JP4457716B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire. More specifically, the present invention relates to a pneumatic tire capable of improving wear resistance on a non-paved road while maintaining at least snow traction when new.

  In general, in a pneumatic tire mounted on a vehicle, a technique for improving wear resistance without affecting traction has been proposed (see, for example, Patent Document 1). The pneumatic tire shown in Patent Document 1 improves wear resistance, particularly wear resistance on a paved road, without affecting traction. Here, in a pneumatic tire, particularly a heavy-duty pneumatic tire mounted on a vehicle such as a truck or a bus, the traction on the snow road under the condition that the vehicle travels not only on a paved road but also on a snowy road and an unpaved road. Are important, i.e. snow traction and wear resistance on unpaved roads. However, in the pneumatic tire shown in Patent Document 1, improvement in wear resistance not only on paved roads but also on snowy roads and non-paved roads is not considered. Under the conditions of traveling on snowy roads and non-paved roads, a block pattern constituted by a plurality of (four or more) circumferential grooves and a plurality of independent blocks formed by lateral grooves communicating with the circumferential grooves is provided. Heavy duty pneumatic tires are used.

  Here, in order to improve the wear resistance on the non-paved road, it is conceivable to increase the rigidity of the plurality of independent blocks. Therefore, if the number of circumferential grooves is reduced to, for example, 2 and each block is enlarged, the wear resistance on the non-paved road can be improved, but the groove on the ground contact surface with the road surface of the heavy-duty pneumatic tire. When the area is reduced and the number of blocks on the ground contact surface is reduced, the edge component in the ground contact surface is reduced, and the snow traction property, which is the traction property on the snowy road, is lowered. On the other hand, in order to improve snow traction, as described above, the number of circumferential grooves is increased in order to increase the groove area on the ground surface and increase the edge component in the ground surface, for example, four or more. It is possible to do. However, since the individual blocks become smaller, the rigidity of the blocks is lowered, and the wear resistance on the unpaved road is lowered.

  Further, in order to improve the wear resistance on the non-paved road, it is conceivable to flatten the contact shape with the road surface of the heavy-duty pneumatic tire, that is, to flatten the contact pressure at the tire center. Thus, when the ground contact shape is flattened, the gauge at the tire shoulder becomes thicker than the gauge at the tire shoulder that is not flattened. In particular, when the deepest groove depth among all circumferential grooves and lateral grooves formed in the tread portion is maintained and the sub-groove gauge at the tire center is maintained, the gauge at the tire shoulder is further increased. If the gauge at the tire shoulder becomes thicker, the heat generated by the rubber in the vicinity of the end portions of the plurality of belts arranged in the tread portion increases, and there is a possibility that belt separation may occur, which decreases the durability of the heavy duty pneumatic tire. There is a fear. Also, if the ground contact shape with the road surface of the heavy duty pneumatic tire is flattened, the contact length with the road surface of the heavy load pneumatic tire will be shortened, so that the traction on snowy roads, that is, the snow traction property will be reduced. It becomes.

JP 2000-190710 A

  Accordingly, the present invention has been made in view of the above, and provides a pneumatic tire capable of improving wear resistance on a non-paved road while maintaining snow traction at least when new. It is intended.

In order to solve the above-described problems and achieve the object, in the present invention, a pneumatic tire having a plurality of independent blocks formed by at least four circumferential grooves and lateral grooves communicating with the circumferential grooves. In the tire center, the surface area Ac of the center block row composed of a plurality of blocks continuous in the tire circumferential direction and the shoulder block row constituted of a plurality of blocks continuous in the tire circumferential direction in any one of the tire shoulders. The surface area ratio A to the surface area As is Ac / As, the outer diameter ratio D between the tire outer diameter Dc at the tire center and the tire outer diameter Ds at the tire shoulder is Dc / Ds, and the surface area ratio A and the outer diameter ratio D are The relationship satisfies the following expression.
A- (D-1) × 100 ≧ 0 (1)

  In the pneumatic tire, it is preferable that the surface area of each block row from a tire center to a tire shoulder constituted by a plurality of blocks continuous in the tire circumferential direction gradually decreases from the tire center toward the tire shoulder.

  According to this invention, it has a plurality of independent blocks formed by at least four circumferential grooves and lateral grooves communicating with the circumferential grooves, that is, a plurality of blocks that are continuous in the tire circumferential direction. Since there are five or more block rows, the groove area on the contact surface and the edge component on the contact surface can be increased, and at least the snow traction property on the snow road when new is maintained. can do. Further, when the surface area ratio A between the surface area Ac of the center block row and the shoulder block row As and the outer diameter ratio D between the center outer diameter Dc and the shoulder outer diameter Ds satisfy the above formula (1), the pneumatic tire and the road surface The contact pressure and the contact length can be set to optimum values for improving the wear resistance on the non-paved road. Thereby, the abrasion resistance in a non-paved road can be improved.

  In the present invention, in the pneumatic tire, the groove depths of the circumferential grooves and the lateral grooves forming the plurality of independent blocks are the same or substantially the same. Here, “substantially the same” means 10% of the groove depth of the groove having the deepest difference between the groove depth of the deepest groove and the groove depth of the shallowest groove among circumferential grooves and lateral grooves forming a plurality of independent blocks. It is within.

  Conventionally, all or a part of the circumferential grooves and the lateral grooves forming the plurality of independent blocks are shallow, that is, by raising all or a part of the circumferential grooves and the lateral grooves, The individual rigidity of the plurality of independent blocks formed by the lateral grooves was increased, and the wear resistance on the unpaved road was improved. Here, the snow traction property is affected by the increase and decrease in the groove area on the ground contact surface which is a tread surface. Increasing the groove area on the ground contact surface increases the shear force of the snow columns formed in the circumferential and lateral grooves and improves snow traction, but raising the bottom raises the wear, especially after the middle wear phase. The area of the groove on the ground contact surface decreases rapidly, the shear force of the snow column formed in the circumferential groove and in the lateral groove decreases rapidly, and snow that is traction on the snow road during wear, especially after the middle wear period There was a possibility that traction property might fall. However, according to the present invention, since the circumferential grooves and the lateral grooves forming the plurality of independent blocks are not raised or hardly raised, it is possible to suppress a reduction in traction during wear. Thereby, the fall of the snow traction property at the time of wear can be suppressed.

  The pneumatic tire according to the present invention has an effect of improving the wear resistance on a non-paved road while maintaining at least the snow traction property when new. Moreover, the effect that the fall of the snow traction property at the time of wear can be suppressed is also produced.

  Hereinafter, the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following examples. In addition, constituent elements in the following embodiments include those that can be easily assumed by those skilled in the art or those that are substantially the same. In the following examples, heavy-duty pneumatic tires mounted on trucks, buses, etc. will be described as pneumatic tires, but the present invention is not limited to this, and pneumatic tires mounted on passenger cars and the like are described. It may be used.

  FIG. 1 is a diagram illustrating a configuration example of a heavy duty pneumatic tire according to an embodiment. Moreover, FIG. 2 is a figure which shows the top view (tread pattern) of the tread part of the pneumatic tire for heavy loads concerning an Example. FIG. 3 is a cross-sectional view of the main part of the heavy duty pneumatic tire according to this embodiment. In addition, the said FIG. 1 is a partial cross section figure of the cross section which cut the pneumatic tire for heavy loads with the meridian surface.

  As shown in FIGS. 1 and 2, the heavy-duty pneumatic tire 1 according to the example includes a tread portion 2, a sidewall portion 3, and a tire bead portion 4. The tread portion 2 is formed with at least an inner liner 5, a carcass layer 6 laminated on the inner liner 5, a plurality of belt layers 7 laminated on the carcass layer 6, and circumferential grooves 21 and lateral grooves 22 described later. The cap tread 24 is configured. The sidewall portion 3 includes an inner liner 5, a carcass layer 6 laminated on the inner liner, and a side tread (not shown). The tire bead portion 3 is composed of a bead core 8 composed of a plurality of steel wires for mounting at least the heavy duty pneumatic tire 1 on the rim, and a bead filler 9.

  On the surface of the tread portion 2 (the surface of the cap tread 24), as shown in FIG. 2, in the embodiment, four circumferential grooves 21 communicating in the tire circumferential direction and lateral grooves communicating these circumferential grooves 21 are provided. 22 is formed. Here, the circumferential groove 21 only needs to communicate with the tire circumferential direction, and may be any of a linear shape, an S shape, and a zigzag shape. Further, the lateral grooves 22 are not limited to being formed in the tire axial direction orthogonal to the tire circumferential direction, and are formed in an oblique direction (a direction between the tire circumferential direction and the tire axial direction) with respect to the tire circumferential direction. May be. In addition, the number of the circumferential grooves 21 formed on the surface of the tread portion 2 may be four or more, and is particularly preferably four or more and an even number. Thereby, on the surface of the tread portion 2, an odd number of block rows to be described later is formed, and the tire center block row Tc can be formed at the tire center.

