CROSS REFERENCE TO RELATED APPLICATION

This application is a U.S. national stage application of PCT/TH2017/000079 filed on Nov. 1, 2017, the contents of which are incorporated herein by reference.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a refrigerating cycle apparatus equipped with a plurality of outdoor units. Each outdoor unit has at least one high pressure type compressor. More specifically, the invention relates to improvement of oil balancing between the compressors in each outdoor unit.

BACKGROUND ART

In a refrigerating cycle apparatus, a plurality of high pressure type compressors are provided having a casing held with a lubricating oil in which the discharging tube and suction tube of these compressors are mutually connected. In the prior art, an imbalance occurs between an amount of lubricating oil discharged from each compressor in a state to be mixed in a refrigerant and an amount of lubricating oil returned back to the respective compressor and sometimes there will occur an oil shortage in the compressors. If such oil shortage occurs, the supply of the oil to sliding motion parts of the compressor is interrupted, thus exerting a bad effect on the service life of the compressor.

In order to solve such problem, a refrigerating cycle apparatus has been proposed. For example, in the Japanese patent Publication No. JPH08159580 A, an oil balancing tube is connected between a side of one compressor and a suction tube of an associated compressor to allow the exceeding oil from the one compressor to be returned back to the associated compressor. However, the oil balancing tubes may involve a complex connection.

In the refrigerating cycle apparatus where there are more than one outdoor unit, problems, such as oil leakage from the interconnected oil balancing pipes' joints and fittings and pipe clog due to dirt and debris during unit installation, caused by unskillful workers, can easily occur and may cause severe damages to the compressor.

In EP 2 397 793B1, a refrigerating cycle apparatus with a plurality of outdoor units is disclosed. The oil amount of the compressor in the respective outdoor units is detected whether it is at a correct level by detecting temperature of the flow substance (refrigerant or oil) in the oil balancing tubes. However, this makes the apparatus complex and incurs high cost. Further, the apparatus still requires oil balancing tubes mutually connected between each outdoor unit.

SUMMARY OF THE INVENTION

In one aspect of the present invention, a refrigerating cycle apparatus is provided which can simply balance oil level of each compressor in each outdoor unit without installation of oil balancing pipes between each outdoor units. This can alleviate the above-mentioned problems, such as oil leakages from the interconnected oil balancing pipes' joints or pipe clog due to installing the interconnected oil balancing pipes after installing multiple outdoor units.

In one embodiment, the refrigerating cycle apparatus is equipped with a plurality of outdoor units, each of which includes at least one high-pressure type compressor. Each one of the compressor has a casing hold therein an oil. A discharge pipe and a suction pipe are connected to the high-pressure side and the low-pressure side of the compressor, respectively. Each one of the discharge pipes of the respective compressor is connected to a main discharge pipe for jointly discharging refrigerant and oil to the indoor unit. Each one of the suction pipes of the respective compressors is connected for returning the refrigerant and the oil from the indoor unit to the compressor. Each one of the plurality of outdoor units comprise a first oil balancing circuit connected between a side surface of the casing of the respective compressor and the main discharge pipe for allowing a flowing-in of an excess amount of the oil in the casing of the respective compressor.

In another embodiment, the refrigerating cycle apparatus may further include a second oil balancing circuit connected between a side surface of the casing of the respective compressor and the main suction pipe. The first and second balancing circuits may be operated periodically and sequentially and controlled by electronic valves.

Therefore, oil balancing between the compressors of the plurality of outdoor units can be realized more efficiently.

In one aspect of the invention, each one of the compressor may further comprise an oil level sensor for detecting oil level of the oil in the casing of the respective compressor.

