JP2006051927A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of enhancing turnover limit performance while maintaining operation stability and abrasion-resistance. <P>SOLUTION: The pneumatic tire 1 has a plurality of longitudinal grooves 2 extending in a tire circumferential direction and a lateral grooves 3 extending in a tire width direction on a tread part and has a shoulder block 4 divided by these grooves 2, 3 on a shoulder part. The pneumatic tire is characterized in that it has a recessed part 41 on a groove wall surface on a lateral groove 3 side of the shoulder block 4 and outward in the tire width direction more than a ground-contact end of the tread part. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire that can improve the tipping limit performance while maintaining the maneuverability and wear resistance.

In recent RV vehicles (recreational vehicle car), there are increasing opportunities for high-speed driving due to higher engine output, etc., so the performance to prevent the vehicle from falling during cornering (falling limit performance) has been highlighted. Yes. For this reason, in the pneumatic tire for RV vehicles, there is a request from the automobile manufacturer to ensure the fall limit performance.

  In this regard, the technology described in Patent Document 1 is known for conventional pneumatic tires. In a conventional pneumatic tire, a tread portion is provided with a longitudinal groove extending in the tire circumferential direction and a plurality of transverse grooves in a direction intersecting with the longitudinal groove. These grooves form at least one block row arranged in the tire circumferential direction. A chamfered portion is formed in each block of the block row by notching the intersection between the block surface and the block wall surface where the block faces the longitudinal groove. In the conventional pneumatic tire, the fall limit performance is improved by such a configuration.

  However, in the conventional pneumatic tire, since the block rigidity in the ground contact surface is reduced due to the formation of the chamfered portion, there is a problem that the maneuverability is lowered.

JP 2002-172916 A

  Therefore, the present invention has been made in view of the above, and an object of the present invention is to provide a pneumatic tire capable of improving the tipping limit performance while maintaining the maneuverability and the wear resistance.

  In order to achieve the above object, a pneumatic tire according to the present invention has a plurality of longitudinal grooves extending in the tire circumferential direction and lateral grooves extending in the tire width direction in the tread portion, and is partitioned by these grooves. In the pneumatic tire having a shoulder block having a shoulder block, the groove wall surface on the lateral groove side of the shoulder block has a concave portion on the outer side in the tire width direction from the ground contact end of the tread portion.

  This pneumatic tire is a groove wall surface on the lateral groove side of the shoulder block and has a concave portion on the outer side in the tire width direction from the ground contact end of the tread portion. In such a configuration, the shoulder block is easily compressed and deformed when the ground pressure is applied to the shoulder block. Thereby, since the rigidity of the shoulder block is reduced and the cornering force is reduced, there is an advantage that the fall limit performance is improved.

  Further, in the pneumatic tire according to the present invention, the concave portion is formed only in a range on the outer side in the tire width direction from the ground contact end of the tread portion.

  In this pneumatic tire, since the concave portion is formed only in the outer side in the tire width direction than the ground contact end of the tread portion, the concave portion is also formed in the ground contact surface (in the tire width direction inner side than the ground contact end). Compared with the configuration (not shown), it is preferable in terms of maintaining the operability and wear resistance during normal running in the same manner as a conventional pneumatic tire.

  Moreover, the pneumatic tire according to the present invention is formed such that the depth of the concave portion becomes deeper from the ground contact end of the tread portion toward the outer side in the tire width direction.

  In this pneumatic tire, since the depth of the concave portion is formed so as to become deeper from the contact end of the tread portion toward the outer side in the tire width direction, when the contact pressure is applied to the shoulder block, There is an advantage that compression deformation is gradually generated and rigidity change of the shoulder block is gradually generated.

  In the pneumatic tire according to the present invention, the concave shape of the concave portion has a wave shape or a zigzag shape in a plan view of the tread portion.

  In this pneumatic tire, the concave shape of the concave portion has a wave shape or a zigzag shape, so that the degree of change in the rigidity of the shoulder block can be adjusted by changing the wave shape or the zigzag shape and the pitch thereof. There is.

  Further, in the pneumatic tire according to the present invention, the cross-sectional view in the tire meridian direction is such that the deepest portion of the recess is closer to the inner side of the shoulder block than a straight line connecting the edge portion of the shoulder block and the tire rotation axis. Is located.

  In this pneumatic tire, the deepest part of the dent in the recess is located inside the shoulder block from the straight line connecting the edge of the shoulder block and the tire rotation axis, effectively preventing cracks during running There are advantages to being.

  In the pneumatic tire according to the present invention, the distance from the surface of the shoulder block to the deepest portion of the recess is in the range of 50 [%] to 70 [%] of the groove depth in a cross-sectional view in the tire meridian direction. It is in.

  In this pneumatic tire, since the distance from the surface of the shoulder block to the deepest part of the recess is in the range of 50 [%] to 70 [%] of the groove depth, there is an advantage that the fall limit performance is more effectively improved. is there.

