JP2017161244A - Flatness measurement method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flatness measurement method that can measure the flatness of a measurement surface of a work with high repeatability and high accuracy without an influence from the squareness between a work rotation axis and a detector movement axis.SOLUTION: A flatness measurement method includes: a first measurement step of obtaining first measurement data (measurement result A) expressing the displacement of a measurement surface of a work by moving a detector in a first radial direction position r1; a second measurement step of obtaining second measurement data (measurement result B) expressing the displacement of the measurement surface of the work by moving the detector in a second radial direction position r2; a third measurement step of obtaining third measurement data (measurement result A') expressing the displacement of the measurement surface of the work by moving the detector in a third radial direction position r1' that is a position symmetric to the first radial direction position r1 with respect to a rotation shaft L; and a flatness calculation step of calculating the flatness of the measurement surface of the work on the basis of the first measurement data, the second measurement data, and the third measurement data.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a flatness measuring method for measuring the flatness of a surface to be measured of a workpiece using a roundness measuring machine.

  The roundness measuring machine makes the detector probe contact the surface of the workpiece (object to be measured) placed on the table and rotate the table or detector to move the detector relative to the workpiece. It is known as a device that measures the roundness of a workpiece by rotating it.

  Further, the roundness measuring machine can measure not only the roundness of the workpiece but also the shape data of the workpiece for evaluating the shape accuracy such as flatness, coaxiality, and cylindricity (for example, (See Patent Documents 1 and 2). When performing these measurements, the operator needs to change the orientation of the detector (measuring element) according to the object to be measured and perform relative alignment between the workpiece and the detector.

  Conventionally, as a flatness measuring method using a roundness measuring machine, for example, when a rotation axis that is a rotation center of relative rotation between a workpiece and a detector is a vertical direction, a surface to be measured of the workpiece is an upper surface. In this case, set the direction of the detector (measuring element) downward, perform relative alignment between the work and the detector, and place the measuring element in contact with the upper surface of the work. On the other hand, the detector is relatively rotated, and the displacement of the probe is detected by the detector. Thereby, measurement data indicating the displacement (unevenness) from the reference point of the surface to be measured (upper surface) of the workpiece can be acquired, and the width between the maximum value and the minimum value of the measurement data can be obtained as flatness.

  Further, in such a flatness measurement method, the measurement data at a plurality of locations on the surface to be measured of the workpiece can be obtained by moving the detector in the horizontal direction and changing the position of the probe to be in contact with the workpiece in the radial direction of the workpiece. A method is known in which each is acquired and the width of the maximum value and the minimum value of all measurement data is obtained as flatness. According to this method, since the flatness is calculated from the measurement data at a plurality of locations on the surface to be measured of the workpiece, the radial direction of the surface to be measured of the workpiece is compared with the case where the flatness is calculated from the measurement data at one location. Therefore, it is possible to accurately evaluate the flatness in consideration of the variation in.

JP 2003-302218 A JP 2009-069067 A

  However, in the flatness measurement method described above, in order to obtain measurement data at a plurality of locations on the surface to be measured of the workpiece, the position of the probe that moves the detector and contacts the workpiece is changed in the radial direction of the workpiece. Therefore, the perpendicular angle between the rotation axis (hereinafter referred to as workpiece rotation axis) and the movement axis (hereinafter referred to as detector movement axis) of the detector, which is the rotation center of the relative rotation between the workpiece and the detector. High accuracy is required.

  That is, when flatness is measured with a deviation in the perpendicularity between the workpiece rotation axis and the detector movement axis, the detector moves to each position when the detector is moved along the detector movement axis. The detected detector (measuring element) is displaced in the direction of the workpiece rotation axis, and an offset error corresponding to this displacement is superimposed on the measurement data. As a result, the measurement result of flatness is affected. is there.

  Conventionally, in order to reduce this effect, the perpendicularity between the workpiece rotation axis and the detector movement axis has been corrected. However, there is a case where recorrection is necessary due to the influence of secular change, etc. It was difficult to maintain the squareness.

  The present invention has been made in view of such circumstances, and the flatness of the surface to be measured of the workpiece is highly reproducible and highly accurate without being affected by the perpendicularity between the workpiece rotation axis and the detector movement axis. An object of the present invention is to provide a flatness measuring method capable of performing measurement.

