GB2116643A

GB2116643A - Fuel injection pump

Info

Publication number: GB2116643A
Application number: GB08303902A
Authority: GB
Inventors: Stanislaus Bodzak
Original assignee: Friedmann and Maier AG
Current assignee: Friedmann and Maier AG
Priority date: 1982-02-12
Filing date: 1983-02-11
Publication date: 1983-09-28
Also published as: ATA54682A; GB8303902D0; DE3304042A1; DE8303263U1; GB2116643B; FR2521640A1; FR2521640B1; AT379662B

Abstract

In a fuel injection pump a deflector body (10) is arranged in the pump housing opposite the spill port (7) in the wall of the pump cylinder (1) which prevents material erosion on pump parts situated in the region of impingement of the diverted fuel jet by fanning out the jet. In order to ensure that any material erosion on the deflector body (10) itself occurs evenly the latter has the shape of a solid of revolution and is mounted freely rotatable in the housing. In a preferred arrangement the deflector body is a cylindrical pin rotatably supported at both ends in a transverse bore (16) in the wall of the cylinder (1). In a modified form the deflector body is a ball. <IMAGE>

Description

SPECIFICATION Fuel injection pump The invention reiates to a fuel injection pump for internal combustion engines of the kind comprising at least one pump cylinder which receives a pump piston, and at least one control edge on the pump piston which co-acts with at least one spill port in the wall of the pump cylinder to control the end of pump delivery, and having a deflector body of cavitation resistant material arranged on that side of the spill portwhich is opposite the pump piston.

Fuel injection pumps with baffle devices are known, for example from Austrian Patent Specification 306445 or from German Patent Specification 22 19 827, in which arrangements, the deflector body which is provided at the mouth of the spill ports in the pump body has the function of preventing the erosion of material at the points of impingement of the jet of fuel which is diverted from the compression chamber of the pumps at the end of the delivery stroke. In most existing arrangements of this kind the surfaces of the deflector element which are exposed directly to the impinging fuel jet are either concave or plane, partly for reasons connected with manufacturing techniques and partly with a view to preventing the diverted, high-energy fuel jet from impinging on adjacent parts of the pump.

However, it was found that, due to the current trend to operate fuel injection systems for internal combustion engines at ever increasing pressures, the diverted fuel jets acquire, towards the end of the delivery stroke, such high outflow-velocities that the diverted fuel jets, even when reflected by deflector bodies of conventional design, still possess enough energy to cause cavitation in parts of the pump that are situated opposite the deflector body. This applies particularly to the control edge on the pump piston which is directly affected at the very moment of jet diversion. This naturally, entails serious disadvantages.In order to avoid these disadvantages various arrangements have been suggested, for example in British Patent Specification 1215584 or in German published Patent Application 2 107 266, concerning devices of the kind specified in which the deflector body is provided with a substantially convex surface on that side which is exposed to the impinging fuel jet.As a result, in contrast with the arrangements in which the deflector body has a concave surface whereby the impinging fuel jet is, to a certain degree, focussed on a point opposite the deflector body and at that point naturally gives rise to increased risk of cavitation, the impinging diverted fuel jet is more widely fanned out so that the energy of the jet is distributed over a substantially larger surface area of the parts that are arranged on the opposite side and can no longer cause serious damage in these areas. In particular such an arrangement, even at high fuel pressures and pump output volumes, prevents cavitation phenomena at the controlling edges being caused by the diverted fuel jet when this is reflected by the deflector body.

The drawback of this known type of arrangement in which the deflector body consists of a spring inserted toroidally in an annular space or of a pin arranged coaxially with the spill port and having a point at one end thereof, resides in that the jet of fuel which emerges from the spill port will always impinge on one and the same point and thus cause rapid wear of the deflector body.

It is the aim of the present invention to construct a fuel injection pump of the kind specified in such a way that the aforementioned disadvantages are avoided and that, in particular, the risk of cavitation on the deflector body itself is eliminated or at least its adverse effects on service life are greatly reduced.

