JP7798192B2 - Manufacturing method for bearing rollers - Google Patents

Description

The present invention relates to a method for manufacturing bearing rollers.

The outer diameter surface of a bearing roller may be crowned to alleviate excessive stress loads that occur at the axial ends. Crowning involves providing a slight curvature or inclination along the entire generatrix of the outer diameter surface or at both axial ends (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 2005-155763

FIG. 7A is a diagram showing a main part of the outer peripheral surface of a conventional bearing roller.
In FIG. 7A, the outer peripheral surface 100 a of the bearing roller 100 has a chamfered portion 102 and an outer diameter surface 104 arranged in order along the axial direction from the first side 100 b of the bearing roller 100 .
The outer diameter surface 104 has a crowning portion 106 adjacent to the chamfered portion 102 and a cylindrical portion 108 connected to the crowning portion 106 .
The crowning portion 106 has a predetermined curvature and smoothly connects the chamfered portion 102 and the cylindrical portion 108 .

As shown in Figure 7B, the crowning portion 106 is formed by bringing the machining surface 202 of the grinding wheel 200 into contact with the outer peripheral surface 110a of the rough-formed product 110 and grinding it. The rough-formed product 110 is the raw material for the bearing roller 100, and becomes the bearing roller 100 by providing the crowning portion 106 and cylindrical portion 108. The outer peripheral surface 110a of the rough-formed product 110 has a chamfered portion 112 and a polished surface 114. The chamfered portion 112 remains as the chamfered portion 102 of the bearing roller 100.

The machining surface 202 has an inclined surface 202a for forming the crowning portion 106 and a cylindrical surface 202b for forming the cylindrical portion 108. Both surfaces 202a and 202b are formed (dressed) into a shape that matches the shapes of the crowning portion 106 and the cylindrical portion 108.

The dressed grinding wheel 200 is repeatedly used to polish the bearing rollers 100 .
The surfaces 202 a, 202 b of the grinding wheel 200 are gradually deformed by wear due to repeated use. This deformation gradually reduces the dimensional accuracy of the formed crowning portion 106. For this reason, after the grinding wheel 200 has been used a predetermined number of times, it is re-dressed and reshaped to match the shapes of the crowning portion 106 and the cylindrical portion 108.

Here, when bearing roller 100 is ground by grindstone 200, as shown in the partial cross-sectional view shown in the dashed circle in Figure 7A, protrusion 120 may be formed in the vicinity of boundary B between chamfered portion 102 and crowning portion 106 of bearing roller 100 after grinding. The radial height of protrusion 120 is about several μm.
The protrusion 120 is generated due to partial wear occurring on the inclined surface 202a of the grinding wheel 200. That is, the amount of polishing is greatest near the boundary B, and the load and surface pressure acting thereon are greater than in other areas. Therefore, wear is prominent in the portion of the inclined surface 202a corresponding to the boundary B. Such partial wear on the inclined surface 202a causes the protrusion 120 near the boundary B.

When the bearing roller 100 is used in a bearing, the projections 120 come into contact with a raceway. Contact between the projections 120 and the raceway may reduce the life of the bearing.
Furthermore, the protrusions 120 are inevitably generated when the crowning portion 106 is formed by polishing.
Therefore, it is desirable to have a method for suppressing a decrease in bearing life even if the above-mentioned protrusions occur.

This embodiment is a method for manufacturing a bearing roller. The outer peripheral surface of the bearing roller rough has a first rough-shaped chamfered portion and a polished surface, which are arranged in order from the first side to the second side in the axial direction of the bearing roller. The outer peripheral surface of the bearing roller has a first chamfered portion, a first crowning portion, and a second crowning portion, which are arranged in order from the first side to the second side in the axial direction of the bearing roller. This manufacturing method includes a polishing step in which a grinding wheel is brought into contact with the polished surface to form the first crowning portion and the second crowning portion on the polished surface while leaving the first rough-shaped chamfered portion as the first chamfered portion, thereby obtaining the bearing roller from the rough. The grinding wheel has a contact surface that contacts the rough-shaped portion and a first non-contact surface adjacent to the contact surface on the first side of the rough-shaped portion. The contact surface has a first inclined surface adjacent to the first non-contact surface and forming the first crowning portion, and a second inclined surface forming the second crowning portion. A boundary between the first non-contact surface and the first inclined surface is defined as a first boundary circle, an imaginary plane including the first boundary circle is defined as a first boundary surface, and a boundary between the first inclined surface and the second inclined surface is defined as a second boundary circle. Furthermore, in a cross section including a central axis of the grinding wheel, a tangent to the second inclined surface on the second boundary circle is defined as a first tangent, and an imaginary conical surface extending the second inclined surface toward a first axial side beyond the second boundary circle and having a generatrix along the first tangent is defined as a first conical surface. A difference between the radius of a first intersecting circle where the first boundary surface and the first conical surface intersect and the radius of the first boundary circle is 3 μm or more and 20 μm or less.

According to the present disclosure, it is possible to obtain bearing rollers that can suppress a decrease in bearing life.

FIG. 1 is a front view of a cylindrical roller. FIG. 2A is an enlarged view of a main part of FIG. FIG. 2B is a further enlarged view of the main part of FIG. 2A. FIG. 3 is a diagram showing a method for manufacturing a cylindrical roller. FIG. 4 is a diagram showing a cross section of the grinding wheel. FIG. 5 is a diagram showing a cross section of the grinding wheel. FIG. 6 is a cross-sectional view of a cylindrical roller bearing in which the cylindrical roller of this embodiment is used. FIG. 7A is a diagram showing a main part of the outer peripheral surface of a conventional bearing roller. FIG. 7B is a diagram showing a grindstone used for a conventional bearing roller.

