Land vehicles: wheels and axles – Wheel – Detachable wheel section
Reexamination Certificate
2002-05-08
2003-06-10
Stormer, Russell D. (Department: 3617)
Land vehicles: wheels and axles
Wheel
Detachable wheel section
C301S035626, C029S894360
Reexamination Certificate
active
06575535
ABSTRACT:
BACKGROUND
A) Field of the Invention
This invention relates generally to a method for manufacturing wheel spindles and more particularly, to a method for forming stud holes in the wheel spindle flange and the improved wheel spindle resulting therefrom.
This invention is particularly applicable to and will be described with specific reference to that portion of the wheel spindle manufacturing process in which stud holes are formed in the bearing steel spindle flange and serrated wheel lug nut studs are press-fitted therein with minimal flange distortion. However, those skilled in the art will recognize that the invention has broader application and can be applied to any manufacturing process wherein studs, shafts or splines are to be pressed into holes formed in flat steel surfaces such as flanges, ribs, spokes and the like with minimal distortion in the flat surface.
B) Prior Art
Known wheel bearings of the type shown in FIG.
1
and indicated generally at
10
, have a stationary outer hub
12
, which is secured to a non illustrated vehicle suspension, and a rotatable wheel spindle, indicated generally at
14
. Spindle
14
rotates about wheel bearing centerline
38
and it carries the vehicle wheel
16
, as well as a brake drum
18
. (Alternatively, brake drum
18
is replaced by a rotor if the vehicle is equipped with disc brakes.) Brake drum
18
is mounted to spindle
14
through an open, central circular hub
20
. Specifically, spindle
14
includes a cylindrical pilot
24
(or shaft) with an outer surface over which the brake drum hub
20
is inserted, with a very close radial clearance. A flat annular wheel flange
26
radiates outwardly from the pilot
24
, perpendicular thereto, with a flat outer or outboard surface
28
against which the brake drum hub
20
is abutted, and an axially opposed flat inner or inboard surface
30
. The brake drum hub
20
is firmly sandwiched between spindle outboard surface
28
and wheel
16
itself, which in turn is bolted onto conventional wheel studs
32
, when the vehicle is operating.
Today's automotive vehicles have improved ride handling characteristics with sensitive and precise steering and braking mechanisms. It is to be appreciated that brake drum hub
20
abuts, in face to face contact, outboard surface
28
of spindle
14
and that wheel
16
similarly contacts brake drum hub
20
50
that spindle flange
26
, brake drum hub
20
, wheel
16
and tire
22
all rotate as one unit when the vehicle is in motion. So long as wheel flange
26
retains perpendicularity with wheel bearing centerline
38
throughout rotation, all components rotate consistently uniform. However, if the flatness of outboard surface
28
is warped or distorted, a lateral movement of all components will be experienced during each wheel rotation which is commonly referred to as lateral run out or LRO in the art. While LRO may occur for any number of reasons, variations in the flatness of outboard surface
29
contributing to LRO produces undesirable effects on the handling characteristics of the vehicle. For example, if spindle flange
26
is or becomes excessively wrapped, the vehicular operator will sense a pulsation in the brake pedal as the brakes are applied and seat against rotating brake drum hub
20
. That is, seating of the brakes will not be uniform because LRO causes the drum to axially slip relative to the brakes and non-uniform seating will produce a force pulsation felt in the brake pedal. This pulsation is not desirable especially in performance or luxury vehicles. Similarly, the long lever arm between tire/road contact and stud circle significantly increases tire displacement attributed to LRO during each wheel rotation. The axial displacement is absorbed by the tire's side wall but not without an adverse effect on the handling characteristics of the vehicle. It is also possible to detect the LRO affects in the vehicle's steering wheel. The discerning car buyer will not purchase a vehicle if the steering is not precise, stable and solid at all vehicular operating speeds.
Wheel spindles are generally formed as forgings from bearing steels. The bearing races in the spindle are locally heat treated such as by induction heat treating methods to relatively high hardness. The remainder of the wheel bearing spindle is at a low hardness such as that produced by the conventional normalizing heat treat process to which the spindle is initially subjected to. Localized heat treat is necessary because outboard and inboard flange surfaces
26
,
28
are machined flat. In particular, outboard surface
28
is machined flat to within a tolerance expressed in microns. Stud holes as well as other holes are then formed in the flange for wheel studs
32
. Wheel studs
32
, which have serrations for an interference fit, are then pressed into the stud holes. The interference fit is such that the stud must shear before it can rotate in the stud hole. The force required to press the studs into the stud holes is large. While flange outboard surface
28
is securely supported or backed up during the stud pressing step, one of the underpinnings of the invention is the recognition that the forces required to press the studs into the wheel flange at the required interference press fit can cause or contribute to flange distortion and LRO no matter what jigs or fixtures are used to support and/or clamp the wheel flange during the stud pressing step.
SUMMARY OF THE INVENTION
Accordingly, one of the major objects of the invention is to provide a method for forming a hole(s) into a flat surface, particularly a wheel spindle flange, into which studs, splines, shafts and the like can be press-fitted with a minimal flange distortion force.
This object along with other features of the invention is achieved in a method for forming an opening in a bearing metal flange into which is pressed a serrated shaft comprising the steps of providing a blanking die having an opening on one side of the flange (bottom side) and a punch having a diameter smaller than the blanking die opening at the opposite side of the flange (top side) and forcing the punch through the flange to produce a frusto-conical, axially-extending flange opening having a minor diameter equal to the punch diameter at the top flange side and a major diameter equal to the blanking die opening at the bottom flange side. A coining punch of diameter equal to or greater than the shaft major diameter is next provided and the coining punch is forced into each end of the frusto-conical opening a set axial distance sufficient to extrude, at least in the frusto-conical opening adjacent the minor diameter, a work hardened upset mass while providing countersunk openings at the axial ends of the frusto-conical opening. A serration punch is then provided and the punch is forced through the frusto-conical opening from the top flange side to produce a cylindrical stud hole axially extending between the countersunk openings while shearing the work hardened upset metal mass from the frusto-conical opening and forming radially outwardly extending serrations which extend for some axial distance in flange metal that is in a substantially non-work hardened state whereby the studs can be pressed through the substantially non-work hardened axial section of the hole with less force than that required if the hole surfaces were conventionally work hardened.
In accordance with another aspect of the invention, a method is provided for assembling studs in a machined flange of a wheel spindle which includes the steps of forming a plurality of circumferentially spaced stud holes axially extending through the flange with substantially non-work hardened hole surfaces. The process then coins stud holes at the inboard and outboard flange surfaces so that countersunk holes of approximately equal diameter extend approximately set axial distances into each stud hole. A stud is provided for each hole having a flat head, a threaded stem and a serrated shank portion between the head and threaded stem and the studs are pressed into the holes such
Beverick John R.
Meeker Steven Eugene
Scheufler, Jr. Richard Allen
Zuck Christopher J.
Delphi Technologies Inc.
McBain Scott A.
Stormer Russell D.
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