Variable Refrigerant Expansion Device with Pressure Relief

A refrigerant expansion assembly for use in a vehicle air conditioning system comprising:

• an orifice inlet port configured to receive a refrigerant from a condenser;
• an orifice outlet port configured to send the refrigerant to an evaporator;
• an orifice channel connecting the orifice inlet port to the orifice outlet port and including a valve seat;
• a variable orifice assembly, mounted in the orifice channel, including a variable orifice body axially slidable in the orifice channel, the variable orifice body including a sealing flange sealingly engageable with the valve seat, an upstream variable orifice passage extending upstream from the sealing flange, a downstream variable orifice passage extending downstream from the sealing flange and a fixed orifice passage extending axially through the variable orifice body, the variable orifice assembly including an orifice spring configured to bias the sealing flange into engagement with the valve seat;
• and
• a pressure relief outlet channel connecting to the orifice channel between the variable orifice assembly and the orifice outlet port, and a burst disk enclosing an end of the pressure relief outlet channel, whereby when a refrigerant pressure adjacent to the pressure relief outlet channel exceeds a predetermined pressure threshold, the burst disk will burst, allowing the refrigerant to escape to atmosphere.

A method of operating a vehicle air conditioning system having a refrigerant expansion assembly, the method comprising the steps of:

• (a) directing a refrigerant through an orifice inlet port, an orifice channel, having a fixed orifice passage through a variable orifice assembly, and an orifice outlet port prior to directing the refrigerant into an evaporator;
• (b) applying a refrigerant pressure upstream of the variable orifice assembly to a check ball, against a bias of a bypass spring, and a variable orifice body of the variable orifice assembly, against a bias of an orifice spring;
• (c) pushing the variable orifice body against the bias of the orifice spring into an open position when the refrigerant pressure exceeds a first predetermined pressure threshold, allowing the refrigerant to flow through an upstream variable orifice passage and a downstream variable orifice passage in the variable orifice assembly;
• (d) pushing the check ball against the bias of the bypass spring into an open position when the refrigerant pressure exceeds a second predetermined pressure threshold that is a higher pressure than the first predetermined pressure threshold, allowing the refrigerant to flow past the check ball through a bypass chamber to thereby bypass the variable orifice assembly;
• (e) the bypass spring biasing the check ball into a closed position when the refrigerant pressure drops below the second predetermined pressure threshold, thereby forcing all of the refrigerant to flow through the variable orifice assembly;
• and
• (f) the orifice spring biasing the variable orifice body into a closed position when the refrigerant pressure drops below the first predetermined pressure threshold, thereby forcing all of the refrigerant to flow through the fixed orifice passage.