US20150276286A1

US20150276286A1 - Expansion Valve

Info

Publication number: US20150276286A1
Application number: US14/437,240
Authority: US
Inventors: Geng Jin; Yibing Ruan
Original assignee: WENLING HENGFA AIRCONDITION COMPONENTS Co Ltd
Current assignee: WENLING HENGFA AIRCONDITION COMPONENTS Co Ltd
Priority date: 2012-10-26
Filing date: 2013-09-29
Publication date: 2015-10-01
Also published as: JP2015530558A; CN102878734A; WO2014063558A1; JP6134386B2; CN102878734B

Abstract

An expansion valve relating to the field of air conditioning technology. The present expansion valve comprises a housing, a cylindrical valve body with an inner cavity fixed inside the housing. In the inner cavity, there is a matched set of the first valve core and the second valve core sliding along it. A retaining ring is fixed in the inner cavity between the two valve cores. At both ends of the inner cavity there are spring assemblies driving the valve cores towards the retaining ring. A damping structure is also installed between the first valve core and the second valve core. In this manner, a cushioning effect is provided when the first valve core approaches the second valve core, which lightens the impacts to valve cores and thereby extend the service life of the expansion valve.

Description

BACKGROUND OF THE INVENTION

1. Field of Invention
The present invention relates generally to the field of air conditioning technology, and more particularly to a mechanical and automatic valve for use in inverter air conditioning and refrigeration.
2. Related Art
The expansion valve is an important component of refrigeration systems, generally installed between the condenser and the evaporator. It enables the gas evaporated by the evaporator passing through the compressor, being pressurized and liquefied into liquid refrigerant at high temperature and high pressure, passing through its throttle orifice and getting throttled into atomized liquid refrigerant at low temperature and low pressure, and, then, the refrigerant absorbs heat in the evaporator to realize a cooling effect. The expansion valve controls the flow rate according to changes in superheat at the end of the evaporator, so as to prevent under utilization of the evaporator surface due to over restricted flow, as well as liquid slugging caused by under evaporated refrigerant being ingested into the compressor due to insufficient evaporator surface and excessive flow rate. The expansion valves used on air conditioners include mechanical expansion valves and electronic ones. Current inverter air conditioners mainly adopt the electronic expansion valves, through aperture adjustment and pressure differential control, to control the liquefaction and gasification of the refrigerant according to design specifications. Instead of the electronic valves, some air conditioners also adopt the mechanical expansion valves.
The electronic valve uses digital signals to drive a motor to control the valve aperture, to ensure a constant pressure differential across the valve and thereby completely explore the capacity of the condenser and the evaporator. Meanwhile, since the rotational speed of the compressor motor can be timely adjusted by the inverter, it can be varied synchronically with the rotation angle of the motor on the electronic expansion valve. This ensures the constant pressure differential across the valve; and, thus, yielding the air conditioner a high efficiency.
However, due to its higher cost, electronic expansion valve, sometimes, may be replaced by capillary tubes, and normal compressors by inverter compressors. When the pressure differential across the capillary tube deviates from design specifications the inverter compressor will vary accordingly so as to fulfill the design requirements on the pressure differential across the capillary tube.
For example, one prior art two-way flow thermal expansion valve comprises a valve body and a power head unit. There are primary and secondary connectors on the valve body, and inside the valve body, there is a valve port connecting the primary connector to the secondary connector. Beneath the valve port, there is a valve core co-supported by a regulating spring and a transmission rod powered by the power head unit. It is characterized in that, on the valve core, there is a throttle orifice connecting the primary and secondary connectors. Inside the orifice, an actuator is installed to keep the orifice open or close. The orifice together with the actuator constitutes a one-way throttle structure inside thermal expansion valve, similar to a one-way throttle valve. The presence of this structure allows two-way flow inside thermal expansion valve. When applied to air conditioning systems, it is easily installed, reduces the number of potential leakage points brought by a large number of welding seams, and cuts down the manufacturing cost of the air conditioning systems. However, although this type of two-way expansion valve does entertain two-way flow, it is actually not meant for two-way flow. Since, only during forward flow, could the valve realize any valve aperture change according to the temperature change sensed by thermometer package. When the flow is backwards, the refrigerant could only pass through the throttle orifice in the valve core, and the valve aperture doesn't change, which increases unnecessary resistance for the refrigerant flow, as well as increased energy waste for the air conditioner. Furthermore, during backwards flow, the orifice will be blocked by the actuator, and the valve core must be pushed open to let any flow through. Hence, the valve core is subject to frequent impacts under the spring force, reducing the valve service life.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the invention to avoid the issues of the prior art stated above.
