Wedge block expander for drum brake

Abstract

The utility model discloses a wedge block expander for a drum brake, which comprises a shell, a push rod and a piston, the push rod and the piston are arranged in the shell, and the push rod can drive the piston to reciprocate in the shell when moving; and a grease storage groove is formed in the surface of the piston. The grease storage groove is formed in the surface of the piston, so that lost grease can be supplemented in time, and good lubricating performance is guaranteed; besides, when metal chippings or powder is generated due to running-in between the piston and the shell, the metal chippings or powder can be contained in the grease storage groove, and therefore the probability that the piston and the shell are stuck is reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of automotive braking systems, and particularly relates to a wedge expander for a drum brake. Background Technique

[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, these two favorable factors have led to its increasing acceptance in the market and growing demand in recent years. 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 transmit the braking force of the brake chamber to the brake shoe to lock the brake drum by the brake shoe, meeting the automotive braking requirements; the second is to realize the real-time adjustment of the braking gap to keep the gap between the brake lining on the brake shoe and the brake drum constant.

[0004] During the braking process and the brake release process of the brake, the piston moves back and forth along the piston channel of the housing with a high movement frequency. To ensure smooth high-frequency movement without jamming, good cooperation and lubrication are required between the two.

[0005] Since the expander is installed inside the brake drum and completely enclosed, it is severely affected by the high temperature of the brake drum, and the sheath is often damaged due to high temperature. At this time, the grease between the piston and the housing will volatilize, resulting in insufficient lubrication between the piston and the housing and movement jamming. Once jamming occurs, it is very difficult for the brake shoe to return, resulting in the brake being locked by the brake shoe and unable to release the brake.

[0006] In addition, to prevent the inner side of the brake drum from being contaminated by artificially adding grease later (which is absolutely unacceptable), no grease filling hole is designed. Therefore, during the entire life cycle of the expander, except when assembling, grease is applied to the inner and outer sides of the piston 3, and no grease is added later. Due to the high-frequency movement of the piston, the only pre-applied grease is easily consumed. Coupled with the fact that metal powder and grease are mixed together due to the early running-in between the piston and the housing, and there is no place to accommodate these metal powders, they exist on the cylindrical surface of the two, which easily leads to jamming faults between the piston and the housing. Content of the Utility Model

[0007] The purpose of the utility model is to provide a wedge expander for a drum brake with reasonable design to solve the technical problems mentioned in the background technique.

[0008] To achieve the above object, the present utility model provides the following technical solution: A wedge expander for a drum brake, comprising a housing and a push rod and a piston disposed within the housing. When the push rod moves, it can drive the piston to reciprocate within the housing; an oil storage groove is formed on the surface of the piston.

[0009] Preferably, the oil storage groove is a plurality of annular grooves distributed on the surface of the piston. The advantage of the annular groove is that a large amount of oil can be pre-stored during assembly.

[0010] Preferably, the oil storage groove is a spiral groove or a concave pit.

[0011] Preferably, one end of the push rod close to the piston is a wedge-shaped conical surface, and a roller is provided between the wedge-shaped conical surface of the push rod and the opposite end surface of the piston. When the push rod moves, it drives the roller to move laterally, thereby pushing the piston to move.

[0012] Preferably, the end surface of the piston close to the push rod is an inclined surface.

[0013] Preferably, an inner hole is formed inwards from the outer end surface of the piston, and a ratchet wheel and an adjusting nut capable of rotating around the axis of the piston are provided within the inner hole. Matching one-way teeth are provided on the opposite surfaces of the ratchet wheel and the adjusting nut, such that the ratchet wheel and the adjusting nut can only rotate in one direction; a spiral guide groove is provided on the surface of the ratchet wheel, and a limit pin matching the spiral guide groove is fixedly provided on the housing; an adjusting bolt passes through the middle of the ratchet wheel and the adjusting nut, the adjusting bolt can move along the axis of the piston, and the adjusting bolt is threadedly coupled to the adjusting nut.

[0014] Preferably, a top block is fixedly provided at the outer end of the adjusting bolt.

[0015] Preferably, a sheath is provided at the outer end of the piston.

[0016] Compared with the prior art, the beneficial effects of the present utility model are as follows: By providing an oil storage groove on the surface of the piston, the present utility model can timely supplement the consumed oil and ensure good lubrication performance; in addition, when metal debris or powder is generated due to running-in between the piston and the housing, these metal debris or powder can be accommodated in the above-mentioned oil storage groove, thereby reducing the probability of jamming between the piston and the housing. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic structural diagram of a drum brake.

