| 摘要 |
A fuel injector offering improved accuracy of fuel delivery is described. The fuel injector comprises a supply means (24, 24a) for high pressure fuel, an injection nozzle (25) including a valve needle (26), a control chamber (42) for the valve needle, a first filling flow path (44) providing flow from the supply means (24) into the control chamber (42), and a control valve (48) for controlling fuel pressure within the control chamber (42). The control valve (48) comprises a first valve chamber (104) and a second valve chamber (106), and a control valve member (60) operable between a first state in which the first valve chamber (104) communicates with the supply means (24), and in which flow between the second valve chamber (106) and a low-pressure drain (21) is prevented, and a second state in which flow between the first valve chamber (104) and the supply means (24) is prevented, and in which the second valve chamber (106) is in communication with the low-pressure drain (21). The fuel injector further comprises a drain flow path (50) including a drain restriction (50a) and permitting flow from the control chamber (42) to the second valve chamber (106) when the control valve member (60) is in the second state, and a second filling flow path (47) permitting flow from the first valve chamber (104) into the control chamber (42) when the control valve member (60) is in the first state, wherein the second filling flow path (47) bypasses the drain restriction (50a). The drain restriction (50a) comprises an orifice. |
