Automated Transmission Control for Downhill Gradient Shift Timing
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Solution Overview
Problem
Current automated transmission control methods result in insufficient utilization of vehicle momentum on downhill gradients, leading to early termination of overrun mode and increased fuel consumption, along with high noise emissions due to prolonged high motor speed.
Innovation Solution
Implement a method for automated multi-step transmission control that detects the end of a downhill gradient and shifts to a higher gear before entering a level area or transitioning to traction mode, reducing drag torque and braking forces, thereby delaying the transition to traction mode and reducing fuel consumption and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the transmission shifts to a higher gear earlier (before entering level area or transitioning to traction mode), then fuel consumption is reduced and noise emissions are lowered, but the vehicle may experience insufficient braking effect on downhill gradients
Solution Approach 1:
The transmission control system performs preliminary detection of the downhill gradient end and executes the gear shift before the vehicle actually enters the level area or transitions to traction mode. This advance action allows the vehicle to maintain momentum through the transition zone while minimizing fuel consumption, as the higher gear reduces drag torque and braking forces during the critical transition period.
Solution Approach 2:
The system continuously monitors vehicle speed, gradient, and transmission state to determine the optimal shift timing. By using feedback from sensors detecting the end of the downhill gradient, the control unit can precisely timing the upshift to occur at the most efficient moment, balancing fuel economy with adequate braking effect throughout the transition.
2Reliability
If the transmission remains in lower gear longer to maintain braking effect, then vehicle control on downhill gradients is improved, but fuel consumption increases and noise emissions rise due to prolonged high motor speed
Solution Approach 1:
The system detects the end of the downhill gradient in advance and executes the gear shift before the vehicle needs maximum braking effect. This preliminary action allows the lower gear to maintain control during the critical downhill section, then transitions to higher gear once the gradient ends, minimizing the time spent in high-speed, high-consumption operation.
Solution Approach 2:
The transmission control system dynamically adjusts gear selection based on real-time detection of gradient changes. The system transitions from a static gear selection approach to a dynamic one where the optimal gear is selected based on the current driving condition, allowing the vehicle to exploit momentum on downhill gradients while minimizing fuel consumption on level sections.
3Object-generated harmful factors
If the transmission shifts to higher gear earlier, then noise emissions are reduced due to lower motor speed, but the vehicle momentum utilization is increased which may affect braking capacity
Solution Approach 1:
The system performs the gear shift in advance, before the vehicle enters the level area or transitions to traction mode. This timing allows the vehicle to utilize momentum through the transition zone with reduced noise emissions, while the shift occurs at a point where braking capacity requirements are naturally lower.
Solution Approach 2:
The system changes the gear ratio parameter at the optimal moment detected by the gradient end detection. By changing this critical parameter (gear ratio) at the precise moment when the gradient ends, the system achieves a balance between noise reduction (through higher gear) and maintaining adequate braking capacity (by shifting before complete transition to level ground).
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 approach leads to significant fuel savings and reduced noise emissions by optimizing gear shifts during downhill driving, allowing the vehicle to maintain momentum and delay the transition to traction mode, especially in routes with frequent changes between hilly and flat sections.
Implementation Method 1
The increased speed of the drive motor increases the drag torque and thus the braking effect of the drive motor
Implementation Method 2
both its braking effect and its braking capacity, which is limited by the cooling, increase with the increased speed of the drive motor
Data Source
Figure 1
AI summary
The invention relates to a method for controlling an automatic multi-step shift transmission which is arranged, within a drivetrain of a motor vehicle, for example of a utility vehicle, in the power flow between a drive engine, which is embodied as an internal combustion engine, and an axle drive of a drive axle or a differential gear, wherein the present roadway inclination (aFB) is determined. To improve the shift behaviour of the multi-step shift transmission at the transition between a downward-sloping roadway (2) and a level roadway (4), it is provided that, at the latest after driving onto the downward-sloping roadway (2) and/or after the transition into the overrun mode, a detection function to determine a downward-slope run-out (3) is started, and that, in the event of a downward-slope run-out (3) being detected, a shift is made into a higher gear in the overrun mode, that is to say an overrun upshift is carried out, even before driving onto the level roadway (4) and/or before the transition into traction operation.