JP2019190868A - Weld quality inspection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inspect the quality of a welding ball formed by welding coil ends of segment coils having different thicknesses. SOLUTION: A step of capturing an image of a welding ball to generate image data, a step of detecting a contour of the welding ball from the image data, and a joining in which a first coil end and a second coil end of the detected contour face each other Direction from the one end on the first coil end side to the second point on the second coil end side shifted by the thickness of the first coil end, and from the other end on the second coil end side in the joining direction of the contour to the second point. A step of detecting a straight line in the direction orthogonal to the joining direction, which is separated by an equal distance from the second point shifted to the first coil end side by the thickness of the coil end, as the center line, and the center line and the contour. A step of detecting the midpoint of the intersection point as a center position, and a step of determining whether or not there is a defect in the welding ball based on the distance of the line segment connecting from the center position to each point on the contour. Is equipped with[Selection diagram] Fig. 6

Description

  The present invention relates to a welding quality inspection method.

  For example, when the coil ends of the segment coils of the stator core are welded to each other and the segment coils are connected to each other, if the shape of the welded portion is distorted, there are problems such as increased electrical resistance and easy disconnection. May occur. Therefore, development of a method and an apparatus for performing such a quality inspection of a welded portion is demanded. Patent Document 1 discloses a defect detection device that analyzes the shape of a welded part by dividing an image of the welded part radially and determines whether or not a defect is generated in the welded part.

Japanese Patent Laid-Open No. 06-027036

  The apparatus described in Patent Document 1 determines whether or not a defect has occurred in the joint by evaluating the symmetry of the joint. However, for example, when the weld ends are formed by welding the coil ends of segment coils having different thicknesses, the intermediate position between the two coil ends may not match the center position of the weld balls. In such a case, even if there is no defect in the weld ball, the shape of the weld ball becomes asymmetrical, and even if the weld ball has a defect, the shape of the weld ball becomes symmetric. Sometimes. Therefore, the method described in Patent Document 1 has a problem that a reliable quality inspection may not be performed.

  This invention is made in view of such a situation, and provides the welding quality inspection method for test | inspecting the quality of the welding ball formed by welding the coil ends of the segment coils from which thickness differs. is there.

  The welding quality inspection method according to the present invention is formed by welding a first coil end of a first segment coil incorporated in a stator core and a second coil end of a second segment coil incorporated in the stator core. A welding quality inspection method for inspecting the quality of a weld ball, comprising: an imaging step for imaging the weld ball to generate image data; a contour detection step for detecting a contour of the weld ball from the image data; Further, the first coil end and the second coil end of the contour are shifted from the one end on the first coil end side in the joining direction facing each other to the second coil end side by the thickness of the first coil end. The first coil end is equal to the thickness of the second coil end from the first point and the other end of the contour in the joining direction on the second coil end side. A center line detecting step for detecting, as a center line, a straight line in a direction perpendicular to the joining direction and spaced apart from the second point shifted to the side, and the midpoint of the intersection of the center line and the contour A center position detecting step for detecting the weld ball as a center position, and a determination for determining whether or not the weld ball has a defect based on a distance of a line segment connected from the center position toward each point on the contour. And a step.

  In such a configuration, the intermediate position between the two coil ends is estimated in consideration of the thickness of each coil end. And the outline shape of a welding ball is evaluated on the basis of the position. Therefore, the quality of the weld ball can be inspected even for a weld ball formed by welding the coil ends of segment coils having different thicknesses.

  The present invention can provide a welding quality inspection method for inspecting the quality of weld balls formed by welding coil ends of segment coils having different thicknesses.

It is sectional drawing of a rotary electric machine. It is a perspective view of a stator. It is a fragmentary perspective view of a stator. It is a figure which shows the coil end of the segment coil which is not welded. It is a figure which shows the coil end of the welded segment coil. It is a side view of a welding quality inspection apparatus. It is an inspection flow of a welding quality inspection method. It is an example of the image data of a weld ball. It is a figure showing a mode that a center position is detected from the image data of a weld ball. It is a graph showing the relationship between the distance from the center position to each point of the contour and the angle. 9B is a graph showing the relationship between the gradient of distance and the angle in the relationship of FIG. 9A. It is a graph showing the relationship between the distance from the center position to each point of the contour and the angle. It is the graph showing the relationship between the gradient of distance and the angle in the relationship of FIG. 10A. It is a side view of the welding quality inspection apparatus which concerns on a modification.

  Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments. In addition, for clarity of explanation, the following description and drawings are simplified as appropriate.

