Concentric Belt Tensioner Layout for Low-Height Timing Drives
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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 timing belt applications where oil presence requires a more compact and efficient tensioning mechanism to prevent synchronization loss between camshafts and crankshafts.
Innovation Solution
A tensioner design featuring a torsion spring disposed within a radially inward receiving portion of a base cylindrical portion, allowing for a concentric arrangement with the pulley, bearing, and eccentric arm, which minimizes height and enables efficient belt tensioning in oil environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a torsion spring is stacked axially with a pulley bearing, then the tensioner can provide belt tensioning force, but the minimum height of the device increases which limits engine and belt system design
Solution Approach 1:
The torsion spring is nested within the base cylindrical portion, specifically positioned in a radially inward receiving portion of the base. This nesting arrangement allows the spring to be contained within the existing structural envelope rather than extending axially outward, thereby reducing the overall height of the tensioner while maintaining the necessary tensioning force capability.
Solution Approach 2:
The design transitions from an axial stacking arrangement (one-dimensional extension) to a radial containment arrangement (two-dimensional utilization). By positioning the torsion spring radially inward within the base cylindrical portion rather than axially adjacent to it, the design exploits the radial dimension to accommodate the spring, thereby reducing axial height without compromising the tensioning function.
2Reliability
If the camshaft loses synchronization with the crankshaft, then catastrophic engine damage can result, but maintaining synchronization requires complex tensioning mechanisms in oil environments
Solution Approach 1:
The design merges the torsion spring housing with the base cylindrical portion, eliminating the need for separate axial stacking components. The torsion spring is integrated within the base structure, and the eccentric arm assembly is combined with the pulley, creating a more compact unit that maintains reliability while reducing overall complexity.
Solution Approach 2:
The eccentric arm is nested within the base structure, and the pulley is journalled to the eccentric arm in a compact arrangement. This nested configuration reduces the number of discrete components and simplifies the overall tensioning mechanism while maintaining the reliability needed to prevent synchronization loss in oil environments.
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 provides a compact and effective tensioning mechanism that maintains synchronization between camshafts and crankshafts, preventing 'tooth jump' and 'ratcheting' while accommodating oil environments, thus enhancing engine performance and reliability.
Implementation Method 1
a torsion spring disposed within the radially inward receiving portion, the torsion spring applying a biasing force to the eccentric arm
Data Source
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.