Start-Assist Engine Transmission for Low-Drag Gear Engagement

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Solution Overview

Problem

Engines face significant drag and wear issues during initial engagement with driven loads due to inertia, particularly during cold start-ups, which leads to undesirable wear on gearing systems.

Innovation Solution

The implementation of an epicyclic gear train with a brake mechanism that allows free rotation of gears to prevent power transfer from the primary power source to the power output, and the use of a start assist motor to rotate the power output, enabling decoupling of the power sources and reducing drag during engine start-up.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the primary power source is directly engaged with the driven load during engine start-up, then power transfer is immediate, but significant drag and wear occur on the gearing system due to the inertia of the driven load

Engineering Contradiction:

Improvegearing system durabilityVSAvoiddrag on gearing system

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The power transfer path is segmented into two independent paths: one through the epicyclic gear train for normal operation, and another through the start assist motor for initial rotation. This segmentation allows the driven load to be decoupled from the primary power source during start-up, eliminating drag on the gearing system while maintaining the ability to transfer power when needed.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The start assist motor acts as an intermediary device that provides the initial rotation needed to overcome the inertia of the driven load. By introducing this intermediate power source, the system avoids direct engagement between the primary power source and the high-inertia load, preventing gear wear and drag during the critical start-up phase.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Power

If the brake is engaged to transfer power from the first power source to the power output, then power transfer is efficient, but the start assist motor cannot provide initial rotation

Engineering Contradiction:

Improvepower transfer efficiencyVSAvoidinitial rotation capability

Core Design Contradiction:

PowerVSEase of operation

Solution Approach 1:

The system dynamically transitions between two operational states: during start-up, the brake is disengaged to allow the start assist motor to rotate the power output; once rotation is achieved, the brake is engaged to transfer power efficiently from the primary power source. This dynamic switching resolves the contradiction by allowing both functions at different times in the operational sequence.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The start assist motor performs the preliminary action of rotating the power output before the brake is engaged for power transfer. This preliminary rotation overcomes the static inertia of the driven load, preparing the system for efficient power transfer once the brake is applied.

Inventive Principle:

Principle #10Preliminary action

3Object-affected harmful factors

If the epicyclic gear train allows free rotation to prevent power transfer, then drag is minimized, but power cannot be transferred to the power output

Engineering Contradiction:

Improvedrag during start-upVSAvoidpower transfer capability

Core Design Contradiction:

Object-affected harmful factorsVSPower

Solution Approach 1:

The system employs periodic action by alternating between two states: free rotation of the epicyclic gear train during start-up to minimize drag, and brake engagement to transfer power when the engine is running. This periodic switching between decoupled and coupled states resolves the contradiction by ensuring the correct state is active at the appropriate time in the operational cycle.

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

This solution effectively reduces drag and wear on engine systems by allowing the engine to start without rotating the driven load, minimizing friction losses and extending the lifespan of gearing components.

Implementation Method 1

braking one of the gears of the epicyclic gear train to transfer power from the first power source to the power output

Methodology Applied

Scientific EffectFriction: Friction

Implementation Method 2

rotating the power output using a start assist motor

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS11028778B2Engine with start assist

Publication Date: 2021.06.08 PRATT & WHITNEY CANADA CORP

AI summary

An engine includes a first power source configured to drive a first power input, a power output, and a transmission engaged with the first power input and the power output. The transmission includes an epicyclic gear train engaged with the first power input and selectively engageable with the power output. A brake is engageable in a drive condition with the epicyclic gear train to transfer power from the first power input to the power output. The brake in a start condition is disengageable to decouple the first power input from the power output. A start assist motor associated with a second power source is engaged with the transmission to rotate the power output.