GB2149848A

GB2149848A - Fuel injection nozzle

Info

Publication number: GB2149848A
Application number: GB08425628A
Authority: GB
Inventors: David John Gaskell
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1983-11-12
Filing date: 1984-10-10
Publication date: 1985-06-19
Also published as: FR2554872B1; ES537557A0; IT1177026B; ES8601406A1; GB2149848B; GB8330258D0; JPS60113063A; GB8425628D0; IT8423294A0; IT8423294A1; DE3440852A1; FR2554872A1

Abstract

A nozzle holder 18 defines a chamber 22 in which is located a coiled compression spring 24 which serves to bias a valve member 11 of the nozzle to the closed position. A spring abutment 25 is axially slidable in the chamber to enable the force exerted by the spring to be adjusted and the abutment is engaged by a coupling member 30 having spherical end portions engaging in a spherical recess 26 in the abutment and in a spherical recess 29 in a plug member 28 adjustably mounted in a bore 27. The axis of the bore is inclined to the axis of the nozzle and axial movement of the plug member within its bore results in axial movement of the abutment to adjust the spring force. <IMAGE>

Description

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

The fuel pressure which is required to move the valve member against the action of the spring depends at least in part on the force exerted by the spring. The spring is confined between an abutment on the valve member and an abutment in the chamber. However, due to manufacturing tolerances it is not possible when assembling the injection nozzle to guarantee that the valve member will start to move against the action of the spring at a predetermined fuel pressure. It is important that each injection nozzle should open at the predetermined pressure and it is known in some forms of injection nozzle to provide an adjustable abutment in the form of a screw threaded member which is accessible from the end of the injection nozzle remote from the nozzle body.When the fuel injection nozzle is of the type having an axially disposed fuel inlet, this form of adjustment is difficult to achieve and it has been the practice to employ shims to adjust the force exerted by the spring. The use of shims however requires repeated assembly and disassembly of the injection nozzle until the correct pressure is achieved.

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 extends through the wall of the nozzle holder transversely to the axis of the injection nozzle.

The screw or pin can be moved inwardly or outwardly to cause axial movement of the abutment. This form of adjustment imposes substantial loading on the screw or pin and also the abutment and is not considered to be very satisfactory.

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 abutments disposed at the opposite ends of the spring, the one abutment remote from the valve member defining a concave recess in its face remote from the spring, a screw threaded bore formed in the holder, said bore being located in a plane containing the longitudinal axis of the nozzle but inclining away from said axis, an adjustable plug located in said bore, said plug defining a concave recess at its inner end and coupling means defining surfaces of convex shape which locate in said recesses respectively, the arrangement being such that adjustment of said plug within its bore will impart axial movement to said one abutment through said coupling means.

An example of a fuel injection nozzle in accordance with the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a sectional side elevation of one example of the nozzle, and Figure 2 is a part section showing a modification to the nozzle of Fig. 1.

Referring to Fig. 1 of the drawings, the fuel injection nozzle comprises a nozzle body 10 in which is slidably mounted a fuel pressure actuated valve member 11, the valve member being located in a bore 1 2. A reduced portion 1 3 of the valve member extends from the bore 1 2 and at its opposite end the valve member is shaped to co-operate with a seating 1 4 defined at the end of the bore upstream of an outlet 1 5. Intermediate its ends the bore is enlarged to define an annular space which communicates with a fuel inlet passage 1 6. The portion of the valve member between the enlargement and the seating is of reduced diameter to permit when the valve member is lifted from its seating, flow of fuel through the outlet.In the particular example the valve member has an extension which protrudes through the outlet, the extension being shaped to modify the effective size of the outlet depending upon the axial position of the valve member.

The exterior surface of the body 10 is of stepped form and the narrower portion of the body extends through an aperture in the base wall of a cap nut 1 7 which secures the nozzle body to a cylindrical nozzle holder 1 8. Interposed between the end of the holder and the nozzle body is a distance member 1 9 which acts to limit the movement of the valve member away from the seating. The nozzle holder at its end remote from the nozzle body, defines an axially arranged fuel inlet 20 which communicates with the inlet passage 1 6 by way of a passage 21 formed in the wall of the nozzle holder and a communicating passage or drilling formed in the distance member 1 9.

