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Geschaltetes Element Disclosure Number: IPCOM000012100D
Published in the Journal: Volume 3 Issue 5 (2003-05-25)
Included in the Prior Art Database: 2003-May-25
Document File: 2 page(s) / 109K

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Es kann Erfordernisse geben, einen Hochspannungs-Schalter (HV-Switch) zu realisieren, welcher bei einer Eingangsspannung von 0 Volt sperrt, jedoch bei angelegter hoeherer Spannung – bei positiver Eingangsspannung auf einem konstanten niedrigen Stromwert – einschaltet und niederohmig wird, wenn die Ausgangsspannung klein wird. Das Verhalten dieses Geschalteten Lambda-Elements (GLA) ist in Abb. 1 dargestellt. Ein solches GLA kann beispielsweise bei Lampenvorschaltgeraeten eingesetzt werden. Eine Schaltskizze des GLA ist in Abb. 2 wiedergegeben. Dabei ist der Transistor T1 ein HV-FET (High Voltage – Field Effekt Transistor) oder ein IGTB (Insulated Gate Bipolar Transistor). Nach dem Einschalten steigt seine Source auf eine Einsatzspannung UT1 (Threshold) von etwa 10 Volt an. Der Niederspannungs-Transistor T3 ist ebenfalls eingeschaltet und bringt die Spannung am Gate des Transistors T2 , einem niederohmigen Niederspannungs-FET, auf 0 Volt. Sinkt die Steueranschluss-Spannung U0 , so erreicht die Einsatzspannung von T1 einen Wert, der das Ausschalten von T3 und Einschalten von T2 bewirkt. Sobald T2 leitet, springt der Strom I vom Anfangswert I0

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© SIEMENS AG 2003 file: ifx_2003J50115.doc page: 1

Snail Disc Torque Measurement System

Idea: Alann Denais, DE-Munich; Richard Gledhill, DE-Munich; Andreas Miller, DE-Munich

Often there is a need to be able to measure the torque in a shaft, i.e. a drive shaft in a car. At present there are some solutions.

First, there is the strain gauge system which uses a strain gauge on the shaft itself. A detection and signal manipulation system measures the torsion in the shaft and then generates an output. Therefore a high precision is needed to make contact with the shaft, connecting the strain gauge, mounting and measuring the size of the system. Little mistakes here may result in bad sensor readings.

The second system uses two tooth wheels, one at each end of the shaft. Pointing at the teeth, a sensor is connected so that a signal is received every time a tooth went past the sensor. From this the wheel speed can be determined, and by comparing the timings of the teeth of each wheel the torque can be calculated. The disadvantage is that this system relies on constant readings as the teeth pass the sensor. When stopping it is possible that an extra reading occurs. Even rotational vibration may cause one or more extra readings. It is impossible to recover from this without resetting the whole system.

This invention comprises two disc wheels (known as snail wheel), the mounting of the sensors and the software used to determine the wheel speed and shaft torque from the data. Each disc wheel is made from ferrous material. As shown in figure 1 the radius varies linearly from one reference point, called the tooth, round the disc, back to the same point; at this point there is a step change in radius back to the first value. This spiral effect forms the shape that gives the disc the name snail wheel. The exact dimensions are to be determined by the installation, but the minimum thickness should be the same as the width of the sensor to maximise signal strength. The variation in radius of the snail disc is more critical, but dependent on the sensor used. So it should be set to g...