It is further object of the invention to provide a expansion valve, which instantly regulates the valve aperture by controlling the compressor flow rate and assures the pressure differential across the valve.
It is further object of the invention to provide a simple, efficient, durable, and cost effective expansion valve.
The above objects of the present invention can be achieved through the following technical solutions:
An expansion valve, characterized in that, the present expansion valve comprises a housing with an inlet end and an outlet end, a cylindrical valve body with an inner cavity fixed inside the housing. On the valve body's side wall there are an inlet and an outlet connecting the inner cavity and housing, and a spacer sleeve between the housing and valve body that separates the inlet and outlet. In the inner cavity, there is a matched set of a first valve core and a second valve core sliding along it. A retaining ring is fixed in the inner cavity between the two valve cores. At both ends of the inner cavity there are spring assemblies driving the valve cores towards the retaining ring. A damping structure is also installed between the first valve core and the second valve core. In this manner, a cushioning effect is provided when the first valve core approaches the second valve core, which lightens the impacts to valve cores and thereby extend the service life of the expansion valve.
For forward flow: when the refrigerant enters the housing from the inlet end, due to presence of the spacer sleeve, it can only enter the inner cavity of the valve body through the inlet. The spring assembly gets compressed by the pressure of the refrigerant, which pushes the second valve core away from the retaining ring, exits the valve body from its outlet and eventually flows out from the outlet end on the housing. For backwards flow: when the refrigerant enters the housing from the outlet end, due to presence of the spacer sleeve, it could only enter the inner cavity of the valve body from its outlet. The spring assembly gets compressed by the pressure of the refrigerant, and pushes the first valve core away from the retaining ring, so the refrigerant flows out of the valve body from its inlet and eventually flow out from the inlet end on the housing. This expansion valve has a matched pair of male valve core and female valve core, namely, the first valve core and the second valve core. The movement of one of the valve cores is controlled by the change in the line pressure differential. Due to presence of the damping structure, the first valve core approaches to the second valve core in a stable and cushioned manner, which lightens the impact between the valve cores, reduces the wear when the two valve cores touch each other, and extends the service life of the expansion valve.
In the present expansion valve, the retaining ring comprises a guide bore, an annular cavity, a diversion hole connecting the annular cavity and the inlet, and a limiter groove which can secure a press fit with the valve body. The guide bore and the first valve core match, so that the first valve core can enter the retaining ring, while the limiter groove secures the retaining ring in the inner cavity.
In the present expansion valve, the damping structure comprises, on the head of the first valve core, in sequential order, the front cylinder, the front throttle cone, the rear cylinder, the rear throttle cone, the guide cylinder, and, on the second valve core, matching the corresponding structures on the head of the first valve core, in sequential order, the front cylinder bore, the front throttle cone bore, the relief groove, the rear cylinder bore and the rear throttle cone bore. There is also a diversion port connecting the front cylinder bore and the outlet on the second valve core. When the front cylinder of the first valve core plugs into the front cylinder bore of the second valve core, a one-way flow through and relatively closed chamber, called the front damping chamber, arises between the first valve core and the second valve core. The guide cylinder of the first valve core fits the guide bore of the retaining ring with a tight clearance so that a relatively closed chamber arises between the first valve core and the retaining ring, called the middle damping chamber. These provide better cushioning effect when the valve cores move forward as the valve closes, minimize impacts to the valve cores and extends valve service life.
In another preferred embodiment of the invention, in the present expansion valve, there is a vent connecting the outside of the valve body and the relief groove on the second valve core. When the flow rate of the refrigerant is small, the first valve core and the second valve core keep static, and the refrigerant can enter the relief groove through the vent, pass the retaining ring and exit from the outlet of the valve body. In this case, both valve cores keep static, reducing wear on valve cores and extending service life of the spring assemblies.
