Method for measuring tire rotation main groove depth, and rotation direction main depth measurement device using the method

Abstract

To provide a device for measuring the depth of a tire rotation direction main groove (circumferential main groove) formed on a tread surface of a tire removed from a vehicle.SOLUTION: Line laser light 100 is irradiated to at least two different places of a tread surface of a tire 40, picked-up images of the line laser light 100 are respectively acquired, light cutting line coordinates being coordinates of the images of the line laser light 100 are detected about each of the picked-up images, groove depths formed on the tread surface are calculated from the respective light cutting line coordinates on the basis of a triangulation method, and the calculated groove depths are respectively determined as the depths of rotation direction grooves 41 with grooves whose rotation direction coordinates of the groove depths approximately coincide respectively regarded as the rotation direction main grooves 41.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a method for measuring the depth of a main groove in the rotational direction formed on the tread surface of tires for automobiles, motorcycles, etc., by capturing an image of a line laser light (image of a light cutting line) irradiated onto the surface of the tire and measuring the depth of the main groove in the rotational direction of the tire based on the captured image, and a measuring device utilizing this method. [Background technology]

[0002] When tires of vehicles such as automobiles become worn to a certain extent, they may break while the vehicle is in motion and cause a serious accident, so it is necessary to replace them with new tires at the appropriate time.

[0003] The lifespan of tires varies greatly depending not only on the mileage of a vehicle, but also on individual factors such as the vehicle model, the condition of the road surface on which the vehicle is driven, and the driver's habits. Therefore, it is not appropriate to determine when to replace tires with new ones based solely on the mileage; it is important to investigate the wear and tear of each tire.

[0004] The main factors that govern the lifespan of a tire are wear on the tread surface and the occurrence of scratches such as cracks and cuts. The progress of wear on the tread surface is often judged from the depth of the tire's grooves. That is, the tread surface is formed with vertical grooves (circumferential grooves) and lateral grooves that run in the direction of tire rotation to allow water trapped between the road surface and the tire to escape to the rear or sides of the tire.

[0005] When the thickness of the rubber decreases due to wear, these grooves become shallower, so the degree of wear can be estimated by measuring the remaining groove depth. Therefore, one of the issues in investigating the state of tire wear is how to measure the remaining groove depth, particularly the longitudinal grooves (circumferential grooves, hereinafter referred to as rotational direction main grooves or simply main grooves).

[0006] Generally, laser displacement meters are often used as a means for three-dimensionally measuring the shape of an object surface. Cases in which a laser displacement meter has been used to measure the remaining tread depth of a tire have also been reported. For example, Patent Document 1 discloses a technique in which, while rotating a tire around its axis of rotation, incident light is irradiated onto the tire tread surface from a predetermined direction, and reflected light at a predetermined angle to the incident light is received by a light receiving unit to obtain data on the tire tread depth. However, the measurement of the remaining tread depth using a laser displacement meter is considered to have the following problems.

[0007] That is, since the measurement is performed on a black rubber surface, a strong laser power is required, which may cause damage to the tire. In addition, since local interference occurs on the surface that causes diffuse reflection, there is a problem that a fairly complicated operation procedure is required to ensure sufficient measurement accuracy. Furthermore, above all, there are disadvantages in that the equipment is expensive and requires a lot of effort for maintenance.

[0008] Meanwhile, Patent Document 2 below discloses a method for measuring the remaining tread depth of a tire by capturing an image of a line laser beam (image of a light-cutting line) and measuring the tire tread depth by a light-cutting method based on the captured image.

[0009] In the document JP 2003-233666 A, a laser or a shadowed light emitting diode is used as a light source irradiated transversely to the direction of tire movement, producing a fan-shaped light beam. Measurements are performed non-orthogonally to the tire surface, so that neither the light source nor the sensor is located in the angular direction of the direct reflection. The sensor is in this case a two-dimensional image analysis camera. Evaluation is performed by generating an envelope of the measured tire tread and by locating the deepest point of the tread grooves.

[0010] According to the technology described in Patent Document 2 below, the deepest point of the tread groove is determined as the remaining groove depth of the tire by the light cutting method. However, since the tread surface of the tire has longitudinal grooves (circumferential grooves) and lateral grooves that run in the direction of tire rotation, it is not possible to determine whether the determined groove is a longitudinal groove (circumferential groove) or a lateral groove. In addition, a tire in use may have various irregularities. For this reason, there is a problem that a groove determined to be a circumferential groove may not actually be a circumferential groove.

