Refrigerating cycle

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to an improvement of a refrigeration cycle provided with an internal heat exchanger used in an automobile air conditioner.

【0002】

[Conventional technology]

Explaining the conventional refrigeration cycle used in a general automobile air conditioner, a compressor, a condenser, a gas-liquid separator, an expansion valve, and an evaporator are connected by a refrigerant pipe to form a closed circuit. The operation will be described with reference to the Moriel diagram shown in FIG. In FIG. 7, the horizontal axis shows the enthalpy, the vertical axis shows the absolute pressure, and the dotted line shows the characteristics of the refrigeration cycle. First, a compressor compresses a low-temperature low-pressure gas refrigerant. In FIG. 7, the dotted line from G to K shows the compression process. Next, the gas refrigerant is condensed by heat exchange with the outside air with a condenser to achieve medium temperature and high pressure. K C indicates the condensation process. Then, the liquid-liquid refrigerant is extracted from the refrigerant in the gas-liquid mixed state by the gas-liquid separator. In FIG. 7, it is the state of C. Then, the expansion valve adiabatically expands the liquid refrigerant to make it a low-temperature low-pressure liquid refrigerant. The dotted line from C to J indicates the adiabatic expansion process. Then, the air inside the vehicle and the liquid refrigerant exchange heat with the evaporator to evaporate and cool the inside of the vehicle, and the liquid refrigerant becomes a low-temperature low-pressure gas refrigerant. The solid line from J to G shows the vaporization process. Again, the refrigerant is returned to the compressor and circulated, forming a refrigeration cycle.

【0003】

An internal heat exchange system provided with an internal heat exchanger to increase the cooling capacity is known. FIG. 6 is a block diagram showing, for example, the configuration of a conventional refrigeration cycle shown in Japanese Patent Application Laid-Open No. 10-62021. In 1, the suction side a for sucking the refrigerant is connected to the low pressure outlet side of the internal heat exchanger 4. Compressor, 2 is a condenser connected to the high pressure piping side b of compressor 1, 3 is a liquid tank connected to the outlet side of condenser 2, and 4 is a liquid tank connected to the outlet side of liquid tank 3 to the high pressure inlet side c. The internal heat exchanger, 5 is an expansion valve in which the high-pressure outlet side d of the internal heat exchanger 4 is connected to the inlet side, and 6 is an evaporator in which the outlet side e of the expansion valve 5 is connected to the inlet side. The outlet side of 6 is connected to the low pressure inlet side g of the internal heat exchanger 4, and returns to the compressor 1 from the low pressure outlet side of the internal heat exchanger 4.

【0004】

The operation of the internal heat exchanger 4 will be described with reference to the Moriel diagram of FIG. In FIG. 7, the solid line shows the characteristics of the refrigeration cycle equipped with the internal heat exchanger 4. Note that A to E and G in FIG. 7 correspond to the positions of each part a to e and g in FIG. 6, and (A) to (E) and (G) in the following explanatory text are A in FIG. Shows the state of the refrigerant corresponding to ~ E and G. First, the compressor 1 compresses a low-temperature low-pressure gas refrigerant. In Fig. 7, the solid line from A to B shows the compression process. Then, the heat of the high-temperature and high-pressure gas refrigerant is thrown out of the vehicle by the condenser 2 and condensed. The solid line from B to C shows the condensation process. Next, the liquid refrigerant (C) separated in the liquid tank 3 is cooled by exchanging heat with the gas refrigerant (G) in the evaporator 6 in the internal heat exchanger 4. The solid line from C to D shows the cooling process. Then, the liquid refrigerant supercooled by the expansion valve 5 is adiabatically expanded. The solid line from D to E shows the adiabatic expansion process. Then, the evaporator 6 exchanges heat between the air inside the vehicle and the liquid refrigerant, and the liquid refrigerant takes away the heat from the surroundings and evaporates to cool the inside of the vehicle and become a gas refrigerant. The solid line from E to G shows the vaporization process. This gas refrigerant (G) exchanges heat with the separated liquid refrigerant (C) in the internal heat exchanger 4. The solid line from G to A shows the heat exchange process. Returning to compressor 1 again, the refrigeration cycle is repeated. When the internal heat exchanger 4 is provided and the gas refrigerant (G) of the evaporator 6 cools the liquid refrigerant (C) of the liquid tank 3, the refrigerating effect is increased by the cooling process of C D. The coefficient COP is improved.

