REDUCTION BEARING AND ELECTRIC MOTOR

Abstract

Reduction bearing having at least three concentric rings that include an inner ring with inner ring axial extension, a center ring with center ring axial extension and an outer ring with outer ring axial extension and at least two concentric rings of/with rolling elements including an inner concentric ring of/with rolling elements and an outer concentric ring of/with rolling elements. Inner ring and center ring are configured as bearing races for inner concentric ring of/with rolling elements and center ring and outer ring are configured as bearing races for the outer concentric ring of/with rolling elements. At least one reduction stage has a common reduction stage plane in which the inner ring extension, the center ring extension and the outer ring extension lie. The center ring extension is configured to transmit a wave-type reduction action between the inner ring extension and the outer ring extension.

Claims

1. A reduction bearing comprising: at least three concentric rings including an inner ring with an inner ring axial extension, a center ring with a center ring axial extension and an outer ring with an outer ring axial extension; at least two concentric rings of or with rolling elements including an inner concentric ring of or with rolling elements and an outer concentric ring of or with rolling elements, wherein the inner ring and the center ring are configured as bearing races for the inner concentric ring of or with rolling elements and the center ring and the outer ring are configured as bearing races for the outer concentric ring of or with rolling elements; and at least one reduction stage having a common reduction stage plane in which the inner ring extension, the center ring extension and the outer ring extension lie, wherein the center ring extension is configured to transmit a wave-type reduction action between the inner ring extension and the outer ring extension.

2. The reduction bearing according to claim 1, wherein the inner ring extension is disk-shaped either with or without a central axial opening, and wherein one of: the inner ring extension has an outer circumferential surface with one or more peaks and the outer ring extension has an inner circumferential surface with grooves; or the inner ring extension has an outer circumferential surface with grooves and the outer ring extension has an inner circumferential surface with one or more peaks.

3. The reduction bearing according to claim 2, wherein, in a bearing part, the inner ring comprises at least one bearing race surface and the center ring comprises at least two bearing race surfaces, wherein the inner ring extension comprises one of: at least one profiled bearing race or at least one eccentric bearing race, and wherein the center ring extension comprises at least one radial channel with one or more radially moving elements.

4. The reduction bearing according to claim 3, wherein the at least one eccentric bearing race comprises at least two eccentric bearing races.

5. The reduction bearing according to claim 2, wherein the center ring extension has structures defining radial channels containing radially moving elements configured to contact the inner circumferential surface of the outer ring extension and the outer circumferential surface of the inner ring extension, wherein the radial channels are located in at least one row arranged at least substantially parallel to the common reduction stage plane, and wherein the radially moving elements comprise at least one row of sliding or rolling elements.

6. The reduction bearing according to claim 5, wherein the structures of the center ring defining the radial channels are one of removably replaceable or of one piece with the center ring.

7. The reduction bearing according to claim 5, wherein the at least one row of sliding or rolling elements comprises needles, balls or cylinders.

8. The reduction bearing according to claim 2, wherein a number of the grooves in the one of the inner circumferential surface of the outer ring extension or in the one of the outer circumferential surface of the inner ring extension is different from a number of the radial channels of the center ring extension.

9. The reduction bearing according to claim 2, wherein a radial depth of the grooves in the inner circumferential surface of the outer ring extension is at least equal to a height in the radial direction of the peak or peaks on the outer circumferential surface of the inner ring extension, and wherein a shape of the peak or peaks on the outer circumferential surface of the inner ring extension is an inverse of a shape of the grooves on the outer ring extension.

10. The reduction bearing according to claim 2, wherein the one of the inner circumferential surface with one or more peaks and the outer circumferential surface with one or more peaks is replaceable or formed by at least two eccentric circumferential surfaces having bearing race surfaces.

11. The reduction bearing according to claim 1, further comprising a radially flexible roller bearing interposed between the outer circumferential surface of the inner ring extension and the center ring extension.

12. The reduction bearing according to claim 11, wherein the radially flexible roller bearing is an integral part of at least one of the inner ring extension and the center ring extension.

13. The reduction bearing according to claim 1, wherein the at least three concentric rings and the at least two concentric rings of or with rolling elements are arranged in a bearing plane, and wherein one of: an even number of peaks on the one of the outer circumferential surface of the inner ring extension or the inner circumferential surface of the outer ring extension, or an odd number with at least three peaks on the one of the outer circumferential surface of the inner ring extension or the inner circumferential surface of the outer ring extension.

