TWI777205B - Calibration method of shape measuring device, reference device and detector - Google Patents

Abstract

[Problem] The present invention provides a shape measuring device that is less likely to cause a deviation in the zero point position during zero point calibration of a detector. [Solution] The detector includes at least three displacement gauges arranged in a row, and is arranged to face the measurement object to detect the displacement of the distance from the at least three displacement gauges to the measurement object. A reference plane for calibration of the detector is provided by the reference device being supported on the support member. The control unit calibrates the reference. The reference device has a support structure supported on the support member at two locations in the direction in which the at least three displacement gauges are arranged. The control device calibrates the detectors in a state in which at least three displacement gauges face the reference plane.

Description

Calibration method of shape measuring device, reference device and detector

The present invention relates to a shape measuring device, a method for calibrating a detector mounted on the shape measuring device, and a reference device for calibrating the detector.

As a method of measuring the straightness of the upper surface of a workpiece, which is an object to be polished, there is known an on-machine measurement method in which a displacement gauge is attached to a grinding wheel head to scan the machined surface by utilizing the workpiece feeding function of a polishing apparatus. In the machine measurement method, the successive three-point method using a detector including three displacement gauges is generally used (for example, Patent Document 1). In the successive three-point method, the positions in the height direction of three points on a straight line on the upper surface of the workpiece are simultaneously measured, and the local curvature (curvature) of the plane is obtained from the measurement results. The straightness of the upper surface of the workpiece is obtained by calculating the second-order integral of the curvature. Straightness is the degree to which a target shape deviates from a geometrically correct straight line. Measuring the straightness of the upper surface of the workpiece is equivalent to measuring the concavo-convex shape related to the height direction of the upper surface of the workpiece.

In order to measure the straightness of the surface of the object to be measured with high accuracy, it is necessary to calibrate the zero point of the detector so that the zero points of the three displacement meters are located on a geometrically correct plane. A datum with a highly straight datum surface is used for zero calibration of the detector. When measuring the straightness of the upper surface of the workpiece ground by the grinding device, for example, a reference device is placed on the upper surface of the ground workpiece to perform zero point correction of the detector so that the zero points of the three displacement gauges are located on the reference plane superior. [Prior Art Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2016-166873

[Problems to be Solved by Invention]

After the zero point calibration of the detector is performed, if a reference is installed at another position on the workpiece and the straightness of the reference surface is measured, the geometrical tolerance of the ideal straightness becomes zero. However, it is clearly known that when the straightness of the reference plane is measured by changing the position where the reference device is installed, the geometrical tolerance of the straightness of the reference plane may not be zero. This means that there is a deviation in the position of the zero point after zero point correction depending on the position where the datum is placed. If high-precision zero point calibration is not performed, the measurement accuracy of the straightness of the upper surface of the workpiece will decrease.

The object of the present invention is to provide a shape measuring device and a calibration method of the detector which are less likely to produce a deviation of the zero point position in the zero point calibration of the detector. Another object of the present invention is to provide a reference device applicable to the calibration method. [Technical means to solve problems]

According to an aspect of the present invention, there is provided a shape measuring device, which has: a detector comprising at least three displacement gauges arranged in a row, and by being arranged opposite to the measurement object, to detect the displacement of the distance from the at least three displacement gauges to the measurement object; a datum, which is supported on a support member to provide a reference plane for calibration of the aforementioned detector; and control means for calibrating the aforesaid reference device, The reference device has a support structure supported on the support member at two locations in the direction in which the at least three displacement gauges are arranged, The control device calibrates the detector in a state in which the at least three displacement gauges face the reference plane.

According to another aspect of the present invention, there is provided a shape measuring device having: a detector comprising at least three displacement gauges arranged in a row, and by being disposed opposite to the measurement object, to detect the displacement of the distance from each of the at least three displacement gauges to the measurement object; a datum that provides a datum for calibrating the detector by being supported on a support member; and control means for calibrating the aforesaid reference device, In a state where the reference tool is supported on the support member, deflection occurs due to its own weight, and the shape of the reference surface in the state of deflection has a structure that is not affected by the unevenness of the upper surface of the support member. The control device calibrates the detector in a state in which the at least three displacement gauges face the reference plane.

According to another aspect of the present invention, a reference device is provided, which has: the reference plane, which is opposite to the three displacement gauges arranged in a row; and three leg portions protruding from the bottom surface on the side opposite to the aforementioned reference surface, Two of the said three leg parts are arrange|positioned at the same position in the longitudinal direction of the said reference plane.

According to yet another aspect of the present invention, there is provided a calibration method for a tester that detects at least three displacement gauges by arranging at least three displacement gauges in a line to face an object to be measured. The displacement of the displacement meter for each distance to the aforementioned measurement object, With the at least three displacement gauges facing the reference plane of the reference device, the reference device is supported on the support member at two positions in the direction in which the at least three displacement gauges are arranged, The detector is calibrated in a state in which the at least three displacement gauges face the reference plane. [Effect of invention]

The deflection shape of the datum is not affected by the unevenness of the upper surface of the support member. Therefore, a reference surface with little shape deviation is provided when the detector is calibrated, and as a result, the deviation of the zero point positions of the at least three displacement gauges of the detector due to the installation position can be suppressed.

Referring to FIGS. 1A to 11B , the shape measuring apparatus of the embodiment will be described. FIG. 1A is a perspective view of a polishing apparatus in which the shape measuring apparatus of the present embodiment is assembled. The grinding device includes a movable table 10 , a table guide mechanism 11 , a grinding wheel head 15 , a grinding wheel 16 , a guide rail 18 , a control device 20 , an input and output device 21 , a reference device 30 and a detector 40 . The movable table 10 is reciprocated in one direction in the horizontal plane by the table guide mechanism 11 . The object to be ground, that is, the workpiece 12 is supported on the movable table 10 . The workpiece 12 corresponds to a measurement object whose straightness is measured by a shape measuring device.

