Continuously Variable Transmission Drive Belt Width Variation

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Solution Overview

Problem

The existing drive belts with transverse members of different thicknesses experience uneven axial load and clamping force distribution due to tilting and radial sliding, leading to irregular contact with pulley sheaves and increased wear.

Innovation Solution

The width of thinner transverse members is increased relative to thicker ones to achieve similar axial loads, with a proportionate adjustment of width dimensions matching thickness differences, ensuring more uniform clamping force across all members.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If transverse members of different thicknesses are used to reduce clearance and attenuate noise, then the amount of clearance between transverse members is reduced and noise is attenuated, but the axial load distribution becomes uneven leading to irregular contact with pulley sheaves

Engineering Contradiction:
Improvecontact regularityVSAvoidload distribution uniformity
Core Design Contradiction:
ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent applies local quality by making the width of transverse members dependent on their thickness. Thinner transverse members have greater width while thicker members have lesser width, creating locally adapted properties that compensate for thickness variations. This ensures uniform axial load distribution across all transverse members despite their different thicknesses, resolving the contradiction between clearance reduction and load uniformity.

Inventive Principle:
Principle #3Local quality

2Length of stationary object

If thinner transverse members are used to reduce clearance, then the clearance between members is reduced, but these members experience lesser axial load leading to irregular contact patterns

Engineering Contradiction:
Improveclearance between membersVSAvoidaxial load on thinner members
Core Design Contradiction:
Length of stationary objectVSForce

Solution Approach 1:

The patent changes the parameters of transverse members by introducing a width parameter that varies with thickness. Thinner members are given greater width to compensate for their reduced thickness, thereby equalizing the axial load they experience. This parameter change resolves the contradiction by maintaining both reduced clearance and uniform load distribution.

Inventive Principle:
Principle #35Parameter changes

3Stability of the object's composition

If transverse members of uniform thickness are used, then the axial load distribution is uniform, but the clearance between members increases and noise attenuation is reduced

Engineering Contradiction:
Improveload distribution uniformityVSAvoidnoise from member impact
Core Design Contradiction:
Stability of the object's compositionVSObject-generated harmful factors

Solution Approach 1:

The patent applies local quality by introducing width variation as a local property that compensates for thickness variation. Instead of using uniform thickness members that generate noise and excessive clearance, the patent creates members with locally adapted width-thickness relationships. This resolves the contradiction by maintaining both low clearance for noise attenuation and uniform load distribution.

Inventive Principle:
Principle #3Local quality

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 configuration ensures a more continuous and regular contact with pulley sheaves, reducing wear and improving the operational efficiency of the drive belt by equalizing axial loads on transverse members.

Implementation Method 1

The friction contact between the transverse members and the conical pulley sheaves allows a force to be transmitted there between, such that the drive belt can transfer a drive torque and rotational movement from one transmission pulley to the other.

Methodology Applied
Scientific EffectFriction: Friction

Data Source

PatentEP2798238B1Drive belt comprising different types of transverse members for a continuously variable transmission
Publication Date: 2020.04.15 ROBERT BOSCH GMBH
  • EP2798238B1 patent drawingFigure 1~3
  • EP2798238B1 patent drawingFigure 4~6

AI summary

The invention relates to a drive belt (3) including an endless carrier (31) and a plurality of transverse members (32) of varying thickness, i.e. the dimension measured in the circumference direction of the belt (3). According to the invention, the design of such drive belt (3) can be improved, at least in terms of durability, by also varying the width, i.e. the dimension measured in the axial direction "W" of the drive belt (3), of the transverse members (32) in such a way that the thinner transverse members (32) of the drive belt (3) are of a larger width than the thicker transverse members (32) thereof.