Bottom bracket gearbox for a bicycle, bottom bracket and bicycle

Abstract

Bottom bracket gearbox for a bicycle, comprising at least four shifting elements, a drive shaft (1), an output shaft (3, 6), a first planetary gear set (PS1) operatively connected to the drive shaft (1), and a second planetary gear set (PS2), wherein the first planetary gear set (PS1) is operatively connected to the second planetary gear set (PS2), wherein the output shaft (3) is connected to the first planetary gear set (PS1) or can be connected to the second planetary gear set (PS2), characterized in that the bottom bracket gearbox comprises an electric machine (7), wherein the electric machine (7) is connected downstream of all planetary gear sets (PS1, PS2; PS3) in the power flow, wherein the planetary gear sets (PS1, PS2; PS3) are arranged coaxially to a bottom bracket crankshaft (2).

Description

[0001] The invention relates to a gearbox for a bicycle, comprising at least four switching elements, a drive shaft, a first planetary set operatively connected to the drive shaft, and a second planetary set.

[0002] Furthermore, the invention relates to a bottom bracket with such a gearbox. In addition, the invention relates to a bicycle with the gearbox or the bottom bracket.

[0003] A variety of gearboxes are known from the prior art. For example, US patent 2011 177 911 A1 discloses a gearbox that has three planetary gear sets connected in series, each with a high-speed reduction ratio. The gearbox has a total of seven gear levels, including numerous stepped planetary gears, resulting in a complex design and therefore a high assembly effort.

[0004] The object of the invention is therefore to provide a gearbox that is simple in design and easy to assemble.

[0005] The problem is solved by a gear unit of the type mentioned at the outset, which is characterized in that a bridge of the first planetary set is connected to a bridge of the second planetary set in a rotationally fixed manner.

[0006] The transmission according to the invention has the advantage that a 4-speed transmission can be provided that does not require planetary gears. The transmission has a simple design and can be assembled quickly. Furthermore, the transmission exhibits good efficiency. The transmission according to the invention also has the advantage that it is suitable for bicycle applications, particularly in conjunction with a pre- or post-shift group described in more detail below.

[0007] The term "shaft" does not exclusively refer to a cylindrical, rotatably mounted machine element for transmitting torques, but rather also includes general connecting elements that connect individual components or elements, in particular connecting elements that non-rotatably join several elements together.

[0008] In a special design, the bridge of the first planetary gear set and the bridge of the second planetary gear set can be manufactured as a single piece. This one-piece design offers the advantage that a common component can be used for both planetary gear sets, thereby reducing the cost of the gearbox and simplifying assembly. Furthermore, the shared component makes the gearbox more compact.

[0009] The first planetary gear set can be a plus planetary gear set and / or the second planetary gear set can be a minus planetary gear set. A minus planetary gear set corresponds to a planetary gear set with a bridge on which the planet gears are rotatably mounted, a sun gear and a ring gear, wherein the teeth of at least one of the planet gears mesh with the teeth of both the sun gear and the ring gear, causing the ring gear and the sun gear to rotate in opposite directions when the sun gear rotates with the bridge stationary.

[0010] In contrast, a plus planetary gear set differs from a minus planetary gear set in that the plus planetary gear set has inner and outer planet gears that are rotatably mounted on the carrier. The teeth of the inner planet gears mesh with the teeth of the sun gear on one side and with the teeth of the outer planet gears on the other. The teeth of the outer planet gears also mesh with the teeth of the ring gear. This results in the ring gear and the sun gear rotating in the same direction when the carrier is stationary.

[0011] The drive shaft can be rotationally fixed to a ring gear of the first planetary gear set. Furthermore, the drive shaft can be operatively connected to, and operatively connectable to, the second planetary gear set. In particular, the drive shaft can be indirectly operatively connected to the web of the second planetary gear set via the first planetary gear set.

[0012] Furthermore, a ring gear of the second planetary gear set can be connected to the drive shaft in a rotationally fixed manner by means of a first switching element of at least four switching elements and / or connected to a gearbox housing in a rotationally fixed manner by means of a second switching element of at least four switching elements. A sun gear of the second planetary gear set can be connected to the gearbox housing in a rotationally fixed manner by means of a third switching element of at least four switching elements.

[0013] The gearbox housing can be an integral part of the bottom bracket housing, i.e., it can be manufactured as a single piece with the bottom bracket housing. Alternatively, the gearbox housing can be manufactured separately from the bottom bracket housing and, when the gearbox is assembled, is located in a cavity within the bottom bracket housing. The gearbox housing can be designed and positioned in such a way that it does not rotate during operation of the gearbox, but remains stationary.

[0014] An output shaft of the transmission can be operatively connected to the first planetary gear set. In particular, the output shaft can be rotationally fixed to a sun gear of the first planetary gear set. Furthermore, the output shaft can be operatively connected to, and operatively connectable to, the second planetary gear set. In particular, the output shaft can be rotationally fixed to, a sun gear of the second planetary gear set by means of a fourth switching element of at least four switching elements. In addition, a web of the second planetary gear set can be indirectly operatively connected to the output shaft by means of the first planetary gear set.

[0015] The transmission according to the invention has the advantage that the switching elements are easily accessible for actuators. The second and third switching elements can be designed as brakes and / or arranged in a radially outer region of the transmission, which simplifies accessibility. The first and fourth switching elements can each be designed as clutches or freewheels. If the first and fourth switching elements are designed as clutches, no switching mechanism or actuator is necessary. Furthermore, the first and fourth switching elements exhibit low support torques, allowing them to be built smaller.

[0016] The drive shaft can be connected to the bottom bracket crank axle in a rotationally fixed manner. In this design, the output shaft can be connected to a traction element, such as a sprocket or pulley, in a rotationally fixed manner. When the gearbox is used in the bicycle, a torque applied to the traction element can then be transmitted to a rear wheel via a traction element, such as a chain or belt.

[0017] The result is a transmission in which exactly four gears can be provided by exactly two planetary gear sets and / or exactly four shift elements. The first gear can be a direct drive, meaning it has a gear ratio of 1. The remaining gears can have a higher gear ratio, meaning a gear ratio of less than 1.

[0018] In a special design, the transmission can have a third planetary gear set that is operatively connected to the first and / or second planetary gear sets. The third planetary gear set can be positioned upstream or downstream of the first and second planetary gear sets. The third planetary gear set can also be a negative planetary gear set.

[0019] A ring gear of the third planetary gear set can be non-rotatably connected to the gearbox housing by means of a fifth switching element. Furthermore, one element of the third planetary gear set can be non-rotatably connected to another element of the third planetary gear set by means of a sixth switching element. When the sixth switching element is closed, the third planetary gear set is locked, thus exhibiting a gear ratio of 1.

[0020] The sixth switching element can be arranged such that the ring gear of the third planetary gear set can be non-rotatably connected to a sun gear of the third planetary gear set. Such an arrangement has the advantage that the sixth switching element only has to provide a small supporting torque. Alternatively, it is of course possible to arrange the sixth switching element such that a web of the third planetary gear set can be non-rotatably connected to the ring gear or sun gear of the third planetary gear set by means of the sixth switching element. The fifth switching element can be designed as a brake. The sixth switching element can be designed as a clutch or freewheel.

[0021] In one configuration, the third planetary gear set can be arranged upstream of the first and second planetary gear sets in a drive system, thus forming a pre-set group. In this configuration, the first and second planetary gear sets, the input shaft, the output shaft, and the four shift elements form a main group. A web of the third planetary gear set can be non-rotatably connected to the bottom bracket crank axle via another input shaft. Additionally, the sun gear of the third planetary gear set can be non-rotatably connected to the input shaft. In this configuration, the output shaft can also be non-rotatably connected to the drive linkage.

[0022] Alternatively, a design is possible in which the third planetary gear set is connected downstream of the first and second planetary gear sets in a pull-type configuration, thus forming a downstream group. In this design, the first and second planetary gear sets, the input shaft, the output shaft, and the four shift elements form a main group. The output shaft can be non-rotatably connected to a web of the third planetary gear set, and / or a sun gear of the third planetary gear set can be non-rotatably connected to another output shaft. This second output shaft can be non-rotatably connected to the pull-type carrier. In this design, the input shaft can also be non-rotatably connected to the bottom bracket crank axle.

