Patent EA-000688-B1 (EA)
Title: Step-down gear unit
Inventor: HIRN HELMUT
IPC: F16H1/32
Filed: 1997-08-14
Abstract: 1. Step-down gear system comprising: - a non-flexible support ring (1), which has a substantially cylindrical supporting surface (2), - a radially flexible rolling bush (5), which has outer peripheral surface (7) having a shorter circumferential length than the supporting surface (2), - a transmission shaft (14), - a drive core (20) the cross section of which is not round and which is rotatable by means of the drive shaft (14) thus defining an enveloping circle, - by rotation of the drive core (20) at least one circumferential portion of the outer peripheral surface (7) of the rolling bush (5) is held in continuous alteration in a substantially slip-free engagement with the supporting surface (2) of the support ring (1), further characterized in that -the enveloping circle of the drive core (20) which is not round has a substantially smaller diameter (Dh) than the basically cylindrical roller bush (5), - the rolling bush (5) is supported on the drive core (29; 20/1) by means of a plurality of essentially radially extending transmission elements (32; 33) which all have the same length. 2. Step-down gear system according to claim 1, characterized in that the supporting surface of the supportring (1) is provided with an internal toothing (2), and the radially flexible rolling bush (5) with an external toothing (7). 3. Step-down gear system according to claim 1 or claim 2, characterized in that the drive core (20) has an eccentric shape, in particular an elliptical shape. 4. Step-down gear system according to one of claims 1 to 3, characterized in that the rolling bush (5) is in, or is designed to be brought into, a rotationally fixed connection with a transmitting shaft (30) via a connecting member (25). 5. Step down gear system according to one of claims 1 to 4, characterized in that the transmission elements are designed to be spokes (32) or rams (33). 6. Step-down gear system according to one of claims 1 to 5, characterized in that the radially inwardly disposed ends of the transmission elements (32, 33) are supported on a radially flexible bearing hub (22) in which the drive core (20, 20/1) is supported for rotation. 7. Step-down gear system according to one of claims 1 to 6, characterized in that the inside diameter (Dn) of the basically cylindrical bearing hub (22) is smaller by at least one quarter to one third than the outside diameter (Da) of the basically also cylindrical rolling bush (5). 8. Step-down gear system according to claim 6 or claim 7, characterized in that the inner circumferential length of the bearing hub (22) is adapted to the circumferential length of the drive core (20; 20/1) such that the bearing hub (22) surrounds the drive core (20; 20/1) at least substantially free of play. 9. Step-down gear system according to one of claims 6 to 8, characterized in that the rolling bush (5) and the bearing hub (22), together with the transmission elements designed to be spokes, form a single-piece structural part (35) of plastics material. 10. Step-down gear system according to claim 9, characterized in that the bearing hub (22), which is of plastics material, is provided with an also radially flexible bearing sleeve (23) of metal, which serves as a sliding bearing for the drive core (20) and surrounds the drive core (20). 11. Step-down gear system according to claim 10, characterized in that the spokes (32) comprise metal inserts (37) which are completely sheathed in plastics material and the foot ends (38) of which are slidingly supported directly on the peripheral surface of the drive core (20). 12. Step-down gear system according to one of claims 9 to 11, characterized in that the bearing hub (22), which is connected to the rolling bush (5) by means of the spokes (32), comprises, as a connecting member (25), a basically cylindrical hollow shaft (26) to which the transmitting shaft (30) is coupled. 13. Step-down gear system according to one of claims 1 to 12, characterized in that the rolling bush (5) comprises an external toothing (9) which meshes with an internal toothing (3) of the support ring (1). 14. Step-down gear system according to claim 13, characterized in that the internal toothing (3) of the support ring (1) has a smaller axial breadth (b1) than the external toothing (9) of the rolling bush (5), and in that a cylindrical driven annular gear (40) is arranged concentrically with the support ring (1) and rotatable relative thereto, and with the internal toothing (41) of which, in each case, at least substantially the same teeth of the rolling bush (5) mesh as with the internal toothing (3) of the support ring (1). 15. Step-down gear system according to one of claims 1 to 14, characterized in that the inner surface (2) of the support ring (1) and the outer surface (7) of the rolling bush (5/1) are in frictional engagement. 