JP6794301B2 - Center misalignment detection device and center misalignment detection method - Google Patents

Description

In the present invention, a workpiece having a rotationally symmetric shape around an axis of symmetry and having an outer peripheral portion in which convex portions and concave portions are periodically repeatedly provided is set as a detection target, and the core deviation of the work with respect to the rotating portion is detected. It relates to detection technology.

As a device for inspecting the appearance of a work that is rotationally symmetric about the axis of symmetry, for example, the work inspection device described in Patent Document 1 is known. In this work inspection device, the work is held by a holder portion connected to the motor. Then, the work is imaged by a plurality of cameras while rotating the work by the motor, and the appearance of the work is inspected based on the captured images.

Japanese Unexamined Patent Publication No. 2012-63268

The device described in Patent Document 1 uses a gear as a work, and inspects the gear for scratches or defects. In this device, the holder portion has a shaft portion that is passed through a through hole that penetrates the work in the axial direction, and a clamp mechanism that clamps the work coaxially with the shaft portion. Then, as the rotation shaft of the motor rotates, the shaft portion and the work rotate integrally. Here, if the outer peripheral surface of the work is a smooth surface, even if the axis of symmetry of the work held by the clamp mechanism and the axis of rotation of the motor do not match, the captured image can be processed. It is possible to inspect the above inspection with relatively high accuracy. On the other hand, when a workpiece such as a gear in which concave portions and convex portions are periodically repeated with respect to the outer peripheral surface is targeted for inspection, it is difficult to perform the above inspection by simple image processing. Therefore, in order to inspect such a work with high accuracy, it is desired to accurately grasp the misalignment of the work with respect to the motor. However, there has been no technique for detecting the above-mentioned misalignment with high accuracy.

The present invention has been made in view of the above problems, and has a highly accurate misalignment with respect to a rotating portion of a work having an outer peripheral portion in which convex portions and concave portions are periodically and repeatedly provided in a rotationally symmetric shape around an axis of symmetry. It is an object of the present invention to provide a misalignment detection technique for detecting a center deviation.

One aspect of the present invention is to detect misalignment of a work with respect to a rotating portion, which rotates a work having an outer peripheral portion in which convex portions and concave portions are periodically and repeatedly provided in a rotationally symmetric shape around an axis of symmetry. An image pickup unit that captures an image including at least one circumference of the outer peripheral portion of the work rotated by the rotating portion, which is a misalignment detection device, and an image captured by the imaging unit are subjected to binarization processing. Derived by an image processing unit that extracts the image data of the outer peripheral portion of the work as edge image data, an edge waveform derivation unit that obtains an edge waveform indicating the shape of the outer peripheral portion of the work based on the edge image data, and an edge waveform derivation unit. the concave portion and the convex portion against the edge waveform repetition period of the phase 1/2 of over a moving average filter size on the basis of the discrete points of maximum or minimum values of each phase included in the moving average waveform created a It is characterized by including a misalignment calculation unit for calculating the misalignment of the work with respect to the rotating portion by using the derived function .

Another aspect of the present invention is a method for detecting misalignment, in which a work holding portion has a work having an outer peripheral portion in which convex portions and concave portions are periodically and repeatedly provided in a rotationally symmetric shape around an axis of symmetry. The first step of holding the work by the rotating part, the second step of rotating the work around the rotation axis of the rotating part by rotating the work holding part holding the work by the rotating part, and the outer circumference of the work during the rotation of the work by the rotating part. The third step of acquiring an image including at least one rotation of the portion, and the third step of performing binarization processing on the image acquired by the third step and extracting the image data of the outer peripheral portion of the work as edge image data. 4 and step movement a fifth step of obtaining an edge waveform showing a shape of the outer peripheral portion of the workpiece based on the edge image data, the repetition period of the concave and convex portions for the edge waveform of half the magnitude of the phase The sixth step of calculating the misalignment of the work with respect to the rotating part using a function derived based on the discrete points of the maximum value or the minimum value of each phase included in the moving average waveform created by applying the average filter. It is characterized by being prepared.

