KR101974661B1 - Pneumatic tire - Google Patents

Abstract

A pneumatic tire capable of suppressing uneven wear of a tread portion of the present invention.
A pair of shoulder land grooves 10 and a pair of middle land portions 20 are separated from each other by forming a center groove 9 so that a pair of shoulder land portions 40 and a pair of middle land portions 20 are separated. The end edges 23 on both sides in the tire circumferential direction of the middle land portion 20 are inclined in the range of 5 to 12 degrees with respect to the axial direction of the tire and extend outward in the axial direction of the tire. The end edges 43 on both sides in the tire circumferential direction of the shoulder land portion 40 are inclined with respect to the axial direction of the tire in the range of the angle? The distance L1 in the tire circumferential direction between the inner end 46 and the outer end 47 of the end edge 43 of the shoulder land portion 40 in the tire axial direction is smaller than the distance L1 in the tire circumferential direction of the shoulder land portion 40 0.03 to 0.12 times of the grounding length L2 of the grounding conductor.

Description

Pneumatic tire {PNEUMATIC TIRE}

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a pneumatic tire which improves the shape of a ground surface and improves the anti-abrasion performance.

As shown in Fig. 5, various pneumatic tires having a main groove (a) extending continuously in the tire circumferential direction in the vicinity of the tread edge (b) are proposed. Such a pneumatic tire has a problem that the shoulder loss wear is liable to occur where the outer end d of the shoulder land portion c between the main groove (a) and the tread ground end (b) in the tire axial direction is uneven.

[0005] Regarding such a problem, for example, Patent Document 1 below proposes a pneumatic tire in which the rigidity of each land portion extending in the tire circumferential direction is specified by specifying the number of sipes formed on the land portion, and the uneven wear of the land portion is suppressed have. However, even in such a pneumatic tire, there has been room for further improvement in suppressing the occurrence of uneven wear.

If the sliding contact with the road surface is suppressed by increasing the contact pressure of the shoulder land portion (c) in order to suppress the wear of the shoulder loss, slippage easily occurs between the middle land portion (f) and the road surface, There is a problem in that the outer end portion e of the outer peripheral portion is worn as a rail type.

Japanese Patent Application Laid-Open No. 2007-182097

SUMMARY OF THE INVENTION It is an object of the present invention to provide a pneumatic tire capable of suppressing uneven wear of a tread portion on the basis of improving the shape of a ground surface of a tread portion.

According to a first aspect of the present invention, there is provided a tire according to the first aspect of the present invention, wherein the tread portion includes a pair of shoulder main grooves extending continuously from the tread most end side in the tire circumferential direction, and a center main groove extending inward from the shoulder main groove in the tire axial direction A pair of shoulder land portions on the outer side in the tire axial direction of each shoulder main groove and a pair of middle land portions between the pair of shoulder main grooves and the center main groove are rim-assembled to the regular rim, And the ground surface when the tread portion is pressed against the plane at a camber angle of 0 degrees by applying a normal load is gradually reduced in length in the tire circumferential direction from the tire equator side toward the tread ground end, The end edges of the middle land portion on both sides in the tire circumferential direction are inclined at an angle (?) Of 5 to 12 degrees with respect to the tire axial direction And the end edges of the shoulder land portions on both sides in the circumferential direction of the tire are inclined at an angle beta of not less than 17 DEG and not more than the angle alpha with respect to the tire axial direction, (L1) between the inner end and the outer end in the tire axial direction of the end edge of the shoulder land portion in the circumferential direction of the tire at the position apart from the tire equator by a distance of 0.97 times the tread ground contact half- And is 0.03 to 0.12 times the grounding length (L2).

