JP5391948B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire in which the groove area ratio in the tread portion is different from each other on both sides of the tire equator, and more specifically, it achieves both drainage performance and steering stability without deteriorating high-speed durability and uniformity. The present invention relates to a pneumatic tire.

  In designing a tread pattern for a pneumatic tire, for example, an asymmetric tread pattern in which the groove area ratio of the tread portion is different from each other on both sides of the tire equator may be formed in order to achieve both drainage performance and steering stability. . However, a pneumatic tire having such an asymmetric tread pattern has a drawback that due to non-uniform rigidity of the tread portion, a proper inflation shape cannot be obtained and a non-uniform grounding shape tends to occur. . Further, in a pneumatic tire having an asymmetric tread pattern, when the groove area ratio is greatly different between the vehicle inner region and the vehicle outer region when the vehicle is mounted, the conicity takes a large value and there is a concern that the steering wheel flow may occur. . Therefore, there is a problem that it is difficult to obtain the required performance improvement effect.

  As a countermeasure, it has been proposed to make the rigidity of the tread portion uniform based on the arrangement of the belt cover layer arranged on the outer peripheral side of the belt layer, the setting of the tension, and the like (for example, see Patent Documents 1 and 2). . More specifically, in these proposals, when the groove area ratio of the tread portion is different on both sides of the tire equator, the winding density and tension of the belt cover layer are relatively high in the region where the groove area ratio is relatively large. doing.

  However, the method as described above has a relatively low restraint force due to the belt cover layer in the region where the groove area ratio is small, i.e., where the rubber volume of the tread portion is large and heat generation due to hysteresis loss is large. At present, it is difficult to adopt pneumatic tires that require high-speed durability at high speeds such as the Y range.

JP-A-2002-337510 JP 2006-213278 A

  An object of the present invention is to provide a pneumatic tire that can achieve both drainage performance and steering stability without deteriorating high-speed durability and uniformity.

  In order to achieve the above object, a pneumatic tire according to the present invention has at least one carcass layer mounted between a pair of bead portions, and the carcass layer is disposed around a pair of bead cores disposed in the bead portion. Winding from the inside of the tire to the outside, at least two belt layers including reinforcing cords inclined with respect to the tire circumferential direction are arranged on the outer circumferential side of the carcass layer in the tread portion, and wound around the outer circumferential side of these belt layers in the tire circumferential direction. In the pneumatic tire in which the belt cover layer including the rotated reinforcing cord is disposed and the groove area ratio in the tread portion is different from each other on both sides of the tire equator, the carcass layer on the side where the groove area ratio is large The maximum winding height is made larger than the maximum winding height of the carcass layer on the side where the groove area ratio is small, and the maximum winding height It is characterized in that the difference was more than 20% of the tire section height SH.

  In the present invention, in the pneumatic tire in which the groove area ratio of the tread portion is different from each other on both sides of the tire equator and the drainage performance and the steering stability are compatible based on the setting of the groove area ratio, the groove area ratio The maximum winding height of the carcass layer on the side with the larger groove area is made larger than the maximum winding height of the carcass layer on the side with the smaller groove area ratio, and the share of the internal pressure by the carcass layer is intentionally different on both sides of the tire equator. This offsets the difference in rigidity due to the groove area ratio of the tread part and optimizes the rigidity of the entire tire, so it is possible to suppress deterioration of conicity and to prevent the occurrence of steering wheel flow. Can do. In addition, in the present invention, the restraining force by the belt cover layer is relatively low in the region where the groove area ratio of the tread portion is small, that is, in the region where the rubber volume of the tread portion is large and heat generation due to hysteresis loss is large. Therefore, there is no deterioration in high-speed durability.

  In the present invention, the difference in the maximum hoisting height is set to 50% or more of the tire cross-section height SH, while the winding density of the belt cover layer is made different on both sides of the tire equator so that the groove area ratio is smaller. The winding density of the belt cover layer is preferably increased by 40% at the maximum with respect to the winding density of the belt cover layer on the side where the groove area ratio is large. In other words, the wet density improved based on the setting of the groove area ratio by excessively increasing the difference in maximum winding height and relatively increasing the winding density of the belt cover layer on the side where the groove area ratio is small. The effect of improving high-speed durability can be obtained without impairing performance or steering stability.

