Planetary bottom bracket gearbox for a bicycle or e-bike

Abstract

A planetary bottom bracket gearbox for a bicycle or pedelec (1) is proposed, comprising a crankshaft (WAn) as the input and a gearbox output shaft (WAb) as the output, as well as further shafts (W1, W2, W3, W4, W5), with three planetary gear sets (RS1, RS2, RS3), and with six shift elements (B1, B2, K1, K2, K3, K4) for realizing multiple gears (G1, G2, G3, G4, G5, G6, G7, G8). Furthermore, a bicycle or pedelec (1) equipped with such a gearbox is proposed.

Description

[0001] The present invention relates to a planetary bottom bracket gear for a bicycle or pedelec, comprising a pedal crankshaft as the input and a transmission output shaft as the output, as well as additional shafts, with three planetary gear sets, and with six shifting elements for implementing multiple gears. Furthermore, the invention relates to a bicycle or pedelec with the bottom bracket gear.

[0002] For example, from the publication DE 10 2022 207 262 B3, a planetary bottom bracket gear for a bicycle or pedelec is known. The bottom bracket gear has a pedal crankshaft as the input and a transmission output shaft as the output, as well as at least five additional shafts, wherein the output is preferably via a chain wheel, a belt wheel, or the like. Furthermore, the bottom bracket gear comprises three planetary gear sets arranged coaxially to the pedal crankshaft and six shifting elements for implementing at least eight gears in the bottom bracket gear. Furthermore, a first sub-transmission with a first planetary gear set is provided, wherein a first shifting element and a fourth shifting element are assigned to the first sub-transmission.Furthermore, a second sub-transmission with a second planetary gear set and a third planetary gear set is provided as a positive planetary gear set, wherein a second shifting element, a third shifting element, a fifth shifting element, and a sixth shifting element are assigned to the second sub-transmission. To interlock the first planetary gear set, two elements of the first planetary gear set can be connected to one another via the fourth shifting element.

[0003] DE 10 2022 203 241 B3 describes a bottom bracket gear in planetary design for bicycles or pedelecs with at least four shafts and at least three planetary gear sets as well as several shifting elements for realizing at least six gears.

[0004] DE 10 2022 206 685 B3 describes a bottom bracket gear in planetary design for bicycles or pedelecs with at least five shafts and three planetary gear sets as well as several shifting elements for the realization of at least six gears.

[0005] DE 10 2016 225 165 A1 describes a bicycle transmission with a manual transmission, an electric motor, and a downstream superposition gear. The electric motor and the manual transmission output shaft are each operatively connected to different elements of the superposition gear.

[0006] The present invention is based on the object of proposing a bottom bracket gear and a bicycle or pedelec with the bottom bracket gear, which have the lowest possible construction effort with improved properties compared to the prior art.

[0007] This object is achieved according to the invention by the subject matter having the features of patent claims 1 and 12, respectively. Advantageous and claimed developments emerge from the subclaims and the description as well as the drawings.

[0008] Thus, a planetary bottom bracket gear for a bicycle or pedelec is proposed. The bottom bracket gear comprises a crankshaft as the input and a transmission output shaft as the output, as well as additional shafts, with the output preferably being provided via a sprocket, a belt pulley, or the like. Furthermore, the bottom bracket gear comprises three planetary gear sets and six shifting elements for implementing, for example, eight gears in the proposed bottom bracket gear.In order to achieve a particularly effective and space-saving design for the bottom bracket transmission, it is provided that the pedal crankshaft is connected to a second element of a second planetary gear set, that the transmission output shaft can be connected to a second element of the third planetary gear set via a fifth switching element, that the transmission output shaft can be connected to a first element of the second planetary gear set and to a first element of a third planetary gear set via a sixth switching element, that a second element of a first planetary gear set is connected to a third element of the second planetary gear set, that a first element of the first planetary gear set is connected to a housing orcan be fixed to any stationary component and can be connected to the second element of the second planetary gear set and to the pedal crankshaft via a third switching element, that a third element of the first planetary gear set can be fixed to the housing via a second switching element and can be connected to the second element of the third planetary gear set via a fourth switching element, and that a third element of the third planetary gear set is fixed to the housing.

