Electric bicycle mid-drive motor mounting system

Abstract

Electric bicycle mid-motor mounting arrangement (10) with a bicycle frame (12) having a frame-side mid-motor receptacle (120) and an electric bicycle mid-motor drive unit (30) mounted in the receptacle (120), wherein the drive unit (30) comprises: a drive housing (30'), a bottom bracket shaft (39) penetrating the drive housing (30') in a transverse direction, an external cylindrical clamping projection (32) which is formed integrally with the drive housing (30') and is provided on at least one lateral side of the drive unit (30) and is arranged coaxially to the bottom bracket shaft axial (A), wherein the clamping projection (32) has a circular outer surface (32'), a hollow cylindrical closed stiffening ring (34) is provided, which sits on the outside of the outer surface (32') of the clamping projection (32), and the stiffening ring body (34') is made of a mechanically stronger metal than the clamping projection (32), and the mid-motor mount (120) has: a clamping ring arrangement (100) attached to a lateral side of the mid-motor mount (120) with at least one tangential tension element (40;400) by which the assembly consisting of the clamping projection (32) and the stiffening ring (34) is clamped to the bicycle frame (12).

Description

[0001] The invention relates to an electric bicycle mid-motor mounting arrangement with a mid-motor receiving arrangement and an electric bicycle mid-motor drive unit mounted in the receiving arrangement.

[0002] For the purposes of this invention, an electric bicycle is defined as any type of bicycle equipped with an electric drive unit that supplements the human power input from the rider into the bottom bracket axle with a corresponding electric motor drive power, as desired. The present invention relates to the mounting of a so-called mid-drive motor unit, which both rotatably supports the crank axle and includes an output shaft. The output shaft drives a rear wheel of the electric bicycle via a drive element, for example, a chainring. In a mid-drive motor unit, very high mechanical forces can act on the drive unit briefly via the bottom bracket axle and the output shaft. These forces must be transmitted from the drive unit to the bicycle frame; these forces include both high translational and high rotational forces.

[0003] From WO 2015 / 015 014 A1, DE 10 2016 115 681 A1, CN 1 04 773 254 A and CN 1 04 787 224 B, central motor mounting arrangements are known in which, at at least one point in the force flow between the drive housing of the drive unit and a frame-side central motor mounting arrangement, in particular the translational vertical forces and / or the rotational forces are transmitted via shear forces in fastening elements between the drive housing and the mounting arrangement.

[0004] From EP 3 766 772 A1, a mid-motor mounting arrangement is known in which the drive unit has an externally cylindrical clamping projection on each of its lateral sides, each of which is clamped in a frame-side clamping ring arrangement. The drive unit housing, which forms the clamping projections, is made of the lightest possible material, for example, aluminum. Since the rider's entire body weight may be transmitted into the drive unit via the bottom bracket axle, high dynamic forces and clamping forces act between the clamping ring arrangement and the clamping projection.

[0005] In contrast, the object of the invention is to create a lightweight electric bicycle mid-motor mounting arrangement with stable power transmission between the drive unit and the frame-side clamping ring arrangement.

[0006] This problem is solved according to the invention with a fastening arrangement having the features of claim 1.

[0007] Unless otherwise stated, the directions refer to a forward-moving e-bike standing on a horizontal plane. A lateral side is therefore the right or left side of the e-bike.

[0008] The electric bicycle mid-motor mounting arrangement according to the invention consists of a bicycle frame with a frame-mounted mid-motor receptacle and a modular electric bicycle mid-motor drive unit mounted on or in the mid-motor receptacle. The drive unit comprises a supporting drive housing, an electric drive motor, a bottom bracket shaft penetrating the drive housing transversely, and an output shaft parallel to it. In principle, the bottom bracket shaft and the output shaft can be formed by a single shaft. However, separate shafts are particularly preferred. The bottom bracket shaft and the output shaft are preferably mounted coaxially to each other within the drive housing.While the bottom bracket shaft penetrates the drive housing on both lateral sides, relative to the direction of travel of the electric bicycle, the output shaft only penetrates the drive housing laterally on one side, usually on the left lateral side.

[0009] The drive housing is equipped with an externally cylindrical clamping projection on at least one lateral side of the drive unit and coaxial with the bottom bracket axis. This clamping projection has a circular outer clamping surface that is essentially cylindrical in shape. The clamping projection is integrally formed with the drive housing and is therefore made of the same material, preferably metal, as the drive housing or the relevant half of the drive housing. The outer diameter of the clamping surface is preferably at least twice the diameter of the bottom bracket axle.

