JP7101586B2 - Pneumatic tires - Google Patents

Description

The present invention relates to a pneumatic tire.

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

Japanese Unexamined Patent Publication No. 2012-76593

Therefore, the problem is to provide a pneumatic tire capable of suppressing deterioration of steering stability performance during turning and braking performance during turning while having an interface of rubber having different rubber hardness on the 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 is arranged in a rubber surface layer portion having an outer surface in the tire radial direction and inside the rubber surface layer portion in the tire radial direction. The rubber surface layer portion is formed of a first rubber portion formed of the first rubber and a second rubber having a rubber hardness higher than that of the first rubber. A rubber portion is provided, 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 the center of at least one of the belt layers in the tire width direction is. , Located outside the rubber surface of the tire when mounted on the vehicle.

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

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

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

Further, the pneumatic tire may be configured to include 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 on the tire meridional surface. FIG. 2 is a developed view of the tread surface of the pneumatic tire according to the embodiment. FIG. 3 is an enlarged view of region III of FIG. FIG. 4 is an enlarged view of the region III of FIG. 1 and is a diagram showing the position of the belt portion. FIG. 5 is an enlarged view of the V region of FIG. 1 and is a diagram showing the position of the belt portion. FIG. 6 is an enlarged view of the VI region of FIG. 1 and is a diagram showing the position of the belt portion. FIG. 7 is a diagram showing the ground contact shape of the pneumatic tire according to the comparative example. FIG. 8 is a diagram showing the 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 the pneumatic tire according to another embodiment on the tire meridional surface, and is a view showing the position of the belt part. FIG. 10 is an enlarged cross-sectional view of a main part of the pneumatic tire according to still another embodiment on the tire meridional surface, and is a diagram showing the position of the 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, an embodiment of the pneumatic tire will be described with reference to FIGS. 1 to 8. In each drawing (the same applies to FIGS. 9 and 10), the dimensional ratio of the drawings does not always match the actual dimensional ratio, and the dimensional ratios between the drawings do not necessarily match. do not have.

In each figure, the first direction D1 is the tire width direction D1 parallel to the tire rotation axis which 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 is the tire radial direction, and the third direction D3 is the tire circumferential direction D3 around the tire rotation axis.

In the tire width direction D1, the inside is the side closer to the tire equatorial plane S1 and the outside is the side far from the tire equatorial plane S1. Further, in the tire radial direction D2, the inner side is on the side closer to the tire rotation axis, and the outer side is on 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 width direction D1 of the tire 1, and the tire meridional plane is a plane including the tire rotation axis and the tire equator. It is a plane orthogonal to the plane S1. The tire equatorial line is a line where the outer surface (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, the tire 1 according to the present embodiment has a pair of bead portions 11 having beads, a sidewall portion 12 extending outward from each bead portion 11 in the tire radial direction D2, and a pair of sidewall portions. It is provided with a tread portion 2 which is connected to the outer end portion of the tire radial direction D2 and whose outer surface in the tire radial direction D2 is in contact with the road surface. In the present embodiment, the tire 1 is a pneumatic tire 1 in which air is introduced, and is mounted on the rim 20.

Further, the tire 1 includes a carcass layer 13 that is bridged between a pair of beads and an inner liner layer 14 that is arranged inside the carcass layer 13 and has an excellent function of blocking gas permeation in order to maintain air pressure. It is equipped with. The carcass layer 13 and the inner liner layer 14 are arranged along the inner circumference of the tire 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 designated to be mounted on a vehicle, and is a tire designated to face the vehicle on the left or right side of the tire 1 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 surface S1.

The orientation of mounting on the vehicle is indicated on the sidewall portion 12. Specifically, the sidewall portion 12 includes a sidewall rubber 12a arranged outside the tire width direction D1 of the carcass layer 13 in order to form a tire outer surface, and is displayed on the surface of the sidewall rubber 12a. Has a part.

