WO2016043507A1

WO2016043507A1 - A flanged bearing made of high-carbon chromium steel and method of manufacturing the same

Info

Publication number: WO2016043507A1
Application number: PCT/KR2015/009684
Authority: WO
Inventors: Dong-Gyun CHOO; Kang-Seok Kim; Kyeong-Ku LEE; Chan-Hyun SON; Min-Hwan Kim
Original assignee: Schaeffler Korea Corp.
Priority date: 2014-09-15
Filing date: 2015-09-15
Publication date: 2016-03-24
Also published as: WO2016043506A1

Abstract

A flanged bearing made of high-carbon chromium steel includes: inner rings 110; an outer ring 130, a flange portion 170, rolling elements 150, and a retainer, wherein the inner rings 110 are annularly formed to extend in a circumferential direction and are provided on their radial outer surfaces with inner ring raceways extending in the circumferential direction, the outer ring 130 is annularly formed to extend in the circumferential direction and is provided on its radial inner surface with an outer ring raceway extending in the circumferential direction, the flange portion 170 is provided in the inner rings 110 or the outer ring 130 and is formed in a plate shape to extend in the circumferential direction, the rolling elements 150 are arranged between the inner rings 110 and the outer ring 130 and are spaced apart in the circumferential direction by the retainer, the retainer is provided between the inner rings 110 and the outer ring 130 and is provided so that the rolling elements 150 are spaced apart in the circumferential direction, and the flange portion 170 is heat treated so as to have a hardness which is in the range of HV 240 to HV 280.

Description

A FLANGED BEARING MADE OF HIGH-CARBON CHROMIUM STEEL AND METHOD OF MANUFACTURING THE SAME

The present invention relates to a flanged bearing made of high-carbon chromium steel and a method of manufacturing the same and, more particularly, to a flanged bearing made of high-carbon chromium steel, in which a bearing flange portion made of high-carbon chromium steel has an increased hardness, and a method of manufacturing the same.

In general, bearings serve to rotatably support shafts. The bearings are largely divided into rolling bearings and sliding bearings. The rolling bearings are divided into ball bearings and roller bearings depending on the kind of rolling elements.

A bearing is composed of an inner ring, an outer ring, rolling elements and a retainer (cage).

In general, a heat treatment is performed in the manufacturing process thereof in order to increase the rigidity of the bearing. The heat treatment includes a quenching process and a tempering process.

The quenching process is a work in which a bearing is heated to a high temperature and is then rapidly cooled using cooling oil or the like, thereby increasing the hardness of the bearing.

After the quenching process, a tempering process is performed so that the stresses generated within the bearing in the quenching process are removed and the internal structure of the bearing is made uniformly. At this time, the tempering process is a low-temperature tempering process in which the bearing is heated to a low temperature of 300℃ or less and is then air-cooled in order to prevent a change in the hardness increased by the quenching process.

In some cases, the inner ring or the outer ring includes a flange integrally formed with the outer surface of the inner ring or the outer ring and extending in a radial direction. The flange is formed in an asymmetric structure with respect to a rotation center of a bearing. If necessary, a bearing is provided with an asymmetric flange.

The flanged bearing is usually made of high-carbon chromium steel such as 100Cr6, 100CrMnSi6-4 or the like. The chromium steel has a carbon content which is in the range of 0.90 wt％ to 1.10 wt％ and a chromium content which is in the range of 0.90 wt％ to 1.70 wt％.

FIG. 1 is a front view illustrating a double-row angular contact ball flanged bearing with an arc-shaped asymmetrical removal portion according to the prior art. FIG. 2 is a sectional view taken along line A-A in FIG. 1.

As illustrated in FIGS. 1 and 2, the double-row angular contact ball bearing 10 having flange with an arc-shaped asymmetrical removal portion according to the prior art includes two inner rings 11 provided on each outer circumferential surface with inner ring raceway and arranged side by side in the axial direction, an outer ring 13 provided on its inner circumferential surface with outer ring raceways which face toward the inner ring raceways and which are spaced radially outward from the inner ring raceways, and a plurality of rolling elements 15 as balls disposed between the inner ring raceways and the outer ring raceways.

