Patent ID: 8583334

Claim:
A method of determining an actuation touch point pressure value (p_ABDW) of a frictionally engagable shift element ( 14 ) of a transmission device ( 8 , 13 ) at which a transmission capability of the shift element ( 14 ) at least approaches zero and at which an increase in actuation pressure (p_IBD) elevates the transmission capability of the shift element ( 14 ), the method comprising the steps of: supplying the shift element ( 14 ) with a predefined target actuation pressure (p_SBDW_ 1 ) at which the transmission capability is zero; increasing target actuation pressure (pSBD) to a pressure level (p_eSBDW_ 1 ) by a specific offset pressure (p_DOW) at a testing time (T 6 ) to transfer the shift element ( 14 ) into a predefined operating state which instigates time monitoring; determining, by an electronic control unit, a characteristic of the actual actuation pressure (p_IBD) of the shift element ( 14 ); comparing a monitoring period (t 1 ) with a specific reference period (t 0 ) after an evaluation time (T_A 1 ) following the testing time (T 6 ) at which the predefined operating state of the shift element ( 14 ) is determined depending on the characteristic of the actual actuation pressure (p_IBD); setting the applied actuation touch pressure value (p_ABDW), when the monitoring period (t 1 ) is found to be less than or equal to the reference period (t 0 ), to be equivalent with the predefined target actuation pressure value (p_SBDW_ 1 ); increasing the predefined target actuation pressure value (p_SBDW_ 1 ) by a specific pressure value when the monitoring period (t 1 ) is greater than the reference period (t 0 ); and supplying the shift element ( 14 ) with the elevated target actuation pressure value (p_SBW_ 2 ), increasing a target actuation pressure (p_eSBDW_ 2 ) by the offset pressure (p_DOW) subsequently being applied in the region of the shift element ( 14 ) at another testing time (T 6 ), and when a current monitoring period (t 2 ) is found to be less than or equal to the reference period (t 0 ), setting the applied actuation pressure value (p_ABDW) to be equivalent to the elevated target actuation pressure value (p_SBDW_ 2 ) increased by the pressure value.