As shown in Figure 1-101, the oil circuit of a type of excavator's rotary hydraulic system is mainly composed of a rotary hydraulic final drive motors, a rotary ring gear and a control valve. The system has braking, oil filling (anti-cavitation), anti-hydraulic shock, and rotation. Priority and other functions.
The slewing motor in the full hydraulic excavator is a key component of the slewing mechanism. It converts the oil pressure supplied by the main pump into mechanical energy and inputs it to the reducer. The performance of the machine will directly affect the rotation speed of the whole machine, driving torque, swing parking and parking brake, which is the key to determine the productivity of the whole machine. The slewing motor is divided into two categories: low-speed high-torque motor and high-speed slewing motor.
Due to its small size and heavy weight, the low-speed and large-torque motor is rarely used in the slewing mechanism of modern excavators. The high-speed slewing drive motors is small in size and light in weight, which is convenient for the reasonable layout of the slewing mechanism and can also meet different slewing speeds and rotations. Moments are required and are widely used.
The high-speed rotary motor is divided into two categories: swash plate type and inclined axis type quantitative plunger motor. The inclined-axis motor is mainly based on the Rexroth AF series. It was widely used in various types of excavators with German technology in the 1980s and 1990s, and its performance has certain deficiencies. At present, excavators at home and abroad widely use oblique-axis through-shaft rotary motors. In order to make the brake smooth, the motor is designed with a hydraulically controlled brake buffer valve in addition to the hydraulic brake (ie wet multi-plate brake).
After the excavator has been working for a long time, the slewing motor of the slewing mechanism often has the phenomenon of lack of rotation and unstable rotation.
2. Fault phenomenon and cause analysis
When the excavator is working at a relatively low temperature, the driving force and the turning speed are not significantly decreased. When the oil temperature rises above 60 degrees Celsius, there is a phenomenon that the turning force is weak, the turning speed is unstable, and the rotating speed is high and low.
In addition to the pumps, valves and other components in the system's swing system, the above-mentioned faults are mainly caused by the internal movement of the swing motor, which causes wear and tear, the gap increases, the leakage increases, the oil return cannot be discharged in time, and the high-pressure oil leaks a lot. The pressure inside the casing increases, the temperature of the oil rises, and the viscosity decreases.
(1) Pressure test The blind motor is used to isolate the rotary motor oil circuit from the main oil circuit. The oil pressure gauge is used to test the forward and reverse oil pressures of the rotary motor, that is, the pressure value of the rotary motor is obtained. Then connect the oil circuit to make it in normal working condition, and the excavator bucket falls and is inserted on the ground. The load on the slewing platform is increased. When the pressure of the relief valve is tested when the motor is driven, the two sets of test data are compared to determine the state of the fault.
(2) Flow test The PFM-6 flowmeter is connected in series with the oil circuit to test the flow and pressure of the slewing motor inlet and outlet, determine whether the output torque and speed of the slewing motor reach its technical performance index, and at the same time judge the faulty part of the slewing motor. .
1) The gap between the plunger and the cylinder plunger hole is increased, resulting in serious gap leakage. Need to replace the plunger.
2) The return spring is fatigued and the spring force is lowered, causing the high and low pressure oil passages of the cylinder to collude. Need to replace the spring.
3) The shoe and the plunger wear and accelerate the sliding dry friction between the shoe and the bearing plate, resulting in an increase in the turning resistance. Need to be repaired or replaced.
4) The final drives bearing is damaged and the bearing positioning is invalid. The specified type of bearing needs to be replaced.
5) Safety method sealing surface wear. Need to be repaired or replaced.
6) Parking brake cylinder seals are aging, failure, and oil leakage, resulting in the brake not being completely released and the rotary resistance increasing. The sealing element must be replaced.
7) The distribution surface of the distribution plate and the cylinder body is worn, resulting in internal leakage and no rotation. Need to be repaired or replaced.
8) Sealing elements are bruised, aged, and ineffective. It should be replaced.
In summary, the above-mentioned faults occur during the use of the excavator, which is a common problem. By summarizing, analyzing and finding out the parts where the fault occurred, the excavator's swing motor is normally and stably operated. https://www.spfinaldrives.com/