GB2144060A - Electromagnetic valve assembly - Google Patents

Abstract

The assembly method comprises forming a hollow body 10 having an inwardly extending end portion 14 the outer end surface of which forms a pole surface. Another pole surface is formed by the end of a core stem 17 which has a flange 18 which can be located in the hollow body. A winding 20 surrounds the stem and the latter is located relative to the pole surface on the body by using a jig and then the flange 18 is secured as by welding within the body prior to assembling the remaining parts of the valve assembly. <IMAGE>

Description

SPECIFICATION Valve assembly This invention relates to a method of manufacturing an electromagnetically operable valve more particularly a plate valve for incorporation in a petrol injector for an internal combustion engine.

An internal combustion engine may be provided with a number of injectors and it is necessary in order to achieve smooth running of the engine, that the operating characterstics of the injectors should be substantially identical. The injector comprises a number of parts which must be secured together and whereas it may be possible to secure the parts together using screw threads this method of connecting the parts is expensive. It is preferable therefore to use a cheaper technique such as welding.

One of the most critical dimensions in an electromagnetically operable valve is the air gap or gaps which exists between the armature and the pole pieces when the solenoid winding is de-energized. Any variation of the size of the gap or gaps between valves will bring about considerable variation in the operating characteristics of the valves. Where the parts of the valve are secured together by means of screw threads it is possible to adjust the gap or gaps using shims but where the parts are secured together as by welding or metal deformation this is not possible. It is possible to provide location faces in the design of the valve but these have to be accurately positioned and add to the cost of production. Moreover, during the welding process or metal deformation process distortion can occur so that the in-built accuracy is lost.

The object of the present invention is to provide a method of manufacturing an electromagnetically operable valve in a simple and convenient form.

According to the invention a method of manufacturing an electromagnetically operated valve comprises forming a hollow body having an inwardly extending portion one end surface of which defines an annular pole face about an opening in said inwardly extending portion, forming a flanged core member, mounting a winding assembly about said core member, locating said core member and winding assembly within said hollow body with the flange in sliding engagement with the internal surface of the body and the core member extending into said opening, the end surface of said core member defining a second pole face, engaging a jig with said pole faces to set the core member within the body, securing said flange to the body, removing the jig, assembling an armature assembly to the body using said annular pole face as a reference surface and securing said armature assembly to the body.

An example of a method of manufacturing an electromagnetically operated valve will now be described with reference to the accompanying drawing which is a sectional side elevation of an assembled petrol injector for an internal combustion engine.

Referring to the drawing the injector comprises a body part which is formed in two parts 10, 11. The part 10 of the body is a cup shaped form having a side wall 1 3 and a base wall 14. The body part 10 is formed from magnetizeable material and has a groove formed in its outer peripheral surface in which is located a sealing ring 1 5 which in use forms a fuel tight seal with the wall of a bore formed in the inlet manifold of the associated engine.

In the base wall 14 of the body part 10 is formed an aperture 1 6 and extending within the aperture is a core member in the form of a hollow stem 1 7 formed from magnetizeable material. The stem is provided with a collar 18 which is a snug fit within the open end of the body part 10 and can be secured thereto by welding. Surrounding the stem 1 7 is a former 1 9 conveniently formed from plastics material, about which is wound a winding 20.

The ends of the winding are connected to a pair of terminal posts 21 which are moulded into the former and which extend through apertures in the collar 1 8. The winding 20 is sealed against the fuel by a first sealing ring 22 located between the former and the base wall 14 and a second sealing ring 23 located between the former and the stem adjacent the collar.

The stem 1 7 extends beyond the collar and within the stem is a plug 24 which forms an abutment for one end of a coiled compression spring 25 which extends within the stem. The plug 24 is a push fit within the stem and forms a fuel tight seal with the wall thereof.

The body part 11 is also of cup shaped form but has a shorter side wall 26 than that of the body part 10. In its base wall 27 is formed a diverging outlet 28 and about a reduced portion of the base wall is located a sealing ring 29 which co-operates with the wall of the bore in the manifold in which the injector is located. The bore in the manifold intermediate the sealings rings 1 5 and 29 defines a fuel inlet passage connected to a source of fuel under pressure.

