JP5623867B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire that achieves low rolling resistance by reducing tire weight.

  In recent years, development of products with a smaller environmental load has been actively conducted. This is due to environmental problems such as global warming, and tires are no exception. Regarding these tires, in order to cope with environmental problems, it is important to secure performance that contributes to reducing fuel consumption of automobiles. One means for achieving this is to reduce the rolling resistance of the tire, and various technical developments have been made in the past.

  First, it is known that a large amount of tire rolling resistance occurs in the rubber of the tread portion. As a direct improvement method, the rubber used for the tread portion may be changed to one having a small loss tangent. However, this method is also known to sacrifice other performance, including wear resistance. On the other hand, a method of reducing the tread thickness can be easily considered in order to reduce the rubber that is a source of increasing rolling resistance. However, in this case, the problem is that the wear life of the tire cannot be ensured.

  By the way, in patent document 1, in order to ensure favorable riding comfort and to improve side cut durability without increasing the weight, the carcass folding portion located on the vehicle outer side in a state where the tire is mounted on the vehicle. A technique for defining the position of the end of the carcass and the end of the carcass folding portion located inside the vehicle is disclosed.

JP 2008-299796 A

However, the present inventor has earnestly studied how to further reduce the tire weight in the conventional tire including the tire described in Patent Document 1, and has completed the present invention. That is, in Patent Document 1, since no study has been made on rubber that greatly contributes to tire weight, the present inventor has room to realize further low rolling resistance by optimizing the amount of rubber. I found out.
Therefore, an object of the present invention is to provide a pneumatic tire that realizes low rolling resistance by reducing the tire weight.

The gist of the present invention is as follows.
(1) In a tire including a carcass extending in a toroidal shape between a pair of bead cores and having at least one belt and a tread on the outer side in the tire radial direction of the carcass,
The carcass is folded from the carcass main body portion extending in a toroidal shape between the pair of bead cores, from the inner side to the outer side in the tire width direction around the bead cores, and extends between the belt and the carcass main body portion. Having a carcass folded portion,
The region where the rubber gauge in the side portion is 0.5 mm to 2.0 mm includes the tire maximum width position, and extends over 30% of the tire cross-sectional height in the tire radial direction.
A pneumatic tire characterized by that.

(2) The bead filler disposed outside the bead core in the tire radial direction and disposed between the carcass main body portion and the carcass folded portion has a tire radial height of 20 mm or less, and the tire radial direction The pneumatic tire according to (1), wherein the outer end is present on the inner side in the tire radial direction from the separation point from the rim flange.

(3) The pneumatic tire according to the above (1) or (2) carcass ply reinforcing layer covering the tire maximum width position of the side portion is characterized in that it is placed.

(4) the carcass main body portion of the cord extends along the tire width direction, the cords of the carcass turnup portion is extended inclined against the tire width direction is the extending direction of the code of the carcass main body portion The pneumatic tire according to any one of the above (1) to (3), characterized in that:
(5) The pneumatic tire according to any one of (1) to (4), wherein a cord of the carcass ply reinforcing layer extends meandering along a tire circumferential direction.
(6) The belt according to any one of (1) to (5), wherein the belt includes a circumferential belt layer, and an upper end of the carcass ply reinforcing layer and an end of the circumferential belt are separated by 5 mm or more and 30 mm or less. Pneumatic tire.
(7) The pneumatic tire according to any one of (1) to (6), wherein a lower end of the carcass ply reinforcing layer is located 10 mm or more and 30 mm or less from the tire maximum width position and on the inner side in the tire radial direction.

It is a width direction cross section of the half part of the pneumatic tire of the present invention. It is a figure for demonstrating the surface distortion of a side part. It is a width direction cross section of the half part of the pneumatic tire which concerns on the other example of this invention.

Hereinafter, the pneumatic tire of the present invention will be described in detail with reference to the drawings.
In FIG. 1, the cross section of the half direction of the pneumatic tire (henceforth a tire) of this invention is shown. This tire 10 has a carcass 2 extending in a toroidal shape between a pair of bead cores 1 as a skeleton, and at least one, in the illustrated example, two inclined belt layers 3a and 3b on the outer side in the tire radial direction of the carcass 2; A belt comprising one circumferential belt layer 4 is disposed, and a tread 5 is provided on the outer side in the tire radial direction of the belt.
The carcass 2 is folded from the carcass main body portion 2h extending in a toroidal shape between the pair of bead cores 1 around the bead core 1 from the inner side to the outer side in the tire width direction, and extends between the belt and the carcass main body portion 2h. It has a carcass folded portion 2o.
The two inclined belt layers 3a and 3b are formed by covering a plurality of cords extending in a direction inclined with respect to the tire equatorial plane CL with rubber, and the circumferential belt layer 4 extends along the tire equatorial plane CL. A lot of cords are covered with rubber. The belt configuration of the present invention is not limited to the illustrated example.