The rolling elements 15 are provided in double rows in an axially spaced-apart each other. The circumferential spacing between the rolling elements 15 is maintained by a cage (not illustrated) provided between the inner ring raceways and the outer ring raceways.

The outer ring 13 includes a plate-like flange 17 extending radially outward and having a disc shape (specifically, a doughnut shape). A plurality of bolt holes 17a for mounting the bearing is axially penetrated through near the edge of the flange 17. In FIG. 1, reference numeral 17b designates an asymmetrical removal portion formed by partially removing the flange 17 in an arc shape. Reference numeral 17-1 designates a UD chamber interference preventing portion which is a hole portion removed for avoidance of interference with, e.g., a protrusion portion of a UD chamber in a mounting structure. In this way, the circular flange is partially removed in the arc-shaped asymmetrical removal portion 17b, whereby the flange 17 becomes asymmetric. The bearing including the flange 17 described above is mounted and used in an automatic transmission which includes a brake locking hinge. The brake locking hinge is axially moved through the flange 17. In order to avoid interference between the brake locking hinge and the flange 17, the arc-shaped asymmetrical removal portion 17b is formed in the flange 17. Furthermore, the UD chamber interference preventing portion 17-1 is formed in the flange 17 so that a UD chamber as an oil flow path can be mounted. In general, the UD chamber interference preventing portion 17-1 is formed in a facing position having a small phase angle with respect to the arc-shaped asymmetrical removal portion 17b.

However, when a bearing provided with a flange portion, such as the flanged bearing 10 illustrated in FIG. 1, is subjected to the aforementioned heat treatment, a problem is raised in that excessive deformation is generated in the flange portion and excessive machining load is generated when lathe-cutting the flange portion whose hardness is increased through hardening heat treatment. Accordingly, when manufacturing the flanged bearing 10 mentioned above, the inner rings 11 are usually manufactured by a through hardening heat treatment, whereas in the case of the outer ring 13 provided with a flange 17, only the outer ring raceways formed on the inner circumferential surface of the outer ring 13 is hardened by the induction hardening heat treatment.

If only the outer ring raceway is subjected to the heat treatment, a problem is raised in that the insufficiently hardened flange portion fails to meet the required strength and may be deformed or broken when the bearing is installed and driven.

And the bearing having disc-shaped flange with the arc-shaped asymmetrical removal portion 17b according to the prior art suffers from a problem in that a large eccentric centrifugal force is generated by asymmetry when the outer ring 13 is held and rotated by a chuck for grinding and turning processes of the outer ring 13. In order to solve this problem, a plurality of weight control hole portions are formed in the flange 17 along with the circumferential direction, thereby preventing generation of an eccentric centrifugal force. However, this poses a problem in that, when the bearing is mounted to and used in a transmission, bolts fastened to bolt fastening holes 17a adjacent to the arc-shaped removal portion 17b are loosened.

The present invention is directed to solve the above-noted problems.

It is an object of the present invention to provide a flanged bearing made of high-carbon chromium steel, which includes a flange portion whose hardness is increased by performing a quenching and tempering heat treatment to the flanged bearing after an intermediate heat treatment, and a method of manufacturing the same.

And it is an another object of the present invention to provide a flanged bearing with an arc-shaped asymmetrical removal portion, which is capable of suppressing generation of an eccentric centrifugal force during a machining process, preventing machining defects, and suppressing a loosening phenomenon of bolts fastened to a flange when in use.

The present invention provides a flanged bearing made of high-carbon chromium steel including: inner rings, an outer ring, a flange portion, rolling elements, and a retainer; wherein the inner rings are annularly formed to extend in a circumferential direction and are provided on their radial outer surfaces with inner ring raceway extending in the circumferential direction; wherein the outer ring is annularly formed to extend in the circumferential direction and is provided on its radial inner surface with an outer ring raceway extending in the circumferential direction; wherein the flange portion is provided in the inner rings or the outer ring and is formed in a plate shape to extend in the circumferential direction; wherein the rolling elements are arranged between the inner rings and the outer ring and are spaced apart in the circumferential direction by the retainer; wherein the retainer is located between the inner rings and the outer ring and is provided so that the rolling elements are spaced apart in the circumferential direction; wherein the flange portion is heat treated so as to have a hardness which is in the range of HV 240 to HV 280.