The grinding wheel head 15 is supported above the workpiece 12 on the movable table 10 by means of the guide rail 18 so as to be ascendable and descendable. The grinding wheel head 15 is movable in a direction orthogonal to the moving direction of the movable table 10 in a horizontal plane. The xyz orthogonal coordinate system is defined as follows: the moving direction of the movable table 10 is the x-axis direction, the moving direction of the grinding wheel head 15 is the y-axis direction, and the vertical downward direction is the positive z-axis direction.

A grindstone 16 is attached to the lower end of the grindstone head 15 . The grinding wheel 16 has a cylindrical shape whose central axis is parallel to the y-axis direction. The grinding wheel head 15 is lowered to such an extent that the grinding wheel 16 contacts the workpiece 12 , and the workpiece 12 is ground by moving the workpiece 12 in the x-axis direction while the grinding wheel 16 is rotated. The entire area of the upper surface of the workpiece 12 can be ground by moving the grinding wheel head 15 in the y-axis direction and repeating the same process.

The control device 20 controls the movement of the movable table 10 in the x-axis direction, the movement and elevation of the grindstone head 15 in the y-axis direction, and the rotation of the grindstone 16 . Various commands are input from the input/output device 21 to the control device 20 , and processing results and the like are output to the input/output device 21 via the control device 20 . The input/output device 21 includes, for example, a display, a pointing device, a keyboard, and the like.

The detector 40 is detachably attached to the side surface of the grinding wheel head 15 . When grinding, the detector 40 is removed from the grinding wheel head 15 . When measuring the straightness of the upper surface of the workpiece 12 , the tester 40 is attached to the grinding wheel head 15 . The detector 40 is attached to the grinding wheel head 15 by, for example, attractive force of a magnet, screwing, or the like. Hereinafter, the structure of the detector 40 will be described in detail with reference to FIG. 1B . When calibrating the detector 40 , the datum 30 is arranged on the upper surface of the workpiece 12 . The datum 30 is supported on the upper surface of the workpiece 12 to provide a reference surface for calibration of the detector 40 . The workpiece 12 functions as a support member for supporting the reference 30 during zero point calibration.

FIG. 1B is a side view of the tester 40 in a state where the tester 40 is mounted on the grinding wheel head 15 .

The detector 40 includes a first displacement gauge 42a, a second displacement gauge 42b, and a third displacement gauge 42c that are mounted on the support base 41 and are aligned in the x-axis direction. As these displacement meters, for example, a non-contact laser displacement meter can be used. Since each of the 1st displacement gauge 42a, the 2nd displacement gauge 42b, and the 3rd displacement gauge 42c is arrange|positioned to oppose the workpiece|work 12, the displacement of the distance from each displacement gauge to the workpiece|work 12 is detected. More specifically, the distance in the z-axis direction from the zero point of each displacement gauge to the point to be measured on the upper surface of the workpiece 12 is measured. In a state where the reference device 30 ( FIG. 1A ) is disposed at the position facing the detector 40 , each displacement meter detects the displacement of the reference surface of the reference device 30 in the z-axis direction.

A temperature sensor 45 is also mounted on the support base 41 . The temperature sensor 45 measures the temperature of the detector 40 . The measurement values of the first displacement gauge 42a, the second displacement gauge 42b, and the third displacement gauge 42c and the measurement value of the temperature sensor 45 are input to the control device 20 (FIG. 1A).

Next, referring to FIG. 2 , a method of measuring the straightness of the upper surface of the workpiece 12 will be described. FIG. 2 is a schematic diagram showing the upper surface of the workpiece 12 , which is a measurement object, and the detector 40 . The upper surface of the workpiece 12 is arranged substantially parallel to the xy plane. In addition, in FIG. 2, the micro unevenness|corrugation of the upper surface of the workpiece|work 12 is enlarged and shown. The first displacement gauge 42a, the second displacement gauge 42b, and the third displacement gauge 42c of the detector 40 are arranged in a row with a pitch P in the x-axis direction.

If the zero point calibration of the three displacement meters is performed, ideally, the zero points A ₀ , B ₀ , and C ₀ of the first displacement meter 42 a , the second displacement meter 42 b , and the third displacement meter 42 c are on a line substantially parallel to the x-axis. They are arranged with a pitch P on a straight line. In addition, in this embodiment, as described below with reference to FIGS. 7A and 7B , the three zero points A ₀ , B ₀ , and C ₀ are not strictly arranged on a straight line, but here it is assumed that the three zero points A ₀ , B . ₀ and C ₀ are arranged on a straight line.

The first displacement gauge 42a measures the distance D _a from the zero point A ₀ to the point A to be measured on the upper surface of the workpiece 12 . Similarly, the second displacement meter 42b and the third displacement meter 42c measure the distance Db from the zero point B ₀ to the point B to be measured, and the distance D _c from the zero point C ₀ to the point _C to be measured, respectively.

The distance between the line segment connecting the points A and C to be measured and the point B to be measured in the z-axis direction is referred to as the offset amount g. The offset amount g is represented by the following equation.

The curvature d ² z/dx ² (x=B) of the upper surface of the workpiece 12 at the point B to be measured of the second displacement gauge 42b can be represented by the following equation.

While moving one of the detector 40 and the workpiece 12 relative to the other in the x-axis direction, the offset amount g is measured by the formula (1). The straightness of the upper surface (that is, the surface shape in the xz cross-section) can be obtained by second-order integration of the curvature distribution of the upper surface of the workpiece 12 obtained using equations (1) and (2).

Next, referring to FIG. 3 , the principle of zero point calibration of the detector 40 will be described. FIG. 3 is a schematic diagram showing the positional relationship between the first displacement gauge 42 a , the second displacement gauge 42 b , and the third displacement gauge 42 c of the detector 40 and the reference tool 30 .

