Automatic belt tensioner for a bicycle

Abstract

This invention relates to an automatic belt tensioner for bicycles, mounted on a frame. A chainring is mounted on the frame and rotatably connected to a swingarm. A rear wheel hub is mounted on the swingarm. The chainring and rear wheel hub are connected by a drive belt. The automatic belt tensioner includes a base mounted on the frame and a tensioning arm rotatably connected to the base. A tensioning torsion spring is positioned between the tensioning arm and the base. The tensioning torsion spring drives the tensioning arm to rotate around the base. The rotation axis of the tensioning arm is parallel to the rotation axis of the chainring. The end of the tensioning arm furthest from the base is a contact end. The contact end extends between the chainring and the rear wheel hub and contacts the side of the drive belt away from the chainring. Along the return rotation direction of the tensioning torsion spring, the contact end swings towards the side closer to the chainring. This invention pushes the drive belt towards the chainring through the contact end, tensioning the drive belt while simultaneously allowing the drive belt to wrap around the chainring at a greater angle, increasing the friction between the drive belt and the chainring, and reducing the risk of drive belt slippage.

Description

Technical Field

[0001] This invention relates to the field of bicycle tensioner technology, and more particularly to an automatic bicycle belt tensioner. Background Technology

[0002] In belt-driven mountain bikes, the rear hub is connected to the frame via a swingarm. When riding over uneven terrain, the rear hub swings up and down around the frame. During this process, the distance between the rear hub and the chainring dynamically changes, causing the belt on both the rear hub and chainring to loosen / tighten. An overly loose belt will cause slippage, while an overly tight belt will accelerate wear and shorten its lifespan. Existing mountain bike tensioners are designed for chain drives and do not address slippage issues; therefore, directly using them for belt tensioning does not improve belt slippage.

[0003] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide an automatic belt tensioner for bicycles to prevent the belt from slipping due to being too tight or too loose.

[0005] The technical solution of the present invention is as follows: Mounted on the frame, the frame houses a chainring that is rotatably connected to a swingarm. A rear wheel hub is mounted on the swingarm. The chainring and rear wheel hub are connected via a drive belt. The self-contained automatic belt tensioner includes a base mounted on the frame and a tensioning arm rotatably connected to the base.

[0006] A tensioning torsion spring is installed between the tensioning arm and the base. The tensioning torsion spring drives the tensioning arm to rotate around the base. The rotation axis of the tensioning arm is parallel to the rotation axis of the gear disc.

[0007] The end of the tensioner arm furthest from the base is the contact end. The contact end extends between the chainring and the rear wheel hub and contacts the side of the drive belt away from the chainring.

[0008] Along the return rotation direction of the tensioning torsion spring, the contact end swings towards the side closer to the gear plate.

[0009] A further technical solution is to set a guide shaft on the base, and torsion spring and tension arm are sleeved on the guide shaft.

[0010] A further technical solution involves a shaft hole on the base, with a guide shaft positioned within the shaft hole. A tensioning arm extends into the shaft hole. A tensioning torsion spring is also positioned within the shaft hole.

[0011] A further technical solution involves a guide shaft passing through a tensioning arm. A first fastening bolt is positioned at the end of the guide shaft furthest from the base. A first washer and a pulley are positioned between the first fastening bolt and the guide shaft. The pulley contacts the side of the tensioning arm furthest from the base.

[0012] A further technical solution involves providing a dust cover at the end of the tensioning arm furthest from the base. The dust cover covers the end of the guide shaft that passes through the tensioning arm.

[0013] A further technical solution involves installing a friction damping ring on the tensioning arm. The friction damping ring is positioned between the tensioning arm and the base.

[0014] A further technical solution involves an interference fit bushing on the tensioning arm. The bushing is fitted onto the guide shaft with a clearance.

[0015] A further technical solution involves installing mounting pins on the tensioning arm. These mounting pins are inserted into the tensioning arm and the base.

