阅读说明：本技术 充气轮胎 (Pneumatic tire ) 是由 本间健太 于 2020-05-22 设计创作，主要内容包括：本发明提供一种充气轮胎,该充气轮胎具备：胎面部,该胎面部具有构成为与路面接触的接地面。该胎面部具有至少一条在该接地面开口的槽。该槽具有：突起区域,该突起区域具备在与该槽内空间相接的槽壁面上呈点状分散而突出的多个微小突起。该微小突起的从该槽壁面起的突出高度H与该槽的从该接地面起的槽深度L1之比H/L1为0.01～0.09。该微小突起的与该微小突起的突出方向正交的宽度W与该槽的槽宽度L2之比W/L2为0.002～0.02。(The present invention provides a pneumatic tire, comprising: and a tread portion having a ground contact surface configured to contact a road surface. The tread portion has at least one groove opened in the ground contact surface. The tank has: and a projection region including a plurality of minute projections which are dispersed and projected in a dot shape on a groove wall surface in contact with the groove space. The ratio H/L1 of the projection height H of the minute projection from the groove wall surface to the groove depth L1 of the groove from the ground surface is 0.01-0.09. The ratio W/L2 of the width W of the minute projection perpendicular to the projection direction of the minute projection to the groove width L2 of the groove is 0.002-0.02.)

1. A pneumatic tire, characterized in that,

the disclosed device is provided with: a tread portion having a ground contact surface configured to contact a road surface,

the tread portion has at least one groove opened in the ground contact surface,

the tank has: a projection region including a plurality of minute projections which are arranged in a dot-like manner on a groove wall surface in contact with the groove space and project from the groove wall surface,

the ratio H/L1 of the projection height H of the minute projection from the groove wall surface to the groove depth L1 of the groove from the ground surface is 0.01-0.09,

the ratio W/L2 of the width W of the micro-protrusions perpendicular to the protruding direction of the micro-protrusions to the groove width L2 of the grooves is 0.002-0.02.

2. The pneumatic tire of claim 1,

the ratio H/W of the protrusion height H to the width W is 0.3 to 30.

3. The pneumatic tire according to claim 1 or 2,

the minute projection has a substantially truncated cone shape in which an area of a cross section orthogonal to the projecting direction of the minute projection becomes smaller as being distant from the groove wall surface,

the ratio S1/S2 of the area S1 of the cross section at the tip of the minute projection to the area S2 of the cross section of the minute projection along the groove wall surface is 0.01 to 0.8.

4. The pneumatic tire according to any one of claims 1 to 3,

the ratio of the total area of the cross sections of the micro-protrusions along the groove wall surface to the area of the protrusion region along the groove wall surface is 0.1-1.0.

5. The pneumatic tire according to any one of claims 1 to 4,

the density of the minute protrusions in the protrusion area is 1mm per minute²The protruding area is more than five.

6. The pneumatic tire of claim 5,

the protruding region has a plurality of regions having different densities.

7. The pneumatic tire of claim 6,

the plurality of regions are arranged along the groove depth direction such that the density of regions located at deeper positions in the groove depth direction increases.

8. The pneumatic tire according to any one of claims 1 to 7,

the groove has a plurality of circumferential main grooves extending in the tire circumferential direction,

the protruding region is provided in a circumferential main groove that is located in a central region of the circumferential main groove, at least on both sides in the tire width direction from the tire center line, at a length that is 40% of the tire width direction length of the ground contact surface, respectively.

9. The pneumatic tire according to any one of claims 1 to 8,

the protruding region is provided on at least a surface of a groove bottom of the groove wall surface.

10. The pneumatic tire according to any one of claims 1 to 9,

the fine protrusions are distributed on the groove wall surface so as to form a plurality of rows extending in a direction intersecting with an extending direction of a boundary between the ground plane and the groove wall surface.

Technical Field

The present invention relates to a pneumatic tire having a groove in a tread portion.

Background

In a pneumatic tire, in order to ensure drainage performance on a wet road surface, the following tread pattern is sometimes provided: the tread portion includes a plurality of main grooves extending in the tire circumferential direction, and the land portion includes a plurality of lug grooves extending in the tire width direction. The pneumatic tire provided with such a tread pattern can ensure drainage performance and improve driving stability on a wet road surface.

However, when the main grooves and the lug grooves are provided in the tread portion, air flows in the grooves in the ground contact surface, which causes noise to be generated and noise performance to be easily deteriorated. Here, if the groove volume of the main groove and the lug groove is reduced to suppress the deterioration of the noise performance, the drainage performance is lowered. As described above, the drainage performance and the noise performance are in a relationship of the two-rhythm reverse.

Conventionally, there has been known a pneumatic tire having a plurality of vertical grooves connected in a tire circumferential direction on a tire tread surface, in which projections having different heights are provided in a groove bottom of the vertical grooves in a pattern in which irregularities are repeated along the tire circumferential direction (see patent document 1). In the tire of patent document 1, it is considered that not only the air column resonance sound but also the noise generated by the pumping action can be effectively exerted, and the vehicle exterior noise of the tire can be reduced.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2002-211210

Disclosure of Invention

Problems to be solved by the invention

In the pneumatic tire described in patent document 1, in order to exhibit the above-described effects, it is necessary to provide a large protrusion in the groove. Therefore, the groove volume of the grooves provided in the tread portion is greatly reduced, and the drainage performance cannot be ensured, thereby degrading the wet performance.

