The air brake clearance automatic adjustment arm is an automatic adjustment device for the clearance between the brake shoe and the brake drum of the air brake system, which ensures that the auto can automatically adjust the gap between the brake shoe and the brake drum in time when the brake pad is worn during driving. There is a gap between the two, so as to ensure that the auto has good braking performance and improve driving safety.
The adjusting arm housing is the support for the important parts of the entire adjusting arm. Two sets of worm gears, worms and self-adjusting mechanisms are located in it, and their mass accounts for most of the entire adjusting arm. If the mass of the adjusting arm housing is reduced, the entire adjusting the mass of the arm, making it lightweight
Parts in a high-quality slack adjustment arm should meet the following requirements
Clearance Adjustment Arm Housing
The force of the brake air chamber is then transmitted to the camshaft and the brake drum through the automatic adjustment arm. Therefore, it must have a certain strength to prevent the casing from breaking and deforming due to insufficient strength and braking failure. Another function of the housing is to enclose the adjustment mechanism in it, which is well protected to avoid moisture, dirt or collisions. Due to the harsh working environment, the surface of the shell itself needs to have a considerable anti-rust treatment (the surface is treated with phosphating belt spray paint). In terms of metal processing, the opening of the worm hole and the worm gear hole must be guaranteed, so as to avoid excessive tolerance of the worm gear and the worm gear, which will affect the automatic adjustment. At the same time, the coaxiality requirements of the stepped holes of the worm must be guaranteed. Different manufacturers and different models have different lengths and directions of the adjustment arms.
Worm and worm gear in automatic adjustment arm
As a transmission part, its strength is required, there should be no obvious deformation under the action of 2.5T force, and there should be no hairpin phenomenon. Especially the worm requires toughness as a whole. The concentricity of 90 small teeth and the outer circle is high, and the tip of the tail end is 120 degree , which has hardness requirements. The hardness of worm gear teeth cannot be too low or too high, too low is easy to deform, too high is easy to break the teeth
One-way clutch in slack adjustment arm
The one-way clutch is composed of a clutch ring, a rectangular spring, and a gear, which mainly converts the linear motion of the rack into axial rotation. The contraction or expansion of the outer circle when the rectangular spring is used for forward and reverse rotation. Disengagement and slippage of the one-way clutch during braking and engagement of the one-way clutch during braking return. In order to better fulfill the requirements of the one-way clutch mentioned above, the rectangular spring must have considerable toughness and strength. Avoid slippage due to wear when combined; the inner teeth of the clutch ring and the inner teeth of the gear should be sharp-in order to increase the coefficient of friction.
Control panel assembly for clearance adjustment arm
The control panel is fixed on the axle. As a base point for adjustment, the riveting panel and the control panel have specific requirements for riveting, and the opening of the control panel directly reflects the inherent gap of its adjustment. Its opening varies due to different manufacturer requirements.
Compression spring for adjusting arm cone clutch
The cone clutch consists of small teeth at the end of the worm and 90 small teeth in the clutch ring. When the adjusting arm is in the elastic region, the cone of the worm is disengaged from the clutch ring (disengaged state). The worm is displaced axially against the pressure of the compression spring. When returning, the braking torque decreases, the compression spring returns to its original state, and the conical clutch is combined. Its function is to ensure that the error caused by elastic deformation does not occur when recording and adjusting the excess clearance. It requires 90 small teeth to have hardness and toughness. The tooth profile is clear and uniform to prevent slippage. The compression spring is an important control that directly affects the accuracy of the adjustment arm adjustment. The permanent deformation should be as small as possible (less than 0.25 percent ) to prevent compression deformation, and its manufacturing process is relatively complicated.
Spring seat in slack adjustment arm
It is installed between the compression spring and the worm, and its main function is to transmit the pressure of the compression spring to the worm. It should have corresponding hardness requirements, and the deformation of Party B will affect the pressure. At the same time, the boss should have good wear resistance
Clearance adjusting arm rack
The main purpose is to accurately transmit the excess time to the gear, which requires considerable strength. The thickness of its convex end affects the adjustment and setting clearance.
Summarize the overall requirements of the automatic adjustment arm
Self-adjusting arms as part of the braking device. Installed between the brake chamber and the camshaft. Automatically adjust the gap between the brake drum and the friction lining, so that it is always within the set range. Must be waterproof, dustproof and corrosion resistant. Its appearance should not have harmful scars, cracks, etc. in use. For specific requirements, please refer to the standard for the automatic adjustment arm of the external brake clearance for urban buses.
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