Method for operating a drive unit of an electric bicycle

Abstract

The present invention relates to a method for operating a drive unit of an electric bicycle, the drive unit comprising a motor and at least one gearbox which is mechanically coupled to the motor, the gearbox comprising at least one gear pair having a first gear and a second gear, and the motor being operated in a noise-reduction operating mode in order to achieve contact of forward tooth flanks of the gears by means of a specific relative torque between the first gear and the second gear.

Description

[0001] Description

[0002] title

[0003] Method for operating a drive unit of an electric bicycle

[0004] State of the art

[0005] The present invention relates to a method for operating a drive unit of an electric bicycle, a drive unit of an electric bicycle, and an electric bicycle.

[0006] Electric bicycles are known with drive units designed to generate motor torque to assist a rider's manual pedaling power. Typically, a gearbox for translating the rotational movement of the electric motor is provided between an electric motor in the drive unit, which generates the motor torque, and a crankshaft, which is usually connected to a chainring. The gearbox often has several interlocking gears. Particularly with changing loads on the chain, which can occur, for example, when riding on uneven surfaces or when the rear end of a full-suspension bicycle compresses, noises such as clattering can occur due to the changing rotational movements of the gears caused by the gear tooth flanks hitting each other.

[0007] Disclosure of the invention

[0008] The method according to the invention with the features of claim 1 is characterized in that particularly quiet operation of a drive unit of an electric bicycle can be enabled. In particular, noise development due to impacting tooth flanks in a gear system can be reduced or avoided. This is achieved according to the invention by a method for operating a drive unit of an electric bicycle, wherein the drive unit comprises a motor and at least one gear system which is mechanically coupled to the motor. Preferably, the motor is coupled to the gear system in such a way that the motor can transmit torque to the gear system, and preferably further components, such as a crankshaft, and thus in particular a chainring, of the electric bicycle can subsequently be driven via the gear system. The gear system has at least one gear pair.The gear pair comprises a first gear and a second gear. In the method, the motor is operated in a noise reduction mode, which is characterized in that the motor is operated in a controlled manner to achieve contact of the forward tooth flanks of the gears, in particular at all times, by means of a specific relative torque between the first gear and the second gear.

[0009] In particular, those tooth flanks of the gears that are in mesh, i.e., in mechanical contact with each other, are considered forward tooth flanks when a predetermined torque transmission occurs via the transmission in a forward direction of rotation. Preferably, the forward direction of rotation is defined such that, when torque is transmitted from the motor via the transmission, a motor torque generated by the motor is suitable for supporting the propulsion of the electric bicycle.

[0010] Preferably, in the noise reduction operating mode, the motor is alternatively or additionally operated in a controlled manner such that a predetermined torque transmission from the first gear to the second gear always occurs exclusively in the forward direction of rotation. Particularly preferably, the motor always provides a predetermined relative, in particular positive, torque from the first gear toward the second gear.

[0011] In other words, the method provides a noise reduction operating mode, which is preferably carried out at least for a limited time. In this noise reduction operating mode, the motor of the drive unit is deliberately controlled in such a way that a specific relative torque between the gears of the transmission provides a type of mechanical preload of the transmission, which ensures that the same tooth flanks in the transmission, namely the forward tooth flanks of the gears, always abut one another. This means that, in particular, the special, targeted operation of the motor compensates for backlash in the same direction at all times. In other words, the first gear is slightly braked relative to the housing of the drive unit so that the forward tooth flanks are not so easily left, i.e., to prevent the forward tooth flanks from rotating away.

[0012] The method offers the advantage that gear backlash can be compensated for in a particularly simple and cost-effective manner, namely through targeted, preferably software-based, control of the drive unit's motor. This makes it possible, for example, to reduce or completely avoid undesired flank changes caused by rotational vibrations on a chainring, which can occur, for example, when riding on uneven ground and / or due to the compression of a rear triangle. In particular, because the operation of the motor always specifically engages the forward tooth flanks of the gears, clattering can be avoided by overcoming the gear backlash. Furthermore, the method offers the advantage of enabling improved responsiveness of the motor, i.e. in particular of the motor assistance, because overcoming the gear backlash is not necessary until effective torque is transmitted.

