KR20120121833A - Pneumatic tire - Google Patents

Abstract

PURPOSE: A pneumatic tire is provided to improve weight performance while preventing the reduction of steering stability and partial abrasion performance. CONSTITUTION: A pneumatic tire comprises a pair of center main grooves(3), a pair of center shoulder major grooves(4), a pair of center land portions(5), a pair of center shoulder land portion(6), a center minor groove(7), and a center lateral groove(8). The center main grooves are extended in the circumferential direction of a tire. The shoulder main groove is extended in the circumferential direction of a tire. The pair of center shoulder land portion is extended between the shoulder main groove and a tread ground end(Te). The center minor groove is formed in the inside portion of the middle portion of a tire. The center minor groove is formed deeper than those of the center main groove and the shoulder main groove. The center lateral groove connects the center main groove and the shoulder main groove.

Description

Pneumatic tire {PNEUMATIC TIRE}

The present invention relates to a pneumatic tire, particularly a pneumatic tire suitable for a small truck, which has improved wet performance while suppressing deterioration in steering stability performance and wear resistance.

BACKGROUND ART Pneumatic tires of a block pattern in which a plurality of blocks are formed in a tread portion are known. In recent years, further improvements in wet performance have been desired for such pneumatic tires. In order to improve the wet performance, for the purpose of smoothly draining the water film between the tread portion and the road surface, for example, it has been proposed to increase the groove width of the main groove or the lateral groove provided in the tread portion.

However, in the above-described method, there is a problem that the pattern stiffness decreases because the ground area decreases, and the steering stability performance and the wear resistance performance deteriorate.

Japanese Patent Laid-Open No. 2002-46427

The present invention has been made in view of the above-described problems, and based on defining the arrangement position of each main groove extending in the circumferential direction of the tire, the groove depth of the sub groove and the transverse groove, the width of the land portion of each land portion, and the shape of the ground plane. It is a main object of the present invention to provide a pneumatic tire having improved wet performance while suppressing deterioration of steering stability performance and wear resistance performance.

The invention according to claim 1 of the present invention includes a center main groove that extends continuously in the tire circumferential direction on the tire equator, and a pair of continuous extension in the tire circumferential direction on both sides of the tire axial direction of the center main groove. A pneumatic tire in which a pair of center land portions extending between the shoulder main groove and the center main groove and a pair of shoulder land portions extending between the shoulder main groove and the tread ground end are separated by a shoulder main groove. In the normal load load state in which the rim is mounted, the normal pressure is applied, the normal load is loaded, and the camber angle is ground to the plane at 0 degrees. 1.05 times the ground length in the circumferential direction of the tire at the shoulder position with a distance of 40% of the ground width to 1 .15 times, the width of the land portion in the tire axial direction of the center land portion is 0.8 times or more and less than 1.0 times the width of the land portion in the tire axial direction of the shoulder land portion. It extends continuously in the tire circumferential direction in the region in the tire axial direction rather than the middle position of the land portion width, and has a groove depth of 0.2 to 0.5 times the average groove depth of the groove depth of the center main groove and the groove depth of the shoulder main groove. A center sub groove and a center transverse groove connecting the center main groove and the shoulder main groove and having a groove depth of 0.2 times to 0.5 times the average groove depth are provided, and the shoulder land portion is a continuous rib without interruption in the circumferential direction of the tire. It is a pneumatic tire characterized by the above-mentioned.

In addition, in the invention according to claim 2, the center land portion includes an inner block in the tire axial direction and an outer block in the tire axial direction than the center sub groove, and the block width in the tire axial direction of the inner block is the outer side. The pneumatic tire of Claim 1 which is 0.6 times-0.9 times the block width of a block.

In addition, according to the invention of claim 3, the inner block is provided with a semi-open type inner sipe extending from the center main groove outward in the tire axial direction, and the outer block has a semi-open extending outward from the shoulder main groove in the tire axial direction. A type of outer sipe is provided, wherein the total number of the inner sipes is smaller than the total number of the outer sipes.

