DE102019201812B3 - Drive device for an electric bike and electric bike with a drive device - Google Patents

Abstract

The proposed solution relates to a drive device (V) for an electric bicycle, with - a bottom bracket shaft (T) rotatable about a first shaft axis (A1), - an output shaft (AT) also rotatable about the first shaft axis (A1) for driving a wheel of the electric bicycle (1), - a first electric motor (E1), which drives a first rotor shaft (R1) for rotation about a third shaft axis (A3), and a second electric motor (E2), which drives a second rotor shaft (R2), and - a planetary gear stage (P) having a superposition gear (UG), the transmission ratio of which can be infinitely adjusted using the first and second electric motors (E1, E2) and via which the bottom bracket shaft (T) and the output shaft (AT) are coupled to one another, one of which Torque generated by the first electric motor (E1) can be at least partially transmitted to the output shaft (AT) by rotating the first rotor shaft (R1) via at least one gear stage (ST4) to e The second rotor shaft (R2) can be driven to rotate about a fourth shaft axis (A4), which rotates with respect to the first, second and third shaft axes (A). A1, A2, A3) is different.

Description

The proposed solution relates to a drive device for an electric bicycle according to the preamble of claim 1 and an electric bicycle with a drive device according to claim 12.

It is known to use two electric motors in combination with a superimposition gearbox having a planetary gear stage on an electric bicycle, that is to say on an e-bike or pedelec, in order to continuously adjust a transmission ratio between drive and output. On the one hand, such a drive device has a bottom bracket shaft, via which a drive torque generated by a driver of the electric bicycle can be introduced and on which pedals are provided for this purpose. Via an output shaft of the drive device to be coupled to a wheel of the electric bicycle, a drive torque introduced on the bottom bracket shaft and / or a torque generated by an electric motor is then transmitted to a wheel, usually a rear wheel of the electric bicycle. The bottom bracket shaft and the output shaft are coupled to one another via the superposition gear, a torque generated by a first electric motor of the two electric motors being at least partially transferable to the output shaft. A transmission ratio can be infinitely adjusted via the second electric motor of the two electric motors, so that the electric bicycle can be accelerated via a drive torque of the first electric motor without having to turn the bottom bracket shaft faster or with greater force. In this way, the second electric motor also serves to support the torque generated by the first electric motor and, for this purpose, can rotate a rotor shaft in different directions of rotation depending on the transmission ratio. A drive device for an electric bicycle with a comparable superposition gear and two electric motors is, for example, from the EP 2 218 634 A1 known.

With the from the EP 2 218 634 A1 Known drive device, a torque generated by the first electric motor can be at least partially transmitted to an output shaft via a pinion connected in a rotationally fixed manner to a first rotor shaft, in that the pinion on the rotor shaft side meshes with an external toothing of a ring gear of the planetary gear stage. An additionally provided second electric motor is connected via a further gear stage to a sun gear of the planet gear stage. A translation into slow speed is provided via the respective gear stages between the rotor shafts of the electric motors and the ring gear on the one hand and the sun gear on the other. Here the EP 2 218 634 A1 expressly certain transmission ratios in order to be able to achieve certain drive characteristics of the proposed drive device. Furthermore, the bottom bracket shaft, the output shaft and the sun gear rotate around the same shaft axis.

The DE 10 2016 121 855 A1 describes a bicycle drive unit which essentially comprises a planetary gear mechanism, a first motor and a worm drive. The planetary gear mechanism includes an input body, an output body, and a gear body. The input body is designed to receive rotation from a crankshaft. The output body is configured to output rotation from the input body to the outside of the bicycle drive unit. The gear body is designed to control a rotation ratio of the input body to the output body. The first motor is designed to transmit rotation to the transmission body. The worm drive is provided in a transmission path that transmits rotation between the first motor and the gear body.