14. The reduction bearing according to claim 1, further comprising a separating element located radially between two rolling elements.

15. The reduction bearing according to claim 1, wherein at least one of the inner ring, the center ring and the outer ring has through-holes for affixation to an external supporting structure.

16. The reduction bearing according to claim 15, wherein the reduction bearing has two outputs at different reduction stages and different reduction values.

17. The reduction bearing according to claim 1, further comprising an axial central opening with a diameter that is one of: 90% of the outer diameter of the outer ring; more than 35% of the outer diameter of the outer ring; more than 50% of the outer diameter of the outer ring; more than 60% of the outer diameter of the outer ring; or more than 70% of the outer diameter of the outer ring.

18. The reduction bearing according to claim 1, wherein the at least one reduction stage comprises at least two reduction stages configured so that at least one first reduction stage is drivingly connected to at least one second reduction stage, wherein the first and second reduction stages are at least one of: axially aligned with each other, and positioned concentrically to each other, and wherein, when axially aligned with each other, one of the inner ring, the center ring and the outer ring of the first reduction stage is connected with one of the inner ring, the center ring and the outer ring of the second reduction stage.

19. The reduction bearing according to claim 18, wherein, when positioned concentrically to each other, the second reduction stage is arranged concentrically around the first reduction stage, wherein the outer ring of the first reduction stage is of one piece with the inner ring of the second reduction stage, and wherein one of the inner ring and the central ring of the first reduction stage and one of the central ring and the outer ring of the second reduction stage are affixed or affixable to a supporting structure.

20. An electric motor with or in which the at least one reduction bearing according to claim 1 is integrated, comprising: a casing of the electric motor configured as a supporting structure for the reduction bearing; and a rotor of the electric motor is one of drivingly connected to or integral with an input ring of the at least one reduction bearing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The invention is described below, without restricting the general intent of the invention, based on exemplary embodiments, wherein reference is made expressly to the drawings with regard to the disclosure of all details according to the invention that are not explained in greater detail in the text, in which like reference numerals represent similar parts throughout the several views of the drawings, and wherein:

[0052] FIG. 1 schematically illustrates a cross sectional representation of an inventive restriction bearing,

[0053] FIG. 2 schematically illustrates a perspective representation of the reduction bearing of FIG. 1,

[0054] FIG. 3a) to c) schematically illustrates a representation of an inner ring of the inventive reduction bearing,

[0055] FIG. 3d) to f) schematically illustrates a representation of an inner ring of an embodiment of the inventive reduction bearing, wherein two eccentric rings are used at the reduction stage,

[0056] FIG. 4a) to c) schematically illustrates a representation of a center ring of the inventive reduction bearing,

[0057] FIG. 4d) schematically illustrates a representation of a center ring of the inventive reduction bearing in a further embodiment,

[0058] FIG. 5a) to c) schematically illustrates a representation of an outer ring of the inventive reduction bearing,

[0059] FIG. 6a) to d) schematically illustrates a representation of a reduction stage of a reduction bearing according to the invention,

[0060] FIG. 7a) to e schematically illustrates a representation of another embodiment of an inventive reduction bearing,

[0061] FIG. 7f) to h) schematically illustrates a representation of a reduction stage of a reduction bearing according to an embodiment of the invention with two eccentric rings at the reduction stage,

[0062] FIG. 8a) to d) schematically illustrates a representation of a two stage inventive reduction bearing in a parallel configuration,

[0063] FIG. 9a) to d) schematically illustrates a representation of a two stage reduction bearing of the invention in serial configuration,

[0064] FIG. 10a), b) schematically illustrates a representation of an electric motor according to the invention, and

[0065] FIG. 10c) schematically illustrates a representation of a further embodiment of an electric motor according to the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0066] The particulars shown herein are by way of example and for purposes of illustrative discussion of the embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the present invention. In this regard, no attempt is made to show structural details of the present invention in more detail than is necessary for the fundamental understanding of the present invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the present invention may be embodied in practice.

[0067] In the drawings, the same or similar types of elements or respectively corresponding parts are provided with the same reference numbers in order to prevent the item from needing to be reintroduced.

