Gearbox for a bicycle

Abstract

Transmission for a bicycle, with at least four shifting elements, a first planetary gear set (PS1) and a second planetary gear set (PS2), wherein a carrier of the first planetary gear set (PS1) is connected in a rotationally fixed manner to a carrier of the second planetary gear set (PS2) and a ring gear of the first planetary gear set (PS1) is connected in a rotationally fixed manner to a ring gear of the second planetary gear set (PS2), characterized in that a sun gear of the first planetary gear set (PS1) is connected in a rotationally fixed manner to an output shaft (2) of the transmission.

Description

[0001] The invention relates to a transmission for a bicycle, with at least four shifting elements, a first planetary gear set and a second planetary gear set.

[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 / 0 177 911 A1 discloses a transmission that features three planetary gears connected in series with a high-speed ratio. The transmission has a total of seven gear planes, including numerous stepped planetary gears, resulting in a complex design and a very high assembly effort.

[0004] From the publication DE 199 49 507 A1, a multi-stage transmission is known as a hub gear for bicycles with four planetary gear sets that are operatively connected to one another.

[0005] From the document DE 101 15 995 A1 a multi-stage transmission is known in which an input shaft is connected to primary gear sets and an output shaft is connected to secondary gear sets, wherein shifting elements for shifting forward gears act on the primary gear sets and the secondary gear sets.

[0006] From the publication DE 10 2014 223 334 A1 a drive train for a pedal bike in a bottom bracket housing with a planetary gear and an electric machine is known.

[0007] Further multi-speed planetary gears for bicycles are known from the publications DE 10 2014 101 726 A1 and DE 11 2010 002 286 T5.

[0008] The object of the invention is therefore to provide a transmission which has a low construction cost.

[0009] The problem is solved by the subject matter of the independent patent claims.

[0010] In the transmission, a carrier of the first planetary gear set is connected in a rotationally fixed manner to a carrier of the second planetary gear set and a ring gear of the first planetary gear set is connected in a rotationally fixed manner to a ring gear of the second planetary gear set.

[0011] The transmission according to the invention has the advantage of providing a 4-speed transmission that does not require stepped planetary gears. The transmission has a simple design, and assembly can be completed quickly, which is advantageous, among other things, in terms of cost. Furthermore, the transmission has good efficiency and smooth gear steps. The transmission according to the invention also has the advantage of being suitable for bicycle applications, particularly in conjunction with a front-mounted or rear-mounted groupset described in more detail below.

[0012] In a special design, the carrier of the first planetary gear set and the carrier of the second planetary gear set can be designed as a single piece, i.e., a single component. Furthermore, the ring gear of the first planetary gear set and the ring gear of the second planetary gear set can be designed as a single piece, i.e., a single component. This offers the advantage that the shared carrier and the shared ring gear create a compact transmission design and simplify transmission assembly.

[0013] The first planetary gear set can be a positive planetary gear set. The second planetary gear set can be a negative planetary gear set. A negative planetary gear set corresponds to a planetary gear set with a carrier on which the planetary gears are rotatably mounted, a sun gear, and a ring gear. The teeth of at least one of the planetary gears mesh with the teeth of both the sun gear and the ring gear, causing the ring gear and sun gear to rotate in opposite directions when the sun gear rotates with the carrier stationary.

[0014] In contrast, a positive planetary gear set differs from a negative planetary gear set in that the positive planetary gear set has inner and outer planetary gears that are rotatably mounted on the carrier. The teeth of the inner planetary gears mesh with the teeth of the sun gear and the teeth of the outer planetary gears. The teeth of the outer planetary gears also mesh with the teeth of the ring gear. This means that when the carrier is stationary, the ring gear and the sun gear rotate in the same direction.

[0015] In a particular embodiment, a drive shaft of the transmission can be operatively connected to the first planetary gear set and / or to the second planetary gear set. In particular, the drive shaft can be rotationally fixedly connected to a carrier of the first planetary gear set by means of a first shifting element of the at least four shifting elements. Furthermore, the drive shaft can be rotationally fixedly connected to a ring gear of the first planetary gear set and / or a ring gear of the second planetary gear set by means of a second shifting element of the at least four shifting elements.

[0016] 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.

[0017] A sun gear of the first planetary gear set can be rotationally fixedly connected to an output shaft of the transmission. A carrier of the second planetary gear set can be rotationally fixedly connected to a transmission housing by means of a third shifting element of the at least four shifting elements. A sun gear of the second planetary gear set can be rotationally fixedly connected to the transmission housing by means of a fourth shifting element of the at least four shifting elements.

[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 is assembled, can be located 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, but is stationary.

[0019] The third and fourth switching elements can each be designed as a brake. The first switching element can be designed as a clutch. The second switching element can be designed as a clutch or as a freewheel. The freewheel design offers the advantage that no actuator is required to operate the switching element.

