JP2013060040A - Run flat tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a run flat tire advantageous on restraining buckling in run flat travel, while securing ride comfort in ordinary travel and the run flat travel.SOLUTION: In this run flat tire 10, a reinforcing rubber layer 24 is arranged inside a sidewall part 14. An end part 24A of the reinforcing rubber layer 24 is positioned inside in the tire radial direction of a longitudinal main groove 30. A steel belt layer 50 is arranged between a carcass 22 and a belt layer 26 on the inside in the tire radial direction of the longitudinal main groove 30. Assuming a width of the longitudinal main groove 30 as W1 and a width of the steel belt layer 50 as W2, a relational expression of 1.0W1≤W2≤4.0W1 is satisfied. Assuming an angle formed to the tire circumferential direction by a steel cord 5002 of the steel belt layer 50 as α°, a relational expression of 35°≤α°≤90° is satisfied. A thickness T of the end part 24A of the reinforcing rubber layer 24 positioned inside in the tire radial direction of the longitudinal main groove 30 is formed in 0.5-2.0 mm.

Description

  The present invention relates to a run-flat tire, and more particularly, during run-flat running (inside the tire) while suppressing a decrease in ride comfort during normal running (running in a state where air pressure is properly filled). The present invention relates to a run-flat tire that is advantageous in suppressing buckling during traveling in a state where air has escaped.

A run-flat tire is a tire that can run for a specified distance at a specified speed even if the air in the tire escapes due to puncture, etc. When the run-flat tire is mounted on a vehicle, it is necessary to mount a spare tire to be used for puncture on the vehicle. Disappears.
For these reasons, in recent years, run flat tires have attracted attention from the viewpoint of reducing the weight of the entire vehicle and from the viewpoint of securing a large living space and a large luggage space.
There are many run-flat tires of the side reinforcing type in which a reinforcing rubber layer having a crescent-shaped cross section is provided in the sidewall portion.

Side-reinforced run-flat tires support the load load of the vehicle with a reinforcing rubber layer on each side wall during run-flat driving, so that the back of the tread is easily lifted off the road surface. When this occurs, the ride comfort during run-flat running is significantly reduced.
In order to suppress this buckling, there is known one in which a layer layer is provided inside the tread portion and outside the belt layer in the tire radial direction (Patent Document 1).

JP 2006-137377 A

The inventor has intensively studied the buckling, and as a result, the buckling is likely to occur starting from the longitudinal main groove, which is a portion where the thickness of the tread portion is thin, and the tire diameter of the tread portion during buckling. We paid attention to the fact that the innermost part of the direction extended the most.
From such a viewpoint, the conventional technique in which the layer layer is provided on the outer side in the tire radial direction of the belt layer is disadvantageous in effectively suppressing buckling.
The present invention has been devised in view of the above circumstances, and an object of the present invention is advantageous in suppressing buckling during run-flat travel while suppressing a decrease in ride comfort during normal travel. It is to provide run-flat tires.

  To achieve the above object, the present invention provides a carcass layer extending from a tread portion to a bead portion through a sidewall portion, a belt layer disposed outside the carcass layer in the tire radial direction inside the tread portion, and the tread. A run-flat provided with a longitudinal main groove provided on the tread surface of the tire portion and extending in the tire circumferential direction, and a crescent-shaped reinforcing rubber layer disposed inside the sidewall portion in the tire axial direction of the carcass layer An end of the reinforcing rubber layer on the outer side in the tire radial direction is located on the inner side in the tire radial direction of the longitudinal main groove, and the carcass layer and the belt layer are disposed on the inner side in the tire radial direction of the longitudinal main groove. A steel belt layer made of a plurality of steel cords and a topping rubber covering them is provided between them and extending in the tire circumferential direction. The width of the longitudinal main groove is W1, and the steel When the width along the tire axial direction of the belt layer is W2, the relational expression of 1.0W1 ≦ W2 ≦ 4.0W1 is satisfied, and the angle formed by the steel cord with respect to the tire circumferential direction is α ° The relational expression of 35 ° ≦ α ° ≦ 90 ° is satisfied, and the thickness of the reinforcing rubber layer located inside the longitudinal main groove in the tire radial direction is formed to be not less than 0.5 mm and not more than 2.0 mm. And

According to the present invention, the end portion of the reinforcing rubber layer having a predetermined thickness is disposed inside the longitudinal main groove in the tire radial direction, and the steel belt layer having a large elongation rigidity is disposed.
Therefore, it is advantageous for suppressing buckling during run-flat traveling while suppressing a decrease in riding comfort during normal traveling, and advantageous for improving riding comfort during run-flat traveling.

