JP2018095048A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire that comprises a buffer layer in an inner surface of the tire and can prevent a side part from being damaged without deteriorating mass of the tire and rolling resistance.SOLUTION: A buffer layer 10 existing over the whole circumference of a tire inside a carcass layer 4 is locally formed in a tire side region S of at least one side wall part 2, where at least part of the buffer layer 10 is constituted of foam rubber and hardness of the layer is set to 15 or more and less than 80. A thickness G1 from an innermost surface of the carcass layer 4 to an innermost surface of the buffer layer 10 in an area in which the buffer layer 10 is formed is set larger than a thickness G2 from the innermost surface of the carcass layer 4 to an innermost surface of the tire in an area other than the area in which the buffer layer 10 is formed, and the thickness G1 is set to 1.0 mm-8.0 mm.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pneumatic tire provided with a buffer layer on the inner surface of the tire, and more particularly to a pneumatic tire that can prevent damage to a side portion without deteriorating the tire mass and rolling resistance.

  When a pneumatic tire rides on an obstacle on a road surface with a certain size such as a curb or a chatter bar (hereinafter referred to as “curbstone”), the side wall portion deforms and the curbstone and the rim flange It is known that there is a failure that causes a puncture due to damage (side cut). Such a failure is difficult to occur if, for example, the rubber thickness of the sidewall portion is large, but in recent years, there has been a strong demand for reduction in tire mass and rolling resistance in order to further improve tire performance. Measures other than increasing the demand are required.

  For example, in Patent Document 1, when a tire rides on a curbstone or the like, a plurality of protrusions that function as cushions that reduce impact and avoid extreme deformation of the sidewall portion are provided on the inner surface of the sidewall portion. Has proposed. However, even with such projections, side cuts cannot always be prevented, and it is difficult to keep the tire mass and rolling resistance sufficiently low depending on the number and material of the projections. It has been.

JP 2005-014809 A

  An object of the present invention is to provide a pneumatic tire provided with a buffer layer on the inner surface of the tire, which can prevent damage to the side portion without deteriorating the tire mass and rolling resistance. There is.

  In order to achieve the above object, a pneumatic tire according to the present invention includes a tread portion that extends in the tire circumferential direction to form an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and the sidewall portions. A pair of bead portions disposed on the inner side in the tire radial direction, a carcass layer mounted between the pair of bead portions, and a plurality of belts disposed on an outer peripheral side of the carcass layer in the tread portion In a pneumatic tire having a layer, a rim flange radially outer end when the rim is assembled with a perpendicular line L1 extending from a tire width direction outermost end portion of the belt layer to a tire inner surface in each of the pair of sidewall portions. When the region between the position L2 corresponding to the portion is a tire side region S, the tie of at least one sidewall portion of the pair of sidewall portions is selected. In the side region S, there is locally provided a buffer layer that exists inside the carcass layer over the entire circumference of the tire, and the buffer layer is at least partially made of foam rubber and has a hardness of 15 or more and less than 80. The thickness G1 from the innermost surface of the carcass layer to the innermost surface of the buffer layer in the region where the buffer layer is provided is the thickness from the innermost surface of the carcass layer to the innermost surface of the tire in the region where the buffer layer is not provided. It is larger than G2, and the thickness G1 is 1.0 mm to 8.0 mm.

  In the present invention, a moderately flexible buffer layer made of foam rubber and having the above-mentioned hardness is disposed at the above-mentioned position, so when the tire rides on a curb stone, etc. It can be avoided that the sidewall portion is strongly sandwiched between the curbstone and the rim flange, and the side cut can be effectively prevented. At this time, in addition to the buffer layer being made of foamed rubber having a specific gravity (weight per unit volume) smaller than that of non-foamed rubber, the rubber gauge inside the carcass layer ( Since the thickness G1) is set in the above-mentioned range, the tire weight can be maintained without being greatly increased or the rolling resistance is not deteriorated. The “hardness” in the present invention is a hardness (so-called JIS-A hardness) measured at a temperature of 20 ° C. by a durometer type A in accordance with JIS K6253. In the case of foamed rubber, it is not the hardness of the raw rubber in a non-foamed state but the hardness as a foam.

  In the present invention, it is preferable that the buffer layer is provided at a portion other than the tire maximum width position P in the tire side region S. In this way, by using a buffer layer that avoids parts that are unlikely to be damaged when riding on a curb or the like (tire maximum width position P), the amount of use of the buffer layer can be suppressed, and side cuts can be made. An increase in tire weight can be suppressed while reliably preventing. In addition, since the tire maximum width position P is a portion that is largely deformed when the tire rolls, by avoiding this, deterioration of rolling resistance can be effectively avoided.

  In the present invention, when the distance along the tire radial direction from the position L2 to the tire maximum width position P is a vertical distance H, the buffer layer is provided in a region from the position L2 to 70% of the vertical distance H. It can also be. In this specification, since the buffer layer can be provided in a limited area that is easily damaged, it is possible to effectively prevent deterioration of tire weight and rolling resistance while reliably preventing side cuts.

  Alternatively, when the rim protect portion is provided on the outer surface of the sidewall portion, the specification may be such that the buffer layer is provided between the perpendicular L1 and the tire maximum width position P. In this specification, a cushioning layer can be provided in a limited area in a tire with a rim protector, so that the tire weight and rolling resistance can be effectively prevented while reliably preventing side cuts. Can be prevented.

  In the present invention, the minimum value of the thickness g1 from the outermost surface of the carcass layer in the tire side region S to the outer surface of the sidewall portion is preferably 0.5 mm to 2.0 mm. By limiting the thickness of the sidewall portion in this way, it is advantageous to keep the tire weight and rolling resistance low.

  In the present invention, the buffer layer is preferably exposed to the tire lumen. Thereby, since the buffer layer functioning as a cushion can directly contact the inner surface of the tire and other portions of the buffer layer when the tire is deformed, it is advantageous for preventing side cuts.

