Engine Crankshaft Bearing Action

The role of crankshaft bearings is to protect the journal and bearing holes, reduce friction and wear, convert the gas force transmitted from the piston and connecting rod assembly into torque for external output, and also to drive the engine's steam distribution mechanism and various other auxiliary devices.

1、 The function and use requirements of crankshaft bearings include connecting rod bearings and main bearings. Their function is to protect the journal and bearing bore, reducing friction and wear. Convert the gas force transmitted from the piston connecting rod assembly into torque for external output. It is also used to drive the engine's steam distribution mechanism and various other auxiliary devices.

Usage requirements: They all withstand alternating loads and high-speed friction, so the bearing material must have sufficient fatigue resistance, and have low friction, wear resistance, and corrosion resistance.

2、 The structure of the crankshaft bearing The connecting rod bearing and the main bearing are formed by pairing the upper and lower bearing shells. Each bearing pad is composed of a steel back and antifriction alloy layer or a steel back, antifriction alloy layer, and soft plating. The former is called a two-layer structural bearing pad, and the latter is called a three-layer structural bearing pad.

3、 The free elastic potential and fit of the crankshaft bearing have been exceeded,

1. The radius of curvature of a free elastic potential bearing bush in a free state is slightly larger than the radius of the seating hole, and the difference in its diameter is called the free elastic potential or the opening amount. Gasoline engines typically range from 0.8 to 1 5mm, 1.5~2.5mm for diesel engines.

2. Due to the fact that the outer diameter and circumference of the bearing bush are slightly larger than the circumference of the seat hole, a certain amount of fit interference will occur after the connecting rod bolts are tightened. Ensure that the bearing bush does not rotate, move, or vibrate during operation, and make the bearing bush closely match the seat hole to facilitate heat dissipation. The bearing height is generally 0.04-0.09mm.

Inspection: Install the bearing into the bearing hole, tighten the fastening bolts on both sides according to the tightening torque specified by the original manufacturer, and then completely loosen the fastening bolts on one side. Use a feeler gauge to check the clearance on the split surface of the bearing hole, which is the bearing's height.

4、 Crankshaft thrust bearing The function of crankshaft thrust bearing: When a car is running, it exerts axial thrust on the crankshaft due to stepping on the clutch, causing the crankshaft to move axially. Excessive axial movement will affect the normal operation of the piston connecting rod assembly and damage the correct valve timing and fuel injection timing of the diesel engine. To ensure axial positioning of the crankshaft, it is necessary to install thrust bearings.