DRIVETRAIN WITH TWO SEPARATE, SWITCHABLE GEARBOXES CONNECTED BY AN INTERMEDIATE GEARBOX

Description

[0001] Drive train with two separate switchable transmissions coupled by means of an intermediate transmission. According to the preamble of the main claim, the invention relates to a drive train for single- or two-track vehicles with a crank-driven bottom bracket transmission which is connected on the output side to a chain or belt drive, from which a chain or belt leads directly or switchably to a pinion on a rear wheel hub which also contains a switchable transmission. Advantageous embodiments are specified in the sub- and auxiliary claims. Switchable transmissions are known from the prior art. CN 2 823 106 Y discloses the features of the preamble of claim 1. The feature of all of these transmissions is that either all gears are accommodated in the rear wheel hub or all gears in a bottom bracket transmission.

[0002] The disadvantage of rear hub gears (e.g., EP 0 915 800 B1) is that their mass in virtually all known bicycle models reaches or exceeds approximately two kg, and they can only transmit a peak input torque of 130 Nm, making them unsuitable for full-suspension bicycles. Modern derailleur systems with 11- or 12-speed cassettes with 10 to 51 teeth, together with a rear hub, longer chain, and rear derailleur, have approximately 1 kg of unsprung mass.

[0003] A disadvantage of conventional bottom bracket transmissions is that they must handle very high peak torques largely undamped. The transmission known from DE 10 2007 004 802 A1 has up to 18 gears and is said to be capable of a peak torque of 250 Nm. This torque can already be generated by riders with a sporty riding style. This means that the transmission has no reserves for shock peaks caused by pedal impacts, tandem drive, the coupling of an additional motor drive, or both.

[0004] A further disadvantage of both of the aforementioned types of gears is that, with the large number of gears each having only one pawl per gear, the gears located on an axle must be engaged with the teeth there, whereby a point-like load occurs in each case, with the further disadvantage that these pawls can also be switched unfavorably under load due to their small contact surfaces.

[0005] The object of the invention is to create a drive train that does not have the aforementioned disadvantages. This solution is provided by a splitter transmission according to the main claim. Advantageous embodiments are specified in the subordinate and subsidiary claims. The following embodiments are preferred.

[0006] The transmission consists of two separate sub-gears. The first sub-gear is a bottom bracket shifter through which the bottom bracket spindle runs. This is where n equally spaced basic gears are engaged. The other gears are provided by a secondary gear with two or three gears, which is located in the rear wheel hub. Therefore, the sub-gearboxes require little axial space and offer sufficient space for the possible coupling of additional drives into the driver of the bottom bracket shifter, i.e. into the bottom bracket spindle, e.g. an additional electric motor and / or a tandem drive. This means that a total of 2n or 3n gears can be shifted in series without changing the gear step, and the bottom bracket shifter can be designed for a peak input torque of e.g. 400 Nm, which is sufficient for all common applications.

[0007] Preferably, both sub-transmissions are coupled so that they can be shifted using a single twist grip. Power transmission is preferably achieved via shift cables, with the second sub-transmission either being controlled by the first sub-transmission via loop-through, or the second sub-transmission being controlled from the twist grip like the first sub-transmission, but with its own cables.

[0008] Alternatively, switching impulses from a manual switch are transmitted electrically, e.g. to stepper motors, which cause the movement of the respective switching device of the individual sub-gearboxes in a linear or rotary manner.

[0009] In a first, preferred embodiment, the drive train consists of a bottom bracket transmission (G01) with n gears, a secondary transmission (G02) with a direct gear and a downshift stage, thus two gears, and a secondary transmission (G04), which can be designed as a chain or belt drive. The bottom bracket transmission is preferably a transmission with input and output coaxial to the bottom bracket shaft, whereby it is irrelevant whether it is an epicyclic transmission or one with countershaft(s). Furthermore, the output shaft is at a certain distance from the bottom bracket shaft, as shown, for example, in WO 2012 / 156613 A1, DE10082555 B4, DE 10 2007 013 443 A and DE 10 2004 045 364 B4. Either a gear, a chain or a friction drive as known from DE: 60 2004 029 557.4 or EP: 04 71 5691.4 is provided.If the bottom bracket transmission (G01) has n gears with nearly equal gear steps of s = 1 + p% / 100, then it has a gear ratio range of s^(n-1), and thus the secondary transmission (G02) has a gear ratio of i = s^n. The total gear ratio range ü is then ü = s^(2n-1).