First, the contents of the embodiment will be listed and explained.
[Outline of the embodiment]
(1) This embodiment is a method for manufacturing a bearing roller. The outer peripheral surface of the bearing roller rough has a first rough-piece chamfer and a polished surface, which are arranged in order from a first side to a second side in the axial direction of the bearing roller. The outer peripheral surface of the bearing roller has a first chamfer, a first crowning, and a second crowning, which are arranged in order from the first side to the second side in the axial direction of the bearing roller. This manufacturing method includes a polishing step of bringing a grinding wheel into contact with the polished surface to form the first crowning and the second crowning on the polished surface while leaving the first rough-piece chamfer as the first chamfer, thereby obtaining the bearing roller from the rough. The grinding wheel has a contact surface that contacts the rough-piece and a first non-contact surface adjacent to the contact surface on the first side of the rough-piece. The contact surface has a first inclined surface adjacent to the first non-contact surface and forming the first crowning portion, and a second inclined surface forming the second crowning portion. A boundary between the first non-contact surface and the first inclined surface is defined as a first boundary circle, an imaginary plane including the first boundary circle is defined as a first boundary surface, and a boundary between the first inclined surface and the second inclined surface is defined as a second boundary circle. Furthermore, in a cross section including a central axis of the grinding wheel, a tangent to the second inclined surface on the second boundary circle is defined as a first tangent, and an imaginary conical surface extending the second inclined surface toward a first axial side beyond the second boundary circle and having a generatrix along the first tangent is defined as a first conical surface. A difference between the radius of a first intersecting circle where the first boundary surface and the first conical surface intersect and the radius of the first boundary circle is 3 μm or more and 20 μm or less.

The radial position of the boundary between the first chamfered portion and the first crowning portion of the bearing roller obtained by the above manufacturing method is closer to the central axis of the bearing roller than the radial position of the boundary between the first chamfered portion and the second crowning portion in a case where only the second crowning portion is provided on the outer peripheral surface of the bearing roller. As a result, even if a protrusion occurs near the boundary between the first chamfered portion and the first crowning portion of the bearing roller obtained by the above embodiment, this protrusion can be contained radially inward of the imaginary extended plane of the second crowning portion, and it is possible to prevent the protrusion from contacting the raceway and reducing the life of the bearing.
If the difference between the radius of the first intersecting circle and the radius of the first boundary circle is less than 3 μm, the protrusion may protrude radially outward beyond the imaginary extension plane of the second crowning portion. Furthermore, if the difference between the radius of the first intersecting circle and the radius of the first boundary circle is greater than 20 μm, the polishing amount of the polished surface becomes greater than necessary. This increased polishing amount may lead to increased costs.
In the above manufacturing method, by setting the difference between the radius of the first intersecting circle and the radius of the first boundary circle to be 3 μm or more and 20 μm or less, it is possible to obtain a bearing roller that is capable of suppressing a decrease in bearing life.

(2) In the above-described method for manufacturing a bearing roller, the outer peripheral surface of the bearing roller rough further has a second rough-piece chamfered portion adjacent to a second axial side of the surface to be polished, and the outer peripheral surface of the bearing roller has, arranged in order from the second axial side to the first axial side of the bearing roller, a second chamfered portion, a third crowning portion, and a fourth crowning portion located between the third crowning portion and the flat portion, and in the polishing step, the second rough-piece chamfered portion is left as the second chamfered portion, and in addition to the first crowning portion and the second crowning portion, the third crowning portion and the fourth crowning portion are formed on the surface to be polished, and the grindstone further has a second non-contact surface adjacent to the contact surface on the second side of the rough-piece, and the contact surface is adjacent to the second non-contact surface. the boundary between the second non-contact surface and the third inclined surface is defined as a third boundary circle, an imaginary plane including the third boundary circle is defined as a second boundary surface, the boundary between the third inclined surface and the fourth inclined surface is defined as a fourth boundary circle, a tangent to the fourth inclined surface on the fourth boundary circle in a cross section including the central axis of the grinding wheel is defined as a second tangent, and a virtual conical surface extending the fourth inclined surface toward a second side in the axial direction beyond the fourth boundary circle and having a generatrix along the second tangent is defined as a second conical surface, it is preferable that the difference between the radius of the second intersecting circle where the second boundary surface and the second conical surface intersect and the radius of the third boundary circle is 3 μm or more and 20 μm or less.
If the difference between the radius of the second intersecting circle and the radius of the third boundary circle is less than 3 μm, the protrusion occurring near the boundary between the second chamfered portion and the third crowning portion may protrude radially outward beyond the imaginary extension plane of the fourth crowning portion. Furthermore, if the difference between the radius of the second intersecting circle and the radius of the third boundary circle is greater than 20 μm, the amount of polishing of the polished surface will be greater than necessary. This increased amount of polishing may lead to increased costs.
In the above manufacturing method, by setting the difference between the radius of the second intersecting circle and the radius of the third boundary circle to 3 μm or more and 20 μm or less, it is possible to more reliably obtain bearing rollers that can suppress a decrease in bearing life.

(3) In the above-described method for manufacturing a bearing roller, the outer peripheral surface of the bearing roller further has a cylindrical portion adjacent to the second crowning portion on a second side of the second crowning portion in the axial direction of the bearing roller, the contact surface further has a cylindrical surface adjacent to the second inclined surface and for forming the cylindrical portion, and the boundary between the second inclined surface and the cylindrical surface is defined as a fifth boundary circle,
When the axial distance between the first boundary circle and the second boundary circle is the first interval, and the axial distance between the first boundary circle and the fifth boundary circle is the second interval, it is preferable that the ratio of the first interval to the second interval is greater than or equal to 1/20 and less than or equal to 1/2.
Setting the ratio of the first distance to the second distance to be less than 1/20 may result in the first crowning portion being unable to achieve the desired axial length depending on the diameter of the bearing roller. Setting the ratio of the first distance to the second distance to be greater than 1/2 may result in the first crowning portion having an unnecessarily large desired axial length, resulting in a large amount of grinding. A large amount of grinding may result in increased costs.
Setting the ratio of the first distance to the second distance to be 1/20 or more and 1/2 or less allows the first crowning portion to be provided within a suitable range in the axial direction.