[0011] The following Patent Document 3 discloses a shape measuring device and method for detecting the surface shape of a measured object by capturing an image of a line of light (an image of a light-section line) that is irradiated onto the surface of the measured object (such as the surface of a rotating tire) that moves relatively, and performing shape detection using a light-section method based on the captured image.

[0012] The technology of the following Patent Document 3 is a shape measuring device characterized by comprising: a line light irradiation means for irradiating a plurality of line lights from a direction different from the detection height direction of the surface of the object to be measured, thereby forming a plurality of separated light section lines on the surface of the object to be measured that extend in a second direction perpendicular to a first direction, which is the movement direction of the surface of the object to be measured, and whose ranges in the second direction are shifted from each other; an imaging means for capturing images of the plurality of separated light section lines formed on the surface of the object to be measured in a direction in which the main ray of each of the plurality of line lights is specularly reflected by the surface of the object to be measured; a light section line coordinate detection means for detecting light section line coordinates, which are the coordinates of the images of the light section lines, from each of images of a plurality of independent image processing target areas that are preset corresponding to each of the plurality of separated light section lines in the coordinate system of the captured image of the imaging means, for each of a plurality of captured images obtained by the imaging means in response to the movement of a certain unit; and a surface shape calculation means for calculating the surface height distribution in the first direction of the object to be measured based on the plurality of light section line coordinates detected by the light section line coordinate detection means.

[0013] The shape measuring device disclosed in the following Patent Document 3 measures the overall shape of a tire by measuring the shape of the tire side and the shape of the tire tread surface while rotating the tire. For this reason, this technology irradiates the tire tread surface with a plurality of separated line lights, and detects the coordinates of the images of these line lights by light section line coordinate detection means corresponding to each line light, thereby preventing delays in processing even when the tire is rotating.

[0014] For this reason, in order to measure the main grooves formed on the tire tread surface using the technology described in Patent Document 3, the tire must be rotated and multiple line lights separated in a direction transverse to the tire rotation direction must be irradiated. This results in a problem that the measurement device becomes complicated and expensive. In order to determine the wear condition of a tire in use, it is not necessary to measure the overall shape of the tire, but it is necessary to accurately measure the depth of the circumferential groove.

[0015] [Prior art documents] [Patent documents]

[0016] [Patent Document 1] Japanese Patent Application Publication No. 2016-161360 [Patent Document 2] Patent No. 5640073 [Patent Document 3] Patent No. 5089286 DISCLOSURE OF THEINVENTION [Problem to be solved by the invention]

[0017] People who live in cold regions where the roads are covered in snow and ice in winter, and even people who live in regions where there is no snow, need to use summer and winter tires when traveling to snowy areas for work or leisure. Therefore, it is necessary to change tires at the beginning and end of the winter season, and to store the unused tires during that period.

[0018] Although ordinary car owners can change tires by themselves, it is rough work that requires considerable physical strength, so women and the elderly have no choice but to rely on businesses that do this professionally or as a side job, such as mass retailers of tires. The same can be said for those who can change tires by themselves but cannot secure storage space at home.

[0019] Such tire replacement and storage businesses require an easy-to-operate, inexpensive measuring device that can obtain information on tire wear, particularly the depth of the main grooves in the direction of tire rotation (remaining tread depth), to help their customers (users) drive safely or to advise them on the appropriate time to replace tires with new ones.

[0020] Therefore, the present invention has an objective of providing an apparatus for measuring the depth of the rotational main groove (circumferential main groove) formed on the tread surface of a tire removed from a vehicle such as an automobile or motorcycle, which has low manufacturing and maintenance costs and allows easy measurement operations. [Means for solving the problem]

[0021] A first aspect of the present invention for solving the above problems is a method for measuring a rotational direction main groove depth, comprising: irradiating a line laser beam onto a tread surface of a tire in a direction transverse to a rotational direction of the tire; capturing an image of the line laser beam on the tread surface with a camera; and detecting depths of a plurality of rotational direction main grooves formed on the tread surface by a light cutting method based on the captured image, A line laser beam is irradiated onto at least two different points on the tread surface, and images of the line laser beam are captured, Detecting light section line coordinates, which are coordinates of an image of the line laser light, for each of the captured images; Calculating the groove depths formed on the tread surface based on the light section line coordinates and a triangulation method; a method for measuring the depth of a rotational main groove formed on the tread surface of a tire, the method comprising determining the depth of a groove whose rotational coordinate approximately coincides with the calculated depth of the groove as the depth of the rotational main groove.

