Causes of common failures of agricultural tractors
(1) Defects in parts. Early wear and tear of parts and components as the use of agricultural tractors increases, or due to improper use and maintenance. As the dimensional accuracy and mating properties of the parts change due to wear and tear, the relative position of some parts also changes. Under normal circumstances, the longer the farm tractor works, the more defects and failures there are due to wear and tear of the parts.
(2) Incorrect driving operation. The driver does not operate the agricultural tractor in accordance with the provisions of the agricultural tractor instruction manual. Here are some examples:
(1) The engine runs at low speed. The engine is running at low speed (2000 r/min) for a long time and is geared down below 2000 r/min. This will make the fuel burn incompletely, which is easy to cause carbon deposition in the combustion chamber and valve of the engine cylinder, causing the engine to shake or even stall when running at low speed. Today's engine design is completely different from what it used to be, with low-speed operation and low-speed upshifting to reduce wear and even save fuel. Nowadays, engine manufacturing technology and materials have been greatly improved, and low-speed operation will accelerate wear and increase fuel consumption.
(2) Cornering braking. When the vehicle passes through a curve, it brakes on the curve. This is easy to cause uneven wear of brake pads, vehicle skidding and tail flicking. The correct way is: release the throttle (accelerator) pedal before entering the corner, lightly step on the brake to achieve the purpose of deceleration, and accelerate in time to pass the curve smoothly and smoothly when passing through the curve 1/2 or 2/3 under the condition of ensuring the safety of driving ahead.
(3) Poor maintenance. Because the user does not pay attention to technical maintenance, can not be maintained in time or the maintenance quality is not high, resulting in accelerated wear and damage of parts, causing failure. If cooling water and lubricating oil are not added in time, the body will be overheated and lubricated poorly, resulting in serious wear and tear of parts, and even "pulling cylinders", "holding shafts" and "burning tiles".
(4) Improper assembly and adjustment. The parts and components of agricultural tractors have strict assembly and adjustment requirements, if they are not assembled and adjusted according to the regulations, the relevant components can not work normally and will cause failures. For example, cylinder liner piston clearance, valve clearance, timing gear chamber meshing clearance, oil supply advance angle, etc., if the assembly and adjustment are improper, the machine will not work normally or cannot work.
Inspection methods for common faults of agricultural tractors
(1) Partial cessation method. Stop the work of a certain part or a certain system, compare the changes in the fault signs before and after stopping the work, and judge the faulty part or the faulty part. For example, the cylinder break method is used for an engine to compare whether the parts of a cylinder are working properly.
(2) Cross-contrast method. When analyzing the fault, if there is doubt about the technical status of a certain part, it can be replaced with a spare part with normal technical status, and whether there is a change in the fault signs before and after the replacement to determine whether the cause of the fault is in the original part.
(3) Temptation. Change the technical state on a local scale to observe the change of fault signs to determine the cause of the failure. If the cylinder compression pressure is insufficient, it is suspected that the cylinder liner and piston are not well sealed, and a small amount of oil can be added to the cylinder, and if the engine pressure increases, the analysis is correct.
(4) Auscultation. This method is commonly used to judge abnormal noise, using a thin steel rod about 0.5 m long, one end is sharpened to touch the part to be inspected, and the other end is made into a circle and attached to the ear, so that the location and size of the abnormal sound of the machine can be heard more clearly. When the agricultural tractor is working normally, the sound emitted has its own special regularity. Temperature, speed, load and lubrication are some of the main factors that affect sound. Some engine noises appear or intensify as the temperature increases; Some sounds weaken or disappear as the temperature increases; There are also some noises, accompanied by fever. The sound has a certain relationship with the engine speed and the locomotive speed, generally when the engine sound is often changed, and the speed of the vehicle is constantly changed when the chassis sound is auscultated. The sound of the drivetrain generally increases with the speed of the vehicle, but sometimes the opposite is true. Depending on the load, the force between the parts will be different, and the sound will change. In general, the sound increases with the load, but some sounds decrease or disappear with the load. No matter what the sound is, it can be severe when the lubrication is poor.