An electronic brake system for a fishing reel

Abstract

This invention discloses an electronic braking system for fishing reels, belonging to the field of fishing tackle technology. The system includes a side cover, an adjustment dial, a brake adjustment actuator, a support cover, a coil base, an electronic control board, and a spool assembly. The electronic control board integrates an optical detection module, a conductivity detection module, and a control unit. The stop block of the brake adjustment actuator moves synchronously with the adjustment dial. Its bottom conductive layer selectively conducts conductive lines and conductive contacts, outputting discrete electrical signals indicating the braking position. Simultaneously, the degree of obstruction of the optical path of the optical detection module by the stop block continuously changes, forming a continuous photosensitive analog signal. The control unit locks the braking position based on the discrete electrical signal and responds to the photosensitive analog signal to achieve stepless adjustment of braking force within the same braking position. This invention employs dual-mode collaborative detection, combining the characteristics of no mechanical wear, high precision, and strong anti-interference. It features a compact structure and controllable cost, effectively improving the casting stability and user experience of fishing reels, and is suitable for various fishing reels requiring precise braking.

Description

Technical Field

[0001] This invention relates to the field of fishing gear technology, specifically to an electronic braking system for fishing reels. Background Technology

[0002] The electronic braking system of a fishing reel effectively prevents line breakage caused by excessive spool rotation during casting by applying adjustable electromagnetic damping force, which is key to improving casting distance and accuracy. The core of this system lies in accurately detecting the target braking force setting set by the user through rotating the adjustment dial, converting this mechanical position signal into an electrical signal, which the control unit (microcomputer) then precisely calculates and outputs the corresponding braking force.

[0003] In existing technologies, detection schemes that convert the mechanical position of the adjustment dial into an electrical signal mainly rely on potentiometers (variable resistors) or electromagnetic induction, but both have significant drawbacks.

[0004] Potentiometer-based detection solutions are simple in structure and low in cost, using a dial to directly drive the potentiometer's slider to change the resistance value and thus characterize position. However, their mechanical electrical contacts suffer from wear and oxidation after long-term use, easily leading to resistance drift, poor contact, or even failure, severely impacting the long-term reliability and stability of the system. Furthermore, their output signal is susceptible to environmental humidity and salt spray corrosion, particularly pronounced in harsh conditions such as fishing reels that are frequently in contact with water.

[0005] To overcome contact wear, some solutions employ non-contact electromagnetic induction. For example, magnets are placed on the adjustment dial or linkage components, and Hall effect elements are correspondingly placed on a circuit board that rotates synchronously with the dial, generating an induced signal through changes in magnetic flux. While electromagnetic induction detection avoids mechanical wear, it presents new problems: First, the strength of the induced electromotive force (voltage or current) is easily affected by the dispersion of the magnet's magnetic field strength, subtle changes in component mounting gaps, and ambient temperature, resulting in poor signal consistency and limited accuracy. Second, the electromagnetic signal is susceptible to stray magnetic field interference generated by other electromagnetic components inside the fishing reel (such as the brake coil itself), leading to output signal fluctuations or even misjudgments. These factors make it difficult for solutions relying solely on electromagnetic induction to achieve high-precision, high-stability continuously variable gear detection.

[0006] In conclusion, neither the potentiometer contact solution, which suffers from physical wear, nor the non-contact electromagnetic induction solution, which is limited by signal dispersion and electromagnetic interference, can achieve an ideal balance in terms of long-term reliability, detection accuracy, anti-interference capability, and cost control. Summary of the Invention

[0007] To address the problems existing in the prior art, the present invention provides an electronic braking system for fishing reels, which can achieve non-contact detection without mechanical wear to ensure long service life, and obtain a high-precision, interference-resistant stable signal to support fine stepless braking force adjustment, thereby comprehensively improving the performance and user experience of the electronic braking system for fishing reels.

