Stepped Planetary Transmission Axial Length Reduction

Solution Overview

Problem

Existing motor vehicle transmissions with five or more shafts in speed order require significant construction complexity and increased axial length, which is a challenge for compact designs, especially in transversely mounted vehicles where space is limited.

Innovation Solution

A transmission design featuring a first stepped planetary gear set with at least two central gears of different diameters and a second planetary gear set with a constant sun gear-ring gear coupling, allowing for a compact axial layout by arranging interconnected central gears radially and integrating the webs with the output shaft, thereby achieving a short overall axial length.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a planetary gear set system with five or more shafts in speed order is implemented, then a high degree of freedom for gear formation is achieved, but construction complexity and axial length increase significantly

Engineering Contradiction:

Improvegear formation freedomVSAvoidconstruction complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent implements nested planetary gear sets where a second planetary gear set is positioned inside the first planetary gear set. The second gear set's planet gears are arranged within the annular space between the first gear set's planet gears and the first ring gear. This nesting arrangement allows five shafts in speed order to be achieved while maintaining compact construction and avoiding excessive axial length increase.

Inventive Principle:

Principle #7Nested doll (Nesting)

2Adaptability or versatility

If a planetary gear set system with five or more shafts in speed order is implemented, then a high degree of freedom for gear formation is achieved, but the axial length of the transmission increases

Engineering Contradiction:

Improvegear formation freedomVSAvoidaxial length

Core Design Contradiction:

Adaptability or versatilityVSLength of stationary object

Solution Approach 1:

The patent implements nested planetary gear sets where a second planetary gear set is positioned inside the first planetary gear set. The second gear set's planet gears are arranged within the annular space between the first gear set's planet gears and the first ring gear. This nesting arrangement allows five shafts in speed order to be achieved while maintaining compact construction and avoiding excessive axial length increase.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

Instead of arranging planetary gear sets axially (one after another along the axis), the patent positions the second planetary gear set radially within the plane of the first gear set. This dimensional change from axial stacking to radial nesting significantly reduces the axial length while still achieving five shafts in speed order through the combined gear sets.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Adaptability or versatility

If dual planet gears with two sun gears and two ring gears are used, then six shafts in speed order are achieved, but the overall axial length increases due to axial arrangement

Engineering Contradiction:

Improvespeed order shaftsVSAvoidaxial length

Core Design Contradiction:

Adaptability or versatilityVSLength of stationary object

Solution Approach 1:

The patent implements nested planetary gear sets where a second planetary gear set is positioned inside the first planetary gear set. The second gear set's planet gears are arranged within the annular space between the first gear set's planet gears and the first ring gear. This nesting arrangement allows five shafts in speed order to be achieved while maintaining compact construction and avoiding excessive axial length increase.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The patent merges the functionality of multiple planetary gear sets by firmly connecting the first sun gear to the second ring gear, and the first carrier to the second carrier. This merging creates a integrated gear system where the two gear sets work together to produce five shafts in speed order without requiring separate axial arrangements, thereby reducing overall axial length.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentEP3147539B1Transmission for a motor vehicle

Publication Date: 2020.11.25 ZF FRIEDRICHSHAFEN AG

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AI summary

Transmission (G) for a motor vehicle, comprising a first planetary gear set (P1) designed as a stepped planetary gear set and a second planetary gear set (P2), wherein the planet gears (PL1) of the first planetary gear set (P1) have at least two different effective diameters, wherein the first planetary gear set (P1) has at least three central gears (E111, E112, E311, E312) formed by a ring gear (E311) and two sun gears (E111, E112) or by two ring gears (E311, E312) and a sun gear (E111), wherein the two sun gears (E111, E112) or the two ring gears (E311, E312) are assigned to different effective diameters of the planet gears (PL1), wherein the second planetary gear set (P2) has two central gears (E12, E32) in the form of a sun gear and a ring gear, wherein one of the central gears (E12, E32) of the second planetary gear set (P2) is permanently and rotationally fixedly connected to one of the central gears (E111, E112, E311, E312) of the first planetary gear set (P1),wherein the central gear (E12, E32) of the second planetary gear set (P2) differs from the type of central gear (E111, E112, E311, E312) of the first planetary gear set (P1) to which it is permanently non-rotatably connected, and is arranged in a common gear set plane (RSE) with this central gear (E111, E112, E311, E312), and wherein a web (E21) of the first planetary gear set (P1) is permanently non-rotatably connected to a web (E22) of the second planetary gear set (P2).