Internal combustion engine sliding bearing is the main friction pair of internal combustion engine. It bears a high dynamic load, and the magnitude and direction of the load change greatly instantaneously. Under the conduction of high temperature in the combustion chamber, the working temperature is generally as high as 100 ℃ to 170 ℃. Single material sliding bearing is difficult to adapt to this working condition, so the composite material composed of steel ridge and antifriction alloy is widely used in internal combustion engine sliding bearing.
Another kind of composite material is used in self-lubricating bearing. It can withstand high load of 250N / mm2 under oil-free lubrication. Operating temperature range: 200 ℃ to 280 ℃. It can bear vibration balance load in vacuum environment or radiation area. It also adopts the composite material composed of steel ridge and other materials, but the material compounded on the steel back is different from that of internal combustion engine sliding bearing.
In order to avoid confusion with the name of rolling bearing, the sliding bearing of internal combustion engine is generally called bearing bush and bushing. The ideal bearing bush material shall meet the following performance requirements:
The bearing bush is subjected to great periodic alternating load during operation, so the bearing bush material should have high fatigue strength.
The bearing shell material must be compatible with the lubricating medium to prevent the adhesion of the bearing shell material under friction conditions.
The so-called compliance refers to the adaptability that the bearing bush material can adapt to the deflection and slight misalignment of the shaft through elastic or plastic deformation (due to poor installation, non concentricity between the shaft and bearing bush seat, deformation or wear of the shaft and bearing seat), and can also maintain normal operation.
Embeddedness is the ability of bearing bush material to embed hard dirt particles in it to reduce journal scratch and wear.
Also has the ability to resist the corrosion of bearing bush by organic acid, inorganic acid and oxide formed by high-temperature oil oxidation and some additives in lubricating oil.
If the strength is low, the working surface of Bearing Bush will be partially collapsed under high load. Under normal operation, the bearing bush material is required to maintain high enough bearing strength.
It can prevent damage caused by high temperature of oil.
The clearance between bearing bush and shaft will not change greatly under high temperature. If the linear expansion coefficient is too high, the clearance between bearing bush and shaft may be sharply reduced and the shaft may be locked. In addition, if the linear expansion coefficient of the bearing shell material is much larger than that of the bearing seat, the bearing shell may be distorted.
Antifriction alloy and steel ridge can produce firm bonding, casting, good fluidity, and good machinability.
Some internal combustion engines with high load should use high-strength bearing bush alloy materials, and the surface performance of high-strength bearing bush alloy is poor. Generally, the surface of high-strength bearing bush is improved by plating a layer of 0.02mm aluminum tin binary or lead tin copper ternary alloy with good surface performance. Babbitt alloy as the material of internal combustion engine bearing bush has a long history. With the progress of material science and the growth of material varieties, Babbitt alloy is only used in machines with small load and corrosive gas, such as refrigerators. The fatigue strength of Babbitt aluminum base alloy and copper base alloy is the mainstream of modern internal combustion engine sliding bearing.