16. Step-down gear system according to claim 15, characterized in that the rolling bush (5/1) comprises an external toothing (9) axially adjacent to its peripheral surface sector (11), which is in frictional engagement with an inner friction surface (11) of the support ring (1), which external toothing, in each case in the region of its peripheral sectors frictionally engaging the support ring (1), meshingly engages the internal toothing (41) of a driven annular gear (40) which is supported for rotation coaxially with the support ring (1). 17. Step-down gear system according to claim 15 or claim 16, characterized in that the driven annular gear (40) is provided with a transmitting shaft (29) which is coaxial with the support ring (1). 18. Step-down gear system according to claims 15 or claim 16, characterized in that the driven annular gear (40/1) is in a transmitting connection with a transmitting shaft (28) via additional gear parts (60). 19. Step-down gear system according to claim 12, characterized in that the internal toothing (41) of the driven annular gear (40; 40/1) meshing with the external toothing (9) of the rolling bush (5) has the same number of teeth (Z1) as the rolling bush (5), but at least substantially the same reference diameter and/or inside diameter as the internal toothing (3) of the support ring (1). 20. Step-down gear system according to claim 13 or claim 19, characterized in that the internal toothing (41) of the driven annular gear (40) meshing with the external toothing (9) of the rolling bush has a different number of teeth (Z3) than the rolling bush (1). 21. Step-down gear system according to one of claims 1 to 8 or 11 to 20, characterized in that the transmission elements, which are designed to be rams (33) and are arranged between the rolling bush (5, 5/1), on the one hand, and the drive core (20; 20/1) or the bearing hub (22), on the other hand, are supported to be radially displaceable in a cylindrical guide cage (45, 45/1) which surrounds the bearing hub (22) or the drive core (20; 20/1), and the outer ends (36) of which transmission elements loosely abut for support against an inner surface (57) of a rolling bush (5/1), which is an annular body (58), and the inner foot ends (38) of which loosely abut for support against the peripheral surface (52) of the drive core (20, 20/1). 22. Step-down gear system according to claim 21, characterized in that the rams (33) are plate-shaped metal parts which are guided, in each case, in radial guides (47) of the guide cage (45, 45/1) of plastics material. 23. Step-down gear system according to one of claims 1 to 22, characterized in that the rams (33) are provided at their radially outwardly disposed ends (36) with widened supporting surfaces (36). 24. Step-down gear system according to claim 22 or claim 23, characterized in that the guide cage (45) is guided and centered via en end wall (49) on an annular surface (49') which is concentric with the support ring (1). 25. Step-down gear system according to claims 22 or claim 23, characterized in that the guide cage (45/1) is integrally moulded on a driven annular gear (40/1) which is also of plastics material. 26. Step-down gear system according to one of claims 1 to 14 or claims 16 to 25, characterized in that the internal toothing (3) of the support ring (1) is designed to be radially flexible. 27. Step-down gear system according to claim 26, characterized in that the internal toothing (3) of the support ring (1) is attached to a thin-walled annular body part (68) which is separated from an outer thick-walled annular body part (69) by a circumferential annular groove (70) which is open on a front side. 28. Step-down gear system according to one of claims 1 to 27, characterized in that the drive core (20/1) comprises three protuberances (55) which are offset by, in each case, 120 degree  relative to one another and are disposed on a circumscribed circle (56) which is concentric with the support ring (1). 29. Step-down gear system according to one of claims 1 to 28, characterized in that the support ring (1) is part of a cylindrical housing which surrounds the rolling bush (5, 5/1) and the possibly provided driven annular gear (40, 40/1), and is provided at least on one end face with an end wall (43, 44). 30. Step-down gear system according to one of claims 1 to 29, characterized in that the drive core comprises three rollers (55/2) which are supported for rotation on axially parallel bearing journals (55/1), which are offset by 120 degree  relative to one another, on a disc (20/2), the cylindrical peripheral surfaces of which rollers are disposed on a common circumscribed circle (56) which is coaxial with the axis of the drive shaft (14).