JP5325656B2 - Run flat tire - Google Patents

Description

  The present invention relates to a run-flat radial tire in which a reinforcing rubber layer having a substantially crescent-shaped cross section is disposed on the inner peripheral side of the radial carcass at least in a portion corresponding to the sidewall portion, in particular, durability performance during run-flat running, The present invention relates to a vehicle that can achieve both a comfortable ride during normal pressure traveling.

  Conventionally, as shown in a cross-sectional view in FIG. 1, each side portion around a tread rubber 91 disposed on a tread portion 11 and constituting a ground contact surface, and a pair of bead cores 2 disposed on each bead portion 12. A radial carcass 3 made of one or more carcass plies wound back outward in the radial direction, a belt 4 made of one or more belt plies disposed between the radial carcass 3 and the tread rubber 1, and at least a sidewall A run-flat radial tire 90 having a substantially crescent-shaped reinforcing rubber layer 5 disposed on the inner side in the tire width direction of the radial carcass 3 at a portion corresponding to the portion 13 is known (see, for example, Patent Document 1). ).

  Such a run-flat radial tire 90 has the reinforcing rubber layer 5 disposed on the sidewall portion 13 in a state where the air pressure in the tire is reduced or even zero, that is, a so-called run-flat state. By maintaining this shape, the vehicle can travel with sufficient durability.

Japanese Patent No. 4104825

  Since the reinforced rubber layer 5 needs to have the above-described functions, it is possible to use a highly rigid rubber material, increase the thickness of the layer, or add a fiber reinforced layer. As a result, there is a problem that the spring constant during normal internal pressure running increases and the ride comfort deteriorates.

  The present invention has been made in view of such problems, and has a substantially crescent-shaped reinforcing rubber that can achieve both durability performance during run-flat traveling and riding comfort during normal internal pressure traveling. An object of the present invention is to provide a run-flat radial tire provided with a layer.

<1> includes a tread portion, a pair of sidewall portions extending radially inward from both side portions of the tread portion, and a bead portion continuous on the inner peripheral side of each sidewall portion, and is disposed in the tread portion. A tread rubber constituting a ground contact surface, a radial carcass composed of one or more carcass plies each having a side portion rolled back radially outward around a pair of bead cores disposed on each bead portion, and a radial carcass A belt composed of one or more belt plies disposed between the tread rubber and a reinforcing rubber layer having a substantially crescent-shaped cross section disposed at the inner side in the tire width direction of the radial carcass at least at a portion corresponding to the sidewall portion. In run flat tires with
In the tire width direction inside from the end face of the belt, the tread de portion of the tire width direction outside of the region from the ground end in the 75% load conditions, to form the rigidity reduction portion for reducing the stiffness of the tire,
The rigidity reducing portion is constituted by a circumferential groove that opens on the tread rubber surface,
The circumferential groove is a run-flat radial tire characterized in that the circumferential groove is discontinuously configured so as not to intersect with other grooves opened on the tread rubber surface .

<2> includes a tread portion, a pair of sidewall portions extending radially inward from both side portions of the tread portion, and a bead portion continuous on the inner peripheral side of each sidewall portion, and is disposed in the tread portion. A tread rubber constituting a ground contact surface, a radial carcass composed of one or more carcass plies each having a side portion rolled back radially outward around a pair of bead cores disposed on each bead portion, and a radial carcass A belt composed of one or more belt plies disposed between the tread rubber and a reinforcing rubber layer having a substantially crescent-shaped cross section disposed at the inner side in the tire width direction of the radial carcass at least at a portion corresponding to the sidewall portion. In run flat tires with
Forming a rigidity reduction portion that reduces the rigidity of the tire in the tread portion in the tire width direction inner side in the tire width direction from the end surface of the belt and in the tire width direction outer side from the ground contact end in the 75% load state,
The run-flat radial tire is characterized in that the rigidity reducing portion is configured by arranging a large number of circumferentially long hole portions opened on a tread rubber surface in the circumferential direction.

<3> In <1> or <2>, the position of the outer side in the tire width direction and the inner end in the tire width direction in the reinforcing rubber layer is positioned on the outer side in the tire width direction from the ground contact end in the 75% load state and from the belt end surface. A run-flat radial tire characterized by being arranged inside.