[0013] The subclaims show preferred developments of the invention.

[0014] Preferably, the noise reduction operating mode is executed, in particular exclusively, during a traveling operation of the electric bicycle. Particularly preferably, the noise reduction operating mode is executed, in particular exclusively, during a locomotion of the electric bicycle. In particular, a sensor-based determination of the traveling operation, in particular the locomotion, can be carried out, in response to which the method is executed. Thus, energy-saving operation with particularly high user comfort can be provided for the rider of the electric bicycle.

[0015] Particularly preferably, the noise reduction operating mode is executed, in particular exclusively, outside of an assistance mode of the drive unit. The assistance mode is characterized in that in it, a motor torque is generated to assist propulsion of the electric bicycle. In other words, the noise reduction operating mode is not performed during active motor assistance during the assistance mode of the drive unit. This allows for unhindered optimal assistance of the cycling operation through the generated motor torque. For example, in the assistance mode, the generation of the assisting motor torque inherently results in a torque transmission from the motor via the transmission such that the forward tooth flanks of the gears are in contact, i.e., are engaged.

[0016] Preferably, the noise reduction operating mode is executed, in particular for a predetermined period of time, immediately before and / or after each execution of the assistance mode. In other words, the backlash in the transmission is overcome by the targeted control of the motor in the noise reduction operating mode immediately before and / or after each operation of the motor in the assistance mode. This allows for optimal response of the motor to assist via the motor torque. This means that the motor can provide the motor torque particularly directly for the assisted propulsion of the electric bicycle. Furthermore, noise generation due to impacts between different tooth flanks in the transmission can be particularly reliably avoided. This allows for a particularly high level of riding comfort.

[0017] The noise reduction operating mode further preferably comprises a controlled actuation of the motor in such a way as to decelerate rotation of a rotor of the motor in a reverse direction. Preferably, the rotation in the reverse direction can be detected by means of a rotor position sensor, and the deceleration is preferably carried out in response to detection of the rotation in the reverse direction. In other words, a reverse rotation of the rotor of the motor opposite to the forward rotation is deliberately decelerated, i.e., slowed down, by a controlled actuation of the motor. This deceleration deliberately brings about the engagement of the forward tooth flanks of the gearwheels of the transmission. For example, a rotation in the reverse direction can be brought about by appropriate chain tension, which can occur, for example, when driving on uneven ground.This makes it particularly easy and reliable to reduce noise during operation of the drive unit.

[0018] Preferably, the rotor is braked by controlled operation of the motor as a generator. This means that the motor is operated in such a way that it generates an electric current as a generator. The force required to rotate the motor's rotor causes the rotor to brake. This allows the targeted engagement of the forward tooth flanks to be provided particularly easily and efficiently. In addition, by operating the motor as a generator, electrical current can be recovered, which can be stored, for example, in an electrical energy storage device on the electric bicycle. This enables particularly advantageous and efficient operation of the electric bicycle.

[0019] Preferably, the rotor is decelerated by generating a predetermined constant braking torque. This allows for particularly simple deceleration. Alternatively, the motor is preferably decelerated using a variable braking torque, which is preferably adjusted as a function of the current reverse speed at which the rotor rotates. For example, in this case, deceleration can be determined based on a predetermined characteristic map of a target braking torque as a function of the speed. This provides a particularly targeted and efficient method for operating the drive unit.

