JP3191397B2 - Automatic flaw detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic flaw detector which detects a surface flaw based on a picked-up image of the surface of a material to be inspected by a magnetic particle flaw detection method or the like, and more particularly, to an automatic flaw detector which moves relative to the material to be inspected. The present invention relates to an improvement in technology for imaging the surface.

[0002]

2. Description of the Related Art A magnetic particle flaw detection method is known as one of methods for detecting a flaw on the surface of a material to be inspected such as a billet. FIG. 8 explains the principle of a fluorescent magnetic particle flaw detection method as an example. Things. In this method, a fluorescent magnetic powder is attached to the surface of the previously magnetized steel slab 80 by spraying or dipping, and the pattern of the magnetic powder excited by irradiation of the ultraviolet lamp 82 is
TV camera 84 arranged opposite to the surface of billet 80
, The surface flaw on the billet 80 is detected. The television camera 84 has a large number of photoelectric conversion units, and is disposed in a fixed position. Light from the surface of the steel slab 80 is made incident on those photoelectric conversion units, so that the television camera 84 is incident on each of the photoelectric conversion units. A predetermined scanning cycle of the image signal corresponding to the light amount, that is, a cycle time for acquiring and processing an image signal for one screen from all photoelectric conversion units,
For example, the output is made at a 1/30 second cycle. When the material to be inspected is long like the billet 80, the television camera 8 is moved while moving the billet 80 in the longitudinal direction.
4, the magnetic powder pattern is continuously imaged to detect surface flaws.

In the case of imaging the surface of the inspecting material moving as described above, when the moving speed of the inspecting material increases, photoelectric conversion of light incident on the imaging device such as a television camera from the surface of the inspecting material is performed. Since the incident position with respect to the part is shifted, the amount of light accumulated in the photoelectric conversion part in the part corresponding to the surface flaw is reduced, and the intensity of the image signal is reduced. There was a problem of lowering. On the other hand, for example, in the patent application No. 176893 filed earlier by the present applicant,
A reflecting mirror is provided which is rotatable around a rotation axis perpendicular to the moving direction of the material to be inspected. The surface of the material to be inspected is imaged by the imaging device via the reflecting mirror, and the imaging range is the surface of the material to be inspected. The surface of the surface is imaged in a substantially still image state regardless of the movement of the material to be inspected by rotating the reflecting mirror in accordance with the movement of the material to be inspected so as to be maintained in substantially the same range as that of the material to be inspected. There has been disclosed an automatic flaw detector which improves accuracy.

[0004]

However, in the above-mentioned automatic flaw detector, the surface of the material to be inspected is sequentially imaged while moving the material to be inspected with respect to the reflecting mirror or the imaging device. There is a problem that a long equipment space is required before and after the automatic flaw detector in the moving direction. In addition, the improved detection accuracy makes it possible to move the inspected material at high speed and perform high-speed flaw detection. However, there is a limit to the moving speed of the relatively heavy inspected material. When it is difficult to increase the speed of the material to be inspected and when the speed of movement of the material to be inspected is detected from the rotation of a roller etc. that is in rolling contact with the material to be inspected, the slip between the material to be inspected and the roller is completely prevented There is still room for improvement, such as the fact that it is not always possible to accurately control the rotation of the reflecting mirror due to the inability to do so.

The present invention has been made in view of the above circumstances, and an object of the present invention is to detect a surface flaw of a material to be inspected with high accuracy and efficiency without requiring a long facility space. It is to make.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the gist of the present invention is to detect a flaw existing on the surface of a test piece arranged at a fixed position on the basis of a captured image of the surface. An automatic flaw detector that automatically detects
(A) a carriage that is linearly moved in a direction parallel to the surface of the material to be inspected, and (b) a single axis provided on the carriage so as to be rotatable around an axis perpendicular to the moving direction of the carriage. A reflecting mirror having a mirror surface parallel to the heart; and (c) a plurality of photoelectric conversion units, which are disposed at a fixed position on the carriage and light from the surface of the material to be inspected passes through the reflecting mirror. An imaging device that outputs an image signal corresponding to the amount of incident light for each of the photoelectric conversion units by being incident on the photoelectric conversion units,
(D) The surface of the inspection object is imaged by the imaging device in a substantially still image state regardless of the movement of the carriage , and
A rotation control means for rotating the reflecting mirror around the one axis in accordance with the movement of the carriage so that the image range is shifted by a predetermined minute amount .

