Heating or air-conditioning ventilation unit for motor vehicles

A heating or air-conditioning ventilation unit for a motor vehicle, comprising:

• a radial blower disposed in a first housing and having a generally rectangular outlet opening of a first size;
• a second housing closely adjacent to said first housing and having a cross-sectional size substantially larger than the size of said outlet opening;
• a diffuser defined by upper and lower wall parts connecting said first housing and said second housing, wherein said upper and lower wall parts open from the size of said outlet opening to the cross-sectional size of said second housing with a wide opening angle;
• a heat exchanger positioned in said second housing in close proximity to said diffuser and having a rear surface which faces said diffuser and which substantially fills the cross-section of said second housing;
• and
• means for providing a uniform admission of air to said heat exchanger, said means comprising a grid comprised of portions of substantially equal thickness wherein the thickness is small in comparison to the area of the grid, said grid being positioned between said diffuser and said heat exchanger and having a generally convex profile, with a portion of said profile of said grid extending into said diffuser, wherein said grid extends over about 60% to 80% of the end face of said heat exchanger and wherein the ratio of the open area to the total area of said grid is from about 0.6:1 to about 0.8:1.