The invention according to claim 2 is characterized in that it comprises a carcass extending from a tread portion to a bead core of a bead portion through a sidewall portion and a belt layer disposed on the outside of the carcass while being inside the tread portion, Wherein the center land has one line extending in the tire circumferential direction on the tire equatorial plane and the middle land portion has one end communicated with the center main groove And the other end is divided into a middle lateral groove communicating with the shoulder main groove and a distance between the shoulder main groove and the tire equatorial direction in the tire axial direction is 0.45 to 0.70 times the half width in the tire axial direction of the belt layer. It is a tire.

The invention according to claim 3 is the pneumatic tire according to claim 2, wherein the carcass comprises two or more carcass ply made of polyester cords, and the belt layer includes two or more belt ply made of steel cords to be.

According to a fourth aspect of the invention, the center main groove includes a first portion and a second portion having a larger groove width than the first portion, wherein the first portion and the second portion are alternately formed in the tire circumferential direction Is the pneumatic tire according to any one of claims 1 to 3.

According to a fifth aspect of the present invention, the middle land portion is divided into middle lateral grooves with one end communicating with the center main groove and the other end communicating with the shoulder main groove. In the middle lateral grooves, And a groove bottom siphing opening is formed in the tie bar.

The invention according to claim 6 is characterized in that each middle land portion has a first middle siphon having one end communicating with the center main groove and the other end terminating in the middle land portion, and a second middle siphon having one end communicating with the shoulder main groove, The airbag according to any one of claims 1 to 5, wherein a second middle siphin terminating in the land portion is formed and the first middle siphon and the second middle siphon are alternately formed in the tire circumferential direction It is a tire.

The invention according to claim 7 is the pneumatic tire according to any one of claims 1 to 6, wherein the shoulder land portion is formed with an outer shoulder siping whose outer end in the axial direction of the tire opens at the tread ground end.

The pneumatic tire according to the present invention is characterized in that on the ground surface when the tread is pressed against the plane at a camber angle of 0 degrees by being rimmed in the normal rim and filled with normal internal pressure and under normal load, The edge is inclined at an angle (alpha) of 5 to 12 degrees with respect to the tire axial direction and extends outward in the tire axial direction. As a result, the grounding length of the ground surface of the middle land portion gradually decreases toward the outer side in the tire axial direction. Therefore, the difference in the contact pressure between the inner end portion in the tire axial direction and the outer end portion of the middle land portion is reduced. Therefore, slippage between the outer end of the middle land portion and the road surface is suppressed, and wear of the track at the outer end portion is suppressed.

The end edges of the shoulder land portions on both sides in the tire circumferential direction are inclined in the range of the angle? As a result, the grounding length of the ground surface of the shoulder land portion gradually decreases toward the outer side in the tire axial direction continuously with the grounding length of the middle land portion. Therefore, the difference in the contact pressure between the shoulder land portion and the middle land portion becomes small, and the progress of the wear of the shoulder land portion and the middle land portion becomes uniform.

The distance L1 between the inner end and the outer end in the tire axial direction of the end edge of the shoulder land portion in the tire circumferential direction is smaller than the distance L1 in the circumferential direction of the shoulder land portion in the tire circumferential direction Is 0.03 to 0.12 times the length (L2). As a result, the difference in contact pressure between the inner end portion and the outer end portion of the shoulder land portion in the tire axial direction is reduced, and further, the shoulder loss wear at the outer end portion of the shoulder land portion is suppressed.

1 is a sectional view showing an embodiment of a pneumatic tire according to the present invention.
Figure 2 is an exploded view of the tread portion of Figure 1;
3 is an exploded view of the ground plane of the tread portion of Fig.
Fig. 4 is a partial enlarged view of the middle land portion and the shoulder land portion of Fig. 2;
5 is a cross-sectional view of a tread portion of a conventional pneumatic tire.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

1 is a tire meridional sectional view including a tire rotation axis in a normal state of a pneumatic tire (hereinafter sometimes simply referred to as " tire ") 1 of the present embodiment. Fig. 2 is an exploded view of the tread portion of the tire of Fig. 1; 1 corresponds to a cross-sectional view taken along line A-A in Fig. Here, the normal state is a state of no-load in which the tire is rimmed in a normal rim (not shown) and filled with a normal internal pressure. Hereinafter, unless otherwise stated, the dimensions etc. of each part of the tire indicate the values measured in this normal state.

Quot; Standard Rim " for JATMA, " Design Rim " for TRA, and " Measuring Rim " for ETRTO in the standard system including the standard on which the tire is based, "to be.

1, the pneumatic tire 1 of the present embodiment includes a carcass 6 extending from a tread portion 2 to a bead core 5 of a bead portion 4 through a side wall portion 3, And a belt layer 7 disposed on the inner side of the tire radially outer tread portion 2 of the carcass 6. In the present embodiment, a pneumatic tire for a light track is shown.

The carcass 6 is constituted by, for example, two carcass plies 6A and 6B. The carcass plies 6A and 6B are composed of a main body portion 6a extending from the tread portion 2 to the bead core 5 of the bead portion 4 through the side wall portion 3, And a folded portion 6b folded outward from the inside of the tire axial direction around the bead core 5. As the carcass cords of the carcass ply 6A and 6B, for example, organic fiber cords such as polyester, aramid and rayon are employed. The carcass cord is arranged at an angle of 70 to 90 degrees with respect to the tire equator C, for example.

In the present embodiment, the belt layer 7 is made up of three belt ply 7A, 7B and 7C arranged in a manner that the belt cord is inclined at an angle of 15 to 45 degrees with respect to the tire equator C, Are formed so as to overlap each other in the tire radial direction. The belt layer 7 of the present embodiment has the largest width belt ply 7M having the largest width in the axial direction of the tire and the belt ply 7A and 7C superimposed on the outside in the tire axial direction of the maximum width belt ply 7M have. As the belt cord, for example, an organic fiber cord such as aramid or rayon or a steel cord is suitably employed.

The curvature radius R1 of the maximum width belt ply 7M in the tire meridional section including the tire rotation axis is preferably 450 mm or more, more preferably 480 mm or more, preferably 550 mm or less Is not more than 520 mm. When the curvature radius R1 of the maximum width belt plies 7M is large, there is a fear that the sliding of the middle land portion 20 becomes large and the track wear is generated. On the other hand, when the radius of curvature R1 of the maximum width belt ply 7M is small, there is a fear that the shoulder land portion 40 is worn with shoulder loss.

2, the tire 1 has a pair of shoulder main grooves 10, 10 extending continuously from the tread most end Te side to the tire circumferential direction, A pair of middle land portions 20 and 20 between the shoulder main groove 10 and the center main groove 9 are formed by forming one center main groove 9 extending from the inside of the tire axial direction than the shoulder main grooves 10 and 10. [ And a pair of shoulder land portions (40, 40) outside the shoulder main groove (10).

The tread ground end Te means a ground position of the outermost tire in the tire axial direction when the normal grounded tire is grounded at a camber angle of 0 DEG by applying a normal load to the tire in the normal state. The term " normal load " refers to a load defined for each tire in a standard system including a standard on which a tire is based, " maximum load capability " in the case of JATMA, and " TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES "and" LOAD CAPACITY "in the case of ETRTO, and when the tire is for a passenger car, the load corresponds to 88% of the load. The distance in the tire axial direction of the tread ground terminals Te and Te becomes the tread ground contact width TW.

The groove width W1 of the center main groove 9 and the groove width W2 of the shoulder main groove 10 are set to be, for example, 3.0 to 6.0% of the tread ground width TW in order to satisfy the drainage performance, steering stability, desirable. The groove depth D1 of the center main groove 9 and the groove depth D2 of the shoulder main groove 10 are preferably 6 to 12 mm. The groove widths of the center main groove 9 and the shoulder main groove 10 are measured in a direction perpendicular to the groove center line and the same applies to other grooves as well.