[0068] FIG. 1 shows schematically a cross section through an exemplary embodiment of a reduction bearing 5 according to the invention. The reduction bearing 5 comprises three concentric rings, namely an inner ring 10, a center ring 20 and an outer ring 30. In the left part, a bearing plane 41 is marked which contains parts of the three concentric rings 10, 20 and 30 and two concentric rings of or with rolling elements 50, 51 placed between, respectively, the inner ring 10 and the center ring 20, and the center ring 20 and the outer ring 30. The elements in the bearing plane 41 therefore constitute a radial rolling bearing with three rotatable rings 10, 20, 30. The rolling elements 50, 51 are cylinders by way of example, but also any other kind of or with rolling elements used in bearings may be used, such as balls, needles, etc.

[0069] The three rings 10, 20, 30 have extensions 16, 26, 36, respectively, which extend axially from the rings 10, 20, 30 and lie in a common reduction stage plane 42. They constitute a reduction stage 7 consisting of a disc-shaped inner ring extension 16 which at its outer circumference is in contact with radially moving elements 40 caged inside radially oriented channels inside the center ring extension 26, as well as the outer ring extension 36, the inner circumferential surface of which contacts the radially moving elements 40. The structure of the circumferential surfaces 12 of the inner ring extension 16 and the outer ring extension 36 will be discussed in connection with FIGS. 3, 5 and 6.

[0070] FIG. 2 shows a schematic perspective view of the reduction bearing 5 according to FIG. 1. It can be seen that the rolling elements 50, 51 of the bearing part are caged in rolling element cages 52, 53. It is also shown that the reduction bearing 5 has a central opening 13 which constitutes a significant portion of its total diameter. In addition, three holes for affixation and connection to input and output devices are shown in the center ring 20 and the outer ring 30, namely in input connection 18 in the inner ring extension 16, an output connection 28 in the center ring 20 and a through hole 38 in the outer ring 30 for affixation to a supporting structure.

[0071] A detailed view of the inner ring 10 is shown in FIGS. 3a), 3b), 3c), 3d), 3e) and 3f). FIG. 3a) shows a perspective view of inner ring 10 having a large central opening 13 and a bearing part configured as a circular bearing race 11. This bearing race 11 supports the inner circle of or with rolling elements 50 shown in FIGS. 1 and 2. In the axial direction, the disc-shaped inner ring extension 16 is shown which has a non-circular outer circumferential surface 12. As depicted in FIG. 3a), the portion next to the reference numeral 16 is configured as a valley 15 having a minimum diameter, whereas above and below this portion, the circumferential surface 12 shows two shallow peaks 14, 14, providing the total circumferential surface 12 with an elliptical shape. Another valley is located opposite to the valley 15. The surface 12 may also have three or more peaks.

[0072] FIG. 3b) shows a more detailed cross-sectional view of the inner ring 10, the part C of which is shown in a magnified version in FIG. 3c). The circumferential surface 12 has a central part slightly elevated over its boundaries, marking a peak 14. This elevated central part will vanish at the position of a valley 15 halfway between two peaks 14, 14. The surface at a valley position is indicated with a dashed line in FIG. 3c). This variation in height causes the linearly moving elements 40 depicted in FIGS. 1 and 2 to perform a radial movement in the respective radial channels in the center ring extension 26.

[0073] FIGS. 3d), 3e) and 3f) show a schematic representation of the inner ring 10. FIG. 3d) is a cross section view, FIG. 3e) is an enlarged view of part B of FIG. 3d), and FIG. 3f) is a perspective view of the inner ring 10. There is shown a preferred embodiment of the invention. At the reduction stage, two eccentric rings 19, 19 of circular shape are used instead of one disk with two peaks. The circumferential surface of the two eccentric rings 19, 19 is formed by two rings radially shifted relative to each other and also to the common axis of the inner ring 10. By this measure, two peaks 14, 14 and two valleys 15, 15 are created on the extension 16 of the inner ring 10. The valley 15 is opposite to the valley 15 and the peak 14 is opposite to the peak 14. The bearing races 17, 17 of the two rings 19, 19 are profiled and are integral part of the inner ring extension 16. With this embodiment, it is preferred to use balls as rolling elements. Having the bearing races 17, 17 being integrated in the inner ring extension, the bearing races 17, 17 are very precisely formed.

