WO2012161314A1

WO2012161314A1 - Tire

Info

Publication number: WO2012161314A1
Application number: PCT/JP2012/063490
Authority: WO
Inventors: 充幸和氣
Original assignee: 株式会社ブリヂストン
Priority date: 2011-05-26
Filing date: 2012-05-25
Publication date: 2012-11-29

Abstract

A tire (100) is provided with: a pair of bead cores (110); a carcass layer (120) that is toroidally-shaped and spans between the pair of bead cores (110); and a tread part (40) that has a road contacting surface. The tread part (40) includes a center section (41A) that does not include a foam rubber layer (42), and an exterior section (41B) that includes the foam rubber layer (42). The ratio (WT/W) of a width (WT), which extends from a tire equator line (CL) to the end of the center section (41A), to a width (W), which extends from the tire equator line (CL) to the end of the road contacting surface is not less than 0.15 and not greater than 0.6. The gauge thickness of the foam rubber layer (42) is less than 20% of the gauge thickness of the exterior section (41B).

Description

tire

The present invention relates to a tire including a pair of bead cores and a carcass layer having a toroidal shape straddling between the pair of bead cores.

Conventionally, a pair of bead cores, a carcass layer having a toroidal shape straddling between a pair of bead cores, a belt layer disposed adjacent to the carcass layer, and a bead core, a carcass layer, and a rubber layer covering the belt layer Tires equipped are known.

The tire includes a bead portion having a bead core, a tread portion having a road surface contact surface, a sidewall portion forming a side surface of the tire, and a shoulder portion provided between the sidewall portion and the tread portion.

Here, it is known that noise is generated by the interaction between the tire and the road surface as the tire rotates. As a technique for reducing such noise, a technique is known in which the road surface contact surface of the tread portion is made of foamed rubber.

For the purpose of improving the grip performance and the performance on ice, techniques for forming the road surface contact surface of the tread portion with foamed rubber have been proposed (for example, Patent Documents 1 and 2).

JP 2004-050963 A Japanese Patent Laid-Open No. 2007-131084

However, the rigidity of foamed rubber is generally low. In the above-described technique, since the entire road surface contact surface of the tread portion is made of foamed rubber, steering stability is lowered.

Therefore, the present invention has been made to solve the above-described problems, and an object of the present invention is to provide a tire that can reduce noise while suppressing a decrease in steering stability.

The tire according to the first feature includes a pair of bead cores, a carcass layer having a toroidal shape straddling between the pair of bead cores, and a tread portion having a road surface contact surface. The tread portion includes a central portion that forms a predetermined range including the tire equator line in the tire width direction, and an outer portion that is adjacent to the outside of the central portion in the tire width direction. A distance W from the tire equator line to the end of the road surface contact surface in the tire width direction is a width W. The distance from the tire equator line to the end of the central portion in the tire width direction is a width WT. A ratio WT / W of the width WT to the width W is 0.15 or more and 0.6 or less. The central portion does not have a foam rubber layer on the surface of the central portion, and the outer portion has a foam rubber layer on the surface of the outer portion. The gauge thickness of the foamed rubber layer in the tire radial direction is less than 20% of the gauge thickness of the outer portion in the tire radial direction.

In the first feature, the gauge thickness of the foamed rubber layer in the tire radial direction is 5% or more and less than 20% of the gauge thickness of the outer portion in the tire radial direction.

FIG. 1 is a view showing a tire 100 according to the first embodiment. FIG. 2 is a view showing the tire 100 according to the first embodiment. FIG. 3 is a diagram showing a road surface ground plane according to the first embodiment. FIG. 4 is a view showing a tire 100 according to the first modification. FIG. 5 is a diagram showing the evaluation result 1. FIG. 6 is a diagram showing the evaluation result 2.

Hereinafter, a tire according to an embodiment of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.

However, it should be noted that the drawings are schematic and ratios of dimensions are different from actual ones. Therefore, specific dimensions and the like should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

[Outline of Embodiment]
The tire according to the embodiment includes a pair of bead cores, a carcass layer having a toroidal shape straddling the pair of bead cores, and a tread portion having a road surface. The tread portion includes a central portion that forms a predetermined range including the tire equator line in the tire width direction, and an outer portion that is adjacent to the outside of the central portion in the tire width direction. A distance W from the tire equator line to the end of the road surface contact surface in the tire width direction is a width W. The distance from the tire equator line to the end of the central portion in the tire width direction is a width WT. A ratio WT / W of the width WT to the width W is 0.15 or more and 0.6 or less. The central portion does not have a foam rubber layer on the surface of the central portion, and the outer portion has a foam rubber layer on the surface of the outer portion. The gauge thickness of the foamed rubber layer in the tire radial direction is less than 20% of the gauge thickness of the outer portion in the tire radial direction.