In the invention configured as described above, an image including at least one circumference of the outer peripheral portion of the work is acquired while the work is rotated by the rotating portion. Here, when the work is misaligned with respect to the rotating portion, the above image includes information reflecting the misalignment. However, in the present invention, convex portions and concave portions are periodically and repeatedly provided on the outer peripheral portion of the work, and since the above image also includes unevenness information, misalignment is immediately detected from the above image. It's difficult to do. Therefore, in the present invention, the above image is subjected to binarization processing, image data of the outer peripheral portion of the work, that is, edge image data is extracted, and the shape of the outer peripheral portion of the work is shown based on the edge image data. We are looking for an edge waveform. Then, the misalignment of the work with respect to the rotating portion is calculated based on the edge waveform.

As described above, according to the present invention, an edge waveform showing the shape of the outer peripheral portion of the work is obtained from an image including at least one circumference of the outer peripheral portion of the work, and the center deviation of the work with respect to the rotating portion is obtained based on the edge waveform. Is calculated, it is possible to detect the misalignment of the work with respect to the rotating portion with high accuracy.

It is a figure which shows the whole structure of the inspection apparatus equipped with one Embodiment of the misalignment detection apparatus which concerns on this invention. It is a block diagram which shows the electrical structure of the inspection apparatus shown in FIG. It is a perspective view which shows the structure of the work holding unit. It is a flowchart which shows the inspection operation of the workpiece by the inspection apparatus shown in FIG. It is a figure which shows the inspection operation schematically. It is a flowchart which shows the misalignment detection process which is one Embodiment of the misalignment detection method which concerns on this invention. It is a figure which shows an example of various waveforms acquired by the misalignment detection method shown in FIG.

FIG. 1 is a diagram showing an overall configuration of an inspection device equipped with the first embodiment of the misalignment detecting device according to the present invention. Further, FIG. 2 is a block diagram showing an electrical configuration of the inspection device shown in FIG. The inspection device 100 is a device that inspects the appearance of a work W having an outer peripheral portion such as a gear or an impeller, which has a shape rotationally symmetric around an axis of symmetry and is provided with convex portions and concave portions periodically and repeatedly. Yes, it has a loading unit 1, a work holding unit 2, an imaging unit 3, an unloading unit 4, and a control unit 5. Here, the work W is a mechanical part in which the gear Wb is provided on the upper portion of the shaft portion Wa as shown in FIG. 1, and is formed by, for example, forging or casting. Then, after the parts are manufactured, the work W is transported to the loading unit 1 by an external transfer robot or an operator.

The loading unit 1 is provided with a work accommodating portion (not shown) such as a table or a stocker. Then, when the work W is temporarily accommodated in the work accommodating portion by an external transfer robot or the like, the work detection sensor 11 (FIG. 2) provided in the work accommodating portion detects the work W and outputs a signal to that effect. It is transmitted to the control unit 5 that controls the whole. Further, the loading unit 1 is provided with a loader 12 (FIG. 2), receives an uninspected work W housed in the work accommodating unit in response to an operation command from the control unit 5, and receives the uninspected work W, and the work holding unit 2 Transport to.

FIG. 3 is a perspective view showing the configuration of the work holding unit. The work holding unit 2 is equipped with holding tables 21A and 21B for holding the work W conveyed by the loader 12. Both of these holding tables 21A and 21B have the same configuration, and can hold a part of the shaft portion Wa of the work W in a posture in which the gear Wb is in a horizontal state. Hereinafter, the configuration of the holding table 21A will be described with reference to FIG. 3, but since the holding table 21B has the same configuration as the holding table 21A, the holding table 21B is designated by the same reference numerals and the description thereof will be omitted.

In the holding table 21A, as shown in FIG. 3, the chuck mechanism 22, the horizontal positioning mechanism 23, the rotating mechanism 24, and the vertical positioning mechanism 25 are stacked and arranged in the vertical direction. The chuck mechanism 22 has a movable member 221 to 223 having a substantially L-shape in side view, and a moving unit 224 that moves the movable members 221 to 223 in a radial manner in response to a movement command from the control unit 5. ing. A protrusion member 225 is projected from the upper end surfaces of the movable members 221 to 223, and the upper end surface and the protrusion member 225 can engage with the stepped portion of the shaft portion Wa. Therefore, the moving portion 224 moves the movable members 221 to 223 close to each other in response to the gripping command from the control unit 5, so that the central axis of the chuck mechanism 22 (reference numeral AX2 in FIG. 5) and the axis of the shaft portion Wa are used. The work W can be held while matching with. On the other hand, the moving unit 224 moves the movable members 221 to 223 apart from each other in response to the release command from the control unit 5, so that the uninspected work W is loaded by the loading unit 1 and the inspected work W is moved by the unloading unit 4. It becomes possible to perform unloading.

