Spring-Biased Pivotable Thermal Fuse for Electric Motor
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Solution Overview
Problem
Existing brushless electric motors for motor vehicle components, such as fan impellers, lack a space-saving and reliable thermal fuse mechanism to prevent overheating.
Innovation Solution
A thermal fuse with a spring-biased contact bridge is integrated into the motor's electronics unit, where the contact bridge is pivotable about an axis perpendicular to the interruption point, and an abutment contour within the plastic encapsulation limits its pivoting range, ensuring reliable triggering and space efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thermal fuse with a spring-biased contact bridge is integrated into the motor's electronics unit, then thermal protection reliability is improved, but device complexity increases
Solution Approach 1:
The thermal fuse mechanism is merged with the existing lead frame structure by integrating the contact bridge directly into the plastic encapsulation of the electronics unit. The contact bridge utilizes the lead frame's current path ends as contact surfaces, combining the thermal protection function with the existing electrical connection structure, thereby improving reliability without proportionally increasing device complexity.
Solution Approach 2:
A spring element is introduced as an intermediary component to bias the contact bridge against the current path ends. This spring mediator provides the necessary contact force to ensure reliable electrical connection during normal operation while allowing automatic separation when thermal damage occurs, achieving both reliability and simplicity through a single passive mechanical element.
2Volume of moving object
If the contact bridge is made pivotable about an axis perpendicular to the interruption point, then space utilization is improved, but manufacturing precision requirements increase
Solution Approach 1:
The contact bridge is designed to pivot about an axis that extends perpendicular to the plane in which the interruption point is located. This dimensional change allows the contact bridge to move in a vertical plane rather than laterally, efficiently utilizing the vertical space within the plastic encapsulation and reducing the horizontal footprint of the thermal fuse mechanism.
Solution Approach 2:
The pivot axis is pre-positioned within the plastic encapsulation during mold manufacturing, establishing the rotation center before assembly. This preliminary action during the molding process eliminates the need for separate precision drilling or machining operations, reducing manufacturing complexity while maintaining the required precision for the pivot axis location.
3Reliability
If an abutment contour is used to limit the pivoting range of the contact bridge, then triggering reliability is improved, but device complexity increases
Solution Approach 1:
The abutment contour is merged with the plastic encapsulation structure itself, forming an integrated stop feature that limits the pivoting range of the contact bridge. By incorporating the stopping mechanism directly into the molded plastic housing rather than adding a separate component, the triggering reliability is improved while avoiding additional device complexity.
Solution Approach 2:
The plastic encapsulation serves a dual function: it provides structural housing for the electronics unit and simultaneously provides the abutment contour that limits contact bridge pivoting. This self-service approach allows the existing structural component to perform an additional functional role, improving triggering reliability without increasing overall device complexity.
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 configuration provides a simple, reliable, and space-saving thermal fuse mechanism that effectively interrupts the current path upon overheating, preventing damage from excessive temperatures while maintaining mechanical and electrical stability.
Implementation Method 1
a spring element which exerts a spring force on the contact bridge in the contact position
Implementation Method 2
when the melting point of the solder is reached, the contact sections of the corresponding conductive strip sections are separated
Data Source
AI summary
An electric motor for driving a motor vehicle component, in particular a fan impeller for cooling cooling water, having an electronics unit that includes a lead frame around which injection-molded plastic is provided and which has a current path conducting the motor current, and having two spaced-apart current path ends that form an interruption point bridged by a thermal fuse in the form of a spring-biased contact bridge. The contact bridge is mounted so as to be pivotable about an axis of rotation extending perpendicular to the plane of the interruption point. An abutment contour, against which the contact bridge pivots as a result of the restoring force of a spring element when the thermal fuse is triggered, limits the pivoting range of the contact bridge.