JP5520028B2 - Tire tread identification line inspection method and inspection apparatus therefor - Google Patents

Description

  The present invention relates to a method for inspecting a tire identification line displayed on a tread surface and an inspection apparatus used therefor.

  An identification line may be displayed on the tread surface of the tire. This identification line goes around the tread surface of the tire in the circumferential direction. The type of tire can be identified from the position, color, and number of the identification lines.

  In the automobile production line, there are many types of tires that can be assembled. The identification line displayed on the tread surface facilitates identification of the tire type. This contributes to the efficiency of tire assembly work in automobile production lines. By this identification line, the type of tire can be identified at a glance. In the automobile production line, this identification line suppresses the erroneous assembly of the tire and reduces the inspection work of the erroneous assembly.

  A rubber sheet is molded from rubber as a tread material by an extrusion molding machine. This rubber sheet is extruded into a long band shape. An identification line is displayed on the rubber sheet. This rubber sheet is cooled. The rubber sheet is cut into units of the tread length of the tire. A tread rubber obtained by cutting into length units is wound around the outer peripheral surface to obtain a green tire. This green tire is vulcanized to obtain a tire.

  Conventionally, after the rubber sheet has been cooled, the identification line has been inspected prior to cutting. Here, a display defect such as an interruption of the identification line is detected. At the time of cutting, the rubber sheet is cut to a predetermined length, and the defective display line of the identification line is removed. Thus, a tread rubber having a good identification line is wound around to obtain a tire. An identification line is displayed on the tread surface of the tire.

JP 2009-115715 A JP-A-4-366638

  For this identification line inspection, an image taken by a camera is used. From this image, the position of the identification line is detected. The position of this identification line is measured as the position in the width direction from the left and right ends of the rubber sheet. The rubber sheet being conveyed meanders with respect to the extrusion molding machine. It is difficult to detect the position of the identification line based on the left and right ends of the rubber sheet. The detection accuracy of the width direction position of the identification line is low.

  An object of the present invention is to provide an inspection method excellent in accuracy and efficiency relating to inspection of an identification line, and an inspection apparatus therefor.

The method for inspecting a tire tread identification line according to the present invention includes:
Detecting the left and right end positions of the rubber sheet for tread from image data obtained by camera photography;
Calculating the center position of the rubber sheet from the left and right end positions of the rubber sheet;
A step of setting a detection area in the image data with reference to the center position;
Detecting the width direction position of the identification line in this detection region;
A step of setting an inspection region in the image data based on the detected width direction position of the identification line;
Inspecting the identification line in this inspection area.

  Preferably, in the step of detecting the left and right end positions of the rubber sheet, illumination is applied from the back side of the rubber sheet, and the front side of the rubber sheet is photographed by the camera. The left and right end positions of the rubber sheet are detected based on image data obtained by illumination from the back side.

  Preferably, in the step of detecting the left and right end positions of the rubber sheet, as the left end position of the rubber sheet, a light and dark change point is detected from the outside of the left end of the rubber sheet toward the center of the tread. As the right end position of the rubber sheet, a light and dark change point is detected from the outside of the right end of the rubber sheet toward the center of the tread.

  Preferably, in the step of inspecting the identification line, a plurality of detection windows are arranged and set in a direction in which the identification line extends in the inspection region. Based on the detection of the identification line in the plurality of detection windows, the display failure of the identification line is detected.

  Preferably, in the step of inspecting the identification line, a detection window positioned on the identification line in the inspection region is set. This inspection window is set as a collection area of pixels of a plurality of cameras. Hue, saturation and lightness are measured in the detection window. The color to which the pixel belongs is determined by comparing with predetermined range data of hue, saturation, and lightness of a predetermined color. The number of pixels belonging to each predetermined color is tabulated. A predetermined color having the largest number of pixels is determined. The color of the identification line is determined to be a predetermined color having the largest number of pixels.

The tire tread identification line inspection device according to the present invention is:
A conveyance unit that conveys a rubber sheet on which an identification line is displayed on the surface of the rubber sheet, a camera that photographs the surface of the tread, an image processing unit that converts the image captured by the camera into image data, and the image Based on the recording unit for recording data and the image data recorded in the recording unit, the left and right end positions of the rubber sheet are detected, and the center position of the rubber sheet is calculated from the left and right end positions of the rubber sheet. An image data detection area for detecting the position of the identification line is set with reference to the image, the position of the identification line is detected in this detection area, and the identification line is inspected based on the detected width direction position of the identification line And an arithmetic unit for setting a data inspection area.

