Drive unit having a transmission unit comprising three planetary gears

Abstract

The invention relates to a drive unit for an electric bicycle (1), having - a motor (M) for providing a supporting torque, generated by external forces, which, in addition to a drive torque generated by muscle force, can be transmitted to an output element (W), and - a multi-stage transmission unit (GE), via which a drive shaft (AT) and the output element (W) are coupled to a motor shaft (MW) of the motor (M) and which comprises three planetary gears (P1, P2, P3) for providing different transmission ratios (i) for transmitting the drive torque. A first planetary gear (P1) and the second and third planetary gears (P2, P3) of the three planetary gears (P1, P2, P3) are arranged on different first and second shaft sections (31, 32), wherein the first shaft section (31) is coaxial to the first planetary gear (P1) and a motor shaft (MW) of the motor (M) is arranged on a third shaft section (33) which is parallel to the first shaft section (31) and to the second shaft section (32).

Description

[0001] Drive unit with three planetary gears comprising gearing device

[0002] Description

[0003] The proposed solution concerns a drive unit for an electric bicycle.

[0004] DE 102018208382 A1 discloses a drive unit for an electric bicycle in which a motor for providing a power-operated assist torque is coupled via a multi-stage transmission to a drive shaft for the muscle-powered introduction of a drive torque and an output element. The multi-stage transmission comprises three planetary gears for providing different ratios for transmitting the drive torque. In DE 10 2018 208 382 A1, a total of eight ratios and thus eight different gears for transmitting the drive torque can be set via a combination of three brakes and three freewheels within the transmission.

[0005] In the prior art solution, the planetary gears are arranged axially in series and coaxially with the drive shaft. This results in comparatively little installation space, especially in the area of ​​the drive shaft of the drive unit. The sensors required for controlling the drive unit must therefore be located elsewhere, which may be relatively complex to install.

[0006] The proposed solution is therefore based on the task of providing a drive unit for an electric bicycle that is more compact and, particularly in the area of ​​the drive shaft, provides more installation space for additional components of the drive unit.

[0007] This object is achieved with a drive unit according to claim 1. In a proposed drive unit, the multi-stage transmission device has three planetary gears for providing different ratios for transmitting the drive torque generated by muscle power to an output element. A first planetary gear—with a first sun gear, first planet carrier, and first ring gear—is arranged on a first shaft train coaxial with the drive shaft, while a second planetary gear—with a second sun gear, second planet carrier, and second ring gear—and a third planetary gear—with a third sun gear, third planet carrier, and third ring gear—are arranged on a second shaft train parallel to the first shaft train.A motor shaft of the motor intended to provide an externally powered assist torque is in turn arranged on a third shaft train which is parallel to the first shaft train and the second shaft train.

[0008] With the proposed arrangement of the three planetary gears and the motor shaft, a variety of transmission ratios for transmitting the drive torque can be achieved comparatively easily. Furthermore, a comparatively large amount of space is available in the area of ​​the drive shaft, which is also referred to here as the bottom bracket shaft, within a housing of the drive unit that accommodates the transmission device. This space can then be used to arrange at least one sensor device in the area of ​​the drive shaft, for example, to detect a torque introduced at the drive shaft and / or a rotational speed of the drive shaft and / or the output element.

[0009] In one embodiment of a proposed drive unit, the (first) ring gear of the first planetary gear is coupled to the (second) planet carrier of the second planetary gear via a gear pair, for example in the form of a spur gear stage.

[0010] The (second) ring gear of the second planetary gear set can, in turn, be connected to the (third) planet carrier of the third planetary gear set. In this case, this includes a rigid connection between the second ring gear and the third planet carrier, so that they are permanently connected to each other in a rotationally fixed manner.

[0011] Furthermore, a (third) ring gear of the third planetary gear set can be coupled to the output element via a (further) gear pair, in particular here also in the form of a spur gear stage. In principle, other couplings or connections can also be provided between the individual components of the three planetary gear sets, in addition to the couplings and connections explained above. However, the interaction of the three planetary gear sets on the components explained above can be particularly advantageous with regard to providing at least four or more, and in particular eight or more, gear ratios with similar gradations between individual gears, as well as a compact design of the drive unit and a space-saving arrangement of the gear unit in a housing.

[0012] In one design variant, the transmission device comprises two or three brakes and two or three freewheels to provide four or more different gear ratios. Thus, the number of adjustable gear ratios can depend on the number of brakes and / or freewheels. For example, if three brakes and three freewheels are provided in the transmission device, each assigned to a planetary gear, eight different gear ratios can be realized via the transmission device.

