Vehicle Drivetrain Torque Control for Near-Standstill Shift Engagement
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Solution Overview
Problem
Form-locking shift elements in vehicle transmissions struggle to engage near standstill without losing the force-fit connection, due to issues like tooth-on-tooth positions and flank clamping, which can cause irreversible damage and disrupt transmission efficiency.
Innovation Solution
Limiting the gradient of the transmission input torque during engagement processes prevents excessive torque buildup, allowing for the release of tooth-on-tooth positions and flank clamping without losing the force-fit connection, by adjusting torque, actuation force, and differential speed within specific thresholds to facilitate smooth engagement of form-locking shift elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the gradient of transmission input torque is not limited during engagement of form-locking shift element near standstill, then the engagement speed may be sufficient, but tooth-on-tooth positions and flank clamping occur causing irreversible damage and loss of force-fit connection
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the gradient of transmission input torque during the engagement process. A control unit monitors engagement conditions and modifies torque parameters in real-time to prevent excessive torque buildup that causes tooth-on-tooth positioning and flank clamping, while maintaining sufficient engagement speed for reliable form-locking shift element engagement near standstill.
2Reliability
If form-locking shift element is engaged close to synchronous speed, then engagement is reliable, but near standstill the differential speed is insufficient causing tooth-on-tooth positions and engagement failure
Solution Approach 1:
The patent implements dynamics by making the torque gradient adaptive during engagement. The control system continuously adjusts the torque application rate based on real-time differential speed conditions. Near standstill where differential speed is low, the system dynamically modifies torque parameters to prevent tooth-on-tooth positioning while still achieving reliable engagement, rather than using a fixed torque profile.
3Force
If excessive torque buildup occurs during engagement, then engagement force is sufficient, but irreversible damage occurs and flank clamping prevents proper engagement
Solution Approach 1:
The patent employs feedback control where a control unit monitors engagement conditions including differential speed and torque levels. Based on this feedback, the system adjusts the gradient of transmission input torque to maintain engagement force within optimal ranges - sufficient to overcome static friction and achieve positive engagement, but below thresholds that would cause flank clamping or irreversible damage to the form-locking shift element.
Data Source
AI summary
A method for operating a vehicle drive train (1) comprising a prime mover (2), transmission (3), and comprising a driven end (4) may include limiting, during a demand for engaging a form-locking shift element (A, F) of the transmission (3) when a rotational speed of the driven end (4) is close to zero, a rate of change of a transmission input torque present at the form-locking shift element (A, F) to a value. Below the value, forces present at the form-locking shift element (A, F) during an engagement process are less than a load limit. Above the value, irreversible damage to the form-locking shift element (A, F) occurs.