[0007] Preferably, the rotation control means comprises a rack fixedly disposed in parallel with the moving direction of the carriage, and a gear rotatably disposed on the carriage so as to mesh with the rack. And the rotation of the reflecting mirror is controlled based on the rotation angle of the gear rotating with the movement of the carriage.

[0008]

In such an automatic flaw detection apparatus, a bogie that is linearly moved in a direction parallel to the surface of the material to be inspected can rotate about one axis perpendicular to the moving direction of the bogie. Provided, and an imaging device for imaging the surface of the inspection target material via the reflection mirror, and the imaging device captures the surface of the inspection target material in a substantially still image state regardless of the movement of the carriage. And the imaging range is
The rotation of the reflecting mirror is controlled by the rotation control means according to the movement of the carriage so that the image is shifted by a predetermined minute amount . For this reason, regardless of the movement of the cart, light from the surface of the material to be inspected is always made incident on the photoelectric conversion unit at a fixed position in the imaging device, and the same light amount as when not moving to each photoelectric conversion unit. Each will be accumulated.
Thereby, even if the surface flaw is short in the moving direction of the carriage, an image signal having an intensity corresponding to the flaw is output from the imaging device, and even when the carriage is moved at high speed, a small surface flaw on the surface of the inspection target material is obtained. Scratches can be reliably detected. It should be noted that the rotation control of the reflecting mirror is repeated with the movement of the cart, so that the surface of the material to be inspected is sequentially imaged by the imaging device in a state of being divided into a plurality in the moving direction of the cart.

Further, as described above, since the image pickup device is moved in parallel with the inspection target material with respect to the inspection target material arranged at a fixed position, the flaw detection is performed in a space substantially equal to the length dimension of the inspection target material. It is possible to perform work, compared to the conventional device that performs flaw detection work while moving the material to be inspected in the longitudinal direction,
The space required for the inspection work is small. For this reason,
For example, by configuring the transport equipment or the like so that the material to be inspected is carried into the inspection position from a direction perpendicular to the direction of movement of the trolley, and unloaded in the same direction after the inspection, the moving direction of the trolley, that is, the longitudinal Equipment space in directions can be saved. In addition, since the cart and the reflecting mirrors and imaging devices provided on the cart are relatively lightweight, it is possible to move the inspection material at a higher speed than in the conventional case where the inspection material is transferred, and to perform inspection. There is an advantage that the efficiency can be further improved.

[0010] Further, the rotation of the carriage is controlled by a rotation control means having a rack fixedly disposed in parallel with the direction of movement of the carriage and a gear rotatably disposed on the carriage so as to mesh with the rack. When the rotation of the reflecting mirror is controlled based on the rotation angle of the gear that rotates with the gear, the movement of the bogie is accurately detected by the engagement of the rack and the gear without slipping, so that the reflecting mirror is Can be accurately controlled in accordance with the movement of the bogie, and blurring of a captured image due to a rotation error of the reflecting mirror can be prevented, and detection accuracy of surface flaws can be further improved.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a perspective view of an automatic flaw detection apparatus 10 using a fluorescent magnetic particle flaw detection method according to one embodiment of the present invention. The test material 12, which is a ferromagnetic steel piece, has a rectangular cross-section and has a long shape, and the plurality of test tables 14 have a substantially horizontal posture in which longitudinal ridges are located vertically and horizontally. It is supported in a fixed position. Then, by a pair of inspection units 16 that are moved in the longitudinal direction of the inspection target material 12,
Flaws existing on the outer peripheral surface 18 (upper two surfaces) are detected. In the magnetic particle flaw detection method, a magnetic flux, which is a ferromagnetic powder, is intensively adsorbed to a flaw portion by a leakage magnetic flux flowing around a flaw (defect) on the surface or in the vicinity of the surface. As shown in FIG. 2, the inspection object 12 is previously carried into a magnetizing device 20 and is magnetized by being exposed to a magnetic field. By immersing the magneto-optical powder in a liquid dispersed and suspended in oil or the like, the fluorescent magnetic powder is attached to the surface 18 thereof. As is clear from FIG. 2, the magnetizing device 20 and the magnetic powder attaching device 22 are sequentially arranged in the direction perpendicular to the longitudinal direction of the inspection target material 12 with respect to the automatic flaw detection device 10, and include a walking beam (not shown) or the like. The inspection material 12 is transported by the transport device, and is conveyed in the same direction when the flaw detection work in the automatic flaw detection device 10 is completed. The automatic flaw detector 10 has a dark room structure in order to capture the magnetic powder pattern of the fluorescent magnetic powder as clearly as possible.

