Control apparatus for an automatic transmission of a vehicle and a control method

Abstract

A control apparatus and a control method for an automatic transmission, improved over those devised to minimize torque fluctuations which, if left unchecked, give vehicle passengers a disagreeable feeling upon a gear shift. The inventive control apparatus and method, aimed at suppressing such torque fluctuations during a shift of the transmission thereby to improve robustness and provide good shift characteristics, involve recognizing an inertia phase in which the engine speed starts to drop during the shift. At the beginning of the inertia phase, hydraulic pressures supplied to frictional engaging devices in the transmission are kept constant to suppress the torque fluctuations.

What is claimed is:  
     
         1 . A control apparatus for an automatic transmission comprising a plurality of frictional engaging devices and pressure control command generation means, said plurality of frictional engaging device being incorporated in an automatic transmission which reduces an output of an engine in a vehicle, transmits the reduced engine output to driving wheels of said vehicle, and varies a speed ratio representing the ratio of the reduction of the engine output, said plurality of frictional engaging devices being frictionally engaged and disengaged to turn on and off the transmission of the reduced engine output, at least one of said plurality of frictional engaging devices being frictionally engaged and at least one of the remaining frictional engaging devices being disengaged to execute a shift to vary said speed ratio, said pressure control command generation means controlling hydraulic pressures supplied to the two frictional engaging devices to effect an engagement and a disengagement of the devices at the time of said shift, said pressure control command generation means further varying characteristics of hydraulic pressure control, said control apparatus comprising: 
 inertia phase recognition means for recognizing during said shift a beginning of an inertia phase in which a speed of said engine varies; and    torque fluctuation suppression means for calculating pressure control command values to keep constant the hydraulic pressures supplied to said frictional engaging devices at the recognized beginning of said inertia phase, the calculated pressure command control values being output to said pressure control command generation means.    
     
     
         2 . A control apparatus for an automatic transmission according to  claim 1 , wherein said pressure control command values calculated by said torque fluctuation suppression means are command values which keep constant the hydraulic pressures supplied to said frictional engaging devices before causing said hydraulic pressures to vary in accordance with a signal representing said recognized beginning of said inertia phase.  
     
     
         3 . A control apparatus for an automatic transmission according to  claim 1 , wherein said pressure control command values calculated by said torque fluctuation suppression means are command values which, for a shift-up with said speed ratio varying from a large to a small value, keep constant the hydraulic pressure supplied to an engaging-side frictional engaging device among said plurality of frictional engaging devices, said pressure control command values being command values which, for a shift-down with said speed ratio varying from a small to a large value, keep constant the hydraulic pressure supplied to a disengaging-side frictional engaging device among said plurality of frictional engaging devices.  
     
     
         4 . A control apparatus for an automatic transmission according to  claim 1 , wherein said torque fluctuation suppression means corrects said pressure control command values to keep constant the hydraulic pressures supplied to said frictional engaging devices in accordance with oil temperature changes in said automatic transmission.  
     
     
         5 . A control apparatus for an automatic transmission according to  claim 1 , wherein said torque fluctuation suppression means corrects said pressure control command values to keep constant the hydraulic pressures supplied to said frictional engaging devices in accordance with load changes of said engine.  
     
     
         6 . A control apparatus for an automatic transmission comprising a plurality of frictional engaging devices and pressure control command generation means, said plurality of frictional engaging device being incorporated in an automatic transmission which reduces an output of an engine in a vehicle, transmits the reduced engine output to driving wheels of said vehicle, and varies a speed ratio representing the ratio of the reduction of the engine output, said plurality of frictional engaging devices being frictionally engaged and disengaged to turn on and off the transmission of the reduced engine output, at least one of said plurality of frictional engaging devices being frictionally engaged and at least one of the remaining frictional engaging devices being disengaged to execute a shift to vary said speed ratio, said pressure control command generation means controlling hydraulic pressures supplied to the two frictional engaging devices to effect an engagement and a disengagement of the devices at the time of said shift, said pressure control command generation means further varying characteristics of hydraulic pressure control, said control apparatus comprising: 
 longitudinal acceleration detection means for detecting a longitudinal acceleration of said vehicle prior to said shift;    acceleration signal change state calculation means for calculating a changing value of said longitudinal acceleration prior to said shift; and    stepped signal calculation means for calculating a stepped signal for causing said pressure control command generation means to disengage the engaged frictional engaging device in accordance with the calculated changing value of said longitudinal acceleration.    
     
     
         7 . A control apparatus for an automatic transmission according to  claim 6 , wherein said stepped signal calculated by said stepped signal calculation means is a signal changed within 200 msec of a target value.  
     
     
         8 . A control apparatus for an automatic transmission according to  claim 6 , wherein said stepped signal calculated by said stepped signal calculation means is a signal for disengaging the engaged frictional engaging device near a beginning of an inertia phase in which the speed of said engine varies during said shift.  
     
