CN217056065U - Self-adjusting drum brake for electric vehicle - Google Patents

Abstract

The utility model discloses a drum brake for self-interacting electric motor car, including brake box shell subassembly, friction shoe block assembly, camshaft, rocking arm, toggle mechanism and self-interacting mechanism, brake box shell subassembly inboard is equipped with friction shoe block assembly, and the cam body outside is equipped with the profile of tooth structure, and toggle mechanism stirs the camshaft and rotates, and self-interacting mechanism keeps the normal position motionless, the same angle of the smooth commentaries on classics of toggle mechanism relatively, still is equipped with reset spring between toggle mechanism and brake box shell subassembly, and toggle mechanism resets under the reset spring effect, and the camshaft keeps an angle under self-interacting mechanism adjusts. The poking mechanism and the self-adjusting mechanism are matched and adjusted through a tooth-shaped structure arranged on the outer side of the ratchet wheel and the cam body. The problems that after the shoe block component of the existing brake is worn for a long time, the gap between the shoe block component and the hub is enlarged, the brake gap is not adjusted timely and accurately, and the hand feeling is heavy are solved.

Description

Drum brake for self-interacting electric motor car

Technical Field

The utility model relates to a motor vehicle or electric motor car brake actuator field especially relate to a self-interacting electric motor car drum brake.

Background

The drum brake drives the cam shaft to rotate through the rotation of the rocker arm, the shoe block components on two sides are driven to be opened and tightly attached to the brake drum, and the friction force between the brake drum and the shoe block components stops the rotation of the wheel. After long-time use, the brake cable can become long under the effect of elasticity, and the clearance grow between the long-time wearing and tearing back of shoe subassembly and wheel hub simultaneously can appear braking performance decline and the malfunctioning phenomenon of brake usually this moment, often tightens up the brake cable or changes the brake through manual regulation brake cable screw, and when manual mode adjustment braking clearance, it is difficult to guarantee timeliness and accuracy relatively.

Automatic brake clearance adjusting devices are widely used in the automotive field. However, drum brakes in electric vehicles, tricycles and motorcycles are rarely used in the prior art.

If the notice number is: CN106050999B has the throw device of automatic adjustment brake clearance function: the automatic hub brake clearance adjusting device comprises a crank throw consisting of a driving arm and a driven arm, wherein the driven arm and the driving arm are sleeved on a cam shaft, the driven arm is fixedly connected with the cam shaft, the driving arm is movably connected with the cam shaft, a ratchet mechanism is arranged on the driving arm, a threaded hole is formed in the center of a ratchet wheel, an adjusting screw rod is arranged on the driven arm, the adjusting screw rod is sleeved in the threaded hole of the ratchet wheel in a rotating mode, a ratchet wheel structure and the adjusting screw rod are adopted to be matched with a limiting block on a hub brake cover, automatic hub brake clearance adjustment is achieved, when the driving arm moves to a set angle, the rod head portion of a pawl rocker on the driving arm contacts the limiting block, and the pawl rocker rotates, so that a tooth is moved on the ratchet wheel by a pawl.

The ratchet wheel device designed by the main crank and the auxiliary crank is complex and heavy in structure and is matched with the limiting block for adjustment, so that the resistance is great during braking, and the hand feeling is heavy; and wherein adjusting screw is a straight rod-shaped part, and the main and the follow crank throw rotate around the camshaft for circumferential motion, can take place the jamming phenomenon in the adjustment turned angle process, and later stage is inconvenient to the wearing clearance adjustment of shoe block group.

SUMMERY OF THE UTILITY MODEL

The utility model provides a not enough to prior art, the utility model provides a drum brake for self-interacting electric motor car, the long-time wearing and tearing back of shoe block subassembly and the clearance grow between wheel hub of having solved current stopper, the adjustment braking clearance untimely, accurate to and the problem of feeling heavy.

In order to achieve the purpose, the utility model discloses a realize through following technical scheme:

the utility model relates to a drum brake for self-interacting electric motor car, including floodgate box shell subassembly, friction shoe block subassembly, camshaft and rocking arm, floodgate box shell subassembly inboard is equipped with friction shoe block subassembly, friction shoe block subassembly first end is rotatable installs on the fixed core pivot of floodgate box shell subassembly, the second end butt is in the cam portion of camshaft one end, camshaft other end cam body pin joint is in the through-hole of floodgate box shell subassembly, rocking arm and cam body end can be dismantled and fix in the floodgate box shell subassembly outside, the cam body outside is equipped with the profile of tooth structure, still includes toggle mechanism and self-interacting mechanism, toggle mechanism toggles the camshaft rotation, self-interacting mechanism keeps the normal position motionless, the relative toggle mechanism slips the same angle, still be equipped with reset spring between toggle mechanism and floodgate box shell subassembly, toggle mechanism resets under the reset spring effect, the camshaft is adjusted by a self-adjusting mechanism to maintain an angle.

