JP2007278606A - Refrigerating cycle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress abnormal rising of a high pressure side pressure of a refrigerating cycle in its starting, even when the refrigerating cycle is provided with a fixed displacement type compressor and a supercritical fluid such as carbon dioxide is used as coolant. <P>SOLUTION: The refrigerating cycle 1 has a subordinate passage 9 different from a main passage 7 comprised by serially joining the compressor 2, a heat radiator 3, an expansion device 4, an evaporator 5, and an accumulator 6 in sequence. In the subordinate passage 9, its upstream end is connected to a high pressure side 7A of the main passage 7 in an upstream side of the expansion device 4, and its downstream end is connected to a low pressure side 7B of the main passage 7 between the evaporator 5 and the accumulator 6. A relief valve 10 is positioned on the subordinate passage 9. The coolant passing through the relief valve 10 bypasses not only a pressure reduction regulating valve 8 of the expansion device 4, but also the evaporator 5. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a refrigeration cycle in which a supercritical fluid such as carbon dioxide (CO2) is used as a refrigerant.

  In a refrigeration cycle in which a supercritical fluid such as carbon dioxide (CO2) of this type is used as a refrigerant, the high pressure side pressure and the low pressure side pressure in the refrigeration cycle are balanced when the refrigeration cycle is stopped. If the outside air temperature is left in a relatively high environment, the temperature around the refrigeration cycle (for example, in the engine room) is higher than the critical temperature (31 ° C.) of the refrigerant. Since it is very high, the equilibrium pressure value rises to near 10 MPa. For this reason, when the refrigeration cycle is started by turning on the air conditioner switch from this state, the high-pressure side pressure easily rises to near the design allowable pressure value of the refrigeration cycle. Also, on the high-pressure side of the refrigeration cycle where supercritical fluid is used as the refrigerant, the refrigerant does not liquefy even in the supercritical state, and the refrigerant density does not increase, so the high-pressure side pressure increases compared to the normal subcritical refrigeration cycle. This is also a factor that the high-pressure side pressure of the refrigeration cycle easily rises.

  In order to eliminate such problems, a method of controlling the refrigerant flow rate by using a variable displacement compressor as a compressor constituting the refrigeration cycle (see, for example, Patent Document 1), or an expansion device on the refrigeration cycle The relief device is arranged in parallel with the valve, and when the high-pressure side pressure exceeds a specified value (for example, 15 MPa), the valve is opened and the high-pressure side and the low-pressure side of the refrigeration cycle are communicated to deal with abnormally high pressure. (See, for example, Patent Document 2) has already been proposed by the present applicant.

On the other hand, the applicant of the present application has already proposed a configuration in which a supercritical fluid such as carbon dioxide (CO2) is used as a refrigerant for a refrigeration cycle having a fixed capacity compressor (see, for example, Patent Document 3). .)
JP 2003-28522 A JP 2000-205671 A Japanese Patent Laid-Open No. 11-63692

  However, as in the above-mentioned Patent Document 3, when a fixed capacity compressor is simply used, naturally, a method of variably controlling the refrigerant flow rate like a variable capacity compressor cannot be adopted. There is a risk that the high-pressure side pressure rises and the safety device repeatedly and continuously engages and disengages the compressor clutch.

  In the structure in which the relief valve is provided only in parallel with the expansion valve (decompression adjusting valve), when both the expansion valve and the relief valve are opened, the refrigerant that has passed through the expansion valve is also the refrigerant that has passed through the relief valve. However, since it will be heated by an evaporator, the amount of heat of the entire refrigeration cycle cannot be easily reduced. Furthermore, the refrigerant released from the high-pressure side of the refrigeration cycle may be sucked into the compressor while being in a gas-liquid mixed state, and conversely the suction refrigerant flow rate of the compressor will increase. It cannot be lowered effectively. As a result, an increase in the high-pressure side pressure of the refrigeration cycle is caused, resulting in a problem that the clutch of the compressor is repeatedly engaged and discontinuously performed.

