JP6593058B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire for icy and snowy roads, and more particularly to a pneumatic tire that can increase snow column shear force and effectively improve performance on snow.

  In a pneumatic tire for icy and snowy roads typified by studless tires, a plurality of circumferential grooves extending in the tire circumferential direction and a plurality of lug grooves extending in the tire width direction are formed in the tread portion, A plurality of blocks are defined by these circumferential grooves and lug grooves. In addition, a plurality of sipes are formed in each block, and the on-ice performance and on-snow performance are enhanced by the edge effect of these sipes (see, for example, Patent Documents 1 to 3).

  The pneumatic tire for an icy and snowy road constructed in this way generates driving force and braking force during running on snow based on the shearing force of the snow column formed in the groove when the snow is stepped and hardened. . Therefore, in order to improve the performance on snow, it is effective to increase the snow column shear force generated when traveling on snow. Generally, increasing the groove depth, groove width, and groove area in the tread portion increases the snow column shear force.

  However, in view of tire performance other than on-snow performance, the groove depth, groove width, and groove area are naturally limited, so there is a limit to improving snow performance based on these factors.

JP 2014-94601 A JP 2014-108653 A JP 2014-172484 A

  An object of the present invention is to provide a pneumatic tire capable of increasing snow column shear force and effectively improving performance on snow.

In order to achieve the above object, a pneumatic tire according to the present invention includes a tread portion that extends in the tire circumferential direction and has an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and these sidewall portions. In a pneumatic tire provided with a pair of bead portions arranged on the inner side in the tire radial direction of
The tread portion has three small grooves gathered in a state where the center line is shifted, and a block group composed of three blocks divided by the small grooves, and the center of the small groove is formed at the portion where the small grooves gather. A triangular part surrounded by a line is formed ,
Of the three small grooves, the groove depth of at least one small groove is gradually increased toward the triangular portion .

  In the present invention, the tread portion is provided with three small grooves that are gathered in a state where the center line is shifted, and a block group composed of three blocks divided by these small grooves, and the center of the small groove is formed at the portion where the small grooves are gathered. Since the triangle part surrounded by the line is formed, when a load is applied to the block group when running on snow, each block constituting the block group is slightly deformed so that it falls to the small groove side, and in the triangle part A compressive force acts on the snow column. As a result, the shear force of the snow column formed in the small groove increases, so that it is possible to increase the driving force and braking force when traveling on snow based on the snow column shear force and effectively improve the performance on snow. it can.

  Of the three small grooves that divide the blocks constituting the block group, it is preferable that the groove width of at least one small groove gradually increases toward the triangular portion. In this case, when the blocks constituting the block group are deformed at the time of ground contact, the snow in the small groove is guided toward the triangular portion, and the snow column shear force can be further increased.

  Of the three small grooves that divide the blocks constituting the block group, it is preferable that the groove depth of at least one small groove gradually increases toward the triangular portion. In this case, when the blocks constituting the block group are deformed at the time of ground contact, the snow in the small groove is guided toward the triangular portion, and the snow column shear force can be further increased.

  Of the three small grooves that divide the blocks constituting the block group, it is preferable that the groove wall inclination angle of at least one small groove gradually increases toward the triangular portion. In this case, when the blocks constituting the block group are deformed at the time of ground contact, the snow in the small groove is guided toward the triangular portion, and the snow column shear force can be further increased.

  The triangular portions are preferably arranged at 15 to 90 locations on the same line in the tire circumferential direction in the tread portion. Thereby, since a triangular part comes to exist in the grounding area | region of a tread part, favorable on-snow performance can be ensured.

  In the present invention, in order to satisfy the required characteristics as a pneumatic tire for icy and snowy roads, the JIS hardness of the tread rubber constituting the tread portion is in the range of 40 to 60, and each block formed in the tread portion has It is preferable to have a plurality of sipes.

