JP4989023B2 - Heavy duty tire - Google Patents

Description

  The present invention relates to a heavy-duty tire that is suitable as an all-season tire and that suppresses a decrease in on-snow performance and wet performance as wear progresses.

  For example, in heavy duty tires for all seasons used for buses, trucks, etc., the tread surface is partitioned into a plurality of land parts including blocks, for example, block patterns and ribs in order to be able to run on snowy roads and maintain high wet performance.・ Block patterns are used. In order to improve various performances such as performance on snow and wet performance, various pattern shapes have been proposed.

  However, although these various performances have been improved to some extent in the state of new products, the reduction of these performances with the progress of wear is insufficient, and in recent years there has been a strong demand for improvements.

  For example, in order to suppress the reduction in wet performance in the late wear phase, a technology has been proposed in which the tread rubber is formed of multiple layers having different rubber compositions, and in the late wear phase, a high frictional rubber layer with excellent wet skid properties is exposed on the tread surface. Yes. However, in such a technique, the rubber layer is not uniformly exposed due to uneven wear or the like, and conversely, the wet performance is deteriorated or delamination occurs between the rubber layers.

In view of such a situation, the present inventor conducted research by paying attention to the component length of the edge formed by the peripheral edge of the land portion in the tread pattern. as a result,
(1) The edge component in the tire circumferential direction is particularly important for the turning performance that is regarded as important as the wet performance. In order to ensure the wet performance as high as that of a new product, the edge component in the tire circumferential direction is used. It is necessary to increase the length rather as the wear progresses;
(2) With regard to the traction performance that is regarded as important on the snow performance, the edge component in the tire axial direction is important, and it is preferable to increase as the wear progresses, as with the edge component length in the tire circumferential direction. However, in winter tires, it is not necessary to ensure the snow performance after 50% wear as high as the wet performance in order to guarantee the performance on the snow until 50% wear, so the edge component in the tire axial direction is at least new. (3) To optimize the ratio of the edge component length between the tire circumferential direction and the tire axial direction at each wear stage. ;
It has been found that the decrease in the performance on the snow and the wet performance as the wear progresses can be kept low.

  That is, according to the present invention, the edge component length in the tire circumferential direction and the edge component length in the tire axial direction at the land portion of the tread pattern are optimized at each wear stage when new, 50% worn, and 90% worn. The object of the present invention is to provide a heavy-duty tire that can suppress a decrease in on-snow performance and wet performance as wear progresses.

  Patent Document 1 discloses a technique for increasing the groove area with the progress of wear and suppressing the decrease in hydroplaning performance (wet performance).

Japanese Patent Laid-Open No. 10-76812

In order to achieve the above object, the tread surface is provided with a tread groove including a plurality of vertical grooves extending in the tire circumferential direction and a horizontal groove extending in a direction intersecting with the vertical grooves. A pneumatic tire partitioned into a plurality of land portions including,
The transverse groove includes an outer longitudinal groove extending most on the tread edge side and an outer transverse groove extending between the tread edges,
The outer lateral groove has a widened portion whose groove width increases toward the outer side in the tire axial direction, and the outer lateral groove has 50% of the deepest tread groove depth of the tread groove. A 50% wear groove portion that wears in a 50% wear state where the wear is worn, and a 90% wear state in which 90% of the groove depth of the deepest tread groove is worn on the outer side in the tire axial direction of the 50% wear groove portion. % Wear groove part is next to each other through a step,
In the 50% wear state, an edge (R12) extending in the tire circumferential direction on the outer side in the tire axial direction of the groove bottom of the 50% wear groove portion appears, and in the 90% wear state, the length in the tire circumferential direction is increased. The edge (R13) of the groove bottom of the 90% wear groove that is longer than the edge (R12) appears in the widened portion, and the land circumferential edge that surrounds the land within the tread surface in the tire circumferential direction. The total axial direction in which the circumferential edge component is summed for the entire land portion located on the tread surface, and the axial edge component in the tire axial direction of the land circumferential edge is summed for the entire land portion. In the edge component EL,
The total circumferential edge component on the tread surface in a new state is EC00, the total axial edge component is EL00, the total circumferential edge component in the 50% wear state is EC50, and the total axial edge component is EL50. When the total circumferential edge component in the 90% wear state is EC90 and the total axial edge component is EL90, the following expressions (1) to (6) are satisfied.
EC50> EC00 ----- (1)
EC90> EC00 ----- (2)
EL50> 0.5 × EL00 ----- (3)
EL90> 0.5 × EL00 ----- (4)
1.5 <EC50 / EL50 <2.2 ----- (5)
2.85 <EC90 / EL90 < 3.4 ----- (6)

The invention according to claim 2 is characterized in that the 50% wear groove portion or the 90% wear groove portion has a narrow groove at the groove bottom.