[Details of the embodiment]
Preferred embodiments will now be described with reference to the drawings.
[Configuration of cylindrical rollers]

FIG. 1 is a front view of a cylindrical roller.
In FIG. 1, a cylindrical roller 1 is a roller for a bearing, and is used as a rolling element in a cylindrical roller bearing or a thrust roller bearing.
The cylindrical roller 1 is a cylindrical member made of bearing steel or the like.
In the following description, the direction along the central axis C1 of the cylindrical roller 1 will be referred to as the "axial direction." The axial direction also includes a direction parallel to the central axis C1 of the cylindrical roller 1. Furthermore, the direction along the diameter of the cylindrical roller 1 will be referred to as the "radial direction."

Cylindrical roller 1 has an outer peripheral surface 1a, a first roller end face 1b which is a first side in the axial direction of cylindrical roller 1, and a second roller end face 1c which is a second side in the axial direction of cylindrical roller 1.
The outer peripheral surface 1 a of the cylindrical roller 1 has a first chamfered portion 2 , an outer diameter surface 4 , and a second chamfered portion 6 .
The first chamfered portion 2 is provided between the first roller end face 1 b of the cylindrical roller 1 and the outer diameter surface 4 .
The second chamfered portion 6 is provided between the second roller end face 1 c of the cylindrical roller 1 and the outer diameter surface 4 .

The outer diameter surface 4 is a polished surface.
The outer diameter surface 4 has a first crowning portion 10 , a second crowning portion 12 , a cylindrical portion (flat portion) 14 , a third crowning portion 16 , and a fourth crowning portion 18 .
The outer diameter surface 4 includes a rolling surface. The rolling surface is a surface that comes into contact with the raceway surfaces of the inner and outer rings of a cylindrical roller bearing in which the cylindrical roller 1 is incorporated. The rolling surface includes the entire second crowning portion 12, the entire cylindrical portion 14, the entire fourth crowning portion 18, a portion of the first crowning portion 10 on the second axial side, and a portion of the third crowning portion 16 on the first axial side.

The cylindrical portion 14 is provided at the axial center of the outer diameter surface 4 .
The first crowning portion 10 and the second crowning portion 12 are provided between the cylindrical portion 14 and the first chamfered portion 2. The first crowning portion 10 and the second crowning portion 12 are inclined surfaces that are inclined so as to reduce in diameter from the cylindrical portion 14 toward the first chamfered portion 2. In a cross section including the central axis of the cylindrical roller 1, the first crowning portion 10 and the second crowning portion 12 are inclined with respect to the cylindrical portion 14.
The third crowning portion 16 and the fourth crowning portion 18 are provided between the cylindrical portion 14 and the second chamfered portion 6. The third crowning portion 16 and the fourth crowning portion 18 are inclined surfaces that are inclined so as to reduce in diameter from the cylindrical portion 14 toward the second chamfered portion 6. In a cross section including the central axis of the cylindrical roller 1, the third crowning portion 16 and the fourth crowning portion 18 are inclined with respect to the cylindrical portion 14.
The outer diameter surface 4 has crowning portions 10, 12, 16, and 18 which are inclined surfaces, and thus has a crowning shape as a whole.

Fig. 2A is an enlarged view of a main part of Fig. 1. Fig. 2A shows an end portion including a first roller end surface 1b of cylindrical roller 1.
As shown in FIG. 2A , on the outer peripheral surface 1 a of the cylindrical roller 1, the first chamfered portion 2, the first crowning portion 10, the second crowning portion 12, and the cylindrical portion 14 are arranged in order along the axial direction from the first roller end face 1 b (first side) of the cylindrical roller 1 to the second roller end face 1 c (second side).
The first crowning portion 10 is connected to the first chamfered portion 2. The second crowning portion 12 is provided between the first crowning portion 10 and the cylindrical portion 14.
The boundary between the first chamfered portion 2 and the first crowning portion 10 is a boundary circle K1 extending in the circumferential direction of the central axis C1 of the cylindrical roller 1.
The boundary between the first crowning portion 10 and the second crowning portion 12 is a boundary circle K2 extending in the circumferential direction of the central axis C1 of the cylindrical roller 1.

As described above, the first crowning portion 10 and the second crowning portion 12 are inclined so that the diameter thereof decreases from the cylindrical portion 14 toward the first chamfered portion 2 .
The first crowning portion 10 has a curved surface. The first crowning portion 10 has a curve with a predetermined curvature such that, in a cross section including the central axis C1 of the cylindrical roller 1, a point on the cross-sectional contour line between any two points exists on the opposite side of an imaginary line connecting any two points on the cross-sectional contour line of the first crowning portion 10 from the central axis C1 of the cylindrical roller 1. The first crowning portion 10 has a circular shape in any plane perpendicular to the central axis C1 of the cylindrical roller 1.
The second crowning portion 12 has a curved surface. The second crowning portion 12 has a curve with a predetermined curvature such that, in a cross section including the central axis C1 of the cylindrical roller 1, a point on the cross-sectional contour line between any two points exists on the opposite side of an imaginary line connecting any two points on the cross-sectional contour line of the second crowning portion 12 from the central axis C1 of the cylindrical roller 1. The second crowning portion 12 has a circular shape in any plane perpendicular to the central axis C1 of the cylindrical roller 1.
In a cross section including the central axis C1 of the cylindrical roller 1, the angle formed by a tangent at any position of the first crowning portion 10 and the central axis C1 of the cylindrical roller 1 is larger than the angle formed by a tangent at any position of the second crowning portion 12 excluding the boundary circle K2 and the central axis C1 of the cylindrical roller 1.

