JPH02169863A - Fuel-injection nozzle - Google Patents

Abstract

PURPOSE: To reduce the slanting of a sleeve and increase the strength of a fuel injection nozzle by providing a piston member having a stepped external surface and slidable in a stepped cylinder, and defining an annular chamber connected to a fuel inlet by the stepped portion of the cylinder. CONSTITUTION: A spacer 12 defines a bore 24 with a piston member of the shape of a sleeve 25 slidable arranged therein. The sleeve 25 has a thin end portion in the vicinity of a nozzle body 10, and is step-shaped. The bore 24 is also stepped, with the stepped portion thereof defining an annular chamber 26 around the sleeve. Thud a stepped portion if formed on the external surface of the sleeve 25, therefore the force acting on the sleeve due to the fuel pressure of a fuel inlet can be adjusted easily.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection nozzle for supplying fuel to an internal combustion engine, in which pressurized fuel supplied to the inlet acts to lift a valve member from a valve seat against the action of an elastic means. a valve member defining a surface on which pressurized fuel from the inlet can act, and defining a surface on which pressurized fuel from the inlet can act, when lifted from the valve seat, allowing flow of fuel from the inlet to the outlet; The present invention relates to a fuel injection nozzle comprising a piston member operative to assist the initial movement of a valve member against the operation of a stop means which limits the movement of the piston member.

Fuel injection nozzles of the type described above have a two-stage configuration in which the valve member is lifted from the valve seat, one stage of lifting allowing fuel supply to the internal combustion chamber of the associated engine at a limited rate; The two stages allow fuel to flow at a substantially unrestricted rate. The fuel pressure required to lift the valve member from its valve seat, conventionally known as the nozzle opening pressure, is less than the fuel pressure required to lift the valve member through two stages of lifting.

The nozzle opening pressure depends on the force exerted by the elastic means and the area of the faces of the valve member and piston member exposed to the inlet fuel pressure. The pressure required to move only the valve member depends on the force exerted by the elastic means and the area of the surface. Here, when the valve member is lifted from the valve seat, a part of the valve member is exposed to the fuel pressure because a part of the valve member is exposed to the fuel pressure when the valve member is in contact with the valve seat. The area increases only slightly.

The above type of fuel injection nozzle is described in British Special Specification No. 153.
No. 1580. In the two examples described in the above specification, the piston member is constituted by one or more pistons slidable in one or more bores. In each case, one end face of the piston is exposed to fuel pressure at the fuel inlet of the nozzle, and the other end of the piston engages the valve member or said resilient means receiver. Other 2 listed in Mei aS
In one embodiment, the piston member is in the form of a slidable sleeve surrounding the valve member, one end face of the sleeve being exposed to fuel pressure at the fuel inlet of the nozzle, and the other end of the sleeve being connected to the valve member or said receiver. to engage the part.

A similar type of injection nozzle in which the piston member is in the form of a sleeve engaging a valve member is disclosed in British Patent Specification No. 2145.
No. 468B. In applications of nozzles of the type described above, the increase in fuel pressure required to move the valve member through the second stage of operation is due to the action of counterpressure waves in the piping connecting the fuel inlet of the nozzle to the associated fuel injection pump. The nozzle opening pressure is significantly lower than the nozzle opening pressure to reduce the risk of the valve member being lifted off its valve seat by the gas pressure in the associated internal combustion chamber of the engine. It is required that it should not be too high. These risks can be minimized by increasing the pressure required to lift the valve member through the nozzle opening and the second stage of operation, but the rear right pressure becomes undesirably high.

To reduce the difference between the two pressures, the area of the piston member exposed to fuel pressure may be reduced. However, in the case of sleeves, the reduced section first causes problems in the manufacture of the sleeve, and secondly, the thinner the sleeve section, the more prone it is to distortion, either by hydraulic or mechanical pressure. . Additionally, the area of the sleeve that engages the valve member or receiver is reduced if the sleeve is not flanged. In the case of pistons, the diameter is reduced, but there is a risk that distortion will occur again.

