GB2192427A - Stroke and spring force adjustment in an electromagnetic fuel-injection valve - Google Patents

Abstract

The bore 8 in the rod 2 which determines the stroke of the valve 12 permits permanent deformation of the rod when the soft-iron housing 1 is squeezed inwardly to fix the rod in the desired position and when the bush 9 is squeezed inwardly after the desired valve biasing force has been set by bush positioning. <IMAGE>

Description

SPECIFICATION InterrnitteritiVatuated eecf:amagrreticfuel-injec- tion valve The invention relates to an intermittently actuated eiectromagneticfuel-injection valve ofthe kind described in the preamble ofthe claim.

Fuel-injection valves ofthis kind are known. In constructing these valves two problems arise. In the first place the spring force acting to close the valve must be sufficientto close it tight and reliably when the exciter current for the electromagnetic coil is switched off, but the spring force must not be so great that it prevents the valve from functioning at high frequencies.

The second problem isthatthe lifting strokeofthe valve head must be precisely adjusted to ensure that exactly the right quantity of fuel is injected each time.

To adjustthe lifting stroke it is known to construct the injection nozzle, which forms the valve-seat, of sheet metal, which is permanently deformed, during manufacture ofthe valve, until thedesired valve-head stroke is obtained. For purposes of adjusting the spring force acting to close the valve, it is known to equip the valve with a central tube in which an element slides axially, the position of the element determining the spring force.

When the adjustment has been made it is necessary to secure the element reliably in place. Various methods are known for ensuring this. If the central tube also functions as the magnet core, againstwhose free end the moving armature strokes at the top of its stroke, it canhappen that after a long period of working the armature becomes tilted due to repeated off-centre impacts, with the resultthatthevalve no longercloses tight.

The intention in the present invention, starting from a fuel-injection valve of the kind described at the beginning, isto constructthevalve in such a way that both spring force and valve-head stroke can be adjusted, precisely and permanently, by a simple method.

The problem is solved bythe provision of an intermittently actuated electromagnetic fuel-injection valve for mixture-compressing internal combustion engines, with a fuel-injection nozzle controlled buy a valve-head urged to close a valve seat by a coil spring, the spring-force being adjustable,the valve-head being lifted off its seat by the magnetic field of an electromagnetic coil with a soft-iron core and a soft-iron housing, the centrally positioned coil-spring enclosing a round-section rod equipped with an axially adjustable thrust-bush which abuts one end of the spring, and wherein the rod has an axial bore whose diåmeterand depth are suchthatthe rod can be permanently deformed, at least in the regiopiof the thrust-bush,the permanent deformation, once effected, ensuring thatth.e partsremaiin ,positiively locked together From the German 0if-entegungssohriit-3 677 it is known to squeeze a thrust-bush so thatthe material flows into indentations intheoutersurfaceofa valve-needle, in order to lockthese parts together. But as the material of construction ofthethrust-bush is considerably resilient in the squeezing region the permanent locking effect obtained must be regarded as doubtful.

One example of the invention is represented diagrammatically and byway of example, in theaccompanying drawing will now be described in greater detail.

An electromagnetic coil 4 is fixed in the interior of a hollow soft-iron housing 3 which has an upper neck 1.

The housing 3, with its upper neck 1, can be made, for example, by impact extrusion orthe like. The coil 4 is supplied with electric currnntover conductors 5.

Contained within the upper neck 1 of the housing 3 there is a central rod 2 which can be adjusted in position axially in the neck 1, as will be described further below.

Liquid fuel flowing inwards under pressure through an inlet port 6 flows overthe surface ofthe coil 4, in the annular space between the coil 4 and the soft-iron housing 3, cooling the coil 4, excess fuel leaving through outlet ports 7.

An axially mobile valve-head 11 has a lower nose cooperating with a valve-seat 12 located in a fuel- injection nozzle 13, for controlling theflow of fuel injected into the engine, the nozzle 13 being fixed to the lower end ofthe hollow soft-iron housing 3.

The rod 2 has, in its upper portion, an internal axial blind bore 8 whose purposewill be described further below. And mounted on its middle portion the rod 2 has a thrust-bush 9 which is adjustable in position axially on the rod 2 buy a method which will be described further below. The thrust-bush 9 applies downwards th rust to the upper end of a compression valve-spring 10, whose lower end thrusts the valve head 11 downwa rds towa rds its seat 1 2; In this example ofthe invention, the lifting stroke of the valve-head 11 is limited by contact between the domed surface of its upper end andthe-lower--endface ofthe rod 2.Alternatively, if desired,the valve-head 11 can take the form of a plate,a ball,a half-sphereorthe- like.

During manufacture ofthe fuel-injection valve, other parts, such as 14,15,16 are attached tothe parts described above, after completing the adjustments which will now be described.

When the fuel-injection valve has been assembled to form the partly completed structure-described above,the stroke of the valve-head 11 is first of all adjusted. Forthis purpose the coil 4 is continuously excited by electric current, to lift the valve-head 11 form its seat 12, and fuel is allowed to flow con tinuously under pressure outthrough the injection nozzle 13.

A tool is then used to move the central rod 2, which in this example forms the magnet core, downwards until fuel flows out ofthe injection nozzle 13 at the desired rate offlow. Then a squeezing tool is used to squeeze the upper neck 1 of the soft-iron housing 3 radially inwards,Jockingthe neck 1 securely to the upper portion ofthe rod-2. The central blind bore 8 in the upper portion ofthe rod 2 is dimensioned, in both diameter and length,'ro allowtherod 2 to be given the necessary amountofpermanent deformation to ensure that the parts 1 and 2 aresecurely locked together by the squeezing.

Afterthat, the second adjustment is made. This is to adjustthe spring force applied bythe-valve-spring 10 in thrusting the valve-head 11-downwards towards its seat 12.

In making this second adjustment the valve is operated dynamically, i.e.the coil 4 is excited with electric current intermittently at a specified frequency whilefuel is supplied under pressure th rough the inlet port 6. The spring forces adjusted by shifting the thrust-bush 9 in position axially along the rod 2. To facilitate the operation the valve has at least four excess-fuel outlet ports 7, arranged in opposite pairs.

With the help of a firsttool inserted through a first opposite pair of ports 7 the thrust-bush 9 is adjusted axially in position on the rod 2until fuel flows out of the injection nozzle 13 atthe desired rate of flow. With the thrust-bush held in this poskionbyth6 first tool, a second, squeezing tool is insertedthrnugh a second opposite pair of ports 7, set at 90 relative to the first pair, and the thrust-bush 9 is squeezed as asto lockthe parts9 and 2 securelytogether.The rod 2 can, if desired, have external serrationsto give a bettergrip.

Claims (3)

1. An intermittently actuated electromagneticfuel- injection valve for mixture-compressing internal combustion engines, with a fuel-injection nozzle controlled by a valve-head urged to close a valve seat by a coilspring, the spring-force being adjustable, the valve-head being lifted off its seat bythe magnetic field of an electromagnetic coil with a soft-iron core and a soft-iron housing, the centrally positioned coil-spring enclosing a round-section rod equipped with an axially adjustable thrust-bush which abuts one end ofthespring, characterisedinthatthe rod (2) has an axial bore whose diameter and depth are such that the rod (2) can be permanently deformed, at least in the region ofthethrust-bush (9).

2. An intermittently actuated electromag netic fuel- injection valve for mixture-compressing internal combustion engines, substantially as hereinbefore described with reference to the accompanying drawing.

3. An electromagneticfuel-injection valve sub stantiallyas hereinbefore describedwith referenceto the accompanying drawings.