[0023] The pre- or post-selector group can provide exactly two gears and / or have exactly two shift elements, namely the fifth and sixth shift elements. The first gear can be a direct drive, and the second gear can have a higher gear ratio. The pre- or post-selector group can have exactly one planetary gear set, namely the third planetary gear set. Furthermore, the third planetary gear set does not have a stepped planetary gear.

[0024] Regardless of whether the transmission has a pre-selector or post-selector group in addition to the main group, all variants result in the same gear ratio series; that is, the overall function of the transmission is the same in all variants. Differences exist in the speed and torque ratios occurring at the individual planetary gear sets. Since both the pre-selector or post-selector group and the main group have direct drive as the first gear, the torque load is similar in all variants. Greater differences arise in the speeds, because the planetary gear sets located further down the power flow operate at a higher input speed in some gears.

[0025] The switching elements used in the transmission, such as clutches or brakes, can be designed as positive-locking or friction-locking components. If the aforementioned switching elements are each designed as freewheels, it is advantageous that, on the one hand, the main group and / or, on the other hand, the upstream or downstream group do not lock, in order to prevent the transmission from locking up when the direction of rotation is reversed at the input or output. This can be achieved by designing the fifth switching element of the upstream or downstream group and / or the second and third switching elements of the main group as a one-way brake, such as a switchable freewheel brake.

[0026] As a result, an 8-speed transmission can be achieved by coupling the main group, which provides four gears, with a pre- or post-selector group, each providing two gears. This transmission is advantageous because eight gears can be achieved with exactly three planetary gear sets, resulting in a compact overall length. Furthermore, the transmission offers suitable gear ratios for stationary operation, allowing the planetary gear sets to have a small diameter. Another advantage is that exactly three shift elements can be configured as brakes. The remaining shift elements can be configured as freewheels. This is advantageous because at least one, and in particular exactly three, actuators are required to actuate the three shift elements configured as brakes.

[0027] In a very specific design, the transmission can incorporate an electric motor that is operatively connected, or operatively connectable, to the output shaft or a further output shaft. The electric motor can be connected downstream of the first, second, and / or third planetary gear set. This downstream connection of the electric motor offers the advantage that the planetary gear sets are not subjected to the torque provided by the electric motor. The electric motor also has the advantage of providing assistance to the cyclist. This eliminates the need for fine gear ratios, as the electric motor significantly reduces the impact of muscle power on propulsion.

[0028] The electric machine consists at least of a rotationally fixed stator and a rotatably mounted rotor and is designed in motor operation to convert electrical energy into mechanical energy in the form of speed and torque, and in generator operation to convert mechanical energy into electrical energy in the form of current and voltage.

[0029] The electric motor can be arranged offset from a central axis of the gearbox and / or the bottom bracket crankshaft, particularly in the radial direction. Specifically, a central axis of the electric motor can run parallel to a central axis of the gearbox. This offers the advantage that the electric motor can be located in an area of ​​the gearbox and / or the bottom bracket housing where sufficient space is available to accommodate it. Furthermore, the inner diameter of the electric motor can be freely chosen, since the bottom bracket crankshaft, which is not part of the gearbox, does not pass through the electric motor.

[0030] The connection of the electric machine to the output shaft or further output shafts can be achieved via a chain drive and / or belt drive and / or a spur gear drive and / or a reduction gear drive. Furthermore, a freewheel can be incorporated into the power flow between the electric machine and the output shaft or further output shaft. The freewheel offers the advantage that, when operating without the electric machine, no losses are caused by the rotating rotor of the electric machine.

[0031] A bottom bracket with the transmission according to the invention is particularly advantageous, wherein the drive shaft or the further drive shaft is rotationally fixed to the bottom bracket crankshaft. The bottom bracket can have a bottom bracket housing, with the transmission arranged in a cavity of the bottom bracket housing. The transmission can be modular in design. Therefore, the transmission as a whole can be inserted into or removed from the cavity. A bicycle with the transmission or the bottom bracket is particularly advantageous.

