An adjusting device of the type mentioned at the outset having a planetary gear as a variator and an electronically commutated motor as a servomotor are known in the field. The device has a camshaft gear wheel which is operatively connected via a drive chain to a gear wheel mounted nonrotatably on the crankshaft of the combustion engine. In this context, the camshaft gear wheel is rotatably mounted on the camshaft and is coupled nonrotatably to the input shaft of the variator. The output shaft of the variator is mounted nonrotatably on the camshaft, and the adjusting shaft is operatively connected to the rotor of the servomotor. The stator of the servomotor is permanently bolted to the engine block of the reciprocating piston engine. In the case of a stationary input shaft, a gear ratio preset by the variator, the so-called stationary gear ratio, exists between the adjusting shaft and the output shaft. When the adjusting shaft rotates, the gear ratio between the input shaft and the output shaft increases or decreases depending on the direction of rotation of the adjusting shaft relative to the camshaft gear wheel. This results in a change in the rotational position of the camshaft relative to the crankshaft. A reciprocating piston engine provided with the camshaft adjusting device has the advantage over a comparable reciprocating piston engine not provided with such a device that an improved cylinder charging of the combustion engine is made possible, thereby enabling fuel to be economized, pollutant emissions to be reduced, and/or the power output of the combustion engine to be increased.
To enable the engine function of the combustion engine to be maintained even in the event of a possible malfunction in the adjusting device, the fixed-to-the-crankshaft input shaft has a stop element attached thereto, which, in a position of normal operational use, co-acts with counterstop elements nonrotatably fixed to the camshaft. The limit stops limit the torsional angle of the camshaft relative to the crankshaft to a practical value range. The stop and counterstop elements are positioned in such a way that a defined phase relation results when a counterstop element is positioned against the stop element. The servomotor is linked to a control device which, in certain situations, such as following start-up of the combustion engine, positions the stop element against a counterstop element, in order to make a phase-angle adjustment. In the process, the servomotor is driven in such a way that it is pulse-width-modulated via an output stage with a predefined pulse-no-pulse ratio. However, this entails the disadvantage that different levels of current are supplied to the servomotor, depending on the existing battery voltage and engine temperature, so that different torques and speeds are reached. For that reason, when the stop element is positioned against the counterstop element, the stop element and/or counterstop element can be subject to wear or even to damage.
USPTO Backgrounds
USPTO Backgrounds