In FIG. 1, above the material 12 to be inspected,
A pair of guide rails 24 and 26 having a dimension longer by a predetermined amount than the entire length of the inspection target material 12 are provided via a frame member (not shown) in parallel with the longitudinal direction of the inspection target material 12. The inspection unit 16 is provided on a carriage 28 that runs on the pair of guide rails 24 and 26, so that flaw detection can be performed over the entire length of the inspection object 12. The carriage 28 includes a controller 56
A servo motor 30 is provided which is driven to rotate in both forward and reverse directions by a drive signal SD1 supplied from FIG. 5 (see FIG. 5), and the driving force of this servo motor 30 is applied to drive wheels 34 and 36 via a timing belt 32. The carriage 28 is caused to travel on the guide rails 24 and 26 at a predetermined moving speed V. Servo motor 30
Is provided with an encoder 38, and the servo motor 3
A rotation angle signal SA1 representing the rotation angle is supplied from the encoder 38 to the control device 56 so that the rotation angle of the drive wheel 34 and the moving speed V of the carriage 28 can be detected based on the rotation angle of 0. A meshing tooth 40 is formed on the upper surface of one guide rail 24, and a meshing tooth 42 meshing with the meshing tooth 40 is formed on the outer periphery of one drive wheel 34 that rolls on the guide rail 24. The engagement of the meshing teeth 40 and 42 causes the carriage 28 to move on the guide rail 24 exactly corresponding to the rotation angle of the drive wheel 34. In the present embodiment, the guide rail 24 on which the meshing teeth 40 are formed corresponds to a rack, and the drive wheel 34 on which the meshing teeth 42 are formed corresponds to a gear.

The pair of inspection units 16 includes the cart 28
And a reflecting mirror 44, a television camera 46, an ultraviolet lamp 48, and the like which are arranged in a predetermined positional relationship. A pair of inspection units 1
Reference numeral 6 denotes a surface 18 of the material to be inspected 12 which faces obliquely upward.
The surfaces are simultaneously flaw-detected, and the respective reflecting mirrors 44, television cameras 46, ultraviolet lamps 48 and the like are arranged symmetrically with respect to a vertical plane passing through the axis of the material 12 to be inspected. . The reflecting mirror 44 is a servo motor 50
And the mirror surface 52 formed in a plane including the axis O of the output shaft is rotated about the axis O. The servo motor 50 Are fixed to the carriage 28 in a posture that is perpendicular to the longitudinal direction of the inspection object 12, that is, the moving direction of the carriage 28, and parallel to the surface 18 of the inspection object 12. The television camera 46 is mounted such that the optical axis of the imaging lens is parallel to the moving direction of the carriage 28 and is orthogonal to the axis O, and the light from the surface 18 of the inspection object 12 is reflected by the reflecting mirror 44. , The magnetic powder pattern on the surface 18 is imaged. This TV camera 46
This is a general imaging device equipped with a solid-state imaging device (CCD) and an imaging tube.
When light is incident on each of them, an image signal SV corresponding to the amount of incident light is output to the control device 56 for each photoelectric conversion unit at a predetermined scanning cycle. Here, the scanning cycle is a cycle time in which one screen of the image signal SV is fetched from all the photoelectric conversion units and is set to, for example, about 1/30 second, and the image signal output from each photoelectric conversion unit is set. S
V corresponds to the amount of light received during the scanning cycle.

FIG. 3 is a diagram showing a specific positional relationship when viewed from a direction parallel to the axis O. The angle between the mirror surface 52 and the surface 18 of the inspection object 12 is 45 °. Is rotated around a position Mc within an angle range Ms-Me of ± θ / 2. When the reflecting mirror 44 is at the position of Mc, the angle of incidence and the angle of reflection of light from the point Pc perpendicular to the surface 18 of the test object 12 from the axis O on the mirror surface 52 are 45 °, and the television Since the point Pc is located at the center of the imaging range of the camera 46, that is, on the imaging optical axis, when the reflecting mirror 44 is rotated from the position of Ms to the position of Me, the imaging optical axis of the television camera 46 is moved to the surface 18 It moves from the upper point Ps to the point Pe. The servo motor 50 is provided with an encoder 54, and supplies a rotation angle signal SA2 representing a rotation angle from a predetermined reference position around the axis O of the reflecting mirror 44 to a control device 56. And the servo motor 5
0 is the control device 56 based on the rotation angle signal SA2.
Is feedback-controlled.