  The pneumatic tire according to the present invention is formed such that the recess starts to be depressed starting from a position at a predetermined distance in the groove depth direction from the edge portion of the shoulder block in a cross-sectional view in the tire radial direction. Yes.

  Further, in this pneumatic tire, since the concave portion starts to be depressed starting from a position at a predetermined distance from the edge portion of the shoulder block in the groove depth direction, damage near the surface of the tread portion is effectively performed. There is an advantage to be suppressed.

  In the pneumatic tire according to the present invention, the distance at which the concave portion starts to be recessed is within a range of 20% to 30% with respect to the groove depth.

  In this pneumatic tire, the distance at which the recess starts to be recessed is in the range of 20% to 30% with respect to the groove depth, so that the edge of the shoulder block is damaged during vehicle travel. In addition to being more effectively suppressed, there are advantages that the block rigidity is suitably reduced and the fall limit performance is improved.

  Further, in the pneumatic tire according to the present invention, when the intersection of the groove wall surface of the shoulder block and the groove bottom surface of the lateral groove is a base portion of the shoulder block in a cross-sectional view in the tire meridian direction, the base portion is It is located on the lateral groove side from a straight line connecting the edge portion of the shoulder block and the tire rotation axis.

  In this pneumatic tire, the shoulder block base is located on the lateral groove side of the straight line connecting the edge of the shoulder block and the tire rotation axis, so the shoulder block cracks during driving and the stone bites in the lateral groove, etc. There is an advantage that the occurrence of is effectively suppressed.

  Further, the pneumatic tire according to the present invention has a straight line connecting the edge portion of the shoulder block and the tire rotation axis in a cross-sectional view in the tire meridian direction. Is the depth of the recess, the depth of the recess is in the range of 15 [%] to 25 [%] of the tire circumferential width of the shoulder block.

  In this pneumatic tire, since the depth of the recess is in the range of 15 [%] or more and 25 [%] or less of the tire circumferential width of the shoulder block, buckling of the shoulder block due to a load during running is suppressed, There is an advantage that generation of cracks is prevented.

  Further, in the pneumatic tire according to the present invention, the recesses are formed on both groove wall surfaces on the lateral groove side of the shoulder block in a cross-sectional view in the tire meridian direction, and these recesses are mutually It is formed symmetrically.

  In this pneumatic tire, since the concave portions of both groove wall surfaces are formed symmetrically with each other, there is an advantage that the rigidity of the shoulder block in the tire circumferential direction is balanced and the wear resistance is improved.

  In the pneumatic tire according to the present invention, a stone ejector is formed along the concave portion in a lateral groove defining the shoulder block.

  In this pneumatic tire, since the stone ejector is formed along the concave portion in the lateral groove defining the shoulder block, the stone ejector suppresses the entry of foreign matters such as stones into the lateral groove when the tire rolls. Thereby, since the breakage of the lateral groove due to the foreign matter is reduced, there is an advantage that the durability performance of the tire is improved. In particular, such a configuration has an advantage that the biting of foreign matter in the lateral groove is remarkably suppressed in the formation range of the recess in the shoulder block.

  In the pneumatic tire according to the present invention, the stone ejector includes a protrusion that protrudes outward in the tire radial direction from the bottom of the lateral groove.

  In this pneumatic tire, the stone ejector is composed of a protruding portion that protrudes outward in the tire radial direction from the groove bottom of the lateral groove, so that intrusion of foreign matter is effectively suppressed by the protruding portion that is easy to mold. Thereby, there exists an advantage which the durable performance of a tire improves effectively with a simple structure.

  In the pneumatic tire according to the present invention, the height H of the protrusion has a relationship of 0.30 ≦ H / D with respect to the groove depth D of the main groove.

  In this pneumatic tire, since the height H of the protrusion is optimized with respect to the groove depth D of the main groove, entry of foreign matter into the lateral groove is effectively reduced. Thereby, there exists an advantage which the durable performance of a tire improves more effectively.

  In the pneumatic tire according to the present invention, a sipe is formed on the wall surface on the lateral groove side of the shoulder block from the concave portion to the edge portion of the shoulder block.

  In this pneumatic tire, a sipe is formed from the recess to the edge (tread surface) on the wall surface on the side groove side of the shoulder block, so that when the tire rolls, the side groove can be opened and closed greatly by opening and closing the sipe, so that the side groove has entered Foreign matter is easily discharged to the outside. Thereby, there exists an advantage by which the biting of the foreign material in a horizontal groove is suppressed.

  In the pneumatic tire according to the present invention, the width Ws of the sipe on the tread surface of the shoulder block has a relationship of 0.50 ≦ Ws / W1 ≦ 1.00 with respect to the depth W1 of the recess.

