JP6754268B2 - Pneumatic tires - Google Patents

Description

The present disclosure relates to a pneumatic tire capable of releasing static electricity generated in a vehicle body or a tire to a road surface.

In recent years, for the purpose of reducing the rolling resistance of a tire, which is closely related to fuel efficiency, a pneumatic tire in which a rubber member such as tread rubber is formed of non-conductive rubber containing a high proportion of silica has been proposed. However, such rubber members have higher electrical resistance than conventional products containing a high ratio of carbon black, and hinder the release of static electricity generated in the vehicle body and tires to the road surface, so that problems such as radio noise are likely to occur. There is a problem.

Patent Document 1 discloses a tire in which a conductive rubber extending in the radial direction is arranged on the equator of the tire. Tires have both straight running performance and turning performance, and it is preferable that they are compatible with each other. However, Patent Document 1 does not describe these at all.

U.S. Pat. No. 6,302,173

The present disclosure has focused on such circumstances, and an object of the present disclosure is to provide a pneumatic tire having both straight running performance and turning performance.

The present disclosure takes the following measures to achieve the above object.

That is, in the pneumatic tire of the present disclosure, a cap rubber formed of non-conductive rubber and forming a ground contact surface, a base rubber provided inside the cap rubber in the tire radial direction, and a mounting direction with respect to the vehicle are displayed. The cap rubber has a tire outer surface, and the cap rubber includes a rib extending in the tire circumferential direction at the tire equatorial line and a conductive rubber extending in the thickness direction of the cap rubber at the rib from the ground contact surface to the bottom surface of the base rubber. The conductive rubber has a lower rubber hardness than the cap rubber, the width at the ground contact surface is larger than the width at the bottom surface, and the conductive rubber at the ground contact surface is the rib of the rib. It is offset to the inside of the tire with respect to the center, and in the tire meridional cross section, the interface between the upper part of the conductive rubber and the cap rubber is a curved surface that expands toward the outside in the radial direction and curves outward in the radial direction. , The average curvature on the outside of the mounting is smaller than the average curvature on the inside of the mounting.

In this way, the conductive rubber has a lower rubber hardness than the cap rubber, and the interface between the upper part of the conductive rubber and the cap rubber is a curved surface that expands toward the outer side in the radial direction, so that the soft rubber increases the contact length. , Straight running performance is improved.
Furthermore, the conductive rubber is offset to the inside of the mounting, the curved surface is curved outward in the radial direction, and the mean curvature of the outside of the mounting is smaller than the mean curvature of the inside of the mounting, so the area of the cap rubber on the outside of the mounting is secured. However, by suppressing the decrease in rigidity, turning performance can be ensured.
Further, since the thickened portion, which is the upper part of the conductive rubber, is formed only by a curved surface, the force at the time of turning is dispersed and heat generation is suppressed as compared with the case where the thickened portion is linear.
Further, since the width of the conductive rubber on the ground surface is larger than the width on the bottom surface, the amount of the conductive rubber, which is a soft rubber, is suppressed and the deterioration of the turning performance is suppressed as compared with the case where the whole is composed of the same width. doing.
Therefore, it is possible to achieve both straight-ahead performance and turning performance.

A tire meridian sectional view showing an example of a pneumatic tire according to the present disclosure. The cross-sectional view which shows the conductive rubber and the structure around it. Sectional drawing which shows the modification. FIG. 5 is a cross-sectional view showing Comparative Example 1. FIG. 2 is a cross-sectional view showing Comparative Example 2.

Hereinafter, the pneumatic tire according to the embodiment of the present disclosure will be described with reference to the drawings.

As shown in FIG. 1, the pneumatic tire T includes a pair of bead portions 1, a sidewall portion 2 extending outward from each bead portion 1 in the tire radial direction RD, and both sidewall portions 2 outside the tire radial direction RD. It is provided with a tread portion 3 connected to the end. The bead portion 1 is provided with an annular bead core 1a formed by coating a convergent body such as a steel wire with rubber, and a bead filler 1b made of hard rubber.

Further, the tire T includes a toroid-shaped carcass layer 4 extending from the tread portion 3 to the bead portion 1 via the sidewall portion 2. The carcass layer 4 is provided between the pair of bead portions 1 and is composed of at least one carcass ply, and the end portions thereof are locked in a wound state via the bead core 1a. The carcass ply is formed by covering a cord extending substantially at right angles to the tire equator CL with topping rubber. Inside the carcass layer 4, an inner liner rubber 4a for holding air pressure is arranged.