It is half part sectional drawing of a run flat tire. It is the expanded view of the tread pattern which showed the steel belt layer with the dotted line. It is an expanded sectional view of an outside vertical main groove part. It is sectional drawing of a steel belt layer. It is a top view which shows the inclination-angle of the steel cord of a steel belt layer. It is the expanded view of the tread pattern which showed the steel belt layer with the dotted line. It is the expanded view of the tread pattern which showed the steel belt layer with the dotted line. It is a figure which shows the test result of a prior art example, a comparative example, and an Example.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the run flat tire 10 is a side reinforcing type, and is a pneumatic radial tire having run flat performance.
The run-flat tire 10 includes a tread portion 12, sidewall portions 14 that extend inward in the tire radial direction from both sides of the tread portion 12, and bead portions 16 that are positioned at end portions in the tire radial direction of the respective sidewall portions 14. ing.
Each bead portion 16 is provided with a bead core 18, and a bead filler 20 is provided on the outer side in the radial direction of the bead core 18 so as to be tapered outward in the tire radial direction.
The carcass 22 passes through the tread portion 12 and the side wall portions 14 on both sides and is spanned to the bead cores 18 at both ends, and both ends of the carcass 22 are folded back by the bead core 18 so as to sandwich the bead core 18 and the bead filler 20. .
The reinforcing rubber layer 24 having a crescent-shaped cross section that supports the load of the vehicle during run-flat traveling is provided on the inner side in the tire axial direction of the carcass 22 inside each sidewall portion 14.
Inside the tread portion 12, a belt layer 26 composed of four belt plies is provided outside the carcass 22 in the tire radial direction.
In FIG. 1, reference numeral 28 denotes an inner liner.

As shown in FIG. 2, a tread pattern that is point-symmetric about an arbitrary point on the tire equator CL is formed on the tread surface 12A where the tread portion 12 contacts the road surface.
In FIG. 2, the symbol TW indicates the tire contact width.
Here, the tire ground contact width TW means that when a pneumatic tire is assembled on a regular rim and filled with a regular internal pressure and 70% of the regular load is applied, the tread surface 12A of the pneumatic tire is grounded to the road surface. This is the maximum width in the tire axial direction of the tire contact area that is the area to be operated. The regular rim is “standard rim” defined by JATMA, “Design Rim” defined by TRA, or “Measuring Rim” defined by ETRTO. The normal internal pressure is “maximum air pressure” defined by JATMA, the maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “INFLATION PRESSURES” defined by ETRTO. The normal load is “maximum load capacity” defined by JATMA, the maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “LOAD CAPACITY” defined by ETRTO.

The tread surface 12A is provided with four vertical main grooves 30 extending in the tire circumferential direction at intervals in the tire axial direction.
Two of the four longitudinal main grooves 30 are inner longitudinal main grooves 30A located on both sides of the tire equator CL, and the remaining two are outer sides located outside the inner longitudinal main grooves 30A in the tire axial direction. This is the longitudinal main groove 30B.
Here, the longitudinal main groove 30 is a circumferential groove having a groove width of 4.0 to 12.0 mm and a groove depth of 8.0 to 9.5 mm.
Further, a narrow vertical groove 32 extending in the tire circumferential direction is provided between the inner vertical main groove 30A and the outer vertical main groove 30B.
A center rib 34 extending in the tire circumferential direction is formed between the inner longitudinal main grooves 30A on both sides, and a narrow rib extending in the tire circumferential direction between the inner longitudinal main grooves 30A and the longitudinal grooves 32. 36 is formed.
Further, an inner block row 40 in which blocks partitioned by lug grooves 38 are arranged in the tire circumferential direction is formed between the vertical grooves 32 and the outer vertical main grooves 30B, and the outer vertical main grooves 30B in the tire axial direction are formed. On the outside, an outer block row 44 is formed in which blocks defined by the lug grooves 42 are arranged in the tire circumferential direction.