[0010] The beginning of this gear range is also determined by the ratio of the secondary transmission. One variant of the design uses a different rear-mounted transmission (G02) in the rear wheel hub, namely with three gears. The first gear translates to low speed with i_1 = s^n, the second gear is the direct gear with i_2 = 1, and the third gear translates to high speed with i_3 = s^(-n). This rear-mounted transmission has only a slightly greater mass than one with two gears and triples the number of shiftable gears of the bottom bracket transmission (G01) without gear overlap while simultaneously maintaining the same gear steps. With the aforementioned configuration, very high gear ranges ü = s^(3n-1) can be achieved. For example, a bottom bracket gearbox (G01) with s = 1.1 has twenty-one gears with a gear ratio range of ü = 1.1 "(21 - 1) = 6.7275, which is approximately 673%.The bottom bracket transmission requires significantly fewer gears, and the reduced number of gears also reduces costs and mass. The splitter transmission described above (G01 with G02) can be implemented with three ring gears, three double planetary gears (three each), and five sun gears. A preferred design for the secondary transmission (G04) is to select the gear ratio so that under normal operating conditions, such as cycling on flat terrain and / or without luggage, the secondary transmission operates predominantly in direct gear.

[0011] If the rear-mounted transmission in the rear wheel hub has three gears, e.g., i_1 = 1.9, i_2 = 1, and i_3 = 1 / 1.9, the gear steps s of the bottom bracket transmission with, e.g., n = 3, n = 4, n = 5, and n = 6 gears are designed as follows, using the same rear wheel hub each time. For the gear steps s(n), we obtain s(n) = {n}sqrt(i_1 = 1.9). This results in approximately s(3) = 1.239, s(4) = 1.174, s(5) = 1.137, and s(6) = 1.113. The following tables show exemplary designs. Table 1: G02 rear-mounted gearbox with 3 gears [s = 1.9 < 2] Number of teeth remark Partial transmission 1 Partial transmission2 Partial transmission 1: ring gear -113 -113 Input: Ring gear 1; Output: Web 1 Partial transmission 2: Bridge / Planets 35 20 20 35 Input: Web2; Output: Ring gear2 SunWheel ---- 58 58 ---- Bridges coupled Table 2: Bottom bracket gearbox G01 with 3 gears [s(3) = 1.239] Number of teeth remark All translations <== 1 ring gear -93 Input: web; output: ring gear Bridge / Planets 34 21 SunWheel 36 48 Table 3: Bottom bracket gearbox G01 with 4 gears [s(4) = 1.174] Number of teeth remark Partial transmission 1 Partial transmission2 All translations <= 1 ring gear -84 -84 Ring gears coupled Partial transmission 1: Bridge / Planets 23 17 17 23 Input: Web1; Output: Ring gear1 SunWheel 42 51 ---- 42 Partial transmission 2: Input: Ring gear2 Output: Web2 Table 4: Bottom bracket gearbox G01 with 5 gears [s(5) = 1.137] Number of teeth remark Partial transmission 1 Partial transmission2 Of the possible seven gears, five consecutive gears are switched with the smallest gear ratios, otherwise like bottom bracket gearbox G01 with 4 gears ring gear -90 -90 Bridge / Planets 32 24 24 32 SunWheel 35 42 42 35 Table 5: Bottom bracket gearbox G01 with 6 gears [s(6) = 1.113] Number of teeth remark Partial transmission 1 Partial transmission2 All translations <= 1 ring gear -93 -93 Ring gears coupled Partial transmission 1: Bridge / Planets 17 26 21 21(24) 26(28) Input: Web1; Output: Ring gear1 SunWheel 54 44 51 ---- 44(41) Partial transmission 2: Input: Ring gear2 Output: Web2

