EP0263734B1 - Rocker arm arrangement on an internal-combustion engine cylinder head - Google Patents

Description

The invention relates to rocker arm ramps for an internal combustion engine and, more particularly, their arrangement on a cylinder head.

It is known that a rocker arm ramp comprises an axis carried by at least one support integral with the cylinder head of the engine, this support being either attached and fixed to the cylinder head or made integrally with the latter. Caps can be used to secure the axle to its supports, just as bearing caps are provided to partially delimit the bearings which rotationally support a camshaft, these caps being fixed to the cylinder head by screws or the like. The rocker arms are mounted to oscillate on the axis and are held and guided laterally along this axis by members having guide surfaces perpendicular to said axis. In the prior art, these members may be constituted by the support caps of the rocker arm ramp or by spacers threaded on the axis and if necessary urged by springs. Such an arrangement requires a relatively large number of parts and results in complex assembly and disassembly operations.

Document EP-A 0 091 096 describes an arrangement of a rocker arm ramp on an internal combustion engine cylinder head, this cylinder head comprising bearings for a camshaft delimited in part by the cylinder head and in part by at least one cap camshaft bearing fixed on the cylinder head, and supports for the rocker arm ramp, the latter comprising an axis fixed on said supports and rocker arms mounted oscillating around said axis and cooperating with the cams of the camshaft, and rocker guide means, defining guide surfaces perpendicular to said axis, at least one camshaft bearing cap comprising at least one lateral extension delimiting said guide surface.

The production in the form of single elements of the camshaft bearings and of the means for fixing the axis of the rocker arms makes the assembly operations of such an assembly particularly complex and delicate. In addition, each of the elements forming the double supports is costly to produce, in particular because of the numerous precise machining operations which it is necessary to carry out.

The object of the invention is to provide an arrangement of a rocker arm ramp on an internal combustion engine cylinder head in which the positioning and lateral guidance of the rocker arms on the rocker arm axis is precise and in which the assembly and disassembly operations be facilitated.

To this end, the subject of the invention is an arrangement of a rocker arm ramp on an internal combustion engine cylinder head, this cylinder head comprising bearings for a camshaft, delimited in part by the cylinder head and in part by at least one camshaft bearing cap fixed on the cylinder head, and supports for the rocker arm ramp, the latter having an axis fixed on said supports, rocker arms mounted oscillating around said axis and cooperating with the cams of the camshaft , and rocker guide means, delimiting guide surfaces perpendicular to said axis, at least one camshaft bearing cap comprising at least one lateral extension delimiting said guide surface, characterized in that said supports for the ramp of rocker arms do not include said camshaft bearing cap and in that the rocker shaft is fixed on at least one support formed in the cylinder head.

• - la Fig. 1 est une vue schématique, partielle, de dessus d'un agencement selon l'invention;
• - la Fig. 2 est une vue en coupe partielle suivant la ligne II-II de la Fig. 1.

The invention will be described in more detail below with reference to the attached drawing, given solely by way of example, and in which:

• - Fig. 1 is a schematic partial view from above of an arrangement according to the invention;
• - Fig. 2 is a partial sectional view along line II-II of FIG. 1.

A rocker rail according to a preferred embodiment of the invention is illustrated in Figs. 1 and 2. A rocker shaft 1 is arranged in a conventional manner parallel to a camshaft 2. Rockers 3 are mounted in an oscillating manner on the axis 1 which is fixed in supports 4a of a cylinder head 4, directly by screws 5 diametrically crossing the axis of rocker arms to be screwed into tapped holes in the cylinder head. In line with these screws, the axis has flats 1 a.

The camshaft is rotatably supported in bearings 6, the upper parts of which consist of bearing caps 7 fixed to the cylinder head 4 by screws 8. The bearing caps 7 have, according to the invention, extensions 9 ensuring the positioning and lateral guiding of the rocker arms. These extensions are precisely machined to provide bearing surfaces 10 which cooperate with bearing surfaces 11 formed on the rocker arms in order to determine their lateral position. Depending on whether they are located at one end or at an intermediate location of the camshaft, the caps 7, 7 ′ may include one or more lateral extensions 9 or 9 ′.

As seen in Fig. 1, two rocker arms are arranged to form an assembly trapped between two guide elements, a spring 12 being arranged between their opposite faces, to separate them from one another and apply them against the adjacent guide surfaces.

• - le fait d'utiliser des prolongements latéraux des chapeaux de palier de l'arbre à cames comme moyens de guidage des culbuteurs permet de supprimer les chapeaux de support de l'axe portant ces culbuteurs. Le nombre de pièces est ainsi réduit et les opérations de montage s'en trouvent facilitées.
• - les culbuteurs sont positionnés et guidés de façon plus précise par rapport aux cames avec lesquelles ils coopèrent.

The advantages obtained through an arrangement are as follows:

• - The fact of using lateral extensions of the bearing caps of the camshaft as means for guiding the rocker arms eliminates the support caps of the axis carrying these rocker arms. The number of parts is thus reduced and assembly operations are thereby facilitated.
• - The rocker arms are positioned and guided more precisely in relation to the cams with which they cooperate.

Claims (4)

1. Rocker arm arrangement on an internal combustion engine cylinder head (4), the latter having bearings (6) for a camshaft (2), partly defined by the cylinder head (4) and partly by at least one camshaft bearing cap (7) fitted to the cylinder head, together with supports (4a) for the rocker arm system, the latter having a shaft (1) fixed to said supports, rocker arms (3) mounted in oscillating manner about said shaft and cooperating with the cams of the camshaft (2), together with means for guiding (9) the rocker arms (3), defining guide surface (10) perpendicular to said shaft, at least one camshaft bearing cap (7) having at least one lateral extension (9) defining said guide surface (10), characterized is that said supports (4a) for the rocker arm arrangement do not include the camshaft bearing cap (7) and that the shaft of the rocker arms (1) is fixed to at least one support (4a) provided in the cylinder head.

2. Arrangement according to claim 1, characterized in that the rocker arm shaft (1) is fixed directly to support (4a) by screws (5) diametrically passing through the same.

3. Arrangement according to one of the claims 1 or 2, characterized in that an intermediate camshaft (2) bearing cap (7) has two lateral extensions (9), each defining a guide surface (10).

4. Arrangement according to one of the claims 1 or 2, characterized in that the camshaft (2) bearing cap (7) located in the vicinity of the ends of said camshaft have in each case a single extension (9') defining a guide surface (10').

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