As shown in FIGS. 1 to 3, a steel belt layer 50 extending in the tire circumferential direction is provided between the carcass 22 and the belt layer 26 on the inner side in the tire radial direction of each outer longitudinal main groove 30 </ b> B.
As shown in FIG. 4, the steel belt layer 50 includes a plurality of steel cords 5002 and a topping rubber 5004 that covers them. The steel belt layer 50 may be the same as the belt ply constituting the belt layer 26. For example, a steel cord 5002 having a diameter of 0.3 to 1 mm is arranged at a pitch of 1 to 1.6 mm. Has been.
As shown in FIG. 3, when the width of the outer longitudinal main groove 30B is W1, and the width W2 of the steel belt layer 50 along the tire axial direction is satisfied, the relational expression of 1.0W1 ≦ W2 ≦ 4.0W1 is satisfied. ing.
Further, as shown in FIG. 5, when the angle formed by the steel cord 5002 with respect to the tire circumferential direction is α °, the relational expression of 35 ° ≦ α ° ≦ 90 ° is satisfied.

As shown in FIGS. 1 and 3, end portions 24 </ b> A on the outer side in the tire radial direction of the respective reinforcing rubber layers 24 are respectively positioned on the inner sides in the tire radial direction of the two outer longitudinal main grooves 30 </ b> B.
The end portion 24A on the outer side in the tire radial direction of each reinforcing rubber layer 24 is formed in a tapered shape that gradually decreases in thickness as it approaches the tire equator CL. As shown in FIG. 3, the tire radial direction of the outer longitudinal main groove 30B is formed. The thickness T of the end 24A of the reinforcing rubber layer 24 located on the inner side is formed to be 0.5 mm or more and 2.0 mm or less at the thinnest place.

According to the present embodiment, the following effects are achieved.
The buckling is likely to occur starting from the longitudinal main groove 30, and the innermost portion in the tire radial direction of the tread portion 12 is most elongated during buckling.
In the present embodiment, the end portion 24A of the reinforcing rubber layer 24 having a predetermined thickness is disposed inside the outer longitudinal main groove 30B in the tire radial direction, and the steel belt layer 50 having high elongation rigidity is disposed.
Therefore, it is advantageous in suppressing buckling during run-flat traveling while suppressing a decrease in riding comfort during normal traveling.
In this case, in the configuration in which only the steel belt layer 50 is provided, the inner side in the tire radial direction of the outer longitudinal main groove 30B is difficult to expand, which is advantageous in suppressing buckling during run-flat travel, but during normal travel. In the configuration in which the decrease in ride comfort cannot be suppressed and only the end portion 24A of the reinforcing rubber layer 24 is disposed, the decrease in ride comfort during normal travel can be suppressed, but the effect of suppressing buckling during run flat travel can be suppressed. Less is.