The chuck mechanism 22 configured in this way is supported by the horizontal positioning mechanism 23. The horizontal positioning mechanism 23 has a so-called XY table that moves in directions orthogonal to each other in the horizontal direction. Therefore, the XY table is driven in response to the movement command from the control unit 5, and the chuck mechanism 22 can be positioned with high accuracy on the horizontal plane. As the XY table, a combination of a motor and a ball screw mechanism, a combination of two linear motors orthogonal to each other in the horizontal direction, and the like can be used.

The rotation mechanism 24 has a motor 241. The rotating shaft of the motor 241 (reference numeral 242 in FIG. 5) extends vertically upward, and the horizontal positioning mechanism 23 is connected to the upper end portion thereof. Therefore, when a rotation command is given from the control unit 5, the motor 241 operates and is gripped by the horizontal positioning mechanism 23, the chuck mechanism 22, and the chuck mechanism 22 around the rotation axis (reference numeral AX3 in FIG. 5) of the motor 241. The work W is integrally rotated.

Here, in the present embodiment, the horizontal positioning mechanism 23 is provided between the chuck mechanism 22 and the rotation mechanism 24, but the technical significance thereof is the work W gripped by the central axis of the chuck mechanism 22 and the chuck mechanism 22. The relative positional relationship between the axis of symmetry of the gear Wb (reference numeral AX4 in FIG. 5) and the rotation axis of the motor 241 can be adjusted by the horizontal positioning mechanism 23. That is, by aligning the central axis of the chuck mechanism 22 with the rotation axis of the motor 241, the work W gripped by the chuck mechanism 22 can be rotated around the shaft portion Wa. However, when the axis of symmetry of the gear Wb is deviated from the shaft portion Wa, the motor 241 is misaligned and the gear Wb rotates eccentrically. Therefore, by providing the horizontal positioning mechanism 23 and driving it so as to correct the deviation amount and the deviation direction, it is possible to match the symmetry axis of the gear Wb with the rotation axis of the motor 241. As a result, the image of the gear Wb by the imaging unit 3 can be captured with high accuracy, and the inspection accuracy of the work W can be improved.

The vertical positioning mechanism 25 vertically connects the holding plate 251 that holds the motor 241 and the base plate 252 that is arranged below the motor 241, the four connecting pins 253 that connect the holding plate 251 and the base plate 252, and the base plate 252. It has an elevating part 254 that elevates and elevates in a direction. The elevating unit 254 raises and lowers the base plate 252 in response to an elevating command from the control unit 5 to integrally move the rotation mechanism 24, the horizontal positioning mechanism 23, and the chuck mechanism 22 in the vertical direction, and the prealignment position described below is described. The height position of the work W can be optimized in the PA and the inspection position PI.

As shown in FIG. 3, the holding tables 21A and 21B configured in this way are fixed on the support plate 261 at a distance of a certain distance. Further, the support plate 261 is supported by the swivel drive unit 262 at an intermediate position between the holding tables 21A and 21B. The swivel drive unit 262 can swivel the support plate 261 180 ° around the swivel shaft AX1 extending in the vertical direction in response to the swivel command from the control unit 5, and the holding tables 21A and 21B are provided as shown in FIG. The first position located at the pre-alignment position PA and the inspection position PI, respectively, and the holding tables 21A and 21B can be switched between the second position located at the inspection position PI and the pre-alignment position PA, respectively. For example, in parallel with performing the pre-alignment process on the work W held on the holding table 21A located at the pre-alignment position PA, the holding table 21A is switched from the first position to the second position by the turning drive unit 262. Shifts from the pre-alignment position PA to the inspection position PI, and the pre-aligned work W can be positioned at the inspection position PI. Further, after the inspection of the work W is completed, the holding table 21A shifts from the inspection position PI to the pre-alignment position PA by turning in the opposite direction, and the inspection-processed work W is positioned at the pre-alignment position PA. Can be done. As described above, in the present embodiment, the position switching mechanism 26 for switching the position of the work W is configured by the support plate 261 and the swivel drive unit 262.

The pre-alignment position PA is a position where the pre-alignment process is performed as described above, and the alignment camera 27 is arranged above the holding table 21A (or 21B) positioned at the pre-alignment position PA. As shown in FIG. 3, the alignment camera 27 is arranged on the opposite side of the motor 241 with respect to the work W, that is, on the upper side of the work W, and extends radially outward with respect to the symmetry axis AX4 of the work W. It has a line sensor 271. Therefore, the upper surface of the work W can be imaged by the line sensor 271 while rotating the work W, and a convex portion (tooth end) formed on the outer peripheral portion of the gear Wb by rotating the work W at least once. ) And all of the recesses (teeth) are included.