【0005】

[Problems to be Solved by the Invention]

However, if the internal heat exchanger 4 is provided in the conventional refrigeration cycle and the internal heat exchange of the refrigerant between the upstream side of the expansion valve 5 and the downstream side of the evaporator 6 is performed, there are the following problems. That is, in FIG. 7, when the liquid refrigerant (C) of the liquid tank 3 is cooled, the gas refrigerant (G) of the evaporator 6 is warmed by that amount and the temperature of the refrigerant rises. The compressor 1 sucks in the gas refrigerant (A) having a high temperature, and the gas refrigerant (A) is further compressed by the compressor 1, so that the discharge temperature of the compressor 1 rises. The discharge temperature rises (corresponding to K B in Fig. 7) compared to the one without the internal heat exchanger 4. That is, as shown by the dotted arrow in the Moriel diagram of FIG. 7, G shifts to A on the right side because C, which contributes to the cooling capacity, shifts to D on the left side. When the discharge temperature rises, the oil is kept at a high temperature, which causes problems such as deterioration of the oil, increased friction, and the inability to maintain airtightness, which causes the compressor 1 to seize or lock. Etc. occur. Further, problems such as a strict clearance value occur, and the reliability of the compressor 1 is lowered.

【0006】

The present invention has been made to solve the above problems, and an object of the present invention is to lower the discharge temperature of the compressor and improve the reliability of the compressor.

【0007】

[Means for solving problems]

In the refrigeration cycle according to claim 1 of the present invention, a gas-liquid separator is provided between the expansion valve and the evaporator so that the separated gas refrigerant is returned to the suction side of the compressor.

【0008】

In the refrigeration cycle according to claim 2 of the present invention, a gas-liquid separator is provided between the expansion valve and the evaporator so that the separated gas refrigerant is returned to the low pressure side of the internal heat exchanger.

【0009】

The refrigeration cycle according to claim 3 of the present invention is provided with a control valve in a pipe for returning the separated gas refrigerant.

【0010】

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

【0011】

Embodiment 1. FIG. 1 is a block diagram showing a configuration of a refrigeration cycle according to a first embodiment of the present invention, FIG. 2 is a Moriel diagram of this refrigeration cycle, and the same reference numerals as those in FIG. 6 are used. There is. In this case, in FIG. 1, 7 is a gas-liquid separator provided between the expansion valve 5 and the evaporator 6, and 8 is a gas refrigerant extracted by the gas-liquid separator 7 to the pipe on the suction side a of the compressor 1. It is a pipe to return. When the refrigerant is adiabatically expanded by the expansion valve 5, the refrigerant is in a state in which a liquid and a gas are mixed (gas-liquid two-phase state). The gas-liquid two-phase state refrigerant is separated into a liquid refrigerant and a gas refrigerant by the gas-liquid separator 7. Then, the gas refrigerant separated by the gas-liquid separator 7 is returned to the low-pressure line on the suction side a of the compressor 1 via the pipe 8 and mixed with the gas refrigerant warmed by the internal heat exchanger 4. By this mixing, the temperature of the gas refrigerant before being compressed by the compressor 1 is lowered, so that the discharge temperature after being compressed is lowered. Since the pressure of the suction side a of the compressor 1 is at least lower than that of the gas-liquid separator 7, the gas refrigerant separated by the gas-liquid separator 7 is naturally supplied to the compressor 1 side without backflow. On the other hand, the liquid refrigerant separated by the gas-liquid separator 7 is sent to the evaporator 6 for normal cooling. By sending the liquid refrigerant having a high freezing effect to the evaporator 6, the freezing effect can be further enhanced as compared with the conventional internal heat exchange system.