<4> is any one of <1> to <3>, wherein the belt includes a crossing belt layer in which two belt plies whose inclination angles with respect to the equator plane are opposite to each other are bonded together. Of the belt plies constituting the belt layer, the end face of the narrow side ply is arranged on the outer side in the tire width direction from the ground contact end in the 75% load state, and the rigidity reducing portion is the end face of the narrow side ply (hereinafter referred to as the end face) , Also referred to as “narrow side ply end”).

  The inventors divide the tire into finite elements, and the normal internal pressure state in which 75% of the predetermined load is applied with the normal internal pressure that simulates the normal internal pressure running state (the same state as the “75% load state”) and Calculate the stress related to each element for the zero internal pressure state where the internal pressure is zero and 75% of the specified load is applied, simulating run-flat running, and the normal internal pressure state generates higher stress than the zero internal pressure state I asked for the part. As a result, it was found that the region is a region in the tire width direction from the vicinity of the ground contact edge of the ground contact region to the belt end during normal internal pressure traveling.

  According to <1>, the rigidity reducing portion that reduces the rigidity in the width direction is provided on the surface of the tread rubber in a region on the inner side in the tire width direction from the end surface of the belt and on the outer side in the tire width direction from the ground contact end in the 75% load state. Since it extends in the circumferential direction, from the above findings found by the inventor, it is possible to effectively reduce the rigidity during normal internal pressure travel without significantly sacrificing the influence of durability during run flat. It can contribute to the improvement of comfort.

In addition, since the rigidity reduction parts such as circumferential grooves are arranged on the outer side in the tire width direction of the ground contact end in the 75% load state, the occurrence of uneven wear called drag wear that tends to occur at the end part in the normal contact region is prevented. be able to. Furthermore, since the rigidity reducing portion is constituted by a circumferential groove that opens on the surface of the tread rubber, it is possible to achieve a reduction in rigidity in a very effective and simple manner. Furthermore, since the circumferential grooves are discontinuously configured so as not to intersect with other grooves opened on the surface of the tread rubber, it is possible to prevent uneven wear that occurs when the grooves intersect with other grooves.

According to <2>, the rigidity reducing portion that reduces the rigidity in the width direction is provided on the surface of the tread rubber in a region on the inner side in the tire width direction from the end surface of the belt and on the outer side in the tire width direction from the ground contact end in the 75% load state. Since it extends in the circumferential direction, from the above findings found by the inventor, it is possible to effectively reduce the rigidity during normal internal pressure travel without significantly sacrificing the influence of durability during run flat. It can contribute to the improvement of comfort.
In addition, since the rigidity reduction parts such as circumferential grooves are arranged on the outer side in the tire width direction of the ground contact end in the 75% load state, the occurrence of uneven wear called drag wear that tends to occur at the end part in the normal contact region is prevented. be able to.
Furthermore, since the rigidity reducing portion is configured by arranging a plurality of circumferentially long holes opened in the circumferentially arranged tread rubber surface in the circumferential direction, this case is also very effective and The rigidity can be reduced by a simple method.

<3> According to <3>, since the position of the outer side in the tire width direction and the inner end in the tire width direction in the reinforcing rubber layer is disposed on the outer side in the tire width direction and on the inner side from the belt end surface in the 75% load state, The rigidity in the vicinity of the end can be reduced.

According to <4>, as described in detail later, since the belt plies constituting the crossing belt layer are arranged on the inner side in the tire width direction from the end surface of the narrow ply, the rigidity during normal internal pressure traveling is further increased. It can be effectively reduced.

It is sectional drawing which shows the conventional run flat tire. It is sectional drawing which shows the run flat tire of embodiment which concerns on this invention. FIG. 3 is an enlarged cross-sectional view schematically showing details in the vicinity of the belt end in FIG. 2. It is sectional drawing which shows the run flat tire of the modification of embodiment which concerns on this invention. It is a schematic diagram which illustrates the shape of the rigidity reduction part of embodiment which concerns on this invention. It is a schematic diagram which illustrates other shapes of the rigidity reduction part of embodiment which concerns on this invention. It is a graph which shows the relationship between the position of a circumferential groove | channel, and a spring constant. It is a tread pattern figure which shows the rigidity reduction part of embodiment which concerns on this invention. It is a tread pattern figure which shows the rigidity reduction part of other embodiment. It is a tread pattern figure which shows the rigidity reduction part of other embodiment. It is a tread pattern figure which shows the rigidity reduction part of other embodiment. It is a tread pattern figure which shows the rigidity reduction part of other embodiment. It is a tread pattern figure which shows the rigidity reduction part of other embodiment.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 2 is a cross-sectional view showing the run-flat tire of this embodiment, FIG. 3 is an enlarged cross-sectional view showing a portion near the belt end of the run-flat radial tire, and the run-flat radial tire 10 is One or more carcasses having a tread rubber 1 disposed on the tread portion 11 and constituting a ground contact surface, and a pair of bead cores 2 disposed on each bead portion 12 and each side portion being rolled back radially outward. The radial carcass 3 made of ply, the belt 4 made of one or more belt plies arranged between the radial carcass 3 and the tread rubber 1, and the tire of the radial carcass 3 at least at a portion corresponding to the sidewall portion 13. A reinforcing rubber layer 5 having a substantially crescent-shaped cross section is provided on the inner side in the width direction.

