Hollow Stabilizer Quenching for Harder Bent Sections

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Solution Overview

Problem

Hollow stabilizers face challenges with low strength and flexural rigidity due to their hollow structure, and bent sections often experience insufficient quenching, leading to low hardness and increased stress concentrations.

Innovation Solution

A method for manufacturing a pipe-shaped hollow stabilizer with specific t/D ratio and enhanced quenching process, including clamping, coolant jetting, and swinging to ensure uniform hardness and improved fatigue resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Weight of moving object

If hollow structure is used for stabilizer, then weight is reduced, but mechanical strength and flexural rigidity deteriorate

Engineering Contradiction:
Improveweight of stabilizerVSAvoidmechanical strength and flexural rigidity
Core Design Contradiction:
Weight of moving objectVSStrength

Solution Approach 1:

The invention optimizes the t/D ratio parameter to be 0.18 or more but less than 0.275, which balances weight reduction with maintaining sufficient mechanical strength and flexural rigidity. This parameter optimization resolves the contradiction by finding the optimal range where the hollow structure provides weight savings while retaining adequate structural performance.

Inventive Principle:
Principle #35Parameter changes

2Ease of manufacture

If conventional quenching method is used, then manufacturing process is simple, but bent sections have insufficient hardness due to poor coolant access

Engineering Contradiction:
Improvesimplicity of quenching processVSAvoidhardness uniformity in bent sections
Core Design Contradiction:
Ease of manufactureVSManufacturing precision

Solution Approach 1:

The quenching process is segmented into two distinct stages: first quenching the arm sections, then quenching the bent sections after rotating the stabilizer by 90 degrees. This segmentation allows each section to receive adequate coolant exposure and achieve the required hardness, resolving the contradiction between process simplicity and hardness uniformity.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The stabilizer is dynamically repositioned (rotated 90 degrees) during the quenching process to change the orientation of bent sections relative to the coolant flow. This dynamic adjustment ensures that bent sections, which are difficult to cool effectively in the initial position, receive sufficient coolant exposure for proper hardening.

Inventive Principle:
Principle #15Dynamics

3Strength

If t/D ratio is increased to improve strength, then flexural rigidity is improved, but weight reduction benefit is diminished

Engineering Contradiction:
Improveflexural rigidityVSAvoidweight reduction benefit
Core Design Contradiction:
StrengthVSWeight of moving object

Solution Approach 1:

The invention defines an optimal t/D ratio range of 0.18 or more but less than 0.275, which balances flexural rigidity improvement with weight reduction benefits. By constraining the t/D ratio within this specific range, the invention prevents excessive wall thickness that would negate weight savings while ensuring sufficient structural strength.

Inventive Principle:
Principle #35Parameter changes

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

The method produces a high-strength, lightweight hollow stabilizer with improved hardness and fatigue resistance, particularly in bent sections, addressing the structural weaknesses of conventional hollow stabilizers.

Implementation Method 1

quenching the bent section by jetting a coolant onto an outer surface of an inner bend side of the bent section

Methodology Applied
Scientific EffectHeat transfer: Conduction (thermal)

Implementation Method 2

As the heat treatment, quenching and tempering are performed

Methodology Applied
Scientific EffectPhase transformation: Phase Change

Data Source

PatentEP3279016B1Hollow stabilizer
Publication Date: 2025.08.27 NHK SPRING CO LTD
  • EP3279016B1 patent drawingFigure 1A~1B
  • EP3279016B1 patent drawingFigure 2A~2B
  • EP3279016B1 patent drawingFigure 3

AI summary

A hollow stabilizer (1) has a tubular shape and is provided with: a torsion section (1a) that is provided to a vehicle and that extends in the vehicle width direction; an arm section (lb) that extends in the front-back direction of the vehicle; and bent sections (1c, 1c) that connect the torsion section (1a) and the arm section (lb). The hollow stabilizer (1) is characterized in that the hardness of the outer surface (1e) of the bent inner sides (lcl, 1c2) of the bent sections (1c, 1c) is 70% or more with respect to the hardness of the outer surface (1e) of the arm section (lb).