JP2016027320A - Automatic screw dimensions measuring system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable, in measuring screws, various dimensions regarding screws to be automatically measured by only setting each screw one time.SOLUTION: An automatic screw dimensions measuring system 10, comprises a gripping part 68, whose object work of measurement is screws and that grips one end of the male screw in the axial direction of each work; a grip rotating part 62 that drives 360-degree rotation of the gripping part 68 around its axial direction; an optical measuring device 32 that optically measures in a non-contact way the dimensions of the work one end of whose male screw in the axial direction is gripped by the gripping part 68; a Y stage 26 that shifts the optical measuring device 32 in the axial direction relative to the gripping part 68; and an arithmetic sequence unit 100 that calculates and outputs the dimensions of the work in the axial direction and around the axis. The arithmetic sequence unit 100 further comprises a screw diameter calculating subunit 110 that calculates dimensions regarding the screw ridge and the screw root of the work and an overall calculating subunit 112 that calculates the overall length in the axial direction of the work.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an automatic thread dimension measurement system, and more particularly to an automatic thread dimension measurement system capable of automatically measuring various dimensions related to a screw.

  A screw manufacturer measures various dimensions of a screw in order to ship the manufactured screw as a product that satisfies a predetermined standard. There are standards for various screw dimensions, and in order to measure to these standards, various types of measuring instruments such as micrometers, vernier calipers, screw gauges, etc. are used properly. Inspection is performed. Each screw has 10 or more dimensions to be managed, and different measuring devices are used for measuring these dimensions, and the inspection results are recorded on the inspection table by the handwriting of the operator.

  Since such screw dimension measurement requires a great deal of labor and time, several automatic measurement methods have been proposed. For example, in Patent Document 1, as a screw inspection device, a screw head is fixed by a chuck unit, a parallel light beam is emitted from a light emitter to the screw portion, and a light reception provided on the side opposite to the light emitter with respect to the screw portion. It is disclosed that a bright and dark image of a screw portion is acquired by a device, and measurement information such as a screw length, a diameter width, and a screw thread is displayed by performing calculation on the acquired image of the screw portion by a computer. It is stated that the light emitter and the light receiver can move along the axial direction of the screw portion, and the outer periphery of the screw can be inspected over 360 degrees by rotating the screw head and changing the direction of the screw portion.

  In Patent Document 2, as a screw shape measuring device, a light source that irradiates light parallel to a screw helix and a telecentric lens that has the same light receiving optical axis as that of the light source and forms an image of only a component parallel to the optical axis are used. An apparatus having an imaging device having a line sensor that acquires a one-dimensional image in a direction orthogonal to the axis of the screw is disclosed. Here, a plurality of one-dimensional images of the thread groove are acquired by scanning, and these are combined to measure the shape of the screw.

JP 2012-112929 A JP 2010-210292 A

  In the prior art, automatic measurement of the dimensional relationship of the threaded portion has been proposed, but measurement of various dimensions of screws other than the threaded portion is not described. For example, in the case of a screw with a head, the shape and dimensions of the head, the radius of curvature at the lower part of the neck between the head and the screw part, the depth of the head hole provided in the head, etc. are not described. Further, in the dimension measurement around the axis of the screw, it is necessary to rotate the screw around the axis, and it is difficult to perform this rotation and measurement continuously. In Patent Document 1, in order to inspect the outer periphery of the screw over 360 degrees, the head is fixed by the chuck unit once, the head is rotated, and the head is fixed again by the chuck unit. The measurement is not performed continuously.

  An object of the present invention is to provide a screw dimension automatic measurement system capable of automatically measuring various dimensions related to a screw by once setting a screw as a workpiece to be measured.

  An automatic thread dimension measurement system according to the present invention includes a gripping part that grips one end of a work screw in the axial direction, and a gripping rotating part that rotates the gripping part 360 degrees around the axial direction. An optical measuring device for optically non-contactingly measuring the dimension of the workpiece whose one end in the axial direction of the male screw is gripped by the gripping portion, and the optical measuring device relative to the gripping portion in the axial direction. And an arithmetic control device that calculates and outputs the dimensions of the workpiece in the axial direction and around the axis, and the arithmetic control device has dimensions related to the thread of the workpiece and dimensions related to the thread valley. A screw diameter calculation unit that calculates the total length, and a total length calculation unit that calculates the total length along the axial direction of the workpiece.

  In the screw dimension automatic measurement system according to the present invention, the gripping portion is an adapter having a disk-shaped outer shape, and is fixed so that the axial direction of the workpiece is not shaken when the tip portion of the male screw of the workpiece is screwed. It is preferable to include an adapter having a female screw having a predetermined meshing length at the center of one end surface, and a clamping chuck that clamps and fixes the outer peripheral side surface of the adapter at at least three points.

  In the screw dimension automatic measuring system according to the present invention, the adapter meshes with a ring gauge in which a reference female thread having a predetermined meshing accuracy corresponding to the thread dimension of the male thread of the workpiece is engraved, and a reference female thread of the ring gauge. It is preferable that the disk shape of the holder is a common shape regardless of the thread size of the workpiece.

  The automatic thread dimension measurement system according to the present invention includes a base having an upper surface parallel to the XZ plane, wherein the axial direction is the Y direction, the surface perpendicular to the Y direction is the XZ plane, and the gripping portion is the upper surface of the base The axial movement unit is a movement table on which an optical measuring device is mounted, and a movement table that can move to an arbitrary Y position along the Y direction with respect to the base. The optical measurement device preferably includes an image projection unit that measures the axial direction of the workpiece and a dimension around the axis.

  In the screw dimension automatic measurement system according to the present invention, the image projection unit is disposed on one side in the Z direction with respect to the Y-direction center line of the workpiece, and outputs a parallel light beam, and the Y-direction center line of the workpiece. An imaging surface that is arranged on the other side in the Z direction and has a light receiving optical axis that is the same as the light source for the projection shape that receives a parallel light beam from the light source and is a shadow of the work, and is parallel to the XY plane. It is preferable to have a projection imaging camera of a telecentric optical system that forms an image on and picks up an image.

  Further, in the screw dimension automatic measurement system according to the present invention, the arithmetic and control unit converts the projection shape data of the workpiece imaged by the projection imaging camera into two-dimensional bitmap data having an arbitrary position resolution. It is preferable to include a contour data calculation unit that binarizes each data of the two-dimensional data into black and white using a predetermined threshold.

  Further, in the screw dimension automatic measurement system according to the present invention, the contour data calculation unit generates data that becomes abnormal when viewed from the cross-sectional figure of the workpiece with respect to data at the boundary of black and white binarization based on a predetermined noise criterion. A smoothing process is performed to remove the noise, and contour data indicating a screw contour profile is obtained. Based on the contour data for each predetermined angular interval when the workpiece is rotated 360 degrees around the Y axis. It is preferable to calculate and output dimensions in the axial direction and around the axis.

  Further, the screw dimension automatic measurement system according to the present invention includes a focus moving unit that moves the projection imaging camera along the Z direction, and the arithmetic and control unit performs imaging with the projection imaging camera as preprocessing for conversion into a bitmap. In the edge region where the projected shape data of the screw is changed from white data to black data, a projection imaging camera is controlled by a focusing moving unit using a predetermined evaluation function so as to take a maximum value at the black-and-white boundary of the projected shape data. An in-focus position calculation unit that obtains the value of the evaluation function at each Z position while moving in the Z direction, and fixes the Z direction position of the projection imaging camera with the Z position at which the value of the evaluation function is the maximum value as the in-focus position; It is preferable.

  Further, in the screw dimension automatic measurement system according to the present invention, the arithmetic and control unit obtains a group of measurement data of the dimension around the Y axis of the work for the contour data at every predetermined angular interval of the work, and from a preset lower threshold value Excluding the measurement data of the dimension outside the range up to the preset upper limit threshold, calculating a value about the dimension around the Y axis based on the remaining group of the measurement data of the dimension, and causing the output device to output the value. preferable.

  Further, in the screw dimension automatic measurement system according to the present invention, the arithmetic and control unit provides contour data for each predetermined angular interval obtained when the workpiece is rotated about the Y axis with respect to the data at the boundary of black and white binarization. In the above, it is preferable to perform the smoothing process by performing a low-pass filter for a predetermined frequency set in advance on the locus of the measurement data continuous along the Y direction of the workpiece.

  Further, in the screw dimension automatic measurement system according to the present invention, the arithmetic and control unit provides contour data for each predetermined angular interval obtained when the workpiece is rotated about the Y axis with respect to the data at the boundary of black and white binarization. The X-direction position trajectory of a point predicted from a plurality of points corrected with the predicted deviation corresponding to the angle around the Y-axis of the work is predicted based on the work being displaced by a predetermined angle. It is preferable to perform a low pass filter to generate filtered contour data, calculate a value about the dimension of the workpiece around the Y axis based on the filtered contour data, and output the calculated value to the output device.

  In the screw dimension automatic measurement system according to the present invention, the workpiece is a head-attached screw having a head and a screw shaft portion, and having a turning groove or a turning hole for a tightening tool on the head, and an optical measuring device Preferably includes a head measuring unit that measures the depth of the head hole of the workpiece.

  In the screw dimension automatic measurement system according to the present invention, the head measurement unit includes a head imaging camera that images the shape of the head hole of the workpiece on an imaging plane parallel to the XZ plane, and a predetermined amount with respect to the Y direction of the workpiece. A laser light source that irradiates a beam extending linearly on the XZ plane at an inclination angle across the top surface of the head of the workpiece and the bottom surface of the head hole. The head dimension calculation unit that calculates the head dimension of the workpiece based on the imaging data, and the projection positions at which the linear beam emitted from the laser light source is projected on the top surface of the head and the bottom surface of the head hole And a head hole depth calculation unit that calculates the depth of the head hole based on the amount of discrepancy on the XZ plane of each detected projection position and a predetermined inclination angle. preferable.

  According to the above configuration, the screw dimension automatic measurement system has the grip portion that grips one end in the axial direction of the male screw that is the workpiece to be measured, and rotates the grip portion by 360 degrees around the axial direction. An optical measuring device that measures the dimensions optically in a non-contact manner is moved along the axial direction relative to the grip portion. As a result, the axial direction of the workpiece and various dimensions around the axis can be automatically measured only by once setting the screw as the workpiece to be measured on the gripping portion.

  In the automatic thread dimension measurement system, the gripping part is an adapter having a disk-shaped outer shape, and can be fixed so that the axial direction of the work is not shaken when the tip part of the male thread of the work is screwed. And an adapter having a female screw having a length of meshing at the center of one end face. As a result, stable measurement can be performed even when the workpiece is rotated around the axis.

  In the automatic thread dimension measurement system, the adapter has a ring gauge in which a reference female thread having a predetermined meshing accuracy corresponding to the thread dimension of the male thread of the workpiece is engraved. The standard internal thread of the ring gauge has an accurate internal thread shape, so if the workpiece is a good product, it can be firmly fixed so that the axial direction of the workpiece does not shake by engaging the complete thread part with the standard internal thread about 1 pitch. it can. In addition, since the male screw that meshes with the reference female thread of the ring gauge has a disk-shaped holder that protrudes from one end face side, the disk shape of the holder is the same regardless of the thread size of the workpiece. Can be easily accommodated for measuring screws with various nominal dimensions.

  In addition, the screw dimension automatic measurement system is provided with a gripping portion that is rotatable about the axial direction on the upper surface of the base having an upper surface parallel to the XZ plane, and moves to an arbitrary Y position along the Y direction with respect to the base. An optical measuring device including an image projection unit that measures the axial direction of the workpiece and the dimension around the axis is mounted on a possible Y table. Thus, by rotating the gripping part around the axis and moving the Y table along the Y direction, the axial direction of the workpiece and the dimension around the axis can be automatically measured using the image projection part.

  Further, in the screw dimension automatic measurement system, the image projection unit has a parallel light source arranged on one side in the Z direction with respect to the center line in the Y direction of the workpiece, and on the other side in the Z direction with respect to the center line in the Y direction of the workpiece. It has a telecentric optical projection imaging camera arranged. Thereby, the outline data of the workpiece can be obtained accurately.

  Further, in the screw dimension automatic measurement system, the arithmetic and control unit uses the projection shape data of the screw imaged by the projection imaging camera for the two-dimensional bitmap data having an arbitrary position resolution and the data at the boundary of black and white binarization. Contour data indicating a screw contour profile obtained by removing, as noise, data that is abnormal when viewed from the cross-sectional shape of the screw is obtained. As a result, noise due to dust or the like adhering to the workpiece can be removed by software processing, so that the axial direction of the workpiece and the dimension around the axis can be accurately calculated and output.

  Further, in the screw dimension automatic measurement system, the in-focus position is calculated in an edge region where the projected shape data of the screw imaged by the projection imaging camera changes from white data to black data. The general autofocus can focus on the surface of the object, but since the screw profile profile is an edge profile of an axial diameter, the focus position is very narrow. In the above configuration, since the evaluation function that is predetermined so as to take the maximum value at the black and white boundary of the projection shape data is used, the in-focus position can be accurately obtained.

  Further, in the screw dimension automatic measurement system, a group of measurement data of the dimension around the Y axis of the workpiece is obtained for the contour data at every predetermined angular interval of the workpiece, and from a range from a preset lower limit threshold to a preset upper limit threshold A value for the dimension around the Y-axis is calculated based on the remaining group of dimension measurement data around the Y-axis, excluding the measurement data around the off-axis dimension. Thereby, even when a foreign substance adheres to the screw, the value about the dimension around the Y axis can be calculated more accurately.

  In the screw dimension automatic measurement system, when the workpiece is a screw with a head, since the head hole cannot be measured with the projection shape data, the optical measuring device is separated from the image projection unit. Includes a head measurement unit that measures the depth of the hole. Thereby, non-contact optical measurement can be performed for the measurement of the head hole.