Therefore, an object of the present invention is to improve noise performance without impairing drainage performance in a pneumatic tire having a groove in a tread portion.

Technical scheme

One aspect of the present invention is a pneumatic tire, including: a tread portion having a ground contact surface configured to contact a road surface,

the tread portion has at least one groove opened in the ground contact surface,

the tank has: a projection region including a plurality of minute projections which are arranged in a dot-like manner on a groove wall surface in contact with the groove space and project from the groove wall surface,

the ratio H/L1 of the projection height H of the minute projection from the groove wall surface to the groove depth L1 of the groove from the ground surface is 0.01-0.09,

the ratio W/L2 of the width W of the micro-protrusions perpendicular to the protruding direction of the micro-protrusions to the groove width L2 of the grooves is 0.002-0.02.

Preferably, a ratio H/W of the protrusion height H to the width W is 0.3 to 30.

Preferably, the minute projection has a substantially truncated cone shape in which an area of a cross section orthogonal to the projecting direction of the minute projection becomes smaller as being apart from the groove wall surface,

the ratio S1/S2 of the area S1 of the cross section at the tip of the minute projection to the area S2 of the cross section of the minute projection along the groove wall surface is 0.01 to 0.8.

Preferably, a ratio of a total area of cross sections of the fine protrusions along the groove wall surface to a projection area of the protrusion region along the groove wall surface is 0.1 to 1.0.

Preferably, the density of the minute projections in the projection region is 1mm per minute²The protruding area is more than five.

Preferably, the protruding region has a plurality of regions having different densities.

Preferably, the plurality of regions are arranged along the groove depth direction such that the density of regions located at deeper positions of the groove in the groove depth direction is increased.

Preferably, the groove has a plurality of circumferential main grooves extending in the tire circumferential direction,

the protruding region is provided in a circumferential main groove that is located in a central region of the circumferential main groove, at least on both sides in the tire width direction from the tire center line, at a length that is 40% of the tire width direction length of the ground contact surface, respectively.

Preferably, the protruding region is provided on at least a surface of the groove bottom of the groove wall surface.

Preferably, the fine protrusions are arranged on the groove wall surface in a dispersed manner so as to form a plurality of rows extending in a direction intersecting with an extending direction of a boundary between the ground plane and the groove wall surface.

Effects of the invention

According to the above aspect, in the pneumatic tire having the groove in the tread portion, the noise performance can be improved without impairing the drainage performance.

Drawings

Fig. 1 is a tire sectional view showing a section of a pneumatic tire according to the present embodiment.

Fig. 2 is a view showing an example of a tread pattern applied to the pneumatic tire of fig. 1.

Fig. 3 is a diagram showing an example of the protruding region.

Fig. 4 (a) is a diagram illustrating a relationship between a projection height of the minute projection and a groove depth of the groove, and fig. 4 (b) is a diagram illustrating a relationship between a width of the minute projection and a groove width of the groove.

Fig. 5 is a diagram showing a modified example of the protruding region.

Fig. 6 is a diagram showing a modified example of the protruding region.

Fig. 7 is a view illustrating the form of the minute protrusions.

Detailed Description

The pneumatic tire of the present embodiment will be described in detail below. The present embodiment includes various embodiments described later.

(Overall description of tire)

Fig. 1 is a tire cross-sectional view showing a cross section of a pneumatic tire (hereinafter referred to as a tire) 10 according to the present embodiment, the cross section being cut along a tire radial direction.

The tire 10 is, for example, a tire for a car. The tire for a car is a tire specified in chapter a of JATMA YEAR BOOK 2012 (japan automobile tire association standard). Further, the present invention can also be applied to a tire for a small truck defined in chapter B, and a tire for a truck or a bus defined in chapter C.

In the following description, the tire width direction is a direction parallel to the rotation axis of the tire 10. The tire width direction outer side is a direction away from a tire centerline CL representing the tire equatorial plane in the tire width direction. Further, the tire width direction inner side is a side closer to the tire centerline CL in the tire width direction. The tire circumferential direction is a direction in which the tire 10 rotates around the rotation axis as the rotation center. The tire radial direction is a direction orthogonal to the rotation axis of the tire 10. The tire radial outer side means a side away from the rotation axis. Further, the tire radial direction inner side means a side close to the rotation axis.

(tire structure)

Fig. 1 is a cross-sectional outline view showing a tire 10 according to the present embodiment. The tire 10 includes: a tread portion 10T having a tread pattern; a pair of bead portions 10B; and a pair of sidewall portions 10S provided on both sides of the tread portion 10T, and connected to the pair of bead portions 10B and the tread portion 10T.

The tire 10 has a carcass layer 12, a belt layer 14, and a bead core 16 as carcass members, and around these carcass members, there are mainly a tread rubber member 18, a sidewall rubber member 20, a bead filler rubber member 22, a rim cushion rubber member 24, and an inner liner rubber member 26.

