| 摘要 |
PURPOSE:To enable a clogging of an air filter to be detected less expensively with a simple fixing structure by a method wherein air speed sensors having a characteristic for varying an amount of thermal radiation in response to an air speed are arranged across an air filter and a clogged state of the air filter is discriminated by an air speed level sensing means. CONSTITUTION:A removable air filter 12 is arranged in a suction duct 11. An air blower 4 is operated and air speed sensors 20 and 21 are arranged at an upstream side and a downstream side of the air filter 12, respectively. The air speed sensors 20 and 21 are integrally shielded with a heater and a temperature sensor. The temperature sensor is heated by a specified amount with the heater and kept at its high temperature state. A radiation heat amount for a surrounding atmosphere is varied in response to an air speed level passing trough the suction duct 11 and then an air speed level is detected. Its temperature characteristic is decreased in response to the air speed level corresponding to the clogged state of the air filter 12 and as an aeration in the suction duct 11 is decreased due to the clogging state, the air speed levels in the air speed sensors 20 and 21 are inputted into the clogged state discriminating means 23 through the air speed level sensing means 22. |
