Brushless Motor Axial Rotor Support for Friction Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Brushless motors for electric power steering systems face challenges in reducing friction losses and cogging torque while maintaining high efficiency and stable rotation, as pre-load bearing structures increase friction but are necessary to prevent rotor movement, and size reduction is required.
Innovation Solution
A brushless motor design with a rotor supported by deep-groove ball bearings without pre-load, allowing axial movement up to 2 mm to minimize friction and cogging torque, and an equal axial length to the stator to prevent excessive cogging, ensuring efficient and stable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a pre-load bearing structure is adopted to prevent rotor movement, then rotor stability is improved, but friction losses increase and motor efficiency decreases
Solution Approach 1:
The invention transitions from a static pre-loaded bearing structure to a dynamic structure where the rotor can move axially within a controlled range (0.5-2mm). This dynamic capability allows the rotor to self-adjust its position to minimize cogging torque while maintaining operational stability, thereby reducing friction losses without sacrificing rotor stability.
2Object-generated harmful factors
If the axial length of the stator is made sufficiently larger than the rotor to eliminate leakage magnetic flux, then cogging torque is reduced, but motor size increases
Solution Approach 1:
The invention changes the operational parameter of rotor position by allowing axial movement within 0.5-2mm range. This parameter change enables the rotor to find optimal positions that minimize the effect of leakage magnetic flux and cogging torque, achieving reduced harmful factors without increasing motor size.
Solution Approach 2:
By making the rotor axially movable rather than fixed, the system dynamically adjusts to minimize cogging torque effects. This dynamic approach allows the rotor to self-position to reduce the impact of leakage flux at the stator ends, achieving smooth rotation without increasing the axial length of the stator.
3Loss of energy
If the rotor is made movable in the axial direction to reduce friction losses, then motor efficiency is improved, but rotor stability deteriorates
Solution Approach 1:
The invention implements a dynamic balance by allowing controlled axial movement (0.5-2mm) that enables the rotor to self-adjust to positions minimizing both friction losses and cogging torque. This controlled dynamics maintains stability while improving efficiency.
Solution Approach 2:
The continuous axial movement capability within the specified range allows the rotor to continuously optimize its position during operation, maintaining low friction losses and stability throughout the operational cycle rather than being fixed in a suboptimal position.
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 design reduces friction losses and cogging torque, achieving high motor efficiency and stable rotation without increasing size, suitable for compact applications like electric power steering systems.
Implementation Method 1
friction losses in the bearing which supports the rotor
Implementation Method 2
rotor is supported by deep-groove ball bearings
Implementation Method 3
A rotating magnetic field is produced inside the housing by controlling the supply of power to these stator coils, and the torque is applied to the magnet in the rotating magnetic field to rotate the rotor
Implementation Method 4
magnet having a plurality of magnetic poles on the outer circumferential surface
Implementation Method 5
the torque is applied to the magnet in the rotating magnetic field
Implementation Method 6
Even at both ends in the axial direction, leakage magnetic flux may change due to a positional displacement between the stator and the rotor
Implementation Method 7
cogging torque can be reduced by making the axial length of the stator sufficiently larger than the axial length of the rotor and eliminating the influence of leakage magnetic flux
Data Source
AI summary
A rotary shaft of a rotor including a magnet with a plurality of magnetic poles arranged at equal intervals on an outer circumference is supported at both ends by bearings. By externally fitting the inner ring of one bearing to the rotary shaft and holding it to be immovable in an axial direction and loosely fitting the outer ring of the bearing into the support hole and positioning it with belleville springs which are in contact resiliently with both sides, the rotary shaft and the rotor are supported so that they are movable in an axial direction within a movement amount of not greater than 2 mm according to a movement of the bearing caused against spring forces of the belleville springs.