GB1373238A - Fuel injection systems - Google Patents

Abstract

1373238 Fuel injection apparatus ROBERT BOSCH GmbH 27 Oct 1971 [28 Oct 1970] 49853/71 Heading F1B A fuel injection system for a multi-cylinder mixture compressing I. C. engine with separate ignition, comprising fuel distributing means and metering valves controlling flow to the injectors, a differential pressure valve in series with each metering valve to maintain a constant pressure drop thereacross, the effective opening of the differential pressure valve being alterable by a yieldable member subject on one side to the pressure downstream of the metering valve and on the other side to the pressure upstream thereof, there being a chopper valve downstream of each differential pressure valve, so that fuel injection is intermittent during the induction stroke at low speeds and automatically becomes continuous with increasing engine speed. The device comprises a housing 1, the lower end of which is closed by a diaphragm 5 clamped by an intermediate plate 2 and a cover 3. A cover 4 closes the top of the housing. Spaced around the axis of the housing are a number of bores (one for each cylinder) 6 and 7. A carrier 10 screwed into the housing above each chamber projects into the chamber and supports a valve seat 9. A spring 13 biases the diaphragm away from the valve seat. Fuel is delivered by a continuously running pump 19 through a bore 20 into each of the chambers 7 and flows through a duct 37 into an annular space 32 between a bush 24 and a reduced diameter portion of a valve slide 31, the upper part of which partly covers slots 34 each leading to one of the chambers 6. The fuel then flows through the orifice in the valve seat 9 to an accumulator space 12, the upper end of which is defined by the end face of a piston 43. Each piston is connected by a leaf spring 44 to a gear-wheel 46 which meshes with a gear-wheel 54 driven by the engine camshaft. Operation. As the flow of fuel permitted by the valve slide 31 varies, the pressure in the chambers 6 increases or decreases and the diaphragm 5 moves against the pressure of the fuel in the chambers 7 to vary the effective opening of the orifice in the valve seat 9 so that the pressure drop across the metering valve, formed by valve slide 31 and slots 34, is substantially constant. The pressure of the fuel in the accumulator spaces 12 lifts the pistons 43 only a small amount at low engine speeds so that fuel flows to the injectors only when a slot 48 in the piston is co-incident with a channel 49 which occurs during the induction stroke of the engine piston. At high engine speeds the pistons are raised so that the end face is above the channel 49 and injection is continuous. Since fuel is injected only during the induction stroke at low engine speeds, escape of the fresh charge through the exhaust valve during the valve overlap period is minimized and unburnt hydrocarbons in the exhuast gas are reduced. In a modification there is a pin and slot connection between the piston 43 and gear-wheel 46 and the upper end of the piston is loaded by fuel at a pre-determined pressure. In a further modification each accumulator space is connected to the injector by a line including a solenoidoperated valve controlled by a monostable multivibrator triggered by pulses generated by contacts in the ignition distributer. The response time of the circuit is such that at high engine speeds, fuel is injected continuously. Reference has been directed by the Comptroller to Specification 1250345.