JP5854661B2 - Calibration method of probe for shape measurement - Google Patents

Description

  The present invention relates to a calibration method for a shape measuring probe that measures the shape of an object to be measured attached to a rotary table.

  Conventionally, the accuracy of a gear that has been 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 above-described workability, gear grinding has been made possible to measure the machining accuracy of the gear grinding machine with the machined gear attached to the mounting position at the time of machining. A board is provided.

  Moreover, in the above-described gear grinding machine having a gear measurement function, it is common to calibrate each drive unit as necessary in order to measure the gear with high accuracy. For example, Patent Document 1 discloses a method for calibrating a rotary table for attaching a workpiece to be measured.

Japanese Patent Laid-Open No. 6-249641

  Similarly, in a gear grinding machine having a gear measurement function, it is also important to calibrate a probe for measuring a gear. In general, in a gear grinding machine, the origin of the Cartesian coordinate system is the center position (rotation axis) of the rotary table. Therefore, calibration of the probe moves the probe to the center of the rotary table. Thus, the center of the probe and the center position of the rotary table are made to coincide with each other.

  However, in a large gear grinder that grinds a large gear, the rotating table for mounting the gear must be enlarged because the gear to be processed is large. And if it is going to employ | adopt the gear measurement function mentioned above to such a large-sized gear grinding machine, the movement range of a measuring element will be restrict | limited by problems, such as interference between a machine and a measuring element, and a rotary table. The center of the probe may not reach the center position of the rotary table. Thereby, especially in a large gear grinding machine having a gear measurement function, it is difficult to calibrate the probe, and as a result, there is a possibility that the processing accuracy of the gear may be lowered.

  Accordingly, the present invention solves the above-described problem, and provides a measuring element that measures the shape of an object to be measured even if the center of the measuring element does not reach the center position of a rotary table for mounting the object to be measured. An object of the present invention is to provide a calibration method for a shape measuring probe that can be calibrated with high accuracy.

The calibration method for the shape measuring probe according to the first invention for solving the above-described problems is as follows.
In the calibration method of the shape measuring probe for measuring the shape of the object to be measured attached to the rotary table,
A calibration reference cylinder disposed at a predetermined inter-axis distance from the rotation axis of the rotary table is provided so as to be rotatable around the rotation axis of the rotary table,
Based on the diameter of the measuring element, the diameter of the reference cylinder, and the turning angle of the reference cylinder in both the left and right directions from the reference axis orthogonal to the rotation axis of the rotary table, the measurement becomes a pair of left and right with respect to the reference axis Set the theoretical center position of the child,
The calculated and the measuring element which is positioned at the theoretical center position, the theoretical swivel angle when in the theoretical contact position and said reference cylinder was pivoted to said turning angle is in contact,
With respect to the measuring element positioned at the theoretical center position, obtain an actual turning angle when the reference cylinder is in an actual contact position when the reference cylinder is turned to the turning angle and brought into contact with the measuring element.
Obtaining a turning angle error which is a difference between the theoretical turning angle and the actual turning angle ;
Based on the distance between the axes, the diameter of the probe, the diameter of the reference cylinder, and the turning angle error, a contact position error between the theoretical contact position and the actual contact position is obtained.
The measuring element is calibrated in accordance with the contact position error.

The calibration method for the shape measuring probe according to the second invention for solving the above-described problems is as follows.
Swiveling the reference cylinder to a plurality of different swivel angles;
The contact position error is obtained for each of the plurality of different turning angles,
The measuring element is calibrated in accordance with the contact position error.

  Therefore, according to the calibration method of the shape measuring probe according to the present invention, the calibration reference cylinder is swung at a predetermined turning angle and brought into contact with the measuring member positioned at the theoretical center position. After obtaining the contact position error between the two, the calibration point is calibrated according to the obtained contact position error, so that the measurement point can be raised even if the center of the measurement point does not reach the center position of the rotary table. It can be calibrated to accuracy.

It is the figure which showed a mode that 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 element for a shape measurement which concerns on one Example of this invention. It is the figure which showed a mode when the rotated reference | standard cylinder contacted the measuring element positioned. It is the figure which showed the deviation | shift amount of the contact position between the positioning probe and the reference | standard cylinder made to rotate. It is the figure which showed the mode when the turning angle of a reference | standard cylinder was changed in steps. It is the flowchart figure which showed the procedure of the calibration method of the measuring element for shape measurement which concerns on one Example of this invention.

  Hereinafter, a method for calibrating a shape measuring probe 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 gear grinding machine (not shown) so as to be rotatable around a table rotation axis C. (Workpiece gear, object to be measured, gear to be measured) W is detachable. The coordinate system of the gear grinding machine is an orthogonal coordinate system having an X axis (reference axis), a Y axis, a Z axis rectilinear axis, and a rotation axis around each axis. The origin is set at the center position of the rotary table 11 (on the table rotation axis C).

