JP2001174076A - Refrigeration cycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid the intermittent fluctuation of a cycle in a low load in a refrigeration cycle using a refrigerant with a low critical point such as CO2. SOLUTION: An expansion device 5 of a refrigerant cycle has characteristics for reducing the fluctuation of an opening area for the pressure fluctuation of high-pressure space in an initial stage where a valve is lifted from a position in that the opening area of a communication path 14 becomes the minimum. A valve 17 may be formed in a shape having characteristics where the smaller the opening area of the communication path 14 becomes, the smaller the fluctuation of a valve travel for the pressure fluctuation of high-pressure space 11 becomes. Also, instead of the adjustment of the shape of the valve 17, the communication path 14 may be formed in a shape where the smaller the opening area of the communication path 14 becomes, the smaller the fluctuation of the valve travel becomes for the pressure fluctuation of the high-pressure space 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

THE INVENTION Field of the Invention The present invention, refrigerant low critical point as the refrigerant, for example, relates to a refrigeration cycle using a refrigerant that can be used in supercritical region as such carbon dioxide (CO _2).

[0002]

_2. Description of the Related Art As a refrigerating cycle using carbon dioxide (CO ₂ ) as a refrigerant, a configuration disclosed in Japanese Patent Application Laid-Open No. 9-264622 is known. This is to control the outlet pressure of the radiator by a pressure control valve, the pressure control valve is formed in the refrigerant flow path, and a partition part that partitions the refrigerant flow path into an upstream space and a downstream space. A valve port formed in the partition wall for communicating the upstream space and the downstream space, and a displacement that forms a sealed space in the upstream space and is displaced according to a pressure difference between the inside and outside of the sealed space. A member and a valve body for opening and closing the valve port, wherein the displacement member is displaced when the pressure in the upstream space becomes larger than the pressure in the closed space by a predetermined amount, and the valve body is The valve port is opened when the displacement member is displaced.

According to such a pressure control valve, when the pressure on the outlet side of the radiator is increased, the displacement member is displaced by the pressure difference between the pressure of the refrigerant sealed in the closed space and the valve body. The part is moved in the direction to open the valve port, so that the outlet side pressure is reduced, and when the refrigerant temperature on the outlet side of the radiator is high, the refrigerant in the closed space expands so that the displacement member Displaces and moves the valve body in the direction to close the valve port, so the outlet pressure of the radiator rises and the outlet pressure of the radiator can be increased without increasing the compression work of the compressor. Accordingly, it is said that the cooling capacity can be ensured while suppressing the deterioration of the coefficient of performance of the refrigeration cycle.

[0004]

[SUMMARY OF THE INVENTION However, in a refrigeration cycle using a low critical point refrigerant as described above in the CO _2, the pressure in the high pressure line while the compressor variable capacity is lower than the critical pressure nitrous When operating at low load in the critical region, the refrigeration cycle is intermittent even during steady-state operation where the discharge rate of the compressor and the load on the radiator and condenser are constant (environmental conditions are constant). A phenomenon that causes large fluctuations has been confirmed.

Various causes have been estimated as the cause of such a phenomenon, but the main causes are considered as follows. That is, regardless of the diaphragm type expansion device or the bellows type expansion device, the gas sealed in the expansion device expands or contracts in accordance with the refrigerant temperature on the inflow side of the expansion device, and the position of the valve element is increased. Is displaced, and the position of the valve body is displaced according to the refrigerant pressure on the inflow side of the expansion device. Therefore, the sealing gas is sealed so that the relationship between the refrigerant temperature and the refrigerant pressure has optimal control characteristics. The opening degree of the expansion device is adjusted to a target opening degree in accordance with the refrigerant temperature and the refrigerant pressure on the inflow side.

However, at low load, when a variable displacement compressor is used, the discharge amount is originally small, and the pressure in the high pressure line is relatively low, so that the expansion device may be closed. It operates in the direction of. In particular, at such a low load, when the opening degree of the expansion device is stable at a position where the optimum refrigerant pressure P is obtained for a certain refrigerant temperature T, the refrigerant temperature may become T for some reason. If it is relatively higher than this, the expansion device will be closed at a low load because the opening degree is small.

[0007] Then, the refrigerant supplied to the low-pressure line via the expansion device disappears. In the variable displacement compressor, the discharge amount is controlled according to the low pressure, and the discharge amount is reduced if the low pressure is low, and the discharge amount is increased if the low pressure is high. From that
When the amount of the refrigerant supplied to the low-pressure line decreases, the discharge amount of the compressor also decreases. When the discharge rate of the compressor is reduced, the operation of reducing the specific volume of the refrigerant by the condensing action of the radiator at low load where the cycle operates in the subcritical region is smaller than the operation of supplying the refrigerant and increasing the volume Therefore, the refrigerant pressure on the high pressure side does not rise for a while, and the closed state of the expansion device is maintained.

[0008] Even in such a state, the compressor continues to discharge the refrigerant little by little to the high pressure side.
As the condensation in the radiator progresses, the area of the radiator that actually releases the heat gradually decreases, so the refrigerant discharged from the compressor is more effective than reducing the specific volume of the refrigerant by the condensation of the radiator. Thus, the operation of increasing the volume is superior, and the high pressure gradually increases. Then, when the high pressure required to open the valve is reached, the expansion device opens and the refrigerant on the high pressure side flows at a stretch to the low pressure side, and the flow of the refrigerant suddenly flows into a cycle where the flow of the refrigerant has almost stagnated until now. Occurs. Then, it is considered that a cycle fluctuates greatly intermittently by repeating such a series of operations thereafter.

In order to avoid such a phenomenon that the expansion device is apt to be closed at the time of a low load, an electric expansion device that adjusts the opening degree by receiving an external electric control signal is used. Whatever the shape of the valve, the desired degree of opening can be arbitrarily adjusted. However, if the temperature-sensitive non-electric expansion device using a diaphragm or a bellows is used, the movement of the valve body can be adjusted. Is determined by the refrigerant temperature and the refrigerant pressure, so that the degree of opening adjustment at a low load requires special consideration.

Nevertheless, as a valve element used in a conventional non-electric expansion device, a ball valve is used as shown in FIGS. 4 and 7 of Japanese Patent Application Laid-Open No. 9-264622. According to the investigation by the inventors, as shown in FIG. 22, the change in the valve opening (opening area of the communication passage) with respect to the high pressure (valve lift) depends on the valve opening with respect to the high pressure (valve lift). Since the (opening area of the communication passage) has a characteristic indicated by A, which is substantially linear, the change in the valve opening (the opening area of the communication passage) increases as the high pressure decreases.
The configuration indicated by B is such that the higher the high pressure, the smaller the change in the valve opening (opening area of the communication passage) becomes.

