JP2004098854A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of suppressing uneven wear while maintaining high wet performance. <P>SOLUTION: A tread 12 has total four peripheral main grooves consisting of two center peripheral main grooves 14 extending along a tire peripheral direction and two shoulder peripheral main grooves 16, developing high draining performance. A center block is in an approximate Z-shape allowing lower rigidity than a rectangular block having the same width and a second block 30 is in an approximately rectangular shape allowing higher block rigidity. A ratio A1: A2: A3 of a dimension A1 of the center block 28 in a tire cross direction: a dimension A2 of the second block 30 in the tire cross direction: a dimension A3 of a shoulder block 32 in the tire cross direction is 100: 50-70: 60-80, thereby optimizing the rigidity of the second block 30 relative to the center block 28 and preventing the uneven wear of the second block 30. <P>COPYRIGHT: (C)2004,JPO

Description

試験の結果から、本発明の適用された実施例のタイヤは、従来例１，２のタイヤに比較して耐偏摩耗性が高く、かつウエットブレーキ性能、及び雪上ブレーキ性能が高いことが分かる。
【００８２】
【発明の効果】
以上説明したように、本発明の空気入りタイヤは上記の構成としたので、高いウエット性能を確保しつつ、偏摩耗を抑制することができる、という優れた効果を有する。
【図面の簡単な説明】
【図１】本発明の第１の実施形態に係る空気入りタイヤのトレッドの平面図である。
【図２】ショルダー周方向主溝の断面図である。
【図３】ショルダーブロックのタイヤ回転軸に直角な断面図である。
【図４】第２の実施形態に係る空気入りタイヤのトレッドの平面図である。
【図５】従来例１に係る空気入りタイヤのトレッドの平面図である。
【図６】従来例２に係る空気入りタイヤのトレッドの平面図である。
【符号の説明】
１０　　　空気入りタイヤ
１２　　　トレッド
１４　　　センター周方向主溝
１６　　　ショルダー周方向主溝
１８　　　偏摩耗犠牲突起
２２Ｌ　　第１のセンター横溝
２２Ｒ　　第２のセンター横溝
２２Ｃ　　センター周方向溝
２４　　　セカンド横溝
２６　　　ショルダー横溝
２８　　　センターブロック
３０　　　セカンドブロック
３２　　　ショルダーブロック[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a pneumatic tire having a block pattern, and more particularly to a pneumatic tire that avoids uneven wear and further improves running performance on a wet road surface.
[0002]
[Prior art]
Conventional pneumatic tires, particularly heavy duty pneumatic tires having a block pattern, include, for example, a pneumatic tire having a block pattern shown in FIG. 5 and a pneumatic tire having a block pattern shown in FIG. See Patent Document 1.).
[0003]
The tread 102 of the pneumatic tire 100 shown in FIG. 5 has a zigzag center-side circumferential main groove 104 disposed on both sides of the tire equatorial plane CL, and a radially outer side of the center-side circumferential main groove 104. A tread that is disposed between a zigzag shoulder-side circumferential main groove 106 and a pair of center-side circumferential main grooves 104 to form a substantially Z-shaped (substantially inverted S-shaped) groove in a tread plan view. A pair of lateral grooves 108 and 110 inclined upward to the left in plan view, a short circumferential groove 112 inclined upward to the right in a tread plan view, and a center-side circumferential main groove 104 and a shoulder-side circumferential main groove 106 are connected. A width direction groove 112 parallel to the tire width direction, and a width direction groove 114 parallel to the tire width direction extending from the shoulder side circumferential groove 106 toward the tread end are formed.
[0004]
At the center of the tread 102 in the tire width direction, a plurality of centers having a substantially S-shape in a tread plan view are defined by a center-side circumferential main groove 104, lateral grooves 108 and 110, and a circumferential short groove 112. A center block row composed of blocks 116 is formed, and a plurality of second blocks 118 defined on the outer side in the tire width direction by a center-side circumferential main groove 104, a shoulder-side circumferential main groove 106, and a width-direction groove 112. A shoulder block row composed of a plurality of shoulder blocks 120 partitioned by the shoulder-side circumferential main groove 106 and the width direction groove 114 is further formed outside the second block row.
