Automatic Transmission Shift Element Torque Management
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Solution Overview
Problem
In automatic transmissions, engaging a form-locking shift element is hindered by residual torque at the form-locking shift element after the synchronizing shift element is disengaged, preventing the claws from being fully pushed home due to the involvement of additional frictional shift elements.
Innovation Solution
A method where a frictional shift element not directly needed for synchronization is actuated to synchronize the form-locking shift element, allowing it to operate with slip by being closed and opened to a defined extent, reducing torque by bringing it to its transmission limit plus a pressure offset, and then reducing pressure to enable full engagement of the form-locking shift element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a synchronizing shift element is actuated to synchronize the form-locking shift element, then the synchronization is achieved, but residual torque remains at the form-locking shift element preventing full engagement
Solution Approach 1:
The patent extracts the harmful residual torque from the system by disengaging the synchronizing shift element before actuating the form-locking shift element. This separation prevents the torque interference that would otherwise block full engagement of the form-locking element, while still achieving synchronization through the sequential control of shift elements.
2Reliability
If a frictional shift element is involved in gear engagement, then the gear realization is achieved, but torque interference prevents claws from being pushed fully home
Solution Approach 1:
The patent applies preliminary action by first bringing the frictional shift element to its transmission limit plus a pressure offset to establish synchronization, then subsequently reducing the pressure to enable full engagement. This two-stage approach ensures that synchronization is achieved before the form-locking element is fully actuated, preventing torque interference during the engagement process.
3Reliability
If pressure is maintained at transmission limit for synchronization, then synchronization is achieved, but torque prevents full engagement of form-locking shift element
Solution Approach 1:
The patent employs dynamics by making the pressure at the frictional shift element variable rather than constant. The pressure is first increased to the transmission limit plus offset to achieve synchronization, then dynamically reduced to a lower level that allows the form-locking shift element to engage fully without torque interference. This dynamic pressure adjustment resolves the contradiction between maintaining synchronization and enabling full engagement.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method effectively reduces torque at the form-locking shift element, allowing the claws to be fully engaged, with the frictional shift element being fully closed when full interlock is recognized or after a specified time if no sensor system is present.
Implementation Method 1
at least one further, frictional shift element is involved in obtaining the gear to be engaged
Implementation Method 2
the torque present at the form locking shift element to be engaged once the synchronizing shift element has been disengaged, is reduced
Data Source
AI summary
A method of engaging a form-interlocking shifting element to obtain a gear in an automatic transmission in which at least one further, frictional shifting element is involved in obtaining the gear to be engaged and a shifting element, not involved in obtaining the gear to be engaged but which serves as a synchronizing shifting element, is actuated in order to synchronize the interlocking shifting element to be engaged. The further, frictional shifting element, involved in engaging the gear, is engaged and then disengaged, to a defined extent, to bring the frictional shifting element to a slipping condition, in order to ensure the engagement of the interlocking shifting element.