DRIVE DEVICE FOR AN ELECTRIC BICYCLE AND ELECTRIC BICYCLE

Description

[0001] Drive device for an electric bicycle and electric bicycle The invention relates to a drive device for an electric bicycle and an electric bicycle with such a drive device.

[0002] Bicycles offer cost-effective, easy-to-use, and emission-free means of transportation. They have also become widespread as sports and fitness equipment, and types particularly suited to different sporting applications have emerged.

[0003] In recent years, enthusiasm for electric bicycles (especially so-called "pedelecs") has grown, despite the high weight and prices of bicycles.

[0004] Potential customers are not only older, less fit, or less athletic cyclists, but also sporty, younger riders, whether for commuting or for the opportunity to extend their range and / or increase their speed without overexerting themselves. Interest in electrically assisted mountain bikes seems to be growing, especially among mountain bikers. For e-bikes, a key requirement is providing a reliable, supportive drive system that enables high power transmission.

[0005] Examples of drive devices for electric bicycles can be found in documents EP 3 480 102 A1, EP 0 700 825 A1, EP 2 939 916 A1 and CN 106 627 965 A. Of these, EP 3 480 102 A1 discloses the features of the preamble to claim 1.

[0006] The invention aims to create a reliable drive concept for electric bicycles that allows for a particularly clear and space-saving design.

[0007] According to one aspect, a drive device for an electric bicycle is disclosed. The drive device comprises a motor unit with an electric motor for propelling the electric bicycle. The drive device further comprises a pedal crank shaft that is rotatable about a rotational axis.Furthermore, the drive device has a gearbox designed to drive the electric bicycle and coupled on one side to the motor unit and on the other side to the pedal crank shaft, and designed to deliver a torque to drive the electric bicycle, wherein the pedal crank shaft is designed in two parts and has a first part element and a separate second part element which are coupled together, wherein the motor unit is designed as a ring motor and is arranged coaxially around the axis of rotation of the pedal crank shaft, so that the ring motor coaxially surrounds the pedal crank shaft, and wherein the pedal crank shaft forms a bearing seat for the ring motor.

[0008] The described drive system enables a reliable drive concept for electric bicycles, allowing for a particularly space-saving design. In particular, the split crank axle allows for a compact design with a radially arranged motor unit and gearbox, which also permits the use of modern crank standards for electric bicycle cranks. The described drive system is especially suitable as an electric bicycle drive system for mounting on the down tube or seat tube of the electric bicycle.

[0009] According to one embodiment of the drive device, the transmission is designed as a planetary gear system with a sun gear and at least one planet gear, and is arranged coaxially around the crankshaft's axis of rotation, so that the planetary gear system coaxially surrounds the crankshaft. This allows the planetary gear system to be arranged radially and in a space-saving manner. The planetary gear system can be configured as a single-stage or multi-stage system.

[0010] According to another embodiment of the drive device, the crankshaft forms a bearing seat for the planetary gear. In this way, the components can be arranged radially and in a particularly space-saving manner, for example by coupling them to the crankshaft using ball and / or roller bearings.

[0011] According to a preferred embodiment of the drive device, the pedal crank shaft is narrower in a central section than in an end section, relative to the axis of rotation. For example, the pedal crank shaft has a diameter of 10-23 mm inclusive in the central section and a diameter of 23-35 mm inclusive in the end section.

[0012] Particularly due to the two-part design of the crank arm, the middle section can be significantly thinner or narrower than the outer sections. Furthermore, the crank arm can also be three-part, four-part, or multi-part. The first and second sections each have two end sections, one of which forms an end section and the other a middle section of the crank arm. The sections are connected to each other via their respective end sections, which form the middle section of the crank arm. This connection is achieved, for example, by being plugged together, pressed, welded, and / or bolted. Thus, the middle section of the assembled crank arm is formed, which can be significantly narrower than the two end sections intended for connection to the crank arms of an e-bike.

[0013] With regard to the design of the gearbox as a planetary gear unit and the motor unit as a ring motor, these components can be attached or slid onto the narrower end section of one or both sub-elements before the sub-elements are coupled together. Accordingly, a method for manufacturing the drive device can include providing and coupling the respective components. For example, the motor unit, as a ring motor, is slid onto a narrower end section of the first sub-element, and then the planetary gear unit is arranged radially around it. Subsequently, a narrower end section of the second sub-element can be rigidly connected to the narrower end section of the first sub-element.

