A cooling circuit for a hybrid electric vehicle and a method cooling

摘要

A hybrid electric vehicle 100 comprises an engine 110 and at least one electric machine 150 arranged to be cooled by coolant flowing through a coolant circuit of the vehicle. The engine 110 and at least one electric machine 150 are coupled in series in the circuit. The hybrid electric vehicle has two modes of operation, a first parallel mode of operation with the engine 110 and electric machine 150 both running an engine-driven fluid pump 117 develops a relatively large pressure at a first inlet 160IN1 of a pressure relief valve 160, thus a relatively large portion of the coolant flows through the bypass conduit 150BC; and a second electric vehicle mode of operation with the engine 110 of and only the electric machine 150 on the pressure at the pressure relief valve inlet 160IN1 is relatively low and the pressure relief valve 160 prevents coolant flowing through the bypass conduit 150BC.