Transmission assembly for a drive unit having at least one damping element for a frictional contact with a gearwheel

Abstract

The proposed solution relates to a transmission assembly for a motorised drive unit (A) for driving a two-wheeled vehicle, wherein the transmission assembly (1) comprises at least two gearwheels (32, 4) which mesh with one another for transmitting a drive torque generated by at least one motor of the drive unit (A). On a proposed transmission assembly (1), at least one damping element (7a, 7B) is provided, which acts on an end face of one gearwheel (4) of the at least two gearwheels (32, 4) via a frictional contact in order to exert a holding force on the gearwheel (4) in the absence of the drive torque.

Description

[0001] Gear assembly for a drive unit with at least one damping element for frictional contact with a gear

[0002] The proposed solution concerns a gearbox assembly for a motor drive unit for propelling a two-wheeler, in particular an electric bicycle.

[0003] Drive units for two-wheelers with at least one electric motor are widely known. At least one electric motor is used to provide externally generated drive torque to a power transmission element of the drive unit. This power transmission element is then connected, for example, via a transmission link such as a belt or chain in the case of an e-bike, to a rear wheel of the two-wheeler to propel the bicycle. The motor-generated drive torque can be provided in addition to muscle-powered drive torque, which is applied via pedals to a bottom bracket assembly.

[0004] Within a housing of the drive unit, a gear assembly with at least two meshing gears is typically provided for transmitting a drive torque generated by the at least one motor of the drive unit. The basic design of such a drive unit is known, for example, from DE 10 2023 106 363 A1. It can be observed that when no drive torque is applied, generated by the at least one motor, disturbing noises can occur at the meshing gears due to backlash.

[0005] The proposed solution is intended to remedy this situation.

[0006] Against this background, a gear assembly for a motor drive unit for driving a two-wheeler, in particular an electric bicycle, is proposed, in which at least one damping element is provided which acts via a friction contact on an end face of a gear of the at least two meshing gears of the gear assembly in order to exert a holding force on one gear when a drive torque generated by at least one motor of the drive unit ceases.

[0007] The basic idea behind the proposed solution is to apply a holding force to the gear via at least one damping element when the gears are stationary. This force counteracts any displacement of the gear around its axis of rotation. The holding force, applied via a frictional contact on one end face of the gear, thus acts as a brake when the motor-generated drive torque ceases, holding the gear in position when the at least one motor is not causing it to rotate. This effectively counteracts, and even completely eliminates, noise generated by backlash in stationary gears.

[0008] In one embodiment, the at least one damping element has at least one elastically displaceable section for establishing the frictional contact. The gear can therefore be axially preloaded with respect to its axis of rotation via the at least one elastically displaceable section of the at least one damping element that acts on the end face of the gear. This supports the frictional contact for applying the holding force.

[0009] For example, the at least one elastically displaceable section is designed as a spring arm projecting from a base of the at least one damping element, for example, a leaf spring. Alternatively, the at least one elastically displaceable section can be part of a damping element made of rubber, which is in frictional contact with the gear at an end face.

[0010] In principle, the frictional contact between the at least one damping element and the face of the gear being held (when the gears are stationary) can be designed such that, when the gears rotate under the influence of the at least one motor, the frictional contact is reduced or even eliminated entirely. This can be readily achieved, for example, by means of an elastically displaceable section of the damping element, particularly if, when the gears are rotating, lubricant is present between the elastically displaceable section of the at least one damping element and the face of the gear, and this lubricant is stored within the transmission assembly. Such a lubricant could, for example, be a grease and, when the gears rotate under the influence of the at least one motor, form a lubricating film between the damping element and the face of the gear.

[0011] In principle, at least one damping element can act on the gear at at least two spatially separated points via frictional contact. By providing frictional contact at several points, the contact area for the local frictional contact on the at least one damping element can be made comparatively small, while still generating a sufficiently high holding force overall.