The carcass layer 12 is made of a carcass material made of rubber-coated organic fibers wound between a pair of annular bead cores 16 in a ring shape. The cord fabric is wound around the bead core 16 and extends to the tire radial direction inner side of the shoulder region of the tread rubber member 18. A belt layer 14 composed of two pieces of belt materials 14a, 14b is provided on the outer side of the carcass layer 12 in the tire radial direction. The belt layer 14 is a rubber-coated member made of a steel cord arranged at a predetermined angle, for example, 20 to 30 degrees, with respect to the tire circumferential direction, and the belt material 14a of the lower layer is longer than the belt material 14b of the upper layer in the width direction of the tire. The steel cords of the two belt materials 14a, 14b are inclined in directions opposite to each other. Thereby, the belt materials 14a and 14b become alternate layers, and the expansion of the carcass layer 12 due to the filled air pressure is suppressed.

A tread rubber member 18 is provided on the outer side of the belt layer 14 in the tire radial direction, and sidewall rubber members 20 are connected to both ends of the tread rubber member 18 to form a sidewall portion 10S. A rim cushion rubber member 24 is provided at an end portion of the sidewall rubber member 20 on the inner side in the tire radial direction, and is in contact with a rim on which the tire 10 is attached. On the outer side of the bead core 16 in the tire radial direction, a bead filler member 22 is provided so as to be sandwiched between a portion of the ply 12 before being wound around the bead core 16 and a wound portion of the ply 12 wound around the bead core 16. An inner liner rubber member 26 is provided on the inner surface of the tire 10 facing the tire cavity region filled with air surrounded by the tire 10 and the rim.

In addition, the tire 10 includes a bead reinforcing material 28 between the carcass layer 12 wound around the bead core 16 and the bead filler member 22, and the tire 10 further includes a three-layer belt cover layer 30 covering the belt layer 14 from the outside of the belt layer 14 in the tire radial direction and covering organic fibers with rubber.

The tire 10 has such a tire structure, but the tire structure of the pneumatic tire of the present invention is not limited to the tire structure shown in fig. 1.

(Tread pattern)

In the area of the tread surface of the tire 10, a tread pattern 50 is formed. Fig. 2 is a pattern development view showing an example in which a portion of the tread pattern 50 formed in the region of the tread surface of the tire 10 shown in fig. 1 on the tire circumference is developed in a plane.

The tread pattern 50 has: four circumferential main grooves 52, 54, 56, 58 that are open in the ground contact surface and extend in the tire circumferential direction; and five land portions 60, 62, 64, 66, 68 demarcated by the circumferential main grooves 52, 54, 56, 58. The circumferential main grooves 58, 56 are not particularly limited, and for example, each have a groove center position at a position 30 to 35% in the tire width direction of the tire contact width GW away from the tire centerline CL in the half-tread regions on both sides in the tire width direction with the tire centerline CL as a boundary. The tire ground contact width GW is a length in the tire width direction between both ends (ground contact ends) in the tire width direction of the tread surface that becomes a ground contact surface when the tire 10 is mounted on a normal rim, filled with normal internal pressure, and grounded on a horizontal plane under a condition where 88% of a normal load is a load. The regular Rim is a "measurement Rim" defined by JATMA, a "Design Rim" defined by TRA, or a "measurement Rim" defined by ETRTO. The normal internal pressure is the "maximum air pressure" defined by JATMA, the maximum value of the "TIRE LOAD LIMITS AT variable COLD INFLATION PRESSURES" defined by TRA, or the "INFLATION PRESSURES" defined by ETRTO. The normal LOAD is a "maximum LOAD CAPACITY" defined by JATMA, a maximum value of "time LOAD conditions AT variaus color optimization requirements" defined by TRA, or "LOAD CAPACITY" defined by ETRTO.

The tire centerline CL passes through the region of the land portion 60. The land portions 64, 68 are provided in a half-tread region on a first side (the direction in which the vehicle is attached is the vehicle outer side) across the tire center line CL, and the land portions 62, 66 are provided in a half-tread region on a second side (the direction in which the vehicle is attached is the vehicle outer side).

The groove center positions of the circumferential main grooves 52, 54 are not particularly limited, but when the center positions of the circumferential main grooves 56, 58 are located within a range of 30 to 35% of the tire contact width GW away from the tire center line CL, the groove center positions of the circumferential main grooves 52, 54 are preferably located within a range of 10 to 15% of the tire contact width GW away from the tire center line CL across the tire center line CL in terms of widening the rib pattern and securing the steering stability.

The land portion 60 is a portion formed by being sandwiched between the circumferential direction main groove 52 and the circumferential direction main groove 54. In the region of the land portion 60, a plurality of lug grooves 60a extending in the tire width direction from the circumferential direction main groove 52 toward the first side are provided at predetermined intervals in the tire circumferential direction. The lug groove 60a extends from the circumferential direction main groove 52 in a direction inclined with respect to the tire width direction, does not communicate with the circumferential direction main groove 54, and is closed in the middle of the region of the land portion 60.

