Predictive Transmission Gear Selection for Downhill Engine Braking
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Solution Overview
Problem
Current transmission control systems for motor vehicles, particularly commercial vehicles, do not effectively manage braking during overrun operations on downhill slopes, leading to inefficient fuel consumption and uncomfortable braking dynamics.
Innovation Solution
A method that predicts the downhill force and gear-dependent maximum braking force for each gear stage, allowing for the selection of a suitable target gear to enable wear-free braking in overrun mode, thereby avoiding the use of the service brake and maintaining vehicle speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current transmission control systems are used for downhill slopes, then vehicle speed can be maintained, but service brake intervention is required leading to wear and reduced comfort
Solution Approach 1:
The system performs preliminary calculations before the overrun situation occurs to determine suitable target gears. By pre-calculating the downhill force profile and evaluating which gears can provide sufficient braking force, the system prepares the optimal gear selection in advance, enabling wear-free braking without service brake intervention
Solution Approach 2:
The system dynamically evaluates multiple gear options based on real-time conditions. It calculates the downhill force for the predicted coasting operation and determines gear-dependent maximum braking forces, selecting from multiple possible target gears the one that provides sufficient braking force while optimizing fuel efficiency and comfort
2Speed
If service brake is used for downhill braking, then vehicle speed can be controlled, but fuel consumption increases and comfort decreases
Solution Approach 1:
The system uses the engine's own braking capability through appropriate gear selection to control vehicle speed during overrun operations. By selecting a target gear that provides sufficient engine braking force, the vehicle self-regulates its speed without requiring service brake intervention, thereby reducing fuel consumption and improving comfort
3Adaptability or versatility
If multiple gear options are evaluated for overrun operation, then optimal target gear can be selected, but calculation complexity increases
Solution Approach 1:
The system segments the gear evaluation process into distinct calculation steps: first calculating the downhill force profile, then determining maximum braking forces for each gear, and finally evaluating which gears provide sufficient braking force. This structured segmentation makes the complex calculation process more manageable and systematic
Data Source
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AI summary
The invention relates to a method for influencing the transmission shifting strategy of a motor vehicle, for example, a commercial vehicle. The invention particularly relates to such a method in which, for a predictive driving strategy, a shift reaction, in particular a target gear, is determined on an upcoming road segment based on topographical data of that segment. The method comprises the following steps: predicting engine braking on an upcoming road segment based on topographical data, in particular gradient and slope information, of the upcoming road segment (S1); determining a target speed for the predicted engine braking (S2); and predictively determining the profile of a downward force acting on the motor vehicle during engine braking (S3).for each gear selectable during coasting, predictive determination of a maximum total braking force that can be generated by the motor vehicle during coasting, assuming that the motor vehicle will move at the specified target speed during coasting, without taking into account any braking force achievable by a service brake (S4); determination of a preselection of possible gears for coasting, whereby a gear whose maximum total braking force that can be generated during coasting is greater than a maximum of the specified slope force curve is added to the preselection (S5); and selection of a gear from the preselection of possible gears as the target gear for coasting (S6).