The content of this section occupies an important position in the chapter "Understanding the overall structure of the automobile" in the sixth volume, which mainly expounds the working process of the gasoline engine and the working process and characteristics of the four-stroke engine. Students' clear understanding of engine working principle will lay a foundation for engine fault diagnosis and maintenance in the future. Therefore, the success or failure of this class directly affects the study of later courses.
Second, the teaching objectives:
To enable students to master the working process of four-stroke gasoline engine, that is, the working principle, and on the basis of mastering the working principle, analyze the working state and mutual working relationship of all components in the working process of four-stroke gasoline engine, so as to improve students' ability to analyze problems in the course of studying professional courses.
Third, the teaching emphasis and difficulty:
Teaching emphasis: Four-stroke gasoline engine completes the working process of each stroke of a working cycle. Teaching difficulty: working characteristics of each working stroke of four-stroke gasoline engine.
Fourth, teaching methods: lectures, discussions and video demonstrations.
Teaching tools: textbooks, blackboards, chalk and PPT.
VI. Schedule: 1 class hour
Seven, the teaching process:
First of all, we invite Wu to preside over the column of "One Class, One Car" in this issue.
[opinion] 1. Write the basic structural name of reciprocating piston internal combustion engine.
2. What are top dead center, bottom dead center, piston stroke and combustion chamber volume?
[teaching new lessons]
First look at a group of engine pictures and put forward the key words: four-stroke engine with working cycle.
Air intake, compression, work, exhaust
Second, ask the question, what is the motion state of engine parts in the four working processes?
Watch the engine installation and working video.
(1) intake stroke
① Piston movement direction: from top to bottom.
② Valve state: the intake valve is open and the exhaust valve is closed.
③ Crankshaft angle: 0- 180.
The gas pressure in cylinder 4 is 0.08-0.09 MPa, and the temperature is 47℃ ~ 107℃. zero