JP2013170918A - Calibration method of measuring instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a calibration method of a measuring instrument with which a gauge can be calibrated easily and with high accuracy regardless of a size of an object to be measured.SOLUTION: According to a calibration method of a measuring instrument, a shape of a work W mounted to a rotary table 11 is measured by bringing a gauge 22 into contact with a tooth surface Wa of the work W and detecting a position of the gauge 22 during the contact. The calibration method includes swiveling a reference cylinder 30 placed at an arbitrary position on the rotary table 11 at an equal swivel angle φ in both right and left directions, positioning the reference cylinder at both right and left sides of an X axis, bringing the gauge 22 into contact with the positioned reference cylinder 30, determining positional errors ΔX and ΔY of the gauge 22 and, thereafter, calibrating the position of the gauge 22 in accordance with the positional errors ΔX and ΔY.

Description

  The present invention relates to a calibration method for a measuring instrument in which a measuring element is brought into contact with the surface of an object to be measured and the shape of the object to be measured is measured.

  Conventionally, the processing accuracy of a gear ground by a gear grinder has been measured using a gear measuring machine provided separately from the gear grinder. However, if a gear grinding machine and a gear measuring machine are provided separately in this way, it is necessary to move gears between them, and to set up and remove gears and center them with each machine. It was causing a decline in sex.

  Therefore, in recent years, for the purpose of improving the workability described above, there has been provided a gear grinding machine capable of measuring the machining accuracy in a state where the machined gear is attached to the attachment position at the time of machining. Yes. And, in such a gear grinding machine having a gear measurement function, by controlling the rotation of the gear by the rotary table and the movement of the measuring element by the measuring instrument, the measuring element is brought into contact with the tooth surface of the gear, The tooth profile and tooth thickness of the gear are measured.

  Moreover, in the gear grinding machine as described above, in order to measure the gear with high accuracy, it is common to calibrate the drive unit such as a rotary table or a measuring instrument as necessary. Patent Document 1 discloses a method for calibrating a rotary table for attaching an object to be measured.

Japanese Patent Laid-Open No. 6-249641

  Similarly, in a gear grinding machine having a gear measurement function, in order to measure a gear with high accuracy, it is also an important factor to calibrate the measuring instrument. In general, in a gear grinding machine, the origin of the orthogonal triaxial coordinate system is the center of the rotary table. Therefore, calibration of the measuring instrument is performed by moving the probe to the center of the rotary table. It is necessary to match the center of the rotary table with the center of the rotary table.

  On the other hand, in a large gear grinding machine that grinds a large gear, the rotating table for mounting the gear becomes larger because the gear to be processed becomes larger. However, if the gear measuring function described above is to be adopted in such a large gear grinding machine, the movement range (measurement range) of the measuring instrument is limited due to problems such as interference between the measuring instrument and the machine. Therefore, the center of the probe may not reach the center of the rotary table.

  In order to solve such a problem, it is conceivable to expand the moving range of the measuring instrument. However, if such a configuration is adopted, the large gear grinding machine will be further increased in size. This makes it difficult to calibrate the measuring instrument particularly in a large gear grinding machine having a gear measuring function.

  Accordingly, the present invention solves the above-described problems, and provides a measuring instrument calibration method that can easily and accurately calibrate the position of the measuring element regardless of the size of the object to be measured. The purpose is to provide.

The calibration method of the measuring instrument according to the first invention for solving the above-mentioned problem is as follows.
In a calibration method of a measuring instrument for measuring the shape of the object to be measured by bringing the probe into contact with the surface of the object to be measured attached to the rotary table and detecting the position of the measuring element at the time of the contact. ,
A cylindrical calibration jig is placed at an arbitrary position on the rotary table, and the center position of the calibration jig placed at the arbitrary position is set as a reference position.
By rotating the turntable in one direction and the other direction, the calibration jig arranged at the reference position is turned at the same turning angle in one direction and the other direction, and the rotation axis of the turntable Positioning on one side and the other side of the reference axis around the orthogonal reference axis,
With respect to the outer peripheral surface of the calibration jig positioned on one side and the other side of the reference axis, the measuring element is contacted a plurality of times at different positions, respectively.
Using the center position of the probe detected when the probe contacts the calibration jig positioned on one side of the reference axis, the diameter of the probe, and the diameter of the calibration jig The center position of the calibration jig positioned on one side of the reference axis is obtained,
Using the center position of the probe, the diameter of the probe, and the diameter of the calibration jig detected when the probe contacts the calibration jig positioned on the other side of the reference axis. Obtaining the center position of the calibration jig positioned on the other side of the reference axis,
Using the center position of the calibration jig positioned on one side and the other side of the reference axis, obtain the position error of the probe,
The position of the measuring element is calibrated according to the position error.

The calibration method of the measuring instrument according to the second invention for solving the above-described problem is as follows.
Swiveling the reference cylinder in one and other directions at a plurality of different swivel angles;
For each of the plurality of different turning angles, determine the position error of the probe.
The position of the measuring element is calibrated in accordance with the position error obtained for each turning angle.

  Therefore, according to the calibration method of the measuring instrument according to the present invention, the calibration jig placed at an arbitrary position on the rotary table is rotated and positioned at the same rotation angle in both directions, and the positioned calibration jig is positioned. Regardless of the size of the object to be measured, the position of the measuring element can be calibrated easily and accurately regardless of the size of the object to be measured by bringing the measuring element into contact with the tool. Can do.

It is the figure which showed a mode that the tooth surface of a workpiece | work was measured with a measuring device in the large gear grinding machine which has a gear measurement function. It is the schematic which showed the calibration method of the measuring device which concerns on one Example of this invention. It is the figure which showed the calibration method of the measuring device which concerns on the other Example of this invention.

  Hereinafter, a calibration method for a measuring instrument according to the present invention will be described in detail with reference to the drawings.

  As shown in FIGS. 1 and 2, a circular rotary table 11 is supported by a large gear grinding machine (not shown) so as to be rotatable around a table rotation axis C. On the upper surface of the rotary table 11, a work (gear to be processed, object to be measured, gear to be measured) W that is a gear, and a reference cylinder 30 as a cylindrical calibration jig, which will be described later, can be attached. It has become. The radius of the reference cylinder 30 is formed to a length R.

  Here, the coordinate system in the gear grinding machine is an orthogonal triaxial coordinate system including three coordinate axes (X axis (reference axis), Y axis, Z axis) orthogonal to each other. The origin is set at the center of the rotary table 11 (on the table rotation axis C). That is, the table rotation axis C indicates a rotation axis around the Z axis.

  Furthermore, the gear grinding machine has a gear measuring function (gear measuring device) that can measure the machining accuracy of the machined workpiece W with the machined work W attached to the mounting position at the time of machining. And the measuring device 21 for gear measurement (for coordinate measurement) is provided.

  That is, the measuring device 21 is supported on the gear grinding machine so as to be movable in the X-axis, Y-axis, and Z-axis directions. In addition, a spherical measuring element 22 is provided at the tip of the measuring instrument 21, and the measuring element 22 is attached to the tooth surface Wa of the workpiece W mounted on the rotary table 11 and the rotary table 11. The outer peripheral surface of the reference cylinder 30 thus made can be contacted. In the measuring instrument 21, when the probe 22 contacts the tooth surface Wa of the workpiece W and the outer peripheral surface of the reference cylinder 30 with a predetermined contact pressure, the center position (center coordinate) of the probe 22 is detected. It has come to be. The radius of the measuring element 22 is formed to a length r.

  Accordingly, when measuring the shape of the workpiece W (tooth profile, tooth trace, pitch, tooth thickness, etc.) with the measuring instrument 21, the rotary table 11 to which the workpiece W is attached is rotated around the table rotation axis C and measured. The probe 21 is moved in the X-axis, Y-axis, and Z-axis directions to measure the tooth surface Wa of the rotating workpiece W or the tooth surface Wa of the workpiece W positioned at a predetermined rotation angle (index angle). 22 is brought into contact. Then, when the probe 22 is brought into contact with the tooth surface Wa of the workpiece W as described above, the center position of the probe 22 is detected, and the shape of the workpiece W is measured based on the detection result.

  When the measuring instrument 21 is calibrated using the reference cylinder 30, the rotary table 11 to which the reference cylinder 30 is attached is rotated around the table rotation axis C, and the measuring instrument 21 is rotated along the X, Y, and Z axes. The tracing stylus 22 is brought into contact with the outer peripheral surface of the reference cylinder 30 which is moved in the axial direction and turned around the table rotation axis C. Then, when the probe 22 is brought into contact with the outer peripheral surface of the reference cylinder 30 as described above, the center position of the probe 22 is detected, and the position of the probe 22 is calibrated based on the detection result.

  That is, in the gear grinding machine, the measuring device 21 is calibrated in advance using the reference cylinder 30 in a state where the workpiece W is not attached to the rotary table 11 before machining, and the workpiece W is machined after machining. The machining accuracy is measured by the calibrated measuring instrument 21 in a state of being attached at the mounting position.

  Next, the calibration method of the measuring instrument 21 will be described in detail with reference to FIGS.

  As shown in FIG. 2, first, the measuring instrument 21 is moved, and the center of the measuring element 22 is arranged on the X axis. Next, the reference cylinder 30 serving as a calibration jig for the measuring instrument 21 is placed on the rotary table 11 at an arbitrary position near the X axis.