In order to satisfy the required characteristics as a pneumatic tire for icy and snowy roads, it is preferable that the snow traction index STI represented by the following formula (1) is 180 or more.
STI = −6.8 + 2202ρg + 672ρs + 7.6Dg (1)
However, ρg: groove density (mm / mm ² ) = gross length of the extended component in the tire width direction of the groove (mm)
/ Total area of ground contact area (mm ² )
ρs: sipe density (mm / mm ² ) = total length of sipe extension components in the tire width direction
(Mm) / Total area of ground contact area (mm ² )
Dg: Average groove depth (mm)

  In the present invention, JIS hardness is durometer hardness measured at a temperature of 20 ° C. using an A type durometer in accordance with JIS K-6253. In addition, the contact area of the tread is based on the contact width in the tire axial direction measured when a normal load is applied by placing the tire on a regular rim and filling it with a normal internal pressure. This area is specified by 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, a standard rim for JATMA, “Design Rim” for TRA, or ETRTO. Then, “Measuring Rim” is set. “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. The maximum air pressure is JATMA, and the table “TIRE ROAD LIMITS AT VARIOUS” is TRA. The maximum value described in “COLD INFRATION PRESURES”, “INFLATION PRESURE” for ETRTO, but 180 kPa when the tire is a passenger car. “Regular load” is a load determined by each standard for each tire in the standard system including the standard on which the tire is based. If JATMA, the maximum load capacity, and if TRA, the table “TIRE ROAD LIMITS AT VARIOUS” The maximum value described in “COLD INFORATION PRESSURES” is “LOAD CAPACITY” if it is ETRTO, but if the tire is a passenger car, the load is equivalent to 88% of the load.

It is meridian sectional drawing which shows the pneumatic tire which consists of embodiment of this invention. FIG. 2 is a development view showing a tread pattern of the pneumatic tire of FIG. 1. It is a top view which shows a center rib and an intermediate | middle block row | line with another dimension line. It is a top view which shows the block group formed in the tread part in this invention. The block group in this invention is shown, (a) is a top view which shows the state at the time of no load, (b) is a top view which shows the state at the time of load. It is VI-VI arrow sectional drawing of FIG. It is a VII-VII arrow sectional view of Drawing 4 .

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. 1 to 2 show a pneumatic tire according to an embodiment of the present invention, and FIGS. 3 to 7 show the main part thereof.

  As shown in FIG. 1, the pneumatic tire of the present embodiment includes a tread portion 1 that extends in the tire circumferential direction and has an annular shape, and a pair of sidewall portions 2, 2 disposed on both sides of the tread portion 1. And a pair of bead portions 3 and 3 disposed inside the sidewall portion 2 in the tire radial direction.

  A carcass layer 4 is mounted between the pair of bead portions 3 and 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction, and is folded from the inside of the tire to the outside around the bead core 5 disposed in each bead portion 3. A bead filler 6 made of a rubber composition having a triangular cross-section is disposed on the outer periphery of the bead core 5.

  On the other hand, a plurality of 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 cross each other between the layers. In the belt layer 7, the inclination angle of the reinforcing cord with respect to the tire circumferential direction is set in a range of, for example, 10 ° to 40 °. A steel cord is preferably used as the reinforcing cord of the belt layer 7. On the outer peripheral side of the belt layer 7, at least one belt cover layer 8 in which reinforcing cords are arranged at an angle of, for example, 5 ° or less with respect to the tire circumferential direction is arranged for the purpose of improving high-speed durability. Yes. As the reinforcing cord of the belt cover layer 8, an organic fiber cord such as nylon or aramid is preferably used.

  In addition, although the tire internal structure mentioned above shows the typical example in a pneumatic tire, it is not limited to this.

  As shown in FIG. 2, the tread portion 1 includes a pair of circumferential main grooves 11 extending zigzag along the tire circumferential direction on both sides of the tire equator CL, and the tire width direction of each circumferential main groove 11. A pair of circumferential main grooves 12 extending in a zigzag shape along the tire circumferential direction is formed on the outside. Thereby, in the tread portion 1, the center rib 30 is defined between the pair of circumferential main grooves 11, 11, and the intermediate block row 40 is formed between the circumferential main groove 11 and the circumferential main groove 12. A shoulder block row 50 is defined outside the circumferential main groove 12 in the tire width direction. E is a grounding end.