The present invention consists in a fuel injection pump for internal combustion engines of the kind comprising at least one pump cylinder which receives a pump piston and at least one control edge on the pump piston which co-acts with at least one spill port in the wall of the pump cylinder to control the end of pump delivery, and having a deflector body made of cavitation-resistant material arranged on that side of the spill port which is opposite the pump piston, the deflector body being turnably supported in the housing of the fuel injection pump for rotation about at least one axis extending at an angle relative to the spill port.

This provision ensures the same part of the surface of the deflector body is no longer always exposed to the impingement of the high-energy fuel jet, which makes for a significantly longer useful service life of the device.

Preferably, the deflector body has the shape of a solid of revolution and in a particularly attractive embodiment it has the form of a cylindrical pin rotatably supported in the transverse bore of the pump housing. This arrangement affords very easy manufacture and fitting of the deflector body. The pin is preferably rotatably supported at both ends and retaining means may be provided to prevent axial movement of the pin in the bore.

According to another embodiment of the invention, the deflector body may take the form of a ball.

The ball is so positioned relative to the spill port that the jet emerging from the spill port, at least at the moment of diversion of the fuel on the delivery stroke, strikes the surface of the ball in a direction which is offset in relation to the axis of rotation of the ball.

Preferably the ball is located in an insert and is offset relative to the axis of the spill port. The ball may also be subjected to spring loading.

The invention is hereinafter more particularly described with reference to the examples of embodiments thereof depicted in the accompanying drawings in which: Figure 1 is a vertical section of part of a fuel injection pump according to the invention, Figure 2 is a section taken on line ll-ll in Figure 1, and Figures 3 and4 each show a section correspond ing to Figure 1 of further embodiments of the invention.

The pump cylinder 1 of the fuel injection pump according to Figure 1, of which no further details are shown in this figure, receives a pump piston 2 which is displaceable in the direction of axis 3 and actuated by a drive member, not shown. The pump piston comprises control edges 4,5 of which one (4) controls the start and the other (5) the termination of fuel delivery by the pump piston.

As soon as the lower control edge 5 reveals the open section 6 on the inside of the cylinder of a spill port 7 in the wall of the cylinder 1 all fuel which is in excess of the currently prevailing demand of the engine is diverted from the compression chamber 8 of the pump cylinder and directed through corresponding milled recesses 9 in the piston 2 into the spill port 7 and further through an outlet 1: into the surrounding suction space in the pump housing.

In order to avoid erosion of material being caused by the diverted fuel jet, which possesses relatively high kinetic energy, in regions of the fuel injection pump which are opposite the outer mouth orifice of the spill port 7 a deflector body 14 of cavitation-resistant material is arranged on that side of the port 7 which is opposite the piston 2.

In the embodiment shown in Figures 1 and 2 this deflector body 14 takes the form of a pin 10 of cylindrical shape and arranged normal to the axis 15 of the spill port 7 in a transverse bore 16 in the cylinder wall. In order to facilitate discharge of the diverted fuel, which has already been deflected by the deflector body 14, an enlarged outlet port 17 is provided in the region of said deflector body which allows the diverted fuel to flow into the surrounding suction space above the deflector body 14.

The convex face of deflector body 14 facing the spill port 7 has the effect of expanding orfanning out the diverted fuel jet passing through the spill port 7 thus effectively avoiding concentration of jet energy on the surfaces of component parts situated opposite the spill port. This applies particularly to the control edge 5 on the piston itself which is directly opposite the deflector body at the instant of opening the passage section 6 of spill port 7 and which would be directly impinged upon by the jet of fuel if this were reflected from a plane or even concave baffle face on the deflector body.

It will be observed particularly clearly from Figure 2 that the transverse bore 16 for the cylindrical deflector body 14 is a blind bore in which the pin 10 is received. In order to prevent the pin 10 from dropping out of this bore 16 the end face of the deflector body 14 which is opposite the open end of the transverse bore 16 is provided with a retaining pin 18 which prevents sliding in the axial direction.