  Here, in the run-flat radial tire 10, as can be seen with reference to FIG. 3, the inner end 5a in the tire width direction of the reinforcing rubber layer 5 is in this case mounted on a predetermined rim and filled with a predetermined internal pressure. The belt is disposed on the inner side in the tire width direction from the ground contact end 15 in the 75% load state in which a load of 75% of the predetermined load is applied, and the outer end 4a in the tire width direction of the belt is disposed on the tire from the ground contact end 15 in the 75% load state. It is arranged outside in the width direction.

  The predetermined load is the maximum load (maximum load capacity) of the single wheel at the application size described in the predetermined industry standard, and the predetermined internal pressure is the single wheel at the application size described in the standard. The air pressure corresponding to the maximum load (maximum load capacity) of the product, and the specified rim is the standard rim (or “Approved Rim” or “Recommended Rim”) in the applicable size described in the same standard. . For such industrial standards, there are standards that are valid in each region where tires are produced or used. For example, in the United States, “The Tire and Rim Association Inc. Year Book” (including design guides) ) In Europe according to “The European Tire and Rim Technical Organization Standards Manual” and in Japan according to “JATMA YEAR BOOK” of the Japan Automobile Tire Association.

  The run-flat radial tire 10 of the present invention is based on the general structure as described above, and the tread rubber in the region in the tire width direction inside the belt end 4a and in the tire width direction outside from the ground contact end 15 in the 75% load state. A rigidity reducing portion 20 for reducing the rigidity in the width direction is extended on the surface in the circumferential direction. Here, the position in the tire width direction of the rigidity reducing portion 20 refers to the position of the inner end 20a in the tire width direction. That is, in FIG. 3, the inner end 20a in the tire width direction is located on the outer side in the tire width direction by the dimension a from the ground contact end 15 in the 75% load state, and is located on the inner side in the tire width direction by the dimension c from the belt end 4a. Yes.

  FIG. 4 shows a modified example of the present embodiment in a cross-sectional view corresponding to FIG. 2, and the tire width direction inner end 5a of the reinforcing rubber layer 5 is connected to the tire width of the ground contact end 15 in a 75% load state. By disposing the outer side in the direction, the rigidity in the vicinity of the ground contact end can be further reduced.

  Here, as a form of the rigidity reduction part 20, what was illustrated to FIG.5 (a)-(c), FIG.6 (a), (b) can be mentioned. That is, the rigidity reducing portion 20 may be a circumferential groove 21 that is continuous in the circumferential direction as shown in FIG. 5A, or may not be crossed with other grooves 29 as shown in FIG. The circumferential grooves 22 divided by the grooves 29, or, as shown in FIG. 5 (c), the circumferentially long holes 23 are arranged in the circumferential direction, or the grooves and holes Instead, as shown in FIG. 6 (a), it is possible to form a low-rigid rubber circumferential band 24 made of, for example, a low-rigid rubber extending in the circumferential direction. Multiple rows can be arranged, and FIG. 6B shows an example in which the circumferential grooves 21 are arranged in two rows.

  Moreover, it can replace with a circumferential groove | channel and it can also be set as an inclination groove | channel, The example was shown to FIGS. 11-12 showing the pattern of the tread piece side of a tire. In these drawings, reference numerals 26 to 28 denote inclined grooves.

