Bottom bracket gear shift device for a bicycle

Abstract

The invention relates to a bottom bracket gear shift device (10) for a bicycle, comprising a bottom bracket shaft (18), a fixed shaft (314, 414, 614) having at least two fixed gears (318A, 418A, 518A, 618A), a shifting shaft (315, 415, 515, 615) having at least two free gears (319A, 419A, 519A, 619A), and a drive-means gear. Each fixed gear (318A, 318B) meshes with a free gear (319A, 319B, 419A), as a result of which a specific transmission ratio (1) is provided in each case. Each of the at least two free gears (319A, 519A, 619A) is connected to the shifting shaft (315, 415, 515, 615) by a clutch (320A, 320B, 420A, K7). During operation of the bicycle, torque can flow from the bottom bracket shaft (18) to, in this order, the fixed shaft (314, 414, 614), a fixed gear (318A, 318B), the free gear (319A, 319B, 419A) that meshes with said fixed gear (318A, 318B), the shifting shaft (315, 415, 515, 615) and the drive-means gear. Thus, the fixed shaft (314, 414, 614) is upstream of the shifting shaft (315, 415, 515, 615) in the torque flow.

Description

[0001] Bottom bracket gearshift for a bicycle

[0002] Description

[0003] The entire content of priority application DE 10 2023 207 638.1 is hereby incorporated by reference into the present application.

[0004] The present invention relates to a bottom bracket gearshift for a bicycle and to a bicycle having a drive train with such a bottom bracket gearshift.

[0005] A gear system on a bicycle ensures that you can pedal at a roughly constant cadence over a wide speed range.

[0006] Bicycles with gears have long been commonly equipped with a hub gear in the driven rear wheel or with a derailleur gear or with a combination of hub and derailleur gears.

[0007] The disadvantages of a rear hub gear are the unwanted weight shift to the rear of the bike, as well as the limited and purely cylindrical space in the rear hub. The heavy weight on the rear hub is a nuisance not only when carrying the bike, but also when cornering or riding off-road.

[0008] The disadvantages of derailleur gears are their high susceptibility to dirt and malfunctions caused by weather and foreign objects due to exposed components such as the chainring, derailleur, chain, rear derailleur, and sprocket with pinions. This is also due to the high wear, particularly on the chain, due to its sometimes very slanted path. Derailleur gears are therefore comparatively maintenance-intensive.

[0009] For these reasons, gear shifts located near the bottom bracket have become increasingly popular in bicycles in recent years. Such bottom bracket shifts can be housed within a completely enclosed housing that is fully or partially integrated into the bicycle frame, thus protecting them from dirt and interference. Furthermore, the installation space for the bottom bracket shift can extend into the adjacent area of ​​the frame, particularly the down tube and / or seat tube, giving the bottom bracket shift designer more design options. Finally, the weight of the gear shift is shifted to the center of the bicycle's longitudinal axis, which improves handling.

[0010] Furthermore, a bottom bracket gear system can be relatively easily combined with an auxiliary drive, particularly an electric motor, which either temporarily supports the rider's pedaling motion (so-called pedelec) or even takes over the entire drive of the bicycle without any additional pedaling motion from the rider (so-called electric bicycle). A bicycle with an auxiliary drive in the form of an electric motor is also commonly referred to as an e-bike, although the aforementioned terms pedelec, electric bicycle, and e-bike are not used interchangeably.

[0011] Regardless of the presence of an auxiliary drive, the present application only considers bicycles with a pedal crank drive.

[0012] Examples of bottom bracket gearshifts with and without auxiliary drive can be found in DE 967 668, DE 197 50 659 A1, US 2011 / 0120794 A1, and EP 1 445 088 A2. The actuating means of a gearshift, and thus also of a bottom bracket gearshift for a bicycle, is usually a shift handle in the form of a push-pull lever, a multi-push lever, or a twist grip, and is usually operated by the human hand on the bicycle handlebars. In newer designs, operation with the aid of control elements is also possible, which then indirectly activate one or more electrical actuators.

[0013] When cycling, the pedals must never slip during gear changes. The rider must not suddenly pedal "into the void." This can cause injuries, especially to the knees. Many common transmissions are designed in such a way that no freewheeling can occur between individual gears during gear changes.

[0014] Examples of bottom bracket shifters with such actuation means can be found in DE 10 2004 045 364 A1 and WO 2009 / 132605 A1. EP 1 982 913 A1 further discloses a so-called superposition gear, with the aid of which a shifting command can be transmitted from a stationary housing to a rotating shaft.

[0015] Furthermore, step-by-step gears are also used for such actuating devices, allowing a mechanical input movement to be divided into two output movements with different timing. Such a step-by-step gear is known, for example, from DE 11 13 618 A1.

[0016] A significantly more advantageous weight distribution compared to hub gears is achieved when, as mentioned, the gear shift is positioned centrally in the bike, as is the case with bottom bracket gears, for example. However, bottom bracket gears can be quite large, leaving no space around the bottom bracket for the electric motor as an auxiliary drive. Furthermore, bottom bracket gears can already be so heavy that the additional weight of an auxiliary drive can result in an electric bike that would be too heavy for everyday use or for continuing to ride when the battery is empty.

[0017] The present invention is based on the object of providing an improved bottom bracket gear system for a bicycle.

[0018] This object is achieved by a bottom bracket shifting system according to claim 1 and by a bicycle with a drive train having such a bottom bracket shifting system according to claim 22. Further advantageous embodiments of the invention are described in the subclaims.

[0019] A bottom bracket gearshift of the type considered here for a bicycle has the following components: a bottom bracket shaft, a fixed shaft on which at least two fixed gears are arranged coaxially and are connected in a rotationally fixed manner to the fixed shaft, a selector shaft on which at least two loose gears are arranged coaxially and are detachably connected in a rotationally fixed manner to the selector shaft, a drive means wheel, in particular a chain wheel or a belt wheel.

[0020] The bottom bracket gearshift is preferably arranged in a housing, which further preferably forms part of the bottom bracket shell and / or other components of the frame of the bicycle, in particular part of the down tube or the seat tube.

[0021] A bottom bracket spindle in the sense of the present invention is, in the sense commonly used in bicycle technology, a shaft which is connected to a pedal crank at each of its ends.

[0022] A fixed shaft in the sense of the present invention is a shaft which rotates during operation and on which at least two fixed gears are arranged coaxially and connected to the fixed shaft in a rotationally fixed manner. The at least two fixed gears thus have the same axis of rotation as the fixed shaft. The fixed shaft is preferably mounted in the housing. The at least two fixed gears are connected, in particular non-detachably, in a rotationally fixed manner to the fixed shaft, wherein the connection is preferably rigid and more preferably one-piece. The fixed shaft and the fixed gears can, for example, be turned and milled together from solid material, or the fixed gears are connected to the fixed shaft by a press fit, by a tongue and groove connection, or by external teeth on the fixed shaft and corresponding internal teeth on the fixed gears. The fixed shaft and all fixed gears therefore rotate at the same speed during operation of the bicycle.

[0023] A selector shaft within the meaning of the present invention is also a shaft that rotates during operation. Accordingly, the at least two loose gears are connected coaxially to the selector shaft and thus have the same axis of rotation as the selector shaft, and the selector shaft is preferably mounted in the housing. The at least two loose gears are releasably and non-rotatably connected to the selector shaft, wherein the non-rotatable connection for each loose gear can be established and released individually and independently of the other loose gears. In contrast to the connection of the fixed gears to the fixed shaft, a "non-rotatable connection" of the loose gears to the selector shaft should also be understood to mean a connection that is non-rotatable in only one direction of rotation and rotatable in the other direction.

[0024] Preferably, a plain bearing, a roller bearing, or a pair of sliding surfaces is arranged between the selector shaft and each idler gear. This allows the idler gear to rotate on the selector shaft when the idler gear is disengaged (and possibly also when the idler gear is connected in a rotationally fixed manner, but then only in one direction). When a idler gear is connected in a rotationally fixed manner, the selector shaft and the respective idler gear thus rotate at the same speed in at least one direction during bicycle operation.

[0025] The fixed gears, as well as the idler gears, are preferably straight-toothed spur gears. However, they can also have other gear shapes, for example, bevel gears, and can, in particular, be helical gears. Furthermore, they can have involute or cycloidal gearing and the same or different modules.

[0026] The module (plural: modules), or the so-called diameter pitch, is a measure of the size of the teeth of gears. Its value is typically based on the unit of length in millimeters and is calculated by dividing the pitch diameter by the number of teeth on the gear.

[0027] A drive wheel in the sense of the present invention is a transmission wheel, in particular a transmission gear, preferably a chain wheel, a belt wheel or a bevel gear for a cardan drive, which drives a wheel of the bicycle, in particular the rear wheel, via an associated transmission element such as a chain, a toothed belt, a V-belt or a cardan shaft, which generates the propulsion of the bicycle.

[0028] The at least two fixed gears and the at least two loose gears are arranged in pairs such that in each case one fixed gear meshes with an loose gear, whereby a specific gear ratio is provided in each case when the fixed gear serves as the drive gear and the loose gear as the output gear.

[0029] Here and in the following, the term "gear ratio" for a drive wheel and an output wheel coupled to the drive wheel directly or indirectly without slip is defined as the ratio of the speed of the output wheel to the speed of the drive wheel when the drive wheel and the output wheel rotate together as a result of the coupling.