  Since the present invention is configured as described above, it is possible to suppress a decrease in on-snow performance and wet performance as wear progresses.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a development view showing an example of a tread pattern of the heavy duty tire of the present invention.
In FIG. 1, the heavy load tire 1 includes a tread groove 5 including a longitudinal groove 3 extending in the tire circumferential direction and a lateral groove 4 extending in a direction intersecting the longitudinal groove 3 on the tread surface 2. Thereby, the tread surface 2 is partitioned into a plurality of land portions 7 including the blocks 6.

Specifically, in this example, the vertical groove 3 includes an internal vertical groove 3c extending on the tire equator C, an external vertical groove 3s disposed on the tread edge Ts side, and the internal vertical groove 3c and the external vertical groove 3c. 3s of vertical grooves 3s and intermediate vertical grooves 3m arranged therebetween. The transverse groove 4 includes an inner transverse groove 4c that traverses between the inner and inner longitudinal grooves 3c, 3m, an inner transverse groove 4m that traverses between the inner and outer longitudinal grooves 3m, 3s, and the outer longitudinal groove 3s and the tread. It is composed of an outer lateral groove 4s crossing between the edge Ts. The outer lateral groove 4s has a widened portion 4s1 whose groove width increases toward the outer side in the tire axial direction.

  Thus, the tread surface 2 is surrounded by a plurality of blocks 6c surrounded by the vertical grooves 3c, 3m and the horizontal grooves 4c, a plurality of blocks 6m surrounded by the vertical grooves 3m, 3s and the horizontal grooves 4m, and the vertical grooves 3s and the tread. A block pattern partitioned into a plurality of outer blocks 6s surrounded by the edge Ts and the lateral grooves 4s is formed. The land portion 7 may include a rib (not shown) extending continuously in the tire circumferential direction in addition to the block 6, and includes at least one of the rows of the blocks 6, for example, the inner block 6c. It is also possible to adopt a rib / block pattern in which the rows are replaced with ribs.

  A straight groove extending linearly in the tire circumferential direction can be used as the vertical groove 3, but a zigzag groove is preferable from the viewpoint of traction, and in this example, the zigzag of the inner and outer vertical grooves 3c and 3s is used. Is set larger than the zigzag amplitude of the inner vertical groove 3m. In each of the longitudinal grooves 3c, 3m, and 3s, the zigzag pitch numbers are the same, and the circumferential phases of the zigzags are shifted from each other.

  Further, as the lateral grooves 4, from the viewpoint of traction, the inner lateral grooves 4c and 4m are inclined in the same direction (the left is the top in FIG. 1), and the angles θc and θm with respect to the tire axial direction are set to 30. The angle is set to be equal to or lower than 20 ° and further equal to or lower than 20 °. In this example, the case of θc = θm is illustrated. On the other hand, the outer lateral groove 4s has an angle θs with respect to the tire axial direction smaller than the angles θc and θm, 10 ° or less, and further 5 ° or less, and has the same orientation as the inner and inner lateral grooves 4c and 4m. Alternatively, it is inclined in the opposite direction. Further, from the viewpoint of drainage, each horizontal groove 4 intersects with the vertical groove 3 at its zigzag bent portion. In addition, although the groove width of the vertical groove 3 and the horizontal groove 4 is not particularly limited in the present application, a groove width in the range of 6.0 to 11.0 mm can be suitably employed as in the case of a conventional heavy load tire.

  Further, in each of the inner wall surfaces of the inner blocks 6c and 6m, at the position facing the zigzag bent portion in the inner vertical groove 3m, in this example, the concave portion 9 aligned with the inner lateral groove 4m, Concave portions 10 arranged in a straight line with the lateral grooves 4c are respectively provided. Thereby, while storing water temporarily and improving drainage, the traction property is improved.

  Next, in the present invention, the component length of the edge formed by the peripheral edge of the land portion 7 (block 6 in this example) of the tread pattern is optimized at a predetermined wear stage.

  Specifically, a value Σec obtained by summing the circumferential edge component ec in the tie circumferential direction in the land circumferential edge e surrounding the land 7 in the tread surface 2 for the entire land located on the tread surface 2 is the total circumferential edge. A component EC is set, and a value Σel obtained by summing the axial edge component el of the land circumferential edge e in the tire axial direction over the entire land portion is set as a total axial edge component EL.

