JP2012140068A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire 2 with improved grip force without impairing stability in turning.SOLUTION: The tread 4 of the tire 2 includes a crown region C positioned on the equator, and a pair of shoulder regions S positioned axially outside of the crown region C. Each of the shoulder regions S is provided with a body 28 and a reinforcing layer 30. The loss compliance of the reinforcing layer 30 at 100°C is higher than the loss compliance of the body 28 at 100°C. The reinforcing layer 30 is constituted of: a main portion 38 forming a part of a tread surface 18 while extending substantially inward in an axial direction from the end 36 of the tread 4; and an auxiliary portion 40 obliquely extending substantially inward in the axial direction with respect to the tread surface 18 further from the main portion 38. The auxiliary portion 40 is buried in the body 28.

Description

  The present invention relates to a pneumatic tire.

  The tread of the tire is made of a crosslinked rubber. The tread has a shape protruding outward in the radial direction. The tread has a tread surface. This tread surface is in contact with the road surface.

  A two-wheeled vehicle turns with its body tilted. The tread of a motorcycle tire has a small radius of curvature from the viewpoint of easy turning. In this tire, the equatorial plane portion (crown region) of the tread is grounded when traveling straight ahead. During cornering, a region outside the crown region in the axial direction is grounded.

  In races, riders often tilt their motorcycles to the limit and turn sharply. This state is called “full bank”. During this sudden turning, the end portion (shoulder region) of the tread is grounded.

  Various studies have been made on treads from the viewpoint of improving tire performance. An example of this study is disclosed in Japanese Patent Application Laid-Open No. 2010-111171.

JP 2010-111171 A

  From the viewpoint of turning performance, the axially outer region of the crown region of the tread may be composed of a highly hard crosslinked rubber. This tire has a problem that the grip force is insufficient when turning sharply.

  A tire tread may be divided in the axial direction and constituted of a plurality of regions. From the viewpoint of improving grip force during turning, the shoulder region of the tread may be composed of a crosslinked rubber having a large loss compliance. With this tire, the grip strength is certainly improved. However, this tire has a problem of insufficient stability.

  An object of the present invention is to provide a pneumatic tire with improved grip force without impairing stability during turning.

  The pneumatic tire according to the present invention includes a tread whose outer surface forms a tread surface. The tread includes a crown region located on the equator and a pair of shoulder regions located on the outer side in the axial direction of the crown region. Each shoulder region includes a main body and a reinforcing layer. The loss compliance at 100 ° C. of the reinforcing layer is larger than the loss compliance at 100 ° C. of the main body. The reinforcing layer extends from the end of the tread substantially inward in the axial direction, forms a part of the tread surface, and further inclines from the main part inward in the axial direction with respect to the tread surface. And a sub part extending. The sub part is embedded in the main body.

  Preferably, in this pneumatic tire, the ratio of the loss compliance at 100 ° C. of the reinforcing layer to the loss compliance at 100 ° C. of the main body is 1.1 or more and 2 or less.

  Preferably, in this pneumatic tire, the thickness of the reinforcing layer is 1 mm or more and 3 mm or less.

  Preferably, in the pneumatic tire, a circumferential length from an end of the tread to a position on the tread surface corresponding to a boundary position between the main part and the sub part is 10 mm or more and 40 mm or less.

  Preferably, in the pneumatic tire, a position on the tread surface corresponding to an end located on the inner side in the axial direction of the sub portion from a position on the tread surface corresponding to a boundary position between the main portion and the sub portion. The circumference is up to 10 mm to 40 mm.

  Preferably, in this pneumatic tire, the angle formed by the sub-portion with respect to the tread surface is not less than 15 ° and not more than 45 °.

  In the pneumatic tire according to the present invention, the grip force can be improved without impairing the stability during turning.

FIG. 1 is a cross-sectional view showing a part of a pneumatic tire according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view showing a part of the tire of FIG.

  Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings.

