Wedge dilator with tail end limiting structure

Abstract

The utility model discloses a wedge block expander with a tail end limiting structure, which comprises a shell and a piston arranged in the shell, the piston is provided with a brake clearance compensation mechanism, the brake clearance compensation mechanism comprises an adjusting nut and an adjusting bolt which are matched with each other through threads, and the adjusting bolt is connected with a brake shoe; a tail end limiting structure is arranged on the adjusting bolt and comprises a steel ball arranged in the adjusting nut and a spherical pit formed in the surface of the adjusting bolt, and the position of the adjusting bolt corresponds to the braking limit position when the steel ball is embedded into the spherical pit. By arranging the tail end limiting structure, when the brake lining is worn to the limit thickness required to be replaced, the adjusting nut and the adjusting bolt are locked, so that excessive brake clearance cannot be compensated, and a driver slowly feels brake fatigue, so that the brake lining is forced to be replaced, and the service life of the brake lining is prolonged. And the occurrence of subsequent braking accidents and the damage to the brake drum and the wedge block expander are avoided.

Description

Technical Field

[0001] The utility model relates to the technical field of automotive braking systems, and particularly relates to a wedge expander with an end limit structure. Background Art

[0002] Since the drum brake with a wedge expander has the characteristics of compact structure and light weight compared with the drum brake with a "camshaft + automatic brake clearance adjustment", its acceptance in the market has been increasing in recent years, and the demand has been growing. It is widely used in small-tonnage urban logistics vehicles, large trailers on highways, and special vehicles in mining areas, disaster relief, etc.

[0003] The wedge expander mainly has two functions in the drum brake system (refer to Figure 1 ). The first is to transfer the braking force of the brake chamber to the brake shoe, so that the brake shoe locks the brake drum to complete the automotive braking requirements; the second is to realize the real-time adjustment of the brake clearance and automatically compensate the brake clearance in real time, so that the brake clearance between the brake lining on the brake shoe and the brake drum remains constant.

[0004] However, due to the improper use by drivers and passengers, frequent failures occur. For example, in a failure case, the brake lining of the left rear wheel of a logistics vehicle was worn to the limit thickness, and the wear alarm wire harness was worn out, and the brake failure alarm light flashed, prompting the driver to replace the brake lining. Since there was still a certain amount of wear on the brake lining that could be used continuously at this time, the driver thought that the braking performance was intact and did not need to be replaced, and continued to run. As a result, after the brake lining was worn out, the brake shoe iron directly rubbed against the brake drum, resulting in serious grooves being worn on the brake drum. During this process, the adjustment bolt in the expander continued to compensate and extended outwards on both sides. Since the adjustment bolt of the expander ran beyond the limit position, the thread of the adjustment bolt was damaged, and the expander could not return to its normal position. However, the after-sales personnel of the vehicle factory simply judged that it was a quality problem of the expander that caused the brake drum to be damaged. Summary of the Utility Model

[0005] The purpose of the utility model is to provide a wedge expander with an end limit structure. When the brake lining is worn to the limit thickness, its gap automatic compensation function is locked, forcing the driver to replace the brake lining, thereby avoiding the brake drum from being worn and the wedge expander itself from being damaged.

[0006] To achieve the above object, the present utility model provides the following technical solution: A wedge expander with an end limit structure, including a housing and a piston disposed within the housing. The piston is provided with a brake clearance compensation mechanism. The brake clearance compensation mechanism includes an adjusting nut and an adjusting bolt that are threadedly matched with each other. The adjusting bolt is connected to a brake shoe; an end limit structure is provided on the adjusting bolt; the end limit structure includes a steel ball disposed within the adjusting nut and a spherical concave pit disposed on the surface of the adjusting bolt, and when the steel ball is embedded into the spherical concave pit, the position of the adjusting bolt corresponds to the braking limit position.

[0007] Preferably, a steel ball receiving hole is formed on the surface of the adjusting nut, and a ring groove is provided circumferentially at the position of the steel ball receiving hole. A wire snap ring for applying elastic pressure to the steel ball is provided within the ring groove.