Moreover, according to invention of Claim 4, the said inner block forms substantially parallelogram shape when the angle with respect to the tire circumferential direction of the said center horizontal groove is 45 degree | times-75 degree | times, and the said outer block has a some by the said outer sipe The outer block piece is divided into an outer block piece, and the outer block piece includes a first outer piece including an acute angle corner portion of a tire axially outer side of the outer block, and a first corner piece including an obtuse corner portion of a tire axially outer side of the outer block. It is a pneumatic tire of Claim 3 including 2 outer pieces, and the minimum length La of the tire circumferential direction of a said 2nd outer piece is shorter than the minimum length Lb of the tire circumferential direction of a said 1st outer piece. .

In addition, according to the invention described in claim 5, the inner block is divided into a plurality of inner block pieces by the inner sipe, and the inner block pieces include a first corner portion at an acute angle in the tire axial direction of the inner block. And a second inner piece including an inner piece and a corner portion of an obtuse angle in the tire axial direction of the inner block, wherein the minimum width Wa in the tire axial direction of the second inner piece is equal to that of the first inner piece. The pneumatic tire according to claim 3 or 4, which is smaller than the minimum width Wb in the tire axial direction.

The pneumatic tire of the present invention includes a center main groove that extends continuously in the tire circumferential direction on the tire equator, and a pair of shoulder main grooves that extend continuously in the tire circumferential direction on both sides of the tire axial direction of the center main groove. By this, a pair of center land portions extending between the shoulder main groove and the center main groove and a pair of shoulder land portions extending between the shoulder main groove and the tread ground end are distinguished.

In the normal load load state in which the rim is mounted on the regular rim, the normal internal pressure is charged, and the normal load is loaded and the camber angle is grounded at 0 degrees, the ground surface of the tread portion has a ground length in the tire circumferential direction on the tire equator. And 1.05 times to 1.15 times the ground length in the circumferential direction of the tire at the shoulder position which is at a distance of 40% of the tread ground width from the tire equator. Such a pneumatic tire can reduce the difference in the ground pressures on both sides of the tire axial direction in the center land portion, and the difference in the ground pressures of the center land portion and the shoulder land portion. Therefore, the pneumatic tire of this invention can suppress uneven wear, such as shoulder drop abrasion which was easy to produce in the shoulder land part, and also improves uneven wear performance.

Further, the land portion width in the tire axial direction of the center land portion is set to 0.8 or more and less than 1.0 times the land portion width in the tire axial direction of the shoulder land portion. As a result, the rigidity of the shoulder land portion to which a large lateral force is applied during turning travel can be improved, and the steering stability performance and the wear resistance performance can be improved.

Further, in the center land portion, an average groove depth of the groove depth of the center main groove and the groove depth of the shoulder main groove is continuously extended in the tire circumferential direction in an area in the tire axial direction than the intermediate position of the land portion width of the center land portion. A center sub groove having a groove depth of 0.2 times to 0.5 times the center side groove and a center side groove having a groove depth of 0.2 to 0.5 times the average groove depth connecting the center main groove and the shoulder main groove are provided. This center sub groove drains the water film between the center land portion and the road surface more reliably. In addition, the center transverse groove helps to easily discharge the water in the center main groove or the center sub groove to the shoulder main groove side. In addition, the center sub groove and the center transverse groove are defined such that the groove depth is 0.2 times to 0.5 times the average depth. Therefore, the pneumatic tire of the present invention can further improve the wet performance while preventing the rigidity of the center land portion from being lowered and ensuring the steering stability performance and the wear-resistant wear resistance in a high dimension.

In addition, the shoulder land portion is a rib that is continuous without breaking in the tire circumferential direction. As a result, the stiffness of the shoulder land portion can be further increased, and a large change in the ground pressure in the vicinity of the tread ground end can be countered, and the steering stability performance and the wear resistance against wear are ensured to a higher level.

