Research On The Transmission Performance Of Quasi Double-lead Spiroid Gearing Pair

The double-lead spiroid drive is used to transmit the motion and power between the two axes. This transmission form has many advantages: more meshing teeth, large carrying capacity; shape of contact line is beneficial to the formation of dynamic pressure oil film, good lubrication; the backlash is easy to adjust; higher transmission efficiency. However, tooth surface of the double-lead spiroid is involute helicoid, that need to customize the hob to process the spiroid gear,which will cause cost is high when the production is small, so the craft performance is not good. On the basis of retaining the many advantages of the double-lead spiroid drive, a new type of spiroid drive is formed by replacing the involute spiral surface with Archimedes’ s spiral surface.We define it as a quasi double-lead spiroid drive.In this way, we can use the standard gear hob to finish machining on the ordinary gear hobbing machine, and the process performance is improved.Firstly, this paper expounds the quasi double-lead spiroid gearing principle, on the basis of this,we analyzed the error of contact line shape which caused by tooth surface using Archimedes spiral surface instead of involute spiral surface. Analysis results show that the Archimedean spiral spiroid and worm gear tooth surface in the base cylinder tangent plane shape of contact line is approximate straight line,and the gear tooth profile error within the general machining precision can ignore. It is feasible to use the Archimedes spiral surface instead of the involute spiral surface, which is a significant advantage of the design and manufacture.Secondly,do the force analysis for the double-lead spiroid gearing, which is the basis of the calculation of the transmission efficiency, the temperature calculation, the strength calculation and the stiffness calculation. In the force analysis, let the contact force on the tooth surface concentrate to a point near thetooth surface section.At the same time, the relative motion of the cone worm and the cone worm gear is regarded as the sliding of the cone worm wheel along the cone worm, cone worm as fixed. That is,when the cone worm is expanded along the tooth surface,we can get a inclined plane with its inclination angle is helix angle,and the relative motion of the conical worm gear cone worm can be seen as the movement of the sliding block on the inclined plane, and the problem is greatly simplified. In this paper, we analyze the external and internal meshing transmission,and derive the corresponding formula.Third, based on the analysis of force, the transmission efficiency calculation formula of transmission pair is derived, and the main factors that affect the meshing efficiency of the drive are the spiral angle of the cone worm and the equivalent friction angle. The equivalent friction angle is related to many factors,the material and the heat treatment method of the cone worm, the type of the lubricating oil, the tooth form angle. In addition to this,relative sliding velocity vs is the important one.With the increase of vs, the oil film will be easy to form, so that the friction coefficient is decreased, and the equivalent friction angle will be reducedand.Cone worm helix angle and transmission efficiency of the relationship can be through the efficiency curve directly reflect, when the helix angle is smaller,transmission efficiency with the helix angle of large rapid increase, when the helix angle greater than 10 degrees, efficiency increases at a slower pace, so the general design of transmission pair in the value between 10 degrees and 20 degrees.Fourth, the derivation process of contact fatigue strength of the gears,bend fatigue strength of gear teeth and the calculation formula of the spiroid axial stiffness.The Compositions of the spiroid has different choices-bronze or steel,The failure occurred on spiroid gear firstly,this is why we just calculate the strength of the spiroid gear.We see the tooth contact of the worm gearing as the rolling contact of two cylinders;by Hertz stress theory,contacting surface strength of gears is finished,but the bending strength of gear tooth root is ready to avouchthe exact contrary. In this case,we can deduce an evaluation formula combining with experimental. On the other hand, out of consideration for the large span of spiroid, small diameter of Intermediate shaft, large flexibility easily, calculating the stiffness of the axis spiroid is necessary. Last, comparison of the finite element analysis with formula calculation show that the error is less than 5%.Finally, with a series of performance experiments in transmission counters reduction gears of double-leed spiroid,such technical indicators-the transmission efficiency, the carrying capacity and the temperature increase of oil sump are measured. By observing tooth surface meshing and wear patterns,it verify the reliability of theoretical analysis.The theory and test of transmission shows that it is correct and useful to build evaluation methods and steps of the performance. The whole set of feasible transmission performance assessment method which conveniences engineering technology workers,reduces labour intensity and provides the foundation for be used for designing double-leed spiroid transmission is conducive to analyze and check the invalidation form of spiroid transmission.