| 摘要 |
PURPOSE:To prevent intrusion of impure gas into a car room, by providing a gas sensor detecting the concentration of harmful gas in the outside air of a car and controlling a selector damper of internal and external air in accordance with a compared result of a required time for change with the reference time when an output of said sensor is changed. CONSTITUTION:A switch 9a in a control switch 9 is closed, if an automatic selecting mode is directed, a microcomputer 6 firstly subtracts a variable N.T (Where N is control variable and T is predetermined fixed value) varying with the time from an update input value of a gas sensor 4 to store its subtraction value L. Secondly, whether this subtraction value L is larger than a prescribed value A or not is decided, and in case of YES, a selector damper 2 of internal and external air is selectively controlled to recirculate internal air. While in case of NO, said subtraction step is reexecuted till the control variable N reaches a prescribed value m+1. During this time, when the increase amount L of a sensor level becomes the prescribed value A or more, similarly said damper 2 is selectively controlled to recirculate the internal air. |
