Tread rubber formation method

Abstract

The present invention provides a tread rubber forming method that can accurately form tread rubber from non-conductive and conductive rubber strips. [Solution] The tread rubber forming method includes a first step S1 of forming a non-conductive layer by winding a first rubber strip multiple times around a cylindrical body; a second step of forming a conductive layer by winding a second rubber strip parallel to the circumferential direction of the cylindrical body; and a third step S3 of forming a non-conductive layer by winding the first rubber strip multiple times around the cylindrical body after the second step S2. The first step S1 and the third step S3 include, in each of the multiple turns, a circumferential winding step of winding the first rubber strip at least 3 / 4 of a turn parallel to the circumferential direction of the cylindrical body to form a circumferential portion, and an inclined winding step of winding the remaining portion of the first rubber strip at an angle to the circumferential direction of the cylindrical body to form an inclined portion.

Description

Technical Field

[0001] The present invention relates to a method for forming an annular tread rubber.

Background Art

[0002] Conventionally, a method of forming a tread rubber by winding a non-conductive rubber strip and a conductive rubber strip around a cylindrical body has been known (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the tread rubber forming method of Patent Document 1 above, a non-conductive rubber strip is wound in a spiral, that is, obliquely with respect to the circumferential direction of the cylindrical body, thereby forming a non-conductive layer.

[0005] Tread rubber is usually designed with a profile in which the thickness varies in the tire axial direction in accordance with the distribution of the rubber volume of the completed tire. Such a tread rubber with this profile is formed by adjusting the axial movement speed (feed amount) of the rubber strip with respect to the rotating cylindrical body.

[0006] However, it is generally difficult to accurately wind the rubber strip so as to conform to the designed profile of the tread rubber, and it has been necessary to devise (1) rotating the cylindrical body at a low speed, (2) bringing the rubber strip applicator as close as possible to the cylindrical body, and the like.

[0007] Furthermore, the tread rubber has a conductive rubber layer called a base pen, which is formed in part to discharge static electricity (charge) accumulated on the vehicle. When conductive rubber strips are wrapped in addition to non-conductive rubber strips to match the aforementioned design profile of the tread rubber, the number of factors to consider increases, and the control becomes more complex.

[0008] On the other hand, in order to discharge sufficiently, the base pen needs to be exposed on the tread surface. Therefore, the wrapping position of the conductive rubber is set so that the areas where the base pen is exposed on the tread surface do not coincide with the positions of the circumferential grooves.

[0009] However, in the method described in Patent Document 1 above, since the conductive rubber strip is wound spirally, the base pen is formed at an angle to the circumferential direction, making it difficult to adjust the positional relationship between the base pen and the circumferential groove.

[0010] This invention was devised in view of the above circumstances, and its main objective is to provide a tread rubber forming method that can accurately form tread rubber from non-conductive and conductive rubber strips. [Means for solving the problem]

[0011] The present invention relates to a method for forming annular tread rubber, A first step involves forming a non-conductive layer by winding a tape-shaped, non-conductive first rubber strip around a cylindrical body in multiple turns, A second step is to form a conductive layer by wrapping a tape-shaped, conductive second rubber strip around the cylindrical body at least once, parallel to the circumferential direction of the cylindrical body, after the first step, so as to overlap a portion of the first rubber strip. The process includes a third step of forming a non-conductive layer by winding the first rubber strip multiple times around the cylindrical body so as to overlap a portion of the second rubber strip, after the second step, The first and third steps are performed in each of the multiple turns, A circumferential winding step in which the first rubber strip is wound around the cylindrical body at least 3 / 4 of a turn parallel to the circumferential direction to form a circumferential portion, The process includes a winding step of inclining the first rubber strip with respect to the circumferential direction of the cylindrical body and winding the remaining portion around it to form an inclined portion. [Effects of the Invention]

[0012] Since the tread rubber forming method of the present invention has the above configuration, tread rubber can be formed accurately from non-conductive and conductive rubber strips. [Brief explanation of the drawing]

