Transmission Neutral State Shift for Torque Management
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Solution Overview
Problem
Automatic transmissions face challenges in efficiently managing multiple neutral states, particularly when engine torque requests exceed threshold values, leading to unwanted vehicle movement due to high inertia-coupling values in certain neutral states.
Innovation Solution
A vehicle powertrain system with a transmission that includes planetary gear sets and shift actuators, controlled by a vehicle controller to shift from a high inertia-coupling neutral state to a lower inertia-coupling state by disengaging specific clutches when an engine-torque request exceeds a threshold, preventing unwanted vehicle movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the transmission operates in a neutral state with high inertia-coupling values, then the transmission structure remains simple, but unwanted vehicle movement occurs when engine torque exceeds threshold values
Solution Approach 1:
The system changes the operational parameters of the transmission by switching between different neutral states (first neutral state with higher inertia-coupling and second neutral state with lower inertia-coupling). The vehicle controller monitors engine torque requests and transitions between neutral states based on torque threshold values, thereby adjusting the inertia-coupling parameter to prevent unwanted vehicle movement while maintaining operational simplicity
Solution Approach 2:
The transmission control system dynamically adapts its configuration by switching between different clutch engagement patterns. Instead of a static neutral state, the system provides multiple dynamic neutral states with different inertia-coupling characteristics, allowing the transmission to optimize its behavior based on real-time engine torque conditions without requiring complex additional hardware
2Ease of operation
If multiple clutches are engaged to create a first neutral state, then the transmission achieves neutral positioning, but high inertia-coupling causes noticeable vehicle movement under torque load
Solution Approach 1:
The neutral state is segmented into multiple distinct configurations (first neutral state and second neutral state), each with different clutch engagement patterns and inertia-coupling characteristics. This segmentation allows the system to select the appropriate neutral state based on operating conditions, preventing harmful vehicle movement while maintaining ease of neutral positioning
Solution Approach 2:
The vehicle controller implements feedback by monitoring engine torque requests and comparing them against threshold values. When the torque request exceeds the threshold while in the first neutral state, the controller triggers a transition to the second neutral state, creating a closed-loop control system that eliminates unwanted vehicle movement through real-time monitoring and adaptive response
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
The solution effectively prevents noticeable vehicle movement by shifting to a neutral state with lower inertia-coupling values, ensuring smooth operation and reducing torque at the output shaft, thus enhancing transmission efficiency and driver control.
Implementation Method 1
A torque converter includes an impeller driven by the engine and a turbine driving the gearbox input while permitting the engine to rotate at an acceptable speed. Torque is transferred from the impeller to the turbine hydrodynamically.
Data Source
AI summary
A vehicle powertrain includes an engine and a transmission coupled to the engine. The transmission has a first neutral state in which a first combination of clutches are engaged and a second neutral state in which a second combination of clutches are engaged. A vehicle controller is programmed to, in response to the transmission being in the first neutral state and an engine-torque request exceeding a threshold value, shift the transmission to the second neutral state.