The datum 30 is placed on the upper surface of the workpiece 12 with the datum surface 31 facing the detector 40 . In this state, the measured points on the reference plane 31 of the first displacement meter 42a, the second displacement meter 42b, and the third displacement meter 42c are set as the first displacement meter 42a, the second displacement meter 42b, and the third displacement meter, respectively. Zero points A ₀ , B ₀ , and C ₀ of the displacement meter 42c.

In addition, while moving the reference device 30 relative to the detector 40 in the x-axis direction, a plurality of measurements may be performed, and the zero points A ₀ , B ₀ , and C ₀ may be set based on the average value of the measured values. The process of performing a plurality of measurements while moving the reference device 30 in the x-axis direction is called scanning. The movement of the reference tool 30 is realized by moving the workpiece 12 in the x-axis direction by the table guide mechanism 11 . By adopting this method, the deviation of the zero point caused by the surface roughness of the reference surface 31 can be reduced. In addition, a plurality of scans may be performed while changing the position of the point to be measured on the reference plane 31 in the y-axis direction, and the zero points A ₀ , B ₀ , and C ₀ may be set based on the average value of the measured values obtained by the plurality of scans. . In addition, even if the mounting positions of the first displacement gauge 42a, the second displacement gauge 42b, and the third displacement gauge 42c on the support base 41 deviate in the z-axis direction, if the reference plane 31 is a geometrically correct plane, the zero point A ₀ , B ₀ , C ₀ are located on a straight line by zero point correction.

Next, referring to FIGS. 4A and 4B , a method for calibrating the detector 40 using the reference device 30 of the comparative example will be described.

4A and 4B are cross-sectional views of a state in which the reference tool 30 of the comparative example is placed on the upper surface of the workpiece 12 . When calibrating the detector 40, on the upper surface of the workpiece 12, the reference 30 in the shape of a rectangular parallelepiped is provided so that its longitudinal direction is parallel to the x-axis. The upper surface of the polished workpiece 12 is substantially flat, but actually has minute irregularities remaining. The datum 30 is thus supported on the workpiece 12 at approximately two points along its length. The reference tool 30 is formed of, for example, a ceramic material that is not easily deformed with a Young's modulus of about 130 GPa, but slightly deflects due to its own weight at a point where it contacts the workpiece 12 as a fulcrum.

In the example shown in FIG. 4A , the reference tool 30 is supported in contact with the workpiece 12 in the vicinity of both ends in the longitudinal direction. At this time, deflection in a downwardly convex shape is generated in the reference tool 30 . In the example shown in FIG. 4B , the reference tool 30 is supported in contact with the workpiece 12 in the vicinity of the center in the longitudinal direction. At this time, deflection in the shape of an upward convex is generated in the reference tool 30 . If the zero point calibration of the detector 40 is performed in a state where deflection occurs on the reference plane 31, the three zero points A ₀ , B ₀ , and C ₀ are not located on a straight line. Further, depending on the position where the reference device 30 is installed, a deviation occurs in the relative positional relationship of the three zero points A ₀ , B ₀ , and C ₀ .

The deflection produced on the datum 30 is influenced by the concavo-convex shape of its support surface (ie, the upper surface of the workpiece 12). Therefore, the shape of the reference surface 31 in the state where the deflection occurs cannot be accurately estimated. Therefore, it is difficult to correct and arrange the three zero points A ₀ , B ₀ , and C ₀ on a straight line.

Next, referring to FIGS. 5 to 7B , a method for performing zero point calibration of the detector 40 using the reference device 30 used in the shape measuring apparatus of the present embodiment will be described.

FIG. 5 is a perspective view of the reference tool 30 used in the shape measuring apparatus of the embodiment as viewed obliquely from below. The datum 30 includes a main body member 32 having a rectangular parallelepiped shape long in one direction. The upper surface of the main body member 32 is set as the reference surface 31 . Three leg portions 33 are attached to the bottom surface of the main body member 32 on the side opposite to the reference surface 31 . One leg portion 33 is attached to one end portion in the longitudinal direction of the bottom surface of the reference tool 30 , and the other two leg portions 33 are attached to the other end portion. Moreover, these two leg parts 33 are attached at intervals in the width direction orthogonal to the longitudinal direction. That is, the two leg portions 33 are installed at the same position in the longitudinal direction, and are installed at different positions in the width direction.

Each leg portion 33 has a hemispherical shape and is bonded to the bottom surface of the main body member 32 on a flat surface. An adhesive, a double-sided tape, or the like can be used for the adhesion of the leg portion 33 . For the leg portion 33, a hard material such as zirconia is used, for example. The height of the leg part 33 is 2 mm or more and 15 mm or less, for example, and is typically 7 mm. However, the height of the leg portion 33 is not limited to this range. When the reference tool 30 is placed on the upper surface of the workpiece 12 , the height of the leg portion 33 may be such that the bottom surface of the main body member 32 of the reference tool 30 does not touch the upper surface of the workpiece 12 .

6A and 6B are cross-sectional views showing a state in which the reference tool 30 used in the shape measuring apparatus of the embodiment is placed on the upper surface of the workpiece 12 . The concavo-convex shape of the upper surface of the workpiece 12 shown in FIGS. 6A and 6B is the same as the concavo-convex shape of the upper surface of the workpiece 12 shown in FIGS. 4A and 4B , respectively. In either case of FIGS. 6A and 6B , the reference tool 30 is supported on the upper surface of the workpiece 12 by the three legs 33 contacting the upper surface of the workpiece 12 . The reference tool 30 does not come into contact with the workpiece 12 except for the three leg portions 33 .

Since two of the three leg portions 33 are arranged at the same position in the longitudinal direction, the reference tool 30 is supported on the upper surface of the workpiece 12 at two locations in the longitudinal direction. Therefore, the reference device 30 has a beam structure that supports evenly distributed loads at both ends. The reference tool 30 is always supported on the support surface at two locations in the longitudinal direction regardless of the uneven shape of the support surface, so the shape and size of the deflection of the reference tool 30 are not affected by the uneven shape of the support surface.

