Variable-Pole EV Drive Motor for Gear-Shift Driving Feel
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Solution Overview
Problem
Electric vehicles without transmissions often cause discomfort to drivers accustomed to engine vehicles due to differences in driving feel, as existing solutions like rotary electric machine controllers do not effectively mimic the gear shifting experience.
Innovation Solution
A vehicle drive system that changes the motor's characteristics by adjusting the number of poles in the stator based on driving operations and travel states, using a motor with a cylindrical stator and rotor, and a control section to manage current flow through primary conductors, thereby altering motor rotation speed and torque to simulate the feel of gear shifting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the motor rotation speed is controlled proportionally to vehicle speed, then favorable acceleration performance is achieved, but the user experiences a go-cart feeling and discomfort
Solution Approach 1:
The patent applies dynamics by making the motor characteristic (number of poles) changeable during operation. The control section dynamically switches between a first motor characteristic (more poles) and a second motor characteristic (fewer poles) based on vehicle speed and acceleration requests, mimicking the gear shifting behavior of traditional vehicles and eliminating the go-cart feeling while maintaining good acceleration performance.
2Device complexity
If the rotary electric machine controller changes the number of poles only when motor rotation speed exceeds a predetermined value, then control is simplified, but the motor characteristic is not changed during gear shifting situations
Solution Approach 1:
The patent makes the motor characteristic dynamically adjustable based on multiple parameters including vehicle speed, acceleration requests, and gear shifting situations. The control section switches between different motor characteristics (number of poles) not only when motor rotation speed exceeds a threshold but also during gear shifting situations, enhancing adaptability while maintaining reasonable controller complexity.
Solution Approach 2:
The patent changes the motor parameter (number of poles) based on multiple conditions including vehicle speed, acceleration requests, and gear shifting situations. This multi-parameter-based approach allows the motor to adapt its characteristics to different driving scenarios, resolving the contradiction between simplified control and enhanced adaptability.
3Force
If the number of poles of the stator is increased, then motor torque is increased, but motor rotation speed is reduced
Solution Approach 1:
The patent resolves this contradiction by making the number of poles dynamically adjustable. The control section switches between a first motor characteristic (more poles for high torque) and a second motor characteristic (fewer poles for high speed) based on vehicle speed and acceleration requests, allowing the motor to provide high torque at low speeds and high speed at higher velocities, eliminating the need for a transmission.
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 system induces a driving feel similar to that of a transmission-equipped vehicle, providing stepwise motor rotation speed changes and unique gear shift sensations, enhancing driver comfort and preference by adjusting torque and braking force according to driver input and travel conditions.
Implementation Method 1
the motor is configured to change a number of poles of the stator when the control section changes a direction of a current flowing through each of the plural primary conductors and increases/reduces a number of primary conductor groups
Data Source
AI summary
The vehicle drive system includes: a motor having a cylindrical stator and a cylindrical rotor provided in the stator and driving a drive wheel of a vehicle by rotation of the rotor; and a motor ECU controlling the motor. The stator has plural primary conductors, and the rotor has plural secondary conductors in a radially outer portion. The motor is configured to change a number of poles of the stator when the motor ECU increases/reduces a number of primary conductor groups through which the current flows in the same direction and are continuously aligned in a circumferential direction. An ECU and the motor ECU are configured to change the number of the poles of the stator on the basis of at least one of a driving operation by a driver and a travel state of an own vehicle.