JP5703973B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire.

  Today, pneumatic tires called so-called run-flat tires have been proposed that can travel a predetermined distance in a state where the internal pressure is zero (atmospheric pressure) or close to zero due to puncture or the like.

  This run-flat tire is mainly mounted on high-performance sports cars and luxury sedan passenger cars, and the driving stability of passenger cars is remarkably improved even when the tires are flat (puncture) during high-speed driving on general roads and highways. It is required to be able to travel to a predetermined place safely, for example, about 100 km without losing.

For example, a pneumatic tire having a flatness ratio of 60 or more, in which run flat durability is remarkably improved as compared with a conventional run flat tire, is known (Patent Document 1).
The pneumatic tire includes a carcass in which a radial array cord of one ply or more that reinforces a pair of sidewall portions and a tread portion between bead cores embedded in a pair of bead portions is covered with rubber, and an outer periphery of the carcass. And a belt for reinforcing the tread portion. Furthermore, the pneumatic tire has a bead filler rubber extending in a tapered manner from the bead core toward the end of the tread portion, and a reinforcing rubber layer having a substantially crescent cross section on the inner surface of the innermost carcass ply. At least one protective rubber sheet that is relatively soft is disposed between the bead filler rubber and the carcass ply surrounding the bead filler rubber and / or between the reinforcing rubber layer and the carcass ply adjacent to the reinforcing rubber layer.

JP 2000-21323 A

The above-mentioned known pneumatic tires are applied to pneumatic tires with a flatness ratio of 60 or more for sports utility vehicles (Sport Utility Vehicles), which have a higher load on the tires than high-performance sports cars and luxury sedan passenger cars. In this case, the crescent-shaped reinforced rubber layer is enlarged in order to support a large load in a run-flat state. At this time, by increasing the crescent-shaped reinforcing rubber layer, the side portion can withstand high load loads, but on the other hand, the bead portion where the rim flange contacts the pneumatic tire is greatly deformed and the bead durability is improved. Deterioration may occur.
In addition, although a bead durability can be improved by providing a reinforcement member in the part of a bead part which a rim flange contacts with a pneumatic tire, the weight of a tire also increases with reinforcement. An increase in the weight of the tire is not preferable because it leads to an increase in rolling resistance, deterioration in steering stability, and an increase in the total weight of the vehicle when it is mounted on the vehicle.

  Therefore, the present invention is a pneumatic tire having a reinforcing rubber layer having a crescent cross-sectional shape provided along the carcass layer on the inner side in the tire width direction of the carcass layer in the side region, and the weight of the tire increases. An object of the present invention is to provide a pneumatic tire with improved bead durability.

One aspect of the present invention includes a pair of bead cores, a carcass ply layer in which a fiber material is coated with a covering rubber, and is wound around each of the pair of bead cores, and each of the bead cores and tire tread portion ends. Reinforced rubber layer having a crescent cross-sectional shape provided along the carcass layer on the inner side in the tire width direction of the carcass layer in the two side regions therebetween,
The pneumatic tire has a rim cushion rubber layer in contact with a rim flange.
The covering rubber of the carcass ply layer has a first portion in which the thickness of the covering rubber is constant, and a second portion that is thicker than the thickness in the first portion. And
In the tire width direction outer portion of the carcass layer wound around each of the bead cores, the portion of the covering rubber located between the rim cushion rubber layer and the fiber material includes the second Part is arranged,
When the maximum thickness in the second part is A and the thickness in the first part is B, A / B is 1.3 to 3.0,
When the maximum thickness of the reinforcing rubber layer is C, A / C is 0.10 to 0.35,
Ri der tanδ of 0.20 or less at 60 ° C. of the coating rubber,
The arrangement position of the second portion in the tire radial direction is within a range of 15 to 40% of the tire cross-section height H based on the innermost position of the pneumatic tire in the tire radial direction.

  At that time, when the thickness of the rim cushion rubber layer is D, A / D is preferably 0.20 to 0.50.

  Further, when the thickness of the rim cushion rubber layer is D and the thickness obtained by adding A and D is F, F / C is preferably 0.60 to 0.90.

  Further, in the carcass layer, a bead filler rubber is provided between the outer portion in the tire width direction and the inner portion in the tire width direction around which the carcass layer is wound, so as to contact each of the bead cores. The tan δ at 60 ° C. is preferably 0.20 or less.

  The tire flatness is preferably 60 or more.

