Maintenance and maintenance of automobile engine

Xiebie automobile inspection Yu maintenance department

Nianji professional 09 Ji automobile maintenance 2 ban

Student name Ye Guangyao

Lecturer xxx

Professional leader xx

Reply date: 20 12 May 10

yantai automobile engineering professional college

catalogue

abstract

keyword

First, the basic structure of the engine

2. Engine failure and maintenance

2. 1 Eight factors of engine failure

2.2 engine fault diagnosis method

2.3 Simple engine maintenance

Three. Main engine maintenance

3. 1 car maintenance knowledge

Common junction

Thank you ... thank you ... thank you ... thank you.

Refer to ................................. 10.

(Abstract

Car maintenance is a headache for everyone. If you don't know how to maintain your car or have bad driving habits, once the car has to be overhauled and specialized, it will not only cost you considerable money, but also waste time and mental torture, which is even more difficult to count. Therefore, you should always pay attention to the maintenance of the car, starting from the first day you own the car, so as to avoid penny wise and pound foolish? Based on the theoretical knowledge of automobile, this paper explains the basic knowledge of automobile engine maintenance for you.

Engine diagnosis, overhaul and maintenance

First, the basic structure of the engine

An engine is a machine that converts some energy into mechanical energy. Its function is to convert chemical energy of liquid or gas into heat energy after combustion, and then convert heat energy into mechanical energy through expansion to output power.

Automobile engine

Gasoline engine is usually composed of crank-connecting rod mechanism, valve train and five systems: oil supply, lubrication, cooling, ignition and starting.

1. Crank-connecting rod mechanism

The crank-connecting rod mechanism consists of a cylinder block, a cylinder head, a piston, a connecting rod, a crankshaft and a flywheel. This is the power generated by the engine, which converts the linear reciprocating motion of the piston into the rotary motion of the crankshaft and outputs the power to the outside.

2. Air valve

The valve mechanism consists of intake valve, exhaust valve, valve spring, tappet, camshaft and timing gear. Its function is to fill the cylinder with fresh gas in time and discharge the waste gas produced by combustion in time.

3. Fuel supply system

Because of the different fuels used, it can be divided into gasoline engine oil supply system and diesel engine oil supply system.

Gasoline fuel supply system is divided into carburetor type and fuel direct injection type. The common carburetor oil supply system consists of oil tank, gasoline pump, gasoline filter, carburetor, air filter, intake and exhaust manifold and exhaust muffler. Its function is to supply the prepared combustible mixture to the cylinder, control the amount of combustible mixture entering the cylinder, thereby adjusting the output power and speed of the engine, and finally discharge the burnt exhaust gas from the cylinder.

4. Cooling system

Motor vehicles generally adopt water-cooled type. Water-cooled is composed of water pump, radiator, fan, thermostat and water jacket (in the machine body). Its function is to use the circulation of cooling water to dissipate the heat of high-temperature parts into the atmosphere through the radiator, thus maintaining the normal working temperature of the engine.

5. Lubrication system

The lubrication system consists of oil pump, filter, oil channel and oil pan. Its function is to distribute lubricating oil to the friction surface of relatively moving parts, so as to reduce friction, slow down the wear of parts and clean and cool the friction surface.

6. Ignition system

The ignition system of gasoline engine consists of power supply (battery and generator), ignition coil, distributor and spark plug, and its function is to ignite the compressed combustible mixture in the cylinder in time according to the specified time.

7. Start the enrichment system

The starting system consists of starter and starting relay. Used to start the stationary engine and make it enter the self-running state.

Principle of internal combustion engine

The process of engine converting thermal energy into mechanical energy is realized through four continuous processes: air intake, compression, work doing and exhaust. Each such process is called a work cycle. A four-stroke engine is an engine in which the crankshaft rotates twice and the piston reciprocates for four strokes to complete a working cycle.

1. Working principle of four-stroke gasoline engine;

(1) intake stroke. The crankshaft drives the piston to move from top dead center to bottom dead center. At this time, the intake valve is opened and the exhaust valve is closed. During the movement of the piston, the internal volume of the cylinder gradually increases, forming a vacuum degree, so the combustible mixture is sucked into the cylinder through the intake valve until the piston reaches the bottom dead center and the intake valve closes.

