Patent Publication Number: US-2023145689-A1

Title: Drive Unit

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is related and claims priority to 102020203714.0 filed in the German Patent Office on Mar. 23, 2020 and is a U.S. national phase of PCT/EP2021/054258 filed in the European Patent Office on Feb. 22, 2021, both of which are incorporated by reference in their entirety for all purposes. 
    
    
     FIELD OF THE INVENTION 
     The invention relates generally to a drive unit for a manually driven vehicle. In addition, the invention relates generally to an assembly with a wiring loom for a manually driven vehicle. 
     BACKGROUND 
     DE 10 2015 100 676 A1 discloses a drive assembly with a manual drive, an electric auxiliary drive, a harmonic drive, and a common driven element. The drive unit has a complex structure with a large number of individual components and bearing points. 
     EP 2 724 926 A1 discloses a central drive unit with a bottom bracket shaft for manual drive and an auxiliary drive with a motor and a planetary transmission downstream from the motor. This drive unit also has a relatively complex structure with a large number of individual components. 
     DE 10 2014 108 611 A1 discloses a bicycle drive device with a drive housing for receiving a bottom bracket shaft, and a harmonic drive which is arranged inside the drive housing and can be connected in driving fashion to a traction means carrier. This bicycle drive device also has a complex structure. Mounting has a complicated form. 
     SUMMARY OF THE INVENTION 
     Example aspects of the invention provide an improved drive unit. In particular, a reduced number of components, functional integration, and package optimization are desirable. 
     The drive unit is designed for a manually driven vehicle (operated by muscular force), in particular for a bicycle or an EPAC (Electrically Power Assisted Cycle). The drive unit can be a bicycle drive mechanism. 
     The drive unit has a housing, an electric motor with a stator and a rotor, a stator carrier, and electronics. The electronics can have an electronic circuit board or be designed as an electronic circuit board. The stator carrier, the stator, the rotor, and the electronics are formed as a premountable unit (assembly) such that the premounted unit can be mounted as a whole in the housing of the drive unit, i.e., be arranged and fastened in the housing. 
     Handling during mounting is facilitated by combining the components to form an assembly. Thus, when assembling the drive unit, the combined components are not mounted in the housing of the drive unit individually and instead as an assembly. As a result, final mounting of the assembly can be optimized. In addition, a premounted and functionally testable assembly is provided by the combination of the components. Because the stator carrier does not fasten just the stator in the drive housing but also further components, the stator carrier fulfills multiple functions and greater functional integration and a reduction in the number of components can be achieved. 
     The drive unit can have a bottom bracket shaft, which is mounted rotatably in the housing of the drive unit, for a manual drive. In addition, the drive unit can have an auxiliary drive which has an electric motor and a harmonic drive as components, wherein the electric motor is coupled mechanically to the harmonic drive. The manual drive and the auxiliary drive can be coupled to a common output element on which, for example, a chain ring or a chain ring carrier is fastened. 
     The output element can be designed as a hollow shaft which surrounds the bottom bracket shaft in the axial direction in some regions radially on the outside. Freewheel clutches can be arranged radially between the bottom bracket shaft and the output element, one freewheel clutch of which couples the auxiliary drive or the harmonic drive to the output element, and a further freewheel clutch couples the bottom bracket shaft to the output element. The freewheel clutches can be arranged axially adjacent to each other and/or interact with an inner surface, in particular of the inner circumferential surface of the output shaft. 
     The harmonic drive can be coupled on the input side to the electric motor and on the output side to the output element. The harmonic drive can have a wave generator, a deformable cylindrical bushing or inner bushing with external teeth (flex spline), and a cylindrical outer ring or outer bushing with internal teeth. The wave generator can be formed as an elliptical disk with a rolling bearing arranged thereon and optionally a deformable raceway. The flex spline can be designed to be annular or cup-shaped. The flex spline usually serves as an output of the harmonic drive. 
     The stator carrier can have an in particular annular or sleeve-shaped carrying section and an in particular disk-shaped fastening section. These two sections can be formed as separate elements and be fastened to each other or be formed as a common structural element in a one-piece design. For example, the stator can be fastened on the carrying section and/or the rotor can be mounted rotatably on the fastening section. The stator carrier can be connected to the housing of the drive unit via the fastening section, i.e., be fastened to or in the drive unit. 