[0012] For example, with 7 gears of the bottom bracket shift transmission, with s(7) = 1.145, the resulting ratio for the rear-mounted transmission is s = 2.58. This configuration is shown in the following tables. Table 6: G02 3-speed rear-mounted gearbox [s = 2.58] Number of teeth remark Partial transmission 1 Partial transmission2 Partial transmission 1: ring gear -96 -96 Input: Web1; Output: Sun gear 1 Bridge / Planets 25 21 21 25 Partial transmission 2: Input: Sun gear 2; Output: Web 2 SunWheel ---- 51 51 ---- Sun gears coupled Table 7: Bottom bracket gearbox G01 with 7 gears [s(7) = 1.145] Number of teeth remark Partial transmission 1 Partial transmission2 Ring gears coupled ring gear -92 -92 Partial transmission 1: Input: Web 1; Output: Ring gear 1 Bridge / Planets 30 22 22 30 Partial transmission 2: SunWheel 39 46 46 39 Input: Ring gear2 Output: Web2

[0013] Another preferred design of a bottom bracket transmission with 7 gears has a gear step s(7) of approximately 1.1627, with the secondary transmission having 3 gears with s = 2.8824. The secondary transmission is constructed with single planetary gears, further reducing mass and axial length. With 13 of 21 gears engaged consecutively, a gear ratio range of approximately 610% is achieved. The following tables show an example configuration. Table 8: Rear-mounted gearbox G02 with 3 gears [s = 2.8824] Number of teeth remark Partial transmission 1 Partial transmission2 Partial transmission 1: ring gear -96 -96 Input: Web1; Output: Sun gear 1 Bridge / Planets ---- 22 22 ---- Partial transmission 2: Input: Sun gear 2; Output: Web 2 SunWheel ---- 51 51 ---- Sun gears coupled Table 9: Bottom bracket gearbox GO1 with 7 gears [s(7) = 1.1627] Number of teeth remark Partial transmission 1 Partial transmission2 Ring gears coupled ring gear -84 -84 Partial transmission 1: Input: Output: Web1; Ring gear1 Bridge / Planets 25 18 18 25 Partial transmission 2: Input: Ring gear2 Output: Web2 SunWheel 41 48 48 41

[0014] Figure 01 shows an example of a drive train according to the invention with the pedals (P01), attached to crank arms (P02). The bottom bracket gear (G01) is attached to a bicycle frame (not shown), for example, by means of fastening tabs (P03). The chain wheel housing also serves as a torque support (G06), with the chain (G04) being led out through openings (G07), only the upper one is visible here. A drive-side housing cover (G08) completes the housing. The two- or three-speed rear gear (G02) is located in the rear wheel hub. The gear is driven by a pinion (G05). Also shown is a brake disc (P04) attached to the hub shell.

[0015] In one advantageous embodiment, the drive train according to the invention has three torque inputs. All torque inputs are located on one side, e.g. on the left in the direction of travel. These are: the normal single rider with pedal cranks on the bottom bracket spindle; a motor drive, which is preferably arranged axially parallel to the bottom bracket spindle and is connected to the bottom bracket spindle / driver by gear, belt / chain coupling, or arranged orthogonal to the bottom bracket spindle and connected to the bottom bracket spindle by an angular gear. The motor drive in each case has an overrunning freewheel; everything that serves to feed the drive is fully encapsulated in a housing; a tandem drive is directly connected to the bottom bracket spindle in a rotationally fixed manner. In this case, both riders are therefore coupled via a chain or belt in a rotationally fixed manner and always in the same relative crank position. Of course, fewer torque inputs can also be set up and / or used.

[0016] Figure 02shows the drive train according to the invention without the housing. The chain (D01) shown and the associated sprocket (D04), which is bolted to the tandem adapter (D06), belong to the tandem drive. The tandem adapter is connected in a rotationally fixed manner to the drive-side crank adapter (A01) via a toothing. The torque of the motor (not shown), which is arranged parallel to the axis, is coupled from the motor pinion (D03) via the chain (D02) to the sprocket (D05), largely concealed here, and from there via the driver (G10) into the gearbox. When the bottom bracket spindle (A02) is stationary, the overrunning clutch (D07, D08) decouples the bottom bracket spindle from the driver so that the pedal cranks are not dragged along by the motor. If the motor is switched off, another freewheel prevents the motor and its reduction gear from being dragged along. Both freewheels are also present when the motor shaft is arranged orthogonally to the bottom bracket shaft