The DE 10 2017 003 945 A1 describes an additional electric motor drive for an electric bicycle that avoids unpleasant jumps in gear ratio due to switching between different gear pairs by implementing a continuously variable transmission ratio of the torques transmitted from the pedal crankshaft and from an auxiliary motor to a driven gear via a planetary gear. For this purpose, the support motor and a crankshaft drive a hollow output shaft via a planet carrier and a sun. In order to vary the gear ratio, the third shaft of two freely rotatable three shafts of the planetary gear is now not fixed, but rotatably supported and variably braked or actively driven in a speed-controlled manner.

Proceeding from this, the proposed solution is based on the object of further improving a drive device for an electric bicycle.

This object is achieved with a drive device according to claim 1 and an electric bicycle according to claim 12.

According to this, it is provided that the second rotor shaft of a second electric motor of the drive device can be driven to rotate about a fourth shaft axis, which is to a first shaft axis for the bottom bracket shaft and the output shaft, to a second shaft axis for a ring gear of the planetary gear stage and thus the gear axis of the planetary gear stage as well as a third shaft axis for the first rotor shaft of a first electric motor is different.

• - die Tretlagerwelle sowie die Abtriebswelle um die erste Wellenachse,
• - das Hohlrad der Planetenradstufe um die zweite Wellenachse,
• - die erste Rotorwelle um die dritte Wellenachse und
• - die zweite Rotorwelle um die vierte Wellenachse

drehbar sind. Durch die räumliche Trennung der Wellenachse der zweiten Rotorwelle einerseits und der Wellenachse für die Tretlagerwelle und die Abtriebswelle andererseits begrenzt die Tretlagerwelle nicht den kleinsten möglichen Durchmesser des zweiten Elektromotors. Durch die Anordnung auf einer zusätzlichen vierten Wellenachse ist es vielmehr möglich, einen zweiten Elektromotor mit - im Vergleich zu dem ersten Elektromotor - kleinerem Motordurchmesser zu verwenden. Hierdurch lässt sich die Antriebsvorrichtung kompakter und mit geringerem Gewicht gestalten.A proposed drive device is consequently designed with four shafts and thus has four shaft axes and thus shaft trains, whereby

• - the bottom bracket shaft and the output shaft around the first shaft axis,
• - the ring gear of the planetary gear stage around the second shaft axis,
• - The first rotor shaft about the third shaft axis and
• - The second rotor shaft around the fourth shaft axis

are rotatable. Due to the spatial separation of the shaft axis of the second rotor shaft on the one hand and the shaft axis for the bottom bracket shaft and the output shaft on the other hand, the bottom bracket shaft does not limit the smallest possible diameter of the second electric motor. The arrangement on an additional fourth shaft axis makes it rather possible to use a second electric motor with a smaller motor diameter than the first electric motor. As a result, the drive device can be made more compact and lighter in weight.

The second rotor shaft can be coupled to a sun gear of the planetary gear stage via at least one further gear stage in order to transmit a torque from the second rotor shaft to the sun gear. In an embodiment variant, the at least one further gear stage translates a rotation of the second rotor shaft into a rotation of the sun gear at a lower speed. The at least one further gear stage is thus provided for a slow translation. In this context, the at least one further gear stage has, for example, a transmission ratio in the range from -1 to -4, in particular -1.8 to -2.5.

In one exemplary embodiment, viewed in a front view along the fourth shaft axis, the first shaft axis for the bottom bracket shaft, the fourth shaft axis for the second rotor shaft and the second shaft axis for the ring gear (and thus the gear axis of the planetary gear stage) are arranged at corner points of a virtual triangle. As a result, the installation space required for the additional fourth shaft axis for the second rotor shaft of the second electric motor is comparatively small, so that all components of the drive device can easily be accommodated together in a comparatively small housing.

Alternatively or in addition, the fourth shaft axis for the second rotor shaft and the third shaft axis for the first rotor shaft lie in a plane to which both the first shaft axis for the bottom bracket shaft and the output shaft and the second shaft axis for the ring gear are spaced apart. Both the first shaft axis and the second shaft axis run parallel to the plane defined by the fourth shaft axis and the third shaft axis, but are spaced apart from each other. A distance between the first shaft axis and this plane can differ from a distance between the second shaft axis and this plane.