  Further, the winding portion on the side where the maximum winding height of the carcass layer is large is extended to a position overlapping with the belt layer, and the overlapping width between the winding portion and the belt layer is 3% or more of the maximum width of the belt layer, more preferably 5% to 25% is preferable. Thereby, the contact pressure distribution in the tread portion can be made uniform, and the merit by the asymmetric tread pattern can be obtained more effectively.

  For pneumatic tires with a specified tire front and back mounting direction when the vehicle is mounted, a groove pattern that is asymmetrical across the tire equator is formed in the tread, and the groove area ratio from the tire equator of the tread to the area outside the vehicle Is set to 20% to 30%, the groove area ratio of the vehicle inner area from the tire equator of the tread portion is set to 25% to 40%, and the groove area ratio of the vehicle inner area is larger than the groove area ratio of the vehicle outer area. It is preferable to do. That is, by making the groove area ratio of the vehicle outer area smaller than the groove area ratio of the vehicle inner area, it is possible to improve the stability during cornering, particularly the stability during limit driving.

  The volume of the pair of bead fillers arranged on the outer periphery of the pair of bead cores is different from each other, and the volume of the bead filler on the side where the maximum winding height of the carcass layer is large is set to the volume of the bead filler on the side where the maximum winding height of the carcass layer is small. It is preferable to make it smaller than the volume. When the maximum winding height of the carcass layer on the side where the groove area ratio is large is relatively increased, uniformity such as radial force variation (RFV) and radial run-out (RRO) deteriorates. Although there is a tendency, deterioration of uniformity can be suppressed by relatively reducing the volume of the bead filler on the side where the maximum winding height of the carcass layer is large.

  In the present invention, the groove area ratio is the ratio (%) of the groove area in the ground contact area to the area of the ground contact area of the tread portion measured under the tire static load radius measurement conditions defined by the standard on which the tire is based. Thus, it is obtained for each region on both sides of the tire equator.

It is meridian sectional drawing which shows the pneumatic tire which consists of embodiment of this invention. It is a top view which shows the tread pattern of the pneumatic tire which consists of embodiment of this invention. It is meridian sectional drawing which shows the pneumatic tire which consists of other embodiment of this invention.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows a pneumatic tire according to an embodiment of the present invention. This pneumatic tire is a tire in which the mounting direction of the tire front and back when the vehicle is mounted is designated. In FIG. 1, IN is the inside of the vehicle when the vehicle is mounted, and OUT is the outside of the vehicle when the vehicle is mounted.

  In FIG. 1, 1 is a tread portion, 2 is a sidewall portion, and 3 is a bead portion. As shown in FIG. 1, a single carcass layer 4 including a plurality of aligned reinforcing cords is mounted between a pair of bead portions 3 and 3, and the carcass layer 4 is attached to each bead portion 3. The bead core 5 is wound from the inner side of the tire to the outer side. The cord angle of the carcass layer 4 with respect to the tire circumferential direction is set in a range of 80 ° to 90 °. A bead filler 6 is disposed on each bead core 5, and the bead filler 6 is sandwiched between the main body portion 4 m of the carcass layer 4 and the winding portions 4 i and 4 o. The winding portions 4i and 4o of the carcass layer 4 have different winding heights, and the winding portion 4i on the vehicle inner side is higher than the winding portion 4o on the vehicle outer side.

