Drum brake of bicycle, wheel assembly and bicycle

Abstract

The utility model relates to a drum brake of a bicycle, a wheel assembly and the bicycle. The drum brake has a braking state and a non-braking state and comprises a drum brake disc arranged on a wheel of the bicycle and provided with a first side and a second side which are opposite to each other; the brake rocker arm is rotatably arranged on the first side of the drum brake disc and faces upwards; the leading shoe is rotatably arranged on the second side of the drum brake disc; the slave shoe is rotatably arranged on the second side of the drum brake disc; the cam is arranged on the second side of the drum brake disc and connected with the brake rocker arm, the cam comprises a first matching surface and a second matching surface which are deviated from each other, in a non-brake state, the first matching surface is in contact with the leading shoe, the second matching surface is in contact with the trailing shoe, and a first distance is formed between the first matching surface and a rotating shaft of the cam; and a second distance is formed between the second matching surface and the rotating shaft of the cam, and the first distance is greater than the second distance, so that the leading shoe is contacted with a lining on a wheel earlier than the trailing shoe in a braking state.

Description

Technical Field

[0001] The present application relates to the field of vehicle technology, and in particular to a drum brake of a bicycle, a wheel assembly and a bicycle. Background Art

[0002] At present, with the increasing air pollution caused by motor vehicles and people's emphasis on sports, the use of bicycles is increasing. Among them, drum brakes are usually installed on the wheels of bicycles for braking operations. However, the brake rocker arm of traditional drum brakes is set downward, which makes the brake rocker arm often bumped and deformed, damaged, resulting in brake failure and accidents. Summary of the invention

[0003] Based on this, it is necessary to provide a bicycle drum brake, a wheel assembly and a bicycle to address the problem of brake failure caused by the brake rocker arm being arranged downward.

[0004] A drum brake for a bicycle has a braking state and a non-braking state, and comprises:

[0005] A drum brake disc is disposed on the wheel of the bicycle and has a first side and a second side that are separated from each other;

[0006] A brake rocker arm is rotatably disposed on a first side of the drum brake disc and faces upward;

[0007] A leading shoe rotatably disposed on a second side of the drum brake disc;

[0008] A slave shoe is rotatably disposed on a second side of the drum brake disc; and

[0009] A cam is arranged on the second side of the drum brake disc and connected to the brake rocker arm, the cam includes a first mating surface and a second mating surface that are opposite to each other, in the non-braking state, the first mating surface contacts the leading shoe, and the second mating surface contacts the trailing shoe, wherein a first distance L1 is provided between the first mating surface and the rotating shaft of the cam, and a second distance L2 is provided between the second mating surface and the rotating shaft of the cam, the first distance L1 is greater than the second distance L2, so that in the braking state, the leading shoe contacts the brake pad on the wheel before the trailing shoe.

[0010] The above-mentioned drum brake can avoid deformation and damage of the brake rocker arm caused by bumps by setting the brake rocker arm upward, thereby ensuring safe driving of the vehicle; in addition, the drum brake can change the opening stroke and braking sequence of the leading shoe and the trailing shoe by adjusting the structure of the cam while adjusting the direction of the brake rocker arm, thereby ensuring that the leading shoe can start braking first and provide the main braking force to ensure effective braking.

[0011] In one embodiment, the first distance L1 is 0.1 mm to 0.3 mm greater than the second distance L2.

[0012] In one embodiment, a threading portion is provided on the drum brake disc, the threading portion faces upward and is adjacent to the brake rocker arm, and the threading portion has a first through hole for passing the brake line of the bicycle;

[0013] One end of the brake rocker arm facing away from the drum brake disc has a second through hole for installing the brake line of the bicycle.

[0014] In one embodiment, an angle α is formed between a line connecting the center of the first through hole and the center of the second through hole and a line connecting the center of the second through hole and the rotating shaft of the brake rocker arm, and the angle α is 45° to 65°.

[0015] In one of the embodiments, the drum brake further comprises a plurality of elastic members;

[0016] The elastic member is connected to the leading shoe and the trailing shoe, and is used to provide a restoring force to the leading shoe and the trailing shoe so that the leading shoe and the trailing shoe can rotate toward each other.

