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Why does a three-cylinder car that is rejected by many people shake?

As the name implies, a three-cylinder engine has three cylinders, and its working principle is the same as that of an ordinary four-cylinder engine, all of which are reciprocating piston engine. Due to the limitation of engine bore and piston formation, the displacement of a three-cylinder engine is generally not very large, mostly between 1- 1.5 liters. In fact, the three-cylinder engine has existed for a long time, and it has only been re-used in recent years, mainly for policy-oriented reasons. Countries all over the world are advocating energy conservation and emission reduction, and have issued a series of policies to promote the development of small-displacement engines.

For example, the consumption tax is directly added to the frame of the car when it leaves the factory. The smaller the displacement is, the lower the tax rate is, and the car has an advantage in sales price. In addition, the three-cylinder engine can reduce the manufacturing cost. After all, there is no cylinder, but a set of connecting rod and valve train structure. Many people think that the three-cylinder engine may lack power, but with the wide application of turbocharging technology, the power and torque of the three-cylinder engine can be greatly improved. Another point is that the three-cylinder engine is relatively small in size, especially in length. This structure can greatly release the space in the front engine room, so as to equip more complicated suspension system.

The above advantages also make many car companies slowly apply the three-cylinder engine, and the biggest disadvantage of the three-cylinder engine is the large vibration. When the engine is working, it needs to go through four stages: inhalation, compression, work and exhaust. During this period, the crankshaft of the piston will rotate twice, that is, 720 degrees. Only the stroke that does work will generate electricity, and the other three strokes will not only generate electricity, but even consume a part. Therefore, when the engine is actually running, the rotation speed of the crankshaft is uneven, which will accelerate in the power stroke and slow down in the other three strokes.

In this process, there will be various forces, such as the pressure caused by fuel combustion in the cylinder, the centrifugal force caused by the high-speed rotation of the crankshaft, and the inertial force caused by the reciprocating motion of the piston. These unbalanced forces will make the engine fall in a certain direction, and the intuitive performance is engine vibration. A self-cylinder engine can do work four times in one cycle, and each time it is 180 degrees, which is exactly 780 degrees. When it works, it can realize end-to-end connection. The four pistons move in opposite directions in two groups, and the inertia force can be completely offset in theory. So its vibration is much smaller than that of a three-cylinder engine.

In a three-cylinder engine, because only three pistons are working, and the work done by the three pistons is 240 degrees different, the inertia force generated by their movement will never be offset, so its vibration is inevitable. The second point is that there are three cylinders. After each cylinder does work, there will be a window period of 60 degrees. During this period, the engine will not generate power, but only consume power, so the unevenness of crankshaft operation will increase obviously, which will also lead to further increase of engine vibration.

For the first factor, a balance shaft is usually designed in the engine to counteract the reciprocating inertia force, and for the second factor, a flywheel with a larger size is usually installed in the engine. However, after the engine is used for a period of time, the imbalance of each cylinder will gradually increase and the vibration of the engine will become more and more obvious, which is one of the reasons why many people are worried about the three-cylinder engine.

When buying a car, some people resolutely reject the three-cylinder car, as long as it is a three-cylinder and seven-cylinder model, some people think that the three-cylinder technology is mature and can be bought. In fact, whether we admit it or not, the three-cylinder engine is constantly developing, the technology is becoming more and more mature and the application is becoming more and more extensive. After all, the trend of the times is unstoppable. Under the current situation, it is a rational choice to choose a three-cylinder engine with mature technology.