Method for acting on gas sensors which are sensitive to noxious substances, for motor vehicles and protective working cabins

摘要

It is known to use gas sensors which are sensitive to noxious substances to control the fresh air/air recirculation flaps and also additionally to switch on and off filter devices in the passenger compartments of motor vehicles and in protective working cabins. With these gas sensors it proves disadvantageous that they have unacceptably large tolerances for the aforesaid application. In order to improve the sensitivity and the stabilisation of the sensors, numerous proposals have been made but when the gas sensor which is sensitive to noxious substances is used, for example in a motor vehicle, the transverse sensitivity to different travel speeds, temperatures, levels of air humidity is unacceptably large. In order to avoid these disadvantages it is proposed according to the invention that at the dividing point between external air and internal air, a gas sensor which is sensitive to noxious substances be provided and that a virtually continuous comparison between the quality of the internal air and of the external air be carried out by switching over within a range of a few seconds. The sensor arrangement can be located in or on the fresh air/air recirculation flap upstream of the switch-over device in the air duct of a motor vehicle. Within the air recirculation flap, the switch-over device alternately feeds the sensor with the air currents to be compared.