Rotor/stator air gap shield for liquid cooled electric machine

To avoid frictional losses in a high speed electric machine a shield 110 is provided in the rotor/stator air gap to guide coolant back to a drain 106 via collector 104 within the machine housing formed by sections 72,73 without coolant gaining access to the rotor 66. The shield comprises a central cylinder and bell mouth end caps which may be secured to the cylinder by one of welding including friction welding, gluing, threading and snapping (Fig 5,6) the cylindrical section being of thinner material than the end caps. Insulation (e.g. ceramic) on the outer portions 208 (Fig 5) of the end caps prevents radiated and conductive heat transfer to the electric machine if said machine is proximate a high temperature component. The machine may form a motor in a electronically controlled turbocharger and the coolant is oil supplied to manifold 82 which lubricates the bearings 76,78. Check valves 92,94,96 prevent bearing starvation by allowing flow to the stator only when oil pressure is sufficient, an electronic control system preventing machine overheating when oil pressure is low (fig 9). A gallery 100,140 formed in the back-iron introduces oil into the stator which exits via voids 144 (see fig 3).