Bow-Shaped Spring Belt Tensioner for Compact Axial Design
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Solution Overview
Problem
Existing belt tensioning devices for starter-generators face challenges with space constraints, complex mounting, and high wear due to resulting torques, particularly around the generator axis and in front of and behind the belt plane, leading to increased manufacturing complexity.
Innovation Solution
A compact belt tensioning device with a base member, pivotably supported tensioning arms, and a bow-shaped spring arrangement that pretensions the arms in a circumferential direction, allowing for a flat axial structure and minimal axial installation height, enabling easy mounting and reduced wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a belt tensioning device with two tensioning arms is used for starter-generator applications, then the belt can be properly tensioned on both sides of the starter-generator pulley, but the axial space requirement increases and the device becomes more complex
Solution Approach 1:
The patent combines two tensioning arms into a single integrated tensioning device that pivots about a common axis. The housing contains both tensioning arms and the spring arrangement in a unified structure, reducing the number of separate components while maintaining the functionality of tensioning the belt on both sides of the starter-generator pulley.
Solution Approach 2:
The single housing structure serves multiple functions: it contains both tensioning arms, provides mounting points for the spring arrangement, supports the common pivot axis, and houses the tensioning rollers. This multi-functional design reduces overall device complexity while achieving the required belt tensioning on both sides.
2Force
If traditional spring arrangements with 360° circumferential extension are used, then sufficient pretension force is provided, but the axial length and space requirement increase
Solution Approach 1:
The spring arrangement uses bow-shaped springs with a curved geometry that extends circumferentially around the pivot axis by less than 360 degrees. The curved shape allows the springs to provide sufficient pretension force through elastic deformation while occupying minimal axial space, fitting within the compact housing structure.
Solution Approach 2:
Instead of extending the springs axially to provide pretension force, the invention uses circumferential extension in a radial plane. The bow-shaped springs arc around the pivot axis, converting axial force requirements into circumferential geometry, thereby reducing axial length while maintaining force output.
3Volume of moving object
If compact tensioning device design is implemented to reduce axial space, then space constraints are satisfied, but mounting difficulty increases due to limited space
Solution Approach 1:
The tensioning device is segmented into distinct modular components: a housing containing the spring arrangement, separate tensioning arms with rollers, and a base member for mounting. This segmentation allows components to be assembled in a compact configuration while maintaining ease of installation, as each component can be positioned and secured independently within the limited space.
Solution Approach 2:
The design nests components within each other to maximize space utilization: the spring arrangement is housed within the housing structure, the tensioning arms pivot within the housing, and the entire assembly mounts to the base member. This nested configuration achieves compact axial dimensions while allowing systematic assembly and disassembly for mounting and maintenance.
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 achieves a compact, easily mountable belt tensioning device with reduced wear and simplified manufacturing, effectively addressing space constraints and torque-related issues while maintaining effective belt tensioning.
Implementation Method 1
a spring arrangement that is arranged between the first tensioning arm and the second tensioning arm such that the first tensioning arm and the second tensioning arm are pretensioned in a circumferential direction towards each other by the spring arrangement
Data Source
AI summary
A belt tensioning device comprises a base member having an attachment portion and an opening for a drive shaft; first and second tensioning arms that are pivotably supported by first and second bearings on the base member around first and second pivot axes and have first and second tensioning rollers 5, 7. A spring arrangement pretensions the two tensioning arms in a circumferential direction towards each other; wherein the spring arrangement has at least one bow-shaped spring that has a circumferential extension of less than 360° around the first and the second pivot axis; wherein the at least one bow-shaped spring has first and second support portions that are supported on the first and second tensioning arm as well as a spring portion extending between the first and second support portion; wherein the at least one bow-shaped spring has an axial length in the area of the first and the second support portion which is axially shorter than a total axial length of the bow-shaped spring.