A drive unit with a transmission system featuring three planetary gear mechanisms.

Abstract

The proposed electric bicycle drive unit (1) includes a motor (M) that provides an assist torque generated by an external power source that can be transmitted to an output member (W) in addition to the drive torque generated by muscle force, and a multi-stage transmission device (GE) that connects the drive shaft (AT) and the output member (W) to the motor shaft (MW) of the motor (M), and includes three planetary gear mechanisms (P1, P2, P3) that provide different gear ratios (i) for transmitting the drive torque. The first planetary gear mechanism (P1) and the second and third planetary gear mechanisms (P2, P3) of the three planetary gear mechanisms (P1, P2, P3) are arranged on different first and second axes (31, 32), respectively. The first planetary gear mechanism (P1) on the first axis (31) is arranged coaxially with the drive shaft (AT), and the motor shaft (MW) of the motor (M) is arranged on a third axis (33) parallel to the first axis (31) and the second axis (32).

Description

Technical Field

[0001] The proposed solution relates to a drive unit for an electric bicycle.

Background Art

[0002] In the drive unit of an electric bicycle disclosed in DE102018208382A1, a motor for providing an assist torque generated by external power is connected via a multi-stage transmission to a drive shaft and an output member for introducing a drive torque generated by muscular force. The multi-stage transmission comprises three planetary gear mechanisms that provide different gear ratios for transmitting the drive torque. In DE102018208382A1, a total of eight gear ratios are obtained by combining three brakes and three overrunning clutches in the transmission, whereby eight different gears can be set for the transmission of the drive torque.

[0003] In the solution according to the known art, the planetary gear mechanisms are connected axially in series and arranged coaxially with the drive shaft. As a result, there is relatively little available installation space, particularly in the region of the drive shaft of the drive unit. Therefore, the sensor devices required for controlling the drive unit have to be arranged in another location, which may in some cases be relatively difficult to install.

Summary of the Invention

Problems to be Solved by the Invention

[0004] Therefore, the proposed solution aims to provide a drive unit for an electric bicycle that has a more compact configuration and can secure more installation space for other components of the drive unit, particularly in the region of the drive shaft.

[0005] This object is achieved by the drive unit according to claim 1.

[0006] In the proposed drive unit, the multi-stage transmission system includes three planetary gear mechanisms that provide different gear ratios to transmit the drive torque generated by muscle force to the output member. The first planetary gear mechanism (including the first sun gear, first planetary carrier, and first ring gear) is located on a first axis coaxial with the drive shaft, while the second planetary gear mechanism (including the second sun gear, second planetary carrier, and second ring gear) and the third planetary gear mechanism (including the third sun gear, third planetary carrier, and third ring gear) are located on a second axis parallel to the first axis. The shaft of a motor provided to supply assist torque generated by external power is further located on a third axis parallel to the first and second axes.

[0007] The arrangement of the three planetary gear mechanisms and motor shafts allows for relatively easy implementation of a variety of gear ratios for driving torque transmission. Furthermore, a relatively large installation space is provided around the drive shaft (also referred to as the bottom bracket shaft in this example) within the housing of the drive unit that houses the transmission device. This installation space allows for the placement of at least one sensor device around the drive shaft, which can, for example, detect the torque introduced to the drive shaft and / or the rotational speed of the drive shaft and output member.

[0008] In one embodiment of the proposed drive unit, the first ring gear of the first planetary gear mechanism is connected to the second planetary carrier of the second planetary gear mechanism via a gear pair, for example, a spur gear stage.

[0009] The second ring gear of the second planetary gear mechanism may be further coupled to the third planetary carrier of the third planetary gear mechanism. In this example, the second ring gear and the third planetary carrier are rigidly coupled to each other permanently in a rotationally fixed state.

[0010] Furthermore, the third ring gear of the third planetary gear mechanism can be connected to an output member via a further gear pair, particularly in the form of a spur gear stage.

[0011] In principle, different connections or links can be provided between the components of the three planetary gear mechanisms described above. However, the interaction of the three planetary gear mechanisms in the components described above can be particularly advantageous in that it provides gear ratios of four or more stages, especially eight or more stages, where the spacing between each gear is nearly equal, as well as in that the drive unit can be made compact and the transmission can be placed in a space-saving manner within the housing.