[0009] In this way, the above-described connection for the proposed bottom bracket gear system, with only three planetary gear sets and only six shifting elements, achieves a particularly simple and compact design for the bottom bracket gear system. In addition, the geometric gear ratios of the bottom bracket gear system result in particularly low component loads and an advantageously high gear efficiency.

[0010] For the mechanical connection of elements, for example rotating elements or the like of the planetary gear sets, in addition to the input and output, further shafts or shaft-like elements are preferably used, whereby the term shaft does not exclusively refer to a cylindrical, rotatably mounted machine element for transmitting torque, but rather also to general connecting elements that connect the individual gear set elements to one another for torque transmission.

[0011] In the bottom bracket transmission, the pedal crankshaft is connected to the second element of the second planetary gear set, wherein the transmission output shaft is connectable to the second element of the third planetary gear set via a fifth shaft when the fifth shifting element is locked, wherein the transmission output shaft is connectable to the first element of the second planetary gear set and to the first element of the third planetary gear set via a fourth shaft when the sixth shifting element is engaged, wherein the first element of the second planetary gear set is fixedly connected to the first element of the third planetary gear set via the fourth shaft, wherein the second element of the first planetary gear set is fixedly connected to the third element of the second planetary gear set via a third shaft,wherein the first element of the first planetary gear set is fixable to the housing via a first shaft when the first shifting element is closed and is connectable to the second element of the second planetary gear set and to the pedal crankshaft when the third shifting element is locked, wherein the third element of the first planetary gear set is fixable to the housing via a second shaft when the second shifting element is closed and is connectable to the second element of the third planetary gear set via the fifth shaft when the fourth shifting element is locked, and wherein the third element of the third planetary gear set is fixed to the housing via a fixed housing connection.

[0012] Within the scope of the present invention, the proposed bottom bracket transmission provides that the provided shifting elements can be designed as brakes, clutches, and / or freewheels. An advantageous embodiment of the invention provides that the first shifting element and the second shifting element are each designed as a positive-locking brake, that the third shifting element, the fourth shifting element, and the fifth shifting element are each designed as a freewheel, and that the sixth shifting element is designed as a positive-locking clutch.

[0013] The switching elements designed as brakes and clutches are preferably designed as positive-locking switching elements, for example as cost-effective brake or switching claws or the like, for example with a toothed brake ring and a corresponding switching pawl. Brakes as switching elements have the advantage that they are easily accessible for operation from the outside. In the case of clutches designed as freewheels, it is advantageous if the brakes are designed, for example, as one-way brakes in order to prevent the gear from jamming when the direction of rotation at the input or output is reversed. Freewheels that cannot be actively switched or actuated are preferably used as freewheels. This has the advantage that no switching operation is required for the passive switching elements. The non-actuable freewheel transmits a torque when it is locked in the blocking direction.No torque is transmitted in the opposite direction of rotation, as the freewheel does not lock in the overrunning drive state. However, it is conceivable that actively switchable freewheels or actively switchable freewheel brakes could also be used.

[0014] A preferred embodiment of the invention can provide for at least one of the planetary gear sets to be designed as a negative planetary gear set, resulting in a particularly space-efficient arrangement. It is also conceivable for one of the planetary gear sets to be designed as a positive planetary gear set.

[0015] A negative planetary gear set can preferably be converted into a positive planetary gear set if the planet carrier and ring gear connections on this gear set are swapped and the amount of the stationary gear ratio is increased by 1. A negative planetary gear set has rotatably mounted planet gears on its planet carrier, which mesh with the sun gear and the ring gear of this planetary gear set, so that the ring gear rotates in the opposite direction to the sun gear rotation when the planet carrier is held stationary and the sun gear is rotating.A plus planetary gear set has inner and outer planetary gears that are rotatably mounted on its planetary gear carrier and mesh with one another, with the sun gear of this planetary gear set meshing with the inner planetary gears and the ring gear of this planetary gear set meshing with the outer planetary gears, so that the ring gear rotates in the same direction of rotation as the sun gear when the planetary gear carrier is held stationary and the sun gear is rotating.