For this reason, at the time of the above-mentioned low load in which the high pressure decreases, the fluctuation of the valve opening degree (opening area of the communication passage) with respect to the pressure fluctuation is almost the same as when the pressure of the high pressure line is high, or When the pressure is higher than when the pressure is high, the opening area of the expansion device is originally small at the time of a low load, so that the valve is closed with a slight pressure fluctuation.
As described above, when the load is low, the movement of the valve body becomes too sensitive to the pressure fluctuation, so that there is a disadvantage that the above-described phenomenon is further induced.

Therefore, according to the present invention, in a refrigeration cycle using a refrigerant having a low critical point such as carbon dioxide (CO ₂ ), by improving the valve element of the expansion device, it is possible to reduce the intermittent load at low load. An object of the present invention is to provide a refrigeration cycle that can make the cycle fluctuation less likely to occur.

[0013]

In order to achieve the above object, a refrigeration cycle according to the present invention comprises a compressor for compressing a refrigerant to make a refrigerant in a high pressure line in a supercritical state depending on operating conditions; A radiator that cools the refrigerant compressed by the expansion device that decompresses the refrigerant cooled by the radiator, and an evaporator that evaporates the refrigerant depressurized by the expansion device,
The expansion device includes a high-pressure space communicating with the radiator side, a low-pressure space communicating with the evaporator side, a communication passage communicating the high-pressure space and the low-pressure space, and a valve that changes an opening area of the communication passage. Body, and a sensing element that changes the opening area of the communication passage by controlling the position of the valve body in accordance with the refrigerant condition on the radiator side. It is characterized in that it has a characteristic of reducing the fluctuation of the opening area with respect to the pressure fluctuation of the high-pressure space at the initial stage when the body is lifted (claim 1).

Therefore, the fluctuation of the opening area with respect to the pressure fluctuation of the high pressure space at the initial stage when the valve element of the expansion device is lifted is reduced, so that the flow rate is small and the movement of the valve element at low pressure and low load is reduced. If it is possible to be insensitive to pressure fluctuations and to minimize the opening area of the communication passage, that is, if the valve body is of a type that closes the communication passage by sitting on a valve seat, the expansion device This can reduce the risk that the valve body easily seats on the valve seat and closes the communication passage.

In order to obtain such characteristics of the expansion device,
The valve body may be formed in a shape having a characteristic that the smaller the opening area of the communication passage, the smaller the variation of the opening area with respect to the pressure variation of the high-pressure space.

Here, as the shape of the valve element such that the smaller the opening area of the communication passage, the smaller the variation of the opening area with respect to the fluctuation of the pressure in the high-pressure space, the communication passage has the same diameter from the high-pressure space to the low-pressure space. When the valve body is formed with a hole, a shape in which the change in diameter per unit axial direction is continuously reduced from the base to the tip of the valve body and the reduction rate of the diameter is gradually increased may be considered. 3).

Since the sensing element can obtain a stroke of the valve element substantially proportional to the high pressure, according to the above-described structure of the valve element, even if the valve element has the same stroke as the conventional one, When the high pressure is low, the amount of change in the valve opening (opening area of the communication passage) with respect to the pressure change becomes small,
When the high pressure is high, the amount of change in the valve opening (opening area of the communication passage) with respect to the pressure change becomes large, and the characteristics of the valve opening (opening area of the communication passage) with respect to the high pressure are as shown in FIG.
As shown by the characteristic line, as the high-pressure pressure is lower (as the valve lift is smaller), the change in the valve opening (opening area of the communication passage) with respect to the pressure fluctuation becomes slower. For this reason, at the time of a low load in which the valve opening degree (opening area of the communication passage) becomes small, it is possible to avoid a disadvantage that the expansion device is easily closed due to the pressure fluctuation.

The above-described configuration for obtaining the characteristics of the expansion device can also be realized by adjusting the shape of the communication passage (ie, the shape of the valve seat) instead of adjusting the shape of the valve body. The shape of the communication passage may be formed such that the smaller the opening area of the communication passage, the smaller the change in the opening area with respect to the change in pressure in the high-pressure space.

For example, when the valve element is formed in a cylindrical shape with its displacement direction as the axis, or when the valve element moves from the base to the tip, the change in diameter per unit axial direction is continuously reduced at an equal rate. When the communication passage is formed in such a shape that the communication passage is changed from the high-pressure space to the low-pressure space, the change in the passage cross section per unit axial direction is continuously reduced, and the reduction rate of the passage cross section is gradually reduced. A configuration is conceivable (claims 5 and 6).

Further, as a configuration for obtaining the above-described characteristic of the expansion device for reducing the variation of the opening area with respect to the pressure variation of the high-pressure space at the initial stage when the valve element is lifted, the communication passage is formed with a through hole having the same diameter from the high-pressure space to the low-pressure space. The valve body is formed in a truncated cone shape in which the change in diameter per unit axial direction is continuously reduced at an equal rate as going from the base to the tip of the valve body. When the valve element is lifted up to the position where the valve element is lifted, the distal end of the valve element is separated from the opening end of the communication passage (claim 7). A first conical portion that gradually reduces the diameter toward the distal end of the valve body, and a second circle that is formed following the distal end side of the first conical portion and gradually decreases in diameter toward the distal end. And the angle of the included angle between the axis of the valve body and the generatrix of the second conical part is the angle of the included angle between the axis of the valve body and the generatrix of the first conical part. A first conical shape in which the angle of the included angle between the communication path and the axis thereof is larger than the angle of the included angle between the axis of the valve body and the generatrix of the first conical portion. And the angle formed by the path and the axis of the communication path, which is formed following the first conical path, is smaller than the angle formed by the axis of the valve element and the generatrix of the second conical portion. A small second conical path, and a transition portion of the valve body from the first conical section to the second conical section is formed from the first conical path of the communication path to the second conical section. It is good also as a structure which can contact the transition part to a road (claim 8).

The valve body may further include a first surface having a predetermined angle between the axis of the valve body and a predetermined angle between the first surface and the first surface. And a second surface having a smaller angle with respect to the axis of the first surface than the first surface, the characteristic of the expansion device is reduced in the initial stage when the valve element is lifted. The variation of the opening area with respect to the pressure variation of the space may be reduced (claim 9).

In such a configuration, the valve body is provided with a guide piece that is continuously inserted into the communication passage even during the lift, thereby adjusting the maximum opening area of the communication passage. May be cut in the axial direction to form a guide surface, and a guide receiving surface for receiving the guide surface may be formed in the communication passage for positioning.

Further, in such a configuration, the first surface of the valve body is seated on the valve seat formed at the end of the communication passage so as to define the position of the valve body where the opening area is minimized. However, a stopper may be provided that is displaced integrally with the valve body, and the stopper may define the position of the valve body where the opening area is minimized.
13).

