DE102021001222A1 - Drive system for a light vehicle - Google Patents

Abstract

The invention relates to a drive system for a light vehicle, comprising a transmission and an electric motor, and a light vehicle.
The drive system (1) according to the invention for a light vehicle comprises a transmission (2) and an electric motor (3), wherein
- the transmission (2) comprises a group transmission with a first (4) and a second (5) group and a shaft (6),
- The first group (4) is designed to absorb an input torque,
- the shaft (6) is connected to the electric motor (3) in such a way that the shaft (6) can absorb a torque from the electric motor (3),
- The shaft (6) is designed to connect the first group (4) and the electric motor (3) to the second group (5), so that the shaft (6) receives the input torque from the first group (4) and the torque of the electric motor (3) can be transferred to the second group (5),
- The shaft (6) is designed to be switchable, so that a transmission ratio of the first (4) and / or the second (5) group can be changed by switching the shaft (6) and
- The second group (5) is designed to output the input torque absorbed by the shaft (6) and the torque absorbed by the shaft (6) from the electric motor (3).

Description

The invention relates to a drive system for a light vehicle, comprising a transmission and an electric motor, and a light vehicle.

From the WO 2020/260772 A1 A drive system for a bicycle is known, the drive system comprising a planetary gear and wherein a pedal shaft of the bicycle is connected to a web of the planetary gear, a ring gear of the planetary gear is connected to an output shaft, a control motor is connected to a sun gear of the planetary gear and an auxiliary motor is connected to the ring gear.

• - das Getriebe ein Gruppengetriebe mit einer ersten und einer zweiten Gruppe und eine Welle umfasst,
• - die erste Gruppe ausgebildet ist, ein Eingangsdrehmoment aufzunehmen,
• - die Welle mit dem Elektromotor so verbunden ist, dass sie ein Drehmoment des Elektromotors aufnehmen kann,
• - die Welle ausgebildet ist, die erste Gruppe und den Elektromotor mit der zweiten Gruppe zu verbinden, so dass die Welle das Eingangsdrehmoment von der ersten Gruppe und das Drehmoment des Elektromotors auf die zweite Gruppe übertragen kann,
• - die Welle schaltbar ausgeführt ist, so dass durch ein Schalten der Welle ein Übersetzungsverhältnis der ersten und/oder der zweiten Gruppe veränderbar ist und
• - die zweite Gruppe ausgebildet ist, das von der Welle aufgenommene Eingangsdrehmoment und das von der Welle aufgenommene Drehmoment vom Elektromotor abzugeben.

The drive system according to the invention for a light vehicle comprises a transmission and an electric motor, wherein

• - The transmission comprises a group transmission with a first and a second group and a shaft,
• - the first group is designed to absorb an input torque,
• - the shaft is connected to the electric motor in such a way that it can absorb a torque from the electric motor,
• - The shaft is designed to connect the first group and the electric motor to the second group, so that the shaft can transmit the input torque from the first group and the torque of the electric motor to the second group,
• - The shaft is designed to be switchable, so that a transmission ratio of the first and / or the second group can be changed by switching the shaft, and
• - The second group is designed to output the input torque absorbed by the shaft and the torque absorbed by the shaft from the electric motor.

Because the shaft is designed to connect the first group and the electric motor to the second group and the input torque and the torque of the electric motor are thereby arranged in parallel, the invention enables the input torque to be introduced independently of the torque of the electric motor. At the same time, the torque of the electric motor can be introduced flexibly as a support for the input torque without impairing driving comfort or at least reducing impairment of driving comfort.

Light vehicles are understood here as vehicles such as bicycles, cargo bikes or rickshaws. They usually include two wheels, but can also be designed with three or four wheels.

The input torque is understood here to be a load that is applied to drive the light vehicle. This is usually provided by a driver on a pedal shaft of the light vehicle.

A group transmission is understood here to mean a transmission that comprises more than one transmission group. Here the group transmission comprises a first and a second group. The first and the second group each comprise at least two gears, so that the first and the second group each have at least one gear ratio. At least the first or the second group preferably has a second gear pair, so that it has two gear ratios. The first and the second group particularly preferably have at least two transmission ratios.

A switchable shaft is understood here to be a shaft that is adjustable or has switchable elements. Here at least one gear of the first and second group is arranged on the switchable shaft. By switching the shaft or the switchable elements, a frictional connection can be established between the switchable shaft and a respective gear wheel of the first and second group. Preferably, if the first and the second group comprise more than one gear pair, a different transmission ratio of the first and / or the second group can be set by switching the switchable shaft.

