Selectable One-Way Clutch Slip Control
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Solution Overview
Problem
Conventional transmissions face challenges in efficiently managing power transmission across a wide range of vehicle speeds, particularly in transitioning between forward and reverse movements, due to the passive nature of one-way clutches which can cause uncomfortable sensations and potential component failures when suddenly transitioning from a passive to an active state without adequate slip control.
Innovation Solution
A transmission system incorporating a selectable one-way clutch and a controller that actively manages the transition from a passive to an active state by ensuring slip is less than a threshold, using friction clutches to establish proportional slip conditions, and engaging additional clutches to achieve desired gear states, thereby controlling the transition smoothly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the one-way clutch transitions from passive to active state without slip control, then the transmission can establish different power flow paths, but uncomfortable sensations and potential component failures occur
Solution Approach 1:
The friction clutch is engaged before the one-way clutch transitions from passive to active state. This preliminary action reduces the relative speed (slip) between the one-way clutch components, ensuring a smooth transition without sudden shocks or vibrations that would cause uncomfortable sensations or component failures.
Solution Approach 2:
The friction clutch acts as an intermediary device between the power source and the one-way clutch. It provides a controlled, gradual engagement that mediates the transition process, allowing the one-way clutch to switch states smoothly by first reducing slip through frictional engagement rather than abrupt locking.
2Productivity
If the one-way clutch is suddenly engaged without slip control, then gear transition is achieved quickly, but parasitic drag increases and component wear occurs
Solution Approach 1:
The friction clutch is engaged in advance to reduce slip before the one-way clutch fully engages. This preliminary reduction of relative motion minimizes the parasitic drag that would otherwise occur during sudden engagement, while still achieving relatively quick gear transition through the coordinated action of both clutches.
Solution Approach 2:
The system dynamically coordinates the engagement of the friction clutch and the one-way clutch transition. By controlling the timing and degree of friction clutch engagement, the system optimizes the balance between transition speed and parasitic drag, allowing adaptive control based on operating conditions.
3Ease of operation
If multiple friction clutches are engaged to control slip, then smooth transition is achieved, but device complexity increases
Solution Approach 1:
The friction clutch serves multiple functions: it controls slip during one-way clutch transition, acts as a friction converter to reduce relative speed, and provides a controlled engagement mechanism. This multi-functionality allows smooth gear transitions without requiring additional dedicated components for each function, thereby limiting the increase in device complexity.
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 ensures smooth transitions between gear states, reducing parasitic drag and preventing component failures by actively managing the one-way clutch's state change based on slip conditions, enhancing the overall efficiency and comfort of vehicle operation.
Implementation Method 1
A first friction clutch is provided. The first friction clutch is configured such that slip across the selectable one-way clutch is proportional to a speed of an output element whenever the first friction clutch is fully engaged.
Implementation Method 2
Transmissions may also use one-way clutches that passively prevent relative rotation between two components in one direction while permitting relative rotation in the opposite direction.
Data Source
AI summary
A transmission includes a selectable one-way clutch with an active state and a passive state. To avoid occupant discomfort and hardware damage, transitions from the passive state to the active state must only be commanded when no or very little slip is present across the selectable one-way clutch. Several methods are presented to eliminate slip, depending on vehicle speed. When the vehicle is stationary, full engagement of a clutch that causes slip to be proportional to vehicle speed eliminates slip. When the vehicle is moving backwards, partial engagement of the above clutch eliminates slip. When the vehicle is moving forwards, full engagement of all but one clutch of a tie-up condition and partial engagement of the remaining clutch of the tie-up condition brings the vehicle to a stop and eliminates slip.