[0024]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, a refrigeration cycle 1
Is a compressor 2 for compressing the refrigerant, a radiator 3 for cooling the refrigerant, an internal heat exchanger 4 for exchanging heat between the high-pressure line and the low-pressure line, an expansion device 5 for depressurizing the refrigerant, and evaporating the refrigerant. The apparatus has an accumulator 7 for separating the refrigerant flowing out of the evaporator 6 into gas and liquid. In this cycle, the discharge side (D) of the compressor 2 is connected to the high pressure passage 4a of the internal heat exchanger 4 via the radiator 3, and the outlet side of the high pressure passage 4a is connected to the expansion device 5, The path from the discharge side of No. 2 to the expansion device 5 is a high-pressure line 8. The outlet side of the expansion device 5 is connected to an evaporator 6, and the outlet side of the evaporator 6 is connected to a low-pressure passage 4 b of the internal heat exchanger 4 via an accumulator 7. The outflow side of the low-pressure passage 4b is connected to the suction side (S) of the compressor 2.
And a path from the outflow side of the expansion device 5 to the compressor 2 is a low-pressure line 9.

In the refrigeration cycle 1, a refrigerant having a low critical point, for example, carbon dioxide (CO ₂ ) is used as a refrigerant, and the refrigerant compressed by the compressor 2 is converted into a radiator 3 as a high-temperature and high-pressure refrigerant. And then radiates heat to cool it. Thereafter, the heat is exchanged with the low-temperature refrigerant flowing out of the evaporator 6 in the internal heat exchanger 4 to be further cooled and sent to the expansion device 5 without being liquefied. And this expansion device 5
Is decompressed into a low-temperature, low-pressure wet steam, and heat-exchanges with air passing therethrough in the evaporator 6 to become gaseous, and then heat-exchanges with the high-temperature refrigerant in the high-pressure line 8 in the internal heat exchanger 4 for heating. Is returned to the compressor 2.

As shown in FIG. 2, the expansion device 5 includes a high-pressure passage 4a of the internal heat exchanger 4 in a housing 10.
High-pressure space 11 and the evaporator 6 that lead to the air (to the radiator side)
A low-pressure space 12 communicating with the low-pressure space 12 is defined by a partition wall 13, and a communication path 14 having a predetermined diameter and having a circular cross section is formed in the partition wall 13 from the high-pressure space 11 to the low-pressure space 12.

The high-pressure space 11 accommodates a pressure-reducing control valve 15. The pressure-reducing control valve 15 is seated on a valve seat 16 formed at the periphery of an opening of the communication passage 14 that opens into the high-pressure space 11. A body 17 and a bellows 18 joined to the valve body 17 and moving integrally therewith.
A predetermined amount of sealing gas is sealed therein.

The opening pressure of the pressure reducing control valve 15 and the movement of the valve element 17 are adjusted by changing the amount of gas and the type of gas sealed in the bellows 18.
Is adapted to respond to the refrigerant pressure and the refrigerant temperature in the high-pressure space 11, and as shown in FIG. 3, the valve body 17 has a diameter that continuously changes from the base to the tip and has a smaller diameter. By having a shape in which the decreasing rate is gradually increased, the needle valve is configured such that the smaller the opening area of the communication passage 14 becomes, the smaller the fluctuation of the opening area with respect to the fluctuation of the pressure of the high-pressure space 11 becomes. Here, as a shape in which the decreasing rate of the diameter gradually increases toward the distal end, even if the generating line α of the valve element 17 is a curve having a constant radius of curvature from the base to the distal end, the radius of curvature is It may be a curve that changes continuously (decreases gradually) toward the tip.

In the above configuration, if the amount of expansion and contraction of the bellows 18 is considered to be substantially proportional to the refrigerant pressure in the high-pressure space 11, the stroke amount of the valve 17 is proportional to the refrigerant pressure in the high-pressure space 11. As the distance 17 from the valve seat 16 increases, the distance between the valve element 17 and the valve seat 16 increases exponentially. Therefore, the opening area of the communication path 14, that is, the substantial opening area of the communication path 14, can be increased exponentially as shown by the solid line in FIG. The change in the substantial opening area of the communication passage 14 decreases as the high-pressure pressure decreases, and increases as the high-pressure pressure increases.

In other words, the lower the high-pressure pressure, the slower the fluctuation of the valve opening (opening area of the communication passage). Therefore, the capacity of the compressor 2 is controlled by the pressure of the low-pressure line 9. And when the cycle is operated in a low-load region where it operates in a subcritical region where the high-pressure pressure is lower than the critical pressure,
Can be easily seated on the valve seat 16 to block the communication passage 14, and therefore, a remarkable decrease in the low pressure and a remarkable decrease in the discharge amount of the compressor 2 can be suppressed. As a result, it is possible to suppress the phenomenon that the refrigeration cycle 1 causes intermittent large fluctuations, and it is possible to stabilize the cooling capacity under a low load.

The above-described configuration realizes a characteristic that the smaller the opening area of the communication passage 14 with the shape of the valve element 17, the smaller the fluctuation of the valve opening (opening area of the communication passage) with respect to the pressure fluctuation of the high-pressure space 11. The communication path 14
, That is, the shape of the valve seat 16 may be provided with similar characteristics.

FIG. 5 shows an example of the construction of the expansion device 5. In the expansion device 5 shown in FIG. 5, the valve body 17 moving integrally with the bellows 18 is displaced with respect to the axis as shown in FIG. The shape of the communication path 14 is such that the diameter of the communication path 14 gradually decreases from the high-pressure space 11 toward the low-pressure space 12, and the rate of decrease in the diameter decreases from the high-pressure space 11 to the low-pressure space 11. By decreasing toward the space 12, a change in the passage cross section per unit axial direction is continuously formed, and a decreasing rate of the passage cross section is reduced toward the low-pressure space 12. The middle part of the communication passage 14 where the diameter of the passage cross section is equal to the diameter of the valve body 17 is defined as a valve seat 16 on which the valve body 17 is seated. still,
Even if the bus β of the communication path 14 is a curve having a constant radius of curvature from the high-pressure space 11 to the low-pressure space 12 of the communication path 14, the radius of curvature continuously changes from the high-pressure space 11 to the low-pressure space 12 (gradually). Curve). Since other configurations are the same as those of the above configuration example, the same portions are denoted by the same reference numerals and description thereof will be omitted.

Even in such a configuration, the distance between the valve body 17 and the valve seat 16 increases exponentially as the valve body 17 moves away from the valve seat 16, so that the refrigerant pressure in the high-pressure space 11 increases. As shown by the solid line in FIG. 4, the change in the opening area of the communication path 14, that is, the change in the substantial opening area of the communication path 14 with respect to the change in the refrigerant pressure in the high-pressure space 11 decreases as the opening area of the communication path 14 decreases. On the other hand, it is possible to provide a characteristic that reduces the fluctuation of the valve opening (opening area of the communication passage).

Therefore, even in the case of such a configuration, in the region where the high pressure is reduced, that is, in the initial stage of lifting in the direction of increasing the opening area of the communication passage, the opening area of the communication passage against the pressure fluctuation of the high pressure space is increased. The compressor 2 is of a variable capacity type whose capacity is controlled by the pressure of the low pressure line 9,
Further, even when this cycle is operated in a low load region where the high pressure is operated in a subcritical region where the high pressure is equal to or lower than the critical pressure, the valve element 17 of the expansion device 5 is seated on the valve seat 16 and the communication passage 14 is formed. Can be reduced, the remarkable decrease in low pressure and the discharge amount of the compressor 2 can be suppressed, and the phenomenon that the refrigerating cycle 1 intermittently fluctuates greatly can be suppressed. This makes it possible to stabilize the cooling capacity under a low load.

