High-Offset Belt Tensioner With Boltless Pulley Retention
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Solution Overview
Problem
Existing ZED-style belt tensioners require improvements in counterbalancing hub load force using a robust spring with fewer parts, particularly in high-offset designs.
Innovation Solution
A high-offset belt tensioner design featuring a torsion spring engaged with the tensioner arm via a spring tang in a pulley pivot tube, with the spring end seated in the pulley pivot tube, and a bushing with a damper tab to dampen movement, eliminating the need for a pulley bolt and allowing the spring to counterbalance hub load force throughout the arm's rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pulley bolt is used to secure the pulley, then the pulley is securely retained, but the device complexity and part count increase
Solution Approach 1:
The pulley retention function is merged with the pivot tube structure itself. The pivot tube is deformed to create an interference fit with the pulley, eliminating the need for a separate pulley bolt. This combines the retention function into the existing structural component, reducing part count while maintaining secure retention.
Solution Approach 2:
The pivot tube performs dual functions: it serves as both the rotational pivot and the pulley retention mechanism. Through deformation, the pivot tube creates its own retention feature (interference fit) without requiring external fastening components, making the system self-sufficient.
2Ease of manufacture
If fewer parts are used in the tensioner design, then manufacturing cost decreases, but the counterbalancing of hub load force may be compromised
Solution Approach 1:
The spring retention and counterbalancing functions are merged into the pivot tube structure. The spring is retained within the pivot tube and directly engages with the arm, allowing the same structural element to perform both retention and force transmission functions, maintaining counterbalancing capability with fewer parts.
Solution Approach 2:
The pivot tube is designed as a multi-functional component that serves as: (1) the rotational pivot axis, (2) the spring housing/retention structure, and (3) the force transmission path for counterbalancing. This multi-functionality allows a single component to replace what would traditionally require multiple separate parts.
3Force
If the spring end is seated in the pulley pivot tube, then counterbalancing is enhanced, but the device complexity increases
Solution Approach 1:
The spring engagement structure is merged with the pulley pivot tube. The spring end seats directly in the pulley pivot tube, combining the spring retention and force application functions into the existing structural element, enhancing counterbalancing without adding separate complex mechanisms.
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 material usage, enhances counterbalancing, and provides cost-effective, durable operation with improved frictional damping, while allowing for easier installation and reduced complexity.
Implementation Method 1
a torsion spring seated around an exterior surface of the arm arbor with a first spring end attached to the base and a second spring end oriented and seated in the pulley pivot tube
Implementation Method 2
a bushing with an axial slit opposite the protruding tab and is compressible against the pivot tube when the coil spring is wound against the exterior surface of the arm to damp movement of the arm
Implementation Method 3
a bushing with an axial slit opposite the protruding tab and is compressible against the pivot tube when the coil spring is wound against the exterior surface of the arm to damp movement of the arm
Implementation Method 4
the bushing having a protruding tab extending through the open window in active engagement with a coil of the torsion spring
Data Source
AI summary
A high-offset belt tensioner has a base having a pivot tube that defines a first axis of rotation, an arm having a pivot tube-receiving body rotatably seated over the pivot tube and having a pulley pivot tube that defines a second axis of rotation. A torsion spring is seated around an exterior surface of the pivot tube-receiving body with a first spring end attached to the base and a second spring end oriented and seated in the pulley pivot tube. A pulley is seated on the pulley pivot tube and rotatable thereabout. A dust cover is seated on the pulley pivot tube juxtaposed to the pulley and a first end of the pivot tube is deformed toward the dust cover to retain the pulley without the use of a pulley bolt.