Segmented Fixed Bearing Structure for Compact Steering Gear Load Capacity

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Solution Overview

Problem

Conventional power steering systems face issues with gear backlash due to component tolerances, thermal expansions, and wear, leading to undesirable noises during alternating steering, and large ball bearings required for high load-carrying capacity occupy excessive space.

Innovation Solution

A fixed bearing design featuring a ball bearing with double-curved guide grooves and multi-part bearing shells allows for a compact, high-load-bearing capacity configuration, where the inner and outer bearing shells are formed by separate partial shells, enabling a large overlap of guide grooves with balls and reducing the need for extensive installation space.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If single-row deep groove ball bearings with one-piece bearing races are used, then the bearing structure is simple and easy to manufacture, but the load-bearing capacity is insufficient due to limited guide groove overlap with balls

Engineering Contradiction:
Improvebearing structure simplicityVSAvoidload-bearing capacity
Core Design Contradiction:
Ease of manufactureVSStrength

Solution Approach 1:

The bearing race is divided into multiple separate guide groove elements instead of using a single one-piece race. This segmentation allows each guide groove element to be optimally positioned to maximize overlap with the balls, thereby increasing load-bearing capacity while maintaining manufacturing simplicity through modular components.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The guide grooves are designed with double curvature (in both circumferential and radial directions) rather than simple single-curvature grooves. This dimensional enhancement in groove geometry increases the contact area and overlap with balls, significantly improving load-bearing capacity without requiring larger bearing dimensions.

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

2Strength

If large ball bearings are used to maximize contact area on the raceway, then the load-bearing capacity increases, but the installation space required becomes excessively large

Engineering Contradiction:
Improveload-bearing capacityVSAvoidinstallation space
Core Design Contradiction:
StrengthVSVolume of moving object

Solution Approach 1:

The geometry parameters of the guide grooves are changed from conventional single-curvature to double-curvature design. This parameter modification increases the effective contact area and overlap with balls within the same bearing dimensions, achieving higher load-bearing capacity without increasing the overall bearing size or installation space requirements.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

By using multiple segmented guide groove elements instead of a single large race, the bearing achieves increased effective contact area through optimized positioning of individual groove segments. This allows maximum ball-raceway overlap within compact dimensions, improving load capacity without requiring larger bearing outer dimensions.

Inventive Principle:
Principle #1Segmentation

3Strength

If the guide groove shoulders overlap the balls radially to the maximum extent possible, then the load-bearing capacity under tilting load increases, but the annular gap between bearing races must be minimized, complicating assembly

Engineering Contradiction:
Improveload-bearing capacity under tilting loadVSAvoidassembly complexity
Core Design Contradiction:
StrengthVSDevice complexity

Solution Approach 1:

The bearing race is segmented into multiple separate guide groove elements that can be independently positioned and assembled. This segmentation allows optimal radial overlap of guide groove shoulders with balls for maximum load-bearing capacity, while the modular nature of separate elements simplifies assembly compared to precision-machined one-piece races requiring minimal annular gaps.

Inventive Principle:
Principle #1Segmentation

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This design effectively minimizes gear backlash and noise during alternating steering while maintaining a compact size, enhancing the load-carrying capacity and service life of the ball bearing.

Implementation Method 1

The outer ring and the bearing sleeve are connected by several torsion bars that are twisted when the outer ring is rotated relative to the bearing sleeve. After assembly of the steering gear, the torsion bars are twisted in such a way that the resulting elastic restoring effect causes the rebound of the pinion shaft.

Methodology Applied
Scientific EffectElasticity: Elasticity

Data Source

PatentEP3538418B1Fixed bearing and steering gear
Publication Date: 2021.03.31 ROBERT BOSCH GMBH
  • EP3538418B1 patent drawingFigure 1~2
  • EP3538418B1 patent drawingFigure 3~6

AI summary

The invention relates to a fixed bearing (6) for a steering gear, comprising a ball bearing (9), which has an inner bearing shell (27) provided for holding a pinion shaft of the steering gear and an outer bearing shell (26), which is held in a bearing sleeve (13), wherein the inner bearing shell (27) and the outer bearing shell (26) each have at least one guide groove (28) for holding and guiding balls (29) of the ball bearing (9), and comprising a pivot ring (14), which has an outer ring (16) and an inner ring (15), which are pivotably connected by means of one or more torsion webs (17), wherein the inner ring (15) is connected to the bearing sleeve (13) and the outer ring (16) is provided for mounting the fixed bearing (6) in a housing of the steering gear. Said fixed bearing is characterized in that the inner bearing shell (27) and/or the outer bearing shell (26) comprises at least two partial shells (30), each of which forms a separate guide groove (28) or a section of a guide groove (28). Since, according to the invention, the inner bearing shell (26) and/or the outer bearing shell (27) of the ball bearing (9) is of a multi-part design, the shoulders of the guide grooves (28) can be made relatively large, whereby correspondingly high load-bearing capacity of the ball bearing (9) is achieved even in the case of a relatively high tilting load, which can occur during the operation of a steering gear comprising the ball bearing (9).