FIG. 2B is a further enlarged view of the main part of FIG. 2A.
As described above, in a cross section including the central axis C1 of the cylindrical roller 1, the angle formed by the tangent at any position of the first crowning portion 10 and the central axis C1 of the cylindrical roller 1 is larger than the angle formed by the tangent at any position of the second crowning portion 12 excluding the boundary circle K2 and the central axis C1 of the cylindrical roller 1. Therefore, the first crowning portion 10 is inclined so as to gradually move away from the first roller extension conical surface E1 as it moves from the second crowning portion 12 toward the first chamfered portion 2.
The first roller extension conical surface E1 is an imaginary conical surface having as its generating line a tangent to the second crowning portion 12 at a boundary circle K2 between the first crowning portion 10 and the second crowning portion 12 in a cross section including the central axis C1 of the cylindrical roller 1. In other words, the first roller extension conical surface E1 is an imaginary extension surface of the second crowning portion 12.

The intersecting circle P1 is a circle where the first roller extension conical surface E1 and the first boundary surface L1 intersect. The first boundary surface L1 is an imaginary plane that includes the boundary circle K1.
The intersection circle P1 is a virtual boundary circle between the first chamfered portion 2 and the second crowning portion 12 when it is assumed that the first chamfered portion 2 and the second crowning portion 12 are connected without providing the first crowning portion 10.

Here, the difference D1 between the radius of the boundary circle K1 and the radius of the intersection circle P1 is set to be 3 μm or more and 20 μm or less.
As a result, even if a protrusion due to grinding occurs near the boundary circle K1, this protrusion will be contained radially inward of the first roller extension conical surface E1 of the second crowning portion 12. As a result, the cylindrical roller 1 can prevent the protrusion from coming into contact with the inner and outer rings and reducing the life of the bearing.

The third crowning portion 16 and the fourth crowning portion 18 have a configuration similar to that of the first crowning portion 10 and the second crowning portion 12, but rotated 180° around the axial center.

[Regarding the polishing process]
FIG. 3 is a diagram showing a manufacturing method of the cylindrical roller 1.
FIG. 3 shows the grinding process for obtaining the cylindrical roller 1 from the rough product 20.
3, a rough-formed product 20 is a material for the cylindrical roller 1. The rough-formed product 20 becomes the cylindrical roller 1 by providing the crowning portions 10, 12, 16, 18 and the cylindrical portion 14.
The blank 20 has an outer peripheral surface 20a, a first blank end surface 20b which is a first side in the axial direction of the blank, and a second blank end surface 20c which is a second side in the axial direction of the blank.
The outer peripheral surface 20a of the rough-formed product 20 has a first rough-formed-product chamfered portion 22, a polished surface 24, and a second rough-formed-product chamfered portion 26. The first rough-formed-product chamfered portion 22 and the second rough-formed-product chamfered portion 26 remain as the first chamfered portion 2 and the second chamfered portion 6 after the polishing process.
On the outer peripheral surface 20a, the first preformed product chamfered portion 22, the polished surface 24, and the second preformed product chamfered portion 26 are arranged in order along the axial direction from the first preformed product end face 20b (first side) of the preformed product 20 to the second preformed product end face 20c (second side).

In the polishing process, the grindstone 30 is brought into contact with the surface 24 to be polished. As a result, the crowning portions 10, 12, 16, 18 and the cylindrical portion 14 are provided on the surface 24 to be polished.
The grindstone 30 is, for example, a grindstone using abrasive grains whose main component is alumina.
The grinding wheel 30 is formed in a substantially cylindrical shape and is rotatable about a central axis C2 of the grinding wheel 30 by a rotating device (not shown).

The grinding wheel 30 has an outer peripheral surface 32, a first grinding wheel end face 30a which is a first axial side of the grinding wheel 30, and a second grinding wheel end face 30b which is a second axial side of the grinding wheel 30.
The outer peripheral surface 32 of the grinding wheel 30 has a first non-contact surface 32a, a contact surface 32b, and a second non-contact surface 32c. Neither of the non-contact surfaces 32a, 32c contacts the blank 20. The contact surface 32b contacts the blank 20.
The first non-contact surface 32a, the contact surface 32b, and the second non-contact surface 32c are arranged in order along the axial direction from the first grinding wheel end surface 30a to the second grinding wheel end surface 30b.

In the polishing process, the grinding wheel 30 and the rough-formed product 20 are positioned so that the central axis C1 of the cylindrical roller 1 and the central axis C2 of the grinding wheel 30 are parallel. Next, the grinding wheel 30 and the rough-formed product 20 are rotated. After that, as shown in the lower part of Figure 3, the surface 24 to be polished of the rough-formed product 20 is brought into contact with the outer peripheral surface (contact surface 32b) of the grinding wheel 30.

The contact surface 32b has a plurality of surfaces for forming the crowning portions 10, 12, 16, 18 and the cylindrical portion 14.
The polished surface 24 is polished by the contact surface 32b. As a result, the shape of the contact surface 32b is transferred to the polished surface 24. As a result, the crowning portions 10, 12, 16, 18 and the cylindrical portion 14 are formed on the polished surface 24. The rough product 20 becomes a cylindrical roller 1 with the crowning portions 10, 12, 16, 18 and the cylindrical portion 14 formed on the polished surface 24.

Fig. 4 is a diagram showing a cross section of the grinding wheel 30. Although Fig. 4 shows a cross section, the following description will mainly focus on each part of the outer shape that appears in the cross section.
As described above, the contact surface 32 b has the first inclined surface 40 , the second inclined surface 42 , and the cylindrical surface (flat surface) 44 .
On the contact surface 32b, the first inclined surface 40, the second inclined surface 42, and the cylindrical surface 44 are arranged in order along the axial direction from the first grinding wheel end face 30a (first side) of the grinding wheel 30 to the second grinding wheel end face 30b (second side) (Figure 3).

The cylindrical surface 44 is a surface for forming the cylindrical portion 14. The cylindrical surface 44 is provided at the axial center of the contact surface 32b.
The first inclined surface 40 and the second inclined surface 42 are provided between the first non-contact surface 32 a and the cylindrical surface 44 .
The first inclined surface 40 is connected to the first non-contact surface 32 a. The first inclined surface 40 is a surface for forming the first crowning portion 10.
The first inclined surface 40 has a curved surface. The first inclined surface 40 has a curve (a first inclined line portion PL1 described later) with a predetermined curvature, in which a point on the cross-sectional contour line between any two points on the cross-sectional contour line of the first inclined surface 40 exists on the side of the central axis C2 of the grinding wheel 30 closer to the central axis C2 of the grinding wheel 30 than an imaginary line connecting any two points on the cross-sectional contour line of the first inclined surface 40. The first inclined surface 40 has a circular shape in any cross-section perpendicular to the central axis C2 of the grinding wheel 30.

The second inclined surface 42 is provided between the first inclined surface 40 and the cylindrical surface 44. The second inclined surface 42 is a surface for forming the second crowning portion 12.
The second inclined surface 42 has a curved surface. The second inclined surface 42 has a curve (a second inclined line portion PL2 described later) with a predetermined curvature, in which a point on the cross-sectional contour between any two points on the cross-sectional contour of the second inclined surface 42 exists on the side of the central axis C2 of the grinding wheel 30 closer to the central axis C2 of the grinding wheel 30 than an imaginary line connecting any two points on the cross-sectional contour of the second inclined surface 42. The second inclined surface 42 has a circular shape in any cross-section perpendicular to the central axis C2 of the grinding wheel 30.
The surfaces included in the contact surface 32b are smoothly connected to each other.

The contour line PL in the axial cross section of the contact surface 32b including the center axis C2 has a first inclined line portion PL1, a second inclined line portion PL2, and a straight line portion PL5.
The first inclined line portion PL1 is a contour line corresponding to the first inclined surface 40. Therefore, the first inclined line portion PL1 is a curve with the same curvature as the curvature of the curve in a cross section including the central axis C1 of the first crowning portion 10.
The second inclined line portion PL2 is a contour line corresponding to the second inclined surface 42. Therefore, the second inclined line portion PL2 is a curve with the same curvature as the curvature of the curve in a cross section including the central axis C1 of the second crowning portion 12.
The straight line portion PL5 is a contour line corresponding to the cylindrical surface 44. The straight line portion PL5 is a straight line parallel to the central axis C2.

4, a first boundary circle B1 is the boundary between the first non-contact surface 32a and the first inclined surface 40. The first boundary circle B1 is tangent to a boundary circle K1 between the first chamfered portion 2 and the first crowning portion 10.
The second boundary circle B2 is the boundary between the first inclined surface 40 and the second inclined surface 42. The second boundary circle B2 is tangent to the boundary circle K2 between the first crowning portion 10 and the second crowning portion 12.

The first conical surface E10 is a virtual conical surface formed by extending the second inclined surface 42 toward the first axial side beyond the second boundary circle B2. The generatrix of the first conical surface E10 is along a first tangent line E110. The first tangent line E110 is a tangent line to the second inclined surface 42 on the second boundary circle B2 in a cross section including the central axis C2.
In other words, the first conical surface E10 is a conical surface obtained by extending the tangent to the second inclined line portion PL2 in the cross section including the center axis C2 of the grinding wheel 30 at the second boundary circle B2 toward the first axial side and integrating it in the circumferential direction of the center axis C2 of the grinding wheel 30.

As described above, the first boundary surface L1 is an imaginary plane that includes the first boundary circle B1 (boundary circle K1).
Therefore, when the boundary circle K1 and the first boundary circle B1 coincide with each other at the end of the polishing process, the first roller extension conical surface E1 and the first conical surface E10 overlap with each other.
The first intersecting circle P10 is a circle where the first boundary surface L1 and the first conical surface E10 intersect.
In this embodiment, the difference D10 between the radius of the first intersection circle P10 and the radius of the first boundary circle B1 is set to be equal to or greater than 3 μm and equal to or less than 20 μm.

The radial position of the boundary circle K1 of the cylindrical roller 1 obtained by the above configuration is closer to the central axis C1 of the cylindrical roller 1 than the radial position of the boundary (intersection circle P1) between the first chamfered portion 2 and the second crowning portion 12 when only the second crowning portion 12 is provided on the outer peripheral surface 1a of the cylindrical roller 1. As a result, even if a protrusion occurs in the vicinity of the boundary circle K1 between the first chamfered portion 2 and the first crowning portion 10, the bearing roller obtained by the above embodiment can accommodate this protrusion radially inward of the first roller extension conical surface E1 (FIG. 2B) of the second crowning portion 12, and it is possible to prevent the protrusion from coming into contact with the inner or outer ring and reducing the life of the bearing.
If the difference D10 is smaller than 3 μm, the protrusion may be formed so as to protrude radially outward beyond the first roller extension conical surface E1 of the second crowning portion 12. If the difference D10 is larger than 20 μm, the amount of polishing of the polished surface 24 becomes greater than necessary. An increase in the amount of polishing may lead to an increase in costs.
In the above manufacturing method, by setting the difference D10 to be 3 μm or more and 20 μm or less, it is possible to obtain cylindrical rollers 1 that are capable of suppressing a decrease in bearing life.

The lower limit of the difference D10 is preferably 5 μm or more. By setting the lower limit to 5 μm or more, the manufacturing method can more reliably confine the protrusions generated in the vicinity of the boundary circle K1 to the radially inward side of the first roller extension conical surface E1.
Moreover, the upper limit of the difference D10 is preferably 10 μm or less. By setting the upper limit to 10 μm or less, the manufacturing method can reliably suppress an increase in costs.

As shown in Figure 4, in this embodiment, when the axial distance between the second boundary circle B2 and the first boundary circle B1 is defined as the first interval W1, and the axial distance between the boundary circle B10 and the first boundary circle B1 is defined as the second interval W2, it is preferable that the ratio of the first interval W1 to the second interval W2 be greater than or equal to 1/20 and less than or equal to 1/2. Note that the boundary circle B10 (fifth boundary circle) is the boundary between the second inclined surface 42 and the cylindrical surface 44.

If the ratio of the first distance W1 to the second distance W2 is made smaller than 1/20, the axial range of the first crowning portion 10 formed by the first inclined surface 40 will be small, depending on the diameter dimension of the cylindrical roller 1, and there is a risk that it will not be possible to ensure the range required for the first crowning portion 10. If the ratio of the first distance to the second distance is made larger than 1/2, the axial range of the first crowning portion 10 formed by the first inclined surface 40 will be larger than necessary, and there is a risk that the increased amount of grinding will lead to increased costs.
By setting the ratio of the first distance W1 to the second distance W2 to 1/20 or more and 1/2 or less, the manufacturing method described above can provide the first crowning portion 10 within a suitable axial range.

The lower limit of the ratio of the first spacing W1 to the second spacing W2 is preferably 1/7 or greater. By setting the lower limit to 1/7 or greater, the manufacturing method described above can more reliably provide the first crowning portion 10 within a suitable axial range.

As shown in FIG. 2A , when the axial width of the first crowning portion 10 of the cylindrical roller 1 formed by the grinding wheel 30 is defined as a first crowning width CW1, and the axial width of the entire crowning portion including the first crowning portion 10 and the second crowning portion 12 is defined as an entire crowning width CW, the first crowning width CW1 relative to the entire crowning width CW can be set as follows:
That is, when the overall crowning width CW is 1.5 mm or more and less than 3 mm, the first crowning width CW1 is preferably set to 0.5 mm.
When the overall crowning width CW is equal to or greater than 3 mm and less than 6 mm, the first crowning width CW1 is preferably set to 1.0 mm.
Furthermore, when the overall crowning width CW is 6 mm or more, the first crowning width CW1 is preferably 2 mm.

Fig. 5 is a diagram showing a cross section of the grinding wheel 30. Fig. 5 shows a cross section including the second grinding wheel end surface 30b of the grinding wheel 30. Although Fig. 5 shows a cross section, the following explanation will mainly focus on each part of the outer shape that appears in the cross section.
As described above, the outer peripheral surface 1 a of the cylindrical roller 1 has the second chamfered portion 6 , the third crowning portion 16 , and the fourth crowning portion 18 .
The second chamfered portion 6, the third crowning portion 16, and the fourth crowning portion 18 are arranged in order along the axial direction from the second roller end face 1c (second side) of the cylindrical roller 1 to the first roller end face 1b (first side).

The third crowning portion 16 is connected to the second chamfered portion 6. The fourth crowning portion 18 is provided between the third crowning portion 16 and the cylindrical portion 14.
The third crowning portion 16 has a shape similar to that of the first crowning portion 10. The fourth crowning portion 18 has a shape similar to that of the second crowning portion 12.
Therefore, a description of the third crowning portion 16 and the fourth crowning portion 18 will be omitted.

The contact surface 32 b further includes a third inclined surface 50 and a fourth inclined surface 52 .
On the contact surface 32b, the third inclined surface 50, the fourth inclined surface 52, and the cylindrical surface 44 are arranged in order along the axial direction from the second grinding wheel end face 30b (second side) of the grinding wheel 30 to the first grinding wheel end face 30a (first side) (Figure 3).
The third inclined surface 50 and the fourth inclined surface 52 are provided between the second non-contact surface 32 c and the cylindrical surface 44 .
The third inclined surface 50 is connected to the second non-contact surface 32 c. The third inclined surface 50 is a surface for forming the third crowning portion 16 .
The third inclined surface 50 has a curved surface. The third inclined surface 50 has a curve (a third inclined line portion PL3 described later) with a predetermined curvature, in which a point on the cross-sectional contour line between any two points on the cross-sectional contour line of the third inclined surface 50 exists on the side of the central axis C2 of the grinding wheel 30 closer to the central axis C2 of the grinding wheel 30 than an imaginary line connecting any two points on the cross-sectional contour line of the third inclined surface 50. The third inclined surface 50 has a circular shape in any cross-section perpendicular to the central axis C2 of the grinding wheel 30.

The fourth inclined surface 52 is provided between the third inclined surface 50 and the cylindrical surface 44. The fourth inclined surface 52 is a surface for forming the fourth crowning portion 18.
The fourth inclined surface 52 has a curved surface. The fourth inclined surface 52 has a curve (a fourth inclined line portion PL4 described later) with a predetermined curvature, in which a point on the cross-sectional contour between any two points on the cross-sectional contour of the fourth inclined surface 52 exists on the side of the central axis C2 of the grinding wheel 30 closer to the central axis C2 of the grinding wheel 30 than an imaginary line connecting any two points on the cross-sectional contour of the fourth inclined surface 52. The fourth inclined surface 52 has a circular shape in any cross-section perpendicular to the central axis C2 of the grinding wheel 30.