  In this pneumatic tire, since the sipe width Ws on the tread surface (tread surface) of the shoulder block is optimized with respect to the depth W1 of the recess, foreign matter that has entered the lateral groove is more easily discharged to the outside. Thereby, there exists an advantage by which the damage of the horizontal groove by a foreign material is reduced effectively.

  According to the pneumatic tire of the present invention, since the groove wall surface on the lateral groove side of the shoulder block has a concave portion on the outer side in the tire width direction from the grounding end of the tread portion, the rigidity of the shoulder block is reduced and the cornering force is reduced. Since it decreases, there is an advantage that the fall limit performance is improved.

  Hereinafter, the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. In addition, constituent elements of the embodiments described below include those that can be easily replaced by those skilled in the art or those that are substantially the same.

  1 is a plan view showing a tread portion of a pneumatic tire according to Embodiment 1 of the present invention. 2 and 3 are a plan view (FIG. 2) showing a shoulder block of the pneumatic tire shown in FIG. 1 and a cross-sectional view in the tire meridian direction (FIG. 3). 4-6 is explanatory drawing which shows the modification of the pneumatic tire described in FIG.

  In this pneumatic tire 1, a plurality of vertical grooves 2 extending in the tire circumferential direction and lateral grooves (lag grooves) 3 extending in the tire width direction are formed in the tread portion. 3 is formed in the shoulder portion (see FIG. 1). A recess 41 is formed in the shoulder block 4. The recesses 41 are respectively formed on both groove wall surfaces (the heel side and toe side groove wall surfaces) of the shoulder block 4 on the side of the lateral groove 3 (see FIG. 2). Thereby, the shoulder block 4 is formed so that the edge part (end edge part) overhangs with respect to the horizontal groove 3 in the cross-sectional view of the tire meridian direction (refer FIG. 3). Moreover, the recessed part 41 is formed in the tire width direction outer side range from the grounding end of the tread part.

  The ground contact end of the tread portion refers to an end portion of the contact surface of the tread portion in the tire width direction in a state where the pneumatic tire 1 is assembled on a regular rim and is grounded with a regular internal pressure and a regular load. (Edge) shall be said (refer FIG. 1). Further, the grounding end and the grounding surface mean the grounding end and the grounding surface during normal travel (during straight traveling), and do not mean the grounding end and the grounding surface during cornering or race change. The regular rim corresponds to a standard rim defined by JATMA, “Design Rim” defined by TRA, or “Measuring Rim” defined by ETRTO. The normal internal pressure corresponds to the maximum air pressure specified by JATMA, the maximum value described in the TRA table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES”, or “INFLATION PRESSURE” specified in ETRTO. The normal load corresponds to the maximum load capacity defined in JATMA, the maximum value described in the table of TRA, or “LOAD CAPACITY” defined in ETRTO.

  In the pneumatic tire 1, when the cornering is performed at a high slip angle (during high G traveling), the grounding range of the tread portion is changed, and the range outside the grounding end during normal traveling is grounded to the road surface. These facts have been proved by the inventors by a double chain test, a fish hook test, and other fall limit performance tests (see JIS D4230). Here, in the pneumatic tire 1, the shoulder block 4 is compressed when the ground pressure is applied to the shoulder block 4, as compared with a conventional pneumatic tire having a shoulder block whose cross section in the tire meridian direction is trapezoidal. Easily deformed (the groove wall of the shoulder block 4 tends to swell). Thereby, the rigidity of the shoulder block 4 is reduced and the cornering force is reduced.

  According to the pneumatic tire 1, since the recess 41 is formed on the groove wall surface on the lateral groove 3 side of the shoulder block 4 and on the outer side in the tire width direction from the ground end of the tread portion, the ground pressure is applied to the shoulder block 4. The shoulder block 4 is easily compressed and deformed when loaded. Thereby, since the rigidity of the shoulder block 4 is reduced and the cornering force is reduced, there is an advantage that the fall limit performance is improved.

  Moreover, according to this pneumatic tire 1, the structure which provides a chamfer part in the shoulder block 4, the structure which increases the angle of a belt, the structure which reduces the rubber hardness of a tread part, the structure which increases a groove area, etc. (illustration omitted) Compared to the above, there is an advantage that steering stability and uneven wear resistance are excellent.

  The pneumatic tire 1 is preferably used by being mounted on, for example, a station wagon, a one-box wagon, an off-road 4WD, a semi-cab wagon, or other RV vehicles (recreational vehicle car). This is because in RV vehicles, opportunities for high-speed running are increasing due to the recent increase in engine output and the like, and in particular, there is a strong demand for overturning limit performance.

