Structure and operation essentials of huayu semi trailer
be held to ground independently by using supporting device. The semi trailer is mainly composed of frame, wagon box, traction device,
braking device, axle assembly, electrical system, etc.
framework structure assembled by welding components such as H longitudinal beam（16Mn special steel plate welded by using
automatic submerged arc welding machine），cross beam，horizontal beam and side beam. It is featured by its proper structure，
be manually separated from tractor by pushing control handle to splay the locking block with longitudinal pivot angle of士12.On
the surface of the fifth wheel, there is an oil container for storing lubrication grease to decrease the abrasion between fifth wheel
and traction plate. The fifth wheel is divided into two kinds of 50# and 90# to match the traction pins of different specifications.
3. Supporting Device (Figure 1一3一1)
single-drive form.With nearly identical structure, the two forms are both composed of base, lead-screw driving mechanism, internal
square cylinder, external square cylinder, gearbox, operating crank, etc. The driven support leg of tandem drive type has no gearbox and
is connected to driving support leg via drive connecting rod. By twisting crank, the supporting device will be lifted or lowered with two-speed
The suspension system is divided into two-axle or three-axle balanced steel-plate spring suspensions. The steel-plate spring
is fixed on the axle by using U-bolts with both ends stuck in the frame support and tandem connection enabled by balance arm
which will freely sway in a certain range to enable the balance of axle loading in a certain range. The steel plate spring mainly support the vertical gravity on the frame.and the horizontal acting force is transmitted by lower support and pullrod.Through
adjusting the pull rod, the two axles can be adjusted in parallel to avoid the exceptional abrasion to the tire.
5. Air Brake Assembly (Figure 1-5一la，1-5一1b)
With dual-line braking system, the semi-trailer is mounted with an emergency relay valve which is a device for the normal driving
braking and automatic emergency braking.
5.1 Air Charging and Safety Braking
When the air compressor is on, the air cylinder is charged through air charging line a via emergency relay valve 4. When the air pressure
is below 392Kpa, some compressed air will pass emergency relay valve and enter brake chamber to enable the brake to work. When the
air pressure is above 392Kpa, the brake will be disabled by emergency relay valve and the air cylinder will be charged with air.
5.2 Service Brake
By stepping down the brake pedal, the compressed air will pass manipulation line band enter the control chamber of emergency valve to
open the compressed air path and enable the air-charging of brake chamber and the brake to work. By releasing the brake pedal, the brake
5.3 Emergency Braking
When the leaking air pressure of air-charging line is below 392Kpa or the line is broken because the tractor accidentally detaches from semi-
trailer on driving, the compressed air in the air cylinder will pass emergency relay valve and enter the brake chamber to enable the brake to
work and the semi trailer to automatically brake.For the semitrailer using energystorage brake chamber, the gas circuit can be controlled by
manual brake valve to stop and break the vehicle. The relief valve of trailer ensures the semi-trailer can quickly relieve the parking
mode in the failure state. The quantity of energy-storage brake chamber shall not less than 2.
The axle assembly is the component used for bearing, driving and braking, which is mainly composed of tire, wheel, wheel hub, brake and axle.
7. Electrical System
to tractor by using the cable with 7pin socket. On the sides of semitrailer there are side signal lights and side steering lights. At the rear,
there are lighting and signal devices for driving, braking, reversing, steering, fog light, license plate, etc.
The semi-trailer manufactured by our company adopts the suspension-chain spare-tire lift. When using it, first lower the chain of the spare-tire chain to the proper position then mount the lift bracket on the center of the wheel rim, twist the crank clockwise to enable the
spare tire to rise via the chain and fasten the nut on the bracket when reaching the required position. Reversely, twist the crank
counter-clockwise and the spare tire will be laid down.