In the embodiment, the center portion does not have the foam rubber layer on the surface of the center portion, and the outer portion has the foam rubber layer on the surface of the outer portion. Therefore, noise can be reduced while suppressing a decrease in steering stability.

Specifically, since the central portion is defined so that the ratio WT / W of the width WT to the width W satisfies a condition larger than 0.1, the central portion having no foamed rubber layer is sufficiently secured. , A decrease in steering stability is suppressed. Further, since the central portion is defined so as to satisfy the condition that the ratio WT / W of the width WT to the width W is 0.6 or less, the outer portion having the foamed rubber layer is sufficiently secured, and the noise reduction effect is achieved. can get.

Also, the gauge thickness of the foam rubber layer is less than 20% of the gauge thickness of the outer part. Therefore, a decrease in steering stability is suppressed.

Also, a groove in contact with the foam rubber layer is provided on the road surface ground contact surface. The maximum gauge thickness of the foamed rubber layer is less than 33% of the maximum groove depth in the tire radial direction. That is, the value obtained by dividing the gauge thickness of the foam rubber layer by the maximum value of the groove depth in the tire radial direction (gauge thickness of the foam rubber layer / maximum value of the groove depth in the tire radial direction) is less than 33%. is there. Since the volume of the pattern noise has a correlation with the groove volume, the volume of the pattern noise decreases if the groove depth decreases due to tire wear. Therefore, when a tire with a high pattern noise volume is new, the foam rubber layer reduces the pattern noise volume with a foam rubber layer, and when the tire with a low pattern noise volume wears, the foam rubber layer decreases or disappears. The decrease in stability can be further suppressed. As a result, it is possible to achieve both suppression of steering stability reduction and noise reduction throughout the tire usage period.

[First Embodiment]
(Tire composition)
Below, the composition of the tire concerning a 1st embodiment is explained. FIG.1 and FIG.2 is a figure which shows the tire 100 which concerns on 1st Embodiment.

First, as shown in FIG. 1, the tire 100 includes a bead portion 10, a sidewall portion 20, a shoulder portion 30, and a tread portion 40.

The bead portion 10 is provided on the innermost side in the tire radial direction among the portions constituting the tire 100. The bead portion 10 is continuously provided along the tire circumferential direction. The bead part 10 is a part for fixing the tire 100 to the rim. The bead portion 10 is covered with rubber.

The sidewall portion 20 is provided outside the bead portion 10 in the tire radial direction among the portions constituting the tire 100. The sidewall portion 20 is continuously provided along the tire circumferential direction. The sidewall portion 20 constitutes the side surface of the tire 100. The sidewall portion 20 is covered with rubber.

The shoulder portion 30 is provided between the sidewall portion 20 and the tread portion 40 among the portions constituting the tire 100. The shoulder portion 30 is continuously provided along the tire circumferential direction. The shoulder portion 30 is covered with rubber.

The tread portion 40 is a portion constituting a road surface contact surface that contacts the road surface among the portions constituting the tire 100. The tread portion 40 is continuously provided along the tire circumferential direction. A tread pattern formed by, for example, a groove (circumferential groove) extending along the tire circumferential direction or a (width groove) extending along the tire width direction is provided on the road surface contact surface of the tread portion 40. .

Second, the tire 100 includes a bead core 110, a carcass layer 120, and a belt layer 130, as shown in FIGS.

The bead core 110 includes a bead core 110 </ b> A and a bead core 110 </ b> B, and configures the bead unit 10. The bead core 110 has a ring shape and is configured by a bead wire (not shown).

The carcass layer 120 has a toroidal shape straddling between the bead core 110A and the bead core 110B. The carcass layer 120 is composed of, for example, a plurality of carcass cords (not shown) extending along the tire radial direction (or tire width direction). The carcass layer 120 is folded back at the bead core 110 toward the outside in the tire width direction.