The contour line PL further has a third inclined line portion PL3 and a fourth inclined line portion PL4.
The third inclined line portion PL3 is a contour line corresponding to the third inclined surface 50. Therefore, the third inclined line portion PL3 is a curve with the same curvature as the curvature of the curve in a cross section including the central axis C1 of the third crowning portion 16.
The fourth inclined line portion PL4 is a contour line corresponding to the fourth inclined surface 52. Therefore, the fourth inclined line portion PL4 is a curve with the same curvature as the curve in a cross section including the central axis C1 of the fourth crowning portion 18.

5, the third boundary circle B3 is the boundary between the second non-contact surface 32c and the third inclined surface 50. The third boundary circle B3 is tangent to the boundary circle K4 between the second chamfered portion 6 and the third crowning portion 16.
The fourth boundary circle B4 is the boundary between the third inclined surface 50 and the fourth inclined surface 52. The fourth boundary circle B4 is tangent to the boundary circle K5 between the third crowning portion 16 and the fourth crowning portion 18.

The second conical surface E12 is a virtual conical surface formed by extending the fourth inclined surface 52 toward the second axial side beyond the fourth boundary circle B4. The generatrix of the second conical surface E12 is along the second tangent line E112. The second tangent line E112 is a tangent line to the fourth inclined surface 52 on the fourth boundary circle B4 in a cross section including the central axis C2.
In other words, the second conical surface E12 is a conical surface obtained by extending the tangent to the second inclined line portion PL4 in the cross section including the center axis C2 of the grinding wheel 30 at the fourth boundary circle B4 toward the second axial side and integrating it in the circumferential direction of the center axis C1 of the grinding wheel 30.

The second boundary surface L2 is an imaginary plane that includes the third boundary circle B3 (boundary circle K4).
Therefore, when the boundary circle K4 and the third boundary circle B3 coincide with each other at the end of the polishing process, the second roller extension conical surface E2 and the second imaginary extension conical surface E12 overlap with each other.
The second roller extension conical surface E2 is an imaginary conical surface having a generatrix that is a tangent to the fourth crowning portion 18 at the boundary circle K5, in a cross section including the central axis C1 of the cylindrical roller 1. In other words, the second roller extension conical surface E2 is an imaginary extension surface of the fourth crowning portion 18.
The second intersecting circle P12 is a circle where the second boundary surface L2 and the second conical surface E12 intersect.

Here, the difference D12 between the radius of the second intersection circle P12 and the radius of the third boundary circle B3 is set to be 3 μm or more and 20 μm or less, similar to the difference D10.
Even if a protrusion occurs near the boundary circle K4 of the cylindrical roller 1 obtained by this grinding wheel 30, the bearing roller obtained by the above embodiment can contain this protrusion radially inward of the second roller extension conical surface E2 of the fourth crowning portion 18, thereby preventing the protrusion from coming into contact with the inner and outer rings and reducing the life of the bearing.

In this way, in this embodiment, inclined surfaces 40, 42, 50, and 52 that meet the above-mentioned conditions are provided on both the first grinding wheel end face 30a and the second grinding wheel end face 30b at the contact surface 32b of the grinding wheel, thereby making it possible to obtain a cylindrical roller 1 that can suppress a decrease in bearing life.

FIG. 6 is a cross-sectional view of a cylindrical roller bearing 60 in which the cylindrical roller 1 of this embodiment is used.
In addition to a plurality of cylindrical rollers 1, cylindrical roller bearing 60 also comprises an inner ring 62, an outer ring 64, and a cage 66. The plurality of cylindrical rollers 1 are interposed so as to be able to roll freely between a raceway surface 62a of inner ring 62 and a raceway surface 64a of outer ring 64. Cage 66 holds the plurality of cylindrical rollers 1 at regular intervals in the circumferential direction.
As described above, the cylindrical roller 1 using the cylindrical roller 1 of this embodiment is prevented from reducing its lifespan.

〔others〕
The embodiments disclosed herein are illustrative in all respects and are not restrictive.
For example, in this embodiment, the first crowning portion 10 and the third crowning portion 16 are convex curved surfaces having a predetermined curvature, and the first inclined line portion PL1 and the third inclined line portion PL3 of the contour line PL of the grinding wheel 30 are curves corresponding to the first crowning portion 10 and the third crowning portion 16. On the other hand, in the present invention, the first crowning portion 10 and the third crowning portion 16 may be conical surfaces, and the first inclined line portion PL1 and the third inclined line portion PL3 may be straight lines.

In addition, in this embodiment, the second crowning portion 12 and the fourth crowning portion 18 are convex curved surfaces having a predetermined curvature, and the second inclined line portion PL2 and the fourth inclined line portion PL4 of the contour line PL of the grinding wheel 30 are curves corresponding to the second crowning portion 12 and the fourth crowning portion 18. On the other hand, in the present invention, the second crowning portion 12 and the fourth crowning portion 18 may be conical surfaces, and the second inclined line portion PL2 and the fourth inclined line portion PL4 may be straight lines.

Furthermore, in this embodiment, the cylindrical roller 1 has the cylindrical portion 14, and the grinding wheel 30 has the cylindrical surface 44. On the other hand, in the present invention, the second crowning portion 12 and the fourth crowning portion 18 of the cylindrical roller 1 may be connected, or may form an integrated crowning portion.
Furthermore, in the present invention, the second inclined surface 42 and the fourth inclined surface 52 of the grindstone 30 may be connected to each other, or may form an integral inclined surface.

In addition, while this embodiment illustrates cylindrical rollers used in cylindrical roller bearings, the roller manufacturing method disclosed in this embodiment can also be applied to rollers other than cylindrical rollers, such as tapered rollers, rod-shaped rollers, and needle rollers.

