Research On Calculation And Accuracy Assessment For Involute Spur Gear Deviation

Gears are critical transmission components, the standards of design andmanufacturing will affect the transmission efficiency, transmission quality and service lifeof machine greatly. In order to ensure the transmission quality, it is imporsible to measurethe work gear and assess the accuracy degree.Involute spur gears have many quality indicators, previously, each indicator havedifferent instruments to measure, most of them are structural precision, expensive, highoperation and maintenance. With the development and popularization of the coordinatemeasuring instrument, the exploration and practice of gear’s coordinate measurement hasbecome a research hotspot in recent years, the main concern is measurement of toothprofile points and the method to calculate each deviation values based on the measuredtooth profile points. In the paper, the involute spur gear was used as the targeted to researchthe ways and means of each deviation calculated. The main contents are as follows:This paper introduced the common method of measuring the gear, determined anexpermental scheme that coordinate measuring machine is used to measure the coordinatevalues of the gear tooth profile and common normal micrometer is used to measure thecommon normal length. Proposed to processing the raw measurement data by the use ofLayida rule.This paper introduced two mothod of caculating the tooth profile deviation, one isinvolute normal method, the other is involute fitting method, analysed the the limitationsand inadequacies in the calculation, and a new method which is named involute originmethod was proposed on the base of the two method above. First, determine the startingpoint of the theory involute tooth profile measured point, then, calculate each deviationvalues based on the measured tooth profile points.According to the normal length principle, get the common normal length andmeasuring teeth number’s calculation formula which is suitable for cylindrical spur gears, dislodgement cylindrical spur gears, helical gears and dislodgement helical gears, the bestvalue method was proposed to select the scope of measuring teeth number, and thenestablish normal length deviation’s mathematical modelling.Three fitting method such as least square method, piecewise cubic Hermiteinterpolation and cubic spline interpolation were intoduced separately, then compare theadvantages and disadvantages of three method, thr least square method is uesed to fittingthe involute gear tooth profile, establish the mathematical modelling of the pitch deviation.According to the processed data and the mathematical model, the software which cancaculate the involute spur gear deviation was developed. Take the involute spur gear for anexample, calculate the gear of each deviation by using the developed calculation software,according to the calculation results to assess the accuracy degree.