JP2017156255A - Roundness measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a roundness measuring apparatus that can detect an amount of inclination of a rotational axis of a spindle when the rotational axis of the spindle is inclined, which is a problem particular to the roundness measuring apparatus, and which can improve measuring accuracy based on the detected amount of inclination of the rotational axis of the spindle.SOLUTION: In a roundness measuring apparatus 10, a displacement amount D1 from a reference value of a spindle 20 detected by a first sensor 56 is subtracted from a displacement amount D2 from the reference value of the spindle 20 detected by a second sensor 58, and this displacement amount subtraction value is divided by a height subtraction value obtained by subtracting a first height position H1 from a second height position H2. This allows an arithmetic processing part 46 to detect an inclination amount B.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a roundness measuring apparatus, and more particularly, to a roundness measuring apparatus that measures the roundness of a work by rotating a work that is an object to be measured.

  A roundness measuring device that measures the roundness of a cylindrical or cylindrical workpiece places the workpiece on a rotatable table, contacts the surface of the workpiece with a detector probe, and accompanies the rotation of the workpiece. The roundness of the workpiece is measured by detecting the displacement of the probe from the reference value with a detector (see Patent Document 1). In such a roundness measuring apparatus, the error component of the roundness measuring apparatus is corrected or the detector is calibrated before measuring the workpiece (see Patent Documents 2 and 3).

  Patent Document 2 discloses a horizontal arm that guides a contact of a first detector horizontally and diametrically with respect to a cylindrical workpiece, and a contact of the first detector provided at the tip of the arm. Roundness composed of a support frame of a first detector that can be contacted toward two points of a diameter position, and a second detector of a diameter reading that detects a horizontal movement amount of a horizontal arm. A measuring device is disclosed. In this roundness measuring apparatus, first, the master piece is set on a turntable, the contact of the first detector is applied to the right side surface of the master piece, and the reading of the second detector is obtained. The contact of the first detector is then applied to the left side of the master piece to obtain a second detector reading, and the error value of the device is determined from the two readings of the second detector according to the known dimensions of the master piece. Ask. Then, the master piece is removed and the work is set, and the diameter of the work is measured in the same manner to correct the error value of the apparatus.

  Patent Document 3 discloses a reference jig for a roundness measuring apparatus that performs origin information acquisition and calibration of a detector that measures the surface shape of a measurement object. The reference jig of Patent Document 3 is detachably mounted on the upper surface of the XY table on the rotary table, and the sensitivity of the probe can be calibrated on the pedestal formed in a stepped disk shape and the upper part of the pedestal. The calibration master is provided with an origin ball arranged above the calibration master so that measurement can be performed in the X-axis direction and the right side surface of the lowermost surface, the right side surface, and the Z-axis direction of the left side surface. The displacement of the stylus provided on the probe in each posture is obtained and used as a correction value. This is because the reference jig is placed on the workpiece rotating mechanism, and the sensor of the roundness measuring device is brought into contact with the reference sphere to obtain the origin information of the roundness measuring device and the sensor of the detector. Is calibrated with the calibration master to calibrate the sensitivity of the detector.

  As described above, the roundness measuring apparatus obtains an accurate measurement result by performing error correction of the apparatus and sensitivity calibration of the detector prior to measurement of the workpiece. Further, the error of the rotational accuracy of the table on which the workpiece is placed is not zero, and the workpiece is measured after removing the error of the rotational accuracy in advance. The rotation accuracy of the table is equivalent to the rotation accuracy of a spindle that is connected to the table and rotates the table.

JP2012-154942A JP-A-1-259211 JP 2004-317159 A

  However, even if the work of removing the error component of the rotational accuracy of the table before measuring the workpiece (hereinafter referred to as “eccentric calibration work”) as in the conventional roundness measuring device, the rotational accuracy of the table is performed. It was difficult to reliably remove the error component.

  This problem is unique to the roundness measuring device. As described below, the roundness measuring device aligns the shape center of the workpiece (the center of the shape and is rotated by the table) with the rotation center of the table, and then rotates the table to adjust the roundness of the workpiece. Measure the degree. Although the roundness measuring device depends on its accuracy, in order to accurately measure the planar shape and to prevent the movement error of the rotational motion of the table from affecting the measurement accuracy of the individual workpiece, Measure by rotating the workpiece to be measured smoothly. In particular, a high-precision table with small motion error is configured to be supported by a hydrostatic bearing such as an air bearing in order to reduce sliding resistance during rotation, but the rigidity is reduced accordingly. Therefore, an error may occur in the rotation accuracy of the table.

