The base section deviation fpb of the base section has positive and negative points, which is greater than the nominal value of the positive deviation, and vice versa. Specific measurement method: put the measured gear on the glass table, adjust the gear so that the tooth profile of the tooth surface is tangent to the center line of the microscope eyepiece, such as the position a, read a Microscope value, then move the workbench so that the tooth surface of the same tooth with the same name is tangent to the center line of the rice division. For example, position b, read the microscope value at b, the difference between the second reading is the actual base of the gear. Section size Pb. When measuring, 46 points should be evenly measured on the circumference of the gear to measure the maximum deviation of the base. The nominal value of the base of the gear (spur gear) can be calculated according to the formula: Pb=mcos. Where: m is the modulus of the measured gear; it is the circular pressure angle of the measured gear. On the Wangong display, two measuring knives can also be used to measure the base of the gear.
Measurement of the length of the common normal line When measuring the length of the common normal line, the number of teeth across the teeth K should be correctly selected so that the measuring plane of the measuring tool is tangent to the middle of the tooth profile. The number of teeth K and the length of the common normal line W can be found in the relevant grid (the grid is omitted here). For a spur gear with a pressure angle of 20, it can be calculated by a simplified formula: K=0111Z 05; W=m2952(K-05) 0014Z Specific measurement method: Place the measured gear on the glass plate, adjust the gear to make a tooth surface and The center line of the microscope eyepiece is tangent to the center line, and the tangent point should be roughly in the middle of the tooth profile, that is, near the index circle. Read the value of the point, move the table, and make the eyepiece line the center line and the first line. The other tooth side of the K teeth is tangent and read, and the difference between the secondary readings is the common normal length of the measured gear. Generally, four places on the circumference of the gear should be measured and the average value should be taken. The difference between the average length of the common normal line and the nominal value is the deviation of the common normal length Ew. The variation of the length of the common normal line refers to the difference between the maximum and minimum values ​​of the actual common normal length in the range of the gear, which can be uniformly distributed from the circumference of the gear. 46 values.
Measurement of Tooth Profile The measurement of the tooth profile error on a universal tool microscope is performed in polar or Cartesian coordinates of the tooth involute. The test method is briefly described as follows: the measured gear is fixed on the optical indexing table, and the centers of the two are coincident, and the working table is moved longitudinally so that the center value of the distance is equal to the radius of the base circle of the measured gear, and the longitudinal direction is locked. The mechanism moves the table laterally with a distance equal to the measured starting point shift value. Rotate the optical indexing table so that the tooth profile is tangent to the center of the line of the microscope's eyepiece. The point is the starting point of the measurement. The optical indexing table is rotated in turn, and the horizontal working table is moved for each angle of rotation. The actual value of the corresponding expansion arc length increment P, the difference between the actual value and the theoretical value, is the tooth profile error of the measured gear. The test point of the tooth surface should be no less than 810 points, the angle of rotation of each test point: = B-An where B is the end point expansion angle; A is the starting point expansion angle; n is the test point number.
The values ​​of P, A, B, etc. can be found and calculated, and will not be discussed in detail here. It is impossible to measure the tooth profile error of all the teeth in the actual test. Generally, the three teeth of the gear 1 are spaced apart from each other by 120 teeth, and the left and right tooth faces of each gear should be measured, and the maximum value in each measurement is taken as the tooth profile error of the gear.
The measured toothing error of the tooth direction is the end face distance between the two nearest design tooth lines that accommodate the actual tooth line in the range of the tooth width working area on the indexing cylindrical surface. The easiest is to measure directly with a universal tool microscope. Fix the measured gear between the double tips of the tool microscope, adjust the focal length, make the image of the top of the tooth tip clear, rotate the rice line in the eyepiece to make the horizontal line coincide with the top edge of the tooth, read directly from the eyepiece. The inclination angle of the top edge of the tooth to the center line is calculated, and then the tooth direction error is calculated according to the gear width.
The above discussion is the measurement of the cylindrical spur gear. For the cylindrical helical gear and the bevel gear, the universal tool microscope can also be used for single measurement. The basic method is similar, but the change of the measurement position and the influence of the helix angle must be considered. Conduct a detailed discussion. Generally speaking, the universal tool microscope can basically meet the measurement of medium and small modulus gears, but the measurement efficiency is low, and the technical quality requirements of the surveyors are also high.
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