  In the present invention, the buffer layer preferably has a specific gravity of 0.1 to 1.1. By keeping the specific gravity of the buffer layer in an appropriate range as described above, the weight of the buffer layer can be suppressed while obtaining an appropriate strength as the buffer layer, and the side cut can be prevented and the tire weight and the rolling resistance can be maintained. It is advantageous to achieve both balances.

  In the present invention, it is preferable that at least a part of the buffer layer is made of foamed rubber composed of closed cells. Thus, by making the bubbles contained in the foamed rubber constituting the buffer layer into closed cells, the buffer layer can be prevented from becoming excessively flexible, and an appropriate strength can be obtained as the buffer layer. It is advantageous to prevent.

  In the present invention, the thickness G3 of the buffer layer is preferably 0.5 mm to 5.0 mm. Thus, by setting the thickness of the buffer layer itself within an appropriate range, it is advantageous to achieve both a balance between prevention of side cuts and maintenance of tire weight and rolling resistance.

  As a method of manufacturing a pneumatic tire for manufacturing the pneumatic tire according to the present invention, an unvulcanized buffer layer is attached to the innermost surface of an unvulcanized pneumatic tire, and then a vulcanized bladder is used to form the unvulcanized bladder. When producing a pneumatic tire by vulcanizing in contact with the buffer layer, the unvulcanized buffer layer is generated during vulcanization in the region of the vulcanization bladder in contact with at least the unvulcanized buffer layer. It is preferable to form irregularities for releasing the gas and perform vulcanization using this vulcanization bladder. By adopting such a manufacturing method, vulcanization failure can be prevented, and in the pneumatic tire obtained by this manufacturing method, excellent performance as a pneumatic tire having the above-described buffer layer (side It is possible to prevent cutting and maintain tire weight and rolling resistance).

  In the present invention, the various dimensions of the tire are measured in a state in which the tire is assembled on the regular rim and filled with the regular internal pressure. The tire maximum width position P is a position in the tire radial direction where the tire width is maximum in this state. The “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based, for example, a standard rim for JATMA, “Design Rim” for TRA, or ETRTO. Then, “Measuring Rim” is set. “Regular internal pressure” is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. The maximum air pressure is JATMA, and the table “TIRE ROAD LIMITS AT VARIOUS” is TRA. The maximum value described in “COLD INFRATION PRESURES”, “INFLATION PRESURE” if it is ETRTO, but if the tire is a new tire, the air pressure displayed on the vehicle is used. “Regular load” is a load determined by each standard for each tire in the standard system including the standard on which the tire is based. If JATA is the maximum load capacity, TRA will be the table “TIRE ROAD LIMITS AT”. If it is ETRTO, the maximum value described in “VARIOUS COLD INFRATION PRESURES” is “LOAD CAPACITY”.

It is a meridian half section view showing a pneumatic tire according to an embodiment of the present invention. It is explanatory drawing which shows typically a deformation | transformation state when the pneumatic tire of this invention rides on a curbstone etc. It is a meridian half section view of the pneumatic tire which consists of another embodiment of the present invention. It is a meridian half section view of the pneumatic tire which consists of another embodiment of the present invention. It is a meridian half section view of the pneumatic tire which consists of another embodiment of the present invention. It is a meridian half section view of the pneumatic tire which consists of another embodiment of the present invention. It is a meridian half section view of the pneumatic tire which consists of another embodiment of the present invention. It is a meridian half section view of the pneumatic tire which consists of another embodiment of the present invention. It is a meridian half section view of the pneumatic tire which consists of another embodiment of the present invention. It is a meridian half section view of the pneumatic tire which consists of another embodiment of the present invention. It is a meridian half section view of the pneumatic tire which consists of another embodiment of the present invention. It is a meridian half section view of the pneumatic tire which consists of another embodiment of the present invention. It is explanatory drawing which expand | deploys and shows a part of pneumatic tire which consists of another embodiment of this invention.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.

  As shown in FIG. 1, the pneumatic tire of the present invention includes a tread portion 1 that extends in the tire circumferential direction and has an annular shape, a pair of sidewall portions 2 that are disposed on both sides of the tread portion 1, And a pair of bead portions 3 disposed inside the wall portion 2 in the tire radial direction. In FIG. 1, CL indicates a tire equator.

  A carcass layer 4 (one layer in the example of FIG. 1) is mounted between the pair of left and right bead portions 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction, and is folded back around the bead core 5 disposed in each bead portion 3 from the vehicle inner side to the outer side. A bead filler 6 is disposed on the outer periphery of the bead core 5, and the bead filler 6 is wrapped by the main body portion and the folded portion of the carcass layer 4. A plurality of layers (two layers in the example of FIG. 1) of belt layers 7 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. Each belt layer 7 includes a plurality of reinforcing cords that are inclined with respect to the tire circumferential direction, and is disposed so that the reinforcing cords cross each other between the layers. In these belt layers 7, the inclination angle of the reinforcing cord with respect to the tire circumferential direction is set in a range of, for example, 10 ° to 40 °. A plurality of belt cover layers 8 (a pair of belt cover layers 8 that locally cover both ends of the belt layer 7 in the example of FIG. 1) are provided on the outer peripheral side of the belt layer 7. The belt cover layer 8 includes an organic fiber cord oriented in the tire circumferential direction, and the organic fiber cord has an angle of, for example, 0 ° to 5 ° with respect to the tire circumferential direction.

  An inner liner layer 9 is provided inside the carcass layer 4. The inner liner layer 9 includes a rubber composition mainly composed of butyl rubber having air permeation prevention performance, a resin having air permeation prevention performance, etc. (thermoplastic resin or thermoplastic elastomer composition in which an elastomer is dispersed in a thermoplastic resin). The air filled in the tire is prevented from permeating out of the tire.