Alternatively or in addition, the first shaft axis for the bottom bracket shaft and the second shaft axis for the ring gear can lie in a plane to which the third shaft axis for the first rotor shaft and the fourth shaft axis for the second rotor shaft are spaced apart, in particular are spaced differently. Depending on the selected transmission ratios of the gear stages provided between the shaft axes, the first shaft axis, the second shaft axis and the third shaft axis can alternatively lie in a common plane, to which only the fourth shaft axis for the second rotor shaft of the second electric motor is spaced.

The ring gear can basically have internal teeth for meshing with planet gears of the planetary gear stage and external teeth for transmitting the rotation of the first rotor shaft to the ring gear. The first electric motor consequently transmits its torque to accelerate the output shaft (and thus, when the drive device is installed as intended, to accelerate the electric bicycle) via the external toothing of the ring gear, which meshes with the planetary gears of the planetary gear stage via an internal toothing.

In one embodiment variant, the at least one gear stage, via which a rotation of the first rotor shaft can be transmitted to the ring gear of the planetary gear stage, is designed as a spur gear stage. Alternatively or in addition, the at least one gear stage can be designed with a traction mechanism drive. This includes in particular that the at least one gear stage is designed as a toothed belt gear stage.

Alternatively or in addition, the drive device for the transmission of a torque from the ring gear to the output shaft has at least one further gear stage. In one exemplary embodiment, this at least one further gear stage implements a translation into slow speed, that is to say that the at least one further gear stage translates a rotation of the ring gear with a first speed into a rotation of the output shaft with a lower second speed in comparison to the first speed of the ring gear. The translation into slow speed can also be realized via exactly one further gear stage between the ring gear and the output shaft.

In one embodiment, at least one gear stage is provided for the transmission of a torque generated by the bottom bracket shaft to the planetary gear stage. The bottom bracket shaft is coupled to a planet gear carrier of the planet gear stage via this gear stage. This gear stage assigned to the bottom bracket shaft is consequently different from the gear stage via which a rotation of the first rotor shaft can be transmitted to the ring gear of the planetary gear stage. In this configuration, it can be easily realized, in particular, that the axis of rotation of the bottom bracket shaft and the output shaft run coaxially to one another and the axes of rotation of the two rotor shafts of the first and second electric motors are arranged parallel to this.

The attached figures illustrate examples of possible design variants of the proposed solution.

• 1 eine Draufsicht auf eine Ausführungsvariante einer vorgeschlagenen Antriebsvorrichtung (ohne Gehäuse);
• 2 eine Vorderansicht der Antriebsvorrichtung der 1;
• 3A eine Schnittdarstellung der Antriebsvorrichtung der 1 und 2 entsprechend der Schnittlinie A-A der 2;
• 3B eine Schnittdarstellung der Antriebsvorrichtung der 1 und 2 entsprechend der Schnittlinie B-B der 2;
• 4 eine Antriebsvorrichtung unter Veranschaulichung eines Überlagerungsgetriebes, das eine Tretlagerwelle mit einer Abtriebswelle koppelt und dessen Übersetzungsverhältnis über zwei Elektromotoren stufenlos einstellbar ist.

Here show:

• 1 a plan view of an embodiment variant of a proposed drive device (without housing);
• 2nd a front view of the drive device of the 1 ;
• 3A a sectional view of the drive device of the 1 and 2nd according to section line AA of 2nd ;
• 3B a sectional view of the drive device of the 1 and 2nd according to the section line BB of the 2nd ;
• 4th a drive device illustrating a superposition gear, which couples a bottom bracket shaft to an output shaft and the transmission ratio is infinitely adjustable via two electric motors.

The 4th shows a drive device V for an electric bike. Here are in one housing G , which is to be attached to a frame of the electric bicycle, the components of a superposition gear Basement as well as two electric motors E1 and E2 housed. The electric motors E1 and E2 can be designed in the same way, that is, for example, with the same power and dimensions. The drive device V also includes a bottom bracket shaft to be connected to pedals T , on the pedal bracket Ta and Tb are provided. By rotating the bottom bracket shaft T A driver of an electric bicycle, which is connected to the drive device V is equipped, initiate a drive torque. The bottom bracket shaft T protrudes through the housing G through so that the pedal bracket Ta and Tb on both sides of the case G protrude.

