Variable Force Tensioner With Internal Reservoirs for Stable Chain Tension

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Solution Overview

Problem

Conventional dual hydraulic variable force tensioners face inefficiencies in fluid flow and pressure distribution, leading to inconsistent tension maintenance in engine chains or belts due to limitations in the design of the primary and secondary pistons and reservoirs.

Innovation Solution

The integration of a primary reservoir within the primary piston and a shared reservoir at the back side of the housing, along with check valves and spring mechanisms, allows for faster fluid flow into high pressure chambers, enhancing the extension of pistons and maintaining consistent tension by controlling fluid flow and pressure distribution.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If fluid flows from a shared reservoir at the back side of the tensioner through check valves to fill high pressure chambers in both pistons, then the tensioner can maintain tension on chain or belt, but the fluid flow path is long and creates pressure loss and inconsistent tension

Engineering Contradiction:

Improvetension consistencyVSAvoidpressure loss

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent divides the single shared reservoir system into two separate reservoirs: one integrated into the primary piston and another integrated into the secondary piston. Each reservoir is positioned adjacent to its corresponding piston, creating separate fluid supply paths. This segmentation eliminates the long fluid flow path through the check valve that caused pressure loss, while maintaining the ability to independently control tension on the chain or belt.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The primary reservoir is integrated within the primary piston structure, and the secondary reservoir is integrated within the secondary piston structure. This nesting approach places the fluid storage capacity directly within the piston bodies, positioning the fluid source immediately adjacent to the point of use. This eliminates intermediate fluid pathways and reduces pressure loss while maintaining reliable tension consistency.

Inventive Principle:

Principle #7Nested doll (Nesting)

2Speed

If a shared reservoir is used at the back side of the tensioner, then the structure is simplified, but the fluid flow speed into high pressure chambers is slow

Engineering Contradiction:

Improvefluid flow speedVSAvoidreservoir configuration

Core Design Contradiction:

SpeedVSDevice complexity

Solution Approach 1:

The patent positions reservoirs in advance within the piston structures, preparing the fluid supply system so that fluid is already positioned adjacent to the high pressure chambers before tensioning action is required. This preliminary positioning of fluid storage eliminates delays associated with long fluid pathways, enabling faster fluid flow speed into the high pressure chambers when tensioning action is needed.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If fluid flows through a long path from the shared reservoir to both pistons, then a single reservoir structure is used, but clearance leakage increases

Engineering Contradiction:

Improvetension maintenanceVSAvoidfluid leakage

Core Design Contradiction:

ReliabilityVSLoss of substance

Solution Approach 1:

The patent segments the fluid supply system into two independent pathways, each with its own reservoir positioned adjacent to the corresponding piston. This eliminates the long fluid flow path that was susceptible to clearance leakage. By placing reservoirs directly within or adjacent to the piston structures, the fluid pathway is minimized, reducing opportunities for leakage through clearances while maintaining reliable tension maintenance.

Inventive Principle:

Principle #1Segmentation

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 improves fluid flow efficiency and pressure distribution, ensuring consistent tension on engine chains or belts by allowing for faster fluid flow into high pressure chambers and reducing clearance leakage, resulting in more reliable and consistent tensioner performance.

Implementation Method 1

a check valve connected to the LPC to HPC inlet and configured to allow fluid to flow from the low pressure chamber to the high pressure chamber

Methodology Applied

Scientific EffectCheck valve one-way flow control: Valve

Implementation Method 2

a spring disposed within the high pressure chamber and applying a bias on the primary piston away from the bottom of the first bore

Methodology Applied

Scientific EffectSpring mechanical force: Spring

Implementation Method 3

the second check valve being connected between the second piston and the second bore LPC to HPC inlet to control the flow of fluid

Methodology Applied

Scientific EffectCheck valve flow control: Valve

Implementation Method 4

A primary piston is forced, by a high pressure within the piston chamber, to contact a tensioner arm to maintain tension on a chain or belt of an engine

Methodology Applied

Scientific EffectHydraulic pressure force: Hydraulic Press

Data Source

PatentUS11448293B2Variable force tensioner with internal reservoir technology primary bore

Publication Date: 2022.09.20 BORGWARNER INC

AI summary

A variable force tensioner (VFT) system that includes a primary piston split into two chambers disposed within a primary bore. The two chambers including a first low pressure chamber having a primary reservoir therein that feeds fluid through a check valve into a second high pressure chamber to control a biasing force on the primary piston. A piston bore clearance path can extend along a groove in the primary bore to feed oil back to the primary reservoir from the high pressure chamber.