[0032] The invention is schematically represented in the figures and is described below with reference to the figures, whereby identical or equivalently acting elements are mostly provided with the same reference numerals. This shows: Fig. 1: a schematic representation of the transmission according to the invention in a first embodiment, Fig. 2: a switching matrix of the in Fig. 1 of the depicted gearbox, Fig. 3: a schematic representation of the transmission according to the invention in a second embodiment, Fig. 4: a schematic representation of the transmission according to the invention in a third embodiment, Fig. 5: a table with values ​​for the standard translation of the three planetary theorems, Fig. 6: a switching matrix for the ones in the Fig. 3 and Fig. 4 gear units shown. Fig. Figure 1 shows a transmission according to a first embodiment of the invention, which is rotationally symmetrical with respect to a bottom bracket crank shaft 2. Fig. Figure 1 shows only the upper half of the gearbox.

[0033] The gearbox has a drive shaft 1 on, which is connected to the bottom bracket crank axle 2 is connected in a rotationally fixed manner. Additionally, the gearbox has a first planetary set. PS1 , which is connected to the drive shaft 1 is interconnected, and a second planetary set PS2 up. A bridge of the first planetary set PS1 is connected to a bridge of the second planetary set PS2 connected in a rotationally fixed manner. In particular, the bridge of the first planetary set is PS1 and the bridge of the second planetary set PS2 manufactured in one piece, i.e., as a single component.

[0034] This is the first set of planetary theorems. PS1 as the plus planetary set and the second planetary set PS2 designed as a negative planetary gear set. The drive shaft 1 is connected to a ring gear of the first planetary set PS1 Fixedly connected in a rotational manner. A sun gear of the first planetary set. PS1 is equipped with an output shaft 3 Connected in a rotationally fixed manner.

[0035] A ring gear of the second planetary gear set PS2 is by means of a first switching element S3 with the drive shaft 1It can be connected in a rotationally fixed manner. Furthermore, the ring gear of the second planetary gear set... PS2 by means of a second switching element S2 with a gearbox housing 4 A rotationally fixed connection. A sun gear of the second planetary set. PS2 is by means of a third switching element S1 with the gearbox housing 4 rotationally fixed connection and by means of a fourth switching element S4 with the output shaft 3 The output shaft can be connected in a rotationally fixed manner. 3 is with a in Fig. 1. The tension member (not shown) is connected in a rotationally fixed manner.

[0036] The first set of planetary theorems PS1 and the second set of planetary theorems PS2 are arranged coaxially to each other. Furthermore, the output shaft 3 coaxial to the bottom bracket crankshaft 2 arranged. The second switching element S2 and the third switching element S1are each designed as brakes. The first switching element S3 and the fourth switching element S4 are each designed as couplings.

[0037] The gearbox is located in a cavity within a bottom bracket housing. 8 arranged. The in Fig. The gearbox shown forms a main group HG , which, as from the Fig. 3 and Fig. As can be seen in section 4, it is interconnected with other area groups.

[0038] Fig. 2 shows a switching matrix for the in Fig. 1. Gearbox shown. The shift elements that are closed for the respective gear are marked with the symbol "X". The shift elements are actuated by suitable actuators. Furthermore, in Fig. 2 for each gear the translation “i” between the drive shaft 1 and the output shaft 3 named. As from Fig. As can be seen in Figure 2, the transmission has four gears, with the first gear being a direct drive. The subsequent gears are higher-ratio transmissions.

[0039] At the in Fig. The first planetary gear set shown in 1 can be used. PS1 One planetary gear set has a fixed gear ratio of 2, and the second planetary gear set can have a fixed gear ratio of -2.6. The fixed gear ratio of a negative planetary gear set corresponds to the negative ratio of teeth between the ring gear and the sun gear. For a positive planetary gear set, the fixed gear ratio corresponds to the positive ratio of teeth between the ring gear and the sun gear.

[0040] Fig. Figure 3 shows the transmission according to the invention in a second embodiment. The transmission differs from the one in Fig. The gear shown in section 1 is characterized by the fact that the gear includes a third planetary gear set. PS3 features a pre-group VG forms the main group HG The drive system is upstream. In particular, the third planetary set is PS3 the first planetary set PS1 and the second planetary set PS2 upstream in terms of drive technology, when considering a power flow from the bottom bracket crankshaft 2 to the output shaft 3 during train operations.