     One or more ducts for electrical signal lines and/or electrical power lines can advantageously be formed on the stator carrier, in particular on the fastening section. This favors simple contacting with short cable lengths because the electrical power lines can be routed through the stator carrier, for example from the electronics to the electric motor. 
     The stator, the electronics, and/or the rotor can optionally be fastened on the stator carrier, wherein the rotor can be mounted on the stator carrier by a rolling bearing. The stator carrier is a central element of the structural unit which accommodates at least the stator with coils, the rolling bearing of the rotor, and the electronics. The electronics, for example an electronic circuit board, can be arranged on one side of the stator carrier or of the fastening section, for example on an outer side, and the electric motor on the other side, for example an inner side. The electronics are thus arranged separately from the electric auxiliary drive. 
     The stator carrier can advantageously have a radially outward projecting fastening section by which the stator carrier can be mounted or fixed in the housing of the drive unit, in particular by a press fit. Compact and stable fastening is possible hereby, for example with no separate fastening elements. The external geometry of the stator carrier, for example the outer circumference, can correspond to the internal geometry of the housing, for example the inner circumference. An oil-tight connection between the fastening section and the housing can be produced by virtue of the press fit, for example by using a sealing compound. Lubrication of the drive components can thus take place on one side of the fastening section without affecting the electronics on the other side of the fastening section. 
     The electric motor can expediently be designed as an external rotor motor, i.e., the rotor of the electric motor can be designed as an external rotor. The rotor surrounds the stator radially on the outside. An advantageous power density and a relatively compact size can be achieved by virtue of this structure. 
     The rotor can advantageously have a sleeve-shaped coupling section on the output side for coupling to a harmonic drive arranged in the housing, wherein the coupling section can have an elliptical outer contour. The coupling section is thus the output-side interface with the harmonic drive. The wave generator is integrated directly in the rotor of the electric motor as a coupling section. The coupling section is configured to receive the rolling bearing of the wave generator (flex bearing). 
     The stator of the electric motor can expediently be potted to the stator carrier. The potting compound can extend at least in some regions over the radially outward projecting fastening section and/or the sleeve-shaped carrying section of the stator carrier. Coil windings of the stator can be fixed, and a stiff connection between the stator and the stator carrier produced, by the potting compound. In addition, thermal linkage with the housing can be effected via the stator carrier. Sealing of the electrical signal and power lines or their ducts can also be obtained by the potting compound. The potting compound can, for example, be thermally conductive and/or electrically insulating. 
     The rotor can advantageously be mounted on the stator carrier in a first bearing point only by just one rolling bearing. Structurally favorable mounting with a small number of components and a small space requirement is created hereby. The magnetic field of the electric motor can represent a second bearing point as a dynamic magnetic bearing as soon as a magnetic field is applied via the stator coils. Mounting of the rotor by a rolling bearing (first bearing point) and a magnetic bearing (second bearing point) is thus produced. 
     An electrical flex conductor, which has two layers and is designed as a double-layer flex conductor and is connected at one end to the electronics, for example the electronic circuit board, and at the other end has an electrical interface with multiple contact surfaces for connection to a vehicle-side plug, can expediently be provided. Particularly compact electrical line guidance is produced hereby. One layer of the flex conductor can be designed for power transmission as an electrically power-transmitting layer, and the second layer for signal transmission as an electrical signal-transmitting layer. 
     A groove, in which the flex conductor and the electrical interface are arranged, can advantageously be formed on the outer side of the housing. By virtue of the design as a flex conductor, only a small groove depth is possible for the purpose of line guidance without influencing the internal geometry of the housing of the drive unit. Sections of the flex conductor, for example contact tabs for connection of the flex conductor to the electronics, can be routed, from radially outside to radially inside, through a slot formed in the housing. 
     The layers of the flex conductor can optionally be covered by a potting compound or a covering, wherein a through opening is formed in the potting compound or the covering at the electrical interface. Mechanical fixing and sealing of the flex conductor in the housing is enabled in this way. The potting compound or the covering can close a groove formed on the outer side of the housing, preferably so that the housing is flush, radially on the outside. 