The inventors came up with the above-described configuration because, as described above, the inventors divided the tire into finite elements and applied the stress of each element during normal internal pressure running. As a result of comparing the normal internal pressure state where 75% of the predetermined load was applied with the normal internal pressure simulating the normal internal pressure state and the zero internal pressure state where the internal pressure simulating run flat running was zero and the 75% load of the predetermined load was applied, Based on this knowledge, the normal internal pressure state generates higher stress than the zero internal pressure state in the tire width direction region from the vicinity of the ground contact edge of the ground contact region to the belt end during normal internal pressure running. in this region, the that nearest given less split against the load bearing of zero internal pressure conditions, since the contribution is too large for the load support of normal running, by reducing the stiffness of the regions, at zero pressure conditions Shadow to durability With minimizing, for he would be able to reduce the spring constant in the normal inner pressure state.

  FIG. 7 shows that a circumferential groove having a width of 2 mm and a depth of 4 mm is formed continuously in a region including the region, and the spring constant obtained by the finite element method is determined according to the position of the circumferential groove in the tire width direction. It is the graph which showed how it changed. The horizontal axis represents the position in the tire width direction with reference to the ground contact edge 15 ("ground contact edge") at 75% load, and 2 mm is a scale. The vertical axis represents the inner edge in the tire width direction at each tire width direction position. The index when it is set as the spring constant 100 of the whole tire with respect to the case where the circumferential groove | channel 21 is not provided when the circumferential groove | channel 21 is arrange | positioned so that may be located is represented.

  In the above calculation, a tire constant of size 245 / 45R19 is used, and the spring constant is obtained by calculating the deflection when the tire is mounted on a predetermined rim, filled with a predetermined internal pressure, and a load load of 75% of the predetermined load is applied. It was. The predetermined internal pressure corresponding to this tire is 230 kPa, and the 75% load of the predetermined load is 5.145 kN.

  As apparent from FIG. 6, the reduction rate of the spring constant is high in the vicinity of the ground contact edge inside the ground contact edge 15, and as the distance from the ground contact edge 15 in the tire width direction, the reduction rate approaches zero, but the reduction effect is The belt ends up to the belt end 4a. However, if this circumferential groove 21 enters the ground contact region, drag wear or step wear associated with a rigid step may occur, so it is necessary to arrange it outside the ground contact surface.

  As described above, as can be seen from the example in which the rigidity reducing portion 20 is configured by the circumferential groove 21, the run flat tire 10 of the present invention has the rigidity reducing portion 20 on the inner side in the tire width direction from the belt end 4a. The belt 4 is disposed on the surface of the tread rubber in the region on the outer side in the tire width direction with respect to the ground contact edge 15 in the% load state. The belt 42 includes a cross belt layer 40 in which a plurality of belt plies 41 and 42 are bonded, and the end 42a of the narrow ply 42 of the belt plies 41 and 42 constituting the cross belt layer 40 is grounded in a 75% load state. In the case of being arranged on the outer side in the tire width direction from the end 15, it is preferable to arrange the inner side in the tire width direction from the narrow side ply end 42 a of the crossing belt layer 40, as shown in FIG. It is white. The belt 4 shown in this embodiment includes a belt reinforcing layer 43 arranged on the outer side in the radial direction of the crossing belt layer 40, and the belt reinforcing layer 43 is outside the outer end in the tire width direction of the crossing belt layer 40. In this case, the belt end 4 a becomes the outer end of the belt reinforcing layer 43.

  For tires of size 245 / 45R19, the position of the tire in the tire width direction, the cross-sectional shape, and the circumferential shape (continuity, length if discontinuous, pitch, etc.) are changed to change the normal internal pressure state and zero internal pressure. The spring constant was measured for each state, and the results are shown in Table 1.

Here, as described above, the normal internal pressure state refers to a state in which the tire is mounted on a predetermined rim, is filled with the predetermined internal pressure, and is loaded with 75% of the predetermined load, and the zero internal pressure state is the tire on the predetermined rim. A state in which the internal pressure is set to zero and 75% of the predetermined load is applied. Therefore, the spring constant in the normal internal pressure state is a parameter that simulates the spring constant during normal internal pressure travel, and the spring constant in the zero internal pressure state can be considered as a parameter that represents durability during run-flat travel. The spring constant was measured by applying a load passing through the central axis in a plane perpendicular to the axial direction of the tire and measuring the deflection in the load direction. Results are as Comparative Example 1 tire case without the groove as rigidity reduction portion was expressed as an index based on the 100 number the spring constant in the tire of Comparative Example 1. Write this index is small means that the spring constants is small.

