Gearbox for a bicycle, bottom bracket and bicycle

Abstract

Transmission for a bicycle, with a first planetary gear set (PS1) which has a planet with at least three planetary stages, a second planetary gear set (PS2) and a transmission input shaft (1) which is connected in a rotationally fixed manner to a web of the first planetary gear set (PS1) and can be connected in a rotationally fixed manner to a bottom bracket crankshaft (2), wherein a sun gear of the first planetary gear set (PS1) is connected in a rotationally fixed manner to an element of the second planetary gear set (PS2) by means of a shaft (4), characterized in that the element of the second planetary gear set (PS2) is a sun gear (21) and in that the sun gear (21) of the second planetary gear set (PS2) can be connected in a rotationally fixed manner to the transmission output shaft (3) by means of a first switching element (S1).

Description

[0001] The invention relates to a transmission for a bicycle, comprising a first planetary gear set having a planet with at least three planetary stages, a second planetary gear set and a transmission input shaft which is connected in a rotationally fixed manner to a web of the first planetary gear set and can be connected in a rotationally fixed manner to a bottom bracket crankshaft.

[0002] The invention also relates to a bottom bracket with such a gearing. Furthermore, the invention relates to a bicycle with the gearing or bottom bracket.

[0003] A variety of transmissions are known from the state of the art. For example, US 2011 177 911 A1 discloses a transmission that features three planetary gears connected in series with a high-speed ratio. The transmission has a total of seven planetary gear planes, including numerous stepped planets, resulting in a complex design and a very high level of assembly effort.

[0004] WO 2011 / 122 787 A2 relates to a bicycle transmission comprising a pedal crank, a gear unit for changing the gear ratio, a control for selecting the gear stages and a clutch for locking one of the gear wheels.

[0005] JP H10 -194 186 A relates to an e-bike comprising a compact arrangement for integrating an automatic transmission into an electric auxiliary drive unit, using an existing torque sensor and a control device to facilitate gear shifting.

[0006] JP H06 -263 080 A relates to a multi-stage bicycle transmission having planetary gear sets and supporting multi-stage gear changes.

[0007] CN 1 02 762 441 A relates to an electric bicycle in which a transmission unit, a speed reducer and an electric motor are arranged along an axis in the rear wheel hub area, wherein both the transmission unit and the speed reducer consist of planetary gears and use the same planet carrier.

[0008] The object of the invention is therefore to provide a gearbox that is simple in design and can be easily assembled.

[0009] The problem is solved by the subject matter having the features of the independent patent claims. Advantageous further developments emerge from the subclaims.

[0010] The transmission according to the invention has the advantage of being simple in design, particularly due to the small number of planetary gear sets, which simplifies assembly. A further advantage of the transmission is its high efficiency due to the small number of gear meshes. Another advantage of the transmission is that purely geometric grading is possible.

[0011] A shaft is not exclusively understood to mean, for example, a cylindrical, rotatably mounted machine element for transmitting torque, but rather also general connecting elements that connect individual components or elements to one another, in particular connecting elements that connect several elements to one another in a rotationally fixed manner.

[0012] The planetary stages all have a toothed area that can mesh with at least one other element of the planetary gear set. The individual planetary stages differ in their diameter. The planet is supported by a carrier of the first planetary gear set. The first planetary gear set can have more than one planet.

[0013] The provision of a transmission with at least two planetary gear sets, in particular exactly two planetary gear sets, offers the advantage that small gear steps in the range of 1.25 can be generated by means of the first planetary gear set, whereas large gear steps can be achieved by means of the second planetary gear set in order to multiply the ratios of the first gear stage.

[0014] The element of the second planetary gear set is a sun gear of the second planetary gear set. The transmission can have a transmission output shaft that is or can be connected in a rotationally fixed manner to another element of the second planetary gear set. The other element of the second planetary gear set can be a carrier of the second planetary gear set.

[0015] According to the invention, the sun gear of the second planetary gear set can be connected in a rotationally fixed manner to the transmission output shaft and thus to the carrier that is connected in a rotationally fixed manner to the transmission output shaft by means of a first switching element, which can be designed as a clutch or as a freewheel. As a result, the first switching element ensures that the second planetary gear set is locked when the first switching element is in the engaged state. When the second planetary gear set is locked, the second planetary gear set has a gear ratio of 1. Of course, the first switching element can also be arranged such that, when the first switching element is in the engaged state, the sun gear of the second planetary gear set is connected in a rotationally fixed manner to the ring gear of the second planetary gear set, or the ring gear of the second planetary gear set is connected in a rotationally fixed manner to the carrier of the second planetary gear set.In these cases, the second planetary gear set is also blocked when the first switching element is closed.