     The electrical contact surfaces can advantageously be formed as flat contacts for transmitting electrical power and an electrical signal. The flat contacts do not project, or only to a small extent, from the flex conductor or from a layer of the flex conductor. Installation of the drive unit in the vehicle can thus be facilitated because there is no risk of a protruding plug element shearing off during mounting. 
     The electronics can expediently have a position sensor system for detecting the rotational position of the bottom bracket shaft of the drive unit, wherein the position sensor system has one or more proximity sensors, fixed to the housing, and an eccentric element, in particular an eccentric ring, fastened non-rotatably to the bottom bracket shaft and interacting with the proximity sensor or sensors. Radial detection of the rotational position of the bottom bracket shaft is thus effected. The proximity sensor or sensors have a detection region in which the eccentric element is situated. The proximity sensor or sensors can be arranged at the electronics or on the electronic circuit board and/or each be designed as a Hall effect sensor, an infrared sensor, or an inductively operating sensor, or the like. The rotational position of the bottom bracket shaft can be determined, based on the spacing, by the proximity sensor because the arrangement of the eccentric element relative to the bottom bracket shaft is known. A change in angle, the angular velocity, and/or the first derivative of the angular velocity can be determined by the position sensor system. 
     The assembly includes an electrical wiring loom for a manually driven vehicle, in particular a bicycle or an EPAC, and a drive unit. The wiring loom can have a connector plug for connection to the electrical interface of the flex conductor, wherein the connector plug has spring-loaded contact pins for electrically contacting contact surfaces of the flex conductor. A retaining clamp, by which the connector plug can be secured to the drive unit, can be provided, wherein the retaining clamp grips the connector plug and latches (at one end or both ends) into recesses which are formed on the outer side of the housing of the drive unit, in particular the shell surface. The wiring loom can form part of a wiring harness of the vehicle. 
     With regard to the advantages which can be obtained hereby, reference should be made to the relevant example embodiments of the drive unit. The measures described in connection with the drive unit can serve for further example embodiments of the assembly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Example aspects of the invention are explained below with the aid of the drawings, wherein the same elements or those with the same function are provided with identical reference numerals, in which: 
         FIG.  1    shows an exemplary embodiment of the drive unit according to example aspects of the invention in a schematic view in section; 
         FIG.  2    shows the stator carrier and the housing of the drive unit from  FIG.  1   ; 
         FIGS.  3   a,b    shows the rotor of the electric motor of the drive unit from  FIG.  1    in a side view ( FIG.  3   a   ) and in a perspective view ( FIG.  3   b   ); 
         FIG.  4    shows the stator carrier with the stator of the drive unit from  FIG.  1   , 
         FIG.  5    shows the stator carrier of the drive unit from  FIG.  1    with a stator and a rotor; 
         FIGS.  6   a,b    show the housing of the drive unit from  FIG.  1    with a flex conductor and a plug of a vehicle-side wiring loom in a perspective view ( FIG.  6   a   ) and in a view in section ( FIG.  6   b   ); 
         FIG.  7    shows the flex conductor and the plug from  FIGS.  6   a,b    in a perspective view from below; 
         FIGS.  8   a,b    show the flex conductor from  FIGS.  6   a,b    and  FIG.  7    in an exploded view ( FIG.  8   a   ) and in an assembled state ( FIG.  8   b   ); and 
         FIGS.  9   a,b    show the position sensor system of the drive unit from  FIG.  1    in a view in section ( FIG.  9   a   ) and in a side view ( FIG.  9   b   ). 
     
    
    
     DETAILED DESCRIPTION 
     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. 
       FIG.  1    shows a drive unit for a manually driven vehicle such as, for example, a bicycle, wherein the drive unit as a whole is designated by the reference numeral  10 . 
     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 manual drive, i.e., 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 , wherein the electric motor  18  is mechanically coupled to the harmonic drive  20 . The bottom bracket shaft  14  and the auxiliary drive  16  are coupled to a common output shaft  22  on which a chain ring carrier or a chain ring can be fastened (not illustrated). 
     The bottom bracket shaft  14  is mounted on a housing cover  26 , which closes the housing  12  of the drive unit  10  on one side (on the left-hand side in  FIG.  1   ), by a first rolling bearing  24 . In addition, the bottom bracket shaft  14  is mounted rotatably on the output shaft  22  by a second rolling bearing  28 . The output element  22  is mounted rotatably in the housing  12  by a third rolling bearing  30  and a fourth rolling bearing  32 . 
