DRIVE UNIT

Description

[0001] The invention relates to a drive unit for a manually driven vehicle having the features of the preamble of claim 1, wherein a manually driven vehicle is in particular a muscle-powered vehicle.

[0002] US 6,152,249 A discloses an electrically assisted bicycle consisting of a bicycle frame, at least two wheels, a manual drive unit, an electric drive unit, a power transmission unit, and a battery. The manual drive unit and the electric drive unit are connected and mounted, together with the battery, on the bicycle frame between the two wheels. The electric drive unit consists of a motor, a wave gear, bearings, sealing components, and fasteners. The rotational axis of the motor and the wave gear is identical to the pedal crankshaft of the manual drive unit and can rotate relative to the motor and the wave gear. The motor is connected to a rear power transmission system via the wave gear.

[0003] DE 10 2015 100 676 A1 discloses a drive assembly with a manual drive, an electric auxiliary drive, and a common output element. The drive unit has a complex structure with numerous individual components and bearing points.

[0004] EP 2 724 926 A1 discloses a central drive unit with a bottom bracket shaft for a manual drive and an auxiliary drive with a downstream planetary gear. This drive unit also has a comparatively complex structure with a multitude of individual components.

[0005] DE 10 2014 108 611 A1 discloses a bicycle drive device with a drive housing for accommodating a pedal crankshaft and a tension shaft gear arranged within the drive housing and connectable to a traction mechanism carrier. This bicycle drive device also has a complex structure.

[0006] WO 2016 / 086526 A1 shows a mid-drive device for a bicycle with an electric motor.

[0007] CN 2 894 047 Y, CN 204 383 714 U and CN 205 239 827 U US 9 789 929 B2 and CN 106 904 240 A show drive devices for bicycles.

[0008] The invention is based on the object of providing a drive unit that is improved over the aforementioned prior art. In particular, package optimization and a compact design are desirable.

[0009] The invention solves this problem by a drive unit having the features of claim 1. The drive unit is designed for a manually powered vehicle, in particular a bicycle or an EPAC (Electrically Power Assisted Cycle). The drive unit has a housing, a pedal crankshaft, an electric auxiliary drive, and an output shaft designed as a substantially pot-shaped hollow shaft. The pedal crankshaft and the output shaft are arranged coaxially to one another, and the output shaft surrounds the pedal crankshaft axially in sections and radially on the outside. Arranged radially between the pedal crankshaft and the output shaft are a first one-way clutch and a second one-way clutch, which are axially adjacent to one another and act on the output shaft.

[0010] The coaxial arrangement of the components allows for optimal use of the available installation space, which promotes a compact design. This allows the drive unit's components, such as an electronics unit or electronics board, an electric motor, a gear unit, an output shaft, and / or one-way clutches, to be arranged centrally around the crankshaft.

[0011] The overrunning clutches act on the output shaft, meaning they are each mechanically coupled to the output shaft on the output side, i.e., via an output of the overrunning clutch, for example, an outer ring. The overrunning clutches can be coupled to an inner peripheral surface of the output shaft. This inner peripheral surface can be axially continuous, in particular with a constant diameter. Independently of this, a chainring or chainring carrier can be attached to the output shaft for coupling to a drive chain.

[0012] The output of the one-way clutch, for example, its outer ring, can be non-rotatably connected to the inner peripheral surface of the output shaft, for example, by pressing the one-way clutch in place. The one-way clutches can each have an inner ring, an outer ring, and control elements located between them that enable torque to be transmitted between the inner and outer rings in only one direction of rotation. The control elements can be, for example, clamping rollers, clamping bodies, locking blades, or the like.

[0013] The electric auxiliary drive can comprise an electric motor and a mechanically coupled gear unit, such as a strain wave gear. With a strain wave gear, high gear ratios can be achieved in a compact design. The strain wave gear comprises a wave generator, a deformable cylindrical bushing with external teeth (flexspline), and a cylindrical outer bushing with internal teeth. The wave generator can be designed as an elliptical disk with a rolling bearing mounted thereon and, optionally, a deformable race. The flexspline can be ring-shaped or cup-shaped. The flexspline typically serves as the output of the strain wave gear.