  Further, as shown in FIG. 2, a plurality of rows (5 rows in FIG. 2) of block rows Tc, Tm are formed on the surface of the tread portion 2 by a plurality of blocks 23c, 23m, 23s continuous in the tire circumferential direction. , Ts are formed. That is, the tread portion 2 is formed with a tread pattern (block pattern) composed of a plurality of independent block blocks 23c, 23m, and 23s. Specifically, the center block row Tc in the tire center is composed of a plurality of blocks 23c that are continuous in the tire circumferential direction at the tire center. Further, the shoulder block rows Ts and Ts in both tire shoulders are constituted by a plurality of blocks 23s and 23s that are continuous in the tire circumferential direction in both tire shoulders. The middle block rows Tm, Tm in the middle of both tires (between the center and the shoulder) between the tire center and both tire shoulders are a plurality of blocks 23m that are respectively continuous in the tire circumferential direction in the middle of both tires. , 23m. Here, when the number of the circumferential grooves 21 formed in the tread portion 2 is four, the middle block rows Tm and Tm are formed one by one between the tire center and both tire shoulders. As described above, when the number of the circumferential grooves 21 increases, a plurality of rows are formed.

  That is, the surface of the tread portion 2 has a plurality of independent blocks 23c, 23m, and 23s formed by at least four circumferential grooves 21 and lateral grooves 22 that communicate the circumferential grooves 21. Since there are five or more rows of block rows Tc, Tm, Ts composed of a plurality of blocks 23c, 23m, 23s that are continuous in the circumferential direction, an increase in the groove area on the ground contact surface of the heavy duty pneumatic tire 1 and within the ground contact surface The edge component can be increased, and at least the snow traction property, which is the traction property on the snow road when it is new, can be maintained.

  Each block row Tc, Tm, Ts, that is, each block row Tc, Tm, Ts from the tire center to the tire shoulder composed of a plurality of blocks 23c, 23c continuous in the tire circumferential direction is the block row Tc, Tm. The surface area Ac, Am, As of Ts is formed on the surface of the tread portion 2 so that Ac> Am> As. That is, each block row Tc, Tm, Ts formed on the surface of the tread portion 2 is directed from the tire center toward the tire shoulder, that is, in the order of the center block row Tc, the middle block row Tm, and the shoulder block row Ts. The surface areas Ac, Am, As are gradually reduced. Here, the surface areas Ac, Am, As of the respective block rows Tc, Tm, Ts are provided in the blocks 23c, 23m, 23s continuous in the tire circumferential direction constituting the respective block rows Tc, Tm, Ts. It also includes the surface area (tread surface side surface area) of the surface of the tread portion 2 of a narrow groove (for example, a groove having a groove width of 4 mm or less) that does not communicate with any of the circumferential groove 21 and the lateral groove 22.

Further, the heavy load pneumatic tire 1 has a surface area ratio A between the surface area Ac of the center block row Tc and the surface area As of the shoulder block row Ts and a center outer diameter Dc which is an outer diameter of the heavy load pneumatic tire 1 at the tire center. The outer diameter ratio D of the shoulder tire outer diameter Ds that is the outer diameter of the heavy-duty pneumatic tire 1 in the tire shoulder satisfies the following formula (2). The center outer diameter Dc and the shoulder outer diameter Ds are both predetermined air pressure (standard air pressure in JATMA or air pressure stamped on the sidewall portion 3 of the heavy load pneumatic tire 1 by the manufacturer). ) Is the outer diameter when the air is inflated.
A- (D-1) × 100 ≧ 0 (2)