In the tire 10, the rubber gauge G at the side portion is thinner than the conventional one. Specifically, the region A where the rubber gauge G in the side portion is 0.5 mm to 2.0 mm includes the tire maximum width position Wmax and extends over 30% of the tire cross-section height SH in the tire radial direction.
The side portion refers to a range from the outer edge in the tire width direction of the tread surface to the separation point B from the rim flange 7 of the bead portion. Further, the rubber gauge G refers to the length from the outside of the cord of the carcass folded portion 2o to the surface of the side rubber.
Since the rubber gauge in the side part of the conventional tire is about 2.5 mm to 4.0 mm, the tire weight can be significantly reduced by reducing the rubber gauge G in the side part. By defining the region A to be 30% or more of the tire cross-section height SH, the above-described weight reduction effect can be sufficiently obtained. Note that the upper limit of the region A is about 60% of the tire cross-section height SH from the outer shape of the tire.

Here, the “maximum tire width” refers to the distance between the side parts excluding convex parts such as patterns on the side of the tire and letters in a tire in a no-load state in which the tire is mounted on the applicable rim and filled with the specified air pressure. It shall be the maximum straight line width.
“Applicable rim” refers to a rim specified in a standard (for example, “JATMA YEA BOOK” of the Japan Automobile Tire Association in Japan) according to the size of the tire. In the standard, the air pressure defined corresponding to the maximum load capacity shall be referred to, and the maximum load capacity shall refer to the maximum mass allowed to be applied to the tire in this standard.

In the present invention, since the carcass folded portion 2o is so-called envelope structure that extends between the inclined belt layer 3a and the carcass main body portion 2h, two layers of carcass plies are arranged on the side portion. The side cut durability against curbstones and the like can be sufficiently secured.
In the envelope structure, the rigidity of the side portion is increased, so that the ride comfort is deteriorated. Moreover, if the rigidity of a side part increases, rolling resistance will deteriorate. That is, when the rigidity of the side portion is increased, the deformation of the side portion is suppressed. Then, the eccentric rigidity, which is the rigidity in the direction perpendicular to the road surface, is increased, and the tread rubber that greatly contributes to the rolling resistance is greatly deformed, and the rolling resistance is deteriorated.
Therefore, in the present invention, the rubber gauge G at the side portion can be reduced to 0.5 mm to 2.0 mm to reduce the rigidity and eccentric rigidity of the side portion, thereby improving riding comfort and lowering rolling resistance. it can. Further, by reducing the rubber gauge G at the side portion, the tire weight can be greatly reduced, and the rolling resistance can be further reduced.

  Furthermore, by reducing the rubber gauge G at the side portion, there is an effect of reducing surface strain at the time of loading, so that cracks occurring at the side portion can be suppressed. That is, when the rubber gauge G in the side portion shown in FIG. 2 (a) is thick, the distance from the bending center P to the side portion surface is long, so that the deformation is large. On the other hand, when the rubber gauge G at the side portion shown in FIG. 2B is thin, the distance from the bending center P to the surface of the side portion is short, so the deformation is small.

  Further, the bead filler 8 is disposed on the outer side in the tire radial direction of the bead core 1 and between the carcass main body portion 2h and the carcass folded portion 2o. It is preferable that the bead filler 8 has a tire radial height BFh of 20 mm or less, and the tire radial outer end 8E is present on the inner side in the tire radial direction from the separation point B from the rim flange 7. By making the bead filler 8 smaller than the conventional one, the rigidity of the side portion can be reduced, and as described above, the ride comfort can be improved and the rolling resistance can be further reduced. Moreover, since the flex zone where the repeated deformation of the side part is large spreads, it also has an effect of suppressing cracks occurring in the side part.

Further, cords of the carcass main body portion 2h extending along the tire width direction, cords of the carcass turnup portion 2o extends in against inclined in the tire width direction is the extending direction of the cords of the carcass main body portion 2h Is preferred. By forming a mesh with the cord of the carcass main body portion 2h and the cord of the carcass folded portion 2o, when the side portion hits a curb or the like, the opening between the cords can be suppressed and the side cut durability can be improved. .