[0014] The electric motor can be designed as an external rotor motor, meaning the rotor of the electric motor can be designed as an external rotor. The rotor surrounds the stator radially on the outside. This allows for advantageous power density and a compact size.

[0015] A stator carrier may be provided, which has a support section, in particular a sleeve-shaped one, and a fastening section, in particular a disc-shaped one. The stator can be fastened to the stator carrier, in particular to the support section, and / or the rotor can be mounted by means of a rolling bearing. Independently of this, electronics, for example an electronic circuit board, can be fastened to the stator carrier, in particular to the fastening section. The stator carrier can be fastened inside the housing of the drive unit via the fastening section.

[0016] The electric auxiliary drive has a strain wave gear with a flexspline, whereby the flexspline is coupled to the second one-way clutch via a preferably annular adapter. The adapter can radially bridge a gap between the flexspline and the second one-way clutch. The output shaft can thus be designed and manufactured more simply. The adapter can optionally be hardened. This increases the adapter's durability. As previously described, the electric auxiliary drive can have an electric motor coupled to the strain wave gear. Thus, torque from the electric motor can be transmitted to the output shaft via the strain wave gear and adapter.

[0017] The Flexspline, as the output of the strain wave gear, has a preferably sleeve-shaped coupling section, via which the Flexspline and the annular adapter are connected to each other in a connection area, wherein a fit and / or an adhesive bond is formed in the connection area. This contributes to a precise and stable coupling of the Flexspline and adapter. Thus, a fit between the Flexspline and the annular adapter can be formed in one part of the connection area (fit area). An adhesive bond can be formed in another part of the connection area (adhesive bond).

[0018] The fitting area and the bonding area can each be separated from each other by a radial shoulder, for example, formed on the adapter and / or the coupling section. This separates the functional surfaces of the fitting area and the bonding area.

[0019] Advantageously, the first freewheel clutch can couple the pedal crankshaft to the output shaft. This allows manual drive of the output shaft, for example, by operating the pedal crankshaft using muscle power. A power flow coupling exists when torque can be transmitted from one component, for example, the pedal crankshaft, to another component, for example, the output shaft.

[0020] The second overrunning clutch can conveniently couple the power flow between the electric auxiliary drive and the output shaft. This enables an electric drive or auxiliary drive of the output shaft. A power flow coupling exists when torque can be transmitted from one component, for example, the auxiliary drive, to another component, for example, the output shaft.

[0021] Advantageously, the pedal crankshaft can have a first shaft part and a separate second shaft part or can be formed from these shaft parts, wherein the shaft parts can be connected to one another, in particular reversibly and axially. The pedal crankshaft can thus be axially divisible, for example. Assembly is facilitated because an assembly can also be easily mounted within the cylindrical housing of the drive unit. In the connecting region, one shaft part can have an axially projecting collar which radially surrounds the other shaft part on the outside when connected, i.e. the shaft parts overlap one another in the connecting region and one shaft part can have an insertion section and the other shaft part a corresponding receiving section.

[0022] The two shaft parts can expediently be fastened to one another by means of a preferably centrally arranged screw connection. This enables a structurally simple and stable fastening. The screw connection can be made using a single screw. The central longitudinal axis of the screw can be aligned axially, i.e., parallel or, in particular, coaxial with the central longitudinal axis of the pedal crank shaft. The screw can be inserted through a through hole in one shaft part, for example, the second shaft part, and screwed into a bore provided with an internal thread in the other shaft part, for example, the first shaft part.

[0023] According to the invention, the pedal crankshaft is rotatably mounted at one end by means of a first bearing on a housing cover that defines the housing, particularly at the front end, and the pedal crankshaft is mounted at the other end by means of a second bearing on the output shaft. This provides a reliable and structurally advantageous bearing for the pedal crankshaft.

[0024] The pedal crankshaft can expediently have a radially outwardly projecting shaft shoulder, via which the pedal crankshaft is coupled to the first freewheel clutch. A torque sensor can be provided to measure the torque applied to the pedal crankshaft at the shaft shoulder, for example, on the front side. This represents a structurally advantageous and simultaneously space-saving design, since, regardless of the measurement method used, conventional torque measurement using a sleeve can be dispensed with.