  The tire 2 shown in FIG. 1 includes a tread 4, a sidewall 6, a bead 8, a carcass 10, a band 12, an inner liner 14 and a chafer 16. The tire 2 is a tubeless type. The tire 2 is attached to the rear wheel of a two-wheeled vehicle. In FIG. 1, the vertical direction is the radial direction, the horizontal direction is the axial direction, and the direction perpendicular to the paper surface is the circumferential direction. The tire 2 has a substantially left-right symmetric shape centered on a one-dot chain line CL in FIG. This alternate long and short dash line CL represents the equator plane of the tire 2.

  The tread 4 is made of a crosslinked rubber. The tread 4 has a shape protruding outward in the radial direction. The tread 4 includes a tread surface 18. The tread surface 18 is in contact with the road surface.

  The sidewall 6 extends substantially inward in the radial direction from the tread 4. The sidewall 6 is made of a crosslinked rubber. The sidewall 6 absorbs an impact from the road surface by bending. Furthermore, the sidewall 6 prevents the carcass 10 from being damaged.

  The bead 8 is located substantially inward of the sidewall 6 in the radial direction. The bead 8 includes a core 20 and an apex 22 that extends radially outward from the core 20. The core 20 has a ring shape. The core 20 is formed by winding a non-stretchable wire. Typically, a steel wire is used for the core 20. The apex 22 is tapered outward in the radial direction. The apex 22 is made of a highly hard crosslinked rubber.

  The carcass 10 includes a carcass ply 24. The carcass ply 24 is bridged between the beads 8 on both sides, and extends along the inside of the tread 4 and the sidewall 6. The carcass ply 24 is folded around the core 20 from the inner side to the outer side in the axial direction.

  Although not shown, the carcass ply 24 includes a large number of cords arranged in parallel and a topping rubber. The absolute value of the angle formed by each cord with respect to the equator plane is usually 70 ° to 90 °. In other words, the carcass 10 has a radial structure. The cord is usually made of organic fibers. Examples of preferable organic fibers include polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers. A carcass having a bias structure may be employed.

  The band 12 is located on the inner side in the radial direction of the tread 4. The band 12 is laminated on the outside of the carcass 10. Although not shown, the band 12 is composed of a cord and a topping rubber. The cord extends substantially in the circumferential direction and is wound spirally. The band 12 has a so-called jointless structure. The band 12 can contribute to the rigidity of the tire 2 in the radial direction. In the tire 2, the influence of the centrifugal force that acts during traveling is suppressed. The cord is usually made of organic fibers. Examples of preferable organic fibers include nylon fibers, polyester fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers.

  In the tire 2, the tread 4 includes a base 26, a main body 28, and a pair of reinforcing layers 30. The base 26 is made of a crosslinked rubber. The main body 28 is laminated on the outer side of the base 26 in the radial direction. The main body 28 is made of a crosslinked rubber.

  In the tire 2, the hardness of the base 26 is preferably 30 or more, and preferably 50 or less, from the viewpoint of straight running stability. From the viewpoint of turning performance, the hardness of the main body 28 is preferably 30 or more, and preferably 45 or less.

  In this specification, the hardness is JIS-A hardness. This hardness is measured by a type A durometer in an environment of 100 ° C. in accordance with the provisions of “JIS-K6253”.

  In the tire 2, each reinforcing layer 30 is made of a crosslinked rubber. The reinforcing layer 30 extends from the end 36 of the tread 4 substantially inward in the axial direction. As shown in the drawing, the tread surface 18 of the tire 2 includes a main body 28 and a reinforcing layer 30.

  In the tire 2, the equatorial plane portion C of the tread 4 is mainly grounded when traveling straight ahead. This portion C is referred to as a crown region. During cornering, the portion S on the outer side in the axial direction than the crown region C is mainly grounded. This portion S is referred to as a shoulder region. In other words, the tread 4 of the tire 2 includes a crown region C positioned on the equator and a pair of shoulder regions S positioned on the outer side in the axial direction of the crown region C.

