Research On Form Errors And In-situ Measurement Method For Crankshaft During Noncircular Grinding Process

As a key part of engine, the crankshaft's roundness has a direct impact for engine performance, such as precision, friction, vibration, noice and so on. To achieve low production cost, high efficiency and precision of the crankshaft manufacture, the noncircular grinding process technology emerged as the times require, which avoids the fixture errors in the conventional grinding process for crankshaft. In the noncircular grinding process, there are various influences affect the process precision and the surface quality of the crankpin. Therefore, the researches on the measurement method of diameter and roundness errors of crankshaft and the way of data feedback have the great significance in theory and economy. These research works can not only improve and commercialize the on-line measurement technology for the crankshaft noncircular grinding, but also can enhance the quality and competition of the domestic advanced manufacture equipment.The main contents of this dissertation are focused on the surface form errors and the geometrical dimension of crankshaft, including the central factors that impair machining quality, the relationship between the vibration and the surface quality in the crankshaft noncircular grinding process, the on-line tracing measurement system for diameter and roundness errors as well as the three-sensor tracing principle adopted for roundness error separation. This dissertation makes some creative researches on the following aspects:The motion process of the crankshaft noncircular grinding is described firstly. The central factors that affect diameter and roundness errors of crankshaft noncircular grinding process are analyzed in depth. The compensation model for the crankpin's deformation due to grinding force is developed. It is shown that the deformation model calculated results coincide with the experimentally observed results. And the machining-error in the radial direction of the crankpin can be easily worked out according to the predictive model of crankpin's deformation, which underpins the error compensation in crankshaft noncircular grinding process.The vibration and its influences occurring in the crankshaft noncircular grinding process are studied. The chattering mechanism of the crankshaft noncircular grinding is explained using dual-regenerate model; the mechanism of the suppression and delay of chattering by variable speed grinding are studied both for the grinding point on the wheel and the variable rotating speed of the crankshaft. The six-degree-freedom dynamics model of the crankshaft noncircular grinding process is developed and the impacts due to the forced vibration are simulated by computer on the basis of decoupling the system dynamics equations via modal analysis method.An on-line tracing measurement method is presented for measurement the diameter and roundness errors of crankshaft's journal same time according with the characteristics of the crankshaft noncircular grinding process. The tracing measurement equipment is also developed and its system errors and influence on measuring precision are conducted.The three-sensor tracing principle is presented for the crankpin's roundness errors separation with system errors from measurement data. The factors that impact the separation precision of the three-sensor tracing principle are presented in detail. Using the wavelet analysis method, the detail imformation of roundness is extracted from the measurement signal after errors separation process.Finally, the simulation and experiments prove the validity of the above research works.