  In the identification line inspection method according to the present invention, erroneous detection of the position of the identification line is suppressed. The inspection time for the identification line is shortened. By using the identification line inspection apparatus according to the present invention, erroneous detection of the identification line can be suppressed, and the inspection time can be shortened.

FIG. 1 is an explanatory view showing a tread production line for tires. FIG. 2 is a bird's-eye view showing a part of the production line of FIG. FIG. 3 is a front view showing a part of the production line of FIG. FIG. 4 is an explanatory diagram showing an image taken on the production line of FIG. FIG. 5 is a partially enlarged view indicated by an arrow V in FIG. 6 is a partially enlarged view indicated by an arrow VI in FIG. FIG. 7 is a partially enlarged view indicated by an arrow VII in FIG. FIG. 8 is a partially enlarged view indicated by an arrow VIII in FIG.

  Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings.

  As shown in FIG. 1, the production line 2 includes an extrusion molding machine 4, a cooling device 6, a cutter 8 as a cutting device, a printing device 10, and an inspection device 12. In the production line 2, a tread rubber 14 used for a tire tread is produced. The material of the tread rubber 14 is extruded by the extrusion molding machine 4 to obtain a belt-like rubber sheet 16. The rubber sheet 16 has a long strip shape. The rubber sheet 16 is cooled by the cooling device 6 with a coolant such as water. After cooling, the rubber sheet 16 is cut into a predetermined length by the cutter 8. This cut is the tread rubber 14. Although not shown, a tire is obtained by vulcanizing the tread rubber 14 while being wound around the outer periphery. The tread rubber 14 is vulcanized to form a tire tread.

  The inspection apparatus 12 includes a roller conveyor 18, a camera 20, an image processing unit 22, a keyboard 23 as an input unit, a recording unit 24, and a calculation unit 26 as a transport unit. The rubber sheet 16 is transported by a transport device (not shown) and a roller conveyor 18 of the inspection device 12. The printing apparatus 10 prints on the surface of the rubber sheet 16 being conveyed. Thereby, the identification line 28 is displayed on the surface of the rubber sheet 16.

  As shown in FIGS. 2 and 3, the inspection apparatus 12 includes illuminations 30, 32, and 34. The rubber sheet 16 is moved from the left to the right in FIG. In this production line 2, the left direction in FIG. 3 is the rear in the traveling direction, and the right side is the front in the traveling direction. In the direction perpendicular to the paper surface of FIG. 3, the back side of the paper surface is leftward, and the front side of the paper surface is rightward. The illumination 30 illuminates from the front of the rubber sheet 16 in the traveling direction. The illumination 32 illuminates from the rear in the traveling direction of the rubber sheet 16. The illumination 34 is illuminated from the back side of the rubber sheet 16.

  In this state, the front surface of the rubber sheet 16 is photographed by the camera 20. In this inspection apparatus 12, the camera 20 is a CCD camera. The captured image is converted from analog data to digital data by the image processing unit 22. The captured image is converted into image data. In the converted image data, the captured image is converted into digital data in units of pixels. This image data is recorded in the recording unit 24.

  The recording unit 24 records information on the number and position of detection areas for each type of rubber sheet. Information for specifying the rubber sheet 16 is input from the keyboard 23 to the inspection device 12 of FIG. Information on the number and position of the detection areas corresponding to the rubber sheet 16 is called from the recording unit 24. As shown in FIG. 4, detection areas A and B are set.

  As shown in FIG. 4, detection areas A and B including the end of the rubber sheet 16 are set in this image data. The detection area A is an area including the left end of the rubber sheet 16. The detection area B is an area including the right end of the rubber sheet 16. This detection area A is set so as to include the left end of the rubber sheet 16 to be inspected by the inspection device 12. Similarly, the detection area B is set so as to include the right end of the rubber sheet 16 to be inspected.

