The requirements of Copeland discus piston are introduced:

1. Piston equipment must have sufficient strength, rigidity, small mass and light weight to ensure the minimum inertial force.
2. Good thermal conductivity, high temperature resistance, high pressure, corrosion resistance, sufficient heat dissipation capacity, 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 change should be small, and the minimum gap should be kept between the cylinder wall.
5. The coefficient of thermal expansion is small, the specific gravity is small, and it has good wear resistance and thermal strength.

The function of the Copeland discus piston is to withstand the gas pressure. The piston equipment is transmitted to the connecting rod through the piston pin to drive the crankshaft to rotate. The top of the piston is also an integral part of the combustion chamber. Copeland discus piston works under high temperature, high pressure, high speed, and poor lubrication conditions. The piston is in direct contact with the high-temperature gas, and the instantaneous temperature can reach more than 2500K. Therefore, the heating is serious and the heat dissipation conditions are very poor, so the temperature of the piston is very high when it is working. When the Copeland discus piston works under such harsh conditions, it will deform and accelerate wear. It will also generate additional load and thermal stress, and will be subject to chemical corrosion from the gas.

The forces acting on the Copeland discus piston include gas pressure, the elastic force of the ring itself, the inertial force of the ring's reciprocating motion, and the friction between the ring and the cylinder and the ring groove. Due to these forces, the ring will produce basic movements such as axial movement, radial movement, and rotational movement.