Freewheel as a freewheel clutch or freewheel brake of a bottom bracket transmission
The freewheel design with a harder inner ring and spring-loaded pawls on the outer ring addresses the torque limitation issue, enhancing torque transmission by leveraging material differences for improved performance.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- ZF FRIEDRICHSHAFEN AG
- Filing Date
- 2025-12-11
- Publication Date
- 2026-06-25
AI Technical Summary
Existing freewheels with pawls on the inner ring and locking teeth on the outer ring, made of less hard materials like aluminum, limit the transmissible torque due to material constraints.
A freewheel design with an inner ring made of a harder material than the outer ring, with a locking mechanism that extends along the outer circumference, and the locking toothing, and spring-loaded pawls on the inner circumference of the outer ring for engaging the locking teeth in a direction-dependent manner.
Enhances torque transmission capacity by allowing the use of harder materials for the inner ring while maintaining the flexibility of softer materials for the outer ring, thereby increasing the overall transmissible torque.
Smart Images
Figure EP2025086472_25062026_PF_FP_ABST
Abstract
Description
[0001] ZF Friedrichshafen AG File 306568 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, comprising an inner ring and an outer ring, and at least one pawl for engaging in a locking toothing 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. In these known freewheels, the pawls are located on the inner ring and the locking teeth on the outer ring. For design reasons, it may be necessary to make the outer ring of the freewheel from a less hard material, such as aluminum, and the inner ring from a harder material, such as steel. In such a case, the locking teeth would have to be made of aluminum, which would undesirably limit the amount of torque that can be transmitted.
[0005] Therefore, the present invention is based on the objective of proposing a freewheel and a bicycle or pedelec with a freewheel in which the transmissible torque is further increased.
[0006] This problem is solved according to the invention by the articles having 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 of a bottom bracket gearbox with an inner ring and an outer ring, as well as with at least one pawl for engaging a locking toothing in a direction-dependent manner. To further increase the transmissible torque, it is provided that the inner ring, made of a harder material than the outer ring, has the locking toothing running along an outer circumference, and that ZF Friedrichshafen AG File 306568 Friedrichshafen 2024-12-19
[0008] The outer ring has or accommodates a spring-loaded pawl arranged on an inner circumference for engaging the locking teeth of the inner ring depending on the direction of rotation.
[0009] The proposed freewheel offers the advantage that the torques to be transmitted are significantly higher than with freewheels where the locking teeth are made of a less hard material.
[0010] For example, in the proposed freewheel, the inner ring, made of a harder material such as steel or the like, can be manufactured, while the outer ring, made of a softer material such as aluminum or the like, can be manufactured.
[0011] In a further development of the present invention, the proposed freewheel can be provided with a pawl arranged in a recess on the inner circumference of the outer ring, which is spring-loaded in the recess by means of a spring element such that the pawl is biased radially inwards in the direction of the locking teeth of the inner ring. In this way, the pawl used for torque transmission can be actuated advantageously simply and cost-effectively.
[0012] A particularly simple design for accommodating the spring element used to actuate the pawl can be achieved by providing the pawl with a receiving groove or similar feature located approximately in the center for the spring element.
[0013] It is also conceivable that the outer ring has a groove for the spring element.
[0014] To further improve torque transmission, the proposed freewheel may be designed with several spring-loaded pawls distributed around the inner circumference of the outer ring. ZF Friedrichshafen AG File 306568 Friedrichshafen 2024-12-19
[0015] It is particularly advantageous when using multiple pawls if the pawls can be actuated together via at least one spring element.
[0016] Various spring rings or similar components can be used as spring elements. The use of a spring clip or similar component as a spring element for actuating the pawls is particularly advantageous.
[0017] To ensure the correct positioning of the pawls on the outer ring, both when the freewheel is unassembled and during operation, the proposed freewheel design may incorporate at least one end of the spring clip or spring ring being secured in a recess or similar feature on the inner circumference of the outer ring. This prevents the spring clip or spring ring from rotating.
[0018] 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.
[0019] The invention will be further explained below with reference to the drawings.
[0020] They show:
[0021] Figure 1 shows a cutaway view of a possible embodiment of a freewheel according to the invention;
[0022] Figure 2 shows a sectioned view along the section line AA according to Figure 1; and
[0023] Figure 3 shows a schematic three-dimensional view of an outer ring of the freewheel with pawls distributed around its inner circumference. ZF Friedrichshafen AG File 306568 Friedrichshafen 2024-12-19
[0024] Figures 1 to 3 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.
