Tires and methods for manufacturing tires

Abstract

To provide a tire and a tire manufacturing method that can improve the vulcanization failure resistance of the tire. [Solution] This tire comprises a pair of bead cores, a carcass layer 13 spanning the pair of bead cores, a pair of cross belts 141 and 142 arranged radially outside the carcass layer 13, a release agent coating layer 19 formed on the inner surface of the tire, and a sound-absorbing material 20 arranged on the inner surface of the tire via the release agent coating layer 19. Furthermore, the maximum value G1_max of the film thickness G1 of the release agent coating layer 19 in a 20 [mm] region centered on the tire's equatorial plane is G1_max relative to the maximum value Ga_max of the film thickness Ga of the release agent coating layer 19 across the entire inner surface of the tire.

Description

Technical Field

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[0001] The present invention relates to a tire and a tire manufacturing method, and more particularly to a tire and a tire manufacturing method capable of improving the vulcanization failure resistance performance of a tire.

Background Art

[0002] In recent tires, in order to reduce the cavity resonance sound during tire rotation and improve the noise performance of the tire, a technique of providing a sound-absorbing material on the inner surface of the tire has been adopted. Such a sound-absorbing material is attached and installed on the tire after vulcanization molding. As a conventional tire adopting such a structure, the technique described in Patent Document 1 is known.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the tire provided with the above-described sound-absorbing material, there is also a problem of reducing vulcanization failure during tire vulcanization molding.

[0005] Therefore, the present invention has been made in view of the above, and an object thereof is to provide a tire and a tire manufacturing method capable of improving the vulcanization failure resistance performance of a tire.

Means for Solving the Problems

[0006] In order to achieve the above object, [1] the tire according to the present invention includes a pair of bead cores, a carcass layer bridged over the pair of bead cores, a pair of cross belts disposed on the radially outer side of the carcass layer, a mold release agent coating layer formed on the inner surface of the tire, and a sound absorption material attached to the inner surface of the tire via the mold release agent coating layer. The tire is characterized in that the maximum value G1_max of the film thickness G1 of the mold release agent coating layer in the region of 20 [mm] centered on the tire equatorial plane has a relationship of G1_max < Ga_max with respect to the maximum value Ga_max of the film thickness Ga of the mold release agent coating layer over the entire inner surface of the tire.

[0007] Also, [2] the tire according to the present invention defines a pair of straight lines Le perpendicular to the inner surface of the tire passing through the edge portions of the wide cross belt in a cross-sectional view in the tire meridian direction. A region of 20 [%] of the belt width Wb2 of the wide cross belt centered on each of the pair of straight lines Le is defined as a pair of shoulder regions. The attachment region of the sound absorption material is defined as a region between the pair of straight lines Le and including the region of 20 [mm] centered on the tire equatorial plane. The maximum value Gc_max of the film thickness Gc of the mold release agent coating layer in the attachment region of the sound absorption material is in the range of 0 < Gc_max / Gs_max ≦ 0.50 with respect to the maximum value Gs_max of the film thickness Gs of the mold release agent coating layer in each of the pair of shoulder regions.

[0008] Further, in the tire manufacturing method according to the present invention [3], in a cross-sectional view in the tire meridian direction, a pair of straight lines Le perpendicular to the inner surface of the tire are defined through respective edge portions of the wide cross belt, and a region of 20% of the belt width Wb2 of the wide cross belt centered on each of the pair of straight lines Le is defined as a pair of shoulder regions, and the mounting region of the sound absorbing material is defined as a region including the region of 20 mm centered on the tire equatorial plane between the pair of straight lines Le, and the maximum film thickness Gc'_max of the mold release agent applied to the region of the outer surface of the tire vulcanization bladder corresponding to the mounting region of the sound absorbing material has a relationship of Gc'_max < Gs'_max with respect to the maximum film thickness Gs'_max of the mold release agent applied to the region corresponding to the pair of shoulder regions.

Advantages of the Invention

[0009] In the tire according to the invention of [1] above, since the film thickness G1 of the mold release agent coating layer in the region R1 of 20 mm centered on the tire equatorial plane is relatively thin, for example, in a tire provided with a sound absorbing material attached to the center region of the inner surface of the tire, there is an advantage that peeling of the sound absorbing material due to a thick mold release agent coating layer is suppressed. On the other hand, since the film thickness Ga of the mold release agent coating layer in other regions is relatively thick, vulcanization failure of the tire is suppressed, and the life of the tire vulcanization bladder is extended. Thereby, there is an advantage that the vulcanization failure resistance performance of the tire is improved.

[0010] Further, in the tire according to the invention of [2] above, since the film thickness Gc of the mold release agent coating layer in the mounting region Rc of the sound absorbing material is relatively thin, the adhesion of the sound absorbing material to the inner surface of the tire is improved, and there is an advantage that peeling of the sound absorbing material during tire rolling is suppressed. Also, since the film thickness Gs of the mold release agent coating layer in the pair of shoulder regions Rsh, Rsh is relatively thick, the film thickness of the mold release agent in the region where the stretch amount during tire vulcanization molding is large is ensured, vulcanization failure of the tire is suppressed, and the life of the tire vulcanization bladder is extended. Thereby, there is an advantage that both the peel resistance performance of the sound absorbing material and the vulcanization failure resistance performance of the tire are achieved.