The nozzle holder defines a chamber 22 into which the reduced portion 1 3 of the valve member extends and which accommodates a coiled compression spring 23 located between abutments 24, 25. The abutment 24 is mounted upon the end of the extension 1 3 and the abutment 25 is slidably mounted in the chamber and in its end surface remote from the spring, is provided with a part spherical recess 26.

Also formed in the nozzle holder is a screw threaded bore 27. The axis of the bore 27 lies in a plane containing the longitudinal axis of the nozzle but is inclined away from the aforesaid longitudinal axis in the direction of the inlet 20. Located in the bore is a complementarily threaded plug 28 in the inner end of which is formed a part spherical recess 29.

A coupling means 30 is provided and this has part spherical convex end portions which are located in the recesses 26 and 29 respectively. The axis of the coupling means is also inclined to the aforesaid longitudinal axis of the nozzle. Conveniently the plug at its outer end, is provided with a recess having hexagonal sides whereby an adjusting key can be engaged therewith and the outer end portion of the plug is enlarged and shaped to provide an interference fit and therefore a fuel tight fit, with the wall of an unthreaded portion of the bore 27. When the plug is moved inwardly or outwardly, appropriate axial movement will occur of the spring abutment 25 thereby to adjust the force exerted by the spring 23 upon the valve member. The aforesaid interference fit between the outer end portion of the plug and the wall of the bore serves to lock the plug against vibration etc.

to which the nozzle is subjected when in use.

In the arrangement shown in Fig. 2, the adjustable plug 31 is of shorter axial length and the locking function is provided by a locking member 32 which is in screw thread engagement with the bore. In addition, an end plug 33 is located in the end of the bore to provide the necessary fuel tight seal for the bore.

In a modification of the arrangement shown in Fig. 2 the plug 31 is locked in position by a screw incorporating a plastics insert or ring which will act to provide a fuel tight seal.

The coupling means 30 illustrated is of one piece construction and is of reduced section intermediate its ends. It can be formed using conventional metal shaping techniques or it can be formed by securing together as by welding for example, a pair of ball bearings.

Alternatively the coupling means may comprise a pair of ball bearings located in the recesses respectively the bearings being either free or captive within the recesses. In this case there is point contact between the balls.

Claims

1. A fuel injection nozzle comprising a nozzle body in which is located a fuel pressure actuated valve member, a hollow nozzle holder which is retained relative to the nozzle body by means of a cap nut, the holder defining an axially disposed fuel inlet which is connected by a passage in the wall of the holder to an inlet passage of the nozzle body, the chamber defined within the holder accommodating a coiled compression spring which biases the valve against the action of fuel under pressure supplied to the fuel inlet, abutments disposed at opposite ends of the spring, the one abutment remote from the valve member defining a concave recess in its face remote from the spring, a screw threaded bore formed in the holder, said bore being located in a plane containing the longitudinal axis of the nozzle but inclining away from said axis, an adjustable plug located in said bore, said plug defining a concave recess at its inner end and coupling means defining surfaces of convex shape which locate in said recesses respectively, the arrangement being such that adjustment of said plug within its bore will impart axial movement to said one abutment through said coupling means.

2. A nozzle according to Claim 1 in which said one abutment is guided for axial movement by the wall of said chamber.

3. A nozzle according to Claim 1 or Claim 2 in which said plug is in screw thread engagement with said bore, and means is provided for restraining said plug against rotation within the bore.

4. A nozzle according to Claim 3 in which said retaining means comprises an enlarged portion at the outer end of the plug said enlarged portion having an interference fit with a plain portion of the bore.

5. A nozzle according to Claim 3 including a locking member in screw thread engagement within the bore, said locking member being engageable with the plug to prevent rotation thereof and means for sealing the outer end of the bore.

6. A nozzle according to Claim 2 in which said coupling means comprises a member having part spherical convex end portions and a reduced intermediate portion.

7. A nozzle according to Claim 6 in which said coupling means comprises a pair of ball bearings which are secured together.

8. A nozzle according to Claim 2 in which said coupling means comprises a pair of ball bearings located in said recesses respectively.

9. A nozzle according to Claim 8 in which said bearings are captive within the respective recesses.

10. A fuel injection nozzle comprising the combination and arrangement of parts substantially as hereinbefore described with reference to Fig. 1 of the accompanying drawings.

11. A fuel injection nozzle comprising the combination and arrangement of parts substantially as hereinbefore described with reference to Fig. 1 as modified by Fig. 2 of the accompanying drawings.