[0017] In one embodiment, the leading shoe includes a first mounting end and a first braking end away from the first mounting end, the trailing shoe includes a second mounting end and a second braking end away from the second mounting end, the first mounting end and the second mounting end are both hinged to the drum brake disc, and the first braking end and the second braking end are both pressed against the cam;

[0018] The elastic members are provided in plurality, a portion of the elastic members are connected to the first mounting end and the second mounting end, and the remaining portion of the elastic members are connected to the first braking end and the second braking end.

[0019] In one embodiment, the drum brake further includes a pin shaft, and the first mounting end and the second mounting end are both hinged to the drum brake disc through the pin shaft;

[0020] Wherein, in the non-braking state, there is an avoidance gap between the first mounting end and the second mounting end.

[0021] In one embodiment, the elastic member is a spring.

[0022] A wheel assembly, comprising a wheel, a brake pad and a drum brake as described in any one of the above items;

[0023] The wheel has a groove, the brake pad is fixedly connected to the circumferential inner wall of the groove, and the drum brake is accommodated in the groove and can cooperate with the brake pad to brake the wheel.

[0024] The above-mentioned wheel assembly can avoid deformation and damage of the brake rocker arm caused by collision by setting the brake rocker arm of the drum brake upward, thereby ensuring safe driving of the vehicle; in addition, when adjusting the direction of the brake rocker arm, the drum brake also changes the opening stroke and braking sequence of the leading shoe and the trailing shoe by adjusting the structure of the cam, ensuring that the leading shoe can start braking first and provide the main braking force to ensure effective braking.

[0025] A bicycle comprises the wheel assembly as described above.

[0026] The above-mentioned bicycle can avoid deformation and damage of the brake rocker arm caused by bumps by setting the brake rocker arm of the drum brake upward, thereby ensuring safe driving of the vehicle; in addition, when adjusting the direction of the brake rocker arm, the drum brake also changes the opening stroke and braking sequence of the leading shoe and the trailing shoe by adjusting the structure of the cam, ensuring that the leading shoe can start braking first and provide the main braking force to ensure effective braking. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG1 is a schematic structural diagram of a drum brake provided in an embodiment of the present application viewed from a first angle.

[0028] FIG. 2 is a partial enlarged schematic diagram of the drum brake at point A provided in FIG. 1 .

[0029] FIG3 is a schematic diagram showing the cooperation between the cam and the leading shoe and the trailing shoe of the drum brake provided in FIG1 in the braking state.

[0030] FIG. 4 is a schematic structural diagram of the drum brake provided in FIG. 1 viewed from a second angle.

[0031] FIG5 is a schematic structural diagram of the drum brake provided in FIG1 viewed from a third angle.

[0032] FIG. 6 is a schematic structural diagram of the cam of the drum brake provided in FIG. 1 .

[0033] FIG. 7 is a schematic diagram of the structure of a wheel assembly provided in an embodiment of the present application without installing a drum brake.

[0034] The reference numerals in the accompanying drawings are described as follows:

[0035] 10. Drum brake; 100. Drum brake disc; 100a. Limiting groove; 110. Threading part; 110a. First through hole; 200. Braking rocker arm; 200a. Second through hole; 300. Leading shoe; 400. Following shoe; 500. Cam; 500a. First mating surface; 500b. Second mating surface; 600. Elastic member; 700. Pin; 800. Linking member; 810. Rotating part; 820. Mounting part; 830. Limiting part; 840. Screw part; 850. Threaded member; P. Rotating shaft of cam; Q. Avoidance gap; 20. Brake line; 30. Wheel; 30a. Groove; 30b. Axle; 40. Brake pad. DETAILED DESCRIPTION

[0036] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0037] In the description of the present application, it should be understood that if the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. appear, the orientation or position relationship indicated by these terms is based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application.

[0038] In addition, if the terms "first" or "second" appear, these terms are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of this application, if the term "plurality" appears, "plurality" means at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0039] In this application, unless otherwise clearly specified and limited, if the terms "installed", "connected", "connected", "fixed" and the like appear, these terms should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integrated connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to the specific circumstances.

[0040] In the present application, unless otherwise clearly specified and limited, if there is a description that a first feature is "above" or "below" a second feature, etc., or similar descriptions appear, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "above" and "above" the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. The first feature being "below", "below" and "below" the second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0041] It should be noted that if an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be a central element. If an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. If any, the terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used in this application are for illustrative purposes only and do not represent the only implementation method.