[0012] In one embodiment, at least one damping element is supported on a lubrication element of the gear assembly, which is designed to retain a (friction-reducing) lubricant in the area of ​​at least one of the gears. A corresponding lubrication element is thus provided and intended to retain lubricant on the meshing gears in order to minimize wear and running noise. A corresponding lubrication element can, for example, ensure that a lubricant introduced into the gear assembly does not spread uncontrollably within a housing space or be displaced during operation of the drive unit to such an extent that adequate lubrication is no longer guaranteed.For example, the lubrication element can be provided with a wall that prevents the displacement of lubricant into an area within the housing where it would no longer be available to lubricate the gears. By supporting the at least one damping element on a lubrication element of the gear assembly, it is also easier to achieve lubrication at the end face of the gear when it is rotating, whereas when the gears are stationary, the at least one damping element is intended to prevent unwanted rotation. For example, lubrication at the end face prevents unwanted squeaking gear noises from occurring at a contact surface of the at least one damping element that is in frictional contact with the end face of the gear.The lubrication element can, in principle, be fixed to a gear carrier of the gear assembly, on which at least two gears are rotatably mounted.

[0013] A lubrication element can, for example, comprise at least one lubrication section extending with a retention area adjacent to an end face of one of the at least two gears. A lubrication section with such a retention area prevents lubricant from flowing away from the end face or being displaced from the lubrication element. Alternatively or additionally, the lubricant can comprise at least one lubrication section extending with a retention area along at least a portion of the circumference of one of the at least two gears. While, in the first case mentioned above, the retention area is formed, for example, with a wall extending perpendicular to an axis of rotation of the respective gear, a wall of a retention area extending along a portion of the circumference of a gear can be formed parallel to the axis of rotation of the respective gear.This would therefore prevent any lubricant from being radially displaced during operation of the drive unit. The respective retention area thus forms a physical barrier within the gear assembly, blocking, for example – relative to the axis of rotation of the respective gear – the displacement and / or flow of lubricant away from the meshing gears in the axial or radial direction.

[0014] To save installation space, the damping element can be at least partially housed in a receptacle of the lubrication element. Alternatively, it is also conceivable that the at least one damping element can be at least partially housed in a receptacle of the transmission carrier on which the at least two gears are rotatably mounted, or in a receptacle of another component of the transmission assembly fixed to the transmission carrier. However, a receptacle on the lubrication element can prove particularly advantageous if it ensures that a minimum amount of lubricant is always present in the area between the damping element and the face of the gear being held (e.g., to prevent the aforementioned gear noise).

[0015] If at least one damping element is designed with a protruding spring arm, the spring arm can extend from the receptacle towards the end face of the gear being held. In this case, for example, the base of the damping element is completely enclosed within the receptacle, and only one or more (at least two) spring arms of the damping element protrude from the receptacle towards the end face of the gear being held.

[0016] For example, the lubrication element is designed with a pocket-shaped recess. Such a pocket-shaped recess is relatively easy to form, for example, in a lubrication element made of a plastic material, particularly in a lubrication element manufactured as an injection-molded plastic part. The at least one damping element can be inserted into this pocket-shaped recess during assembly of the gearbox assembly without much effort and thus positioned as intended.

[0017] To increase the holding force, at least two damping elements can be provided, each acting via a frictional contact on the face of one of the at least two gears, in order to exert a holding force on that gear when the drive torque is removed. The at least two damping elements can then act on the gear at at least two, three, or four spatially spaced points via a frictional contact.

