Vehicle Slope Speed Control via Clutch-Adjusted Threshold
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Solution Overview
Problem
Existing vehicle speed control systems on slopes are limited by minimum engine rotational speed and gear ratio, leading to inadequate speed reduction on steep slopes or low traction conditions, which can compromise vehicle stability and control.
Innovation Solution
A speed control function that automatically adjusts the transmission to lower the minimum speed threshold when the clutch is partially open, allowing for more precise control of vehicle speed on slopes, independent of or varying with the slope gradient, using sensors and vehicle operation data to detect transmission openness and adjust accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the minimum speed threshold is set based on the lowest admissible rotational speed of the engine and the gear ratio engaged, then the engine can prevent stalling, but the vehicle speed cannot be reduced below this threshold which may be too high on steep slopes or low grip conditions
Solution Approach 1:
The patent applies the dynamics principle by making the minimum speed threshold variable rather than fixed. The threshold dynamically adjusts based on transmission openness state: when the clutch is partially open, the threshold is lowered below the preset value (which is based on engine minimum rotational speed and gear ratio). This allows the system to adapt the speed limit to current operating conditions, enabling lower speeds on steep slopes or low grip conditions while maintaining engine protection under normal conditions.
Solution Approach 2:
The patent applies parameter changes by modifying the minimum speed threshold parameter based on the transmission openness detection. When the clutch is partially open, the system changes the threshold parameter from the preset value (engine-based) to a lowered value that allows greater speed reduction. This parameter adjustment enables the vehicle to achieve lower descent speeds without causing engine stalling, as the transmission openness indicates a decoupled state where engine speed constraints are less critical.
2Speed
If the transmission is kept engaged to maintain engine braking, then speed control is limited by engine constraints, but if the transmission is opened to reduce speed further, the engine may stall
Solution Approach 1:
The patent applies the intermediary principle by using the clutch as a mediator between the engine and the speed control system. When the clutch is partially open, it creates an intermediate state that decouples the engine from the drivetrain constraints. This allows the speed control function to lower the minimum threshold and reduce vehicle speed further without directly affecting engine operation, as the clutch absorption accommodates the speed difference.
Solution Approach 2:
The system dynamically adjusts the minimum speed threshold based on the clutch openness state. When the clutch is partially open, the threshold is lowered to allow greater speed reduction. This dynamic adaptation enables the system to safely reduce speed below the engine-constrained threshold by detecting the transmission openness and adjusting the control parameter accordingly, preventing engine stalling while achieving lower descent speeds.
Data Source
AI summary
Function for controlling the speed, on a slope, of a motor vehicle comprising a transmission comprising a means of disengaging this transmission, which controls and automatically limits the speed of the vehicle progressing downhill when the driver releases the accelerator pedal, to a predetermined speed that is higher than a minimum speed threshold given by a predefined value dependent on the minimum speed at which the engine has to turn over in order to prevent this engine from stalling, and on the transmission ratio engaged, characterized in that when the transmission is at least partially disengaged, the minimum speed threshold is dropped below the predefined value.