FIG. 7 shows another configuration example. The communication passage of the expansion device 5 shown in FIG.
2, gradually decrease the diameter of the communication passage 14,
In addition, by reducing the rate of decrease in the diameter toward the low-pressure space 12, the rate of decrease in the cross section of the communication passage 14 is reduced toward the low-pressure space 12 in FIG.
However, the valve element 17 that moves integrally with the bellows is formed in a truncated conical shape having the generatrix α as a straight line. That is, the valve element 17 is formed in a shape in which the diameter continuously decreases at an equal rate from the base to the tip. A middle portion of the communication passage 14 where the diameter of the passage cross section is equal to the tip diameter of the valve body 17 is defined as a valve seat 16 on which the valve body 17 is seated. The bus β of the communication passage 14
Is a curve having a constant radius of curvature from the high-pressure space 11 to the low-pressure space 12 of the communication passage 14, but a curve in which the radius of curvature continuously changes (increases gradually) from the high-pressure space 11 to the low-pressure space 12. There may be. Since other configurations are the same as those of the above configuration example, the same portions are denoted by the same reference numerals and description thereof will be omitted.

Even in such a configuration, when the valve element 17 is used, the distance between the valve element 17 and the valve seat 16 increases exponentially as the valve element 17 moves away from the valve seat 16. come. In addition, the change in the distance between the valve body 17 and the valve seat 16 per unit axial direction in the initial stage of separation of the valve body is shown in FIG.
6 can be made smaller than the configuration shown in FIG.
That is, the change in the substantial opening area of the communication passage 14 can be made smaller as the high-pressure pressure becomes lower than that indicated by the solid line in FIG. It becomes possible to provide the expansion device 5 having such characteristics.

Therefore, when such an expansion device 5 is used, the fluctuation of the valve opening (opening area of the communication passage) can be made more gentle in a region where the high pressure is low, and the compressor 2 Even if the cycle is operated in a low load range where the capacity is controlled by the pressure of the low pressure line and the cycle is operated in a subcritical region where the high pressure is equal to or lower than the critical pressure, the expansion is Device 5
The possibility that the valve body 17 easily seats on the valve seat 16 and closes the communication passage 31 can be further reduced, and the intermittent intermittent operation can be suppressed by suppressing a remarkable decrease in low pressure and a remarkable decrease in the discharge amount of the compressor 2. The fluctuation of the refrigeration cycle 1 that occurs can be suppressed, and the cooling capacity under a low load can be stabilized.

It should be noted that the various configurations described above are examples of configurations for obtaining the characteristics shown in FIG.
By appropriately changing the shape of the valve seat and communication passage and combining them,
It is possible to obtain similar characteristics, and the present invention covers the range not included in these listed configurations. Further, in the above-described configuration, the example in which the bellows 18 is used as the sensing element of the inflation device has been described. However, the configuration is also realized in the inflation device using the diaphragm as the sensing element, and the same operation and effect can be obtained. Obtainable.

In any of the various configurations described above, the smaller the opening area of the communication passage 14 becomes, the higher the pressure in the high-pressure space 11 becomes.
Although the opening degree of the valve (opening area of the communication passage) with respect to the pressure fluctuation is reduced, the opening area of the communication passage is initially reduced when the valve element is lifted from the position where the opening area of the communication passage is minimized. At the initial stage when the valve element is lifted in the direction of increasing the pressure, if the fluctuation of the opening area of the communication passage due to the pressure fluctuation of the high-pressure space can be reduced, the fluctuation of the cycle can be suppressed.

From such a viewpoint, the needle-shaped valve element shown in FIG. 7 is formed into a predetermined diameter as shown in FIGS. 8 and 9 in place of the conventionally used ball valve. It may be used for the communication path 14. That is, in the configuration shown in FIGS. 8 and 9, the valve element 17 that moves integrally with the bellows is formed in a truncated cone shape whose diameter gradually decreases toward the distal end and whose straight line is the generating line α. , And is separated from the open end of the communication passage 14 by a predetermined lift or more. In this example, the diameter of the communication passage is about 2.0 mm, and the total lift amount of the valve body 17 is about 1.0 mm.
mm from the state where the valve element 17 is seated on the valve seat 16 formed at the open end of the communication passage 14.
In the state of the lift, the bottom surface of the valve element 17 coincides with the opening end face of the communication passage 14 and further separates from the opening end face by about 0.6 mm. Since the other configuration is the same as the configuration described above, the same reference numerals are given to the same portions and the description will be omitted.

In such a configuration, the bellows 18
Considering that the amount of expansion and contraction is substantially proportional to the refrigerant pressure in the high-pressure space 11, the stroke amount of the valve body 17 is substantially proportional to the refrigerant pressure in the high-pressure space 11.
In the initial stage of lifting away from the valve, the change in the opening area with respect to the pressure change (change in valve lift) in the high-pressure space is smaller than the characteristic shown by the ball valve (I line indicated by the broken line in FIG. 10), After the bottom surface of the communication passage 17 coincides with the opening end surface of the communication passage 14, the variation of the opening area with respect to the pressure variation of the high-pressure space increases, and thereafter, the solid line in FIG. (Line II). In FIG. 10, since the lift amount of the valve body 17 is determined substantially in proportion to the pressure of the high-pressure space 11, the horizontal axis represents the lift amount of the valve body (from the position where the opening area of the communication passage 14 is minimized). Lift amount).

Therefore, when the expansion device 5 having such a valve body configuration is used, the variation of the valve opening degree (opening area of the communication passage) in a region where the high-pressure pressure is low is changed by using the conventional ball valve. The compressor 2 may be of a variable capacity type whose capacity is controlled by the pressure of the low pressure line, and the cycle may be performed in a subcritical region where the high pressure is equal to or lower than the critical pressure. Even when operating in a low load range where the valve operates, the valve 1
The refrigeration cycle that occurs intermittently by suppressing the possibility of the seat 7 being easily seated on the valve seat 16 and closing the communication passage 31 can be reduced, and the remarkable decrease in low pressure and the discharge amount of the compressor 2 can be suppressed. 1 can be reduced, and the cooling capacity under a low load can be stabilized.