  Further, among the workpieces, there are sometimes workpieces whose shape center does not coincide with the position of the center of gravity of the workpiece. In the case of such a workpiece, even if the center of the workpiece shape is aligned with the rotation center of the table, the center of gravity of the workpiece does not coincide with the rotation center of the table. In this case, the measurement accuracy is greatly affected. As described above, the rotation axis of the spindle (table) at the time of measurement (the rotation axis of the spindle in the rotation state at the time of workpiece measurement) and the rotation axis of the spindle at the time of the eccentricity calibration work (the rotation stop state before the measurement of the workpiece is started). The rotation axis of the spindle (hereinafter referred to as “A axis”) is relatively inclined (the axis touch is also equivalent to the inclination), and the rotation axis (A axis) even if the workpiece shape is an ideal perfect circle. Since it does not trace the outer periphery of the cross section perpendicular to the cross section, the shape of the outer periphery of the cross section becomes an elliptical shape. In other words, the conventional roundness measuring device has the above-mentioned specific problems, and therefore the problem arises that the rotation axis of the spindle is inclined during measurement. As a result, it may be difficult to perform highly accurate measurement.

  The present invention has been made in view of such circumstances, and has a unique problem with the roundness measuring device, that is, when the spindle rotation axis is inclined during measurement, the amount of inclination of the spindle rotation axis is detected. Then, it aims at providing the roundness measuring apparatus which can aim at the improvement of a measurement precision based on the detected amount of inclination of the rotating shaft of a spindle.

  In order to achieve the object of the present invention, a roundness measuring apparatus of the present invention includes a table on which a work is placed, a spindle connected to the table and rotating the table, and a surface of the work placed on the table. The relative amount of tilt between the detector that detects the displacement of the probe contacting the workpiece, the rotation axis of the spindle in the rotation stopped state before the workpiece measurement is started, and the rotation axis of the spindle in the rotation state at the time of workpiece measurement A detection unit for detecting B.

  According to the detection unit of the roundness measuring device of the present invention, the rotation axis (A axis) of the spindle in the rotation stop state before the workpiece measurement is started and the rotation axis of the spindle in the rotation state at the workpiece measurement are relative to each other. A typical inclination amount B is detected. Thus, according to the present invention, it is possible to detect a specific problem of the roundness measuring device, that is, when the spindle rotation axis is inclined during measurement, the amount B of inclination of the spindle rotation axis. The tilt amount B of the rotation axis of the spindle may be the tilt amount with respect to the A axis or the tilt amount with respect to an axis orthogonal to the A axis.

  Here, the A axis refers to the rotation axis of the spindle in the rotation stopped state before the workpiece measurement is started. In other words, the A axis indicates the rotation axis of the spindle that is error-corrected to the reference value by the eccentricity calibration work performed before the measurement. Further, the work is placed on the table in a state where the shape center of the work is aligned with the spindle rotation axis equivalent to the rotation center of the table. However, as described above, the rotation axis of the spindle is inclined with respect to the A axis when measuring the workpiece due to a problem specific to the roundness measuring apparatus. Therefore, when the inclination amount B affects the measurement accuracy. There is. For this reason, in this invention, the inclination amount B of the rotating shaft of the rotating spindle is detected by the detecting unit while measuring the workpiece. The inclination amount B described in the present invention refers to, for example, an inclination amount (separation amount) in a direction perpendicular to the A axis of the rotation axis of the spindle with respect to the unit length of the A axis. The amount of tilt that you want to detect is the amount of tilt at the center of rotation of the rotating table. However, in a normal device, a spindle whose axis length is longer than that of the table can increase the resolution of the amount of tilt compared to the table. The degree of freedom in the location of the parts is also wide. Therefore, in the present invention, the tilt amount B of the rotation axis of the table is indirectly detected by detecting the tilt amount B of the rotation axis of the spindle by the detection unit.

  In one aspect of the present invention, the table preferably includes alignment means for aligning the rotation center of the table and the shape center of the workpiece.

  According to one aspect of the present invention, the roundness measuring apparatus is required to match the table rotation center (or the rotation center of the measuring element) with the shape center of the workpiece. By the alignment means, the center of rotation and the center of shape can be matched, and an environment for measuring the roundness with high accuracy can be set. In addition, for a workpiece or the like whose shape center and center of gravity do not coincide with each other, it is possible to accurately correct the displacement amount of the probe by the detecting means for detecting the inclination amount.

  In one embodiment of the present invention, the spindle is preferably rotatably supported by an air bearing.

  According to one aspect of the present invention, the air bearing has a feature that the sliding resistance is extremely small and noise accompanying the sliding resistance of the air bearing is extremely small, but the rigidity is small. For workpieces whose center of shape does not match the center of gravity, highly accurate roundness measurement is achieved by correcting the amount of table tilt due to insufficient bearing rigidity.

  One aspect of the present invention preferably includes a calculation unit that calculates the roundness of the workpiece based on the inclination amount B and the displacement amount of the measuring element.