  In order to achieve the above object, one aspect of the flatness measuring method according to the present invention is to bring a measuring element of a detector into contact with a surface to be measured of the workpiece, and relatively rotate the workpiece and the detector around a rotation axis. A flatness measurement method for measuring the flatness of a surface to be measured of a workpiece by detecting the displacement of a probe with a detector, and is a first radial distance away from a rotation axis in a radial direction perpendicular to the rotation axis. The first radial position is obtained by moving the detector to the first radial position, bringing the probe of the detector into contact with the surface to be measured of the workpiece, and detecting the displacement of the probe with relative rotation by the detector. A first measurement step for acquiring first measurement data indicating the displacement of the surface to be measured of the workpiece, and a second radial position separated from the rotation axis in a radial direction by a second radial distance different from the first radial distance Move the detector to the surface of the workpiece to be measured A second measurement step of acquiring second measurement data indicating the displacement of the surface to be measured of the workpiece in the second radial position by touching and detecting the displacement of the probe with relative rotation by the detector; On the other hand, the detector is moved to a third radial position that is symmetrical to the first radial position, and the probe of the detector is brought into contact with the surface to be measured of the workpiece. , A third measurement step of acquiring third measurement data indicating the displacement of the surface to be measured of the workpiece at the third radial direction position, the first measurement data, the second measurement data, and the third A flatness calculating step of calculating the flatness of the surface to be measured of the workpiece based on the measurement data.

  In one aspect of the flatness measuring method according to the present invention, the detector is moved to a fourth radial position that is symmetrical to the second radial position with respect to the rotation axis, and is detected on the surface to be measured of the workpiece. A fourth measurement step of acquiring fourth measurement data indicating the displacement of the surface to be measured of the workpiece at the fourth radial position by detecting the displacement of the probe due to relative rotation with a detector. The flatness calculating step calculates a first offset amount indicating a distance in the rotation axis direction between the first radial position and the second radial position based on the first measurement data and the third measurement data. A second offset amount indicating a distance in the rotation axis direction between the second radial position and the fourth radial position is calculated based on the first offset amount calculating step, the second measurement data, and the fourth measurement data. Second offset amount calculating step and first off A correction value calculating step for calculating a correction value indicating an offset error between the first measurement data and the second measurement data accompanying the movement of the detector based on the offset amount and the second offset amount; and the first measurement data based on the correction value And calculating the flatness of the surface to be measured of the workpiece by correcting the offset error between the second measurement data and the second measurement data.

  In one aspect of the flatness measuring method according to the present invention, the flatness calculating step is based on the first measurement data and the third measurement data, and the rotation axis direction between the first radial position and the second radial position. A first offset amount calculating step of calculating a first offset amount indicating the distance of the first detector, an inclination angle calculating step of detecting an inclination angle of the moving direction of the detector with respect to the rotation axis based on the first offset amount, and an inclination angle A correction value calculating step for calculating a correction value indicating an offset error between the first measurement data and the second measurement data accompanying the movement of the detector, and an offset error between the first measurement data and the second measurement data by the correction value. A calculation step of correcting and calculating the flatness of the surface to be measured of the workpiece.

  In one aspect of the flatness measurement method according to the present invention, the flatness calculation step includes a determination step of determining whether the correction value is greater than a preset threshold value, and the calculation step includes a correction value determined by the determination step. Is determined to be larger than the threshold value, the offset error between the first measurement data and the second measurement data is corrected to calculate the flatness of the surface to be measured of the workpiece. If it is determined to be small, the flatness of the surface to be measured of the workpiece is calculated without correcting the offset error between the first measurement data and the second measurement data.

  According to the present invention, the flatness of the surface to be measured of the workpiece can be measured with high reproducibility and high accuracy without being affected by the perpendicularity between the workpiece rotation axis and the detector movement axis.

1 is an overall configuration diagram showing a roundness measuring machine according to an embodiment of the present invention. The figure which showed the state which measures the flatness of the to-be-measured surface of a work using a roundness measuring machine The figure for demonstrating the procedure in the case of measuring the flatness of the to-be-measured surface of a workpiece | work by the conventional roundness measuring method. The figure for demonstrating the procedure in the case of measuring the flatness of the to-be-measured surface of a workpiece | work by the conventional roundness measuring method. Diagram for explaining problems in conventional roundness measurement methods Diagram for explaining the effect on the measurement result of the flatness of the workpiece by the roundness measuring machine Diagram for explaining the effect on the measurement result of the flatness of the workpiece by the roundness measuring machine The flowchart which showed an example of the flatness measuring method which concerns on 1st Embodiment The figure for demonstrating the measurement procedure in the flatness measuring method which concerns on 1st Embodiment. The figure for demonstrating the measurement procedure in the flatness measuring method which concerns on 1st Embodiment. The figure for demonstrating the measurement procedure in the flatness measuring method which concerns on 1st Embodiment. The figure for demonstrating the measurement procedure in the flatness measuring method which concerns on 1st Embodiment. The figure for demonstrating the measurement principle in the roundness measuring method which concerns on 1st Embodiment. The figure which showed an example of the measurement result obtained with the roundness measuring method which concerns on 1st Embodiment The figure which showed an example of the measurement result obtained with the roundness measuring method which concerns on 1st Embodiment The figure which showed an example of the measurement result obtained with the roundness measuring method which concerns on 1st Embodiment The flowchart which showed the flatness measuring method which concerns on 2nd Embodiment The flowchart which showed the flatness measuring method which concerns on 3rd Embodiment

