JP2020059384A - Pneumatic tire - Google Patents

Abstract

To provide a pneumatic tire that has at a rubber superficial layer part rubber interfaces with different rubber hardness and can suppress deterioration in steering stability performance during turning and braking performance during turning.SOLUTION: In the pneumatic tire, a rubber superficial layer part 6 comprises a first rubber part 6a formed of first rubber and a second rubber part 6b formed of second rubber having rubber hardness larger than rubber hardness of the first rubber. The first rubber part 6a is arranged inside when mounted on the vehicle and the second rubber part 6b is arranged outside when mounted on the vehicle. An interface between the first rubber part 6a and the second rubber part 6b is arranged between a pair of main grooves arranged outermost in a tire width direction D1. A belt part 4 comprises at least one belt layer 41 or 42 and a center 41c or 42c in the tire width direction of at least one of the belts are positioned closer to outside than a tire equatorial plane S1 when the tire is mounted on the vehicle.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a pneumatic tire.

  Conventionally, for example, a pneumatic tire includes a rubber surface layer portion having an outer surface in the tire radial direction, and the first side and the second side in the tire width direction of the rubber surface layer portion are formed of rubbers having different rubber hardnesses. (For example, Patent Document 1). In such a pneumatic tire, it is difficult to suppress a decrease in both steering stability performance during turning and braking performance during turning.

JP2012-76593A

  Therefore, a problem is to provide a pneumatic tire that can suppress deterioration of steering stability performance during turning and braking performance during turning while having an interface of rubbers having different rubber hardness in a rubber surface layer portion. It is to be.

  The pneumatic tire is a pneumatic tire having a plurality of main grooves extending in the tire circumferential direction, and a rubber surface layer portion having an outer surface in the tire radial direction, and arranged inside the tire radial direction with respect to the rubber surface layer portion. A first rubber portion formed of a first rubber and a second rubber formed of a second rubber having a rubber hardness higher than that of the first rubber. A rubber portion, wherein the first rubber portion is arranged inside when the vehicle is mounted, the second rubber portion is arranged outside when the vehicle is mounted, and the first rubber portion and the second rubber portion are arranged. The interface is arranged between a pair of main grooves arranged on the outermost side in the tire width direction, the belt portion includes at least one belt layer, and at least one of the belt layers has a center in the tire width direction. , Outside the equatorial plane of the tire when mounted on the vehicle It is located.

  Further, in the pneumatic tire, all the belt layers may be configured so as to overlap the inside ground contact end in the tire radial direction when mounted on the vehicle.

  Further, the pneumatic tire includes a plurality of land portions defined by the plurality of main grooves and a ground contact end, and the void ratio of the land portion configured by the first rubber portion is configured by the second rubber portion. It may be configured to be smaller than the void ratio of the land portion to be formed.

  Further, in the pneumatic tire, the belt portion includes a first belt layer and a second belt layer arranged outside of the first belt layer in a tire radial direction, The tire width direction center may be located outside the tire width direction center of the first belt layer when the vehicle is mounted.

  Further, the pneumatic tire may have a center land portion including the tire equatorial plane by being partitioned by the plurality of main grooves, and the interface may be located at the center land portion.

FIG. 1 is a cross-sectional view of a main part of a pneumatic tire according to an embodiment in a tire meridian plane. FIG. 2 is a development view of the tread surface of the pneumatic tire according to the same embodiment. FIG. 3 is an enlarged view of the area III in FIG. FIG. 4 is an enlarged view of the area III in FIG. 1, showing the position of the belt portion. FIG. 5 is an enlarged view of the area V in FIG. 1, showing the position of the belt portion. FIG. 6 is an enlarged view of the VI region in FIG. 1, showing the position of the belt portion. FIG. 7 is a diagram showing a ground contact shape of a pneumatic tire according to a comparative example. FIG. 8 is a diagram showing a ground contact shape of the pneumatic tire according to FIGS. 1 to 6. FIG. 9 is an enlarged cross-sectional view of a main part of a tire meridian surface of a pneumatic tire according to another embodiment, showing a position of a belt part. FIG. 10 is an enlarged cross-sectional view of a main part of a meridian plane of a pneumatic tire according to another embodiment, showing a position of a belt part. FIG. 11 is an evaluation table of examples of pneumatic tires. FIG. 12 is an evaluation table of examples of pneumatic tires.

  Hereinafter, one embodiment of a pneumatic tire will be described with reference to FIGS. 1 to 8. In each drawing (also in FIGS. 9 and 10), the dimensional ratio in the drawings does not always match the actual dimensional ratio, and the dimensional ratio in each drawing does not necessarily match. Absent.

  In each drawing, the first direction D1 is a tire width direction D1 that is parallel to the tire rotation axis that is the rotation center of the pneumatic tire (hereinafter, also simply referred to as “tire”) 1, and the second direction D2 is The tire radial direction D2, which is the diameter direction of the tire 1, and the third direction D3 is the tire circumferential direction D3 around the tire rotation axis.

  In the tire width direction D1, the inner side is the side closer to the tire equatorial plane S1, and the outer side is the side farther from the tire equatorial plane S1. Further, in the tire radial direction D2, the inner side is the side closer to the tire rotation axis, and the outer side is the side far from the tire rotation axis.

  The tire equatorial plane S1 is a plane orthogonal to the tire rotation axis and located at the center of the tire 1 in the tire width direction D1, and the tire meridian plane is a plane including the tire rotation axis and the tire equator. It is a surface orthogonal to the surface S1. The tire equatorial line is a line at which the outer surface (the tread surface 2a, which will be described later) of the tire 1 in the tire radial direction D2 intersects with the tire equatorial surface S1.

  As shown in FIG. 1, a tire 1 according to the present embodiment includes a pair of bead portions 11 having beads, a sidewall portion 12 extending from each bead portion 11 to the outside in the tire radial direction D2, and a pair of sidewall portions. The tread portion 2 is connected to the outer end portion of the tire radial direction D2 and has an outer surface in the tire radial direction D2 that contacts the road surface. In the present embodiment, the tire 1 is a pneumatic tire 1 into which air is put and is mounted on the rim 20.

  Further, the tire 1 includes a carcass layer 13 spanned between a pair of beads, an inner liner layer 14 disposed inside the carcass layer 13 and having an excellent function of preventing gas permeation in order to retain air pressure. Is equipped with. The carcass layer 13 and the inner liner layer 14 are arranged along the tire inner circumference over the bead portion 11, the sidewall portion 12, and the tread portion 2.

  The tire 1 has a structure that is asymmetric with respect to the tire equatorial plane S1. In the present embodiment, the tire 1 is a tire whose mounting direction in the vehicle is designated, and which of the left and right sides of the tire 1 is designated to face the vehicle when mounted on the rim 20. The tread pattern formed on the tread surface 2a of the tread portion 2 has a shape that is asymmetric with respect to the tire equatorial plane S1.

  The mounting direction on the vehicle is displayed on the sidewall portion 12. Specifically, the sidewall portion 12 includes a sidewall rubber 12a arranged outside the carcass layer 13 in the tire width direction D1 so as to form an outer surface of the tire, and a display is provided on the surface of the sidewall rubber 12a. Have a section.

  For example, one side wall portion 12 arranged on the inner side (the left side in each drawing and hereinafter also referred to as “vehicle inner side”) D11 when mounted on the vehicle is a display indicating that the side wall portion 12 is on the vehicle inner side (for example, “INSIDE”). Etc.) are attached. Further, for example, when the vehicle is mounted, the other side wall portion 12 arranged on the outside (the right side in each drawing and hereinafter, also referred to as “vehicle outside”) D12 is a display indicating that it is outside the vehicle (for example, “ OUTSIDE "and the like). The vehicle inner side D11 is a side closer to the vehicle center when the tire 1 is mounted on the vehicle, and the vehicle outer side D12 is a side farther from the vehicle center when the tire 1 is mounted on the vehicle.

  The tread portion 2 includes a tread rubber 3 having a tread surface 2 a that comes into contact with the road surface, and a belt portion 4 arranged between the tread rubber 3 and the carcass layer 13. In addition, the tread portion 2 includes a belt reinforcing portion 5 arranged between the tread rubber 3 and the belt portion 4 in order to reinforce the belt portion 4.

  The tread surface 2a has a ground surface that actually contacts the road surface, and the outer ends of the ground surface in the tire width direction D1 are referred to as ground ends 2b and 2c. Of the grounding ends 2b and 2c, the grounding end 2b on the vehicle inside D11 is referred to as the vehicle inside grounding end 2b, and the grounding end 2c on the vehicle outside D12 is referred to as the vehicle outside grounding end 2c. Further, the tread surface 2a is formed by assembling the tire 1 to the regular rim 20 and placing the tire 1 vertically on a flat road surface in a state of being filled with the regular internal pressure, and grounding the road surface when a regular load is applied. Refers to.

  The regular rim 20 is a rim 20 that is defined for each tire 1 in the standard system including the standard on which the tire 1 is based. For example, if it is JATMA, it is a standard rim, and if it is TRA, it is “Design Rim”, ETRTO. If so, it becomes “Measuring Rim”.

  The normal internal pressure is the air pressure that each standard defines for each tire 1 in the standard system including the standard on which the tire 1 is based. For JATMA, the maximum air pressure is used, and for TRA, the table "TIRE LOAD LIMITS AT VARIOUS COLD" is used. The maximum value described in “INFLATION PRESSSURES” is “INFLATION PRESSURE” for ETRTO, but 180 kPa for tire 1 for passenger cars.

  The regular load is a load that each standard defines for each tire 1 in the standard system including the standard on which the tire 1 is based. If JATMA is the maximum load capacity, if TRA, the maximum load described in the above table If the value is ETRTO, it is "LOAD CAPACITY", but when the tire 1 is for passenger cars, it is 85% of the corresponding load with an internal pressure of 180 kPa.

  The belt portion 4 includes at least one (two in the present embodiment) belt layers 41 and 42. Specifically, the belt portion 4 includes a first belt layer 41 and a second belt layer 42 arranged outside the first belt layer 41 in the tire radial direction D2. Each of the belt layers 41 and 42 includes a plurality of belt cords arranged in parallel and a topping rubber that covers the belt cords. The number of layers of the belt layers 41 and 42 is not particularly limited.

  The belt cords of the belt layers 41 and 42 are arranged in the tire width direction D1 so as to intersect with the tire circumferential direction D3 at a predetermined inclination angle (for example, 5 ° or more, preferably 15 ° to 35 °). Has been done. The belt cords of the first and second belt layers 41, 42 are arranged so as to incline in opposite directions with respect to the tire circumferential direction D3 and intersect each other. The material of the belt cord is not particularly limited, but for example, organic fibers such as polyester, rayon, nylon, or aramid, and metal such as steel are preferably used.

  The belt reinforcing portion 5 includes a cap reinforcing layer 51 arranged so as to cover the belt layers 41, 42 in the tire width direction D1, and end portions 41a, 41b, 42a of the belt layers 41, 42 in the tire width direction D1. Edge reinforcement layers 52 and 53 arranged so as to cover 42b. The presence and position of the belt reinforcing portion 5 is not particularly limited.

  The belt reinforcing portion 5 includes a reinforcing cord and a topping rubber that covers the reinforcing cord. The material of the reinforcing cord is not particularly limited, but for example, organic fibers such as polyester, rayon, nylon, or aramid are preferably used.

  The belt reinforcing portion 5 is formed by spirally winding at least one reinforcing cord covered with topping rubber along the tire circumferential direction D3. Thereby, the reinforcing cords of the respective reinforcing layers 51 to 53 are arranged along the tire circumferential direction D3 (for example, so that the inclination angle crosses the tire circumferential direction D3 at less than 5 °, preferably at 3 ° or less, Alternatively, they are arranged in parallel in the tire width direction D1 so as to be parallel to the tire circumferential direction D3).

  As shown in FIGS. 1 and 2, the tread rubber 3 includes a plurality of main grooves 3a and 3b extending in the tire circumferential direction D3. The main grooves 3a and 3b continuously extend in the tire circumferential direction D3. In the present embodiment, the main grooves 3a, 3b have a configuration in which they extend straight along the tire circumferential direction D3, but the configuration is not limited to such a configuration, and for example, extends in zigzag by repeating refraction. The configuration may be such that the curved shape is repeated, and for example, the curved shape is repeated to extend in a wavy shape.

  The main grooves 3a, 3b are provided with a so-called treadwear indicator (not shown) in which the grooves are shallow so that the degree of wear can be known by exposing the main grooves 3a, 3b as they wear. Further, for example, the main grooves 3a and 3b have a groove width of 3% or more of the distance between the ground contact ends 2b and 2c (the dimension in the tire width direction D1 between the ground ends 2b and 2c). Further, for example, the main grooves 3a and 3b have a groove width of 5 mm or more.

  In the plurality of main grooves 3a, 3b, the pair of main grooves 3a, 3a arranged on the outermost side in the tire width direction D1 is called a shoulder main groove 3a, and is arranged between the pair of shoulder main grooves 3a, 3a. The formed main groove 3b is referred to as a center main groove 3b. The presence and the number of the center main grooves 3b are not particularly limited, but in the present embodiment, the number of the center main grooves 3b is two.

  The tread rubber 3 includes a plurality of land portions 3c to 3e defined by the main grooves 3a and 3b and the ground ends 2b and 2c. In the plurality of land portions 3c to 3e, the land portion 3c defined by the shoulder main groove 3a and the ground contact ends 2b, 2c is referred to as a shoulder land portion 3c, and is defined by the adjacent main grooves 3a, 3b. The land portions 3d and 3e arranged between the pair of shoulder land portions 3c and 3c are referred to as middle land portions 3d and 3e.

  Of the middle land portions 3d and 3e, the land portion 3d defined by the shoulder main groove 3a and the center main groove 3b is referred to as a mediate land portion 3d, and is defined by the center main grooves 3b and 3b. The part 3e is called the center land part 3e. In the present embodiment, the center main grooves 3b, 3b are arranged so as to sandwich the tire equatorial plane S1, whereby the center land portion 3e is arranged so as to include the tire equatorial plane S1.

  The land portions 3c to 3e include a plurality of land grooves 3f and 3g. The plurality of land grooves 3f and 3g extend so as to intersect the tire circumferential direction D3. Of the land grooves 3f and 3g extending so as to intersect the tire circumferential direction D3, the land groove 3f having a groove width of 1.6 mm or more is referred to as a width groove 3f, and the groove width is 1.6 mm. Land groove 3g which is less than is called sipe 3g. The land portions 3c to 3e may have land grooves each having a groove width smaller than the groove widths of the main grooves 3a and 3b and extending continuously or intermittently along the tire circumferential direction D3. The groove is called a circumferential groove.

  As shown in FIG. 3, the tread rubber 3 includes a rubber surface layer portion 6 having a tread surface 2a that is an outer surface in the tire radial direction D2, and a rubber inner layer arranged inside the rubber surface layer portion 6 in the tire radial direction D2. And part 7. The presence or absence of the rubber inner layer portion 7 and the number of layers are not particularly limited. Further, among the rubber inner layer portions 7, the rubber inner layer portion 7 arranged on the innermost side in the tire radial direction D2 is referred to as a base rubber, and the rubber surface layer portion 6 and the other rubber inner layer portions 7 are referred to as a cap rubber.

  The rubber surface layer portion 6 includes a first rubber portion 6a formed of a first rubber and a second rubber portion 6b formed of a second rubber having a rubber hardness higher than that of the first rubber. . The rubber hardness is the hardness measured at 23 ° C. based on “JIS K6253-1-2012 3.2 Durometer hardness”.

  Although the rubber hardness of each rubber is not particularly limited, for example, the rubber hardness of the first rubber may be 66 to 70, and the rubber hardness of the second rubber may be 70 to 74, for example. Further, for example, the rubber hardness difference between the first rubber and the second rubber is not particularly limited, but may be, for example, 2 to 6.

  The rubber surface layer portion 6 includes an interface 6c between the first rubber portion 6a and the second rubber portion 6b. The interface 6c is arranged between the pair of shoulder main grooves 3a, 3a. As a result, strain is generated in the interface 6c arranged between the pair of shoulder main grooves 3a, 3a during braking, and the strain becomes resistance to the road surface. Therefore, since the braking distance can be reduced, the braking performance can be improved.

  Further, in the present embodiment, the interface 6c is located not on the main grooves 3a and 3b but on the land portion 3e so as to appear on the tread surface 2a. As a result, the strain generated at the interface 6c becomes a direct resistance to the road surface.

  Moreover, in the present embodiment, the interface 6c is located at the center land portion 3e, specifically, the tire equatorial plane S1. As a result, the ground contact pressure during braking increases as the tire equatorial plane S1 is closer to the tire, whereas the interface 6c is closest to the tire equatorial plane S1 (specifically, including the tire equatorial plane S1). It is located at 3e. As a result, the strain generated at the interface 6c becomes effective resistance to the road surface, so that the braking distance can be effectively reduced.

  The first rubber portion 6a is arranged on the vehicle inner side D11 of the rubber surface layer portion 6, and the second rubber portion 6b is arranged on the vehicle outer side D12 of the rubber surface layer portion 6. As a result, the second rubber portion 6b having a relatively large rubber hardness is arranged on the vehicle outer side D12 where a large force acts when turning as an outer wheel. Therefore, since the rigidity of the rubber outer layer portion 6 on the vehicle outer side D12 can be increased, the steering stability performance during turning can be improved.

  The interface 6c may be located in the main grooves 3a and 3b, for example, and may not appear on the tread surface 2a. Further, the interface 6c may be located at the middle land portions 3d and 3e, but at the mediate land portion 3d instead of the center land portion 3e.

  The interface 6c may be located at the center land portion 3e, but may be located away from the tire equatorial plane S1. For example, the distance between the interface 6c and the tire equatorial plane S1 is preferably 10% or less of the distance between the ground contact ends 2b and 2c (the dimension in the tire width direction D1 between the ground contact ends 2b and 2c), and It is more preferably 5% or less, and most preferably 3% or less.

  Returning to FIG. 2, in the present embodiment, the void ratio of the land portions 3c to 3e formed of the first rubber portion 6a is higher than that of the land portions 3c to 3e formed of the second rubber portion 6b. It is getting smaller. As a result, the void ratio of the land portions 3c to 3e formed of the first rubber portion 6a having a relatively low rubber hardness is such that the land portions 3c to 3e formed of the second rubber portion 6b having a relatively large rubber hardness. It is smaller than the void ratio of. Therefore, it is possible to suppress an increase in the difference in rigidity between the land portions 3c to 3e on the vehicle inner side D11 and the land portions 3c to 3e on the vehicle outer side D12.

  It should be noted that the land portions 3c to 3e configured by the first rubber portion 6a include the shoulder land portion 3c and the mediate land portion 3d on the vehicle inner side D11, and the interface 6c (tire equatorial plane S1) of the center land portion 3e. Is also an area inside the vehicle D11. Therefore, the void ratio of the land portions 3c to 3e configured by the first rubber portion 6a means the area of the land portions 3c to 3e between the vehicle inner ground contact end 2b and the interface 6c (excluding the main grooves 3a and 3b). , Including the land grooves 3f and 3g) is the ratio of the sum total of the areas of the land grooves 3f and 3g.

  In addition, the land portions 3c to 3e configured by the second rubber portion 6b are formed from the shoulder land portion 3c and the mediate land portion 3d on the vehicle outer side D12 and the interface 6c (tire equatorial plane S1) of the center land portion 3e. Is also an area outside the vehicle D12. Therefore, the void ratio of the land portions 3c to 3e configured by the second rubber portion 6b means the area of the land portions 3c to 3e between the vehicle outer ground contact end 2c and the interface 6c (excluding the main grooves 3a and 3b). , Including the land grooves 3f and 3g) is the ratio of the sum total of the areas of the land grooves 3f and 3g.

  The pitch of the width grooves 3f (excluding sipes 3g) in the mediate land portion 3d on the vehicle inner side D11 (the interval in the tire circumferential direction D3) is determined by the width groove 3f (sipes on the mediate land portion 3d on the vehicle outer side D12). It is larger than the pitch (excluding 3 g). Further, the pitch of the width groove 3f (excluding the sipe 3g) in the shoulder land portion 3c of the vehicle inner side D11 is larger than the pitch of the width groove 3f (excluding the sipe 3g) in the shoulder land portion 3c of the vehicle outer side D12. Has become.

  Here, the configuration of the belt portion 4 will be described with reference to FIGS. 4 to 6. 4 to 6 (the same applies to FIGS. 9 and 10), the belt portion 4 (belt layers 41 and 42) is illustrated by hatching.

  As shown in FIGS. 4 to 6, the dimension of the first belt layer 41 in the tire width direction D1 is larger than the dimension of the second belt layer 42 in the tire width direction D1. The end portions 41a and 41b of the first belt layer 41 are arranged outside the end portions 42a and 42b of the second belt layer 42 in the tire width direction D1.

  As shown in FIG. 4, the centers 41c and 42c of the first and second belt layers 41 and 42 in the tire width direction D1 are located on the vehicle outer side D12 with respect to the tire equatorial plane S1. The center 41c of the first belt layer 41 and the center 42c of the second belt layer 42 are at the same position in the tire width direction D1. That is, the distance W1 between the center 41c of the first belt layer 41 and the tire equatorial plane S1 is the same as the distance W2 between the center 42c of the second belt layer 42 and the tire equatorial plane S1.

  As a result, the area of the belt layers 41, 42 arranged on the vehicle outer side D12 is larger than the area of the belt layers 41, 42 arranged on the vehicle inner side D11 with respect to the tire equatorial plane S1. The distances W1 and W2 between the centers 41c and 42c of the belt layers 41 and 42 and the tire equatorial plane S1 are not particularly limited. For example, the distances W1 and W2 are the tire width direction D1 of the first belt layer 41. It is preferable that the size is 3% or less.

  As shown in FIG. 5, the first and second belt layers 41, 42 are arranged on the vehicle inner side grounding end, even though the first and second belt layers 41, 42 are shifted to the vehicle outer side D12. 2b and the tire radial direction D2. Specifically, the vehicle inner end portions 41a, 42a of the first and second belt layers 41, 42 are located outside the vehicle inner ground contact end 2b in the tire width direction D1, specifically, on the vehicle inner side D11. positioned.

  The vehicle inner end portion 41a of the first belt layer 41 and the outer surface of the tire 1 are separated by a predetermined distance (hereinafter, also referred to as "rubber thickness distance") W3. Further, the vehicle inner end portion 41a of the first belt layer 41 and the vehicle inner end portion 42a of the second belt layer 42 are only a predetermined distance (hereinafter, also referred to as “belt end portion distance”) W4 in the tire width direction D1. is seperated.

  Further, as shown in FIG. 6, the first and second belt layers 41, 42 overlap the vehicle outer ground contact end 2c in the tire radial direction D2. Specifically, the vehicle outer side end portions 41b, 42b of the first and second belt layers 41, 42 are located outside the vehicle outer side ground contact end 2c in the tire width direction D1, specifically, on the vehicle outer side D12. positioned.

  The vehicle outer end portion 41b of the first belt layer 41 and the outer surface of the tire 1 are separated by a predetermined distance (rubber thickness distance) W5. Further, the vehicle outer end 41b of the first belt layer 41 and the vehicle outer end 42b of the second belt layer 42 are separated by a predetermined distance (belt end distance) W6 in the tire width direction D1.

  The rubber thickness distances W3 and W5 are not particularly limited. However, when the rubber thickness distances W3 and W5 are small, cracks are likely to occur on the outer surface of the tire 1 due to use. Therefore, the rubber thickness distances W3 and W5 are preferably, for example, 8 mm or more.

  Further, the distances W4, W6 between the belt end portions are not particularly limited. However, when the distances W4, W6 between the belt end portions are small, air easily mixes between the end portions 41a, 42a (41b, 42b) of the belt layers 41, 42 during manufacturing. Therefore, the distances W4, W6 between the belt ends are preferably, for example, 5 mm or more.

  The configuration of the pneumatic tire 1 according to this embodiment is as described above. Next, the operation of the pneumatic tire 1 according to this embodiment will be described in comparison with a comparative example.

  The tire according to the comparative example is a tire modified to have a configuration in which the centers 41c and 42c of the belt layers 41 and 42 are located on the tire equatorial plane S1 as compared with the tire 1 according to the present embodiment. FIG. 7 shows a ground contact shape of the tire according to the comparative example, and FIG. 8 shows a ground contact shape of the tire 1 according to the present embodiment. Specifically, the ground contact shape according to FIGS. 7 and 8 shows the ground contact shape when the vehicle turns as an outer wheel. The land grooves 3f and 3g are not shown in FIGS. 7 and 8.

  As shown in FIG. 7, when turning as an outer wheel, a large force acts on the vehicle outer side D12, so that the ground contact length of the vehicle inner side D11 (the length of the ground contact shape in the tire circumferential direction D3) is equal to that of the vehicle outer side D12. It is very short with respect to the contact length. As a result, in the tire according to the comparative example, the ground contact area of the tire 1 as a whole becomes small, so that the braking performance during turning deteriorates.

  On the other hand, in the tire 1 according to the present embodiment, the centers 41c and 42c of the belt layers 41 and 42 are located on the vehicle outer side D12 with respect to the tire equatorial plane S1 (see FIG. 4). As a result, the region of the belt layers 41, 42 arranged on the vehicle inner side D11 of the tire equatorial plane S1 is smaller than the region of the belt layers 41, 42 arranged on the vehicle outer side D12 of the tire equatorial plane S1. Also becomes smaller.

  As a result, the rigidity of the region inside the vehicle D11 can be reduced, so that it is possible to prevent the ground contact length in the region inside the vehicle D11 from becoming short, as shown in FIG. Therefore, the ground contact area of the entire tire 1 is increased, so that the braking performance during turning can be improved.

  Further, the second rubber portion 6b having a relatively large rubber hardness is arranged on the vehicle outer side D12, and moreover, the region of the belt layers 41, 42 arranged on the vehicle outer side D12 with respect to the tire equatorial plane S1. , Is getting bigger. As a result, the rigidity of the region outside the vehicle D12 can be increased, and therefore the steering stability performance during turning can also be improved. As described above, in the tire 1 according to the present embodiment, the steering stability performance at the time of turning and the braking performance at the time of turning are deteriorated even though the rubber surface layer portion 6 has the rubber interface 6c having different rubber hardness. Can be suppressed.

  Further, since the first and second belt layers 41 and 42 are shifted and positioned on the vehicle outer side D12, there is a concern that the rigidity of the region on the vehicle inner side D11 is excessively reduced. On the other hand, the first and second belt layers 41 and 42 overlap with the vehicle-inside ground contact end 2b in the tire radial direction D2 (see FIG. 5). As a result, it is possible to prevent the rigidity of the region inside the vehicle D11 from being excessively reduced.

  Further, the center 41c of the first belt layer 41 and the center 42c of the second belt layer 42 are at the same position in the tire width direction D1. As a result, not only can the steering stability performance during turning and the braking performance during turning be prevented from deteriorating, but the first belt layer 41 and the second belt layer 42 can also be separated (separated) from the surroundings. Can be suppressed.

  As described above, the pneumatic tire 1 according to the present embodiment is the pneumatic tire 1 including the plurality of main grooves 3a and 3b extending in the tire circumferential direction D3, and the rubber surface layer portion 6 having the outer surface in the tire radial direction D2. And a belt portion 4 disposed inside the rubber surface layer portion 6 in the tire radial direction D2, the rubber surface layer portion 6 including a first rubber portion 6a formed of a first rubber and the first rubber portion 6a. A second rubber portion 6b formed of a second rubber having a rubber hardness higher than that of the first rubber portion, the first rubber portion 6a being disposed on the inner side D11 when the vehicle is mounted, The portion 6b is arranged on the outer side D12 when the vehicle is mounted, and the interface 6c between the first rubber portion 6a and the second rubber portion 6b has a pair of main grooves 3a, 3a arranged on the outermost side in the tire width direction D1. The belt portion 4 disposed at least between It comprises one of the belt layers 41 and 42, at least one, the center 41c of the tire width direction D1 of said belt layers 41 and 42, 42c is located outside D12 than the tire equatorial plane S1 when the vehicle mounting.

  According to this structure, strain is generated at the interface 6c between the first rubber portion 6a and the second rubber portion 6b during braking. Since the interface 6c is arranged between the pair of main grooves 3a, 3a arranged on the outermost side in the tire width direction D1, the strain becomes resistance to the road surface. Therefore, since the braking distance can be reduced, the braking performance can be improved.

  Further, when turning as an outer wheel, a large force acts on the region of the outer side D12 when the vehicle is mounted, whereas the second rubber portion 6b having a relatively large rubber hardness is arranged on the outer side D12 when the vehicle is mounted. There is. As a result, the rigidity of the region of the outer side D12 can be increased when the vehicle is mounted, so that the steering stability performance during turning can be improved.

  By the way, in the outer wheel when turning, the ground contact length in the region of the inner side D11 tends to be short when the vehicle is mounted. Therefore, at least one of the belt layers 41, 42 in the tire width direction D1 has a center 41c, 42c located outside the tire equatorial plane S1 when the vehicle is mounted. As a result, the rigidity of the region of the inner side D11 can be reduced when the vehicle is mounted, so that it is possible to suppress the shortening of the ground contact length of the region of the inner side D11 when the vehicle is mounted when turning as an outer wheel.

  Therefore, since the ground contact area of the entire tire 1 becomes large in the outer wheel during turning, braking performance during turning can be improved. As a result, it is possible to prevent the steering stability performance during turning and the braking performance during turning from being deteriorated even though the rubber surface layer portion 6 has the rubber interface 6c having different rubber hardness.

  Further, in the pneumatic tire 1 according to the present embodiment, all the belt layers 41 and 42 are configured to overlap the ground contact end 2b of the inner side D11 in the tire radial direction D2 when the vehicle is mounted.

  According to such a configuration, at least one of the belt layers 41, 42 has the centers 41c, 42c in the tire width direction D1 located outside the tire equatorial plane S1 when the vehicle is mounted, while All the belt layers 41 and 42 overlap the ground contact end 2b of the inner side D11 in the tire radial direction D2 when the vehicle is mounted. As a result, since all the belt layers 41, 42 overlap the ground contact end 2b of the inner side D11 in the tire radial direction D2 when the vehicle is mounted, it is possible to prevent the rigidity of the region of the inner side D11 from being excessively lowered when the vehicle is mounted. be able to.

  Further, the pneumatic tire 1 according to the present embodiment includes a plurality of land portions 3c to 3e defined by the plurality of main grooves 3a and 3b and ground contact ends 2b and 2c, and includes the first rubber portion 6a. The void ratio of the land portions 3c to 3e is smaller than the void ratio of the land portions 3c to 3e formed of the second rubber portion 6b.

  According to such a configuration, the void ratio of the land portions 3c to 3e formed of the first rubber portion 6a having a relatively low rubber hardness is equal to that of the land portion 3c formed of the second rubber portion 6b having a relatively large rubber hardness. It is smaller than the void ratio of the portions 3c to 3e. This can prevent the rigidity difference between the land portions 3c to 3e arranged on the inner side D11 when mounted on the vehicle and the land portions 3c to 3e arranged on the outer side D12 when mounted on the vehicle from becoming too large.

  Further, the pneumatic tire 1 according to the present embodiment includes the center land portion 3e including the tire equatorial plane S1 by being partitioned by the plurality of main grooves 3a and 3b, and the interface 6c is the center land. It is located in the section 3e.

  According to such a configuration, since the interface 6c is located at the center land portion 3e, the strain generated at the interface 6c becomes a direct resistance to the road surface. Moreover, as the ground contact pressure during braking increases as the tire equatorial plane S1 becomes closer, the interface 6c is located at the center land portion 3e that is closest to the tire equatorial plane S1. However, it becomes an effective resistance to the road surface.

  In addition, the pneumatic tire 1 is not limited to the configuration of the above-described embodiment, and is not limited to the above-described operational effects. Needless to say, the pneumatic tire 1 can be variously modified without departing from the scope of the present invention. For example, it is needless to say that one or a plurality of configurations and methods according to the various modified examples described below may be arbitrarily selected and applied to the configurations and methods according to the above-described embodiments.

(1) In the pneumatic tire 1 according to the above embodiment, the center 41c of the first belt layer 41 and the center 42c of the second belt layer 42 are at the same position in the tire width direction D1. . However, the pneumatic tire 1 is not limited to such a configuration. For example, as shown in FIG. 9, the center 41c of the first belt layer 41 and the center 42c of the second belt layer 42 may be at different positions in the tire width direction D1.

  In the pneumatic tire 1 according to FIG. 9, the belt portion 4 includes a first belt layer 41 and a second belt layer 42 arranged outside the first belt layer 41 in the tire radial direction D2. The center 42c of the second belt layer 42 in the tire width direction D1 is located outside the center 41c of the first belt layer 41 in the tire width direction D1 when the vehicle is mounted. That is, the distance W2 between the center 42c of the second belt layer 42 and the tire equatorial plane S1 is larger than the distance W1 between the center 41c of the first belt layer 41 and the tire equatorial plane S1.

  According to such a configuration, the second belt layer 42 located on the outer side in the tire radial direction D2 is larger than the first belt layer 41 located on the inner side in the tire radial direction D2 with respect to the rigidity of the rubber surface layer portion 6. In contrast to this, the center 42c of the second belt layer 42 in the tire width direction D1 is located outside the center 41c of the first belt layer 41 in the tire width direction D1 on the outer side D12 when worn. As a result, the rigidity of the region of the rubber surface layer portion 6 inside the vehicle D11 can be effectively reduced.

  Therefore, for example, when turning as an outer wheel, it is possible to effectively suppress a reduction in the ground contact length in the area of the inner side D11 when the vehicle is mounted. The configuration is not limited to such a configuration. For example, the center 41c of the first belt layer 41 may be located outside the center 42c of the second belt layer 42 on the outer side D12 when the vehicle is mounted.

(2) Further, in the pneumatic tire 1 according to the above-described embodiment, the centers 41c, 42c of all the belt layers 41, 42 are arranged outside the tire equatorial plane S1 on the outer side D12 when the vehicle is mounted. is there. However, the pneumatic tire 1 is not limited to such a configuration. For example, as shown in FIG. 10, only one center 42c of one of the plurality of belt layers 41, 42 may be located outside D12 of the tire equatorial plane S1 when the vehicle is mounted. .

(3) Further, in the pneumatic tire 1 according to the above-described embodiment, all the belt layers 41 and 42 are configured to overlap the vehicle-inside ground contact end 2b in the tire radial direction D2. However, although the pneumatic tire 1 preferably has such a configuration, it is not limited to such a configuration. For example, at least one vehicle inner end portion 41a, 42a of the plurality of belt layers 41, 42 may be located on the inner side in the tire width direction D1 than the vehicle inner ground contact end 2b.

(4) Further, in the pneumatic tire 1 according to the above embodiment, the void ratios of the land portions 3c to 3e formed of the first rubber portion 6a are equal to those of the land portions 3c to 3e formed of the second rubber portion 6b. It is smaller than the void ratio of. However, although the pneumatic tire 1 preferably has such a configuration, it is not limited to such a configuration. For example, the void ratio of the land portions 3c to 3e formed of the first rubber portion 6a may be equal to or higher than the void ratio of the land portions 3c to 3e formed of the second rubber portion 6b.

  A preferred embodiment of the tire 1 will be described below with reference to FIGS. 11 and 12.

<Crack occurrence rate>
After mounting each tire on a vehicle and running 100,000 km on an ordinary road under the condition of an internal pressure of 200 kPa, cracks were generated on the outer surface of the tire (position near the vehicle outer end 41b of the first belt layer 41). The existence of cracks was calculated and the probability was calculated.

<Air mixing ratio>
20 tires were manufactured, the tires were cut along the meridian plane, and air having a diameter of 1 mm or more was mixed between the end portions 41a, 42a (41b, 42b) of the belt layers 41, 42. The number of products was investigated and the probability that air-contaminated products were generated was calculated.

<Example 1>
The tire according to Example 1 is the tire according to the above embodiment and has the following configuration.
-The distance W5: 10mm between the vehicle outer end 41b of the first belt layer 41 and the tire surface
-Distance W4, W6: 8 mm between the end portions 41a, 41b of the first belt layer 41 and the end portions 42a, 42b of the second belt layer 42

<Examples 2 and 3>
The tire according to the second embodiment is a tire obtained by moving the belt layers 41 and 42 to the vehicle outer side D12 by about 2 mm each, as compared with the tire according to the first embodiment. Therefore, in the tire according to Example 2, the distance W5 between the vehicle outer end 41b of the first belt layer 41 and the tire surface is 8 mm.
The tire according to Example 3 is a tire obtained by moving each belt layer 41, 42 to the vehicle outer side D12 by about 5 mm with respect to the tire according to Example 1. Therefore, in the tire according to Example 3, the distance W5 between the vehicle outer end 41b of the first belt layer 41 and the tire surface is 5 mm.

<Examples 4 and 5>
The tire according to Example 4 is a tire in which the dimension of the second belt layer 42 in the tire width direction D1 is increased by 3 mm on the vehicle inner side D11 and the vehicle outer side D12 by 3 mm, respectively. Therefore, in the tire according to Example 4, the distances W4, W6 between the end portions 41a, 41b of the first belt layer 41 and the end portions 42a, 42b of the second belt layer 42 are 5 mm.
The tire according to Example 5 is a tire in which the dimension of the second belt layer 42 in the tire width direction D1 is made longer by 5 mm on the vehicle inner side D11 and the vehicle outer side D12, respectively. Therefore, in the tire according to Example 5, the distances W4, W6 between the end portions 41a, 41b of the first belt layer 41 and the end portions 42a, 42b of the second belt layer 42 are 3 mm.

  As shown in FIG. 11, in the tire according to Example 3 in which the distance W5 between the vehicle outer end 41b of the first belt layer 41 and the tire surface is 5 mm, the crack occurrence rate is 5%. In the tires according to Examples 1 and 2 in which the distance W5 is 8 mm or more, the crack occurrence rate is 0%. Therefore, the distances W3, W5 between the end portions 41a, 41b, 42a, 42b of the belt layers 41, 42 and the tire surface are preferably 8 mm or more.

  Further, as shown in FIG. 12, in the tire according to Example 5 in which the distances W4 and W6 between the end portions 41a and 41b of the first belt layer 41 and the end portions 42a and 42b of the second belt layer 42 are 3 mm, In contrast to the air mixture rate of 10%, in the tires according to Examples 1 and 4 in which the distances W4 and W6 are 5 mm or more, the air mixture rate is 0%. Therefore, the distances W4, W6 between the end portions 41a, 41b of the first belt layer 41 and the end portions 42a, 42b of the second belt layer 42 are preferably 5 mm or more.

DESCRIPTION OF SYMBOLS 1 ... Pneumatic tire, 2 ... Tread part, 2a ... Tread surface, 2b ... Vehicle inside ground contact end, 2c ... Vehicle outside ground contact end, 3 ... Tread rubber, 3a ... Shoulder main groove, 3b ... Center main groove, 3c ... Shoulder Land part, 3d ... Middle land part (Mediate land part), 3e ... Middle land part (center land part), 3f ... Land groove (width groove), 3g ... Land groove (sipe), 4 ... Belt part, 5 ... Belt reinforcing portion, 6 ... Rubber surface layer portion, 6a ... First rubber portion, 6b ... Second rubber portion, 6c ... Interface, 7 ... Rubber inner layer portion, 11 ... Bead portion, 12 ... Sidewall portion, 12a ... Sidewall rubber , 13 ... Carcass layer, 14 ... Inner liner layer, 20 ... Rim, 41 ... First belt layer, 41a ... Vehicle inner end portion, 41b ... Vehicle outer end portion, 41c ... Center, 42 ... Second belt layer, 42a ... Vehicle inner end, 42b ... Vehicle outer side Part, 42c ... Center, 51 ... Cap reinforcing layer, 52 ... Edge reinforcing layer, 53 ... Edge reinforcing layer, D1 ... Tire width direction, D2 ... Tire radial direction, D3 ... Tire circumferential direction, D11 ... Vehicle inner side, D12 ... Vehicle Outside, S1 ... tire equatorial plane

Claims (5)

A pneumatic tire having a plurality of main grooves extending in the tire circumferential direction,
A rubber surface layer portion having an outer surface in the tire radial direction, and a belt portion arranged inside the tire radial direction with respect to the rubber surface layer portion,
The rubber surface layer portion includes a first rubber portion formed of a first rubber and a second rubber portion formed of a second rubber having a rubber hardness higher than that of the first rubber,
The first rubber portion is arranged inside when mounted on a vehicle,
The second rubber portion is arranged outside when the vehicle is mounted,
The interface between the first rubber portion and the second rubber portion is arranged between a pair of main grooves arranged on the outermost side in the tire width direction,
The belt unit includes at least one belt layer,
A pneumatic tire in which the center of at least one of the belt layers in the tire width direction is located outside the tire equatorial plane when the vehicle is mounted.   The pneumatic tire according to claim 1, wherein all the belt layers overlap the inner ground contact end in the tire radial direction when mounted on a vehicle. A plurality of land portions defined by the plurality of main grooves and a ground end,
The pneumatic tire according to claim 1, wherein the void ratio of the land portion formed of the first rubber portion is smaller than the void ratio of the land portion formed of the second rubber portion. The belt portion includes a first belt layer and a second belt layer arranged outside the first belt layer in the tire radial direction,
The pneumatic tire according to any one of claims 1 to 3, wherein the center of the second belt layer in the tire width direction is located outside the center of the first belt layer in the tire width direction when mounted on the vehicle. tire. By being divided by the plurality of main grooves, a center land portion including the tire equatorial plane is provided,
The pneumatic tire according to any one of claims 1 to 4, wherein the interface is located in the center land portion.

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