GB2254114A

GB2254114A - Fuel injection pumps for internal combustion engines

Info

Publication number: GB2254114A
Application number: GB9206604A
Authority: GB
Inventors: Manfred Kraemer; Anton Pischinger
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1991-03-27
Filing date: 1992-03-26
Publication date: 1992-09-30
Anticipated expiration: 2012-03-26
Also published as: JPH0587011A; DE4110011A1; GB9206604D0; GB2254114B

Description

2254114

DESCRIPTION FUEL INJECTION PUMPS FOR INTERNAL COMBUSTION ENGINES

The present invention relates to fuel injection pumps for internal combustion engines.

Fuel injection pumps are known having a slider control in which the injection quantity and/or the commencement of injection is determined by the axial position of the control slider or sleeve. However, pumps are known in which, besides axial displacement of the control sleeve on the pump piston, fuel management may be influenced by rotation of the control sleeve.

It is also known that, by rotating the pump piston in the control sleeve, which is locked against rotation, with the aid of a suitable adjusting device, and by means of grooves on the pump piston, e.g. slanting grooves, in conjunction with recesses in the grooves, an injection stroke of differing length and hence quantity control may be achieved.

The end of high-pressure injection (regarded on the one hand, in terms of time, as the end of injection and on the other hand as the end of highpressure delivery which determines injection quantity) is in any case determined by the fact that the control -2opening on the pump piston is uncovered by the control sleeve so that the highly pressurised fuel is discharged from the pump working chamber via the relief channel and the control openings into the recess of the cylinder liner or of the pump housing.

It is known that pressures of 1300 bar and higher arise in the pump working chamber and that, during the discharge brought about by a control edge of the control sleeve, the discharged fuel jet has an extremely high kinetic energy. This leads to an extreme loading of the materials impinged by the fuel jet and as a result of the rapidly alternating pressure cavitation can arise.

Between the pump working chamber and the point of discharge the energy losses are relatively low because, after discharge (end of delivery), injection is abruptly interrupted in order to guarantee a rapid closure of the injector needle.

A series injection pump is known (DE-OS 31 36 751), in which the discharge bore is always disposed at the same point and, to prevent cavitation or erosion phenomena, a so-called anti-impact ring made of hardened steel is provided between the pump housing and the discharge bore. Said arrangement cannot be utilised in sleeve controlled pumps because the location of the discharge bore changes with the axial -3position of the control sleeve valve about the pump piston. The gap between the control sleeve and the wall of the recess must be permanently connected in a throttled manner to the intake chamber in order to prevent undesired influences upon the fuel management during the intake stroke or during discharge. The arrangement of an additional anti-impact element of the type described above would also mean a weakening of the pump cylinder and this would necessitate an unacceptable increase in the size of the combustion chamber.

A fuel injection pump is also known (DE-OS 35 40 052), which has in the control sleeve a radial discharge bore which, after the effective injection stroke has been travelled, is opened by means of a slanting control groove disposed as a control opening on the pump piston. Upon release through this discharge bore, the discharged fuel jet strikes unimpeded against the wall of the recess of the pump cylinder and, as the axial position of the control sleeve about the pump piston changes, so too does the position of the discharge jet in relation to the impact point of the jet. Due to the narrowness of the gap between the wall of the recess and the mouth of the discharge bore, the jet is deflected by the wall of the recess into the gap and therefore passes with -4its high energy into the intake chamber of the pump housing. This has the disadvantage that the deflected jet, which still has a very high kinetic energy, strikes the wall of the pump housing, made of a relatively soft material, e.g. aluminium, and causes cavitation and erosion damage there. Damage of this kind may similarly occur at the control parts situated in the intake chamber.

A further fuel injection pump is known (DE-OS 36 33 899), in which a recess for a control sleeve, which is axially displaceable on the pump piston for controlling the start of injection, is provided in a cylinder lining and in which there is disposed on either side of the control sleeve an apron, which covers the radial gap between cylinder lining and control sleeve at the entrance to the pump intake chamber and thereby deflects at least one more time and hence reduces the kinetic energy of the fuel jet discharged and deflected by the side walls of the recess, i. e. the fuel velocity is slowed down, the static pressure rises and cavitation bubbles disappear before the fuel flows above or below the apron to the pump intake chamber. With this method of reducing the kinetic energy of the discharge jet, however, the jet still directly strikes the wall of the recess of the cylinder lining, which may lead to the drawbacks -5 described above.