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is an overall configuration diagram showing a roundness measuring machine according to an embodiment of the present invention. As shown in FIG. 1, the roundness measuring machine in this embodiment includes a base 1, a rotatable rotary table 2 provided on the base 1, a motor for rotating the rotary table 2, and the like. A rotation drive unit 3 having a base 4, a column 4 provided on the base 1, a carriage 5 movable along the column 4, an arm 6 movable relative to the carriage 5, and a tip of the arm 6. The detector holder 7, the detector 8 attached to the detector holder 7, an arithmetic processing unit 12 configured with a computer or the like, and a display unit 14 configured with a monitor or the like. The detector 8 has a probe 9 and a displacement detector such as a differential transformer, and outputs an electrical signal indicating the displacement of the probe 9. The arithmetic processing unit 12 processes the output signal from the detector 8 and creates workpiece shape data for performing various measurements. The display unit 14 is connected to the calculation processing unit 12 and displays the calculation result of the workpiece shape (roundness, flatness, etc.) calculated by the calculation processing unit 12.

  The workpiece 10 is placed on the rotary table 2 and rotated so that the central axis of the cylindrical surface of the workpiece 10 substantially coincides with the rotary axis of the rotary table 2. The column 4 is a column that extends parallel to the rotation axis of the turntable 2. The carriage 5 is movable along the column 4, and generally the movement is moved along the guide surface of the column 4. The arm 6 is moved along the guide surface of the carriage 5. The detector holder 7 is an L-shaped member, with one end attached to the tip of the arm 6 and the detector 8 attached to the other end.

  When performing measurement, the workpiece 10 is placed on the rotary table 2 so that the central axis of the cylindrical surface of the workpiece 10 substantially coincides with the rotation axis L of the rotary table 2 (hereinafter referred to as the workpiece rotation axis L). Put. The carriage 5 is moved to adjust the position in the vertical direction (Z direction) and the arm 6 is moved to adjust the position in the radial direction (X direction) so that the probe 9 contacts the position to be measured by the workpiece 10. To do. In this state, the roundness of the workpiece 10 is measured.

  When measuring the flatness of the surface to be measured (the upper surface of the collar portion) of the workpiece 10 using the roundness measuring machine configured as described above, as shown in FIG. 2, an L-shaped detector holder is used. 7 is rotated 90 degrees with respect to the tip of the arm 6 (holder fixing portion), and the carriage 5 and the arm 6 are moved so that the workpiece 10 and the detector 8 are relatively aligned with each other. Is arranged so as to contact the surface to be measured of the workpiece 10. Thereby, it will be in the state which can start measurement of the flatness of the to-be-measured surface of the workpiece | work 10. FIG.

  Here, problems in the conventional roundness measurement method will be described in detail.

  3A and 3B are diagrams for explaining a procedure in the case where the flatness of the surface to be measured of the workpiece 10 is measured by a conventional roundness measuring method, and FIG. 3A shows the roundness measuring machine from above. FIG. 3B is a front view when the roundness measuring machine is viewed from the front side.

  In the conventional roundness measurement method, first, as shown by a solid line in FIGS. 3A and 3B, the detector 8 is moved to the first radial direction position by the movement of the arm 6, and the probe is placed on the surface to be measured of the workpiece 10. The workpiece 10 is rotated while the 9 is in contact, and the detector 8 detects the displacement of the probe 9. Next, as indicated by broken lines in FIGS. 3A and 3B, the detector 8 is moved to a second radial position different from the first radial position by the movement of the arm 6, and the probe is placed on the surface to be measured of the workpiece 10. The workpiece 10 is rotated while the 9 is in contact, and the detector 8 detects the displacement of the probe 9. A detection signal output from the detector 8 along with the rotation of the workpiece 10 at each radial position is input to the arithmetic processing unit 12. The arithmetic processing unit 12 processes the detection signal from the detector 8, and the width of the maximum value and the minimum value of all the measurement data is referred to as flatness (this flatness may be referred to as “flatness (double)”. ).