[0025] The sensor for torque measurement can be mounted and attached to the crankshaft, for example, on the end face of the shaft shoulder. The sensor can thus be applied to the measuring point and rotates with the shaft. Power can be supplied from an electronic unit, such as an electronic circuit board, via sliding contacts or inductively. A signal from the sensor can be transmitted to the electronic unit, such as the electronic circuit board, via radio or sliding contact.

[0026] The sensor system for torque measurement can expediently comprise one or more strain gauges, which are attached, for example, to the front of the shaft shoulder. This allows for reliable torque measurement. Torque determination, i.e., the torque applied to the crankshaft, can be performed based on the detected deformation of the shaft shoulder relative to the crankshaft.

[0027] Alternatively or additionally, the sensor system can advantageously comprise one or more magnetostrictive measuring elements for torque measurement, which are mounted, for example, on the front side of the shaft shoulder. This can also be used to determine the torque. Torque determination, i.e., the torque applied to the pedal crankshaft, can be performed based on the measured shear stresses of the shaft shoulder.

[0028] A sleeve can expediently be provided which is pushed or pressed onto the pedal crankshaft, wherein the sleeve has a receiving section for one or more rolling bearings of the Flexspline, wherein the rolling bearing(s) can be axially fixed in the receiving section. This enables axial positioning of the bearing of the Flexspline in a structurally simple manner. The rolling bearing(s) are rolling bearings of the Flexspline arranged on the output side, which are arranged, for example, on the coupling section of the Flexspline. An opening, for example extending axially, for the passage of electrical cables can be formed on the receiving section. This allows electronics of the drive unit to be easily connected to the sensor system, i.e. to electronics belonging to the sensor system.

[0029] Advantageously, the sleeve can be used to form a sealing surface for a sealing point between the pedal crankshaft and a stator carrier through which the pedal crankshaft is guided. This creates a reliable separation on the stator carrier. This allows an electronic unit, such as an electronic circuit board, located on one side of the stator carrier to be separated from mechanical components, which may need to be lubricated, located on the other side of the stator carrier. This reduces the risk of electronic damage.

[0030] The sleeve and the crankshaft can be expediently sealed by means of a sealing element, such as an O-ring, arranged radially between the crankshaft and the sleeve. This prevents capillary action radially between the crankshaft and the sleeve. This further reduces the risk of electronic damage.

[0031] Advantageously, a cable guide, for example a channel, can be formed on or in the sleeve, in which electrical lines for power transmission and / or signal transmission can be arranged between a sensor for torque measurement, which is arranged, for example, on the shaft shoulder, and an electronics unit, for example, an electronics board arranged on the stator carrier. This allows electrical energy and / or signals to be transmitted through the sleeve in a particularly space-saving manner.

[0032] One or more slip rings for electrical power transmission and / or signal transmission between the electronics unit and a sensor for torque measurement can be conveniently mounted on the sleeve. Preferably, the electronics, for example, an electronic circuit board, can have one or more sliding contacts, each of which interacts with a slip ring. This enables space-saving and easy-to-install power transmission and / or signal transmission. The sensor signal can be modulated onto one of the slip rings, for example, via a radio frequency.

[0033] The invention is explained in more detail below with reference to the figures, in which identical or functionally equivalent elements are provided with identical reference numerals. They show: Fig. 1 shows an embodiment of the drive unit in sectional view; Fig. 2 shows the output shaft and the freewheel clutches of the drive unit from Fig. 1 in an enlarged partial view; Fig. 3 the flexspline of the wave gear of the drive unit from Fig. 1 in an enlarged partial view; Fig. 4 the pedal crankshaft of the drive unit from Fig. 1 in sectional view; Fig. 5 the pedal crankshaft of the drive unit from Fig. 1 in perspective view; and Fig. 6a, bthe pedal crankshaft, the sleeve and the stator carrier of the drive unit from Fig. 1 in frontal view ( Fig. 6a ) and section view ( Fig. 6b ).