The present invention further provides a method of manufacturing a flanged bearing made of high-carbon chromium steel, including: a forging step, an intermediate heat treatment step, a heat treatment step, a lathe-cutting step, a raceway induction hardening heat treatment step, and a raceway machining step; wherein the high-carbon chromium steel is pressed at the forging step in conformity with the shape of the bearing, and the forged bearing is heat treated at the intermediate heat treatment step so that the machinability of the bearing is improved, and the bearing is subjected to a quenching process and a tempering process at the heat treatment step; wherein the corners and surfaces of inner rings, an outer ring and a flange portion are machined at the lathe-cutting step, and the raceway of the bearing is processed at the induction hardening heat treatment step. The raceways of the bearing are lathe-cut at the raceway machining step to form raceway.

The method is characterized in that in the quenching process of the heat treatment step, the high-carbon chromium steel is heated to a temperature which is in the range of 820℃ to 890℃ and is then quenched.

The method is characterized in that in the tempering process of the heat treatment step, the high-carbon chromium steel is heated to a temperature equal to or higher than a recrystallization temperature.

The method is characterized in that in the tempering process, the high-carbon chromium steel is heated to a temperature which is in the a range of 630℃ to 700℃ and is then air-cooled.

The method is characterized in that at the heat treatment step, a normalizing process may be performed instead of the quenching process and the tempering process, and the high-carbon chromium steel is heated to a temperature equal to or higher than an austenitizing temperature, kept at the heating temperature for a predetermined time and then slowly cooled in the normalizing process.

The method is characterized in that in the normalizing process, the high-carbon chromium steel is heated to a temperature which falls within a range of 820℃ to 890℃ and is then slowly cooled.

A flanged bearing characterized in the flange comprises an arc-shaped asymmetrical removal portion formed at one side of a circular plate, a plurality of bolt fastening holes formed in an edge in a spaced-apart relationship along with a circumferential direction, and one or more hole portions formed in the positions circumferentially spaced-apart from the arc-shaped asymmetrical removal portion, wherein the arc-shaped asymmetrical removal portion has a radius of curvature which is in the range of 80％ to 95％ of a radius of the flange, and wherein the hole portions do not go beyond a line which extends from a bearing axis center toward the arc-shaped asymmetrical removal portion and makes an angle of 16 with respect to a line B-B parallel to a line tangential to the inner end of the arc-shaped asymmetrical removal portion and passing through the bearing axis center.

A flanged bearing characterized in that the area of the arc-shaped asymmetrical removal portion is in a range of 10％ to 15％ of the area of the flange.

The flanged bearing made of high-carbon chromium steel and the method of manufacturing the same according to the present invention have an effect of increasing the hardness of the flange portion by performing the quenching and tempering heat treatment to the bearing provided with the flange and an effect of preventing the flange portion of the flanged bearing from being deformed or broken when installed and operated.

And the flanged bearing with an arc-shaped asymmetrical removal portion according to the present invention has an effect of suppressing generation of an eccentric centrifugal force during a machining process, preventing machining defects otherwise generated by the eccentric centrifugal force, suppressing a loosening phenomenon of bolts fastened to the flange 170, particularly bolts inserted into and fastened to the bolt fastening holes adjacent to the arc-shaped asymmetrical removal portion, when in use, and reducing the secondary roundness of an outer ring raceway.

FIG. 1 is a front view illustrating an angular contact ball flanged bearing with an arc-shaped asymmetrical removal portion according to the prior art.

FIG. 2 is a sectional view taken along line A-A in FIG. 1.

FIG. 3 is a front view illustrating an angular contact ball flanged bearing with an arc-shaped asymmetrical removal portion according to a preferred embodiment of the present invention.

FIG. 4 is a sectional view taken along line A-A in FIG. 3.

FIG. 5 is a front view illustrating a modification of the angular contact ball flanged bearing with an arc-shaped asymmetrical removal portion.

FIG. 6 is a sectional view taken along line A-A in FIG. 5.