[0030] For example, a gear ratio of 0.5 causes the output gear to rotate at half the speed of the drive gear, while a gear ratio of 2, for example, causes the output gear to rotate twice as fast as the drive gear. A gear ratio of less than 1 is commonly referred to as a "reduction ratio" and results in a slower speed. A gear ratio of 1 is also referred to as a "direct gear ratio" and results in no change in speed. A gear ratio greater than 1 is also referred to simply as a "ratio" and results in a faster speed.

[0031] Each gear stage of the bottom bracket shifting system is characterized by a specific gear ratio between the bottom bracket spindle as the input shaft and the shaft on which the drive gear is located as the output shaft. In the present invention, each gear stage of the bottom bracket shifting system is preferably characterized by the gear ratio provided by a pair of a fixed gear and a meshing idler gear, possibly in conjunction with additional gear ratios provided by other components.

[0032] Each of the at least two loose gears is connected to the selector shaft by a respective clutch, which can be brought into a closed state in which the loose gear is connected to the selector shaft in a rotationally fixed manner in at least one direction of rotation, and into an open state in which the loose gear is connected to the selector shaft in a rotationally fixed manner in both directions of rotation.

[0033] During bicycle operation, outside of gear shifting, the clutches are preferably controlled such that only one of the clutches is engaged at any one time, while the others are disengaged. Thus, torque is transmitted only via the pair consisting of a fixed gear and the associated idler gear whose clutch is engaged. The gear ratio provided by this pair thus at least partially determines the gear engaged in the bottom bracket shift. According to the state of the art, brief situations can occur during a gear shift from one gear to another in which more than one clutch is engaged.If a loose gear is only connected to the selector shaft in one direction of rotation when the associated clutch is closed, the clutch acts like a switchable freewheel, which only allows rotation between a shaft and a hub in one direction of rotation and creates a rotationally fixed connection between the shaft and the hub in the other direction of rotation.

[0034] Such a freewheel function between the selector shaft and the individual idler gears may be desirable, for example, if the control of the clutches of the individual idler gears cannot rule out the possibility that several clutches are simultaneously engaged - even if only briefly - and the respective idler gears are thus simultaneously rotationally connected to the selector shaft. In this case, the fixed shaft and the selector shaft would be simultaneously connected to each other in a torque-transmitting manner by several pairs, each consisting of a fixed gear and a meshing idler gear, with the two pairs of fixed gear and idler gear generally providing different gear ratios. This would lead to temporary blocking of the transmission and thus to uneven running or even damage to or destruction of the transmission.However, the freewheel function in the clutches means that when two clutches are closed at the same time, one of them, in particular the one on the idler gear with the lower speed, “freewheels” or “slips” and thus prevents the transmission from locking.

[0035] According to the invention, during operation of the bicycle, a torque flow is enabled from the bottom bracket shaft in this order to the fixed shaft, to a fixed gear, to the loose gear meshing with this fixed gear, to the shift shaft and to the drive gear.

[0036] In particular, the fixed shaft is thus arranged upstream of the selector shaft in the torque flow. This arrangement opens up the design possibility of increasing the speed when transmitting torque from the fixed gears to the idler gears by having a larger number of pairs, preferably all pairs, of fixed gears and idler gears provide a transmission ratio greater than 1. Such an increase in speed can have the advantage of simultaneously causing a corresponding reduction in the torque acting between the idler gears and the selector shaft, and thus on the clutches arranged there. Since in a clutch, various components generally have to be engaged and disengaged under load, it is desirable for the lowest possible torques to be effective in the clutches.If the selector shaft were positioned in front of the fixed shaft in the torque flow, the aforementioned increase in speed and the associated reduction in torque could not be achieved in this way.

[0037] In a gear transmission, every transition in the torque flow between meshing gears has a negative impact on the transmission's efficiency. The torque flow according to the invention includes only three such transitions: between the bottom bracket shaft and the fixed shaft, between the fixed shaft and the selector shaft, and between the selector shaft and the output shaft, on which the drive gear is located.

[0038] In a preferred embodiment of the invention, therefore, at least half of the pairs of one fixed gear and one idler gear each provide a gear ratio greater than 1. More preferably, all pairs of one fixed gear and one idler gear each provide a gear ratio greater than 1.

[0039] In a further preferred embodiment of the invention, at least two of the at least two loose gears have different moduli, wherein the modulus of a first loose gear whose diameter is greater than or equal to the diameter of a second loose gear is also greater than or equal to the modulus of the second loose gear. By using different moduli, the number of teeth and thus the gear ratios of the pairs of fixed gears and loose gears can be more precisely adapted to the desired gear ratios of the bottom bracket gearshift. The smaller the gear ratio between a fixed gear and the associated loose gear, the larger the modulus of the two gears of the respective pair is preferably selected compared to most of the other pairs. This feature is advantageous with regard to the tooth root strength of the fixed gears and the loose gears.

[0040] Additionally, and in particular, this allows for more consistent gear ratio increments between successive gears in the bottom bracket shifting system. A gear increment is the percentage change in the gear ratio from one gear to the next higher gear in a manual transmission.

[0041] In a further preferred embodiment of the invention, the bottom bracket gearshift further comprises an auxiliary drive, in particular an electric motor, the torque of which can be introduced into the torque flow from the bottom bracket shaft to the drive wheel, wherein a torque flow from the auxiliary drive shaft of the auxiliary drive to the drive wheel is enabled via an auxiliary drive gear, which is one of the following gears: one of the at least two fixed gears, one of the at least two loose gears, a further gear arranged coaxially on the fixed shaft and connected in a rotationally fixed manner to the fixed shaft, which is neither one of the at least two fixed gears, a further gear arranged coaxially on the selector shaft, which is neither one of the at least two loose gears.

[0042] An auxiliary drive shaft is understood to be an output shaft of the auxiliary drive, in particular a motor shaft. The advantages that can be achieved by an auxiliary drive, in particular by an electric motor, have already been described above. By introducing the torque of the auxiliary drive via the auxiliary drive gear according to this embodiment, the auxiliary drive can be easily combined with the transmission in the bottom bracket gearshift. This combination can be realized with a small number of additional components, particularly when the auxiliary drive gear is one of the at least two fixed gears or one of the at least two loose gears.

[0043] In a preferred variant of this embodiment, the auxiliary drive shaft is connected in a torque-transmitting manner directly or indirectly, in particular via a reduction gear, to an auxiliary drive pinion, which is neither one of the at least two fixed gears nor one of the at least two loose gears, wherein the auxiliary drive pinion meshes with the auxiliary drive gear.

[0044] In this context, the term “torque-transmitting connected” means that a torque of the auxiliary drive shaft can be transmitted to the auxiliary drive pinion, in particular by a rotationally fixed arrangement of the auxiliary drive pinion on the auxiliary drive shaft or by interposing further components such as the aforementioned reduction gear.

[0045] The auxiliary drive pinion allows the torque of the auxiliary drive to be easily introduced into the transmission via the auxiliary drive gear. An indirect connection of the auxiliary drive pinion to the auxiliary drive shaft via a reduction gear can be particularly advantageous when the auxiliary drive is an electric motor with a relatively high speed, in order to match this to the relatively low speed of the transmission driven by a human driver.

[0046] In a further preferred variant, the gear ratio provided by the auxiliary drive pinion and the auxiliary drive gear is less than 1 when the auxiliary drive pinion serves as the drive gear and the auxiliary drive gear serves as the output gear.

[0047] Such a gear ratio of less than 1 can also achieve an additional reduction in the speed of the auxiliary drive upon introduction into the transmission, without the need for additional components. In a further preferred variant of the embodiment, in which the torque of the auxiliary drive is introduced via an auxiliary drive gear, the auxiliary drive gear is one of the at least two fixed gears, and the diameter of the auxiliary drive gear is greater than or equal to the median of the diameters of all fixed gears. Particularly preferably, the diameter of the auxiliary drive gear is the largest diameter of all fixed gears.

[0048] The term “median” is used in the usual mathematical sense, i.e. as the middle value of an ascending number of numerical values ​​if this number is odd, and as the arithmetic mean of the two middle values ​​if this number is even.

[0049] In other words, the diameter of the auxiliary drive gear is the "larger half" of the diameters of all fixed gears. By choosing a fixed gear with a relatively large diameter as the auxiliary drive gear, the aforementioned advantage of reducing the auxiliary drive speed when introducing the auxiliary drive torque into the transmission can be achieved particularly effectively. This is especially true if the diameter of the auxiliary drive gear is actually the largest diameter of all fixed gears.

[0050] In a further preferred embodiment of the invention, the fixed shaft and / or the shift shaft do not run parallel to the bottom bracket shaft.

[0051] On a bicycle, the so-called stance width, which is defined as the lateral distance between the pedal mounting points and the cranks and is also known as the Q-factor, limits the width of the bottom bracket shell or, in the case of bottom bracket shifters, the width of the gear housing. If the gear housing exceeds a certain width, the Q-factor becomes too large, which leads to ergonomic and biomechanical disadvantages.

[0052] Depending on the number of gear stages provided and thus the pairs of fixed gears and loose gears, which are arranged axially one after the other on the fixed shaft or on the selector shaft, the fixed shaft and / or the selector shaft can have a relatively long length.

