Pneumatic tire

Abstract

To provide a pneumatic tire that can effectively reduce stone drilling occurring due to stone biting.SOLUTION: In a pneumatic tire having a groove 20 formed on an outer surface of a tread 1, the groove 20 has: a groove bottom 21 forming a deepest part; a pair of side walls 22 extending from a tread surface of the tread 1 to a side of the groove bottom; and a projection portion 23 projecting into the groove 20 from at least one of the side walls 22. A regular state is defined as a state in which the pneumatic tire is mounted on a normal rim and inflated to a regular internal pressure, and a standard ground contact state is defined as a state in which the pneumatic tire in the regular state contacts a flat surface and is loaded with 100% of a regular load. When the groove 20 is located directly below ground contact in the standard ground contact state, a groove width W1a of the groove 20 measured at a position of the projection portion 23 and a groove width W2a of the groove 20 measured at a position of an opening portion of the groove 20 satisfy W1a / W2a≤0.75.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a pneumatic tire suitable for use as a heavy-duty tire, and more particularly to a pneumatic tire that can effectively suppress stone drilling caused by stone entrapment. [Background technology]

[0002] Heavy-duty pneumatic tires used on trucks and other vehicles are used not only on-road but also off-road, and as such, stone entrapment can occur in the grooves formed on the outer surface of the tread. When stone entrapment occurs, the stone trapped in the groove gradually moves toward the groove bottom and eventually reaches the groove bottom. This phenomenon is called stone drilling. When the stone reaches the groove bottom, it can cause cracks to form in the groove bottom. Furthermore, if cracks at the groove bottom reach the belt layer and damage the belt layer, this can reduce the durability of the pneumatic tire and make it impossible to retread the pneumatic tire.

[0003] In order to prevent cracks at the bottom of the groove due to stone entrapment, it has been proposed to provide protrusions that protrude into the groove from both side walls, and to use these protrusions to promote the discharge of stones (see, for example, Patent Document 1). However, the current situation is that simply providing protrusions in the groove is not necessarily sufficient to prevent stone drilling. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5804823 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a pneumatic tire that can effectively suppress stone drilling caused by stone entrapment. [Means for solving the problem]

[0006] In order to achieve the above object, a pneumatic tire of the present invention includes a tread portion extending in a circumferential direction of the tire to form an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed radially inward of the sidewall portions in the tire outer diameter direction, wherein a carcass layer is fitted between the pair of bead portions, a belt layer is disposed radially outward of the carcass layer, and grooves are formed on the outer surface of the tread portion. The groove has a groove bottom that forms the deepest portion of the groove, a pair of side walls that extend from the tread surface of the tread portion toward the groove bottom, and a protrusion that protrudes into the groove from at least one of the pair of side walls, When the state in which the pneumatic tire is mounted on a regular rim and inflated to a regular internal pressure is defined as the regular state, and the state in which the pneumatic tire in the regular state is brought into contact with a flat surface and a load of 100% of the regular load is applied is defined as the standard contact state, In the standard contact state, when the groove is located in the area directly below the contact point, the groove width W1a of the groove measured at the position of the protrusion and the groove width W2a of the groove measured at the position of the opening of the groove satisfy the relationship W1a / W2a≦0.75. [Effects of the Invention]

[0007] As a result of extensive research into the relationship between the cross-sectional shape of the grooves formed on the outer surface of the tread portion and stone drilling, the inventor discovered that optimizing the cross-sectional shape of the grooves under standard contact conditions is important in suppressing stone drilling due to stone entrapment, and thus arrived at the present invention.

[0008] That is, in the present invention, when a groove formed on the outer surface of the tread portion has a protrusion protruding into the groove from at least one sidewall, and when the groove is located directly under the ground under normal ground contact conditions, the groove width W1a of the groove measured at the position of the protrusion and the groove width W2a of the groove measured at the groove opening satisfy the relationship W1a / W2a≦0.75, thereby preventing stones that have entered the groove from reaching the groove bottom and effectively suppressing stone drilling, and as a result, cracks at the groove bottom due to stone entrapment can be effectively suppressed.

