Refrigeration – Automatic control – Refrigeration producer
Reexamination Certificate
2000-03-28
2001-07-31
Tanner, Harry B. (Department: 3744)
Refrigeration
Automatic control
Refrigeration producer
C062S200000, C062S228300, C062S231000, C062S227000
Reexamination Certificate
active
06266967
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application is related to and claims priority from Japanese Patent Application No. Hei. 11-89786 filed on Mar. 30, 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 refrigerant cycle system having first and second evaporators disposed parallel to each other. The refrigerant cycle system is suitable for a vehicle air conditioner having a front air-conditioning unit for controlling air blown toward a front seat side of a vehicle, and a rear air-conditioning unit for controlling air blown toward a rear seat side of the vehicle.
2. Description of Related Art
In recent years, a request of a large-type vehicle such as a minivan is increased. This type vehicle is necessary to have an air conditioner having a large capacity, such as a dual air conditioner. In a refrigerant cycle of the dual air conditioner, both front and rear evaporators are disposed, while a single compressor and a single condenser are used.
In a vehicle dual air conditioner described in JP-A-9-109656, when the air conditioner operates only for a front seat side of the vehicle, an electromagnetic valve for switching a refrigerant flow toward a rear evaporator is forcibly opened for a short time at predetermined intervals, so that refrigerant staying in the rear evaporator is returned into a compressor. However, in a vehicle where an electromagnetic valve for the rear evaporator is not provided for reducing cost of the air conditioner, when a rear air-conditioning unit is stopped, a lubrication oil staying in the rear evaporator does not return to the compressor, and an oil amount returning to the compressor becomes insufficient. As a result, durability of the compressor is deteriorated.
SUMMARY OF THE INVENTION
In view of the foregoing problems, it is an object of the present invention to provide a refrigerant cycle system having a first evaporator and a second evaporator, which prevents an oil amount returning to a compressor from being insufficient without using an electromagnetic valve for the second evaporator, when only the first evaporator operates.
As a result of experiments and studies by the inventor of the present invention, in a refrigerant cycle system having first and second evaporators, when a compressor operates in a long time when only the first evaporator operates and the second evaporator does not have an electromagnetic valve, a thermal expansion valve of the second evaporator repeats minute opening/closing operations, and an oil amount returning to the compressor becomes insufficient.
Thus, according to the present invention, a refrigerant cycle system including: a compressor for compressing and discharging refrigerant, a condenser for cooling and condensing gas refrigerant discharged from the compressor, a first pressure-reducing unit for decompressing and expanding liquid refrigerant from the condenser, a first evaporator for evaporating refrigerant from the first pressure-reducing unit, a first blower for blowing air toward the first evaporator, a second pressure-reducing unit for decompressing and expanding liquid refrigerant from the condenser, a second evaporator for evaporating refrigerant from the second pressure-reducing unit, and a second blower for blowing air toward the second evaporator. The second pressure-reducing unit is disposed parallel to the first pressure-reducing unit relative to a refrigerant flow direction, and the second evaporator is disposed parallel to the first evaporator relative to the refrigerant flow direction. In the refrigerant cycle system, a control unit controls operation of the compressor to change a refrigerant pressure at a suction side of the compressor when a continuous operation time of the compressor passes a predetermined time after the compressor operates, and the second pressure-reducing unit is a thermal expansion valve which adjusts a super-heating degree of refrigerant at an outlet of the second evaporator by adjusting a valve opening degree. Thus, even when the compressor continuously operates in a long time when only the first evaporator operates, the refrigerant pressure the suction side (low-pressure side) is forcibly changed. Therefore, it is possible to forcibly open the thermal expansion valve of the second evaporator. As a result, lubrication oil staying in the second evaporator, a low-pressure pipe and the like is returned to the suction side of the compressor with a refrigerant flow due to the forcibly opening of the thermal expansion valve. Accordingly, the refrigerant cycle system prevents an oil amount returning to a compressor from being insufficient without using an electromagnetic valve for the second evaporator, when only the first evaporator operates.
Preferably, the control unit forcibly interrupts the operation of the compressor by predetermined number of plural interruptions during a forcible interruption control of the compressor, when the continuous operation time of the compressor passes the predetermined time after the compressor operates. Therefore, a forcibly variation of the refrigerant pressure at the low-pressure side is actually performed.
Preferably, the control unit controls an interruption operation of the compressor in accordance with an air temperature blown from the first evaporator. Therefore, it prevents the first evaporator from frosting.
Further, when the refrigerant cycle system is applied to a vehicle air conditioner having a front air-conditioning unit and a rear air-conditioning unit, an oil amount returning to the compressor is prevented from being insufficient when only the front air-conditioning unit operates.
REFERENCES:
patent: 4628700 (1986-12-01), Alsenz
patent: 4928500 (1990-05-01), Funahashi et al.
patent: 6145325 (2000-11-01), Hanselmann et al.
patent: 0 842 799 A2 (1998-05-01), None
patent: 9-109656 (1997-04-01), None
patent: 11-20463 (1999-01-01), None
Denso Corporation
Harness, Dickey & Pierce, PPLC
Tanner Harry B.
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