  The gear grinder has a gear measurement function (gear measurement device) that enables the accuracy measurement of the workpiece W after grinding on the gear grinder, and is used for gear measurement (for coordinate measurement). A measuring device 21 is provided. This measuring instrument 21 is supported on a gear grinding machine so as to be movable in the X-axis, Y-axis, and Z-axis directions, and has a spherical measuring element 22.

  Therefore, by moving the measuring instrument 21 in the X-axis, Y-axis, and Z-axis directions, the measuring element 22 can be brought into point contact with the tooth surface of the workpiece W attached to the rotary table 11. At this time, by detecting the center position (coordinates) of the probe 22, the shape (tooth profile, tooth trace, pitch, etc.) of the workpiece W is measured.

  That is, in the gear grinding machine, before grinding the workpiece W, the measuring element 22 is calibrated in a state where the workpiece W is not attached to the rotary table 11, and after grinding the workpiece W, the workpiece W is ground. The shape of the workpiece W is measured by the probe 22 in a state of being attached at the attachment position.

  Next, a method for calibrating the probe 22 will be described with reference to FIGS.

  First, as shown in FIG. 2, a reference cylinder 30 as a calibration jig is installed on the rotary table 11. At this time, the reference cylinder 30 is arranged such that the distance between the center of the reference cylinder 30 and the table rotation axis C of the turntable 11 is a predetermined inter-axis distance L.

Therefore, the reference cylinder 30 can be turned around the table rotation axis C by rotating the turntable 11. That is, by rotating the turntable 11 at a predetermined rotation angle α _t from the X axis as the rotation reference axis in both the left and right rotation directions, the reference cylinder 30 is moved in both the left and right directions from the X axis as the turning reference axis. Towards the turning angle α _t .

Then, with respect to the center position of the measuring element 22 disposed on the X axis, the left side (minus side of the Y-axis) and the right pair of the theoretical center position disposed (Y-axis positive side of) O _L, O _R Set.

The theoretical center position O _L, O _R is a made of a center position of the theoretical swivel angle α measuring element 22 in contact with the reference cylinder 30 to pivot _t, the radius r, the reference of the probe 22 It is set based on the radius R and the turning angle α _t of the cylinder 30.

Then, as shown in FIG. 3, after positioning the measuring element 22 to the theoretical center position O _L, with respect to measuring element 22 that this positioning, contacting swirled the reference cylinder 30 to pivot the angle alpha _t.

Here, if the actual center position of the positioning the measuring element 22 becomes the same position as the preset theoretical center position O _L, i.e., if there is no error in the actual center position of the positioning the measuring element 22 is The probe 22 and the reference cylinder 30 are in contact at the theoretical contact position P _L.

The theoretical contact position P _L, to the measuring element 22 has been positioned to the theoretical center position O _L, turning angle α reference cylinder 30 to pivot _t becomes the contact position of theoretical contact the Y-axis direction It is those determined from the radius r and the theoretical center position O _L of the probe 22. In other words, the theoretical center position O _L of the probe 22, the contact direction connecting the center position of the reference cylinder 30 to pivot the turning angle alpha _t is parallel to the Y-axis direction.

On the other hand, actually the center position of the positioning the measuring element 22, if a preset theoretical center position O _L a different position, i.e., when there is an error in the actual center position of the positioning the measuring element 22 is The measuring element 22 and the reference cylinder 30 are in contact with each other at the actual contact position P _L ′.

At this time, as the center position error of the probe 22 which actually positioned with respect to the theoretical center position O _L, between the actual axial distance such is longer than the distance L between the predetermined axis, when the error is The actual contact position P _L ′ is shifted in the positive direction of the X axis from the theoretical contact position P _L. Further, as the center position error of the gauge head 22 of actual positioning with respect to the theoretical center position O _L, such as between the actual axial distance is shorter than the distance L between the predetermined axis, when the error is real The contact position P _L ′ is shifted in the minus direction of the X axis from the theoretical contact position P _L.

Further, as described above, actually the center position of the positioning the measuring element 22 is equal to or preset theoretical center position O _L a different position, even the turning angle alpha _t of the reference cylinder 30, an error may occur become.

Therefore, as shown in FIG. 4, after _obtaining the turning angle error Δα _tL generated at the turning angle α _t , the inter-axis distance L, the radius r of the probe 22, the radius R of the reference cylinder 30 and the turning angle error Δα _tL. Based on the above, the contact position error ΔX _{L in the} X-axis direction and the contact position error ΔY _L in the Y-axis direction of the actual contact position P _L ′ with respect to the theoretical contact position P _L are obtained.