[0034] Figur 1 shows a drive unit for a manually driven vehicle such as a bicycle or an EPAC, the drive unit being designated overall by the reference numeral 10.

[0035] 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 a pedal crankshaft 14 for manual drive by muscle power, which is rotatably mounted in the housing 12 of the drive unit 10. The drive unit 10 also has an electric auxiliary drive 16, which has an electric motor 18 and a strain wave gear 20. Furthermore, the drive unit 10 has a substantially pot-shaped output shaft 22, which is designed as a hollow shaft.

[0036] The pedal crankshaft 14 and the output shaft 22 are arranged coaxially with each other, and the output shaft 22 surrounds the pedal crankshaft 14 axially in sections and radially outwardly. Arranged radially between the pedal crankshaft 14 and the output shaft 22 are a first one-way clutch 24 and a second one-way clutch 26, which are axially adjacent to each other and act on the output shaft 22.

[0037] The freewheel clutches 24, 26 ( Fig. 2 ) act mechanically on the output shaft 22, i.e. are each coupled to the output shaft 22 on the output side, i.e. via an output of the one-way clutches 24, 26, for example an outer ring. The one-way clutches 24, 26 can be coupled to an inner circumferential surface 28 of the output shaft 22, as in the example. The inner circumferential surface 28 can be axially continuous, in particular with a constant diameter. A chainring or a chainring carrier for coupling to a drive chain can be fastened to the output shaft 22 (not shown). The output of the one-way clutches 24, 26, for example their outer rings, can be connected in a rotationally fixed manner to the inner circumferential surface 28 of the output shaft 22, for example by pressing in the respective one-way clutch.

[0038] The auxiliary drive 16 comprises an electric motor 18 and a coupled wave gear 20 ( Fig. 1 ). The wave gear 20 has a wave generator 30, a deformable cylindrical inner bushing 32 with external teeth (flexspline) and a cylindrical outer bushing 34 with internal teeth.

[0039] The electric motor 18 has a stator 36 with stator windings 37 and a rotor 38. In the example, the electric motor 18 is designed 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.

[0040] A stator carrier 40 is provided ( Fig. 1 , Fig. 6b ), which has a particularly sleeve-shaped support section 42 and a disc-shaped fastening section 44. As in the example, the stator 36 can be fastened to the stator support 40, in particular to the support section 42, and / or the rotor 38 can be mounted by means of a rolling bearing 46. Independently of this, an electronics unit 48, for example an electronic circuit board, can be fastened to the stator support 40, in particular to the fastening section 44. The stator support 40 can be fastened in the housing 12 via the fastening section 44.

[0041] The first one-way clutch 24 couples the pedal crankshaft 14 to the output shaft 22. This allows torque to be transmitted from the pedal crankshaft 14 to the output shaft 22 in one direction of rotation. The second one-way clutch 26 couples the electric auxiliary drive 16 to the output shaft 22. This allows torque to be transmitted from the auxiliary drive 16 to the output shaft 22 in one direction of rotation.

[0042] As already explained, the electric auxiliary drive 16 has a strain wave gear 20 with a flexspline 32, wherein the flexspline 32 is coupled to the second overrunning clutch 26 via a preferably annular adapter 50. The adapter 50 can optionally be hardened.

[0043] The flexspline 32 has a preferably sleeve-shaped coupling section 52, via which the flexspline 32 and the adapter 50 are connected to one another in a connecting area 54 ( Fig. 2 and 3), wherein a fit 56 and / or an adhesive bond 58 are formed in the connection region. In a part 60 of the connection region 54, a fit 56 is formed between the flexspline 32 and the adapter 50 (fitting region 60). In a further part 62 of the connection region 54, an adhesive bond 58 is formed (adhesive region 62). The fitting region 60 and the adhesive region 62 can, as in the example, each be separated from one another by a radial shoulder 64 formed on the adapter 50 and on the coupling section 52.

[0044] The pedal crank shaft 14 has a first shaft part 66 and a separate second shaft part 68 ( Fig. 4 ) and is formed from these shaft parts 66, 68, wherein the shaft parts 66, 68 are reversibly connectable to one another. The pedal crankshaft 14 is thus axially divisible. In the connecting region, the second shaft part 68 has an axially projecting collar 70, which radially surrounds the first shaft part 66 on the outside when connected. Thus, the shaft parts 66, 68 overlap one another in the connecting region when connected.

