Freewheel as a freewheel clutch or a freewheel brake of a bottom bracket transmission
The freewheel design with a radially mounted outer ring on an inner ring via a sliding bearing and plain bearing sections addresses the issue of space and cost inefficiencies in existing freewheels, resulting in a compact and cost-effective solution.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- ZF FRIEDRICHSHAFEN AG
- Filing Date
- 2025-12-12
- Publication Date
- 2026-06-25
AI Technical Summary
Existing freewheels in bicycle drivetrains require separate ball bearings for the inner and outer rings, increasing installation space and manufacturing costs.
A freewheel design where the outer ring is mounted radially on the inner ring via a sliding bearing, eliminating the need for additional bearing components and utilizing plain bearing sections along the locking teeth, with materials of differing hardnesses for the inner and outer rings.
Achieves a compact design with reduced installation space and lower manufacturing costs while maintaining functionality.
Smart Images
Figure EP2025086749_25062026_PF_FP_ABST
Abstract
Description
[0001] ZF Friedrichshafen AG File 306560 Friedrichshafen 2024-12-19
[0002] Freewheel as a freewheel clutch or freewheel brake of a pedal drive
[0003] The present invention relates to a freewheel as a freewheel clutch or freewheel brake of a bottom bracket gearbox with an inner ring and an outer ring, wherein the outer ring has a locking toothing extending along an inner circumference and the inner ring has several spring-loaded pawls distributed over an outer circumference for engaging the locking toothing of the outer ring in a direction-dependent manner. The invention further relates to a bicycle or pedelec with a bottom bracket gearbox having at least one freewheel.
[0004] These types of freewheels, or pawl freewheels, are commonly used in the rear hubs of bicycle drivetrains. The outer and inner rings of the freewheels are each supported by ball bearings on a single component. The requirement for separate ball bearings for the inner and outer rings results in a disadvantageous increase in installation space.
[0005] Therefore, the present invention is based on the objective of proposing a freewheel and a bicycle or pedelec with the freewheel which have the smallest possible installation space requirement and can be manufactured as cost-effectively as possible.
[0006] This problem is solved according to the invention by the features of claim 1 or 10. Advantageous and claimed embodiments are described in the dependent claims, the description, and the drawings.
[0007] Thus, a freewheel is proposed as a freewheel clutch or freewheel brake for a bottom bracket gearbox, comprising an inner ring and an outer ring. The outer ring has a locking toothing or similar feature extending along its inner circumference, and the inner ring has several spring-loaded pawls or similar features distributed around its outer circumference for engaging the locking toothing of the outer ring in a direction-dependent manner. To achieve the most cost-effective and space-saving freewheel or pawl freewheel design, the outer ring is mounted on the inner ring. ZF Friedrichshafen AG File 306560 Friedrichshafen 2024-12-19
[0008] Because the inner and outer rings of the proposed freewheel are radially mounted directly inside or on top of each other, additional bearing components can be omitted, resulting in a smaller installation space requirement and lower manufacturing costs. Consequently, a space-neutral radial mounting of the inner and outer rings is achieved.
[0009] A particularly cost-effective and space-saving design is achieved in the proposed freewheel by mounting the outer ring with its inner circumference on the outer circumference of the inner ring via a sliding bearing.
[0010] A preferred design for the plain bearing in the proposed freewheel can be achieved by providing several plain bearing sections along the locking teeth of the outer ring. These plain bearing sections allow for a particularly cost-effective plain bearing design. The plain bearing sections must be dimensioned such that a sufficiently large sliding surface is provided between each tooth of the locking teeth.
[0011] For example, in the proposed freewheel, a sliding bearing section could be formed by a flattened tooth of the locking teeth on the outer ring. Other designs are also conceivable; however, flattening the teeth of the locking teeth is a particularly cost-effective solution, as no additional components are required for the sliding bearing.
[0012] It is particularly advantageous if the flattened tooth of the locking tooth has a cross-sectional radius adapted to the radius of the outer circumference of the inner ring.
[0013] To make the proposed freewheel particularly efficient, in addition to the advantages of small installation space requirements and low manufacturing costs, the present invention provides that the contact surfaces between the inner and outer rings are made of materials with different hardnesses. For example, the inner ring can be made of aluminum and the outer ring of steel, or vice versa.
[0014] The problem underlying the invention is also solved by a bicycle or pedelec with a bottom bracket gearbox having at least one freewheel as described above. This results in the advantages already described and further advantages.
[0015] The invention will be further explained below with reference to the drawings.
[0016] They show:
[0017] Figure 1 shows a cutaway view of a possible embodiment of a freewheel according to the invention; and
[0018] Figure 2 shows a cut view along the section line AA according to Figure 1.
