Drive Unit

Abstract

A drive unit (10) for a manually driven vehicle, in particular a bicycle or an EPAC, includes a housing (12), a bottom bracket shaft (14), an electric auxiliary drive (16), and an output shaft (22) designed as a hollow shaft. The bottom bracket shaft (14) and the output shaft (22) are coaxial. The output shaft (22) surrounds the bottom bracket shaft (14) at least partially along an axial direction. A first freewheel clutch (24) and a second freewheel clutch (26) are arranged radially between the bottom bracket shaft (14) and the output shaft (22). The freewheel clutches are axially adjacent and act on the output shaft (22).

Claims

1-12. (canceled)

13. A drive unit (10) for a manually driven vehicle, namely a bicycle or an EPAC, comprising: a housing (12); a bottom bracket shaft (14); an electric auxiliary drive (16); an output shaft (22) designed as a hollow shaft, the output shaft (22) arranged coaxially with the bottom bracket shaft (14), the output shaft (22) partially surrounding the bottom bracket shaft (14) along an axial direction; and a first freewheel clutch (24) adjacent to a second freewheel clutch (26) along the axial direction, the first and second freewheel clutches (24, 26) acting on the output shaft (22) and arranged radially between the bottom bracket shaft (14) and the output shaft (22).

14. The drive unit (10) of claim 13, wherein the first freewheel clutch (24) couples the bottom bracket shaft (14) to the output shaft (22), and the second freewheel clutch (26) couples the electric auxiliary drive (16) to the output shaft (22).

15. The drive unit (10) of claim 13, wherein the electric auxiliary drive (16) comprises a harmonic drive (20) with a flex spine (32), and the flex spine (32) is coupled to the second freewheel clutch (26) via an adapter (50).

16. The drive unit (10) of claim 15, wherein the adapter (50) is annular.

17. The drive unit (10) of claim 15, wherein the flex spine (32) comprises a coupling section (52) via which the flex spine (32) is connected to the adapter (50) in a connecting region (54), and one or both of an interference fit (56) and an adhesive bond (58) are formed in the connecting region (54).

18. The drive unit (10) of claim 13, wherein the bottom bracket shaft (14) comprises a first shaft part (66) connectable to a separate second shaft part (68).

19. The drive unit (10) of claim 18, wherein the first shaft part (66) is fastened to the second shaft part (68) by a screw connection (72).

20. The drive unit (10) of claim 19, wherein the screw connection (72) is centrally arranged with the first and second shaft parts (66, 68).

21. The drive unit (10) of claim 13, wherein the bottom bracket shaft (14) is mounted rotatably on a housing cover (80) delimiting the housing (12) by a first bearing (78), and the bottom bracket shaft (14) is mounted on the output shaft (22) by a second bearing (82).

22. The drive unit (10) of claim 13, further comprising a sensor system (92), wherein the bottom bracket shaft (14) comprises a radially outward projecting shaft shoulder (88) via which the bottom bracket shaft (14) is coupled to the first freewheel clutch (24), the sensor system (92) configured for detection of torque applied to the bottom bracket shaft (14) at the shaft shoulder (88).

23. The drive unit (10) of claim 22, wherein the sensor system (92) comprises one or more strain gauges or one or more magnetostrictive measuring elements (94).

24. The drive unit (10) of claim 13, further comprising a sleeve (96) pushed or pressed onto the bottom bracket shaft (14), wherein the sleeve (96) comprises a socket section (98) for axially fixing one or more rolling bearings (100, 102) of the flex spine (32).

25. The drive unit (10) of claim 24, wherein the sleeve (96) forms a sealing surface (104) for a sealing point between the bottom bracket shaft (14) and a stator carrier (40), the bottom bracket shaft (14) guided through the sealing surface (104).

