Oscillating Rack CVT for Friction-Free Variable Speed Transmission

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Solution Overview

Problem

Conventional continuously variable transmissions (CVTs) rely on friction elements, which are expensive, have high maintenance requirements, and suffer from energy loss and potential catastrophic failure due to heat and wear, limiting their ability to achieve fast gear ratio changes compared to fixed gear ratio transmissions.

Innovation Solution

A CVT with oscillating racks that uses cams, racks, pinions, and intermittent shafts to achieve a continuously variable speed ratio without friction elements, utilizing a cam lobe profile that produces a rotational speed profile of A sin2(ωt) + A cos2(ωt), ensuring uniform circular rotation and reducing oscillatory disturbances.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If friction elements are used in conventional CVTs, then power transmission is achieved, but energy loss increases and reliability decreases due to heat and wear

Engineering Contradiction:

Improveenergy lossVSAvoidreliability

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The patent replaces the friction-based mechanical power transmission system with a positive displacement cam-rack-pinion mechanism. The cam lobes directly drive the racks which engage with pinions to transmit power, eliminating friction elements and their associated energy losses from heat and wear.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The invention extracts and removes the friction elements from the CVT system entirely. By eliminating belts, chains, or other friction-based power transmission components, the system avoids the energy loss and reliability issues inherent in friction-based mechanisms.

Inventive Principle:

Principle #2Taking out (Extraction)

2Ease of repair

If friction elements are used in conventional CVTs, then power transmission is achieved, but maintenance requirements increase and cost increases

Engineering Contradiction:

Improvemaintenance requirementsVSAvoidcost

Core Design Contradiction:

Ease of repairVSEase of manufacture

Solution Approach 1:

The patent substitutes the maintenance-intensive friction-based power transmission system with a positive displacement cam-rack-pinion mechanism that has no friction elements requiring maintenance, thereby reducing both maintenance requirements and overall system cost.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The cam-rack-pinion components are designed as durable, maintenance-free elements that eliminate the need for periodic replacement of friction elements, reducing long-term operational costs.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Speed

If friction elements are used in conventional CVTs, then continuous variable ratio is achieved, but speed of ratio change is limited

Engineering Contradiction:

Improvespeed of ratio changeVSAvoidenergy loss

Core Design Contradiction:

SpeedVSLoss of energy

Solution Approach 1:

The patent employs periodic oscillation of the racks driven by rotating cam lobes to achieve continuous variable ratio changes. The cam profile controls the rack oscillation amplitude, enabling rapid and precise speed ratio changes without the energy loss associated with friction-based continuous adjustment mechanisms.

Inventive Principle:

Principle #19Periodic action

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 CVT with oscillating racks eliminates the need for friction elements, improving fuel economy and reducing emissions by providing a nearly infinite number of speed ratios while maintaining uniform rotation and reducing energy loss, thus enhancing the reliability and efficiency of the transmission system.

Implementation Method 1

a plurality of cams that are coupled with the input shaft. The cams are configured to rotate with a rotation of the input shaft

Methodology Applied

Scientific EffectCam mechanism: Cam

Implementation Method 2

a plurality of racks that are coupled to respective cams. The racks are configured to oscillate with the rotation of the input shaft

Methodology Applied

Scientific EffectOscillation: Vibration

Implementation Method 3

a plurality of pinions that are coupled to respective racks

Methodology Applied

Scientific EffectGear mechanism: Gear

Implementation Method 4

a plurality of racks that are coupled to respective cams. The racks are configured to oscillate with the rotation of the input shaft

Methodology Applied

Scientific EffectRack and pinion: Rack and Pinion

Data Source

PatentUS11773951B1Continuously-variable transmission with oscillating racks

Publication Date: 2023.10.03 APTIV TECHNOLOGIES AG

AI summary

Described herein is a continuously variable transmission (CVT) with oscillating racks. The CVT includes an input shaft and a plurality of cams that are coupled with the input shaft. The cams are configured to rotate with a rotation of the input shaft. The CVT also includes a plurality of racks that are coupled to respective cams. The racks are configured to oscillate with the rotation of the input shaft. The CVT further includes a plurality of pinions that are coupled to respective racks and a plurality of intermittent shafts that are coupled with respective pinions. The CVT also includes an output shaft that is coupled with the intermittent shafts. The output shaft is configured to rotate with a uniform rotation and a speed ratio relative to the rotation of the input shaft. Because the CVT does not use friction elements, many downsides of conventional CVTs may be mitigated.