FIG. 7A is a schematic diagram of a datum 30 having a beam structure with uniformly distributed loads supported at both ends. If the length of the reference device 30 is denoted by L, the load per unit length is denoted by w, the Young's modulus is denoted by E, and the two-dimensional moment of elasticity is denoted by I, the deflection amount at a point at a distance x from one end δ(x) is represented by the following formula.

When the reference tool 30 is placed on the upper surface of the workpiece 12 , the shape and size of the deflection generated on the reference surface 31 can be obtained in advance using the equation (3). Information defining the shape of the deflection is stored in the control device 20 (FIG. 1A).

FIG. 7B is a schematic diagram showing the positional relationship between the reference device 30 and the detector 40 used in the shape measuring apparatus of the embodiment. The reference surface 31 is deflected as shown in FIG. 7A . In FIG. 7B, the amount of deflection is shown enlarged from the actual amount of deflection. The height of the reference plane 31 is detected by the first displacement gauge 42a, the second displacement gauge 42b, and the third displacement gauge 42c of the detector 40, and zero point correction is performed. Thereby, the zero point A ₀ , the zero point B ₀ , and the zero point C ₀ are set on the reference plane 31 .

The intersection of the straight line passing through the zero point B ₀ and parallel to the z-axis and the line segment connecting the zero point A ₀ and the zero point C ₀ is defined as the true zero point B ₀₁ of the second displacement meter 42b. Let the distance between the zero point B ₀ and the true zero point B ₀₁ be the zero point offset g ₀ . The deflection shape of the reference plane 31 can be obtained by calculation from the formula (3). Since the information defining the shape is stored in the control device 20 ( FIG. 1A ) in advance, the zero point offset amount can be obtained by calculation g ₀ . The control device 20 stores the zero offset amount g ₀ obtained by the calculation. In order to strictly calculate the straightness of the upper surface of the workpiece 12 at the true zero point _B01 , it is preferable to use the true zero point _B01 as the zero point of the second displacement gauge 42b. That is, it is preferable to correct the offset amount g ( FIG. 2 ) corresponding to the zero point offset amount g ₀ . Specifically, it is preferable to calculate the offset amount g by the following formula instead of formula (1).

Next, with reference to FIGS. 8A to 9B , an evaluation experiment and results of an evaluation experiment performed to confirm that the deflection shape of the reference tool 30 is not affected by the unevenness of the upper surface of the workpiece 12 will be described.

8A to 8C are diagrams showing the positional relationship of the workpiece 12 , the reference device 30 , and the detector 40 when the evaluation experiment is performed. First, as shown in FIG. 8A , the datum 30 is placed on the region R1 of the workpiece 12 , and the offset g ( FIG. 2 ) is measured by the detector 40 performing zero point correction using equation (1). The reference device 30 is moved within the region R1, and the offset amount g of plural times is measured using the equation (1).

Next, as shown in FIG. 8B, the reference tool 30 is moved on the region R2 of the workpiece 12, and the offset amount g is measured a plurality of times in the same manner. Further, as shown in FIG. 8C, the reference 30 is moved on the region R3 of the workpiece 12, and the offset amount g is measured a plurality of times in the same manner.

FIG. 9A is a graph showing the distribution of the offset amount g measured using the reference device 30 having the rectangular parallelepiped shape without the leg portion 33 . 9B is a graph of the distribution of the offset amount g measured using the reference device 30 ( FIG. 5 ) used in the shape measuring apparatus of the embodiment, that is, the reference device 30 having the leg portion 33 . The horizontal axis of the graphs of FIGS. 9A and 9B corresponds to the regions R1 , R2 , and R3 , and the vertical axis represents the offset amount g. A black circle symbol in the graph represents the offset g calculated by one measurement. A plurality of black circle symbols are displayed in one area because the reference 30 is moved in each area R1, R2, R3 and a plurality of measurements are performed.

In the case of using the reference device 30 without the leg portion 33, as shown in FIG. 9A, in the case where the reference device 30 is placed on the region R1 for measurement and in the case where the reference device 30 is placed on the region R2 or R3 for measurement, the offset A large difference occurs in the shift amount g. In general, a deviation of about 0.075 μm occurs in the offset amount g. This means that the shape of the reference surface 31 after the reference tool 30 is deflected varies depending on the position where the reference tool 30 is installed.

On the other hand, when the reference device 30 having the leg portion 33 is used, as shown in FIG. 9B , even if the reference device 30 is placed on any one of the regions R1 , R2 , and R3 , the offset amount g There will be no big difference. The deviation of the offset amount g is within the range of 0.02 μm or less. This means that the shape of the reference surface 31 after the reference tool 30 is deflected is substantially constant regardless of the position where the reference tool 30 is installed. In addition, the calculated value of the offset amount g is substantially equal to the zero point offset amount g ₀ ( FIG. 7B ).

It was confirmed from the evaluation experiments shown in FIGS. 8A to 9B that, by using the datum 30 having the legs 33 , the deflection shape of the datum 30 hardly depends on the concavo-convex shape of the supporting surface supporting the datum 30 .

Next, referring to FIGS. 10 to 11B , a method of measuring the straightness of the upper surface of the workpiece 12 ( FIG. 1A ) by the shape measuring apparatus of the embodiment will be described.

FIG. 10 is a flowchart of the shape measurement method of the embodiment. When the grinding of the workpiece 12 is completed, the operator attaches the detector 40 to the grinding wheel head 15 (step SA01 ), and sets the reference 30 to the upper surface of the workpiece 12 (step SA02 ). Then, the zero point calibration of the detector 40 is performed using the reference surface 31 of the reference device 30 . When the zero point calibration of the detector 40 is completed, the reference tool 30 is removed from the upper surface of the workpiece 12 .

