Electric Vehicle Drive System Motor Switching Efficiency
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Solution Overview
Problem
Electric vehicle drive systems face inefficiencies due to the rapid decrease in motor speed and increase in electrical input power as load increases, leading to overheating and reduced range, especially when drivers shift gears incorrectly, mimicking habits from internal combustion engine vehicles.
Innovation Solution
A vehicle drive system utilizing multiple electric motors connected through bi-directional and unidirectional motor drive units, with an electronic control unit that adjusts voltage to maintain each motor within a high efficiency range, automatically switching between motors to optimize speed and efficiency, and incorporating an electrically operated clutch for regenerative braking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single electric motor is used to drive the vehicle, then the device complexity is reduced, but the motor efficiency drops rapidly as load increases and speed decreases
Solution Approach 1:
The drive system is segmented into multiple electric motors, each optimized for specific speed and load ranges. This segmentation allows the system to maintain high efficiency across a broader operating range by selecting the appropriate motor for each condition, resolving the contradiction between device simplicity and energy efficiency.
Solution Approach 2:
The system changes operating parameters by switching between different motors based on speed and load requirements. Each motor operates within its optimal efficiency range by adjusting which motor is active, thereby maintaining high efficiency without requiring a single complex motor design.
2Loss of energy
If manual transmission shifting is used to maintain motor efficiency, then energy efficiency can be improved, but driver error causes the motor to operate at low speed and high load reducing efficiency
Solution Approach 1:
The control system automatically selects and switches between motors based on real-time speed and load conditions, eliminating the need for manual intervention. This self-service approach ensures consistent efficient operation regardless of driver behavior, resolving the contradiction between energy efficiency and operational reliability.
Solution Approach 2:
The control system continuously monitors motor speed, load, and efficiency parameters, using this feedback to automatically switch between motors to maintain optimal efficiency. This closed-loop control ensures reliable efficient operation without depending on driver skill or attention.
3Ease of operation
If automatic hydraulic torque converter transmission is used to maintain motor efficiency, then ease of operation improves, but efficiency drops and the system becomes too inefficient for EVs
Solution Approach 1:
The patent replaces hydraulic torque converter transmissions with electrically controlled motor switching. This substitution maintains automatic operation for ease of use while eliminating the inherent inefficiencies of hydraulic systems, achieving both ease of operation and high transmission efficiency suitable for EVs.
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 efficiency and range of electric vehicles by optimizing motor speed and power distribution, reducing unnecessary drag, and enabling regenerative braking, thus improving overall performance and reducing the risk of overheating.
Implementation Method 1
A unidirectional device (e.g., roller clutch bearing) in each of the UMD units allows the next higher speed drive unit to drive the shaft faster than the other lower speed drive unit/s without unnecessary drag and loss of efficiency.
Implementation Method 2
There are currently many different types of highly efficient electric motors available for use in EVs.
Data Source
AI summary
An electric powered vehicle includes a first drive unit and a second drive unit. The first drive unit and the second drive unit are coupled to one of the drive wheels. At its maximum power within the system, the second drive unit drives the vehicle at a higher speed than the first drive unit. A clutch automatically disengages the first drive unit from the drive wheel while the second drive unit is operating. The clutch may include a uni-directional device. An electronic control unit automatically adjusts the voltage supplied to the second drive unit to maintain the efficiency of the second electric drive unit within a predetermined efficiency range.