  The center rib 30 is formed with a plurality of closing grooves 31 having one end opened in the circumferential main groove 11 and the other end terminated in the center rib 30 and a plurality of sipes 34 extending in the tire width direction. Yes.

  The intermediate block row 40 includes five blocks 42A, 42B,... Between a plurality of lug grooves 41 extending in the tire width direction and a pair of lug grooves 41, 41 adjacent in the tire circumferential direction. A plurality of small grooves 43 that divide 42C, 42D, and 42E are formed (see FIG. 3). In each of the blocks 42A to 42E, a plurality of sipes 44 extending in the tire width direction are formed.

  A plurality of lug grooves 51 extending in the tire width direction are formed in the shoulder block row 50, and a plurality of blocks 52 are divided by these lug grooves 51. In each of the blocks 52, a plurality of sipes 54 extending in the tire width direction are formed. Note that the sipes 34, 44, and 54 may extend in a straight line or may extend in a zigzag shape.

  In the pneumatic tire, as shown in FIG. 4, a block group including three blocks 42A, 42B, and 42C is formed in the intermediate block row 40 of the tread portion 1, and the blocks 42A to 42C are divided. The three small grooves 43 are gathered with the center line G shifted. That is, the three small grooves 43 that divide the blocks 42A to 42C extend in three different directions, and are assembled in a state where the center lines G do not coincide with each other. A triangular portion 43 </ b> X surrounded by the center line G of the small groove 43 is formed at a portion where the small grooves 43 are gathered.

  In the pneumatic tire described above, the tread portion 1 is provided with three small grooves 43 that are gathered in a state where the center line G is shifted, and a block group that includes three blocks 42A to 42C divided by the small grooves 43. Since the triangular portion 43X surrounded by the center line G of the small groove 43 is formed at the portion where the small grooves 43 are gathered, when a load is applied to the block group consisting of the blocks 42A to 42C when traveling on snow, the block group Each block 42A to 42C is slightly deformed so as to fall to the small groove 43 side, and a compressive force acts on the snow column at the triangular portion 43X. That is, as shown in FIG. 5A, the small groove 43 (shaded portion) is in a state of being greatly opened at no load, but the small groove 43 is narrowed at the time of load as shown in FIG. 5B. Thus, the snow that has entered the small groove 43 is compressed, and a large compressive force acts on the snow column in the triangular portion 43X. Thereby, since the shear force of the snow column formed in the small groove 32 becomes large, the driving force and the braking force at the time of running on snow are increased based on the snow column shear force, and the performance on snow is effectively improved. Can do.

  In order to obtain the above effects, it is desirable to optimize the area of the triangular portion 43X. For example, when the area of the triangular portion 43X is A1, and the sum of the areas (including the sipe area) on the treads of the blocks 42A to 42C is A2, the ratio A1 / A2 is 0.01 ≦ A1 / A2 ≦ 0.10. Satisfy the relationship. If the ratio A1 / A2 is smaller than 0.01, the effect of improving the performance on snow is reduced. Conversely, if the ratio A1 / A2 is larger than 0.10, the contact area of the blocks 42A to 42C is relatively reduced, so that other tire performances are reduced. May decrease.

  In the pneumatic tire, among the three small grooves 43 that divide the blocks 42A to 42C, it is preferable that the groove width of at least one small groove 43 gradually increases toward the triangular portion 43X. In this case, when each block 42A-42C which comprises a block group deform | transforms at the time of grounding, the snow in the small groove 43 is guide | induced toward the triangular part 43X, and it becomes possible to further raise a snow column shear force. Such a configuration is preferably applied to all the small grooves 43 that divide the blocks 42A to 42C.

