A ZL50 loader adopts hydraulic and hydraulic mechanical transmission, featuring stable shifting, large transmission ratio, high working efficiency and stepless speed change. It is widely used. The transmission uses a planetary gear-type power shift transmission, and the shift operating system is hydraulic. In the use, there is sometimes a shift shock failure, that is, the loader cannot start smoothly after shifting, but a short power transmission interruption occurs and then suddenly combines to cause a load shock phenomenon. The hydraulic transmission method involves the coupling of the hydraulic transmission and the mechanical transmission, and the analysis of the cause of the failure is difficult. Based on the analysis of the working principle of the transmission control system, this paper proposes a fault analysis and judgment method, which solves many similar faults in practical applications.
1, failure analysis
The shift operating hydraulic system of the ZL50 loader transmission is shown in Figure 1. The shift control valve is mainly composed of a main pressure valve, a spring accumulator, a reversing valve and a brake release valve. The function of the main pressure valve is to ensure that the proper oil pressure (1.1-1.5 MPa) of the transmission control valve leads the pressure oil to the shift control valve on the one hand and to the torque converter on the other hand, when the oil pressure is too high Safeguarding. The reversing valve is used to control the operation of 2 brakes and 1 clutch, so that different gears can be changed according to the needs of use. The brake release valve is used to automatically disengage the transmission when braking, thereby enhancing the braking effect and reducing power consumption.
The key components to ensure a smooth shifting of the loader are the spring accumulator and the main pressure valve. The working principle: the piston at the end of the accumulator is installed in the piston cylinder, the right end (lower in the figure) is placed on the spring, and the right end of the large and small springs are respectively placed on the main pressure valve and the boss of the housing. An oil chamber A is formed between the left end of the piston and the screw plug of the end portion, and communicates with the communication oil passage of the reversing valve through the oil passage. A check valve and an orifice are provided in this oil passage. When shifting, the hydraulic pressure of the oil passage flows into the cylinder of the shifting clutch, so that the oil pressure in the oil passage is lowered, and the oil chamber of the accumulator oil chamber A replenishes the oil through the check valve to quickly combine the brake or the clutch. At the same time, due to the oil outflow of the oil chamber A, under the action of the main pressure valve control oil passage (ab), the valve stem is moved to the left to lower the oil pressure of the system. When the main and driven discs are in close contact, the cylinder stops moving and the oil pressure rises. A part of the oil flows through the orifice to the oil chamber A. The pressure of the oil chamber A gradually rises, pushing the piston to the right, compressing the spring, and the valve stem of the main pressure valve is moved to the right, so that the oil pressure of the system is gradually increased, so that The main and driven components are combined smoothly to achieve smooth and *shifting.
The function of the check valve is to replenish the oil of the shift brake or the clutch cylinder in time to make the shift quickly. At the same time, after the oil is replenished, the valve stem of the main pressure valve is moved to the left to reduce the pressure of the system at the start of the shift. The function of the orifice is to gradually increase the pressure of the system after shifting, so that the main and driven friction plates of the shift brake or the clutch are gradually pressed, so that the shift is soft and shock-free.
It can be seen from the analysis of the action process of the shift control valve when shifting above, the smooth shifting requires the cooperation of the spring accumulator and the main pressure valve, so that the oil pressure gradually rises after shifting. If there is no spring accumulator and the check valve and orifice on the oil passage, it can also shift gears, but the shifting process will have an impact because there is no system oil pressure first drop and then rise.
In practice, if there is a shift shock, check the orifice of the check valve on the valve body between the ends of the oil chamber A for blockage. It can be dredged with compressed air or fine copper wire. In addition, since only the piston of the spring accumulator and the valve stem of the main pressure valve can change the oil pressure of the system, it is also necessary to check whether the piston and the stem are stuck. According to practical experience, if the oil circuit system is not cleaned according to the specified time, too much oil impurities will easily lead to blockage of the orifice and the piston being stuck. This is a common cause of shifting shocks.
2, matters needing attention
In order to ensure that the loader performance of the loader is intact, the following items should be noted during use.