BRIEF DESCRIPTION OF THE DRAWINGS The exploded view of the tread part which shows the pneumatic tire of one Embodiment of this invention.
Fig. 2 (a) is a plan view showing a ground plane in which the pneumatic tire of the present embodiment is grounded on the road surface, and (b) is a cross sectional view parallel to the tire equator plane showing the state of (a).
3 is a partially enlarged view of FIG. 1.

As shown in FIG. 1, the pneumatic tire (hereinafter, simply referred to as "tire") of the present embodiment is suitably used as, for example, a tire for a small truck, and the tread portion 2 has a tire equator ( One center main groove 3 continuously extending in the tire circumferential direction on C) and a pair of shoulder main grooves 4 extending continuously in the tire circumferential direction on both sides of the tire axial direction of the center main groove 3 are provided. do. Accordingly, the tread portion 2 has a pair of center land portions 5 extending between the center main groove 3 and the shoulder main groove 4, and between the shoulder main groove 4 and the tread ground end Te. A pair of extended shoulder land portions 6 are distinguished. Therefore, the tire of this embodiment is equipped with four land parts in the tread part 2 in total.

Here, the "tread ground end" (Te) is a tire when the rim is mounted on a normal rim, and the tire 1 of a normal state is loaded with a normal internal pressure, and is grounded in a plane with a camber angle of 0 degrees. It is set as the ground position of the outermost tire axial direction. The distance in the tire axial direction between the tread ground ends Te and Te is determined as the tread ground width TW. In addition, unless otherwise indicated, the dimension of each part of a tire shall be a value in the said normal state.

The term "regular rim" refers to a rim defined by the tire for each tire in a standard system including a standard on which the tire is based, for example, "standard rim" for JATMA, "Design Rim" for TRA, and "" for ETRTO. Measuring Rim ".

In addition, in the standard system including the standard on which the tire is based, the "normal internal pressure" refers to the air pressure determined by each tire for each tire, and the maximum air pressure for JATMA and the table "TIRE LOAD LIMITS AT VARIOUS COLD" If it is the maximum value described in "INFLATION PRESSURES" and ETRTO, "INFLATION PRESSURE" is used. If the tire is for a passenger car, it is 180 kPa.

In addition, "regular load" is a load defined by each tire in the standard system including the standard on which the tire is based, "JATMA" Maximum load capacity ", TRA table" TIRE LOAD LIMITS AT VARIOUS COLD " "LOAD CAPACITY" is the maximum value described in "INFLATION PRESSURES" and ETRTO. If the tire is for a passenger car, the load corresponds to 88% of the load.

In the present embodiment, the center main groove 3 includes a straight portion 3A in which the groove width of the center main groove 3 is constant over the tire circumferential direction, and a bulging portion in which the groove width is larger than the straight portion 3A. 3B) are formed alternately. In the center portion 3A, such a center main groove 3 can restrain unstable behavior such as whistling and tilting of the vehicle during braking, and can smoothly discharge the drainage in the straight portion 3A. In addition, in the bulge portion 3B, the water film on the road surface can be effectively collected. Therefore, the center main groove 3 can improve steering stability performance or wet performance.

Moreover, the said shoulder main groove 4 is linear along a tire circumference direction, and is formed in fixed width in this embodiment. In addition, the shoulder main groove 4 of the present embodiment is formed wider than the center main groove 3. This shoulder main groove 4 helps to increase steering stability or wet performance.

In addition, the groove widths of the center main grooves 3 and the shoulder main grooves 4 are groove widths perpendicular to the longitudinal direction of the grooves, which are also the same in other grooves below (W1, W2) and groove depths (not shown). This can be done according to convention. However, when the groove widths W1 and W2 and / or the groove depths are excessively large, the rigidity of each land portion 5 and 6 is deteriorated, and steering stability performance and wear resistance performance tend to deteriorate, and conversely, excessively. Smallness tends to deteriorate drainage. Therefore, the groove widths W1 and W2 are preferably, for example, 2.5% to 8.0% of the tread width TW, and the groove depth is preferably 8.0 mm to 15.0 mm.