  Therefore, the present invention can suppress an abnormal increase in the high-pressure side pressure of the refrigeration cycle even when the refrigeration cycle includes a fixed capacity compressor and uses a supercritical fluid such as carbon dioxide as a refrigerant. For the purpose.

  The refrigeration cycle according to the present invention is a refrigeration cycle that uses carbon dioxide as a refrigerant, and is cooled by a compressor that compresses the refrigerant, a heat radiating device that cools the refrigerant compressed by the compressor, and the heat radiating device. An expansion device having a pressure reducing valve for reducing the pressure of the refrigerant, an evaporator for evaporating the refrigerant flowing out of the expansion device, and a relief valve for communicating the high pressure side and the low pressure side under a predetermined condition The relief valve is located on a secondary path different from the main path of the refrigerant formed by joining the compressor, the heat dissipation device, the expansion device, and the evaporator in series. The path is characterized in that its upstream end is connected to the main path upstream from the expansion device, and its downstream end is connected to the main path downstream from the evaporator. (Claim 1). Here, the refrigerant is a supercritical fluid such as carbon dioxide (CO2). The compressor is mainly a fixed capacity type compressor. The same applies to the refrigerant and compressor described below. The refrigeration cycle according to the present invention includes an accumulator that gas-liquid separates the refrigerant flowing out of the evaporator, and a downstream end of the secondary path is connected to the main path upstream of the accumulator. You may make it (Claim 7).

  In addition, the refrigeration cycle according to the present invention includes a compressor that compresses the refrigerant, a heat radiating device that cools the refrigerant compressed by the compressor, and a pressure reducing valve that depressurizes the refrigerant cooled by the heat radiating device. An expansion device, an evaporator for evaporating the refrigerant flowing out of the expansion device, an accumulator for separating the refrigerant flowing out of the evaporator from gas and liquid, and a relief valve for communicating the high pressure side and the low pressure side under predetermined conditions The relief valve is arranged on a secondary path different from a refrigerant main path formed by joining the compressor, the heat dissipation device, the expansion device, the evaporator, and the accumulator in series. The secondary path has an upstream end connected to the main path upstream of the expansion device, and a downstream end connected between the evaporator and the accumulator. Connect with It is characterized in that (claim 2).

  The expansion device is characterized in that the pressure reducing adjustment valve and the relief valve are integrated (claim 3). Specifically, the expansion device includes an inflow passage through which refrigerant flows in from a high pressure side of the main path, an outflow path through which refrigerant flows out upstream of the evaporator in the main path, and these. A high-pressure space in which the passage is opened, a pressure-reducing control valve that opens and closes the opening of the outflow passage, one end is connected to an upstream portion of the secondary path, and the other is a downstream portion of the secondary path It is characterized by having a communicating path to be connected and a relief valve for opening and closing a communicating hole that communicates the communicating path and the high-pressure space (claim 4). This decompression control valve controls the valve opening degree by, for example, the pressure difference between the high pressure side and the low pressure side of the refrigeration cycle, the high pressure side refrigerant temperature, and the like. The relief valve uses a high-pressure sensor or the like, and opens when the high-pressure side pressure becomes a high pressure equal to or higher than a predetermined value.

  Further, the expansion device includes an inflow passage through which refrigerant flows in from a high pressure side of the main path, an outflow path through which refrigerant flows out upstream of the evaporator in the main path, and these passages in the housing. A high-pressure space that opens, a communication path that has one end connected to an upstream part of the secondary path and the other connected to a downstream part of the secondary path, and an opening of the outflow path by a primary valve And a pressure reducing adjustment / relief valve that opens and closes a communication hole that communicates the communication path and the high-pressure space with a secondary valve (Claim 5). The decompression adjustment / relief valve uses a high-pressure pressure sensing element or the like, and opens the secondary valve body together with the primary valve body when the high-pressure side pressure becomes a high pressure equal to or higher than a predetermined value.

