Heater/cooler unit of automotive air conditioning system

A heater/cooler unit of an automotive air conditioning system for use in a vehicle having a firewall separating a forward engine compartment from a passenger compartment, the heater/cooler unit comprising:

• a casing having a front wall adapted to face the firewall, a rear wall adapted to face the passenger compartment, and opposing side walls, the casing defining an air flow passage for flow of air upwardly, the casing having an enlarged lower portion and a reduced upper portion, the casing further having at least one air inlet opening and at least one air outlet opening communicating with the air flow passage, the reduced upper portion formed at each side wall of the casing forming a first opposing pair of outer contours, the enlarged lower portion formed at each side wall of the casing forming a second opposing pair of outer contours, wherein the first pair of outer contours are laterally depressed with respect to the second pair of outer contours of the side walls, whereby a dead space is formed on each side laterally between the depressed first outer contour and a vertical extension of the second outer contour of the enlarged lower portion;
• an evaporator positioned in the air flow passage at the enlarged lower portion of the casing;
• a heater, having a width and a length smaller than those of the evaporator, positioned in the air flow passage at the reduced upper portion of the casing, with an air flow space being formed between the heater and the evaporator, the heater being smaller than the reduced upper portion and positioned adjacent to the front wall so that an air flow space is formed between the heater and the rear wall of the casing;
• a ventilation opening formed in the casing, downstream of the air flow space;
• the at least one air outlet opening including a pair of heat openings formed in the casing, one on each side wall above the heater;
• and
• a pair of heat ducts, one communicating with each of the heat openings and lying adjacent to and following, over the at least the major part of its length, the depressed outer contours formed at the side walls of the casing such that a substantial portion of the cross-section of the heat ducts is coextensive with the dead space formed on each side, each of the heat ducts extending toward the enlarged lower portion of the casing and, in the distance between the heater and evaporator, having a laterally outer surface that does not extend substantially laterally beyond the outer contour of the enlarged lower portion,
• whereby the overall lateral size of the heater/cooler unit can be minimized in the upper portion to be not significantly larger than the outer contour of the enlarged lower portion.