Electric Vehicle CVT Control for Range Optimization
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Solution Overview
Problem
Electric vehicles often have inferior performance and range compared to gasoline-powered vehicles, with manufacturer-stated values not representing real-world conditions, necessitating technology to enhance their competitiveness.
Innovation Solution
Integration of a continuously variable transmission (CVT) system with a control system that manages power distribution, adjusts transmission speed ratios, and includes sensors and actuators to optimize drivetrain efficiency and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed-ratio transmission is used in electric vehicles, then the structure is simple and cost-effective, but the performance and range are inferior compared to gasoline-powered vehicles
Solution Approach 1:
The patent applies a continuously variable transmission (CVT) system that dynamically adjusts the transmission ratio based on driving conditions, allowing the electric motor to operate at optimal speeds across various vehicle speeds. This dynamic adjustment resolves the contradiction by enabling simple structure to achieve high performance through continuous optimization of power delivery.
Solution Approach 2:
The control system changes the transmission ratio parameter continuously to match motor operating conditions with driving demands. By varying the transmission ratio parameter in real-time, the system maintains high motor efficiency across different vehicle speeds and loads, thereby improving both performance and range without significantly increasing structural complexity.
2Speed
If the electric motor operates at high speed to increase maximum vehicle speed, then the top speed improves, but the motor efficiency decreases and battery current draw increases
Solution Approach 1:
The CVT system dynamically adjusts the transmission ratio to keep the electric motor operating within its optimal efficiency range regardless of vehicle speed. At high vehicle speeds, the transmission provides appropriate gear reduction, allowing the motor to run at lower, more efficient speeds while still achieving high vehicle speeds, thus resolving the contradiction between speed and energy consumption.
Solution Approach 2:
The transmission system acts as an intermediary between the electric motor and the wheels, decoupling the motor speed from vehicle speed. This intermediary mechanism allows the motor to operate at optimal speeds while the transmission handles the speed multiplication needed for high vehicle speeds, reducing direct correlation between vehicle speed and motor speed, and thereby reducing battery current draw.
3Use of energy by moving object
If the electric motor operates at low speed to minimize battery current draw, then energy efficiency improves, but the vehicle acceleration and hill climb ability deteriorate
Solution Approach 1:
The control system dynamically adjusts the transmission ratio based on driver demand and vehicle conditions. During acceleration or hill climbing, the transmission provides lower gear ratios that multiply torque, allowing the motor to operate at lower speeds while still delivering high power to the wheels. This resolves the contradiction by enabling low motor speeds to produce high vehicle power through mechanical advantage.
Solution Approach 2:
The transmission ratio parameter is changed in real-time based on power demand. During high-power situations like acceleration or hill climbing, the system selects lower transmission ratios to amplify torque output. This parameter adjustment allows the motor to maintain low operating speeds (low current draw) while the transmission delivers high power to the wheels, resolving the contradiction between energy efficiency and power output.
Data Source
AI summary
Disclosed here are inventive systems and methods for a powertrain of an electric vehicle (EV) having a continuously variable transmission (CVT) coupled to an electric drive motor, wherein a control system is configured to control the CVT and/or the drive motor to optimize various efficiencies associated with the EV and/or its subsystems. A control system is configured to operate the EV in an economy mode. Operating in said mode, the control system simultaneously manages the CVT and the drive motor to optimize the range of the EV. The control system can be configured to manage the current provided to the drive motor, as well as adjust a transmission speed ratio of the CVT. Other modes of operation are also possible. The control system can be configured to manage the power to the drive motor and adjust the transmission speed ratio of the CVT taking into account battery voltage, throttle position, and transmission speed ratio, for example.