Electric drive unit for an electric bicycle

Abstract

Electric drive unit for an electric bicycle, with a drive housing (20) which defines an interior housing space (26), an electric motor (50) arranged in the drive housing (20), which has a stator (52) and a rotor (54), an output element (31) which is rotatably mounted on the drive housing (20) and can be driven by the rotor (54) of the electric motor (50), a gearbox (60) which is arranged in the drive housing (20) and is interposed between the rotor (54) of the electric motor (50) and the output element (31), and a bearing arrangement (78) for rotatably mounting the rotor (54) of the electric motor (50), the output element (31) and / or at least one gear component (70) of the gearbox (60) on the drive housing (20), wherein the bearing arrangement (78) has at least one bearing element (80, 82), characterized by the fact that A plastic element (92, 102) is arranged on an inner circumferential surface and / or on an outer circumferential surface of the bearing element (80, 82), wherein the plastic element (92, 102) is designed in a sleeve-like manner and is arranged radially between the bearing element (80, 82) and the drive housing (20) such that the bearing element (80, 82) is supported on the drive housing (20) via the plastic element (92, 102), and wherein the sleeve-like plastic element (92, 102) has a radially inwardly projecting projection (93, 103) at at least one axial end, wherein the projection (93, 103) bears axially against the drive housing (20) with a first axial end facing away from the bearing element (80, 82) and with a second axial end facing the bearing element (92, 102) 102) is axially attached.

Description

[0001] An electric drive unit for an electric bicycle is considered, comprising a drive housing which delimits a housing interior, an electric motor arranged in the drive housing, which has a stator and a rotor, an output element which is rotatably mounted on the drive housing and can be driven by the rotor of the electric motor, a transmission which is arranged in the drive housing and is interposed between the rotor of the electric motor and the output element, and a bearing arrangement for the rotatable mounting of the rotor of the electric motor, the output element and / or at least one transmission component of the transmission on the drive housing, wherein the bearing arrangement has at least one bearing element.

[0002] Such electric drive units for pedelecs are well known in the art. The electric motor is controlled depending on the torque applied by the rider to the pedal crankshaft and depending on the assistance level set by the rider. The rotor of the electric motor is connected via a gear to the pedal crankshaft, which serves as the output element. Starting from the pedal crankshaft, the rider's torque and the motor torque provided by the electric motor are transmitted, for example, via a chainring and a chain, to a bicycle wheel, thereby driving the bicycle wheel.

[0003] The output element, the rotor of the electric motor, and the transmission components of the transmission are typically rotatably mounted on the drive housing via bearing elements of the bearing assembly. The problem here is that vibrations of the components rotatably mounted on the drive housing via the bearing elements—i.e., the rotor, the output element, or the transmission components—are transmitted to the drive housing, thereby exciting the drive housing or sections of the drive housing. This results in undesirable, disruptive noise from the electric drive unit, which can be perceived as annoying by the driver.

[0004] DE 10 2019 205 246 A1 discloses a drive unit for an electric bicycle, comprising a drive housing, an electric motor arranged in the drive housing, which has a stator and a rotor, an output element rotatably mounted on the drive housing and drivable by the rotor of the electric motor, a gear arranged in the drive housing and interposed between the rotor of the electric motor and the output element, and a bearing arrangement. The bearing arrangement has two bearing elements for supporting a rotor shaft of the rotor on the drive housing. Furthermore, a preload and / or damping bearing is provided, which is axially supported on the drive housing via a plastic element 39 and serves exclusively for axial preload and damping.

[0005] Furthermore, DE 10 2020 106 337 A1 and DE 10 2020 106 461 A1 disclose an electric drive unit for an electric bicycle, which comprises a drive housing, an electric motor arranged in the drive housing, which motor has a stator and a rotor, a transmission, and a bearing assembly. The bearing assembly comprises a plurality of bearing elements for supporting a rotor shaft of the rotor, wherein one of the bearing elements is supported on the drive housing via a plastic layer to provide electrical insulation between the bearing element and the drive housing.

[0006] Furthermore, DE 10 2018 116 428 A1 discloses a bottom bracket for a bicycle which is mounted on a bicycle frame, wherein a pedal shaft is rotatably mounted on a housing part which can be produced from a plastic via two bearing elements arranged at the ends of the pedal shaft, wherein the housing parts are inserted into a through opening of the bicycle frame.

[0007] The object of the invention is to provide an electric drive unit in which the noises, in particular the noises perceived by the driver, are reduced in a simple and cost-effective manner during operation of the electric drive unit.

[0008] The problem is solved by the features of claim 1.

[0009] By arranging a plastic element on the inner and / or outer peripheral surface of the bearing element, the vibrations emanating from the electric motor, the output element, and / or the transmission components can be dampened, thereby reducing the excitation of the drive housing. This allows the noise perceived by the driver to be reduced in a simple and cost-effective manner.

[0010] The plastic element is arranged radially between the bearing element and the drive housing such that the bearing element is supported on the drive housing via the plastic element. Preferably, the bearing element is attached to the drive housing via the plastic element, with the bearing element resting on a first side of the plastic element and the drive housing resting on a second side facing away from the first side. Alternatively, additional components can be arranged radially between the bearing element and the drive housing.

[0011] The plastic element is sleeve-like. The bearing element is in particular a rolling bearing, which has an outer ring, an inner ring, and a plurality of rolling elements arranged between the outer ring and the inner ring. Preferably, the inner ring is arranged on a component to be supported, in particular a component of the transmission, and the outer ring is supported on the drive housing. The plastic element radially surrounds the outer ring of the rolling bearing, whereby the outer ring is supported radially on the drive housing via the plastic element. In addition, the outer ring is axially fastened to the drive housing, whereby this can be achieved via a press connection or a form-fitting connection, in particular via a retaining ring which is arranged in a groove in the drive housing. Alternatively, the component to be supported can also be fastened to the outer ring, with the inner ring being supported on the drive housing via the plastic element.

[0012] The sleeve-like plastic element has a radially inwardly projecting projection on at least one axial end, wherein the projection bears axially against the drive housing with a first axial end facing away from the bearing element and axially against the bearing element with a second axial end facing the bearing element. This also allows for a reliable and simple reduction or almost complete prevention of vibration transmission from the gearbox, the electric motor, and / or the output element via the axial contact of the bearing element with the drive housing. In a preferred embodiment, the sleeve-like plastic element has a radially inwardly projecting projection on each of its axial ends.

[0013] Preferably, the plastic element is manufactured by injection molding, and the bearing element is overmolded by the plastic element. This allows the plastic element to be manufactured and assembled easily and cost-effectively. The bearing element is inserted into a designated injection mold of an injection molding machine, and the plastic element is injection-molded. After the melt has cooled, the bearing element can be removed from the mold together with the plastic element, with the plastic element permanently attached to the bearing element.

[0014] The transmission preferably has a first gear stage and a second gear stage, wherein a first gear stage has a first gear wheel that is non-rotatably connected to the rotor of the electric motor and a second gear wheel that is operatively connected to the first gear wheel, and the second gear stage has a third gear wheel that is non-rotatably connected to the second gear wheel of the first gear stage and a fourth gear wheel that is operatively connected to the third gear wheel and connected to the output element, wherein the second gear wheel and the third gear wheel are fastened to an intermediate shaft, wherein the intermediate shaft is rotatably mounted on the drive housing at least via the bearing element. The intermediate shaft is thus supported on the drive housing via the plastic element and the bearing element.

[0015] In a preferred embodiment, the output element is a pedal crankshaft, which has a pedal crank with a pedal at each axial end. A chainring accommodating a chain is attached to the output element to transmit motor torque and rider torque. Alternatively, the output element can also be a separate summing element accommodating the chainring, with a gear being interposed, for example, between the electric motor and the summing element, as well as between the pedal crankshaft and the summing element.

[0016] This provides an electric drive unit for an electric bicycle in which the vibrations emanating from the electric motor, the output element, and / or the transmission components, which potentially excite the drive housing, can be dampened in a simple and cost-effective manner. This allows the noise perceived by the rider to be reduced in a simple and cost-effective manner.

[0017] An embodiment of the invention is explained in more detail with reference to the figure.

[0018] The figure shows an electric drive device in a sectional view.

[0019] The figure shows an electric drive unit 10 of an electric bicycle. The drive unit 10 has a drive housing 20, which is rigidly mounted on a bicycle frame (likewise not shown) via an interface not shown in the figure. The drive housing 20 has a base body 22 and a cover 24, which are screwed together and together define a housing interior 26. A pedal crankshaft 30 is arranged in the housing interior 26, with a first pedal crank 33 being fastened to a first longitudinal end of the pedal crankshaft 30, which protrudes from the housing interior 26 via a first opening 32, and a second pedal crank 35 being fastened to the opposite, second longitudinal end, which protrudes via a second opening 34. A rider torque applied by a rider can be introduced into the pedal crankshaft 30 via the pedal cranks 33, 35.

[0020] The pedal crankshaft 30 is rotatably mounted on the drive housing 20 via a first roller bearing 36 and a second roller bearing 40. The first roller bearing 36 is arranged between an annular projection 42 formed on the base body 22 and the pedal crankshaft 30. The second roller bearing 40 is arranged between the cover 24 and the pedal crankshaft 30, with the cover 24 having an annular projection 44 for this purpose.

[0021] Also arranged in the housing interior 26 are an electric motor 50, which is shown very schematically and has a stator 52 and a rotor 54, and a gear 60 interposed between the pedal crankshaft 30 and the electric motor.

[0022] During operation of the electric drive unit 10, a rider torque introduced into the crankshaft 30 by the pedal cranks 33, 35 and a motor torque emanating from the electric motor 50 and transmitted to the crankshaft 30 via the transmission 60 are summed to form a total torque, so that the crankshaft 30 serves as the output element 31. A chainring 38 is fixedly arranged on the crankshaft 30, via which the total torque or the total drive power is transmitted to a chain. The chain is also connected to a chain pinion that is rotationally fixed to a wheel hub of a rear wheel of the pedelec.

[0023] The transmission 60 has a first gear stage 62 and a second gear stage 64, wherein in this case both gear stages 62, 64 are designed as spur gear stages. The first gear stage 62 has a first gear 66 and a second gear 68. The first gear 66 is connected to the rotor 54 in a rotationally fixed manner and is driven by the electric motor 50. The second gear 68 of the first gear stage 62 meshes with the first gear 66 and is fixedly arranged on an intermediate shaft 70. The second gear stage 64 also has two gears 72, 74 designed as spur gears, wherein the first gear 72 is fixedly arranged on the intermediate shaft 70 and thus rotates together with the second gear 68 of the first gear stage 62 about a common axis of rotation. The second gear wheel 74 of the second gear stage 64 is fixedly arranged on the pedal crank shaft 30 and meshes with the corresponding first gear wheel 72.In addition, several freewheels or other components could be provided which are not shown in the figure.

[0024] The intermediate shaft 70 is rotatably mounted on the drive housing 20 at both axial ends, with a first bearing element 80 arranged at a first axial end and a second bearing element 82 arranged at a second axial end. The bearing elements 80, 82 are components of a bearing assembly 78, which also includes the rolling bearings 36, 40 and the bearing elements (not shown in the figure) for supporting the rotor 54 and the first gear wheel 66 of the first gear stage 62.

[0025] The first bearing element 80 is designed as a ball bearing and has an inner ring 84, an outer ring 86, and a plurality of rolling elements 88 arranged between the inner ring 84 and the outer ring 86. The inner circumferential surface of the inner ring 84 is fastened to the intermediate shaft 70. The outer ring 86 is supported by its outer circumferential surface on the base body 22. A sleeve-shaped plastic element 92 is arranged radially between the outer circumferential surface of the outer ring 86 and a circumferential surface of a projection 90 formed on the base body 22 for receiving the first bearing element 82, so that the first bearing element 80 is radially supported on the projection 90 via the plastic element 92. The plastic element 92 has, at an end axially facing the base body 22, a radially inwardly extending projection 93, via which the first bearing element 80 is axially supported on the base body 22.The plastic element 92 is manufactured by an injection molding process, wherein the outer ring 86 is overmolded by the plastic element 92.

