JP7367543B2 - tire - Google Patents

Description

The present invention relates to tires.

Patent Document 1 below describes a tire in which a tread portion is provided with four zigzag circumferential grooves extending in a zigzag shape in the tire circumferential direction and hexagonal blocks divided between the zigzag circumferential grooves. ing.

JP2019-104411A

In recent years, there has been a demand for improving the rolling resistance performance and life performance of tires. In order to meet such demands, it is conceivable to increase the pattern rigidity of the tread portion by reducing the groove depth and groove width of the zigzag circumferential groove.

However, the method of simply reducing the groove depth and groove width of the zigzag circumferential groove has a problem in that wet performance deteriorates.

The present invention was devised in view of the above-mentioned circumstances, and its main purpose is to provide a tire that can improve rolling resistance performance and life performance without significantly impairing wet performance.

The present invention provides a tire having a tread portion, wherein the tread portion is provided with a plurality of circumferential grooves extending in a zigzag shape in the circumferential direction of the tire, thereby dividing a plurality of land portions, and the circumferential The directional grooves include a pair of crown circumferential grooves disposed on both sides of the tire equator, and a pair of shoulder circumferential grooves disposed on the outer side of each of the crown circumferential grooves in the tire axial direction, and the land portion is , a crown land portion disposed between the pair of crown circumferential grooves, and a pair of middle land portions disposed between the crown circumferential groove and the shoulder circumferential groove, the crown land portion is divided into a plurality of hexagonal-shaped crown blocks by a crown lateral groove, the middle land portion is divided into a plurality of hexagonal-shaped middle blocks by a middle lateral groove, and the groove width of the crown circumferential groove is: The groove width of the shoulder circumferential groove is 0.01 to 0.2 times, and the groove depth of the crown circumferential groove is 1.0 to 1.2 times the groove depth of the shoulder circumferential groove. be.

In the tire according to the present invention, it is desirable that the groove depth of the crown circumferential groove is greater than 1.0 times the groove depth of the shoulder circumferential groove.

In the tire according to the present invention, it is preferable that the groove depth of the crown circumferential groove is 1.1 times or less the groove depth of the shoulder circumferential groove.

In the tire according to the present invention, the crown block is provided with a sipe extending in the tire axial direction, the tread surface of the crown block is divided into a first part and a second part sandwiching the sipe, and the first part The length in the tire circumferential direction is preferably 0.9 to 1.1 times the length of the second portion in the tire circumferential direction.

In the tire according to the present invention, it is preferable that the area of the tread surface of the middle block is larger than the area of the tread surface of the crown block.

In the tire according to the present invention, it is preferable that the area of the tread surface of the middle block is 1.10 times or less the area of the tread surface of the crown block.

In the tire according to the present invention, it is preferable that the groove bottom of the crown lateral groove is provided with a sipe that extends linearly in the longitudinal direction of the crown lateral groove.

In the tire according to the present invention, it is desirable that the groove width of the shoulder circumferential groove is 10 mm or more.

In the tire according to the present invention, the tread portion is provided with a shoulder lateral groove extending outward in the tire axial direction from each of the shoulder circumferential grooves, and the groove depth of the shoulder lateral groove is the groove depth of the shoulder circumferential groove. It is desirable that it is 0.1 to 0.4 times the height.

In the tire according to the present invention, it is preferable that the groove depth of the shoulder lateral groove is 0.2 to 0.3 times the groove depth of the shoulder circumferential groove.

The groove width of the crown circumferential groove is 0.2 times or less the groove width of the shoulder circumferential groove. As a result, the hexagonal crown block and middle block come into contact with each other and support each other on the ground contact surface of the tread portion. Therefore, deformation and slippage of both blocks are suppressed, and rolling resistance performance and life performance are improved.

Further, the groove width of the crown circumferential groove is 0.01 times or more the groove width of the shoulder circumferential groove. As a result, drainage performance within the crown circumferential groove is ensured, so that deterioration in wet performance can be suppressed.

Further, the groove depth of the crown circumferential groove is 1.0 times or more the groove depth of the shoulder circumferential groove. This further suppresses deterioration in wet performance. The groove depth of the crown circumferential groove is 1.2 times or less the groove depth of the shoulder circumferential groove. This makes it possible to suppress the occurrence of cracks and the like at the bottom of the crown circumferential groove, which has a small groove width. This helps improve life performance.

