FR2633333A1 - ELECTROMAGNETIC FUEL DOSING AND SPRAYING VALVE COMPRISING A FLAT SHUTTER ELEMENT - Google Patents

Abstract

Valve comprising a housing 1 housing an annular coil 13 and a core 14 located inside the latter; a nozzle 2 in which is formed at least one fuel supply hole 3; and a movable closure element 4 coming in one piece with a tubular armature 18 activated by an electromagnet. The closure element 4 comprises a plate having a flat surface 19 designed to rest on a seat 20 located on the nozzle 2 and to thereby seal the fuel supply hole 3, and which is fixed to the armature 18, the inner surface 15 of which is slidably adapted to the outer surface of a guide coupling 16. The axial length of the coupling part 17 projecting axially relative to the core 14 and the axial length of the armature 18 being chosen such that when the closure element 4 is in the open position, the plate remains on the end edge of the coupling 16, so as to block the opening movement of the element shutter 4.

Description

Electromagnetic fuel metering and spraying valve

  The invention relates to an electromagnetic fuel metering and spraying valve for a fuel supply device of an internal combustion engine. Known valves of the type mentioned above essentially comprise a housing housing an annular coil and a tubular core situated inside the latter; and a nozzle attached to the housing and having at least one fuel supply hole. Said valves also include a closure member adapted to move between a first and a second position within said supply hole, which is respectively closed and open, and which is in one

  part with a tubular armature activated by an electromagnet.

  The closure member includes a plate having a substantially flat surface adapted to rest on a seat on said nozzle and thereby seal said fuel supply hole. The closure element is fixed to the armature, the inner surface of which slidably adapts to the outer surface of a guide coupling fixed to and projecting axially.

on said core.

  The core is usually placed in an annular stop element which is usually made of a non-magnetic material, in order to block the armature when the obturation element arrives in limit stop position, corresponding to the maximum opening. of the valve, and to avoid direct contact between the armature and the core and allow an increased operating rate on the part of the valve. Valves of the type indicated above have

many disadvantages.

  Firstly, by being determined by the contact of the armature with said non-magnetic stop element, the opening stroke of the valve is not really precise. Due to the difficulties of ensuring correct positioning of the stop member relative to the core, which is what determines the valve opening stroke, this may become incompatible or vary over the life of the valve. In addition, the opening stroke of the closure element is difficult to determine precisely at the valve assembly stage; because the complex operations involved in manufacturing and assembling valves with stop elements

  result in a high overall production cost of the valve.

  The operating speed of these valves is also

  limited due to the general weight of the induced assembly-

  closure element, and in particular the weight of the metal plate and the closure element, the dynamic effect of the latter affecting the operation of the valve; The quality of the sealing of such a sealing element, that is to say consisting of an active flat surface adapting to a flat surface on the nozzle for closing the fuel supply hole is invariably low, especially if the pressure exerted by the spring normally fixing the element

  shutter in the closed position is really low.

  Finally, the manufacture of the obturation element and of the nozzle provided with said seat supporting the plate involves mechanical machining to extremely tight tolerances and a special surface treatment to ensure a good finish on the surfaces adapting to one other, and sufficient hardness of the components on which said surfaces

are formed.

  The object of the present invention is to provide a

  electromagnetic metering and spraying valve.

  arranged to avoid the typically associated disadvantages

  to known valves of the above-mentioned type.

  An object of the present invention is therefore to provide a valve of the type indicated above, allow the opening stroke of the valve to be precisely adjusted and to be kept substantially constant

  during the life of the valve.

  Another object of the present invention is to provide a valve provided with an armature-shutter assembly of relatively low weight, thereby allowing a significant increase in the speed of

valve operation.

  Another object of the present invention is to provide a valve allowing an excellent seal between the closure element and the respective seat on the nozzle, and which is relatively inexpensive to produce by not implementing any complex machining or operation

  tight tolerances.

