Vehicle Transmission Control for Reverse Rollback Mitigation
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Solution Overview
Problem
Vehicle engines often stall or experience rollback when shifting from reverse to forward gear, particularly at elevated reverse speeds, due to uncompensated reverse engine torque and delayed transmission engagement, which can be objectionable to drivers and lead to further stalling issues.
Innovation Solution
Applying vehicle brakes and maintaining the current gear when shifting from reverse to forward at elevated speeds, delaying the transmission shift until the vehicle speed drops below a threshold, and allowing the engine to stall if necessary, to prevent rollback and reduce the likelihood of engine stalls.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the transmission is shifted to forward gear while the vehicle is traveling in reverse at elevated speed, then the vehicle can immediately move in the requested direction, but the engine may stall due to uncompensated reverse engine torque
Solution Approach 1:
The system applies brake torque to the wheels before the transmission gear shift is completed, preliminary reducing the reverse vehicle speed to below a threshold speed. This preliminary braking action prevents the engine from stalling during the gear transition by ensuring the vehicle speed is appropriate before the forward gear engages.
Solution Approach 2:
The system applies brake torque in opposition to the reverse vehicle motion before and during the gear shift transition. This preliminary anti-action (braking) counteracts the reverse engine torque that would otherwise cause the engine to stall when shifting to forward gear at elevated speeds.
2Reliability
If the transmission gear engagement is delayed until vehicle speed falls to a threshold speed, then engine stalls are reduced, but vehicle rollback occurs and forward motion is delayed
Solution Approach 1:
The system preliminarily applies brake torque to reduce reverse vehicle speed before the forward gear engagement is finalized. By performing this speed reduction action in advance, the system eliminates the need for prolonged delay in gear engagement, thus preventing both engine stalls and excessive rollback.
Solution Approach 2:
The system changes the parameter of vehicle speed from above threshold to below threshold through brake torque application, enabling the transmission to shift to forward gear without causing engine stall. This parameter change (speed reduction) allows immediate forward motion without the harmful effects of stalled engines or prolonged rollback.
3Reliability
If the transmission is held fully disengaged or with controlled slip during direction change, then engine stalls are reduced, but vehicle rollback increases and driver satisfaction decreases
Solution Approach 1:
The system applies brake torque preliminarily to reduce reverse vehicle speed before the transmission shifts to forward gear. This preliminary braking prevents the need for full disengagement or controlled slip of the transmission, thereby preventing both engine stalls and excessive rollback, resulting in smoother transitions and higher driver satisfaction.
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 effectively mitigates rollback and reduces the delay in forward transmission engagement, improving driver satisfaction by ensuring smoother transitions and preventing unintended engine stalls during direction changes.
Implementation Method 1
A brake system may be applied to the vehicle wheels to reduce the reverse vehicle speed before the transmission is shifted from the reverse gear to the forward gear
Data Source
AI summary
Methods and systems are provided for mitigating reverse vehicle rollback. In one example, in response to a request to shift a transmission from reverse to forward when vehicle speed is elevated, vehicle brakes are applied and the actual transmission shift is delayed until the vehicle motion in the reverse direction is sufficiently decelerated. Additionally, the engine may be stalled and restarted before the transmission shift is performed.