[0011] Furthermore, in the tire manufacturing method according to the invention described in [3] above, the thickness Gc' of the release agent coating layer 19 in the mounting area Rc of the sound-absorbing material 20 in the tire after vulcanization molding is relatively thin, which has the advantage of improving the adhesion of the sound-absorbing material 20 to the inner surface of the tire and suppressing the peeling of the sound-absorbing material 20 when the tire rolls. In addition, the thickness Gs' of the release agent coating layer 19 in the pair of shoulder areas Rsh, Rsh is relatively thick, which ensures sufficient film thickness of the release agent in areas with large stretch amounts during tire vulcanization molding, which has the advantage of suppressing tire vulcanization failures and extending the life of the tire vulcanization bladder. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a cross-sectional view of a tire in the meridian direction, showing a tire according to an embodiment of this invention. [Figure 2] Figure 2 is a magnified view of the tire shown in Figure 1. [Figure 3] Figure 3 is an explanatory diagram showing the mounting structure of the sound-absorbing material described in Figure 2. [Figure 4] Figure 4 is an explanatory diagram showing the film thickness of the release agent coating layer described in Figure 3. [Figure 5] Figure 5 is a diagram showing the results of a performance test of a tire according to an embodiment of this invention. [Modes for carrying out the invention]

[0013] The present invention will be described in detail below with reference to the drawings. However, this embodiment does not limit the present invention. Furthermore, the components of this embodiment include those that are substituted and obvious for substitution while maintaining the identity of the invention. In addition, the various modifications described in this embodiment can be arbitrarily combined within the scope of what is obvious to those skilled in the art.

[0014] [Sound-absorbing tires] Figure 1 is a meridian-direction cross-sectional view of a tire 1 according to an embodiment of the present invention. The figure shows a cross-sectional view of one side region in the radial direction of the tire. In this embodiment, a pneumatic radial tire for passenger cars will be described as an example of a tire. In the configuration of Figure 1, the release agent coating layer 19, which will be described later, is very thin, so the release agent coating layer 19 and the inner liner 18 are shown as a single unit.

[0015] In the figure, the tire meridian cross-section is defined as the cross-section obtained when the tire is cut by a plane containing the tire rotation axis (not shown). The tire equatorial plane CL is defined as a plane that passes through the midpoint of the tire cross-sectional width as defined by JATMA and is perpendicular to the tire rotation axis. The tire width direction is defined as the direction parallel to the tire rotation axis, and the tire radial direction is defined as the direction perpendicular to the tire rotation axis. Point T is the tire contact point.

[0016] The tire 1 has an annular structure centered on the tire rotation axis and comprises a pair of bead cores 11, 11, a pair of bead fillers 12, 12, a carcass layer 13, a belt layer 14, a tread rubber 15, a pair of sidewall rubbers 16, 16, a pair of rim cushion rubbers 17, 17, an inner liner 18, and a release agent coating layer 19 (see Figure 1).

[0017] Each pair of bead cores 11, 11 is made by winding one or more bead wires made of steel in a ring-like and multi-layered manner, and is embedded in the bead portion to form the core of the left and right bead portions. Each pair of bead fillers 12, 12 is positioned on the outer circumference of the pair of bead cores 11, 11 in the radial direction of the tire to reinforce the bead portion.

[0018] The carcass layer 13 has a single-layer structure composed of one carcass ply or a multi-layer structure formed by laminating a plurality of carcass plies, and is bridged in a toroidal shape between the left and right bead cores 11, 11 to constitute the skeleton of the tire. Also, both ends of the carcass layer 13 are wound back and locked to the outside in the tire width direction so as to wrap the bead core 11 and the bead filler 12. Further, the carcass ply of the carcass layer 13 is formed by covering a plurality of carcass cords made of steel or an organic fiber material (e.g., aramid, nylon, polyester, rayon, etc.) with a coating rubber and performing rolling processing, and has a cord angle (defined as the inclination angle of the longitudinal direction of the carcass cord with respect to the tire circumferential direction) of 80° or more and 100° or less.

[0019] The belt layer 14 is formed by laminating a plurality of belt plies 141 to 144, and is disposed so as to be wound around the outer circumference of the carcass layer 13. The belt plies 141 to 144 include a pair of cross belts 141, 142 and a pair of belt covers 143, 144.

[0020] The pair of cross belts 141, 142 are formed by covering a plurality of belt cords made of steel or an organic fiber material with a coating rubber and performing rolling processing, and have a cord angle (defined as the inclination angle of the longitudinal direction of the belt cord with respect to the tire circumferential direction) of 15° or more and 55° or less in absolute value. Also, the pair of cross belts 141, 142 have cord angles of opposite signs to each other, and are laminated with the longitudinal directions of the belt cords crossing each other (so-called cross-ply structure). Further, the pair of cross belts 141, 142 are laminated and disposed on the outside in the tire radial direction of the carcass layer 13.

[0021] The belt covers 143 and 144 are formed by coating a belt cover cord made of steel or organic fiber material with a coat rubber, and have a cord angle of 0° or more and 10° or less in absolute value. Further, the belt covers 143 and 144 are, for example, strip materials formed by coating one or a plurality of belt cover cords with a coat rubber, and this strip material is wound around the outer peripheral surfaces of the cross belts 141 and 142 a plurality of times in a spiral pattern in the tire circumferential direction. Further, the belt covers 143 and 144 are arranged to cover the entire area of the cross belts 141 and 142.

[0022] The tread rubber 15 is disposed on the outer periphery in the tire radial direction of the carcass layer 13 and the belt layer 14 to form the tread portion of the tire 1. Further, the tread rubber 15 is made of a rubber material excellent in ground contact characteristics and weather resistance, and is exposed over the entire outer peripheral surface of the tire to form a tread surface. The pair of sidewall rubbers 16, 16 are respectively disposed on the outer sides in the tire width direction of the carcass layer 13 to form the left and right sidewall portions. The pair of rim cushion rubbers 17, 17 extend from the inner side in the tire radial direction to the outer side in the tire width direction of the left and right bead cores 11, 11 and the folded-back portion of the carcass layer 13 to form the rim fitting surface of the bead portion.

[0023] The inner liner 18 is an air permeation prevention layer disposed on the inner cavity surface of the tire to cover the carcass layer 13, suppresses oxidation due to the exposure of the carcass layer 13, and prevents leakage of the air filled in the tire. Further, the inner liner 18 may be formed of, for example, a rubber composition mainly composed of butyl rubber, or a thermoplastic elastomer composition in which an elastomer component is blended in a thermoplastic resin or a thermoplastic resin.

[0024] The mold release coating layer 19 is a coating layer made of a mold release agent and is formed over the entire inner surface of the tire and the entire inner surface of the inner liner 18. Specifically, the mold release coating layer 19 is formed when the mold release agent applied to the surface of the tire vulcanization bladder during the tire vulcanization molding process remains on the inner surface of the tire. Such a mold release agent is used to make it easier to peel the tire from the tire vulcanization bladder after vulcanization molding, and its main components are, for example, silicone components, inorganic components, and surfactants.

[0025] [Sound-absorbing material] Figure 2 is an enlarged view of the tire 1 shown in Figure 1. This figure shows the tread portion of one side region bounded by the tire equatorial plane CL. Figure 3 is an explanatory diagram showing the mounting structure of the sound-absorbing material 20 shown in Figure 2. Note that because the release agent coating layer 19 is very thin, in Figure 2 the release agent coating layer 19 and the inner liner 18 are shown as a single unit, while in Figure 3 the release agent coating layer 19 is shown in an exaggerated manner.

[0026] The sound-absorbing material 20 is a component that reduces cavity resonance noise during tire rolling, and is made of, for example, a porous material having open cells. The sound-absorbing material 20 is also placed on the inner surface of the tire and extends around the entire circumference of the tire. For example, in the configuration of Figure 1, the sound-absorbing material 20 has a rectangular cross-sectional shape and is placed in the center region of the tire and crosses the tire equatorial plane CL. The sound-absorbing material 20 is also temporarily fixed to the inner surface of the tire using an adhesive or adhesive sheet and then pressed into place. The width Wa of the sound-absorbing material 20 is in the range of 0.30 ≤ Wa / Wb2 ≤ 0.90 relative to the belt width Wb2 of the wide cross belt 141, and preferably in the range of 0.35 ≤ Wa / Wb2 ≤ 0.85. Furthermore, the sound-absorbing material 20 may consist of a pair of sound-absorbing members that are separated from each other and are placed spaced apart from each other in the tire width direction with the tire equatorial plane CL in between (not shown).

[0027] The width Wa of the sound-absorbing material 20 is defined as the maximum width of the area where the sound-absorbing material 20 is placed on the inner surface of the tire. In the configuration described above, where the sound-absorbing material 20 consists of a pair of sound-absorbing members that are separated from each other, the width Wa of the sound-absorbing material 20 is measured using the outermost edge portion in the tire width direction of the pair of sound-absorbing members as the measurement point.

[0028] The belt width Wb2 of the cross belt 141 is the distance in the tire width direction between the left and right edges of the belt ply (more specifically, the outermost belt cord in the tire width direction), and is measured with the tire mounted on a specified rim, with a specified internal pressure applied, and under no-load conditions.

[0029] The specified rim refers to the "applicable rim" specified by JATMA, the "Design Rim" specified by TRA, or the "Measuring Rim" specified by ETRTO. The specified internal pressure refers to the "maximum air pressure" specified by JATMA, the maximum value of "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or the "INFLATION PRESSURES" specified by ETRTO. The specified load refers to the "maximum load capacity" specified by JATMA, the maximum value of "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or the "LOAD CAPACITY" specified by ETRTO. However, in JATMA, for passenger car tires, the specified internal pressure is 180 [kPa] air pressure, and the specified load is 88 [%] of the maximum load capacity.

[0030] In Figure 1, a pair of straight lines Le, Le are defined that pass through each edge of the wide cross belt 141 (see Figure 1) and are perpendicular to the inner surface of the tire. Furthermore, as shown in Figure 2, a pair of shoulder regions Rsh are defined as areas representing 20% ​​of the belt width Wb2 of the wide cross belt 141, centered on each of the pair of straight lines Le. That is, the areas extending from the pair of straight lines Le, Le in the inner and outer directions of the tire width to 10% of the belt width Wb2 are defined as the pair of shoulder regions Rsh. The pair of shoulder regions Rsh are defined as areas in the tire width direction along the inner surface of the tire.

[0031] Furthermore, as shown in Figure 1, the sound-absorbing material 20 is positioned between a pair of straight lines Le, Le. That is, the sound-absorbing material 20 is positioned in the inner region in the tire width direction, demarcated by the pair of straight lines Le, Le, so as not to intersect the pair of straight lines Le, Le. In this case, it is preferable that the entire sound-absorbing material 20 is positioned in a region of 80% of the belt width Wb2 of the wide intersecting belt 141 centered on the tire equatorial plane CL. That is, it is preferable that the outermost edge portion of the sound-absorbing material 20 in the tire width direction is positioned at a distance of 10% or more of the belt width Wb2 from the edge portion of the wide intersecting belt 141 so as not to intersect the pair of shoulder regions Rsh (see Figure 2). This suppresses peeling of the sound-absorbing material 20 caused by repeated deformation during tire rolling.

[0032] Furthermore, as shown in Figure 2, the sound-absorbing material 20 is attached to the inner surface of the tire via a release agent coating layer 19. Specifically, as shown in Figure 3, the release agent coating layer 19 is formed on the inner surface of the inner liner 18, and the sound-absorbing material 20 is attached to the inner surface of the tire via this release agent coating layer 19. In this case, as described above, the sound-absorbing material 20 may be fixed to the inner surface of the tire using an adhesive, or it may be attached detachably from the inner surface of the tire via an intermediate member such as an engagement sheet having a fastener or hook (not shown).

[0033] Also, in FIG. 2, an attachment region Rc of the sound-absorbing material 20 to the inner surface of the tire is defined. In the configuration of FIG. 2, as described above, the sound-absorbing material 20 has a rectangular cross-section and is adhered to the inner surface of the tire via a release agent coating layer 19 over the entire area of one side surface thereof. Therefore, the attachment region Rc of the sound-absorbing material 20 is continuous along the inner surface of the tire. Further, by including a region R1 (see FIG. 1) of 20 [mm] centered on the tire equatorial plane CL where the attachment region Rc of the sound-absorbing material 20 intersects the tire equatorial plane CL, peeling of the sound-absorbing material 20 is effectively suppressed.

[0034] However, it is not limited to this. For example, as described above, the sound-absorbing material 20 may be composed of a pair of sound-absorbing members separated from each other and arranged to be spaced apart from each other in the tire width direction across the tire equatorial plane CL (not shown). In such a configuration, a pair of attachment regions Rc separated from each other are defined.

[0035] [Film thickness of the release agent coating layer] FIG. 4 is an explanatory view showing the film thickness of the release agent coating layer 19 described in FIG. 3.

[0036] In FIG. 1, a region of 20 [mm] centered on the tire equatorial plane CL, that is, a region R1 from the tire equatorial plane CL to ±10 [mm] in the tire axial direction is defined. At this time, the maximum value G1_max (see FIG. 4) of the film thickness G1 of the release agent coating layer 19 in the region R1 has a relationship of G1_max < Ga_max with respect to the maximum value Ga_max (see FIG. 4) of the film thickness Ga of the release agent coating layer 19 over the entire area Ra of the inner surface of the tire (reference numerals in the figure are omitted; see FIG. 4), and preferably, it is in the range of 0.01 ≦ G1_max / Ga_max ≦ 0.50. Therefore, the film thickness G1 of the release agent coating layer 19 in the region R1 is set so as not to be the maximum over the entire area Ra of the inner surface of the tire. Also, the film thickness G1 of the release agent coating layer 19 in the region R1 is in the range of 0.1 [μm] ≦ G1 ≦ 300 [μm]. Further, the film thickness Ga of the release agent coating layer 19 over the entire area Ra of the inner surface of the tire is in the range of 0.1 [μm] ≦ Ga ≦ 500 [μm].

[0037] In such a configuration, since the film thickness G1 of the mold release agent coating layer 19 in the region R1 of 20 [mm] centered on the tire equatorial plane CL is relatively thin, for example, in a tire (see FIG. 1) provided with a sound-absorbing material 20 attached to the center region of the inner surface of the tire, peeling of the sound-absorbing material 20 due to the thick film thickness G1 of the mold release agent coating layer 19 is suppressed. On the other hand, since the film thickness Ga of the mold release agent coating layer 19 in other regions is relatively thick, vulcanization failure of the tire is suppressed, and the life of the bladder for tire vulcanization is extended. As a result, the vulcanization failure resistance performance of the tire is improved.

[0038] Also, the film thickness of the mold release agent coating layer 19 is preferably set to be thin at the center portion 191 of the mold release agent coating layer 19 and thick at the shoulder portion 192. Specifically, as shown in FIG. 3, the film thickness Gc of the mold release agent coating layer 19 in the attachment region Rc of the sound-absorbing material 20 is set to be thinner than the film thickness Gsh of the mold release agent coating layer 19 in the shoulder region Rsh. Further, the maximum value Gc_max of the film thickness Gc of the mold release agent coating layer 19 in the attachment region Rc of the sound-absorbing material 20 is in the range of 0 < Gc_max / Gs_max ≦ 0.50 with respect to the maximum value Gs_max of the film thickness Gs of the mold release agent coating layer 19 in each of the pair of shoulder regions Rsh, Rsh, and preferably in the range of 0.05 ≦ Gc_max / Gs_max ≦ 0.30.

[0039] The film thicknesses Gc and Gs of the mold release agent coating layer 19 are measured from a tire cross-section sample product using a laser microscope.

[0040] In the above configuration, since the film thickness Gc of the mold release agent coating layer 19 in the attachment region Rc of the sound-absorbing material 20 is relatively thin, the adhesion of the sound-absorbing material 20 to the inner surface of the tire is improved, and peeling of the sound-absorbing material 20 during tire rolling is suppressed. Also, since the film thickness Gs of the mold release agent coating layer 19 in the pair of shoulder regions Rsh, Rsh is relatively thick, the film thickness of the mold release agent in the region where the stretch amount during tire vulcanization molding is large is ensured, vulcanization failure of the tire is suppressed, and the life of the bladder for tire vulcanization is extended.

[0041] Furthermore, the film thickness Gc of the release agent coating layer 19 in the mounting area Rc of the sound-absorbing material 20 (see Figure 3) is in the range of 0.1 [μm] ≤ Gc ≤ 300 [μm], preferably in the range of 1 [μm] ≤ Gc ≤ 50 [μm]. The lower limit ensures that the tire can be easily removed from the tire vulcanization bladder during tire vulcanization molding, and the upper limit ensures that the sound-absorbing material 20 has good peel resistance due to the thin film thickness Gc of the release agent coating layer 19.

[0042] Furthermore, in Figure 4, the film thickness Gs of the release agent coating layer 19 in each of the pair of shoulder regions Rsh, Rsh is in the range of 5 [μm] ≤ Gs ≤ 500 [μm], preferably in the range of 20 [μm] ≤ Gs ≤ 200 [μm]. In addition, in each of the pair of shoulder regions Rsh, Rsh, the lower limit ensures that the tire can be released from the tire vulcanization bladder during tire vulcanization molding, and the upper limit suppresses peeling of the release agent coating layer 19 (adhesion of the release agent to the tire) caused by an excessive film thickness Gs of the release agent coating layer 19.

[0043] Furthermore, it is preferable that the film thickness Gs of the release agent coating layer 19 in each of the pair of shoulder regions Rsh, Rsh, takes its maximum value Gs_max in a region of 5% of the belt width Wb2 of the wide cross belt 141 centered on the perpendicular line Le, or in a region R1 of 20 mm centered on the perpendicular line Le. This ensures that the tire can be more properly released from the tire vulcanization bladder during the vulcanization molding of the tire.

[0044] [Tire manufacturing method] In the tire manufacturing process, first, each component (see Figure 1), such as the bead wire that makes up the bead core 11, the carcass ply that makes up the carcass layer 13, the belt ply 141-143 that make up the belt layer 14, the tread rubber 15, the sidewall rubber 16, and the rim cushion rubber 17, is put through a molding machine to form the green tire.

[0045] Next, the green tire is mounted and held in place on the molding surface of the tire vulcanization mold. At this time, a release agent is applied to the molding surface of the tire vulcanization mold and the outer surface of the tire vulcanization bladder.

[0046] Next, the green tire is vulcanized. Specifically, the tire vulcanization mold is heated, and the tire vulcanization bladder expands to press the green tire against the molding surface of the mold. As the green tire is heated, the rubber molecules and sulfur molecules in the tread combine, and vulcanization takes place. Then, the molding surface of the tire vulcanization mold is transferred to the green tire, and the tire's tread pattern is formed. After that, the vulcanized tire is removed from the tire vulcanization mold.

[0047] Next, the sound-absorbing material 20 is attached to the tire. Specifically, the sound-absorbing material 20 is temporarily fixed to the inner surface of the tire using adhesive or adhesive tape, and then the sound-absorbing material 2 is pressed against the inner surface of the tire.

[0048] In this tire manufacturing process, the film thickness Gc and Gs of the release agent coating layer 19 are formed to the configuration described above. Specifically, (1) in the release agent application process before vulcanization molding described above, the release agent is applied to the entire outer surface of the tire vulcanization bladder with a uniform thickness. Then, after vulcanization molding, the tire is cleaned before the sound-absorbing material 20 is attached, and the film thickness of the release agent coating layer formed in the center region of the inner surface of the tire is adjusted. As a result, the film thickness Gc of the release agent coating layer 19 in the mounting region Rc of the sound-absorbing material 20 is reduced, and a difference is formed between the film thickness Gs of the release agent coating layer 19 in each of the pair of shoulder regions Rsh, Rsh.

[0049] Further, not limited to this, (2) in the step of applying the mold release agent before the vulcanization molding described above, the mold release agent may be applied so that the film thickness of the mold release agent on the outer surface of the bladder for tire vulcanization is thin in the center region of the inner surface of the tire and becomes thin in a pair of shoulder regions Rsh, Rsh. Specifically, the film thickness Gc' (not shown) of the mold release agent in the region corresponding to the attachment region Rc of the sound absorption material 20 on the outer surface of the bladder for tire vulcanization is thinner than the film thickness Gs' of the mold release agent in the regions corresponding to the pair of shoulder regions Rsh, Rsh, respectively. The mold release agent is applied to the outer surface of the bladder for tire vulcanization. Further, the film thicknesses Gc' and Gs' of the mold release agent in the regions corresponding to the attachment region Rc of the sound absorption material 20 and the pair of shoulder regions Rsh, Rsh are in the ranges of 0.1 [μm] ≤ Gc' ≤ 500 [μm] and 0.1 [μm] ≤ Gs' ≤ 500 [μm]. Even with such a configuration, the film thickness Gc of the mold release agent coating layer 19 in the attachment region Rc of the sound absorption material 20 is reduced, and a difference from the film thickness Gs of the mold release agent coating layer 19 in each of the pair of shoulder regions Rsh, Rsh is formed.

[0050] [Effect] As described above, [1] this tire 1 includes a pair of bead cores 11, 11, a carcass layer 13 bridged over the pair of bead cores 11, 11, a pair of cross belts 141, 142 disposed on the radially outer side of the carcass layer 13, a mold release agent coating layer 19 formed on the inner surface of the tire, and a sound absorption material 20 disposed on the inner surface of the tire via the mold release agent coating layer 19 (see FIG. 1). Further, the maximum value G1_max (see FIG. 4) of the film thickness G1 of the mold release agent coating layer 19 in the region R1 (see FIG. 1) of 20 [mm] centered on the tire equatorial plane CL has a relationship of G1_max < Ga_max with respect to the maximum value Ga_max of the film thickness Ga of the mold release agent coating layer 19 over the entire area Ra of the inner surface of the tire (reference numerals in FIG. 1 are omitted; see FIG. 4).

[0051] In such a configuration, since the film thickness G1 of the mold release agent coating layer 19 in the region R1 of 20 [mm] centered on the tire equatorial plane CL is relatively thin, for example, in a tire (see FIG. 1) provided with a sound-absorbing material 20 attached to the center region of the inner surface of the tire, there is an advantage that peeling of the sound-absorbing material 20 due to the thick mold release agent coating layer 19 is suppressed. On the other hand, since the film thickness Ga of the mold release agent coating layer 19 in other regions is relatively thick, vulcanization failure of the tire is suppressed, and the life of the bladder for tire vulcanization is extended. Thereby, there is an advantage that the vulcanization failure resistance performance of the tire is improved.

[0052] Also, [2] in this tire 1, in a cross-sectional view in the tire meridian direction, a pair of straight lines Le, Le perpendicular to the inner surface of the tire are defined passing through each of the edge portions of the wide cross belt 141. Also, a region of 20 [%] of the belt width Wb2 of the wide cross belt 141 centered on each of the pair of straight lines Le, Le is defined as a pair of shoulder regions Rsh, Rsh (see FIG. 2). Also, the attachment region Rc of the sound-absorbing material 20 (see FIG. 2) is defined as a region including the above-mentioned region of 20 [mm] centered on the tire equatorial plane between the pair of straight lines Le, Le. Also, the maximum value Gc_max of the film thickness Gc (see FIG. 3) of the mold release agent coating layer 19 in the attachment region Rc of the sound-absorbing material 20 is in the range of 0 < Gc_max / Gs_max ≦ 0.50 with respect to the maximum value Gs_max of the film thickness Gs of the mold release agent coating layer 19 in each of the pair of shoulder regions Rsh, Rsh. In such a configuration, since the film thickness Gc of the mold release agent coating layer 19 in the attachment region Rc of the sound-absorbing material 20 is relatively thin, the adhesiveness of the sound-absorbing material 20 to the inner surface of the tire is improved, and peeling of the sound-absorbing material 20 during tire rolling is suppressed. Also, since the film thickness Gs of the mold release agent coating layer 19 in the pair of shoulder regions Rsh, Rsh is relatively thick, the film thickness of the mold release agent in the region where the stretch amount during tire vulcanization molding is large is ensured, vulcanization failure of the tire is suppressed, and the life of the bladder for tire vulcanization is extended. Thereby, there is an advantage that both the peel resistance performance of the sound-absorbing material and the vulcanization failure resistance performance of the tire are achieved.

[0053] Furthermore, [3] in this tire 1, as in the tire 1 described in [1] or [2] above, the film thickness Gc of the release agent coating layer 19 in the mounting area Rc of the sound-absorbing material 20 is in the range of 0.1 [μm] ≤ Gc ≤ 300 [μm]. The lower limit ensures that the tire can be peeled off the tire from the tire vulcanization bladder during vulcanization molding, and the upper limit ensures that the sound-absorbing material 20 has peel resistance due to the thin film thickness Gc of the release agent coating layer 19.

[0054] Furthermore, [4] in this tire 1, in the tire 1 described in any one of [1] to [3] above, the film thickness Gs of the release agent coating layer 19 in each of the pair of shoulder regions Rsh, Rsh is in the range of 5 [μm] ≤ Gs ≤ 500 [μm]. The above lower limit ensures that the tire can be released from the tire vulcanization bladder during the vulcanization molding of the tire, and the above upper limit has the advantage of suppressing peeling of the release agent coating layer 19 (especially adhesion of the release agent to the tire) caused by an excessive film thickness Gs of the release agent coating layer 19.

[0055] Furthermore, [5] in this tire 1, in the tire 1 described in any one of [1] to [4] above, the film thickness Gs of the release agent coating layer 19 in each of the pair of shoulder regions Rsh, Rsh takes its maximum value Gs_max in a region of 5[%] of the belt width Wb2 of the wide cross belt 141 centered on the perpendicular Le, or in a region of 20[mm] centered on the perpendicular Le. This has the advantage of ensuring better release of the tire from the tire vulcanization bladder during the vulcanization molding of the tire.

[0056] Furthermore, [6] in this tire manufacturing method, the film thickness G1 of the release agent coating layer 19 in a 20 [mm] region R1 centered on the tire equatorial plane CL is relatively thin, which suppresses tire vulcanization failures and extends the life of the tire vulcanization bladder. This has the advantage of improving the tire's resistance to vulcanization failures.

[0057] In such a configuration, in the tire after vulcanization molding, since the film thickness G1 of the mold release agent coating layer 19 in the region R1 of 20 [mm] centered on the tire equatorial plane CL is relatively thin, vulcanization failure of the tire is suppressed, and the life of the bladder for tire vulcanization is extended. As a result, there is an advantage that the vulcanization failure resistance performance of the tire is improved.

[0058] Also, [7] in this tire manufacturing method, in the tire manufacturing method described in [6] above, in a cross-sectional view in the tire meridian direction, a pair of straight lines Le perpendicular to the tire inner surface passing through each of the edge portions of the wide cross belt 141 are defined. Further, a region of 20 [%] of the belt width Wb2 of the wide cross belt 141 centered on each of the pair of straight lines Le is defined as a pair of shoulder regions Rsh, Rsh (see FIG. 2). Further, the attachment region Rc of the sound-absorbing material 20 (see FIG. 2) is defined as a region including the region of 20 [mm] centered on the tire equatorial plane between the pair of straight lines Le, Le. Further, the tire manufacturing method includes a step of applying a mold release agent to the outer surface of a bladder for tire vulcanization (not shown), a step of pressing a green tire against a tire vulcanization molding die using the bladder for tire vulcanization, and a step of attaching the sound-absorbing material 20 to the attachment region Rc of the tire after vulcanization molding. Also, the film thickness Gc'_max (not shown) of the mold release agent applied to the region of the outer surface of the bladder for tire vulcanization corresponding to the attachment region Rc of the sound-absorbing material 20 has a relationship of Gc'_max < Gs'_max with respect to the film thickness Gs'_max of the mold release agent applied to the regions corresponding to the pair of shoulder regions Rsh, Rsh. In such a configuration, in the tire after vulcanization molding, since the film thickness Gc' of the mold release agent coating layer 19 in the attachment region Rc of the sound-absorbing material 20 is relatively thin, the adhesion of the sound-absorbing material 20 to the tire inner surface is improved, and there is an advantage that peeling of the sound-absorbing material 20 during tire rolling is suppressed. Also, since the film thickness Gs' of the mold release agent coating layer 19 in the pair of shoulder regions Rsh, Rsh is relatively thick, the film thickness of the mold release agent in the region where the stretch amount during tire vulcanization molding is large is ensured, and vulcanization failure of the tire is suppressed, and the life of the bladder for tire vulcanization is extended.

[0059] Furthermore, [8] in this tire manufacturing method, the film thicknesses Gc' and Gs' of the release agent are in the range of 0.1 [μm] ≤ Gc' ≤ 500 [μm] and 0.1 [μm] ≤ Gs' ≤ 500 [μm], respectively, in the tire manufacturing method described in [7] above. This has the advantage of optimizing the film thicknesses Gc' and Gs' of the release agent on the outer surface of the tire vulcanization bladder. [Examples]

[0060] Figure 5 is a diagram showing the results of a performance test of a tire according to an embodiment of this invention.

[0061] In this performance test, several types of test tires were evaluated for (1) the peel resistance of the sound-absorbing material and (2) the vulcanization failure resistance. In addition, a test tire with size 235 / 45ZR18 was prototyped.

[0062] (1) In evaluating the peel resistance performance of the sound-absorbing material, each test tire was mounted on a wheel with a standard rim specified by JATMA, and a running test was conducted on a drum testing machine under the conditions of a temperature of 20°C, a running speed of 81 km / h, an air pressure of 160 kPa, a load of 5 kN, and a running distance of 6,480 km. After that, the presence or absence of rupture of the sound-absorbing material was visually confirmed. An index evaluation was then performed, with a value of 100 if the amount of detachment and peeling of the sound-absorbing material was between 1 / 8 and 1 / 4 of the total sound-absorbing material. In this evaluation, a higher value indicates less detachment and peeling of the sound-absorbing material, which is preferable.

[0063] (2) In the evaluation of vulcanization failure resistance, the appearance defects on the inner surface of 100 test tires were visually observed and evaluated. This evaluation was performed using an index evaluation with the comparative example as the baseline (100), and a higher value is preferable.

[0064] The test tires of the comparative example and the example have the configuration shown in Figures 1 and 2, and are equipped with a sound-absorbing material 20 with a rectangular cross-section on the inner surface of the tire. The belt width Wb2 of the wide cross belt 141 is 210 [mm], and the width Wa of the sound-absorbing material 20 is 140 [mm]. Furthermore, as shown in Figure 4, the release agent coating layer 19 has a constant film thickness Gs (=Gsh_max) in a pair of shoulder regions Rsh, Rsh, and a constant film thickness Gc (=Gc_max) in the mounting region Rc of the sound-absorbing material 20.

[0065] As the test results show, the test tire in this example demonstrates that both the peel resistance of the sound-absorbing material and the vulcanization failure resistance of the tire are achieved. [Explanation of Symbols]

[0066] 1 Tire; 2 Sound-absorbing material; 11 Bead core; 12 Bead filler; 13 Carcass layer; 141, 142 Cross belts; 143, 144 Belt cover; 14 Belt layer; 15 Tread rubber; 16 Sidewall rubber; 17 Rim cushion rubber; 18 Inner liner; 19 Release agent coating layer; 191 Center section; 192 Shoulder section; 20 Sound-absorbing material

Claims

1. A tire comprising a pair of bead cores, a carcass layer spanning the pair of bead cores, a pair of cross belts arranged radially outward of the carcass layer, a release agent coating layer formed on the inner surface of the tire, and a sound-absorbing material attached to the inner surface of the tire via the release agent coating layer, A tire characterized in that the maximum value G1_max of the film thickness G1 of the release agent coating layer in a 20 [mm] region centered on the tire's equatorial plane has the relationship G1_max < Ga_max with respect to the maximum value Ga_max of the film thickness Ga of the release agent coating layer over the entire inner surface of the tire.

2. In a cross-sectional view along the tire meridian, a pair of straight lines Le are defined that pass through each of the edges of the wide intersecting belt and are perpendicular to the inner surface of the tire. A pair of shoulder regions are defined, each centered on one of the pairs of straight lines Le and representing 20% ​​of the belt width Wb2 of the wide intersecting belt. The mounting area for the sound-absorbing material is defined as an area that includes the region between the pair of straight lines Le and centered on the tire equatorial plane, with a width of 20 mm. The tire according to claim 1, characterized in that the maximum value Gc_max of the film thickness Gc of the release agent coating layer in the mounting area of ​​the sound-absorbing material is in the range of 0 < Gc_max / Gs_max ≤ 0.50 with respect to the maximum value Gs_max of the film thickness Gs of the release agent coating layer in each of the pair of shoulder areas.

3. The tire according to claim 1, wherein the thickness Gc of the release agent coating layer in the mounting area of ​​the sound-absorbing material is in the range of 0.1 [μm] ≤ Gc ≤ 300 [μm].

4. The tire according to claim 1, wherein the thickness Gs of the release agent coating layer in each of the pair of shoulder regions is in the range of 5 [μm] ≤ Gs ≤ 500 [μm].

5. The tire according to claim 1, wherein the thickness Gs of the release agent coating layer in each of the pair of shoulder regions takes its maximum value Gs_max in a region of 5% of the belt width Wb2 of the wide cross belt centered on the perpendicular Le, or in a region of 20 mm centered on the perpendicular Le.

6. A method for manufacturing a tire comprising: a pair of bead cores; a carcass layer spanning the pair of bead cores; a pair of cross belts arranged radially outward from the carcass layer; a release agent coating layer formed on the inner surface of the tire; and a sound-absorbing material arranged on the inner surface of the tire via the release agent coating layer, The process includes the steps of applying a release agent to the outer surface of a tire vulcanization bladder, pressing a green tire into a tire vulcanization mold using the tire vulcanization bladder, and attaching the sound-absorbing material to the mounting area of ​​the tire after vulcanization. A tire manufacturing method characterized in that the maximum value G1'_max of the film thickness G1' of the release agent applied to a region of the outer surface of the tire vulcanizing bladder corresponding to a 20 [mm] region centered on the tire equatorial plane has the relationship G1'max < Ga'max with respect to the maximum value Ga_max of the film thickness Ga of the release agent applied to a region corresponding to the entire inner surface of the tire.

7. The tire manufacturing method according to claim 6, characterized in that, in a cross-sectional view in the meridian direction of the tire, a pair of straight lines Le are defined that pass through each of the edges of the wide intersecting belt and are perpendicular to the inner surface of the tire, a region of 20% of the belt width Wb2 of the wide intersecting belt centered on each of the pair of straight lines Le is defined as a pair of shoulder regions, the mounting region of the sound-absorbing material is defined as a region between the pair of straight lines Le and including the region of 20 mm centered on the tire equatorial plane, and the film thickness Gc'_max of the release agent applied to the region of the outer surface of the tire vulcanizing bladder corresponding to the mounting region of the sound-absorbing material has the relationship Gc'_max < Gs'_max with respect to the film thickness Gs'_max of the release agent applied to the region corresponding to the pair of shoulder regions.

8. The tire manufacturing method according to claim 6, wherein the film thicknesses Gc' and Gs' of the mold release agent are in the ranges of 0.1 [μm] ≤ Gc' ≤ 500 [μm] and 0.1 [μm] ≤ Gs' ≤ 500 [μm].

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