  The welding quality inspection method according to the present invention is, for example, a method for inspecting the quality of a weld ball formed by welding the coil ends of two segment coils incorporated in a stator core of a rotating electrical machine. The welding quality inspection method is realized by, for example, a welding quality inspection apparatus.

FIG. 1 is a cross-sectional view of a rotating electrical machine 1 that is a three-phase AC motor. As shown in FIG. 1, the rotating electrical machine 1 includes a housing 2, a stator 3 (stator), a rotor 4, and a pair of bearings 5. The stator 3 is accommodated in the housing 2.
The rotor 4 is disposed on the inner peripheral side of the stator 3 and is rotatably supported by the housing 2 via a pair of bearings 5. The rotor 4 has, for example, eight magnetic poles by including a permanent magnet.

FIG. 2 is a perspective view of the stator 3. As shown in FIGS. 1 and 2, the stator 3 includes a stator core 6 (stator core), a three-phase stator coil 7, and a plurality of insulating papers 8.
The stator core 6 is formed in a cylindrical shape by laminating a plurality of electromagnetic steel plates. A plurality of slots 9 (winding accommodation spaces) are formed in the stator core 6.
The plurality of slots 9 are formed at equal intervals in the circumferential direction of the stator core 6. Each slot 9 is elongated along the central axis direction of the stator core 6.
A plurality of U-shaped first segment coils 11 and second segment coils 12 are formed from the stator winding 10. The three-phase stator coil 7 is formed by joining the plurality of formed first segment coils 11 and coil ends of the second segment coils 12 by welding. The stator winding 10 is composed of a conductor part and an insulating film part covering the conductor part. The conductor portion is typically copper. The insulating film portion is, for example, fluorine, nylon, polyamideimide, or polyphenylene sulfide.

  FIG. 3 is a partially enlarged view of the stator 3. The first coil end 21 is a portion of the first segment coil 11 located outside the slot 9 as shown in FIG. The second coil end 22 is a portion of the second segment coil 12 that is located outside the slot 9 as shown in FIG. In the present embodiment, the first coil end 21 and the second coil end 22 are formed in an octagonal cross section.

  4A shows a state in which the first coil end 21 of the first segment coil 11 and the second coil end 22 of the second segment coil 12 face each other with a slight gap in the radial direction of the stator core 6. FIG. If the 1st coil end 21 and the 2nd coil end 22 are heated simultaneously in this state, as shown to FIG. 4B, the welding ball 23 which joins the 1st coil end 21 and the 2nd coil end 22 will be formed. This welding ball 23 makes the first coil end 21 and the second coil end 22 conductive to each other.

FIG. 5 is a plan view showing a welding quality inspection apparatus 30 that performs the welding quality inspection method according to the present embodiment. The welding quality inspection device 30 according to the present embodiment includes a control unit 31, a camera 32, illuminations 33 a to 33 c, and a reflection plate 34.
As a matter of course, the right-handed xyz coordinates shown in FIG. 5 and other drawings are for convenience in explaining the positional relationship of the components. Usually, the z-axis positive direction is vertically upward, and the xy plane is a horizontal plane, which is common between the drawings. In the present embodiment, it is assumed that a portion where the first coil end 21 and the second coil end 22 face each other extends in the z-axis positive direction, and a welding ball 23 is formed at the end thereof. Also, the joining direction, which is the direction in which the first coil end 21 and the second coil end 22 face each other, is the x-axis direction, the first coil end 21 side is the x-axis negative direction side, and the second coil end 22 side is the The x-axis positive direction side.

  The camera 32 is, for example, a CCD (Charge Coupled Device) camera. The camera 32 images the weld ball 23 to be inspected from above (z-axis positive direction) and generates image data of the weld ball 23. The generated image data is output to the control unit 31.

  The illuminations 33a and 33b are, for example, blue LEDs (light emitting diodes) that emit blue light. The illuminations 33a and 33b are provided to face the x-axis direction with the welding ball 23 interposed therebetween. The illuminations 33a and 33b are arranged so as to irradiate the welding ball 23 with blue light from a substantially horizontal direction or a slightly oblique direction from a horizontal plane. Specifically, the illuminations 33a and 33b are arranged so that the angle formed by the blue light to be irradiated and the horizontal plane (xy plane) is within 20 °. As shown in FIG. 5, the blue light emitted from the illuminations 33 a and 33 b toward the welding ball 23 is reflected by the welding ball 23 and reaches the camera 32. Since the blue light emitted by the illuminations 33a and 33b is light that is complementary to the colors of the first segment coil 11 and the second segment coil 12, the contour of the weld ball 23 is raised in the image captured by the camera 32. Can do.