1) The degree of cleanliness of the transmission fluid has a certain influence on the performance of the transmission control valve. Therefore, the hydraulic oil must be replaced according to the specified cycle to clean the oil sump.
2) The main pressure valve has been debugged when the machine is shipped from the factory, taking care not to damage its balance. If the part is replaced, it must be re-adjusted carefully.
1, failure analysis
The shift operating hydraulic system of the ZL50 loader transmission is shown in Figure 1. The shift control valve is mainly composed of a main pressure valve, a spring accumulator, a reversing valve and a brake release valve. The function of the main pressure valve is to ensure that the proper oil pressure (1.1-1.5 MPa) of the transmission control valve leads the pressure oil to the shift control valve on the one hand and to the torque converter on the other hand, when the oil pressure is too high Safeguarding. The reversing valve is used to control the operation of 2 brakes and 1 clutch, so that different gears can be changed according to the needs of use. The brake release valve is used to automatically disengage the transmission when braking, thereby enhancing the braking effect and reducing power consumption.
The key components to ensure a smooth shifting of the loader are the spring accumulator and the main pressure valve. The working principle: the piston at the end of the accumulator is installed in the piston cylinder, the right end (lower in the figure) is placed on the spring, and the right end of the large and small springs are respectively placed on the main pressure valve and the boss of the housing. An oil chamber A is formed between the left end of the piston and the screw plug of the end portion, and communicates with the communication oil passage of the reversing valve through the oil passage. A check valve and an orifice are provided in this oil passage. When shifting, the hydraulic pressure of the oil passage flows into the cylinder of the shifting clutch, so that the oil pressure in the oil passage is lowered, and the oil chamber of the accumulator oil chamber A replenishes the oil through the check valve to quickly combine the brake or the clutch. At the same time, due to the oil outflow of the oil chamber A, under the action of the main pressure valve control oil passage (ab), the valve stem is moved to the left to lower the oil pressure of the system. When the main and driven discs are in close contact, the cylinder stops moving and the oil pressure rises. A part of the oil flows through the orifice to the oil chamber A. The pressure of the oil chamber A gradually rises, pushing the piston to the right, compressing the spring, and the valve stem of the main pressure valve is moved to the right, so that the oil pressure of the system is gradually increased, so that The main and driven components are combined smoothly to achieve smooth and *shifting.
The function of the check valve is to replenish the oil of the shift brake or the clutch cylinder in time to make the shift quickly. At the same time, after the oil is replenished, the valve stem of the main pressure valve is moved to the left to reduce the pressure of the system at the start of the shift. The function of the orifice is to gradually increase the pressure of the system after shifting, so that the main and driven friction plates of the shift brake or the clutch are gradually pressed, so that the shift is soft and shock-free.
It can be seen from the analysis of the action process of the shift control valve when shifting above, the smooth shifting requires the cooperation of the spring accumulator and the main pressure valve, so that the oil pressure gradually rises after shifting. If there is no spring accumulator and the check valve and orifice on the oil passage, it can also shift gears, but the shifting process will have an impact because there is no system oil pressure first drop and then rise.
In practice, if there is a shift shock, check the orifice of the check valve on the valve body between the ends of the oil chamber A for blockage. It can be dredged with compressed air or fine copper wire. In addition, since only the piston of the spring accumulator and the valve stem of the main pressure valve can change the oil pressure of the system, it is also necessary to check whether the piston and the stem are stuck. According to practical experience, if the oil circuit system is not cleaned according to the specified time, too much oil impurities will easily lead to blockage of the orifice and the piston being stuck. This is a common cause of shifting shocks.
2, matters needing attention
In order to ensure that the loader performance of the loader is intact, the following items should be noted during use.
1) The degree of cleanliness of the transmission fluid has a certain influence on the performance of the transmission control valve. Therefore, the hydraulic oil must be replaced according to the specified cycle to clean the oil sump.
2) The main pressure valve has been debugged when the machine is shipped from the factory, taking care not to damage its balance. If the part is replaced, it must be re-adjusted carefully.
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