Slow rotation and weak braking; If the arm of the stick is extended, so that the reversing valve lever is in the middle position and the engine is turned off, in this state (on the flat ground), the machine can easily push the boom to rotate with only one person's strength. The following is the main content of How to Eliminate the Rotary Failure of Excavators written by Foshan Zhongte Vocational and Technical Training School. Let's have a look.
The fault may be in the swing motor and the safety valve of the motor.
When disassembling the rotating motor, it was found that the locating ring at the upper end of the motor for axially locating the slipper had loosened and was stirred into iron filings. There are many pits on the upper swash plate surface, and grooves have appeared on the port plate; When removing the motor safety valve, it was found that the valve core and valve seat of the safety valve were badly worn and could not be sealed.
The rotary motor used in this machine is a double swash plate axial plunger motor. The plunger cylinder of the motor is connected with the transmission shaft, the plunger is hinged with the slider, and the slider slides along the plane of the swash plate. Because the positioning ring of the axial positioning slipper is loose, the positioning ring is cut into iron filings and many pits during the rotation of the motor. When the machine is rotating, whenever the slipper passes through these pits, the machine will vibrate violently and you will find the sound of "hook-hook". In addition, because the scratch groove on the sealing surface of the port plate is deep, the motor leaks oil when feeding oil, and the motor cannot rotate because of the low feeding pressure.
According to the working principle of the braking system of this machine, when the high-pressure oil above 9.8Mpa flows through the safety valve of the motor, the high-pressure oil pushes open its valve core and discharges the oil through the oil return channel, so that the pressure is always kept at 9.8 MPa. When the turntable needs to stop rotating, just put the control valve lever in the middle position. At this time, the original oil discharge chamber and oil inlet chamber of the hydraulic motor are closed. Due to inertia, the oil pressure of the original oil discharge chamber rises, resulting in braking effect. Because the valve core and valve seat of the motor safety valve are worn and the sealing is not strict, the pressure of the motor oil discharge cavity is released, resulting in incomplete rotary braking. ?
Smooth the groove in the oil pan, reprocess the locating ring, and then assemble the motor; Grind the spool and seat of the motor safety valve. After modification and debugging, the fault phenomenon has disappeared.