[0016] For those skilled in the art, this means that in the case of single gear sets designed as a negative planetary gear set, a first element or gear set element is designed as a sun gear, a second element as a planetary gear carrier or web, and a third element as a ring gear. Furthermore, this means that in a single gear set designed as a positive planetary gear set, the first element is designed as a sun gear, the second element as a ring gear, and the third element as a planetary gear carrier or web.

[0017] Furthermore, with the proposed bottom bracket gear, it is conceivable for stepped planetary gears to be used in both a negative planetary gear set and a positive planetary gear set. In a negative stepped planetary gear set, the assignment of the elements or gear set elements remains the same as in a conventional negative planetary gear set. In a positive stepped planetary gear set, it is provided that the first element is designed as the first sun gear, the second element as the second sun gear, and the third element as the planet gear carrier, or that the first element is designed as the first ring gear, the second element as the second ring gear, and the third element as the planet gear carrier.

[0018] In order to further optimize the control of the proposed bottom bracket gear, it is provided that at least one torque sensor or the like is provided on the drive and / or on the output.

[0019] To electrically assist the drive in the proposed bottom bracket transmission, at least one electric motor or the like can be connected or connectable to the drive or to the pedal crankshaft or transmission input shaft and / or to the output or to the transmission output shaft, or can be permanently or detachably coupled. Preferably, the electric motor can be arranged axially parallel to the pedal crankshaft or transmission input shaft, while the planetary gear sets are arranged coaxially to the pedal crankshaft or transmission input shaft.

[0020] A further aspect of the present invention claims a bicycle or pedelec with the above-described bottom bracket gear. This results in the advantages already described and further advantages.

[0021] The present invention is further explained below with reference to the drawings. Fig. 1 a schematic principle view of a bottom bracket gear according to the invention with three planetary gear sets, each designed as a minus planetary gear set, on a bicycle or a pedelec; Fig. 2 a shifting diagram with eight switchable gears of the bottom bracket gearbox; Fig. 3 a schematic principle view of a planetary gear set as a minus planetary gear set; Fig. 4 a schematic principle view of a planetary gear set as a plus planetary gear set; Fig. 5 a schematic principle view of a planetary gear set as a minus-step planetary gear set; Fig. 6 a schematic principle view of a planetary gear set as a plus-stepped planetary gear set with two sun gears; Fig. 7 a schematic principle view of a planetary gear set as a plus-stepped planetary gear set with two ring gears; Fig. 8 a schematic diagram of the bottom bracket gear according to Fig. 1 with an exemplary torque sensor on the drive; Fig. 9 a schematic diagram of the bottom bracket gear according to Fig. 8 with an electric machine arranged on the drive as an example; Fig. 10 a schematic principle view of the bottom bracket gear according to Fig. 8 with an electric machine arranged at the output as an example; and Fig. 11 a schematic diagram of the bottom bracket gear according to Fig. 8 with a freewheel provided between the pedal crankshaft and the gearbox input shaft.

[0022] In the Fig. 1 to 11 show various design variants and embodiments or a circuit diagram of a planetary gear system according to the invention merely by way of example. Fig. 1 shows an example of a bicycle or pedelec 1 with the bottom bracket gear, only schematically indicated.

[0023] The bottom bracket gear is shown in a housing or bottom bracket shell 2 with a pedal crankshaft or pedal crank with pedals, wherein the pedal crankshaft WAn is connected to the gear input of the bottom bracket gear. Furthermore, the bottom bracket gear comprises a gear output shaft WAb as the output with a chain or belt pulley (not shown in detail). The bottom bracket gear comprises a first planetary gear set RS1 and a second planetary gear set RS2 as well as a third planetary gear set RS3, to which a first shifting element B1, a second shifting element B2, a third shifting element K1, a fourth shifting element K2, a fifth shifting element K3, and a sixth shifting element K4 are assigned.

