Multi-speed Gearbox with Four Planetary Sets and Five Clutches

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Solution Overview

Problem

Existing automatic transmissions for motor vehicles with planetary designs face challenges in achieving a sufficient number of forward gears and a reverse gear with a high overall transmission-ratio spread while minimizing gearshifting elements and avoiding double shifts during sequential shifting.

Innovation Solution

A multi-speed transmission design utilizing four planetary gearsets and five gearshifting elements (two brakes and three clutches) to achieve eight forward gears and one reverse gear, with coordinated gearshifting to maintain efficiency and reduce drag losses.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the number of forward gears and reverse gear is increased to achieve a high overall transmission-ratio spread, then the versatility and adaptability of the transmission is improved, but the device complexity and the number of gearshifting elements increase

Engineering Contradiction:

Improvenumber of forward gears and reverse gearVSAvoidnumber of gearshifting elements

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The transmission is divided into four independent planetary gearsets (first, second, third, and fourth), each capable of providing different gear ratios. This segmentation allows the system to achieve a wide transmission-ratio spread with multiple forward gears and reverse gear without requiring a proportional increase in gearshifting elements, as each planetary gearset can be selectively engaged to provide different gear stages.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The five gearshifting elements (two brakes and three clutches) are designed to serve multiple functions across different gearsets and operating conditions. Each gearshifting element can engage different planetary gearsets to provide various forward gears and reverse gear, allowing a minimal number of elements to control a large number of gears through coordinated engagement patterns.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Adaptability or versatility

If more gearshifting elements are added to achieve more gears, then the adaptability is improved, but the drag losses and energy consumption increase

Engineering Contradiction:

Improvenumber of gearsVSAvoiddrag and gear losses

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The transmission employs a minimal number of gearshifting elements (only five elements: two brakes and three clutches) to control four planetary gearsets, using partial engagement of available elements rather than requiring one element per gear. This partial action approach reduces the number of simultaneously engaged friction elements, thereby minimizing drag losses and energy consumption while still achieving eight forward gears and one reverse gear.

Inventive Principle:

Principle #16Partial or excessive action

3Adaptability or versatility

If the number of planetary gearsets is increased to achieve more gears, then the transmission-ratio spread is improved, but the device complexity and construction difficulty increase

Engineering Contradiction:

Improvetransmission-ratio spreadVSAvoidconstruction complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

4Productivity

If coordinated gearshifting is implemented to avoid double shifts, then the productivity and shifting efficiency are improved, but the control complexity increases

Engineering Contradiction:

Improveshifting efficiencyVSAvoidcontrol complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The transmission design pre-establishes coordinated engagement patterns for the five gearshifting elements across the four planetary gearsets, where each gear stage has a predetermined combination of engaged elements. This preliminary arrangement of engagement patterns allows sequential shifting between gears to proceed efficiently without double shifts, as the control system can directly transition between predefined gear states rather than managing complex real-time coordination.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS8251855B2Multi-speed gearbox

Publication Date: 2012.08.28 ZF FRIEDRICHSHAFEN AG

AI summary

A transmission which comprises an input shaft and an output shaft, first, second, third and fourth planetary gear sets, third, fourth, fifth, sixth, seventh and eighth shafts, first, second, third, fourth and fifth gearshifting elements for achieving eight forward gears and one reverse gear. The first gearshifting element, when engaged, couples the third shaft with a housing of the transmission. The second gearshifting element, when engaged, couples the fourth shaft with the housing of the transmission. The third gearshifting element, when engaged, couples the input first shaft with the fifth shaft. The eighth shaft (8) is coupled with the fourth gearshifting element and the fifth gearshifting element (E), when engaged, couples the fifth shaft (5) and the seventh shaft (7).