GB2204640A

GB2204640A - I.C. engine fuel injection nozzle

Info

Publication number: GB2204640A
Application number: GB08810653A
Authority: GB
Inventors: David John Gaskell
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1987-05-09
Filing date: 1988-05-05
Publication date: 1988-11-16
Also published as: GB8711019D0; GB8810653D0

Abstract

The valve member (16) is biased by a pair of springs 26, 27 which act against the opposite ends of a beam 24 which is pivotally mounted on the valve member. The stronger spring 27 is a preloaded spring and the initial movement of the valve member away from the seating is against the action of the weaker spring 26. A stop 29 limits the initial movement of the valve member so that a restricted flow of fuel takes place. The valve member moves further against the stronger spring alone when the fuel pressure is further increased. Alternative arrangements for varying the spring load and maximum spring compression by valve lift are described (Figs. 2 to 4). <IMAGE>

Description

"FUEL INJECTION NOZZLES" This invention relates to a fuel injection nozzle for supplying fuel to a compression ignition engine the nozzle being of the so-called inwardly opening type and comprising a valve member which can be subjected to fuel under pressure supplied to a nozzle inlet, to lift the valve member away from a seating thereby to allow fuel flow from said inlet to an outlet, the valve member being lifted against the action of resilient means.

For some types of compression ignition engine it is desirable to be able to restrict the initial rate of fuel flow through the outlet and it is known to restrict the flow using valves in or adjacent the inlet of the nozzle. Such valves contain sliding components and are expensive to manufacture and furthermore, it is not easy to manufacture the valves so that they have identical characteristics. It is also known to restrict the flow of fuel through the outlet by controlling the initial movement or lift of the valve member away from the seating. The control of the lift can be effected by using dash pot action but such arrangements are sensitive to the viscosity of the liquid medium usually fuel, and also require to be very carefully constructed particularly in view of the small movement of the valve member from the closed to the fully open position.It is also known to provide two springs which may be arranged so that for the initial lift one spring only restrains the movement of the valve member with the second spring being brought into operation after the initial lift of the valve member and the present invention is concerned with a nozzle of this type and has for its object to provide such a nozzle in a simple and convenient form.

According to the invention a fuel injection nozzle of the kind specified comprises a beam pivotally mounted intermediate its ends on the valve member or a part coupled thereto, a pair of compression springs acting on the opposite ends of the beam respectively to urge the valve member into contact with the seating, the springs being mounted in side by side relationship and a stop means for limiting the movement of the end of the beam associated with the weaker of said springs the arrangement being such that when fuel under pressure is supplied to said inlet, the valve member will initially move against the action of the weaker of the springs, the extent of movement being determined by said stop means, to allow a restricted flow of fuel through said outlet, the valve member moving against the action of the other spring as the pressure at the inlet is increased.

Examples of fuel injection nozzle in accordance with the invention will now be described with reference to the accompanying drawings each of which is a sectional side elevation of part of the nozzle.

Referring to Figure 1 of the drawings the nozzle comprises a nozzle body 10 which is secured within a nozzle holder 11 and formed in the nozzle body is a bore 12 which terminates in a seating 13 downstream of which is an outlet orifice 14. Trapped between the nozzle body and the nozzle holder is the flange of a bush 15 in which is slidably mounted a valve member 16, the end of the valve member being shaped for co-operation with the seating 13. The portion of the valve member which extends through the bore 12 is smaller in diameter than'the bore and the annular space thus created is connected to a fuel inlet not shown.

The valve member extends through the bush into a chamber 17 defined in the holder and extending into the chamber are a pair of elongated cylindrical openings 18, 19. The openings are disposed in spaced side by side relationship and located in the openings are tubular inserts 20 respectively. Each insert at its end adjacent the chamber, defines an inwardly extending step 21 against which is located a spring abutment 22, the spring abutments defining pivots 23 which extend into the chamber 17. Located in the chamber is a beam 24 and this is pivotally mounted intermediate its ends upon a pivot 25 defined by the end of the valve member. Moreover, the pivots 23 engage the opposite ends of the beam respectively.