More specifically, since the steel belt layer 50 has elongation rigidity, when the steel belt layer 50 is disposed on the inner side in the tire radial direction of the outer vertical main groove 30B, the inner side in the tire radial direction of the outer vertical main groove 30B is Although it becomes difficult to expand, if the width W2 of the steel belt layer 50 is smaller than the width W1 of the outer longitudinal main groove 30B, the expansion rigidity is insufficient and the effect of suppressing buckling is reduced. Further, when the width W2 of the steel belt layer 50 is larger than four times the width W1 of the outer longitudinal main groove 30B, the spring rigidity in the tire radial direction of the run-flat tire 10 is increased, and the riding comfort during normal driving is remarkably increased. descend.
In this embodiment, since the relational expression of 1.0W1 ≦ W2 ≦ 4.0W1 is satisfied, it is possible to suppress buckling during run-flat traveling while suppressing deterioration in riding comfort during normal traveling. It will be advantageous.
Further, if the angle α ° formed by the steel cord 5002 with respect to the tire circumferential direction is smaller than 35 °, the elongation rigidity in the tire axial direction is insufficient, and the effect of suppressing buckling is reduced. , 35 ° ≦ α ° ≦ 90 ° must be satisfied.
Further, the end 24A of the reinforcing rubber layer 24 is disposed inside the outer longitudinal main groove 30B in the tire radial direction, and the thickness T of the end 24A of the reinforcing rubber layer 24 is formed to be not less than 0.5 mm and not more than 2.0 mm. While suppressing an increase in the tire stiffness in the tire radial direction, it is possible to increase the elongation rigidity of the outer longitudinal main groove 30B on the inner side in the tire radial direction, while suppressing a decrease in ride comfort during normal running, and during run flat running This is advantageous in suppressing buckling.
In this case, if the thickness T of the end portion 24A of the reinforcing rubber layer 24 is less than 0.5 mm, the elongation rigidity is insufficient and the effect of suppressing buckling is small, and if it exceeds 2.0 mm, the tire radial spring Rigidity is affected, and riding comfort during normal driving is reduced.

  Further, as shown in FIG. 3, both ends in the width direction along the tire axial direction of the steel belt layer 50 are respectively inwardly in the tire radial direction from the tread surface 12A at the edge portions at both ends in the width direction of the outer longitudinal main groove 30B. When the lines L1 and L2 are lowered, if they are located outside the range sandwiched between the normal lines L1 and L2, it is more advantageous in suppressing buckling. When the steel belt layer 50 is arranged in this way, a boundary portion having a difference in strength of elongation rigidity is surely shifted in the tire axial direction from a location on the inner side in the tire radial direction of the longitudinal main groove 30 serving as a starting point of buckling. It is.

In the present embodiment, the steel belt layer 50 is provided on the inner side in the tire radial direction of the longitudinal main grooves 30 on both sides provided in the tread shoulder region (region in the range of 30% of the tire contact width from the outer end of the tire contact width). However, even if the steel belt layer 50 is disposed on the inner side in the tire radial direction of any one of the outer vertical main grooves 30B, or the inner vertical main grooves 30A and the outer vertical main grooves 30B. Even if the steel belt layer 50 is disposed on the inner side in the tire radial direction of any one of the longitudinal main grooves 30, as long as the requirements of the present invention are satisfied, a decrease in ride comfort during normal driving is suppressed, and during run flat driving Of course, it is advantageous to suppress buckling in the case.
In addition, as shown in FIG. 6, even if the steel belt layer 50 is disposed on the inner side in the tire radial direction of all the longitudinal main grooves 30, as long as the requirements of the present invention are satisfied, a decrease in riding comfort during normal traveling is suppressed. This is advantageous in suppressing buckling during run-flat running.
Furthermore, the present invention is not limited to the point-symmetric tread pattern, and can be applied to the run flat tire 10 having various conventionally known tread patterns. For example, as shown in FIG. 7, even when the steel belt layer 50 is disposed on the inner side in the tire radial direction of the longitudinal main groove 30 in the tread shoulder region of the run-flat tire 10 having the asymmetric tread pattern, the riding comfort during normal running is provided. This is advantageous in suppressing buckling during run-flat running while suppressing a decrease in performance.