  To achieve these goals, there is provided, according to the present invention, an electromagnetic metering and spraying valve for a fuel supply device of an internal combustion engine, said valve essentially comprising a housing housing an annular coil and a tubular core. located inside the latter; a nozzle having at least one fuel supply hole and fixed to said housing; and a movable closure element adapted to move between a first and a second position inside said hole which is respectively closed and open, and come in one piece with a tubular armature activated by an electromagnet; said shutter member comprises a plate having a substantially planar surface adapted to rest on a seat located on said nozzle and to thereby seal said fuel supply hole, and which is fixed to said armature whose interior surface fits slidably to the outer surface of a guide coupling fixed to, and axially projecting from, said core; characterized in that the axial length of the portion of said coupling projecting axially from said core and the axial length of said tubular armature are chosen such that, when the closure element is in said second position, said plate remains on the end edge of said coupling part, so as to block the opening movement of said closure element and so that said armature is kept at a

determined distance from said core.

  Various other features and benefits of

  device the invention will emerge from the description

  detailed below. An embodiment of the invention is shown by way of nonlimiting example in the appended drawings in which: FIG. 1 represents a partially cut side view of the valve according to the present invention; Figures 2 and 3 show partial sections of the bottom of the valve in position respectively

closed and open.

  The valve according to the present invention comprises

  essentially a housing 1 provided on the front of a.

  injection nozzle 2 having a fuel supply hole 3, controlled by a movable closure element 4. As clearly shown in FIG. 2, the nozzle 2 is fixed to the housing 1 by turning the annular end edge 5 of the case 1 around an annular collar 6 located on the nozzle 2. A spacer 8 is suitably placed between the nozzle 2 and the shoulder 7 of the

housing 1.

  The nozzle 2 has a sleeve 9 which, together with the nozzle 2 and an end retaining ring 10, defines an annular cavity 11 housing a sealing ring 12 intended to seal the nozzle 2 at

  the interior of its seat (not shown).

  The housing 1 houses a substantially annular coil 13 and a core 14 integrally formed with the housing 1 and which is located coaxially inside the coil 13. A coupling 16 is forcibly mounted on the cylindrical surface 15 of the core 14; it has a portion 17 axially projecting from the core 14; and acts as a guide for a movable armature 18. The slots 16a are suitably formed on the top of

nozzle 2.

  As clearly shown in the drawings, the closure element 4 is defined by a conical surface portion 21 around which the end edge 24 of the armature 18 is permanently deformed. A pin adequately projecting from the top of the plate 4 and a washer 26 are mounted between the

  plate 4 and a shoulder 27 formed on the armature 18.

  According to the present invention, the plate 4 is formed from a highly deformable material, which is suitably a plastic and preferably thermoplastic, while the washer 26 is made

  hard metal, i.e. suitable steel.

  According to the present invention, the axial length L1 of the coupling part 17 axially projecting from the core 14 is always greater than the axial distance L2 between the contact surface 28 of the washer 26

  and the upper end surface 2 of the armature 18.

  Thus, when the closure element 4 is placed in the limit stop position corresponding to the maximum opening of the supply hole 3 (FIG. 31, the contact surface 28 of the washer 26 brings the edge into contact. end 30 of the coupling 16, so as to leave a gap G (FIG. 3) between the top surface 29 of the armature 18 and the opposite surface 31 of the core 14. The armature 18 and the core 14 suitably have radial holes 34 allowing fuel to flow from the axial hole 35, located in the coupling 16, in the annular chamber 36 communicating with the fuel supply hole 3. The flat bottom surface of the plate 4 suitably has a series of projections 37 substantially coaxial with the hole 3, as shown in the detail drawn on a larger scale in FIG. 2. Due to the highly deformable nature of the material of the plate 4, during the operation of the valve, said projections 37 constitute an effective labyrinth insulating so

  seals the seat 20 of the nozzle 2.

  The seat 20 is adequately defined by a

annular cavity 38.

  The height of the projections 37 is preferably

less than 0.5 mm.

  The valve according to the present invention operates

as following.

  The fuel is supplied in an annular chamber 36 by the axial hole 35, the slots 16a and the radial holes 34 formed on the armature 18 and on the core 14. The plate 4 is normally fixed on the seat 20 by a helical spring 39 resting on the washer 26. If the magnet 13 is activated, the magnetic flux established essentially between the armature 18 and the core 14 produces an electromagnetic force which pulls the armature 18 towards the core 14, against the action of the spring 39. The the closure element thus moves to the highest limit position, in which the top surface 28 of the washer 26 rests against the edge 30 of the coupling 16 (FIG. 3) and the fuel is supplied from the chamber

36, in the exit hole 3.