  FIG. 5 is an enlarged view of a portion indicated by an arrow V in FIG. The arithmetic unit 26 shown in FIG. 1 takes out the image data located in the detection area A from the recording unit 24. The calculation unit 26 extracts the first threshold value from the recording unit 24. The first threshold value is a value for determining a position where the image data is equal to or lower than the first threshold value as a light / dark change point. In this detection area A, the image data and the first threshold value are compared in order from the outside toward the center from the left end of the rubber sheet 16. At the left end of the rubber sheet 16, the light of the illumination 34 is blocked by the rubber sheet 16. At the left end of the rubber sheet 16, the image data changes from light to dark. In this way, a position below this first threshold is detected. A position that is equal to or less than the first threshold is detected as the position of the light-dark change point. This position is determined as the left end position of the rubber sheet 16. Although not shown, in this detection region B, the rubber sheet 16 is compared with the first threshold value in order from the outside toward the center from the right end. Otherwise, the position of the right end of the rubber sheet 16 is determined in the same manner as the method for determining the position of the left end of the rubber sheet 16. In this way, the left and right end positions of the rubber sheet 16 are detected (STEP 1).

  A line located at an intermediate point between the left and right end positions is calculated on the image data recorded in the recording unit 24. This line is the center L of the rubber sheet 16. The position of the center L in the width direction of the rubber sheet 16 is calculated. In this way, the position of the center L is calculated from the left and right end positions of the rubber sheet 16 (STEP 2).

  The calculation unit 26 sets a detection region C for detecting the identification line 28a with reference to the position of the center L. Similarly, the calculation unit 26 sets a detection region D for detecting the identification line 28b. The computing unit 26 sets a detection area E for detecting the identification line 28c. In this way, the detection areas C, D and E are set on the image data for detecting the width direction positions of the identification lines 28a, 28b and 28c with reference to the position of the center L of the rubber sheet 16 (STEP 3). ).

  FIG. 6 shows the detection areas C, D, and E. The calculation unit 26 extracts the second threshold value from the recording unit 24. The second threshold value is a value for determining a position where the image data is equal to or higher than the second threshold value as a light / dark change point. In this detection area C, the image data and the second threshold value are sequentially compared from the left end side of the rubber sheet 16 toward the center L. The surface of the rubber sheet 16 is black. At the boundary of the identification line, the image data changes from dark to bright. A position where the image data is equal to or greater than the second threshold is detected. Thus, the change point of the image data is detected. This change point is detected as the position in the width direction of the identification line 28a.

  Next, the computing unit 26 extracts the third threshold value from the recording unit 24 in the same manner as the second threshold value. In the detection area D, the image data and the third threshold value are sequentially compared from the side of the identification line 28a toward the center L. Thus, the change point of the image data is detected. This change point is detected as the position in the width direction of the identification line 28b. Further, the calculation unit 26 extracts the fourth threshold value from the recording unit 24. In the detection region E, the image data and the fourth threshold value are sequentially compared from the right end side of the rubber sheet 16 toward the center L. Thus, the change point of the image data is detected. This change point is detected as the position in the width direction of the identification line 28c (STEP 4).

  As shown in FIG. 7, the inspection region F is set in the direction in which the position-detected identification line 28a extends. In this inspection area F, a plurality of detection windows F1 to F19 are set. The plurality of detection windows F1 to F19 are continuously arranged in the longitudinal direction of the identification line 28a. Here, the plurality of detection windows F <b> 1 to F <b> 19 are arranged in parallel to the center L of the rubber sheet 16. The identification line 28a is detected with the image data corresponding to each of the detection windows F1 to F19. When the identification line 28a is not detected continuously in a predetermined number of detection windows among the detection windows F1 to F19, the calculation unit 26 determines that the identification line 28a is disconnected. Here, similarly to the identification line 28a, the positions of the identification lines 28b and 28c are detected, and the presence or absence of interruption is determined (STEP 5).

  When the calculation unit 26 determines that the interruption is present, a signal is output to the spike 36 in FIG. With this signal, the spike 36 makes a dent 38 on the rubber sheet 16. After the rubber sheet 16 is cut by the cutter 8, the tread rubber 14 with the dent 38 is discarded. The presence or absence of the dent 38 is determined based on image data taken by another camera (not shown).

  In this detection method, the left and right ends of the rubber sheet 16 are detected as changing points from light to dark. The boundaries of the identification lines 28a, 28b and 28c are detected as changing points from dark to bright. As a result, the left and right ends of the rubber sheet 16 and the identification lines 28a, 28b, and 28c are prevented from being erroneously detected.

  In this detection method, the positions of the identification lines 28a, 28b, and 28c are detected. Thereafter, inspection areas for the identification lines 28a, 28b, and 28c are set. In this inspection method, the inspection areas of the identification lines 28a, 28b, and 28c can be limited to a narrow area in the image data. In this inspection method, the identification lines 28a, 28b and 28c can be inspected in a short time.