The further improvement lies in that: the toggle mechanism is a first ratchet wheel device arranged on the rocker arm, the self-adjusting mechanism is a second ratchet wheel device arranged on the brake box shell assembly, the first ratchet wheel device comprises a first ratchet wheel and a first pressure spring, the second ratchet wheel device comprises a second ratchet wheel and a second pressure spring, and the first ratchet wheel and the second ratchet wheel are respectively matched with the tooth-shaped structure; one end of the rocker arm is provided with a brake cable connecting part, the other end of the rocker arm is provided with a fixing hole, a first special-shaped groove is formed in the inner side of the fixing hole, an opening in one side of the first special-shaped groove is communicated with the fixing hole, a second special-shaped groove is formed in one side of the brake box shell component, and an opening in one side of the second special-shaped groove is communicated with the through hole; the first ratchet device is arranged in the special-shaped groove, and the second ratchet device is arranged in the second special-shaped groove.

The further improvement lies in that: the first ratchet wheel and the second ratchet wheel are respectively provided with a ratchet and a positioning pivot, the ratchet is meshed with the tooth-shaped structure, the first special-shaped groove and the second special-shaped groove are internally provided with positioning hole groove structures, and the positioning pivot is matched with the positioning hole groove structures.

The further improvement is that: first ratchet, second ratchet are equipped with first side respectively, second side and the spacing portion of pressure spring, the first side of first ratchet is laminated with a special-shaped groove side, first ratchet second side is equipped with the spacing portion of pressure spring, first pressure spring butt is between pressure spring spacing portion and special-shaped groove.

The further improvement is that: first dysmorphism groove still is equipped with first baffle, first baffle adaptation lid closes in first dysmorphism groove, second dysmorphism groove adaptation lid has closed the second baffle.

The further improvement lies in that: the first ratchet wheel and the second ratchet wheel are arranged in a mirror symmetry structure from top to bottom along the cam shaft.

The further improvement is that: the cam body is arranged into an upper toothed structure and a lower toothed structure, the middle section of the cam body is a cylindrical structure, a circumferential annular groove is formed in the end portion of the cam body, and a clamping piece is arranged in the annular groove and is connected with the rocker arm in a clamping mode.

The further improvement is that: still be equipped with the lug structure on the floodgate box shell subassembly, the lug is equipped with the brake cable on the structure and wears dress structure and constitutes manual wearing and tearing clearance adjustment structure with the brake cable connecting portion of rocking arm.

The utility model has the advantages that:

1. the combined stirring mechanism and the self-adjusting mechanism are adopted, and the interaction between the reset spring and the cam shaft is adopted, so that the cam shaft does not reset after the friction shoe group component is worn, the rocker arm resets to compensate the gap between the worn friction shoe group component and the brake drum, the gap between the worn friction shoe group component and the brake drum is kept constant, the brake rocker arm is ensured to be always in an effective and controllable range, the normal gap between the friction shoe group component and the hub is always kept, the friction shoe group component can be automatically adjusted by braking in the advancing direction after being worn, and the adjustment of the abrasion gap is flexible, rapid, accurate and timely; the safety of the rider is ensured, and the riding is more humanized;

2. the ratchet device of the shifting mechanism and the self-adjusting mechanism arranged on the rocker arm and the brake box shell component is matched with the tooth-shaped structure on the cam shaft, and the braking process is adjusted flexibly, quickly, accurately and timely. The ratchet wheel device is matched in the open special-shaped groove by a ratchet wheel and a pressure spring, and has firm and stable structure, and vibration and buffering functions. Keep the clearance invariable, can effectually prevent to produce the jamming because of clearance adjustment undersize.

Drawings

Fig. 1 is a schematic structural view of a drum brake for a self-adjusting electric vehicle.

Fig. 2 is a sectional view of a drum brake for a self-adjusting electric vehicle.

