JP4977987B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire in which bead unseating resistance is improved without impairing weight reduction and rim assembly.

  When the vehicle is cornering, a large lateral force acts on the tire. In order to ensure safe driving, an important requirement for tire performance is to provide the tire with a resistance that prevents the bead from coming off the wheel rim even when such a large lateral force acts on the tire. It has become. Therefore, in the JIS standard, a bead unseating minimum resistance value is set for each tire cross-sectional width as a safety index indicating a resistance force when the bead portion is detached from the rim due to a lateral force applied to the tire (JIS D4230). .

  In particular, in pneumatic tires with a low flatness ratio, the bead part is easily removed from the rim due to lateral force, so the bead unseating minimum resistance value is set high, and in order to clear this set value, the side wall Measures have been taken, such as arranging a reinforcing layer at the part to increase the side rigidity, or increasing the number of wire turns of the bead core to increase the bead rigidity (for example, see Patent Documents 1 and 2).

However, since the former measure is accompanied by an increase in the weight of the tire, it goes against the demand for energy saving. In the latter measure, in addition to the increase in the weight of the tire, the rim when the tire is incorporated into the rim. Assemblability deteriorated, and none of them were satisfactory measures.
Japanese Patent Laid-Open No. 2001-233023 JP-A-11-198617

  An object of the present invention is to solve such a conventional problem, and to provide a pneumatic tire in which bead unseating resistance is improved without impairing weight reduction and rim assembly. is there.

The pneumatic tire of the present invention includes a pair of left and right bead portions, sidewall portions extending radially outward from the bead portions, and a cylindrical tread portion that connects the radially outer sides of the sidewall portions. In the pneumatic tire in which a plurality of belt layers are arranged inside the tread portion, the tread portion is made of rubber having a JIS-A hardness of 46 to 70, and the sidewall portion has a JIS-A hardness of 50. together constitute at 65 of rubber, the rather large hardness than the tread portion and sidewall portions, and a reinforcing rubber layer JIS-a hardness of 65 to 95, wherein the ends of said plurality of belt layers towards the sidewall portion is disposed so as to protrude outward from the terminal of the tread portion, 70 to 130 the maximum thickness of the reinforcing rubber layer of the total thickness of the belt layer% It is characterized in that the.

According to the present invention, the tread portion is made of rubber having a JIS-A hardness of 46 to 70, and the sidewall portion is made of rubber having a JIS-A hardness of 50 to 65. hardness much larger than the parts, and JIS-a hardness of the reinforcing rubber layer is 65 to 95, which protrudes outside the terminal of the tread portion toward the ends of a plurality of belt layers on the side wall portion This reinforcing rubber layer improves the bending rigidity between the tread part and the side wall part, and plays a role like a stick between the belt layer and exerts compression resistance. The acting lateral force can be efficiently borne and the bead unseating resistance in the bead portion can be improved.

Moreover, since the maximum thickness of the reinforcing rubber layer is set to 70 to 130% of the total thickness of the belt layer, the bead unseating resistance can be improved more reliably. Further , since no special reinforcing layer is added to the sidewall portion and no special reinforcing means is provided to the bead core, the weight of the tire and the rim assemblability are not impaired.

Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a half sectional view showing an example of a pneumatic tire according to an embodiment of the present invention, and FIG. 2 is a partial sectional view showing an enlarged main part of the tire of FIG.

  In FIG. 1, a pneumatic tire 1 includes a pair of left and right bead portions 2, 2, sidewall portions 3, 3 extending radially outward from the bead portions 2, 2, and radial directions of the sidewall portions 3, 3. And a cylindrical tread portion 4 that connects the outer sides. The pneumatic tire 1 according to the present embodiment is arranged so that both end portions of the tread rubber 4g constituting the tread portion 4 are wrapped in the radially outer end portions of the side tread rubber 3g constituting the sidewall portion 3. .

A carcass layer 6 is mounted between the pair of left and right bead portions 2, 2, and bead fillers 8 around the bead cores 7, 7 where both end portions 6 a, 6 a of the carcass layer 6 are embedded in the bead portions 2, 2, respectively. 8 is wrapped from the tire inner side toward the outer side, and a plurality of belt layers 9 are arranged on the outer peripheral side of the carcass layer 6 of the tread portion 4. In the figure, reference numeral 5 denotes an inner liner layer.

On the outer peripheral side of the carcass layer 6 in the tread portion 4, as shown in FIGS. 1 and 2, a reinforcing rubber layer 10 made of rubber 10 g having a hardness higher than that of the tread rubber 4 g and the side tread rubber 3 g is provided on the belt layer 9. It arrange | positions so that it may protrude outside the terminal 4a of the tread rubber 4g toward the side wall part 3 side from an edge part. 1 and 2 show a case where the rubber 10g constituting the reinforcing rubber layer 10 is made of a single rubber harder than the side tread rubber 3g.

As a result, the reinforcing rubber layer 10 improves the bending rigidity between the tread portion 4 and the sidewall portion 3 and also acts as a stick with the belt layer 9 to exert compression resistance. The acting lateral force can be efficiently borne and the bead unseating resistance in the bead portion can be improved. In addition, since no special reinforcing layer is added to the side wall portion 3 and no special reinforcing means is provided to the bead core 7, the weight of the tire and the rim assemblability are not impaired.

In the present invention, the ratio at which the tip 10a of the reinforcing rubber layer 10 protrudes from the end 4a of the tread rubber 4g is not particularly limited, but the reinforcing rubber layer is not affected so as to affect various performances of the tire. It is preferable to keep the tip 10a of 10 at least at a position radially outside the tire maximum width position (not shown).

In the pneumatic tire of the present invention, J IS-A hardness using rubber 46-70 Doo Reddogomu 4g, J IS-A hardness of the side tread rubber 3g uses the rubber 50-65 Yes.

As the rubber 10g constituting the reinforcing rubber layer 10 in the present invention, rubber having a hardness higher than that of the tread rubber 4g and the side tread rubber 3g is used, and the JIS-A hardness of the rubber is 65 to 95, preferably 70 to 90. Is set . Thereby, the lateral force acting on the tire can be efficiently received by the pushing back action of the belt layer 9, and the bead unseating resistance in the bead portion 2 can be further improved.

The reinforcing rubber layer 10 is composed of a single rubber 10g as shown in FIGS. 1 and 2, and as exemplified in FIG. 3, a rubber having a higher hardness than the core rubber 10j on both sides of the core rubber 10j. It can be comprised with the laminated body which laminated | stacked 10g. As a result, the rubbers 10g and 10g disposed on both outer sides exhibit a greater resistance to the bending direction, so that the bending rigidity between the tread portion 4 and the sidewall portion 3 is further improved, and the bead portion 2 The bead unseating resistance can be further improved. Even in this case, the JIS-A hardness of the rubber 10g disposed on both outer sides may be set to 65 to 95, preferably 70 to 90.

In the present invention, the reinforcing rubber layer 10 is preferably formed in a substantially triangular shape having a cross-sectional shape having a maximum thickness on the end side of the plurality of belt layers 9 and gradually tapering toward the side wall 3 side. In the present invention, the maximum thickness h of the above-described reinforcing rubber layer 10 is set to 70 to 130%, preferably 80 to 120% of the total thickness H of the belt layer 9 . If the maximum thickness h of the reinforced rubber layer 10 is less than 70% of the total thickness H of the belt layer 9, the effect of improving the bead unseating resistance may not be sufficiently obtained. In some cases, the thickness difference is too large, resulting in a manufacturing failure.

FIG. 4 is a partial cross-sectional view corresponding to FIG. 2 according to another embodiment of the present invention. In the pneumatic tire according to this embodiment, a tread rubber 4g constituting the tread portion 4 forms a side tread. Since the rubber 3g is disposed on the outer peripheral side, the reinforcing rubber layer 10 is disposed between the tread rubber 4g and the side tread rubber 3g. In the case of this embodiment, since the tip 10a side of the reinforcing rubber layer 10 is exposed to the outside, it is preferable to use a material having excellent weather resistance for the rubber 10g constituting the reinforcing rubber layer 10. .

