Automated Starting Gear Selection via Brake Pressure
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Solution Overview
Problem
In motor vehicles with automated or automatic transmissions, the existing methods for disconnecting the drive engine from the drive axle to prevent forward crawling require active brake actuation, leading to increased fuel consumption and can result in difficult starting situations, especially on inclines or when towing trailers, due to inappropriate pre-set starting gears.
Innovation Solution
A method that automatically determines and adjusts the starting gear based on brake pressure, overriding pre-set gears if necessary to ensure safe starting, particularly on inclines, by using a control unit connected to the service brake system to select an appropriate gear combination of group and powershift gears based on detected brake pressure levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If a pre-set starting gear is automatically selected after brake actuation, then the function for disconnecting the drive engine from the drive axle is activated, but the motor vehicle may be in a difficult operating situation when starting on an incline due to inappropriate gear selection
Solution Approach 1:
The starting gear selection is made dynamic by adjusting the pre-set gear based on detected driving resistance. The control unit automatically determines an adjusted starting gear that is lower than the pre-set gear when high driving resistance is detected, allowing the transmission to adapt to different operating conditions (level ground vs. incline) rather than using a fixed gear selection
Solution Approach 2:
The system changes the gear selection parameter based on detected brake pressure or driving resistance. By monitoring the brake pressure magnitude, the control unit determines whether to select the original pre-set starting gear or an adjusted lower gear, thereby adapting the transmission ratio parameter to match the actual driving conditions
2Use of energy by moving object
If the drive engine connection is disconnected to prevent forward crawling, then fuel consumption is reduced, but the drive engine may stall due to inappropriate starting gear when starting on an incline
Solution Approach 1:
The system dynamically adjusts the starting gear selection based on detected driving resistance. When high resistance is detected (indicating incline starting), the control unit selects a lower adjusted starting gear that provides sufficient torque to prevent engine stalling, while still maintaining the energy-saving disconnect function on level ground
Solution Approach 2:
The control unit uses feedback from brake pressure sensors or driving resistance detection to determine the appropriate starting gear. This closed-loop approach ensures the selected gear is appropriate for the actual operating conditions, preventing both unnecessary engine stalling and maintaining fuel efficiency
Data Source
AI summary
A method of operating a drive-train (1) of a motor vehicle, in particular an agricultural or municipal utility vehicle, having a drive engine (2), a motor vehicle transmission (4) and at least one drive axle (6). A connection between the drive engine (2) and the at least one drive axle (6) of the motor vehicle is separate automatically by way of a function, and a service brake (11) of the motor vehicle has to be actuated for activation of the function. To ensure an appropriate starting gear selection in various operating situations, during the course of the function triggered by a braking process, a brake pressure (pBrems), applied during the process, is determined and a starting gear is automatically determined as a function of the brake pressure (pBrems).