The land portion 62 is a portion formed by being sandwiched between the circumferential direction main groove 56 and the circumferential direction main groove 52. In the region of the land portion 62, a plurality of lug grooves 62a extending in the tire width direction from the circumferential direction main groove 56 toward the first side are provided at predetermined intervals in the tire circumferential direction. The lug groove 62a extends from the circumferential direction main groove 56 in a direction inclined with respect to the tire width direction (the same direction as the inclined direction of the lug groove 60 a), does not communicate with the circumferential direction main groove 52, and is closed in the middle of the land portion 62 region.

The land portion 64 is a portion formed by being sandwiched between the circumferential direction main groove 54 and the circumferential direction main groove 58. In the land portion 64 region, a plurality of lug grooves 64a extending from the circumferential direction main groove 54 toward the first side in a direction inclined with respect to the tire width direction (the same direction as the inclination direction of the lug grooves 60 a) are provided at predetermined intervals in the tire circumferential direction. The lug groove 64a is not communicated from the circumferential direction main groove 54 to the circumferential direction main groove 58, but is closed in the middle of the region of the land portion 64.

Further, in the region of the land portion 64, a plurality of notches 65a extending from the circumferential direction main groove 58 toward the second side in a direction inclined with respect to the tire width direction (a direction opposite to the inclination direction of the lug groove 60 a) are provided at predetermined intervals in the tire circumferential direction. The notch 65a is not communicated from the circumferential direction main groove 58 to the circumferential direction main groove 54, but is closed in the middle of the region of the land portion 66.

The inclination angle of the lug grooves 60a, 62a, 64a with respect to the tire width direction is, for example, 20 to 55 degrees. A chamfer is provided at one side portion in the tire circumferential direction around the lug grooves 60a, 62a, 64 a.

Land portions 66 are provided in the circumferential main groove 56 and the pattern end E₂In the meantime. In the region of the land portion 66, a plurality of shoulder lug grooves 66a are provided at predetermined intervals in the tire circumferential direction. Each shoulder rib groove 66a extends from the pattern end E₂The first side extends in the tire width direction, but is not open in the circumferential direction main groove 56, but is closed in the middle of the region of the land portion 66.

The land portion 68 is provided between the circumferential main groove 58 and the pattern end E₁In the meantime. In the region of the land portion 68, a plurality of land portions are provided at predetermined intervals in the tire circumferential directionShoulder rib grooves 68 a. Each shoulder rib groove 68a extends from the pattern end E₁Extends in the tire width direction toward the second side, and opens in the circumferential direction main groove 58. Chamfers 68b, 68b are provided around the shoulder lug grooves 66a, 68 a.

The above lug grooves 60a, 62a, 64 a; a notch 65 a; and shoulder rib grooves 66a, 68a are open to the ground.

The groove width of the circumferential main groove 58 is W₁The groove width of the circumferential main groove 54 is set to W₂The groove width of the circumferential main groove 52 is set to W₃The groove width of the circumferential main groove 56 is set to W₄At the time, the groove width W₁～W₄Middle, groove width W₁Minimum, groove width W₂And max. Preferred groove width W₁Width W of groove₂Ratio W of₂/W₁Is 4 to 5. Further, the groove area ratio in the region on the first side when viewed from the tire centerline CL in the tread pattern 50 is set to S_outThe groove area ratio in the region of the second side is set to S_inIs compared with S_in/S_outPreferably 1.1 to 1.2.

The groove depths of the circumferential main grooves 52, 54, 56, 58 are, for example, 5 to 8.5mm, respectively. Groove width W of circumferential main grooves 58, 54, 52, 56₁、W₂、W₃、W₄For example, 4.0 to 7.5mm, 12 to 18mm, 10 to 16mm, and 10 to 16mm in this order.

The tread pattern 50 is configured as described above, but the tread pattern of the pneumatic tire of the present invention is not limited to the tread pattern shown in fig. 2.

(protruding region)

Fig. 3 is a diagram showing an example of the protruding region 40 provided in the circumferential main groove 54.

As shown in fig. 3, each of the circumferential main grooves 52, 54, 56, 58 has a projection region 40, and the projection region 40 includes a plurality of minute projections 41 which are arranged in a dot-like manner on a groove wall surface 54a facing (contacting) the groove space and project from the groove wall surface 54 a. The groove wall surface includes: a pair of side wall surfaces facing each other with the space in the groove interposed therebetween, and a bottom surface between the side wall surfaces. The bottom surface is a portion of a groove wall surface in which an inclination angle of a normal direction with respect to a groove depth direction is smaller than 40 ° in a profile cross section of the tread portion along a tire width direction. Fig. 3 shows the minute projection 41 provided on a part of the groove wall surface of the circumferential direction main groove 54 (a part surrounded by a dotted circle in fig. 1). In the following description, the minute protrusions 41 provided in the circumferential direction main groove 54 are described as an example, but it is preferable that the minute protrusions 41 provided in the circumferential direction main grooves 52, 56, 58 are configured similarly.

Fig. 4 (a) is a diagram illustrating a relationship between a projection height H of the minute projection 41 from the groove wall surface 54a and a groove depth L1 of the circumferential main groove 54 from the ground surface, and fig. 4 (b) is a diagram illustrating a relationship between a width W of the minute projection 41 and a groove width L2 of the circumferential main groove 54. In fig. 4, only one minute projection 41 is shown for easy understanding of the description. In fig. 4, the cross-sectional shape of the circumferential main groove 54 is different from that shown in fig. 1.