[0005]
Here, the dimension (maximum dimension) of the center block 116 in the tire width direction is A1, the dimension (maximum dimension) of the second block 118 in the tire width direction is A2, and the dimension (maximum dimension) of the shoulder block 120 in the tire width direction is A3. Then, the ratio A1: A2: A3 of A1, A2, and A3 was set to 100: 47: 63.
[0006]
In the tread 202 of the pneumatic tire 200 shown in FIG. 6, a zigzag center circumferential main groove 204 arranged at the center in the tread width direction, and a center side circumferential main groove 204 are arranged outside in the tire width direction. The zigzag shoulder-side circumferential main groove 206, the center-side circumferential main groove 204, and the shoulder-side circumferential main groove 206 are disposed between the shoulder-side circumferential main groove 204 and the shoulder-side circumferential main groove 206. A pair of lateral grooves 208 and 210 inclined upward to the right in plan view of the tread, a short circumferential groove 212 inclined to the left upward in plan view of the tread, and a tire extending from the shoulder-side circumferential groove 206 toward the tread end. A width direction groove 208 parallel to the width direction is formed.
[0007]
On both sides of the tire equatorial plane CL of the tread 202, a plurality of center blocks having a substantially crank shape in a tread plan view defined by a center-side circumferential main groove 204, lateral grooves 208 and 210, and a circumferential short groove 212. A center block row consisting of 214 is formed, and a shoulder block row consisting of a plurality of shoulder blocks 216 partitioned by the shoulder side circumferential main groove 206 and the width direction groove 208 is formed on the outer side in the tire width direction. .
[0008]
At the groove bottom of the shoulder-side circumferential main groove 206, uneven wear sacrificial projections 218 are provided along the shoulder circumferential main groove.
[0009]
[Non-patent document 1]
Bridgestone Corporation Truck and bus tires Truck and bus retreaded tires Industrial vehicle tire general catalog Created in December 2001
[0010]
[Problems to be solved by the invention]
However, in the conventional pneumatic tire 100 having the block pattern shown in FIG. 5, the rigidity of the second block 118 is lower than the rigidity of the center block 116. There was a concern that uneven wear, etc. would occur.
[0011]
Further, the conventional pneumatic tire 200 having the block pattern shown in FIG. 6 has three circumferential main grooves, and it is difficult to achieve both wet performance compared to the pneumatic tire 100 having the block pattern shown in FIG. Was.
[0012]
An object of the present invention is to provide a pneumatic tire that can suppress uneven wear while ensuring high wet performance in consideration of the above fact.
[0013]
[Means for Solving the Problems]
The invention according to claim 1 is a pneumatic tire provided with four circumferential main grooves extending along the tire circumferential direction, and a tread pattern having a block pattern, wherein the two tires on the tire equatorial plane side are provided. A plurality of first circumferential grooves extending beyond the tire equatorial plane from one circumferential main groove toward the other circumferential main groove and terminating without being connected to the other circumferential main groove; The center lateral groove and the first center lateral groove are alternately arranged in the tire circumferential direction, and extend beyond the tire equatorial plane from the other circumferential main groove toward the one circumferential main groove, and A plurality of second center lateral grooves that terminate without being connected to one circumferential main groove; and a center circumferential groove extending along the tire circumferential direction that connects the first center groove and the second center groove. And the tire width direction A second lateral groove for connecting the outer circumferential main groove on the outer side and the circumferential main groove on the tire equatorial plane side; and a shoulder lateral groove extending from the outermost circumferential main groove in the tire width direction toward the tread end. In the center portion of the tread in the tire width direction, two circumferential main grooves on the tire equatorial plane side, the first center groove, the second center groove, and a center circumferential groove are defined. A plurality of center blocks are formed in a row along the tire circumferential direction to form a center block row, and the outer side of the center block in the tire width direction is partitioned by two circumferential main grooves and a second lateral groove. A plurality of second blocks are formed in a row along the tire circumferential direction to form a second block row, and the circumferential main groove and the shoulder are formed outside the second block in the tire width direction. -A plurality of shoulder blocks defined by the lateral grooves are arranged in a row along the tire circumferential direction to form a shoulder block row, and the size of the center block in the tire width direction is A1, and the size of the second block in the tire width direction is A2. And A1: A2: A3 = 100: 50 to 70:60 to 80 when the dimension of the shoulder block in the tire width direction is A3.