The scope of the present invention is not limited to the above-described embodiments, but includes all modifications within the scope of equivalents to the configurations described in the claims.

DESCRIPTION OF SYMBOLS 1 Cylindrical roller 1a Outer peripheral surface 1b First roller end face 1c Second roller end face 2 First chamfered portion 4 Outer diameter surface 6 Second chamfered portion 10 First crowning portion 12 Second crowning portion 14 Cylindrical portion 16 Third crowning portion 18 Fourth crowning portion 20 Roughly shaped product 20a Outer peripheral surface 20b First roughly shaped product end face 20c Second roughly shaped product end face 22 First roughly shaped product chamfered portion 24 Polished surface 26 Second roughly shaped product chamfered portion 30 Grinding stone 30a First grinding stone end face 30b Second grinding stone end face 32 Outer peripheral surface 32a First non-contact surface 32b Contact surface 32c Second non-contact surface 40 First inclined surface 42 Second inclined surface 44 Cylindrical surface 50 Third inclined surface 52 Fourth inclined surface 60 Bearing 62 Inner ring 62a Raceway surface 64 Outer ring 64a Raceway surface 66 Cage B1 First boundary circle B2 Second boundary circle B3 Third boundary circle B4 Fourth boundary circle B10 Boundary circle (fifth boundary circle) C1 Central axis C2 Central axis CW Overall crowning width CW1 First crowning width E1 First roller extended conical surface E10 First conical surface E110 First tangent E112 Second tangent E12 Second conical surface E2 Second roller extended conical surface K1 Boundary circle K2 Boundary circle K4 Boundary circle K5 Boundary circle L1 First boundary surface L2 Second boundary surface P1 Intersection circle P10 First intersection circle P12 Second intersection circle PL Contour line PL1 First inclined line portion PL2 Second inclined line portion PL3 Third inclined line portion PL4 4th slope line part PL5 Straight line part

Claims (3)

A method for manufacturing a bearing roller, comprising:
an outer peripheral surface of the bearing roller rough has a first rough-piece chamfered portion and a polished surface, which are arranged in order from a first side to a second side in an axial direction of the bearing roller rough,
the outer peripheral surface of the bearing roller has a first chamfered portion, a first crowning portion, and a second crowning portion arranged in this order from a first side to a second side in an axial direction of the bearing roller,
a polishing step of bringing a grindstone into contact with the surface to be polished, forming the first crowning portion and the second crowning portion on the surface to be polished while leaving the chamfered portion of the first rough product as the first chamfered portion, and obtaining the bearing roller from the rough product,
the grinding wheel has a contact surface that contacts the blank and a first non-contact surface that is adjacent to the contact surface on the first side of the blank;
the contact surface has a first inclined surface adjacent to the first non-contact surface and forming the first crowning portion, and a second inclined surface forming the second crowning portion,
a boundary between the first non-contact surface and the first inclined surface is defined as a first boundary circle, an imaginary plane including the first boundary circle is defined as a first boundary surface, and a boundary between the first inclined surface and the second inclined surface is defined as a second boundary circle;
In a cross section including a central axis of the grindstone, a tangent to the second inclined surface on the second boundary circle is defined as a first tangent;
When the second inclined surface is an imaginary conical surface extending from the second boundary circle toward a first side in the axial direction, and the imaginary conical surface has a generatrix along the first tangent line, the imaginary conical surface is defined as a first conical surface,
A method for manufacturing a roller for a bearing, wherein the difference between the radius of a first intersecting circle where the first boundary surface and the first conical surface intersect and the radius of the first boundary circle is 3 μm or more and 20 μm or less. the outer peripheral surface of the bearing roller blank further has a second blank chamfer portion adjacent to a second axial side of the polished surface,
the outer peripheral surface of the bearing roller has a second chamfered portion, a third crowning portion , and a fourth crowning portion arranged in this order from a second side to a first side in an axial direction of the bearing roller,
In the polishing step, the chamfered portion of the second rough product is left as the second chamfered portion, and in addition to the first crowning portion and the second crowning portion, the third crowning portion and the fourth crowning portion are formed on the polished surface;
the grinding wheel further has a second non-contact surface adjacent the contact surface on the second side of the blank;
the contact surface further includes a third inclined surface adjacent to the second non-contact surface and forming the third crowning portion, and a fourth inclined surface forming the fourth crowning portion,
a boundary between the second non-contact surface and the third inclined surface is defined as a third boundary circle, an imaginary plane including the third boundary circle is defined as a second boundary surface, and a boundary between the third inclined surface and the fourth inclined surface is defined as a fourth boundary circle;
a tangent to the fourth inclined surface on the fourth boundary circle in a cross section including the central axis of the grindstone is defined as a second tangent;
When the fourth inclined surface is defined as a virtual conical surface extending from the fourth boundary circle toward a second side in the axial direction, and the virtual conical surface has a generatrix along the second tangent line, the virtual conical surface is defined as a second conical surface,
2. The method for manufacturing a roller for a bearing according to claim 1, wherein the difference between the radius of a second intersecting circle where the second boundary surface and the second conical surface intersect and the radius of the third boundary circle is 3 μm or more and 20 μm or less. the outer peripheral surface of the bearing roller further has a cylindrical portion adjacent to the second crowning portion on a second side of the second crowning portion in the axial direction of the bearing roller,
the contact surface further includes a cylindrical surface adjacent to the second inclined surface and forming the cylindrical portion;
a boundary between the second inclined surface and the cylindrical surface is defined as a fifth boundary circle;
When the axial distance between the first boundary circle and the second boundary circle is a first interval, and the axial distance between the first boundary circle and the fifth boundary circle is a second interval,
2. The method for manufacturing rollers for a bearing according to claim 1, wherein a ratio of the first spacing to the second spacing is 1/20 or more and 1/2 or less.