In the present specification, the width W of the minute projection 41 refers to the width of a portion (hereinafter, also referred to as a bottom surface) of the minute projection 41 at a position (along the extending direction of the groove wall surface) at the same height as the groove wall surface along the direction orthogonal to the projecting direction of the minute projection 41. The groove width of the groove provided with the chamfer means the groove width including the chamfer as well. In this case, when the length of the chamfer in the groove width direction changes in the extending direction of the groove, the average value of the lengths is taken as the width of the chamfer, and the groove width of the groove is calculated. In addition, the width W in the case where the sectional shape of the minute projection 41 is a polygonal shape described later is represented by the diameter of a circle having the same area.

According to one embodiment, the bottom surfaces of the respective minute projections 41 are surrounded by the groove wall surface 53a, but according to another embodiment, the bottom surfaces of the minute projections 41 may be in contact with each other.

In the projection region 40, the ratio H/L1 of the projection height H of the minute projection 41 along the projection direction of the minute projection 41 to the groove depth L1 of the circumferential main groove 54 is 0.01 to 0.09. Further, the ratio W/L2 of the width W of the minute projection 41 in the direction orthogonal to the projecting direction to the groove width L2 of the circumferential main groove 54 is 0.002 to 0.02. The inventors have made the following findings according to their studies: by providing such minute protrusions 41, the noise performance can be improved without impairing the drainage performance. The following effects by the minute projections 41 are considered to contribute to the improvement of the noise performance. That is, in the circumferential direction main groove 54 in which the projection region 40 is provided, frictional resistance is generated between the air flowing in the circumferential direction main groove 54 and the minute projection 41, and the flow velocity of the air in the circumferential direction main groove 54 is decreased. As a result, air column resonance that amplifies the vibration of the circumferential main groove 54 is reduced, and noise due to air column resonance sound is reduced. Namely, the noise performance is improved. Since a part of the energy of the air flowing in the circumferential main groove 54 is converted into thermal energy by the collision between the air and the minute protrusions 41, the flow velocity of the air flowing in the circumferential main groove 54 is reduced. On the other hand, the minute protrusions 41 are protrusions having a minute size satisfying the above range in the ratio H/L1 and the ratio W/L2, and therefore the groove volume of the circumferential direction main groove 54 hardly decreases. Therefore, the drainage performance by the circumferential main groove 54 can be ensured. That is, according to the tire 10 of the present embodiment, the noise performance can be improved without impairing the drainage performance. This can achieve both of driving stability (wet performance) and noise performance on a wet road surface.

If the ratio H/L1 is greater than 0.09, the flow path cross-sectional area of the circumferential main groove 54 becomes small, and drainage performance deteriorates. If the ratio H/L1 is less than 0.01, the contact area with the air flowing in the circumferential direction main groove 54 becomes small, and noise cannot be reduced.

If the ratio W/L2 is greater than 0.02, the flow path cross-sectional area of the circumferential main groove 54 becomes small, and drainage performance deteriorates. If the ratio H/L2 is less than 0.002, the contact area with the air flowing in the circumferential direction main groove 54 becomes small, and noise cannot be reduced.

The H/L1 ratio is preferably 0.025-0.0625, and more preferably 0.035-0.05. The W/L2 ratio is preferably 0.0035 to 0.01, and more preferably 0.005 to 0.008.

The height H of the minute projection 41 is, for example, 0.08 to 0.72mm, and the width W is, for example, 0.03 to 0.3 mm. The range of the projection height H and the width W is suitable for the condition that the groove depth of the circumferential main groove is 6-8 mm, and the groove width is 5-16 mm.

The shape of the minute projection 41 is, for example, a columnar shape, a tapered shape, or a truncated cone shape. The shape of a cross section of the minute projection 41 along a direction orthogonal to the projecting direction (hereinafter simply referred to as a cross section) is, for example, circular, elliptical, or polygonal. The polygon is preferably a regular polygon, but may be a concave polygon having at least one vertex angle exceeding 180 degrees, such as a Y-shape, a cross shape, or a star shape.

According to one embodiment, as shown in fig. 3, the protruding direction of the minute projection 41 is preferably aligned with the normal direction of the groove wall surface, but according to another embodiment, the protruding direction of the minute projection 41 is also preferably inclined with respect to the normal direction of the groove wall surface. In this case, the inclination angle with respect to the normal direction of the groove wall surface is, for example, more than 0 ° and 10 ° or less.

According to one embodiment, the minute projection 41 is preferably not branched halfway extending in the projecting direction.

According to one embodiment, the adjacent minute projections 41 may be disposed at intervals on the groove wall surface, or may be in contact with each other.

The protruding region 40 is formed by molding the tire 10 using a molding die obtained by performing a predetermined process on a wall surface of a molding die for molding a groove wall surface, for example. As a method of processing the wall surface of the molding die, for example, laser processing in which imprinting is performed by irradiation of laser light is exemplified. Another method for forming the projection region 40 is, for example, a method in which a groove wall surface of a tire after molding is subjected to a predetermined process. For example, the following laser processing can be cited: the laser beam is irradiated to condense the light energy on the surface of the tire, and the rubber around the minute projection 41 is heated and sublimated by the concentrated light energy.

