| 摘要 |
First and second thresholds are established which define a pressure difference relative to a maximum pressure level for a fluid under pressure, which maximum pressure level is detected by a pressure detecting device, and a third threshold is also established which is lower than the maximum pressure level and higher than the first and second thresholds. While a pressure detected by the pressure detecting device ranges between the first and second thresholds, an output signal is supplied to a drive member. When a pressure lower than the third threshold is detected by the pressure detecting device, an output signal indicative of a predicted failure is produced. The output signal indicative of a predicted failure is produced when a pressure lower than the third threshold is detected a plurality of times by the pressure detecting device. |
