The gearbox is one of the important transmission components of the wheel loader. It is responsible for transmitting the speed and torque transmitted from the engine to the final drive system, changing the transmission ratio between the engine and the wheel, and realizing the forward and reverse gear operation of the loader. The power transmitted to the running device can be cut off when the engine is running, so as to adapt to the needs of the loader operation and driving, and the engine starting and parking safety is facilitated.
However, during the operation of the loader, the gearbox failure rate caused by improper use and maintenance has been high, especially in the use of strict maintenance procedures, lack of timely inspection and daily maintenance, will accelerate the transmission damage And the formation of faults, and even increase the harm of the consequences of failure.
First, the purpose of preventive maintenance
1. Through the follow-up inspection of the loader operation, stop the plan in a planned manner, and make maintenance and repair arrangements for the gearbox.
2, to prevent major mechanical failures and related parts damage, repair before the failure of the germination, to save a lot of maintenance costs.
3. Make the whole machine parts have a long service life, improve the efficiency of the equipment machine and maintain good working performance.
4. Reduce maintenance difficulty and workload.
Second, the common faults and causes of the wheel loader gearbox
1. When the gear is engaged, it cannot enter the gear smoothly. The reasons are:
(1) The pressure of the pressure valve is too low;
(2) The hydraulic pump is in poor working condition and the sealing is not good;
(3) The hydraulic line is blocked;
(4) The clutch seal ring is damaged or leaked;
(5) The stop valve stem is not in place.
2. When the gearbox is shifting, the gear can't be opened. The reasons are:
(1) The piston ring swells;
(2) The clutch friction plate is burnt;
(3) The clutch return spring is invalid or damaged;
(4) The return line is blocked.
3. The gear has been hung up, but the loader is running weak and can't even walk. The reasons are:
(1) The friction plate is seriously worn and the gap is too large;
(2) The clutch automatic empting valve is not tightly sealed, so that the pressure is lowered;
(3) The pipeline of the shift control valve is blocked;
(4) The shut-off valve cannot be returned;
(5) The shifting valve positioning spring is fatigued or broken, and the steel ball is beating;
(6) Clutch piston ring, the seal ring is seriously worn, causing serious leakage.
4. The operating pressure is too low. The reasons are:
(1) The oil content of the transmission oil sump is insufficient;
(2) The main oil passage leaks oil;
(3) The transmission filter is clogged;
(4) The steering pump (or hydraulic pump) is damaged, causing serious internal leakage;
(5) The pressure of the transmission pressure regulating valve is improperly adjusted;
(6) The spring of the load pressure valve is broken or broken.
5. The gearbox is automatically disengaged or disordered. The reasons are:
(1) The shifting control valve positioning device fails, and the main cause of the failure is that the positioning steel ball is seriously worn or the spring fails;
(2) Due to long-term use of the shift lever, the position and length of the rod change, and the proportion of the rod is inaccurate, which causes deviations in 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 and repair, the following rules should be followed:
(1) Daily maintenance: check the low oil level of the oil;
(2) 50 hours (or weekly): Check if the shift control handle is flexible and effective;
(3) 250 hours (only after the first 250 hours of work): cleaning the transmission oil sump and the gearbox filter element;
(4) 500 hours: clean the oil pan filter and replace the gearbox oil;
(5) 2000 hours: Check and repair the gearbox and torque converter.
2. 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 transmission, Pay special attention to the inspection and replacement of hydraulic transmission oil.
(1) Fixed oil change interval
Changing oil at the right time intervals is the key to getting the longest working life of the components in the gearbox. Lubrication and protection of lubricating oils can only be achieved if a reasonable oil change interval is ensured. Under normal circumstances, it should be based on the maintenance cycle recommended by the whole machine manufacturer, but this can only be relative. It must be combined with the oil sample extraction analysis results to know the actual working conditions. For example, in the maintenance manual, the oil change interval of the gearbox is 500h. According to the operation of the loader, the oil sample is sampled every 250h or 100h to determine when to change the oil, but the oil should be used up to 1000h. Replace it now.
In addition to regular replacement of new oil, in the usual inspection, if the oil is found to be deteriorated or mixed with impurities, it should also be cleaned and replaced with new oil.
(2) Adopt the correct row and oil change method
When draining oil, the oil temperature should reach 40~50 °C, and the oil flow should be discharged under agitation. The dirty oil should be drained as completely as possible. When refueling, the oil should be added by using a tanker with a filtering device.
(3) Use the correct transmission system oil, the lubricant used in the gearbox must meet the specifications. It should be noted that diesel engine oil cannot be added to the gearbox because the diesel engine oil will reduce the friction between the moving parts such as the piston, and the oil for the drive train should have a certain friction between the friction plates when they are combined. This friction is critical to the proper functioning of the drive train. Only when the lubricant is used correctly can the working life of the clutch friction plate be effectively extended. At the same time, the correct use of oil can significantly improve the anti-wear performance of the gear, eliminate the clutch slip phenomenon, control the tremor and abnormal noise of the brake, increase the braking force, and provide greater traction. At present, the most used hydraulic transmission oil for transmissions is 6#, 8# hydraulic transmission oil.
(4) Refer to the replacement filter period provided by the maintenance manual, replace the filter in time, clean the filter screen, drain the magnet plug, and vent plug, and fill the lubricant according to the standard amount. If the viscosity of the transmission oil is too large, the transmission transmission efficiency will be low, the fluidity is not good, and the heat dissipation is unfavorable, and local dry friction may occur between the parts moving at high speed, which is unfavorable lubrication; if the viscosity of the transmission oil is too small The leakage amount can be increased, causing the gearbox control oil pressure to be too low, forming a fault, and the oil film strength between the transmission components with large load is insufficient, causing early wear of the transmission component, and thus unfavorable lubrication.
At the same time, the gearbox generates a small amount of air bubbles due to the oil mixing of the gear during normal operation. In order to prevent the air bubbles from accumulating more, cavitation occurs, resulting in a decrease in the thickness of the oil film and affecting the operation of the internal clutch of the transmission and its control valve. The transmission oil must have anti-foaming properties.
Therefore, the use of appropriate gearbox oil can protect the gearbox, extend the life of the gearbox, reduce the failure rate of the gearbox, reduce the direct cost of the gear change and reduce the maintenance and maintenance of the gearbox. Parking time.
(5) All kinds of lubricating oils must be pure and precipitated after a period of time to meet the specified quality requirements.
Refueling tools, containers and oil filling ports should be cleaned to prevent moisture and dirt from entering the oil.
When checking the amount of oil, the vehicle must be horizontal in both the vertical and horizontal directions.
Be sure to check for oil leakage after refueling or oil change.
Therefore, it is necessary to strengthen the fault prevention and daily maintenance of the gearbox during daily use, which not only can reduce the work efficiency caused by the shutdown and maintenance, delay the working hours, but also prevent and avoid further follow-up faults. The occurrence, reduce maintenance costs, improve the safety of the machine.