FIG. 4 shows the automatic flaw detection device 10 connected to the material 12 to be inspected.
FIG. 3 is a cross-sectional view as viewed from the longitudinal direction of
Reference numeral 8 is attached so that the actual imaging range corresponding to the moving range of the imaging optical axis of the television camera 46 from the point Ps to the point Pe by the rotation of the reflecting mirror 44 can be irradiated with an appropriate amount of ultraviolet rays. . Further, a pair of ridge lines 58 located on the left and right of the four ridge lines extending in the longitudinal direction of the test object 12.
A pair of edge irradiating lamps 62 are disposed below the mirrors 60 and 60 at substantially the same position as the reflecting mirror 44 in the moving direction of the carriage 28, and irradiate the ridges 58 and 60 with visible light to capture images. Edge 58 in the image
And 60 edges are clarified. In addition, a pair of light emitters 64 and light receivers 66 are disposed on both sides of the inspection target material 12. The light emitter 64 and the light receiver 66 function as a photoelectric switch, and after the carriage 28 starts moving from the initial position where the light emitted from the light emitter 64 toward the light receiver 66 is not blocked, the material to be inspected is started. 12 that the light is blocked by passing through the terminal 68 on the flaw detection start side.
The control unit 5 determines the start time of the flaw detection of the inspection object 12
6 can be determined.

The control device 56 includes a CPU, a ROM, and a RAM.
As shown in FIG. 5, based on an input signal, the microcomputer performs a calculation process using a temporary storage function of a RAM in accordance with a program stored in a ROM in advance. It outputs a drive signal and the like. The control contents related to the rotation control of the reflecting mirror 44 will be specifically described.
Is a rotation angle signal S supplied from the encoder 38.
A moving speed V of the carriage 28 is calculated based on A1, and a drive signal SD1 is output so that the moving speed V matches a predetermined target speed to feedback-control the servomotor 30 and to move the carriage 28. Regardless, the rotation angular velocity ω of the reflecting mirror 44 is calculated in accordance with the moving speed V so that the surface 18 of the inspection object 12 is imaged in a substantially still image state by the television camera 46, and the reflecting mirror 44 The servo motor 50 reads the rotation angle signal SA2 from the encoder 54 so as to rotate at the rotation angular velocity ω.
And outputs a drive signal SD2 to perform feedback control.

That is, in FIG. 3, the case where the reflecting mirror 44 and the television camera 46 move to the right side in FIG. 3 with the movement of the carriage 28, that is, the case where the test object 12 relatively moves to the left side in FIG. Considering that, when the reflecting mirror 44 is rotated from the position of Mc to the position of Me at the rotation angular velocity ω, the imaging center of the television camera 46 moves from the point Pc to the point P.
e, so that the carriage 28 moves by the same distance x as the distance x.
And the angular velocity ω is defined. Here, assuming that the angle between the straight line O-Pc and the straight line O-Pe is θ and the distance from the axis O to the point Pc is y, x = y tan θ
However, from the optical relationship in reflection, the rotation angle of the imaging optical axis of the television camera 46 is twice the rotation angle of the reflection mirror 44, and the angle θ corresponds to 2ω and the distance x Corresponds to the moving speed V, so that the angular speed ω may be determined according to the actual moving speed V so that the moving speed V and the angular speed ω satisfy the following expression (1). When 2ω, that is, θ becomes 90 ° or more, the expression (1) is not satisfied. Therefore, as the moving speed V and the angular speed ω, for example, a moving amount per control cycle time of feedback control, a rotation angle, and the like are used. Becomes

[0019]

V = y tan (2ω) (1)

From this relationship, the rotational angular velocity ω of the reflecting mirror 44 is determined in accordance with the moving speed V of the carriage 28, and the rotation control is performed so that the imaging optical axis of the reflecting mirror 44 follows one point on the surface 18. By doing so, substantially the same range of the surface 18 of the inspection object 12 is imaged by the television camera 46 moving together with the carriage 28. FIG. 6 is a time chart showing an example of a change in the angle (rotational position with respect to the center position of 45 °) of the reflecting mirror 44, which is rotationally controlled based on the above concept. The rotation control of the reflecting mirror 44 is started in synchronization with the time when the detection signal SP from the light receiver 66 detects that the terminal 68 of the inspection object 12 has passed, and the angle of the reflecting mirror 44 is set to the position of the Ms. At the above angular velocity ω from -θ / 2 at
It is rotated to follow + θ / 2 at the position of e. During this time, in practice, for example, the inspection unit 16 moves rightward at the moving speed V by a distance 2x from the state where the reflecting mirror 44 is at the position of Ms at the position of the axis O in FIG. However, the imaging optical axis of the television camera 46 is caused to follow the position of the point Ps on the test object 12 which is stationary, so that the point Ps is positioned on the surface 18 of the test object 12 at the center of the screen. Can be captured in the state of the still image located at the position. Thus, the magnetic powder pattern due to the scratch can be clearly captured by the television camera 46 regardless of the movement of the carriage 28, and the presence / absence and position of the scratch can be determined with high accuracy from the signal strength of the image signal SV.