[0009] In the present invention, it is preferable that the grooves formed in the outer surface of the tread portion have a protrusion protruding into the groove from one of a pair of side walls, and that no protrusion is present on the other side wall. A groove having a protrusion provided only on one groove wall in this manner can effectively expel stones that have entered the groove, thereby suppressing stone drilling.

[0010] In a standard contact state, when the groove is located directly under the ground, the groove depth Da and the protrusion height d1a preferably satisfy the relationship 0.10≦d1a / Da≦0.70. By setting the protrusion height d1a in relation to the groove depth Da within the above range, stones that have entered the groove can be effectively expelled, thereby suppressing stone drilling.

[0011] In a standard ground contact state, when a groove is located in a region directly under the ground contact, it is preferable that the groove depth Da of the groove and the distance Ha from the belt layer to the groove bottom satisfy the relationship 0.1≦Ha / Da≦0.7. By setting the distance Ha from the belt layer to the groove bottom in the above range in relation to the groove depth Da of the groove, it is possible to effectively suppress stone drilling while ensuring a sufficient groove volume.

[0012] In the normal state, it is preferable that the cross-sectional area S2b of the groove from the groove opening to the protrusion and the cross-sectional area S1b of the groove from the protrusion to the groove bottom satisfy the relationship S1b / S2b≦0.4. By setting the cross-sectional area S1b of the groove from the protrusion to the groove bottom in the above range in relation to the cross-sectional area S2b of the groove from the groove opening to the protrusion, stones that have entered the groove are less likely to penetrate to the groove bottom side, thereby suppressing stone drilling.

[0013] In the normal state, the sum of the distance Hb from the belt layer to the groove bottom and the height d1b of the protrusion is preferably 6 mm or more. This increases the apparent under-groove rubber gauge when the tire is in contact with the ground, thereby suppressing stone drilling.

[0014] In the normal state, the protrusion preferably has curved surfaces at the portion connected to the side wall and the portion connected to the groove bottom, and a bent surface at the tip where the surface connected to the side wall and the surface connected to the groove bottom are connected to each other. Since strain concentrates at the portion connected to the side wall and the portion connected to the groove bottom of the protrusion when the protrusion touches the ground, providing curved surfaces at these portions can prevent strain concentration. On the other hand, providing a bent surface at the tip where the surface connected to the side wall and the surface connected to the groove bottom of the protrusion are connected to each other can effectively prevent stones from entering the groove bottom.

[0015] In the normal state, the cross-sectional area S3b of the groove from the position halfway through the groove depth Db to the protrusion and the cross-sectional area S1b of the groove from the protrusion to the groove bottom preferably satisfy the relationship S1b / S3b≦0.6. By setting the cross-sectional area S1b of the groove from the protrusion to the groove bottom in the above range in relation to the cross-sectional area S3b of the groove from the position halfway through the groove depth Db to the protrusion, stones that have entered the groove are less likely to penetrate to the groove bottom even when wear has progressed, thereby suppressing stone drilling.

[0016] In the normal state, the groove width W1b of the groove measured at the position of the protrusion is preferably 1 mm or more and 8 mm or less, which makes it possible to suppress stone drilling while ensuring a sufficient groove volume.

[0017] It is preferable that the groove width W1b of the groove measured at the position of the protrusion in the normal state and the groove width W1a of the groove measured at the position of the protrusion in the standard contact state satisfy the relationship W1a / W1b≦0.7. By setting the groove width W1a in the standard contact state within the above range relative to the groove width W1b in the normal state, stones that have entered the groove can be effectively prevented from reaching the groove bottom.

[0018] In a standard ground contact state, when the groove is located directly below the ground contact area, the pair of side walls preferably have a shape that bulges inward of the groove. By having the pair of side walls have a shape that bulges inward of the groove in a standard ground contact state, stone discharge performance can be improved and stone drilling can be suppressed.