[0008] The technical solution adopted in this invention is as follows: an electronic braking system for fishing reels, including a side cover, an adjustment dial rotatably disposed on the side cover, a brake adjustment execution component pulsatingly connected to the adjustment dial, a support cover plate connected to the side cover, a coil base connected to the support cover plate, an induction coil and an electronic control board housed in the coil base, a spool assembly cooperating with the coil base, and further including an optical detection module, a conductivity detection module, and a control unit integrated on the electronic control board;

[0009] The optical detection module includes multiple light-emitting elements and multiple photosensitive elements arranged along a preset trajectory, with the light-emitting elements and the photosensitive elements correspondingly arranged to form a detection optical path;

[0010] The conductivity detection module includes a long strip of conductive line disposed on the end face of the control board, and multiple independent conductive contacts; the conductive line extends along the preset trajectory, and each of the conductive contacts is arranged at intervals on one or both sides of the conductive line along the extension direction of the conductive line, and maintains an insulating gap with the conductive line.

[0011] The brake adjustment actuator includes a stop block that moves synchronously with the adjustment dial. The stop block is located in the optical path between the light-emitting element and the photosensitive element, and its bottom surface is provided with a conductive layer. The adjustment dial drives the stop block to move, so that it passes through the detection areas of the optical detection module and the conductive detection module along a preset path.

[0012] The control unit is electrically connected to the photosensitive element, the conductive circuit and each of the conductive contacts;

[0013] The block is configured such that when it moves to different positions, the conductive layer at its bottom can selectively connect the conductive line to one of the conductive contacts to output discrete contact electrical signals that identify different preset brake gears to the control unit; at the same time, the degree of blockage of the detection optical path by the block changes continuously with its position, so that the photosensitive element outputs a continuously changing photosensitive analog signal corresponding to the degree of blockage to the control unit.

[0014] The control unit is configured to: determine the current preset braking gear based on the discrete contact electrical signal, and generate a control command to steplessly adjust the electronic braking force of the fishing reel in response to the light-sensing analog signal that changes within the preset braking gear.

[0015] Furthermore, the projection of the block on the preset path covers all or part of the photosensitive area of ​​at least one of the photosensitive elements, and the area of ​​the block covering the photosensitive element changes linearly with its movement.

[0016] Furthermore, the width of the conductive layer is greater than or equal to the width of the conductive line, and less than the distance between two adjacent conductive contacts.

[0017] Furthermore, multiple conductive contacts are distributed on both sides of the conductive line and are arranged alternately at intervals.

[0018] Furthermore, the light-emitting element is a light-emitting diode, and the photosensitive element is a phototransistor or a photoresistor.

[0019] Furthermore, the stop block moves along an arc-shaped trajectory around the rotation axis of the adjustment dial; each of the light-emitting elements and each of the photosensitive elements are respectively arranged on a first arc trajectory and a second arc trajectory with different radii centered on the rotation axis, and the movement path of the stop block is located between the first and second arc trajectories.

[0020] Furthermore, the brake adjustment actuator also includes a knob, which is rotatably mounted on the support cover plate, with its rotation axis coaxial with the rotation axis of the adjustment dial; the upper end of the knob is connected to the adjustment dial, and the stop block is eccentrically connected to the lower end of the knob; the support cover plate has an arc-shaped guide groove that runs vertically through it, and the extension trajectory of the arc-shaped guide groove is adapted to the movement trajectory of the stop block; the stop block passes through the arc-shaped guide groove, and the conductive layer at its bottom contacts the conductive line on the end face of the electronic control board, with its body located in the optical path between the light-emitting element and the photosensitive element.

[0021] Furthermore, a cylindrical positioning seat is protruding from the support cover plate, and the knob is rotatably fitted onto the positioning seat.

[0022] Furthermore, a first limiting block is protruding on the circumferential inner wall of the positioning seat; a second limiting block is protruding on the inner top wall of the knob; the first limiting block and the second limiting block are configured to abut against each other when the knob is rotated to its limit position, so as to limit the rotation range of the knob.

[0023] Furthermore, an assembly opening is provided on the side cover, through which a portion of the adjustment dial is exposed; a positioning damping structure is provided between the adjustment dial and the side cover, the positioning damping structure being configured to provide phased positioning resistance to the rotation of the adjustment dial, so as to provide a positioning feel when the user operates it.

