Anti-cavitation throttle for injector control valve
A needle type fuel injector has a needle control chamber at a pressure subject to a control valve in a control valve chamber which in an opening phase is lifted from its seat to expose the control valve chamber, connecting passage, and needle control chamber to a low pressure drain and in a closing phase is urged against the seat to isolate the control valve chamber, connecting passage, and needle control chamber from the drain. The potential for cavitation at high fuel injection pressure is reduced by throttling the flow of fuel past the control valve seat when the control valve opens, thereby maintaining sufficient back pressure in the control valve chamber and upstream connecting passages.
1. In a fuel injector having a needle that closes off an injection orifice when subjected to high fuel supply pressure at upper and lower elevations of the needle and opens when the needle is subjected to a reduced pressure at the upper elevation, said upper elevation situated in a needle control chamber at a pressure subject to a control valve in a control valve chamber exposed to fuel at said supply pressure, whereby in an opening phase the control valve is lifted from a control valve seat to expose the control valve chamber and needle control chamber to a low pressure drain through a flow passage extending from the control valve seat to said low pressure drain and in a closing phase is urged in a closing direction against said control valve seat to isolate the control valve chamber and needle control chamber from the drain, the improvement comprising a throttling collar on a pintle on said control valve, extending into said low pressure passage, for decreasing fuel flow in the closing direction through the control valve seat toward said drain as the control valve opens.
2. The fuel injector of claim 1 , wherein a pressure regulating valve is in said flow passage between the throttling collar and the drain.
3. The fuel injector of claim 2 , wherein said pressure regulating valve is a plate valve.
4. The fuel injector of claim 1 , wherein the flow passage includes a cylindrical bore wall immediately downstream of the control valve seat; and said pintle extends within said bore wall and said collar defines an annular throttled flow area between the collar and the bore wall.
5. The fuel injector of claim 1 , wherein said pintle on said control valve comprises a frustoconical angled surface which is downstream of the control valve seat when the control valve is in a closed position.
6. The fuel injector of claim 1 , wherein said pintle on said control valve comprises a nose, said nose further comprising one or more recesses.