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Adapter Sleeves (9)
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Ball Bearings (11)
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Ball Screw Bearings (2)
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Ceramic Bearings (27)
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Pillow Block Bearings (4)
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Plain Bearings (32)
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Roller Bearings (12)
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Slewing Bearings (43)
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Sliding Block (3)
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Stainless Steel Bearings (27)
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Super Precision Bearings (6)
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Thin Section Bearings (9)
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Track Rollers (4)
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Universal Joints (1)
Understanding Engine Bearings: An Essential Guide
Introduction
Among the complex components that make up an internal combustion engine, bearings play a key role and, although often overlooked, are vital to the smooth operation of the engine. From distributing load to reducing friction, engine bearings are critical to longevity and performance. In this guide, we dive into engine bearings’ basic functions and service life considerations, illustrating their importance in automotive engineering.
Understanding Engine Bearings
Engine bearings, also known as the crankshaft bearing, are a crucial component of an engine. It serves to support the crankshaft, enabling it to rotate smoothly within the engine block.
In a typical engine, there are two main types of bearings: main bearings and connecting rod bearings.
What Are Main Bearings
Main bearings are a type of engine bearing that supports the crankshaft in an internal combustion engine. They are typically located within the engine block and provide support to the crankshaft as it rotates. And can reduce friction and wear between the crankshaft and engine block.
What Are Connecting Rod Bearings
Connecting rod bearings are another type of engine bearing that support the connecting rods within an internal combustion engine. These bearings are positioned between the connecting rod and the crankshaft, allowing the connecting rod to pivot smoothly as the crankshaft rotates，and reduce friction and wear between connecting rods and crankshaft journals
What are the characteristics of engine bearings materials?
Engine bearings are generally made of materials such as copper alloy, aluminum alloy, steel or polymer. The characteristics of these materials include:
- High strength and hardness
- High temperature and wear resistance
- Fatigue resistance, corrosion resistance
- Good thermal conductivity
- Better impact toughness
What Are The Functions Of Engine Bearings?
The primary functions of engine bearings are:
1. Supporting Rotating Components: Engine bearings support and facilitate the smooth rotation of critical components such as the crankshaft and connecting rods within the engine block.
2. Reducing Friction: They help to minimize friction between moving parts, such as the crankshaft and the engine block, by providing a low-friction surface for them to operate against.
3. Bearing working load: During the operation of the engine, rotating parts such as the crankshaft need to bear the huge combustion impact force and torque load from the piston. Another important function of engine bearings is to carry these severe dynamic loads and prevent the rotating parts from being displaced or damaged.
4. Absorbing Shock: They absorb and dampen the shock and vibration produced during the engine’s combustion process, contributing to smoother and quieter engine operation.
5. Maintaining Lubrication: Engine bearings help to maintain proper lubrication between moving parts by retaining oil film and ensuring adequate oil flow throughout the engine.
How Engine Bearings Work
The working principle of engine bearings is to use the “rolling-sliding” compound motion mode between the inner and outer rolling rings and multiple rolling elements to meet the specific geometric position constraints of the engine rotating parts. Rolling contact carries the huge radial load and axial thrust generated during engine operation, and greatly reduces the motion resistance and energy loss between the inner and outer rings due to the rolling motion characteristics;
Under high-speed working conditions, a dynamic pressure lubricating oil film will be formed between the rolling elements and the rolling rings to further reduce friction; at the same time, there is a sealing structure inside the bearing, which can isolate the harsh high-temperature and high-pressure environment of the engine, extend the service life of the bearing, and make the bearing reasonable The unique vibration reduction and noise reduction design also helps suppress noise problems, thereby comprehensively ensuring the efficient, precise, smooth and reliable operation of the engine’s internal rotating parts.
Engine Bearings Operating Conditions
1 . High-temperature environment
When the engine is running, due to the high temperature generated by internal combustion and the friction heat between parts, the ambient temperature of the bearing is extremely high, generally exceeding 150°C, and sometimes even reaching more than 200°C.
2 .High load
Engine rotating parts such as the crankshaft need to bear huge combustion impact loads and torques during the piston operation. These concentrated loads act directly on the bearings, causing great stress to the bearings. Bearings must have excellent load-carrying capabilities.
3 .High speed movement
In order to pursue power, modern engines generally have high rotational speeds. The high-speed tangential motion endured by the bearings is very intense, and the relative motion of the inner and outer rings is very intense, which requires high wear resistance and geometric accuracy of the materials.