(2) compression stroke. At the end of the intake stroke, driven by the crankshaft, the piston moves from the bottom dead center to the top dead center, and the internal volume of the cylinder gradually decreases. At this time, the intake valve and exhaust valve are closed, and the combustible mixture is compressed until the piston reaches the top dead center. In the compression process, the gas pressure and temperature increase at the same time, and the mixed gas is further mixed evenly. At the end of compression, the cylinder pressure is about 0.6 MPa ~ 1.2 MPa, and the temperature is about 600 K ~ 800 K ..

(3) Power stroke. At the end of the compression stroke, the spark generated by the spark plug ignites the mixture and burns rapidly, so that the temperature and pressure of the gas rise rapidly, thus pushing the piston to move from the top dead center to the bottom dead center, and rotating the crankshaft through the connecting rod to do work until the piston reaches the bottom dead center.

At the beginning of the work, the gas pressure and temperature in the cylinder rose sharply, and the instantaneous pressure could reach 3 MPa ~ 5 MPa, and the instantaneous temperature could reach 2200 K ~ 2800 K

(4) Exhaust stroke. When the power stroke comes to an end, the exhaust valve opens and the intake valve closes, and the crankshaft pushes the piston to move from the bottom dead center to the top dead center through the connecting rod. Exhaust gas is discharged from the cylinder under its own residual pressure and the push of the piston. When the piston reaches the top dead center, the exhaust valve closes and the exhaust is over. Due to the exhaust resistance of the exhaust system, at the end of the exhaust stroke, the in-cylinder pressure is slightly higher than atmospheric pressure, about 0.105 MPa ~ 0.15 MPa, and the temperature is about 900 k ~1200 K.

2. About engine failure and maintenance

Eight main factors of engine failure in1

Everyone has a heart. If the heart stops beating, life will die. The automobile is no exception, the engine is the heart of the automobile, and the quality of maintenance directly affects the performance and service life of the automobile. In order to keep our car away from "heart disease", we should love the engine of the car as much as our own heart. The following eight main causes of vehicle "heart disease" may benefit you.

Due to one, irregular maintenance.

Usually, people always like to invest a lot of money in modification, but it is easy to ignore the scheduled maintenance of the engine. According to an experienced mechanic, "in the cars they repair, the faults caused by poor engine maintenance account for 50% of the total faults." It can be seen that the maintenance of the engine can play a vital role in prolonging the service life of the vehicle. Of course, it will also reduce unnecessary losses for you, otherwise there will be a saying of "keeping without repairing".

Second, oil deterioration and poor oil filter.

The oil quality of different grades of lubricating oil will change during use. After a certain mileage, the performance of the vehicle will deteriorate, which may bring various problems to the engine. In order to avoid these failures, it is necessary to change the oil of the car regularly according to the use situation, so that the oil quantity is moderate, generally between the upper limit and the lower limit of the oil meter.

When the oil passes through the pores of the oil filter element, solid particles and viscous substances in the oil will accumulate in the filter. If the filter is blocked and the oil cannot pass through the filter element smoothly, the filter element will burst or the safety valve will be opened, and the dirt will still be brought back to the lubrication part through the bypass valve, which will accelerate the engine wear and increase internal pollution. Therefore, it is equally important to change the oil filter regularly.

Because three, the air filter is blocked.

The intake system of an engine is mainly composed of an air filter element and an intake passage. According to different use conditions, the air filter element should be cleaned regularly. Available methods include blowing high-pressure air from the inside out to blow out the dust in the filter element. Because the air filter element is paper, pay attention to the air pressure when blowing to avoid damaging the filter element. Generally, the air filter element should be replaced after three cleanings, and the cleaning cycle can be determined according to the air quality in the daily driving area.

Due to four, the intake pipe is too dirty.

If the vehicle often travels on dusty roads with poor air quality, attention should be paid to cleaning the intake pipe to ensure smooth intake. The intake pipe is very important for the normal operation of the engine. If the intake pipe is too dirty, the charging efficiency will be reduced, so that the engine can not work within the normal output power range, which will aggravate the wear and aging of the engine.