FIG. 7 is a front view illustrating another modification of the angular contact ball flanged bearing with an arc-shaped asymmetrical removal portion.

FIG. 8 is a sectional view taken along line A-A in FIG. 7.

FIG. 9 is a sectional view taken along line F-F in FIG. 3.

FIGS. 10 to 12 are views for explaining an analysis model, FIG. 10 illustrating a case where hole portions are formed to go beyond an angle of 16 degrees, FIG. 11 illustrating a case where the end portions of the hole portions are formed at an angle of 16 degrees, and FIG. 12 illustrating a case where the end portions of the hole portions are formed in an angular range greater than 16 degrees.

FIGS. 13 and 14 are views illustrating deformation amounts of a bolt, FIG. 13 illustrating the deformation amount of a bolt fastened to a model illustrated in FIG. 10, and FIG. 14 illustrating the deformation amount of a bolt fastened to a model illustrated in FIG. 12.

FIG. 15 is a view illustrating steps of a method of manufacturing a flanged bearing made of high-carbon chromium steel according to the present embodiment.

FIG. 16 is a view illustrating a temperature change in a quenching process performed in the method of manufacturing the flanged bearing illustrated in FIG. 15.

FIG. 17 is a view illustrating a temperature change in a high-temperature tempering process performed in the method of manufacturing the flanged bearing illustrated in FIG. 15.

A flanged bearing made of high-carbon chromium steel and a method of manufacturing the same according to the present invention will now be described with reference to the drawings.

FIG. 3 is a front view illustrating an angular contact ball bearing having the flange with an arc-shaped asymmetrical removal portion according to a preferred embodiment of the present invention. FIG. 4 is a sectional view taken along line A-A in FIG. 3. FIG. 5 is a front view illustrating a modification. FIG. 6 is a sectional view taken along line A-A in FIG. 5. FIG. 7 is a front view illustrating another modification. FIG. 8 is a sectional view taken along line A-A in FIG. 7. FIG. 9 is a sectional view taken along line F-F in FIG. 3. FIGS. 10 to 12 are views for explaining an analysis model, FIG. 10 illustrating a case where hole portions are formed to go beyond an angle of 16 degrees, FIG. 11 illustrating a case where the end portions of the hole portions are formed at an angle of 16 degrees, FIG. 12 illustrating a case where the end portions of the hole portions are formed in an angular range greater than 16 degrees, FIGS. 13 and 14 are views illustrating deformation amounts of a bolt, FIG. 13 illustrating a deformation amount of a bolt fastened to a model illustrated in FIG. 10, and FIG. 14 illustrating a deformation amount of a bolt fastened to a model illustrated in FIG. 12, FIG. 15 is a view illustrating steps of a method of manufacturing a flanged bearing made of high-carbon chromium steel according to the present embodiment, FIG. 16 is a view illustrating a temperature change in a quenching process performed in the method of manufacturing the flanged bearing illustrated in FIG. 15, and FIG. 17 is a view illustrating a temperature change in a high-temperature tempering process performed in the method of manufacturing the flanged bearing illustrated in FIG. 15.

In the descriptions of the present invention, a double row angular contact ball bearing will be described as an example of a bearing having disc-shaped flange with an arc-shaped asymmetrical removal portion. However, the present invention is not limited thereto but may be applied to a bearing which includes an inner ring, an outer ring, rolling elements and an asymmetric flange provided with an arc-shaped asymmetrical removal portion at one side, such as a taper roller bearing, a cylindrical roller bearing, a self-aligning roller bearing, or the like. Hereinafter, descriptions will be made on a bearing in which a disc-shaped asymmetric flange provided with an arc-shaped asymmetrical removal portion is integrally formed with an outer ring. However, the flange may be integrally formed with an inner ring.

As illustrated in FIGS. 3 and 4, the double-row angular contact ball bearing 100 having flange with an arc-shaped asymmetrical removal portion according to the present invention includes two inner rings 110 provided on each circumferential surface with inner ring raceway and arranged side by side in the axial direction, an outer ring 130 provided on its inner circumferential surface with outer ring raceways which face toward the inner ring raceways and which are spaced radially outward from the inner ring raceways, and a plurality of rolling elements 150 as balls disposed between the inner ring raceways and the outer ring raceways. A cage for maintaining a circumferential spacing of the rolling elements 150 is not illustrated. A flange 170 of a plate shape having a circular edge is provided at the radially outer side of the outer ring 130.

