Hybrid Gear-Shift Control for Low-Friction Regenerative Braking
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Solution Overview
Problem
Conventional hybrid vehicles face challenges in managing regenerative braking torque during deceleration in rear-wheel drive vehicles, leading to wheel slip and oversteering, which compromises fuel efficiency and vehicle stability.
Innovation Solution
A vehicle gear-shifting control apparatus that adjusts the downshift point based on road surface friction, delaying gear-shifting until the vehicle recovers from slip conditions and optimizing regenerative braking torque application to rear wheels, thereby enhancing both regeneration amount and vehicle robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the motor performs regeneration operation during deceleration, then fuel efficiency is improved, but rear wheels are apt to slip and oversteering occurs
Solution Approach 1:
The control apparatus dynamically adjusts the downshift point parameter based on vehicle deceleration state and road conditions. When deceleration exceeds a threshold, the downshift point is lowered to delay gear-shifting, which modulates the regenerative braking torque application to prevent rear wheel slip while maintaining fuel efficiency benefits
Solution Approach 2:
The system continuously monitors vehicle deceleration rate and compares it against threshold values. Based on this feedback, the controller automatically adjusts the downshift point and gear-shifting timing to optimize the balance between regeneration amount and vehicle stability, preventing oversteering conditions
2Use of energy by moving object
If the downshift point is set high to increase regeneration amount, then fuel efficiency improves, but gear-shifting may occur during slip state causing oversteering
Solution Approach 1:
The downshift point is not fixed but dynamically adjusted based on real-time deceleration conditions. During moderate deceleration, a higher downshift point enables increased regeneration. When deceleration exceeds thresholds indicating slip risk, the downshift point is automatically lowered to delay gear-shifting, thus preventing oversteering while optimizing regeneration across varying conditions
Solution Approach 2:
The control system proactively adjusts the downshift point before gear-shifting occurs during slip-prone deceleration. By anticipating the deceleration state and pre-adjusting the downshift point threshold, the system prevents the harmful effect of oversteering before it can occur, rather than reacting after the problem arises
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 apparatus achieves improved fuel efficiency and stability by securing a larger regeneration amount while preventing oversteering, particularly on low-friction surfaces, by dynamically adjusting gear-shifting and regenerative braking strategies.
Implementation Method 1
a motor which generates another travel drive force of the vehicle and which supplies a battery with regenerative energy during deceleration of the vehicle
Implementation Method 2
a hydraulically controlled automatic transmission which has an input shaft connected to the engine and the motor and an output shaft connected to rear wheels of the vehicle and which subjects an input rotation to gear-shifting
Data Source
AI summary
A vehicle gear-shifting control apparatus is equipped with an engine, a motor, an automatic transmission, a friction brake system, and a controller which executes a regeneration control of imparting a regenerative braking torque to rear wheels by causing the motor to perform a regeneration operation and a gear-shifting control of changing a shift stage of the automatic transmission by outputting a gear-shifting signal in accordance with the rotation speed of an input shaft. The controller starts the gear-shifting control, triggered by the rotation speed decreasing to a predetermined downshift point during a downshift of the shift stage, and during deceleration of the vehicle when a coefficient of friction of a road surface is lower than a predetermined threshold in the regeneration control, the controller sets the downshift point lower than when the coefficient of friction is equal to or higher than the threshold.