JP6075954B2 - Pneumatic radial tire - Google Patents

Description

  The present invention relates to a pneumatic radial tire.

In recent years, as the demand for lower fuel consumption of vehicles has increased, it has been required to reduce the rolling resistance of tires.
As a technique for reducing the rolling resistance value of the tire, for example, Patent Document 1 proposes that the loss tangent of the tread rubber be made small.
However, if the loss tangent of the tread rubber is made small, there is a problem that other performances of the tire such as the wear resistance of the tire are deteriorated.

It is also conceivable to reduce the weight of the tire and reduce rolling resistance by reducing the gauge thickness of the sidewall portion of the tire.
However, when the gauge thickness of the tire sidewall is reduced in the so-called low turn-up and high turn-up tires where the carcass folding end is not arranged from the belt end to the inside in the tire width direction, the rolling resistance value decreases. However, since the tire rigidity is reduced, there is a problem that steering stability is lowered.

JP-A-6-297911

  An object of the present invention is to provide a pneumatic radial tire that can ensure steering stability while reducing the rolling resistance value of the tire.

The present inventor has intensively studied to solve the above problems.
As a result, in the tire having a so-called envelope structure, a new finding has been obtained that the above-described problem can be advantageously solved by reducing the gauge thickness of the sidewall portion and making the tire an asymmetric shape.

The gist configuration of the present invention is as follows.
(1) In a pneumatic radial tire including a belt composed of at least one belt layer on a radially outer side of a carcass straddling a toroidal shape between a pair of bead cores,
The carcass extends from the carcass main body portion straddling between the pair of bead cores in a toroidal shape around the bead core from the inner side to the outer side in the tire width direction and extending between the belt and the carcass main body portion. Has a folded portion,
The region where the rubber gauge in the sidewall portion of the tire is 2 mm or less, including the tire maximum width portion, over 20% of the tire cross-section height,
In the tire width direction cross section, in a half part on the outer side of the vehicle when the vehicle is mounted when the tire center line that is perpendicular to the line connecting the centers of the pair of bead cores and that passes through the midpoint of the line segment is a boundary. The inner peripheral length, which is the distance from the intersection of the line segment and the tire inner surface along the inner surface of the tire to the intersection of the tire center line and the tire inner surface, is a half of the vehicle inner side when the vehicle is mounted In the inner surface of the tire, along the inner surface peripheral length which is the distance from the intersection of the line segment and the tire inner surface to the intersection of the tire center line and the tire inner surface,
The amount of overlap in the tire width direction between the carcass folded portion in the one half and the innermost belt layer in the tire radial direction among the belt layers is the carcass folded in the other half. Greater than the overlap amount in the tire width direction between the belt portion and the innermost belt layer in the tire radial direction of the belt layer,
Overlapping amount in the other half, Ri 10% to 80% der overlap amount in the half of the one,
The pneumatic radial tire according to claim 1, wherein the amount of overlap in the inner half of the vehicle when mounted on the vehicle is 2/3 of the amount of overlap in the outer half of the vehicle when mounted on the vehicle .

( 2 ) The overlap amount in the outer half of the vehicle when mounted on the vehicle and the inner half of the vehicle when mounted on the vehicle is 5 to 35% of the width in the tire width direction of the innermost belt layer. 1 ) A pneumatic radial tire described in 1 ).

( 3 ) The bead filler has a bead filler on the outer side in the tire radial direction of the bead core, and the height of the bead filler in the tire radial direction is 11 to 25% of the tire cross-sectional height, as described in (1) or (2) above. Pneumatic radial tire.

  ADVANTAGE OF THE INVENTION According to this invention, the pneumatic radial tire which can ensure steering stability can be provided, reducing the rolling resistance value of a tire.

