Electric Motor Resilient Rotor Shaft Torque Limiting
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Solution Overview
Problem
Electric motors in shift range change apparatuses face mechanical damage due to excessive rotational torque when operating under 'low temperature×high voltage' conditions, leading to potential damage in the rotation transmission system and drive subject components.
Innovation Solution
Incorporating a rotor shaft with a resilient member and a supportive contact member that tilts or decenters upon decentering force application, limiting rotational torque through contact between the rotor core and stator core, thereby preventing excessive load application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electric motor is designed to generate required torque under worst condition (high temperature×low voltage), then the drive current is sufficient in worst condition, but a large rotational torque is produced in opposite condition (low temperature×high voltage) causing excessive load
Solution Approach 1:
The resilient member is pre-installed between the rotor shaft and stator core to provide beforehand cushioning. When excessive rotational torque occurs under low temperature×high voltage conditions, the resilient member deforms to absorb the excess torque before it can damage the drive subject, thus cushioning the harmful effect in advance
Solution Approach 2:
The resilient member acts as an intermediary element between the rotor shaft and stator core. It mediates the torque transmission by deforming under excessive torque conditions, allowing the motor to generate high torque when needed while preventing damage during abutment control operations
2Measurement precision
If the electric motor generates excessive rotational torque during abutment control operation, then the reference position can be learned, but mechanical damage is applied to components of the rotation transmission system and drive subject
Solution Approach 1:
The resilient member is positioned to provide beforehand cushioning during abutment control operations. When the rotor shaft contacts the stator core during reference position learning, the resilient member deforms to absorb the impact torque, preventing mechanical damage to the drive subject while still allowing the control operation to complete
3Reliability
If the resilient member is made more compliant to better limit torque, then excessive load is better prevented, but the motor response speed and torque delivery may be affected
Solution Approach 1:
The resilient member is designed with specific local properties - it is positioned only between the rotor shaft and stator core where torque limiting is needed, while maintaining rigidity in other directions. This localized compliance allows torque limiting during abutment control without affecting overall motor response speed and torque delivery capability
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 solution effectively limits rotational torque during abutment control operations, preventing mechanical damage and enhancing the reliability of the shift range change apparatus by managing torque across varying temperature and voltage conditions.
Implementation Method 1
The resilient member enables tilting or decentering of the rotor shaft upon application of a decentering force on the rotor shaft
Data Source
AI summary
In an electric motor of an SBW actuator, a rotor shaft is rotated upon energization of the motor. A rotor core is rotated integrally with the rotor shaft. A resilient member enables tilting or decentering of the rotor shaft upon application of a decentering force on the rotor shaft. A stator core contacts the rotor core when the rotor shaft is tilted or decentered.