The front-view shape of the flange 170 is circular. An asymmetrical removal portion 170b removed in an arc shape (hereinafter referred to as an "arc-shaped asymmetrical removal portion") is formed at one side of the flange 170. A UD chamber interference preventing portion 171 is formed at an angular position circumferentially spaced-apart from the arc-shaped asymmetrical removal portion 170b.

A plurality of screw holes 170a for mounting the bearing are formed along the radial outer edge of the flange 170 in a circumferentially spaced-apart relationship. The screw holes 170a are formed so as to axially penetrate the flange 170.

In the following descriptions, the high-carbon chromium steel, of which the flanged bearing according to the present invention is made, refers to steel that has a carbon content which is in the range of 0.90 wt％ to 1.10 wt％ and a chromium content which is in the a range of 0.90 wt％ to 1.70 wt％.

By forming the arc-shaped asymmetrical removal portion 170b at one side of the flange, there may be generated a phenomenon that the screws fastened to the screw holes 170a-a formed adjacent to the arc-shaped asymmetrical removal portion 170b among the screw holes 170a formed along the edge of the flange 170 are loosened due to the vibration generated in operation.

In FIGS. 3 and 9, reference numeral 173 designates hole portions formed in the flange 170. The hole portions 173 are radially spaced apart from the center of the bearing and are formed in a plural number so as to extend in an arc shape along with the circumferential direction. The hole portions 173 are formed in such a fashion that the hole portions 173 are recessed toward the arc-shaped asymmetrical removal portion 170b and extended in the circumferential direction.

Referring to FIG. 3, a line B-B parallel to a line D tangential to the inner end of the arc-shaped asymmetrical removal portion 170b and passing through an axis center will be referred to as an "axis center line."

Two lines E extending from the axis center toward the arc-shaped asymmetrical removal portion 170b so as to make an angle with respect to the axis center line will be referred to as slant lines E. In this case, it is preferred that the end portions of the hole portions 173 nearest to the arc-shaped asymmetrical removal portion 170b do not go beyond the slant lines having an angle of 16 The two slant lines are positioned between the axis center line B-B and the arc-shaped asymmetrical removal portion 170b.

Particularly, if the arc-shaped asymmetrical removal portion 170b has a radius of curvature which is in the range of 80％ to 95％ of a radius of the flange and if the area of the arc-shaped asymmetrical removal portion 170b is in the range of 10％ to 15％ of the area of the flange, it is further preferred that the end portions of the hole portions 173 do not go beyond the slant lines E having an angle of 16. When the area of the flange 170 from which the arc-shaped asymmetrical removal portion 170b is not removed is assumed to be 100, the area of the arc-shaped asymmetrical removal portion 170b is in the range of 10 to 15.

As illustrated in FIG. 5, when limited with respect to the arc angle 1 of the arc-shaped asymmetrical removal portion, if the arc-shaped asymmetrical removal portion 170b has a radius of curvature which is in the range of 80％ to 95％ of a radius of the flange and if the arc angle 1 of the arc-shaped asymmetrical removal portion is set to fall within a range of 60 to 80, it is further preferred that the end portions of the hole portions 173 do not go beyond the slant lines E having an angle of 16

By ensuring that the end portions of the hole portions 173 nearest to the arc-shaped asymmetrical removal portion 170b do not go beyond the slant lines having an angle of 16 as set forth above, it is possible to suppress the breakage or loosening of screws fastened to the screw holes 170a-a formed nearest to the arc-shaped asymmetrical removal portion 170b.

For reference, the screw holes formed nearest to the arc-shaped asymmetrical removal portion 170b are designated by reference numeral "170a-a" in order to distinguish the same from other screw holes.

The inventors have confirmed the influence of the angle through a simulation while changing the thickness of the flange 170. It was confirmed that the influence of the angle on the change in the thickness of the flange 170 is nothing or very insignificant.