There is too much sludge in the crankcase.

During the operation of the engine, high-pressure unburned gas, acid, water, sulfur and nitrogen oxides in the combustion chamber enter the crankcase through the gap between the piston ring and the cylinder wall, so that they are mixed with the metal powder produced by the wear of parts to form sludge. A small amount of sludge can be suspended in the engine oil. When the equivalent is large, it will be separated from the engine oil, blocking the filter and oil hole, making it difficult to lubricate the engine, thus aggravating the engine wear. In addition, the oxidation of engine oil at high temperature will produce paint film and carbon deposit, which will stick to the piston, increase fuel consumption, reduce engine power, and even make the piston ring jam and pull the cylinder seriously.

6. Poor maintenance of fuel system.

The maintenance of the fuel system includes replacing the gasoline filter element, cleaning the carburetor or fuel nozzle and the oil supply pipeline. When the fuel is supplied to the combustion chamber through the fuel passage, it will inevitably form colloid and carbon deposits, which will be deposited in the fuel passage, carburetor, fuel nozzle and combustion chamber, interfere with the fuel flow, destroy the normal air-fuel ratio, cause poor fuel atomization, and cause engine jitter, knock, unstable idle speed, poor acceleration and other performance problems. Cleaning the fuel system with fuel system cleaning agent can always keep the engine in the best condition.

Due to seven, water tank rust, scaling.

Rusting and scaling of engine water tank are the most common problems. Rust and scale will limit the flow of coolant in the cooling system, reduce the heat dissipation effect, lead to overheating of the engine and even cause engine damage. Oxidation of cooling liquid will also form acidic substances, which will corrode the metal parts in the water tank, resulting in water tank damage and water leakage. Regular use of powerful and efficient water tank cleaning agent can not only ensure the normal operation of the engine, but also prolong the overall life of the water tank and engine.

Eight, the cooling system is in poor condition.

In the maintenance of automobile engines, people pay special attention to the lubrication system and seldom pay attention to the cooling system. I don't know the most common faults of automobile engine, such as piston cylinder pulling, knocking, internal leakage of cylinder block punch, serious noise, decreased acceleration power, etc. All of them are caused by abnormal working temperature, excessive pressure and poor cooling system of automobile engine. The poor condition of the cooling system will directly lead to the failure of the engine to work at room temperature, which will lead to the above-mentioned serious failure phenomenon.

2.2 engine fault diagnosis method

Fault diagnosis definition

Fault diagnosis refers to determining the technical condition of the engine without disassembling (or only disassembling a few small parts), and finding out the fault location and reason.

Fault diagnosis method

When diagnosing faults, we should follow the principle of "easy first, difficult later, simple first, complicated later, outside first, searching by sections, and gradually narrowing the scope". Usually, artificial intuition method, instrument and equipment method and fault tree analysis method are used to analyze and diagnose faults.

Artificial intuition method

The artificial intuition method is a method to determine the technical condition and fault of the machine by directly asking, seeing, smelling, touching, trying and listening, or with the help of simple tools.

( 1) Q。

That is, ask the driver before and after checking the fault, such as vehicle mileage, service life, maintenance, fault omen, fault occurrence process, etc.

(2) Look

That is, observe the conditions of suspected failure mechanisms, assemblies and parts, such as the indicated values of various instruments, cracks and deformation of engine body, color, oil stain and water stain of exhaust gas from muffler, and then analyze and judge the working conditions of the engine in combination with other relevant conditions.

(3) Smell

That is, judge the fault location according to the abnormal smell when the engine is running. If there is gasoline, it means oil leakage or poor combustion.

Step 4 touch

Is it possible to touch it with your hands? Temperature and vibration at the fault location, etc. , so as to judge the tightness of cooperation, the size of bearing clearance, the balance between parts and weight, the pulsation of diesel pipeline and the temperature of oil and water.

(5) Try

Through various test methods, the fault phenomena can be fully revealed, such as pressing the horn, turning on the ignition switch or light switch, "extinguishing" the spark plug, pulling the throttle, rapidly increasing or decreasing the engine speed, etc. If necessary, replace components or parts for comparative test.

