Group Transmission Synchronization via Clutch Preselection
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Solution Overview
Problem
Existing motor vehicle drive trains with group transmissions experience long synchronization times when transitioning from a non-friction-locking to a friction-locking state, affecting comfort and efficiency during gear shifts, especially when decelerating.
Innovation Solution
A method where the separating clutch is opened when vehicle speed falls below a threshold, allowing sub-transmissions to be changed to neutral or friction-locking conditions, and then partially closed to achieve a defined rotation speed, enabling quicker synchronization and transition to a friction-locking state for gear shifts, including driver-requested gear changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the separating clutch is opened when vehicle speed falls below a threshold, then the drive aggregate is decoupled from the transmission, but the input shaft of the group transmission slows down and synchronization time increases
Solution Approach 1:
The patent applies preliminary action by pre-selecting a target gear and pre-positioning the separating clutch before the actual gear change is needed. When the vehicle decelerates below a threshold speed, the control device already has a target gear determined and the separating clutch prepared to open, allowing the input shaft to slow down in advance rather than during the critical synchronization phase. This preparatory decoupling enables faster subsequent engagement without compromising synchronization time.
2Ease of operation
If the group transmission is changed to a friction-force-locking state for carrying out gearshift, then gear shifting can be performed, but the synchronization times become quite long and the changing process takes a very long time
Solution Approach 1:
The control device determines a target gear in advance based on current vehicle conditions (speed, acceleration, gear position) before the driver actually requests a gear change. This preliminary determination allows the system to prepare the friction-force-locking state and synchronization process ahead of time, so when the driver actuates the gear change, the transmission is already partially prepared, significantly reducing the perceived synchronization time.
Solution Approach 2:
The patent implements dynamic control of the separating clutch and friction-force-locking elements based on real-time vehicle conditions. The clutch engagement and transmission state changes are dynamically adjusted according to the current speed, acceleration, and target gear requirements, allowing optimal synchronization timing rather than fixed predetermined sequences. This dynamic approach enables faster adaptation to varying driving conditions.
3Reliability
If the separating clutch remains closed during deceleration, then the drive aggregate remains coupled to the transmission, but energy efficiency is reduced and unnecessary wear occurs
Solution Approach 1:
The patent replaces continuous mechanical coupling with selective electromagnetic control. Instead of keeping the separating clutch permanently engaged (mechanical connection), the control device uses electronic sensors to monitor vehicle speed and acceleration, then selectively actuates the clutch based on programmed criteria. This substitution of mechanical always-on coupling with electronic decision-making reduces unnecessary wear and improves energy efficiency by disengaging the drive aggregate only when conditions warrant it.
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 reduces the time required to change the group transmission from a non-friction-locking to a friction-locking condition, improving gear shift speed and preventing tooth-on-tooth positions during starting gear shifts, thus enhancing vehicle comfort and operational efficiency.
Implementation Method 1
the sub-transmission that is in neutral is synchronized by means of a transmission brake
Data Source
AI summary
A method for operating a drive train of a motor vehicle, where the drive train includes a drive aggregate, a group transmission connected between the drive aggregate and a drive output, and a separating cutch connected between the drive aggregate and the group transmission. If a speed is lower than a limit value, the separating clutch is opened and for transmission preselection one or all the other sub-transmission(s) is/are changed to a friction-force-locking condition. The separating clutch is then at least partially closed and the drive aggregate is brought to a defined rotation speed. When a friction-force-locking group transmission is required, it is checked whether a starting gearshift or a driver-desired shift for the group transmission is called for and the target rotation speed of the drive aggregate is checked. Depending on the results, the sub-transmission can be synchronized by a transmission brake or by the drive aggregate.