[0008] Preferably, a piston sleeve is provided outside the adjusting nut. A spiral tooth groove is provided on the outer surface of the adjusting nut, and a spiral tooth matching the spiral tooth groove is provided on the inner surface of the piston sleeve; a one-way clutch structure is provided between the piston sleeve and the housing; the piston and the adjusting nut can only rotate relative to each other in one direction.

[0009] Preferably, a rectangular wire torsion spring is provided between the piston and the adjusting nut, so that the piston and the adjusting nut can only rotate relative to each other in one direction.

[0010] Preferably, one-way ratchet teeth are respectively provided on the surfaces of the piston sleeve and the housing that are in relative contact.

[0011] Preferably, a rotation prevention spring piece is provided between the brake shoe and the adjusting bolt. The rotation prevention spring piece is fixedly connected to the brake shoe. The rotation prevention spring piece is provided with a convex point, and a plurality of notches matching the convex point are provided circumferentially at the end of the adjusting bolt.

[0012] Preferably, a push rod is provided within the housing. One end of the push rod close to the piston is in the shape of a wedge-shaped conical surface, and a roller that can move horizontally is provided between the wedge-shaped conical surface of the push rod and the opposite end surface of the piston.

[0013] Preferably, the end surface of the piston close to the push rod is in the shape of an inclined surface.

[0014] Compared with the prior art, the beneficial effects of the present utility model are as follows: By providing an end limit structure, when the brake lining wears to the limit thickness that needs to be replaced, the adjusting nut and the adjusting bolt are locked, so that excessive brake clearance cannot be compensated. The driver will gradually feel that the braking is weak, thereby forcing the replacement of the brake lining, avoiding subsequent braking accidents and damage to the brake drum and the wedge expander. Description of the Drawings

[0015] Figure 1It is a schematic structural diagram of a drum brake system in the prior art.

[0016] Figure 2 It is a schematic internal structure diagram of the wedge expander of the present utility model.

[0017] Figure 3 It is a schematic diagram of the principle of the clearance compensation process in the present utility model.

[0018] Figure 4 It is a schematic structural diagram of the adjusting nut in the present utility model.

[0019] Figure 5 It is a schematic plan view of the piston sleeve in the present utility model.

[0020] Figure 6 It is a schematic side view of the piston sleeve in the present utility model.

[0021] Figure 7 It is a schematic structural diagram of the adjusting bolt in the present utility model.

[0022] Figure 8 It is a schematic diagram of the mating of the anti-rotation spring plate and the adjusting bolt in the present utility model.

[0023] Figure 9 It is a schematic simplified diagram of the structure of the rectangular wire torsion spring in the present utility model. Detailed implementation manners

[0024] In order to make the purpose, technical solutions and advantages of the present utility model clearer and more understandable, the present utility model will be further specifically described below through embodiments.

[0025] Embodiment: A wedge expander with an end limit structure. Referring to the figure, its main structural components include a push rod 1, a roller 2, a housing 3, an adjusting nut 4, a wire snap ring 5, a steel ball 6, an anti-rotation spring plate 7, an adjusting bolt 8, a piston sleeve 9, a rectangular wire torsion spring 10, and a piston 11.

[0026] The push rod 1 is arranged relatively in the middle of the housing 3 and is connected to the output end of the brake chamber, and the bottom end thereof is in the shape of a wedge-shaped cone surface. There are two pistons 11, and piston channels are respectively opened on the left and right sides of the housing 3, and the pistons 11 are respectively movably arranged in the piston channels; the end surface of the piston 11 close to the center of the housing is in the shape of an inclined surface, and a roller 2 is arranged between the wedge-shaped cone surface of the push rod 1 and the inclined surface of the piston 11, and the roller 2 can move horizontally. When the air chamber pushes the push rod 1 to move downward, at this time, the wedge-shaped cone surface at the lower end of the push rod 1 pushes the two rollers 2 to both sides, and the two rollers 2 act on the inclined surfaces of the pistons 11, pushing the pistons 11 on both sides to the left and right sides, so as to expand the brake shoes connected to the pistons 11 to both sides around the brake shoe pins, and lock the brake drum to achieve braking.