[0045] The two shaft parts 66, 68 can be fastened to one another by means of a preferably centrally arranged screw connection 72. The screw connection 72 can be made using a single screw 74. The central longitudinal axis of the screw 74 is axially aligned, i.e., parallel or, in particular, coaxial with the central longitudinal axis of the pedal crank shaft 14. The screw 74 can be inserted through a through-bore in the second shaft part 68 and screwed into a bore 76 provided with an internal thread in the first shaft part 66.

[0046] The pedal crankshaft 14 is supported at one end by a first bearing 78 ( Fig. 1 ) is rotatably mounted on a housing cover 80 that defines the front end of the housing 12. Furthermore, the pedal crankshaft 14 is rotatably mounted on the output shaft 22 by means of a second bearing 82. The output shaft 22 is, in turn, rotatably mounted on the output shaft 22 by means of a third bearing 84 and a fourth bearing 86.

[0047] The pedal crankshaft 14 has a radially outwardly projecting shaft shoulder 88 ( Fig. 1 and 2 ), via which the pedal crankshaft 14 is coupled to the first freewheel clutch 24. A sensor 92 is provided for torque detection ( Fig. 2 and 6b ), which detects the torque applied to the pedal crankshaft 14 at the shaft shoulder 88, in particular at the front side, i.e. at the front side 90 of the shaft shoulder 88.

[0048] The sensor 92 for torque measurement can be mounted on and secured to the crankshaft 14, for example, on the end face 90 of the shaft shoulder 88. The sensor 92 can thus be applied to the measuring point, i.e., the end face 90 of the shaft shoulder 88, and rotates with the crankshaft 14.

[0049] The sensor system 92 for torque detection can comprise one or more strain gauges (not shown) mounted on the front side of the shaft shoulder 88. A torque determination can be made based on the detected deformation of the shaft shoulder 88 relative to the pedal crankshaft 14.

[0050] Alternatively or additionally, the sensor system 92 for torque detection can comprise one or more magnetostrictive measuring elements 94, which are mounted on the front side, i.e., on the front side 90 of the shaft shoulder 88. A torque determination can be carried out based on the detected shear stresses of the shaft shoulder 88.

[0051] The drive unit 10 has a sleeve 96 which is pushed or pressed onto the pedal crank shaft 14 ( Fig. 3 and 6b), wherein the sleeve 96 has a receiving section 98 for one or more rolling bearings 100, 102 of the flexspline 32, wherein the rolling bearing(s) 100, 102 can be axially fixed in the receiving section 98. The rolling bearings 100, 102 support the flexspline 32 on the coupling section 52. An axially extending opening 87 for the passage of electrical lines 89 is formed on the receiving section 98. The lines 89 connect the electronics 48 of the drive unit 10 to an electronics system (not shown) belonging to the sensor system 92.

[0052] By means of the sleeve 96, a sealing surface 104 is formed for a sealing point between the pedal crankshaft 14 and the stator carrier 40, through which the pedal crankshaft 14 is guided.

[0053] The sleeve 96 and the pedal crank shaft 14 are sealed by means of a sealing element 106, for example an O-ring 106, arranged radially between the bottom bracket shaft 14 and the sleeve 96.

[0054] Advantageously, a line guide, for example a channel (not shown), can be formed on or in the sleeve 96, in which the electrical lines 89 for power transmission and / or signal transmission between the sensor system 92 for torque measurement to the electronic unit 48 can be arranged.