[0053] When operating the gearshift with a superimposed gear, which is usually designed as a planetary gear and is usually arranged coaxially with the selector shaft at one end thereof, the selector shaft, including the superimposed gear, can become very long. The same applies to the use of a stepping gear or other actuation and transmission mechanisms at one end or within the selector shaft.

[0054] An arrangement of the fixed shaft and / or the shift shaft not parallel to the bottom bracket shaft, but at least partially in a different direction, i.e. (with a usual arrangement of the bottom bracket shaft transverse to the longitudinal direction of the bicycle) at least partially in the longitudinal direction of the bicycle and / or in the vertical direction, thus makes it possible to design the gearbox housing more narrowly, since the Q factor no longer has to be at least the length of the fixed shaft or the shift shaft including any operating devices or the like.

[0055] Arranging the fixed shaft and / or the shift shaft longitudinally of the bicycle also allows the transmission to be positioned substantially in front of the bottom bracket spindle, i.e., toward the front wheel. Conversely, this allows for a smaller distance between the bottom bracket spindle and the rear wheel, which can be advantageous for riding dynamics.

[0056] In a preferred variant of the last-mentioned embodiment, an imaginary extension of the fixed shaft and / or an imaginary extension of the shift shaft intersects the bottom bracket shaft.

[0057] An "imaginary extension" of a shaft is understood to be an infinitely long, cylindrical continuation of the shaft in both directions along the shaft's rotational axis, assuming that the shaft itself is a cylindrical body. The aforementioned feature, that the imaginary extension of the respective shaft intersects the bottom bracket spindle, describes in particular an arrangement in which the respective shaft is positioned in front of the bottom bracket spindle in the direction of travel and "runs toward" it. Conversely, it specifically excludes the case in which the two shafts "run past each other." This defines a compact and therefore space-saving arrangement of the shafts involved.

[0058] In a preferred variant of the embodiment with non-parallel shafts, the axis of rotation of the fixed shaft or the axis of rotation of the selector shaft each lie substantially in the same plane as the axis of rotation of the bottom bracket shaft, or the axis of rotation of the fixed shaft and the axis of rotation of the selector shaft lie substantially in the same plane and the axis of rotation of the bottom bracket shaft lies substantially parallel to this plane, or the axis of rotation of the fixed shaft, the axis of rotation of the selector shaft and the axis of rotation of the bottom bracket shaft lie substantially in the same plane.

[0059] The first and third of these arrangements also describe compact and thus space-saving arrangements of the shafts involved, while the second arrangement describes a largely geometrically “ordered” arrangement due to the parallelism of the bottom bracket shaft with the plane of the fixed shaft and the selector shaft.

[0060] In a preferred variant of the embodiment with non-parallel shafts, the direction vector of the rotation axis of the fixed shaft and / or the direction vector of the rotation axis of the switching shaft is substantially orthogonal to the direction vector of the rotation axis of the bottom bracket shaft.

[0061] This arrangement is technically particularly simple to implement, since torque transmission between mutually orthogonal shafts can be achieved using standard machine elements. This also generally allows for better efficiency within the relevant gear pairs. In a further preferred variant of the embodiment with non-parallel shafts, at least one crown gear and at least one crown gear pinion meshing with one of the crown gears are arranged in the torque flow between the bottom bracket shaft and the fixed shaft and / or in the torque flow between the selector shaft and the drive gear.

[0062] Both the crown gear and the crown gear pinion are preferably connected coaxially and (if necessary detachably) in a rotationally fixed manner to a respective shaft.

[0063] Depending on the torque flow through the entire bottom bracket gear system, a drive-side and / or an output-side crown gear transmission is defined.

[0064] In this context, a crown gear is typically understood to be a gear in which the teeth, from the tooth roots to the tooth tips, all extend in the same direction, essentially orthogonal to the plane of the gear and thus parallel to the shaft on which the crown gear is mounted. A crown gear pinion is accordingly understood to be a gear, in particular a spur gear, that is suitable for meshing with a crown gear. A combination of a crown gear and a crown gear pinion according to this variant represents a simple way of transmitting torque between two non-parallel shafts with good efficiency.

[0065] Instead of a crown gear and a crown gear pinion, bevel gears can always be used here and in the following. A combination of two bevel gears also represents a simple way to transmit torque between two non-parallel shafts.

[0066] In a preferred variant of this embodiment, at least one crown gear and at least two crown gear pinions meshing with one of the crown gears at different radial positions are arranged in the torque flow between the bottom bracket shaft and the fixed shaft and / or in the torque flow between the selector shaft and the drive means gear, wherein the at least two crown gear pinions are arranged coaxially on a shaft, in particular on the selector shaft, and are releasably connected to the shaft in a rotationally fixed manner by a respective coupling which can be brought into a closed state in which the respective crown gear pinion is rotationally fixedly connected to the shaft in at least one direction of rotation, and into an open state in which the respective crown gear pinion is rotatably connected to the shaft in both directions of rotation.

[0067] A crown gear within the meaning of the present invention can have one or more running gears, in particular arranged coaxially to one another. A running gear is understood here as a closed ring of teeth with which another gear, in particular a crown gear pinion, can mesh.

[0068] By means of an arrangement with at least two crown gear pinions, at least two further transmission ratios can be easily realized in the drive-side or output-side crown gear and thus at least two further gear stages of the bottom bracket gearshift, which can optionally be combined with the gear stages realized by the pairs of fixed gears and loose gears, whereby the total number of gear stages of the bottom bracket gearshift can be multiplied.

[0069] In a preferred variant of this embodiment, at least two of the at least two crown gear pinions have different diameters.

[0070] In this way, even further apart gear ratios can be achieved by the two crown gear pinions, in that a crown gear pinion with a smaller diameter preferably meshes with a radially further outward running toothing of one of the crown gears, ie on a larger diameter, and another crown gear pinion with a larger diameter preferably meshes with a radially further inward running toothing, ie on a smaller diameter, of one of the crown gears.In a preferred variant of the embodiment with at least two crown gear pinions, when the gear ratios provided by the pairs of one fixed gear and one loose gear are arranged in ascending order, the ratio of the larger to the smaller of any two consecutive of these gear ratios is in each case smaller than the ratio between a larger and a smaller gear ratio, which is in each case provided by a pair of one of the at least two crown gear pinions and the crown gear meshing therewith, when the crown gear pinion serves as the drive gear and the crown gear as the output gear.

[0071] In other words, the step increments between the individual gear ratios defined by the pairs of fixed gears and idler gears are each smaller than a step increment between two gear ratios defined by the respective crown gear.

[0072] By combining the former with the latter gear ratios (in the sense of connecting the two corresponding gear stages in series), a total range of gear stages of the bottom bracket gearshift can be realized, which essentially consists of two halves of gear stages, with the two halves overlapping only slightly or not at all.

[0073] In a preferred variant, the ratio between the largest and the smallest of the gear ratios provided by the pairs of a fixed gear and a loose gear is smaller than the ratio between a larger and a smaller gear ratio, which is provided in each case by a pair of one of the at least two crown gear pinions and the crown gear meshing therewith, when the crown gear pinion serves as the drive gear and the crown gear as the output gear.

[0074] In other words, in this case, even the step difference between the largest and the smallest of the gear ratios defined by the pairs of fixed gears and idler gears is smaller than a step difference between two gear ratios defined by the respective crown gear.

[0075] When combining the former with the latter gear ratios, the total gear range of the bottom bracket shifting system consists of two halves that do not overlap. By appropriately defining the individual gear ratios and the corresponding step increments, a continuous, evenly spaced gear range of the bottom bracket shifting system can be achieved with twice as many gears as there are pairs of fixed gears and loose gears.

[0076] In a further preferred embodiment of the invention, a planetary gear is arranged in the torque flow between the bottom bracket shaft and the drive gear, which provides at least one smaller and one larger gear ratio between a respective drive gear and a respective output gear of the planetary gear.

[0077] In this design too, the number of available gear steps can be doubled by combining the gear ratios provided by the pairs of fixed gears and idler gears with the at least two gear ratios provided by the planetary gear.

[0078] A planetary gear is a standard gear design in which all shafts are coaxial. Therefore, the planetary gear is preferably arranged coaxially with the bottom bracket shaft.

[0079] In a preferred variant of this embodiment, when the gear ratios provided by the pairs of one fixed gear and one idler gear are arranged in ascending order, the ratio of the larger to the smaller of any two consecutive of these gear ratios is smaller than the ratio between the larger and the smaller gear ratio provided by the planetary gear.

[0080] The advantages achieved in this way are the same as with a crown gear drive with at least two crown gear pinions and are therefore not repeated here.

[0081] In a further preferred variant of the embodiment with a planetary gear, the ratio between the largest and the smallest of the gear ratios provided by the pairs of one fixed gear and one loose gear is smaller than the ratio between the larger and the smaller gear ratio provided by the planetary gear.

[0082] The advantages achieved in this way are the same as with a crown gear drive with at least two crown gear pinions and are therefore not repeated here.

[0083] In a further preferred variant of the embodiment with a planetary gear, the larger gear ratio provided by the planetary gear has the value 1 and is realized by a direct transmission in the planetary gear.

