JP5163331B2 - Tire manufacturing process management method - Google Patents

Description

  The present invention relates to a method for managing a tire manufacturing process using a cross-sectional shape of a tire mold, and more specifically, the cause of a failure is effectively investigated based on the cross-sectional shape of the tire mold, and a tire manufacturing failure occurs. The present invention relates to a method for managing a tire manufacturing process that makes it possible to prevent the problem from occurring.

  The occurrence site and frequency of tire manufacturing failures vary depending on the tire size, reinforcing structure, and cross-sectional shape. For this reason, it is strongly required to take measures against failure based on a certain theory for tires having different tire sizes, reinforcing structures, and cross-sectional shapes.

  By the way, in tire manufacture, the technique which estimates the cross-sectional shape of a green tire based on the physical property conditions and molding conditions of a tire structural member is proposed (for example, refer patent document 1). In this technology, the cross-sectional shape of the carcass at a specific process is calculated based on the physical property conditions and molding conditions of the carcass, and other components are geometrically arranged inside and outside the carcass based on the cross-sectional shape of the carcass. By doing so, the predicted cross-sectional shape of the green tire is obtained.

By obtaining the predicted cross-sectional shape of the green tire in this way, it is possible to determine an appropriate vent hole position at the design stage, and the predicted cross-sectional shape of the green tire can also be used for investigating the cause of failure. . However, since the above method depends on the predicted cross-sectional shape of the green tire, there is a drawback that the cause of the failure cannot always be determined accurately.
JP 2006-168294 A

  An object of the present invention is to provide a tire manufacturing process management method capable of effectively investigating the cause of a failure based on the cross-sectional shape of a tire mold and preventing the occurrence of a tire manufacturing failure. .

  In order to achieve the above object, the tire manufacturing process management method of the present invention extracts the coordinate points of the tire molding surface at equal intervals in the tire radial direction from the cross-sectional shape of the tire mold, and connects adjacent coordinate points with straight lines. The contour line is drawn with, the inclination angle with respect to the tire axial direction of each line segment of the contour line is obtained, the size of the unevenness at each coordinate point is obtained from the difference in the inclination angle of the adjacent line segments, and the size of the unevenness Is used as an index of the cause of failure in the tire manufacturing process.

  In the present invention, the coordinate points of the tire molding surface are extracted at equal intervals in the tire radial direction from the cross-sectional shape of the tire mold, and the inclination angle of each line segment of the contour line obtained by connecting adjacent coordinate points with a straight line is obtained. By determining the size of the unevenness at each coordinate point from the difference in the inclination angle of adjacent line segments, it is possible to easily predict and identify the cause of failure in the tire manufacturing process based on the size of the unevenness Can do.

  In the present invention, it is necessary to extract the coordinate points of the tire molding surface at equal intervals in order to equally compare tires having different sizes and cross-sectional shapes, but in order to increase the accuracy, It is preferable to set 100 or more coordinate points in the entire range. That is, by extracting more coordinate points, the unevenness can be detected more accurately. The size of the unevenness can be treated as a dimensionless quantity composed of a sine component, a cosine component, or a tangent component.

  In the present invention, while determining the size of irregularities for at least one type of tire mold for molding a plurality of types of tires, the failure rate of any part of these types of tires is determined, and the irregularities at each coordinate point are determined. It is preferable to obtain a correlation coefficient between the size and the failure rate, and to specify a portion having a high correlation between the size of the unevenness and the failure rate. If the unevenness is large, it tends to cause a failure, but the unevenness size and the failure rate are not necessarily in a proportional relationship. Therefore, by specifying a portion having a high correlation between the size of the unevenness and the failure rate, the cause of the failure can be predicted and specified more effectively. In that case, it is preferable that the plurality of types of tires have at least one of a size, a cross-sectional shape, and a reinforcing structure in common.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a view showing a cross-sectional shape of a tire mold. As shown in FIG. 1, the tire mold M includes a tire molding surface 1 that extends from the tread portion to the bead portion. The specific structure of the tire mold M is not limited, and the tire mold M may be either a split type or a sectional type.

  2 is a diagram showing a contour line drawn based on the coordinate points of the tire molding surface extracted from the cross-sectional shape of the tire mold in FIG. 1, and FIG. 3 is an enlarged view of a portion A in FIG. Here, the X axis indicates the position in the tire axial direction, and the Y axis indicates the position in the tire radial direction. The cross-sectional shape of the tire mold M described above is an aggregate of a large number of coordinate points. From the cross-sectional shape, the coordinate points of the tire molding surface are extracted at equal intervals in the tire radial direction, and adjacent coordinate points are connected by straight lines. When the contour line L is drawn as shown in FIG.