  Moreover, in this pneumatic tire 1, the recessed part 41 is formed ranging from the contact end of a tread part to the design end of a tread part. Further, the concave portion 41 is formed only in a range on the outer side in the tire width direction from the ground contact end, and is not formed in the ground contact surface (inward in the tire width direction from the ground contact end). In this configuration, the rigidity of the shoulder block 4 in the ground contact surface is a conventional pneumatic tire (the cross section in the tire meridian direction is trapezoidal) compared to the configuration in which the recess 41 is also formed in the ground contact surface (not shown). This is ensured in the same manner as a conventional pneumatic tire having a shoulder block. Therefore, it is preferable in terms of maintaining the stability and wear resistance during normal running in the same manner as a conventional pneumatic tire.

  In the pneumatic tire 1, the depth W1 of the recess 41 is formed to be substantially uniform from the ground contact end toward the outer side in the tire width direction (see FIG. 2). It is preferable because the rigidity of the shoulder block outside the outer wall can be effectively reduced. However, the present invention is not limited to this, and the depth W1 of the recess 41 may be formed so as to gradually increase from the ground contact end toward the outer side in the tire width direction (see FIG. 4). Such a configuration has an advantage that when the ground pressure is applied to the shoulder block 4, the shoulder block 4 is gradually compressed and the shoulder block 4 is gradually changed in rigidity.

  Moreover, in this pneumatic tire 1, the concave shape of the concave portion 41 (the trajectory of the bottom portion P) is linearly formed in a plan view of the tread portion (see FIG. 3). However, the present invention is not limited thereto, and the concave shape of the concave portion 41 may be formed in a wave shape or a zigzag shape (see FIG. 5). In such a configuration, there is an advantage that the degree of change in rigidity of the shoulder block 4 can be adjusted by changing the wavy or zigzag shape and its pitch.

  In this pneumatic tire 1, the deepest portion P of the recess 41 is a straight line (from the edge portion of the shoulder block 4) connecting the edge portion of the shoulder block 4 and the tire rotation axis in a cross-sectional view in the tire meridian direction. A straight line drawn in the height direction of the shoulder block 4) is located on the inner side of the shoulder block 4 (see FIG. 3). In other words, in the plan view of the tread portion, the deepest portion P of the recess 41 is configured to be located inside the circumferential width of the shoulder block 4 (inside the end of the surface) (see FIG. 2). Thereby, there exists an advantage by which generation | occurrence | production of the crack at the time of driving | running | working is suppressed effectively.

  Moreover, in this pneumatic tire 1, the distance D2 from the surface of the shoulder block 4 to the deepest part P of the recessed part 41 is 50 [%]-70 [%] of the groove depth D in the cross-sectional view in the tire meridian direction. It is preferable that it exists in the range. Thereby, there exists an advantage which a fall limit performance improves more effectively.

  Moreover, in this pneumatic tire 1, the recessed part 41 is formed so that it may begin to dent from the edge part of the shoulder block 4 in the cross-sectional view of a tire meridian direction (refer FIG. 3). Such a configuration is preferable because the rigidity of the shoulder block outside the ground contact end can be effectively reduced. However, the present invention is not limited to this, and the concave portion 41 may begin to be depressed starting from the position of the distance D1 in the groove depth direction from the upper portion of the tread portion (the edge portion of the shoulder block 4) (see FIG. 6). In such a configuration, the edge portion of the shoulder block 4 is reinforced by the distance D1, so that there is an advantage that damage near the surface (tread surface or groove wall surface) of the tread portion is effectively suppressed. The distance D1 is preferably in the range of 20% or more with respect to the groove depth D. Thereby, since sufficient distance D1 is ensured, there exists an advantage by which the damage of the edge part of the shoulder block 4 at the time of vehicle travel is suppressed more effectively. The distance D1 is preferably within a range of 30% or less with respect to the groove depth D. Thereby, there exists an advantage which block rigidity is reduced suitably and a fall limit performance improves.

  Moreover, in this pneumatic tire 1, the recessed part 41 has a substantially U-shaped cross-sectional shape in a cross-sectional view in the tire meridian direction (see FIG. 3). However, the present invention is not limited to this, and the recess 41 may have a substantially arc shape, a corrugated shape, or other shapes.

  In the pneumatic tire 1, the base portion B of the shoulder block 4 (the intersection of the groove wall surface and the groove bottom surface in a cross-sectional view in the tire meridian direction) is defined by a straight line l connecting the edge portion of the shoulder block 4 and the tire rotation axis. Is also located on the outer side (lateral groove 3 side) of the shoulder block 4 (see FIG. 3). In such a configuration, the cross-sectional area of the base portion of the shoulder block 4 is larger than the configuration in which the base B is located inside the shoulder block 4 rather than the straight line l. Thereby, since the rigidity of the shoulder block 4 is ensured suitably, there exists an advantage by which generation | occurrence | production of the crack of the shoulder block 4 at the time of driving | running | working, the stone biting in the horizontal groove 3, etc. is suppressed effectively.