The belt layer 130 includes a belt layer 130 </ b> A and a belt layer 130 </ b> B, and constitutes the tread portion 40. The belt layer 130 is disposed on the outer side in the tire radial direction with respect to the carcass layer 120. The belt layer 130 has a configuration in which a belt cord is covered with rubber. The belt cord provided in the belt layer 130A may intersect with the belt cord provided in the belt layer 130B.

In the first embodiment, the tread portion 40 includes a central portion 41A constituting a predetermined range including the tire equator line in the tire width direction, and an outer portion 41B (outer portion 41B ₁₎ adjacent to the outside of the central portion 41A in the tire width direction. And an outer portion 41B ₂ ).

The central portion 41A does not have a foam rubber layer on the surface (road surface grounding surface) of the central portion 41A. In contrast, the outer portion 41B has a foam rubber layer 42 on the surface (road surface ground surface) of the outer portion 41B.

The foamed rubber layer 42 is made of a rubber material having bubbles. The foaming rate of the foamed rubber layer 42 is less than 40%. The foaming rate is the ratio of the volume of bubbles to the volume other than bubbles in a unit volume.

The gauge thickness 42g of the foamed rubber layer 42 in the tire radial direction is less than 20% of the gauge thickness 41Bg of the outer portion 41B in the tire radial direction. As a result, a decrease in steering stability associated with the arrangement of the foam rubber layer 42 is suppressed. Here, the gauge thickness 41Bg of the outer portion 41B is the maximum gauge thickness from the tread surface (road surface contact surface) to the belt layer 130B located on the outermost side in the tire radial direction.

The gauge thickness 42g of the foamed rubber layer 42 is preferably 5% or more of the gauge thickness 41Bg of the outer portion 41B. Thereby, the noise reduction effect accompanying the arrangement of the foamed rubber layer 42 is sufficiently obtained.

Here, the gauge thickness 42g of the foamed rubber layer 42 is the gauge thickness 42g of the foamed rubber layer 42 at the position where the gauge thickness 41Bg of the outer part 41B is maximum in the outer part 41B. Therefore, the gauge thickness 42g of the foam rubber layer 42 and the gauge thickness 41Bg of the outer portion 41B are measured at the same position.

(Road surface contact surface)
In the following, the road surface contact surface according to the first embodiment will be described. FIG. 3 is a diagram showing a road surface ground plane according to the first embodiment.

As shown in FIG. 3, the road surface ground surface is provided with a circumferential main groove 43, a circumferential sub groove 44, a width direction groove 45, a lug groove 46, and the like.

The circumferential main groove 43 is a groove extending along the tire circumferential direction. The circumferential main groove 43 is arranged on the inner side in the tire width direction than the circumferential sub groove 44.

The circumferential sub-groove 44 is a groove extending along the tire circumferential direction. The circumferential sub-groove 44 is disposed outside the circumferential main groove 43 in the tire width direction.

The width direction groove 45 is a groove extending along the tire width direction. Here, the width direction groove 45 communicates with the circumferential main groove 43 and the circumferential sub groove 44.

The lug groove 46 is a groove extending along the tire width direction. Here, the lug groove 46 communicates with the circumferential sub-groove 44.

2 and 3, in the present embodiment, the circumferential main groove 43, the circumferential sub groove 44, the width groove 45, and the lug groove 46 are in contact with the foamed rubber layer 42.

Here, when the load is a normal load, the internal pressure is a normal internal pressure, and the environmental condition is a normal environmental condition, the road surface contact surface is a surface in contact with the road surface of the tire 100 under normal conditions. means. Specifically, when traveling straight ahead, the road surface contact surface is a surface in contact with the road surface among the surfaces of the tire 100. The road surface contact surface may be constituted by the shoulder portion 30 in addition to the tread portion 40.

Here, the normal load and the normal internal pressure are values determined by standard organizations such as JATMA, ETRTO, and TRA. The normal environmental conditions are an atmospheric pressure of 1 atm and an air temperature of 20 ° C.

As shown in FIG. 3, the distance (width) from the tire equator line CL to the end of the road surface contact surface in the tire width direction is represented by “W”. The distance (width) from the tire equator line CL to the end of the central portion 41A in the tire width direction is “WT”.