  According to the pneumatic tire, the bead durability is improved without increasing the weight of the tire.

It is a figure showing the section of the pneumatic tire of this embodiment. It is the elements on larger scale which expanded the bead part circumference of the pneumatic tire shown in FIG. It is a figure explaining winding around the bead core of the 1st ply material of the pneumatic tire shown in FIG. (A), (b) is a figure which shows the other example of this embodiment.

  Hereinafter, the pneumatic tire of the present invention will be described in detail.

FIG. 1 is a view showing a cross section of a pneumatic tire (hereinafter referred to as a tire) 10 of the present embodiment. Although the tire 10 of the present embodiment will be described as a tire having a tire size of 225 / 65R17, the present invention is not limited to this tire size.
The pneumatic tire 10 is, for example, a passenger car tire. Passenger car tires are tires defined in Chapter A of JATMA YEAR BOOK 2009 (Japan Automobile Tire Association Standard). In addition, the present invention can also be applied to light truck tires defined in Chapter B.

  The tire circumferential direction described below refers to the direction of rotation of the tread surface when the pneumatic tire 10 is rotated about the tire rotation axis, and the tire radial direction is orthogonal to the tire rotation axis. The extending radial direction refers to the tire radial direction outer side, which is the side away from the tire rotation axis in the tire radial direction. The tire width direction refers to a direction parallel to the tire rotation axis direction, and the tire width direction outer side refers to both sides of the pneumatic tire 10 away from the tire center line CL.

  The pneumatic tire 10 includes a carcass ply layer 12, a belt layer 14, and a pair of bead cores 16 as a skeleton material, and a tread rubber layer 18, a side rubber layer 20, and a bead around these skeleton materials. It mainly includes a filler rubber layer 22, a rim cushion rubber layer 24, an inner liner rubber layer 26, and a reinforcing rubber layer 27.

  The carcass ply layer 12 is a member in which a toroidal shape is formed by winding between a pair of annular bead cores 16 and includes a first ply material 12a and a second ply material 12b. . The end portion of the first ply material 12 a is positioned on the outer side in the tire radial direction as compared with the maximum width position R of the side portion of the tire 10, and the end portion of the second ply material 12 b is the end portion of the bead filler rubber layer 22. It is located on the outer side in the tire radial direction and on the inner side in the tire radial direction from the maximum width position R. A belt layer 14 is provided outside the carcass ply layer 12 in the tire radial direction. The belt layer 14 includes steel belt members 14a and 14b obtained by coating rubber on steel cords inclined at a predetermined angle, for example, 20 to 30 degrees with respect to the tire circumferential direction, and parallel to the tire circumferential direction or in the tire circumferential direction. And an organic fiber reinforcing material 14c in which organic fibers inclined at a predetermined angle are covered with rubber. The lower steel belt material 14a has a longer width in the tire width direction than the upper steel belt material 14b. The steel belt materials 14a and 14b are inclined in the opposite directions of the steel cords, and the steel belt materials 14a and 14b form a crossing layer. Furthermore, since the organic fiber reinforcing material 14c is provided on the outer side in the tire radial direction of the crossing layer, the belt layer 14 suppresses the expansion of the carcass ply layer 12 due to the filled air pressure.

A tread rubber layer 18 is provided outside the belt layer 14 in the tire radial direction, and a side rubber layer 20 is connected to an end of the tread rubber layer 18 to form a side portion. A rim cushion rubber layer 24 is provided at the inner end in the tire radial direction of the side rubber layer 20 and is in contact with a rim flange _{Rf of} a wheel on which the tire 10 is mounted. The bead core 16 is sandwiched between the portion of the carcass ply layer 12 before being wound around the bead core 16 and the portion of the carcass ply layer 12 wound around the bead core 16 on the outer side in the tire radial direction of the bead core 16. A bead filler rubber layer 22 is provided so as to be in contact with each of the above. An inner liner rubber layer 26 is provided on the inner surface of the tire 10 facing the tire cavity region filled with air surrounded by the tire 10 and the wheel.

  The reinforcing rubber layer 27 is a crescent cross section provided along the carcass layer on the inner side in the tire width direction of the carcass ply layer 12 of the two side regions formed between each of the pair of bead cores 16 and the end of the tire tread. It is a shaped layer. The reinforcing rubber layer 27 is a member that supports the side portion so that it does not bend due to a load when it is in a run-flat state.