On the other hand, if the surface 18 of the material to be inspected 12 is subjected to a shot peening process in order to remove black scales caused by the quenching process or the like, if fine irregularities are present over the entire surface, the complete When the surface 18 is imaged in a still image state, the magnetic powder pattern caused by these irregularities is also detected by the television camera 4.
6 is relatively clear. For this reason, the image signal SV _N due to such unevenness and the image signal SV _{N due} to scratches
The S / N (flaw signal-to-noise ratio) with _S is likely to decrease, and the threshold level for flaw determination must be set relatively high, which reduces the detection accuracy of small flaws.

On the other hand, in this embodiment, the period of the follow-up rotation of the reflecting mirror 44 with respect to the surface 18, specifically, the surface 18
In order to capture an image in a substantially stationary state for at least two screens, the imaging range of the television camera 44 is shifted by a predetermined minute amount within a time period of about three screen scanning periods, for example. The detection accuracy for small scratches is maintained. That is,
The amount of incident light from the magnetic powder pattern due the asperities in the photoelectric conversion unit of the television camera 46 is averaged by the deviation of the minute amount, the signal intensity of the image signal SV _N also flat output with it from the photoelectric conversion portion On the other hand, with respect to the image signal SV _S due to the flaw, if the size of the flaw is longer than at least the amount of displacement of the image in the moving direction of the carriage 28, the signal intensity can be reduced only slightly.
/ N can be improved, and the threshold level for flaw determination can be lowered so that even small flaws can be detected satisfactorily. The minute amount is, for example, the flaw detection capability (minimum detectable value) in the captured image or the surface 1
8 is determined in advance by an experiment or the like based on the size of the unevenness existing in the sample No. 8. Since the material to be inspected 12 is elongated by rolling or the like, the shape of the flaw is generally long in the longitudinal direction of the material to be inspected 12 and is detected satisfactorily regardless of the displacement of the image in the longitudinal direction. Therefore, the actual rotational angular velocity ω ₀ is
In the above equation (1) in the case where the image is captured in a complete still image state, it is determined according to the following equation (2) in which the adjustment value α corresponding to the minute amount is added to the movement speed V, that is, the movement amount per predetermined unit time. You. The adjustment value α is determined in consideration of the control cycle time of the servo motor 50 and the scanning cycle of the television camera 46. Note that the adjustment value α may be subtracted from the moving speed V.

[0023]

V + α = y tan (2ω ₀ ) (2)

In the case where a dent due to shot peening is present on substantially the entire surface 18 of the test object 12 and a flaw having a depth of about 0.4 mm and a length of about 20 mm is present in the longitudinal direction, When the deviation amount of the imaging range in the follow-up rotation period of the reflector 44 is rotated controlled reflector 44 at an angular velocity omega ₀ serving as the 1 mm, the intensity of the image signal SV _S wound part as shown in Table 1 is about 15 in the intensity of the image signal SV _N other parts is about 4.5, S / N was about 3.33. In contrast, a complete still image state, that is, when the displacement of the imaging range is zero, the image signal SV _S of intensity approximately 23, the intensity of the image signal SV _N is about 7.5, S / N is about 3 .07,
It can be seen that although the signal strength is high, the S / N is better when shifted by 1 mm. When the rotation of the reflecting mirror 44 is controlled at an angular velocity ω ₀ at which the shift amount of the imaging range during the following rotation of the reflecting mirror 44 is 2 mm, the intensity of the image signal SV _S is about 13, and the image signal SV _N Of about 4.2, S / N
About 3.12 becomes, compared to the case where shifted 1 mm, the image signal SV _N image signals SV whereas hardly changes
_S decreases, and S / N becomes equivalent to that in the case of imaging in a still image state.