[0014] According to a further preferred embodiment of the drive device, the first sub-element and / or the second sub-element are designed in a sleeve-like form at least in a coupling area, such that at least one of the two sub-elements extends into the other. The coupling area forms the region of the end sections of the sub-elements to be joined, which form a central section of the pedal crank axle and may, in particular, be narrower than the other end sections. The sub-element(s) may be designed in a sleeve-like form either continuously or only partially.

[0015] According to a further preferred embodiment of the drive device, the first and second sub-elements are coupled to each other by means of a predetermined coupling structure, which connects the two sub-elements in a form-fit, force-fit, and / or material-fit manner. Such a coupling structure can also include a screw element that extends along the axis of rotation into both sub-elements and screws them together. Alternatively or additionally, the coupling structure can be designed such that one sub-element has a protruding or raised area which is predefined in relation to a corresponding recess on the other sub-element. For example, one or more pins are formed on an outer surface of the first sub-element, which engage in correspondingly designed recesses on an inner surface of the sleeve-shaped second sub-element.This allows for a reliable connection between the two sub-elements, which can specify a certain position of the two sub-elements, which can additionally be screwed, glued and / or welded together.

[0016] According to a further preferred embodiment, the drive device also includes a speed sensor unit comprising a speed sensor and a speed disk, wherein the speed disk is rotatably coupled to the pedal crank shaft about the axis of rotation. The speed disk has, for example, a spiral or helical contour with respect to the axis of rotation, and the speed sensor is arranged, depending on the contour of the speed disk, such that radial or axial speed measurement is provided with respect to the axis of rotation. The speed sensor unit includes, for example, a speed sensor in the form of a Hall sensor, which enables a high, virtually stepless sampling rate based on the Hall effect and the magnetic fields to be measured.Alternatively or additionally, the speed sensor unit can also be designed in such a way that a different speedometer method can be implemented, for example by means of a magnetized speed disc.

[0017] The drive device can further comprise a motor housing in which the motor unit and the gearbox are arranged, and through which the crankshaft extends. The speed control disc is then preferably arranged outside the motor housing with respect to the axis of rotation. Thus, for example, the motor unit and the gearbox, particularly in the configuration of a ring motor and planetary gearbox, can be positioned in a particularly space-saving manner around the narrow central section of the crankshaft within the motor housing. The end sections of the crankshaft then extend, for example, beyond the motor housing and can, in particular, also be designed as bearing seats for the motor housing and may feature stepped edges or a stepped design that define a predetermined position of the motor housing relative to the crankshaft and can also contribute to a stable and secure hold.

[0018] The speed sensor can be located outside the engine housing or inside it, positioned to enable reliable measurement in conjunction with the external speed disc. Positioning the speed disc and, if applicable, the speed sensor outside the engine housing allows for easier access and facilitates efficient servicing of the speed disc and / or the speed sensor.

[0019] According to a further embodiment, the drive device has a cover that protects the speed disc and is coupled to the motor housing, so that the speed disc is positioned between the cover and the motor housing. This allows the speed disc to be reliably and securely positioned outside the motor housing and protected against unwanted external influences. The speed disc is then, for example, connected to the outer end section of the first component of the crank axle and, when mounted on the e-bike, is rotatably mounted between the crank and the motor housing.

[0020] The drive unit can further include a torque sensor located outside the motor housing with respect to the axis of rotation. A chainring system can also be provided, coupled to the crank axle for driving the e-bike, with the torque sensor integrated into the chainring system. Integrating the torque sensor outside the motor housing into the spider allows for a compact housing design, resulting in a particularly slim frame design, and, due to its easier accessibility, facilitates serviceability of the torque sensor. The chainring system comprises multiple interconnected chainrings or gear-shaped elements and can also be referred to as a "spider."The torque sensor then monitors in particular the relative movement of interlocking structures of the chainring system and enables safe operation of the electric bicycle with improved riding comfort.

[0021] The described embodiments of the drive device each enable a compact, lightweight, and / or cost-effective electric drive system for an e-bike. In particular, in a version with a ring motor and a planetary gear unit arranged coaxially around a narrow center point of the crank axle, which can also serve as a bearing seat, functional integration allows for a particularly space-saving and robust design of the drive device. Preferably, a speed sensor with a speed disc is also provided, which is designed as a helix, spiral, or multi-tooth gear and is arranged outside the housing space of the motor housing, thus further contributing to a slim frame design of the e-bike.

[0022] According to a further aspect, an electric bicycle is disclosed which has a bicycle frame with a lower frame section extending to a bottom bracket with a crank arm. The electric bicycle has a drive device according to one of the previously described embodiments, which is arranged in or on the frame section, such that the crank arm shaft is coupled to the crank arm and a torque for driving the electric bicycle can be transmitted via the transmission. The electric bicycle essentially enables the aforementioned properties, advantages, and functions.