  The illumination 33c is, for example, a red LED that emits red light. The illumination 33c is disposed so as to irradiate red light from above on the imaging region of the camera 32 including the weld ball 23. The illumination 33c is arranged, for example, so that the angle formed by the emitted red light and the imaging direction (z-axis negative direction) of the camera 32 is within 20 °. When the illumination 33c irradiates the welding ball 23 with red light, the reflected light from the welding ball 23 of the blue light irradiated by the illuminations 33a and 33b can be further raised.

  The reflecting plate 34 is, for example, a blue resin plate-like member, and is provided below the welding ball 23 (z-axis negative direction). Even if the gloss of the weld ball 23 is high, the secondary reflected light or scattered light of blue light or red light reflected by the reflector 34 provided on the back of the weld ball 23 strikes the weld ball 23. 23 contours are extracted. Therefore, the image of the weld ball 23 can be acquired accurately and stably.

  The control unit 31 includes, for example, a central processing unit (CPU) as a central processing unit, a read / write free RAM (Random Access Memory), and a read only ROM (Read Only Memory). Then, the CPU reads and executes the quality inspection program stored in the ROM so that the quality inspection program causes hardware such as the CPU to function, and the control unit 31 controls the operation of each part of the welding quality inspection device 30. . Moreover, the control part 31 evaluates the quality of the welding ball 23 from the image data which the camera 32 imaged with the method mentioned later.

Here, the welding quality inspection method of this embodiment is demonstrated using FIG. FIG. 6 is a flowchart showing the flow of the welding quality inspection method of the present embodiment.
First, as shown in FIG. 6, in step S <b> 1 (imaging step), the illuminations 33 a to 33 c irradiate the welding ball 23 with light, and the camera 32 images the welding ball 23 to generate image data.

  FIG. 7 is an example of the image data 20 of the weld ball 23 captured by the camera 32. A bright part surrounded by the outline 24 in the image data 20 is the imaged weld ball 23. It is assumed that the first coil end 21 and the second coil end 22 are respectively arranged at positions indicated by two-dot chain lines in the image data 20. The two-dot chain line shown in the image data 20 is a virtual line for explanation, and is not actually displayed.

  Next, when proceeding to step S2 (contour detection step), the control unit 31 detects the contour 24 of the weld ball 23 from the image data 20 as shown in FIG. 6 (see FIG. 7). For example, the control unit 31 detects a region corresponding to the weld ball 23 based on the luminance of each pixel of the image data 20. Specifically, for example, the control unit 31 detects a region where pixels having a luminance equal to or higher than a predetermined luminance value are continuous, and if the area of the region is equal to or larger than a predetermined area value, the region is welded. It is determined that it corresponds to the ball 23. In this way, the control unit 31 detects the boundary between the region of the weld ball 23 and the other region as the contour 24.

  Thereafter, when the process proceeds to step S3 (center line detection step), the control unit 31 detects a center line indicating the center of joining of the first coil end 21 and the second coil end 22. After the control unit 31 detects the center line, the process proceeds to step S4.

Here, a specific example of processing in step S3 will be described with reference to FIG. FIG. 8 is a diagram in which the contour 24 detected in step S2 is extracted from the image data 20 of FIG.
First, the control unit 31 has one end P _x1 on the first coil end 21 side (x-axis negative direction side) in the joining direction (x-axis direction) where the first coil end 21 and the second coil end 22 of the contour 24 face each other. Is detected. Further, the control unit 31 detects the other end P _x2 on the second coil end 22 side (x-axis positive direction side) in the joining direction (x-axis direction) of the contour 24.
Further, the control unit 31 detects the first point P _x3 shifted from the one end P _x1 to the second coil end 22 side (x-axis positive direction side) by the thickness T ₁ of the first coil end 21. Moreover, detecting the second point _{P x4} obtained by shifting the amount corresponding first coil end 21 side of the thickness _{T 2} (x-axis negative direction side) from the other end _{P x2} second coil end 22.
Then, the control unit 31 detects, as the center line L _yc , a straight line that is separated from the first point P _x3 and the second point P _x4 by an equal distance and orthogonal to the joining direction (y-axis direction). To do.

Here, since one end P _x1 is considered to be on the end side of the first coil end 21 on the x-axis negative direction side, the first point P _x3 is the end of the first coil end 21 on the x-axis positive direction side. It can be estimated that it corresponds to the side. Since the other end P _x2 is considered to be on the end side of the second coil end 22 on the x-axis positive direction side, the second point P _x4 is the end of the second coil end 22 on the x-axis negative direction side. It can be estimated that it corresponds to the side.
Therefore, the region between the first point P _x3 and the second point P _x4 in the joining direction (x-axis direction) is estimated to correspond to the region between the first coil end 21 and the second coil end 22. can do. For this reason, it can be estimated that the center line L _yc is a line representing the middle between the first coil end 21 and the second coil end 22.