In such a case, the ratio WT / W of the width WT to the width W is 0.15 or more and 0.6 or less. That is, the central portion 41A is defined so that the condition that the ratio WT / W is 0.15 or more is satisfied. Similarly, the central portion 41A is defined so that the condition that the ratio WT / W is 0.6 or less is satisfied.

Thus, since the central portion 41A is defined so that the condition that the ratio WT / W is 0.15 or more is satisfied, the central portion 41A that does not have the foamed rubber layer 42 is sufficiently secured, and steering stability is improved. The decline in sex is suppressed. Since the central portion 41A is defined so that the condition where the ratio WT / W is smaller is satisfied, the outer portion 41B having the foamed rubber layer 42 is sufficiently secured, and a noise reduction effect is obtained.

In particular, of the grooves (circumferential main groove 43, circumferential sub-groove 44, width direction groove 45, and lug groove 46) in contact with the foamed rubber layer 42, the groove having the maximum groove depth in the tire radial direction (for example, A value obtained by dividing the maximum value of the gauge thickness of the foamed rubber layer by the maximum value of the circumferential main groove 43) (for example, the gauge thickness of the foamed rubber layer 42 / the maximum value of the depth of the circumferential main groove 43) is 33. It is preferable that it is less than%. For example, when the groove depth of the lug groove 46 is maximized, the maximum value of the gauge thickness of the foamed rubber layer 42 / the groove depth of the lug groove 46 is preferably less than 33%.

If the maximum value of the gauge thickness of the foamed rubber layer 42 exceeds 33% of the maximum value of the groove depth in the tire radial direction, the noise reduction effect does not increase significantly. For this reason, by setting the maximum value of the gauge thickness of the foam rubber layer to less than 33% of the maximum value of the groove depth in the tire radial direction, the volume of pattern noise is reduced by the foam rubber layer when new. On the other hand, the steering stability can be improved by eliminating the foamed rubber layer 42 at the time of wear of the tire in which the volume of the pattern noise is reduced by reducing the volume of the groove.

(Function and effect)
In the first embodiment, the central portion 41A does not have the foam rubber layer 42 on the surface of the central portion 41A, and the outer portion 41B has the foam rubber layer 42 on the surface of the outer portion 41B. Therefore, noise can be reduced while suppressing a decrease in steering stability.

[Modification 1]
Hereinafter, Modification Example 1 of the first embodiment will be described. In the following, differences from the first embodiment will be described.

In the first embodiment, the foam rubber layer 42 is provided on the surface of the outer portion 41B.

On the other hand, in the modified example 1, as shown in FIG. 4, the foamed rubber layer 42 is not only on the surface of the outer portion 41B, but also on the groove bottoms of the circumferential main grooves 43 and the circumferential sub grooves 44 described above. Provided. The foamed rubber layer 42 may be provided on the groove walls of the circumferential main groove 43 and the circumferential subgroove 44 described above.

Alternatively, in the first modification, the foamed rubber layer 42 may be provided on the bottoms of the width direction grooves 45 and the lug grooves 46 described above in addition to the surface of the outer portion 41B. The foamed rubber layer 42 may be provided on the groove walls of the width direction groove 45 and the lug groove 46 described above.

[Evaluation results]
Hereinafter, evaluation results of the tire according to the embodiment will be described. Specifically, the tires were mounted on the vehicle in accordance with the following conditions, the vehicle running test was performed, and the tire characteristics were evaluated.

For the noise evaluation, the actual measured noise value was evaluated under the following common conditions. The noise was evaluated according to “Directive 2001/43 / EC”. Note that the noise was evaluated based on the sum of sounds having a frequency of 20 to 20 kHz.
(Common conditions)
Tire size = 195 / 65R15
Tire internal pressure = 180 kPa
Load = 4.4kN
Vehicle speed = 80km / h

The steering stability was evaluated subjectively in the range of -5 to +5 under the following common conditions. In the evaluation of steering stability, the tire according to the conventional example was evaluated with reference (0).
(Common conditions)
Tire size = 195 / 65R15
Tire internal pressure = 220 kPa
Load = 4.2kN front wheel, 3.5kN rear wheel
Vehicle speed = 80km / h