[0024] The electronic braking system for fishing reels provided by this invention, through the creative integration of a dual-mode collaborative detection mechanism of optical and conductive detection, combined with corresponding control logic, achieves significant progress compared to existing technologies, resulting in multiple positive and beneficial technical effects:

[0025] (1) The optical detection module adopts a completely non-contact optical path design. There is no physical contact or mechanical linkage between its light-emitting and photosensitive elements, which avoids the inherent failure modes such as wear, oxidation and poor contact caused by long-term sliding of mechanical sliding arms in potentiometer solutions, and significantly extends the lifespan. Although the conductive detection module is a contact type, the contact form is a low-friction contact of "conductive layer - conductive line / contact". The conductive line and the contact are made of wear-resistant and corrosion-resistant materials, which reduces the wear and oxidation rate of the contact points and improves the long-term reliability of the module.

[0026] (2) The continuously changing "photosensitive analog signal" output by the optical detection module can achieve delicate and continuous position perception within any preset gear position, support stepless adjustment, and improve the precision of control. At the same time, the "discrete contact electrical signal" output by the conductivity detection module provides a clear and stable absolute gear position reference point, effectively overcoming the drift problem that may exist in pure analog signals and ensuring the accuracy of gear position recognition;

[0027] (3) While improving performance, this invention does not increase cost and structural complexity. The core components (light-emitting diode, phototransistor, conductive circuit) are all low-cost general-purpose electronic components. There is no need for expensive components such as high-precision magnets and special Hall sensors. The overall cost is lower than that of electromagnetic induction schemes and far superior to the comprehensive life cost of high-end potentiometer schemes.

[0028] (4) The optical detection module and the conductive detection module are integrated on the same electronic control board. The stop and brake adjustment execution components are integrated into one design, which is compact and does not require additional space inside the fishing reel. It is compatible with the assembly size of existing fishing reels and facilitates technological iteration and upgrading. The positioning damping structure of the adjustment dial provides phased positioning resistance. When operating, the user can confirm the current adjustment position through "feel feedback + gear signal", which takes into account both "the fineness of stepless adjustment" and "the certainty of gear operation". It is easy for beginners to use and professional users can control the force accurately, which greatly improves the casting experience. Attached Figure Description

[0029] Figure 1 This is an exploded view of the overall structure of the electronic braking system for fishing reels of the present invention.

[0030] Figure 2 This is a schematic diagram of the assembly and cooperation between the brake adjustment actuator and the support cover plate of the present invention.

[0031] Figure 3 This is a schematic diagram showing the alignment and cooperation between the brake adjustment actuator and the electronic control board of the present invention.

[0032] Figure 4 This is a schematic diagram of the planar structure of the electronic control board of the present invention.

[0033] In the diagram: 1 - Side cover; 2 - Adjustment dial; 3 - Brake adjustment actuator; 31 - Stop block; 32 - Knob; 4 - Support cover plate; 41 - Arc-shaped guide groove; 42 - Positioning seat; 43 - First limit block; 5 - Electronic control board; 6 - Coil base; 7 - Snap-in coil assembly; 8 - Optical detection module; 81 - Light-emitting element; 82 - Photosensitive element; 9 - Conductivity detection module; 91 - Conductive circuit; 92 - Conductive contact. Detailed Implementation

[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0035] like Figure 1-4 As shown, this embodiment discloses an electronic braking system for fishing reels, which is applicable to various fishing reels that require precise braking force adjustment. Its core lies in achieving wear-free, high-precision stepless adjustment of braking force through a dual-mode collaborative mechanism of "optical detection + conductive detection". The specific structure is as follows.

[0036] The electronic braking system of the fishing reel includes a side cover 1, an adjustment dial 2, a brake adjustment actuator 3, a support cover 4, an electronic control board 5, a coil base 6, and a spool assembly 7, wherein:

[0037] The side cover 1 serves as an integral mounting base, and its surface has an assembly opening. The adjustment dial 2 is rotatably embedded in the side cover 1, with part of its structure exposed from the assembly opening for user operation.

[0038] The support cover plate 4 is fixedly connected to the side cover 1 by bolts to form the mounting support surface of the internal components; the coil base 6 is fastened to the side of the support cover plate 4 away from the side cover 1, and a receiving cavity is formed inside it. The induction coil (not shown in the figure) and the electronic control board 5 are fixedly installed in the receiving cavity, and the detection end face of the electronic control board 5 is set towards the support cover plate 4.

[0039] The spool assembly 7 is rotatably mounted on one side of the coil base 6 and is positioned opposite to the induction coil. The electromagnetic damping force generated when the induction coil is energized directly acts on the spool assembly 7 to achieve braking control.