Therefore, the tire of the present invention can improve rolling resistance performance and life performance without impairing wet performance.

1 is a developed view of a tread portion of a tire showing an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line AA in FIG. 1. (a) is an enlarged view of the crown circumferential groove, and (b) is an enlarged view of the shoulder circumferential groove. It is an enlarged view of a crown block and a middle block. (a) is a cross-sectional view taken along line BB in FIG. 4, and (b) is a cross-sectional view taken along line CC in FIG.

Hereinafter, one embodiment of the present invention will be described based on the drawings.
FIG. 1 is a developed view of a tread portion 2 of a tire 1 showing one embodiment of the present invention. FIG. 1 shows a tread portion 2 of a pneumatic tire for heavy loads. The present invention can be applied to various tires 1, such as pneumatic tires for passenger cars and industrial vehicles, and non-pneumatic tires in which pressurized air is not filled inside the tire (for example, airless tires). I can do it.

As shown in FIG. 1, the tread portion 2 of this embodiment is divided into a plurality of land portions 5 by providing a plurality of circumferential grooves 3 extending in a zigzag shape in the circumferential direction of the tire. The circumferential grooves 3 increase driving force and braking force on wet road surfaces and suppress deterioration of wet performance.

The circumferential grooves 3 of this embodiment include a pair of crown circumferential grooves 3A, 3A disposed on both sides of the tire equator C, and a pair of shoulder circumferential grooves disposed on the outside of each crown circumferential groove 3A in the tire axial direction. directional grooves 3B, 3B. In this embodiment, four circumferential grooves 3 are provided. It is desirable that at least four circumferential grooves 3 are provided.

The land portion 5 includes a crown land portion 5A disposed between the pair of crown circumferential grooves 3A, and a pair of middle land portions 5B disposed between the crown circumferential groove 3A and the shoulder circumferential groove 3B. , 5B. In this embodiment, the land portion 5 includes a pair of shoulder land portions 5C, 5C disposed between each shoulder circumferential groove 3B and the tread end Te. In this way, the tread portion 2 of this embodiment is formed with at least five land portions 5.

The above-mentioned "tread edge Te" is obtained by applying a regular load to the tire 1 in a regular state, which is assembled to a regular rim (not shown) and filled with a regular internal pressure, and is grounded on a flat surface at a camber angle of 0 degrees. This is determined as the axially outermost point of contact with the tire at the time of the tire. The length in the tire axial direction between both tread ends Te, Te is determined as the tread width TW. Unless otherwise specified, the dimensions of each part of the tire 1 are the values in the normal state.

In addition, the above-mentioned "regular rim" refers to a rim defined by each standard for each tire 1 in the standard system including the standard on which the tire 1 is based, and in the case of JATMA it is a "standard rim" and in the case of TRA it is a rim. "Design Rim" is "Measuring Rim" for ETRTO.

In addition, the above-mentioned "regular internal pressure" is the air pressure specified for each tire 1 by each standard in the standard system including the standard on which the tire 1 is based, and for JATMA it is the "maximum air pressure", and for TRA it is the air pressure specified for each tire 1. The maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" is "INFLATION PRESSURE" for ETRTO.

In addition, the above-mentioned "regular load" is the load specified for each tire 1 by each standard in the standard system including the standard on which the tire 1 is based, and for JATMA it is the "maximum load capacity", for TRA For example, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and for ETRTO it is "LOAD CAPACITY".

The crown land portion 5A is divided into a plurality of hexagonal crown blocks 8 by a crown lateral groove 4A. The hexagonal crown block 8 has high rigidity and improves rolling resistance performance and life performance.

The middle land portion 5B is divided into a plurality of hexagonal middle blocks 9 by middle lateral grooves 4B.

The groove width W1 of the crown circumferential groove 3A is 0.01 to 0.2 times the groove width W2 of the shoulder circumferential groove 3B. Since the groove width W1 of the crown circumferential groove 3A is less than 0.2 times the groove width W2 of the shoulder circumferential groove 3B, the hexagonal crown block 8 and middle block 9 come into contact with each other on the ground contact surface of the tread portion 2. and support each other. Therefore, deformation and slippage of both blocks 8 and 9 are suppressed, so rolling resistance performance and life performance are improved. Since the groove width W1 of the crown circumferential groove 3A is 0.01 times or more the groove width W2 of the shoulder circumferential groove 3B, drainage performance in the crown circumferential groove 3A is ensured, thereby suppressing deterioration in wet performance. can do.