[0016] In a special design, the planetary gear has exactly three planetary stages: a first planetary stage, a second planetary stage, and a third planetary stage. In this design, three gears can be provided by the first planetary gear set.

[0017] A toothing region of the first planetary stage can be in engagement with a first ring gear of the first planetary set. The first ring gear can be connected in a rotationally fixed manner to a transmission housing by means of a second shifting element. A toothing region of the second planetary stage can be in engagement with a second ring gear of the first planetary set and with the sun gear of the first planetary set. The second ring gear can be connected in a rotationally fixed manner to the transmission housing by means of a third shifting element. A toothing region of the third planetary stage can be in engagement with a third ring gear of the first planetary set. The third ring gear can be connected in a rotationally fixed manner to the transmission housing by means of a fourth shifting element. The second to fourth shifting elements can be designed as a brake.

[0018] The gear housing can be part of a bottom bracket shell, i.e., it can be constructed in one piece with the bottom bracket shell. Alternatively, the gear housing can be constructed separately from the bottom bracket shell and, when the gear unit is assembled, can be arranged in a cavity of the bottom bracket shell. The gear housing can be designed and arranged such that it does not rotate during operation of the gear unit, but remains stationary.

[0019] The second planetary stage can be arranged between the first planetary stage and the third planetary stage, viewed along the axial direction of the transmission. Furthermore, the diameter of the second planetary stage can be larger than the diameter of the first planetary stage, but smaller than the diameter of the third planetary stage.

[0020] In an alternative embodiment, the first planetary gear set can have a planetary gear with exactly four planetary stages. In this case, four gears can be realized by the first planetary gear set. In this embodiment, a toothed area of ​​a fourth planetary gear stage can mesh with a fourth ring gear. The fourth ring gear can be rotationally fixedly connected to the transmission housing by means of a fifth shifting element. The fifth shifting element can be designed as a brake.

[0021] In a very special design, the second planetary gear set can have a planet with at least one other planetary stage. The planet is supported by a carrier of the second planetary gear set. Of course, the second planetary gear set can also have more than one planet. In particular, the planet can be single-stage, meaning it has only one other planetary stage, or it can have exactly three other planetary stages.

[0022] In an alternative embodiment, the planetary gear is single-stage and meshes with a ring gear of the second planetary gear set and with the sun gear of the second planetary gear set. The ring gear can be connected to the transmission housing in a rotationally fixed manner by means of a sixth shifting element. In this embodiment, two gears can be realized by the second planetary gear set. Thus, a transmission with exactly eight gears can be provided, with the transmission comprising the second planetary gear set and the first planetary gear set with a planetary gear with four planetary stages. The sixth shifting element can be designed as a brake.

[0023] In an alternative embodiment of the second planetary gear set, the planet can have exactly three other planetary stages, namely a first other planetary stage, a second other planetary stage, and a third other planetary stage. A toothing region of the first other planetary stage can mesh with a first ring gear of the second planetary gear set. The first ring gear can be rotationally fixedly connected to the transmission housing by means of a seventh shifting element. A toothing region of the second other planetary stage can mesh with a second ring gear. The second ring gear can be rotationally fixedly connected to the transmission housing by means of an eighth shifting element. A toothing region of a third planetary stage can mesh with the sun gear of the second planetary gear set. The seventh and eighth shifting elements can be designed as a brake.

[0024] The third planetary gear stage can be arranged in the axial direction of the transmission between the first planetary gear stage and the second planetary gear stage. The diameter of the third planetary gear stage can be larger than the diameter of the first planetary gear stage and smaller than the diameter of the second planetary gear stage. A second planetary gear set configured in this way can achieve three gears. Thus, a transmission with exactly nine gears can be realized, with the transmission comprising the second planetary gear set and the first planetary gear set with a planetary gear with three planetary gear stages.

[0025] The arrangement of the second to eighth shifting elements such that the ring gears of the first planetary gear set and / or the ring gear(s) of the second planetary gear set can be connected to the transmission housing in a rotationally fixed manner by means of the shifting elements offers the advantage that the shifting elements are easily accessible from the outside. This simplifies the installation of the transmission in the bottom bracket. As already mentioned above, the second to eighth shifting elements can be designed as a brake. It is particularly advantageous if at least one shifting element is designed as a freewheel brake. This makes it possible to push the bicycle backward.

[0026] The first and / or second and / or third planetary gear sets can be designed as negative planetary gear sets. Alternatively, it is conceivable that the first and / or second and / or third planetary gear sets are designed as positive planetary gear sets.

