In-Wheel Motor Rotor Decoupling for Brake-Compliant Loss Reduction
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Solution Overview
Problem
Electric vehicles face challenges in providing full brake torque on all wheels through regenerative braking alone, necessitating additional braking systems like friction brakes, which can lead to electric motor losses and legal braking compliance issues when the rotor is decoupled from the wheel.
Innovation Solution
An in-wheel electric motor design that allows the rotor to be decoupled from the wheel while maintaining stationary alignment with the stator, using engagement means like selector sleeves or clutches, enabling synchronized coupling and decoupling under electrical control, thus reducing motor losses and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the rotor is decoupled from the wheel to reduce electric motor losses, then energy efficiency is improved, but the vehicle may fail to meet legal braking requirements
Solution Approach 1:
The system dynamically couples and decouples the rotor from the wheel based on operating conditions. During normal operation, the rotor is decoupled to reduce motor losses. During braking operations, the rotor is coupled to the wheel to ensure legal braking requirements are met. This dynamic adjustment resolves the contradiction by allowing the system to optimize for energy efficiency when possible while ensuring safety compliance when necessary.
Solution Approach 2:
A friction brake system acts as an intermediary between the rotor and the wheel. The friction brake can apply braking force directly to the wheel even when the rotor is decoupled from the wheel, thereby maintaining legal braking requirements without requiring the rotor to remain coupled during non-braking operations. This intermediary mechanism allows the system to achieve both energy efficiency and braking compliance.
2Object-generated harmful factors
If the rotor is decoupled from the wheel to reduce noise and vibration, then comfort is improved, but the braking system reliability may be compromised
Solution Approach 1:
The system dynamically adjusts the coupling state between rotor and wheel based on whether braking is required. During non-braking operations, the rotor is decoupled to minimize noise and vibration. During braking operations, the rotor is coupled to ensure reliable braking performance. This dynamic control resolves the contradiction by allowing noise reduction when possible while ensuring braking reliability when necessary.
Solution Approach 2:
The friction brake serves as an intermediary that can provide reliable braking force to the wheel independently of the rotor's coupling state. This allows the rotor to remain decoupled during normal operation, reducing noise and vibration, while still ensuring that legal braking requirements are met through the friction brake mechanism.
3Loss of energy
If engagement means are added to enable rotor decoupling, then energy efficiency is improved, but device complexity increases
Solution Approach 1:
The engagement means are extracted as a separate, modular component system that can be independently controlled. The clutch or brake mechanism is designed as a distinct subsystem with its own control logic, separate from the main motor control system. This modular extraction reduces the overall system complexity by allowing independent optimization and control of the engagement/disengagement function while still achieving the energy efficiency benefits of rotor decoupling.
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
Reduces electric motor losses and noise, ensures compliance with legal braking requirements by allowing rotor-stator synchronization during decoupling, and provides a fail-safe mechanism for motor failure scenarios.
Implementation Method 1
a clutch, selectively coupling and decoupling the rotor from the wheel
Implementation Method 2
a friction brake attached to a rotor of an in-wheel electric motor
Data Source
AI summary
An in-wheel electric motor for a vehicle comprising a stator, a first rotor arranged to be housed within a wheel of the vehicle, and coupling means for selectively coupling the first rotor to the wheel of the vehicle and decoupling the first rotor to the wheel, such that when the first rotor is coupled to the wheel, the first rotor is arranged to rotate with the wheel, and when the first rotor is decoupled from the wheel, the first rotor is arranged to be stationary with respect to the stator when the wheel rotates relative to the stator.