For safety purposes, it is preferred that the hole portions 173 are formed so as to be positioned at the opposite side of the arc-shaped asymmetrical removal portion 170b with respect to the line B-B parallel to the line tangential to the inner end of the arc-shaped asymmetrical removal portion 170b and passing through the bearing axis center. The end portions of the hole portions 173 are formed so as to be positioned at the opposite side of the arc-shaped asymmetrical removal portion 170b with respect to the line B-B.

FIGS. 5 and 6 illustrate a modification of the flanged bearing provided with an arc-shaped asymmetrical removal portion according to the present invention. In this modification, grooves 172 recessed in the axial direction may be formed instead of forming the hole portions 173. By forming the grooves 172 in this way, it is possible to provide an effect of preventing generation of eccentricity while preventing the rigidity of the flange 170 from being reduced by the formation of holes. In the case where the grooves 172 are formed in the aforementioned manner, the generation of loosening or breakage of bolts is reliably suppressed. Thus, there is no need to limit the positions of the end portions of the grooves 172 existing near the arc-shaped asymmetrical removal portion 170b to the inside of the line B-B. It is also not necessary to limit the angle with respect to the line B-B. However, if the end portions of the grooves 172 existing near the arc-shaped asymmetrical removal portion 170b are limited to lie inside the line B-B, or if the angle is limited with respect to the line B-B, it is possible to reliably prevent the screw loosening phenomenon.

FIGS. 7 and 8 illustrate another modification of the flanged bearing provided with an arc-shaped asymmetrical removal portion according to the present invention. In this modification, protrusion portions 174 protruding in the axial direction are formed in the flange 170. The protrusion portions 174 are formed at both sides of the arc-shaped asymmetrical removal portion 170b toward the arc-shaped asymmetrical removal portion 170b with respect to the line B-B. The protrusion portions 174 are provided at both sides of the arc-shaped asymmetrical removal portion 170b in the circumferential direction. By forming the protrusion portions 174 in the flange 170 as mentioned above, it is possible to prevent generation of eccentricity while avoiding reduction in the rigidity of the flange 170.

In the state in which the protrusion portions 174 are provided at both sides of the arc-shaped asymmetrical removal portion 170b, one or more hole portions 173 or one or more axially-recessed grooves 172 may be formed at the opposite side of the arc-shaped asymmetrical removal portion 170b from the protrusion portions174. It may be also possible to form both the hole portions 173 and the recessed grooves 172.

The deformation amount of the flange 170, the deformation amounts of the bolts and the roundness of the outer ring raceway were confirmed through a computer simulation (finite element analysis) by applying a load to the bearing 100 having flange with an arc-shaped asymmetrical removal portion according to the present invention. The analysis was conducted with respect to a case where the arc-shaped asymmetrical removal portion 170b has a radius of curvature which is in the range of 80％ to 95％ of a radius of the flange 170, the area removed by the arc-shaped asymmetrical removal portion 170b is in a range of 10％ to 15％ of the area of the flange 170, and the arc angle 1 of the arc-shaped asymmetrical removal portion 170b measured at the bearing axis center is set to fall within a range of 60 to 80.

In the computer simulation, modeling was performed under the assumption that the bearing is mounted to a housing by fastening (nine) M8 bolts to the screw holes 170a of the flange, the friction coefficient between the flange and the housing is set at 0.1 and the friction coefficient of the inner ring width surfaces, with which the end portions face and make contact, is set at 0.1. The material properties (the elastic modulus and the Poisson's ratio) of a material of the bearing are set equal to the physical property values of bearing steel. The housing is made of a material ADC12 having an elastic modulus of 71,000 MPa and a Poisson's ratio of 0.3. As for the rolling elements 150, modeling was performed using load transfer elements (e.g., rigid bars) which make contact with an inner ring and an outer ring at contact points and transfer a load acting on the inner ring to the outer ring.

Calculation was performed under the assumption that the load and moment acting on the bearing is a load that acts on the bearing at a maximum engine torque when a motor vehicle is in a first-shift gear ratio and that the acting point of the loads lies at the center of the bearing.