  In one aspect of the present invention, the calculation unit is configured to determine the displacement amount C for each angular position of the probe detected by the detector, and the inclination of the rotation axis of the spindle at the detected position of the probe calculated based on the inclination amount B. It is preferable to calculate the roundness of the workpiece by correcting based on the amount D.

  According to the calculation unit of one aspect of the present invention, each angular position of the probe detected by the detector based on the inclination amount D of the rotation axis of the spindle at the detection position of the probe calculated based on the inclination amount B. The amount of displacement C is corrected. Thereby, since the measurement which remove | eliminated the error component of the rotation accuracy of the table produced when measuring a workpiece | work can be implemented, the measurement accuracy of a workpiece | work improves.

  In one aspect of the present invention, it is preferable that the calculation unit calculates the roundness of the workpiece based on the correction value E for each angular position obtained by subtracting the inclination amount D from the displacement amount C.

  According to the calculation unit of one aspect of the present invention, since the roundness of the workpiece is calculated based on the correction value E for each angular position obtained by subtracting the inclination amount D from the displacement amount C, the measurement accuracy is improved. To do.

  In one aspect of the present invention, when the inclination amount B is larger than the set threshold value, the calculation unit calculates the roundness of the workpiece based on the correction value E obtained by correcting the displacement amount C by the inclination amount D. If it is smaller than the threshold value, it is preferable to calculate the roundness of the workpiece based on the displacement amount C without correcting the displacement amount C with the inclination amount D.

  According to one aspect of the present invention, the threshold value that does not affect the measurement accuracy is set in the tilt amount B detected by the detection unit. When the inclination detected by the detection unit is smaller than the set value, the roundness of the workpiece is calculated using the displacement C as it is without correcting the displacement C with the inclination D. . On the other hand, when the inclination amount detected by the detection unit exceeds the set value, the roundness of the workpiece is calculated based on the correction value E obtained by correcting the displacement amount C by the inclination amount D. As a result, the measurement can be performed with the error component of the rotation accuracy of the table that affects the measurement accuracy removed, so that the workpiece measurement accuracy is improved.

  In one aspect of the present invention, the calculation unit preferably calculates the shape of the workpiece in real time based on the displacement amount C or the correction value E.

  According to the calculation unit of one aspect of the present invention, the roundness of the workpiece is calculated for each angular position based on the displacement amount C continuously detected by the detector or based on the correction value E. Thereby, the roundness of the workpiece can be calculated simultaneously (in real time) with the rotation of the table.

  In one aspect of the present invention, the detection unit is disposed at different height positions in the axial direction of the rotation axis of the spindle in the rotation stopped state, and detects the distance or the displacement amount to the table or the spindle. It is preferable to provide a sensor and detect the tilt amount B based on the detection results of the first sensor and the second sensor.

  According to the detection unit of one aspect of the present invention, the distance or displacement detected by the first sensor is subtracted from the distance or displacement detected by the second sensor, and the displacement subtraction value is used as the second sensor. Is divided by a height subtraction value obtained by subtracting the first height position of the first sensor from the second height position. Accordingly, the detection unit can detect the inclination amount B.

  In one embodiment of the present invention, it is preferable that the calculation unit calculates the roundness by deleting the vibration component from the detection result based on the detection results of the first sensor, the second sensor, and the detector.

  In one embodiment of the present invention, it is preferable that the calculation unit calculates the roundness by deleting the eccentric component from the detection result based on the detection results of the first sensor, the second sensor, and the detector.

  According to the roundness measuring apparatus of the present invention, a unique problem of the roundness measuring apparatus, that is, the amount of tilt of the spindle rotation axis is detected when the spindle rotation axis is tilted during measurement. The measurement accuracy can be improved based on the tilt amount of the rotation axis of the spindle.

1 is an external perspective view of a roundness measuring device according to an embodiment of the present invention. Block diagram showing the configuration of the roundness measuring device Flow chart showing an example of workpiece measurement method based on the amount of tilt Explanatory diagram showing work eccentricity calibration work Explanatory drawing which showed the measurement form of the workpiece | work performed after the eccentricity calibration work of FIG. Explanatory drawing which showed the work measurement method when the amount of inclination is smaller than a threshold Explanatory drawing which showed the work measurement method when the amount of inclination is larger than a threshold Explanatory drawing showing the calibration method when vibration occurs on the spindle Explanatory drawing showing a calibration method when the rotation axis at the time of measuring the spindle is eccentric with respect to the A axis

  Hereinafter, preferred embodiments of a roundness measuring apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is an external perspective view of a roundness measuring apparatus 10 according to an embodiment of the present invention. FIG. 2 is a block diagram showing the configuration of the roundness measuring apparatus 10.