  By the way, when flatness measurement is performed by the conventional roundness measurement method, for example, as shown in FIG. 4, the expansion of the base 1 (see FIGS. 1 and 2) due to a temperature change and the column 4 that supports the arm 6. If the perpendicularity of the detector movement axis (movement axis of the arm 6) M with respect to the workpiece rotation axis (rotation axis of the turntable 2) L is shifted due to tilting or the like, the following effects are exerted on the flatness measurement result: Occurs.

  5A and 5B are diagrams for explaining the influence on the measurement result of the flatness of the workpiece 10 by the roundness measuring machine. FIG. 5A shows measurement results when there is no deviation in perpendicularity, and FIG. 5B shows measurement results when there is deviation in perpendicularity. 5A and 5B, “measurement result A” indicates measurement data obtained when the detector 8 is moved to the first radial position, and “measurement result B” indicates that the detector 8 has the second diameter. The measurement data obtained when moved to the directional position is shown.

  In the flatness measurement by the conventional roundness measurement method, when there is a deviation in the perpendicularity between the workpiece rotation axis L and the detector movement axis M, as shown in FIG. Moves along the detector movement axis M, the height position of the detector 8 relative to the surface to be measured of the workpiece 10 changes relatively. Therefore, as shown in FIG. 5B, the measurement data obtained when the detector 8 is moved to the second radial position (measurement result B) should be obtained when there is no deviation in perpendicularity. An offset error corresponding to the perpendicularity deviation amount is superimposed rather than (measurement result B ′). As a result, the flatness Y2 calculated when there is a deviation in perpendicularity as shown in FIG. 5B is relative to the flatness Y1 calculated when there is no deviation in perpendicularity as shown in FIG. 5A. The offset error increases in proportion to the amount of deviation of the perpendicularity of the detector movement axis M with respect to the workpiece rotation axis L.

  Therefore, the flatness measurement method using the roundness measuring machine in the present embodiment is a problem in the conventional flatness measurement method, and the deviation amount of the perpendicularity between the workpiece rotation axis L and the detector movement axis M. It is an object of the present invention to eliminate the influence of an offset error according to the above and to enable highly accurate flatness measurement with good reproducibility. This will be described in detail below.

(First embodiment)
First, the flatness measuring method according to the first embodiment will be described.

  FIG. 6 is a flowchart illustrating an example of the flatness measurement method according to the first embodiment. 7A to 7D are diagrams for explaining a measurement procedure in the flatness measurement method according to the first embodiment. FIG. 8 is a diagram for explaining the measurement principle in the roundness measurement method according to the first embodiment. 9A to 9C are diagrams illustrating examples of measurement results obtained by the roundness measurement method according to the first embodiment. At the start of the flowchart shown in FIG. 6, as shown in FIG. 2, the workpiece 10 is placed so that the central axis of the cylindrical surface of the workpiece 10 substantially coincides with the rotation axis of the turntable 2, and the L-shaped The mounting direction of the detector holder 7 with respect to the tip of the arm 6 (holder fixing portion) is rotated by 90 degrees, and the carriage 5 and the arm 6 are moved, so that the relative alignment between the detector 8 and the workpiece 10 is performed. It is assumed that

(Step S10)
First, as shown in FIG. 7A, the detector 8 is moved to a first radial position r1 (for example, a position of +30 mm) separated from the workpiece rotation axis L by one first radial direction distance R1 on one side (positive polarity side). Then, the probe 9 is brought into contact, the workpiece 10 is rotated by the rotary table 2, and the displacement of the probe 9 is detected by the detector 8. The detection signal output from the detector 8 is processed by the arithmetic processing unit 12, and first measurement data (measurement result A) indicating the displacement of the surface to be measured of the workpiece 10 at the first radial position r1 is acquired (FIG. 5). 9A). Step S10 is an example of a first measurement process.