  In the automatic thread dimension measurement system, the hole depth is measured by applying a laser beam extending linearly on the XZ plane at a predetermined inclination angle with respect to the Y direction of the workpiece and When irradiated across the bottom surface, this linearly extending beam utilizes the fact that the projection position shifts in accordance with the hole depth between the top surface of the head and the bottom surface of the head hole. Thus, the depth of the head hole can be measured by non-contact optical measurement without using a gauge or the like.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram of the screw dimension automatic measuring system of embodiment which concerns on this invention, and is a front view of a screw dimension automatic measuring apparatus. FIG. 2A is a left side view and FIG. 2B is a top view of the screw dimension automatic measuring device of FIG. It is a figure which shows the screw which is the measurement object workpiece | work hold | gripped with the holding part of the screw dimension automatic measurement system of embodiment which concerns on this invention. FIG. 3A is a side view of the fastening chuck, FIG. 3B is a side view of the adapter, and FIG. 3C is a view showing a screw of the workpiece to be measured. (D) is an exploded view of the adapter. (E) to (g) are top views corresponding to (a) to (c). FIG. 4A is a diagram illustrating an adapter for a M12 screw, and FIG. 4B is a diagram illustrating an adapter for a M6 screw. c) is an adapter for an M3 screw. It is a flowchart which shows the procedure of the measurement in the screw dimension automatic measurement system of embodiment which concerns on this invention. It is a figure which shows the measurement location corresponding to the measurement procedure of FIG. FIG. 6A is a diagram illustrating measurement points in the side view, and FIG. 6B is a diagram illustrating measurement points in the top view. It is a figure which shows the measurement of the head hole depth in FIG. FIG. 7A is a diagram in an arbitrary gripping state of the measurement target workpiece, and FIG. 7B is a diagram illustrating a state in which the measurement target workpiece is rotated around the axis from the state of FIG. c) is a diagram illustrating a state in which the position of the head hole is measured by moving the position of the laser light source in the Y direction with respect to the workpiece to be measured. It is a figure which shows the calculation method of a focus position in the screw dimension automatic measurement system of embodiment which concerns on this invention. FIG. 8A is a diagram showing a projected state of a screw outline, FIG. 8B is a diagram showing a captured monochrome state when the focal position of the projection imaging camera is A to E, and FIG. FIG. 5 is a diagram showing a change in the monochrome state by a change in the gradation value I, (d) is a diagram showing a differential waveform with respect to the Z position of the gradation value I, and (e) is a half width of the waveform in (d). It is a figure which shows the relationship with respect to Z position. It is a figure which shows the noise removal method of an outline profile in the screw dimension automatic measurement system of embodiment which concerns on this invention. FIG. 9A is a diagram showing rules for the contour tracking process, FIG. 9B is a screw contour profile obtained by performing the contour tracking process on the workpiece to be measured, and FIG. It is a figure which shows the contour data which removed the noise from. In FIG. 5, it is a figure which shows the measurement of lower neck R. FIG. FIG. 10A is a diagram showing contour data of the lower neck of the workpiece to be measured, and FIG. 10B is a diagram showing a measurement method of the neck R. It is a figure which shows the measurement of the crest diameter in FIG. FIG. 11 (a) is a diagram showing contour data along the axial direction of the workpiece to be measured, (b) is a diagram for finding a regression line of the contour data of the peak portion of (a), and (c) is It is a figure which shows the calculation method of a mountain diameter. It is a figure which shows the measurement of the valley diameter in FIG. FIG. 11A is a diagram showing the contour data along the axial direction of the workpiece to be measured, FIG. 11B is a diagram for obtaining a regression line of the contour data of the valley portion in FIG. 11A, and FIG. It is a figure which shows the calculation method of a valley diameter. It is a figure which shows another measuring method of head hole depth. FIG. 13A is a side view showing a state in which a predetermined head hole reference bit is inserted into the head hole, and FIG. 13B is a top view corresponding to FIG. FIG. 14A is a diagram showing a head hole bit for a M12 screw, and FIG. 14B is a diagram for a M6 screw. (C) is a figure which shows the head hole bit for M3 screws. It is a front view of the principal part of the screw dimension automatic measurement apparatus which comprises the screw dimension automatic measurement system of another example of embodiment which concerns on this invention. It is a right view of the screw dimension automatic measuring apparatus of FIG. FIG. 17A is a top view showing a state in which the head imaging camera is retracted to the right side, and FIG. 17B is a diagram illustrating a state where the head imaging camera is moved to the imaging position. It is a top view which shows the state. It is the figure which abbreviate | omitted the head imaging camera in the top view of the screw dimension automatic measuring apparatus of FIG. FIG. 16 is a diagram showing a bit gripping unit in the left side view of FIG. 15. In the screw dimension automatic measurement system of another example of an embodiment concerning the present invention, it is a figure showing a method of calculating a crest diameter and a trough diameter at a predetermined angle after calculating contour data, and is an enlarged view of FIG. is there. FIG. 21A is a diagram showing measurement data of the crest diameter dmax and the trough diameter dmin at a predetermined angle by a curve and showing the relationship with the angle θ, and FIG. 21B is a part in the axial direction of the workpiece which is a screw. FIG. In the relationship between the measurement data of the crest diameter dmax and the number of measurement data at a predetermined angle, a diagram showing the case of an ideal model (a) and a case of excluding measurement data out of a predetermined range in one example (b). is there. It is a figure which shows the primary screw | thread outline profile (a) of a workpiece | work, and the secondary screw | thread outline profile (b) after a filter process, when performing a low-pass filter to the contour data in the predetermined angle of a workpiece | work. FIG. 7 is a diagram showing a change in a primary screw contour profile when a workpiece is rotated by a predetermined angle when an abnormal portion in the X direction is removed by a low-pass filter when obtaining contour data at a predetermined angle of the workpiece. is there. (A) shows the locus (a) before the filtering process and the filtering process when the abnormal part is removed by the low-pass filter in the locus about the X direction position at a predetermined angle at a part of the contour profile of the workpiece. It is a figure which shows the following locus | trajectory (b). It is a figure corresponding to FIG. 4 which shows the other example of the adapter for fixing a workpiece | work.

  Embodiments according to the present invention will be described below in detail with reference to the drawings. In the following description, a hexagon socket head cap screw having a nominal thread size of M3 and a nominal length of 30 mm will be mainly described as a workpiece to be measured. This is an illustrative example. In addition to metric coarse threads, the types of screws are metric fine threads, pipe taper screws, pipe parallel threads, Whitworth coarse threads, unified coarse threads, unified fine threads, miniature screws, metric trapezoidal screws. Also good. The nominal length may be other than 30 mm. The head hole is a turning groove or turning hole for a tightening tool provided in the head. In addition to a hexagonal hole, a slot (minus groove), cross hole, plus / minus hole, square hole, Torx (registered trademark), It may be a hexagonal star-shaped hex lobe hole or triangular hole such as Torx Plus (registered trademark) which is an improved version thereof. Moreover, it does not need to have a head, and may have a head or no head hole.

  The shapes, dimensions, materials, measurement locations, and the like described below are examples for explanation, and can be appropriately changed in accordance with the specifications of the screw dimension automatic measurement system. In the following description, the same elements are denoted by the same reference symbols in all the drawings, and redundant description is omitted.

  FIG. 1 is a configuration diagram of a screw dimension automatic measurement system 10 according to an embodiment. The automatic screw dimension measuring system 10 includes an automatic screw dimension measuring device 12, an arithmetic control device 100, and a pneumatic control device 102. The screw dimension automatic measuring device 12 is configured to include a vibration isolation table 14 and a base 16 disposed inside a housing 15 provided on the vibration isolation table 14. FIG. 1 shows a front view of the screw dimension automatic measuring device 12. FIG. 2 shows a left side view and a top view of the internal part of the housing 15 of the screw dimension automatic measuring device 12. 2A is a left side view, and FIG. 2B is a top view. 1 and 2 show the X direction, the Y direction, and the Z direction which are orthogonal to each other. The XZ plane is a plane parallel to the upper surface of the base 16, and the direction perpendicular to the upper surface of the base 16 is the Y direction parallel to the direction of gravity. The X direction is the left-right direction in the left side view, and the Z direction is the left-right direction in the front view.

  Although it is not a component of the screw dimension automatic measuring device 12, the workpiece 8 to be measured is shown. The workpiece 8 is a hexagon socket head cap screw having a nominal thread size of M12 and a nominal length of 30 mm. The axial direction of the workpiece 8 is a direction parallel to the Y direction. In other words, the Y direction is the axial direction of the workpiece 8.

  The column portions 18 and 19 erected in parallel with the Y direction from the upper surface of the base 16 and the top plate portion 20 connecting the upper ends of the two column portions 18 and 19 form a frame space together with the base 16. To do. Guide rails 22 and 23 are provided on the mutually facing surfaces of the column portions 18 and 19, and screw columns 24 and 25 are parallel to the Y direction from the upper surface of the base 16 on the inner side between the guide rails 22 and 23. Established. The screw columns 24 and 25 are rotatable shaft columns that are threaded along the axial direction on the outer peripheral surface and are rotatably supported by the base 16. The ends of the screw columns 24 and 25 in the −Y direction protrude downward from the top plate of the base 16 and are provided with pulleys.

  As shown in FIG. 2 (b), the Y stage 26 has slide portions that can slide on the guide rails 22 and 23 at both ends in the Z direction. It is a flat table base. Of the two sets of bearing portions 27, 28, one bearing portion 27 is provided on the + Z side of the guide rail 22, and the other bearing portion 28 is provided on the −Z side of the guide rail 23. The two sets of bearing portions 27 and 28 are constituted by ball nuts that mesh with screws engraved on the outer periphery of the screw columns 24 and 25. The screw columns 24 and 25 having threads on the outer periphery and the bearing portions 27 and 28 including ball nuts constitute a ball screw mechanism, and the screw columns 24 and 25 correspond to a ball screw for the ball screw mechanism. The Y stage 26 is a moving table that is guided by the guide rails 22 and 23 and moves in the Y direction when the screw columns 24 and 25 are rotationally driven by the action of the ball screw mechanism.

  A Y motor 29 that is a servo motor that rotationally drives the screw columns 24 and 25 is attached to the base 16. The output shaft of the Y motor 29 protrudes downward from the top plate of the base 16 and is provided with a pulley. The belt 31 is a power transmission member installed between a pulley provided on the output shaft of the Y motor 29 and a pulley provided on the ends of the screw columns 24 and 25 in the −Y direction. As such three pulleys, a timing pulley provided with irregularities along the circumferential direction can be used, and as the belt 31, a timing belt having irregularities on the surface can be used. An AC servo motor can be used as the Y motor 29.

  The Y motor 29 is a lift motor that is driven under the control of the arithmetic and control unit 100 and rotates the screw columns 24 and 25 to move the Y stage 26 up and down in the Y direction. The Y motor 29 is provided with a sensor 30 for detecting the rotation state of the output shaft. Sensors that detect the rotational states of the screw pillars 24 and 25 may be provided. An encoder can be used as the sensor 30. The detection data detected by the sensor 30 is transmitted to the arithmetic and control unit 100 using an appropriate signal line. The arithmetic and control unit 100 calculates the Y direction position of the Y stage 26 based on the transmitted data. As described above, the sensor 30 provided in the Y motor 29 or the screw pillars 24 and 25 is a Y sensor that detects the position of the Y stage 26 in the Y direction. As the sensor 30 as the Y sensor, a position sensor that directly detects the Y-direction position of the Y stage 26 may be used instead of the sensor that detects the rotational state of the Y motor 29. As the position sensor, a linear scale type optical sensor, a differential transformer type displacement sensor for detecting displacement of a magnetic material, a capacitance type displacement sensor, or the like can be used.

  The Y motor 29, the belt 31, the screw columns 24 and 25, and the bearing portions 27 and 28 provided on the Y stage 26 constitute an axial movement unit that moves the Y stage 26 with respect to the base 16 in the Y direction.

  The optical measuring device 32 mounted on the upper surface of the Y stage 26 is a measuring device that measures the size and shape of the workpiece 8 optically in a non-contact manner. The optical measuring device 32 includes an image projecting unit 34 that measures the axial direction of the workpiece 8 and dimensions around the axis, and a head measuring unit 40 that measures the size and shape of the head of the workpiece 8 and the depth of the head hole. It is comprised including.

  The image projection unit 34 is disposed on one side in the Z direction with respect to the Y-direction center line of the work 8 and is disposed on the other side in the Z direction with respect to the Y-direction center line of the work 8. Only a component having the same light receiving optical axis as that of the light source 36 and parallel to the optical axis is projected on an imaging surface parallel to the XY plane with respect to a projection shape that receives a parallel light beam from the light source 36 and becomes a shadow of the work 8. A projection imaging camera 38 of a telecentric optical system for imaging. As the light source 36, a light source having an appropriate light collimating means such as a collimator or a light source including a telecentric optical system can be used. As the projection imaging camera 38, a CCD camera using a CCD image sensor or a camera device using a CMOS image sensor can be used. For example, a CCD camera in which one pixel is about 8 μm and the size of the imaging surface is about 20 mm square can be used.

  The arrangement position of the light source 36 of the image projection unit 34 is provided on the + Z side from the center of the Y stage 26 and is fixed to the Y stage 26. The projection imaging camera 38 is provided on the −Z side from the center of the Y stage 26, but is mounted on a focusing moving unit 50 provided on the Y stage 26 and is movable in the Z direction. A combination of the projection imaging camera 38 and the focusing movement unit 50 is a projection imaging unit.

  The in-focus moving unit 50 includes a Z stage 52 that can move in the Z direction with respect to the Y stage 26, and a Z motor 54 that moves and drives the Z stage 52 along the Z direction. The operation of the Z motor 54 is controlled by the arithmetic and control unit 100. The function of the focusing moving unit 50 will be described later with reference to FIG. As the Z motor 54, an AC servo motor or a DC servo motor can be used.

  The head measurement unit 40 includes a head imaging camera 42 that images the shape of the head hole of the workpiece 8 on an imaging plane parallel to the XZ plane, and a predetermined inclination angle with respect to the Y direction of the workpiece 8 on the XZ plane. And a laser light source 44 that irradiates the beam extending linearly across the top surface of the head of the workpiece 8 and the bottom surface of the head hole. The beam of the laser light source 44 extends linearly in parallel with the Z direction. The actuator 45 is a driving unit that moves the laser light source 44 along the Y direction. As the actuator 45, a small motor can be used. A head hole depth measurement method using such a linearly extending laser beam will be described later with reference to FIG.

  The head imaging camera 42 is an imaging camera that faces the upper surface of the head of the work 8 and whose imaging surface is parallel to the XZ plane. As the head imaging camera 42, a CCD camera using a CCD image sensor or a camera device using a CMOS image sensor can be used. The ring illumination unit 46 is an annular lamp that is provided on the −Y direction side of the head imaging camera 42 and illuminates the upper surface of the workpiece 8. The head imaging camera 42, the laser light source 44, and the ring illumination unit 46 are fixedly attached to the attachment plate 48 by positioning relative positional relationships.

  The retreat movement unit 56 is a mechanism that allows the mounting plate 48 to move in the X direction, and an X stage 58 that can move along the X direction, and a piston that moves the X stage 58 in the ± X direction by a predetermined movement distance L. -It is comprised including the cylinder mechanism 60. The piston / cylinder mechanism 60 operates under the control of the arithmetic and control unit 100, and can reciprocate the piston by a distance of ± L by the air pressure supplied from the pneumatic control unit 102.

  When the piston moves + L, the head imaging camera 42 attached to the mounting plate 48, the laser light source 44, and the ring illumination unit 46 move together in the + X direction, and the optical axis of the head imaging camera 42 is exactly the workpiece. Come to the center of 8 heads. This state is a measurement state in which head shape measurement and hole depth measurement can be performed. When the piston moves -L, the head imaging camera 42, the laser light source 44, and the ring illumination unit 46 attached to the attachment plate 48 move together in the -X direction. This state is a retracted state in which the head imaging camera 42 or the like does not interfere with the work 8 even when the Y stage 26 is lowered in the −Y direction.

  The gripping portion 68 is a device that is disposed on the base 16 via the gripping rotation portion 62 and grips one end in the axial direction of the male screw of the workpiece 8. The gripping portion 68 includes an adapter 80 having a disk-like outer shape and a fastening chuck 70 that clamps and fixes the outer peripheral side surface of the adapter 80 at at least three points. The gripping rotation unit 62 includes a θ motor 64 that rotates the fastening chuck 70 360 degrees in the axial direction, and a rotary joint portion 66 provided between the θ motor 64 and the fastening chuck 70.

  The rotary joint unit 66 is a pneumatic relay unit for supplying the pneumatic pressure from the pneumatic control device 102 to the fastening chuck 70. The rotary joint portion 66 has a function of relaying a supply tube for supplying air pressure so that the supply tube is not entangled by the axial rotation of the fastening chuck 70. The rotation operation of the θ motor 64 is controlled by the arithmetic and control unit 100. As the θ motor 64, an AC servo motor or a DC servo motor can be used.

  FIG. 3 is an exploded view showing details of the grip portion 68. Here, detailed configurations of the clamping chuck 70 constituting the gripping portion 68, the adapter 80 fixed by the clamping chuck 70, and the workpiece 8 gripped by the adapter 80 are shown. FIGS. 3A to 3C are sectional views of the fastening chuck 70, the adapter 80, and the workpiece 8, FIG. 3D is an exploded view of the adapter 80, and FIGS. The top view of each of the fastening chuck 70, the adapter 80, and the workpiece 8 is shown.