[0084] By selecting and implementing one of the gear ratios using the planetary gear system, the following behavior of the bottom bracket gear system can be achieved, which is advantageous in practice: Due to legal regulations, pedal assistance from the electric auxiliary motor on electric bicycles is only available at speeds of up to 25 km / h. Lower gear steps on the bottom bracket gear system generally correspond to lower speeds and vice versa. From an ergonomic point of view, it therefore makes sense to implement the gear steps for which motor assistance is available, i.e. the lower gear steps, using gear steps with a lower efficiency. This is because when riding in these gear steps there is sufficient torque available from the electric motor anyway and the lower efficiency therefore has little or no effect on riding comfort.Conversely, the gear ratios without motor assistance, i.e. the higher gear ratios, should be realized by those gear ratios with a better efficiency, since in this case the driver has to generate the torque exclusively through muscle power.

[0085] In this variant, precisely this is achieved by implementing the larger gear ratio of 1 provided by the planetary gear unit through a direct transmission, thus transmitting torque only via rigidly connected components. This eliminates transmission losses, resulting in very good efficiency. The smaller gear ratio provided by the planetary gear unit, on the other hand, can be achieved through meshing gears, which will generally result in lower efficiency.

[0086] In a preferred variant of the design with both a planetary gear set and two crown gear pinions, the planetary gear set comprises a sun gear, a carrier connecting at least two planetary gears, and a ring gear. The shaft on which the at least two crown gear pinions are arranged is the selector shaft. The sun gear and the carrier of the planetary gear set are each designed as one of the crown gears. The sun gear forms the drive gear of the planetary gear set for the smaller gear ratio, and the carrier forms the drive gear of the planetary gear set for the larger gear ratio. The carrier forms the output gear of the planetary gear set for both the smaller and the larger gear ratio.

[0087] This describes a specific technical design with a planetary gear and two crown gear pinions. Because the planetary gear carrier forms both the drive gear and the output gear for the higher gear ratio, the previously described configuration of a direct transmission of the planetary gear, which is advantageous in the practical operation of an electric bicycle, results in a correspondingly high level of efficiency in the higher gear ratios.

[0088] A bicycle according to the invention has a drive train comprising a bottom bracket gear system according to the invention, a wheel for generating propulsion of the bicycle, and a drive means, in particular a chain or belt, for transmitting torque from the drive gear to the wheel. A planetary gear is arranged in the torque flow behind the drive gear, providing at least one smaller and one larger gear ratio between a respective drive gear and a respective output gear of the planetary gear.

[0089] The position of the planetary gear in the torque flow behind the drive gear is preferably in the rear wheel hub of the bicycle. This position is well known from conventional bicycles with hub gears and can therefore be easily implemented. The bicycle according to the invention thus features a combined bottom bracket and rear wheel hub gear system. Separating the two gear systems results in a more even distribution of weight and the required installation space for the entire gear system, which can be advantageous from both a riding and design perspective.

[0090] Further advantages, features and possible applications of the present invention will become apparent from the following description in conjunction with the figures.

[0091] They show:

[0092] Fig. 1 is a side view of an electric bicycle with bottom bracket gears;

[0093] Fig. 2 is an enlarged side view of the bottom bracket area of ​​the bicycle in Fig. 1; Fig. 3 is a section through a bottom bracket gearshift according to the invention along the line A-B in Fig. 2 in a first embodiment;

[0094] Fig. 4 shows a section through a bottom bracket gearshift according to the invention along the line A - B in Fig. 2 in a second embodiment;

[0095] Fig. 5 is a section through a bottom bracket gearshift according to the invention along the line A - B in Fig. 2 in a third embodiment;

[0096] Fig. 6 shows a section through a bottom bracket gearshift according to the invention along the line A - B in Fig. 2 in a fourth embodiment;

[0097] Fig. 7 is a table with a concrete configuration of the gear stages of the bottom bracket shifting system according to Fig. 5.

[0098] Fig. 8 is a table with a concrete configuration of the gear stages of the bottom bracket shifting system according to Fig. 6.

[0099] Fig. 1 shows a side view of an electric bicycle with a bottom bracket gear system 10 into which an electric drive motor (not visible) is integrated. The frame 1 has a top tube 2, a down tube 3 and a seat tube 4. The battery 5 for the electric drive motor is integrated in the down tube 3. At the lower end of the seat tube 4 and the down tube 3 there is a bracket 9 into which the bottom bracket gear system 10 is screwed. The rear wheel 13 is attached to a swing arm 14 and rotates about the rotation axis 19. The electric bicycle has a front wheel suspension 15 and a rear wheel suspension 16. The rider applies his or her mechanical power to the pedals 6 and thus the cranks 7, whereby the bottom bracket gear system 10 is subjected to the human drive power.Within the bottom bracket shifting system 10, the gear selected by the rider via a control element 11 on the handlebar 17 is set. Within the bottom bracket shifting system 10, additional drive power is added to the pedaling power provided by the rider. This additional power is provided by an electric motor. The illustration in Fig. 1 is only an example. The bottom bracket shifting system 10 can be designed with or without an auxiliary drive.

[0100] In the embodiment shown in Fig. 1, the electric bicycle has a belt drive. However, it can instead have, for example, a conventional chain drive or a cardan drive. The output shaft of the bottom bracket gear 10 runs coaxially with the bottom bracket shaft 18 and carries the front pulley 8 as the drive gear, which thus forms the transmission output. The pulley 8 rotates at different speeds relative to the pedal cranks 7, depending on which gear has been engaged by the rider. The mechanical power is transmitted to the rear wheel 13 via a belt 12, in particular a toothed belt.

[0101] Fig. 2 shows an enlarged side view of the bottom bracket area of ​​the bicycle shown in Fig. 1. For clarity, not all components are shown. In particular, the cranks 7, the pedals 6, and the belt 12 have been omitted in Fig. 2. Clearly visible in Fig. 2 is the position of the bottom bracket gearshift 10 in a housing 20 in front of the bottom bracket and below the down tube 3 and the seat tube 4.

[0102] Fig. 3 shows a section through a bottom bracket gearshift 10 according to the invention along the line A - B in Fig. 2 in a first embodiment.

[0103] 1 and 2, the torque generated by the rider is introduced into the bottom bracket gearshift 10 via the bottom bracket spindle 18. The bottom bracket spindle 18 is supported relative to the housing 20 on the left side as seen in the direction of travel by a bearing 301. The bearing 301, as well as all of the bearings mentioned below, is preferably designed as a rolling bearing, in particular as a ball bearing, needle bearing or roller bearing. On the right side as seen in the direction of travel, the bottom bracket spindle 18 is not directly supported relative to the housing 20, but only indirectly via a bearing 302, which supports an output shaft 303, which is designed as a hollow shaft and is in turn supported relative to the housing 20 by a bearing 304. As already mentioned, the front pulley 8 is also fastened coaxially and rotationally fixed to the output shaft 303.

[0104] Via a flange mounted axially approximately in the center of the bottom bracket spindle 18, the torque is transmitted to a measuring shaft 305, which is designed as a hollow shaft coaxial with the bottom bracket spindle 18. The measuring shaft 305 is supported relative to the bottom bracket spindle 18 by an additional measuring shaft bearing 306. The measuring shaft 305 has a thin-walled section in which it can be twisted relatively strongly. A sensor 307 is arranged in this section, which determines the torque applied to the measuring shaft 305 from this torsion. A sensor for the speed of the measuring shaft 305 can also be arranged at the sensor 307.

[0105] The torque is then transmitted via a freewheel 308. This is only active during the forward pedaling movement of the pedal cranks 7. The freewheel 308 ensures that the electric motor 321, which is described further below, cannot inadvertently drive the rider's legs due to a malfunction. Such a torque could cause the rider to lose control of the pedal cranks 7, which in the worst case could lead to a fall. The freewheel 308 also allows the rider to move the pedal cranks 7 backward, for example, to bring them into the correct position for starting again after stopping.

[0106] The freewheel 308 transmits the torque during forward pedaling to a drive-side crown gear 309, which is supported relative to the bottom bracket spindle 18 by a bearing 310. The drive-side crown gear 309 meshes with a drive-side crown gear pinion 311, whose rotational axis, in the exemplary embodiment, is oriented orthogonally to the rotational axis of the bottom bracket spindle 18, with the two rotational axes intersecting. However, other relative positions of the two rotational axes of the bottom bracket spindle 18 and the drive-side crown gear pinion 311 are also conceivable, for example, such that the two rotational axes enclose a non-right angle or such that the two rotational axes do not intersect, which would result in an axial offset between the drive-side crown gear 309 and the drive-side crown gear pinion 311.

[0107] The arrangement of the drive-side crown gear 309 and the drive-side crown gear pinion 311 is also referred to as the drive-side crown gear transmission.

[0108] The drive-side crown gear pinion 311 is rotationally and permanently connected to a fixed shaft 314, which thus lies in a plane parallel to the center plane of the bicycle and offset to the left. However, it is clear from Fig. 2 that the fixed shaft 314 is not aligned horizontally during operation of the bicycle, but rather has a slight upward inclination in the direction of travel, corresponding to the inclination of the section plane AB.

[0109] The fixed shaft 314 is mounted relative to the housing 20 by shaft bearings 316 and 317. In addition to the drive-side crown gear 311, several fixed gears 318A-H—eight in the embodiment shown in Fig. 3—are arranged coaxially on the fixed shaft 314 and are non-rotatably and permanently connected to the fixed shaft 314.

[0110] A selector shaft 315 is arranged essentially mirror-inverted to the fixed shaft 314 with respect to the center plane of the bicycle. This shaft is also mounted relative to the housing 20 by shaft bearings 316 and 317. A driven-side crown pinion 313 and eight idler gears 319A-H are arranged coaxially on the selector shaft 315 at corresponding axial positions, mirror-inverted to the drive-side crown pinion 311, wherein the driven-side crown pinion 313 is non-rotatably and permanently connected to the selector shaft 315, and the idler gears 319A-H are detachably and non-rotatably connected.

[0111] The fixed gears 318A-H form pairs with the idler gears 319A-H, with the fixed gear 318A meshing with the idler gear 319A, the fixed gear 318B meshing with the idler gear 319B, and so on. While the diameters of the fixed gears 318A-H decrease in this order, the diameters of the idler gears 319A-H increase in this order. This results in descending gear ratios for the pairs in the above order. An axially interchanged arrangement on the fixed shaft 314 and the selector shaft 315 is also possible, of course.

[0112] As will be described in more detail below, of the pairs consisting of one of the fixed gears 318A-H and one of the loose gears 319A-H, only one pair is active at a time, i.e., the torque is transmitted from the fixed shaft 314 to the shift shaft 315 only via such a pair. If several such pairs were active at the same time, as is immediately apparent, the bottom bracket shift 10 would lock due to the different gear ratios of the various pairs. In the bottom bracket shift 10 according to Fig. 3, the active pair determines the engaged gear. The bottom bracket shift 10 according to Fig. 3 thus has eight different gears.

[0113] Also arranged in a mirror image with respect to the center plane of the bicycle to the drive-side crown gear 309 is an output-side crown gear 312, which is coaxially and rotationally fixedly connected to the output shaft 303 and is thus also supported by the bearing 304 relative to the housing 20. The output-side crown gear 312 meshes with the output-side crown gear pinion 313 and transmits the torque via the output shaft 303 directly to the front pulley 8. As described above in connection with Fig. 1, but not shown again in Fig. 3, the rear wheel 13 is driven by the front pulley 8 via the belt 12 and thus ensures the propulsion of the bicycle.

[0114] The arrangement of the output-side crown gear 312 and the output-side crown gear pinion 313 is also referred to as the output-side crown gear transmission. Since the drive-side crown gear 309 has a diameter several times larger than the drive-side crown gear pinion 311, the drive-side crown gear transmission results in a large gear ratio, which is significantly greater than 1. In other words, during operation of the bicycle, the fixed shaft 314 and the shift shaft 315 rotate at a speed several times higher than the bottom bracket shaft 18. The bottom bracket shaft 18 rotates at the rider's pedaling frequency, which is typically in the range of 60-90 rpm. A reciprocal transmission ratio results between the output-side crown gear pinion 313 and the output-side crown gear 312, which is therefore significantly smaller than 1 for the output-side crown gear transmission.The front pulley 8 thus rotates at the same speed as the bottom bracket shaft 18, if the change in speed due to the engaged gear, ie due to the transmission ratio of the active pair consisting of a fixed gear 318A-H and a loose gear 319A-H, is ignored.

[0115] Since, as already mentioned, only one of the pairs consisting of a fixed gear 318A-H and an idler gear 319A-H may be active at a time, each idler gear 319A-H is releasably connected to the selector shaft 315 by a respective clutch 320A-H. For the sake of clarity, only one of the clutches 320A-H, namely clutch 320A, is identified by a reference numeral in Fig. 3.

[0116] The clutches 320A-H are preferably designed as switchable freewheels, which, even when closed, allow rotation of the respective idler gear 319A-H relative to the shift shaft 315 in the non-drive direction, so that the bottom bracket gearshift 10 does not lock if several pairs of one fixed gear 318A-H and one idler gear 319A-H are briefly active. For example, if the pair of the fixed gear 318A and the idler gear 319A, as well as the pair of the fixed gear 318B and the idler gear 319B, were active simultaneously, the idler gear 319A, which rotates faster due to the gear ratios of these two pairs, would "overtake" the idler gear 319B, which rotates slower, and the clutch 320B on the idler gear 319B, which rotates slower, would "slip" due to its freewheel function.

[0117] In the embodiment shown in Fig. 3, the clutches 320A-H are internal ratchet clutches, which are actuated via a camshaft 334 rotating in the selector shaft 315. Such ratchet clutches are generally known to those skilled in the art and are therefore not described in further detail.

[0118] Particularly when shifting under load, there is increased surface pressure between the power-transmitting components within the 320A-H clutches, making it difficult to operate the 320A-H clutches. Therefore, it is desirable that the torque applied to the 320A-H clutches be as low as possible.

[0119] This is taken into account by the speed and torque curve within the bottom bracket gearshift 10: The speed of the bottom bracket shaft 18 is greatly increased via the drive-side crown gear and, with the appropriate selection of the gear ratios of the pairs of fixed gears 318A-H and idler gears 319A-H, increased again, thereby reducing the torque accordingly, so that only the desired, relatively small torque is applied to the clutches 320A-H. This increase in speed and reduction in torque are compensated for by the output-side crown gear and, if applicable, by the gear ratio of the belt drive consisting of the front pulley 8, the belt 12, and the rear pulley, so that the entire drive train of the bicycle ultimately provides the desired gear ratios for driving the rear wheel.

[0120] The camshaft 334 in the selector shaft 315 is controlled via a so-called superposition gear 329, whose function is to adjust the rotating camshaft 334's rotational position by specific angular increments to actuate the rotating clutches 320A-H. Such a superposition gear is also generally known to those skilled in the art and will therefore not be described in detail. Control via such a superposition gear is known, for example, from EP 1 982 913 A1.

[0121] The actual switching movement through a specific angle of rotation, which is transmitted to the camshaft 334 by the superposition gear 329, is generated by an actuator motor 332, which is preferably designed as an electric servomotor. Since such a motor generally has a very high speed, a reduction gear 333 is connected downstream of the actuator motor 332, which reduces the motor speed and simultaneously increases the motor torque, so that a slower but more powerful switching movement is available at the input of the superposition gear 329. The actuator motor 332 is in turn connected via an electrical connection (not shown) to the control element 11 on the handlebar 17 of the bicycle. This control element can be, for example, a rocker switch with two buttons for shifting up and down the individual gears or a rotary switch.

[0122] A sensor 331, in particular a rotary encoder, is also arranged at the output of the reduction gear 333 to monitor the correct generation of the desired switching movement. The sensor 331 is connected to processing electronics 330, which is capable of transmitting signals, for example, via a bus system (not shown).

[0123] The bottom bracket shifting system 10 additionally has an auxiliary drive in the form of an electric motor 321, which is integrated with the transmission in the housing 20. In the exemplary embodiment according to Fig. 3, the electric motor 321 is arranged at the front left in the housing 20, as viewed in the direction of travel, and the motor shaft 322, with the motor shaft pinion 323, is arranged parallel to the fixed shaft 314 and the shift shaft 315 and thus orthogonal to the bottom bracket shaft 18. The motor shaft 322 is mounted both by a bearing within the electric motor 321 (not shown) and by a bearing 324 supported on the housing 20 outside the electric motor 321. The motor shaft pinion 323 meshes with a reduction gear 325, which has a significantly larger diameter than the motor shaft pinion 323, thereby reducing the motor speed. The shaft of the reduction gear 325 is supported by two bearings 326 on both sides of the reduction gear 325 relative to the housing 20.

[0124] At the end of the shaft of the reduction gear 325 facing the bottom bracket shaft 18, a freewheel 327 is arranged, which transmits the reduced motor speed to a motor drive pinion 328 in the drive direction of the bottom bracket gear 10, but slips in the non-drive direction. This ensures that torque is never transmitted from the transmission to the electric motor 321. In this case, the electric motor 321 would act as a generator and thus exert mechanical resistance on the rider's pedaling movement, thus reducing the drive power available for propelling the bicycle. Even if the rider pedals backward, no torque can be transmitted from the transmission to the electric motor 321, since in this case the freewheel 308 would already slip, as described above.

[0125] The torque is then transferred from the motor drive pinion 328 to the fixed gear 318A, where it is further reduced. In this way, the (reduced-speed) torque of the electric motor 321 is introduced into the torque flow from the bottom bracket shaft 18 to the pulley 8 and can thus be used to assist the rider's pedaling motion.

[0126] At the same time, the fixed gear 318A is the one of the fixed gears 318A-H with the largest diameter, resulting in the smallest possible gear ratio between the motor drive pinion 328 and one of the fixed gears 318A-H. Thus, the fixed gears 318A-H, in particular the largest fixed gear 318A, can be used to reduce the speed and correspondingly increase the torque of the electric motor 321. This is the case regardless of whether the pair of the fixed gear 318A and the idler gear 319A is active or not, i.e., whether the corresponding gear position is engaged in the bottom bracket shift 10 or not. If this pair is not currently active, the motor torque is still transmitted from the motor drive pinion 328 via the fixed gear 318A to the fixed shaft 314 and from there to the fixed gear 318A-H and to the associated idler gear 319A-H of the currently active pair.If the pair of fixed gear 318A and idler gear 319A is currently active, the motor torque is transmitted from the motor drive pinion 328 via the fixed gear 318A directly to the associated idler gear 319A.

[0127] Figs. 4 to 6 show further embodiments of the bottom bracket gearshift 10 according to the invention, which differ only in certain details from the first embodiment according to Fig. 3.

[0128] The following conventions apply to the reference numerals in Figs. 3 to 6: Elements that correspond to those in previous figures and do not differ or differ only insignificantly from them are not provided with reference numerals again. Elements that correspond to those in previous figures but differ significantly from them are provided with corresponding reference numerals as in the previous figure, with the first digit replaced by the number of the previous figure. For example, the selector shaft in Fig. 3 has the reference numeral 315 and in Fig. 4 the reference numeral 415. Elements that have no equivalent in the previous figures are provided with new reference numerals.

[0129] Fig. 4 shows a section through a bottom bracket gearshift 10 according to the invention along the line A - B in Fig. 2 in a second embodiment.

[0130] The bottom bracket shifting system 10 according to Fig. 4 has, in contrast to the one according to Fig. 3, only four pairs of fixed gears 418A-D and four loose gears 419A-D. The bottom bracket shifting system 10 according to Fig. 4 thus has four different gear stages. In contrast to the exemplary embodiment according to Fig. 3, the shift shaft 415 is designed as a solid shaft. Accordingly, the clutches 420A-D are not internal ratchet clutches, but external dog clutches, which are arranged flange-like and coaxially on the shift shaft 415 next to the associated loose gear 419A-D. Each clutch 420A-D can be moved into the open or closed position by an associated actuator 435A-D. The actuators 435A-D are controlled by a common camshaft 434, which is arranged parallel to the shift shaft 415 in the housing 20. The camshaft 434 is - in a similar manner as in the embodiment according to Fig.3 - controlled via a reduction gear 433 by an actuator motor 432, which is only shown schematically in Fig. 4. Only the superposition gear is omitted in this embodiment, since the actuators 435A-D do not rotate. In the schematic representation of Fig. 4, the switching commands are transmitted to the rotating claw clutches 420A-D by the protruding arms of the actuators 435A-D. An actuator actuates the four claw clutches 420A-D, which are also designed as switchable freewheels, via an actuating device (neither shown).

[0131] Furthermore, in the embodiment shown in Fig. 4, additional sensors are mounted that individually monitor the rotational speeds of various shafts, allowing the overall function of the bottom bracket gear system 10 to be monitored. These are sensor 436 for the fixed shaft 414, sensor 437 for the selector shaft 415, sensor 438 for the input shaft or for the output shaft of the reduction gear 433, and sensor 439 for the shaft of the electric motor 321.

[0132] The basic function and the torque flow of the bottom bracket gearshift 10 in the embodiment according to Fig. 4 correspond to the embodiment according to Fig. 3 and are therefore not described again in detail.

[0133] Fig. 5 shows a section through a bottom bracket shifting system 10 according to the invention along line A-B in Fig. 2 in a third embodiment. The clutches for the idler gears 519A-D are shown only schematically in Fig. 5 and are designated K1 to K4. Like the clutches 420A-D in Fig. 4, they can be implemented as external clutches. The controls of these clutches are also indicated only in solid lines in Fig. 5. At this point, it is possible to use clutch devices and actuating devices according to the prior art.

[0134] The essential difference between the embodiment shown in Fig. 5 and that shown in Fig. 4 is that the output-side crown gear 512 has two separate, coaxially arranged gear rings 512A-B at different radial positions, which form two running gears for two crown gear pinions. The gear rings 512A-B have different numbers of teeth. Accordingly, two output-side crown gear pinions 513A-B are arranged on the selector shaft 515, each meshing with a gear ring 512A-B. The different radial positions of the gear rings 512A-B result in two different gear ratios in the output-side crown gear transmission.

[0135] The two output-side crown gear pinions 512A-B are connected to the selector shaft 515 by additional clutches, designated K5 and K6 in Fig. 5. Clutches K5 and K6, like clutches 320A-H in Fig. 3, can be implemented as internal clutches. The controls of clutches K5 and K6 are also indicated in Fig. 5 in the form of solid lines; they can be implemented by an internal camshaft 334 in the selector shaft 515, as in Fig. 3.

[0136] Each of the four gear ratios of the pairs of fixed gears 518A-D and idler gears 519A-D can be combined with the two gear ratios of the output-side crown gear. The bottom bracket shift 10 according to Fig. 5 thus has a total of eight different gear stages. By appropriately selecting the individual gear ratios, these can preferably be arranged such that the four gear ratios of the pairs of fixed gears 518A-D and idler gears 519A-D combined with the smaller gear ratio of the output-side crown gear are all below the corresponding four gear ratios combined with the larger gear ratio of the output-side crown gear.

[0137] In order to engage the eight gears of the bottom bracket shift 10 shown in Fig. 5 in a continuous, ascending sequence, the clutches K1 to K4, on the one hand, and the clutches K5 and K6, on the other hand, must be engaged alternately in a specific sequence. For example, in the preferred arrangement of the individual gear ratios just mentioned, starting with all the clutches K1 to K6 open:

[0138] - K5 closed and K4 closed (gear stage 1),

[0139] - K3 closed and K4 open (gear stage 2),

[0140] - K2 closed and K3 open (gear stage 3),

[0141] - Ki closed and K2 opened (gear stage 4),

[0142] - K5 open, K6 closed, K1 open and K4 closed (gear stage 5),

[0143] - K3 closed and K4 open (gear stage 6),

[0144] - K2 closed and K3 open (gear stage 7),

[0145] - Ki closed and K2 opened (gear stage 8).

[0146] In order to generate these alternating shifting commands for the two clutch groups K1 to K4 or K5 and K6, a stepping gear is additionally integrated into the reduction gear 533. This stepping gear not only reduces the speed of the actuating movement of the actuator motor 432, but also divides it into two separate, synchronized movements for the two clutch groups according to the desired clutch control. Such a stepping gear is again generally known to those skilled in the art and is therefore not described in detail here. The embodiment according to Fig. 5 thus results, just like the embodiment according to Fig. 3, in a bottom bracket shift 10 with eight gear steps, but with a reduced number of components and thus lower manufacturing costs, as well as—due to the reduction from eight to four fixed gears 518A-D and loose gears 519A-D—with a shorter length transverse to the bottom bracket axis 18.

[0147] For the exemplary embodiment shown in Fig. 5, the table in Fig. 7 shows exemplary tooth counts of the gears involved, as well as exemplary gear ratios. For this exemplary design of the bottom bracket gearshift 10, the step difference between the largest and smallest of the eight gear steps is approximately 305 percent. Of course, the bottom bracket gearshift 10 can also be designed with other tooth counts and / or gear ratios.

[0148] Fig. 6 shows a section through a bottom bracket gearshift 10 according to the invention along the line A - B in Fig. 2 in a fourth embodiment.

[0149] The embodiment according to Fig. 6 differs from that according to Fig. 5 in that six instead of four pairs of fixed gears 618A-F and idler gears 619A-F are provided. As in Fig. 5, two output-side crown gear pinions 613A-B are provided. Also, as shown in Fig. 5, external clutches K1 to K6 are provided for the idler gears 619A-F, and internal clutches K7 and K8 are provided for the output-side crown gear pinions 613A-B.

[0150] The clutches Ki to K8 are controlled by an actuator motor 632, similar to Fig. 5. Downstream of this—shown separately in Fig. 6—are a reduction gear 633, which reduces the motor speed, and a stepping gear 647, which generates the different switching movements for the clutches Ki to K6, on the one hand, and K7 to K8, on the other hand. Also shown in Fig. 6 is a control electronics unit 648, which controls the actuator motor 632 (but not the electric auxiliary motor 321) and receives the signals from the following sensors, particularly for speeds, angles of rotation, and / or torques (indicated by dashed or dotted lines):

[0151] Sensor S1 for the bottom bracket shaft 18,

[0152] Sensor S2 for the motor shaft 322,

[0153] Sensor S3 for the web 644 of the planetary gear 640 connected to the output shaft 303, which is explained below,

[0154] Sensor S4 for the fixed shaft 614,

[0155] Sensor S5 for the selector shaft 615,

[0156] Sensor S6 for the reduction gear 633,

[0157] Sensor S7 for the actuator motor 632 and

[0158] Sensor S8 for the motor temperature and motor current of the electric motor 321 .

[0159] However, the essential design difference of the bottom bracket gearshift 10 according to Fig. 6 compared to that according to Fig. 5 is that the output-side crown gear has been extended by a planetary gear 640 arranged coaxially with respect to the bottom bracket shaft 18.

[0160] The planetary gear 640 has a ring gear 641, which is riveted to the housing 20 and thus permanently connected thereto for rotation, a sun gear 643, which is rotatably mounted on the bottom bracket shaft 18 by a bearing 602, and a circumferential web 644, which has two parallel, rigidly connected flanges, between which several, for example four, planet gears 645 are arranged distributed over the circumference. The planet gears 645 mesh radially inward with the sun gear 643 and radially outward with the fixed ring gear 641. The flange of the web 644 directed toward the output shaft 303 is formed integrally with the output shaft 303.

