Rotary shafts – gudgeons – housings – and flexible couplings for ro – Separate coupling device movable radially of axes of torque...
Patent
1993-05-21
1995-05-23
Stodola, Daniel P.
Rotary shafts, gudgeons, housings, and flexible couplings for ro
Separate coupling device movable radially of axes of torque...
74568R, 123 9017, F01L 134, F16D 304
Patent
active
054176115
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to driving connections between two rotatable bodies having parallel but laterally-displaceable axes of rotation, the first body being hollow and the second body being located within it. The invention applies particularly to connections in which the two bodies are both shafts, the first body being a hollow shaft and the second body--which is probably solid and the driving member of the combination - being located within it.
2. Description of Related Art
The presently claimed invention thus relates especially to mechanisms of the kind described in Patent Specifications GB-B-2066361 and GB-A-2206179 which operate the valves of Internal combustion engines, which are capable of varying the valve timing during operation to suit changes in operating conditions, and in which hollow camshafts are driven by solid driving shafts located within them.
The connections between the driving shafts and camshafts, described by way of example in specification GB-B-2066361, are suitable for an engine with in-line cylinders, but with the inlet valves of the cylinders offset from the outlet valves relative to that line. The invention behind specification GB-A-2206179 arose from the need for a mechanism capable of use in a compact engine in which the cylinders are in-line, and in which the inlet and exhaust valves are also in-line with the cylinder centers. Another factor behind that invention was an increasing preference for valve-operating cams to operate directly onto bucket tappets, instead of onto rockers or levers as in GB-B-2066361.
In the design shown by way of example in specification GB-A-2206179, the driving connection between a central driving shaft and the hollow camshaft that surrounds it is made by way of an arm which projects radially from the driving shaft. The outer end of the arm has the shape of part of a cylinder whose axis lies parallel to that of the shaft. The outer end thus has a part-circular outline, and this engages rotatably in a corresponding recess formed Within a block which is mounted to slide in a radial slot formed within a flange mounted on the hollow camshaft. Such a connection has the advantage of being very compact axially, because all the essential components just recited lie in the same transverse plane relative to the axes of rotation of the driving and driven members, unlike the connections of GB-A-2066361 and also EP-A-0179581, in both of which there is an axial gap, spanned by a pin or the like, within the driving connection between the two rotatable bodies.
SUMMARY OF THE INVENTION
The present invention arises from appreciating the benefit of adding, to the axial compactness of the design of GB-A-2206179, the potential of greater radial compactness and in particular a reduction in the radius Y between the axis of the driving shaft and the center of rotation of the rotary joint. With such a driving connection, the obtainable range of variation of valve timing is proportional to the function X/Y, where X is the distance by which the axes of the driving and driven shafts can move apart, and Y is as defined above. In any practical design the maximum value of quantity X will be limited by the bore of the hollow driven camshaft, because any Increase In that dimension tends also to increase both the frictional losses at the hollow camshaft bearings, and also the surface speed and frictional losses at the surfaces of the driven cams because the cam base circle diameter must Increase In proportion. It is therefore advantageous to maximise the value of function X/Y by minimising the value of Y.
The invention is defined by the claims, the disclosure of which is to be read as included within the disclosure of this specification, and includes driving connections and valve-timing mechanisms as described by way of example with reference to the accompanying diagrammatic drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A is a transverse section through driving and driven shafts and the driving connection between them;
REFERENCES:
patent: Re31917 (1985-06-01), Mitchell
patent: 3010339 (1961-11-01), Brock
patent: 3491604 (1970-01-01), Levi
patent: 4505235 (1985-03-01), Mitchell
patent: 4872428 (1989-10-01), Mitchell
Automotive Engineering, vol. 88, No. 10, 10 Oct. 1980, Dallas, pp. 120-124; D. Scott: 'eccentric cam drive varies valve timing.
British Technology Group Limited
Dunn Eileen A.
Stodola Daniel P.
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