JPH01189510A - Method for measuring dimension of tire tread - Google Patents

Abstract

PURPOSE:To realize a method for accurately and rapidly measuring the dimension of every part of a tire tread, by measuring the distance from a reference position to the surface of the tire tread over the entire width of said tread in a non-contact manner and extracting the feature of a contour shape to calculate the position of a specific point. CONSTITUTION:A motor 8 is driven wile treads 1a, 1b are fed in the direction shown by an arrow A to allow a distance sensor 12 to run at a constant speed to perform scanning in a tread width direction. At this time, since a rotary encoder 10 generates a pulse signal showing the moving quantity of the sensor 12, the scanning position on each of the treads is detected and the sensor 12 measures the distances up to the surfaces of the treads in a non-contact manner and stores said distance data in the memory of an operator 18 in correspondence to the positions on the treads. The distance data taken in the operator 18 are processed according to predetermined algorithm to detect the positions of specific points like the position of a set line for a position standard or a boundary position and the dimension of each member is calculated from these specific points and, therefore, dimension is measured without being affected by the variation of the reflectivity of a tread surface.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for non-contactly measuring the width direction dimension of an unvulcanized tire tread when manufacturing a pneumatic tire.

(Prior Art) Fig. 11 shows the cross-sectional shape of a tire tread that is conveyed by bonding together a plurality of rubber sheets on an extrusion train, which are extruded after being molded into a desired cross-section using an extruder. This example has a structure in which three rubber sheets (31, 32, and 33) are pasted together with their edges slightly overlapped. A set line 32a is formed approximately in the center of the center sheet 32, which serves as a reference position when forming a tire.

Figure 12 shows the cross-sectional shape of a pneumatic tire manufactured by molding and vulcanizing the tire tread described above, with a side tread 34 on the side portion and a wear-resistant top tread on the road surface. There are 35. side tread 3
Rubbers 34a to 34C in No. 4 correspond to the rubber sheets 31 to 33 of the side tread before vulcanization, respectively, and the rubber 34a is in contact with the rim 36 and is made of wear-resistant rubber.
The rubber 34b is made of a bend-resistant rubber, and the rubber 34C is made of a rubber that has good adhesion to both the top tread 35 and the rubber 34b and is easy to conform to. In such a tire, if the side tread rubber 34a or 34C is insufficient and the rubber 34b comes into direct contact with the rim 36 or the top tread 35, sufficient wear resistance cannot be obtained and the rubber 34a, 34b If it is too long, it will not be able to withstand bending sufficiently and may break. Therefore, in order to manage the performance of such a tire tread, it is necessary to control not only the overall width W, but also the overall width W as shown in Fig. 11.
Distance x1 and x from both side edges to set line 32a
2. Measure the distance Y1 from one side edge to the boundary between rubber sheets 31 and 32, and the distance Y2 from the other side edge to the boundary between rubber sheets 32 and 33, and make sure that these dimensions are within the desired range. You need to check whether it is there.

Conventionally, in order to measure the dimensions of each part of a tire tread that is conveyed on an extrusion train at a speed of 20 to 30 m per minute, a part of the tire tread is pulled out from the conveyance line,
Measurements were made using a regular scale, such as a tape measure. With this measurement method, the dimensions of each part mentioned above can be measured with an accuracy of ±1 to 2 mm, but since it is not an online measurement, it takes a long time to obtain the measurement results.
It takes time to correct deviations in tire tread dimensions, and since the tire tread is measured by sampling, there is a drawback that consistency with subsequent processes is poor. It was desired to develop a method for measuring the dimensions of. For example, Japanese Patent Application Laid-open No. 57-110907 discloses that a light beam is projected onto a tire tread running on a conveyance line, the reflected light is received by a photoelectric conversion element, and the area on the tire tread is identified based on the amount of received light. A method is disclosed in which the positions of points are determined and the dimensions of each part are determined from these points. It is also conceivable to illuminate the tire tread surface, capture the optical image with a television camera, and process this image to determine the dimensions of each part.

