JP2001133057A - Supercritical refrigeration cycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a refrigeration cycle in which delivery temperature rise of a compressor or temperature rise of the compressor itself is suppressed. SOLUTION: A refrigeration cycle employing carbon dioxide as refrigerant is provided with a bypath 7 for branching a part of refrigerant delivered from a radiator 5 and returning it back to a compressor 3 without passing through a heat absorber 4. The bypath is provided with a capillary 8 for converting the refrigerant into gas-liquid mixture phase. Temperature rise is suppressed by supplying refrigerant of gas-liquid mixture phase to the compressor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
₂ ) A refrigeration cycle that can be used as a refrigerant in a supercritical region.

[0002]

2. Description of the Related Art Refrigeration cycles are used in various fields such as air conditioners for vehicles. In a refrigeration cycle of a vehicle air conditioner, R134a is usually used as a refrigerant. The refrigerant has a specific heat ratio (Cp / Cv) of 1.178.
(At 0 ° C.). Therefore, the temperature of the refrigerant discharged from the compressor included in the refrigeration cycle, that is, the discharge temperature of the compressor does not particularly increase, and therefore, no special measures are required for the increase in the discharge temperature.

Recently, to prevent global warming, vehicles
As a refrigerant in the refrigeration cycle of₂Use
It has been proposed. In the refrigeration cycle,
CO ₂Is used in the supercritical region and may not condense. So
Therefore, this kind of refrigeration cycle is a vapor compression refrigeration cycle
Or supercritical vapor compression cycle
However, here, it is called a supercritical refrigeration cycle.

A supercritical refrigeration cycle is generally connected to a compressor having a suction port for sucking refrigerant and a discharge port for discharging refrigerant, a heat absorber (evaporator) connected to the suction port, and a discharge port. Radiator (gas cooler), and expansion means connected between the heat absorber and the radiator (for example, Japanese Patent Application Laid-Open No. 9-264).
622 and JP-B-7-18602).

[0005]

The supercritical refrigeration cycle can be expected to contribute to the prevention of global warming.

However, the specific heat ratio of CO ₂ used as a refrigerant in the supercritical refrigeration cycle is 2.143, and R13
4a, the discharge temperature of the compressor and the temperature of the compressor itself increase according to the operation of the supercritical refrigeration cycle. These rises in temperature promote the deterioration of the organic materials and lubricating oil used in the compressor.

It is therefore an object of the present invention to provide a refrigeration cycle in which the discharge temperature of the compressor and the temperature of the compressor itself are prevented from rising.

Another object of the present invention is to provide a refrigeration cycle that solves the problem of using CO ₂ as a refrigerant.

[0009]

According to the present invention, in a refrigeration cycle using carbon dioxide as a refrigerant, a bypass passage for partially branching the refrigerant discharged from a radiator and returning the refrigerant to a compressor without passing through a heat absorber; Means for converting the refrigerant passing through the bypass passage into a gas-liquid mixed phase, wherein the refrigerant in the gas-liquid mixed phase is supplied to the compressor to suppress a rise in temperature, thereby obtaining a refrigeration cycle.

According to the present invention, a compressor having a suction port for sucking refrigerant and a discharge port for discharging refrigerant, a heat absorber connected to the suction port, and a radiator connected to the discharge port In a refrigeration cycle including circuit-side expansion means connected between the heat absorber and the radiator, a part of the refrigerant that has flowed out of the radiator,
A bypass passage that bypasses the circuit-side expansion unit and the heat absorber and leads to the compressor; and a bypass-side expansion unit that is connected to the bypass passage and that causes a refrigerant passing therethrough to be in a gas-liquid mixed phase. Refrigeration cycle is obtained.

[0011] The bypass passage may be connected in a crankcase of the compressor.

[0012] The bypass-side expansion means may be provided in the crankcase.

[0013] The bypass passage may be connected to a suction port of the compressor.

[0014] The bypass passage may be connected to a compression area of the compressor.

[0015] An internal heat exchanger may be provided for exchanging heat between the refrigerant exiting the radiator and the refrigerant exiting the heat absorber.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A refrigeration cycle according to a first embodiment of the present invention will be described with reference to FIG.

The refrigeration cycle shown in FIG. 1 is a supercritical refrigeration cycle using CO2 as a refrigerant. The supercritical refrigeration cycle includes a compressor 3 having a suction port 1 for sucking refrigerant and a discharge port 2 for discharging refrigerant, an evaporator or heat absorber 4 connected to the suction port 1, and a connection to the discharge port 2. A gas cooler or radiator 5 and an expansion valve 6 as a circuit-side expansion means connected between the heat absorber 4 and the radiator 5 are included.

Further, in this supercritical refrigeration cycle, a part of the refrigerant that has flowed out of the radiator 5 is connected to the bypass passage 7 that bypasses the expansion valve 6 and the heat absorber 5 and guides the refrigerant to the compressor 3. Further, a capillary 8 is provided as bypass-side expansion means for converting the refrigerant passing therethrough into a gas-liquid mixed phase.