  On the other hand, two belt layers 7 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. These belt layers 7 include a plurality of reinforcing cords inclined with respect to the tire circumferential direction, and are arranged so that the reinforcing cords are inclined with respect to each other between the layers. The cord angle of the belt layer 7 with respect to the tire circumferential direction is set in a range of 20 ° to 35 °. Further, a belt cover layer 8 including at least one reinforcing cord oriented in the tire circumferential direction is embedded on the outer peripheral side of the belt layer 7. The belt cover layer 8 has a jointless structure in which a strip material formed by rubber-covering at least one reinforcing cord is spirally wound in the tire circumferential direction. The cord angle of the belt cover layer 8 with respect to the tire circumferential direction is 5 ° or less, more preferably 3 ° or less.

  FIG. 2 shows a tread pattern of a pneumatic tire according to an embodiment of the present invention. In FIG. 2, CL is a tire equator. As shown in FIG. 2, a plurality of main grooves 9 extending in the tire circumferential direction are formed in the tread portion 1. The groove width of the main groove 9 is relatively larger in the region inside the vehicle from the tire equator CL than in the region outside the vehicle from the tire equator CL. A plurality of land portions 10, 20, 30, 40, 50 are partitioned by these main grooves 9 from the outside of the vehicle toward the inside of the vehicle.

  A plurality of lug grooves 11 extending in the tire width direction and not communicating with the main groove 9 are formed in the land portion 10 located on the outermost side of the vehicle. A plurality of cutout grooves 21 extending in the tire width direction are formed in the land portion 20. The land portion 30 located on the tire equator CL is formed with a plurality of curved grooves 31 that extend while being curved in the tire circumferential direction. The land portion 40 extends in the tire circumferential direction and includes the land portion 40. A plurality of crossing inclined grooves 41 and a plurality of cutout grooves 42 extending in the tire width direction are alternately formed in the tire circumferential direction. A plurality of lug grooves 51 that extend in the tire width direction and communicate with the main groove 9 are formed in the land portion 50 located on the innermost side of the vehicle.

  In the pneumatic tire described above, an asymmetric groove pattern is formed on the tread portion 1 with the tire equator CL interposed therebetween, and as a result, the groove area ratios in the tread portion 1 are different from each other on both sides of the tire equator CL. More specifically, the groove area ratio from the tire equator CL of the tread portion 1 to the region outside the vehicle is set to a range of 20% to 30%, and the groove area ratio from the tire equator CL of the tread portion 1 to the region inside the vehicle is set. Is set in the range of 25% to 40%, and the groove area ratio in the vehicle inner region is larger than the groove area ratio in the vehicle outer region.

  By setting the groove area ratios of the regions on both sides of the tire equator CL of the tread portion 1 within the above range, it becomes possible to achieve both drainage and steering stability based on the setting of the groove area ratio. In particular, the area outside the vehicle from the tire equator CL of the tread portion 1 has a relatively small groove area ratio, which contributes to improvement in steering stability (particularly stability during turning), and the tire equator CL of the tread portion 1. Therefore, the area inside the vehicle contributes to the improvement of drainage because the groove area ratio is relatively large. If these groove area ratios are too large, the steering stability is lowered, whereas if it is too small, the drainage performance is lowered.

  In the pneumatic tire, as shown in FIG. 1, the maximum hoisting height of the carcass layer 4 on the side where the groove area ratio is large (in the present embodiment, the vehicle inner side) is the side where the groove area ratio is small (in the present embodiment, the vehicle It is larger than the maximum hoisting height of the carcass layer 4 on the outer side, and the difference D of the maximum hoisting height is set to 20% or more of the tire cross-section height SH. Here, the maximum winding height of the carcass layer 4 means the height in the tire radial direction from the bead heel position serving as a reference for the tire cross-section height SH to the end of the carcass layer 4, and there are a plurality of carcass layers 4. If so, it is the maximum value.

  In the pneumatic tire in which the groove area ratio of the tread portion 1 is different from each other on both sides of the tire equator CL as described above, and both drainage performance and steering stability are achieved based on the setting of the groove area ratio, The maximum winding height of the carcass layer 4 on the side where the area ratio is large is made larger than the maximum winding height of the carcass layer 4 on the side where the groove area ratio is small, and the share of the internal pressure by the carcass layer 4 is on both sides of the tire equator. By intentionally differing, the rigidity difference resulting from the groove area ratio of the tread portion 1 can be offset, and the rigidity of the entire tire can be optimized. As a result, deterioration of conicity can be suppressed, and furthermore, the occurrence of handle flow can be prevented.