26. The drive unit (10) of claim 24, wherein one or both of: a line guide is formed on or in the sleeve (96), the line guide configured such that electrical lines (89) for power transmission and/or signal transmission between a sensor system for torque measurement and an electronic unit (48) are received in the line guide; and one or more slip rings (108, 110) for the power transmission and/or the signal transmission between the electronic unit (48) and the sensor system for torque measurement are attached on the sleeve (96).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Example aspects of the invention are explained in detail below with the aid of the drawings, wherein the same elements or those with the same function are provided with identical reference numerals. In the drawings:

[0031] FIG. 1 shows an exemplary embodiment of the drive unit in a view in section;

[0032] FIG. 2 shows the output shaft and the freewheel clutches of the drive unit from FIG. 1 in an enlarged partial view;

[0033] FIG. 3 shows the flex spline of the harmonic drive of the drive unit from FIG. 1 in an enlarged partial view;

[0034] FIG. 4 shows the bottom bracket shaft of the drive unit from FIG. 1 in a view in section;

[0035] FIG. 5 shows the bottom bracket shaft of the drive unit from FIG. 1 in a perspective view; and

[0036] FIGS. 6a,b show the bottom bracket shaft, the sleeve, and the stator carrier of the drive unit from FIG. 1 in a front view (FIG. 6a) and a view in section (FIG. 6b).

DETAILED DESCRIPTION

[0037] Reference will now be made to embodiments of the invention, one or more examples of which are shown in the drawings. Each embodiment is provided by way of explanation of the invention, and not as a limitation of the invention. For example, features illustrated or described as part of one embodiment can be combined with another embodiment to yield still another embodiment. It is intended that the present invention include these and other modifications and variations to the embodiments described herein.

[0038] FIG. 1 shows a drive unit for a manually driven vehicle such as, for example, a bicycle or an EPAC, wherein the drive unit as a whole is designated by the reference numeral 10.

[0039] The drive unit 10 has a housing 12 on or in which the components of the drive unit 10 are arranged. The drive unit 10 has, for a manual drive by muscular force, a bottom bracket shaft 14 which is rotatably mounted in the housing 12 of the drive unit 10. In addition, the drive unit 10 has an electric auxiliary drive 16, which has an electric motor 18 and a harmonic drive 20. The drive unit 10 furthermore has an essentially cup-shaped output shaft 22 which is designed as a hollow shaft.

[0040] The bottom bracket shaft 14 and the output shaft 22 are arranged coaxially with each other and the output shaft 22 surrounds the bottom bracket shaft 14 axially in some regions and radially on the outside. A first freewheel clutch 24 and a second freewheel clutch 26, which are axially adjacent to each other and act on the output shaft 22, are arranged radially between the bottom bracket shaft 14 and the output shaft 22.

[0041] The freewheel clutches 24, 26 (FIG. 2) act mechanically on the output shaft 22 and are thus in each case coupled to the output shaft 22 on the output side, i.e., via an output of the freewheel clutches 24, 26, for example an outer ring. The freewheel clutches 24, 26 can, as in the illustrated example embodiment, be coupled to an inner circumferential surface 28 of the output shaft 22. The inner circumferential surface 28 can be designed to be axially continuous, in particular with a constant diameter. A chain ring or a chain ring carrier for coupling to a drive chain can be fastened (not illustrated) to the output shaft 22. The output of the freewheel clutches 24, 26, for example the outer rings of the freewheel clutches 24, 26, can be connected non-rotatably to the inner circumferential surface 28 of the output shaft 22, for example by pressing in the respective freewheel clutch.

[0042] The auxiliary drive 16 has an electric motor 18 and a coupled harmonic drive 20 (FIG. 1). The harmonic drive 20 has a wave generator 30, a deformable cylindrical inner bushing 32 with external teeth (flex spine) and a cylindrical outer bushing 34 with internal teeth.

[0043] The electric motor 18 has a stator 36 with stator windings 37 and a rotor 38. The electric motor 18 is designed in the illustrated example embodiment as an external rotor motor, i.e., the rotor 38 of the electric motor 18 is designed as an external rotor, and the rotor 38 surrounds the stator 36 radially on the outside.

[0044] A stator carrier 40, which has an in particular sleeve-shaped carrying section 42 and a disk-shaped fastening section 44, is provided (FIG. 1, FIG. 6b). The stator 36 can, as in the illustrated example embodiment, be fastened and/or the rotor 38 mounted by a rolling bearing 46 on the stator carrier 40, in particular on the carrying section 42. Independently thereof, an electronic unit 48, for example an electronic circuit board, can be fastened on the stator carrier 40, in particular on the fastening section 44. The stator carrier 40 can be fastened in the housing 12 via the fastening section 44.