[0024] Regardless of the respective design variants, the bottom bracket transmission is provided with the pedal crankshaft WAn being connected to a second element of a second planetary gear set RS2, with the transmission output shaft WAb being connectable to a second element of the third planetary gear set RS3 via a fifth shifting element K3, with the transmission output shaft WAb being connectable to a first element of the second planetary gear set RS2 and to a first element of a third planetary gear set RS3 via a sixth shifting element K4, with a second element of a first planetary gear set RS1 being fixedly connected to a third element of the second planetary gear set RS2, with a first element of the first planetary gear set RS1 being fixable to a housing 2 via a first shifting element B1 and being connectable to the second element of the second planetary gear set RS2 and to the pedal crankshaft WAn via a third shifting element K1,that a third element of the first planetary gear set RS1 can be fixed to the housing 2 via a second switching element B2 and can be connected to the second element of the third planetary gear set RS3 via a fourth switching element K2, and that a third element of the third planetary gear set RS3 is fixed to the housing 2.,

[0025] In the Fig. 1 and 8 to 11, the three proposed planetary gear sets RS1, RS2, and RS3 are each designed as space-saving negative planetary gear sets. The first element of the planetary gear sets RS1, RS2, and RS3 is a sun gear SR1, SR2, and SR3, the second element is a carrier or planetary gear carrier PT1, PT2, and PT3, and the third element is a ring gear HR1, HR2, and HR3.

[0026] In Fig. 1, the bottom bracket transmission is provided in detail such that the pedal crankshaft WAn is connected to the planetary gear carrier PT2 of the second planetary gear set RS2, that the transmission output shaft WAb is connectable to the planetary gear carrier PT3 of the third planetary gear set RS3 via a fifth shaft W5 when the fifth shifting element K3 is locked, that the transmission output shaft WAb is connectable to the sun gear SR2 of the second planetary gear set RS2 and to the sun gear SR3 of the third planetary gear set RS3 via a fourth shaft W4 when the sixth shifting element K4 is engaged, that the sun gear SR2 of the second planetary gear set RS2 is fixedly connected to the sun gear SR3 of the third planetary gear set RS3 via the fourth shaft W4, that the planetary gear carrier PT1 of the first planetary gear set RS1 is fixedly connected to the ring gear HR2 of the second planetary gear set RS2 via a third shaft W3,that the sun gear SR1 of the first planetary gear set RS1 can be fixed to the housing 2 via a first shaft W1 when the first shifting element B1 is closed and can be connected to the planetary gear carrier PT2 of the second planetary gear set RS2 and to the pedal crankshaft WAn when the third shifting element K1 is locked; that the ring gear HR1 of the first planetary gear set RS1 can be fixed to the housing 2 via a second shaft W2 when the second shifting element B2 is closed and can be connected to the planetary gear carrier PT3 of the third planetary gear set RS3 via the fifth shaft W5 when the fourth shifting element K2 is locked; and that the ring gear SR3 of the third planetary gear set RS3 is fixed to the housing 2 via a fixed housing connection W0.

[0027] In Fig. Figure 2 shows a shift diagram for the bottom bracket gear train as an eight-speed transmission, so that a total of eight gears G1, G2, G3, G4, G5, G6, G7, G8 are implemented. The shift diagram shows the shift elements B1, B2, K1, K2, K3, K4 used for the respective gear G1, G2, G3, G4, G5, G6, G7, G8. An X for the freewheels K1, K2, K3 as shift elements in the shift diagram means that the freewheels K1, K2, K3 are locked. This works automatically without external activation. Furthermore, an X for a brake B1, B2 and a clutch K4 as a shift element in the shift diagram means that the brake B1, B2 and the clutch K4 are closed. This works via a suitable actuator.

