Bottom bracket gear for a bicycle, hybrid gear, bottom bracket and bicycle

Abstract

Bottom bracket gear for a bicycle, characterized by a manual transmission (1), a manual transmission input shaft (2) and a manual transmission output shaft (3), wherein the manual transmission (1) has a first planetary gear set (PS1) designed as a minus planetary gear set and a second planetary gear set (PS2) designed as a plus planetary gear set, wherein one element of the first planetary gear set (PS1) is permanently connected in a rotationally fixed manner to the manual transmission input shaft (2) and another element of the first planetary gear set (PS1) is permanently connected in a rotationally fixed manner to the manual transmission output shaft (3), and one element of the second planetary gear set is permanently connected in a rotationally fixed manner to the manual transmission output shaft (3).

Description

[0001] The invention relates to a bottom bracket gear for a bicycle. Furthermore, the invention relates to a hybrid transmission with such a bottom bracket gear. Furthermore, the invention relates to a bottom bracket with the bottom bracket gear or the hybrid transmission, and to a bicycle with the bottom bracket gear or the hybrid transmission or the bottom bracket.

[0002] A variety of bottom bracket gears are known from the state of the art for use in bicycles. For example, US 2011 177 911 A1 discloses a bottom bracket gear featuring three planetary gears connected in series. The planetary gears are designed to provide high-speed gearing. The gear is a 12-speed bottom bracket gear, but it has a total of seven planetary gear planes, including numerous stepped planetary gears. This means that the construction of the bottom bracket gear is very complex.

[0003] DE 11 2004 000 779 B4 discloses a bicycle drive which has two independently rotatable, coaxially arranged drive shafts, each with its own freewheels, which are connected to a ring gear and chain wheel via a planetary gear.

[0004] DE 10 2010 004 552 A1 discloses a drive device for a bicycle, wherein the device comprises a pedal crankshaft which can be connected to at least three planetary gear sets via a plurality of switchable clutches, wherein a common switching element enables engagement of individual or combined gear stages which are coupled to a chainring or an electric machine.

[0005] DE 11 2010 002 286 T5 discloses a multi-stage transmission comprising a fixed center shaft, a coaxially arranged rotatable input element and a hub, several planetary gear pairs, and a transmission shaft with clutch assemblies for selecting different gear ratios by changing the direction of rotation.

[0006] WO 2012 / 093 214 A2 discloses a transmission for bicycles, which comprises several coaxially arranged planetary gear sets with planetary gears of different sizes that are rotatably mounted, as well as a switching and selection module with a rotating actuator and cam for the targeted selection of the gear ratios by shifting the planetary gears.

[0007] DE 20 2007 002 366 U1 discloses a transmission for a bicycle having two differently designed sun gears or ring gears with rotationally fixed coupled planetary gear pairs on a common planetary carrier, which serves as drive or output, wherein the drive can be combined with a high-speed electric motor.

[0008] The object of the invention is therefore to provide a bottom bracket gear for a bicycle which has a reduced construction cost.

[0009] This object is achieved by a bottom bracket transmission characterized by a manual transmission, a manual transmission input shaft, and a manual transmission output shaft. The manual transmission has a first planetary gear set designed as a negative planetary gear set and a second planetary gear set designed as a positive planetary gear set. One element of the first planetary gear set is connected in a rotationally fixed manner to the manual transmission input shaft, another element of the first planetary gear set is connected in a rotationally fixed manner to the manual transmission output shaft, and one element of the second planetary gear set is connected in a rotationally fixed manner to the manual transmission output shaft. Furthermore, this object is achieved by the further subject matter having the features of the further independent patent claims. Advantageous developments emerge from the subclaims.

[0010] The bottom bracket gear according to the invention has the advantage of being simple in design and thus requiring little construction effort. This is because the gearshift mechanism has a small number of planetary gear sets, in particular exactly two. Furthermore, construction effort is reduced because no stepped planetary gears are required. However, the bottom bracket gear can still provide multiple gears. Thus, with the two planetary gear sets and at least four, in particular exactly four, shifting elements, it is possible to achieve exactly four gears, in particular with constant gear ratios. The bottom bracket gear also has good efficiency and a low stationary gear ratio. The bottom bracket gear is designed such that the gear series is particularly well-suited for bicycle applications, in particular with a range group described in more detail below, such as a primary gear or secondary gear.

