4WD Drive Torque Split for Stable Regen-to-Friction Braking
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Solution Overview
Problem
Existing drive systems for electric-motor propelled four-wheel drive vehicles face instability during deceleration due to sudden changes in the allocation ratio of brake torque between the front-wheel and rear-wheel sides, particularly when regenerative braking transitions to friction braking, especially on low-friction surfaces.
Innovation Solution
A drive system with differential mechanisms that allocate at least 50% of the output torque to the front-wheel side, combining regenerative and friction braking to stabilize vehicle behavior by maintaining a consistent torque distribution ratio, using a control device to manage the transition from regenerative to friction braking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If regenerative braking force is used during deceleration, then energy recovery is improved, but the allocation ratio of braking force between front and rear wheels changes suddenly causing vehicle instability
Solution Approach 1:
The differential mechanisms are configured with a fixed front-wheel torque allocation ratio of 50% or more, creating a dynamic balance that adapts to varying braking conditions. This dynamic configuration ensures that as regenerative braking force varies, the front-wheel braking force maintains a stable proportion of total braking force, preventing sudden changes in braking force distribution and vehicle instability while allowing full utilization of regenerative energy recovery
Solution Approach 2:
The patent specifies a parameter threshold (front-wheel torque allocation ratio of 50% or more) that fundamentally changes the braking force distribution characteristics. By setting this parameter in the differential mechanism configuration, the system ensures that front-wheel braking force remains sufficiently high even when regenerative braking varies, maintaining vehicle stability while maximizing energy recovery from the motors
2Force
If friction braking force is increased during deceleration, then stopping performance is improved, but the allocation ratio of braking force changes suddenly causing understeer or spinout
Solution Approach 1:
The differential mechanisms are configured with a fixed front-wheel torque allocation ratio of 50% or more, creating a dynamic balance that adapts to varying braking conditions. This dynamic configuration ensures that as friction braking force varies, the front-wheel braking force maintains a stable proportion of total braking force, preventing sudden changes in braking force distribution and vehicle instability while allowing full utilization of regenerative energy recovery
Solution Approach 2:
By pre-configuring the differential mechanisms to allocate 50% or more of braking torque to the front wheels, the system proactively counteracts the potential harmful effect of sudden braking force distribution changes. This preliminary configuration prevents understeer and spinout by ensuring front-wheel braking force remains sufficiently high before any instability can occur
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 system stabilizes vehicle behavior by reducing the likelihood of understeer or spinout by maintaining a consistent torque allocation ratio, enhancing control flexibility and stability during deceleration.
Implementation Method 1
control regenerative braking force acting as a result of causing the first motor and the second motor to operate in a regeneration mode
Implementation Method 2
friction braking force generated by the friction brake system
Data Source
AI summary
A drive system for a four-wheel drive vehicle including a friction brake system includes a first motor and a second motor, a propeller shaft for transmitting power between a front-wheel side and a rear-wheel side, a first differential mechanism configured to divide output torque of the first motor between a left wheel on one side of the front-wheel side and the rear-wheel side and the other side, a second differential mechanism configured to divide output torque of the second motor between a right wheel on the one side and the other side, and a control device for controlling regenerative braking force related to the first motor and the second motor and friction braking force related to the friction brake system. The first and second differential mechanisms are configured such that the ratio of output torque allocated to the front-wheel side is 50% or more.