The deflector body 14 has a small amount of clearance or play relative to the sides of the transverse bore 16 which allows it to turn about its own axis with the result that the cylindrical surface thereof will not have the same part exposed to the action of the high-energy diverted fuel jet at each diversion, so that the useful service life of the device is prolonged.

Advantages may further be obtained with the modifications shown in Figures 3 and 4 of the embodiment according to Figures 1 and 2 according to which the deflector body 14 is a ball 10' arranged to be freely rotatable in a corresponding insert 20.

The bail 10' is positioned relative to the spill port 7 in such a way that, either the horizontal axis of the ball is co-axial with the horizontal axis 15 of the spill port and the jet of fuel, at the moment of diversion, is offset relative to the spill port axis 15, or the axis of rotation of the ball is offset in any direction relative to the spill port axis with the resultthat in either case the jet impinges on a part of the ball which is offset in relation to its axis of rotation and thereby induces rotation at each diversion of the fuel jet. Preferably, the arrangement is such that the jet strikes the lower part of the ball as shown in Figures 3 and 4 and intermittent rotation occurs in the direction of arrow 22. This ensures substantially even wear over the whole surface of the ball.

In the arrangement according to Figure 4 the ball 10' is biased in the insert 20' by a spring 21 but otherwise also freely rotatable. Here, too, even wear over the whole surface of the ball and thus longer service life of the device as a whole can be achieved by simple means. The embodiment according to Figure 4 differs further from that shown in Figure 3 in that the horizontal axis of the ball 10' is offset upwards, as viewed in this figure, relative to the axis 15 of the spill port which arrangement increases the angular momentum imparted to the ball 10' by the diverted fuel jet.

it will be appreciated that the principles applied to effect intermittent rotation of the ball may also be applied to the cylindrical body 10 of Figures 1 and 2.

In all the illustrated embodiments that side of the pump cylinder 1 which is opposite the spill port 7 is provided with a suction port 19 which is exposed either, not at all, or only some little time after the spill port 7 is opened by the controlling edge 5 of piston 2 so that this suction port 19 9 need not be provided with a deflector body of its own. However, it will be appreciated further that within the framework of this invention other constructions of fuel injection pumps are also perfectly conceivable in which both said ports would participate in fuel jet diversion and in that event a deflector body would then also have to be provided in the second outlet port in the manner hereinbefore described.

Claims

1. A fuel injection pump for internal combustion engines of the kind comprising at least one pump cylinder which receives a pump piston and at least one control edge on the pump piston which co-acts with at least one spill port in the wall of the pump cylinder to control the end of pump delivery, and having a deflector body made of cavitation-resistant material arranged on that side of the spill port which is opposite the pump piston, the deflector body being turnably supported in the housing of the fuel injection pump for rotation about at least one axis extending at an angle relative to the spill port.

2. Afuel injection pump as claimed in claim 1, wherein the deflector body has the shape of a solid of revolution.

3. Afuel injection pump as claimed in claim 2, wherein the deflector body is a cylindrical pin supported for rotation in a transverse bore of the housing.

4. Afuel injection pump as claimed in claim 3, wherein the pin is rotatably supported at both ends.

5. Afuel injection pump as claimed in claim 3 or claim 4, wherein retaining means is provided to prevent axial movement of the pin.

6. Afuel injection pump as claimed in claim 2, wherein the deflector body is a ball.

7. Afuel injection pump as claimed in claim 6, wherein the ball is subjected to spring loading.

8. Afuel injection pump as claimed in any preceding claim wherein the deflector body is so positioned that the jet through the spill port at least at the moment of diversion of the fuel strikes the surface of the deflector body in a direction which is offset in relation to the axis of rotation of the deflector body.

9. Afuel injection pump as claimed in claim 8, wherein the deflector body is offset relative to the axis of the spill port.

10. Afuel injection pump substantially as hereinbefore described with reference to and as shown in Figures 1 and 2 of the accompanying drawings.

11. Afuel injection pump substantially as herein before described with reference to and as shown in Figure 3 of the accompanying drawings.

12. Afuel injection pump substantially as herein before described with reference to and as shown in Figure 4 of the accompanying drawings.