Abstract: Main journal is crucial for the crankshaft of the diesel engine. The machining accuracy of parallelism is one of the determining factors to ensure the strength and reliability of the crankshaft. At present,there are some limitations in manual or non-contact detection methods,such as low automation,low measurement accuracy or susceptible to surface factors.Therefore,a contact detection method is proposed based on wireless transmission. By designing a contact sensor ring array device to collect data of the main journal in turn,coordinates of contour points are extracted and analyzed by using the principle of spatial analytic geometry.The parallelism of the main journal is obtained in real time during working time. The experimental results showed that the maximum error in detecting the parallelism of the main journal was 9.65 %. This detection method can effectively measure the parallelism between the crankshaft main journal and the centerline,providing a theoretical basis for crankshaft in machine inspection.

Key words: main journal of crankshaft, parallelism, contact detection