[0016] A further technical solution involves providing a guide post at the contact end. The axis of the guide post is parallel to the rotation axis of the tensioning arm. A pulley is rotatably mounted on the guide post.

[0017] A further technical solution involves a guide post. An annular groove is formed along the outer edge of the pulley. An O-ring is fitted onto the pulley along the annular groove.

[0018] The beneficial technical effects of the present invention are as follows: (1) The automatic belt tensioner for bicycles in this invention has a base mounted on the frame to prevent it from swinging up and down with the rear wheel hub, thus improving its operational stability. The tensioning arm is rotatably connected to the base via a tensioning torsion spring, and the spring force continuously compresses and tensions the drive belt. The contact end extends between the rear wheel hub and the chainring and is driven by the tensioning torsion spring to move towards the chainring, pushing the drive belt towards the chainring side through the contact end. This tensions the drive belt while allowing it to wrap around the chainring at a larger angle, increasing the friction between the drive belt and the chainring and reducing the risk of belt slippage.

[0019] (2) Furthermore, a shaft hole is opened on the base and a guide shaft is set. The tensioning torsion spring and the tensioning arm are sleeved on the guide shaft and their degrees of freedom are restricted, thereby improving the stability of the tensioning torsion spring and the tensioning arm. Moreover, the tensioning arm extends into the shaft hole and is further restricted in its degrees of freedom, thereby improving the stability of the swing time of the tensioning arm.

[0020] (3) Furthermore, a pulley is provided at the contact end, and the contact end rolls against the transmission belt through the pulley, reducing the friction between the tension arm and the transmission belt, reducing the wear of the transmission belt at the contact end, and extending the service life of the transmission belt. At the same time, the reduction of friction reduces the resistance in the belt transmission process, making it easier for the rider to ride. Attached Figure Description

[0021] Figure 1 A schematic diagram of the structure of an automatic belt tensioner for bicycles according to an embodiment of the present disclosure is shown when it is mounted on the frame.

[0022] Figure 2 A perspective structural schematic diagram of an automatic belt tensioner for bicycles according to an embodiment of the present disclosure is shown.

[0023] Figure 3 An exploded structural schematic diagram of an automatic belt tensioner for bicycles according to an embodiment of the present disclosure is shown.

[0024] Marked in the attached diagram: 1. Frame; 11. Swing arm; 111. Rear wheel hub; 12. Chainring; 121. Drive belt; 2. Base; 21. Mounting hole; 22. Shaft hole; 3. Tensioning torsion spring; 31. Guide shaft; 32. Pulley; 321. First fastening bolt; 322. First washer; 4. Friction damping ring; 5. Tensioning arm; 51. Bushing; 52. Dust cover; 53. Assembly pin; 54. Contact end; 541. Guide post; 6. Pulley; 61. Bearing; 62. Second washer; 63. Second fastening bolt; 64. Annular groove; 654. O-ring. Detailed Implementation

[0025] To make the objectives, features, and advantages of this invention more apparent and understandable, please refer to the accompanying drawings. It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings are merely for illustrative purposes and to aid those skilled in the art in understanding and reading the invention. They are not intended to limit the implementation conditions of the invention and therefore have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to the size, without affecting the effects and objectives achieved by the invention, should still fall within the scope of the technical content disclosed in this invention.