An output torque is understood here to be a torque that can be output at the output of the drive system. Usually this is used to drive a chain or a belt, which in turn can set a rear wheel of the light vehicle in a rotational movement.

The drive system is preferably designed in such a way that the input torque and the output torque can be received or output coaxially. For this purpose, the gears of the first and the second group, which are not arranged on the switchable shaft, are arranged on two axially aligned shafts. These two axially aligned shafts are particularly preferably designed as hollow shafts.

The first and / or the second group preferably comprises at least three gear ratios.

Because the first and / or the second group comprises at least three gear ratios, the invention enables at least one 9-gear transmission and an advantageous gear range to be achieved by multiplying the gear ratios of the first and second group (3x3).

The first and the second group preferably comprise three gear ratios. The gear ratio bandwidth of the group transmission is particularly preferably greater than 450%.

• - das Planetengetriebe einen Steg mit zumindest zwei Umlaufrädern, ein Hohlrad und ein Sonnenrad umfasst,
• - das Planetengetriebe der ersten Gruppe des Gruppengetriebes vorgeschaltet ist und
• - das Planetengetriebe ausgebildet ist, das Eingangsdrehmoment über den Steg aufzunehmen und über das Sonnenrad an die erste Gruppe abzugeben.

Preferably, the transmission comprises a planetary gear, wherein

• - The planetary gear comprises a web with at least two planetary gears, a ring gear and a sun gear,
• - The planetary gear of the first group of the group gear is connected upstream and
• - The planetary gear is designed to absorb the input torque via the web and to deliver it to the first group via the sun gear.

Because the transmission comprises a planetary gear connected upstream of the first group and the planetary gear absorbs the input torque via the web and outputs it to the first group via the sun gear, the invention enables an input speed to be increased and the input torque to be reduced.

This is particularly advantageous since the input torque applied by a driver usually has relatively high peak torques above 200 Nm at low speeds of below 150 rpm, usually even below 100 rpm. Since gearboxes can be made smaller when peak torques are lower, it is therefore advantageous to reduce the input torque. Since electric motors, especially those with specifications such as those built into bicycles, are usually characterized by low torques at high speeds, a connection between the electric motor and the switchable shaft is also simplified, since there is a lower speed difference and thus a lower gear ratio between the electric motor and the switchable shaft is needed.

The planetary gear train preferably reduces the input torque and increases the input speed by at least a factor of 2, particularly preferably by at least a factor of 3.

The switchable shaft is preferably detachably connected to the electric motor, so that the switchable shaft can be decoupled from the electric motor.

Because the switchable shaft can be decoupled from the electric motor, the invention enables the drive unit to be operated without an electric motor and thereby preventing or at least reducing high losses as a result of the electric motor being dragged along.

The ring gear of the planetary gear is preferably secured against rotating in at least one direction of rotation.

Because the ring gear of the planetary gear is secured against rotating in at least one direction of rotation, the invention enables the input torque to be advantageously transmitted to the first group of the group gear via the sun gear.

The ring gear is preferably secured against rotation in only one direction of rotation, in order to enable freewheeling in this way. The ring gear is particularly preferably secured against rotation by a pawl and the pawl or a holder of the pawl comprises a force transducer, for example a so-called strain gauge, for measuring the input torque.

The drive system preferably comprises an electrical switching device, wherein the electrical switching device comprises a servomotor, the shaft is designed to be electrically switchable and the servomotor is designed to switch the shaft electrically via a spindle.

Because the drive system comprises an electrical switching device, the invention enables the switchable shaft to be adjusted electrically. This can increase comfort and enable automatic switching.

The light vehicle according to the invention comprises a drive system according to the invention.

Because the light vehicle according to the invention comprises a drive system according to the invention, the invention enables the transmission and electric motor to be advantageously integrated. The drive system is preferably implemented as a mid-engine, since this leads to an advantageous center of gravity.

Furthermore, the invention reduces maintenance costs compared to open transmissions and enables functions such as electrical shifting, electrically assisted shifting, automatic shifting and / or recovery of braking energy to be used.

The dependent claims describe further advantageous embodiments of the invention.

• 1 ein Ausführungsbeispiel eines Antriebssystems für ein Fahrrad,
• 2 eine schematische Darstellung eines Ausführungsbeispiels eines Antriebssystems für ein Fahrrad,
• 3 eine Schnittdarstellung eines Ausführungsbeispiels eines Antriebssystems für ein Fahrrad,
• 4 ein Ausführungsbeispiel eines Antriebssystems für ein Fahrrad mit einer Sperrklinke,
• 5 ein Ausführungsbeispiel einer elektrischen Schaltvorrichtung eines Antriebssystems für ein Fahrrad,
• 6 ein weiteres Ausführungsbeispiel einer elektrischen Schaltvorrichtung eines Antriebssystems für ein Fahrrad,
• 7 ein Ausführungsbeispiel einer Entkopplungsvorrichtung eines Antriebssystems für ein Fahrrad und
• 8 ein weiteres Ausführungsbeispiel einer Entkopplungsvorrichtung eines Antriebssystems für ein Fahrrad.