[0017] The innovative bottom bracket spindle consists of the middle section (A 02) and the two crank adapters (A 01.1, A 01.2), which are each connected to one another by means of a positive-locking and self-centering spur gear (A 01.3) using an axial screw connection (not shown). The crank adapters have a gearing (A 01.4) with the help of which the pedal cranks are connected in a rotationally fixed manner to the bottom bracket spindle. The crank adapter (A 01.1) may also contain the tandem adapter (D 06), a locking ring (P 06), and a freewheel disc (D 07) with spur gearing that has a locking function in only one direction. The freewheel disc and the tandem adapter are screwed together (D 06.1) and axially fixed by the locking ring (P 06). The adapter-mounted freewheel disc (D 07) is rotatably connected to the driver (G 10) via the plain bearing (P 08). Torque is transmitted to the driver via the axially mounted gearing (G 10).1) of the driver (G 10), a freewheel disc (D 08) which can be moved in one direction and which has a locking function in one direction of rotation, engages with the teeth of the freewheel (D07). The coiled spring (P 07) ensures that torque is only interrupted when the motor is overrunning or when pedaling backwards. The chain, belt, or crown wheel responsible for driving the motor is mounted on the drive and is connected to it by means of a decoupling freewheel and a rolling bearing. If the motor is switched off, the connection between motor and driver is interrupted, and the rolling bearing ensures low friction losses. In a further advantageous embodiment, the bottom bracket gear train (G01) is a planetary gear train and corresponds, for example, to the known design of the first two stages of a transmission according to EP 0 915 800 B1, whereby a design with triple-stage planetary gears provides 11 gears, or one with double-stage planetary gears provides 7 gears.The gear steps, for example, are 9% for triple planetary gears and 13.6% for double planetary gears. The innovative first sub-gearbox does not have an intermediate gear; instead, the bottom bracket shaft coincides with the rotational axis of the gear box.

[0018] For a transmission of this new type, the following inventive features are provided: The bearing of the bottom bracket spindle is located in the crank arm plane according to the Figures 03 and 04 The bottom bracket spindle rests on the outer races of the roller bearings (P 05). The ends of the bottom bracket spindle have an annular groove running axially around them. The bottom bracket spindle therefore consists of at least two parts, but preferably three: a crank adapter on the output side (A 01.2), a crank adapter on the drive side (A 01.1), and a bottom bracket spindle without bearings (A 02).

[0019] The three parts are connected via a shepherd's tooth system (A 01.3), for example. The parts are clamped against each other.

[0020] Figure 05a : For the second bottom bracket of a tandem, the same construction is used as in the previous one. Instead of a multi-part gear axle, two axle stubs (T1) and (T2) are used. Figure 05aIt can be screwed or pressed directly into the bottom bracket shell with the corresponding bearing seats, or it can be made in one piece and screwed into the bottom bracket shell, or it can be designed as a single-piece bottom bracket shell. The tandem adapter for accommodating a chain / belt wheel is mounted on the crank adapter (A01.1) as described above. Another preferred embodiment is to swap the crank adapters so that the tandem adapter is mounted on the right in the direction of travel. This allows this innovative bottom bracket spindle to be installed in all bicycles. The length of the bottom bracket spindle depends on the structural requirements of the bicycle.

[0021] The transmission axis is newly designed as follows, Figure 05The hollow transmission axle consists of two parts (A 03) and (A 04), with a bearing journal attached to the end of each part, onto which the ball bearings (P 05) of the bottom bracket shaft are pushed. The transmission-side part houses the pawls or, more recently, the axial couplings, which can connect the sun gears to the axle in a rotationally fixed manner. (Ref. No.: DE-10 2018 007 326.3)

[0022] The Figures 05 , 06 and 07 show further details: The bottom bracket spindle (A02) is located coaxially and freely rotatably within the two-part gear axle. Both parts are rotatably connected to each other by means of the aforementioned ball bearings (P05) mounted within the crank adapters (A01.1; A01.2).

[0023] Coaxially located between the bottom bracket shaft and the transmission axle is a freely rotatable shift drum (S 02) of a known type. This contains shift cams (S 02.1) and / or control cams (S 02.2), but preferably only control cams, with only axial couplings used to lock the sun gears (reference number: DE-10 2018 007 326.3). At the output end of the shift drum is a gearing (S 02.3) for coupling a control drive.