[0025]

[Table 1]

Then, the reflecting mirror 44 is rotated following the rotation angular velocity ω ₀ determined as described above, and slightly while the reflecting mirror 44 rotates from the position Ms to the position Me in FIG. While a predetermined range on the surface 18 of the inspection material 12 is imaged in a state where the displacement occurs, the next block in the movement direction of the carriage 28 divided into a plurality of parts based on the terminal 68 of the inspection material 12 in the movement direction forward. In order to image the (imaging range), for example, T in the time chart of FIG.
e to Ts, the reflecting mirror 44 moves from the position of Me to Ms.
Is quickly returned to the position, and then rotated again from the position of Ms to the position of Me at the rotation angular velocity ω ₀ , and imaging is performed in the same manner. By repeatedly performing such control, a flaw detection operation is performed over the entire length of the inspection target material 12.

FIG. 7 shows the inspection unit 16 as described above.
3 shows an actual imaging state when the angle of the reflecting mirror 44 is controlled in accordance with the movement of the mirror, partially expanded so that the imaging range becomes forward. In (a) of this figure, the reflecting mirror 44 is located at the position of the Ms, and the imaging of the surface 18 of the n-th block n from the terminal 68 of the inspection object 12 is started. Then, with the movement of the carriage 28 traveling rightward in the figure at the speed V, the reflecting mirror 44 is rotated by the rotational angular velocity ω.
₀ , the reflecting mirror 44 is turned to follow the M
c, and then in (c), the reflecting mirror 44 is
When the position of e is reached and the imaging of block n ends, T in FIG.
The state at the time corresponding to e. In this state (c), the reflecting mirror 44 is returned and rotated, and in (d), the reflecting mirror 44 returns to the position of Ms and the next block (n)
+1) imaging is started. Therefore, the TV camera 46
The surface image 18 of the block n is captured in a substantially still image state from (a) to (c). In the return rotation, at least a predetermined number of rotations faster than the angular velocity ω ₀ in accordance with the moving speed V of the carriage 28 so that an unimaged portion does not occur at the boundary between the block n and the block (n + 1). Returned at dynamic angular velocity.

When the image signal SV thus picked up is supplied from the television camera 46 to the control device 56, the edge line of the front surface 18 on the picked-up image by the light of the edge irradiation lamp 62 is referenced one screen at a time. Screen correction is performed so as to match the position, and a flaw map indicating the presence / absence of flaw and the flaw position is created for each block based on the corrected image.

As described above, in this embodiment, the carriage 28 which is linearly moved in a direction parallel to the surface 18 of the inspection object 12 has the axis O parallel to the surface 18 at right angles to the moving direction of the carriage 28. An inspection unit 1 including a reflecting mirror 44 that is rotatable around and a television camera 46 that captures an image of the surface 18 of the inspection object 12 via the reflecting mirror 44.
6 is provided, and the controller 56 controls the moving speed V of the carriage 28 so that the surface 18 of the inspection object 12 is imaged in a substantially still image state by the television camera 46 regardless of the movement of the carriage 28. The turning angular velocity ω ₀ of the reflecting mirror 44 is determined, and the turning of the reflecting mirror 44 is controlled. Therefore, irrespective of the movement of the cart 28, the light from the fluorescent magnetic powder pattern on the surface 18 is always made incident on the photoelectric conversion unit at a fixed position in the television camera 46 and moves to each photoelectric conversion unit. The same amount of light as when there is no light is accumulated for each screen scanning cycle. Thus, even if the surface scratch is short in the moving direction of the cart 28, the image signal SV having the strength corresponding to the scratch is output from the television camera 46, and even when the cart 28 is moved at high speed, the material to be inspected is Small flaws on the surface 18 of the twelve can be reliably detected.

Further, as described above, since the inspection unit 16 is moved in parallel with the inspection material 12 with respect to the inspection material 12 placed on the inspection table 14, the length of the inspection material 12 is reduced. The flaw detection work can be performed in substantially the same space as that described above, and the space required for the flaw detection work can be smaller than that of a conventional apparatus that performs the flaw detection work while moving the inspection target material 12 in the longitudinal direction. Moreover, in the present embodiment, the material to be inspected 12
Is transported to the inspection table 14 of the automatic flaw detector 10 from a direction perpendicular to the moving direction of the carriage 28, and is carried out in the same direction after the inspection.
The equipment space in the moving direction of 8, ie, in the longitudinal direction of the material to be inspected 12, can be saved.

Further, since the cart 28 and the inspection unit 16 such as the reflecting mirror 44 and the television camera 46 provided on the cart 28 are relatively lightweight, the inspection unit 12 can be moved when the inspection object 12 is moved as in the prior art. This has the advantage that it can be moved at a higher speed and the inspection efficiency can be further improved.

