Shift Gearbox With Switchable Planetary Stage

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Solution Overview

Problem

Existing shift gearboxes with spur gears on the rotor shaft are engaged permanently, making simple gear shifting complex and inefficient, and the freewheel clutch is bypassed when the other clutch is closed, leading to torque transmission issues.

Innovation Solution

A shift gearbox design incorporating a switchable planetary stage connected to the output shaft, with a single-direction clutch allowing power flow only in the first gear and immobilizing the planetary stage for shifting into the second gear, using a freewheel or jaw clutch for recuperation, and a dry-running brake for efficient actuation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If spur gears on the rotor shaft are permanently engaged, then torque transmission is ensured, but gear shifting becomes complex and inefficient

Engineering Contradiction:

Improvetorque transmissionVSAvoidgear shifting efficiency

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent employs a switchable planetary stage that can dynamically change between engaged and disengaged states. The planetary stage is connected to the output shaft and can be selectively activated to provide different gear ratios, allowing the gearbox to adapt its transmission characteristics based on operating conditions while maintaining simple shifting mechanics

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The transmission system is segmented into distinct functional stages: a permanent spur gear stage for basic torque transmission and a switchable planetary stage for gear ratio variation. This segmentation allows each stage to perform its specific function optimally without interfering with the other, simplifying the overall shifting mechanism

Inventive Principle:

Principle #1Segmentation

2Adaptability or versatility

If the freewheel clutch is bypassed when the other clutch is closed, then alternative torque path is provided, but torque transmission issues occur

Engineering Contradiction:

Improvetorque path flexibilityVSAvoidtorque transmission

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The planetary stage acts as an intermediary element between the input and output shafts, providing a controlled alternative torque path when the single-direction clutch is bypassed. This intermediary mechanism ensures smooth torque transition and prevents transmission issues that would occur with direct clutch bypassing

Inventive Principle:

Principle #24Intermediary (Mediator)

3Ease of operation

If a switchable planetary stage is added for gear shifting, then simple gear shifting is enabled, but device complexity increases

Engineering Contradiction:

Improvegear shifting simplicityVSAvoidgearbox structure

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The planetary stage is merged with the existing single-direction clutch mechanism, sharing common mounting structures and control systems. This integration allows the planetary stage to provide additional gear ratio capabilities without requiring completely separate control and mounting systems, thereby limiting the increase in overall device complexity

Inventive Principle:

Principle #5Merging (Combining)

4Device complexity

If splash lubrication is used instead of oil pump, then device complexity is reduced, but lubrication effectiveness may be compromised

Engineering Contradiction:

Improvelubrication systemVSAvoidlubrication effectiveness

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The gearbox utilizes splash lubrication where the rotating planetary stage and gear components automatically generate lubrication by splashing oil throughout the housing. This self-service lubrication system eliminates the need for external oil pumps while maintaining adequate lubrication through the natural motion of the gear components themselves

Inventive Principle:

Principle #25Self-service

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

Enables simple and efficient gear shifting with minimal load on planetary gear components, high efficiency, and low slip losses, allowing for independent wheel drive with simultaneous shifting of both drives using a single actuator, and eliminates the need for an oil pump due to splash lubrication.

Implementation Method 1

a single-direction clutch (4) which permits a power flow only in the first gear (1)

Methodology Applied

Scientific EffectSingle-direction clutch mechanism: Ratchet

Implementation Method 2

The sun gear (17) preferably is immobilized by an actuator, such as a brake and particularly a dry-running brake

Methodology Applied

Scientific EffectFriction: Friction

Data Source

PatentUS9140335B2Shift gearbox for use with an electric machine

Publication Date: 2015.09.22 DR ING H C F PORSCHE AG

AI summary

A shift gearbox (1) has two gears. An input shaft (2) of the gearbox (1) can be driven by an electric machine (3). The input shaft (2) is connected via at least one single-direction clutch (4) to an output shaft (5) of the gearbox (1). A planetary stage (6) arranged parallel to the clutch (4) is connected to the output shaft (5) of the gearbox (1) for driving a wheel (30) of a motor vehicle, or an axle (7) that has wheels (30). The planetary stage (6) is switchable. A shift gearbox of this type permits simple shifting of the gears of the gearbox while being of simple design.