As shown in FIG. 3, the contour line L includes a plurality of coordinate points P (P _i , P _{i + 1} , P _{i + 2} , P _{i + 3} , P _{i + 4} ) and a plurality of line segments S (S _i , S _{i + 1} , S _{i + 2} , S _{i + 3} , S _{i + 4} ). Each line segment S is inclined at an inclination angle θ (θ _i , θ _{i + 1} , θ _{i + 2} , θ _{i + 3} , θ _{i + 4} ) with respect to the tire axial direction. When the difference between the inclination angles of adjacent line segments is small, the tire molding surface is flat. When the difference between the inclination angles of adjacent line segments is large, the tire molding surface has irregularities. For example, since the adjacent line segments S _i and S _{i + 1} are connected in a straight line, the difference (θ _{i + 1} −θ _i ) between the inclination angles of the line segments S _i and S _{i + 1} is relatively small. On the other hand, since the adjacent line segments S _{i + 2} and S _{i + 3} are connected while being bent, the difference in inclination angle (θ _{i + 3} −θ _{i + 2} ) between these line segments S _{i + 2} and S _{i + 3} becomes relatively large. In this way, the size of the unevenness at each coordinate point can be obtained from the difference in the inclination angle of adjacent line segments.

  In FIG. 2, in order to accurately detect the size of the unevenness at each coordinate point, 100 or more, more preferably 300 or more coordinate points are set in the entire radial range of the tire molding surface. . If the number of coordinate points is less than 100, accurate uneven information may not be obtained because the interval between the coordinate points is too wide.

  The size of the unevenness is based on the inclination angle of the adjacent line segment, but even if a dimensionless quantity consisting of a sine component (sin θ), cosine component (cos θ) or tangent component (tan θ) obtained from the inclination angle is used. good. When a dimensionless amount is obtained for each line segment, the difference between the dimensionless amounts of adjacent line segments can be regarded as the size of the unevenness at each coordinate point.

  FIG. 4 is a diagram showing a contour drawn based on the coordinate points of the tire molding surface extracted from the cross-sectional shape of another tire mold, and FIG. 5 is a diagram showing the size of the irregularities in the contour of FIG. It is. In FIG. 5, the size of the unevenness is represented by a difference in dimensionless amount (cos θ) obtained from the inclination angle of adjacent line segments. In FIG. 5, the vertical axis indicates the position in the tire radial direction, the lower side is the bead side, and the upper side is the tread side. Although abnormal peaks are shown in parts B and C in FIG. 5, there is a tendency for manufacturing failures to occur in parts where such abnormal peaks exist, that is, parts B and C in FIG. is there. Therefore, by using the size of such irregularities as an index of the cause of failure in the tire manufacturing process, it is possible to easily and visually predict the cause of the failure.

  As described above, when the size of the unevenness is used as an index of the cause of failure in the tire manufacturing process, if the unevenness is large, it tends to cause the failure, but the size of the unevenness and the failure rate are necessarily proportional to each other. Do not mean. Therefore, while determining the size of the unevenness of at least one type of tire mold (preferably, a plurality of types of tire molds) for molding a plurality of types of tires having a common configuration, Obtaining the failure rate of an arbitrary part, obtaining the correlation coefficient between the size of the unevenness at each coordinate point and the failure rate, and identifying the part having a high correlation between the size of these unevenness and the failure rate is predicting the cause of the failure And is extremely meaningful when specifying.

  FIG. 6 is a diagram illustrating a correlation coefficient between the size of the unevenness and the failure rate at each coordinate point of at least one type of tire mold for molding a plurality of types of tires. In FIG. 6, the vertical axis indicates the position in the tire radial direction, the lower side is the bead side, and the upper side is the tread side. In order to obtain FIG. 6, data relating to the size of the unevenness as shown in FIG. 5 is created for at least one type of tire mold for molding a plurality of types of tires, while arbitrary portions of these types of tires ( For example, the failure rate in the side portion) is obtained. And the correlation coefficient of the magnitude | size of the unevenness | corrugation in each coordinate point and a failure rate is calculated | required about multiple types of tires and the tire metal mold | die corresponding to it. For example, for a plurality of types of tires and corresponding tire molds, the correlation coefficient between the unevenness size and the failure rate is obtained at the coordinate point on the bead side, and the value is plotted at the lowest position in FIG. By performing such calculation individually from the coordinate point on the most bead side to the coordinate point on the tread side, FIG. 6 can be drawn.

