JP7489703B2 - Expansion valve - Google Patents

Description

The present invention relates to an expansion valve.

Conventionally, in refrigeration cycles used in air conditioners installed in automobiles, a temperature-sensing thermal expansion valve that adjusts the amount of refrigerant passing through depending on the temperature is used. Such thermal expansion valves use a power element that drives the valve body using the pressure of the enclosed working gas.

The power element provided in the expansion valve generally comprises a diaphragm, an upper cover member that arranges a pressure actuated chamber in which a working gas is sealed between the diaphragm and the upper cover member, a receiving member that has a through hole in the center and is arranged on the opposite side of the diaphragm to the upper cover member, and a stopper member that is arranged in a fluid inflow chamber formed between the diaphragm and the receiving member and is connected to an actuating rod that drives the valve body. The diaphragm is formed from a thin, flexible metal plate.

If the temperature of the refrigerant flowing into the fluid inlet chamber is low, it will contract by removing heat from the working gas in the pressure actuated chamber, and if the temperature of the refrigerant is high, it will expand by adding heat to the working gas in the pressure actuated chamber. The diaphragm deforms in response to the contraction/expansion of the working gas, so the valve body can be opened and closed via the stopper member and actuating rod in response to the amount of deformation, thereby adjusting the flow rate of the refrigerant passing through the expansion valve.

The amount and temperature of the refrigerant flowing into the fluid inlet chamber changes from moment to moment depending on the operating conditions of the refrigeration cycle. Therefore, under certain conditions, the diaphragm may react too sensitively, causing the valve body to open and close repeatedly, resulting in unstable refrigerant temperature control. This is known as the hunting phenomenon. When hunting occurs, the air temperature control in the air conditioner becomes unstable, which may cause discomfort to users of the air conditioner.

In response to this, Patent Document 1 discloses an expansion valve that can suppress the hunting phenomenon by placing a disk with a hole that restricts the inflow of refrigerant in the passage connecting the refrigerant flow path of the expansion valve and the fluid inlet chamber of the power element.

JP 2018-115799 A

However, the operating conditions of a refrigeration cycle equipped with an expansion valve vary depending on the air conditioning device to which it is applied and the external temperature environment. Therefore, even if a disk attached to an expansion valve can effectively suppress the hunting phenomenon under certain operating conditions, it may not be able to suppress the hunting phenomenon under other operating conditions.

In such cases, one idea is to suppress the hunting phenomenon by replacing the disk with one that has a different hole diameter. However, in the expansion valve of Patent Document 1, the power element must be removed to replace the disk, making the replacement work large-scale and time-consuming. In addition, removing and attaching the power element can lead to changes in conditions such as a change in the volume of the fluid inlet chamber, and it is anticipated that problems such as the hunting phenomenon not being resolved even after the disk hole diameter has been changed can occur.

Therefore, the present invention aims to provide an expansion valve that can easily suppress the hunting phenomenon.

In order to achieve the above object, the expansion valve according to the present invention comprises:
A power element including a diaphragm that drives an actuating rod that presses a valve body in a valve opening direction , an upper cover member that arranges a pressure actuated chamber between one surface of the diaphragm and a receiving member, and a fluid inflow chamber that arranges a fluid inflow chamber between the other surface of the diaphragm and a receiving member;
A refrigerant flow path to which a pipe can be connected;
a communication passage that communicates the fluid inlet chamber and the refrigerant flow passage;
a shielding member that is inserted into the refrigerant flow path to shield a portion of the communication passage ,
The shielding member is a cylindrical member attached to a pipe connected to the refrigerant flow path, and a tip of the cylindrical member shields a part of the communication passage .
The expansion valve according to the present invention comprises:
A power element including a diaphragm that drives an actuating rod that presses a valve body in a valve opening direction, an upper cover member that arranges a pressure actuated chamber between one surface of the diaphragm and a receiving member, and a fluid inflow chamber that arranges a fluid inflow chamber between the other surface of the diaphragm and a receiving member;
A refrigerant flow path to which a pipe can be connected;
a communication passage that communicates the fluid inlet chamber and the refrigerant flow passage;
a shielding member that is inserted into the refrigerant flow path to shield a portion of the communication passage,
the shielding member is a pipe connected to the refrigerant flow path, and a tip of the pipe shields a part of the communication passage,
The actuating rod is inserted into the communication passage, and a notch is formed at the tip to avoid interference with the actuating rod.
The expansion valve according to the present invention comprises:
A power element including a diaphragm that drives an actuating rod that presses a valve body in a valve opening direction, an upper cover member that arranges a pressure actuated chamber between one surface of the diaphragm and a receiving member, and a fluid inflow chamber that arranges a fluid inflow chamber between the other surface of the diaphragm and a receiving member;
A refrigerant flow path to which a pipe can be connected;
a communication passage that communicates the fluid inlet chamber and the refrigerant flow passage;
a shielding member that is inserted into the refrigerant flow path to shield a portion of the communication passage,
The shielding member is characterized by having an adjustment member for adjusting an overlap amount between the shielding member and the communication passage.