[0011] A shaft is not exclusively understood as a cylindrical, rotatably mounted machine element for transmitting torque. Rather, it also includes general connecting elements that connect individual components together, particularly connecting elements that connect multiple components in a rotationally fixed manner.

[0012] A minus planetary gear set corresponds to a planetary gear set with a carrier on which the planet gears are rotatably mounted, with a sun gear and with a ring gear, wherein the toothing of at least one of the planet gears meshes with both the toothing of the sun gear and the toothing of the ring gear, whereby the ring gear and the sun gear rotate in opposite directions of rotation when the sun gear rotates with the carrier stationary.

[0013] In contrast, a positive planetary gear set differs from a negative planetary gear set in that the positive planetary gear set has inner and outer planetary gears that are rotatably mounted on the carrier. The teeth of the inner planetary gears mesh with the teeth of the sun gear and the teeth of the outer planetary gears. The teeth of the outer planetary gears also mesh with the teeth of the ring gear. This means that when the carrier is stationary, the ring gear and the sun gear rotate in the same direction.

[0014] In a particular embodiment, the element of the first planetary gear set can be a carrier and the other element of the first planetary gear set can be a ring gear. The element of the second planetary gear set can be a sun gear. In particular, an embodiment is advantageous in which the manual transmission has a first shaft and a second shaft. The first planetary gear set can have the ring gear, which is rotationally fixedly connected to the manual transmission output shaft, a carrier, which is rotationally fixedly connected to the manual transmission input shaft, and a sun gear, which is rotationally fixedly connected to the first shaft. The second planetary gear set can have a ring gear, which is rotationally fixedly connected to the first shaft, a carrier, which is rotationally fixedly connected to a transmission housing, and the sun gear, which is rotationally fixedly connected to the manual transmission output shaft.

[0015] The gear housing can be part of the bottom bracket shell, i.e., it can be constructed in one piece with the bottom bracket shell. Alternatively, the gear housing can be a separate housing from the bottom bracket shell that can be inserted into a cavity in the bottom bracket shell. The gear housing can be designed and arranged such that it does not rotate during operation of the gear.

[0016] The first shaft can be connected in a rotationally fixed manner to the carrier of the first planetary gear set by means of a first shifting element, to the second shaft by means of a second shifting element, and can be connected in a rotationally fixed manner to the transmission housing by means of a fourth shifting element. The second shaft can be connected in a rotationally fixed manner to the carrier of the first planetary gear set by means of a third shifting element. As a result, a simply constructed bottom bracket transmission with a multitude of gears can be realized.

[0017] The first gear of a manual transmission can be a direct gear, i.e., a gear with a ratio of 1. The other three gears can be a fast gear, so that the ratio is less than 1.

[0018] The switching elements can be arranged in such a way that they are easily accessible to an actuator by means of which the respective switching element can be actuated. In particular, the switching elements can be easily accessible from the outside. It is particularly advantageous if the switching elements are arranged and designed in such a way that they can be actuated by a single actuator. The actuator can actuate a single switching element or several switching elements simultaneously. The actuator can have a switching drum.

[0019] The first switching element can be implemented as a freewheel, which offers the advantage that no actuator is required for the switching element. Furthermore, the first switching element can be designed to be small, as it only needs to provide low support torques. Alternatively, the first switching element can be implemented as a clutch, in particular a switchable clutch. The second and third switching elements can be designed as clutches, in particular switchable clutches. The fourth switching element can be designed as a brake.

[0020] The manual transmission input shaft can be connected in a rotationally fixed manner to a bottom bracket crankshaft that is not part of the transmission. Alternatively, a pre-gearbox can be connected upstream of the manual transmission, whereby at least one, in particular at least two or exactly two, gears can be realized by means of the pre-gearbox. A first gear of the pre-gearbox can be a direct gear. A second gear of the pre-gearbox can provide a high-speed transmission. As a result, the manual transmission and the pre-gearbox can provide an eight-speed transmission.