  In the tire 2, the crown region C of the tread 4 includes a base 26 and a main body 28. The shoulder region S is composed of a base 26, a main body 28 and a reinforcing layer 30.

  FIG. 2 shows a portion of the end 36 of the tread 4 of the tire 2. The shoulder region S of the tire 2 includes a main body 28 and a reinforcing layer 30. As shown in the drawing, a part of the reinforcing layer 30 is laminated on the main body 28. Another part of the reinforcing layer 30 is embedded in the main body 28. In this specification, a part of the reinforcing layer 30 laminated on the main body 28 is referred to as a main part 38, and the other part embedded in the main body 28 is referred to as a sub part 40. In the tire 2, the reinforcing layer 30 includes a main part 38 and a sub part 40.

  In the tire 2, the main portion 38 extends substantially inward in the axial direction from the end 36 of the tread 4. The main portion 38 forms a part of the tread surface 18.

  In the tire 2, the sub part 40 further extends inward in the axial direction from the main part 38. The sub part 40 is embedded in the main body 28. The sub portion 40 extends from the main portion 38 with an inclination with respect to the tread surface 18.

  As described above, in the tire 2, the main body 28 and the reinforcing layer 30 are made of a crosslinked rubber. In the tire 2, the loss compliance LCr of the reinforcing layer 30 at 100 ° C. is larger than the loss compliance LCt of the main body 28 at 100 ° C. The main portion 38 of the reinforcing layer 30 is exposed at the end 36 of the tread 4. The reinforcing layer 30 can contribute to an improvement in grip force during turning.

The loss compliance LC is represented by the ratio [E ″ / (E *) ² ] of the loss elastic modulus E ″ to the square of the complex elastic modulus E *. In the present invention, the loss compliance LCr of the reinforcing layer 30 was calculated using a viscoelastic spectrometer (manufactured by Iwamoto Seisakusho Co., Ltd.) under the following measurement conditions in accordance with the provisions of “JIS K 6394”. The complex elastic modulus Er * and the loss elastic modulus Er ″ at 100 ° C. of the reinforcing layer 30 are used.

Initial strain: 10%
Amplitude: ± 2.5%
Frequency: 10Hz
Deformation mode: Tensile
Measurement temperature: 100 ° C

  For the measurement of the complex elastic modulus Er * and the loss elastic modulus Er ″, a test piece formed of a rubber composition forming the reinforcing layer 30 is used. This test piece is plate-shaped and its length is 45 mm. , The width is 4 mm, and the thickness is 2 mm, both ends of the test piece are chucked and measurement is performed, and the length of the displacement portion of the test piece is 30 mm. LCt is also calculated in the same manner as that of the reinforcing layer 30. The cap 28 of the tread 4 is used to measure the complex elastic modulus Et * and the loss elastic modulus Et ″ at 100 ° C. of the main body 28 used for the calculation. A test piece formed from a rubber composition is used.

  In the tire 2, the main portion 38 of the reinforcing layer 30 is laminated on the main body 28. The loss compliance LCt of the main body 28 is larger than the loss compliance LCr of the reinforcing layer 30. The main body 28 can support the main portion 38 from the inside during turning. The main body 28 can suppress a decrease in stability during turning. In the tire 2, an improvement in grip force is achieved without impairing stability during turning. Since the reinforcing layer 30 is provided at the end 36 of the tread 4, the tire 2 can travel stably while maintaining a sufficient grip force even during a sudden turn.

  In the tire 2, the ratio of the loss compliance LCr of the reinforcing layer 30 at 100 ° C. to the loss compliance LCt of the main body 28 at 100 ° C. is 1 from the viewpoint that an improvement in grip force can be achieved without impairing stability at the time of turning. .1 or more is preferable, and 2 or less is preferable.