According to one embodiment, it is preferable that the protruding region 40 is provided in the circumferential direction main groove in a central region of a length (length of 80% in total) of 40% of a tire width direction length (ground contact width) of the ground contact surface at least from the tire center line CL on both sides in the tire width direction. For example, it is preferable that the protruding areas 40 are provided at least in the circumferential main grooves 52, 54. This is because the circumferential direction main grooves 52 and 54 are located closer to the tire center line CL than the circumferential direction main grooves 56 and 58, and the contact length is long, so that noise tends to increase. Furthermore, according to one embodiment, it is more preferable that the protrusion areas 40 are provided to all the circumferential main grooves 52, 54, 56, 58. Thus, noise can be effectively reduced and noise performance can be improved. The density of the minute projections 41 may also differ between the circumferential direction main grooves depending on the distance from the tire centerline CL.

Furthermore, according to one embodiment, the raised areas 40 are preferably provided in the cross grooves 60a, 62a, 64 a; a notch 65 a; shoulder rib grooves 66a, 68 a. In this case, noise can be effectively reduced and noise performance can be improved.

Fig. 5 and 6 are views showing modified examples of the minute projection 41.

The minute projections 41 can take various forms within the above-mentioned ratio H/L1 and ratio W/L2. For example, as shown in FIG. 5, the ratio H/W may be 1 or less, or as shown in FIG. 6, the ratio H/W may exceed 1.

According to one embodiment, the ratio H/W (aspect ratio) of the protrusion height H to the width W of the groove is preferably 0.3 to 30. If the ratio H/W is less than 0.3, the height of the fine protrusions 41 is too low, and the noise reduction effect may not be obtained. If the ratio H/W is greater than 30, the width of the fine protrusions 41 is too short, the fine protrusions 41 are likely to fall (are difficult to stand by themselves), and the space between the fine protrusions 41 is reduced, so that the effect of reducing noise by the air in the groove coming into contact with the fine protrusions 41 may not be obtained. In this case, when the protruding height of the minute projection 41 is high, the groove volume is reduced, and therefore, the drainage performance may be reduced, and the wet performance may be reduced.

According to one embodiment, the minute projection 41 preferably has a substantially truncated cone shape in which the area of the cross section of the minute projection 41 (hereinafter referred to as the cross-sectional area) becomes smaller as it is farther from the groove wall surface. In this case, the ratio S1/S2 of the cross-sectional area S1 (see FIG. 7) (cross-sectional area of the tip) of the tip end surface 41a of the minute projection 41 to the cross-sectional area S2 (see FIG. 7) of the projection base of the minute projection 41 in the direction in which the groove wall surface extends is preferably 0.01 to 0.8. Fig. 7 is a diagram illustrating the form of the minute projection 41. If the ratio S1/S2 is less than 0.01, it becomes difficult to form the fine protrusions 41 having a substantially truncated cone shape in the tread rubber. If S1/S2 is greater than 0.8, the area of the distal end surface 41a of each of the fine protrusions 41 becomes too large, and the space between the fine protrusions 41 decreases. Therefore, the effect of reducing noise is reduced.

According to one embodiment, as shown in fig. 7, the distal end surface 41a of the minute projection 41 is preferably a plane parallel to the groove wall surface, but according to another embodiment, may have a shape expanding in the projecting direction (for example, with a circular arc). In this case, the cross-sectional area S1 of the distal end surface 41a may be an area of a cross-section cut out with a plane parallel to the groove wall surface at a height position of the substantially frustum-shaped upper surface. The cross-sectional area S1 of the distal end surface 41a when the distal end surface 41a of the minute projection 41 is a plane parallel to the groove wall surface is an area of the upper surface of a substantially truncated cone shape.

According to one embodiment, the ratio of the total cross-sectional area of the fine protrusions 41 in the direction in which the groove wall surface extends to the convex area of the protrusion region 40 in the direction in which the groove wall surface extends (in-plane direction) is preferably 0.1 to 1.0. The area of the projection region 40 is the area of the entire projection region 40 including the area of the bottom surface of the fine projection 41. When the convex area ratio is within the above range, the size of the space between the fine protrusions 41 is not excessively large but is appropriately large, and the effect of reducing noise is increased. The convex area ratio is preferably an average value of the convex area ratios at a plurality of positions obtained for a partial region of the projection region 40 having a plurality of (for example, 2 to 10) fine projections 41 among the projection regions 40. If the convex area ratio is less than 0.1, the volume occupied by the micro-protrusions 41 in the groove space is small, and the effect of reducing noise tends to be insufficient. If the convex area ratio is larger than 1.0, it is difficult to form the minute projection 41. The convex area ratio is preferably 0.5 to 1.0. The minute projections 41 may be arranged such that the bottom surfaces of adjacent minute projections 41 partially overlap each other.