[0020] The noise reduction operating mode further preferably comprises the step of controlled rotation of the motor rotor by a predetermined angle of rotation. The predetermined angle of rotation is preferably at least 3°, preferably at least 5°, and particularly preferably a maximum of 15°. This means that in the method, the motor rotor is rotated by a small angle in the forward direction of rotation in a targeted manner, for example at specific times and / or in response to predetermined operating conditions, such as immediately before and / or after the assistance mode. This makes it particularly easy to ensure that the forward tooth flanks of the gears are in contact as frequently as possible to ensure low-noise operation.The noise reduction operating mode preferably comprises the step of controlled generation of a, in particular predetermined, tooth engagement torque, which is preferably a maximum of 10 Nm, preferably a maximum of 3 Nm, in particular at least 1 Nm. The tooth engagement torque is preferably generated outside of the support mode. In other words, in the method, the motor is specifically controlled, for example at specific times and / or in response to predetermined operating conditions, such that it generates a small torque in the forward direction of rotation in order to engage the forward tooth flanks as much as possible at all times. The tooth engagement torque is so small that it cannot lead to driving the chain.

[0021] Furthermore, the invention leads to a drive unit of an electric bicycle, comprising a motor, which is in particular an electric motor, at least one transmission that is mechanically coupled to the motor, in particular in a torque-transmitting manner, and a control unit. The transmission has at least one gear pair with a first gear and a second gear. The control unit is configured to carry out the described method for operating the drive unit.

[0022] Preferably, the drive unit further comprises a crankshaft configured for connection to cranks of the electric bicycle. The transmission mechanically couples the motor and the crankshaft. This means that the transmission can transmit the torque generated by the motor to the crankshaft. In addition, the crankshaft can be actuated by pedaling force from a rider of the electric bicycle via cranks.

[0023] The drive unit preferably further comprises a freewheel arranged between the motor and the crankshaft. For example, the freewheel can be arranged directly between a gear of the transmission and the crankshaft. In particular, the freewheel thus acts as a motor freewheel in order to decouple the motor from the crankshaft. The freewheel is preferably designed as a bidirectional freewheel, i.e., the freewheel can open and close in both directions of rotation. With such a drive unit, the special method is particularly advantageous for ensuring simple and quiet operation. The invention further relates to an electric bicycle comprising the described drive unit.

[0024] Short description of the drawings

[0025] An embodiment of the invention will be described in detail below with reference to the accompanying drawings. In the drawing:

[0026] Figure 1 is a simplified schematic view of an electric bicycle in which a method for operating a drive unit of the electric bicycle is carried out according to a preferred embodiment of the invention,

[0027] Figure 2 shows a simplified schematic detailed view of the

[0028] Drive unit of the electric bicycle of Figure 3, and

[0029] Figure 3 shows a detailed view of the drive unit of Figure 2.

[0030] Embodiments of the invention

[0031] Preferably, all identical components, elements and / or units in all figures are provided with the same reference numerals.

[0032] Figure 1 shows a simplified schematic view of an electric bicycle 100 in which a method for operating a drive unit 1 of the electric bicycle 100 is carried out according to a preferred embodiment of the invention.

[0033] The electric bicycle 100 comprises a drive unit 1, which includes a motor 3, which is in particular an electric motor. The motor 3 can be supplied with electrical energy by means of an electrical energy storage device 109 of the electric bicycle 100.

[0034] The drive unit 1 is arranged in the region of a bottom bracket of the electric bicycle 100. The motor torque generated by the motor 3 can provide motor assistance to the pedaling force generated by the muscular power of a rider of the electric bicycle 100.

[0035] The driver's muscle power can be applied to a crankshaft 6 via a crank mechanism comprising cranks 104. The crankshaft 6 extends along a crank axis. A first gear 41 of a transmission 4 of the drive unit 1 is arranged coaxially to the crankshaft 6 (see Figure 2). The engine 3 can transmit the engine torque to the crankshaft 6 via the transmission 4.

[0036] The transmission 4 can preferably, as in the illustrated embodiment of Figure 2, comprise a total of four gears 41, 42, 43, 44, which form a total of three gear pairs 4. The fourth gear 44, opposite the first gear 41, is connected to a motor shaft 31 of the motor 3 in a torque-transmitting manner.

[0037] To enable decoupling of the engine 3 from the crankshaft 6, the drive unit 1 comprises a freewheel 7, which is arranged between the crankshaft 6 and the first gear 41. The freewheel 7 is preferably designed as a bidirectional freewheel, which allows locking and unlocking of rotation in both directions.

