Electric Actuator Sensor Thermal Stress Reduction
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Solution Overview
Problem
In rotary actuators, the difference in thermal expansion coefficients between the rotation sensor and the case can lead to thermal deformation, causing stress on the sensor chip and reducing detection accuracy.
Innovation Solution
An electric actuator design that includes a motor with a motor shaft, a deceleration mechanism, a case with a recess to house the rotation sensor, and a holding member that supports the sensor chip, minimizing thermal stress by accommodating thermal expansion differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the rotation sensor is held directly in the case, then the device complexity is reduced, but the sensor chip may be distorted or damaged due to thermal stress from differential thermal expansion
Solution Approach 1:
The case is segmented into multiple functional regions: a first recess for accommodating the rotation sensor, a second recess for accommodating the projection, and a support surface. This segmentation allows the sensor to be isolated from direct thermal stress while maintaining integration within the case structure.
Solution Approach 2:
The projection acts as an intermediary element between the rotation sensor and the case. It provides a supported contact point that accommodates thermal expansion differences, preventing direct stress transmission to the sensor chip while maintaining structural integration.
2Reliability
If the rotation sensor is held in the case with proper thermal isolation, then the sensor chip reliability is improved, but the device complexity increases
Solution Approach 1:
The holding member integrating the projection is merged with the case structure, combining multiple functions (sensor accommodation, thermal isolation, and mechanical support) into a single integrated component. This reduces overall device complexity while maintaining sensor reliability.
Solution Approach 2:
The case structure serves multiple functions: it provides mechanical protection, thermal isolation through the recess design, and positional support through the projection. This multi-functionality eliminates the need for separate components, reducing overall device complexity.
3Volume of moving object
If the sensor main body is placed close to the bottom surface of the recess, then the space utilization is improved, but the sensor chip is more susceptible to thermal stress and distortion
Solution Approach 1:
The recess design creates a local quality difference: the first recess accommodates the sensor main body while the second recess (with support surface) provides a specific support zone for the projection. This localized structural differentiation protects the sensor chip from thermal stress while maintaining compact space utilization.
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 design reduces distortion and damage to the sensor chip, maintaining detection accuracy and stability while reducing the number of components by integrating the sensor holder within the case.
Implementation Method 1
depending on a difference between coefficients of thermal expansion of the rotation sensor and the case, an amount of thermal deformation of the rotation sensor may be different from an amount of thermal deformation of the case
Data Source
AI summary
An electric actuator is provided. The electric actuator includes a motor, a deceleration mechanism, case, an output part, a first rotation sensor and a holding member that holds the first rotation sensor in the case. The case includes a first recess that is recessed from an inner surface of the case to one side in a first direction and a support surface that faces the other side in the first direction. The first rotation sensor includes a sensor main body which includes a sensor chip and is accommodated in the first recess and a projection that protrudes in a second direction orthogonal to the first direction from the sensor main body. The projection is supported on the support surface from one side in the first direction. The sensor main body is disposed on the other side in the first direction away from the bottom surface of the first recess.