JP2013124046A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the durability of a carcass cord while having a projection for improving driving performance on a mud surface.SOLUTION: The pneumatic tire in which a plurality of lug grooves 23 which extend and are opened to the outside in a tire width direction of a tread 2 are formed with prescribed intervals in a tire circumferential direction, includes projections 9 formed from a groove bottom in the lug groove 23 to the outside of the tire width direction in a tire radial direction inside a groove bottom extension line RD which is extended from a ground end groove bottom position SD where a groove bottom of the lug groove 23 corresponds to a ground end S of the tread 2 between the ground end groove bottom position SD and a tire maximum width position P.

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire that improves running performance in a muddy area.

  Off-road pneumatic tires that travel on rough roads such as muddy ground are known in which protrusions are provided on the buttress and sidewalls in order to improve the travelability (for example, Patent Document 1). To Patent Document 4).

  A pneumatic tire (a tire with a lug) described in Patent Document 1 includes a tread block (lug) that protrudes outward in the tire radial direction and a tire width direction of the tread block that is located on the inner side in the tire radial direction from the root of the tread block. And a protrusion protruding outward.

  The pneumatic tire described in Patent Document 2 (pneumatic tire having sidewall tread protrusions) has a sidewall portion having a substantially rectangular extending block and a triangular extending block, and the rectangular extending block is in the tire width direction. The triangular protruding block protrudes outward by a second amount by a second amount, and the first amount is smaller than the second amount. These rectangular projecting blocks and triangular projecting blocks are formed in alignment with the tread blocks.

  The pneumatic tire described in Patent Literature 3 has a circumferential protrusion extending in an annular shape along the tire circumferential direction on the outer wall surface of the sidewall portion, and extending radially inward from the circumferential protrusion, and spaced in the tire circumferential direction. And a plurality of radial protrusions arranged so as to open the gap formed between the radial protrusions inwardly in the tire radial direction.

  In the pneumatic tire (pneumatic radial tire) described in Patent Document 4, a plurality of protrusions having a height of 5 mm or more are arranged at intervals in the tire circumferential direction on the buttress portion, and the surface of the protrusion in the tire circumferential direction is arranged. The length and the length in the tire radial direction are longer than the height of the protrusion, the area increases from the surface of the protrusion to the bottom surface, and the area of the bottom surface of the protrusion is more than twice the surface area of the protrusion. .

JP 2007-168520 A JP 2010-47251 A JP 2010-264962 A JP 2004-291936 A

  However, in the pneumatic tires described in Patent Document 1 and Patent Document 2, since the protrusion is arranged on the outer side in the tire width direction of the tread block, the rubber volume near the groove portion between the tread blocks in the buttress portion. Since the rubber volume of the protruding portion is greatly different, the stress applied to the carcass cord constituting the tire skeleton becomes uneven, and the durability of the carcass cord may be reduced.

  Further, although the pneumatic tire described in Patent Document 3 has circumferential protrusions, the radial protrusions are mainly formed in alignment with the tread blocks. Since the rubber volume of the protruding portion is greatly different from the rubber volume, the durability of the carcass cord may be reduced.

  On the other hand, the pneumatic tire described in Patent Document 4 tries to suppress the rubber volume of the buttress portion from becoming non-uniform, but since the protrusion is separated from the groove portion, the tread block is still in the buttress portion. Since the difference in the rubber volume of the protruding portion occurs with respect to the rubber volume in the vicinity of the groove portion between them, it is difficult to obtain the effect of improving the durability of the carcass cord.

  The present invention has been made in view of the above, and an object of the present invention is to provide a pneumatic tire that can further improve the durability of the carcass cord while being provided with a protrusion that improves traveling performance in a muddy area. To do.

  In order to solve the above-described problems and achieve the object, the pneumatic tire according to the present invention includes a plurality of lug grooves that extend outward in the tire width direction of the tread portion and open at predetermined intervals in the tire circumferential direction. In the pneumatic tire, the groove bottom of the lug groove is on the inner side in the tire radial direction from the groove bottom extension line extending from the ground end end groove bottom position coincident with the ground end of the tread portion to the tire width direction, and A protrusion formed from the bottom of the lug groove to the outer side in the tire width direction is provided between the ground contact end groove bottom position and the tire maximum width position.

