Crankcase oil return valve

Abstract

This invention provides a direct oil return system from the accumulator tank in the refrigerant circuit of a transport refrigeration system to the crankcase of the compressor for returning oil entrained in the refrigerant to the oil sump. A pressure relief valve in the lubricating oil circulating system positively opens under the influence of oil pressure from the positive displacement oil pump whenever the compressor is operating to bleed excess oil from the pump back to the sump. The oil return line from the accumulator tank of the refrigeration system is connected to the valve to enter through another inlet port which opens in response to the pressure relief valve being opened and flows therethrough to another outlet in the valve also in communication with the sump. As the pressure relief valve and thus the inlet ports in the oil return line remain closed whenever the compressor is not operating, liquid refrigerant is unable to migrate therethrough to the sump and, in the heating mode of operation of the refrigerant system, which is the mode in which liquid refrigerant is most likely to be entrained in the returning oil, an external heat source heats the line draining the oil from the accumulator tank to vaporize the liquid refrigerant therein to prevent liquid refrigerant being returned to the sump when the compressor is operating.