GB2153429A

GB2153429A - Fuel injection nozzles for i c engines

Info

Publication number: GB2153429A
Application number: GB08430496A
Authority: GB
Inventors: Michael Ronald Bungay; John William Stevens; Richard Michael Turner; Richard James Andrews
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1984-01-31
Filing date: 1984-12-03
Publication date: 1985-08-21
Also published as: GB2153429B; GB8430496D0; GB8402469D0; DE3500415A1; US4624135A

Description

1

SPECIFICATION Fuel injection nozzles

This invention relates to fuel injection nozzles for supplying fuel to internal combustion engines, the nozzles being of the kind comprising a valve member slidable within a bore, a seating defined at one end of the bore, the valve member being shaped for co-operation with the seating, resilient means acting to bias the valve member into contact with the seating, an outlet from said one end of the bore, a step defined on the valve member, passage means extending from a nozzle inlet and through which the pressure of fuel supplied to said inlet can act on said step to lift the valve member from the seating to allow fuel flow through said outlet, a chamber which accommodates said resilient means and into which the end of said valve member remote from the seating extends and a drain extending from said chamber.

Such nozzles are well known in the art being 85 commonly known as '1nwardly opening ". In order to satisfy emission laws now enacted in many countries of the world and in order to economise so far as is possible, on the consumption of fuel it is necessary to be able to control the instant of fuel delivery to the engine and for accurate control it is necessary to know when the valve member lifts X rom its seating. Various nozzles are known which incorporate means responsive to the movement of the valve member to provide the desired signal. In some cases the performance of the nozzle is affected by the additional components which are required. On nozzle, the performance of which is not affected by the modifications to it, is described in British Patent Specification 1586254. In this nozzle the resilient means in the form of a coiled spring which electrically connects the valve member to a terminal on the exterior of the nozzle body and the valve member and seating constitute a simple electrical switch which is opened when the valve member is lifted from its seating. Reliance is placed upon the thin film of fuel in the working clearance between the wall of the bore and the valve member to insulate the valve member when the latter is lifted from the seating. It has been found that this is not entirely satisfactory and attempts have been made to provide an insulating coating on the wall of the bore or the valve member. The provision of such coatings again adds to the cost of manufacture of the nozzle.

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 a fuel injection nozzle of the kind specified comprises a sensing device 120 responsive to the displacement of fuel which occurs in said chamber as the valve member is lifted from the seating.

An example of a fuel injection nozzle in accordance with the invention will now be described 125 with reference to the accompanying drawing.

Referring to the drawing the nozzle comprises a nozzle body 10 of stepped cylindrical form in which is defined a bore 11 in which is located a valve GB 2 153 429 A 1 member 12. Fuel under pressure can act upon the valve memberto lift the valve member from a seating to allow fuel flow through an outlet in known manner, the fuel being supplied by way of a passage 13.

The valve member extends from the end of the bore in an extension 14 of reduced diameter. The nozzle body is secured to a generally cylindrical holder 15 by means of a cap nut 16 through the base wall of which the nozzle body extends. The cap nut and holder are provided with engaging screw threads. The holder 15 defines a fuel inlet 17 which communicates with the passage 13 by way of a passage 18 and a communicating passage 19 which is formed in a stop member 20.

Formed within the holder 15 is a chamber 21 into which the extension 14 of the valve member extends. Mounted upon the extension is a spring abutment 22 which serves as an abutment for a coiled compression spring 24 the opposite end of the spring engaging the end of the chamber. A fuel leak off passage 25 communicates with the chamber 21 and through which fuel leaking between the valve member and the wall of the bore can escape from the chamber. The chamber in use is full of fuel.

In operation, when fuel under pressure is supplied to the inlet 17, the fuel pressure acts upon the valve member and when the pressure is sufficient, the valve member is lifted from the seating to permit fuel flow through the outlet. The extent of movement of the valve member against the action of the spring is limited by its abutment with an inwardly extending portion of the end surface of the stop member 20. When the valve member lifts from the seating there is a displacement of fuel into the chamber 21 and as a result there is also a displacement of fuel through the passage 25.

The spring abutment 22 has a diameter which is larger than that of the valve member 12 and in addition for design considerations has a small working clearance with the wall of the chamber 21 and it therefore tends to act like a piston. The pordon 21A of the chamber experiences an increase in volume as the valve member is moved to the open position and the pressure therein fails. When the valve member closes onto its seating the pressure in the portion 21A of the chamber tends to increase.

The variation in pressure within the portion 21A of the chamber is utilized to operate a sensing device generally indicated at 26. The sensing device enables an electrical signal to be produced which is indicative of the lifting of the valve memberfrom its seating. The device 26 comprises a spring loaded metal piston 27 which is slidable within a cylinder 28 defined in a cup shaped member 29. The member 29 is formed from metal and has a terminal member 30 integrally formed therewith. The member 29 is supported in an electrically insulating housing 31 which is of generally cylindrical form and having a flange at its open end with which is engaged a hollow threaded retaining member 32 which holds the housing against the base wall of a recess in the holder 15. The dimensions of the components are such that a clearance exists between the end of the 2 GB 2 153 429 A 2 cup shaped member 29 and the base wall of the recess. In the base wall of the recess is a port which communicates with the passage 25. The piston 27 is biased into contact with the base wall by a coiled compression spring which also ensures an electrical connection between the piston and the cup shaped member 29. The portion of the cylinder 28 which accommodates the spring is in communication with the portion 21A of the chamber by way of a passage 33 so that the piston 27 is subjected to the pressure difference which occurs when the valve member is moved on the opposite sides of the abutment 22.