[0014]
Next, the operation of the pneumatic tire according to claim 1 will be described.
[0015]
First, in the pneumatic tire of the present embodiment, since the tread is provided with four circumferential main grooves extending along the tire circumferential direction, high drainage performance is obtained.
[0016]
It is substantially Z-shaped (substantially inverted S-shape) in a tread plan view defined by two circumferential main grooves on the tire equatorial plane side, a first center horizontal groove, a second center horizontal groove, and a center circumferential groove. The center block can reduce the block stiffness as compared with a block having the same width (tire width direction) having a tread planar shape of a rectangle (rectangle, parallelogram, etc.), and is more skewed than a rectangular block. Wear (heel and toe wear) hardly occurs.
[0017]
In addition, the second block defined by the circumferential main groove and the second lateral groove has a substantially rectangular shape in a tread plan view, and therefore has a high block rigidity.
[0018]
Here, when the dimension (maximum dimension) of the center block in the tire width direction is A1, the dimension (maximum dimension) of the second block in the tire width direction is A2, and the dimension (maximum dimension) of the shoulder block in the tire width direction is A3. In addition, since A1: A2: A3 = 100: 50-70: 60-80, the rigidity of the second block with respect to the center block is optimized, that is, the rigidity difference between the rigidity of the center block and the rigidity of the second block. And the rigidity of the second block can be ensured so that uneven wear (block punch) does not easily occur.
[0019]
For wet performance and snow performance, the edge component near the tire equatorial plane where the contact pressure is high is effective, but since the block rigidity is roughly determined by the size of the block, the center block is made smaller to reduce the rigidity. The edge component can be concentrated near the equatorial plane of the tire, and wet performance and snow performance can be improved.
[0020]
According to a second aspect of the present invention, in the pneumatic tire according to the first aspect, a position of a top is set lower than a tread surface at a bottom portion of the circumferential main groove on an outermost side in a tire width direction, and a road surface is provided at the time of ground contact. The uneven wear sacrifice projection which comes into contact with the peripheral main groove is provided along the circumferential main groove.
[0021]
Next, the operation of the pneumatic tire according to claim 2 will be described.
[0022]
Since there is a diameter difference between the diameter of the tread and the diameter at the top of the uneven wear sacrificial projection, when the pneumatic tire rotates and comes into contact with the road surface, the uneven wear sacrificial protrusion is dragged with respect to the road surface and is worn. Suppresses uneven wear adjacent to the circumferential groove. Also, the uneven wear of the land portion is prevented from progressing toward the center.
[0023]
In the case of a pneumatic tire provided with a plurality of circumferential grooves in the tread, uneven wear tends to occur particularly on the land portion on the shoulder side.
[0024]
Therefore, if the uneven wear sacrificial projection is provided on the groove bottom of the outer circumferential groove in the tire width direction that defines the land portion on the shoulder side, uneven wear on the land portion on the shoulder side can be effectively suppressed, and It is possible to effectively suppress the uneven wear of the land portion on the side from progressing to the center side.
[0025]
According to a third aspect of the present invention, in the pneumatic tire according to the first or second aspect, at least one of the center block, the second block, and the shoulder block is compared with at least a circumferential central portion. And the circumferential block ends are formed low.
[0026]
Next, the operation of the pneumatic tire according to claim 3 will be described.
