U.S. patent application number 11/634080 was filed with the patent office on 2007-04-05 for cross joint.
This patent application is currently assigned to Koyo Seiko Co., Ltd.. Invention is credited to Nobuo Komeyama, Mitsumasa Ozeki.
Application Number | 20070077869 11/634080 |
Document ID | / |
Family ID | 31884821 |
Filed Date | 2007-04-05 |
United States Patent
Application |
20070077869 |
Kind Code |
A1 |
Komeyama; Nobuo ; et
al. |
April 5, 2007 |
Cross joint
Abstract
In a cross joint outwardly fitting a bearing cup to each of four
pieces of shafts of a cross shaft member via a cylindrical member,
race portions formed on a side of the cross shaft member and on a
side of the bearing cup and a shoulder portion provided between
respectives of neck portions of two of the shafts of the cross
shaft member contiguous to each other are subjected to roller
burnishing.
Inventors: |
Komeyama; Nobuo; (Nara,
JP) ; Ozeki; Mitsumasa; (Nara, JP) |
Correspondence
Address: |
MCGINN INTELLECTUAL PROPERTY;LAW GROUP, PLLC
Suite 200
8321 Old Courthouse Road
Vienna
VA
22182-3817
US
|
Assignee: |
Koyo Seiko Co., Ltd.
Osaka
JP
|
Family ID: |
31884821 |
Appl. No.: |
11/634080 |
Filed: |
December 6, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10660754 |
Sep 12, 2003 |
7163461 |
|
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11634080 |
Dec 6, 2006 |
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Current U.S.
Class: |
451/49 |
Current CPC
Class: |
Y10S 464/902 20130101;
B24B 39/00 20130101; B22F 2003/166 20130101 |
Class at
Publication: |
451/049 |
International
Class: |
B24B 1/00 20060101
B24B001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 13, 2002 |
JP |
P.2002-268761 |
Claims
1. A method of manufacturing a cross joint which includes: a cross
shaft member including, four shafts each having a neck portion and
a race portion, and shoulder portions provided between adjacent two
neck portions; rolling members adapted to rotate around the race
portions; and outer ring members fitted to the respective shafts
via the rolling members, the method comprising roller burnishing
the race portions and the shoulder portions.
2. The method according to claim 1, further comprising roller
burnishing a race portion formed on the outer ring member.
3. The method according to claim 1, wherein the cross joint
comprises one of bearing steel and carbon steel for mechanical
structure.
4. The method according to claim 3, wherein the outer ring members
comprise one of bearing steel and carbon steel for mechanical
structure.
5. A method of manufacturing a cross joint which includes: a cross
shaft member including four shafts each having a neck portion and a
race portion, and shoulder portions provided between adjacent two
neck portions; rolling members adapted to rotate around the race
portions; and outer ring members fitted to the respective shafts
via the rolling members, the method comprising: first finishing the
race portions and the shoulder portions by at least one of cutting
and polishing; and second roller burnishing the race portions and
the shoulder portions after the first subjecting step.
Description
RELATED APPLICATIONS
[0001] The present Application is a Divisional Application of U.S.
patent application Ser. No. 10/660,754, filed on Sep. 12, 2003.
BACKGROUND OF THE DISCLOSURE
[0002] The present invention relates to a cross joint (joint cross
coupling, universal joint) used in a steel rolling mill or the
like.
[0003] In, for example, a steel rolling mill, a cross joint is
interposed between a roll and a drive shaft for driving to rotate
the roll, a steel rolling processing of the steel material can be
carried out by rotating to move the role in accordance with
rotation of the shaft while the roll is allowed to move in an up
and down direction relative to a steel material which is being
rolled. The cross joint includes: a cross shaft member (cross)
having four shafts arranged in a cross-like shape; and a cross
bearing which has a plurality of cylindrical rollers as rolling
members aligned at surroundings of the respective shafts of the
member, and a bearing cup as an outer ring mounted to an outer side
of outer peripheries of the rollers. Each of outer peripheral
portions of the shafts is used as an inner ring race portion.
Further, according to the cross joint, the roll and the drive shaft
are connected to a first shaft and a second shaft comprising
respective pairs of shafts arranged on straight lines in the four
shafts respectively via the cross bearings and (rotational) torque
from the shaft is transmitted to the roll via the cross joint.
[0004] Meanwhile, according to the above-described conventional
cross joint, such a cross shaft member and the bearing cup are
provided, which are generally constituted by bearing steel of
carburized steel or the like.
[0005] However, when large torque acts on the cross joint such as
in the steel rolling mill, the joint is used under a very severe
condition and there is a concern that even when the bearing steel
is used, malfunction is brought about at an early stage. In
details, the cylindrical roller is rolled on the inner ring race
portion or the like formed at the cross shaft member under high
contact surface pressure and therefore, exfoliation is liable to be
brought about at the race portion. Further, according to the cross
member, since the roll and the drive shaft are respectively
connected to the contiguous pairs of shafts and therefore, large
bending stress may be operated to a shoulder portion between shaft
root (shaft neck) portions thereof and fatigue breaking of bending
fatigue breaking or the like is liable to be brought about at the
member.
SUMMARY OF THE INVENTION
[0006] In view of the above-described conventional problem, it is
an object of the invention to provide a cross joint capable of
prolonging rolling fatigue life of a rolling portion (life of
rolling bearing), capable of increasing a fatigue strength of the
cross joint and therefore, capable of achieving long life formation
(ling fatigue life).
[0007] In order to solve the aforesaid object, an exemplary
embodiment of the invention has a cross joint with a cross shaft
member including four shafts, each having a neck portion and a race
portion, and shoulder portions between two neck portions, rolling
members adapted to rotate around the race portions, and bearing
cups fitted to the respective shafts via the rolling members. The
race portions and the shoulder portions are subjected to roller
burnishing.
[0008] In another exemplary embodiment of the invention, a race
portion formed on the outer ring member is subjected to roller
burnishing.
[0009] In a further exemplary embodiment of the invention, a
residual compressive stress at a depth of approximately 0.3 mm from
each of the surfaces of the race portions and the shoulder portions
subjected to the roller burnishing is equal to or larger than 800
MPa.
[0010] In yet another exemplary embodiment of the invention, the
cross shaft member and the bearing cup includes a carbon steel
having a carbon content equal to or larger than 0.42 weight %.
[0011] In another exemplary embodiment of the invention, a method
of manufacturing a cross joint which includes: a cross shaft member
including, a four shafts each having a neck portion and a race
portion, and shoulder portions between two neck portions, rolling
members adapted to rotate around the race portions, and bearing
cups fitted to the respective shafts via the rolling members. The
method includes subjecting the race portions and the shoulder
portions to roller burnishing.
[0012] In a further exemplary embodiment of the invention, a method
includes subjecting a race portion formed on a bearing cup to
roller burnishing.
[0013] According to the above-described cross joint, by subjecting
the race portion and the shoulder portion of the cross shaft member
to roller burnishing, the hardness of each of surfaces of the race
portion and the shoulder portion can be increased and a residual
compressive stress immediately below the surface can be increased.
Further, a roughness of each of the surfaces can also be
decreased.
[0014] According to the cross joint, the hardness of the surface of
the race portion of the outer ring member can be increased and the
residual compressive stress immediately below the surface can also
be increased. Further, the roughness of the surface can also be
decreased.
[0015] According to the cross joint, in comparison with the
above-described conventional product, the fatigue strength of the
race portion and the shoulder portion can further effectively be
increased.
[0016] According to the cross joint, the fatigue strength
substantially comparable to that of the conventional bearing steel
can be achieved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is an outline sectional view showing an essential
portion of a cross joint according to an embodiment of the
invention.
[0018] FIG. 2 is a graph diagram showing a result of measuring a
hardness at each depth from a surface of a race portion.
[0019] FIG. 3 is a graph diagram showing a result of measuring a
residual compressive stress at each depth from the surface of the
race portion.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0020] A preferable embodiment showing a cross joint of the
invention will be explained in reference to the drawings as
follows. Further, in the following explanation, an explanation will
be given of a case of applying the invention to a cross joint for
driving a roll integrated into a steel rolling mill.
