Multi-Spring Tensioner with Variable Stiffness
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Solution Overview
Problem
In vehicle front engine accessory drive systems, high belt tension leads to increased parasitic losses, contributing to higher fuel consumption, as the engine must overcome these losses, reducing the torque available for driving the vehicle.
Innovation Solution
A tensioner system with adjustable spring rates, utilizing a combination of high and low stiffness springs, controlled by an actuator to maintain optimal belt tension based on engine fan engagement, switching between high and low tension modes to minimize energy wastage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high spring rate tensioner is used to maintain belt tension, then the belt tension is sufficient to prevent slip and engage the fan, but the parasitic losses increase and fuel consumption rises
Solution Approach 1:
The tensioner system dynamically adjusts the spring rate based on operating conditions. When the fan is engaged, a high spring rate maintains sufficient belt tension to prevent slip. When the fan is disengaged, the system switches to a low spring rate to reduce parasitic losses and improve fuel economy, thus making the tensioner adaptive rather than static
Solution Approach 2:
The invention changes the physical parameter of spring rate in the tensioner system. By switching between a first spring with high stiffness coefficient and a second spring with low stiffness coefficient, the system optimizes the balance between maintaining reliable belt engagement and minimizing energy losses during different operating phases
2Loss of energy
If a low spring rate tensioner is used to reduce parasitic losses, then fuel consumption decreases, but the belt tension becomes insufficient to prevent contact of the tensioner arm against its load stop when the fan is on
Solution Approach 1:
The system dynamically switches between low and high spring rates based on fan engagement status. During normal operation with fan disengaged, the low spring rate minimizes parasitic losses. When cooling demand arises and the fan engages, the system transitions to high spring rate to ensure sufficient belt tension and prevent tensioner arm contact with the load stop
Solution Approach 2:
The invention implements parameter changes by selecting different spring stiffness coefficients based on operational requirements. The low stiffness coefficient reduces energy losses during cruise, while the high stiffness coefficient ensures reliable belt tension and prevents mechanical failure during high-load cooling conditions
3Device complexity
If a single spring rate is used in the tensioner, then the device complexity is low, but the system cannot optimize belt tension for different operating conditions
Solution Approach 1:
The tensioner system is segmented into multiple spring components with different stiffness characteristics. Instead of a single monolithic spring, the invention uses a first spring with high stiffness coefficient and a second spring with low stiffness coefficient, allowing selective engagement based on operating conditions
Solution Approach 2:
The multi-spring tensioner system performs multiple functions: it maintains belt tension during fan engagement, reduces parasitic losses during fan disengagement, and adapts to varying operational requirements. This universal design allows one tensioner system to handle diverse operating scenarios effectively
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 tensioner system reduces fuel consumption by optimizing belt tension, minimizing parasitic losses when the engine fan is not needed, while ensuring adequate tension for engine cooling and preventing overheating.
Implementation Method 1
a first resilient element connected between the base and the first body, the first resilient element having a first stiffness coefficient
Data Source
AI summary
In a first aspect, a tensioner is provided which includes: an arm, including a pivot mount; a pulley rotatably mounted to the arm; and a strut pivotally connected to the arm. The strut includes: a base, having a pivot mount; a first body moveable relative to the base; a first resilient element connected between the base and the first body, the first resilient element having a first stiffness coefficient; a second body moveable relative to the first body, the second body having a pivot mount; a second resilient element connected between the first body and the second body, the second resilient element having a second stiffness coefficient that is lower than the first stiffness coefficient; and an actuator, connected to the base and first body, for selectively moving the first body towards the base and compressing the first resilient element.