  In particular, in FIGS. 6 and 7, the ratio W2 / W1 between the minimum value W1 and the maximum value W2 of the groove width of each small groove 43 should satisfy the relationship of 1.2 ≦ W2 / W1 ≦ 2.0. If this ratio W2 / W1 is smaller than 1.2, the effect of guiding the snow in the small groove 43 toward the triangular portion 43X is reduced, and conversely if it is greater than 2.0, the compression effect at the gathering portion is reduced. . The minimum value W1 of the groove width of the small groove 43 is desirably set in the range of 1.0 mm to 3.5 mm.

  In the pneumatic tire, it is preferable that the groove depth of at least one small groove 43 among the three small grooves 43 dividing the blocks 42A to 42C is gradually increased toward the triangular portion 43X. In this case, when each block 42A-42C which comprises a block group deform | transforms at the time of grounding, the snow in the small groove 43 is guide | induced toward the triangular part 43X, and it becomes possible to further raise a snow column shear force. Such a configuration is preferably applied to all the small grooves 43 that divide the blocks 42A to 42C.

  In particular, in FIGS. 6 and 7, the ratio D2 / D1 between the minimum value D1 and the maximum value D2 of the groove depth of each small groove 43 should satisfy the relationship of 1.2 ≦ D2 / D1 ≦ 2.0. If the ratio D2 / D1 is smaller than 1.2, the effect of guiding the snow in the small groove 43 toward the triangular portion 43X is reduced. Conversely, if the ratio D2 / D1 is larger than 2.0, the drainage capacity is reduced due to the decrease in the groove volume. Tire performance may be reduced. Moreover, it is desirable to set the minimum value D1 of the groove depth of the small groove 43 in the range of 5.0 mm to 10.0 mm.

  Furthermore, in the pneumatic tire, it is preferable that the groove wall inclination angle of at least one small groove 43 among the three small grooves 43 dividing the blocks 42A to 42C is gradually increased toward the triangular portion 43X. . The groove wall inclination angle referred to here is the inclination angle of the wall surface of the small groove 43 with respect to the normal direction of the tread surface of the tread portion 1. In this case, when the blocks 42A to 42C constituting the block group are deformed at the time of ground contact, the amount of deformation increases toward a portion away from the triangular portion 43X, so that the snow in the small groove 43 is guided toward the triangular portion, and the snow column It becomes possible to further increase the shearing force. Such a configuration is preferably applied to all the small grooves 43 that divide the blocks 42A to 42C.

  In particular, in FIGS. 6 and 7, it is preferable that the minimum value θ1 and the maximum value θ2 of the groove wall inclination angle of each small groove 43 satisfy the relationship of 0 ° ≦ θ1 <θ2 ≦ 5 °. If the minimum value θ1 of the groove wall inclination angle of the small groove 43 is smaller than 0 °, that is, if the wall surface of the small groove 43 has an overhang shape, snow cannot be sufficiently taken into the small groove 43 at the time of ground contact, If the maximum value [theta] 2 of the groove wall inclination angle of the small groove 43 is larger than 5 [deg.], The rigidity of the blocks 42A to 42C becomes too high, and the tire performance such as the performance on ice may be deteriorated.

  In the pneumatic tire, the triangular portions 43X are arranged so as to be scattered at 15 to 90 locations on the same line in the tire circumferential direction in the tread portion 1, more preferably at 20 to 40 locations. Thereby, since the triangular part 43X comes to exist reliably in the grounding area | region of the tread part 1, favorable on-snow performance can be ensured. If the number of the triangular portions 43X installed on the tire circumference is too small, the triangular portion 43X may not exist in the ground contact surface depending on the contact position. Conversely, if the number is too large, the block is relatively small with respect to the tire circumferential length. Therefore, the performance of other tires may be reduced.

  In the pneumatic tire, the JIS hardness of the tread rubber constituting the tread portion 1 is set in the range of 40 to 60, more preferably in the range of 45 to 55. When the JIS hardness of the tread rubber constituting the tread portion 1 is set in the above range, the tread portion 1 flexibly follows the road surface, which is suitable for icy and snowy roads. Further, in the pneumatic tire, the snow traction index STI is set to 180 or more, more preferably in the range of 180 to 240.