[0021] The primary transmission can have at least one, in particular precisely a single, third planetary gear set that is operatively connected to the manual transmission input shaft. In particular, a carrier of the third planetary gear set can be rotationally fixedly connected to the bottom bracket crankshaft, and / or a sun gear of the third planetary gear set can be rotationally fixedly connected to the manual transmission input shaft, and / or a ring gear of the third planetary gear set can be rotationally fixedly connected to the transmission housing by means of a fifth shifting element. The fifth shifting element can be designed as a brake.

[0022] Furthermore, two elements of the third planetary gear set can be connected to one another in a rotationally fixed manner by means of a sixth shifting element. It is particularly advantageous if the ring gear and the sun gear of the third planetary gear set can be connected to one another in a rotationally fixed manner by means of the sixth shifting element, since this design results in the lowest support torques. Alternatively, it is possible for the ring gear and the carrier, or the carrier and the sun gear, to be connected to one another in a rotationally fixed manner by means of the sixth shifting element. The sixth shifting element can be designed as a freewheel or as a clutch, in particular a switchable clutch.

[0023] The design with a primary gearbox and manual transmission has the advantage that eight gears can be achieved with just three planetary gear sets. A transmission designed this way also has a short overall length, which is advantageous since the available installation space in bottom brackets is limited. The stationary gear ratios of the planetary gear sets are also selected to allow for a small diameter for the planetary gear components. A further advantage is that, even with the primary gearbox, no stepped planetary gears need to be used in the bottom bracket transmission, which is advantageous in terms of construction effort. The result is a simply constructed eight-speed group transmission.

[0024] In a special embodiment, a secondary transmission can be connected downstream of the manual transmission, whereby at least one, in particular at least two or exactly two, gears can be realized by means of the secondary transmission. A first gear of the secondary transmission can be a direct gear. A second gear of the secondary transmission can be a high-speed gear ratio, so that the ratio has a value less than 1. As a result, an eight-speed transmission can be provided by the manual transmission and the secondary transmission.

[0025] The rear-mounted transmission can have a fourth planetary gear set, in particular a single one, that is operatively connected to the manual transmission output shaft. In particular, a sun gear of the fourth planetary gear set can be rotationally fixedly connected to a rear-mounted transmission output shaft, and / or a carrier of the fourth planetary gear set can be rotationally fixedly connected to the manual transmission output shaft, and / or a ring gear of the fourth planetary gear set can be rotationally fixedly connected to the transmission housing by means of a seventh shifting element. The seventh shifting element can be designed as a brake.

[0026] The rear-mounted transmission can have an eighth shifting element by means of which two elements of the fourth planetary gear set can be connected to one another in a rotationally fixed manner. In particular, the eighth shifting element can be arranged such that the sun gear and the ring gear, or the sun gear and the carrier, or the ring gear and the carrier can be connected to one another in a rotationally fixed manner by means of the eighth shifting element. It is particularly advantageous if the eighth shifting element is arranged such that the ring gear and the sun gear can be connected to one another in a rotationally fixed manner, because the lowest support torques occur in this design. In order to achieve blocking of the fourth planetary gear set, the seventh shifting element must be open and the eighth shifting element must be closed. The eighth shifting element can be designed as a freewheel or as a clutch, in particular a switchable clutch.

[0027] The clutches and / or brakes used in the primary gearbox and / or manual gearbox and / or secondary gearbox can be designed as positive-locking or friction-locking.

[0028] Furthermore, regardless of whether the bottom bracket transmission has a primary gear and a manual transmission or a manual transmission and a secondary gear, the gear ratios are the same in both versions. Differences exist in the speed and torque ratios occurring at the respective planetary gear sets. Since the first gear is a direct gear in both versions, the torque load is the same in both versions. Differences arise in the speeds, since the planetary gear sets located at the rear in the power flow operate at higher input speeds in some gears.

[0029] A particularly advantageous design is one in which the first, sixth, and eighth shifting elements are designed as freewheels, the second and third shifting elements as clutches, and the fourth and fifth shifting elements as brakes. In this case, the number of actuators required is reduced, since the freewheels do not need to be engaged. The shifting elements can be designed as individual shifting elements. Alternatively, two shifting elements can be combined to form a double shifting element. However, it is possible for each shifting element to be assigned an actuator. Alternatively, one actuator can be assigned to multiple shifting elements.