[0022] A second aspect of the present invention is a method for measuring a rotational direction main groove depth, comprising: irradiating a line laser beam onto a tread surface of a tire in a direction transverse to a rotational direction of the tire; capturing an image of the line laser beam on the tread surface with a camera; and detecting depths of a plurality of rotational direction main grooves formed on the tread surface by a light cutting method based on the captured image, A line laser beam is irradiated onto at least two different points on the tread surface, and images of the line laser beam are obtained, Detecting light section line coordinates, which are coordinates of an image of the line laser light, for each of the captured images; Selecting point A, which is one of the coordinates of the light section line coordinates, point B, which is one of the coordinates of the light section line coordinates and is separated by w from point A in a direction transverse to the tire rotation direction, and point C, which is one of the coordinates of the light section line coordinates and is separated by 2w from point A in a direction transverse to the tire rotation direction, and repeatedly calculating the area of ​​a triangle formed by point A, point B, and point C until any of point A, point B, and point C reaches all of the coordinates of the light section line coordinates; Calculating a groove depth from the area of ​​the triangle thus calculated; Each of the grooves having a depth equal to or greater than a predetermined value is determined as a main groove candidate. a method for measuring the depth of a rotational main groove formed on the tread surface of a tire, the method comprising determining the depth of a groove whose rotational coordinates approximately coincide with those of the main groove candidate as the depth of the rotational main groove.

[0023] A third aspect of the present invention is a line laser light irradiation device that irradiates a line laser light onto at least two different points on a tread surface of a tire in a direction transverse to a rotation direction of the tire; A camera that captures an image of the line laser light on the tread surface; a line laser image detection processing unit that detects and processes an image of a line laser beam from an image captured by the camera; a light section line coordinate detection unit that detects light section line coordinates, which are coordinates of an image of the line laser light; a groove depth calculation unit that calculates a depth of a groove formed on the tread surface based on a light section method from the light section line coordinates; a main groove determining section for determining that each of a plurality of grooves having substantially the same coordinate in the rotational direction of the calculated groove depth is a rotational direction main groove; and a measuring device for measuring the depth of a rotational direction main groove formed on a tread surface of a tire, comprising:

[0024] In the present invention, a line laser beam is irradiated onto at least two different points on the tread surface of a tire, and an image of the line laser beam on the tread surface of the tire is captured by a camera. The image of the line laser beam is detected from each captured image, and the coordinates of the image of the line laser beam, that is, the light section line coordinates, are detected.

[0025] The depth of the groove can be calculated based on the arrangement of the line laser light irradiation device and the camera, and the light section line coordinates, based on a triangulation method using the principle of the light section method. There are at least two images of the line laser light, and a groove whose rotational coordinates of the groove detected by the light section method are approximately the same is a longitudinal groove, so the depth of that groove is determined to be the depth of the main groove. This makes it possible to prevent, for example, lateral grooves or irregularities on the tread surface from being erroneously determined to be the main groove in the rotational direction.

[0026] In addition to the determination of the rotational direction main groove as described above, for each of the light section line coordinates, point A, which is one coordinate of the light section line coordinates, point B, which is one coordinate of the light section line coordinates that is w away from point A in a direction transverse to the tire rotational direction, and point C, which is one coordinate of the light section line coordinates that is 2w away from point A in a direction transverse to the tire rotational direction, are selected, and the area of ​​the triangle formed by point A, point B, and point C is repeatedly calculated until any of point A, point B, and point C represents all of the coordinates of the light section line coordinates. The groove depth is calculated from the area of ​​the triangle thus calculated, and the depths of grooves whose groove depths are equal to or greater than a predetermined value and whose rotational direction coordinates are approximately the same are determined to be the depths of the rotational direction main grooves.

[0027] Here, the tread surface of the tire is a gently curved surface, and the image of the line laser light captured by the camera also has a gently curved shape. For this reason, when calculating the groove depth, it is necessary to calculate the groove depth in a direction perpendicular to the normal line of the light section line that is divided (separated) by the groove portion. For this purpose, it is preferable to select three points from the light section line coordinates, calculate the area of ​​the triangle formed by the three points for all the light section line coordinates, and determine the maximum value of the groove depth obtained from them as the groove depth.