[0018] Figure 2 is a schematic internal structure diagram of the wedge expander in the present utility model.

[0019] Figure 3 is a schematic structural diagram of the adjusting nut in the present utility model.

[0020] Figure 4 It is a schematic structural view of the ratchet wheel in the present utility model.

[0021] Figure 5 It is the position transformation of the gap H during the braking process in the present utility model Figure 1 .

[0022] Figure 6 It is the position transformation of the gap H during the braking process in the present utility model Figure 2 .

[0023] Figure 7 It is a schematic structural view of the groove structure on the piston surface in the present utility model. Specific embodiments

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

[0025] Embodiment: A wedge expander for a drum brake, referring to Figure 2-7 , the main structural components of the wedge expander are a housing 1, a push rod 2, a piston 3, an adjusting nut 4, a top block 5, an adjusting bolt 6, a ratchet wheel 7, a limit pin 8, a roller 9, and a sheath 10.

[0026] The push rod 2 is arranged in the relative middle of the housing 1 and is connected to the output end of the brake chamber. The bottom end thereof is in the shape of a wedge-shaped conical surface 2a. There are two pistons 3. Piston channels 1a are respectively opened on the left and right sides of the housing 1. The pistons 3 are respectively movably arranged in the piston channels 1a; the end surface of the piston 3 close to the center is in the shape of an inclined surface 3a, and a roller 9 is arranged between the wedge-shaped conical surface 2a of the push rod and the inclined surface 3a of the piston. The roller 9 can move horizontally. When the air chamber pushes the push rod 2 to move downward, at this time, the wedge-shaped conical surface 2a at the lower end of the push rod 2 pushes the two rollers 9 to both sides, and the two rollers 9 act on the inclined surface 3a of the piston 3, pushing the pistons 3 on both sides to the left and right sides, so as to open the brake shoes connected to the pistons to both sides around the brake shoe pins, and lock the brake drum to achieve braking.

[0027] In this embodiment, an inner hole is opened inward on the outer end surface of the piston 3, and a ratchet wheel 7 and an adjusting nut 4 that can rotate around the piston axis are arranged in the inner hole. As Figure 3 , 4 shown, a ratchet one-way tooth 7a is arranged on the surface of the ratchet wheel 7 opposite to the adjusting nut 4. Correspondingly, a matching adjusting nut one-way tooth 4a is arranged on the corresponding end surface of the adjusting nut 4, so that the ratchet wheel 7 and the adjusting nut 4 can only rotate relative to the left direction and cannot rotate relative to the right direction.

[0028] The surface of the ratchet wheel 7 is provided with a spiral guide groove 7b, and a limit pin 8 (a relief groove for the limit pin 8 to pass through is also correspondingly opened on the surface of the piston 3) matching the spiral guide groove 7b is fixedly arranged on the housing 1. When the ratchet wheel 7 moves horizontally along with the piston, the rotation of the ratchet wheel 7 can be realized through the cooperation between the limit pin 8 and the spiral guide groove 7b.

[0029] An adjusting bolt 6 is passed through the middle of the ratchet wheel 7 and the adjusting nut 4, and the adjusting bolt 6 is threadedly connected with the adjusting nut 4. A top block 5 is fixed to the outer end of the adjusting bolt 6 through a stop circlip. A sheath 10 is arranged outside the piston 3 and its components to protect the internal components. And the circumferential freedom degree of the adjusting bolt 6 is restricted in the system.

[0030] During the braking process, first, the piston 3 moves towards both sides, pushing the brake shoes to open outwards and approaching the brake drum to eliminate the normal clearance. The so-called normal clearance is the clearance reserved in the design between the brake and the brake lining, which is the clearance value that must be guaranteed. At this time, the piston 3 drives the ratchet wheel 7 to move outwards by a corresponding distance. At this time, the gap H between the original limit pin 8 and the spiral guide groove 7b changes from the end close to the inner side (see Figure 5 ) to the end close to the outer side (see Figure 6 ).