[0024] In the area where the two axle sections connect there is a planetary gear set (S 03), which is designed as a stationary gear, with stepped planets if more than one revolution of the shift drum is required for all gears, or with single planets if at most one revolution of the shift drum is required to shift through all gears (S 04.1; S 04.2) as a manual gear set. Its ring gear (S 04.1) provides the input, and a sun gear (S 02.3), which is connected in a rotationally fixed manner to the shift drum (S 02), provides the output. A circumferential gap between the two axle halves, through which claws (S 03.1.1) attached to the ring gear reach outwards, enables the shift drum to be driven, for example by a cable pulley that contains corresponding recesses. The overall gear ratio from a twist grip of the gearshift on the handlebar to the shift shaft is, for example, 1:2 or 1:1.

[0025] Figure 06This image shows a shift rotor and shift ring for an eleven-speed transmission. The shift rotor (S 05) and shift ring (S 07), together with 11 ball detents (S 06), form the shift detents. The shift ring also centers the two axle halves, which are bolted together. The number of detents corresponds to the number of gears that can be shifted with one shift drum revolution.

[0026] Figure 01 shows a torque arm (G 06), which transmits the counter-torques transmitted from the fixed sun gears to the axle via the axial couplings or pawls into the frame via the gearbox housing. This is advantageously designed to also serve as a sprocket housing; it is provided with openings (G 07) that allow the chain (belt) (G 04) to enter / exit the housing. The torque arm is bolted to the axle and the housing. If the sprocket (G 11) Figure 02), the torque support can be easily removed. The cable pulley (S 01, Figure 03 ), which rotates in a circumferential groove of the torque arm, remains in place. This allows the gearshift control to be easily decoupled from the transmission without opening it.

[0027] Figure 02A shows a version of the gearbox (G01) with a motor (G09) arranged orthogonally to the bottom bracket shaft, a further version (G10) of the torque support (G10) with shift cable outer spirals (G13), a belt pulley (G12), a housing flange (G14) and a housing (G15).

[0028] Figure 02B shows the drive side of the gearbox with a tandem adapter (D06) and a pulley (G16) and a known BCD 104mm bolt circle diameter connection.

[0029] Figure 02Cshows the gear plan for the reduction gear consisting of the motor pinion (M02), the spur gear (M03) which is connected to the spur gear (M04) for a fixed rotation therewith, and the cone gear (M05). The crown gear is mounted on the driver / web with planets (M09) using the rolling bearing (M06). A decoupling freewheel, consisting of the coupling parts (M07a), (M07b) and the spring (M08) works automatically. This means that the freewheel function is triggered in the known manner when the motor is at a standstill and the bottom bracket spindle continues to rotate. The coupling (M07a) is connected to the crown gear for a fixed rotation therewith, whereby the coupling part (M07b) is connected to the driver / web in a fixed rotation therewith but can be moved. The position (M09) symbolically shows the web / driver with planets and a ring gear.

[0030] Figure 02D shows a three-quarter section of the gearbox (G01) without a gearbox block. Figure 08shows the possibilities of the gearbox concept. The gearbox (G01) is designed so that the gearbox blocks are Figures 8A to 8D into the assembly according to Figure 2d can be installed. Figure 8A a three-speed gearbox block according to Table 2, Figure 8B a four-speed gearbox block according to Table 3, Figure 8C Five- or seven-speed gearboxes according to Tables 4, 7 and 9, as well as Figure 8D a six-speed gearbox block according to Table 5. A three-quarter section of the gearbox constructed according to Table 2 is shown in the Figures 09A and 09B in different views, but without housing.

[0031] The drivetrain according to the invention also provides an advantageous design for a drivetrain swing arm. Numerous designs are known for the rear triangle of full-suspension bicycles. What they all have in common is that the axis of rotation of the rear triangle, with the rear wheel mounted there, is positioned at least close to the rotation axis of the bottom bracket spindle. There are two types of swing arms: either the bottom bracket pivots virtually around the bottom bracket spindle or another suitable point using multi-joints; or, in the second variant, the swing arm is articulated to the frame by means of a bearing located more or less remote from the bottom bracket rotation axis.

[0032] None of the aforementioned solutions remains free of feedback on the pedals due to compression, nor does the rider's drive torque have feedback on the suspension. A drivetrain swingarm is known (https: / / www.mtb-news.de / news / 2015 / 07 / 27 / hnf-heisenberg-xf1-e-mtb-pedelec-bmw-i-nicolai / ) that incorporates the entire drivetrain, including the motor, into a single swingarm using numerous elements of a coupling mechanism. This version requires complex kinematics, numerous joints with corresponding bearings, to keep the swingarm pivoting approximately around the bottom bracket axis. The previously described inventive designs for coupling the rear triangle avoid the aforementioned disadvantages and can be manufactured with low kinematic complexity and few parts. Only one bearing unit is required for the movement of the swingarm (without the damper / spring bearings).With a bottom bracket gear fixed to the frame, with the swing arm rotating around the gear housing and a secondary gear ratio of the chain or belt drive of i_Sek = 1, the pedal movement remains unaffected by the deflection of the swing arm.