[0026] In the description of this invention, the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "top," "bottom," "inner," "outer," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0027] Figure 1 A schematic diagram of the structure of an automatic belt tensioner for bicycles according to an embodiment of the present disclosure is shown when it is mounted on the frame. Figure 2 A perspective structural schematic diagram of an automatic belt tensioner for bicycles according to an embodiment of the present disclosure is shown. Figure 3 An exploded structural diagram of an automatic bicycle belt tensioner according to an embodiment of this disclosure is shown. Please refer to... Figure 1 , Figure 2 and Figure 3 An automatic belt tensioner is mounted on a frame 1, on which a chainring 12 is mounted and rotatably connected to a swing arm 11. A rear wheel hub 111 is mounted on the swing arm 11. The chainring 12 and the rear wheel hub 111 are connected by a drive belt 121. The automatic belt tensioner includes a base 2 mounted on the frame 1 and a tensioning arm 5 rotatably connected to the base 2. The base 2 is mounted on the frame 1 to prevent the automatic belt tensioner from swinging up and down with the rear wheel hub 111, thus improving the stability of the automatic belt tensioner. In some embodiments, the base 2 has a mounting hole 21, in which a threaded fastener (not shown) is installed to connect to the frame 1, and the base 2 is fixed to the frame 1 by the threaded fastener. A tensioning torsion spring 3 is provided between the tensioning arm 5 and the base 2. The tensioning torsion spring 3 drives the tensioning arm 5 to rotate around the base 2. The rotation axis of the tensioning arm 5 is parallel to the rotation axis of the chainring 12. Specifically, the tensioning arm 5 and the base 2 are respectively provided with torsion spring stops (not shown in the figure) that abut against the end of the tensioning torsion spring 3. The tensioning arm 5 is driven to rotate around the base 2 by the elastic force of the tensioning torsion spring 3, thereby continuously compressing and tensioning the drive belt 121. The end of the tensioning arm 5 away from the base 2 is the contact end 54. The contact end 54 extends between the chainring 12 and the rear wheel hub 111 and contacts the side of the drive belt 121 away from the chainring 12. Along the return rotation direction of the tensioning torsion spring 3, the contact end 54 swings towards the side closer to the chainring 12. That is, the contact end 54 pushes the drive belt 121 towards the chainring 12, tensioning the drive belt 121 while allowing the drive belt 121 to wrap around the chainring 12 at a larger angle, increasing the friction between the drive belt 121 and the chainring 12, and reducing the risk of the drive belt 121 slipping.

[0028] Please refer to Figure 2 and Figure 3 A guide shaft 31 is provided on the base 2, and a tensioning torsion spring 3 and a tensioning arm 5 are sleeved on the guide shaft 31. In some embodiments, the guide shaft 31 is interference-fitted with the base 2. The tensioning torsion spring 3 and the tensioning arm 5 are restricted in their degrees of freedom by being sleeved on the guide shaft 31, thereby improving the stability of the tensioning torsion spring 3 and the tensioning arm 5.

[0029] Preferably, the base 2 has a shaft hole 22, and the guide shaft 31 is disposed within the shaft hole 22. The tension arm 5 extends into the shaft hole 22. The tension torsion spring 3 is disposed within the shaft hole 22. The tension arm 5, extending into the shaft hole 22, is further restricted in its degree of freedom, improving the stability of the swing time of the tension arm 5. Specifically, the diameter of the shaft hole 22 varies along its length to facilitate the interference fit between the guide shaft 31 and the shaft hole 22, the placement of the tension torsion spring 3 into the shaft hole 22, and the extension of the tension arm 5 into the shaft hole 22.

[0030] More preferably, the guide shaft 31 passes through the tensioning arm 5. A first fastening bolt 321 is provided at the end of the guide shaft 31 away from the base 2. A first washer 322 and a pulley 32 are provided between the first fastening bolt 321 and the guide shaft 31. The pulley 32 contacts the side of the tensioning arm 5 away from the base 2. The pulley 32 restricts the axial position of the tensioning arm 5 along the guide shaft 31, and at the same time, the pulley 32 rotates to contact the tensioning arm 5, reducing the friction between the guide shaft 31 and the tensioning arm 5, and ensuring that the tensioning torsion spring 3 drives the rotation of the tensioning arm 5 smoothly.

[0031] Please refer to Figure 2 and Figure 3 A friction damping ring 4 is also fitted onto the tensioning arm 5. The friction damping ring 4 is positioned between the tensioning arm 5 and the base 2. The friction damping ring 4 fills the gap between the tensioning arm 5 and the base 2, preventing the tensioning arm 5 from radially shifting along the shaft hole 22 of the base 2. Furthermore, the friction damping ring 4 is clamped between the tensioning arm 5 and the base 2, forming static friction. When the tensioning arm 5 swings around the base 2, the elastic deformation of the friction damping ring 4 absorbs the vibration energy of the tensioning arm 5 and converts it into heat energy, further improving the stability of the tensioning arm 5 during rotation.

