GB2221251A - Electromagnetic i.c. engine fuel injector - Google Patents

Description

2221251 1 ELECTROMAGNETIC FUEL METERING AND ATOMIZING VALVE FEATURING A

FLAT PLUGGING MEMBER The present invention relates to an electromagnetic fuel metering and atomizing valve for an internal combustion engine fuel supply device.

Known valves of the aforementioned type substantially comprise a casing housing an annular coil and a tubular core located inside the same; and a nozzle secured to the casing and presenting at least a fuel supply hole. Said valves also comprise a plugging member designed to move between a first and second position wherein said supply hole is closed and opened respectively, and which is integral with a tubular anchor activated by an electromagnet. The plugging member comprises a plate having a substantially flat surface designed to rest on a seat on the nozzle and so close the fuel supply hole. The plugging member is secured to the anchor. the inner surface of which mates in sliding mariner with the outer surface of a guide coupling secured 2 1 to and projecting axially from said core.

The core is usually fitted' with an annular stop member, usually made of non-magnetic material, for arresting the anchor when the plugging member moves into the limit stop position corresponding to maximum opening of the valve, and so prevent direct contact between the anchog. and core and enable an increase in valve operating rate.

Valves of the aforementioned type present numerous 10 drawbacks.

Firstly, by virtue of being determined by the anchor contacting said nonmagnetic stop member, the valve opening stroke is not consistently accurate. Due to difficulties in accurately positioning the stop member in relation to the core, which is what determines the valve opening stroke, this may prove inconsistent or vary over the working life of the valve. Moreover, the opening stroke of the plugging member is difficult to determine accurately at the valve - assembly stage; while the complex operations involved for manufacturing and assembling valves featuring said stop members result in high production cost of the valve as a whole.

The operating rate of such valvess is also limited due t o the overall weight of the anchor-plugging-member assembly, and particularly the weight of the metal plate on the plugging member, the dynamic effect of which seriously impairs operation-of the valve.

The sealing performance of such a plugging member, i.e. featuring a flat active surface -mating with a flat surface on the nozzle for closing the fuel supply 1 hole, is invariably poor, particularly when the pressureexerted by the spring normally securing the plugging member in the closed position is fairly weak.

Finally, manufacture of the plugging member and nozzle 5 featuring said plate supporting seat involves mechanical machining to extremely close tolerances and special surface treatment for ensuring a good finish on the mating surfaces, and sufficient hardness of the component parts on which said surfaces are formed.

The aim of the present invention is to provide an electromagnetic fuel metering and atomizing valve designed to overcome the drawbacks typically associated with known valves of the aforementioned type.

One aim of the present invention, therefore, is to provide a valve of the aforementioned type enabling the valve opening stroke to be regulated accurately and maintained substantially constant throughout the working life of the valve.

A further aim of the present invention is to provide a valve featuring a relatively lightweight anchor-plug- assembly, thus enabling a considerable increase in valve operating rate.

A further aim of the present invention is to provide enabling excellent sealing between the plugmember and respective seat on the nozzle, and is relatively cheap to produce by virtue of involving no complex closetolerance machining or assembly operations.

With these aims in view, according to the present inven30 tion, there is provided an electromagnetic fuel metering ging-member f= a valve ging which 1 and atomizing valve for an internal combustion engine fuel supply device, said valve substantially comprising a casing housing an annular coil and a tubular core located inside the a fuel supply _hole and member comprising surface designed same; a nozzle having at least secured to. said casing; and a plugging member designed to move between a first and second position wherein said hole is respectively closed and opened, and which is integral with a tubular anchor activated by an electromagnet; said plugging a plate having a substantially flat to rest on a seat on said nozzle and so close said hole, and which is secured to said anchor, the inner the outer surface of which mates in sliding manner with surface of a guide coupling secured to and projecting axially from said core; characterised by the fact that the axial leng-th of the portion of said coupling projecting axially from said core and the axial length of said tubular anchor are so selected that, when said plugging member is in said second posi- tion, said plate rests on the end edge of said coupling portion, so as to arrest the opening movement of said plugging member, and so that said anchor is maintained a given distance from said core.