[0041] A bridge of the third planetary theorem PS3 is by means of another drive shaft 5 with the bottom bracket crankshaft 2 The drive shaft is connected in a rotationally fixed manner. 1 is with a sun wheel of the third planetary set PS3 Fixed in a rotationally rigid manner. A ring gear of the third planetary gear set. PS3 is by means of a fifth switching element S5 with the gearbox housing 4 It can be connected in a rotationally fixed manner. Furthermore, the ring gear can be connected by means of a sixth switching element. S6 with the sun wheel of the third planetary set PS3 The third planetary set can be connected in a rotationally fixed manner. PS3 is coaxial to the first planetary set PS1 and / or the second planetary set PS2 arranged.

[0042] The fifth switching element S5 It serves as a brake and the sixth switching element S6 is designed as a freewheel. Another difference to the one in Fig. The gearbox shown in section 1 consists in the fact that the first switching element S3 and fourth switching element S4 each is designed as a freewheel.

[0043] Fig. Figure 4 shows a transmission according to a third embodiment. The one in Fig. The gearbox shown in section 4 differs from the one in Fig. The gears shown in the 3 diagrams are such that the third planetary set PS3 not a pre-group VG , but a downstream group NG forms. This means that the third planetary theorem PS3 the main group HG is downstream in terms of drive technology, when considering the power flow from the bottom bracket crankshaft 2 to another output shaft 6 during train operations.

[0044] The bridge of the third planetary theorem PS3 is connected to the output shaft 3 Fixedly connected in a rotationally rigid manner. The sun gear of the third planetary set. PS3 is connected to the further output shaft 6 connected in a rotationally fixed manner. The further output shaft 6 is connected to a tension member (not shown) in a rotationally fixed manner. Furthermore, the output shaft is 6 coaxial to bottom bracket crankshaft 2 arranged. The ring gear of the third planetary gear set PS3 is by means of the fifth switching element S5 with the gearbox housing 4 and by means of the sixth switching element S6 Can be connected to the sun wheel in a rotationally fixed manner.

[0045] Another difference is that the gearbox is an electric machine. 7 features which are connected to the further output shaft 6 The connection is functionally linked, as shown by the dashed line. The connection of the electrical machine 7 to the further output shaft 6 This can be achieved via a superimposed gearbox, a spur gearbox, a chain drive and / or a belt drive, with the connection in Fig. 4 is not shown. The connection of the electric machine is carried out in this process. 7 in one of the downstream group NG downstream area in terms of drive technology.

[0046] The electric machine 7 is not rotationally symmetrical to the bottom bracket crankshaft 2 executed. In particular, the electric machine 7 offset in a radial direction to the bottom bracket crankshaft 2 arranged.

[0047] Another difference is that the gearbox has a torque sensor. 9 features, by means of which the bottom bracket crankshaft 2 on the drive shaft 1 The transmitted torque can be measured. The torque sensor 9 It can be disc-shaped. Of course, other designs and / or arrangements of the torque sensor are also possible. 9 possible.

[0048] Fig. 5 shows a table with values ​​for the standard translation of the in the Fig. 3 and Fig. The four planetary sets are shown. As can be seen from the table, the first planetary set exhibits PS1 a standard translation of 2.0, the second planetary theorem PS2 a standard translation of -2.6 and the third planetary theorem PS3 a standard translation of -1.6.

[0049] Fig. Figure 6 shows a switching matrix for the [unclear text]. Fig. 3 and Fig. The transmission is shown in Figure 4. The shift elements that are closed in the respective gear are marked with the symbol "X". If the shift element is designed as a freewheel, "X" means that the freewheel is locked. This occurs automatically without external actuation. The shift elements designed as brakes are closed by at least one actuator.