[0027]
In a block in which the circumferential block ends are formed at least lower than at least the circumferential center, the maximum position of the contact pressure at the time of brand-new and at the beginning of wear is the circumferential center of the block. Therefore, when the pneumatic tire rotates, the portion with a low contact pressure, that is, the stepping end of the block slides more on the road surface than the center in the circumferential direction of the block, and the speed of progress of wear of the stepping end increases, The development of heel-and-toe wear after the initial wear can be delayed.
[0028]
According to a fourth aspect of the present invention, in the pneumatic tire according to any one of the first to third aspects, the first center groove and the second center groove rise leftward in a tread plan view. Characterized by the following:
[0029]
Next, the operation of the pneumatic tire according to claim 5 will be described.
[0030]
In the case of left lane driving like in Japan, the road is designed to descend left, so the amount of wear work increases due to the side force input from the left side in the traveling direction, but the center block is divided for the side force input By inclining the first center groove and the second center groove upward to the left in a tread plan view, an edge component extending in a direction intersecting the input direction can be secured, and at the same time, the first center groove , And the second center groove can be easily opened, so that, for example, the snow column shearing force caused by gripping the snow can be improved, thereby improving wet and on-snow performance.
[0031]
According to a fifth aspect of the present invention, in the pneumatic tire according to any one of the first to third aspects, the second lateral groove is inclined upward to the right in plan view of the tread.
[0032]
Next, the operation of the pneumatic tire according to claim 5 will be described.
[0033]
In the case of left lane driving like in Japan, the road is designed to descend left, so the work input wears from the left side in the direction of travel, which increases wear work, but in response to the side force input, the second block rises to the right. By doing so, it is possible to secure the rigidity of the second block with respect to the input from the front wheel, thereby improving the uneven wear resistance of the second block.
[0034]
According to a sixth aspect of the present invention, in the pneumatic tire according to any one of the first to fifth aspects, the shoulder lateral groove is inclined upward to the right in a tread plan view. .
[0035]
Next, the operation of the pneumatic tire according to claim 6 will be described.
[0036]
In the case of left lane driving like in Japan, the road is designed to descend left, so the amount of wear work increases due to the side force input from the left side in the traveling direction, but the shoulder block is divided for the side force input By inclining the shoulder lateral groove upward to the right in plan view of the tread, it is possible to secure the rigidity of the shoulder block with respect to input from the front wheel, thereby improving the uneven wear resistance of the shoulder block.
[0037]
According to a seventh aspect of the present invention, in the pneumatic tire according to any one of the first to third aspects, the first center groove and the second center groove rise rightward in a tread plan view. It is characterized by being inclined.
[0038]
Next, the operation of the pneumatic tire according to claim 7 will be described.
[0039]
For example, in the case of driving in the right lane such as the United States, the road is designed to descend to the right, so the amount of wear work increases due to the side force input from the right side in the traveling direction. By inclining the first center groove and the second center groove to be divided upward in the tread plan view, it is possible to secure an edge component extending in a direction intersecting the input direction. Since the center groove and the second center groove can be easily opened, for example, the snow column shearing force caused by gripping snow can be improved, thereby improving wet and on-snow performance.
[0040]
According to an eighth aspect of the present invention, in the pneumatic tire according to any one of the first to third aspects and the seventh aspect, the second lateral groove is inclined leftward and upward in a tread plan view. It is characterized by.
[0041]
Next, the operation of the pneumatic tire according to claim 8 will be described.
[0042]
For example, when driving in the right lane like in the United States, the road is designed to descend to the right, so the amount of wear work increases due to the side force input from the right side in the traveling direction, but a second block is added to the side force input. By raising it to the left, the rigidity of the second block with respect to the input from the front wheels can be ensured, whereby the uneven wear resistance of the second block can be improved.
[0043]
According to a ninth aspect of the present invention, in the pneumatic tire according to any one of the first to third aspects, the seventh aspect, and the eighth aspect, the shoulder lateral groove inclines leftward upward in a tread plan view. It is characterized by that.