(Step S12)
Next, as shown in FIG. 7B, a second radial position r2 (for example, a second radial distance R2 different from the first radial distance R1 on one side (positive polarity side) from the workpiece rotation axis L (for example, The detector 8 is moved to a position of +10 mm to bring the probe 9 into contact with it, the work 10 is rotated by the rotary table 2, and the detector 8 detects the displacement of the probe 9. The detection signal output from the detector 8 is processed by the arithmetic processing unit 12, and second measurement data (measurement result B) indicating the displacement of the surface to be measured of the workpiece 10 at the second radial position r2 is acquired (FIG. 5). 9A). Step S12 is an example of a second measurement process.

(Step S14)
Next, the arithmetic processing unit 12 calculates the flatness Y of the measured surface of the workpiece 10 from the measurement result A obtained in step S10 and the measurement result B obtained in step S12. Specifically, as shown in FIG. 9A, the flatness Y is calculated as the width of the minimum value and the maximum value of all measurement data composed of the measurement result A and the measurement result B. The flatness Y calculated in step S14 corresponds to the flatness obtained by the conventional roundness measurement method. In step S30, which will be described later, when it is not necessary to output the flatness Y calculated in step S14, the processing in step S14 may be omitted.

(Step S16)
Next, as shown in FIG. 7C, the first rotational direction position R1 with respect to the work rotation axis L, that is, the position away from the work rotation axis L by the first radial distance R1 on the other side (minus polarity side). The detector 8 is moved to the third radial position r1 ′ (for example, a position of −30 mm) which is a symmetric position, the measuring element 9 is brought into contact, the work 10 is rotated by the rotary table 2, and the measurement is performed by the detector 8. The displacement of the child 9 is detected. The detection signal output from the detector 8 is processed by the arithmetic processing unit 12, and third measurement data (measurement result A ′) indicating the displacement of the surface to be measured of the workpiece 10 at the third radial position r1 ′ is acquired. (See FIG. 9B). The third measurement data (measurement result A ′) acquired at this time is measured at the third radial position r1 ′ that is symmetrical to the first radial position r1 with respect to the workpiece rotation axis L. It is assumed that the processing unit 12 performs processing with a phase shift of 180 degrees. Step S16 is an example of a third measurement process.

(Step S18)
Next, based on the first measurement data (measurement result A) obtained in step S10 and the third measurement data (measurement result A ′) obtained in step S16, the arithmetic processing unit 12 performs the first radial position. A first offset amount P1 indicating a distance in the workpiece rotation axis L direction between r1 and the third radial position r1 ′ is calculated (see FIG. 8). Specifically, the difference between the measurement values at the same angular position in the first measurement data (measurement result A) and the third measurement data (measurement result A ′) is calculated as the first offset amount P1. Step S18 is an example of a first offset amount calculation step.

(Step S20)
Next, as shown in FIG. 7D, the workpiece is separated from the workpiece rotation axis L by the second radial distance R2 on the other side (negative polarity side), that is, at the second radial position r2 with respect to the workpiece rotation axis L. The detector 8 is moved to a fourth radial position r2 ′ (for example, a position of −10 mm) which is a symmetric position, the measuring element 9 is brought into contact, the work 10 is rotated by the rotary table 2, and the measurement is performed by the detector 8. The displacement of the child 9 is detected. The detection signal output from the detector 8 is processed by the arithmetic processing unit 12, and fourth measurement data (measurement result B ′) indicating the displacement of the surface to be measured of the workpiece 10 at the fourth radial position r2 ′ is acquired. (See FIG. 9B). Since the fourth measurement data (measurement result B ′) acquired at this time is measured at the fourth radial position r2 ′ that is symmetrical to the second radial position r2 with respect to the workpiece rotation axis L, It is assumed that the processing unit 12 performs processing with a phase shift of 180 degrees. Step S20 is an example of a fourth measurement process.

(Step S22)
Next, the arithmetic processing unit 12 determines the second radial position based on the second measurement data (measurement result B) obtained in step S12 and the fourth measurement data (measurement result B ′) obtained in step S20. A second offset amount P2 indicating the distance in the workpiece rotation axis L direction between r2 and the fourth radial position r2 ′ is calculated. Specifically, the difference between the measurement values at the same angular position in the second measurement data (measurement result B) and the fourth measurement data (measurement result B ′) is calculated as the second offset amount P2. Step S22 is an example of a second offset amount calculation step.