Preferred exemplary embodiments are explained in more detail with reference to the following figures. It shows

• 1 an embodiment of a drive system for a bicycle,
• 2 a schematic representation of an embodiment of a drive system for a bicycle,
• 3rd a sectional view of an embodiment of a drive system for a bicycle,
• 4th an embodiment of a drive system for a bicycle with a pawl,
• 5 an embodiment of an electrical switching device of a drive system for a bicycle,
• 6th another embodiment of an electrical switching device of a drive system for a bicycle,
• 7th an embodiment of a decoupling device of a drive system for a bicycle and
• 8th Another embodiment of a decoupling device of a drive system for a bicycle.

1 shows a drive system 1 for a bike. The drive system 1 includes a transmission 2 and an electric motor 3rd . As both gear 2 as well as an electric motor 3rd as a unit in the propulsion system 1 are integrated, the drive system 1 compact and therefore space-saving dimensions, comparable to current, more powerful e-bike mid-motors. The drive system shown here 1 is installed in a bicycle, not shown, as a mid-engine.

2 shows a schematic representation of the drive system 1 . An input torque of a rider of the bicycle is provided via a pedal shaft 20th to the gearbox 2 transfer. The input torque is made up of two torques (M in _{, L} , M in _{, R} ), a left crank seen in the direction of travel and a right crank seen in the direction of travel.

Since torques applied by a driver usually have high values, which can be greater than 200 Nm, at low speeds, usually below 100 rpm, the transmission includes a planetary gear at the input 7th . The planetary gear 7th is designed to reduce the input torque and to increase the input speed accordingly. The planetary gear 7th is a group transmission of the transmission 2 upstream, the group transmission comprising a first 4 and a second 5 group. The gear 2 further comprises a switchable shaft 6th who is trained, the first group 4th as well as the electric motor 3rd with the second group 4th connect to. The switchable shaft 6th comprises a first 23 and a second 24 actuating element, which are in the axial direction of the switchable shaft 6th are movable, and so a shifting of the transmission 2 enable.

The planetary gear 7th includes a bridge 8th with three rotating gears 9 , a ring gear 10 and a sun gear 11 . The planetary gear 7th takes the input torque via the web 8th and is there via the sun gear 11 and the first group 4th from. The planetary gear 7th has a gear ratio of about 0.3, so that the input speed is approximately tripled and the input torque is approximately three-fold.

The first group 4th is designed to be the input torque of the sun gear 11 to record. This is what the first group instructs 4th three pairs of gears 21 on, with one gear of each gear pair 21 with a first hollow shaft 22nd is connected, with which also the sun gear 11 connected is. The other gear of each pair of gears 21 is on the switchable shaft 6th arranged. There is a non-positive connection between the switchable shaft 6th and a pair of gears 21 but only if the switchable shaft 6th and a pair of gears 21 by the first actuating element 23 are positively connected.

In 2 is the first actuator 23 switched so that the switchable shaft 6th and the middle gear pair 21 are positively connected. Thus, the input torque is via the middle gear pair 21 transferred to the switchable shaft, as the two gears of each gear pair 21 are engaged with each other. The two outer gear pairs 21 rotate here without transmitting a torque as they are from the hollow shaft 20th be driven, but with the switchable shaft 6th are not positively connected.

The switchable shaft 6th is with the electric motor 3rd connected so that the switchable shaft 6th a torque of the electric motor 3rd can accommodate. To a torque of the electric motor 3rd to increase and to decrease a speed are the switchable shaft 6th and the electric motor 3rd via two pairs of gears 25th , 26th which are engaged with each other. By adjusting the torque and speed of the electric motor 3rd an adjustment to the input torque and speed is achieved, so that the input torque and Torque from the electric motor 3rd via the switchable shaft 6th to the second group 5 can be transferred.

The second group 5 is formed by the switchable shaft 6th input torque and that of the switchable shaft 6th torque absorbed by the electric motor 3rd submit. This includes the second group 5 like the first group 4th three pairs of gears 27 . One gear of each gear pair 27 is with a second hollow shaft 28 positively connected. The other gear of each gear pair 27 is on the switchable shaft 6th arranged. There is a non-positive connection between the switchable shaft 6th and a pair of gears 27 but only if the switchable shaft 6th and a pair of gears 27 by the second actuating element 24 are positively connected.