[0042] Referring to FIG. 1 , FIG. 1 shows a schematic diagram of the structure of a bicycle drum brake 10 in a non-braking state in an embodiment of the present application. The drum brake 10 provided in an embodiment of the present application has a braking state and a non-braking state, and includes a drum brake disc 100, a brake rocker arm 200, a leading shoe 300, a trailing shoe 400 and a cam 500; the drum brake disc 100 is arranged on the wheel of the bicycle and has a first side and a second side that are separated from each other; the brake rocker arm 200 is rotatably arranged on the first side of the drum brake disc 100 one side and facing upward; the leading shoe 300 is rotatably disposed on the second side of the drum brake disc 100; the trailing shoe 400 is rotatably disposed on the second side of the drum brake disc 100; the cam 500 is disposed on the second side of the drum brake disc 100 and is connected to the brake rocker arm 200, as shown in Figure 2, the cam 500 includes a first mating surface 500a and a second mating surface 500b that are opposite to each other. In the non-braking state, the first mating surface 500a contacts the leading shoe 300, and the second mating surface 500b contacts the trailing shoe 400.

[0043] The drum brake 10 can be installed on the rear wheel of a bicycle, as shown in FIG7 , the brake rocker arm 200 of the drum brake 10 is connected to the handbrake of the bicycle through the brake line 20, and the drum brake disc 100 is installed in the wheel hub 30 of the rear wheel, and can cooperate with the brake pad 40 on the wheel 30 to brake the rear wheel. Specifically, as shown in FIG7 , the wheel 30 has a groove 30a and a wheel axle 30b, the wheel axle 30b extends from the groove 30a and is installed on the bicycle frame, the brake pad 40 is fixedly connected to the circumferential inner wall of the groove 30a, and the drum brake disc 100 is sleeved on the wheel axle 30b and accommodated in the groove 30a.

[0044] It should be noted that the brake pad 40 rotates synchronously with the rear wheel, while the drum brake disc 100 is fixed. When the leading shoe 300 and the trailing shoe 400 of the drum brake 10 contact the brake pad 40, a large friction force will be applied to the brake pad 40, so that the brake pad 40 cannot rotate, and the rear wheel cannot continue to rotate, thereby achieving braking of the bicycle. In order to prevent the drum brake disc 100 from rotating synchronously with the rear wheel, the drum brake disc 100 can be matched with the rear fork at the rear end of the frame. As an example, as shown in FIG. 5, a first side of the drum brake disc 100 is provided with a limiting groove 100a, and a limiting protrusion is convexly provided on one side of the rear fork facing the drum brake disc 100, and the limiting protrusion is accommodated in the limiting groove 100a.

[0045] Of course, in some other embodiments, the drum brake 10 can also be installed on the front wheel of a bicycle. The bicycle can be a human-powered bicycle or an electric bicycle. It should be noted that the dotted line in Figure 2 represents the direction of the brake line 20.

[0046] When braking is required, the user presses the handbrake, and the brake rocker 200 rotates, thereby driving the cam 500 to rotate, so that the leading shoe 300 and the trailing shoe 400 open, thereby contacting the brake pad 40 on the wheel and generating a braking force. In the drum brake process, in order to ensure that the drum brake 10 can generate a greater friction force with the brake pad 40, the leading shoe 300 needs to generate a braking force before the trailing shoe 400. It should be noted that the opening direction of the leading shoe 300 is the same as the rotation direction of the wheel, while the opening direction of the trailing shoe 400 is opposite to the rotation direction of the wheel. For example, as shown in Figure 1, the opening direction of the leading shoe 300 and the rotation direction of the wheel are both clockwise, while the opening direction of the trailing shoe 400 is counterclockwise. It should be noted that the arc arrow in Figure 1 represents the rotation direction of the wheel.

[0047] However, as shown in FIG1 , since the brake rocker arm 200 is facing upward, when the brake rocker arm 200 is pulled by the brake wire 20, it rotates upward clockwise, and the cam 500 also rotates clockwise, which causes the rotation radius R1 of the leading shoe 300 to be greater than the rotation radius R2 of the trailing shoe 400 (see FIG3 ), so that the opening angle of the leading shoe 300 is smaller than the opening angle of the trailing shoe 400, and the requirement that the leading shoe 300 generates braking force before the trailing shoe 400 cannot be met. In this regard, further, in this embodiment, as shown in FIG2 , there is a first distance L1 between the first mating surface 500a and the rotation axis P of the cam 500, and there is a second distance L2 between the second mating surface 500b and the rotation axis P of the cam 500, and the first distance L1 is greater than the second distance L2, so that in the braking state, the leading shoe 300 contacts the brake pad 40 of the bicycle before the trailing shoe 400. By eccentrically setting the rotating shaft P of the cam 500, the portion above the rotating shaft P of the cam 500 is thicker, while the portion below the rotating shaft P of the cam 500 is thinner, so that the opening stroke of the leading shoe 300 can be greater than the opening stroke of the trailing shoe 400, so that the leading shoe 300 contacts the brake pad 40 of the bicycle before the trailing shoe 400.