Fig. 3 is an exploded view of a drum brake for a self-adjusting electric vehicle.

FIG. 4 is a schematic view of the toggle mechanism and self-adjusting mechanism position of a drum brake for a self-adjusting electric vehicle.

Fig. 5 is a schematic diagram of the structure of a toggle mechanism and a self-adjusting mechanism of a drum brake for a self-adjusting electric vehicle.

FIG. 6 is a schematic diagram of a drum brake rocker arm for a self-adjusting electric vehicle.

FIG. 7 is a schematic view of a drum brake housing for a self-adjusting electric vehicle.

FIG. 8 is a schematic view of a cam shaft structure of a drum brake for a self-adjusting electric vehicle.

The attached drawings are as follows: the brake box comprises a brake box shell assembly 10, a friction shoe assembly 20, a cam shaft 30, a rocker arm 40, a toggle mechanism 50, a self-adjusting mechanism 60, a return spring 70, a fastener 80, a fixed core rotating shaft 11, a through hole 12, a second special-shaped groove 13, a second baffle plate 14, a lug structure 15, a cam part 31, a cam body 32, a tooth-shaped structure 33, an annular groove 34, a brake cable connecting part 41, a fixing hole 42, a first special-shaped groove 43, a first baffle plate 44, a first ratchet gear 51, a first ratchet gear 52, a first pressure spring 53, a first side surface 521, a second side surface 522, a second side surface 622, a pressure spring limiting part 523, a second ratchet gear 623, a second ratchet gear 61, a second ratchet 62, a second pressure spring 63, 524, 624, a positioning pivot 520, a positioning hole groove structure 430, and a positioning hole groove structure 130.

Detailed Description

In order to deepen the understanding of the present invention, the present invention will be further described in detail with reference to the attached drawings, and this embodiment is only used to explain the present invention, and does not constitute a limitation to the protection scope of the present invention. It is obvious that the described embodiments are only some of the embodiments of the present invention, and not all of them. Based on the embodiments in the present invention, all other embodiments obtained by the person skilled in the art without creative work all belong to the protection scope of the present invention.

The present invention will be described in further detail with reference to the accompanying drawings and examples.

1-3 show a drum brake for an embodiment of self-adjusting electric vehicle, which comprises a brake box housing assembly 10, a friction shoe block assembly 20, a cam shaft 30 and a rocker arm 40, wherein the friction shoe block assembly 20 is arranged inside the brake box housing assembly 10, the friction shoe block assembly 20 is rotatably mounted on a fixed core rotating shaft 11 of the brake box housing assembly 10 at a first end, a cam part 31 at one end of the cam shaft 30 is abutted at a second end, a cam body 32 at the other end of the cam shaft 30 is pivoted in a through hole 12 of the brake box housing assembly 10, the rocker arm 40 and the end of the cam body 32 are detachably fixed outside the brake box housing assembly 10, a tooth-shaped structure 33 is arranged outside the cam body 32, and the drum brake further comprises a toggle mechanism 50 and a self-adjusting mechanism 60, wherein the toggle mechanism 50 toggles the cam shaft 30 to rotate, the self-adjusting mechanism 60 keeps in place and slides at the same angle relative to the toggle mechanism 50, a return spring 70 is further arranged between the toggle mechanism 50 and the brake box housing assembly 10, the toggle mechanism 50 is reset under the action of the return spring 70, and the cam shaft 30 keeps an angle under the adjustment of the self-adjusting mechanism 60; under the combined action of the toggle mechanism, the self-adjusting mechanism and the camshaft with the structure, the friction shoe assembly 20 is kept at an open point, and the braking clearance generated by the friction shoe assembly 20 due to abrasion is compensated and adjusted, so that the adjustment-free function without manual adjustment is realized.

As shown in fig. 4 and 5, the toggle mechanism 50 is a first ratchet device 51 disposed on the rocker arm 40, the first ratchet device 51 includes a first ratchet wheel 52 and a first compression spring 53, the self-adjusting mechanism 60 is a second ratchet device 61 disposed on the brake shoe housing assembly 10, the second ratchet device 61 includes a second ratchet wheel 62 and a second compression spring 63, and the first ratchet wheel 52 and the second ratchet wheel 62 are respectively provided with ratchet teeth 524 and 624 to engage with the tooth-shaped structure 33; one end of the rocker arm 40 is provided with a brake cable connecting part 41, the other end of the rocker arm is provided with a fixing hole 42, the inner side of the fixing hole 42 is provided with a first special-shaped groove 43, one side opening of the first special-shaped groove 43 is communicated with the fixing hole 42, the first ratchet wheel device 51 is installed in the special-shaped groove 43, a ratchet 524 penetrates through the opening to be meshed with a tooth-shaped structure 33 of the camshaft 30, one side of the brake box shell component 10 is provided with a second special-shaped groove 13, and one side opening of the second special-shaped groove 13 is communicated with the through hole 12; the second ratchet means 61 is mounted in the second profiled groove 13.

Through the interaction among the tooth-shaped structures of the combined ratchet device, the torsion spring and the cam shaft, after the cam shaft 30 is stirred to rotate for a certain angle and the friction shoe component 20 is propped open for braking, the rocker arm resets under the action of the reset spring, and the cam shaft does not reset under the action of the self-adjusting mechanism after the friction shoe component is worn, so that the self-adjusting compensation of the brake clearance increased by the wear of the shoe component is realized. One side opening of the second special-shaped groove 13 is communicated with the through hole 12, and one side opening of the first special-shaped groove 43 is communicated with the fixing hole 42; the ratchet wheel arranged in the cam shaft can be reliably meshed with the tooth-shaped structure of the cam shaft.

As shown in fig. 4-7, the first ratchet 52 and the second ratchet 62 are respectively provided with a positioning pivot 520 and 620, the first profiled groove 43 and the second profiled groove 13 are respectively provided with a positioning hole groove structure 430 and 130, and the positioning pivot 520 and 620 is matched with the positioning hole groove structure 430 and 130; the first ratchet 52 and the second ratchet 62 are respectively provided with a first lateral surface 521, a second lateral surface 522, a second lateral surface 622 and a pressure spring limiting part 523, 623, the first lateral surface 521 of the first ratchet 52 is attached to one lateral surface of the first special-shaped groove 43, the second lateral surface 522 of the first ratchet 52 is provided with a pressure spring limiting part 523, and the first pressure spring 53 abuts between the pressure spring limiting part 523 and the first special-shaped groove 43. The second ratchet wheel 62 is provided with a first side 621, a second side 622 and a pressure spring limiting portion 623 corresponding to the first ratchet wheel 52. The first ratchet 52 and the second ratchet 62 are arranged along the cam shaft 30 in a vertically mirror-symmetrical structure.

Therefore, the ratchet wheel can be firmly connected with the special-shaped groove, and the braking and resetting are reliable; during braking, the first pressure spring is abutted between the pressure spring limiting part 523 and the other side surface of the first special-shaped groove 43, the first side surface 521 of the first ratchet wheel 52 is attached to one side surface of the first special-shaped groove 43, the ratchet 520 is driven by the rocker arm 40 to dial the tooth-shaped structure 33 of the cam shaft 30 to drive the cam shaft 30 to rotate, and at the moment, the first pressure spring 53 plays a role in stabilizing and supporting the ratchet wheel 52; the second ratchet wheel 62 is installed in the second special-shaped groove 13 of the brake box housing assembly 10 and is vertically symmetrical to the first ratchet wheel 52, when braking is performed, the rocker arm 40 drives the cam shaft 30 to rotate together, the brake box housing assembly 10 does not move, the second ratchet wheel 62 needs to be kept in a fixed position, sliding teeth are needed to be kept in the fixed position relative to the cam shaft 30, and at the moment, the second pressure spring 63 plays a role in vibrating the sliding teeth of the second ratchet wheel 62.

When braking is finished, the rocker arm 40 is reset under the action of the counter force of the return spring 70, the first ratchet wheel 52 slides down and teeth reset under the action of the first pressure spring 53 and the return spring 70, and at the moment, the first pressure spring 53 plays a role of vibrating and sliding teeth on the ratchet wheel 52; when the cam shaft 30 is reset along with the rocker arm 40, the second ratchet wheel 62 rotates by a small angle and is attached to one side surface of the second special-shaped groove 13 and then is meshed with a tooth-shaped structure of the cam shaft 30 to be clamped, so that the cam shaft 30 is prevented from rotating and resetting, the abrasion gap generated by the friction shoe block assembly 20 due to braking is compensated, the second pressure spring 63 is meshed with the second ratchet wheel 63 after rotating by a small angle when the rocker arm is reset to play a buffering role, namely, the abrasion gap is not slippery when the abrasion gap is too small and is not equal to one tooth pitch, and the second ratchet wheel is buffered through the pressure spring, so that the braking gap is kept constant, and clamping stagnation generated due to too small gap adjustment can be effectively prevented; the second ratchet 62, the second compression spring 63 and the second profile groove 13 are therefore provided here as required with regard to their structural dimensions.

