Paper on New Technology of Automobile Maintenance (2)

New Technology of Automobile Maintenance (Ⅱ)

Analysis of Automobile Engine Maintenance Technology

As the heart of the car, the engine plays a vital role in the normal operation and operation of the car. Therefore, we should strengthen the maintenance of the engine at ordinary times. For the maintenance of automobile generators, comprehensive technical knowledge and practical operation ability are needed. Therefore, the maintenance of automobile engine can be said to be a hard work that requires skill and technology. In this paper, the related maintenance techniques are elaborated in detail from two aspects: automobile engine inspection, automobile engine diagnosis and maintenance, hoping to be helpful to those who study automobile engine maintenance.

Keywords automobile; Engine; Maintenance; technology

China Library ClassificationNo. U46 Document IdentificationNo. A1674-6708 (2014)114-0109-02.

1 traditional engine maintenance technology

Inspection of engine internal parts;

Because the crankshaft and piston inside the automobile engine are often prone to failure, for example, the automobile suddenly fails to start, and it is likely that the piston inside the automobile engine cannot operate. Therefore, when the automobile engine fails and needs maintenance, the crankshaft and piston can be checked first, and the specific steps are as follows:

1. 1 crankshaft inspection

For crankshaft faults that are easy to occur, the journal is easy to wear, deform or fatigue crack, so it is necessary to carry out key inspection. 1) crack detection: For crankshaft crack detection, the corresponding detection methods include ultrasonic flaw detection, oil immersion knocking, magnetic flaw detection and X-ray flaw detection. When the crankshaft is inspected by oil immersion knocking method, it is necessary to soak the crankshaft in kerosene for a period of time, then take it out of kerosene, clean it, sprinkle some white powder on the crankshaft, and then knock on different parts of the crankshaft. If there is obvious oil stain, it means that there is a crack in this part of the crankshaft. When the magnetic flaw detector detects, its magnetic field lines will penetrate the detected part of the crankshaft. If there is a crack in this part, the magnetic field lines in this part will diverge, and then the magnetic powder will be scattered in this part, thus showing the specific size and location of the crack. 2) Inspection of bending deformation: For the inspection of bending deformation of crankshaft, you can first support the two top ends of the whole crankshaft with V-shaped blocks, as shown in figure 1, and then use the contact of dial indicator to abut in the middle of the main shaft. When the crankshaft rotates once, find out the minimum and maximum angles on the pointer and calculate the difference between them. This difference is the difference of crankshaft bending deformation. If it is greater than 0. 1 1 mm, the crankshaft is severely bent. In order to ensure the normal operation of the engine, it is necessary to replace the crankshaft in time.

1.2 piston connecting rod group inspection.

The inspection of the corresponding piston position is mainly to check whether the size of the piston pin seat and the diameter of the skirt have changed, or whether there is blockage during use. There are usually two main inspection methods. The first inspection method is to measure with a micrometer. By measuring the skirt diameter and the worn part of the piston cylinder, these two measured data are subtracted and then compared with the cylinder clearance value. If the difference is greater than 0. 10mm, it means that the piston is badly worn and cannot be used again. Another method is to measure with a feeler gauge, and judge whether the piston in the automobile engine can be used normally by measuring the cylinder clearance. First, put the feeler gauge into the ring groove where the gas ring is installed, then gently rotate the feeler gauge with a pulling force of 35N, and stop rotating when slight resistance is felt, so that the difference between the piston skirt and the piston side clearance can be measured with the feeler gauge. The more the piston wears, the greater the corresponding difference. When the value exceeds 0. 12mm, the piston can no longer be used, and it is necessary to equip the automobile engine with a new piston. As shown in figure 2.

Figure 2 Figure 3 Figure 4

2 Diagnosis and maintenance of automobile generators

2. 1 engine stall fault

If the engine stalls, its general performance is that the engine speed will be lower and lower, which is a common engine stall fault. The main reason for this failure is the failure of the ignition control system, or the failure of the fuel nozzle system, or the failure of the intake system of the whole engine. For example, if the fuel nozzle system is faulty, it is likely that the line contact is unstable, the oil pipe is deformed or the fuel filter has too many ash layers. For different reasons, different measures can be taken for maintenance.

Relevant troubleshooting and maintenance methods are as follows: 1) If there is a problem with the fuel injection system, check whether it is a poor line contact. If so, you can adjust the circuit or replace the lead for maintenance. If there are too many dust layers such as the oil filter cover, it can be repaired by cleaning the filter cover. 2) If there is something wrong with the air inlet pipe, carefully check whether each hose or its joint leaks air, or check whether the PVC valve pipe is ventilated normally. If not, consider repairing or replacing the corresponding pipeline; 3) In view of the problems existing in the ignition control system, it is necessary to check whether the spark plugs of each cylinder work normally. For example, there are too many dust layers on the spark plug, which leads to abnormal engine speed and can be repaired by thoroughly cleaning the spark plug.

2.2 Engine Idle Failure

The fault phenomenon of poor engine idle speed is mainly that the engine idle speed is unstable and it is easy to stall when parking. In the aspect of fault diagnosis, the engine fuel pressure can be detected first. Connect the fuel pressure gauge to the oil pressure detection hole and start the engine. The oil pressure gauge indicates that the pressure is normal and the pressure is 265kPa. Remove the vacuum tube of the oil pressure regulator, and the oil pressure rises to 340kPa. The above results are within the standard range, indicating that the fuel pipeline system is fault-free. Then check the cylinder pressure. Preheat the engine to 85℃, open the throttle, and measure the pressure of each cylinder with the cylinder pressure gauge. When the pressure values are all around l 1000 kpa and the pressure difference between cylinders is 300kPa, the above situation shows that the sealing performance of engine cylinders is problematic.

The maintenance methods for this fault are as follows: clean the idle motor and throttle body. Remove the idle motor and throttle body, thoroughly clean all air passages and blow them with compressed air. Use multimeter to measure the resistance of idle motor. The resistance is 20Ω, which is within the normal range of18 ~ 24Ω. When measuring the throttle position sensor, the output resistance changes linearly and is within the normal range. If any foreign matter is found in the intake manifold, clean it with iron wire wrapped with linen. In order to completely eradicate the fault, the injector can also be cleaned and tested.

3 Conclusion

As can be seen from the above analysis, this paper briefly introduces the common faults of automobile engines, their causes and solutions. In fact, the maintenance coverage of the whole automobile engine is relatively wide, and its corresponding maintenance technology is also relatively comprehensive and complicated. To master the maintenance skills and related technologies of automobile engines skillfully, we need to learn and practice a lot of knowledge, such as the inspection and maintenance of electronically controlled fuel system, so I won't go into details here.

refer to

[1] Zhu,,. Exploration on maintenance and inspection technology of automobile generators [J]. Automobile and Technology, 2004 (1): 235-248.

[2]__ Bin, Luo Luo. Some thoughts on the maintenance technology of automobile generators [J]. Automobile and Technology, 2007 (2): 129- 137.

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