The present invention provides an expansion valve that can easily suppress the hunting phenomenon.

FIG. 1 is a schematic cross-sectional view showing an example in which an expansion valve according to a first embodiment is applied to a refrigerant circulation system. FIG. 2 is a cross-sectional view taken along line AA of FIG. FIG. 3 is a vertical cross-sectional view of an expansion valve according to the second embodiment. FIG. 4 is a cross-sectional view taken along the line BB of FIG. FIG. 5 is a vertical sectional view of an expansion valve according to a modified example of the second embodiment. FIG. 6 is a cross-sectional view similar to FIG. 4, showing another modified example of the second embodiment. FIG. 7 is a cross-sectional view similar to FIG. 4 according to the third embodiment. FIG. 8 is a cross-sectional view similar to FIG. 4, showing a modified example of the third embodiment. FIG. 9 is an enlarged view of a portion E in FIG.

The following describes an embodiment of the present invention with reference to the drawings.

(Direction definition)
In this specification, the direction from the valve disc 3 to the actuating rod 5 is defined as the "upward direction," and the direction from the actuating rod 5 to the valve disc 3 is defined as the "downward direction." Therefore, in this specification, regardless of the attitude of the expansion valve 1, the direction from the valve disc 3 to the actuating rod 5 is called the "upward direction."

First Embodiment
An overview of an expansion valve 1 including a power element in a first embodiment will be described with reference to Fig. 1. Fig. 1 is a schematic cross-sectional view showing an example in which the expansion valve 1 in this embodiment is applied to a refrigerant circulation system 100. In this embodiment, the expansion valve 1 is fluidly connected to a compressor 101, a condenser 102, and an evaporator 104. The axis of the expansion valve 1 is designated as L.

In FIG. 1, the expansion valve 1 comprises a valve body 2 having a valve chamber VS, a valve element 3, a biasing device 4, an actuating rod 5, and a power element 8.

In addition to the valve chamber VS, the valve body 2 has a first flow path 21, a second flow path 22, an intermediate chamber 221, and a return flow path (also called a refrigerant flow path) 23. The first flow path 21 is a supply side flow path, and refrigerant is supplied to the valve chamber VS via the supply side flow path. The second flow path 22 is a discharge side flow path, and the fluid in the valve chamber VS is discharged outside the expansion valve via the valve hole 27, the intermediate chamber 221, and the discharge side flow path.

The end of a metal first pipe 51 connected to the capacitor 102 is inserted into the first flow path 21, and the space between the first flow path 21 and the first pipe 51 is sealed by an O-ring OR1 placed in a circumferential groove 51a formed on the outer periphery of the first pipe 51.

The end of a metal second pipe 52 connected to the inlet of the evaporator 104 is inserted into the second flow path 22, and the space between the second flow path 22 and the second pipe 52 is sealed by an O-ring OR2 placed in a circumferential groove 52a formed on the outer periphery of the second pipe 52.

The first flow path 21 and the valve chamber VS are connected by a connection path 21a having a smaller diameter than the first flow path 21. The valve chamber VS and the intermediate chamber 221 are connected via the valve seat 20 and the valve through hole 27.

