| 摘要 |
In order to reduce the friction and mechanical stressing in a valve gear of a four-stroke reciprocating piston internal combustion engine with inlet and exhaust valves, which are arranged essentially parallel to the axis of the cylinders assigned to the engine, opened by desmodromic valve gear and closed under the action of valve springs, it is proposed to design the spring force of the valve springs so that in the maximum operating speed range the valve closing acceleration is at least temporarily less than the valve closing acceleration resulting from the cam drop flank. At the same time it may be advantageous to design the valve springs of the valves so that the springs assigned to the inlet valves increase the frictional connection before the maximum operating speed is attained, but the valve springs assigned to the exhaust valves on the other hand eliminate it shortly after the maximum operating speed. In order to prevent damage to the valve stem guide and to the valve discs when the valves collide with the piston heads, at least the exhaust valves may have concentrically projecting stop cams on that side of the valve discs facing the piston, whilst the surfaces of the piston heads coming into contact with these stop cams have an increased impact strength and wear resistance.
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