[0031] If the braking clearance is not eliminated at this time, it means that there is an excessive clearance between the brake shoe lining and the brake drum (this is the clearance that needs to be eliminated, otherwise it will cause adverse braking reactions). Under the action of the roller 9, the piston 3 continues to move towards both sides, and the adjusting nut 4 and the ratchet wheel 7 also continue to move outwards. At this time, due to the limiting and guiding action of the limit pin 8, the ratchet wheel 7 rotates clockwise by an angle. Until the braking clearance is completely eliminated and the braking function is completed. During this process, the ratchet wheel 7 does not drive the adjusting nut 4 to rotate.

[0032] When the braking release function needs to be completed, the push rod of the brake chamber retracts, the push rod 2 moves upwards, the acting force on the piston 3 disappears, and the return spring acting on the brake shoe pulls the brake shoe to rotate inwards around the brake shoe pin, pressing the adjusting bolt 6, thereby driving the whole piston 3 to move towards the center of the expander.

[0033] At this time, the gap between the spiral guide groove 7b of the ratchet wheel 7 and the 8 limit pins (see Figure 5 ) turns from the outer side to the inner side. At this time, the normal clearance value appears between the brake lining and the brake drum.

[0034] Since the piston 3 has not returned to the initial position at this time, the brake shoe will continue to press the piston 3 to move inwards. During this process, the ratchet wheel 7 rotates counterclockwise under the action of the limit pin 8. Due to the interaction of the one-way teeth between the ratchet wheel 7 and the adjusting nut 4, the adjusting nut 4 is driven to rotate counterclockwise.

[0035] When the adjusting nut 4 rotates leftward, since the adjusting bolt 6 cannot rotate, the adjusting bolt 6 extends outward by a certain distance. When the piston 3 returns to the initial position, the adjusting bolt 6 does not return to the initial position, nor does the brake lining return to the initial position, thus reducing the braking gap.

[0036] After repeating this process many times, the braking gap is adjusted to the normal gap value range.

[0037] In this embodiment, multiple annular grooves 3b are added to the outer circle of the piston 3, as Figure 7 shown. Adding multiple annular grooves 3b has two advantages: First, a large amount of grease can be pre-stored during assembly. The grease can be stored in these annular grooves 3b, and the consumed grease can be replenished in a timely manner to ensure good lubrication performance. Second, when metal debris or powder is generated due to running-in between the piston 3 and the housing 1, it can be accommodated in the annular grooves 3b, thereby reducing the probability of jamming between the piston 3 and the housing 1.

[0038] Of course, in other embodiments of the present invention, the shape of the grease storage groove can also be a spiral groove or a concave pit, etc. These structures can all play the role of storing grease and accommodating foreign objects.

[0039] The above embodiments are only for explaining the technical concept and features of the present invention, and their purpose is to enable those who are familiar with this technology to understand the content of the present invention and implement it accordingly. It should not be used to limit the protection scope of the present invention. Any 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 for a drum brake, comprising a housing, a push rod and a piston arranged in the housing, wherein the push rod can drive the piston to reciprocate in the housing when moving; characterized in that: A grease storage groove is provided on the surface of the piston.

2. A wedge expander for drum brakes according to claim 1, characterized in that: The grease storage grooves are multiple annular grooves distributed on the surface of the piston.

3. A wedge expander for drum brake according to claim 1, characterized in that: The grease storage groove is a spiral groove or a concave pit.

4. A wedge expander for a drum brake according to any one of claims 1 to 3, characterized in that: The end of the push rod close to the piston is in a wedge-shaped conical surface, and a roller capable of horizontal movement is arranged between the wedge-shaped conical surface of the push rod and the opposite end surface of the piston.

5. A wedge expander for drum brake according to claim 4, characterized in that: The end surface of the piston close to the push rod is an inclined surface.

6. A wedge expander for a drum brake according to any one of claims 1 to 3, characterized in that: An inner hole is formed inwardly on the outer end surface of the piston, and a ratchet and an adjusting nut which can rotate around the piston axis are arranged in the inner hole, and mutually matching one-way teeth are arranged on the opposite surfaces of the ratchet and the adjusting nut, so that the ratchet and the adjusting nut can only rotate in one direction; A spiral guide groove is provided on the surface of the ratchet, and a limit pin matching the spiral guide groove is fixedly provided on the housing; An adjusting bolt is inserted between the ratchet and the adjusting nut, and the adjusting bolt is threadedly connected with the adjusting nut.

7. A wedge expander for drum brakes according to claim 6, characterized in that: A top block is fixedly arranged on the outer end of the adjusting bolt.

8. A wedge expander for drum brakes according to claim 7, characterized in that: A sheath is provided at the outer end of the piston.

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