[0044]
Next, the operation of the pneumatic tire according to claim 9 will be described.
[0045]
In the case of right lane driving such as in Japan, the road is designed to descend to the right, so the amount of wear work increases due to the side force input from the right side in the traveling direction, but the shoulder block is divided for the side force input By inclining the shoulder lateral groove upward to the left in a tread plan view, rigidity of the shoulder block with respect to input from the front wheel can be ensured, and thereby uneven wear resistance of the shoulder block can be improved.
[0046]
BEST MODE FOR CARRYING OUT THE INVENTION
[First Embodiment]
First Embodiment A pneumatic tire according to a first embodiment of the present invention will be described with reference to FIGS.
[0047]
FIG. 1 shows a pattern (part) of a tread 12 of a pneumatic tire 10 according to the present embodiment.
[0048]
The tread 12 has a center circumferential main groove 14 extending in a zigzag manner along the tire circumferential direction (the direction of the arrow A and the direction of the arrow A. The direction of the arrow A is the tire rotation direction) on both sides of the tire equatorial plane CL. A shoulder circumferential main groove 16 extending in a zigzag manner along the tire circumferential direction is formed outside the center circumferential main groove 14 in the tire width direction (arrow W direction).
[0049]
As shown in FIG. 1 and FIG. 2, a rib-shaped uneven wear sacrificial projection 18 whose top is set lower than the tread surface and which is in sliding contact with the road surface when touching the ground is provided at the bottom of the shoulder circumferential main groove 16. It is provided continuously along the direction main groove 16. A plurality of sipes 20 extending in the tire width direction are formed on the uneven wear sacrifice projection 18.
[0050]
As shown in FIG. 1, between the pair of center circumferential main grooves 14 of the tread 12, the zigzag of the left center circumferential main groove 14 from the top of the tire equatorial plane CL side to the right center circumferential main groove 14. And a plurality of first center lateral grooves 22L extending beyond the tire equatorial plane CL toward the right side and terminating without being connected to the right central circumferential main groove 14, and the first center lateral grooves 22L extend in the tire circumferential direction. The zigzag of the left center circumferential main groove 14 is arranged alternately and extends beyond the tire equatorial plane CL toward the right center circumferential main groove 14 from the top of the zigzag side of the tire equatorial plane CL. A plurality of second center lateral grooves 22R that terminate without being connected to the groove 14, and a tire equatorial plane CL that connects the first center lateral groove 22L and the second center lateral groove 22R. Center circumferential groove 22C extending linearly are formed a.
[0051]
The first center lateral groove 22L, the second center lateral groove 22R, and the center circumferential groove 22C form a crank groove portion 22 having a substantially crank shape in a tread plan view.
[0052]
Here, the first center lateral groove 22L and the second center lateral groove 22R are inclined to the upper left.
[0053]
Between the center circumferential main groove 14 and the shoulder circumferential main groove 16 of the tread 12, a second lateral groove 24 connecting the center circumferential main groove 14 and the shoulder circumferential main groove 16 has an interval in the tire circumferential direction. A plurality of openings are formed. The second lateral groove 24 is inclined upward to the right.
[0054]
A shoulder lateral groove 26 extending from the shoulder circumferential main groove 16 toward the tread end 12E is formed outside the shoulder circumferential main groove 16 in the tire width direction. The shoulder lateral groove 26 is inclined upward to the right.
[0055]
At the center of the tread 12 in the tire width direction, a center block 28 having a substantially Z (substantially inverted S-shape) shape in a tread plan view is defined by a center circumferential main groove 14 and a crank groove 22 in a tire circumferential direction. Along the rows, a center block row is formed.
[0056]
On the outer side of the center block 28 in the tire width direction, a substantially rectangular second block 30 defined by the center circumferential main groove 14, the shoulder circumferential main groove 16, and the second lateral groove 24 forms a line along the tire circumferential direction. To form a second block row.