In 2 is the second actuator 24 switched so that the switchable shaft 6th and the middle gear pair 27 are positively connected. Thus, the input torque and the torque become from the electric motor 3rd via the middle pair of gears 27 on the second hollow shaft 28 transferred as the two gears of each gear pair 27 are engaged with each other. The two outer gear pairs 27 rotate here without transmitting a torque as they are from the second hollow shaft 28 be driven, but with the switchable shaft 6th are not positively connected.

The first group 4th and the second group 5 have gear ratios here, so that a spread or a deployment of 450% is achieved over nine largely evenly stepped gear steps. In other exemplary embodiments (not shown), the first 4 and second 5 groups have higher or lower folds depending on the application.

By switching the switchable shaft 6th , i.e. by axially shifting the first 23 and / or the second 24 actuating element, a transmission ratio of the first 4 and / or the second 5 group can be changed by frictionally engaging different gear pairs 21, 27 of the first 4 and / or the second 5 group the switchable shaft 6th get connected.

At the outer end of the second hollow shaft 28 is a ring gear 29 arranged frictionally, the / which serves as an output. Here this is done by the middle gear pair 27 on the second hollow shaft 28 transmitted input torque and the torque of the electric motor 3rd as output torque Mab from the ring gear 29 transmitted via a chain to a rear wheel of the bicycle. In an exemplary embodiment not shown, a belt is used instead of a chain and a belt pulley is used instead of the toothed ring 29 .

3rd shows the drive system 1 in a sectional view. The coaxial arrangement of the first 22 and the second 28 hollow shaft can be seen. The pedal shaft 20th is mounted within the first 22 and the second 28 hollow shaft.

The switchable shaft 6th is also shown, in particular an internal structure for switching the shaft 6th recognizable. Inside the switchable shaft 6th the first 23 and the second 24 actuating element are arranged to be axially displaceable. The first 23 and second 24 actuating elements are formed between a pair of gears 21 the first group 4th and a pair of gears 27 the second group and the switchable shaft 6th establish a positive connection.

To adjust the first 23 and the second 24 actuating element, i.e. to switch the switchable shaft 6th , includes the drive system 1 a first 30 and a second 31 rod. The first pole 30th is via a first gear lever 32 , the second rod 31 actuated via a second, not shown shift lever.

The ring gear 10 of the planetary gear 7th is there jetty 8th , Planetary gears 9 and sun gear 11 are movable and a torque is to be transmitted to secure against rotation. 4th shows securing of the ring gear 10 against twisting in one direction of rotation by a pawl 12th . By securing the ring gear 10 freewheeling is enabled against twisting in one direction of rotation. As an alternative to the pawl solution shown, a clamping body freewheel is also conceivable.

In addition, the recovery of braking energy is also advantageously implemented. The transmission is used to recover braking energy 2 operated in reverse. The braking energy is therefore via the ring gear 29 in the second group 5 introduced via a force fit with the switchable shaft 6th connected gear pair 27 on the switchable shaft 6th transmitted and via the gear pairs 25,26 to the electric motor 3rd which can then be used as a generator. To represent this function, however, there must be no freewheel in the power flow between the driven wheel of the vehicle and the electric motor.

A freewheel function is necessary for the driver, since otherwise the pedals would turn continuously when the vehicle is moving. This freewheel function is advantageous on the ring gear 10 implemented. Alternatively, the first actuating element would have to 23 have an additional switching position in which none of the gear pairs 21 frictionally with the switchable shaft 6th connected, adding complexity to the transmission 2 would be increased, especially with regard to a control. The freewheel, on the other hand, makes it easy to decouple the gear 2 and pedal movement implemented.

In the 4th pawl shown 12th is through a bracket 13th attached. The bracket 13th includes a strain gauge here 14th as a force transducer to record the input torque. The acquisition of the input torque using a strain gauge 14th Compared to systems for torque determination that are usually installed on e-bikes, it can be implemented more easily and is also cheaper. The recorded torque is used here to control the electric motor 3rd used.

The 5 and 6th show an electrical switching device 15th of the drive system. The electrical switching device 15th includes a servomotor 16 holding a spindle 17th actuated. That in the 1 , 2 and 3rd shown drive system 1 comprises an electrical switching device with two servomotors 16 and two spindles 17th . One of the spindles 17th operates the first gear lever 32 , via which the first actuating element 23 is moved. The other spindle 17th actuates the second shift lever, via which the second actuating element 24 is moved.

