Cage of a roller bearing and method for producing such a cage

Abstract

A cage for a roller bearing is provided. The cage has a ring-shaped base body with a plurality of pockets for receiving rolling elements. The base body is formed by two side rings arranged in a defined axial distance and by a plurality of pocket elements, which are located between the side rings. Each pocket element has two face sides designed for contacting a rolling element. The connection between the pocket element and each of the side rings is established by at least one beam joined with one of the side rings and the pocket element. The beam is a positive substance joined with one of the side rings and the pocket element and has a ring-shaped or elliptical cross section in a section perpendicular to the longitudinal extension of the beam.

Claims

1. A cage for a roller bearing comprising: a base body with a plurality of pockets for receiving rolling elements, wherein the base body comprises: two side rings arranged in a defined axial distance; and a plurality of pocket elements located between the side rings, wherein each of the plurality of pocket element comprises: two face sides designed for contacting a rolling element, wherein the connection between the pocket element and each of the side rings is established by at least one beam that is joined with one of the side rings and the pocket element, wherein beside the at least one beam no further connection exists between the pocket element and each of the side rings and wherein the at least one beam has a ring-shaped or elliptical cross section in a section perpendicular to the longitudinal extension of the beam; the at least one beam further comprising four or six beams arranged to establish the connection between the pocket element and each of the side rings.

2. The cage according to claim 1, wherein the at least one beam has a rounding radium at the location where it merges with the side ring and/or with the pocket element wherein the rounding radium is 0.2 mm to 0.3 mm or 2.0% to 3.0% of the diameter of the rolling element, whichever is greater.

3. The cage according to claim 1, wherein the two side rings are spaced in an axial distance in which a radial outer opening (OP) for the rolling elements is given between 92.5% and 97.5% of the diameter of the rolling elements in the case of a ball bearing and of the length of the rolling elements in the case of a rolling bearing.

4. The cage according to claim 1, wherein the side rings have a concave shape at a face side.

5. The cage according to claim 1, wherein the side sings extend radially between an inner radius which corresponds to a pitch circle of the roller bearing and an outer radius which corresponds to the pitch circle plus half of the diameter of the rolling element.

6. The cage according to claim 1, wherein the surface of the side rings which are facing the rolling elements comprise a substantially radial outer rectangular portion and an adjoining radial inner trapezoid portion seen perpendicular onto the surface.

7. The cage according to claim 1, wherein the face sides of the pocket elements have a concave surface, wherein the concave surface is spherical and has a radium which is between 105% and 115% of the diameter of the rolling elements.

8. A cage for a roller bearing comprising: a base body with a plurality of pockets for receiving rolling elements, wherein the base body comprises: two side rings arranged in a defined axial distance; and a plurality of pocket elements located between the side rings, wherein each of the plurality of pocket element comprises: two face sides designed for contacting a rolling element, wherein the connection between the pocket element and each of the side rings is established by at least one beam that is joined with one of the side rings and the pocket element, wherein beside the at least one beam no further connection exists between the pocket element and each of the side rings and wherein the at least one beam has a ring-shaped or elliptical cross section in a section perpendicular to the longitudinal extension of the beam, wherein the at least one beam has a minimum diameter which is between 10% and 20% of the diameter of the rolling element, wherein the at least one beam has an enlarged diameter at the location where it merges with the side ring and/or with the pocket element, wherein the diameter at that location is double the value of the minimum diameter.

9. The cage according to claim 8, wherein the at least one beam has a rounding radium at the location where it merges with the side ring and/or with the pocket element wherein the rounding radium is 0.2 mm to 0.3 mm or 2.0% to 3.0% of the diameter of the rolling element, whichever is greater.

10. The cage according to claim 8, wherein the two side rings are spaced in an axial distance in which a radial outer opening (OP) for the rolling elements is given between 92.5% and 97.5% of the diameter of the rolling elements in the case of a ball bearing and of the length of the rolling elements in the case of a rolling bearing.

11. The cage according to claim 8, wherein the side rings have a concave shape at a face side.

12. The cage according to claim 8, wherein the side sings extend radially between an inner radius which corresponds to a pitch circle of the roller bearing and an outer radius which corresponds to the pitch circle plus half of the diameter of the rolling element.

13. The cage according to claim 8, wherein the surface of the side rings which are facing the rolling elements comprise a substantially radial outer rectangular portion and an adjoining radial inner trapezoid portion seen perpendicular onto the surface.

14. The cage according to claim 8, wherein the face sides of the pocket elements have a concave surface, wherein the concave surface is spherical and has a radium which is between 105% and 115% of the diameter of the rolling elements.