[0028] The three points are selected as point A, which is one coordinate on the light section line coordinate system, point B, which is one coordinate on the light section line coordinate system w away from point A in a direction transverse to the tire rotation direction, and point C, which is one coordinate on the light section line coordinate system 2w away from point A in a direction transverse to the tire rotation direction. The area of ​​the triangle formed by points A, B, and C is repeatedly calculated until any of points A, B, and C is included in all coordinates on the light section line coordinate system, and the groove depth is calculated from the maximum area. The above w (base of the triangle) is at least the width of the main groove of the tire to be measured, and it is preferable that the width be greater than or equal to that width and less than twice as large. Effect of the Invention

[0029] According to the present invention, it is possible to provide an apparatus for measuring the depth of the rotational main groove (circumferential main groove) formed on the tread surface of a tire removed from a vehicle such as an automobile or motorcycle, which has low manufacturing and maintenance costs and is easy to operate for measurement. The apparatus for measuring the depth of the rotational main groove formed on the tread surface of a tire according to the present invention has the characteristics of low equipment costs, easy maintenance, and simple measurement effort. BEST MODE FOR CARRYING OUT THEINVENTION

[0030] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings of the examples. Fig. 1 is a perspective view showing the configuration of a measuring device 1 for measuring the depth of a rotational direction main groove formed on a tire tread surface, which is a first embodiment of the present invention. This device includes a table 50 on which a tire 40 is placed, a line laser light irradiation device 10, a camera 20 for capturing an image of the line laser light, and a data processing device 30 for analyzing and processing the image captured by the camera. Although not shown in Fig. 1, it is preferable to include a light source that makes the tread surface of the tire 40 clear depending on environmental conditions.

[0031] The tire 40 is placed on the table 50 so that the tire side is horizontal. The line laser irradiation device 10 is arranged symmetrically around the camera 20, and irradiates the tread surface of the tire 40 with a line laser beam in a direction transverse to the tire rotation direction, forming an image of the line laser beam at two different points on the tread surface. The camera 20 captures the image of the line laser beam appearing at two different points on the tread surface, and the captured image is sent to the data processing device 30. The image of the line laser beam is intended to obtain information on the remaining groove depth of the tire 40. In the embodiment shown in FIG. 1, the camera 20 is arranged between the two line laser irradiation devices 20, but the present invention is not limited to this, and it is sufficient to specify the arrangement (height, separation, angle, etc.) relationship between the camera 20, the line laser beam irradiation device 10, and the tread surface of the tire, which is necessary for the triangulation method used in the principle of the light cutting method.

[0032] The present invention is characterized in that, when acquiring an image of the line laser light on the tread surface in a direction transverse to the tire rotation direction, the line laser light is irradiated on two different points on the tread surface and the image is captured by the image camera 20. This is because the tread surface has lateral grooves and oblique grooves in addition to the main groove in the rotation direction, and the tread surface may have unevenness due to use. The reason for irradiating the line laser light on two different points on the tread surface is to distinguish between the main groove in the rotation direction and other grooves. Here, it is preferable to irradiate the line laser light on two different points on the tread surface simultaneously, but it may also be performed by synthesizing images obtained by irradiating the line laser light on two different points on the tread surface with a time lag.

[0033] In the present invention, in order to distinguish between these various grooves and the rotational direction main groove, the characteristic that the rotational direction main groove is always continuous in the rotational direction is utilized. That is, a groove whose rotational direction coordinates are almost the same based on the coordinates of the light cutting line 11 (see FIG. 3), which is an image of the line laser light, is determined as the rotational direction main groove, and this point is one of the points of the present invention. However, there are cases where the main groove is formed in a meandering shape in the tire rotational direction, and there are also cases where the main groove is formed in a manner that is not necessarily continuous in the rotational direction due to its relationship with the lateral groove. Even in such cases, a groove whose rotational direction coordinates are almost the same based on the coordinates of the light cutting line 11 is determined as the rotational direction main groove.

[0034] Fig. 2 is a diagram showing the positional relationship in the height direction between the camera 20 of the measuring device 1 according to one embodiment of the present invention shown in Fig. 1, the line laser light emitting device 10, the tread surface of the tire 40, and the rotational direction main groove 41. The laser emitting device 10 is disposed symmetrically in the rotational direction of the tire 40 with the camera 20 in between.

