JP2012140070A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire that has reduced weight, and further strikes a balance between the driving stability and the ride quality at high dimension.SOLUTION: The pneumatic tire 1 includes: a tread section 2; a pair of side wall sections 3 and 3 which extend inward in a tire radial direction from both ends of the tread section 2; and bead sections 4 and 4 provided at inner sides of the side wall sections 3 and 3 respectively. The side wall section 3 is composed of an outer side wall section 3o which faces vehicle outside when mounted in a vehicle, and an inner side wall section 3i which faces a vehicle inside when mounted in the vehicle. In the outer side wall section 3o, a plurality of radial-direction grooves 11 are formed which extend in a tire-radial direction and disposed at intervals in a tire-circumferential direction, while in the inner side wall section 3i, at least one circumferential-direction groove 12 which extends in a tire circumferential direction is formed.

Description

  The present invention relates to a pneumatic tire in which handling stability and riding comfort are balanced at a high level while achieving weight reduction.

  Conventionally, in order to improve steering stability, it has been generally performed to increase the rigidity of the sidewall portion. In order to increase the rigidity of the sidewall portion, for example, it is effective to add a side reinforcing rubber layer or increase the thickness of the inner liner to increase the rubber thickness of the sidewall portion. Related technologies include the following.

JP 2006-219087 A

  However, tires such as those described above have problems that the fuel consumption performance deteriorates as the tire mass increases due to an increase in the rubber volume, and that the rigidity of the sidewall portion is excessively increased, and the ride comfort is likely to decrease. It was.

  The present invention has been devised in view of the actual situation as described above, and on the outer sidewall portion, a plurality of radial grooves extending in the tire radial direction and spaced apart in the tire circumferential direction are formed. Providing pneumatic tires that balance driving stability and riding comfort at a high level while reducing weight based on the formation of at least one circumferential groove extending in the tire circumferential direction in the sidewall. The main purpose is to do.

  The invention according to claim 1 of the present invention includes a tread portion, a pair of sidewall portions extending inward in the tire radial direction from both ends of the tread portion, and a bead portion provided inside each sidewall portion. The sidewall portion is composed of an outer sidewall portion that faces the outside of the vehicle when the vehicle is mounted, and an inner sidewall portion that faces the inner side of the vehicle when the vehicle is mounted, and the outer sidewall portion includes A plurality of radial grooves extending in the tire radial direction and spaced apart in the tire circumferential direction are formed, and at least one circumferential groove extending in the tire circumferential direction is formed in the inner sidewall portion. It is characterized by that.

  The invention according to claim 2 is provided with a carcass made of a carcass ply extending from the tread portion through the sidewall portion to the bead portion, and the circumferential groove and the radial groove extend through each sidewall portion. The pneumatic tire according to claim 1, wherein the pneumatic tire is formed on a rubber layer disposed inside the carcass ply.

  The invention according to claim 3 is the pneumatic tire according to claim 2, wherein the rubber layer is an inner liner made of air-impermeable rubber.

  In the invention according to claim 4, the maximum thickness of the inner liner is 2.5 to 6.0 mm, and the depths of the circumferential groove and the radial groove are 0.5 to 3.5 mm. A pneumatic tire according to claim 3.

  The invention according to claim 5 is the pneumatic tire according to claim 1, wherein the radial groove and the circumferential groove are formed on a tire outer surface side of each sidewall portion.

  In the present specification, unless otherwise specified, the size of each part of the tire is a value specified in a normal state with no load loaded with a normal rim and filled with a normal internal pressure.

  The “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based. For example, “Standard Rim” for JATMA and “Design Rim” for TRA. "If ETRTO," Measuring Rim ".

  Furthermore, “regular internal pressure” is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. “JAMATA” is the “highest air pressure”, TRA is the table “TIRE LOAD” The maximum value described in LIMITS AT VARIOUS COLD INFLATION PRESSURES is "INFLATION PRESSURE" if it is ETRTO, but it is uniformly 180 kPa if the tire is for passenger cars.

