Steering Joint Yoke Clamp Structure for Higher Torsional Stiffness

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Solution Overview

Problem

Existing ball joints in motor vehicle steering systems face issues with high shear and bending loads, leading to potential twisting and deformation, particularly due to continuous clamping slots that weaken axial shear stiffness.

Innovation Solution

The design incorporates closed clamping slots with a meandering bridge between them, where the bridge is connected to the bottom sections of the slots in opposite circumferential directions, enhancing shear and torsional stiffness by absorbing axial shear stresses and reducing twisting.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If continuous clamping slots are used to clamp the ball joint to the steering shaft, then the clamping connection is achieved, but the axial shear stiffness is weakened leading to twisting and deformation

Engineering Contradiction:
Improveclamping connectionVSAvoidaxial shear stiffness
Core Design Contradiction:
ReliabilityVSStrength

Solution Approach 1:

The continuous clamping slots are divided into separate individual slots spaced circumferentially around the connecting section. This segmentation prevents the formation of continuous shear stress paths that would cause twisting, while each slot still provides clamping function. The slots are arranged such that they do not form a continuous circumferential path, thereby maintaining shear stiffness.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The clamping slots are positioned at specific locations around the connecting section rather than being continuous. This local arrangement provides clamping where needed while preserving the overall structural integrity and shear stiffness of the connecting section. The slots are strategically placed to avoid creating weak planes that would compromise axial shear resistance.

Inventive Principle:
Principle #3Local quality

2Force

If the clamping slots extend along the entire length of the through-opening, then the clamping force is distributed, but the shear and bending loads on the clamping device increase

Engineering Contradiction:
Improveclamping force distributionVSAvoidshear and bending load capacity
Core Design Contradiction:
ForceVSStrength

Solution Approach 1:

The clamping force distribution is achieved through multiple discrete slots rather than a continuous slot. This segmentation allows the clamping force to be applied at multiple points around the circumference, distributing the load effectively while avoiding the creation of long continuous lever arms that would increase bending moments and shear loads on the clamping device.

Inventive Principle:
Principle #1Segmentation

3Ease of manufacture

If complex manufacturing and assembly are avoided, then the production process is simplified, but the connection rigidity may be compromised

Engineering Contradiction:
Improvemanufacturing and assembly simplicityVSAvoidconnection rigidity
Core Design Contradiction:
Ease of manufactureVSStrength

Solution Approach 1:

The segmented slot design can be easily manufactured using standard machining operations such as drilling and slotting. The discrete nature of the slots simplifies the manufacturing process compared to creating complex continuous structures, while the strategic arrangement of slots maintains the required connection rigidity and torsional stiffness.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The clamping function and the structural reinforcement function are merged into a single feature set. The same slots that provide clamping also serve to reinforce the connecting section by providing material removal patterns that enhance stiffness while maintaining ease of manufacture.

Inventive Principle:
Principle #5Merging (Combining)

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 configuration provides a more torsionally rigid connection, minimizing twisting and deformation, while allowing for a compact, reliable, and easy-to-assemble arrangement with improved torque transmission.

Implementation Method 1

the clamping means is designed to exert a clamping force on the slots during clamping, directed towards a reduction of the slot width, whereby the inner cross-section of the through-hole is narrowed and clamped to the steering shaft by friction

Methodology Applied
Scientific EffectFriction: Friction

Implementation Method 2

a bridge is arranged meanderingly between the clamping slots, such that one end of the bridge is connected circumferentially to the bottom section of one of the clamping slots and the other end of the bridge is connected to the bottom section of the other clamping slot in the opposite circumferential direction

Methodology Applied
Scientific EffectShear stress: Shear Stress

Data Source

PatentEP4377582B1Joint yoke, universal joint, steering shaft and steering system for a motor vehicle
Publication Date: 2025.12.24 THYSSENKRUPP PRESTA AG
  • EP4377582B1 patent drawingFigure 1~2
  • EP4377582B1 patent drawingFigure 3~6
  • EP4377582B1 patent drawingFigure 7~8

AI summary

The present invention relates to a joint head (4), comprising a joint fork having two arms (43) which are opposite relative to an axis (L) and protrude axially from a connecting portion (41) which has an axially continuous through-opening (42) and which has two clamping slots (5, 6) spaced apart in the circumferential direction and a tensioning means (8), wherein the clamping slots (5, 6) each extend in a slot direction and have an open slot width transverse thereto, and the tensioning means (8) is designed to exert a tensioning force, directed to reducing the slot width, on the slots (5, 6) during tensioning. According to the invention, in order to allow an improved, more torsion-resistant connection of a joint head (4), the clamping slots (5, 6) extend from a slot opening (51, 61) to a slot bottom (52, 62), and a bridge (7) is arranged in a serpentine-like manner between the clamping slots (5, 6).