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

According to the invention, in a particular type of nozzle, the piston member has a stepped outer circumferential surface and is slidable within a stepped cylindrical portion, the stepped portion of the cylinder defining an annular chamber connected to a fuel inlet. DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a fuel injection nozzle according to the invention will now be described with reference to the drawings.

Referring to the drawings, the injection nozzle consists of a stepped nozzle body 10 fixed to a tubular long nozzle holder 11.

There is a spacer 12 intermediate the holder and the nozzle body, and these components are held in assembled relationship by a cap nut 13.

The nozzle body defines a blind hole 14 in which a valve seat 15 is formed which leads to a sac-shaped deposit extending to an outlet hole 16. An annular chamber 17 is defined intermediate the end of the hole 14, which is connected to a fuel inlet passage 18 extending through a spacer and a retainer to a fuel inlet (not shown), the fuel input being in use via piping. Connected to the outlet of the fuel injection pump.

A valve member 19 is disposed within the bore 14 . A portion of the valve member lies between the chamber 17 and the valve seat, which is reduced in diameter so as to define an annular gap with the wall of the bore. A portion of the valve material between chamber 17 and the open 1'' end of the hole is an open fit in the wall of the hole. The inner end of the valve member is shaped to cooperate with the valve seat, the opposite end of the valve member extends from the bore, and the portion proximate the spacer 12 is enlarged to accommodate a flange 20 formed on the valve member. .

The holding body 11 has a cylindrical chamber 21 in which a coil compression spring 22 is located.
Define. The end of the spring remote from the spacer engages a suitable spring receiver adjustably mounted within the holder.

The end of the spring 22 near the spacer engages a spring receiver 23 that engages the end of the valve member 19 away from the valve seat.

The spacing hole 12 defines a bore 24 in which a piston member in the form of a sleeve 25 is slidably disposed.

As is clear from the drawings, the sleeve 25 has a stepped shape with a narrow end located near the nozzle body. hole 2
4 is also stepped, but the stepped part of the hole is an annular chamber 2 surrounding the sleeve.
6, the chamber 26 communicates with a portion of the passage 18 within the spacer by a borehole 27. The diameter of the narrow end of the sleeve is such that the diameter of the bore in the nozzle body is such that a step is defined that moves to limit the downward movement of the sleeve.
slightly larger than the diameter of the enlarged part. In the closed position of the valve member, a gap, indicated by reference symbol A, exists between the two flanges 20 on the valve member and the adjacent ends of the nozzle body. Furthermore, the reference symbol B indicates the amount by which the spring receiver 23 projects beyond the end of the retainer in the closed position of the valve member.

Furthermore, the I of the sleeve 25 supported by the nozzle body 10 is
[At the l end, a small gap, indicated by reference symbol C, exists between the wide end of the sleeve and the spring receiver.

The end of the spring receiver 23 that engages with the valve member overhangs the valve member to be engaged by a sleeve 25 as described below.

The hole in the sleeve has a larger diameter than the valve, so that a gap exists between the valve member and the sleeve and communicates with the enlarged portion of the hole 14 that receives the flange 20 and also with the borehole 2 in the receiver 23.
8 and a groove in the end face of the valve member or spring receiver also communicates with the chamber 21 accommodating the spring. In use, this chamber is connected to a drain.

It is understood that the opposite end faces of the sleeve are exposed to the same pressure.

In operation, when pressurized fuel is supplied through the fuel inlet, fuel pressure acts on the valve member to generate a force that acts to lift the valve member from the valve seat. In addition, the pressure fuel supplied to the annular chamber 26 causes a force to act on the spring receiver 23 due to the difference in diameter of the sleeve 25, causing the sleeve to move upwardly to eliminate the gap C and engage with the spring receiver. generates an acting force. The forces acting on the valve member and the sleeve are therefore in the same direction; if the fuel pressure rises to a sufficient value, the force exerted by the spring 22 is overcome and the valve member directs the fuel from the chamber 17 through the outlet 16. It is lifted from its valve seat so that it can be flushed. The further movement of the valve member is determined by the gap B.