In order to effectively exhibit the above-mentioned effect, the groove width W1 of the crown circumferential groove 3A is preferably 0.05 times or more, and preferably 0.13 times or less, the groove width W2 of the shoulder circumferential groove 3B. In order to greatly suppress the deterioration of wet performance, the groove width W2 of the shoulder circumferential groove 3B is preferably 10 mm or more, and more preferably 12 mm or more. In order to suppress a decrease in pattern rigidity of the middle land portion 5B, the groove width W2 of the shoulder circumferential groove 3B is preferably 18 mm or less, and more preferably 16 mm or less.

FIG. 2 is a cross-sectional view taken along line AA in FIG. As shown in FIG. 2, the groove depth D1 of the crown circumferential groove 3A is 1.0 to 1.2 times the groove depth D2 of the shoulder circumferential groove 3B. Since the groove depth D1 of the crown circumferential groove 3A is 1.0 times or more the groove depth D2 of the shoulder circumferential groove 3B, deterioration in wet performance can be further suppressed. Since the groove depth D1 of the crown circumferential groove 3A is 1.2 times or less than the groove depth D2 of the shoulder circumferential groove 3B, cracks etc. occur at the groove bottom 3s of the crown circumferential groove 3A where the groove width W1 is small. can be suppressed. This helps improve life performance.

The groove depth D1 of the crown circumferential groove 3A of this embodiment is greater than 1.0 times the groove depth D2 of the shoulder circumferential groove 3B. This greatly suppresses deterioration in wet performance. Furthermore, the groove depth D1 of the crown circumferential groove 3A of this embodiment is 1.1 times or less the groove depth D2 of the shoulder circumferential groove 3B. Therefore, the occurrence of cracks and the like at the groove bottom 3s is greatly suppressed.

FIG. 3(a) is an enlarged view of the crown circumferential groove 3A. As shown in FIG. 3(a), the crown circumferential groove 3A of the present embodiment includes a first crown inclined part 10A and a second crown inclined part 10B which is inclined in the opposite direction to the first crown inclined part 10A. Contains. The first crown inclined portion 10A is inclined, for example, to one side (lower right in FIG. 3(a)) with respect to the tire circumferential direction. For example, the second crown inclined portion 10B is inclined toward the other side (lower left in FIG. 3(a)) with respect to the tire circumferential direction. In this embodiment, the first crown inclined portions 10A and the second crown inclined portions 10B are arranged alternately in the tire circumferential direction.

The angle θ1 of the first crown inclined portion 10A and the second crown inclined portion 10B with respect to the tire circumferential direction is preferably 5 to 25 degrees. Since the crown circumferential groove 3A has an edge component in the tire axial direction, it increases the braking force and driving force on wet road surfaces and smoothly drains water inside the groove.

The crown circumferential groove 3A includes, for example, a first crown convex portion 11a that protrudes toward the tread end Te side, and a second crown convex portion 11b that protrudes toward the tire equator C side. The first crown convex portion 11a and the second crown convex portion 11b are formed at the connection portion between the first crown inclined portion 10A and the second crown inclined portion 10B. In this embodiment, the first crown convex portions 11a and the second crown convex portions 11b are arranged alternately in the tire circumferential direction.

FIG. 3(b) is an enlarged view of the shoulder circumferential groove 3B. As shown in FIG. 3(b), the shoulder circumferential groove 3B of this embodiment includes a first sloped portion 12A and a second sloped portion 12B that slopes in the opposite direction to the first sloped portion 12A. There is. The first inclined portion 12A is inclined, for example, to one side (lower right in FIG. 3(b)) with respect to the tire circumferential direction. The second inclined portion 12B is, for example, inclined toward the other side (lower left in FIG. 3(b)) with respect to the tire circumferential direction. In this embodiment, the first inclined portions 12A and the second inclined portions 12B are arranged alternately in the tire circumferential direction.

