Dual-Path Power Shift Transmission for Asynchronous Gear Meshing

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Solution Overview

Problem

Conventional gear ratio changing assemblies in work vehicle transmissions require synchronous shifts, limiting flexibility and the ability to maintain a wide range of travel speeds, and often result in complex and costly power shift assemblies that exacerbate space constraints.

Innovation Solution

An electronically-variable, dual-path power shift transmission system that includes an input assembly, an electric machine, a variator with a single planetary set, and a power shift assembly with parallel countershafts and power shift clutches, allowing for asynchronous gear meshing and flexible gear ratio adjustments without the need for synchronous shifts.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If synchronous shifts are used in conventional gear ratio changing assemblies, then the transmission structure is simpler, but the flexibility and ability to maintain wide range of travel speeds is limited

Engineering Contradiction:

Improveflexibility and ability to maintain wide range of travel speedsVSAvoidcomplexity of power shift assembly

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The transmission system is divided into two independent parallel countershafts (first and second countershafts), each capable of receiving power independently from the variator. This segmentation allows asynchronous operation of gear meshing on each shaft, enabling flexible speed maintenance without requiring synchronous shifts across the entire transmission system.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system dynamically switches between different power flow paths using power shift clutches. The control system can selectively engage or disengage clutches to route power through different countershafts and gear combinations, allowing continuous adaptation to varying speed and torque requirements without fixed synchronous shift constraints.

Inventive Principle:

Principle #15Dynamics

2Adaptability or versatility

If conventional power shift assemblies are used to achieve wide power band, then the transmission can handle various speeds, but the assembly becomes more complex and costly

Engineering Contradiction:

Improvewide power band capabilityVSAvoidcomplexity and cost of power shift assembly

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The variator with single planetary set serves multiple functions: it can selectively receive rotational power from either the electric machine or the input assembly, and can sum both power sources simultaneously. This multi-functionality eliminates the need for separate dedicated mechanisms for each power source, reducing overall assembly complexity while maintaining wide power band capability.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The system employs asymmetric power flow paths through the two parallel countershafts, where each shaft can operate independently with different gear ratios and power levels. This asymmetry allows optimized power distribution across different operating conditions without requiring symmetric, redundant components, thereby reducing complexity and cost.

Inventive Principle:

Principle #4Asymmetry

3Power

If multiple power sources are combined using planetary arrangements, then the power delivery is enhanced, but the space constraints are exacerbated

Engineering Contradiction:

Improvepower delivery capabilityVSAvoidspace constraints

Core Design Contradiction:

PowerVSVolume of moving object

Solution Approach 1:

The variator combines multiple power sources (electric machine and input assembly) through a single planetary set into a unified rotational output. This merging approach consolidates what would otherwise require separate transmission paths and components, delivering enhanced power capability while minimizing the space required compared to multiple independent planetary arrangements.

Inventive Principle:

Principle #5Merging (Combining)

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 system provides a wide power band with reduced gear ratio step delta, enabling fewer shifts at low speeds and better control at higher speeds, while using smaller electric machines and reducing the complexity and cost of the power shift assembly.

Implementation Method 1

power shift clutches configured to dissipate energy from asynchronous gear meshing

Methodology Applied

Scientific EffectFriction: Friction

Implementation Method 2

The variator is configured to sum the rotational power from the electric machine and from the engine to provide a split-path rotational power

Methodology Applied

Scientific EffectMechanical Advantage: Mechanical Advantage

Data Source

PatentUS11585412B1Electronically-variable, dual-path power shift transmission for work vehicles

Publication Date: 2023.02.21 DEERE & CO

AI summary

A transmission includes an input assembly, an electric machine, a variator and a power shift assembly. The input assembly has directional clutches and is configured to receive rotational engine power. The variator has only a single planetary set configured to selectively receive rotational power from the electric machine and from the input assembly. The power shift assembly is configured to receive rotational power from the variator. Power shift clutches are configured to dissipate energy from asynchronous gear meshing and include a first power shift clutch carried by a first countershaft and a second power shift clutch carried by a second countershaft. The power shift assembly is configured to effect multiple different rotational power flows to effect unique gear ratios.