     The harmonic drive  20  has a wave generator  34 , a deformable cylindrical bushing or inner bushing  36  with external teeth (flex spine), and a cylindrical outer ring  38  with internal teeth. The harmonic drive  20  is coupled on the input side to the electric motor  18  and on the output side to the output element  22 , and to be precise by a first freewheel clutch  40 . The bottom bracket shaft  14  is coupled to the output element  22  by a further second freewheel clutch  42 . 
     The electric motor  18  has a stator  44  with stator coils  45  and a rotor  46 . The drive unit  10  furthermore has a stator carrier  48  and an electronic unit  50  which is formed as an electronic circuit board. The stator carrier  48  ( FIGS.  1 ,  2 ,  4 , and  5   ) has a, for example, sleeve-shaped carrying section  52  and a, for example, disk-shaped fastening section  54 . The carrying section  52  and the fastening section  54  are designed as a single piece in the illustrated example embodiment. 
     The stator carrier  48 , the stator  44 , the rotor  46 , and the electronics  50  are formed as a premountable unit  56  ( FIGS.  2  and  5   ) such that the premounted unit  56  can be mounted as a whole in the housing  12  of the drive unit  10 . 
     The stator  44  is fastened to the carrying section  52  ( FIG.  5   ) and the rotor  46  is mounted rotatably on the carrying section  52  by a rolling bearing  58 . The stator carrier  48  can be connected to the housing  12  of the drive unit  10  via the fastening section  54 . 
     Ducts for the electrical signal lines  60  and for the electrical power lines  62  are formed on the stator carrier  48  ( FIG.  2   ), in particular on the fastening section  54 . The stator  44 , the electronics  50 , and the rotor  46  are fastened to the stator carrier  48 , wherein the rotor  46  is mounted on the stator carrier  48  by the rolling bearing  58 . The electronics or the electronic circuit board  50  are arranged on one side of the stator carrier  48  or the fastening section  54 , and the electric motor  18  on the other side. 
     As already explained, the stator carrier  48  has a radially outward projecting fastening section  54  by which the stator carrier  48  can be mounted in the housing  12  of the drive unit  10 , this being effected by a press fit in the example. The external geometry  49  of the stator carrier  48  or the fastening section  54  corresponds to the internal geometry  13  of the housing  12  ( FIG.  2   ). An oil-tight connection between the fastening section  54  and the housing  12  can be produced by virtue of the press fit, for example by using a sealing compound (not illustrated). 
     The electric motor  18  ( FIGS.  1 ,  5   ) is designed as an external rotor motor, i.e., the rotor  46  of the electric motor  18  is designed as an external rotor and surrounds the stator  44  radially on the outside. 
     The rotor  46  ( FIGS.  1 ,  2 ,  3     a ,  3   b ) has on the output side a sleeve-shaped coupling section  64  for coupling to the harmonic drive  20  arranged in the housing  12 , wherein the coupling section  64  has an elliptical outer contour  65 . The coupling section  64  is thus the output-side interface with the harmonic drive  20 . The coupling section  64  is configured to receive the rolling bearing  66  as a flex bearing of the wave generator  20 . 
     In the illustrated example embodiment, the stator  44  ( FIG.  4   ) of the electric motor  18  is fixed to the stator carrier  48  by a potting compound  68 . The potting compound  68  extends in some regions over the fastening section  54  and the carrying section  52  of the stator carrier  48 . The potting compound  68  mechanically fixes the coil windings  45  of the stator  44 . In addition, the potting compound  68  seals the signal and power lines or their ducts  60 ,  62 . 
     The rotor  46  ( FIG.  5   ) is mounted on the stator carrier  48  only by one rolling bearing  58  as the first bearing point. The magnetic field of the electric motor  18  forms a second bearing point  70  as a “dynamic magnetic bearing” as soon as a magnetic field is applied via the stator coils. 
