When the platform rotates, it stops and moves suddenly, that is, the rotation is discontinuous. Slow speed and insufficient strength.
1. Cause analysis
Hydraulic motor is an energy conversion device, that is, the input liquid pressure energy is converted into mechanical energy output. If the efficiency of the hydraulic motor itself is not considered, the input of energy should be equal to the output. Therefore, the weak rotation of the hydraulic motor must be the reduction of the energy input to the hydraulic motor. When the energy is difficult to overcome the rotation resistance of the platform, it will stop. According to the principle of hydraulic transmission, the hydraulic motor rotates by liquid pressure. When the hydraulic motor stops when the control valve is connected to the pressure oil circuit, it must stop because the working pressure of the oil input to the plunger cylinder of the hydraulic motor is not enough to overcome the running resistance of the platform. When the accumulated energy is enough to overcome the resistance, the hydraulic motor makes the hydraulic motor jump and rotate to overcome the resistance, the oil pressure in the system drops sharply, and the motor stops again. In this way, the platform "crawling" is formed repeatedly, or the "crawling" is caused by too much resistance to prevent the hydraulic motor from rotating. As for the decrease of input hydraulic fluid flow and working pressure, please refer to the cause analysis and diagnosis of slow lifting of boom cylinder. In short, the "crawling" of hydraulic motor makes the oil pressure in the system unstable. Most of the instability of oil pressure is caused by air in the system. The reason for entering air in the system is the same as that in the first part. The reason why the rotation resistance of hydraulic motor is too large leads to the low mechanical efficiency of the motor itself. For example, the friction resistance between the plunger and the mating friction pair is too large, the friction resistance between the swashplate and the plunger is too large, the friction resistance caused by poor bearings is too large, or the mechanical transmission efficiency of the transmission box is low. Or the mechanical friction resistance of the turntable of the platform is too large.
2. Diagnosis and troubleshooting
If the oil cylinder of the hydraulic working device also has the phenomenon of "crawling", the fault is in the main oil circuit of the hydraulic system, the diagnosis method described in the first part of the slow lifting of the boom oil cylinder shall be followed, with emphasis on checking the cavitation, finding out the cause and troubleshooting. If the boom hydraulic cylinder of the working device works normally, the "crawling" fault of the hydraulic motor shall be at the end of the hydraulic motor and transmission, that is, the mechanical transmission box and platform turntable.
(1) Inspection of hydraulic motor safety valve
Try to adjust the safety valve at the lower part of the hydraulic motor control valve. Unscrew the nut of the safety valve, rotate the adjusting screw plug with an Allen wrench, and change the pressure by 2.345mpa every turn. Therefore, the pressure gauge test shall be 9.8MPa. If it is lower than 9.8MPa, it indicates that the "crawling" fault is mostly caused by the low set pressure of the hydraulic motor.
(2) Check the hydraulic motor and mechanical transmission
If the set pressure of the test hydraulic motor safety valve is 9.8mps, it means that the "crawling" is due to excessive mechanical friction resistance between the hydraulic motor and the slewing platform. Touch the shell of the hydraulic motor by hand. If it feels hot, it indicates that the friction force of the hydraulic motor is too large, which proves that it is the fault cause of "crawling" and should be eliminated. If the temperature of the hydraulic motor is normal, you can use the hand mold to observe the temperature of the transmission box and rotary table, or observe the lubrication. If there are parts with high temperature and poor lubrication, it indicates that most of them are the cause of "crawling" fault, that is, excessive friction resistance, which should be eliminated.