(Step S24)
Next, the arithmetic processing unit 12 determines between the first radial position r1 and the second radial position r2 based on the first offset amount P1 calculated in step 18 and the second offset amount P2 calculated in step S22. The third offset amount P3 indicating the distance in the workpiece rotation axis L direction is calculated (see FIG. 8). Specifically, the third offset amount P3 is calculated by the following equation (1). Step S24 is an example of a correction value calculation step.
P3 = (P1-P2) / 2 (1)

(Step S26)
Next, the arithmetic processing unit 12 corrects the second measurement data (measurement result B) obtained in step S12 using the third offset amount P3 calculated in step S24 as a correction value. Specifically, the third offset amount P3 is subtracted from the measurement value at each angular position of the second measurement data (measurement result B). As a result, as shown in FIG. 9C, corrected second measurement data (measurement result B0) is obtained. That is, in this step S26, the offset error between the first measurement data (measurement result A) and the second measurement data (measurement result B) accompanying the movement of the detector 8 is corrected.

(Step S28)
Next, based on the first measurement data (measurement result A) obtained in step S10 and the corrected second measurement data (measurement result B0) obtained in step S26, the arithmetic processing unit 12 performs the correction after the correction. The flatness Y ′ is calculated. Thereby, the measurement result of the flatness similar to the case where there is no deviation in the perpendicularity between the workpiece rotation axis L and the detector movement axis M is obtained. Steps S26 and S28 are an example of a calculation process. Moreover, the process from step S18 to step S28 is an example of a flatness calculation process.

(Step S30)
Next, the arithmetic processing unit 12 performs a process of outputting the corrected flatness Y ′ calculated in step S28 to the display unit 14 as a flatness measurement result. As a result, the corrected flatness Y ′ is displayed on the display unit 14, and the flatness measurement process ends.

  In step S30, the arithmetic processing unit 12 outputs not only the corrected flatness Y ′ calculated in step S28 but also the flatness Y calculated in step S14 as the flatness measurement result. May be. Thereby, on the display unit 14, the flatness Y and the corrected flatness Y ′ can be displayed simultaneously so that they can be compared, or can be selectively displayed according to the operator's switching operation. The operator can confirm the effect of the measurement result of the flatness of the surface to be measured of the workpiece 10 and can grasp the state of the perpendicularity between the workpiece rotation axis L and the detector movement axis M.

  As described above, according to the flatness measuring method according to the first embodiment, after measurement is performed by the same method as the conventional flatness measuring method, a position symmetrical to the workpiece rotation axis L (diameter to the opposite) is further obtained. Position) is also measured in the same manner, and the measurement results at the same angular position are compared from these measurement results, so that an offset error corresponding to the amount of perpendicularity between the workpiece rotation axis L and the detector movement axis M is obtained. Can be corrected. Therefore, the flatness of the surface to be measured of the workpiece 10 can be measured with high reproducibility and high accuracy without being affected by the deviation of the perpendicularity between the workpiece rotation axis L and the detector movement axis M.

(Second Embodiment)
Next, a flatness measurement method according to the second embodiment will be described. Hereinafter, description of parts common to the above-described embodiment will be omitted, and description will be made focusing on characteristic parts of the present embodiment.

  FIG. 10 is a flowchart showing a flatness measurement method according to the second embodiment. In FIG. 10, steps S32, S34, and S36 are added instead of steps S20, S22, and S24 shown in FIG. 6, and descriptions of common processes are simplified or omitted.

(Step S10 to Step S18)
Each process in step S10 to step S18 is performed in the same manner as the flatness measurement method according to the first embodiment.

  That is, the arithmetic processing unit 12 moves the detector 8 to the first radial position r1 and the second radial position r2, respectively, and performs first measurement data (measurement result A) and second measurement when measurement is performed. Data (measurement result B) is sequentially acquired (step S10, step S12), and flatness Y is calculated from these measurement results A and B (step S14).

  The arithmetic processing unit 12 further moves the detector 8 to the third radial position r1 ′ that is symmetrical to the first radial position r1 with respect to the workpiece rotation axis L, and performs the third measurement. Measurement data (measurement result A ′) is acquired (step S16). Then, based on the first measurement data (measurement result A) and the third measurement data (measurement result A ′), the workpiece rotation axis L direction between the first radial position r1 and the third radial position r1 ′. A first offset amount P1 (see FIG. 8) indicating the distance is calculated (step S18).

