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Assembly of connecting rod bearing

2020-04-16

 The connecting rod assembly is composed of connecting rod body, connecting rod cover, connecting rod bolt and connecting rod bearing.

Two ends of the connecting rod, a small end at one end is used to install the piston pin to connect the piston; one end is connected to the connecting rod journal of the crankshaft with a large end. A bronze bush is pressed in the small end of the connecting rod, which is sleeved on the piston pin. There is a certain gap on the side of the small head to prevent it from being stuck at the pin hole seat during work. An oil collecting hole is glued above the small end of the connecting rod and the bush, and communicates with the oil groove on the inner surface of the bush. When the diesel engine is working, the splashed oil falls into the hole to lubricate the piston pin and the bush. The connecting rod bolt is a special bolt used to connect the connecting rod cover and the connecting rod into one. The connecting rod bearing is installed in the big-end hole seat of the connecting rod, and it is installed together with the connecting rod journal on the crankshaft. It is one of the most important matching pairs in the engine.


The connecting rod bearing is installed in the large end hole of the connecting rod. It is a sliding bearing (only a very small number of rolling bearings for small engines), consisting of two semi-circular tiles, usually called a bearing. Most modern engines use thin-walled bearings. Thin-walled bearing bush is a layer of friction-reducing alloy (0.3 ~ 0.8 mm) cast on the back of the steel bush. The connecting rod bearing can protect the large end hole of the connecting rod and the connecting rod journal of the crankshaft, so that the connecting rod and the crankshaft can be used for a longer period of time.

The connecting rod bearing should be replaced in a complete set, and the size should correspond to the size of the connecting rod journal. The connecting rod bearing bush can be interchanged. The connecting rod and connecting rod cover are processed in pairs, and replacement is not allowed. When selecting the bearing bush, first check the elasticity of the tile. When the tile is pressed into the tile cover, the tile and the tile cover must have a certain tightness. If the tile can fall freely from the tile cover, the tile cannot continue Use; after the tile is pressed into the tile cover, it should be slightly higher than the tile cover plane, generally 0.05 ~ 0. 10 mm.

The connecting rod bearing is a vulnerable part, and its wear rate is mainly affected by the quality of the lubricating oil, the fit clearance and the roughness of the journal surface. The oil quality is poor, there are many impurities, and the bearing gap is too small, which is easy to cause the bearing bush to scratch or burn. If the gap is too large, the oil film is not easy to form, and the bearing alloy layer is prone to fatigue cracks or even flake. Before selecting the connecting rod bearing, the end gap of the large end of the connecting rod should be checked. There is a certain gap between the side of the large end of the connecting rod and the crankshaft crank. The general engine is 0.17 ~ 0.35 mm, the diesel engine is 0.20 ~ 0.50 mm, if it exceeds the specified value, the big end side of the connecting rod can be repaired.

When installing the connecting rod bearing, you must ensure that it is replaced according to the original installation position, and it must not be installed by mistake. The tiles and tile seats must be clean and tightly fitted, and the specified fit clearance between the bearing pad and the journal should be ensured. When assembling the bearing bush, attention must be paid to the height of the bearing bush. When the height is too large, it can be filed or polished with sandpaper; if the height is too small, the tile should be re-arranged or the seat hole should be repaired. Note that it is strictly forbidden to add pads to the back of the tile to increase the bearing bush, so as not to affect the heat dissipation and cause the bearing bush to be loose and damaged. The connecting rod bearing should be assembled according to the matching number and sequence number, and the nuts and bolts should be evenly tightened according to the specified torque. A positioning lip is made on the connecting rod bearing bush. During installation, the two positioning lips are respectively embedded in the corresponding grooves on the big end of the connecting rod and the connecting rod cover to prevent the bearing bush from rotating and moving axially.