[0028] In detail, the circuit diagram according to Fig. 2, that to realize or shift a first gear G1, the third shifting element K1, designed as a freewheel, the fourth shifting element K2, designed as a freewheel, and the fifth shifting element K3, designed as a freewheel, are locked; that to realize a second gear G2, the first shifting element B1, designed as a brake, is closed, and the fourth shifting element K2, designed as a freewheel, and the fifth shifting element K3, designed as a freewheel, are locked; that to realize a third gear G3, the second shifting element B2, designed as a brake, is closed, and the third shifting element K1, designed as a freewheel, and the fifth shifting element K3, designed as a freewheel, are locked; that to realize a fourth gear G4, the first shifting element B1, designed as a brake, and the second shifting element B2, designed as a brake, are closed, and the fifth shifting element K3, designed as a freewheel, is locked;that to achieve a fifth gear G5, the third switching element K1, designed as a freewheel, and the fourth switching element K2, designed as a freewheel, are locked and the sixth switching element K4, designed as a clutch, is closed; that to achieve a sixth gear G6, the first switching element B1, designed as a brake, is closed, the fourth switching element K2, designed as a freewheel, is locked and the sixth switching element K4, designed as a clutch, is closed; that to achieve a seventh gear G7, the second switching element B2, designed as a brake, is closed, the third switching element K1, designed as a freewheel, is locked and the sixth switching element K4, designed as a clutch, is closed;and / or that to realize an eighth gear G8, the first switching element B1 designed as a brake and the second switching element B2 designed as a brake are closed and the sixth switching element K4 designed as a clutch is closed.,

[0029] In Fig. 3 shows an example of a minus planetary gear set in which the first element is designed as a sun gear 1-SR, the second element as a planet gear carrier 2-PT and the third element as a ring gear 3-HR.

[0030] In Fig. 4 shows an example of a plus planetary gear set in which the first element is designed as a sun gear 1-SR, the second element as a ring gear 2-HR and the third element as a planet gear carrier 3-PT.

[0031] In Fig. 5 shows an example of a minus-stepped planetary gear set in which the first element is designed as a sun gear 1-SR, the second element as a planet gear carrier 2-PT and the third element as a ring gear 3-HR.

[0032] In Fig. 6 shows an example of a plus-stepped planetary gear set in which the first element is designed as the first sun gear 1-SRA, the second element as the second sun gear 2-SRB and the third element as the planet gear carrier 3-PT.

[0033] In Fig. 7 shows an example of a further embodiment of a plus-stepped planetary gear set, in which the first element is designed as a first ring gear 1-HRA, the second element as a second ring gear 2-HRB and the third element as a planet gear carrier 3-PT.

[0034] The Fig. The possible designs shown in Figures 3 to 7 using a planetary gear set can be implemented on the specific planetary gear sets RS1, RS2, RS3 of the bottom bracket gear according to the invention.

[0035] In Fig. 8 is an embodiment of the bottom bracket gear according to the invention based on Fig. 1, in which a torque sensor 3 is connected or connectable to the pedal crankshaft or to the transmission input shaft WAn. For example, a disk-shaped torque sensor 3 can be arranged at the transmission input. However, the torque sensor 3 can also be designed in a different way.

[0036] In the Fig. 9 and Fig. 10 is an embodiment of the bottom bracket gear according to the invention based on Fig. 8 with an additional electric machine EM. The electric machine EM can be connected to the pedal crankshaft WAn, as shown in Fig. 9. It is also conceivable that the electric machine EM is connected to the transmission output shaft WAb, as shown in Fig. 10. The electric machine EM is preferably arranged axially parallel to the pedal crankshaft or transmission input shaft WAn. However, a coaxial arrangement of the electric machine EM to the pedal crankshaft would also be possible. Irrespective of this, it is advantageous to connect the electric machine EM via a freewheel F0 or similar device so that, when operating without the electric machine EM, no losses are caused by the co-rotating electric machine EM.