The grinding wheel head 15 (FIG. 1A) is moved to the measurement position of the workpiece 12 in the y-axis direction (step SA05). Then, the straightness of the upper surface of the workpiece 12 along a line parallel to the x-axis direction is measured (step SA06). Specifically, the control device 20 ( FIG. 1A ) moves the workpiece 12 in the x-axis direction, while the first displacement meter 42 a , the second displacement meter 42 b , and the third displacement meter 42 c of the detector 40 are moved at constant time intervals. Obtain measured values. Based on the acquired measurement values, the shape of the upper surface of the workpiece 12 is obtained by the successive three-point method described with reference to FIG. 2 . At this time, the offset amount g is calculated using Equation (4).

After measuring the straightness along a line of the upper surface of the workpiece 12, the measurement result is output to the input/output device 21 (FIG. 1A) (step SA07). In the case of measuring the straightness along another line, the process from the process of disposing the reference 30 on the upper surface of the workpiece 12 (step SA02 ) to the process of outputting the measurement result (step SA07 ) (step SA08 ) is repeated. The measurement ends after measuring the straightness of the upper surface of the workpiece 12 along all lines to be measured.

FIG. 11A is a diagram showing an image of a control window displayed on the display of the input/output device 21 by the control device 20 . The control window includes a measurement value display window 22 , a basic setting window 23 and a calibration window 24 . In addition, a measurement start button 26 is displayed on the control window.

The measured value display window 22 includes output fields for displaying the measured values of the first displacement meter 42a, the second displacement meter 42b, and the third displacement meter 42c. The basic setting window 23 displays the length of the workpiece 12 (dimension in the x-axis direction), the moving speed of the movable table 10 during measurement, and a data input field for inputting the number of times of reciprocation. The number of times of measurement reciprocation is input, for example, in the form of a pull-down menu. In the calibration window 24, an output field displaying the zero point value and a calibration start button 25 are displayed.

When the operator selects the calibration start button 25, the control device 20 (FIG. 1A) performs zero-point calibration of the detector 40 (step SA03). The selection of the button is performed by, for example, aligning the pointer of the mouse on the button and clicking the mouse, or by touching the button. The value of the offset g calculated using the formula (1) is displayed in the output field of the zero point. When the zero point correction is performed, since the distances D _a , D _b , and D _c ( FIG. 2 ) are all reset to zero, the value displayed in the zero point output field becomes 0.

When the operator selects the measurement start button 26, the control device 20 executes the measurement of the straightness along a line of the upper surface of the workpiece 12 (step SA06).

FIG. 11B is a diagram showing an example of an image of the measurement result displayed on the display of the input/output device 21 . On the display, the position of the upper surface of the workpiece 12 in the height direction is displayed graphically. The horizontal axis represents the position of the workpiece 12 in the longitudinal direction (x-axis direction), and the vertical axis represents the surface displacement amount (position in the z-axis direction). In addition, the linear component of the height fluctuation is removed, and the surface displacement amount is corrected so that the heights of both ends of the workpiece 12 become zero. An example in which the central portion has a lower shape than both ends is shown in FIG. 11B . The absolute value of the value of the upper surface of the workpiece 12 at the position where the displacement amount from 0 is the largest (the lowest point of the curve in FIG. 11B ) corresponds to the geometric tolerance of straightness. In the example shown in FIG. 11B , the geometrical tolerance of straightness is about 22 μm.

Next, the excellent effect of the above-mentioned embodiment will be described. In the above-described embodiment, when the zero point is corrected, the deflection shape of the reference device 30 is constant regardless of the position on the workpiece 12 on which the reference device 30 is provided. Therefore, the relative positional relationship of the three zero points A ₀ , B ₀ , and C ₀ can be made constant. In addition, in the above-mentioned embodiment, the zero point A ₀ of the first displacement meter 42a, the true zero point B ₀₁ of the second displacement meter 42b, and the zero point C ₀ of the third displacement meter 42c are located on a straight line. By measuring the straightness of the upper surface of the workpiece 12 with reference to the three zero points A ₀ , B ₀₁ , and C ₀ located on a straight line, the measurement accuracy of the straightness can be improved.

Next, referring to FIGS. 12 to 14 , a shape measuring apparatus and a shape measuring method according to another embodiment will be described. Hereinafter, descriptions of the same structures as those of the embodiment shown in FIGS. 1A to 11B are omitted.

FIG. 12 is a flowchart of the shape measurement method of the present embodiment. In the embodiment shown in FIG. 10, each time the straightness of the upper surface of the workpiece 12 along a line is measured (step SA06), the zero point calibration of the detector 40 is performed before the measurement (step SA03). On the other hand, in the embodiment shown in FIG. 12 , the difference between the temperature measurement value at the current time by the temperature sensor 45 ( FIG. 1B ) and the temperature measurement value at the time of the previous zero point calibration is equal to or less than the threshold value. In this case, the zero point correction processing (steps SA02 to SA04) is omitted (step SA10). Only when the difference between the temperature measurement value at the current time based on the temperature sensor 45 ( FIG. 1B ) and the temperature measurement value at the time when the zero point correction was performed last time exceeds the threshold value, the zero point correction process is executed again (steps SA02 to SA04 ) .

FIG. 13 is a diagram showing an image of a control window displayed by the control device 20 on the display of the input/output device 21 (FIG. 1A). In the present embodiment, in the calibration window 24, in addition to the zero point output field and the calibration start button 25, output fields respectively displaying the temperature during calibration, the calibration time and the current temperature are displayed. A temperature measurement button 27 is also displayed.

In the output field of the temperature at the time of calibration, the control device 20 displays the temperature measurement value measured by the temperature sensor 45 at the time of the latest zero-point calibration. In the output field of the correction time, the control device 20 displays the time of the latest zero point correction. In the output field of the current temperature, the control device 20 displays the temperature measurement value at the current time measured by the temperature sensor 45 . If the operator selects the temperature measurement button 27, the control device 20 acquires the temperature measurement value at the current time from the temperature sensor 45, and updates the measurement value displayed in the output field of the current temperature.