[0025] 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.
[0026] Regardless, the freewheel comprises an inner ring 3 and an outer ring 4 as well as at least one pawl 6 for engaging in a locking tooth 5 depending on the direction of rotation.
[0027] To further increase the transmissible torque of the proposed freewheel, the inner ring 3, made of a harder material than the outer ring 4, is designed to have a locking toothing 5 extending along its outer circumference. The outer ring 3 also features spring-loaded pawls 6 arranged on its inner circumference for engaging the locking toothing 5 of the inner ring 3 in a direction-dependent manner. Thus, even with the freewheel where the inner ring 3 with the locking toothing is made of steel, for example, and the outer ring 4 with the pawl 6 is made of aluminum, for example, higher torques can still be transmitted.
[0028] As can be seen particularly from Figure 1, the at least one pawl 6 arranged in a recess on the inner circumference of the outer ring 4 is spring-loaded in the recess by means of a spring ring or spring clip 8 such that the pawl 6 is biased radially inwards in the direction of the locking teeth 5 of the inner ring 4.
[0029] The cutaway view in Figure 2 clearly shows that the pawl 6 has an approximately centrally located receiving groove 7 for the spring ring or spring clip 8. ZF Friedrichshafen AG File 306568 Friedrichshafen 2024-12-19
[0030] Figure 3 shows, by way of example, two spring-loaded pawls 6 arranged around the inner circumference of the outer ring 4. A spring clip 8 is provided, for example, to actuate the two pawls 6 together. To prevent the spring ring or spring clip 8 from rotating on the inner circumference of the outer ring 4, a bent end 9 of the spring clip 8 engages in a recess 10 on the inner circumference of the outer ring 4 and is thus fixed to the outer ring 4 in a rotationally fixed manner.
[0031] ZF Friedrichshafen AG File 306568 Friedrichshafen 2024-12-19
[0032] Reference sign
[0033] 1 bottom bracket gearbox
[0034] 2 Bicycle or pedelec
[0035] 3 Inner ring of the freewheel
[0036] 4 Outer ring of the freewheel
[0037] 5 locking teeth on the inner ring
[0038] 6 pawls on the outer ring
[0039] 7 recordings
[0040] 8 Spring element as spring clip or spring ring
[0041] 9. bent end of the spring clip or spring ring
[0042] 10 Recess on the inner circumference of the outer ring
Claims
ZF Friedrichshafen AG File 306568 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) and at least one pawl (6) for engaging in a locking toothing (5) depending on the direction of rotation, characterized in that the inner ring (3), which is made of a harder material than the outer ring (4), has the locking toothing (5) extending along an outer circumference, and that the outer ring (3) accommodates the spring-loaded pawl (6) arranged on an inner circumference for engaging in the locking toothing (5) of the inner ring (3) depending on the direction of rotation.
2. Freewheel according to claim 1, characterized in that the inner ring (3) is made of steel and that the outer ring (4) is made of aluminium.
3. Freewheel according to one of the preceding claims, characterized in that the pawl (6) arranged in a recess on the inner circumference of the outer ring (4) is spring-loaded in the recess by means of a spring element (8) such that the pawl (6) is biased radially inwards in the direction of the locking teeth (5) of the inner ring (4).
4. Freewheel according to claim 3, characterized in that the pawl (6) has a receiving groove (7) arranged approximately centrally for the spring element (8).
5. Freewheel according to claim 3, characterized in that the inner ring (3) has a receiving groove (9) for the spring ring (8).
6. Freewheel according to one of the preceding claims, characterized in that several spring-loaded pawls (6) are provided distributed over the inner circumference of the outer ring (4).
7. Freewheel according to claim 6, characterized in that the pawls (6) can be actuated jointly via at least one spring element (8). ZF Friedrichshafen AG File 306568 Friedrichshafen 2024-12-19 8. Freewheel according to claim 6 or 7, characterized in that a spring clip (8) is provided as a spring element.
9. Freewheel according to claim 8, characterized in that at least one end (9) of the spring clip (8) is attached in a recess (10) on the inner circumference of the outer ring (4).
10. Bicycle or pedelec (2) with a bottom bracket gearbox (1 ) with at least one freewheel according to one of the preceding claims.