Research On Error Separation Technology In Pitch Deviation Measurement Of Ultra-precision Gear

Gear is the key part of mechanical transmission and it’s manufacturing quality depends on test level. The pitch deviation is necessary measuring item in precision detection of gear. The error of test instrument is an important part in test results of precision measurement. Error correction procedure is necessary in today’s precision measurement equipment such as gear testing machine. Some domestic universities presented error compensation method to eliminate impact of the eccentric for installing gear. The Japan National Institute of Advanced Industrial Science and Technology (NMIJ/AIST) and the German national metrology institute(the Physikalisch-Technische Bundesanstalt, PTB) have each developed closure technology to correct the measuring results.This article belongs to the precision measurement for spur gear. Combined with domestic and foreign development of precision measurement, we make the following study:(1) This paper analyzes the characteristics of the pitch measuring apparatus in the domestic and abroad. Dividing error of program-controlled multi-tooth dividing table is verified and it’s dividing error is less than0.5". Device for positioning the probe is designed to ensure the repeat error of probe less than0.2μm. Adjustable spindle structure is designed to make sure radial runout of mandrel less than0.5μm.(2) The closure technology of PTB and NMIJ is analyzed. The reference to a closure technique-two-step method and multi-step method for measuring pitch deviation-is introduced, of which the measurement process is relatively simple, and systematic errors can also be eliminated.(3) Compared the multiple measuring technique with the two-stage technique and multiple-step technique for the gear No.6002(m=6mm, z=20), No.3001(m=3mm,z=40),4003(m=4mm, z=30), the difference of single pitch deviation for gear No.6002and No.3001are not greater than0.2μm. In order to make sure two-stage technique and multiple-step technique are right, PTB testing results and laboratory test results for gear No.4003are compared at last. Finally the uncertainty of test results was analyzed. The difference is not greater than0.17μm.(4) In the multi-step method, the least-squares method is used to calculate the best estimates of single pitch deviations. Reference introduced the standard deviation’s analysis process of the estimates calculated using the least-squares method. As an example, the measurement uncertainty of the multi-step method and the closure technology for gear3001and6002is analyzed.The measuring accuracy and the superiority of the multi-step measurement method and two step method are proved. The two methods can be used in ultra-precision tests to improve the measurement precision to control machine parameters and improve the accuracy of manufacture.