1. It shall have sufficient strength, stiffness, small mass, and light weight to ensure minimum inertial force.
2. Good thermal conductivity, high temperature resistance, high pressure, corrosion resistance, sufficient heat dissipation ability, and small heating area.
3. There should be a small coefficient of friction between the piston and the piston wall.
4. When the temperature changes, the size and shape changes should be small, and the minimum clearance between the cylinder wall and the cylinder should be maintained.
5. Low coefficient of thermal expansion, small specific gravity, good wear reduction and thermal strength.
Role of the piston
With the increasingly strict requirements for the power, economy, environmental protection, and reliability of the engine in the entire vehicle, the piston has developed into a high-tech product that integrates multiple new technologies such as lightweight and high-strength new materials, special-shaped cylindrical composite surfaces, and special-shaped pin holes, to ensure the heat resistance, wear resistance, stable guidance, and good sealing function of the piston, reduce the friction work loss of the engine, and reduce fuel consumption Noise and emissions.
In order to meet the above functional requirements, the outer circle of the piston is usually designed as a special-shaped outer circle (convex to elliptical), that is, the cross section perpendicular to the piston axis is an ellipse or a modified ellipse, and the ovality changes along the axis direction according to a certain rule (as shown in Figure 1), with an ovality accuracy of 0.005mm; The outer contour of the piston longitudinal section is a fitting curve of a higher order function, with a contour accuracy of 0.005 to 0.01 mm; In order to improve the bearing capacity of the piston and increase the engine power, the pin hole of the high load piston is usually designed as a micro internal cone type or a normal stress curved surface type (special-shaped pin hole), with a pin hole size accuracy of IT4 and a contour accuracy of 0.003mm.
Piston, as a typical key automotive component, has strong technological characteristics in machining. In the domestic piston manufacturing industry, machining production lines are usually composed of general-purpose machine tools and specialized equipment that combine the characteristics of piston technology.
Therefore, special equipment has become the key equipment for piston machining, and its function and accuracy will directly affect the quality indicators of the key characteristics of the final product.
Post time: Mar-17-2023