It is desirable that the angle θ2 of the first inclined portion 12A and the second inclined portion 12B with respect to the tire circumferential direction is 5 to 25 degrees. Such shoulder circumferential grooves 3B also increase braking force and driving force on wet road surfaces, and drain water smoothly in the grooves. Although not particularly limited, the absolute value of the difference between the angle θ1 of the crown first inclined portion 10A and the angle θ2 of the first inclined portion 12A is desirably 5 degrees or less.

The shoulder circumferential groove 3B includes, for example, a first shoulder convex portion 13a that protrudes toward the tread end Te side, and a second shoulder convex portion 13b that protrudes toward the tire equator C side. The first shoulder convex portion 13a and the second shoulder convex portion 13b are formed at a connecting portion between the first inclined portion 12A and the second inclined portion 12B. In this embodiment, the first shoulder convex portions 13a and the second shoulder convex portions 13b are arranged alternately in the tire circumferential direction.

As shown in FIG. 1, in the present embodiment, the crown circumferential groove 3A has a zigzag phase shifted from the adjacent shoulder circumferential groove 3B by about 1/2 pitch in the circumferential direction.

FIG. 4 is an enlarged view of the crown block 8 and middle block 9. As shown in FIG. 4, the crown block 8 of this embodiment is formed so that the maximum length LA in the tire circumferential direction is larger than the maximum width WA in the tire axial direction. Since such a crown block 8 has high circumferential rigidity, movement and deformation of the block at the time of contact with the ground are suppressed to a low level, and the crown block 8 has excellent wear resistance.

In order to effectively exhibit the above-mentioned effect, it is desirable that the maximum length LA of the crown block 8 in the tire circumferential direction is 1.2 to 1.8 times the maximum width WA in the tire axial direction. Since the maximum length LA of the crown block 8 is less than 1.8 times the maximum width WA, the balance between the circumferential rigidity and the axial rigidity of the crown block 8 is maintained, and wear due to loads when traveling straight or turning is avoided. can be suppressed. It is desirable that the maximum length LA of the crown block 8 is, for example, 20% to 40% of the tread width TW.

For example, the width Wa of the crown block 8 in the tire axial direction increases from both outer sides in the tire circumferential direction toward the center side in the tire circumferential direction. Such a crown block 8 has high circumferential rigidity and high lateral rigidity. In this embodiment, the crown block 8 has an inwardly bulging shape that tapers inversely from both outer sides in the tire circumferential direction toward the center in the tire circumferential direction.

In this embodiment, the crown block 8 is provided with a sipe 15 extending in the tire axial direction. Since such a sipe 15 is a narrow cut, it is possible to scratch and discharge a thin water film on the road surface without significantly impairing block rigidity.

A sipe is herein defined as a notch-like body having a width of less than 1.5 mm. Further, the grooves including the circumferential grooves and the lateral grooves are groove-shaped bodies having a groove width of 1.5 mm or more. Sipe and groove are distinguished by their width.

The sipe 15 crosses the crown block 8, for example. Further, the sipe 15 is arranged on the center side in the tire circumferential direction where the width Wa of the crown block 8 is large. Thereby, the above-mentioned effect is effectively exhibited. In this embodiment, the sipe 15 communicates with the middle lateral grooves 4B on both sides via the crown circumferential groove 3A.

The sipe 15 is, for example, a three-dimensional sipe (a so-called Miura-fold structure sipe) extending in a zigzag shape in the longitudinal direction and depth direction. In such a sipe 15, the unevenness of the wall surface of the sipe 15 meshes with each other, so that an excessive decrease in the rigidity of the crown block 8 is further suppressed, and rolling resistance performance and life performance are maintained high. Note that the sipes 15 are not limited to three-dimensional sipes, and may extend linearly in the depth direction.

FIG. 5(a) is a sectional view taken along the line BB in FIG. 4. As shown in FIG. 5(a), the depth D3 of the sipe 15 is smaller than the groove depth D1 of the crown circumferential groove 3A. Such sipes 15 suppress slipping and deformation of the crown block 8. Although not particularly limited, the depth D3 of the sipe 15 is preferably 70% to 90% of the groove depth D1 of the crown circumferential groove 3A.

As shown in FIG. 4, the tread surface 8a of the crown block 8 is divided into a first portion 8A and a second portion 8B, which sandwich the sipe 15 therebetween. The length L1 of the first portion 8A in the tire circumferential direction is preferably 0.9 to 1.1 times the length L2 of the second portion 8B in the tire circumferential direction. Since the length L1 of the first portion 8A is 0.9 times or more and 1.1 times or less the length L2 of the second portion 8B, uneven wear such as heel-and-toe wear is suppressed.