  Further, in this pneumatic tire 1, when a straight line l connecting the edge portion of the shoulder block 4 and the tire rotation axis is drawn in the depth of the concave portion 41 (in the sectional view in the tire meridian direction), the straight line l and the concave portion 41 (the distance from the deepest portion P of the recess 41) W1 is preferably in the range of 15% or more of the width (tire circumferential width) W between the design ends of the shoulder block 4 (see FIG. 3). Thereby, there exists an advantage which block rigidity is reduced suitably and a fall limit performance improves. Moreover, it is preferable that the depth W1 of the recessed part 41 exists in the range of 25 [%] or less of the width W between design ends. Thereby, since buckling of the shoulder block 4 due to a load during traveling is suppressed, there is an advantage that generation of cracks is prevented.

  Moreover, in this pneumatic tire 1, the recessed part 41 is each formed in the both groove | channel wall surface concerning the horizontal groove 3 side of the shoulder block 4 by sectional view of the tire meridian direction, and these recessed parts 41 are mutually symmetrical. (See FIG. 3). Such a configuration is preferable in that the wear resistance of the shoulder block 4 is improved because the rigidity of the shoulder block 4 in the tire circumferential direction is balanced. However, the present invention is not limited to this. For example, in the pneumatic tire 1 having a directional tread pattern, the concave portions 41 and 41 of both groove wall surfaces may be formed asymmetrically with respect to the shoulder block 4 (not shown).

[performance test]
FIG. 7 is a chart showing the results of the performance test of the pneumatic tire according to the present invention. In this performance test, each pneumatic tire 1 having a tire size of 256 / 65R17 is assembled on a rim of 17 × 71 / 2JJ, loaded with an internal pressure of 200 [kPa], and mounted on a four-wheel drive test vehicle. And a predetermined test is performed about a fall limit performance, handling, uneven wear resistance, etc., and the performance of each pneumatic tire is evaluated. In addition, the evaluation shown in FIG. 7 is more preferable as the index is larger with a conventional pneumatic tire as a reference (100). Further, if the index increases by 5 or more, it is judged that a beneficial effect is obtained.

  Here, in the fall limit performance test, a load of 4.9 [kN] is applied to the pneumatic tire 1 on the drum testing machine, and the cornering force applied to the pneumatic tire 1 under running conditions is measured. Evaluation is performed. Also, in the operability test, lane change performance and cornering performance are comprehensively evaluated by running a test vehicle on a test course and performing a feeling evaluation by a test driver. Further, in the uneven wear resistance test, the test vehicle traveled on a 8000 [km] road (mountain road 59 [%], general road 17 [%], highway 24 [%]) and then a pneumatic tire. The groove depth D of 1 is measured, the wear life is calculated and evaluated.

  Further, in the evaluation of occurrence of cracks and breakage (breakage of the upper part of the lateral groove wall surface), a round course of 3 [km] having a point A and a point B installed at intervals of 1500 [m] is provided. Then, the test vehicle accelerates from 40 [km / h] to 100 [km / h] in the section of 500 [m] from the point A, and the next section of 1000 [m] is 100 [km / h]. ] And decelerate from 100 [km / h] to 40 [km / h] in the section of 500 [m] from the point B, and the next section of 1000 [m] to 40 [km / h] ] And run. Then, after the test vehicle has made 20 laps, the presence or absence of cracks and breakage of the pneumatic tire 1 is investigated and evaluated.

  As the test results show, the pneumatic tires 1 according to the inventive examples 1 to 4 have improved overturning limit performance as compared with the conventional pneumatic tires (conventional examples 1 and 2). In addition, no reduction in handling and uneven wear resistance was observed, and no cracks or breakage occurred.

  Further, in the pneumatic tire 1 of Invention Examples 1 to 4 and the pneumatic tire of Comparative Example 1, the shoulder block 4 has a base B which is more than the straight line l connecting the edge of the shoulder block 4 and the tire rotation axis. 4 is different depending on whether it is located outside of 4. As the test results show, the pneumatic tires 1 of Invention Examples 1 to 4 are superior to the pneumatic tire of Comparative Example 1 in that cracks are less likely to occur.

  Further, in the pneumatic tire 1 of Invention Examples 1 to 4 and the pneumatic tires of Comparative Examples 2 and 3, the depth W1 of the recess 41 is 15 [%] to 25 [%] of the circumferential width W of the shoulder block 4. ] In terms of whether they are within the range. As the test results show, the pneumatic tires 1 of the inventive examples 1 to 4 are sufficiently superior in fall limit performance than the pneumatic tire of the comparative example 2. In addition, the pneumatic tires 1 of Invention Examples 1 to 4 are superior to the pneumatic tire of Comparative Example 3 in that cracks are less likely to occur.

  Further, in the pneumatic tire 1 of Invention Examples 1 to 4 and the pneumatic tires of Comparative Examples 4 and 5, the recess start position of the recess 41 (distance D1 in the groove depth direction from the upper part of the tread portion) is the groove depth. It differs depending on whether it is within the range of 20% to 30% with respect to the thickness D. As the test results show, the pneumatic tires 1 of the inventive examples 1 to 4 are superior to the pneumatic tire of the comparative example 4 in that the upper part is less likely to break, and moreover than the pneumatic tire of the comparative example 5. The fall limit performance is excellent enough.