【0012】

The state of the refrigerant will be described below with reference to the Moriel diagram of FIG. Note that A to I in FIG. 2 correspond to the positions of each part a to i in FIG. 6, and (A) to (I) in the following explanatory text indicate the states of the refrigerant corresponding to A to I in FIG. Is shown. In FIG. 2, the refrigerant (E) is flowing into the gas-liquid separator 7, but the actual state of the refrigerant is a state in which the liquid refrigerant (F) and the gas refrigerant (I) are mixed. This gas refrigerant (I) is extracted by the gas-liquid separator 7 and mixed with the gas refrigerant (H) from the low-pressure outlet side h of the internal heat exchanger 4, and the temperature of this gas refrigerant (H) is lowered. The refrigerant (A) is supplied to the suction side a of the compressor 1. In other words, the temperature of the refrigerant sucked by compressor 1 is lowered (corresponding to H + I A in Fig. 2), the compression process (solid line of A B) shifts to the left, and compressor 1 is shown by the dotted arrow. The discharge temperature of the compressor 1 can be lowered, and the reliability of the compressor 1 is improved.

【0013】

The gas-liquid separator 7 may be capable of gas-liquid separation, and its size is preferably small. Further, the thickness and shape of the pipe 8 are set to predetermined dimensions, and the flow rate of the separated gas refrigerant is determined by the pressure difference between the pressure of the gas-liquid separator 7 and the suction side a of the compressor 1.

【0014】

Further, as an example, the separated gas refrigerant is returned to the pipe on the suction side a of the compressor 1, but it may be returned to the pipe from the low pressure outlet side h of the internal heat exchanger 4 to the pipe a on the suction side a of the compressor 1. , The separated gas refrigerant may be returned to the region before being compressed. Further, the compressor 1 may be provided with a dedicated suction port for returning the gas refrigerant.

【0015】

Further, as shown in FIG. 3, a control valve 8b may be provided in the pipe 8. For example, when the vehicle suddenly accelerates or starts suddenly, the pressure on the suction side a of the compressor 1 drops from that during normal operation, and the gas-liquid separator When the liquid refrigerant supplied from the gas-liquid separator 7 to the evaporator 6 side decreases due to the increase in the flow rate of the gas refrigerant from 7, the flow rate of the gas refrigerant is reduced by closing or closing the control valve 8b. This makes it possible to prevent a decrease in the amount of liquid refrigerant supplied to the evaporator 6 side. The control valve 8b can be controlled by detecting the engine speed as an example. The pressure drop may be detected by a sensor or the like.

【0016】

Further, as shown in FIG. 3, a bypass passage 4a may be provided between the inlet and the outlet on the low voltage side of the internal heat exchanger 4, and a control valve 4b may be provided in the bypass passage 4a. When the discharge temperature of the compressor 1 rises too much above a predetermined value, the discharge temperature can be lowered by bypassing the refrigerant to the bypass passage 4a so as not to operate the internal heat exchanger 4.

【0017】

Further, the liquid tank 3 may be omitted. The reason is that the internal heat exchanger 4 is provided, and the refrigerant is cooled by the internal heat exchanger 4 and approaches the liquid to become a liquid refrigerant. In this case, it is necessary to increase the capacity of the gas-liquid separator 7 to serve as a liquid tank. Further, the internal heat exchanger 4 may be omitted, and the discharge temperature of the compressor 1 can be lowered even if the expansion valve 5 is provided between the liquid tank 3 and the gas-liquid separator 7.

【0018】

Embodiment 2. In the above-described first embodiment, the case where the separated gas refrigerant is returned to the piping on the suction side a of the compressor 1 has been described, but in the second embodiment, as shown in FIG. 4, gas and liquid A pipe 10 is provided between the separator 7 and the low pressure side of the internal heat exchanger 4, and the gas refrigerant separated by the gas-liquid separator 7 is returned to the low pressure side of the internal heat exchanger 4 through this pipe 10. It may be. In this case, return to the pipe on the low voltage inlet side m of the internal heat exchanger 4.