[0010] On the outer surface of the clamping projection is a substantially hollow cylindrical and closed stiffening ring. The body of the stiffening ring is made of a mechanically stronger metal than the clamping projection. The clamping projection, which is formed integrally with the drive housing or one half of the drive housing, can therefore be made of a weight-optimized material, such as aluminum. However, aluminum does not possess sufficient mechanical strength to withstand the localized transmission of short-term, high dynamic force peaks without deformation or damage to the clamping projection. The stiffening ring is made of a significantly stronger and stiffer metal than the clamping projection. The stiffening ring thus ensures that the forces acting radially on it are never localized but always distributed over a large area.The force is transferred across the entire surface of the clamping projection without permanently deforming or damaging the stiffening ring. This avoids the need to manufacture the entire drive housing from a material sufficiently strong for power transmission, which would then be relatively heavy, in order to provide sufficient mechanical strength on the drive unit side.

[0011] On one lateral side of the mid-motor mount, a substantially annular clamping ring arrangement with at least one tangential tension element is present. The assembly, consisting of the clamping projection and the stiffening ring mounted on it, is firmly clamped to the mount or the bicycle frame by the clamping ring arrangement. Since the clamping ring arrangement transmits the forces emanating from it, directly or indirectly, first to the mechanically stable and rigid stiffening ring, the clamping ring arrangement can be clamped with high clamping forces, which in turn ensures a large-area force distribution between the affected interfaces, even in the long term. Nevertheless, the drive housing, including the clamping projection, can be made of a relatively lightweight material.

[0012] This ensures a mechanically stable connection and mounting of the drive unit in the mid-motor mount, even in the long term. The mid-motor drive unit can be adapted to different boundary conditions or to a different mid-motor mount, for example, with different diameters, simply by adjusting the stiffening ring, while the drive housing itself remains unchanged.

[0013] In this context, a tangential tension element is understood to be a machine element that contracts the entire circular inner surface of the clamping ring assembly or the clamping ring formed by it in the circumferential and radial directions. The tangentiality of the tension element refers to its effect of narrowing the clamping ring of the clamping ring assembly. The tangential tension element preferably lies in the vertical plane defined by the clamping ring of the clamping ring assembly.

[0014] The mid-motor mounting arrangement places relatively low demands on manufacturing tolerances, particularly for the mid-motor mount. This is of great importance in practice because the drive unit is usually from a different manufacturer than the bicycle frame into which it is installed.

[0015] Preferably, the stiffening ring is pressed onto the clamping projection. This ensures a certain radial and tangential preload of the clamping ring even in the long term, thus guaranteeing full-surface contact and a large-area force transmission between the clamping projection and the stiffening ring.

[0016] Preferably, the body of the stiffening ring is made of high-strength steel. Preferably, the drive housing, including the clamping projection, is made of a lightweight non-ferrous metal, for example, aluminum or magnesium, or of a plastic, for example, a fiber-reinforced plastic, so that the drive housing can be made lightweight.

[0017] Preferably, the tangential pulling element is designed as a U-shaped pull bar, both ends of which are anchored in the central motor mount. Particularly preferably, the pull bar forms a precisely semicircular loop, so that the two ends are aligned exactly parallel to each other. In this way, the pull bar can be inserted into corresponding tangential bores in the central motor mount and fixed there. The fixing or anchoring of the bar ends in the central motor mount can be achieved, for example, with threaded nuts that are screwed onto the two bar ends, each of which has an external thread.

[0018] Preferably, the pull bar is formed from a single round steel body, so that the cross-section of the pull bar body is essentially the same everywhere, i.e., both in the area of ​​the semicircular loop and in the two adjoining linear legs. Such a pull bar can be manufactured very inexpensively.

[0019] In a particularly preferred embodiment, a further ring, namely an elastic damping ring, is provided radially between the clamping ring assembly and the stiffening ring. The damping ring serves, in particular, to almost completely prevent the transmission of structure-borne noise from the drive unit to the bicycle frame. This significantly reduces the noise emissions caused by the drive unit, thus improving the overall noise profile. The damping ring also contributes to a more homogeneous distribution of all forces transmitted between the drive unit on the one hand and the mid-motor mount on the other, both temporally and spatially. Furthermore, the elastic damping ring, insofar as it is electrically non-conductive, provides galvanic isolation, thereby preventing bimetallic corrosion.

[0020] Preferably, the damping ring is bonded to the stiffening ring by a material bond. This reliably and permanently prevents the damping ring from slipping relative to the stiffening ring, particularly in the direction of the bottom bracket axle axis. The material bond can be achieved, in particular, by vulcanization and / or bonding.

[0021] It is particularly preferred that the clamping ring arrangement on the one hand and the damping ring on the other hand are positively fixed to each other by a ring groove-ring bar connection in the direction of the bottom bracket shaft axials.

