Nested Torsion Spring Tensioner for Low-Height Belt Timing
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Solution Overview
Problem
Existing tensioners are constrained in size due to the axial arrangement of torsion springs, which limits the minimum height and affects engine and belt system design, particularly in applications where oil is present, as they require precise synchronization between camshafts and crankshafts to prevent catastrophic engine damage from loss of synchronization.
Innovation Solution
A tensioner design featuring a torsion spring disposed within a radially inward receiving portion of a base cylindrical portion, allowing for a fully concentric and nested arrangement of components that minimizes height while maintaining functionality in oil environments, using a bushing with a dynamic coefficient of friction and retaining rings to transmit axial forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a torsion spring is stacked axially with a pulley bearing, then the tensioner can maintain synchronization between camshafts and crankshafts, but the minimum height of the device increases
Solution Approach 1:
The torsion spring is positioned inside the radially inward receiving portion of the base cylindrical portion, nesting the spring within the base structure rather than stacking it axially with the bearing. This nested arrangement allows the spring to provide torsional biasing force while occupying radial space instead of axial space, thereby reducing the overall height of the tensioner device.
Solution Approach 2:
The design transitions from an axial arrangement (stacking spring and bearing along the same axis) to a radial arrangement (positioning spring inside the base's radially inward receiving portion). This dimensional change moves the spring from the axial dimension to the radial dimension, freeing up axial space and reducing the minimum height requirement of the device.
2Volume of moving object
If a compact tensioner design is used, then the device can be installed in cramped applications, but the complexity of ensuring proper tensioning increases
Solution Approach 1:
The design combines multiple functions into integrated components. The base cylindrical portion with its radially inward receiving portion serves both as a structural support and as a housing for the torsion spring. The eccentric arm assembly integrates the pulley, bearing, and spring interaction into a unified mechanism that automatically provides tensioning through the eccentric geometry, reducing the need for separate adjustment mechanisms.
Solution Approach 2:
The eccentric arm mechanism automatically converts the rotational motion into radial displacement that maintains belt tension. The torsion spring provides continuous biasing force through the eccentric arm's geometry, creating a self-regulating tensioning system that adapts to belt elongation and wear without requiring external adjustment, thereby simplifying the overall system despite the compact size.
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 enables a compact tensioner that maintains synchronization between camshafts and crankshafts, preventing engine damage by applying a variable load to the belt, even in oil environments, and allows for use in cramped applications with reduced risk of 'tooth jump' or 'ratcheting'.
Implementation Method 1
a torsion spring disposed within a radially inward receiving portion of a base cylindrical portion
Implementation Method 2
using a bushing with a dynamic coefficient of friction to transmit axial forces
Data Source
Figure 1
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Figure 6
AI summary
A tensioner comprising a base having a cylindrical portion extending axially, the cylindrical portion comprising a radially outer surface and a receiving portion that is radially inward of the radially outer surface, an eccentric arm pivotally engaged with the radially outer surface, a torsion spring disposed within the radially inward receiving portion, the torsion spring applying a biasing force to the eccentric arm, and a pulley journalled to the eccentric arm.