The center main groove 9 has a single line extending linearly in the tire circumferential direction on the tire equator C. [ The center main groove 9 of the present embodiment includes a first portion 9a and a second portion 9b having a larger groove width than the first portion 9a and the groove width changes in the tire circumferential direction. The first portion 9a and the second portion 9b are preferably formed alternately in the tire circumferential direction. The center main groove 9 maintains the rigidity near the tire equator C to improve the steering stability and improve the wet performance.

The ratio W1a / W1b between the groove width W1a of the first portion 9a and the groove width W1b of the second portion 9b can be improved by improving the wet performance of the tire while maintaining the rigidity of the middle land portion 20 For example, 0.60 or more, more preferably 0.65 or more, preferably 0.80 or less, more preferably 0.75 or less.

The shoulder main groove 10 extends linearly in the tire circumferential direction. As shown in Fig. 1, the shoulder grooves 10, 10 are formed on the inner side of the tire axial direction outer end 7e, 7e of the belt layer 7, respectively, in the tire axial direction. On the other hand, when the shoulder groove 10 approaches the tire equator C excessively, there is a fear that uneven wear may occur in the middle land portion 20. The distance L8 in the tire axial direction between the shoulder groove 10 and the tire equator C is preferably not less than 0.50 times the half width BWh of the belt layer 7 in the tire axial direction, 0.55 times or more, preferably 0.70 times or less, more preferably 0.65 times or less.

Fig. 3 shows a developed view of the ground surface 2s of the tread portion 2. Fig. The ground plane 2s shown in Fig. 3 is obtained by being rimmed in a normal rim, filled with a normal internal pressure, loaded with a normal load, and pressing the tread portion 2 to a plane at a camber angle of 0 deg.

The grounding pressure of the tread portion 2 gradually decreases from the tire equator C toward the tread ground end Te side as the ground surface of the tread portion 2 curves. Therefore, the tire circumferential length L0 of the ground contact surface 2s is decreased from the tire equator C side toward the tread ground end Te.

The end edges 23 and 23 of the middle land portion 20 on both sides in the tire circumferential direction of the middle land portion 20 are inclined in the range of 5 to 12 degrees with respect to the axial direction of the tire, Respectively. As a result, the ground contact length L3 of the ground surface of the middle land portion 20 is decreased toward the outer side in the tire axial direction. Therefore, the difference in the contact pressure between the inner end portion 24 and the outer end portion 25 in the tire axial direction of the middle land portion 20 becomes small. Thus, slippage between the outer end 25 of the middle land portion 20 and the road surface is suppressed, and the wear of the outer end portion 25 is suppressed.

When the angle alpha is less than 5 DEG, the contact pressure of the inner end portion 24 of the middle land portion 20 is excessively lowered, and the inner end portion 24 may cause wear of the track. On the other hand, when the angle? Is larger than 12 degrees, the difference in the grounding pressure between the inner end portion 24 and the outer end portion 25 of the middle land portion 20 becomes larger and the amount of slip between the outer end portion 25 and the road surface increases , There is a fear that the outer end 25 wears orbitally. Therefore, the angle? Is more preferably 7 ° or more, further preferably 8 ° or more, more preferably 10 ° or less, further preferably 9 ° or less.

The end edges 43 and 43 of the shoulder land portion 40 on both sides in the tire circumferential direction are inclined in the range of the angle? Thus, the ground contact length L4 of the ground contact surface of the shoulder land portion 40 gradually decreases toward the tire axial outer side with respect to the ground contact length L3 of the middle land portion 20. Therefore, the difference in the contact pressure between the shoulder land portion 40 and the middle land portion 20 becomes small, and the progress of wear of the shoulder land portion 40 and the middle land portion 20 becomes uniform.