[0012] In one embodiment, the transmission includes two or three brakes and two or three overrunning clutches, providing four or more different gear ratios. Thus, the number of adjustable gear ratios may depend on the number of brakes and overrunning clutches. For example, if the transmission includes three brakes and three overrunning clutches, each assigned to a planetary gear mechanism, then eight different gear ratios can be achieved through the transmission.

[0013] For example, a first brake can be provided to lock the ring gear of the first planetary gear mechanism. When the first brake is activated and the mechanism switches to a locked state, the first ring gear of the first planetary gear mechanism is locked, thereby preventing the ring gear from rotating relative to the housing of the drive unit.

[0014] Alternatively or additionally, a second brake may be provided to lock the second sun gear of the second planetary gear mechanism and / or the third sun gear of the third planetary gear mechanism. Thus, such an embodiment includes providing a single brake to lock both the sun gear of the second planetary gear mechanism and the sun gear of the third planetary gear mechanism, which is located on the same second axis as the second planetary gear mechanism, thereby preventing both from rotating.

[0015] To provide a wider range of gear ratios and, consequently, more gears for driving torque transmission, another embodiment provides a second brake for locking the second sun gear of the second planetary gear mechanism, and further provides a third brake, specifically independently actuated, for locking the third sun gear of the third planetary gear mechanism. In this way, the sun gears of the second and third planetary gear mechanisms can be locked, preventing them from rotating independently of each other.

[0016] In principle, and especially considering the compact configuration of the drive unit, the sun gear of the second planetary gear mechanism and the sun gear of the third planetary gear mechanism may be provided to be locked relative to the same section of the housing of the drive unit housing the transmission device, or to the same component fixed to the housing, at least partially, via the second and third brakes. Thus, the second and third brakes are located on the same section of the housing or on the same component fixed to the housing, and when the brakes are locked relative to these parts, the sun gear is blocked and held in a non-rotatable state.

[0017] Overrunning clutches, provided to offer different gear ratios, are installed in different planetary gear mechanisms, similar to brakes. For example, a first planetary carrier of a first planetary gear mechanism can be connected to the ring gear of the first planetary gear mechanism in a rotationally fixed state via a first overrunning clutch. Therefore, when the first overrunning clutch is disengaged, the first planetary carrier is connected to the first ring gear of the first planetary gear mechanism in a rotationally fixed state. In other words, when the first overrunning clutch is disengaged, relative movement of the first planetary carrier with respect to the first ring gear of the first planetary gear mechanism is impossible. Conversely, when the first overrunning clutch is not disengaged, i.e., in a so-called overrun operation state, the connection between the first planetary carrier and the first ring gear of the first planetary gear mechanism is released. Therefore, the first planetary carrier having the first planetary gear can rotate relative to the first ring gear of the first planetary gear mechanism, resulting in different gear ratios for the transmission.

[0018] Similarly, the third planetary carrier of the third planetary gear mechanism can be connected to the third ring gear of the third planetary gear mechanism in a rotationally fixed state via the third overrunning clutch. Here, when the third overrunning clutch is disengaged, the third planetary carrier is connected to the third ring gear of the third planetary gear mechanism in a rotationally fixed state. On the other hand, when the third overrunning clutch is not disengaged, the third planetary carrier and the third ring gear become rotatable relative to each other.

[0019] Similarly, the second planetary carrier of the second planetary gear mechanism can be connected to the second ring gear of the second planetary gear mechanism in a rotationally fixed state via the second overrunning clutch. Therefore, the second planetary carrier and the second ring gear of the second planetary gear mechanism are connected in a rotationally fixed state via the second overrunning clutch in the disengaged state. On the other hand, when the second overrunning clutch is not disengaged, the second planetary carrier and the second ring gear can rotate relative to each other around the same axis of rotation of the second axis.

[0020] Although not mandatory, one embodiment of the proposed drive unit allows for the operation of not only the brakes but also the overrunning clutch.

[0021] In one embodiment, a motor shaft positioned on the second axis is optionally connected to the second planetary carrier of the second planetary gear mechanism via a gear pair in the form of spur gears. In particular, in the above-described embodiment, the first ring gear of the first planetary gear mechanism is connected to the second planetary carrier of the second planetary gear mechanism via the first gear pair. However, the present invention includes a modified configuration in which the second planetary carrier of the second planetary gear mechanism is connected to an intermediate shaft in a rotationally fixed state. This intermediate shaft is configured to have a gear wheel that meshes with both a gear wheel that is rotationally fixed to the first ring gear for the first gear pair, and a gear wheel that is fixedly connected to the motor shaft for the second gear pair.