The arrangement is such that when the valve member is opened, the piston 27 is moved away from the base wall of the recess thereby breaking the electrical connection between the terminal 80 member 30 and the holder 15. The break in the electrical connection provides an indication of lifting of the valve member from the seating. The provision of the device 26 and the fuel connections thereto helps to minimise the risk of cavitation of the fuel in the portion 21A of the chamber 21. It will be understood that the piston 27 can be replaced by for example a diaphragm which may carry an electrical contact so that it can function in the same manner as the piston.

In a modification a restrictor is incorporated in the passage 25 downstream of its connection with the aforesaid port. The effect of the restrictor is to enhance the increase in the pressure in the main portion of the chamber 21 when the valve member is lifted from the seating. The piston 27 will therefore be subjected to a larger pressure difference than is the case with the example illustrated.

In a further modification the passage 25 is omitted 100 although the port in the base wall of the recess is still connected to the chamber 21. A leakage channel is formed in the terminal member 30 or it may extend from the passage 33.

In a still further modification the passage 33 is omitted and a restrictor is provided in the passage 25. The piston in this case is subjected only to the increase in pressure in the main portion of the chamber and the portion of the cylinder 28 which contains the spring may need to be vented to the exterior of the nozzle.

In a yet still further modification the passage 33 is omitted, the passage 25 omitted although the port still communicates with the main portion of the chamber 21, and a passage is formed in the terminal 115 member 30. The piston 27 in this case is a loose fit in the cylinder 28 to allow leakage fuel to pass. In this case the piston is subjected only to the increase in pressure in the main portion of the chamber 21.

It has been found that the time required for the 120 piston 27 to move through its allowed stroke is proportional to the rate of movement of the valve member 12. Therefore by providing a contact member which is engaged by the piston at the end of its stroke a signal can be obtained indicative of 125 the lift of the valve member.

Claims

1. A fuel injection nozzle for supplying fuel to an internal combustion engine, comprising a valve member slidable within a bore, a seating defined at one end of the bore, the valve member being shaped for co-operation with the seating, resilient means acting to bias the valve member into contact with the seating, an outlet from said one end of the bore, a step defined on the valve member, passage means extending from a nozzle inlet and through which the pressure of fuel supplied to said inlet can act on said step to lift the valve member from the seating to allow fuel flow through said outlet, a chamber which accommodates said resilient means and into which the end of said valve member remote from the seating extends, a drain extending from said chamber, and a sensing device responsive to the displacement of fuel which occurs in said chamber as the valve member is lifted from the seating.

2. A nozzle according to Claim 1 in which said sensing device includes a spring loaded plunger responsive to pressures generated in said chamber upon movemnet of said valve member.

3. A nozzle according to Claim 2 including a spring abutment located in said chamber and mounted upon said end of the valve member, said spring abutment extending into close proximity to the wall of the chamber, a port communicating with a first portion of the chamber on the one side of the spring abutment remote from the valve member, a cylinder in which said plunger is slidable, said port opening into one end of the cylinder and passage means through which a second portion of the chamber on the other side of the spring abutment adjacent the valve member communicates with the other end of the cylinder, said plunger being subjected to the pressure difference between said portions of the chamber.

4. A nozzle according to Claim 3 in which said drain extends from said first portion of the chamber.

5. A nozzle according to Claim 4 including a 105 restrictor in said drain.

6. A nozzle according to Claim 3 in which said drain communicates with said second portion of the chamber and extends from said other end of the cylinder.

7. A nozzle according to Claim 2 including a cylinder in which said plunger is slidable, a port communicating with said chamber and opening into one end of said cylinder whereby an increase in pressure in said chamber will cause movement of the plunger against the action of its spring.

8. A nozzle according to Claim 7 in which the other end of the cylinder is vented and a restrictor is located in said drain.

9. A nozzle according to Claim 7 in which said plunger is a loose fit in said cylinder, the drain from said chamber being constituted by the clearance between the plunger and the wall of the cylinder and a drain conduit leading from the other end of the cylinder.

10. A nozzle according to any one of the preceding claims in which said cylinder is defined in a metallic part, means mounting said part in electrically insulating relationship with a metal body which defines said chamber, and an electrical terminal 3 connected to said metallic part, the plunger being formed from metal and with its spring providing an electrical connection between the part and said body, said electrical connection being broken upon movement of the plunger against the action of its spring due to movement of the valve member away GB 2 153 429 A from its seatincl

11. A fuel injection nozzle for supplying fuel to an internal combustion engine comprising the 10 combination and arrangement of parts substationally as hereinbefore described with reference to the accompanying drawings.

Printed for Her Majesty's Stationery Office by Courier Press, Leamington Spa. 811985. Demand No. 8817443. Published by the Patent Office, 25 Southampton Buildings, London, WC2A lAY, from which copies may be obtained.