Refrigeration – Automatic control – Selective heating or cooling
Reexamination Certificate
1999-09-08
2001-06-12
Tanner, Harry B. (Department: 3744)
Refrigeration
Automatic control
Selective heating or cooling
C062S151000, C062S278000, C062S324500
Reexamination Certificate
active
06244057
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an air conditioner comprising one outdoor unit and one or more indoor units, the outdoor unit having two lines composed of a four-way valve, an outdoor heat exchanger and an outdoor expansion valve, and more particularly, to an air conditioner which is suitable for performing switching between operation modes of cooling, heating and defrosting smoothly without any trouble.
PRIOR ART
In an air conditioner of heat pump refrigerating cycle, a refrigerant in an outdoor heat exchanger becomes hard to evaporate and so decreases in evaporating pressure and temperature when outside air temperature decreases during heating operation. Therefore, air, which is performing heat exchange, decreases in condensing temperature, and moisture in the air sticks to surfaces of the outdoor heat exchanger as frost, which must be removed. In a refrigerating cycle with one four-way valve, defrosting methods include an inverse cycle defrosting method, in which switching of a four-way valve causes a high-pressure and high-temperature refrigerant to flow into an outdoor heat exchanger in the same forward circulating direction as that in cooling operation, and a hot gas defrosting method, in which a bypass circuit for bypassing to an outdoor heat exchanger from the vicinity of a compressor discharge port is opened/closed to permit a high-temperature refrigerant to inflow.
When the inverse cycle defrosting is performed, the four-way valve is switched, at which there is a fear that the four-way valve becomes inoperative. With a conventional air conditioner operating in refrigerating cycle and having only one four-way valve, it suffices that a pressure difference between compressor refrigerant discharge pressure (high pressure side) and compressor refrigerant suction pressure (low pressure side) be taken into account with respect to inoperability of the four-way valve when inverse cycle defrosting is performed. The reason for this is that a pressure difference between the high pressure side and the low pressure side serves as a drive force for operating the four-way valve, and so when the pressure difference is sufficient, the four-way valve operates even upon transmission of a signal for operating the four-way valve, without becoming inoperative. However, in the inverse cycle defrosting in refrigerating cycle having only one four-way valve, building-up of pressure difference for avoiding inoperability imparts a shock to piping constituting the refrigerating cycle, which results in vibrations of the piping and impulsive sound caused thereby.
On the other hand, in an air conditioner of refrigerating cycle having a plurality of four-way valves, shocks on piping can be reduced since the plurality of four-way valves are switched successively when modes of cooling, heating, and defrosting are switched. However, in the air conditioner of refrigerating cycle having a plurality of four-way valves, only a pressure difference between the high pressure side and the low pressure side may possibly be insufficient. More specifically, the air conditioner is put into an inoperative mode as in the case of ON-ON combination shown in FIG.
8
D. Specifically, a high pressure refrigerant discharged from the compressor passes through a second four-way valve
10
-
2
to branch into two parts, and one of the parts is fed toward an indoor unit, but the other of the parts flows into a suction side (low pressure side) of a compressor
6
through a check valve and a first four-way valve
10
-
1
, whereby the high pressure side and the low pressure side are short-circuited and so cannot provide a pressure difference between the high pressure side and the low pressure side, resulting in an inoperative mode, in which the four-way valve cannot be operated once again.
An object of the present invention is to provide an air conditioner provided with an outdoor unit having two lines composed of a four-way valve, an outdoor heat exchanger, and an outdoor expansion valve, and the air conditioner being capable of avoiding an inoperative mode, and has high reliability and stability.
SUMMARY OF THE INVENTION
To solve the above problems, the present invention provides an air conditioner comprising an outdoor unit,
an indoor unit or units connected to the outdoor unit by a liquid-side piping and a gas-side piping, and a forward circulating path of a refrigerant, the outdoor unit being constructed such that one of pipes branching on a discharge side of a drive frequency variable type compressor is connected to a first four-way valve, a first outdoor heat exchanger and a first outdoor expansion valve in this order, the other of the pipes is connected to a second four-way valve, a second outdoor heat exchanger and a second outdoor expansion valve in this order, and outflowing sides of the respective outdoor expansion valves join together to be connected to the liquid-side piping, and the indoor unit or units being constructed such that an indoor expansion valve and an indoor heat exchanger are connected in this order from the liquid piping side, and that one of pipes, which returns to the outdoor unit from the gas-side piping connected to the indoor heat exchanger and branch, is connected to the first four-way valve via a check valve placed in communication in a forward direction, and the other of the pipes is connected to the second four-way valve, the refrigerant flowing along the forward circulating path at the time of cooling and defrosting operations and flowing in a direction reverse to the forward circulating path at the time of heating operation, the air conditioner comprising respective means for sensing discharge pressure and suction pressure of the compressor, respectively, respective means for sensing gas-side pressures of the respective outdoor heat exchangers, and a four-way valve control device for operating the first and second four-way valves on the basis of detected values of the respective pressures, the four-way valve control device controlling, when heating operation is switched over to defrosting operation, (
2
) to first switch the second four-way valve (
1
) if a pressure difference between the compressor discharge pressure and the compressor suction pressure is equal to or above a predetermined value, and (
4
) to switch the first four-way valve (
3
) after the gas-side pressure of the second outdoor heat exchanger has risen.
Also, the four-way valve control device controls, when defrosting operation is returned to heating operation, (
2
′) to first switch the first four-way valve (
1
′) if a pressure difference between the compressor discharge pressure and the compressor suction pressure is equal to or above a predetermined value, and (
4
′) to switch the second four-way valve (
3
′) after the gas-side pressure of the first outdoor heat exchanger has decreased.
REFERENCES:
patent: 4779425 (1988-10-01), Yoshihisa et al.
patent: 5159817 (1992-11-01), Hojo et al.
patent: 5720179 (1998-02-01), Jung
patent: 5823006 (1998-10-01), Jung
patent: 5-141817 (1993-06-01), None
Japanese Patent Unexamined Publication No. 5-71822.
Japanese Patent Unexamined Publication No. 6-341726.
Naito Koji
Nakayama Susumu
Takenaka Hiroshi
Yoshida Satoru
Yoshida Yasutaka
Antonelli Terry Stout & Kraus LLP
Hitachi , Ltd.
Tanner Harry B.
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