[0019] Figures 1 and 2 show different views of a freewheel according to the invention as a freewheel clutch or freewheel brake in a bottom bracket gearbox 1, using a bicycle or pedelec 2 as an example.
[0020] The freewheel shown in the figures can be used as a freewheel clutch or as a freewheel brake in the bottom bracket gearbox 1. The difference between a freewheel clutch and a freewheel brake lies essentially in the fact that the freewheel clutch connects two shafts together, while the freewheel brake locks a shaft against a housing or the like.
[0021] Regardless of the above, the freewheel comprises an inner ring 3 and an outer ring 4, wherein the outer ring 4 has a locking toothing 5 extending along an inner circumference and the inner ring 3 has several spring-loaded pawls 6 distributed around its outer circumference for engaging the locking toothing 5 of the outer ring 4 in a direction-dependent manner. ZF Friedrichshafen AG File 306560 Friedrichshafen 2024-12-19
[0022] To achieve a cost-effective and space-saving freewheel, the outer ring 4 is radially supported on the inner ring 3 by a plain bearing. This eliminates the need for additional bearing components.
[0023] As can be seen particularly in Figure 1, several sliding bearing sections 7 are arranged along the locking teeth 5 over the inner circumference of the outer ring 4, with the sliding bearing sections 7 forming the sliding bearing. The sliding bearing sections 7 are realized by flattened teeth of the locking teeth 5, the flattened tooth having a cross-sectional radius adapted to the radius of the outer circumference of the inner ring 3.
[0024] As can be seen in particular from Figure 2, the pawls 6 arranged in adapted recesses on the outer circumference of the inner ring 3 are spring-loaded in the respective recess via a common spring ring 8 such that the pawls 6 are biased radially outwards in the direction of the locking teeth 5 of the outer ring 4.
[0025] Each pawl 6 has a receiving groove 9 located approximately in the center, in which the spring ring 8 runs. For example, separate springs can also be used for each pawl 6, or a so-called worm spring can be used instead of the spring ring 8, to preload the pawls 6 against the locking teeth 5.
[0026] It is also conceivable that the inner ring 3 has a corresponding receiving groove 9 for the spring ring 8.
[0027] ZF Friedrichshafen AG File 306560 Friedrichshafen 2024-12-19
[0028] Reference sign
[0029] 1 bottom bracket gearbox
[0030] 2 Bicycle or pedelec
[0031] 3 Inner ring of the freewheel
[0032] 4 Outer ring of the freewheel
[0033] 5 locking teeth on the outer ring
[0034] 6 pawls on the inner ring
[0035] 7 sliding bearing sections as sliding bearings
[0036] 8 spring or spring ring
[0037] 9 recordings
Claims
ZF Friedrichshafen AG File 306560 Friedrichshafen 2024-12-19 Patent claims 1. Freewheel as a freewheel clutch or freewheel brake of a bottom bracket gearbox (1), comprising an inner ring (3) and an outer ring (4), wherein the outer ring (4) has a locking toothing (5) extending along an inner circumference and the inner ring (3) has several spring-loaded pawls (6) arranged distributed over an outer circumference for engaging in the locking toothing (5) of the outer ring (4) depending on the direction of rotation, characterized in that the outer ring (4) is mounted on the inner ring (3).
2. Freewheel according to claim 1, characterized in that the outer ring (4) is mounted with its inner circumference on the outer circumference of the inner ring (3) via a sliding bearing.
3. Freewheel according to claim 1 or 2, characterized in that several sliding bearing sections (7) are provided as sliding bearings along the locking teeth (5) of the outer ring (4).
4. Freewheel according to claim 3, characterized in that a sliding bearing section (7) is formed by a flattened tooth of the locking toothing (5) on the outer ring (4).
5. Freewheel according to claim 4, characterized in that the flattened tooth of the locking toothing (5) has a radius in cross-section adapted to the radius of the outer circumference of the inner ring (3).
6. Freewheel according to one of the preceding claims, characterized in that the contact surfaces between inner ring (3) and outer ring (4) are made of materials with different hardness.
7. Freewheel according to one of the preceding claims, characterized in that the pawls (6) arranged in recesses on the outer circumference of the inner ring (3) are spring-loaded in the ZF Friedrichshafen AG File 306560 Friedrichshafen 2024-12-19 respective recesses are mounted in such a way that each pawl (6) is preloaded radially outwards in the direction of the locking teeth (5) of the outer ring (4).
8. Freewheel according to claim 7, characterized in that each pawl (6) has a receiving groove (9) arranged approximately centrally for the spring ring (8).
9. Freewheel according to claim 7, characterized in that the inner ring (3) has a receiving groove (9) for the spring ring (8).
10. Bicycle or pedelec (2) with a bottom bracket gearbox (1 ) with at least one freewheel according to one of the preceding claims.