  Here, it is preferable to arrange the center of the measuring element 22 and the center of the reference cylinder 30 on the X-axis serving as the reference axis. By arranging the measuring element 22 and the reference cylinder 30 in this way, the calibration operation by the movement of the measuring element 22 and the turning of the reference cylinder 30 can be performed simply and easily.

  However, since the measuring instrument 21 is supported so as to be movable in the X-axis, Y-axis, and Z-axis directions, it is easy to place the center of the measuring element 22 on the X-axis, while the reference cylinder 30 is not Since it is placed on the rotary table 11 by human visual observation, it is difficult to place the center of the reference cylinder 30 on the X axis.

  Thus, in practice, the reference cylinder 30 placed on the turntable 11 has a length L between the center and the table rotation axis C of the turntable 11 in the XY plane. In addition, the phase shift with respect to the X axis is set to Δθ.

  Therefore, the center position Oc of the reference cylinder 30 placed in this way is set as a reference position (turning start position), and the reference cylinder 30 arranged at this reference position is turned in the same direction in both the left and right directions (one direction and the other direction). It is swung at an angle φ and positioned on the left side (one side) and the right side (the other side) around the X axis.

  Specifically, by rotating the turntable 11 counterclockwise at a predetermined rotation angle φ, the reference cylinder 30 disposed at the reference position is turned leftward at the turning angle φ, and leftward from the X axis (Y Position on the negative side of the shaft.

Next, the measuring instrument 21 arranged on the X axis is moved, and the measuring element 22 is brought into contact with the outer peripheral surface of the reference cylinder 30 positioned on the left side of the X axis three or more times at different positions. Thus, when the probe 22 is brought into contact with the reference cylinder 30, the center positions Om _L-1 , Om _L-2 , Om _L-3, ... Of the probe 22 at the time of each contact are detected.

FIG. 2 shows a state in which the measuring element 22 is brought into contact with the reference cylinder 30 at three different locations. Hereinafter, the center position Om _L−1 of the measuring element 22 at the time of each contact will be described. As for Om _L-2 , Om _L-3 ..., Only the center positions Om _L-1 , Om _L-2 , Om _L-3 are described as representatives.

Then, using the radius R of the reference cylinder 30, the radius r of the measuring element 22, and the center positions Om _L-1 , Om _L-2 , and Om _L-3 of the measuring element 22, the reference is positioned on the left side of the X axis. The center position Oc _L of the cylinder 30 is obtained.

  Similarly, by rotating the turntable 11 to the right at a predetermined rotation angle φ, the reference cylinder 30 arranged at the reference position is turned to the right at the turning angle φ, and the right side of the X axis (the Y axis Position it on the positive side.

Next, the measuring instrument 21 arranged on the X axis is moved, and the measuring element 22 is brought into contact with the outer peripheral surface of the reference cylinder 30 positioned on the right side of the X axis three or more times at different positions. In this way, when the probe 22 is brought into contact with the reference cylinder 30, the center positions Om _R-1 , Om _R-2 , Om _R-3, ... Of the probe 22 at the time of each contact are detected.

FIG. 2 shows a state in which the probe 22 is brought into contact with the reference cylinder 30 at three different points. Hereinafter, the center position Om _R−1 of the probe 22 at the time of each contact will be described. As for Om _R-2 , Om _R-3 ..., Only the center positions Om _R-1 , Om _R-2 , and Om _R-3 are described as representatives.

Then, using the radius R of the reference cylinder 30, the radius r of the probe 22, and the center positions Om _R-1 , Om _R-2 , and Om _R-3 of the probe 22, the reference is positioned on the right side of the X axis. The center position Oc _R of the cylinder 30 is obtained.

Next, the position error ΔX in the X-axis direction and the position error ΔY in the Y-axis direction of the measuring element 22 are obtained using the center positions Oc _L and Oc _R of the reference cylinder 30. That is, the center position Oc _L, the mean value of the position error ΔX next X-coordinate in Oc _R, the center position Oc _L, the difference value of the Y coordinate in Oc _R becomes the position error [Delta] Y.

  Since the position errors ΔX and ΔY become calibration values of the probe 22 in the XY plane, the shape of the workpiece W can be changed to the probe by calibrating the position of the probe 22 according to the position errors ΔX and ΔY. 22 can be measured with high accuracy.

  Further, as described above, since the position errors ΔX and ΔY serving as calibration values are obtained by turning the reference cylinder 30, the turning accuracy of the reference cylinder 30, that is, the rotation accuracy (positioning) of the rotary table 11 is determined. Accuracy) directly affects the calibration accuracy of the measuring instrument 21. That is, by improving the rotation accuracy of the turntable 11, the calculation accuracy of the position errors ΔX and ΔY can be improved, but there is a limit to improving the rotation accuracy of the turntable 11.

