GB2128677A

GB2128677A - Fuel injection nozzle for i.c. engines

Info

Publication number: GB2128677A
Application number: GB08326475A
Authority: GB
Inventors: Robert Thomas John Skinner
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1982-10-22
Filing date: 1983-10-04
Publication date: 1984-05-02
Also published as: GB2128677B; GB8326475D0

Abstract

A fuel injection nozzle of the outwardly opening type includes a valve member 20 having a head 21 which is moved away from a seating 17 by fuel under pressure to allow fuel flow through outlet orifices 19. The initial lift of the valve member 20 is opposed by a spring 26 which therefore determines the nozzle opening pressure but further movement is opposed by a stiffer second spring 28 which is brought into operation by a collet mechanism including spring biased collets 32. <IMAGE>

Description

SPECIFICATION Fuel injection nozzle This invention relates to fuel injection nozzles of the so-called outwardly opening type comprising a valve body, a bore defined in the body, a seating defined adjacent one end of the bore, the bore downstream of said seating defining an enlargement, a valve member movable axially within said bore, said valve member defining a head for co-operation with said seating, the head being located within said enlargement, said bore at its other end extending into a chamber to which in use, fuel under pressure can be supplied, the valve member having a stem extending into said chamber and resilient means located in said chamber for biasing the valve head into contact with the seating.

Such nozzles have the advantage over the socalled inwardly opening form of nozzle in that they are smaller and cheaper to construct. In addition, they require no "leak off" connection thereby facilitating the installation of a nozzle or nozzles on an engine. There are however disadvantages to the known forms of nozzle especially when the valve head is used to control the effective area of an outlet orifice through which the fuel flows into a combustion chamber of an engine. It is difficult to design and construct a spring which is sufficiently stiff to control the movement of the valve head away from the seating in the required manner and yet which is sufficiently accurate to provide the required nozzle opening pressure.

Shims or other forms of adjustment can be used to initially set the opening pressure but as soon as wear takes place the fine adjustment is lost.

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

According to the invention said resilient means comprises a first spring, the force exerted by which acts on the valve member to determine the pressure of fuel required to effect the initial lift of the valve head from the seating and a second spring which is stiffer than the first spring and which opposes further movement of the valve member following the initial lift of the valve head from the seating.

Three examples of injection nozzles in accordance with the invention will now be described with reference to the accompanying drawings, which show part-sectional side elevations.

Referring to Figure 1 of the drawings, the injection nozzle comprises a nozzle body 10 having a flange 11 which in use, is retained by a cap nut 12, the nut being secured to a nozzle holder 13 in which is defined a chamber 14 to which in use, liquid fuel under pressure can be supplied by way of an inlet passage 1 5. Formed in the body 10 is a bore 1 6 which is open at its inner end to the chamber and which adjacent its other end, defines a seating 1 7. Downstream of the seating the bore defines an enlargement 1 8 having a right cylindrical wall. Extending outwardly from the wall is, in the particular example, a pair of outlet orifices 1 9.

Slidable withint the bore 1 6 is a valve member 20, the valve member extending from the bore into the chamber 14. The valve member has a head 21 which is shaped for co-operation with the seating 1 7 and which is a sliding fit within the enlargement 18. The valve member has a fluted portion 22 which is a sliding fit in the bore and extending into the bore from the chamber is a pair of apertures 23, the valve member at this point being of reduced diameter so as to permit when the valve head orifices 1 9.

Mounted about the stem of the valve member is a sleeve 24 having a flange 25 against which engages one end of a first coiled compression spring 26. The other end of the spring engages against the flange 11 of the valve body. The valve member at its end remote from the head 21 defines an enlargement with which is engaged a retainer member 27, the sleeve 24 engaging the retainer member.

In operation, when fuel under pressure is supplied by way of the inlet passage 1 5 to the chamber, the pressure of fuel acting on the valve member will eventually overcome the force exerted by the spring 26 to permit the valve head 21 to move away from the seating 17, thereby to allow fuel flow through the outlet orifices 1 9. The valve head controls the effective area of the orifices but in order to provide accurate control of the effective area of the orifices 19, the movement of the valve member itself must be carefully controlled and for this purpose a coiled compression spring 28 is provided which is stiffer than the spring 26. One end of the spring 28 engages against an inwardly turned flange formed on a hollow cylindrical spacer member 29 which engages with the flange 11 of the valve body.The other end of the spring 28 bears against an annular abutment ring 29 which has a hollow cylindrical extension 30. The inner surface 31 of the extension 30 is of truncated conical form, the surface flaring outwardly towards the inlet passage. Moreover, located between the surface 31 and the outer surface of the retaining member 27, is a plurality of collets 32. The collets have an inner surface conforming to the outer surface of the retainer member 27 and an outer surface of truncated conical form complementary to the surface 31. The collets are biased by a light coiled compression spring 33 into engagement with the surface 31.

In operation, the spring 33 applies a force to the collets which is opposed by the spring 28. This force however is so small as to cause substantially no deflection of the spring 28. As a result, the initial force required to lift the valve head from the seating is determined by the spring 26 but as soon as such movement does occur the spring 28 is brought into operation to assist the spring 26 in opposing movement of the valve member. The movement of the valve member and therefore the flow area of the orifices 19, is dependent upon the pressure at which fuel is supplied to the chamber and the combined spring forces.

If any wear takes place of, for example, the seating and the valve head, the nozzle opening pressure will be substantially unchanged because of the lower rating of the spring 26 which determines the nozzle opening pressure. The adjustment for wear in the connection between the valve member and the spring 28 is effected automatically by the action of the collets.

