JP6838366B2 - How to make a pneumatic tire - Google Patents

Description

The present invention relates to the production how the pneumatic tire, and more particularly, by arranging the unvulcanized rubber member for a side rubber having a shape similar to the final shape of the vulcanized tire in a tire meridian cross section, to reduce the entrainment of rubber relates to the production how the pneumatic tire capable of preventing the occurrence of cracks.

The green tire is configured so that large undulations such as a tread pattern are approximated to the shape of the mold in the tread portion to suppress the flow of rubber during vulcanization and improve the weight balance of the tire. .. However, at present, such an attempt has not been made in the side rubber layer near the bead portion.

On the other hand, when vulcanizing a pneumatic tire, cracks may occur in the vicinity of the bead portion. On the other hand, by adjusting the shape of the mold near the bead portion, the inner surface of the mold and the unvulcanized tire do not come into contact with the outer peripheral surface of the tire corresponding to the arrangement position of the bead filler member. It has been proposed to prevent the formation of regions and suppress the occurrence of cracks (for example, Patent Document 1). However, adjusting the shape of the mold has a drawback that cracks caused by the flow of rubber during vulcanization cannot be sufficiently suppressed.

Japanese Unexamined Patent Publication No. 2003-300212

An object of the present invention is to reduce rubber entrainment and prevent the occurrence of cracks by arranging an unvulcanized rubber member for side rubber having a shape similar to the final shape of a vulcanized tire in a tire meridional cross-sectional view. It is to provide a manufacturing how the pneumatic tire capable.

In the method for manufacturing a pneumatic tire of the present invention for achieving the above object, a side rubber layer exposed on the outer surface of the tire is provided on the sidewall portion, and a protrusion for a rim cushion is formed on the side rubber layer, and the protrusion is formed. A method for manufacturing a pneumatic tire in which the thickness of the side rubber layer in the portion exceeds 33% of the total thickness of the tire in the protrusion, and the cross-sectional shape is close to the final cross-sectional shape of the side rubber layer in the vulcanized tire. A green tire including an unvulcanized rubber member for side rubber having a constriction portion is molded, and the green tire is vulcanized in a mold provided with a recess corresponding to the protrusion portion. It is something to do.

As a result of diligent research on the flow of rubber during vulcanization, the present inventor placed unvulcanized rubber members for side rubber having a uniform thickness in a tire in which a large protrusion for rim cushion was formed on the side rubber layer. When a green tire is used, a considerable amount of rubber flows in the direction of the periphery, and as a result of moving on the surface of the mold, rubber is caught in the vicinity of the protrusion for the rim cushion. It was found that it is important to suppress the flow of rubber in the vicinity of the bead portion including the bead portion, and the present invention was reached.

That is, in the method for manufacturing a pneumatic tire of the present invention, in manufacturing a pneumatic tire in which the thickness of the side rubber layer at the protrusion exceeds 33% of the total thickness of the tire at the protrusion, the side rubber layer in the vulcanized tire is manufactured. A rim cushion by molding a green tire containing an unvulcanized rubber member for side rubber having a cross-sectional shape close to the final cross-sectional shape, and vulcanizing the green tire in a mold having a recess corresponding to a protrusion. Since the flow of rubber can be suppressed in the vicinity of the bead portion including the protrusion for use and the entrainment of rubber can be reduced, the occurrence of cracks can be prevented.

In the method for producing a pneumatic tire of the present invention, the rubber thickness measured at at least 6 points along the peripheral of the side rubber layer in the vulcanized tire and at least 6 points of the unvulcanized rubber member for the side rubber in the green tire. It is preferable that the correlation coefficient with the rubber thickness measured at the corresponding position is 0.6 or more. As a result, it is possible to reduce the widespread flow of rubber during vulcanization, and it is possible to effectively suppress the occurrence of cracks due to the entrainment of rubber.

In the method for manufacturing a pneumatic tire of the present invention, it is preferable to provide a constricted portion on an unvulcanized rubber member for side rubber. As a result, it is possible to reduce the widespread flow of rubber during vulcanization, and it is possible to effectively suppress the occurrence of cracks due to the entrainment of rubber.

FIG. 5 is a cross-sectional view taken along the meridian showing a pneumatic tire according to an embodiment of the present invention. It is sectional drawing which shows the part of the pneumatic tire of FIG. 1 enlarged. (A) and (b) are sectional views showing a part of a green tire, and (a) shows a green tire according to the embodiment of the present invention, and shows a conventional green tire. It is sectional drawing which shows an example of the mold used in the manufacturing method of the pneumatic tire of this invention. It is explanatory drawing which shows the relationship between the side gauge of a green tire and the side gauge of a vulcanized tire. (A) and (b) are explanatory views schematically showing a part of the unvulcanized rubber member for side rubber in a green tire. It is explanatory drawing which shows the rubber thickness of each part of the side rubber layer in the pneumatic tire which concerns on embodiment of this invention.

Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. FIGS. 1 and 2 show a pneumatic tire T (vulcanized tire T) according to an embodiment of the present invention. In FIG. 1, CL is the tire center line.

As shown in FIG. 1, the vulcanized tire T of the present embodiment has a tread portion 1 extending in the tire circumferential direction and forming an annular shape, and a pair of sidewall portions 2 arranged on both sides of the tread portion 1. , 2 and a pair of bead portions 3, 3 arranged inside the sidewall portions 2 in the tire radial direction.

A carcass layer 4 is mounted between the pair of bead portions 3 and 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction, and is folded back from the inside to the outside of the tire around the bead core 5 arranged in each bead portion 3. A bead filler 6 made of a rubber composition having a triangular cross section is arranged on the outer periphery of the bead core 5.

On the other hand, a plurality of belt layers 7 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. These belt layers 7 include a plurality of reinforcing cords that are inclined with respect to the tire circumferential direction, and the reinforcing cords are arranged so as to intersect each other between the layers. In the belt layer 7, the inclination angle of the reinforcing cord with respect to the tire circumferential direction is set in the range of, for example, 10 ° to 40 °. As the reinforcing cord of the belt layer 7, a steel cord is preferably used. At least one belt cover layer 8 is arranged on the outer peripheral side of the belt layer 7 so that the reinforcing cords are arranged at an angle of, for example, 5 ° or less with respect to the tire circumferential direction for the purpose of improving high-speed durability. There is. As the reinforcing cord of the belt cover layer 8, an organic fiber cord such as nylon or aramid is preferably used.

In the vulcanized tire T, a side rubber layer 10 exposed to the outer surface of the tire is arranged on the outside of the carcass layer 4 in the sidewall portion 2. A protrusion 11 for a rim cushion is formed on the side rubber layer 10. As shown in FIG. 2, at the position where the protrusion 11 is formed, the thickness of the vulcanized tire T is defined as the total tire thickness t1, and the thickness of the side rubber layer 10 is defined as the thickness t2. The thickness t2 of the side rubber layer 10 is configured to exceed 33% of the total tire thickness t1. The total tire thickness t1 and the thickness t2 of the side rubber layer 10 are both lengths measured along the normal line of the inner surface of the vulcanized tire T, and are the vulcanized tire T or the side rubber layer 10. It is the length from the inner peripheral side of the tire to the outer peripheral side of the tire.

On the other hand, in the green tire G, the unvulcanized rubber member 12 for the side rubber has a cross-sectional shape close to the final cross-sectional shape of the side rubber layer 10 in the vulcanized tire T. In the embodiment shown in FIG. 3A, the unvulcanized rubber member 12 for the side rubber is provided with a constricted portion 13 which is a portion where the rubber gauge is relatively thin, and the constricted portion 13 is used as a boundary for the side rubber. The vulcanized rubber member 12 has two chevron shapes along the periphery direction. On the other hand, as shown in FIG. 3B, the conventional unvulcanized rubber member 12 for side rubber has no constricted portion and exhibits one chevron shape along the periphery direction. Further, the unvulcanized rubber member 12 for the side rubber is preferably configured so that a portion called a fixed point where the rubber does not flow during vulcanization is located at the constricted portion 13. Thereby, the effect of suppressing the occurrence of cracks can be effectively improved.

FIG. 4 shows a mold 20 used in the method for manufacturing a pneumatic tire of the present invention. The alternate long and short dash line shown in FIG. 4 shows the shape of the inner surface of the vulcanized tire T. The mold 20 has a recess 21 corresponding to a protrusion 11 for a rim cushion formed on the vulcanized tire T. A vulcanized tire T can be obtained by pressing the green tire G from the inside against the inner surface of the mold 20 with a bladder and vulcanizing using such a mold 20. Further, since the mold 20 is provided with the recess 21 corresponding to the protrusion 11 of the vulcanized tire T, the protrusion 11 of the vulcanized tire T can be formed according to the design cross section.

According to the above-described method for manufacturing a pneumatic tire, the sidewall portion 2 has a side rubber layer 10 exposed to the outer surface of the tire, and the side rubber layer 10 is formed with a protrusion 11 for a rim cushion. In manufacturing a pneumatic tire in which the thickness t2 of the side rubber layer 10 exceeds 33% of the total tire thickness t1 of the protrusion 11, the side rubber layer 10 has a cross-sectional shape close to the final cross-sectional shape of the side rubber layer 10 in the vulcanized tire T. A protrusion for a rim cushion is formed by molding a green tire G including an unvulcanized rubber member 12 for side rubber and vulcanizing the green tire G in a mold 20 having a recess 21 corresponding to the protrusion 11. Since the flow of rubber can be suppressed in the vicinity of the bead portion 3 including 11 and the entrainment of rubber can be reduced, the occurrence of cracks can be prevented.

In the above method for manufacturing a pneumatic tire, when measuring the side gauges (rubber thickness of the side rubber layer) of the vulcanized tire T and the green tire G, the vulcanized tire T is along the periphery of the side rubber layer 10. The measurement is performed at at least 6 points, preferably 10 to 12 points, and in the green tire G, the measurement is performed at at least 6 points of the unvulcanized rubber member 12 for the side rubber, or at a position corresponding to the above 10 to 12 points. The position corresponding to the measurement point of the unvulcanized rubber member 12 for the side rubber in the green tire G is obtained as follows. For example, when the measurement is performed so that the six measurement points on the peripheral of the side rubber layer 10 of the vulcanized tire T are approximately equally spaced, both ends of the side rubber layer 10 of the vulcanized tire T are of the green tire G. The six measurement points on the periphery of the side rubber layer 10 correspond to the positions corresponding to both ends of the unvulcanized rubber member 12 for the side rubber, respectively, and the above-mentioned unvulcanized rubber member 12 for the side rubber of the green tire G. It corresponds to each of the positions corresponding to the six measurement points.

Based on the correspondence of the measurement points as described above, the rubber thickness of the side rubber layer 10 of the vulcanized tire T and the rubber thickness of the unvulcanized rubber member for the side rubber of the green tire G are measured. The rubber thickness of the side rubber layer 10 of the vulcanized tire T is such that the measurement points are approximately equally spaced between the positions of the inner surfaces of the tires with reference to the positions of the inner surfaces of the tires corresponding to both ends of the side rubber layers 10. It is measured at various measurement points. Specifically, as shown in FIG. 7, points on the periphery on the inner surface of the tire where the normal line drawn from the inner surface of the tire intersects both ends 10a and 10b of the side rubber layer 10 are designated as points PA and PB. The area between these points PA and PB is divided into seven equal parts so that the peripheries on the inner surface of the tire are evenly spaced, and the measurement points P1 to P6 are set in order from the measurement points on the outer side in the tire radial direction. Further, as shown in the enlarged view near the measurement point P6 in FIG. 7, a normal line (thin line) on the inner surface of the tire is drawn from each measurement point P1 to P6, and from the intersection of the normal line and the inner peripheral surface of the side rubber layer 10. Draw a line segment TL (thick line). When drawing this line segment TL, the angle α formed by the tangent line of the outer peripheral surface of the side rubber layer 10 and the line segment TL is the same as the angle β formed by the tangent line of the inner peripheral surface of the side rubber layer 10 and the line segment TL. Adjust so that The length of the line segment TL drawn in this way is defined as the rubber thickness of the side rubber layer 10 at each measurement point P1 to P6.

On the other hand, the rubber thickness of the unvulcanized rubber member 12 for the side rubber of the green tire G is measured at a position corresponding to the measurement points P1 to P6 on the periphery of the side rubber layer 10. That is, the positions corresponding to the measurement points P1 to P6 of the unvulcanized rubber member 12 for the side rubber of the green tire G are such that the peripheries of the unvulcanized rubber member 12 for the side rubber of the green tire G are evenly spaced. Corresponds to each position divided into 7 equal parts.

In the rubber thickness measured as described above, the rubber thickness measured at a plurality of points along the periphery of the side rubber layer 10 of the vulcanized tire T and the unvulcanized rubber member for the side rubber of the green tire G. The correlation coefficient with the rubber thickness measured at the positions corresponding to the plurality of points 12 is preferably 0.6 or more, and more preferably 0.8 or more.

According to the method for manufacturing a pneumatic tire described above, the correlation coefficient between the rubber thickness of the side rubber layer 10 in the vulcanized tire T and the rubber thickness of the unvulcanized rubber member 12 for the side rubber in the green tire G is high. Therefore, it is possible to reduce the widespread flow of rubber during vulcanization, and it is possible to effectively suppress the occurrence of cracks due to the entrainment of rubber.

For example, when the rubber thickness is measured so that the 10 measurement points on the periphery of the side rubber layer 10 are substantially evenly spaced, the side gauge of the green tire and the side gauge of the vulcanized tire as shown in FIG. It becomes a relationship with. The vertical axis is the side gauge of the green tire, and the horizontal axis is the side gauge of the vulcanized tire. The plurality of points Pa (circular points) shown in FIG. 5 are the green tire G when the green tire G on which the unvulcanized rubber member 12 for the rim cushion is arranged as shown in FIG. 3A is vulcanized. It is plotted based on each side gauge of the vulcanized tire T. On the other hand, the plurality of points Pb (square points) shown in FIG. 5 are added to the green tire when the green tire on which the unvulcanized rubber member for the rim cushion is arranged as shown in FIG. 3 (b) is vulcanized. It is plotted based on each side gauge of the vulcanized tire.

Ideally, the point Pa plotted in FIG. 5 is close to the auxiliary line L having an inclination of 1. In this case, the rubber thickness of the side rubber layer 10 and the unvulcanized rubber for the side rubber in the green tire G It can be said that there is a correlation with the rubber thickness of the member 12. On the other hand, the points Pb plotted in FIG. 5 are not close to the auxiliary line L in comparison with the point Pa and are scattered. That is, when vulcanized using the conventional unvulcanized rubber member for the rim cushion as shown in FIG. 3 (b), the rubber thickness of the side rubber layer in the vulcanized tire and the unvulcanized rubber for the side rubber in the green tire. Since the correlation with the rubber thickness of the rubber member is relatively low, a wide range of flow of the rubber occurs during vulcanization, and the occurrence of cracks cannot be sufficiently suppressed.

In the method for manufacturing a pneumatic tire, the moving distance D from the unvulcanized state at each part of the side rubber layer 10 can be measured by using the position of the side rubber layer 10 along the periphery as a scale. For example, in the green tire G, after applying a line segment EL inclined with respect to the tire radial direction as shown in FIG. 6A to the surface of the unvulcanized rubber member 12 for the side rubber, the green tire G is added. Vulcanize. When the line segment EL changes as shown in FIG. 6B after vulcanization, the displacement amount of the line segment EL is measured to move each part of the tire in the tire radial direction from the unvulcanized state. The distance D is measurable.

Next, the pneumatic tire of the present invention will be described. The pneumatic tire of the present invention has a side rubber layer 10 exposed on the outer surface of the tire on the sidewall portion 2, a protrusion 11 for a rim cushion is formed on the side rubber layer 10, and the thickness of the side rubber layer 10 on the protrusion 11 is formed. The t2 is configured to exceed 33% of the total tire thickness t1 at the protrusion 11. Further, using the position of the side rubber layer 10 along the periphery as a scale, the moving distance from the unvulcanized state at each part of the side rubber layer 10 is 20% or less of the thickness t2 of the side rubber layer 10 at the protrusion 11. It is configured in.

Since the pneumatic tire T is configured in this way, the flow of rubber can be suppressed in the vicinity of the bead portion including the protrusion 11 for the rim cushion, and the entrainment of rubber can be reduced, so that the occurrence of cracks can be prevented. It will be possible. As a result, a high quality pneumatic tire can be obtained without causing unnecessary rubber entrainment. Here, if the moving distance exceeds 20% of the thickness t2 of the side rubber layer 10 in the protrusion 11, the entrainment of the rubber cannot be suppressed and cracks may occur, which is not preferable.

A tire with a tire size of 195 / 65R16, a sidewall portion having a side rubber layer exposed on the outer surface of the tire, a protrusion for a rim cushion formed on the side rubber layer, and the thickness of the side rubber layer on the protrusion is a tire on the protrusion. Whether or not an unvulcanized rubber member for side rubber having a cross-sectional shape close to the final cross-sectional shape of the side rubber layer of the vulcanized tire at the time of molding is used in the method of manufacturing a pneumatic tire exceeding 33% of the total thickness. , Whether or not the mold has a recess corresponding to the protrusion during vulcanization, the outline of the outer circumference of the unvulcanized rubber member for the side rubber, and the presence or absence of the constricted portion in the unvulcanized rubber member for the side rubber. Comparative Examples and Examples 1 to 3 in which the rubber thickness (mm) and the correlation coefficient R at the positions corresponding to the measurement points (P1 to P6) in the unvulcanized rubber member for the side rubber of the green tire were set as shown in Table 1. The manufacturing method of was carried out.

In Table 1, the positions of the measurement points P1 to P6 are the same as those shown in FIG. 7. The rubber thickness at the measurement point along the periphery of the side rubber layer is the same in all of the manufacturing methods of Comparative Examples and Examples 1 to 3 (final dimensions in Table 1). The correlation coefficient R is a correlation coefficient calculated from the rubber thickness at the measurement point along the periphery of the side rubber layer and the rubber thickness at the position corresponding to the measurement point of the unvulcanized rubber member for the side rubber of the green tire. Is.

The occurrence of cracks was evaluated for the production methods of Comparative Examples and Examples 1 to 3, and the results are also shown in Table 1.

Regarding the occurrence of cracks, the side rubber layers of each of the 100 test tires obtained by these manufacturing methods were cut out and immersed in toluene for 7 days under the condition of 23 ° C. to carry out a swelling test, and then the state of the side rubber layers. Was visually confirmed. The evaluation result showed the presence or absence of cracks in the cut out side rubber layer.

As can be seen from Table 1, in Examples 1 to 3, the rubber thickness at a plurality of measurement points along the periphery of the side rubber layer and the positions corresponding to the measurement points of the unvulcanized rubber member for the side rubber in the green tire. By setting the correlation coefficient R with the rubber thickness in the above to be relatively high, the occurrence of cracks could be suppressed. On the other hand, in the comparative example, since vulcanization was performed using an unvulcanized rubber member for side rubber which has no constricted portion and exhibits one chevron shape along the periphery direction, the occurrence of cracks could not be suppressed. ..

1 Tread part 2 Side wall part 3 Bead part 10 Side rubber layer 11 Protrusion part 12 Unvulcanized rubber member for side rubber 13 Constriction part 20 Mold 21 Recessed part T Vulcanized tire G Green tire

Claims (2)

The sidewall portion has a side rubber layer exposed on the outer surface of the tire, and a protrusion for a rim cushion is formed on the side rubber layer, and the thickness of the side rubber layer on the protrusion is the total thickness of the tire on the protrusion. A method of manufacturing more than 33% pneumatic tires
A green tire including an unvulcanized rubber member for side rubber having a cross-sectional shape close to the final cross-sectional shape of the side rubber layer in the vulcanized tire and having a constricted portion is formed, and a recess corresponding to the protrusion is formed. A method for manufacturing a pneumatic tire, which comprises vulcanizing the green tire in a provided mold. The rubber thickness measured at at least 6 points along the periphery of the side rubber layer in the vulcanized tire and the position corresponding to at least 6 points of the unvulcanized rubber member for the side rubber in the green tire. The method for manufacturing a pneumatic tire according to claim 1, wherein the correlation coefficient with the rubber thickness is 0.6 or more.

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