EV Transmission with Form-Locking Shift Elements

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing electric vehicle transmissions lack an efficient mechanism to realize multiple gears for integrating high-speed electric machines, leading to inefficiencies and increased production costs due to the need for bearings and lubrication in planetary gear sets.

Innovation Solution

An electric vehicle transmission design featuring three planetary gear sets with fixed connections and actuable shift elements allows for different gear ratios between the input and output shafts, eliminating the need for bearings in certain areas and reducing drag losses by using form-locking shift elements, thereby achieving a compact and efficient power transmission system.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If multiple planetary gear sets are used to achieve different gear ratios, then the adaptability for integrating high-speed electric machines is improved, but the device complexity increases due to the need for bearings and lubrication systems

Engineering Contradiction:

Improveadaptability for integrating high-speed electric machinesVSAvoidcomplexity of planetary gear sets with bearings and lubrication

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The transmission system is divided into multiple independent planetary gear sets (first, second, and third planetary gear sets), each capable of providing different gear ratios. This segmentation allows the system to achieve multiple gears while maintaining simpler individual components that don't all require bearings and lubrication simultaneously.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent employs shift elements that can dynamically connect or disconnect different planetary gear sets based on the required gear ratio. This dynamic reconfiguration allows the system to adapt to different operating conditions and electric machine speeds without requiring all gear sets to be permanently engaged with complex bearing and lubrication systems.

Inventive Principle:

Principle #15Dynamics

2Ease of manufacture

If fixed connections are used in planetary gear sets, then production costs are reduced by eliminating bearings, but the ability to shift between different gears is limited

Engineering Contradiction:

Improveproduction costs reduced by eliminating bearingsVSAvoidability to shift between different gears

Core Design Contradiction:

Ease of manufactureVSAdaptability or versatility

Solution Approach 1:

Shift elements are introduced as intermediary components that selectively connect or disconnect the fixed planetary gear sets. These shift elements enable gear ratio changes without requiring the planetary gear sets themselves to have complex movable bearing structures, thus maintaining the cost benefits of fixed connections while restoring gear-shifting capability.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Loss of energy

If form-locking shift elements are used instead of bearings, then rotational losses are minimized, but the mechanism for achieving different gear ratios becomes more complex

Engineering Contradiction:

Improverotational losses in planetary gear setsVSAvoidcomplexity of form-locking shift element mechanism

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The patent replaces traditional bearing-based mechanical support systems with form-locking shift elements that use geometric interlocking (such as claw-shaped engagement) to transmit torque. This substitution eliminates the sliding friction and rotational losses associated with bearings, achieving more efficient power transmission despite the increased complexity of the shifting mechanism.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS11668380B2Electric vehicle transmission

Publication Date: 2023.06.06 ZF FRIEDRICHSHAFEN AG

AI summary

An electric vehicle transmission (7) includes an input shaft (10), an output shaft (11), a first planetary gear set (P1), a second planetary gear set (P2), and a third planetary gear set (P3). The input shaft (10) is provided for coupling to an electric machine (6). A first shift element (A), a second shift element (B), and a third shift element (C) are provided at least functionally as well. Also disclosed is a drive system (4), a vehicle drive train (5), and an electric vehicle.