  The workpiece 8 includes a male screw portion 2, a head portion 4, and a neck lower portion 3 between the male screw portion 2 and the head portion 4. The head portion 4 is provided with a hexagonal head hole 6. It is done. The workpiece 8 is an M12 screw nominal and a metric coarse screw having a nominal length of 30 mm. According to Japanese Industrial Standard values, the length of the external thread 2 where the screw can be fixed is about 30 mm, the maximum diameter of the external thread 2 is about 13.7 mm, the pitch of the screw is 1.75 mm, and the reference outline of the head 4 The dimension is 18mm, the reference height dimension of the head 4 is 12mm, the head hole 6 is a hexagonal hole, the nominal dimension of the width across flats is 10mm, the minimum dimension of the hole depth is 6mm, and the maximum roundness of the lower neck 3 The neck radius R, which is the state radius, is a minimum of 0.6 mm. The width across flats is the dimension between opposite sides of the hexagon. The bottom surface of the head hole 6 is not flat but has a conical shape with an opening angle of 120 degrees. The incomplete threaded portion of the male threaded portion 2 has a maximum of 2 pitches, and in this case, 2 pitch = 3.50 mm.

  In the clamping chuck 70, three slide bases 74a, 74b, and 74c are arranged on the support base 72 with their tip portions facing each other. In the initial state, the three slide bases 74 a, 74 b and 74 c are retracted to the outer peripheral side of the support base 72. By the pistons 78a and 78b of the piston / cylinder mechanism operated by the air pressure supplied from the pneumatic controller 102, the three slide bases 74a, 74b and 74c are synchronized with each other between the outer peripheral side of the support base 72 and the central axis side. Driven between.

  Clamping claw portions 76a, 76b, and 76c are attached to the three slide bases 74a, 74b, and 74c, respectively. The tip portions of the three clamping claws 76a, 76b, and 76c are arranged so as to face the direction of the central axis of the support base 72, respectively. In the initial state, the clamping claws 76 a, 76 b and 76 c are also retracted to the outer peripheral side of the support base 72. The three slide bases 74a, 74b, and 74c are synchronously moved in the direction of the central axis of the support base 72, so that the tip portions of the clamping claws 76a, 76b, and 76c are synchronously centered on the central axis of the support base 72. The adapter 80 is moved so as to be gathered in the direction, and the adapter 80 disposed at the center of the support base 72 is centered so as to match the position of the central axis, and the outer peripheral side surface of the adapter 80 is clamped and fixed. Thus, the clamping chuck 70 is a three-part chuck mechanism that is driven to move by air pressure between the retracted state and the tightening state.

  The centering clamping operation of the clamping chuck 70 is performed under the control of the arithmetic and control unit 100. The adapter 80 is clamped by the clamping chuck 70 at the tip portions of the three clamping claws 76a, 76b, and 76c. Since the tip portions of the three clamping claws 76a, 76b, and 76c are flat surfaces, respectively, when the outer shape of the adapter 80 is disk-shaped, its outer peripheral side surface has three points, more precisely, 3 along the axial direction. It is pinched by the tangent of the book. The holding of the outer peripheral side surface of the adapter 80 may be performed at least at three points. For example, it is good also as a structure which clamps the outer peripheral side surface of the adapter 80 by the shape of the front-end | tip part of a clamping nail | claw part with two clamping claw parts which mutually face. In this case, the outer peripheral side surface of the adapter 80 is clamped at four points.

  The adapter 80 has a disk-shaped outer shape sandwiched between the fastening chucks 70 and can be fixed so that the axial direction of the workpiece 8 is not shaken when the distal end portion of the male screw portion 2 of the workpiece 8 is screwed. A workpiece fixing jig having a female screw having a predetermined meshing length at the center of one end face.

  The adapter 80 includes a ring gauge 82a into which the distal end portion of the external thread portion 2 of the work 8 is screwed with a predetermined engagement length, a holder 86 having a disk-shaped outer portion sandwiched by the fastening chuck 70, a ring A spacer 84 a disposed between the gauge 82 a and the holder 86 is configured integrally.

  The ring gauge 82a is a member having a disk shape and having a reference female screw 83a cut along its central axis. The reference female screw 83a is a female screw having a predetermined meshing accuracy corresponding to the thread size of the male thread portion 2 of the workpiece 8. As the ring gauge 82a, a screw outer diameter gauge used for screw inspection can be used as it is. When the standard thread outer diameter gauge is M12, an 8-pitch reference female thread 83a is engraved. Since 1 pitch = 1.75 mm, the thickness of the ring gauge 82a is accurately controlled to 8 pitch = 14.00 mm. The reference female screw 83a does not have an incomplete screw portion.

  The distal end portion of the male thread portion 2 of the workpiece 8 is screwed with a predetermined engagement length from the upper surface side which is one end surface side of the ring gauge 82a. The predetermined meshing length is set to such an extent that when the tip of the male thread portion 2 of the work 8 is screwed into the reference female thread 83a of the ring gauge 82a and meshed, the workpiece 8 does not shake in the axial direction. The amount of axial deflection of the workpiece 8 is preferably zero, but is acceptable as long as the measurement accuracy of various dimensions of the workpiece 8 is not affected. If the workpiece 8 is a non-defective product, if the effective thread portion of the male thread portion 2 of the workpiece 8 is engaged with the reference female screw 83a of the ring gauge 82a by about one pitch, the axial deflection of the workpiece 8 is almost within the allowable range. It will fit. Since the male thread portion 2 of the workpiece 8 has incomplete thread portions corresponding to two pitches at the maximum, the predetermined meshing length as the screwing amount of the workpiece 8 is (the length corresponding to the number of pitches of the incomplete thread portion + It is preferable to set the length as long as possible as compared to the length of one pitch of the complete thread portion.

  Since the ring gauge 82a has high accuracy that can be used for the thread inspection of the workpiece 8, when the workpiece 8 cannot be screwed into the ring gauge 82a with a predetermined engagement length, the workpiece 8 is regarded as a defective product. The Therefore, the tip portion screwed into the reference female screw 83a of the ring gauge 82a of the workpiece 8 is determined to be a non-defective part. However, since the portion is not quantitatively measured by the automatic screw dimension measurement system 10, it is preferable to set the predetermined engagement length as short as possible. Thus, there is a conflict between the viewpoint of reducing the axial deflection of the workpiece 8 and the viewpoint of increasing the range in which quantitative measurement by the screw dimension automatic measurement system 10 can be performed.

  Therefore, in the following, a predetermined meshing length = a length corresponding to three pitches of the male thread portion 2 of the workpiece 8 = 5.25 mm. The predetermined meshing length is set to a length corresponding to 3 pitches, which is an integral multiple of the length of 1 pitch, because the screwing depth of the tip of the male threaded portion 2 of the workpiece 8 into the ring gauge 82a is 1 pitch. This is to obtain an accurate value that is an integer multiple. The work 8 is a metric coarse screw having a nominal length of M12 and a nominal length of 30 mm. According to Japanese Industrial Standard values, the incomplete threaded portion of the male threaded portion 2 has a maximum of 2 pitches. Therefore, one pitch is added to the maximum two pitches, and the predetermined meshing length is set to a length corresponding to three pitches so that at least one pitch can be meshed with the complete thread portion.

  In the case of the work 8 with a low quality level, the incomplete thread portion may be 2 pitches or more, and even if the meshing length is 3 pitches, the work 8 may sway in the axial direction. In such a case, the predetermined meshing length is increased from the length of 3 pitches to the length of 1 pitch as a unit. For example, the predetermined meshing length is 4 pitches or 5 pitches. On the contrary, in the case of a screw processed for high accuracy and the incomplete thread portion can be accommodated in 1 pitch or less, the predetermined meshing length is changed from a length of 3 pitches to a length unit of 1 pitch. It can be shortened. For example, the predetermined meshing length may be a length corresponding to two pitches. Adjustment of the predetermined meshing length in increments of 1 pitch is performed by increasing or decreasing the number of spacers 84a, as will be described later.

  The holder 86 is a disk-shaped member having an upper surface that is one end surface from which the external thread 92a that meshes with the reference female thread 83a of the ring gauge 82a protrudes. If the side on which the male thread portion 2 of the workpiece 8 is screwed into the ring gauge 82a is the upper surface side of the ring gauge 82a, the male screw 92a of the holder 86 is screwed from the lower surface side of the ring gauge 82a. The disc-shaped portion of the holder 86 has a holding ring portion 88 and a stopper flange portion 90 having a larger outer diameter so that the positioning in the Y direction is accurately performed when the disk 86 is held by the fastening chuck 70. . Even if the nominal dimensions of the workpiece 8 are different, it is preferable that the clamping ring portion 88 has the same outer diameter because the clamping chuck 70 can be standardized. Here, the outer diameter of the sandwiching ring portion 88 is 20 mm, and the outer diameter of the stopper flange 90 is 35 mm. When the holder 86 is clamped by the clamping chuck 70 by the lower surface, which is the end surface on the −Y direction side, of the stopper collar 90 abutting against the upper surfaces of the three clamping claws 76 a, 76 b, 76 c of the clamping chuck 70. Is accurately positioned in the Y direction. Note that, by partially cutting off the outer periphery of the stopper flange 90, the holder 86 can be prevented from rolling when the holder 86 is placed on a work table or the like.

  The male screw 92a protrudes from the upper surface, which is one end surface of the stopper flange 90 of the holder 86, with a preset protrusion amount. The male screw 92a may have an incomplete screw portion.

  The length by which the male thread 92a is screwed into the reference female thread 83a of the ring gauge 82a is {(the thickness of the ring gauge 82a) − (the predetermined meshing length with which the male thread portion 2 of the workpiece 8 meshes with the ring gauge 82a). } Is set accurately. In the above case, {(thickness of the ring gauge 82a) − (predetermined engagement length with which the male thread portion 2 of the work 8 is engaged with the ring gauge 82a)} = {(8 pitch length) − (3 pitch length) Length)} = (Length of 5 pitches) = (14.00 mm−5.25 mm) = 8.75 mm.

  The predetermined protruding amount of the male screw 92a from the stopper flange 90 can be (the length of 5 pitches) = 8.75 mm, but in consideration of the fact that a lower neck is formed on the male screw 92a, (Length of 5 pitches) = It is preferable to set longer than 8.75 mm. When setting a longer value, the length corresponding to an integral multiple of the pitch is increased. As a result, the protruding amount of the male screw 92a is accurately an integral multiple of the pitch, and the screwing depth of the tip of the male thread portion 2 of the workpiece 8 into the ring gauge 82a is an accurate value of an integral multiple of one pitch. Can do. Here, the protruding amount of the external thread 92a = (7 pitch length) = 12.25 mm.

  The male screw 92a of the holder 86 is engaged with the reference female screw 83a of the ring gauge 82a from the lower surface side of the ring gauge 82a, and the tip of the female screw portion 2 of the workpiece 8 is connected to the reference female screw of the ring gauge 82a from the upper surface side of the ring gauge 82a. When screwed into 83a, the distal end portion of the male thread portion 2 of the workpiece 8 stops at the distal end of the male thread 92a of the holder 86. The screwing depth of the tip of the male thread portion 2 of the workpiece 8 into the ring gauge 82a is (a predetermined meshing length with which the male thread portion 2 of the workpiece 8 meshes with the ring gauge 82a), {(of the ring gauge 82a (Thickness) − (length in which the male screw 92a of the holder 86 is screwed into the ring gauge 82a)}.

  As described above, the protruding amount of the male screw 92a of the holder 86 may be changed by a unit of length corresponding to one pitch, and as already described, the male screw portion 2 of the work 8 is attached to the ring gauge 82a. The predetermined meshing length for meshing may be adjusted in units of length for one pitch. Even in such a case, the screwing depth of the tip of the threaded portion 2 of the workpiece 8 into the ring gauge 82a is an accurate value that is an integral multiple of one pitch. By doing in this way, the Y position of the front-end | tip part of the external thread part 2 of the workpiece | work 8 can be calculated | required correctly from the measured value of the Y position of the upper surface of the ring gauge 82a. The spacer 84a is used for adjusting this one pitch length unit.

  The spacer 84a is an annular thin plate having a through hole through which the male screw 92a can pass. One spacer 84 a has a thickness corresponding to exactly one pitch of the workpiece 8. In FIG. 3, the number of the spacers 84a is shown as two. However, as described in some examples below, the number of spacers is not limited to two, and may be one or three. In the above example, when the thickness of the ring gauge 82a = 8 pitches and the protruding amount of the male screw 92a of the holder 86 is a length corresponding to 7 pitches, the stopper flange 90 of the holder 86 and the ring Two spacers 84a having a thickness of one pitch are inserted between the gauges 82a. Accordingly, a predetermined meshing length between the tip end portion of the male thread portion 2 of the workpiece 8 and the ring gauge 82a = [(thickness of the ring gauge 82a) − {(protruding amount of the external thread 92a) − (of the spacer 84a). Thickness)}] = [(length for 8 pitches) − {(length for 7 pitches) − (length for 2 pitches)}] = length for 3 pitches. By doing in this way, from the measured value of the Y position on the upper surface of the ring gauge 82a, the position lowered in the -Y direction by 3 pitches is accurately obtained as the Y position of the tip of the threaded portion 2 of the workpiece 8. be able to.

  When it is necessary to change the predetermined meshing length between the tip of the male thread 2 of the workpiece 8 and the ring gauge 82a from the length corresponding to three pitches, the number of inserted spacers 84a may be increased or decreased. For example, when it is desired to increase the predetermined meshing length from 3 pitches to 4 pitches for reasons such as the length of the incomplete threaded portion of the male threaded portion 2 of the work 8, in the above example, the number of inserted spacers 84a Increase by one. As a result, the position lowered in the −Y direction by 4 pitches from the measured value of the Y position on the upper surface of the ring gauge 82a can be accurately obtained as the Y position of the tip of the male thread 2 of the workpiece 8. When the predetermined meshing length is sufficient for two pitches, the number of inserted spacers 84a is reduced by one in the above example. As a result, the position lowered in the −Y direction by two pitches from the measured value of the Y position on the upper surface of the ring gauge 82a can be accurately obtained as the Y position of the tip of the threaded portion 2 of the workpiece 8.

  When it is necessary to change the protruding amount of the male screw 92a of the holder 86 from the length corresponding to 7 pitches, the number of inserted spacers 84a may be increased or decreased. For example, when it is desired to set the protruding amount of the male screw 92a from 7 pitches to 8 pitches for reasons such as the length of the neck portion of the male screw 92a of the holder 86, the number of inserted spacers 84a is increased by one. When the protruding amount of the male screw 92a is sufficient for 6 pitches, the number of inserted sheets is reduced by one. Thereby, in any case, the position lowered in the −Y direction by 3 pitches is accurately obtained as the Y position of the tip of the threaded portion 2 of the workpiece 8 from the measured value of the Y position on the upper surface of the ring gauge 82a. be able to.

  In this way, only by increasing / decreasing the number of spacers 84a, a wide range of variations such as the length of the incomplete screw portion of the male screw portion 2 of the work 8 and the length of the neck portion of the male screw 92a of the holder 86 can be handled over a wide range. The position of the distal end portion of the male thread portion 2 of the workpiece 8 can be set to a position that is accurately lowered from the upper surface of the ring gauge 82a of the adapter 80 in the −Y direction by an integral multiple of the length of one pitch. As a result, even if the tip of the male thread portion 2 of the workpiece 8 is gripped by the adapter 80, the total length of the workpiece 8 can be calculated by measuring the Y position of the upper surface of the ring gauge 82a of the adapter 80. it can.