In the tire 2, from the viewpoint of the reinforcing layer 30 can effectively contribute to the improvement of the gripping force, loss compliance LCr at 100 ° C. of the reinforcing layer 30 is preferably at least 0.18 MPa ^-1, 0.3 MPa ^-1 or less Is preferred. From the viewpoint of the body 28 can effectively contribute to stability, loss compliance LCt at 100 ° C. of the body 28 is preferably at least 0.12 MPa ^-1, preferably 0.2 MPa ^-1 or less.

  In FIG. 2, what is indicated by a double arrow t is the thickness of the reinforcing layer 30. The thickness t is preferably 1 mm or more from the viewpoint that the reinforcing layer 30 can effectively contribute to exerting the gripping force. From the viewpoint of suppressing the influence on the stability of the reinforcing layer 30, the thickness t is preferably 3 mm or less.

  As described above, the sub-portion 40 of the reinforcing layer 30 is embedded in the main body 28, and extends in an inclined manner with respect to the tread surface 18. The sub portion 40 is disposed so that the distance between the tread surface 18 and the sub portion 40 gradually decreases outward in the axial direction. In the tire 2, the characteristics of the tread 4 do not change abruptly at the time of transition from straight running to turning. Since the distance between the tread surface 18 and the sub-portion 40 gradually increases inward in the axial direction, the characteristics of the tread 4 do not change abruptly even during the transition from turning to straight running. According to the tire 2, the rider can drive the two-wheeled vehicle without feeling uncomfortable.

  In FIG. 2, what is indicated by a symbol PB is a position on the tread surface 18 corresponding to a boundary position between the main portion 38 and the sub portion 40. What is indicated by the solid line LT is the tangent line of the tread surface 18 at this position PB. The angle α is an angle formed by the reference surface 42 on the tread surface 18 side of the sub part 40 of the reinforcing layer 30 with respect to the tangent LT. In the present invention, this angle α is the inclination angle of the sub-portion 40.

  In the tire 2, the inclination angle α of the sub-portion 40 is preferably 15 ° or more and more preferably 45 ° or less from the viewpoint that a sudden change in the characteristics of the tread 4 can be prevented.

  In FIG. 1, what is indicated by a double-pointed arrow La is a tread surface from the end 36 of the tread 4 to the position PB on the tread surface 18 corresponding to the boundary position between the main portion 38 and the sub-portion 40 described above. This represents a length of 18 (hereinafter referred to as a circumferential length). What is indicated by the reference character PC is a position on the tread surface 18 corresponding to the end 44 positioned on the inner side in the axial direction of the sub-portion 40. What is indicated by a double-headed arrow Lb is the circumference from the position PB to the position PC.

  In the tire 2, the peripheral length La is preferably 10 mm or more, and preferably 40 mm or less, from the viewpoint that the main portion 38 can effectively contribute to the exertion of the gripping force. From the viewpoint that a sudden change in the characteristics of the tread 4 can be prevented, the circumferential length Lb is preferably 10 mm or more, and more preferably 40 mm or less.

  In the present invention, the size and angle of each member of the tire 2 are measured in a state where the tire 2 is incorporated in a regular rim and the tire 2 is filled with air so as to have a regular internal pressure. At the time of measurement, no load is applied to the tire 2. In the present specification, the normal rim means a rim defined in a standard on which the tire 2 depends. “Standard rim” in the JATMA standard, “Design Rim” in the TRA standard, and “Measuring Rim” in the ETRTO standard are regular rims. In the present specification, the normal internal pressure means an internal pressure defined in a standard on which the tire 2 relies. “Maximum air pressure” in JATMA standard, “Maximum value” published in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in TRA standard, and “INFLATION PRESSURE” in ETRTO standard are normal internal pressures.

  Hereinafter, the effects of the present invention will be clarified by examples. However, the present invention should not be construed in a limited manner based on the description of the examples.

