METHOD FOR PRODUCING ROLLING BODIES FOR ANTI-FRICTION BEARINGS

Abstract

Cylindrical rolling bodies, methods of producing the rolling bodies, and anti-friction bearings including the rolling bodies are disclosed. A method of producing the rolling bodies may include a) providing a spherical blank having a diameter (D) and a radius; and b) grinding the spherical blank into a cylindrical shape having a predefined diameter (d) and a length (L) that corresponds to the diameter (D) to form a cylindrical rolling body. After grinding, the cylindrical rolling body may have crowned end surfaces each having a radius corresponding to the radius of the spherical blank. Centerless cylindrical plunge grinding or centerless cylindrical throughfeed grinding may be used as the grinding method.

Claims

1. A method for producing a cylindrical rolling body with crowned end surfaces for anti-friction bearings, the method comprising: a) providing a spherical blank having a diameter (D) which corresponds to a length (L) of the cylindrical rolling body; and b) grinding the spherical blank into a cylindrical shape having a predefined diameter (d) to form the cylindrical rolling body, wherein centerless cylindrical plunge grinding or centerless cylindrical throughfeed grinding is used as the grinding method.

2. A cylindrical rolling body having crowned end surfaces, produced by a method as claimed in claim 1.

3. The cylindrical rolling body as claimed in claim 2, wherein the cylindrical rolling body is a bearing needle having a diameter (d) of less than 2 mm and a length (L) of less than 4 mm.

4. The cylindrical rolling body as claimed in claim 3, wherein a ratio of the length (L) to the diameter (d) is no more than 3:1.

5. An anti-friction bearing, comprising a rolling body ring, which has a cage and furthermore a plurality of rolling bodies as claimed in claim 2.

6. A method of operating the anti-friction bearing as claimed in claim 5, wherein the anti-friction bearing is operated at bearing speeds of up to 10,000 revolutions per minute.

7. A method comprising: a) providing a spherical blank having a diameter (D) and a radius; and b) grinding the spherical blank into a cylindrical shape having a predefined diameter (d) and a length (L) that corresponds to the diameter (D) to form a cylindrical rolling body; wherein, after grinding, the cylindrical rolling body has crowned end surfaces each having a radius corresponding to the radius of the spherical blank.

8. The method of claim 7, wherein the grinding is performed using centerless cylindrical plunge grinding or centerless cylindrical throughfeed grinding.

9. A cylindrical rolling body having crowned end surfaces, produced by a method as claimed in claim 7.

10. The cylindrical rolling body as claimed in claim 9, wherein the cylindrical rolling body is a bearing needle having a diameter (d) of less than 2 mm and a length (L) of less than 4 mm.

11. The cylindrical rolling body as claimed in claim 10, wherein a ratio of the length (L) to the diameter (d) is no more than 3:1.

12. An anti-friction bearing comprising a rolling body ring, which has a cage and furthermore a plurality of rolling bodies as claimed in claim 9.

13. A method of operating the anti-friction bearing as claimed in claim 12, wherein the anti-friction bearing is operated at bearing speeds of up to 10,000 revolutions per minute.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The disclosure is explained by way of example below by means of FIGS. 1 to 4, where:

[0025] FIG. 1 shows an axial plan view of a rolling body ring of an axial bearing having a cage with bearing needles accommodated in cage pockets,

[0026] FIG. 2 shows a section through a spherical blank and through the rolling body produced therefrom,

[0027] FIG. 3 shows a method for using centerless cylindrical plunge grinding or centerless cylindrical throughfeed grinding, in side view, and

[0028] FIG. 4 shows a three-dimensional view of the method using centerless cylindrical throughfeed grinding.