[0022] In one embodiment of the proposed drive unit, a plurality of gear ratios can be set in the range of 0.18 to 1.0 via a transmission device. This particularly includes the ability to configure, via a plurality of brakes and overrunning clutches, such that the individual gear ratios for each gear stage, i.e., for each gear, are approximately equally spaced. Thereby, a gear ratio difference that is sufficiently fine and efficient for the user can be realized.

[0023] The proposed solution also relates to an electric bicycle comprising one embodiment of the proposed drive unit.

Brief Description of the Drawings

[0024] The accompanying drawings show examples of possible embodiments of the proposed solution.

[0025] [Figure 1] FIG. 1 schematically shows one embodiment of the proposed drive unit that houses three planetary gear mechanisms within the housing of the drive unit. [Figure 2] FIG. 2 is a shift diagram showing eight gear stages corresponding to each shift state of the overrunning clutch and brake provided in the drive unit of FIG. 1. [Figure 3] FIG. 3 schematically shows an electric bicycle comprising one embodiment of the proposed drive unit.

[0026] Figure 3 shows an electric bicycle 1 having a drive unit A. The electric bicycle 1 has a frame 10 to which the drive unit A is attached. The drive unit A includes control electronics SE and a sensor device 15. The sensor device 15 is constituted by, for example, a torque sensor and a position sensor, and detects torque introduced by muscular force based on a sensor on a drive shaft constituting a bottom bracket shaft AT of the drive unit A. The sensor device 15 alternatively or additionally includes a rotational speed sensor, and can detect the rotational speed of the bottom bracket shaft AT via this. An output member of the drive unit A (for example, a hollow output shaft W attached coaxially with the bottom bracket shaft AT) is engaged with a rear wheel 12 of the electric bicycle 1 via a belt or chain 13 as a transmission member, whereby the electric bicycle 1 can be driven. A wheel sensor 14 for determining the traveling speed of the electric bicycle 1 is provided, for example, on the rear wheel 12. Of course, the wheel sensor 14 may be provided on a front wheel 11 of the electric bicycle 1.

[0027] The drive unit A is a part of a drive system of the electric bicycle and also includes an operation unit 2. In FIG. 3, the operation unit 2 is fixed, for example, to a handle region of the electric bicycle 1 and is connected to the control electronics SE of the drive unit A. User input can be acquired via the operation unit 2 and used for control of the drive unit A. For example, the operation unit 2 further includes at least one display to inform a user of the electric bicycle 1 of the current operating state of the drive unit A. This operating state includes, for example, the currently set assist level, the charge state of a battery that supplies energy to the drive unit A, and / or a set gear that defines a gear ratio when drive torque generated by muscular force and introduced to the bottom bracket shaft AT is transmitted to the output shaft W.

[0028] In one embodiment of the proposed drive unit A, three planetary gear mechanisms P1, P2, and P3 are provided as part of the drive unit A's transmission GE, and these are housed in the housing of the drive unit A. Through these three planetary gear mechanisms P1, P2, and P3, the bottom bracket shaft AT and the output shaft W are connected to the motor shaft MW of the drive unit A's motor M (usually an electric motor). Figure 1 schematically shows the arrangement of the three planetary gear mechanisms P1, P2, and P3 proposed for this purpose.

[0029] The first planetary gear mechanism P1 comprises a first sun gear S1, a first planetary carrier T1, and a first ring gear H1, and is positioned on a first axis 31 coaxial with the bottom bracket axis AT and the output axis W, which is configured as a hollow axis. The first planetary gears R11 and R12 are rotatably mounted on the first planetary carrier T1, mesh with the first sun gear S1, and engage with the internal teeth of the first ring gear H1.

[0030] In the drive unit A shown in Figure 1, the transmission GE has a second planetary gear mechanism P2 and a third planetary gear mechanism P3 arranged on a second axis 32 parallel to the first axis 31. The second sun gear S2, the second planetary carrier T2 that rotatably supports the second planetary gears R21 and R22, and the second ring gear H2 of the second planetary gear mechanism P2 are rotatably mounted around the (second) axis of rotation of the second axis 32. Similarly, the third sun gear S3, the third planetary carrier T3 that rotatably supports the third planetary gears R31 and R32, and the third ring gear H3 of the third planetary gear mechanism P3 are also rotatably mounted around this axis of rotation. The axis of rotation of the second axis 32 is defined here by a support shaft LW. This support shaft LW may be composed of a portion formed on the housing G, or it may be provided as a separate component fixed to the housing G.

[0031] The third axis 33 is located parallel to the first axis 31 and the second axis 32. The motor shaft MW of the motor M is located on this third axis 33.

[0032] A motor gear wheel is mounted on the motor shaft MW in a fixed rotational state, and this motor gear wheel can transmit assist torque to the second planetary carrier T2 via the second spur gear stage V2. The second planetary carrier T2 of the second planetary gear mechanism P2 is further connected to the first sun gear S1 of the first planetary gear mechanism P1 via the first spur gear stage V1. In addition, the bottom bracket shaft AT introduces the driving torque generated by muscle force to the first planetary carrier T1, and transmits this driving torque to the first sun gear S1 via the first planetary gears R11 and R12. Therefore, both the driving torque generated by muscle force and the assist torque generated by the motor M can act on the second planetary carrier T2 of the second planetary gear mechanism P2.

[0033] In this embodiment, the second ring gear H2 of the second planetary gear mechanism P2 is further rigidly connected to the third planetary carrier T3 of the third planetary gear mechanism P3. The combined torque is then transmitted to the output shaft W via the third ring gear H3 of the third planetary gear mechanism P3 and through the third spur gear stage V3.

[0034] In this example, three brakes B1, B2, and B3 and three overrunning clutches F1, F2, and F3 are assigned to the three planetary gear mechanisms P1, P2, and P3 of the transmission unit GE. Each planetary gear mechanism P1, P2, and P3 is assigned one of the brakes B1, B2, and B3 and one of the overrunning clutches F1, F2, and F3. By activating the three brakes B1, B2, and B3 to fix the rotation of one component of the corresponding planetary gear mechanism P1, P2, and P3 and lock it against the housing G, and by switching the overrunning clutches F1, F2, and F3 between the disengaged and undisengaged states in a so-called overrunning operation, an 8-speed forward gear can be realized via the transmission unit GE.

[0035] A first brake B2 is provided to lock the first ring gear H1 of the first planetary gear mechanism P1. A first overrunning clutch F1 is further provided between the first planetary carrier T1 and the first sun gear S1 of the first planetary gear mechanism P1. When the first brake B2 is activated, the first ring gear H1 of the first planetary gear mechanism P1 is locked, preventing the first axis 31 from rotating around the (first) rotation axis. When the first overrunning clutch F1 is disengaged, the first planetary carrier T1 and the first sun gear S1 of the first planetary gear mechanism P1 are connected in a rotationally fixed state. When the sun gear S1 rotates at a higher speed, the connection with the first planetary carrier T1 is released via the first overrunning clutch F1.

[0036] The second planetary gear mechanism P2 is further provided with a second brake B1 for locking the second sun gear S2 against the support shaft LW as needed, i.e., for changing the gear ratio. When the second overrunning clutch F3 is disengaged, the second planetary carrier T2 is rotationally fixed to the second ring gear H2 of the second planetary gear mechanism P2.

[0037] The third planetary gear mechanism P3 is further provided with a third brake B3 to lock the third sun gear S3 against the support shaft LW. The third overrunning clutch F2 of the third planetary gear mechanism P3 connects the third planetary carrier T3 to the third ring gear H3 when disengaged.

[0038] As shown in the shift diagram of Figure 2, the gear ratio i can be switched between 0.18 and 1.0 by switching the overrunning clutches F1, F2, and F3 between the disengaged and undisengaged states, and by activating the brakes B1, B2, and B3 to lock the corresponding parts of each planetary gear mechanism P1, P2, and P3 (i.e., the first ring gear H1, the second sun gear S2, and the third sun gear S3). In this way, the operation of the drive unit A realizes the 8-speed forward gear of the electric bicycle 1.

[0039] In the shift diagram of Figure 1, "×" indicates that the respective overrunning clutches F1, F2, and F3 are disengaged, and brakes B1, B2, and B3 are engaged. For example, when the gear ratio i=1, brakes B1, B2, and B3 are not engaged, and overrunning clutches F1, F2, and F3 are all disengaged. When the fourth gear has a gear ratio i=0.487, the second brake B1 and third brake B3 are engaged, and the first overrunning clutch F1 is disengaged. When the minimum gear ratio i=0.18, overrunning clutches F1, F2, and F3 are all not disengaged, and brakes B1, B2, and B3 are all engaged.

