GB2204357A

GB2204357A - I. C. engine fuel injection nozzle

Info

Publication number: GB2204357A
Application number: GB08807701A
Authority: GB
Inventors: David John Gaskell
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1987-05-08
Filing date: 1988-03-31
Publication date: 1988-11-09
Also published as: GB8807701D0; GB8710976D0

Abstract

The fuel pressure operated valve member 15 carries in a bore 20, a slidable flow restricting pin 21 which is biased into engagement with a portion of the seating 12. The flow restricting pin 21 and/or said portion of the seating define grooves 30 and the arrangement is such that when the valve member is first lifted from the seating fuel flow through the outlets takes place at a restricted rate due to the grooves but when the valve member is lifted further the flow restricting pin is also lifted from the seating to allow unrestricted flow of fuel. <IMAGE>

Description

"FUEL INJECTION NOZZLE" This invention relates to a fuel injection nozzle for supplying fuel to an internal combustion engine of the compression ignition type, the nozzle being of the so-called inwardly opening type and comprising a valve member which is resiliently biased into contact with a seating and which is lifted from the seating to allow fuel flow from an inlet to an outlet which is disposed downstream of the seating, by fuel under pressure supplied to the inlet.

In many engine applications it is customary to construct the fuel system of which the nozzle forms part in such a manner that the initial flow of fuel to the engine takes place at a restricted rate. It is common practice to arrange that the clearance between the valve member and the seating forms the restriction to the flow of fuel through the outlet. However, this requires very careful control of the initial lift of the valve member as well as very accurate machining of the valve member and the seating so that the fuel flows through the outlet at the desired restricted rate.

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 in a fuel injection nozzle of the kind specified the valve member defines a central bore, a flow restricting pin slidable in said bore, further resilient means biasing the flow restricting pin to an operative position to restrict fuel flow through said outlet and interengageable means on the valve member and flow restricting pin whereby after a predetermined movement of the valve member away from the seating the flow restricting pin will be moved from its operative position.

An example of a fuel injection nozzle in accordance with the invention will now be described with reference to the accompanying drawing which is a sectional side elevation through part of the nozzle.

Referring to the drawing the fuel injection nozzle includes a body 10 in which is formed a bore 11 at one end of which is defined a seating 12 of frustoconical form. The seating leads into a so-called "sac" volume 13 from which extends outlet orifices 14.

Slidable in the bore 11 is a valve member 15 the portion of the valve member which is seen in the drawing being of reduced diameter to define a clearance 16 with the bore, the clearance being connected to a fuel inlet 17 formed in another part of the body. The valve member has a double tapered portion 18 for co-operation with the seating 12 and the valve member is biased into contact with the seating by means of first resilient means in the form of a coiled compression spring diagrammatically illustrated at 19.

The valve member defines a surface against which the fuel under pressure supplied through the inlet 17 can act to lift the valve member from the seating against the action of the spring 19 in the usual manner.

The portion 18 of the valve member is provided with a central bore 20 in which is slidably mounted a flow restricting pin 21 which is shaped to co-operate with the portion of the seating 12 adjacent the sac volume 13. In addition, the pin is provided with a flange 22 which is engaged by a further resilient means in the form of a coiled compression spring 23 which is housed within a chamber 24 formed in the valve member and communicating by way of a passage 25, with a drain.

In order to assemble the valve member the portion 18 is constructed separately from the main portion of the valve member and it is provided with a skirt portion 26 which locates about a reduced portion 27 of the main portion of the valve member. The two parts of the valve member can be secured together in any convenient manner such for example as by electron beam or laser welding or by utilizing a press fit.

The movement of the flow restricting pin 21 relative to the valve member is determined by the abutment of the flange 22 with a step 28 defined by the main portion of the valve member and by an abutment surface 29 defined by the portion 18 of the valve member.

In operation, when fuel under pressure is supplied through the fuel inlet 17 the pressure acts upon the valve member to move the main portion of the valve member together with the portion 18, against the action of the spring 19 away from the seating. The flow restricting pin is however maintained in contact with the seating by means of the spring 23 and a restricted flow of fuel occurs due to the fact that the flow restricting pin and/or the portion of the seating 12 adjacent the sac, is/are grooved such grooves being indicated at 30. Fuel can therefore flow through the outlet orifices 14 at a restricted rate. As the valve member continues to move the abutment surface 29 will engage the flange 22 and the flow restricting pin will be lifted out of engagement with the seating thereby allowing an increased rate of fuel flow to the associated engine.As the pressure at the inlet continues to rise, the flow restricting pin will be moved against the action of the spring 23, the extent of such movement being limited by the abutment of the flange with the step 28.

In the nozzle as described the movement of the valve member will be limited by a stop which will be spaced from the valve member when the latter is in the position as shown, by a distance greater than the distance between the abutment face 29 and the flange.

It is possible however to utilize the construction as described with a valve member which has two stages of lift. In this case the first stage of lift of the valve member would involve movement of the valve member away from the seating by a distance equal to or less than the distance between the surface 29 and the flange 22. As the valve member moves through the second stage of lift, the flow restricting pin would be lifted from the seating to allow unrestricted flow of fuel to the associated engine.

Claims

1. A fuel injection nozzle for supplying fuel to an internal combustion engine of the compression ignition type, the nozzle being of the so-called inwardly opening type and comprising a valve member which is resiliently biased into contact with a seating and which is lifted from the seating to allow fuel flow from an inlet to an outlet disposed downstream of the seating, by fuel under presusre supplied to the inlet, the valve member defining a central bore, a flow restricting pin slidable in said bore, further resilient means biasing the flow restricting pin to an operative position to restrict fuel flow through said outlet and interengageable means on the valve member and the flow restricting pin whereby after a predetermined movement of the valve member away from the seating the flow restricting pin will be moved from its operative position.

2. A fuel injection nozzle according to Claim 1 in which said flow restricting pin is shaped to co-operate with a portion of said seating, said portion of the seating and/or the shaped portion of the pin being provided with a groove which provides for the restricted flow of fuel.

3. A fuel injection nozzle according to Claim 1 or Claim 2 in which said flow restricting pin is formed with a flange which co-operates with an abutment surface to move the flow restricting pin from its operative position.

4. A fuel injection nozzle according to Claim 3 in which said bore and said abutment surface are defined in a tapered portion of the valve member which is secured to the main portion of the valve member and which in the closed position of the valve member co-operates with said seating.

5. A fuel injection nozzle according to Claim 4 in which said second resilient means comprises a coiled compression spring which is housed within a chamber defined in the main portion of the valve member.

6. A fuel injection nozzle according to Claim 5 in which said chamber is in communication with a drain.

7. A fuel injection nozzle for supplying fuel to an internal combustion engine of the compression ignition type comprising the combination and arrangement of parts substantially as hereinbefore described with reference to the accompanying drawing.