[0045] The first freewheel clutch 24 couples the bottom bracket shaft 14 to the output shaft 22. As a result, a torque can be transmitted to the output shaft 22 by the bottom bracket shaft 14 in a direction of rotation. The second freewheel clutch 26 couples the electric auxiliary drive 16 to the output shaft 22. As a result, a torque can be transmitted to the output shaft 22 by the auxiliary drive 16 in a direction of rotation.

[0046] As already explained, the electric auxiliary drive 16 has a harmonic drive 20 with a flex spine 32, wherein the flex spine 32 is coupled to the second freewheel clutch 26 via a preferably annular adapter 50. The adapter 50 can optionally be hardened.

[0047] The flex spine 52 has a preferably sleeve-shaped coupling section 52 via which the flex spine 32 and the adapter 50 are connected to each other in a connecting region 54 (FIGS. 2 and 3), wherein an interference fit 56 and/or an adhesive bond 58 are formed in the connecting region. A fit 56 between the flex spine 32 and the adapter 50 is formed in one part 60 of the connecting region 54 (fit region 60). An adhesive bond 58 is formed in a further part 62 of the connecting region 54 (adhesive bond region 62). The fit region 60 and the adhesive bond region 62 can, as in the illustrated example embodiment, in each case be separated from each other by a radial shoulder 64 formed on the adapter 50 and on the coupling section 52.

[0048] The bottom bracket shaft 14 has a first shaft part 66 and a separate second shaft part 68 (FIG. 4) and is formed from the first and second shaft parts 66, 68, wherein the shaft parts 66, 68 can be connected to each other in particular reversibly or removably. The bottom bracket shaft 14 can thus be divided axially. In the connecting region, the second shaft part 68 has an axially projecting collar 70 which surrounds the first shaft part 66 radially on the outside in the connected state. Thus, the shaft parts 66, 68 overlap each other in the connecting region in the connected state.

[0049] The two shaft parts 66, 68 can be fastened to each other by a preferably centrally arranged screw connection 72. The screw connection 72 can be effected by just one screw 74. The central longitudinal axis of the screw 74 is aligned axially, i.e., oriented parallel or in particular coaxially with respect to the central longitudinal axis of the bottom bracket shaft 14. The screw 74 can be pushed through a through hole in the second shaft part 68 and be screwed into a bore 76, provided with an internal thread, of the first shaft part 66.

[0050] The bottom bracket shaft 14 is mounted rotatably at one end on a housing cover 80 delimiting the housing 12 at the front by a first bearing 78 (FIG. 1). In addition, the bottom bracket shaft 14 is mounted rotatably at the other end on the output shaft 22 by a second bearing 82. The output shaft 22 is in turn mounted rotatably on the output shaft 22 with a third bearing 84 and a fourth bearing 86.

[0051] The bottom bracket shaft 14 has a radially outward projecting shaft shoulder 88 (FIGS. 1 and 2) via which the bottom bracket shaft 14 is coupled to the first freewheel clutch 24. A sensor system 92 for torque detection is provided (FIGS. 2 and 6b), which detects the torque at the shaft shoulder 88 that is applied to the bottom bracket shaft 14, in particular at the front, i.e., at the front side 90 of the shaft shoulder 88.

[0052] The sensor system 92 for torque detection can be attached to the bottom bracket shaft 14, for example to the front side 90 of the shaft shoulder 88, and be fastened thereon. The sensor system 92 can thus be applied at the measuring point, i.e., the front side 90 of the shaft shoulder 88, and co-rotates with the bottom bracket shaft 14.

[0053] The sensor system 92 for torque detection can have one or more strain gauges (not illustrated) which are attached to the shaft shoulder 88 at the front. Torque determination can be effected with the aid of the detected deformation of the shaft shoulder 88 relative to the bottom bracket shaft 14.