[Overall Configuration of Roundness Measuring Device 10]
As shown in FIGS. 1 and 2, the roundness measuring apparatus 10 includes a box-shaped base 12, a table 16 that is rotatably provided on the upper surface of the base 12, and on which a substantially cylindrical workpiece 14 is placed, A spindle 20 provided in the interior and incorporating a motor 18 (see FIG. 2) for rotationally driving the table 16, a column 22 erected on the upper surface of the base 12 in the Z direction (vertical direction), and along the column 22 A carriage 24 movable in the Z direction, an arm 26 movably attached to the carriage 24 in the X direction (horizontal direction), a detector holder 28 attached to an end of the arm 26, and a detector holder 28. And a detector 32 having a probe 30 at the tip.

  The table 16 is rotated with the work 14 placed thereon, and the rotation angle of the table 16 is detected by a rotation angle signal output from an encoder 52 connected to the spindle 20.

  The column 22 is a column erected in parallel with the rotation axis A (A axis) of the spindle 20 that is the rotation center of the table 16 in the Z direction, and a lower end portion thereof is fixed to the upper surface of the base 12. A carriage 24 is attached to the column 22 so as to be movable in the Z direction. The driving means for moving the carriage 24 in the Z direction with respect to the column 22 is not particularly limited. For example, the driving means is constituted by a combination of a motor, a ball screw, a guide rail, and the like.

  The rotation axis A (A axis) of the spindle 20 refers to the rotation axis of the spindle 20 in a rotation stopped state before the measurement of the workpiece 14 is started. That is, the rotation axis A indicates the rotation axis of the spindle 20 that has been error-corrected to the reference value by the eccentricity calibration work performed before the workpiece measurement. However, when the workpiece 14 is placed on the table 16, the rotation axis of the spindle 20 may be inclined with respect to the rotation axis A due to a specific problem of the roundness measuring device 10. The amount (inclination amount B described later) may affect the measurement accuracy. This will be described later.

  The arm 26 is attached to the carriage 24 along the X direction, and is moved integrally with the carriage 24 in the Z direction. The lower end of the detector holder 28 is attached to the tip of the arm 26. Further, the arm 26 is attached to the carriage 24 so as to be movable in the X direction. The driving means for moving the arm 26 in the X direction with respect to the carriage 24 is not particularly limited, and is configured by a combination of a motor, a ball screw, a guide rail, and the like. With the above configuration, the detector holder 28 attached to the arm 26 is configured to be movable in the Z direction along the column 22 and the X direction along the arm 26.

  The detector holder 28 is an L-shaped member, the lower end is connected to the arm 26, and the detector 32 is attached to the upper end.

  The detector 32 includes a measuring element 30 that contacts the surface of the workpiece 14 and a displacement amount detection unit (not shown) such as a differential transformer. An electric signal indicating the displacement amount of the measuring element 30 is converted into an analog voltage value. Output as. The detection direction of the detector 32 is the horizontal direction.

  Further, the table 16 is provided with an XY drive mechanism (alignment means) including an X direction fine movement knob 34 and a Y direction fine movement knob 36. The X direction fine movement knob 34 and the Y direction fine movement knob 36 are respectively connected to the spindle 20, and the table 16 is moved in the X direction and the Y direction (in the X direction) by operating the X direction fine movement knob 34 and the Y direction fine movement knob 36. It can be finely fed in an orthogonal horizontal direction. Thereby, the horizontal position of the table 16 is finely adjusted. Further, the table 16 is provided with an X direction tilt knob (not shown) and a Y direction tilt knob (not shown). By operating the X direction tilt knob and the Y direction tilt knob, the table 16 is moved in the X direction. And can be tilted in the Y direction. Thereby, the attitude | position of the inclination direction of the table 16 is finely adjusted. By such a fine adjustment operation in the horizontal direction and the inclination direction, that is, the eccentricity calibration operation of the table 16, an error in the rotation accuracy of the table 16 is removed.

  Further, alignment work is described in which the work 14 is placed on the table 16 and the center axis that is the center of the cylindrical surface of the work 14 is aligned with the rotation axis A of the spindle 20 that is the rotation center of the table 16. In this alignment operation, the work 14 is first placed on the table 16 so that the center axis of the cylindrical surface of the work 14 substantially coincides with the center of the rotation axis of the spindle 20. Next, the carriage 24 is moved to adjust the vertical position so that the probe 30 contacts the position to be measured by the workpiece 14, and the arm 26 is moved to adjust the radial position.

  In this state, the work 14 is rotated to measure the eccentricity between the central axis of the cylindrical portion of the work 14 and the rotation axis of the spindle 20, and the X direction fine adjustment knob 34 of the XY moving mechanism provided on the table 16 and the Y direction are measured. The fine movement knob 36 is operated so that the central axis of the cylindrical portion of the work 14 is exactly aligned with the rotation axis of the spindle 20. By performing this alignment operation, it is possible to set an environment for measuring the roundness with high accuracy. In addition, as will be described later, the displacement of the probe 30 can be accurately corrected by the detecting means that detects the inclination amount B of the workpiece 14 or the like whose shape center and center of gravity do not coincide with each other.