4 .Vibration effects
Due to the unbalanced explosive force of the cylinder and other factors, a certain amount of vibration will occur inside the engine. This vibration load will also be transmitted to the bearings, affecting its working accuracy and service life.
5 .Polluted environment
There are residual fuel, combustion residues, wear particles, moisture, and other pollutants inside the engine. These impurities can easily penetrate the bearings, exacerbating wear, corrosion, and other problems.
6 . Lubrication challenges
Engine bearings rely on lubricating oil to form a sufficient oil film to reduce wear, but high temperature and high-speed movement will aggravate the damage to the oil film and increase the difficulty of the lubrication system design.
What Is The Service Life Of Engine Bearings?
Engine bearings are key consumable parts that are extremely prone to wear in the engine. Their service life mainly depends on the working load the bearings bear, the harshness of the operating environment and the good lubrication state. Normally, a better quality engine Under normal use and maintenance conditions, the service life of bearings is generally about 50,000 to 200,000 kilometers. However, if the use conditions are poor or the maintenance is improper, the service life of the bearings will be greatly shortened, thus affecting the reliability and service life of the entire engine system.
What Are The Symptoms Of Engine Bearings Wear?
During long-term use, engine bearings will gradually wear out and show the following symptoms:
- Increased engine bearings noise: Bearing wear will cause the gap to increase and the surface roughness to increase, thereby producing abnormal noise, such as noisy metal friction, whistling, etc.
- Increased vibration: Uneven wear of the inner or outer rings of the bearings will destroy the rotation accuracy and cause imbalance in the rotor, thereby aggravating the vibration of the engine.
- Obvious temperature rise: After the bearing is damaged, the heat loss between the moving pairs will increase, causing the temperature of the bearing and surrounding parts to rise rapidly.
- Decreased fuel economy: Bearing wear increases internal movement resistance and reduces power transmission efficiency, thereby increasing fuel consumption.
- Signs of oil leakage: Severe wear may cause bearing failure and cracking or damage to seals, resulting in traces of oil leakage.
- Metal wear debris: The presence of a large number of metal particles or bearing material wear debris in the engine oil indicates that the bearing is in a state of severe wear.
- Reduced flexibility: Bearing wear will reduce the flexibility of the rotating parts, resulting in poor movement when the engine shakes.
- Abnormal noises: When the bearings are worn to a certain extent, abnormal noises such as “rustling” or metal impact will be heard.
Causes And Prevention Of Engine Bearing Failure
The main causes of engine bearing failure include excessive load exceeding the load-bearing limit, poor lubrication destroying the oil film, pollutant erosion aggravating wear, improper installation operations causing early failure, inherent material defects affecting performance, excessive temperature causing thermal instability problems, and engine The combined effect of internal vibration and other adverse factors.
Therefore, to prevent these bearing failures, the load must be accurately calculated when designing the bearing. The sealing performance of the bearing must also be standardized. At the same time, a complete lubrication system must be provided. During the manufacturing process, quality monitoring and standardized assembly processes must be strengthened. ; Excessive engine temperature will directly threaten the service life of the bearings, so the cooling system must be reasonably optimized. At the same time, the dynamic balance of the engine rotor must be reasonably designed to avoid excessive vibration when the engine is running.
How To Correctly Install Engine Bearings
The steps to correctly install engine bearings are as follows:
1 . Before installation, ensure that the engine bearings are clean, free of debris, and properly lubricated with engine oil.
2 . Thoroughly inspect the crankshaft journals for any signs of damage or wear.
3 . Verify that the bearing clearances are within the manufacturer’s specifications. Use plastigage or a micrometer to measure the clearance between the bearing and the crankshaft journal.
4 . Apply a thin layer of assembly lube or engine oil to the bearing surfaces to provide initial lubrication during startup.
5 . Carefully place the bearings into their respective positions in the engine block and bearing caps. Ensure that the bearings are correctly aligned and seated flush against the bearing surfaces.
6 . Gradually torque the bearing cap bolts or studs to the manufacturer’s specified torque values in the proper sequence. Use a torque wrench to ensure uniform and accurate torque application.
7 . After torquing the bearing caps, recheck the bearing clearances to ensure they are still within the acceptable range.
8 . Double-check that the bearings are securely installed and have proper clearance with the crankshaft journals. Verify that there is no binding or interference.
9 . Once all bearings are installed and torqued to specification, proceed with the reassembly of the engine components.
References
- 1. Introduction to main bearings in ”engine bearings“ from TriboNet;
- 2. Requirements for ”engine bearings materials“ from SubsTech Company ;
- 3. Detailed introduction to” engine bearings“ failures and prevention from SubsTech Company.