Step 6 listen

It is to judge which is normal and which is abnormal according to the sound and sound law of different working conditions and parts of the engine. Such as whether there is knocking sound in the cylinder, whether there is "backfire" in the carburetor, and whether there is shooting sound or "sudden, sudden" sound in the exhaust muffler.

The above methods, not every fault diagnosis should follow this procedure, and different faults should be applied flexibly according to their specific conditions.

2.3 Simple maintenance of the engine

(1) First, check whether the liquid level of automobile antifreeze is appropriate. The correct liquid level position should not be lower than the bottom line and not higher than the middle of the highest line, which is the most suitable liquid level position!

(2) Vehicle battery The vehicle battery inspection is divided into three small steps. Step 1 is to check whether the battery electrolyte is insufficient (except maintenance-free batteries). The second step is to check whether the "positive electrode" and (negative electrode) of the battery are loose. The third step is to remove the oxide on the battery electrode!

(3) Check and replace the oil. In this step, first pull out the dipstick to check the oil level, and then observe the color of the oil. If it is as sticky as sesame paste and water, it must be replaced.

(4) Check or replace the air filter. This task is simple. Just remove the filter and check it. If it is not particularly dirty, it can be blown clean with a high-pressure air gun without replacement!

(5) Check and clean the radiator and air inlet. This work must be checked after spring, because when spring comes, a lot of impurities such as catkin wool will stick to the radiator, which will affect the heat dissipation of the engine after the car enters summer. You must go to the maintenance station and blow it clean with a high-pressure air gun!

(6) Check whether the exposed rubber hoses (including water pipes, oil pipes and gas pipes) in the engine compartment of the automobile are aging and cracked!

(7) Check the exposed wires in the engine compartment of the automobile for glue!

(8) Check whether the screws of the parts in the engine compartment of the automobile are loose, and tighten them immediately if any!

(9) Check whether the belt strength in the engine compartment of the automobile is sufficient.

Three main aspects of engine maintenance

3. 1 Common sense of automobile maintenance

Car maintenance on time is the key, and car maintenance, like fitness, is of great help to prolong the service life of cars. Many car owners are too busy at work at ordinary times, and then spend their time on leisure travel on holidays. In this way, I have neither time nor professional maintenance knowledge, and eventually the car will protest against the failure, and it will be too late to regret it.

According to the different environmental conditions and models, cars are generally maintained every 5000 kilometers or so. Its main content is to replace engine oil and mechanical filter. Because oil is easy to oxidize when exposed to air and heated, with the increase of acid substances, colloid and iron filings in oil, the color of oil will gradually turn black and the viscosity will gradually decrease. It is necessary to change the new oil within the specified oil change cycle. If the oil is not changed for a long time, these deposits may block the oil circuit, leading to dry grinding of the engine and seriously affecting the service life of the engine.

In addition to the replacement items, there are many inspection items in the maintenance items, and the process is quite detailed and complicated. First of all, in order to ensure the lubrication and oil leakage of various systems of the automobile, it is necessary to check various liquid levels: oil level, antifreeze level, brake oil level, power steering oil level, gear oil level, electrolyte level, glass cleaning level, etc. What needs to be supplemented should be supplemented in time. If leakage is found, minor illnesses can be found early and solved in advance to minimize the damage to vehicles. Secondly, the braking, exercise and power system, which are closely related to the driver's life, are also the focus of maintenance inspection. The contents include: brake friction parts wear, hand brake clearance fit, tire wear and air pressure detection, clutch clearance adjustment and other items. Don't covet the cheap maintenance of roadside stalls. In those places, inspections and additions are often ignored and there is no quality assurance. Only oneself will suffer in the end. In addition, the inspection of vehicle lighting and indicator lights is also essential. At present, the provisions of the law are getting more and more detailed every day, and the punishment is getting bigger and bigger every day. There is no doubt that it is unwise to drive on the road in poor light.

