Vapor injection heat pump and control method

A method of heating and cooling a vehicle comprising the steps of:

• providing a vapor injection heat pump operating in at least a first mode of operation and a second mode of operation;
• compressing a refrigerant;
• receiving a refrigerant output by the compressor in a first heat exchanger;
• receiving the refrigerant output by the first heat exchanger in a first expansion valve and (1) directing the refrigerant to a first separator valve when the vapor injection heat pump is in the first mode of operation or (2) expanding the refrigerant into a first liquid and vapor refrigerant mix output to the first separator valve when the vapor injection heat pump is in the second mode of operation;
• receiving the refrigerant or first liquid and vapor refrigerant mix output by the first expansion valve in the first separator valve and (1) directing the refrigerant to a second heat exchanger when the vapor injection heat pump is in one of the first or second mode of operation or (2) separating a vapor component of the first liquid and vapor refrigerant mix and injecting the separated vapor component into a second port of the compressor and directing a liquid component of the first liquid and vapor refrigerant mix to an orifice of the first separator valve and expanding the liquid component into a second liquid and vapor refrigerant mix and directing the second liquid and vapor refrigerant mix to the second heat exchanger when the vapor injection heat pump is in the other one of the first or second mode of operation;
• directing the flow of refrigerant output by the second heat exchanger using a valve positioned between the second heat exchanger and a first port of the compressor to the first port of the compressor when the vapor injection heat pump is in one of the first or second mode of operation or a second expansion valve when the vapor injection heat pump is in the other one of the first or second mode of operation;
• receiving the refrigerant output by the second heat exchanger in a second expansion valve and (1) directing the refrigerant to a second separator valve when the vapor injection heat pump is in one of the first or second mode of operation or (2) expanding the refrigerant output by the second heat exchanger into a third liquid and vapor refrigerant mix output to the second separator valve when the vapor injection heat pump is in the other one of the first or second mode of operation;
• receiving the refrigerant or third liquid and vapor refrigerant mix output by the second expansion valve in the second separator valve and (1) directing the refrigerant to a third heat exchanger when the vapor injection heat pump is in one of the first or second mode of operation or (2) separating a vapor component of the third liquid and vapor refrigerant mix output by the second expansion valve and injecting the separated vapor component into the second port of the compressor and directing a liquid component of the third liquid and vapor refrigerant mix output by the second expansion valve to an orifice of the second separator valve and expanding the liquid component into a fourth liquid and vapor refrigerant mix and directing the fourth liquid and vapor refrigerant mix to the third heat exchanger when the vapor injection heat pump is in the other one of the first or second mode of operation;
• and controlling at least the valve, the first and second expansion valves, and the first and second separator valves.