[0018] For example, the at least two damping elements are arranged offset from each other in a circumferential direction around the axis of rotation of one gear, for example by at least 45°. This allows the damping elements to establish frictional contact at different areas of the gear's face. This ensures that the gear is prevented from rotating about its axis of rotation with a higher holding force when no motor-generated drive torque is being transmitted by the gear assembly. In one embodiment, for example, exactly two damping elements are provided, which are arranged offset from each other in a circumferential direction around the axis of rotation of the gear by 75° to 100°. For this purpose, correspondingly offset receptacles for the two damping elements are provided, for example, on a single lubrication element.The proposed solution further relates to a drive unit for propelling a two-wheeler, wherein the drive unit comprises at least one motor for generating a drive torque and furthermore includes an embodiment of a proposed transmission assembly to transmit the drive torque generated by the at least one motor, for example in the direction of a power transmission element, via which a drive force is to be delivered to propel a rear wheel of the two-wheeler (in particular an electric bicycle).

[0019] The attached figures illustrate possible implementation variants of the proposed solution.

[0020] This shows:

[0021] Figure 1 shows a perspective and partially cutaway view of a variant embodiment of a proposed gear assembly;

[0022] Figure 2 shows an enlarged section of Figure 1 without depicting various elements of the gear assembly, so that part of a lubrication element with two pocket-shaped receptacles for a damping element each is visible.

[0023] Figure 3 shows an exploded view of the gear assembly of Figure 1;

[0024] Figures 4A-4B Front and bottom view of the lubrication element of the gear assembly of Figures 1, 2 and 3;

[0025] Figure 5 shows a sectional view of the gear assembly of Figure 1, showing the friction contacts of one of the damping elements with an end face of an (intermediate) gear of the gear assembly;

[0026] Figure 6 shows a perspective view of a single damping element, which in this case is designed as a double-armed leaf spring;

[0027] Figure 1 shows a side view of a drive unit for the motor drive of a two-wheeler, including the gearbox assembly of Figure 1; Figure 8 shows a partial exploded view of one housing half of a housing of the drive unit of Figure 7 with the components pre-assembled therein.

[0028] Figure 7 shows a drive unit A with a housing G in a side view. The drive unit A is intended, for example, to power a motor-assisted electric bicycle. Accordingly, an end of a bottom bracket shaft assembly T protrudes from the housing G on both sides. A crank arm can be attached to each of these ends to generate a drive torque through muscle power. In this case, exactly one electric motor is housed within the housing G to provide an additional drive torque. This drive torque powers a power transmission element K, to which, for example, a rear wheel of the electric bicycle is coupled.

[0029] The housing G of the embodiment shown in Figure 7 consists of two housing parts G1 and G2. Figure 8 shows an exploded view of the first housing part G1 of the drive unit A. The first housing part G1 is designed as a housing half, which, together with the second housing half G2, defines a housing space in which electronic and mechanical components of the drive unit A are to be accommodated. For connection to the second housing part G2, and thus a second housing half, the first housing part G1 has several (at least two) fastening points B1, B2 distributed around its outer circumference. In addition, the first housing part G1 has a housing opening for the bottom bracket axle assembly T of the drive unit A and a bearing opening for a rotor shaft 2 of an electric motor of the drive unit A.The first housing part G1 forms a motor bearing point with a bearing pot for the arrangement of a stator ST of the electric motor.

[0030] In the illustrated embodiment, a gear assembly 1 with a two-stage gearbox is provided on a gear carrier 10, which is mounted to and fixed to the first housing part G1. The rotor shaft 2 meshes with a stepped gear 31 of a stepped gear assembly 3 of the gear assembly 1 in order to transmit a drive torque generated by the electric motor and applied to the rotor shaft 2. A bearing plate D is attached to the gear carrier 10 of the gear assembly 1, which provides, in particular, a bearing element in the form of a stepped bolt 5. An intermediate gear 4 of the gear assembly 1 is rotatably mounted on this bearing element and meshes with a stepped pinion 32 of the stepped gear assembly 3.

[0031] In the assembled state of the drive unit A, an electrically generated drive torque can be transmitted via the intermediate gear 4 to an output gear, which is rotatably connected to a power transmission element K shown in Figure 7. The power transmission element K is accessible on an outer side of the housing G to transmit torque to a rear wheel of the two-wheeler. In an electric bicycle, for example, the power transmission element K is rotatably connected to a pulley or chainring, so that the rear wheel can be driven via a transmission link, such as a belt or chain.

