JPH04176709A - Pneumatic tire and manufacture therefor - Google Patents

Abstract

PURPOSE:To improve the wet preformance maintaining life by embedding a rubber body having the equal or nearly equal quality to a tread rubber into a tread rib, positioning the outer edge in the radial direction on the outside in the radial direction from the groove bottom of a tread main groove, and allowing a rubber body exposed through the wearing-out of the tread to be separated. CONSTITUTION:A rubber body 18 which is made of the rubber material equal to or similar to a tread rubber and is previously vulcanized is embedded continuously in the circumferential direction of a tire, in two ribs 16 positioned on the center side of the tire width of a tread part 12. The rubber body 18 has a nearly rectangular form on the section in the tire radial direction, and the edge part 18a on the outside in the tire radial direction is positioned on the outside in the tire radial direction from the groove bottom 14a of a main groove 14. With this constitution, if the edge part 18a of the rubber body 18 is exposed through the wearing-out of the tread part 12, the rubber body 18 is separated from the tread part in simple manner, since the rubber body is previously vulcanized separately from the tread rubber, and a new groove is formed, and the wet performance is kept.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a pneumatic tire that can maintain wet performance over a long period of time, and a method for manufacturing the same.

(Prior art) Tires have a plurality of grooves in the tread and ribs or blocks defined by these grooves, mainly to ensure friction with the road surface and ensure driving, braking performance, and cornering performance. (hereinafter simply referred to as ribs), these grooves and ribs are created by vulcanizing a green tire in a mold, which is formed by pasting unvulcanized tread rubber on a green case. can get.

(Problems to be Solved by the Invention) By the way, the grooves formed in the tread portion impart desired rigidity to the ribs, and also facilitate the removal of the protruding portions of the mold forming the ribs. In order to prevent grooves from becoming stoney, it is customary for tires to have a cross-sectional shape that widens outward in the radial direction, and as the tread wear progresses, the opening area, that is, the negative ratio, decreases. It is known that wet performance deteriorates.

Here, the negative ratio is a value defined as a value obtained by subtracting the ratio of the effective ground contact area of the tread portion to the apparent ground contact area from 1.

For this reason, even if the tire has no problems other than a decrease in groove depth due to tread surface wear, it is necessary to replace it with a new tire within a relatively short period of time to ensure wet performance. There was a problem in that the worn tread portion had to be rehabilitated.

The present invention has been made in view of these problems, and an object of the present invention is to provide a pneumatic tire that can exhibit sufficient wet performance over a long period of time, and a method for manufacturing the same.

(Means for Achieving the Object) In order to achieve this object, the present invention provides a pneumatic tire comprising a plurality of grooves and a plurality of ribs partitioned by the grooves in the tread portion of the tire. A vulcanized rubber body of the same or similar rubber quality to the tread rubber is buried in at least one of the ribs, and the outer portion of the rubber body in the tire radial direction is extended from the bottom of the groove in the tire radial direction. It is located on the outside.

Such pneumatic tires use a pre-vulcanized rubber body that is the same or similar to the tread rubber.
Unvulcanized tread rubber is provided on the green case in correspondence with at least one rib, and molded so that the groove bottom of the groove is located inside the tire radial direction from the tire radial outer end of the rubber body. By vulcanizing in
An unvulcanized tread rubber with a rubber body attached to the inside or back side of the rubber body corresponding to at least one rib is pasted on the green case, and the groove bottom of the main groove is in the radial direction of the tire from the outer edge of the rubber body in the radial direction of the tire. It is obtained by vulcanization in a mold so that it is located inside.

(Function) In tires obtained by vulcanizing green tires, the bottom of the circumferential groove is located radially inward of the tire radially outer portion of the rubber body, so the tread portion thereof is subject to wear. When the groove depth of the circumferential groove decreases with this, the end of the rubber body within the rib located outside the bottom of the main groove in the tire radial direction is exposed.

However, since the rubber body is vulcanized prior to the vulcanization of the green tire, it easily separates from the tread when a certain amount of external force is applied to it. A groove extending into the tread portion appears in the tread portion. Therefore, even if the wear of the tread progresses, the negative ratio does not decrease, and sufficient wet performance is ensured.

(Embodiments) Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a pneumatic radial tire 1 to which the present invention is applied.
The internal structure of the tire 10 is the same as that of a radial tire for boat fishing, so its explanation will be omitted here.

The tread portion 12 includes three main grooves 14 that are spaced apart from each other in the tire width direction and extend in the tire circumferential direction;
Four ribs 1 partitioned by and extending in the tire circumferential direction
6, and a pre-vulcanized rubber body 18 made of the same or similar rubber material as the tread rubber is continuous in the tire circumferential direction within the two ribs located on the center side of the tire width of the tread portion 12. Each of them has been buried.

Here, the reason why the rubber body 18 is made to be the same or close to that of the tread rubber is to prevent local wear from occurring in the tread portion 12 due to the difference in rigidity from the tread rubber. This is to suppress it. Therefore, a different rubber can be used as long as it is equivalent to the tread rubber in terms of rigidity.

As clearly shown in FIG. 1(b), in this embodiment, the rubber body 18 is an elongated body whose cross section in the tire radial direction is approximately rectangular. A plurality of notches 22 are formed in the section, passing through the rubber body in the width direction and at predetermined intervals in the circumferential direction of the tire. Wear. The end portion 18a of the rubber body 18 located on the outer side in the tire radial direction is located on the outer side in the tire radial direction than the groove bottom 14a of the main groove 14.

Therefore, as the wear of the tread portion 12 progresses, the groove depth of the grooves 14 that partition the ribs 16 becomes shallower, and the rubber body 1
The tire radial outer end 18a of No. 8 is exposed. However, since the rubber body 18 is previously vulcanized separately from the tread rubber, it easily separates from the tread portion 12 under the action of a relatively small external force. Therefore, in the tread portion 12 from which the rubber body 18 has come off, a groove corresponding to the volume occupied by the rubber body 18 appears, and although the opening area of the conventional groove 14 is reduced, the negative It is possible to maintain the ratio above a certain level and suppress deterioration of wet performance. Note that since the rubber body 18 has a plurality of notches 22, it is easily detached from the rubber body 18 since it has been previously vulcanized.

As shown in FIG. 1(C), the width of each rubber body 18 in the tire width direction is Cm (however,
k indicates the th rubber body), and the groove width of the groove 14 when the rubber body appears is 1. (However, n indicates the groove of the nth grain of wood), the tread width at that time is S, the tread width of the trend portion 12 is W, and the width of the nth groove on the tread surface 12a is wn, then 0. .5, ≦2≦2K.

However, KI = (wl +W2 +・・)/WKz
It is appropriate to satisfy the following relationship: = (1+ +1g+... 10c, +cz+...)/S.

This is because when K2 is smaller than 0.5+, the negative ratio becomes too small, making it difficult to maintain wet performance, and when K2 is larger than 2+, wear resistance decreases.

In order to manufacture such a tire, a pre-vulcanized rubber body 18 is applied to each rib 1 of the tire after vulcanization.
6, the tire is placed on a green case, and then unvulcanized tread rubber is attached to form a green tire, so that the groove bottom of the groove 14 in the vulcanized tire is located outside the rubber body 18 in the tire radial direction. It may be vulcanized and molded in a mold so that it is located radially inward of the tire from the end.

In this case, the rubber bodies 18 may be arranged on the green case at predetermined intervals in the tire width direction, and unvulcanized tread rubber may be stuck on the green case partitioned by the rubber bodies. As shown in the unvulcanized tread rubber 24 whose half part is schematically shown in Fig. 2 with respect to the tire equatorial plane, the back part of the unvulcanized tread rubber corresponding to the ribs of the tire after vulcanization, that is, the green case. Using tread rubber in which a groove 24 corresponding to the shape of the rubber body is formed in the opposing portion and a vulcanized rubber body is installed in the groove,
It is possible to integrate the rubber body 18 by sandwiching it between unvulcanized rubber sheets, to use tread rubber in which the rubber body is directly embedded during extrusion molding of the tread rubber, or to make the rubber body continuous in the circumferential direction of the tire. The ribs may be separated or may be bent to correspond to the ribs extending in a zigzag shape in the circumferential direction of the tire, and various modifications are possible within the scope of the claims.

(Effects of the Invention) Thus, according to the present invention, it is possible to provide a pneumatic tire that still exhibits good wet performance even in the final stage of wear without affecting rib rigidity or the like.

[Brief explanation of drawings]

FIG. 1(a) is a cross-sectional view of the tread portion of the pneumatic tire of the present invention, and FIG. 1(a) is a perspective view showing a part of a rubber body suitable for the tire shown in FIG. 1(a). , FIG. 1(C) is an enlarged view of a part of the tread portion,
FIG. 2 is an explanatory diagram showing a half of an unvulcanized tread rubber suitable for use in the method of the present invention, with respect to the tire equatorial plane.

Claims (1)

[Claims] 1. A pneumatic tire having a plurality of grooves and a plurality of ribs partitioned by the grooves in the tread portion of the tire, comprising: a vulcanized rubber material that is the same as or similar to the tread rubber; A rubber body is embedded in at least one of the ribs, and the outer portion of the rubber body in the tire radial direction is located outside the groove bottom of the groove in the tire radial direction, so that the rubber body is buried as the tread wears. A pneumatic tire characterized in that the rubber body is separable when exposed. 2. When manufacturing a pneumatic tire with a plurality of grooves and a plurality of ribs partitioned by the grooves in the tread portion of the tire, pre-vulcanized rubber of the same or similar quality to the tread rubber is used. A body is provided on the green case in correspondence with at least one rib, and unvulcanized tread rubber is pasted thereon;
A method for manufacturing a pneumatic tire, comprising vulcanizing the tire in a mold so that the groove bottom of the groove is positioned radially inward of the outer end of the rubber body in the tire radial direction. 3. When manufacturing a pneumatic tire having a plurality of grooves in the tread portion of the tire and ribs defined by the grooves, at least one vulcanized rubber body of the same or similar rubber quality as the tread rubber is used. Unvulcanized tread rubber attached to the inside or back surface of the rubber body corresponding to the two ribs is attached to the green case, and the bottom of the main groove is positioned radially inward of the outer end of the rubber body in the tire radial direction. A method for manufacturing a pneumatic tire, characterized by vulcanization in a mold.