  According to this pneumatic tire, when traveling on a rough road such as a muddy area, the effect of improving the traction performance can be obtained by scratching the mud with the protrusion. In this pneumatic tire, since the rubber volume at the bottom of the lug groove is increased by providing a protrusion between the ground end groove bottom position and the tire maximum width position, the land existing on both sides of the lug groove is increased. The difference in rubber volume with the part is reduced. As a result, the rubber volume at the portion where the protrusion is provided is made uniform, and the stress applied to the carcass cord of the carcass layer is made uniform, so that the durability of the carcass cord can be improved. Moreover, by providing a protrusion on the inner side in the tire radial direction from the groove bottom extension line extending from the bottom position of the contact end groove to the tire width direction, the protrusion does not block the lug groove at the time of ground contact. The traction performance in the muddy area can be secured without impairing the discharge performance of the muddy soil.

  Further, in the pneumatic tire of the present invention, with respect to the protrusion, when the dimension in the tire width direction is L, the dimension in the tire radial direction is H, the maximum protruding dimension is h, and the radius of the top in the tire meridian section is α, 10 [mm] ≦ L ≦ Nominal width × 1/4, which is a range inside the tire width direction from the tire maximum width position, and 30 [mm] ≦ H ≦ flatness × 1/2 and the tire from the tire maximum width position The range is radially inward, 5 [mm] ≦ h ≦ 15 [mm], and the range from the groove bottom extension line to the inside in the tire radial direction and from the tire maximum width position to the inside in the tire width direction is 5R [mm]. ≦ α.

  According to this pneumatic tire, if the dimension L in the tire width direction, the dimension H in the tire radial direction, and the maximum protruding dimension h are equal to or greater than the prescribed minimum value, the traction performance is improved by scratching mud with sufficient rigidity. The effect can be obtained remarkably. On the other hand, if the dimension L in the tire width direction, the dimension H in the tire radial direction, and the maximum protruding dimension h are not more than the prescribed maximum values, the tire will not protrude significantly from the outer shape of the tire itself, Collisions can be reduced. Moreover, if the radius α at the top of the tire meridional section is equal to or greater than a specified value, the protrusions are not extremely sharp and the rigidity can be prevented from being lowered.

  The pneumatic tire of the present invention is characterized in that, with respect to the protrusion, when the dimension in the tire circumferential direction is W and the groove bottom width of the lug groove is T, 0.3T ≦ W ≦ 0.9T. The pneumatic tire according to claim 1 or 2.

  According to this pneumatic tire, if the dimension W in the tire circumferential direction is equal to or greater than a specified minimum value, the effect of improving the traction performance can be obtained by scratching the mud with sufficient rigidity. On the other hand, if the dimension W in the tire circumferential direction is equal to or less than the prescribed maximum value, the drainage of the lug groove to the outside in the tire width direction can be maintained.

  The pneumatic tire of the present invention is characterized in that 3W ≦ X ≦ 10W, where X is the dimension between the protrusions and W is the dimension in the tire circumferential direction.

  According to this pneumatic tire, when the dimension X between the protrusions is equal to or greater than the prescribed minimum value, the mud discharge performance between the protrusions can be improved, and the effect of improving the traction performance can be significantly obtained. On the other hand, if the dimension X between the protrusions is equal to or less than the prescribed maximum value, the effect of scratching the mud can be improved and the effect of improving the traction performance can be significantly obtained.

  The pneumatic tire according to the present invention can further improve the durability of the carcass cord while being provided with a protrusion that improves traveling performance in a muddy area.

FIG. 1 is a meridional sectional view of a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a plan view of the pneumatic tire according to the embodiment of the present invention. FIG. 3 is a perspective view of the pneumatic tire according to the embodiment of the present invention. FIG. 4 is a chart showing the results of the performance test of the pneumatic tire according to the example of the present invention.

  Embodiments of the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. The constituent elements of this embodiment include those that can be easily replaced by those skilled in the art or those that are substantially the same. In addition, a plurality of modifications described in this embodiment can be arbitrarily combined within a range obvious to those skilled in the art.

  1 is a meridional sectional view of a pneumatic tire according to the present embodiment, FIG. 2 is a plan view of the pneumatic tire according to the present embodiment, and FIG. 3 is a perspective view of the pneumatic tire according to the present embodiment. FIG.