The folding end 2oE of the carcass folding portion 2o is preferably the widest of the belt layers, and in the illustrated example, is located 5 mm or more and 30 mm or less inside the tire width direction from the belt end 4E of the circumferential belt layer 4.
If the distance between the folded end 2oE and the belt end 4E is less than 5 mm, separation may occur at the folded end 2oE and the belt end 4E.
On the other hand, it is sufficient that the folded end 2oE and the belt end 4E overlap each other up to 30 mm. If they overlap each other longer than 30 mm, the tire weight may increase, and the low rolling resistance may not be sufficiently achieved.

In FIG. 3, the cross section of the half direction of the pneumatic tire which concerns on the other example of this invention is shown. In the tire 20, the carcass ply reinforcement layer 9 is disposed so as to cover the tire maximum width position Wmax of the side portion. The carcass ply reinforcement layer 9 can reinforce the side portion (particularly the buttress portion), and when the side portion hits a curb or the like without causing extra distortion in normal times, the gap between the cords of the carcass 2 is opened. Can be suppressed and side cut durability can be improved. In the illustrated example, the carcass ply reinforcement layer 9 is disposed on the outer side in the tire width direction of the carcass folded portion 2o, and this configuration is preferable. However, the carcass ply reinforcing layer 9 may be disposed between the carcass folded portion 2o and the carcass main body portion 2h. Good.
Moreover, it is preferable that the cord of the carcass ply reinforcement layer 9 extends meandering along the tire circumferential direction so that the cord is not broken or input between the cords of the carcass 2 by an input of a curbstone or the like. In addition, “meandering and extending” means extending while bending in a wavy or zigzag shape, and “meandering along the tire circumferential direction” is microscopically relative to the tire circumferential direction. Although extending in the inclined direction, when viewed macroscopically, it means a state extending substantially in the same direction as the tire circumferential direction.
The rubber gauge G in the illustrated example refers to the length from the outer side of the cord of the belt reinforcing layer 9 to the surface of the side rubber.

The upper end 9UE of the carcass ply reinforcing layer 9 is preferably separated from the belt end 4E of the circumferential belt layer 4 by 5 mm or more and 30 mm or less. If the distance between the upper end 9UE and the belt end 4E is less than 5 mm, separation may occur at the upper end 9UE and the belt end 4E. On the other hand, if the distance between the upper end 9UE and the belt end 4E is more than 30 mm, the effect of reinforcing the buttress portion may be reduced.
The lower end 9LE of the carcass ply reinforcing layer 9 is preferably located 10 mm to 30 mm from the tire maximum width position Wmax and on the inner side in the tire radial direction. Since the vicinity of the tire maximum width position Wmax is largely bent at the time of load rolling, if the lower end 9LE exists at this position, there is a possibility that separation occurs at the lower end 9LE. Therefore, the lower end 9LE is preferably separated from the tire maximum width position Wmax by 10 mm or more. On the other hand, if the carcass ply reinforcing layer 9 is unnecessarily long, there is a possibility that the rigidity of the side portion is increased and the rolling resistance is deteriorated. Therefore, it is preferable that the lower end 9LE is within 30 mm from the tire maximum width position Wmax.

Examples of the present invention will be described below, but the present invention is not limited thereto.
Invention example tires, comparative example tires and conventional example tires were prototyped, and side cut durability performance, rolling resistance performance, riding comfort performance and side crack durability performance were evaluated.
Each test tire (tire size: 195 / 65R15) has the specifications shown in Table 1.
The invention example tire and the comparative example tire have an envelope structure carcass 2 as shown in FIG. 1 or FIG.
The conventional tire has a carcass 2 having a high turn-up structure.

The items in Table 1 are as follows.
Side gauge: Rubber gauge at tire maximum width position Wmax AH: Length in tire radial direction of region A where rubber gauge G at the side portion is 0.5 mm to 2.0 mm SH: Tire cross-sectional height BFh: Tire diameter of bead filler 8 Directional height Cord angle of the folded portion: angle of the cord of the carcass folded portion 2o with respect to the tire width direction Distance between ends: Belt of the folded end 2oE of the carcass folded portion 2o and the widest circumferential belt layer 4 of the belt layers Distance 4E-9UE between end 4E: Distance between belt end 4E of circumferential belt layer 4 and upper end 9UE of carcass ply reinforcement layer 9 Wmax-9LE: Maximum tire width position Wmax and lower end 9LE of carcass ply reinforcement layer 9 Distance to

(Side cut durability)
Each test tire was mounted on a rim (6J), filled with internal pressure (210 kPa), and then given a normal load (applicable size / maximum load in ply rating defined in “JATMA YEAR BOOK”). Each test tire mounted on a passenger car was made to collide with a specific square steel material (110 mm x 110 mm x 1000 mm) at an entry speed of 10 km / h and an entry angle of 75 °. The rate at which air leakage occurred was measured. The results are shown as indexes with the speed of the conventional tire as 100. In addition, it shows that it is excellent in performance, so that an index | exponent is large.

