Oil pump and engine lubrication system

An oil pump 100 provides positive displacement of oil through a valve member 112 by actuation of a solenoid moving a piston (or plunger) 106. The piston 106 incorporates a one way or 'check valve 112 allowing oil to flow into a pumping chamber 120 during the return stroke of the piston under influence of a return spring 110 when solenoid field windings 108 are sufficiently de-energised. As the piston 106returns, the outlet 122 valve is closed by its valve closing spring 124 and oil flows from the pump's inlet 102, through the piston and past the unseated valve member 112a of the valve 112 in the piston 106 and into the pumping chamber 120. The valve member 112a can have a valve face 114 unseated from a valve seat 116 during this return stroke of the piston. For a pumping stroke (Figure 3B), the valve member 112a in the piston 106 is closed with the valve face 114 seated against the valve seat 116 under influence of a return spring 118. During a pumping stroke (Figure 3B), the valve member 11 2a remains closed by its return spring 118, and the oil in the pumping chamber is forced under pressure to open the outlet valve 122, overcoming the outlet valve closing spring 124, and positively displacing a metered amount of oil from the pump through the outlet 104. The valve 112 can be a piston valve or 'poppet valve', an umbrella or reed type valve. The pump 100 can form part of a lubrication system including a reservoir 126 supplying an engine 10. 118 108 116 100 11 6 1201 102 106 0\ 104 10 0 0104 Fig 3A 112 112a 114 Fig 3B 112 112a 114 Fig 4