Further, a sidewall rubber 6 is provided on the outside of the carcass layer 4 in the sidewall portion 2. Further, on the outside of the carcass layer 4 in the bead portion 1, a rim strip rubber 7 that comes into contact with the rim (not shown) when the rim is attached is provided. In the present embodiment, the topping rubber and the rim strip rubber 7 of the carcass layer 4 are formed of conductive rubber, and the sidewall rubber 6 is formed of non-conductive rubber.

On the outside of the carcass layer 4 in the tread portion 3, a belt 4b for reinforcing the carcass layer 4, a belt reinforcing material 4c, and a tread rubber 5 are provided in order from the inside to the outside. The belt 4b is composed of a plurality of belt plies. The belt reinforcing material 4b is configured by covering a cord extending in the tire circumferential direction with topping rubber. The belt reinforcing material 4b may be omitted if necessary.

As shown in FIGS. 1 and 2, the tread rubber 5 includes a cap rubber 50 formed of non-conductive rubber and forming a ground contact surface E, and a base rubber 51 provided inside the cap rubber 50 in the tire radial direction. Has. A plurality of main grooves 5a extending along the tire circumferential direction are formed on the surface of the cap rubber 50. The cap rubber 50 has a rib Rb extending in the tire circumferential direction CD at the tire equatorial CL, and a conductive rubber 52 extending in the thickness direction of the cap rubber 50 at the rib Rb from the ground contact surface E to the bottom surface of the base rubber 51. The rib Rb is partitioned by a main groove 5a and is continuous with the CD in the tire circumferential direction. Although not shown, the mounting direction with respect to the vehicle is indicated on the outer surface of the tire (the sidewall rubber 6 in this embodiment).

In the above, the ground contact surface E is a surface that is rim-assembled on the regular rim, the tire is placed vertically on a flat road surface with the regular internal pressure charged, and is in contact with the road surface when a regular load is applied, and the tire width direction thereof. The outermost position of the WD is the grounding end. The normal load and the normal internal pressure are the maximum load (design normal load in the case of passenger car tires) specified in JIS D4202 (specifications of automobile tires) and the air pressure corresponding to this, and the normal rim is As a general rule, the standard rim specified in JIS D4202 etc. shall be used.

In the present embodiment, a sidewall on tread (SWOT) structure in which the sidewall rubbers 6 are placed on both side ends of the tread rubber 5 is adopted, but the structure is not limited to this. It is also possible to adopt a tread on side (TOS) structure in which both end portions of the tread rubber are placed on the outer end of the tire radial RD of the sidewall rubber.

Here, the conductive rubber is exemplified rubbers showing less than a volume resistivity of 10 ⁸ Ω · cm, is prepared by blending a carbon black a high proportion as a reinforcing agent, for example, raw rubber. In addition to carbon black, it can also be obtained by blending carbon fibers, carbon-based materials such as graphite, and known metal-based conductivity-imparting materials such as metal powders, metal oxides, metal flakes, and metal fibers.

The non-conductive rubber is exemplified rubber showing a volume resistivity of more than 10 ⁸ Ω · cm, silica those formulated in high proportions is illustrated as a reinforcing agent to the raw material rubber. The silica is blended in an amount of 30 to 100 parts by weight with respect to 100 parts by weight of the raw material rubber component, for example. Wet silica is preferably used as the silica, but those widely used as reinforcing materials can be used without limitation. The non-conductive rubber may be produced by blending calcined clay, hard clay, calcium carbonate or the like in addition to silicas such as precipitated silica and silicic anhydride.

Examples of the above-mentioned raw material rubber include natural rubber, styrene-butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (IR), butyl rubber (IIR), and the like, and these may be used alone or in admixture of two or more. Is used. A vulcanizing agent, a vulcanization accelerator, a plasticizer, an antiaging agent, and the like are appropriately blended in the raw rubber.

