Core tips: Volvo excavator brake failure analysis and elimination method: a Volvo VOLVO-EC360 type excavator, when the working time reached 3000h, when the start of the upper turntable rotating braking failure, so that the rotation can not stop in time; then continue to work the 2H, the above failure phenomenon is becoming more and more serious.
A Volvo VOLVO-EC360 excavator, when the working time reaches 3000h, the brake failure begins when the upper turntable rotates, so that the rotation can not be stopped in time; after that, it continues to work 2h, and the above failure phenomenon is becoming more and more serious. In the inspection, it is found that the turntable can not be stopped immediately after the rapid rotation, and the rotation of the turntable can be stopped after a period of rotation in the same direction; when the turntable is slalom, it should be slowly rotated more than 90 degrees in the opposite direction to stop.
1. fault analysis
From the fault phenomenon, it is mainly caused by insufficient braking force. There are several reasons for the lack of brake power, so they are investigated one by one.
(1) the wear of the brake disc and the insufficient spring force
Stop the machine on the slope to turn the upper turntable to the slope perpendicular to the slope, turn off the engine, and turn the turntable to the low side by gravity; stop the oil path at the brake control valve PG, start the engine, operate the pilot valve, and the turntable can't turn back at this time. The above conditions indicate that there is no problem with brake pads and springs.
(2) due to the wear and tear of other parts, after stopping the pilot valve, there is still pressure oil entering the SH (A12) end.
The return position of the pilot valve is incorrect or not in time; or the reversing valve 6 is worn, so that the main pump pressure oil is entered into the pilot oil path through the wear gap through PAs (or PBs), through the shuttle valve 3 and 4 into the SH (A12) pipeline; the other parts are leaked, the pressure oil is entered into SH (A12), such as AM, A1, A13, Psp, etc., so that the brake control valve does not return to the position. It is always in the state of connecting with the brake piston, and the PG pressure oil still enters the brake piston cavity continuously, which causes the brake disc 11 to be separated and can not play the role of braking.
By pressure testing, when the pilot valve is operated, the pressure at SH (A12) is 3.6MPa. When the pilot valve is stopped, the pressure is rapidly reduced from 3.6MPa to 0, so it is not a problem to determine the above hypothetical fault points.
(3) choking valve 2 choke hole, brake control valve 1 does not return.
After closing the pilot valve, the pressure in the brake cylinder can not be relieved and the brake device does not function because the throttle hole of the speed regulating valve 2 is blocked and the 1 card of the brake control valve is stuck in the connection position.
Through pressure testing, the pressure of the brake piston chamber is reduced from 3.6MPa to 0 (about 3S) after stopping the operation pilot valve, but when the pressure in the cavity is 0, the rotation of the turntable can still not stop. The speed control valve and the brake control valve can be identified without problem.
(4) wear of rotary motor
After stopping the operation of the pilot valve, the hydraulic pressure in the rotary motor also plays the role of hydraulic brake at this time, and acts as the brake disc 11 at the same time, so that the motion of the turntable is stopped. When the slipper and disks of the rotary motor wear, the oil film which is supposed to form static liquid support in these parts is destroyed. Because the sealing performance decreases, the pressure oil in the plunger is leaked through the wear part, and it can not play the role of hydraulic braking, resulting in the slow braking of the turntable.
According to the above analysis and monitoring, the focus of troubleshooting should be on rotary motors.
2. troubleshooting
Through the pressure testing of the rotary motor A (BH) and B (LH) two, it is found that the rotating initial pressure of the rotary motor must reach 16MPa when the rotary pressure must reach to 16MPa, indicating that the rotary resistance is too large; the excavator is placed on the ground, the pilot valve is operated, the maximum pressure value is only 20MPa, and the difference from the standard value 26MPa is great.
When the filter element 7 is removed, it is found that there are many metal scraps on the filter element, which is determined by the wear of the rotary motor. As a result, the disintegration of the rotary motor found a large number of metal chips inside, and there was a trace of pull on the surface of the flow plate. The seal ring after the flow plate had been squeezed out. The surface of the Slipper Boots, the surface of the inclined plate and the surface of the nine holes had obvious scratch marks, and the metal on the surface of the lower bearing had also fallen off.
After measurement, the bearing height after wear is 29.7mm, and the standard height of the same kind bearing is only 29.0mm. Therefore, it is determined that the unqualified bearing is used when the installation is installed. Because the axial force is too tight, the radial force of the bearing is too large to cause Ma Dafei's normal wear and tear.
Therefore, the standard bearings are replaced, and the slipper, the flow plate, the inclined plate and the nine hole plate are grafted by hand. In addition, the pipeline and hydraulic oil tank are cleaned and the hydraulic oil filter and hydraulic oil are replaced. When the car was loaded, the fault had disappeared. The surface of the flow plate has been squeezed out, the surface of the Slipper Boots, the surface of the slanting disc and the surface of the nine hole board have obvious scratch marks, and the metal on the surface of the lower bearing surface has also fallen off.
After measurement, the bearing height after wear is 29.7mm, and the standard height of the same kind bearing is only 29.0mm. Therefore, it is determined that the unqualified bearing is used when the installation is installed. Because the axial force is too tight, the radial force of the bearing is too large to cause Ma Dafei's normal wear and tear.
Therefore, the standard bearings are replaced, and the slipper, the flow plate, the inclined plate and the nine hole plate are grafted by hand. In addition, the pipeline and hydraulic oil tank are cleaned and the hydraulic oil filter and hydraulic oil are replaced. When the car was loaded, the fault had disappeared.