  Further, in the pneumatic tires 1 of the inventive examples 1 to 4 and the pneumatic tires of the comparative examples 6 and 7, the distance D2 from the surface of the shoulder block 4 to the deepest portion P of the recess 41 is 50 of the groove depth D. It is different in whether it is in the range of [%] to 70 [%]. As the test results show, the pneumatic tires 1 of Invention Examples 1 to 4 are sufficiently superior in fall limit performance than the pneumatic tires of Comparative Examples 6 and 7.

  8-14 is explanatory drawing which shows the modification of the pneumatic tire described in FIG. FIG. 14 is a chart showing the results of the performance test of the pneumatic tire according to the present invention. In these drawings, the same components as those of the pneumatic tire 1 of the first embodiment are denoted by the same reference numerals, and description thereof is omitted. 8, 10 and 12 show plan views of the shoulder portion, and FIGS. 9, 11 and 13 show sectional views of the shoulder portion in the tire axial direction.

[Modification 1]
In the pneumatic tire 1 described above, the stone ejector 5 is preferably formed along the recess 41 in the lateral groove 3 that defines the shoulder block 4 (see FIGS. 8 and 9). For example, in a configuration in which the concave portion 41 is formed on the outer side in the tire width direction from the ground contact end of the shoulder block 4 in a plan view of the tread portion, the stone ejector 5 is formed in the same range along the concave portion 41.

  In such a configuration, the stone ejector 5 suppresses the intrusion of foreign matters such as stones into the lateral grooves 3 when the tire rolls. Thereby, since the damage of the horizontal groove 3 by a foreign material is reduced, there exists an advantage which the durable performance of a tire improves. In particular, in such a configuration, there is an advantage that biting of foreign matter in the lateral groove 3 is remarkably suppressed in the formation range of the recess 41 in the shoulder block 4.

  The stone ejector 5 does not have to be disposed in the entire formation range of the recess 41, and may be disposed only in a part of the range (not shown). Further, the stone ejector 5 may be disposed regardless of the formation range of the recess 41 (not shown).

  Here, the stone ejector 5 is preferably composed of, for example, a protruding portion 5 that protrudes outward in the tire radial direction from the groove bottom of the lateral groove 3. In such a configuration, the intrusion of foreign matter is effectively suppressed by the protrusion 5 that is easy to mold. Thereby, there exists an advantage which the durable performance of a tire improves effectively with a simple structure.

  For example, at least one projection 5 is formed for each lateral groove 3 and has a longitudinal shape in a plan view of the shoulder portion and is disposed in the groove length direction along the center line of the lateral groove 3. (See FIG. 8). Further, the longitudinal shape of the protruding portion 5 may have any shape such as a rectangular shape, a zigzag shape, and a corrugated shape.

  Moreover, it is preferable that the projection part 5 has a substantially trapezoidal cross-sectional shape in a cross-sectional view in the tire axial direction (a direction perpendicular to the groove length direction) (see FIG. 9). Thereby, there exists an advantage by which the intensity | strength of the projection part 5 with respect to a foreign material is ensured. However, the present invention is not limited thereto, and the protrusion 5 may have a cross-sectional shape such as a substantially triangular shape.

  Further, the protrusion 5 preferably has a height H of 0.30 ≦ H / D with respect to the groove depth D of the main groove 3 (see FIG. 9). Thereby, since the penetration | invasion of the foreign material to the horizontal groove 3 is reduced effectively, there exists an advantage which the durability performance of a tire improves more effectively. Note that the height H of the protrusion 5 is a distance from the groove bottom to the top of the protrusion 5.

  Moreover, it is preferable that the protrusion part 5 has the relationship of H / D <= 0.5 with respect to the groove depth D of the horizontal groove 3 (refer FIG. 9). Thereby, there exists an advantage by which the drainage performance of the horizontal groove 3 is ensured.

  The stone ejector 5 may be formed by a plurality of protrusions (not shown) formed at the groove bottom of the lateral groove 3 and arranged along the groove length direction. Even with such a configuration, there is an advantage that the intrusion of foreign matter is effectively suppressed and the durability performance of the tire is improved. As the stone ejector 5, a well-known one can be adopted within a range obvious to those skilled in the art.

[Modification 2]
In the pneumatic tire 1 described above, it is preferable that a sipe 42 is formed on the wall surface of the shoulder block 4 on the side of the lateral groove 3 from the recess 41 to the edge (tread) (see FIGS. 10 and 11). In other words, it is preferable that a sipe 42 is formed on the groove wall surface of the lateral groove 3 that defines the shoulder block 4 from the concave portion 41 to the edge portion of the shoulder block 4. In such a configuration, when the tire rolls, the lateral groove 3 can be largely opened and closed by opening and closing the sipe 42, so that foreign matter that has entered the lateral groove 3 is easily discharged to the outside. Thereby, there exists an advantage by which the biting of the foreign material in the horizontal groove 3 is suppressed.