  In the pneumatic tire described above, the restraint force by the belt cover layer is relatively low in a region where the groove area ratio of the tread portion is small, that is, in a region where the rubber volume of the tread portion is large and heat generation due to hysteresis loss is large. Therefore, the high-speed durability is not deteriorated.

  In the pneumatic tire described above, the maximum winding height difference D is set to 50% or more of the tire cross-section height SH, while the winding density of the belt cover layer 8 is made different on both sides of the tire equator CL so that the groove area ratio is The winding density of the belt cover layer 8 on the small side may be increased by 40% at the maximum with respect to the winding density of the belt cover layer 8 on the side where the groove area ratio is large. Here, the winding density of the belt cover layer 8 means the density of the reinforcing cord of the belt cover layer 8 in each region on both sides of the tire equator CL. The density of the reinforcing cord of the belt cover layer 8 is specified based on the sum of the cross-sectional areas of the reinforcing cords of the belt cover layer 8 existing in the respective regions on both sides of the tire equator CL. When the thickness of the reinforcement cord is constant, the reinforcement cord is specified based on the number of reinforcement cords of the belt cover layer 8 present in each region on both sides of the tire equator CL.

  In general, the portion of the tread portion 1 on the side where the groove area ratio is small has a large rubber volume and tends to generate heat, which is disadvantageous in terms of high-speed durability. Therefore, the groove area ratio is set by relatively increasing the winding density of the belt cover layer 8 on the side where the groove area ratio is small while excessively increasing the maximum winding height difference D of the carcass layer 4. The improvement effect of high-speed durability can be obtained without impairing the improved wet performance and steering stability.

  FIG. 3 shows a pneumatic tire according to another embodiment of the present invention. This pneumatic tire is a tire in which the mounting direction of the tire front and back when the vehicle is mounted is designated. In FIG. 3, IN is the inside of the vehicle when the vehicle is mounted, and OUT is the outside of the vehicle when the vehicle is mounted. In addition, the same code | symbol is attached | subjected to the same thing as FIG. 1, and detailed description of the part is abbreviate | omitted.

  In FIG. 3, the winding portion 4 i on the side where the maximum winding height of the carcass layer 4 is large (in the vehicle inside in this embodiment) extends to a position overlapping the belt layer 7, and the winding portion 4 i overlaps with the belt layer 7. The width Wi is set to 3% or more of the maximum width Wb of the belt layer 7, more preferably in the range of 5% to 25%.

  Thus, by extending the winding portion 4i on the side where the maximum winding height of the carcass layer 4 is large to a position where it overlaps with the belt layer 7, the rigidity difference caused by the groove area ratio of the tread portion 1 is effectively offset. The contact pressure distribution in the tread portion 1 can be made uniform. As a result, the merit by the asymmetric tread pattern of achieving both drainage performance and steering stability can be obtained more effectively. Here, if the overlap width Wi of the winding portion 4i of the carcass layer 4 and the belt layer 7 is too small, the effect of reducing the rigidity difference of the tread portion 1 is reduced, and conversely if it is too large, the increase in material cost and mass is remarkable. become.

  In each of the above-described embodiments, a pair of bead fillers 6 are arranged on the outer periphery of the pair of bead cores 5. The volume of these bead fillers 6 is different from each other, and the maximum winding height of the carcass layer 4 is large. The volume of the bead filler 6i (inside the vehicle in each embodiment) may be smaller than the volume of the bead filler 6o on the side where the maximum winding height of the carcass layer 4 is small (outside the vehicle in each embodiment). When the maximum winding height of the carcass layer 4 on the side where the groove area ratio is large is relatively increased, the uniformity of radial force variation (RFV), radial run-out (RRO), etc. deteriorates. However, the volume of the bead filler 6i on the side where the maximum winding height of the carcass layer 4 is large, that is, on the side where the vertical spring based on the winding portion 4i of the carcass layer 4 is large is relatively small, thereby reducing the uniformity. Can be prevented. From the relationship between mass balance and cost and effect, it is desirable that the volume of the larger bead filler 6o is 115% at maximum with respect to the volume of the smaller bead filler 6i.

