Throttle unit for internal combustion engines

The invention relates to a throttle unit for internal combustion engines, particularly for vehicles, of the type comprising a throttle (12), capable of taking up a blow-by position (TR), a position corresponding to the normal engine idling condition, a fully-open position (WOT), a plurality of intermediate positions between the previous ones and a "limp home" position (LH), and in which the shaft (11) of the throttle (12) is controlled by an electric motor (10) through a mechanical transmission equipped with a sprocket gear reduction unit (13, 14). According to the invention, the transmission from the sector gear (14) to the shaft (11) of the throttle (12) consists of an articulated quadrilateral kinematic mechanism (15), the dead-centre condition of which corresponds to the throttle blow-by position, there being further provided a spring (19) opposing the rotations imparted by the motor (10) to the sector gear (14) to bring the throttle (12) towards the fully-open position (WOT).