Selectable One-Way Clutch Transition Control
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Solution Overview
Problem
Existing vehicle transmissions face challenges in efficiently transitioning a selectable one-way clutch from an active to a passive state, particularly when torque is being transmitted against the direction allowed in the passive state, which can cause uncomfortable vehicle sensations and potential component failures.
Innovation Solution
A transmission system with a controller that commands the selectable one-way clutch to transition from an active to a passive state by partially engaging and then releasing specific friction clutches, and verifying the transition by detecting slip across the clutch, ensuring the clutch changes state only when torque is reversed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the selectable one-way clutch transitions from active to passive state while torque is transmitted against the allowed direction, then the clutch state change is achieved, but uncomfortable vehicle sensations and potential component failures occur
Solution Approach 1:
The controller partially engages a first friction clutch before commanding the selectable one-way clutch to transition from active to passive state. This preliminary action prepares the transmission system by establishing a controlled torque path, ensuring the one-way clutch can transition safely without transmitting torque in the wrong direction, thereby preventing vehicle sensations and component failures
2Ease of operation
If the controller uses multiple friction clutches with sequential engagement and release, then smooth clutch transition is achieved, but the control process complexity increases
Solution Approach 1:
The clutch transition process is segmented into distinct phases: partial engagement of first friction clutch, command to transition one-way clutch, release of first friction clutch upon lash crossing detection, and engagement of second friction clutch upon slip detection. This segmentation allows each step to be controlled and verified independently, ensuring smooth transitions while managing complexity through structured control logic
Solution Approach 2:
The controller uses feedback from sensors detecting lash crossing and slip conditions to control the engagement and release of friction clutches. This feedback mechanism ensures the transition process proceeds only when appropriate conditions are met, achieving smooth transitions while the control logic manages complexity through condition-based decision making
3Measurement precision
If the controller verifies clutch transition by detecting slip across the clutch, then transition verification accuracy is improved, but the transition time increases
Solution Approach 1:
The controller partially engages friction clutches rather than fully engaging them during the verification process. This partial engagement provides sufficient torque control to detect slip and verify the one-way clutch state change accurately, while avoiding the full torque application that would extend the transition time unnecessarily
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 ensures smooth and reliable transitions of the selectable one-way clutch, preventing component failures and enhancing the driving experience by ensuring the clutch only changes states under controlled conditions.
Implementation Method 1
one-way clutches that passively prevent relative rotation between two components in one direction while permitting relative rotation in the opposite direction
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
When the fluid pressure is reduced, a return spring forces the piston away from the clutch pack removing the normal force such that relative rotation is possible with minimal drag
Data Source
AI summary
A transmission includes a selectable one-way clutch with active and passive states. Successful transition from the active state to the passive state is only possible when there is no torque tending to cause overrunning. After commanding a transition from the active state to the passive state, a controller partially engages a first friction clutch to induce a torque tending away from overrunning until a lash crossing is detected. Then, the controller releases the first clutch and partially applies a second clutch to induce a torque toward overrunning. When slip is detected, indicating successful achievement of the passive state, the second clutch is released.