[0035] In FIG. 2, the irradiation angle of the line laser irradiation device 10 is set to an angle at which the center of the tire 40 to be measured is irradiated. Although the diameter of the tire to be measured varies, for example, the angle is set to an angle at which the center of the tire with the smallest diameter is irradiated. The height of the camera 20 from the tread surface is set to a height at which the images of the two line laser beams can be acquired (the viewing angle can be secured), and the camera 20 is installed at the same height. If the depth of the main groove 41 in the rotational direction of the tire 40 is D, the angle of incidence of the line laser beam 100 on the tread surface of the tire 40 is θ, and the width of the main groove 41 is w, then D=tan θ×w. Here, w is preferably wider than the width of the main groove 41, for example, about 1 to 2 times the width of the main groove 41. This is because the width of the main groove may change due to wear of the tire, and the main groove may be formed in a meandering shape in the tire rotational direction.

[0036] FIG. 3 is a diagram showing a tire 40 placed so that its side is horizontal, and a line laser irradiation device 10 irradiates a line laser beam onto the tread surface of the tire 40. Line laser beams 100 are irradiated from two line laser irradiation devices 10 to two different locations on the tread surface, and two light cutting lines 11, which are images of the line laser beams, appear on the tread surface. The image of the light cutting line 11 appears not as an image reflected from the tread surface but as an image reflected from the bottom surface of the main groove 41 at a location where the tire rotation direction main groove 41 is formed. That is, as shown in FIG. 2(b), the image of the light cutting line 11 of the main groove 41 of the light cutting line 11 appears on the irradiation direction side of the line laser beam 100 according to the depth of the main groove 41, rather than the image appearing on the tread surface.

[0037] As described above, in the present invention, in order to distinguish the rotational main groove formed on the tread surface from the lateral grooves and the unevenness, the characteristic that the rotational main groove is continuous in the rotational direction is used as a discrimination means. That is, two images of the line laser light are generated on the tread surface, and the grooves with the same coordinates in the rotational direction are discriminated as the rotational main groove from the coordinates (light cutting line coordinates) of the light cutting lines 11 (light cutting lines 11-1 and 11-2) which are the images of the line laser light.

[0038] 4 is a diagram showing an embodiment of the present invention in which the depth of the rotational main groove is calculated from a cutting line 11, which is an image of a line laser beam. When measuring the groove depth by placing a gauge on an actual tire, the tire groove gauge (tire groove depth gauge) is placed in the normal direction to the tread surface, and the groove depth is measured by making the measuring needle hit the bottom of the groove at a right angle to the normal to the tread surface. This is because the tread surface is a gently curved surface. The image of the line laser beam formed on the tread surface by the rotational main groove measuring device 1, which is an embodiment of the present invention, also appears as a gently curved line.

[0039] As described above, the depth of the main groove can be calculated by triangulation using the distance h between the image of the line laser light on the tread surface and the image of the line laser light on the main groove. However, the distance between the coordinates of the light section line on the tread surface and the coordinates of the light section line on the main groove differs depending on how the coordinates are taken. Note that the coordinate axes shown in FIG. 4 have a resolution of 1000×1000 dots for the image of the tread surface, that is, the coordinates on the X axis are 0 to 1000, and the coordinates on the Y axis are also 0 to 1000.

[0040] As a method for calculating the depth of the main groove from the optical cutting line 11 shown in FIG. 4, point A, which is one coordinate of the optical cutting line 11, point B, which is one coordinate of the optical cutting line 11 that is w away from point A in a direction transverse to the tire rotation direction, and point C, which is one coordinate of the optical cutting line 11 that is 2w away from point A in a direction transverse to the tire rotation direction, are selected.

[0041] Then, the area of ​​the triangle formed by points A, B, and C is calculated. This is repeated until point A, B, or C is at all coordinates of the light section line 11, and the area of ​​the triangle thus calculated is graphed with the Y coordinate value of the light section line 11 as the X axis and the area of ​​the triangle as the Y axis, to obtain a diagram like that shown in Figure 4(b). From the maximum value of the area of ​​the triangle thus obtained, the groove depth of each is calculated, and the groove depth at a location that is equal to or greater than a predetermined depth, for example, equal to or greater than the groove depth indicated by the slip sign (1.6 mm for four-wheeled vehicles, 0.8 mm for two-wheeled vehicles), is determined to be the main groove depth.