[0021] FIG. 1 is an outline sectional view showing an essential
portion of a cross joint according to an embodiment of the
invention. In the drawing, a cross joint 1 according to the
embodiment is provided with a cross shaft member 2 integrally
constituted with a base portion 2a and four shafts 2b arranged to
project from the base portion 2a in a cross-like shape, and roller
bearings 5 each having a bearing cup 4 as an outer ring member
outwardly fitted to an outer side of an outer periphery of each of
the shafts 2b via cylindrical rollers 3.
[0022] The outer peripheral portions of the respective shafts 2b of
the cross shaft member 2 are formed with inner ring race portions
2c with which the cylindrical rollers 3 are brought into rolling
contact and the respective shafts 2b of the member 2 are made to
function as inner ring members of corresponding ones of the roller
bearings 5. The base portion 2a of the cross shaft member 2 is
provided with shoulder portions 2d each having a section in a
round-shape in which a center of a radius of curvature is set to an
outer side of the base portion 2a and a center portion thereof is
recessed to a side of a center portion of the base portion 2a, at
respective intervals between necks (shaft necks) of two of the
shafts 2b contiguous to each other. An inside of the roller bearing
5 is constituted to be able to be hermetically sealed by attaching
a seal member in a ring-like shape (not illustrated) to the
shoulder portion 2d.
[0023] The bearing cup 4 is provided with an outer ring race
portion 4a and the cylindrical rollers 3 are rolled at inside of
the cup 4. Further, the bearing cups 4 are attached to the roll or
the drive shaft such that the roll of the steel rolling mill and
the drive shaft are respectively connected to horizontal shafts and
vertical shafts of the cross shafts comprising two pairs of the
shafts 2b respectively aligned linearly (not illustrated). Rotation
of the shaft is transmitted to the roll to rotate it in a state
that the cross joint permits the roll to rock relative to the shaft
axis. Further, the bearing cup 4 is provided with a grease nipple
(not illustrated) and grease can pertinently be supplied to
portions of the cylindrical rollers 3 rolling on the respective
race portions 2c and 4a.
[0024] Further, other than the above-described explanation, in
place of the cylindrical roller 3, a needle-shape needle roller can
also be used as a rolling member rolling between the respective
race portions 2c and 4a.
[0025] The cross shaft member 2 and the bearing cup 4 are
constituted by using bearing steel or the like or a steel material
which is carburized or carbonitride by subjecting the material
steel to high-frequency quenching or the like. Further, the race
portion 2c and the shoulder portion 2d of the cross shaft member 2
and the race portion 4a of the bearing cup 4 are finished to
predetermined accuracy by being subjected to finishing by cutting,
machining, grinding or polishing.
[0026] Further, the race portions 2c and 4a and the shoulder
portion 2d are subjected to roller burnishing (deep rolling) after
the finishing. According to the roller burnishing, while a mirror
finish ball (mirror finished surface ball) made of ceramics held
by, for example, hydraulic pressure is pressed to a surface of a
working portion of the race portion 2c of the like to bring into
rolling contact therewith by strong pressure, the mirror finish
ball is moved on the surface of the working portion. According to
the roller burnishing, working conditions of an amount of
burnishing, press force and the like are selected such that, for
example, hardness at a depth of up to 0.4 mm from the surface of
the working portion is work-hardened to be equal to or larger than
Hv700 and a residual compressive stress at a depth of up to 0.3 mm
from the surface of the working portion becomes equal to or larger
than 800 MPa.
[0027] As clearly illustrated by FIG. 1, an exemplary embodiment of
the cross-shaft includes a round-shaped section (shoulder 2d) with
a center of curvature (not shown) that is at an outer side of the
cross shaft member.
[0028] Further, FIG. 1 clearly illustrates that the round-shaped
section (shoulder 2d) does not include a concave angled corner.