[0050] The switching matrix also shows that the ones in the Fig. 3 and Fig. The 4 depicted gearboxes have eight gears. Furthermore, the gear ratio “i” between the bottom bracket crankshaft and the gearbox is shown in the shift matrix for each gear. 2 and called the traction element carrier. Reference symbol list 1 drive shaft 2 Bottom bracket crankshaft 3 Output shaft 4 Gearbox housings 5 additional drive shafts 6 additional output shafts 7 electric machine 8 bottom bracket shells 9 Torque sensor S1 third switching element S2 second switching element S3 first switching element S4 fourth switching element S5 fifth switching element S6 sixth switching element HG Main Group NG downstream group VG pre-group PS1 first planetary set PS2 second planetary set PS3 third planetary set QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] US 2011177911 A1

[0003]

Claims

[1] transmission for a bicycle, with at least four shifting elements, a drive shaft (1), a first planetary gear set (PS1), which is operatively connected to the drive shaft (1), and a second planetary gear set (PS2), characterized that a web of the first planetary gearset (PS1) is non-rotatably connected to a web of the second planetary gearset (PS2). [2] Transmission according to claim 1, characterized that the web of the first planetary gear set (PS1) and the web of the second planetary gear set (PS2) are made in one piece. [3] Transmission according to claim 1 or 2, characterized , that a. the first planetary gearset (PS1) is a plus planetary gearset and / or that b. the second planetary set (PS2) is a minus planetary set. [4] Transmission according to one of claims 1 to 3, marked by a drive shaft (1) which is non-rotatably connected to a ring gear of the first planetary gearset (PS1). [5] Transmission according to one of claims 1 to 4, characterized , that a. a ring gear of the second planetary gear set (PS2) can be connected in a rotationally fixed manner to the drive shaft (1) by means of a first shifting element (S3) and / or that b. can be non-rotatably connected to a transmission housing (4) by means of a second switching element (S2). [6] Transmission according to one of claims 1 to 5, characterized that a sun gear of the second planetary gear set (PS2) can be connected in a torque-proof manner to a transmission housing (4) by means of a third switching element (S1). [7] Transmission according to one of claims 1 to 6, characterized by an output shaft (3) which a. is rotatably connected to a sun gear of the first planetary gear set (PS1) and / or b. can be connected in a torque-proof manner to a sun gear of the second planetary gear set (PS2) by means of a fourth switching element (S4). [8] Transmission according to one of claims 4 to 7, characterized that the drive shaft (1) with the bottom bracket crankshaft (2) is rotatably connected. [9] Transmission according to one of claims 1 to 8, marked by a third planetary gearset (PS3), which is operatively connected to the first planetary gearset (PS1) and / or to the second planetary gearset (PS2). [10] Transmission according to claim 9, characterized , that a. a ring gear of the third planetary gear set (PS3) can be connected in a rotationally fixed manner to a transmission housing (4) by means of a fifth shifting element (S5) and / or that b. an element of the third planetary gearset (PS3) can be connected in a rotationally fixed manner to another element of the third planetary gearset (PS3) by means of a sixth shifting element (S6). [11] Transmission according to claim 9 or 10, insofar as the claim is dependent on claims 1 to 7, characterized , that a. a web of the third planetary gear set (PS3) can be connected in a torque-proof manner to the bottom bracket crankshaft (2) by means of a further drive shaft (5) and / or that b. a sun wheel of the third planetary gear set (PS3) can be connected in a torque-proof manner to the drive shaft (1). [12] Transmission according to claim 9 or 10, characterized , that a. the output shaft (3) is non-rotatably connected to a carrier of the third planetary gear set (PS3) and / or that b. a sun wheel of the third planetary gear set (PS3) is connected in a torque-proof manner to a further output shaft (6). [13] Transmission according to one of claims 1 to 12, marked by an electrical machine (7), the a. the first planetary gear set (PS1) and / or the second planetary gear set (PS2) and / or the third planetary gear set (PS3) is connected downstream in terms of drive technology and / or the b. is operatively connected or operatively connectable to the output shaft (3) or the further output shaft (6). [14] bottom bracket with a gear according to any one of claims 1 to 13, wherein the drive shaft (1) or the further drive shaft (5) with the bottom bracket crankshaft (2) is rotatably connected. [15] Bicycle with a transmission according to any one of claims 1 to 13 or a bottom bracket according to claim 14.

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