GB2149453A

GB2149453A - Fuel injector

Info

Publication number: GB2149453A
Application number: GB08425629A
Authority: GB
Inventors: David Michael Harvey; Roger Cedric Lloyd
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1983-11-08
Filing date: 1984-10-10
Publication date: 1985-06-12
Also published as: JPS60113062A; ES8601405A1; GB8329798D0; FR2554511A1; IT1177025B; GB8425629D0; ES537469A0; IT8423293A1; IT8423293A0; DE3440574A1

Abstract

A fuel nozzle body 10 is secured to one end of a holder 12 by means of a cap nut 18. The end of the holder remote from the body 10 defines a fuel inlet 17 and there is formed in the holder an opening 24 through which a tool 25 can be inserted to engage teeth on a plate 21 serving as an abutment for one end of a compression spring 19. A plastics plug 26 is inserted in the opening 24 after adjustment to engage the plate teeth and prevent plate rotation. <IMAGE>

Description

SPECIFICATION Fuel injector This invention relates to fuel injection nozzles ofthe kind comprising a nozzle body in which is located a fuel pressure actuated valve member, a hollow nozzle holderwhich is retained relative to the nozzle body by means of a cap nut, the holder defining an axially disposed fuel inlet which is connected buy a passage in the wall ofthe holderto an inlet passage in the nozzle body,the chamber defined within the holderaccommodating a coiled compression spring which biases the valve member against the action of fuel under pressure supplied to the fuel inlet.

The fuel pressure which is required to move the valve memberagainstthe action of the spring depends at least in partupontheforceexertedbythe spring. The spring is confined between an abutment on thevalve member and an abutment in the chamber. However, due to manufacturing tolerances it is not possible when assembling the injection nozzle to guarenteethatthevalve member will startto move againstthe action ofthe spring at a predetermined fuel pressure. It is important that each injection nozzle should open ata predetermined pressure and it is known in someforms of injection nozzle to provide an adjustable abutment in the form of a screwthreaded member which is accessible from the end of the injection nozzle remote from the nozzle body.When the fuel injection nozzle is ofthetype having an axially disposed fuel inlet this form of adjustment is difficult to achieve and it has been the practice to employ shivs to adjustthespring pressure. The use of shims however requires repeated assembly and disassembly ofthe injection nozzle until the correct lifting pressure is achieved.

However, it is known with injection nozzles of the kind specified to provide an adjustable abutment in the holder and to actuate the abutment by means of a screw or pin which extendsthrough the wall of the nozzle holder transversely to the axis ofthe injection nozzle. The screw or pin can be moved inwardly or outwardly to cause axial movement ofthe abutment.

This form of adjustment imposes substantial loading on the screw or pin and the abutment and is not considered to be very satisfactory since the abutment can tip due to the clearance between the abutment and the spring chamber.

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

According to the invention a fuel injection nozzle of the kind specified comprises an axially extending cylindrical recess formed in the wall of said chamber which is presented to the nozzle body, an adjusting member in screw thread engagement with the wall of said recess, a plate carried by said adjusting member and forming an abutment for one end of said spring, an opening in the wall of said holder, said opening opening onto the periphery of said adjusting member, and extending from an end surface of said holder, formations on the peripheral surface of said ajusting memberwhereby said adjusting membercan be rotated using a tool inserted through said opening and a plug engageable in said opening to prevent rotation ofthe adjusting member once adjustment has been effected.

An example of a fuel injection nozzle in accordance with the invention will now be described with refer ence to the accompanying drawing which shows the nozzle in part sectional side elevation.

Referring to the drawing the fuel injection nozzle comprises a nozzle body 10 in which is slidably mounted in known manner, a fuel pressure actuated valve member not shown. The valve member has a reduced portion 11 protruding from the body and the opposite end ofthe valve member is shaped as is well known in the art, to co-operate with a seating to preventtheflowoffuelthrough an outletorifice.The nozzle body 10 incorporates a fuel inlet passage through which fuel under pressure can flow to act upon the valve memberto lift the valve memberfrom its seating.

