DIWA.5 Adaptation

In order to achieve optimal shifting quality, the principle of adaptive control is used in the DIWA.5. It allows the control unit to largely compensate for individual manufacturing tolerances and ageing conditions that reduce the shifting quality. In short: The transmission software is optimized to low wear and high shifting comfort.

With the DIWA.5, shifting operations are always performed by engaging or disengaging the clutches. For this purpose, the clutch disks are pressurized with a control pressure that is controlled by solenoid valves. The control pressure profile thus determines when a disk is disengaged, slips (with what resistance) or is engaged. The ideal control pressure profile has been preset individually for each gear change (1-2, 2-3, 3-4, 4-3 etc.). The most important shifting quality feature is the slip time of the clutch disks. During the slip time, the drive shaft is synchronized with the output shaft. Due to manufacturing tolerances and ageing conditions, the actual disk slip time may be different from the ideal slip time. This is where adaptation becomes active. A correction factor is calculated for the difference between the ideal and the actual disk slip time, which adapts the control pressure profile for the next shifting operation.

Adaptation is performed in two steps: Running in the vehicle (rough adaptation) and fine adjustment. Rough adaptation is done during the first five shifting operations (adaptation counter) where the control pressure profile is set with major correction values. This quickly compensates for greater deviations. Afterwards, fine adaptation is done. This includes only minor corrections. Because of this splitting into rough and fine adaptation, the adaptation data must be deleted after maintenance work has been done on the disks. Otherwise, the transmission control unit would attempt to correct major changes on the disks in small steps using the fine adaptation feature.

The control pressure profile consists of a short controlled filling stroke and a pressure ramp for the solenoid valve to be switched on. The pressure ramp begins with the starting pressure PA and climbs during the delay time to reach the control pressure PR. The control pressure PR remains constant throughout the slip time. Once the slip time has elapsed, the control pressure will be set to maximum. This engages the clutch completely.

If the pressure PR is increased to PR' by means of adaptation, the slip time is reduced from t_slip to t_slip'. If the pressure PR is increased to PR", the slip time is reduced from t_slip to t_slip''. The same principle is applied to the pressure PA and the delay time. The following generally applies to the relationship between times and control pressure:

Time ΔPA ΔPR

Delay time too short PA is reduced

Delay time too long PA + PR are increased

Slip time and delay time too short PR is reduced

Slip time too long PR is increased

The correction values PA and PR are divided into eight engine torque classes for each shifting operation. The engine torque class 0 is equivalent to zero load and the engine torque class 6 is equivalent to full load. The engine torque class 7 is used for kickdown shifts. Separate adaptation data is calculated for braking operations. The current adaptation data is displayed in the ALADIN Report .

The optimum shifting quality is a compromise between shifting comfort and transmission load.

If the disk slip times are long, shifting becomes smooth but the load on the disks (especially the thermal load) becomes very high. In addition, very long slip times may interrupt the powerflow between the drive shaft and the output shaft, which results in jerky driving.

If the disk slip times are too short, shifting will also become jerky but the load on the disks will be minimized. Very short slip times would result in a jerking load on the disks, bearings and shafts.

This is why slip time setpoints have been defined for every gear change, thus representing a compromise between shifting comfort and transmission load.

Both the correction factor ΔPR and the maximum slip time are monitored by the early-warning system during adaptation. If the maximum / minimum limits are exceeded, an entry will be made in the early-warning system.

More information on: Report

More information on: Delete adaptation data

More information on: FAQ

Up > Higher-level section