[0048] The first distance L1 is 0.1mm to 0.3mm larger than the second distance L2, for example, 0.1mm, 0.15mm, 0.2mm, 0.25mm, 0.3mm, etc. This arrangement ensures that the opening stroke of the leading shoe 300 is greater than the opening stroke of the trailing shoe 400 without increasing the size of the cam 500.

[0049] It can be seen that the drum brake 10 can avoid deformation and damage of the brake rocker arm 200 caused by collision by setting the brake rocker arm 200 upward, thereby ensuring safe driving of the vehicle; in addition, the drum brake 10 can change the opening stroke and braking sequence of the leading shoe 300 and the trailing shoe 400 by adjusting the structure of the cam 500 while adjusting the direction of the brake rocker arm 200, thereby ensuring that the leading shoe 300 can start braking first and provide the main braking force to ensure effective braking.

[0050] As shown in FIG. 4 and FIG. 5 , in some embodiments, a threading portion 110 is provided on the drum brake disc 100, the threading portion 110 is upward and adjacent to the brake rocker arm 200, and the threading portion 110 has a first through hole 110a for passing the bicycle brake line 20; the brake rocker arm 200 has a second through hole 200a for installing the bicycle brake line 20 at one end away from the drum brake disc 100. The first through hole 110a and the second through hole 200a facilitate the connection between the brake line 20 and the brake rocker arm 200.

[0051] As shown in FIG5 , there is an angle α between the line connecting the center of the first through hole 110a and the center of the second through hole 200a and the line connecting the center of the second through hole 200a and the rotating shaft of the brake rocker arm 200, and the angle α is 45° to 65° (for example, 45°, 50°, 55°, 60°, 65°, etc.). By setting the position of the brake rocker arm 200 in this way, the most comfortable braking operating force and the best braking effect can be ensured.

[0052] As shown in FIG6 , in some embodiments, the drum brake 10 further includes a linkage 800, which is used to connect the cam 500 with the brake rocker arm 200, wherein the linkage 800 includes a connected rotating portion 810 and a mounting portion 820; the mounting portion 820 is located on the first side of the drum brake disc 100 and is used to mount the brake rocker arm 200; the rotating portion 810 is passed through the drum brake disc 100 and is connected to the cam 500, playing a role in power transmission. When the brake rocker arm 200 rotates, the cam 500 can be driven to rotate synchronously through the rotating portion 810 of the linkage 800. It should be noted that the rotating shaft of the brake rocker arm 200 and the cam 500 mentioned above can refer to the central axis of the rotating portion 810 of the linkage 800.

[0053] The cross-sectional shape of the mounting portion 820 may be a non-circular shape, so that the braking rocker arm 200 can rotate while driving the rotating portion 810 to rotate synchronously. The cross-sectional shape of the mounting portion 820 may be a polygon, such as a triangle, a quadrilateral as shown in FIG. 6 , or a polygon of other shapes; of course, it may be a special shape composed of a straight line and an arc line.

[0054] Furthermore, as shown in FIG. 6 , the cam 500 also includes a limiting portion 830 and a screw portion 840. The limiting portion 830 is disposed between the rotating portion 810 and the cam 500, and the screw portion 840 is disposed at one end of the mounting portion 820 away from the rotating portion 810. The screw portion 840 is used to install a threaded member 850 (such as a nut). Through the cooperation between the threaded member 850 and the limiting portion 830, the cam 500 can be prevented from moving between the first side and the second side of the drum brake disc 100, thereby ensuring the normal use of the drum brake 10 and the driving safety performance of the vehicle.