<The arithmetic processing unit 40 of the roundness measuring apparatus 10>
As shown in FIG. 2, the roundness measuring device 10 includes an arithmetic processing device 40.

  An electric signal (analog voltage value) indicating the amount of displacement of the probe 30 output from the detector 32 is input to the arithmetic processing unit 40. The arithmetic processing unit 40 includes an amplifier 42, an A / D converter 44, an arithmetic processing unit 46, and a memory 48 in which an operation program is stored, and further includes a display 50 that displays measurement results.

  An electrical signal obtained by bringing the probe 30 into contact with the workpiece 14 is transmitted from the detector 32 to the arithmetic processing unit 40. In the arithmetic processing unit 40, the electric signal is first amplified by the amplifier 42, then converted into a digital signal by the A / D converter 44, and arithmetic processing is performed by the arithmetic processing unit 46.

<Example of Method for Measuring Workpiece 14 by Roundness Measuring Device 10>
First, prior to the measurement of the workpiece 14, the error correction of the roundness measuring device 10, the sensitivity calibration of the detector 32, and the eccentricity calibration work of the table 16 are performed, and the roundness measuring device 10 is set as a reference value. Set. That is, the roundness measuring apparatus 10 is set to the reference value so that the roundness obtained by placing the masterpiece on the table 16 and measuring the masterpiece with the detector 32 becomes a perfect circle.

  Thereafter, the workpiece 14 as the object to be measured is placed on the upper surface of the table 16. First, the alignment operation for aligning the central axis of the cylindrical surface of the workpiece 14 with the rotation axis A of the spindle 20, and the rotation axis A of the spindle 20. The inclination correction of the work 14 with respect to is performed. Thereby, the rotation axis A of the spindle 20 and the center of the workpiece 14 are set to coincide with each other.

  Next, with the probe 30 of the detector 32 in contact with the side surface of the workpiece 14, the table 16 is rotated once by the spindle 20, and data for one round of the side surface of the workpiece 14 is obtained from the detector 32 as an analog voltage value. Collect as The electrical signal obtained as the analog voltage value is amplified by the amplifier 42 as described above, converted into a digital signal by the A / D converter 44, and input to the arithmetic processing unit 46. The arithmetic processing unit 46 is rotation angle data output from the encoder 52 and is detected by the detector 32 for each of the plurality of angular positions divided in the rotational direction of the table 16 and for each angular position described above. Based on the displacement amount thus calculated, the roundness of the workpiece 14 is calculated, and the calculation result is displayed on the display 50.

  By the way, as described above, when the workpiece 14 is placed on the table 16, the rotation axis of the spindle 20 may be inclined with respect to the rotation axis A due to a specific problem of the roundness measuring device 10. This tilt amount B may affect the measurement accuracy. Therefore, in order to increase the measurement accuracy of the workpiece 14, it is important to detect the inclination amount B.

  In view of this, the roundness measuring apparatus 10 according to the embodiment has a spindle for the A axis when the table 16 is rotated once by the spindle 20 with the workpiece 14 placed on the table 16 in order to detect the tilt amount B. A detection unit 54 that detects the inclination amount B of the 20 rotation shafts for each of a plurality of angular positions divided in the rotation direction is provided. In other words, the detection unit 54 has a relative amount of inclination between the rotation axis (A axis) of the spindle 20 in the rotation stopped state before the measurement of the workpiece 14 and the rotation axis of the spindle 20 in the rotation state at the time of measuring the workpiece 14. B is detected.

<Example of detection unit 54>
As shown in FIG. 2, the detection unit 54 includes a first sensor 56 that detects a distance or a displacement amount to the spindle 20 at a first height position H1 in the A-axis direction with respect to a reference position RP (Reference Position), and a reference position RP. A second sensor 58 that detects a distance to the spindle 20 and a displacement amount at a second height position H2 in the A-axis direction and at a second height position H2 that is higher than the first height position H1. , And the calculation processing unit 46 calculates the inclination amount B based on the distance or displacement amount (detection result) detected by the first sensor 56 and the second sensor 58. That is, the detection unit 54 includes a first sensor 56 and a second sensor 58 that are arranged at different height positions in the A-axis direction, and an arithmetic processing unit 46.

  The detection directions of the first sensor 56 and the second sensor 58 are horizontal directions, and are parallel to the measurement direction of the detector 32 of the roundness measuring apparatus 10. The detector 32, the first sensor 56, and the second sensor 58 are disposed on the same vertical line parallel to the A-axis direction, and each of the detector 32, the first sensor 56, and the second sensor 58 is detected. The points are located on the same vertical line. In the embodiment, the bottom of the base 12 of the roundness measuring device 10 is set to the reference position RP, but the position is not limited to this position, and any position below the first sensor 56 may be used. . Further, as the first sensor 56 and the second sensor 58, it is preferable to apply a non-contact type displacement sensor such as an eddy current type sensor or a differential transformer type sensor, but even a contact type sensor is applicable. can do.