In the expansion valve above, a capillary tube is embedded into the vent. The cooling system can produce a predetermined pressure drop, with the capillary tube producing a longitudinal pressure drop according to flow resistance, so as to control the flow rate of the refrigerant and maintain the pressure difference between the condenser and the evaporator. This assures minimum continuous refrigeration for different refrigeration setup.
In another preferred embodiment of the invention, in the expansion valve above, there is a diversion slot connecting the relief groove and the front cylinder bore on the first valve core. When the flow rate is small, the refrigerant can enter the front cylinder bore through the relief groove directly, so as to avoid the relative movements between the two valve cores, and to reduce the wear as a result.
In another preferred embodiment of the invention, in the expansion valve above, there is a vent connecting the relief groove and the diversion port on the second valve core. When the flow rate is small, the refrigerant can enter the diversion port from the relief groove directly.
In another preferred embodiment of the invention, in the expansion valve above, there is a vent connecting the rear throttle cone bore and the front cylinder bore on the first valve core. When the flow rate is small, the refrigerant can enter the front cylinder bore from the rear throttle cone bore directly
In another preferred embodiment of the invention, in the expansion valve above, there is a vent axially passing throughout the first valve core. The refrigerant of small flow rate can enter the inside of the valve body through this passage in the valve core directly, and exit the valve body from a small hole on the spring seat.
In the expansion valve above, the spring assembly comprises a first spring seat, a first spring, a second spring seat and a second spring, with one end of the first spring abutting the first valve core, and the other end abutting the first spring seat, and with one end of the second spring abutting the second valve core, and the other end abutting the second spring seat. The first spring seat and the second spring seat are respectively affixed to each end of the valve body, and at the end of the first spring seat and at the end of the second spring seat there is a small hole venting to the housing mentioned above. There is a cylinder and a damping ring groove each at the rear end of the first valve core and the rear end of the second valve core. A damping ring is installed in each of the damping ring grooves. Rear damping cavities are formed by the first spring seat and the second spring seat, the valve body, the first valve core or the second valve core and the damping rings, and serve as the expansion valve's direction control cavities.
In the expansion valve above, there is a limiting rod each on the first spring seat and the second spring seat, limiting the oscillation of the springs. With the limiting rods added, the range of the axial oscillations of the first spring and the second spring are limited. This ensures that the first spring and the second spring will not be overloaded, thereby extends the service life of the spring.
In the expansion valve above, a filter assembly is installed at the inlet end and the outlet end of the housing. The filter assembly comprises a filter screen and a mounting racket fixed to the housing. The filter assembly is used to filter debris mixed in the refrigerant, to avoid clogging the components of the expansion valve.
Compared to the prior art, the present expansion valve has the following advantages:
1. The structure is simple. The direction of the expansion valve can be controlled by controlling the pressure change of the cooling pipeline with a reversing valve.
2. The damping structure keeps the differences between the pressure of the inner cavity and the outlet and the inlet pressures balanced, and maintains the required pressure for refrigerant compressing and liquefying. Meanwhile, the valve cores keep static when the flow rate of the refrigerant is small, which reduces the frequent movements of the spring, and extends the service life of the components of the expansion valve.
3. The front damping chamber arising between the first valve core and the second valve core provides good cushion when the first valve core the second valve core contact each other, lightens the impacts and extends the service life of the expansion valve.
4. The middle damping chamber arising between the retaining ring and the first valve core, as well as the rear damping chambers arising between the first valve core or the second valve core and the valve body, provide good cushion when the first valve core or the second valve core separates from the limiting rod, preventing vibration due to sudden movements of the first and the second springs, reducing spring noise, and extending the expansion valve's service life.
5. The appropriate fit between the head of the first valve core and the second valve core can vary according to the flow rate of the refrigerant and the size of the throttle clearance. This can reduce the flow resistance of the refrigerant, and contribute a lot to the improvement of the energy efficiency ratio (EER) of the air conditioner.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a structural diagram of a first preferred embodiment of the expansion valve.

FIG. 2 is a structural diagram of retaining ring of the first preferred embodiment.

FIG. 3 is a structural diagram of the first and the second spring seats of the first preferred embodiment.

FIG. 4 is a structural diagram of the first valve core of the first preferred embodiment.

FIG. 5 is a structural diagram of the second valve core of the first preferred embodiment.

FIG. 6 is a structural diagram of a second preferred embodiment showing the flow path for small flow.

FIG. 7 is a structural diagram of a third preferred embodiment showing the flow path for small flow.

FIG. 8 is a structural diagram of a fourth preferred embodiment showing the flow path for small flow.

FIG. 9 is a structural diagram of a fifth preferred embodiment showing the flow path for small flow.

FIG. 10 is a structural diagram of a sixth preferred embodiment showing the flow path for small flow.

DETAILED DESCRIPTION OF THE INVENTION

The embodiments of the invention will be described below and the technical solutions of the invention will be further illustrated in connection with the accompanying figures. However, the present invention shall not be limited to these embodiments.

First Embodiment

As shown in FIG. 1, An expansion valve comprises a housing (10) with an inlet end (101) and an outlet end (102), a cylindrical valve body (1) with an inner cavity fixed inside the housing (10), on the side of the valve body (1) wall there are an inlet (11) and an outlet (12) connecting the inner cavity and housing (10), and a spacer sleeve (8) between the housing (10) and valve body (1) that separates the inlet (11) and outlet (12). In the inner cavity, there is a matched set of the first valve core (2) and the second valve core (3) sliding along its inside. A retaining ring (7) is fixed to the mid-section of the inner cavity between the two valve cores. At both ends of the inner cavity there are spring assemblies pressing the first valve core (2) and the second valve core (3) towards the retaining ring (7). A damping structure is provided between the first valve core (2) and the second valve core (3).
Specifically, as shown in FIGS. 1 through 5, the retaining ring (7) comprises a guide bore (73), an annular cavity (74), a diversion hole (71) connecting the annular cavity (74) and the inlet (11), and a limiter groove (72) which can secure a press fit with the valve body (1). The damping structure comprises the front cylinder (21), the front throttle cone (22), the rear cylinder (23), the rear throttle cone (24), the guide cylinder (25) successively on the head of the first valve core (2), and the rear throttle cone bore (31), the rear cylinder bore (32), the relief groove (33), the front throttle cone bore (35) and the front cylinder bore (36) successively on the head of the second valve core (3) that match the corresponding structures on the first valve core (2). There is also a diversion port (37) connecting the front cylinder bore (36) and the outlet (12) on the second valve core (3).
The spring assembly comprises a first spring seat (43), a first spring (41), a second spring seat (44) and a second spring (42), with one end of the first spring (41) abutting the first valve core (2) and the other end abutting the first spring seat (43), with one end of the second spring (42) abutting the second valve core (3) and the other end abutting the second spring seat (44). There is a limiting rod (51) each on the first spring seat (43) and the second spring seat (44) limiting the oscillation of the springs. With incorporation of the limiting rods (51), axial oscillation amplitudes of the first spring (41) and the second spring (42) are limited, ensuring that the first spring (41) and the second spring (42) are not overloaded, extending the springs' service life. The first spring seat (43) and the second spring seat (44) are respectively affixed to each end of the valve body (1), and on each end of the first spring seat (43) and the second spring seat (44), there is a small hole (52) venting to the housing (10). At each rear end of the first valve core (2) and the second valve core (3), there is a cylinder (103) and a damping ring groove (26) installed with a damping ring (6). One each filter assembly (9) is installed at the inlet end (101) and the outlet end (102) of the housing (10). The filter assembly (9) comprises a filter screen and a mounting racket affixed to the housing (10).