[0055] As shown in FIG. 1 , in some embodiments, the drum brake 10 further includes a plurality of elastic members 600; the elastic members 600 are connected to the leading shoe 300 and the trailing shoe 400, and are used to provide a restoring force to the leading shoe 300 and the trailing shoe 400, so that the leading shoe 300 and the trailing shoe 400 can rotate toward each other. When braking is completed, under the action of the elastic members 600, the leading shoe 300 and the trailing shoe 400 can rotate toward each other for restoration, so that the braking force disappears, and the bicycle can travel normally.

[0056] In one embodiment, the leading shoe 300 may include a first mounting end and a first braking end away from the first mounting end, the trailing shoe 400 may include a second mounting end and a second braking end away from the second mounting end, the first mounting end and the second mounting end are both hinged to the drum brake disc 100, and the first braking end and the second braking end are both pressed against the cam 500; the elastic member 600 is provided in plurality, a portion of the elastic members 600 are connected to the first mounting end and the second mounting end, and the remaining portion of the elastic members 600 are connected to the first braking end and the second braking end. The position distribution of the elastic members 600 is set in this way, so as to ensure that the leading shoe 300 and the trailing shoe 400 can be effectively reset after the braking is completed.

[0057] The elastic member 600 can be installed on the leading shoe 300 and the trailing shoe 400 by welding, hanging, etc. Considering that the hanging method is convenient for replacing the elastic member 600, it can be preferably adopted. Among them, the leading shoe 300 and the trailing shoe 400 can be both provided with ear plates, and the ear plates have hanging holes. The two ends of the elastic member 600 can be respectively provided with hooks, and the hooks of the elastic member 600 are hung in the corresponding hanging holes.

[0058] The number of the elastic members 600 can be set accordingly according to the requirements. For example, as shown in FIG1 , there are two elastic members 600, one of which is connected to the first mounting end of the leading shoe 300 and the second mounting end of the trailing shoe 400, and the other elastic member 600 is connected to the first braking end of the leading shoe 300 and the second braking end of the trailing shoe 400. Specifically, the first mounting end of the leading shoe 300 is provided with a first connecting ear plate, and the second mounting end of the trailing shoe 400 is provided with a second connecting ear plate, the first connecting ear plate has a first hanging hole, and the second connecting ear plate has a second hanging hole, and the corresponding hooks at both ends of the elastic member 600 are hung in the first hanging hole and the second hanging hole respectively; the first braking end of the leading shoe 300 is provided with a third connecting ear plate, and the second braking end of the trailing shoe 400 is provided with a fourth connecting ear plate, the third connecting ear plate has a third hanging hole, and the fourth connecting ear plate has a fourth hanging hole, and the corresponding hooks at both ends of the elastic member 600 are hung in the third hanging hole and the fourth hanging hole respectively.

[0059] The elastic member 600 may be a spring. Such elastic member 600 has good resilience and is easy to obtain.

[0060] As shown in FIG1 , in some embodiments, the drum brake 10 further includes a pin 700, and the first mounting end of the leading shoe 300 and the second mounting end of the trailing shoe 400 are both hinged to the drum brake disc 100 through the pin 700; wherein, in the non-braking state, there is an avoidance gap Q between the first mounting end of the leading shoe 300 and the second mounting end of the trailing shoe 400. The leading shoe 300 and the trailing shoe 400 can share a pin 700 to achieve the hinge connection with the drum brake disc 100, which can simplify the structure of the drum brake 10 and make the drum brake 10 compact. It should be noted that the avoidance gap Q is provided between the first mounting end of the trailing shoe 400 and the second mounting end of the trailing shoe 400 to prevent the leading shoe 300 and the trailing shoe 400 from interfering with each other during rotation.

[0061] The first mounting end of the leading shoe 300 has a first accommodating groove, and the second mounting end of the trailing shoe 400 has a second accommodating groove. The first accommodating groove and the second accommodating groove are used to cooperate with each other to accommodate the pin shaft 700 .

[0062] On the other hand, an embodiment of the present application further provides a wheel assembly, which includes a wheel 30, a brake pad 40 and a drum brake 10 as described in any one of the above items; the wheel 30 has a groove 30a, the brake pad 40 is fixed to the circumferential inner wall of the groove 30a, and the drum brake 10 is accommodated in the groove 30a and can cooperate with the brake pad 40 to brake the wheel.

[0063] It should be noted that the wheel 30 may be a rear wheel or a front wheel.

