WO1992019857A1

WO1992019857A1 - Fuel injection nozzle

Info

Publication number: WO1992019857A1
Application number: PCT/GB1992/000675
Authority: WO
Inventors: John Southwood
Original assignee: Lucas Industries Public Limited Company
Priority date: 1991-04-26
Filing date: 1992-04-13
Publication date: 1992-11-12
Also published as: GB9109066D0

Abstract

A fuel injection nozzle of the two stage lift type has a valve member (13) movable axially in a nozzle body (10). The valve member is biased to the closed position by a first spring (27) which is housed in a spring chamber (17) defined in a spring housing (16). A second spring (28) surrounds the first spring and acts upon the valve member after a predetermined movement. The spring chamber and the springs have their axis offset from the axis of the valve member and this leaves the thickened wall of the spring housing through which extends a fuel supply passage (20) which conveys fuel to outlet orifices (11) controlled by the valve member (13).

Description

FUEL INJECTION NOZZLE

This invention relates to a fuel injection nozzle for supplying fuel to an internal combustion engine and of the kind comprising a nozzle body in which is mounted a fuel pressure actuated valve member movable from a closed position in which the valve member engages a seating, by fuel under pressure to allow flow of fuel through an outlet orifice, a first coiled compression spring acting on the valve member through a first spring abutment, a second coiled compression spring which acts on the valve member after a predetermined movement of the valve member away from the seating and means for limiting the movement of the valve- member away from the seating.

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 distance piece interposed between the nozzle body and a generally cylindrical spring housing, the nozzle body, the distance piece and the spring housing being held in assembled relationship by a cap nut, a cylindrical spring chamber formed in the housing, the axis of the spring chamber being offset from the axis of the valve member, a high pressure fuel supply passage formed in the spring housing and which communicates with a passage formed in the distance piece which in turn communicates with a passage formed in the nozzle body, the first and second springs being located in co-axial relationship within the chamber with the first spring being mounted within the second spring, the first spring abutment having a flange portion which engages after said predetermined movement of the valve member, with a second spring abutment engaged by said second spring, the second spring abutment in the closed position of the valve member engaging a first stop surface defined by said distance piece and a step on the valve member engaging with a second stop surface on the distance piece to limit the movement of the valve member away from the seating.

Examples of fuel injection nozzles in accordance with the invention will now be described with reference to the accompanying drawings which show portions of the nozzles in sectional side elevation.

Referring to Figure 1 of the drawings there is provided a nozzle body 10 of stepped cylindrical form and in the narrower end of which is formed a plurality of outlet orifices 11. Extending axially within the nozzle body is a guide bore 12 in which is mounted in known manner, a valve member 13 which adjacent the orifices is shaped for engagement with a seating to prevent flow of fuel through the orifices. The nozzle body defines a fuel inlet passage 14 which extends from the wider end of the body to a space defined about the valve member whereby when the valve member is lifted from its seating by the pressure of fuel in the space, fuel can flow through the outlet orifices 11.

Engaged with the wider end of the nozzle body is a distance piece 15 and this in turn is engaged by an end surface of a generally cylindrical spring housing 16. Formed in the spring housing is a cylindrical spring chamber 17, the axis of the chamber being offset from the longitudinal axis of the valve member 13. The distance piece defines a passage 18 which communicates with the passage 14 in the nozzle body 10 and with a passage 19 in the spring housing, the passage 19 including a portion 20 which is located in the thicker portion of the wall of the spring chamber. The .passage 19 conveniently extends to the axis of the spring housing and communicates with a further passage 21 which is formed in a nozzle holder 22, the passage 21 communicating with a fuel inlet which in use, is connected to the outlet of a high pressure fuel injection pump. The nozzle body, the distance piece, and the spring housing are held in assembled relationship by means of a cap nut 23 which is in threaded engagement with the holder 22.

Formed in the distance piece 15 is an axial drilling 24 in which is located an extension 25 of the valve member. The drilling opens into a cylindrical guide chamber 26 formed in the face of the distance piece adjacent the spring housing.

Located in the spring chamber is a pair of coiled compression springs 27, 28. The first spring 27 is mounted within the second spring and engages a first spring abutment 29 having a flange portion 30 which is located within the chamber 26. The peripheral surface of the flange 30 is rounded and the wall of the chamber 26 serves to locate the spring abutment which engages the extension 25 of the valve member. The second spring 28 engages an annular spring abutment 31 which in the closed position of the valve member as shown, engages a first stop surface 32 defined by the distance piece. Furthermore, in the closed position of the valve member a gap exists between the flange 30 and the spring abutment 31. The ends of the springs remote from the abutments engage through the intermediary of shims respectively, with the end wall of the spring chamber and the spring chamber is vented to a low pressure by means of a passage 34.

