Drum brake

Abstract

The utility model discloses a drum brake, belongs to the technical field of brakes, solves the problem that idle stroke is reduced after brake shoes of the drum brake are abraded, and adopts the technical scheme that an elastic resetting piece capable of enabling the two brake shoes to be close to each other is arranged between the two brake shoes; one ends of the two brake shoes are rotationally connected to the drum brake frame, the other ends of the two brake shoes abut against and clamp the cam, and the rocker arm can drive the cam to rotate and open the two brake shoes outwards when rotating. The drum brake is characterized in that the ends, abutting against the cam, of the brake shoes are provided with outer protruding parts protruding towards one side of the cam, and the protruding faces of the outer protruding parts are arc faces; when the cam rotates and expands the brake shoes outwards, the cam abuts against the protruding face. The utility model has the main effects that after the brake shoe is worn, the brake idle stroke is not obviously improved when an operator operates the rocker arm, the brake timeliness is ensured, and the brake is more in line with the operation habit.

Description

Technical Field

[0001] The utility model relates to the technical field of brakes, in particular to a drum brake. Background Art

[0002] Drum brakes use the brake shoes to contact the inner edge of the brake drum when braking, and the friction generated by the contact suppresses the rotation of the tire to achieve the purpose of braking. At present, conventional electric vehicle drum brakes are mainly composed of brake covers, brake shoes, brake rods, and brake arm assemblies that support and expand the brake shoes outward through reverse movement. The brake arm assembly consists of two corresponding connections with two brake shoes, and is controlled to move by the brake rod. The brake rod drives the brake arm assembly to move in the opposite direction to expand the two brake shoes outward to achieve the purpose of braking the wheels.

[0003] The contact surface between the brake shoe and the cam in the prior art is a plane. After the brake shoe has been used for a period of time, the idle braking stroke of the brake device will increase significantly, resulting in failure to quickly brake in an emergency. Utility Model Content

[0004] The purpose to be achieved by the utility model is to provide a drum brake to solve the problem of a significant increase in the idle travel of the drum brake after the brake shoe is worn. The effect is that after the brake shoe is worn, the idle travel of the brake when the operator operates the rocker arm will not increase significantly, thereby ensuring the timeliness of braking and being more in line with operating habits.

[0005] In order to achieve the above-mentioned purpose, the utility model adopts the following technical scheme: a drum brake, comprising a drum brake frame, two brake shoes arranged opposite to each other, a rocker arm and a cam fixed to the rocker arm, an elastic reset member is provided between the two brake shoes, which can make the two brake shoes approach each other, one end of the two brake shoes is rotatably connected to the drum brake frame, and the other end of the two brake shoes abuts and clamps the cam, and the rocker arm can drive the cam to rotate and spread the two brake shoes outward when rotating, and is characterized in that the end of the brake shoe abutting the cam is provided with an outer convex portion protruding toward one side of the cam, and the convex surface of the outer convex portion is an arc surface, and when the cam rotates and spreads the brake shoe outward, the cam abuts against the convex surface.

[0006] The operation process of this technical solution is as follows: when braking is needed, the cam is driven by rotating the rocker arm, so that the cam rotates and presses against the outer convex part of the brake shoe, so that the cam pushes the two brake shoes away from each other, and the brake shoes abut against the brake disc of the wheel to increase the friction of the wheel rotation, so that the wheel reduces the speed. At this time, after releasing the rocker arm, due to the elastic force of the elastic reset part, the two brake shoes are moved closer to each other and squeeze the cam, so that the cam returns to the center, and at the same time drives the rocker arm to return to the center.

[0007] After adopting the above technical solution, the utility model has the following advantages: under the same cam rotation angle, due to the existence of the outer convex part of the brake shoe, after the brake shoe is worn, the moving distance will be greater than that of the brake shoe without the outer convex part, thereby reducing the braking angle of the brake. The moving distances of the two brake shoes are: Figure 6 As shown, when the cam contacts and pushes the brake shoe with the convex portion, the distance moved by the brake shoe is H2-H1+H3; while the distance moved by the brake shoe without the convex portion is only H2-H1, wherein H1 is the height difference between the cam's initial state and the brake shoe contact point C to the cam's rotation axis, H2 is the height difference between the cam and the brake shoe contact point D to the cam's rotation axis after rotation by an angle of α, and H3 is the height difference between the contact point C between the convex portion and the cam in the initial state and the contact point D between the convex portion and the cam after the cam rotates by an angle of α. In comparison, after the brake shoe is worn, the operator needs less idle travel when braking, so that the brake shoe can perform braking work earlier.