  Here, the ring gauge 82a, the spacer 84a, and the male screw 92a of the holder 86 constituting the adapter 80 have different thicknesses and threaded portions depending on the type of the workpiece 8, but the clamping ring portion 88 and the stopper flange 90 are It has a common shape and dimensions regardless of the eight types.

  FIG. 4 is a diagram illustrating an example of an adapter that varies depending on the type of the workpiece 8. Here, adapters corresponding to three types of workpieces 8 are shown, but adapters of different types of workpieces 8 other than this can also have the same structure. FIG. 4A shows the case where the thread of the workpiece 8 is called M12, and is the same as the adapter 80 described in FIG.

  FIG. 4B is a diagram illustrating the adapter 80b when the thread name of the workpiece 8 is M6. The clamping ring part 88 and the stopper collar part 90 are the same as (a). Here, since the pitch of M6 is 1.00 mm, the thickness of the ring gauge 82b is 8 pitch = 8.00mm, the thickness of one spacer 84b is 1 pitch = 1.00mm, The protruding amount of the external thread 92b is 7 pitch = 7.00 mm.

  FIG. 4C is a diagram showing the adapter 80c when the nominal thread name of the workpiece 8 is M3. The clamping ring part 88 and the stopper collar part 90 are the same as (a). Here, since the pitch of M3 is 0.50 mm, the thickness of the ring gauge 82c is 8 pitch = 4.00 mm, the thickness of one spacer 84c is 1 pitch = 0.50 mm, and the distance from the stopper flange 90 is The protruding amount of the external thread 92c is 7 pitch = 3.50 mm.

  Returning to FIG. 1 again, the arithmetic and control unit 100 controls each element constituting the screw size automatic measuring device 12 and the operation of the pneumatic control device 102 as a whole, and calculates the axial direction of the workpiece 8 and the dimensions around the axis. The calculated result is transmitted to the output device 104 such as a printer, and the output device 104 has a function of printing it out as the inspection table 106. The arithmetic and control unit 100 can be configured with an appropriate computer.

  The arithmetic and control unit 100 includes a screw diameter calculation unit 110, a total length calculation unit 112, a focusing position calculation unit 114, a contour data calculation unit 116, a neck R calculation unit 118, a head dimension calculation unit 120, and a head hole depth calculation. Unit 122 and measurement data output unit 124. These functions can be realized by software executed by the arithmetic and control unit 100. Specifically, the functions can be realized by executing a screw automatic measurement program. Some of these functions may be realized by hardware.

  The operation of the screw dimension automatic measurement system 10 having the above-described configuration, particularly each function of the arithmetic and control unit 100, will be described in more detail with reference to FIGS. FIG. 5 is a flowchart showing a measurement procedure in the screw dimension automatic measurement system 10. FIG. 6 is a diagram illustrating measurement points of the workpiece 8 in which each procedure of FIG. 5 is performed. FIG. 6A is a diagram illustrating measurement points in the side view, and FIG. 6B is a diagram illustrating measurement points in the top view.

  In order to measure the workpiece 8, the screw dimension automatic measurement system 10 is first initialized. In the initialization, the power is turned on, the pneumatic control device 102 is started, and the arithmetic control device 100 is set to the initial state. As a result, the Y stage 26 returns to a predetermined initial Y position. The initial Y position is set to a position sufficiently higher along the Y direction than the tip position of the grip portion 68. Further, the Z stage 52 returns to a predetermined initial Z position, and the X stage 58 returns to the retracted state. The gripper 68 returns to the predetermined initial θ position. The three clamping claws 76a, 76b, 76c of the fastening chuck 70 return to the retracted state.

  When the initialization is completed, the workpiece 8 is set on the grip portion 68 (S10). As described with reference to FIG. 4, the workpiece 8 is held and fixed by the holding portion 68 for three pitches at the tip of the male screw portion 2. In this processing, the adapter 80 for M12 is prepared in advance, and the distal end portion of the male thread portion 2 of the workpiece 8 is screwed into the ring gauge 82a of the adapter 80. Since the predetermined meshing length of the adapter 80 for M12 is set to 3 pitch of the screw of M12 = 5.25 mm, the work 8 stops when it is screwed in by 5.25 mm. Next, the adapter 80 that grips the workpiece 8 is set in a space between the three clamping claws 76 a, 76 b, 76 c in the retracted state of the fastening chuck 70. The processing so far is performed manually by the operator.

  When the workpiece 8 is set on the gripping portion 68, the operator presses a tightening fixing button or the like, so that the arithmetic control device 100 issues a command to the pneumatic control device 102, and the tightening chuck 70 of the gripping portion 68 is pressed. A predetermined tightening air pressure is supplied to the piston / cylinder mechanism. As a result, the three clamping claws 76a, 76b, and 76c move synchronously to the central axis side of the support base 72, and the workpiece 8 is firmly tightened and fixed. From this state, measurement of the shape and dimension of the workpiece 8 starts.

  After S10, head dimension measurement is performed (S12). This process is executed by the function of the head dimension calculator 120 of the arithmetic and control unit 100. Specifically, the Y stage 26 is lowered so that the focal position of the head imaging camera 42 is exactly the position of the upper surface of the head 4 of the workpiece 8. Then, the imaging data of the shape of the head 4 of the work 8 is acquired by the head imaging camera 42, the imaging data is binarized, and the diameter dimension of the head 4 and the head hole 6 are detected using an edge detection method or the like. Calculate the width across flats. In FIG. 6, this is shown as a top view of the head 4 as S12.

  Since the outer shape of the head 4 is circular, the workpiece 8 is rotated 360 degrees around the axis at intervals of 1 degree, and the measurement of the diameter of the head 4 is repeated at each angle. The maximum value, the minimum value, and the average value of these measurement results are taken as the measurement values of the diameter dimension of the head 4. The two-sided width of the head hole 6 is the interval between the opposite sides of the hexagon, and there are three pairs of opposite sides of the hexagon. Therefore, the workpiece 8 is rotated 360 degrees around the axis at an interval of 120 degrees. Measure the width across flats. The maximum value, the minimum value, and the average value of these measurement results are taken as the measurement values of the two-surface width of the head hole 6.

  Next, head hole depth measurement is performed (S14). The head hole 6 is a turning groove or turning hole for a fastening tool provided in the head of the workpiece 8, and is a hexagonal hole in this case. This process is executed by the function of the head hole depth calculation unit 122 of the arithmetic and control unit 100. Specifically, a beam extending linearly on the XZ plane from the laser light source 44 at a predetermined inclination angle with respect to the Y direction of the workpiece 8 is straddled across the top surface of the head 4 of the workpiece 8 and the bottom surface of the head hole 6. Irradiate. The amount of discrepancy on the XZ plane between the projection position at which the irradiated linearly extending beam is projected on the upper surface of the head 4 and the projection position projected on the bottom surface of the head hole 6 depends on the depth of the head hole 6. Use different things.

  FIG. 7 is a diagram showing a procedure for measuring the depth of the head hole 6. FIG. 7A is a diagram in which the workpiece 8 is in an arbitrary gripping state, and FIG. 7B is a diagram illustrating a state in which the workpiece 8 is rotated by Δθ around the axis from the state of FIG. ) Is a diagram illustrating a state in which the head hole depth is measured by moving the position of the laser light source 44 in the Y direction with respect to the workpiece 8 by ΔY. In these drawings, the upper diagram is a top view of the head 4, and the lower diagram is a cross-sectional view of the workpiece 8.

  FIG. 7A shows a beam 130 extending linearly from the laser light source 44 at a predetermined inclination angle ψ with respect to the Y direction with the hexagonal opposite sides of the head hole 6 parallel to the Z direction. It is the figure irradiated to the bottom surface 7 of the top surface 5 and the head hole 6. The beam 130 is a line beam extending linearly in parallel with the Z direction. For example, when the laser light source 44 is a red light emitting type, the red line is projected onto the upper surface 5 of the head 4 and the bottom surface 7 of the head hole 6. FIG. 7A shows a red line 132 projected on the upper surface 5 of the head 4 and a red line 133 projected on the bottom surface 7 of the head hole 6. Since the bottom surface of the head hole 6 is not flat but has a conical shape having an opening angle of 120 degrees, the red line 133 projected on the bottom surface 7 has an arc shape.

  When inspecting the depth of the head hole 6 with the depth gauge, the depth gauge abuts on the bottom surface 9 of the hexagonal corner of the head hole 6. The bottom surface 9 of the hexagonal corner of the head hole 6 is different from the bottom surface 7 which is a conical conical surface having an opening angle of 120 degrees. Therefore, in order to optically measure the depth of the head hole 6, the beam is so arranged that the red line projected on the bottom surface of the head hole 6 hits the bottom surface 9 of the hexagonal corner of the head hole 6. It is preferable to irradiate 130. In FIG. 7A, the red line 133 hits the bottom surface 7 that is a conical surface, does not hit the bottom surface 9 of the hexagonal corner of the head hole 6, and the red line 133 is shaded by the shadow of the top surface 5 of the head 4. The end of 133 does not extend to the hexagonal side of the head hole 6.

  FIG. 7B is a diagram illustrating a state in which the work 8 is rotated by Δθ around the axis so that the hexagonal sides are parallel to the X direction. Here, a red line 134 projected onto the top surface 5 of the head 4 and a red line 135 projected onto the bottom surface 7 which is the conical surface of the head hole 6 are shown, but the end of the red line 135 is the head It extends to the hexagonal side of the hole 6. However, the red line 135 does not hit the bottom surface 9 of the hexagonal corner of the head hole 6.

  FIG. 7C is a diagram illustrating a state in which the position of the laser light source 44 in the Y direction is shifted by ΔY in the + Y direction with respect to the workpiece 8 with respect to the state of FIG. The beam moves in the + X direction according to the magnitude of ΔY. In FIG. 7C, a red line 136 projected on the upper surface 5 of the head 4 and a red line 137 projected on the bottom surface of the head hole 6 are shown. The X direction positions of the red lines 136 and 137 move according to the Y direction movement amount ΔY of the beam 131. Here, ΔY in a state where the red line 137 projected on the bottom surface of the head hole 6 hits the bottom surface 9 of the hexagonal corner of the head hole 6 is shown. Whether or not the red line 137 is in contact with the bottom surface 9 of the hexagonal corner of the head hole 6 can be determined based on the imaging data of the head 4 acquired by the head imaging camera 42.

  ΔY can be arbitrarily set by controlling an actuator 45 that moves and drives the laser light source 44 in the Y direction. When the focal depth of the head imaging camera 42 is sufficiently deep, the actuator 45 may be omitted, the position of the laser light source 44 may be fixed with respect to the Y stage 26, and the Y stage 26 may be moved by -ΔY.

  In FIG. 7C, the depth D of the head hole 6 is based on a predetermined inclination angle ψ with respect to the Y direction of the beam 131, and the amount of discrepancy L at the X position on the XZ plane between the red line 136 and the red line 137. Thus, D = Lcotψ can be calculated. The discrepancy amount L is a difference between the X position of the intersection of the hexagon of the head 4 and the red line 136 and the X position of the intersection of the hexagon of the head 4 and the red line 137. In this manner, the depth D of the head hole 6 is measured optically in a non-contact manner.

  When the head hole 6 is hexagonal, the workpiece 8 is rotated 360 degrees around the axis at intervals of 120 degrees, and the above measurement is repeated. The maximum value, the minimum value, and the average value of these measurement results are used as the depth measurement value of the head hole 6.

  Returning to FIG. 5 again, when the process of S14 is completed, the measurement using the head imaging camera 42 is completed, so the piston / cylinder mechanism 60 is operated and the X stage 58 is returned to the retracted state. Thereafter, the axial direction of the workpiece 8 and the dimensions around the axis are calculated based on the imaging data of the workpiece 8 acquired by the projection imaging camera 38.

  What is necessary for the projection shape data of the workpiece 8 imaged by the projection imaging camera 38 is data at a position where the white data changes to the black data. The workpiece 8 has a cylindrical shape on the XZ plane and a screw threaded on the male screw portion 2 and the head portion 4. Therefore, the position of transition from white data to black data in the projected shape is the apex position of the arcuate curved surface at the cylindrical edge. For this reason, it is necessary to adjust the focal position of the projection imaging camera 38 to the vertex position of the curved surface. Further, if dust or the like adheres to the curved surface, noise is generated in the projection shape data.

  The calculation of the in-focus position in S16 in FIG. 5 and the calculation of the contour data in S18 are processes performed in advance when various dimensions are calculated from the projection shape data of the workpiece 8 acquired by the projection imaging camera 38.

  The focus position calculation (S16) is executed by the function of the focus position calculation unit 114 of the arithmetic and control unit 100. Specifically, the Z stage 52 of the in-focus moving unit 50 is moved, the focal position of the projection imaging camera 38 is moved in the Z direction, and the Z position at which the transition from white data to black data is the steepest at that time. Is determined as the in-focus position. The in-focus position calculation process is a so-called auto-focus process, but the general auto-focus is in-focus on the surface of the object. In the in-focus position calculation in S16, the projection shape data is converted from white data to black. In the edge region where the data transitions, the position for focusing on the curved surface of the workpiece 8 is calculated.

FIG. 8 is a diagram illustrating a method for calculating the in-focus position. FIG. 8A is a diagram showing a projected state of the contour of the workpiece 8, and FIG. 8B is a diagram showing a captured monochrome state when the focal position of the projection imaging camera 38 is A to E. ) Is a diagram showing a change in the black and white state by a change of the gradation value I, (d) is a diagram showing a differential waveform with respect to the Z position of the gradation value I, and (e) is a waveform of the waveform of (d). it is a diagram showing a relationship Z position of the half-width [Delta] Z _0.5.

  FIG. 8A is a diagram showing a relationship among the light source 36, the projection imaging camera 38, and the workpiece 8 in a plane parallel to the XZ plane. The parallel rays from the light source 36 are blocked by the work 8, and a shadow area 140 is generated on the downstream side of the work 8. When this shadow area is imaged by the projection imaging camera 38, black data is obtained. A black and white boundary 142 transitioning from white data to black data is indicated by a line in contact with the curved surface of the workpiece 8. When the projection imaging camera 38 is moved in the ± Z direction with respect to the workpiece 8, the focal position of the projection imaging camera 38 moves in the ± Z direction corresponding to the movement distance. FIG. 8A shows the focal positions A, B, C, D, and E on the curved surface of the workpiece 8 when the amount of movement in the Z direction of the projection imaging camera 38 is changed to five.

  FIG. 8B is a diagram illustrating a black and white state on the imaging surface captured by the projection imaging camera 38 when the focal position of the projection imaging camera 38 is A to E. The black and white state is a state where the shaded state is completely black, a state represented by a set of fine dots is neither completely black nor completely white, or a state where there is neither a shaded line nor a set of fine dots is a completely white state It is. When the focal position is on the downstream side of the work 8 when viewed from the light source, it is indicated that the black and white boundary 142 is not completely white or completely black. When the focal position is on the upstream side of the workpiece 8, since the focal point is not focused on the workpiece 8, the whole is neither completely white nor completely black.

  FIG. 8C is a diagram showing the change in the monochrome state of FIG. The horizontal axis is the Z position, and the vertical axis is the gradation value I. When the focus position is C, the gradation value I changes rapidly with respect to the change in the Z position, but at other focus positions, the change in the gradation value I with respect to the change in the Z position becomes gradual.

FIG. 8D is a diagram showing a differential waveform of the gradation value I with respect to the Z position in order to clarify the degree of change of the gradation value I with respect to the change of the Z position. The horizontal axis is the Z position, and the vertical axis is dI / dZ. The change in the gradation value I is indicated by a pulse waveform. The larger the peak value of the pulse waveform and the smaller the half-value width ΔZ _0.5 of the pulse waveform, the greater the change in the gradation value I.

