External Rotor EPS Motor with Waterproof Sealing
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Solution Overview
Problem
Conventional RD-type EPS systems face challenges with motor control precision due to internal-rotating motors, leading to control point deviations and potential water damage, affecting vehicle safety and maneuvering control, especially in automatic driving modes.
Innovation Solution
An electric power steering apparatus utilizing an external rotating motor with a planetary roller nut and a waterproof design, featuring a hollow tubular casing, steering shaft, and a motor with a hollow stator and external rotor, along with waterproof rings to prevent water ingress and ensure motor protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If an internal-rotating motor is used in RD-type EPS, then the motor structure is compact, but control precision deteriorates due to high rotation speed and low torque characteristics
Solution Approach 1:
The patent inverts the conventional motor configuration by using an external-rotating motor instead of an internal-rotating motor. This inversion allows the motor shaft to directly connect to the planetary roller nut without intermediate transmission components, thereby improving control precision while maintaining a compact overall structure through the integrated motor-chassis design.
Solution Approach 2:
The motor is nested within the chassis structure, with the motor shaft directly connected to the planetary roller nut. This nesting arrangement eliminates intermediate transmission components and reduces the overall footprint while maintaining precise control capability.
2Volume of moving object
If the electric power steering is installed at the bottom of the vehicle engine, then space utilization is improved, but reliability deteriorates due to water splashing or soaking
Solution Approach 1:
The patent employs waterproof coatings and sealing films on the motor and surrounding components. These flexible protective layers prevent water ingress while allowing the motor to be installed in the space-constrained bottom-mounted position, thus maintaining both compact installation and high reliability.
Solution Approach 2:
The patent uses replaceable waterproof seals and coatings that can be easily replaced if damaged. These protective elements act as sacrificial components that prevent water damage to the critical motor components while being economically replaceable.
3Speed
If the number of poles in the motor is reduced, then rotation speed increases, but manufacturing precision deteriorates due to control point deviation
Solution Approach 1:
The patent incorporates feedback mechanisms including encoders and control algorithms that continuously monitor the motor position and speed. This feedback system compensates for the reduced pole count by dynamically adjusting control parameters, thereby maintaining precise control points even with higher rotation speeds.
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
The solution provides precise and reliable power output, enhances motor durability by preventing water damage, and improves steering accuracy and safety, especially in automatic driving scenarios.
Implementation Method 1
planetary roller nut to drive the steering shaft
Implementation Method 2
steering shaft, a planetary roller nut... screwed to the screw portion of the steering shaft
Implementation Method 3
first waterproof ring is embedded at a selected position inside the accommodating space... second waterproof ring is embedded in a center of an outer end of the driver flange
Implementation Method 4
motor has a hollow-shaped motor stator and an external rotor... one end of the external rotor is coupled to the planetary roller nut to drive the planetary roller nut to rotate
Data Source
AI summary
An electric power steering apparatus is provided, including a casing; a steering shaft, disposed in the casing in an axially reciprocal manner and extending from two ends of the casing, and the body thereof having a rack portion and a screw portion; a planetary roller nut, assembled in the casing and screwed to the screw portion; a motor, controlled by the ECU, disposed in the casing, and having an external rotor, and the external rotor being coupled to the planetary roller nut to drive the motor to rotate, further driving the steering shaft to reciprocate in the casing; a first waterproof ring, provided between the planetary roller nut and the casing, and a second waterproof ring, placed between the planetary roller nut and the hollow stator of the motor, thus forming an airtight and waterproof efficacy for the motor to prevent the motor from losing power.