【0019】

The state of the refrigerant will be described below with reference to the Moriel diagram shown in FIG. Note that A to G, I, and M in FIG. 5 correspond to the positions of each part a to g, i, and m in FIG. 4, and (A) to (G), (I), in the following explanatory text. (M) shows the state of the refrigerant corresponding to A to G, I, and M in FIG. The gas refrigerant (I) separated by the gas-liquid separator 7 is mixed with the gas refrigerant (G) of the evaporator 6, the temperature of this gas refrigerant (G) is lowered, and the low-pressure inlet side of the internal heat exchanger 4 is used. Gas refrigerant (M) is supplied to m. This gas refrigerant (M) is heated by exchanging heat in the internal heat exchanger 4, and the refrigerant (A) flows out from the low pressure outlet side h of the internal heat exchanger 4 and is returned to the suction side a of the compressor 1. Since the refrigerant (M) on the low-voltage inlet side m of the internal heat exchanger 4 is cooled, the amount of heat transfer in heat exchange is improved. When the internal heat exchanger 4, the expansion valve 5, and the gas-liquid separator 7 are integrated, the length of the pipe 10 can be shortened as compared with the case where the internal heat exchanger 4 is returned to the suction side a of the compressor 1. Further, a control valve may be provided in the pipe 10.

【0020】

Also, as an example, the separated gas refrigerant was returned to the pipe on the low pressure inlet side m of the internal heat exchanger 4, but it should be returned to the pipe from the outlet side of the evaporator 6 to the low pressure inlet side m of the internal heat exchanger 4. Alternatively, the separated gas refrigerant may be returned to the region before the heat exchange. Further, a dedicated suction port for returning the gas refrigerant may be provided on the low pressure side of the internal heat exchanger 4. Further, the gas refrigerant may be returned in the middle of the heat exchange process of the inlet and outlet on the low voltage side of the internal heat exchanger 4. That is, the present application cools the refrigerant in a substantially low pressure state flowing in the region from the outlet side of the evaporator 6 to the suction side of the compressor 1 with the separated gas refrigerant.

【0021】

[Effect of the invention]

As described above, according to the invention of claim 1, a gas-liquid separator is provided between the expansion valve and the evaporator so that the separated gas refrigerant is returned to the suction side of the compressor. The discharge temperature of the compressor can be lowered to improve the reliability of the compressor.

【0022】

Further, according to the invention of claim 2, a gas-liquid separator is provided between the expansion valve and the evaporator so that the separated gas refrigerant is returned to the low pressure side of the internal heat exchanger. The amount of heat transferred by the exchanger increases.

【0023】

Further, according to the invention of claim 3, since the control valve is provided in the pipe for returning the separated gas refrigerant, the flow rate of the gas refrigerant is reduced when the vehicle suddenly starts or accelerates, and the evaporator is used. It is possible to prevent a decrease in the amount of liquid refrigerant supplied to the side.

[Simple explanation of drawings]

[Figure 1]

It is a block diagram which shows the structure of the refrigeration cycle which concerns on Embodiment 1 of this invention.

[Figure 2]

It is a Moriel diagram of the refrigeration cycle according to the first embodiment.

[Fig. 3]

It is a block diagram which shows the structure of the refrigeration cycle which concerns on Embodiment 1. FIG.

[Fig. 4]

It is a block diagram which shows the structure of the refrigeration cycle which concerns on Embodiment 2.

[Fig. 5]

It is a Moriel diagram of the refrigeration cycle according to the second embodiment.

[Fig. 6]

It is a block diagram which shows the structure of the conventional refrigeration cycle.

[Fig. 7]

It is a Moriel diagram of a conventional refrigeration cycle.

[Explanation of symbols]

1 compressor, 2 condenser, 3 liquid tank, 4 internal heat exchanger, 5 expansion valve, 6 evaporator, 7 gas-liquid separator, 8 piping.