According to one embodiment, the density of the micro-protrusions 41 within the protrusion area 40 is preferably per 1mm²The protruding areas 40 are five or more. The density of the fine protrusions 41 can be set to a plurality of (for example, 2 to 10) measurement regions (for example, 1 mm) in the protrusion region 40²Square area) of the minute protrusions 41. If the density of the minute projections 41 is less than 1mm per unit²Five, namely, the micro-protrusions 4The number of 1 s is too small, and the effect of reducing noise is likely to be insufficient. On the other hand, the density of the minute projections 41 is preferably 1mm per minute²The number of the protruding areas 40 is one hundred or less, and more preferably twenty or less. This ensures a space between the minute projections 41, and facilitates noise reduction.

In this embodiment, it is preferable that the protruding area 40 has a plurality of areas having different densities of the fine protrusions 41 according to one embodiment. In this way, the contact area between the air in the groove and the minute projection changes in the groove, and becomes uneven, thereby increasing the effect of reducing noise. The number of the plurality of regions having different densities is two or more, and according to one embodiment, the protruding region 40 is preferably configured such that a plurality of regions having a small density difference (for example, 10 or more) are connected to each other and the density is continuously changed. The ratio of the density of the highest density region to the density of the lowest density region among the plurality of regions is, for example, 1.3 to 10.

In this embodiment, according to another embodiment, it is preferable that the plurality of regions having different densities of the fine protrusions 41 are arranged along the groove depth direction of the groove so that the deeper the region is in the groove depth direction, and the higher the density of the fine protrusions 41 in the region is. In this case, the effect of reducing noise becomes large.

The raised area 40 is provided on at least a portion of the wall surface of the channel.

According to one embodiment, the projection region 40 is preferably provided in a region of at least a part of the groove wall surface in a profile section along the tire width direction. For example, the projection region 40 is preferably provided at least on the bottom surface of the groove wall surface. In the profile cross section, the bottom surface of the groove wall surface has a smaller amount of deformation at the time of grounding than the side wall surface inclined with respect to the extending direction of the bottom surface, and therefore the effect of reducing the flow velocity by contact with the air flowing in the groove is large. According to one embodiment, the raised areas 40 are preferably provided in all areas of the groove wall surface in the profile cross-section.

Further, according to one embodiment, the projection region 40 is preferably provided in a region of at least a part of the groove wall surface along the extending direction of the groove. For example, the groove is preferably provided in a region along at least a part of the extending direction of the groove, and is preferably provided in the entire region of the extending direction of the groove. On the other hand, the protruding region 40 may be interrupted in a region along a part of the extending direction of the groove, for example, or may be provided intermittently so as to be interrupted in a plurality of regions.

When the groove has a chamfer, the protruding region 40 is preferably also formed on the chamfered surface.

According to one embodiment, the fine protrusions 41 are preferably arranged in a distributed manner on the groove wall surface so as to form a plurality of rows extending in a direction intersecting with an extending direction of a boundary (edge of the land portion) between the ground plane and the groove wall surface. The rows preferably extend in mutually parallel directions. The adjacent intervals of the minute projections 41 constituting the rows are equal to or smaller than the adjacent intervals of the rows. By the arrangement of the minute projections 41, the effect of smoothly discharging the water in the groove to the outside can be obtained, and the drainage property is improved. Further, according to one embodiment, the minute projections 41 are more preferably arranged in a row in a direction perpendicular to the boundary. As an example of the arrangement of the minute projections 41, there is a mode in which the minute projections 41 are arranged at lattice points of a lattice (regular triangle lattice) in which regular triangles are laid on the groove wall surface.

(examples, comparative examples, and conventional examples)

In order to confirm the effects of the present invention, four tires each having a tire size of 205/55R16 were produced for each of the following examples, comparative examples, and conventional examples, and a front-wheel-drive passenger car having an exhaust gas volume of 2L was attached as a test vehicle to examine the noise performance and the wet performance. The rim size of the vehicle was 16X 6.5J, and the air pressure was set to 210 kPa.

The tires of the conventional examples, comparative examples 1 to 4, and examples 1 to 6 have the tire structure shown in fig. 1 and the tread pattern 50 shown in fig. 2 as a base tone, except for the points shown in tables 1 and 2 and the following points.

In any of comparative examples 1 to 4 and examples 1 to 6, the protruding regions are provided in the circumferential main grooves 52, 54, 56, 58; and lug grooves 60a, 62a, 64 a; a notch 65 a; all regions of the groove wall surfaces (including the chamfered surfaces) of the shoulder lug grooves 66a, 68 a.

The conventional example is the same as example 1 except that the protruding region is not provided.

In each of comparative examples 1 to 4 and examples 1 to 6, the projection direction of the minute projection was aligned with the normal direction of the groove wall surface. In the tires of the conventional example, comparative examples 1 to 4, and examples 1 to 6, the groove depth L1 of the circumferential main groove 54 was set to 8mm, and the groove width L2 was set to 14 mm.

In tables 1 and 2, "the presence or absence of a density difference" means whether or not the projected area has per 1mm²The plurality of regions in the protruding region have different densities of fine protrusions.

In example 5, the plurality of regions having different densities are provided in the circumferential main grooves 52, 54, 56, 58 among the grooves of the tread portion so that the densities in the tire circumferential direction are different. Specifically, two kinds of regions having different densities are alternately provided in the tire circumferential direction so that the regions having different densities always exist in the ground contact surface. The ratio of the density of the maximum density region to the density of the minimum density region is set to a value within the range of 1.3 to 10.

