Structure and Principle

Structural Composition: The semi-trailer series leaf springs are usually composed of several pieces of alloy spring steel sheets that are of equal width but unequal length (the thickness can be equal or unequal), forming an approximately uniformly strong elastic beam. Multi-leaf springs are stacked with steel sheets of different lengths but the same width, forming an inverted triangle shape; while single-leaf springs are stacked with steel sheets that are thin at both ends and thick in the middle, all of equal width and length.

Working Principle: When the leaf spring is installed in the semi-trailer suspension and bears vertical loads, each spring leaf deforms under stress, tending to arch upwards, bringing the axle and the frame closer together; when the axle and the frame move apart, the positive vertical load and deformation on the leaf spring gradually decrease, sometimes even reversing.

Function and Role

Damping and Shock Absorption: It can effectively buffer and absorb the impact and vibration energy generated during the semi-trailer operation due to uneven road surfaces and other factors, reducing damage to the vehicle body and cargo, and improving driving smoothness.

Support and Load Bearing: It bears the weight of the semi-trailer body and the cargo, evenly distributing the weight onto the axle, ensuring the stability and safety of the vehicle during operation.

Guidance and Positioning: One end is hinged to the frame, capable of transmitting various forces and moments, and determining the bouncing trajectory of the wheels, playing a guiding role to keep the wheels in the correct direction of movement.

Maintenance and Care

Regular Inspection: Regularly check the leaf springs for cracks, fractures, significant thinning, etc. If such issues are found, they should be replaced in a timely manner; also check if the elasticity of the leaf springs has diminished, which can be judged by inspecting changes in their curvature. If elasticity has decreased, reshaping can be done in a cold state, followed by appropriate heat treatment to restore elasticity, and shot peening can be performed on the concave surface to improve fatigue strength.

Lubrication Treatment: Regularly lubricate the leaf springs, generally after the break-in period of new vehicles and during the summer and winter seasons when in use. During lubrication, first remove the leaf spring, open the central through bolt to spread the steel sheets, then evenly apply lithium-based grease or graphite grease on both sides of the steel sheets. After reassembly, an oil film can form between the two friction surfaces, reducing friction, preventing rust, and avoiding a decrease in elastic strength.

Inspection of Other Components: Check the wear of the leaf spring pins and bushings; if the gap is greater than 1 millimeter or if the rubber bushing is damaged, they need to be replaced with new ones; check if the riding bolts are deformed or damaged, and replace them promptly if damaged; check if the leaf spring clamps are broken or riveted, and replace them if necessary.