[0032] The intermediate gear 4 meshes with the stepped pinion 32 of the stepped gear assembly 3 of the gear assembly 1. The stepped pinion 32 is rotatably connected to the stepped gear 31. A first bearing, here in the form of a rolling bearing, is provided for the rotatable mounting of the intermediate gear 31 and the stepped pinion 32 on the gear carrier 10. Its outer ring is fixed in a bearing seat of the gear carrier 10. A bearing shaft, which rotatably couples the stepped gear 31 and the stepped pinion 32, is rotatably mounted via an inner ring of this first bearing. A second bearing 33, also for example in the form of a rolling bearing, is provided at a shaft end spaced apart from the bearing opening of the gear carrier 10.This second bearing 33 is fixed to a bearing point DL of the bearing shield D, so that the bearing shaft and thus the stepped gear 31 and the stepped pinion 32 are rotatably mounted on the gear carrier 10 about a first rotation or gear axis of the gear assembly 1 defined by the bearing shaft.

[0033] The bearing shield D also has an insertion opening DO for an end section of the stepped bolt 5 that projects axially from the intermediate gear 4. When the bearing shield D is mounted to the gear carrier 10 as intended, the second bearing 33 is consequently received and supported at the bearing point DL. Furthermore, the end section of the stepped bolt 5 passes through the insertion opening DO in the bearing shield D and is positively engaged therein. The bearing shield D thus provides complete radial support to the stepped bolt 5 at its second end section.

[0034] As illustrated in Figures 2 to 6 for an embodiment of a gear assembly 1 designed according to the proposed solution, the gear assembly 1 in this case additionally features a lubrication element 6 on the gear carrier 10. This lubrication element 6, shown in detail views in Figures 4A and 4B, is designed with two interconnected lubrication sections 63 and 64, wherein one lubrication section 63 is assigned to the stepped gear assembly 3 and the other lubrication section 64 is assigned to the intermediate gear 4. The lubrication sections 63 and 64 are intended to prevent lubricant present on the gears 32 and 4 from being displaced uncontrollably within the housing space and to ensure that the lubricant, for example grease, remains on the meshing gears 4 and 32 during operation of the drive unit A.The lubrication element 6 is fixed to the gear carrier 10, such that the lubrication element 6, with its planar wall sections, extends largely between the bearing points for the stepped gear assembly 3 and the intermediate gear 4 and the end faces of the gears 32, 4. The lubrication section 63, located adjacent to the stepped pinion 32, has a retention area 630 extending axially with respect to the axis of rotation of the stepped pinion 32. This retention area 630 has a projecting wall running along part of the circumference of the stepped pinion 32. This allows lubricant to collect at the circumference of the stepped pinion 32 on the retention area 630 and be carried away tangentially when the gears 31, 32, and 4 rotate, driven by the rotor shaft 2. The lubricant cannot be displaced radially past the axially extended retention area 630 and thus remains on the stepped gear assembly 3 and in particular the stepped pinion 32.

[0035] A semi-ring-shaped, planar wall of a retention area 640 of the lubrication section 64 associated with the intermediate gear 4 prevents the axial displacement or flow of lubricant away from the intermediate gear 4. In particular, the retention area 640, which extends perpendicular to the axis of rotation of the intermediate gear 4, prevents lubricant from penetrating openings, recesses, or gaps in the gear carrier 10 covered by the retention area 640 and thus preventing it from being available for lubricating the intermediate gear 4. As can be seen particularly from the enlarged partial view in Figure 2, the retention area 640 extends circumferentially around a bearing point for one end of the stepped bolt 5, on which the intermediate gear 4 is rotatably mounted.