The invention will be described by way of example with 25 reference to the accompanying drawings, in, which Fig.1 shows a partially sectioned side view of the valve according to the present invention; Fig.s 2 and 3 show partial sections of the bottom of the valve in the closed and open positions respectively.

The valve according to the present invention substantially 1 1 t comprises a casing 1 fitted at the front with an injection nozzle 2 having a fuel supply hole 3 controlled by a mobile plugging member 4. As shown clearly in Fig.2, nozzle 2 is secured to casing 1 by turning the annular end edge 5 of casing 1 about an annular collar 6 on nozzle 2. A spacer 8 is conveniently provided between nozzle 2 and shoulder 7 of casing 1.

Nozzle 2 presents a bush 9 which, together with nozzle 2 and an end retaining ring 10, defines an annular cavity 11 housing a sealing ring 12 for sealing nozzle 2 inside its seat (not shown).

Casing 1 houses a substantially annular coil 13 and a tubular core 14 integral with casing 1 and located coaxially inside coil 13. A coupling 16 is force-fittt-d on to cylindrical surface 15 of core 14; presents a portion 17 projecting axially from core 14; and acts as a guide member for tubular mobile anchor 18. Slots 10a are conveniently formed on coupling 16.

The bottom of anchor 18 is fitted with plugging member 4, which is substantially in the form of a plate having a flat bottom surface 19 designed to rest on a seat defining the top of nozzle 2.

As shown clearly in the drawing, plugging member 4 is defined by a conical surface portion 21 about which end edge 24 of anchor 18 is permanently deformed. A pin 25 conveniently projects from the top of plate 4, and a washer 26 is fitted between plate 4 and a shoulder 27 formed on anchor 18.

According to the present invention, plate 4 is formed 30 from highly deformable material, conveniently synthetic 1 1 1 and preferably thermoplastic whereas washer 26 is made of hard metal,e.g. suitable alloy steel.' According to the present invention, the axial length L1 of coupling portion 17 projecting axially from core 14 is always greater than the axial distance L2 between the contact surface 28 of washer 26 and the top end surface 29 of anchor 18. Thus, when plugging member 4 is in the topmost limit stop position corresponding to maximum opening of supply hole 3 (Fig.3), contact surface 28 of washer 26 contacts bottom end edge 30 of coupling 16, so as to leave an air gap G (Fig.3) between top surface 29 of anchor 18 and'opposite surface 31 of core 14.

Anchor 18 and core 14 conveniently present radial holes 34 enabling fuel to flow from axial hole 35 in coupling 16 into an annular chamber 36 communicating with fuel supply hole 3.

The flat bottom surface of plate 4 conveniently presents a series of projections 37 substantially coaxial with hole 3 as shown in the larger-scale detail in Fig.2. Due to the highly deformable nature of the material of plate 4, during operation of the valve, said projections 37 provide for effective labyrinth sealing of scat 20 of nozzle 2.

Seat 20 is conveniently 38.

The height 0.5 mm.

The valve as follows.

defined by an annular cavity of projections 37 is according to the preferably less than present invention operates L 1 1 Fuel is fed into annular chamber 36 through axial hole 35, slots 16a and radial holes 34 formed on anchor 18 and core 14. Plate 4 is normally secured on scat 20 by a helical spring 39 resting on washer 26. When magnet 13 is energized, the magnetic flux established substantially between anchor 18 and core 14 produces an electromagnetic force which draws anchor 18 towards core 14 against the action of spring 39. The plugging member thus moves into the topmost limit position wherein top surface 28 of washer 26 rests against edge 30 of coupling 16 (Fig.3) and fuel is supplied from chamber 36 into outlet hole 3.

With the plugging member in said topmost limit position, an air gap G (Fig.3) is left as required between surface 29 of anchor 18 and surface 31 of core 14.

When electromagnet 13 is de-energized, spring 39 restores the plugging member to the closed position shown in Fig.2.

