Selectable One-Way Clutch Engine Braking Control
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Solution Overview
Problem
Automatic transmissions do not enable engine braking without requiring a separate clutch, which limits the use of engine compression for deceleration and increases wear on conventional brake systems.
Innovation Solution
A method for controlling a selectable one-way clutch (SOWC) that allows engine braking by setting the relative speed across the clutch to zero using electronic throttle control or hydraulic engagement, enabling torque transfer from the transmission to the engine without a separate clutch, thereby facilitating smoother shifts and reducing impact loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional one-way clutch is used to interrupt reverse torque transfer, then torque transfer from transmission to engine is blocked, but engine braking capability is lost
Solution Approach 1:
The one-way clutch is modified to be selectable/reversible, allowing it to dynamically switch between one-way torque interruption and two-way torque transmission. The clutch can be actuated to engage both forward and reverse clutch members with the drum, enabling bidirectional torque transfer for engine braking when needed, while maintaining standard one-way operation during normal driving.
Solution Approach 2:
The clutch's torque transmission parameter is changed from unidirectional (one-way) to bidirectional (two-way) through actuation. By controlling the engagement state of both forward and reverse clutch members, the system transforms the clutch's fundamental operating characteristic to enable engine braking functionality.
2Adaptability or versatility
If a separate clutch is added to enable engine braking, then engine braking capability is improved, but device complexity increases
Solution Approach 1:
The existing one-way clutch structure is enhanced to perform multiple functions: standard one-way torque interruption during normal operation, and bidirectional torque transmission when actuated for engine braking. This eliminates the need for a separate clutch component, as the same clutch mechanism adapts to different operational requirements.
Solution Approach 2:
The functionality of a separate engine braking clutch is merged into the existing one-way clutch assembly. By integrating both forward and reverse clutch members within the same drum structure, the patent combines multiple clutch functions into a single unified component system.
3Reliability
If the SOWC is actuated with non-zero relative speed, then engagement is achieved, but impact load and shift quality deteriorate
Solution Approach 1:
The control system preliminarily adjusts engine throttle to bring the relative speed between the clutch members to approximately zero before actuation occurs. This preparatory speed synchronization ensures that when the clutch engages, there is minimal speed differential, thereby reducing impact loads and improving shift quality.
4Object-affected harmful factors
If engine throttle is used to synchronize relative speed, then impact load is reduced, but control complexity increases
Solution Approach 1:
The control system continuously monitors the relative speed across the SOWC using transmission input and output speed sensors, and adjusts engine throttle accordingly to maintain relative speed at approximately zero before actuation. This feedback control ensures smooth engagement while managing the complexity through automated speed synchronization.
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
Enables engine braking without a separate clutch, extending the lifespan of conventional brake systems by reducing wear and heat generation, and providing a smoother shifting experience.
Implementation Method 1
the SOWC is actuated or 'locked-up' such that it holds torque in both clockwise and counter-clockwise directions. As the SOWC is configured to hold torque in both directions, torque is transmittable from the transmission to the engine thereby producing engine braking.
Implementation Method 2
According to one aspect of the invention, electronic throttle control, or ETC, is implemented to set the relative speed across the SOWC to approximately zero.
Implementation Method 3
According to another aspect of the invention, the SOWC is hydraulically engaged.
Implementation Method 4
the relative speed across the SOWC is identifiable using a transmission input speed sensor and a transmission output speed sensor.
Data Source
AI summary
The present invention provides a method for controlling a selectable one-way clutch, or SOWC, such that engine braking is enabled. Additionally, the method of the present invention is adapted to provide engine braking using the SOWC such that a separate clutch is not required. The method is initiated by identifying a downshift command. After the downshift command has been identified, the off-going clutch associated with the current speed ratio is released. Engine speed is preferably increased to bring the relative speed across a selectable one-way clutch to approximately zero. Thereafter, the selectable one-way clutch is engaged such that is capable of holding torque in both directions. As the selectable one-way clutch can hold torque in both directions, torque is transmittable from the transmission to the engine and engine braking is thereby enabled.