Further, in the present embodiment, the meshing teeth 40 are provided on one of the guide rails 24 and are meshed with the meshing teeth 42 provided on the drive wheels 34 of the bogie 28, so that the bogie 28
The rotation of the reflecting mirror 44 is controlled based on the rotation angle of the meshing tooth 42 that rotates with the movement of the reflecting mirror 44.
Can be accurately performed in accordance with the movement of the carriage 28, blurring of a captured image is prevented, and detection accuracy of surface flaws is further improved.

Further, in this embodiment, the rotation angular velocity ω ₀ for controlling the follow-up rotation of the reflecting mirror 44 is determined by a minute amount predetermined according to the size of the unevenness existing on the surface 18 and the ability to detect a flaw. (For example, the shift amount of the reflecting mirror 44 during the follow-up rotation period is 1 mm) is obtained according to the above equation (2) so that the imaging range of the television camera 46 is shifted. Therefore, while the image signal SV _N signal intensity of the incident light intensity from the magnetic powder pattern due to unevenness is output from the photoelectric conversion unit is averaged by the deviation of the minute amount becomes flat, the image in the direction of movement of the carriage 28 As for the image signal SV _S due to a flaw having a dimension longer than the deviation amount of the image signal SV, a decrease in the signal intensity is suppressed to a small level, so that the overall S / N of the image signal SV is improved. As a result, the threshold level for flaw determination can be set low, and small flaws can be detected well, and the occurrence of undetected flaws and erroneous detection of flaws due to unevenness can be satisfactorily avoided.

In this embodiment, a rotation control means is constituted by the servo motor 50 for rotating the reflecting mirror 44 about the axis O and the control device 56 for controlling the operation of the servo motor 50.

While the embodiment of the present invention has been described in detail with reference to the drawings, the present invention can be embodied in other forms.

For example, in the above-described embodiment, the inspection material 12 which is a long steel piece having a square cross section is automatically flaw-detected. However, other inspection materials such as polygons and circles are used. The size and shape of 12 are arbitrary, and the inspection unit 16 can be appropriately configured together with the carriage 28 by arranging the reflecting mirror 44 and the television camera 46 according to the size and shape of each. In addition, the flaw detection is not limited to the case where two surfaces of the surface 18 are simultaneously flaw-detected.
For example, a case where a plurality of inspection units 16 are arranged on a surface may be adopted.

In the above-described embodiment, the magnetizing device 20 magnetizes the magnetic powder in the magnetizing device 20 in advance.
In this case, the inspection material 12 having the magnetic powder pattern formed thereon was carried into the automatic flaw detector 10 and was automatically flaw-detected.
The inspection material 12 may be magnetized on the inspection table 14 and the magnetic particles may be adhered to the inspection table 12 to perform automatic flaw detection.

In the above-described embodiment, the carriage 28
A reflecting mirror 44 is provided which is rotatable about an axis O parallel to the surface 18 of the material 12 to be inspected at right angles to the moving direction of the workpiece 12 and has a mirror surface 52 including the axis O. The center O may not necessarily be parallel to the surface 18 of the material 12 to be inspected, and the mirror surface 52 may be offset from the axis O if it is parallel to the axis O. Various forms of reflectors may be used, provided that light from surface 18 can be incident on television camera 46.

In the above-described embodiment, the television camera 46 is used as an image pickup device. Alternatively, an electronic still camera or the like having a large number of photoelectric conversion units and having an image corresponding to the amount of incident light may be used. Other imaging devices that output signals can also be used, and effects can be similarly obtained by applying the present invention.

In the above-described embodiment, the carriage 28
And the rotational angular speed ω ₀ of the reflecting mirror 44 is determined according to the moving speed V.
Instead, the carriage 28 from the terminal 68 of the inspection object 12 is
And a moving position from a predetermined reference position on which the test material 12 is positioned and placed, and a predetermined position corresponding to the moving distance or the moving position is detected in accordance with the moving distance or the moving position. The turning position of the reflecting mirror 44 may be controlled so as to become the turning angle.