[0027] In this embodiment, the piston 11 is provided with a brake clearance compensation mechanism. Specifically, the piston 11 is connected with an adjusting nut 4, the adjusting nut 4 is internally threaded with an adjusting bolt 8, and a piston sleeve 9 is sleeved outside the adjusting nut 4.

[0028] In the above structure, a rectangular wire torsion spring 10 is arranged between the piston 11 and the adjusting nut 4 to realize the one-way rotation of the two. Specifically, the rectangular wire torsion spring 10 is in a left-handed shape. When the two (the adjusting nut 4 and the piston 11) rotate relatively to the left, the rectangular wire torsion spring 10 expands outward in diameter, locking the two (the adjusting nut 4 and the piston 11) so that they cannot rotate relatively; when the two (the adjusting nut 4 and the piston 11) rotate relatively to the right, the rectangular wire torsion spring 10 contracts inward in diameter, releasing the two (the adjusting nut 4 and the piston 11), and the two are in an automatic state and can rotate relatively.

[0029] In this embodiment, a spiral tooth groove 4a is provided on the outer surface of the adjusting nut 4, and a spiral tooth 9b matching the spiral tooth groove 4a is provided on the inner surface of the piston sleeve 9. When the rotational freedom of the piston sleeve 9 is restricted, it can be made to rotate while linearly moving on the adjusting nut 4.

[0030] In the above structure, a one-way clutch structure is provided between the inner surface of the piston sleeve 9 and the corresponding housing 1. Specifically, one-way ratchet teeth 9a are respectively provided on the surfaces of the piston sleeve 9 and the housing 1 in relative contact, so that when the piston sleeve 9 is driven by the piston 11 to move outward, the piston sleeve 9 can be disengaged from the restriction of the rotational freedom of the housing 1 on it, but when the piston 11 moves inward, the piston sleeve 9 is locked by the housing 1 through the action of the one-way ratchet teeth 9a and cannot rotate.

[0031] In this embodiment, a spherical pit 8a is provided on the surface of the adjusting bolt 8, there is a steel ball receiving hole 4c for installing a steel ball 6 on the adjusting nut 4, and a ring groove 4b is provided in the circumferential direction at the position of the steel ball receiving hole 4c, and a wire snap spring 5 for applying elastic pressure to the steel ball 6 is provided in the ring groove 4b. When the adjusting bolt 8 extends outward to the braking limit position, the steel ball 6 just fits into the spherical pit 8a, and under the elastic force of the wire snap spring 5, the adjusting nut 4 and the adjusting bolt 8 are locked.

[0032] In the above structure, since there is relative rotation between the adjusting nut 4 and the adjusting bolt 8, a single-thread connection is adopted between the two in this embodiment, and the holes are aligned according to the limit position during manufacturing and processing, ensuring that the steel ball receiving hole 4c and the spherical pit 8a can coincide both axially and circumferentially when the adjusting bolt 8 rotates to the extreme braking distance, ensuring that the steel ball 6 can just fall into the spherical pit 8a.

[0033] In addition, a rotation-preventing spring piece 7 is provided between the brake shoe and the adjusting bolt 8. The rotation-preventing spring piece 7 is fixedly connected to the brake shoe. The rotation-preventing spring piece 7 is provided with two symmetrical bumps 7a, and the end of the adjusting bolt 8 is provided with a plurality of stop grooves 8b that match the bumps along the circumferential direction. The rotation-preventing spring piece locks the adjusting bolt 8 by the bumps 7a thereon, so that the two can relatively rotate only under the action of a sufficiently large external force. The purpose is to release the locking relationship between the adjusting nut 4 and the adjusting bolt 8 through a sufficiently large external force when they are locked. The rotation-preventing spring piece 7 is stuck by the brake shoe and cannot rotate during operation, and always maintains its relative position with the brake shoe unchanged, so as to be able to limit the circumferential freedom degree of the adjusting bolt 8 during operation.