[0019] In the present invention, the "normal state" refers to a state in which a pneumatic tire is mounted on a normal rim and inflated to the normal internal pressure, and the "normal contact state" refers to a state in which a pneumatic tire in the normal state is in contact with a flat surface and is subjected to a load of 100% of the normal load. The "normal rim" refers to a rim specified for each tire by the standard system including the standard on which the tire is based, for example, a standard rim for JATMA, a "Design Rim" for TRA, or a "Measuring Rim" for ETRTO. The "normal internal pressure" refers to the air pressure specified for each tire by the standard system including the standard on which the tire is based, for example, the maximum air pressure for JATMA, the maximum value listed in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURE" table for TRA, and the "INFLATION PRESSURE" for ETRTO. "Normal load" is the load specified for each tire by each standard in the standard system, including the standard on which the tire is based. In the case of JATMA, it is the maximum load capacity, in the case of TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and in the case of ETRTO, it is "LOAD CAPACITY". [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a meridian cross-sectional view showing a heavy-duty pneumatic tire according to an embodiment of the present invention. [Figure 2] 2 is a cross-sectional view showing grooves formed on the outer surface of the tread portion of the pneumatic tire of FIG. 1 (in a standard contact state). [Figure 3] 2 is a cross-sectional view showing grooves (in a normal state) formed on the outer surface of the tread portion of the pneumatic tire of FIG. 1. FIG. [Figure 4] 1. FIG. 4 is another cross-sectional view showing the grooves (in a normal state) formed on the outer surface of the tread portion of the pneumatic tire of FIG. [Figure 5] 1. FIG. 4 is yet another cross-sectional view showing grooves (in a normal state) formed on the outer surface of the tread portion of the pneumatic tire of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0021] The configuration of the present invention will be described in detail below with reference to the accompanying drawings. Fig. 1 shows a heavy-duty pneumatic tire according to an embodiment of the present invention, and Figs. 2 to 5 show its main parts.

[0022] As shown in FIG. 1, the pneumatic tire of this embodiment includes a tread portion 1 extending circumferentially in a ring shape, a pair of sidewall portions 2, 2 arranged on both sides of the tread portion 1, and a pair of bead portions 3, 3 arranged radially inward of the sidewall portions 2.

[0023] A carcass layer 4 is mounted between a pair of bead portions 3, 3. This carcass layer 4 includes a plurality of steel cords extending in the tire radial direction, and has a structure in which the carcass layer 4 is wound from the inside to the outside of the tire around a bead core 5 disposed in each bead portion 3. A bead filler 6 made of a rubber composition and having a triangular cross section is disposed on the outer periphery of the bead core 5.

[0024] Four belt layers 7 are embedded on the outer diameter side of the carcass layer 4 in the tread portion 1. Each belt layer 7 includes a plurality of belt cords (steel cords) inclined with respect to the tire circumferential direction. These belt layers 7 include two central main belt layers 72, 73 in which the belt cords intersect with each other, and auxiliary belt layers 71, 74 arranged on the inner diameter side and outer diameter side of these main belt layers 72, 73. The inclination angle of the belt cords constituting the main belt layers 72, 73 with respect to the tire circumferential direction is set in the range of 15° to 35°, for example, and the inclination angle of the belt cords constituting the auxiliary belt layers 71, 74 with respect to the tire circumferential direction is set in the range of 15° to 75°, for example.

[0025] In the pneumatic tire, a steel reinforcing layer 10 including a plurality of steel cords is disposed in each bead portion 3 so as to envelop the carcass layer 4, the bead core 5, and the bead filler 6. Organic fiber reinforcing layers 11, 12 are disposed on the outer side in the tire width direction of the steel reinforcing layer 10. Each of these organic fiber reinforcing layers 11, 12 includes a plurality of organic fiber cords aligned in one direction, and the organic fiber cords constituting the organic fiber reinforcing layers 11, 12 are oriented so as to cross each other between the layers.

[0026] The above-described tire internal structure shows a typical example of a heavy-duty pneumatic tire, but is not limited to this.