     
         9 . A control apparatus for an automatic transmission comprising a plurality of frictional engaging devices and pressure control command generation means, said plurality of frictional engaging device being incorporated in an automatic transmission which reduces an output of an engine in a vehicle, transmits the reduced engine output to driving wheels of said vehicle, and varies a speed ratio representing the ratio of the reduction of the engine output, said plurality of frictional engaging devices being frictionally engaged and disengaged to turn on and off the transmission of the reduced engine output, at least one of said plurality of frictional engaging devices being frictionally engaged and at least one of the remaining frictional engaging devices being disengaged to execute a shift to vary said speed ratio, said pressure control command generation means controlling hydraulic pressures supplied to the two frictional engaging devices to effect an engagement and a disengagement of the devices at the time of said shift, said pressure control command generation means further varying characteristics of hydraulic pressure control, said control apparatus comprising: 
 rotating speed detection means for detecting at least one of an output shaft rotating speed and an input shaft rotating speed of said automatic transmission;    vehicle speed signal calculating means for calculating a speed of said vehicle based on the rotating speed detected by said rotating speed detection means; and    clutch engagement-disengagement timing calculation means for calculating timings of clutch engagement and disengagement of said frictional engaging devices on the basis of the calculated vehicle speed.    
     
     
         10 . A control apparatus for an automatic transmission according to  claim 9 , wherein said clutch engagement-disengagement timing calculation means varies the timings of said clutch engagement and disengagement in accordance with a type of said shift.  
     
     
         11 . A control method for an automatic transmission comprising a plurality of frictional engaging devices and pressure control command generation means, said plurality of frictional engaging device being incorporated in an automatic transmission which reduces an output of an engine in a vehicle, transmits the reduced engine output to driving wheels of said vehicle, and varies a speed ratio representing the ratio of the reduction of the engine output, said plurality of frictional engaging devices being frictionally engaged and disengaged to turn on and off the transmission of the reduced engine output, at least one of said plurality of frictional engaging devices being frictionally engaged and at least one of the remaining frictional engaging devices being disengaged to execute a shift to vary said speed ratio, said pressure control command generation means controlling hydraulic pressures supplied to the two frictional engaging devices to effect an engagement and a disengagement of the devices at the time of said shift, said pressure control command generation means further varying characteristics of hydraulic pressure control, said control method comprising the steps of: 
 recognizing during said shift a beginning of an inertia phase in which a speed of said engine varies; and    keeping constant the hydraulic pressures supplied to said frictional engaging devices at the recognized beginning of said inertia phase.    
     
     
         12 . A control method for an automatic transmission comprising a plurality of frictional engaging devices and pressure control command generation means, said plurality of frictional engaging device being incorporated in an automatic transmission which reduces an output of an engine in a vehicle, transmits the reduced engine output to driving wheels of said vehicle, and varies a speed ratio representing the ratio of the reduction of the engine output, said plurality of frictional engaging devices being frictionally engaged and disengaged to turn on and off the transmission of the reduced engine output, at least one of said plurality of frictional engaging devices being frictionally engaged and at least one of the remaining frictional engaging devices being disengaged to execute a shift to vary said speed ratio, said pressure control command generation means controlling hydraulic pressures supplied to the two frictional engaging devices to effect an engagement and a disengagement of the devices at the time of said shift, said pressure control command generation means further varying characteristics of hydraulic pressure control, said control method comprising the steps of: 
 detecting a longitudinal acceleration of said vehicle prior to said shift;    calculating a changing value of said longitudinal acceleration prior to said shift; and    calculating a stepped signal for disengaging the engaged frictional engaging device in accordance with the calculated changing value of said longitudinal acceleration.    
     
     
         13 . A control method for an automatic transmission comprising a plurality of frictional engaging devices and pressure control command generation means, said plurality of frictional engaging device being incorporated in an automatic transmission which reduces an output of an engine in a vehicle, transmits the reduced engine output to driving wheels of said vehicle, and varies a speed ratio representing the ratio of the reduction of the engine output, said plurality of frictional engaging devices being frictionally engaged and disengaged to turn on and off the transmission of the reduced engine output, at least one of said plurality of frictional engaging devices being frictionally engaged and at least one of the remaining frictional engaging devices being disengaged to execute a shift to vary said speed ratio, said pressure control command generation means controlling hydraulic pressures supplied to the two frictional engaging devices to effect an engagement and a disengagement of the devices at the time of said shift, said pressure control command generation means further varying characteristics of hydraulic pressure control, said control method comprising the steps of: 
 detecting at least one of an output shaft rotating speed and an input shaft rotating speed of said automatic transmission;    calculating a speed of said vehicle based on the detected rotating speed; and    calculating timings of clutch engagement and disengagement of said frictional engaging devices on the basis of the calculated vehicle speed.