cycle.
[0066] In the embodiment described above, an example in which the expansion valve is a valve
for throttling and expanding a refrigerant having flowed therein via an external heat
exchanger and supplying the resulting refrigerant to an evaporator (internal evaporator)
has been presented. In a modification, the expansion valve may be applied to a heat
pump automotive air conditioner and disposed downstream of an internal condenser (internal
heat exchanger). Specifically, the expansion valve may be a valve for throttling and
expanding a refrigerant having flowed therein via an internal condenser and supplying
the resulting refrigerant to an external heat exchanger (external evaporator).
[0067] The present invention is not limited to the above-described embodiment and modifications
only, and the components may be further modified to arrive at various other embodiments
without departing from the scope of the invention.
1. An expansion valve (1) for throttling and expanding a refrigerant flowing from an
upstream side and supplying the expanded refrigerant to an evaporator and for sensing
a pressure and a temperature of the refrigerant returning from the evaporator to control
an opening degree of a valve section, the expansion valve (1) comprising:
a body (2) having a first passage (13) through which the refrigerant flowing from
the upstream side toward the evaporator passes, a second passage (14) through which
the refrigerant returning from the evaporator passes, a valve hole (16) formed in
the first passage (13), and a mounting hole (50) communicating with the second passage
(14);
a valve element (18) that moves toward and away from the valve hole (16) to adjust
an opening degree of the valve section;
a power element (3, 203) having a housing (25) mounted on the body (2) in such a manner
as to close the mounting hole (50), a diaphragm (28) partitioning an inside of the
housing (25) into a closed space (S1) in which a temperature sensing medium is sealed
and an open space (S2) communicating with the second passage (14), and a disc (29)
located in the open space (S2) in contact with the diaphragm (28);
a shaft (33) extending through a partition (35) between the first passage (13) and
the second passage (14), having a first end connected to the diaphragm (28) through
the disc (29) and a second end connected to the valve element (18), and being configured
to transmit a drive force in an axial direction to the valve element (18), the drive
force being generated by displacement of the diaphragm (28); and
an inflow regulating part (31, 231, 331) that separates the open space (S2) from the
second passage (14), has an insertion hole (36), through which the shaft (33) extends,
coaxially along a central axis of the inflow regulating part (31, 231, 331), and limits
a flow of the refrigerant from the second passage (14) into the open space (S2) to
a flow through a clearance between the shaft (33) and the insertion hole (36),
wherein the insertion hole (36) is formed such that an opening area of the clearance
between the shaft (33) and the insertion hole (36) is 7.0 mm2 or smaller, characterized in that
the inflow regulating part (31, 231, 331) is constituted by a shield member (31, 231,
331) located between the body (2) and the housing (25) and prevented from dropping
off from the mounting hole (50).
2. The expansion valve (1) according to claim 1, wherein the shield member (31, 231,
331) is a flat, circular plate (31, 231, 331) and has the insertion hole (36) at the
center.
3. The expansion valve (1) according to claim 1 or claim 2,
wherein the body (2) has a communication hole (52) through which the mounting hole
(50) and the second passage (14) communicate with each other, and
the shield member (31, 231, 331) is supported by a stepped portion formed at a boundary
of the mounting hole (50) and the communication hole (52).
4. The expansion valve (1) according to claim 3, wherein the shield member (31, 231,
331) has an outer diameter smaller than an inner diameter of the mounting hole (50),
and the shield member (31, 231, 331) is not fixed to the mounting hole (50) in a radial
direction.
5. The expansion valve (1) according to any one of claims 1 to 4, wherein the shield
member (31, 231, 331) is held between the housing (25) and the body (2).
6. The expansion valve (1) according to any one of claims 1 to 5, wherein the inflow
regulating part (31, 231, 331) is made of a resin material having a smaller hardness
than the housing (25).
7. The expansion valve (1) according to any one of claims 1 to 6, wherein the insertion
hole (36) has a cross section of a perfect circular shape.