In operation, when fuel is delivered by the fuel pump, a force is exerted on the valve member 13 and as the fuel pressure increases the valve member will be moved axially against the action of the spring 27. This movement continues until the flange 30 on the first spring abutment is in full engagement with the second spring abutment 31. The predetermined movement of the valve member permits fuel to flow through the orifices 11 at a restricted rate and as the fuel pressure continues to increase, the fuel pressure acting on the valve member will be sufficient to cause the valve member to move against the action of both springs. The maximum movement of the valve member away from its seating to its fully open position, is limited by the engagement of a step defined on the valve member with a second stop surface 33 defined by the distance piece 15.

The thickness of the shims associated with the springs, determine the initial pressure required to lift: the valve member from the seating and the pressure at which the valve member moves against the action of both springs. As is well known in the art, fuel can leak past the working clearance defined between the valve member 13 and the guide bore 12 and this fuel flows into the spring chamber and through the passage 34 to a drain. In the particular example the fuel flows to the exterior of the nozzle through drain ports 35 formed in the cap nur 23.

The adjustment of the first stage of lift is achieved by selective assembly of the spring abutment 29 in particular the flange 30 thereof or the distance piece 15. Alternatively the parts could be ground as required.

In the example shown in Figure 2, the extension 25 on the needle is replaced by a separate cylindrical member 36 which is guided for movement in the bore m the distance piece 15.

The cylindrical member 36 is provided with a longitudinal or as shown, a helical groove 37, which defines with the wall of the drilling a leakage path along which fuel leaking past the valve member, can escape into the spring chamber 17. Adjustment of the first stage of lift is achieved as described or by selective assembly or grinding of the cylindrical member 36.

In the example shown in Figures 1 and 2 the edge of the flange 30 is rounded to minimise the risk of jamming if the spring abutment 29 tilts due to the fact that the line of action of the spring 27 is offset relative to the valve member 13 or the cylindrical member 36. In the example of Figure 3 the flange 40 of the spring abutment 39 is smaller in diameter and the spring abutment is held against tilting by the fact, that the cylindrical member 41 is integrally formed with the spring abutment.

Claims

1. A fuel injection nozzle for supplying fuel to an internal combustion engine and of the kind comprising a nozzle body (10) in which is mounted a fuel pressure actuated valve member (13) movable from a closed position in which the valve member engages a seating, by fuel under pressure to allow flow of fuel through an outlet orifice (11), a first coiled compression spring (27) acting on the valve member through a first spring abutment (29), a second coiled compression spring (28) which acts on the valve member after a predetermined movement of the valve member away from the seating, a distance piece (15) interposed between the nozzle body (10) and a generally cylindrical spring housing (16), a cap nut (23) which holds the nozzle body, the distance piece and the spring housing in assembled relationship, a cylindrical spring chamber (17) formed in the spring housing, the axis of the spring chamber being offset from the axis of the valve member (13), a high pressure fuel supply passage (20) formed in the wall of the spring housing, the supply passage (18) communicating with a transfer passage (18) in the distance piece (15) which in turn communicates with an inlet passage (14) in the nozzle body (10), the first and second springs (27, 28) being located in co-axial relationship within the chamber (17) with the first spring being located within the second spring, the first spring abutment (29) having a flange portion (30) which engages after said predetermined movement of the valve member with a second spring abutment (31) engaged by said second spring (28), the second spring abutment in the closed position of the valve member engaging a first stop surface (32), defined by the distance piece (15) and a step on the valve member engaging with a second stop surface defined by the distance piece to limit the movement of the valve member away from the seating.

2. A nozzle according to Claim 1, in which said supply passage (20) is formed in part in the thicker portion of the wall of the spring housing (16).

3. A nozzle according to Claim 1, in which said valve member (13) is provided with an extension (25) which extends through a drilling (24) in the distance piece into engagement with the first spring abutment (29).

4. A nozzle according to Claim 1, including a cylindrical member (36, 41) which is guided for movement in a drilling (24) formed in the distance piece, said cylindrical member extending between the valve member (13) and the first spring abutment (29, 39).

5. A nozzle according to Claim 4, in which said cylindrical member (41) is integral with the first spring abutment (39).

6. A nozzle according to Claim 4 or Claim 5, in which the cylindrical member (36, 41) and the wall of the drilling (24) define a leakage path for fuel which leaks past the valve member.

7. A nozzle according to Claim 1, in which the flange portion (30) is located within a chamber (26) defined in the distance piece (15).

8. A nozzle according to Claim 7, in which the peripheral surface of the flange portion (30) is rounded for co-operation with the wall of said chamber (26).