FIG. 8E is a diagram showing the relationship of the half-value width ΔZ _0.5 of the waveform of FIG. The horizontal axis is the Z position, and the focal positions A, B, C, D, and E of the projection imaging camera 38 are also provided for reference. The vertical axis is ΔZ _0.5 . Here, ΔZ _0.5 is the minimum value at the focal position C. If the reciprocal of ΔZ _0.5 or the peak value of the pulse-like waveform in (d) is used as the evaluation function for focusing, the Z position Z _{0 at} which the value of the evaluation function takes the maximum value is calculated, whereby the projection imaging camera 38 is obtained. The in-focus position can be calculated. In the case of FIG. 8E, the Z position when the focal position is C is Z ₀ . The position of the Z stage 52 is fixed in a state where the Z position of the projection imaging camera 38 is the Z position Z ₀ .

  Returning to FIG. 5 again, the contour data calculation (S18) process is executed by the function of the contour data calculation unit 116 of the arithmetic and control unit 100. Specifically, the contour tracking process is performed using the black-and-white boundary of the projection shape data of the workpiece 8 as the contour of the projection shape of the workpiece 8 to calculate primary screw contour profile data. Then, a secondary screw contour profile is calculated by performing a smoothing process for removing data that becomes abnormal when viewed from the cross-sectional pattern of the workpiece 8 as noise. The noise-removed screw contour profile is used as contour data for subsequent calculation of various dimensions.

  FIG. 9 is a diagram illustrating a noise removal method for a contour profile. FIG. 9A is a diagram illustrating a rule of the contour tracking process. (B) is the data of the primary screw contour profile obtained by performing the contour tracking process on the workpiece 8, and (c) is a diagram showing the contour data obtained by removing noise from (b).

  In the contour data calculation, in order to increase the resolution of the contour data, the projection shape data of the workpiece 8 imaged by the projection imaging camera 38 is converted into bitmap two-dimensional data having an arbitrary position resolution. For example, if the pixel resolution on the imaging surface of the projection imaging camera 38 is about 8 μm, one pixel is divided into 8 × 8 sub-pixels and converted into a two-dimensional bitmap with a position resolution of 1 μm. In this way, a two-dimensional bitmap having a sufficient position resolution can be obtained. In the following, contour tracking processing and noise removal processing are performed using data of the two-dimensional bitmap.

  FIG. 9A is a diagram illustrating a rule of the contour tracking process. The contour tracking process is a process for tracking a black-and-white boundary in a two-dimensional bitmap. The rule for the contour tracking process is a rule for determining the order in which the next black data is searched from one black data position. The binarization process for distinguishing between black data and white data is performed using a predetermined threshold for the gradation value of the data.

  FIG. 9A is a diagram showing a known rule for the contour tracking process. This rule sequentially determines whether or not the black data is counterclockwise for the eight data positions around the position of one black data, and the first black data position is determined as the next black data position. To do. Numbers 1 to 8 in FIG. 9A indicate a tracking order for searching for the next black data from the position of the first black data, and the tracking is sequentially performed from the position of the number 1 to the position of the number 8.

  FIG. 9B is a diagram in which the projection shape data of the work 8 is converted into two-dimensional bitmap data and the position of the black data at the black and white boundary is connected by applying the contour tracking processing rule of FIG. is there. A bent line 144 shows the trace of the tracking process. The shaded data position is the black data position of the black-and-white boundary, and the result of connecting this is the primary screw profile.

  First, scanning is performed to search for the presence or absence of black data in the right direction from the upper left position of the two-dimensional bitmap. Here, the first black data is detected by the scanning of the second row from the top. This is the position 145 of the first black data. The eight data positions around the black data position 145 are searched for the next black data position according to the rule (a). In the example of (b), the data position obliquely below the black data position 145, and the fourth data position in the tracking order shown in (a) is the position of the next black data. This is repeated, and contour tracking ends when the end of the two-dimensional bitmap is reached.

  In FIG. 9B, the bent line 144, which is the locus of the tracking process, returns backward at the black data positions 146, 148, 150. Since the contour shape of the workpiece 8 changes smoothly even in the external thread portion 2, these three black data positions 146, 148, and 150 have a high possibility of noise due to the presence of dust and the like, and the cross-sectional shape of the screw. It is judged abnormal from

  FIG. 9C shows that the contour shape of the workpiece 8 is considered to be normal by performing a smoothing process for removing the three black data positions 146, 148, and 150 that are judged to be abnormal when viewed from the cross-sectional shape of the screw. It is the figure which produced | generated the next screw profile profile. The bent line 152 is a tracking track of a monotonous change with no backtracking. Here, the presence / absence of backtracking in the bent line 144 indicating the locus of contour tracking is used as a noise judgment criterion. Instead of the presence or absence of backtracking, the degree of change in the direction of the bent line 144 may be used as a noise determination criterion. In addition, when the actual tracking trajectory is normalized with the tracking trajectory of the contour shape considered normal, the difference between the tracking trajectory of the contour shape considered normal and the tracking trajectory of the actual contour shape exceeds a predetermined threshold range. A noise judgment criterion for noise may be used.

  In this way, smoothing processing for removing noise is performed by applying a predetermined noise judgment criterion to contour profile data obtained by known contour tracking processing, and contour data indicating the thread contour profile of the workpiece 8 is calculated. be able to.

When the processes of S16 and S18 are completed, various dimension measurements are performed using the projection shape data of the workpiece 8 acquired by the projection imaging camera 38. Since the workpiece 8 has a shape extending in the Y direction, it is efficient to sequentially measure the size of the workpiece 8 while lowering the projection imaging camera 38 in the −Y direction from the initial Y position. Therefore, following the head dimension measurement (S12) and the head hole depth measurement (S14), the height dimension of the head 4 is performed based on the projection shape data acquired by the projection imaging camera 38. This measurement is performed as part of the total length calculation (S26) described later. Specifically, as shown in FIG. 6, the Y position Y _{10 on} the upper surface of the head 4 and the Y position Y ₉ on the lower surface are measured.

Here, the operation of the Y motor 29 is controlled so that the contour data indicating the upper surface of the head 4 enters the imaging surface of the projection imaging camera 38, and the data value of Y ₁₀ is acquired by the sensor 30. Next, the position of the contour data of the upper surface of the head 4 acquired by the projection imaging camera 38 for each angle in the Y direction is obtained on the two-dimensional bitmap while rotating the work 8 360 degrees around the axis at intervals of 1 degree. For example, a precise value of Y ₁₀ is calculated in units of 1 μm. For each angle, the precise value of the calculated Y _10, the maximum value and the minimum value and the average value, this adds the data values from the sensor 30, the maximum value of Y _10, the minimum value, the average value And

Similarly, with respect to the lower surface of the head 4, data from the sensor 30 is acquired, and then the contour data of the lower surface of the head 4 acquired by the projection imaging camera 38 while rotating the work 8 around the axis at intervals of 1 degree. Is obtained on a two-dimensional bitmap, and for example, a precise value of Y ₉ is calculated in units of 1 μm. For each angle, the maximum value, minimum value, and average value of the calculated precise value of Y ₉ are obtained, and the data value from the sensor 30 is added to this value to obtain the maximum value, minimum value, and average value of Y _9. Value.

  When the measurement of the height dimension of the head 4 is completed, the Y stage 26 is further lowered in the Y direction, and the lower neck R measurement (S20) is performed. The lower neck R is a radius of curvature at the lower neck between the head 4 and the external thread 2. This process is executed by the function of the lower head R calculation unit 118 of the arithmetic and control unit 100. Specifically, the contour data of the lower neck 3 of the workpiece 8 acquired by the projection imaging camera 38 is obtained on the two-dimensional bitmap using the method described with reference to FIG. This is shown as S20 for the lower neck portion 3 of the workpiece 8 in FIG. An angle dividing line that bisects the angle formed by the two straight lines on both sides of the R portion of the contour data is obtained, and the length of the perpendicular line drawn from the two lines to the previous two straight lines is calculated as the lower neck R. .

  FIG. 10 is a diagram illustrating a method of calculating the lower neck R. FIG. 10A is a diagram showing the contour data 160 on the two-dimensional bitmap of the neck 3 of the work 8. In FIG. 10B, two straight lines 162 and 163 constituting the contour data 160 of FIG. 10A are obtained, and an angle dividing line 164 that bisects the angle formed by the two straight lines 162 and 163 is obtained. It is a figure which shows the perpendicular lines 166 and 167 which respectively dropped from this angle division line 164 to the straight lines 162 and 163. FIG.

  Based on the lengths of the perpendicular lines 166 and 167, the value of the neck R is calculated. That is, the workpiece 8 is rotated 360 degrees around the axis at intervals of 1 degree, and the lengths of the perpendicular lines 166 and 167 are obtained for each angle. Since 360 degrees are obtained at intervals of 1 degree, a total of 720 vertical length values are obtained. The maximum value, the minimum value, and the average value of the obtained values are set as the value of the lower neck R.

Returning to FIG. 5 again, next to S20, peak diameter measurement (S22) and valley diameter measurement (S24) are performed. The thread diameter is the outer diameter dimension of the thread, and the valley diameter is the inner diameter dimension of the thread valley. This process is executed by the function of the screw diameter calculation unit 110 of the arithmetic and control unit 100. The mountain diameter measurement (S22) and the valley diameter measurement (S24) are performed at a plurality of locations along the axial direction of the external thread portion 2 of the workpiece 8. In FIG. 6, the three Y positions Y ₈ , Y ₇ and Y ₆ where the peak diameter measurement (S22) and the valley diameter measurement (S24) are performed are shown as S22 and S24. The number of measurement locations can be determined as appropriate depending on the length of the external thread 2 of the workpiece 8.

  FIG. 11 is a diagram showing a method for measuring a mountain diameter. FIGS. 11A and 11C are diagrams showing contour data of the male thread portion 2 of the workpiece 8 on the two-dimensional bitmap, and FIG. 11B is an enlarged view of a part of FIG.

  FIG. 11A shows two contour data 170 and 171 of the male thread portion 2 of the workpiece 8. The two contour data 170 and 171 are data indicating contour shapes on both the left and right sides of the male thread portion 2 of the workpiece 8. (B) is a partially enlarged view of (a), and shows a method of obtaining a regression line 172 of the peak portion of the contour data 170 using this. The peak regression line 172 is a straight line that passes through the average position of the plurality of peak vertices of the male thread 2.

  When the regression line 172 is obtained, peak vertices on the outer diameter side of the regression line 172 are obtained for the entire contour data 170. This obtains a line 173 perpendicular to the regression line 172 and moves the position of the regression line 172 along the direction in which the vertical line 173 extends. Then, the maximum value a of the movement amount of the regression line 172 caught on at least one peak of the contour data 170 is obtained. The amount of movement is measured along a line 173 perpendicular to the regression line 172. “a” is a value indicating the position of the peak portion on the outermost diameter side in the contour data 170 when viewed from the regression line 172.

  Next, as shown in FIG. 11C, the regression line 172 is moved to the contour data 171 side along the line 173 perpendicular to the regression line 172, and the regression lines 172 caught on a plurality of peak vertices in the contour data 171 are obtained. The maximum value b of the movement amount is obtained. “b” is a value indicating the position of the peak portion on the outermost diameter side in the contour data 171 when viewed from the regression line 172. Since the ridge diameter is the outer diameter of the ridge portion of the male thread portion 2 of the work 8, (a + b) corresponds to the value of the ridge diameter for the two contour data 170 and 171 of the male thread portion 2 of the work 8.

  Here, the workpiece 8 is rotated 360 degrees around the axis at intervals of 1 degree, and (a + b) of two contour data at each angle is obtained. When 360 (a + b) values are obtained, the maximum value, the minimum value, and the average value are taken as the measured values of the peak diameter at the measurement location. The ridge diameter is calculated for each of the three measurement points as shown in FIG. The positions of the three measurement points are set so as to substantially cover the entire length of the male thread portion 2 of the workpiece 8. The number of measurement points may be other than three. For example, it may be 4 or more, or 2 or less.

  FIG. 12 is a diagram illustrating a method for measuring a valley diameter. Similarly to FIG. 11, FIGS. 12A and 12C are diagrams showing the contour data of the male thread portion 2 of the workpiece 8 on the two-dimensional bitmap, and FIG. 12B is an enlarged view of a part of FIG. FIG. FIG. 12A shows the same two contour data 170 and 171 as FIG. The trough measurement is similar to the crest measurement, and the regression line 176 shown in FIG. 12B is a straight line passing through the average position at a plurality of trough bottom points of the external thread portion 2.

  When the regression line 176 is obtained for the valley, as shown in FIG. 12B, the position of the valley bottom point located on the inner diameter side of the regression line 176 is obtained for the entire contour data 170. This obtains a line 177 perpendicular to the regression line 176 and moves the position of the regression line 176 along the direction in which the vertical line 177 extends. Then, the maximum value c of the amount of movement of the regression line 176 caught on at least one valley bottom point in the contour data 170 is obtained. The amount of movement is measured along a line 177 perpendicular to the regression line 176. c is a value indicating the position of the bottom of the valley that is closest to the inner diameter side in the contour data 170 when viewed from the regression line 176.

  Next, as shown in FIG. 12C, the regression line 176 is moved to the contour data 171 side along the line 177 perpendicular to the regression line 176, and the regression line 176 is caught on at least one valley bottom point in the contour data 171. The maximum value d of the movement amount is obtained. d is a value indicating the position of the valley bottom point that is closest to the inner diameter side in the contour data 171 when viewed from the regression line 176. Since the valley diameter is the minimum inner diameter at the valley portion of the workpiece 8, (dc) corresponds to the valley diameter value for the two contour data 170, 171 of the male thread portion 2 of the workpiece 8.

  Here, the workpiece 8 is rotated 360 degrees around the axis at intervals of 1 degree, and (dc) of two contour data at each angle is obtained. When 360 (d−c) values are obtained, the maximum value, the minimum value, and the average value are taken as the measured values of the valley diameter at the measurement location. The valley diameter measurement is performed as a pair with the mountain diameter measurement, and the measurement location of the valley diameter is the same as the measurement location of the mountain diameter.

  When the measured value of the peak diameter and the measured value of the valley diameter are calculated, the effective diameter = (peak diameter + valley diameter) / 2 is calculated. For the effective diameter, the maximum value, minimum value, and average value are calculated. The maximum value is calculated from the maximum value of the peak diameter and the minimum value of the valley diameter, the minimum value is calculated from the minimum value of the peak diameter and the maximum value of the valley diameter, and the average value is the average value of the peak diameter and the valley diameter. Calculated from the average value of Various calculations related to the effective diameter may be performed using other calculation methods.

S22, the S24 measurements is completed, further lowers the Y stage 26, the measurement of the Y-position Y ₁ of the upper surface of the ring gauge 82a of the adapter 80 for gripping the leading end portion of the male screw portion 2 of the workpiece 8 is carried out. Specifically, it can be performed in the same procedure as the measurement of the Y position Y _{10 on} the upper surface of the head 4 and the Y position Y ₉ on the lower surface which has already been described. That is, the operation of the Y motor 29 is controlled so that the contour data indicating the upper surface of the ring gauge 82 a enters the imaging surface of the projection imaging camera 38, and the data value of Y ₁ is acquired by the sensor 30. Next, the position in the Y direction of the contour data of the upper surface of the ring gauge 82a acquired by the projection imaging camera 38 is obtained on the two-dimensional bitmap while rotating the work 8 around the axis by 360 degrees at intervals of 1 degree, for example, 1 μm Calculate the precise value of Y ₁ in units. The maximum value, the minimum value, and the average value are obtained for the calculated precise value of Y ₁ for each degree, and the data value from the sensor 30 is added to this, and the maximum value, minimum value, and average value of Y ₁ are calculated. To do.

