Shift Element Travel Detection for Tooth-On-Tooth Gear Engagement
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Solution Overview
Problem
Form-locking shift elements in transmissions face challenges with accurate determination of actuating-travel range, leading to inefficient gear shifts due to tooth-on-tooth positions and flank clamping, which affect ride comfort and shift times.
Innovation Solution
A method to determine the actuating-travel range between shift-element halves, identifying when a tooth-on-tooth position occurs and adjusting engagement forces to release such positions, ensuring accurate engagement and disengagement of form-locking shift elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If form-locking shift elements are used to reduce drag torques and improve transmission efficiency, then transmission efficiency is improved, but accurate determination of actuating-travel range becomes difficult leading to shifted or faulty gear changes
Solution Approach 1:
A sensor is introduced as an intermediary component to monitor the actuating movement of the shift-element half. The sensor provides indirect measurement of the actuating-travel range by detecting the position and movement of the shift-element half during engagement and disengagement processes, enabling accurate determination without direct measurement of the travel range itself.
Solution Approach 2:
The sensor signals are fed back to the control device, which uses this feedback information to determine the actuating-travel range and detect tooth-on-tooth positions. The control device adjusts the actuating process based on this feedback, ensuring accurate engagement and disengagement while preventing faulty gear changes.
2Device complexity
If simple software-based evaluation of actuating current is used for friction-locking shift elements, then control complexity is reduced, but form-locking shift elements cannot be properly controlled leading to prolonged engagement times
Solution Approach 1:
The patent replaces simple software-based current evaluation with a sensor-based detection system that directly monitors the mechanical movement of the shift-element half. This substitution enables precise detection of engagement status and tooth-on-tooth positions, allowing for timely intervention and faster gear shifting despite increased system complexity.
Solution Approach 2:
The sensor continuously monitors the actuating movement before complete engagement occurs, allowing the control device to detect potential tooth-on-tooth positions in advance and take preliminary corrective actions. This preliminary detection and intervention prevents prolonged engagement times and ensures smooth gear transitions.
3Reliability
If engagement force is increased to ensure positive engagement of form-locking shift elements, then engagement reliability is improved, but tooth-on-tooth positions occur more frequently causing flank clamping and shifted gear changes
Solution Approach 1:
The control device dynamically adjusts the actuating process based on real-time sensor feedback. Instead of applying constant high engagement force, the system monitors the actuating-travel range and detects tooth-on-tooth positions dynamically, then adjusts the actuating force accordingly to prevent flank clamping and shifted gear changes while maintaining engagement reliability.
Solution Approach 2:
The sensor-based detection system provides preliminary warning of approaching tooth-on-tooth positions before they occur. The control device can then apply preliminary counter-actions by reducing or reversing the actuating force to prevent the harmful tooth-on-tooth engagement, thereby avoiding flank clamping and ensuring reliable gear changes.
Data Source
AI summary
A method for determining an actuating-travel range between two shift-element halves of a form-locking shift element (A, F) during an engagement of the shift element (A, F) and in the presence of a tooth-on-tooth position between the two shift-element halves is provided. An actuating movement of the at least one movable shift-element half with respect to the other shift-element half is monitored by a sensor. A tooth-on-tooth position is detected when it is determined, by the sensor, within an actuating-travel range of the at least one movable shift-element half between a disengaged condition and an engaged condition of the shift element, that the actuating movement of the movable shift-element half in the engagement direction is zero. A ratio between an engagement force applied at the shift element and a radial force acting on the shift-element halves is within a value range, which facilitates a tooth-on-tooth position and an actuating movement of the shift-element half in the engagement direction is detected by the sensor after the reduction of the engagement force and/or after an increase of the applied torque.