Via the superposition gear Basement becomes a rotation of the bottom bracket shaft T into a rotation of an output shaft AT translated. The output shaft AT is with a shaft-side, first coupling part K non-rotatably connected. The first coupling part on the shaft side K For example, has a sprocket or a pulley and is connected via a power transmission link, for example a chain or a belt, to a wheel-side, second coupling part, for example in the form of a sprocket or a pulley, in order to drive a rear wheel of the electric bicycle.

A gear ratio of the transmission gear Basement is using the two electric motors E1 and E2 infinitely adjustable. A first electric motor E1 can generate a torque that is at least partially connected to the output shaft AT is transferable to drive the electric bike with electric motor support. With the two electric motors E1 and E2 a stepless electrical actuator is thus formed.

This drives the electric motors E1 and E2 each have a rotor shaft assigned to them R1 or R2 on. The bottom bracket shaft T , the output shaft AT and the rotor shafts R1 and R2 are about the multi-stage superposition gear Basement coupled with each other. For this purpose, the superposition gear comprises Basement several gear stages, here in the form of spur gear stages ST1 to ST4 , and a planetary gear stage P . The planetary gear stage P is designed with three shafts and includes a sun gear S a planet carrier PT with multiple planet gears PR and a rotatable ring gear H .

The bottom bracket shaft T , the output shaft AT and the (second) the second electric motor E2 assigned rotor shaft R2 are arranged coaxially to each other. The (first) rotor shaft runs parallel to this R2 of the first electric motor E1 . The bottom bracket shaft T is about a first spur gear stage ST1 of the superposition gear Basement torque transmitting with a first coupling shaft KW1 connected. This first coupling shaft KW1 is with the planet carrier PT the planetary gear stage P connected. The output shaft AT stands over a second spur gear stage ST2 with a second coupling shaft KW2 in connection with the ring gear H connected is. While on the first spur gear stage ST1 the speed of the bottom bracket shaft T to a higher absolute speed of the first coupling shaft KW1 is increased by the second spur gear ST2 the speed the second coupling shaft KW2 in a lower speed of the output shaft AT translated.

The second, supporting electric motor E2 transmits torque via its second rotor shaft R2 using a third spur gear ST2 the sun gear on one S bearing third coupling shaft KW3 . Here is about the translation of the third spur gear ST3 a slow translation is planned. On the part of the first electric motor E1 Torque generated is via its first rotor shaft R1 using a fourth spur gear stage ST4 again to the ring gear H transfer. The first rotor shaft R1 of the first electric motor E1 is accordingly (via the ring gear H ) torque transmitting with the output shaft AT connected. It is therefore an output-side power split in the drive device shown V intended.

About the first electric motor E1 can a torque to accelerate the output shaft in the configuration shown AT and thus generated to accelerate the electric bike. This is the second electric motor E2 with the help of control electronics SE the drive device V depending on the speed of the first electric motor E1 or its rotor shaft R1 controlled. As a result, the gear ratio of the superposition gear Basement variably adjustable and one on the output shaft AT provided and to the shaft-side coupling part K transmitted output torque can be varied by an electric motor, without there being a rotational speed of the bottom bracket shaft T would have to change. Depending on the speed of the first electric motor E1 the direction of rotation of the second rotor shaft can also change R2 to change.

In development of the drive device V the 4th sees one in the 1 , 2nd , 3A and 3B shown embodiment of a drive device V according to the proposed solution that the second rotor shaft R2 of the second, supporting electric motor E2 not coaxial to a shaft axis of the bottom bracket shaft T and the output shaft AT runs. Rather, in the embodiment variant 1 , 2nd , 3A and 3B a fourth shaft axis is provided around which the second rotor shaft R2 of the second electric motor E2 can be driven to rotate.