(Evaluation result 1)
Hereinafter, the evaluation result 1 will be described with reference to FIG. The tires according to the conventional example, the comparative example 1, the comparative example 2, and the examples 1 to 3 are provided with the circumferential main grooves extending in the tire circumferential direction on the road surface contact surface. Except for the tire according to the conventional example, the circumferential main groove is adjacent to the foamed rubber layer. In any tire, the maximum depth of the circumferential main groove in the tire radial direction is 6.8 mm. However, as shown in FIG. 5, the ratio of the maximum gauge thickness of the foam rubber layer and the maximum depth of the circumferential main groove (foam rubber layer gauge thickness / maximum groove depth) is different. Here, the tire according to the conventional example is a tire having no foamed rubber layer. The tires according to Comparative Example 1, Comparative Example 2, and Examples 1 to 3 are tires having a foamed rubber layer on the surface of the outer portion. However, as shown in FIG. 5, the ratio of the gauge thickness of the foam rubber layer to the gauge thickness of the outer portion (gauge thickness ratio) is different. Further, the tires according to Comparative Example 1, Comparative Example 2, and Example 1 are tires having a foamed rubber layer at the groove bottom of the groove provided on the road surface ground surface.

In Comparative Example 1, Comparative Example 2, and Examples 1 to 3, it should be noted that W is 72 mm, WT is 32 mm, and the ratio WT / W is the same value. is there.

As shown in FIG. 5, in Comparative Examples 1 and 2, since the gauge thickness ratio was larger than 20%, the steering stability was lowered. On the other hand, in Examples 1 to 3, since the gauge thickness ratio was less than 20%, a decrease in steering stability was suppressed.

In Comparative Example 1, Comparative Example 2, and Examples 1 to 3, a noise reduction effect was obtained by providing a foamed rubber layer on the surface of the outer portion. In addition, compared with Comparative Example 1 and Comparative Example 2 in which the gauge thickness ratio is greater than 20%, Examples 1 to 3 have a sufficient noise reduction effect.

Further, as shown in Example 3, it was confirmed that the gauge thickness ratio is preferably 5% or more.

(Evaluation result 2)
Hereinafter, the evaluation result 2 will be described with reference to FIG. The tires according to Comparative Example 3, Comparative Example 4, Example 1, Example 4, and Example 5 are tires having a foam rubber layer on the surface of the outer portion.

It should be noted that in Comparative Example 3, Comparative Example 4, Example 1, Example 4, and Example 5, the gauge thickness ratio is a similar value.

As shown in FIG. 6, in Comparative Example 3, the noise reduction effect was not obtained because the ratio WT / W was larger than 0.6. In Comparative Example 4, since the ratio WT / W was smaller than 0.15, the steering stability was lowered. On the other hand, in Example 1, Example 4, and Example 5, since the ratio WT / W is 0.15 or more and 0.6 or less, a noise reduction effect is achieved while suppressing a decrease in steering stability. Obtained.

[Other Embodiments]
Although the present invention has been described with reference to the above-described embodiments, it should not be understood that the descriptions and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

Note that the entire content of Japanese Patent Application No. 2011-118161 (filed on May 26, 2011) is incorporated herein by reference.

According to the present invention, it is possible to provide a tire that can reduce noise while suppressing a decrease in steering stability.

Claims

A tire comprising a pair of bead cores, a carcass layer having a toroidal shape straddling the pair of bead cores, and a tread portion having a road surface contact surface,
The tread portion has a central portion that constitutes a predetermined range including a tire equator line in the tire width direction, and an outer portion that is adjacent to the outside of the central portion in the tire width direction,
The distance from the tire equator line to the end of the road surface contact surface in the tire width direction is a width W,
The distance from the tire equator line to the end of the central portion in the tire width direction is a width WT,
The ratio WT / W between the width WT and the width W is 0.15 or more and 0.6 or less,
The central portion does not have a foam rubber layer on the surface of the central portion,
The outer portion has a foam rubber layer on the surface of the outer portion;
The tire characterized in that the gauge thickness of the foamed rubber layer in the tire radial direction is less than 20% of the gauge thickness of the outer portion in the tire radial direction.
2. The tire according to claim 1, wherein a gauge thickness of the foamed rubber layer in the tire radial direction is 5% or more and less than 20% of a gauge thickness of the outer portion in the tire radial direction.
The road surface ground surface is provided with a groove in contact with the foam rubber layer,
The tire according to claim 1 or 2, wherein the maximum value of the gauge thickness of the foamed rubber layer is less than 33% of the maximum value of the depth of the groove in the tire radial direction.