  In the above-described embodiment, the pneumatic tire in which the mounting direction of the tire front and back when the vehicle is mounted is described. However, the present invention does not specify the mounting direction of the tire front and back when the vehicle is mounted. The present invention can also be applied to pneumatic tires having different area ratios on both sides of the tire equator. In such a case, the maximum winding height of the carcass layer on the side with a larger groove area ratio may be made larger than the maximum winding height of the carcass layer on the side with a smaller groove area ratio.

  In a pneumatic tire having a tire size of 295 / 35R21 and a direction in which the front and back of the tire are mounted when the vehicle is mounted, a carcass layer is mounted between a pair of bead portions, and the carcass layer is disposed on the bead portion. Two belt layers including reinforcing cords which are wound around the pair of bead cores from the inner side of the tire to the outer side and are inclined with respect to the tire circumferential direction are disposed on the outer peripheral side of the carcass layer in the tread portion. A belt cover layer including a reinforcing cord wound in the tire circumferential direction is arranged on the side, and the groove area ratio in the tread portion is made different on both sides of the tire equator so that the maximum carcass layer on the side where the groove area ratio is large The tires of Examples 1 to 5 were manufactured in which the winding height was larger than the maximum winding height of the carcass layer on the side where the groove area ratio was small.

  Regarding the tires of Examples 1 to 5, the ratio of the difference between the maximum winding height of the carcass layer on the side where the groove area ratio is large and the maximum winding height of the carcass layer on the side where the groove area ratio is small to the tire cross-section height SH (Referred to as “the ratio of the difference in maximum winding height”), the ratio of the winding density of the belt cover layer on the side with a small groove area ratio to the winding density of the belt cover layer on the side with a large groove area ratio (“belt cover The ratio of the winding density of the layer ”), the ratio of the overlapping width of the winding portion on the side where the maximum winding height of the carcass layer is large and the belt layer to the maximum belt width (referred to as the“ ratio of the overlapping width of the winding portion ”) Carcass layer maximum winding with respect to the volume of the bead filler on the side where the maximum winding height of the carcass layer is larger, Lower height of the volume of the small side of the bead filler ratio (called "ratio of bead filler volume") was set as shown in Table 1.

  For comparison, a comparative example having the same structure as in Example 1 except that the groove area ratio is the same on the vehicle outer side and the vehicle inner side, and the maximum winding height of the carcass layer is the same on the vehicle outer side and the vehicle inner side. 1 and Comparative Example 2 having the same structure as Example 1 except that the maximum winding height of the carcass layer was made the same on the vehicle outer side and the vehicle inner side.

  About the test tire which consists of Comparative Examples 1 and 2 mentioned above and Examples 1-5, wet braking performance, steering stability, high-speed durability, and uniformity were evaluated by the following test method, and the results are also shown in Table 1. It was.

Wet braking performance:
The test tire was fitted to a wheel with a rim size of 21 × 10.5J, mounted on a test vehicle with an air pressure of 260 kPa, braked from a traveling state at a speed of 100 km / h on a test course consisting of a wet road surface, and the braking distance was measured. . The evaluation results are shown as an index with the comparative example 2 being 100, using the reciprocal of the measured value. A larger index value means better wet braking performance.

Steering stability:
The test tire was fitted to a wheel having a rim size of 21 × 10.5 J, mounted on a test vehicle with an air pressure of 260 kPa, and sensory evaluation was performed by a test driver using a test code formed of a dry road surface. The evaluation results are indicated by an index with Comparative Example 2 as 100. The larger the index value, the better the steering stability on the dry road surface.

