| 摘要 |
The invention relates to a spring-less valve timing gear, especially for motor vehicle engines, the valve opening and closing movements of which are positively controlled, directly by a (conventional) opening cam, determining the valve timings, and indirectly by way of an offset lever arm, by a reciprocal closing cam of the camshaft arranged next to this. The superiority of a so-called desmodromic valve gear, in terms of the volumetric efficiency of the cylinder, compared to conventional valve gears with valve closing springs lies in the fact that due to the absence of closing spring forces the opening and closing accelerations, up to the limit load of the Hertzian stress, can be designed steeply in such a way that with only two valves for the charge cycle, time/cross-section ratios approximately equal to those on the comparable four-valve cylinder can be obtained, but without adversely affecting the torque at low speeds, due to the effects both of the large overlaps of the valve opening times in the area of the piston bottom dead centre by reducing the effective compression ratio, and in the area of the top dead centre due to exhaust gas reversions and reduction of the volumetric efficiency of the cylinder. The invention solves the difficult problem of simplifying the necessary clearance adjustments of this type of timing gear in such a way that these adjustments conform approximately to the usual standard for this and in addition [...] a hydraulic zero-clearance device ... Original abstract incomplete.
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