It is often encountered that the excavator deviates and does not walk in a straight line when walking. Although the fault will not affect the loading operation of the excavator, it is very difficult to dig a straight ditch. The deviation of the excavator is mainly caused by the inconsistent speed of the traveling motors on both sides of the excavator. Such a seemingly simple fault, however, the cause of the fault is not one, and there are many parts to be inspected. This article will summarize which parts should be checked when there is a walking deviation fault, for reference only.
1. Foot valve of travel motor
The valve is located at the bottom of the cab and is a valve block for operating the travel action. If the foot valve core is worn and jammed, resulting in inconsistent oil passing through the left and right valve blocks, it will affect the different opening of the main control valve stem, and eventually lead to the deviation of the excavator travel motor.
2. Main control valve travel stem
The travel valve stem is located on the rearmost side of the main control valve. The valve rod on the left controls the left travel. On the right side is the right travel valve rod, which controls the right travel. The inspection of the main control valve stem mainly depends on whether the surface of the valve stem is worn, damaged, oil stains, etc., whether the spring at the top of the valve stem is fatigue broken, and whether there are no foreign matters and scratches in the valve stem hole.
3. Center swivel
The central swivel joint is composed of a shell and a mandrel. The shell is installed on the upper vehicle body, and the mandrel is installed on the lower vehicle body. The mandrel is provided with annular grooves equal to the number of oil pipes, and the hydraulic oil from the shell flows from the vertical holes on the mandrel to the traveling motor through these oil grooves. Therefore, even if the shell rotates continuously with the upper vehicle body, the groove on the mandrel can remain unblocked with the oil port on the shell. The hydraulic oil can enter and exit freely to ensure the normal walking of the excavator. However, if the sealing ring is damaged, the speed of the traveling motors on both sides is different due to the pressure oil leakage on one side of the machine, resulting in the deviation of the machine.
4. Traveling motor
1) Balance valve. When the machine is traveling, if dirt blocks the small hole of the balance valve, the parking brake cannot be released, resulting in traveling deviation.
2) Travel motor overflow valve (safety valve): if the valve core of the safety valve is worn and leaks oil, the pressure in the system will be too low, so that the speed of the travel motor is not enough, resulting in travel deviation. When judging, the safety valves of the left and right travel motors can be exchanged to see whether they deflect during reverse travel.
5. Hydraulic pump (non single valve)
Because when operating the traveling motor, the traveling motor is controlled unilaterally, that is, a pump alone provides high-pressure oil to the corresponding traveling motor. If the flow or pressure of the front and rear pumps are not equal, the rotation speed of the left and right travel motors will be different, resulting in travel deviation.
6. Hydraulic pump proportional solenoid valve
The corresponding control oil pressure is output according to the length of the control stroke of the operating handle (foot valve), so that the main control valve has a corresponding movement, so as to control the speed of the working device. If the slide valve in the valve is jammed, the control oil cannot flow to the main swing control valve through the swing proportional valve on the deflection side of the machine, resulting in travel deviation.