In accordance with the present invention a fuel injection pump for internal combustion engines is provided having at least one pump cylinder in the form of a cylinder lining and fixed in a corresponding bore of a pump housing, at least one pump piston which is reciprocatingly driven for a working stroke and is rotatable for fuel management, and having at least one control sleeve which is prevented from turning and is disposed inside a recess of the pump cylinder or of the pump housing so as to be axially displaceable on the pump piston for fuel management, said control sleeve being provided with at least one discharge bore directed at right angles to the pump piston, wherein, in the region of the discharge bores, a deflector ring disposed between two stops loosely surrounds the control sleeve, and a deflection chamber is situated between the inner surface of the deflector ring and the adjacent outer surface of the control sleeve.

This has the advantage that the fuel jet which has a very high kinetic energy when discharged from the pump working chamber through the discharge bore in the control sleeve does not directly strike the wall of the recess in the pump cylinder or pump housing. It is instead deflected in the region of the discharge bore by the loose arrangement of a deflector ring on -6the control sleeve and flows off preferably through further discharge bores into the recess of the pump cylinder, so that the energy of the jet is substantially consumed and rendered harmless.

A further advantage is that the recess portion of the deflector ring or of the control sleeve produces between the surface area of the control sleeve and the deflector ring a deflection chamber, in which the kinetic energy is consumed before the fuel flows off into the intake chamber.

According to an advantageous development of the invention, the discharge is effected via radial discharge bores on the periphery of the deflector ring which, in their axial position, are offset relative to the axis of the discharge bore in the control sleeve so that they do not or only partially overlap, thereby guaranteeing deflection or at least refraction of the fuel jet as it is discharged.

To achieve a reliable and stable mode of operation of the arrangement according to the invention, it is advantageous if the further discharge bores directed radially in the deflector ring are uniformly disposed along one or two peripheral lines. In the case of arrangement along two peripheral lines, the discharge bores are advantageously situated centrallv in relation to said peripheral lines.

According to a further advantageous development of the invention, in which the deflector ring is easily and automatically rotatable on the control sleeve, cavitation damage is avoided in that the fuel leaving the further discharge bores does not always strike the same point in the recess of the pump cylinder or of the pump housing.

According to an additional advantageous development of the invention, the deflector ring may easily be held axially on the control sleeve between two stops. One of said stops is constructed in the form of a collar on the control sleeve using conventional techniques, e.g. turning and grinding, and the other stop takes the form of a locking ring which is seated in a recessed portion of the control sleeve.

According to a further advantageous development of the invention, there may further be disposed between the deflector ring and the locking ring a retaining disk, which guarantees reliable automatic rotation of the deflector ring without the risk of the deflector ring possibly being inhibited in its rotational movement by the open ends of the locking ring.

By way of example only, specific embodiments of the present invention will now be described with -8reference to the accompanying drawings, in which:Fig. 1 shows a partial longitudinal sectional view of a first embodiment of a fuel injection pump constructed in accordance with the present invention; Fig. 2 is a partial longitudinal sectional view of a second embodiment of the fuel injection pump; and Fig. 3 is a partial longitudinal sectional view of a third embodiment of the fuel injection pump.

In the embodiment of Fig. 1, a cylinder lining 3, in which a pump piston 4 is reciprocatingly driven by means (not shown), is inserted in a pump housing 1 (only partially illustrated) having a pump cylinder 2. Provided in the pump cylinder 2 is a recess 5 formed in the manner of a blind hole for receiving a control sleeve 6 which is axially displaceable on the pump piston 4. Pump cylinder 2, cylinder lining 3 and pump piston 4 have a common axis X-X. Provided in the side wall of the recess 5 is a rotation guide 7, in which a lug 8 of the control sleeve slides, so that the control sleeve 6 may execute an axial movement but is locked against rotation.

Axial actuation of the control sleeve 6 is effected by means of a rotatable control rod 9 (shown in simplified form), which acts upon a journal 11 of the control sleeve 6 with the aid of a suitable driving element 10.

Advantageously, in a fuel injection pump, a plurality of such pump elements 2, 3, 4 with control sleeves 6 are lined up in the pump housing 1 and are then jointly operated by the control rod 9, which has the same number of driving elements 10 as there are pump elements. The control rod 9 and the driving elements 10 are disposed in a pump intake chamber 12 which, in a manner not shown in detail, is supplied with fuel at low pressure from a fuel tank via a feed PUMP.

The entrance 13 of the recess 5 of the pump cylinder 2 is turned towards said pump intake chamber 12 so that there is an open connection between the recess 5 and the pump intake chamber 12.

Disposed in the control sleeve 6 is a discharge bore 14, in the region of which there is a deflector ring 15 having a recess 16 and forming, with the surface area 17 of the control sleeve 6, a deflection chamber 18. Further discharge bores 19 are disposed uniformly over the periphery of the deflector ring 15 and their axes are offset relative to the axis of the discharge bore 14 so that they do not overlap.

