Nested Ring Belt Tensioner for Symmetric Reversible Torque
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Solution Overview
Problem
Conventional tensioners for accessory drives in motor vehicles with reversible electric machines face challenges in maintaining optimal belt tension across different operating conditions, particularly in space-constrained applications and when achieving symmetrical characteristics in positive and negative torque conditions.
Innovation Solution
A tensioner design featuring a base fixed to the electric machine's casing, with a first ring rotating around a first axis and a second ring rotating around a second axis eccentric to the first axis, utilizes elastic means to maintain pulleys in contact with the belt, reducing installation tension and optimizing torque transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a tensioner with two arms hinged on a common pin is used to maintain belt tension on both spans, then the belt tensioning function is improved, but the overall dimensions of the base and spring increase making it unsuitable for space-constrained applications
Solution Approach 1:
The patent implements nesting by placing the second pulley inside the first pulley, with the second ring rotating about an axis within the first ring. This nested configuration allows both tensioning functions to be achieved in a compact space, resolving the contradiction between reliable dual-span tensioning and small base dimensions.
Solution Approach 2:
The patent transitions from a planar two-arm mechanism to a three-dimensional nested ring structure where the second ring rotates about an axis eccentric to the first ring's axis. This dimensional change enables compact packaging of the tensioning mechanism while maintaining effective belt contact on both spans.
2Area of stationary object
If the tensioner is mounted on the electric machine with annular elements rotating around the electric machine axis, then the space constraint is addressed, but relatively high belt tension is required for optimal functioning in recuperation and boost conditions
Solution Approach 1:
The patent employs asymmetry by positioning the second ring's rotation axis eccentrically relative to the first ring's axis. This asymmetric arrangement creates optimal force distribution that reduces the required belt tension for effective torque transmission during recuperation and boost conditions, while maintaining compact mounting on the electric machine.
3Device complexity
If an arm hinged to an annular element is used in the tensioner, then the structure is simplified, but symmetrical characteristics in positive and negative torque conditions cannot be achieved
Solution Approach 1:
The patent deliberately introduces asymmetry through the eccentric positioning of the second ring's axis relative to the first ring's axis. This asymmetric configuration enables the tensioner to achieve symmetrical performance characteristics in both positive and negative torque conditions by creating balanced force distribution, while maintaining relatively simple structural implementation.
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 reduces the installation tension of the belt while maintaining torque transmission capacity, and optimizes the drive's operation in both positive and negative torque conditions, achieving symmetric characteristics and improved efficiency.
Implementation Method 1
A spring acts between the two annular elements configured to exert an elastic force between said elements in order to maintain the first and the second pulleys in contact with respective spans of the belt
Data Source
AI summary
A tensioner for an accessory drive of an internal combustion engine has a belt on a first pulley connected to a drive shaft of the engine and a second pulley connected to an electric machine. The tensioner has a base configured to be fixed to a casing of the electric machine, a first ring rotating with respect to the base about a first axis, a second ring rotating with respect to the first ring about a second axis distinct from the first axis, a first tensioning pulley carried by the first ring and rotating with respect to it about its own axis, a second tensioning pulley carried by the second ring and rotating with respect to it about its own axis and elastic means acting on the first and on the second ring to push the first and the second pulleys into contact with respective spans of the belt.