  At least one sipe 42 is formed for one recess 41. For example, in the example shown in FIG. 10, three sipes 42 are formed for one recess 41. Further, these sipes 42 are arranged along the concave portions 41 with a predetermined interval therebetween. In addition, a pair of sipes 42 and 42 are disposed so as to face each other between the opposing groove walls. In such a configuration, compared to a configuration in which the plurality of sipes 42 are alternately arranged along the groove length direction between the opposing groove walls, the foreign matter that has entered the lateral groove 3 is more easily discharged to the outside. Thereby, there exists an advantage by which the damage of the horizontal groove 3 by a foreign material is reduced effectively.

  Further, the sipe 42 preferably has a relationship in which the width Ws of the tread surface (tread surface) of the shoulder block 4 is 0.50 ≦ Ws / W1 ≦ 1.00 with respect to the depth W1 of the recess 41. That is, the sipe 42 is formed from the recess 41 of the shoulder block 4 to the tread surface as described above, and the depth (the amount of cut from the groove wall surface of the lateral groove 3 to the inside of the shoulder block 3) is the depth of the recess 41. The height W1 is optimized as described above. For example, the sipe 42 has a cross-sectional shape including a line connecting the inner end point Q of the sipe on the tread surface of the shoulder block 4 and the deepest portion P of the recess 41. The width Ws of the sipe 42 refers to the sipe length in the tire width direction on the tread surface of the shoulder block 4.

  With such a configuration, there is an advantage that foreign matter that has entered the horizontal groove 3 is more easily discharged to the outside, and damage to the horizontal groove 3 due to the foreign matter is effectively reduced. Specifically, when Ws / W1 <0.50, the effect of discharging foreign matter is not sufficiently obtained, and when 1.00 <Ws / W1, damage to the tread of the shoulder block 4 may occur.

  Moreover, it is preferable that said sipe 42 is used together with said stove ejector 5 (refer FIG. 12 and FIG. 13). Thereby, there exists an advantage by which the damage of the horizontal groove 3 by the biting of a foreign material is suppressed more effectively.

[performance test]
In Example 3, with respect to a plurality of types of pneumatic tires having different conditions, (1) tipping limit performance, (2) resistance to foreign matter biting (number of stone bites), and (3) cracks and breakage (of lateral groove wall surfaces) A performance test relating to evaluation (endurance performance) of occurrence of damage on the upper part was performed (see FIG. 14). In this performance test, a pneumatic tire 1 having a tire size of 256 / 65R17 is assembled on a rim of 17 × 71 / 2JJ, loaded with an internal pressure of 200 [kPa], and mounted on a four-wheel drive test vehicle.

  (1) The performance test relating to the evaluation of the fall limit performance and crack and (3) occurrence of breakage is performed by the same test method as in Example 2 described above.

  (2) In the performance test related to the resistance to foreign matter biting, the number of stone bites in the lateral groove of the shoulder block when the test vehicle travels a distance of 1 km at a speed of 40 km / h on a road surface covered with gravel. Is measured. The smaller the number of stone bites, the better.

  The pneumatic tire 1 of Invention Example 5 has a configuration in which stone ejectors (protrusions) 5 are formed in the lateral grooves 3 of the shoulder block 3 in the pneumatic tire 1 of Invention Example 1 (see FIGS. 8 and 9). . The pneumatic tire 1 of the invention example 5 and the invention example 7 has the structure by which the sipe 5 was formed in the edge part of the shoulder block 3 in the pneumatic tire 1 of the invention example 5 (refer FIG. 12 and FIG. 13).

  As shown in the test results, it can be seen that the pneumatic tires 1 of Invention Examples 5 to 7 all have improved fall limit performance as compared with the pneumatic tire of Conventional Example 1 (see FIG. 7). In addition, the pneumatic tires 1 of the inventive examples 6 and 7 having the sipes 42 have improved resistance to foreign matter biting compared with the pneumatic tire 1 of the inventive example 5 (the number of stone bites is reduced). I understand).

  Further, when Invention Example 6 and Comparative Example 8 are compared, it can be seen that the foreign object biting performance is improved by optimizing the height H of the protrusion 5. Further, when Invention Example 6, Invention Example 7, Comparative Example 9 and Comparative Example 10 are compared, the cutting depth of the sipe 42 (ratio between the width Ws of the sipe 42 and the depth W1 of the recess 42 on the tread surface) is optimized. As a result, the foreign object biting performance is improved and the occurrence of racks and breakage is reduced.