[0008] Furthermore, two retaining surfaces are arranged at intervals on the outer circumference of the cam, and both of the two retaining surfaces are outwardly convex arc surfaces, and the axes of the two retaining surfaces coincide with the rotation axis of the cam.

[0009] By adopting the above-mentioned technical solution, the operator does not know the usage of the brake shoe when using the brake device. After the retaining surface on the cam contacts the outer convex part, the cam continues to be rotated and the movement distance of the brake shoe will not change. At this time, the operator will be reminded that the brake shoe has reached the time to be replaced, thereby ensuring the normal working condition of the brake device.

[0010] Furthermore, the curvature of the retaining surface is α, 90°≤α≤100°.

[0011] When adopting the above-mentioned technical solution, if the retaining surface is too small, the idle stroke of the cam in driving the brake shoe will increase, while if it is too large, the cutting angle of the cam to the outer convex part will be too large when rotating, increasing the resistance. Therefore, it is necessary to keep the curvature of the retaining surface within the above-mentioned range.

[0012] Furthermore, the arc radius of the retaining surface is greater than the arc radius of the convex surface.

[0013] By adopting the above technical solution, when the arc radius of the retaining surface is greater than the arc radius of the protruding surface, the brake shoe can be lifted to a relatively high height.

[0014] Furthermore, the cam is provided with two inner recesses, which are arranged opposite to each other, and when the brake shoe is in a reset state, the outer protrusion extends into the corresponding inner recess.

[0015] By adopting the above-mentioned technical solution, the outer protrusion of the brake shoe extends into the corresponding inner concave portion, so that the distance between the brake shoes in the reset state is reduced, the thickness of the brake pad is thicker in the brake disc of the same volume, and it can be used more times, effectively increasing the replacement cycle of the brake pad.

[0016] Furthermore, the inner concave surface of the inner concave portion is matched with the convex surface, and when the brake shoe is in a reset state, the inner concave surface is in close contact with the corresponding convex surface.

[0017] By adopting the above-mentioned technical solution, since the inner concave surface is in close contact with the corresponding convex surface, it is possible to prevent sand and dust impurities from entering between the inner concave surface and the corresponding convex surface during operation, thereby preventing wear between the inner concave surface and the corresponding convex surface.

[0018] Furthermore, the cam is provided with two inner recesses, which are arranged opposite to each other. When the brake shoe is in a reset state, the outer protrusion extends into the corresponding inner recess, and the inner recess has an inner concave surface. The inner concave surface and the retaining surface are alternately arranged on the outer periphery of the cam. The inner concave surface and the retaining surface are transitioned through a circular arc to form a contact portion.

[0019] By adopting the above-mentioned technical solution, because the inner concave surface and the retaining surface are transitioned through a circular arc to form a contact portion, the friction between the contact surface and the outer convex portion and the contact portion is more moderate, the damage to the outer convex portion and the contact portion is reduced, and the life of the outer convex portion and the contact portion is extended.

[0020] Furthermore, transition portions are provided on both sides of the outer protrusion, and when the brake shoe is in a reset state, a partial structure of the abutment portion abuts against the transition portion.

[0021] By adopting the above-mentioned technical solution, a partial structure of the abutting portion abuts against the transition portion, so that the contact between the brake shoe and the cam is smoother and gentler, thereby increasing the service life of the brake shoe and the cam, and because the contact surface between the brake shoe and the cam is large in the reset state, the wear of the brake shoe when the cam is rotated will be evenly distributed on the contact surface. If there is no contact between the transition portion and the abutting portion, the abutting portion will be in line contact with the outer convex portion, and the wear of the cam and the outer convex portion will be greater.

[0022] Furthermore, the brake shoe comprises a shoe body and a wear-resistant part fixed to the shoe body and close to one end of the cam, the cam abuts against the wear-resistant part; and the wear-resistant part is embedded in the shoe body.

[0023] By adopting the above technical solution, the cam abuts against the wear-resistant part, so that the brake shoe does not need to use wear-resistant materials, the cost is reduced, and the cam can be embedded in the shoe body, which is simple to operate and the manufacturing cost is further reduced.

