1. Field of the Invention
The present invention relates to an automobile air conditioning system which can be operative in various airflow modes, and more particulary to a control apparatus for an automobile air conditioning apparatus in which a quantitative ratio of outlet air blows off from two different air ducts in a dual airflow mode.
2. Description of the Prior Art
Generally, automobile air conditioning systems have an evaporator and a heater core disposed in a main air duct through which air, recirculated or outside, taken in the main air duct is cleaned, dehumidified, brought and kept at a selected temperature. Air thus controlled is caused to flow through air distributor ducts such as vent duct, a defroster duct and a heated air duct and to blow out into the car through individual outlet assemblies. In these air distributor ducts, there are control vanes, shutters, doors or dampers controlled to open and close by manually operated dash controls or automatic control means so as to create various airflow modes, such as vent, bi-level, heat, defroster-and-heat (which is explained as def-and-heat for short in this specification), and defroster modes.
For selectively changing the air conditioning system to any desired airflow mode, as is disclosed in, for example, Japanese Utility Model Unexamined Publication No. 61-203,113 entitled "Display Panel of an Automobile Air Conditioning Control System", filed on Dec. 20, 1986, manually operated airflow mode selecting switch buttons are provided one individually to each airflow mode. These selecting switch buttons are selectively operated to establish a desired airflow mode. As the selecting switch buttons can be promptly operated in a driver's compartment of the car, any desired airflow mode is swiftly selected.
The bi-level and def-and-heat air flow modes are generally named as intermediate or dual airflow modes; two different airflow modes are simultaneously effective in each intermediate or dual airflow mode. In the bi-level airflow mode, while a control door in a defroster air duct is closed, control doors in vent and heat air ducts are opened to blow off air through vent air and heat air outlets, respectively. In the def-and-heat airflow mode, while the control door in the vent air duct is closed, the control doors in the defroster and heat air ducts are opened to blow off air through the defroster and heat air outlets, respectively. In such dual airflow modes, for example in the bi-level airflow mode, when air is blown off too much through the vent air outlet and directed to the upper halves of passengers in the car, the passengers feel chilly and, on the other hand, when air is blown off too much through the heat air outlet, the passengers feel too warm in their legs. However, the conventional automobile air conditioning systems, despite the fact that any desired airflow mode can be quickly created, are very difficult if not impossible to regulate in the dual airflow modes to control appropriately airflow conditions.