For example, a display indicating that one sidewall portion 12 arranged on the inside (the left side in each figure, hereinafter also referred to as “inside the vehicle”) D11 when mounted on the vehicle is inside the vehicle (for example, “INSIDE””. Etc.) are attached. Further, for example, a display indicating that the other sidewall portion 12 arranged on the outside (on the right side in each figure, hereinafter also referred to as “outside the vehicle”) D12 when mounted on the vehicle is outside the vehicle (for example, “outside the vehicle”). "OUTSIDE" etc.) is attached. The vehicle inner D11 is on the side closer to the vehicle center when the tire 1 is mounted on the vehicle, and the vehicle outer D12 is on the 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 2a that is in contact with the road surface, and a belt portion 4 that is arranged between the tread rubber 3 and the carcass layer 13. Further, 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 contact surface that actually touches the road surface, and the outer end of the ground contact surface in the tire width direction D1 is referred to as a ground contact end 2b, 2c. Of the grounding ends 2b and 2c, the grounding end 2b of the vehicle inner side D11 is referred to as the vehicle inner grounding end 2b, and the grounding end 2c of the vehicle outer side D12 is referred to as the vehicle outer grounding end 2c. Further, as the contact patch, the tire 1 is rim-assembled on the regular rim 20, the tire 1 is placed vertically on a flat road surface with the regular internal pressure charged, and the tread surface 2a touches the road surface when a regular load is applied. Point to.

The regular rim 20 is a rim 20 defined for each tire 1 in the standard system including the standard on which the tire 1 is based. For example, JATTA is a standard rim, TRA is "DesignRim", and ETRTO. If so, it will be "Measuring Rim".

The regular internal pressure is the air pressure defined for each tire 1 in the standard system including the standard on which the tire 1 is based. The maximum value described in "INFLATION PRESSURES" is "INFRATION PRESSURE" in the case of ETRTO, but 180 kPa when the tire 1 is for a passenger car.

The normal load is the load defined for each tire 1 in the standard system including the standard on which the tire 1 is based. If it is JATTA, the maximum load capacity, and if it is TRA, the maximum described in the above table. If the value is ETRTO, it is "LOAD CAPACITY", but if the tire 1 is for a passenger car, it is 85% of the corresponding load of an internal pressure of 180 kPa.

The belt portion 4 includes at least one (two in this 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 tire radial direction D2 from the first belt layer 41. Each of the belt layers 41 and 42 includes a plurality of belt cords arranged in parallel and a topping rubber for covering the belt cords. The number of belt layers 41 and 42 is not particularly limited.

The belt cords of the belt layers 41 and 42 are parallel to the tire width direction D1 so as to intersect 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 and 42 are inclined in opposite directions with respect to the tire circumferential direction D3, and are arranged so as to 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 metals 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 and 42 over the tire width direction D1, and the end portions 41a, 41b, 42a of the belt layers 41 and 42 in the tire width direction D1. It is provided with edge reinforcing layers 52 and 53 arranged so as to cover 42b. The presence / absence and position of the belt reinforcing portion 5 are 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, and aramid are preferably used.

The belt reinforcing portion 5 is formed by winding at least one reinforcing cord coated with topping rubber in a spiral shape along the tire circumferential direction D3. As a result, the reinforcing cords of the reinforcing layers 51 to 53 intersect along the tire circumferential direction D3 (for example, at an inclination angle of less than 5 °, preferably 3 ° or less with respect to the tire circumferential direction D3). Alternatively, it is parallel to 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 extend continuously in the tire circumferential direction D3. In the present embodiment, the main grooves 3a and 3b are configured to extend straight along the tire circumferential direction D3, but the configuration is not limited to such a configuration, and for example, the main grooves 3a and 3b are repeatedly refracted and extend in a zigzag shape. It may be configured that the tires are curved, or, for example, the tires may be repeatedly curved and extended in a wavy shape.

The main grooves 3a and 3b are provided with, for example, a portion in which the groove is shallow, a so-called tread wear indicator (not shown) so that the degree of wear can be known by being exposed as the wear progresses. 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 of the tire width direction D1 between the ground contact 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 and 3b, the pair of main grooves 3a and 3a arranged on the outermost side in the tire width direction D1 are referred to as shoulder main grooves 3a, and are arranged between the pair of shoulder main grooves 3a and 3a. The main groove 3b to be formed is referred to as a center main groove 3b. The presence / absence 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 partitioned by main grooves 3a and 3b and ground contact ends 2b and 2c. In the plurality of land portions 3c to 3e, the land portion 3c partitioned by the shoulder main groove 3a and the ground contact ends 2b, 2c is called the shoulder land portion 3c, and is partitioned 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 parts 3d and 3e, the land part 3d partitioned by the shoulder main groove 3a and the center main groove 3b is called the mediate land part 3d, and the land divided 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 and 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 with respect to 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 called a width groove 3f and has a groove width of 1.6 mm. The land groove 3 g that is less than 3 g is called a sipe 3 g. The land portions 3c to 3e may be provided with land grooves 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 peripheral groove.

As shown in FIG. 3, the tread rubber 3 has a rubber surface layer portion 6 having a tread surface 2a which is an outer surface in the tire radial direction D2, and a rubber inner layer arranged inside the tire radial direction D2 with respect to the rubber surface layer portion 6. It is equipped with a part 7. The presence / 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 cap rubbers.

The rubber surface layer portion 6 includes a first rubber portion 6a formed of the 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 a hardness measured at 23 ° C. based on "JIS K6253-1-2012 3.2 durometer hardness".

The rubber hardness of each rubber is not particularly limited, but for example, the rubber hardness of the first rubber may be 66 to 70, and the rubber hardness of the second rubber may be, for example, 70 to 74. Further, for example, the difference in rubber hardness 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 and 3a. As a result, during braking, strain is generated at the interface 6c arranged between the pair of shoulder main grooves 3a and 3a, 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 in the main grooves 3a and 3b but in 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 closer to the tire equatorial plane S1, the greater the contact pressure during braking, whereas the interface 6c is the closest to the tire equatorial plane S1 (specifically, the center land portion including the tire equatorial plane S1). It will be located at 3e. As a result, the strain generated at the interface 6c becomes an effective resistance to the road surface, so that the braking distance can be effectively reduced.

Further, 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 high rubber hardness is arranged on the vehicle outer side D12 on which a large force acts when turning as an outer ring. Therefore, since the rigidity of the vehicle outer side D12 of the rubber surface layer portion 6 can be increased, the steering stability performance at the time of turning can be improved.

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

Further, 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 of the tire width direction D1 between the ground contact ends 2b and 2c). It is more preferably 5% or less, and very preferably 3% or less.

Returning to FIG. 2, in the present embodiment, the void ratio of the land portion 3c to 3e composed of the first rubber portion 6a is higher than the void ratio of the land portion 3c to 3e composed of the second rubber portion 6b. It's getting smaller. As a result, the void ratio of the land portion 3c to 3e composed of the first rubber portion 6a having a relatively low rubber hardness is the land portion 3c to 3e composed 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 a large difference in rigidity between the land portion 3c to 3e of the vehicle inner side D11 and the land portion 3c to 3e of the vehicle outer side D12.

The land portion 3c to 3e composed of the first rubber portion 6a is from the interface 6c (tire equatorial plane S1) of the shoulder land portion 3c and the mediate land portion 3d of the vehicle inner D11 and the center land portion 3e. Is also the area of D11 inside the vehicle. Therefore, the void ratio of the land portion 3c to 3e composed of the first rubber portion 6a is the area of the land portion 3c to 3e between the vehicle inner ground contact end 2b and the interface 6c (excluding the main grooves 3a and 3b). , The ratio of the total area of the land grooves 3f, 3g to the total of the land grooves 3f, 3g).

Further, the land portion 3c to 3e composed of the second rubber portion 6b is from the interface 6c (tire equatorial plane S1) of the shoulder land portion 3c and the mediat land portion 3d of the vehicle outer side D12 and the center land portion 3e. Is also the area of D12 on the outside of the vehicle. Therefore, the void ratio of the land portion 3c to 3e composed of the second rubber portion 6b is the area of the land portion 3c to 3e between the vehicle outer ground contact end 2c and the interface 6c (excluding the main grooves 3a and 3b). , The ratio of the total area of the land grooves 3f, 3g to the total of the land grooves 3f, 3g).

The pitch (distance of the tire circumferential direction D3) of the width groove 3f (excluding the sipes 3g) in the media land portion 3d of the vehicle inner side D11 is the width groove 3f (sipe) in the media land portion 3d of the vehicle outer side D12. It is larger than the pitch (excluding 3g). Further, the pitch of the width groove 3f (excluding the sipes 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 sipes 3g) in the shoulder land portion 3c of the vehicle outer side D12. It has become.

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

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 outer side D12 of the vehicle 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 region of the belt layers 41 and 42 arranged on the vehicle outer side D12 is larger than the region of the belt layers 41 and 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 preferably 3% or less of the size of.

Although the first and second belt layers 41 and 42 are shifted to the vehicle outer side D12, as shown in FIG. 5, the first and second belt layers 41 and 42 have the vehicle inner ground contact end. It overlaps with 2b in the tire radial direction D2. Specifically, the vehicle inner end portions 41a and 42a of the first and second belt layers 41 and 42 are located on the outer side of the tire width direction D1, specifically on the vehicle inner side D11, with respect to the vehicle inner ground contact end 2b, respectively. 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 “distance between belt ends”) W4 in the tire width direction D1. is seperated.

Further, as shown in FIG. 6, the first and second belt layers 41 and 42 overlap with the vehicle outer ground contact end 2c in the tire radial direction D2. Specifically, the vehicle outer end portions 41b and 42b of the first and second belt layers 41 and 42 are located outside the vehicle outer ground contact end 2c, respectively, outside the tire width direction D1, specifically, the vehicle outside 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 portion 41b of the first belt layer 41 and the vehicle outer end portion 42b of the second belt layer 42 are separated by a predetermined distance (distance between the belt ends) W6 in the tire width direction D1.

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

Further, the distances W4 and W6 between the belt ends are not particularly limited. However, if the distances W4 and W6 between the belt ends are small, air is likely to be mixed between the ends 41a and 42a (41b, 42b) of the belt layers 41 and 42 during manufacturing. Therefore, the distances W4 and W6 between the belt ends are preferably, for example, 5 mm or more.

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

The tire according to the comparative example is a tire whose configuration has been changed so that 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 the ground contact shape of the tire according to the comparative example, and FIG. 8 shows the 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 outer ring is turned. In addition, in FIGS. 7 and 8, the land grooves 3f and 3g are not shown.

As shown in FIG. 7, when turning as an outer ring, a large force acts on the outer D12 of the vehicle, so that the ground contact length of the inner D11 of the vehicle (the length of the tire circumferential direction D3 of the ground contact shape) is the outer D12 of the vehicle. It is very short with respect to the ground contact length. As a result, in the tire according to the comparative example, the contact area of the entire tire 1 becomes smaller, so that the braking performance at the time of turning is deteriorated.

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 outer side D12 of the vehicle with respect to the tire equatorial plane S1 (see FIG. 4). As a result, the region of the belt layers 41 and 42 arranged on the vehicle inner side D11 of the tire equatorial plane S1 is larger than the region of the belt layers 41 and 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, and as shown in FIG. 8, it is possible to suppress the shortening of the ground contact length in the region inside the vehicle D11. Therefore, since the contact area of the entire tire 1 is large, the braking performance during turning can be improved.

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

Further, there is a concern that the rigidity of the region of the vehicle inner side D11 may be excessively lowered due to the positions of the first and second belt layers 41 and 42 shifted to the vehicle outer side D12. On the other hand, the first and second belt layers 41 and 42 overlap with the vehicle inner 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 lowered.

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. This not only suppresses deterioration of steering stability performance during turning and braking performance during turning, but also prevents the first belt layer 41 and the second belt layer 42 from being separated from the surroundings. It can be suppressed.

From the above, the pneumatic tire 1 according to the present embodiment is a pneumatic tire 1 having a plurality of main grooves 3a and 3b extending in the tire circumferential direction D3, and is a rubber surface layer portion 6 having an outer surface in the tire radial direction D2. The rubber surface layer portion 6 includes a belt portion 4 arranged inside the rubber surface layer portion 6 in the tire radial direction D2, and the rubber surface layer portion 6 includes a first rubber portion 6a formed of the 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 one rubber is provided, and the first rubber portion 6a is arranged on the inner D11 when mounted on a vehicle, and the second rubber is provided. The portion 6b is arranged on the outer D12 when mounted on the vehicle, and the interface 6c between the first rubber portion 6a and the second rubber portion 6b is a pair of main grooves 3a, 3a arranged on the outermost side in the tire width direction D1. Arranged between them, the belt portion 4 includes at least one belt layer 41, 42, and at least one of the belt layers 41, 42, the center 41c, 42c in the tire width direction D1, is the tire equatorial line when mounted on a vehicle. It is located on the outer side D12 of the surface S1.

According to such a configuration, distortion occurs 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 and 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 ring, a large force acts on the region of the outer D12 when the vehicle is mounted, whereas the second rubber portion 6b having a relatively large rubber hardness is arranged on the outer D12 when the vehicle is mounted. There is. As a result, the rigidity of the region of the outer 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 ring when turning, the contact length of the inner D11 region tends to be shortened when the vehicle is mounted. Therefore, at least one of the belt layers 41 and 42, the center 41c and 42c in the tire width direction D1, is located on the outer side D12 of the tire equatorial plane S1 when mounted on the vehicle. As a result, the rigidity of the inner D11 region can be reduced when the vehicle is mounted, so that it is possible to prevent the ground contact length of the inner D11 region from becoming shorter when the vehicle is mounted as an outer ring.

Therefore, in the outer ring during turning, the contact area of the entire tire 1 becomes large, so that the braking performance during turning can be improved. As a result, it is possible to suppress deterioration of steering stability performance during turning and braking performance during turning while having a rubber interface 6c having different rubber hardness on the rubber surface layer portion 6.

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

According to such a configuration, at least one of the belt layers 41 and 42, the center 41c and 42c in the tire width direction D1, is located on the outer side D12 of the tire equatorial plane S1 when mounted on the vehicle. All the belt layers 41 and 42 overlap with the ground contact end 2b of the inner D11 in the tire radial direction D2 when mounted on the vehicle. As a result, all the belt layers 41 and 42 overlap with the ground contact end 2b of the inner D11 in the tire radial direction D2 when the vehicle is mounted, so that the rigidity of the region of the inner D11 is suppressed 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 partitioned by the plurality of main grooves 3a and 3b and the ground contact ends 2b and 2c, and is composed of the first rubber portion 6a. The void ratio of the land portion 3c to 3e is smaller than the void ratio of the land portion 3c to 3e composed of the second rubber portion 6b.

According to such a configuration, the void ratio of the land portion 3c to 3e composed of the first rubber portion 6a having a relatively small rubber hardness is the land composed of the second rubber portion 6b having a relatively large rubber hardness. It is smaller than the void ratio of parts 3c to 3e. As a result, it is possible to prevent the difference in rigidity between the land portions 3c to 3e arranged on the inner D11 when mounted on the vehicle and the land portions 3c to 3e arranged on the outer D12 when mounted on the vehicle from becoming too large.

Further, the pneumatic tire 1 according to the present embodiment is provided with a 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 configured to be located in the part 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, the closer to the tire equatorial plane S1, the larger the contact pressure during braking, whereas the interface 6c is located at the center land portion 3e closest to the tire equatorial plane S1, so that the strain generated at the interface 6c. However, it becomes an effective resistance to the road surface.

The pneumatic tire 1 is not limited to the configuration of the above-described embodiment, and is not limited to the above-mentioned action and effect. Further, it goes without saying that the pneumatic tire 1 can be modified in various ways within a range that does not deviate from the gist of the present invention. For example, it is of course possible to arbitrarily select one or a plurality of configurations and methods according to the following various modified examples and adopt them in the configurations and methods according to the above-described embodiment.

(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 located 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 tire radial direction D2 from the first belt layer 41. The center 42c of the second belt layer 42 in the tire width direction D1 is located outside the center 41c of the tire width direction D1 of the first belt layer 41 when mounted on a vehicle. 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 outside the tire radial direction D2 is larger than the first belt layer 41 located inside the tire radial direction D2 with respect to the rigidity of the rubber surface layer portion 6. On the other hand, the center 42c of the second belt layer 42 in the tire width direction D1 is located on the outer side D12 of the first belt layer 41 with respect to the center 41c of the tire width direction D1. Thereby, the rigidity of the region of the vehicle inner side D11 of the rubber surface layer portion 6 can be effectively reduced.

Therefore, for example, when turning as an outer ring, it is possible to effectively suppress the shortening of the ground contact length of the region of the inner D11 when the vehicle is mounted. The configuration is not limited to this, and for example, the center 41c of the first belt layer 41 may be located on the outer side D12 of the center 42c of the second belt layer 42 when mounted on a vehicle.

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

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

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

Preferred embodiments of tire 1 will be described below with reference to FIGS. 11 and 12.

<Crack occurrence rate>
After mounting each tire on the vehicle and traveling 100,000 km on a general road under the condition of an internal pressure of 200 kPa, a crack occurred on the outer surface of the tire (position near the vehicle outer end 41b of the first belt layer 41). We investigated whether cracks occurred and calculated the probability of cracks.

<Air mixing rate>
Twenty tires are manufactured, the tires are cut along the meridional plane of the tire, and air having a diameter of 1 mm or more is mixed between the ends 41a, 42a (41b, 42b) of the belt layers 41, 42. We investigated the number of products and calculated the probability that air-contaminated products were generated.

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

<Examples 2 and 3>
The tire according to the second embodiment is a tire in which the belt layers 41 and 42 are moved to the outer side D12 of the vehicle by about 2 mm with respect to the tire according to the first embodiment. Therefore, in the tire according to the second embodiment, the distance W5 between the vehicle outer end portion 41b of the first belt layer 41 and the tire surface is 8 mm.
The tire according to the third embodiment is a tire in which the belt layers 41 and 42 are moved to the outer side D12 of the vehicle by about 5 mm with respect to the tire according to the first embodiment. Therefore, in the tire according to the third embodiment, the distance W5 between the vehicle outer end portion 41b of the first belt layer 41 and the tire surface is 5 mm.

<Examples 4 and 5>
The tire according to the fourth embodiment is a tire in which the dimension of the tire width direction D1 of the second belt layer 42 is longer than the tire according to the first embodiment by 3 mm each on the vehicle inner side D11 and the vehicle outer side D12. Therefore, in the tire according to the fourth embodiment, 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 5 mm.
The tire according to the fifth embodiment is a tire in which the dimension of the tire width direction D1 of the second belt layer 42 is longer than the tire according to the first embodiment by 5 mm on the inner side D11 and the outer side D12 of the vehicle. Therefore, in the tire according to the fifth embodiment, 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.

As shown in FIG. 11, in the tire according to the third embodiment in which the distance W5 between the vehicle outer end portion 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 and W5 between the ends 41a, 41b, 42a, 42b of the belt layers 41 and 42 and the tire surface are preferably 8 mm or more.

Further, as shown in FIG. 12, in the tire according to the fifth embodiment, 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. The air mixing rate is 0% in the tires according to Examples 1 and 4 in which the distances W4 and W6 are 5 mm or more, while the air mixing rate is 10%. Therefore, the distances W4 and W6 between the ends 41a and 41b of the first belt layer 41 and the ends 42a and 42b of the second belt layer 42 are preferably 5 mm or more.

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 (medium land part), 3e ... Middle land part (center land part), 3f ... Land groove (width groove), 3g ... Land groove (sipe), 4 ... Belt part, 5 ... Belt reinforcement part, 6 ... rubber surface layer part, 6a ... first rubber part, 6b ... second rubber part, 6c ... interface, 7 ... rubber inner layer part, 11 ... bead part, 12 ... sidewall part, 12a ... sidewall rubber , 13 ... Carcus layer, 14 ... Inner liner layer, 20 ... Rim, 41 ... First belt layer, 41a ... Vehicle inner end, 41b ... Vehicle outer end, 41c ... Center, 42 ... Second belt layer, 42a ... Vehicle inner end, 42b ... Vehicle outer end, 42c ... Center, 51 ... Cap reinforcement layer, 52 ... Edge reinforcement layer, 53 ... Edge reinforcement layer, D1 ... Tire width direction, D2 ... Tire radial direction, D3 ... Tire circumference Direction, D11 ... inside the vehicle, D12 ... outside the vehicle, S1 ... tire equatorial plane

Claims (5)

A pneumatic tire with multiple 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 rubber surface layer portion in the tire radial direction are provided.
The rubber surface layer portion includes a first rubber portion formed of the 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 on the outside when mounted on the vehicle.
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 portion includes a plurality of belt layers and has a plurality of belt layers.
The center of all belt layers in the tire width direction is a pneumatic tire located outside the equatorial plane of the tire when mounted on a vehicle. The pneumatic tire according to claim 1, wherein all the belt layers overlap with the inner ground contact end in the tire radial direction when mounted on a vehicle. It is provided with a plurality of land portions partitioned by the plurality of main grooves and the grounding end.
The pneumatic tire according to claim 1 or 2, wherein the void ratio of the land portion composed of the first rubber portion is smaller than the void ratio of the land portion composed 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 inflator 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 a vehicle. tire. By being partitioned by the plurality of main grooves, the center land portion including the equatorial plane of the tire is provided.
The pneumatic tire according to any one of claims 1 to 4, wherein the interface is located on the land portion of the center.

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