Transmission L1-L2 Shift During Engine Braking
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Solution Overview
Problem
Existing transmission systems are unable to seamlessly shift between 1st gear low (L1) and 2nd gear low (L2) while engine braking, as the selectable one-way clutch is typically applied only at low speeds and cannot overrun or freewheel, limiting engine braking functionality.
Innovation Solution
A transmission system incorporating a selectable one-way clutch (SOWC) and a controller that momentarily releases the SOWC during engine braking to allow shifting from L1 to L2 mode, by releasing the first clutch when slip exceeds a calibrated threshold and reapplying it when slip across the SOWC exceeds another threshold, enabling engine braking in both modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the selectable one-way clutch is applied continuously at low speeds, then the transmission can maintain engine braking in L1 mode, but the transmission cannot shift to L2 mode during engine braking
Solution Approach 1:
The controller periodically releases and reapplies the selectable one-way clutch during the shift maneuver. The clutch is released momentarily to allow the shift from L1 to L2 mode, then reapplied to restore engine braking capability. This periodic action enables both shift maneuverability and continuous engine braking functionality.
Solution Approach 2:
The controller releases the selectable one-way clutch before the actual shift occurs to prepare the transmission for the gear change. This preliminary release of the clutch allows the transmission to transition smoothly from L1 to L2 mode without being constrained by the engaged clutch, enabling the shift maneuver while maintaining the ability to resume engine braking afterward.
2Ease of operation
If the selectable one-way clutch is released to allow shifting, then the transmission can shift from L1 to L2 mode, but engine braking is lost during the transition
Solution Approach 1:
The controller minimizes the duration of clutch release to only the essential moment needed for the shift maneuver. The clutch is released briefly to enable the shift, then immediately reapplied to restore engine braking. This continuous action approach maintains engine braking force throughout the transition by ensuring the clutch is engaged for the majority of the time, with only a brief interruption during the actual gear change.
Solution Approach 2:
The selectable one-way clutch undergoes periodic engagement and disengagement during the shift process. It is released momentarily to permit the shift maneuver, then reapplied to restore engine braking capability. This periodic action sequence ensures that engine braking is temporarily suspended only long enough to complete the shift, then immediately restored to maintain continuous useful action.
3Ease of operation
If a traditional friction clutch is used instead of a selectable one-way clutch, then shifting during engine braking is possible, but fuel economy and cost benefits are lost
Solution Approach 1:
The patent replaces the traditional friction clutch mechanism with a selectable one-way clutch system. This mechanical substitution allows the transmission to achieve shift maneuverability through controlled release and reapplication of the one-way clutch, eliminating the need for a friction clutch while maintaining the ability to shift during engine braking. The one-way clutch provides the desired functionality with improved fuel economy and cost benefits.
Solution Approach 2:
The controller changes the operational parameters of the selectable one-way clutch by dynamically adjusting its engagement state. By controlling the release and reapplication timing of the clutch, the system achieves shift maneuverability that would traditionally require a friction clutch, while maintaining the fuel economy and cost advantages of the one-way clutch design.
4Use of energy by moving object
If the selectable one-way clutch is engaged during engine braking, then fuel economy benefits are maintained, but the transmission is locked in L1 mode and cannot shift
Solution Approach 1:
The system dynamically adjusts the engagement state of the selectable one-way clutch based on the shift maneuver requirements. During normal engine braking, the clutch remains engaged to maintain fuel economy benefits. During a shift maneuver, the controller temporarily releases the clutch to allow the transmission to shift from L1 to L2 mode, then reapplies it to restore engine braking. This dynamic control provides gear selection flexibility while maintaining fuel economy benefits.
Solution Approach 2:
The selectable one-way clutch undergoes periodic engagement and disengagement controlled by the controller. It is released momentarily during the shift maneuver to enable gear changes, then reapplied to restore engine braking and fuel economy benefits. This periodic action sequence provides the necessary gear selection flexibility while maintaining fuel efficiency during normal operation.
Data Source
AI summary
A transmission includes a stationary member, an input member, and gear sets each having a plurality of nodes. The transmission includes a first clutch that connects a node of one gear set to the stationary member to establish an L1 mode, and a second clutch that connects a node of another gear set to the stationary member to establish a 2L mode. A SOWC is connected between nodes of two gear sets, and a controller, in response to a requested shift L1-L2 shift while engine braking, executes a method to release the first clutch and thereby enters a neutral mode. The SOWC is released when slip across the first clutch exceeds a first threshold, then the first clutch reapplied when a SOWC slip level exceeds another threshold to thereby enter a 1st gear freewheeling mode. The second clutch is reapplied to enter the L2 mode and resume engine braking.