[0033] Figure 10 shows the main frame (F01), consisting of the frame tubes (F01.1) to (F01.4), the adapter (F01.5), the clamp (F01.6), and the screws (F01.6.1). The roller bearings (F01.6.2) and (F01.6.3) serve to support the transmission when it is non-rotatably connected to the swing arm. Figure 11 shows the complete frame with the rear triangle (F02), consisting of the parts (F02.1) and a spring and a damper (F03).

[0034] Human-powered single- or multi-track vehicles, with or without a supporting engine, require only moderate power for their drive, but at very low speeds, namely between approximately 60 and 120 revolutions per minute. This requires high torques, often reaching several hundred Nm. The demands on manual transmissions with gears are correspondingly high. Typically, involute gears are used, which have a pressure angle of approximately 20 degrees and a symmetrical profile. If the demands are high, they can be met by selecting the appropriate material, post-treatment of the teeth, such as hardening and grinding, and a suitable selection of the tooth module and tooth width, or by profile shifts, optimizing the tooth root contour and, last but not least, by increasing the pressure angle. This can increase the load-bearing capacity, to name just a few of the known possibilities.However, there are strict limits to the increase in the pressure angle (peak limit).

[0035] A further advantageous design of a bicycle transmission or its drive train provides asymmetric toothing of the gear wheels.

[0036] The fact that the teeth are predominantly loaded in only one direction is exploited to eliminate the aforementioned limitations according to the invention. According to the invention, the toothing is designed asymmetrically, meaning that the load-bearing flank, subject to tensile stress, has a large pressure angle—e.g., 30 to 45 degrees and above—and the unloaded flank, subject to compressive stress, has one of approximately 20 degrees or less. Thus, one flank is strengthened at the expense of the other. In conjunction with tooth root optimization, significantly improved load-bearing capacities can be achieved. Figure 12shows the meshing situation for a spur gear pair. Position (03) is the driving gear, position (04) the driven gear. The flank (01) has a pressure angle of approximately 25 degrees, and the flank (02) has a pressure angle of 35 degrees.

Claims

1. Drive train for muscle-powered single- or multi-track vehicles with a crank-driven bottom bracket gearbox, which is coupled on the output side to a chain or belt drive, from which a chain or belt leads directly or shiftably to a respective pinion of a rear wheel hub, wherein, in the drive train, apart from the bottom bracket gearbox, which is designed as a primary gearbox (GO1) with n gears or with variable transmission, a secondary gearbox (G02) is arranged as a shiftable rear wheel hub gearbox with m = two or m = three gears, wherein n and m are natural numbers, wherein the drive train comprises up to n times m gears, wherein n gears are arranged in the bottom bracket gearbox and m gears are arranged in the secondary gearbox, characterized in that the drive train comprises a single rotary or shift lever, and the bottom bracket gearbox and the rear wheel hub gearbox each comprise shift means which are to be shifted continuously from the single rotary or shift lever.

2. Drive train according to claim 1, characterized in that the rotary or shift lever is coupled to the shift means via a looped cable or respective associated cables.

3. Drive train according to claim 1, characterized in that the aforementioned gearboxes are planetary gears (epicyclic gears).

4. Drive train according to claim 1, characterized in that the primary gearbox (GO1) has n gears with almost identical gear transitions of s = (1+p% / 100), i.e. a first transmission range of s^(n-1), and the secondary gearbox (G02) comprises two further gear ratios of i_1= s^(n) and i_2 = 1, whereby a total transmission range of s^(2n-1) is achieved, or the secondary gearbox has three evenly spaced gears, wherein the first gear with i_1=s^(n) shifts to slow, the second gear with i_2=1 is the direct gear and the third gear with i_3 = s^(-n) shifts to fast, whereby a total transmission range of s^(3n-1) is obtained.

5. Drive train according to claim 4, characterized in that of 2n or 3n shiftable gears, only consecutive k_1 < 2n or k_2 < 3n gears are shifted.