[0161] The sun gear 643 has a radially outwardly directed flange on which a gear ring 642B with teeth parallel to the bottom bracket shaft 18 is arranged. The gear ring 642B functions as an output-side crown gear and meshes with the radially inner output-side crown gear pinion 613B.

[0162] The web 644 also has a gear ring 642A with teeth aligned parallel to the bottom bracket shaft 18, which is arranged coaxially to and radially outside the gear ring 642B. The gear ring 642A also functions as an output-side crown gear and meshes with the radially outer output-side crown gear pinion 613A.

[0163] When clutch K7 is closed and clutch K8 is opened, the torque is transmitted from the selector shaft 615 to the radially outer output-side crown gear pinion 613A and from there to the radially outer gear ring 642A, which is formed integrally with the flange of the web 644 directed away from the output shaft 303 and is thus non-rotatably connected to the output shaft 303 via the other flange of the web 644. This results in a direct transmission with a transmission ratio of 1 to the output shaft 303 and to the front pulley 8 within the planetary gear 640.

[0164] When clutch K7 is opened and clutch K8 is closed, the torque is transmitted from the selector shaft 615 to the radially inner output-side crown gear pinion 613B and from there to the radially inner gear ring 642B and thus to the sun gear 643, which meshes with the planet gears 645, and from the planet gears 645 via the web 644 to the output shaft 303 and to the front pulley 8. This results in a transmission with a transmission ratio of less than 1 within the planetary gear 640.

[0165] Each of the six gear ratios of the pairs of fixed gears 618A-F and idler gears 619A-F can in turn be combined with the two gear ratios of the planetary gear 640. The bottom bracket gearshift 10 according to Fig. 6 thus has a total of twelve different gear steps. In contrast to the bottom bracket gearshift 10 according to Fig. 5, in Fig. 6, in addition to the step change between the two gear ratios of the output-side crown gear, a further step change can be achieved between the two gear ratios of the planetary gear 640. This further step change in the planetary gear 640 enables an arrangement of the total of twelve gear steps of the bottom bracket gearshift 10 according to Fig.6 such that the six gear ratios of the pairs of fixed gears 618A-F and idler gears 619A-F combined with the smaller gear ratio of the planetary gear 640 are all below these six gear ratios combined with the larger gear ratio of the planetary gear 640. In the bottom bracket gearshift 10 according to Fig. 5, the step change in the output-side crown gear is sufficient for a corresponding arrangement of the gear ratios, since the bottom bracket gearshift 10 there does not have two times six, but only two times four gear steps.

[0166] For the embodiment shown in Fig. 6, the table in Fig. 8 shows exemplary tooth counts of the gears involved, as well as exemplary gear ratios. For this exemplary design of the bottom bracket gearshift 10, the step difference between the largest and smallest of the twelve gear steps is approximately 575 percent. Of course, the bottom bracket gearshift 10 can also be designed with other tooth counts and / or gear ratios.

[0167] List of reference symbols

[0168] 1 frame

[0169] 2 top tube

[0170] 3 down tube

[0171] 4 seat tube

[0172] 5 Battery

[0173] 6 pedals

[0174] 7 crank

[0175] 8 Front pulley

[0176] 9 Bracket

[0177] 10 bottom bracket gears

[0178] 11 Control element

[0179] 12 belts

[0180] 13 Rear wheel

[0181] 14 Swingarm

[0182] 15 Front wheel suspension

[0183] 16 Rear wheel suspension

[0184] 17 handlebars

[0185] 18 bottom bracket spindle

[0186] 19 Rear wheel rotation axis

[0187] 20 housings

[0188] 301 warehouses

[0189] 302 warehouses

[0190] 303 Output shaft

[0191] 304 warehouses

[0192] 305 measuring shaft

[0193] 306 measuring shaft bearings

[0194] 307 Sensor

[0195] 308 freewheel

[0196] 309 Drive-side crown gear

[0197] 310 crown gear bearing

[0198] 311 Drive-side crown gear pinion 312 Output-side crown gear

[0199] 313 Output-side crown gear pinion

[0200] 314 fixed shaft

[0201] 315 shift shaft

[0202] 316 shaft bearings

[0203] 317 shaft bearings

[0204] 318A-H fixed gear

[0205] 319A-H idler gear

[0206] 320A-H coupling

[0207] 321 electric motor

[0208] 322 Motor shaft

[0209] 323 Motor shaft pinion

[0210] 324 engine mounts

[0211] 325 reduction gear

[0212] 326 Reduction gear bearing

[0213] 327 freewheel

[0214] 328 Motor drive pinion

[0215] 329 superposition gear

[0216] 330 Processing electronics

[0217] 331 Sensor

[0218] 332 Actuator motor

[0219] 333 Reduction gear

[0220] 334 camshaft

[0221] 414 fixed shaft

[0222] 415 shift shaft

[0223] 418A-D fixed gear

[0224] 419A-D idler gear

[0225] 420A-D clutch

[0226] 432 Actuator motor

[0227] 433 Reduction gear

[0228] 434 camshaft

[0229] 435A-D Actuator

[0230] 436 Sensor 437 Sensor

[0231] 438 Sensor

[0232] 439 Sensor

[0233] 512 Output-side crown gear

[0234] 512A-B Gear ring of the output side crown gear

[0235] 513A-B Output-side crown gear pinion

[0236] 514 fixed shaft

[0237] 515 shift shaft

[0238] 518A-D fixed gear

[0239] 519A-D idler gear

[0240] 533 Reduction and indexing gears

[0241] 602 warehouses

[0242] 612A-B Output side crown gear

[0243] 613A-B Output side crown gear pinion

[0244] 614 fixed shaft

[0245] 615 shift shaft

[0246] 618A-F fixed gear

[0247] 619A-F idler gear

[0248] 632 Actuator motor

[0249] 633 Reduction gear

[0250] 640 planetary gear

[0251] 641 ring gear

[0252] 642A-B Planetary gear ring

[0253] 643 Sun gear

[0254] 644 jetty

[0255] 645 planetary gear

[0256] 646 warehouses

[0257] 647 stepping gear

[0258] 648 Control electronics

Claims

Patent claims 1. Bottom bracket gear (10) for a bicycle, comprising: - a bottom bracket shaft (18), - a fixed shaft (314, 414, 514, 614) on which at least two fixed gears (318A-H, 418A-D, 518A-D, 618A-F) are arranged coaxially and are connected to the fixed shaft (314, 414, 514, 614) in a rotationally fixed manner, - a selector shaft (315, 415, 515, 615) on which at least two loose gears (319A-H, 419A-D, 519A-D, 619A-F) are arranged coaxially and are detachably and non-rotatably connected to the selector shaft (315, 415, 515, 615), - a drive means wheel (8), in particular a chain wheel or a belt wheel, wherein the at least two fixed gear wheels (318A-H, 418A-D, 518A-D, 618A-F) and the at least two loose gear wheels (319A-H, 419A-D, 519A-D, 619A-F) are arranged in pairs such that in each case a fixed gear wheel (318A-H, 418A-D, 518A-D, 618A-F) meshes with a loose gear wheel (319A-H, 419A-D, 519A-D, 619A-F), whereby in each case a specific transmission ratio is provided when the fixed gear wheel (318A-H, 418A-D, 518A-D, 618A-F) is used as a drive wheel and the loose gear wheel (319A-H, 419A-D, 519A-D, 619A-F) serves as the output gear, wherein a gear ratio is defined as the ratio of the speed of the output gear to the speed of the drive gear, wherein each of the at least two idler gears (319A-H, 419A-D, 519A-D, 619A-F) is connected to the selector shaft (315, 415, 515, 615) by a respective clutch (320A-H, 420A-D; Ki,..., K6) which can be brought into a closed state in which the loose gear (319A-H, 419A-D, 519A-D, 619A-F) is connected to the selector shaft (315, 415, 515, 615) in a rotationally fixed manner in at least one direction of rotation, and into an open state in which the loose gear (319A-H, 419A-D, 519A-D, 619A-F) is connected to the selector shaft (315, 415, 515, 615) in a rotationally fixed manner in both directions of rotation. wherein, during operation of the bicycle, a torque flow is enabled from the bottom bracket shaft (18) in this order to the fixed shaft (314, 414, 514, 614), to a fixed gear (318A-H, 418A-D, 518A-D, 618A-F), to the loose gear (319A-H, 419A-D, 519A-D, 619A-F) meshing with this fixed gear (318A-H, 418A-D, 518A-D, 618A-F), to the selector shaft (315, 415, 515, 615) and to the drive gear (8).

2. Bottom bracket gearshift (10) according to claim 1, characterized in that at least half of the pairs of one fixed gear (318A-H, 418A-D, 518A-D, 618A-F) and one loose gear (319A-H, 419A-D, 519A-D, 619A-F) each provide a gear ratio which is greater than 1.

3. Bottom bracket gearshift (10) according to claim 1 or 2, characterized in that at least two of the at least two loose gears (319A-H, 419A-D, 519A-D, 619A-F) have different modules, wherein in each case the module of a first loose gear (319A-H, 419A-D, 519A-D, 619A-F), the diameter of which is greater than or equal to the diameter of a second loose gear (319A-H, 419A-D, 519A-D, 619A-F), is also greater than or equal to the module of the second loose gear (319A-H, 419A-D, 519A-D, 619A-F).

