Asymmetric Motor Power Allocation for Four-Wheel Drive Efficiency
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Solution Overview
Problem
Existing four-wheel drive vehicles face limitations in maintaining high efficiency across a wide output range due to the inherent limitations of motor configurations, where either motors are coupled to a common shaft with different builds for high efficiency in different ranges or are identical, leading to restricted operational efficiency.
Innovation Solution
A driving power control apparatus with first and second motors having different rated outputs, capable of independent operation, along with dedicated power transmission mechanisms and drive circuits, dynamically allocates power between them based on vehicular speed and torque requirements to maximize total efficiency across a wide output range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If motors are coupled to a common output shaft with different builds for high efficiency in different output ranges, then total efficiency is improved, but device complexity increases
Solution Approach 1:
The patent divides the drive system into two independent drive trains: one connecting the first motor to the left drive wheel, and another connecting the second motor to the right drive wheel. This segmentation eliminates the need for a common output shaft and differential mechanism, allowing each motor to operate independently in its optimal efficiency range while reducing overall transmission system complexity.
Solution Approach 2:
The patent applies different motor builds (first motor with different characteristics than second motor) to different wheel drives, allowing each motor to be optimized for specific output ranges. The control unit dynamically allocates power between the two motors based on real-time efficiency maps, ensuring each motor operates in its high-efficiency zone while accommodating varying total power requirements.
2Device complexity
If identical motors are used for both drive wheel units, then device complexity is reduced, but adaptability to different output ranges is limited
Solution Approach 1:
The patent employs asymmetric motor configuration where the first motor and second motor have different builds and efficiency characteristics. This asymmetry allows the system to cover a broader range of output requirements by selecting from two different motor efficiency maps, enhancing adaptability while maintaining manageable complexity through independent control.
Solution Approach 2:
The control unit dynamically determines power allocation between the two motors based on real-time operating conditions, referencing pre-stored efficiency maps for each motor. This dynamic control strategy allows the system to adapt to varying power requirements and maintain high efficiency across different output ranges, transforming the static motor configuration into a dynamically optimized system.
3Loss of energy
If only one motor is driven to maximize efficiency, then energy loss is reduced, but power output capability is limited
Solution Approach 1:
The patent merges the power output capabilities of two different motors by operating them simultaneously when high total power is required. The control unit can allocate power to both motors based on their respective efficiency maps, combining their outputs to meet high power demands while maintaining overall system efficiency, thus resolving the trade-off between single-motor efficiency and multi-motor power capability.
4Loss of energy
If different builds of motors are used for high efficiency in different ranges, then total efficiency is improved, but ease of manufacture decreases
Solution Approach 1:
The patent achieves universality through the control unit, which manages two different motor types with different efficiency characteristics. While the motors themselves are different builds, the control system provides a unified interface for power allocation, torque distribution, and efficiency optimization. This multi-functionality allows the system to handle various power requirements using two standardized motor platforms, improving manufacturability compared to custom single-motor solutions.
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 solution enhances the total efficiency of the motors, allowing for improved mileage and stability in four-wheel drive vehicles by optimizing power allocation between motors with different characteristics, thereby overcoming the limitations of existing configurations.
Implementation Method 1
At least one of the first and second power transmission mechanisms includes a speed reducer that transmits the motive power generated by an associated motor of the motors to an associated drive wheel unit of the drive wheel units such that the speed reducer reduces a rotational speed of the motive power
Data Source
AI summary
Front left and right wheel units are driven by an engine and a motor generator. Rear left and right wheel units are independently driven by in-wheel motor type motor generators. The motor generator and the motor generator are configured to have different rated outputs, respectively, and be subjected to different speed reduction ratios, respectively, between the motor generators and their respectively associated drive wheel units, and thus have characteristics, respectively, in efficiency with respect to torque and vehicular speed, that exhibit high efficiency in mutually different output ranges, respectively. When a mileage oriented mode is selected as a traveling mode, an ECU determines how a drive torque should be allocated between the motor generators, as based on the motors' required drive torque and vehicular speed and on each motor generator's characteristic in efficiency, to maximize the motor generators' total efficiency.