  The obturation element being located in the highest limit position, a gap G (FIG. 3) is kept, as required, between the surface 29 of the armature 18

and the surface 31 of the core 14.

  When the electromagnet 13 is no longer activated, the spring 39 returns the closure element to the closed position shown in FIG. 2. On the valve according to the present invention, the closure element is fixed in the position highest limit by the washer 26 bringing the coupling 16 into contact, thereby achieving an extremely precise opening stroke, due to the extremely precise finish of the parts in contact involved and the precision of the thickness of the washer 26. In addition, due to the narrow contact surface created between the end edge 30 of the coupling 16 and washer 26, the residual magnetism, or remanent, now these surfaces is weak, thereby allowing the spring 39 return the shutter element quickly to the closed position. The hardness of the material of the washer 26 is also such that wear is negligible on the

washer 26.

  Due to the low weight of the assembly consisting of the armature 18, the plate 4 and the washer 26, the dynamic effect exerted on the latter is practically negligible, thereby allowing the valve to operate at an operating rate. extremely fast. The projections 37 located on the plate 4 create an effective seal between the seat 20 and the surface 19 of the plate 4. In fact, the small contact surface existing between the projections 37 and surface 19 creates an extremely high contact pressure and ensures by consequently an excellent seal, even in the event of the exertion of a very low pressure on the part of the spring 39. The seal is further improved by the labyrinth effect of the projections 37 and of the nature

  deformable of the material of the plate 4.

  Finally, the valve according to the present invention can be manufactured and assembled inexpensively due to the elimination of complex machining with tight tolerances.

and assembly operations.

  It will be clear to those skilled in the art that changes can be made to the valves thus described and shown above, without thereby departing

of the scope of the present invention.

Claims (7)

  1. Electromagnetic fuel metering and spraying valve for a fuel supply device of an internal combustion engine, comprising a housing (1) housing an annular coil (13) and a tubular core (14) located at the inside the latter; a nozzle (2) having at least one fuel supply hole (3) and fixed to said housing (1); and a movable closure element (4) adapted to move between a first and a second position inside said hole (3) which is respectively closed and open, and formed in one piece with a tubular armature (18 ) activated by an electromagnet; said shutter member (4) comprises a plate having a substantially flat surface (19) adapted to rest on a seat (20) located on said nozzle (2) and to thereby seal said fuel supply hole (3 ), and which is fixed to said armature (18) whose inner surface (15) is slidably adapted to the outer surface of a guide coupling (16) fixed to, and projecting axially from, said core (14 ); characterized in that the axial length of the part (17) of said coupling (16) projecting axially from said core (14) and the axial length of said tubular armature (18) are chosen such that, when the element of obturation is in said second position, said plate (4) remains on the end edge (30) of said coupling part, so as to block the opening movement of said closure element and so that said armature ( 18) be kept at a distance determined from said core (14).   2. Valve according to claim 1, characterized in that said plate (4) consists of a plastic material, and that it is provided between said plate (4) and said end edge (30) of said part coupling (17), a contact element (28) arranged to remain on said end edge (30) when said closure element is located in said second position. 3 valve according to claim 1 or 2, characterized in that the axial length (Li) of said coupling portion (17) projecting from said core (14) is greater than the distance (L2) between the upper edge (29) of said armature (18) and said surface   contact (28) of said washer (26).   4. Valve according to any one of the claims   1, 2 or 3, characterized in that said plate (4) comprises an axial pin (25) and that. said contact element consists of a washer (26) into which said pin (25) is inserted, said plate (4) and said washer (26) being fixed between an annular shoulder (27) and an end edge (24) facing down from said induced (18).   5. Valve according to claims 3 or 4,   characterized in that said plate (4) is   made of a thermoplastic material.   6. Valve according to any one of the claims   previous, characterized in that the flat surface (19) of said plate (4) is arranged to rest on said seat (20) and said nozzle (2) has projections (37) substantially coaxial with said fuel supply hole (3), to ensure fuel-tightness   between said surface (19) and said seat (20).   7. Valve according to claim 6, characterized in that the height of said projections (37) is less than 0.5 mm.