Also forming part of the nozzle is a holder 12 which like the nozzle body 10 is of generally cylindrical form.

The holder defines a chamber 13 which extends inwardlyfrom the end of the holder presented to the nozzle body 10. Interposed between the nozzle body 10 and the holder is a spacer 14which is provided with an aperture through which the portion 11 ofthe valve member can extend. In addition, the spacer member defines fuel supply passages 15 which communicate with a passage l6formed in the wall ofthe holder and extending to an axially disposed fuel inlet 17 which in use, is connected to the outlet of a fuel injection pump.

The holder 12,the spacer 14 and the nozzle body 10 are held in assembled relationship by means of a cap nut 18which is in screwthread engagement with the outer peripheral wall ofthe holder and which defines a step which engages with a flange on the nozzle body 10.

Within the chamber is a coiled compression spring 19 one end of which is located upon an abutment 20 which is mounted on the end portion 11 ofthevalve member. The other end of the spring bear against a plate 21 which is supported integral with an adjusting member 22. The member 22 is in screwthread engagementwiththewall of an axially extending blind cylindrical recess 23 which isformed inthe end wall ofthe chamber 13.

In operation, when fuel under pressure is supplied to the inlet 17 the fuel pressure acts upon the valve member to create a force acting to move the valve member againstthe action ofthe spring. When the pressure reaches a sufficient value, the valve member is lifted from its seating to allowfuel flowthrough the outlet. Itis important that the valve member should lift art a predetermined pressure and this pressure can be determined byadjustingtheforceexertedbythe spring. In orderto do this the adjusting member 22 is moved angularlythereby imparting axial movement to the plate 21.

The plate 21 is provided on its peripheral edgewith a plurality of teeth. Moreover, formed in the holder is a drilling 24which opens onto the plate 21, the drilling extending from an end surface ofthe nozzle. The drilling is inclined to the longitudinal axis of the nozzle and provides access for a tool 25 having a toothed end portion. The toothed end of the tool 25 can be engaged with the teeth on the plate 21 to enablethe plate to be rotated to achieve adjustment ofthe spring force.

Once adjustment has been effected the tool is removed and the drilling can be closed by a plug 26.

This is formed from plastic material which engages with the teeth on the plate 21 to retain same against angular movement.

The chamber 13 is provided with a drain outlet which opens into an annularchamberdefined be tweentheexteriorsurface ofthe nozle holder 12 and a sleeve 28which surrounds the holder and which mounts a nipple 29 to which a drain pipe can be connected when the nozzle is mounted on an engine.

The sleeve 28 is retained in position by a retaining nut 30 and seal members 31,32 are provided between the sleeve member and the holderto prevent leakage of fuel.

With the construction described the injection nozzle can be fully assembled priorto adjustment ofthe spring force and this adjustment could, if necessary, be carried outwith the nozzle mounted on an engine.

Claims

1. Afuel injection nozzle comprising a nozzle body in which is located a fuel pressure actuated valve member, a hollow nozzle holderwhich is retained relative to the nozzle body by means of a cap nut, the holderdefining an axially disposed fuel inletwhich is connected by a passage in the wall ofthe holderto an inlet passage in the nozzle body, the chamber defined within the holder accommodating a coiled compression spring which biases the valve member againstthe action offuel under pressure supplied to the fuel inlet, an axially extending cylindrical recess formed in the wall of said chamberwhich is presented to the nozzle body, an adusting member in screwthread engagementwith the wall of said recess, a plate carried by said adjusting memberandforming an abutmentfor one end of said spring, an opening in the wall of said holder, said opening opening onto the periphery of said adjusting member, and extending from an end surface of said holder, formations on the peripheral surface of said adjusting member whereby said adjusting member can be rotated using a tool inserted through said opening and a plug engageable in said opening to prevent rotation of the adjusting member once adjustment has been effected.

2. A nozzle according to Claim 1 in which said plug is formed from plastics material.

3. Afuel injection nozzle comprising the combination and arrangement of parts substantially as hereinbefore described with reference to the accompanying drawings.