When such a frusto-conical valve element is used, assuming that the communication passage 14 is a through hole having a constant diameter, the included angle between the axis of the valve element 17 and the generatrix is assumed. It is said that the limit is 20 degrees. If the included angle is smaller than this lower limit, there is a concern that the valve element 17 may bite into the communication passage 14 and cannot come off. For this reason, a valve element having a simple frustoconical shape can improve the rising characteristic of the valve opening (opening area of the communication passage), but reaches the maximum valve opening (opening area of the communication passage). Since the lift is about the same as a conventional ball valve,
There is room for further improvement. That is, if the lift amount until the valve opening (opening area of the communication passage) becomes maximum can be increased, the amount of refrigerant flowing to the low pressure side via the expansion device can be reduced accordingly, and the expansion device 5 If the amount of the refrigerant passing through the valve can be reduced, the valve opening time of the expansion device 5 can be lengthened, and the fluctuation due to hunting can be reduced as the valve opening time increases.

From this point of view, it is difficult to further improve the characteristics of the opening area by improving only the valve body 17. Therefore, the shape of both the valve body 17 and the communication passage 14 is optimized. Therefore, a combination of the valve element 17 and the communication passage 14 as shown in FIGS. 11 to 13 has been considered.

The valve element 17 in this configuration has a first conical portion 20 whose diameter gradually decreases toward the distal end, and is formed continuously from the first conical portion 20 on the distal side and gradually toward the distal end. And a second conical portion 21 for reducing the diameter. As shown in FIG. 13, the angle γ of the included angle γ between the axis of the valve element 17 and the generatrix of the second conical portion 21. Is formed smaller than the angle β of the included angle between the axis of the valve body 17 and the generatrix of the first conical portion 20. The communication passage 14 has a first conical path 22 that opens into the high-pressure space 11 and gradually decreases in diameter as the distance from the high-pressure space 11 increases.
And is formed in the low-pressure space 12 to open the low-pressure space 1.
The second conical path 23 whose diameter gradually decreases toward 2
And the angle δ of the included angle between the axis of the communication passage 14 and the generatrix of the second conical path 23.
Is formed to be smaller than the included angle α between the axis of the communication passage 14 and the generatrix of the first conical path 22, and the transition from the first conical path 22 to the second conical path 23 is a valve body. 17
The portion that transitions from the first conical portion 20 to the second conical portion 21 is the seat 16 to be seated. And α, β, γ, δ
Is defined as α ≧ β>γ> δ.

In such a configuration, the bellows 18
Considering that the amount of expansion and contraction is substantially proportional to the refrigerant pressure in the high-pressure space 11, the stroke amount of the valve body 17 is substantially proportional to the refrigerant pressure in the high-pressure space 11.
In the initial stage of lifting away from the valve, the fluctuation of the valve opening (opening area of the communication passage) with respect to the pressure fluctuation of the high-pressure space becomes small, and then, when the bottom surface of the second conical part reaches the first conical path, The fluctuation of the valve opening (opening area of the communication passage) with respect to the pressure fluctuation of the high-pressure space (change of the valve lift) somewhat increases, and this state continues until the bottom surface of the valve body coincides with the opening end face of the communication passage. Thereafter, the variation in the opening area with respect to the pressure variation in the high-pressure space further increases.
The characteristic is as shown by the dashed line (III line) in FIG. 10 which reaches the opening area corresponding to the passage cross section of FIG.

Therefore, when the expansion device 5 having such a valve body configuration is used, the valve opening degree (the opening area of the communication passage 14) is obtained in the initial region of the lift where the high pressure is low.
Can be made as slow as the valve body shown in FIG.
In addition, the time required for the opening area of the communication passage 14 to become fully open can be lengthened, so that a variable displacement type compressor whose capacity is controlled by the pressure of the low pressure line is used as the compressor 2, and Is operated in a sub-critical region where the high pressure is equal to or lower than the critical pressure, the valve body 17 of the expansion device 5 easily seats on the valve seat 16 to close the communication passage 31 and It is possible to further reduce the possibility that the refrigerating cycle will occur, suppress the remarkable decrease in the low pressure and the remarkable decrease in the discharge amount of the compressor 2, and suppress intermittent fluctuations in the refrigeration cycle 1, thereby allowing cooling at a low load. Ability to stabilize.

FIGS. 14 to 16 show another example of the structure of the valve element 17 and the communication passage 14. In this configuration, the valve element 17 has a predetermined angle (angle of inclination with respect to the axis) with respect to its axis. First surface 3 formed at an angle (θ1)
0 and an angle (θ) formed between the first face 30 and the tip side and formed at a larger angle (θ) with respect to the axis of the valve element 17 than the first face 30.
And 2) a second surface 31 formed in 2).

In this example, a first surface 30 which is cut flat at an inclination of θ1 with respect to the axis from one point around the base end is formed on the columnar material, and θ1 is defined with respect to the axis.
The second surface 31 cut flat by the inclination of 2
From the middle to the tip, following the first surface 30. In addition, on the side surface of the valve body that does not reach the first surface 30, in this example, on the side surface opposite to the first surface 30 with respect to the axis of the valve body, a flat shape is formed in the axial direction from the base end to the distal end. A guide surface 32 formed by cutting is formed.

On the other hand, the communication passage 14 has a passage cross section having substantially the same shape as a cross section cut by a plane passing through the middle of the first surface 30 of the valve element 17 and perpendicular to the axis. The edge of the open end facing the first surface 30 is defined as the valve seat 16. Therefore, the valve element 17
The valve seat 16 is seated in the middle of the first surface 30 to close the communication passage 14. Further, the communication passage 14 receives the guide surface 32 of the valve body 17, and thereby the guide receiving surface 33 for positioning the valve body 17 in the communication passage 14 is provided.
Are formed along the axis. In this example, θ1
Is set to about 20 degrees, and the passage cross-sectional area of the communication passage 14 is approximately the same as that of a hole having a diameter of about 1.5 to 3.0 mm.

In such a configuration, the bellows 18
Considering that the amount of expansion and contraction is substantially proportional to the refrigerant pressure in the high-pressure space 11, the stroke amount of the valve body 17 is substantially proportional to the refrigerant pressure in the high-pressure space 11.
Initially, the first surface 30 is lifted away from the
The opening area characteristic is determined by this, and the fluctuation of the valve opening (opening area of the communication passage) with respect to the pressure fluctuation (change of the valve lift) of the high-pressure space becomes small. When it reaches, the fluctuation of the valve opening degree (opening area of the communication passage) with respect to the pressure fluctuation of the high-pressure space (change of the valve lift) increases, and then increases to the opening area corresponding to the passage cross section of the communication passage 14, It is possible to obtain characteristics as shown by the solid line (II line) in FIG.

Therefore, when the expansion device 5 having such a valve element configuration is used, the valve element 17 is initially lifted in a region where the high pressure is reduced, that is, in a direction in which the opening area of the communication passage 14 is increased. In the above, the fluctuation of the valve opening degree (opening area of the communication passage) with respect to the pressure fluctuation of the high-pressure space (change of the valve lift) can be reduced, so that the compressor 2
Even if the cycle is operated in a low load range where the capacity is controlled by the pressure of the low pressure line and the cycle is operated in a subcritical region where the high pressure is equal to or lower than the critical pressure, the expansion is The valve element 17 of the device 5 has a valve seat 16
And the possibility that the communication passage 31 is closed by the seat can be further reduced, and a remarkable decrease in the low pressure and a remarkable decrease in the discharge amount of the compressor 2 can be suppressed to suppress intermittent fluctuations in the refrigeration cycle 1. It is possible to stabilize the cooling capacity under a low load.