  In the following description, the tire radial direction refers to a direction orthogonal to the rotational axis (not shown) of the pneumatic tire, and the tire radial inner side refers to the side toward the rotational axis in the tire radial direction, the tire radial outer side, and Means the side away from the rotation axis in the tire radial direction. Further, the tire circumferential direction refers to a direction around the rotation axis as a central axis. Further, the tire width direction refers to a direction parallel to the rotation axis, the inner side in the tire width direction is the side toward the tire equatorial plane (not shown) in the tire width direction, and the outer side in the tire width direction is in the tire width direction. The side away from the tire equator. The tire equator plane is a plane that is orthogonal to the rotational axis of the pneumatic tire and passes through the center of the tire width of the pneumatic tire. The tire width is the width in the tire width direction between the portions located outside in the tire width direction, that is, the distance between the portions farthest from the tire equatorial plane in the tire width direction. Further, the tire equator line is a line along the tire circumferential direction of the pneumatic tire that is on the tire equator plane, although not explicitly shown in the drawing. The pneumatic tire described below is configured so as to be substantially symmetric with respect to the tire equatorial plane. Therefore, the meridian when the pneumatic tire is cut on a plane passing through the rotation axis of the pneumatic tire is described. In the cross-sectional view (FIG. 1), only one side (right side in FIG. 1) is illustrated and only one side is described, and description of the other side (left side in FIG. 1) is omitted.

  As shown in FIG. 1, the pneumatic tire according to the present embodiment includes a tread portion 2, shoulder portions 3 on both sides thereof, and a sidewall portion 4 and a bead portion 5 that are sequentially continuous from the shoulder portions 3. doing. The pneumatic tire has a carcass layer 6, a belt layer 7, and a belt reinforcing layer 8.

  The tread portion 2 is made of a rubber material (tread rubber), and is exposed at the outermost side in the tire radial direction of the pneumatic tire, and the surface thereof is the contour of the pneumatic tire. A tread surface 21 is formed on the outer peripheral surface of the tread portion 2, that is, on the tread surface that contacts the road surface during traveling. The tread surface 21 is provided with a main groove 22 extending along the tire circumferential direction. The main groove 22 is substantially parallel to the tire equator line (for example, ± 5 degrees), and is mainly formed as a straight groove along the tire circumferential direction. Further, the tread surface 21 is provided with a plurality of lug grooves 23 that intersect with the main groove 22 and are formed at predetermined intervals in the tire circumferential direction. The lug groove 23 is mainly formed to extend along the tire width direction, and is formed to open to the outer side in the tire width direction on the outermost side in the tire width direction of the tread portion 2. The tread surface 21 has a block-shaped land portion 24 formed by the main groove 22 and the lug groove 23. In the present embodiment, a dividing groove 25 that divides the land portion 24 into a plurality of small blocks is provided.

  The shoulder portion 3 is a portion on both outer sides in the tire width direction of the tread portion 2. The sidewall portion 4 is exposed at the outermost side in the tire width direction of the pneumatic tire. The bead unit 5 includes a bead core 51 and a bead filler 52. The bead core 51 is formed by winding a bead wire, which is a steel wire, in a ring shape. The bead filler 52 is a rubber material disposed in a space formed by folding the end portion in the tire width direction of the carcass layer 6 at the position of the bead core 51.

  The carcass layer 6 is configured such that each tire width direction end portion is folded back from the tire width direction inner side to the tire width direction outer side by a pair of bead cores 51 and is wound around in a toroidal shape in the tire circumferential direction. It is. This carcass layer 6 has a 90 ° (± 5 °) angle with respect to the tire circumferential direction, and a plurality of carcass cords (not shown) arranged in the tire circumferential direction along the tire meridian direction and covered with a coat rubber. It is. The carcass cord is made of organic fibers (polyester, rayon, nylon, etc.). In addition, although the carcass layer 6 of this Embodiment is provided by 1 layer, you may be provided by multiple layers. In addition, the carcass layer 6 is provided with a carcass auxiliary layer 61 on the outer side in the tire width direction of the bead filler 52.

  The carcass auxiliary layer 61 is laminated on the outer side in the tire radial direction of the carcass layer 6 so as to cover the carcass layer 6 in the tire circumferential direction, and each tire width direction end portion extends from the outer side in the tire width direction of the bead core 51 to the inner side in the tire width direction. It is wound and arranged toward the. The carcass auxiliary layer 61 is formed by coating a plurality of cords (not shown) arranged in parallel at a predetermined angle with respect to the tire circumferential direction with a coat rubber. The cord is made of organic fibers (polyester, rayon, nylon, etc.).

