Automobile engine balance shaft function

The balance shaft technology is a simple structure and very useful engine technology, it can effectively slow down the vibration of the vehicle and improve the comfort of driving. Some consumers may ask, why plan this structure in some engines? To understand this problem, we first need to clarify one thing-"the principle of engine oscillation".

When the engine is in working condition, the movement speed of the piston is very fast, and the speed is very uneven. When the piston is located at the top and bottom dead center position, its speed is zero, but the speed in the middle position of the top and bottom dead center reaches the highest. Because the piston makes repeated high-speed linear motions in the cylinder, large inertial forces must occur on the piston, piston pin and connecting rod. Although the counterweight on the connecting rod can effectively balance these inertial forces, as long as a part of the moving mass participates in the linear motion, the other part participates in the rotation. Therefore, except for the top and bottom dead center position, other inertial forces cannot completely reach the equilibrium state, and the engine oscillates at this time.

In order to eliminate this oscillation, planners have chosen many methods, such as choosing lightweight pistons to reduce the mass of moving parts, improving the stiffness of the crankshaft, and choosing a "V"-shaped engine with an angle of 60 degrees. Adding a balance shaft (the part shown in the middle position in the above figure) is also one of these methods. In short, the balance shaft is actually a shaft equipped with an eccentric weight and rotating synchronously with the crankshaft, using the reverse oscillating force generated by the eccentric weight , So that the engine achieves a good balance effect and reduces engine oscillation.

The balance shaft can be divided into two types: single balance shaft and double balance shaft. Single balance shaft Wang Wenshengyi selects a single balance shaft and uses a gear transmission method to work. The fixed balance shaft drive gear, balance shaft driven gear and balance shaft are driven by the rotation of the crankshaft. The single balance shaft can balance the first-order oscillation which accounts for a considerable share of the entire oscillation, so that the oscillation of the engine is significantly improved. Because the single balance shaft has a simple structure and takes up less space, it is widely used in single-cylinder and small-displacement engines. The double balance shaft uses a chain drive method to drive the rotation of two balance shafts, in which one balance shaft and the engine speed are the same, which can eliminate the first-order oscillation of the engine; the other balance shaft speed is twice the engine speed , Can eliminate the second-order oscillation of the engine, and then achieve an even more ideal damping effect. Because the structure of the double balance shaft is relatively messy, the cost is high, and the space occupied by the engine is relatively large, it is generally used in large-displacement vehicles. In addition, there is a dual balance shaft installation method, that is, the two balance shafts are arranged symmetrically with the center line of the cylinder, the rotation direction is opposite, and the rotation speed is the same as the crankshaft rotation speed to balance the first-order reciprocating inertial force of the engine.