GB2205628A - Adjusting means for a fuel infection pump - Google Patents

Description

2 2'0 5 6 2 8 ADJUSTING MEANS FOR A FUEL INJECTION PUMP The present

invention relates to adjusting means for a fuel injection pump, especially of an internal combustion engine, such as a Diesel engine.

Adjusting means for that purpose may be arranged between drive and camshaft of the injection pump and can represent an angular adjust' ment coupling actuated through a hydraulic control dependent on engine parameters.

In DE-OS 2 726 801 there is disclosed an injection adjuster in which setting pistons are loaded against a spring force and rotatably act by means of transmission elements, for example double-armed pivot levers, racks and toothings on adjusting eccentrics, or pushrods, on the adjusting eccentrics. This adjuster is constructionally complicated in view of the intermediately connected transmission elements and, due to the springs used as restoring means, provides a P-regulation characteristic.

There is also known, from DE-OS 2 726 800, an injection adjuster equipped with centrifugal weights and restoring springs and with a parallelly connected hydraulic setting arrangement.' In this adjuster not only the centrifugal weights but also the setting pistons directly engage adjusting pins of the adjusting eccentric. As a result, the additional transmission elements of the first-mentioned adjuster for the coupling of the setting pistons and adjusting eccentrics are redundant. Similarly, due to the restoring springs in this construct ion only a P-regulation characteristic is achieved.

Both above-described injection adjuster constructions require a control pressure, the height of which must be regulated, dependent 2 on adjusting angle. This disadvantage results from the restoring springs, which must be counteracted in dependence on travel by a higher or lower control pressure.

In DE-PS 1 022 419 there are disclosed adjusting gears for angular adjusting couplings with adjusting and compensating eccentrics arranged one within the other, while in DE-PS 26 49 986 there is dis closed an adjuster with radially arranged but externally loaded pistons which have inwardly acting wedge surfaces to determine the spacing between drive element and driven element. A hydraulically controllable injection adjuster with setting pistons loaded at both sides and an I-regulation characteristic is known from DE-OS 29 35 117, but this employs a mechanical adjusting gear of a kind other than eccentrics.

There is thus a need for hydraulically controllable adjusting means which operates with adjusting and compensating eccentrics and which may provide an I-regulation characteristic and a low-play force transmission.

According to the present invention there is provided adjusting means for a fuel injection pump, comprising a rotary drive element, a rotary driven element, a plurality of coupling devices coupling the driven element to the drive element for rotation therewith about an axis and each comprising a compensating eccentric and an adjusting eccentric which is rotatable relative thereto to effect relative rotation of the elements, a piston carrier mounted to be rotationally displaceable relative to the elements about said axis, a plurality of pistons arranged in the carrier to extend substantially radially of said axis and each drivablY coupled by a pin to a respective one of the adjusting eccentrics, and means to supply a pressure fluid for 3 loading the pistons selectablY at their radially inner or radially outer ends thereby to cause radially inward or radially outward dis placement of the pistons and rotation of the adjusting eccentrics by way of the pins.

Adjusting means embodying the invention may have a simple, low- play construction, which permits a standardisation of the coupling devices for centrifugal force and hydraulic injection adjusters. A wedge-free coupling can be achieved if, for example, the pins between the adjusting eccentrics and the pistons engage by part-spherical portions in, for preference, the pistons.

Advantageous assembly relationships may result if the piston carrier is pivotably mounted in the drive element and, by means of spacing holders penetrating therethrough, is axially guided at the drive element.

End abutments can be functionally and simply realised if openings in the piston carrier for the pins are constructed so that their edges serve as abutments to limit piston travel.

A compact assembly unit may result if the means for supplying pressure fluid comprises a pressure fluid transmission unit having a cover provided with a three-position valve and electromagnets for operation of the valve, the electromagnets preferably being arranged on a transverse axis of the cover.

Expediently, for providing a determined end setting of the pistons, the pistons in unloaded state can be held in determined positions by means of springs.

An embodiment of the present invention will now be more particular- V4 ly described by way of example with reference to the accompan. ing 4 drawings, in which:

Fig. 1 is a sectional elevation of adjusting means embodying the invention; Fig. 2 is a diagram showing an electronic and hydraulic control system of the adjusting means; and Fig. 3 is a view of housing cover of the adjusting means, the cover including a three-position valve and electromagnets.

Referring now to the drawings, there is shown adjusting means for a fuel injection pump, the adjusting means comprising a drive element 1 'driven, deriving from the crankshaft of an internal com bustion engine, by way of gears, a chain or a cogbelt. Adjusting eccentrics 2 are mounted at their external circumference at the drive element 1, and compensating eccentrics 3 are mounted at their external circumference in the adjusting eccentrics 2 and also mounted eccentric ally on bolts firmly seated in a driven flange 4. The drive element 1 is thereby mounted for limited rotation on the driven flange 4 and secured by screws to the latter by means of a fixing ring 7, the screws extending to the drive element 1 through arcuate slots (not shown).

A piston carrier 6 is rotatablY mounted in the drive element 1 by way of a guide 8 and held axially at the drive element 1 for limited rotary movement. For the axial holding, screws, provided with spacer bushes, in arcuate slots extend through the piston carrier 6 and are screwed into the drive element 1 (not shown).

The piston carrier 6 is provided with setting pistons 9 which are sealingly but displaceably arranged in a radially continuous bore, each of the pistons being loadable by way of an inner pressure fluid chamber 10 and an outer pressure fluid chamber 11. The outer diameter of the piston carrier 6 is so shaped that it extends only in the region of the continuous bore up to the outer diameter of the drive element 1. Thus, on mounting of the adjusting means in an auxiliary drive of the engine, meshing in a counter gearwheel is ensured.

