Electric Hub Serration Coupling Design for Force Transmission
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Solution Overview
Problem
Conventional electric hubs face issues with transmitting human driving force without increasing serration length, waterproofing bearings, preventing rattles and heat dissipation in electric bicycles.
Innovation Solution
An electric hub design featuring serration couplings with integral input and output serration sections, unshielded thrust needle roller bearings with grease holding sections, and a locking mechanism to prevent rattles and enhance heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If serration sections are extended in the axial direction to transmit large turning force, then the strength is improved, but the width of the electric hub increases
Solution Approach 1:
The invention transitions from axial extension (one dimension) to radial expansion (another dimension) by increasing the diameter of the output serration section. This allows the serration coupling to transmit larger forces without increasing the hub width, effectively resolving the contradiction between strength and compactness.
2Reliability
If shield bearings are used to prevent rainwater entry, then waterproofness is improved, but design freedom is reduced due to limited available types
Solution Approach 1:
The invention changes the parameters of unshielded bearings (adding grease holding sections and seal structures) to achieve waterproofness, rather than being constrained to pre-designed shield bearing types. This maintains design freedom while achieving the desired reliability.
3Ease of manufacture
If locking members are engaged with hub spindles only by chamfered portions, then assembly is simplified, but rattles occur and damage may happen
Solution Approach 1:
The invention uses a composite engagement structure combining chamfered portions (for easy assembly) with flat surface contact areas (for stable locking and heat dissipation). This composite approach maintains assembly simplicity while eliminating rattles and preventing damage.
4Device complexity
If motor housing is directly engaged with hub spindle, then structure is simplified, but heat dissipation is insufficient
Solution Approach 1:
The locking member acts as an intermediary between the motor housing and hub spindle, providing both mechanical engagement and a heat dissipation pathway. This maintains structural simplicity while effectively transferring heat from the motor housing to the hub spindle.
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 effectively transmits human driving force without serration length extension, ensures waterproofing, reduces rattles, and improves heat dissipation, enhancing the reliability and compactness of the electric hub.
Implementation Method 1
a serration coupling that transmits a human driving force from the human-driving-force transmitting wheel to the hub body
Implementation Method 2
an unshielded bearing that rotatably supports the hub body
Implementation Method 3
a grease holding section that is capable of holding grease, the grease holding section being formed in the hub body so as to hold grease in a location facing at least one bearing
Implementation Method 4
a locking member that is fit onto the hub spindle, is engaged with the frame, and is attached so as not to rotate about the axis of the hub spindle
Implementation Method 5
a motor provided in the hub body so as to rotate the hub body
Data Source
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AI summary
Provided is an electric hub that can properly transmit a human driving force to a hub body without considerably increasing the length of a serration section in an axial direction. A serration coupling 53 that transmits a human driving force from sprockets 60 to a cover member 28 of a hub body 23 is provided. The serration coupling 53 includes an input serration section 53b and an output serration section 53a that are integrally formed. The input serration section 53b receives a human driving force from the sprockets 60 and the output serration section 53a transmits a human driving force to the cover member 28. The output serration section 53a is larger in diameter than the input serration section 53b.