[0013] For example, a first brake can be provided to lock a ring gear of the first planetary gear set. If the first brake is activated and thus locked, the (first) ring gear of the first planetary gear set is locked and thus immobilized relative to the housing of the drive unit.

[0014] Alternatively or additionally, a second brake can be provided for locking the (second) sun gear of the second planetary gear set and / or for locking the (third) sun gear of the third planetary gear set. Such a variant design therefore includes the provision of exactly one brake for locking and thus blocking both the sun gear of the second planetary gear set and the sun gear of the third planetary gear set, which brake is arranged on the same second shaft train as the second planetary gear set.

[0015] To provide a larger number of ratios and thus gears for transmitting the drive torque, an alternative design variant provides for a second brake to lock the second sun gear of the second planetary gear set, while a separate (in particular, separately switchable) third brake is provided to lock the third sun gear of the third planetary gear set. This allows the sun gears of the second and third planetary gear sets to be locked independently of each other.In principle, it can be provided—especially with a view to a compact design of the drive unit—that the sun gear of the second planetary gear and the sun gear of the third planetary gear can be fixed via the second brake and the third brake relative to the same section of a housing of the drive unit that at least partially accommodates the transmission device, or relative to the same component fixed in the housing. The second and third brakes are thus arranged on the same section of the housing or on the same component fixed in the housing, relative to which the sun gears are blocked and thus held non-rotatably when the brakes are engaged.

[0016] The freewheels intended to provide different gear ratios are - analogous to the brakes - assigned to different planetary gears. For example, the first planet carrier of the first planetary gear can be connected in a rotationally fixed manner to a ring gear of the first planetary gear via a first freewheel. When the first freewheel is locked, the first planet carrier is consequently connected in a rotationally fixed manner to the first ring gear of the first planetary gear. When the first freewheel is locked, a relative movement of the first planet carrier to the first ring gear of the first planetary gear is therefore not possible. In contrast, when the first freewheel is not locked - and thus in a so-called overrunning mode - a connection between the first planet carrier and the first ring gear on the first planetary gear is released.The first planet carrier carrying the (first) planetary gears is consequently rotatable relative to the first ring gear of the first planetary gear, which in turn leads to a different gear ratio of the gear device.

[0017] In a similar manner, it can be provided that the third planet carrier of the third planetary gear set is rotationally fixed to the third ring gear of the third planetary gear set via a third freewheel. Consequently, in the locked state of the third freewheel, the third planet carrier is rotationally fixed to the third ring gear of the third planetary gear set, while in the unlocked state of the third freewheel, the third planet carrier and the third ring gear are rotatable relative to each other.

[0018] Likewise, a second freewheel can be provided, via which the second planet carrier of the second planetary gear set can be connected in a rotationally fixed manner to the second ring gear of the second planetary gear set. In a locked state, the second freewheel thus connects the second planet carrier and the second ring gear of the second planetary gear set in a rotationally fixed manner, while in a non-locking state of the second freewheel, the second planet carrier and the second ring gear can rotate relative to one another about the same rotational axis of the second shaft train.

[0019] Although not mandatory, not only the brakes but also the freewheels can be switchable in a variant of the proposed drive unit.

[0020] In one embodiment, the motor shaft arranged on the second shaft train is coupled to the second planet carrier of the second planetary gear train via a gear pair, optionally again in the form of a spur gear stage. With particular reference to the embodiment explained above, in which the first ring gear of the first planetary gear train is coupled to the second planet carrier of the second planetary gear train via a (first) gear pair, this includes a variant in which the second planet carrier of the second planetary gear train is rotationally fixedly connected to an intermediate shaft, and this intermediate shaft carries a gear that meshes both with a gear for the first gear pair that is rotationally fixedly connected to the first ring gear, and with a gear for the further (second) gear pair that is fixedly connected to the motor shaft.

[0021] In one embodiment of the proposed drive unit, it can be provided that several gear ratios in the range of 0.18 to 1.0 can be provided via the transmission device. This includes, in particular, that the individual ratios per gear ratio, and thus gears, have a similar gradation across multiple brakes and freewheels. This allows for a sufficiently fine, yet at the same time efficient, gear gradation for the user.

[0022] The proposed solution further relates to an electric bicycle with a variant of a proposed drive unit.