[0057]
On the outer side in the tire width direction of the second block 30, a substantially rectangular shoulder block 32 defined by the shoulder circumferential main groove 16 and the shoulder lateral groove 26 forms a row along the tire circumferential direction to form a shoulder block row. I have.
[0058]
Here, the dimension (maximum dimension) of the center block 28 in the tire width direction is A1, the dimension (maximum dimension) of the second block 30 in the tire width direction is A2, and the dimension (maximum dimension) of the shoulder block 32 in the tire width direction is A3. In this case, it is preferable to satisfy A1: A2: A3 = 100: 50 to 70:60 to 80.
[0059]
In this embodiment, A1: A2: A3 is set to 100: 58: 67.
(Action)
In the pneumatic tire 10 of the present embodiment, the tread 12 has two center circumferential main grooves 14 extending along the tire circumferential direction and two shoulder circumferential main grooves 16, that is, four circumferential main grooves in the entire tread. Since it has grooves, high drainage performance can be obtained.
[0060]
The center block 28 having a substantially t-shape in a tread plan view has a lower block rigidity compared to a rectangular (rectangular, parallelogram, etc.) block in a tread plan view having the same tread area. It can be set and it is hard to generate uneven wear (heel and toe wear).
[0061]
On the other hand, the second block 30 having a substantially rectangular tread plan shape has a high block rigidity.
[0062]
Further, in this embodiment, the ratio A1: A2: A3 of the dimension A1 of the center block 28 in the tire width direction, the dimension A2 of the second block 30 in the tire width direction, and the dimension A3 of the shoulder block 32 in the tire width direction is 100: 58. : 67, the rigidity of the second block 30 with respect to the center block 28 can be optimized, that is, the difference in rigidity between the rigidity of the center block 28 and the rigidity of the second block 30 can be reduced, and uneven wear of the second block 30 ( Block punch).
[0063]
It should be noted that the wet performance and the performance on snow are effective in the edge component near the tire equatorial plane CL having a high contact pressure, and the block rigidity is substantially determined by the size of the block. By setting the shape of the block 28 and setting the ratio of the area to the other blocks as described above, it is possible to concentrate the edge component near the tire equatorial plane CL, and improve wet performance and snow performance. Can be done.
[0064]
When the pneumatic tire 10 rotates, the uneven wear sacrifice projection 28 comes into sliding contact with the road surface at the time of contact with the ground, due to the diameter difference between the diameter of the tread surface of the tread 12 and the diameter of the top of the uneven wear sacrifice projection 28, and The uneven wear (along the shoulder circumferential main groove 16) to be generated in the adjacent shoulder block 32 is worn as a shoulder.
[0065]
In particular, the uneven wear of the shoulder block 32 can be effectively suppressed by providing the uneven wear sacrificial projections 18 in the shoulder circumferential main groove 16 that defines the shoulder block 32 that is likely to be unevenly worn. Can be suppressed from progressing to the tire equatorial plane CL side.
[0066]
In the shoulder block 32 in which heel-and-toe wear easily occurs, as shown in a cross-sectional view perpendicular to the tire rotation axis in FIG. 3, the tread surface of the shoulder block 32 is formed in a substantially arc shape, and the stepped end and kick-out are performed. If the end is set lower than the center in the circumferential direction, the maximum position of the contact pressure at the time of new and initial wear is the center in the circumferential direction. As a result, the rate of wear development near the stepped end increases, and the progress of heel-and-toe wear after the initial stage of wear can be delayed.
[0067]
Further, if the treads of the center block 28 and the second block 30 are also formed in a substantially circular arc shape like the tread of the shoulder block 32, the progress of heel-and-toe wear can be delayed.
[0068]
Note that, here, the shape of the block tread surface when viewed in a cross section perpendicular to the tire rotation axis is a substantially arc shape, but at least the stepping end and the vicinity of the kicking end are set lower than the block central portion. The chamfer may be applied to the stepping end and the kicking end.