[0040] The brake adjustment actuator 3 is connected between the adjustment dial 2 and the electronic control board 5, and is used to convert the mechanical rotational motion of the adjustment dial 2 into a dual-mode detection signal.

[0041] The optical detection module 8 is integrated on the detection end face of the electronic control board 5, and includes multiple light-emitting elements 81 and multiple photosensitive elements 82, as specifically configured as follows:

[0042] The light-emitting element 81 is a surface-mount light-emitting diode, and the photosensitive element 82 is a phototransistor (or photoresistor), forming a detection optical path between the two.

[0043] Each light-emitting element 81 is evenly arranged along the first arc trajectory, and each photosensitive element 82 is evenly arranged along the second arc trajectory. The first arc trajectory and the second arc trajectory are centered on the rotation axis of the adjustment dial 2, and have different radii.

[0044] The first and second circular arc trajectories are concentrically set, forming a ring detection area between them. This area is the movement path of the block 31, ensuring that the block 31 is always located between the light-emitting element 81 and the photosensitive element 82.

[0045] The conductivity detection module 9 is also integrated on the detection end face of the electronic control board 5, and is set on the same side as the optical detection module 8. It includes a long strip of conductive line 91 and multiple independent conductive contacts 92.

[0046] The conductive line 91 is made of gold-plated copper foil and extends along the above-mentioned annular detection area in an arc-shaped long strip.

[0047] The conductive contacts 92 are also made of gold-plated conductive sheets, and their number corresponds to the preset brake gears (preferably 10 gears, corresponding to 10 conductive contacts 92). They are arranged at intervals on both sides of the conductive line 91 along the extension direction of the conductive line 91, and are distributed in an alternating staggered manner.

[0048] The conductive contact 92 and the conductive line 91 maintain an insulating gap to prevent natural conduction; each conductive contact 92 is electrically connected to the control unit (such as the MCU chip integrated in the control board 5) through an independent wire, and the conductive line 91 is also electrically connected to the control unit.

[0049] The brake adjustment actuator 3 includes a stop block 31 and a knob 32. The knob 32 is a cylindrical structure and is rotatably sleeved on the positioning seat 42 protruding on the support cover plate 4. The rotation axis of the knob 32 is coaxial with the rotation axis of the adjustment dial 2.

[0050] The upper end of the knob 32 is connected to the bottom of the adjustment dial 2 via a spline, ensuring that the knob 32 rotates synchronously when the adjustment dial 2 rotates; the upper end of the stop block 31 is eccentrically fixed to the lower end face of the knob 32, and the lower end passes through the arc-shaped guide groove 41 opened on the support cover plate 4 and extends to the detection end face of the electronic control board 5.

[0051] The extension trajectory of the arc-shaped guide groove 41 is consistent with the above-mentioned annular detection area, which is used to restrict the movement of the stop block 31 along the preset arc path and avoid deviation.

[0052] The bottom surface of the stop 31 is covered with a conductive layer (using conductive silicone or gold-plated film). The width of the conductive layer is greater than or equal to the width of the conductive line 91 and less than the distance between two adjacent conductive contacts 92, ensuring that when the stop 31 moves, the conductive layer can only conduct conductive line 91 and one conductive contact 92 at the same time.

[0053] The block 31 is made of an opaque material, and its projection in the detection area covers the photosensitive area of ​​at least one photosensitive element 82. When it moves along an arc-shaped path, the area of ​​the block covering the photosensitive element 82 changes linearly and continuously.

[0054] The positioning seat 42 has a first limiting block 43 protruding on its circumferential inner wall, and the knob 32 has a second limiting block (not shown in the figure) protruding on its inner top wall. When the knob 32 is rotated to the limit position, the first limiting block 43 and the second limiting block abut against each other to limit the rotation angle of the knob 32 and avoid excessive rotation that could damage the components.

[0055] A positioning damping structure (using a damping rubber ring or steel ball damping mechanism, not shown in the figure) is provided between the adjustment dial 2 and the side cover 1. This structure provides phased positioning resistance to the rotation of the adjustment dial 2, indicating to the user that the corresponding gear has been switched.

