Bumper (motor)
The bumper in an internal combustion engine is part of the valve control on engines with side camshafts and overhead valves . It is also possible for only the inlet valve to be actuated via a bumper, this is called alternating control or Inlet over Exhaust (IOE). The cam of the camshaft actuates a tappet mounted in the crankcase or a lever that absorbs the lateral force. The tappet or lever drives the bumper, which in turn actuates the valve via a rocker arm . With water-cooled engines, the bumpers run in cavities in the engine block, with air-cooled engines outside in protective tubes. With very old or ship engines, they can be exposed.
The construction described here is the typical construction. In the course of the development of valve trains , many variants have been tried, e.g. B. Valve drives with two levers, but without a tappet and without a bumper, or the actuation of exhaust valves with a tappet, two bumpers and two rocker arms on the engine of the BMW 328 .
Reciprocating piston engines with pushrods in the valve train are also known as pushrod engines .
Modern engines have overhead camshafts that typically operate the valves via rocker arms or rocker arms or directly via bucket tappets. There are also engines with overhead camshafts and bumpers.
In automotive engines , bumper lengths of up to 70 cm have been achieved. The large oscillating (reciprocating) mass, however, limits the maximum speed of the motor, so they are designed to be as short and light as possible.
In motorcycles you can still find various engines with bumpers, traditionally in the air-cooled two-cylinder V-engines from Harley-Davidson & Buell and the engines of the R-series from BMW . Yamaha uses bumper motors in the MT-01 and Yamaha XV1900A Midnight Star models . A historical example is the Horex Regina . Here, the bumpers run in a common thick protective tube on the right side of the single cylinder, which looks like the engine has a vertical shaft .
Colloquially, the term pushrod is often used for the bumper , which may come from the much-produced engine of the VW Beetle , in which the pushrod and bumper were combined into one part until 1961.
literature
- Richard van Basshuysen, Fred Schäfer: Handbook Internal Combustion Engine Basics, Components, Systems, Perspectives. 3rd edition, Friedrich Vieweg & Sohn Verlag / GWV Fachverlage GmbH, Wiesbaden 2005, ISBN 3-528-23933-6