As shown in fig. 3: the first shaped groove 43 is further provided with a first baffle 44, the first baffle 44 is adapted to cover the first shaped groove 43, and the second shaped groove 13 is adapted to cover the second baffle 14. By the design, the structure is firmer and more reliable, and the scattering is not easy to happen.

As shown in fig. 8: the cam body 32 is arranged into an upper toothed structure and a lower toothed structure 33, the middle section of the cam body is a cylindrical structure, a circumferential annular groove 34 is formed in the end part of the cam body, and a clamping piece 80 is arranged in the annular groove 34 and is connected with the rocker arm 40 in a clamping mode; the whole connection of the brake is firm and reliable, and the assembly and maintenance are convenient.

The two sections of tooth-shaped structures 33 can be arranged into ratchets in opposite directions, which are matched with the ratchets 524 and 624 of the first ratchet wheel 52 and the second ratchet wheel 62; the structure is more convenient and reasonable when the sliding teeth and the meshing latch are driven, and the transmission is reliable. The cam body 32 can also be mainly set to be a full-tooth structure, and the full teeth are divided into two sections of ratchets in opposite directions; or the ratchet teeth 524, 624 of the first ratchet wheel 52 and the second ratchet wheel are arranged in opposite directions to cooperate with the same direction tooth-shaped structures on the cam shaft.

More preferably: the brake box shell assembly 10 is further provided with a lug structure 15, and a brake cable penetrating structure arranged on the lug structure 15 and a brake cable connecting part 41 of the rocker arm 40 form a manual abrasion gap adjusting structure. So set up, jointly adjust manual clearance adjustment and automatic clearance adjustment, the product regulation performance is more convenient, superior, has guaranteed to ride passerby's safety, more humanized physics and chemistry.

The action principle of the utility model is as follows:

during braking: after the rocker arm 40 is shifted, the first lateral surface 521 of the first ratchet wheel 52 is attached to one lateral surface of the first special-shaped hole 43 after being stressed, the cam shaft 30 is driven to rotate through the meshing stress of the ratchet 524 on the first ratchet wheel 52 and the external tooth-shaped structure 33 on the cam shaft 30, the sliding teeth of the second ratchet wheel 62 are fixed relative to the brake box housing assembly 10 along with the rotation of the cam shaft 30 under the action of the second pressure spring 63, the rotation of the cam shaft 30 is not influenced, and therefore the friction shoe block assembly 20 is spread along with the rotation of the cam shaft 30, and the braking effect is achieved;

after braking is finished: when the rocker arm 40 is released, the rocker arm 40 is driven by the torsion spring of the return spring 70 to reset, at this time, the second side surface 522 of the first ratchet wheel is in contact with the first pressure spring 53, the first ratchet wheel can rotate along with the sliding teeth of the rocker arm 40 to reset under the action of the first pressure spring 53, and the rocker arm 40 returns to the position before braking; the first side surface 621 of the second ratchet wheel 62 is attached to the side surface of the second special-shaped hole 13 of the brake box housing assembly 10, the second ratchet 624 is engaged with the tooth structure 33 of the cam shaft 30 to prevent the cam shaft 30 from resetting, and the cam shaft 30 is in a spread angle state without resetting shoe blocks, so that the increased brake clearance of the friction shoe assembly 20 caused by brake wear is compensated and adjusted;

the steps are repeated in the following way: after the next shoe block is worn, the drum brake operation principle is the same as that described above, the rocker arm automatically resets, the shoe block is always spread, and the purpose of maintenance-free is achieved.

The embodiment of the present invention discloses a preferred embodiment, but not limited thereto, and those skilled in the art can easily understand the spirit of the present invention according to the above-mentioned embodiment, and make different applications and changes, but do not depart from the spirit of the present invention, all of which are within the protection scope of the present invention.