[0023] For attachment to the frame section, this section has, for example, a recess so that the drive device can be reliably accommodated. According to one embodiment, the drive device is, for example, arranged as an assembly in an already coupled state on the frame section, in particular mounted.

[0024] The drive unit enables an efficient and space-saving mechanical system for assisting while cycling. This is made possible in particular by the two- or multi-part design of the crank axle, which allows for a significantly smaller outer diameter in the inner or middle section than in the outer end sections.

[0025] The embodiments, advantages, and functions are explained in the following description using exemplary embodiments and the attached figures. The figures show: Figure 1 is a schematic view of an electric bicycle with a mounted drive unit, Figure 2 is a schematic sectional view of an embodiment of the drive unit for the electric bicycle, Figure 3 is a further schematic sectional view of components of the drive unit according to Figure 2, and Figures 4-5 schematic embodiments of a speed sensor unit of the drive device according to Figure 2 .

[0026] Identical, similar, or equivalent elements are marked with the same reference symbols in the figures. For the sake of clarity, not all elements shown in every figure may be marked with their corresponding reference symbols.

[0027] Figure 1 Figure 1 schematically shows an electric bicycle 1 with a bicycle frame 2, which includes a lower frame section 3 forming a down tube. The frame section 3 extends towards a bottom bracket, which includes a crank arm 4 that is coupled or can be coupled to an electric drive unit 5 for the electric bicycle 1.

[0028] The Figures 2-5 schematically show an embodiment of the drive device 5 or of components of the drive device 5. Figure 2Figure 1 shows a sectional view through the drive device 5, which includes, among other things, a motor unit with an electric motor designed as a ring motor 6 for driving the electric bicycle 1. The drive device 5 further includes a pedal crank shaft, which is rotatable about a rotational axis R and is designed in two parts, comprising a first sub-element 11 and a second sub-element 12, which are coupled to each other.

[0029] The drive device 5 further comprises a transmission designed as a planetary gear 15 with a sun gear and at least one planet gear for driving the electric bicycle 1. The planetary gear 15 is coupled on one side to the ring motor 6 and on the other side to the pedal crank shaft 11, 12 and is configured to deliver a torque for driving the electric bicycle 1.

[0030] The planetary gear 15 and the ring motor 6 are each arranged coaxially around the rotational axis R of the pedal crank shaft 11, 12, so that they coaxially surround the pedal crank shaft 11, 12. The pedal crank shaft 11, 12 forms a bearing seat for the planetary gear 15 and the ring motor 6. In particular, because the pedal crank shaft 11, 12 is narrower in a central section than at its ends, a particularly space-saving and clear design of the drive device 5 can be achieved.

[0031] Figure 3 shows in a clearer representation a possible design of the two-part pedal crank shaft 11, 12 according to Figure 2The two sub-elements 11 and 12 each have two end sections, one of which faces the other sub-element 11, 12, and the other of which forms an outer end section of the assembled pedal crank axle. The two outer end sections are connected to the pedal cranks 4 of the electric bicycle 1.

[0032] The first sub-element 11 is significantly narrower in the section coupled to the second sub-element 12 than in its opposite end section. For example, the first sub-element 11 has a diameter D1 at its outer end section that is larger than the diameter D2 of an inwardly oriented adjoining section. A further section of the first sub-element 11 adjoins this section, having a diameter D3 that is smaller than the diameter D2. The various diameters D1-D3 are specifically designed with regard to the arrangement of the interacting components of the drive device 5. The first sub-element 11 is sleeve-shaped, so the described diameters D1-D3 refer to the outer diameters of such a shaft sleeve.

[0033] The second sub-element 12 is also designed in a sleeve-like form and has a predetermined outer diameter D4, which corresponds, for example, to the diameter D1. In the section that is coupled to the first sub-element 11, the second sub-element 12 preferably has an inner diameter that corresponds essentially to the diameter D3 of the first sub-element 11 and is only slightly smaller. Thus, the first sub-element 11 can extend into the second sub-element 12 and be inserted, pressed, and / or welded together with it.

[0034] The crank arm, for example, has diameters D2 and D3 of the first sub-element 11 in its central section, which have a value between 15 and 23 mm inclusive. In the outer end sections, which correspond on the one hand to the area of ​​the first sub-element 11 with diameter D1 and on the other hand to the area of ​​the second sub-element 12 with diameter D4, the crank arm has a dimension of 23 to 35 mm inclusive.

