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EP-4741147-A1 - TREAD RUBBER FORMING METHOD

EP4741147A1EP 4741147 A1EP4741147 A1EP 4741147A1EP-4741147-A1

Abstract

A tread rubber forming method comprises the steps of: forming a non-conductive layer 10 by winding a non-conductive first rubber strip 3 around a cylindrical body 2 for plural turns; forming a conductive layer 20 by winding a conductive second rubber strip 4 around the cylindrical body for at least one turn in parallel to the circumferential direction of the cylindrical body; and forming a non-conductive layer 10 by winding the first rubber strip 3 around the cylindrical body for plural turns. When winding the non-conductive rubber strip 3 for each one turn of the plural turns, the first rubber strip 3 is wound in parallel to the circumferential direction to form at least 3/4 portion of the one turn, and wound obliquely to form the remaining portion of the one turn.

Inventors

  • HASHIMOTO, Yuto
  • SAKAMOTO, MASAYUKI
  • TIFTIKOI, Semih Yucel
  • SAKIK, Tolga

Assignees

  • SUMITOMO RUBBER INDUSTRIES, LTD.

Dates

Publication Date
20260513
Application Date
20250806

Claims (10)

  1. A tread rubber forming method comprising: a first step of forming a non-conductive layer by winding a non-conductive first rubber strip in the shape of a tape, around a cylindrical body for plural turns; a second step of forming a conductive layer after the first step, by winding a conductive second rubber strip in the shape of a tape, around the cylindrical body for at least one turn, in parallel to the circumferential direction of the cylindrical body so as to overlap a portion of the first rubber strip ; and a third step of forming a non-conductive layer after the second step, by winding the first rubber strip around the cylindrical body for plural turns so as to overlap a portion of the second rubber strip , wherein each of the first step and the third step includes, when making each one turn of the plural turns, a circumferential winding step in which the first rubber strip is wound in parallel to the circumferential direction of the cylindrical body by at least 3/4 of the one turn to form a circumferential segment constituting a portion of the one turn, and an oblique winding step in which the first rubber strip is wound obliquely to the circumferential direction of the cylindrical body to form an oblique segment constituting the remaining portion of the one turn.
  2. The tread rubber forming method according to claim 1, wherein, in the circumferential winding step, the first rubber strip is wound by at least 7/8 of the one turn.
  3. The tread rubber forming method according to claim 1 or 2, wherein the circumferential segments wound in the first step and the circumferential segments wound in the third step are arranged in the same phase in a rotational direction of the cylindrical body.
  4. The tread rubber forming method according to claim 1, 2 or 3, wherein the oblique segments wound in the first step and the oblique segments wound in the third step are inclined to opposite directions to each other.
  5. The tread rubber forming method according to claim 1, 2 or 3, wherein the oblique segments wound in the first step and the oblique segments wound in the third step are inclined in the same direction as each other.
  6. The tread rubber forming method according to claim 1, 2, 3, 4 or 5 wherein a winding start position or a winding stop position of the first rubber strip and circumferential ends of the oblique segments are arranged in the same phase in the rotational direction of the cylindrical body.
  7. The tread rubber forming method according to any one of claims 1 to 6, wherein the non-conductive layer includes a base tread rubber layer made of a rubber compound comprising 10% by mass of carbon black with respect to the total reinforcing agent of the rubber compound.
  8. The tread rubber forming method according to claim 7, wherein the non-conductive layer includes a cap tread rubber layer wound on the radially outside of the base tread rubber layer, and the cap tread rubber layer is made of a rubber compound different from that of the base tread rubber layer.
  9. The tread rubber forming method according to claim 8, wherein the circumferential segments of the base tread rubber layer and the circumferential segments of the cap tread rubber layer are arranged in the same phase in the rotational direction of the cylindrical body.
  10. The tread rubber forming method according to claim 9, wherein the oblique segments of the base tread rubber layer and the oblique segments of the cap tread rubber layer are inclined to opposite directions to each other.

Description

Technical field The present invention relates to a method for forming an annular tread rubber. Background art There has been known a method for forming a tread rubber in which a non-conductive rubber strip and a conductive rubber strip are wound around a cylindrical body to form an annular tread rubber (see, Patent Document 1). Prior art document Patent Documents Patent Document 1: Japanese Patent Application Publication No. 2021-130222 Summary of the Invention Problems to be solved by the Invention In the tread rubber forming method of Patent Document 1, a non-conductive layer is formed by winding a non-conductive rubber strip around a cylindrical body in a helical manner, namely, obliquely relative to the circumferential direction of the cylindrical body. Usually, a tread rubber is designed to have such a contour that the thickness of the tread rubber is varied in the tire axial direction according to the rubber volume distribution in the tire axial direction of the finished tire. And when the tread rubber having such contour is formed by winding a rubber strip, the traversing speed, namely, the speed of the axial movement of the fed rubber strip has to be changed relative to the rotating cylindrical body. Generally, it is difficult to wind the rubber strip precisely so as to achieve the tread rubber having the designed intended contour, so the following measures have been required; (1) rotating the cylindrical body at a slow speed; and (2) locating the head of the rubber strip applicator as close as possible to the cylindrical body. In addition, when the tread rubber is provided with a conductive path (called base pen) made of a conductive rubber compound and used to discharge vehicle's static electricity to the ground, since a conductive rubber strip and a non-conductive rubber strip have to be wound so as to fit the designed intended contour of the tread rubber , the number of factors to be considered when winding two kinds of rubber strips is increased, and controlling the plural applicators becomes more complicated. On the other hand, it is necessary that, in the ground contacting surface of the tread rubber, the conductive path is exposed to the outside in order to achieve a sufficient discharge effect. Therefore, when winding a conductive rubber strip constituting the conductive path, the position of the conductive rubber strip has be controlled so that the portion of the conductive path to be exposed in the ground contacting surface does not position within the width of a circumferential groove. In the method described in Patent Document 1, since the conductive rubber strip is wound in an helical manner, the conductive path is formed obliquely to the circumferential direction, making it difficult to adjust the positional relationship between the conductive path and the circumferential groove. The present invention was made in view of the above circumstances, and a primary objective of the present invention is to provide a tread rubber forming method in which a tread rubber can be accurately formed from a non-conductive rubber strip and a conductive rubber strip. Means for solving the problems According to the present invention, a tread rubber forming method is for forming an annular tread rubber and comprises: a first step of forming a non-conductive layer by winding a non-conductive first rubber strip in the shape of a tape, around a cylindrical body for plural turns;a second step of forming a conductive layer after the first step by winding a conductive second rubber strip in the shape of a tape, around the cylindrical body for at least one turn, in parallel to the circumferential direction of the cylindrical body so as to overlap a portion of the first rubber strip ; anda third step of forming a non-conductive layer after the second step by winding a first rubber strip around the cylindrical body for plural turns so as to overlap a portion of the second rubber strip , wherein each of the first step and the third step includes, when making each one turn of the plural turns,a circumferential winding step in which the first rubber strip is wound in parallel to the circumferential direction of the cylindrical body by at least 3/4 of the one turn to form a circumferential segment constituting a portion of the one turn, andan oblique winding step in which the first rubber strip is wound obliquely to the circumferential direction of the cylindrical body to form an oblique segment constituting the remaining portion of the one turn. Effects of the Invention In the tread rubber forming method according to the present invention, since the non-conductive rubber strip and the conductive rubber strip are wound in the specific manner as described above, the tread rubber having a conductive path can be formed with precision. Brief description of the drawings FIG. 1 is a schematic cross-sectional view of an example of the tread rubber formed by the tread rubber forming method according to the present invention.