[0022] Preferably, the damping ring, with its proximal-axial projection, provides a permanent axial distance between the drive housing and the mid-motor mount, preventing direct physical contact between the drive housing and the mid-motor mount during operation, even under high-amplitude vibrations. This prevents structure-borne noise transmission from the mid-motor drive unit to the mid-motor mount, even under extreme operating conditions.

[0023] Two embodiments of the invention will be explained in more detail below with reference to the drawings. The drawings show: Fig. 1 A side view of an electric bicycle mid-motor mounting arrangement with a mid-motor mount into which a mid-motor drive unit is mounted, Fig. 2 a vertical cross-section II - II of the mid-engine mounting arrangement of the Fig. 1, and Fig. 3 a partial vertical cross-section of a second embodiment of a pull bar of the mid-engine mounting arrangement of the Fig. 1 and Fig. 2.

[0024] The figures show an electric bicycle mid-motor mounting arrangement 10 including an electric drive unit 30 of an electric bicycle, which is a so-called pedelec. The drive unit 30 is designed as a mid-motor, meaning it supports and mounts both a bottom bracket axle 39 and an output shaft, which is not shown. During normal riding, the drive unit 30 provides purely assistance, supporting the rider's power input via two crank arms (not shown) into the bottom bracket axle 39. The total output power, i.e., the sum of the rider's power input and the electric motor's power input, is transmitted to the rear wheel of the electric bicycle via a chain or belt through a drive element, such as a chainring, which is non-rotatably connected to the output shaft.

[0025] The figures each show an incomplete electric bicycle frame 12, in which a mounting base 20 rigidly connects a mid-motor mount 120 to two rear stays 121, a seat tube 122, and a down tube 123. The mounting base 20 and all other parts of the bicycle frame 12 are made of metal, for example, suitable aluminum or steel, although the bicycle frame can alternatively be partially made of fiber-reinforced plastic.

[0026] The mid-drive motor unit 30 comprises a drive housing 30' composed of two housing shells, in which the bottom bracket shaft 39, which penetrates the drive housing 30' transversely, and an output shaft (not shown) arranged coaxially and parallel to it, are rotatably mounted relative to each other and rotatably to the drive housing 30'. The bottom bracket shaft 39 and the coaxially arranged output shaft (not shown) rotate about the bottom bracket shaft axials A. A positive-locking structure 39' is provided at each of the two longitudinal ends of the bottom bracket shaft 39, onto which a pedal crank can be fixed in a rotationally fixed manner.

[0027] The drive housing 30', made of aluminum, contains an electric drive motor and a gearbox. The bottom bracket axle 50 exits the drive housing 30' through openings on both lateral sides. The drive unit 30 has an external cylindrical clamping projection 32 on each of its lateral sides, which is integrally formed with the drive housing 30'. The two cylindrical clamping projections 32 are precisely coaxial with the bottom bracket axle axis A and each has a circular cylindrical outer surface 32' of the same diameter.

[0028] A hollow cylindrical and circumferentially closed steel stiffening ring 34 is mounted on the outer surface of the cylindrical outer surface 32' of the clamping projection 32. The stiffening ring 34 has a rectangular cross-section. The stiffening ring body 34' is made of a high-strength steel that is mechanically considerably stronger than the drive housing body of the drive housing 30' and, in particular, than the clamping projection 32. The stiffening ring 34 is pressed onto the clamping projection 32, so that the stiffening ring 34 is positively engaged with the clamping projection 32 under permanent radial and tangential preload.

[0029] An annular, rubber-elastic damping ring 50 is fixed to the outside of the stiffening ring 34 and is preferably bonded to the stiffening ring 34 by adhesive. The elastic damping ring body 51 has a substantially rectangular cross-section, as shown in the Fig. 2 shown, but has on the outside a circumferential and in cross-section approximately semicircular ring groove 52.

[0030] The shell-shaped mid-motor mount 120 has two frame-side side walls 28, each oriented in a vertical plane XY, which are integrally formed with the bicycle frame 12. Each side wall 28 forms a mounting shell 26 extending over an angle of approximately 180°. The frame-side mounting shell 26 is essentially cylindrical but features an annular web 27 oriented in a vertical plane, extending symmetrically over approximately 100°. In this area, the mounting shell's annular web 27 and the damping ring's annular groove 52 form an annular groove-annular web connection 110.

[0031] On each lateral side, the central motor mount 120 has a tangential pull element 40, which in the present embodiment is designed as a U-shaped pull bar 42. The one-piece pull bar 42 is formed by a metal pull bar body 40' and has a central semicircle 49 of 180° and two linear and mutually parallel bar arms 43, 43', the bar ends 44, 44' of which are anchored in the mount 120. For this purpose, an external thread 47 is provided on each bar end 44, 44', onto which a retaining nut 46 is screwed. The bar end 44, 44' and the retaining nut 46 are each recessed in an anchor pocket 22, 22' of the central motor mount 120 such that the bar end 44, 44' does not protrude from the contour of the central motor mount 120.In the region of the semicircular arc 49, the tensioning bracket body 40' has an approximately rectangular cross-section, but features an annular web 41 on its proximal surface, which engages complementarily in the damping ring annular groove 52. The tensioning bracket annular web 41 and the damping ring annular groove 52 form a second annular groove-annular web connection 112.

