GB2305707A

GB2305707A - Cam arrangement for an internal combustion engine

Info

Publication number: GB2305707A
Application number: GB9619887A
Authority: GB
Inventors: Alfred Beier; Dietrich Distler; Christian Heimermann
Original assignee: Volkswagen AG
Current assignee: Volkswagen AG
Priority date: 1995-09-28
Filing date: 1996-09-24
Publication date: 1997-04-16
Anticipated expiration: 2016-09-24
Also published as: GB9619887D0; DE19638331A1; GB2305707B; FR2739410A1; FR2739410B1

Abstract

A cam arrangement for an internal combustion engine comprises a camshaft formed from an inner shaft 1 with cam elements 2 arranged thereon. Each cam element 2 comprises a carrier element 4 on which cam discs 3 are located, the carrier element 4 being located on the inner shaft 1. To achieve a variable closing time of gas exchange valves actuated by the cam discs 3, the said closing time being dependent on the rotational speed of the internal combustion engine, at least one of the cam discs 3 is mounted on the carrier element 4 so as to be pivotable to a limited extent in relation to the carrier element 4. The pivoting movement is limited by an arrangement involving a stop 10 in a recess 9.

Description

DESCRIPTION A CAM ARRANGEMENT FOR AN INTERNAL COMBUSTION ENGINE The present invention relates to a cam arrangement for an internal combustion engine.

DE-43 22 246 Al discloses a cam arrangement of the relevant generic type in which two cams located at a distance from one another are arranged on a carrier element designed in the form of a sleeve. This sleeve is arranged coaxially relative to an inner shaft and, during production, can be pushed onto the latter.

This known arrangement affords many advantages in terms of the manufacture of a camshaft, since individual cams or the entire cam element can be manufactured independently of the inner shaft.

An aim of the present invention is to provide a cam arrangement for an internal combustion engine, by means of which the torque behaviour, idling, fuel consumption and exhaust-gas emissions can be improved.

This is to be achieved, inter alia, by means of controlled charge movement. Furthermore, this cam arrangement is to work with low noise.

According to the present invention there is provided a cam arrangement for an internal combustion engine, comprising a camshaft, formed from an inner shaft with cam elements arranged thereon, for the periodic actuation of gas exchange valves, each cam element having at least two cam discs located at an axial distance from one another, on a sleeve-shaped carrier element which has a continuous cylindrical bore for coaxially receiving the inner shaft, at least one of the cam discs being arranged on the carrier element so as to be pivotable to a limited extent in relation to the latter.

If, in a cam arrangement of the relevant generic type for an internal combustion engine with at least two cam discs located at an axial distance from one another on a carrier element, at least one of these cam discs is arranged on the carrier element so as to be pivotable to a limited extent in relation to the latter, the valve elevation curves occurring as a rlt cf periodic actuation can be influenced on their closing flank in such a way that, in dependence on the speed of the internal combustion engine, with a rising speed the cam width increases and consequently the inlet closing time is retarded.

In a further embodiment, the carrier element can serve at the same time for mounting the camshaft, formed from an inner shaft and a carrier element, in bearing seats. In one embodiment of the present invention having a carrier element arranged rigidly on the camshaft, one or more or all of the cam discs can be held so as to be pivotable in relation to this carrier element. At the same time, in a further advantageous embodiment, if, for example, the cam discs have an identical profile, then they can be arranged in phase opposition to one another or be provided with valve strokes different from one another. Individual adaptation to specific types of internal combustion engine or their areas of use is thus possible.If there are, for example, three inlet valves, therefore, the first inlet valve, having a small dimension also in terms of cross-section, can be actuated by a cam disc having a comparatively small stroke, in order to take effect in a low load or rotational speed range. A cam disc provided with maximum stroke can be used in phase opposition so as to be relatively pivotable, with the result that an ample torque curve is obtained.

In a further embodiment of the present invention, the carrier element can additionally be arranged so as to be pivotable to a limited extent in relation to the inner shaft. In this case, the cam discs arranged rigidly on the carrier element follow the pivoting movement of this carrier element in relation to the inner shaft, whilst the cam discs arranged non-rigidly on this carrier element are additionally pivotable.

Individual adaptation can thereby be carried out in dependence on the position of recesses limiting the pivotability and on their relative position in relation to one another.

The present invention will now be further described by way of example, with reference to the accompanying drawings, in which: Fig. 1 shows a side view of a first embodiment of the present invention; Fig. 2 shows a section along line II-II according to Fig. 1; Fig. 3 shows a side view of a second embodiment of the present invention; and Fig. 4 shows a section through the second embodiment of the present invention illustrated in Fig.