  The belt layer 7 has a multilayer structure in which at least two layers of belts 71 and 72 are laminated from the inner side to the outer side in the tire radial direction, and on the outer side in the tire radial direction that is the outer periphery of the carcass layer 6 (carcass auxiliary layer 61) in the tread portion 2. Arranged and covers the carcass layer 6 (carcass auxiliary layer 61) in the tire circumferential direction. The belts 71 and 72 are made by coating a plurality of cords (not shown) arranged in parallel at a predetermined angle (for example, 20 degrees to 30 degrees) with a coat rubber with respect to the tire circumferential direction. The cord is made of steel or organic fiber (polyester, rayon, nylon, etc.). Further, the overlapping belts 71 and 72 are arranged so that the cords intersect each other.

  The belt reinforcing layer 8 is disposed on the outer side in the tire radial direction which is the outer periphery of the belt layer 7 and covers the belt layer 7 in the tire circumferential direction. In the present embodiment, the belt reinforcing layer 8 includes two reinforcing layers 81 and 82 arranged from the inner side to the outer side in the tire radial direction so as to cover the outer periphery of the belt layer 7, and end portions in the tire width direction of the belt layer 7. And a reinforcing layer 83 for covering. The reinforcing layers 81 and 82 are formed by coating a plurality of cords (not shown) arranged in parallel in the tire width direction and in parallel with the tire circumferential direction (not shown) with a coat rubber. The cord is made of steel or organic fiber (polyester, rayon, nylon, etc.). The reinforcing layer 83 is disposed only at the end portion in the tire width direction on the outer side in the tire radial direction of the reinforcing layer 82 on the outer side in the tire radial direction. The belt reinforcing layer 8 (reinforcing layers 81, 82, 83) is provided by winding a strip-shaped strip material (for example, width 10 [mm]) in the tire circumferential direction.

  In the pneumatic tire configured as described above, the protrusion 9 is provided from the groove bottom of the lug groove 23 that extends and opens outward in the tire width direction to the outer side in the tire width direction. The protrusion 9 has a buttress portion between the ground end groove bottom position SD where the bottom of the lug groove 23 coincides with the ground end S of the tread portion 2 and the tire maximum width position P of the sidewall portion 4. It is formed on the inner side in the tire radial direction from the groove bottom extension line RD extending from the position SD to the outer side in the tire width direction, and extends from the groove bottom of the lug groove 23 to the outer side in the tire width direction in the range of the buttress portion. Further, the protrusions 9 are provided so as to avoid the outer sides in the tire width direction of the land portions 24 sandwiching the lug grooves 23.

  Here, when the pneumatic tire is assembled on the regular rim, filled with the regular internal pressure, and applied with 80% of the regular load, the tread surface 21 of the pneumatic tire is the road contact surface S. When the maximum width in the tire width direction of a region to be grounded (hereinafter referred to as a grounding region) is defined as the ground width, the outermost ends in the tire width direction of the ground width are referred to as the ground width. Shown continuously in the direction. The grounding end groove bottom position SD is a portion that coincides with the grounding end S in the groove bottom of the lug groove 23 as shown in FIG.

  The regular rim is “standard rim” defined by JATMA, “Design Rim” defined by TRA, or “Measuring Rim” defined by ETRTO. The normal internal pressure is “maximum air pressure” defined by JATMA, the maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “INFLATION PRESSURES” defined by ETRTO. The normal load is “maximum load capacity” defined by JATMA, a maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “LOAD CAPACITY” defined by ETRTO.

  According to the pneumatic tire of this embodiment, the effect of improving the traction performance can be obtained by scratching the mud with the protrusion 9 when traveling on a rough road such as a muddy ground.

  In the pneumatic tire according to the present embodiment, the protrusion 9 is provided in the buttress portion (between the ground end groove bottom position SD and the tire maximum width position P of the sidewall portion 4), so that the groove of the lug groove 23 is provided. Since the rubber volume at the bottom increases, the difference in rubber volume from the land portion 24 existing in the paddle portion is reduced. As a result, the rubber volume of the buttress portion is made uniform and the stress applied to the carcass cord of the carcass layer 6 is made uniform, so that the durability of the carcass cord can be improved. Moreover, by providing the protrusion 9 on the inner side in the tire radial direction from the groove bottom extension line RD extending from the ground end groove bottom position SD to the tire width direction outer side, the protrusion 9 does not block the lug groove 23 at the time of ground contact. It is possible to ensure the traction performance in the muddy area without impairing the drainage property of the lug groove 23 and the discharge property of the mud.

