GB2310893A

GB2310893A - Fuel injection valve for i.c. engines

Info

Publication number: GB2310893A
Application number: GB9702798A
Authority: GB
Inventors: Erguen Filiz; Friedrich Boecking
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1996-03-09
Filing date: 1997-02-12
Publication date: 1997-09-10
Anticipated expiration: 2017-02-12
Also published as: FR2745853A1; GB9702798D0; CN1160815A; DE19609218A1; FR2745853B1; DE19609218B4; JPH09242650A; CN1077224C; GB2310893B

Description

2310893 1 Fuel jMjection valve for internal combustion - i

Background art

The invention proceeds from a fuel injection valve for internal combustion engines according to the preamble of claim 1. In such a fuel injection valve known from DE-OS 33 06 078, a piston-shaped valve element (valve needle) is guided so as to be axially displaceable counter to a closing force in a pilot bore in the form of a blind hole in a valve body. The valve element at its end directed towards the combustion chwnber has a conical valve sealing surface, by means of which the valve element cooperates with a conical valve seating face at the inwardly projecting, closed end of the blind hole. At least one injection opening leads from the conical valve seating face into the combustion chamber of the i.c. engine to be supplied and is sealed by the valve sealing surface of the valve element when the injection valve is closed. Adjoining the upstream end of the valve seating face is a pressure channel Mi the valve body, which pressure channel is formed between the valve element stem and the wall of the blind hole and through which the highly pressurized fuel is conveyed to the valve seat.

The closed end of the blind hole in the known fuel injection valve is of a cylindrical or spherical construction mi order to form a run-out surface for a grinding tool used to machine the valve seating face. This however has the drawback of forming, in combination with the valve element tip, a relatively large dead volume in the closed end of the blind hole, in which a detrimental fuel quantity impairing the injection process collects.

Advantages of the invention 2 In contrast the fuel injection valve for i.c. engines according to the invention having the characterizing features of claim 1 has the advantage that by virtue of the improved geometry of the closed end of the blind hole mi the valve body the detrimental volume formed theremi may be reduced to a minimum. This is achieved in a constructionally simple manner by a cylindrical annular web in the region of the closed end of the blind hole, which annular web enables a separation of the valve seating face from the surface running into the closed end. Said annular web disposed between the valve seating face and the surface of the closed end of the blind hole provides a tool run-out for machining the valve seating face, which run-out is midependent of the construction of the closed end of the blind hole. Consequently, the closed end may, in terms of its shape, be constructed independently of the valve seating face. For a particularly low detrimental volume, said closed end is of a cone- shaped construction so that only a low gap dimension remains between the wall of the blind hole and the valve sealing surface of the valve element. The bottom or apex of the cone-shaped closed end of the blind hole is advantageously rounded off given a flattened-out valve element tip so that, here too, only a minimal detrimental volume remamis when the valve element is applied against the valve seat.

To achieve the described advantageous effect of a free tool run-out of the valve seating face requires only a very small cylindrical annular gap, the axial extension of which need not therefore be greater than 0. 1 mm. In addition, it is particularly advantageous to make the cone angles of the conical valve seating face and the cone-shaped closed end of the blind hole substantially identical in size because it is then possible, mi combination with the cone of the valve sealing surface, to achieve residual gap dimensions which are as small as possible.

The cone-shaped end piece adjoinffig the annular gap is advantageously drilled as a small cone which is subsequently reduced by seat-grinding to a minimum value.

3 Further advantages and advantageous reflinements of the subject matter of the invention are indicated in the description, the drawings and the claims.

Drawing An embodiment of the fuel injection valve for i.c. engines according to the invention is illustrated in the drawing and explained in detail in the following description.

Figure 1 shows a longitudinal section through the injection end of an otherwise known fuel injection valve having the refinement according to the invention of the closed end of the blind hole.

