JP2011037415A - Pneumatic tire and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire which regulates the movement of groove bottom portions of main grooves to improve the driving stability performance while preventing a peaky behavior, and a method for manufacturing the pneumatic tire. <P>SOLUTION: The pneumatic tire is provided on the tread surface Tr with main grooves 8 extending in the tire circumferential direction, and land portions 9 partitioned by the main grooves 8. Reinforcing materials 10 each curved in a U-shaped cross section are embedded along the groove bottom portions of the main grooves 8 in the inner area of the main grooves 8. The reinforcing materials 10 are omitted in the inner area of the land portions 9 adjacent to the main grooves 8. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a pneumatic tire having improved tread rigidity and improved steering stability performance, and a method for manufacturing the pneumatic tire.

  Usually, a main groove is extended on the tread surface of a pneumatic tire along the tire circumferential direction for the purpose of enhancing drainage performance in rainy weather, and a plurality of land portions are defined by the main groove. ing. The land portion is constituted by a rib or a plurality of blocks continuously extending in the tire circumferential direction. In the latter case, the land portion is divided in the tire circumferential direction by a lateral groove extending in a direction intersecting the main groove. By these grooves, various tread patterns corresponding to required tire performance and use conditions are formed on the tread surface.

  Among the tread patterns, the configuration related to the main groove (number, depth, etc.) has a great influence on the rigidity of the tread part, and is involved in the steering stability performance (handling performance) of the tire. The inventor conducted extensive research on this point, and by controlling the movement of the groove bottom of the main groove during traveling, it is effective in improving the steering stability performance by effectively increasing the rigidity of the tread. There was found.

  Patent Document 1 below describes a pneumatic tire in which a reinforcing layer extending along the tire width direction is disposed in the inner region of the main groove. However, this reinforcing layer merely reinforces the rubber directly under the main groove and does not have a form that can restrain the main groove, so that the movement of the bottom of the main groove can be sufficiently restricted. is not. In the first place, in the tire, a high-frequency road noise is reduced by a reinforcing layer provided in the tread portion, and the reinforcing layer is disposed between the belt layer and the carcass layer or between the carcass layer and the inner liner. It may be between.

  Patent Document 2 listed below describes a pneumatic tire in which a reinforcing material composed of a woven fabric or a nonwoven fabric made of a fiber member is disposed in a tread portion. This reinforcing material is provided over the entire region of the tread surface, is located on the tread surface side of the inner region of the land portion than the inner region of the main groove, and has a curved shape in the inner region of the main groove. . However, in such a tire structure, since the entire region of the tread portion is firmly reinforced, there is a problem that when the cornering limit is exceeded, the flexibility of the land portion is difficult to be exhibited, and a peaky behavior is exhibited.

  The above “peeky behavior” refers to a state where the tire starts to slide at once when the cornering limit is exceeded. When the cornering limit is exceeded, it is desirable that the tire starts to slip while gradually sticking to the road surface by utilizing the flexibility of the land portion, thereby improving the steering stability performance. Therefore, it is important to regulate the movement of the groove bottom portion of the main groove while traveling while preventing the above-mentioned peaky behavior.

JP 2005-35345 A JP 2003-285609 A

  The present invention has been made in view of the above circumstances, and the object thereof is a pneumatic tire capable of improving steering stability performance by restricting movement of the groove bottom portion of the main groove while preventing peaky behavior, and its pneumatic It is providing the manufacturing method of a tire.

  The above object can be achieved by the present invention as described below. That is, the pneumatic tire according to the present invention is a pneumatic tire in which a tread surface is provided with a main groove extending along a tire circumferential direction and a land portion partitioned by the main groove. In the area, a reinforcing material curved in a U-shaped cross section along the bottom of the main groove is embedded, and the reinforcing material is omitted in the inner area of the land portion adjacent to the main groove. is there.

  According to the above pneumatic tire, since the reinforcing material curved in a U-shaped cross section along the groove bottom portion of the main groove is embedded in the inner region of the main groove, the movement of the groove bottom portion of the main groove is suppressed. The rigidity of the tread portion can be improved by sufficiently restricting. Nevertheless, since the reinforcing material is missing in the inner region of the land, the flexibility of the land can be exhibited even when the cornering limit is exceeded, and peaky behavior can be prevented. Thus, according to the present invention, it is possible to improve the steering stability performance by restricting the movement of the bottom of the main groove while preventing peaky behavior.

  In the pneumatic tire according to the present invention, it is preferable that both end portions of the reinforcing material are arranged in a range of 15 to 35% of the main groove depth from the deepest end of the main groove to the tread surface side. Thereby, it is possible to accurately arrange the reinforcing material around the groove bottom of the main groove, and to secure a restraining force on the main groove while preventing peaky behavior. That is, if the arrangement of the both end portions deviates from the above range to the tire inner surface side, the restraining force on the main groove is weakened and the effect of improving the rigidity of the tread portion tends to be reduced. On the other hand, if it comes off to the tread surface side, the restraining force with respect to the main groove becomes strong and tends to cause a peaky behavior.

  In the pneumatic tire according to the present invention, the reinforcing member is formed of a ply including a cord extending substantially in the tire circumferential direction. In the reinforcing member corresponding to the main groove on the outer side in the tire width direction, the main member on the inner side in the tire width direction is used. It is preferable that the cords are arranged more densely than the reinforcing material corresponding to the groove. During cornering, a large load acts on the outer region in the tire width direction, and the main groove in the outer region becomes particularly easy to move. Therefore, according to the above configuration of the present invention, it is possible to firmly restrain the main groove on which a large load tends to act during cornering, and to enhance the improvement effect of the steering stability performance.

  In the pneumatic tire of the present invention, the reinforcing member is composed of a ply including a cord extending substantially in the tire circumferential direction, and the cord is denser in the outer portion in the tire width direction of the reinforcing member than in the inner portion in the tire width direction. Those arranged are preferred. During cornering, a large load acts on the outer region in the tire width direction, and the outer portion of the main groove in the tire width direction becomes particularly easy to move. Therefore, according to the above-described configuration of the present invention, it is possible to firmly restrain the outer portion of the main groove in the tire width direction where a large load tends to act during cornering, thereby enhancing the improvement effect of the steering stability performance.

  In addition, the method for manufacturing a pneumatic tire according to the present invention includes a step of winding a rubber ribbon along the tire circumferential direction to form a semi-finished product of tread rubber having a concave groove at a main groove forming position, and a groove of the concave groove. A curved reinforcing material is disposed at the bottom, and a rubber ribbon is further wound to cover the reinforcing material to obtain a finished cross-sectional shape of the tread rubber, and a mold protrusion on the surface of the tread rubber during vulcanization molding. And a step of forming a main groove by pressing.

  According to this method, the pneumatic tire of the present invention described above can be easily manufactured. That is, in this method of manufacturing a pneumatic tire, a curved reinforcing material is disposed in advance in a concave groove that is a main groove forming portion, and the main groove is formed during vulcanization molding by covering it with a rubber ribbon. When doing so, it is possible to easily embed a reinforcing material curved in a U-shaped cross section along the groove bottom in the inner region of the main groove. The “finished cross-sectional shape of the tread rubber” refers to the cross-sectional shape of the tread rubber required for forming the green tire before vulcanization.

  In the method for manufacturing a pneumatic tire according to the present invention, the reinforcing member is formed of a ply including a cord extending substantially in the tire circumferential direction, and one or a plurality of the cords covered with rubber are provided on the concave grooves. It is preferable to arrange the reinforcing material by winding it spirally while curving along the groove bottom. In this case, it is possible to simply arrange a curved reinforcing material at the groove bottom of the concave groove, and it is possible to easily adjust the width of the reinforcing material and the driving density (the number of cords per unit width).

  In the method for manufacturing a pneumatic tire according to the present invention, it is preferable that the finished cross-sectional shape of the tread rubber has a shallow groove shallower than the concave groove at a position where the main groove is formed. As a result, the amount of rubber interposed between the mold protrusion and the reinforcing material is reduced, and the relative position between the main groove and the reinforcing material is easily determined, so when forming the main groove during vulcanization molding, A reinforcing material curved in a U-shaped cross section can be easily disposed along the groove bottom of the groove.

Tire meridian cross-sectional view showing an example of a pneumatic tire according to the present invention The figure which expanded the principal part of FIG. Sectional drawing for demonstrating the modification of a reinforcing material Sectional drawing for demonstrating the modification of a reinforcing material Sectional drawing which shows an example of the manufacturing method of the pneumatic tire which concerns on this invention

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a tire meridian cross-sectional view showing an example of a pneumatic tire according to the present invention. FIG. 2 is an enlarged view of the main part.

  The pneumatic tire includes a pair of annular bead portions 1, a sidewall portion 2 extending outward in the tire radial direction from the bead portion 1, a tread portion 3 connected to an outer peripheral side end of the sidewall portion 2, and a pair of the tires. A radial tire including a carcass layer 4 that reinforces a space between bead portions 1. The carcass layer 4 is made of a carcass ply having a toroidal shape, and its end is folded back so as to sandwich the bead core 1a and the bead filler 1b.

  On the outer periphery of the tread portion 3 of the carcass layer 4, a belt layer 5 that reinforces the carcass layer 4 with a gag effect is disposed. The belt layer 5 includes two belt plies 5a and 5b having cords inclined at an angle of 20 to 30 ° with respect to the tire circumferential direction, and the plies are laminated so that the cords cross in opposite directions. ing. Examples of the material for the cord include steel cords and organic fibers such as polyester, rayon, nylon, and aramid. A belt reinforcing layer may be laminated on the outer periphery of the belt layer 5 as necessary.

  A tread rubber 7 is provided on the outer peripheral side of the belt layer 5, and a main groove 8 extending along the tire circumferential direction and a land portion 9 partitioned by the main groove 8 are formed on the tread surface Tr which is the outer peripheral surface. Is provided. The land portion 9 is configured by ribs extending continuously in the tire circumferential direction, or a plurality of blocks. In the latter case, the land portion 9 is divided in the tire circumferential direction by a lateral groove extending in a direction intersecting the main groove 8. In the present embodiment, an example is shown in which a total of four main grooves 8 are formed on the tread surface Tr, two on each side.

  In this pneumatic tire, the reinforcing material 10 curved in a U-shaped cross section along the groove bottom portion 8 a of the main groove 8 is embedded in the inner region of the main groove 8, and the land portion adjacent to the main groove 8 is embedded. In the inner region 9, the reinforcing material 10 is missing. The reinforcing material 10 extends in a hook shape along the extending direction of the main groove 8 and is disposed away from the belt layer 5 toward the tread surface Tr. In the present embodiment, the reinforcing material 10 is disposed corresponding to all the main grooves 8. However, in the present invention, the reinforcing material 10 may be disposed corresponding to at least one main groove 8. An example of the driving density of the reinforcing member 10 is 19 / inch.

  By embedding the reinforcing member 10 so as to wrap the groove bottom portion 8a as described above, the movement of the groove bottom portion 8a of the main groove 8 can be sufficiently restricted during traveling, and the rigidity of the tread portion 3 can be improved. In addition, since the inner area of the land portion 9 is not reinforced, when the cornering limit is exceeded, the land portion 9 is softened to prevent its peaky behavior, and the slipping out gradually sticks to the road surface. It can be expressed. As a result, it is possible to improve the steering stability performance by restricting the movement of the groove bottom 8a of the main groove 8 while preventing peaky behavior.

  The reinforcing member 10 is made of a ply including a cord C extending substantially in the tire circumferential direction, and is formed by rubber coating a plurality of cords C arranged in parallel. Examples of the material of the cord C include organic fibers such as nylon, aramid, polyester, and rayon, and any of a twisted cord and a monofilament cord can be used. By reinforcing with such a ply, the movement of the groove bottom portion 8a during running can be tightly restricted as compared with a case where the peripheral rubber of the groove bottom portion 8a is simply hardened.

  As shown in FIG. 2, it is preferable that both end portions 10 a and 10 b of the reinforcing member 10 are arranged in the range A, respectively. This range A is a range that is 15 to 35% of the main groove depth D from the deepest end of the main groove 8 to the tread surface side. For example, when the main groove depth D is 8.0 mm, Both end portions 10a and 10b are arranged at a position 2.0 mm away from the deepest end of the groove 8 on the tread surface side. Moreover, when ensuring the restraint force with respect to the main groove 8, it is preferable that the distance from the deepest end of the main groove 8 is 1.5 mm or less in the bottom inner surface part 10c of the reinforcing material 10.

  The thickness of the rubber interposed between the main groove 8 and the reinforcing material 10 is preferably about 1 to 1.5 mm. By making this thickness 1 mm or more, exposure to the inner surface of the main groove 8 of the reinforcing material 10 can be prevented, and the durability of the tread rubber 7 can be secured. Further, by setting the thickness to 1.5 mm or less, the effect of the reinforcing member 10 accurately restraining the main groove 8 and restricting the movement of the groove bottom 8a is enhanced.

  The width W10 of the reinforcing member 10 is preferably 170% or less with respect to the width W8 of the main groove 8. Thereby, it becomes a structure effective in suppressing advance of the reinforcing material 10 to the inward region of the land portion 9 and preventing peaky behavior. The width W8 of the main groove 8 is measured at the deepest end depth position. Usually, since the corner of the groove bottom 8a is formed by a curved surface, the extension of the groove wall as shown in FIG. It is calculated using a line.

  3A and 3B are cross-sectional views for explaining a modification of the reinforcing member 10, in which FIG. 3A is a main groove 8 </ b> A located on the outer side in the tire width direction, and FIG. 3B is a main groove 8 </ b> B located on the inner side in the tire width direction. Is shown. In this modification, the driving density of the reinforcing material 10 is varied according to the relative position of the main groove, and the reinforcing material 10 corresponding to the main groove 8A is corded more than the reinforcing material 10 corresponding to the main groove 8B. C is densely arranged. Thereby, the main groove 8A in which a large load tends to act during cornering is firmly restrained, and the improvement effect of the steering stability performance can be enhanced. Such a configuration can be similarly applied to the other main grooves 8C and 8D. In this case, the ratio of the driving density between the main grooves 8A, 8D and the main grooves 8B, 8C is exemplified as 2: 1. Specifically, the reinforcing material 10 corresponding to the main grooves 8A, 8D is 37 / inch, The reinforcing material 10 corresponding to the main grooves 8B and 8C may be 19 / inch.

  4A and 4B are cross-sectional views for explaining a modified example of the reinforcing member 10, in which FIG. 4A is a main groove 8 </ b> A whose left side is the outer side in the tire width direction, and FIG. A groove 8D is shown. In this modification, the driving density is partially varied with respect to the reinforcing member 10, and the cords C are more densely arranged in the outer portion of the reinforcing member 10 in the tire width direction than in the inner portion of the tire width direction. Thereby, the tire width direction outer side part of the main grooves 8A and 8D in which a large load tends to act during cornering can be firmly restrained, and the improvement effect of the steering stability performance can be enhanced. Such a configuration can be similarly applied to the other main grooves 8B and 8C. In this case, the ratio of the driving density between the outer portion and the inner portion is 2: 1. Specifically, the outer portion may be 18 lines / inch and the inner portion may be 9 lines / inch. The base point of the outer part and the inner part is the center of the main groove 8 (a position where W8 becomes 1/2).

  The pneumatic tire of the present invention is the same as a normal pneumatic tire except that the reinforcing material as described above is provided in the tread portion, and any conventionally known material, shape, structure, etc. are adopted in the present invention. Can do.

  Next, a method for manufacturing the pneumatic tire will be described with reference to FIG. In addition, the manufacturing method of the pneumatic tire which concerns on this invention can be performed like the conventional tire manufacturing process except the process regarding a tread rubber. In the present invention, the tread rubber is formed by a so-called ribbon winding method. In the ribbon winding method, a rubber member having a desired cross-sectional shape can be formed by winding an unvulcanized rubber ribbon spirally along the tire circumferential direction.

  First, belt plies 5a and 5b are wound around a base (not shown) such as a rotating drum, the belt layer 5 is disposed in a cylindrical shape, and a rubber ribbon is wound around the outer circumference along the tire circumferential direction. A tread rubber semi-finished product 11 having a concave groove 12 as shown in FIG. The concave groove 12 is provided at a location where the main groove 8 is formed, and the groove bottom 12a has a curved shape. According to the ribbon winding method, the semi-finished product 11 can be easily formed by adjusting the winding of the rubber ribbon. In addition, FIG. 5 is showing typically and illustration is abbreviate | omitted about each cross-sectional shape of a rubber ribbon.

  Subsequently, as shown in FIG. 5B, the curved reinforcing material 10 is disposed on the groove bottom portion 12 a of the concave groove 12. At this time, the reinforcing material 10 can be simply and easily wound by spirally winding one or more cords C covered with rubber along the extending direction of the groove 12 while curving along the groove bottom 12a. Can be arranged. In addition, with this method, the width and driving density of the reinforcing material 10 can be easily adjusted, which is also useful in implementing the structures as shown in FIGS.

  And as shown in FIG.5 (c), a rubber ribbon is further wound so that the reinforcement material 10 may be coat | covered, and the finishing cross-sectional shape of the tread rubber 7 is obtained. This finished cross-sectional shape is a cross-sectional shape required for forming a green tire before vulcanization, and does not have to exactly match the cross-sectional shape shown in FIG. In the present embodiment, shallow grooves 13 that are shallower than the recessed grooves 12 are formed at the positions where the main grooves having a finished cross-sectional shape are formed. The shallow groove 13 is formed by adjusting the winding of the rubber ribbon.

  The tread rubber 7 having the finished cross-sectional shape is affixed to the outer periphery of a cylindrical member including the bead core 1a and the carcass layer 4 together with the belt layer 5, and is used for forming a green tire. At the time of vulcanization molding, as shown in FIG. 5D, the main groove 8 is formed by pressing the projection 21 of the mold 20 against the surface of the tread rubber 7. At this time, the reinforcing member 10 is in a posture to wrap the tip portion of the protrusion 21 that is deeply pushed into the shallow groove 13, and has a U-shaped cross section along the groove bottom 8 a of the main groove 8 as shown in FIGS. It is arranged.

  Since the steering stability performance was evaluated to specifically show the configuration and effects of the present invention, it will be described below. Steering performance was evaluated by turning the vehicle with a test tire (size 225 / 45R18 91W) and using a point system based on a driver's sensory test. The result of the comparative example 1 was set to 0, and it evaluated by the point piled up from there, and it shows that it is excellent in steering stability, so that a numerical value is large.

Comparative Examples 1-4
In the tire structure shown in FIG. 1, those in which no reinforcing material is embedded in the inner region of the main groove are referred to as Comparative Examples 1 and 2. However, in Comparative Example 2, one belt reinforcing layer was laminated on the outer periphery of the belt layer. Moreover, what embedded the reinforcing material extended along the tire width direction in the inner area of the main groove was made into Comparative Example 3, and what embedded the reinforcing material over the whole tread surface including the inner area of the main groove was compared with Comparative Example 3. It was set to 4. Each of the belt reinforcing layer and the reinforcing material was constituted by a ply containing a nylon cord.

Examples 1-3
In the tire structure shown in FIG. 1, a reinforcing material curved in a U-shaped cross section along the bottom of the main groove is embedded in the inner region of the main groove, and the reinforcing material is missing in the inner region of the land portion. This was designated as Example 1. In Example 1, the driving density of the reinforcing material corresponding to each main groove was uniformly 19 / inch. Further, as shown in FIG. 4, Example 2 was obtained by densely arranging the cords of the outer portion in the tire width direction of the reinforcing material. In Example 2, the driving density was 18 / inch at the outer portion and 9 / inch at the inner portion. Furthermore, as shown in FIG. 3, Example 3 was obtained by densely arranging reinforcing material cords corresponding to the main grooves on the outer side in the tire width direction. In Example 3, the driving density was 37 / inch on the outer side in the tire width direction and 19 / inch on the inner side. Each of the above-described reinforcing materials was constituted by a ply including a nylon cord. The evaluation results are shown in Table 1.

  From Table 1, it can be seen that in Examples 1 to 3, the steering stability performance can be improved as compared with Comparative Examples 1 to 4. This is considered to be because, in Examples 1 to 3, the movement of the bottom of the main groove can be sufficiently restricted by the reinforcing material while preventing peaky behavior. Particularly in Examples 2 and 3, the improvement effect can be improved by adjusting the density of the cords of the reinforcing material. On the other hand, Comparative Examples 1 to 3 do not have a structure capable of restraining the main groove, and Comparative Example 4 is a structure that hardly exhibits the flexibility of the land portion when the cornering limit is exceeded. Therefore, the steering stability performance is relatively low.

3 tread portion 4 carcass layer 5 belt layer 7 tread rubber 8 main groove 8a groove bottom portion 9 land portion 10 reinforcing material 11 semi-finished product 12 concave groove 13 shallow groove 20 mold 21 protrusion C code Tr tread surface

Claims (7)

  In a pneumatic tire in which a main groove extending along a tire circumferential direction and a land portion defined by the main groove are provided on a tread surface, an inner region of the main groove is formed at a groove bottom portion of the main groove. A pneumatic tire characterized by burying a reinforcing material curved in a U-shaped cross section along the inner region of the land portion adjacent to the main groove.   2. The pneumatic tire according to claim 1, wherein both ends of the reinforcing material are arranged in a range of 15 to 35% of a main groove depth from a deepest end of the main groove to a tread surface side.   The reinforcing material is a ply including a cord extending substantially in the tire circumferential direction, and the reinforcing material corresponding to the main groove on the outer side in the tire width direction is more than the reinforcing material corresponding to the main groove on the inner side in the tire width direction. The pneumatic tire according to claim 1 or 2, wherein the cords are densely arranged.   The reinforcing material comprises a ply including a cord that extends substantially in the tire circumferential direction, and the cord is more densely arranged in the tire width direction outer portion of the reinforcing material than in the tire width direction inner portion. 3. The pneumatic tire according to any one of 3 above. A step of winding a rubber ribbon along the tire circumferential direction to form a semi-finished product of tread rubber having a concave groove in the formation position of the main groove;
Arranging a curved reinforcing material at the groove bottom of the concave groove, further winding a rubber ribbon so as to cover the reinforcing material, and obtaining a finished cross-sectional shape of the tread rubber;
Forming a main groove by pressing a projection of the mold against the surface of the tread rubber at the time of vulcanization molding. The reinforcing material is composed of a ply including a cord extending substantially in the tire circumferential direction,
The pneumatic tire manufacturing method according to claim 5, wherein the reinforcing material is disposed by spirally winding one or a plurality of the cords coated with rubber while being curved along a groove bottom portion of the concave groove. Method.   The method for manufacturing a pneumatic tire according to claim 5 or 6, wherein a finished cross-sectional shape of the tread rubber has a shallow groove shallower than the concave groove at a position where the main groove is formed.

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