When the compressor 3 is driven, the refrigerant is discharged from the discharge port 2 of the compressor 3 to the radiator 5 where it is radiated. Most of the refrigerant flowing out of the radiator 5 flows into the heat absorber 4 through the expansion valve 6, and absorbs heat there. The refrigerant that has exited the heat absorber 4 is drawn into the suction port 1 of the compressor 3. Thus, most of the refrigerant circulates through compressor 3, radiator 5, expansion valve 6, and heat absorber 4 in that order. The operation by the circulation of the refrigerant is the same as the conventional one, and therefore the description is omitted.

When the compressor 3 is driven, a part of the refrigerant flowing out of the radiator 5 is branched into a bypass passage 7,
A gas-liquid mixed phase is formed through the capillary 8. The gas-liquid mixed phase refrigerant flows into the crankcase 9. Since the gas-liquid mixed-phase refrigerant flowing into the crankcase 9 has a low temperature,
The temperature rise of the compressor 3 itself is suppressed.
Further, the refrigerant in the crankcase 9 is compressed and discharged from the discharge port 2, so that the discharge temperature of the compressor 3 is also prevented from rising.

FIG. 2 shows the rotation speed and discharge temperature of the compressor 3.
Shows the relationship with degrees. CO as refrigerant ₂If you use
When the compressor 3 is rotating at low speed (800 rpm),
There is no great difference in the discharge temperature between the conventional example (a) and the present invention (b).
However, at high speeds (8000 rpm)
It can be seen that the discharge temperature of the present invention is significantly lower
You. According to the present invention, R134a is used as the refrigerant.
The same discharge temperature as in the conventional example (c) used above can be obtained.
Wear.

A modification will be described with reference to FIG. In this modification, the bypass passage 7 of the crankcase 9 is
Is provided with a valve device 10 serving as bypass-side expansion means. An opening 11 that allows the bypass passage 7 to communicate with the inside of the crankcase 9 is provided in the crankcase 9.
Are formed. The valve device 10 includes a valve case 12 mounted inside the crankcase 9, a valve body 13 built in the valve case 12 and facing the opening 11, and a valve case 12.
And a biasing means 14 made of an elastic body such as a spring which biases the valve 13 toward the opening 11.
According to this structure, the gap between the edge of the opening 11 and the valve body 13 functions as a capillary. This corresponds to providing the bypass-side expansion means in the crankcase 9.

The bypass passage 7 may be connected to the suction port 1 of the compressor 3 or may be connected to the compressor 3 compression area.

A refrigeration cycle according to a second embodiment of the present invention will be described with reference to FIG. Similar parts are denoted by the same reference numerals, and description thereof is omitted.

The refrigeration cycle further includes an internal heat exchanger 15 for exchanging heat between the refrigerant exiting the radiator 5 and heading for the heat absorber 4 and the refrigerant exiting the heat absorber 4 and heading for the compressor 3. ing. According to this structure, the temperature of the refrigerant drawn into the suction port 1 of the compressor 3 is reduced in advance, so that the rise in the temperature of the compressor 3 and the discharge temperature can be suppressed.

[0026]

As described above, according to the present invention,
It is possible to provide a refrigeration cycle in which a rise in compressor temperature is prevented and a rise in discharge temperature of the compressor is suppressed. Therefore, the deterioration of the organic material and the lubricating oil in the compressor included in the refrigeration cycle can be prevented.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a refrigeration cycle according to a first embodiment of the present invention.

FIG. 2 is a graph showing a relationship between a rotation speed of a compressor and a discharge temperature.

FIG. 3 is a sectional view of a main part of a compressor in a modification of the refrigeration cycle of FIG. 1;

FIG. 4 is a circuit diagram of a refrigeration cycle according to a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Intake port 2 Discharge port 3 Compressor 4 Heat sink 5 Heat radiator 6 Expansion valve 7 Bypass passage 8 Capillary 9 Crankcase 10 Valve device 11 Opening 12 Valve case 13 Valve element 14 Energizing means 15 Internal heat exchanger

Claims (7)

[Claims] 1. In a refrigeration cycle using carbon dioxide as a refrigerant, a refrigerant that is partially branched from a radiator and returned to a compressor without passing through a heat absorber, and a refrigerant that passes through the bypass is converted into a gas-liquid mixed phase. And a means for supplying the refrigerant in the gas-liquid mixed phase to the compressor to suppress a rise in temperature. 2. A compressor having a suction port for sucking refrigerant and a discharge port for discharging refrigerant.
In a refrigeration cycle including a heat sink connected to the suction port, a radiator connected to the discharge port, and a circuit-side expansion means connected between the heat sink and the radiator, the refrigeration cycle includes A part of the refrigerant that has bypassed the circuit-side expansion unit and the heat absorber, and a bypass passage that leads to the compressor; and a bypass-side expansion unit that is connected to the bypass passage and converts the refrigerant passing therethrough into a gas-liquid mixed phase. A refrigeration cycle comprising: 3. The refrigeration cycle according to claim 1, wherein the bypass passage is connected inside a crankcase of the compressor. 4. The refrigeration cycle according to claim 3, wherein said bypass-side expansion means is provided in said crankcase. 5. The refrigeration cycle according to claim 1, wherein the bypass passage is connected to a suction port of the compressor. 6. The refrigeration cycle according to claim 1, wherein the bypass passage is connected to a compression region of the compressor. 7. The refrigeration cycle according to claim 1, further comprising an internal heat exchanger for exchanging heat between the refrigerant exiting the radiator and the refrigerant exiting the heat absorber.