[0027] In the pneumatic tire, a plurality of grooves 20 (main grooves) extending in the tire circumferential direction are formed in the outer surface of the tread portion 1. As shown in Fig. 3, each groove 20 has a groove bottom 21 that forms the deepest portion of the groove 20, a pair of side walls 22 that extend from the tread surface S of the tread portion 1 toward the groove bottom, and a protrusion 23 that protrudes into the groove 20 from at least one of the pair of side walls 22. In this embodiment, the groove 20 has the protrusion 23 that protrudes into the groove 20 from one side wall 22, and the other side wall 22 does not have the protrusion 23.

[0028] Here, the state in which the pneumatic tire is mounted on a standard rim and inflated to the standard internal pressure is defined as the standard state, and the state in which the pneumatic tire in the standard state is brought into contact with a flat surface and subjected to a load of 100% of the standard load is defined as the standard contact state. FIG. 2 shows the groove 20 in the standard contact state, and FIG. 3 shows the groove 20 in the standard state. In the standard contact state, when the groove 20 is located in the area directly below the contact area, the groove width W1a of the groove 20 measured at the position of the protrusion 23 and the groove width W2a of the groove 20 measured at the position of the opening of the groove 20 satisfy the relationship W1a / W2a≦0.75. Note that the groove 20 being located in the area directly below the contact area means that the groove 20 is located directly below the tire rotation axis.

[0029] In the pneumatic tire described above, the grooves 20 formed in the outer surface of the tread portion 1 have protrusions 23 protruding into the grooves 20 from at least one sidewall 22. When the grooves 20 are positioned directly under the ground under normal ground contact conditions, the groove width W1a of the grooves 20 measured at the protrusions 23 and the groove width W2a of the grooves 20 measured at the openings of the grooves 20 satisfy the relationship W1a / W2a≦0.75. This prevents stones that have entered the grooves 20 from reaching the groove bottom 21, effectively preventing stone drilling. As a result, cracks at the groove bottom 21 due to stone entrapment can be effectively prevented. This prevents cracks at the groove bottom 21 from reaching the belt layer 7 and damaging the belt layer 7, thereby preventing a decrease in the durability of the pneumatic tire and preventing the pneumatic tire from becoming impossible to retread.

[0030] Here, if W1a / W2a is greater than 0.75, the effect of suppressing stone drilling becomes insufficient. In particular, the groove width W1a of the groove 20 measured at the position of the protrusion 23 and the groove width W2a of the groove 20 measured at the position of the opening of the groove 20 preferably satisfy the relationship W1a / W2a≦0.5, and more preferably satisfy the relationship W1a / W2a≦0.2. W1a / W2a=0.0 (groove 20 completely closed) is also a preferred embodiment.

[0031] In the pneumatic tire, the groove 20 formed in the outer surface of the tread portion 1 preferably has a structure in which one of the pair of side walls 22 has a protrusion 23 protruding into the groove 20 from the other side wall 22, with no protrusion 23 being present on the other side wall 22. According to the groove 20 in which the protrusion 23 is provided only on one groove wall 22 in this manner, stones that have entered the groove 20 can be effectively discharged, thereby suppressing stone drilling.

[0032] 2, when the groove 20 is located directly under the ground, it is preferable that the groove depth Da of the groove 20 and the height d1a of the protrusion 23 satisfy the relationship 0.10≦d1a / Da≦0.70. By setting the height d1a of the protrusion 23 within the above range in relation to the groove depth Da of the groove 20, stones that have entered the groove 20 can be effectively expelled, thereby preventing stone drilling.

[0033] If d1a / Da is less than 0.10, the apparent under-groove rubber gauge is not sufficiently secured when the tire is in contact with the ground, reducing the effect of suppressing stone drilling, while if it is greater than 0.70, the volume of the grooves 20 is not sufficiently secured, reducing wet performance. In particular, it is desirable that the groove depth Da of the grooves 20 and the height d1a of the protrusions 23 satisfy the relationship 0.15≦d1a / Da≦0.40.