[0034] When the vehicle is driving normally, there is a certain amount of braking clearance between the brake shoe and the brake drum. When braking the vehicle, the control valve fills the air chamber with air, and the air chamber pushes the push rod 1 on the expander downward. The conical surface at the end of the push rod 1 pushes the roller 2 downward together. The roller 2 acts on the inclined surface of the piston 11, pushing the piston 11, the adjusting nut 4, and the adjusting bolt 8 to move to the left and right sides. In this way, the two brake shoes are forced to open outward around the brake shoe pin and contact the brake drum. When the brake shoe gives the brake drum sufficient positive pressure, a sufficiently large frictional torque is generated, thereby preventing the brake drum from rotating and the vehicle from stopping, realizing the braking function.

[0035] There is a brake lining on the outer side of the brake shoe, which is a consumable part with a high friction coefficient. As braking is carried out frequently, the brake lining will gradually be worn and become thinner. In this way, the clearance between the brake shoe and the brake drum will become larger. To eliminate the increased braking clearance, it is necessary to increase the stroke of the push rod 1 to complete it. However, the stroke of the brake air chamber and the push rod 1 is limited and cannot be increased infinitely. When the braking clearance is too large, braking cannot be completed. At the same time, as the braking clearance increases, the braking response time of the vehicle will also increase, resulting in an increase in the time to complete braking - this is very dangerous.

[0036] The braking clearance compensation mechanism can solve this problem and keep the braking clearance at a stable value all the time. Its specific working principle is as follows:

[0037] For the convenience of description, it is assumed that the braking clearance is too large at this time, which consists of the normal clearance S (this is a necessary clearance value to ensure the normal operation of the vehicle) and the excessive clearance.

[0038] In the first stage, the normal clearance is eliminated first. When the air chamber pushes the push rod 1 downward, it pushes the piston 11, the adjusting nut 4, and the adjusting bolt 8 to move to the left and right sides, forcing the two brake shoes to open outward around the brake shoe pin, approach the brake drum, and reduce the braking clearance.

[0039] At this time, the brake shoe does not contact the brake drum.

[0040] The second stage is to complete braking. Under the action of the air chamber, the push rod continues to move downward, continuously pushing the piston 11, the adjusting nut 4, and the adjusting bolt 8 to move to the left and right sides. The two brake shoes continue to expand outward around the brake shoe pins until they contact the brake drum and generate a large enough positive pressure to lock the brake drum and complete braking. At this time, the adjusting bolt 8 is in the position shown in Figure 3 "Position when braking is completed".

[0041] During this process, when the adjusting nut 4 crosses the corresponding normal clearance stroke, the original inner gap near the center position between the adjusting nut 4 and the piston sleeve 9 is eliminated and transferred to the outer end near the center position.

[0042] At this time, when the adjusting bolt 8 continues to move outward, it pushes the piston sleeve 9 to move outward as well, and the piston sleeve 9 is disengaged from the restriction of the housing 3.

[0043] When eliminating excessive braking clearance, the adjusting nut 4 moves outward and drives the piston sleeve 9 to rotate counterclockwise by an angle relying on the spiral tooth groove 4a.

[0044] At this time, the adjusting bolt 8 is in the position shown in Figure 3 "Position when braking is completed".

[0045] Next is the braking release stage.

[0046] The third stage: Generate normal braking clearance. As the braking air chamber deflates, the push rod 1 moves upward. Under the action of the return spring, the brake shoes rotate inward, driving the adjusting bolt 8, the adjusting nut 4, and the piston 11 to move inward. The original inner gap near the center position between the adjusting nut 4 and the piston sleeve 9 is eliminated and transferred to move inward at the outer end near the center position. At this time, a normal clearance is generated between the brake shoes and the brake drum.

[0047] At this time, the adjusting bolt 8 and the adjusting nut 4 have not returned to the most original position yet.

[0048] The fourth stage: Automatically compensate for braking clearance.

[0049] Under the reaction force of the brake shoes, the adjusting bolt 8, the adjusting nut 4, and the piston 11 continue to move inward. Since the piston sleeve 9 is locked by the housing 3 and cannot rotate, the adjusting nut 4 will rotate clockwise by an angle under the action of the spiral tooth groove 4a and the spiral tooth 9b.

[0050] During this process, the adjusting nut 4 and the piston 11 can also rotate freely relative to the right.