Next, when proceeding to step S4 (center position detection step), as shown in FIG. 6, the control unit 31 determines the midpoints of the intersections P _y1 and P _y2 between the center line L _yc and the contour 24 as the center position P _c. (See FIG. 8).

Thereafter, when the process proceeds to step S5 (determination step), the control unit 31 determines whether or not the weld ball 23 is defective based on the distance of the line segment connected from the center position _Pc toward each point on the contour 24. Determine whether. Thereafter, the flow ends.

Here, a specific example of processing in step S5 will be described with reference to FIGS. 8, 9A, 9B, 10A, and 10B.
First, as shown in FIG. 8, the control unit 31 detects a reference line L _xc that is a half line drawn in the positive direction of the x axis with the center position P _c as an end point. Next, the control unit 31 detects a half line L _θ that is rotated by an angle θ from the reference line L _xc around the center position P _c . Next, the control unit 31 detects an intersection P _θ between the contour 24 and the half line L _θ . Next, the control unit 31 measures the distance r between the center position _Pc and the intersection point _Pθ .
In this way, the control unit 31 measures the distance r between the corresponding intersection point _Pθ and the center position _Pc while changing the angle θ. When the weld ball 23 does not have a defect and does not have an irregular shape, the distance r is constant regardless of the angle θ, or the distance r changes gently with a change in the angle θ. To do.

9A and 10A are examples of graphs showing the relationship between the distance r and the angle θ. FIG. 9A shows a case where the distance r is constant with respect to the angle θ, and FIG. 10A shows a case where the distance r is not constant with respect to the angle θ. 9B and 10B are examples of graphs showing the relationship between the gradient g and the angle θ, which is a value obtained by differentiating the distance r by the angle θ. 9B shows the relationship between the gradient g and the angle θ corresponding to FIG. 9A, and FIG. 10B shows the relationship between the gradient g and the angle θ corresponding to FIG. 10A.
As shown in FIG. 9A, when the distance r is constant with respect to the angle θ, the gradient g is zero regardless of the angle θ as shown in FIG. 9B. On the other hand, as shown in FIG. 10A, when the distance r is not constant with respect to the angle θ, the gradient g takes a maximum value or a minimum value at an angle θ where the amount of change in the distance r is large, as shown in FIG. 10B.

  The magnitude of the absolute value of the maximum value and the minimum value of the gradient g obtained in this way represents the abrupt change in the distance r. That is, when the absolute value of the maximum value and the minimum value of the gradient g is large, it can be determined that the outline 24 of the weld ball 23 has an irregular shape. Therefore, for example, if the absolute values of the maximum value and the minimum value of the gradient g are all smaller than a predetermined value, the control unit 31 can determine that the weld ball 23 has no defect. Conversely, if either of the maximum value and the absolute value of the minimum value of the gradient g is greater than or equal to a predetermined value, the control unit 31 can determine that the weld ball 23 has a defect.

As described above, in the welding quality inspection method according to the present embodiment, the first coil end 21 and the second coil end 21 are considered in consideration of the thicknesses T ₁ and T ₂ of the first coil end 21 and the second coil end 22. A center position P _c that is an intermediate position of the second coil end 22 is estimated. Then, the shape of the outline 24 of the weld ball 23 is evaluated based on the center position _Pc .
Therefore, the quality of the weld ball can be inspected even for a weld ball formed by welding the coil ends of segment coils having different thicknesses.

Note that the present invention is not limited to the above-described embodiment, and can be modified as appropriate without departing from the spirit of the present invention.
For example, in the process of step S5 (determination step), when the angle θ is changed, the angle θ may be changed by a predetermined increment instead of continuously. In such a configuration, since the number of points for measuring the distance r can be reduced, the processing can be simplified.

Further, in the process of step S5 (determination step), measuring the distance r only for intersections P _theta in the region between the welding direction (x-axis direction) and the first point P _x3 in the second point P _x4 You may make it do. In such a configuration, it is possible to omit the shape evaluation of the contour of the region of the weld ball 23 that can be estimated to correspond to the first coil end 21 or the second coil end 22, thereby simplifying the processing. can do.