When the angle beta is smaller than the angle alpha, there is a fear that the outer end 25 of the middle land portion 20 is worn out. On the contrary, when the angle? Is larger than 17 degrees, the amount of slippage between the shoulder land portion 40 and the road surface becomes large, and the shoulder land portion 40 wears with shoulder loss. Therefore, the angle beta is more preferably 12 degrees or more, still more preferably 13 degrees or more, more preferably 16 degrees or less, further preferably 15 degrees or less.

The distance L1 in the tire circumferential direction between the inner end 46 and the outer end 47 of the end edge 43 of the shoulder land portion 40 in the tire axial direction is calculated from the tire equator C to the tread grounding half width 0.03 to 0.12 times the grounding length L2 of the shoulder land portion 40 in the circumferential direction of the tire at a position apart from the distance of 0.97 times of the grounding distance TWh. This reduces the difference in the contact pressure between the inner end portion 44 and the outer end portion 45 of the shoulder land portion 40 in the axial direction of the tire and further reduces the shoulder loss wear of the outer end portion 45 of the shoulder land portion 40 Is suppressed.

The shape of the ground plane 2s of the tread portion 2 can vary greatly depending on the profile of the tread portion 2 in the normal state and the rubber volume of the tread rubber Tg of the tread portion 2 have. Therefore, it is preferable that the profile of the tread portion 2 be convex outward in the tire radial direction. It is also preferable that the thickness of the tread rubber from the outer surface of the maximum width belt ply of the tread rubber to the ground surface of the tread portion is constant in the axial direction of the tire or gradually decreases from the tire equator C toward the tire axial direction outer side.

In order to obtain the shape of the ground plane 2s of the tread portion 2 described above, it is preferable that the thickness of the tread rubber Tg be specified. More specifically, the inner land portion thickness t1, which is the tread rubber thickness at a position 0.30 times the tread ground contact half width TWh from the tire equator C, It is preferable that the negative thickness tb is set to 0.96 to 0.97 times. The intermediate land thickness t2 which is the tread rubber thickness at the position 0.65 times the tread ground contact half width TWh from the tire equator C is set to 0.89 to 0.95 times the standard land thickness tb, desirable. The outer land portion thickness t3 which is the tread rubber thickness at the position 0.90 times the tread ground contact half width TWh from the tire equator C is set to 0.86 to 0.92 times the standard land portion thickness tb desirable.

In the case where grooves are formed at the measurement positions of the inner land portion thickness t1, the middle land portion thickness t2 and the outer land portion thickness t3, the respective thicknesses t1 to t3 virtually fill the grooves Measured in one state.

4, the middle land portion 20 of the present embodiment is provided with a middle horizontal groove (one end) 27 communicating with the center main groove 9 and the other end 28 communicating with the shoulder main groove 10 26 are formed. Thereby, the middle block 29 is spaced apart in the tire circumferential direction. Further, in each middle block 29, a middle siping 30 is formed.

The groove width W7 of the middle lateral groove 26 is preferably formed to be smaller than the groove width W2 of the shoulder groove 10 (shown in Fig. 1), for example, 0.30 times or more of the groove width W2, Is 0.35 times or more, preferably 0.45 times or less, more preferably 0.40 times or less. These middle lateral grooves 26 provide both steering stability and wet performance.

One end 27 of the middle lateral groove 26 preferably communicates with the second portion 9b of the center main groove 9. [ As a result, the drainage performance of the middle lateral grooves 26 is improved, and further, the wet performance is improved.

It is preferable that the other end 28 of the middle lateral groove 26 is continuous to the hollow recessed portion 32 toward the tire axial direction inner side edge 31 of the middle land portion 20 on the tire axial direction outer side . Thereby, the deformation area of the middle block is secured. Therefore, when the ground pressure from the road surface acts on the ground surface 2s, the middle block 29 is deformed along the road surface while suppressing slippage with the road surface. Therefore, the uneven wear of the middle block 29 is suppressed.