Further, the arrangement position of the shoulder main groove 4 is, for example, the tire axial distance L1 between the center line G2 and the tire equator C is preferably 13% or more of the tread ground width TW, More preferably, it is 20% or more, Preferably it is 26% or less, More preferably, it is 25% or less. By setting the shoulder main groove 4 in such a range, the rigid balance of each of the center land portion 5 and the shoulder land portion 6 is improved and the steering stability performance is improved.

As shown in (a) of FIG. 2 and (b) which is a cross section near the tire equator C, the ground plane Se of the tread part 2 under the normal load state (ground in this drawing) The area surrounded by the edge YY] is a shoulder position at which the ground length Lc in the tire circumferential direction on the tire equator C is 40% of the tread ground width TW from the tire equator C. It is set to 1.05 times to 1.15 times the ground length Ls in the tire circumferential direction in Sh). That is, in the present invention, the ground plane Se is set smaller than the ground plane of the conventional tire Lc / Ls, thereby being substantially rectangular in shape. Such a tire has a small difference between the ground pressures on both sides of the tire axial direction in the center land portion 5, and a difference in the ground pressures between the center land portion 5 and the shoulder land portion 6. Shoulder drop wear, which was more likely to occur, can be suppressed, and further, wear resistance performance is improved. On the other hand, in the present embodiment, since the center main groove 3 is provided on the tire equator C, the ground length Lc is a virtual ground edge that smoothly connects the ground edges Y on both sides of the tire axial direction ( Y1) is determined based on.

Here, when the ratio (Lc / Ls) of the ground length Lc on the tire equator C and the ground length Ls at the shoulder position Sh is smaller than 1.05, the shoulder land portion 6 at the time of straight traveling is carried out. The grounding pressure increases, the straightness deteriorates, the wear energy of the shoulder land portion 6 increases, and shoulder wear easily occurs. On the contrary, when the ratio Lc / Ls is larger than 1.15, the grounding pressure of the shoulder land portion 6 becomes excessively smaller than that of the center land portion 5, dragging occurs in the shoulder land portion 6, and also the shoulder drop. Wear is easy to occur. From this point of view, the ratio (Lc / Ls) is preferably 1.07 or more, and more preferably 1.13 or less.

As shown in FIG. 1, the center land portion 5 has a land portion width Wc in the tire axial direction of the center land portion 5 in the tire axial direction of the shoulder land portion 6. It is set to 0.8 times or more and less than 1.0 times the land portion width Ws. The center land portion 5 and the shoulder land portion 6 secure the balance of the rigidity of each land portion 5 and 6 to increase steering stability performance and wear resistance performance. On the other hand, when the land portion widths Wc and Ws of the land portions 5 and 6 are not constant widths, the maximum width is defined as the land portion width.

In addition, the center land portion 5 is a center sub groove 7 that extends continuously in the tire circumferential direction in an area in the tire axial direction from an intermediate position of the land portion width Wc of the center land portion 5. And a center transverse groove 8 connecting the center main groove 3 and the shoulder main groove 4. As a result, the center land portion 5 includes the inner block rows 10R in which the inner blocks 10 divided in the tire axial direction than the center sub grooves 7 are arranged side by side in the tire circumferential direction and the center sub grooves 7. The outer blocks 11 separated on the outside in the tire axial direction are divided into outer row rows 11R arranged side by side in the tire circumferential direction.

The center sub groove 7 of this embodiment extends linearly along the tire circumferential direction. The center sub groove 7 can effectively discharge the water film between the center land portion 5 and the road surface.

The center lateral groove 8 extends inclined with respect to the tire axial direction. In the pair of center land portions 5 and 5, the inclination of the center transverse groove 8 may be in the same direction or in the opposite direction. In this embodiment, the center lateral grooves 8 inclined in the same direction (right upward in this example) are provided in each center land part 5. The center lateral groove 8 can smoothly discharge the water in the center main groove 3 to the shoulder main groove 4 by using the centrifugal force at the time of turning regardless of the rotation direction of the tire.