  As described above, the pneumatic tire according to the present invention is useful in that the fall limit performance can be improved while maintaining the maneuverability and wear resistance.

It is a top view which shows the tread part of the pneumatic tire concerning Example 1 of this invention. It is a top view which shows the shoulder block of the pneumatic tire described in FIG. It is sectional drawing of the tire meridian direction which shows the shoulder block of the pneumatic tire described in FIG. It is explanatory drawing which shows the modification of the pneumatic tire described in FIG. It is explanatory drawing which shows the modification of the pneumatic tire described in FIG. It is explanatory drawing which shows the modification of the pneumatic tire described in FIG. It is a graph which shows the result of the performance test of the pneumatic tire concerning this invention. It is explanatory drawing which shows the modification of the pneumatic tire described in FIG. It is explanatory drawing which shows the modification of the pneumatic tire described in FIG. It is explanatory drawing which shows the modification of the pneumatic tire described in FIG. It is explanatory drawing which shows the modification of the pneumatic tire described in FIG. It is explanatory drawing which shows the modification of the pneumatic tire described in FIG. It is explanatory drawing which shows the modification of the pneumatic tire described in FIG. It is a graph which shows the result of the performance test of the pneumatic tire concerning this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Vertical groove 3 Horizontal groove 4 Shoulder block 41 Concave part 42 Sipe 5 Stone ejector (projection part)

Claims (16)

In a pneumatic tire having a plurality of vertical grooves extending in the tire circumferential direction and lateral grooves extending in the tire width direction in the tread portion, and a shoulder block defined by these grooves in the shoulder portion,
A pneumatic tire characterized by having a recess on the lateral groove side of the shoulder block on the outer side in the tire width direction from the ground contact end of the tread portion.   The pneumatic tire according to claim 1, wherein the concave portion is formed only in a range outside the tread portion on the outer side in the tire width direction from the ground contact end.   3. The pneumatic tire according to claim 1, wherein a depth of the concave portion is formed so as to become deeper from a contact end of the tread portion toward an outer side in the tire width direction.   The pneumatic tire according to any one of claims 1 to 3, wherein the concave shape of the concave portion has a wave shape or a zigzag shape in a plan view of the tread portion.   The cross-sectional view in the tire meridian direction is characterized in that the deepest portion of the recess is located inside the shoulder block with respect to a straight line connecting an edge portion of the shoulder block and a tire rotation axis. Item 5. The pneumatic tire according to any one of Items 1 to 4.   The distance from the surface of the shoulder block to the deepest portion of the concave portion in a cross-sectional view in the tire meridian direction is in the range of 50 [%] to 70 [%] of the groove depth. The pneumatic tire according to any one of 5.   7. The concave portion is formed so as to start to be depressed starting from a position at a predetermined distance in the groove depth direction from the edge portion of the shoulder block in a sectional view in the tire radial direction. A pneumatic tire according to any one of the above.   The pneumatic tire according to claim 7, wherein a distance at which the concave portion starts to be depressed is within a range of 20% to 30% with respect to the groove depth. When the intersection of the groove wall surface of the shoulder block and the groove bottom surface of the lateral groove is the base of the shoulder block in a cross-sectional view in the tire meridian direction,
The pneumatic tire according to any one of claims 1 to 8, wherein the base portion is located on the side of the lateral groove with respect to a straight line connecting an edge portion of the shoulder block and a tire rotation axis. When a straight line connecting the edge portion of the shoulder block and the tire rotation axis is drawn in a cross-sectional view in the tire meridian direction, the distance between the straight line and the deepest portion of the recess is the depth of the recess. In addition,
The depth of the said recessed part exists in the range of 15 [%] or more and 25 [%] or less of the tire circumferential direction width of the said shoulder block, The pneumatic as described in any one of Claims 1-9 characterized by the above-mentioned. tire.   The recesses are formed in both groove wall surfaces on the lateral groove side of the shoulder block in a cross-sectional view in the tire meridian direction, and these recesses are formed symmetrically with each other. The pneumatic tire according to any one of claims 1 to 10.   The pneumatic tire according to any one of claims 1 to 11, wherein a stone ejector is formed along the concave portion in a lateral groove that defines the shoulder block.   The pneumatic tire according to claim 12, wherein the stone ejector includes a protrusion that protrudes outward in the tire radial direction from a groove bottom of the lateral groove.   The pneumatic tire according to claim 13, wherein the height H of the protrusion has a relationship of 0.30 ≦ H / D with respect to the groove depth D of the main groove.   The pneumatic tire according to any one of claims 1 to 14, wherein a sipe is formed on a wall surface on the lateral groove side of the shoulder block from the concave portion to an edge portion of the shoulder block.   The pneumatic tire according to claim 15, wherein a width Ws of the sipe on the tread surface of the shoulder block has a relationship of 0.50 ≦ Ws / W1 ≦ 1.00 with respect to a depth W1 of the recess.

Images