| 摘要 |
<p>1. A control circuit for an electric motor driving an internal combustion engine cooling fan, in which a regulating loop is connected between a set value generator and a thermistor (3) on one hand, and a power switching device connected in series with the driving motor (2) on the other hand, said thermistor (3) being placed in contact with a heat-carrying fluid whose temperature reflects the temperature of the internal combustion engine, said set value generator, said regulating loop and the power switching device each comprising n sections (25a, 25b, 21a, 21b) respectively assigned to n ranges of evolution of the temperature, while said power switching device comprises at least n relay contacts (23a, 23b) controlled by respective sections of said regulating loop, the control circuit further comprising a protection circuit (12c) comprising sections of set value generator, regulating loop and power switching device (17c, 25c, 22c), characterised in that each of said relay contacts is connected in parallel with a resistor (14a, 24b) which is shorted when said section of the regulating loop delivers an output signal, the parallel circuits thus formed being all connected in series in the circuit of said electric motor (2), the switching device of the protection circuit (12c) is a relay contact connected in parallel with all the relay contacts (23a, 23b, 23d) of the other switching device sections for connecting the motor (2) directly to the supply when a temperature which is considered dangerous is reached, the terminal of the thermistor (3) delivering the measuring signal which is the image of the temperature of the heat-carrying fluid is connected to a comparator (30) to which is also connected a set value generator (27), and the output of this comparator (30) is connected in the regulating loop of the protection circuit (12c) for initiating the switching device (21c, 23c) of the protection circuit in the event of breakage of the connections of said thermistor.</p> |