Moreover, you may use the welding quality inspection apparatus 40 as shown in FIG. 11 as a modification of the welding quality inspection apparatus 30 shown above. FIG. 11 is a side view of the welding quality inspection apparatus 40.
As shown in FIG. 11, the welding quality inspection device 40 includes a control unit 41, a camera 42, and illuminations 43 a and 43 b instead of the control unit 31, the camera 32, and the illuminations 33 a to 33 c of the welding quality inspection device 30. .

  The camera 42 is a CCD camera, for example. The camera 42 is arranged so that the imaging direction is substantially perpendicular to the joining direction (x-axis direction) and has a predetermined tilt angle with respect to the negative z-axis direction. Specifically, in the camera 42, an angle between the imaging direction and the positive x-axis direction is 80 ° to 100 °, and an angle between the imaging direction and the z-axis negative direction is 10 ° to 50 °. It is arranged to be °. The camera 42 images the weld ball 23 to be inspected and generates image data of the weld ball 23. The generated image data is output to the control unit 41.

  The illumination 43a is, for example, an LED that emits blue or red light. The illumination 43b is, for example, a white LED that emits white light. The illumination direction of the illumination 43a is arranged on the side opposite to the camera 42 with the welding ball 23 to be imaged as a boundary. The illumination direction of the illumination 43b is arranged on the same side as the camera 42 with the welding ball 23 to be imaged as a boundary. The light emitted from the illumination 43 a toward the welding ball 23 is reflected by the welding ball 23 and reaches the camera 42. Since the light emitted by the illumination 43a is light complementary to or the same color as the colors of the first segment coil 11 and the second segment coil 12, the contour of the weld ball 23 can be raised in the image captured by the camera 42. it can.

Further, the white light emitted from the illumination 43 b is reflected by the first coil end 21, the second coil end 22, and the welding ball 23 and reaches the camera 42. Therefore, the camera 42 can capture images of the first coil end 21 and the second coil end 22. That is, the camera 42 can image the first coil end 21, the second coil end 22, and the weld ball 23. In such a configuration, the control unit 41 can directly detect the regions corresponding to the first coil end 21 and the second coil end 22 from the image data acquired from the camera 42, so that the welding ball 23 It is possible to directly detect the center position _Pc of the junction. That is, the processing of steps S3 to S4 can be simplified.

  Further, since the camera 42 images the weld ball 23 from an oblique direction, it can also capture an image of the weld ball 23 in the z-axis direction. Therefore, the control unit 41 can obtain information on the penetration depth d that is the depth of the weld ball 23 in the z-axis direction. At this time, the control unit 41 may determine that the weld ball 23 has a defect even when the penetration depth d of the weld ball 23 is smaller than a predetermined value.

Note that the welding quality inspection device 30 and the welding quality inspection device 40 may be used in combination. For example, the center position _Pc of the welding ball 23 may be detected by the welding quality inspection device 40 and the shape of the outline 24 of the welding ball 23 may be evaluated by the welding quality inspection device 30.

DESCRIPTION OF SYMBOLS 1 Rotating electrical machine 2 Housing 3 Stator 4 Rotor 5 Bearing 6 Stator core 7 Stator coil 8 Insulating paper 9 Slot 10 Stator winding 11 First segment coil 12 Second segment coil 20 Image data 21 First coil end 22 Second coil end 23 Weld ball 24 Contour 30, 40 Weld quality inspection device 31, 41 Control unit 32, 42 Cameras 33a, 33b, 33c, 43a, 43b Illumination 34 Reflector plate d Depth of penetration L _xc Reference line L _yc Center line L _θ half line P _c center position P _x1 one end P _x2 other end P _x3 first point P _x4 second point P _y1 , P _y2 , P _θ intersection r distance

Claims (1)

Welding quality inspection for inspecting the quality of the weld ball formed by welding the first coil end of the first segment coil incorporated in the stator core and the second coil end of the second segment coil incorporated in the stator core. A method,
An imaging step of imaging the weld ball to generate image data;
A contour detecting step for detecting a contour of the weld ball from the image data;
From the one end of the first coil end side in the joining direction where the first coil end and the second coil end of the detected contour are opposed to each other toward the second coil end side by the thickness of the first coil end. The shifted first point and the second point shifted from the other end on the second coil end side in the joining direction of the contour toward the first coil end side by the thickness of the second coil end. And a centerline detection step for detecting a straight line in a direction perpendicular to the joining direction and separated by an equal distance as a centerline,
A center position detecting step of detecting a midpoint of an intersection of the center line and the contour as a center position;
A determination step of determining whether or not the weld ball has a defect based on a distance of a line segment connected from the center position toward each point on the contour.
Welding quality inspection method.