Refrigeration – Automatic control – Refrigeration producer
Reexamination Certificate
1999-09-16
2001-05-29
Doerrler, William (Department: 3744)
Refrigeration
Automatic control
Refrigeration producer
C062S324100, C062S324600, C062S113000
Reexamination Certificate
active
06237351
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application is related to and claims priority from Japanese Patent Applications No. Hei. 10-269964 filed on Sep. 24, 1998 and No. Hei. 11-76563 filed on Mar. 19, 1999, the contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a heat pump type refrigerant cycle system which improves heating capacity by injecting middle-pressure gas refrigerant into a compressor. The refrigerant cycle system is suitably used for an electrical vehicle air conditioner, for example.
2. Description of Related Art
In a vehicle such as an electrical vehicle, because it is impossible to heat a passenger compartment by using engine-cooling water as a heating source, a heat pump type refrigerant cycle system is mounted on the vehicle, and the passenger compartment is heated by refrigerant-condensing heat in a condenser. However, when the refrigerant cycle system is used in an outside air temperature lower than −10° C., heat-absorbing amount of refrigerant in an exterior heat exchanger used as an evaporator for heating operation is decreased, and pressure of refrigerant sucked into a compressor is decreased. Therefore, refrigerant specific volume sucked into the compressor is increased, and an amount of refrigerant circulating in the refrigerant cycle system is decreased. Consequently, there occurs a problem that heating capacity for the passenger compartment becomes insufficient.
To overcome the problem, in a refrigerant cycle system described in U.S. Pat. No. 5,704,219, high-pressure refrigerant is pressure-reduced to a middle pressure during the heating operation, the middle-pressure refrigerant is separated into gas refrigerant and liquid refrigerant in a gas-liquid separator, and the gas refrigerant having the middle pressure is injected into a compressor. Therefore, a compression amount of refrigerant in the compressor is increased in the heating operation, and the heating capacity for the passenger compartment is improved. Further, in the conventional refrigerant cycle system, an evaporator of the refrigerant cycle system is disposed on an upstream air side of an air passage of an air conditioning unit, and a condenser of the refrigerant cycle system is disposed in the air passage on a downstream air side from the evaporator, so that defrosting operation for defrosting a windshield is performed.
However, in the conventional refrigerant cycle system, during heating operation, the middle-pressure gas refrigerant separated in the gas-liquid separator is decompressed to a low pressure by a thermal expansion valve, and the low-pressure refrigerant is evaporated in the exterior heat exchanger, so that super-cooling degree of refrigerant sucked into the compressor is adjusted by the thermal expansion valve. Therefore, when the heating operation is performed with low load, a flow rate of refrigerant flowing into the exterior heat exchanger is decreased by decreasing a rotation speed of the compressor, and oil contained in refrigerant tends to stay in the exterior heat exchanger. As a result, an oil amount returning to the compressor is decreased.
On the other hand, a refrigerant flow in the refrigerant cycle system is switched by using a four-way valve disposed in a refrigerant discharge side of the compressor, so that gas refrigerant discharged from the compressor is introduced into the exterior heat exchanger during the cooling operation or is introduced into the interior condenser during the heating operation. Further, middle-pressure gas refrigerant is separated from liquid pressure in the gas-liquid separator before being injected into the compressor. Thus, refrigerant pipe structure of the refrigerant cycle system becomes complex, and component number thereof is increased.
SUMMARY OF THE INVENTION
In view of the foregoing problems, it is an object of the present invention to provide a refrigerant cycle system which improves both heating capacity and oil-returning performance into the compressor.
In is a second object of the present invention to provide a refrigerant cycle system which improves heating capacity by injecting middle-pressure gas refrigerant into a compressor while a refrigerant passage structure becomes simple.
According to the present invention, in a refrigerant cycle system, high-pressure gas refrigerant discharged from a discharge port of a compressor flows into a condenser disposed in an air passage to be condensed in the condenser, a part of high-pressure refrigerant discharged from the condenser is decompressed in a first pressure reducing unit to have a middle pressure during a heating mode for heating a compartment, and the other part of high-pressure refrigerant discharged from the condenser flows into a refrigerant-refrigerant heat exchanger to be heat-exchanged with middle-pressure refrigerant having passed through the first pressure reducing unit in the refrigerant-refrigerant heat exchanger during the heating mode. Therefore, in the refrigerant-refrigerant heat exchanger, middle-pressure refrigerant having passed through the first pressure reducing unit is evaporated and high-pressure refrigerant directly from the condenser is cooled, during the heating mode. In the refrigerant cycle system, during the heating mode, evaporated middle-pressure gas refrigerant is introduced into a gas injection port of the compressor. Thus, a compression amount of the compressor can be increased during the heating mode, and heating capacity for the compartment can be improved in the refrigerant cycle system. Further, because the gas refrigerant injection into the compressor is performed by using the refrigerant-refrigerant heat exchanger, a gas-liquid separator for separating middle-pressure gas-liquid refrigerant is not necessary.
Preferably, the refrigerant cycle system further includes a second pressure reducing unit for decompressing high-pressure refrigerant cooled in the refrigerant-refrigerant heat exchanger to a low pressure during the heating mode, an exterior heat exchanger for performing heat exchange between low-pressure refrigerant after passing through the second pressure reducing unit and outside air during the heating mode, and an accumulator for separating low-pressure refrigerant from the exterior heat exchanger during the heating mode into gas refrigerant and liquid refrigerant and for introducing gas refrigerant and liquid refrigerant containing oil into a suction port of the compressor. Therefore, oil contained in liquid refrigerant can be accurately returned from the accumulator into the compressor together with gas refrigerant, even in low-load heating operation where the compressor is rotated with a low rotation speed and a refrigerant amount flowing through the exterior heat exchanger is decreased. Thus, the refrigerant cycle system improves heating capacity by injecting middle-pressure gas refrigerant from the refrigerant-refrigerant heat exchanger into the compressor, while improving oil-returning performance into the compressor.
Further, the refrigerant cycle system includes an evaporator disposed in the air passage on an upstream air side from the condenser, and a third pressure reducing unit for decompressing refrigerant before being introduced into the evaporator to a low pressure during a cooling mode for cooling the compartment. During the cooling mode in the refrigerant cycle system, high-pressure gas refrigerant discharged from the compressor is heat-exchanged with outside air in the exterior heat exchanger, and low-pressure refrigerant having passed through the evaporator is separated in the accumulator.
When the heating mode is set in the refrigerant cycle system, air passes through the condenser, and refrigerant discharged from the discharge port of the compressor circulates through the condenser, the refrigerant-refrigerant heat exchanger, the second pressure reducing unit, the exterior heat exchanger, the accumulator and the suction port of the compressor in this order, while refrigerant discharged from the discharg
Iritani Kunio
Itoh Satoshi
Denso Corporation
Doerrler William
Harness Dickey & Pierce PLC
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