[0034] 2, when the groove 20 is located in the area directly under the ground contact, it is preferable that the groove depth Da of the groove 20 and the distance Ha from the belt layer 7 to the groove bottom 21 of the groove 20 satisfy the relationship 0.1≦Ha / Da≦0.7. By setting the distance Ha from the belt layer 7 to the groove bottom 21 of the groove 20 within the above range in relation to the groove depth Da of the groove 20, stone drilling can be effectively suppressed while ensuring a sufficient volume of the groove 20.

[0035] Here, if Ha / Da is smaller than 0.1, the apparent under-groove rubber gauge at the time of contact with the ground is not sufficiently secured, thereby reducing the effect of suppressing stone drilling, and conversely, if it is larger than 0.70, the volume of the groove 20 is not sufficiently secured, thereby reducing wet performance. In particular, when the groove 20 is located in the area directly under the ground contact, it is desirable that the groove depth Da of the groove 20 and the distance Ha from the belt layer 7 to the groove bottom 21 of the groove 20 satisfy the relationship 0.15≦Ha / Da≦0.40.

[0036] 4, in the normal state, it is preferable that the cross-sectional area S2b (diagonal lines slanting upward to the right) of the groove 20 from the opening of the groove 20 to the protrusion 23 and the cross-sectional area S1b (diagonal lines slanting upward to the left) of the groove 20 from the protrusion 23 to the groove bottom 21 satisfy the relationship S1b / S2b≦0.4. By setting the cross-sectional area S1b of the groove 20 from the protrusion 23 to the groove bottom 21 within the above range in relation to the cross-sectional area S2b of the groove 20 from the opening of the groove 20 to the protrusion 23, stones that have entered the groove 20 are less likely to enter the groove bottom 21, thereby suppressing stone drilling.

[0037] Here, if S1b / S2b is greater than 0.4, the effect of suppressing stone drilling is reduced. In particular, it is desirable that the cross-sectional area S2b of the groove 20 from the opening of the groove 20 to the protrusion 23 and the cross-sectional area S1b of the groove 20 from the protrusion 23 to the groove bottom 21 satisfy the relationship S1b / S2b≦0.2.

[0038] In the normal state, as shown in Fig. 3, the sum of the distance Hb from the belt layer 7 to the groove bottom 21 of the groove 20 and the height d1b of the protrusion 23 is preferably 6 mm or more. This increases the apparent under-groove rubber gauge when the tire is in contact with the ground, thereby suppressing stone drilling.

[0039] Here, if the value of Hb+d1b is less than 6 mm, the effect of suppressing stone drilling decreases. The sum of the distance Hb from the belt layer 7 to the groove bottom 21 of the groove 20 and the height d1b of the protrusion 23 is preferably 6 mm or more and 12 mm or less.

[0040] In the normal state, as shown in Figure 3, the protrusion 23 has curved surfaces with a radius of curvature R at the portion connected to the side wall 22 and the portion connected to the groove bottom 21, and preferably has a bent surface (corner) at the tip where the surface connected to the side wall 22 and the surface connected to the groove bottom 21 are connected to each other. Since strain concentrates at the portion of the protrusion 23 connected to the side wall 22 and the portion connected to the groove bottom 21 when the protrusion 23 comes into contact with the ground, providing curved surfaces at these portions can prevent strain concentration. On the other hand, providing a bent surface at the tip where the surface of the protrusion 23 connected to the side wall 22 and the surface connected to the groove bottom 21 are connected to each other can effectively prevent stones from entering the groove bottom side.

[0041] 5, in the normal state, the cross-sectional area S3b (diagonal lines slanting upwards to the right) of the groove 20 from the position halfway through the groove depth Db of the groove 20 to the protrusion 23 and the cross-sectional area S1b (diagonal lines slanting upwards to the left) of the groove 20 from the protrusion 23 to the groove bottom 21 should satisfy the relationship S1b / S3b≦0.6. By setting the cross-sectional area S1b of the groove 20 from the protrusion 23 to the groove bottom 21 within the above range in relation to the cross-sectional area S3b of the groove 20 from the position halfway through the groove depth Db of the groove 20 to the protrusion 23, stones that have entered the groove 20 are less likely to penetrate to the groove bottom side even when wear has progressed, and stone drilling can be suppressed.