Description

In the embodiment of the fuel injection valve for i.c. engines according to the invention, of which only the part directed towards the combustion chamber and central to the invention is shown in Figure 1, a pistonshaped valve element 1 is guided in an axially displaceable manner in a blind hole 3 of a valve body 5. The valve element 1 at its bottom end directed towards the combustion chamber has a conical valve sealing surface 7, by means of which the valve element cooperates with a conical valve seating face 9 on the inwardly projecting closed end of the blind hole 3. Leading from the valve seating face 9 are two injection openings 11 which open at the periphery of the valve body 5 into the combustion chamber of the i.c. engine. When the in ection valve is closed, i.e. when a closing spring (not j shown) keeps the valve element 1 applied against the valve seat 9, the inlet openings of the injection openings 11 are sealed by the valve sealing surface 7 on the valve element 1. For supplying the highly pressurized fuel from a highpressure fuel source, preferably an injection pump, a pressure chamber 13 is 4 formed between the stem of the valve element 1 and the wall of the blind hole 3 and extends as far as the upstream end of the valve seating face 9.

To enable the geometry of the closed end of the blind hole 3 to be fashioned independently of the valve seating face 9, the downstream end of the valve seating face 9 is adjoined by a cylindrical annular step or annular web 15 having a diameter of at most 0.6 nun and an axial extension X of at most 0. 1 mm. The end of the annular web 15 remote from the valve seating face 9 adjoins a surface 17 of the closed end of the blind hole 3 which is constructed in the shape of a hollow cone. The conical valve seating face 9 and the hollow cone-shaped end 17 of the blind hole 3 preferubly have the same cone angle so that, when the valve element 1 is applied against the valve seat 9, the gap dimension between the sealing surface 7 of the valve element 1 and the wall of the blind hole 3 is kept as small as possible. By way of adaptation to the flattened tip 19 of the valve element 1, the closed bottom 21 of the hollow cone-shaped end 17 of the blMid hole 3 is moreover rounded off in such a way that, when the valve element 1 is applied against the valve seat 9, only a very low clearance rernamis between the valve element tip 19 and the bottom 21 of the blind hole 3.

It is therefore possible with the fuel injection valve according to the invention substantially to reduce the detrimental volume enclosed between the valve element 1 and the closed end of the blind hole 3 without impairing the high quality of machining of the valve seating face 9 serving as a sealing surface.

Claims

1.

2.

3.

4.

Fuel injection valve for internal combustion engines, having a valve element (1), which is guided so as to be axially displaceable counter to a closing force in a blind hole (3) of a valve body (5) and at its one end has a conical valve sealing surface (7), by means of which the valve element cooperates with a conical valve seating face (9) at the inwardly projecting, closed end of the blind hole (3), and having at least one injection opening (11), which leads from the valve seating face (9) into the combustion chaniber of the i. c. engine and is covered by the valve sealing surface (7) when the injection valve is closed, characterized in that the blind hole (3) at its closed end (17) is of a cone-shaped construction, a cylindrical annular web (15) being provided between the conical valve seating face (9) and the cone-shaped end (17) of the blind hole (3).

Fuel injection valve according to claim 1, characterized in that the axial extension of the cylindrical annular web (15) between valve seating face (9) and cone-shaped end (17) of the blind hole (3) is at most 0. 1 min.

Fuel injection valve according to claim 1, characterized in that the conical valve seating face (9) and the cone surface of the closed end (17) of the blind hole (3) have the same cone angle.

Fuel injection valve according to claim 1, characterized in that the tip (19) of the valve element (1) adjoining the conical valve sealing surface (7) is flattened out.

6 5.

6.

Fuel injection valve according to claim 4, characterized in that the bottom (2 1), delimiting the cone surface ( 17), of the closed end of the blind hole (3) is rounded ofT in such a way that, when the valve element (1) is applied against the valve seat (9), only a minimal dead volume remains between the flattened valve element tip (19) and the bottom (2 1) of the blind hole (3).

A fuel injection valve substantially as herein described with reference to the accompanying drawing.