1. Phenomenon: the rotation speed of the platform is less than 6r/min during operation.

2. Reason analysis: The structure and working principle of the hydraulic motor and the axial piston pump are basically the same. The axial piston pump generates power by sucking oil and pressing oil, that is, converting mechanical energy into liquid pressure energy. The hydraulic motor enters the high-pressure oil, and the low-pressure oil is discharged, that is, the liquid pressure energy is converted into mechanical energy. It appears that the hydraulic motor is substantially equivalent to a combination of a plurality of single-cylinder plunger cylinders, that is, a plurality of unidirectional cylinders are circumferentially distributed, and the outer end of the plunger is placed on the swash plate. When the oil pump supplies the pressure oil to the cylinder, the plunger protrudes under the action of the pressure oil and slides down on the swash plate, thus generating a torque, and the oil pump continuously supplies the hydraulic oil to the hydraulic motor, and the hydraulic motor continuously Rotation, and through the gearbox, the final drive gear meshes with the fixed ring gear of the frame to drive the platform to rotate.

It can be seen from the above that the construction and working principle of the hydraulic motor are basically the same as those of the aforementioned hydraulic cylinder. If the hydraulic motor has a slow rotation speed, the method of analysis, diagnosis and elimination and the hydraulic cylinder and axial column of the working device The plug pump is similar and will not be described here. Please refer to the above for analysis, diagnosis and troubleshooting of hydraulic motors.

Second, the hydraulic motor "crawling"

1. Phenomenon: When the platform rotates, it will suddenly stop and move, that is, the rotation will be discontinuous. Slow speed, insufficient strength, etc.

2. Analysis of the cause: The hydraulic motor is an energy conversion device, that is, the input liquid pressure can convert the mechanical energy output. If the efficiency of the pressure motor itself is not considered, the input of energy should be equal to the output. From this point of view, the rotation of the hydraulic motor is inevitable, and the energy of the input hydraulic motor is reduced. When the energy is difficult to overcome the resistance of the platform rotation, a stall occurs.

According to the hydraulic transmission principle, the hydraulic motor is rotated by the liquid pressure. The hydraulic motor stops when the control valve is connected to the pressure oil passage, which is inevitably caused by the hydraulic working pressure of the input hydraulic motor plunger cylinder being insufficient to overcome the running resistance of the platform. When the energy to be accumulated is enough to overcome the resistance, the hydraulic motor makes the overcoming resistance and oscillates, the oil pressure in the system drops sharply, and the motor stops again, thus repeatedly forming a platform "crawling" or preventing the hydraulic motor from rotating. Excessive resistance leads to “crawling”. As for the flow reduction and working pressure reduction of the input hydraulic fluid, please refer to the analysis and diagnosis of the slow lifting of the boom cylinder.

In short, the hydraulic motor “crawling” makes the oil pressure in the system unstable, and the oil pressure instability is mostly caused by the air in the system. The reason for entering the air in the system is the same as the first part.

The motor's own mechanical efficiency is low due to excessive rotational resistance of the hydraulic motor. If the resistance of the plunger and the friction pair is too large, the frictional resistance between the swash plate and the plunger is too large, the frictional resistance caused by the bearing is too large, or the mechanical transmission efficiency of the transmission case is low. Or the mechanical resistance of the rotary disc of the platform is too large.

3. Diagnosis and elimination

If the cylinder of the hydraulic working device also has a phenomenon of “crawling”, the fault is in the total oil path part of the hydraulic system, and the diagnosis should be carried out according to the diagnostic method described in the first part of the boom cylinder. The focus is on the cavitation and the cause is ascertained. After the disease is ruled out.

If the boom hydraulic cylinder of the work unit is working properly, the “crawling” of the hydraulic motor should be at the end of the hydraulic motor and drive, ie the mechanical gearbox and platform turntable.

(1) Check the hydraulic motor safety valve and adjust the safety valve at the lower part of the hydraulic motor control valve. Unscrew the safety valve nut and use the inner hexagonal wrench to rotate the adjusting screw plug. The pressure is changed to 2.345 MPa for each revolution. Therefore, the pressure gauge test should be 9.8 MPa. If it is lower than 9.8 MPa, it means that the "crawling" fault is mostly caused by the set pressure of the hydraulic motor being too low.

(2) Check the hydraulic motor and mechanical transmission part If the test hydraulic motor safety valve set pressure is 9.8MPs, it means that “crawling” is excessive mechanical friction resistance of the hydraulic motor to the rotary platform.

Touch the hydraulic motor casing by hand. If there is a hot feeling, it means that the hydraulic motor has too much friction, which proves that it is the cause of the "crawling" failure and should be excluded.

If the hydraulic motor temperature is normal, you can manually mold the temperature of the gearbox and turntable, or observe the lubrication. If the hand feels a higher temperature part and the lubrication is also poor, it indicates that most of the "crawling" faults are caused, that is, the resistance friction is too large and should be excluded.

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