Control apparatus and method for a vehicle automatic transmission to suppress shock upon changing speed

Abstract

An apparatus for controlling an automatic transmission of an automobile and a control method thereof. When a feedback control is executed by the automatic transmission while the speed is being changed, the control operation may often lose stability. This is due to a large deviation between a target value and a practical value at the start of the feedback control operation being caused by a change in the opening degree of the throttle and a change in the oil temperature in the automatic transmission. To solve such a technical problem, the invention employs a control apparatus which detects that the automatic transmission is changing the speed, operates the output shaft torque of the automatic transmission, recognizes a point of inflection of the output shaft torque while the speed is being changed, sets a target output shaft torque of the automatic transmission, and sets an initial target value at a moment of said point of inflection.

What is claimed is:  
     
         1 . An apparatus for controlling an automatic transmission having a pressure-regulating instruction generator which changes the speed by coupling or decoupling a predetermined friction coupling device in the automatic transmission coupled to an engine, regulates the oil pressure that acts on said friction coupling device at the time of changing the speed, and changes the pressure-regulating characteristics, comprising: 
 a speed-changing recognizing means for recognizing that said automatic transmission is changing the speed;    a torque calculation means for calculating the output shaft torque of said automatic transmission when a speed-changing is recognized by the speed-changing recognizing means;    a point-of-inflection recognizing means for recognizing a point of inflection in the output shaft torque of said transmission;    a target value-setting means for setting a target value of the output shaft torque of said transmission;    an initial value-setting means for setting said initial target value at a moment of said point of inflection; and    a transmission output shaft torque instruction means for outputting an instruction to said pressure-regulating instruction generator so that said output shaft torque of said transmission follows said target value.    
     
     
         2 . An apparatus for controlling an automatic transmission according to  claim 1 , wherein said point-of-inflection recognizing means recognizes said point of inflection based upon a change rate of the output shaft torque of said transmission.  
     
     
         3 . An apparatus for controlling an automatic transmission according to  claim 1 , wherein said point-of-inflection recognizing means recognizes said point of inflection based upon a ratio between the input and output revolution speeds of the transmission.  
     
     
         4 . An apparatus for controlling an automatic transmission according to  claim 1 , further comprising: 
 a throttle-opening-degree detector for detecting the opening degree of the throttle that is varied by the acceleration pedal operation by a driver; and    an amount-of-correction calculating means for calculating the amount of correction for said target value depending upon a change in the opening degree of the throttle from said throttle-opening-degree detector.    
     
     
         5 . A method of controlling an automatic transmission having a pressure-regulating instruction generator which changes the speed by coupling or decoupling a predetermined friction coupling device in the automatic transmission coupled to an engine, regulates the oil pressure that acts on said friction coupling device at the time of changing the speed, and changes the pressure-regulating characteristics, wherein: 
 when said automatic transmission is changing the speed, the output shaft torque of said automatic transmission is calculated;    a point of inflection of the output shaft torque of said transmission is recognized;    a target value of the output shaft torque of the transmission is set, and said initial target value is set at a moment of said point of inflection; and    an instruction is output to said pressure-regulating instruction generator, so that said output shaft torque of the transmission follows said target value.    
     
     
         6 . An method of controlling an automatic transmission according to  claim 5 , wherein said point-of-inflection is recognized based upon a change rate of the output shaft torque of said transmission.  
     
     
         7 . A method of controlling an automatic transmission according to  claim 5 , wherein said point-of-inflection is recognized based upon a ratio between the input and output revolution speeds of the transmission.  
     
     
         8 . A method of controlling an automatic transmission according to  claim 5 , wherein the amount of correction for said target value is calculated depending upon a change in the opening degree of the throttle that is varied by the acceleration pedal operation by a driver.