Processing Technology of Automobile Engine Connecting Rod

The connecting rod is a power functional component connecting the piston and the crankshaft. The small end of the connecting rod is connected with the piston through the piston pin, and the large end of the connecting rod is connected with the connecting rod journal of the crankshaft, and the gas pressure borne by the piston is transmitted to the crankshaft, so that the reciprocating motion of the piston is transformed into the rotary motion of the crankshaft.

The shape of the connecting rod is irregular and complex, which makes it difficult to locate. The reducer is connected by a slender rod body, which is easy to deform; At the same time, there are high requirements for dimensional tolerance, geometric tolerance and surface roughness. The processing procedure of connecting rod follows the principle of face first, then hole, and datum first, then others. The connecting rod is a part with poor rigidity, so the positioning and clamping should reduce the influence of deformation on the machining accuracy.

As a new manufacturing technology, the connecting rod expanding and breaking processing technology (namely connecting rod cracking) is gradually applied in the large-scale production field. Connecting rod splitting is a new technology for cutting the joint surface between the connecting rod body and the connecting rod cap without chips. It has the characteristics of economic operation, novel conception and significant benefits.

The main characteristics of the process are:

1： Big head hole processing. Generally, the traditional process is to broach the big head hole after cutting, or process it into an ellipse before cutting, while the expanding and breaking process processes the big head hole into a circle.

2： The connecting rod body and cover are separated. The traditional process uses the method of breaking (or milling, sawing), while the breaking process is breaking after the bolt hole is processed. After adopting the expansion breaking process, the separation surface of the connecting rod and the connecting rod cap is fully engaged, which improves the joint quality of the connecting rod cap and the connecting rod separation surface.

3： Machining of mating surfaces. The traditional process is to grind the joint surface after breaking, and the assembly and positioning of the connecting rod body/cover is based on the matching of the positioning holes in the two bolt holes and the positioning parts of the bolts. Therefore, there are strict requirements for the perpendicularity of the bolt holes and their separation surfaces and the center distance between the two bolt holes. The size error causes residual stress left in the connecting rod assembly after the connecting rod and the connecting rod cover are assembled.

4： Bolt hole processing. The assembly and positioning of the connecting rod body/cover processed by the expansion and fracture process is based on the expansion and fracture section, while the assembly and positioning of the connecting rod body/cover processed by the traditional process is based on the matching of the positioning holes in the two bolt holes and the positioning part of the bolts, and has high requirements for the accuracy of the bolt holes and bolts.

5:   Bolt assembly. Install the bolt feeding through the bolt feeding device with vibrating accumulator, the separating device and the feeder with guide pipe and air nozzle, and pre tighten with the fast BOSCH tightening machine installed on the rack mounting bracket and the hydraulic driven vertical sliding platform. When tightening to a certain set torque, loosen the bolts through the device with the waiting function, clean the joint surface, and finally tighten the bolts to meet the requirements.

The technology of connecting rod breaking is of great significance in the history of connecting rod processing. At present, the connecting rod expanding and breaking processing technology has been widely used in China. Among them, Shanghai Volkswagen, FAW Volkswagen, Brilliance, Chery and other manufacturers all adopt this connecting rod process, and some professional connecting rod manufacturers also begin to use this process. Domestic equipment manufacturers have manufactured relevant special equipment