15. A method for producing a cage of a roller bearing comprising: providing a ring-shaped base body with a plurality of pockets for receiving rolling elements, wherein the base body is formed by two side rings arranged in a defined axial distance and by a plurality of pocket elements located between the side rings, wherein each pocket element has two face sides designed for contacting a rolling element, wherein the connection between the pocket element and each of the side rings is established by at least one beam that is joined with one of the side rings and the pocket element, wherein beside the at least one beam no further connection exists between the pocket element and each of the side rings, wherein the at least one beam has a ring-shaped or elliptical cross section in a section perpendicular to the longitudinal extension of the beam, and producing the cage by means of an additive manufacturing process, and wherein a plastic material is used for the production of the cage.

16. The method according to claim 15, the production of the cage is carried out by means of a 3-D printing process.

17. The method according to claim 15, the production of the cage is carried out by means of a stereo-lithographic process.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

(1) The drawings show embodiments of the invention.

(2) FIG. 1 shows a perspective view of a common cage of a roller bearing, wherein the used coordinate systems CS (cage system) and PS (pocket system) are depicted,

(3) FIG. 2 shows a perspective view of a cage according to the invention,

(4) FIG. 3 shows the shape of the contact surface for a rolling element of a part of a side ring of the cage, seen in an x-z-plane of the PS,

(5) FIG. 4 shows the shape of the contact surface for a rolling element of a pocket element, seen in an x-y-plane of the PS,

(6) FIG. 5 shows the section through a part of a side ring, seen in an x-y-plane of the PS,

(7) FIG. 6 shows the shape of the contact surface for a rolling element of a pocket element, seen in an x-y-plane of the PS,

(8) FIG. 7 shows the view in radial direction R onto a part of the cage and onto a pocket element between two side rings,

(9) FIG. 8 shows the view in direction z of the PS onto a pocket element between two side rings,

(10) FIG. 9 shows a cross section through a part of the cage at a location about 25% from the face side of the cage, showing three beams which connect the side ring with the pocket element, and

(11) FIG. 10 shows a cross section of one of the beams, wherein the cross section is oriented according to the beam direction.

DETAILED DESCRIPTION OF THE INVENTION

(12) In FIG. 1 a cage 1 according to the state of the art is shown with a basis geometry which is hollow-cylindrical. The cage 1 has a plurality of pockets 2 for receiving rolling elements; the pockets 2 form surfaces for contacting the rolling element (which are not depicted). The cage 1 is thus composed of multiple pockets, each pocket providing the space for a rolling element.

(13) In FIG. 1 the coordinate systems are depicted which are used for the further explanation of the design of the cage according to the invention. For the definition, two coordinate systems are used.

(14) A global cylindrical coordinate system CS (cage system) is defined with the radial direction R being normal to the outer ring outer surface of the bearing and the axial direction z being the middle axis of the bore of the bearing.

(15) A Cartesian coordinate system PS (pocket system) is placed at the center of the rolling element, with the x direction pointing in insertion direction of the rolling element, normal to the outer ring outer surface, the y direction pointing in axial direction of the bearing and the z direction pointing in the main direction of motion of the rolling element.

(16) Using these definitions, a lightweight cage as shown in FIG. 2 can be realized in the following way:

(17) The cage 1 consist generally of two side rings 3 and 4 (being backbones of the cage) and a plurality of pocket elements 5, which are parts which are connected to the side rings 3, 4 by beams 8, 9, 10 (see specifically FIGS. 7 and 8). The pocket elements 5 are establishing the same function like the cage bars in well-known cages.

(18) The side rings 3, 4 have an inner diameter being the pitch diameter of the bearing and an outer diameter being the pitch diameter plus 50% of the rolling element diameter. The rings 3, 4, have a minimum thickness being the larger of about 0.25 mm and 2.5% of the rolling element diameter.

(19) The radial section in the x-y-plane of PS of the side ring 3, 4 is shown in FIG. 5. Here, a cross sectional view of a side ring is shown. Some preferred geometry data are shown in this figure: e is the maximum of 0.25 mm and 0.05% of the rolling element diameter. b=2 e, d=1.5 e, a=4 e, c=4 e. Thus, a concave section 11 is formed which is arranged at a face side of the side ring 3.

(20) In FIG. 2 also OP is shown which is the opening at the radial outer side of the cage 1 for inserting the rolling elements. More specifically, the two side rings 3, 4 are placed with an axial gap of about 95% of the rolling element diameter in case of a ball bearing and the rolling element length in case of a roller bearing.

(21) The pocket elements 5 have two face sides 6 and 7 which are designed for the contact of the rolling elements which are arranged in the pockets 2. The two surfaces in the circumferential direction of a pocket provide a conformal contact surface for the rolling element. The center of all surfaces is the rolling element center. For a ball bearing (e.g. for a Deep Groove Ball Bearing DGBB or an Angular Contact Ball Bearing ACBB) cage these surfaces are spherical, with a radius about 10% larger than half the rolling element diameter.