In this embodiment, the middle block 9 has substantially the same configuration as the crown block 8. Therefore, in this specification, the structure of the middle block 9 that is different from that of the crown block 8 will be explained, and the same structure as the crown block 8 will be denoted by the same reference numeral, and detailed explanation thereof will be omitted.

The area Am of the tread surface 9a of the middle block 9 is larger than the area Ac of the tread surface 8a of the crown block 8. The middle block 9 adjacent to the shoulder circumferential groove 3B is more likely to deform during ground contact than the crown block 8. Therefore, by increasing the area Am of the middle block 9, the difference in wear between the middle block 9 and the crown block 8 can be reduced. In this specification, the area Am of the tread surface 9a of the middle block 9 and the area Ac of the tread surface 8a of the crown block 8 are the areas of virtual tread surfaces obtained by filling the sipes 15.

If the difference between the area Am of the middle block 9 and the area Ac of the crown block 8 becomes large, the difference in wear may even become large. Therefore, the area Am of the middle block 9 is preferably 1.2 times or less, and preferably 1.1 times or less, the area Ac of the crown block 8.

The crown lateral groove 4A of this embodiment connects between the crown second convex portions 11b, 11b of each crown circumferential groove 3A. The crown lateral groove 4A extends linearly, for example. Note that the crown lateral groove 4A may extend in an arc shape.

As shown in FIG. 5A, the crown lateral groove 4A of this embodiment has a crown groove wall surface 20 that connects the deepest groove bottom 4s and the tread surface 8a of the crown block 8. In this embodiment, the crown groove wall surface 20 includes a crown first wall surface portion 20a and a crown second wall surface portion 20b. For example, the crown first wall surface portion 20a is inclined with respect to the tire normal direction from the tread surface 8a. The crown first wall portion 20a of this embodiment extends linearly. For example, the crown second wall surface portion 20b is continuous with the crown first wall surface portion 20a and the groove bottom 4s and is inclined at a larger angle than the crown first wall surface portion 20a. The crown second wall portion 20b of this embodiment extends in an arc shape.

It is desirable that the groove depth D4 of the crown lateral groove 4A is smaller than the groove depth D1 of the crown circumferential groove 3A. Such crown lateral grooves 4A greatly improve rolling resistance performance and life performance. In this embodiment, the groove depth D4 of the crown lateral groove 4A is smaller than the groove depth D2 of the shoulder circumferential groove 3B.

A sipe 21 extending linearly in the longitudinal direction of the crown lateral groove 4A is provided at the groove bottom 4s of the crown lateral groove 4A. Such a sipe 21 is useful for increasing the volume of the crown lateral groove 4A, and greatly suppresses deterioration in wet performance. The sipes 21 of this embodiment communicate with the crown circumferential grooves 3A (shown in FIG. 4) on both sides. Thereby, the above-mentioned effect is effectively exhibited.

The depth D5 of the sipe 21 is preferably 1 mm or more, more preferably 1.5 mm or more. Note that if the depth D5 of the sipes 21 becomes excessively large, deformation and slippage of the block cannot be suppressed, and there is a risk that rolling resistance performance and life performance may deteriorate. Therefore, the depth D5 of the sipe 21 is preferably 3 mm or less, and more preferably 2.5 mm or less. Further, in this embodiment, the sum (D4+D5) of the depth D5 of the sipe 21 and the groove depth D4 of the crown lateral groove 4A is smaller than the groove depth D1 of the crown circumferential groove 3A, and the shoulder circumferential groove It is smaller than the groove depth D2 of 3B and larger than the depth D3 of the sipe 15.

As shown in FIG. 4, the middle lateral groove 4B connects the crown first convex portion 11a of the crown circumferential groove 3A and the shoulder second convex portion 13b of the shoulder circumferential groove 3B. The middle lateral groove 4B extends linearly, for example. Note that the middle lateral groove 4B may extend in an arc shape.

