The gearbox is one of the important transmission components of the front end loader. It is responsible for transmitting the speed and torque from the engine to the final drive system, changing the transmission ratio between the engine and the wheels, and realizing the forward and reverse gear control of the loader. It can also cut off the power transmitted to the walking device when the engine is running, so as to meet the needs of the loader's operation and driving, and facilitate the safety of starting and stopping the engine.

However, in the working process of the loader, the failure rate of the gearbox caused by improper use and maintenance has been high, especially if the maintenance procedures are not strictly during use, and the lack of timely inspection and daily maintenance will accelerate the damage of the gearbox. The formation of faults and faults will even expand the harmfulness of the consequences of the faults.

1. The purpose of preventive maintenance

A. Through the follow-up inspection of the operation of the loader, shut down in a planned manner, and make arrangements for the maintenance and repair of the gearbox.

B. Prevent major mechanical failures and related parts damage, and repair them before the failures occur, so as to save a lot of maintenance costs.

C. Make the parts of the whole machine have a longer service life, improve the efficiency of the equipment and the machine, and maintain good working performance.

D. Reduce maintenance difficulty and workload.

2. Common faults and causes of wheel loader gearboxes

A. When gear is engaged, the gear cannot be entered smoothly. The reasons are:

(1) The pressure of the pressure valve is too low;

(2) The hydraulic pump works poorly and the seal is not good;

(3) The hydraulic pipeline is blocked;

(4) The clutch sealing ring is damaged or leaked;

(5) The gear lever is not in place.

B. When the gearbox is shifting, the gear cannot be disengaged. The reasons are:

(1) The piston ring swells to death;

(2) The clutch friction plate is burned out;

(3) The clutch return spring is invalid or damaged;

(4) The oil return line is blocked.

C. The gear has been engaged, but the loader is running weak and even unable to walk. The reasons are:

(1) The friction plate is severely worn and the clearance is too large;

(2) The clutch automatic emptying valve is not tightly sealed, causing the pressure to drop;

(3) The shift control valve pipeline is blocked;

(4) The shut-off valve cannot be returned;

(5) The positioning spring of the variable speed valve is fatigued or broken, and the steel ball bounces;

(6) The clutch piston ring and sealing ring are worn out seriously, causing serious leakage.

D. The operating pressure is too low. The reasons are:

(1) The amount of oil in the gearbox oil pan is insufficient;

(2) Oil leakage in the main oil passage;

(3) The filter of the gearbox is blocked;

(4) The steering pump (or hydraulic pump) is damaged, causing serious internal leakage;

(5) Improper pressure adjustment of the transmission pressure regulating valve;

(6) The gear-shifting pressure valve spring fails or breaks.

E. The gearbox is automatically out of gear or out of gear. The reasons are:

(1) The positioning device of the shift control valve fails, and the main cause of the failure is the serious wear of the positioning steel ball or the failure of the spring;

(2) The position and length of the shift control lever have changed due to long-term use, and the ratio of the levers is not Accurate, causing deviation of the operating position, resulting in misalignment.
Third, how to carry out preventive maintenance of the gearbox

1. According to JB/Z194-83, combined with the actual maintenance, the following regulations should be :

(1) Routine maintenance: check the oil level of the low oil shell;

(2) 50 hours (or weekly): check whether the speed control handle is flexible and effective;

(3) 250 hours (only after the first 250 hours of work): cleaning the gearbox oil pan and gearbox oil filter element;

(4) 500 hours: clean the oil pan filter and replace the transmission fluid;

(5) 2000 hours: check and repair the gearbox and torque converter disassembly.

2. The hydraulic transmission oil is the energy carrier for the normal operation of the gearbox. In the hydraulic transmission system, the pressure, temperature and flow of the working fluid determine whether the transmission can work normally. Therefore, in the daily maintenance work of the gearbox, Pay special attention to the inspection and replacement of hydraulic transmission oil.
(1) Fix the oil change interval to change the oil at the correct time interval is the key to get the longest working life of the parts in the gearbox. Only by ensuring a reasonable oil change interval can the lubricating and protective properties of the lubricating oil be brought into play. Under normal circumstances, it should be based on the maintenance period recommended by the manufacturer of the complete machine, but this can only be relative and must be combined with the results of the oil sample extraction analysis to know the actual working conditions. For example, the maintenance manual requires that the oil change interval of the gearbox is 500h. According to the operation of the loader, we sample and analyze the oil samples every 250h or 100h to determine when to change the oil. However, when the lubricating oil is used for 1000h, it should Replace immediately. In addition to regular replacement of new oil, if the oil is found to be deteriorated or mixed with impurities during usual inspections, it should also be cleaned and inspected and replaced with new oil.

(2) When using the correct method of draining and changing the oil, the oil temperature should reach 40～50℃, and the oil flow should be drained under agitation, and the dirty oil should be drained as thoroughly as possible; when refueling, use The oil dispenser of the filter device is used to add oil.

(3) Use the correct oil for the transmission system, and the lubricating oil used by the gearbox must meet the specifications. It should be noted that diesel oil cannot be added to the gearbox, because diesel oil will reduce the friction between moving parts such as pistons, while the oil used in the drive train must allow friction between the friction plates to have a certain amount of friction when they are combined. This frictional force is essential for the normal operation of the transmission system. Only the correct use of lubricating oil can effectively extend the working life of the clutch friction plate. At the same time, the correct use of oil can significantly improve the anti-wear performance of the gear, eliminate the phenomenon of clutch slip, control the tremor and abnormal noise of the brake, increase the braking force, and provide greater traction. At present, the most commonly used hydraulic transmission oils for gearboxes are 6# and 8# hydraulic transmission oils.

(4) Refer to the filter replacement cycle provided in the maintenance manual, replace the filter in time, clean the filter screen, the oil drain magnet screw plug, and the vent plug, and fill in the standard amount of lubricating oil. If the viscosity of the transmission oil is too high, it will cause low transmission efficiency, poor fluidity, and unfavorable heat dissipation, and there may be local dry friction between the relatively moving parts at high speed, which is unfavorable for lubrication; if the viscosity of the transmission oil is too small , It can increase the leakage, cause the transmission control oil pressure to be too low, cause failures, and the oil film strength between the transmission parts with heavier load is not enough, which causes the early wear of the transmission parts, which is also unfavorable for lubrication. At the same time, during normal operation of the gearbox, a small amount of air bubbles will be generated due to the stirring of the gear oil. In order to prevent the accumulation of bubbles and cavitation, the thickness of the oil film is reduced, which affects the operation of the internal clutch of the gearbox and its control valve. , Transmission oil must have anti-foaming properties. Therefore, the use of appropriate gearbox oil can protect the gearbox, extend the service life of the gearbox, reduce the failure rate of the gearbox, and reduce the direct cost of gearbox oil change and maintenance, and reduce the maintenance labor and maintenance of the gearbox. Parking time.

(5) All kinds of lubricating oil must be pure, and after a period of precipitation, meet the specified quality requirements. Oiling tools, containers and all oil filling ports should be scrubbed clean to prevent water and dirt from entering the oil. When checking the fuel level, the vehicle must be horizontal in both longitudinal and lateral directions. Be sure to check for oil leakage after refueling and oil change.

Therefore, it is very necessary to strengthen the failure prevention and routine maintenance of the gearbox during daily use. This can not only reduce the inefficiency and delays caused by shutdown and maintenance, but also prevent and avoid larger subsequent failures. Occurrence, reduce maintenance costs, and improve the safety of the machine.