The actuating rod insertion hole 28 formed above the intermediate chamber 221 has the function of guiding the actuating rod 5, and the annular recess 29 formed above the actuating rod insertion hole 28 has the function of accommodating the ring spring 6. The ring spring 6 applies a predetermined biasing force by abutting multiple spring pieces against the outer periphery of the actuating rod 5.

The return flow passage 23 of the valve body 2 is formed adjacent to the annular recess 29 and penetrates the valve body 2. The axis O of the return flow passage 23 is perpendicular to the axis L of the expansion valve 1. The return flow passage 23 is connected to a cylindrical communication passage 2b that communicates with the internal space of the recess 2a in which the power element 8 is attached. The operating rod 5 penetrates the communication passage 2b.

The end of the metal third pipe 53 connected to the outlet of the evaporator 104 is inserted into the inlet side of the return flow passage 23 (left side in FIG. 1), and the return flow passage 23 and the third pipe 53 are sealed by an O-ring OR3 placed in a circumferential groove 53a formed on the outer periphery of the third pipe 53. The outer diameter of the end of the third pipe 53 is approximately equal to the inner diameter of the return flow passage 23.

A large diameter portion 23a (see FIG. 2, described later) is formed on the outlet side of the return flow passage 23 (the right side in FIG. 1). The end of a fourth metal pipe 54 connected to the compressor 101 is inserted into this large diameter portion 23a, and the return flow passage 23 and the fourth pipe 54 are sealed by an O-ring OR4 disposed in a circumferential groove 54a formed on the outer periphery of the fourth pipe 54.

Figure 2 is a cross-sectional view taken along the line A-A in Figure 2. In Figure 2, as viewed in the axial direction of the actuation rod 5, the tip of the third pipe 53 overlaps the communication passage 2b with an overlap amount Δ. In other words, a portion of the communication passage 2b is shielded by the third pipe 53, which is a shielding member. It is preferable that the overlap amount Δ is 1 mm or more. It is also preferable that the area where the communication passage 2b is shielded is 10% or more of the minimum cross-sectional area of the communication passage 2b.

For example, a female thread can be formed on the outer periphery of the third pipe 53, and a male thread can be formed on the inner periphery of the ring-shaped member RG as shown by the dotted line, and these threads can be screwed together to attach the ring-shaped member RG to the outer periphery of the third pipe 53 so that its position can be adjusted in the direction along the axis O. The third pipe 53 with the ring-shaped member RG attached can be inserted into the return flow path 23, and the ring-shaped member RG can be abutted against the valve body 2 to ensure the desired overlap amount Δ. If it is desired to change the overlap amount Δ, the ring-shaped member RG can be screwed relative to the third pipe 53. "Screwed" refers to the relative axial movement of the engaged threads caused by rotating them relative to each other. The ring-shaped member RG constitutes the adjustment member.

However, the adjustment member is not limited to the annular member RG. For example, multiple small holes may be formed along the axis O on the outer periphery of the third pipe 53, and a pin as an adjustment member may be inserted into one of the small holes from the outside and abutted against the valve body 2 when the third pipe 53 is inserted into the return flow path 23. A tapered inner circumferential surface 53b is formed near the tip of the third pipe 53.

In FIG. 1, the valve disc 3 is disposed in the valve chamber VS. When the valve disc 3 is seated on the valve seat 20 of the valve body 2, the flow of refrigerant through the valve hole 27 is restricted. This state is called the non-communicating state. However, even when the valve disc 3 is seated on the valve seat 20, a restricted amount of refrigerant may flow. On the other hand, when the valve disc 3 is separated from the valve seat 20, the flow of refrigerant passing through the valve hole 27 increases. This state is called the communicating state.

The actuating rod 5 is inserted through the valve through hole 27 with a specified gap. The lower end of the actuating rod 5 is in contact with the upper surface of the valve body 3. The upper end of the actuating rod 5 is fitted into the fitting hole 84c of the stopper member 84 described later.

The actuating rod 5 can press the valve body 3 in the valve opening direction against the biasing force of the biasing device 4. When the actuating rod 5 moves downward, the valve body 3 moves away from the valve seat 20, and the expansion valve 1 opens.