[0030] If the first and / or sixth and / or eighth shifting element is not designed as a freewheel but as a clutch, it is advantageous if the fourth and / or fifth and / or seventh shifting element is designed as a single-acting brake to prevent the transmission from locking when the direction of rotation is reversed at the input or output. For example, switchable freewheel brakes can be used, since it is sufficient for either the primary transmission or the manual transmission or the secondary transmission to remain locked.

[0031] A hybrid transmission with the bottom bracket gear according to the invention and an electric motor is particularly advantageous. The electric motor can be connected to a hybrid transmission output shaft, wherein the electric machine is connected downstream of the transmission in terms of drive technology. The hybrid transmission output shaft can correspond to the manual transmission output shaft or the secondary transmission output shaft and can be connected in a rotationally fixed manner to a traction mechanism carrier, such as a sprocket or belt pulley. Connecting the electric motor downstream in terms of drive technology offers the advantage that the planetary gear sets of the manual transmission are not loaded with the torque provided by the electric motor. The electric motor also has the advantage that it can assist the cyclist during cycling. This eliminates the need for fine gear grading, since the electric machine means that muscle power plays a less important role in the drive.

[0032] The electrical machine consists of at least a rotationally fixed stator and a rotatably mounted rotor and is designed to convert electrical energy into mechanical energy in the form of speed and torque in motor operation, and to convert mechanical energy into electrical energy in the form of current and voltage in generator operation.

[0033] The electric motor can be arranged offset from a central axis of the transmission, particularly in the radial direction. In particular, a central axis of the electric motor can run parallel to a central axis of the transmission. This offers the advantage that the electric motor can be arranged in an area of ​​the bottom bracket where sufficient space is available to accommodate the electric motor.

[0034] In addition, the electric motor can be connected to the hybrid transmission output shaft in a rotationally fixed manner by means of a ninth shift element, which can be a freewheel. This ensures that, when driving without the electric motor, no losses are caused by the rotating rotor of the electric motor. The electric motor can be connected to the hybrid transmission output shaft via a chain drive and / or belt drive and / or a spur gear and / or a transmission gear.

[0035] The hybrid transmission can be designed modularly. This means that the electric motor and the bottom bracket gear are integrated into the bottom bracket shell as a single functional unit and / or can be installed or removed from the bottom bracket shell as a single functional unit.

[0036] A bottom bracket with a bottom bracket gear or hybrid transmission is particularly advantageous. The transmission input shaft or the carrier of the third planetary gear set can be non-rotatably connected to the bottom bracket crankshaft. In particular, the bottom bracket can have a bottom bracket shell, with the bottom bracket gear or hybrid transmission being arranged within the bottom bracket shell. This offers the advantage that the gear or hybrid transmission is arranged as a functional unit within the bottom bracket shell, thus allowing for a compact bottom bracket design. A bicycle with a bottom bracket gear or hybrid transmission or bottom bracket is particularly advantageous.

[0037] The subject matter of the invention is schematically illustrated in the figures and is described below with reference to the figures, wherein identical or equivalent elements are generally provided with the same reference numerals. Herein: Fig. 1 a schematic representation of the bottom bracket gear according to the invention according to a first embodiment, Fig. 2 a switching matrix of the Fig. 1 bottom bracket gear, Fig. 3 a schematic representation of the bottom bracket gear according to the invention according to a second embodiment, Fig. 4 a schematic representation of the bottom bracket gear according to the invention according to a third embodiment, Fig. 5 a table with values ​​for the standard translations of the Fig. 3 and Fig. 4 planetary gear sets shown, Fig. 6 a switching matrix for the Fig. 3 bottom bracket gears shown, Fig. 7 a switching matrix for the Fig. 4 bottom bracket gears shown.