  Here, the “land portion circumferential edge e” means a peripheral edge located in the tread surface 2 among the peripheral edges surrounding the land portion 7. Therefore, when the land portion 7 is arranged across the inside and outside of the tread surface 2, the peripheral edge located outside the tread surface 2 is excluded from the land portion circumferential edge e. Further, the “circumferential edge component ec” indicates that the land circumferential edge e is aligned with the tire circumferential surface (surface parallel to the tire equator) in the tire axial direction, as shown by the block 6m in FIG. The sum of the lengths ec1, ec2,... When projected from the one side and the other side, respectively, and the “axial edge component el” represents the land circumferential edge e on the tire circumferential surface (tire axis). Is the sum of lengths el1, el2,... When projected from one side and the other side in the tire circumferential direction.

Further, the total circumferential edge component in the new state Y00 is EC00, the total axial edge component is EL00, the total circumferential edge component in a 50% wear state is EC50, and the total axial edge component is EL50, and When the total circumferential edge component in the 90% wear state is EC90 and the total axial edge component is EL90, the following expressions (1) to (6) are satisfied.
EC50> EC00 ----- (1)
EC90> EC00 ----- (2)
EL50> 0.5 × EL00 ----- (3)
EL90> 0.5 × EL00 ----- (4)
1.5 <EC50 / EL50 <2.2 ----- (5)
2.85 <EC90 / EL90 < 3.4 ----- (6)

  The “50% wear state Y50” means a wear state in which 50% of the groove depth H of the deepest tread groove 5A in the tread groove 5 is worn, as shown in FIG. The wear state in which 90% of the depth H is worn is called “90% wear state Y90”, and the unworn state is called “new state Y00”. In this example, the vertical grooves 3c, 3m, 3s constitute the deepest tread groove 5A.

  As a result of the present inventors' research, the total circumferential direction edge component EC is important for the turning performance particularly important in the wet performance, and in order to ensure this wet performance as high as when new, It has been found that it is necessary to increase the total circumferential edge component EC rather than when it is new as wear progresses. This is because the wet performance is important in the entire range from the new product to the end of wear, but the groove volume inevitably decreases as the wear progresses. Therefore, it is necessary to compensate for the decrease in the groove volume by increasing the total circumferential edge component EC. Therefore, in Equations (1) and (2), the total circumferential edge components EC50 and EC90 in each of the wear states Y50 and Y90 are made larger than the total circumferential edge component EC00 in the new state. At this time, the relationship between EC50 and EC90 is not particularly restricted, but EC50 ≦ EC90 and further EC50 <EC90 are preferable.

  Further, regarding the traction property particularly important in performance on snow, the total axial direction edge component EL is important, and it is preferable that it is large like the total circumferential direction edge component EC. However, winter tires guarantee on-snow performance up to 50% wear, and the snow performance after 50% wear need not be as high as the wet performance. Therefore, although not as much as the total circumferential edge component EC, in equations (3) and (4), the total axial edge components EL50 and EL90 in the respective wear states Y50 and Y90 are set to 0 of the total axial edge component EL00 when new. Increased more than 5 times. At this time, the relationship between EL50 and EL90 is not particularly restricted, but it is preferable to secure EL90 at least 0.6 times EL50, further 0.7 times or more, and to improve performance on snow after 90% wear as much as possible.

  In the conventional tire, in the 90% wear state Y90, the total circumferential edge component EC90 is 80% or less of the total circumferential edge component EC00 (the new state Y00), and the total axial edge component EL90 is The axial edge component EL00 (new state Y00) is 30% or less, which is very low.

Further, as described above, the performance on snow after 50% wear does not need to be as high as the wet performance, and the importance of the performance on snow and the wet performance differs with the progress of wear. Therefore, in order to exhibit the performance on the snow and the wet performance in a comprehensive manner, the ratio EC / EL between the total circumferential edge component EC and the total axial edge component EL is optimized in each wear stage Y50, Y90. It is necessary. Therefore, EC50 / EL50 and EC90 / EL90 are regulated within predetermined ranges in the equations (5) and (6) .