6. Drive train according to claim 1, characterized in that the bottom bracket gearbox (G01) is traversed coaxially by a bottom bracket shaft, which is coupled on the input side to a respective auxiliary electric motor and / or a tandem drive, and in that at least one further chain wheel or belt wheel is arranged on the bottom bracket shaft.

7. Drive train according to claim 6, characterized in that the auxiliary electric motor is arranged together with an overrunning freewheel and a decoupling freewheel parallel to the axis or perpendicular to the axis of the bottom bracket shaft on the gear housing or bicycle frame.

8. Drive train according to claim 6, characterized in that the bottom bracket shaft is three-part, consisting of a central tubular part (A02) with end-mounted crank adapters (A01.1; A01.2) that are self-centering, rotationally fixed, face-tooth meshed, axially bolted and braced, or consists of two parts made only of matching long crank adapters.

9. Drive train according to claim 8, characterized in that a tandem adapter (D06), a retaining ring (P06) and a freewheel disc (D07) are arranged on a crank adapter (A01.1) as part of a decoupling freewheel, which is screwed to the tandem adapter and is axially displaceable in only one direction of rotation by means of a toothing (G10.1) so that it is axially slidable and can only be coupled in one direction of rotation with a driver (G10) of the bottom bracket gearbox (GO1).

10. Drive train according to claim 6, characterized in that the bottom bracket shaft (A02) is mounted by means of ball bearings (P05) on a hollow gear axle (A03) in which a gear shifting drum (S02) is rotatably supported, which carries control cams (S02.2) or control grooves for gear shifting of the planetary gear (G17) arranged on the gear axle (A03) and can be driven at the end via a planetary stand gear (S03) by a rope pulley (S01) for gear setting.

11. Drive train according to claim 10, characterized in that the gear axle (A03, A04) is designed in at least two parts and carries a shift ring (S07) which is mounted so as not to rotate and carries recesses (S07.1) for ball detents (S06) which are mounted on a shift rotor (S05) and determine the gearshift positions of the gear shifting drum.

12. Drive train according to claim 1, characterized in that the bottom bracket gearbox (GO1), including the chain wheel or belt wheel, is enclosed by an at least three-part housing, wherein one housing part surrounds the chainor belt wheel and comprises the passages for the chain or belt and, as a torque support, connects the axle in a rotationally fixed manner to at least one of the other housing parts, which in turn are connected to a bicycle frame.

13. Drive train according to claim 12, characterized in that a rear frame (F02) is mounted pivotably around the housing of the bottom bracket gearbox (G01), which is connected in a rotationally fixed manner to the bicycle frame (FO1), coaxially to the bottom bracket shaft (A02).

14. Drive train according to claim 12, characterized in that the housing of the bottom bracket gearbox (GO1) is connected in a rotationally fixed manner to a rear frame (F02) and is mounted in a bicycle frame (FO1) so as to be coaxially pivotable about the bottom bracket shaft (A02).

15. Drive train according to claim 1, characterized in that in at least one gearbox (G01) (G02), load-bearing flanks of the gear teeth comprise a large angle of engagement and unloaded flanks comprise a small angle of engagement.

16. Drive train according to claim 3 or 4, characterised in that the rear wheel hub gearbox (G02) consists of two symmetrical partial gearboxes with transmission ratios i_a=s^n < 2 and i_b=1 / i_a, the drive and output of which are respectively via their web or ring gear, wherein the two partial gearboxes are coupled via their webs and their ring gears effect the drive and output, or wherein the two partial gearboxes are coupled via their ring gears and their ring gears effect the drive and output, and wherein the two partial gearboxes are coupled via their webs and their ring gears effect the drive and output. ring gear, wherein the two partial gearboxes are coupled to each other via their webs and their ring gear wheels effect the drive and the drive, or wherein the two partial gearboxes are coupled to each other via their ring gear wheels, which are kept flying and whose webs effect the drive and the drive.

17. Drive train according to claim 3 or 4, characterized in that the rear wheel hub gearbox (G02) consists of two symmetrical partial gearboxes with transmission ratios i_a=s^n >2 and i_b=1 / i_a, the input and output of which are effected via their sun gear wheels and their webs, respectively, wherein the sun gear wheels are coupled to one another and their webs effect the input and output.