Wheel bearing apparatus for a vehicle

• US 8,794,844 B2
• Filed: 05/04/2011
• Issued: 08/05/2014
• Est. Priority Date: 11/05/2008
• Status: Active Grant

• Current Assignee: NTN Corporation
• Original Assignee: NTN Corporation
• Inventors: Komori, Kazuo
• Primary Examiner(s): Hannon, Thomas R
• Assistant Examiner(s): Rogers, Adam D
• Application Number:
  US13/100,429
• Publication Number:
  US 20110206307A1
• Time in Patent Office: 1,189 Days
• Field of Search: 384/544, 384/589, 294/070.5
• US Class Current: 384/544
• CPC Class Codes: B60B 27/0005 with ball bearings
• CPC Class Codes: B60B 27/0084 caulking to fix inner race
• CPC Class Codes: B60B 27/0094 one or more of the bearing races are formed by the hub
• CPC Class Codes: C21D 1/42 Induction heating
• CPC Class Codes: C21D 1/63 for bath quenching
• CPC Class Codes: C21D 2211/005 Ferrite
• CPC Class Codes: C21D 2221/02 Edge parts
• CPC Class Codes: C21D 2221/10 Differential treatment of inner with respect to outer regions, e.g. core and periphery, respectively
• CPC Class Codes: C21D 9/40 for rings; for bearing races
• CPC Class Codes: C22C 38/04 containing manganese
• CPC Class Codes: F16C 19/186 with three raceways provided integrally on parts other than race rings, e.g. third generation hubs
• CPC Class Codes: F16C 2240/80 Pitch circle diameters [PCD]
• CPC Class Codes: F16C 2326/02 Wheel hubs or castors
• CPC Class Codes: F16C 33/62 Selection of substances
• CPC Class Codes: F16C 43/04 Assembling rolling-contact bearings
• CPC Class Codes: Y02P 10/25 Process efficiency

Abstract

A vehicle wheel bearing apparatus has an outer member; an inner member and double row balls freely rollably contained between outer raceway surfaces and inner raceway surfaces. An inner ring is axially secured relative to a wheel hub by a caulked portion. The caulked portion is formed by plastically deforming the cylindrical portion radially outward. The wheel hub is formed from medium-high carbon steel including carbon of 0.40-0.80% by weight and with a ferrite grain size number selected larger than #3.

Claims

1. A vehicle wheel bearing apparatus comprising:

an outer member formed with double row outer raceway surfaces on its inner circumference;

an inner member including a wheel hub and at least one inner ring, the wheel hub is integrally formed with a wheel mounting flange on one of its ends, the wheel hub has an outer circumference with an inner raceway surface and an axially extending cylindrical portion, the at least one inner ring is press-fit onto the cylindrical portion of the wheel hub, an outer circumference of the at least one inner ring includes an inner raceway surface that opposes one of the double row outer raceway surfaces of the outer member;

double row balls are freely rollably contained between the outer raceway surfaces and inner raceway surfaces, respectively, of the outer member and the inner member;

the at least one inner ring is axially secured relative to the wheel hub by a caulked portion, the caulked portion is formed by deforming the cylindrical portion radially outward;

the wheel hub is formed of medium-high carbon steel including carbon of 0.40-0.80% by weight and with a ferrite grain size number that is selected larger than #3; and

a draft (La−

Lb)/La of a caulking work is set at 0.55 or less, “

La”

is a length amount of a projection from a larger end of the at least one inner ring to a tip of the projection, a recess is formed with a bottom at a base of the projection, the bottom is substantially coplanar with a larger end face of the at least one inner ring, the projection has a substantially constant thickness extending beyond the bottom of the recess and the larger end face of the at least one inner ring before the caulking of the cylindrical portion and “

Lb”

is a height of the caulked portion which is the thickness of the caulked portion from the bottom of the recess and the larger end face of the at least one inner ring after the caulking and an entire portion extending beyond the bottom of the recess of the cylindrical portion is caulked, wherein the vehicle wheel bearing apparatus prevents the generation of cracks in the caulked portion during the caulking work.

2. The vehicle wheel bearing apparatus of claim 1, wherein the medium-high carbon steel further including carbon:

0.50-0.70 wt %, manganese;

0.1-2.0 wt %, chromium;

1.0 wt % or less and residues;

iron and inevitable impurities.

3. The vehicle wheel bearing apparatus of claim 2, further comprising sulfur in the wheel hub in the amount limited to 0.02 wt % or less.

4. The vehicle wheel bearing apparatus of claim 2, further comprising silicon in the wheel hub in an amount limited to 0.2 wt % or less.

5. The vehicle wheel bearing apparatus of claim 1, wherein the wheel hub is directly formed on its outer circumference with the inner raceway surface that opposes one of the double row outer side outer raceway surfaces of the double row outer raceway surfaces, the inner raceway surface and a region from an inner side base of the wheel mounting flange to the cylindrical portion are hardened by induction hardening to have a surface hardness of 58-64 HRC, the caulked portion is not hardened and remained as is after forging to have a surface hardness of 13-30 HRC.

6. The vehicle wheel bearing apparatus of claim 1, wherein a pitch circle diameter of an outer side ball group is set larger than a pitch circle diameter of an inner side ball group.

7. The vehicle wheel bearing apparatus of claim 6, wherein a number of outer side balls of the double row balls is set larger than a number of inner side balls.

8. The vehicle wheel bearing apparatus of claim 6, wherein an outer diameter of each ball of the outer side ball group of the double row balls is set smaller than an outer diameter of each ball of the inner side ball group.

9. The vehicle wheel bearing apparatus of claim 7, wherein an outer diameter of each ball of the outer side ball group of the double row balls is set smaller than an outer diameter of each ball of the inner side ball group.