| 摘要 |
PROBLEM TO BE SOLVED: To properly detect choking of a filter without using a special part, such as a sensor. SOLUTION: When the rotational speed of a fan motor 76 is set according to an air flow by a rotational speed setting part 130, a microcomputer 74 sets a step for a control signal based on the setting thereof. By the step for the control signal, PWM control of the fan motor is performed. Further, the microcomputer corrects the actual step through the operation of a step comparing correction part 132 based on the output of a generator 122 corresponding to the rotation of a fan motor and effects feedback control. In this case, the set step for the control signal is compared with the step for the actual control signal, and based on the comparison result, it is decided by a deciding part 134 whether the filter is clogged or not. |