In FIG. 1, the biasing device 4 has a coil spring 41 made of a wire material with a circular cross section wound in a spiral shape, a valve body support 42, and a spring receiving member 43.

The valve body support 42 is attached to the upper end of the coil spring 41, and the spherical valve body 3 is welded to its upper surface, so that the two are integrated.

The spring bearing member 43 that supports the lower end of the coil spring 41 can be screwed into the valve body 2 and has the functions of sealing the valve chamber VS and adjusting the biasing force of the coil spring 41.

Next, the power element 8 will be described. The power element 8 has a plug 81, an upper cover member 82, a diaphragm 83, a receiving member 86, and a stopper member 84.

The top cover member 82 is formed, for example, by pressing a metal plate material. An opening 82a is formed in the center of the dome-shaped top cover member 82, which can be sealed with a plug 81.

The receiving member 86 that faces the top cover member 82 is formed, for example, by pressing a metal plate, and a male screw 86e is engraved on the outer periphery of the hollow cylindrical portion 86d formed at the bottom.

On the other hand, as shown in FIG. 1, a female thread 2c that screws into the male thread 86e is formed on the inner circumference of the recess 2a of the valve body 2 to which the hollow cylindrical portion 86d is attached.

The diaphragm 83 sandwiched between the top cover member 82 and the receiving member 86 is made of a thin, flexible metal (e.g., SUS) plate material and has an outer diameter approximately the same as the outer diameters of the top cover member 82 and the receiving member 86.

The stopper member 84 has a cylindrical body 84a with a flange at the top end and a blind hole 84c formed in the center of the bottom surface of the body 84a. The central top surface of the body 84a is in contact with the central bottom surface of the diaphragm 83.

The power element 8 is integrated by overlapping the top cover member 82, diaphragm 83, and receiving member 86 in that order and pressing them in the axial direction while welding the outer periphery by, for example, TIG welding, laser welding, plasma welding, etc., so that the entire circumference is welded together.

Next, the working gas is injected into the space (pressure actuated chamber PO) surrounded by the upper cover member 82 and the upper surface of the diaphragm 83 through the opening 82a formed in the upper cover member 82, and then the opening 82a is sealed with a plug 81, which is then fixed to the upper cover member 82 by projection welding or the like. The space (lower space LS) surrounded by the lower surface of the diaphragm 83 and the receiving member 86 is used as the fluid inflow chamber.

When the power element 8 assembled as described above is attached to the valve body 2, the male thread 86e on the outer periphery of the lower end of the hollow cylindrical portion 86d of the receiving member 86 is screwed into the female thread 2c formed on the inner periphery of the recess 2a of the valve body 2. When the male thread 86e of the hollow cylindrical portion 86d is screwed into the female thread 2c, the shoulder of the receiving member 86 comes into contact with the upper end surface of the valve body 2. This allows the power element 8 to be fixed to the valve body 2.

At this time, a packing PK is interposed between the power element 8 and the valve body 2, sealing the space in the recess 2a that is connected to the lower space LS, preventing the refrigerant from leaking from the recess 2a. In this state, the lower space LS of the power element 8 is connected to the return flow path 23 via the communication passage 2b.

(Expansion valve operation)
An example of the operation of the expansion valve 1 will be described with reference to Fig. 1. The refrigerant pressurized by the compressor 101 is liquefied by the condenser 102 and sent to the expansion valve 1. The refrigerant adiabatically expanded by the expansion valve 1 is sent to the evaporator 104, where it is heat exchanged with the air flowing around the evaporator. The refrigerant returning from the evaporator 104 is returned to the compressor 101 side through the return flow path 23 of the expansion valve 1. At this time, by passing through the evaporator 104, the fluid pressure in the second flow path 22 becomes greater than the fluid pressure in the return flow path 23.

The expansion valve 1 is supplied with high-pressure refrigerant from the condenser 102. More specifically, the high-pressure refrigerant from the condenser 102 is supplied to the valve chamber VS via the first flow path 21.