In the above-described embodiment, the engagement teeth 40 are provided on the guide rail 24 and the drive wheels 34 are provided.
Are provided with the meshing teeth 42, but the guide rails 24,
A rack and gears are provided separately from the drive wheels 34, and the moving speed V of the carriage 28 is detected based on the number of rotations of the gears, and the rack 28 is brought into rolling contact with a position fixing member such as the guide rail 24. A roller is provided, and the moving speed V of the carriage 28 is detected based on the number of rotations of the roller.
A linear motor is provided for driving the carriage 28, and the moving speed V of the carriage 28 is determined based on an output signal to the linear motor.
Or it can be configured to detect

In the above-described embodiment, the reflecting mirror 44 is rotated by the servo motor 50 electrically controlled by the control device 56. However, for example, the reflecting mirror 44 is moved along the moving direction of the carriage 28. A cam surface formed at a predetermined pitch and a roller rolling on the cam surface are disposed, and the reflecting mirror 44 is rotated in conjunction with the movement of the roller in a direction perpendicular to the moving direction of the carriage 28. Or a rack provided with intermittent teeth intermittently in the direction of movement of the cart 28 and rotated by meshing with the rack while being reversely rotated by the urging means during the period when the teeth of the rack are absent. A gear is provided, and the reflecting mirror 44 is rotated in conjunction with the rotation of the gear, and is reflected by mechanical rotation control means according to the moving position of the carriage 28. Mirror 44 It is also possible to rotate the control is performed.

In the above-described embodiment, the driving wheels 3
Although the cart 28 has the wheels 4 and 36 and can be moved on the guide rails 24 and 26, there is a cart in which a frame member having no wheels is guided by a guide rod or the like and moved by a high-speed cylinder or the like. It may be used.

In the above-described embodiment, the turning of the reflecting mirror 44 is performed in order to maintain a high detection accuracy for small flaws without being affected by fine irregularities on the surface 18 of the material 12 to be inspected. Although the angular velocity ω ₀ has been determined according to the above equation (2), the follow-up rotation control of the reflecting mirror 44 is performed based on the rotation angular velocity ω obtained according to the above equation (1) so as to capture an image in a complete still image state. It may be performed.

[0045]

Further, in the above-described embodiment, the automatic flaw detection apparatus 10 using the fluorescent magnetic particle flaw detection method has been described. However, the automatic flaw detection apparatus using other magnetic particle flaw detection method or the penetrant flaw detection method can be used. The invention can be applied as well.

Although not specifically exemplified, the present invention can be embodied with various modifications and improvements based on the knowledge of those skilled in the art.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a main configuration of an automatic flaw detector according to one embodiment of the present invention.

FIG. 2 is a plan view illustrating a transport path and the like of a material to be inspected detected by the automatic flaw detection apparatus of FIG. 1;

FIG. 3 is a diagram illustrating in detail a positional relationship between a reflecting mirror, an imaging device, and a material to be inspected in the automatic flaw detector of FIG. 1;

FIG. 4 is a cross-sectional view of the automatic flaw detector of FIG. 1 as viewed from a longitudinal direction of a material to be inspected.

FIG. 5 is a diagram illustrating a mechanical and electrical configuration of the automatic flaw detector of FIG. 1;

6 is a time chart showing an example of a change in the turning angle of the reflecting mirror controlled by the control device of FIG. 5;

FIG. 7 is a diagram illustrating an imaging situation when the rotation of the reflecting mirror is controlled by the control device of FIG. 5;

FIG. 8 is a diagram illustrating an example of a conventional automatic flaw detector.

[Explanation of symbols]

 10: Automatic flaw detector 12: Inspection material 18: Surface 24: Guide rail (rack) 34: Drive wheel (gear) 44: Reflector mirror 46: Television camera (imaging device) 50: Servo motor (rotation control means) 52 : Mirror surface 56: Control device (rotation control means) O: Axis (uniaxial)

Claims (2)

(57) [Claims] 1. An automatic flaw detector which automatically detects a flaw present on a surface of a material to be inspected arranged at a fixed position on the basis of a captured image of the surface. A cart that is linearly moved in a parallel direction; a reflecting mirror that is provided on the cart so as to be rotatable about an axis perpendicular to the direction of movement of the cart and that has a mirror surface parallel to the axis. It has a photoelectric conversion unit and is disposed at a fixed position on the carriage, and light from the surface of the material to be inspected is incident on the photoelectric conversion unit via the reflecting mirror, so that each of the photoelectric conversion units is An imaging device that outputs an image signal corresponding to the amount of incident light; and a surface of the inspection object is imaged by the imaging device in a substantially still image state regardless of movement of the carriage , and an imaging range
So that the image is shifted by a predetermined minute amount ,
An automatic flaw detection device, comprising: a rotation control means for following and rotating the reflecting mirror around the one axis in accordance with the movement of the carriage. 2. The rotation control means includes: a rack fixedly disposed in parallel with a moving direction of the carriage; and a gear rotatably disposed on the carriage so as to mesh with the rack. 2. The automatic flaw detection apparatus according to claim 1, wherein the rotation control of the reflecting mirror is performed based on a rotation angle of the gear rotating with the movement of the bogie.