[0032] As in the Fig. As shown in Figure 2, the damping ring 50 has an axial projection 140 of a few millimeters, and the proximal side surface 54 of the damping ring 50 rests against the distal opposite side surface 31 of the drive housing 30', so that the drive housing 30' is permanently spaced laterally a few millimeters away from the receiving side wall 28 and the tangential tension element 40. In this way, the transmission of structure-borne noise between the drive unit 30 and the bicycle frame 12 is minimized.

[0033] Both lateral sides of the mid-motor mount 120 are essentially mirror-symmetrical to a vertical longitudinal plane XY.

[0034] A torque support 130 is provided for the rotational fixing of the drive unit 30 relative to the mid-motor mount 120, which is arranged as far away as possible from the bottom bracket shaft axial A.

[0035] In the Fig.Figure 3 shows a second embodiment of a tangential tension element 400 with a tension bracket 420, which is formed by a round steel body 420' that is circular in cross-section over its entire extent. The round steel body 420' has a relatively large outer diameter of 7–20 mm, wherein the inner diameter of the corresponding circular annular groove 52' of the damping ring 500 is at least 1 mm larger in cross-section than the outer diameter of the round steel body 420'. The opposing annular web 27' is also designed according to the cross-section of the tension bracket 420 and has an outer diameter in cross-section that is at least 1 mm smaller than the inner diameter of the cross-section of the annular groove 52' of the damping ring 500. In this way, stress-free self-centering in the transverse direction is achieved.

Claims

[1] Electric bicycle mid-motor mounting arrangement (10) with a bicycle frame (12) having a frame-side mid-motor receptacle (120) and an electric bicycle mid-motor drive unit (30) mounted in the receptacle (120), wherein the drive unit (30) comprises: a drive housing (30'), a bottom bracket shaft (39) penetrating the drive housing (30') in a transverse direction, an external cylindrical clamping projection (32) which is formed integrally with the drive housing (30') and is provided on at least one lateral side of the drive unit (30) and is arranged coaxially to the bottom bracket shaft axial (A), wherein the clamping projection (32) has a circular outer surface (32'), a hollow cylindrical closed stiffening ring (34) is provided, which sits on the outside of the outer surface (32') of the clamping projection (32), and the stiffening ring body (34') is made of a mechanically stronger metal than the clamping projection (32), and the mid-motor mount (120) has: a clamping ring arrangement (100) attached to a lateral side of the mid-motor mount (120) with at least one tangential tension element (40;400) by which the assembly consisting of the clamping projection (32) and the stiffening ring (34) is clamped to the bicycle frame (12). [2] Electric bicycle mid-motor mounting arrangement (10) according to claim 1, wherein the stiffening ring (34) is pressed onto the clamping projection (32). [3] Electric bicycle mid-motor mounting arrangement (10) according to one of the preceding claims, wherein the stiffening ring body (34') is made of steel. [4] Electric bicycle mid-motor mounting arrangement (10) according to one of the preceding claims, wherein the clamping projection (32) is made of a non-ferrous metal, for example aluminium or magnesium, or of plastic, for example a carbon fiber composite. [5] Electric bicycle mid-motor mounting arrangement (10) according to one of the preceding claims, wherein the tangential pull element (40;400) is designed as a U-shaped pull bar (42; 420) whose two bar ends (44,44') are anchored in the receptacle (120). [6] Electric bicycle mid-motor mounting arrangement (10) according to claim 5, wherein the pull bar (420) is formed from a single round steel body (420'). [7] Electric bicycle mid-motor mounting arrangement (10) according to one of the preceding claims, wherein an elastic damping ring (50) is provided radially between the clamping ring arrangement (100) and the stiffening ring (34). [8] Electric bicycle mid-motor mounting arrangement (10) according to claim 7, wherein the damping ring (50) is materially bonded to the stiffening ring (34). [9] Electric bicycle mid-motor mounting arrangement (10) according to claim 7 or 8, wherein the clamping ring arrangement (100) and the damping ring (50) are axially fixed to each other by an annular groove-ring rib connection (110, 112). [10] Electric bicycle mid-motor mounting arrangement (10) according to one of the preceding claims 7 to 9, wherein the damping ring (50) with an axial projection (140) axially spaces the drive housing (30') from the mid-motor receptacle (120).

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