  The pneumatic tire of the present invention includes a tread portion, a pair of sidewall portions extending inward in the tire radial direction from both ends of the tread portion, and a bead portion provided inside each sidewall portion. The side wall portion includes an outer side wall portion that faces the outside of the vehicle when the vehicle is mounted, and an inner side wall portion that faces the inner side of the vehicle when the vehicle is mounted.

  The outer sidewall portion is formed with a plurality of radial grooves extending in the tire radial direction and spaced apart in the tire circumferential direction, while the inner sidewall portion has at least one circumferential groove extending in the tire circumferential direction. Directional grooves are formed.

  A large load acts on the outer side wall portion during turning, but the outer side wall portion can maintain a large vertical spring constant while reducing the weight by a radial groove, thereby improving steering stability. sell.

  On the other hand, the inner sidewall portion tends to have a high ground pressure when going straight. Such an inner side wall portion can reduce the longitudinal spring constant while reducing the weight by the circumferential groove, and can reduce its rigidity as compared with the outer side wall portion. Can be improved.

It is sectional drawing which shows the pneumatic tire of this embodiment. It is a fragmentary perspective view which shows the outer side wall part of FIG. It is a fragmentary perspective view which shows the inner side wall part of FIG. (A) is a side view which shows the radial direction groove | channel of other embodiment, (b) is a side view which shows the radial direction groove | channel of other embodiment. It is sectional drawing of a tire vulcanization metal mold | die. It is sectional drawing which shows the pneumatic tire of other embodiment. It is a fragmentary perspective view which shows the outer side wall part of FIG. It is a fragmentary perspective view which shows the inner side wall part of FIG.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, a pneumatic tire 1 according to the present embodiment (hereinafter sometimes simply referred to as “tire”) includes a tread portion 2 and a pair extending inward in the tire radial direction from both ends of the tread portion 2. The side wall portions 3 and 3 and the bead portion 4 provided inside each side wall portion 3 are provided, and the tire is configured as a passenger vehicle tire in which the mounting direction to the vehicle is specified. The direction of mounting on the vehicle is clearly indicated by letters (for example, “INSIDE” and / or “OUTSIDE”) on the sidewall portion 3 of the tire 1 (not shown).

  Further, the tire 1 includes a carcass 6 extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and a belt layer 7 disposed on the outer side in the tire radial direction of the carcass 6 and inside the tread portion 2. With

  The carcass 6 is composed of at least one carcass ply 6A, in this embodiment, one carcass ply 6A. The carcass ply 6A is folded back from the inner side to the outer side in the tire axial direction around the bead core 5 extending from the main body 6a and extending from the main body 6a to the bead core 5 of the bead part 4 through the sidewall part 3 and the bead part 4. And the folded portion 6b.

  Further, a bead apex 8 made of hard rubber extending from the bead core 5 to the outer side in the tire radial direction is disposed between the main body portion 6a and the folded portion 6b, and the bead portion 4 is appropriately reinforced.

  Further, the carcass ply 6A has carcass cords arranged at an angle of, for example, 80 to 90 degrees with respect to the tire equator C. As the carcass cord, for example, an organic fiber cord such as polyester, nylon, rayon, or aramid is suitably employed.

  The belt layer 7 includes at least two belt plies 7A, in which the belt cord is inclined with respect to the tire equator C at a small angle of, for example, 10 to 40 degrees, and in the present embodiment, the inner and outer two belt plies 7A, 7B is configured by superimposing the belt cords so that the belt cords cross each other. Steel cords are used for the belt cords of the present embodiment, but highly elastic organic fiber cords such as aramid and rayon can also be used as necessary.

  In the tire 1 of the present embodiment, when the mounting direction to the vehicle is specified, the sidewall portion 3 includes an outer sidewall portion 3o facing the vehicle outer side and an inner sidewall portion facing the vehicle inner side when the vehicle is mounted. 3i.