Next, examples will be described.
FIG. 8 is an explanatory diagram showing test results of a conventional example, a comparative example, and an example.
A run-flat tire having a tire size of 245 / 45R17 having the structure shown in FIGS. 1 to 3 was manufactured based on the specifications shown in FIG.
In this case, the outer vertical main groove 30B had a groove width of 8.0 mm and a groove depth of 8.5 mm.
Further, the steel belt layer 50 used was a steel cord 5002 having a diameter of 1 mm arranged at a pitch of 1.35 mm.
[Ride comfort]
The run-flat tire 10 of the conventional example, the comparative example, and the example is mounted on the “Measuring Rim” defined by ETRTO, “INFLATION PRESSURES” defined by ETRTO is filled inside the tire, and the vehicle of the FR drive system with a displacement of 2000 cc is used. Our test panel evaluated the feeling of riding comfort on an actual vehicle.
The evaluation was a sensory evaluation by our test panel, and the comparison was made using an index with the conventional example as 100. The larger the index, the better the ride performance feeling during normal driving.
[Contact area change rate]
"Load CAPACITY", which includes the run-flat tire 10 of the conventional example, the comparative example, and the example in the "Measuring Rim" defined by ETRTO, and the tire is filled with "INFLATION PRESSURES" defined by ETRTO, and the tire is defined by ETRTO. The ground contact area at the time of loading was measured as “normal ground contact area”.
Further, the contact area when the inside of the tire was 0 kPa and “LOAD CAPACITY” defined by ETRTO was loaded on the tire was measured as “run-flat contact area”.
Then, the ratio of “run-flat contact area” / “normal contact area” is calculated and displayed as “contact area change rate” as an index with the conventional example being 100. This means that buckling is suppressed.
In the measurement of the contact area, paint such as vermilion is applied to the tire contact surface and the tire is loaded on a transfer paper placed on the ground. From the ground plane obtained by this method, the grounding blocks and ribs were measured by a planimeter.
[Comprehensive evaluation]
It is a value obtained by adding an index for evaluating ride comfort and an index for evaluating the rate of change in contact area, and based on this value, tire performance was comprehensively evaluated.

In Comparative Example 1, although the steel belt layer 50 is provided, the ratio of the width of the steel belt layer 50 to the width of the outer longitudinal main groove 30B is smaller than 1, and the angle of the steel cord 5002 with respect to the tire circumferential direction is more than 35 °. The reinforcing rubber layer 24 is not located inside the outer longitudinal main groove 30B in the tire radial direction. For this reason, although the decrease in ride comfort during normal driving is suppressed, the improvement in the change rate of the contact area is smaller than that of the conventional example, and the effect of suppressing buckling is small.
In Comparative Example 2, although the steel belt layer 50 is provided and the angle of the steel cord 5002 with respect to the tire circumferential direction is 65 °, the ratio of the width of the steel belt layer 50 to the outer longitudinal main groove 30B width is smaller than 1, and the outer side The reinforcing rubber layer 24 is not positioned inside the longitudinal main groove 30B in the tire radial direction. Therefore, although the fall of the riding comfort at the time of normal driving | running | working is suppressed and the contact area change rate is improving rather than the comparative example 1, the effect which suppresses buckling is still small.
In Comparative Example 3, the reinforcing rubber layer 24 is positioned inside the outer longitudinal main groove 30B in the tire radial direction and the thickness thereof is 0.3 mm, but the steel belt layer 50 is not provided. For this reason, although the decrease in ride comfort during normal driving is suppressed, the improvement in the contact area change rate is smaller than in the conventional example, and the effect of suppressing buckling is small.
In Comparative Example 4, although the steel belt layer 50 is not provided, the reinforcing rubber layer 24 is positioned on the inner side in the tire radial direction of the outer longitudinal main groove 30B, and the thickness thereof is 2 mm. Therefore, although the fall of the ride comfort at the time of normal driving | running | working is suppressed and the effect which suppresses a buckling is larger than the comparative example 3, since the steel belt layer 50 is not provided, the contact area change rate is still Improvement is small, and the effect of suppressing buckling is small.
In Comparative Example 5, although the steel belt layer 50 is not provided, the reinforcing rubber layer 24 is positioned on the inner side in the tire radial direction of the outer longitudinal main groove 30B, and the thickness thereof is 2.5 mm. For this reason, the rate of change in contact area is improved as compared with Comparative Example 4 and the effect of suppressing buckling is greater than that of Comparative Example 4, but the riding comfort during normal running is reduced.
In Comparative Example 6, the steel belt layer 50 is provided and the angle of the steel cord 5002 with respect to the tire circumferential direction is set to 45 °, so that the contact area change rate is improved and the effect of suppressing buckling is increased. The ratio of the width of the steel belt layer 50 to the width of the longitudinal main groove 30B is larger than 4, and the reinforcing rubber layer 24 is not located on the inner side in the tire radial direction of the outer longitudinal main groove 30B. Has fallen.

