Heating and air-conditioning installation for motor vehicles

Abstract

A heating and air-conditioning installation for motor vehicles, in which an adjustable desired temperature is kept constant in the interior space of the motor vehicle independently of changing conditions, includes a heat-exchanger connected to the hot water circulation of the engine as well as an adjusting member on whose position is dependent the heat quantity supplied to the vehicle interior space; the position of the adjusting member is controlled by an output signal produced by an electronic circuit as a function of the sensor detecting the heat quantity supplied to the vehicle interior space, an interior sensor, a setting device and an outside sensor; a switching device operable to switch from fresh-air operation to recirculated-air operation is also controlled as a function of a signal of the electronic circuit; the electronic circuit includes a delay element to produce a time-delayed intermediate signal from the values obtained from the interior sensor, the outside sensor and the setting device; the intermediate signal produces together with the value determined by the sensor detecting the heat quantity supplied to the vehicle interior space, an output signal for the adjusting member; the electronic circuit also produces a signal as a function of the difference between the value detected by the outside sensor and the value determined at the setting device which controls the switching over from fresh-air circulation to recirculated-air operation.