  FIG. 2 is a partially enlarged view in which the periphery of the bead portion is enlarged. FIG. 3 is a view for explaining winding around the bead core 16 of the first ply material 12a. In FIG. 3, the second ply material 12 b is not shown for easy understanding of the first ply material 12 a. As shown in FIG. 2 and FIG. 3, the covering rubber of the first ply material 12a of the carcass ply layer 12 includes a first portion having a constant thickness of the covering rubber and a constant portion in the first portion. A second portion that is thick relative to the thickness. As shown in FIG. 3, the rim cushion rubber layer 24 and the organic fibers of the first ply material 12a are the outer portions of the first ply material 12a of the carcass ply layer 12 wound around the bead core 16 in the tire width direction. The second portion S is disposed in the portion of the covering rubber located between the materials. That is, the thickness of the reinforcing rubber layer of the first ply material 12a is partially increased between the organic fiber material layer of the first ply material 12a and the rim cushion rubber layer 24. The second portion S, which is thicker than the first portion, is disposed on the covering rubber between the organic fiber material layer of the first ply material 12a and the rim cushion rubber layer 24 in this manner. This is to ensure bead durability when 10 is in a run-flat state.

  Describing in more detail with reference to the definition of dimensions A to E shown in FIG. 2, let A be the maximum thickness in the second portion S of the covering rubber of the first ply material 12a of the carcass ply layer 12; When the constant thickness in the first portion is B, A / B is 1.3 to 3.0, preferably 1.5 to 2.5. Moreover, when the maximum thickness of the crescent cross-sectional shape of the reinforcing rubber layer 27 is C, A / C is 0.10 to 0.35, preferably 0.15 to 0.30. Further, the tan δ at 60 ° C. of the coated rubber is 0.20 or less, preferably 0.18 or less. Here, the “thickness” is the closest point on the cross-sectional line inside the tire width direction from the point on the cross-sectional line outside the tire width direction in the cross-sectional shape when a member or layer is cut along the tire radial direction. The shortest distance to.

In the run-flat state of the tire 10, the boundary surface between the rim cushion rubber layer 24 and the carcass ply layer 14 that is positioned in a direction perpendicular to the contact surface including the contact end from the contact end of the tire 10 that contacts the rim flange _Rf. Peeling easily occurs. However, in the tire 10, by increasing the thickness of the coated rubber having a tan δ at 60 ° C. of 0.20 or less, that is, A / B is 1.3 to 3.0, and A / C is 0.10. The said peeling can be suppressed by setting it to -0.35. Conventionally, a reinforcing material or a rubber sheet for suppressing the above-described separation is disposed between the carcass ply layer and the rim cushion rubber layer, so that the tire weight increases, the cost also increases, and the tire productivity Was also falling. However, in the present embodiment, the above configuration can suppress the increase in tire weight and the decrease in productivity, and improve the bead durability. That is, this embodiment can suppress an increase in tire weight and a decrease in productivity while improving bead durability.
The second portion S of the covering rubber may be provided from the stage of producing the first ply material 12a, or the first ply consisting of the first portion where the covering rubber has a certain thickness before the tire molding. The second portion S may be produced by partially attaching a rubber material having the same rubber physical properties as the first portion to the material. In the tire 10 after vulcanization, even if the rubber part is partially attached and the second part S is provided, or the first ply material 12a is provided with the second part S from the production stage, the same rubber physical properties are obtained. Since a rubber member is used, it cannot be distinguished.

Furthermore, when the maximum thickness of the rim cushion rubber layer is D, A / D is preferably 0.20 to 0.50 from the viewpoint of further improving the bead durability. When A / D is less than 0.20, the bead durability is not improved, and when it is more than 0.5, the weight of the tire 10 increases, which is not preferable in terms of cost and total vehicle weight.
Further, when F is a thickness obtained by adding the thickness A and the thickness D, F / C is preferably 0.60 to 0.90. When F / C is less than 0.60, the bead durability is insufficient, and when it is greater than 0.90, the bead durability is excessively improved, and deformation concentrates on the reinforcing rubber layer 27 and the reinforcing rubber layer 27 is damaged. .

