Automatic Planetary Transmission with Four Gear Sets

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Solution Overview

Problem

Existing automatic transmissions in planetary design face challenges in achieving a high number of gears with a wide gear ratio spread while minimizing construction expenditure and avoiding grouped shifting, while maintaining a compact and cost-effective design.

Innovation Solution

The automatic transmission incorporates seven shift elements and four planetary gear sets, with the option to replace minus planetary gear sets with plus sets, allowing for a compact and cost-effective design that supports a wide range of gear ratios, including additional launching and overdrive gears, and enabling sequential shifting without grouped shifting.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the number of planetary gear sets and shift elements is increased to achieve a high number of gears with wide gear ratio spread, then the transmission capability is improved, but the construction expenditure and device complexity increase

Engineering Contradiction:

Improvenumber of gears and gear ratio spreadVSAvoidnumber of shift elements and construction expenditure

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The transmission is divided into two independent gear sets: an upstream gear set with two planetary gear sets and a main gear set with two planetary gear sets. Each gear set can operate independently or in combination, allowing multiple gear ratios to be achieved through different combinations of engaged clutches and brakes rather than requiring a single complex gear train with many components.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The four planetary gear sets serve multiple functions: they can operate individually to provide different gear ratios, or in combination to achieve additional ratios. The same physical components (planetary gear sets, clutches, brakes) fulfill multiple gear ratio functions, reducing the need for dedicated components for each gear ratio and thereby lowering overall device complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Ease of operation

If more shift elements are used to enable sequential shifting without grouped shifting, then the shifting precision is improved, but the device complexity and construction expenditure increase

Engineering Contradiction:

Improvesequential shifting without grouped shiftingVSAvoidnumber of shift elements

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The shifting function is segmented across two independent gear sets, each with its own set of clutches and brakes. This segmentation allows one gear set to shift while the other remains engaged, enabling sequential shifting without grouped shifting where only one shift element changes state at a time, thereby achieving precise sequential control.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The transmission employs hydraulically actuatable clutches and brakes that can be dynamically engaged and disengaged in sequence. The dynamic control of these shift elements allows for smooth, sequential gear changes without the need for multiple shift elements simultaneously, optimizing the balance between shifting precision and device complexity.

Inventive Principle:

Principle #15Dynamics

3Device complexity

If a compact design with fewer components is used to reduce construction expenditure, then the device complexity is reduced, but the capability to achieve high gear ratio spread and multiple gears is limited

Engineering Contradiction:

Improveconstruction expenditure and component countVSAvoidgear ratio spread and number of gears

Core Design Contradiction:

Device complexityVSAdaptability or versatility

Solution Approach 1:

Two complete planetary gear sets are merged into a single transmission unit, with the upstream gear set and main gear set connected through shared input and output shafts. This merging allows the transmission to achieve a wide gear ratio spread and multiple gears using a compact arrangement of components rather than requiring separate gear trains for each ratio, thereby reducing overall component count and construction expenditure.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The upstream gear set and main gear set are nested within a shared housing structure with common input and output shafts. This nesting arrangement allows multiple planetary gear sets to be packed into a compact space, achieving high gear ratio spread and multiple gears without proportionally increasing the transmission's external dimensions or component count.

Inventive Principle:

Principle #7Nested doll (Nesting)

Data Source

PatentUS10428909B2Automatic planetary transmission

Publication Date: 2019.10.01 ZF FRIEDRICHSHAFEN AG

AI summary

An automatic transmission with housing, input shaft, output shaft, four planetary gear sets, and six shift elements. Second element of second planetary gear set forms first shaft; second element of third planetary gear set forms second shaft; first elements of first and second planetary gear sets form third shaft; third element of third planetary gear set forms fourth shaft; second element of first planetary gear set and third element of second planetary gear set form fifth shaft; third element of first planetary gear set forms sixth shaft; first elements of third and fourth planetary gear sets form seventh shaft; and third element of fourth planetary gear set forms eighth shaft. First shift element is between third shaft and housing; second shift element is between fourth shaft and housing; third shift element is between second and eighth shafts; fourth shift element is between fourth and fifth shafts; fifth shift element is between fifth and seventh shafts; sixth shift element is between sixth and seventh shafts.