Angle (theta) 1 with respect to the tire circumferential direction of the center horizontal groove 8 becomes like this. Preferably it is 45 degrees or more, More preferably, it is 50 degrees or more, More preferably, it is 75 degrees or less, More preferably, it is 65 degrees or less. When the angle θ1 is increased, the drainage property at the time of straight traveling may deteriorate. On the contrary, when the angle θ1 is decreased, the rigidity of the center land portion 5 may be lowered. On the other hand, in this invention, since the ground pressure in the center land part 5 was made uniform, the said angle (theta) 1 of the center horizontal groove 8 can be made small.

3, the center horizontal groove 8 of this embodiment is formed in the center part of the center horizontal groove 8, and the width | variety 12 which the groove width was constant, etc. The width of the groove 12 is connected to the center main groove 3 and the width of the groove is increased from the center main groove 3 to the first wide part 13, and the equal width 12 and the shoulder main groove 4 are connected to each other. The 2nd widening part 14 which becomes large in this shoulder main groove 4 side is included. This center lateral groove 8 helps to improve the wet performance by making the drainage between the center main groove 3 and the shoulder main groove 4 more smoothly.

In order to exert such an effect effectively, the groove width ratio W4a / W4 of the groove width W4a of the first widening portion 13 and the groove width W4 of the equal width portion 12 is preferably 1.1 or more, and more. Preferably it is 1.3 or more. Similarly, the groove width ratio W4 b / W4 of the groove width W4b of the second widening portion 14 and the groove width W4 of the equal width portion 12 is preferably 1.5 or more, and more preferably 2.0 or more. to be. On the other hand, when the groove width ratios W4a / W4 and W4b / W4 become large, the rigidity of the inner block 10 and / or the outer block 11 may be lowered. From this point of view, the groove width ratio W4a / W4 is preferably 2.1 or less, and more preferably 1.9 or less. The groove width ratio W4b / W4 is preferably 4.5 or less, more preferably 4.0 or less. In addition, to smoothly drain to the tread ground end Te side, the groove width W4b of the second widening portion 14 is preferably larger than the groove width W4a of the first widening portion 13.

In addition, the groove depth D3 (not shown) of the center sub groove 7 and the groove depth D4 (not shown) of the center transverse groove 8 are both the groove depth of the center main groove 3 and the shoulder main groove 4. ) Is set to 0.2 to 0.5 times the average groove depth DA (not shown) of the groove depth. The center sub groove 7 and the center horizontal groove 8 can smoothly discharge the water film between the center land portion 5 and the road surface, while preventing the rigidity of the center land portion 5 from being lowered. On the other hand, if the groove depth D3 of the center sub groove 7 and the groove depth D4 of the center lateral groove 8 are less than 0.2 times the average groove depth DA, the improvement of the wet performance cannot be expected. When the depths D3 and D4 exceed 0.5 times the average groove depth DA, the rigidity of the center land portion 5 is lowered, and the steering stability performance and the wear resistance performance deteriorate. In particular, the groove depths D3 and D4 are more preferably 0.3 times or more of the average groove depth DA, and still more preferably 0.4 times or less.

Further, in view of exerting the above-described action, the groove width W3 of the center sub groove 7 is preferably 15% or more, more preferably 20% of the groove width W2 of the shoulder main groove 4. It is more than 45%, More preferably, it is 45% or less, More preferably, it is 40% or less. Similarly, the minimum groove width of the center lateral groove 8 (the groove width of the equal width portion 12 in this example) W4 is preferably 1.0 mm or more, more preferably 2.0 mm or more, and preferably 5.0. Mm or less, More preferably, it is 3.5 mm or less.

The block width W6 in the tire axial direction of the outer block 11 is larger than the block width W5 of the inner block 10. Thereby, the lateral rigidity of the outer block 11 to which a large lateral force acts at the time of turning becomes large, and can improve abrasion resistance performance and steering stability performance. On the other hand, if the block width W6 of the outer block 11 is made excessively large, the lateral rigidity of the inner block 10 will be excessively lowered, which may deteriorate steering stability performance and wear resistance performance of this portion. . Therefore, the block width W5 of the inner block 10 is preferably 0.6 times or more, more preferably 0.7 times or more, and preferably 0.9 times or less of the block width W6 of the outer block 11. More preferably, it is 0.8 times or less.