[0013] [Figure 1] This is a cross-sectional view showing an example of tread rubber formed by the tread rubber forming method of the present invention. [Figure 2] This is a schematic perspective view of a tread rubber forming method, which is one embodiment of the present invention. [Figure 3] Figure 2 is a flowchart showing the procedure for forming the tread rubber. [Figure 4] Figure 3 is a perspective view showing the first step. [Figure 5] Figure 3 is a perspective view showing the second step. [Figure 6] Figure 3 is a perspective view showing the third step. [Figure 7] This is a schematic diagram showing the tread rubber formed in the first step. [Figure 8] Following Figure 7, this is a schematic unfolded view showing the tread rubber formed in the second step. [Figure 9] Following Figure 8, this is a schematic unfolded diagram showing the tread rubber formed in the third step. [Figure 10] Figure 9 is a schematic unfolded diagram showing a modified example of the tread rubber. [Figure 11] Figure 1 is a cross-sectional view showing a modified example of the tread rubber. [Figure 12] This is a schematic unfolded diagram showing the base layer formed in the first step. [Figure 13] FIG. 12 is an exploded view schematically showing a radially inner conductive layer formed in the second step, following FIG. 12. [Figure 14] FIG. 13 is an exploded view schematically showing a base layer formed in the third step, following FIG. 13. [Figure 15] FIG. 14 is an exploded view schematically showing a cap layer formed on the radially outer side of the base layer in the first step, following FIG. 14. [Figure 16] FIG. 15 is an exploded view schematically showing a radially outer conductive layer formed in the second step, following FIG. 15. [Figure 17] FIG. 16 is an exploded view schematically showing a cap layer formed on the radially outer side of the base layer in the third step, following FIG. 16. [Figure 18] An enlarged view of a part of the base layer in FIG. 14. [Figure 19] An enlarged view of a part of the cap layer in FIG. 17. [Figure 20] FIG. 12 to FIG. 14 is an exploded view schematically showing a base layer formed by a modified example of the tread rubber forming method 100A shown in FIGS. 12 to 14. [Figure 21] FIG. 20 is an exploded view schematically showing a radially outer conductive layer formed in the second step, following FIG. 20. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, an embodiment of the present invention will be described based on the drawings. It should be understood that the drawings include exaggerated expressions and expressions different from the actual structural dimensional ratios in order to assist in understanding the content of the invention. Also, throughout each embodiment, the same or common elements are denoted by the same reference numerals, and redundant descriptions are omitted. Further, the specific configurations shown in the embodiments and the drawings are for understanding the content of the present invention, and the present invention is not limited to the specific configurations shown.

[0015] FIG. 1 shows a meridional cross-section of an annular tread rubber 1 formed by the tread rubber forming method 100 of the present embodiment.

[0016] The tread rubber 1 includes a non-conductive layer 10 made of a non-conductive first rubber and a conductive layer 20 made of a conductive second rubber. The conductive layer 20 penetrates the non-conductive layer 10 and is formed from the inner circumferential surface to the outer circumferential surface of the tread rubber 1. The tread rubber 1 undergoes a vulcanization process to form the tread portion of the finished tire.

[0017] Figure 2 shows a schematic of the tread rubber forming method 100 of this embodiment. The tread rubber forming method 100 is a method for forming an annular tread rubber 1 including a non-conductive layer 10 and a conductive layer 20. In the drawings of this application, the conductive layer 20 is shown by a mesh-like hatching. The non-conductive layer 10 includes a first non-conductive layer 11 on one tread end and a second non-conductive layer 12 on the other tread end.

[0018] Figure 3 is a flowchart showing the procedure of the tread rubber forming method 100. The tread rubber forming method 100 includes a first step S1 for forming a non-conductive layer 10, a second step S2 for forming a conductive layer 20, and a third step S3 for forming a non-conductive layer 10.

[0019] Figure 4 shows the first step S1. In the first step S1, a non-conductive layer 10 is formed by winding a first rubber strip 3 multiple times around a cylindrical body 2, also called a molding drum. The first rubber strip 3 is formed in the shape of a tape from non-conductive rubber.

[0020] The first rubber strip 3 may be wrapped directly around the outer surface of the cylindrical body 2, or it may be wrapped around the outer surface of a reinforcing layer, such as a belt layer, formed on the outer surface of the cylindrical body 2. In this case, the first rubber strip 3 is wrapped around the cylindrical body 2 via the reinforcing layer. The same applies to the second rubber strip 4, which will be described later.

[0021] The cylindrical body 2 is configured to be rotatable about its axis.

[0022] The non-conductive rubber constituting the first rubber strip 3 is realized by, for example, so-called silica-rich rubber, which is compounded with a large amount of silica instead of carbon as a reinforcing agent. Such silica-rich rubber has excellent fuel efficiency and wet performance. The first rubber strip 3 is supplied via a first applicator AP1 that is movable relative to the cylindrical body 2 in the axial direction.

[0023] In this application, the volume resistivity after vulcanization is 1 × 10⁻⁶. 8 Rubber materials with a volume resistivity of Ωcm or more are considered non-conductive rubber. Volume resistivity can be measured, for example, using a 15cm square and 2mm thick rubber sample with an electrical resistance meter under conditions of 500V applied voltage, 25°C temperature, and 50% humidity.

[0024] In the first step S1, a first non-conductive layer 11 is formed on one tread edge. In the first step S1, a non-conductive first rubber strip 3 is wrapped around the tread rubber 1 from one tread edge to partway along the tread rubber 1 (for example, the central part of the tread rubber 1). This non-conductive layer 10, consisting of the first rubber strip 3, makes up the majority of the tread rubber 1 and contributes to improving the fuel efficiency and wet performance of the finished tire.

[0025] Figure 5 shows the second step S2. The second step S2 is performed after the first step S1. In the second step S2, a conductive layer 20 is formed by wrapping the second rubber strip 4 around the cylindrical body 2 at least once, so as to overlap a portion (axial end) of the first rubber strip 3. The second rubber strip 4 is formed in the shape of a tape made of conductive rubber. The second rubber strip 4 is wrapped parallel to the circumferential direction of the cylindrical body 2. Considering wear resistance and other factors, it is desirable to limit the number of turns of wrapping the second rubber strip 4 to one.

[0026] The conductive rubber constituting the second rubber strip 4 is realized, for example, by a (carbon-rich) rubber that contains a large amount of carbon black as a reinforcing agent. Carbon-rich rubber generally has conductive properties. In this application, the volume resistivity after vulcanization is 1 × 10⁻⁶.7 A rubber material with a conductivity of Ωcm or less is defined as conductive rubber. The second rubber strip 4 is supplied via the second applicator AP2.

[0027] In the second step S2, the conductive second rubber strip 4 is wrapped around the tire at least once to form a base pen that is continuous at least once in the circumferential direction of the tire. This base pen effectively discharges static electricity accumulated on the tire and, consequently, on the vehicle.

[0028] The widths of the first rubber strip 3 and the second rubber strip 4 are not particularly limited and can be determined considering the production efficiency of the tread rubber 1 and the uniformity of the finished tire. The widths of the first rubber strip 3 and the second rubber strip 4 may be equal or different.

[0029] Figure 6 shows the third step S3. The third step S3 is performed after the second step S2. In the third step S3, the second nonconductive layer 12 on the other tread end is formed.

[0030] In the third step S3, a non-conductive layer 10 is formed by winding the first rubber strip 3 around the cylindrical body 2 in multiple turns so that it overlaps with a portion (axial end) of the second rubber strip 4. More specifically, the non-conductive first rubber strip 3 is wound from adjacent to the second rubber strip 4 to the other tread end so that the second rubber strip 4 is exposed on the outer surface of the tread rubber 1 for at least one turn.

[0031] In the first step S1 and third step S3, which precede and follow the second step S2, the wrapping of the first rubber strip 3 is performed in two stages, making it easy to position the conductive layer 20 at any axial position on the tread rubber 1 (for example, in the central part avoiding the circumferential grooves). As a result, even when a slip angle or camber angle is applied to the tire while driving, the conductive layer 20 can more easily make contact with the ground, and the discharge effect can be easily enhanced.

[0032] Figure 7 shows the procedure for winding the first rubber strip 3 in the first step S1 in an unfolded diagram. In this diagram, the axial length of the cylindrical body 2 is shown in the horizontal direction, and the rotation angle of the cylindrical body 2 around its axis is shown in the vertical direction. The same applies to the unfolded diagrams from Figure 8 onward.

[0033] In Figure 7, the first rubber strip 3 begins winding from the starting position 3s at the tread edge and ends winding at the ending position 3e in the center of the tread. The starting position 3s of the first rubber strip 3 may be located at any of the above positions in the axial direction of the tread rubber 1, and the ending position 3e may be located at the tread edge.

[0034] The first step S1 includes a circumferential winding step S1c and an inclined winding step S1s. The circumferential winding step S1c and the inclined winding step S1s are performed in each of the multiple turns of the first step S1.

[0035] In the circumferential winding process S1c, the first rubber strip 3 is wound parallel to the circumferential direction of the cylindrical body 2, forming a circumferential portion 10c in the nonconductive layer 10. In the circumferential winding process S1c, the first rubber strip 3 is wound for 3 / 4 of a turn (i.e., a rotation angle of 270° around the axis of the cylindrical body 2) or more. In the circumferential winding process S1c, the circumferential portion 10c is formed by winding the first rubber strip 3 while rotating the cylindrical body 2 and fixing it in the axial direction.