<Detection method of the amount of inclination B by the arithmetic processing unit 46>
The arithmetic processing unit 46 subtracts the displacement amount (may be a distance) from the reference value detected by the first sensor 56 from the displacement amount (may be a distance) from the reference value detected by the second sensor 58, and The displacement amount subtraction value is divided by a height subtraction value obtained by subtracting the first height position H1 from the second height position H2. Accordingly, the detection unit 54 can detect the tilt amount B.

  More specifically, the amount of displacement detected for each of a plurality of angular positions of the rotation angle data output from the encoder 52, and the amount of displacement from the reference value detected by the first sensor 56 is represented by D1 and second. When the displacement amount from the reference value detected by the sensor 58 is D2, the arithmetic processing unit 46 calculates the inclination amount B by the following equation (1).

B = (D2-D1) / (H2-H1) (1)
Thereby, according to the roundness measuring apparatus 10 of embodiment, the inclination amount B of the rotating shaft at the time of the measurement of the spindle 20 with respect to the A axis can be detected.

<Method of measuring workpiece 14 based on tilt amount B>
The calculation processing unit 46 according to the embodiment functions as a calculation unit that calculates the roundness of the workpiece 14. That is, the arithmetic processing unit 46 that is a calculation unit calculates the displacement amount C for each angular position of the probe 30 detected by the detector 32, and the spindle 20 at the detection position of the probe 30 calculated based on the inclination amount B. The roundness of the workpiece 14 is calculated by performing correction based on the tilt amount D of the rotation axis. Specifically, the roundness of the workpiece 14 is calculated based on the correction value E for each angular position obtained by subtracting the inclination amount D from the displacement amount C.

  FIG. 3 is a flowchart showing an example of a workpiece measuring method based on the inclination amount B.

  First, the measuring element 30 of the detector 32 is brought into contact with the workpiece 14 placed on the table 16 to rotate the table 16 (Step (S) 100).

  Next, the arithmetic processing unit 46 acquires the following displacement amount. That is, the displacement amount (detection value) D1 from the reference value detected by the first sensor 56 for each angular position of the table 16, the displacement amount (detection value) D2 from the reference value detected by the second sensor 58, and A displacement amount (detection value) C detected by the detector 32 is acquired (S110).

  Next, the arithmetic processing unit 46 calculates the tilt amount B by the above equation (1), and then calculates the tilt amount D of the rotation axis of the spindle 20 at the detection position of the probe 30 calculated based on the tilt amount B. Is calculated by the following equation (2). H3 in Expression (2) indicates a third height position from the reference position RP to the detection position of the probe 30.

D = (D2-D1) * (H3-H2) / (H2-H1) = B * (H3-H2) (2)
Next, the arithmetic processing unit 46 calculates a correction value E for each angular position obtained by subtracting the inclination amount D from the displacement amount C by the following equation (3) (S120).

E = C−D (4)
And the arithmetic processing part 46 calculates the roundness of the workpiece | work 14 from the correction value E for every angle position (S130). Thereby, since the measurement which remove | eliminated the error component of the rotation accuracy of the table 16 produced when measuring the workpiece | work 14 can be implemented, the measurement accuracy of the workpiece | work 14 improves.

  Further, it is preferable that the arithmetic processing unit 46 calculates the roundness of the workpiece 14 in real time based on the correction value E.

  That is, the arithmetic processing unit 46 subtracts the inclination amount D constantly calculated by the detection unit 54 from the displacement amount C constantly detected by the detector 32. Based on the correction value E obtained by this, the roundness of the workpiece 14 is measured for each angular position. Thereby, the roundness of the workpiece 14 can be calculated simultaneously (in real time) with the rotation of the table 16. Further, as will be described later, when the tilt amount B is smaller than the threshold value, the roundness of the workpiece 14 is measured for each angular position based on the displacement amount C without being corrected by the correction value E. Here, for example, when the inclination amount B is smaller than a certain threshold value, it may be calculated as it is without correcting the roundness as positive. That is, in the present invention, the arithmetic processing unit 46 may not always be used.

<Other measurement methods for workpiece 14>
FIG. 4 is an explanatory view showing an example of the eccentricity calibration work of the work 14, and FIG. 5 is an explanatory view showing a measurement form of the work 14 performed after the eccentricity calibration work of FIG.

  The eccentricity calibration work of the table 16 shown in FIG. 4 is carried out by finely adjusting the table 16 in the horizontal direction and the tilt direction as described above, thereby correcting the elliptical true position at the first height position H1 detected by the first sensor 56. Roundness data RD (Roundness Data) 1 is calibrated to a reference perfect circle. Then, the elliptical roundness data RD2 at the second height position H2 detected by the second sensor 58 is calibrated to a reference perfect circle. This completes the eccentricity calibration work.

