Research of quality of production of the key connections basic units

Abstract

When considering the work of key connections with broken geometry of the working surfaces of the units, we can observe that often the key is not properly fixed in the groove of the shaft and sleeve and when rotating the coupling, it skews and perceives the transmitted torque unevenly at some point, which is a stress concentrator. (Research purpose) The research purpose is to increase the durability of keyways by preventing failures through quality control of the manufacture of their basic units. (Materials and methods) Authors have noted that the standard keyway has three fitments: "shaft-hub", "shaft-keyway" and "hub-keyway". It was shown that in these couplings the manufacturer provided gaps of various sizes for the convenience of disassembly and assembly of the connection, directly affecting the performance and durability of the connection as a whole. The geometric dimensions of keyway coupling were monitored by contact method using electronic micrometers MCC-25, MCC-50 and MCC-75 to measure the width of the keys and the diameter of the shafts and indicator nutromers NI-18 and NI-50 with an indicator head 1IG for keyways and internal diameters of pulleys. (Results and discussion) It has been revealed that the dispersion of the tolerance fields of the key width coincides with the law of normal distribution. It was found the presence of defects in width in the supplied keys, the value of which reached 15 percent. It was determined that the technical requirements for hardness and roughness corresponded to GOST 23360-78. It was noticed when checking the diametrical dimensions of the coupling "shaft-sleeve" the presence of deviations from the technical conditions, which during assembly can lead to the formation of a large gap in the keyway coupling. (Conclusions) Performed theoretical and experimental studies have allowed to establish the probability of obtaining gaps and tightness in common key coupling.