Brushless Motor Resolver Bracket for Axial Miniaturization
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Solution Overview
Problem
Conventional electric power steering (EPS) systems face issues with cogging and torque ripple transmission to the steering wheel, leading to motor vibration and unreliable position detection due to inadequate resolver placement and fixation, resulting in low workability and potential damage.
Innovation Solution
The solution involves dividing a bracket into two parts, allowing the resolver stator to be circumferentially movable, with a bolt fixation and circular arc through holes for easier adjustment, and forming an enclosing space around the connection base to prevent contact with the bus bar, enabling axial miniaturization and increased pole count.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the resolver is disposed on the axial outside of the space between ball bearings, then the space between ball bearings can be narrowed, but the shaft accuracy cannot be assured and the shaft swings causing motor vibration
Solution Approach 1:
The resolver is moved from the axial outside (one-dimensional arrangement) to the radial inside space between stator and rotor (changing the spatial dimension). This allows the axial space between ball bearings to be narrowed while maintaining shaft accuracy, as the resolver no longer occupies axial space but utilizes radial space instead.
2Ease of operation
If the resolver is disposed on the axial outside, then it is accessible for position adjustment, but it is exposed to external contact and may be damaged
Solution Approach 1:
The resolver is nested inside the motor housing between the stator and rotor, rather than being exposed on the outside. This protective enclosure prevents external contact and damage while the nested structure allows access through the housing for position adjustment during assembly or maintenance.
3Ease of manufacture
If the board holder is fixed by only three screws from the upper side, then assembly is simple, but the board holder cannot be fixed with reliability and may come off due to vibrations or collision
Solution Approach 1:
The bracket is divided into a first bracket part (fixed to housing) and a second bracket part (holding board holder), connected by a movable connection. This segmentation allows the board holder to be reliably fixed in multiple directions while maintaining assembly simplicity, as the modular structure can be assembled in stages.
4Measurement precision
If the circumferential position adjustment is performed by moving the screw head, then position adjustment is possible, but it is difficult to move the board holder and workability is low
Solution Approach 1:
A circumferential movement guiding structure is introduced as an intermediary mechanism between the screw and the board holder. This mediator allows smooth circumferential movement of the board holder along a predetermined path, making position adjustment easier while maintaining precision through the guided movement path.
5Length of moving object
If the motor axial length is shortened by narrowing ball bearing space, then miniaturization is achieved, but shaft accuracy deteriorates and vibration increases
Solution Approach 1:
The resolver is relocated from axial positioning to radial positioning between stator and rotor. This dimensional change allows the axial length to be shortened for miniaturization while the radial placement of the resolver does not interfere with shaft accuracy, as the resolver is positioned away from the shaft support region.
Data Source
AI summary
A second bracket part for holding a resolver stator of a resolver as position detecting means is inserted in an opening hole in a first bracket part. An expanded part formed in the second bracket part and the opening hole in the first bracket hole are connected to each other with a fixing member. A through hole in which the fixing member for the expanded part is inserted has a circular arc shape. By reducing the fixing strength of the fixing member, the second bracket part can be made movable in the circumferential direction.