  In this inspection method, the center L of the tread is calculated from both ends in the width direction of the rubber sheet 16. Based on the center L of the tread, the positions of the identification lines 28a, 28b and 28c are calculated. Since the end of the rubber sheet 16 is uneven, the detection error of the position of the end in the width direction is large. In this inspection apparatus 12, the calculation accuracy of the positions of the identification lines 28a, 28b, and 28c is improved as compared with the prior art by calculating the center L of the tread from a pair of width direction ends and using it as a reference. The influence of meandering of the rubber sheet is suppressed.

  The detection order of the identification lines 28a, 28b and 28c is detected from at least one of the identification lines 28a or 28c. According to the inspection order of the identification lines 28a, 28b, and 28c, the other identification lines adjacent to each other or the left and right ends, and the other identification lines that have already been detected or the identification lines that are detection targets from the left and right ends. The inspection object is detected in the direction of approaching. Thereby, it is suppressed that the identification line which is a detection target is erroneously detected as another identification line or left and right ends.

  In this detection method, by setting the detection region, the inspection region, and the window with the center L of the tread as a reference, the identification lines 28a, 28b, and 28c can be inspected in a short time while suppressing erroneous detection. Further, the detection of the position of the identification line is detected from a known tread edge position or another known identification line position side. Thereby, erroneous detection of the positions of the identification lines 28a, 28b, and 28c can be further suppressed. By suppressing this erroneous detection, the detection area can be set small, so that the inspection time can be shortened.

  Here, as shown in FIG. 1, the detection areas A to E and the inspection areas F to H are set so as not to overlap, but may be set as areas overlapping each other. Here, the rubber sheet 16 having the three identification lines 28a, 28b, and 28c has been described, but the number of identification lines may be one or more.

  In FIG. 7, 19 inspection windows F1 to F19 are arranged, but any number of inspection windows may be used as long as there are a plurality of inspection windows. Shorter breaks can be detected by more finely dividing the inspection window. By setting the width of the inspection windows F1 to F19 to a narrow range, the range of the image to be analyzed can be reduced. By narrowing the width of the inspection windows F1 to F19, an image can be analyzed in a shorter time. According to this inspection method, it is easy to perform inspection over the entire length of the identification line even with the operation unit 26 having relatively limited performance.

  In this inspection method, spikes 36 are used for sorting display defects, but other sorting methods may be used. For example, after the calculation unit 26 detects a display defect, a predetermined time until cutting by the cutter 8 is measured. When the predetermined time has elapsed, the tread rubber 14 cut by the cutter 8 may be discarded. Further, here, the display failure due to the disconnection of the identification line has been described, but other display failures such as the thickness of the identification line, the number of the identification lines, and the position can also be inspected.

  FIG. 8 is a conceptual diagram relating to another inspection method according to the present invention. Here, a configuration different from the above-described one inspection method will be described. The description of the same configuration is omitted. This inspection method includes steps 1 to 4 as in the above-described one inspection method.

  In this inspection device 12, the recording unit 24 records the number of identification lines and the color of each identification line for each type of rubber sheet. In the recording unit 24, hue, saturation and brightness range data of a predetermined color is recorded in advance. Information for specifying the rubber sheet 16 is input to the inspection device 12 from the keyboard 23. Table 1 shows the color of the identification line recorded in the recording unit 24. Red, yellow, green, white, brown and blue are recorded as identification line colors. Hue, saturation, and lightness range data of each color is recorded. The range is specified from 256 levels from 000 to 255.

  As shown in FIG. 8, a detection window J is set in the identification line 28a whose position has been detected. The image data located in the detection window J is composed of a set of a plurality of pixels. In this detection window J, hue, saturation, and brightness are measured. This measurement data is measured for each pixel. The calculation unit 26 determines the color to which the pixel belongs in comparison with the range data shown in Table 1. The number of pixels belonging to each color is totaled and recorded in the recording unit 24. The total number of pixels is listed in Table 1. The color with the largest number of pixels is determined. The arithmetic unit 26 determines that the color of the identification line 28a is the color having the largest number of pixels. Here, 2000 pixels are determined to be red. This identification line 28a is determined to be red (STEP 5).