[0056] The core working logic of this embodiment is to achieve "precise gear positioning + stepless adjustment within the gear range" through the collaborative processing of dual-mode detection signals. The specific process is as follows:

[0057] Gear shifting and discrete signal detection: The user rotates the adjustment dial 2, which drives the knob 32 to rotate synchronously, thereby driving the stop block 31 to move along the arc-shaped guide groove 41 and the annular detection area; when the stop block 31 moves to a certain preset position, the conductive layer on its bottom surface simultaneously contacts the conductive line 91 and a corresponding conductive contact 92, forming a conductive circuit and outputting discrete contact electrical signals to the control unit; the control unit accurately determines the current brake gear (such as 1-10 gears) based on the encoding of the electrical signal.

[0058] Stepless adjustment within the gear position and continuous signal detection: When the adjustment dial 2 is rotated continuously within the same gear position, the conductive layer of the stop block 31 remains connected to the current conductive contact 92 (the discrete signal remains unchanged), but the area of ​​the stop block 31 blocking the optical path of the optical detection module 8 changes linearly with the rotation angle; the photosensitive element 82 converts the change in the blocking area into a continuously changing light-sensing analog signal (current or voltage signal) and transmits it to the control unit;

[0059] Braking force control command generation: The control unit first locks the braking force reference range corresponding to the current gear based on the discrete contact electrical signal, and then calculates the precise target braking force within the reference range based on the change of the light-sensing analog signal, and then outputs the corresponding control current to the induction coil; the induction coil generates an electromagnetic damping force proportional to the control current, which acts on the spool assembly 7 to realize stepless continuous adjustment of the braking force within the same gear.

[0060] This embodiment effectively solves the core problems of wear, interference, and insufficient precision in the prior art through the above structural design. Its structure is compact, the cost is controllable, and it can be directly adapted to the assembly size of existing fishing reels, thus possessing strong industrial application value.

[0061] Those skilled in the art will understand that, to ensure the long-term stable operation of the electronic control board 5, optical detection module 8, and conductive detection module 9 in the humid and dusty environment where the fishing reel is located, conventional sealing and protection methods in the art can be used to protect the core detection area. For example, a sealing ring can be set between the joint surfaces of the support cover plate 4 and the coil base 6 to form a sealed accommodating cavity, housing the electronic control board 5 and its optical detection module 8 and conductive detection module 9, thus achieving basic overall protection. Based on this, further targeted protection methods conventional in the art can be implemented: using a high-transmittance, aging-resistant optical adhesive (such as silicone or epoxy resin) to coat and encapsulate the surface of each light-emitting element and photosensitive element; the conductive lines 91 and each conductive contact 92 of the conductive detection module 9 are plated with a highly corrosion-resistant gold layer, which is a conventional and effective anti-corrosion treatment method in electronic circuits; the conductive layer on the bottom surface of the stop 31 can be made of conventional elastic conductive materials such as conductive silicone to ensure stable contact with the conductive lines 91. Those skilled in the art can readily select and implement one or more of the above conventional solutions based on the specific product structure design, thereby reliably solving the protection problem.

[0062] The above description is merely an example and illustration of the structure of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the inventive concept of the present invention, and all such modifications or additions should fall within the protection scope of the present invention.