(Step S32)
Next, the arithmetic processing unit 12 has a radial distance perpendicular to the workpiece rotation axis L between the first offset amount P1 calculated in step S18, the first radial position r1 and the third radial position r1 ′ ( From the first radial distance 2 × R1), the inclination angle θ of the detector movement axis M with respect to the rotation axis L of the turntable 2 is calculated (see FIG. 8). Specifically, the tilt angle θ is calculated by the following equation (2). Step S32 is an example of the tilt angle calculation step.
θ = tan ⁻¹ (P1 / (2 × R1)) (2)

(Step S34)
Next, the arithmetic processing unit 12 is perpendicular to the workpiece rotation axis L between the first radial position r1 and the second radial position r2 from the difference between the first radial distance R1 and the second radial distance R2. A third radial distance R3, which is a radial distance, is calculated (see FIG. 8). Specifically, the third radial distance R3 is calculated by the following equation (3).
R3 = R1-R2 (3)

(Step S36)
Next, the arithmetic processing unit 12 calculates the workpiece between the first radial position r1 and the second radial position r2 from the inclination angle θ calculated in step S32 and the third radial distance R3 calculated in step S34. A third offset amount P3 indicating the distance in the rotation axis L direction is calculated. Specifically, the third offset amount P3 is calculated by the following equation (4). Step S36 is an example of a correction value calculation step.
P3 = R3 × tanθ (4)

(Step S26 to Step S30)
Each process in step S26 to step S30 is performed in the same manner as the flatness measurement method according to the first embodiment.

  That is, the arithmetic processing unit 12 corrects the second measurement data (measurement result B) obtained in step S12 using the third offset amount P3 calculated in step S36 as a correction value (step S26). Thereby, the corrected second measurement data (measurement result B0) is obtained.

  The arithmetic processing unit 12 further corrects the flatness Y ′ after correction from the first measurement data (measurement result A) obtained in step S10 and the corrected second measurement data (measurement result B0) obtained in step S26. Is calculated (step S28), and the measurement result of flatness is output to the display unit 14 (step S30). As a result, the flatness measurement process ends.

  As described above, according to the flatness measurement method according to the second embodiment, the same effects as those of the first embodiment can be obtained, and the number of movements of the detector 8 can be reduced as compared with the first embodiment. Since the number of times of measurement can be reduced, the measurement efficiency of flatness can be improved.

(Third embodiment)
Next, a flatness measurement method according to the third embodiment will be described. Hereinafter, description of parts common to the above-described embodiment will be omitted, and description will be made focusing on characteristic parts of the present embodiment.

  FIG. 11 is a flowchart showing a flatness measurement method according to the third embodiment. Note that FIG. 11 is obtained by adding step S38 to the processing content shown in FIG. 6, and description of common processing will be simplified or omitted.

  In the third embodiment, as shown in FIG. 11, after each processing of step 10 to step S <b> 24 is performed as in the first embodiment, the arithmetic processing unit 12 has a third offset amount P <b> 3. It is determined whether it is larger than a preset threshold value (step S38). Step S38 is an example of a determination process.

  In step S38, when it is determined that the third offset amount P3 is larger than the threshold value (in the case of Yes), the arithmetic processing unit 12 calculates the third offset amount P3 as a correction value, as in the first embodiment. As described above, the second measurement data (measurement result B) obtained in step S12 is corrected (step S26), and the arithmetic processor 12 obtains the first measurement data (measurement result A) obtained in step S10 and step S26. Based on the corrected second measurement data (measurement result B0) obtained, the corrected flatness Y ′ is calculated (step S28), and the corrected flatness Y ′ is displayed as the measurement result of flatness. Processing to output to the unit 14 is performed (step S30). Note that, as in the first embodiment, the flatness Y calculated in step S14 may be output to the display unit 14 together with the corrected flatness Y ′.

  On the other hand, when it is determined that the third offset amount P3 is smaller than the threshold value (in the case of No), the arithmetic processing unit 12 does not perform each process in step S26 and step S28, proceeds to step S30, As a measurement result, the flatness Y calculated in step S14 is output to the display unit 14 (step S30).

  As described above, according to the third embodiment, when the offset error (third offset amount P3) due to the perpendicularity deviation between the workpiece rotation axis L and the detector movement axis M is larger than a preset threshold value. In the same manner as in the first embodiment, the second measurement data (measurement result B) is corrected, while the offset error (third offset amount P3) is smaller than the threshold value, that is, the workpiece rotation axis L and When the offset error (third offset amount P3) is small enough to ignore the influence of the perpendicularity with respect to the detector moving axis M, the second measurement data (measurement result B) is not corrected. Therefore, when the accuracy of perpendicularity between the workpiece rotation axis L and the detector movement axis M is high, the flatness measurement process can be simplified.

  In the third embodiment, the case where the process of step S38 is added to the first embodiment has been described. However, the present invention is not limited to this, and the process of step S38 is added to the second embodiment. The same effect can be obtained.