1, a tie bar 33 in which a groove bottom surface 26d is raised and a groove bottom ciping 34 which is opened in the tie bar 33 are formed in the middle lateral groove 26 . Thus, the movement of the middle block 29 (shown in Fig. 4) is suppressed, and the wear resistance of the middle block 29 is improved.

The height h1 of the tie bar 33 is preferably 0.40 times or more, more preferably 0.45 times or more of the groove depth D1 of the center main groove 9, 0.60 times or less, and more preferably 0.55 times or less. Likewise, the depth D3 of the groove bottom siphon 34 is preferably at least 0.80 times, more preferably at least 0.85 times, and preferably at most 1.00 times the height h1 of the tie bars 33, And more preferably 0.95 times or less.

As shown in Fig. 4, the middle siphon 30 is formed, for example, in the center portion 29m in the tire circumferential direction of each middle block 29 in parallel with the middle lateral grooves 26. [ The middle siphoning 30 includes a first middle siphoning 35 in which one end 35a communicates with the center main groove 9 and the other end 35b terminates in the middle land portion 20, And a second middle siphon 36 communicating with the shoulder main groove 10 and terminating in the middle land portion 20 at the other end 36b. The first middle siphon 35 and the second middle siphon 36 are formed in the middle block 29, for example, alternately arranged in the tire circumferential direction. This middle siping 30 improves the wet performance and also uniformizes the progress of wear of the middle land portion 20 and the shoulder land portion 40, thereby suppressing uneven wear.

The shoulder land portion 40 of the present embodiment is formed as a rib continuous in the tire circumferential direction. The shoulder land portion 40 is provided with an inner lug groove 48 and an inner shoulder siphon 49 communicating with the shoulder main groove 10 and an outer lug groove 50 opening at the tread grounding end Te, A shoulder siphon 51 is formed. This shoulder land portion 40 uniformizes the progress of wear of the inner end portion 44 and the outer end portion 45 of the shoulder land portion 40 and suppresses the shoulder loss wear of the shoulder land portion 40. [

The inner lug groove 48 has one end 52 communicating with the shoulder main groove 10 and the other end 53 terminating in the shoulder land portion 40. The inner lug groove 48 has a first portion 48a communicating with the shoulder main groove 10 and decreasing in groove width toward the outer side in the axial direction of the tire and a second portion 48b continuous to the first portion 48a, And a second portion 48b extending outwardly and axially outwardly of the tire. The inner lug grooves 48 are formed at regular intervals in the tire circumferential direction, for example. As a result, a deformation area of the shoulder land portion 40 is secured, and slippage between the outer surface of the shoulder land portion 40 and the road surface is suppressed. In addition, the inner lug grooves 48 enhance the drainage performance of the shoulder groove 10, and further improve the wet performance of the tire.

The length L5 of the inner lug groove 48 in the axial direction of the tire is preferably 1.10 times or more than the groove width W2 of the shoulder groove 10 (shown in Fig. 2) 1.15 times or more, preferably 1.30 times or less, more preferably 1.25 times or less.

The inner shoulder siphon 49 is for example one end 54 communicating with the shoulder groove 10 and the other end 55 terminating within the shoulder land portion 40. In addition, a plurality of inner shoulder siphons 49 are formed between the inner lug grooves 48, 48, for example, 1 to 5, in the present embodiment, three. This inner shoulder siphon 49 uniformizes the progress of the wear of the inner end portion 44 of the shoulder land portion 40 and the outer end portion 25 of the middle land portion 20 so that the outer side of the middle land portion 20 Thereby suppressing the track wear of the end portion 25. [

The length L6 of the inner shoulder siphon 49 in the axial direction of the tire is preferably not less than 0.40 times, more preferably not less than 0.43 times the length L5 of the inner lug grooves 48 Preferably 0.50 times or less, and more preferably 0.47 times or less.

