GB2248088A

GB2248088A - I.C. Engine fuel injection nozzle

Info

Publication number: GB2248088A
Application number: GB9020349A
Authority: GB
Inventors: Robert Brian Seaman; Antonio Michele Gio De-Sciscio
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1990-09-18
Filing date: 1990-09-18
Publication date: 1992-03-25
Also published as: GB9020349D0

Abstract

A nozzle valve member 16 comprises a metallic elongated core member 30 shaped at one end for engagement with a seating and having a flange 33 adjacent its other end. A layer 35 of electrically insulating material is applied to the core member between the flange and the shaped end and on the adjacent face of the flange. A metallic sleeve 36 is located about the layer and engages the portion of the layer on the flange. The layer together with an insulating washer 34 act to insulate the core member from the body of the nozzle except when the shaped end engages with the seating. <IMAGE>

Description

FUEL INJECTION NOZZLES This invention relates to fuel injection nozzles for supplying fuel to an internal combustion engine the nozzles being of the kind comprising a valve member slidable within a bore formed in a nozzle body, a seating defined at one end of the bore, the valve member being shaped for cooperation with the seating to prevent fuel flow from a fuel inlet to an outlet.

'V Such nozzles are well known in the art and the valve member is usually resiliently loaded to the closed position and movable away from the seating against the action of the resilient loading, by the action of fuel under pressure supplied to the inlet. In modern fuel injection systems for internal combustion engines it is desirable to know the instant at which the valve member moves away from the seating in order that the timing of delivery of fuel to the engine can be closely controlled.

It has been proposed to provide sensors in the holder to which the nozzle body is secured, which sensors provide an electrical signal upon movement of the valve member. In some cases the sensors are responsive to the movement of the valve member and in other cases to an increase in the stress in the spring biasing the valve member. The provision of such sensors is inconvenient and it has been proposed to use the valve member and the seating as a simple electrical switch. This requires that the valve member should be electrically insulated from the wall of the bore in which it is located.

British patent specification 2125894 describes a method of achieving the desired insulation in which a coating of insulating material is provided on the valve member or in the bore in which it is located. This method has not proved to be entirely reliable due to the difficulty of finding a suitable coating material which can withstand the heat and pressures to which the nozzle is subject to in use.

The object of the present invention is to provide a fuel injection nozzle of the kind specified in a simple and convenient form.

According to the invention in afuel injection nozzle of the kind specified said valve member comprises an elongated cylindrical member which at one end is shaped for cooperation with the seating and is formed from electrically conductive material, a layer of electrically insulating material surrounding said member and a sleeve formed from electrically conductive material mounted about the member and insulated therefrom by the layer of insulating material, said sleeve in use cooperating with the wall of the bore to guide the movement of the valve member, said elongated member being electrically insulated from the nozzle body except when it is in contact with the seating.

The invention will now be described with reference to the accompanying drawings in which:- Figure 1 is a sectional side elevation of a known form of fuel injection nozzle, Figure 2 is an enlarged view of a portion of the nozzle seen in Figure 1, and Figure 3 is a part sectional side view to an enlarged scale of part of the nozzle seen in Figure 1 and modified in accordance with the invention.

Referring to Figure 1 of the drawings, the nozzle comprises a holder 10 which is of generally cylindrical form and which is provided with a lateral extension 11 having a threaded aperture which receives a pipe union 12 which constitutes the fuel inlet for the nozzle. At one end of the holder 10 there is secured a valve body 13 which is of stepped cylindrical form. The narrower end portion of the valve or nozzle body projects in use, through the wall of a combustion spaceJof an engine and the nozzle body is retained relative to the holder by a cup shaped retaining member 14 having an aperture formed in its base wall through which the narrower portion of the nozzle body extends.

Formed within the nozzle body 13 is a bore 15 and this extends to adjacent the end of the narrower portion of the nozzle body and defines a seating for a valve member 16 which is slidable within the bore. The valve member is shaped for cooperation with the seating to prevent flow of fuel through outlet orifices which communicate with the blind end of the bore. The valve member 16 is of stepped form, the narrower portion of the valve member lying generally within the portion of the bore 15 which is formed in the narrower portion of the nozzle body. There is defined between the valve member and the bore a clearance which is connected by cooperating passages 17, 18 in the nozzle body and the holder respectively with the aforementioned fuel inlet.

Formed in the holder 10 is a further axially extending bore which accommodates a push rod 19. The push rod is engages about an axial projection on the valve member and at its other end opens into an enlarged chamber 20 and at this end is provided with an abutment 21 for resilient means in the form of a coiled compressipn spring 22. The other end of the coiled compression spring is engages about a further abutment 23 which is turn engages a cup shaped member 24 which is in screw thread engagement with the wall of the chamber 20.