[0029] Here, a specific explanation will be given of operation and
effect of the roller burnishing in reference to FIG. 2 and FIG. 3
showing an example of a result of a verifying test which has been
carried out by the inventors of the invention. Further, in the
following explanation, an explanation will be given by exemplifying
a verified result at the race portion 2c on the side of the cross
shaft member 2 and a mention will also be given of a measured
result of a material only subjected to a carburizing treatment
before roller burnishing and a material subjected to shot peening
in addition to the carburizing treatment for comparison.
[0030] As has been apparent from FIG. 2, each race portion 2c after
roller burnishing is ensured with a hardness equal to or larger
than Hv700 at a depth of up to about 0.4 mm from the surface and is
considerably harder than a product before roller burnishing and a
shot-peened product. Further, at a depth less than 0.1 mm from
surface, the surface hardness of the shot-peened product is more or
less harder than that of each roller burnished race portion 2c, the
shot-peened product is deteriorated in the surface roughness after
working (the surface is roughened) and needs postworking for
smoothing the surface for making the cylindrical roller 3 roll in
an oil-lubricated state. Specifically, according to the shot-peened
product, it is necessary to remove a surface layer thereof at a
depth of about 0.05 mm from the surface by the postworking.
[0031] In contrast thereto, according to each race roller burnished
portion 2c, since the surface is pressed by point contact with the
mirror finish ball in roller burnishing, the surface hardness can
be hardened while improving (reducing) the surface roughness by
smoothly deforming the surface, and contrary to the shot-peened
product, it is not necessary to subject the surface to postworking.
Therefore, the surface hardness of each race portion 2c is
substantially harder than that of the shot-peened product. Further,
according to a test by the inventor of the present invention, it
has been confirmed that the surface roughness of each race portion
2c by roller burnishing can be made to be equal to or less than a
half of that before working in a maximum height roughness (Rmax)
and a surface hardening coefficient can be increased compared with
that before working. In this way, the fatigue strength of the race
portion 2c can be increased by improving the surface hardening
coefficient of the race portion 2c and increasing the surface
hardness and surface originated flaking (surface layer flaking) at
the race portion 2c can effectively be restrained from being
brought about.
[0032] Further, as shown in FIG. 3, at each race portion 2c, a
residual compressive stress equal to or larger than 800 MPa is
generated at a depth of up to 0.3 mm from the surface and work
hardening is produced up to a depth about twice as much as that of
the short-peened product.
[0033] FIG. 3 also illustrates that a residual compressive stress
at a depth of approximately 0.1 mm from the roller burnished
surface is larger than a residual compressive stress a depth of
less than approximately 0.1 mm from the roller burnished surface, a
residual compressive stress at a depth of approximately 0.2 mm from
the roller burnished surface is larger than a residual compressive
stress a depth of greater than approximately 0.2 mm from the roller
burnished surface, and a residual compressive stress at a depth of
approximately 0.01 mm from the roller burnished surface is less
than a residual compressive stress at a depth of approximately 0.3
mm from the roller burnished surface.
[0034] By producing the large residual compressive stress at the
race portion 2c in this way, inner portion originated flaking at
the race portion 2c can effectively be restrained from being
brought about and the fatigue strength against stresses generated
at inside of the race portion 2c can be increased. That is, at the
shoulder portion 2d subjected to roller burnishing, the fatigue
strength against bending stress operated by two of the shafts 2b
continuous to the shoulder portion 2d can be increased and the
bending fatigue breaking (fracture) can effectively be restrained
from being brought about.
[0035] As described above, according to the cross joint 1 according
to the embodiment, by subjecting the race portions 2c and 4a
provided at the cross shaft member 2 and the bearing cup (outer
ring member) 4 and the shoulder portion 2d of the cross shaft
member 2 to roller burnishing, while improving roughnesses of the
respective surfaces of the race portions 2c and 4a and the shoulder
portion 2d, the surface harnesses can be increased and the residual
compressive stresses immediately below the surfaces can be
increased. As a result, in comparison with the conventional product
which is not subjected to roller burnishing, exfoliation life of
the race portions 2c and 4a can be prolonged and the fatigue
strength of the race portions 2c and 4a and the shoulder portion 2d
can be increased and therefore, long life formation of the cross
joint 1 can be achieved. Further, since the cross joint 1 is
provided with the race portions 2c and 4a having long flaking life
(life of rolling bearing) and provided with the cross shaft member
2 and the bearing cup 4 having excellent fatigue strength, a cross
joint used under a very severe condition by being integrated to a
transmitting mechanism for transmitting high torque from a drive
shaft to a driven shaft can simply be constituted.