From the viewpoint of improving durability and energizing performance, the conductive rubber has a nitrogen-adsorbed non-surface surface: N ₂ SA (m ² / g) × carbon black compounding amount (mass%) of 1900 or more, preferably 2000 or more. It is desirable that the amount of dibutyl phthalate oil absorbed: DBP (ml / 100 g) x carbon black compounding amount (mass%) satisfies 1500 or more, preferably 1700 or more. N ₂ SA is determined according to ASTM D3037-89 and DBP is determined according to ASTM D2414-90.

FIG. 2A is a cross-sectional view showing the conductive rubber 52. The conductive rubber 52 has a lower rubber hardness than the cap rubber 50, and the conductive rubber 52 is softer than the cap rubber 50. The rubber hardness referred to here means the hardness measured according to the durometer hardness test (type A) of JIS K6253. In the present embodiment, the conductive rubber 52 has a curved surface portion 53 that has a tapered shape toward the outer RD1 in the radial direction and is exposed to the ground plane E, and a stretched portion that extends linearly from the curved surface portion 53 to the bottom surface of the base rubber 51. 54 and.

In the tire meridian cross section, the width D3 of the conductive rubber 52 on the ground plane E is larger than the width D2 on the bottom surface. In a plan view, the conductive rubber 52 on the ground plane E is offset to the mounting inner IN with respect to the center CL of the rib Rb. In the present embodiment, the center CL of the rib Rb and the tire equator CL coincide with each other, but they do not have to coincide with each other.

As shown in the figure, the interface between the curved surface portion 53, which is the upper part of the conductive rubber 52, and the cap rubber 50 is a curved surface that expands toward the radial outer RD1 and curves toward the radial outer RD1. The mean curvature R2 of the mounting outer OUT is smaller than the mean curvature R1 of the mounting inner IN. The mean curvature means the curvature when there is a single curved surface, and means the average value of those curvatures when there are multiple curved surfaces.

In the present embodiment, the amount D1 at which the width center C1 at the connecting portion between the curved surface portion 53 and the extending portion 54 is offset toward the mounting inner IN with respect to the center CL of the rib Rb is 5.0 mm. Of course, the offset amount D1 is not limited to this, and is preferably 2.0 mm to 20.0 mm.

In the present embodiment, the mean curvature R1 of the mounting inner IN on the curved surface portion 53 is 5.0 mm. Of course, the average curvature R1 of the mounting inner IN is not limited to this, and is preferably 3 mm to 7 mm.

In the present embodiment, the mean curvature R2 of the mounting outer OUT on the curved surface portion 53 is 3.0 mm. Of course, the average curvature R2 of the mounting outer OUT is not limited to this, and is preferably 1 mm to 5 mm. However, it is preferable that the mean curvature R1 of the mounting inner IN> the mean curvature R2 of the mounting outer OUT.

In the present embodiment, the width D2 of the stretched portion 54 is 2.0 mm. Of course, the width D2 of the stretched portion 54 is not limited to this, and is preferably 0.2 mm to 3 mm.

In the example of FIG. 2, the stretched portion 54, which is the lower portion of the conductive rubber 52, extends in the radial inner RD2 and is offset from the center CL of the rib Rb to the mounting inner IN. According to this configuration, the amount of the cap rubber 50 on the outer side OUT of the mounting is increased, so that deterioration of turning performance can be suppressed.

On the other hand, as shown in FIG. 3, the conductive rubber 52 may be formed. In the example of FIG. 3, the lower portion 54 of the conductive rubber 52 extends toward the center CL of the rib Rb toward the radial inner RD2. In general, pneumatic tires are often mounted on vehicles with a negative camber, and the load is input diagonally. With this configuration, the direction in which the load acts and the direction in which the stretched portion 54, which is the lower part of the conductive rubber 52, extends coincide with or are close to each other, so that the load can be appropriately received.

In order to concretely show the structure and effect of the present disclosure, the following evaluations were carried out for the following examples.

(1) Straight-line performance (dry & wet)
Each tire was attached to a Japanese sedan (2000cc), and the internal pressure was specified as the vehicle. The two passengers traveled straight at 60 to 140 km / h, performed a braking test, and evaluated by a sensory test of the driver. The result of the tire of Comparative Example 1 was expressed by an index of 100. The larger the value, the better the straight-line performance. On a wet road surface, the vehicle ran on a 1 mm water film road surface.

