| 摘要 |
<p>PURPOSE:To prevent the damage of a control circuit even if a back switch is turned on erroneously in the course of advancing by forming the back switch by a normally opening switch, and invalidating the signal of the back switch, based on the output of a driving detecting circuit for detecting a forward rotation of a driving wheel. CONSTITUTION:When a back switch 14 is turned on at the time of moving backward, whether a driving wheel is executing a forward rotation or not is detected by a driving detecting circuit 20, and unless it is executing a forward rotation, an instruction for inverting a field voltage is given to a field voltage inversion circuit 21 from an arithmetic circuit 19, a triangular wave of a constant voltage is generated by a speed voltage generating circuit, and by a motor driving circuit 18, a motor 2 is driven to rotate. When the back switch 14 is depressed erroneously in the course of advance running, since the forward rotation of the driving wheel is detected by the driving detecting circuit 20, the back switch 14 being a normally opening switch does not become a turn-on state. Accordingly, it does not occur that the advance is changed suddenly to the backward motion and a large current does not flow to a control circuit, therefore, the control circuit is not damaged.</p> |
