Thermal model of cone drill bit bearing with air flushing

Abstract

Cone drill bits are used in various-purpose drilling in difficult geotechnical conditions, as well as in drilling-and-blasting in open-pit mining. The reliability of the drill bits depends on the rock-breaking source and on the bearing support. One of the causes of low reliability of a drill bit is the failure of the retaining ball bearing due to destruction of roller path and journal of the bearing under high contact and bending stresses. Based on the general provisions of similarity theory, a physical model of the retaining bearing of a roller bit was created. The test data of the bearing on a friction and wear testing machine are presented as the dependences of the bearing temperature, friction moment and clearances on time. The dependence of the bearing temperature on the thermal power is determined. In extreme conditions of lubricant shortage, the contact stresses in the bearing rings and balls and the temperature significantly exceed the permissible values. The methodology is proposed to be used in development of a cone rock bit drilling tool. The article discusses the method of determining the moment of friction of the bearing of a cone drill bit. The design of bearings without retainers features increased clearances. To determine the moment of friction under these conditions, a simple design of the test bench is proposed, which includes a load and a counterweight connected by a thread thrown over a rolling bearing. The calculations to determine the reduced moment of friction of the rolling bearing in the conditions of the test bench are described. The study was carried out under the state contract between the Ministry of Science and Higher Education of the Russian Federation and the Ural State Mining University.