Shandong FUHUA Axle Co., Ltd. used more than 20 years of experience in the production of automotive front axles to find that the brake shoes of cars and light trucks are widely made of T-shaped steel rolled or welded with steel plates, and the brake shoes of heavy trucks are mostly cast iron or cast. Cast steel. The cross-sectional shape and size of the brake shoe should ensure its rigidity. However, the brake shoe web made of steel plates for small cars often has one or two radial grooves to make the bending rigidity of the shoe smaller. Its purpose is to wear the lining more uniformly and reduce the screaming during braking sound.
According to relevant information, the thickness of the web and flange of the brake shoe is 5mm. In order to improve efficiency, increase the service life of the brake shoe and reduce wear, the cast brake shoes of the medium and heavy trucks are near the end of the open cam It is provided with a roller or a shim supporting the expansion cam. Brake shoes and friction plates can be riveted or bonded. The advantage of bonding is that the thickness of the lining is allowed to wear before replacement, and its disadvantage is that the process is more complicated and it is not easy to replace the lining. The noise of riveting is small.
Friction lining (liner) The material of the friction lining (liner) should meet the following requirements:
Has a certain stable friction factor. When the temperature, pressure and working speed change, the friction factor changes as small as possible.
(1) Has good wear resistance. Not only should the friction lining (block) have a sufficient service life, but the wear of the dual friction pair should also be as small as possible.
(2) The compression rate and expansion rate should be as small as possible. Too much compression deformation affects the displacement and pedal stroke of the master cylinder, reducing braking sensitivity. If the thermal expansion is too large, friction linings and brake discs must be dragged, especially after the drum brake linings are thermally expanded to eliminate the gap, it may cause a seizure phenomenon.
(3) It is not easy to produce noise when braking, and it has no pollution to the environment.
(4) Friction materials that are harmless to the human body should be used.
(5) It has high compressive strength and impact strength, and sufficient shear resistance.
The thermal conductivity of the friction pad should be controlled within a certain range. Previously, brake friction linings used asbestos friction materials composed of reinforcing materials, adhesives, and friction performance modifiers. It has the advantages of easy manufacturing, low cost, and not easy to scratch the dual, because it has poor heat resistance, with the temperature and sound, the friction factor is reduced, the wear is increased, and the environment is polluted, especially asbestos can cause cancer, so it has gradually Suffer from elimination. The semi-metal friction material composed of metal fiber, binder and friction performance modifier has high heat resistance and wear resistance, especially because it has no pollution from asbestos dust, and has been widely used recently. Powder metallurgy inorganic metal friction material, although it has the advantages of good heat resistance and stable friction performance, but its manufacturing process is complex, high cost, easy to produce noise and scratches and other shortcomings, currently not widely used, only used for On heavy trucks.
?Automatic gap adjustment device between brake drum and lining (block) In order to ensure that the brake drum can rotate freely when not braking, a certain gap must be maintained between the brake drum and the brake lining (block). The amount of this gap should be as small as possible, because many performances of the braking system are affected by this gap. In use, this gap is increased due to wear, and an excessively large gap will bring many adverse consequences:
The time for the brake to produce a braking effect increases; due to the different wear and the different gaps of the brakes, the time for the brake to produce a braking effect is different, that is, the synchronous braking performance is deteriorated; the consumption of compressed air or only fluid is increased, and Increase the stroke of the brake pedal or handle. In order to ensure that the initially set gap between the brake drum and the brake lining (block) is always used, it is required to adopt an automatic gap adjustment device. Now, the gap adjustment of the disc brake has been automated, and the automatic adjustment of the gap used in the drum brake is also increasing.