Further, although not shown in FIG. 3, an alignment illumination unit 28 (FIG. 2) is provided for illuminating the work W held on the holding table 21A (or 21B) to perform an alignment process satisfactorily. Has been done. Therefore, the work W can be rotated by the rotation mechanism 24, and the work W can be imaged by the alignment camera 27 while the work W is illuminated by the alignment illumination unit 28. Then, the image data of the work W is sent to the control unit 5, and the misalignment is corrected to match the symmetry axis of the gear Wb with the rotation axis of the motor 241, that is, the prealignment process is executed.

On the other hand, the inspection position PI is a position where the inspection process is performed, and the imaging unit 3 is arranged above the holding table 21A (or 21B) positioned at the inspection position PI. In this inspection position PI, the work W can be imaged by the image pickup unit 3 while rotating the work W in a state where the axis of symmetry of the gear Wb and the axis of rotation of the motor 241 coincide with each other. Then, the image data of the work W is sent to the control unit 5, and an inspection process for inspecting the presence or absence of scratches or defects in the gear Wb is executed.

As shown in FIG. 2, the imaging unit 3 has a plurality of inspection cameras 31 and a plurality of inspection lighting units 32. In the imaging unit 3, a plurality of inspection lighting units 32 are arranged so as to illuminate the work W held by the holding table 21A (or 21B) positioned at the inspection position PI from various directions. Then, the work W can be rotated by the rotation mechanism 24, and the work W can be imaged from various directions by the plurality of inspection cameras 31 while the work W is illuminated by the inspection illumination unit 32. These plurality of image data are sent to the control unit 5, and the work W is inspected by the control unit 5.

The holding table 21A (or 21B) for holding the work W inspected in this way is shifted from the inspection position PI to the prealignment position PA by the position switching mechanism 26 as described above. Then, the inspected work W is carried out from the holding table 21A (or 21B) by the unloading unit 4. The unloading unit 4 is basically the same as the loading unit 1. That is, the unloading unit 4 has a work accommodating portion (not shown) for temporarily accommodating the inspected work W, a work detection sensor 41 (FIG. 2), and an unloader 42 (FIG. 2), and is a control unit. The inspected work W is conveyed from the holding table 21A (or 21B) to the work accommodating portion in response to the operation command from 5.

As shown in FIG. 2, the control unit 5 temporarily stores a well-known CPU (Central Processing Unit) that executes logical operations, a ROM (Read Only Memory) that stores initial settings, and various data during device operation. It is composed of a RAM (Random Access Memory) and the like for storing data. The control unit 5 functionally includes an arithmetic processing unit 51, a memory 52, a drive control unit 53, an external input / output unit 54, an image processing unit 55, and a lighting control unit 56.

The drive control unit 53 controls the drive of drive mechanisms such as the loader 12 and the chuck mechanism 22 provided in each unit of the device. The external input / output unit 54 inputs signals from various sensors equipped in each part of the device, and outputs signals to various actuators and the like equipped in each part of the device. The image processing unit 55 takes in image data from the alignment camera 27 and the inspection camera 31 and performs image processing such as binarization. The lighting control unit 56 controls lighting and extinguishing of the alignment lighting unit 28 and the inspection lighting unit 32.

The arithmetic processing unit 51 has an arithmetic function, and is described below by controlling the drive control unit 53, the image processing unit 55, the lighting control unit 56, and the like according to a program stored in the memory 52. Execute the processing of.

Reference numeral 6 in FIG. 2 is a display unit that functions as an interface with the operator. In addition to the function of being connected to the control unit 5 to display the operating state of the inspection device 100, it is composed of a touch panel and is input from the operator. It also has a function as an input terminal that accepts. Further, the present invention is not limited to this configuration, and a display device for displaying an operating state and an input terminal such as a keyboard or a mouse may be adopted.

FIG. 4 is a flowchart showing an inspection operation of the work by the inspection device shown in FIG. Further, FIG. 5 is a diagram schematically showing an inspection operation. In FIG. 5, dots are added to the holding table 21B and the work W held by the holding table 21B in order to clearly distinguish the operations of the holding tables 21A and 21B.

