Neutral State Movement Protection for Automatic Transmission
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Solution Overview
Problem
Automatic transmissions often fail to prevent inadvertent vehicle movement when in neutral or park, due to issues like clutch drag, park-by-wire mechanism failures, or broken gears, as the controller struggles to differentiate between intentional and unintentional movement.
Innovation Solution
A system utilizing a controller that responds to signals from a grade sensor and speed sensor to actuate a vehicle holding mechanism, which includes inducing a transmission tie-up condition, applying an electronic parking brake, or engaging a parking pawl with a parking gear to stop the vehicle, and features an indicator light for warning the driver.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the controller uses logic to determine vehicle motion status, then the vehicle can be controlled properly during operation, but the logic fails to function when the transmission is in neutral or park, allowing inadvertent movement
Solution Approach 1:
The controller dynamically adjusts its monitoring and response behavior based on transmission state. In neutral or park, the controller activates additional monitoring of vehicle speed and grade conditions, and implements automatic intervention (activating holding mechanisms) when unsafe conditions are detected, rather than relying solely on driver input or standard operational logic.
Solution Approach 2:
The system introduces an intermediary safety intervention mechanism that acts between the driver's neutral/park selection and the actual vehicle state. When the controller detects excessive speed on a grade while in neutral/park, it automatically activates the vehicle holding mechanism (parking brake, transmission tie-up) to prevent inadvertent movement, serving as a mediator that overrides the normal operational state for safety.
2Reliability
If the controller activates vehicle holding mechanisms to stop the vehicle, then inadvertent movement is prevented, but the system complexity increases with multiple stopping mechanisms
Solution Approach 1:
The vehicle holding mechanism serves multiple functions: it acts as a primary parking brake, a safety intervention device for preventing inadvertent movement on grades, and a transmission protection mechanism. The same hardware infrastructure (parking brake actuator, transmission holding mechanisms) is used for both normal parking operations and emergency safety interventions, eliminating the need for separate dedicated safety stopping systems.
Solution Approach 2:
The safety intervention system merges with the existing vehicle holding mechanism infrastructure. Rather than adding a completely separate stopping system, the controller integrates safety monitoring and activation logic with the existing parking brake and transmission holding mechanisms, combining safety functions with conventional vehicle systems.
Data Source
AI summary
A controller is provided to, in response to a speed of the vehicle exceeding an allowable speed based on a measured grade while the vehicle is running and in neutral or park, actuating a vehicle holding mechanism to stop the vehicle.