  Therefore, according to the first aspect of the present invention, when the high-pressure side pressure of the refrigeration cycle rises at the start of the refrigeration cycle, the pressure reducing adjustment valve and the relief valve are opened, and the refrigerant expanded by the relief valve is heated by the evaporator. Without opening to the low pressure side of the refrigeration cycle. Thereby, the calorie | heat amount of the whole refrigerating cycle can be reduced rapidly, and the raise of the pressure of the high voltage | pressure side of a refrigerating cycle is suppressed in connection with it.

  According to the invention described in claim 2, the liquid refrigerant in the gas-liquid mixed state refrigerant that has passed through the relief valve accumulates in the accumulator, and only the decompressed gaseous refrigerant is returned to the compressor. Excess refrigerant in the refrigeration cycle is stored in the accumulator, and the low-pressure side pressure of the refrigeration cycle decreases. And since the refrigerant | coolant suction refrigerant density also falls by the low pressure side pressure of a refrigerating cycle falling, the refrigerant | coolant flow volume which circulates in a refrigerating cycle reduces. However, an increase in the high-pressure side pressure of the refrigeration cycle is suppressed by reducing the circulating refrigerant flow rate of the refrigerant. When the high-pressure side pressure of the refrigeration cycle is reduced, the relief valve is closed and the operation shifts to a normal operation in which the refrigerant passes only through the pressure reducing adjustment valve.

  In particular, according to the third to fifth aspects of the present invention, the mechanism of the valve body and the like are compared with the case where the expansion valve and the relief valve are separated from each other by integrating the decompression adjustment valve and the relief valve into the expansion device. As a result, the size can be reduced and the manufacturing cost can be reduced.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows an example of a refrigeration cycle 1 according to the present invention. The refrigeration cycle 1 is a supercritical refrigeration cycle using, for example, a supercritical fluid such as carbon dioxide (CO2) as a refrigerant. The compressor 2 boosts the refrigerant to a pressure exceeding its critical pressure, and the compressor. For example, a heat radiating device 3 such as a gas cooler that cools the refrigerant compressed in 2, an expansion device 4 having a pressure reducing adjustment valve 8 that depressurizes the refrigerant cooled by the heat radiating device 3, and the pressure reducing pressure adjusting valve 8 reduces the pressure. For example, an evaporator 5 such as an evaporator for evaporating and evaporating the refrigerant and an accumulator 6 for separating the refrigerant flowing out of the evaporator 5 into gas and liquid are provided. The refrigeration cycle 1 includes an internal heat exchanger (not shown) for exchanging heat between the low-pressure refrigerant guided from the accumulator 6 to the compressor 2 and the high-pressure refrigerant guided from the heat radiating device 3 to the pressure reducing adjustment valve 8 of the expansion device 4. Further, it may be configured.

  That is, in the refrigeration cycle 1, the discharge side of the compressor 2 is connected to the expansion device 4 via the radiator 3, and the outflow side of the expansion device 4 is connected to the suction side of the compressor 2 via the evaporator 5. The main path 7 is connected. Therefore, the main path 7 is configured with a high pressure side 7A (indicated by an arrow in FIG. 1) from the discharge side of the compressor 2 to the expansion device 4 via the heat radiating device 3, and evaporates from the outflow side of the expansion device 4. A low pressure side 7B (indicated by a white arrow in FIG. 1) reaching the compressor 2 via the device 5 and the accumulator 6 is configured.

  Further, the refrigeration cycle 1 has a secondary path 9 in addition to the main path 7. The secondary path 9 has an upstream end connected to the main path 7 upstream of the expansion device 4, and a downstream end connected to the main path 7 between the evaporator 5 and the accumulator 6. Therefore, the relief valve 10 is located on the secondary path 9. That is, the relief valve 10 is positioned in parallel with the pressure reducing adjustment valve 8 of the expansion device 4 and enters the secondary path 9 from the high pressure side 7A of the main path 7 by opening the relief valve 10. The refrigerant bypasses the pressure reducing adjustment valve 8 and the evaporator 5 and is sent to the low pressure side 7B of the main path 7 which is upstream of the accumulator 6 in the main path 7.