Replacing parts in maintenance is different according to the needs of mileage. Various automobile brands arrange maintenance plans for different models under their names, and replace fuel filters, air filters, air-conditioning filters, spark plugs, timing belts, brake fluid, gear oil and other components. Replacing the above parts in time is of great significance for maintaining and restoring the technical performance of the automobile, ensuring the good performance and reliability of the automobile and prolonging the service life of the automobile. The majority of drivers and friends should change the old concept of "repair without insurance" and don't not maintain their cars in order to save money, so as not to lose big because of small.

18 key points of automobile sensor fault diagnosis

1, the failure of the computer power cord will make the performance of the automobile engine worse and the economy lower, so you should check the computer power cord before replacing the automobile computer.

2. If the voltage signal of the oxygen sensor is higher than the standard value, it may be that the sensor is polluted, which will make the air-fuel ratio rich in many cases.

3. If the voltage signal of the oxygen sensor is lower than the standard value, it may be that the sensor is out of order, which will lead to the lean air-fuel ratio of the engine.

4, check the oxygen sensor must use digital multimeter or oscilloscope.

5. If the oxygen sensor heater is faulty, it may prolong the open-loop working time of the engine and increase fuel consumption.

6. Engine coolant temperature sensor can check its performance with digital meter or analog meter.

7. In some computer ECT circuits, an internal resistor is controlled to change the voltage on the sensor at a certain temperature of the engine. If the voltage at this time is abnormal during the measurement, it does not mean that the sensor is faulty.

8. Testing the engine coolant temperature sensor and the air temperature sensor can use exactly the same operating procedure. The only thing to note is that their temperature change curves are different, so there will be no same voltage signal at the same temperature.

9. When the throttle is opened and the voltage signal of the throttle position sensor is checked, the stability of the sensor can be checked by vibration with appropriate force. This method is very effective for virtual connection faults of some circuits.

10, many four-wire throttle position sensors include an idle position switch, which is used to provide the engine control unit with the working state information when the throttle is in the idle position.

1 1. In some cases, when the throttle is in the idle position, you can loosen the fixing screw of the throttle position sensor and rotate the sensor housing to adjust the voltage signal.

12. If the absolute pressure sensor of the intake manifold outputs a frequency signal, it can't be detected by a common multimeter.

13. Many intake manifold absolute pressure sensors output voltage signals converted from atmospheric pressure. This signal can be checked by turning on the ignition switch.

14. When checking the output voltage signal of the absolute pressure sensor of the intake manifold, there should be a certain degree of vacuum in the sensor. In most cases, it can be judged by detecting its output signal every 10 kPa.

15. When measuring the voltage signal of the vane-type intake air flow sensor, you can check when the vane of the sensor turns from fully closed to fully open, and observe the voltage value and continuity of the output signal.

16. Some intake air flow sensors with thermal resistors or hot wires are provided with voltage signals of different frequencies by the engine computer. This kind of sensor can only check its voltage with a multimeter that can test the frequency.

17. The voltage signal of the exhaust gas recirculation valve position sensor will change from 0.8V when the valve is closed to 4.5V when the valve is fully opened.

18, the computer uses the signal of the speed sensor to control the clutch of the torque converter, shift gears while driving, and collect data from the driving computer.

The engine is the heart of a car, and how to keep the engine young forever is the key to car maintenance. First of all, we should pay attention to the maintenance of running-in period, which is the basis of prolonging the service life of the engine. In addition, we should be careful of three common engine diseases:

1, engine wear. One is cold start (that is, the engine stops for more than 6 hours), which produces dry wear at the moment of starting, and the damage to the engine is the greatest at this time. Another situation is that the engine runs at high speed to produce high temperature and the oil is relatively thin. At this time, the engine is in a semi-dry wear state, which is also a phenomenon that cannot be ignored.

2, the phenomenon of oil loss. This situation is caused by the gap between the combustion chamber and the cylinder, which causes the oil to escape into the combustion chamber. The way to find the engine oil shortage is to see whether the exhaust pipe emits blue smoke, and put your hand into the exhaust pipe to smell whether your fingers smell of engine oil. If there is a smell, it proves that oil has escaped into the combustion chamber.