In addition, the inner block 10 of the present embodiment is provided with a semi-open type inner sipe 15 that extends from the center main groove 3 outward in the tire axial direction and whose outer end is terminated in the inner block 10. As a result, the inner block 10 is divided into a plurality of inner block pieces 10a by the inner sipe 15. The inner side block piece 10a of this embodiment is the 1st inner side piece 10a1 containing the corner part Ku1 of the acute angle inside of the tire axial direction of the inner block 10, and the tire shaft of the inner block 10. As shown in FIG. It consists of the 2nd inner side piece 10a2 containing the corner part Ku2 of obtuse angle of a direction inner side.

In addition, the outer block 11 is provided with a semi-open type outer sipe 16 which extends from the shoulder main groove 4 in the tire axial direction and whose inner end is terminated in the outer block 11. Accordingly, the outer block 11 is divided into a plurality of outer block pieces 11a by the outer sipe 16. In the present embodiment, the outer block piece 11a includes the first outer piece 11a1 and the tire of the outer block 11 that include the corner portion Ks1 of the acute angle on the outside of the tire axial direction of the outer block 11. And a second outer piece 11a2 comprising an angularly obtuse corner portion Ks2.

The inner sipe 15 and the outer sipe 16 reduce strain and suppress heel and toe wear of each block 10 and 11 without excessively reducing the rigidity of the center land portion 5, Demonstrates the edge effect and improves traction on wet roads.

In addition, it is preferable that the total number of the inner sipes 15 is smaller than the total number of the outer sipes 16. Thereby, while restraining the rigidity fall of the inner block 10 with a large ground pressure at the time of a straight run, many edge components can be provided to the outer block 11 with a large lateral force at the time of turning. In addition, it becomes possible to equalize the ground pressure of the outer block 11 with a large block width in the tire axial direction, to reduce deformation, and the like.

In addition, it is preferable that both the inner sipe 15 and the outer sipe 16 extend in the same direction as the center side groove 8, and furthermore, the angle with respect to the tire circumferential direction of each sipe 15, 16 is equal to that of the center side groove. It is preferable to form at the same angle as the angle θ1. Each of these sipes 15, 16 helps to ensure high rigidity of each block piece 10a, 11a divided by the inner block 10 and the outer block 11.

In addition, in order to further improve the above-mentioned action, the tire axial length L5 of the inner sipe 15 is preferably 65% or more and 85% or less of the block width W5 of the inner block 10. Similarly, the tire axial length L6 of the outer sipe 16. Preferably it is 65% or more and 85% or less of the block width W6 of the outer block 11.

In addition, in this embodiment, the minimum length La of the tire circumferential direction of the 2nd outer side piece 11a2 is formed smaller than the minimum length Lb of the tire circumferential direction of the said 1st outer side piece 11a1. That is, the obtuse corner portion Ks2 of the block whose rigidity is sufficiently easy to secure the minimum length Lb of the first outer piece 11a1 including the acute angle corner portion Ks1 of the block whose rigidity tends to decrease. By making it larger than the minimum length La of the 2nd outer piece 11a2 containing the, the rigid balance of each outer piece 11a1 and 11a2 can be ensured, and the uneven | wearing abrasion etc. which tend to generate | occur | produce in the outer block 11 can be suppressed. . On the other hand, when the minimum length La is excessively smaller than the minimum length Lb, the rigid balance of each of the outer pieces 11a1 and 11a2 may be lowered to deteriorate the wear resistance performance. Therefore, the ratio La / Lb of the minimum length La of the second outer piece 11a2 and the minimum length Lb of the first outer piece 11a1 is preferably 0.65 or more, more preferably It is 0.75 or more, More preferably, it is 0.95 or less, More preferably, it is 0.85 or less.

