GB2161859A

GB2161859A - Throttling pintle-type i.c. engine fuel injection nozzle

Info

Publication number: GB2161859A
Application number: GB08517978A
Authority: GB
Inventors: Hans-Joachim Schopf; Frank Thoma
Original assignee: Daimler Benz AG
Current assignee: Daimler Benz AG
Priority date: 1984-07-21
Filing date: 1985-07-17
Publication date: 1986-01-22
Also published as: FR2567966A1; GB2161859B; GB8517978D0; IT1185285B; IT8521617A0; DE3426950A1

Abstract

The longitudinal fuel bores (6a, 6b, 6c) which run through the nozzle body (7) and lead to a pressure chamber (12) have asymmetry such that fuel flowing into the pressure chamber (12) exerts forces on the injector valve (10), causing the valve to rotate and prevent carbon deposition in the nozzle outlet. The bores may differ in size, inclination relative to the nozzle axis or location relative to the nozzle axis. <IMAGE>

Description

SPECIFICATION Throttling pintle-type nozzle for fuel injection in an air compressing internal combustion engine, particularly a pre-combustion chamber engine The invention relates to a throttling pintle-type nozzle for fuel injection in an air compressing internal combustion engine, particularly a precombustion chamber engine, in which a fuel pressure controlled rotatable injector needle has its pressure shoulder in a pressure chamber to which leads a fuel supply, formed by longitudinal fuel bores extending through, successively, the nozzle holder, an intermediate section (where this is included) and the nozzle body.

Nozzles of this type are provided with a spray pintle which is intended for pre-injection and whereby, upon the opening of the injector needle, at first only a small annular gap or throttling gap is freed or opened to admit only a small amount of fuel. The desired throttling effect is achieved because of the shape of the spray pintle, together with the characteristic of the compression spring in the nozzle holder which counteracts the opening movement of the injector needle and with the clearance in the throttling gap.

However, throttling pintle-type nozzles prove to be susceptible to trouble in the course of engine operation because carbon residue forms in the spray hole, narrowing the annular gap and thus causing unacceptably great variations in the quantities of fuel injected. As a result, these variations also have an adverse effect on the noise of combustion.

A throttling pintle-type nozzle is known from German Offenlungsschrift 29 30 176, which nozzle prevents carbon formation in the throttling gap - even after prolonged engine operation - because, as a result of the special design of this nozzle, the injector needle is rotated by a specific amount with each closing stroke. Rotation is achieved because, after the opening stroke has occurred - the injector needle had previously still been without any mechanical connection to the intermediate piston lying above - the injector needle is now firmly supported during its closing stroke on the intermediate piston which, because of it being supported at the other end on the closing spring, also undergoes rotation in the same direction each time as a result of this spring being in the form of a helical spring.

The problem underlying the invention is to adopt simple measures on a throttling pintletype nozzle whereby it is possible to achieve, without any mechanical influence on the injector needle, a metering cross-section which is insensitive to carbon formation and which, when in a stabilized state, permits permanent and uniform quantities of injected fuel.

According to the invention, there is provided a throttling pintle-type nozzle for fuel injection in an air compressing internal combustion engine, comprising a fuel-pressure controlled rotatable injector needle which lies with its pressure shoulder in a pressure chamber leading to which is a fuel supply formed by longitudinal fuel bores which extend through the nozzle holder, through an intermediate section, if necessary, and through the nozzle body, wherein longitudinal fuel bores which run through the nozzle body are arranged and/or designed asymmetrically in relation to the longitudinal axis of the injector needle in such a manner that fuel flowing into the pressure chamber exerts forces on the injector needle, causing the needle to rotate.

The longitudinal fuel bores, in one feature of the invention, leading to the pressure chambers, have different radial and/or tangential components, they can, in accordance with another feature of the invention have different conducting cross-sections.

In accordance with further features of the invention, the longitudinal fuel bores can be in sections of the nozzle body having differing sizes: the longitudinal fuel bores can also lie in an unevenly distributed arrangement in a section of the nozzle body.

The longitudinal fuel bores can also be designed to have different stages and/or to have a tapered form. In yet another feature of the invention, blind holes are provided in the nozzle body in addition to the longitudinal fuel bores; the blind holes leading from the end of the nozzle body remote from the combustion chamber and which are asymmetric with respect to each other; alternatively some of the longitudinal fuel bores may be in the form of blind holes having differing depths.

The hitherto conventionai symmetry of the bore arrangement is consequently replaced in the present invention by the arrangement and/ or design of the longitudinal fuel bores in the nozzle body.

Because of the longitudinal fuel bores which are arranged differently from one another or which have different diameters and/or bore depths, forced rotation of the injector needle takes place, resulting in a reduction in knocking (noise reduction) and in carbonization.

Embodiments of the invention will now be described in more detail, by way of example and with reference to the accompanying drawings, in which: Figure 1 shows a longitudinal section through a throttling pintle-type nozzle with longitudinal fuel bores in the nozzle body, which bores have different tangential components.

