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What is a turbo bearing? Types of turbocharged bearings

Turbo bearing is the bearing in the turbocharger, to understand the turbocharger, first we need to know the turbocharger and its moving parts.

 

What turbocharger?

A turbocharger, which we commonly find in cars, is actually an air compressor that compresses air to increase the amount of air taken in. It uses the inertial impulse of the exhaust gas discharged by the engine to push the turbine in the turbine chamber, and the turbine drives the coaxial impeller, and the impeller pressurizes the air sent by the air filter pipe to pressurize it into the cylinder. When the engine speed increases, the exhaust gas discharge speed and the turbine speed also increase synchronously, the impeller compresses more air into the cylinder, the pressure and density of the air increase can burn more fuel, increase the amount of fuel and adjust the speed of the engine, you can increase the output power of the engine.

 

What are the moving parts of a turbocharger?

The moving parts of the turbocharger are also the core components - the turbine wheel, compressor impeller and rotor shaft, and the supercharger housing have high-speed relative movement, which is unbearable for ordinary bearings, so the bearing of the supercharger is a special floating bearing.

 

It is actually a copper ring that is sleeved over the shaft and housing, with clearances between the ring and the shaft and between the ring and the housing. When the engine is working, under the action of oil pressure, a double oil film is formed in these parts, and the rotor actually floats on the oil film and rotates at high speed.

 

Due to the extremely high rotational speeds and extremely high temperatures, this area also places extremely high demands on lubrication and cooling.

 

If the supercharger is not well lubricated and cooled, it will cause abnormal wear of the bearing, greatly shorten the service life of the bearing, increase the gap between the rotor and the housing, and part of the oil will enter the intake pipe or exhaust pipe from this part, resulting in serious oil burning failure.

 

Types of turbocharged bearings

As the key moving part of the turbocharger, the structure of the bearing is related to the reliability and durability of the turbine. There are two main types of turbocharger bearings, one is floating bearings and the other is ball bearings.

 

At present, most of the major automobile manufacturers use floating bearings, which should be durable and affordable. The floating bearing is actually a ring on the shaft, and there is a gap between the ring and the shaft and between the ring and the bearing housing, forming a double oil film. The ring floats between the shaft and the housing. Generally, the inner layer gap is about 0.05mm, and the outer layer gap is about 0.1mm. The wall thickness of the bearing is about 3.0-4.5mm, and it is made of tin-lead bronze alloy, and the surface of the bearing is coated with a layer of lead-tin alloy or metal indium with a thickness of about 0.005-0.008mm. When the supercharger is working, the bearing rotates between the shaft and the housing. Therefore, we can find the disadvantages of floating bearings: high running resistance of turbine shafts, high oil pressure and quality requirements, and unstable dynamic control of turbine shafts.

 

Ball bearings are more commonly found in performance cars, and as the name suggests, ball bearings are the position of installing balls on the turbine shaft to replace the oil in the floating bearing. The advantage of ball bearings is precisely the opposite of floating bearings: less friction, lower turbine hysteresis, and more favorable for the pressing of dynamic limits; The dynamics of the turbine shaft can be effectively controlled; Oil pressure and quality can be slightly reduced, which indirectly increases the life of the turbine. Its shortcomings are also obvious, that is, the life is not as good as the floating bearing, generally 70,000 to 80,000 kilometers to the life limit, and the maintenance cost is expensive, maintenance is difficult. However, due to the allure of ball bearings in terms of power, they are still the mainstream equipment on performance cars.