With the electrical switching device 15th electrical switching is enabled. Automatic switching can also be made possible in this way. Automatic switching using the strain gauge is used here 14th detected torque implemented by switching the switchable shaft 6th is preferably carried out when an input torque is low in the course of the revolution. In addition, the electric motor can actively apply a counter-torque to the input torque. This increases comfort and increases wear on the transmission 2 decreased.

The embodiment of the electrical switching device shown here 15th includes a preloaded, bi-directional spring assembly 18th . This has the advantage that the servomotor 16 can perform a complete movement, even if that is via the spindle 17th actuated first 23 or second 24 actuating element cannot be coupled to a corresponding gear pair 21, 27 and thus cannot perform its complete actuating movement. Due to the bidirectional spring arrangement 18th only one spring is required despite a bidirectional effect.

The switchable shaft 6th des in the 1 , 2 and 3rd shown drive system 1 is with the electric motor 3rd releasably connected. For this purpose, the drive system comprises one in the 7th and 8th shown decoupling device 40 through which the switchable shaft 6th from the electric motor 3rd can be decoupled. This has the advantage that the bike can be operated without the assistance of the electric motor 3rd can be driven. The electric motor 3rd does not have to be dragged along, so that friction losses are reduced.

The decoupling device 40 includes a knob 41 with a spiral groove 42 . The knob 41 can be rotated, but cannot be moved axially. The gear 34 of the gear pair 26th is designed to be axially displaceable. A warehouse seat 43 of the gear 34 includes a radial bolt for this purpose 44 that goes into the spiral groove 42 of the pommel 41 engages and which is also axially displaceable in a housing groove, not shown.

7th and 8th show the gear 34 in mesh with the gear 33 , a torque of the electric motor 3rd can therefore use the switchable shaft 6th be transmitted. When the knob 41 is rotated, the bolt will 44 through the spiral groove 42 set in axial movement, whereby the bearing seat 43 and with it the gear 34 be moved axially. Then are the gears 34 and 33 no longer engaged and a torque of the electric motor 3rd can no longer use the switchable shaft 6th be transmitted.

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• WO 2020/260772 A1 [0002]

Claims (10)

Drive system (1) for a light vehicle, comprising a transmission (2) and an electric motor (3), wherein - the transmission (2) comprises a group transmission with a first (4) and a second (5) group and a shaft (6), - The first group (4) is designed to absorb an input torque, - the shaft (6) is connected to the electric motor (3) in such a way that the shaft (6) can absorb a torque from the electric motor (3), - The shaft (6) is designed to connect the first group (4) and the electric motor (3) to the second group (5), so that the shaft (6) receives the input torque from the first group (4) and the torque of the electric motor (3) can be transferred to the second group (5), - The shaft (6) is designed to be switchable, so that a transmission ratio of the first (4) and / or the second (5) group can be changed by switching the shaft (6) and - The second group (5) is designed to output the input torque absorbed by the shaft (6) and the torque absorbed by the shaft (6) from the electric motor (3). Drive system (1) Claim 1 , wherein the first (4) and / or the second (5) group comprises at least three gear ratios. Drive system (1) Claim 1 or 2 - The gear (2) comprises a planetary gear (7), - the planetary gear comprises a web (8) with at least two planetary gears (9), a ring gear (10) and a sun gear (11), - the planetary gear (7) the first group (4) of the group transmission is connected upstream and - the planetary gear (7) is designed to absorb the input torque via the web (8) and to deliver it to the first group (4) via the sun gear (11). Drive system (1) according to one of the preceding claims, wherein the switchable shaft (6) is detachably connected to the electric motor (3) so that the switchable shaft (6) can be decoupled from the electric motor (3). Drive system (1) according to one of the preceding claims in connection with Claim 3 , wherein the ring gear (10) is secured against turning in at least one direction of rotation. Drive system (1) Claim 5 , wherein the ring gear (10) is secured against rotation by a pawl (12) and the pawl (12) or a holder (13) of the pawl (12) comprises a force transducer (14). Drive system (1) according to one of the preceding claims, wherein the drive system (1) comprises an electrical switching device (15), the electrical switching device (15) comprises a servomotor (16), the shaft (6) is designed to be electrically switchable and the servomotor ( 16) is designed to switch the shaft (6) electrically via a spindle (17). Drive system (1) Claim 7 , wherein the electrical switching device (15) comprises at least one pretensioned, bidirectional spring arrangement (18). Drive system (1) Claim 8 wherein the preloaded, bidirectional spring assembly (18) comprises only one spring. Light vehicle, comprising a drive system (1) according to one of the Claims 1 to 9 .

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