Claims

1. An electronic braking system for a fishing reel, comprising a side cover (1), an adjustment dial (2) rotatably disposed on the side cover (1), a brake adjustment actuator (3) pultrusively connected to the adjustment dial (2), a support cover plate (4) connected to the side cover (1), a coil base (6) connected to the support cover plate (4), an induction coil and an electronic control board (5) housed within the coil base (6), and a spool assembly (7) cooperating with the coil base (6), characterized in that: It also includes an optical detection module (8), a conductivity detection module (9), and a control unit integrated on the electronic control board (5); The optical detection module (8) includes a plurality of light-emitting elements (81) and a plurality of photosensitive elements (82) arranged along a preset trajectory. The light-emitting elements (81) and the photosensitive elements (82) are arranged correspondingly to form a detection optical path. The conductive detection module (9) includes a strip-shaped conductive line (91) disposed on the end face of the control board (5) and a plurality of independent conductive contacts (92); the conductive line (91) extends along the preset trajectory, and each of the conductive contacts (92) is arranged at intervals on one or both sides of the conductive line (91) along the extension direction of the conductive line (91) and maintains an insulating gap with the conductive line (91). The brake adjustment actuator (3) includes a stop (31) that moves synchronously with the adjustment dial (2). The stop (31) is located in the optical path between the light-emitting element (81) and the photosensitive element (82), and its bottom surface is provided with a conductive layer. The adjustment dial (2) drives the stop (31) to move, so that it passes through the detection area of ​​the optical detection module (8) and the conductive detection module (9) along a preset path. The control unit is electrically connected to the photosensitive element (82), the conductive line (91) and each of the conductive contacts (92); The stop (31) is configured such that when it moves to different positions, the conductive layer at its bottom can selectively connect the conductive line (91) to one of the conductive contacts (92) to output discrete contact electrical signals that identify different preset brake gears to the control unit; at the same time, the degree of obstruction of the detection optical path by the stop (31) changes continuously with its position, so that the photosensitive element (82) outputs a continuously changing light-sensing analog signal corresponding to the degree of obstruction to the control unit; The control unit is configured to: determine the current preset braking gear based on the discrete contact electrical signal, and generate a control command to steplessly adjust the electronic braking force of the fishing reel in response to the light-sensing analog signal that changes within the preset braking gear.

2. The electronic braking system for a fishing reel as described in claim 1, characterized in that: The projection of the block (31) on the preset path covers all or part of the photosensitive area of ​​at least one of the photosensitive elements (82), and the area of ​​the block covering the photosensitive element (82) changes linearly with its movement.

3. The electronic braking system for a fishing reel as described in claim 1, characterized in that: The width of the conductive layer is greater than or equal to the width of the conductive line (91), and less than the distance between two adjacent conductive contacts (92).

4. The electronic braking system for a fishing reel as described in claim 1, characterized in that: Multiple conductive contacts (92) are distributed on both sides of the conductive line (91) and are arranged alternately at intervals.

5. The electronic braking system for a fishing reel as described in claim 1, characterized in that: The light-emitting element (81) is a light-emitting diode, and the photosensitive element (82) is a phototransistor or a photoresistor.

6. The electronic braking system for a fishing reel as described in any one of claims 1-5, characterized in that: The stop block (31) moves along an arc-shaped trajectory around the rotation axis of the adjustment dial (2); each of the light-emitting elements (81) and each of the photosensitive elements (82) are respectively arranged on a first arc trajectory and a second arc trajectory with two different radii centered on the rotation axis, and the movement path of the stop block (31) is located between the first and second arc trajectories.

7. The electronic braking system for a fishing reel as described in claim 6, characterized in that: The brake adjustment actuator (3) also includes a knob (32), which is rotatably mounted on the support cover plate (4), and its rotation axis is coaxial with the rotation axis of the adjustment dial (2); the upper end of the knob (32) is connected to the adjustment dial (2) in a transmission manner, and the stop block (31) is eccentrically connected to the lower end of the knob (32); the support cover plate (4) is provided with an arc-shaped guide groove (41) that runs vertically through it, and the extension trajectory of the arc-shaped guide groove (41) is adapted to the movement trajectory of the stop block (31); the stop block (31) passes through the arc-shaped guide groove (41), and the conductive layer at its bottom contacts the conductive line (91) on the end face of the electronic control board (5), and its body is located in the optical path between the light-emitting element (81) and the photosensitive element (82).

8. The electronic braking system for a fishing reel as described in claim 7, characterized in that: A cylindrical positioning seat (42) is protruding on the support cover plate (4), and the knob (32) is rotatably sleeved on the positioning seat (42).

9. The electronic braking system for a fishing reel as described in claim 8, characterized in that: The positioning seat (42) has a first limiting block (43) protruding on its circumferential inner wall; the knob (32) has a second limiting block protruding on its inner top wall; the first limiting block (43) and the second limiting block are configured to abut against each other when the knob (32) is rotated to its limit position, so as to limit the rotation range of the knob (32).

10. The electronic braking system for a fishing reel as described in claim 7, characterized in that: An assembly opening is provided on the side cover (1), and part of the adjustment dial (2) is exposed from the assembly opening; a positioning damping structure is provided between the adjustment dial (2) and the side cover (1), and the positioning damping structure is configured to provide phased positioning resistance to the rotation of the adjustment dial (2) so as to provide positioning feel when the user operates.

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