[0069]
By the way, in the case of traveling in the left lane as in Japan, since the road is designed to descend left, the amount of wear work increases due to the side force input from the left side in the traveling direction. By inclining the first center lateral groove 22L and the second center lateral groove 22R that partition the left upward in the tread plan view, it is possible to secure an edge component extending in a direction intersecting the input direction. Since the first center lateral groove 22L and the second center lateral groove 22R can be easily opened, for example, it is possible to improve the snow column shearing force caused by grabbing snow, thereby improving wet and on-snow performance. Can be.
[0070]
Further, by raising the second block 30 to the right in response to the side force input from the left side in the traveling direction described above, the rigidity of the second block 30 with respect to the input from the front wheels can be ensured. The uneven wear property can be improved.
[0071]
Furthermore, in response to the side force input from the left side in the traveling direction described above, the shoulder lateral groove 26 that defines the shoulder block 32 is inclined upward to the right in plan view of the tread, so that the rigidity of the shoulder block 32 with respect to the input from the front wheels is ensured. Accordingly, the uneven wear resistance of the shoulder block 32 can be improved.
[Second embodiment]
Next, a second embodiment of the pneumatic tire of the present invention will be described with reference to FIG. The same components as those of the above embodiment are denoted by the same reference numerals, and description thereof will be omitted.
[0072]
Since the block pattern of the pneumatic tire 10 according to the first embodiment is a block pattern suitable for traveling in the left lane, it is not suitable for traveling in the right lane.
[0073]
Since the input direction of the side force when traveling in the right lane is the opposite direction to the input direction of the side force when traveling in the left lane, the tread 12 of the pneumatic tire 40 is, as shown in FIG. The first center lateral groove 22L and the second center lateral groove 22R are inclined to the right, the second lateral groove 24 is inclined to the left, and the shoulder lateral groove 26 is inclined to the left.
[0074]
The operation and effect are the same as those of the first embodiment.
(Test example)
In order to confirm the effects of the present invention, two types of conventional tires and one type of tire according to the example to which the present invention was applied were prepared, and a field test and a real vehicle test were performed.
[0075]
Practical test: The test tire was mounted on a rim (7.50 × 22.5) and mounted on a vehicle (3-axle 20t vehicle, 2D4 format) with an internal pressure of 900 kPa, and was driven on a general road for 50,000 km. In the evaluation, the uneven wear amount (depth × width × length) after traveling 50,000 km was examined for the center block and the second block, and expressed as an index with the reciprocal of the uneven wear amount of Conventional Example 1 being 100. The evaluation indicates that the larger the index value, the smaller the uneven wear and the better the uneven wear resistance.
[0076]
Actual vehicle test: Wet brake performance and snow performance were examined. For the wet brake performance, a braking distance from 35 k / m on a test course at a depth of 2 mm was measured. The on-snow performance measured the braking distance from 30 k / m on the on-snow road surface. The evaluation was expressed by an index with the reciprocal of the braking distance of Conventional Example 1 being 100. The evaluation indicates that the larger the index value, the shorter the braking distance and the better the performance.
[0077]
Example tire: The tire according to the first embodiment (see FIGS. 1 and 2).
[0078]
Conventional example 1 tire: A tire having a tread pattern shown in FIG. 5 described in the conventional example.
[0079]
Conventional example 2 tire: A tire having the tread pattern shown in FIG. 6 described in the conventional example.
[0080]
The test results are as described in Table 1 below.
[0081]
[Table 1]

The test results show that the tires of the examples to which the present invention is applied have higher uneven wear resistance and higher wet braking performance and snow braking performance than the tires of Conventional Examples 1 and 2.
[0082]
【The invention's effect】
As described above, since the pneumatic tire of the present invention has the above-described configuration, it has an excellent effect of suppressing uneven wear while ensuring high wet performance.
[Brief description of the drawings]
FIG. 1 is a plan view of a tread of a pneumatic tire according to a first embodiment of the present invention.