  Note that the protrusions 9 may be formed in a rectangular shape having the same tire circumferential direction dimension W from the bottom of the lug groove 23 to the outer side in the tire width direction in plan view as shown in FIG. It may be formed in a trapezoidal shape with the tire circumferential direction dimension W gradually differing from the groove bottom to the tire width direction outside, and can be made the best shape according to the opening shape of the lug groove 23 on the tire width direction outside It is. Further, the protrusion 9 may be subjected to surface processing such as a convex part or a concave part on the surface thereof, thereby making it possible to favorably remove the mud from the surface of the protrusion 9.

  In the pneumatic tire of the present embodiment, as shown in FIGS. 1 and 2, the protrusion 9 has a dimension L in the tire width direction, a dimension H in the tire radial direction, a maximum protrusion dimension h, and a tire meridian. When the radius of the top (Rmm) in the cross section is α, 10 [mm] ≦ L ≦ nominal width × 1/4, and the range in the tire width direction from the tire maximum width position P, and 30 [mm] ≦ H ≦ flat × 1/2, and the range in the tire radial direction from the tire maximum width position P, and 5 [mm] ≦ h ≦ 15 [mm], the tire radial direction inner side and the tire from the groove bottom extension line RD It is preferable to set the range from the maximum width position P to the inner side in the tire width direction so that 5R [mm] ≦ α and less than the radius of the buttress portion (preferably 5R [mm] ≦ α ≦ 25R [mm]). The maximum projecting dimension h is the most projecting part from the surface of the buttress part, and indicates the dimension in the normal direction of the surface of the buttress part.

  If the dimension L in the tire width direction, the dimension H in the tire radial direction, and the maximum protrusion dimension h are equal to or greater than the prescribed minimum values, it is possible to obtain a significant improvement in traction performance by scratching mud with sufficient rigidity. become. On the other hand, if the dimension L in the tire width direction, the dimension H in the tire radial direction, and the maximum protruding dimension h are not more than the prescribed maximum values, the tire will not protrude significantly from the outer shape of the tire itself, Collisions can be reduced. Moreover, if the radius α of the top portion of the tire meridian section is equal to or greater than a specified value, the protrusion 9 does not have an extremely sharp shape, and it is possible to prevent a decrease in rigidity.

  In order to obtain the above effect more remarkably, 30 [mm] ≦ L and the tire width direction inner side range from the tire maximum width position P, and 50 [mm] ≦ H and the tire from the tire maximum width position P. It is more preferable that the radial inner range is 5 [mm] ≦ h ≦ 8 [mm], and the inner radius direction inner side of the groove bottom extension line RD and the inner tire width direction inner side of the tire maximum width position P. preferable.

  Further, in the pneumatic tire of the present embodiment, with respect to the protrusion 9, when the tire circumferential dimension is W and the groove bottom width of the lug groove is T, 0.3T ≦ W ≦ 0.9T may be satisfied. preferable.

  If the dimension W in the tire circumferential direction is equal to or greater than the prescribed minimum value, it is possible to obtain a significant improvement in traction performance by scratching the mud with sufficient rigidity. On the other hand, if the dimension W in the tire circumferential direction is equal to or less than the prescribed maximum value, it is possible to maintain the drainage of the lug groove to the outside in the tire width direction.

  In order to obtain the above effect remarkably, it is more preferable that 0.5T ≦ W ≦ 0.9T.

  Further, in the pneumatic tire of the present embodiment, with respect to the protrusions 9, when the dimension between the protrusions 9 is X and the dimension in the tire circumferential direction is W, it is preferable that 3W ≦ X ≦ 10W.

  If the dimension X between the protrusions 9 is equal to or greater than the prescribed minimum value, it is possible to improve the traction performance by improving the performance of discharging mud between the protrusions 9. On the other hand, if the dimension X between the protrusions 9 is equal to or less than the prescribed maximum value, it is possible to improve the traction performance by improving the action of scratching mud.

  In order to obtain the above effect more remarkably, it is more preferable to satisfy 3W ≦ X ≦ 7W.

  In the present embodiment, performance tests relating to carcass cord durability, muddy road running straightness, and muddy road running acceleration were performed for a plurality of types of pneumatic tires with different conditions (see FIG. 4).

  In this performance test, a test tire having a tire size of 225 / 65R17 was mounted on a regular rim.

  In the performance test of carcass cord durability, the test tire is filled with a test air pressure of 140 [KPa], and a normal load is applied at a running speed of 45 [km / h] on a drum type durability tester. The load is increased by 10 [%] of the normal load every step (every 24 hours), and the travel distance until the tire breaks is measured. Based on this measurement result, index evaluation is performed with the conventional example as a reference (100). This evaluation shows that the greater the index, the longer the travel distance and the better the carcass cord durability.