  In FIG. 6, when the correlation coefficient is positive, it means that the side failure rate increases as the unevenness increases, and when the correlation coefficient is negative, it means that the side failure rate decreases as the unevenness increases. To do. Particularly, when the absolute value of the correlation coefficient is 0.55 or more from a statistical viewpoint, it can be determined that the correlation between the size of the unevenness and the failure rate is high. In FIG. 6, the correlation coefficient increases in a positive value in the vicinity of the filler top (part D) below the center in the tire radial direction, and the correlation between the size of the unevenness and the failure rate is high in this vicinity. Therefore, when large unevenness is recognized in the corresponding part, it can be determined that the unevenness is likely to cause a failure.

  The above determination can be preferably applied to a plurality of types of tires having a common configuration. Here, the plurality of types of tires having a common configuration are those in which at least one of a size, a cross-sectional shape, and a reinforcing structure is common. In the tires having a common configuration, there is a similar tendency regarding the correlation between the size of the unevenness and the failure rate. Therefore, by accumulating data related to tires manufactured in the past, it becomes possible to predict a manufacturing failure of a new tire having a common configuration.

  When creating data as shown in FIG. 6, it is preferable to obtain a correlation coefficient between the size of the unevenness and the failure rate at each coordinate point of the tire mold corresponding to 10 or more types of tires. In other words, by collecting data on many types of tires having a common configuration, it is possible to accurately identify a portion having a high correlation between the size of the unevenness and the failure rate.

  According to the tire manufacturing process management method described above, it is possible to visually and easily predict and identify the cause of failure in the tire manufacturing process based on the size of the irregularities in the contour line obtained from the cross-sectional shape of the tire mold. it can. Accordingly, it is possible to predict the cause of the failure at the stage of simulation before actually manufacturing the tire and to design the tire so that the cause of the failure is eliminated. Further, when a manufacturing failure occurs in the actual tire manufacturing process, it is possible to quickly identify the cause of the failure and take appropriate measures. As a result, the production efficiency of the tire can be greatly improved.

It is a figure which shows the cross-sectional shape of a tire metal mold | die. It is a figure which shows the outline drawn based on the coordinate point of the tire molding surface extracted from the cross-sectional shape of the tire metal mold | die of FIG. It is an enlarged view of the A section of FIG. It is a figure which shows the outline drawn based on the coordinate point of the tire molding surface extracted from the cross-sectional shape of another tire metal mold | die. It is a figure which shows the magnitude | size of the unevenness | corrugation in the outline of FIG. It is a figure which shows the correlation coefficient with the magnitude | size of an unevenness | corrugation in each coordinate point of at least 1 type of tire metal mold | die for shape | molding multiple types of tire, and a failure rate.

Explanation of symbols

M Tire mold P Coordinate point L Contour line S line segment θ Inclination angle

Claims (5)

  Coordinate points of the tire molding surface are extracted at equal intervals in the tire radial direction from the cross-sectional shape of the tire mold, and adjacent contour points are connected by straight lines to draw contour lines, and the tire lines in the tire axial direction of the contour lines are drawn. A tire manufacturing characterized in that an inclination angle is obtained, a size of unevenness at each coordinate point is obtained from a difference in inclination angles of adjacent line segments, and the size of the unevenness is used as an index of a cause of failure in a tire manufacturing process. Process management method.   The tire manufacturing process management method according to claim 1, wherein 100 or more coordinate points are set in the entire radial range of the tire molding surface.   The tire manufacturing process management method according to claim 1, wherein the size of the unevenness is a dimensionless amount including a sine component, a cosine component, or a tangent component.   While determining the size of the irregularities for at least one type of tire mold for molding multiple types of tires, the failure rate of any part of these multiple types of tires is determined, and the size of the irregularities and failures at each coordinate point are determined. The tire manufacturing process management method according to any one of claims 1 to 3, wherein a correlation coefficient with the rate is obtained, and a portion having a high correlation between the size of the unevenness and the failure rate is specified.   The tire manufacturing process management method according to claim 4, wherein the plurality of types of tires have at least one of a size, a cross-sectional shape, and a reinforcing structure.

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