  In the present embodiment, as shown in FIGS. 1 and 2, a plurality of rubber layers 9 arranged on the inner side of the carcass ply 6 </ b> A of the outer side wall portion 3 o extend in the tire radial direction and are spaced in the tire circumferential direction. A radial groove 11 is formed. As shown in FIGS. 1 and 3, the rubber layer 9 of the inner sidewall portion 3i is formed with at least one circumferential groove 12 extending in the tire circumferential direction, in the present embodiment, three circumferential grooves 12.

  The outer side wall portion 3o is designed to reduce the tire weight by the radial groove 11, but the rib portion 13 between the radial grooves 11 and 11 suppresses the bending in the tire radial direction, and the longitudinal spring constant is reduced. growing. Thereby, as for the tire 1, the rigidity of the outer side wall part 3o is maintained moderately, and steering stability improves. In addition, in the tire on the outer side of the turn, the vertical spring constant of the outer side wall portion 3o where the load becomes the largest is increased, so that the steering stability can be reliably improved.

  On the other hand, the inner sidewall portion 3i is greatly reduced in weight in the tire radial direction by the circumferential groove 12 while being reduced in weight, and its longitudinal spring constant is reduced. As a result, the tire 1 can reduce the rigidity of the inner sidewall portion 3i as compared with the outer sidewall portion 3o, so that the riding comfort is further improved especially for a vehicle having a negative camber during straight running. improves. In addition, in the tire on the inside of the turn, the inner sidewall portion 3i flexes flexibly with respect to the lateral force from the road surface, and the ground contact surface of the tread portion 2 can be increased to exhibit a grip, further improving steering stability. Can improve.

  Furthermore, in the present embodiment, the radial grooves 11 and the circumferential grooves 12 are formed in the rubber layer 9 disposed on the inner side of the carcass ply 6A, so that the appearance of the tire 1 is not deteriorated.

As shown in FIG. 2, when the length L1 in the tire radial direction along the tire cavity surface is reduced, the radial groove 11 cannot be reduced in weight, and conversely, the length L1 is increased. Then, the rubber volume of the outer side wall portion 3o is excessively reduced, the steering stability is reduced,
Tire uniformity is likely to deteriorate, and there is a risk that conicity will increase. From this point of view, the length L1 is preferably 40% or more, more preferably 60% or more, and preferably 80% or less, more preferably 70% or less of the tire cross-section height H.

  Similarly, the width W1 in the tire circumferential direction of the radial groove 11 is preferably 10 mm or more, more preferably 14 mm or more, and preferably 20 mm or less, more preferably 18 mm or less. Further, the depth D1 of the radial groove 11 is preferably 0.5 mm or more, more preferably 2.0 mm or more, and preferably 3.5 mm or less, more preferably 3.0 mm or less.

  In addition, when the distance S1 between the radial grooves 11 and 11 adjacent to each other in the tire circumferential direction is small, the rubber volume of the rubber layer 9 is excessively reduced, and the distortion generated in the rib portion 13 between the adjacent radial grooves 11 and 11 is reduced. May cause damage such as cracks. On the contrary, if the interval S1 is increased, there is a possibility that weight reduction cannot be expected. From such a viewpoint, the interval S1 is preferably 15 mm or more, more preferably 17 mm or more, and preferably 25 mm or less, more preferably 21 mm or less. The interval S1 is measured at the center position 11c of the radial groove 11 in the tire radial direction.

  The radial groove 11 of the present embodiment is exemplified as extending along the tire radial direction, but may be inclined as shown in FIG. Such a radial groove 11 can slightly increase the longitudinal spring constant and improve the steering stability as compared with those extending along the tire radial direction.

  If the angle α1 of the radial groove 11 with respect to the tire radial direction is increased, the longitudinal spring constant may be excessively decreased, and the steering stability may be deteriorated. From such a viewpoint, the angle α1 is preferably 40 ° or less, and more preferably 30 ° or less.