[0038] Fig. Figure 1 shows a bottom bracket transmission comprising a manual transmission 1, a manual transmission input shaft 2, which is connected in a rotationally fixed manner to a bottom bracket crankshaft 8, and a manual transmission output shaft 3. The manual transmission 1 comprises a first planetary gear set PS1 designed as a negative planetary gear set and a second planetary gear set PS2 designed as a positive planetary gear set. Furthermore, the manual transmission 1 comprises four shifting elements, namely a first shifting element S1, a second shifting element S2, a third shifting element S3, and a fourth shifting element S4. Furthermore, the manual transmission comprises a first shaft 4 and a second shaft 5. Fig. 1 only the upper half of the manual transmission 1 is shown. In particular, the manual transmission is rotationally symmetrical to the Fig. 4 shown central axis M of the bottom bracket gear.

[0039] The first planetary gear set PS1 has a ring gear that is non-rotatably connected to the manual transmission output shaft 3, a carrier that is non-rotatably connected to the manual transmission input shaft 2, and a sun gear that is non-rotatably connected to the second shaft 5. The second planetary gear set PS2 has a ring gear that is non-rotatably connected to the first shaft 5, a carrier that is non-rotatably connected to a transmission housing 6, and a sun gear that is non-rotatably connected to the manual transmission output shaft 3.

[0040] The first shaft 4 is rotationally fixedly connected to the carrier of the first planetary gear set PS1 by means of the first shifting element S1, and to the second shaft 5 by means of the second shifting element S2. Furthermore, the first shaft 4 is rotationally fixedly connected to the transmission housing 6 by means of the fourth shifting element S4. The second shaft 5 is rotationally fixedly connected to the carrier of the first planetary gear set PS1 by means of the third shifting element S3. The second and third shifting elements S2, S3 are designed as clutches. The first shifting element S1 is designed as a freewheel, and the fourth shifting element S4 is designed as a brake.

[0041] Fig. 2 shows a switching matrix of the Fig. 1. The table also shows the gear ratio values ​​"i" between the manual transmission input shaft 2 and the manual transmission output shaft 3.

[0042] The bottom bracket transmission has four gears. A first gear is achieved by engaging the first shifting element S1, while the remaining shifting elements are open. This means that the first shifting element S1, designed as a freewheel, locks, particularly without external influence. A second gear is achieved by engaging the second shifting element S2, while the remaining shifting elements are open, and a third gear is achieved by engaging the fourth shifting element S4, while the remaining shifting elements are open. A fourth gear is achieved by engaging the third shifting element S3, while the remaining shifting elements are open.

[0043] Fig. Figure 3 shows a bottom bracket gear according to a second embodiment. The bottom bracket gear differs from the one shown in Fig. 1 shown bottom bracket gear in that a pre-gearbox 7 is connected upstream of the manual transmission 1.

[0044] The primary transmission 7 has a third planetary gear set PS3, which is operatively connected to the manual transmission input shaft 2. In particular, a sun gear of the third planetary gear set PS3 is rotationally fixedly connected to the manual transmission input shaft 2. A web of the third planetary gear set PS3 is rotationally fixedly connected to the bottom bracket crankshaft 8, wherein the bottom bracket crankshaft 8 has a pedal 13 at each of its ends. A ring gear of the third planetary gear set PS3 is rotationally fixedly connected to the transmission housing 6 by means of a fifth shifting element S5. Furthermore, the ring gear of the third planetary gear set PS3 is rotationally fixedly connected to the manual transmission input shaft 2 by means of a sixth shifting element S6. The fifth shifting element S5 is designed as a brake, and the sixth shifting element S6 as a freewheel. The manual transmission 1 and the primary transmission 7 are arranged in a cavity of the bottom bracket shell 12.

[0045] Fig. 4 shows a bottom bracket gear according to a fourth embodiment and having an electric machine 11. The bottom bracket gear differs from that shown in Fig. 3 in that there is no primary gear 7, but rather a secondary gear 9. The secondary gear 9 is connected downstream of the manual transmission 1 in terms of drive technology.

