Compact Steering Gear Layout With Overlapping Reducer Stages

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Solution Overview

Problem

Conventional electric power steering systems are bulky due to the misalignment of the speed reducer and operating mechanism, leading to inefficient use of space.

Innovation Solution

The steering device is designed with a first gear mechanism that converts rotational direction and a second gear mechanism that decelerates, arranged to overlap each other along a common axial direction, incorporating a drive device that assists steering wheel operation, all within the width of the second gear mechanism, reducing the overall thickness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If the speed reducer and operating mechanism are disposed such that their axial directions intersect, then the functional requirements are met, but the device becomes bulky

Engineering Contradiction:
Improvefunctional requirementVSAvoiddevice size
Core Design Contradiction:
Ease of operationVSVolume of moving object

Solution Approach 1:

The patent merges the operating mechanism and speed reducer into a integrated unit where the operating mechanism is positioned within the width of the speed reducer along the axial direction. This combining of functions into a single compact structure reduces the overall device volume while maintaining both operational functionality and speed reduction capabilities

Inventive Principle:
Principle #5Merging (Combining)

2Ease of operation

If the first gear mechanism and second gear mechanism are arranged separately, then the functional requirements are met, but the device thickness increases

Engineering Contradiction:
Improvefunctional requirementVSAvoiddevice thickness
Core Design Contradiction:
Ease of operationVSLength of stationary object

Solution Approach 1:

The patent transitions from a sequential arrangement of gear mechanisms to an overlapping configuration where the first gear mechanism is positioned within the width of the second gear mechanism along the axial direction. This dimensional reorganization allows both mechanisms to occupy overlapping spatial zones, significantly reducing the overall thickness of the device

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

3Ease of operation

If the drive device is positioned outside the second gear mechanism, then the functional requirements are met, but the device becomes larger

Engineering Contradiction:
Improvefunctional requirementVSAvoiddevice volume
Core Design Contradiction:
Ease of operationVSVolume of moving object

Solution Approach 1:

The patent implements a nested arrangement where the drive device is positioned within the width of the second gear mechanism along the axial direction. This nesting of components allows the drive device to utilize the same spatial envelope as the second gear mechanism, minimizing the overall device volume while ensuring both components can function independently

Inventive Principle:
Principle #7Nested doll (Nesting)

Data Source

PatentEP4707128A1Steering device
Publication Date: 2026.03.11 NABTESCO CORP
  • EP4707128A1 patent drawingFigure 1A~1B
  • EP4707128A1 patent drawingFigure 2
  • EP4707128A1 patent drawingFigure 3

AI summary

A steering device (10) according to one aspect of the invention includes: a first gear mechanism (11) configured to receive rotation of steering wheel operation, convert a direction of the rotation, and output converted rotation as primary rotation; and a second gear mechanism (20) configured to receive the primary rotation output from the first gear mechanism (11), decelerate the primary rotation, and output decelerated rotation. When a second axial direction (F2) is defined as an axial direction of an output shaft (25) included in the second gear mechanism (20), the first gear mechanism (11) is located such that at least a portion of the first gear mechanism (11) falls within a width (H2) of the second gear mechanism (20) along the second axial direction (F2).