Returning again to FIG. 5, next, the total length calculation (S26) is performed. This process is executed by the function of the total length calculation unit 112 of the arithmetic and control unit 100. Specifically, the predetermined measured lengths of the Y positions Y ₁₀ , Y ₉ , Y ₁ and the predetermined internal engagement length between the reference female thread 83a of the ring gauge 82a and the tip of the male thread 2 of the work 8 are measured. The total length of the workpiece 8 is calculated based on the length of 3 pitches = 5.25 mm. The total length of the male thread portion 2 is calculated as {(Y ₉ −Y ₁ ) +5.25 mm}. The total length of the workpiece 8 including the head 4 is calculated as {(Y ₁₀ −Y ₁ ) +5.25 mm}. In the total length calculation, the maximum value, minimum value, and average value of the total length are calculated based on the maximum value, minimum value, and average value of Y ₁₀ , Y ₉ , and Y ₁ . For example, the maximum value of the total length of the external thread portion 2 is calculated from the maximum value of Y ₉ and the minimum value of Y _1. The average value of the total length of the external thread portion 2 is the average value of Y _{9 and} the average value of Y ₁ . Calculate from Various calculations relating to the total length may be performed using other calculation methods.

  When the total length calculation (S26) ends, measurement data output (S28) of various dimensions of the workpiece 8 is performed. This process is executed by the function of the measurement data output unit 124 of the arithmetic and control unit 100. Specifically, various dimensions obtained by S12 head dimension measurement, S14 head hole depth measurement, S20 neck R measurement, S22 peak diameter measurement, S24 valley diameter measurement, and S26 total length calculation. The maximum value, minimum value, average value, etc. are entered in a predetermined entry location according to a predetermined inspection table format, printed out as an inspection table 106 from the output device 104, and output.

  Thus, according to the screw dimension automatic measurement system 10, various dimensions relating to the screw can be automatically measured, and the measurement result can be automatically output as an inspection table in a predetermined format.

  In the above description, the head hole depth is measured optically in a non-contact manner. Instead, although it is a contact type, the head hole depth can be measured using a head hole bit for screw inspection. In FIG. 13, a head hole bit 180 is inserted into the workpiece 8 in the head hole 6 of the workpiece 8, the state is imaged by the projection imaging camera 38, and the head hole depth D is acquired based on the acquired projection shape data. It is a figure which shows the method of calculating. FIG. 13A is a cross-sectional view, and FIG. 13B is a top view.

  The head hole bit 180 for screw inspection includes a head hole fitting portion 182, a disk-shaped flange portion 184, a gripping cylindrical portion 186, and a conical top portion 188. In order to insert the head hole bit 180 into the head hole 6 of the work 8, the collar 184 and the gripping cylindrical part 186 are gripped by a split chuck or the like and conveyed above the head hole 6. This can be done by releasing the split chuck or the like and dropping the head hole bit 180. When the head hole bit 180 is dropped into the head hole 6 of the work 8, it is preferable to push the head hole bit 180 from the upper side to the lower side. The gripping and releasing of the head hole bit 180 of the split chuck and the pushing of the cone top portion 188 may be automatically performed by using a piston / cylinder mechanism operated by air pressure supplied from the pneumatic control device 102. Is possible.

  The height G and the shape of the head hole fitting portion 182 of the head hole bit 180 are changed depending on the type of the workpiece 8. The dimensions and shapes of the other flange portion 184, the gripping cylindrical portion 186, and the conical top portion 188 can be the same regardless of the type of the workpiece 8.

The state in which the head hole bit 180 is inserted into the head hole 6 of the workpiece 8 is imaged by the projection imaging camera 38, and the upper surface of the head of the workpiece 8 and the wrinkles of the head hole bit 180 are based on the contour data. The distance dimension Y ₂ along the Y direction between the lower surface of the portion 184 can be calculated. Based on the calculated distance dimension Y ₂ and the height dimension G of the head hole fitting portion 182 of the head hole bit 180, the head hole depth dimension D = (G−Y ₂ ) can be calculated.

  FIG. 14 is a diagram showing different head hole bits depending on the type of the workpiece 8. Here, the head hole bits corresponding to the types of the three workpieces 8 are shown, but the head hole bits of other types of workpieces 8 other than this can also have the same structure. FIG. 14A shows the case where the thread of the workpiece 8 is called M12, which is the same as the head hole bit 180 described in FIG.

  FIG. 14B is a diagram showing the head hole bit 180b when the nominal thread name of the workpiece 8 is M6. The flange portion 184, the gripping cylindrical portion 186, and the conical top portion 188 are the same as (a). What is different from (a) is the shape and dimensions of the head hole fitting portion 182b. FIG. 4C is a view showing the head hole bit 180c when the nominal thread of the workpiece 8 is M3. The flange portion 184, the gripping cylindrical portion 186, and the conical top portion 188 are the same as (a) and (b). The difference from (a) and (b) is the shape and dimensions of the head hole fitting portion 182c.

  In this way, by sharing the shape and dimensions of the elements other than the head hole fitting portion 182, the split chuck or the like that grips the head hole bits 180, 180 b, 180 c can be used regardless of the type of the workpiece 8. It can be used in common.

  FIG. 15 is a front view of a main part of an automatic screw size measuring device 12a constituting an automatic screw size measuring system of another example of the embodiment. FIG. 16 is a right side view of the screw dimension automatic measuring device 12a of FIG. FIG. 17A is a top view of the screw dimension automatic measuring device 12a, showing a state in which the head imaging camera 42 is retracted to the right side, and FIG. 17B is a diagram illustrating the head imaging camera 42 at the imaging position. It is a top view which shows the state moved. FIG. 18 is a top view of the screw dimension automatic measuring device 12a, in which the head imaging camera 42 is omitted.

  In another example of the automatic thread dimension measurement system, the basic configurations of the vibration isolator 14, the casing 15, the base 16, the arithmetic control device 100, the pneumatic control device 102, and the output device 104 (see FIG. 1) are as follows: The configuration is the same as that shown in FIGS. A screw dimension automatic measuring device 12a constituting a screw dimension automatic measuring system of another example is a gantry type. Specifically, a pillar member 190 having a quadrangular prism is erected and fixed to the upper surface plate 16a that forms the upper surface of the base 16 of the screw dimension automatic measuring device 12a. As shown in FIG. 17, the pillar member 190 has a substantially rectangular shape when viewed from the Y direction. A lift actuator 192 is attached to the front surface of the column member 190 (the front side surface in FIG. 15, the left side surface in FIG. 16, the lower side surface in FIG. 17A).

  The lift actuator 192 includes an actuator case 194 fixed to the front surface (+ X direction side) of the column member 190, a screw shaft (not shown), a Y motor 29a, and a nut member (not shown). The actuator case 194 has a long shape along the Y direction which is the vertical direction. The case of the Y motor 29a is fixed to the upper surface of the actuator case 194, and the screw shaft extends in the actuator case 194 along the -Y direction to the output shaft extending downward (-Y direction) from the Y motor 29a. The actuator case 194 is rotatably supported. Thereby, the screw shaft is rotated by the rotation of the Y motor 29a. The driving of the Y motor 29a is controlled by the arithmetic and control unit 100 (FIG. 1). On the −X side (the back side in FIG. 15, the left side in FIG. 16, the upper side in FIG. 17A) of the column member 190, an elevating member 212 that forms a bit gripping unit 210 described later is supported to be movable in the Y direction. The

  Two guide holes 195 that are substantially parallel to the entire length along the Y direction are formed at both ends in the Z direction on the front side (+ X side) of the actuator case 194. A Y table 196 is supported by the actuator case 194 so as to be movable in the Y direction. The Y table 196 is a substantially flat moving table along the YZ plane. In FIG. 15, the Y table 196 is shown in sand for easy understanding.

  The nut member in the actuator case 194 meshes with the threaded portion of the screw shaft via a plurality of balls to constitute a ball screw mechanism. Two parallel slide legs 198 (FIG. 17A) are formed at both ends of the nut member in the Z direction. Each slide leg 198 protrudes outward from the actuator case 194 through the guide hole 195. A Y table 196 is fixed to the tip of each slide leg 198. Thus, the Y table 196 is moved along the Y direction by the rotation of the Y motor 29a. The lift actuator 192 constitutes an axial movement unit that moves the Y table 196 in the Y direction with respect to the base 16.

  Further, as shown in FIG. 16, a linear scale type position sensor 200 is attached to the + Z side end of the actuator case 194. That is, the position sensor 200 detects the position of the Y table 196 in the Y direction. The position sensor 200 may detect the position of the moving member 202 attached to the Y table 196 in the Y direction with high accuracy, either optically or magnetically. For example, in the magnetic position sensor 200, an excitation coil for passing current and a detection coil are attached to the moving member 202, and fixed coils (not shown) are arranged at a plurality of positions in the Y direction of the fixed member 204 fixed to the actuator case 194. ) Is arranged. When the moving member 202 moves in the Y direction, the excitation coil and the detection coil of the moving member 202 are in close proximity to one of the plurality of fixed coils, and the position of the moving member 202 is determined from the voltage change at both ends of the detection coil. Detected. A signal indicating the detection position of the moving member 202 is transmitted to the arithmetic and control unit 100 (FIG. 1).

  An optical measuring device 32a is supported on the front (+ X direction) side of the Y table 196. The optical measurement device 32a includes an image projection unit 34a and a head measurement unit 40a. The image projection unit 34a is fixed to the front side of the Y table 196 and is long in the Z direction, the light source 36 fixed to the −Z side end of the lower fixing table 230, and the lower fixing table. 230 and a projection imaging camera 38 supported by the + Z side end portion.

  A Z movement table 232 is supported on the lower fixed table 230 so as to be movable in the Z direction. The Z movement table 232 is moved in the Z direction with respect to the lower fixed table 230 by the linear actuator 234. The linear actuator 234 includes an electric motor and a ball screw mechanism, and moves a nut member engaged with the screw shaft of the ball screw mechanism via the ball in the Z direction by the rotation of the electric motor. The Z movement table 232 is fixed to the nut member, and the Z movement table also moves in the Z direction when the nut member moves in the Z direction. The electric motor is controlled by the arithmetic and control unit 100. Thereby, the projection imaging camera 38 moves in the + Z direction or the −Z direction by the rotation of the electric motor. The linear actuator 234 and the Z movement table 232 constitute the focusing movement unit 50. The projection imaging camera 38 and the light source 36 oppose each other in the Z direction with a workpiece 8 that is an imaging target screw interposed therebetween. An AC servo motor or a stepping motor can be used as the electric motor constituting the linear actuator.

  The workpiece 8 is screwed into the ring gauge 82 c of the adapter 80 in the same manner as the configuration of FIGS. 1 to 13, and the adapter 80 is held by the tightening chuck 70. The support base 72 of the clamping chuck 70 is fixed to the upper side of the rotating member 236 that extends in the vertical direction with respect to the base 16.

  The rotary member 236 is supported by a rotary joint 238 having a lower end fixed to the base 16 so as to be rotatable around the Y axis. The pulley 240 fixed to the intermediate portion in the Y direction of the rotating member 236 and the output shaft of the θ motor 64 fixed to the lower side of the upper surface plate 16a of the base 16 in the + Z direction (right side in FIG. 15) are fixed. A belt 244 is wound around the pulley 242. Accordingly, the rotation member 236 is rotated through the belt 244 by the rotation of the θ motor 64, and the fastening chuck 70 rotates around the Y axis together with the workpiece 8. Any configuration may be used as long as the support base 72 can be rotated.

  The projection imaging camera 38 receives the parallel rays from the light source 36 and forms an image on the imaging plane parallel to the XY plane for imaging the projection shape that is a shadow of the work 8.

  The head measuring unit 40a disposed above the workpiece 8 includes an upper fixed table 250 fixed to the upper side of the lower fixed table 230 on the front side (+ X side) of the Y table 196, and the front surface of the upper fixed table 250. A head camera moving unit 252 attached to the side and a head imaging camera 42 are provided. The head camera moving unit 252 includes a rod part 254 with the head imaging camera 42 fixed to the tip part, and a piston / cylinder mechanism 256 that expands and contracts the rod part 254 in the Z direction. The piston / cylinder mechanism 256 is controlled by the arithmetic and control unit 100 (FIG. 1), and can reciprocate the piston in the Z direction by the air pressure supplied from the pneumatic control unit 102 (FIG. 1). The rod portion 254 is fixed to the piston. When the piston moves in the -Z direction, the head imaging camera 42 also moves in the -Z direction. When the piston moves in the + Z direction, the head imaging camera 42 also + Z. Move in the direction. As a result, the head imaging camera 42 has at least a position retracted in the + Z direction from the position P of the work 8 on the XZ plane as shown in FIG. 17A and a position P of the work as shown in FIG. It is possible to move between two positions with the position directly above.

  The head imaging camera 42 acquires the imaging data of the shape of the head of the workpiece 8 in the same manner as the configuration shown in FIGS. 1 to 12, and the diameter dimension of the head and the head hole 6 (see FIG. 3). Calculate the width across flats. Unlike the configuration shown in FIGS. 1 to 12, the head measurement unit 40 a does not include a laser light source for measuring the head hole depth of the workpiece 8 or an actuator for moving the laser light source. Instead, the automatic screw dimension measuring device 12a includes a bit gripping unit 210 that grips and moves the head hole bit 180 (FIG. 19).

  FIG. 19 is a diagram showing the bit gripping unit 210 in the left side view of FIG. As shown in FIGS. 15, 17, and 19, the bit gripping unit 210 is attached to the −Z side of the column member 190 (the left side of FIGS. 15 and 17A, the front side of FIG. 19) and is in the Y direction. A long guide member 214 and an elevating member 212. In FIG. 19, the column member 190 and the elevating actuator 192 are not shown.

  The elevating member 212 is supported so as to be movable in the Y direction on the −Z side of the guide member 214. A telescopic arm 216 that can expand and contract in the X direction is attached to the elevating member 212. The telescopic arm 216 is expanded and contracted by a piston / cylinder mechanism 218. Air pressure to the piston / cylinder mechanism 218 is controlled by the pneumatic control device 102 (FIG. 1). A bit gripping portion 220 is attached to the distal end portion of the telescopic arm 216 so as to face the upper surface of the work 8. The bit gripping part 220 is a two-part chuck having two claw parts 221 at the lower end part. The two claw portions 221 are operated by the air pressure supplied from the pneumatic control device 102 and move in the radial direction of the bit gripping portion 220. The two claw portions 221 have a function of gripping the head hole bit 180 (FIG. 19) for measuring the head hole depth of the work 8 and releasing the grip of the head hole bit 180 above the work 8. The head hole bit 180 is dropped toward the head hole 6 (see FIG. 3).

  As shown in FIG. 19, the elevating member 212 is fixed to the distal end portion of the upper and lower rods 222 supported by the base 16. The upper and lower rods 222 are provided along the Y direction and are displaced in the Y direction by the piston / cylinder mechanism 224. The piston / cylinder mechanism 224 is controlled by the pneumatic control device 102. As a result, the pneumatic control device 102 controls the air pressure applied to the piston / cylinder mechanisms 218, 224 and the bit gripping part 220 of the bit gripping unit 210, so that the bit gripping part 220 is in a predetermined position at the head hole bit 180. Can be moved to a predetermined position in the X and Y directions, and the head hole bit 180 can be released above the workpiece 8 and dropped into the head hole 6.

