Patent Application
20170305499
The present invention relates to a friction ring transmission for a vehicle operable using motor power and/or pedal power, including a crankshaft for pedal cranks and including a crankshaft center axis, which is to be understood as a theoretical axis and not as a fixed physical axis, the friction ring transmission being capable of being used, in particular, in an electric bicycle. The friction ring transmission includes an inner friction ring and an outer friction ring and at least one rotatable double tapered roller, which frictionally engages the inner friction ring and the outer friction ring. When a torque is transmitted, a contact force is transmitted in each case for the purpose of producing friction between the double tapered roller and the friction rings. Since these contact forces act on the double tapered roller at least partially in the opposite direction, a power flow path exists between the inner friction ring and the outer friction ring, along which contact forces are conducted from the one friction ring to the other friction ring. Situated within this power flow path is a force return device for transmitting contact force from one friction ring to the other friction ring. One of the friction rings is fixedly situated in relation to the force return device. The other friction ring is rotatable in relation to the force return device.
In vehicles, in particular, conventional electric bicycles, drive is possible both using muscle power as well as motor power and, in particular, using motor-assisted muscle power. Since there is an optimum range for the pedaling frequency of the rider and the possible pedaling frequency is upwardly limited, transmissions on such vehicles are advantageous, because with them, the pedaling frequency may be brought into the optimal or possible range. Friction ring transmissions have the advantage that they are adjustable continuously and also when stationary. The disadvantage of friction ring transmission, however, is the comparatively poor efficiency, which is caused both by the friction processes as well as by the transmission components such as, for example, bearings. A bicycle transmission based on the fundamental principle of the double cone friction ring transmission is described in German Patent Application No. DE 2012 209 0696 A1, which is integrated near the pedal bearing and situated axially in parallel to the crankshaft in a pedelectric/eBike drive. In PCT Application No. WO 2014/026 754 A1, a bicycle transmission is described which includes such a double cone friction ring transmission also situated axially in parallel to the crankshaft and near the pedal bearing.
A disadvantage of the design of the friction ring transmission described in German Patent Application No. DE 10 2012 209 096 A1 is that the force return device, which enables the friction rings to be pressed against the double cones, extends on the outside around the friction ring transmission. As a result, the force return device is a part having a large surface and is correspondingly heavy, which runs contrary to the lightweight concept applicable to vehicles in general.
Conventional transmissions also have the disadvantage that the adjustment of the gear ratio is carried out exclusively by the inside of the drive shaft or output shaft of the friction ring transmission and as thread adjustment. This significantly hampers the design freedom in the integration of such a transmission into a vehicle; in particular, adjustment requires a rotational movement of several rotations to be generated. In addition, this rotational movement is locally fixed at a center position in relation to the transmission. Even the rotation axis of the adjustment rotation is permanently predefined and extends coaxially to the center axis of the transmission.
The friction ring transmission according to the present invention includes, for example, an adjusting device for the gear ratio of the friction ring transmission, which is movable along an adjustment path. The adjustment path has a component of its course in the direction of a center axis of the roller carrier, the component at the same time extending at most less than a full rotation about the friction ring transmission, preferably less than 180 degrees, particularly preferably less than 90 degrees. The adjustment path extends particularly preferably straight and follows the direction of an imaginary center axis of the friction ring transmission. This center axis normally coincides with the center axis of a roller carrier of the double tapered rollers.
The adjusting device preferably penetrates a housing surrounding the friction ring transmission. The adjustment path extends preferably along a recess in the housing. Therefore, it is advantageous that the adjustment path extends circumferentially less than 360 degrees, preferably less than 180 degrees, more preferably less than 90 degrees. The housing may then be manufactured in particular, as a single piece, which is generally less costly than a multi-piece composite approach. The housing is particularly strong if at least a half rotation of the housing is not breached by the adjustment path. Less than a 90 degree circumferential extension of the adjustment path about the friction ring transmission has the advantage that the adjustment is simplified by the smaller encompassing angle. A particularly simple adjustment is achieved by a purely linear movement generally in the direction of the center axis of the roller carrier. The adjusting device is particularly preferably non-rotatably connected to the roller carrier, i.e., it is not movable relative to the roller carrier, so that an actuation of the adjusting device immediately shifts the roller carrier in the axial direction, as a result of which the gear ratio of the friction ring transmission is changed. It is possible that the roller carrier is rotated during adjustment; preferably, however, the roller carrier is not rotated and shifted only linearly. The adjusting device preferably includes no adjustable thread. The adjusting device preferably does not extend through the central area of the friction ring transmission. The adjusting device according to the present invention creates the possibility of rapidly and simply setting the gear ratio of the friction ring transmission.
The inner friction ring and the outer friction ring extend preferably around the crankshaft. This makes it possible to situate the crankshaft in the center of the friction ring transmission. The friction ring transmission is preferably filled with a traction fluid, which has good lubricating properties and nevertheless creates a high friction between the friction partners during intensive friction contact.