[0074] In FIGS. 4a), 4b), 4c), the center ring 20 is depicted schematically in more detail. As shown in the perspective view in FIG. 4a), center ring 20 includes a bearing part with a circular bearing race 21 on the outside and a circular bearing race 22 on the inside, the bearing races 21, 22, respectively, being in contact with the rolling elements 50 and 51 of FIGS. 1 and 2.

[0075] The axial center ring extension 26 comprises a cage with radial channels 24 for guiding the linear movement of the radially moving elements 40 depicted in FIGS. 1 and 2. The center ring extension 26 itself is of cylindrical shape. Its inner diameter is slightly larger than the outer diameter of the inner ring extension 16 at peak diameter 14, 14.

[0076] In FIG. 4d) it is shown that the center ring extension 26 is further elongated and additional radial channels 124 which can also be grooves are added. Due to this embodiment, the carrying capacity of the reduction bearing is enhanced. The radial channels 24 and 124 are arranged in two rows.

[0077] FIGS. 5a), 5b), 5c) show a schematic representation of the outer ring 30 of the inventive reduction bearing 5 of FIGS. 1 and 2. The outer ring 30 has an inner circumferential bearing surface configured as a bearing race 31 contacting the rolling elements 51 of the outer ring of or with rolling elements shown in FIGS. 1 and 2. In the axial direction, the outer ring extension 36 has an inner circumferential surface whose diameter is smaller than the diameter of the bearing race 31 and has grooves 32, the depth of which roughly matches the difference between peak height 14, 14 and valley height 15, 15 of the peaks on the inner ring extension 16. The variation in the radial height of the grooves 32 follows the variation of the circumferential surface 12 of the inner ring extension 10, shortened in circumferential direction by the reduction ratio of the reduction stage.

[0078] The number of grooves 32 is different from the number of radial channels 24, 124 in the center ring extension 26 by a small number, usually by 2, especially in case of 2 peaks.

[0079] FIGS. 6a), 6b) and 6c) show a further exemplary embodiment of a single-stage reduction bearing 5 according to the invention with inner ring 10, center ring 20 and outer ring 30, in a cross section through the reduction stage plane 42. The center ring extension 26, which is built as a separator 23, is of circular shape. The outer circumferential surface 12 of the inner ring extension 16 matches the inner diameter of the separator 23 in the top and in the bottom positions while leaving a narrow gap to the inner surface of the separator 23 in the left and right positions shown in FIG. 6a). This implies that the outer circumferential surface 12 of the inner ring separator 16 is not round, but exhibits two peaks, shown in the top and bottom positions. The inner circumferential surface of the outer ring extension 36 in contrast exhibits a multitude of grooves 32, which are slightly broader than the radially moving elements 40 located inside radial channels 24 of the separator 23.

[0080] To increase the carrying capacity of the reduction bearing with respect to keep minimal diameter of reduction bearing there can be placed more rolling elements 40 in two or more rows in a cage with radial grooves 24. See for example FIG. 6b).

[0081] To further enhance the carrying capacity of the reduction bearing, there can be skipped every second groove in the separator and herewith to enlarge thickness of wall separators 23 while the reduction ratio will be kept. Through the enlarged wall separators 23 can be guided openings 29 in the axial direction over the center ring 20. For example a screw can be screwed into a guided opening 29.

[0082] As can be seen in FIG. 4d), a further enhancement of carrying capacity of the reduction bearing can be achieved by elongation of center ring extension 26 and adding additional grooves 124 and rolling elements, shifted by one tooth in radial direction.

[0083] Rotating the inner ring 10 will result in a collective revolving wave-type motion of the radially moving elements 40 in the separator 23. Since the number of grooves is greater by 2 than the number of radial channels 24, a rotation of the inner ring 10 as input of the inventive reduction bearing 5 will cause the radially moving elements 40 to be pushed into the respective grooves 32 of the outer ring extension 36 from off-center into the center of the grooves 32 at the passing of a peak 14, 14, thereby causing the center ring 20 and the outer ring 30 to rotate relative to each other by the amount of one groove 32 with each passing of a peak 14, 14 on the outer circumferential surface 12 of the inner ring extension 16, that is, for each half revolution of the inner ring 10.