The cup shaped member 24 is prevented from rotation in the holder, by a lock nut and an aperture 29 is provided to allow fuel leakage from the chamber 20. In operation, when fuel under pressure is admitted to the clearance defined between the valve member and tbe bore 15, the valve member is moved against the action of the spring 22, to permit fuel flow through the aforesaid outlets and when the supply of fuel under pressure ceases the valve member is returned into contact with the seating by the coiled compression spring. Any fuel which leaks between the working clearance defined between the valve member and the wall of the bore 15, accumulates in the chamber 20 and can flow to a drain. The maximum extent of movement of the valve member against the action of the spring is limited by the engagement of the valve member with the end surface of the holder.

In order to provide an indication of the movement of the valve member 16 away from the seating, the valve member has a special construction which will be described. The push rod 19 is formed from metal and has an electrical connection with the central part of the valve member which engages the seating. The push rod and the spring 22 together with the abutment 21 are spaced from the walls of the holder and cup shaped member 24 respectively and the abutment 23 is electrically insulated from the cup shaped member 24 by means of an electrically insulating disc 28 so that the only direct electrical connection between the valve member and the holder occurs when the valve member is in contact with the seating.The abutment 23 has secured thereto an electrical conductor 27 which passes through an insulating collar 25 locating within an aperture in the base wall of the cup shaped member and it is connected to an electrical connector 26 which in use is connected to an electrical circuit forming part of the engine management system.

Turning now to Figure 3 the valve member 16 comprises a centrally disposed elongated cylindrical member 30 which at one end is provided with a truncated profile 31 for engagement with the seating.

The member 30 is provided near its opposite end, with a flange 33 and located against the end surface of the flange 33 presented to the holder 10 is an annular washer 34 formed from insulating material and which when the valve member is moved to the fully open position, engages with the end surface of the holder. Intermediate the flange and the portion of the member adjacent the seating, there is provided an electrically insulating layer 35 and this is surrounded by a metallic sleeve 36 which in use, engages the surface of the bore 15 to guide the movement of the valve member.

The layer 35 is conveniently formed by push fitting a sleeve of electrically insulating material onto the cylindrical member with the sleeve engaging the collar 33. The sleeve is then machined to a reduced diameter leaving a portion adjacent the collar 33 unmachined, after which the sleeve 36 is push fitted over the machined layer into engagement with the portion of the sleeve of insulating material which is unmachined.

Finally, the outer surface of the sleeve 36 is machined to provide the required working clearance with the wall of the bore 15. In its machined state the outside diameter of the sleeve 36 is slightly larger than that of the unmachined portion of the insulating sleeve. In this example the insulating material is a synthetic resin material.

Alternative materials which can be used to form the insulating sleeve are ceramic materials and one such material is that sold under the trade name MONITOX by Monito coatings and Engineers Limited of Wallsend, Tyne and Wear, England. The material is described as ceramic based on a complex chromia-silica matrix intraspersed with hard aluminum particles. The coating is applied in liquid form by either dipping or spraying, to the member 30 after which thermo-chemical treatment is carried out to provide a hard coating which is then machined to the desired diameter after which the sleeve 36 is passed into position.

The construction described provide the desired electrical insulation of the member 30 from the nozzle body when the valve member is lifted from the seating.

Claims

1. A fuel injection nozzle for supplying fuel to an internal combustion engine comprising a valve member slidable within a bore formed in a nozzle body, a seating defined at one end of the bore, the valve being shaped for cooperation with the seating to prevent fuel flow from a fuel inlet to a fuel outlet, a valve member comprising an elongated member which at one end is shaped for cooperation with the seating, a flange defined by the member adjacent the other end thereof, a layer of electrically insulating material surrounding the portion of the member intermediate the flange and the other end of the member, and the adjacent end face of the flange, and a metallic sleeve mounted about said layer of insulating material with its end surface engaging the layer of material on said end face of the flange, said flange acting to guide the movement of the valve member, said layer affording electrical insulation of the member from the nozzle body except when the member is in contact with the seating.

A A method cf forming a valve member for a fuel Injection nozzle for an internal combustion engine substantially as hereinbefore described with reference to Figure 3 of the accompanying drawings.

3. A fuel injection nozzle for supplying fuel to an internal combustion engine comprising the combination and arrangement of parts substantially as hereinbefore described with reference to the accompanying drawings.

AMENDMENTS TO THE CLAIMS HAVE BEEN FILED AS FOLLOWS 1. A fuel injection nozzle for supplying fuel to an internal combustion engine comprising a valve member slidable within a bore formed in a nozzle body, a seating defined at one end of the bore, the valve being shaped for cooperation with the seating to prevent fuel flow from a fuel inlet to a fuel outlet, a valve member comprising an elongated member which at one end is shaped for cooperation with the seating, a flange defined by the member adjacent the other end thereof, a layer of electrically insulating material surrounding the portion of the member intermediate the flange and the other end of the member, and the adjacent end face of the flange, and a metallic sleeve mounted about said layer of insulating material with its end surface engaging the layer of material on said end face of the flange, said sleeve acting to guide the movement of the valve member, said layer affording electrical insulation of the member from the nozzle body except when the member is in contact with the seating.

2. A method of forming a valve member for a fuel injection nozzle for an internal combustion engine substantially as hereinbefore described with reference to Figure 3 of the accompanying drawings.