[0032] Preferably, a bushing 51 is interference-fitted onto the tensioning arm 5. The bushing 51 is loosely fitted onto the guide shaft 31. When the tensioning arm 5 rotates, the bushing 51 and the guide shaft 31 rotate through friction, without wearing the tensioning arm 5. When the bushing 51 wears out, it can be replaced directly without replacing the tensioning arm 5, reducing subsequent maintenance costs. In some embodiments, along the axial direction of the guide shaft 31, two or more bushings 51 can be provided between the guide shaft 31 and the tensioning arm 5. Multiple bushings 51 jointly connect the guide shaft 31 and the tensioning arm 5, improving the stability of the tensioning arm 5 when rotating around the guide post 541.

[0033] More preferably, the tensioning arm 5 is also provided with an assembly pin 53. The assembly pin 53 is inserted into both the tensioning arm 5 and the base 2. When assembling / disassembling the tensioning arm 5 and the base 2, the position between the tensioning arm 5 and the base 2 can be fixed by the assembly pin 53, preventing the tensioning arm 5 from rotating around the base 2 and simplifying the assembly / disassembly between the tensioning arm 5 and the base 2.

[0034] Please refer to Figure 1 and Figure 3 A guide post 541 is provided at the contact end 54. The axis of the guide post 541 is parallel to the rotation axis of the tensioning arm 5. A pulley 6 is rotatably sleeved on the guide post 541. The tensioning arm 5 rolls against the transmission belt 121 through the pulley 6, reducing the friction between the tensioning arm 5 and the transmission belt 121, reducing wear on the transmission belt 121 at the contact end 54, and extending the service life of the transmission belt 121. At the same time, the reduction in friction reduces the resistance in the belt drive process, making it easier for the rider to ride. In some embodiments, a bearing 61 is provided on the guide post 541, and the pulley 6 is sleeved on the bearing 61, with the pulley 6 interference-fitting the bearing 61.

[0035] Preferably, an annular groove 64 is formed around the guide post 541. An O-ring 654 is fitted onto the outer edge of the pulley 6 along the annular groove 64. In some embodiments, two or more O-rings 654 may be provided; this application does not limit this. The O-ring 654 reduces the contact area between the pulley 6 and the drive belt 121, thus reducing the friction between them. Furthermore, when the pulley 6 abuts against the tensioned drive belt 121, wear occurs between the O-ring 654 and the drive belt 121. During subsequent maintenance of the pulley 6, only the O-ring 654 needs to be replaced, eliminating the need to replace the entire pulley 6 and reducing maintenance costs.

[0036] More preferably, a second fastening bolt 63 is provided at the end of the guide post 541 away from the tensioning arm 5. A second washer 62 is provided between the second fastening bolt 63 and the guide post 541, and the second washer 62 contacts the side of the bearing 61 away from the tensioning arm 5. The second washer 62 cooperates with the tensioning arm 5 to position the pulley 6 on the guide post 541 in an axial direction.

[0037] Please refer to Figure 3 Dust covers 52 are provided at the ends of the tensioning arm 5 away from the base 2 and the pulley 6 away from the tensioning arm 5, respectively. The dust covers 52 cover the end of the guide shaft 31 that passes through the tensioning arm 5, and the dust covers 52 cover the end of the guide post 541 that passes through the pulley 6. The dust covers 52 are interference-fitted with the tensioning arm 5 and the pulley 6. The dust covers 52 shield the rotating assembly position of the tensioning arm 5 and the pulley 6, preventing foreign objects from getting stuck in the rotational assembly gap of the tensioning arm 5 and the pulley 6.