[0036] Figure 2, in particular, shows that the lubrication section 64 forms two recesses in the form of pockets 647A and 647B. These pockets 647A and 647B are radially spaced from the retention area 640 and offset from each other by approximately 90° with respect to the axis of rotation of the intermediate gear 4. In this case, the pockets 647 and 647B each have a rectangular cross-section.

[0037] Each pocket 647A, 647B contains a damping element in the form of a double-armed leaf spring 7A or 7B. A longitudinally extended base 70 of each leaf spring 7A, 7B is inserted into the respective pocket 647A or 647B, such that the base 70, as shown in Figure 5, is bent around a central section with a weakening area and is housed within the respective receptacle 647A, 647B. The double-armed leaf spring 7A or 7B is thus pre-tensioned when the transmission assembly 1 is mounted. Two spring arms 71 and 72 are angled from each base 70, extending towards each other and elastically spaced from the base 70. The spring arms 71 and 72 protrude from the associated pocket 647A or 647B with contact surfaces 710 and 720 formed at the ends of the respective spring arm 71, 72, in the present case in the direction of an end face of the intermediate gear 4.This is particularly evident from the sectional view in Figure 5, in addition to Figure 2.

[0038] Via the aforementioned contact surfaces 710, 720, each leaf spring 7A, 7B is in frictional contact with the intermediate gear 4 at two points and exerts a holding force on the intermediate gear 4. This force acts axially with respect to the axis of rotation of the intermediate gear 4 and thus also results in an axial preload of the intermediate gear 4. The four local frictional contacts of the offset leaf springs 7A, 7B counteract rotation of the intermediate gear 4 and hold it in a rotational position when no drive torque is generated by the motor of the drive unit A and the rotor shaft 2 is stationary. This counteracts, in particular, any noise that could result from rotation of the intermediate gear 4 relative to the stepped pinion 32 due to the existing backlash.

[0039] By accommodating the double-armed leaf springs 7A, 7B in a lubricated area of ​​the gear assembly 1, which is delimited by the lubrication element 6 and thus always remains at least partially filled with a sufficient quantity of lubricant, lubrication can be present between the contact surfaces 710, 720 of a leaf spring 7A or 7B when a motor-generated drive torque is applied and gears 31, 32 and 4 are driven by the rotor shaft 2, preventing any relevant braking of the intermediate gear 4 by the leaf springs 7A, 7B. The lubricant present between the end face of the intermediate gear 4 contacted by the leaf springs 7A, 7B and the retention area 640 of the lubrication section 64 can also, when gears 31, 32 and 4 are stationary, prevent disturbing and undesirable gear noises (e.g.,Squeaking noises) due to the occurrence of riding contact.

[0040] The exploded view in Figure 3 further illustrates the structure of the gear assembly 1. A spring washer F is also visible, which axially preloads the stepped gear assembly 3. For this purpose, the spring washer F is arranged in the area of ​​bearing point DL between the bearing shield D and the rolling bearing 33.

[0041] Figures 4A and 4B show again in detail, looking at a top (Figure 4A) and a bottom (Figure 4B), the lubrication element 6 with the two lubrication sections 63 and 64 with the semi-ring-shaped retention area 630 and the axially projecting retention area 640.

[0042] As explained above, Figure 5 shows the frictional contact of the two spring arms 71 and 72 of the double-armed leaf spring 7A, while Figure 6 illustrates the geometry of the identically designed leaf spring 7A, 7B via a single view of the leaf spring 7A, 7B.

