Device for detecting the speed of the shaft of an exhaust gas turbocharger

摘要

The invention relates to a device for detecting the speed of the shaft of an exhaust gas turbocharger. Guided on the periphery of the shaft are two limbs of a ferromagnetic component having an induction coil in which as a result of the changes in the magnetic flux during rotation of a permanent magnet connected to the shaft voltage pulses are induced which are fed to an evaluation device for the purpose of determining the speed of the shaft. The permanent magnet is arranged in such a way that the opposite poles of the permanent magnet are situated in a periodic alternation opposite a different limb, but each limb is respectively simultaneously faced by a pole of the permanent magnet. This produces, in corresponding rotary positions of the permanent magnet, an iron-cored yoke in which a strong magnetic field builds up. The limbs of the ferromagnetic component to which the induction coil is assigned can be extended, without substantial weakening of the magnetic flux, until they project out of the flow space of an exhaust gas turbocharger onto the outside of the flow housing, where they are joined to one another. The induction coil and all the other electrical components can then be situated on the outside of the flow housing in a way which facilitates production and assembly. Strong voltage pulses are induced nonetheless in the induction coil and also still permit low speeds of the shaft to be measured. <IMAGE>