Two-Stage Gearbox Control for Hill Descent Stability
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Solution Overview
Problem
Existing methods for controlling two-stage reduction gears in motor vehicles do not adequately minimize the loading on starting elements and can result in unintentional vehicle rolling, especially on inclines, particularly when a trailer is attached and brake pressure is insufficient.
Innovation Solution
A method that involves manual switching by the driver, with the vehicle's control unit determining necessary brake pressure based on incline and vehicle speed, and using different minimum brake pressure characteristics for with and without a trailer, to prevent rolling during gear shifts, and maintaining brake pressure for a predetermined period to ensure stable switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If gear shifting is performed without sufficient brake pressure monitoring, then switching speed is improved, but vehicle stability deteriorates due to unintentional rolling
Solution Approach 1:
The control unit determines the minimum brake pressure characteristic before allowing gear switching to occur. By pre-establishing the required brake pressure threshold based on incline and vehicle speed, the system ensures stability conditions are met before the switching process begins, preventing unintentional rolling while maintaining efficient switching.
Solution Approach 2:
The system continuously monitors actual brake pressure and compares it against the determined minimum brake pressure characteristic. This feedback mechanism ensures that gear switching only proceeds when sufficient brake pressure is applied, dynamically adjusting the switching decision based on real-time brake pressure conditions to maintain vehicle stability.
2Stability of the object's composition
If brake pressure requirement is increased for all conditions, then vehicle stability is improved, but ease of operation deteriorates
Solution Approach 1:
The minimum brake pressure characteristic is not applied uniformly but is specifically determined based on local conditions such as incline angle and vehicle speed. The control unit adjusts the brake pressure requirement locally for each switching scenario, applying higher requirements only when necessary (steep inclines, high speeds) and lower requirements when conditions permit, thus maintaining stability without unnecessarily complicating operation.
Solution Approach 2:
The system dynamically changes the minimum brake pressure parameter based on varying operating conditions. By adjusting the brake pressure threshold according to incline and vehicle speed parameters, the system adapts the stability requirement to match actual conditions, ensuring adequate stability protection while allowing ease of operation under favorable conditions.
3Stability of the object's composition
If gear switching is prohibited on steep inclines, then vehicle stability is improved, but productivity deteriorates
Solution Approach 1:
Instead of imposing a blanket prohibition on gear switching during hill descent, the system dynamically determines the minimum brake pressure characteristic based on the specific incline angle and vehicle speed. This allows gear switching to proceed when brake pressure can be sufficiently maintained, improving productivity while still ensuring stability when conditions require it.
Solution Approach 2:
The control unit pre-determines the minimum brake pressure requirement before allowing gear switching during hill descent. By establishing the brake pressure threshold in advance based on incline and speed conditions, the system enables productive gear changes when feasible while maintaining stability safeguards, rather than imposing unnecessary restrictions.
Data Source
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AI summary
The invention relates to a method (1, 21) for controlling a two-stage reduction gearbox of a motor vehicle in an open-loop and/or closed-loop manner, wherein two gears can be selected, namely a high gear and a low gear, wherein a shifting element is operated by the driver in order to shift from the high gear to the low gear or to shift from the low gear to the high gear, wherein a slope of the driving surface is determined and wherein a vehicle speed is determined. The loading of drive-off elements is minimised and, in particular, unintentional rolling of the motor vehicle is avoided in that a manual shift occurs during a standstill of the motor vehicle if the shifting element is operated and the brake pressure is greater than a minimum brake pressure characteristic curve (6, 7, 8, 9, 10, 11), wherein the minimum brake pressure characteristic curve (6, 7, 8, 9, 10, 11) depends on the slope of the driving surface, and/or in that a manual shift occurs while the motor vehicle is being driven if the shifting element is operated and if the speed of the motor vehicle is greater than a slope-dependent minimum speed.