Figure 2 shows the nozzle body having been rotated through 90 , Figure 3 shows an embodiment of the nozzle body with longitudinal fuel bores having different radial components each being also shown on an enlarged scale in cross section, Figure 4 shows a further embodiment of the nozzle body in which the longitudinal fuel bores have different conducting cross-sections, Figure 5 shows another embodiment of the nozzle body in which the longitudinal fuel bores lie in circle sectors of different sizes, Figure 6 shows a further embodiment of the nozzle body in which the longitudinal fuel bores lie in an unevenly distributed arrangement in one sector, Figure 7 shows longitudinal fuel bores with additional blind holes in the nozzle body, and Figure 8 shows the nozzle body in a view indicating longitudinal fuel bores which are distributed uniformly on the circumference and some of which are designed in the form of blind holes.

The construction of an injection valve, in the form of a throttling pintle-type nozzle 1, for an air compressing injection-type internal combustion engine is shown in Fig. 1. Fuel is supplied through a longitudinal fuel bore 2 in an upper holder 3, further longitudinal fuel bores 4a, 4b in an intermediate section 5 and, finally, three longitudinal fuel bores 6a, 6b, 6c (Figs. 1 to 8) in a nozzle body 7. The longitudinal fuel bores 2 and 4a, 4b and 4a, 4b and 6a, 6b, 6c are connected to one another by means of annular grooves 8 and 9. Both annular grooves 8, 9 are arranged in the intermediate section in order to avoid deformation in the sensitive area of the bore 11 guiding the injector needle 10 when the individual parts of the injection valve are braced and, at the same time, to facilitate the forced rotation of the injector needle 10.The longitudinal fuel bores 6a, 6b and 6c which run through the nozzle body 7 lead into a pressure chamber 1 2 which is in the form of a toroidal chamber.

The bore arrangement in the nozzle body 7 is designed asymmetrically in order to produce the effect of needle rotation in a controlled manner.

The longitudinal fuel bores 6a, 6b, 6c have different tangential components (Fig. 1 and 2). They are arranged to run obliquely to the axis 1 3 of the injector needle 10 by an angle (Fig. 2). The longitudinal fuel bores 6a, 6b, 6c can, however, also have radial components as shown in Fig. 3, the angle which is formed by the injector needle axis 1 3 and the axis of each longitudinal fuel bore being designated by Fig. 4 shows an embodiment in which the conducting cross-sections of the three longitudinal fuel bores 6a, 6b, 6c lying in a sector T, differ from one another in size, whilts in Fig.

5 the longitudinal fuel bores have the same conducting cross-sections, but lie in different sectors T1, T2, T3. In Fig. 6 the longitudinal fuel bores 6a, 6b, 6c are situated in a sector T, just as in Fig. 4, but in this case the bores lie at different intervals from one another in this sector. The respective intervals are indicated by, 2 and .

If necessary, designs are also conceivable which contain both the features from Figs. 4 and 5 or 6, or vice versa. Exemplary embodiments of this type are mainly to be found in connection with thos longitudinal fuel bores having the tangential component.

Asymmetry can also be achieved by designing some of the longitudinal bores 6a, 6b, 6c in the form of blind holes which are not continuous, but have different depths. In Fig.

8 the nozzle body 7 contains a continuous longitudinal fuel bore 6b which is in the form of an inlet port, whilst the longitudinal bores 6a, 6c are designed as blind holes each having a different hole depth.

In the event of the conducting cross-sections of the conventional continuous longitudinal fuel ports 6a, 6b, 6c having to be retained, additional blind holes 6d-f which are designed asymmetrically relative to one another can also be provided as shown in Fig.

7.

The described embodiments cause the needle 10 to rotate in such a manner that, in the event of carbon being deposited in the spray hole 1 5 of the nozzle body 7 during the injection operation, the spray hole 1 5 or the nozzle opening is "cleared".

Claims

1. A throttling pintle-type nozzle for fuel injection in an air compressing internal combustion engine, comprising a fuel-pressure controlled rotatable injector needle which lies with its pressure shoulder in a pressure chamber leading to which is a fuel supply formed by longitudinal fuel bores which extend through the nozzle holder, through an intermediate section, if necessary, and through the nozzle body, wherein longitudinal fuel bores which run through the nozzle body are arranged and/or designed asymmetrically in relation to the longitudinal axis of the injector needle in such a manner that fuel flowing into the pressure chamber exerts forces on the injector needle.

2. A nozzle according to Claim 1, wherein the longitudinal fuel bores which lead into the pressure chamber have different radial and/or tangential components.

3. A nozzle according to Claim 1 or Claim 2, wherein the longitudinal fuel bores in the nozzle body have different conducting crosssections.

4. A nozzle according to any one of the preceding Claims, wherein the longitudinal fuel bores lie in sectors of different sizes in the nozzle body.

5. A nozzle according to any one of the preceding Claims, wherein the longitudinal fuel bores lie in an unevenly distributed ar rangement in a sector in the nozzle body.

6. A nozzle according to any one of the preceding Claims, wherein the longitudinal fuel bores are designed in different stages and/or have a tapered design.

7. A nozzle according to any one of the preceding Claims, wherein blind holes which start from that end of the nozzle body remote from the combustion chamber and which are designed asymmetrically relative to one another, are provided in the nozzle body in addition to the longitudinal fuel bores, or some of the longitudinal fuel bores are designed in the form of blind holes each having a different depth.

8. A throttling pintle-type nozzle for fuel injection in an air compressing internal combustion engine, substantially as hereinbefore described and with reference to the accompanying drawings.