[0035] The two sub-elements 11 and 12 are coupled to each other by means of a screw element 13, which extends along the axis of rotation R through the second sub-element 12 into the first sub-element 11 and screws the two sub-elements 11 and 12 together. The first sub-element 11 has a threaded section on its inner side, which interacts with the screw element 13. According to this embodiment, the second sub-element 12 is preferably designed as a shaft sleeve with a transverse wall that has a through-opening corresponding to the screw element 13. According to the Figures 2 and 3 In the sectional illustration, such a wave sleeve corresponds to a letter "H" lying on its side.

[0036] Alternatively or additionally, the first and second sub-elements 11, 12 can be coupled to each other by means of a further coupling structure, which couples the two sub-elements 11, 12 to each other in a form-fitting, force-fitting and / or material-fitting manner.

[0037] Furthermore, the drive device 5 has a speed sensor unit 10 and a torque sensor 14, each of which is arranged outside a motor housing 7.

[0038] The ring motor 6 and the planetary gear 15 are arranged in the motor housing 7. The pedal crank shaft 11, 12 extends through the motor housing 7. The motor housing 7 serves to protect the ring motor 6, the planetary gear 15, and other interacting components, such as ball or roller bearings. Furthermore, the motor housing 7 enables a reliable connection of the drive unit 5 to the bicycle frame 2 or the frame section 3.

[0039] The speed sensor unit 10 comprises a speed sensor 9 and a speed disc 8, the latter being rotatably coupled to the pedal crank shaft 11, 12 about the axis of rotation R (see Figure 2 The speed disc 8 is arranged outside the motor housing 7, between the pedal crank 4 and the motor housing 7, with respect to the axis of rotation R. The speed disc 8 is connected at a predetermined position on the end section of the pedal crank shaft 11, 12, where the first sub-element 11 changes its dimension from D1 to D2. Such a transition can be inclined, angular, or curved and is specifically designed to accommodate the connection of the speed disc 8. The drive device 5 also has a cover 17, which covers the speed disc 8 and protects it from external influences. The cover 17 is coupled to the motor housing 7, so that the speed disc 8 is positioned between the cover 17 and the motor housing 7.

[0040] The torque sensor 14 is integrated into a chainring system 16, which is coupled to the pedal crank shaft 11, 12 for driving the electric bicycle 1 and has a plurality of chainrings or gear-shaped elements that initiate manual operation of the electric bicycle 1 and engagement of the electric drive device 5 to assist the rider of the electric bicycle 1 when required.

[0041] The Figures 4 and 5 The illustrated embodiments of the turntable 8, which have a spiral shape with respect to the axis of rotation R (see. Figure 4 ) or a helical contour (see Figure 5 ). The speed sensor 9, which is implemented, for example, as a Hall sensor, is arranged depending on the contour of the speed disk 8 such that radial speed detection is possible with respect to the axis of rotation R (see figure). Figure 4 ) or an axial speed measurement (see Figure 5 ) is set up.

[0042] Radial speed measurement is in Figure 4 The process is schematically illustrated and is carried out by measuring the distance of the rotating speed disk 8 in a direction transverse to the axis of rotation R, and in particular perpendicular to it. The speed disk 8 has an edge or a stepped contour 81 on its circumference, which can be reliably detected by the speed sensor 9. The distance D between the speed sensor 9 and the contour of the speed disk 8 undergoes an abrupt change in the region of the stepped contour 81. Furthermore, the distance D also changes continuously due to the spirally rotating contour of the speed disk 8. The distance D to be measured is therefore variable.

[0043] The same applies analogously to axial speed measurement according to Figure 5to which the distance measurement of the rotating speed disk 8 is carried out in the axial direction, for example parallel to the axis of rotation R. The speed disk 8 is helically or helically shaped, so that the distance D between the speed sensor 9 and a surface of the speed disk 8 facing the speed sensor 9 changes. In particular, such a change occurs continuously until a sudden change is detected in the area of ​​step contour 81. The distance D to be measured is therefore also variable according to such an orientation of the speed sensor unit 10. In particular, with such axial speed detection, the speed sensor 9 can, for example, be arranged in an existing free space in the motor housing 7 and detect a rotation of the externally mounted speed disk 8. Figure 2The speed sensor 9 can be arranged, for example, in the area between the ring motor 6 and the speed disc 8. The motor housing 7 can then, for example, have an opening towards the speed disc 8, enabling reliable speed measurement. Furthermore, the drive device 5 can also include two or more speed sensors 9 and speed discs 8, allowing, for example, axial and radial speed measurement.