(2) Turning performance (dry & wet)
Each tire was attached to a Japanese sedan (2000cc), and the internal pressure was specified as the vehicle. The two passengers ran slalom at 60 to 140 km / h and evaluated by a sensory test of the driver. The result of the tire of Comparative Example 1 was expressed by an index of 100. The larger the value, the better the turning performance. On a wet road surface, the vehicle ran on a 1 mm water film road surface.

Example 1
The embodiment shown in FIG. 2 was designated as Example 1.

Comparative Example 1
As shown in FIG. 4, a conductive rubber 151 is provided on the rib Rb from the ground contact surface E to the bottom surface of the base rubber 51. The conductive rubber 151 is composed of only a straight portion parallel to the tire radial direction RD from the ground contact surface E to the bottom surface of the base rubber 51. The offset amount D1 of the conductive rubber 151 was the same as that of the first embodiment. Others are the same as in Example 1.

Comparative example 2
As shown in FIG. 5, the curved surface of the curved surface portion 253 constituting the conductive rubber 252 is the same for the mounting inner IN and the mounting outer OUT. In both cases, the mean curvature R1 = 5.0 mm. Other than that, it was the same as in Example 1.

From Table 1, Comparative Example 2 has improved straight-line performance as compared with Comparative Example 1, but has lower turning performance. The straight-line performance has improved because the amount of conductive rubber (soft rubber) exposed on the ground surface has increased, and the soft rubber swells due to internal pressure, resulting in a longer ground contact length and a larger ground contact area (that is, grip). The area becomes larger), and as a result, it is considered that the straight running performance (driving performance, braking performance) is improved. On the other hand, it is considered that the increase in soft rubber makes it difficult for the treading to work during turning, and the turning performance deteriorates.

In the first embodiment, the straight running performance is improved while maintaining the turning performance as compared with the comparative example 1. It is considered that this is because the area of the cap rubber 50 of the mounting outer OUT is increased by making the mean curvature of the mounting outer OUT smaller than the mounting inner IN, and the rigidity is less likely to decrease. Further, since the thickened portion, which is the upper part of the conductive rubber 52, is formed only by a curved surface, it is considered that the force during turning is dispersed and heat generation is suppressed as compared with the case where the thickened portion is linear. ..

As described above, the pneumatic tire of the present embodiment has a pair of bead portions 1, a sidewall portion 2 extending outward in the tire radial direction from each of the bead portions 1, and a tire radial outer side of each of the sidewall portions 2. A tread portion 3 connected to an end, a tread-shaped carcass layer 4 provided between a pair of bead portions 1, and a tread rubber 5 provided on the outside of the carcass layer 4 of the tread portion 3 are provided. The tread rubber 5 includes a cap rubber 50 formed of non-conductive rubber and forming a ground contact surface E, a base rubber 51 provided on the inner RD2 of the cap rubber 50 in the tire radial direction, and a tire on which the mounting direction with respect to the vehicle is displayed. With an outer surface. The cap rubber 50 has a rib Rb extending in the tire circumferential direction CD at the tire equatorial CL, and a conductive rubber 52 extending in the thickness direction of the cap rubber 50 at the rib Rb from the ground contact surface E to the bottom surface of the base rubber 51. The conductive rubber 52 has a lower rubber hardness than the cap rubber 50, and the width D3 on the ground contact surface E is larger than the width D2 on the bottom surface. In a plan view, the conductive rubber 52 on the ground plane E is offset inward with respect to the center CL of the rib Rb. In the tire meridian cross section, the interface between the upper portion of the conductive rubber 52 and the cap rubber 50 is a curved surface that expands toward the radial outer RD1 and curves toward the radial outer RD1. The mean curvature R2 of the mounting outer OUT is smaller than the mean curvature R1 of the mounting inner IN.

As described above, the conductive rubber 52 has a lower rubber hardness than the cap rubber 50, and the interface between the upper portion of the conductive rubber 52 and the cap rubber 50 is a curved surface that expands toward the outer side RD1 in the radial direction. The ground contact length becomes longer and the straight running performance improves.
Further, the conductive rubber 52 is offset to the mounting inner IN, the curved surface is curved to the radial outer RD1, and the mean curvature R2 of the mounting outer OUT is smaller than the mean curvature R1 of the mounting inner IN. By securing the region of the OUT cap rubber 50 and suppressing the decrease in rigidity, the turning performance can be ensured.
Further, since the thickened portion which is the upper part of the conductive rubber 52 is formed only by a curved surface, the force at the time of turning is dispersed and heat generation is suppressed as compared with the case where the thickened portion is linear.
Further, since the width D3 on the ground contact surface E of the conductive rubber 52 is larger than the width D2 on the bottom surface, the amount of the conductive rubber which is a soft rubber is suppressed and the turning performance is suppressed as compared with the case where the whole is configured to have the same width. It suppresses the deterioration of.
Therefore, it is possible to achieve both straight-ahead performance and turning performance.