1. Expansionsventil (1) zum Drosseln und Expandieren eines Kältemittels, das von einer
stromaufwärtigen Seite fließt, und Zuführen des expandierten Kältemittels an einen
Verdampfer, und zum Erfassen eines Drucks und einer Temperatur des von dem Verdampfer
zurückkehrenden Kältemittels, um einen Öffnungsgrad eines Ventilabschnitts zu steuern,
wobei das Expansionsventil (1) umfasst:
einen Körper (2) mit einem ersten Kanal (13), den das von der stromaufwärtigen Seite
hin zu dem Verdampfer fließende Kältemittel durchläuft, einem zweiten Kanal (14),
den das von dem Verdampfer zurückkehrende Kältemittel durchläuft, einer in dem ersten
Kanal (13) gebildeten Ventilbohrung (16) und einer Montagebohrung (50) in Verbindung
mit dem zweiten Kanal (14);
ein Ventilelement (18), das sich hin zu und weg von der Ventilbohrung (16) bewegt,
um einen Öffnungsgrad des Ventilabschnitts anzupassen;
ein Leistungselement (3, 203) mit einem Gehäuse (25), das in solcher Weise an dem
Körper (2) befestigt ist, dass es die Montagebohrung (50) verschließt, eine Membran
(28), die einen Innenraum des Gehäuses (25) in einen geschlossenen Raum (S1), in dem
ein Temperaturerfassungsmedium versiegelt ist, und einen offenen Raum (S2) in Verbindung
mit dem zweiten Kanal (14) teilt, und eine in dem offenen Raum (S2) angeordnete Scheibe
(29) in Kontakt mit der Membran (28);
eine Welle (33), die sich durch eine Teilung (35) zwischen dem ersten Kanal (13) und
dem zweiten Kanal (14) erstreckt, mit einem ersten Ende, das mit der Membran (28)
durch die Scheibe (29) verbunden ist, und einem zweiten Ende, das mit dem Ventilelement
(18) verbunden ist, und konfiguriert zum Übertragen einer Antriebskraft in einer Axialrichtung
an das Ventilelement (18), wobei die Antriebskraft durch Verlagerung der Membran (28)
erzeugt wird; und
einen Zuflussregelungsteil (31, 231, 331), der den offenen Raum (S2) von dem zweiten
Kanal (14) trennt, eine Einführbohrung (36) aufweist, durch die sich die Welle (33)
koaxial entlang einer Mittelachse des Zuflussregelungsteils (31, 231, 331) erstreckt,
und einen Fluss des Kältemittels aus dem zweiten Kanal (14) in den offenen Raum (S2)
auf einen Fluss durch einen Zwischenraum zwischen der Welle (33) und der Einführbohrung
(36) begrenzt, wobei die Einführbohrung (36) derart ausgebildet ist, dass ein Öffnungsbereich
des Zwischenraums zwischen der Welle (33) und der Einführbohrung (36) 7,0 mm2 groß oder kleiner ist, dadurch gekennzeichnet, dass
der Zuflussregelungsteil (31, 231, 331) aus einem Abschirmelement (31, 231, 331) besteht,
das zwischen dem Körper (2) und dem Gehäuse (25) angeordnet ist und daran gehindert
wird, von der Montagebohrung (50) abzufallen.
2. Expansionsventil (1) nach Anspruch 1, wobei das Abschirmelement (31, 231, 331) eine
flache, kreisförmige Platte (31, 231, 331) ist und die Einführbohrung (36) in der
Mitte aufweist.
3. Expansionsventil (1) nach Anspruch 1 oder Anspruch 2,
wobei der Körper (2) eine Verbindungsbohrung (52) aufweist, durch die die Montagebohrung
(50) und der zweite Kanal (14) miteinander verbunden sind, und
das Abschirmelement (31, 231, 331) durch einen abgestuften Abschnitt getragen wird,
der an einer Grenze der Montagebohrung (50) und der Kommunikationsbohrung (52) gebildet
ist.
4. Expansionsventil (1) nach Anspruch 3, wobei das Abschirmelement (31, 231, 331) einen
Außendurchmesser aufweist, der kleiner als ein Innendurchmesser der Montagebohrung
(50) ist, und das Abschirmelement (31, 231, 331) in einer radialen Richtung nicht
an der Montagebohrung (50) befestigt ist.
5. Expansionsventil (1) nach einem der Ansprüche 1 bis 4, wobei das Abschirmelement (31,
231, 331) zwischen dem Gehäuse (25) und dem Körper (2) gehalten wird.
6. Expansionsventil (1) nach einem der Ansprüche 1 bis 5, wobei der Zuflussregelungsteil
(31, 231, 331) aus einem Harzmaterial mit einer geringeren Härte als das Gehäuse (25)
gefertigt ist.