FIG. 2 is a sectional view of a shoulder circumferential main groove.
FIG. 3 is a cross-sectional view of the shoulder block perpendicular to the tire rotation axis.
FIG. 4 is a plan view of a tread of a pneumatic tire according to a second embodiment.
FIG. 5 is a plan view of a tread of a pneumatic tire according to Conventional Example 1.
FIG. 6 is a plan view of a tread of a pneumatic tire according to Conventional Example 2.
[Explanation of symbols]
10 Pneumatic tires
12 tread
14 Center circumferential main groove
16 Shoulder circumferential main groove
18 Irregular wear sacrificial projection
22L 1st center lateral groove
22R 2nd center horizontal groove
22C Center circumferential groove
24 Second horizontal groove
26 Shoulder lateral groove
28 Center block
30 Second Block
32 shoulder block

Claims (9)

A pneumatic tire including four circumferential main grooves extending along the tire circumferential direction, and a tread pattern serving as a block pattern,
One of the two circumferential main grooves on the tire equatorial plane side extends beyond the tire equatorial plane from one circumferential main groove toward the other circumferential main groove and is connected to the other circumferential main groove. A plurality of first center transverse grooves terminating without
The first center lateral grooves are alternately arranged in the tire circumferential direction, extend from the other circumferential main groove toward the one circumferential main groove beyond the tire equatorial plane, and have one circumferential main groove. A plurality of second center transverse grooves terminating without being connected to the grooves;
A center circumferential groove extending along the tire circumferential direction connecting the first center groove and the second center groove;
A second lateral groove connecting the circumferential main groove on the outermost side in the tire width direction and the circumferential main groove on the tire equatorial plane side,
A shoulder lateral groove extending from the circumferential main groove on the outermost side in the tire width direction toward the tread end, on the tread,
At the center of the tread in the tire width direction, a plurality of sections are defined by two circumferential main grooves on the tire equatorial plane side, the first center groove, the second center groove, and a center circumferential groove. Center blocks are formed in a row along the tire circumferential direction to form a center block row,
On the outer side of the center block in the tire width direction, a plurality of second blocks partitioned by the two circumferential main grooves and the second lateral grooves form a row along the tire circumferential direction to form a second block row,
On the outer side in the tire width direction of the second block, a plurality of shoulder blocks partitioned by the circumferential main groove and the shoulder lateral groove are arranged in a row along the tire circumferential direction to form a shoulder block row,
When the size of the center block in the tire width direction is A1, the size of the second block in the tire width direction is A2, and the size of the shoulder block in the tire width direction is A3, A1: A2: A3 = 100: 50 to 70:60. A pneumatic tire that satisfies 80. At the bottom of the circumferential main groove on the outermost side in the tire width direction, the position of the top is set lower than the tread surface, and uneven wear sacrifice protrusions that come into contact with the road surface at the time of ground contact are provided along the circumferential main groove. The pneumatic tire according to claim 1, wherein: The peripheral block end is formed lower than at least the peripheral center part in any one of the said center block, the said 2nd block, and the said shoulder block, The Claim 1 or Claim 2 characterized by the above-mentioned. 3. The pneumatic tire according to 2. The pneumatic tire according to any one of claims 1 to 3, wherein the first center groove and the second center groove are inclined upward and left in a tread plan view. . The pneumatic tire according to any one of claims 1 to 4, wherein the second lateral groove is inclined upward to the right in a tread plan view. The pneumatic tire according to any one of claims 1 to 5, wherein the shoulder lateral groove is inclined upward to the right in a tread plan view. The pneumatic tire according to any one of claims 1 to 3, wherein the first center groove and the second center groove are inclined rightward upward in a tread plan view. . The pneumatic tire according to any one of claims 1 to 3, wherein the second lateral groove is inclined upward and left in a tread plan view. The pneumatic tire according to any one of claims 1 to 3, wherein the shoulder lateral groove is inclined upward and left in a tread plan view.

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