  By setting the surface area ratio A and the outer diameter ratio D that satisfy the above formula (2), the contact pressure and the contact length between the heavy-duty pneumatic tire 1 and the road surface are set to optimum values that improve the wear resistance on the unpaved road. be able to. Thereby, the abrasion resistance in a non-paved road can be improved. Here, at least the center block row Tc and the shoulder block row Ts of the tread portion 2 of the heavy duty pneumatic tire 1 are the ratio of the surface area Ac of the center block row Tc and the surface area As of the shoulder block row Ts, which is the surface area ratio A. Is preferably formed on the surface of the tread portion 2 so as to be in the range of 1.8 to 2.8. This is because if the surface area ratio A is lower than 1.8 or higher than 2.8, the wear resistance on the non-paved road cannot be improved significantly. The heavy duty pneumatic tire 1 is preferably formed so that the ratio of the center outer diameter Dc, which is the outer diameter ratio D, to the shoulder outer diameter Ds is in the range of 1.014 to 1.019. . This is because if the outer diameter ratio D is lower than 1.014, the wear resistance on the non-paved road cannot be significantly improved. Further, when the outer diameter ratio D is higher than 1.019, the ground contact shape of the heavy duty pneumatic tire 1 is remarkably flattened, and the gauge at the tire shoulder is more than the gauge at the tire shoulder that is not flattened. This is because the thickness is increased, belt separation is likely to occur, and durability may be reduced.

  Further, as shown in FIG. 3, the circumferential grooves 21 and the lateral grooves 22 forming the plurality of independent blocks 23c, 23m, 23s on the surface of the tread portion 2 are groove depths S of the circumferential grooves 21 and the lateral grooves 22. Are all the same or substantially the same. Here, when the groove depths S of the circumferential grooves 21 and the lateral grooves 22 are substantially the same, the maximum groove depth Smax that is the deepest groove depth among the groove depths S of all the circumferential grooves 21 and the lateral grooves 22. On the other hand, a plurality of independent blocks 23c, 23m, and 23s are formed on the surface of the tread portion 2 so that the minimum groove depth Smin that is the shallowest groove depth has a relationship of Smin ≧ Smax × 0.9. Preferably, circumferential grooves 21 and transverse grooves 22 are formed. That is, the groove depth of the shallowest groove (minimum groove depth Smin) among all the circumferential grooves 21 and the lateral grooves 22 is 90% or more of the groove depth of the deepest groove (maximum groove depth Smax). Is preferred. This is the difference between the depth of the deepest groove (maximum groove depth Smax) and the depth of the shallowest groove (minimum groove depth Smin) of all the circumferential grooves 21 and the lateral grooves 22. It means that the length s is in the relationship of s ≦ Smax × 0.1, that is, the bottom-up ratio is within 10% of the maximum groove depth Smax. Accordingly, in order to increase the individual rigidity of the plurality of independent blocks 23c, 23m, and 23s formed by the circumferential grooves 21 and the lateral grooves 22 as in a conventional heavy-duty pneumatic tire, these circumferential grooves 21 are used. In addition, since the groove depth S of all or part of the lateral groove 22 is not reduced, the groove area (the area of the circumferential groove 21 and the lateral groove in the contact surface with the road surface of the heavy-duty pneumatic tire 1 at the time of wear, particularly after the middle stage of wear) 22) is rapidly reduced, and it is possible to suppress a sharp decrease in the shear force of the snow column formed in the groove (in the circumferential groove 21 and in the lateral groove 22). The fall of the snow traction property which is the traction property on the snowy road after the middle stage of wear can be suppressed.

  Below, the implementation result of the running test with the heavy load pneumatic tire of a prior art example and a comparative example and the heavy load pneumatic tire 1 concerning this invention is demonstrated. Here, the tire size of each tire used in this running test is common to 11R22.5. The running test was carried out by assembling the above tires on a rim having a rim size of 22.5 × 7.50 and setting each tire to an air pressure of 700 Kpa and mounting it on a 2-DD drive shaft.

  A- (D-1) × 100: a relational expression between the surface area ratio A and the outer diameter ratio D according to the present invention.

  A: Surface area ratio between the surface area Ac of the center block row Tc and the surface area As of the shoulder block row Ts.

D: The outer diameter ratio between the center outer diameter Dc and the shoulder outer diameter Ds.
.

  Abrasion resistance: It runs on a fixed course of 80% paved road and 20% non-paved road, and the distance traveled until any of the independent blocks 23c, 23m, 23s is 4mm in height is an index. It is shown by. Here, the conventional example is “100”, and the higher the numerical value, the better the wear resistance.

