Machine element or mechanism – Elements – Cams
Patent
1982-05-25
1985-02-12
Novosad, Stephen J.
Machine element or mechanism
Elements
Cams
123 9017, F16H 5300
Patent
active
044983522
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a cam apparatus where a cam means, which is rotatable by means of a drive shaft, is intended to coact via its flank with a moving contact means or follower for controlling the follower motion as a function of the cam means rotation, said cam means comprising two cam members, at least one of which being settable relative to the other in the peripheral direction of the drive shaft, for resetting the shape of the cam means.
Cam apparatuses are to be found in a multitude of different connections within the technique of motion control. Such apparatuses are particularly used in internal combustion engine technology for controlling valve motion. In such cases it is usual for the cam means to be formed integral with its drive shaft to form a cam shaft which directly or indirectly actuates the valves so that their motion patterns are synchronized with the cam shaft rotation. This results in that the valves will be opened or closed at the same crank shaft position, independent of engine speed (rpm).
In an internal combustion engine intended for operation in vehicles, it is desirable that the engine functions well within a wide rpm range. The valve timing is therefore usually selected so that the best flow conditions in the engine will be achieved close to the middle of the rpm interval in which the engine is normally intended to work. This normal operational rpm interval can be selected arbitrarily within the total engine rpm range. A given engine can thereby be adapted to operate optimally, e.g. at low rpm, or medium rpm or at high rpm, mainly by selecting suitable valve timing during design.
Every internal combustion engine, e.g. of the four-stroke type, thus has a definite rpm at which the engine can function optimally (as during operation at full working load). When the engine operates at rpm which are lower or higher than the optimum rpm, the flow conditions in the engine will gradually deteriorate the further away from the optimum rpm the engine works. This signifies that the work per revolution by the engine decreases when the flow conditions deteriorate in the engine, due to the valve timing no longer suiting the rpm at which the engine is operating. It is obvious that improved engine efficiency would be achieved if it were possible to allow the engine to operate with different valve timing for different rpm. Also in connections other than those with internal combustion engines, enabling the variation of the motion pattern during operation would be very often desirable in such cases where a cam apparatus described in the introduction is utilized, e.g. in workshop machine technology.
Against this background it has been suggested, e.g. for aircraft radial engines, to use a variable cam apparatus where two cam members are mutually hydraulically displaceable by means of hydraulic passages provided in the cam members. Such a solution, however, is not feasible for an in-line type engine.
The object of the invention is to provide an improved cam apparatus enabling variation of the motion pattern in a simple and reliable manner for a follower controlled by a rotatable cam member.
A further object of the invention is to provide a cam apparatus which in a simple manner can be utilized to improve the efficiency in internal combustion engines, especially of the in-line type.
A cam apparatus in accordance with the invention is implemented such that each cam member surrounds the drive shaft like a sleeve and is in non-rotatable engagement therewith via a guide means which is so formed that mutual axial displacement between the drive shaft and the cam member provides relative displacement in the peripheral direction between drive shaft and cam member. It is to advantage if the cam members are adapted to move in opposite peripheral directions of the drive shaft for resetting.
With a simple and reliable cam apparatus in accordance with the invention it will thus be possible to vary the cam means profile during operation, resulting in that the follower is actuated in different ways, depending on what
REFERENCES:
patent: 1757046 (1930-05-01), Horine
patent: 2829540 (1958-04-01), Niemeyer
patent: 2888837 (1959-06-01), Hellmann
patent: 3523465 (1970-08-01), Harrell
patent: 3688593 (1972-09-01), Ustin
Artobolevski, I., Les Mecanismes dans la Technique Moderne, vol. 4, Editions MIR, Moscow, 1977, p. 126.
McKenzie, Jr. Frank H.
Novosad Stephen J.
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