If the ratio EC50 / EL50 is less than 1.5, the wet performance at the 50% wear stage is lowered. This is due to the fact that the edge component in the circumferential direction is relatively reduced and the grip force during turning is reduced. On the other hand, when it is larger than 2.2, the performance on snow in the 50% wear stage is deteriorated. This is because the edge component in the axial direction is relatively reduced, and the traction performance in starting on snow is lowered. Therefore, the lower limit of the ratio EC50 / EL50 is preferably 2.0 or more.
On the other hand, when the ratio EC90 / EL90 is smaller than 2.85, the wet performance at the 90% wear stage is lowered. This is because the edge component in the circumferential direction is relatively reduced, and the grip force during turning is reduced. On the other hand, when it is larger than 3.4 , the wet grip performance as well as the performance on the snow in the 90% wear stage are deteriorated .

  In this example, in order to satisfy the above formulas (1) to (6), as shown in FIG. 2, the tread groove 5 has a 50% wear groove portion 12 that wears in the 50% wear state Y50, and A 90% wear groove 13 that wears in the 90% wear state Y90 is formed.

  The 50% worn groove portion 12 is shallower than the deepest tread groove 5A, so that it is worn in the 50% worn state Y50, and the groove bottom B12 is exposed on the tread surface in the 50% worn state Y50. It is. Therefore, as shown in FIG. 4, the groove depth H1 is 50% or less of the deepest groove depth H. However, if it is too shallow, it will be worn away at an early stage, and the effect of the present application cannot be sufficiently exhibited. Therefore, the groove depth H1 is set to 40 to 50%, preferably 45 to 50% of the deepest groove depth H. The 90% wear groove portion 13 is a shallow groove portion where the groove bottom B13 is exposed on the tread surface in the 90% wear state Y90, and the groove depth H2 is 90% or less of the deepest groove depth H. Preferably it is set to 80 to 90%, more preferably 85 to 90%.

The wear groove portions 12 and 13 can be provided at appropriate positions of the vertical groove 3 and the horizontal groove 4. Furthermore, all of the vertical groove 3 and the horizontal groove 4 may be formed as the wear groove portions 12 and 13. In this example, as shown in FIG. 2, the 50% wear groove portion 12 is formed on the center portion side of the inner lateral groove 4m and on the inner end side in the tire axial direction of the outer lateral groove 4s, and the 90% wear groove portion 13 is formed. The 50% wear groove 12 provided in the outer lateral groove 4s is adjacent to the outer side in the tire axial direction via a step K.

For example, as shown in the case of the outer lateral groove 4s, when the wear progresses and the 50% wear state Y50 is reached, the groove bottom B12 of the 50% wear groove 12 is formed as shown in FIG. It is exposed and the groove side edge Q12 of the 50% wear groove part 12 can be lost, and both end edges R12 of the groove bottom B12 can newly appear. In addition, the edge R12 on the outer side in the tire axial direction extends in the tire circumferential direction. When the wear further progresses and the 90% wear state Y90 is reached, as shown in FIG. 5B, the groove bottom B13 of the 90% wear groove 13 is exposed, and the groove side edge Q13 of the 90% wear groove 13 is defined. In addition to the loss, the edge R13 of the groove bottom B13 whose length in the tire circumferential direction is longer than the edge R12 can appear instead of the edge R12.

  In this manner, the wear groove portions 12 and 13 can freely abolish the edges that are the side edges and the end edges as wear progresses, and can satisfy the expressions (1) to (6). As shown in FIG. 6, a narrow groove 16 parallel to the horizontal groove 4m is formed in the groove bottom B12 of the 50% wear groove 12 provided in the horizontal groove 4m. In such a case, the circumferential edge component ec composed of both end edges R12 can be increased such that the appearance of the edge of the narrow groove 16 can cancel out the loss of the groove side edge Q12.

  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.

A heavy-duty tire of size 11R22.5 having the tread pattern of FIG. 1 was prototyped based on the specifications in Table 1, and the performance on the snow and wet performance of each sample tire were compared with the state when new, 50% worn state, and While evaluating in the 90% wear state, the results are shown in Table 1.
In Table 1, the values of EL00, EL50, and EL90 in Table 1 are displayed as indices in Comparative Example 1 where the length L1 of the total axial edge component of the Comparative Example 1 is 100. Similarly, in Comparative Example 2, the total axial edge component of the new example 1 in the first example is used as an index with the length L2 of the total axial edge component of the new example 2 set to 100 in the first comparative example. In the third embodiment, the length L3 of the total axial direction edge component of the third embodiment is indicated by an index with the length L3 being 100.
In Table 1, each value of EC00, EC50, and EC90 in Table 1 is represented by an index with the length C1 of the total circumferential edge component of Comparative Example 1 as new as 100. Similarly, in Comparative Example 2, the total circumferential direction edge component of the new example 1 in the first example is used as an index in which the length C2 of the total circumferential direction edge component in the new example 2 is 100. In the third embodiment, the length C3 is indicated by an index with the length C4 of the total circumferential edge component at the time of a new article as 100.
FIG. 7 shows the state of the tread surface in each wear state in the tire of Example 1, and FIG. 8 shows the state of the tread surface in each wear state in the tire of Comparative Example 1.