[0038] A chainring 107 is also connected, in particular in a rotationally fixed manner, to the crankshaft 6. Upon rotation of the crankshaft 6, a chain 105 can be driven via the chainring 107, via which a rear wheel of the electric bicycle 100 can be driven to propel the electric bicycle 100.

[0039] During operation of the electric bicycle 100, the method according to the invention for operating the drive unit 1 is executed, which is described below. The method is preferably executed only during a traveling operation of the electric bicycle 100. In particular, the method is only executed when the electric bicycle 100 is moving in a direction of travel A (see Figure 1).

[0040] In particular, the procedure is carried out exclusively outside of a

[0041] The support mode of the drive unit 1 is executed, in which the drive unit 1 provides a motor torque that directly, in particular in addition to the rider's pedaling torque, causes the propulsion of the electric bicycle 100. Preferably, this is carried out for a predetermined period of time immediately before and / or after each execution of the support mode.

[0042] In the method, the motor 3 is operated in a noise reduction operating mode in which the operation of the motor 3 is carried out in such a way as to specifically cause a certain relative torque between the first gear 41 and the second gear 42 of the transmission 2, so that a contact of forward tooth flanks 45 of the two gears 41, 42 is always achieved (see also Figure 3).

[0043] Preferably, the motor 3 is operated in such a way that only the forward tooth flanks 45 are in contact between all gears 41, 42, 43, 44 of each gear pair 4 of the transmission 2.

[0044] The special tooth engagement of only the forward tooth flanks 45 of the gears 41, 42 is shown in more detail in Figure 3. As can be seen in Figure 3, the reverse tooth flanks 47 of each tooth of the gears 41, 42, which are opposite in the direction of rotation, are not in engagement with each other.

[0045] Preferably, the motor 3 is operated in the noise reduction mode as frequently as possible during travel of the electric bicycle 100. This operation offers the advantage that the drive unit 1 can be operated with particularly low noise emissions and with particularly low wear. The noise reduction mode ensures that the gear pairs 4 of the transmission 2 are always preloaded such that the forward tooth flanks 45 are in engagement with one another. This prevents the need to overcome backlash between the gear pairs 4 when the motor assistance is activated, which could cause the forward tooth flanks 45 to noisily strike one another. Such situations can occur particularly when the electric bicycle 100 is traveling over uneven ground and / or, in the case of a fully suspended electric bicycle 100, during the compression and rebound of the rear frame.This can cause vibrations of the chain 105 to occur, which are schematically indicated in simplified form in Figure 2, for example, by the arrows 50. These vibrations of the chain 105 can cause the chain to move alternately in different directions, or at least briefly opposite to the drive direction, which can, for example, release the engagement of the forward tooth flanks 45 of the gears 41, 42. By specifically controlling the motor 3 in such a way as to engage the forward tooth flanks 45, torque can be transmitted during subsequent motor operation without the need to overcome the play. In addition to the noise reduction, this also results in the advantage of a particularly direct response of the motor assistance.

[0046] In a first embodiment, the noise reduction operating mode comprises a controlled actuation of the motor 3 in such a way as to decelerate the rotation of the rotor of the motor 3 in a reverse direction. For example, such a rotation can be detected using a rotor position sensor. This means that if a chain hoist causes the rotor of the motor 3 to rotate in the reverse direction, this rotation can be decelerated by a braking torque by specifically controlling the motor 3. This braking torque is generated by operating the motor 3 as a generator.

[0047] Braking can be achieved either by means of a constant braking torque or alternatively by means of a variable braking torque, which can preferably be adjusted depending on a current reverse speed of the rotor based on a predetermined characteristic curve.

[0048] Preferably, an electric current generated by the generator operation of the motor 3 can be stored, i.e. recuperated, in the electric energy storage device 109 of the electric bicycle 100.

[0049] By braking the rotor of the motor 3 during a reverse rotation, it can thus be achieved in a particularly simple and reliable manner that the forward tooth flanks 45 of the gear wheels 41, 42 are brought into contact.