  Thereafter, as shown in FIG. 5, the workpiece 14 is measured using the calibrated value as a reference value. This measurement is the same as the measurement procedure of the above embodiment. In FIG. 5, the rotation axis at the time of measurement of the spindle 20 with respect to the A axis is indicated by reference numeral A1. The arithmetic processing unit 46 detects the displacement D1 from the reference value detected by the first sensor 56 for each angular position of the table 16, the displacement D2 from the reference value detected by the second sensor 58, and the detector 32. Based on the displacement amount C and the height positions H1, H2, and H3, the correction value E for each angular position is calculated, and the roundness of the workpiece 14 is calculated from the correction value E (formula (1)). , (2), (3)). That is, FIG. 5 shows that the ellipticity of the elliptical shape of the workpiece 14 measured with the displacement amount C is corrected by the correction value E.

  FIG. 6 is an explanatory diagram showing a workpiece measurement method when a threshold value is set for the tilt amount B and the tilt amount B is smaller than the threshold value. FIG. 7 is an explanatory diagram showing a workpiece measurement method when the inclination amount B is larger than the threshold value.

  When the inclination amount B detected by the arithmetic processing unit 46 is smaller than the set threshold value, the roundness of the workpiece 14 is calculated based on the displacement amount C without being corrected with the correction value E as shown in FIG. . The roundness data RD1 and RD2 in FIG. 6 indicate that it is not necessary to calibrate because the circular shape is close to the reference perfect circle.

  When the inclination amount B is larger than the set threshold value, the roundness of the workpiece 14 is calculated based on the correction value E obtained by correcting the displacement amount C with the inclination amount D as shown in FIG. The roundness data RD1 and RD2 in FIG. 7 indicate that calibration is necessary because the ellipses have different shapes with respect to the reference perfect circle.

  In order to implement the above embodiment, a threshold value of the tilt amount B that does not affect the measurement accuracy is set, and this threshold value is stored in the memory 48 (see FIG. 2). If the inclination amount B detected by the detection unit 54 is smaller than the threshold value, the roundness of the workpiece 14 is calculated using the displacement amount C detected by the detector 32 as it is as shown in FIG. To do. On the other hand, when the inclination amount B detected by the detection unit 54 exceeds the set value, the roundness of the workpiece 14 is calculated based on the correction value E as shown in FIG. Thereby, since the measurement which remove | eliminated the error component of the rotation accuracy of the table 16 which affects measurement accuracy can be implemented, the measurement accuracy of the workpiece | work 14 improves.

  In the above-described embodiment, the inclination amount B of the rotation axis A1 of the spindle 20 is detected by the detection unit 54 to indirectly detect the inclination amount of the rotation axis A1 when the table 16 is measured. The amount of inclination of the rotation axis A1 during the measurement may be directly detected. That is, the first sensor 56 and the second sensor 58 detect the amount of inclination B based on the amount of displacement from the reference position RP at the two height positions of the table 16 and the two height positions. Also good. This is because the amount of inclination that is actually desired to be detected is the amount of inclination of the rotation center when the table 16 is measured with respect to the A axis. However, in a normal apparatus, the spindle 20 whose axial length is longer than that of the table 16 can increase the resolution of the tilt amount more than that of the table 16, and the arrangement positions of the first sensor 56 and the second sensor 58 constituting the detection unit 54. In this embodiment, the amount of inclination B of the rotation axis A1 when measuring the table 16 is indirectly detected by detecting the amount of inclination B of the rotation axis A1 of the spindle 20 by the detection unit 54. Yes.

<Other calibration methods using the detector 54>
FIG. 8 is an explanatory diagram showing a calibration method when sudden vibration is generated in the spindle 20.

  The spindle 20 has an air bearing. In the roundness measuring apparatus 10, sudden vibrations occur due to the gap between the air bearing 21 and the spindle 20 when the spindle 20 rotates, and the roundness data RD1, RD2, and ED (Error Data) that is a vibration component is superimposed on the displacement amount C. In this case, the arithmetic processing unit 46 performs processing for excluding ED generated at the same angular position from the measurement data. That is, the arithmetic processing unit 46 calibrates the displacement amount C so as to delete the ED detected by the first sensor 56 and the second sensor 58 from the displacement amount C, and outputs the calculation result. Thereby, the measurement of the workpiece | work 14 which removed ED is attained.

  Here, the spindle 20 of the roundness measuring device 10 of the embodiment is rotatably supported by the air bearing 21, but the air bearing 21 has extremely small sliding resistance, and the sliding resistance of the air bearing 21 is reduced. While there is a feature that the accompanying noise is extremely small, there is a drawback that rigidity is small. For the workpiece 14 whose center of gravity and center of gravity do not coincide, it is possible to realize highly accurate roundness measurement by correcting the tilt amount B of the table 16 due to insufficient rigidity of the air bearing 21.

