Hybrid Gearbox Torque Continuity via Epicyclic Coupling

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Solution Overview

Problem

Existing gearboxes in hybrid vehicles face challenges such as torque interruption during gear changes, high weight and cost due to conventional clutch mechanisms, and limited reliability and compactness, especially in vehicles requiring multiple gear steps like lorries and buses, with regenerative braking systems further affecting energy storage lifespan.

Innovation Solution

A gearbox design featuring two epicyclic gears with planet gear carriers connected to sun gears, allowing torque to be transferred without interruption and enabling regenerative braking, using coupling units to lock and unlock components for efficient torque distribution, and a control system to manage electrical machines for balanced operation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a conventional clutch mechanism is used to disconnect the input shaft from the combustion engine during gear changes, then gear changes can be performed, but torque interruption occurs and the mechanism becomes heavy and expensive

Engineering Contradiction:

Improvegear change capabilityVSAvoidtorque continuity

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent replaces the conventional mechanical clutch mechanism with an epicyclic gear system that uses planetary gears, sun gears, and ring gears to achieve gear changes without torque interruption. The epicyclic gear arrangement allows continuous torque transmission from the combustion engine through the planetary gear set to the output shaft, eliminating the need for clutch disengagement during gear changes.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent employs a composite gear system combining multiple gear types (planetary gears, sun gears, ring gears) working together in an integrated epicyclic arrangement. This composite mechanical system achieves both gear changing capability and continuous torque transmission, resolving the contradiction between operational flexibility and torque continuity.

Inventive Principle:

Principle #40Composite materials

2Ease of operation

If a conventional clutch mechanism is used for gear changes, then gear exchange is possible, but weight and cost increase

Engineering Contradiction:

Improvegear exchange capabilityVSAvoidclutch mechanism weight

Core Design Contradiction:

Ease of operationVSWeight of moving object

Solution Approach 1:

The patent merges the gear changing function and torque transmission function into a single epicyclic gear system. The planetary gear set simultaneously provides multiple gear ratios and maintains continuous torque connection, eliminating the need for a separate clutch mechanism and thereby reducing overall weight.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The epicyclic gear system performs multiple functions: it provides gear changing capability, maintains continuous torque transmission, and eliminates the need for a clutch mechanism. This multi-functional design reduces the total number of components and associated weight.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Weight of moving object

If the electrical machine has lower torque than the combustion engine, then the electrical machine can be smaller, but the combustion engine cannot transfer its highest torque to the gearbox

Engineering Contradiction:

Improveelectrical machine sizeVSAvoidtorque transfer capability

Core Design Contradiction:

Weight of moving objectVSPower

Solution Approach 1:

The patent uses the epicyclic gear system's inherent mechanical advantage and torque multiplication capability to overcome the electrical machine's lower torque output. The planetary gear arrangement can multiply torque from the combustion engine, allowing the smaller electrical machine to still enable the system to utilize the combustion engine's full torque potential through the gear ratio advantage.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Data Source

PatentEP2978623B1Gearbox for a hybrid powertrain and method to control such a gearbox

Publication Date: 2019.05.08 SCANIA CV AB

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AI summary

A gearbox comprising an input shaft (8) and an output shaft (20); a first epicyclic gear (10) that is connected to the input shaft (8); a second epicyclic gear (12) that is connected to the first epicyclic gear (10); a first electrical machine (14) that is connected to the first epicyclic gear (10); a second electrical machine (16) that is connected to the second epicyclic gear (12); a first gear pair (60) that is arranged between the first epicyclic gear (10) and the output shaft (20); and a second gear pair (66) that is arranged between the second epicyclic gear (12) and the output shaft (20); A first planet gear carrier (50) at the first epicyclic gear (10) is connected to a second sun gear (32) at the second epicyclic gear (12); a first sun gear (26) at the first epicyclic gear (10) is connected to a first main shaft (34); and a second planet gear carrier (51) at the second epicyclic gear (12) is connected to a second main shaft (36). The invention concerns also a vehicle (1) that comprises such a gearbox (2), and a method to control such a gearbox (2). The invention concerns also a computer program (P) to control a gearbox, and a computer program product comprising program code for an electronic control unit (48) or another computer (53) in order to implement the method according to the invention.