Internal-combustion engines – Poppet valve operating mechanism – Rocker
Patent
1999-02-24
2000-02-08
Lo, Weilun
Internal-combustion engines
Poppet valve operating mechanism
Rocker
123 9044, 123 9039, 74559, F01L 118
Patent
active
060217502
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention concerns a finger lever made as a sheet metal part without chip removal for a valve drive of an internal combustion piston engine, the finger lever, as seen in cross-section, having a U-shaped profile formed by an upper crosswall facing a cam and comprising, in a central region of the finger lever, an opening of essentially rectangular shape as seen in a top view, said opening receiving a roller which is in rolling contact with the periphery of the cam, the U-shaped profile being further formed by side walls which extend downwards from the crosswall and receive a pin with the roller mounted for rotation thereon, while edges of the side walls which delimit the opening have a convex shape.
BACKGROUND OF THE INVENTION
Rocker arms for the valve drive of internal combustion piston engines were generally made in the past as castings and provided with a roller mounted on a rolling bearing to reduce friction at the point of contact of the cam on the rocker arm. This structure has also been used in making finger levers out of sheet metal by cold forming without chip removal. However, problems have been encountered in such sheet metal finger levers which are relatively thin-walled, and therefore lighter and more economical than cast finger levers, because it was not possible to design them with an adequate rigidity.
A cold-formed finger lever of the generic type described above is known from DE-A 39 29 486. To rigidify this sheet metal finger lever, outwards projecting ribs are arranged on the side walls below the location of the pin. It has been determined on the one hand that these ribs do not stiffen the finger lever sufficiently and, on the other hand, said ribs increase the width of the finger lever. But since, precisely in multi-valve cylinder units only a small space is available for the finger levers arranged next to each other, the finger levers cannot be provided with such ribs.
OBJECTS OF THE INVENTION
It is an object of the invention to rigidify a finger lever made of sheet metal without chip removal without influencing the width of the finger lever.
SUMMARY OF THE INVENTION
The invention achieves this object by modifying the vertical extent of the side walls to make them so large that the roller is situated within this extent of the side walls. Thus the rigidity of the finger lever can be increased by enlarging the side walls in the direction of the cam. All the other dimensions of the finger lever remain unchanged so that this structural modification does not influence the rest of the design dimensions of the finger lever.
According to a further development of the invention, a radius of the convex edges corresponds to a radius of the roller. Thus the side walls, the apex of whose convex edges is situated in the region of a plane passing through a central longitudinal axis of the pin, end with the radius of the roller. However, it is also possible to lengthen the side walls to such an extent that a distance is obtained between said edges and the periphery of the roller situated at a lower level. In this case, the cam would have to penetrate into the rectangular opening.
According to still another feature of the invention, the surfaces of the edges adjacent to the two end faces of the roller comprise recesses. These recesses reliably prevent the cam which actuates the finger lever from coming into contact with the side walls of the finger lever due to slight axial displacements of the finger lever. A further advantage of these recesses is that splash oil can collect in them and be transferred to the end faces of the roller and thus into the rolling bearing.
As an alternative to the recesses in the side walls of the above embodiment, it is also possible to configure the side walls in a Z-shape in vertical direction in the region of the opening above the pin location. A Z-shaped configuration means that starting from their vertical extent, the side walls are at first bent into a horizontal portion and then again into a vertical portion. Due to the Z-shaped sid
REFERENCES:
patent: 4872429 (1989-10-01), Anderson
patent: 5048475 (1991-09-01), Mills
patent: 5642693 (1997-07-01), Kotani
patent: 5720245 (1998-02-01), Calka
INA Walzlager Schaffler oHG
Lo Weilun
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