4. Bottom bracket gearshift (10) according to one of the preceding claims, characterized in that the bottom bracket gearshift (10) further comprises an auxiliary drive (321), in particular an electric motor, the torque of which can be introduced into the torque flow from the bottom bracket shaft (18) to the drive gear (8), wherein a torque flow from the auxiliary drive shaft (322) of the auxiliary drive (321) to the drive gear (8) is enabled via an auxiliary drive gear (318A, 418A, 518A, 618A), which is one of the following gears: - one of at least two fixed gears (318A-H, 418A-D, 518A-D, 618A-F), - one of at least two idler gears (319A-H, 419A-D, 519A-D, 619A-F), - another gearwheel arranged coaxially on the fixed shaft (314, 414, 514, 614) and connected to the fixed shaft (314, 414, 514, 614) in a rotationally fixed manner, which is not one of the at least two fixed gearwheels (318A-H, 418A-D, 518A-D, 618A-F), - another gearwheel arranged coaxially on the selector shaft (315, 415, 515, 615), which is not one of the at least two loose gearwheels (319A-H, 419A-D, 519A-D, 619A-F).

5. Bottom bracket gearshift (10) according to claim 4, characterized in that the auxiliary drive shaft (322) is connected in a torque-transmitting manner directly or indirectly, in particular via a reduction gear, to an auxiliary drive pinion (323), which is neither one of the at least two fixed gears (318A-H, 418A-D, 518A-D, 618A-F) nor one of the at least two loose gears (319A-H, 419A-D, 519A-D, 619A-F), wherein the auxiliary drive pinion (323) is connected to the auxiliary drive gear (318A, 418A, 618A) combs.

6. Bottom bracket gearshift (10) according to claim 5, characterized in that the gear ratio provided by the auxiliary drive pinion (323) and the auxiliary drive gear (318A, 418A, 618A) is less than 1 when the auxiliary drive pinion (323) serves as the drive gear and the auxiliary drive gear (318A, 418A, 518A, 618A) serves as the output gear.

7. Bottom bracket gearshift (10) according to one of claims 4 to 6, characterized in that the auxiliary drive gear (318A, 418A, 518A, 618A) is one of the at least two fixed gears (318A-H, 418A-D, 518A-D, 618A-F) and the diameter of the auxiliary drive gear (318A, 418A, 518A, 618A) is greater than or equal to the median of the diameters of all fixed gears (318A-H, 418A-D, 518A-D, 618A-F), in particular that the diameter of the auxiliary drive gear (318A, 418A, 518A, 618A) is the largest diameter of all fixed gears (318A-H, 418A-D, 518A-D, 618A-F).

8. Bottom bracket gearshift (10) according to one of the preceding claims, characterized in that the fixed shaft (314, 414, 514, 614) and / or the switching shaft (315, 415, 515, 615) do not run parallel to the bottom bracket shaft (18).

9. Bottom bracket gearshift (10) according to claim 8, characterized in that an imaginary extension of the fixed shaft (314, 414, 514, 614) and / or an imaginary extension of the switching shaft (315, 415, 515, 615) intersects the bottom bracket shaft (18).

10. Bottom bracket gearshift (10) according to claim 8 or 9, characterized in that the rotational axis of the fixed shaft (314, 414, 514, 614) or the rotational axis of the selector shaft (315, 415, 515, 615) each lies substantially in the same plane as the rotational axis of the bottom bracket shaft (18), or that the rotational axis of the fixed shaft (314, 414, 514, 614) and the rotational axis of the selector shaft (315, 415, 515, 615) lie substantially in the same plane and the rotational axis of the bottom bracket shaft (18) lies substantially parallel to this plane, or that the rotational axis of the fixed shaft (314, 414, 514, 614), the rotational axis of the selector shaft (315, 415, 515, 615) and the The axis of rotation of the bottom bracket shaft (18) lies essentially in the same plane.

11. Bottom bracket shifting system (10) according to one of claims 8 to 10, characterized in that the direction vector of the rotational axis of the fixed shaft (314, 414, 514, 614) and / or the direction vector of the rotational axis of the shifting shaft (315, 415, 515, 615) is substantially orthogonal to the direction vector of the rotational axis of the bottom bracket shaft (18).

12. Bottom bracket gearshift (10) according to one of claims 8 to 11, characterized in that in the torque flow between the bottom bracket shaft (18) and the fixed shaft (314, 414, 514, 614) and / or in the torque flow between the shift shaft (315, 415, 515, 615) and the drive means gear (8) at least one crown gear (309, 312, 512, 612A-B) and at least one crown gear pinion (311, 313, 513A-B, 613A-B) meshing with one of the crown gears (309, 312, 512, 612A-B) are arranged.

13. Bottom bracket gearshift (10) according to claim 12, characterized in that in the torque flow between the bottom bracket shaft (18) and the fixed shaft (514, 614) and / or in the torque flow between the selector shaft (515, 615) and the drive gear (8) at least one crown gear (512, 612A-B) and at least two crown gear pinions (513A-B, 613A-B) meshing with one of the crown gears (512, 612A-B) at different radial positions are arranged, wherein the at least two crown gear pinions (513A-B, 613A-B) are arranged coaxially on a shaft, in particular on the selector shaft (515, 615), and are releasably connected to the shaft in a rotationally fixed manner by a respective coupling (K5, K 6;; K7, K8) which can be brought into a closed state in which the respective crown gear pinion (513A-B, 613A-B) is connected to the shaft in a rotationally fixed manner in at least one direction of rotation, and into an open state in which the respective crown gear pinion (513A-B, 613A-B) is connected to the shaft in a rotationally fixed manner in both directions of rotation.

14. Bottom bracket gearshift (10) according to claim 13, characterized in that at least two of the at least two crown gear pinions (513A-B, 613A-B) have different diameters.

15. Bottom bracket gearshift (10) according to claim 13 or 14, characterized in that when the gear ratios provided by the pairs of a fixed gear (518A-D, 618A-F) and a loose gear (519A-D, 619A-F) in ascending order are arranged, the ratio of the larger to the smaller of any two consecutive of these gear ratios is in each case smaller than the ratio between a larger and a smaller gear ratio, which is in each case provided by a pair of one of the at least two crown gear pinions (513A-B, 613A-B) and the crown gear (512, 612A-B) meshing therewith, when the crown gear pinion (513A-B, 613A-B) serves as the drive gear and the crown gear (512, 612A-B) serves as the output gear.

16. Bottom bracket gearshift (10) according to claim 15, characterized in that the ratio between the largest and the smallest of the gear ratios provided by the pairs of a fixed gear (518A-D, 618A-F) and a loose gear (519A-D, 619A-F) is smaller than the ratio between a larger and a smaller gear ratio, which is provided in each case by a pair of one of the at least two crown gear pinions (513A-B, 613A-B) and the crown gear (512, 612A-B) meshing therewith, when the crown gear pinion (513A-B, 613A-B) serves as the drive gear and the crown gear (512, 612A-B) serves as the output gear.

17. Bottom bracket gearshift (10) according to one of the preceding claims, characterized in that a planetary gear (640) is arranged in the torque flow between the bottom bracket shaft (18) and the drive gear (8), which planetary gear provides at least one smaller and one larger gear ratio between a respective drive gear and a respective output gear of the planetary gear (640).

18. Bottom bracket gearshift (10) according to claim 17, characterized in that, when the gear ratios provided by the pairs of a fixed gear (518A-D, 618A-F) and a loose gear (519A-D, 619A-F) are arranged in ascending order, the ratio of the larger to the smaller of any two consecutive of these gear ratios is smaller is the ratio between the larger and the smaller gear ratio provided by the planetary gear (640).

19. Bottom bracket gearshift (10) according to claim 18, characterized in that the ratio between the largest and the smallest of the gear ratios provided by the pairs of a fixed gear (518A-D, 618A-F) and a loose gear (519A-D, 619A-F) is smaller than the ratio between the larger and the smaller gear ratio provided by the planetary gear (640).

20. Bottom bracket gearshift (10) according to one of claims 17 to 19, characterized in that the larger gear ratio provided by the planetary gear (640) has the value 1 and is realized by a direct transmission in the planetary gear (640).

21. Bottom bracket gearshift (10) according to one of claims 17 to 20 and according to claim 13, characterized in that the planetary gear (640) has a sun gear (643), a web (644) connecting at least two planetary gears (645) and a ring gear (641), that the shaft on which the at least two crown gear pinions (613A-B) are arranged is the switching shaft (615) and that the sun gear (643) and the web (644) are each designed as one of the crown gears (612A-B), wherein the sun gear (643) forms the drive gear of the planetary gear (640) for the smaller gear ratio and the web (644) forms the drive gear of the planetary gear (640) for the larger gear ratio and the web (644) forms the output gear of the planetary gear (640) for both the smaller and the larger gear ratio.

22. Bicycle with a drive train, which comprises a bottom bracket gear (10) according to one of the preceding claims, a wheel (13) for generating propulsion of the bicycle and a drive means (12), in particular a chain or a belt, for transmitting a Torque from the drive wheel (8) to the impeller (13), characterized in that a planetary gear is arranged in the torque flow behind the drive wheel (8), which planetary gear provides at least one smaller and one larger transmission ratio between a respective drive wheel and a respective Output gear of the planetary gear.

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