(Problems to be Solved by the Invention) In the measurement method disclosed in Japanese Patent Application Laid-open No. 57-110907 mentioned above, based on the amount of light reflected from the tire tread, it is possible to measure not only the edge of the tire tread but also the position reference. Although the position of the set line and the boundary position of the rubber sheet are also detected, the amount of received light reflected from the tire tread fluctuates greatly, as shown in Fig. 13.
It is difficult in practice to accurately determine the above-mentioned positions. The reason why the amount of received light fluctuates in this way is not only because the amount of reflected light changes depending on the contour shape of the tire surface, but also because components such as oil contained in the surface plane and kneaded rubber seep into the surface. This is because the reflectance of the tire surface changes significantly due to variations in the reflectance caused by the mottled pattern, scratches on the surface when the tire comes out of the nozzle, minute irregularities on the surface, etc. Furthermore, as shown in Fig. 11, side treads are manufactured by molding three rubber sheets into a predetermined cross-sectional shape using separate extruders, extruding them and pasting them together on a conveyor train. As mentioned above, since the rubber properties of each rubber sheet are different, the gloss of the surface thereof is greatly different, so the reflectance is also changing, and therefore the amount of reflected light is changing greatly.

Furthermore, with the method of capturing an optical image of the tire tread with a television camera and processing the image to measure the dimensions of each part, it is difficult to determine set lines and boundary positions due to the low contrast of the tire tread surface. If you try to accurately determine the image, the calculation operations for image processing become extremely complicated, which increases the cost of the system and increases the time required for measurement, which has the disadvantage that online measurement becomes less meaningful.

SUMMARY OF THE INVENTION The object of the present invention is to eliminate the above-mentioned drawbacks and provide a method for measuring the dimensions of a tire tread, which makes it possible to measure the dimensions of a tire tread accurately and quickly, and therefore also allows for on-line 100% inspection. It is.

(Means for Solving the Problems) The tire tread dimension measuring method of the present invention measures the distance to the tread surface at multiple points in the width direction of the tire tread whose dimensions are to be measured using a non-contact distance sensor. reading out the distances stored in the memory and processing them according to a predetermined algorithm to determine a plurality of specific positions on the tire tread; The method is characterized by comprising a step of determining a dimension in the tread width direction based on the position.

According to the measuring method of the present invention, focusing on the contour shape of the surface of the tire tread, this is detected by a non-contact sensor,
Based on this information, specific points such as the position of the set line for position reference and the boundary position are first detected, and the dimensions of each part are determined from these specific points. Dimensions can be measured accurately and quickly without being affected by changes in reflectance.

(Example) FIG. 1 shows the configuration of an example of an apparatus for carrying out the tire tread dimension measuring method of the present invention.

In this example, the dimensions of the side treads are measured, but one tire requires two side treads, and these are simultaneously extruded by an extruder and transported. In FIG. 1, left and right side treads 1a and 1b are conveyed by a roller conveyor 2 in the direction indicated by arrow A.

This tread may be continuous, or may be cut into individual tires using a cutter. In this example, each tread la, lb is formed by overlapping two rubber sheets, which are formed continuously in the longitudinal direction. The roller conveyor 2 is rotatably mounted between a pair of bases 3, a frame 4 is mounted on these bases, and a shaft 5 is mounted parallel to the horizontal beam of this frame.
to be placed. A bearing member 6 is provided on the shaft 5 so as to be slidable in the horizontal direction, and a belt 7 is attached to the bearing member.
is attached and the belt is rotated by the reversible motor 8, so that the bearing member 6 is reciprocated in the horizontal direction as shown by arrow B. A shaft is attached to the pulley 9 on which the belt 7 is hung, and a rotary encoder 10 is connected to this shaft to control the amount of rotation of the pulley, and therefore the bearing member 6.
to detect the amount of movement. An optical distance sensor 12 is attached to the bearing member 6 via the arm 11 to detect the distance to the treads la and lb in a non-contact manner.

The optical distance sensor 12 includes a laser light source and a light-receiving cell array.The laser light source emits laser light onto the tread surface, projects the reflected light onto the light-receiving cell array, detects the position on the array, and sends the sensor to the tread surface. It measures the distance to.

The distance sensor 12 and encoder 10 are part of the signal processing circuit 1
Connect to 5. This signal processing circuit 15 is connected to the distance sensor 12.
The rotary encoder includes an amplifier 16 that amplifies the output signal from the rotary encoder, an A/D converter 17 that converts the output signal of this amplifier into a digital signal, an arithmetic unit 18 that processes the digital signal, and a display device 19. is arithmetic unit 1
Supply to 8.

While the treads la and lb are being conveyed in the direction of arrow A, the motor 8 is driven to make the distance sensor 12 run at a constant speed in the tread width direction to scan in the tread width direction. The time for scanning the distance sensor 12 in the width direction can be, for example, 10 seconds. At this time, the row encoder 10 generates a pulse signal representing the amount of movement of the distance sensor 12, so that it is possible to accurately know which position on the tread is being scanned. In this example, it is assumed that the encoder 10 generates one pulse every time the distance sensor 12 moves by 0.1 mm. In this way, while detecting the position on the tire tread using the output of the encoder 10, the distance from the distance sensor 12 to the surface of the tire tread is measured in a non-contact manner, and the measured distance information is correlated with the position on the tire tread. The data is stored in the memory within the arithmetic unit 18. The computing unit processes the distance information captured in this way according to a predetermined algorithm to detect the position of a specific point on the tire tread, then calculates the dimensions of each member from the position of this specific point, and calculates this. Display device 1
Display it as 9.

In FIG. 2, the vertical axis represents the distance detected by the distance sensor 12, and the horizontal axis represents the moving distance as the cumulative value of pulses supplied from the low-return encoder 10. The first 100 pulses represent the distance to the surface of the roller conveyor 2, and 100 to 1000 pulses represent the distance to the tire tread 1a. Here, a large step occurs at the transition from the roller conveyor 2 to the tread surface, but this is because the measurement optical axis of the distance sensor 12 is shifted from the central axis of the roller conveyor 2, as shown in FIG. This is because there is a step H in the distance to the distance sensor. Providing such a step has the advantage that the position of both end members of the tread can be detected easily and accurately.

In this example, as mentioned above, the tire tread la,
Since lb is made by overlapping two rubber sheets, there are four positions: both edge positions 21a and 21d, a set line position 21G serving as a position reference, and a boundary position 21b between both sheets.
Points are defined as specific points and their positions are detected. The order of this detection is as explained below.
, boundary position 21b.

Set line position 2IC and other edge position 21d
The order shall be Hereinafter, a method for detecting the positions of these specific points will be described in detail. Here, it is assumed that the distance sensor 12 detects distance digitally, and one digit of its output corresponds to about 5 μm, for example.

Edge Position Detection To detect the left edge position 21a, first 100 pieces of distance data x1 to X are used. . The average value of the data up to the temporary detection height BHI of roller conveyor 2
Find it as.

Next, sequentially distance data X,, X,... from i=1
(hereinafter, the search in this direction is referred to as the positive direction), and detects a portion where 20 consecutive points exceed the level higher by, for example, 3 mm (equivalent to 600 digits) than the previously determined BHI. . Next, as shown in Figure 4, centering on the first point P of these 20 consecutive pieces of data, ±
A window L having a width of 3 mm is set. Next, the detected height BI3 of the roller surface is detected again from 100 pieces of data counted from the left end of this window cover to the left.

Next, the distance data within the window Wl is subjected to a moving average.

Xi = (Xs-2+Xt-1+X1+Xt+++Xi
+z) 15...(a) Next, search for data in the negative direction from the right edge of window W to the left, and for the first time Xi
A point TP where -1≧20 (digits) is detected. This point TP is shown in FIG. Next, the intermediate height MLV between the points TP and BI3 obtained in this manner is calculated.

MLV= (XTP+BH2)/2 Next, data is searched in the negative direction from point TP, and level ML
Detect the point that crosses V for the first time, and set the point PGC just one point to the right of that point to the left edge position 21a of the tire tread.
Detected as.

Detection of boundary position Since the standard values of various dimensions of the tire tread are known,
The standard value from the point PGC representing the edge position 21a detected as described above to the boundary position.

If a window W2 having a width of ±5 mm centered at is set as shown in FIG. 6, all tire tread boundary positions will necessarily fall within the range of this window.

First, moving averaging is performed on the distance data within the window W2 described above.

Xs = (Xt-2+Xt-1+Xt+Xt+++Xt
+z)15 (4) Next, find the point P1 where the moving average value Xt is the minimum. This point P1 is shown in FIG. Next, data is searched in the positive direction from point P1, and a point P2 is found that first exceeds a level 60 digits (=0.3 mm) higher than the distance data value of point P1. That is, Xi
Find the point where >Xp++60. Next, data is searched in the negative direction from point P2 obtained in this way, and for the first time
A point BP where 1Xi-1≦0 is detected. Data is searched in the positive direction from this point BP, and for the first time Xi −Xi−1≦
A point TP corresponding to 4 digits is detected. Next, the intermediate height MLV between the two points BP and TP obtained as described above is
Calculate.

ML, V= (XBP+XTP)/2”...
”(5) Next, the intermediate height MLV between points BP and TP
The point PDB having the closest value to is determined as the point representing the boundary position 21b.

Detection of the set line position As shown in FIG. 8, a window W3 of standard value L2 ± 3 mm is set from the point PDB indicating the boundary position 21b detected as described above, and the moving average value X1 of the data within this window is set. seek.

Xt = (Xt-++L+Xt-+)/3 Generally, the surface of the tire tread where the set line is formed is sloped, and as it is, it is difficult to accurately detect the set line. The moving average value Xi is corrected so that it disappears. As shown in Figure 9, a straight line l representing the slope is found from the moving averaged data (indicated by a circle), then the slope angle θ of this straight line is calculated, and the data is adjusted so that this slope angle θ becomes 0. Correct. Data corrected in this way is indicated by an X mark. The data corrected in this way also retains the original unevenness information. In the following explanation, data modified in this way is also used for convenience of explanation.
Let us express it as

Next, the difference D+ = (
Xt++Xi) is determined, and a point PF exceeding a preset first limit level SLI in the "+" direction is determined as shown in FIG. Next, set the second limit level SL2 to "-"
Find the point PB that crosses in the direction. At this time, if a point exceeding SLI in the "+" direction is detected before point 2 is detected, point PF is updated to that point.

The points PF and PB obtained in this way represent the positions of both ends of the mountain of the set line.

Next, the point PSL where the moving average value X is maximum between the two points PF and PB detected as described above is set as the set line position 21C.

Edge Position Detection Detection of the right edge position of the tire tread is the same as the left edge position detection, except in the opposite direction, and will therefore be omitted.

As described above, the left and right edge positions 21a.

After finding the positions of the point representing 21d, the point representing the boundary position 21b, and the point representing the set line position 21C, calculate the distance from the tire tread gold plate, the length from one edge to the boundary position and the set line, and the set line from the other edge. You can find the length to the line.

The present invention is not limited to the embodiments described above, and numerous changes and modifications are possible. For example, the distance sensor is not limited to an optical type, and any sensor that can measure distance without contact may be used.

In addition, in the above-mentioned example, the dimensions of each part of the side tread formed by laminating two rubber sheets were measured, but the dimensions of each part of the side tread formed by laminating three or more rubber sheets are measured. can also be measured in the same way. Further, the algorithm for detecting a specific point on the tire tread is not limited to the above-mentioned embodiment, but can be detected using various algorithms that utilize the characteristics of the contour shape of each part.

(Effects of the Invention) According to the tire tread dimension measuring method of the present invention described above, the distance from the reference position to the tire tread surface is measured in a non-contact manner throughout the tire tread to determine the contour shape. , the position of a specific point on the tire tread is determined by feature extraction of the contour shape, and finally the dimensions of each part of the tire tread are determined from the position of the specific point determined in this way. Can be measured accurately and quickly. Therefore, on-line measurements can be made and quality control information can be displayed quickly to correct even small dimensional deviations, improving the quality of the tire tread. In addition, since defective tire treads can be easily found and eliminated, tires can be molded using only tire treads with guaranteed dimensions, producing high-precision, high-performance tires. can do.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the configuration of an embodiment of an apparatus for implementing the tire tread dimension measurement method according to the present invention; FIG. 2 is a graph showing the distance to the tire tread surface measured by a distance sensor; The figure is a side view showing the relative positional relationship between the optical axis of the distance sensor and the roller conveyor. Figures 4 and 5 are diagrams showing the algorithm for detecting edge positions. Figures 6 and 7 are diagrams showing the boundary position. Figures illustrating the algorithm for detection; Figures 8, 9 and 10 are diagrams explaining the algorithm for detecting the set line position; Figure 11 illustrates the part where side tread dimensions are to be measured. FIG. 12 is a sectional view showing the structure of a tire, and FIG. 13 is a graph showing the amount of light reflected from the tire tread in a conventional method for measuring dimensions. la, lb...Tire tread 2...Roller conveyor Motor 10...Rotary encoder 12...Distance sensor 15...Signal processing circuit Figure 6 pcrc
w2 →ye

Claims (1)

[Claims] 1. A step of measuring the distance to the tread surface at multiple points in the width direction of the tire tread whose dimensions are to be measured using a non-contact distance sensor and storing the measured distance in a memory; a step of reading out the distance and processing it according to a predetermined algorithm to determine a plurality of specific positions on the tire tread; and a step of determining a dimension in the tread width direction based on the thus determined specific positions. A method for measuring tire tread dimensions, comprising: