Refrigeration – Time or program actuator – Defrosting
Patent
1994-11-29
1996-06-11
Tanner, Harry B.
Refrigeration
Time or program actuator
Defrosting
62278, 62509, F25B 4702
Patent
active
055244491
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a system for controlling operation of a refrigeration device which is arranged to perform a reverse cycle defrost operation and, more particularly, to an arrangement for preventing liquid back-flow to a compressor.
BACKGROUND ART
An air conditioning system including a refrigerant circuit wherein a compressor, a heat source-side heat exchanger, a pressure-reducing valve, and a utilization end-side heat exchanger are sequentially connected and wherein its refrigerating cycle is switchable between forward cycle and reverse cycle, has been known which, as disclosed in, for example, Japanese Utility Model Application Laid-Open No. 63-15434, can perform a so-called reverse cycle defrost operation such that when, during a heating operation, frosting occurs at the heat-source-side heat exchanger, the refrigerant circuit, upon receipt of a defrost command, is operative to switch the refrigerating cycle to a cooling cycle so that a discharge gas refrigerant (hot gas) is flowed into the heat source-side heat exchanger for a predetermined time or until the temperature at the heat-source-side heat exchanger rises to more than a predetermined temperature value, whereby the frost at the heat-source-side heat exchanger is melted for restoring the capability of the heat exchanger.
In such an air conditioning system, when, at the beginning or end of a defrost operation, the refrigerating cycle is forwardly or reversely changed, liquid refrigerant begins to flow toward the compressor as a result of a functional change to an evaporator of the heat-source-side heat exchanger or utilization-side heat exchanger, which has been functioning as a condenser and which, therefore, has a large amount of liquid refrigerant stored therein. In such conventional type of air conditioning system, therefore, an accumulator is disposed before the compressor to absorb the liquid refrigerant thereby to prevent liquid back-flow to the compressor.
With the accumulator so disposed, however, the system may involve various troubles including a power decrease due to pressure reduction, and separation of oil and liquid refrigerant into two phases. Essentially, therefore, an accumulatorless arrangement is desired.
SUMMARY OF THE INVENTION
The present invention has been developed in view of the foregoing facts, and accordingly it is an object of the invention to provide means for causing liquid refrigerant to be efficiently received into the receiver at the start/end of each defrost operation and before a mode changeover in refrigeration cycle takes place, thereby to prevent a liquid flow-back to the compressor without provision of an accumulator.
FIG. 1 is a schematic diagram illustrating the arrangement of the present invention.
A system for controlling operation of a refrigerating device according to the present invention is used in a refrigerating device which, as shown in FIG. 1, includes a refrigerant circuit (9) in which a compressor 1, a condenser 6, a receiver 4 for storing liquid refrigerant, a pressure-reducing valve 5, and an evaporator 9 are connected together, and a cycle change-over mechanism 2 for changing a refrigeration cycle of the refrigerant circuit 9 between forward operation and reverse operation, the refrigerating device being of such arrangement that the pressure-reducing valve 5 is positioned downstream of the receiver 4 during either one of the refrigerating cycles. And the system comprises:
a bypass path 4a connecting a top portion of the receiver 4 to a liquid line on the downstream side of the pressure-reducing valve 5;
a normally closed on-off valve SV for opening and closing the bypass path
defrost operation control means 51 for switching the cycle change-over mechanism 2 to a reverse cycle position upon receipt of a defrost command during operation of the refrigerating device, thereby to control the device so as to perform a defrost operation; and
at least one of (a) a before-defrost on-off control means 52 for controlling the on-off valve SV to be opened for at leas
REFERENCES:
patent: 2597729 (1952-05-01), Homeyer
patent: 3110164 (1963-11-01), Smith
patent: 4171622 (1979-10-01), Yamaguchi et al.
patent: 4313313 (1982-02-01), Chrostowski et al.
Nakajima Hiroto
Ueno Takeo
Daikin Industries Ltd.
Tanner Harry B.
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