When the difference between the temperature during the latest zero-point calibration and the current temperature exceeds the threshold, the control device 20 displays a message 28 in the calibration window 24 urging to perform the zero-point calibration again. In addition, other alarm information can be output instead of the message 28, such as a sound for improving the efficiency of zero point calibration, an alarm sound, and the like.

FIG. 14 is a graph showing changes over time in the measurement result of the geometrical tolerance of the straightness of the upper surface of the workpiece 12 and the measurement value of the temperature measured by the temperature sensor 45 ( FIG. 1B ). The process of measuring the straightness of the upper surface of the workpiece 12 along each of the six lines L1 to L6 parallel to the x-axis is performed 10 times, and the geometrical tolerance of the straightness is obtained for each measurement process. Each of the plurality of black circle symbols shown in FIG. 14 represents the calculation result of the geometric tolerance of the straightness obtained by one measurement process.

Before measuring the straightness along the line L1, a zero point calibration of the detector 40 is performed. Then, from the measurement of the straightness along the line L1 to the measurement of the straightness along the line L5, the zero point calibration of the detector 40 is not performed. After measuring the straightness along the line L5, a zero point calibration of the detector 40 is performed before measuring the straightness along the line L6.

During the period from when the measurement of the straightness along the line L1 is started to when the measurement of the straightness along the line L4 is completed, the temperature measurement value by the temperature sensor 45 hardly changes. From the line L1 to the line L4 measured during a period when the temperature is almost constant, the measured value of the geometrical tolerance of the straightness along each line is substantially constant.

After measuring the straightness along line L4, the temperature starts to rise due to external factors. When the straightness along the line L5 is measured in a state where the temperature rises, the measured value of the geometrical tolerance of the straightness greatly changes from the geometrical tolerance of the straightness measured before the temperature rises.

When the zero point correction is performed again to measure the geometrical tolerance of the straightness along the line L6, a measurement approximately equal to the measured value of the geometrical tolerance of the straightness along each of the lines L1 to L4 measured before the temperature rise is obtained value. In addition, after measuring the straightness along the line L5, the temperature was slightly lowered due to external factors, but remained higher than when the straightness along each of the lines L1 to L4 was measured.

From the measurement results shown in Fig. 14, the following two insights were obtained. First, if the temperature around the detector 40 does not fluctuate, the straightness can be measured with high accuracy without performing zero point calibration. Second, when the temperature around the detector 40 changes to a certain extent, the measurement accuracy of straightness decreases, but by performing the zero point calibration again, the measurement accuracy of straightness can be restored to the original high accuracy.

Next, the excellent effects of the embodiments shown in FIGS. 12 to 14 will be described. In this embodiment, as shown in FIG. 13 , the temperature at the time of the latest zero point correction and the temperature at the current time are displayed on the display of the input/output device 21 ( FIG. 1A ). The operator can easily judge whether to perform zero calibration again by viewing the temperature display. Specifically, if the temperature change exceeds the threshold, the zero point correction can be performed again. The threshold value can be predetermined according to the required accuracy in the measurement of straightness. For example, as the threshold value, it can be set to 0.5°C. In addition, by displaying the message 28 to supervise the execution of the zero point calibration, it is possible to prevent the operator from forgetting to execute the zero point calibration in advance.

In addition, in this embodiment, the time when the zero point correction was performed most recently is displayed. When the detector 40 has the characteristic that the measured value fluctuates with the passage of time due to some factor, the operator can judge whether or not to perform the zero point again based on the elapsed time from the time when the zero point calibration was most recently performed. Correction.

In addition, in this embodiment, as shown in FIG. 12 , when the temperature change is below the threshold value, the zero point correction is not performed, and the straightness of the upper surface of the workpiece 12 along the next line is measured, so that the measurement time can be shortened. The total time required for the straightness of the upper surface of a workpiece 12.

Next, referring to FIGS. 15A and 15B , a shape measuring apparatus according to another embodiment will be described. Hereinafter, descriptions of the same structures as those of the embodiment shown in FIGS. 1A to 11B are omitted.

FIG. 15A is a diagram showing an image of a control window displayed by the control device 20 on the display of the input/output device 21 (FIG. 1A). In the present embodiment, the window 29 of past measurement results is displayed within the control window. A "select past measurement result" button is displayed in the window 29 of the past measurement result.

If the operator selects the button of "select past measurement results", the control device 20 (FIG. 1A) displays a list of storage locations of the measurement data of the straightness measured in the past and stored on the display. The operator can select at least one straightness measurement from this list.

FIG. 15B is a diagram showing an example of an image displayed on the display of the input/output device 21 ( FIG. 1A ). In the embodiment shown in FIG. 11B, the surface shape corresponding to the straightness measured at the current time is displayed on the display in the form of a graph. On the other hand, in this embodiment, the straightness measured at the current time and the straightness measured in the past selected by the operator are superimposed and displayed on one graph as the distribution of the surface displacement amount. In FIG. 15B , the thick solid line and the thin solid line represent the straightness measured at the current moment and the straightness measured in the past, respectively.

Next, the excellent effects of the present embodiment will be described. In the present embodiment, the operator can easily compare the straightness of the upper surface of the workpiece 12 measured at the current moment with the straightness of the upper surface of the workpiece 12 measured in the past. For example, in the case where the cutting depth of the grinding wheel 16 is increased after the first grinding process is performed on one workpiece 12 and the second grinding process is performed, the straightness after the first grinding process and the second grinding process can be easily compared. Straightness after machining. This comparison result is advantageous as basic information for estimating the necessity of additional grinding, or processing conditions when performing additional grinding, for example, the additional depth of cut of the grinding wheel 16 .