The maximum deformation amount of the flange was 0.86 mm in the model illustrated in FIG. 10, 0.67 mm in the model illustrated in FIG. 11 and 0.66 mm in the model illustrated in FIG. 12. The roundness of the outer ring raceway was calculated to be 0.023 mm in the model illustrated in FIG. 10 and 0.020 mm or less in the models illustrated in FIGS. 11 and 12. Furthermore, as illustrated in FIGS. 13 and 14, in the case of the radial deformation amount of the bolt, it was confirmed that the deformation amount of a bolt head portion is significantly larger in the model illustrated in FIG. 10 than in the models illustrated in FIGS. 11 and 12. FIG. 14 illustrates the deformation amount of a bolt head portion fastened to the model illustrated in FIG. 12. The deformation amount of a bolt head portion fastened to the model illustrated in FIG. 11 is also similar to the deformation amount of a bolt head portion fastened to the model illustrated in FIG. 12. The bolt described with respect to the deformation amount is the bolt which is fastened to each of the screw holes 170a-a formed nearest to the arc-shaped asymmetrical removal portion 170b. As can be noted from the above analysis results, it was confirmed that an angle of 16 degrees is a critical value for the evaluation of flange rigidity in the flanged bearing provided with an arc-shaped asymmetrical removal portion.

The flange portion 170 is thermally treated so as to have a hardness which is in the range of HV 240 to HV 280.

A method of manufacturing a flanged bearing made of high-carbon chromium steel according to the present invention will be described with reference to FIGS. 15 to 17.

As illustrated in FIG. 15, the method of manufacturing a flanged bearing made of high-carbon chromium steel includes a forging step (ST-110), an intermediate heat treatment step (ST-120), a heat treatment step (ST-130), a lathe-cutting step (ST-140), a raceway induction hardening heat treatment step (ST-150), and a raceway machining step (ST-160).

At the forging step (ST-110), the high-carbon chromium steel is pressed in conformity with the shape of the bearing.

At the intermediate heat treatment step (ST-120), the forged bearing is thermally treated so that the machinability of the bearing is improved. The bearing which has gone through the intermediate heat treatment step is easily subjected to plastic working and is high in toughness and fatigue strength.

At the heat treatment step (ST-130), the bearing is subjected to a quenching process and a tempering process.

As illustrated in FIG. 16, in the quenching process, the bearing made of high-carbon chromium steel is heated to a temperature which is in the range of 820℃ to 890℃, kept at the temperature for 40 minutes and then quenched. In the quenching process, the bearing is through hardened so as to have an increased hardness.

As illustrated in FIG. 17, in the tempering process, the bearing made of high-carbon chromium steel is heated to a temperature equal to or higher than a recrystallization temperature. In the tempering process, the high-carbon chromium steel is heated to a high temperature which falls within a range of 630℃ to 700℃, kept at the temperature for 100 minutes and then air-cooled.

The flange portion 170 subjected to the quenching process and the tempering process has a hardness which is in the range of HV 240 to HV 260.

The heat treatment step (ST-130) may be composed of a normalizing process.

At the heat treatment step (ST-130), the high-carbon chromium steel is heated to a temperature equal to or higher than an austenitizing temperature, kept at the temperature for a predetermined time (e.g., 40 minutes) and then slowly cooled. At the heat treatment step (ST-130), the high-carbon chromium steel is heated to a temperature which is in the range of 820℃ to 890℃, kept at the temperature for a predetermined time and then slowly cooled. The flange portion 170 subjected to the normalizing process of the treatment step (ST-130) described above has a hardness which falls is in the range of HV 240 to HV 280.

At the lathe-cutting step (ST-140), the corners and surfaces of the inner rings 110, the outer ring 130 and the flange portion 170 are machined.

At the raceway induction hardening heat treatment step (ST-150), the raceways of the bearing are subjected to induction hardening heat treatment. The raceways thermally treated at the raceway induction hardening heat treatment step (ST-150) provides an effect in that the hardened depth becomes larger than that of the prior art due to the heat treatment step (ST-130) performed earlier.

At the raceway machining step (ST-160), the raceways of the bearing are lathe-cut to form raceways. The raceways machined at the raceway machining step (ST-160) guides the movement of the rolling elements 150.