Furthermore, when the thickness of the second portion S is a, the portion E in which a / C is 0.10 to 0.35 is based on the innermost position of the rim cushion rubber layer 24 in the tire radial direction. Tire cross-section height H (the length in the tire radial direction from the innermost position of the rim cushion rubber layer 24 in the tire radial direction to the outermost position of the tread rubber layer 18 in the tire radial direction: FIG. It is preferable that the tire is disposed in a range of 15 to 40% in the tire radial direction. The position of 15 to 40% of the tire cross-section height H is a position where the rim cushion rubber layer 24 is provided. By arranging the second portion S at a position in this range, the second portion S is a rim cushion. A boundary surface is reliably formed with the rubber layer 24. On the other hand, even if the second portion S is disposed at a position in the tire radial direction that is less than 15% or more than 40% of the tire cross-section height H, the bead durability is not improved and only the weight is increased.
Further, the tan δ at 60 ° C. of the bead filler rubber layer 22 is preferably 0.20 or less, and particularly preferably 0.15 or less. When tan δ exceeds 0.20, heat generation at the bead portion increases, and the bead durability decreases. The tan δ determined by the covering rubber and the bead filler rubber layer 22 is, for example, an initial strain of 10%, an amplitude of ± 2%, and a frequency of 20 Hz using a viscoelastic spectrometer (for example, Rheograph-Solid manufactured by Toyo Seiki Seisakusho Co., Ltd.). Measured in

  By defining the dimensions related to the thickness and position of the tire 10 as described above, it is possible to improve the bead durability while suppressing an increase in the weight of the tire, as will be described later.

Note that the tire 10 of the present embodiment uses the carcass ply material 12 having two layers of the ply material of the first ply material 12a and the second ply material 12b, but the carcass ply layer having one ply material may also be used. Good. Moreover, the fiber used for the carcass ply layer 12 is not limited to an organic fiber, and a steel wire can also be used.
4 (a) and 4 (b) are views showing a form in which the shape of the second portion S of the coated rubber is different from that of the above embodiment when one carcass ply layer is used as the carcass ply layer 12. FIG. is there. The form shown in FIG. 3A is a form in which the thickness of the second portion S gradually increases from the lower side in the tire radial direction, reaches the maximum thickness A, and then gradually decreases. The form shown in FIG. 3 (b) is a form in which the thickness of the second portion S suddenly increases on the lower side in the tire radial direction to the maximum thickness A and then gradually decreases. As the tire flattening ratio increases, the size of the reinforcing rubber layer 27 having a crescent-shaped cross section used for the side portion increases, and therefore, the weight increase of the tire becomes more significant. For this reason, it is preferable to apply the tire 10 of the present embodiment that improves the bead durability while suppressing the weight of the tire to a tire having a tire flatness ratio of 60 or more.
Thus, the thickness distribution of the second portion S is not particularly limited as long as it is thicker than the first portion having a constant thickness.

[Example]
Hereinafter, in order to investigate the effect of the pneumatic tire of the present invention, various tires were produced and the weight of the tire and the bead durability were evaluated.
The size of the produced tire is 225 / 65R17. For evaluation of bead durability, the tire was tested under the run durability test drum endurance test conditions described in ECE30, and the travel distance until the tire broke was obtained. Specifically, the manufactured tire was mounted on a rim having a rim size of 17 × 6.5 J, an internal pressure was set to 0 MPa (atmospheric pressure), and a traveling speed was set to 80 km / hour. The tire load was 65% of the maximum load specified by JATMA.
Table 1 below shows the specifications of the conventional examples, Examples 1 to 9, and Comparative Examples 1 to 6, and the evaluation results at that time. In Table 1, the obtained travel distance is indexed based on the conventional example. The index indicates that the higher the value, the better the bead durability. Moreover, the weight of the tire of Table 1 is shown by an index, and the higher the index value, the lower the weight.

  As can be seen from the following Table 1, from the comparison of Examples 1 to 3 and Comparative Examples 1 and 2, it is necessary that A / B is 1.3 to 3.0, Examples 4 to 6 and Comparative Examples From the comparison of 3 and 4, it is necessary that A / C is 0.1 to 0.35. From Examples 7 to 9 and Comparative Example 5, tan δ of the coated rubber is 0.2 or less. is necessary. From this, A / B is set to 1.3 to 3.0, A / C is set to 0.1 to 0.35, and tan δ (60 ° C.) is set to 0.2 or less, thereby reducing the weight of the tire. It turns out that bead durability can be improved, suppressing.