A friction ring transmission including the adjusting device according to the present invention is particularly preferably installed on the pedal bearing. An integrated design of the pedal bearing and the motor is also preferred. This results in the advantages of an optimal mass distribution, which is achieved by a low, central center of gravity and a lightweight rear wheel. The results are an improved handling, minimal spring-loaded masses and good driving dynamics. In addition, the assembly and disassembly of the rear wheel is simplified. Moreover, the bicycle manufacturer is only required to install one single integrated drive unit in the bicycle instead of multiple separate components. The customer may be presented with a uniform module made up of gear ratio control and drive control.
Preferred refinements of the present invention are described herein.
In one specific embodiment, the force return device extends inside the friction rings. This reduces weight as compared to the conventional force return device according to the related art, which extends outside the friction rings. At least one section of the force return device extends preferably in the direction of the center axis of the roller carrier. This section has, in particular, a smaller diameter than the friction diameter of the inner friction ring. It is particularly advantageous in this case, that the force return device according to this specific embodiment extending circumferentially in the inside allows the adjusting device to run from the friction ring support to an opening in the housing. According to the related art, this requisite installation space between the roller holder and the housing is already occupied by the circumferentially extending force return device.
In another specific embodiment, the roller carrier and the housing of the friction ring transmission are rotatably fixedly connected to one another. However, the roller carrier may be shifted relative to the friction wheels. The friction wheels in this case are rotatably designed, but preferably fixed in their position relative to the housing except for this rotation. The adjusting device may be fixedly connected to the roller carrier. It may be fitted as a movable arm, which extends, in particular, from the roller carrier to outside the transmission. The arm in this case extends preferably through the housing. As a result of the rotatably fixed connection to the housing, a course of the adjustment path along the center axis of the transmission or of the roller carrier is possible.
In another specific embodiment, the vehicle is equipped with a servomotor, with which the adjusting device is adjustable. The servomotor may be situated on the friction ring transmission and/or in an integrated unit made up of motor, transmission and crankshaft.
In another specific embodiment, the friction ring transmission includes two expanding clutches, which expand when loaded and increase the contact pressure between the friction rings and the double tapered rollers. Each one of the expanding clutches is preferably assigned to one each of the friction rings. The expanding clutches have an annular design, whereby the power return path extends at least through one of the expanding clutches.
In another specific embodiment, the force return device is situated around the crankshaft for the pedal cranks of the vehicle. The force return device is designed, in particular as a sleeve, the sleeve including a section extending axially along the crankshaft and a section extending radially in the direction of at least one of the friction rings. This design is lightweight and also simple to assemble and therefore easy to manufacture. The radially extending section may be manufactured separately from the axially extending section and joined subsequently, resulting subsequently in an integrated or a composite sleeve.
In another specific embodiment, the interior force return device is designed to be rotatable in relation to the crankshaft. In this way, the rotational speed of a friction ring rotatably fixedly connected to the force return device may differ from the rotational speed of the crankshaft. In this way, the crankshaft may be integrated into the interior of the friction ring transmission.
In another specific embodiment, a pilot transmission is connected in front of the friction ring transmission, which increases the rotational speed of the friction ring transmission. A planetary gear, which is also situated concentrically to the crankshaft, is preferred, in particular, in an integrated assembly, in which the crankshaft extends in the interior of the friction ring transmission. One advantage of the higher rotational speed of the friction ring transmission is that lower torques occur. As a result, the friction force to be transmitted may be reduced. This in turn allows the friction ring transmission to be designed lighter.
A rear transmission is preferably connected behind the friction ring transmission, which is designed preferably as a planetary gear, and which reduces the output rotational speed of the friction wheel transmission at its own output. In this way, the torque at the output is increased. The rear transmission with its reduction ratio may, in particular, again neutralize the gear ratio of the pilot transmission.
The pilot transmission is preferably driven with a torque, which is present on the crankshaft. For this purpose, a gear wheel may be connected to the crankshaft, into which its torque may be transmitted. In the case of a planetary gear as the pilot transmission, it is preferable to rotatably fixedly attach the annulus gear thereof to the crankshaft. As an alternative to a rotatably fixed attachment, a freewheel, which enables a reverse pedaling independently of the rotation of the motor, may also be situated in the course of the torque transmission between the crankshaft and the annulus gear. A friction ring of the friction ring transmission is preferably driven with the output of the pilot transmission. The friction ring may be driven as a result of the pilot transmission driving the force return device. The larger or the outer ring of the friction rings is preferably driven. The force return device is particularly preferably rotatably fixedly connected to the larger of the two friction wheels.
In another specific embodiment, the smaller or the innermost ring of the two friction rings is rotatably mounted in relation to the force return device, in particular, via a roller bearing. In many cases, this enables a small ball bearing having a small diameter to be used for this function, which generates a low torque loss and is lightweight.