[0054] Alternatively or supplementarily, the sensor system 92 for torque determination can have one or more magnetostrictive measuring elements 94 which are attached at the front, i.e., to the front side 90 of the shaft shoulder 88. Torque determination can be effected with the aid of the detected shear stress of the shaft shoulder 88.

[0055] The drive unit 10 has a sleeve 96 which is pushed or pressed onto the bottom bracket shaft 14 (FIGS. 3 and 6b), wherein the sleeve 96 has a socket section 98 for one or more rolling bearings 100, 102 of the flex spine 32, wherein the rolling bearing or bearings 100, 102 can be fixed axially in the socket section 98. Axial positioning of the bearing of the flex spine is thus possible in a structurally simple fashion. The rolling bearings 100, 102 mount the flex spine 32 on the coupling section 52. A perforation 87, extending axially, for the passage of electrical lines 89 is formed on the socket section 98. The lines 89 connect the electronics 48 of the drive unit 10 to electronics (not illustrated) which are part of the sensor system 92.

[0056] A sealing surface 104 for a sealing point between the bottom bracket shaft 14 and the stator carrier 40, through which the bottom bracket shaft 14 is guided, is formed by the sleeve 96.

[0057] The sleeve 96 and the bottom bracket shaft 14 are sealed by a sealing element 106, for example an O-ring 106, arranged radially between the bottom bracket shaft 14 and the sleeve 96.

[0058] A line guide, for example a duct, in which can be arranged electrical lines 89 for power transmission and/or signal transmission between the sensor system 92 for torque detection and the electronic unit 48, can advantageously be formed (not illustrated) on or in the sleeve 96.

[0059] One or more slip rings 108, 110 (FIGS. 6a,b) for power transmission and/or signal transmission between the electronic unit 48, in particular the electronic circuit board, and the sensor system 92 for torque measurement are attached to the sleeve 96. The electronic unit 48, for example the electronic circuit board, has one or more electrical sliding contacts 112, 114 which each interact with a slip ring 108, 110.

[0060] Modifications and variations can be made to the embodiments illustrated or described herein without departing from the scope and spirit of the invention as set forth in the appended claims. In the claims, reference characters corresponding to elements recited in the detailed description and the drawings may be recited. Such reference characters are enclosed within parentheses and are provided as an aid for reference to example embodiments described in the detailed description and the drawings. Such reference characters are provided for convenience only and have no effect on the scope of the claims. In particular, such reference characters are not intended to limit the claims to the particular example embodiments described in the detailed description and the drawings.

LIST OF REFERENCE NUMERALS

[0061] 10 drive unit [0062] 12 housing [0063] 14 bottom bracket shaft [0064] 16 auxiliary drive, electric [0065] 18 electric motor [0066] 20 harmonic drive [0067] 22 output shaft [0068] 24 first freewheel clutch [0069] 26 second freewheel clutch [0070] 28 inner circumferential surface [0071] 30 wave generator [0072] 32 deformable inner bushing, flex spine [0073] 34 outer bushing [0074] 36 stator [0075] 37 stator windings [0076] 38 rotor [0077] 40 stator carrier [0078] 42 carrying section [0079] 44 fastening section [0080] 46 rolling bearing [0081] 48 electronic unit, circuit board [0082] 50 adapter [0083] 52 coupling section [0084] 54 connecting region [0085] 56 fit [0086] 58 adhesive bond [0087] 60 fit region [0088] 62 adhesive bond region [0089] 64 radial shoulder [0090] 66 first shaft part [0091] 68 second shaft part [0092] 70 projecting collar [0093] 72 screw connection [0094] 74 screw [0095] 76 bore [0096] 78 first bearing [0097] 80 housing cover [0098] 82 second bearing [0099] 84 third bearing [0100] 86 fourth bearing [0101] 87 perforation [0102] 88 shaft shoulder [0103] 89 electrical lines [0104] 90 front side [0105] 92 sensor system [0106] 94 magnetostrictive measuring elements [0107] 96 sleeve [0108] 98 socket section [0109] 100 rolling bearing [0110] 102 rolling bearing [0111] 104 sealing surface [0112] 106 sealing element [0113] 108 slip ring [0114] 110 slip ring [0115] 112 sliding contact [0116] 114 sliding contact