  In the bit gripping unit 210, a laser light source is attached to the tip of the telescopic arm 216 to form a laser irradiation unit, and the laser light is irradiated from the laser light source toward the head from an oblique upper side of the head of the work 8. Good. For this purpose, the bit gripping part 220 of the bit gripping unit 210 is preferably configured to be exchangeable with a laser irradiation member including a laser light source.

According to said structure, the projection imaging camera 38 can be moved to the desired position of a Y direction and a Z direction, and the head imaging camera 42 can also be moved to the desired position of a Y direction and a Z direction. Further, the axial direction of the workpiece 8 and various dimensions around the axis can be automatically measured only by setting the workpiece 8 as a screw on the gripping portion 68 including the adapter 80 and the fastening chuck 70. Similarly to the processing of S18 of FIG. 5 described above, after the contour data is calculated by the contour data calculation unit 116 of the arithmetic and control unit 100, the height of the workpiece 8 is measured when the projection imaging camera 38 is measured. Y-direction position calculated from the contour data, for example, the maximum and minimum values of the Y ₁₀ and the average value, it adds the detected data of the high accuracy of the position sensor 200. Thereby, the dimension of the workpiece 8 in the height direction can be measured with higher accuracy. Other configurations and operations are the same as those shown in FIGS.

  On the other hand, in the configuration of FIGS. 1 to 12 or the configuration of FIGS. 15 to 19, when measuring a dimension around the Y axis of the workpiece 8, for example, a peak diameter and a valley diameter, foreign matter adheres as described below. In consideration of this, measurement can be performed with higher accuracy. FIG. 20 is a diagram showing a method for calculating a crest diameter at a predetermined angle after calculating contour data in a screw dimension automatic measurement system according to another example of the embodiment of the present invention, and is an enlarged view of FIG. It is. FIG. 21A is a diagram showing the measurement data of the crest diameter dmax and the trough diameter dmin at a predetermined angle by a curve, and shows the relationship with the angle θ, and FIG. 21B is the axis of the workpiece 8 that is a screw. It is sectional drawing of the one part direction. FIG. 22 shows the relationship between the measurement data of the peak diameter dmax and the number of measurement data at a predetermined angle in the case of an ideal model (a), and in the case of excluding measurement data outside a predetermined range in one example (b). FIG.

  As shown in FIG. 20, when calculating the crest diameter dmax and the trough diameter dmin of the work 8, after calculating the two contour data 170, 171 of the work 8 at a certain angle around the Y axis of the work 8, the above-mentioned FIG. 12, the crest diameter dmax and the trough diameter dmin of the work 8 are calculated at a plurality of positions in the Y direction that is the axial direction of the male thread portion 2 of the work 8. At this time, the peak diameter dmax (= a + b) of the contour data 170 and 171 is obtained from the regression lines 172 and 174 caught on the apexes of the peak portions of the two contour data 170 and 171 as described above. Further, a measured value of the peak diameter dmax is obtained at predetermined angular intervals around the Y axis of the workpiece 8, for example, at intervals of 1 degree. Similarly, a measured value of the valley diameter dmin is obtained from a regression line that catches the bottom of the valley of the contour data 170, 171.

  At this time, regarding the peak diameter dmax and the valley diameter dmin, when the maximum value, the minimum value, and the average value are obtained from the entire measurement data group for each angle at a predetermined angle interval, foreign matter adheres to the workpiece 8. A large error may occur. Specifically, as shown in FIG. 21B, there is a possibility that foreign matters 11 such as dust and dust may adhere to the male thread portion 2 of the work 8. In FIG. 21 (a), the peak diameter dmax and the valley diameter dmin are shown on the vertical axis, and the rotation angle θ around the Y axis of the workpiece 8 at the time of measurement is shown on the horizontal axis. At this time, an error greatly deviating from the average values da and db of all the measurement data of the peak diameter dmax and the valley diameter dmin as shown by the portions surrounded by the alternate long and short dash lines Q1 and Q2 based on the adhesion of the foreign matter 11 described above. Will occur. Further, in the case where the same calculation process is repeated a plurality of times to obtain the peak diameter dmax and the valley diameter dmin, the error of the measurement data at some angles θ is amplified and the finally calculated value greatly deviates from the true value. there is a possibility. For this reason, instead of obtaining the maximum value, the minimum value, and the average value of the peak diameter dmax and the valley diameter dmin from the entire group of measurement data for each predetermined angular interval for the peak diameter dmax and the valley diameter dmin, Perform the filtering process. The filtering process calculates a maximum value, a minimum value, and an average value of the peak diameter dmax and the valley diameter dmin by excluding some data from the group of measurement data.

  In this filtering process, first, a distribution of measurement data of an ideal model in which the foreign matter 11 does not adhere to the male thread portion 2 of the workpiece 8 is considered. At this time, as shown in FIG. 22A, when the peak diameter dmax is indicated on the horizontal axis and the number of measurement data is indicated on the vertical axis, the measurement data of the peak diameter dmax is a normal distribution. The “ideal model” can be set in advance according to the design dimension of the screw to be measured. On the other hand, in one example in which foreign matter adheres to the male thread portion 2 of the workpiece 8, the measurement data is distributed as shown in FIG. Specifically, in FIG. 22B, due to the presence of foreign matter, the average value da1 and the mode value db1 are shifted to the positive side from the average value da of the ideal model indicated by the broken line β as indicated by the solid line α. The mode value of the ideal model is the same as the average value da.

  Then, the arithmetic and control unit 100 performs, as a filtering process, an average value da of measurement data of the ideal model set in advance from a group of measurement data of the crest diameter dmax of the workpiece 8 for the contour data for each predetermined angular interval of the workpiece 8. As a reference, a part of the measurement data of the mountain diameter dmax is excluded. Then, based on the remaining group of the measurement data of the mountain diameter dmax, a value, for example, a maximum value for the mountain diameter dmax is calculated.

  Specifically, in the filtering process, the lower limit cut value, which is a lower limit threshold value for excluding some data, and the upper limit cut value, which is an upper limit threshold value, are each set based on the average value da of the ideal model as a standard deviation. Set as a range proportional to σ. At this time, as arbitrary proportional constants capable of changing K, values separated by Kσ from the average value da of the ideal model to the lower side and the upper side are the lower limit cut value (da−Kσ) and the upper limit cut value (da + Kσ), respectively. To do. For example, K is an arbitrary number such as 1.0, 1.2, or 0.7. Then, as shown in FIG. 22B, in the measurement data curve of the crest diameter dmax indicated by the solid line α, the measurement data deviating from the range from the lower limit cut value (da−Kσ) to the upper limit cut value (da + Kσ) (FIG. 22). 22 (b) is excluded. Then, based on the remaining group of measurement data, a value for the mountain diameter dmax, for example, a maximum value, a minimum value, and an average value of the mountain diameter dmax are calculated. For the valley diameter dmin, similarly to the mountain diameter dmax, an upper limit cut value and a lower limit cut value are set, and measurement data deviating from the range from the lower limit cut value to the upper limit cut value is excluded. The maximum value, minimum value, and average value of the valley diameter are calculated. Then, the arithmetic and control unit 100 causes the output device 104 (see FIG. 1) to print and output the values calculated for the peak diameter dmax and the valley diameter dmin.

  According to said structure, the value about the dimension around the Y-axis of the workpiece | work 8 can be calculated more accurately. For example, as indicated by the hatched portion in FIG. 22 (b), measurement data less than the lower limit cut value and measurement data exceeding the upper limit cut value for the peak diameter dmax are excluded. Maximum values, minimum values, and average values closer to the true value of the peak diameter dmax can be obtained. In the above description, the magnitude from the average value da to the lower limit cut value and the magnitude from the average value da to the upper limit cut value are set to the same value Kσ. However, the magnitudes may be different from each other. For example, the proportional constant may be two different values K1 and K2, the lower limit cut value may be (da−K1σ), and the upper limit cut value may be (da + K2σ). At this time, the proportionality constant K2 for the upper limit cut value may be smaller than the proportionality constant K1σ for the lower limit cut value. Further, the upper limit cut value and the lower limit cut value may be set to arbitrary values set in advance according to the design dimensions of the workpiece 8 without using the standard deviation σ for setting the upper limit cut value and the lower limit cut value.

  Further, in the example shown in FIG. 9 described above, the contour tracking process for the workpiece 8 is performed, the data judged to be abnormal is removed from the data of the two-dimensional bitmap, and the smoothing process is performed to generate the screw contour profile. Explained when to do. On the other hand, as described below, a secondary thread contour profile may be generated by performing a smoothing process by performing a low-pass filter on a primary thread contour profile of a two-dimensional bitmap.

  FIG. 23 shows the primary screw contour profile (a) of the workpiece 8 and the secondary screw contour profile (b) after the filtering process when the low-pass filter is applied to the contour data of the workpiece 8 at a predetermined angle. FIG. The primary screw profile is a locus of measurement data continuous along the axial direction of the workpiece 8.

  In FIG. 23, in the primary screw profile, the abnormal portion and noise due to the adhesion of foreign matter are removed by a low-pass filter. Specifically, the arithmetic and control unit 100 obtains the contour data from the black data at the black and white binarization boundary shown in FIG. In the contour data at predetermined angular intervals obtained when the work 8 is rotated around the Y axis, the arithmetic and control unit 100 uses the primary screw to convert the measurement data trajectory continuous along the Y direction of the work 8. Set as contour profile. Further, a smoothing process is performed by performing a low-pass filter for a predetermined frequency set in advance on the primary screw contour profile, so that a secondary screw contour profile which is contour data for each predetermined angular interval of the workpiece 8 is obtained. Ask for. Thereby, the arithmetic and control unit 100 removes abnormal portions and noise from the screw profile.

  For example, a curve indicated by a solid line γ in FIG. 23A may be obtained as a primary screw profile. In this curve γ, a high-frequency waveform curve based on noise is superimposed on a low-frequency waveform curve along the screw contour. In the curve γ, foreign matter adheres to the male screw at the portion surrounded by the alternate long and short dash line Q3, and the portion where the foreign matter adheres also has a high-frequency waveform. The arithmetic and control unit 100 leaves a waveform having a frequency equal to or lower than a predetermined frequency fA set in advance along the Y direction that is the axial direction with respect to the curve γ, and removes a waveform having a frequency exceeding the predetermined frequency fA. Do. The predetermined frequency fA is set in advance so as to be somewhat higher than the pitch of the ideal model screw based on the design dimension of the screw to be measured. As a result, a high-frequency waveform based on noise and foreign matter is removed from the primary contour profile of the curve γ, and a low-frequency smooth waveform 2 is obtained as shown by a solid line δ in FIG. The following contour profile is obtained.

  This secondary contour profile is determined according to each angle. Then, as in the configuration shown in FIG. 11, FIG. 12, or FIGS. 21 and 22, the dimensions around the Y axis of the work 8, for example, the peak diameter, the valley diameter, Maximum, minimum and average values are calculated. Then, the arithmetic and control unit 100 causes the output device 104 (see FIG. 1) to print and output the values calculated for the peak diameter and the valley diameter.

  Note that the processing by the low-pass filter shown in FIG. 23 described above performs Fourier transform on the primary contour profile, removes high frequency components exceeding the predetermined frequency fA, and then performs inverse Fourier transform to perform the process shown in FIG. Processing for obtaining a curve such as the curve δ may be used. For example, the Fourier transform can be a fast Fourier transform (FFT), and the inverse Fourier transform can be an inverse fast Fourier transform (IFFT). In the above description, the case where the low-pass filter is applied to the contour profile of the male thread portion 2 of the workpiece 8 has been described. On the other hand, when there is a part other than the male thread part 2 of the workpiece 8, for example, the contour data 160 of the lower neck R in FIG. Or can be eliminated.

  In FIG. 23, the case where the low-pass filter is performed in the Y direction in the contour profile of the workpiece 8 has been described. On the other hand, in the primary contour profile of FIG. 23 (a) or the secondary contour profile of FIG. 23 (b), a shift in the Y direction position due to a shift in the angle θ around the Y axis can be predicted. Then, a low-pass filter can be applied to the locus about the position in the X direction based on the point corrected by the predicted deviation. Specifically, the arithmetic and control unit 100, for the black data at the boundary of black and white binarization in FIG. 9 as described above, for each predetermined angular interval obtained when the work 8 is rotated around the Y axis. Are set as a primary screw profile. Then, the arithmetic and control unit 100 predicts a deviation in the Y direction based on the deviation of the workpiece 8 by a predetermined angle with respect to the contour profile at every predetermined angular interval of the workpiece 8. Then, the arithmetic and control unit 100 performs a low pass filter on the trajectory of the position in the X direction of the point predicted from the point corrected by the predicted deviation corresponding to the angle of the workpiece 8 around the Y axis. Then, by repeating this at a plurality of points of the primary contour profile, a secondary thread contour profile after filtering is generated. Furthermore, the arithmetic and control unit 100 calculates a value for the dimension around the Y axis of the workpiece 8 based on the contour profile after the filtering process. Then, the arithmetic control device 100 causes the output device 104 (see FIG. 1) to print and output the value calculated for the dimension around the Y axis.

  FIG. 24 shows a primary screw profile when the workpiece 8 is rotated by a predetermined angle when the abnormal portion in the X direction is removed by a low-pass filter when calculating the contour data of the workpiece 8 at a predetermined angle. It is a figure which shows the change of. FIG. 25A shows the locus (a) before the filter processing and the post-filter processing when the low pass filter is applied to the locus about the X direction position at a predetermined angle at some points of the contour profile of the workpiece 8. It is a figure which shows a locus | trajectory (b).

  As shown in FIGS. 24A, 24B, and 24C, consider a case where the workpiece 8 is rotated in the same direction by a predetermined angle to become angles θ1, θ2, and θ3. In this case, since the male thread portion 2 of the workpiece 8 has a spiral shape, the primary screw contour profile gradually shifts along the Y direction. In addition, the contour profile for each predetermined angle may deviate in either the X direction or the Y direction. For example, attention is paid to the vertex G3 of one mountain portion among the plurality of vertices G1, G3, G5... And the bottom points G2, G4. At this time, the deviation of the vertex G3 in the Y direction is predicted in advance as L1 and L2 based on the pitch of the screw to be measured. As a result, a vertex existing within a predetermined distance from the points G3a and G3b whose X-direction position is the same as the point G3 by correcting with the deviations L1 and L2 is predicted as the point G3 at each angle θ1 and θ2. In FIG. 24, the point G3 at each angle θ1, θ2 is shifted from the points G3a, G3b by D1, D2 in the X direction. And the locus | trajectory about the X direction position of the estimated vertex G3 is shown by (eta) 1 of FIG. The horizontal axis of Fig.25 (a) has shown rotation angle (theta) around the Y-axis of the workpiece | work 8, and a vertical axis | shaft is the X direction position of the vertex G3.

  As is clear from FIG. 25 (a), the curve η1 that is the locus of the position of the vertex G3 in the X direction has a high-frequency waveform curve based on noise superimposed on a low-frequency waveform curve. In the curve η1, the portion surrounded by the alternate long and short dash line Q4 has a high-frequency waveform due to the adhesion of foreign matter to the male thread of the workpiece 8.

  The arithmetic and control unit 100 performs a low-pass filter so as to leave a waveform having a frequency equal to or lower than a predetermined frequency fB set in advance along the Y direction with respect to the curve η1 and to remove a waveform having a frequency exceeding the predetermined frequency fB. The predetermined frequency fB is set in advance from predetermined design dimensions such as a pitch of a screw to be measured and a lead. As a result, the high-frequency waveform based on the noise and the foreign matter is removed from the curve η1, and the influence of the foreign matter is removed and smoothed as shown by the curve η2 in FIG. The locus of the position of the vertex G3 in the X direction is ideally a straight line with the X direction position being constant, but the workpiece 8 is in the vertical direction (Y) while being held by the clamping chuck 70 (FIG. 1 or FIG. 15). Direction). When the workpiece 8 is inclined as described above, the position in the X direction tends to be a curve as shown in FIG. The configuration shown in FIGS. 24 and 25 is effective in that the influence of noise and foreign matter can be reduced when the workpiece 8 is inclined as described above.