(1) Performance on snow;
Tires are attached to all wheels of a rim (7.50 × 22.5) and internal pressure (800 kPa) on a vehicle (2-D vehicle with a load of 8 t), and a 10% gradient of pressure snow in a constant volume state The time until the vehicle started from the stop state on the uphill and traveled 10 m was measured in each wear state (new state, 50% wear state, 90% wear state). And the reciprocal number of the measurement time was displayed by the index | exponent which set the comparative example 1 to 100 for every abrasion state. The larger the value, the better the traction on the snow.

(2) Wet performance;
Using the same vehicle as above, the lap time for one round of a course with a radius of 30 m in a wet state is measured in each wear state, and the reciprocal of the measurement time is an index with Comparative Example 1 as 100 for each wear state. displayed. The larger the value, the better the wet performance.

  As shown in the table, it can be confirmed that the tires of the examples can suppress the decrease in the performance on the snow and the wet performance as the wear progresses.

It is an expanded view which shows one Example of the tread pattern of the tire for heavy loads of this invention. It is an expanded view which expands and shows the right half. It is a top view explaining the circumferential direction edge component and axial direction edge component of a land part circumferential edge. It is sectional drawing explaining the state at the time of a new article, a 50% wear state, and a 90% wear state. (A), (B) is a top view explaining increase / decrease in the edge component by an abrasion groove part. It is a top view which shows a narrow groove. It is an expanded view which shows the condition of the tread surface of each abrasion state in the tire of Example 1 of Table 1. FIG. 3 is a development view illustrating a state of a tread surface in each wear state in the tire of Comparative Example 1 in Table 1.

Explanation of symbols

2 Tread surface 3 Vertical groove 4 Horizontal groove 5 Tread groove 5A Deepest tread groove 6 Block 7 Land portion 12 50% wear groove portion 13 90% wear groove portion 16 Narrow groove e Land portion circumferential edge sc Circumferential edge component el Axial edge component Y50 50% wear state Y90 90% wear state

Claims (2)

By providing a tread groove on the tread surface including a plurality of vertical grooves extending in the tire circumferential direction and a horizontal groove extending in a direction crossing the vertical grooves, the tread surface is partitioned into a plurality of land portions including blocks. A pneumatic tire,
The transverse groove includes an outer longitudinal groove extending most on the tread edge side and an outer transverse groove extending between the tread edges,
The outer lateral groove has a widened portion whose groove width increases toward the outer side in the tire axial direction, and the outer lateral groove has 50% of the deepest tread groove depth of the tread groove. A 50% wear groove portion that wears in a 50% wear state where the wear is worn, and a 90% wear state in which 90% of the groove depth of the deepest tread groove is worn on the outer side in the tire axial direction of the 50% wear groove portion. % Wear groove part is next to each other through a step,
In the 50% wear state, an edge (R12) extending in the tire circumferential direction on the outer side in the tire axial direction of the groove bottom of the 50% wear groove portion appears, and in the 90% wear state, the length in the tire circumferential direction is increased. The edge (R13) of the groove bottom of the 90% wear groove that is longer than the edge (R12) appears in the widened portion, and the land circumferential edge that surrounds the land within the tread surface in the tire circumferential direction. The total axial direction in which the circumferential edge component is summed for the entire land portion located on the tread surface, and the axial edge component in the tire axial direction of the land circumferential edge is summed for the entire land portion. In the edge component EL,
The total circumferential edge component on the tread surface in a new state is EC00, the total axial edge component is EL00, the total circumferential edge component in the 50% wear state is EC50, and the total axial edge component is EL50. A heavy-duty tire satisfying the following formulas (1) to (6), where EC90 is the total circumferential edge component and EL90 is the total axial edge component in the 90% wear state.
EC50> EC00 ----- (1)
EC90> EC00 ----- (2)
EL50> 0.5 × EL00 ----- (3)
EL90> 0.5 × EL00 ----- (4)
1.5 <EC50 / EL50 <2.2 ----- (5)
2.85 <EC90 / EL90 < 3.4 ----- (6)   The heavy duty tire according to claim 1, wherein the 50% worn groove portion or the 90% worn groove portion includes a narrow groove at a groove bottom thereof.

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