Pneumatic tire and method for manufacturing the same

Abstract

To provide a pneumatic tire which can improve a balance of the tire and a method for manufacturing the same.SOLUTION: A pneumatic tire includes a tread part 1 which extends in a tire circumferential direction and forms an annular shape, a pair of side wall parts arranged on both sides of the tread part 1, and a pair of bead parts arranged inside in a tire radial direction of the side wall parts, where a belt-like sound absorption material 10 is stuck to a tire inner surface Ts in the tread part 1 in the tire circumferential direction; the sound absorption material 10 has a missing part 11 in one place in the tire circumferential direction; and a length A [mm] in the tire circumferential direction of the missing part 11, a rim diameter RD [mm], an outer diameter OD [mm] of the tire, total thickness Ga [mm] of the tire, density d [kg / m3] of the sound absorption material 10, a width w [mm] of the sound absorption material 10 and thickness u [mm] of the sound absorption material 10 satisfy Expression (1).SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a pneumatic tire and a method for manufacturing the same, and more particularly to a pneumatic tire and a method for manufacturing the same that enable improvement of the balance of the tire.

Background Art

[0002] One of the causes of tire noise is cavity resonance noise caused by the vibration of the air filled in the tire cavity. This cavity resonance noise is generated when the tread portion of the tire in contact with the road surface vibrates due to the unevenness of the road surface during vehicle travel, and this vibration causes the air in the tire cavity to vibrate. Among this cavity resonance noise, the sound in a specific frequency band is perceived as noise, so it is important to reduce the sound pressure level (noise level) in that frequency band in order to reduce the cavity resonance noise.

[0003] As a method for reducing the noise caused by such a cavity resonance phenomenon, an acoustic material made of a porous material such as sponge is directly adhered to the inner surface of the tire. Further, it has been proposed to provide a missing portion (gap) at at least one location in the tire circumferential direction with respect to the acoustic material (see, for example, Patent Document 1). However, when a gap is provided in a part of the acoustic material in the tire circumferential direction, there is a problem that the balance of the tire deteriorates if the length of the gap in the tire circumferential direction is excessive in relation to the tire size and various dimensions of the acoustic material.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] An object of the present invention is to provide a pneumatic tire and a method for manufacturing the same that enable improvement of the balance of the tire.

Means for Solving the Problem

[0006] The pneumatic tire of the present invention for achieving the above object is a pneumatic tire including a tread portion extending in the tire circumferential direction to form an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed on the tire radial direction inner side of these sidewall portions. In the pneumatic tire, a strip-shaped sound absorbing material is attached along the tire circumferential direction to the inner surface of the tire in the tread portion, the sound absorbing material has a missing portion at one location in the tire circumferential direction, and the length A [mm] of the missing portion in the tire circumferential direction, the rim diameter RD [mm], the outer diameter OD [mm] of the tire, the total thickness Ga [mm] of the tire, the density d [kg / m 3 of the sound absorbing material, the width w [mm] of the sound absorbing material, and the thickness u [mm] of the sound absorbing material satisfy the following formula (1).

Number

[0007] The method for manufacturing a pneumatic tire of the present invention for achieving the above object is a method for manufacturing the above pneumatic tire. After manufacturing the pneumatic tire excluding the sound absorbing material and the sealant layer, when forming the sealant layer by applying a sealant to the inner surface of the tire in the tread portion, the temperature of the sealant applied to the inner surface of the tire is set to 70°C or lower, and a sound absorbing material is installed along the tire circumferential direction on the tire radial direction inner side of the sealant layer.

Effect of the Invention

[0008] The present inventor earnestly studied the influence of the sound absorbing material on the balance of the tire in consideration of the relationship between the dynamic balance, the static balance, and the moment balance, and as a result, found that the influence of the sound absorbing material is manifested in the static balance. Based on this, the present inventor found that it is important to specify the configuration of the sound absorbing material by paying attention to the static balance, and thus arrived at the present invention.

[0009] In the present invention, by setting the length A in the tire circumferential direction of the missing portion of the sound-absorbing material to satisfy the above formula (1), the length A in the tire circumferential direction is optimized according to the tire size and various dimensions of the sound-absorbing material, etc., and a tire with excellent balance can be obtained.

[0010] In the pneumatic tire of the present invention, it is preferable that a sealant layer is formed along the tire circumferential direction on the tire inner surface, and the sound-absorbing material is fixed to the tire inner surface by the sealant layer.

[0011] It is preferable that the absolute value of the difference between the glass transition temperature of the sealant of the sealant layer and the glass transition temperature of the sound-absorbing material is 60°C or less. Thereby, while ensuring the puncture sealing property, the durability of the sealant layer can be effectively improved.

[0012] It is preferable that the ratio A / u of the length A [mm] in the tire circumferential direction of the missing portion to the thickness u [mm] of the sound-absorbing material is in the range of 0.5 to 6.0. Thereby, it is possible to suppress the adverse effect on the balance of the tire due to the provision of the missing portion, and it is possible not to deteriorate the productivity.

[0013] The glass transition temperature of the sealant of the sealant layer is equal to or lower than the glass transition temperature of the sound-absorbing material, and it is preferable that the glass transition temperature of the sound-absorbing material is in the range of -60°C to -40°C. By using a sealant with a relatively low glass transition temperature, the sealant layer does not brittlely fracture in a low-temperature environment, which is advantageous for durability. Since the glass transition temperature of the sound-absorbing material is in the range of -60°C to -40°C, it is possible to prevent the sound-absorbing material from being damaged in a low-temperature environment.

[0014] When the temperature t [°C] of the sound-absorbing material is at least in the range of -20°C to 80°C, it is preferable that the elongation at break y [%] of the sound-absorbing material satisfies the relationship of y≥t + 100 and y≤2t + 440 with respect to the temperature t [°C] of the sound-absorbing material. Thereby, it is possible to sufficiently ensure the sound absorption effect of the sound-absorbing material during high-speed driving, and it is possible to prevent the sound-absorbing material from peeling or breaking at low temperatures.

[0015] The sealant of the sealant layer is preferably composed of a silicone-based composition. When using such a sealant, the temperature dependence is low, and physical properties can be maintained over a wide range of temperatures from low to high temperatures. Therefore, it tends to be difficult to flow at high temperatures and difficult to crack at low temperatures. Moreover, it is possible to achieve both puncture sealability and durability. Also, in terms of adhesiveness to the sound-absorbing material, the temperature dependence is low, and good adhesiveness can be maintained over a wide range of temperatures.

[0016] It is preferable to have a release layer containing a silicone-based composition on the inner surface of the tire, and a sealant layer is formed on the inner side in the tire radial direction of the release layer in the tread portion, and the absolute value of the difference between the contact angle of water with respect to the release layer and the contact angle of water with respect to the sealant layer is 30° or less. As a result, since both the release layer and the sealant layer contain a silicone-based composition, it contributes to improving compatibility. Furthermore, by setting the absolute value of the difference between the contact angle of water with respect to the release layer and the contact angle of water with respect to the sealant layer within a specific range (30° or less), the compatibility can be made very good. As a result, the adhesiveness between the inner surface of the tire and the sealant layer can be enhanced, and the durability of the tire can be improved.

[0017] The silicone-based composition constituting the sealant of the sealant layer is preferably a two-component curable silicone. Since the two-component curable silicone has a low viscosity immediately after the two components are mixed, it can be applied even at low temperatures.

[0018] At all locations of the belt layer located at the innermost side in the tire radial direction, the distance L from the belt layer to the sealant layer is preferably 10 mm or less. As a result, when a foreign object such as a nail penetrates the tread portion, the sealant easily flows to the belt layer, so that good puncture sealability can be ensured.

[0019] The distance in the tire width direction between the center position in the width direction of the sealant layer and the tire equator is preferably 10 mm or less. As a result, the sealant layer does not adversely affect the balance of the tire.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Mode for Carrying Out the Invention

[0021] Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. FIGS. 1 to 4 show a pneumatic tire according to an embodiment of the present invention.

[0022] As shown in FIG. 1, the pneumatic tire of the present embodiment includes a tread portion 1 that extends in the tire circumferential direction and forms an annular shape, a pair of sidewall portions 2 disposed on both sides of the tread portion 1, and a pair of bead portions 3 disposed on the inner side in the tire radial direction of these sidewall portions 2.

[0023] Between a pair of bead portions 3, at least one layer (one layer in FIG. 1) of carcass layer 4 formed by arranging a plurality of carcass cords in the radial direction is mounted. As the carcass cords constituting the carcass layer 4, organic fiber cords such as nylon and polyester are preferably used. An annular bead core 5 is embedded in each bead portion 3, and a bead filler 6 made of a rubber composition having a triangular cross section is disposed on the outer periphery of the bead core 5.

[0024] On the other hand, on the tire outer peripheral side of the carcass layer 4 in the tread portion 1, a plurality of layers (two layers in FIG. 1) of belt layers 7 are embedded. The belt layer 7 includes a plurality of reinforcing cords inclined with respect to the tire circumferential direction, and the reinforcing cords are arranged so as to cross each other between the layers. In the belt layer 7, the inclination angle of the reinforcing cords with respect to the tire circumferential direction is set in the range of, for example, 10° to 40°. As the reinforcing cords of the belt layer 7, steel cords are preferably used.

[0025] On the tire outer peripheral side of the belt layer 7, at least one layer (two layers in FIG. 1) of belt cover layer 8 formed by arranging reinforcing cords at an angle of, for example, 5° or less with respect to the tire circumferential direction is disposed for the purpose of improving high-speed durability. It is desirable that this belt cover layer 8 has a jointless structure in which a strip material formed by rubber-coating at least one reinforcing cord aligned is continuously wound at substantially 0° with respect to the tire circumferential direction. As the reinforcing cords of the belt cover layer 8, organic fiber cords such as nylon and aramid are preferably used.

[0026] Note that the above-described tire internal structure shows a typical example in a pneumatic tire, but is not limited thereto. An inner liner layer 9 is disposed along the carcass layer 4 as a member constituting the tire inner surface Ts.

[0027] In the above-mentioned pneumatic tire, a sound-absorbing material 10 is fixed to the inner surface Ts of the tread portion 1 along the tire circumferential direction via an adhesive layer. As the adhesive layer, for example, any one of an adhesive, a double-sided adhesive tape, and a sealant can be used. In FIGS. 1 to 4, a sealant is used to fix the sound-absorbing material 10 to the inner surface Ts of the tire. The sound-absorbing material 10 is adhered onto the sealant layer 20 based on the adhesiveness of the sealant layer 20 after the formation of the sealant layer 20.

[0028] The sound-absorbing material 10 is composed of a porous material having closed cells and has predetermined sound-absorbing characteristics based on its porous structure. It is preferable to use foamed polyurethane as the porous material of the sound-absorbing material 10. Further, as shown in FIG. 3, the sound-absorbing material 10 has a missing portion 11 at only one location in the tire circumferential direction. The missing portion 11 is a portion where the sound-absorbing material 10 does not exist on the tire circumference. By providing the missing portion 11 in the sound-absorbing material 10, it is possible to withstand the shear strain of the adhesive surface caused by the inflation and the ground rolling of the tire for a long time, and it is possible to effectively relieve the shear strain generated on the adhesive surface of the sound-absorbing material 10.

[0029] The sealant layer 20 is formed so as to be continuous in the tire circumferential direction on the inner surface Ts of the tread portion 1. The sealant of the sealant layer 20 is preferably composed of a silicone-based composition. The silicone-based composition includes a synthetic polymer compound having a main skeleton by a siloxane bond. When such a sealant is used, the temperature dependence is low, and the physical properties can be maintained at a wide range of temperatures from low temperature to high temperature. Therefore, it tends to be difficult to flow at high temperature and difficult to crack at low temperature. Moreover, both puncture sealing property and durability can be achieved. Also, in terms of the adhesiveness with the sound-absorbing material 10, the temperature dependence is low, and good adhesiveness can be maintained at a wide range of temperatures.

[0030] FIG. 4 shows various dimensions of the tire and the sound-absorbing material. In the present invention, the length A [mm] of the missing portion 11 in the tire circumferential direction, the rim diameter RD [mm], the outer diameter OD [mm] of the tire, the total thickness Ga [mm] of the tire, and the density d [kg / m of the sound-absorbing material 10 3The width w [mm] of the sound-absorbing material 10 and the thickness u [mm] of the sound-absorbing material 10 satisfy the following formula (1). In the following formula (1), the product of the virtual weight Vw [g] of the missing part 11 and the distance d1 [mm] from the rotation axis X of the tire to the missing part 11 is Vw×d1, and the product of the static balance weight Sw [g] corresponding to the weight of the counterweight installed on the rim and the distance d2 [mm] from the rotation axis X of the tire to the counterweight is Sw×d2. It is assumed that the product Vw×d1 and the product Sw×d2 are equal and the forces are balanced. The distance d1 corresponds to half of the inner diameter of the tire (that is, the value obtained by subtracting the total thickness Ga of the tire from half of the outer diameter OD of the tire), and the distance d2 corresponds to half of the rim diameter RD. The total thickness Ga of the tire is the thickness from the outer surface of the tire to the adhesion surface of the sound-absorbing material 10 on the tire center line CL, and includes the thickness of the adhesive layer (the sealant layer 20 in FIG. 4). When there is a groove on the tire center line CL, the total thickness Ga of the tire is the thickness from the intersection of the virtual line connecting both ends of the groove in the tire width direction and the tire center line CL to the adhesion surface of the sound-absorbing material 10.

Number

[0031] In the pneumatic tire described above, by satisfying the above formula (1), the length A in the tire circumferential direction is optimized according to the tire size and various dimensions of the sound-absorbing material, etc., and a tire with excellent balance can be obtained.

[0032] In particular, the ratio A / u of the length A [mm] in the tire circumferential direction of the missing portion 11 to the thickness u [mm] of the sound-absorbing material 10 is preferably in the range of 0.5 to 6.0. Thereby, it is possible to suppress an adverse effect on the balance of the tire due to the provision of the missing portion 11, and the productivity is not deteriorated. Here, when the ratio A / u is less than 0.5 (that is, the length A of the missing portion 11 is excessively short), the adverse effect on the balance of the tire becomes small, but when the sound-absorbing material 10 is attached to the tire inner surface Ts, the productivity deteriorates, such as the end portions of the sound-absorbing material 10 in the tire circumferential direction overlapping. Conversely, when the ratio A / u exceeds 6.0 (that is, the length A of the missing portion 11 is excessively long), the adverse effect on the balance of the tire becomes large, and when the sound-absorbing material 10 is attached to the tire inner surface Ts, the crimping roller pressing the sound-absorbing material 10 and the sealant layer 20 stick together, and the yield deteriorates.

[0033] In the pneumatic tire described above, the absolute value of the difference between the glass transition temperature of the sealant of the sealant layer 20 and the glass transition temperature of the sound-absorbing material 10 is preferably 60°C or less. At that time, the glass transition temperature of the sealant is preferably in the range of -120°C to -40°C. By satisfying the range of the absolute value of the difference described above, it is possible to effectively improve the durability while ensuring the puncture sealing property. Here, when the absolute value of the difference described above exceeds 60°C, due to the temperature dependence, either the sealant or the sound-absorbing material 10 becomes hard, and peeling occurs due to stress concentration, leading to deterioration of the durability.

[0034] Furthermore, the glass transition temperature of the sealant of the sealant layer 20 is equal to or lower than the glass transition temperature of the sound-absorbing material 10, and the glass transition temperature of the sound-absorbing material 10 is preferably in the range of -60°C to -40°C. By using a sealant with a relatively low glass transition temperature, the sealant layer 20 does not brittlely fracture in a low-temperature environment, which is advantageous for durability. By the glass transition temperature of the sound-absorbing material 10 being in the range of -60°C to -40°C, it is possible to prevent the sound-absorbing material 10 from being damaged in a low-temperature environment.

[0035] The pneumatic tire described above can be manufactured by the following method. First, a pneumatic tire having a tread portion 1, a pair of sidewall portions 2, and a pair of bead portions 3 as described above is manufactured. Next, after applying a sealant made of a butyl rubber or a silicone-based composition to the tire inner surface Ts in the tread portion 1 to form a sealant layer 20, a sound-absorbing material 10 is installed on the sealant layer 20. When a silicone-based composition is used, since the silicone-based composition has good fluidity even at low temperatures, the temperature of the sealant applied to the tire inner surface Ts is set to 70°C or lower. If this temperature exceeds 70°C, in the process of applying the sealant to the tire inner surface Ts, the distortion generated in the pneumatic tire becomes large, and the durability of the tire deteriorates. In particular, the temperature of the sealant when applying the sealant to the tire inner surface Ts is preferably in the range of 5°C to 40°C, more preferably in the range of 10°C to 35°C, and most preferably in the range of 15°C to 30°C. Thereby, over-vulcanization of the rubber member is suppressed by heating during the formation of the sealant layer 20. Also, even when there is a mold release component on the tire inner surface Ts, since it is the same material, the sealant layer 20 can be well adhered to the tire inner surface Ts.

[0036] FIG. 5 shows a specific manufacturing method of a pneumatic tire according to an embodiment of the present invention, and FIG. 6 shows a sealant layer formed on the tire inner surface in the tread portion. In FIG. 5, a sealant extruding device 31 mixes the sealant supplied from pumps 32 and 33, and continuously discharges the mixed sealant from a nozzle 34 as a strip material 21. This sealant extruding device 31 is configured such that the position of the nozzle 34 is displaceable. Therefore, by moving the nozzle 34 in the tire axial direction while rotating the tire from a state where the nozzle 34 is close to the tire inner surface Ts, the strip material 21 of the sealant can be arranged in a spiral shape while being inclined with respect to the tire circumferential direction Tc on the tire inner surface Ts (see FIG. 6). The circumferential portions of the strip material 21 of the sealant arranged in a spiral shape are in close contact with each other. The strip material 21 of the sealant arranged in this spiral shape is integrated to form a sealant layer 20.

[0037] As the silicone-based composition constituting the sealant of the sealant layer 20, one-part curable silicone or two-part curable silicone can be used, but it is particularly preferable to use two-part curable silicone. Examples of the one-part curable silicone include moisture curable silicone. The two-part curable silicone is composed of a first liquid and a second liquid. By mixing these first liquid and second liquid, the curing reaction starts, and the stability as the sealant layer 20 is ensured after curing. In the above-described apparatus, the first liquid and the second liquid of the two-part curable silicone are respectively supplied from the pumps 32 and 33. Since the two-part curable silicone has a low viscosity immediately after the two liquids are mixed, it can be applied even at a low temperature.

[0038] The two-part curable silicone is composed of, for example, a condensation curable silyl-terminated polymer, a silane crosslinking agent, a condensation catalyst, a filler, etc. Examples of the condensation curable silyl-terminated polymer include polydialkylsiloxane, alkylphenylsiloxane, an organic polymer having a silyl group (for example, silyl polyether, silyl acrylate), polyisobutylene having a silyl group, etc. Examples of the silane crosslinking agent include alkoxy-functional silane, oximosilane, acetoxysilane, enoxysilane, etc. Examples of the filler include iron oxide, titanium dioxide, carbon black, talc, etc. Examples of the condensation catalyst include titanate, zirconate, etc. These condensation curable silyl-terminated polymer, silane crosslinking agent, condensation catalyst, and filler are stored in a state divided into the first liquid and the second liquid in a combination in which the curing reaction does not proceed, and are mixed at the time of use.

[0039] FIG. 7 is a graph showing the relationship between the temperature t [° C.] and the elongation at break y [%] in the sound absorbing material used in the pneumatic tire of the present invention. In the present invention, it is preferable that the elongation at break y [%] of the sound absorbing material 10 satisfies the relationship of y ≧ t + 100 and y ≦ 2t + 440 with respect to the temperature t [° C.] of the sound absorbing material 10. In particular, it is more preferable to satisfy the relationship of y ≧ t + 170 and / or y ≦ 2t + 350. Such a relational expression between the temperature t and the elongation at break y of the sound absorbing material 10 is satisfied when the temperature t of the sound absorbing material 10 is in the range of at least -20 ° C to 80 ° C.

[0040] As shown in Fig. 7, the shaded area Z indicates the range of the physical properties of the sound-absorbing material 10 employed in the pneumatic tire of the present invention. In Fig. 7, when the elongation at break y of the sound-absorbing material 10 is outside the area Z downward, peeling or breakage of the sound-absorbing material 10 is likely to occur during driving in a low-temperature environment. On the other hand, when the elongation at break y of the sound-absorbing material 10 is outside the area Z upward, the hardness of the sound-absorbing material 10 also tends to decrease, so deformation of the sound-absorbing material 10 is likely to occur during high-speed driving.

[0041] When the temperature t of the sound-absorbing material 10 is at all temperature values in the range of -20°C to 80°C, the elongation at break y [%] of the sound-absorbing material satisfies both relationships of y ≥ t + 100 and y ≤ 2t + 440 with respect to the temperature t [°C] of the sound-absorbing material, so that the sound-absorbing effect of the sound-absorbing material 10 can be sufficiently ensured during high-speed driving, and peeling or breakage of the sound-absorbing material 10 can be prevented at low temperatures.

[0042] In Fig. 2, a release layer 40 formed by applying or transferring a release agent is formed on the inner side in the tire radial direction of the tire inner surface Ts. The release layer 40 preferably contains a silicone-based composition. The silicone-based composition includes, for example, those containing a synthetic polymer compound having a main skeleton formed by siloxane bonds. That is, the sound-absorbing material 10, the sealant layer 20, the release layer 40, and the tire inner surface Ts (inner liner layer 9) are laminated in this order from the inner side in the tire radial direction.

[0043] In such a release layer 40 and sealant layer 20, the absolute value of the contact angle θ of water with respect to the release layer 40 10 and the absolute value of the contact angle θ of water with respect to the sealant layer 20 20 are preferably in the range of 90° to 120° respectively. The absolute value of the contact angle θ of the release layer 40 10 and the absolute value of the contact angle θ of the sealant layer 20 20 are approximate, and the absolute value of the difference in the contact angles θ 10 , θ 20 |θ 10 - θ 20 | is 30° or less. In particular, the absolute value of the difference |θ 10 - θ 20is preferably 20° or less, and more preferably 10° or less. The contact angle of water is an index of compatibility, and adherends with similar contact angles tend to have high adhesion. Therefore, the absolute value of the difference |θ 10 -θ 20 When | is small, the adhesiveness is high, so that the sealant layer 20 can be prevented from falling off or floating up during running, which is advantageous for the durability of the tire.

[0044] In the present invention, the contact angle θ of water 10 ,θ 20 is measured in accordance with JIS R3257. For example, a cut sample is cut out from a product tire along the tire width direction, and the contact angle θ of water between the release layer and the sealant layer on the cut sample is measured. 10 ,θ 20 Alternatively, the measurement can be performed using a sheet sample prepared by dismantling the inner surface of the tire and processing it into a sheet. Alternatively, a sheet prepared by processing the sealant into a certain thickness before application to the inner surface of the tire, or a rubber sheet to which the release agent used on the inner surface of the tire is attached may be used. Water is dropped onto each of the thus obtained release layer sample 51 and sealant layer sample 52, and the contact angle θ of the water droplet WD is measured. 10 ,θ 20 (See Fig. 8(a) and (b)). In Fig. 8, the contact angle θ 20 The contact angle θ 10 Although the contact angle θ 10 ,θ 20 The magnitude relationship is not limited to this.

[0045] In this way, the contact angle θ 10 and the contact angle θ of water with the sealant layer 20 20 Absolute value of difference |θ 10 -θ 20 By setting | in a specific range (30° or less), it is possible to improve the compatibility. This makes it possible to increase the adhesion between the tire inner surface Ts and the sealant layer 20 and improve the durability of the tire. Here, the absolute value of the difference |θ 10 -θ 20When | is more than 30°, since the release layer 40 and the sealant layer 20 are less likely to fit well, the adhesiveness between the two decreases, and the durability of the tire tends to decrease.

[0046] In the pneumatic tire described above, it is preferable that the thickness g (see FIG. 2) of the release layer 40 is in the range of 0.1 μm to 100.0 μm. By appropriately setting the thickness g of the release layer 40 in this way, the durability of the tire can be effectively improved. Here, when the thickness g of the release layer 40 is less than 0.1 μm, it becomes difficult to fit well with the sealant layer 20, and the durability of the tire deteriorates. Conversely, when it is greater than 100.0 μm, when the tire is deformed and applied to the release layer 40, the deformation of the release layer 40 becomes remarkable, the destruction of the release layer 40 is promoted, and the sealant layer 20 may fall off. The thickness g of the release layer 40 is the average thickness. Such a thickness g of the release layer 40 can be detected, for example, using an electron microscope. When measuring the thickness g of the release layer 40 with an electron microscope, a cut sample cut out along the tire width direction is used, and the thicknesses at a plurality of locations (for example, 4 locations in the tire circumferential direction and 3 locations in the tire width direction) in the cut sample are measured, and the thickness g of the release layer 40 can be calculated by averaging the measured values measured at these plurality of locations.

[0047] In the pneumatic tire described above, as shown in FIG. 2, it is preferable that the distance (shortest distance) L from the belt layer 7 to the sealant layer 20 is 10 mm or less at all locations of the belt layer 7 located at the innermost side in the tire radial direction. Thereby, when a foreign object such as a nail penetrates the tread portion 1, the sealant easily flows to the belt layer 7, so that good puncture sealing performance can be ensured. If there is a portion where the distance L from the belt layer 7 to the sealant layer 20 is greater than 10 mm, the puncture sealing performance at that portion may be insufficient.

[0048] Further, it is preferable that the center position of the sealant layer 20 in the tire width direction coincides with the tire equator, but the center position may be shifted toward either one side in the tire width direction from the tire equator. The distance in the tire width direction between the center position of the sealant layer 20 in the tire width direction and the tire equator is preferably 10 mm or less, more preferably 5 mm or less. Thereby, the sealant layer 20 does not adversely affect the balance of the tire.

[0049] Also, the thickness S (see FIG. 2) of the sealant layer 20 is preferably in the range of 2.0 mm to 5.0 mm. Thereby, in addition to the shoulder portion, puncture sealing performance at the center portion can be sufficiently ensured. Here, if the thickness S of the sealant layer 20 is less than 2.0 mm, the puncture sealing performance deteriorates. Conversely, if it is greater than 5.0 mm, the sealant layer 20 flows due to the centrifugal force of the tire, and the balance of the tire during running deteriorates. The thickness S of the sealant layer 20 is the overall average thickness. Such an average thickness of the sealant layer 20 can be calculated, for example, by photographing the tire meridian cross section at 8 locations on the tire circumference by CT scan, and measuring the thickness of the sealant layer 20 at 5 points in each of the photographed images, namely, the tire equator position, the outer edge positions (both sides) 10 mm inward in the tire width direction from the ends of the sealant layer 20, and the intermediate positions (both sides) between the tire equator position and the outer edge positions, and then calculating from the measured values at a total of 40 points.

Example

[0050] In a pneumatic tire having a tire size of 255 / 45R19 and including a tread portion, a pair of sidewall portions, and a pair of bead portions, a strip-shaped sound absorbing material is attached along the tire circumferential direction to the inner surface of the tread portion. The sound absorbing material has a missing portion at one location in the tire circumferential direction. A sealant layer is formed along the tire circumferential direction on the inner surface of the tire. The sound absorbing material is fixed to the inner surface of the tire by the sealant layer. The calculation result according to formula (1), the length A of the missing portion, the absolute value of the difference in glass transition temperature between the sealant and the sound absorbing material, the glass transition temperature of the sealant, the glass transition temperature of the sound absorbing material, the type of the sealant, the contact angle θ 10 , θ 20The absolute value of the difference, the distance L, was set as shown in Table 1, and tires of a conventional example and Examples 1 to 6 were manufactured.

[0051] In the conventional example and Examples 1 to 6, the rim diameter RD was 19 [inch] × 25.4 [mm] = 482.6 [mm], the outer diameter OD of the tire was 255 [mm] × 0.45 × 2 + 19 [inch] × 25.4 [mm] = 712.1 [mm], the total thickness Ga of the tire was 15 [mm], the density d of the sound-absorbing material was 23 [kg / m 3 , the width w of the sound-absorbing material was 180 [mm], the thickness u of the sound-absorbing material was 30 [mm], and the calculation result by the formula (1) using these various dimensions was 114 [mm].

[0052] For these test tires, durability, tire balance, and puncture sealing performance were evaluated by the following test methods, and the results are shown in Table 1 together.

[0053] Durability: Each test tire was assembled to a wheel with a rim size of 19 × 8.5J, and after a running test was carried out on a drum tester under the conditions of an air pressure of 120 kPa, 100% of the maximum load, a running speed of 80 km, and a running distance of 6000 km, the state of the sealant layer was visually confirmed. The evaluation result is indicated as "◎ (excellent)" when there is no lifting in the sealant layer and the sealant function can be exerted, and as "○ (good)" when there is a slight lifting in the sealant layer but the sealant function can be exerted.

[0054] Tire balance: Each test tire was assembled to a wheel with a rim size of 19 × 8.5J, and after filling the tire with air so that the internal pressure of the tire became 230 kPa, it was attached to a balancer tester, and the mass of the weight (counterweight) required to take the static balance was measured. The evaluation result is indicated as "〇 (good)" when it is within the range of ±5 g compared to the case without the sound-absorbing material, and as "× (not acceptable)" when it is more than +5 g and 10 g or less compared to the case without the sound-absorbing material.

[0055] Puncture sealing performance: Each test tire was assembled onto a wheel with a rim size of 19×8.5J and mounted on a vehicle with a displacement of 2400 cc. The initial air pressure was set at 230 kPa. A nail with a diameter of 5 mm was driven into the center of the tread portion, and after driving for 10 km, the tire was left for 24 hours with the nail removed, and the air pressure was measured again. The evaluation results were indicated as "◎ (excellent)" when the air pressure was 210 kPa or more, "〇 (good)" when the air pressure was 190 kPa or more and less than 210 kPa, and "△ (fair)" when the air pressure was less than 190 kPa.

[0056]

Table 1

[0057] As can be seen from Table 1, the pneumatic tires of Examples 1 to 6 had improved tire balance compared to the conventional example.

[0058] This disclosure includes the following inventions [1] to

[12] . Invention [1] is a pneumatic tire including a tread portion extending in the tire circumferential direction to form an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed on the inner side in the tire radial direction of these sidewall portions. In the pneumatic tire, a strip-shaped sound-absorbing material is attached along the tire inner surface in the tread portion in the tire circumferential direction, the sound-absorbing material has a missing portion at one location in the tire circumferential direction, and the length A [mm] of the missing portion in the tire circumferential direction, the rim diameter RD [mm], the outer diameter OD [mm] of the tire, the total thickness Ga [mm] of the tire, the density d [kg / m 3 of the sound-absorbing material, the width w [mm] of the sound-absorbing material, and the thickness u [mm] of the sound-absorbing material satisfy the following formula (1). The pneumatic tire is characterized by this.

Equation

[10] is a pneumatic tire according to any one of inventions [2], [3], [5], [7] to [9], characterized in that at all locations of the belt layer located at the innermost side in the tire radial direction, the distance L from the belt layer to the sealant layer is 10 mm or less. The invention

[11] is a pneumatic tire according to any one of inventions [2], [3], [5], [7] to

[10] , characterized in that the distance in the tire width direction between the center position in the width direction of the sealant layer and the tire equator is 10 mm or less. The invention

[12] is a method for manufacturing a pneumatic tire according to any one of inventions [7] to [9], wherein after manufacturing a pneumatic tire excluding the sound-absorbing material and the sealant layer, when forming the sealant layer by applying a sealant to the inner surface of the tire in the tread portion, the temperature of the sealant applied to the inner surface of the tire is set to 70°C or less, and a sound-absorbing material is installed along the tire circumferential direction on the inner side in the tire radial direction of the sealant layer.

Explanation of reference numerals

[0059] 1 Tread portion 2 Sidewall portion 3 Bead portion 4 Carcass layer 5 Bead core 6 Bead filler 7 Belt layer 10 Sound-absorbing material 11 Missing portion 20 Sealant layer 40 Release layer Ts Inner surface of the tire

Claims

1. In a pneumatic tire comprising a tread portion extending in the tire circumferential direction and having an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed on the inner side in the tire radial direction of these sidewall portions, A strip-shaped sound-absorbing material is attached along the tire circumferential direction to the inner surface of the tire in the tread portion, the sound-absorbing material has a missing portion at one location in the tire circumferential direction, and the length A [mm] of the missing portion in the tire circumferential direction, the rim diameter RD [mm], the outer diameter OD [mm] of the tire, the total thickness Ga [mm] of the tire, and the density d [kg / m 3 of the sound-absorbing material, the width w [mm] of the sound-absorbing material, and the thickness u [mm] of the sound-absorbing material satisfy the following formula (1). A pneumatic tire characterized by this. 【Number 1】

2. The pneumatic tire according to claim 1, wherein a sealant layer is formed along the tire circumferential direction on the inner surface of the tire, and the sound absorbing material is fixed to the inner surface of the tire by the sealant layer.

3. The pneumatic tire according to claim 2, wherein the absolute value of the difference between the glass transition temperature of the sealant of the sealant layer and the glass transition temperature of the sound absorbing material is 60° C. or less.

4. The pneumatic tire according to any one of claims 1 to 3, wherein the ratio A / mm of the length A [mm] in the tire circumferential direction of the missing portion to the thickness u [mm] of the sound absorbing material is in the range of 0.5 to 6.

0.

5. The pneumatic tire according to claim 2 or 3, wherein the glass transition temperature of the sealant of the sealant layer is equal to or lower than the glass transition temperature of the sound absorbing material, and the glass transition temperature of the sound absorbing material is in the range of -60° C. to -40° C.

6. The pneumatic tire according to any one of claims 1 to 3, wherein when the temperature t [° C.] of the sound absorbing material is at least in the range of -20° C. to 80° C., the elongation at break y [%] of the sound absorbing material satisfies the relationship of y ≧ t + 100 and y ≦ 2t + 440 with respect to the temperature t [° C.] of the sound absorbing material.

7. The pneumatic tire according to claim 2 or 3, wherein the sealant of the sealant layer is composed of a silicone-based composition.

8. The pneumatic tire according to claim 7, having a release layer containing a silicone-based composition on the inner surface of the tire, wherein the sealant layer is formed on the inner side in the tire radial direction of the release layer in the tread portion, and the absolute value of the difference between the contact angle of water with respect to the release layer and the contact angle of water with respect to the sealant layer is 30° or less.

9. The pneumatic tire according to claim 7, wherein the silicone-based composition constituting the sealant of the sealant layer is a two-component curable silicone.

10. The pneumatic tire according to claim 2 or 3, wherein at all locations of the belt layer located at the innermost side in the tire radial direction, the distance L from the belt layer to the sealant layer is 10 mm or less.

11. The pneumatic tire according to claim 2 or 3, wherein a distance in the tire width direction between a center position in the width direction of the sealant layer and the tire equator is 10 mm or less.

12. A method for manufacturing a pneumatic tire according to claim 7, comprising: After manufacturing a pneumatic tire excluding the sound-absorbing material and the sealant layer, When forming the sealant layer by applying a sealant to the inner surface of the tire in the tread portion, the temperature of the sealant applied to the inner surface of the tire is set to 70° C. or less, and a sound-absorbing material is installed along the tire circumferential direction on the inner side in the tire radial direction of the sealant layer. A method for manufacturing a pneumatic tire, characterized in that.

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