In example 6, the plurality of regions having different densities in the depth direction are provided in all of the circumferential main grooves, the lug grooves, the notches, and the shoulder lug grooves among the grooves of the tread portion. Specifically, the side wall surface and the bottom surface of the groove wall surface are different in density. The ratio of the density of the maximum density region to the density of the minimum density region is set to a value within the range of 1.3 to 10.

The "convex area ratio" shown in table 1 is an average value of the convex area ratios obtained for 10 fine protrusions randomly selected in the protrusion region.

The "density" shown in tables 1 and 2 was set to 1mm at 10 randomly selected points in the protrusion area²Average of the densities in square measurement areas.

Performance of wet land

Each test tire was attached to a test vehicle, and when the test run was performed on a test track having a water depth of 3mm on a wet road surface over a range (range) of 0 to 80 km/hour, the performance such as turning performance and straight-ahead performance when the test driver traveled was evaluated by sensory evaluation, and the evaluation was expressed by an index in which the conventional example was set to 100. The larger the index is, the more excellent the wet performance is.

Noise performance

Each test tire was attached to a test vehicle, and the passing noise outside the vehicle when running at 60 km/hour was measured in accordance with european noise regulations (ECE R117). The evaluation result is expressed by an index in which the conventional example is 100 using the reciprocal of the measured value. The larger the index is, the more excellent the noise performance is.

As a result, the case where the index of the wet performance was 100 or more and the index of the noise performance exceeded 100 was evaluated as the possibility of improving the noise performance without impairing the drainage performance.

[ Table 1]

	Conventional example	Example 1	Comparative example 1	Comparative example 2	Comparative example 3	Comparative example 4	Example 2
								With or without raised areas	Is free of	Is provided with	Is provided with	Is provided with	Is provided with	Is provided with	Is provided with
Shape of the micro-protrusions	Is substantially cylindrical	Is substantially cylindrical	Is substantially cylindrical	Is substantially cylindrical	Is substantially cylindrical	Is substantially cylindrical	Is substantially cylindrical
								Height ratio H/L1	-	0.0625	0.2	0.005	0.0625	0.0625	0.0625
Width ratio W/L2	-	0.015	0.015	0.015	0.1	0.001	0.005
								Aspect ratio H/W	-	2.4	7.6	0.19	0.36	36	7.1
Cross-sectional area ratio S1/S2	-	1	1	1	1	1	1
								Convex area ratio (%)	-	40	40	40	40	40	40
Density (pieces/mm)2)	-	4	4	4	Less than 1	4	4
								Presence or absence of density difference	-	Is free of	Is free of	Is free of	Is free of	Is free of	Is free of
Presence or absence of density difference in depth direction	-	Is free of	Is free of	Is free of	Is free of	Is free of	Is free of
								Noise performance	100	102	102	100	102	100	103
Performance of wet land	100	100	97	100	95	100	100

[ Table 2]

As is clear from comparison between the conventional example and example 1, the provision of the projection region in the groove can improve the noise performance without impairing the drainage performance.

As is clear from comparison between example 1 and comparative example 1, the height ratio H/L1 of the fine protrusions was 0.09 or less, and the decrease in wet performance was suppressed.

As is clear from comparison between example 1 and comparative example 2, the noise performance is improved by setting the height ratio H/L1 of the fine protrusions to 0.01 or more.

As is clear from comparison between example 1 and comparative example 3, the decrease in wet performance can be suppressed by setting the width ratio W/L2 of the fine protrusions to 0.02 or less.

As is clear from comparison between example 1 and comparative example 4, the noise performance is improved by setting the width ratio W/L2 of the fine protrusions to 0.002 or more.

As is clear from comparison between example 2 and example 3, the noise performance is further improved by setting the cross-sectional area ratio S1/S2 to 0.8 or less.

As is clear from comparison between example 3 and example 4, the density of the fine protrusions was 1mm per minute²The noise performance is further improved by more than five protruding areas.

As can be seen from the comparison of example 4 with example 5, the unexpected effect of greatly improving the noise performance is obtained by the difference in density of the protrusion areas.

As is clear from comparison between example 5 and example 6, the noise performance is greatly improved by the difference in density in the depth direction of the projected region.

Although the pneumatic tire of the present invention has been described in detail above, the present invention is not limited to the above embodiments and examples, and various improvements and modifications can be made without departing from the scope of the present invention. The pneumatic tire of the present invention may be filled with a gas other than air (e.g., an inert gas such as nitrogen gas) in addition to air in the cavity region surrounded by the pneumatic tire and the rim. The pneumatic tire of the present invention can be applied to tires other than pneumatic tires such as solid tires and run flat tires.

Description of the reference numerals

10 pneumatic tire

12 ply

14 Belt layer

16 bead core

18 tread rubber component

20 side wall rubber component

22 bead filler rubber component

24 rim cushion rubber member

26 lining rubber component

28 bead reinforcing Member

30 Belt overlay

40 raised area

41 minute projection

50 Tread pattern

52. 54, 56, 58 circumferential main grooves

60. 62, 64, 66, 68 land ring portion

60a, 62a, 64a striated grooves

66a, 68a shoulder cross groove

66b, 68b chamfer