Air conditioning system for vehicles

Abstract

Disclosed is an air conditioning system for vehicles capable of operating control with a high degree of operating efficiency even in operating states wherein efficiency would be expected to decline, and while adhering to conventional control ideas. The air conditioning system for vehicles comprises a compressor that compresses a refrigerant; a condenser that condenses the compressed refrigerant; an expansion mechanism that expands the condensed refrigerant; an evaporator that evaporates the expanded refrigerant and brings the evaporated refrigerant into contact with air, cooling and dehumidifying the air; a blower that sends the air to the condenser; and a displacement control signal calculation means for determining a displacement control signal, using a displacement control signal calculation formula, which is to be inputted to the compressor from the outside. In the displacement control signal calculation means, a target air temperature at the evaporator exit is inputted, the displacement control signal is determined using the difference between the air temperature and the target air temperature at the evaporator exit when a displacement control signal calculated value is less than or equal to a predetermined value (A), and the displacement control signal is determined from the displacement control signal calculation formula when the displacement control signal calculated value is greater than the predetermined value (A).

1 . An air conditioning system for vehicles, comprising a compressor for compressing a refrigerant, a condenser for condensing a compressed refrigerant, an expansion mechanism for expanding a condensed refrigerant, an evaporator for evaporating an expanded refrigerant so as to contact an air to be cooled and dehumidified, a blower for blowing an air to said condenser, and a displacement control signal calculation means for determining a displacement control signal according to a calculation formula for said displacement control signal to be input from an outside to said compressor in order to control a displacement in said compressor, wherein
 at least a target value of an air temperature at an evaporator exit is input to said displacement control signal calculation means, said displacement control signal is determined from a difference between an air temperature at said evaporator exit and said target value of said air temperature at said evaporator exit if a calculated value of said displacement control signal which is calculated according to said calculation formula for said displacement control signal is less or equal to a predetermined value A, and said displacement control signal is determined from said calculated value of said displacement control signal if said calculated value of said displacement control signal is more than said predetermined value A.   
     
     
         2 . The air conditioning system for vehicles according to  claim 1 , wherein said displacement control signal is determined to be either a predetermined value m which corresponds to a minimum displacement in said compressor or a predetermined value B, if said calculated value of said displacement control signal is less or equal to said predetermined value A. 
     
     
         3 . The air conditioning system for vehicles according to  claim 2 , wherein said predetermined value B is determined according to a thermal load of said air conditioning system. 
     
     
         4 . The air conditioning system for vehicles according to  claim 2 , wherein said predetermined value B is determined to be always more or equal to said predetermined value A. 
     
     
         5 . The air conditioning system for vehicles according to  claim 2 , wherein said blower is stopped if said calculated value of said displacement control value is less or equal to said predetermined value A while said displacement control signal is equal to said predetermined value m, and said blower is operated if said displacement control signal is equal to said predetermined value B. 
     
     
         6 . The air conditioning system for vehicles according to  claim 1 , wherein an airflow rate of said blower is controlled according to a vehicle speed. 
     
     
         7 . The air conditioning system for vehicles according to  claim 6 , wherein said blower is stopped if said calculated value of said displacement control value is less or equal to said predetermined value A while vehicle speed is more or equal to a predetermined value C, and said blower is operated if said vehicle speed is less than said predetermined value C. 
     
     
         8 . The air conditioning system for vehicles according to  claim 1 , wherein an airflow rate of said blower is controlled according to a torque of said compressor. 
     
     
         9 . The air conditioning system for vehicles according to  claim 1 , wherein at least one physical parameter in a group consisting of an insolation, an outdoor temperature, an indoor temperature, an indoor humidity, an airflow rate to said compressor, a vehicle speed, and rotation speed of a vehicle engine is input to said displacement control signal calculation means.