3.

A cam arrangement for an internal combustion engine comprises a camshaft, formed from an inner shaft 1 and from cam elements 2 arranged thereon, for the periodic actuation of gas exchange valves (not shown) designed as inlet or exhaust valves. The cam elements 2 comprise a plurality of cam discs 3 located at an axial distance from one another on a sleeveshaped carrier element 4 having a continuous hollowcylindrical bore 5 for coaxially receiving the inner shaft 1.

The inner shaft 1 is hollow and has a pressure-oil duct 6 with transverse bores 7 branching off from it.

When the cam arrangement is incorporated in an engine the carrier element 4 is arranged in the region of a bearing seat 8 for mounting the camshaft, so that the carrier element 4 and thus the camshaft, are supported by the bearing seat 8.

In a first embodiment of the present invention according to Figs. 1 and 2, the cam element 2 has altogether three cam discs 3 which act in a way not shown on gas exchange valves, with coupling elements interposed. Whilst the cam discs 3 arranged on the left of the bearing seat 8 in Fig. 1 are arranged rigidly on the carrier element 4, the third cam disc 3 is held on the carrier element 4 so as to be pivotable to a limited extent in relation to the latter.

This relative pivotability extends over a maximum pivoting angle al and is achieved by means of a recess 9 which extends essentially over this pivoting angle al and is located in the third cam disc 3 and into which projects a stop element 10 arranged rigidly on the carrier element 4. The transverse bore 7 continuing in the carrier element 4 and intended for the supply of pressure oil serving for damping the relative rotational movement opens into this recess 9.

A second embodiment of the present invention is shown in Fig. 3 and additionally includes a further cam element 3 which is pivotable to a limited extent in relation to the inner shaft 1. For this purpose, a further stop element 100 is fixed to the inner shaft 1 and projects into a further recess 90 of the carrier element 4. The circumferential extent of the recess 90 defines a further pivoting angle a2 which, according to Fig. 4, can follow al in the direction of rotation R shown or can be designed to overlap with al. The transverse bores 7 supply the recess 9 by means of further transverse bores 70, arranged in the carrier element 4, and a groove 11 in the inner shaft 1.

In both above described versions of the present invention, the individual cam discs 3 cam have profiles deviating from one another or phase relationships with one another. Thus, Fig. 3 shows, for example, a stroke difference D between the maximum strokes of the two cam discs 3.

A phase-opposed arrangement of the rigid cam discs according to Fig. 1 can be seen in Fig. 2.

A plurality of recesses 9 or 90 can also in each case be arranged in the cam disc 3 or the carrier element 4, respectively.

On account of different opening times and/or strokes, the above described cam arrangement is suitable for generating a controlled charge movement in combustion spaces of an internal combustion engine.

Furthermore, by virtue of the hydraulic damping, it works with extremely low noise and makes it possible to reduce the manufacturing costs.

Claims

1. A cam arrangement for an internal combustion engine, comprising a camshaft, formed from an inner shaft with cam elements arranged thereon, for the periodic actuation of gas exchange valves, each cam element having at least two cam discs located at an axial distance from one another, on a sleeve-shaped carrier element which has a continuous cylindrical bore for coaxially receiving the inner shaft, at least one of the cam discs being arranged on the carrier element so as to be pivotable to a limited extent in relation to the latter.

2. A cam arrangement as claimed in claim 1, in which the carrier element is arranged in the region of a bearing seat for the camshaft.

3. A cam arrangement as claimed in claim 1 or 2, in which the cam discs have an identical profile which is arranged out of phase on the cam element.

4. A cam arrangement as claimed in claim 2 or 3, in which the cam element carries three cam discs which are arranged out of phase with respect to one another.

5. A cam arrangement as claimed in claim 1 or 2, in which the cam discs have maximum strokes different from one another and/or the associated profiles are arranged on the cam element out of phase with one another.

6. A cam arrangement as claimed in any one or more of the preceding claims 1 to 5, in which the carrier element is connected fixedly in terms of rotation to the inner shaft.

7. A cam arrangement as claimed in one or more of the preceding claims 1 to 5, in which the carrier element is arranged on the inner shaft so as to be pivotable to a limited extent in relation to the latter.

8. A cam arrangement as claimed in claim 6 and/or 7, in which for relative pivotability between the cam disc and carrier element and/or the carrier element and the inner shaft, there is arranged at least one recess which extends essentially over the maximum pivoting angle and in which a stop element limits the pivoting angle.

9. A cam arrangement for an internal combustion engine, constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.