[0064] The wheel assembly can prevent the brake rocker arm 200 from being bumped and deformed and damaged by setting the brake rocker arm 200 of the drum brake 10 upward, thereby ensuring safe driving of the vehicle; in addition, when adjusting the direction of the brake rocker arm 200, the drum brake 10 also changes the opening stroke and braking sequence of the leading shoe 300 and the trailing shoe 400 by adjusting the structure of the cam 500, thereby ensuring that the leading shoe 300 can start braking first and provide the main braking force to ensure effective braking.

[0065] On the other hand, an embodiment of the present application further provides a bicycle, which includes the wheel assembly described above.

[0066] It should be noted that the bicycle can be a human-powered bicycle or an electric bicycle, such as a motorcycle.

[0067] The bicycle can avoid deformation and damage of the brake rocker arm 200 caused by collision by setting the brake rocker arm 200 of the drum brake 10 upward, thereby ensuring safe driving of the vehicle; in addition, when adjusting the direction of the brake rocker arm 200, the drum brake 10 also changes the opening stroke and braking sequence of the leading shoe 300 and the trailing shoe 400 by adjusting the structure of the cam 500, thereby ensuring that the leading shoe 300 can start braking first and provide the main braking force to ensure effective braking.

[0068] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described 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.

[0069] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached claims.

Claims

1. A bicycle drum brake, characterized in that: It has a brake state and a non-brake state, and includes: A drum brake disc is disposed on the wheel of the bicycle and has a first side and a second side that are separated from each other; A brake rocker arm is rotatably disposed on a first side of the drum brake disc and faces upward; A leading shoe rotatably disposed on a second side of the drum brake disc; A slave shoe is rotatably disposed on a second side of the drum brake disc; and A cam is arranged on the second side of the drum brake disc and connected to the brake rocker arm, the cam includes a first mating surface and a second mating surface that are opposite to each other, in the non-braking state, the first mating surface contacts the leading shoe, and the second mating surface contacts the trailing shoe, wherein a first distance L1 is provided between the first mating surface and the rotating shaft of the cam, and a second distance L2 is provided between the second mating surface and the rotating shaft of the cam, the first distance L1 is greater than the second distance L2, so that in the braking state, the leading shoe contacts the brake pad on the wheel before the trailing shoe.

2. The drum brake according to claim 1, characterized in that: The first distance L1 is greater than the second distance L2 by 0.1 mm to 0.3 mm.

3. The drum brake according to claim 1, characterized in that: The drum brake disc is provided with a threading portion, the threading portion is upward and adjacent to the brake rocker arm, and the threading portion has a first through hole for passing the brake line of the bicycle; One end of the brake rocker arm facing away from the drum brake disc has a second through hole for installing the brake line of the bicycle.

4. The drum brake according to claim 3, characterized in that: An angle α is formed between a line connecting the center of the first through hole and the center of the second through hole and a line connecting the center of the second through hole and the rotating shaft of the brake rocker arm, and the angle α is 45° to 65°.

5. The drum brake according to any one of claims 1 to 4, characterized in that: The drum brake also includes a plurality of elastic members; The elastic member is connected to the leading shoe and the following shoe, and is used to provide a restoring force to the leading shoe and the following shoe so that the leading shoe and the following shoe can rotate toward each other.

6. The drum brake according to claim 5, characterized in that: The leading shoe comprises a first mounting end and a first braking end away from the first mounting end, the trailing shoe comprises a second mounting end and a second braking end away from the second mounting end, the first mounting end and the second mounting end are both hinged to the drum brake disc, and the first braking end and the second braking end are both pressed against the cam; The elastic members are provided in plurality, a portion of the elastic members are connected to the first mounting end and the second mounting end, and the remaining portion of the elastic members are connected to the first braking end and the second braking end.

7. The drum brake according to claim 6, characterized in that: The drum brake further includes a pin shaft, and the first mounting end and the second mounting end are both hinged to the drum brake disc through the pin shaft; Wherein, in the non-braking state, there is an avoidance gap between the first mounting end and the second mounting end.

8. The drum brake according to claim 5, characterized in that: The elastic member is a spring.

9. A wheel assembly, characterized in that: A drum brake comprising a wheel, a brake pad and the drum brake according to any one of claims 1 to 8; The wheel has a groove, the brake pad is fixedly connected to the circumferential inner wall of the groove, and the drum brake is accommodated in the groove and can cooperate with the brake pad to brake the wheel.

10. A bicycle, characterized in that: Comprising the wheel assembly as claimed in claim 9.

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