In the arrangement which is shown in Figure 2, the spring 26 operates as described with reference to Figure 1. The retainer member 27 is replaced by a modified retainer member 34 which forms an abutment for one end of the second and stiff spring 35. The other end of this spring engages with collets 36 having outer surfaces for engagement with the inner wall of the chamber and inner truncated surfaces for engagement with a truncated surface 37 formed on the external periphery of an annular member 38 which is biased by a light spring 39 in the direction towards the inlet passage 1 5. The mode of operation of the example shown in Figure 2 is substantially the same as the example shown in Figure 1 except that in this case the force exerted by the spring 39 is applied by way of the spring 35 to the retainer member 34 and it therefore assists the action of the spring 26.The nozzle opening pressure will however be largely determined by the spring 26 as in the example of Figure 1 and compensation for wear takes place in the same manner as in the example of Figure 1.

Turning now to Figure 3 the retainer member 34 is engaged by a spring abutment 35 which is of sleeve-like form but which has a flange engaged by one end of the spring 36 which isthe stiffer of the two springs, the other spring being the which is referenced 37. The other end of the spring 36 engages an annular member 38, the inner surface of which is of truncated form and which flares outwardly away from the inlet passage 15. The member 38 is also engaged by the spring 37 and the opposite end of the latter engages the flange 11 of the nozzle body 1 0. For engagement with the member 38 collets 39 are provided, these being biased towards the member 38 by means of a light spring 40.The collets 39 are engaged about an extended portion of the valve body 1 0. In the rest position of the nozzle as shown in the drawings, the springs 36 and 37 are effectively connected in series but the spring 36 being stiffer than the spring 37, is substantially uncompressed. The force exerted by the spring 37 is therefore applied to the valve member by way of the spring 36 and the nozzle opening pressure is therefore determined by the spring 37. When the pressure of fuel applied to the inlet 15 increases, the valve head will start to lift away from the seating at a pressure which is determined by the spring 37 but as soon a such movement takes place, the collets 39 will anchor the member 38 to the extended portion of the valve body. As a result, there will be no further compression of the spring 37 as the valve head moves away from the seating and the force opposing such movement of the valve head will be provided by the spring 36.

In this construction therefore the spring 37 only sets the opening pressure of the nozzle and once the member 38 has been anchored, it plays no further part. This of course is not the case with the springs 26 of the examples shown in Figures 1 and 2. in these cases the spring 26 resists movement of the valve member through the whole of its movement.

In the example shown in Figure 1, the clearance between the outer surface of the flange 25 and the inner surface of the spacer member 29 can be controlled so as to limit the rate of displacement of the valve member, the flange acting in conjunction with the inner surface of the spacer member, in the manner of a dashpot.

Claims

1. A fuel injection nozzle of the so-cafled outwardly opening type comprising a valve body, a bore defined in the body, a seating defined adjacent one end of the bore, the bore downstream of said seating defining an enlargement, a valve member movable axially within said bore, said valve member defining a head for co-operation with said seating, the head being located within said enlargement, said bore at its other end extending into a chamber to which in use, fuel under pressure can be supplied, the valve member having a stem extending into said chamber and resilient means located in said chamber for biasing the valve head into contact with the seating, said resilient means comprising a first spring the force exerted by which acts on the valve member to determine the pressure of fuel required to effect the initial lift of the valve head away from the seating and a second spring which is stiffer than the first spring and which opposes further movement of the valve member following the initial lift of the valve head from the seating.

2. a fuel injection nozzle according to Claim 1 including a collet mechanism operable following said initial lift, to render said second spring operative to oppose movement of the valve member.

3. A fuel injection nozzle according to Claim 2 in which said collet mechanism serves to couple one end of said second spring to a member connected to the valve member, the other end of said second spring being located against a part fixed relative to the valve body.

4. A fuel injection nozzle according to Claim 3 in which said member comprises a retainer member engaged with a stem of the valve member, said retainer member defining an outer surface, a plurality of collets located about said member and having surfaces engageable with said outer surface of the retainer member, said collets defining further surfaces for engagement with the internal surface of a hollow extension of an abutment ring engaged with said one end of the second spring, and a third spring for biasing said collets into wedging engagement with said internal and said outer surfaces.

5. A fuel injection nozzle according to Claim 2 in which one end of said second spring is operatively coupled to said valve member, said collet mechanism serving to operatively couple the other end of said second spring to said valve body.

6. A fuel injection nozzle according to Claim 5 including a holder to which said valve body is secured, said holder defining a chamber having an internal surface, said collet mechanism including a plurality of collets engaged with the other end of said second spring, the collets defining surfaces engageable with said internal surface and further surfaces engageable with the external surface of an annular member, and a third spring biasing said annular member whereby said collets are urged into gripping engagement with said internal surface.

7. A fuel injection nozzle according to Claim 5 including an annular member engaging at one end by the other end of said second spring, said annular member at its other end being engaged by one end of the first spring, the other end of the first spring engaging with said valve body so that the two springs act in series to oppose the initial lift of the valve head from the seating, said collet mechanism acting to couple said annular member to said valve body following said initial lift.

8. A fuel injection nozzle according to Claim 7 in which said annular member defines an internal surface, a plurality of collets having surfaces engageable with said internal surface and with an external surface of said valve body and a third spring operable to urge said collets into engagement with said surfaces.

9. A fuel injection nozzle comprising the combination and arrangement of parts substantially as hereinbefore defined with reference to Figure 1 of the accompanying drawings.

10. Afuel injection nozzle comprising the combination and arrangement of parts substantially as hereinbefore defined with reference to Figure 2 of the accompanying drawings.

11. A fuel injection nozzle comprising the combination and arrangement of parts substantially as hereinbefore defined with reference to Figure 3 of the accompanying drawings.