[0040] The drive unit A, equipped with the transmission device GE shown in Figure 1, has a relatively large installation space around the bottom bracket shaft AT. This space can be used, for example, to accommodate a sensor system including the aforementioned sensor device 15. [Explanation of Symbols]

[0041] 1. Electric bicycle 10 frames 11 Front Wheel 12 Rear wheels 13. Chains / Belts (Power Transmission Components) 14 Wheel Sensors 15 Sensor device 2. Operation Unit 31,32,33 Axis A Drive Unit AT bottom bracket shaft / drive shaft B1, B2, B3 brakes F1, F2, F3 Overrunning Clutch G Housing GE Power Transmission H1, H2, H3 ring gears i Gear ratio LW support shaft (section fixed to the housing) M Motor MW motor shaft P1, P2, P3 Planetary Gear Mechanism R11, R12, R21, R22, R31, R32 Planetary Gears S1, S2, S3 Sun Gear SE Control Electronics T1, T2, T3 Planetary Carriers V1, V2, V3 Spur Gear / Gear Pair W output shaft

Claims

1. A drive unit for an electric bicycle (1), A drive shaft (AT) capable of generating driving torque through muscle force, An output member (W) for driving the wheels (12) of the electric bicycle (1), A motor (M) that provides an assist torque generated by external power, which can be transmitted to the output member (W), in addition to the driving torque generated by muscle force, A drive unit comprising a planetary gear mechanism (P1, P2, P3) that provides different gear ratios (i) for transmitting drive torque, and a multi-stage transmission device (GE) that connects the drive shaft (AT) and the output member (W) to the motor shaft (MW) of the motor (M), Of the three planetary gear mechanisms (P1, P2, P3) mentioned above, the first planetary gear mechanism (P1) is arranged on a first axis (31) coaxial with the drive shaft (AT). Of the three planetary gear mechanisms (P1, P2, P3), the second planetary gear mechanism (P2) and the third planetary gear mechanism (P3) are arranged on a second axis 32 parallel to the first axis 31. A drive unit characterized in that the motor shaft (MW) is arranged on a third axis (33) parallel to the first axis (31) and the second axis (32).

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

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

4. A drive unit according to any one of claims 1 to 3, characterized in that the ring gear (H3) of the third planetary gear mechanism (P3) is connected to the output member (W) via a gear pair (V3).

5. The drive unit according to any one of claims 1 to 4, characterized in that the transmission (GE) comprises two or three brakes (B1, B2, B3) and two or three overrunning clutches (F1, F2, F3) for providing four or more different gear ratios (i).

6. The drive unit according to claim 5, characterized in that a first brake (B2) is provided to lock the ring gear (H1) of the first planetary gear mechanism (P1).

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

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

9. The drive unit according to claim 8, characterized in that the second brake (B1) and the third brake (B3) can lock the sun gear (S2) of the second planetary gear mechanism (P2) and the sun gear (S3) of the third planetary gear mechanism (P3) relative to the same section (LW) of the housing (G) of the drive unit (A) housing the transmission device (GE), or the same component (LW) fixed to the housing (G).

10. A drive unit according to any one of claims 5 to 9, characterized in that the planetary carrier (T1) of the first planetary gear mechanism (P1) can be connected to the ring gear (H1) of the first planetary gear mechanism (P1) in a rotationally fixed state via a first overrunning clutch (F1).

11. A drive unit according to any one of claims 5 to 10, characterized in that the planetary carrier (T1) of the third planetary gear mechanism (P3) can be connected to the ring gear (H3) of the third planetary gear mechanism (P3) in a rotationally fixed state via a third overrunning clutch (F2).

12. A drive unit according to any one of claims 5 to 11, characterized in that the planetary carrier (T2) of the second planetary gear mechanism (P2) can be connected to the ring gear (H2) of the second planetary gear mechanism (P3) in a rotationally fixed state via a second overrunning clutch (F3).

13. A drive unit according to any one of claims 5 to 12, characterized in that the overrunning clutches (F1, F2, F3) are operable.

14. A drive unit according to any one of claims 1 to 13, characterized in that the motor shaft (MW) is connected to the planetary carrier (T2) of the second planetary gear mechanism (P2) via a gear pair (V2).

15. The drive unit according to any one of claims 1 to 14, characterized in that the transmission device (GE) is configured to provide a plurality of gear stages in the range of 0.18 to 1.

0.

16. An electric bicycle comprising a drive unit (A) as described in any one of claims 1 to 15.

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