  The range data for determining each color includes an overlapping range. In Table 1, for example, the range of the hue range data of 60 to 65 overlaps yellow and green. Pixels whose measurement data belong to this overlapping range data are counted in an overlapping manner with yellow and green. In this color determination method, the color of one pixel may be added up to the number of pixels of two types of colors. The number of pixels of each color is totaled including the data of the pixels totaled in these two types of colors. The number of pixels in the inspection window J does not necessarily match the total sum of the number of pixels of each color in Table 1. In this way, the color having the largest number of pixels is determined. In this determination method, a range in which the color to which the pixel belongs is overlapped is set, and the color having the largest number of pixels is totaled, thereby facilitating the color determination.

  Similarly, for the identification lines 28b and 28c, the color of the identification line is determined. When a color difference is detected in this color determination, the calculation unit 26 outputs a signal. The production line 2 is stopped by this signal.

  In the region of the detection window J, the identification line 28a may include cracks, fading, width variation, and the like. Here, the crack means a state in which one identification line is broken and displayed in two or more along the longitudinal direction of the identification line. In this inspection method, the color having the largest number of pixels is determined as the color of the identification line 28a. Therefore, in the determination of the color of the identification line, it is possible to suppress the influence of cracks, blurring, width variation, etc. on the identification line. For example, there is a method of determining using the average color of all pixels in the detection window J. In this method, if the identification line is cracked, blurred, or has a width variation, the average color of all the pixels varies. In this method, the average color of all pixels is easily affected by cracks, blurring, width fluctuations, etc. in the identification line. In addition, the average color tends to fluctuate due to light adjustment. As described above, the detection of the color by the inspection device 12 is suppressed from erroneous detection as compared with the method using the average color.

2 ... Production line 4 ... Extruder 6 ... Cooling device 8 ... Cutter 10 ... Printing device 12 ... Inspection device 14 ... Tread rubber 16 ... Rubber sheet 18. .... Roller conveyor 20 ... Camera 22 ... Image processing unit 23 ... Keyboard 24 ... Recording unit 26 ... Calculation unit 28 (28a, 28b, 28c) ... Identification line 30, 32, 34 ... Illumination 36 ... Spike 38 ... Scar

Claims (6)

Detecting the left and right end positions of the rubber sheet for tread from image data obtained by camera photography;
Calculating the center position of the rubber sheet from the left and right end positions of the rubber sheet;
A step of setting a detection area in the image data with reference to the center position;
Detecting the width direction position of the identification line in this detection region;
A step of setting an inspection region in the image data based on the detected width direction position of the identification line;
A method for inspecting a tread identification line for a tire, comprising the step of inspecting the identification line in the inspection region.   In the step of detecting the left and right end positions of the rubber sheet, illumination is applied from the back side of the rubber sheet, and the front side of the rubber sheet is photographed by the camera. Based on the image data obtained by illumination from the back side The inspection method according to claim 1, wherein the left and right end positions of the rubber sheet are detected. In the step of detecting the left and right end positions of the rubber sheet,
As the left end position of this rubber sheet, a light and dark change point is detected from the outside of the left end of the rubber sheet toward the center of the tread,
The inspection method according to claim 1 or 2, wherein a change point of lightness and darkness is detected from the outside of the right end of the rubber sheet toward the center of the tread as the right end position of the rubber sheet. In the step of inspecting the identification line in the inspection area, a plurality of detection windows are arranged in the extending direction of the identification line, and a display defect of the identification line is detected based on the detection of the identification line in the plurality of detection windows. The inspection method according to any one of claims 1 to 3 . In the step of inspecting the identification line in the inspection area, a detection window located on the identification line is set, and this inspection window is set as a collection area of pixels of a plurality of cameras. And the brightness is measured, the color to which the pixel belongs is determined in comparison with the preset hue, saturation, and brightness range data, and the number of pixels belonging to each predetermined color is aggregated. 4. The inspection method according to claim 1, wherein a predetermined color having a large number of pixels is determined, and a color of the identification line is determined to be a predetermined color having the largest number of pixels . Identification line is displayed on the rubber sheet surface of the tread, and a conveying unit for conveying the rubber sheet,
A camera for photographing the surface of this rubber sheet ,
An image processing unit that converts the image captured by the camera into image data;
A recording unit for recording the image data;
Based on the image data recorded in the recording unit, the left and right end positions of the rubber sheet are detected, the center position of the rubber sheet is calculated from the left and right end positions of the rubber sheet, and the position of the identification line is based on the center position. An operation for setting a detection area for image data for detecting image data, detecting the position of the identification line in this detection area, and setting an inspection area for the image data for inspecting the identification line based on the position in the width direction of the detected identification line And a tire tread identification line inspection device.

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