The flange portion of the flanged bearing manufactured by the method of manufacturing a flanged bearing made of high-carbon chromium steel has a hardness which is 20％ to 30％ higher than that of the prior art. In addition, as described above, there is provided an effect in that the hardened depth becomes larger when the raceways are subjected to the induction hardening heat treatment.

While the flanged bearing made of high-carbon chromium steel and the method of manufacturing the same according to the present invention have been described thus far, they are nothing more than one example. It will be understood by those skilled in the art that different modifications and other equivalent embodiments can be derived from the foregoing. Accordingly, the true technical protection scope shall be determined by the technical concept of the appended claims.

Claims

A flanged bearing made of high-carbon chromium steel, comprising: inner rings, an outer ring, a flange portion, rolling elements, and a retainer, wherein the inner rings are annularly formed to extend in a circumferential direction and are provided on their radial outer surfaces with inner ring raceway extending in the circumferential direction, wherein the outer ring is annularly formed to extend in the circumferential direction and is provided on its radial inner surface with an outer ring raceway extending in the circumferential direction, wherein the flange portion is provided in the inner rings or the outer ring and is formed in a plate shape to extend in the circumferential direction, wherein the rolling elements are arranged between the inner rings and the outer ring and are spaced apart in the circumferential direction by the retainer, wherein the retainer is located between the inner rings and the outer ring and is provided so that the rolling elements are spaced apart in the circumferential direction, wherein the flange portion is heat treated so as to have a hardness which is in the range of HV 240 to HV 280, and wherein the raceway of the inner rings or the outer ring provided with the flange portion is subjected to induction hardening after the flange portion is heat treated.
A method of manufacturing a flanged bearing made of high-carbon chromium steel, comprising: a forging step (ST-110), a heat treatment step (ST-130), a lathe-cutting step (ST-140), a raceway induction hardening heat treatment step (ST-150), and a raceway machining step (ST-160); wherein the heat treatment step (ST-130) includes a quenching process and tempering process; wherein the raceway induction hardening heat treatment step (ST-150) is performed after the heat treatment step (ST-130) so as to subject raceway surfaces to induction hardening heat treatment, and wherein raceways are machined at the raceway machining step (ST-160) on the raceways of the bearing subjected to the induction hardening heat treatment.
The method of Claim 2, characterized in that in the quenching process of the heat treatment step (ST-130), the flanged bearing is heated to a temperature which is in the range of 820℃ to 890℃ and then quenched.
The method of Claim 2, characterized in that in the tempering process of the heat treatment step (ST-130), the flanged bearing is heated to a temperature equal to or higher than a recrystallization temperature of high-carbon chromium steel.
The method of Claim 4, characterized in that in the tempering process, the high-carbon chromium steel is heated to a high temperature which is in the range of 630℃ to 700℃ and is then air-cooled.
The method of Claim 2, characterized in that the heat treatment step (ST-130) is a normalizing process, and the high-carbon chromium steel is heated to a temperature equal to or higher than an austenitizing temperature, kept at the heating temperature and then slowly cooled in the normalizing process so that the flange portion has a hardness which is in the range of HV 240 to HV 280.
The method of Claim 6, characterized in that in the normalizing process, the high-carbon chromium steel is heated to a temperature which is in the range of 820℃ to 890℃ and is then slowly cooled.
A flanged bearing of Claim 1, characterized in the flange comprises an arc-shaped asymmetrical removal portion formed at one side of a circular plate, a plurality of bolt fastening holes formed in an edge in a spaced-apart relationship along with a circumferential direction, and one or more hole portions formed in the positions circumferentially spaced-apart from the arc-shaped asymmetrical removal portion, wherein the arc-shaped asymmetrical removal portion has a radius of curvature which is in the range of 80％ to 95％ of a radius of the flange, and wherein the hole portions do not go beyond a line which extends from a bearing axis center toward the arc-shaped asymmetrical removal portion and makes an angle of 16 with respect to a line B-B parallel to a line tangential to the inner end of the arc-shaped asymmetrical removal portion and passing through the bearing axis center.
A flanged bearing of Claim 8, characterized in that the area of the arc-shaped asymmetrical removal portion is in a range of 10％ to 15％ of the area of the flange.