Excavator computer board working principle and maintenance

The excavator computer board (scientific name controller) is called the "brain" of the control machine. It plays a vital role in the normal operation of the excavator. The computer board is like our human brain. It will collect various sensors. The information is compared, calculated, processed and output, and the engine speed is controlled to coordinate with the hydraulic system action. Each excavator has a computer board, but the installation place is different, such as: Komatsu machine is driving, right rear side, Hyundai 220-5 is under the left hand joystick, Carter 320 is generally outside the cab, battery side on.

First, the basic principle of general-purpose computer board

Function Description:

(1) It is possible to replace the diggered brand throttle computer board that uses DC motor (such as Daewoo, Hyundai, Xugong, Liugong, Longgong, Shanhe Intelligent, Xiagong, Foton Lovol, Sany, etc.). (If the electronic throttle function and the hydraulic plate are on a computer board, if the throttle is partially damaged, the universal throttle plate can be replaced by the electronic throttle function).

(2) Peripheral wiring as shown above, requires external power supply, 2 pressure switches, throttle knob potentiometer, throttle motor, and speed sensor. The electronic throttle function can be provided by wiring as shown above.

(3) The throttle can be added or decremented by the throttle knob. After the automatic idle switch is turned on, if the rotation speed is above 1200 rpm, the automatic idle speed adjustment is performed after 5 seconds. When the pressure switch, the automatic idle switch, and the throttle knob change, the automatic exit will automatically exit. Idle to the speed position set by the throttle knob.

(4) There are differences in the number of teeth of different engine flywheels, so there will be differences in the detection of the speed signal.

(5) The pressure switch is normally open. That is, when the pressure switch is off, it is a necessary condition for automatic idling, and when the pressure switch is turned on, it is automatically idling when it is grounded.

(6) The speed sensor connection only needs to be connected in parallel, that is, it is not necessary to disconnect the original vehicle line, only need to peel off the original vehicle speed sensor harness, and connect two wires in parallel.

Second, the cause of computer board damage

The most common cause of damage to the computer board is water ingress and mechanical impact. In addition, lightning strikes, electric welding surges, pin corrosion, internal component ablation, etc. can also cause damage to the computer board. The usual practice of preventing electric welding surges is to disconnect the power supply of the whole machine, that is, to cut off the battery switch. Some manufacturers even require users to disconnect the computer board and the complete wiring harness before using the electric welding. The most common cause of stitch corrosion is the poor sealing performance of the large plug of the computer board, which leads to moisture intrusion, which may result in broken stitches or poor contact.

Computer board damage generally has the following conditions:

1. The generator is faulty, resulting in a high voltage in the circuit.

2. When the user starts the engine, the battery is connected in series.

3, private pull the use of electrical spare parts, increase the power load, because the current is too large and burned.

4. The generator regulator fails, causing the generator to generate too much power.

5. The positive and negative terminals of the battery are connected incorrectly, and the wire harness is aging, and the short grounding is poor.

6. Do not repair according to the operation specifications, and plug and unplug the ECM.

7. The excavator spare parts the cable and suffers from an external high-voltage electric shock.

8. Misuse of large capacity fuses.

9. The computer board enters the water, causing a short circuit.

10. The computer board is incorrectly wired or improperly inserted or removed.

Computer board repair

Third, the basic steps of computer board maintenance

In the absence of any schematic diagram, it is necessary to repair a relatively unfamiliar circuit board. The so-called "experience" in the past is very good, although the probability of improving the repaired circuit board is greatly increased by means of the circuit online maintenance tester, but if the method is not correct, It’s just half the effort to work. So, what can we do to improve maintenance efficiency? Summarize the following principles:

Principle one, look at the amount first

Use tools: digital (or analog) multimeter, magnifying glass

When holding a circuit board to be repaired, the good habit is to first visually measure it. If necessary, use a magnifying glass to see what? Mainly

1. Is there a disconnection? Is there any trace of burning?

2. Are there discrete components such as resistors, capacitors, inductors, diodes, and triodes?

3. Is there any crack or adhesion on the printed circuit board connection on the circuit board?

4. Has anyone ever repaired it? What Komatsu excavator spare parts components have been moved? Are there any mistakes in operations such as soldering, soldering, and plugging?

After determining that the board is not repaired, first measure the resistance between the power supply of the board and the ground with a multimeter. Usually, the resistance of the board is above 70-80Ω. If the resistance is too small, only a few or a dozen An ohm, indicating that components on the board are broken down or partially broken down, and measures must be taken to find out the components that are broken down. The specific method is to supply power to the repaired board, and touch the temperature of each device on the circuit board by hand. The hot hand will be the key object of doubt.

If the resistance is normal, you can use a multimeter for fault detection. Because there are many factors that cause the circuit board to fail, the discrete components such as resistors, capacitors, diodes, transistors, FETs, and dial switches on the measuring board are designed to ensure that the measured components are normal and repaired. The principle is that you can solve problems with a multimeter and don't complicate it.

Principle 2, first and second, enumeration test

Use tools: HY circuit online maintenance tester series, marker pen

Since the HY circuit online maintenance tester series has two fault diagnosis technologies, one is based on the standard test method (ie ICFT) of the device test library; the other is the real-time comparison scan test based on the VI curve. Law (ie ASA-VI).

When using ICFT for chip testing, the following two test dead zones may occur:

1. The test library has not yet established a test program for a chip, that is, there is no such chip in the library.

2. Even if the test library has established a test program for the chip, the "online test" does not pass.

The computer board of the excavator is rarely damaged when it is used normally. It is not a consumable part, and it is usually caused by man-made or force majeure. Generally, the cause of damage caused by force majeure is lightning strike and ultrasonic interference. The working environment of the excavator is complicated and varied, and the causes of damage to the computer board are also various. It is the first priority to take precautionary measures in advance. https://jnjmzm.wixsite.com/sdjygcjx