The deflector ring 15 is dimensionally so toleranced that it may easily rotate on the control sleeve 6 and lies with one end adjacent to a collar 20 of the control sleeve 6, while being held in position -lo- on the control sleeve 6 at its other end by means of a locking ring 21 seated in a radial recess 22.

The control sleeve 6, which is axially displaceable on the pump piston 4, is connected via the discharge bore 14 by opposing slanting grooves 23 to recesses 24 on the pump piston 4 and by transverse bores 25 and 26 as well as an axial bore 27 to the pump working chamber (not shown).

In the second embodiment shown in Fig. 2, as in Fig. 1 the pump housing 1 contains the pump cylinder 2 and the cylinder lining 3, in which the pump piston 4 executes a reciprocating axial movement. The recess 5 receives the axially movable control sleeve 6, which is locked against rotation by the rotation guide (groove) 7 in conjunction with the lug 8, both of which are shown covered. The control rod 9 engages via a journal 30 having a spherical end into a suitably shaped driving element 60 on the control sleeve 6. The control rod 9 is disposed with the journal/journals (in the case of a plurality of pump elements) 30 in the pump intake chamber 12, which is connected to the recess 5 via the entrance 13.

Provided in the control sleeve 6 are discharge bores 14, over which lies the deflector ring 15, which has the recess 16 and the further discharge bores 19 uniformly distributed over its periphery and which, -11with the surface area 17 of the control sleeve 6, forms the deflection chamber 18. The axes of the further discharge bores 19 are arranged so as to be offset relative to the axes of the discharge bores 14 in order to prevent unimpeded discharge of the fuel from the discharge bores 14 into the recess 5.

The deflector ring 14, which is easily rotatable on the control sieeve 6, lies with one end adjacent to the collar 20 of the control sleeve 6 and with its other end adjacent to a retaining disk 28, which is held in position by the locking ring 21 situated in a recess 22 of the control sleeve 6.

The control sleeve 6 and/or its discharge bores are/is connected via slanting grooves 23 arranged diametrically on the pump piston 4 and having recesses 24 as well as via transverse bores 25 and 26 and an axial bore 27 in the pump piston 4 to the pump working chamber 29.

The embodiment of Fig. 2 therefore differs from the embodiment of Fig. 1 in the altered association and connection of the control sleeve 6 and the control rod 9, the insertion of the retaining disk 28 and the. specification of the pump working chamber 29. However, the mode of operation of the embodiments shown in Figs. 1 and 2 is identical. A camshaft (not shown) sets the pump piston 4 into a reciprocating -12movement against the action of a spring (not shown). The pump piston 4 may be rotated in the cylinder lining 3 by means of a known control device. Depending on the rotational position of the pump piston 4 with the slanting grooves 23 and recesses 24 in the control sleeve 6, the consequently determined distance of the slanting grooves 23 from the discharge bores 14 differs, wnich likewise corresponds to an injection stroke of differing length and hence to the duration of injection.

A further device used for fuel management but shown in simplified form is the control rod 9 with driving element 10, 60 on the journal 11, 30 of the control sleeve 6 for axial displacement of the control sleeve 6 on the pump piston 4.

The pump working chamber 29 (Fig. 2), which is not shown in Fig. 1, is filled during the intake stroke with fuel from the pump intake chamber 12, which also surrounds the control sleeve 6, via the transverse bores 25 and 26 and the axial bore 27. During the delivery stroke, fuel flows back via the axial bore 27, the transverse bores 25 and 26 and the slanting grooves 23 into the pump intake chamber 12 until the transverse bores 25 and 26 are plunged into the control sleeve 6. Only then does the actual highpressure injection - which is therefore dependent upon - 13the stroke position of the control sleeve 6 on the pump piston 4 - to the internal combustion engine begin. Said injection is interrupted when, in the course of the delivery stroke, the slanting grooves 23 are opened by the discharge bores 14. At that moment, the highly pressurised fuel in the pump working chamber shoots through the axial bore 27, the transverse bore 25, the slanting grooves 23 and the discharge bores 14 into the deflection chamber 18, where it is deflected or refracted as a result of the offset position of the further discharge bores 19, and then flows through the further discharge bores 19 back into the pump intake chamber 12 comprising the recess 5, with the kinetic energy still inherent in the fuel as a result of the high pressure in the pump working chamber being virtually cancelled out.