Next, referring to FIGS. 16A to 16D , the reference device 30 according to the modification of the embodiment shown in FIG. 5 will be described.

16A to 16D are perspective views of the reference device 30 according to the modified example of the embodiment shown in FIG. 5 as viewed obliquely from below. In the embodiment shown in FIG. 5 , three hemispherical leg portions 33 are attached to both ends in the longitudinal direction of the bottom surface of the main body member 32 . On the other hand, in the modification shown in FIG. 16A , the three leg portions 33 are attached to positions slightly inward of both ends of the bottom surface of the main body member 32 in the longitudinal direction. Like the embodiment shown in FIG. 5 , two of the three leg portions 33 are installed at the same position in the longitudinal direction. Therefore, the reference tool 30 is supported on the upper surface of the workpiece 12 at two locations in the longitudinal direction.

In the modification shown in FIG. 16B , the leg portion 33 has a rectangular parallelepiped shape long in the width direction of the main body member 32 . The two leg portions 33 are respectively attached to both ends in the longitudinal direction of the bottom surface of the main body member 32 . Even in the modification shown in FIG. 16B , the reference tool 30 is supported on the upper surface of the workpiece 12 at two locations in the longitudinal direction.

In the modification shown in FIG. 16C , the leg portion 33 has a semi-cylindrical shape long in the width direction of the main body member 32 . The two leg portions 33 are respectively attached to both ends in the longitudinal direction of the bottom surface of the main body member 32 with a cylindrical surface facing downward. Even in the modification shown in FIG. 16C , the reference tool 30 is supported on the upper surface of the workpiece 12 at two locations in the longitudinal direction. In addition, in the modification shown in FIG. 16B , the leg portion 33 is in surface contact with the workpiece 12 , but in the modification shown in FIG. 16C , the leg portion 33 is in line contact with the workpiece 12 . Therefore, in the modification shown in FIG. 16C , compared with the modification shown in FIG. 16B , the reference tool 30 can be more stably supported on the upper surface of the workpiece 12 . In addition, the shape of the leg part 33 does not necessarily have to be a semi-cylindrical shape, and may be a shape that is in contact with a plane line on a straight line parallel to the width direction of the main body member 32 .

In the modification shown in FIG. 16D , four hemispherical legs 33 are attached to the four corners of the bottom surface of the main body member 32 . Even in the modification shown in FIG. 16D , the reference tool 30 is supported on the upper surface of the workpiece 12 at two locations in the longitudinal direction.

As described above, even in the modified example shown in FIGS. 16A to 16D , the reference device 30 has a support structure supported by two parts in the longitudinal direction. Therefore, as in the case of the embodiment shown in FIG. 5 , the deflection shape of the reference surface 31 does not depend on the concavo-convex shape of the upper surface of the workpiece 12 when it is provided on the upper surface of the workpiece 12 . Therefore, by using the reference device 30 to perform the zero point calibration of the detector 40 by the method described with reference to FIG. 7B , the zero point offset amount g ₀ can be determined as the zero point A ₀ and the second displacement of the three first displacement meters 42 a . The true zero point B ₀₁ of the gauge 42b and the zero point C ₀ of the third displacement gauge 42c are located on a straight line.

Next, referring to FIGS. 17A and 17B , a reference device 30 according to another modification of the embodiment shown in FIG. 5 will be described.

FIG. 17A is a side view of the reference tool 30 in a weightless state, and FIG. 17B is a side view of the reference tool 30 in a state where it is installed on the upper surface of the workpiece 12 . In the embodiment shown in FIG. 5 , in a state in which the reference tool 30 is set on the upper surface of the workpiece 12 , the reference surface 31 has a deflection that protrudes downward. On the other hand, in this modification, in the weightless state, the reference surface 31 ( FIG. 17A ) is curved so as to protrude upward. When the reference tool 30 is installed on the upper surface of the workpiece 12, the reference tool 30 is deflected due to its own weight. The shape of the deflected reference plane 31 (FIG. 17B) becomes a geometrically correct plane.

In the modification shown in FIGS. 17A and 17B , the reference plane 31 becomes a flat surface in a state where the reference device 30 is set on the upper surface of the workpiece 12 , so the zero offset g ₀ of the detector 40 becomes zero. Therefore, the offset amount g can be calculated using Equation (1) instead of Equation (4).

In the above-described embodiment, the detector 40 has three displacement meters in total, the first displacement meter 42a, the second displacement meter 42b, and the third displacement meter 42c, but may be configured to include four or more displacement meters.

The above embodiments and modifications are examples. Of course, the structures shown in different embodiments can be partially replaced or combined. The same functions and effects based on the same structure of the plurality of embodiments will not be described one by one for each embodiment. In addition, the present invention is not limited by the above-mentioned embodiments. It will be apparent to those skilled in the art that various alterations, improvements, combinations and the like can be made.

10: Movable workbench 11: Workbench guide mechanism 12: Workpiece 15: Wheel head 16: Grinding wheel 18: Rails 20: Control device 21: Input and output device 22: Measurement display window 23: Basic Settings Window 24: Correction window 25: Calibration start button 26: Measurement start button 27: Temperature measurement button 28: Message to urge zero point calibration 29: Past measurement results window 30: Benchmark 31: Datum plane 32: Main components 33: Legs 40: Detector 41: Support base 42a: 1st Displacement Gauge 42b: 2nd displacement gauge 42c: 3rd displacement gauge 45: Temperature sensor