  In the present invention, a buffer layer 10 is provided on the inner surface of the sidewall portion 2 of such a general pneumatic tire as described later. Therefore, the basic cross-sectional structure of the pneumatic tire excluding the buffer layer 10 is not limited to the above-described structure.

  In the present invention, the buffer layer 10 is locally provided inside the carcass layer 4 in the tire side region S of the sidewall portion 2. As shown in the figure, the side region S is a perpendicular line L1 extending from the outermost end portion in the tire width direction of the belt layer 7 to the tire inner surface in each sidewall portion 2 and the radially outer end of the rim flange when the rim is assembled. It is an area between the position L2 corresponding to the part. The buffer layer 10 is at least partially made of foam rubber and has a hardness of 15 or more and less than 80. Further, by providing the buffer layer 10 in this manner, the thickness G1 from the innermost surface of the carcass layer 4 to the innermost surface of the buffer layer 10 in the region where the buffer layer 10 is provided is equal to the carcass in the region where the buffer layer 10 is not provided. It is larger than the thickness G2 from the innermost surface of the layer 4 to the innermost surface of the tire, and the thickness G1 is set to 1.0 mm to 8.0 mm.

  By providing the buffer layer 10 that is made of foamed rubber and has the above-mentioned hardness and having an appropriate flexibility, when the tire rides on a curb or the like and the tire (sidewall portion 2) is deformed, FIG. Since the buffer layer 10 is interposed as shown in FIG. 2, it is possible to mitigate the impact and avoid that the side wall 2 is strongly sandwiched between the curbstone and the rim flange, thereby effectively preventing the side cut. can do. At this time, in addition to the buffer layer 10 being made of foamed rubber having a specific gravity (weight per unit volume) smaller than that of the non-foamed rubber, the region inside the carcass layer is also provided in the region where the buffer layer 10 is provided. Since the rubber gauge (thickness G1) is set in the above range, the tire weight can be maintained without significantly increasing the rolling resistance or the rolling resistance.

  If the hardness of the buffer layer 10 is less than 15, the buffer layer 10 is too soft, so that the inner surface of the deformed sidewall portion 2 cannot be sufficiently protected, and the side cut cannot be sufficiently prevented. If the buffer layer 10 has a hardness of 80 or more, the buffer layer 10 is too hard, so that deformation of the tire (sidewall portion 2) during running may be hindered, and the running performance of the tire may be adversely affected. The hardness of the buffer layer 10 is preferably 16 to 80, more preferably 17 to 70, still more preferably 18 to 60, and most preferably 20 to 50.

  If the thickness G1 is smaller than 1.0 mm, the buffer layer 10 is too thin, so that the effect of providing the buffer layer 10 is hardly obtained. If the thickness G1 is greater than 8.0 mm, the entire sidewall portion 2 including the buffer layer 10 is too thick, so that deformation of the tire during running (sidewall portion 2) is hindered, resulting in tire running performance. There is a risk of adverse effects. The thickness G1 of the buffer layer 10 is preferably 1.2 mm to 7.5 mm, more preferably 1.4 mm to 7.0 mm, still more preferably 1.5 mm to 6.5 mm, and most preferably 1.6 mm to 6.mm. It is better to set it to 0 mm.

  In setting the thickness G1 within the above range, the thickness G3 of the buffer layer 10 itself is preferably set within a range of 0.5 mm to 5.0 mm, more preferably 0.8 mm to 3.5 mm. As described above, the thickness G3 of the buffer layer 10 itself is also set to an appropriate range, which is advantageous in achieving both balanced prevention of side cut and maintenance of tire weight and rolling resistance. If the thickness G3 is smaller than 0.5 mm, the buffer layer 10 is too thin, which is substantially equivalent to the absence of the buffer layer 10, and the effect of providing the buffer layer 10 is hardly obtained. When the thickness G3 is larger than 5.0 mm, the striking layer 10 becomes bulky, and deformation of the tire (sidewall portion 2) during travel is hindered, which may adversely affect the travel performance of the tire.

  The minimum value of the thickness g1 from the outermost surface of the carcass layer 4 to the outer surface of the sidewall portion 2 in the tire side region S is, for example, 0.5 mm to 2 with respect to the thickness G1 and the thickness G3 described above. It is preferable to set to 0.0 mm. By limiting the thickness of the sidewall portion 2 in this way, it is advantageous to keep the tire weight and rolling resistance low. If the thickness g1 is smaller than 0.5 mm, the distance from the outer surface of the sidewall portion 2 to the carcass layer 4 is too small, and it becomes difficult to sufficiently maintain the durability of the tire. When the thickness g1 is larger than 2.0 mm, the sidewall portion 2 becomes too thick, so that it is difficult to keep the tire weight and rolling resistance low.

  Although the buffer layer 10 preferably has the above-described hardness, the specific gravity of the buffer layer 10 is preferably in the range of 0.1 to 1.1, more preferably 0.2 to 1.0. By keeping the specific gravity of the buffer layer 10 in an appropriate range as described above, the weight of the buffer layer 10 can be suppressed while obtaining an appropriate strength as the buffer layer 10, and the side cut can be prevented and the tire weight and rolling resistance can be reduced. It is advantageous to achieve both maintenance and balance. If the specific gravity of the buffer layer 10 is smaller than 0.1, it will be difficult to obtain sufficient strength as the buffer layer 10, and it will be difficult to effectively prevent side cuts. When the specific gravity of the buffer layer 10 is larger than 1.1, the weight increase due to the use of the buffer layer 10 becomes more significant than the amount (volume) of use of the buffer layer 10, preventing side cuts, tire weight and rolling. It becomes difficult to balance the maintenance of resistance in a balanced manner.

  As described above, the buffer layer 10 is made of foamed rubber, but is preferably made of foamed rubber composed of at least a part of closed cells. Moreover, it is preferable that the foaming rate of foamed rubber is 1.5 times-4.0 times, for example. The elastic modulus of the foamed rubber is preferably set so that the stress at a strain of 50% is 0.2 MPa to 0.45 MPa, for example. Thus, by using foamed rubber composed of closed cells or foamed rubber having a specific foaming rate or elastic modulus, the buffer layer 10 can be prevented from becoming excessively flexible, and an appropriate strength can be obtained as the buffer layer 10. This is advantageous for preventing side cuts.

  As the foam rubber constituting the buffer layer 10, for example, a predetermined amount of a chemical foaming agent described later is blended in a rubber composition containing 40 parts by weight or more of butyl rubber and / or halogenated butyl rubber with respect to 100 parts by weight of the rubber component. A foamed rubber obtained by foaming this chemical foaming agent during vulcanization can be used. Examples of the halogenated butyl rubber include chlorinated butyl rubber (Cl-IIR) and brominated butyl rubber (Br-IIR). By containing 40 parts by weight or more of butyl rubber and / or butyl halide, it is possible to efficiently foam by a gas generated from a foaming agent during vulcanization and obtain a low specific gravity rubber. Rubbers other than butyl rubber and / or halogenated butyl are not particularly limited. For example, natural rubber (NR), isoprene rubber (IR), styrene butadiene rubber (SBR), butadiene rubber (BR), acrylonitrile butadiene rubber (NBR), chloroprene. A rubber (CR) etc. can be illustrated and these can be used individually or as arbitrary blends. Also, olefin rubbers such as ethylene propylene diene rubber (EPDM), styrene isoprene rubber, styrene isoprene butadiene rubber, isoprene butadiene rubber and the like can be blended. Among the rubber compositions described above, it is preferable to use natural rubber, styrene butadiene rubber, butadiene rubber, or butyl rubber as the diene rubber. In particular, in order to increase the tensile breaking strength of the rubber composition and the adhesion to the inner liner layer, the natural rubber is preferably contained in an amount of 10% by mass or more, more preferably 20% by mass.

  Examples of the chemical foaming agent include a carbonamide foaming agent, a nitroso foaming agent, a sulfonyl hydrazide foaming agent, an azo foaming agent, and an azide foaming agent. Among these, it is preferable to use at least one selected from a carbonamide foaming agent, a nitroso foaming agent, and a sulfonylhydrazine foaming agent. A physical foaming agent (foamable microcapsule or the like) is not suitable for use as the buffer layer 10 of the present invention because the foamed rubber obtained has a significantly increased hardness. Azodicarbonamide (ADCA) or the like as the carbonodiamide foaming agent, N, N′-dinitrosopentamethylenetetramine (DPT), N, N′-dimethyl-N, N′-dinitrosotephthale as the nitroso foaming agent An amide etc. can be illustrated. Examples of the sulfonyl hydrazide-based blowing agent include benzenesulfonyl hydrazide (BSH), p, p′-oxybis (benzenesulfonyl hydrazide) (OBSH), toluenesulfonyl hydrazide (TSH), diphenylsulfone-3,3′-disulfonyl hydrazide, and the like. It can be illustrated. Examples of the azo foaming agent include azobisisobutyronitrile (AZBN), azobiscyclohexylnitrile, azodiaminobenzene, barium azodicarboxylate, and the like. Examples of the azide-based blowing agent include calcium azide, 4,4'-diphenyldisulfonyl azide, p-toluenesulfonyl azide and the like. These chemical foaming agents can be used alone or in admixture of two or more.

  In using the above-mentioned chemical foaming agent, it is preferable to add a urea-based foaming aid to the rubber composition. By blending the urea foaming aid, the temperature at which the chemical foaming agent is thermally decomposed can be adjusted to be low, and a foamed rubber suitable for use as the buffer layer 10 can be obtained.

  The foamed rubber constituting the buffer layer 10 includes a vulcanizing agent, a vulcanization accelerator, a vulcanization aid, a rubber reinforcing agent, a softening agent (plasticizer), an anti-aging agent, a processing aid, a defoaming agent, an activator, Compounding agents usually used for industrial rubber compositions and foamed rubber molded articles such as mold release agents, heat stabilizers, weathering stabilizers, antistatic agents, colorants, lubricants, thickeners, etc. can be added. . These compounding agents can be used in the usual compounding amounts as long as they do not contradict the object of the present invention, and can be added, kneaded or mixed by a usual preparation method.

  The buffer layer 10 may be provided by adhering foamed rubber foamed in advance to the tire inner surface. However, the buffer layer 10 is vulcanized by attaching an unvulcanized buffer layer to the innermost surface of the unvulcanized pneumatic tire. It may be provided. In the latter case, gas is generated from the buffer layer 10 by the foaming agent as described above. However, since the buffer layer 10 is vulcanized between the vulcanization bladder and the inner liner having excellent gas barrier properties, the generated gas is released. It is preferable to take measures for this. Specifically, after pasting an unvulcanized buffer layer on the innermost surface of an unvulcanized pneumatic tire, the vulcanization bladder is brought into contact with the unvulcanized buffer layer and vulcanized. When manufacturing a pneumatic tire, the vulcanization bladder is formed with irregularities for escaping gas generated from the unvulcanized buffer layer at the time of vulcanization in an area in contact with at least the unvulcanized buffer layer of the vulcanization bladder. It is preferable to perform vulcanization using By adopting such a production method, vulcanization failure can be prevented, and in the pneumatic tire obtained by this production method, excellent performance as a pneumatic tire provided with the buffer layer 10 described above ( Side cut prevention and maintenance of tire weight and rolling resistance) can be achieved.

  When the sidewall portion 2 is deformed as shown in FIG. 2, the buffer layer 10 comes into contact with the tire inner surface, another portion of the buffer layer 10, or the buffer layer 10 to be paired. As described above, the surface layer of the buffer layer 10 exposed to the tire lumen is preferably a layer having no air bubbles (skin layer). Thereby, the intensity | strength of the surface layer of the buffer layer 10 contact | abutted with another site | part can be raised, and it becomes advantageous in preventing a side cut.

  Although the buffer layer 10 is provided inside the carcass layer 4 as described above, it is particularly preferable to provide the buffer layer 10 so as to be exposed to the tire lumen. As described above, when the buffer layer 10 is exposed in the tire lumen, if the buffer layer 10 has an air barrier property, the inner liner 9 is unnecessary in the portion where the buffer layer 10 is provided, and this is omitted. It becomes possible.

  The buffer layer 10 may be provided in any manner as long as it is within the tire side region S. For example, as shown in FIG. 1, the tire side region S may be provided so as to cover substantially the entire region of the tire side region S from the end portion on the bead portion 3 side to the end portion on the tread portion 1 side. Or as shown in FIG. 3, you may arrange | position limitedly to a part of tire side area | region S (Bead part 3 side from the tire maximum width position P in the example of illustration). Alternatively, as shown in FIG. 4, a pair of buffer layers 10 may be provided on the tread portion 1 side and the bead portion 3 side with respect to the tire maximum width position P. In any case, as shown in FIG. 2, when the sidewall portion 2 is deformed, the buffer layer 10 is interposed on the tire inner surface of the portion sandwiched between the curbstone and the rim flange. The side cut can be prevented by avoiding that the portion 2 is strongly sandwiched between the curbstone and the rim flange.

  In particular, as shown in FIGS. 3 and 4, when the buffer layer 10 is provided to avoid the tire maximum width position P in the tire side region S, the amount of use of the buffer layer can be suppressed, and an increase in tire weight is suppressed. can do. That is, as shown in FIG. 2, when the tire rides on a curb or the like, the tire maximum width position P or the vicinity thereof becomes a bending point, and it is difficult to be crushed by the curb and the rim flange, and the side cut is difficult to occur. The layer 10 is not necessarily provided. On the other hand, since the tire maximum width position P is the place where the deformation at the time of rolling of the tire is the largest, if the rubber thickness increases or an additional member such as the buffer layer 10 is attached, the tire will roll. Resistance may be adversely affected. For this reason, providing the buffer layer 10 at a portion other than the tire maximum width position P in the tire side region S is advantageous in preventing side cuts and maintaining rolling resistance.

  As shown in FIG. 3, when the buffer layer 10 is provided in a part of the tire side region S (bead part 3 side with respect to the tire maximum width position P), it extends along the tire radial direction from the position L2 to the tire maximum width position P. The buffer layer 10 is preferably provided in a region from the position L2 to 70% of the vertical distance H with respect to the distance (vertical distance H). By disposing the buffer layer 10 at this position, the buffer layer 10 can be provided in a limited area that is easily damaged, so that the tire weight and rolling resistance are effectively deteriorated while reliably preventing side cuts. Can be prevented.

  Of course, contrary to the example of FIG. 3, the buffer layer 10 may be provided on the tread portion 1 side with respect to the tire maximum width position P. In particular, as shown in FIG. 5, a rim protect portion 20 (a thick portion for preventing the rim R from being damaged when the tire rides on a curbstone or the like) is provided on the outer surface of the sidewall portion 2. In this case, it is preferable to provide the buffer layer 10 between the perpendicular L1 and the tire maximum width position P (on the tread portion 1 side with respect to the tire maximum width position P). Since the rim protect portion 20 is provided to reinforce the bead portion 3 side with respect to the tire maximum width position P, the buffer layer 10 is limited to a region susceptible to damage in the tire including the rim protect portion 20. It can be provided, and deterioration of tire weight and rolling resistance can be effectively prevented while reliably preventing side cuts.

  From the above viewpoint, as shown in FIG. 6, the buffer layer 10 is provided so as to cover substantially the entire region of the tire side region S from the end portion on the bead portion 3 side of the tire side region S to the end portion on the tread portion 1 side. In addition, the thickness of the buffer layer 10 may decrease toward the tire maximum width position P.

  The arrangement of the buffer layer 10 may be determined by the structure of the bead filler 6 and / or the carcass layer 4. That is, side cuts are likely to occur depending on the structure of the bead filler 6 (particularly, the position of the outer end in the tire radial direction of the bead filler 6) and the structure of the carcass layer 4 (particularly, the number of carcass layers 4 and the position of the folded end). Since the position changes, it is preferable to dispose the buffer layer 10 accordingly.

  Specifically, the folded end of the carcass layer 4 and the outer end in the tire radial direction of the bead filler 6 reach the position 70% of the vertical distance H from the position L2, and the folded portion of the carcass layer 4 and the bead filler 6 are When the region from the position L2 to 70% of the vertical distance H is covered, a side cut is less likely to occur in this region, and therefore the buffer layer 10 is more tread than the tire maximum width position P as shown in FIG. It is preferable to provide on the part 1 side.

  Alternatively, when a plurality of carcass layers 4 are provided, the plurality of carcass layers 4 are present at least on the inner side in the tire width direction of the bead filler 6 in the vicinity of the region from the position L2 to 70% of the vertical distance H. Since the carcass layer 4 (folded portion) is further added to the outer side in the tire width direction of the bead filler 6 due to the structure of the folded portion of the carcass layer 4, the carcass layer 4 increases the distance from the position L2 to 70% of the vertical distance H. Since the region is sufficiently reinforced and the side cut is suppressed, it is preferable to provide the buffer layer 10 on the tread portion 1 side with respect to the tire maximum width position P as shown in FIG.

  As described above, the vicinity of the bead portion 3 (region from the position L2 to 70% of the vertical distance H) is reinforced by the structure of the carcass layer 4 and the bead filler 6, and side cuts in this region are suppressed in advance. In this case, a sufficient effect can be obtained even if the thickness of the buffer layer 10 is reduced compared to other examples in which the reinforcing effect in the vicinity of the bead portion 3 due to the basic structure of the tire is small.

  Of course, even if it is possible to suppress the side cut in the vicinity of the bead portion 3 by the structure of the carcass layer 4 and the bead filler 6 as described above, the buffer layer disposed on the bead portion 3 side from the tire maximum width position P. It is possible to use 10 together. At this time, in order to balance the reinforcement effect by the carcass layer 4 and the bead filler 6 and the effect by the buffer layer 10, the region that is on the bead part 3 side from the tire maximum width position P and does not overlap with the bead filler 6 It is preferable to provide the buffer layer 10 in a region where the thickness of the bead filler 6 is small (a region overlapping with the outer portion of the bead filler 6 in the tire radial direction) and a region not overlapping with the folded portion of the carcass layer 4. Thereby, since the buffer layer 10 can protect a portion where the reinforcing effect by the carcass layer 4 and the bead filler 6 is weak, the side cut can be efficiently prevented.

  7-10, when the tire radial direction outer side end of the bead filler 6 is located on the bead part 3 side from the position L2, the bead filler 6 is up to 70% of the vertical distance H from the position L2. Since it does not overlap with the region, this region is not reinforced by the bead filler 6, and a side cut is likely to occur near the bead portion 3. Therefore, even if the position of the folded end of the carcass layer 4 is located within a region from the position L2 to 70% of the vertical distance H as shown in FIG. 7, the vertical distance H from the position L2 as shown in FIG. Even if it is located on the tread portion 1 side with respect to the 70% region, the buffer layer 10 is provided on the bead portion 3 side with respect to the tire maximum width position P (particularly, the region from the position L2 to 70% of the vertical distance H). It is preferable. At this time, in consideration of the reinforcing effect of the carcass layer 4, the buffer layer 10 is limited to a range that does not overlap with the folded portion of the carcass layer 4 within a region of 70% of the vertical distance H from the position L2, as shown in FIG. You may make it arrange | position to. Of course, even in the case where the bead portion 3 side (region from the position L2 to 70% of the vertical distance H) is positively protected in this way, the tread portion is more than the tire maximum width position P as shown in FIG. It is possible to use the buffer layer 10 disposed on one side in combination.

  The degree of overlap between the bead filler 6 and the buffer layer 10 may be controlled according to not only the position of the outer end in the tire radial direction of the bead filler 6 but also the strength of the bead filler 6. That is, when the strength of the bead filler 6 is weak, the bead filler 6 and the buffer layer 10 are sufficiently overlapped to obtain an excellent side-cut preventing effect by the cooperation of the bead filler 6 and the buffer layer 10. . On the other hand, when the strength of the bead filler 6 is strong, the overlapping amount of the bead filler 6 and the buffer layer 10 is reduced or arranged so as not to be overlapped, so that a region not reinforced by the bead filler 6 is placed in the buffer layer 10. To prevent side cuts efficiently.

  Similarly, the degree of overlap between the folded portion of the carcass layer 4 and the buffer layer 10 may be controlled according to the strength of the carcass layer 4. That is, when the strength of the carcass layer 4 is weak, the carcass layer 4 and the buffer layer 10 are sufficiently overlapped to obtain an excellent side-cut preventing effect by the cooperation of the carcass layer 4 and the buffer layer 10. . On the other hand, when the strength of the carcass layer 4 is strong, the overlapping amount between the carcass layer 4 and the buffer layer 10 is reduced or arranged so as not to overlap, so that the region not reinforced by the carcass layer 4 is disposed. To prevent side cuts efficiently.

  Of course, side cuts are unlikely to occur at a portion where the rubber thickness of the sidewall portion 2 is large, and therefore the arrangement of the buffer layer 10 may be determined according to the rubber thickness of the sidewall portion 2. Specifically, the side cut can be efficiently prevented by disposing the buffer layer 10 in a portion where the rubber thickness is small while avoiding a portion where the rubber thickness of the sidewall portion 2 is large. At this time, it is preferable to determine the arrangement of the buffer layer 10 in consideration of the structures of the carcass layer 4 and the bead filler 6.

  When the buffer layer 10 is disposed in consideration of the basic structure of the tire as described above, it is preferable that the buffer layer 10 be disposed in the basic structure (the tread portion 1 side or the bead from the tire maximum width position P). The buffer layer 10 may be provided not only on one side on the part 3 side but also on another part (the other on the tread part 1 side or the bead part 3 side with respect to the tire maximum width position P). In other words, as shown in FIG. 4, when a pair of buffer layers 10 are provided on the tread portion 1 side and the bead portion 3 side with respect to the tire maximum width position P, the tread portion 1 side and / or the bead portion 3 side are provided. The buffer layer 10 may be arranged at a suitable position in consideration of the basic structure of the tire as described above.

  In consideration of the basic structure of the tire as described above, the buffer layer 10 of the present invention has a carcass layer 4 as one layer as shown in FIG. 11 in order to reduce the tire weight and rolling resistance. In the pneumatic tire having a structure in which both the folded end 4 and the outer end in the tire radial direction of the bead filler 6 are arranged closer to the bead part 3 than the position L2, when the rubber thickness of the sidewall part 2 is further reduced, It is most effective as a means of suppressing side cuts.

  The buffer layer 10 only needs to be at least partially composed of a foamed rubber layer. For example, as shown in FIG. 12, a structure composed of a foamed portion (shaded portion in the figure) and a non-foamed portion is adopted. You can also. Alternatively, as shown in FIG. 4, a pair of buffer layers 10 (the buffer layer 10 on the tread 1 side with respect to the tire maximum width position P and the buffer layer 10 on the bead portion 3 side with respect to the tire maximum width position P) are provided. Alternatively, one can be made of foamed rubber and the other can be made of non-foamed rubber. Thus, even when non-foamed rubber is used in combination, the foamed rubber functions as a cushion, so that excellent side cut prevention performance can be obtained. In addition, when using non-foamed rubber in this way, as the non-foamed rubber, for example, polyurethane, nylon or the like can be used instead of a rubber composition obtained by removing a foaming agent from foamed rubber.

  The buffer layer 10 may be provided on at least one of the pair of sidewall portions 2, and side cuts can be prevented on the side where the buffer layer 10 is provided. Preferably, the buffer layer 10 is provided on both of the pair of sidewall portions 2. Or if it is a tire with which the mounting direction with respect to the vehicle was specified, you may make it provide only in the side wall part 2 (side which a side cut tends to produce) which becomes the outer side with respect to a vehicle.

  In the present invention, the buffer layer 10 has not only a structure that continuously extends over the entire circumference (a structure in which the same cross section continues over the entire circumference of the tire), but also, for example, as shown in FIG. The structure may exist intermittently. In other words, the buffer layer 10 may be composed of a plurality of buffer bodies arranged at intervals in the tire circumferential direction. However, even if it exists intermittently in this way, it is necessary that some of the circumferential direction of the buffer overlap and the buffer layer 10 exists over the entire circumference. In the example of FIG. 13, the buffer layer 10 on the bead portion 3 side and the buffer layer 10 on the tread portion 1 side are inclined in the same direction in a plan view, so when they are deformed as shown in FIG. Since the crossing contacts, the buffering effect can be effectively exhibited (when the buffer layer 10 on the bead part 3 side and the buffer layer 10 on the tread part 1 side do not cross at the time of contact, the bead part 3 There is a possibility that the other buffer body enters the gap between the buffer bodies adjacent to each other in the tire circumferential direction in one of the buffer layers 10 on the side or the tread portion 1 side, and a sufficient buffering effect cannot be exhibited.

Even when the buffer layer 10 how provided, in meridian section, it is preferable that the total cross-sectional area of the buffer layer 10 in each of the tire side region S is in the range of 40mm ² ~400mm ^2. Moreover, it is preferable that the total mass of the buffer layer 10 in each tire side area | region S is the range of 30g-300g.

  In any case, in consideration of the structure and characteristics of the tire body, the buffer layer 10 is limited to function as a cushion when the sidewall portion 2 is deformed at a place where the side cut is most concerned in the tire. It is effective in order to achieve both the prevention of the side cut and the maintenance of the tire weight and rolling resistance.

  About 8 kinds of foam rubbers (foam rubbers 1 to 8) having the composition shown in Table 1, each of the blending components excluding sulfur, vulcanization accelerator, curing agent, chemical foaming agent or physical foaming agent, and foaming aid is weighed. Then, the mixture was kneaded for 5 minutes with a 1.7 L closed Banbury mixer, and the master batch was discharged at a temperature of 150 ° C. and cooled to room temperature. Thereafter, the master batch is subjected to a heating roll, and sulfur, a vulcanization accelerator, a curing agent, a chemical foaming agent and a urea foaming aid are added and mixed to prepare eight types of rubber compositions, and these rubber compositions. An unvulcanized rubber molded body made of Each unvulcanized rubber molded body was filled in a mold having a predetermined shape (length 100 mm, width 100 mm), and these were heated at a temperature 180 for 15 minutes for vulcanization molding. Thus, vulcanization and foaming proceeded simultaneously for each unvulcanized rubber molded body, and a foamed rubber molded body having a thickness of about 15 mm was molded. The hardness, foaming rate, and specific gravity of the obtained foamed rubber molded bodies (foam rubbers 1 to 8) were measured, and the results obtained are shown in Table 1. The hardness was measured according to JIS K6253, the foaming rate was measured according to JIS K7222, and the specific gravity was measured according to JIS K6268.

The types of raw materials used in Table 1 are shown below.
-BrIIR: Brominated butyl rubber, EXXON Bromobutyl 2255, manufactured by Exxonmobile Chemical Company
NR: natural rubber, PT. SIR20 made by NURISA
-CB: Carbon black, HTC # G made by Nippon Nihon Carbon
・ Zinc oxide: 3 types of zinc oxide manufactured by Shodo Chemical Co., Ltd. ・ Stearic acid: manufactured by Chiba Fatty Acid Co., Ltd. Bead stearic acid paulownia ・ Anti-aging agent: VULKANOX 4020 manufactured by Bayer
・ Tackifier: FR WATER Oct. 31, 2016, manufactured by AIR WATER ・ Oil: Diana Process NH-60, manufactured by Idemitsu Kosan Co., Ltd.
・ Sulfur: Tsurumi Chemical Industry Co., Ltd. Jinhua stamp fine powder sulfur 150 mesh
・ Vulcanization accelerator: NOCELLER DM manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
・ Chemical foaming agent: Cellular D manufactured by Eiwa Kasei Kogyo Co., Ltd.
・ Physical foaming agent: foamable microcapsule, FRY-2012 manufactured by Matsumoto Yushi Seiyaku Co., Ltd.
-Foaming aid: Cell paste K4 manufactured by Eiwa Chemical Industry Co., Ltd.

  Next, the tire size is 195 / 65R15, and includes the above-mentioned foamed rubber (foam rubber 1-8) or a non-foamed rubber cushion layer, the arrangement of the buffer layer in the meridian section, the cushion layer in the tire circumferential direction Conventional example 1 in which arrangement, buffer layer material, buffer layer hardness, buffer layer foaming rate, buffer layer specific gravity, thickness G1, thickness G3, and thickness g1 are set as shown in Tables 2 and 3, and Comparative Example 1-2 types of pneumatic tires of 1-2 and Examples 1-18 were produced.

  In addition, in the column of “buffer layer arrangement (cross section)” in Tables 2 and 3, the numbers of the drawings corresponding to the buffer layer arrangement in the meridian cross section of each example are shown. In the column of “arrangement of buffer layer (circumferential direction)”, the case where the buffer layer is provided continuously over the entire circumference of the tire is “all circumference”, and the case where the buffer layer is provided intermittently as shown in FIG. This is shown in FIG. In the column of “Material of buffer layer”, it indicates which one of foam rubbers 1 to 8 in Table 1 (indicated as “foam 1” to “foam 8” in the table) is used, and when non-foam rubber is used Is labeled “non-foamed”.

  With respect to these 21 types of pneumatic tires, the damage rate, tire weight, and rolling resistance when climbing over curbs were evaluated by the following evaluation methods, and the results are also shown in Tables 2 and 3.

Damage speed Each test tire is assembled to a wheel with a rim size of 15 × 6J, mounted on a 2L class test vehicle with an air pressure of 230 kPa, and tested over a curb with a height of 90 mm. The side is damaged and air leaks. The speed was increased stepwise from 10 km / h to 2.5 km / h until the damage speed was measured. The measured value was shown as an evaluation result. A larger measured value means that a side cut is less likely to occur.

Tire Weight The weight of each test tire was measured. The evaluation results are shown as an index with the reciprocal of the measured value of Conventional Example 1 being 100. A larger index value means a smaller tire weight. If the index value is “92” or more, it means that a sufficiently low tire weight is maintained while maintaining the conventional level.

Rolling resistance Each test tire is assembled on a wheel with a rim size of 15 × 6J, and in accordance with ISO28580, using a drum testing machine with a drum diameter of 1707.6 mm, rolling under conditions of air pressure 210 kPa, load 4.82 kN, speed 80 km / h. Resistance was measured. The evaluation results are shown as an index with the reciprocal of the measured value of Conventional Example 1 being 100. It means that rolling resistance is so low that this index value is large. If the index value is “94” or more, it means that the conventional level is maintained and a sufficiently low rolling resistance is maintained.

  As is clear from Tables 2 and 3, in each of Examples 1 to 18, the damage rate was increased, and side cuts were less likely to occur. In addition, the tire weight and rolling resistance could be kept low compared to Conventional Example 1 that does not include a buffer layer. In particular, Examples 2 to 4 and Examples 8 to 18 in which BrIIR is sufficiently blended, a chemical foaming agent is used as a foaming agent, and the hardness, foaming rate, and specific gravity of the buffer layer are included in a preferable range are tire weights. And while maintaining low rolling resistance, side cuts were effectively prevented, and these performances were balanced.

  On the other hand, since non-foamed rubber was used as the buffer layer in Comparative Example 1, side cuts could not be sufficiently prevented, and the tire weight and rolling resistance could not be maintained. In Comparative Example 2, since the hardness of the buffer layer was too low, a sufficient buffer effect could not be obtained, and side cuts could not be sufficiently prevented.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 5 Bead core 6 Bead filler 7 Belt layer 8 Belt cover layer 9 Inner liner layer 10 Buffer layer CL Tire equator R Rim P Tire maximum width position

Claims (10)

An annular tread portion extending in the tire circumferential direction, 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 the sidewall portions. A pneumatic tire having a carcass layer mounted between the pair of bead portions and a plurality of belt layers disposed on an outer peripheral side of the carcass layer in the tread portion,
Between the perpendicular line L1 dropped from the outermost end portion in the tire width direction of the belt layer to the inner surface of the tire in each of the pair of sidewall portions and the position L2 corresponding to the outer end portion in the radial direction of the rim flange when the rim is assembled. When the region is a tire side region S, a buffer layer that exists over the entire circumference of the tire inside the carcass layer is locally present in the tire side region S of at least one of the pair of sidewall portions. The buffer layer is made of foamed rubber and has a hardness of 15 or more and less than 80, and from the innermost surface of the carcass layer to the innermost surface of the buffer layer in the region where the buffer layer is provided The thickness G1 is larger than the thickness G2 from the innermost surface of the carcass layer to the innermost surface of the tire in the region where the buffer layer is not provided, and the thickness G1 is 1.0. A pneumatic tire characterized in that it is a m~8.0mm.   2. The pneumatic tire according to claim 1, wherein the buffer layer is provided in a portion of the tire side region S excluding a tire maximum width position P. 3.   When the distance along the tire radial direction from the position L2 to the tire maximum width position P is a vertical distance H, the buffer layer is provided in a region from the position L2 to 70% of the vertical distance H. The pneumatic tire according to claim 1 or 2.   3. The pneumatic according to claim 1, wherein a rim protect portion is provided on an outer surface of the sidewall portion, and the buffer layer is provided between the perpendicular line L <b> 1 and a tire maximum width position P. 4. tire.   The minimum value of the thickness g1 from the outermost surface of the carcass layer to the outer surface of the sidewall portion in the tire side region is 0.5 mm to 2.0 mm. The described pneumatic tire.   The pneumatic tire according to claim 1, wherein the buffer layer is exposed to the tire lumen.   The pneumatic tire according to claim 1, wherein a specific gravity of the buffer layer is 0.1 to 1.1.   The pneumatic tire according to any one of claims 1 to 7, wherein the buffer layer is made of foamed rubber having at least a part of closed cells.   The pneumatic tire according to any one of claims 1 to 8, wherein a thickness G3 of the buffer layer is 0.5 mm to 5.0 mm.   10. An unvulcanized buffer layer is affixed to the innermost inner surface of an unvulcanized pneumatic tire and then vulcanized with a vulcanization bladder in contact with the unvulcanized buffer layer. A pneumatic tire manufacturing method for manufacturing the pneumatic tire according to claim 1, wherein the vulcanized bladder is generated from the unvulcanized buffer layer at the time of vulcanization at least in a region in contact with the unvulcanized buffer layer. The manufacturing method of the pneumatic tire characterized by forming the unevenness | corrugation for letting gas escape, and performing the said vulcanization | cure using this vulcanization bladder.

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