[0027] A minus planetary gear set corresponds to a planetary gear set with a carrier 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 the sun gear as well as with the teeth of the ring gear, whereby the ring gear and the sun gear rotate in opposite directions when the sun gear rotates with the carrier stationary. In contrast, a plus planetary gear set differs from the minus planetary gear set in that the plus planetary gear set has inner and outer planet gears which are rotatably mounted on the carrier. The teeth of the inner planet gears mesh with the teeth of the sun gear on the one hand 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 means that when the web is stationary, the ring gear and the sun gear rotate in the same direction.

[0028] In a special design, the transmission can have an electric motor that is operatively connected or can be operatively connected to the transmission output shaft. The electric motor can be connected downstream of the first and / or second planetary gear set. Connecting the electric motor downstream of the first and / or second planetary gear set offers the advantage that the planetary gear sets are not burdened by the torque provided by the electric motor. The electric motor also has the advantage of being able to assist the cyclist during cycling. This eliminates the need for fine gear ratios, as the electric motor reduces the importance of muscle power for the drive.

[0029] The electrical machine consists of at least a rotationally fixed stator and a rotatably mounted rotor and is designed to convert electrical energy into mechanical energy in the form of speed and torque in motor operation, and to convert mechanical energy into electrical energy in the form of current and voltage in generator operation.

[0030] The electric motor can be arranged offset, particularly in a radial direction, from a center axis of the transmission and / or the bottom bracket crankshaft. In particular, a center axis of the electric motor can run parallel to a center axis of the transmission. This offers the advantage that the electric motor can be arranged in an area of ​​the transmission where sufficient space is available to accommodate the electric motor. Furthermore, the inner diameter of the electric motor can be freely selected, since the bottom bracket crankshaft, which is not part of the transmission, does not extend through the electric machine.

[0031] In addition, the electric motor can be connected to the transmission output shaft in a rotationally fixed manner by means of a ninth switching element, which can be a freewheel. This ensures that, when driving without the electric motor, no losses are caused by the rotating motor of the electric motor. The electric motor can be connected to the transmission output shaft via a chain drive and / or belt drive and / or a spur gear and / or a transmission gear.

[0032] The transmission can be designed modularly. This means that the electric motor and / or the planetary gear sets are integrated into the bottom bracket shell as a single functional unit and / or can be installed or removed from the bottom bracket shell as a single functional unit.

[0033] A bottom bracket with the gearbox is particularly advantageous. The gearbox input shaft can be connected to the bottom bracket crankshaft in a rotationally fixed manner. In particular, the bottom bracket can incorporate the bottom bracket shell, with the gearbox located within the bottom bracket. A bicycle with the gearbox is particularly advantageous.

[0034] The subject matter of the invention is schematically illustrated in the figures and is described below with reference to the figures, wherein identical or equivalent elements are generally provided with the same reference numerals. Herein: Fig. 1 a schematic representation of the transmission according to the invention according to a first embodiment, Fig. 2 a switching matrix of the Fig. 1 shown gearbox, Fig. 3 a schematic representation of the transmission according to the invention according to a second embodiment, Fig. 4 a switching matrix of the Fig. 3 shown gearbox.

[0035] The Fig. The transmission shown in Figure 1 comprises a first planetary gear set PS1 and a second planetary gear set PS2, which are arranged coaxially with one another. Furthermore, the transmission has a transmission input shaft 1, which is rotationally fixedly connected to a carrier of the first planetary gear set PS1 and a bottom bracket crankshaft 2. A sun gear of the first planetary gear set PS1 is rotationally fixedly connected to a sun gear of the second planetary gear set PS2 by means of a shaft 4. The sun gear of the second planetary gear set PS2 is rotationally fixedly connected to a transmission output shaft 3 by means of a first shifting element S1.

[0036] The first planetary gear set PS1 has a planetary gear with exactly three planetary stages, namely a first planetary stage 5, a second planetary stage 7, and a third planetary stage 9. A toothed area of ​​the first planetary stage 5 meshes with a first ring gear 6 of the first planetary gear set PS1. The first ring gear 6 of the first planetary gear set PS1 is rotationally fixedly connected to a transmission housing 13 by means of a second shifting element S2.

[0037] A toothing area of ​​the second planetary stage 7 engages with a second ring gear 8 of the first planetary gear set PS1, and a toothing area of ​​the third planetary stage 9 engages with a third ring gear 10 of the first planetary gear set PS1. The second ring gear 8 is rotatably connected to the transmission housing 13 by means of a third shifting element S3, and the third ring gear is rotatably connected to the transmission housing 13 by means of a fourth shifting element S4. The second planetary stage 7 has a larger diameter than the first planetary stage 5 and a smaller diameter than the third planetary stage 9.