The refrigerant enters the housing (10), passes through the filter assembly (9), and enters the present valve through either the controlled passage or the flowing passage.
If the refrigerant enters the outlet end (102) on the second valve core (3) side of the valve:
Controlled Passage: the refrigerant enters the valve at the outlet end (102) of the housing (10), passes through the filter assembly (9) at the outlet end (102), and the small holes (52) on the first spring seat (43) and the second spring seat (44), and then acts on the second valve core (3). Since the pressure at outlet (12) is higher than that at inlet (11), the second valve core (3) will be squeezed. Now, the refrigerant in the cavity enclosed by the first valve core (2), the valve body (1), the first spring seat (43) and the second spring seat (44) passes through the small holes (52) on the first spring seat (43) and the second spring seat (44), flows out of the valve body (1) and joins the Flowing Passage. When the second valve core (3) abuts the retaining ring (7), it (3) stops and releases the loads.
Flowing Passage: Since the inlet (11) and outlet (12) of the valve body (1) are separated by the spacer sleeve (8), the refrigerant can only enter the outlet (12) of the valve body (1), and the diversion port (37) of the second valve core (3), pass through the gap between the first valve core (2) and the second valve core (3), the annular cavity (74) of the retaining ring (7), flow out of the valve body (1) from the diversion hole (71) of the retaining ring (7) and the inlet (11) of the valve body (1), continue to pass through the gap between the valve body (1) and the housing (10), joining the Controlled Passage, and then enter the filter assembly (9) comprising the filter screen and the mounting racket at the inlet end (101), and eventually flow out of the present valve from the inlet end (101) of the housing (10).
If the refrigerant enters the inlet end (101) on the first valve core (2) side of the valve:
Controlled Passage: the refrigerant enters the small holes (52) on the first spring seat (43) and the second spring seat (44), and acts on the first valve core (2). Since the pressure at the inlet (11) is higher than that at the outlet (12), the first valve core (2) will be squeezed towards the retaining ring (7). Now, the refrigerant in the cavity enclosed by the second valve core (3), the valve body (1) and the first spring seat (43) and the second spring seat (44) passes through the small holes (52) on the first spring seat (43) and the second spring seat (44), flows out of the valve body (1) joining the Flowing Passage. When the first valve core (2) abuts the retaining ring (7), the first valve core (2) stops and releases the loads.
Flowing Passage: Since the inlet (11) and outlet (12) of the valve body (1) are separated by the spacer sleeve (8), the refrigerant can only enter the inlet (11) of the valve body (1). Through the diversion hole (71) of the retaining ring (7), it enters the annular cavity (74) of the retaining ring (7), passes through the gap between the first valve core (2) and the second valve core (3), flows out of the valve body (1) from the diversion port (37) of valve coer II (3) and the outlet (11) of the valve body (1), continues to pass through the gap between the valve body (1) and the housing (10), joining the Controlled Passage, enters the filter assembly (9) comprising the filter screen and the mounting racket at the inlet end (101), and eventually flows out of the present valve from the outlet end (102) of the housing (10)
Because a relatively closed cavity between the first valve core (2) and the second valve core (3), a relatively closed cavity between the retaining ring (7) and the first valve core (2), together with the relatively closed cavities enclosed by either the valve body (1), the first spring seat (43) and the first valve core (2) or the valve body (1), the second spring seat (44) and the second valve core (3) are designed along the trajectory of the valve cores, there are several damping mechanisms provided along the movements of the first valve core (2) or the second valve core (3). Due to their presence, the movements of the first valve core (2) or the second valve core (3) are smoothly cushioned, which lightens impacts to both valve cores, reduces the wear as a result of the impact of the head of the first valve core (2) against the second valve core (3), and extends the service life of the expansion valve.