7. Expansionsventil (1) nach einem der Ansprüche 1 bis 6, wobei die Einführbohrung (36)
einen Querschnitt mit einer perfekten Kreisform aufweist.
1. Vanne d'expansion (1) pour étrangler et dilater un réfrigérant s'écoulant depuis un
côté amont et acheminer le réfrigérant dilaté vers un évaporateur, et pour détecter
une pression et une température du réfrigérant revenant de l'évaporateur pour commander
un degré d'ouverture d'une section de vanne, la vanne d'expansion (1) comprenant :
un corps (2) ayant un premier passage (13) à travers lequel passe le réfrigérant s'écoulant
depuis le côté amont vers l'évaporateur, un second passage (14) à travers lequel passe
le réfrigérant revenant de l'évaporateur, un trou de vanne (16) formé dans le premier
passage (13), et un trou de montage (50) communiquant avec le second passage (14)
;
un élément de vanne (18) qui se rapproche et s'éloigne du trou de vanne (16) pour
ajuster un degré d'ouverture de la section de vanne ;
un élément d'alimentation (3, 203) ayant un logement (25) monté sur le corps (2) de
façon à fermer le trou de montage (50), une membrane (28) séparant l'intérieur du
logement (25) en un espace fermé (S1) dans lequel un milieu de détection de température
est scellé et un espace ouvert (S2) communiquant avec le second passage (14), et un
disque (29) situé dans l'espace ouvert (S2) en contact avec la membrane (28) ;
une tige (33) s'étendant à travers une cloison (35) entre le premier passage (13)
et le second passage (14), ayant une première extrémité reliée à la membrane (28)
par l'intermédiaire du disque (29) et une seconde extrémité reliée à l'élément de
vanne (18), et qui est configurée pour transmettre une force d'entraînement dans une
direction axiale à l'élément de vanne (18), la force d'entraînement étant générée
par déplacement de la membrane (28) ;
et
une partie de régulation de flux entrant (31, 231, 331) qui sépare l'espace ouvert
(S2) du second passage (14), a un trou d'insertion (36), à travers lequel la tige
(33) s'étend, coaxialement le long d'un axe central de la partie de régulation de
flux entrant (31, 231, 331), et limite un écoulement du réfrigérant depuis le second
passage (14) dans l'espace ouvert (S2) à un écoulement à travers un jeu entre la tige
(33) et le trou d'insertion (36), le trou d'insertion (36) étant formé de telle sorte
qu'une zone d'ouverture du jeu entre la tige (33) et le trou d'insertion (36) est
de 7,0 mm2 ou moins,
caractérisée par le fait que
la partie de régulation de flux entrant (31, 231, 331) est constituée d'un élément
de protection (31, 231, 331) situé entre le corps (2) et le logement (25) et est empêchée
de tomber du trou de montage (50).
2. Vanne d'expansion (1) selon la revendication 1, dans laquelle l'élément de protection
(31, 231, 331) est une plaque circulaire plate (31, 231, 331) et a le trou d'insertion
(36) au centre.
3. Vanne d'expansion (1) selon la revendication 1 ou la revendication 2, dans laquelle
le corps (2) a un trou de communication (52) à travers lequel le trou de montage (50)
et le second passage (14) communiquent l'un avec l'autre, et l'élément de protection
(31, 231, 331) est porté par une partie étagée formée au niveau d'une limite du trou
de montage (50) et du trou de communication (52).
4. Vanne d'expansion (1) selon la revendication 3, dans laquelle l'élément de protection
(31, 231, 331) a un diamètre externe plus petit qu'un diamètre interne du trou de
montage (50), et l'élément de protection (31, 231, 331) n'est pas fixé au trou de
montage (50) dans une direction radiale.
5. Vanne d'expansion (1) selon l'une quelconque des revendications 1 à 4, dans laquelle
l'élément de protection (31, 231, 331) est maintenu entre le logement (25) et le corps
(2).
6. Vanne d'expansion (1) selon l'une quelconque des revendications 1 à 5, dans laquelle
la partie de régulation de flux entrant (31, 231, 331) est réalisée en un matériau
de résine ayant une dureté inférieure à celle du logement (25).
7. Vanne d'expansion (1) selon l'une quelconque des revendications 1 à 6, dans laquelle
le trou d'insertion (36) a une section transversale d'une forme circulaire parfaite.