  Furthermore, as shown in FIG. 4B, the radial groove 11 may include a plurality of types having different lengths L1 and widths W1. The radial groove 11 of the present embodiment includes a long radial groove 11A having a large length L1 and a width W1, and a short radial groove 11B having a small length L1 and a width W1, which are alternately arranged.

  It is preferable that the short radial groove 11B is arranged close to the outer side in the tire radial direction of the outer sidewall portion 3o. Such a short radial groove 11B can relieve the longitudinal spring constant centering on the outer side in the tire radial direction of the sidewall portion 3, so that the riding comfort can be improved while maintaining the steering stability. .

  As shown in FIG. 3, when the width W2 in the tire radial direction along the tire cavity surface is reduced, the circumferential groove 12 may not be able to sufficiently improve riding comfort by reducing the longitudinal spring constant. On the other hand, when the width W2 is increased, the rubber volume of the rubber layer 9 is excessively decreased, and the conicity may be increased. From such a viewpoint, the width W2 is preferably 4.0 mm or more, and more preferably 5.0 mm or more. Further, it is preferably 7.0 mm or less, and more preferably 6.0 mm or less.

  Similarly, the distance S2 between the circumferential grooves 12 adjacent to each other in the tire radial direction is preferably 10 mm or more, more preferably 11 mm or more, and preferably 15 mm or less, more preferably 14 mm or less. Further, the depth D2 of the circumferential groove 12 is preferably 0.5 mm or more, more preferably 2 mm or more, preferably 3.5 mm or less, more preferably 3 mm or less.

  Further, the number of the circumferential grooves 12 can be appropriately set as long as it is one or more, but if the number is small, the vertical spring constant may not be sufficiently reduced. On the other hand, if the number is large, the rubber volume is excessively reduced, and there is a possibility that damage such as cracks may occur. From such a viewpoint, the number is preferably 1 or more, more preferably 2 or more, and is preferably 5 or less, more preferably 4 or less.

  The rubber layer 9 is preferably made of an inner liner 10 made of air impermeable rubber. As a result, the tire 1 can be provided with the radial groove 11 and the circumferential groove 12 without adding a new rubber material, so that a reduction in riding comfort and a deterioration in fuel consumption performance associated with an increase in tire mass can be achieved. Can be prevented.

  As shown in FIG. 1, when the maximum thickness W3 of the inner liner 10 is small, the depths D1 and D2 of the radial groove 11 and the circumferential groove 12 cannot be sufficiently formed, and the steering stability performance. In addition, the ride comfort may not be improved sufficiently. On the other hand, even if the maximum thickness W3 is large, the rubber volume may increase excessively and the ride comfort and fuel consumption performance may deteriorate. From such a viewpoint, the maximum thickness W3 is preferably 2.5 mm or more, more preferably 3.0 mm or more, and preferably 6.0 mm or less, more preferably 5.0 mm or less.

A method for manufacturing the tire 1 having the radial grooves 11 and the circumferential grooves 12 as described above will be described.
In the manufacturing method of the present embodiment, as shown in FIG. 5, for example, a vulcanizing mold 16 having a cavity 16s that forms the outer surface of the raw tire 1L, and an inner liner 10 that forms the tire lumen surface of the raw tire 1L. A bladder 17 that presses is used. The bladder 17 is provided with a projection 18 obtained by inverting the radial groove 11 (not shown) and the circumferential groove 12. Such a bladder 17 can easily form the radial groove 11 and the circumferential groove 12 by pressing the tire lumen surface of the raw tire 1L during vulcanization molding. Needless to say, the radial groove 11 and the circumferential groove 12 may be processed after vulcanization molding, for example, without being limited to such a manufacturing method.

6, 7, and 8 show a tire 1 according to another embodiment of the present invention.
As shown in the figure, in the tire 1 of this embodiment, a radial groove 11 and a circumferential groove 12 are formed on the tire outer surface 21 side of each sidewall portion 3. Such a tire 1 can also achieve both steering stability and riding comfort while achieving weight reduction by the radial groove 11 and the circumferential groove 12.