[0046] The secondary transmission 9 has a fourth planetary gear set PS4, which is operatively connected to the manual transmission output shaft 3. In particular, the fourth planetary gear set PS4 has a sun gear that is rotationally fixedly connected to a secondary transmission output shaft 10. The secondary transmission output shaft 10 is rotationally fixedly connected to a traction mechanism carrier 14. The traction mechanism carrier can be a chain or belt wheel. The chain or belt connected to the traction mechanism carrier can be operatively connected to a rear wheel of the bicycle (not shown in the figures) and can transmit the torque applied to the secondary transmission output shaft 10 to the rear wheel.

[0047] Furthermore, the fourth planetary gear set PS4 has a carrier that is non-rotatably connected to the manual transmission output shaft 3. A ring gear of the fourth planetary gear set is non-rotatably connected to the transmission housing 6 by means of a shift element S7 and is non-rotatably connected to the secondary transmission output shaft 10 by means of an eighth shift element S8. The seventh shift element S7 is designed as a brake, and the eighth shift element S8 is designed as a freewheel.

[0048] The electric motor 11 is operatively connected to the secondary transmission output shaft 10. The operative connection between the electric motor 11 and the secondary transmission output shaft 10 takes place in a region downstream of the fourth planetary gear set PS4. The operative connection is realized by means of a gear stage or a belt drive, shown in dashed lines. The electric motor is axially offset in the radial direction from a center axis M of the bottom bracket transmission.

[0049] In addition, the bottom bracket gear has a torque sensor 15, in particular a disc-shaped one, by means of which the torque applied to the gearbox input shaft is measured.

[0050] Fig. Figure 5 shows a table with values ​​for the stationary gear ratios of the four planetary gear sets. For the negative planetary gear sets PS1, PS3, and PS4, the stationary gear ratio corresponds to the negative tooth count ratio of the ring gear to the sun gear. In the positive planetary gear set PS2, two planets mesh with each other. The stationary gear ratio therefore corresponds to the positive tooth count ratio of the ring gear to the sun gear.

[0051] Fig. 6 shows the switching matrix of the Fig. 3 bottom bracket gear and Fig. 7 shows the switching matrix of the Fig. 4, where the letter "X" symbolizes that the respective switching element is closed, and in the case of a freewheel design, the letter "X" symbolizes that the freewheel is locked. The freewheel is locked automatically without external activation. Fig. 3 and Fig. The bottom bracket gears shown in 4 each have exactly eight gears.

[0052] In addition, the Fig. 6 and Fig. 7 the ratios “i” in the individual gears between the connection of the bottom bracket gear with the bottom bracket crankshaft 8 and the manual transmission output shaft 3 or the secondary transmission output shaft 10. Reference symbol 1 manual transmission 2 manual transmission input shaft 3 Manual transmission output shaft 4 first wave 5 second wave 6 Gearbox housing 7 primary gearbox 8 bottom bracket crankshaft 9 rear-mounted gearboxes 10 Rear-mounted gearbox output shaft 11 electric machine 12 bottom bracket shell 13 Pedal 14 traction mechanism carriers 15 Torque sensor S1 first switching element S2 second switching element S3 third switching element S4 fourth switching element S5 fifth switching element S6 sixth switching element S7 seventh switching element S8 eighth switching element S9 ninth switching element PS1 first planetary set PS2 second planetary gear set PS3 third planetary set PS4 fourth planet set

