Excavator deviation will greatly increase the driver's labor intensity, affect work efficiency or even unable to work, so it must be eliminated in time. Now take WY20 hydraulic excavator as an example to analyze the reason and judgment method of deviation. The hydraulic system principle of this machine is shown in Figure 1-15.
1. Cause analysis
(1) One of the variable double pumps P1 and P2 is damaged or the leakage is too large, resulting in unequal output flow of the two pumps, and the oil supply of the motor 1 and the motor 2 is also unequal, so that the speeds of the two motors are different Cause the excavator to deviate.
(2) One of the valve spools in the directional valve 4, 10 is stuck, so that it cannot be fully opened, the oil is throttled when passing through the valve, so that the oil supply of the motor 1 and the motor 2 is not equal, causing a run Partial.
(3) One of the safety valves 8 and 9 is stuck or the set pressure is too low. When the driving resistance of the excavator is large, the safety valve with a low set pressure will open, and part of the flow output by the pump will be Through this valve, it flows back to the fuel tank, causing the left and right motors to supply different amounts of fuel, causing deviation.
(4) The valve 6 is stuck, so that the pump P1 and the oil inlets of the motors 1 and 2 are connected at the same time. When the load of the right travel motor 1 is less than the load of the left travel motor 2, the partial flow output by the pump P1 and the output of the pump P2 The entire flow of will flow into the right travel motor 1 at the same time, making the rotation speed of the right motor greater than the rotation speed of the left motor, thus causing the excavator to deviate to the left.
(5) The seal in the rotary joint 3 is damaged, and the oil inlet and return passages of one of the motors are connected in series, resulting in a reduction in the oil intake of the motor and a reduction in the rotation speed, resulting in the excursion of the excavator.
(6) One of motor 1 and motor 2 has a large leakage or is damaged, resulting in different speeds of the two motors.
(7) One of the main safety valves 5, 7 has an adjustment pressure that is too low or the valve core is stuck. When the driving resistance of the excavator is large, the safety valve with a low adjustment pressure will open and overflow, then flow into the left, The flow rate of the right motor is also unequal, which causes the excavator to deviate. However, in this case, the movement of other working devices will appear slow and weak.
2. Judgment method
There are many reasons for deviation, and it is difficult to determine which cause is caused at once. However, if you follow the method of excluding one by one from the beginning to the end, you can quickly find the cause of deviation and avoid blind disassembly.
First, replace the oil pipes of pumps P1 and P2, and then test the machine. If the deflection direction also changes accordingly, it means that the deflection caused by the variable double pump can be found according to the lower speed motor. Machine maintenance; if the direction of deviation is unchanged, it is not a problem with the pump.
Then replace the two oil pipes between the directional valve 4 and the rotary joint 3 with the two oil pipes between the valve 10 and the rotary joint 3. If the deviation direction also changes, it means that it is caused by the multi-way valve. That is caused by the reasons (2), (3) and (4) in the above reason analysis. Deviation to the left indicates that it is caused by the main safety valve 7, safety valve 8 and valve 6. Deviation to the right indicates that it is caused by the main safety valve 5 and safety valve 9, which can be cleaned and adjusted separately Press to the specified value. If the deviation direction does not change, it means that it is not caused by the multi-way valve.
Finally, install the inlet and outlet pipes of the motor 1 and the inlet and outlet pipes of the motor 2 interchangeably and test the machine. If the deflection direction changes, it is caused by the problem of the rotary joint 3, which can be replaced or repaired: if it runs If the deflection direction is unchanged, it means that the motor with lower speed has a problem.
In addition, the servo control valve stuck or damaged can also cause deviation.