The outer lug grooves 50 are, for example, open at the tread ground end Te and the inner end 57 in the tire axial direction terminates in the shoulder land portion 40. The outer lug groove 50 includes a first portion 50a extending in the tire axial direction outside and a constant width in the tire axial direction and a second portion 50b continuous to the first portion 50a and having a groove width decreasing in the shoulder land portion 40 And terminating second portion 50b. The outer lug grooves 50 are preferably spaced equidistantly in the tire circumferential direction. As a result, the deformation area of the shoulder land portion 40 is secured, and slippage between the outer surface of the shoulder land portion 40 and the road surface is suppressed. This outer lug groove 50 improves the rigidity of the shoulder land portion 40 and improves the wandering performance.

The groove width W8 of the outer lug grooves 50 is preferably at least 0.60 times, more preferably at least 0.65 times the length L5 of the inner lug grooves 48, 0.75 times or less, and more preferably 0.70 times or less.

The outer shoulder siphon 51 is open at the tread ground end Te, for example, and the inner end 58 terminates in the shoulder land portion 40. The outer shoulder siphon 51 extends, for example, in parallel to the tire axial direction. A plurality of outer shoulder siphons 51, for example, 1 to 5, in this embodiment, three, are formed between the outer lug grooves 50 and 50, for example. This outer shoulder siping 51 improves wet performance and wandering performance.

The length L7 in the tire axial direction from the inner end 58 of the outer shoulder siphon 51 to the tread ground end Te is preferably equal to the length L6 of the inner shoulder siphon 49 in the tire axial direction Is at least 2.2 times, more preferably at least 2.3 times, preferably at most 2.6 times, more preferably at most 2.5 times. This outer shoulder siphon 51 uniformizes the progress of the wear of the inner end portion 44 and the outer end portion 45 of the shoulder land portion 40, thereby suppressing the uneven wear.

The pneumatic tire of the present invention has been described in detail above. However, the present invention is not limited to the specific embodiment described above, but can be modified into various aspects.

[Example]

The pneumatic tires for the light track of the size 185 / 65R15 having the basic structure of Fig. 1 and having the tread pattern shown in Fig. 2 were tested and manufactured based on the specifications of Table 1, and the wear amount of each sample tire, Presence, wandering performance and heat generation of the shoulder land portion were tested.

The test method is as follows.

<Wear amount>

Each sample tire was mounted on the actual vehicle under the following conditions, and the amount of uniaxial wear after running 8000 km was measured. The amount of uneven wear means the difference between the remaining groove depth of the center main groove and the remaining groove depth of the shoulder main groove. The result is an index showing the uneven wear amount of Comparative Example 1 as 100. The smaller the numerical value is, the smaller the amount of uneven wear is.

Mounting rim: 5.0 J × 15

Withstand pressure: 600 ㎪

Mounted vehicles: light track, 2-D vehicle with a maximum capacity of 2t

Tire mounting position: front wheel

<Presence of shoulder loss wear>

During the measurement of the uneven wear amount, presence or absence of shoulder loss wear of the shoulder land portion was visually inspected. The results are shown in the following three-step evaluation.

A: The shoulder loss is good because no abrasion occurs.

B: Shoulder wear is worn, but it can be commercialized.

C: Shoulder loss wear occurs at a level that can not be commercialized.

<Wandering performance>

The wandering performance when the test vehicle in a static state under the following conditions ran on the road surface of the wheel was evaluated by the sensory characteristics of the driver. Wandering performance means steering stability and riding sensibility of the vehicle in entering the wheel rim, going straight in the rim, and escaping from the wheel rim. The result is a rating of 100 for Comparative Example 1. The larger the value, the better the wandering performance is.

Mounting rim: 5.0 J × 15

Withstand pressure: 600 ㎪

Mounted vehicles: light track, 2-D vehicle with a maximum capacity of 2t

Tire mounting position: front wheel

Speed: 60 km / h

<Heat generation of the shoulder land portion>

The temperature of the shoulder land portion when running on the drum tester under the following conditions was measured. The result is an index of 100 in Comparative Example 1. The smaller the numerical value is, the smaller the heat generation of the shoulder land portion is, and the higher the durability of the shoulder land portion is.

