This invention relates to the use of a check valve to prevent backflow of refrigerant into an economizer line in a compressor during portions of the operational cycle of the compressor.
As known, a typical refrigeration cycle includes a compressor, a condenser, an expansion valve and an evaporator. Refrigerant is compressed at the compressor and sent to the condenser, wherein it is cooled by an external environment. Refrigerant from the condenser then passes to the expansion valve, and from the expansion valve to the evaporator. In the evaporator, air from an environment to be cooled, is cooled by the refrigerant. The refrigerant then returns to the compressor. This basic refrigeration cycle has been improved upon by many efficiency features.
Modern refrigeration cycles are typically provided with many functional characteristics to improve the efficiency of the circuits.
One major improvement in the refrigeration cycle is the use of an economizer circuit. In an economizer circuit, the refrigerant is further treated between the condenser and the expansion valve. Basically, the refrigerant leaving the condenser is split into two flow paths. One of the two flow paths is passed through an expansion valve, and then into an economizer heat exchanger. The gas in the second flow path is further cooled by the first path refrigerant which has been expanded. Thus, the refrigerant passing through the second line is cooled to a point that is lower than it otherwise would have been when it approaches the main expansion valve.
Economizers are utilized to provide a high degree of cooling capacity. The refrigerant in the first path which has passed through the expansion valve and to the economizer heat exchanger must be returned to the compressor. Thus, compressors incorporating an economizer circuit typically have an economizer return path leading to an injection port in the compressor. A valve on the return path selectively opens and closes flow to provide or block use of the economizer cycle.
One type of compressor which is achieving wide acceptance in refrigerant compression applications is a scroll compressor. In a scroll compressor, a pair of scroll members each have a base and a generally spiral wrap extending from the base. The wraps interfit to define compression chambers. One of the two scroll members is driven to orbit relative to the other, and as this orbiting occurs, compression chambers defined between the interfitting wraps are reduced in volume to compress an entrapped refrigerant. As compression occurs, the pressure within the compression chambers cyclically increases and decreases.
When an economizer circuit is utilized in a scroll compressor, the economizer injection port typically extends through one of the scroll members and into one of the compression chambers. Often the economizer port extends through the non-orbiting scroll member. The economizer injection port will communicate with a chamber which is thus at a pressure which varies during the operational cycle of the scroll compressor. At times, the pressure in this chamber may be higher than the pressure in the economizer return path. At such times, there can be backflow of refrigerant through the economizer port, and out of the compression chambers.
This backflow results in efficiency and pumping loses, which are undesirable. These pumping losses can also occur during periods of time when the economizer circuit is closed since there typically is a relatively long distance between the economizer shutoff valve and the injection port.
These variations in operational pressures occur in other types of compressors, and are not limited to scroll compressors. Thus, while the invention will be described with reference to a scroll compressor, it should be understood that the invention described in this application can apply to other type compressors.