[0042] 5 is a block diagram showing the configuration of an apparatus 1 for measuring the depth of a rotational direction main groove formed on a tire tread surface according to one embodiment of the present invention. Two line lasers 10 irradiate different locations on the tire tread surface with line laser light. A camera 20 captures an image of the line laser light appearing on the tread surface. The line laser 10 is controlled by a line laser control unit 310 of the control unit 31, and the camera 20 is controlled by an imaging control unit 311 of the control unit 31.

[0043] The image captured by the camera 20 is sent to a data processing unit 32. The data processing unit 32 includes a line laser image detection unit 320 that detects an image of the line laser light, a light cutting line coordinate detection unit 321 that detects light cutting line coordinates that are the coordinates of the image of the line laser light detected by the line laser image detection unit 320, a groove depth calculation unit 322 that calculates the groove depth from the coordinates detected by the light cutting line coordinate detection unit 321, and a main groove determination unit 323 that determines the rotational direction main groove from the groove depth calculated by the groove depth calculation unit 322 and the coordinates of the light cutting line 11.

[0044] 6 is a diagram of the depth of the rotational main groove formed on the tread surface of a tire (size: 215 / 55R17) obtained by the tire rotational main groove depth measuring device 1 according to one embodiment of the present invention. The line laser used has a wavelength of 600 nm, power consumption of 40 mW, and power supply voltage of 5 VD, and the resolution of the camera 20 is 2048 x 1536. The image obtained under these specifications was processed to determine the coordinates of the light cutting line 11 and calculate the rotational main groove depth, and a depth of 5.4 mm to 5.9 mm was detected as the depth of the three main grooves 42 formed on the tread surface.

[0045] 7 is a flow chart showing an example of a method for measuring the depth of a rotational main groove according to an embodiment of the present invention. Two line laser beams are irradiated onto the tire tread surface, and the image of the line laser beams appearing on the tread surface is emphasized and filtered (S1, S2). Next, the image of the line laser beams is binarized into two colors, for example, red and white, or black and white, and then noise is removed (S3, S4).

[0046] Next, the line width of the two line laser light images is adjusted to, for example, 1 dot (1 pixel = 1 dot) from the average of each coordinate. Also, pixels (missing points) that are originally present in the line laser light images but have disappeared are linearly complemented (S5, S6), and the coordinates of the light cutting line 11, which is the image of the line laser light, are extracted (S7).

[0047] Next, points A, B, and C are selected from the coordinates of each light-section line 11, and the area of ​​the triangle formed by points A, B, and C is calculated (S8, S9). This is repeated until point A is the coordinate of all light-section lines 11, and the area of ​​the triangle formed by points A, B, and C is calculated (S10), and the maximum value of a graph with the area of ​​the triangle as the Y-axis and the Y-axis coordinate of the light-section line 11 as the X-axis is determined as a candidate for the main groove (S11).

[0048] Among the candidates for the main groove obtained from the coordinates of each light section line, the one whose Y coordinate almost coincides with the light section line 11, for example, the one whose Y coordinate does not deviate by more than the width of the rotational direction main groove, is determined to be the rotational direction main groove. Then, the depth of the main groove is calculated from the area of ​​the one determined to be the main groove (S12, S13). [Brief description of the drawings]

[0049] [Figure 1] 1 is a perspective view showing a configuration of a measurement device for measuring the depth of a rotational direction main groove formed in a tread surface of a tire according to one embodiment of the present invention. FIG. [Diagram 2] 1 is a diagram showing the positional relationship in the height direction between the camera and line laser light irradiation device of a tire rotational direction main groove measuring device according to one embodiment of the present invention, and the tire tread surface. FIG. [Diagram 3] 3 is a diagram showing a line laser beam projected onto a tire tread surface by a line laser projection device according to an embodiment of the present invention. FIG. [Figure 4] FIG. 13 is a diagram showing an embodiment of the present invention in which the depth of a rotational direction main groove is calculated from cutting line coordinates 11 which are an image of a line laser beam. [Diagram 5]FIG. 1 is a block diagram showing a configuration of an apparatus 1 for measuring the depth of a rotational direction main groove formed in a tread surface of a tire according to an embodiment of the present invention. [Figure 6] FIG. 4 is a diagram showing the depth of a rotational direction main groove obtained by a line laser irradiation device according to one embodiment of the present invention. [Figure 7] 4 is a flowchart showing an example of a method for measuring the depth of a rotational direction main groove formed in the tread surface of a tire according to an embodiment of the present invention. [Explanation of symbols]