In addition, in this embodiment, the minimum width Wa of the tire axial direction of the 2nd inner side piece 10a2 is formed smaller than the minimum width Wb of the tire axial direction of the said 1st inner side piece 10a1. That is, the obtuse-angle corner part Ku2 of the block which is easy to ensure sufficient rigidity for the said minimum width Wb of the 1st inner side piece 10a1 containing the acute-angle corner part Ku1 of the block from which rigidity tends to fall. By making it larger than the minimum width Wa of the 2nd inner piece 10a2 containing, comprehensively secures the rigid balance of each inner piece 10a1 and 10a2, and improves steering stability performance. On the other hand, when the minimum width Wa is excessively smaller than the minimum width Wb, the rigid balance of each of the inner pieces 10a1 and 10a2 may be lowered to deteriorate the wear resistance performance. Therefore, the ratio Wa / Wb of the minimum width Wa of the second inner piece 10a2 and the minimum width Wb of the first inner piece 10a1 is preferably 0.85 or more, more preferably It is 0.87 or more, Preferably it is 0.95 or less, More preferably, it is 0.93 or less.

In addition, the shoulder land portion 6 is a rib that is continuous without breaking in the tire circumferential direction. Thereby, the rigidity of the shoulder land part 6 becomes higher, and steering stability performance and abrasion resistance performance are further improved. In addition, the effect of suppressing uneven wear in the vicinity of the tread ground terminal Te where the change in the ground pressure becomes large is great.

On the tire equator C side of the shoulder land portion 6 of the present embodiment, the shoulder inner lug groove 20 extending shortly from the shoulder main groove 4 in the tire axial direction and terminated in the shoulder land portion 6. ) And a shoulder inner sipe 21 having a shorter length in the tire axial direction than the shoulder inner lug groove 20 is provided. The shoulder inner lug groove and the shoulder inner sipe help to alleviate the deformation of the rib and to suppress the track wear and the like that tends to occur on the lateral edge of the rib. Further, on the tread ground end Te side of the shoulder land portion 6, the shoulder outer lug groove 22 extending from the tread ground end Te in a shorter length in the tire axial direction and terminated in the shoulder land portion 6. ) And a shoulder outer sipe 23 having a shorter length in the tire axial direction than the shoulder outer lug groove 22 is provided.

As mentioned above, although especially preferable embodiment of this invention was described in detail, this invention is not limited to embodiment shown and can be variously modified and implemented.

Example

Pneumatic tires for small trucks (size: 205 / 85R15) having the pattern of FIG. 1 and based on the specifications in Table 1 were prepared and tested for each performance of these pneumatic tires. In addition, a common specification is as follows.

Tread Ground Width (TW): 150 mm

Rim Size: 15 × 5.5J

Center Home

Groove width (W1) / tread ground width (TW): 5.1%

Groove depth: 10.1 mm

<Shoulder main home>

Groove width (W2) / tread ground width (TW): 6.5%

Groove depth: 10.1 mm

Center Center Home

Groove width (W3) / tread ground width (TW): 1.8%

Center horizontal groove

Groove width (W4): 2.2 mm

Groove depth (D4): 2.3 mm

<Inner sipe>

Width: 6.0 mm to 9.0 mm

Sipe depth: 8.5 mm

<Outside sipe>

Width: 6.0 mm to 9.0 mm

Sipe depth: 6.0 mm

Etc

<Each shoulder rug home>

Groove depth: 7.7 mm

<Each shoulder sipe>

Width: 2.0 mm to 5.0 mm

Sipe Depth: 5.0 mm to 10.0 mm

Steering Stability Performance

Each construction tire is equipped with four wheels on a Japanese light truck having the following specifications, and the test course on the dry asphalt road surface is driven by one driver, and the steering stability regarding steering wheel responsiveness, rigidity, grip, etc. Was evaluated by the sensory evaluation of the driver. The result was represented by the index which makes the comparative example 1 100. The larger the value, the better.

