The hydraulic motor is an energy conversion device, that is, the input liquid pressure can be converted into mechanical energy output. If the efficiency of the compressor itself is not considered, the energy input should be equal to the output. From this point of view, the inability of the hydraulic motor to rotate is necessarily a reduction in the energy input to the hydraulic motor. When the energy is difficult to overcome the resistance of the platform, the rotation will stop.

According to the principle of hydraulic transmission, the hydraulic motor rotates by hydraulic pressure. When the hydraulic motor stops rotating when the control valve is connected to the pressure oil circuit, it must be stopped because the working pressure of the oil input to the plunger cylinder of the hydraulic motor is not enough to overcome the operating resistance of the platform. When the accumulated energy is enough to overcome the resistance, the hydraulic motor makes the hydraulic motor to overcome the resistance and jump and rotate, the oil pressure in the system drops sharply, and the motor stops again. This repeatedly causes the platform to "crawl" or prevent the hydraulic motor from rotating. Excessive resistance leads to "crawling".

The excessive rotation resistance of the hydraulic motor leads to the low mechanical efficiency of the motor itself. For example, the friction resistance between the plunger and the matching friction pair is too large, the friction resistance between the swash plate and the plunger is too large, the friction resistance is too large due to poor bearings, or the mechanical transmission efficiency of the transmission box is low. Or it is caused by excessive mechanical friction of the turntable of the platform.

Diagnose and rule out

If the boom hydraulic cylinder of the working device is working normally, the "crawling" failure of the hydraulic motor should be at the end of the hydraulic motor and transmission, that is, the mechanical transmission box and the platform turntable.

(1) Check the safety valve of the hydraulic motor. Test and adjust the safety valve at the lower part of the hydraulic motor control valve. Unscrew the safety valve nut, use an inner hexagonal wrench to rotate the adjustment screw plug, and change the pressure to 2.345 MPa every turn. Therefore, the pressure gauge test should be 9.8MPa. If it is lower than 9.8MPa, it means that the "creeping" 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 setting pressure of the safety valve of the hydraulic motor is tested to be 9.8MPs, it means that the "creeping" is the excessive mechanical friction resistance of the hydraulic motor to the rotary platform.

Touch the casing of the hydraulic motor with your hands. If you feel hot, it means that the friction of the hydraulic motor is too large, which proves that it is the cause of the "crawling" fault and should be eliminated.

If the temperature of the hydraulic motor is normal, you can use the hand to model the temperature of the transmission box and turntable, or observe the lubrication. If there are parts with high temperature in the hand and poor lubrication, it indicates that most of the "crawling" faults are caused by excessive friction resistance, which should be eliminated.

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