1 is a cross-sectional view in the width direction of a tire according to an embodiment of the present invention. It is a figure for demonstrating the surface distortion of a sidewall part. It is sectional drawing of the width direction of the tire concerning a comparative example.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a sectional view in the tire width direction of a pneumatic radial tire (hereinafter referred to as a tire) according to an embodiment of the present invention.
FIG. 1 shows a tire when the tire is mounted on an applicable rim, filled with a prescribed internal pressure by JATMA or the like, and brought into a no-load state.
As shown in FIG. 1, the tire of this embodiment includes a belt 3 composed of at least one belt layer on the outer side in the tire radial direction of a carcass 2 straddling a toroidal shape between a pair of bead cores 1. The tire also includes a tread 4 on the outer side in the radial direction of the belt 3.
Here, the carcass 2 is folded between the pair of bead cores in a toroidal shape, the carcass main body 2a from the carcass main body 2a around the bead core 1 toward the outer side in the tire width direction, and the belt 3 and the carcass main body. It consists of a carcass folded-back portion 2b extending to the portion 2a.
In the illustrated example, the belt 3 includes two inclined belt layers 3a and 3b and a circumferential belt layer 3c disposed on the radially outer side of the inclined belt layer. In the illustrated example, the two inclined belt layers 3a and 3b are formed by covering a large number of cords extending obliquely with respect to the tire equatorial plane with rubber, and the cords cross each other between the layers. In the illustrated example, the circumferential belt layer 3c is formed by rubber-covering a cord extending substantially in the tire circumferential direction. The belt configuration of the present invention is not limited to the illustrated example.

Further, as shown in FIG. 1, the tire has a thin rubber gauge G in the sidewall portion 5. Specifically, in the sidewall portion 5, the region A where the rubber gauge G is 2 mm or less includes the tire maximum width portion B and extends over 20% of the tire cross-section height SH.
Here, the sidewall portion 5 refers to a range from the outer edge in the tire width direction of the tread surface to the separation point E from the rim flange of the bead portion.
Moreover, the rubber gauge G shall mean the shortest distance from the point on the outer side in the tire width direction of the cord of the carcass folded portion 2b to the surface of the sidewall portion.
The tire maximum width part means that when the tire is mounted on an applicable rim and filled with the prescribed internal pressure by JATMA or the like and is in a no-load state, the side surface of the tire, and convex parts such as letters are excluded, The maximum width in the tire width direction between the sidewall portions shall be said.

Furthermore, as shown in FIG. 1, in the tire width direction cross section, a straight line that is perpendicular to a line segment L connecting the centers of the pair of bead cores 1 and passes through the midpoint of this line segment is a tire center line C.
At this time, an intersection point Q between the tire center line C and the tire inner surface 6 from an intersection point P1 between the line segment L and the tire inner surface 6 along the tire inner surface 6 in one half portion with the tire center line C as a boundary. The inner peripheral length D1 that is the distance from the intersection P2 between the line segment L and the tire inner surface 6 along the tire inner surface 6 in the other half to the intersection Q between the tire center line C and the tire inner surface 6 Is longer than the inner peripheral length D2.
Hereinafter, the operation and effect when the tire according to the present embodiment is mounted on the vehicle such that the one half portion is on the vehicle outer side and the other half portion is on the vehicle inner side will be described.

According to the tire of the present embodiment, the carcass folded portion 2b has a so-called envelope structure that extends between the inclined belt layer 3a and the carcass main body portion 2a. Since the ply is arranged, the side cut durability against the curbstone or the like can be improved.
Here, in general, in the envelope structure, the rigidity of the sidewall portion is increased, so that the ride comfort is lowered. Further, when the rigidity of the sidewall portion is increased, the deformation of the sidewall portion is suppressed, the eccentric rigidity is increased, and the deformation of the tread rubber is increased, so that the rolling resistance is deteriorated.

  Therefore, in the tire of the present embodiment, the rubber gauge G in the sidewall portion is thin, and the range in which the rubber gauge G is thin is also a certain range or more with respect to the tire cross-section height, so that the tire weight is reduced, and the sidewall portion Thus, the rolling resistance value can be reduced and the riding comfort can be improved.

  Furthermore, by reducing the rubber gauge of the sidewall portion, the surface distortion at the time of loading can be reduced, so that the occurrence of cracks in the sidewall portion can be suppressed. That is, as shown in FIG. 2A, when the rubber gauge G of the sidewall portion is thick, the rubber is greatly deformed because the distance from the bending center M to the sidewall portion surface is long. On the other hand, as shown in FIG. 2 (b), when the rubber gauge G of the sidewall portion is thin, the distance from the bending center M to the sidewall portion surface is short, so the deformation of the rubber is small and the generation of cracks is suppressed. .