In the embodiment shown in Fig. 3, a pump cylinder 32, in which a pump piston 33 is set in reciprocating movement by means (not shown) is inserted in, only partially illustrated, pump housing 31. Provided in the pump cylinder 32 is a recess 34 for receiving a control sleeve 35, which is axially displaceable on the pump piston 33. Located in the side wall of the recess 34 in the pump cylinder 32 is a guide pin 36, which engages into a groove 37 on the control sleeve 35, this locks the control sleeve -14against rotation about a common axis Y-Y of pump cylinder 32, pump piston 33 and control sleeve 35 but allows the sleeve to move axially on the pump piston 33. The axial movement of the control sleeve 35 is effected by means of a control rod 38 which engages, with the aid of a spherical journal 39 mounted on an adjusting screw 40, into a slot 41 of the control sleeve 35 and moves said valve on the pump piston 33 depending on the selected start of injection. As a rule, in a fuel injection pump, a plurality of such pump elements 32 and 33 with control sleeve 35 are lined up in the pump housing 31. They are jointly actuated by the control rod 38; the number of adjusting screws 40 corresponds to the number of pump elements associated in each case therewith. The control rod 38 with the adjusting screws 40 is disposed in a pump intake chamber 42, which is supplied with fuel under low pressure from a fuel tank (not shown) via a feed pump. An entrance 43 connects the recess 34 to the pump intake chamber 42 so that there is always an open connection here.

Disposed in the control sleeve 35 are two discharge bores 44, which intersect at right angles in one axis and centrally in the region of which a deflector ring 45 surrounds the control sleeve 35, said ring having a recess 46 which, with the adjacent 2 -15outer surface 47 of the control sleeve 35, forms a deflection chamber 48. Uniformly distributed over the periphery of the deflector ring 45 are at least two rows of radially directed further discharge bores 49, whose axes are offset relative to the axes of the discharge bores 44 and in such a way that the impact region of the jet directly flowing from the discharge bores 44 lies approximately central of the two rows of further discharge bores 49. The deflector ring 45 is so dimensioned that it may rotate loosely on the control sleeve 35. Provided on the control sleeve 35 is a recess 50 forming a collar 51, on which the deflector ring 45 rests, while the deflector ring 45 is held in position at its other end by a locking ring 52, which is in turn seated in a recess 53 of the control sleeve 35.

An axial bore 54 is provided in the pump piston 33 and is intersected by a transverse bore 55 having opposing slanting grooves 56. Almost at the end of the axial bore 54, a further transverse bore 57 intersects the pump piston 33. A pump working chamber 58 is therefore connected via the axial bore 54, the transverse bore 55 with slanting grooves 56, the transverse bore 57, the discharge bores 44, the further discharge bores 49, the recess 34 and the entrance 43 to the pump intake chamber 42.

The embodiment of Fig. 3 operates in a similar manner to those of Figs. 1 and 2. It should be noted that the deflector ring 45 has a different shape and two rows of further discharge bores 49 along two peripheral lines. Also, the arrangement of the discharge bores 44 is different. The way in which the control rod 38 is connected to the control sleeve 35 also differs from that of Fig. 1.

Claims

1. Fuel injection pump for an internal combustion engine, having at least one pump cylinder in the form of a cylinder lining and fixed in a corresponding bore of a pump housing, at least one pump piston which is reciprocatingly driven for a working stroke and is rotatable for fuel management, and having at least one control sleeve which is prevented from turning and is disposed inside a recess of the pump cylinder or of the pump housing so as to be axially displaceable on the pump piston for fuel management, said control sleeve being provided with at least one discharge bore directed at right angles to the pump piston, wherein, in the region of the discharge bores, a deflector ring disposed between two stops loosely surrounds the control sleeve, and a deflection chamber is situated between the inner surface of the deflector ring and the adjacent outer surface of the control sleeve.

2. Fuel injection pump according to claim 1, wherein radially directed further discharge bores are situated in the deflector ring and are arranged in an offset manner relative to the discharge bore.

3. Fuel injection pump according to claim 2, wherein the further discharge bores are disposed along -18at least one peripheral line of the deflector ring.

4. Fuel injection pump according to claim 3, wherein the further discharge bores are disposed along two peripheral lines and the discharge bores are situated approximately midway between the two peripheral lines of the further discharge bores.

5. Fuel injection pump according to claim 4, wherein the deflector ring is rotatably supported on the control sleeve.

6. Fuel injection pump according to at least one of the preceding claims, wherein the deflector ring and/or the control sleeve each have on their opposing surfaces a recess portion of such a width that the piston-side openings of the further discharge bores lie in the region of said recess portion (53).

7. Fuel injection pump according to claim 1 wherein a collar is provided on the control sleeve at one end of the deflector ring.

8. Fuel injection pump according to claim 1, wherein a radial recess portion for a locking ring is provided on the control sleeve at the opposite end of the deflector ring to the collar.

9. Fuel injection pump according to claim 8, wherein a retaining disk is disposed between the deflector ring and the locking ring.

10. Fuel injection pump for internal combustion -19engines substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.