High speed durability:
The test tire is mounted on a drum testing machine, the load is 0.68 times the maximum load capacity, the air pressure is 360 kPa, and the vehicle runs under the high-speed durability test conditions specified by ECE R30 up to a speed of 290 km / h. Stepping up by 10 km / h every 10 minutes, the running time until the tire broke was measured. The evaluation results are indicated by an index with Comparative Example 2 as 100. It means that high speed durability is excellent, so that this index value is large.

Uniformity:
The test tire was fitted to a wheel with a rim size of 21 × 10.5 J, and the radial force variation (RFV) and the conicity (CON) were measured with a uniformity measurement test apparatus at an air pressure of 200 kPa. However, the measurement conditions conformed to the JASO standard.

  As shown in Table 1, the tire of Comparative Example 2 employs an asymmetric tread pattern, and the groove area ratio in the vehicle inner region is larger than the groove area ratio in the vehicle outer region. Compared to, it was possible to improve steering stability while maintaining wet braking performance. However, in the tire of Comparative Example 2, the conicity deteriorated due to the asymmetric tread pattern.

  On the other hand, in the tires of Examples 1 to 5, it is possible to obtain wet braking performance and steering stability equal to or higher than those of Comparative Example 2 while maintaining good uniformity represented by conicity and radial force variation. did it. In the tires of Examples 1 to 5, good results were also obtained with respect to high-speed durability.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 4m Body part 4i, 4o Roll-up part 5 Bead core 6 Bead filler 7 Belt layer 8 Belt cover layer 9 Main groove

Claims (6)

  At least one carcass layer is mounted between the pair of bead portions, and the carcass layer is wound from the inside of the tire to the outside around the pair of bead cores arranged in the bead portion, and the outer periphery side of the carcass layer in the tread portion At least two belt layers including reinforcing cords inclined with respect to the tire circumferential direction are disposed, and a belt cover layer including reinforcing cords wound in the tire circumferential direction is disposed on the outer peripheral side of these belt layers, In a pneumatic tire in which the groove area ratio in the tread portion is different from each other on both sides of the tire equator, the maximum winding height of the carcass layer on the side where the groove area ratio is large is the side where the groove area ratio is small. It is larger than the maximum hoisting height of the carcass layer, and the difference in the maximum hoisting height is 20% or more of the tire cross-section height SH. Pneumatic tire to be.   While the difference in the maximum hoisting height is 50% or more of the tire cross-section height SH, the winding density of the belt cover layer is made different on both sides of the tire equator, and the belt on the side where the groove area ratio is small 2. The pneumatic tire according to claim 1, wherein the winding density of the cover layer is increased by 40% at maximum with respect to the winding density of the belt cover layer on the side where the groove area ratio is large.   The winding portion on the side where the maximum winding height of the carcass layer is large is extended to a position overlapping the belt layer, and the overlapping width of the winding portion and the belt layer is set to 3% or more of the maximum width of the belt layer. The pneumatic tire according to claim 1 or 2, characterized in that.   The pneumatic tire according to claim 3, wherein the overlap width between the rolled-up portion of the carcass layer and the belt layer is 5% to 25% of the maximum width of the belt layer.   A pneumatic tire in which the mounting direction of the front and back of the tire when the vehicle is mounted is designated, and a groove pattern that is asymmetric with respect to the tire equator is formed in the tread portion, and a region outside the vehicle from the tire equator of the tread portion is formed. The groove area ratio is set to 20% to 30%, the groove area ratio in the vehicle inner area from the tire equator of the tread portion is set to 25% to 40%, and the groove area ratio in the vehicle inner area is set to the area outside the vehicle. The pneumatic tire according to claim 1, wherein the pneumatic tire is larger than a groove area ratio.   The volume of the pair of bead fillers arranged on the outer periphery of the pair of bead cores is different from each other, and the volume of the bead filler on the side where the maximum winding height of the carcass layer is large is set to the side where the maximum winding height of the carcass layer is small The pneumatic tire according to any one of claims 1 to 5, wherein the volume is smaller than the volume of the bead filler.