According to Examples 1-8, the fall of the riding comfort at the time of normal driving | running | working is suppressed.
In addition, the contact area change rate is improved and the effect of suppressing buckling is great.
Moreover, in Examples 2-8, comprehensive evaluation exceeds the conventional example and the comparative example.

  Moreover, according to Examples 1-8, when the ratio of the width | variety of the steel belt layer 50 with respect to the width | variety of the outside vertical main groove 30B is enlarged, it is clear that the effect which suppresses buckling becomes large. Further, it can be seen that when the ratio of the width of the steel belt layer 50 to the width of the outer longitudinal main groove 30B is 3 or 4, the riding comfort during normal running is lower than when the ratio is 1 or 2.

Further, when Example 2 is compared with Example 3, Example 3 in which the thickness of the reinforcing rubber layer 24 is increased on the inner side in the tire radial direction of the outer longitudinal main groove 30B is more effective in suppressing buckling. I understand that.
Similarly, when Example 4 is compared with Example 5, Example 5 in which the thickness of the reinforcing rubber layer 24 is increased on the inner side in the tire radial direction of the outer longitudinal main groove 30B is more effective in suppressing buckling. You can see that it ’s big.

Moreover, when Example 2 and Example 4 are compared, it turns out that the effect which suppresses a buckling is larger in Example 4 with a larger angle of the steel cord 5002 with respect to the tire circumferential direction.
Similarly, when Example 3 and Example 5 are compared, it can be seen that Example 5 having a larger angle of the steel cord 5002 with respect to the tire circumferential direction has a greater effect of suppressing buckling.

  DESCRIPTION OF SYMBOLS 10 ... Run-flat tire, 12 ... Tread part, 14 ... Side wall part, 16 ... Bead part, 22 ... Carcass, 24 ... Reinforcement rubber layer, 24A ... End, 26... Belt layer, 30... Longitudinal main groove, 30 A... Inner longitudinal main groove, 30 B .. outer longitudinal main groove, 50.

Claims (3)

A carcass layer extending from the tread portion through the sidewall portion to the bead portion, a belt layer disposed outside the carcass layer in the tire radial direction inside the tread portion, and a tire circumferential direction provided on the tread surface of the tread portion A run-flat tire comprising a longitudinal main groove extending to the inside of the sidewall portion and a crescent-shaped reinforcing rubber layer disposed inside the carcass layer in the tire axial direction,
An end of the reinforcing rubber layer on the outer side in the tire radial direction is located on the inner side in the tire radial direction of the longitudinal main groove,
A steel belt layer is provided between the carcass layer and the belt layer on the inner side in the tire radial direction of the longitudinal main groove, and includes a plurality of steel cords and a topping rubber that covers them, and extends in the tire circumferential direction.
When the width of the longitudinal main groove is W1 and the width of the steel belt layer along the tire axial direction is W2, the relational expression of 1.0W1 ≦ W2 ≦ 4.0W1 is satisfied,
When the angle formed by the steel cord with respect to the tire circumferential direction is α °, the relational expression of 35 ° ≦ α ° ≦ 90 ° is satisfied,
The thickness of the reinforcing rubber layer located on the inner side in the tire radial direction of the longitudinal main groove is formed to be not less than 0.5 mm and not more than 2.0 mm.
A run-flat tire characterized by that. A plurality of the longitudinal main grooves are provided at intervals in the tire axial direction on the tread surface,
An end of the reinforcing rubber layer on the outer side in the tire radial direction is located on the inner side in the tire radial direction of the outer vertical main groove located on the outer side in the tire axial direction among the plurality of vertical main grooves,
The steel belt layer is provided between the carcass layer and the belt layer on the inner side in the tire radial direction of the outer longitudinal main groove.
The run flat tire according to claim 1, wherein: Both ends of the steel belt layer in the width direction along the tire axial direction are normal to the edge portions of the longitudinal main grooves at the both ends in the width direction when the normal lines are lowered from the tread surface inward in the tire radial direction. Located outside the sandwiched area,
The run flat tire according to claim 1 or 2, wherein

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