Claims

[1] Bottom bracket gear for a bicycle, characterized by a manual transmission (1), a manual transmission input shaft (2) and a manual transmission output shaft (3), wherein the manual transmission (1) has a first planetary gear set (PS1) designed as a minus planetary gear set and a second planetary gear set (PS2) designed as a plus planetary gear set, wherein one element of the first planetary gear set (PS1) is permanently connected in a rotationally fixed manner to the manual transmission input shaft (2) and another element of the first planetary gear set (PS1) is permanently connected in a rotationally fixed manner to the manual transmission output shaft (3), and one element of the second planetary gear set is permanently connected in a rotationally fixed manner to the manual transmission output shaft (3). [2] Bottom bracket gear according to claim 1, characterized by that the gearbox (1) has a first shaft (4) and a second shaft (5), wherein a. the first planetary gear set (PS1) comprises a ring gear which is connected in a rotationally fixed manner to the manual transmission output shaft (3), a web which is connected in a rotationally fixed manner to the manual transmission input shaft (2), and a sun gear which is connected in a rotationally fixed manner to the first shaft (4), and / or wherein b. the second planetary gear set (PS2) comprises a ring gear which is connected in a rotationally fixed manner to the second shaft (5), a web which is connected in a rotationally fixed manner to a transmission housing (6), and a sun gear which is connected in a rotationally fixed manner to the manual transmission output shaft (3), and / or wherein c. the first shaft (4) is rotatably connected to the carrier of the first planetary gear set (PS1) by means of a first switching element (S1) and is rotatably connected to the second shaft (5) by means of a second switching element (S2) and is rotatably connected to the transmission housing (6) by means of a fourth switching element (S4) and / or wherein d. the second shaft (5) can be connected in a rotationally fixed manner to the web of the first planetary gear set (PS1) by means of a third switching element (S3). [3] Bottom bracket gear according to claim 1 or 2, characterized by that the manual transmission input shaft (2) can be connected in a rotationally fixed manner to a bottom bracket crankshaft (8). [4] Bottom bracket gear according to claim 1 or 2, characterized by that a pre-shift gearbox (7) is connected upstream of the manual gearbox (1) in terms of drive technology, wherein at least one, in particular exactly two, gears can be realized by means of the pre-shift gearbox (7). [5] Bottom bracket gear according to claim 4, characterized by that the primary transmission (7) has at least one, in particular a single, third planetary gear set (PS3) which is operatively connected to the manual transmission input shaft (2). [6] Bottom bracket gear according to claim 5, characterized bythat a web of the third planetary gear set (PS3) is rotatably connected to the bottom bracket crankshaft (8), a sun gear of the third planetary gear set (PS3) is rotatably connected to the manual transmission input shaft (2), and a ring gear of the third planetary gear set (PS3) is rotatably connected to the transmission housing (6) by means of a fifth switching element (S5). [7] Bottom bracket gear according to claim 5 or 6, characterized by that two elements of the third planetary gear set (PS3), in particular the ring gear and the sun gear of the third planetary gear set (PS3), can be connected to one another in a rotationally fixed manner by means of a sixth switching element (S6). [8] Bottom bracket gear according to one of claims 1 to 7, characterized by that a secondary transmission (9) is connected downstream of the manual transmission (1) in terms of drive technology, wherein at least one, in particular exactly two, gears can be realized by means of the secondary transmission (9). [9] Bottom bracket gear according to claim 8, characterized bythat the secondary transmission (9) has at least one, in particular a single, fourth planetary gear set (PS4) which is operatively connected to the manual transmission output shaft (3). [10] Bottom bracket gear according to claim 9, characterized by that a sun gear of the fourth planetary gear set (PS4) is connected in a rotationally fixed manner to a secondary transmission output shaft (10), a web of the fourth planetary gear set (PS4) is connected in a rotationally fixed manner to the transmission output shaft (3) and a ring gear of the fourth planetary gear set (PS4) is rotatably connected to the transmission housing (6) by means of a seventh switching element (S7). [11] Bottom bracket gear according to claim 9 or 10, characterized by that two elements of the fourth planetary gear set (PS4), in particular the ring gear and the sun gear, can be connected to one another in a rotationally fixed manner by means of an eighth switching element (S8). [12] Hybrid transmission with a bottom bracket transmission according to one of claims 1 to 11 and an electric machine (11), characterized by that the electric machine (11) is operatively connected or operatively connectable to a transmission output shaft, in particular the manual transmission output shaft or secondary transmission output shaft, wherein the electric machine (11) is connected downstream of the bottom bracket transmission in terms of drive technology. [13] Hybrid transmission according to claim 12, characterized by , that a. the electric machine (11) is arranged offset to a central axis (M) of the transmission and / or that b. the electric machine (11) can be operatively connected to the transmission output shaft by means of a ninth switching element, in particular a freewheel. [14] Bottom bracket with a bottom bracket gear according to one of claims 1 to 11 or a hybrid gear according to claim 12 or 13. [15] A bicycle with a bottom bracket transmission according to any one of claims 1 to 11 or a hybrid transmission according to claim 12 or 13 or a bottom bracket according to claim 14.

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