Dual Motor EV Power System with Differential Reduction Gears
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Solution Overview
Problem
Electric vehicles face challenges in maintaining stable battery charging and achieving efficient power performance due to the high cost and energy loss associated with using large-capacity motors and traditional transmission systems, which are inefficient at low speed/low load conditions and complicate the vehicle's structure.
Innovation Solution
A power system for electric vehicles that uses two small-capacity motors with different reduction gears connected on the same shaft, controlled by a motor controller to determine optimal driving points based on demand torque and vehicle conditions, allowing for efficient torque combination and reduced power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a large-capacity motor is used to satisfy maximum power performance, then the vehicle can achieve high output equivalent to engine output, but the motor operates inefficiently in low speed/low load conditions and manufacturing cost increases
Solution Approach 1:
The patent divides the single large-capacity motor function into two small-capacity motors with different reduction gears. The first motor is optimized for low speed/low load conditions while the second motor handles high speed/high load conditions, allowing each motor to operate in its efficient range and eliminating the efficiency problems of using a single large motor across all operating conditions.
2Adaptability or versatility
If a transmission system is implemented to compensate for motor performance limitations, then the vehicle can respond to both high torque demand and high rotation demand, but the structure becomes complicated and power loss occurs in the transmission process
Solution Approach 1:
The patent makes each motor capable of handling multiple operating conditions by equipping them with different reduction gears. The first motor with its reduction gear can handle both low speed/high torque and high speed/low torque conditions, while the second motor with its different reduction gear covers complementary operating ranges, eliminating the need for a separate transmission system.
3Power
If a transmission system is implemented to satisfy various driving demands, then the vehicle can achieve required power performance, but power loss occurs in the transmission process and manufacturing cost increases
Solution Approach 1:
The patent extracts and eliminates the transmission system from the vehicle powertrain by directly connecting the two small-capacity motors with different reduction gears to the driving wheels. This direct connection eliminates the intermediate transmission components that cause power loss, while still achieving the required power performance through coordinated operation of the two motors.
4Ease of manufacture
If two small-capacity motors with different reduction gears are used instead of a single large motor, then manufacturing cost is reduced and power efficiency is improved, but the system complexity increases
Solution Approach 1:
The patent merges the control functions of two motors into a single motor controller that manages both motors based on driving conditions. The controller determines when to use the first motor, second motor, or both motors together, simplifying the control architecture while enabling efficient operation across all driving conditions and reducing overall system complexity.
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 reduces manufacturing costs, improves power efficiency, and enhances stability and reliability by using low-cost small-capacity motors, eliminating the need for transmission and minimizing power loss across various driving conditions.
Implementation Method 1
a first motor and a second motor configured as a power source
Implementation Method 2
a first reduction gear connected to the first motor and a second reduction gear connected to the second motor
Data Source
AI summary
Disclosed are a power system for an electric vehicle and a control method of a power system for an electric vehicle. The power system may include a first motor and a second motor configured as a power source, first and second reduction gears connected to the first and second motors and having different deceleration ratios, a driving shaft transmitting outputs of the first and second reduction gears, and a motor controller configured to determine a first driving point where the first motor responds according to a demand torque of a driver and a driving condition of the vehicle and a second driving point where the second motor responds according to the demand torque of the driver and the driving condition of the vehicle, and control driving by using at least one of an output torque of the first motor and/or an output torque of the second motor according to the determined driving point.