When the valve body 3 is seated on the valve seat 20 (in a non-communicating state), the flow rate of the refrigerant sent from the valve chamber VS through the valve hole 27, the intermediate chamber 221, and the second flow path 22 to the evaporator 104 is restricted. On the other hand, when the valve body 3 is separated from the valve seat 20 (in a communicating state), the flow rate of the refrigerant sent from the valve chamber VS through the valve hole 27, the intermediate chamber 221, and the second flow path 22 to the evaporator 104 increases. The expansion valve 1 is switched between the closed state and the open state by the operating rod 5 connected to the power element 8 via the stopper member 84.

In FIG. 1, the power element 8 is provided with a pressure actuated chamber PO and a lower space LS separated by a diaphragm 83. Therefore, when the working gas in the pressure actuated chamber PO is liquefied, the diaphragm 83 rises, and the stopper member 84 and the working rod 5 move upward in response to the biasing force of the coil spring 41. On the other hand, when the liquefied working gas is vaporized, the diaphragm 83 and the stopper member 84 are pressed downward, and the working rod 5 moves downward. In this way, the expansion valve 1 is switched between the open and closed states.

Furthermore, the lower space LS of the power element 8 is connected to the return flow path 23 via the communication passage 2b. Therefore, the refrigerant flowing through the return flow path 23 flows into the lower space LS via the communication passage 2b, and the volume of the working gas in the pressure actuated chamber PO changes depending on the temperature and pressure of the refrigerant, driving the actuating rod 5. In other words, in the expansion valve 1 shown in FIG. 1, the amount of refrigerant supplied from the expansion valve 1 to the evaporator 104 is automatically adjusted depending on the temperature and pressure of the refrigerant returning from the evaporator 104 to the expansion valve 1.

When the overlap amount Δ between the tip of the third pipe 53 and the communication passage 2b is a specified value, the volume of the working gas in the pressure actuated chamber PO periodically changes depending on the amount and temperature of the refrigerant flowing into the lower space LS from the return flow passage 23, and this may cause the diaphragm 83 to react sensitively, resulting in a hunting phenomenon in which the valve body 3 repeatedly opens and closes.

According to this embodiment, for example, if the hunting phenomenon occurs when the overlap amount Δ is a specified value, the annular member RG can be twisted to change the insertion amount of the third pipe 53, thereby changing the overlap amount Δ. This makes it possible to adjust the amount of refrigerant entering the lower space LS from the return flow path 23, thereby suppressing the hunting phenomenon.

In addition, by spirally rotating the annular member RG while operating the actual refrigeration cycle, it is possible to find the optimal range of overlap amount Δ in which the hunting phenomenon does not occur. Note that if the annular member RG is joined to the third pipe 53, the overlap amount Δ can be changed by replacing the third pipe 53 with one that has a different insertion size into the return flow path 23.

Second Embodiment
Fig. 3 is a vertical cross-sectional view of the expansion valve of the second embodiment. Fig. 4 is a cross-sectional view taken along the line B-B in Fig. 3. The expansion valve 1A of this embodiment differs from the above-described embodiment in that a cylindrical member 55 is attached to the third pipe 53A. Other configurations similar to those of the first embodiment are given the same reference numerals and will not be described again.

The unique configuration of the second embodiment will be described. In FIG. 4, the third pipe 53A has a reduced diameter outer periphery 53c formed at its tip, and an outer periphery annular protrusion 53d formed at the end of the reduced diameter outer periphery 53c. The outer periphery annular protrusion 53d has a tapered surface 53e on its periphery that reduces in diameter toward the end. Although not shown, the third pipe 53A is capable of mounting an annular member RG.

The resin cylindrical member 55 has a thin cylindrical portion 55a and a thick cylindrical portion 55b connected in the axial direction. The thick cylindrical portion 55b has the same outer diameter and inner diameter as the third pipe 53A. An inner circumferential annular protrusion 55c is formed at the end of the thin cylindrical portion 55a, and a tapered inner circumferential surface 55d is formed on the opposing end side of the thick cylindrical portion 55b. The cylindrical member 55 constitutes a shielding member.

