| In common worm transmission, worm wheel is made of cast tin bronze, and forms with the alloy steel worm a meshing pair with nicer antifriction erosion. But there are still the following disadvantages to choose bronze worm wheel: the use of precious nonferrous metals and complicated assembly lead to higher cost; The poor wear resistance of steel-copper contact pair and severe abrasion under heavy load conditions shorten the service life of the product; The contact and bending fatigue strength of bronze alloy are far lower than alloy steel, which augments the module of worm wheel transmission. To solve these problems, based on the meshing analysis of complete-condition meshing theory of worm transmission, the paper adopts surface engineering strengthening technology and tooth surface upgrading theory to create functional coating on steel worm wheel successfully, has systemic theoretical and experimental investigations, and achieves the target to replace bronze of steel in worm transmission. The concrete research works include:①Based on the method of worm pair meshing theory and 3D solid modeling thought, the paper builds a 3D solid model of Archimedes worm transmission pair; based on elastic contact theory, the paper makes a contact FEM analysis to steel-steel and steel-copper worm wheel pair respectively. The analysis indicate that mechanical characteristic and mechanical properties of material of the meshing pair can directly affect the transmission performance of worm wheel pair, and the surface of steel-steel one should have a running-in performance②Based on friction and wear theory, a wear depth distribution of tooth surface is achieved; based on the established contact wear model of worm wheel tooth, the effects of the mechanical properties to abrasion of worm wheel are analyzed in this paper. The research shows that the wear rate is related to a few factors such as the wear coefficient of the pairing materials,the rigidity of the softer material,equivalent elastic modulus and so on.③The paper sets up a mathematical model of the bulk temperature of worm wheel tooth, and after simulating the steady temperature field with FEA, obtains the characteristics of temperature distribution of tooth. The research gains the friction coefficient of contact pair,thermal distribution coefficient,thermal conductivity,the model of the relationship of the amalgamation and the bulk temperature, and demonstrates theoretically the anti-scuffing capacity of surface wear reduction coating over the steel worm wheel.④The author makes standard specimen coated with superfine manganous phosphate conversion coating and ferrous sulfide solid lubricant coating, carries through a friction and wear test to the standard specimen on friction-wear tester, analyzes coating wear surface morphology and microstructure and combining the results of energy spectrum analysis, studies the antifriction wear mechanism and running-in properties of the coatings. The results show that both of the two coatings have excellent antifriction wear properties and loading running-in properties.⑤The author prepares two different coating on the surface of designed steel worm wheel pair: superfine manganous phosphate conversion coating and ferrous sulfide solid lubricant coating. At the same time, the author carries out a comprehensive experiment to the coated steel worm wheel pair on worm transmission test-bed and comparatively studies its transmission performance. The experimental results show that the coated worm wheel pair, compared with the uncoated one, shortens the running-in time in which transmission pair arrives at predetermined contact state, has higher transmission efficiency and better anti-scuffing capacity, simultaneously, compared with sulfurizing treatment steel worm wheel pair, manganese phosphate coat steel worm wheel pair operates more smoothly.
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