Service HotlineThe mechanism of damage caused by the pulling of bimetallic cylinder liners is mostly due to local damage to the lubricating oil film at the sliding parts. At this time, the protruding parts of the two relative moving surfaces first come into contact with each other, and then a small "melting" phenomenon occurs locally in the bimetallic cylinder liner. The melting part is then torn due to the relative movement of the components.
During this process, the metal surface forms a hardened layer. When the hardened layer is damaged, the metal abrasive particles generated will become the abrasive material that exacerbates surface wear The uneven wear marks parallel to the cylinder centerline that appear on the surface of the piston and gas bimetallic cylinder liner during the short period of so-called "melting wear" are called cylinder pulling phenomenon.
In severe cases, the sliding parts may completely adhere or get stuck, and even cracks may occur in weak areas on both surfaces, causing damage to the components, known as cylinder biting. Therefore, the fundamental cause of cylinder pulling is melting and wear.
The bimetallic cylinder liner should have sufficient strength, stiffness, and heat resistance, as well as good wear resistance. Good lubrication and cooling should be provided during work. The inner surface of the cylinder is prone to wear due to the action of high-temperature and high-pressure gas and contact with the high-speed moving piston. There are different cylinder structure forms and surface treatment methods to improve the wear resistance and prolong the service life of cylinders. There are three types of cylinder structures: non bimetallic cylinder liner type, dry bimetallic cylinder liner type, and wet bimetallic cylinder liner type.
The body without bimetallic cylinder liners is a body without embedded bimetallic cylinder liners, and cylinders are directly machined on the body. The advantage is that it can shorten the center distance of the cylinder, reducing the size and mass of the body. But the cost is relatively high. The dry bimetallic cylinder liner does not come into contact with the coolant, with a wall thickness of 2-3mm. The outer surface and the inner surface of the bimetallic cylinder liner seat hole must be precision machined to ensure necessary positional accuracy and facilitate disassembly and assembly. The advantages are high body stiffness, small cylinder center distance, light weight, and simple processing technology. The disadvantage is poor heat transfer, uneven temperature distribution, and easy occurrence of local deformation.
The outer wall of the wet bimetallic cylinder liner is in direct contact with the coolant, with a wall thickness of 5-8mm. Radial positioning is achieved using upper and lower positioning rings, while axial positioning is achieved by matching the upper flange of the bimetallic cylinder liner with the corresponding support surface at the top of the engine body. The advantage of wet bimetallic cylinder liner is that there is no sealed water jacket on the body, making it easy to cast, with good heat transfer, uniform temperature distribution, and convenient repair. The bimetallic cylinder liner can be replaced without removing the engine from the car. The disadvantage is that the body has poor rigidity and is prone to water leakage.