[0038] The transmission output shaft 3 is rotationally fixedly connected to the carrier of the second planetary gear set PS2. Furthermore, the transmission output shaft 3 is rotationally fixedly connected to a traction mechanism carrier (not shown in the figures), such as a sprocket or a belt pulley. The torque provided by the transmission can be transmitted to a rear wheel of the bicycle (not shown in the figures) via the traction mechanism carrier and a traction mechanism, such as a chain or a belt.

[0039] The second planetary gear set PS2 has a planet with three planetary stages, namely a first other planetary stage 16, a second other planetary stage 17, and a third other planetary stage 14. The diameter of the third other planetary stage 14 is larger than the diameter of the first other planetary stage 16 and smaller than the diameter of the second other planetary stage 17.

[0040] A toothing area of ​​the first other planetary stage 16 is in engagement with a first ring gear 18 of the second planetary gear set PS2, and a toothing area of ​​the second other planetary stage 17 is in engagement with a second ring gear 19 of the second planetary gear set PS2. A toothing area of ​​the third other planetary stage 14 is in engagement with the sun gear 21 of the second planetary gear set PS2. The first ring gear 18 is rotatably connected to the transmission housing 13 by means of a seventh shifting element S7, and the second ring gear 19 is rotatably connected to the transmission housing 13 by means of an eighth shifting element S8.

[0041] The first shifting element S1 is designed as a clutch or freewheel, and the remaining shifting elements mentioned above are designed as brakes. The transmission is arranged in a cavity of a bottom bracket shell 20 of a bicycle's bottom bracket.

[0042] Fig. 2 shows the switching matrix of the Fig. 1 shown gearbox. In addition, Fig. 1 shows the ratio "i" in the individual gears between the transmission input shaft 1 and the transmission output shaft 3. The table also shows the gear steps "phi." The letter "X" means that the respective shift elements are closed. The table shows that with the gear ratio shown in Fig. 1 shown gearboxes have exactly nine gears.

[0043] The Fig. 3 differs from the gearbox shown in Fig. 1 is that the planet of the first planetary gear set PS1 has four planetary stages. Thus, in addition to the three planetary stages 5, 7, 9, the planet of the first planetary gear set PS1 also has a fourth planetary stage 11. A toothed area of ​​the fourth planetary gear stage 11 is in engagement with a fourth ring gear 12. The fourth ring gear 12 is rotatably connected to the transmission housing 13 by means of a fifth shift element S5. In this embodiment, four gears can be realized by the first planetary gear set PS1. The transmission input shaft 1 is furthermore connected to the Fig. 3 not shown bottom bracket crankshaft and the gearbox output shaft is still connected to the Fig. 3 traction mechanism carriers not shown are connected in a rotationally fixed manner.

[0044] Another difference is that the planet of the second planetary gear set PS2 is single-stage, meaning it does not have multiple planetary stages. The planet of the second planetary gear set PS2 meshes with the sun gear 21 of the second planetary gear set PS2 and a ring gear 15 of the second planetary gear set. The ring gear 15 is rotationally fixedly connected to the transmission housing 13 by means of a sixth shift element S6.

[0045] The two shift elements S5 and S6 are designed as brakes. The second planetary gear set PS2 enables two gears.

[0046] Fig. 4 shows a switching matrix of the Fig. 3 shown gearbox. In addition, Fig. 4 shows the ratio "i" of the individual gears between the transmission input shaft 1 and the transmission output shaft 3. The table also contains values ​​for the gear steps "phi". The letter "X" means that the respective shift element is closed. The table shows that the gear ratio shown in Fig. The gearbox shown in Figure 3 has exactly eight gears. Reference symbol 1 transmission input shaft 2 bottom bracket crankshaft 3 Gearbox output shaft 4th wave 5 first planetary stage 6 first ring gear of the first planetary gear set 7 second planetary stage 8 second ring gear of the first planetary gear set 9 third planetary stage 10 third ring gear of the first planetary gear set 11 fourth planetary stage 12 fourth ring gear of the first planetary gear set 13 Gearbox housing 14 third other planetary stage 15 Ring gear of the second planetary gear set 16 first other planetary stage 17 second other planetary stage 18 first ring gear of the second planetary gear set 19 second ring gear of the second planetary gear set 20 bottom bracket shell 21 Sun gear of the second planetary gear set S1 first switching element S2 second switching element S3 third switching element S4 fourth switching element S5 fifth switching element S6 sixth switching element S7 seventh switching element S8 eighth switching element PS1 first planetary gear set PS2 second planetary gear set