When the thin cylindrical portion 55a of the cylindrical member 55 is brought coaxially opposite to the reduced diameter outer peripheral portion 53c of the third pipe 53A while the O-ring OR3 is placed on the reduced diameter outer peripheral portion 53c in advance, the inner peripheral annular protrusion 55c first comes into contact with the outer peripheral annular protrusion 53d. When the two are brought closer together, the inner peripheral annular protrusion 55c made of resin is elastically deformed by the tapered surface 53e so as to expand in diameter, and overcomes the outer peripheral annular protrusion 53d. When it reaches the reduced diameter outer peripheral portion 53c, it returns from elastic deformation and comes into contact with the reduced diameter outer peripheral portion 53c all around. The outer peripheral annular protrusion 53d also comes into close contact with the thin cylindrical portion 55a. This allows the cylindrical member 55 to be attached to the tip of the third pipe 53A. To remove the cylindrical member 55 from the third pipe 53A, a force should be applied in the opposite direction to that described above.

When the third pipe 53A with the cylindrical member 55 attached is inserted into the return flow path 23, the O-ring OR3 seals the return flow path 23 and the third pipe 53A. According to this embodiment, when the third pipe 53A is assembled, the cylindrical member 55 can block part of the communication passage 2b, so that the hunting phenomenon can be suppressed in the same way as in the above-mentioned embodiment.

In addition, since the outer diameter of the cylindrical member 55 is the same as the outer diameter of the third pipe 53A, the cylindrical member 55 and the third pipe 53A can be smoothly inserted into the return flow path 23. In addition, since there is no step between the inner circumference of the cylindrical member 55 and the inner circumference of the third pipe 53A, the refrigerant can smoothly flow from the third pipe 53A to the return flow path 23 via the cylindrical member 55.

In this embodiment, it is preferable to prepare multiple types of cylindrical members 55 with different overall lengths. For example, if hunting occurs when using a certain cylindrical member 55, the third pipe 53A to which it is attached can be removed and replaced with a cylindrical member 55 of a different length and then reinserted, which makes it easy to change the overlap amount Δ (see FIG. 2), and is effective in suppressing the hunting phenomenon.

(Variation 1)
5 is a vertical cross-sectional view of an expansion valve according to a modification of the second embodiment. The expansion valve 1B of this modification is different from that of the second embodiment in the shape of the cylindrical member 55B. Specifically, a tapered outer peripheral surface 55e is formed in the vicinity of the end of the cylindrical member 55B, facing a tapered inner peripheral surface 55d. Other configurations similar to those of the second embodiment are given the same reference numerals and will not be described again.

In this modified example, a tapered outer peripheral surface 55e is formed facing the communication passage 2b, so that the refrigerant flowing from the lower space LS through the communication passage 2b toward the return flow passage 23 can be smoothly returned to the return flow passage 23 as shown by arrow C. In addition, the return flow of the refrigerant to the lower space LS can be suppressed, thereby further suppressing the hunting phenomenon.

Furthermore, because the tapered outer peripheral surface 55e is formed facing the annular recess 29, the refrigerant leaking from the intermediate chamber 221 through the gap between the actuating rod 5 and the actuating rod insertion hole 28 and the annular recess 29 can be smoothly returned to the return flow path 23 as shown by the arrow D, thereby suppressing the refrigerant heading toward the communication passage 2b and further suppressing the hunting phenomenon. A similar tapered outer peripheral surface may be provided, for example, on the third pipe of the first embodiment.

(Variation 2)
Fig. 6 is a cross-sectional view similar to Fig. 4 of another modified example of the second embodiment. The expansion valve 1C of this modified example differs from the second embodiment in the shape of the cylindrical member 55C. Specifically, semicircular arc-shaped notches 55f are formed at two locations 180 degrees apart at the end of the cylindrical member 55C to prevent interference with the actuation rod 5. Other configurations similar to those of the second embodiment are given the same reference numerals and will not be described again.

In this modified example, a notch 55f is formed in the cylindrical member 55C, so that even if the actuating rod 5 is inserted into the communicating passage 2b, the amount of overlap with the communicating passage 2b can be increased. In the example of FIG. 6, the cylindrical member 55C can block approximately half of the cross-sectional area of the communicating passage 2b. This makes it possible to more effectively suppress the hunting phenomenon.