(Other)
In each of the above embodiments, the case where the present invention is applied to a table rotation type roundness measuring device has been described. The present invention can also be applied to a measuring machine, and similar effects can be obtained.

  As mentioned above, although embodiment of this invention was described in detail, this invention is not limited to the above example, Of course, in the range which does not deviate from the summary of this invention, various improvement and deformation | transformation may be performed. It is.

  DESCRIPTION OF SYMBOLS 1 ... Base, 2 ... Rotary table, 3 ... Rotation drive part, 4 ... Column, 5 ... Carriage, 6 ... Arm, 7 ... Detector holder, 8 ... Detector, 9 ... Measuring element, 10 ... Workpiece, 12 ... Calculation Processing unit, 14 ... display unit

Claims (4)

By contacting the measuring element of the detector with the surface to be measured of the workpiece, and detecting the displacement of the measuring element with the detector while relatively rotating the workpiece and the detector around the rotation axis, A flatness measurement method for measuring flatness of a measurement surface,
The detector is moved to a first radial position separated from the rotary shaft by a first radial distance in a radial direction perpendicular to the rotary shaft, and the probe of the detector is brought into contact with the surface to be measured of the workpiece. A first measurement step of acquiring first measurement data indicating a displacement of a surface to be measured of the workpiece at the first radial position by detecting a displacement of the probe with the relative rotation by the detector; ,
The detector is moved to a surface to be measured of the workpiece by moving the detector to a second radial position that is separated from the rotation axis in the radial direction by a second radial distance different from the first radial distance. The second measurement data indicating the displacement of the surface to be measured of the workpiece at the second radial position is acquired by contacting the probe and detecting the displacement of the probe with the relative rotation by the detector. Two measurement steps;
Moving the detector to a third radial position that is symmetrical to the first radial position with respect to the rotation axis to bring the measuring element of the detector into contact with the surface to be measured of the workpiece; A third measurement step of acquiring third measurement data indicating the displacement of the surface to be measured of the workpiece at the third radial position by detecting the displacement of the probe with relative rotation by the detector;
A flatness calculation step of calculating flatness of the surface to be measured of the workpiece based on the first measurement data, the second measurement data, and the third measurement data;
A flatness measuring method comprising: Moving the detector to a fourth radial position that is symmetrical to the second radial position with respect to the rotation axis to bring the probe of the detector into contact with the surface to be measured of the workpiece; A fourth measurement step of acquiring fourth measurement data indicating the displacement of the surface to be measured of the workpiece at the fourth radial position by detecting the displacement of the probe with relative rotation by the detector. ,
The flatness calculation step includes
Based on the first measurement data and the third measurement data, a first offset amount for calculating a first offset amount indicating a distance in the rotation axis direction between the first radial position and the second radial position. A calculation process;
Based on the second measurement data and the fourth measurement data, a second offset amount for calculating a second offset amount indicating a distance in the rotation axis direction between the second radial position and the fourth radial position. A calculation process;
A correction value calculating step of calculating a correction value indicating an offset error between the first measurement data and the second measurement data associated with movement of the detector based on the first offset amount and the second offset amount;
A calculation step of calculating a flatness of a surface to be measured of the workpiece by correcting an offset error between the first measurement data and the second measurement data by the correction value;
The flatness measuring method according to claim 1, comprising: The flatness calculation step includes
A first offset for calculating a first offset amount indicating a distance in the rotational axis direction between the first radial position and the second radial position based on the first measurement data and the third measurement data. A quantity calculation step;
An inclination angle calculation step of detecting an inclination angle of the moving direction of the detector with respect to the rotation axis based on the first offset amount;
A correction value calculation step of calculating a correction value indicating an offset error between the first measurement data and the second measurement data according to the movement of the detector based on the tilt angle;
A calculation step of calculating a flatness of a surface to be measured of the workpiece by correcting an offset error between the first measurement data and the second measurement data by the correction value;
The flatness measuring method according to claim 1, comprising: The flatness calculation step includes
A determination step of determining whether or not the correction value is greater than a preset threshold;
The calculation step corrects an offset error between the first measurement data and the second measurement data when the correction value is determined to be larger than the threshold value by the determination step, and the surface to be measured of the workpiece The flatness of the workpiece is calculated, and when the determination step determines that the correction value is smaller than the threshold value, the offset error between the first measurement data and the second measurement data is not corrected. Calculate the flatness of the measured surface,
The flatness measuring method according to claim 2 or 3.

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