[0026] The second bearing element 82 is also designed as a ball bearing and has an inner ring 94, an outer ring 96, and a plurality of rolling elements 98 arranged between the inner ring 94 and the outer ring 96. The inner circumferential surface of the inner ring 94 is fastened to the intermediate shaft 70. The outer ring 96 is supported by its outer circumferential surface on the cover 24. A sleeve-shaped plastic element 102 is arranged radially between the outer circumferential surface of the outer ring 96 and a circumferential surface of a projection 100 formed on the cover 24 for receiving the second bearing element 82, so that the second bearing element 82 is supported radially on the projection 100 via the plastic element 102. The plastic element 102 has, at an end axially facing the cover 24, a radially inwardly extending projection 103, via which the second bearing element 82 is axially supported on the cover 24.The plastic element 102 is also manufactured by an injection molding process, wherein the outer ring 96 is overmolded by the plastic element 102.

[0027] The plastic elements 92, 102 allow the transmission 60 to be vibrationally decoupled from the drive housing 20. The vibrations present in the transmission 60, i.e., at the intermediate shaft 70, can be dampened by the plastic elements 92, 102, thereby reducing the excitation of the housing 20 by the vibrations present at the intermediate shaft 70.

[0028] It should be clear that other structural embodiments of the electric drive unit 10 are also possible compared to the described embodiment without departing from the scope of the main claim. In particular, plastic elements can be provided on the rolling bearings 36, 40. Furthermore, the plastic elements 92, 102 can also be arranged between the intermediate shaft 70 and the bearing elements 80, 82, in which case the damping effect would also be present.

Claims

[1] Electric drive unit for an electric bicycle, with a drive housing (20) which delimits a housing interior (26), an electric motor (50) arranged in the drive housing (20), which has a stator (52) and a rotor (54), an output element (31) which is rotatably mounted on the drive housing (20) and can be driven by the rotor (54) of the electric motor (50), a gear (60) which is arranged in the drive housing (20) and is interposed between the rotor (54) of the electric motor (50) and the output element (31), and a bearing arrangement (78) for rotatably supporting the rotor (54) of the electric motor (50), the output element (31) and / or at least one transmission component (70) of the transmission (60) on the drive housing (20), wherein the bearing arrangement (78) has at least one bearing element (80, 82), characterized by , that a plastic element (92, 102) is arranged on an inner circumferential surface and / or on an outer circumferential surface of the bearing element (80, 82), wherein the plastic element (92, 102) is designed in the form of a sleeve and is arranged radially between the bearing element (80, 82) and the drive housing (20) in such a way that the bearing element (80, 82) is supported on the drive housing (20) via the plastic element (92, 102), and wherein the sleeve-like plastic element (92, 102) has a radially inwardly projecting projection (93, 103) on at least one axial end, wherein the projection (93, 103) bears axially against the drive housing (20) with a first axial end facing away from the bearing element (80, 82) and with a second axial end facing the bearing element (92, 102) on the bearing element (92, 102) is axially applied. [2] Electric drive unit according to claim 1, characterized bythat the plastic element (92, 102) is produced by injection molding and the bearing element (80, 82) is overmolded by the plastic element (92, 102). [3] Electric drive unit according to claim 1 or 2, characterized byin that the transmission (60) has a first gear stage (62) and a second gear stage (64), wherein a first gear stage (62) has a first gear wheel (66) which is connected in a rotationally fixed manner to the rotor (54) of the electric motor (50) and a second gear wheel (68) which is operatively connected to the first gear wheel (66), and the second gear stage (64) has a third gear wheel (72) which is connected in a rotationally fixed manner to the second gear wheel (68) of the first gear stage (62) and a fourth gear wheel (74) which is operatively connected to the third gear wheel (72) and is connected in a rotationally fixed manner to the output element (31), wherein the second gear wheel (68) and the third gear wheel (72) are fastened to an intermediate shaft (70), wherein the intermediate shaft (70) is rotatably mounted on the drive housing (20) via at least the bearing element (80, 82). [4] Electric drive unit according to one of the preceding claims, characterized bythat the output element (31) is a pedal crankshaft (30) which has a pedal crank (33, 35) with a pedal at each of the axial ends, wherein a chain or belt wheel (38) receiving a chain is fastened to the output element (31) for transmitting an engine torque and a driver torque.

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