Displacement: 3000 cm 3

Pressure resistance: 600 kPa

Loading load: 1t

<Lateral hydroplaning test>

In the test vehicle, the vehicle was entered while increasing the speed step by step on a course in which a pavement having a depth of 10 mm and a length of 20 m was installed on an asphalt road surface having a radius of 100 m, and measuring the lateral acceleration (lateral G), 55 The average transverse G of the front wheel at the speed of km / h to 80 km / h was calculated. The result was represented by the index which makes comparative example 1 100. The larger the value, the better.

<My Wear Wear Performance>

The difference in the amount of wear at both edges of the tire axial direction of the shoulder main groove after running under the same vehicle condition was measured. Specifically, each construction tire was mounted on four wheels, the dry asphalt road surface was run 15000 km, and five points were measured on the tire circumference to calculate an average value. The result was represented by the exponent which makes the reciprocal of the comparative example 1 100. The larger the value, the smaller the amount of uneven wear and the better.

The test results are shown in Table 1.

As a result of the test, it can be confirmed that the tire of the example has improved various performances as compared with the comparative example.

2: tread part 3: center main home
4: shoulder main groove 5: center land part
6: shoulder land part 7: center sub groove
8: Center horizontal groove C: Tire equator
Wc: Land part width of center land part Ws: Land part width of shoulder land part
Te: Tread Ground

Claims (5)

The shoulder main groove and the center are formed by a center main groove extending continuously in the tire circumferential direction on the tire equator and a pair of shoulder main grooves extending continuously in the tire circumferential direction on both sides of the tire axial direction of the center main groove. A pneumatic tire in which a pair of center land portions extending between main grooves and a pair of shoulder land portions extending between the shoulder main groove and the tread ground end are divided,
In the normal load load condition where the rim is mounted on the normal rim, filled with the normal internal pressure, loaded with the normal load, and grounded on the plane at 0 degrees to the camber angle.
The ground surface of the tread portion is 1.05 times to 1.15 times the ground length in the circumferential direction of the tire at the shoulder position where the ground length in the circumferential direction on the tire equator is 40% of the tread ground width from the tire equator,
The center land portion has a land portion width in the tire axial direction of the center land portion of which is 0.8 to 1.0 times the width of the land portion in the tire axial direction of the shoulder land portion.
The center land portion extends continuously in the tire circumferential direction in an area in the tire axial direction than the middle position of the land portion width, and is 0.2 times the average groove depth between the groove depth of the center main groove and the groove depth of the shoulder main groove. A center sub groove having a groove depth of 0.5 times, and a center transverse groove connecting the center main groove and the shoulder main groove and having a groove depth of 0.2 times to 0.5 times the average groove depth,
The shoulder land portion is a pneumatic tire, characterized in that the continuous rib in the tire circumferential direction without breaking. According to claim 1, wherein the center land portion, the inner block in the tire axial direction and the outer block in the tire axial direction than the center sub groove,
The block width in the tire axial direction of the inner block is 0.6 to 0.9 times the block width of the outer block. The said inner block is provided with the semi-open type inner sipe extended from a center main groove to a tire axial direction outer side,
The outer block is provided with a semi-open type outer sipe extending from the shoulder main groove inward in the tire axial direction,
And the total number of said inner sipes is less than the total number of said outer sipes. The said inner block forms a parallelogram shape by the angle with respect to the tire circumferential direction of the said center horizontal groove being 45-75 degree | times,
The outer block is divided into a plurality of outer block pieces by the outer sipe,
The outer block piece includes a first outer piece including an acute angle corner of a tire axially outer side of the outer block, and a second outer piece including an obtuse corner of a tire axially outer side of the outer block,
The pneumatic tire according to claim 1, wherein the minimum length La in the tire circumferential direction of the second outer piece is shorter than the minimum length Lb in the tire circumferential direction of the first outer piece. The inner block is divided into a plurality of inner block pieces by the inner sipe,
The inner block piece includes a first inner piece including an acute angle corner of a tire axially inner side of the inner block, and a second inner piece including an obtuse corner of a tire axially inner side of the inner block,
The pneumatic tire according to claim 1, wherein the minimum width Wa in the tire axial direction of the second inner piece is smaller than the minimum width Wb in the tire axial direction of the first inner piece.

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