Electric Bicycle Motor Unit Thermal Conduction via Through-Hole Foil
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Solution Overview
Problem
Existing electric bicycle motor units face challenges in effectively dissipating heat from switching elements, which can lead to reduced reliability and performance.
Innovation Solution
The motor unit design includes a switching element thermally connected to a sheet of metal foil through a through hole in the board, with the case also thermally connected to the foil, allowing for efficient heat dissipation. Additional features such as solder with thermal conductivity, an insulating member, and strategically located heat-dissipating portions enhance heat transfer and reduce solder outflow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If switching elements are thermally connected to the case through conventional methods, then heat dissipation is achieved, but the quantity of heat dissipated is insufficient
Solution Approach 1:
The invention introduces a through-hole structure that penetrates the board in the thickness direction, creating a three-dimensional heat dissipation path. The sheet of metal foil is positioned within this through-hole to provide thermal conduction from the switching element to the case, effectively utilizing the vertical dimension for heat transfer rather than relying solely on surface-level thermal connection.
Solution Approach 2:
The sheet of metal foil serves as a thermal intermediary between the switching element and the case. It is positioned within the through-hole to facilitate heat transfer from the switching element's reverse surface to the case, acting as a mediator that enhances thermal conduction efficiency and increases the quantity of heat dissipated.
2Loss of energy
If a through hole is provided in the board for thermal connection, then heat dissipation efficiency increases, but solder may outflow through the through hole
Solution Approach 1:
The insulating member is preliminarily positioned to cover the through-hole on the reverse surface of the board before soldering occurs. This preliminary protective action prevents solder from flowing out through the through-hole during the soldering process, while still allowing thermal conduction to occur through the insulating member's thermal pathway.
Solution Approach 2:
The insulating member acts as a dual-function intermediary: it covers the through-hole to prevent solder outflow while simultaneously providing a thermal conduction pathway from the switching element to the case. This mediator resolves the conflict between heat dissipation efficiency and solder containment.
3Loss of energy
If the sheet of metal foil covers the inner peripheral surface of the through hole, then thermal conduction is enhanced, but the board structure becomes more complex
Solution Approach 1:
The invention uses a thin sheet of metal foil to line the inner peripheral surface of the through-hole. This thin film structure provides effective thermal conduction from the switching element to the case without significantly increasing structural complexity. The flexibility of the thin foil allows it to conform to the through-hole geometry while maintaining thermal contact.
Solution Approach 2:
The board structure becomes a composite system incorporating the original board material, the through-hole structure, the sheet of metal foil for thermal conduction, and the insulating member for protection. This composite structure integrates multiple functions (structural support, thermal conduction, solder protection) within a unified design that manages complexity through functional integration.
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 significantly increases heat dissipation from the switching element, improving the reliability and performance of the motor unit by effectively transferring heat generated by the switching element to the case.
Implementation Method 1
The switching element is thermally connected to the sheet of metal foil. A part, located opposite from the switching element with respect to the board, of the case is thermally connected to the sheet of metal foil.
Implementation Method 2
The switching element is thermally connected to the sheet of metal foil via the solder.
Data Source
AI summary
A motor unit for use in an electric bicycle includes a motor, a switching element, a board, and a case. The switching element has the motor driven. The board has a principal surface and a reverse surface. The principal surface includes a mounting surface to mount the switching element thereon. The reverse surface faces opposite from the principal surface. The case houses the board therein. The board further has a through hole provided to penetrate through the board from the mounting surface through the reverse surface and a sheet of metal foil covering an inner peripheral surface of the through hole at least partially. The switching element is thermally connected to the sheet of metal foil. A part, located opposite from the switching element with respect to the board, of the case is thermally connected to the sheet of metal foil.