Furthermore, the tires of Examples 10 to 15 were prepared by setting A / B = 2.0, A / C = 0.15, tan δ = 0.10, and variously changing A / D. The weight and bead durability were evaluated. The tire size, rim size, internal pressure, running speed, and tire load were the same as in Examples 1 to 9, Comparative Examples 1 to 5, and the conventional example. Evaluation was also performed in the same manner as in Examples 1 to 9, Comparative Examples 1 to 5, and the conventional example.
Table 2 below shows the specifications of Examples 10 to 15 and the evaluation results at that time. The travel distance obtained in the bead durability test is indexed based on the conventional example in Table 1. The index indicates that the higher the value, the better the bead durability. The tire weight is indicated by an index, and the higher the index value, the lower the weight.

  From the comparison of Examples 10 to 15, it can be seen that it is preferable to set A / D to 0.2 to 0.5 in terms of improving the bead durability while suppressing the weight of the tire.

Further, A / B = 2.0, A / C = 0.15, tan δ = 0.10, A / D = 0.30, and various values of F / C and E (%) are changed. The tires of Examples 16 to 19 were prepared, and the weight of the tire and the bead durability were evaluated. The tire size, rim size, internal pressure, running speed, and tire load were the same as in Examples 1 to 9, Comparative Examples 1 to 5, and the conventional example. Evaluation was also performed in the same manner as in Examples 1 to 9, Comparative Examples 1 to 5, and the conventional example.
Table 3 below shows the specifications of Examples 16 to 19 and the evaluation results at that time. The travel distance obtained in the bead durability test is indexed based on the conventional example in Table 1. The index indicates that the higher the value, the better the bead durability. The tire weight is indicated by an index, and the higher the index value, the lower the weight.

From Table 3, it can be said that Examples 16-19 whose F / C is 0.6-0.9 all improve bead durability, suppressing the weight of a tire. Moreover, it can be said that Examples 16-19 whose E value (%) is 15-40% improve bead durability, suppressing the weight of a tire.
As mentioned above, the effect of the tire of this embodiment is clear.

  As mentioned above, although the pneumatic tire of this invention was demonstrated in detail, this invention is not limited to the said embodiment, Of course, in the range which does not deviate from the main point of this invention, you may make a various improvement and change. is there.

DESCRIPTION OF SYMBOLS 10 Pneumatic tire 12 Carcass ply layer 12a 1st ply material 12b and 2nd ply material 14 Belt layers 14a and 14b Steel belt material 14c Organic fiber reinforcement 16 Bead core 18 Tread rubber layer 20 Side rubber layer 22 Bead filler rubber layer 24 Rim cushion Rubber layer 26 Inner liner rubber layer 27 Reinforced rubber layer

Claims (5)

A pair of bead cores;
A carcass ply layer coated with a covering rubber and wound around each of the pair of bead cores;
A reinforcing rubber layer having a crescent cross-sectional shape provided along the carcass layer on the inner side in the tire width direction of the carcass layer in two side regions between each of the bead cores and a tire tread portion end;
A pneumatic tire having a rim cushion rubber layer in contact with the rim flange;
The covering rubber of the carcass ply layer has a first portion in which the thickness of the covering rubber is constant, and a second portion that is thicker than the thickness in the first portion. And
In the tire width direction outer portion of the carcass layer wound around each of the bead cores, the portion of the covering rubber located between the rim cushion rubber layer and the fiber material includes the second Part is arranged,
When the maximum thickness in the second part is A and the thickness in the first part is B, A / B is 1.3 to 3.0,
When the maximum thickness of the reinforcing rubber layer is C, A / C is 0.10 to 0.35,
Ri der tanδ of 0.20 or less at 60 ° C. of the coating rubber,
The arrangement position of the second portion in the tire radial direction is within a range of 15 to 40% of the tire cross-section height H with reference to the innermost position of the pneumatic tire in the tire radial direction. A pneumatic tire characterized by that.   The pneumatic tire according to claim 1, wherein A / D is 0.20 to 0.50, where D is a thickness of the rim cushion rubber layer.   3. The F / C is 0.60 to 0.90, where D is a thickness of the rim cushion rubber layer and F is a thickness obtained by adding the A and the D. 4. Pneumatic tire. Further, in the carcass layer, a bead filler rubber is provided between the outer portion in the tire width direction and the inner portion in the tire width direction around which the carcass layer is wound, so as to contact each of the bead cores. The pneumatic tire according to any one of claims 1 to 3 , wherein tan δ at 60 ° C is 0.20 or less. The pneumatic tire according to any one of claims 1 to 4 , wherein a tire flatness ratio is 60 or more.

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