Each adjusting eccentric 2 has a pin with a ball-shaped head 14 which engages, with low play, in a preferably central transverse bore 12 of the associated piston 9. Each pin extends through the piston carrier 6 in the region of corresponding radi ally- directed opening 15. The outer contour of the respective recess 15 at the same time forms an abutment for the end position of the associated piston 9 on installation of the pins 13.

By means of a central duct 100, the inner chamber 10 is, and by means of radial ducts 111 and peMpheral ducts 110 the outer chambers 11 are, fillable with and emptiable of pressure fluid. The ducts 100 and 110 lead to a pressure fluid transmission unit 16, which connects the ducts in the rotating adjusting means with pressure lines 101 and 112 at a cover 18 of a housing 17 enclosing the adjusting means.

In Fig. 2 are shown the connections of the pressure lines 101 and 112 at the cover 18 of the housing 17, which effect the inflow and outflow of fluid to and from the chambers 10 and 11. Fluid flow is controlled by a three-position valve 20, which is controlled by two electromagnets 21 and 22. The valve is, for example, connected to the lubricating oil circuit 30 of the engine at the pressure and return side R and the electromagnets 21 and 22 are switched by a control apparatus 40.

6 In use, when the electromagnets 21 and 22 are switched off, the chambers 10 and 11 are closed and the pistons 9 are thus hydraulically held in their respective settings. When the electromagnet 21 is switched on, the inner chamber 10 is loaded by the lubricating oil circuit and the outer chamber 11 is unloaded for return flow. The pistons 9 move outwardly and correspondingly rotate the adjusting eccentrics 2 by way of the pins 13. When the electromagnet 22 is switched on, the outer chambers 11 are loaded by the lubricating oil circuit and the inner chamber 10 is unloaded for the return flow.

The pistons 9 move inwardly and rotate the adjusting eccentric 2 by way of the pins 13 inwardly and counter to the previously described movement. During such adjusting operations, compensating pivot move ments are executed by the piston carrier 6 relative to the drive element 1.

Fig. 3 shows a cover with built-in valve 20 and electromagnets 21 and 22. This gives rise to the advantage of low volumes of the control ducts between the valve 20 and the chambers 10 and 11 and thus low response times. It also provides a favourable arrangement at the housing with only one pressure connection 31, wherein the return from the chambers 10 and 11 is conducted directly into the housing by way of the valve 20.

The control apparatus 40 controls the electromagnets 21 and 22 according to target angular adjusting values determined in depend ence on engine parameters by an internal microprocessor and to actual angular adjusting values detected at the drive element and drive flange by rotational angle sensors. In this way the actual values of the adjusting means are assimilated to the target values 7 issued by the microprocessor. It is also conceivable to hold the pistons 9, in unloaded state, in a determined position by means of springs (not shown). In that case the springs are arranged between the pistons 9 and/or between the pistons 9 as well as the piston carrier 6 in the outer chambers 11. When the pistons 9 are unloaded, a determined adjustment start setting is thus provided.

8

Claims (10)

1. Adjusting means for a fuel injection pump, comprising a rotary drive element, a rotary driven element, a plurality of coupling devices coupling the driven element to the drive element for rotation therewith about an'axis and each comprising a compensating eccentric and an adjusting eccentric which is rotatable relative thereto to. effect relative rotation of the elements, a piston carrier mounted to be rotationallY displaceable relative to the elements about said axis, a plurality of pistons arranged in the carrier to extend substantially radially of said axis and each drivably coupled by a pin to a respect ive one of the adjusting eccentrics, and means to suoply a pressure fluid for loading the pistons selectably at their radially inner or radially outer ends thereby to cause radially inward or radially out ward disolacement of the pistons and rotation of the adjusting eccentrics by way of the pins.

2. Adjusting means as claimed in claim 1, wherein each of the pins has a part-spherical head and is coupled to one of the respective piston and the respective adjusting eccentric by engagement of the head therein.

3. Adjusting means as claimed in either claim 1 or claim 2, wherein the carrier is pivotably mounted in the drive element and is guided axially relative to the drive element by holding means extending therethrough.

4. Adjusting means as claimed in any one of the preceding claims, wherein the pins extend through openings in the carrier and edges of 9 the openings are arranged to serve as abutments for the pins to limit travel of the pistons.

5. Adjusting means as claimed in any one of the preceding claims, the means to supply a pressure fluid comprising a fluid feed unit having a cover which is provided with a three-position val.ve to control fluid flow in the unit and electromagnets to control operation of the valve.

6. Adjusting means as claimed in claim 5, the electromagnets being arranged on an axis transverse to said axis of rotation.

7. Adjusting means as claimed in any one of the preceding claims, comprising spring means arranged to hold each piston in a predetermined position when the piston is in an unloaded state.

8. Adjusting means substantially as hereinbefore described with reference to the accompanying drawings.

9. An internal combustion engine equipped with a fuel injection pump and with adjusting means for the pump, the adjusting means being as claimed in any one of the preceding claims.

10. An engine as claimed in claim 9, the engine being a Diesel engine.

Published 1988 tit The Patent Office.,tCbe House. 66 71 Fi92. Holborn. London WC1R 4TP Further copies may be obtained from The Patent Office, Sa3es Bra=1r. Sz Ma:,, C.-av. Orpineton. Ker' BIR.5 3RD Printed by Multiplex techniques ltd. St Mary Cry. Kei,. Con. 187