Transmission Neutral Control Using Input Tie-Up Clutch States
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Solution Overview
Problem
Existing vehicle transmissions face challenges in ensuring zero torque transmission when the vehicle is in neutral mode, particularly due to parasitic drag torque from friction clutches and internal inertia, which can result in unintended torque transmission even when all controllable clutches are disengaged.
Innovation Solution
A transmission system utilizing a fluid coupling with a gearbox and clutches, where a vehicle controller manages the engagement and disengagement of clutches to hold the turbine shaft stationary and allow the output element to rotate, establishing specific clutch states to achieve an input tie-up condition that prevents torque transmission from the engine to the wheels in neutral mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all controllable clutches are disengaged in neutral mode, then the transmission should prevent torque transmission, but parasitic drag torque from friction clutches and internal inertia still cause unintended torque transmission
Solution Approach 1:
The patent applies preliminary anti-action by proactively engaging specific clutches (such as the neutral clutch or parking clutch) before torque transmission can occur in neutral mode. These clutches are engaged as a preventive measure to counteract the parasitic drag torque and internal inertia effects that would otherwise cause unintended torque transmission, ensuring the turbine shaft is held stationary and the output shaft is decoupled from the input shaft.
2Reliability
If multiple clutches are engaged to prevent torque transmission, then torque blocking is improved, but device complexity increases
Solution Approach 1:
The patent applies multi-functionality by designing clutches (such as the neutral clutch and parking clutch) that serve multiple purposes: they can engage in neutral mode to prevent torque transmission, they can engage in park mode to lock the output shaft, and they can be used to hold the turbine shaft stationary. This reduces the need for dedicated components for each function and simplifies the overall control logic despite the complex clutch engagement patterns.
3Use of energy by moving object
If the turbine shaft is held stationary in neutral mode, then fuel consumption is reduced, but transition speed between modes may be affected
Solution Approach 1:
The patent applies dynamics by implementing a threshold-based control strategy for transitioning between neutral and drive modes. The system monitors the absolute value of the turbine shaft speed, and only when this speed exceeds a predetermined threshold does the system engage the drive mode clutches. This dynamic approach allows the turbine shaft to remain stationary (saving fuel) during normal neutral operation, while automatically enabling smooth transitions when vehicle operation requires it, thus balancing fuel efficiency with transition performance.
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 torque transmission from the engine to the wheels in neutral mode, ensuring smoother and faster transitions between gear modes, while minimizing the risk of unintended torque and reducing fuel consumption by maintaining the turbine shaft stationary, thus addressing the issue of parasitic drag and internal inertia.
Implementation Method 1
a fluid coupling having an impeller and a turbine
Implementation Method 2
Friction between the friction plates and separator plates prevents relative rotation, thereby coupling the two components to each other
Implementation Method 3
An actively controlled one-way clutch includes selectable states such as permitting relative rotation in both directions or preventing relative rotation in both directions
Data Source
AI summary
Ideally, when a transmission is in Neutral, no torque should be exerted on the vehicle wheels by the powertrain. However, even with all clutches in a gearbox disengaged, some torque may be transmitted from a turbine shaft to the transmission output due to clutch drag and transmission component inertia. To avoid transmitting torque, a subset of clutches may be engaged to produce an input tie-up state, this holding the turbine shaft against rotation while permitting rotation of the output element.