Refrigeration – Automatic control – Refrigeration producer
Reexamination Certificate
2000-07-10
2001-06-12
Buiz, Michael Powell (Department: 3744)
Refrigeration
Automatic control
Refrigeration producer
C062S324600
Reexamination Certificate
active
06244060
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
This application relates to and claims priority from Japanese Patent Application No. 11-217900 filed on Jul. 30, 1999, the contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to refrigeration cycles, and particularly to a refrigeration cycle for a vehicle air conditioner in which high-temperature gas refrigerant discharged from a compressor is directly introduced into an evaporator. The evaporator functions as a radiator for radiating heat of the gas refrigerant to improve heating performance of the air conditioner.
2. Related Art
Conventionally, when a vehicle air conditioner is operated in a heating mode in winter, high-temperature engine coolant for cooling an engine of a vehicle flows through a heating heat exchanger. The heat exchanger performs heat exchange between air and engine coolant so that air is heated. However, when a temperature of engine coolant is relatively low, air passing through the heat exchanger may insufficiently heated and a temperature of air blown into a passenger compartment of the vehicle may be lowered. Thus, heating performance of the air conditioner may be declined.
JP-A-5-272817 discloses a refrigeration cycle for a vehicle air conditioner. In the refrigeration cycle, when a temperature of engine coolant is relatively low at a time of starting the engine, high-temperature gas refrigerant discharged from a compressor directly introduced into an evaporator through a bypass passage while bypassing a condenser. The evaporator radiates heat of gas refrigerant toward air to heat air.
Further, excess or shortage of an amount of refrigerant circulating through the cycle is detected according to a cycle high pressure of refrigerant detected in the vicinity of an outlet of the compressor. When the amount of refrigerant circulating through the cycle is judged excessive, refrigerant is supplied to the condenser. When the amount of refrigerant circulating through the cycle is judged insufficient, refrigerant staying in the condenser is forced to be discharged and introduced to the evaporator. Refrigerant staying in the condenser is returned to the evaporator by operating the compressor while an inlet of the condenser is opened and an inlet of the bypass passage is closed, that is, in a normal cooling mode.
Generally, a separator which separates gas-liquid two-phase refrigerant into gas refrigerant and liquid refrigerant and stores liquid refrigerant therein is connected to an outlet of the condenser. In the cooling mode, high-pressure liquid refrigerant discharged from the separator is decompressed by a thermostatic expansion valve, and low-pressure refrigerant decompressed by the expansion valve is evaporated by the evaporator. An opening degree of the expansion valve is adjusted so that refrigerant discharged from the evaporator has a predetermined degree of superheat such as 10° C., under normal operation conditions in the cooling mode such as a cycle low pressure is set to 2-5 kg/cm
2
G.
However, when outside air has an extremely low temperature such as −10° C. or lower, since a temperature sensor of the expansion valve also has a temperature substantially the same as a temperature of outside air at a time of starting a heating mode, a pressure of refrigerant in the temperature sensor is decreased to an extremely low value in comparison with that in the cooling mode. As a result, an opening degree of the expansion valve becomes small, and the expansion valve may be eventually closed when the temperature of outside air is further decreased. Therefore, even when refrigerant staying in the condenser is forced to be returned to the evaporator, refrigerant may not be sufficiently returned to the evaporator.
SUMMARY OF THE INVENTION
In view of the foregoing problems, it is an object of the present invention to provide a refrigeration cycle in which refrigerant staying in a condenser is forced to be returned to an evaporator even when a temperature of outside air is extremely low.
According to the present invention, a refrigeration cycle through which a refrigerant flows has a compressor which compresses the refrigerant and discharges a gas refrigerant, a condenser which condenses the gas refrigerant discharged from the compressor, a decompressing unit which decompresses the refrigerant condensed by the condenser, an evaporator which evaporates the refrigerant decompressed by the decompressing unit, a bypass passage which directly connects an outlet of the compressor to an inlet of the evaporator. The gas refrigerant discharged from the compressor is directly introduced into the evaporator through the bypass passage in a heating mode. The decompressing unit is disposed in a passage between the condenser and the evaporator. The passage between the condenser and the evaporator is opened a predetermined amount when a refrigerant recovery mode in which the refrigerant staying in the condenser is forced to be discharged and introduced into the evaporator is set.
As a result, communication between the condenser and the evaporator is secured during the refrigerant recovery mode, and refrigerant staying in the condenser is securely returned to the evaporator even when a temperature of outside air is extremely low.
Preferably, the decompressing unit is a thermostatic expansion valve including a temperature detector which detects a temperature of the refrigerant discharged from the evaporator. The thermostatic expansion valve is opened until a temperature of the refrigerant discharged from the evaporator detected by the temperature detector is decreased −30° C. and lower.
REFERENCES:
patent: 4025041 (1977-05-01), Tyler
patent: 4136528 (1979-01-01), Vogel et al.
patent: 5291941 (1994-03-01), Enomoto et al.
patent: 5477700 (1995-12-01), Lio
Ito Hajime
Izawa Satoshi
Takano Yoshiaki
Ali Mohammad M
Buiz Michael Powell
Denso Corporation
Harness Dickey & Pierce PLC
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