[0020] The drive shaft can be connected to a bottom bracket crankshaft in a rotationally fixed manner. In this design, the output shaft can be connected to a transmission element, such as a chain sprocket or a belt pulley, in a rotationally fixed manner. When the transmission is used in a bicycle, the torque applied to the transmission element can be transmitted to a rear wheel via a transmission element, such as a chain or belt.

[0021] 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, i.e., with a gear ratio of 1. The remaining gears can have a high-speed gear ratio, i.e., a gear ratio less than 1.

[0022] In a special design, the transmission can have a third planetary gear set that is operatively connected to the first planetary gear set and / or the second planetary gear set. The third planetary gear set can be arranged upstream or downstream of the first and second planetary gear sets. The third planetary gear set can be a negative planetary gear set.

[0023] In this case, one element of the third planetary gear set can be connected in a rotationally fixed manner to another element of the third planetary gear set by means of a fifth shifting element. When the fifth shifting element is closed, the third planetary gear set is blocked, i.e., it has a gear ratio of 1. The fifth shifting element can be arranged such that the ring gear of the third planetary gear set can be connected in a rotationally fixed manner to a sun gear of the third planetary gear set. Such an arrangement has the advantage that the fifth shifting element has to apply a small supporting torque. Of course, it is alternatively possible to arrange the fifth shifting element such that a carrier of the third planetary gear set can be connected in a rotationally fixed manner to the ring gear of the third planetary gear set or to the sun gear of the third planetary gear set by means of the sixth shifting element.

[0024] The ring gear of the third planetary gear set can be connected to the transmission housing in a rotationally fixed manner by means of a sixth shifting element. The fifth shifting element can be designed as a clutch or freewheel. The sixth shifting element can be designed as a brake.

[0025] In one embodiment, the third planetary gear set can be connected upstream of the first and second planetary gear sets in traction operation, thus forming a pre-assembled group. In this embodiment, the first and second planetary gear sets, the input shaft, the output shaft and the four shift elements form a main group. A carrier of the third planetary gear set can be rotationally fixedly connected to the bottom bracket crankshaft by means of another input shaft and / or a sun gear of the third planetary gear set can be rotationally fixedly connected to the input shaft. In this embodiment, the output shaft is rotationally fixedly connected to a traction mechanism carrier. The traction mechanism carrier can be operatively connected to a rear wheel of the bicycle, for example by means of a chain or a belt.

[0026] Alternatively, a design is possible in which the third planetary gear set is connected downstream of the first and second planetary gear sets in traction operation, thus forming a downstream group. The first and second planetary gear sets, the input shaft, the output shaft, and the four shifting elements form a main group in this design. The carrier of the third planetary gear set can be connected to the output shaft in a rotationally fixed manner, and the sun gear of the third planetary gear set can be connected to another output shaft in a rotationally fixed manner. The other output shaft can be connected to the traction mechanism carrier in a rotationally fixed manner. In this design, the input shaft is connected to the bottom bracket crankshaft in a rotationally fixed manner.

[0027] The front-mounted or rear-mounted group can provide exactly two gears and / or have exactly two shifting elements, namely the fifth and sixth shifting elements. A first gear can be a direct gear, and a second gear can have a high-gear ratio. The front-mounted or rear-mounted 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. Furthermore, the front-mounted or rear-mounted group provides a four-step gear step. The main group has approximately geometrically stepped gear steps, for example, in the range of 1.22 to 1.28.

[0028] Regardless of whether the transmission has a front-mounted or rear-mounted group in addition to the main group, all variants result in the same gear ratio series, meaning that the overall function of the transmission is the same for all variants. Differences exist in the speed and torque ratios occurring at the individual planetary gear sets. Since the front-mounted or rear-mounted group, on the one hand, and the main group, on the other, have the direct gear as the first gear, the torque load is similar for all variants. Larger differences arise in the speeds, since the planetary gear sets located further back in the power flow already operate at a higher input speed in some gears.

[0029] The shifting elements used in the transmission, such as clutches or brakes, can be designed as positive-locking or friction-locking. If the shifting elements are designed as freewheels, it is advantageous that the main section and / or the front-mounted or rear-mounted section do not lock, preventing the transmission from jamming when the direction of rotation is reversed at the input or output. This can be achieved by designing the sixth shifting element of the front-mounted or rear-mounted section and / or the third and fourth shifting elements of the main section as a single-acting brake, such as a switchable freewheel brake.

[0030] If the second and / or sixth shifting element is designed as a freewheel, the freewheels can be designed to have a large diameter. This allows the load on the clamping bodies of the freewheels to be kept low. In particular, the freewheels can have essentially the same diameter or the same diameter as the shifting elements designed as brakes.

