GB1314017A - Fuel injection nozzles - Google Patents

Abstract

1314017 Fuel injectors CAV Ltd 26 June 1970 [7 July 1969] 34132/69 Heading F1B In a fuel injection nozzle of the kind in which fuel pressure unseats a valve member 15, Fig. 1, to commence fuel injection through an orifice 11 a mechanical connection between the valve member and resilient means 18 loading it is divided to define a variable volume chamber to which fuel is supplied from an inlet, the maximum volume of the chamber being limited and so arranged that fuel flowing though the inlet initially flows at a restricted rate to the orifice and when the chamber has attained its maximum volume the valve member is lifted to allow substantially unrestricted flow through the orifice. Fuel supplied from pump 8 to groove 25 passes via restrictor 24, passage 23 and grooves 22, 21 to the chamber between piston 16 and valve member 15 and also passes to gallery 13, to unseat valve member 15. Fuel continues to flow into the chamber moving piston 16 until groove 22 is closed to port 23 whereafter piston 16 and valve member 15 move together so that fuel can flow through orifices 11 at an unrestricted rate. When the fuel-flow ceases the fuel in the chamber escapes via grooves 21, 22, port 26 and non- return valve 27. The restriction imposed by restrictor 24 can be made variable in accordance with speed. In another embodiment fuel is supplied through a restrictor 24, Fig. 2 to a chamber between piston 16 and valve member 15 and supplied directly to gallery 13. Initially piston 16 rises and valve member 15 and distance member 28 then rise to allow a restricted fuel-flow. During lifting fuel flows into the chamber beneath distance member 28 and piston 16 eventually opens port 31 to allow fuel pressure to act on piston 33. The latter rises to cut off the incoming fuel-flow and thereafter the valve member 15 rises under the action of fuel pressure in gallery 13 to allow unrestricted fuel-flow through the orifices 11. Piston 33 has a restricted through opening to allow its return during non-injection periods. In another embodiment a valve member (50) Fig. 3 (not shown) is initially lifted to allow fuelflow at a restricted rate. Meanwhile fuel at a higher pressure lifts a piston (52) having a groove (55) which eventually registers with a bore to permit a full pressure flow to gallery (13) causing unseating of the valve member (50) and fuelflow at an unrestricted rate. The gallery (13) is fed through a restrictor 51. The restriction imposed can be modified to obtain different delivery curves.