[0042] Here, if S1b / S3b is greater than 0.6, the effect of suppressing stone drilling is reduced. In particular, it is desirable that the cross-sectional area S3b of the groove 20 from the position halfway through the groove depth Db of the groove 20 to the protrusion 23 and the cross-sectional area S1b of the groove 20 from the protrusion 23 to the groove bottom 21 satisfy the relationship S1b / S3b≦0.3.

[0043] In the normal state, as shown in Fig. 3, it is preferable that the groove width W1b of the groove 20 measured at the position of the protrusion 23 is 1 mm or more and 8 mm or less. This makes it possible to suppress stone drilling while ensuring a sufficient volume of the groove 20.

[0044] If the groove width W1b is smaller than 1 mm, the volume of the groove 20 is not sufficiently secured, resulting in poor wet performance, while if it is larger than 8 mm, the groove 20 does not close effectively at the groove bottom when in contact with the tire, resulting in poor stone drilling prevention. In particular, it is preferable that the groove width W1b of the groove 20 measured at the position of the protrusion 23 be 1 mm or more and 4 mm or less.

[0045] It is preferable that the groove width W1b of the groove 20 measured at the position of the protrusion 23 in the normal state and the groove width W1a of the groove 20 measured at the position of the protrusion 23 in the standard contact state satisfy the relationship W1a / W1b≦0.7. By setting the groove width W1a in the standard contact state to be within the above range relative to the groove width W1b in the normal state, stones that have entered the groove 20 can be effectively prevented from reaching the groove bottom 21.

[0046] Here, if W1a / W1b is greater than 0.7, the effect of suppressing stone drilling will be insufficient. In particular, the groove width W1b of the groove 20 measured at the position of the protrusion 23 in the normal state and the groove width W1a of the groove 20 measured at the position of the protrusion 23 in the standard ground contact state preferably satisfy the relationship W1a / W1b≦0.5, and more preferably satisfy the relationship W1a / W1b≦0.2. W1a / W1b=0.0 (the groove 20 is completely closed) is also a preferred embodiment.

[0047] In a standard ground contact state, when the groove 20 is located directly below the ground contact state, the pair of side walls 22 preferably have a shape that bulges inward of the groove 20. By having the pair of side walls 22 have a shape that bulges inward of the groove 20 in a standard ground contact state, stone discharge is improved and stone drilling can be suppressed.

[0048] In the above-described embodiment, a specific groove shape is applied to the grooves 20 extending in the tire circumferential direction on the outer surface of the tread portion 1, but in the present invention, a specific groove shape can be applied to the lug grooves extending in the tire width direction. [Example]

[0049] In a pneumatic tire having a tread portion, a pair of sidewall portions, and a pair of bead portions, a carcass layer mounted between the pair of bead portions, a belt layer disposed on the outer diameter side of the carcass layer, and grooves formed on the outer surface of the tread portion, tires of the conventional example and Examples 1 to 10 were manufactured with W1a / W2a, d1a / Da, Ha / Da, S1b / S2b, Hb+d1b, the presence or absence of curved surfaces at the portions connected to the side walls of the protrusions and the portions connected to the groove bottoms, the presence or absence of bent surfaces at the tip portions where the surfaces connected to the side walls of the protrusions and the surfaces connected to the groove bottoms are connected to each other, S1b / S3b, W1b, W1a / W1b, and the presence or absence of a bulged shape of the side walls in a standard contact state set as shown in Table 1.

[0050] These test tires were evaluated for stone drilling suppression effect and wet braking performance by the following test methods, and the results are shown in Table 1.

[0051] Stone drilling prevention effect: Each test tire (11R22.5) was mounted on a JATMA-specified rim, fitted to a 2-D·D dump truck, inflated to the JATMA-specified air pressure, and driven off-road for a set distance, after which the number of stones that had reached the bottom of the groove due to stone entrapment (stone drilling count) was counted. The evaluation results were expressed as an index using the reciprocal of the measurement value, with the conventional example being set at 100. The higher the index value, the greater the stone drilling prevention effect.

