Research On Electromagnetic Induction Heating System For Tire Direct Pressing Sulfide Metal Inner Mold

The production of tires requires multiple processes such as pretreatment,molding,and vulcanization of rubber components.Among them,vulcanization is the most important process in tire production,which can transform linear macromolecular rubber into a threedimensional network structure under certain temperature and pressure conditions,endowing the rubber with the performance required for practical application.At present,the tire industry mostly relies on capsules with high elasticity and low rigidity to determine the inner cavity contour of the tire.Steam or superheated water is used as the medium to provide the required pressure and temperature for tire vulcanization.Because of the high elasticity and bottom rigidity of the capsules,it is difficult to obtain uniform geometric structure and Mass distribution.During the vulcanization process,steam will produce condensate,which will affect the uniformity of the overall temperature field,Moreover,traditional vulcanization methods generally adopt the method of over vulcanization,which involves introducing steam higher than the tire vulcanization temperature,making it difficult to ensure the consistency of vulcanization temperatures in various parts of rubber products.The Yinglan team from Beijing University of Chemical Technology proposed a direct pressure vulcanization technology that utilizes a high rigidity and high thermal conductivity controllable telescopic metal inner mold to replace the capsule inner mold,and uses electromagnetic induction heating instead of steam heating,in response to various shortcomings of traditional vulcanization.The main research content of this article is based on the electromagnetic induction heating system of the guide rail type direct pressure vulcanization internal mold.Due to the complex requirements of tire vulcanization and the complex structure of the metal inner mold,it is difficult to ensure the uniformity of the surface temperature of the inner mold through electromagnetic induction heating.Further adjustments to the induction heating system are needed.The main work of this article is as follows:(1)In response to the problem of uneven electromagnetic induction heating on the surface of the internal mold,starting from the basic theory of electromagnetic induction,the factors that affect the uniformity of electromagnetic induction heating were identified,and the two easily adjustable influencing factors,the magnetic conductor and the coil winding,were selected from them,providing the main research direction and theoretical support for future research.(2)The temperature and magnetic field distribution of the electromagnetic induction heating equipment for direct pressure vulcanization were analyzed using Comsol software.The areas where the surface temperature of the internal mold was too high and too low during the electromagnetic induction heating process were identified.The reasons for this phenomenon were analyzed based on the principle of electromagnetic induction heating.Based on the simulation results,a simulation model was established from two aspects: the magnet and coil winding,with different magnet lengths,coil winding wiring methods,and coil winding wiring positions.By comparing the simulation results,the influence of adjusting the parameters of the magnet and coil winding on the surface temperature field of the internal mold was found,and the optimal range of parameters for achieving uniformity of electromagnetic induction heating on the surface of the drum tile was determined through continuous parameter adjustment and simulation.(3)We have built an electromagnetic induction heating experimental platform and verified the reliability of the simulation results through experiments.Based on the experimental results of the induction heating process,further adjustments were made to the parameters of the magnet and coil winding to make the electromagnetic induction heating on the surface of the internal mold more uniform.During the experiment,there was a problem of iron loss in the guide magnet.In order to solve the problem and improve the service life of the guide magnet,this article successfully solved the iron loss problem by increasing the crosssectional size of the guide magnet,making the parameters obtained from the experiment more practical.(4)By closed-loop control,the internal mold after the heating stage is controlled within the optimal vulcanization temperature range to ensure smooth vulcanization of the embryo.During the temperature maintenance stage,it was found that the temperature at both ends of the drum pad decreased significantly compared to the heating stage.Based on the theory of heat transfer,the reasons for the temperature decrease at both ends of the drum pad were analyzed,and the parameters of the magnetic conductor and coil winding were further adjusted to ensure that the surface of the drum pad can still maintain temperature uniformity during the temperature maintenance stage.In order to prevent mutual interference of magnetic fields between wide and narrow tiles during the vulcanization process,alternating heating is generally used for electromagnetic induction heating.In order to verify that the obtained parameters can adapt to the alternating heating method,this paper designs an alternating heating experiment with wide and narrow tiles,and verifies the reliability and stability of the parameters through experiments.