[0036] Further, according to the embodiment, the residual
compressive stress at the depth of up to 0.3 mm from the respective
surfaces of the race portions 2c and 4a and the shoulder portion 2d
is made to be equal to or larger than 800 MPa and therefore, in
comparison with the above-described conventional product, the
fatigue strength of the race portions 2c and 4a and the shoulder
portion 4d can effectively be increased.
[0037] Further, although according to the above-described
explanation, an explanation has been given of a case of applying to
the cross joint integrated into the steel rolling mill, the
invention is not limited thereto but is applicable to various kinds
of cross joints (universal joints) connected to, for example, a
propeller shaft of an automobile and the like.
[0038] Further, although according to the above-described
explanation, an explanation has been given of the constitution in
which the center of the radius of curvature is set on the outer
side of the base portion 2a and the shoulder portion 2d having the
section in the round-shape in which the central portion is recessed
to the side of the center portion of the base portion 2a is
subjected to roller burnishing, according to the invention, each
shoulder portion between two of the shaft neck portions of the
cross shaft member (cross or spider) phases of which are shifted
from each other by 90 degrees may be subjected to roller burnishing
and the shape of the shoulder portion is not limited to the
above-described at all. Specifically, there may be constructed a
constitution in which a shoulder portion having a section in a
linear shape or a shoulder portion having a section in a round
shape in which the center of a radius of curvature is set to a
center side portion of a base portion such that a central portion
thereof bulges to an outer side of the base portion is subjected to
roller burnishing.
[0039] Further, although according to the above-described
explanation, an explanation has been given of a case of
constituting the cross shaft member 2 and the bearing cup 4 by
using bearing steel, the invention is not limited thereto but there
may be constructed a constitution in which a cross shaft member, a
bearing cup or the like is constituted by carbon steel having a
carbon content of, for example, 0.42 weight % or more, or a steel
material hardened to a hardness of about HRC55 by subjecting the
material steel to a heat treatment or a high-frequency quenching
treatment and the race portion and the shoulder portion is
subjected to roller burnishing. By using carbon steel for
mechanical structure in this way, a cross shaft member having a
fatigue strength substantially comparable to that of the
conventional product comprising bearing steel and restraining
material cost can easily be constituted and the cross joint can be
fabricated at low cost.
[0040] The invention constituted as described above achieves the
following effects.
[0041] According to the cross joint of the invention, by subjecting
the race portion and the shoulder portion of the cross shaft member
to roller burnishing, the hardness of each of the surfaces of the
race portion and the shoulder portion is increased and the residual
compressive stress immediately before the surface is increased and
therefore, in addition to that the roughness of each of the
surfaces can be decreased, in comparison with the conventional
product which is not subjected to roller burnishing, exfoliation
life of the race portion can be prolonged, the fatigue strength of
the cross shaft member can effectively be increased and therefore,
long life formation of the cross joint can be achieved.
[0042] Further, according to the cross joint of the invention, by
subjecting the race portion of the outer ring member to roller
burnishing, the hardness of the surface of the race portion is
increased, the residual compressive stress immediately below the
surface is increased and therefore, in addition to that the
roughness of the surface can be increased, in comparison with the
conventional product which is not subjected to roller burnishing,
the exfoliation life of the race portion can be prolonged.
[0043] Further, according to the cross joint of the invention, in
comparison with the conventional product, the fatigue strength of
the race portion and the shoulder portion can further effectively
be increased and long life formation of the cross joint can further
effectively be achieved.
[0044] Further, according to the cross joint of the invention, the
life substantially comparable to that of the cross joint comprising
bearing steel can be ensured by an inexpensive material.
* * * * *