[0023] The attached figures illustrate possible embodiments of the proposed solution.

[0024] Here we show:

[0025] Figure 1 is a schematic view of a variant of a proposed drive unit with three planetary gears housed within a housing of the drive unit; Figure 2 is a circuit diagram showing eight different gear ratios for different switching states of the freewheels and brakes provided in the drive unit of Figure 1;

[0026] Figure 3 shows a schematic representation of an electric bicycle equipped with a variant of the proposed drive unit.

[0027] Figure 3 illustrates an electric bicycle 1 with a drive unit A. The electric bicycle 1 has a frame 10 to which the drive unit A is attached. Part of the drive unit AS are control electronics SE and a sensor device 15, for example, configured with a torque sensor and a position sensor for sensing a torque introduced by muscle power onto a drive shaft in the form of a bottom bracket shaft AT of the drive unit A. The sensor device 15 can alternatively or additionally comprise a speed sensor, via which the speed of the bottom bracket shaft AT can be detected. An output element of the drive unit A, for example, a hollow output shaft W mounted coaxially to the bottom bracket shaft AT, is connected to a rear wheel 12 of the electric bicycle 1 via a belt or chain 13 as a power transmission element in order to drive the electric bicycle 1.This rear wheel 12 is assigned, by way of example, a wheel sensor for determining a driving speed of the electric bicycle 1. Of course, the wheel sensor 14 can instead be provided on a front wheel 11 of the electric bicycle 1.

[0028] The drive unit A is part of a drive device of the electric bicycle, which further comprises an operating unit 2. The operating unit 2 is fastened in Figure 3, for example, in the area of ​​a handlebar of the electric bicycle 1 and is coupled to the control electronics SE of the drive unit A. A user input can be detected via the operating unit 2 and used to control the drive unit A. For example, the operating unit 2 further comprises at least one display to inform a user of the electric bicycle 1 about a current operating state of the drive unit A, for example with regard to a currently set assistance class, a charge state of a battery supplying the drive unit A with energy and / or a set gear that specifies the ratio with which a drive torque introduced by muscle power at the bottom bracket shaft AT is transmitted to the output shaft W.

[0029] For one embodiment of a proposed drive unit A, it is provided that this comprises three planetary gears P1, P2 and P3 as part of a gear device GE of the drive unit A, which is accommodated in a housing of the drive unit A. Via these three planetary gears P1, P2 and P3, the bottom bracket shaft AT and the output shaft W are coupled to a motor shaft W of a motor M of the drive unit A, typically in the form of an electric motor. Figure 1 shows schematically a proposed arrangement of the three planetary gears P1, P2 and P3.

[0030] In this case, it is provided that a first planetary gear P1 with a first sun gear S1, a first planet carrier T1 and a first ring gear H1 is arranged on a first shaft train 31 which is coaxial with the bottom bracket shaft AT and the output shaft W designed as a hollow shaft. First planet gears R11 and R12 are rotatably mounted on the first planet carrier T1, which mesh with the first sun gear S1 and engage with an internal toothing of the first ring gear H1.

[0031] A second planetary gear P2 and a third planetary gear P3 are arranged in the transmission device GE of the drive unit A of Figure 1 on a second shaft train 32, which is parallel to the first shaft train 31. A second sun gear S2, a second planet carrier T2 rotatably supporting second planet gears R21 and R22, and a second ring gear H of the second planetary gear P2 are thus rotatably mounted about a (second) axis of rotation of the second shaft train 32, about which a third sun gear S2, a third planet carrier T3 rotatably supporting third planet gears R31 and R32, and a third ring gear H3 of the third planetary gear P3 are also rotatably mounted. The axis of rotation of the second shaft train 32 is defined in the present case by a bearing shaft LW. This bearing shaft LW can be formed by a section molded onto the housing G, or the bearing shaft LW can be provided as a separate component fixed to the housing G.

[0032] A third shaft train 33 runs parallel to the first and second shaft trains 31 and 32. The motor shaft MW of the motor M is arranged on this third shaft train 33.

[0033] The motor shaft W carries a motor gear connected thereto in a rotationally fixed manner, which can transmit an assistance torque to the second planetary carrier T2 via a second spur gear stage V2. The second planetary carrier T2 of the second planetary gear P2 is in turn coupled to the first sun gear S1 of the first planetary gear P1 via a first spur gear stage V1. Furthermore, since the bottom bracket shaft AT introduces a muscle-powered drive torque into the first planetary carrier T1 and transmits it to the first sun gear S1 via the first planetary gears R11 and R12, both the muscle-powered drive torque and the assistance torque generated by the motor M using external power can be applied to the second planetary carrier T2 of the second planetary gear P2.