  Furthermore, in the tire according to the present embodiment, the inner peripheral length on the vehicle mounting outer side is larger than the inner peripheral length on the vehicle mounting inner side, so that conicity is generated. For this reason, in combination with ensuring the rigidity of the tire with the envelope structure, the steering stability of the tire can be ensured.

In the present invention, the rubber gauge G of the sidewall portion is preferably 0.5 mm or more. This is to ensure the rigidity of the tire.
The range where the rubber gauge G is 0.5 mm to 2 mm is preferably set to 60% or less of the tire cross-section height in consideration of the outer shape of the tire.

Here, in the present invention, the overlap amount w1 in the tire width direction between the carcass folded portion 2b in one half and the belt layer 3a on the innermost side in the tire radial direction among the belt layers is the other half. The overlap amount w2 in the tire width direction between the carcass folded portion 2b and the innermost belt layer 3a is larger .
The operation and effect will be described for the case where the tire is mounted on the vehicle so that the one half is on the vehicle outer side and the other half is on the vehicle inner side.
As described above, by varying the overlap amount with the tire center line as a boundary, the ground contact shape can be made different between the vehicle outer side and the inner side. Thereby, combined with the effect of the asymmetry of the inner peripheral length described above, further steering stability can be ensured.

The overlap amount w2 in the one half and the other half is preferably 5 to 35% of the width w3 in the tire width direction of the innermost belt layer 3a.
By setting it to 5% or more, separation at the folded end 2b and the belt end can be suppressed, while by setting it to 35% or less, an increase in tire weight can be suppressed. Specifically, the folded end and the belt end are preferably separated by 5 mm or more.
Furthermore, the overlap amount w2 in the other half is 10 to 80% of the overlap amount w1 in the other half . By setting the ratio to 10% or more, separation at the folded end 2b and the belt end in the other half can be suppressed, while by setting the ratio to 80% or less, the above-described ground shape asymmetry can be suppressed. The steering stability can be further ensured by further increasing the steering angle .

Further, in the present invention, as shown in FIG. 1, the bead core 7 has a bead filler 7 on the outer side in the tire radial direction, and the height h of the bead filler 8 in the tire radial direction is 11 of the tire cross-section height SH. It is preferably ˜25%. That is, it is possible to reduce the rolling resistance value by reducing the bead filler while securing the rigidity of the tire by the envelope structure.
Specifically, by setting it to 11% or more, the rigidity of the bead portion can be secured, while by setting it to 25% or less, the tire can be reduced in weight and the rolling resistance value can be further reduced. Because.
As shown in FIG. 1, the height h of the bead filler refers to the distance in the tire radial direction from the bead toe to the outer end in the tire radial direction of the bead filler.

In order to confirm the effect of the present invention, tires according to Reference Examples 1 and 2, Invention Examples 3 to 4 and Comparative Examples 1 and 2 were manufactured as trials, and tests for evaluating the performance of the tires were performed.
Here, the tires according to Reference Examples 1 to 2 and Invention Examples 3 to 4 have a carcass having a so-called envelope structure, the rubber gauge G of the sidewall portion is 2 mm or less, and the inner peripheral length is the boundary of the tire center line. The halves are different from each other.
The tire according to Comparative Example 1 has a carcass having a so-called high turn-up structure, the rubber gauge of the sidewall portion is more than 2 mm, and the inner peripheral length is the same in the halves with the tire center line as a boundary. There is something.
Further, the tire according to Comparative Example 2 has a carcass having a so-called envelope structure, the rubber gauge of the sidewall portion is more than 2 mm, and the inner peripheral length is the same in the halves with the tire center line as a boundary. It is.
The specifications of each tire are shown in Table 1 below. In the following evaluation, the inventive example was mounted with the longer inner peripheral as the vehicle outer side.