[0084] FIGS. 6b) and 6c) show magnified excerpts F and G from FIG. 6a), respectively, namely at peak height 14 and valley height 15. At peak height 14, as shown in FIG. 6b), the centrally depicted radially moving elements 40 are pushed into the opposing grooves 32 to the maximum extent. At valley height 15, as shown in FIG. 6c), the linearly moving elements 40 are opposed by an edge between two adjacent grooves 32. Further rotation of the inner ring 10 will cause the separator 23 to rotate slightly in the clockwise or anti-clockwise direction, depending on the direction of rotation of the inner ring 10, so that with the arrival of the next peak 14 on the outer circumferential surface 12 of the inner ring extension 16, the linearly moving elements 40 will be pushed into the next adjacent groove 32.

[0085] As can be seen in FIG. 1, this is achieved in a very compact design which at the same time assures a reduction action and radial bearing capacity.

[0086] It is furthermore advantageous, as shown in FIG. 6d), to separate the moving elements 40 radially by a separating element 43, which is located between a first and further, in this case, two, moving elements 40 and can be moved radially together with the moving elements 40. This separating element 43 preferably has low-friction surfaces or is made wholly out of a low-friction material and decouples the rotation of the rolling elements 40 from each other, thus reducing friction and wear of the rolling elements 40.

[0087] FIGS. 7a) to 7e) show a further embodiment of a reduction bearing 5 according to the invention. The structure of the reduction bearing 5 shown in a half-open perspective in FIG. 7a) is almost identical to the one shown in FIGS. 1 and 2, with the exception that a radially flexible roller bearing 60 is interposed between the outer circumferential surface 12 of the inner ring extension 16 and the separator 23 with the radially moving elements 40. As can best be seen in FIG. 7e), the radially flexible roller bearing 60 comprises rolling elements 61 positioned between an inner bearing race 62 and an outer bearing race 63. Further details are shown in cross section and perspectively in FIGS. 7b), 7c) and 7d). The use of a radially flexible roller bearing 60 reduces friction and enhances the longevity and efficiency of the reduction bearing 5. The radially flexible roller bearing 60 itself does not need to withstand large radial forces, which are absorbed by the rolling elements 50, 51 in the bearing plane 41 instead.

[0088] In a preferred embodiment shown in FIGS. 7f), 7g) and 7h), the bearing ring 62 can be replaced by a profiled extension of the inner ring 12, which can act as a bearing race. FIG. 7f) shows a schematic cross sectional view of a reduction bearing according to the invention, in case two eccentric rings 19 and 19 are used as an extension of the inner ring 10 as shown in FIGS. 3d), 3e) and 3f) and as an extension of the center ring of FIG. 4d).

[0089] FIG. 7g) is an enhanced view of the section K of FIG. 7f) in a schematic view. FIG. 7h) shows the embodiment in a schematic three-dimensional view. It is furthermore shown that bearing races 17, 17 are integrated into the rings 19 and 19 or a part of the surface of the rings 19 and 19. Furthermore, rolling elements 60, 61 and 40, 40 as well as rings 63 and 63, which can be used from standard bearings, are inserted. The shafts of the two eccentric rings 19, 19 are eccentric. There is no flexible roller bearing or roller racing in this embodiment. This embodiment is more easily to be produced with high precision than the embodiment, in which an ellipsoid is used with two peaks and two valleys instead of two eccentric rings 19, 19. In case of an ellipsoid, one roller racing or one bearing ring is advantageously flexible.

[0090] FIGS. 8a) to 8d) show a further exemplary embodiment of an inventive reduction bearing 105 having two reduction stages 107, 109, arranged concentrically inside each other. A first reduction stage 107 shown in FIG. 8a) comprises inner ring 10, center ring 20 and outer ring 30. The second reduction stage 109 comprises inner ring 110, center ring 120 and outer ring 130. Outer ring 30 of the first reduction stage 107 is the same as the inner ring 110 of the second reduction stage 109. This middle ring 30/110 of the parallel, that is, concentric two stage configuration shown in FIG. 8 has two bearing races in the bearing plane 41, namely one on the inside and one on the outside. Accordingly, the parallel configuration two-stage reduction bearing 105 of FIG. 8 has four concentric circles of the rolling elements 50, 51 in the bearing plane.