In the present embodiment, the conductive rubber 52 has a curved surface portion 53 that has a tapered shape toward the outer RD1 in the radial direction and is exposed to the ground plane E, and a stretched portion that extends linearly from the curved surface portion 53 to the bottom surface of the base rubber 51. 54 and.

According to this configuration, the amount of the soft conductive rubber can be suppressed by the linear stretched portion 54, so that the deterioration of the turning performance can be suppressed.

In the present embodiment, the amount D1 at which the width center C1 at the connecting portion between the curved surface portion 53 and the extending portion 54 is offset toward the mounting inner IN with respect to the center CL of the rib Rb is 2 to 20 mm, and the mounting at the curved surface portion 53. The mean curvature R1 of the inner IN is 3 to 7 mm, and the mean curvature R2 of the mounting outer OUT on the curved surface 53 is 1 to 5 mm. However, the mean curvature R1 of the mounting inner IN> the mean curvature R2 of the mounting outer OUT.

This configuration is a good example.

In the present embodiment, the stretched portion 54, which is the lower part of the conductive rubber 52, extends in the radial inner RD2 and is offset from the center CL of the rib Rb to the mounting inner IN.

According to this configuration, the amount of the cap rubber 50 on the outer side OUT of the mounting is increased, so that deterioration of turning performance can be suppressed.

In the present embodiment, the stretched portion 54, which is the lower portion of the conductive rubber 52, extends so as to approach the center CL of the rib Rb toward the radial inner RD2.

With this configuration, the direction in which the load acts and the direction in which the stretched portion 54, which is the lower part of the conductive rubber 52, extends coincide with or are close to each other, so that the load can be appropriately received.

It is possible to adopt the structure adopted in each of the above embodiments in any other embodiment. The specific configuration of each part is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present disclosure.

50 ... Cap rubber 51 ... Base rubber 52 ... Conductive rubber 53 ... Curved surface 54 ... Stretched part Rb ... Rib E ... Ground plane

Claims (5)

It has a cap rubber formed of non-conductive rubber and forming a ground contact surface, a base rubber provided inside the cap rubber in the tire radial direction, and a tire outer surface on which the mounting direction with respect to the vehicle is displayed.
The cap rubber has a rib extending in the tire circumferential direction at the equator of the tire and a conductive rubber extending in the thickness direction of the cap rubber from the ground contact surface to the bottom surface of the base rubber at the rib.
The conductive rubber has a lower rubber hardness than the cap rubber, and the width at the ground contact surface is larger than the width at the bottom surface.
In a plan view, the conductive rubber on the ground plane is offset inwardly mounted with respect to the center of the rib.
In the tire meridian cross section, the interface between the upper part of the conductive rubber and the cap rubber is a curved surface that expands toward the outside in the radial direction and curves outward in the radial direction.
Pneumatic tires with a smaller mean curvature on the outside than the mean curvature on the inside. The first aspect of the present invention, wherein the conductive rubber has a curved surface portion that is tapered outward in the radial direction and is exposed to a ground contact surface, and a stretched portion that extends linearly from the curved surface portion to the bottom surface of the base rubber. Pneumatic tires. The amount by which the center of width at the connecting portion between the curved surface portion and the extending portion is offset inward with respect to the center of the rib is 2 to 20 mm.
The mean curvature inside the mounting on the curved surface is 3 to 7 mm.
The pneumatic tire according to claim 2, wherein the average curvature of the mounted outer surface of the curved surface portion is 1 to 5 mm. The pneumatic tire according to any one of claims 1 to 3, wherein the lower portion of the conductive rubber extends radially inward and is offset inward from the center of the rib. The pneumatic tire according to any one of claims 1 to 3, wherein the lower portion of the conductive rubber extends toward the center of the rib as it goes inward in the radial direction.

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