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The measurement of the tooth accuracy of large gears (especially super large gears) is a major problem in the field of measurement, which is determined by the special size of the large gear structure and the weight. The structural integrity of the benchtop meter limits its ability to measure oversized diameter gears, and the top gauges are difficult to achieve with higher precision measurements due to their rough positioning. People naturally turned their attention to the side-mounted measuring instrument and invested a lot of manpower and material resources to study the on-machine measurement of the gear tooth error.
This paper aims to explore the principle and technology of the machine measurement with high precision and high-precision gear tooth error.
2 large gear tooth direction in-machine measurement key problem analysis large gear tooth error The structure of the machine measuring instrument should be made smaller and easy to operate, and how to ensure the high precision of measurement is the main problem in this field. Specifically, the following aspects may be included: the reference of the large gear tooth direction measurement is the center of rotation of the gear, that is, the center of rotation of the machine table. In the tooth direction measurement, the shape error (straightness) of the tooth-measuring guide rail and the position error relative to the center of rotation of the gear have a great influence on the measurement accuracy, especially the error in the tangential direction of the gear is almost 1:1. In the measurement data. Eliminating the influence of this factor is the primary key issue to improve the accuracy of tooth measurement.
When measuring the tooth error of large helical gears in the cylindrical coordinate method, it is required to have a higher precision angle signal (the gear tooth error specified by the gear accuracy standard is calculated by the line value on the indexing circle, for the same point The indexing error of the device is large, and the above-mentioned line value error is correspondingly large, resulting in a decrease in measurement accuracy. The sampling accuracy of the measured gear angle signal is improved. A key issue.
Starting from the above problems, this paper studies and discusses the in-machine measurement technology of the cylindrical gear coordinate method.
3 large gear tooth direction on-machine measurement principle Large gear tooth direction The on-machine measurement principle adopts the principle of developing cylindrical polar coordinates. As shown in the figure, the computer samples the measured gear rotation angle signal in real time, and controls the servo motor drive to be located according to the internal theoretical calculation formula. The probe on the measuring gear pitch circle moves along the axial direction of the gear (linear motion). At the same time, the computer samples the corner (circular grating), the tooth displacement (tooth measurement grating), the probe (sensor) three signals, the computer Through the internal data processing and calculation, the tooth orientation error of the measured gear can be obtained. Specifically, the following considerations are made on the above key issues: when measuring the toothing error of the large gear, it is necessary to ensure that the tooth direction measurement reference is the rotation center line of the measured gear, including the straightness of the tooth direction measuring guide and its rotation relative to the measured gear. The parallelism of the centerline is two precisions. There are two considerations: the specific operation of the solution described in this paper is: the straightness accuracy of the tooth-to-measurement guide rail is guaranteed by manufacturing, and its positional accuracy (the tooth-to-gauge measurement guide car's financial position is parallel to the center line of the measured gear) The guarantee method: firstly adjust to ensure a certain range, and then measure the parallelism error data of the two directions (tangential and radial directions of the measured gear) relative to the center of rotation of the gear (see), and The measured data is compensated accordingly to finally obtain the tooth direction error data. In the adjustment and measurement, this paper uses high-precision electronic level (with plumb line) as the medium tool, the adjustment and measurement accuracy is only determined by the precision of the high-precision level.
In order to improve the sampling accuracy of the corner signal, it is convenient to install a pair of friction disc indexing mechanisms with large diameter ratio in the radial direction of the measured gear (the accuracy and resolution of the electrical angle components can be not high), and the friction disc can be processed. It has high precision and is easy to achieve high indexing accuracy. For its indexing mechanism schematic.
4 large gear tooth direction in-machine measurement compensation principle The principle of the indexing mechanism measures the parallelism error of the gear center. This error has a great influence on the measurement accuracy, including the tangential error Xwt and the radial error Xwr (in terms of the tilt angle). As shown. Then the measurement error caused by it is: the error is unacceptable (the 6-stage tooth tolerance is only 28m). Equations (1) and (2) become the mathematical model of compensation.
(2) The compensation idea of ​​the following error of the probe movement corresponding to the measured gear rotation angle and the compensation model trajectory method. When measuring the large helical gear tooth direction, according to the measurement principle, corresponding to the helix angle of the measured gear, the probe is along the measured gear The axial displacement and the rotation angle of the measured gear should satisfy a certain relationship. Due to the uncontrollable rotation of the large gear, the probe should follow the rotation of the gear in real time. This following error will have a great influence on the measurement accuracy of the tooth error, and the larger the helix angle of the measured gear, the factor is measured. The greater the impact of accuracy. If the following error of the probe is AS, the resulting measurement error is as follows: For example, a gear with a diameter of 04000 mm, a modulus of 20 mm and a tooth width of 600 mm is taken as an example, and the error must be compensated. From the analysis of the 5 large gear teeth to the on-machine measurement error, the measurement error of the large gear tooth direction is discussed on the basis of compensation.
The influence of the geometric error of the tooth-to-measurement guide rail on the measurement accuracy includes the straightness error X along the tangential direction of the measured gear and the straightness error X along the radial direction of the measured gear. The influence of geometric eccentricity on the tooth-to-tooth error is measured. When the machine measures the tooth direction of the helical gear, the error component caused by the geometric eccentricity cannot be measured, and the measurement error will be caused by ignoring it.
The meshing line error caused by geometric eccentricity is: a tooth angle f gear angle (symbol + refers to the left tooth surface, one finger right tooth surface) and then the geometrical eccentricity caused by the tooth direction error (only the left tooth surface is studied): machine tool work The influence of the spindle rotation error on the measurement accuracy is set. The spindle rotation error of the machine tool table is divided into radial components, r and tangential components are called, then the total error of measurement is: =20 tooth root circle helix angle 45=45 large gear as an example The above-mentioned error factors are respectively: X 6 conclusions have the advantages of convenient operation and feasibility in measuring the gear tooth error of the large gear. After solving the key technical problems, the measurement accuracy of the gear tooth error can be realized.
The use of a high-precision level makes the corresponding operation in the measurement process convenient, simple and ensures high precision.
The data processing capability of the computer is utilized, and the systematic error existing in the measurement is compensated corresponding to the actual measurement data, and the measurement operation is more convenient on the basis of ensuring the measurement accuracy.
Large gear tooth error error in machine measurement technology