[0036] The inclined winding process S1s is performed immediately following the circumferential winding process S1c. In the inclined winding process S1s, the first rubber strip 3 is wound around the cylindrical body 2 at an angle to the circumferential direction, forming an inclined portion 10s in the nonconductive layer 10. In the inclined winding process S1s, the inclined portion 10s is formed by rotating the cylindrical body 2 while moving the first rubber strip 3 in the axial direction and winding it.

[0037] The amount of axial movement of the first rubber strip 3 in a single inclined winding process S1s is less than or equal to the width of the first rubber strip 3. By adjusting this amount of movement, the tread rubber 1 is formed with a desired profile.

[0038] Note that in Figure 7, for the sake of drawing convenience, the amount of movement of the first rubber strip 3 is shown to be equal to the width of the first rubber strip 3, but the amount of movement may be less than the width of the first rubber strip 3. The same applies to the unfolded diagrams from Figure 8 onward.

[0039] In the inclined winding process S1s, the remaining portion of the first rubber strip 3 is wound around the first rubber strip 3. That is, one turn of the first rubber strip 3 is wound by one circumferential winding process S1c and one inclined winding process S1s. Then, following the inclined winding process S1s, the circumferential winding process S1c for the next turn is performed. In other words, by alternately repeating the circumferential winding process S1c and the inclined winding process S1s, the first rubber strip 3 is wound over multiple turns, and a non-conductive layer 10 extending in the axial direction is formed on the first rubber strip 3.

[0040] Since the circumferential portion 10c formed in the circumferential winding process S1c does not contain an axial component, it is possible to accurately wind the first rubber strip 3 to conform to the design profile of the tread rubber 1.

[0041] On the other hand, the inclined portion 10s, which includes an axial component, is located exclusively on a portion of the circumferential direction of the tread rubber 1. As a result, when considering the tread rubber 1 as a whole, the first rubber strip 3 can be easily and accurately wrapped around it with a desired profile.

[0042] Figure 8 shows an unfolded diagram of the procedure for winding the second rubber strip 4 in the second step S2. In the tread rubber forming method 100 of the present invention, in the second step S2, the conductive second rubber strip 4 is wound parallel to the circumferential portion 10c. Similar to the circumferential portion 10c, the second rubber strip 4, which does not contain an axial component, is wound with precision to conform to the design profile of the tread rubber 1.

[0043] As a result, since the tread rubber forming method 100 has the above configuration, the tread rubber 1 can be formed accurately from the non-conductive first rubber strip 3 and the conductive second rubber strip 4.

[0044] From the above viewpoint, it is desirable that the circumferential winding process S1c in the first process S1 be configured to perform, for example, 7 / 8 of a rotation of the cylindrical body 2 (i.e., a rotation angle of 315° around the axis of the cylindrical body 2) or more during one turn. Also, although it depends on the width of the first rubber strip 3, considering the uniformity of the finished tire, it is desirable that the circumferential winding process S1c in the first process S1 be configured to perform, for example, 15 / 16 of a rotation or less of the cylindrical body 2 during one turn.

[0045] Figure 9 shows, in an unfolded view, the procedure for winding the first rubber strip 3 in the third step S3 after the second step S2. The procedure for winding the first rubber strip 3 in the third step S3 is substantially the same as that in the first step S1.

[0046] In other words, the third step S3 includes a circumferential winding step S1c and an inclined winding step S1s. The circumferential winding step S1c and the inclined winding step S1s of the third step S3 are the same as those of the circumferential winding step S1c and the inclined winding step S1s of the first step S1, and are performed in each of the multiple turns of the third step S3. As a result, a circumferential portion 10c and an inclined portion 10s are formed in the second nonconductive layer 12.

[0047] As shown in Figure 9, the circumferential portion 10c of the first nonconductive layer 11 and the circumferential portion 10c of the second nonconductive layer 12 are arranged in phase with respect to the rotational direction of the cylindrical body 2. In other words, the inclined portion 10s of the first nonconductive layer 11 and the inclined portion 10s of the second nonconductive layer 12 are arranged in phase with respect to the rotational direction of the cylindrical body 2.

[0048] Here, phase is defined as the rotation angle around the axis from the reference position of the cylindrical body 2 (for example, the winding start position 3s of the first rubber strip 3), and same phase means that the rotation angles from the reference position of the cylindrical body 2 are the same. For example, in Figures 8 and 9, the rotation angle of the cylindrical body 2 is shown in the vertical direction, so the circumferential portion 10c of the first nonconductive layer 11 and the circumferential portion 10c of the second nonconductive layer 12 are shown at the same position in the vertical direction.

[0049] In the tread rubber forming method 100, the circumferential portions 10c of the first nonconductive layer 11 and the second nonconductive layer 12, and the second rubber strip 4 are all wound parallel to the circumferential direction of the cylindrical body 2. As a result, the circumferential portions 10c of the first nonconductive layer 11 and the second nonconductive layer 12, and the second rubber strip 4 are wound without including any axial components, so that they are wound with high precision to conform to the design profile of the tread rubber 1.

[0050] Since the inclined portion 10s of the first nonconductive layer 11 and the inclined portion 10s of the second nonconductive layer 12 are arranged in phase with respect to the rotational direction D of the cylindrical body 2, they are located only in a limited area in the circumferential direction of the tread rubber 1. As a result, when considering the tread rubber 1 as a whole, the first rubber strip 3 can be easily and accurately wound around it with a desired profile.

[0051] In the inclined section 10s shown in Figures 7 and 9, there is a region where the first rubber strip 3 is insufficient. By making this region coincide with a region where there is an excess of material in other components of the tire (e.g., sidewall rubber), the deterioration of the overall uniformity of the finished tire can be suppressed.

[0052] It is desirable that the inclined portion 10s of the first nonconductive layer 11 and the inclined portion 10s of the second nonconductive layer 12 are inclined in opposite directions to each other. "Inclined in opposite directions" means that the pair of first rubber strips 3 are inclined in opposite axial directions to each other with respect to the rotational direction D of the cylindrical body 2.

[0053] Figure 9 shows a configuration in which a pair of first rubber strips 3 are inclined outward in the axial direction relative to each other with respect to the rotational direction D of the cylindrical body 2.

[0054] On the other hand, as shown in Figure 10, the pair of first rubber strips 3 may be inclined inward in the axial direction relative to each other with respect to the rotational direction D of the cylindrical body 2.

[0055] These inclined portions 10s cancel out the weight imbalance between the inclined portions 10s of the first nonconductive layer 11 and the inclined portions 10s of the second nonconductive layer 12, thereby improving the conicity and lateral force variation of the finished tire.

[0056] The inclined portion 10s of the first nonconductive layer 11 and the inclined portion 10s of the second nonconductive layer 12 may be inclined in the same direction.

[0057] As shown in Figures 7 to 10, it is desirable that the winding start position 3s or winding end position 3e of the first rubber strip 3 and the circumferential edge of the inclined portion 10s are arranged in phase with the rotation direction D of the cylindrical body 2. In the present invention, since the circumferential portion 10c and the inclined portion 10s are formed continuously, the above configuration can also be rephrased as the winding start position 3s or winding end position 3e and the circumferential edge of the circumferential portion 10c being arranged in phase with the rotation direction D of the cylindrical body 2. With such a configuration, the first step S1 can be easily performed and the uniformity of the finished tire is improved.

[0058] Furthermore, the starting position 3s and ending position 3e of the first rubber strip 3 may be located at a position in the middle of the inclined portion 10s, rather than at the circumferential edge of the inclined portion 10s. Similarly, the starting position 3s and ending position 3e of the first rubber strip 3 may be located at a position in the middle of the circumferential portion 10c, rather than at the circumferential edge of the circumferential portion 10c.

[0059] Figure 11 shows a meridional cross-section of tread rubber 1A, which is a modified example of tread rubber 1 shown in Figure 1. In tread rubber 1A, the non-conductive layer 10 includes a base layer 15. For parts of tread rubber 1A not described below, the configuration of tread rubber 1 described above may be adopted.

[0060] In this embodiment, the proportion of carbon in the rubber reinforcing agent of the base layer 15 is 10% by mass or less, and the proportion of silica is 70% by mass or more. Such a base layer 15 contributes to reducing the rolling resistance and improving the high-speed durability of the finished tire. The base layer 15 is, for example, arranged radially outward of a reinforcing layer (e.g., a belt layer) for reinforcing the tread portion. The non-conductive layer 10 and the radially inward conductive layer 20, which are composed of the base layer 15, can be formed in the manner shown in Figures 4 to 0.

[0061] Figures 12 to 17 show a modified version of the tread rubber forming method 100, called tread rubber forming method 100A. Tread rubber forming method 100A is a tread rubber forming method for forming tread rubber 1A. For parts of the tread rubber forming method 100 that are not described below, the configuration of the tread rubber forming method 100 described above may be adopted.

[0062] Figures 12 to 14 show the process of forming the base layer 15 and the radially inner conductive layer 20.

[0063] Figure 12 shows the first step S15 in which one of the base layers 15 is formed. In the first step S15, the first rubber strip 3 that constitutes the base layer 15 is wrapped around the cylindrical body 2.

[0064] The first step S15 includes a circumferential winding step S1c and an inclined winding step S1s, similar to the first step S1 of the tread rubber forming method 100 described above.

[0065] Figure 13 shows the second step S2 in which a conductive layer 20 is formed on the axial edge of the base layer 15. In the second step S2, similar to the second step S2 of the tread rubber forming method 100, a conductive second rubber strip 4 is wrapped around the base layer 15 so that the conductive layer 20 penetrates from the inner circumferential surface to the outer circumferential surface.

[0066] Figure 14 shows the third step S15' for forming the other base layer 15. In the third step S15', the first rubber strip 3 that constitutes the base layer 15 is wrapped around the axial edge of the conductive layer 20.

[0067] The third step S15' includes a circumferential winding step S1c and an inclined winding step S1s, similar to the third step S3 of the tread rubber forming method 100 described above.

[0068] As shown in Figure 11, it is preferable that the non-conductive layer 10 in the tread rubber 1A includes a cap layer 16. The cap layer 16 is formed radially outward of the base layer 15 after the base layer 15 has been formed. The cap layer 16 is made of, for example, rubber with excellent grip performance and wear resistance. The non-conductive layer 10 and the radially outward conductive layer 20, which are formed by the cap layer 16, can be formed in the manner shown in Figures 4 to 10.

[0069] Figures 15 to 17 show the process of forming the cap layer 16 and the radially outer conductive layer 20.

[0070] Figure 15 shows the first step S16 for forming one of the cap layers 16. In the first step S16, the first rubber strip 3 that constitutes the cap layer 16 is wrapped around the radially outer side of one of the base layers 15.

[0071] The first step S16 includes a circumferential winding step S1c and an inclined winding step S1s, similar to the first step S1 of the tread rubber forming method 100 described above.

[0072] Figure 16 shows the second step S2 in which a conductive layer 20 is formed on the axial edge of the cap layer 16. In the second step S2, similar to the second step S2 of the tread rubber forming method 100, a conductive second rubber strip 4 is wrapped around the cap layer 16 so that the conductive layer 20 penetrates from the inner circumferential surface to the outer circumferential surface. The radially inner conductive layer 20 and the radially outer conductive layer 20 are in contact with each other. As a result, a series of conductive layers 20 are formed from the base layer 15 to the cap layer 16.

[0073] Figure 17 shows the third step S16' for forming the other cap layer 16. In the third step S16', the first rubber strip 3 that constitutes the cap layer 16 is wrapped around the axial edge of the conductive layer 20.

[0074] Step S16' includes a circumferential winding step S1c and an inclined winding step S1s, similar to the first step S1 of the tread rubber forming method 100 described above.

[0075] In the tread rubber forming method 100A, it is desirable that the circumferential portion 10c of the base layer 15 and the circumferential portion 10c of the cap layer 16 are arranged in phase with respect to the rotational direction D of the cylindrical body 2. As a result, the circumferential portions 10c of the base layer 15 and the cap layer 16 and the second rubber strip 4 are wound together without including any axial components, so that they are wound together with precision to conform to the design profile of the tread rubber 1.

[0076] On the other hand, since the inclined portion 10s of the base layer 15 and the inclined portion 10s of the cap layer 16 are arranged in the same phase in the rotational direction of the cylindrical body 2, they are located only in a limited area in the circumferential direction of the tread rubber 1. As a result, when considering the tread rubber 1 as a whole, it becomes possible to wrap the first rubber strip 3 with precision in the desired profile.

[0077] Figure 18 is an enlarged unfolded view showing the area around the winding start position 3s and winding end position 3e of the base layer 15 shown in Figure 14. As shown in Figure 18, in the vicinity of the winding start position 3s and winding end position 3e of the first rubber strip 3 that constitutes the base layer 15, there is a region A1 in which the volume of the first rubber strip 3 is insufficient.

[0078] Figure 19 is an enlarged unfolded view showing the area around the winding start position 3s and winding end position 3e of the cap layer 16 shown in Figure 17. In the configuration shown in Figure 19, the winding start position 3s and winding end position 3e are adjusted so that a portion of the circumferential portion 10c and the inclined portion 10s of the first rubber strip 3 overlap. More specifically, the circumferential portion 10c is formed over one turn from the winding start position 3s, and then the inclined portion 10s is formed. The circumferential portion 10c is also formed over one turn until it reaches the winding end position 3e.

[0079] As shown in Figure 19, near the winding start position 3s and winding end position 3e of the first rubber strip 3 constituting the cap layer 16, there is a region A2 in which the volume of the first rubber strip 3 is exceeded due to the overlap of the circumferential portion 10c and the inclined portion 10s.

[0080] In the base layer 15 and cap layer 16, the first rubber strips 3 are wound around each such base layer 15 and cap layer 16 such that their respective inclined portions 10s are arranged in phase with respect to the rotational direction D of the cylindrical body 2, thereby making region A1 and region A2 adjacent in the circumferential direction. As a result, the volume deficiency in region A1 and the volume surplus in region A2 are offset by the rubber flow during the vulcanization process, forming a tread rubber 1A with a uniform thickness in the circumferential and axial directions.

[0081] Figures 20 and 21 show a modified version of the tread rubber forming method 100A, which is the tread rubber forming method 100B. The tread rubber forming method 100A is a tread rubber forming method for forming the base layer 15. For parts of the tread rubber forming method 100B that are not described below, the configuration of the tread rubber forming method 100A described above may be adopted.

[0082] As shown in Figure 20, in the tread rubber forming method 100B, the base layer 15 is formed by first step S1, which involves step S17 for forming the first nonconductive layer 11, followed by step S18, and then step S19 for forming the second nonconductive layer 12.

[0083] Step S18 includes the step of winding the first rubber strip 3, on which the first nonconductive layer 11 is formed, spirally across a gap 30 without cutting it, and guiding it to the second nonconductive layer 12. The gap 30 is formed by setting a large axial movement of the first rubber strip 3 when winding the inclined portion 10s.

[0084] In the tread rubber forming method 100B, the first nonconductive layer 11, the gap 30, and the second nonconductive layer 12 are formed in a series of steps S17, S18, and S19, thereby improving the production efficiency of the tread rubber 1.

[0085] Then, as shown in Figure 21, the second rubber strip 4 is wrapped around the region of the gap 30, forming the conductive layer 20. The wrapping of the second rubber strip 4 is the same as in the second step S2 shown in Figure 9.

[0086] Furthermore, in the tread rubber forming method 100B, it is possible to start winding the second rubber strip 4 immediately after the gap 30 is created in step S18. In other words, steps S19 and the second step S2 can be partially executed simultaneously, making it possible to further improve production efficiency.

[0087] In addition, in the tread rubber forming method 100A, the first step S15 and the third step S15' for forming the base layer 15 may be the first step S1 and the third step S3 shown in Figure 10. Similarly, the first step S16 and the third step S16' for forming the cap layer 16 may also be the first step S1 and the third step S3 shown in Figure 10.

[0088] Although the tire tread rubber forming method 100 and other aspects of the present invention have been described in detail above, the present invention is not limited to the above-described specific embodiments and can be implemented in various modified forms.

[0089] [Note] The present invention includes the following embodiments.

[0090] [Invention 1] A method for forming an annular tread rubber, A first step involves forming a non-conductive layer by winding a tape-shaped, non-conductive first rubber strip around a cylindrical body in multiple turns, A second step is to form a conductive layer by wrapping a tape-shaped, conductive second rubber strip around the cylindrical body at least once, parallel to the circumferential direction of the cylindrical body, after the first step, so as to overlap a portion of the first rubber strip. The process includes a third step of forming a non-conductive layer by winding the first rubber strip multiple times around the cylindrical body so as to overlap a portion of the second rubber strip, after the second step, The first and third steps are performed in each of the multiple turns, A circumferential winding step in which the first rubber strip is wound around the cylindrical body at least 3 / 4 of a turn parallel to the circumferential direction to form a circumferential portion, The process includes a winding step in which the first rubber strip is inclined with respect to the circumferential direction of the cylindrical body and the remaining portion is wound around it to form an inclined portion. Method for forming tread rubber. [2nd Invention] The tread rubber forming method according to the present invention 1, wherein the circumferential winding process is performed at least 7 / 8 of a rotation of the cylindrical body during one turn. [Invention 3] The tread rubber forming method according to the present invention 1, wherein the circumferential portion wound in the first step and the circumferential portion wound in the third step are arranged in the same phase in the rotational direction of the cylindrical body. [4th Invention] The tread rubber forming method according to the present invention, wherein the inclined portion wrapped in the first step and the inclined portion wrapped in the third step are inclined in opposite directions. [5th ​​Invention] The tread rubber forming method according to the present invention, wherein the inclined portion wrapped in the first step and the inclined portion wrapped in the third step are inclined in the same direction to each other. [Invention 6] The tread rubber forming method according to the present invention 1, wherein the starting position or ending position of the first rubber strip and the circumferential edge of the inclined portion are arranged in the same phase in the rotational direction of the cylindrical body. [7th Invention] The tread rubber forming method according to any one of claims 1 to 7 of the present invention, wherein the non-conductive layer includes a base layer in which the proportion of carbon in the rubber reinforcing agent is 10% by mass or less. [8th Invention] The tread rubber forming method according to the present invention, wherein the non-conductive layer includes a cap layer wound around the radially outer side of the base layer. [Invention 9] The tread rubber forming method according to the present invention, wherein the circumferential portion of the base layer and the circumferential portion of the cap layer are arranged in the same phase in the rotational direction of the cylindrical body, as described in the 8th of the present invention. [Invention 10] The tread rubber forming method according to the present invention, wherein the inclined portion of the base layer and the inclined portion of the cap layer are inclined in opposite directions to each other. [Explanation of Symbols]

[0091] 1: Tread rubber 1A: Tread rubber 2: Cylindrical body 3: First rubber strip 3e :Position 3s :Position 4: Second rubber strip 10: Non-conductive layer 10c: Circumferential part 10s: Inclined part 15: Base layer 16: Cap layer 20: Conductive layer 100: Tread Rubber Forming Method 100A: Tread rubber forming method 100B: Tread Rubber Forming Method D: Direction of rotation S1: 1st process S1c: Circumferential winding process S1s: Inclined winding process S2: 2nd process S3: 3rd process S15: 1st process S15': 3rd step S16: 1st process S16': 3rd process

Claims

1. A method for forming an annular tread rubber, A first step involves forming a non-conductive layer by winding a tape-shaped, non-conductive first rubber strip around a cylindrical body in multiple turns. A second step is to form a conductive layer by wrapping a tape-shaped, conductive second rubber strip around the cylindrical body at least once, parallel to the circumferential direction of the cylindrical body, after the first step, so as to overlap a portion of the first rubber strip. The process includes a third step of forming a non-conductive layer by winding the first rubber strip multiple times around the cylindrical body so as to overlap a portion of the second rubber strip, after the second step, The first and third steps are performed in each of the multiple turns, A circumferential winding step in which the first rubber strip is wound around the cylindrical body at least 3 / 4 of a turn parallel to the circumferential direction to form a circumferential portion, The process includes a winding step in which the first rubber strip is inclined with respect to the circumferential direction of the cylindrical body and the remaining portion is wound around it to form an inclined portion. Method for forming tread rubber.

2. The method for forming tread rubber according to claim 1, wherein the circumferential winding process is performed at least 7 / 8 of a rotation of the cylindrical body during one turn.

3. The tread rubber forming method according to claim 1, wherein the circumferential portion wound in the first step and the circumferential portion wound in the third step are arranged in the same phase in the rotational direction of the cylindrical body.

4. The tread rubber forming method according to claim 3, wherein the inclined portion wrapped in the first step and the inclined portion wrapped in the third step are inclined in opposite directions to each other.

5. The tread rubber forming method according to claim 3, wherein the inclined portion wrapped in the first step and the inclined portion wrapped in the third step are inclined in the same direction to each other.

6. The method for forming a tread rubber according to claim 1, wherein the starting position or ending position of the first rubber strip and the circumferential edge of the inclined portion 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 layer in which the proportion of carbon in the rubber reinforcing agent is 10% by mass or less.

8. The tread rubber forming method according to claim 7, wherein the non-conductive layer includes a cap layer wound around the radially outer side of the base layer.

9. The tread rubber forming method according to claim 8, wherein the circumferential portion of the base layer and the circumferential portion of the cap 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 inclined portion of the base layer and the inclined portion of the cap layer are inclined in opposite directions to each other.

Images