DE2344723A1 - Fuel injection system for I.C. engine - has control valves with diaphragm loaded by spring in bore of valve seat carrier - Google Patents

Abstract

Continuous fuel injection system for an external ignition I.C. engine has a distributor and metering valve which are axially displaceable in common to alter the flow cross section for fuel to the injection valves, with as constant as possible a pressure drop at each metering valve, and with a control valve downstream of each metering valve, each with its flow cross section variable by a yieldable element separating two chambers. In the first chamber, the press. downstream of the metering valve acts to open the element, and the second chamber is exposed to the pressure upstream of the metering valve, whose flow cross section can be linearly varied by displacement of a control slider. The control valve is a flat seat valve with a movable diaphragm and fixed valve seat; the diaphragm is loaded in the opening direction by a spring with a flat characteristic. The spring is in an inner bore of the valve seat carrier. Mounting and setting of the individual control valves is simple.

Description

R. 17 15

1ο.οδ.1975 Kh / Sc

Attachment to
Patent and

Utility model registration

ROBERT BOSCH GMBH, 7 Stuttgart

Continuously working fuel injection system

The invention relates to a continuously operating fuel injection system for multi-cylinder, mixture-compressing, spark-ignited internal combustion engines, with a distributor device and metering valves which, in order to change their flow cross-section, determine the amount of fuel flowing to the injection valves in an axially adjustable manner _w which a control valve is switched on in the fuel flow downstream of the metering valves, the flow cross-section of which can be changed by a flexible member separating two chambers, with the pressure of the fuel downstream of the metering valve in the first chamber in the sense of opening the control valve to the flexible one Member acts while the second chamber is exposed to the pressure of the fuel upstream of the metering valve, and the

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Flow cross-section of the metering valves by moving a control slide is linearly changeable and a flat seat valve with a membrane as the control valve serves as a movable valve part and a fixed valve seat and in which the membrane in the opening direction of loaded by a spring with a flat characteristic.

In a known fuel injection system this Art, the control valves have a common membrane, which is installed as free of tension and buckling as possible should be to ensure an equal effect of the individual control valves. When assembling with the springs the control pressure valves there is a risk of tension and bulges occurring in the membrane. Furthermore, it is desirable that the distributor device can still be readjusted after assembly.

The invention is therefore based on the object of providing a fuel injection system with a voltage and Buckling-free membrane of the distributor device to be developed, with the individual control valves still being able to be readjusted after assembly is.

This object is achieved according to the invention in that the spring is arranged in an inner bore of the valve seat support.

An advantageous embodiment of the invention is such that the spring is through a hole in the inner hole of the valve seat support arranged adjusting bushing can be changed in its bias.

Another advantageous embodiment of the invention is that the spring with its facing away from the adjustment bushing

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End over a arranged in an overflow hole Transmission body acts on the membrane in the opening direction and the transmission body on the one hand a Has guide part for the spring and, on the other hand, radially arranged sliding surfaces, the transmission body has three radial sliding surfaces.

Two exemplary embodiments of the invention are shown in simplified form in the drawing and are described below described in more detail. Show it:

Fig '. 1 shows a fuel injection system with the first exemplary embodiment along the line I-I in FIG Fig. 2,

Fig. 2 shows a cross section along the line II-II in Fig. 1,

3 shows a section from the fuel injection system with the second embodiment,

Fig. 4 shows a detail from Fig. 3

In the distributor device according to the invention, a housing 1, an intermediate plate 2 and a base cover 3 are axially clamped together by screws 4. A metal foil 5 is clamped between housing Λ and intermediate plate 2, which serves as a membrane of membrane valves in the area of axial bores evenly distributed around the housing axis, dividing these into chambers 7 and 8. In this exemplary embodiment, it is a question of a distributor device for a four-cylinder engine, that is to say four diaphragm valves. In each of these valves, the membrane forms with a stationary ^^ er & x ^ sx ^ arranged in a plane with the membrane restraint

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The valve seat 9 is a precision part that is received by a valve seat carrier 1o that is inserted into the housing 1 is pressed in and serves as a connector for the lines 3o, which lead to the injection valves 31, of each of which only one or one is shown. The valve seat support 1o has an inner bore 12 with a arranged therein spring 11, which has a characteristic running as flat as possible and on the one hand to an adjusting bushing 41 pressed into the inner bore and on the other hand on the membrane 5. This coil spring 11 loads the membrane in the opening direction, see above that the diaphragm valve is open out of operation.

The sections of the chambers 8 located in the bottom cover are connected to one another by an annular channel 13 running successively through these sections, so that a flow of liquid can pass from the first via the second and third to the fourth section, but not from the first directly to the fourth section. A line J4 leads from a fuel tank 33 via a continuously delivering fuel pump 35 and a connection part 14 to said first section of the chambers 8. From the last, i.e. fourth section, a line 33 leads via a connection part 37 to a pressure holding valve 39 and from there back to the fuel tank 33

A bushing 17 is arranged in an axial bore 16 extending through the entire distributor device. These The bushing is prevented from shifting and twisting by an elastic sealing bushing 18, which can be made of rubber secured, for which purpose the sealing bushing is supported by a plug 19 against one between the base cover 3 and the intermediate plate 2 Disc 2o is axially compressed. This also ensures that no fuel between

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Liner on the one hand and housing and intermediate plate on the other hand can leak through.

In the bushing 17 slides axially against the force of a spring 15, a control slide 21, the one Has ring groove 22. In the bushing 17 there are longitudinal grooves 23, which are formed by exactly the same axially parallel longitudinal slots 24 (control slots) are connected to the inner bore of the liner. Depending on the position of the control spool 21 thus controls the annular groove 22 on a more or less long section of the control slots 24. In the liner are also radial bores 25ι a permanent connection between the annular groove 22 and one arranged in the base cover through the intermediate plate 2 and sealing bushing 18 and bushing 17 limited annular channel 26 establishes a permanent connection. From this annular channel 26 lead essentially radially extending channels 27 to the ring channel 13 »whereby the ring channel 26 with the chambers 8 of the diaphragm control valves connected is. The longitudinal grooves 23 of the liner 17 are connected to the chamber 7 of the diaphragm control valves via channels 28 connected to each diaphragm control valve a longitudinal groove 23 with its control slots 24 is assigned and wherein the chambers 7 of these diaphragm control valves are separated from one another.

The mode of operation of the device described is as follows: The fuel passes over from the fuel tank 33 the line 34, the continuously conveying pump 35 and the connecting part 14 into one of the chambers 8 of the diaphragm control valves and flows from there through the annular channel to the other chambers 8 of the further diaphragm control valves, until it then partly via the connector 37 »the Line 38 and the pressure holding valve 39 »that the pressure

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Determined in the distribution system, returned to the fuel tank 33. In this flow through, possible any air bubbles that collect under the membrane are washed away. The other part of the fuel flows via the channels 27, which are made so long that they bring about a certain calming of the fuel, to the annular channel 26. Certain pressure losses in the annular channel 13 cannot be achieved with such a flow avoid. But since it is a prerequisite for a uniform control that the pressure in the annular channel 26 is a mean value between the higher inlet pressure and the lower outlet pressure from the annular channel 13 or the chambers 8 of the Is membrane control valves, the channels 27 (Fig. 2) branch off at radially opposite points of the annular channel 13, wherein the distance of the first branch point from the inflow point of the fuel is as far away as that last point from where the fuel flows out.

Part of the fuel flows from this annular channel 26 via the radial bore 25 into the annular groove 22 of the control slide. The fuel flows from the annular groove 22 through the metered control slots 24 into the longitudinal grooves 23 and from there via the channel 28 into the chambers 7 of the diaphragm control valves.

Membranstexfigkeit and force of the spring 11 are designed so that when changing an intended pressure gradient between the two chambers 7 and 8 of the membrane control valves is the flow cross-section between the membrane and valve seat changes until this pressure drop is reached again. With the present flat seat valve this is achieved in an extremely short time, since the flow cross-section is already at a low stroke of the membrane i The spring force, on the other hand, is only changed slightly due to this small stroke, so that the control can work very precisely, i.e. the pressure gradient is independent of the flow rates

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is almost Vonstant.

In the arrangement according to the invention of the spring 11 within the valve seat support 1o, not only is the springless Assembly of the distribution device possible and thus tension-free and dent-free installation of the membrane, rather, the spring preload 11 can be readjusted at any time without dismantling.

The embodiment shown in Fig. 3 and 4 of Invention is characterized in that the spring 11 with its in the inner bore 12 of the valve seat support 1o pressed-in adjusting bushing 41 at the end facing away from the membrane 5 via a transmission body 42, wherein the spring 11 of a guide part 45 leads GE and the transmission body 42 radial sliding surfaces 44 has, by means of which the transmission body slide in an overflow bore 45 of the valve seat 9 can. The number of sliding surfaces is at least three, but they can also be chosen to be larger.

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Claims (5)

"715 Expectations Continuously operating fuel injection system for multi-cylinder internal mixture-compressing, spark-ignited internal combustion engines, with a distributor device and metering valves, the axially adjustable together determine the Indians their throughflow flowing to the injectors amount of fuel, wherein at each metering valve as constant as possible pressure drop prevails in _w the the the fuel stream downstream Metering valves each have a control valve, which can be changed by a flexible member separating two chambers in the Durdisfcrömquehre, the pressure of the fuel downstream of the metering valve in the first chamber acting on the flexible member in the sense of opening the control valve, while the second chamber is exposed to the fuel pressure prevailing upstream of the metering valve and the flow cross section of the metering valves can be changed linearly by moving a control slide and as S control valve is a flat seat valve with a membrane as a movable valve part and a fixed valve seat and in which the membrane is loaded in the opening direction by a spring with flat characteristics, characterized in that the spring (11) 509810/061 1 1 7 I 5 in an inner bore C12) of the valve seat support (io) is arranged. 2. Fuel injection system according to claim 1, characterized in that the spring (11) by one in the Inner bore C12) of the valve seat support (1o) Adjusting socketC ^ i) is changeable in its preload. 3. Fuel injection system according to claim 2, characterized characterized in that the spring (11) with its end facing away from the adjustment bushing C 4-1) has an in one Transfer body arranged overflow hole C45) (42) the membrane C 5) acted upon in the opening direction. 4.. Fuel injection system according to claim 3j thereby characterized in that the transmission body C ^ -2 on the one hand a guide part (H-3) for the spring C11) and
on the other hand, has radially arranged sliding surfaces C ^). 5. Fuel injection system according to Claim 4, characterized in that the transmission body C4-2) has three radial sliding surfaces C44). ■■ ·, 509810/061 1 4ο Blank page