[0052] Wet braking performance: Each test tire (275 / 80R22.5) was mounted on a JATMA-specified rim and installed on a 2-D·4 track, inflated to the JATMA-specified air pressure, and the braking distance from braking to a complete stop on a wet road surface was measured. The evaluation results were expressed as an index using the reciprocal of the measurement value, with the conventional example being set at 100. The higher the index value, the better the wet braking performance.

[0053] [Table 1]

[0054] As can be seen from Table 1, the tires of Examples 1 to 10 were able to fully exert the stone drilling suppression effect while maintaining good wet braking performance in comparison with the conventional tire.

[0055] The present disclosure includes the following inventions [1] to

[11] . Invention [1] is a pneumatic tire comprising a tread portion extending in the tire circumferential direction and forming an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed on the tire outer radial inside of these sidewall portions, a carcass layer mounted between the pair of bead portions, a belt layer disposed on the outer radial side of the carcass layer, and grooves formed on the outer surface of the tread portion, The groove has a groove bottom that forms the deepest portion of the groove, a pair of side walls that extend from the tread surface of the tread portion toward the groove bottom, and a protrusion that protrudes into the groove from at least one of the pair of side walls, When the state in which the pneumatic tire is mounted on a regular rim and inflated to a regular internal pressure is defined as the regular state, and the state in which the pneumatic tire in the regular state is brought into contact with a flat surface and a load of 100% of the regular load is applied is defined as the standard contact state, In the standard contact state, when the groove is located in the area directly under the contact area, a groove width W1a of the groove measured at the position of the protrusion and a groove width W2a of the groove measured at the position of the opening of the groove satisfy the relationship W1a / W2a≦0.75. Invention [2] is a pneumatic tire according to invention [1], characterized in that the groove has a protrusion protruding into the groove from one of the pair of side walls, and the other side wall does not have the protrusion. Invention [3] is the pneumatic tire according to invention [1] or [2], characterized in that, in the standard contact state, when the groove is located in the area directly under the contact surface, the groove depth Da of the groove and the height d1a of the protrusion satisfy the relationship 0.10≦d1a / Da≦0.70. Invention [4] is a pneumatic tire according to any one of inventions [1] to [3], characterized in that, in the standard contact state, when the groove is located in the area directly under the contact, the groove depth Da of the groove and the distance Ha from the belt layer to the groove bottom of the groove satisfy the relationship 0.1≦Ha / Da≦0.7. Invention [5] is a pneumatic tire according to any one of inventions [1] to [4], characterized in that in the normal state, a cross-sectional area S2b of the groove from the opening of the groove to the protrusion and a cross-sectional area S1b of the groove from the protrusion to the groove bottom satisfy the relationship S1b / S2b≦0.4. Invention [6] is the pneumatic tire according to any one of inventions [1] to [5], characterized in that in the normal state, the sum of the distance Hb from the belt layer to the groove bottom of the groove and the height d1b of the protrusion is 6 mm or more. Invention [7] is a pneumatic tire according to any one of Inventions [1] to [6], characterized in that, in the normal state, the protrusion has curved surfaces at the portion connected to the side wall and the portion connected to the groove bottom, and has a bent surface at the tip portion where the surface connected to the side wall and the surface connected to the groove bottom are connected to each other. Invention [8] is a pneumatic tire according to any one of inventions [1] to [7], characterized in that in the normal state, a cross-sectional area S3b of the groove from a position halfway between the groove depth Db of the groove and the protrusion and a cross-sectional area S1b of the groove from the protrusion to the groove bottom satisfy the relationship S1b / S3b≦0.6. Invention [9] is a pneumatic tire according to any one of inventions [1] to [8], characterized in that in the normal state, the groove width W1b of the groove measured at the position of the protrusion is 1 mm or more and 8 mm or less. Invention