On the valve according to the present invention, therefore, the plugging member is arrested in the topmost limit stop position by washer 26 contacting coupling 16. thus providing for a highly accurate opening stroke by virtue of the highly accurate finish of the contact parts involved and the precise thickness of washer 26. Moreover, by virtue of the small contact surface provided between end edge 30 of coupling 16 and washer 26, the residual magnetism holding the surfaces of the same together is poor, thus enabling spring 39 to return position.

the plugging member rapidly to the closed Also, the hardness of the material of washer 1 1 8 - 1 26 is such that wear on washer 26 is negligible.

By virtue of the light weight of the assembly consist ing of anchor 18, plate 4 and washer 26., the dynamic effect of the same is practically negligible, thus enabling the valve to be operated at an extremely fast rate.

Projections 37 on plate 4 provide for effective sealing between seat 20 and surface 19 of plate 4. In fact, the small contact surface between projections 37 and surface 19 provides for extremely high contact pressure and, consequently, excellent sealing, even in the event of very little pressure being exerted by spring 39. Sealing is further improved by the labyrinth effect of projections 37 and the deformable nature of the material of plate 4.

Finally, the valve according to the present invention may be manufactured and assembled cheaply by virtue of eliminating complex close-tolerance machining and assembly operations.

To those skilled in the art it will be clear that changes may be made to the valve as described and illustrated herein- without, however, departing from the scope of the present invention.

W

Claims (1)

1) - An electromagnetic fuel metering and atomizing valve for an internal combustion engine fuel supply device, said valve substantially comprising a casing housing an annular coil located and a tubular'core inside the same; a nozzle having at least a fuel supply hole and secured to said casing; and a plugging member designed to move between a first and second position wherein said hole respectively closed and opened, and with a tubular anchor activated by an electromag net; said plugging member comprising a plate having a substantially flat surface designed to rest on a seat on said nozzle and so close said hole the inner with the to and terised said anchor member on the so as member, a given 2) A the fact is which is inteffral and which is secured to said anchor 3 surface of which mates in slidingmanner outer surface of a guide coupling secured projecting axially from said core charac- by the fact that the axial length of the portion of said coupling projecting axially from and the axial selected that is end length of said tubular are so, when said plugging in said second position, said plate rests edge to arrest the and so that distance from said core valve as claimed that said plate of said coupling portion 3 opening movement of said plugging said anchor is maintained in Claim 1, characterised by is made of synthetic mate- - 10 i rial, and provision is made between said plate and said end edge for a contact member of said coupling portion made of hard metal and having a contact surface designed to reston said end edge when said plugging member is in said second position.

3) - A valve as claimed in Claim 1 or 2, characterised by the fact that the axial length of said coupling portion projecting from said core is greater than the distance between the top edge of said anchor and said contact surface of said washer 4) - A valve as claimed in Claim 1, 2 or 3, character ised by the fact that said plate comprises an axial pin and said contact member consists of a washer in which is fitted said pin; said plate and said washer being locked between an annular shoulder and a downturned end edge of said anchor 5) - A valve as claimed in Claim 3 or 4, characterised by the fact that said plate is made of thermoplastic material.

6) - A valve as claimed in one of the foregoing Claims, characterised by the fact that the flat surface of said plate designed to rest on said seat of said nozzle presents projections substan- tially coaxial with said fuel supply hole and design ed., during operation of the valve, to provide for fuel scaling between said surface and said seat 7) - A valve as claimed in Claim 6. characterised by 1 1 h the fact that the height of said projections less than 0.5 mm. 8) - An electromagnetic fuel metering and atomizing valve, substantially as described and illustrated herein with reference to the accompanying drawings.

Published 1990 at The Patent Office. State House. 66 71 High Holborn. London WC1R4TP. Further copies maybe obtainedfrom The Patent Office Sales Branch. St Marv Cray. Orpington. Kent BR5 3Rr Printed by Maltiplex teeb=ques ltd. St Mary Cray. Kent. Con. 187