Mounting rim: 5.0 J × 15

Withstand pressure: 600 ㎪

Load weight: 12 kN

Speed: 80 km / h

The test results are shown in Table 1.

As a result of the test, it was confirmed that the tire of the embodiment has improved anti-abrasion performance as compared with the tire of the comparative example.

2: Tread 9: Center main groove
10: shoulder groove 20: middle land portion
23: end edge 40: shoulder land portion
43: end edge

Claims (7)

A pair of shoulder grooves extending continuously in the tire circumferential direction from the tread most end side of the tread portion and a center circumferential groove extending from the shoulder circumferential direction inside the tire axial direction are formed in the tread portion, A pair of shoulder land portions on the outer side and a pair of middle land portions between the pair of shoulder main grooves and the center main groove,
The ground surface when the tread portion is pressed against the plane at a camber angle of 0 degrees by being loaded with a normal load and being loaded with a normal internal pressure by riming in a normal rim has a ground length in the tire circumferential direction from the tire equator side to the tread ground end Wherein in the ground plane,
The end edges of the middle land portion on both sides in the tire circumferential direction are inclined in the range of 5 to 12 degrees with respect to the tire axial direction and extend outward in the tire axial direction,
The end edges of the shoulder land portions on both sides in the tire circumferential direction are inclined in a range of the angle? And not more than 17 占 with respect to the tire axial direction,
The distance L1 between the inner end and the outer end in the tire axial direction of the end edge of the shoulder land portion in the tire circumferential direction is set to be smaller than the distance L1 in the circumferential direction of the shoulder land portion, 0.03 to 0.12 times the grounding length L2 in the circumferential direction,
Each of the middle land portions includes a plurality of middle blocks each of which is divided into a plurality of middle lateral grooves communicating with the center main groove and the other end communicating with the shoulder main groove in a tire circumferential direction,
Wherein the middle lateral groove is formed with a tie bar having a raised bottom surface and a bottom groove siping opening at the tie bar, the bottom trench having both ends terminated in the tie bar,
Each of the middle blocks is provided with a first middle siphin having one end communicating with the center main groove and the other end terminating in the middle land portion, or one end communicating with the shoulder main groove, Only one of the second middle siphing terminating in the middle land portion is formed,
Wherein the middle block provided with the first middle ciping and the middle blocks provided with the second middle ciping are alternately formed in the tire circumferential direction. The tire according to claim 1, further comprising: a carcass extending from the tread portion to the bead core of the bead portion after passing through the sidewall portion; and a belt layer disposed inside the tread portion and outside the carcass,
Wherein an outer end of the belt layer in the tire axial direction is located on an outer side in the tire axial direction with respect to the pair of shoulder main grooves,
Wherein the center main groove has a single line extending in the tire circumferential direction on the tire equator,
Wherein the middle land portion is divided into a middle horizontal groove having one end communicating with the center main groove and the other end communicating with the shoulder main groove,
And a distance between the shoulder groove and the tire equator in the axial direction of the tire is 0.45 to 0.70 times the half-width of the belt layer in the axial direction of the tire. 3. The tire according to claim 2, wherein the carcass comprises two or more carcass ply made of polyester cords,
Wherein the belt layer comprises two or more belt ply made of steel cords. 4. The apparatus according to any one of claims 1 to 3, wherein the center main groove includes a first portion and a second portion having a larger groove width than the first portion,
Wherein the first portion and the second portion are alternately formed in the tire circumferential direction. The pneumatic tire according to any one of claims 1 to 3, wherein the second middle siphing is terminated inside the tire axial direction more than the axially outer end of the first middle siphon. The pneumatic tire according to any one of claims 1 to 3, wherein the shoulder land portion is formed with an outer shoulder siping, the axially outer end of which opens at the tread ground end. delete

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