  Therefore, the position errors ΔX and ΔY may be obtained for each of the plurality of different turning angles φ while changing the turning angle φ stepwise, and then averaged.

For example, as shown in FIG. 3, first, the reference cylinder 30 is positioned by turning at three different turning angles φ1, φ2, and φ3, and then the center positions Oc _L1 , Oc at the turning angles φ1, φ2, and φ3. _R1 , center positions Oc _L2 and Oc _R2 and center positions Oc _L3 and Oc _R3 are obtained.

Next, the position errors ΔX1, ΔY1 are obtained using the center positions Oc _L1 , Oc _R1 , the position errors ΔX2, ΔY2 are obtained using the center positions Oc _L2 , Oc _R2 , and the center positions Oc _L3 , Oc _R3 are further obtained. Using these, position errors ΔX3 and ΔY3 are obtained.

  Then, the position errors ΔX1, ΔX2, ΔX3 and the position errors ΔY1, ΔY2, ΔY3 are averaged to obtain final position errors ΔX, ΔY.

  Thereby, in the rotation of the turntable 11, if the rotation angle φ is changed, a rotation angle error is generated within the rotation angle φ, and further, the rotation angle error also varies, so that a plurality of different rotations are generated. By setting the angles (turning angles) φ1, φ2, and φ3, it is possible to easily extract the rotation angle errors in the rotation angles φ1, φ2, and φ3. Then, by averaging the position errors ΔX1, ΔX2, ΔX3 and the position errors ΔY1, ΔY2, ΔY3, the rotation angle errors are also averaged, so that the final position errors ΔX, ΔY The influence of each rotation angle error can be minimized. As a result, the calculation accuracy of the position errors ΔX and ΔY, that is, the calibration accuracy of the measuring instrument 21 can be further improved.

  Therefore, according to the calibration method of the measuring instrument 21 according to the present invention, the reference cylinder 30 placed at an arbitrary position on the rotary table 11 is swung at the same swivel angle φ in both the left and right directions, so Then, the measuring element 22 is brought into contact with the reference cylinder 30 positioned at these two positions, and the position errors ΔX and ΔY of the measuring element 22 are obtained, so that the rotating table 11 and the rotating table 11 are attached. Regardless of the size of the workpiece W, the position of the probe 22 can be calibrated easily and with high accuracy.

  In addition, by rotating the reference cylinder 30 step by step at a plurality of different turning angles φ1, φ2, and φ3, the influence of the rotation angle error of the rotary table 11 on the position errors ΔX and ΔY of the probe 22 is affected. It can be made sufficiently small. Thereby, the position of the measuring element 22 can be calibrated with higher accuracy.

  The present invention is applicable to a calibration method for a three-dimensional measuring machine that measures a three-dimensional shape of a measurement object while contacting the measurement object with the measurement object rotated by a rotary table.

11 Rotary table 21 Measuring instrument 22 Measuring element 30 Reference cylinder W Work C Table rotation axis r Radius of measuring element R Radius of reference cylinder φ Turning angle Oc, Oc _L , Oc _R Center position of the reference cylinder Om _L , Om _R measuring element Center position ΔX, ΔY Position error

Claims (2)

In a calibration method of a measuring instrument for measuring the shape of the object to be measured by bringing the probe into contact with the surface of the object to be measured attached to the rotary table and detecting the position of the measuring element at the time of the contact. ,
A cylindrical calibration jig is placed at an arbitrary position on the rotary table, and the center position of the calibration jig placed at the arbitrary position is set as a reference position.
By rotating the turntable in one direction and the other direction, the calibration jig arranged at the reference position is turned at the same turning angle in one direction and the other direction, and the rotation axis of the turntable Positioning on one side and the other side of the reference axis around the orthogonal reference axis,
With respect to the outer peripheral surface of the calibration jig positioned on one side and the other side of the reference axis, the measuring element is contacted a plurality of times at different positions, respectively.
Using the center position of the probe detected when the probe contacts the calibration jig positioned on one side of the reference axis, the diameter of the probe, and the diameter of the calibration jig The center position of the calibration jig positioned on one side of the reference axis is obtained,
Using the center position of the probe, the diameter of the probe, and the diameter of the calibration jig detected when the probe contacts the calibration jig positioned on the other side of the reference axis. Obtaining the center position of the calibration jig positioned on the other side of the reference axis,
Using the center position of the calibration jig positioned on one side and the other side of the reference axis, obtain the position error of the probe,
A measuring instrument calibration method, wherein the position of the probe is calibrated according to the position error. The measuring instrument calibration method according to claim 1,
Swiveling the reference cylinder in one and other directions at a plurality of different swivel angles;
For each of the plurality of different turning angles, determine the position error of the probe.
A measuring instrument calibration method, wherein the position of the probe is calibrated according to the position error obtained for each turning angle.

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