[0050] 1: Measurement device for main grooves in the direction of tire rotation 10: Line laser light irradiation device 20: Camera 30: Data processing device 31: Control unit 32: Data processing section 40: Tires 41: Main groove in the direction of tire rotation 50: Table 310: Line laser control unit 311: Imaging control unit 320: Line laser image detector 321: Optical cutting line coordinate detection unit 322: Groove depth calculation unit 323:Main groove determination section

Claims

1. A method for measuring a rotational direction main groove depth, comprising: irradiating a line laser light onto a tread surface of a tire in a direction transverse to a rotational direction of the tire; capturing an image of the line laser light on the tread surface with a camera; and detecting depths of a plurality of rotational direction main grooves formed on the tread surface by a light cutting method based on the captured image, A line laser beam is irradiated onto at least two different points on the tread surface, and images of the line laser beam are captured, Detecting light section line coordinates, which are coordinates of an image of the line laser light, for each of the captured images; Calculating the groove depths formed on the tread surface based on the light section line coordinates and a triangulation method; A method for measuring the depth of a rotational main groove formed on the tread surface of a tire, characterized in that the depth of a groove whose rotational coordinate approximately matches the calculated groove depth is determined to be the depth of the rotational main groove.

2. A method for measuring a rotational direction main groove depth, comprising: irradiating a line laser light onto a tread surface of a tire in a direction transverse to a rotational direction of the tire; capturing an image of the line laser light on the tread surface with a camera; and detecting depths of a plurality of rotational direction main grooves formed on the tread surface by a light cutting method based on the captured image, A line laser beam is irradiated onto at least two different points on the tread surface, and images of the line laser beam are obtained, Detecting light section line coordinates, which are coordinates of an image of the line laser light, for each of the captured images; a point A which is one of the coordinates of the light section line coordinates, a point B which is one of the coordinates of the light section line coordinates and is separated from the point A by w in a direction transverse to the tire rotation direction, and a point C which is one of the coordinates of the light section line coordinates and is separated by 2w from the point A in a direction transverse to the tire rotation direction, and the area of ​​a triangle formed by the point A, the point B, and the point C is repeatedly calculated until any of the points A, B, and C reaches all of the coordinates of the light section line coordinates; Calculating a groove depth from the area of ​​the triangle thus calculated; Each of the grooves having a depth equal to or greater than a predetermined value is determined as a main groove candidate. A method for measuring the depth of a rotational main groove formed on the tread surface of a tire, characterized in that the depth of a groove whose rotational coordinates of the main groove candidates approximately coincide is determined to be the depth of the rotational main groove.

3. 3. The method for measuring the depth of a main groove formed on a tire tread surface according to claim 2, wherein the width w is equal to or greater than the width of the rotational main groove, and the predetermined value is equal to or greater than the value of a slip sign provided in the rotational main groove.

4. a line laser light irradiation device that irradiates a line laser light onto at least two different points on a tread surface of the tire in a direction transverse to a rotation direction of the tire; A camera that captures an image of the line laser light on the tread surface; a line laser image detection processing unit that detects and processes an image of a line laser beam from an image captured by the camera; a light section line coordinate detection unit that detects light section line coordinates, which are coordinates of an image of the line laser light; a groove depth calculation unit that calculates a depth of a groove formed on the tread surface based on a light section method from the light section line coordinates; a main groove determining section for determining that each of a plurality of grooves having substantially the same coordinate in the rotational direction of the calculated groove depth is a rotational direction main groove; A device for measuring the depth of a rotational direction main groove formed on a tread surface of a tire, comprising:

5. The rotational direction main groove depth measuring device according to claim 4, further comprising a means for selecting point A which is one coordinate of the light section line coordinates, point B which is at w distance from point A in a direction transverse to the tire rotation direction, and point C which is at 2w distance from point A in the direction transverse to the tire rotation direction, and repeatedly calculating an area of ​​a triangle formed by point A, point B, and point C until any of point A, point B, and point C reaches all coordinates of the light section line coordinates, and calculating a groove depth from the area of ​​the triangle thus calculated.

6. 6. The rotational main groove depth measuring device according to claim 4, wherein the width w is equal to or greater than the width of the rotational main groove, and the predetermined depth is equal to or greater than the value of a slip sign provided in the rotational main groove.

Images