In the inspection device 100, the arithmetic processing unit 51 controls each unit of the device according to an inspection program stored in advance in the memory 52 of the control unit 5 to execute the following operations. Here, various operations performed on one work W will be described with reference to FIGS. 4 and 5. In the control unit 5, the work W does not exist in the holding table 21A located at the prealignment position PA as shown in the column (a) of FIG. 5, and the uninspected work W is loaded by the work detection sensor 11. After confirming that the work W is housed in the work housing unit of No. 1, loading of the work W onto the holding table 21A is started (step S1). In this loading step, the loader 12 grips the uninspected work W in the work accommodating portion and conveys it from the loading unit 1 to the holding table 21A. In this embodiment, in order to smoothly perform the loading step and the subsequent misalignment detection step, the horizontal positioning mechanism is shown in the column (a) of FIG. 5 before the work W is transferred to the holding table 21A. The central axis AX2 of the chuck mechanism 22 and the rotation axis AX3 of the motor 241 are aligned by 23, and the three movable members 221 to 223 are separated from each other to prepare for receiving the work W.

When the work W is conveyed to the holding table 21A by the loader 12, the chuck mechanism 22 moves the three movable members 221 to 223 close to each other as described above to sandwich a part of the shaft portion Wa of the work W. Hold the work W. More specifically, during the loading operation, the movable members 221 to 223 move close to each other, and the upper end surfaces of the movable members 221 to 223 and the protrusion member 225 engage with the stepped portion of the shaft portion Wa to form the chuck mechanism 22. The work W is held while aligning the central axis AX2 with the axis of the shaft portion Wa (see column (b) in FIG. 5). In this way, the loading step is completed, and at the time of completion, the rotation shaft AX3 of the motor 241, the central shaft AX2 of the chuck mechanism 22, and the shaft cores of the shaft portion Wa are aligned. However, in the work W manufactured by forging or casting, for example, as shown in column (b) of FIG. 5, the symmetric axis AX4 of the gear Wb deviates from the axis of the shaft portion Wa, and the work W is misaligned with respect to the motor 241. May have occurred.

Therefore, in the present embodiment, the uninspected work W is illuminated by the alignment illumination unit 28 (FIG. 2), and the gear Wb is imaged by the alignment camera 27 while the uninspected work W is rotated by the motor 241 of the holding table 21A. The image data is stored in the memory 52 (step S2).

After the imaging is completed, the swivel drive unit 262 switches from the first position to the second position. That is, the swivel drive unit 262 swivels the support plate 261 around the swivel shaft AX1 by 180 °, whereby the holding table 21A for holding the uninspected work W as shown in column (c) of FIG. 5 is in the prealignment position PA. The work W is moved to the inspection position PI and the work W is moved to a height position where the image pickup unit 3 can take an image by the elevating part 254 (step S3).

Further, in the present embodiment, in parallel with the above movement, the image data of the work W is read from the memory 52, and the work W is misaligned with respect to the rotation mechanism 24 (motor 241) (in the present embodiment, the misalignment amount Δ and the misalignment direction). (Corresponding to the information including and) is detected (step S4), and subsequently, the misalignment correction in the holding table 21A is performed (step S5). The misalignment detection step (step S4) will be described in detail later. In this misalignment correction, the chuck mechanism 22 is moved by the horizontal positioning mechanism 23 so as to eliminate the misalignment detected in step S4. As a result, as shown in column (c) of FIG. 5, the symmetry axis of the gear Wb and the rotation axis of the motor 241 coincide with each other when the holding table 21A reaches the inspection position PI or before and after the arrival, and the work imaging step is performed immediately. (Step S6) can be started.

In this step S6, the rotation mechanism 24 of the holding table 21A positioned at the inspection position PI operates to start the work rotation. At this time, the work W held by the holding table 21A is in a so-called centering state that has undergone the above-mentioned misalignment correction, and rotates around the axis of symmetry AX4. Further, a plurality of inspection lighting units 32 are lit in response to the rotation to illuminate the rotating work W from a plurality of directions. Although the inspection lighting unit 32 is turned on after the work is rotated, the lighting timing is not limited to this, and the inspection lighting unit 32 is started to be turned on at the same time as the rotation starts or before the rotation starts. May be good.

While rotating and illuminating the work W in this way, a plurality of inspection cameras 31 image the work W from various directions, and image data of the work W image (hereinafter referred to as “work image”) from the plurality of directions. Is transmitted to the control unit 5. On the other hand, the control unit 5 stores the image data in the memory 52 and inspects the work W based on the image data at the following timings.