  In the straightness performance test, the test tires are filled with normal internal pressure and mounted on a test vehicle (four-wheel drive vehicle), and the straightness in a muddy area is an average of 10 sensory evaluations by five test drivers. Do by value. Based on this sensory evaluation, index evaluation is performed with the conventional pneumatic tire as a reference (100). This index evaluation indicates that the greater the numerical value, the better the straightness.

  In the performance test for acceleration, the test tire is filled with normal internal pressure, mounted on a test vehicle (four-wheel drive vehicle), accelerated from a stop in a muddy area, and accelerated up to 50 [m] (speed and speed). Time). Based on this measurement result, index evaluation is performed with the conventional example as a reference (100). This evaluation shows that the larger the index, the shorter the acceleration time and the better the acceleration performance.

  In FIG. 4, the conventional pneumatic tire has no protrusions. Further, in the pneumatic tire of the comparative example, a plurality of protrusions having a height of 5 mm or more are arranged at intervals in the tire circumferential direction, and the length of the surface of the protrusion in the tire circumferential direction and the length in the tire radial direction are protruding. Longer than the height of the protrusion, and the area increases from the surface to the bottom of the protrusion, and the area of the bottom surface of the protrusion is more than twice the surface area of the protrusion (corresponding to the pneumatic tire of Patent Document 4). . In the pneumatic tire of this comparative example, no protrusion is formed on the groove bottom of the lug groove, and the pneumatic tire is also disposed on the outer side in the tire width direction of each land portion sandwiching the lug groove.

  In FIG. 4, the pneumatic tires of Examples 1 to 11 are on the inner side in the tire radial direction from the groove bottom extension line extending from the ground contact end groove bottom position to the tire width direction outer side, and from the ground contact end groove bottom position. A protrusion is formed from the bottom of the lug groove to the outside in the tire width direction up to the tire maximum width position. In the pneumatic tires of Examples 2 to 11, the protrusions have a dimension L in the tire width direction, a dimension H in the tire radial direction, a dimension W in the tire circumferential direction, a maximum protruding dimension h, and a top portion in the tire meridional section. The radius α and the dimension X between the protrusions are set within a prescribed range.

  As shown in the test results of FIG. 4, the pneumatic tires of Examples 1 to 11 are superior in straightness and acceleration in a muddy area due to the provision of protrusions, and carcass cord durability. It can be seen that is improved.

2 tread portion 21 tread surface 22 main groove 23 lug groove 24 land portion 6 carcass layer 61 carcass auxiliary layer 9 protrusion h protrusion maximum protrusion dimension H protrusion diameter direction dimension L protrusion width direction dimension P tire maximum width Position RD Groove bottom extension line S Grounding edge SD Grounding edge groove bottom position T Lug groove groove bottom width W Projection tire circumferential dimension X Protrusion dimension α Radius of projection top

Claims (4)

In the pneumatic tire in which a plurality of lug grooves that extend and open outward in the tire width direction of the tread portion are formed at predetermined intervals in the tire circumferential direction,
The groove bottom of the lug groove is on the inner side in the tire radial direction of the groove bottom extension line extending from the ground end end groove bottom position that coincides with the ground end of the tread portion to the tire width direction outside, and from the ground end end groove bottom position. A pneumatic tire comprising a protrusion formed from the bottom of the lug groove to the outer side in the tire width direction up to the tire maximum width position. About the protrusion, when the dimension in the tire width direction is L, the dimension in the tire radial direction is H, the maximum protrusion dimension is h, and the radius of the apex in the tire meridian section is α,
10 [mm] ≦ L ≦ Nominal width × 1/4, and the range in the tire width direction from the tire maximum width position,
30 [mm] ≦ H ≦ flat × 1/2, and the range in the tire radial direction from the tire maximum width position,
5 [mm] ≦ h ≦ 15 [mm], and the range from the groove bottom extension line to the tire radial direction inner side and the tire maximum width position to the tire width direction inner side,
5R [mm] ≦ α,
The pneumatic tire according to claim 1.   3. The air according to claim 1, wherein the protrusion has a size of 0.3T ≦ W ≦ 0.9T, where W is a dimension in the tire circumferential direction and T is a groove bottom width of the lug groove. Enter tire.   The pneumatic according to any one of claims 1 to 3, wherein when the dimension between the projections is X and the dimension in the tire circumferential direction is W, 3W≤X≤10W. tire.

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