(22) When projecting the contact surface of the pocket element 5 on the x-z-plane of the PS (see the depiction in FIG. 3 and in FIG. 6) the surface has the shape of a trapezoid 13 merged with a rectangle 12 and is located in the two quadrants with positive x-values of the coordinate system. The shorter side a (see FIG. 3) of the trapezoid is closer to the z axis of the coordinate system than the longer side. The width of the shorter side is about 25% of the rolling element diameter. The width of the longer side b (see FIG. 3) is about 75% of the rolling element diameter. The height H1, H2 (see FIG. 3) is about 12.5% of the rolling element diameter.

(23) The thickness of the pocket surface is the maximum of 0.25 mm and 2.5% of the rolling element diameter.

(24) The two surfaces in the axial direction of a pocket provide a conformal contact surface to guide the rolling element axially. For a ball bearing, the surface is a spherical indentation of the side ring (backbone) surface with a radius of about 10% more than the radius of the rolling element.

(25) As can be seen in FIG. 7, the central radial contact surface is placed between the tangential contact surface. It has an X-shape due to its attachment to the radial extremities of the adjacent tangential rolling element contact surface and the reduction of the axial width in towards its center. The axial width in the center is about 50% to 75% of the axial width at the attachment locations to the tangential rolling element contact surfaces.

(26) The side ring (backbone) axial contact surface is on top of the side rings and ensures smooth contact with the outer ring.

(27) An important aspect of the present invention is the fact that the pocket elements 5 are connected with the side rings 3, 4 on both sides by means of beams 8, 9 and 10.

(28) Thus, each tangential ball contact surface (i.e. the pocket element 5) is connected to both side rings 3, 4 by six beams 8, 9 and 10 in the depicted embodiment. Reference is made to FIGS. 7 and 8.

(29) The beam 8 is defined according to FIGS. 9 and 10. The cross-section of the beam 8 is elliptical with the major axis being oriented according to the x-direction of PS and the minor axis being oriented according to the y-direction of PS, rotated by about 25 degrees around the x-axis of PS. The direction of the beam 8 is the y-direction of PS, rotated about 25 degrees around the x-axis of PS. The thickness of the beam varies.

(30) At the thinnest position, the length of the major axis is about 15% of the rolling element diameter, the length of the minor axis is about 10% of the rolling element diameter. At the attachment points to the surfaces, these values are approximately double. The attachment point on the side ring 3, 4 is at the top of the side ring, prolonging the rolling element contact surface, i.e. about 10% of the rolling element diameter in y-direction of PS. The attachment point at the rolling element contact surface, i.e. at the pocket element 5, is in prolongation of this surface, i.e. at the top of the rolling element contact surface about 25% of the rolling element diameter in z-direction of PS.

(31) The orientation of the beam 9 can be seen in FIG. 9. The cross-section of the beam is elliptical and, when projected on the x-y-plane of PS with the major axis being oriented in y-direction of PS and a length of about 15% of the rolling element diameter, the minor axis being oriented in x-direction of PS and a length of about 10% of the rolling element diameter, both measured in the middle of the beam. At the attachment points to the respective surfaces these values are approximately double.

(32) The attachment point of beam 9 on the side ring 3, 4 in y-direction of PS is located about half the rolling element diameter away from the center of the rolling element, at the location of the contact point between the tangential surface and the rolling element. In x-direction of PS, the attachment point is at 75% of the radius of the rolling element. The attachment point to the pocket surface and the central radial contact surface is at the middle between the largest and the smallest axial width of this surface. The beam is oriented in z-direction of PS, rotated about +45 around the y-direction of PS so that the beam points in direction out of the center of the cage.

(33) The orientation of beam 10 is also depicted in FIG. 9. The cross-section of the beam 10 is elliptical and, when projected on the x-y-plane of PS with the major axis being oriented in y-direction of PS and a length of about 15% of the rolling element diameter, the minor axis being oriented in x-direction of PS and a length of about 10% of the rolling element diameter, both measured in the middle of the beam. At the attachment points to the respective surfaces these values are approximately double.

(34) The attachment point of beam 10 on the side ring 3, 4 in y-direction of PS is located about half the rolling element diameter away from the center of the rolling element, at the location of the contact point between the tangential surface and the rolling element. In x-direction of PS, the attachment point is at 50% of the radius of the rolling element. The attachment point to the pocket surface and the central radial contact surface is at the middle between the largest and the smallest axial width of this surface. The beam 10 is oriented in z-direction of PS, rotated about 30 around the y-direction of PS so that the beam 10 points in direction of the center of the cage.

(35) Due to their diameter and location, the beams 8, 9, 10 might intersect with each other. If this is the case, they are joined with a rounding radius of the maximum of 0.25 mm and 2.5% of the rolling element diameter.

(36) The beams are blended into the surfaces they are attached to with a rounding radius of the maximum of 0.25 mm and 2.5% of the rolling element diameter.

REFERENCE NUMERALS

(37) 1 Cage 2 Pocket 3 Side ring 4 Side ring 5 Pocket element 6 Face side 7 Face Side 8 Beam 9 Beam 10 Beam 11 Concave section 12 Rectangular portion 13 Trapezoid portion OP Opening