  Then, the arithmetic and control unit 100 includes X-direction positions of a plurality of positions of the contour profile including the vertexes G1, G5... Of the peaks other than the vertex G3 in FIG. Also for, a low pass filter is performed in the same manner as the vertex G3. Then, the arithmetic and control unit 100 generates a secondary screw contour profile after filtering at each angle θ based on each vertex and each bottom point. As a result, in the secondary screw profile, abnormal portions and noise due to the adhesion of foreign matter are removed. Then, the arithmetic and control unit 100 determines the Y axis of the workpiece 8 based on the secondary contour profile of each angle θ after the filtering process as in the configuration shown in FIG. 11, FIG. 12, or FIG. Surrounding dimensions such as peak diameter and valley diameter, and the maximum value, minimum value, and average value of each are calculated.

  Note that Fourier transform and inverse Fourier change may also be used when performing the processing by the low-pass filter shown in FIG. Specifically, Fourier transform is performed on the locus of the position in the X direction of the contour profile shown in FIG. 25A, high frequency components exceeding a predetermined frequency fA are removed, and then inverse Fourier transform is performed to perform FIG. 25B. A process for obtaining a curve such as At this time, FFT may be used as Fourier transform and IFFT may be used as inverse Fourier transform.

  FIG. 26 is a view corresponding to FIG. 4 showing another example of an adapter for fixing a workpiece. 3 and 4, in the adapter 80 for fixing the workpiece 8, in order to accurately adjust the screwing depth of the male thread 2 of the workpiece 8 into the ring gauge 82a in units of one pitch length, Spacers 84a, 84b and 84c are used. On the other hand, in any one of the configurations shown in FIGS. 1 to 25, the adapter 80d may have no spacer as shown in FIG.

  In the adapter 80 d shown in FIG. 26, the lower surface that is the other end surface of the ring gauge 82 a is abutted against the upper surface of the stopper flange 90 of the holder 86.

  At this time, the male screw 92a of the holder 86 is screwed into the reference female screw 83a of the ring gauge 82a from below. In this case, the length from the lower end of the ring gauge 82a to the upper end of the male screw 92a is the same as the protrusion height HS of the male screw 92a from the upper surface of the stopper flange 90. In the adapter 80d, the screwing length Lw, which is the length that allows the male thread 2 (see FIGS. 3 and 4) of the workpiece 8 to be screwed from the upper side of the reference female screw 83a, is {(the thickness of the ring gauge 82a). DR)-(projection height HS of the male screw 92a of the holder 86)}. This screwing length Lw is set to an integral multiple (= N × Pc) of the pitch Pc of the reference female screw 83a. Here, N is an arbitrary integer.

  Further, with N1 and N2 being arbitrary integers, the thickness DR of the ring gauge 82a is set to an integral multiple (= N1 × Pc) of the pitch Pc of the reference female screw 83a, and the projection of the male screw 92a of the holder 86 is made. The height Hs may also be set to an integral multiple of the pitch Pc (= N2 × Pc).

  When the holder 86 is coupled to the ring gauge 82a, the male thread 92a of the holder 86 is screwed into the reference female thread 83a of the ring gauge 82a from the lower surface side of the ring gauge 82a. Further, from the upper surface side of the ring gauge 82a, the tip end portion of the male thread portion 2 of the workpiece 8 shown in FIG. 3 is screwed into the reference female screw 83a of the ring gauge 82a, and the tip end of the male thread portion 2 of the workpiece 8 is inserted into the holder 86. It abuts against the tip of the male screw 92a. Thereby, the work 8 is fixed to the ring gauge 82a. At this time, as described above, the screwing length Lw on the upper side of the ring gauge 82a is set to an integral multiple of the pitch Pc of the reference female screw 83a. This screwing length Lw is a meshing length Lw in which the male thread portion 2 of the workpiece 8 meshes with the ring gauge 82a, and can be accurately adjusted in units of length corresponding to one pitch. For example, when the length DR of the ring gauge 82a is 8 pitches and the protrusion height Hs of the male thread 92a of the holder 86 is 5 pitches, the meshing length Lw of the male thread portion 2 of the workpiece 8 is The length can be adjusted to 3 pitches. Therefore, the Y position of the tip of the male thread 2 of the workpiece 8 can be accurately obtained from the measured value of the Y position on the upper surface of the ring gauge 82a.

  Even when screws of the same standard are used as the workpiece 8, the tip of the male screw portion 2 may not fully engage the reference female screw 83a due to an incomplete screw portion at the tip. In consideration of this, it is preferable to prepare a plurality of types of adapters in which the upper screwing length Lw is an integer multiple of the pitch Pc in the adapter 80d.

  3 and 4, the spacer 84a, 84b, 84c is arranged between the ring gauge 82a and the holder 86 to adjust the screw engagement length, so that the dimensional accuracy of the spacer Is important. On the other hand, increasing the dimensional accuracy of the spacer is difficult compared to increasing the dimensional accuracy of the ring gauge 82a having a large thickness. As a result, the measurement accuracy may be lower in the configuration using the spacer than in the configuration in FIG. Further, the spacer is more easily deformed than the ring gauge 82a. According to the configuration of FIG. 26, the measurement accuracy can be increased compared to the configuration using spacers. In particular, in the case of a small screw having a small pitch Pc, it is preferable to use a member that meshes with a more accurate shape, and the configuration of FIG. 26 is advantageous in that respect. Further, since the spacer can be omitted, the cost can be reduced. For example, the manufacturing cost of a high-precision adapter without a spacer may be approximately the same as the manufacturing cost of a high-precision spacer.

  2 Male thread part, 3 neck lower part, 4 head part, 5 upper face, 6 head hole, 7, 9 bottom face, 8 workpiece, 10 thread dimension automatic measuring system, 11 foreign object, 12, 12a thread dimension automatic measuring apparatus, 14 prevention Shaking table, 15 housing, 16 base, 16a top plate, 18, 19 column, 20 top plate, 22, 23 guide rail, 24, 25 screw column, 26 Y stage, 27, 28 bearing unit, 29, 29a Y motor, 30 sensor, 31 belt, 32, 32a optical measuring device, 34, 34a image projection unit, 36 light source, 38 projection imaging camera, 40, 40a head measurement unit, 42 head imaging camera, 44 laser light source , 45 Actuator, 46 Ring illumination part, 48 Mounting plate, 50 Focusing movement part, 52 Z stage, 54 Z motor, 58 X stage, 60 Piston sillin Mechanism, 62 gripping rotation part, 64 θ motor, 66 rotary joint part, 68 gripping part, 70 clamping chuck, 72 support base, 74a, 74b, 74c slide base, 76a, 76b, 76c clamping claw part, 78a, 78b piston , 80, 80b, 80c, 80d Adapter, 82a, 82b, 82c Ring gauge, 84a, 84b, 84c Spacer, 86 Holder, 88 Holding ring part, 90 Stopper collar part, 100 Arithmetic controller, 102 Pneumatic controller, 104 Output device 106 Inspection table 110 Screw diameter calculation unit 112 Total length calculation unit 114 In-focus position calculation unit 116 Contour data calculation unit 118 Neck R calculation unit 120 Head dimension calculation unit 122 Head hole depth Calculation unit, 124 measurement data output unit, 130, 131 beam, 132, 133 134, 135, 136, 137 Red line, 140 Shadow area, 142 Black / white border, 144, 152 Bend line, 145, 146, 148, 150 Position, 160, 170, 171 Outline data, 162, 163 Line, 164 Angle division line , 166, 167 perpendicular, 172, 174, 176 regression line, 173, 177 vertical line, 180, 180b, 180c head hole bit, 182, 182b, 182c head hole fitting part, 184 collar, 186 Cylindrical part, 188 Conical top part, 190 Column member, 192 Lifting actuator, 194 Actuator case, 195 Guide hole, 196 Y table, 198 Slide leg part, 200 Position sensor, 202 Moving member, 204 Fixed side member, 210 Bit gripping unit, 212 Elevator , 214 guide member, 216 telescopic arm, 218 piston / cylinder mechanism, 220 bit gripping part, 221 claw part, 222 vertical rod, 224 piston / cylinder mechanism, 230 lower fixed table, 232 Z moving table, 234 linear actuator, 236 Rotating member, 238 rotary joint, 240, 242 pulley, 244 belt, 250 upper fixed table, 252 head camera moving part, 254 rod part, 256 piston / cylinder mechanism.

Claims (13)

With a screw as a workpiece to be measured, a gripping part that grips one end of the male screw in the axial direction;
A gripping rotation unit that rotates the gripping unit 360 degrees around the axial direction;
An optical measuring device for optically non-contactingly measuring the dimensions of the workpiece gripped at one end in the axial direction of the male screw by the gripping portion;
An axial movement unit that moves the optical measuring device along the axial direction relative to the gripping unit; and
An arithmetic and control unit that calculates and outputs dimensions of the workpiece in the axial direction and around the axis;
With
The arithmetic and control unit is
A screw diameter calculation unit for calculating a dimension related to the thread of the workpiece and a dimension related to the thread valley;
A total length calculation unit that calculates the total length along the axial direction of the workpiece;
A screw dimension automatic measuring system comprising: The automatic thread dimension measurement system according to claim 1,
The gripping part is
An adapter having a disk-like outer shape, and having a female screw having a predetermined meshing length that can be fixed so that the axial direction of the workpiece does not shake when the tip of the male screw of the workpiece is screwed An adapter at the center of the end face;
A clamping chuck that clamps and fixes the outer peripheral side surface of the adapter at at least three points;
A screw dimension automatic measuring system comprising: The screw dimension automatic measuring system according to claim 2,
The adapter is
A ring gauge engraved with a reference female thread having a predetermined meshing accuracy corresponding to the thread size of the external thread of the workpiece;
A disk-shaped holder having one end face from which the male thread that meshes with a reference female thread of the ring gauge;
Have
The screw size automatic measuring system according to claim 1, wherein the disk shape of the holder is a common shape regardless of the screw size of the workpiece. The automatic thread dimension measurement system according to claim 1,
The axial direction is the Y direction, and the plane perpendicular to the Y direction is the XZ plane.
A base having an upper surface parallel to the XZ plane;
The grip portion is provided on the upper surface of the base so as to be rotatable around the axial direction,
The axial movement unit is
A moving table on which the optical measuring device is mounted, including a moving table movable to an arbitrary Y position along the Y direction with respect to a base;
The optical measuring device is
An automatic thread dimension measurement system comprising an image projection unit for measuring an axial direction of the workpiece and a dimension around the axis. The screw dimension automatic measurement system according to claim 4,
The image projection unit
A light source arranged on one side in the Z direction with respect to the center line in the Y direction of the workpiece, and outputs a parallel light beam;
An optical axis that is disposed on the other side in the Z direction with respect to the center line in the Y direction of the workpiece and has the same light receiving optical axis as the light source with respect to a projection shape that receives the parallel rays from the light source and becomes a shadow of the workpiece A projection imaging camera of a telecentric optical system that forms an image on an imaging plane parallel to the XY plane and images only the component parallel to the XY plane;
A screw size automatic measuring system characterized by comprising: In the screw dimension automatic measurement system according to claim 5,
The arithmetic and control unit is
Converting the projection shape data of the workpiece imaged by the projection imaging camera into two-dimensional bitmap data having an arbitrary position resolution;
An automatic screw size measurement system comprising: a contour data calculation unit that binarizes each data of the two-dimensional data of the bitmap into black and white using a predetermined threshold value. The screw dimension automatic measurement system according to claim 6,
The contour data calculation unit
Contour data showing a screw contour profile by performing a smoothing process for removing data that becomes abnormal when viewed from the cross-sectional figure of the workpiece as noise with respect to data at the boundary of the black and white binarization based on a predetermined noise judgment standard Is what
A screw size automatic characterized in that the axial direction of the workpiece and the dimension around the axis are calculated and output based on the contour data for every predetermined angular interval when the workpiece is rotated 360 degrees around the Y axis. Measuring system. The screw dimension automatic measurement system according to claim 7,
A focusing movement unit that moves the projection imaging camera along the Z direction;
The arithmetic and control unit is
As preprocessing for converting to the bitmap,
In the edge region where the projected shape data of the screw imaged by the projection imaging camera transitions from white data to black data, a predetermined evaluation function is used so as to take a maximum value at the black-and-white boundary of the projected shape data. The value of the evaluation function at each Z position is obtained while moving the projection imaging camera in the Z direction by a focus moving unit, and the Z position at which the value of the evaluation function is the maximum value is set as the in-focus position. An automatic thread dimension measurement system including an in-focus position calculator for fixing a direction position. In the screw dimension automatic measurement system according to claim 7 or 8,
The arithmetic and control unit is
A group of measurement data of dimensions around the Y axis of the workpiece is obtained for the contour data at each predetermined angular interval of the workpiece,
Excluding the measurement data of the dimension that falls outside the range from the preset lower limit threshold to the preset upper limit threshold, a value for the dimension around the Y axis is calculated based on the remaining group of the measurement data of the dimension. Screw size automatic measurement system, characterized in that the output is output to an output device. The screw dimension automatic measuring system according to any one of claims 6 to 9,
The arithmetic and control unit is
Concerning the data at the boundary between the binarization of black and white, in the contour data for each predetermined angular interval obtained when the work is rotated around the Y axis, the locus of measurement data continuous along the Y direction of the work An automatic thread size measurement system that performs smoothing processing by performing a low-pass filter for a predetermined frequency set in advance. The screw dimension automatic measuring system according to any one of claims 6 to 9,
The arithmetic and control unit is
Regarding the data at the boundary of the binarization of black and white, the deviation in the Y direction based on the deviation of the workpiece by a predetermined angle with respect to the contour data for each predetermined angular interval obtained when the workpiece is rotated around the Y axis. A low-pass filter is applied to the locus of the position in the X direction of a point predicted from a plurality of points corrected by the predicted deviation corresponding to the angle around the Y axis of the workpiece, and contour data after filtering is generated. Then, a screw dimension automatic measurement system characterized in that a value about a dimension around the Y axis of the workpiece is calculated based on the filtered contour data and output to an output device. The automatic thread dimension measurement system according to claim 1,
The workpiece has a head and a screw shaft, and is a head-attached screw having a turning groove or a turning hole for a tightening tool in the head.
The optical measuring device is
A screw dimension automatic measuring system comprising a head measuring unit for measuring a depth of a head hole of the workpiece. The screw dimension automatic measurement system according to claim 12,
The head measurement unit is
A head imaging camera that images the shape of the head hole of the workpiece on an imaging surface parallel to the XZ plane;
A laser light source that irradiates a beam extending linearly on the XZ plane at a predetermined inclination angle with respect to the Y direction of the workpiece across the top surface of the head of the workpiece and the bottom surface of the head hole;
Have
The arithmetic and control unit is
A head dimension calculator that calculates a head dimension of the workpiece based on imaging data of the head imaging camera;
The projection positions at which the linear beams emitted from the laser light source are projected onto the top surface of the head and the bottom surface of the head hole are detected by the head imaging camera, and the detected projection positions are detected. An automatic screw size measurement system including a head hole depth calculation unit that calculates the depth of the head hole based on a discrepancy amount on the XZ plane and a predetermined inclination angle.

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