In another specific embodiment, the friction ring transmission includes a summation gear wheel, which is used to add the torque generated by muscle power and that which is motor-driven. The summation gear wheel may be rotatably fixedly connected to one of the two friction rings. It is rotatably fixedly connected preferably to the larger friction ring, which in one specific embodiment including a pilot transmission may mean that it is connected to the output of the pilot transmission. The summation takes place by introducing torques into the summation gear wheel in various ways, namely centrally by a shaft onto which the summation gear wheel is set and by an additional gear wheel, which engages in the outer circumference of the summation gear wheel. This additional gear wheel is preferably a gear wheel, which is drivable by the motor.
In another specific embodiment, a roller bearing is situated between the force return device and one of the friction wheels, in which the force transmission line is at an acute angle to the center axis of the roller carrier. Contact forces, which constitute axial forces, extend via the bearing between the friction rings and the rollers. In addition, it fulfills the function of a radial guide of the parts mounted rotatably relative to one another. For this reason, angular ball bearings or tapered roller bearings are preferably used. The force return device extends preferably in the interior of the roller bearing. The inner ring is preferably attached to or pressed onto the force return device. This enables a simple design of the friction ring transmission. The roller bearing advantageously runs at the differential rotational speed between the rotational speed of the inner friction ring and of the outer friction ring, which in many operating states is lower than the rotational speeds of the friction rings themselves. As a result, the bearing losses and the bearing wear are reduced compared to an approach according to the related art, in which the friction rings are supported individually on the housing with axial bearings.
In another aspect of the present invention, a vehicle operable using motor power and/or pedal power is provided, which includes a friction ring transmission according to one of the specific embodiments described above.
In still another aspect, a drive device is provided for a vehicle operable using motor power and/or pedal power, which includes a friction ring transmission according to one of the specific embodiments described above.
Exemplary embodiments of the present invention are described in detail below with reference to the figures.
Intermediate transmission 7 includes an intermediate shaft 13, at one end of which a sprocket 14 is situated, which meshes with summation gear wheel 5. The mounting of intermediate shaft 13 is not depicted. Sprocket 14 has a significantly smaller diameter than summation gear wheel 5. An intermediate gear wheel 15, which has a significantly larger diameter than sprocket 14, is situated at the other end of intermediate shaft 13. Intermediate gear wheel 15 meshes with an output gear wheel 16 of an electric motor 6, which is part of drive unit 1. This effectuates a significant reduction of the rotational speed of electric motor 6 relative to the rotational speed of summation gear wheel 5 via intermediate transmission 7. A mechanical connection between electric motor 6 and housing 10 of friction ring transmission 2 is not depicted.
Rear transmission 4 is designed as a planetary gear, the output of which is planet carrier 17. Planet carrier 17 is rotatably fixedly connected to output sprocket 8 of the integrated transmission unit. The planetary gear is driven by sun wheel 35, whereas annulus gear 36 is rotatably fixedly connected to housing 10. An outer cover of rear transmission 4 is not depicted, which may be designed to be fully covered.
Friction ring transmission 2 includes an outer friction ring 20, which frictionally engages with multiple double cones 23. Double cones 23 are situated on a roller carrier 22 and revolve on axles 25 fastened thereto. Roller carrier 22 has a non-visible part located further inside of friction ring transmission 2. Outer friction ring 20 is connected to an expanding clutch 21 which, in turn, is supported via an axial bearing 24 on a housing part not depicted. Expanding clutch 21 expands in an axial direction of crankshaft 9 when a drive torque from summation gear wheel 5 acts on friction ring transmission 2. This increases the contact force between outer friction ring 20 and double tapered rollers 23. Adjusting lever 12 is connected to roller carrier 25, which is designed for displaceable movement in the axial direction of crankshaft 9. Expanding clutch 21 may include springs or may be connected to springs, which create a pretensioning force between outer friction ring 20 and double tapered rollers 23.
The interior part of roller carrier 22 is depicted in
The power flow through the part of drive unit 1 depicted in
Outer friction ring 20 and inner friction ring 26 are, as previously mentioned, supported on housing 10 by assigned axial bearings 24 and 28. Thus, housing 10 in the specific embodiment of
Crankshaft 9 is situated concentrically to roller carrier 22, axial bearings 24 and 28, expanding clutches 21 and 27 as well as to small friction ring 26 and large friction ring 20. Pilot transmission 3 and rear transmission 4, both of which are designed as planetary gears, are also situated concentrically to crankshaft 9. The same also applies for summation gear wheel 5 and the sprocket of output 8.
Unlike the first specific embodiment shown in
Unlike the specific embodiment of
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2014 221 514.5 | Oct 2014 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2015/071065 | 9/15/2015 | WO | 00 |