[0091] Each of the five rings 10, 20, 30/110, 120, 130 has its own axial extensions which are in principle structured in the same way as the ones depicted in the previous figures.

[0092] FIG. 8b) shows the two-stage reduction bearing 105 from one side with three areas opened up to show different parts of the interior of the reduction bearing 105. The opened area in the upper right allows a view into the bearing plane 41 with the rings 10, 20, 30/110, 120, 130 and the rolling elements 50, 51, 50, 51 constituting the radial bearing functionality of the reduction bearing 105.

[0093] The lowermost opening with area A is magnified in FIG. 8d). It is clearly visible that the innermost and first stage 107 is configured in the same way as the single stage embodiment of, for example, FIG. 6. FIG. 8c) shows a magnification of area B. FIGS. 8c) and 8d) correspond to the views in figures in FIGS. 6b) and 6c), respectively.

[0094] In the interior view containing the area B, a glimpse can be had inside the reduction stage plane 42 of the second reduction stage 109, showing that, whereas the radially moving elements 40 in the second reduction stage 109 are bigger than those in the first reduction stage 107 shown, for example, in the area B in FIG. 8b). The principle of action is the same in the second reduction stage 109 as in the first reduction stage 107.

[0095] With this parallel concentric configuration, it is possible to combine two reduction stages into a reduction action having a very large reduction factor calculated as the product of the reduction factor of the first reduction stage 107 and of the reduction factor of the second reduction stage 109. Reduction factors of 10.000 and more can be thus achieved.

[0096] Since radial forces are observed by the bearing parts in the bearing plane 41 of the inventive reduction bearing 5, 105, the reduction action incorporated in the structures in the reduction stage plane 42 are largely free of radial forces, so that blocking because of radial forces is effectively eliminated.

[0097] FIGS. 9a) to 9d) show a further exemplary embodiment of an inventive reduction bearing 205. The reduction bearing 205 is a two-stage in a serial configuration, that is, the two stages 207, 209 are aligned axially along central axis 6 of the reduction bearing 205, which again has a basically circular shape, as shown in FIG. 9b). Each of the two reduction stages 207 and 209 comprise three concentric rings 10, 20, 30 and 210, 220, 230, respectively, which are mainly structured as shown in the previous figures.

[0098] In the configuration shown in FIG. 9a), the inner ring 10 of the first reduction stage 207 is driven by an input connection 18. The outer ring 30 may be affixed to a supporting structure (not shown) by through hole 38. Rotation of the inner ring 10 will cause a slower rotation of the center ring 20 of the first reduction stage 207.

[0099] The center ring 20 of the first reduction stage 207 is connected via a driving connection 212, which is built as a spline connection, to the inner ring 210 of the second reduction stage 209. The spline connection, which is shown in an expanded view in FIG. 9d), has a circumferential toothing shown in an expanded view in FIG. 9c).

[0100] The center ring 220 has an output connection 225. The outer ring 230 likewise has a through hole 238 for connection to a supporting structure. A rotation at the input 18 of the inner ring 10 of the first reduction stage 207 therefore leads to a very slow rotation of the output 225 in the center ring 220 of the second reduction stage 209.

[0101] The reduction stages 207, 209 may be built in a modular manner such that reduction stages may be chosen with desired reduction ratios and combined in the way shown in FIG. 9a) to arrive at freely selectable high reduction ratios.

[0102] As in the case of the reduction bearing 105 in the parallel configuration of FIG. 8d), the rotating motion of the two reduction stages 207 and 209 may be used separately and in parallel, adding to the versatility of the invention reduction bearing 205. The two stages 207, 209 may be oriented in the same way, as in the present example shown in FIG. 9a), or may have back-to-back bearing planes or reduction planes, depending on the desired configuration.

[0103] Two exemplary embodiments of electric motors 2, 2 according to the invention are shown schematically in FIGS. 10a), 10b).

[0104] The electric motor 2 shown in FIG. 10a) comprises a casing 72 housing a stator 73 arranged around a rotor 71 with rotor coils 74, wherein the rotor 71 is supported against the casing 72 by motor bearings 70 at each side of the coils 74 in the axial direction. A reduction bearing 5 according to the invention is affixed to the casing 72 through a casing connection 76. The rotor 71 is drivingly connected to the inner ring 10 of the reduction bearing 5 by, e.g., a spline connection 75. The center ring 20 has an output connection 28 rotating with a reduced speed with respect to the rotor 71. Here, the reduction bearing 5 is integrated with the electric motor 2 by connections 75 and 76.