[0043] Reference symbol list

[0044] 1 Gearbox assembly

[0045] 10 Gearbox carriers

[0046] 2 Rotor shaft

[0047] 3-step gear assembly

[0048] 31 stepped gear

[0049] 32-step sprocket

[0050] 33 (rolling) bearings

[0051] 4 Intermediate gear

[0052] 5 stepped bolts (bearing element)

[0053] 6 Lubrication element

[0054] 63, 64 Lubrication section

[0055] 630 containment area

[0056] 640 containment area

[0057] 647A, 647B Bag (Recording)

[0058] 70 base

[0059] 71, 72 Spring arm

[0060] 710, 720 contact area

[0061] 7A, 7B Leaf spring (damping element)

[0062] A drive unit

[0063] B1, B2 junction

[0064] D Storage shield

[0065] DL storage facility

[0066] DO insertion opening

[0067] F Spring washer

[0068] G Housing

[0069] G1, G2 Housing half (housing part)

[0070] K Power transmission element

[0071] ST Stator

[0072] TT retlagerbaugruppe

Claims

Patent claims 1. Gear assembly for a motor drive unit (A) for driving a two-wheeler, wherein the gear assembly (1) comprises at least two meshing gears (32, 4) for transmitting a drive torque generated by at least one motor of the drive unit (A), characterized in that at least one damping element (7A, 7B) is provided on the transmission assembly (1), which acts via a frictional contact on an end face of a gear (4) of the at least two gears (32, 4) in order to exert a holding force on the gear (4) when the drive torque is removed, in order to counteract a rotation of one gear (4) and to hold one gear (4) in a rotational position.

2. Gear assembly according to claim 1, characterized in that the at least one damping element (7A, 7B) has at least one elastically displaceable section (71, 72) for producing the frictional contact.

3. Gear assembly according to claim 2, characterized in that the at least one elastically displaceable section (71, 72) is designed as a spring arm (71, 72) projecting from a base (70) of the at least one damping element (7A, 7B) or the at least one elastically displaceable section is part of a damping element made of rubber.

4. Gear assembly according to one of claims 1 to 3, characterized in that the at least one damping element (7A, 7B) acts on the one gear (4) at at least two spatially spaced locations via a friction contact.

5. Gear assembly according to one of the preceding claims, characterized in that the at least one damping element (7A, 7B) is supported on a lubrication element (6) of the gear assembly (1) which is provided to hold a lubricant in the area of ​​at least one of the gears (32, 4).

6. Gear assembly according to claim 5, characterized in that the lubrication element (6) is fixed to a gear carrier (10) of the gear carrier assembly (1) on which the at least two gears (32, 4) are rotatably mounted.

7. Gear assembly according to claim 5 or 6, characterized in that the lubrication element (6) comprises at least one lubrication section (63, 64) which extends with a retention area (640) adjacent to an end face of a gear (32) of the at least two gears (32, 4) or which extends with a retention area (630) along at least a part of a circumference of a gear (32) of the at least two gears (32, 4).

8. Gear assembly according to one of claims 5 to 7, characterized in that the at least one damping element (7A, 7B) is at least partially received in a receptacle (647A, 647B) of the lubrication element (6).

9. Gear assembly according to claims 3 and 8, characterized in that in a damping element (7A, 7B) designed with at least one spring arm (70, 71) the spring arm (70, 71) projects out of the receptacle (647A, 647B) in the direction of the end face of the gear (4) to be held.

10. Gear assembly according to claim 8 or 9, characterized in that the receptacle (647A, 647B) is formed with a pocket-shaped recess on the lubrication element (6).

11. Gear assembly according to one of the preceding claims, characterized in that at least two damping elements (7A, 7B) are provided, each of which acts via a frictional contact on the end face of one gear (4) of the at least two gears (32, 4) in order to exert a holding force on one gear (4) when the drive torque is removed.

12. Gear assembly according to claim 11, characterized in that the at least two damping elements (7A, 7B) act on the one gear (4) at at least three or four spatially spaced locations via a frictional contact.

13. Gear assembly according to claim 11 or 12, characterized in that the at least two damping elements (7A, 7B) are arranged offset from each other in a circumferential direction about an axis of rotation of one gear (4), in particular offset from each other by at least 45°.

14. Drive unit for propelling a two-wheeler, wherein the drive unit (A) comprises at least one motor for generating a drive torque and comprises a transmission assembly (1) according to one of the preceding claims to transmit the drive torque generated by the at least one motor.

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