  Bottom raised groove ratio: The bottom raised which is the difference between the groove depth of the deepest groove (maximum groove depth Smax) and the groove depth of the shallowest groove (minimum groove depth Smin) among all the circumferential grooves 21 and the lateral grooves 22. The ratio of the height s to the maximum groove depth Smax.

  Snow traction (when new): The performance of climbing on a pressure snowy slope and the braking distance on a pressure snowy road when the heavy duty pneumatic tire 1 is new is shown as an index. Here, it is assumed that the present invention 5 is “100”, and the lower the numerical value, the worse the snow traction.

  Snow traction (at the time of 50% wear): This is an index showing the climbing performance on the pressure snow slope and the braking distance on the pressure snow road when the heavy duty pneumatic tire 1 is worn 50% from the new time. Here, it is assumed that the present invention 5 is “100”, and the lower the numerical value, the worse the snow traction.

  [Table 1] and [Table 2] below show the results of the running test.

  As is apparent from Table 1, the present inventions 1 to 4 which are heavy-duty pneumatic tires 1 according to the present invention maintain the snow traction property at the time of a new article, as compared with the conventional example, while on a non-paved road. Abrasion resistance can be significantly improved. In Comparative Examples 1 and 2 having a surface area ratio A lower than 1.8, the wear resistance on the non-paved road can be significantly improved as compared with the conventional example, even if the snow traction property can be maintained when new. Can not. Similarly, in Comparative Examples 3 and 4 having an outer diameter ratio D higher than 1.019, the wear resistance on the non-paved road is remarkably improved as compared with the conventional example even if the snow traction property at the time of the new article can be maintained. Can not do it.

  As apparent from Table 2, the present invention 5 and the bottom raising, in which the bottom raising ratio of the heavy-duty pneumatic tire 1 according to the present invention is 0 (the groove depth S of all the circumferential grooves 21 and the lateral grooves 22 is the same). The present invention 6 in which the ratio is 10 (the groove depths S of all the circumferential grooves 21 and the lateral grooves 22 are substantially the same) is compared with the present invention 7 in which the bottom raising ratio is 20 and the present invention 8 in which the bottom raising ratio is 30. Thus, while maintaining the snow traction property at the time of a new article, it is possible to suppress a decrease in the snow traction property at the time of wear, particularly after the middle stage of wear, while improving the wear resistance on the non-paved road.

  As described above, the heavy-duty pneumatic tire according to the present invention is useful for pneumatic tires that run not only on paved roads but also on non-paved roads, and at least maintains snow traction properties at least when new. However, it is suitable for improving the wear resistance on an unpaved road.

It is a figure which shows the structural example of the pneumatic tire for heavy loads concerning an Example. It is a figure which shows the top view (tread pattern) of the tread part of the pneumatic tire for heavy loads concerning an Example. It is principal part sectional drawing of the heavy-duty pneumatic tire concerning an Example.

Explanation of symbols

1 Pneumatic tire for heavy load 2 Tread part 21 Circumferential groove 22 Horizontal groove 23c, 23m, 23s Block 3 Side wall part 4 Tire bead part A Surface area ratio Ac, Am, As Surface area D Outer diameter ratio Dc Center outer diameter Ds Shoulder outer diameter Tc Center block row Tm Middle block row Ts Shoulder block row Smax Maximum groove depth Smin Minimum groove depth s Bottom raising height

Claims (3)

In a pneumatic tire having a plurality of independent blocks formed by at least four circumferential grooves and lateral grooves communicating with the circumferential grooves,
The surface area Ac of the center block row composed of a plurality of blocks continuous in the tire circumferential direction at the tire center and the surface area As of the shoulder block row composed of a plurality of blocks continuous in the tire circumferential direction at any one of the tire shoulders. And the surface area ratio A to Ac / As,
The outer diameter ratio D between the tire outer diameter Dc at the tire center and the tire outer diameter Ds at the tire shoulder is Dc / Ds,
A pneumatic tire characterized in that the relationship between the surface area ratio A and the outer diameter ratio D satisfies the following formula.
A- (D-1) × 100 ≧ 0 (1)   The pneumatic tire according to claim 1, wherein the circumferential grooves and the lateral grooves forming the plurality of independent blocks have the same or substantially the same groove depth.   The surface area of each block row from the tire center configured by a plurality of blocks continuous in the tire circumferential direction to the tire shoulder gradually decreases from the tire center toward the tire shoulder. Pneumatic tire described in 2.

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