[0051] When the adjusting nut 4 rotates clockwise by a certain angle, the adjusting bolt 8 will extend outward by a certain distance under the action of the thread.

[0052] Thus, when the adjusting nut 4 and the piston 11 return to the original position, the adjusting bolt 8 does not return to the original position, but moves a certain distance outward (such as Figure 3 the "position after compensation" shown), so the brake shoe does not return to the original position either, but rotates outward by a certain angle, thereby reducing the gap with the brake drum.

[0053] Repeat "brake, release brake, brake again, release brake again..." like this until the brake clearance is adjusted within the normal value.

[0054] As the brake lining wears continuously, the compensation function of the expander keeps working. When the brake lining wears to the thickness that needs to be replaced, when the adjusting bolt 8 extends to the Figure 3 "limit position" shown, the steel ball 6 falls into the spherical pit 8a on the adjusting bolt 8 under the action of the wire snap ring 5. At this time, the adjusting bolt 8 and the adjusting nut 4 are locked with each other and cannot rotate relative to each other. In this way, the excessive brake clearance cannot be compensated, and the driver will gradually feel that the braking is weak, thus forcing the replacement of the brake lining.

[0055] If restoration is needed, just rotate the adjusting bolt 8 with a sufficient external force to make the convex point 7a of the anti-rotation spring piece 7 disengage from the corresponding stop groove 8b, and the steel ball 6 will be pushed outwards to return to the initial position, which is convenient and fast.

[0056] The above embodiments are only for explaining the technical concept and features of the present invention, and the purpose is to enable those who are familiar with this technology to understand the content of the present invention and implement it accordingly, and it cannot be used to limit the protection scope of the present invention. All equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A wedge expander with an end limit structure, comprising a housing and a piston disposed in the housing, wherein the piston is provided with a brake clearance compensation mechanism, wherein the brake clearance compensation mechanism comprises an adjustment nut and an adjustment bolt with mutually matching threads, wherein the adjustment bolt is connected to a brake shoe; characterized in that: The adjusting bolt is provided with an end limit structure; the end limit structure comprises a steel ball arranged in the adjusting nut and a spherical pit arranged on the surface of the adjusting bolt, and when the steel ball is embedded in the spherical pit, the position of the adjusting bolt corresponds to the braking limit position.

2. A wedge expander with an end limit structure according to claim 1, characterized in that: A steel ball receiving hole is provided on the surface of the adjusting nut, and an annular groove is provided along the circumferential direction at the position of the steel ball receiving hole. A steel wire clamping spring for applying elastic pressure to the steel ball is provided in the annular groove.

3. A wedge expander with an end limit structure according to claim 1 or 2, characterized in that: A piston sleeve is arranged outside the adjusting nut, a spiral tooth groove is arranged on the outer surface of the adjusting nut, and a spiral tooth matching with the spiral tooth groove is arranged on the inner surface of the piston sleeve; a one-way clutch structure is arranged between the piston sleeve and the housing; the piston and the adjusting nut can only rotate in one direction relative to each other.

4. A wedge expander with an end limit structure according to claim 3, characterized in that: A rectangular steel wire torsion spring is arranged between the piston and the adjusting nut.

5. A wedge expander with a terminal limit structure according to claim 3, characterized in that: The surfaces of the piston sleeve that are in relative contact with the housing are respectively provided with one-way ratchet teeth.

6. A wedge expander with an end limit structure according to claim 1 or 2, characterized in that: A rotation-stopping spring piece is arranged between the brake shoe and the adjusting bolt, the rotation-stopping spring piece is fixedly connected to the brake shoe, the rotation-stopping spring piece is provided with a convex point, and the end of the adjusting bolt is provided with a plurality of stop openings matching with the convex points along the circumferential direction.

7. A wedge expander with an end limit structure according to claim 1 or 2, characterized in that: A push rod is arranged in the shell, and one end of the push rod close to the piston is a wedge-shaped cone surface. A roller capable of horizontal movement is arranged between the wedge-shaped cone surface of the push rod and the opposite end surface of the piston.

8. A wedge expander with a terminal limit structure according to claim 7, characterized in that: The end surface of the piston close to the push rod is an inclined surface.

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