Moreover, according to such a valve element 17, the first
The opening area characteristics can be adjusted depending on how the surface 30 is processed. That is, according to the above-described configuration, the example in which the first surface 30 is formed flat has been described. However, the inclination angle (θ1) of the first surface 30 is changed, or the first surface 30 is formed into a curved surface. By doing so, it becomes possible to set the fluctuation of the valve opening (opening area of the communication passage) with respect to the fluctuation of the pressure in the high-pressure space (change of the valve lift) in the initial stage of the lift of the valve element 17 to a desired characteristic.

The configuration shown in FIGS. 14 to 16 is an example in which the valve element 17 is lifted until it is separated from the open end face of the communication path 14. However, even when the valve element 17 is lifted, A guide piece that is continuously inserted may be provided on the valve body 17. An example of such a configuration is shown in FIG. 17 and FIG.
4 to 16, a guide piece 35 extends in the axial direction of the valve element 17 from the distal end of the second surface 31, and the guide surface 32 is provided on the back surface of the guide piece 35.
Of the valve element 17
Regardless of the lift, the guide surface 32 is always in contact with the guide receiving portion 33 in which the communication path 14 is formed. Other configurations are the same as those shown in FIGS. 14 to 16, and therefore, the same portions are denoted by the same reference numerals and description thereof will be omitted.

In such a configuration, the maximum opening area of the communication path 14 is defined by the guide piece 35 inserted into the communication path 14, and in this example, the maximum opening area is about 1.5 to 3.0 mm in diameter. It is set to be approximately the same as the hole. Further, similarly to the valve element shown in FIG. 14, the opening area characteristic of the valve element 17 with respect to the lift is defined by the first and second surfaces 30, 31.

That is, when the amount of expansion and contraction of the bellows 18 is
1 is substantially proportional to the refrigerant pressure, the valve element 17
Is substantially proportional to the refrigerant pressure in the high-pressure space 11, the opening area characteristic is determined by the first surface 30 in the initial stage when the valve element 17 separates from the valve seat 16 and lifts. When the second surface reaches the opening end face of the communication passage, the fluctuation of the valve opening (opening area of the communication passage) with respect to the pressure fluctuation (change of the valve lift) becomes small. Of the valve opening (opening area of the communication passage) with respect to the change in the opening of the communication passage 14, and thereafter, the opening opening area corresponding to the passage cross section of the communication passage 14 becomes large, and is indicated by a solid line (II line) in FIG. Such characteristics can be obtained.

Therefore, when the expansion device 5 having such a valve body configuration is used, the valve opening degree (the communication passage of the communication passage) with respect to the pressure fluctuation of the high pressure space in the region where the high pressure is low, that is, in the early stage of the lift of the valve body. (Aperture area) can be reduced, so that a variable capacity compressor whose capacity is controlled by the pressure of the low pressure line is used as the compressor 2 and the cycle is such that the high pressure becomes lower than the critical pressure. Even when operating in a low load region that operates in the critical region, the risk that the valve element 17 of the expansion device 5 easily seats on the valve seat 16 and closes the communication passage 31 can be reduced, and low pressure pressure can be reduced. It is possible to suppress a remarkable decrease and a remarkable decrease in the discharge amount of the compressor 2 to suppress the intermittent fluctuation of the refrigeration cycle 1, and to stabilize the cooling capacity under a low load.

Further, according to such a valve element, FIG.
As in the configuration shown in FIG. 16 to FIG. 16, the opening area characteristic can be adjusted by processing the first surface. Moreover, according to such a valve element, the maximum opening area is limited to the communication path 1.
4 is a portion excluding the portion occupied by the guide piece 35 in the cross section of the passage, so that by adjusting the portion occupied by the guide piece 35 (cross section of the guide piece), it is possible to adjust the opening area when fully opened. Become. That is, even if the shape of the communication passage 14 is not changed, the shape of the valve body 17, that is, the guide piece 3
By changing the shape of 5, it is possible to adjust the opening area when fully opened.

According to the above-described valve structure, the position where the opening area of the communication passage 14 is minimized by bringing the valve body 17 into contact with the valve seat 16 provided at the opening end of the communication passage 14 is defined. However, the same applies to a spool type valve element that adjusts the valve opening (opening area of the communication path) by adjusting the amount of insertion into the communication path 14 of the valve element without providing a valve seat. Alternatively, the opening area characteristics may be obtained. For example, in order to construct a spool-type valve structure using the valve element 17 shown in FIG. 17, as shown in FIG. 19, the shape of the communication passage 14 is set so that the entire valve element 17 can be inserted. 17 is formed in accordance with the shape of the base end portion, and the position where the opening area of the communication passage 14 is minimized is preferably defined by the stopper 36.

Here, as the stopper 36, for example,
When the valve element 17 enters the communication path 14 and is fixed to the valve element 17 and is displaced in accordance with the movement of the valve element 17, the partition wall 13 surrounds the portion where the communication path 14 opens. The valve body 17 may be configured to be in contact with the valve body 17 to prevent further displacement of the valve body 17. In such a configuration of the stopper 36, the notch 37 is formed at an appropriate position on the side wall so that the flow of the refrigerant is not blocked when the stopper 36 contacts the periphery of the opening of the communication passage 14. Good to keep.
Note that the other configuration is the same as the configuration of the valve body shown in FIG. 17, and therefore the same portions are denoted by the same reference numerals and description thereof will be omitted.

Therefore, when the expansion device 5 having such a spool-type valve body is used, in addition to the same operation and effect as the valve body shown in FIG. 17, the opening area of the communication passage 14 is closed. 19, that is, the position at which the opening area of the communication passage 14 is minimized is determined by the stopper 36. Therefore, the lower limit value of the included angle of the valve body 17, that is, the valve body shown in FIG. In this case, it can be set freely without considering the lower limit of the included angle (the inclination angle with respect to the axis) between the first surface 30 and the axis. As a result, by further reducing the included angle between the first surface 30 and the axis, the pressure fluctuation in the high-pressure space 11 (change in valve lift) in the initial stage when the valve body lifts from the position where the opening area is minimized. ) For the opening area
As shown by the two-dot chain line (IV line) in FIG. 10, it is possible to further reduce the fluctuation of the refrigeration cycle 1 which occurs intermittently, and to stabilize the cooling capacity under a low load. Will be able to

[0062]

As described above, according to the present invention,
In a non-electric expansion device having a sensing element in which the movement of the valve body is controlled in accordance with the refrigerant condition on the radiator side, the high pressure is applied to the valve body at the initial stage when the valve body is lifted from the position where the opening area of the communication passage is minimized. By giving the characteristic of reducing the variation of the opening area of the communication passage with respect to the pressure fluctuation of the space, for example, the valve element of the expansion device can be made to reduce the variation of the opening area with respect to the pressure fluctuation of the high-pressure space as the opening area of the communication passage becomes smaller. It is formed into a shape having a characteristic of reducing the size, and a communication path communicating the high pressure space and the low pressure space of the expansion device is provided with a characteristic that the smaller the opening area, the smaller the variation of the opening area with respect to the pressure fluctuation of the high pressure space. As shown in the characteristic line of FIG. 4, the characteristic of the valve opening area with respect to the high pressure is reduced as the high pressure is reduced (the valve lift is small). The fluctuation of the valve opening (opening area of the communication passage) can be reduced, and at a low load when the valve opening (opening area of the communication passage) decreases, the expansion device easily closes due to pressure fluctuation. By avoiding the inconvenience, it is possible to make it difficult for intermittently occurring cycle fluctuations at a low load to occur, thereby stabilizing the cooling capacity at a low load.