[0105] The alternative embodiment of an electric motor 2 shown in FIG. 10b) differs from the one shown in FIG. 10a) in that the reduction bearing 5 is fully integrated. The casing 72 is integral with the outer ring 30, the rotor 71 is integral with the inner ring 10 of the reduction bearing 5. There is only one motor bearing 70, since the radial forces on the other side are born by the reduction bearing, in particular the bearing parts arranged in the bearing plane 41.

[0106] In a further embodiment depicted in FIG. 10c), an electric motor 2 can be arranged to perform with a higher integration. In particular, a thin-Gap type electric motor 2 is shown in FIG. 10c). The reduction bearing 5 is fully integrated. The casing 172 is integral with the center ring 20. The rotor 171 is integral with the inner ring 10 of the reduction bearing 5. The stator 173 has a small gap to the rotor 171. An electric motor 2 can thus be used which can be built very small in size.

[0107] Both exemplary embodiments constitute very efficient and compact designs of electric motors 2, which are of great use in robotics and other technical fields requiring compact reduced electric motor action.

[0108] All named characteristics, including those taken from the drawings alone, and individual characteristics, which are disclosed in combination with other characteristics, are considered alone and in combination as important to the invention. Embodiments according to the invention can be fulfilled through individual characteristics or a combination of several characteristics. Features which are combined with the wording in particular or especially are to be treated as preferred embodiments.

[0109] It is noted that the foregoing examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the present invention. While the present invention has been described with reference to an exemplary embodiment, it is understood that the words which have been used herein are words of description and illustration, rather than words of limitation. Changes may be made, within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the present invention in its aspects. Although the present invention has been described herein with reference to particular means, materials and embodiments, the present invention is not intended to be limited to the particulars disclosed herein; rather, the present invention extends to all functionally equivalent structures, methods and uses, such as are within the scope of the appended claims.

LIST OF REFERENCES

[0110] 2, 2, 2 electric motor [0111] 5 reduction bearing [0112] 6 central axis [0113] 7 reduction stage [0114] 10 inner ring [0115] 11 bearing race [0116] 12 circumferential surface [0117] 13 central opening [0118] 14, 14 peak [0119] 15, 15 valley [0120] 16 inner ring extension [0121] 17, 17 bearing race [0122] 18 input connection [0123] 19, 19 eccentric circumferential surface [0124] 20 center ring [0125] 21 bearing race [0126] 22 bearing race [0127] 23 separator [0128] 24 radial channels [0129] 26 center ring extension [0130] 28 output connection [0131] 29 opening [0132] 30 outer ring [0133] 31 bearing race [0134] 32 grooves [0135] 36 outer ring extension [0136] 38 through hole [0137] 40, 40 radially moving elements [0138] 41 bearing plane [0139] 42 reduction stage plane [0140] 43 separating element [0141] 50, 50 rolling elements [0142] 51, 51 rolling elements [0143] 52, 53 rolling element cage [0144] 60 radially flexible roller bearing [0145] 61, 61 rolling element [0146] 62 inner bearing race [0147] 63, 63 outer bearing race [0148] 70 motor bearings [0149] 71 rotor [0150] 72 casing [0151] 73 stator [0152] 74 rotor coils [0153] 75 spline connection [0154] 76 casing connection [0155] 105 reduction bearing [0156] 107 first reduction stage [0157] 109 second reduction stage [0158] 110 inner ring [0159] 111 bearing race [0160] 120 center ring [0161] 121 bearing race [0162] 122 bearing race [0163] 123 separator [0164] 124 additional radial channel [0165] 130 outer ring [0166] 171 rotor [0167] 172 casing [0168] 173 stator [0169] 205 reduction bearing [0170] 207 first reduction stage [0171] 209 second reduction stage [0172] 210 inner ring [0173] 211 bearing race [0174] 212 driving connection [0175] 220 center ring [0176] 221 bearing race [0177] 222 bearing race [0178] 225 output connection [0179] 230 outer ring