As a specific calculation method of the contact position errors ΔX _L and ΔY _L , if the angle from the theoretical contact position P _L to the actual contact position P _L ′ around the center position of the probe 22 is a contact angle error β _L , A relational expression as shown in the following expression (1) is obtained. Thereby, since the following formula (2) can be obtained from the formula (1), the contact angle error β _L is obtained.

(R + R) · sin (β _L / 2) = L · sin (Δα _tL / 2) (1)
β _L = 2sin ⁻¹ {[L / (r + R)] · sin (Δα _tL / 2)} (2)

Next, using the contact angle error β _L obtained from the above equation (2), the contact position errors ΔX _L and ΔY _L can be obtained from the following equations (3) and (4).

ΔX _L = r · sinβ _L (3)
ΔY _L = r · (1-cosβ _L ) (4)

The contact between the measuring element 22 and the reference cylinder 30, since the measuring element 22 is performed in the left and right sides when it is positioned in the theoretical center position O _L, O _R, in the same way as calculation method described above, the turning using angle error [Delta] [alpha] _tR and contact angle error beta _R, to determine the theoretical contact position P X-axis direction of the contact position error of the actual contact position P _R 'for _R [Delta] X _R and Y-axis direction of the contact position error [Delta] Y _R To do.

Then, the position error ΔX in the X-axis direction and the position error ΔY in the Y-axis direction of the final measuring element 22 are the left contact position errors ΔX _L and ΔY _L and the right contact position errors ΔX _R and ΔY _R. These position errors ΔX and ΔY are obtained by use, and become calibration values of the probe 22 in the XY plane.

That is, as shown in the following formulas (5) and (6), the position error ΔX is an average value of the left and right contact position errors ΔX _L and ΔX _R , and the position error ΔY is the left and right contact positions. This is the difference value between the errors ΔY _L and ΔY _R.

ΔX = (ΔX _L + ΔX _R ) / 2 (5)
ΔY = ΔY _L −ΔY _R (6)

  Therefore, the workpiece W can be measured with high accuracy by the measuring element 22 by calibrating the measuring element 22 according to the position errors ΔX and ΔY.

Further, as described above, the position errors ΔX and ΔY serving as calibration values are obtained using the turning angle errors Δα _tL and Δα _tR of the reference cylinder 30, so that the turning accuracy of the reference cylinder 30, that is, rotation The indexing accuracy (positioning accuracy) of the table 11 directly affects the calibration accuracy. That is, by improving the indexing accuracy of the rotary table 11, the calculation accuracy of the position errors ΔX and ΔY can be improved, but there is a limit to improving the indexing accuracy of the rotary table 11.

Therefore, the calibration value calculation by the pair of left and right contacts is performed a plurality of times while changing the turning angle α _t in stages, and after obtaining the position errors ΔX and ΔY for each turning angle α _t , You may average.

For example, as shown in FIG. 5, after setting three turning angles α _t1 , α _t2 , and α _t3 , the position errors ΔX1, ΔX2, ΔX3 and the position are set for each of the turning angles α _t1 , α _t2 , α _t3. Errors ΔY1, ΔY2, and ΔY3 are obtained. Further, 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 indexing of the rotary table 11, when the indexing angle changes, an indexing angle error occurs within the indexing accuracy, and further, the indexing angle error also varies. ), The indexing angle error of the rotary table 11 can be easily extracted. Then, by averaging the position errors ΔX1, ΔX2, ΔX3 and the position errors ΔY1, ΔY2, ΔY3, each index angle error of the rotary table 11 is also averaged, so that the final position errors ΔX, ΔY are obtained. On the other hand, the influence of the index angle error of the rotary table 11 can be minimized. As a result, the calculation accuracy of the position errors ΔX and ΔY, that is, the calibration accuracy of the probe 22 can be improved.

  Next, the procedure of the calibration method of the probe 22 will be described with reference to FIG.

First, in step S1, the inter-axis distance L, the radius r of the measuring element 22, the radius R of the reference cylinder 30, the turning angle α _t , and the number of measurements N are input.

Then, in step S2, based on the radius r, the radius of the reference cylindrical 30 R and the turning angle alpha _t of the probe 22, the theoretical center position O _L of the probe 22, after setting the O _R, with this, The theoretical contact positions P _L and P _R are obtained.

  In step S3, the rotary table 11 is rotated, and the reference cylinder 30 is positioned so that the center position thereof is arranged on the X axis.

Then, in step S4, the reference cylinder 30 by turning the turning angle alpha _t toward both left and right, into contact with the measuring element 22 which has been pre-positioned theoretical center position O _L, the O _R. Thus, it is determined whether or not the reference cylinder 30 is in contact with the left and right measuring elements 22 evenly.

  If yes, it is determined that the reference cylinder 30 is positioned on the X-axis, and the process proceeds to the next step S5. If NO, it is determined that the reference cylinder 30 is not positioned on the X axis, and the process returns to the previous step S3.