  Thus, since the refrigerant bypasses the evaporator 5, the refrigerant expanded by the relief valve 10 is opened to the low pressure side 7 </ b> B of the main path 7 without being heated by the evaporator 5. The amount of heat can be quickly reduced, and accordingly, an increase in pressure on the high-pressure side 7A of the main path 7 is suppressed.

  Further, when the pressure on the high pressure side 7A of the main path 7 of the refrigeration cycle 1 is increased when the refrigeration cycle 1 is started, both the pressure reducing adjustment valve 8 and the relief valve 10 are opened, so that the gas-liquid expanded by the relief valve 10 Among the mixed refrigerants, the liquid refrigerant is accumulated in the accumulator 6 and only the decompressed gaseous refrigerant is returned to the compressor 2, so that the pressure on the low pressure side 7 </ b> B in the main path 7 of the refrigeration cycle 1 decreases. And since the suction refrigerant density of the compressor 2 also falls by the pressure of the low pressure side 7B of the main path | route 7, the refrigerant | coolant flow volume which circulates in the refrigerating cycle 1 reduces. However, an increase in pressure on the high pressure side 7A of the main path 7 is suppressed by reducing the circulating refrigerant flow rate of the refrigerant.

  By the way, in this embodiment, the pressure-reducing adjustment valve 8 and the relief valve 10 are integrated with the expansion device 4 as shown in FIG. That is, the expansion device 4 is connected to the high pressure side 7A of the main path 7 in the housing 12, and the inflow passage 13 serving as the high pressure side from which the refrigerant flows in from the high pressure side 7A of the main path 7 and the low pressure of the main path 7 are provided. An outlet passage 14 that is connected to the side 7B and that flows out of the refrigerant to the upstream side of the evaporator 5 of the main passage 7 is a low-pressure side, and a high-pressure that opens the opposite end of the passages 13 and 14 to the outside of the housing 12. A space 15 is defined. Further, the expansion device 4 has a communication path 16 having one end connected to the upstream part 9A of the secondary path 9 and the other connected to the downstream part 9B of the secondary path 9. Is communicated with the high-pressure space 15 through the through-hole 17 on the side thereof.

  In the high-pressure space 15, the pressure reducing adjustment valve 8 and the relief valve 10 are arranged. Among these, the pressure reducing adjustment valve 8 is a non-electric type in this embodiment, and a valve body 20 having a shape that can be seated on, for example, a tapered valve seat in the high-pressure space side opening of the outflow passage 14, A rod 21 that is integrated with the valve body 20 and a bellows 22 that is sealed with gas and is joined to the rod 21 and moves integrally with the valve body 20 are configured. However, although not shown, the pressure reducing adjustment valve 8 is an electric that controls the communication state between the inflow passage 13 and the outflow passage 14 by controlling the excitation current supplied to the drive coil and adjusting the position of the valve body. It may be of the formula.

  The relief valve 10 includes a valve body 24 having a shape that can be seated on, for example, a tapered valve seat in the opening on the high-pressure space side of the through-hole 17, a rod 25 integrated with the valve body 24, and gas or the like. The rod 25 is joined to the rod 25 and a bellows 26 that moves integrally with the valve body 24.

  Further, as shown in FIG. 3, the expansion device 4 may adopt a decompression adjustment / relief valve 29 so that the decompression adjustment valve and the relief valve are structurally integrated. The structure of the expansion device 4 will be described below with reference to FIG. The expansion device 4 includes an inflow passage 13, an outflow passage 14, and a high-pressure space 15 that is open at the opposite end of the passages 13 and 14 to the outside of the housing 12. The communication path 16 is defined, and the communication path 16 is communicated with the high-pressure space 15 via the through-hole 17 on the side thereof in the same manner as the expansion device 4 shown in FIG. In addition, description of these inflow / outflow passages 13 and 14, the high-pressure space 15, the communication path 16, and the communication hole 17 is omitted by attaching the same reference numerals as in the previous embodiment.