The body part 11 forms a housing of a valve assembly and located against the base wall of the body part 11 is a valve seat member 30 in which is formed an outlet orifice 31. A sealing ring 32 is located in a groove in the base wall so as to establish a fuel tight seal between the base wall and the seat member 30. Located against the inner face of the valve seat member is an annular guide member 33 which guides the movement of a disc like valve member 34 formed from magnetizeable material. The valve mem ber is biased towards the seat member by the aforesaid spring, the valve member being provided with a recess to locate the end of the spring.The seat member on its face presented to the valve member defines a pair of spaced annular ribs, the inner rib 35 forms a seating for the valve member and the outer rib 36 acts to minimize the risk of the valve member tilting as it moves into contact with the seating formed by the inner rib.

The valve member is provided with a plurality of through holes 37 which lie outside the inner rib 35 and these holes in the particular example allow fuel flow from a space 38 through the outlet orifice when the valve member is lifted away from the inner rib 35.

The body part 11 is secured to the body part 10 by welding indicated at 39 and to provide accurate lateral location of the body parts a tongue and groove connection is provided. In the example the body part 10 is provided with an annular groove 39A and the body part 11 with an annular tongue or rib 40. Moreover, before the parts are secured together a non magnetic washer 41 is positioned between the guide member 33 and the adjacent surface of the base wall 14.

Fuel is communicated to the space 38 from the exterior of the body by way of a pair or more slots 42 which are formed in the base wall 14 and the fuel entering the slots is filtered by an annular filter 43 which conveniently is formed from plastics material and which is engaged about the body. The filter has openings which are covered by a filter net.

In operation, when the winding is supplied with electric current, the base wall 14 and the stem are polarized to opposite magnetic polarity and the valve member 34 is lifted against the action of the spring 25 away from the rib 35 to permit fuel flow through the outlet orifice 31, the fuel passing through the holes 37 in the valve member. When the solenoid winding is de-energised the valve member returns into contact with the rib to halt the flow of fuel under the action of the spring, the washer 41 acting to minimize the possibility of the valve member "sticking" due to remanent magnetic flux.

The slots 42 are radially disposed, however, they may be tangentially disposed to impart swirl to the fuel entering the space 38.

The outer end face of the base wall 14 of the body part 10 and the end face of the stem 1 7 form the pole faces of the electromagnet and it is necessary to ensure that these faces are accurately set relative to each other and also the the valve member 34. An additional complication is the thickness of the washer 41. The end face of the base wall 14 forms a reference surface against which the guide member 33 and the valve seat member 30 are located, the seat member in the closed position of the valve member providing location for the valve member.

The first stage of assembly after manufacture of the various components is to assemble the core member or stem 1 7 within the body part 10, the winding and the various seal members being in position. Next a jig is located against the reference surface defined by the base wall 14. The end of the stem is then moved into contact with the jig so as to set the pole faces correctly relative to each other. The welding of the flange 1 8 to the wall 1 3 of the body is then carried out. With the pole faces in the correct relative position the valve assembly including the valve seat member, the guide member, the washer and the valve member can be assembled in the body part 11 and secured in position.

Conveniently the jig has a central recess to locate the end of the stem, the base wall of the recess being such that the end of the stem projects beyond the reference surface but lies behind the surface of the washer. In this manner when in use the winding is energised the valve member will move into engagement with the washer but will be spaced from the end of the stem.

The jig also defines an annular rib which locates in the groove 39A. The recess in the jig also acts to centralise the stem 1 7.

Claims (5)

1. A method of manufacturing an electromagnetically operated valve comprises forming a hollow body having an inwardly extending portion one end surface of which defines an annular pole face about an opening in said inwardly extending portion, forming a flanged core member, mounting a winding assembly about said core member, locating said core member and winding assembly within said hollow body with the flange in sliding engagement with the internal surface of the body and the core member extending into said opening, the end surface of said core member defining a second pole face, engaging a jig with said pole faces to set the core member within the body, securing said flange to the body, removing the jig, assembling an armature assembly to the body using said annular pole face as a reference surface and securing said armature assembly to the body.

2. A method according to Claim 1 including the step of welding said flanges to the body.

3. A method according to Claim 1 or Claim 2 including the step of locating a body part of said valve assembly on said reference surface by means of a tongue and groove connection.

4. An electromagnetically operable valve whenever manufactured in accordance with the methods of any one of the preceding claims.

5. A method of manufacturing an electromagnetically operable valve substantially as hereinbefore described.