  In step S5, the position error measurement operation is started.

  In step S6, the count number I is set to 1 and the total count number is set to 2.

Then, in step S7, positioning the measuring element 22 to the left of the theoretical center position O _L.

Then, in step S8, pivoting the reference cylinder 30 to pivot the angle alpha _t.

In step S9, when the reference cylinder 30 comes into contact with the probe 22, the actual contact position P _L ′ is obtained, and then the turning angle error Δα _tL is obtained.

Then, in step S10, positioning the measuring element 22 to the right of the theoretical center position O _R.

Then, in step S11, turning the reference cylinder 30 to pivot the angle alpha _t.

Next, when the reference cylinder 30 contacts the measuring element 22 in step S12, the actual contact position P _R ′ is obtained, and then the turning angle error Δα _tR is obtained.

  Then, in step S13, it is determined whether or not the number of measurements N is less than the total count number I. If yes, it is determined that the current number of measurements has reached a preset number of measurements N, and the process proceeds to the next step S14. If not, it is determined that the current number of measurements has not reached the preset number of measurements N, and the process returns to the previous step S5.

Next, after _obtaining the contact angle errors β _L and β _R based on the inter-axis distance L, the radius r of the probe 22, the radius R of the reference cylinder 30 and the turning angle errors Δα _tL and Δα _tR in step S14, Using the contact angle errors β _L and β _R , the left contact position errors ΔX _L and ΔY _L and the right contact position errors ΔX _R and ΔY _R are obtained. As a result, the final position errors ΔX and ΔY of the probe 22 are obtained.

  In step S15, the probe 22 is calibrated according to the position errors ΔX and ΔY.

Therefore, according to the calibration method of a shape measuring for measuring element according to the present invention, the theoretical center position O _L, with respect to measuring element 22 has been positioned in the O _R, pivots the reference cylinder 30 for correction to the turning angle alpha _t Thus, the position errors ΔX and ΔY of the measuring element 22 can be easily obtained. Then, by calibrating the measuring element 22 in accordance with the position errors ΔX and ΔY, the measuring element 22 can be moved even if the center does not reach the center position (table rotation axis C) of the rotary table 11. It can be calibrated with high accuracy.

Further, by setting the turning angle α _t stepwise at a plurality of different turning angles, it is possible to sufficiently reduce the influence of the index angle error of the rotary table 11 on the position errors ΔX and ΔY. Thereby, the measuring element 22 can be calibrated with higher accuracy.

  The present invention can be applied to a calibration method for a three-dimensional measuring machine that measures a three-dimensional shape of a measurement object while bringing a measuring element for shape measurement into contact with the measurement object rotated by a rotary table.

11 radius L between axis distance of the rotary table 21 meter 22 measuring element 30 reference cylinder W radius R criteria cylindrical workpiece C table rotation axis r feeler O _L, O _R theoretical center position P _L, P _R theoretical contact position P _L ', P _R ' actual contact position α _t turning angle Δα _tL , Δα _tR turning angle error β _L , β _R contact angle error ΔX _L , ΔY _L , ΔX _R , ΔY _R contact position error ΔX, ΔY position error

Claims (2)

In the calibration method of the shape measuring probe for measuring the shape of the object to be measured attached to the rotary table,
A calibration reference cylinder disposed at a predetermined inter-axis distance from the rotation axis of the rotary table is provided so as to be rotatable around the rotation axis of the rotary table,
Based on the diameter of the measuring element, the diameter of the reference cylinder, and the turning angle of the reference cylinder in both the left and right directions from the reference axis orthogonal to the rotation axis of the rotary table, the measurement becomes a pair of left and right with respect to the reference axis Set the theoretical center position of the child,
The calculated and the measuring element which is positioned at the theoretical center position, the theoretical swivel angle when in the theoretical contact position and said reference cylinder was pivoted to said turning angle is in contact,
With respect to the measuring element positioned at the theoretical center position, obtain an actual turning angle when the reference cylinder is in an actual contact position when the reference cylinder is turned to the turning angle and brought into contact with the measuring element.
Obtaining a turning angle error which is a difference between the theoretical turning angle and the actual turning angle ;
Based on the distance between the axes, the diameter of the probe, the diameter of the reference cylinder, and the turning angle error, a contact position error between the theoretical contact position and the actual contact position is obtained.
The shape measuring probe calibration method, wherein the measuring probe is calibrated according to the contact position error. In the calibration method of the shape measuring probe according to claim 1,
Swiveling the reference cylinder to a plurality of different swivel angles;
The contact position error is obtained for each of the plurality of different turning angles,
The measuring element is calibrated in accordance with the contact position error. A calibration method for a shape measuring measuring element.

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