The drive device V the 1 , 2nd , 3A and 3B consequently has four shaft axes A1 , A2 , A3 and A4 and four shaft strands defined thereby. The bottom bracket shaft T as well as the output shaft AT are about a first shaft axis A1 rotatable. The ring gear H the planetary gear stage P is about a second shaft axis A2 rotatable, which means the gear axis of the planetary gear stage P Are defined. The first rotor shaft R1 is about a third shaft axis A3 rotatable while the second rotor shaft R2 around a fourth shaft axis A4 is rotatable. The four shaft axes A1 , A2 , A3 and A4 run parallel to each other, but are spatially spaced apart.

Analogous to the drive device V the 4th sees the variant of the 1 , 2nd , 3A and 3B this continues before that the first electric motor E1 about his first rotor shaft R1 and the spur gear ST4 a torque on an external toothing AR of the ring gear H transmits. With an internal toothing IR with the planet gears PR the planetary gear stage P Intermeshing ring gear R is accordingly also in the variant of the 1 , 2nd , 3A and 3B rotatable with the coupling shaft KW2 connected so that via the spur gear stage ST2 a rotation of the ring gear H in a rotation of the output shaft AT is feasible.

Via the spur gear stage ST1 is also analogous to the drive device V the 4th also in the variant of the 1 , 2nd , 3A and 3B a torque coaxial with the output shaft AT arranged bottom bracket shaft T to the planet carrier PT the planetary gear stage P transfer.

In the embodiment variant shown, the second rotor shaft R2 continue via a spur gear stage ST3 with the sun gear S the planetary gear stage P coupled to torque from the second rotor shaft R2 to the sun gear S transferred to. A slow translation selected here is in the range from -1.8 to -2.5, for example 2.1.

A gear ratio of the spur gear stage ST1 is, for example, in the range from -4 to -1, in particular at -3.1, while a gear ratio of the spur gear stage ST2 for example in the range from -1 to -3, in particular at -1.3. For the spur gear stage ST4 to a torque from the first rotor shaft R1 to the ring gear H To transmit, for example, a gear ratio in the range from -10 to -6, in particular from -7.8 is provided. A stand translation of the drive device shown V is, for example, in the range from -6 to -2, in particular -4.

As especially from the 2nd can be seen are in the illustrated embodiment of the drive device V , in a front view along the fourth shaft axis A4 seen the first shaft axis A1 for the bottom bracket shaft T and the output shaft AT , the fourth shaft axis A4 for the second rotor shaft R2 and the second shaft axis A2 for the ring gear H arranged at corner points of a virtual triangle. The third and fourth shaft axes are also located A3 , A4 for the first and second rotor shafts R1 , R2 in a plane to which both the first shaft axis A2 for the bottom bracket shaft T and the output shaft AT as well as the second shaft axis A2 for the ring gear H run parallel but are spaced apart. The planetary gear stage P with the second shaft axis A2 is therefore in the front view of the 2nd on the one hand between the first shaft axis of the bottom bracket shaft T and the output shaft AT and the third shaft axis A3 the second rotor shaft R2 . On the other hand there is the planetary gear stage P with the second shaft axis A2 , especially due to the selected gear ratios of the individual spur gear stages ST1 to ST4 between the third and fourth shaft axes of the first and second rotor shafts R1 , R2 of the first and second electric motors E1 and E2 (Here, however, spaced apart from the plane in which the third and fourth shaft axes A3 and A4 lie).

Nevertheless with the drive device V the 1 , 2nd , 3A and 3B electric motors of the same type and thus essentially identical in terms of their output E1 and E2 this is not mandatory. In particular the second, supporting electric motor E2 can given the arrangement on a separate fourth shaft axis A4 easily be designed with a smaller motor diameter. The second electric motor E2 can therefore be dimensioned smaller in terms of its output than the first electric motor E1 .