Third Embodiment
Fig. 7 is a cross-sectional view similar to Fig. 4 according to the third embodiment. In the expansion valve 1D of the present embodiment, a cylindrical member 56 is also attached to the fourth pipe 54D, unlike the second embodiment. Other configurations similar to those of the second embodiment are given the same reference numerals and will not be described again.

The unique configuration of the third embodiment will be described. In FIG. 7, the fourth pipe 54D has a first reduced diameter outer periphery 54g having an outer diameter approximately equal to the inner diameter of the large diameter portion 23a of the return flow passage 23, a circumferential groove 54b formed in the first reduced diameter outer periphery 54g, a second reduced diameter outer periphery 54c having a smaller diameter than the first reduced diameter outer periphery 54g, and an outer periphery annular protrusion 54d formed at the tip of the second reduced diameter outer periphery 54c. The outer periphery annular protrusion 54d has a tapered surface 54e on its outer periphery that reduces in diameter toward the end.

The fourth pipe 54D is capable of inserting the first reduced diameter outer periphery 54g into the large diameter portion 23a, and is positioned in the axial direction by abutting the step 54f between the outer periphery of the fourth pipe 54D and the first reduced diameter outer periphery 54g against the valve body 2. An O-ring OR4 is placed in the circumferential groove 54b in advance to seal the large diameter portion 23a and the fourth pipe 54D.

The resin cylindrical member 56 has a thin-walled cylindrical section 56a and a thick-walled cylindrical section 56b connected in the axial direction. The thick-walled cylindrical section 56b has the same inner diameter as the fourth pipe 54D and also has the same inner diameter as the return flow path 23. An inner circumferential annular protrusion 56c is formed at the tip of the thin-walled cylindrical section 56a. A tapered surface may be formed on the outer periphery of the end of the thick-walled cylindrical section 56b (see FIG. 5).

When the thin cylindrical portion 56a of the cylindrical member 56 is brought coaxially opposite to the second reduced diameter outer peripheral portion 54c of the fourth pipe 54D and brought close to each other, the inner peripheral annular protrusion 56c first comes into contact with the outer peripheral annular protrusion 54d. When the two are brought closer to each other, the inner peripheral annular protrusion 56c made of resin is elastically deformed by the tapered surface 54e so as to expand in diameter, and overcomes the outer peripheral annular protrusion 54d. When it reaches the second reduced diameter outer peripheral portion 54c, it returns from elastic deformation and comes into contact with the second reduced diameter outer peripheral portion 54c over its entire circumference. The outer peripheral annular protrusion 54d also comes into close contact with the thin cylindrical portion 56a. This allows the cylindrical member 56 to be attached to the tip of the fourth pipe 54D. A gap is formed between the end face of the cylindrical member 56 and the first reduced diameter outer peripheral portion 54g, but the two may also be brought into close contact with each other.

According to this embodiment, when the fourth pipe 54D to which the cylindrical member 56 is attached is inserted into the large diameter portion 23a of the return flow path 23, the cylindrical member 56 can block a portion of the downstream side of the communication passage 2b. Therefore, in combination with the cylindrical member 55 attached to the third pipe 53 blocking a portion of the upstream side of the communication passage 2b, the hunting phenomenon can be suppressed in the same manner as in the above-mentioned embodiment.

(Modification)
FIG. 8 is a cross-sectional view similar to FIG. 4 according to a modified example of the third embodiment. FIG. 9 is an enlarged view of the E portion of FIG. 8. The expansion valve 1E of this modified example differs from the third embodiment in the shapes of the cylindrical members 55E and 56E. Specifically, the end of the cylindrical member 55E has two semicircular notches 55g formed at 180 degrees out of phase with each other to prevent interference with the actuation rod 5, and the end of the cylindrical member 56E has two semicircular notches 56g formed at 180 degrees out of phase with each other to prevent interference with the actuation rod 5. The cylindrical members 55E and 56E are assembled to the expansion valve 1E with their opposing end faces in contact with each other. Other configurations similar to those of the second embodiment are given the same reference numerals and will not be described again.

