Compared with the spur gear, the helical gear has wide application because of its strong bearing capacity, stable transmission, low impact and low noise. Generally speaking, if a pair of helically toothed cylindrical gears parallel to the mutual meshing axis are machined on the same equipment without changing the absolute value of the differential hanging gear transmission ratio, even if there is an error in the processed helix angle, Make sure it is properly engaged. However, a pair of helical gears that cross each other with the meshing axis and helical gears that cannot be machined on the same equipment due to structural limitations may have problems of incorrect meshing after processing. When making an accessory to one of the helical gears, the helix angle of the gear must be known. In many imported equipment, especially paper and beer canning equipment, because the transmission and structure need to be a large helical gear (ring gear) and one or more smaller helical gears around, due to the short life of the small gear It is common to use pinion gears, and these devices often have no original drawings. In order to ensure that the processed pinion gear can properly mesh with the large gears to obtain sufficient life, it is necessary to accurately measure the helix angle. In order to solve the above practical problems, we designed a cylindrical gear helix angle measuring instrument.
1 The structure and working principle of the measuring instrument is a structural diagram of the measuring instrument. The main shaft 4 is supported and supported by a pair of C36112 high-precision bearings 3, and is placed in an equilibrium position by four tension springs 6 acting on the horizontal shaft 5 passing through the tail thereof. . The measured gear 1 is clamped on the main shaft of the measuring instrument by the expandable mandrel 2, and can be rotated together with the main shaft within a range of ±45, and the corner can be rotated by the circular inductive synchronizer 7 and the digital display table (resolved) The rate of 1 arc second is measured. The stepping motor 9 (75BF003) drives the probe 10 to move along the vertical rolling guide through the reducer and the screw-nut mechanism. The accurate movement amount is determined by the linear inductive synchronizer 8 mounted on the side. The meter (resolution 0.001 mm) was measured.
During the measurement, the probe 10 is placed on the surface of the teeth near the indexing circle of the measured gear, and the computer 14 controls more than 20 parts of the stepping motor. Yan Zhi niece, engineer, born in 1951. Main research directions: precision machining and measurement.
The driving probe moves along the axial direction of the measured gear, and the circumferential component generated by the probe and the tooth surface pushes the gear to rotate against the spring pulling force.
After each distance of the probe, the computer reads the BCD code of the two digital display at the same time, so that the moving amount of the probe and the rotation angle of the gear establish an accurate correspondence. After the sampling is completed, the helix angle of the measured gear is calculated by the computer.
For helical helical gears, the helix angles of the spirals on the cylindrical surface of the root circle, the index circle, the addendum circle, and the involute tooth profile are different, as shown, but their lead It is the same, that is, the lead T=nmZ/sinU, so whether the probe measures the point on which the involute tooth profile is located, when the probe moves AL along the gear axis, the angle at which the gear rotates is AT. It is the same, and has nothing to do with the gear displacement coefficient. In the case of the known gear modulus m and the number of teeth Z, the method can accurately measure the helix angle U of the gear to ensure parallel with the spindle axis during the movement. Error 2 The measurement data processing can take 30-60 sample points depending on the tooth length of the measured gear. The computer sets the two sets of data of the linear inductive synchronizer digital display and the circular inductive synchronizer digital display in a certain measurement process as the heart. , L, and T, T, T, for the convenience of calculation, draw the measurement curve in the LT coordinate system by means of the quantity coordinate, for example. The theoretical snail 71994-2014 ChinaAcademicournalElectronic rotation line should be a straight line T=k'L in the LT coordinate system. In fact, the measured LT is caused by the error of the hanging wheel and the differential drive chain during the machining process. There is no linear relationship between them, but the curve connecting the measuring points. We use the linear regression method to fit the measured points (L, T) with the line of kL+b, i=where when we find k And b, according to the total movement amount LT of the probe along the axial direction of the gear to calculate the true rotation angle T of the gear, from the following public, a total of 51 points, the computer calculates the helix angle U according to the sampled value, the probe The reverse movement is measured and calculated once; then, the above measurement process is repeated every 10 teeth, so that each gear measures 10 sets of data, thereby calculating 10 different U values, and comparing 10 different U values. The dispersion is small, Uax-3 angular seconds, indicating that the meter has good repeatability.
The pair of design values ​​of the helix angle U and the measured average value are shown in Table 1. It is seen from the table that the actual helix angle of the measured gear is very small from the design value, and the influence on the meshing state during use is negligible.
Table 1 measurement result part number u design value u measured value according to the above method for a imported paper machine mechanical deceleration system Z = 5mm pinion gear shaft, the original pinion used 4 years after damage) spiral angle measured, measured spiral Angle right-handed U= 10108". Once processed parts according to the helix angle 10, because the helix angles are too different to be installed, only the overcut method (tooth thickness reduction, ie negative displacement) can be used to solve the problem. The helix angles are not equal and cannot be properly meshed. The pinion gear is negatively displaced and the strength is reduced. Therefore, the use time is not more than 2 months after the replacement (the shortest time is only about 2 hours). The tooth breaks, which seriously affects the factory production. After processing the pinion according to the helix angle 10, the installation is smooth, and there is no problem after half a year of use. The pinion gear has a small wear and uniform wear over the entire length, indicating that the measurement result is correct. .
This measurement method not only solves the problem of precise measurement of the helical angle of the spur gear, but also can be used to measure the toothing error of the spur gear and to find the actual machining process of the hobbing machine differential transmission chain based on the result of the harmonic analysis of the measured data. Source of error.
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