As described above, in the pneumatic tire of the present invention, the reinforcing rubber layer having a hardness higher than that of the tread portion and the sidewall portion is disposed outside the end of the tread portion from the end portion of the belt layer toward the sidewall portion side. By arranging so as to protrude, the bead unseating resistance is improved without impairing the weight reduction and rim assembly of the tire, and it is particularly preferable for a pneumatic tire having a large cross-sectional width and a low flatness. Applied.

With the tire size and 195 / 65R15, a tire structure except for the presence of the reinforcing rubber layer as a condition that in FIG. 1, not arranged reinforcing rubber layer and the conventional tire (conventional example), the winding of the bead wire in the conventional tire Comparative tires (comparative examples) with the number increased by 5% and tires of the present invention (Examples 1 and 2) in which the JIS-A hardness of the reinforcing rubber layer was changed as shown in Table 1 were produced. In addition, the total thickness H of the belt layer in the tire of the present invention was 2 mm, the thickness of the reinforcing rubber layer at the portion in contact with the end of the belt layer was maximized, and the maximum thickness h was 2 mm.

With respect to these four types of tires, the fitting pressure of the bead portion and the bead unseating resistance value were measured by the following methods, respectively, and the results are also shown in Table 1.
[Measurement of bead fitting pressure]
The circumference of the bead portion of each tire is wiped with soapy water, and the fitting pressure (kPa) when fitted to a standard rim (15 × 6JJ) is measured. displayed. The smaller the value, the higher the fitting pressure and the worse the rim assembly.
[Measurement of bead unseating resistance value]
Each tire was filled with a test air pressure of 180 kPa, and the bead unseating resistance value (N) was measured in accordance with JIS D4230. A larger value indicates better bead unseatability.

  From Table 1, it can be seen that the tire of the present invention improves the bead unseatability without impairing the rim assembling property as compared with the conventional tire and the comparative tire.

1 is a half sectional view showing an example of a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a partial cross-sectional view showing an enlarged main part of the tire of FIG. 1. It is sectional drawing which illustrates the structure of the reinforcement rubber layer by embodiment of this invention. FIG. 3 is a cross-sectional view corresponding to FIG. 2 according to another embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Bead part 3 Side wall part 3g Side tread rubber 4 Tread part 4g Tread rubber 5 Inner liner layer 6 Carcass layer 7 Bead core 8 Bead filler 9 Belt layer 10 Reinforcement rubber layer H Total thickness of belt layer h Reinforcement rubber Maximum layer thickness

Claims (3)

A pair of left and right bead portions, sidewall portions extending radially outward from each of the bead portions, and a cylindrical tread portion connecting the radially outer sides of the sidewall portions are provided, and a plurality of inner sides of the tread portions are provided. In a pneumatic tire with a belt layer of
The tread portion is made of rubber having a JIS-A hardness of 46 to 70, the sidewall portion is made of rubber having a JIS-A hardness of 50 to 65, and is harder than the tread portion and the sidewall portion. so that the rather large, and the JIS-a hardness of projecting the reinforcing rubber layer is 65 to 95, outside the terminal of the tread portion toward the end portions of the plurality of belt layers on the side wall portion A pneumatic tire in which the maximum thickness of the reinforcing rubber layer is 70 to 130% of the total thickness of the belt layer . The pneumatic tire according to claim 1, wherein the reinforcing rubber layer is formed of a laminate in which rubber having a hardness higher than that of the core rubber is laminated on both surfaces of the core rubber. The cross-sectional shape of the reinforcing rubber layer is formed in a substantially triangular shape having a maximum thickness on the end side of the plurality of belt layers and gradually tapering toward the side wall portion side. Pneumatic tire.

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