[0038] The specific workflow of this invention is as follows: When the bicycle travels over uneven terrain, the rear wheel hub 111 and the rocker arm 11 swing around the frame 1. During this process, the tension arm 5, driven by the elastic force of the tension torsion spring 3, always presses against the tension drive belt 121 towards the chainring 12. As the center distance between the rear wheel hub 111 and the chainring 12 increases and the drive belt 121 tightens, the drive belt 121 overcomes the elastic force of the tension torsion spring 3 and pushes the tension arm 5 away from the chainring 12 until the tension of the drive belt 121 and the tension of the tension torsion spring 3 are balanced, thus preventing excessive pressure and wear between the drive belt 121 and the chainring 12 / rear wheel hub 111. When the center distance between the rear wheel hub 111 and the chainring 12 decreases and the drive belt 121 loosens, the elastic force of the tensioning torsion spring 3 drives the tensioning arm 5 to swing towards the chainring 12. The tensioning arm 5 then pushes the drive belt 121 to cover the chainring 12 more until the tension of the drive belt 121 and the elastic force of the tensioning torsion spring 3 are balanced, thus preventing the tension of the drive belt 121 from being too small and slipping between the chainring 12 and the rear wheel hub 111.

[0039] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0040] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A self-contained automatic belt tensioner, characterized in that, The device is mounted on a frame, on which a chainring is mounted and rotatably connected to a swing arm; a rear wheel hub is mounted on the swing arm; the chainring and the rear wheel hub are connected by a drive belt; the self-automatic belt tensioner includes a base mounted on the frame and a tensioning arm rotatably connected to the base; A tensioning torsion spring is provided between the tensioning arm and the base; the tensioning torsion spring drives the tensioning arm to rotate around the base; the rotation axis of the tensioning arm is parallel to the rotation axis of the gear plate; The end of the tensioning arm away from the base is the contact end; the contact end extends between the chainring and the rear wheel hub and contacts the side of the drive belt away from the chainring; Along the return rotation direction of the tensioning torsion spring, the contact end swings toward the side closer to the toothed disc.

2. The self-contained automatic belt tensioner as described in claim 1, characterized in that: A guide shaft is provided on the base, and the tensioning torsion spring and the tensioning arm are sleeved on the guide shaft.

3. The self-contained automatic belt tensioner as described in claim 2, characterized in that: The base has a shaft hole, and the guide shaft is disposed in the shaft hole; the tensioning arm extends into the shaft hole; the tensioning torsion spring is disposed in the shaft hole.

4. The self-contained automatic belt tensioner as described in claim 3, characterized in that: The guide shaft passes through the tensioning arm; a first fastening bolt is provided at the end of the guide shaft away from the base; a first washer and a pulley are provided between the first fastening bolt and the guide shaft; the pulley contacts the side of the tensioning arm away from the base.

5. The self-contained automatic belt tensioner as described in claim 4, characterized in that: A dust cover is provided at the end of the tensioning arm away from the base; the dust cover covers the end of the guide shaft that passes through the tensioning arm.

6. The self-contained automatic belt tensioner as described in claim 1, characterized in that: A friction damping ring is also fitted onto the tensioning arm; the friction damping ring is disposed between the tensioning arm and the base.

7. The self-contained automatic belt tensioner as described in claim 2, characterized in that: The tensioning arm is fitted with an interference fit bushing; the bushing is fitted onto the guide shaft with a clearance.

8. The self-contained automatic belt tensioner as described in claim 1, characterized in that: The tensioning arm is also provided with an assembly pin; the assembly pin is inserted into the tensioning arm and the base.

9. The self-contained automatic belt tensioner as described in claim 1, characterized in that: The contact end is provided with a guide post; the axis of the guide post is parallel to the rotation axis of the tensioning arm; a pulley is rotatably sleeved on the guide post.

10. The self-contained automatic belt tensioner as described in claim 9, characterized in that: A ring groove is formed around the guide post; an annular groove is formed on the outer edge of the pulley; an O-ring is fitted on the pulley along the annular groove.

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