[0034] The second ring gear H2 of the second planetary gear set P2 is, in this case, rigidly connected to the third planet carrier T3 of the third planetary gear set P3. A combined torque is then transmitted to the output shaft W via the third ring gear H3 of the third planetary gear set P3 via a third spur gear stage V3.

[0035] In this case, three brakes B1, B2 and B3 and three freewheels F1, F2 and F3 are assigned to the three planetary gears P1, P2 and P3 of the transmission unit GE. For each planetary gear P1, P2, P3, exactly one brake B1, B2 or B3 and one freewheel F1, F2 or F3 is assigned. By switching the three brakes B1, B2 and B3 so that they each block one of the components of an assigned planetary gear P1, P2 or P3 against rotation and thus fix it relative to the housing G, and by switching the freewheels F1, F2 and F3 between a locked state and a non-locking state in a so-called overrunning operation, eight geometrically stepped forward gears can be implemented via the transmission unit GE.

[0036] A first brake B2 is provided for locking the first ring gear H1 of the first planetary gear P1. A first freewheel F1 is in turn provided between the first planet carrier T1 and the first sun gear S1 of the first planetary gear P1. If the first brake B2 is activated, the first ring gear H1 of the first planetary gear P1 is locked and blocked against rotation about the (first) axis of rotation of the first shaft train 31. When the first freewheel F1 is locked, the first planet carrier T1 and the first sun gear S1 of the first planetary gear P1 are connected to one another in a rotationally fixed manner. If the sun gear S1 rotates faster, the connection to the first planet carrier T1 via the first freewheel F1 is released.

[0037] A second brake B1 is provided on the second planetary gear P2 in order to fix the second sun gear S2 against the bearing shaft LW when necessary, i.e., to change a gear ratio. When the second freewheel F3 is locked, the second planet carrier T2 is connected in a rotationally fixed manner to the second ring gear H2 on the second planetary gear P2. A third brake B3 is provided on the third planetary gear P3 in order to fix the third sun gear S3 relative to the bearing shaft LW. A third freewheel F2 of the third planetary gear P3 in turn couples the third planet carrier T3 to the third ring gear H3 when locked.

[0038] As illustrated by the circuit diagram in Figure 2, by switching the freewheels F1, F2 and F3 between the locked state and the non-locking state and by activating the brakes B1, B2 and B3 in order to fix an associated component of the respective planetary gear P1, P2, P3 (i.e. the first ring gear H1, the second sun gear S2 or the third sun gear S3), a change between different gear ratios i in the range from 0.18 to 1 can be realized. Thus, eight different gears can be realized for forward travel of the electric bicycle 1 when the drive unit A is in operation.

[0039] In the circuit diagram of Figure 1, an “x” indicates a locked state of the respective freewheel F1, F2 or F3 and an actively switched brake B1, B2 or B3. For example, for a gear ratio i=1 none of the brakes B1, B2 and B3 are active and all freewheels F1, F2 and F3 are in their locked state. For a fourth gear with a gear ratio of i=0.487, for example, the second brake B1 and the third brake B3 are active and the first freewheel F1 is in a locked state. For the smallest gear ratio of i=0.18, all freewheels F1, F2 and F3 are in a non-locking state and all brakes B1, B2 and B3 are actively switched.

[0040] The drive unit A with the transmission device GE of Figure 1 also provides a comparatively large amount of installation space in the area of ​​the bottom bracket shaft AT, which can be used, for example, to accommodate the sensors, in particular, for example, a sensor device 15 mentioned above.

[0041] List of reference symbols

[0042] 1 electric bike

[0043] 10 frames

[0044] 11 Front wheel

[0045] 12 rear wheel

[0046] 13 Chain / belt (power transmission link)

[0047] 14 Wheel sensor

[0048] 15 Sensor device

[0049] 2 Control panel

[0050] 31, 32, 33 Shaft assembly

[0051] A drive unit

[0052] AT bottom bracket shaft / drive shaft

[0053] B1, B2, B3 brake

[0054] F1, F2, F3 freewheel

[0055] G Housing

[0056] GE transmission device

[0057] H1, H2, H3 ring gear i gear ratio

[0058] LW bearing shaft (housing-fixed section)