DETAILED DESCRIPTION

[0029] FIG. 1 shows an axial plan view of a rolling body ring 1 of an axial bearing having a cage 2 and having pockets 3, in each of which a cylindrical rolling body 4 in the form of a bearing needle is accommodated. The radial forces generated by the rolling bodies at very high speeds must be absorbed without destruction by the radially outer boundary surface 6 of the pockets 3. For this purpose, the rolling bodies 4 have, at each of the axial ends thereof, a crowned end surface 7, which has a high surface finish, thus ensuring that the rolling bodies 4 do not dig into said outer boundary surfaces 6 of the pockets 3. The diameter d of the bearing needles is typically less than 2 mm, while the length L is less than 4 mm. For economic reasons, the ratio of length L to diameter d may be no more than 3:1.

[0030] FIG. 2 shows a section through a spherical blank 5 and through the rolling body 4 produced therefrom. Here, the production of the rolling bodies 4 from the spherical blank 5 involves an anti-friction bearing ball. The length L of the rolling bodies 4 corresponds to the diameter D of the spherical blank 5, while the diameter d of the rolling bodies 4 is a matter of free choice. The rolling body 4 with the axis of rotation 8 thereof is produced by grinding the hatched region 9 to the diameter d, wherein the crowned end surfaces 7 of the rolling body 4 have the radius of the spherical blank 5 and may not require any re-machining. FIG. 2 shows an enlargement of a spherical blank 5 having a diameter of 2.25 mm, from which a bearing needle 4 having a length L=2.25 mm and a diameter d of 1 mm is produced. Here, the blank 5 is ground by means of centerless cylindrical plunge grinding or centerless cylindrical throughfeed grinding to enable the method to be used for mass production.

[0031] FIG. 3 shows a method according to the disclosure using centerless cylindrical plunge grinding or centerless cylindrical throughfeed grinding on the spherical blanks 5, in side view. Here, the blank 5 is not clamped but is guided between a grinding disk 10 rotating about axis of rotation 10a in the direction of the arrow and a control disk 11 rotating about axis of rotation 11a in the direction of the arrow and, during this process, is held from below by means of a rail 12. A distinction is drawn between plunge grinding, in which in each case only one blank 5 is guided and machined between the grinding disk 10 and the control disk 11, and throughfeed grinding, in which a multiplicity of blanks 5, which are arranged in a row on the rail 12, are transferred in succession between the grinding disk 10 and the control disk 11 by means of the rail 12. During this process, there is a movement of the rail 12 in the direction of the z axis in FIG. 3, i.e. perpendicular to the x-y plane defined by the plane of the drawing.

[0032] FIG. 4 shows a three-dimensional view of the method shown in FIG. 3 using centerless cylindrical throughfeed grinding. The same reference signs as those in the previous figures denote the same elements. The rail 12 carries a multiplicity of spherical blanks 5 between the grinding disk 10 and the control disk 11, where the blanks 5 are ground into a cylindrical shape of the rolling bodies 4. In this method, very high throughputs can be achieved. After grinding, the crowned end surfaces 7 of the rolling bodies 4 have the radius of the spherical blank 5 and do not require any further remachining.

[0033] All the features mentioned in the preceding description of the figures, in the claims and in the introduction to the description can be used both individually and in any desired combination and also include the use of a profiled control disk (feed screw) of the kind used in the production of taper rollers, for example. Thus, the disclosure is not restricted to the combinations of features described and claimed; on the contrary, all combinations of features should be regarded as disclosed.

LIST OF REFERENCE SIGNS

[0034] 1 rolling body ring [0035] 2 cage [0036] 3 pocket [0037] 4 rolling body [0038] 5 spherical blank [0039] 6 radially outer boundary surface of a pocket [0040] 7 crowned end surface of the rolling body [0041] 8 axis of the rolling body [0042] 9 region of the spherical blank which is to be ground [0043] 10 grinding disk [0044] 10a axis of rotation of the grinding disk [0045] 11 control disk [0046] 11a axis of rotation of the control disk [0047] 12 rail [0048] D diameter of the spherical blank [0049] L length of the rolling body [0050] d diameter of the rolling body