[0031] As a result, an 8-speed transmission can be realized by coupling the main group, which provides four gears, with a front- or rear-mounted group, each providing two gears. This transmission is advantageous because eight gears can be realized with exactly three planetary gear sets, allowing the transmission to be compact.

[0032] In addition, the transmission features suitable values ​​for the stationary gear ratios, allowing the planetary gear sets to have a small diameter. In particular, the second planetary gear set and the third planetary gear set can have the same stationary gear ratio. This is advantageous because more common parts are possible. The same stationary gear ratio can also be selected for the first planetary gear set. Since the first planetary gear set can be a plus planetary gear set, only the sun gear and the ring gear can be the same as the second and / or third planetary gear sets.

[0033] In a very special design, the transmission can have an electric motor that is operatively connected or can be operatively connected to the output shaft or the additional output shaft. The electric motor can be connected downstream of the first and / or second and / or third planetary gear set. The advantage of connecting the electric motor downstream of the planetary gear sets is that they 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 steps, as the electric motor means that muscle power plays a less significant role in the drive.

[0034] 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.

[0035] 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.

[0036] The electric motor can be connected to the output shaft or additional output shaft via a chain drive, a belt drive, a spur gear, and / or a transmission. A freewheel can also be arranged in the power flow between the electric motor and the output shaft or additional output shaft. The freewheel offers the advantage that, when operating without an electric motor, no losses are caused by the rotating rotor of the electric motor.

[0037] A bottom bracket with the gearing according to the invention is particularly advantageous, with the drive shaft or the additional drive shaft being connected to the bottom bracket crankshaft in a rotationally fixed manner. The bottom bracket can have a bottom bracket shell, with the gearing arranged in a cavity of the bottom bracket shell. The gearing can be modular. Therefore, the gearing can be inserted into or removed from the cavity as a whole. A bicycle with the gearing or the bottom bracket is particularly advantageous.

[0038] The subject matter of the invention is illustrated schematically 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 a transmission according to a first embodiment, Fig. 2: a switching matrix of the Fig. 1 shown gearbox, Fig. 3: a schematic representation of a transmission according to the invention according to a second embodiment, Fig. 4: a schematic representation of a transmission according to a third embodiment, Fig. 5: a table with values ​​for the stationary ratio of the planetary gear sets, Fig. 6: a switching matrix of the Fig. 3 and Fig. 4 shown gearbox.

[0039] Fig. 1 shows a transmission according to the invention according to a first embodiment, which is rotationally symmetrical with respect to a bottom bracket crankshaft 4. In Fig. 1 only the upper half of the gearbox is shown.

[0040] The transmission has four shift elements: a first shift element S1, a second shift element S2, a third shift element S3, and a fourth shift element S4. Furthermore, the transmission has a first planetary gear set PS1 and a second planetary gear set PS2. The first planetary gear set PS1 is designed as a positive planetary gear set, and the second planetary gear set PS2 is designed as a negative planetary gear set.

[0041] A carrier of the first planetary gear set PS1 is rotationally fixedly connected to a carrier of the second planetary gear set PS2, and a ring gear of the first planetary gear set PS1 is rotationally fixedly connected to a ring gear of the second planetary gear set PS2. The carrier of the first planetary gear set and the carrier of the second planetary gear set PS2 are designed as a single piece, in particular as a common component. The ring gear of the first planetary gear set PS1 and the ring gear of the second planetary gear set PS2 are designed as a single piece, in particular as a common component.

[0042] An input shaft 1 of the transmission is rotatably connected to the carrier of the first planetary gear set PS1 by means of the first shifting element S1. Furthermore, the input shaft 1 is rotatably connected to the ring gear of the first planetary gear set PS1 and to the ring gear of the second planetary gear set PS2 by means of the second shifting element S2. A sun gear of the first planetary gear set PS1 is rotatably connected to an output shaft 2. The output shaft 2 is connected to a Fig. 1 not shown traction means carrier, such as a chain wheel or belt wheel, is connected in a rotationally fixed manner.

[0043] The carrier of the second planetary gear set PS2 is rotationally fixedly connected to a transmission housing 3 by means of the third shifting element S3. A sun gear of the second planetary gear set PS2 is rotationally fixedly connected to the transmission housing 3 by means of the fourth shifting element S4.

[0044] The gear is arranged in a cavity of a bottom bracket shell 8. The Fig. 1 shows a main group HG, which, as can be seen from the Fig. 3 and Fig. 4, is effectively linked to other area groups.

[0045] Fig. 2 shows a switching matrix for the Fig. 1. The symbol “X” indicates the switching elements that are closed for the respective gear. In addition, Fig. 2 for each gear, the ratio “i” between the input shaft 1 and the output shaft 2 is called. The table also calls the gear steps “phi”. As can be seen 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 geared up. The shifting elements are operated by a suitable actuator.

