Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing
Patent
1993-02-25
1994-04-26
Nelli, Raymond A.
Internal-combustion engines
Poppet valve operating mechanism
With means for varying timing
123 9031, 464 2, F01L 134
Patent
active
053057171
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to an arrangement for the automatically controlled varying of the relative rotating position of two shafts in an internal-combustion engine, comprising at least one camshaft which can be rotated relative to a shaft driving it, as a function of parameters of the internal-combustion engine, and a driving wheel which drives the camshaft. The driving wheel carries a first toothing or set of gear teeth and, by way of a coupling member which is axially displaceable at least in two end positions, acts upon a second toothing connected with the camshaft. At least one of the toothings is a helical toothing.
It is known to adapt the valve timing of an internal-combustion engine to its rotational speed in order to be able to operate it optimally in a rotational speed range that is as wide as possible. As a result, the torque, the performance, the exhaust emission, the idling action and the fuel consumption can be improved.
One possibility of changing the valve timing during the operation of the internal-combustion engine comprises rotating the intake canshaft in its position relative to the crankshaft driving it by means of a phase converter. For example, European Patent Document EP 0 335 083 shows a coupling member that is axially shifted and which is coaxially surrounded by the wheel driving the camshaft, as a function of oil pressure. The coupling member carries two toothings of which at least one is helically geared and which interact with one corresponding toothing respectively on the camshaft or in the wheel. Disadvantages of this construction are the high expenditures with respect to components for the leading-in and gradual shut-off of the pressure oil as well as the large size.
The British Patent Document GB-21 89 086 shows a camshaft which is coaxially surrounded by a hollow shaft section which carries a can for the actuating of a charge cycle valve. An annular gap constructed and sealed off between the camshaft and the shaft section is filled with an electroviscous fluid (EVF). By feeding an electric voltage between the camshaft and the insulatedly held shaft section, the viscosity of the EVF is increased to such an extent that a rigid coupling is created so that the shaft section rotates synchronously with the camshaft. When the voltage is disconnected, the electroviscous fluid will liquify, whereby the shaft section is uncoupled from the camshaft. With this arrangement, for example, a charge cycle valve can be connected and disconnected, or the valve overlap can be varied between intake valves and exhaust valves. If the valve overlap is varied between intake valves and exhaust valves, this arrangement achieves the same effect that can be achieved by a change of the relative rotating position between an inlet camshaft and an outlet camshaft.
An object of the present invention is to provide an arrangement of the above-mentioned type which reduces the component expenditures and size and has a simple and low-cost construction.
This and other objects are achieved by the present invention which provides an arrangement for automatically controlled varying of a relative rotating position of two shafts in an internal-corabustion engine, the shafts including a camshaft and a second shaft, the camshaft being rotatable relative to the second shaft as a function of parameters of the internal-combustion engine. The arrangement comprises a driving wheel which drives the camshaft and carries a first toothing. A second toothing is connected with the camshaft, with at least one of the first and second toothings being a helical toothing. A coupling member is provided that is axially displaceable between at least two end positions and is arranged between the driving wheel and the camshaft to act upon the second toothing. A stationary intermediate timing gear bearing ring coaxially surrounds the coupling member at least in sections and bounds an annulus formed between the bearing ring and the coupling member. A fluid is provided in the annulus, this fluid having a vis
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Dr. Ing. h.c.F. Porsche AG
Lo Weilun
Nelli Raymond A.
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