3. The oil seal ring is aging. The oil seal ring is aging, and the oil slowly leaks out. For the phenomenon of slight oil burning, a certain amount of repairing agent can be added when changing the oil. If the situation is serious, you need to disassemble the engine.

In order to maintain the engine, it is necessary to change the oil and three filters regularly. In addition, it is necessary to observe and check frequently at ordinary times to eliminate faults in time, so as to keep the engine in good technical running condition.

summary

The car is a rare means of transportation in our life now, so it is very noteworthy to maintain the car. Ordinary cars need to go to the repair shop for different maintenance every 5000 km to 10000 km or more. Car maintenance is mainly carried out from the aspects of keeping the car in good technical condition and prolonging its service life. In fact, its content is wider, including the knowledge of automobile beauty care. To sum up, it mainly focuses on the following three aspects: body maintenance, body maintenance and body renovation.

thank you

Here, I sincerely thank the xxx teacher who helped me. In the process of writing my thesis, the teacher devoted a lot of effort and sweat. No matter in the topic selection, conception and data collection of the paper, or in the research method and finalization of the paper, it has been carefully taught and selflessly helped by the teacher. Thank you for your help and support!

In the process of writing this paper, I also got valuable suggestions from many classmates, and I also got the support and help from many colleagues in the work process. I also thank the authors and units of all the references in this article, and I would like to express my sincere thanks here. Thanks to all my mentors and friends who have cared about me, supported me and helped me.

Finally, I would like to express my heartfelt thanks to the experts who took time out of their busy schedules to review this article and put forward valuable opinions!

Step 6 refer to

[1] Zhao Yingxun. Automotive Detection and Diagnosis Technology Beijing: Machinery Industry Press, July 2008.

[2] Cai. Automobile structure and principle. Part I Engine and Body Beijing: Machinery Industry Press, August 2004.

[3] Guan Wenda. Automobile Structure Beijing: Machinery Industry Press 1998

[4] Liao Xiangbing male Wei Long. Automobile Maintenance Technology Beijing Jindun Press, 2006.

7. concluding remarks

After half a year's preparation, the paper was finally successfully completed. Because the model of my internship is not a high-end car, but an economical Wuling minibus, I find that the maintenance of automobile engine is the most important. I hope this technology can be presented simply and clearly. In the middle, I also completed it in a state of ignorance to half understanding, which is not only the process of self-learning, but also the result of self-efforts.

At first, I always thought that maintenance was very important in cars, but after writing this paper, I found that maintenance is as important as machine maintenance, or even more important. Therefore, we should pay special attention to car maintenance in the future work.

After writing this paper, I also benefited a lot. Only with clear goals can I stick to it, and there must be specific plans to arrange it, step by step, step by step!

Yantai Automobile Engineering Vocational College Graduation Design (Thesis) Task Book

Department: Automobile Inspection Department Major: Automobile Inspection and Maintenance Technology Name: Ye Guangyao

Class: 09 Auto Maintenance Class II Student ID: xxxxx

Graduation Design (Thesis) Topic Maintenance and Maintenance of Automobile Engine

Automobile inspection department is a department specializing in automobile inspection and maintenance technology.

Significance and research value of the subject Engine is the heart of the car, and the quality of maintenance directly affects the performance and service life of the car. In order to keep our car away from "heart disease", we should love the engine of the car as much as our own heart. Studying the maintenance of automobile engine is helpful to reduce accidents, avoid unnecessary losses and improve our work efficiency.

Main contents and main research methods This paper mainly introduces eight main factors of automobile engine fault, fault diagnosis methods, simple maintenance and automobile maintenance knowledge.

This paper introduces the engine structure, eight main factors, fault diagnosis methods and the influence of simple maintenance. Understand the most direct cause of automobile engine maintenance, and introduce the analysis steps to deal with the fault. Finally, let's talk about how to maintain them.

Time schedule: determine the topic and conceive the paper before February 10, and start writing the paper on February 10.

Submit the first draft at the beginning of March and submit it in writing at the end of April.

Lecturer's opinion

Teacher's signature: year month day.

Departmental opinion

Signature of department head: year month day.