[0046] In the Fig. In the transmission shown in Figure 1, the first planetary gear set PS1 can have a static gear ratio of 1.56, and the second planetary gear set can have a static gear ratio of -1.56. For a negative planetary gear set, the static gear ratio corresponds to the negative tooth ratio of the ring gear and the sun gear. For a positive planetary gear set, the static gear ratio corresponds to the positive tooth ratio of the ring gear and the sun gear.

[0047] Fig. Figure 3 shows a transmission according to a second embodiment. The transmission differs from the one shown in Fig. 1 is that the transmission has a third planetary gear set PS3, which forms a front-mounted group VG, which is connected upstream of the main group HG in terms of drive technology. In particular, the third planetary gear set PS3 is connected upstream of the first planetary gear set PS1 and the second planetary gear set PS2 in terms of drive technology, considering a power flow from the bottom bracket crankshaft 4 to the output shaft 2 during traction operation.

[0048] A carrier of the third planetary gear set PS3 is rotationally fixedly connected to the bottom bracket crankshaft 4 by means of another drive shaft 5. A sun gear of the third planetary gear set PS3 is rotationally fixedly connected to the drive shaft 1. A ring gear of the third planetary gear set PS3 is rotationally fixedly connected to the sun gear of the third planetary gear set PS3 by means of a fifth shifting element S5. Furthermore, the ring gear of the third planetary gear set PS3 is rotationally fixedly connected to the transmission housing 3 by means of a sixth shifting element S6.

[0049] The fifth switching element S5 is designed as a brake and the sixth switching element S6 is designed as a freewheel.

[0050] Fig. 4 shows a transmission according to a third embodiment. Fig. 4 differs from the gearbox shown in Fig. 3 is that the third planetary gear set PS3 does not form a front-mounted group VG, but rather a rear-mounted group NG. This means that the third planetary gear set PS3 is connected downstream of the main group HG in terms of drive technology, considering the power flow from the bottom bracket crankshaft 4 to another output shaft 6 during traction operation.

[0051] The output shaft 2 is connected to the carrier of the third planetary gear set PS3 in a rotationally fixed manner. The sun gear of the third planetary gear set PS3 is connected to the further output shaft 6 in a rotationally fixed manner. The further output shaft 6 is connected to a Fig. 4 is connected to a traction mechanism carrier (not shown). The drive shaft 1 is connected to the bottom bracket crankshaft 4 in a rotationally fixed manner.

[0052] A further difference is that the transmission has an electric machine 7, which is operatively connected to the further output shaft 6, as shown by the dashed line. The connection of the electric machine 7 to the further output shaft 6 can be made via a superposition gear, a spur gear, a chain drive and / or a belt drive, whereby the connection in Fig. 4 is not shown. The connection of the electric machine 7 takes place in a drive-related area downstream of the NG rear-mounted group.

[0053] The electric machine 7 is not rotationally symmetrical to the bottom bracket crankshaft 4. In particular, the electric machine 7 is arranged offset in the radial direction relative to the bottom bracket crankshaft 4.

[0054] Another difference is that the transmission has a torque sensor 9, which can be used to measure the torque transmitted from the bottom bracket crankshaft 2 to the drive shaft 1. The torque sensor 9 can be disc-shaped. Of course, a different design and / or arrangement of the torque sensor 9 is also possible.

[0055] Fig. 5 shows a table with values ​​for the standard translation of the Fig. 3 and Fig. 4 planetary gear sets. As can be seen Fig. As can be seen in Figure 5, the second planetary gear set PS2 and the third planetary gear set PS3 have the same idle ratio of -1.56. The first planetary gear set PS1 has a idle ratio of 1.56.

[0056] Fig. 6 shows a switching matrix for the Fig. 3 and Fig. 4. The symbol "X" indicates the shift elements that are engaged in the respective gear. If the shift element is designed as a freewheel, "X" means that the freewheel is locked. This occurs automatically without external activation. The shift elements designed as brakes are engaged by at least one actuator.

[0057] The switching matrix also shows that the Fig. 3 and Fig. The transmission shown in Figure 4 has eight gears. Furthermore, the shift matrix specifies the gear ratio "i" between the bottom bracket crankshaft 4 and the transmission link for each gear. The gear step "phi" can also be derived from the shift matrix. Reference symbol 1 drive shaft 2 output shaft 3 Gearbox housing 4 bottom bracket crankshaft 5 additional drive shafts 6 additional output shafts 7 electric machine 8 bottom bracket shell 9 Torque sensor S1 first switching element S2 second switching element S3 third switching element S4 fourth switching element S5 fifth switching element S6 sixth switching element HG main gearbox NG rear-mounted gearbox VG primary gearbox PS1 first planetary gear set PS2 second planetary gear set PS3 third planetary set

Claims

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

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