(Rolling resistance performance)
Each test tire is mounted on a rim (6J) and filled with internal pressure (210 kPa), and then the rolling resistance of the axle is tested using a drum testing machine (speed: 80 km / h) having a steel plate surface with a diameter of 1.7 m. Asked. The rolling resistance was measured according to ISO18164, using a smooth drum and force type. The results are shown as an index with the rolling resistance of the conventional tire as 100. In addition, it shows that it is excellent in performance, so that an index | exponent is large.

(Ride comfort performance)
Each test tire was mounted on a rim (6J) and filled with internal pressure (210 kPa), and then a normal load was applied. Each test tire was mounted on a passenger car, and it was run on a test course. A special driver performed a feeling test on ride performance. The results are shown as an index with the conventional tire evaluation being 100. In addition, it shows that it is excellent in performance, so that an index | exponent is large.

(Side crack durability)
Each test tire was mounted on a rim (6J) and filled with internal pressure (210 kPa), and then a normal load was applied. Each test tire was mounted on a passenger car, and the occurrence of cracks in the side portion was measured after traveling on a general road of 20000 km. The results are shown as an index with the conventional tire evaluation being 100. In addition, it shows that it is excellent in performance, so that an index | exponent is large.

As shown in Table 1, the tires of the invention are improved in side cut durability compared to the conventional tires by adopting the envelope structure, and the rolling resistance performance and riding comfort performance are comparable by making the rubber gauges in the side portions thinner. Or you can see that it is improving.
In addition, it was confirmed that the separation durability of the inventive tires 16, 20, and 24 was deteriorated.

DESCRIPTION OF SYMBOLS 1 Bead core 2 Carcass 2h Carcass main-body part 2o Carcass folding | turning part 3 Inclined belt layer 4 Circumferential belt layer 5 Tread 6 Bead toe 7 Rim flange 8 Bead filler 9 Carcass ply reinforcement layer 10 Tire 20 Tire CL Tire equatorial plane

Claims (7)

In a tire having a carcass extending in a toroidal shape between a pair of bead cores and having at least one belt and a tread on the outer side in the tire radial direction of the carcass,
The carcass is folded from the carcass main body portion extending in a toroidal shape between the pair of bead cores, from the inner side to the outer side in the tire width direction around the bead cores, and extends between the belt and the carcass main body portion. Having a carcass folded portion,
The region where the rubber gauge in the side portion is 0.5 mm to 2.0 mm includes the tire maximum width position, and extends over 30% of the tire cross-sectional height in the tire radial direction.
A pneumatic tire characterized by that.   The bead filler disposed outside the bead core in the tire radial direction and between the carcass main body portion and the carcass folded portion has a tire radial height of 20 mm or less, and the tire radial outer end is The pneumatic tire according to claim 1, wherein the pneumatic tire is located on the inner side in the tire radial direction from a separation point from the rim flange. The pneumatic tire according to claim 1 or 2, characterized in that the carcass ply reinforcing layer covering the tire maximum width position of the side portion is placed. Code of the carcass main body portion extends along the tire width direction, the code of the carcass folded section that extends to be inclined against the tire width direction is the extending direction of the code of the carcass main body portion The pneumatic tire according to any one of claims 1 to 3. The pneumatic tire according to any one of claims 1 to 4, wherein the cord of the carcass ply reinforcing layer extends meandering along the tire circumferential direction. The pneumatic tire according to any one of claims 1 to 5, wherein the belt includes a circumferential belt layer, and an upper end of the carcass ply reinforcing layer and an end of the circumferential belt are separated by 5 mm or more and 30 mm or less. The pneumatic tire according to any one of claims 1 to 6, wherein a lower end of the carcass ply reinforcement layer is located 10 mm or more and 30 mm or less from the tire maximum width position and on the inner side in the tire radial direction.

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