Further, the communication passage is formed as a through-hole having the same diameter from the high-pressure space to the low-pressure space, and the change in the diameter per unit axial direction is continuously reduced at an equal rate from the base to the front end thereof. Frustoconical shape
During the lift of the valve body from the position where the opening area becomes the minimum to the position where the opening area becomes the maximum, the valve body is lifted from the opening end of the communication passage by moving away from the opening end of the valve body. A valve comprising: a first conical portion having a diameter gradually reduced; and a second conical portion formed following the first conical portion and having a diameter gradually reduced toward the distal end. The angle between the axis of the body and the generatrix of the second conical portion is smaller than the angle of the angle between the axis of the valve body and the generatrix of the first conical portion. Angle between the valve body axis and the first axis
A first conical path formed to be larger than an angle of an included angle between the conical portion and the generatrix, and an angle of an included angle formed between the first conical path and the axis of the communication path formed following the first conical path. And a second conical path smaller than the angle of the included angle between the axis of the second cone and the generatrix of the second cone, and connecting the transition from the first cone to the second cone of the valve body. From the first conical path of the passage to the second
By being configured to be able to abut the transition to the conical path, the valve body further includes a first surface having a predetermined angle formed by the included angle with the axis thereof, and a first surface. And a second surface formed at a smaller angle than the first surface and formed at a smaller angle than the first surface. If the variation of the opening area with respect to the pressure variation of the high-pressure space is reduced in the early stage when the valve element is lifted, the characteristics of the valve opening area with respect to the high-pressure pressure are changed to II, III, or FIG.
As shown by the IV line, the lower the high-pressure pressure (the smaller the valve lift), the smaller the variation in the valve opening (opening area of the communication passage), and the smaller the valve opening (opening area of the communication passage). ) At low loads, the inconvenience of the expansion device being easily closed due to pressure fluctuations is avoided, and cycle fluctuations at low loads, which can occur intermittently, are less likely to occur, thus cooling at low loads. The ability can be stabilized.

Here, in the above-described configuration in which the first surface and the second surface are formed on the valve body, if the guide piece that is continuously inserted into the communication passage even during the lift is provided on the valve body, The maximum opening area of the communication passage can be adjusted without changing the shape of the communication passage, and a side surface of the valve body is cut in the axial direction to form a guide surface. If the guide receiving surface for receiving the surface is formed, the positioning of the valve body can be easily performed. In the above-described valve body having the first surface and the second surface, the valve whose opening area is minimized by seating the first surface of the valve body on the valve seat formed at the end of the communication passage. Even if the position of the body is defined, a stopper that is displaced integrally with the valve body is provided, and the stopper defines the position of the valve body that minimizes the opening area, thereby seating the valve body on the valve seat. In this case, the valve body may be of a spool type.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration example of a refrigeration cycle according to the present invention.

FIG. 2 is an enlarged sectional view of an expansion device used in the refrigeration cycle shown in FIG.

FIG. 3 is an enlarged sectional view showing the vicinity of a valve body and a communication passage shown in FIG. 2;

FIG. 4 is a characteristic diagram showing a change in a valve opening (opening area of a communication passage) with respect to a high pressure (valve lift) of the expansion device according to the present invention.

FIG. 5 is a sectional view showing another example of the expansion device.

FIG. 6 is an enlarged sectional view showing the vicinity of the valve body and the communication passage shown in FIG. 5;

FIG. 7 shows still another configuration example.
It is an expanded sectional view showing the vicinity of a valve element and a communication passage.

FIG. 8 shows still another configuration example.
FIG. 4 is an enlarged perspective view showing the vicinity of a valve body and a communication passage.

FIG. 9 is an enlarged sectional view showing the vicinity of the valve body and the communication passage shown in FIG. 8;

FIG. 10 is a characteristic diagram showing a change in an opening area of a communication passage with respect to a valve lift of an expansion device.

FIG. 11 is a perspective view showing another example of the configuration, and is an enlarged perspective view showing the vicinity of a valve body and a communication passage.

12 is an enlarged cross-sectional view showing the vicinity of the valve element and the communication passage shown in FIG. 11, in which a state where the valve element is lifted is indicated by a solid line, and a state where the valve element is seated on a valve seat is indicated by a broken line. .

FIG. 13 is a diagram for explaining the included angle of each part of the valve body and the communication passage shown in FIG. 11;

FIG. 14 is an enlarged perspective view showing yet another configuration example, showing the vicinity of a valve body and a communication passage.

15 is an enlarged cross-sectional view showing the vicinity of the valve element and the communication passage shown in FIG. 14, where a lifted state of the valve element is indicated by a solid line, and a state where the valve element is seated on a valve seat is indicated by a broken line. .

FIG. 16 is a view for explaining an included angle of each part of the valve body shown in FIG. 14;

FIG. 17 is a magnified perspective view showing yet another configuration example and showing the vicinity of a valve body and a communication passage.

18 is an enlarged cross-sectional view showing the vicinity of the valve body and the communication passage shown in FIG. 17, where a lifted state of the valve body is shown by a solid line, and a state where the valve body is seated on a valve seat is shown by a broken line. .

FIG. 19 is a magnified perspective view showing yet another configuration example and showing the vicinity of a valve body and a communication passage.

FIG. 20 is a perspective view showing only the stopper of FIG. 19;

21 is an enlarged sectional view showing the vicinity of the valve element and the communication passage shown in FIG. 19, in which the lifted state of the valve element is indicated by a solid line, and the state in which the valve element is seated on a valve seat is indicated by a broken line. .