After acquiring such an image, the work rotation is stopped at the holding table 21A, and the inspection illumination unit 32 is turned off at the imaging unit 3. Further, the swivel drive unit 262 reversely swivels the support plate 261 around the swivel shaft AX1 by 180 °, whereby the holding table 21A moves from the inspection position PI to the prealignment position PA while holding the inspected work W and moves up and down. The work W is moved to the original height position by the portion 254 (step S7). In parallel with the movement of the work W, the control unit 5 reads the image data from the memory 52, determines whether or not the gear Wb has scratches or defects based on the work image, and holds the work W in the holding table 21A. A work inspection is performed on the work W (step S8).

The work W that has returned to the prealignment position PA is gripped by the unloader 42, and then handed over from the holding table 21A to the unloader 42 by releasing the grip by the movable members 221 to 223. Subsequently, the unloader 42 conveys the work W to the unloading unit 4 and conveys it to the work accommodating portion (not shown) (step S9). The series of steps (steps S1 to S9) described above are alternately repeated by the holding tables 21A and 21B.

Next, the misalignment detection step (step S4) executed in the present embodiment will be described in detail with reference to FIGS. 6 and 7. FIG. 6 is a flowchart showing a misalignment detection step according to an embodiment of the misalignment detection method according to the present invention, and FIG. 7 shows an example of various waveforms acquired by the misalignment detection method shown in FIG. It is a figure. The misalignment detection step is executed by the arithmetic processing unit 51 operating as follows according to the misalignment detection program stored in advance in the memory 52 of the control unit 5.

In the present embodiment, the central axis AX2 of the chuck mechanism 22 and the rotation axis AX3 of the motor 241 are matched by the horizontal positioning mechanism 23 and held by the chuck mechanism 22 prior to executing the misalignment detection step. The shaft portion Wa of the work W coincides with the rotation shaft AX3 of the motor 241. However, in the work W formed by forging or the like, the symmetric axis AX4 of the gear Wb may deviate from the axis of the shaft portion Wa, and the motor 241 may be misaligned. Therefore, in the present embodiment, the misalignment of the work W loaded on the holding table 21A is detected by the procedure described in detail below. Since misalignment is detected in the work W held on the holding table 21B in exactly the same manner, the description of the misalignment detection of the work W will be omitted.

When the loading of the uninspected work W onto the holding table 21A is completed, the gear Wb is imaged from above by the alignment camera 27 while rotating the work W while the work W is illuminated by the alignment illumination unit 28. As a result, the work image I1 for one round of the gear Wb is acquired, and the image data of the work image I1 is sent to the image processing unit 55 (step S401). The image processing unit 55 creates a continuous image I3 for three laps of the work by connecting three work images I1 (step S402). Further, the noise component is removed by the smoothing filter processing to create a smoothed image Is (step S403). Furthermore, the smoothed image Is is converted into a binary image by a binarization process such as Otsu's method, and the binary image data of the region corresponding to the gear Wb of the work W (hereinafter referred to as "edge region") is converted into edge image data. Is extracted as (step S404).

Next, the arithmetic processing unit 51 executes the following series of processes (steps S405 to S412) to obtain the misalignment of the work W from the edge image data. That is, by converting the edge image data indicating the edge region into run length data, for example, as shown in column (a) of FIG. 7, an edge waveform F indicating the shape of the edge region for three laps is derived (step). S405). The horizontal axis X in each of the graphs shown in columns (a) and (b) of FIG. 7 indicates the pixel position of the smoothed image Is (corresponding to the rotation angle of the work W and the position in the circumferential direction of the gear Wb). The vertical axis Y indicates the edge position of the line sensor 271 in the longitudinal direction (radial direction of the gear Wb).

Further, the edge waveform F is subjected to a moving average process to derive the moving average waveform Fs shown in column (b) of the figure (step S406). Here, in the gear Wb of the work W (corresponding to an example of the "outer peripheral portion of the work" of the present invention), the convex portion and the concave portion are repeatedly provided, and a periodic phase exists. Assuming that the number of pixels in the phase (range of rotation angle) is L1, the filter size of the moving average filter is set to (L1 / 2). Each phase in the moving average waveform Fs thus obtained has one maximum value and one minimum value, one of which corresponds to the tooth tip position of the gear Wb and the other corresponds to the tooth bottom position. ..