Second Embodiment

The principle and structure of this embodiment are substantially similar to that of the first preferred embodiment. As shown in FIG. 6, the difference from the first preferred embodiment is that a flow path for small flow is added. Its structure comprises a vent (34) on the second valve core (3), connecting the outside of the valve body (1) and the relief groove (33). Capillary tubes are installed in the trough hole (34). The flow rate of the vent (34) can be changed by installing capillary tubes.

Third Embodiment

The principle and structure of this embodiment are substantially similar to that of the second preferred embodiment. As shown in FIG. 7, the difference from the second preferred embodiment is in the flow path for small flow. Its structure comprises a diversion slot (27) on the first valve core (2), connecting the relief groove (33) and the front cylinder bore (36).

Fourth Embodiment

The principle and structure of this embodiment are substantially similar to that of the second preferred embodiment. As shown in FIG. 8, the difference from the second preferred embodiment is in the flow path for small flow. Its structure comprises a vent (38) on the second valve core (3), connecting the relief groove (33) and the diversion port (37).

Fifth Embodiment

The principle and structure of this embodiment are substantially similar to that of the second preferred embodiment. As shown in FIG. 9, the difference from the second preferred embodiment is in the flow path for small flow. Its structure comprises a vent (39) on the first valve core (2), connecting the rear throttle cone bore (31) and the front cylinder bore (36).

Sixth Embodiment

The principle and structure of this embodiment are substantially similar to that of the second preferred embodiment. As shown in FIG. 10, the difference from the second preferred embodiment is in the flow path for small flow. Its structure comprises a there is a vent (40) axially passing throughout the first valve core (2). The refrigerant of small flow rate flows out of the valve body (1) from the small hole (52) on the spring seat (5), instead of from the outlet (12) of the valve body (1)
The embodiments described herein serve only as exemplar illustration of the spirit of the invention. In the specifically described embodiments those skilled in the art of the present invention may be able to make various modifications, additions, or substitutions by similar mechanisms, without departing from the spirit of this invention or surpassing the scope as defined by the appended claims.

LIST OF REFERENCE NUMERALS

- 1 Valve Body
- 2 First Valve Core
- 3 Second Valve Core
- 6 Damping Ring
- 7 Retaining Ring
- 8 Spacer Sleeve
- 9 Filter Assembly
- 10 Housing
- 11 Inlet
- 12 Outlet
- 21 Front Cylinder
- 22 Front Throttle Cone
- 23 Rear Cylinder
- 24 Rear Throttle Cone
- 25 Guide Cylinder
- 26 Damping Ring Groove
- 27 Diversion Slot
- 30 Vent
- 31 Rear Throttle Cone Bore
- 32 Rear Cylinder Bore
- 33 Relief Groove
- 34 Vent
- 35 Rear Throttle Cone Bore
- 36 Front Cylinder Bore
- 37 Diversion Port
- 38 Vent
- 39 Vent
- 41 First Spring
- 42 Second Spring
- 43 First Spring Seat
- 44 Second Spring Seat
- 51 Limiting Rod
- 52 Small Hole
- 71 Diversion Hole
- 72 Limiter Groove
- 73 Guide Bore
- 74 Annular Cavity
- 101 Inlet End
- 102 Outlet End
- 103 Cylinder

Claims

What is claimed is:

1. An expansion valve comprising:

a housing (10) with an inlet end (101) and an outlet end (102);

a cylindrical valve body (1) with an inner cavity fixed inside the housing (10);

an inlet (11) and an outlet (12) provided on a side wall of the valve body (1), connecting the inner cavity and the housing (10);

a spacer sleeve (8) between the housing (10) and valve body (1) that separates the inlet (11) and outlet (12);

a matched pair of a first valve core (2) and a second valve core (3) capable of sliding along an interior of inner cavity;

a retaining ring (7) fixed to a mid-section of the inner cavity between the first valve core (2) and the second valve core (3);

spring assemblies at both ends of the inner cavity, pressing the first valve core (2) and the second valve core (3) towards the retaining ring (7); and

a damping structure provided between the first valve core (2) and the second valve core (3), which provides a cushioning effect.

2. The expansion valve as claimed in claim 1, further comprising:

a guide bore (73);

an annular cavity (74);

a diversion hole (71) connecting the annular cavity (74) and the inlet (11); and

a limiter groove (72) capable of securing a press fit to the valve body (1).

3. The expansion valve as claimed in claim 1, wherein:

the front cylinder (21), the front throttle cone (22), the rear cylinder (23), the rear throttle cone (24), and the guide cylinder (25) are structures on the head of the first valve core (2) and positioned in sequential order; and

the front cylinder bore (36), the front throttle cone bore (35), the relief groove (33), the rear cylinder bore (32), and the rear throttle cone bore (31) on the second valve core (3) are positioned in reverse sequential order and match the corresponding structures on the head of the first valve core (2);

wherein a diversion port (37) connects the front cylinder bore (36) and the outlet (12) on the second valve core (3).

4. The expansion valve as claimed in claim 2, wherein:

5. The expansion valve as claimed in claim 3, further comprising:

a vent (34) connecting the outside of the valve body (1) and the relief groove (33) on the second valve core (3).

6. The expansion valve as claimed in claim 4, further comprising:

7. The expansion valve as claimed in claim 3, further comprising:

a diversion slot (27) connecting the relief groove (33) and the front cylinder bore (36) on the first valve core (2).

8. The expansion valve as claimed in claim 4, further comprising:

9. The expansion valve as claimed in claim 3, further comprising:

a vent (38) connecting the relief groove (33) and the diversion port (37) on the second valve core.

10. The expansion valve as claimed in claim 4, further comprising:

11. The expansion valve as claimed in claim 3, further comprising:

a vent (39) connecting the rear throttle cone bore (31) and the front cylinder bore (36) on the first valve core (2).

12. The expansion valve as claimed in claim 4, further comprising:

13. The expansion valve as claimed in claim 3, further comprising:

a vent (34) axially passing throughout the first valve core (2).

14. The expansion valve as claimed in claim 4, further comprising:

a vent (34) axially passing throughout the first valve core (2).

15. The expansion valve as claimed in claim 5, further comprising:

a spring assembly having a first spring seat (43), a first spring (41), a second spring seat (44) and a second spring (42), with one end of the first spring (41) abutting the first valve core (2) and the other end abutting the first spring seat (43), with one end of the second spring (42) abutting the second valve core (3) and the other end abutting the second spring seat (44), and with the first spring seat (43) and the second spring seat (44) respectively affixed to each end of the valve body (1);

a small hole (52) each at the end of the first spring seat (43) and the end of the second spring seat (44), venting to the housing (10);

a cylinder (103) and a damping ring groove (26) each at the rear end of the first valve core (2) and the rear end of the second valve core (3); and

a damping ring (6) installed in each of the damping ring grooves (26).

16. The expansion valve as claimed in claim 6, further comprising:

a damping ring (6) installed in each of the damping ring grooves (26).

17. The expansion valve as claimed in claim 15, further comprising:

a filter assembly (9) installed at the inlet end (101) and the outlet end (102) of the housing (10), the filter assembly (9) having a filter screen and a mounting racket fixed to the housing (10).

18. The expansion valve as claimed in claim 16, further comprising: