JP2013071633A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce vehicle exterior noise while maintaining wet braking.SOLUTION: In a pneumatic tire, shoulder lands 4a, 4b and three ribs 4c, 4d, 4e are formed on a tread face 2a with four main grooves 3, a vehicle inside shoulder land lug groove 5a with one end communicating with the main groove of a vehicle innermost side is formed on a vehicle inside shoulder land, and a vehicle outside shoulder land lug groove 5c isolated from the main groove of a vehicle outermost side is formed on a vehicle outside shoulder land. In addition, a center rib lug groove 5d with one end communicating with the main groove of a vehicle inside and the other end terminating at the rib is formed at the center rib, a vehicle outside rib lug groove 5e with one end communicating with the main groove of the vehicle inside and the other end terminating at the rib is formed at a vehicle outside rib, a vehicle inside rib first lug groove 5f with one end communicating with the main groove of the vehicle inside and the other end terminating in the rib is formed at the rib of the vehicle inside, and a vehicle inside rib second lug groove 5g with one end communicating with the main groove of the vehicle outside and the other end terminating in the rib is formed at the rib of the vehicle inside. In the pneumatic tire, the width W1 of the rib of the vehicle inside is 1.2-1.5 times larger than the widths W2, W3 of the other rib.

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire that reduces outside noise while maintaining wet braking performance.

  Conventionally, Patent Document 1 discloses a pneumatic tire for the purpose of improving skid resistance when wet and snow while maintaining braking performance. In this pneumatic tire, four main grooves extending in the tire circumferential direction are arranged on the tread surface at predetermined intervals in the tire width direction, and the four main grooves are arranged in a center region located between the outer main grooves. Three ribs are divided and formed by grooves, and each rib has a first lug groove that communicates with the main groove only at one end and extends in the tire width direction at predetermined intervals in the tire circumferential direction. Only one end of each of the first lug grooves communicates with the first lug groove, and at least one sipe extending in the tire circumferential direction at a position where the rib width is substantially equally divided is 0 [ It is arranged in the range of [°] to 5 [°], and the length of the sipe in the tire circumferential direction is set in the range of 40 [%] to 60 [%] of the distance between the first lug grooves, and from the outer main grooves. Auxiliary grooves extending in the tire circumferential direction are arranged in both shoulder regions located on the outer side, and each auxiliary groove and the outer side are arranged. Ribs are formed between the main grooves and the second lug grooves extending outward from the auxiliary grooves in the tire width direction are arranged at predetermined intervals in the tire circumferential direction.

Japanese Patent No. 4581732

  The pneumatic tire described in Patent Document 1 described above is excellent in wet braking performance and dry braking performance. However, since one end of the first lug groove is disposed so as to communicate with the main groove on the outer side in the tire width direction, further improvement is desired from the viewpoint of reducing outside noise.

  The present invention has been made in view of the above, and an object of the present invention is to provide a pneumatic tire capable of reducing outside noise while maintaining wet braking performance.

  In order to solve the above-described problems and achieve the object, the pneumatic tire according to the present invention is designated in the direction of the inside and outside of the vehicle when the vehicle is mounted, and is extended to the tread surface in the tire circumferential direction. The main grooves are arranged at predetermined intervals in the tire width direction, so that the shoulder land portions on the outer side in the tire width direction of the main grooves on the outermost side in the tire width direction and the main grooves on the outermost side in the tire width direction are arranged. A pneumatic tire in which three ribs on the inner side in the tire width direction are sectioned, provided on the shoulder land portion on the inner side of the vehicle, and extending in the tire width direction and arranged in parallel in the tire circumferential direction. One end is provided on the vehicle inner shoulder land lug groove that communicates with the main groove on the innermost side of the vehicle and the shoulder land portion on the outer side of the vehicle, and extends in the tire width direction and arranged in parallel in the tire circumferential direction. One end facing the main groove on the outermost side of the vehicle It is provided in a vehicle outer shoulder land lug groove that terminates in the shoulder land portion and is separated from the main groove on the outermost side of the vehicle, and in the center rib, and extends in the tire width direction and plural in the tire circumferential direction. A central rib lug groove that is arranged in parallel and has one end communicating with the main groove inside the vehicle and the other end terminating in the rib, and the rib outside the vehicle, extends in the tire width direction and extends around the tire circumference. Are provided in the outer rib rib groove on the vehicle inner side, the one end communicating with the main groove on the vehicle inner side and the other end terminating in the rib, and the rib on the vehicle inner side, and extending in the tire width direction. A plurality of side-by-side tire circumferential directions, one end communicating with the main groove inside the vehicle and the other end terminating in the rib, and a first lug groove on the vehicle inner rib and the rib on the vehicle inner side. , Extending in the tire width direction, multiple in the tire circumferential direction A vehicle inner rib second lug groove with one end communicating with the main groove on the vehicle outer side and the other end terminating in the rib, and the width of the rib on the vehicle inner side is It is characterized by being formed to be 1.2 times or more and 1.5 times or less with respect to the width of the rib.

  According to this pneumatic tire, in the shoulder land portion on the vehicle outer side, the vehicle outer shoulder land portion lug groove is provided separately from the main groove on the vehicle inner side of the shoulder land portion on the vehicle outer side, The central rib lug groove is provided separately from the main groove on the vehicle outer side of the central rib, and the vehicle outer rib lug groove is separated from the main groove on the vehicle outer side of the vehicle outer rib. The vehicle inner rib has a vehicle inner rib second lug groove communicating with the main groove on the vehicle outer side. For this reason, radiation of pattern noise to the outside of the vehicle can be suppressed. Moreover, during braking, the contact pressure of the tread surface around the outermost main groove in the tire width direction increases and drainage becomes important, but the vehicle that communicates with the main groove on the vehicle outer side at the shoulder land portion on the inner side of the vehicle. By providing the inner shoulder land portion lug groove, drainage to the vehicle inner side can be improved.

  By the way, if the width of the ribs on the inner side of the vehicle exceeds 1.5 times the width of the ribs on the center and the outer side of the vehicle, the arrangement of the main grooves is biased on the outer side of the vehicle. If it is less than 1.2 times, the width of each rib on the center and the outside of the vehicle becomes wide and the drainage tends to deteriorate. In this regard, according to the pneumatic tire of the present invention, the width of the rib on the inside of the vehicle is formed to be 1.2 times or more and 1.5 times or less than the width of each rib on the center and the outside of the vehicle, By providing the vehicle inner rib first lug groove communicating with the main groove inside the vehicle on the wide inner rib, the air column resonance sound does not stand out on the outer side of the vehicle, and the rib on the inner side of the vehicle The drainage is improved.

  As a result, according to the pneumatic tire of the present invention, it is possible to reduce vehicle exterior noise while maintaining wet braking performance.

  In the pneumatic tire of the present invention, each lug groove provided in each rib extends at an angle of 30 [°] or more and 60 [°] or less with respect to the tire circumferential direction. And

  According to this pneumatic tire, if the angle of each lug groove provided on each rib with respect to the tire circumferential direction is in the range of 30 [°] or more and 60 [°] or less, Drainability becomes good and tends to maintain wet braking more.

In the pneumatic tire of the present invention, the tread surface is formed of a plurality of arcs having different radii of curvature, the rim is assembled to a normal rim, and 5% of the normal internal pressure is filled. The tread surface has a central arc located at the center in the tire width direction, and a shoulder formed at two locations on both ends of the central arc in the tire width direction, with the two arcs having substantially the same radius of curvature. A side arc and a shoulder arc that forms a shoulder located at an end of the tread surface in the tire width direction, the radius of curvature of the central arc is TR1, and the center from the tire equator plane to the center The contour range that is the width of the partial arc to the end in the tire width direction is L1, the tread deployment width that is the width of the tread surface in the tire width direction is TDW, and the tire width SW is the total width that is the width in the tire width direction of the outermost portions in the tire width direction among the opposing sidewall portions that are located at both ends in the direction, and the diameter in the tire radial direction of the tread surface is SW The outer diameter of the tire, which is the diameter of the largest portion, is OD, and the flatness is β, which is obtained by the following formula (1), which is a relational expression between the contour range L1 and the tread development width TDW. While K1 is within the range of 0.6 ≦ K1 ≦ 0.8, it is obtained by the following equation (2) that is an equation for obtaining the ratio between the radius of curvature TR1 of the central arc and the tire outer diameter OD. K2 is in the range of 0.9 ≦ K2 ≦ 2.0, and K3 obtained by the following equation (3), which is a relational expression of the flatness ratio β, the tread development width TDW, and the total width SW, Within the range of 0.40 ≦ K3 ≦ 0.48, before Distance from the tire equatorial plane to one end of the lug grooves provided in the shoulder land portion, characterized in that a 0.97 × L1 or 1.03 × L1 below.
K1 = L1 / (TDW × 0.5) (1)
K2 = TR1 / OD (2)
K3 = (β × TDW) / (100 × SW) (3)

  In the present invention, the relationship K1 between the contour range L1 and the tread development width TDW is calculated by the above formula, and K1 falls within the range of 0.6 ≦ K1 ≦ 0.8, and the radius of curvature TR1 of the central arc is By setting the ratio K2 to the tire outer diameter OD to be in the range of 0.9 ≦ K2 ≦ 2.0, the profile of the tread surface approaches a flat shape. Thereby, for example, the contact area at the time of low load such as 40% load of the maximum load can be increased, and the maximum cornering force at the time of low load can be increased. Therefore, it is possible to ensure steering stability at low loads. Further, by calculating K3, which is the relationship between the flat rate β, the tread development width TDW, and the total width SW by the above formula, so that K3 is within the range of 0.40 ≦ K3 ≦ 0.48, Since the tread development width can be narrowed, for example, the ground contact area at the time of maximum load, that is, at the time of high load such as 100% load can be reduced, and the maximum cornering force at the time of high load can be reduced. Therefore, it is possible to improve the rollover resistance at high loads. Furthermore, by setting the distance from the tire equator surface to the lug groove start position provided on the shoulder land portion to be 0.97 × L1 or more and 1.03 × L1 or less, the ground contact front end of the pneumatic tire has a square shape. Since the shape is closer to a circle from the close shape, the region where the pneumatic tire slides near the shoulder portion is reduced. As a result, rollover resistance can be improved while maintaining steering stability, and high-frequency road noise can be reduced.

  The pneumatic tire according to the present invention can reduce outside noise while maintaining wet braking performance.

FIG. 1 is a plan view showing a tread pattern of a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a partially enlarged view of the plan view of FIG. FIG. 3 is a meridional sectional view of the pneumatic tire according to the embodiment of the present invention. FIG. 4 is a chart showing the results of the performance test of the pneumatic tire according to the example of the present invention. FIG. 5 is a chart showing the results of the performance test of the pneumatic tire according to the example of the present invention.

  Embodiments of the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. The constituent elements of this embodiment include those that can be easily replaced by those skilled in the art or those that are substantially the same. In addition, a plurality of modifications described in this embodiment can be arbitrarily combined within a range obvious to those skilled in the art.

  FIG. 1 is a plan view showing a tread pattern of the pneumatic tire according to the present embodiment. In the following description, the tire radial direction refers to a direction orthogonal to the rotation axis (not shown) of the pneumatic tire 1, and the tire radial direction inner side refers to the side toward the rotation axis in the tire radial direction, the tire radial direction outer side. The term “side away from the rotation axis” in the tire radial direction. Further, the tire width direction means a direction parallel to the rotation axis, the inner side in the tire width direction means the side toward the tire equator plane (tire equator line) CL in the tire width direction, and the outer side in the tire width direction means the tire width. The direction away from the tire equatorial plane CL in the direction. The tire circumferential direction is a circumferential direction with the rotation axis as a central axis. The tire equatorial plane CL is a plane that is orthogonal to the rotational axis of the pneumatic tire 1 and passes through the center of the tire width of the pneumatic tire 1. The tire equator line is a line along the circumferential direction of the pneumatic tire 1 on the tire equator plane CL. In the present embodiment, the same sign “CL” as that of the tire equator plane is attached to the tire equator line.

  When the pneumatic tire 1 of the present embodiment is mounted on a vehicle (not shown), the direction with respect to the inside and outside of the vehicle is specified in the tire width direction. The designation of the direction is not clearly shown in the figure, but is indicated by, for example, an index provided on the sidewall portion 11 described later. Hereinafter, the side facing the inside of the vehicle when mounted on the vehicle is referred to as the inside of the vehicle, and the side facing the outside of the vehicle is referred to as the outside of the vehicle. In addition, designation | designated of a vehicle inner side and a vehicle outer side is not restricted to the case where it mounts | wears with a vehicle. For example, when the rim is assembled, the direction of the rim with respect to the inside and outside of the vehicle is determined in the tire width direction. For this reason, when the rim is assembled, the pneumatic tire 1 is designated with respect to the inner side (vehicle inner side) and the outer side (vehicle outer side) of the vehicle in the tire width direction.

  As shown in FIG. 1, the pneumatic tire 1 has a tread portion 2. The tread portion 2 is made of a rubber material and is exposed at the outermost side in the tire radial direction of the pneumatic tire 1, and the tread surface 2 a that is the surface thereof is the contour of the pneumatic tire 1.

  In the tread surface 2a, four main grooves 3 extending along the tire circumferential direction are arranged side by side in the tire width direction. The tread surface 2a includes, by the four main grooves 3, shoulder land portions 4a and 4b extending in the tire circumferential direction on the outer side in the tire width direction of the main grooves 3 on the outermost side in the tire width direction, and the tire width direction. Three ribs 4c, 4d, and 4e extending in the tire circumferential direction on the inner side in the tire width direction of the outermost main grooves are sectioned. The main groove 3 has a groove width of 3 [%] to 6 [%] of the grounding width TW. Further, the width W1 of the rib 4e on the vehicle inner side is set to be 1.2 times or more and 1.5 times or less than the widths W2 and W3 of the ribs 4c and 4d on the center side and the vehicle outer side.

  Here, the contact width TW means that the tread surface 2a of the pneumatic tire 1 when the pneumatic tire 1 is assembled on a regular rim, filled with a regular internal pressure and 70% of the regular load is applied. This is the maximum width in the tire width direction of the area that contacts the road surface.

  The regular rim is “standard rim” defined by JATMA, “Design Rim” defined by TRA, or “Measuring Rim” defined by ETRTO. The normal internal pressure is “maximum air pressure” defined by JATMA, the maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “INFLATION PRESSURES” defined by ETRTO. The normal load is “maximum load capacity” defined by JATMA, a maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “LOAD CAPACITY” defined by ETRTO.

  The vehicle inner shoulder land portion 4a is provided with a vehicle inner shoulder land portion lug groove 5a. The vehicle inner shoulder land lug groove 5a extends in the tire width direction and is arranged in parallel in the tire circumferential direction, and one end communicates with the main groove 3 on the innermost side of the vehicle. The vehicle inner shoulder land lug groove 5a is formed to be curved in the tire circumferential direction. Further, the vehicle inner shoulder land portion 4a is provided with a vehicle inner shoulder land portion sub lug groove 5b. The vehicle inner shoulder land portion auxiliary lug groove 5b extends in the tire width direction and is arranged in parallel in the tire circumferential direction, and one end facing the innermost main groove 3 in the vehicle is within the shoulder land portion 4a on the vehicle inner side. It terminates and is spaced apart from the innermost main groove 3 of the vehicle. The vehicle inner shoulder land portion sub lug groove 5b is formed to be curved in the tire circumferential direction similarly to the vehicle inner shoulder land portion lug groove 5a, and is disposed between the vehicle inner shoulder land portion lug grooves 5a.

  The vehicle outer shoulder land portion 4b is provided with a vehicle outer shoulder land portion lug groove 5c. A plurality of vehicle outer shoulder land lug grooves 5c extend in the tire width direction and are arranged side by side in the tire circumferential direction, and one end facing the vehicle outermost main groove 3 terminates in the shoulder land portion 4b outside the vehicle. However, they are arranged apart from the innermost main groove 3 of the vehicle. In the present embodiment, one auxiliary groove 6 extending in the tire circumferential direction is provided on the outer side of the main groove 3 on the outermost side of the vehicle on the shoulder land portion 4b on the outer side of the vehicle. One end of the vehicle outer shoulder land lug groove 5c communicates with the groove 6 so that the vehicle outer shoulder land lug groove 5c is spaced from the innermost main groove 3 of the vehicle. The auxiliary groove 6 is a groove having a groove width of 10% to 30% of the groove width of the main groove 3. The vehicle outer shoulder land lug groove 5c is formed to be curved in the tire circumferential direction opposite to the vehicle inner shoulder land lug groove 5a. The shoulder land portion 4b outside the vehicle is provided with a shoulder land portion sipe 7a. The shoulder land sipe 7a extends in the tire width direction and is arranged in parallel in the tire circumferential direction. One end of the shoulder land sipe 7a facing the main groove 3 on the innermost side of the vehicle communicates with the auxiliary groove 6, thereby The main groove 3 is spaced apart. The shoulder land portion sipe 7a is curved in the tire circumferential direction similarly to the vehicle outer shoulder land lug groove 5c, and is disposed between the vehicle outer shoulder land lug groove 5c. In the present embodiment, the sipe refers to a groove having a groove width of 1.5 [mm] or less.

  The central rib 4c is provided with a central rib lug groove 5d. The central rib lug grooves 5d extend in the tire width direction and are arranged in parallel in the tire circumferential direction, with one end communicating with the main groove 3 on the vehicle inner side and the other end terminating in the central rib 4c. Has been. The central rib lug groove 5d is provided to be inclined with respect to the tire circumferential direction. Further, the central rib lug groove 5d is formed so that the groove width gradually increases from the other end toward one end communicating with the main groove 3, and the water in the groove is easily drained into the main groove 3. The central rib 4c is provided with a central rib sipe 7b. The central rib sipe 7b extends in the tire circumferential direction, and one end thereof communicates with the central rib lug groove 5d and the other end terminates in the central rib 4c. In the present embodiment, the central rib sipe 7b communicates in the middle of the central rib lug groove 5d and extends in the tire circumferential direction toward the opposite side of the inclined direction of the central rib lug groove 5d inclined from one end to the other end. Are arranged. By providing the central rib sipe 7b, it is possible to effectively exhibit the edge effect against skidding during wet traveling or snow traveling.

  The vehicle outer rib 4d is provided with a vehicle outer rib lug groove 5e. The vehicle outer rib lug grooves 5e extend in the tire width direction and are arranged in parallel in the tire circumferential direction. One end communicates with the main groove 3 on the vehicle inner side, and the other end terminates in the rib 4d on the vehicle outer side. Are arranged. The vehicle outer rib lug groove 5e is provided to be inclined in the tire circumferential direction. In the present embodiment, the vehicle outer rib lug groove 5e is inclined from one end to the other end in the same direction as the central rib lug groove 5d. Further, the vehicle outer rib lug groove 5e is formed so that the groove width is gradually increased from the other end toward one end communicating with the main groove 3, and the water in the groove is easily drained into the main groove 3. The vehicle outer rib 4d is provided with a vehicle outer rib sipe 7c. The vehicle outer rib sipe 7c extends in the tire circumferential direction, and has one end communicating with the vehicle outer rib lug groove 5e and the other end terminated in the vehicle outer rib 4d. In the present embodiment, the vehicle outer rib sipe 7c communicates in the middle of the vehicle outer rib lug groove 5e, and from there, the tire circumferential direction toward the opposite side of the inclination direction of the vehicle outer rib lug groove 5e inclined from one end to the other end. It is arranged to extend. By providing the vehicle outer rib sipe 7c, it is possible to effectively exhibit the edge effect against skidding during wet traveling or snow traveling.

  The vehicle inner rib 4e is provided with a vehicle inner rib first lug groove 5f and a vehicle inner rib second lug groove 5g. The vehicle inner rib first lug grooves 5f extend in the tire width direction and are arranged in parallel in the tire circumferential direction, with one end communicating with the main groove 3 on the vehicle inner side and the other end in the rib 4e on the vehicle inner side. It is arranged at the end. The vehicle inner rib first lug groove 5f is provided to be inclined in the tire circumferential direction. In the present embodiment, the vehicle inner rib first lug groove 5f is inclined from one end to the other end in the opposite direction to the central rib lug groove 5d. Further, the vehicle inner rib first lug groove 5f is formed so that the groove width is gradually increased from the other end toward one end communicating with the main groove 3, and the water in the groove is easily drained into the main groove 3. Yes.

  The vehicle inner rib second lug grooves 5g extend in the tire width direction and are arranged in parallel in the tire circumferential direction, one end communicating with the main groove 3 on the vehicle outer side, and the other end in the rib 4e on the vehicle inner side. It is arranged at the end. The vehicle inner rib second lug groove 5g is provided to be inclined in the tire circumferential direction. In the present embodiment, the vehicle inner rib second lug groove 5g is inclined from one end to the other end in the same direction as the central rib lug groove 5d. Further, the vehicle inner rib second lug groove 5g is formed so that the groove width is gradually increased from the other end toward one end communicating with the main groove 3, and the water in the groove is easily drained into the main groove 3. Yes.

  The vehicle inner rib 4e is provided with a vehicle inner rib first sipe 7d and a vehicle inner rib second sipe 7e. The vehicle inner rib first sipe 7d extends in the tire circumferential direction, and has one end communicating with the vehicle inner rib first lug groove 5f and the other end terminated in the vehicle inner rib 4e. . In the present embodiment, the vehicle inner rib first sipe 7d communicates with the other end where the vehicle inner rib first lug groove 5f terminates, and from there, the vehicle inner rib first lug groove 5f is inclined from one end to the other end. The tire extends in the tire circumferential direction toward the inclination direction. The vehicle inner rib second sipe 7e extends in the tire circumferential direction, and one end communicates with the vehicle inner rib second lug groove 5g and the other end terminates in the vehicle inner rib 4e. ing. In the present embodiment, the vehicle inner rib second sipe 7e communicates with the other end of the vehicle inner rib second lug groove 5g, and from there, the vehicle inner rib second lug groove 5g is inclined from one end to the other end. The tire extends in the tire circumferential direction toward the inclination direction. By providing the vehicle inner rib first sipe 7d and the vehicle inner rib second sipe 7e, the edge effect can be effectively exhibited against skidding during wet traveling or snow traveling.

  As described above, the pneumatic tire 1 according to the present embodiment is designated in the direction of the inside and outside of the vehicle when the vehicle is mounted, and the tire has four main grooves 3 extending in the tire circumferential direction on the tread surface 2a. By disposing at predetermined intervals in the width direction, the shoulder land portions 4a and 4b on the outer side in the tire width direction of the main grooves 3 on the outermost side in the tire width direction and the tire widths on the main grooves 3 on the outermost side in the tire width direction The three ribs 4c, 4d, 4e on the inner side in the direction are sectioned. And the vehicle inside shoulder land part lug which is provided in the shoulder land part 4a inside a vehicle, is extended in the tire width direction, is arranged in parallel by the tire circumferential direction, and one end communicates with the main groove 3 inside the vehicle. A vehicle outer shoulder land lug that is provided in the groove 5a and the shoulder land portion 4b on the vehicle outer side, extends in the tire width direction and is arranged in parallel in the tire circumferential direction and is separated from the main groove 3 on the vehicle outermost side. A groove 5c and a central rib 4c are provided, extend in the tire width direction and arranged in parallel in the tire circumferential direction, with one end communicating with the main groove 3 on the vehicle inner side and the other end within the central rib 4c. Are provided in a central rib lug groove 5d that terminates in the vehicle and a rib 4d on the outer side of the vehicle, extending in the tire width direction and arranged in parallel in the tire circumferential direction, with one end communicating with the main groove 3 on the vehicle inner side and the other end. Vehicle outer rib that ends in the vehicle outer rib 4d The groove 4e and the rib 4e on the vehicle inner side extend in the tire width direction and are arranged in parallel in the tire circumferential direction, with one end communicating with the main groove 3 on the vehicle inner side and the other end on the vehicle inner side. The inner lug first lug groove 5f that terminates in the rib 4e and the rib 4e on the inner side of the vehicle extend in the tire width direction and are arranged in parallel in the tire circumferential direction. A vehicle inner rib second lug groove 5g that communicates with the groove 3 and terminates in the rib 4e on the vehicle inner side. The width W1 of the rib 4e on the vehicle inner side is the ribs 4c, 4d on the center and the vehicle outer side. The widths W2 and W3 are 1.2 times or more and 1.5 times or less.

  According to this pneumatic tire 1, in the shoulder land portion 4b outside the vehicle, the vehicle outside shoulder land portion lug groove 5c is provided separately from the main groove 3 inside the vehicle of the shoulder land portion 4b outside the vehicle, In the central rib 4c, a central rib lug groove 5d is provided separately from the main groove 3 on the vehicle outer side of the central rib 4c, and in the rib 4d on the vehicle outer side, the vehicle outer rib lug groove 5e is formed on the outer rib of the vehicle. The rib 4e on the vehicle inner side is provided with a vehicle inner rib second lug groove 5g that communicates with the main groove 3 on the vehicle outer side. For this reason, radiation of pattern noise to the outside of the vehicle is suppressed. Moreover, during braking, the contact pressure of the tread surface 2a around the outermost main groove 3 in the tire width direction increases and drainage becomes important. However, in the shoulder land portion 4a on the inner side of the vehicle, the main groove 3 on the outer side of the vehicle. By providing the vehicle inner shoulder land lug groove 5a communicating with the vehicle, drainage to the vehicle inner side is improved.

  Further, if the width W1 of the rib 4e on the vehicle inner side exceeds 1.5 times the widths W2 and W3 of the ribs 4c and 4d on the center and the vehicle outer side, the arrangement of the main grooves 3 is biased on the vehicle outer side, so The air column resonance sound is easily noticeable, and if it is less than 1.2 times, the widths W2 and W3 of the ribs 4c and 4d on the center and the outside of the vehicle become wide and the drainage tends to deteriorate. In this regard, according to the pneumatic tire 1 of the present embodiment, the width W1 of the rib 4e on the vehicle inner side is 1.2 times or more than the width W2 and W3 of the ribs 4c and 4d on the center and vehicle outer side. By forming the vehicle inner rib first lug groove 5f communicating with the vehicle inner main groove 3 in the vehicle inner rib 4e having a width of less than 5 times and having a relatively wide width W1, air column resonance noise is generated. It does not stand out on the outside of the vehicle and improves the drainage at the rib 4e inside the vehicle.

  As a result, according to the pneumatic tire 1 of the present embodiment, it is possible to reduce vehicle exterior noise while maintaining wet braking performance.

  Moreover, as shown in FIG. 2 which is a partially enlarged view of the plan view of FIG. 1, the pneumatic tire 1 of the present embodiment has lug grooves 5 d, 5 e, provided in the ribs 4 c, 4 d, 4 e. It is preferable that 5f and 5g extend at an angle θ of 30 [°] or more and 60 [°] or less with respect to the tire circumferential direction.

  Here, as shown in FIG. 2, the lug grooves 5 d, 5 e, 5 f, and 5 g are formed in a wide opening for the purpose of preventing chipping at an acute angle portion communicating with the main groove 3. The angle θ is determined by the center P1 of the portion where the original groove width communicates with the main groove 3 (the tire circumferential direction) on one end side and the center P2 of the portion terminating on the other end side of the lug groove 5d, 5e, 5f, 5g. Is defined as the angle between the imaginary line connecting the two and the tire circumferential direction.

  If the angle θ of the lug grooves 5d, 5e, 5f, and 5g with respect to the tire circumferential direction is in the range of 30 ° to 60 °, the drainage to the main groove 3 by the lug grooves 5d, 5e, 5f, and 5g. As a result, the wet braking performance tends to be maintained.

  FIG. 3 is a meridional sectional view of the pneumatic tire according to the present embodiment. The pneumatic tire 1 of the present embodiment is configured to be substantially symmetric about the tire equatorial plane CL except for the tread pattern of the tread portion 2 described above. In the meridional section (FIG. 3) when the pneumatic tire is cut in a plane passing through the shaft, only one side centered on the tire equator plane CL (right side in FIG. 3) is shown and only the one side is shown. The description on the other side (left side in FIG. 3) will be omitted.

  As shown in FIG. 3, when viewed in a meridional section, the pneumatic tire 1 has an end in the tire width direction of the tread portion 2, that is, an end in the tire width direction on the outer side in the tire width direction of the tread portion 2. A shoulder portion 10 is formed to fall on the shoulder. Further, a sidewall portion 11 is provided from the vicinity of the shoulder portion 10 to a predetermined position on the inner side in the tire radial direction. That is, the sidewall portions 11 are provided at both ends of the pneumatic tire 1 in the tire width direction. Further, a bead portion 12 is provided inside the sidewall portion 11 in the tire radial direction. The bead portions 12 are provided at two locations of the pneumatic tire 1 and are also provided on the opposite side of the tire equatorial plane CL so as to be symmetric about the tire equatorial plane CL. The bead portion 12 is provided with a bead core 13, and a bead filler 14 is provided on the outer side of the bead core 13 in the tire radial direction.

  Further, the tread portion 2 is provided with a plurality of belt layers 20 on the inner side in the tire radial direction. A carcass 21 is continuously provided on the inner side in the tire radial direction of the belt layer 20 and the tire equatorial plane CL side of the sidewall portion 11. The carcass 21 is folded back outward in the tire width direction along the bead core 13 at the bead portion 12. A bead filler 14 is provided in a portion where the carcass 21 is folded. An inner liner 22 is formed along the carcass 21 on the inner side of the carcass 21 or on the inner side of the carcass 21 in the pneumatic tire 1.

  Further, in the tread portion 2, when the pneumatic tire 1 is viewed in a meridional section, the tread surface 2 a is formed by a plurality of arcs having different curvature radii. More specifically, the tread surface 2a includes the central arc 31, the shoulder-side arc 32, and the shoulder in a state where the pneumatic tire 1 is assembled on a regular rim and filled with 5% of the regular internal pressure. It is formed by the partial arc 33.

  Of the plurality of arcs forming the tread surface 2a, the central arc 31 is located in the center of the tread surface 2a in the tire width direction, includes the tire equatorial plane CL, and the tire equatorial plane CL is the center of the tire equatorial plane CL. It is formed on both sides in the tire width direction of CL. The shape is an arc that is convex outward in the tire radial direction and has the largest diameter in the tire radial direction near the tire equatorial plane CL.

  Further, the shoulder-side arc 32 is located at two locations on both outer sides in the tire width direction of the central arc 31. The two shoulder-side arcs 32 are both convex outward in the tire radial direction and are arcs having substantially the same radius of curvature.

  Further, the shoulder arc 33 is located on the outer side in the tire width direction of both the shoulder arcs 32 of the two shoulder arcs 32. The shoulder arc 33 forms the shoulder 10 and is an arc that protrudes outward in the tire radial direction.

  That is, in the tread surface 2a, the shoulder-side arcs 32 are positioned at two locations on both sides in the tire width direction of the central arc 31 located in the central portion in the tire width direction, and the respective tire width directions of the two shoulder-side arcs 32 are The shoulder arc 33 is located outside. The central arc 31 and the shoulder-side arc 32, and the shoulder-side arc 32 and the shoulder arc 33 are connected and continuously formed. The radius of curvature TR1 of the central arc 31 positioned in this way, the radius of curvature TR2 of the shoulder side arc 32, and the radius of curvature SHR of the shoulder arc 33 are all different.

  A side arc 34 is formed on the outer side of the shoulder arc 33 in the tire width direction. The side arc 34 is located on the outer side in the tire width direction of the shoulder arc 33 and is connected to the shoulder arc 33, and is formed from the shoulder arc 33 toward the sidewall 11.

  Further, the above-described sidewall portions 11 are provided at two locations on the inner side in the tire radial direction of the tread portion 2 and at both ends in the tire width direction of the pneumatic tire 1. Are curved so that the shape of the meridional section is convex outward in the tire width direction. In addition, since the two sidewall portions 11 are curved so as to protrude outward in the tire width direction, the two sidewall portions 11 are farthest from the tire equatorial plane CL in the tire width direction among the both sidewall portions 11. The distance between the portions in the tire width direction is the total width of the pneumatic tire 1.

As shown in FIG. 3, the pneumatic tire 1 formed in this way has a width in the tire width direction from the center arc end point 35, which is the end of the center arc 31 in the tire width direction, to the tire equatorial plane CL. A contour range is L1, the outer diameter of the pneumatic tire 1, that is, the outer diameter of the tread surface 2a having the largest diameter in the tire radial direction is OD, and the tread surface 2a in the tire width direction is OD. The relationship between the contour range L1 and the tread development width TDW is obtained by the following equation (1), and the K1 obtained by the equation (1) is 0.6 ≦ K1 ≦. Within the range of 0.8, the ratio of the radius of curvature TR1 of the central arc 31 and the tire outer diameter OD is obtained by the following equation (2), and K2 obtained by the equation (2) is 0.9 ≦ K2. ≦ 2 To be in the range of 0, the tread surface 2a is formed.
K1 = L1 / (TDW × 0.5) (1)
K2 = TR1 / OD (2)

  Here, the tread development width TDW is a tread development width TDW as a distance between the virtual tread ends 40 positioned on both ends in the tire width direction of the tread portion 2. That is, as shown in FIG. 3, in the meridional plane cross section of the pneumatic tire 1, among the shoulder-side arcs 32 positioned on both sides in the tire width direction, one shoulder-side arc 32 is extended outward in the tire width direction. Shoulder side arc extension line 41 that is a line and side part arc extension line 42 that is a virtual line obtained by extending a side part arc 34 connected to a shoulder part arc 33 continuous with the shoulder side arc 32 outward in the tire radial direction. Let the intersection with the virtual tread end 40 be. Since the virtual tread ends 40 are formed on both ends in the tire width direction, the distance between the virtual tread ends 40 in the tire width direction is defined as a tread development width TDW.

Furthermore, when the flat rate of the pneumatic tire 1 is β and the total width in the tire width direction of the pneumatic tire 1 is SW, the relationship between the flat rate β, the tread deployment width TDW, and the total width SW is as follows. The pneumatic tire 1 is formed so that K3 obtained by the equation (3) and K3 obtained by the equation (3) is within a range of 0.40 ≦ K3 ≦ 0.48.
K3 = (β × TDW) / (100 × SW) (3)

  When the pneumatic tire 1 is mounted on a vehicle and travels, the pneumatic tire 1 rotates while the tread surface 2a positioned below the tread surface 2a contacts the road surface (not shown). When the vehicle is traveling, the tread surface 2a is in contact with the road surface in this way, so a load due to the weight of the vehicle acts on the tread surface 2a. The load acting on the tread surface 2a varies depending on the traveling state of the vehicle, and the load acting on the tread surface 2a is relatively low during cornering when the vehicle is traveling at a low speed, and the vehicle is traveling at a high speed. At the time of lane change or cornering, the load acting on the tread surface 2a becomes relatively high.

  When the vehicle travels, the tread surface 2a contacts the road surface while changing the load acting in this way. However, since the tread surface 2a is deformed by the acting load, the cornering force in each state according to the deformation of the tread surface 2a. The maximum value, i.e., the maximum cornering force, changes.

  Specifically, when the load acting on the tread surface 2a is low, the tread surface 2a is not easily deformed, but the tread surface 2a of the pneumatic tire 1 of the present embodiment has the contour range L1 and the tread deployment width TDW. K1 is in the range of 0.6 ≦ K1 ≦ 0.8, and the ratio K2 between the radius of curvature TR1 of the central arc 31 and the tire outer diameter OD is 0.9 ≦ It is in the range of K2 ≦ 2.0. As a result, the shape of the tread surface 2a at the time of low load, for example, when the maximum load of the pneumatic tire 1 is 40 [%] is close to a flat shape, and the ground contact area at the time of low load is widened.

  That is, by setting the ratio K2 between the radius of curvature TR1 of the central arc 31 and the tire outer diameter OD to be 0.9 or more, the radius of curvature TR1 of the central arc 31 can be appropriately increased. Is set to 2.0 or less, it is possible to suppress the difference in curvature radius between the central arc 31 and the shoulder-side arc 32 from becoming too large, and a large stress acts near the central arc end point 35. Can be suppressed.

  Further, by setting K1 which is the relationship between the contour range L1 and the tread development width TDW to be 0.6 or more, the range in which the central arc 31 having a large curvature radius is formed in the tire width direction is increased. By making K1 0.8 or less, the formation range of the shoulder-side arc 32 in the tire width direction can be secured, and the radius of curvature from the central arc 31 to the shoulder arc 33 is gentle. Can be made smaller.

  Accordingly, K1 which is the relationship between the contour range L1 and the tread development width TDW is set within the range of 0.6 ≦ K1 ≦ 0.8, and the radius of curvature TR1 of the central arc 31 and the tire outer diameter OD are set. By setting the ratio K2 within the range of 0.9 ≦ K2 ≦ 2.0, the profile of the tread surface 2a can be brought close to a flat shape. For this reason, the ground contact area at the time of low load, such as 40% of the maximum load, can be increased, and the maximum cornering force at the time of low load can be increased. Therefore, it is possible to ensure steering stability at low loads. The maximum load referred to here is the “maximum load capacity” specified by JATMA, the maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” specified by TRA, or “LOAD CAPACITY” specified by ETRTO. is there.

  Further, when the load acting on the tread surface 2a is large, the tread surface 2a is easily deformed, but the pneumatic tire 1 of the present embodiment has the flatness β, the tread development width TDW, and the total width SW. Since the relationship K3 is in the range of 0.40 ≦ K3 ≦ 0.48, the ground contact area is not so wide even under high loads.

  That is, by making K3 which is the relationship between the flat rate β, the tread development width TDW, and the total width SW be 0.40 or more, the tread development width TDW with respect to the total width SW of the pneumatic tire 1 is reduced. By setting K3 to 0.48 or less, the minimum necessary tread development width TDW for the total width SW can be secured. For this reason, when the load is 100 [%], that is, when the pneumatic tire 1 is at the maximum load, when the high load is applied to the tread surface 2a, the increase in the contact area can be reduced, and the maximum cornering force at the time of the high load Can be reduced. Therefore, it is possible to improve the rollover resistance at high loads. As a result, it is possible to improve rollover resistance while maintaining steering stability.

  By the way, when viewed in the meridian plane cross section, the tread surface 2a which is the surface of the cap tread is formed by a plurality of arcs having different curvature radii as described above, and satisfies the above formulas (1) to (3). In the pneumatic tire 1 having such a shape (hereinafter referred to as a rollover resistant profile), the shape of the ground contact surface is close to a square. Then, the area | region where the pneumatic tire 1 slips in the vicinity of the shoulder part 10 becomes large, As a result, high frequency road noise becomes large.

  Therefore, as shown in FIG. 1, in the pneumatic tire 1 of the present embodiment, shoulder land portion lug grooves 5a and 5c are provided in the shoulder land portions 4a and 4b on the tread surface 2a. The shoulder land portion lug grooves 5a and 5c have a groove width of 1.5 [mm] or more. In the pneumatic tire 1, the distance from the tire equatorial plane CL to the start position RS that is one end of the shoulder land lug grooves 5 a and 5 c is 0.97 × L1 or more and 1.03 × L1 or less. That is, the distance from the tire equatorial plane CL to the start position RS of the shoulder land lug grooves 5a and 5c is set to fall within the range of L1 ± ΔL (ΔL = 0.03 × L1). That is, the difference between L1 and the distance from the tire equatorial plane CL to the start position RS of the shoulder land lug grooves 5a and 5c is ± 3% of L1. In this way, the shoulder land lug grooves 5a and 5c are located near the position where the curvature radius TR1 of the central arc 31 changes to the curvature radius TR2 of the shoulder arc 32 (based on the central arc end point 35). , Region of ± 3% of L1). As a result, the ground contact front end side of the ground contact surface of the pneumatic tire 1 approaches a circle from a shape close to a square, so that a region where the pneumatic tire 1 slides in the vicinity of the shoulder portion 10 is reduced. As a result, according to the pneumatic tire 1 of the present embodiment, high-frequency road noise is reduced while maintaining steering stability and rollover resistance. In addition, the front-end end side is an end portion on the rotational direction side of the pneumatic tire 1 among the end portions of the ground contact surface in the tire circumferential direction of the pneumatic tire 1, and the pneumatic tire 1 attached to the vehicle is on the road surface. It is the edge part of the back side of a vehicle in the state where it grounded.

  In this example, performance tests on wet braking performance and passing sound were performed on a plurality of types of pneumatic tires having different conditions (see FIGS. 4 and 5).

  In this performance test, a pneumatic tire having a tire size of 175 / 65R15 was assembled on a regular rim, filled with a regular internal pressure, and mounted on a test vehicle (domestic FF small vehicle).

  In the wet braking performance test, the distance to stop when braking from 100 [km / h] on a road surface with a water depth of 3 [mm] is measured with the test vehicle. And this measurement is performed 5 times, the average value of 3 times except the maximum and minimum is calculated, and the index evaluation which used the conventional example as a reference | standard (100) is performed. In this index evaluation, the wet braking performance is better as the numerical value is larger than the reference.

  In the performance test of the passing sound, the passing sound (external noise) was measured when the test vehicle traveled at 53 [km / h] on the ISO road surface test course. The evaluation is performed with the measured value (passing sound [dB]) of the conventional example as the reference value (± 0.0 [dB]). In this evaluation, the passing sound is smaller as it is smaller than the reference value.

  In the pneumatic tires of the conventional example, the comparative example, and the example, in the tread pattern diagrams of FIGS. 4 and 5, the left side in the figure is the vehicle inner side and the right side is the vehicle outer side. And as shown to the tread pattern figure of FIG. 4, the pneumatic tire of a prior art example is a pneumatic tire of the patent document 1 mentioned above. Further, in the pneumatic tire of Comparative Example 1, the lug groove of the rib on the outside of the vehicle communicates with the main groove on the inside of the vehicle as compared with the conventional example. The pneumatic tire of the comparative example 2 replaces the rib on the inside of the vehicle and the rib on the center with respect to the conventional example. The pneumatic tire of Comparative Example 3 is different from Comparative Example 2 in that the lug groove of the rib on the vehicle outer side communicates with the main groove on the vehicle inner side. The pneumatic tire of Comparative Example 4 is different from Comparative Example 3 in that the lug groove on the shoulder portion on the vehicle outer side communicates with the main groove on the vehicle inner side. The pneumatic tire of Comparative Example 5 has the same tread pattern as that of the example, but the ratio of the rib width on the vehicle inner side to the other rib width is 1.1 times that is outside the specified range. The pneumatic tire of Comparative Example 6 has the same tread pattern as that of the example, but the ratio of the rib width on the vehicle inner side to the other rib width is 1.6 times outside the specified range.

  On the other hand, as shown in FIG. 5, in the pneumatic tires of Examples 1 to 9, the tread pattern is specified, and the ratio of the rib width on the vehicle inner side to the other rib width is within the specified range. . And as for the pneumatic tire of Example 5-Example 9, the angle of the lug groove provided in a rib is in a regulation range. Furthermore, the pneumatic tire of Example 9 has a profile defined as an anti-overturn profile.

  As shown in the test results of FIGS. 4 and 5, it can be seen that the pneumatic tires of Examples 1 to 9 have improved wet braking performance and passing sound.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 2a Tread surface 3 Main groove 4a Shoulder land part inside vehicle 4b Shoulder land part outside vehicle 4c Center rib 4d Rib outside vehicle 4e Rib inside vehicle 5a Vehicle inner shoulder land part lug groove 5b Vehicle inner shoulder land portion auxiliary lug groove 5c Vehicle outer shoulder land lug groove 5d Central rib lug groove 5e Vehicle outer rib lug groove 5f Vehicle inner rib first lug groove 5g Vehicle inner rib second lug groove 10 Shoulder portion 11 Side wall portion 31 Center Section arc 32 Shoulder side arc 33 Shoulder section CL CL Tire equatorial plane L1 Contour range OD Tire outer diameter SW Total width TDW Tread development width TR1 Curvature radius of center arc W1 Vehicle inner rib width W2 Center rib width W3 Vehicle Outer rib width β Flatness θ Lug groove angle

Claims (3)

The direction inside and outside the vehicle when the vehicle is mounted is specified, and the four main grooves extending in the tire circumferential direction are arranged on the tread surface at predetermined intervals in the tire width direction, so that the outermost side in the tire width direction A pneumatic tire in which each shoulder land portion on the outer side in the tire width direction of each of the main grooves and three ribs on the inner side in the tire width direction of the main grooves on the outermost side in the tire width direction are separately formed,
A vehicle inner shoulder land lug groove that is provided in the shoulder land portion on the vehicle inner side, extends in the tire width direction and is arranged in parallel in the tire circumferential direction, and one end communicates with the main groove on the innermost vehicle side; ,
The vehicle is provided on the shoulder land portion on the vehicle outer side, and extends in the tire width direction and is arranged in parallel in the tire circumferential direction, and one end facing the main groove on the vehicle outermost side terminates in the shoulder land portion. A vehicle outer side shoulder land lug groove that is separated from the outermost main groove;
A central rib lug groove provided in the central rib, extending in the tire width direction and arranged in parallel in the tire circumferential direction, with one end communicating with the main groove inside the vehicle and the other end terminating in the rib When,
A vehicle outer side that is provided on the rib on the vehicle outer side, extends in the tire width direction, and is arranged in parallel in the tire circumferential direction, with one end communicating with the main groove on the vehicle inner side and the other end terminating in the rib. Rib lug groove,
A vehicle inner side that is provided on the rib on the vehicle inner side, extends in the tire width direction, and is arranged in parallel in the tire circumferential direction, with one end communicating with the main groove on the vehicle inner side and the other end terminating in the rib. A rib first lug groove,
A vehicle inner side provided on the rib on the vehicle inner side, extending in the tire width direction and arranged in parallel in the tire circumferential direction, one end communicating with the main groove on the vehicle outer side and the other end terminating in the rib A rib second lug groove,
With
The pneumatic tire is characterized in that a width of the rib on the vehicle inner side is 1.2 times or more and 1.5 times or less than a width of the rib on the center side and the vehicle outer side.   2. The pneumatic according to claim 1, wherein each of the lug grooves provided in each of the ribs extends at an angle of 30 ° to 60 ° with respect to a tire circumferential direction. tire. In the state where the tread surface is formed of a plurality of arcs having different curvature radii, assembled to a normal rim and filled with 5% of the normal internal pressure, the tread surface is at the center in the tire width direction. A central arc that is positioned, a shoulder-side arc that is located at two locations on both ends of the central arc in the tire width direction, and the two arcs have substantially the same radius of curvature, and the tire width of the tread surface A shoulder arc that forms a shoulder located at the end of the direction, and
The radius of curvature of the central arc is TR1,
The contour range that is the width from the tire equatorial plane to the end of the central arc in the tire width direction is L1,
The tread deployment width, which is the width of the tread surface in the tire width direction, is TDW,
SW is the total width that is the width in the tire width direction between the outermost portions in the tire width direction of the sidewall portions that are located at opposite ends in the tire width direction, and
The tire outer diameter which is the diameter of the largest portion in the tire radial direction of the tread surface is defined as OD,
When the flatness ratio is β,
K1 obtained by the following expression (1), which is a relational expression between the contour range L1 and the tread development width TDW, falls within the range of 0.6 ≦ K1 ≦ 0.8,
K2 obtained by the following equation (2), which is an equation for obtaining the ratio between the radius of curvature TR1 of the central arc and the tire outer diameter OD, is in the range of 0.9 ≦ K2 ≦ 2.0,
K3 obtained by the following equation (3), which is a relational expression between the flatness ratio β, the tread development width TDW, and the total width SW, falls within a range of 0.40 ≦ K3 ≦ 0.48.
The distance from the tire equatorial plane to one end of the lug groove provided in the shoulder land portion is 0.97 × L1 or more and 1.03 × L1 or less. Pneumatic tire.
K1 = L1 / (TDW × 0.5) (1)
K2 = TR1 / OD (2)
K3 = (β × TDW) / (100 × SW) (3)