Wheel Bearing Outer Member Hardening and Rigidity
Solution Overview
Problem
Existing vehicle wheel bearing apparatuses face challenges in reducing weight and size while maintaining rigidity and durability, leading to increased manufacturing costs and potential grease leakage due to asymmetric bearing arrangements and material loss during machining processes.
Innovation Solution
A vehicle wheel bearing apparatus with an outer member made of medium carbon steel, hardened by high frequency induction quenching to prevent quenching cracks, featuring a larger pitch circle diameter for the outer side ball group and optimized ball distribution to enhance rigidity, along with a tapered shoulder configuration to reduce material loss and improve machining accuracy, and controlled grease filling to prevent leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the outer member is made thinner to reduce weight and size, then the weight and size are reduced, but quenching cracks occur during high frequency induction quenching
Solution Approach 1:
The patent changes the material parameter by specifying medium carbon steel with 0.40-0.80% carbon content, which provides optimal hardenability and strength. It also changes the quenching parameter by controlling the hardened layer depth to 2-4mm and limiting wall thickness to 4-8mm, preventing quenching cracks while achieving sufficient hardness (58-64 HRC) for reliable operation.
Solution Approach 2:
The patent creates a composite structure with a hardened outer layer (58-64 HRC) and a softer inner core. This composite material structure allows the outer surface to have high wear resistance and hardness while the inner core maintains toughness and prevents quenching cracks, resolving the contradiction between weight reduction and reliability.
2Strength
If the pitch circle diameter of the outer side ball group is increased to improve rigidity during curved way running, then the rigidity is improved, but the weight and size of the bearing apparatus increase
Solution Approach 1:
The patent applies local quality by making the outer side ball group (facing the outer raceway) have a larger pitch circle diameter than the inner side ball group. This localized asymmetry provides enhanced rigidity specifically where needed for curved way running, while the overall bearing size and weight are minimized by not increasing all dimensions uniformly.
3Ease of manufacture
If the wall thickness of the outer member is reduced to reduce material loss and manufacturing cost, then the manufacturing cost is reduced, but the strength and durability decrease
Solution Approach 1:
The patent optimizes the wall thickness parameter to a specific range of 4-8mm, which is thin enough to reduce material loss and manufacturing cost but thick enough to prevent quenching cracks and maintain structural strength. The controlled hardened layer depth (2-4mm) further enhances surface strength without requiring excessive wall thickness.
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 solution effectively reduces the weight and size of the bearing apparatus while increasing rigidity and durability, improving manufacturing efficiency and maintaining optimal lubrication conditions, thus enhancing the bearing's life and reliability.
Implementation Method 1
The outer member is hardened by high frequency induction quenching so that each of the outer raceway surfaces is formed with a hardened layer having a surface hardness of 58 ̃64 HRC. The effective depth of the hardened layer is set at at least 2 mm.
Data Source
AI summary
A vehicle wheel bearing apparatus has a double row angular ball bearing including double rows of ball groups. A pitch circle diameter of the double row ball group of the outer side is larger than a pitch circle diameter of the double row ball group of the inner side. The outer member is made of medium carbon steel including carbon of 0.40˜0.80% by weight. It is hardened by high frequency induction quenching so that each of the outer raceway surfaces is formed with a hardened layer having a surface hardness of 58˜64 HRC. The effective depth of hardened layer is set at at least 2 mm. The minimum wall thickness of the outer member at these outer raceway surfaces is set at at least 4 mm.