| 摘要 |
PROBLEM TO BE SOLVED: To reliably detect abnormal vibration for various operating conditions by detecting that axial torque vibration exceeds first and second set levels respectively and remains as it is for a predetermined time. SOLUTION: When an axial torque detection signalτA (5 to 12Hz) is passed through a 1-Hz filter, a constant average axial torque signalτP is obtained, and a deviation detection part 16 detects deviation between the detection signalτA and the average axial torque signalτP, that isΔτA-ΔτP. If each vibration exceeds a first set level, comparators 18, 21 are turned ON, and off-delay timers 19, 22 are also turned ON. Therefore, an AND circuit 23 outputs 1, and an on-delay timer 24 determines abnormal vibration if this state continues for 10 seconds. In addition, when vibration higher than a high level of second setting continues for 3 seconds, an on-delay timer 36 determines abnormal vibration. Further time since the detection signal exceeds the first level until it exceeds the second level is less than 2 seconds, an AND circuit 35 outputs 1, and suddenly increasing abnormal vibration is determined.
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