FIG. 5(b) is a sectional view taken along the line CC in FIG. As shown in FIG. 5(b), the middle lateral groove 4B of this embodiment has a middle groove wall surface 22 that connects the deepest groove bottom 4t and the tread surface 9a of the middle block 9. In this embodiment, the middle groove wall surface 22 includes a middle first wall surface portion 22a, a middle second wall surface portion 22b, and a middle third wall surface portion 22c. The middle first wall surface portion 22a is, for example, inclined from the tread surface 9a with respect to the tire normal direction. In this embodiment, the middle first wall portion 22a extends linearly. The middle second wall section 22b of this embodiment is continuous with the middle first wall section 22a and is inclined at a smaller angle than the middle first wall section 22a. In this embodiment, the middle second wall portion 22b extends linearly. The middle second wall portion 22b extends, for example, in parallel to the tire normal direction. In this embodiment, the middle third wall portion 22c is continuous with the middle second wall portion 22b and the groove bottom 4t. The middle third wall portion 22c extends, for example, in an arc shape.

The middle lateral groove 4B can have a relatively smaller groove volume than the crown lateral groove 4A. The middle lateral groove 4B is provided in the middle land portion 5B where deformation and slippage of the block is relatively large when the block touches the ground. Therefore, the middle lateral groove 4B can suppress a decrease in pattern rigidity of the middle land portion 5B more than a decrease in pattern rigidity of the crown land portion 5A provided with the crown lateral groove 4A. This reduces the difference in wear between the crown land portion 5A and the middle land portion 5B.

It is desirable that the groove depth D6 of the middle lateral groove 4B is smaller than the groove depth D1 of the crown circumferential groove 3A. Such middle lateral grooves 4B greatly improve rolling resistance performance and life performance. In this embodiment, the groove depth D6 of the middle lateral groove 4B is smaller than the groove depth D2 of the shoulder circumferential groove 3B. The groove depth D6 of the middle lateral groove 4B is, for example, the same as the groove depth D4 of the crown lateral groove 4A.

Although not particularly limited, the groove depth D6a of the middle first wall surface portion 22a is preferably 60% or more, more preferably 70% or more, and preferably 90% or less of the groove depth D6 of the middle lateral groove 4B. More preferably, it is 80% or less.

A sipe 21 extending linearly in the longitudinal direction of the middle lateral groove 4B is provided at the groove bottom 4t of the middle lateral groove 4B. In this embodiment, the sipes 21 of the middle lateral groove 4B have the same configuration as the sipes 21 of the crown lateral groove 4A, so the explanation thereof will be omitted.

As shown in FIG. 1, the shoulder land portion 5C is provided with a shoulder lateral groove 4C extending outward in the tire axial direction from the shoulder circumferential groove 3B.

The shoulder lateral groove 4C is arranged between the first shoulder convex portion 13a and the tread end Te. Such a shoulder lateral groove 4C smoothly discharges water in the shoulder circumferential groove 3B to the outside of the tread end Te by utilizing rolling of the tire 1.

The shoulder lateral groove 4C connects the first groove portion 25a that extends from the shoulder circumferential groove 3B toward the outside in the tire axial direction with the same groove width W4a, and connects the first groove portion 25a and the tread end Te, and also extends the groove toward the outside in the tire axial direction. The second groove portion 25b has a width W4b that continuously increases. Such shoulder lateral grooves 4C further suppress deterioration of wet performance.

As shown in FIG. 2, the groove depth D7 of the shoulder lateral groove 4C is preferably 0.1 to 0.4 times the groove depth D2 of the shoulder circumferential groove 3B. Such a shoulder lateral groove 4C suppresses deformation and slippage of the shoulder land portion 5C and improves rolling resistance performance and life performance. From this point of view, the groove depth D7 of the shoulder lateral groove 4C is preferably 0.2 times or more, and preferably 0.3 times or less, the groove depth D2 of the shoulder circumferential groove 3B. The first groove portion 25a and the second groove portion 25b are formed to have the same groove depth, for example.

Although particularly preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the illustrated embodiments, and can be modified and implemented in various ways.