  In Table 1, “tire width direction position (mm)” represents a separation distance from the ground contact edge E in a state where a 75% load is applied to the inner end of the circumferential groove in the tire width direction. Note that the narrow ply end of the crossing belt layer 40 was 6 mm away from the ground contact end E in the tire width direction outside, and the belt end was 14 mm away from the ground contact end E in the tire width direction outside.

  In Table 1, “Cross-sectional shape of circumferential groove” is “A” when the cross section is 4 mm deep and 2 mm wide, and “B” when the cross section is 2 mm deep and 4 mm wide. The “circumferential shape of the circumferential groove” is “K” in the tread pattern shown in FIG. 8 so as to be continuous in the circumferential direction, and the same tread pattern as in FIG. The circumferential groove 22 provided so as to be intermittent in the circumferential direction is “L”, and the same tread pattern as that in FIG. 8 is formed by arranging the circumferentially long holes 23 in the circumferential direction as shown in FIG. "

DESCRIPTION OF SYMBOLS 1 Tread rubber 2 Bead core 3 Radial carcass 4 Belt 4a Belt end 5 Reinforcement rubber layer 5a Reinforcement rubber layer inner end of tire width direction 10 Run flat tire 11 Tread portion 12 Bead portion 15 Ground contact end in 75% load state 16 Concave surface uneven surface 20 Rigidity reduction part 20a Tire width direction inner side end 21 of rigidity reduction part 21 Circumferential groove 22 Divided circumferential groove 23 Long hole in circumferential direction 24 Low rigidity rubber circumferential band 26, 27, 28 Inclined groove 29 Other grooves 40 intersecting belt layers 41 Berutopura Lee 42a intersecting belt layers narrow side ply end 43 the belt reinforcing layer constituting the crossing belt layer

Claims (4)

Provided with tread portion, a pair of sidewall portions extending radially inward from both sides of the tread portion, and a bead portion continuous on the inner peripheral side of each sidewall portion, and is arranged on the tread portion to constitute a grounding surface A tread rubber, a radial carcass composed of one or more carcass plies, each of which is wound around a pair of bead cores arranged in each bead portion radially outward, and between the radial carcass and the tread rubber. A run-flat comprising a belt composed of one or more belt plies disposed in the belt, and a reinforcement rubber layer having a substantially crescent-shaped cross section disposed at the inner side in the tire width direction of the radial carcass at least at a portion corresponding to the sidewall portion. In the tire,
In the tire width direction inside from the end face of the belt, the tread de portion of the tire width direction outside of the region from the ground end in the 75% load conditions, to form the rigidity reduction portion for reducing the stiffness of the tire,
The rigidity reducing portion is constituted by a circumferential groove that opens on the tread rubber surface,
2. The run-flat radial tire according to claim 1, wherein the circumferential grooves are discontinuously configured so as not to intersect with other grooves opened on the tread rubber surface . Provided with tread portion, a pair of sidewall portions extending radially inward from both sides of the tread portion, and a bead portion continuous on the inner peripheral side of each sidewall portion, and is arranged on the tread portion to constitute a grounding surface A tread rubber, a radial carcass composed of one or more carcass plies, each of which is wound around a pair of bead cores arranged in each bead portion radially outward, and between the radial carcass and the tread rubber. A run-flat comprising a belt composed of one or more belt plies disposed in the belt, and a reinforcement rubber layer having a substantially crescent-shaped cross section disposed at the inner side in the tire width direction of the radial carcass at least at a portion corresponding to the sidewall portion. In the tire,
Forming a rigidity reduction portion that reduces the rigidity of the tire in the tread portion in the tire width direction inner side in the tire width direction from the end surface of the belt and in the tire width direction outer side from the ground contact end in the 75% load state,
The rigidity reduction portion, wherein the to Lula down flat radial tire that long hole in the circumferential direction which opens to the tread rubber surface number, formed by arranging in the circumferential direction. Claim 1 or 2, characterized in that the position in the tire width direction outside and the tire width direction inner end of the reinforcing rubber layer was disposed on the inner side of the tire width direction outside and the belt end surface than the ground end in the 75% load state Run-flat radial tire described in 1. The belt includes a crossing belt layer in which two belt plies whose inclination angles with respect to the equator plane of the cord are opposite to each other are bonded together, and the end surface of the narrow ply among the belt plies constituting the crossing belt layer is the arranged in the tire width direction outer side than the ground end in the 75% load, the rigidity reduction portion according to claim 1, characterized in that it is arranged inside the tire width direction from the end face of the narrow side ply ~ 4. The run flat radial tire according to any one of 3 above.

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