Three-Bearing Motor-Gearbox Layout for Shaft Alignment

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Solution Overview

Problem

Existing motor systems with four bearings along a drive axis are costly and large, while two-bearing systems are inefficient; there is a need for a bearing architecture that reduces the number of bearings while maintaining alignment and torque transfer efficiency.

Innovation Solution

A three-bearing architecture is introduced, featuring a central bearing with separate race sections for interfacing with a gear shaft and a rotor shaft, allowing direct torque transfer between the gear shaft and rotor shaft without the central bearing being in the torque path.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If four bearings are used along a drive axis, then shaft alignment and torque transfer are maintained, but system cost and size increase

Engineering Contradiction:

Improveshaft alignmentVSAvoidnumber of bearings

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The central bearing is designed with a unified structure that combines two separate bearing functions into one component. The central bearing supports both the gear shaft and rotor shaft simultaneously, merging what would traditionally require four separate bearings (two for each shaft) into a single integrated component, thereby reducing system complexity while maintaining alignment functionality

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The central bearing performs multiple functions: it supports the gear shaft, supports the rotor shaft, and enables torque transfer between them. This multi-functional design allows one bearing to replace what would traditionally require multiple specialized bearings, reducing the total bearing count while maintaining all necessary support and alignment functions

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If two bearings are used for each shaft, then shaft support is provided, but the number of total bearings increases system cost and size

Engineering Contradiction:

Improveshaft supportVSAvoidtotal bearing count

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The central bearing merges the support functions for both the gear shaft and rotor shaft into a single component. Instead of using two separate bearings for each shaft (four total), the central bearing's unified structure provides simultaneous support for both shafts, reducing the total bearing count to three while maintaining adequate shaft support

Inventive Principle:

Principle #5Merging (Combining)

3Power

If the central bearing is in the torque path, then torque transfer is achieved, but torque transfer efficiency decreases

Engineering Contradiction:

Improvetorque transferVSAvoidtorque transfer efficiency

Core Design Contradiction:

PowerVSLoss of energy

Solution Approach 1:

The central bearing acts as an intermediary that enables torque transfer between the gear shaft and rotor shaft through its dual race section design. The first race section interfaces with the gear shaft and the second race section interfaces with the rotor shaft, creating a mediated torque path that allows efficient torque transfer while maintaining bearing support functions

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The central bearing is segmented into two separate race sections: a first race section for the gear shaft and a second race section for the rotor shaft. This segmentation allows each race section to be optimized for its specific interface while maintaining overall bearing integrity, enabling efficient torque transfer through the bearing without requiring the bearing to be in the direct torque path

Inventive Principle:

Principle #1Segmentation

4Reliability

If shafts are aligned using multiple bearings, then alignment is maintained, but independent serviceability is reduced

Engineering Contradiction:

Improveshaft alignmentVSAvoidindependent serviceability

Core Design Contradiction:

ReliabilityVSEase of repair

Solution Approach 1:

The central bearing is segmented into two separate race sections that can interface with different shafts independently. The first race section can interface with the gear shaft while the second race section interfaces with the rotor shaft, allowing each shaft to be serviced independently by removing only the necessary race section or shaft without requiring removal of both shafts and all bearings

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS12241538B2Bearing architecture for high-speed motor drive systems

Publication Date: 2025.03.04 RIVIAN HOLDINGS LLC

AI summary

A drive system includes a motor and a gearbox. A three-bearing architecture is used to constrain a rotor shaft of the motor and a gear shaft of the gearbox. A first bearing interfacing with the gear shaft, a second bearing interfacing to the rotor shaft, and a central bearing are arranged between the first and second bearings. The central bearing includes a first race section configured to interface with the gear shaft and a second race section for interfacing to the rotor shaft. The first race section and the second race section are separate from each other and may be axially proximate to each other. The gear shaft includes a first section configured to interface with an inner race of the central bearing, and a second section configured to interface with the rotor shaft. The first and second sections are separate and may include the same pitch circle diameter.