Located within the inserts 20 are a pair of coiled compression springs 26, 27 respectively, the springs at one end engaging the respective spring abutment and at their opposite ends engaging with adjustable plugs 28.

The plugs define screw threaded bores in which are located stop members 29 respectively for engagement by extensions of the spring abutments 22.

The springs 26, 27 are preloaded by adjustment of the plugs 28 and assuming that the spring 26 is preloaded to a lesser extent than the spring 27, when fuel under pressure is supplied through the inlet, the fuel pressure acting on the valve member will generate a force acting to move the valve member into the chamber 17. When this force is sufficient, it will overcome the force exerted by the spring 26 and as a result the valve member will be lifted from its seating to allow fuel through the outlet 14. The extent of movement of the valve member against the action of the spring 26 is limited by the engagement of the spring abutment 22 associated with the spring 26, with the rod 29 and the rod 29 is adjusted so that the desired restricted flow of fuel to the associated engine takes place.As the pressure of fuel supplied to the inlet continues to increase, so the force exerted on the valve member will increase and eventually it will overcome the preload of the spring 27 so that the valve member will be able to move a further distance away from its seating to allow substantially unrestricted flow of fuel through the outlet 14, the extent of such movement being determined by contact of the rod 29 with the abutment 22 associated with the spring 27.

With the arrangement shown in Figure 1 very careful setting of the inserts 20 is required to ensure that the valve member 16 is in contact with the seating 13 with the spring abutments engaging the steps 21.

A modified arrangement is seen in Figure 2 in which only the stronger and preloaded spring 27 is located within an insert 20. The spring 26 is freely located in the opening 18 which in this case is of slightly smaller diameter. The spring abutment 22 moves freely within the opening 18 so that in the assembled position as shown in Figure 2, the spring 26 exerts a force on the valve member tending to hold the valve member in contact with the seating. The operation of the nozzle is as described with reference to Figure 1 and in order to set the various spring forces etc. it is convenient to set the force exerted by the spring 27 prior to assembly of the associated insert 20 into the holder. At the same time the stop 29 within the spring 27 can be adjusted to provide the desired clearance between the stop 29 and the spring abutment 22, this clearance determining the second stage of movement of the valve member. With the insert 20 inserted into the holder and secured therein, the nozzle opening pressure is set by adjustment of the force exerted by the spring 26 and then the extent of movement of the valve member against the action of the spring 26 is set by adjustment of the associated stop 29 either by advancing the stop into contact with the abutment and then backing it off by a predetermined amount or by utilizing high pressure flow measurement.

In the example shown in Figure 3 the stop which limits the movement of the valve member against the action of the spring 26 is of slightly different form and it comprises a stop ring 30 together with an associated locking ring 31 which are located in the end of the bore 18 adjacent the chamber 17. The spring abutment is formed in two parts 32, 33, the part 32 being engaged by the spring and the part 33 mounting the pivot for engagement with the beam 24. The parts 32 and 33 are spaced apart and are interconnected by a push rod 34. In this example the adjustment of the extent of movement of the valve member against the action of the spring 26 must be set before the spring 26 and the part 32 of the spring abutment are assembled into the opening 18 so that the setting of the nozzle opening pressure is the last stage in the setting procedure.

In the example of Figure 4 the divided spring abutment as described with reference to Figure 3 is utilized for both springs with the part 33 of the abutment associated with the spring 27 being restrained against movement by a step 19A defined in the opening 19. With this arrangement adjustment is effected in a slightly different way and it is convenient to set the initial lift of the valve member first this being effected by firstly screwing down the stop ring 30 associated with the spring 27 so that the portion 33 of the spring abutment is in contact with the aforesaid step. The stop ring 30 associated with the spring 26 can then be adjusted to give the desired initial lift following which the spring 26 is inserted and the nozzle opening pressure set. The stop ring 30 associated with the spring 27 is then unscrewed by a predetermined amount to determine the maximum lift of the valve member following which the spring 27 is assembled and the force exerted by the spring 27 adjusted.

The pivots 23 are shown to be of the ball and socket type and the pivot 25 can be formed as an edge corresponding to the diameter of the valve member.

