| 摘要 |
PURPOSE:To detect a failure in operation of a hammer and enable to protect a driving circuit, by a method wherein a comparing and discriminating operation for a reference current and an exciting current is conducted in each of periods of time set on the first and second timers, and an abnormal value of the exciting current is detected. CONSTITUTION:A driving circuit 2 for the hammer 1 outputs the exciting current I1 to an exciting coil 4 in response to a printing command S1 from a controlling circuit 3. The current value I1 is fed out to a detecting circuit 11 as a current detection signal S2. The detecting circuit 11 starts the timers 111, 112 in accordance with the signal S1, the current detection signal S2 and a reference voltage V corresponding to the reference current iS are compared with each other by a comparator 113 in each of the periods of time set on the timers 111, 112, and when the signal S2 is discriminated to be abnormal, an error signal S3 is outputted to operate an alarm, and operation of the printer is stopped. Accordingly, a failure in operation of the hammer can be detected, and the driving circuit can be protected. |
