Method and system for determining fill time for friction elements of automatic transmission

A system for determining a fill time of friction elements of an automatic transmission comprising:

• a shift lever detector for detecting a position of a shift lever, which is operated by a driver, and outputting a corresponding shift lever change signal;
• a timing device for measuring time intervals between a change in position of the shift lever, and outputting a corresponding time signal;
• and
• an electronic control unit for calculating a friction element fill time when the shift lever change signal is input in which the friction element fill time is calculated based on a piston stroke ratio of a piston that drives a friction element,
• wherein the electronic control unit compensates the piston stroke ratio by detecting an N-range hold time and by using the detected N-range hold time and a pre-installed map when an N to D/R shift signal indicating shifting into one of the D- and R-ranges from the N-range is detected, compensates the piston stroke ratio by detecting a D/R-range hold time and using the detected D/R-range hold time and the pre-installed map when a D/R to N shift signal indicating shifting into the N-range from one of the D- and R-ranges is detected, the D/R-range hold time being a time during which the shift range is held at said one of the D- and R-ranges, and calculates a fill time using the compensated piston stroke ratio.

A system for determining a fill time for friction elements in an automatic transmission, the friction elements being actuated by hydraulic pistons, the pistons having at any given time a present stroke and a stroke ratio, the system comprising:

• a shift lever detector adapted to monitor a driver operated transmission shift lever and generate a shift lever change signal in response to movement of the shift lever between gears;
• a timer adapted to generate a time signal;
• and
• a control unit including a processor communicating with said shift lever detector and timer to receive said generated signals, wherein the processor is programmed to
• (a) initialize the timer and present stroke;
• (b) detect a N to D/R shift or a D/R to N shift based on signals generated by the shift level detector, and, in response to a detected N to D/R shift execute a first set of instructions, or in response to a detected D/R to N shift execute a second set of instructions, wherein
• the first set of instructions comprises detecting a N-range hold time and initializing the timer, calculating a change in the N to D/R stroke ratio, compensating for the change in said N to D/R stroke ratio, and calculating a fill time based on the compensated N to D/R stroke ratio;
• and
• the second set of instructions comprises detecting a D/R range hold time and initializing the timer, calculating a change in the D/R to N stroke ratio, compensating for the change in said D/R to N stroke ratio, and calculating a fill time based on the compensated D/R to N stroke ratio.