[0037] In Fig. 11 is an embodiment of the bottom bracket gear according to the invention based on Fig.8 is shown with an additional freewheel F1 between the pedal crank and the input of the bottom bracket gear. This allows the freewheel to open when pedaling is interrupted, decoupling the pedal crank from the inertial masses of the gear set and, in particular, the electric motor EM, so that no inertial forces are felt at the pedal. Reference symbol 1 bicycle or pedelec 2 Housing or bottom bracket shell 3 Torque sensor EM electric machine F0 Freewheel for electric machine F1 additional freewheel SR1 sun gear of the first planetary gear set PT1 planetary gear carrier of the first planetary gear set HR1 ring gear of the first planetary gear set SR2 sun gear of the second planetary gear set PT2 planetary gear carrier of the second planetary gear set HR2 ring gear of the second planetary gear set SR3 sun gear of the third planetary gear set PT3 planetary gear carrier of the third planetary gear set HR3 ring gear of the third planetary gear set RS1 first planetary gear set RS2 second planetary gear set RS3 third planetary gear set WAn gearbox input shaft or crankshaft WAB gearbox output shaft W1 first wave W2 second wave W3 third wave W4 fourth wave W5 fifth wave W0 fixed housing connection G1 first gear of the bottom bracket gearbox G2 second gear of the bottom bracket gearbox G3 third gear of the bottom bracket gearbox G4 fourth gear of the bottom bracket gearbox G5 fifth gear of the bottom bracket gearbox G6 sixth gear of the bottom bracket gearbox G7 seventh gear of the bottom bracket gearbox G8 eighth gear of the bottom bracket gearbox B1 first switching element designed as a brake B2 second switching element designed as a brake K1 third switching element designed as a freewheel K2 fourth switching element designed as a freewheel K3 fifth switching element designed as a freewheel K4 sixth switching element designed as a clutch 1-SR first element as sun gear 2-PT second element as planetary gear carrier 2-HR second element as ring gear 3-HR third element as ring gear 3-PT third element as planetary gear carrier 1-SRA first element as first sun gear 2-SRB second element as second sun gear 1-HRA first element as first ring gear 2-HRB first element as second ring gear