[0024] Furthermore, the drum brake frame has a drum cover for covering the outer side of the brake shoe, the end of the rocker arm away from the cam is connected to a brake line, the rocker arm is provided with a spring, and the spring has a tendency to reset the rocker arm, a brake pad is fixed to the outer side of the brake shoe, and a mounting hole is provided in the center of the drum brake frame, and two brake shoes are symmetrically arranged on opposite sides of the mounting hole.

[0025] By adopting the above-mentioned technical solution, the user can drive the rocker arm to rotate the cam by pulling the brake line, thereby lifting the brake shoe, causing the brake pad to rub against the wheel to slow down the wheel. The mounting hole can install the drum brake frame on the wheel, and the drum cover can prevent dust from entering the brake shoe and causing abnormal wear of the brake pad. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The utility model is further described below in conjunction with the accompanying drawings:

[0027] Figure 1 It is a schematic diagram of a drum brake of the utility model;

[0028] Figure 2 It is a front view of a drum brake;

[0029] Figure 3 It is a connection diagram of the internal parts of a drum brake;

[0030] Figure 4 for Figure 2 A magnified image of point A;

[0031] Figure 5 for Figure 2 Right view of;

[0032] Figure 6 Schematic diagram of a drum brake with and without an external protrusion after the cam rotates a certain angle.

[0033] Description of the drawings: 1. Drum brake frame; 2. Brake shoe; 21. Outer convex portion; 22. Transition portion; 23. Wear-resistant part; 24. Brake pad; 25. Protruding surface; 3. Rocker arm; 4. Cam; 41. Retaining surface; 42. Inner concave portion; 43. Abutment portion; 44. Inner concave surface; 5. Elastic reset member; 6. Mounting hole; 7. Spring. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solutions and advantages of the embodiments of the utility model clearer, the technical solutions in the embodiments of the utility model will be clearly and completely described below in conjunction with the drawings in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, rather than all the embodiments.

[0035] The terms "first", "second", etc. (if any) in the specification and claims of the present utility model are used to distinguish similar objects, rather than to describe a specific order or sequence. Even if "second" is used to distinguish a certain technical feature, it does not necessarily mean that it has "first". It should be understood that in the present utility model, "including" and "having" and any of their variations are intended to cover non-exclusive inclusions. It should be understood that in the present utility model, "multiple" refers to two or more. "And / or" is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, X and / or Y can represent: X exists alone, X and Y exist at the same time, and Y exists alone. The character " / " generally indicates that the related objects before and after are in an "or" relationship. "Contains X, Y and Z", "Contains X, Y, Z" means that X, Y, and Z are all included, "Contains X, Y or Z" means that one of X, Y, and Z is included, and "Contains X, Y and / or Z" means that any one, any two, or three of X, Y, and Z are included.

[0036] The technical solution of the utility model is described in detail with specific embodiments below. The following specific embodiments can be combined or replaced with each other according to actual conditions, and the same or similar concepts or processes may not be repeated in some embodiments.

[0037] like Figures 1 to 5 As shown, the utility model provides a drum brake, comprising a drum brake frame 1, two brake shoes 2 arranged opposite to each other, a rocker arm 3 and a cam 4 fixed to the rocker arm 3, an elastic reset member 5 is provided between the two brake shoes 2 for bringing the two brake shoes 2 closer to each other, one end of the two brake shoes 2 is rotatably connected to the drum brake frame 1, the other end of the two brake shoes 2 abuts against and clamps the cam 4, the rocker arm 3 can drive the cam 4 to rotate and spread the two brake shoes 2 outward when rotating, and is characterized in that an end of the brake shoe 2 abutting against the cam 4 is provided with an outer convex portion 21 protruding toward one side of the cam 4, the convex surface 25 of the outer convex portion 21 is an arc surface, and when the cam 4 rotates and spreads the brake shoe 2 outward, the cam 4 abuts against the convex surface 25.

[0038] The operation process of this technical solution is as follows: when braking is needed, the cam 4 is driven by rotating the rocker arm 3, so that the cam 4 rotates and presses against the outer protrusion 21 of the brake shoe 2, so that the cam 4 pushes the two brake shoes 2 away from each other, and the brake shoe 2 abuts against the brake disc of the wheel to increase the friction of the wheel rotation, so that the wheel reduces the rotation speed. At this time, after releasing the rocker arm 3, due to the elastic force of the elastic reset member 5, the two brake shoes 2 are moved closer to each other and squeeze the cam 4, so that the cam 4 returns to the center, and at the same time drives the rocker arm 3 to return to the center.

[0039] After adopting the above technical solution, the utility model has the following advantages: when the rotation angle of the same cam 4 is the same, due to the presence of the outer protrusion 21 of the brake shoe 2, after the brake shoe 2 is worn, the moving distance will be greater than that of the brake shoe 2 without the outer protrusion 21, thereby reducing the braking angle of the brake. The moving distances of the two types of brake shoes 2 are: Figure 6 As shown, when the cam 4 contacts and pushes the brake shoe 2 with the outer protrusion 21, the distance moved by the brake shoe 2 is H2-H1+H3; while the distance moved by the brake shoe 2 without the outer protrusion 21 is only H2-H1, wherein H1 is the height difference between the contact point C of the cam 4 and the brake shoe 2 in the initial state and the rotation axis of the cam 4, H2 is: the height difference between the contact point D of the cam 4 and the brake shoe 2 after the rotation angle α and the rotation axis of the cam 4, and H3 is: the height difference between the contact part C of the outer protrusion 21 and the cam 4 in the initial state and the contact part D of the outer protrusion 21 and the cam 4 after the cam 4 rotates by an angle α. In comparison, after the brake shoe 2 is worn, the operator needs to brake with less idle travel, so that the brake shoe 2 can perform braking work earlier.

[0040] Furthermore, two retaining surfaces 41 are arranged at intervals on the outer circumference of the cam 4 . Both of the two retaining surfaces 41 are outwardly convex arc surfaces, and the axes of the two retaining surfaces 41 coincide with the rotation axis of the cam 4 .

[0041] By adopting the above-mentioned technical solution, when the cam 4 is rotated until the retaining surface 41 and the protruding surface 25 abut against each other, the two brake shoes 2 are rotated by equal distances, so that the braking effect is best, and the retaining surface 41 is designed to be an arc surface, so that the friction between the retaining surface 41 and the protruding surface 25 is more moderate, and the surfaces of the retaining surface 41 and the protruding surface 25 will not be damaged, so that the retaining surface 41 and the protruding surface 25 have a longer service life.

[0042] Furthermore, the curvature of the retaining surface 41 is α, 90°≤α≤100°.

[0043] With the above technical solution, if the retaining surface 41 is too small, the idle stroke of the cam 4 in driving the brake shoe 2 will increase, while if it is too large, the cam 4 will cut into the outer protrusion 21 too much when rotating, thereby increasing the resistance.

[0044] Furthermore, the arc radius of the retaining surface 41 is greater than the arc radius of the convex surface 25 .

[0045] By adopting the above technical solution, when the arc radius of the retaining surface 41 is greater than the arc radius of the protruding surface 25, the brake shoe 2 can be lifted to a relatively high height.

[0046] Furthermore, the cam 4 is provided with two inner recesses 42 , and the two inner recesses 42 are arranged opposite to each other. When the brake shoe 2 is in the reset state, the outer protrusion 21 extends into the corresponding inner recess 42 .

[0047] By adopting the above-mentioned technical solution, the outer protrusion 21 of the brake shoe 2 extends into the corresponding inner recess 42, so that the distance between the brake shoes 2 in the reset state is reduced, and the thickness of the brake pad 24 is thicker in the brake disc of the same volume, and it can be used more times, effectively increasing the replacement cycle of the brake pad 24.

[0048] Furthermore, the inner concave surface 44 of the inner concave portion 42 is matched with the outer convex portion 21 , and when the brake shoe 2 is in the reset state, the inner concave portion 42 is in close contact with the corresponding outer convex portion 21 .

[0049] By adopting the above technical solution, since the inner concave surface 44 is in close contact with the corresponding convex surface 25, it is possible to prevent sand and dust impurities from entering between the inner concave surface 44 and the corresponding convex surface 25 during operation, thereby preventing wear between the inner concave surface 44 and the corresponding convex surface 25.

[0050] Furthermore, the cam 4 is provided with two inner recesses 42, and the two inner recesses 42 are arranged opposite to each other. When the brake shoe 2 is in the reset state, the outer protrusion 21 extends into the corresponding inner recess 42, and the inner recess 42 has an inner concave surface 44. The inner concave surface 44 and the retaining surface 41 are alternately arranged on the outer periphery of the cam 4, and the inner concave surface 44 and the retaining surface 41 are transitioned through an arc to form a contact portion 43.

[0051] By adopting the above-mentioned technical solution, because the inner concave surface 44 and the retaining surface 41 are transitioned through a circular arc to form a butt portion 43, the friction between the butt surface and the outer convex portion 21 and the butt portion 43 is more moderate, thereby reducing the damage to the outer convex portion 21 and the butt portion 43, and extending the life of the outer convex portion 21 and the butt portion 43.

[0052] Furthermore, transition portions 22 are provided on both sides of the outer protrusion 21 , and when the brake shoe 2 is in the reset state, a part of the abutting portion 43 abuts against the transition portion 22 .

[0053] Using the above technical solution, such as Figure 4In the area B shown, the cam 4 abuts against the transition portion 22 through a partial structure of the abutment portion 43, so that the contact between the brake shoe 2 and the cam 4 is smoother and gentler, thereby increasing the service life of the brake shoe 2 and the cam 4. In addition, since the contact surface between the brake shoe 2 and the cam 4 in the reset state is large, the wear of the brake shoe 2 when the cam 4 is rotated will be evenly distributed on the contact surface. If there is no contact between the transition portion 22 and the abutment portion 43, the abutment portion 43 of the cam 4 will be in line contact with the outer protrusion 21 when the cam 4 moves, and the wear of the cam 4 and the outer protrusion 21 will be greater.

[0054] Furthermore, the brake shoe 2 includes a shoe body and a wear-resistant part 23 fixed to the shoe body and close to one end of the cam 4, and the cam 4 abuts against the wear-resistant part 23; the wear-resistant part 23 is embedded in the shoe body.

[0055] By adopting the above technical solution, the cam 4 abuts against the wear-resistant part 23, so that the brake shoe 2 does not need to use wear-resistant materials, the cost is reduced, and it can be embedded in the shoe body, which is simple to operate and the manufacturing cost is further reduced.

[0056] Furthermore, the drum brake frame 1 has a drum cover for covering the outer side of the brake shoe 2, the end of the rocker arm 3 away from the cam 4 is connected to the brake line, the rocker arm 3 is provided with a spring 7, and the spring 7 has a tendency to reset the rocker arm 3, a brake pad 24 is fixed to the outer side of the brake shoe 2, and a mounting hole 6 is provided in the center of the drum brake frame 1, and two brake shoes 2 are symmetrically arranged on opposite sides of the mounting hole 6.

[0057] By adopting the above-mentioned technical solution, the user can drive the rocker arm 3 to rotate the cam 4 by pulling the brake line, thereby lifting the brake shoe 2, causing the brake pad 24 to rub against the wheel to slow down the wheel, and the mounting hole 6 can install the drum brake frame 1 on the wheel, and the drum cover can prevent dust from entering the brake shoe 2 and causing abnormal wear of the brake pad.

[0058] The operation process of the technical solution is as follows: when braking is needed, the cam 4 is driven by rotating the rocker arm 3, so that the cam 4 rotates and presses the outer convex part 21 of the brake shoe 2, so that the cam 4 pushes the two brake shoes 2 away from each other, so that the brake shoe 2 abuts against the brake disc of the wheel to increase the friction of the wheel rotation, so that the wheel reduces the speed, and when the cam 4 rotates until the retaining surface 41 abuts against the outer convex part 21, the deceleration effect is best at this time; when braking is not needed, after releasing the rocker arm 3, due to the elastic force of the elastic reset member 5, the two brake shoes 2 are brought closer to each other and squeeze the cam 4, so that the cam 4 returns to the center, and at the same time drives the rocker arm 3 to return to the center, and when the retaining surface 41 and the outer convex part 21 When abutting, the cam is rotated to a state where the transition portion and the outer convex portion abut each other through a certain restoring force of the brake line, and then the two brake shoes 2 approach each other and squeeze the cam 4, so that the cam 4 is returned to the center, and the rocker arm 3 is driven to return to the center; after adopting the above technical scheme, the utility model has the following advantages: when braking is required, the abutting portion of the cam abuts the transition portion, so the abutment between the cam and the brake shoe is smoother, reducing the wear on each other, and because the convex surface 25 of the outer convex portion 21 is arc-shaped, the friction between the brake shoe 2 and the cam 4 is more moderate when the cam 4 rotates and abuts the convex surface 25, further extending the service life of the brake shoe 2 and the cam 4.

