Device for diffusing air to the forward section of a motor vehicle passenger compartment

The invention relates to a device for distributing ventilation air at the front of the passenger compartment (6) of a motor vehicle, this ventilation air being delivered by a distribution box (10) of a heating ventilation and/or air conditioning assembly, said device comprising at least one ventilation duct (9) supplying at least one ventilation opening (16a, 16b, 17a, 17b) provided in the dashboard (1), said ventilation duct (9) being formed in a diffusion module (8) which extends transversely under the upper face (2) of the dashboard (1), dividing downstream in the direction of ventilation air flow into at least one "soft" ventilation duct (13) which opens onto the upper face (2) of the dashboard (1) by ventilation orifices (14) of large cross-section, and into at least one "forced" ventilation duct (15) which supplies at least one ventilation opening (16a, 16b, 17a, 17b) of small cross-section arranged on the dashboard (1) facing the passenger compartment (6). At least one air distribution flap (21) is provided at the junction of the three ducts (9, 13, 15).