• Final Drives motor

Trouble shooting four types of hydraulic motors

Rotational forcelessness: The reason is that the main pump output pressure and flow rate are insufficient or the clearance of the internal fitting of the hydraulic motor is increased.

Inspection and troubleshooting methods:

(1) Under the premise of the main circuit safety valve, overload valve and other accessories intact, seal the inlet pipe and final drive motor interface (no oil leakage), and measure the maximum pressure of the oil supply circuit when the motor is positive and reverse; Turn on the motor line and measure the pressure at load; finally, compare the measured value with its technical requirements to determine the fault location.

(2) Because the flow rate of the hydraulic pump is insufficient or the pressure is low, the output power of the travel motors is reduced, and the torque and the rotational speed are simultaneously reduced. Therefore, the measured flow rate should be synchronized with the measured pressure.

(3) Check if the clearance between the distribution shaft and the rotor hole is within the allowable range (see Appendix 1), check whether the center line of rotation of the distribution shaft and the cylinder hole are consistent, and reassemble if the allowable value is exceeded. If the matching clearance between the distribution shaft and the rotor hole exceeds 0.6 mm, or the groove in the rotor is grooved in the circumferential direction; the clearance between the plunger and the rotor exceeds 0.05 mm, and the clearance between the square shaft of the roller and the chute exceeds 0.05 mm. It will make the curve motor in the low speed and high torque turn weak. If the two travel motors are not synchronized, the track will be deflected.

Schedule 1

(4) The swash plate type axial piston final drives, after long-term high-speed operation, the bearing clearance of the motor output shaft will increase, and the axial positioning clearance exceeds the large value of the large disc spring; the center between the cylinder (rotor) and the distribution plate The four disc springs on the positioning rod can not normally press the rotor cylinder against the valve disc (the fatigue strength of the disc spring is reduced, when the spring force is lowered, the motor can operate normally in the cold state, and the disc spring deformation will increase in the hot state), resulting in The flow capacity is reduced, causing the motor to run weakly. When the gap between the rotor and the cylinder bore exceeds 0.05mm, or the wear exceeds the normal value, it will cause the motor to be weak and slow to run.

2. Leakage

The reason may be: the distribution plate (distribution hole) is worn or strained, the plunger hole and the plunger are worn out, the sealing between the high and low pressure chambers is poor, the working chamber is difficult to form a high pressure, and the oil intake is insufficient; the leakage amount is different from the motor inlet and outlet pressure difference, Oil viscosity, displacement and distribution structure and processing and assembly quality are related. The unstable leakage will cause the motor speed to be unstable, jitter or time-stop. The oil return pipeline is not smooth, and the low-pressure oil pressure is promoted, resulting in the skeleton oil seal. The sealing effect is reduced, so that the oil leaks from the motor output shaft end to the reducer housing (or inside the brake); the motor output shaft support bearing is damaged, which will cause eccentric leakage and abnormal noise; the internal leakage will cause the motor to lock the brake performance and decline. Accurate stopping at a certain location can cause the excavator to slip and be extremely unsafe.

Inspection and elimination method: Check whether the inner surface of the oil distribution shaft or cylinder hole is scratched, first clean, if it is serious, it should be replaced; if there is pulling, groove, grinding and polishing mating surface when checking the matching surface of plunger and plunger hole After the grinding, the replacement is severe; check whether the clearance between the plunger and the plunger hole is too large (generally within 8% of the diameter of the plunger), if necessary, replace it; the leakage in the high-speed hydraulic final drive motor can be discharged through the motor The oil pipe measures the oil leakage per unit time of the casing during idling and load to determine the degree of failure.


The reasons may be: unstable leakage, damage to the motor support frame, change in bearing positioning, wear of parts, serious oil contamination, and incorrect phase of the distribution shaft and the curved surface of the guide rail, causing misalignment of the oil distribution and inconsistent rotation speed. The inspection and elimination method is: cleaning or replacing the distribution shaft or cylinder. If the motor support frame is damaged, the bearing position changes or the parts are worn, the bearing positioning should be replaced and re-adjusted; if the phase of the distribution shaft and the guide rail surface is incorrect, the matching is caused. If the oil is not accurate, perform the no-load test run, loosen the fixing nut on the fine adjustment cam, turn the fine adjustment cam, adjust the relative position of the distribution shaft and the curved surface of the guide rail until the phenomenon disappears, and then calibrate the phase angle of the distribution shaft in the lock nut test machine. After that, generally do not move at will.

4. The rotor is stuck

The reason may be: the gap between the plunger and the plunger hole, the rotor hole and the distribution shaft is increased, the grinding debris in the oil enters the motor with the high pressure oil, and the motor is stuck; the back pressure in the heat dissipation circuit is blocked by the oil throttle orifice , causing poor heat dissipation, can not wash away the internal pollutants of the motor, so that the local temperature of the precision fittings such as the flow distribution pair and the plunger pair rises, causing thermal shock and being stuck; the grinding disc of the high-speed plunger motor and the impurities in the system enter. The plunger hole is pulled, the cylinder is stuck, and the cylinder is loose; the looseness of the return disk screw causes the return disk to be deformed, which makes the plunger spherical surface inflexible, causing the plunger and the return disk to be stuck.

The inspection and elimination methods are: disassemble the hydraulic motor, clean the parts, replace the damaged parts; replace the matching parts and the plunger pair when the clearance is incorrect; if necessary, replace the oil. https://www.spfinaldrives.com/





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9249 S.Broadway #200-204

Highlands Ranch, CO. 80129

United States

1(877) 774-9372