When the sleeve 25 engages the retaining body 11, the force acting on the sleeve due to the fuel pressure is no longer transmitted to the spring receiver. This limited movement of the valve member allows limited flow of fuel to the associated engine due to the restriction of the small gap between the valve member and its seat. As the inlet fuel pressure continues to increase, the fuel pressure acting on the valve member will eventually generate a force sufficient to move the valve member against the action of the spring, causing the valve member to move so that the flange 2o is against the sleeve 25. Move to its fully open position to engage. The maximum movement of the valve member from the closed position to the fully open position is the sum of gaps A, B and C, and the movement of the valve member in the first stage is equal to gap B.

When the inlet fuel pressure is reduced, the valve member returns to the closed position and the residual fuel pressure tends to cause the sleeve to remain in contact with the spring receiver 23.

By providing a step on the outer circumference of the sleeve, the force exerted on the sleeve by the fuel pressure at the fuel inlet can be easily adjusted by varying the difference in diameter between the wide and narrow portions of the sleeve. At the same time, the walls of the sleeve have sufficient thickness so that the sleeve can withstand hydraulic and mechanical forces.

As shown, the nozzle body 10 is constructed in two parts.

Of course, it can be formed from a single piece.

If desired, the spacer 12 can be formed integrally with the nozzle body.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional side view showing a substantial portion of the nozzle, and FIG. 2 is an enlarged view of a portion of the nozzle shown in FIG. 10... Nozzle body, 11... Nozzle holder, 12
... Spacer, 13... Cap nut, 14...
・Blind hole, 15... Valve seat, 16... Outlet, 17.
...Annular chamber, 18...Inlet passage, 19...Valve material, 2o
... flange, 21 ... cylindrical chamber, 22 ... coil pressure spring, 23 ... spring receiver, 24 ... hole, 25 ...
...Sleeve, 26...Chamber, 27.28...Drilling hole. Patent Applicant Lucas Industries Public
Limited Company IG2

Claims (1)

Claims: (1) defining a surface on which pressurized fuel supplied to the inlet can act to lift the valve member from the valve seat (15) against the action of the elastic means (22); a valve member (19) which, when lifted from the seat, allows the flow of fuel from the inlet to the outlet (16) and a resilient means (22) defining a surface on which the pressurized fuel from the inlet can act; and the valve member (19) against the operation of the stop means limiting the movement of the piston material
) act to assist in the initial movement of the piston member (2
5), in which the piston member (25) has a stepped outer circumferential surface and is slidable within the stepped cylindrical portion (24); A fuel injection nozzle, characterized in that the stepped part of the cylindrical part is accentuated to define an annular chamber (26) connected to the fuel inlet, and the end face of the piston member (25) is exposed to the same pressure. 2. A fuel injection nozzle as claimed in claim 1, characterized in that the piston member (25) is in the form of a sleeve from which the valve member extends. (3) The valve member (19) is connected to the sleeve (2) with a gap.
5) The fuel injection nozzle of claim 2, wherein the sleeve extends through a drain, the gap communicating with a drain so that the opposite end of the sleeve is exposed to drain pressure. (4) The end of the sleeve (25) remote from the valve seat (15) has a spring retainer (2) to assist movement of the valve member (19).
3), and said end of the sleeve is also engageable with an end surface of the nozzle holder (11) so as to limit the movement of the sleeve. nozzle. (5) Valve member (1) in which the flange separates from the valve seat (15)
a flange (2) on the valve member (19) which is engageable with the opposite end of the sleeve (25) to limit the total movement of the sleeve (25);
5. The fuel injection nozzle according to claim 4, wherein the fuel injection nozzle has: 0). (6) The fuel injection nozzle according to claim 5, characterized in that the cylindrical portion (24) is formed within a spacer (12) located between the nozzle body (10) and the nozzle holder (11).