In the present embodiment, the maximum values of each phase included in the moving average waveform Fs are extracted, and a function Fn indicating a change in the tooth tip position (or tooth bottom position) with rotation of the work W is derived from those discrete points. (Step S407). The graph shown in column (c) of FIG. 7 is an example of the function Fn, and the steep left end of the graph is a problem in data processing when deriving the function. The data does not indicate the tooth tip position (tooth base position). Therefore, in the present embodiment, the mean value AV of the function Fn is derived by removing the steep data of the left end portion (step S408). Here, as is clear from the column (c) of FIG. 7, when the misalignment does not occur, the tooth tip position (tooth bottom position) is the average value AV line regardless of the rotation angle of the work W. It is located above (broken line in the figure). On the other hand, when misalignment occurs, it fluctuates with the rotation cycle of the work W as shown by the solid line in the figure, and the maximum value of the amount of fluctuation from the average value AV corresponds to the misalignment amount Δ (see FIG. 5). , The rotation angle indicating the maximum value corresponds to the deviation direction.

Therefore, in the present embodiment, as shown in the column (d) of FIG. 7, a function Fz indicating the relative variation amount from the average value AV for one round of the work W is extracted (step S409), and based on the function Fz. Along with deriving the deviation direction (step S410), the deviation amount Δ is derived (step S411). More specifically, the deviation direction is set by the following equation based on the pixel position Xmax at which the function Fz shows the maximum and the number of pixels L corresponding to one round of the work W. The deviation direction = Xmax / L × 360 °.
Seeking by. Of course, instead of the pixel position Xmax, the pixel position Xmin whose function Fz indicates the minimum may be used. Further, the amplitude A is calculated from the maximum value Ymax and the minimum value Ymin of the function Fz by the following equation A = (Ymax−Ymin) / 2.
The value obtained by multiplying the amplitude A by the resolution of the line sensor 271 is defined as the deviation amount Δ.

As described above, in the present embodiment, the edge image data (image data of the outer peripheral portion of the gear Wb) is obtained from the smoothed image Is created based on the work image I1 obtained by imaging while rotating the work W. At the same time as extracting, the edge image data is converted into run length data to obtain the edge waveform F. The edge waveform F accurately indicates the shape of the outer peripheral portion of the gear Wb, and the misalignment of the work W with respect to the rotation axis AX3 of the motor 241 can be calculated with high accuracy based on the edge waveform F. Then, the misalignment can be satisfactorily corrected by driving the horizontal positioning mechanism 23 so as to eliminate the misalignment (= misalignment direction + misalignment amount Δ) derived in this way. Further, since the work W is inspected by imaging the work W while rotating the work W after correcting the misalignment, the work inspection can be performed with high accuracy.

Further, in the present embodiment, three work images I1 for one round of the gear Wb are connected to create a continuous image I3, and the misalignment is detected based on the continuous image I3. Therefore, the following operations are performed. The effect is obtained. For example, the continuous image I3 may be acquired while rotating the work W three times at the prealignment position PA, but the amount of rotation of the work W required for detecting the misalignment is large, and the detection time of the misalignment becomes long. On the other hand, in the present embodiment, the amount of rotation of the work W can be set to one round, and the time required for detecting the misalignment can be shortened.

As described above, the rotation mechanism 24 in the present embodiment corresponds to an example of the "rotating unit" of the present invention, and the alignment camera 27 corresponds to an example of the "imaging unit" of the present invention. Further, the arithmetic processing unit 51 functions as the "edge waveform derivation unit" and the "center misalignment calculation unit" of the present invention. The rotation mechanism 24, the alignment camera 27, the arithmetic processing unit 51, and the image processing unit 55 constitute the "center misalignment detection device" of the present invention. Further, the holding tables 21A and 21B correspond to an example of the "work holding portion" of the present invention.

The present invention is not limited to the above-described embodiment, and various modifications other than those described above can be made without departing from the spirit of the present invention. For example, in the above embodiment, the continuous image I3 is created by connecting three work images I1 for one round of the gear Wb, but the continuous image I3 may have a work image of at least one round or more.

Further, in the above embodiment, as shown in FIG. 7, the function Fn is derived from the maximum value of each phase included in the moving average waveform Fs, but the function Fn may be derived from the minimum value.

Further, the method for deriving the edge waveform F is not limited to the above-mentioned conversion of the edge image data into run-length data, and the edge waveform F may be derived by another method.