Claims

[1] Transmission for a bicycle, with a first planetary gear set (PS1) having a planet with at least three planetary stages, a second planetary gear set (PS2) and a transmission input shaft (1) which is connected in a rotationally fixed manner to a web of the first planetary gear set (PS1) and is rotatably connectable to a bottom bracket crankshaft (2), wherein a sun gear of the first planetary gear set (PS1) is connected in a rotationally fixed manner to an element of the second planetary gear set (PS2) by means of a shaft (4), characterized by that the element of the second planetary gear set (PS2) is a sun gear (21) and that the sun gear (21) of the second planetary gear set (PS2) can be connected in a rotationally fixed manner to the transmission output shaft (3) by means of a first switching element (S1). [2] Transmission according to claim 1, characterized by a transmission output shaft (3) which is or can be connected in a rotationally fixed manner to another element, in particular a web, of the second planetary gear set (PS2). [3] Transmission according to one of claims 1 to 2, characterized by , that a toothing area of ​​a first planetary stage (5) is in engagement with a first ring gear (6) of the first planetary gear set and / or that b. a toothed area of ​​a second planetary stage (7) is in engagement with a second ring gear (8) and with the sun gear of the first planetary set (PS2) and / or that c. a toothed area of ​​a third planetary stage (9) is in engagement with a third ring gear (10) and / or that d. a toothing region of a fourth planetary stage (11) is in engagement with a fourth ring gear (12). [4] Transmission according to claim 3, characterized by , that a. the first ring gear (6) of the first planetary gear set can be connected in a rotationally fixed manner to a transmission housing (13) by means of a second shift element (S2) and / or that b. the second ring gear (8) of the first planetary gear set can be connected in a rotationally fixed manner to a transmission housing (13) by means of a third shift element (S3) and / or that c. the third ring gear (10) of the first planetary gear set can be connected in a rotationally fixed manner to a transmission housing (13) by means of a fourth shift element (S4) and / or that d. the fourth ring gear of the first planetary gear set can be connected in a rotationally fixed manner to a transmission housing (13) by means of a fifth shift element (S5). [5] Transmission according to one of claims 1 to 4, characterized by that a planet of the second planetary set has a first other planetary stage (16), a second other planetary stage (17) and a third other planetary stage (14). [6] Transmission according to claim 5, characterized bythat a toothing region of the first other planetary stage (16) is in engagement with a first ring gear (18) of the second planetary gear set (PS2), wherein the first ring gear (18) of the second planetary gear set (PS2) is rotatably connected to the transmission housing (13) by means of a seventh shift element (S7). [7] Transmission according to claim 5 or 6, characterized by that a toothing region of the second other planetary stage (17) is in engagement with a second ring gear (19) of the second planetary gear set (PS2), wherein the second ring gear (19) of the second planetary gear set (PS2) is rotatably connected to the transmission housing (13) by means of an eighth shift element (S8). [8] Transmission according to one of claims 5 to 7, characterized by that a toothing area of ​​a third other planetary stage (14) is in engagement with the sun gear (21) of the second planetary stage (PS2). [9] Transmission for a bicycle, with a first planetary gear set (PS1) and a second planetary gear set (PS2) having a single-stage planet, and a transmission input shaft (1) which is connected in a rotationally fixed manner to a web of the first planetary gear set (PS1) and is rotatably connectable to a bottom bracket crankshaft (2), wherein a sun gear of the first planetary gear set (PS1) is connected in a rotationally fixed manner to an element of the second planetary gear set (PS2) by means of a shaft (4), characterized bythat the element of the second planetary gear set (PS2) is a sun gear (21), that the sun gear (21) of the second planetary gear set (PS2) is rotatably connected to the transmission output shaft (3) by means of a first switching element (S1), that the planet is in engagement with the sun gear (21) of the second planetary gear set (PS2) and a ring gear (15) of the second planetary gear set (PS2), and that the ring gear (15) of the second planetary gear set (PS2) is rotatably connected to the transmission housing (13) by means of a sixth switching element (S6). [10] Bottom bracket with a bottom bracket crankshaft (2) and a transmission according to one of claims 1 to 8 or 9, characterized by that the transmission input shaft (1) is connected to the bottom bracket crankshaft (2) in a rotationally fixed manner. [11] Bottom bracket according to claim 10, characterized by a bottom bracket shell (20), wherein the gear is arranged within a cavity of the bottom bracket shell (20). [12] A bicycle with a transmission according to any one of claims 1 to 8 or 9, or with a bottom bracket according to claim 10 or 11.

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