Reference list

A1, A2, A3, A4

Shaft axis

AR

External teeth

AT

Output shaft

E1

1. Electric motor

E2

2. Electric motor

G

casing

H

Ring gear

IR

Internal teeth

K

Coupling part

KW1-KW3

Coupling shaft

P

Planetary gear stage

PR

Planet gear

PT

Planet carrier

R1, R2

Rotor shaft

S

Sun gear

SE

Control electronics

ST1-ST4

Helical gear stage (gear stage)

T

Bottom bracket shaft

Ta, Tb

Pedal holder

Basement

Superposition gear

V

Drive device

Claims (12)

Drive device (V) for an electric bicycle, with - a bottom bracket shaft (T) rotatable about a first shaft axis (A1), - an output shaft (AT) also rotatable about the first shaft axis (A1) for driving a wheel of the electric bicycle, - a first electric motor (E1), which drives a first rotor shaft (R1) for rotation about a third shaft axis (A3), and a second electric motor (E2), which drives a second rotor shaft (R2), and - a superposition gear having a planetary gear stage (P) (UG), whose transmission ratio is infinitely adjustable with the aid of the first and second electric motors (E1, E2) and via which the bottom bracket shaft (T) and the output shaft (AT) are coupled to one another, at least one torque generated by the first electric motor (E1) is partially transferable to the output shaft (AT) by rotating the first rotor shaft (R1) via at least one gear stage (ST4) to a rotatable one about a second shaft axis (A2) s ring gear (H) of the planetary gear stage (P) can be transmitted, characterized in that the second rotor shaft (R2) can be driven to rotate about a fourth shaft axis (A4) which leads to the first, second and third shaft axes (A1, A2, A3) is different. Drive device (V) after Claim 1 , characterized in that the second rotor shaft (R2) is coupled via at least one further gear stage (ST3) to a sun gear (S) of the planetary gear stage (P) in order to apply a torque from the second rotor shaft (R2) to the sun gear (S) transfer. Drive device (V) after Claim 2 , characterized in that the at least one further gear stage (ST3) translates a rotation of the second rotor shaft (R2) into a rotation of the sun gear (S) at a lower speed. Drive device (V) after Claim 3 , characterized in that the at least one further gear stage (ST3) has a transmission ratio in the range from -1.8 to -2.5. Drive device (V) according to one of the preceding claims, characterized in that, seen in a front view along the fourth shaft axis (A4), the first shaft axis (A1) for the bottom bracket shaft (T) and the output shaft (AT), the fourth shaft axis (A4) for the second rotor shaft (R2) and the second shaft axis (A2) for the ring gear (H) are arranged at corner points of a virtual triangle. Drive device (V) according to one of the preceding claims, characterized in that the fourth shaft axis (A4) for the second rotor shaft (R2) and the third shaft axis (A3) for the first rotor shaft (R1) lie in a plane to which both first shaft axis (A1) for the bottom bracket shaft (T) and the output shaft (AT) and the second shaft axis (A2) for the ring gear (H) are spaced apart. Drive device (V) according to one of the preceding claims, characterized in that the ring gear (H) for meshing with planet gears (PR) of the planetary gear stage (P) has an internal toothing (IR) and for transmitting the rotation of the first rotor shaft (R1) the ring gear (H) has external teeth (AR). Drive device (V) according to one of the preceding claims, characterized in that the at least one gear stage, via which a rotation of the first rotor shaft (R1) can be transmitted to the ring gear (H) of the planetary gear stage (P), is designed as a spur gear stage (ST4) . Drive device (V) according to one of the preceding claims, characterized in that the drive device (V) for the transmission of a torque from the ring gear (H) to the output shaft (AT) has at least one further gear stage (ST2). Drive device (V) after Claim 9 , characterized in that the at least one further gear stage (ST2) translates a rotation of the ring gear (H) into a rotation of the output shaft (AT) at a lower speed. Drive device (V) according to one of the preceding claims, characterized in that a torque generated by the bottom bracket shaft (T) can be transmitted via at least one gear stage (ST1) to a planet gear carrier (PT) of the planetary gear stage (P) which is connected to the gear stage (ST4 ) is different, via which a rotation of the first rotor shaft (R1) can be transmitted to the ring gear (H) of the planetary gear stage (P). Electric bicycle with a drive device (V) according to one of the preceding claims.

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