[0059] Specifically, in order to reduce the idle travel of the brake under the same rotation angle of the cam 4, the drum brake of the prior art is designed to be flatter or longer. The former design will result in low strength of the cam 4, and the latter will cause the entire brake device to be too large. Therefore, the former will reduce the life of the cam 4 after long-term use, and the latter will be due to the problem of the design shape of the brake shoe 2, such as Figure 6 As shown, after the cam 4 rotates the same angle ∠α for the brake shoe 2 without the external protrusion 21 and the brake shoe 2 with the external protrusion 21, the distance moved by the brake shoe 2 without the external protrusion 21 is the thickness of the wear-resistant part 23, while the brake shoe 2 with the external protrusion 21 will apply displacement to the external protrusion 21 in the rotation direction and the direction away from the center of the circle. Therefore, the distance moved by the brake shoe 2 is significantly greater than the thickness of the wear-resistant part 23. It can be seen that in the case of the brake shoe 2 with the external protrusion 21, the brake idle stroke when used by the operator is shorter.

[0060] In addition to the above-mentioned preferred embodiments, the present invention also has other implementation modes. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work are within the scope of protection requested by the present invention.

Claims

1. A drum brake, comprising a drum brake frame, two brake shoes arranged opposite to each other, a rocker arm and a cam fixed to the rocker arm, an elastic reset member capable of bringing the two brake shoes closer to each other is provided between the two brake shoes, one end of the two brake shoes is rotatably connected to the drum brake frame, the other end of the two brake shoes abuts against and clamps the cam, and the rocker arm can drive the cam to rotate and spread the two brake shoes outward when rotating, characterized in that: One end of the brake shoe abutting against the cam is provided with an outer convex portion protruding toward one side of the cam, and the convex surface of the outer convex portion is an arc surface. When the cam rotates and pushes the brake shoe outward, the cam abuts against the convex surface.

2. A drum brake according to claim 1, characterized in that: Two retaining surfaces are arranged at intervals on the outer periphery of the cam, and both of the two retaining surfaces are outwardly convex arc surfaces, and the axes of the two retaining surfaces coincide with the rotation axis of the cam.

3. A drum brake according to claim 2, characterized in that: The curvature of the retaining surface is α, 90°≤α≤100°.

4. A drum brake according to claim 2, characterized in that: The arc radius of the retaining surface is greater than the arc radius of the convex surface.

5. A drum brake according to claim 1, characterized in that: The cam is provided with two inner concave parts, which are arranged opposite to each other. When the brake shoe is in a reset state, the outer convex part extends into the corresponding inner concave part.

6. A drum brake according to claim 5, characterized in that: The inner concave surface of the inner concave portion is matched with the convex surface, and when the brake shoe is in a reset state, the inner concave surface is in close contact with the corresponding convex surface.

7. A drum brake according to claim 2, characterized in that: The cam is provided with two inner recesses, which are arranged opposite to each other. When the brake shoe is in a reset state, the outer protrusion extends into the corresponding inner recess, and the inner recess has an inner concave surface. The inner concave surface and the retaining surface are alternately arranged on the outer periphery of the cam. The inner concave surface and the retaining surface are transitioned through an arc to form a contact portion.

8. A drum brake according to claim 7, characterized in that: Transition parts are provided on both sides of the outer protrusion, and when the brake shoe is in a reset state, a part of the structure of the abutting part abuts against the transition part.

9. A drum brake according to claim 1, characterized in that: The brake shoe comprises a shoe body and a wear-resistant part fixed to the shoe body and close to one end of the cam, the cam abuts against the wear-resistant part; the wear-resistant part is embedded in the shoe body.

10. A drum brake according to claim 1, characterized in that: The drum brake frame is provided with a drum cover for shielding the outer side of the brake shoe, the end of the rocker arm away from the cam is connected to a brake line, the rocker arm is provided with a spring, and the spring has a tendency to reset the rocker arm, a brake pad is fixed to the outer side of the brake shoe, a mounting hole is provided in the center of the drum brake frame, and two brake shoes are symmetrically arranged on opposite sides of the mounting hole.

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