  On the other hand, the decompression adjustment / relief valve 29 is a non-electric type in this embodiment, and is a first shape that can be seated on, for example, a tapered valve seat in the high-pressure space side opening of the outflow passage 14. The secondary valve body 30, the secondary valve body 31 that extends in the axial direction from the tip of the primary valve body 30 and can be inserted into the communication hole 17, and the rod 32 that is integral with the valve bodies 30 and 31. And a bellows 33 which is filled with gas and joined to the rod 32 and moves integrally with the rod 32 and the valve bodies 30 and 31.

  By adopting the expansion device 4 as described above, it is possible to reduce the size and the manufacturing cost by integrating the valve mechanism and the like as compared with the case where the expansion valve and the relief valve are separate devices. .

FIG. 1 is a schematic diagram showing a refrigeration cycle of the present invention. FIG. 2 is an example of an expansion device used in the refrigeration cycle of the present invention. FIG. 3 shows another example of the expansion device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Refrigeration cycle 2 Compressor 3 Heat radiating device 4 Expansion device 5 Evaporator 6 Accumulator 7 Main path 7A High pressure side of main path 8 Depressurization adjusting valve 9 Secondary path 10 Relief valve 12 Housing 13 Inflow path 14 Outflow path 15 High pressure chamber 29 Depressurization Adjustment and relief valve

Claims (7)

A refrigeration cycle using carbon dioxide as a refrigerant,
A compressor that compresses the refrigerant; a heat radiating device that cools the refrigerant compressed by the compressor; an expansion device that includes a pressure reducing valve that depressurizes the refrigerant cooled by the heat radiating device; and an outflow from the expansion device An evaporator that evaporates the refrigerant, and a relief valve that communicates the high pressure side and the low pressure side under a predetermined condition,
The relief valve is located on a secondary path different from the refrigerant main path formed by joining the compressor, the heat dissipation device, the expansion device, and the evaporator in series. The refrigerating cycle is characterized in that its upstream end is connected to the main path upstream from the expansion device, and its downstream end is connected to the main path downstream from the evaporator. . A compressor that compresses the refrigerant; a heat radiating device that cools the refrigerant compressed by the compressor; an expansion device that includes a pressure reducing valve that depressurizes the refrigerant cooled by the heat radiating device; and an outflow from the expansion device An evaporator that evaporates the refrigerant, an accumulator that gas-liquid separates the refrigerant that has flowed out of the evaporator, and a relief valve that communicates the high-pressure side and the low-pressure side under predetermined conditions,
The relief valve is located on a secondary path different from the refrigerant main path formed by serially joining the compressor, the heat dissipation device, the expansion device, the evaporator and the accumulator. The next path has an upstream end connected to the main path upstream from the expansion device, and a downstream end connected to the main path between the evaporator and the accumulator. A refrigeration cycle characterized by The refrigerating cycle according to claim 1 or 2, wherein in the expansion device, the decompression control valve and the relief valve are integrated. The expansion device has an inflow passage through which a refrigerant flows in from a high pressure side of the main path, an outflow path through which the refrigerant flows out upstream of the evaporator in the main path, and the passages in the housing. A high-pressure space, a pressure-reducing control valve that opens and closes an opening of the outflow passage, a communication passage that has one end connected to an upstream portion of the secondary path and the other connected to a downstream portion of the secondary path The refrigeration cycle according to claim 1, further comprising a relief valve that opens and closes a communication hole that communicates the communication path and the high-pressure space. The expansion device has an inflow passage through which a refrigerant flows in from a high pressure side of the main path, an outflow path through which the refrigerant flows out upstream of the evaporator in the main path, and the passages in the housing. Opening and closing the opening of the outflow passage with a high pressure space, one end connected to the upstream portion of the secondary path, the other connected to the downstream portion of the secondary path, and a primary valve The refrigeration cycle according to claim 1, 2 or 3, further comprising: a pressure reducing adjustment / relief valve that opens and closes a communication hole that communicates the communication path and the high-pressure space with a secondary valve. The refrigeration cycle according to claim 1 or 2, wherein the compressor is a fixed capacity type compressor. 2. An accumulator for separating the refrigerant flowing out of the evaporator from gas and liquid, and a downstream end of the secondary path is connected to the main path upstream of the accumulator. The refrigeration cycle described in 1.

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