Air conditioning system for automotive vehicles having discharge air temperature control function

Claim 1

An air conditioning system for automotive vehicles, which comprises: a casing having an air passage formed therewithin; an evaporator core arranged in said air passage; a compressor operatively connected to said evaporator core; a heater core arranged at a location downstream of said evaporator core in said air passage; a passage bypassing said heater core; a pivotally mounted air-mix damper for guiding an air flow from said evaporator core, through said by-pass passage alone at a first angular position thereof, through said heater core alone at a second angular position thereof, and through both said by-pass passage and said heater core at a position between said first angular position and said second angular position; a temperature control lever disposed for pivoting between a first extreme position thereof and a second extreme position thereof with a predetermined intermediate position provided between said first and second extreme positions, temperature control lever being operatively connected to said air-mix damper; said air-mix damper being adapted to be pivotally displaced between said first angular position and said second angular position as said temperature control lever is moved between said predetermined intermediate position and said first extreme position, and said air-mix damper being adapted to be always held at said first angular position when said temperature control lever is moved between said predetermined position and said second extreme position; and compressor-operation control means operatively connected to said temperature control lever for controlling the operation of said compressor, said compressor-operation control means being adapted to be kept inoperative to keep said compressor at rest when said temperature control lever is positioned between said predetermined intermediate position and said first extreme position, and said compressor-operation control means being adapted to vary the rate of operation of said compressor with movement of said temperature control lever between said predetermined intermediate position and said second extreme position, said compressor-operation control means comprising: a magnetic clutch having a solenoid and coupled with said compressor; an output transistor coupled to said solenoid for energizing said solenoid; a timer formed by an integrated circuit for supplying pulses to said output transistor for turning said output transistor on or off; a resetting switch operatively connected to said timer and to said temperature control lever for rendering said timer inoperative when said temperature control lever is positioned on the side of said first extreme position with respect to said predetermined intermediate position; and a time constant circuit operatively connected to said temperature control lever for varying the duty factor of pulses from said timer with movement of said temperature control lever between said predetermined intermediate position and said second extreme position.