  FIG. 9 is an explanatory diagram showing a calibration method when the rotation axis A1 at the time of measurement of the spindle 20 is eccentric with respect to the A axis.

  When the centers of the roundness data RD1 and RD2 detected by the first sensor 56 and the second sensor 58 are shifted by the same amount from the center of the reference value set in the eccentricity calibration work, the arithmetic processing unit 46 The rotation axis A1 is not inclined with respect to the axis A and is determined to be eccentric by the difference, and the calculation result obtained by deleting the eccentric component is output.

  As described above, by making effective use of the detection values output from the first sensor 56 and the second sensor 58 constituting the detection unit 54, not only the inclination amount B is detected, but also the sudden vibration generated in the spindle 20 And the calculation result obtained by removing the eccentricity can be obtained. Therefore, the shape of the workpiece 14 can be accurately measured.

  The detection unit 54 calculates the tilt amount B at two upper and lower points in the radial direction with respect to the rotation axis A of the spindle 20, but is not limited thereto. For example, it is possible to add the first sensor 56 and the second sensor 58 at any location such as a thrust surface below the table 16. That is, the tilt amount B of the rotation axis A1 of the spindle 20 is not limited to the A-axis reference, and may be, for example, the tilt amount B based on an axis orthogonal to the A-axis. However, in order to obtain and correct a more quantitative amount of inclination, the first sensor 56 and the second sensor 58 are attached to the upper and lower two points in the radial direction as shown in FIG. It becomes possible.

  DESCRIPTION OF SYMBOLS 10 ... Roundness measuring device, 12 ... Base, 14 ... Workpiece, 16 ... Table, 18 ... Motor, 20 ... Spindle, 21 ... Air bearing, 22 ... Column, 24 ... Carriage, 26 ... Arm, 28 ... Detector holder , 30 ... Measuring element, 32 ... Detector, 34 ... X direction fine movement knob, 36 ... Y direction fine movement knob, 40 ... Arithmetic processing device, 42 ... Amplifier, 44 ... A / D converter, 46 ... Arithmetic processing section, 48 ... Memory, 50 ... Display, 52 ... Encoder, 54 ... Detector, 56 ... First sensor, 58 ... Second sensor

Claims (11)

A table on which the workpiece is placed;
A spindle coupled to the table for rotating the table;
A detector that detects the amount of displacement of the probe contacting the surface of the workpiece placed on the table;
A detection unit that detects a relative inclination amount B between the rotation axis of the spindle in a rotation stopped state before the measurement of the workpiece and the rotation axis of the spindle in a rotation state at the time of measurement of the workpiece;
A roundness measuring device.   The roundness measuring apparatus according to claim 1, wherein the table includes an alignment unit that aligns a rotation center of the table and a shape center of the workpiece.   The roundness measuring device according to claim 1, wherein the spindle is rotatably supported by an air bearing.   The roundness measuring apparatus according to claim 1, 2 or 3, further comprising an arithmetic unit that calculates the roundness of the workpiece based on the tilt amount B and the displacement amount of the measuring element.   The computing unit calculates a displacement amount C for each angular position of the probe detected by the detector, and a tilt amount of the spindle of the spindle at the detected position of the probe calculated based on the tilt amount B. The roundness measuring apparatus according to claim 4, wherein the roundness of the workpiece is calculated by correcting based on D.   6. The perfect circle according to claim 5, wherein the calculation unit calculates a roundness of the workpiece based on a correction value E for each angular position obtained by subtracting the inclination amount D from the displacement amount C. Degree measuring device. When the inclination amount B is larger than a set threshold, the calculation unit calculates the roundness of the workpiece based on the correction value E obtained by correcting the displacement amount C by the inclination amount D, and If it is smaller than the threshold value, the roundness of the workpiece is calculated based on the displacement amount C without correcting the displacement amount C with the inclination amount D.
The roundness measuring apparatus according to claim 6.   The roundness measuring device according to claim 6 or 7, wherein the calculation unit calculates the roundness of the workpiece in real time based on the displacement amount C or the correction value E. The detector is
A first sensor and a second sensor which are arranged at different height positions in the axial direction of the rotation axis of the spindle in the rotation stopped state and detect a distance or a displacement amount to the table or the spindle;
The roundness measuring device according to any one of claims 4 to 8, wherein the inclination amount B is detected based on detection results of the first sensor and the second sensor.   10. The perfect circle according to claim 9, wherein based on detection results of the first sensor, the second sensor, and the detector, the calculation unit calculates a roundness by deleting a vibration component from the detection result. Degree measuring device.   10. The perfect circle according to claim 9, wherein based on detection results of the first sensor, the second sensor, and the detector, the calculation unit calculates a roundness by deleting an eccentric component from the detection result. Degree measuring device.

Images