The invention is applicable to more conventional forms of injector in which the valve member is located in a separate nozzle body which is detachably secured to the nozzle holder by means of a cap nut with or without the provision of an adaptor plate intermediate the body and the holder.

Claims

1. A fuel injection nozzle for supplying fuel to a compression ignition engine, the nozzle being of the so-called inwardly opening type and comprising a valve member which can be subjected to fuel under pressure supplied to a nozzle inlet, to lift the valve member away from a seating to allow fuel flow from said inlet to an outlet, a beam pivotally mounted intermediate its ends on the valve member or a part coupled thereto, a pair of compression springs acting on the opposite ends of the beam respectively to urge the valve member into contact with the seating, the springs being mounted in side by side relationship and a stop means for limiting the movement of the end of the beam associated with the weaker of said springs the arrangement being such that when fuel under pressure is supplied to said inlet, the valve member will initially move against the action of the weaker of the springs, the extent of movement being determined by said stop means, to allow a restricted flow of fuel through said outlet, the valve member moving against the action of the other spring as the pressure at the inlet is increased.

2. A nozzle according to Claim 1 in which the stronger of said springs is a preloaded spring, means being provided to adjust the preload of the spring and further stop means being provided for limiting the movement of the valve member against the action of the spring.

3. A nozzle according to Claim 2 in which the stronger of said springs is mounted in an insert which is located in an opening in a nozzle holder, said insert being of tubular form and defining an inwardly extending step at its end adjacent the beam, a spring abutment which is engaged by the stronger of said springs and which is urged against said step by the spring, the abutment defining a pivot which is engaged with the beam, a plug adjustably mounted in the insert and between which and the abutment the spring is located, said further stop means comprising a stop member adjustably mou-nted in the plug and engageable by said abutment.

4. A nozzle according to Claim 3 in which said insert is secured against a shoulder defined in said opening.

5. A nozzle according to Claim 3 in which the other of said springs is a preloaded spring and is mounted in a further insert located in a further opening in said holder, said openings being spaced from and parallel to each other.

6. A nozzle according to Claim 3 in which the other of said springs is mounted in a further opening in said holder, one end of the other spring engaging an abutment from which extends a pivot engaged with said beam, the other end of the other spring bearing against a plug adjustably mounted in the opening, said plug mounting an adjustable rod which forms said first mentioned stop means.

7. A nozzle according to Claim 3 in which the other of said springs is mounted in a further opening in said holder, one end of the other spring engaging one part of an abutment which is formed in two parts, the two parts being spaced apart and interconnected by a push rod, the other part mounting a pivot engaged with the end of the beam, and a stop ring adjustably mounted in the opening, said stop ring being positioned between the two parts and acting to limit the movement of the valve member against the action of the weaker of the springs.

8. A nozzle according to Claim 2 in which said springs are located in a pair of spaced openings formed in a nozzle holder, the openings carrying adjustable plugs for engagement with the ends of the springs respectively remote from said beam, the opposite ends of the springs engaging one part of a pair of two part spring abutments respectively, the other parts of the spring abutments carrying pivots engaged with the opposite ends of said beam, the two parts of each spring abutment being interconnected by push rods respectively, the openings mounting stop rings respectively for engagement by the other parts of the spring abutments respectively to limit the movement of the valve member against the action of the respective spring and the other part of the spring abutment associated with the stronger of the springs being engageable against a step defined in the respective opening.

9. A fuel injection nozzle for supplying fuel to a compression ignition engine comprising the combination and arrangement of parts substantially as hereinbefore described with reference to Figure 1 of the accompanying drawings.

10. A fuel injection nozzle for supplying fuel to a compression ignition engine comprising the combination and arrangement of parts substantially as hereinbefore described with reference to Figure 2 of the accompanying drawings.

11. A fuel injection nozzle for supplying fuel to a compression ignition engine comprising the combination and arrangement of parts substantially as hereinbefore described with reference to Figure 3 of the accompanying drawings.

12. A fuel injection nozzle for supplying fuel to a compression ignition engine comprising the combination and arrangement of parts substantially as hereinbefore described with reference to Figure 4 of the accompanying drawings.