Use the three in one tester to detect the proportional valve of the main pump of the hydraulic excavator

Use the three in one tester to detect the proportional valve of the main pump of the hydraulic excavator

The excavator electro-hydraulic proportional valve reduces the pressure of the pilot oil and outputs the secondary oil pressure to adjust the force of the servo piston of the main pump, so as to change the flow of the main pump. The proportional valve of the main pump is an important component of the excavator. When the input current of the proportional valve is too large or too small, or the proportional valve is worn or stuck, it may cause the excavator to slow down or the engine stalls or even stalls. The three in one electronic / electrical tester can easily detect and diagnose the faults of the proportional valve.

1. Test method

The proportional valve has undergone strict quality inspection before delivery, including static characteristic test (input current pressure characteristic test, internal leakage test, load characteristic test) and dynamic characteristic test (frequency response test, instantaneous response test). When the fault diagnosis is carried out on site, the on-line detection is carried out on the machine, including the resistance measurement of the solenoid coil of the proportional valve, the input current test and the output secondary oil pressure test.

(1)       Measurement of electromagnetic coil resistance. Turn off the ignition switch, disconnect the plug CN between the proportional valve of the main pump and the output interface of the pump controller (see Figure 3), measure the resistance between the two wires and the resistance between the ground wire and the body, so as to judge whether the solenoid coil of the proportional valve has a short circuit, open circuit or grounding.

(2)       Measurement of input current of proportional valve. Disconnect one wire of the proportional valve, connect a multimeter in series, and measure the input current according to the test conditions of different models, as shown in Figure 4. It is quite simple to test with a DC Clamp gauge, without pulling the plug CN or disconnecting the wire (see Figure 5).

Under different power modes or different engine speeds, whether the electronic control part before the proportional valve is faulty can be judged according to the correctness of the DC current signal output from the pump controller to the proportional valve.

(3) Test the output pressure of proportional valve. As shown in Figure 6, connect a pressure gauge with a range of 6Mpa to the measuring point of secondary oil pressure, and check the output pressure of proportional valve for different models according to their respective test conditions. If the pressure is incorrect, it can be adjusted. For the non adjustable proportional valve, after confirming that the input pilot oil pressure and the current of the proportional valve are normal, the valve core should be disassembled for cleaning or the proportional valve should be replaced.

2. Test examples

(1) Test of proportional valve of Liebherr excavator. Taking the commissioning of the main pump of r984 excavator as an example, the standard values of the detection parameters of the proportional valve are shown in the table below.

Standard value of detection parameters of proportional valve of Liebherr excavator

(2) Test of proportional valve of caterpillar excavator. Take cat320b excavator as an example. During the scanning test of EPR proportional valve, you need to enter the password through the monitoring board to enter the maintenance mode, the throttle knob is located at "10", and the operating handle is fully set to the middle position. Connect a pressure gauge with a measuring range of 6Mpa at the output end of EPR proportional valve (secondary oil pressure P. measuring point), and put a clamp on ammeter into the EPR valve wire. Turn on the start switch when the engine is off.

In the 20s scanning cycle, when the current increases from 200mA to l750ma, if the secondary oil pressure increases from 490kpa to 3450kpa, the EPR valve is normal.

(3)       Test of proportional valve of Shengang excavator. Taking the proportional valve for the main pump of Sk-6 series excavator as an example, the coil resistance value on it should be (17.5 ± 1) n. The standard values of input current and secondary oil pressure detection parameters are shown in the table below.

Standard value of detection parameters of proportional valve of Shengang excavator

(4) Test of proportional valve of Komatsu excavator. Take Komatsu pc200-6 and PC220-6 excavators as examples. If the resistance of the coil is 7 ~ 14 Ω and the resistance between the ground wire and the body is more than 1m Ω, it is normal. The starting switch is powered on, the engine is placed at the maximum throttle position, and the operating handle is neutral. If the input current is (320 ± 80) MA, it is normal.

(5) Test of proportional valve of Daewoo excavator. Taking Dayu dh220ijc- Ⅲ excavator as an example, the standard values of the detection parameters of the proportional valve are shown in the table below.

Standard value of proportion detection parameters of Daewoo excavator

(6)       Testing of proportional valve of modern excavator. Take modern r290-3 excavator as an example. When testing the proportional valve, after starting the engine, operate the bucket control handle under the specified power mode and engine speed. See the following table for the standard values of the input current and the corresponding secondary oil pressure detection parameters when the bucket circuit is in the overflow position.

Standard values of the detection parameters of the proportional valve of modern excavators