A pneumatic tire having a tire size of 225 / 65R17 102Q, including a tread portion, a pair of sidewall portions, and a pair of bead portions, a tread rubber constituting the tread portion having a JIS hardness of 51 and a snow traction index STI of 200. In the tire, as shown in FIG. 1 to FIG. 7, the tread portion is provided with three small grooves that are gathered in a state in which the center line is shifted, and a block group including three blocks divided by these small grooves, Tires of Reference Examples 1 to 4 and Examples 1 to 3 in which a triangular portion surrounded by a center line of the small groove was formed at a portion where the small grooves gathered were manufactured.

In Reference Examples 1 to 4 and Examples 1 to 3 , the ratio W2 / W1 between the minimum value W1 and the maximum value W2 of the groove width of the small groove, and the minimum value θ1 and the maximum value θ2 of the groove wall inclination angle of the small groove are As shown in Table 1, the ratio D2 / D1 between the minimum value D1 and the maximum value D2 of the groove depth and the number of installations on the tire circumference of the triangular portion were set.

  For comparison, Example 1 is the same as Example 1 except that the center lines of the three small grooves that divide the three blocks constituting the block group are matched so that a triangular portion is not formed at the portion where the small grooves are gathered. A conventional tire having the same structure was prepared.

  For these test tires, braking performance on snow was evaluated by the following test method, and the results are also shown in Table 1.

Snow braking performance:
The test tire is mounted on a wheel with a rim size of 17 x 7 J and mounted on a four-wheel drive vehicle (RV) with a displacement of 2400 cc. The air pressure after warm-up is 220 kPa, and the speed is 40 km / h on a test course consisting of a snowy road surface ABS braking was performed from the state, and the braking distance was measured. The evaluation results are shown as an index with the conventional example being 100, using the reciprocal of the measured value. A larger index value means better snow braking performance.

As can be seen from Table 1, the tires of Reference Examples 1 to 4 and Examples 1 to 3 were able to greatly improve the braking performance on snow in comparison with the conventional example.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 11,12 Circumferential main groove 30 Center rib 31 Closure groove 34,44,54 Sipe 40,50 Block row 41,51 Lug groove 42A, 42B, 42C, 42D, 42E, 52 Block 43 Kozo

Claims (6)

An annular tread portion extending in the tire circumferential direction, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed on the inner side in the tire radial direction of the sidewall portions. In the provided pneumatic tire,
The tread portion has three small grooves gathered in a state where the center line is shifted, and a block group composed of three blocks divided by the small grooves, and the center of the small groove is formed at the portion where the small grooves gather. A triangular part surrounded by a line is formed ,
A pneumatic tire characterized in that a groove depth of at least one of the three small grooves gradually increases toward the triangular portion .   The pneumatic tire according to claim 1, wherein a groove width of at least one of the three small grooves gradually increases toward the triangular portion. Of small grooves of the three pneumatic tire according to any one of claims 1-2, characterized in that at least one groove wall angle of inclination of the small groove of gradually increases toward the triangular portion . The pneumatic tire according to any one of claims 1 to 3 , wherein the triangular portions are arranged at 15 to 90 locations on the same line in the tire circumferential direction in the tread portion. In the range of tread JIS hardness of the rubber is 40 to 60 constituting the tread portion, to any one of claims 1 to 4, characterized in that it has a plurality of sipes in each block formed in the tread portion The described pneumatic tire. The pneumatic tire according to any one of claims 1 to 5 , wherein a snow traction index STI represented by the following formula (1) is 180 or more.
STI = −6.8 + 2202ρg + 672ρs + 7.6Dg (1)
However, ρg: groove density (mm / mm ² ) = gross length of the extended component in the tire width direction of the groove (mm)
/ Total area of ground contact area (mm ² )
ρs: sipe density (mm / mm ² ) = total length of sipe extension components in the tire width direction
(Mm) / Total area of ground contact area (mm ² )
Dg: Average groove depth (mm)

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