Claims (8)

1. The utility model provides a drum brake for self-interacting electric motor car, includes cassette shell subassembly (10), friction shoe block subassembly (20), camshaft (30) and rocking arm (40), cassette shell subassembly (10) inboard is equipped with friction shoe block subassembly (20), friction shoe block subassembly (20) first end is rotatable installs on the fixed core pivot (11) of cassette shell subassembly (10), and second end butt is in cam portion (31) of camshaft (30) one end, camshaft (30) other end cam body (32) pin joint is in through-hole (12) of cassette shell subassembly (10), rocking arm (40) can be dismantled with cam body (32) tip and fix in the cassette shell subassembly (10) outside, the cam body (32) outside is equipped with profile of tooth structure (33), its characterized in that: still include toggle mechanism (50) and self-interacting mechanism (60), toggle mechanism (50) stir camshaft (30) and rotate, self-interacting mechanism (60) keep the normal position motionless, relative toggle mechanism (50) the same angle of slip, still be equipped with reset spring (70) between toggle mechanism (50) and box shell subassembly (10), toggle mechanism (50) resets under reset spring (70) effect, camshaft (30) keep an angle under self-interacting mechanism (60) is adjusted.

2. The drum brake for self-adjusting electric vehicles of claim 1, wherein: the toggle mechanism (50) is a first ratchet gear device (51) arranged on the rocker arm (40), the self-adjusting mechanism (60) is a second ratchet gear device (61) arranged on the brake box shell assembly (10), the first ratchet gear device (51) comprises a first ratchet gear (52) and a first pressure spring (53), the second ratchet gear device (61) comprises a second ratchet gear (62) and a second pressure spring (63), and the first ratchet gear (52) and the second ratchet gear (62) are respectively matched with the tooth-shaped structure (33); one end of the rocker arm (40) is provided with a brake cable connecting part (41), the other end of the rocker arm is provided with a fixing hole (42), a first special-shaped groove (43) is formed in the inner side of the fixing hole (42), an opening in one side of the first special-shaped groove (43) is communicated with the fixing hole (42), a second special-shaped groove (13) is formed in one side of the brake box shell assembly (10), and an opening in one side of the second special-shaped groove (13) is communicated with the through hole (12); the first ratchet means (51) is mounted in a profiled groove (43) and the second ratchet means (61) is mounted in a second profiled groove (13).

3. The drum brake for self-adjusting electric vehicles of claim 2, wherein: the first ratchet wheel (52) and the second ratchet wheel (62) are respectively provided with ratchet teeth (524, 624) and positioning pivot shafts (520, 620), the ratchet teeth (524, 624) are meshed with the tooth-shaped structure (33), positioning hole groove structures (430, 130) are arranged in the first special-shaped groove (43) and the second special-shaped groove (13), and the positioning pivot shafts (520, 620) are matched with the positioning hole groove structures (430, 130).

4. The drum brake for self-adjusting electric vehicles of claim 2, wherein: first ratchet (52), second ratchet (62) are equipped with first side (521, 621) respectively, second side (522, 622) and the spacing portion of pressure spring (523, 623), the laminating of first side (521) of first ratchet (52) and first dysmorphism groove (43) side, first ratchet (52) second side (522) is equipped with the spacing portion of pressure spring (523), first pressure spring (53) butt is between pressure spring spacing portion (523) and first dysmorphism groove (43).

5. The drum brake for self-adjusting electric vehicles of claim 2, wherein: the first special-shaped groove (43) is further provided with a first baffle plate (44), the first baffle plate (44) is matched and covered on the first special-shaped groove (43), and the second special-shaped groove (13) is matched and covered with a second baffle plate (14).

6. A drum brake for self-adjusting electric vehicles as claimed in claim 2, wherein: the first ratchet wheel (52) and the second ratchet wheel (62) are arranged along the cam shaft (30) to be of a structure which is vertically mirror-symmetrical to each other.

7. A drum brake for self-adjusting electric vehicles as claimed in claim 1, wherein: the cam body (32) is arranged into an upper toothed structure and a lower toothed structure, the middle section of the cam body is a cylindrical structure, a circumferential annular groove (34) is formed in the end part of the cam body, and a clamping piece (80) is arranged in the annular groove (34) and is connected with the rocker arm (40) in a clamping mode.

8. A drum brake for self-adjusting electric vehicles as claimed in claim 1, wherein: still be equipped with lug structure (15) on the brake box shell subassembly (10), be equipped with brake cable on lug structure (15) and wear dress structure and constitute manual wearing and tearing clearance adjustment structure with brake cable connecting portion (41) of rocking arm (40).

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