[0050] In a further embodiment, the noise reduction operating mode comprises a controlled rotation of the rotor of motor 3 by a predetermined angle of rotation in the forward direction of rotation. The predetermined angle of rotation can, for example, correspond to at least 5°. This controlled rotation is preferably carried out before and / or after each assistance mode. Alternatively or additionally, the controlled rotation can be carried out at specific time intervals during the operation of the electric bicycle 100. This means that the rotor of motor 3 is regularly rotated forward by a small angle, so that any existing gear play is overcome and the forward tooth flanks 45 are brought into contact in a targeted manner.

[0051] In a further embodiment, the noise reduction operating mode comprises a controlled generation of a predetermined meshing torque, which is particularly small enough to prevent driving of the chain 105, i.e., movement of the chain 105. The meshing torque is preferably a maximum of 3 Nm.

[0052] In this way, in a similar manner to the controlled forward rotation by the predetermined angle of rotation, it can be made possible in a simple and reliable manner that the forward tooth flanks 45 are always in contact, whereby an influence on the driving operation of the electric bicycle 100 can be avoided or kept particularly low.

[0053] It should be noted that the described embodiments of the method can be combined with one another as desired. That is, each embodiment can be implemented individually. Alternatively, several of the described embodiments can be implemented simultaneously during operation of the electric bicycle 100.

Claims

Claims 1. Method for operating a drive unit (1) of an electric bicycle (100), wherein the drive unit (1) comprises a motor (3) and at least one transmission (2) which is mechanically coupled to the motor (3), wherein the transmission (2) comprises at least one gear pair (4) with a first gear (41) and a second gear (42), and wherein the motor (3) is operated in a noise reduction operating mode in such a way as to achieve an engagement of forward tooth flanks (45) of the gears (41, 42) by means of a specific relative torque between the first gear (41) and the second gear (42).

2. The method according to claim 1, wherein the noise reduction operating mode is carried out during a ferry operation, in particular during a locomotion, of the electric bicycle (100).

3. Method according to one of the preceding claims, wherein the noise reduction operating mode is carried out, in particular exclusively, outside of a support mode of the drive unit (1) in which a motor torque is generated to support propulsion of the electric bicycle (100).

4. The method according to claim 3, wherein the noise reduction operating mode is executed, in particular for a predetermined period of time, immediately before and / or after each execution of the support mode.

5. The method according to any one of the preceding claims, wherein the noise reduction mode of operation comprises: controlled actuation of the motor (3) such as to decelerate rotation of a rotor of the motor (3) in a reverse direction of rotation.

6. Method according to claim 5, wherein the braking of the rotor is effected by a controlled operation of the motor (3) as a generator.

7. Method according to one of claims 5 or 6, wherein the braking of the rotor (31) takes place by generating a predetermined constant braking torque or a variable braking torque by means of the motor (3), in particular wherein the variable braking torque is adjusted as a function of a reverse rotational speed.

8. Method according to one of the preceding claims, wherein the noise reduction operating mode comprises the step of: controlled rotation of the rotor of the motor (3) by a predetermined angle of rotation, in particular of at least 3°, preferably of at least 5°, preferably of a maximum of 15°.

9. Method according to one of the preceding claims, wherein the noise reduction operating mode comprises the step of: controlled generation of a tooth engagement torque, in particular of a maximum of 10 Nm, preferably of a maximum of 3 Nm, in particular of at least 1 Nm. 10 Drive unit of an electric bicycle (100), comprising: a motor (3), at least one transmission (2) which is mechanically coupled to the motor (3), wherein the transmission (2) has at least one gear pair with a first gear (41) and a second gear (42), and a control unit (10) which is configured to carry out a method according to one of the preceding claims.

11. Drive unit according to claim 10, further comprising a crankshaft (6) for connection to cranks (104) of the electric bicycle (100), wherein the transmission (2) mechanically couples the motor (3) and the crankshaft (6) to one another.

12. Drive unit according to claim 11, further comprising a freewheel (7) which is arranged between the engine (2) and the crankshaft (6).

13. Electric bicycle comprising a drive unit (1) according to one of claims 10 to 12.

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