[Example 1]
A pneumatic tire of Example 1 having the basic configuration shown in FIGS. 1 and 2 and having the specifications shown in Table 1 below was obtained. The size of this tire is 210 / 60R420. This tire is for a rear wheel of a two-wheeled vehicle. The loss compliance LCr at 100 ° C. of the reinforcing layer is 0.24 MPa ⁻¹ . The loss compliance LCt at 100 ° C. of the main body in the shoulder region is 0.16 MPa ⁻¹ . Therefore, the ratio (LCr / LCt) is 1.5. The thickness t of this reinforcing layer is 2.0 mm. The circumferential length La is 30 mm. The circumferential length Lb is 30 mm. The inclination angle α of the sub part of the reinforcing layer is 30 °.

[Example 2-5 and Comparative Example 2]
Tires were obtained in the same manner as in Example 1 except that the loss compliance LCr of the reinforcing layer was changed and the ratio (LCr / LCt) was changed as shown in Table 1 below.

[Example 6-9]
A tire was obtained in the same manner as in Example 1 except that the thickness t of the reinforcing layer was as shown in Table 2 below.

[Example 10-13]
A tire was obtained in the same manner as in Example 1 except that the inclination angle α of the sub part was as shown in Table 2 below.

[Example 14-21]
A tire was obtained in the same manner as in Example 1 except that the circumferential length La and the circumferential length Lb were as shown in Table 3 below.

[Comparative Example 1]
Comparative Example 1 is a conventional tire. This tire is not provided with a reinforcing layer. The tread loss compliance LCt of this tire is 0.16 MPa ⁻¹ .

[Grip strength and stability]
The prototype tire was mounted on the rear wheel of a sports-type two-wheeled vehicle (4-cycle) with a displacement of 1000 cc and filled with air so that the internal pressure was 200 kPa. A commercially available tire (size: 125 / 80R420) was attached to the front wheel and filled with air so that the internal pressure was 200 kPa. This motorcycle was run on a circuit course with asphalt on the road surface, and sensory evaluation was performed by the rider. Evaluation items are grip strength and stability. The results are shown in Table 1, Table 2 and Table 3 below as indices. Larger numbers are preferable.

  As shown in Table 1, Table 2, and Table 3, the tires of the examples have higher evaluation than the tires of the comparative examples. From this evaluation result, the superiority of the present invention is clear.

  The pneumatic tire described above can be applied to various vehicles.

DESCRIPTION OF SYMBOLS 2 ... Tire 4 ... Tread 18 ... Tread surface 26 ... Base 28 ... Main body 30 ... Reinforcement layer 38 ... Main part 40 ... Sub part

Claims (6)

It has a tread whose outer surface forms a tread surface,
The tread is composed of a crown region located on the equator and a pair of shoulder regions located on the outer side in the axial direction of the crown region,
Each shoulder region has a main body and a reinforcing layer,
The loss compliance at 100 ° C. of the reinforcing layer is larger than the loss compliance at 100 ° C. of the main body,
The reinforcing layer extends from the end of the tread substantially inward in the axial direction and forms a part of the tread surface, and further inclines from the main part inward in the axial direction with respect to the tread surface. And consists of sub-parts that extend,
A pneumatic retire in which the sub-portion is embedded in the main body.   The pneumatic tire according to claim 1, wherein a ratio of loss compliance at 100 ° C of the reinforcing layer to loss compliance at 100 ° C of the main body is 1.1 or more and 2 or less.   The pneumatic tire according to claim 1 or 2, wherein a thickness of the reinforcing layer is 1 mm or more and 3 mm or less.   The pneumatic according to any one of claims 1 to 3, wherein a circumferential length from an end of the tread to a position on the tread surface corresponding to a boundary position between the main part and the sub part is 10 mm or more and 40 mm or less. tire.   The circumferential length from the position on the tread surface corresponding to the boundary position between the main part and the sub part to the position on the tread surface corresponding to the end located on the inner side in the axial direction of the sub part is 10 mm or more and 40 mm. The pneumatic tire according to any one of claims 1 to 4, wherein:   The pneumatic tire according to any one of claims 1 to 5, wherein an angle formed by the sub part with respect to the tread surface is 15 ° or more and 45 ° or less.

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