     In addition, a flex conductor  72  ( FIGS.  6   a,b   ,  7 ,  8   a ,  8   b ), which is designed as a double-layer flex conductor and has two layers  74 ,  76  and is connected at one end to the electronics  50 , or the electronic circuit board, and at the other end has an electrical interface  78  with multiple flat contact surfaces  79  for connection to a vehicle-side plug  204 , can be provided. A first layer  74  of the flex conductor  72  is designed as an electrically power-transmitting layer  74  and the second layer  76  as an electrically signal-transmitting layer  76 . 
     A groove  82 , in which the flex conductor  72  and the electrical interface  78  are arranged, is formed on the outer side  80  of the housing  12  ( FIGS.  6   a,b   ). Sections of the flex conductor  72 , for example contact tabs  84  for connection of the flex conductor  72  to the electronics  50 , can be routed (from radially outside to radially inside) through a slot  86  formed in the housing  12 . 
     The layers  74 ,  76  of the flex conductor  72  can be covered by a potting compound or a covering  88 , wherein a through-opening  89  is formed (in the potting compound or the covering  88 ) at the electrical interface  78 . The potting compound or covering  88  can close the groove, preferably so that the housing  12  is flush, radially on the outside. 
     The contact surfaces  79  are designed as flat contacts  79  and do not project, or only to a small extent, from the flex conductor  72  or from a layer  74 ,  76  of the flex conductor  72  ( FIGS.  8   a,b   ). 
       FIGS.  6   a ,  6   b   ,  7 ,  8   a , and  8   b  show an assembly  200  including a wiring loom  202 , illustrated only partially, for a manually driven vehicle and a drive unit  10 . The wiring loom  202  has at one of the ends of the wiring loom  202  a plug  204  for connection to the electrical interface  78  of the flex conductor  72 . The connector plug  204  has spring-loaded contact pins  206  for electrically contacting the corresponding contact surfaces  79  of the flex conductor  72 . 
     In addition, a retaining clamp  208 , by which the connector plug  204  can be secured to the drive unit  10 , can be provided ( FIG.  6   a   ). The retaining clamp  208  is designed so as to grip the connector plug  204  and to engage at one end or both ends in recesses  91  which are formed on the outer side  80  of the housing  12  of the drive unit  10 . The connector plug  204  is consequently secured on the housing  12 . 
     The electronics ( FIGS.  9   a,b   ) have a position sensor system  90  for detecting the rotational position of the bottom bracket shaft  14  of the drive unit  10 , wherein the position sensor system  90  has a plurality of proximity sensors  92 , four proximity sensors  92  in the example embodiment illustrated here, distributed over the circumference and an eccentric element, for example an eccentric ring  94 , fastened non-rotatably to the bottom bracket shaft  14  and interacting with the proximity sensors  92 . 
     The proximity sensors  92  are arranged on the electronics  50  or on the electronic circuit board. The proximity sensors  92  can each be designed as a Hall effect sensor, an infrared sensor, or an inductively operating sensor or the like. 
     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 
     
         
         
           
               10  Drive unit 
               12  housing 
               13  internal geometry 
               14  bottom bracket shaft 
               16  auxiliary drive, electric 
               18  electric motor 
               20  harmonic drive 
               22  output element 
               24  first rolling bearing 
               26  housing cover 
               28  second rolling bearing 
               30  third rolling bearing 
               32  fourth rolling bearing 
               34  wave generator 
               36  inner bushing, flex spline 
               38  outer ring 
               40  first freewheel clutch 
               42  second freewheel clutch 
               44  stator 
               45  coil 
               46  rotor 
               48  stator carrier 
               49  external geometry 
               50  electronics, electronic circuit board 
               52  carrying section 
               54  fastening section 
               56  premountable unit 
               58  first bearing point, rolling bearing 
               60  duct for signal lines 
               62  duct for power lines 
               64  coupling section 
               65  elliptical outer contour 
               66  rolling bearing (flex bearing) 
               68  potting compound 
               70  second bearing point, magnetic bearing 
               72  flex conductor 
               74  first layer 
               76  second layer 
               78  electrical interface 
               79  contact surfaces 
               80  outer side 
               82  groove 
               84  contact tab 
               86  slot 
               88  potting compound, covering 
               89  through opening 
               90  position sensor system 
               91  recess 
               92  proximity sensor 
               94  eccentric element, eccentric ring 
               200  assembly 
               202  wiring loom 
               204  plug 
               206  contact pins 
               208  retaining clamp