Each of the above tires having a tire size of 195 / 65R15 was incorporated into a rim of 15-6J, and the internal pressure was set to 180 kPa, and the following evaluation was performed.
<Rectangle ratio>
In the ground contact shape with a load of 5.3 kN applied to each tire, the ratio a / b between the circumferential length a at the tire center line and the circumferential length b at a position 80% of the ground contact width is Obtained as a rectangular ratio. Note that the INDEX display is made with Comparative Example 1 being 100.
<Rolling resistance value>
Each tire was loaded with a load of 5.3 kN, a drum test was performed, and the rolling resistance value of the axle was obtained. An index evaluation was performed with Comparative Example 1 taken as 100, and a larger value indicates a smaller rolling resistance.
<Ride comfort>
Each tire was mounted on a vehicle, and the vehicle was run on a test course, and a driver's sensitivity test was performed. Index evaluation is performed when Comparative Example 1 is set to 100, and a larger numerical value indicates better ride comfort.
<Steering stability>
Each tire was mounted on a vehicle, and the vehicle was run on a test course, and a driver's sensitivity test was performed. Index evaluation is performed when Comparative Example 1 is set to 100, and a larger numerical value indicates better ride comfort.
The evaluation results are shown in Table 1 below.

As shown in Table 1, it can be seen that the tires according to the reference examples and the invention examples can ensure the steering stability while reducing the rolling resistance value.

DESCRIPTION OF SYMBOLS 1 Bead core 2 Carcass 2a Carcass main-body part 2b Carcass folding | turning part 3 Belt 3a Inclined belt layer 3b Inclined belt layer 3c Circumferential belt layer 4 Tread 5 Side wall part 6 Tire inner surface 7 Bead filler A Area B Tire maximum width part C Tire centerline D1 , D2 Internal peripheral length E Separation point G Rubber gauge P1, P2 Intersection point Q Intersection point L Segment M Bending center w1, w2 Overlap amount

Claims (3)

In a pneumatic radial tire including a belt composed of at least one belt layer on the outer side in the tire radial direction of the carcass straddling a toroidal shape between a pair of bead cores,
The carcass extends from the carcass main body portion straddling between the pair of bead cores in a toroidal shape around the bead core from the inner side to the outer side in the tire width direction and extending between the belt and the carcass main body portion. Has a folded portion,
The region where the rubber gauge in the sidewall portion of the tire is 2 mm or less, including the tire maximum width portion, over 20% of the tire cross-section height,
In the tire width direction cross section, in a half part on the outer side of the vehicle when the vehicle is mounted when the tire center line that is perpendicular to the line connecting the centers of the pair of bead cores and that passes through the midpoint of the line segment is a boundary. The inner peripheral length, which is the distance from the intersection of the line segment and the tire inner surface along the inner surface of the tire to the intersection of the tire center line and the tire inner surface, is a half of the vehicle inner side when the vehicle is mounted In the inner surface of the tire, along the inner surface peripheral length which is the distance from the intersection of the line segment and the tire inner surface to the intersection of the tire center line and the tire inner surface,
The overlap amount in the tire width direction between the carcass folded-back portion in the outer half of the vehicle when mounted on the vehicle and the innermost belt layer in the tire radial direction of the belt layer is the inner side of the vehicle when mounted on the vehicle. More than the overlap amount in the tire width direction between the carcass folded portion in the half portion and the innermost belt layer in the tire radial direction among the belt layers,
Overlapping amount of the vehicle mounting when half of the vehicle inner side, Ri 10% to 80% der overlap amount in the vehicle when mounted outboard halves,
The pneumatic radial tire according to claim 1, wherein the amount of overlap in the inner half of the vehicle when mounted on the vehicle is 2/3 of the amount of overlap in the outer half of the vehicle when mounted on the vehicle .   2. The overlap amount between the outer half of the vehicle when mounted on the vehicle and the inner half of the vehicle when mounted with the vehicle is 5 to 35% of the width in the tire width direction of the innermost belt layer. Pneumatic radial tires.   The pneumatic radial tire according to claim 1 or 2, wherein a bead filler is provided on an outer side of the bead core in a tire radial direction, and a height of the bead filler in a tire radial direction is 11 to 25% of a tire cross-sectional height.

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