[0059] M engine

[0060] MW motor shaft

[0061] P1, P2, P3 planetary gear

[0062] R11, R12, R21, R22, R31, R32 planetary gear

[0063] S1, S2, S3 sun gear

[0064] SE control electronics

[0065] T1, T2, T3 planet carrier

[0066] V1, V2, V3 spur gear stage / gear pairing

[0067] W Output shaft

Claims

Claims 1 . Drive unit for an electric bicycle (1), with - a drive shaft (AT) on which a drive torque can be generated by muscle power, - an output element (W) for driving a wheel (12) of the electric bicycle (1), - a motor (M) for providing an externally powered assist torque which can be transmitted to the output element (W) in addition to a muscle-powered drive torque, and - a multi-stage transmission device (GE), via which the drive shaft (AT) and the output element (W) are coupled to a motor shaft (MW) of the motor (M) and which comprises three planetary gears (P1, P2, P3) for providing different transmission ratios (i) for transmitting the drive torque, characterized in that - a first planetary gear (P1) of the three planetary gears (P1, P2, P3) is arranged on a first shaft train (31) coaxial with the drive shaft (AT), - a second and third planetary gear (P2, P3) of the three planetary gears (P1, P2, P3) are arranged on a second shaft train (32) which is parallel to the first shaft train (31), and - the motor shaft (MW) is arranged on a third shaft train (33) which is parallel to the first shaft train (31) and the second shaft train (32).

2. Drive unit according to claim 1, characterized in that a ring gear (H1) of the first planetary gear (P1) is coupled via a gear pair (V1) to a planet carrier (T2) of the second planetary gear (P2).

3. Drive unit according to claim 1 or 2, characterized in that a ring gear (H2) of the second planetary gear (P2) is connected to a planet carrier (T3) of the third planetary gear (P3).

4. Drive unit according to one of claims 1 to 3, characterized in that a ring gear (H3) of the third planetary gear (P3) is coupled to the output element (W) via a gear pair (V3).

5. Drive unit according to one of the preceding claims, characterized in that the transmission device (GE) comprises two or three brakes (B1, B2, B3) and two or three freewheels (F1, F2, F3) for providing four or more different gear ratios (i).

6. Drive unit according to claim 5, characterized in that a first brake (B2) is provided for locking a ring gear (H1) of the first planetary gear (P1).

7. Drive unit according to claim 5 or 6, characterized in that a second brake (B1, B3) is provided for locking a sun gear (S2) of the second planetary gear (P2) and / or for locking a sun gear (S3) of the third planetary gear (P3).

8. Drive unit according to claim 5 or 6, characterized in that a second brake (B1) is provided for locking a sun gear (S2) of the second planetary gear (P2) and a third brake (B3) is provided for locking a sun gear (S3) of the third planetary gear (P3).

9. Drive unit according to claim 8, characterized in that the sun gear (S2) of the second planetary gear (P2) and the sun gear (S3) of the third planetary gear (P3) can be fixed via the second brake (B1) and the third brake (B3) relative to the same section (LW) of a housing (G) of the drive unit (A) which at least partially accommodates the gear device (GE) or relative to the same component (LW) fixed in the housing (G).

10. Drive unit according to one of claims 5 to 9, characterized in that a planet carrier (T1) of the first planetary gear (P1) can be connected in a rotationally fixed manner to a ring gear (H1) of the first planetary gear (P1) via a first freewheel (F1).

11. Drive unit according to one of claims 5 to 10, characterized in that a planet carrier (T1) of the third planetary gear (P3) can be connected in a rotationally fixed manner to a ring gear (H3) of the third planetary gear (P3) via a third freewheel (F2).

12. Drive unit according to one of claims 5 to 11, characterized in that a planet carrier (T2) of the second planetary gear (P2) can be connected in a rotationally fixed manner to a ring gear (H2) of the second planetary gear (P3) via a second freewheel (F3).

13. Drive unit according to one of claims 5 to 12, characterized in that the freewheels (F1, F2, F3) are switchable.

14. Drive unit according to one of the preceding claims, characterized in that the motor shaft (MW) is coupled to a planet carrier (T2) of the second planetary gear (P2) via a gear pair (V2).

15. Drive unit according to one of the preceding claims, characterized in that the transmission device (GE) is designed and provided to provide a plurality of gear ratios in the range from 0.18 to 1.

0.

16. Electric bicycle with a drive unit (A) according to one of the preceding claims.

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