FIG. 1A is a perspective view of a grinding device incorporating the shape measuring device of the embodiment, and FIG. 1B is a side view of the tester in a state where the tester is attached to the grinding wheel head. Fig. 2 is a schematic diagram showing the upper surface of the workpiece, which is the measurement object, and the detector. Fig. 3 is a schematic diagram showing the positional relationship between the first displacement gauge, the second displacement gauge, the third displacement gauge, and the reference device of the detector. [ Fig. 4A ] and [ Fig. 4B ] are cross-sectional views of a state in which a reference device used in the calibration method of the detector of the comparative example is placed on the upper surface of the workpiece. [ Fig. 5] Fig. 5 is a perspective view of the reference tool used in the shape measuring device of the embodiment as viewed obliquely from below. [ Fig. 6A ] and [ Fig. 6B ] are cross-sectional views of a state in which the reference tool used in the shape measuring device of the embodiment is placed on the upper surface of the workpiece. Fig. 7A is a schematic diagram of a datum having a beam structure supporting uniformly distributed loads at both ends, and [ Fig. 7B ] is a schematic diagram showing the positional relationship between the datum and the detector used in the shape measuring device of the embodiment. [FIG. 8A to FIG. 8C] are diagrams showing the positional relationship between the workpiece, the benchmark, and the detector in the evaluation experiment. [ Fig. 9A ] is a graph showing the distribution of the offset amount g measured using a reference device having a rectangular parallelepiped shape without legs, and [ Fig. 9B ] is a graph showing a reference device ( Fig. 5) is a graph of the distribution of the offset g measured by the reference device with the feet. 10 is a flowchart of the shape measurement method of the embodiment. 11A is a diagram showing an image of a control window displayed by the control device on the display of the input/output device, and [ FIG. 11B ] is a diagram showing an example of an image of a measurement result displayed on the display of the input/output device. [ Fig. 12 ] A flowchart of a shape measurement method according to another embodiment. 13 is a diagram showing an example of an image of a control window displayed on the display of the input/output device ( FIG. 1A ) by the control device of the embodiment shown in FIG. 12 . [ Fig. 14 ] It is a graph showing the measurement result of the geometrical tolerance of the straightness of the upper surface of the workpiece and the time-dependent change of the temperature measurement value measured by the temperature sensor ( Fig. 1B ). [ Fig. 15A ] A diagram showing an example of an image of a control window displayed on the display of the input/output device ( Fig. 1A ) by the control device of the shape measuring device according to another embodiment, and [ Fig. 15B ] A diagram of an example of an image displayed on the display of FIG. 1A). 16A to 16D are perspective views of a reference device of a modification example of the embodiment shown in FIG. 5 as viewed obliquely from below. [ Fig. 17A ] is a side view of the reference device in a weightless state according to another modification of the embodiment shown in Fig. 5 , and [ Fig. 17B ] is a side view of the reference device in a state of being installed on the upper surface of a workpiece.

12: Workpiece

30: Benchmark

31: Datum plane

32: Main components

33: Legs

Claims (9)

A shape measuring device is characterized by having: a detector including at least three displacement gauges arranged in a row, and by being arranged opposite to the measurement object to detect the distance from the at least three displacement gauges to the measurement object Displacement of the distance up to; a reference device, which is supported on a support member to provide a reference plane for calibration of the detector; and a control device for calibrating the reference device, the reference device having the at least three displacement meters arranged in the above-mentioned The support structure is supported on the support member at two positions in the direction of the control device, and the control device is used to calibrate the at least three displacement gauges by calibrating the detector in a state where the at least three displacement gauges face the reference plane. The deviation of the upper and lower positions of each detector. The shape measuring device according to claim 1, wherein the reference tool has a shape elongated in one direction, the support structure includes three leg portions protruding from a bottom surface on a side opposite to the reference surface, the three Two of the leg portions are arranged at the same position in the longitudinal direction of the reference tool. A shape measuring device is characterized by having: a detector including at least three displacement gauges arranged in a row, and by being arranged opposite to a measurement object to detect from each of the at least three displacement gauges to the above Displacement of the distance to the measurement object; a reference device, which is supported on a support member to provide a reference plane for calibrating the detector; and A control device for calibrating the reference device, in a state where the reference device is supported on the support member, deflection occurs due to its own weight, and the shape of the reference surface in the state where the deflection occurs has a shape that is not affected by the support member. In the structure affected by the unevenness of the surface, the control device calibrates the detector in a state in which the at least three displacement gauges face the reference plane. The shape measuring device according to any one of Claims 1 to 3, wherein the control means stores the shape of the deflection generated on the reference plane when the reference device is placed on the support member, and The detector is calibrated according to the stored shape of the deflection. The shape measuring device according to any one of claim 1 to claim 3, further comprising: an input/output device for inputting an instruction to the control device, and for outputting a measurement result by the control device; and a temperature sensing device The device measures the temperature of the part where the temperature of the detector is reflected, and the control device outputs the measured value based on the temperature sensor at the latest calibration and the measured value based on the temperature sensor at the current time to the input and output device. The shape measuring device according to claim 5, wherein if the difference between the measured value based on the temperature sensor at the latest calibration and the measured value based on the temperature sensor at the current time exceeds a threshold value, the control means makes the prompt Correct the alarm information of the aforementioned detector from the aforementioned input output from the device. The shape measuring device according to claim 5, wherein the control device measures and stores the measurement object while moving one of the measurement object and the detector relative to the other in the direction in which the at least three displacement meters are arranged For the straightness of the object surface, a plurality of measurement results of the straightness of the surface of the object to be measured are output to the aforementioned input/output device in a form that can be compared. A reference device is characterized in that it has: a reference plane, which is opposite to three displacement meters arranged in a row; Two of the leg portions are arranged at the same position in the longitudinal direction of the reference plane. A calibration method, which is a calibration method of a detector that detects from each of the at least three displacement meters to the measurement object by arranging at least three displacement meters in a row to face the measurement object The characteristic of the above-mentioned calibration method is to make the above-mentioned at least three displacement gauges face the reference plane of the reference device in two positions in the direction in which the above-mentioned at least three displacement gauges are arranged. Each position is supported on the support member, and the detector is calibrated in a state where the at least three displacement gauges face the reference plane, so as to correct the deviation of the upper and lower positions of the at least three detectors.

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