FIG. 22 is a characteristic diagram showing a change in a valve opening degree (opening area of a communication passage) of a communication passage with respect to a high pressure (valve lift) of a conventional expansion device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Refrigeration cycle 2 Compressor 3 Radiator 5 Expansion device 6 Evaporator 11 High pressure space 12 Low pressure space 14 Communication path 15 Pressure reducing valve 16 Valve seat 17 Valve body 18 Bellows 20 1st conical part 21 2nd conical part 22 1st conical Shaped road 23 Second conical road 30 First surface 31 Second surface 32 Guide surface 33 Guide receiving surface 35 Guide piece 36 Stopper

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shunichi Furuya 39, Higashihara, Chiyo-ji, Odai-gun, Osato-gun, Saitama Pref. 39: Xexelvaleo Climate Control Co., Ltd. (72) Inventor Shunji Muta 39, Higashihara, Chiyo-ji, Konan-cho, Osato-gun, Saitama Prefecture In-house Co., Ltd. 39, Higashihara, Zexel Valeo Climate Control Co., Ltd. (72) Inventor Sakae Hayashi 39, Higashihara, Chiyo, Oji-gun, Osato-gun, Saitama Prefecture, Japan Inside Xexel Valeo Climate Control Co., Ltd. (72) Inventor Hiroshi Kanai 39, Higashihara, Chiyo, Oyo-gun, Osato-gun, Saitama Prefecture Inside of Xexelvaleo Climate Control Co., Ltd. 72) Inventor Dai Mitsukawa 39, Higashihara, Chiyo, Onan-gun, Osato-gun, Saitama Prefecture Inside Xexel Valeo Climate Control Co., Ltd.

Claims (13)

[Claims] 1. A compressor for compressing a refrigerant to make a refrigerant in a high pressure line in a supercritical state depending on operating conditions, a radiator for cooling the refrigerant compressed by the compressor, and a refrigerant cooled by the radiator A refrigerating cycle comprising at least an expansion device for reducing pressure and an evaporator for evaporating the refrigerant decompressed by the expansion device, wherein the expansion device is connected to a high-pressure space communicating with the radiator side, and communicating with the evaporator side. A low-pressure space, a communication path communicating the high-pressure space and the low-pressure space, a valve element that changes an opening area of the communication path, and a position of the valve element that is controlled according to a refrigerant condition on the radiator side. A sensing element for changing the opening area of the communication passage by performing the above operation. The valve element is lifted from a position where the opening area is minimized before the pressure fluctuation of the high pressure space. Refrigeration cycle, characterized in that it comprises a characteristic to reduce the variation in the opening area. 2. The characteristic of the expansion device, wherein the valve element is formed in a shape having a characteristic of reducing a variation in the opening area with respect to a pressure variation in the high-pressure space as an opening area of the communication passage becomes smaller. 2. The refrigeration cycle according to claim 1, wherein a variation in the opening area with respect to a variation in pressure in the high-pressure space is reduced in an early stage when the valve element is lifted. 3. The communication path is formed as a through-hole having the same diameter from the high-pressure space to the low-pressure space, and a change in diameter per unit axial direction is continuously reduced as the valve element moves from its base to its tip. 3. The method according to claim 2, wherein the change rate of the opening area with respect to the pressure change of the high-pressure space is reduced as the opening area of the communication passage is reduced by gradually increasing the reduction rate of the diameter.
Refrigeration cycle as described. 4. The method according to claim 1, wherein the communication path is formed in a shape having a characteristic of reducing a variation in the opening area with respect to a pressure variation in the high-pressure space as an opening area of the communication path is reduced by the valve element. 2. The refrigeration cycle according to claim 1, wherein a characteristic of the expansion device is such that a change in the opening area with respect to a pressure change in the high-pressure space is reduced in an early stage when the valve element is lifted. 5. The valve body is formed in a cylindrical shape with its displacement direction as an axis, and the communication passage continuously changes in a passage cross section per unit axial direction from the high-pressure space to the low-pressure space. By reducing the reduction rate of the cross-section of the passage and reducing the opening area of the communication passage by the valve body, the variation of the opening area with respect to the pressure variation of the high-pressure space is reduced as the opening area of the communication passage decreases. The refrigeration cycle according to claim 4, wherein 6. The valve body is formed in such a shape that a change in diameter per unit axial direction is continuously reduced at an equal rate as going from a base to a tip thereof, and the communication path is formed from the high-pressure space to the low-pressure space. By continuously reducing the change in the passage cross section per unit axial direction as it goes, and forming the passage cross section in such a shape that the reduction rate of the passage cross section is gradually reduced,
The refrigeration cycle according to claim 4, wherein, as the opening area of the communication passage is reduced by the valve body, a variation in the opening area with respect to a pressure variation in the high-pressure space is reduced. 7. The communication passage is formed as a through-hole having the same diameter from the high-pressure space to the low-pressure space, and the change in the diameter per unit axial direction is continuously equal from the base toward the tip of the valve. The valve body is lifted from the position where the opening area is the smallest to the position where the opening area is the largest, and the tip of the valve body is separated from the opening end of the communication passage. 2. The refrigeration cycle according to claim 1, wherein a characteristic of the expansion device is such that a variation in the opening area with respect to a pressure variation in the high-pressure space is reduced at an early stage when the valve element is lifted. 8. A first conical portion having a diameter gradually reduced toward the distal end, and a valve body which is formed on the distal end side of the first conical portion and gradually decreases in diameter toward the distal end. A second conical portion to be reduced, and the angle of the included angle between the axis of the valve element and the generatrix of the second conical portion is defined by the angle of the axis of the valve element and the generatrix of the first conical portion. The angle of the included angle is smaller than the angle of the included angle, and the angle of the included angle between the communication path and the axis is larger than the angle of the included angle between the axis of the valve body and the generatrix of the first conical portion. A first conical path, and a continuation of the first conical path;
A second conical path in which the angle of the included angle with the axis of the communication passage is smaller than the angle of the included angle between the axis of the valve body and the generatrix of the second conical portion; By allowing a transition portion of the valve body from the first conical portion to the second conical portion to abut on a transition portion of the communication passage from the first conical passage to the second conical passage, 2. The refrigeration cycle according to claim 1, wherein a characteristic of the expansion device is such that a variation in the opening area with respect to a variation in pressure in the high-pressure space is reduced in an early stage of the lift of the valve element. 3. 9. The valve body, wherein the valve body is formed with a first surface having an included angle formed with a predetermined angle with respect to an axis thereof, the valve body being formed continuously from the first surface on a tip side with respect to the first surface. And a second surface having a smaller angle with respect to the axis of the first surface than the first surface, the characteristic of the expansion device is reduced in the initial stage when the valve element is lifted. 2. The refrigeration cycle according to claim 1, wherein a variation in the opening area with respect to a pressure variation in a space is reduced. 10. The refrigeration cycle according to claim 9, wherein a guide piece that is continuously inserted into the communication path even during a lift is provided on the valve body. And a guide surface formed by cutting a side surface of the valve body in an axial direction, and a guide receiving surface for receiving the guide surface is formed in the communication path. The refrigeration cycle according to claim 9 or 10, wherein: 12. The valve body according to claim 1, wherein a position where the opening area is minimized is defined by seating the first surface on a valve seat formed at an end of the communication path. The refrigeration cycle according to claim 9, wherein: 13. The valve body according to claim 9, further comprising a stopper that is displaced integrally with the valve body, wherein the valve body defines a position where the opening area is minimized by the stopper. Refrigeration cycle as described.