[0055] One or more slip rings 108, 110 ( Fig. 6a, b ) for power transmission and / or signal transmission between the electronics unit 48, in particular the electronics board, and the sensor system 92 for torque measurement. The electronics unit 48, for example the electronics board, has one or more electrical sliding contacts 112, 114, each of which interacts with a slip ring 108, 110. Bezugszeichenliste

[0056] 10 Drive unit 12 Housing 14 Pedal crankshaft 16 Auxiliary drive, electric 18 Electric motor 20 Wave gear 22 Output shaft 24 First overrunning clutch 26 Second overrunning clutch 28 Inner peripheral surface 30 Wave generator 32 Deformable inner bushing, Flexspline 34 Outer bushing 36 Stator 37 Stator windings 38 Rotor 40 Stator carrier 42 Support section 44 Fastening section 46 Rolling bearing 48 Electronics unit, circuit board 50 Adapter 52 Coupling section 54 Connection area 56 Fit 58 Adhesive joint 60 Fit area 62 Adhesive area 64 Radial shoulder 66 First shaft part 68 Second shaft part 70 Projecting collar 72 Screw connection 74 Screw 76 Bore 78 First bearing 80Housing cover 82Second bearing 84Third bearing 86Fourth bearing 87Breakthrough 88Shaft shoulder 89Electrical cables 90End face 92Sensors 94Magnetostrictive measuring elements 96Sleeve 98Holding section 100Rolling bearing 102Rolling bearing 104Sealing surface 106Sealing element 108Slip ring 110Slip ring 112Sliding contact 114Sliding contact

Claims

1. Drive unit (10) for a manually driven vehicle, in particular a bicycle or an electrically power assisted cycle, with a housing (12), a bottom bracket shaft (14), an electric auxiliary drive (16), and an output shaft (22) designed as a hollow shaft, wherein 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 areas and radially on the outside, wherein a first freewheel clutch (24) and a second freewheel clutch (26), which are adjacent to each other axially and act on the output shaft (22), are arranged radially between the bottom bracket shaft (14) and the output shaft (22), wherein 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), wherein the flex spine (32) has a coupling section (52) via which the flex spine (32) and the adapter (50) are connected to each other in a connecting region (54), wherein a fit (56) and / or an adhesive bond (58) are formed in the connecting region (54), characterized in that the bottom bracket shaft (14) is mounted rotatably on a housing cover (80) delimiting the housing (12) by means of a first bearing (78), and in that the bottom bracket shaft (14) is mounted on the output shaft (22) by means of a second bearing (82).

2. Drive unit (10) according to Claim 1, characterized in that the first freewheel clutch (24) couples the bottom bracket shaft (14) to the output shaft (22), and in that the second freewheel clutch (26) couples the electric auxiliary drive (16) to the output shaft (22).

3. Drive unit (10) according to either of the preceding claims, characterized in that the bottom bracket shaft (14) has a first shaft part (66) and a separate second shaft part (68) which can be connected to each other.

4. Drive unit (10) according to Claim 3, characterized in that the two shaft parts (66, 68) can be or are fastened to each other by means of a preferably centrally arranged screw connection (72).

5. Drive unit (10) according to any of the preceding claims, characterized in that the bottom bracket shaft (14) has a radially outward projecting shaft shoulder (88) via which the bottom bracket shaft (14) is coupled to the first freewheel clutch (24), wherein a sensor system (92) for torque detection is provided which detects the torque at the shaft shoulder (88) which is applied to the bottom bracket shaft (14).

6. Drive unit (10) according to Claim 5, characterized in that the sensor system (92) for torque detection has one or more strain gauges or one or more magnetostrictive measuring elements (94).

7. Drive unit (10) according to any of the preceding claims, characterized in that a sleeve (96) which is pushed or pressed onto the bottom bracket shaft (14), is provided, wherein the sleeve (96) has a socket section (98) for one or more rolling bearings (100, 102) of the flex spine (32), in which the rolling bearing or bearings (100, 102) can be fixed axially.

8. Drive unit (10) according to Claim 7, characterized in that a sealing surface (104) for a sealing point between the bottom bracket shaft (14) and a stator carrier (40), through which the bottom bracket shaft (14) is guided, is formed by means of the sleeve (96).

9. Drive unit (10) according to Claim 7 or 8, characterized in that a line guide, in which can be arranged electrical lines (89) for power transmission and / or signal transmission between a sensor system for torque measurement and an electronics unit (48), is formed on or in the sleeve (96), and / or in that one or more slip rings (108, 110) for power transmission and / or signal transmission between the electronics unit (48) and a sensor system for torque measurement are attached on the sleeve (96).