[10] is a pneumatic tire according to any one of inventions [1] to [9], characterized in that a groove width W1b of the groove measured at the position of the protrusion in the normal state and a groove width W1a of the groove measured at the position of the protrusion in the standard contact state satisfy the relationship W1a / W1b≦0.7. Invention

[11] is a pneumatic tire according to any one of inventions [1] to

[10] , characterized in that, in the standard contact state, when the groove is located in the area directly under the contact, the pair of side walls have a shape that bulges inward of the groove. [Explanation of symbols]

[0056] 1 Tread section 2 Sidewall 3 Bead section 4 carcass layers 5 bead core 6 Bead filler 7 Belt Layer 20 grooves 21 Groove bottom 22 Side wall 23 Protrusion

Claims

1. A pneumatic tire comprising a tread portion extending in a circumferential direction of the tire to form an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed radially inward of the sidewall portions in the tire outer diameter direction, a carcass layer mounted between the pair of bead portions, a belt layer disposed radially outward of the carcass layer, and grooves formed in the outer surface of the tread portion, The groove has a groove bottom that forms the deepest portion of the groove, a pair of side walls that extend from the tread surface of the tread portion toward the groove bottom, and a protrusion that protrudes into the groove from at least one of the pair of side walls, When the state in which the pneumatic tire is mounted on a regular rim and inflated to a regular internal pressure is defined as a regular state, and when the pneumatic tire in the regular state is brought into contact with a flat surface and a load of 100% of the regular load is applied, the state is defined as a standard contact state. In the standard contact state, when the groove is located in the area directly under the contact area, a groove width W1a of the groove measured at the position of the protrusion and a groove width W2a of the groove measured at the position of the opening of the groove satisfy the relationship W1a / W2a≦0.

75.

2. 2. The pneumatic tire according to claim 1, wherein the groove has a protrusion protruding into the groove from one of the pair of side walls, and the other side wall does not have the protrusion.

3. 3. The pneumatic tire according to claim 1, wherein, in the standard contact state, when the groove is located in a region directly under the contact area, a groove depth Da of the groove and a height d1a of the protrusion satisfy the relationship 0.10≦d1a / Da≦0.

70.

4. 3. The pneumatic tire according to claim 1, wherein, in the standard contact state, when the groove is located in a region directly under the contact area, a groove depth Da of the groove and a distance Ha from the belt layer to a groove bottom of the groove satisfy a relationship of 0.1≦Ha / Da≦0.

7.

5. 3. The pneumatic tire according to claim 1, wherein in the normal state, a cross-sectional area S2b of the groove from the opening of the groove to the protrusion and a cross-sectional area S1b of the groove from the protrusion to the groove bottom satisfy a relationship of S1b / S2b≦0.

4.

6. 3. The pneumatic tire according to claim 1, wherein in the normal state, a sum of a distance Hb from the belt layer to a groove bottom of the groove and a height d1b of the protrusion is 6 mm or more.

7. 3. The pneumatic tire according to claim 1, wherein, in the normal state, the protrusion has curved surfaces at a portion connected to the side wall and a portion connected to the groove bottom, and has a bent surface at a tip portion where the surface connected to the side wall and the surface connected to the groove bottom are connected to each other.

8. 3. The pneumatic tire according to claim 1, wherein in the normal state, a cross-sectional area S3b of the groove from a position halfway through the groove depth Db of the groove to the protrusion and a cross-sectional area S1b of the groove from the protrusion to the groove bottom satisfy a relationship of S1b / S3b≦0.

6.

9. 3. The pneumatic tire according to claim 1, wherein in the normal state, a groove width W1b of the groove measured at the position of the protrusion is 1 mm or more and 8 mm or less.

10. 3. The pneumatic tire according to claim 2, wherein a groove width W1b of the groove measured at the position of the protrusion in the normal state and a groove width W1a of the groove measured at the position of the protrusion in the standard contact state satisfy the relationship W1a / W1b≦0.

7.

11. 3. The pneumatic tire according to claim 1, wherein the pair of side walls have a shape that bulges inward of the groove when the groove is located in a region directly under the ground contact in the standard ground contact state.

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