  Furthermore, since the radial groove 11 and the circumferential groove 12 of the present embodiment are formed on the tire outer surface 21 side without being provided in the inner liner 10 as in the previous embodiment, the internal pressure retaining property is not impaired. In addition, the widths W1, W2, and the like of the radial groove 11 and the circumferential groove 12 are preferably set within the same range as in the previous embodiment.

  In order to manufacture the tire 1 having such radial grooves 11 and circumferential grooves 12, for example, the vulcanization mold 16 shown in FIG. A concave portion (not shown) obtained by inverting the radial groove 11 and the circumferential groove 12 shown in FIG. 6 is provided, and the green tire 1L can be easily formed by being pressed against the sidewall molding surface 22s by the bladder 17.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

Tires having the basic structure shown in FIG. 1 and having radial grooves and circumferential grooves shown in Table 1 were manufactured, and their performance was evaluated. For comparison, tires without comparative radial grooves and circumferential grooves (Comparative Example 1) and tires with increased outer side rubber volume (Comparative Example 2) were similarly tested. . The common specifications are as follows.
Tire size: 255 / 40R18
Rim size: 10JJ × 18
Tire cross-section height H: 60mm
The test method is as follows.

<Tire mass>
The mass per tire was measured. The results are displayed as an index with the mass of Comparative Example 1 as 100. The smaller the value, the better.

<Conicity>
The uniformity (CON) of 20 test tires was measured using a uniformity testing machine, and the standard deviation was obtained. The results are displayed as an index with Comparative Example 1 being 100 with respect to the reciprocal of each standard deviation. The larger the value, the better.

<Steering stability>
Each test tire is assembled on the above rim, filled with 190kPa internal pressure, mounted on all wheels of a four-wheel drive vehicle with a displacement of 2000cc, and run on a dry asphalt road test course with one driver on the wheel. The characteristics of handle response, rigidity, grip, etc. were evaluated by professional driver sensuality. The results are displayed as a score with the value of Comparative Example 1 being 100. The larger the value, the better.

<Ride comfort>
Each test tire was assembled on the rim under the above conditions and mounted on the vehicle, and was run on a stepped road, a Belgian road, and a Bitzmann road on a dry asphalt road surface. And, the sensation, push-up and dumping were comprehensively evaluated by the sensuality by professional drivers. The results are displayed as a score with the value of Comparative Example 1 being 100. The larger the value, the better.
The test results are shown in Table 1.

  As a result of the test, it was confirmed that the tires of the examples can achieve both high handling stability and ride comfort while reducing the weight.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 3 Side wall part 3o Outer side wall part 3i Inner side wall part 4 Bead part 11 Radial direction groove | channel 12 Circumferential direction groove | channel

Claims (5)

A pneumatic tire having a tread portion, a pair of sidewall portions extending inward in the tire radial direction from both ends of the tread portion, and a bead portion provided inside each sidewall portion,
The sidewall portion is composed of an outer sidewall portion facing the vehicle outer side when the vehicle is mounted, and an inner sidewall portion facing the vehicle inner side when the vehicle is mounted,
The outer sidewall portion is formed with a plurality of radial grooves extending in the tire radial direction and spaced apart in the tire circumferential direction,
The pneumatic tire according to claim 1, wherein at least one circumferential groove extending in the tire circumferential direction is formed in the inner sidewall portion. While having a carcass made of a carcass ply from the tread part through the sidewall part to the bead part,
2. The pneumatic tire according to claim 1, wherein the circumferential groove and the radial groove are formed in a rubber layer disposed inside a carcass ply extending through each sidewall portion.   The pneumatic tire according to claim 2, wherein the rubber layer is an inner liner made of air impermeable rubber.   The pneumatic tire according to claim 3, wherein the maximum thickness of the inner liner is 2.5 to 6.0 mm, and the depth of the circumferential groove and the radial groove is 0.5 to 3.5 mm.   The pneumatic tire according to claim 1, wherein the radial groove and the circumferential groove are formed on a tire outer surface side of each sidewall portion.

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