[0044] The described drive device 5 enables a reliable drive concept for electric bicycles, which allows for a particularly space-saving design. The drive device 5 is especially suitable for mounting on a down tube or seat tube of the electric bicycle 1 and enables an advantageous drive system, particularly with regard to high efficiency and small size. Reference symbol list

[0045] 1 Bicycle 2 Bicycle frame 3 Frame section 4 Crank arm 5 Drive unit 6 Motor unit 7 Motor housing 8 Speedometer disc 8 Step contour 9 Speed ​​sensor 10 Speed ​​sensor unit 11 First crank arm section 12 Second crank arm section 13 Crank arm screw 14 Torque sensor 15 Planetary gear 16 Chainring system 17 Cover D Measuring distance between speed sensor and speed disc D1 First diameter of the pedal crank shaft D2 Second diameter of the pedal crank shaft D3 Third diameter of the pedal crank shaft D4 Fourth diameter of the pedal crank shaft R Rotation axis of the motor unit / pedal crank

Claims

1. Drive device (5) for an electric bicycle (1), comprising: - a motor unit (6) with an electric motor for driving the electric bicycle (1), - a pedal crank shaft (11, 12) that is rotatable about an axis of rotation (R), and - a gearbox (15) configured to drive the electric bicycle (1), coupled on one side to the motor unit (6) and on the other side to the pedal crank shaft (11, 12), and configured to deliver torque for driving the electric bicycle (1), wherein the pedal crank shaft (11, 12) is designed in two parts and comprises a first sub-element (11) and a second sub-element (12) that are coupled to one another, wherein the motor unit is designed as a ring motor (6) and is arranged coaxially with respect to the axis of rotation (R) of the pedal crank shaft (11, 12) so that the ring motor (6) coaxially surrounds the pedal crank shaft (11, 12), characterized in that the pedal crank shaft (11, 12) forms a bearing seat for the ring motor (6).

2. Drive device (5) according to claim 1, wherein the gearbox is designed as a planetary gearbox (15) with a sun gear and at least one planet gear and is arranged coaxially with respect to the axis of rotation (R) of the pedal crank shaft (11, 12) so that the planetary gearbox (15) surrounds the pedal crank shaft (11, 12) coaxially.

3. Drive device (5) according to claim 2, wherein the pedal crank shaft (11, 12) forms a bearing seat for the planetary gearbox (15).

4. Drive device (5) according to one of the preceding claims, wherein the pedal crank shaft (11, 12) is narrower in a central section than in an end section relative to the axis of rotation (R).

5. Drive device (5) according to claim 4, wherein the pedal crank shaft (11, 12) has a diameter (D2, D3) of 15-23 mm inclusive in the middle section and a diameter (D1, D4) of 23-35 mm inclusive in the end section.

6. Drive device (5) according to one of the preceding claims, wherein the first sub-element (11) and / or the second sub-element (12) are sleeve-shaped at least in a coupling region, and at least one of the two sub-elements (11, 12) extends into the other.

7. Drive device (5) according to one of the preceding claims, wherein the first sub-element (11) and the second sub-element (12) are coupled to one another by means of a coupling structure (13) which couples the two sub-elements (11, 12) to one another by form fit, force fit, and / or material bond.

8. Drive device (5) according to one of the preceding claims, comprising: a speed sensor unit (10) comprising a speed sensor (9) and a speed disc (8), wherein the speed disc (8) is rotatably coupled to the pedal crank shaft (11, 12) about the axis of rotation (R).

9. Drive device (5) according to claim 8, wherein the speed disc (8) has a spiral-shaped or helical contour relative to the axis of rotation (R), and the speed sensor (9) is arranged in dependence on the contour of the speed disc (8) such that radial or axial speed detection is configured relative to the axis of rotation (R).

10. Drive device (5) according to claim 8 or 9, comprising: a motor housing (7), in which the motor unit (6) and the gearbox (15) are arranged and through which the pedal crank shaft (11, 12) extends, wherein the speed disc (8) is arranged outside the motor housing (7) with respect to the axis of rotation (R).

11. Drive device (5) according to claim 10, comprising: a torque sensor (14) arranged outside the motor housing (7) with respect to the axis of rotation (R).

12. Drive device (5) according to claim 11, comprising: a chainring system (16) coupled to the pedal crank shaft (11, 12) for driving the electric bicycle (1), wherein the torque sensor (14) is integrated into the chainring system (16).

13. An electric bicycle (1) comprising: - a bicycle frame (2) having a lower frame section (3) extending to a bottom bracket comprising a pedal crank (4), and - a drive device (5) according to one of the preceding claims, which is coupled to the bicycle frame (2) for driving the electric bicycle (1) such that the pedal crank shaft (11, 12) is coupled to the pedal crank (4).