Claims

[1] Bottom bracket gear in planetary design for a bicycle or a pedelec (1), with a pedal crankshaft (WAn) as input and a gearbox output shaft (WAb) as output and further shafts (W1, W2, W3, W4, W5), with three planetary gear sets (RS1, RS2, RS3), and with six switching elements (B1, B2, K1, K2, K3, K4) for realizing several gears (G1, G2, G3, G4, G5, G6, G7, G8), characterized by that the pedal crankshaft (WAn) is connected to a second element of a second planetary gear set (RS2), that the transmission output shaft (WAb) can be connected to a second element of a third planetary gear set (RS3) via a fifth switching element (K3), that the transmission output shaft (WAb) can be connected via a sixth shift element (K4) to a first element of the second planetary gear set (RS2) and to a first element of the third planetary gear set (RS3), that a second element of a first planetary gear set (RS1) is connected to a third element of the second planetary gear set (RS2), that a first element of the first planetary gear set (RS1) can be fixed to a housing (2) via a first switching element (B1) and can be connected to the second element of the second planetary gear set (RS2) and to the pedal crankshaft (WAn) via a third switching element (K1), that a third element of the first planetary gear set (RS1) can be fixed to the housing (2) via a second switching element (B2) and can be connected to the second element of the third planetary gear set (RS3) via a fourth switching element (K2), and that a third element of the third planetary gear set (RS3) is fixed to the housing (2) via a fixed housing connection. [2] Bottom bracket gear according to claim 1, characterized bythat the pedal crankshaft (WAn) is connected to the second element of the second planetary gear set (RS2), that the transmission output shaft (WAb) can be connected to the second element of the third planetary gear set (RS3) via a fifth shaft (W5) when the fifth shift element (K3) is locked, that the transmission output shaft (WAb) can be connected to the first element of the second planetary gear set (RS2) and to the first element of the third planetary gear set (RS3) via a fourth shaft (W4) when the sixth shift element (K4) is closed, that the first element of the second planetary gear set (RS2) is firmly connected to the first element of the third planetary gear set (RS3) via the fourth shaft (W4), that the second element of the first planetary gear set (RS1) is fixedly connected to the third element of the second planetary gear set (RS2) via a third shaft (W3), that the first element of the first planetary gear set (RS1) can be fixed to the housing (2) via a first shaft (W1) when the first switching element (B1) is closed and can be connected to the second element of the second planetary gear set (RS2) and to the pedal crankshaft (WAn) when the third switching element (K1) is locked, that the third element of the first planetary gear set (RS1) can be fixed to the housing (2) via a second shaft (W2) when the second shifting element (B2) is closed and can be connected to the second element of the third planetary gear set (RS3) via the fifth shaft (W5) when the fourth shifting element (K2) is locked, and that the third element of the third planetary gear set (RS3) is fixed to the housing (2) via a fixed housing connection (W0). [3] Bottom bracket gear according to one of the preceding claims, characterized bythat the first switching element (B1) and the second switching element (B2) are each designed as a positive-locking brake, that the third switching element (K1), the fourth switching element (K2) and the fifth switching element (K3) are each designed as a freewheel and / or the sixth switching element (K4) is designed as a positive-locking clutch. [4] Bottom bracket gear according to one of the preceding claims, characterized by that the first planetary gear set (RS1) and / or the second planetary gear set (RS2) and / or the third planetary gear set (RS3) is designed as a minus planetary gear set. [5] Bottom bracket gear according to claim 4, characterized by that in a minus planetary gear set the first element is designed as a sun gear (SR1, SR2, SR3), the second element as a planet gear carrier (PT1, PT2, PT3) and the third element as a ring gear (HR1, HR2, HR3). [6] Bottom bracket gear according to one of the preceding claims, characterized bythat the first planetary gear set (RS1) and / or the second planetary gear set (RS2) and / or the third planetary gear set (RS3) is designed as a plus planetary gear set. [7] Bottom bracket gear according to claim 6, characterized by that in a plus planetary gear set the first element is designed as a sun gear (SR1, SR2, SR3), the second element as a ring gear (HR1, HR2, HR3) and the third element as a planet gear carrier (PT1, PT2, PT3). [8] Bottom bracket gear according to one of the preceding claims, characterized by that a torque sensor (3) is connected to the pedal crankshaft (WAn). [9] Bottom bracket gear according to one of the preceding claims, characterized by that at least one electrical machine (EM) is connected or connectable to the pedal crankshaft (WAn) or to the transmission output shaft (WAb). [10] Bottom bracket gear according to claim 9, characterized by that the electric machine (EM) is arranged axially parallel to the pedal crankshaft (WAn). [11] Bottom bracket gear according to one of the preceding claims, characterized by that in order to realize a first gear (G1), the third switching element (K1) designed as a freewheel, the fourth switching element (K2) designed as a freewheel and the fifth switching element (K3) designed as a freewheel are locked, that to realize a second gear (G2), the first switching element (B1) designed as a brake is closed and the fourth switching element (K2) designed as a freewheel and the fifth switching element (K3) designed as a freewheel are locked, that to realize a third gear (G3), the second switching element (B2) designed as a brake is closed and the third switching element (K1) designed as a freewheel and the fifth switching element (K3) designed as a freewheel are locked, that to realize a fourth gear (G4), the first switching element (B1) designed as a brake and the second switching element (B2) designed as a brake are closed and the fifth switching element (K3) designed as a freewheel is locked, that to realize a fifth gear (G5), the third switching element (K1) designed as a freewheel and the fourth switching element (K2) designed as a freewheel are locked and the sixth switching element (K4) designed as a clutch is closed, that to realize a sixth gear (G6), the first switching element (B1) designed as a brake is closed and the fourth switching element (K2) designed as a freewheel is locked and the sixth switching element (K4) designed as a clutch is closed, that to realize a seventh gear (G7), the second switching element (B2) designed as a brake is closed and the third switching element (K1) designed as a freewheel is locked and the sixth switching element (K4) designed as a clutch is closed, and / or that in order to realize an eighth gear (G8), the first switching element (B1) designed as a brake and the second switching element (B2) designed as a brake are closed and the sixth switching element (K4) designed as a clutch is closed. [12] Bicycle or pedelec (1) with the bottom bracket gear according to one of the preceding claims.

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