Further, in the above embodiment, the work W having the gear Wb is set as the detection target, but by using the present invention, the outer circumference is provided with the convex portion and the concave portion periodically and repeatedly provided in a rotationally symmetric shape around the axis of symmetry. It is possible to detect misalignment of the entire work having a portion with high accuracy.

Further, in the above embodiment, the misalignment detection device according to the present invention is applied to the inspection device 100 that detects the misalignment by alternately positioning the two holding tables 21A and 21B at the prealignment position PA. The present invention can also be applied to an inspection device having one or more holding tables. Further, in the above embodiment, the present invention is applied to the inspection device 100 in which the prealigned position PA is separated from the inspection position PI, but the prealigned position PA is made to match the inspection position PI, that is, the center is misaligned at the inspection position. The present invention can also be applied to an inspection device that performs an inspection process after performing detection and misalignment correction. Further, in the inspection device configured in this way, a part of the inspection camera 31 may also function as the alignment camera 27.

The present invention is applied to a general misalignment detection technique for detecting misalignment with respect to a rotating portion of a work having an outer peripheral portion in which convex portions and concave portions are periodically and repeatedly provided in a rotationally symmetric shape around an axis of symmetry. Can be done.

5 ... Control units 21A, 21B ... Holding table (work holding unit)
24 ... Rotation mechanism (rotating part)
27 ... Alignment camera (imaging unit)
51 ... Arithmetic processing unit (edge waveform derivation unit, misalignment calculation unit)
55 ... Image processing unit 100 ... Inspection device 241 ... Motor (rotating part)
271 ... Line sensor AX3 ... Rotation axis (of motor 241) AX4 ... Symmetry axis F ... Edge waveform I1 ... Work image PA ... Prealignment position W ... Work Δ ... Deviation amount

Claims (5)

A misalignment detection device that detects misalignment of the work with respect to the rotating portion by rotating a work having an outer peripheral portion in which convex portions and concave portions are periodically and repeatedly provided in a rotationally symmetric shape around an axis of symmetry. ,
An imaging unit that captures an image including at least one circumference of the outer peripheral portion of the work rotated by the rotating unit.
An image processing unit that performs binarization processing on the image captured by the imaging unit and extracts image data of the outer peripheral portion of the work as edge image data.
An edge waveform deriving unit that obtains an edge waveform indicating the shape of the outer peripheral portion of the work based on the edge image data,
Maximum of each phase included in the moving average waveform created by multiplying the repetition period 1/2 the size the moving average filter of the phase of the concave and convex portions for the edge wave derived by the edge wave deriving unit A misalignment calculation unit that obtains the misalignment of the work with respect to the rotating portion by using a function derived based on the discrete points of the value or the minimum value .
A misalignment detection device characterized by being provided with. The misalignment detecting device according to claim 1.
The imaging unit is a misalignment detecting device having a line sensor extending radially outward with respect to the axis of symmetry of the work on the opposite side of the rotating part with respect to the work. The misalignment detecting device according to claim 1 or 2.
The misalignment calculation unit is a misalignment detecting device that obtains the misalignment amount and the misalignment direction of the axis of symmetry with respect to the rotation axis of the rotating portion as the misalignment. The misalignment detecting device according to any one of claims 1 to 3.
The edge waveform deriving unit is a misalignment detecting device that converts the edge image data into run-length data and obtains the edge waveform. The first step of holding the work work having the outer peripheral portion in which the convex portion and the concave portion are periodically and repeatedly provided in a rotationally symmetric shape around the axis of symmetry by the work holding portion.
The second step of rotating the work around the rotation axis of the rotating portion by rotating the work holding portion holding the work by the rotating portion, and
A third step of acquiring an image including at least one circumference of the outer peripheral portion of the work during rotation of the work by the rotating portion.
In the fourth step, the image acquired in the third step is subjected to binarization processing, and the image data of the outer peripheral portion of the work is extracted as edge image data.
The fifth step of obtaining an edge waveform indicating the shape of the outer peripheral portion of the work based on the edge image data, and
Based on the discrete points of maximum or minimum values of each phase included in the moving average waveform wherein for the edge waveform created by multiplying the moving average filter of half the magnitude of the phase of the repetition period of the recesses and projections A method for detecting a misalignment, which comprises a sixth step of obtaining a misalignment of the work with respect to the rotating portion by using a derived function .

Images