A heavy-duty pneumatic tire having the basic pattern shown in Figure 1 was prototyped. Then, tests were conducted on the wet performance, life performance, and rolling resistance performance of each test tire. The test methods and common specifications are as follows.
Size: 11R22.5
Groove depth D2 of shoulder circumferential groove: 12.5mm
Groove width W2 of shoulder circumferential groove: 14mm
Maximum length of crown block LA/TW: 30%

<Wet performance>
A test driver drove a test vehicle with test tires installed on all wheels on a wet asphalt road with a water depth of 1 mm. The brakes were applied when the test vehicle was traveling at a speed of 60km/h, and the braking distance until it came to a stop was measured. The results are shown as an index with the braking distance of Comparative Example 1 being 100. The smaller the number, the better the wet performance.
Rim: 7.50 x 22.5
Internal pressure: 830kPa
Test vehicle: 2-D vehicle (loading capacity 10t)

<Life performance>
A test driver drove the above-mentioned vehicle on an asphalt road test course, and after driving, the rear wheel (drive wheel) tires showed cracks formed at the bottom of the crown circumferential groove and heel-and-toe wear that occurred in each groove. Uneven wear and occurrence of wear were confirmed. The overall situation was then evaluated by the test driver's senses. The results are shown as a score with Comparative Example 1 being 100. The larger the number, the better the life performance.
Mileage: 10,000km

<Rolling resistance performance>
Using a rolling resistance tester, the rolling resistance of the test tire was measured under the following conditions based on ISO28580. The results are shown as an index with the rolling resistance of Comparative Example 1 as 100. The smaller the number, the better the rolling resistance. The results of the tests are shown in Tables 1 and 2.
Internal pressure: 830kPa
Load: 25.01kN
Speed: 80km/h

As shown in Table 1, the tires of the examples have improved rolling resistance performance and life performance while suppressing deterioration in wet performance.

1 Tire 3 Circumferential groove 3A Crown circumferential groove 3B Shoulder circumferential groove 5 Land portion 5A Crown land portion 5B Middle land portion 8 Crown block 9 Middle block

Claims (10)

A tire having a tread portion,
The tread portion is provided with a plurality of circumferential grooves extending in a zigzag shape in the circumferential direction of the tire, thereby dividing a plurality of land portions,
The circumferential grooves include a pair of crown circumferential grooves disposed on both sides of the tire equator, and a pair of shoulder circumferential grooves disposed on the outer side of each of the crown circumferential grooves in the tire axial direction,
The land portion includes a crown land portion disposed between the pair of crown circumferential grooves, and a pair of middle land portions disposed between the crown circumferential groove and the shoulder circumferential groove,
The crown land portion is divided into a plurality of hexagonal crown blocks by a crown lateral groove,
The middle land portion is divided into a plurality of hexagonal middle blocks by a middle lateral groove,
The groove width of the crown circumferential groove is 0.01 to 0.2 times the groove width of the shoulder circumferential groove,
The groove depth of the crown circumferential groove is 1.0 to 1.2 times the groove depth of the shoulder circumferential groove.
tire. The tire according to claim 1, wherein the groove depth of the crown circumferential groove is greater than 1.0 times the groove depth of the shoulder circumferential groove. The tire according to claim 1 or 2, wherein the groove depth of the crown circumferential groove is 1.1 times or less the groove depth of the shoulder circumferential groove. The crown block is provided with a sipe extending in the axial direction of the tire,
The tread surface of the crown block is divided into a first part and a second part sandwiching the sipe,
The tire according to any one of claims 1 to 3, wherein the length of the first portion in the tire circumferential direction is 0.9 to 1.1 times the length of the second portion in the tire circumferential direction. . The tire according to any one of claims 1 to 4, wherein the area of the tread surface of the middle block is larger than the area of the tread surface of the crown block. The tire according to claim 5, wherein the area of the tread of the middle block is 1.10 times or less the area of the tread of the crown block. The tire according to any one of claims 1 to 6, wherein the groove bottom of the crown lateral groove is provided with a sipe that extends linearly in the longitudinal direction of the crown lateral groove. The tire according to any one of claims 1 to 7, wherein the shoulder circumferential groove has a groove width of 10 mm or more. The tread portion is provided with shoulder lateral grooves extending outward in the tire axial direction from each of the shoulder circumferential grooves,
The tire according to any one of claims 1 to 8, wherein the groove depth of the shoulder lateral groove is 0.1 to 0.4 times the groove depth of the shoulder circumferential groove. The tire according to claim 9, wherein the groove depth of the shoulder lateral groove is 0.2 to 0.3 times the groove depth of the shoulder circumferential groove.

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