As shown in Fig. 9, with the opposing end faces of cylindrical members 55E and 56E in contact, notches 55g and 56g form a single cylinder whose inner diameter X is approximately 0.1 mm to 0.2 mm larger than the outer diameter Y of working rod 5. The area of this gap, ( ^X2 - ^Y2 )π/4, is the effective cross-sectional area of communicating passage 2d. By making the effective cross-sectional area of communicating passage 2d as small as possible in this way, the hunting phenomenon can be more effectively suppressed.

The present invention is not limited to the above-described embodiment. Any of the components of the above-described embodiment may be modified within the scope of the present invention. Any of the components of the above-described embodiment may be added or omitted.

1, 1A, 1B, 1C, 1D, 1E: Expansion valve 2: Valve body 3: Valve element 4: Biasing device 5: Actuating rod 6: Ring spring 8: Power element 20: Valve seat 21: First flow path 22: Second flow path 221: Intermediate chamber 23: Return flow path 27: Valve through hole 28: Actuating rod insertion hole 29: Annular recess 41: Coil spring 42: Valve element support 43: Spring support member 51: First pipe 52: Second pipe 53, 53A: Third pipe 54, 54D: Fourth pipe 55, 55B, 55C, 55E: Cylindrical member 56, 56E: Cylindrical member 81: Plug 82: Top cover member 83: Diaphragm 84: Stopper member 86: Support member 100: Refrigerant circulation system 101: Compressor 102: Condenser 104 : Evaporator VS : Valve chest

Claims (9)

A power element including a diaphragm that drives an actuating rod that presses a valve body in a valve opening direction , an upper cover member that arranges a pressure actuated chamber between one surface of the diaphragm and a receiving member, and a fluid inflow chamber that arranges a fluid inflow chamber between the other surface of the diaphragm and a receiving member;
A refrigerant flow path to which a pipe can be connected;
a communication passage that communicates the fluid inlet chamber and the refrigerant flow passage;
a shielding member that is inserted into the refrigerant flow path to shield a portion of the communication passage ,
The expansion valve , wherein the shielding member is a cylindrical member attached to a pipe connected to the refrigerant flow path, and a tip of the cylindrical member shields a part of the communication passage . 2. The expansion valve according to claim 1, wherein the actuating rod is inserted through the communication passage, and a notch is formed at the tip to avoid interference with the actuating rod. 2. The expansion valve according to claim 1 , wherein a tapered surface is formed on the outer periphery of the tip. 4. The expansion valve according to claim 1 , further comprising an adjustment member for adjusting an overlap amount between the blocking member and the communication passage. A power element including a diaphragm that drives an actuating rod that presses a valve body in a valve opening direction, an upper cover member that arranges a pressure actuated chamber between the diaphragm and one surface of the upper cover member, and a receiving member that arranges a fluid inflow chamber between the diaphragm and the other surface of the upper cover member;
A refrigerant flow path to which a pipe can be connected;
a communication passage that communicates the fluid inlet chamber and the refrigerant flow passage;
a shielding member that is inserted into the refrigerant flow path to shield a portion of the communication passage,
the shielding member is a pipe connected to the refrigerant flow path, and a tip of the pipe shields a part of the communication passage,
An expansion valve, characterized in that the operating rod is inserted into the communication passage, and a notch is formed at the tip to avoid interference with the operating rod. A power element including a diaphragm that drives an actuating rod that presses a valve body in a valve opening direction, an upper cover member that arranges a pressure actuated chamber between the diaphragm and one surface of the upper cover member, and a receiving member that arranges a fluid inflow chamber between the diaphragm and the other surface of the upper cover member;
A refrigerant flow path to which a pipe can be connected;
a communication passage that communicates the fluid inlet chamber and the refrigerant flow passage;
a shielding member that is inserted into the refrigerant flow path to shield a portion of the communication passage,
an adjustment member for adjusting an overlap amount between the blocking member and the communication passage, 7. The expansion valve according to claim 6, wherein the blocking member is a pipe connected to the refrigerant flow path, and a tip of the pipe blocks a part of the communication passage. 8. The expansion valve according to claim 7, wherein the actuating rod is inserted through the communication passage, and a notch is formed at the tip to avoid interference with the actuating rod. 8. The expansion valve according to claim 7, wherein a tapered surface is formed on the outer periphery of the tip.

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