Pneumatic tires

Abstract

To provide a pneumatic tire which improves a traction performance on a soft road.SOLUTION: A pneumatic tire 1 has a pair of side wall parts 3. An outer surface in a tire axial direction of at least one side wall part 3 includes a base surface 10, at least one first projection part 11 projecting to an outside in a tire axial direction from the base surface 10, and a recess 13 extending in the base surface 10 so that the first projection part 11 is separated from the base surface 10. The first projection part 11 includes a first surface 16 having a first projection amount h1 to the base surface 10, and a second surface 17 having a second projection amount h2 different from the first projection amount h1 to the base surface 10, and the surfaces are connected to each other to form a step.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a pneumatic tire. [Background technology]

[0002] For example, Patent Document 1 listed below proposes a tire that can achieve a higher level of compatibility between performance on icy road surfaces and performance on dry road surfaces, particularly wear resistance, by defining pattern elements of the tread portion. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-045099 A Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, there has been a demand for improved driving performance on various road surfaces in pneumatic tires designed for driving on rough terrain, and in particular for improved traction performance on soft roads such as snowy roads and sandy ground.

[0005] The inventors focused on providing a protrusion on the sidewall portion and improved the shape of the protrusion, thereby completing the present invention.

[0006] The present invention has been devised in view of the above circumstances, and has as its main object to provide a pneumatic tire with improved traction performance on soft roads. [Means for solving the problem]

[0007] The present invention is a pneumatic tire having a pair of sidewall portions, wherein the axial outer surface of at least one of the pair of sidewall portions includes a base surface, at least one first protrusion portion protruding axially outwardly beyond the base surface, and a recess portion extending through the base surface to separate the first protrusion portion from the base surface, and the first protrusion portion includes a first surface having a first protrusion amount relative to the base surface and a second surface having a second protrusion amount different from the first protrusion amount relative to the base surface, and these are connected to form a step.

[0008] In the pneumatic tire of the present invention, it is preferable that, in the first protruding portion, the first surface and the second surface are aligned in the tire radial direction.

[0009] In the pneumatic tire of the present invention, it is preferable that the second protrusion amount is smaller than the first protrusion amount, and the second surface is located outside the first surface in the tire radial direction.

[0010] In the pneumatic tire of the present invention, it is preferable that a cross-sectional area of ​​the first protruding portion along the base surface increases toward a bottom side of the recess.

[0011] In the pneumatic tire of the present invention, it is desirable that at least one of the sidewall portions has a plurality of the first protruding portions, and that second protruding portions protruding axially outward from the base surface are arranged between the first protruding portions.

[0012] In the pneumatic tire of the present invention, it is preferable that the second protruding portion protrudes directly from the base surface outward in the axial direction of the tire.

[0013] In the pneumatic tire of the present invention, it is preferable that the amount of protrusion of the second protruding portion from the base surface decreases toward the inside in the tire radial direction.

[0014] In the pneumatic tire of the present invention, it is preferable that a maximum protrusion amount of the second protrusion portion from the base surface is smaller than a maximum protrusion amount of the first protrusion portion from the base surface.

[0015] In the pneumatic tire of the present invention, it is preferable that a maximum length in the tire radial direction of the second protruding portion is smaller than a maximum length in the tire radial direction of the first protruding portion.

[0016] In the pneumatic tire of the present invention, it is preferable that a maximum length in the tire circumferential direction of the second protrusion be smaller than a maximum length in the tire circumferential direction of the first protrusion.

[0017] In the pneumatic tire of the present invention, it is preferable that the second protruding portion includes a top surface facing axially outward of the tire, and that the top surface is provided with a recessed groove.

[0018] In the pneumatic tire of the present invention, it is preferable that the recessed groove extends in the tire radial direction on the top surface of the second protruding portion.

[0019] In the pneumatic tire of the present invention, it is preferable that a groove portion is provided on a bottom surface of the recess, the groove portion extending along the shape of an opening of the recess.

[0020] In the pneumatic tire of the present invention, it is preferable that the at least one sidewall portion is provided with a circumferential groove extending in the circumferential direction of the tire, radially outward of the first protruding portion.

[0021] In the pneumatic tire of the present invention, the circumferential groove includes an edge continuing to the base surface and a bottom that is the deepest position from the base surface, and in a cross section of the circumferential groove, it is desirable that an angle of a normal line passing through the bottom relative to the tire axial direction is smaller than an angle of a normal line passing through the edge relative to the tire axial direction. Effect of the Invention

[0022] By adopting the above-mentioned configuration, the pneumatic tire of the present invention can improve traction on soft roads. [Brief description of the drawings]

[0023] [Figure 1] 1 is a cross-sectional view of one embodiment of a tire of the present invention. [Diagram 2] FIG. 2 is an enlarged perspective view of a sidewall portion of FIG. [Diagram 3] FIG. 3 is an end view taken along line AA in FIG. 2. [Figure 4] FIG. 11 is an enlarged perspective view of a sidewall portion according to another embodiment of the present invention. [Diagram 5] FIG. 5 is an end view taken along line BB in FIG. 4. [Figure 6] FIG. 11 is an enlarged perspective view of a sidewall portion according to still another embodiment of the present invention. [Figure 7] FIG. 7 is an end view taken along line CC in FIG. 6. [Figure 8] FIG. 11 is an enlarged perspective view of a sidewall portion according to still another embodiment of the present invention. [Figure 9] 9 is an enlarged plan view of the top surface of the first protrusion and the opening surface of the recess in FIG. 8. FIG. [Figure 10] FIG. 10 is an end view taken along line DD in FIG. [Figure 11] 9 is an end view taken along line EE of FIG. 8. [Figure 12] FIG. 2 is an enlarged perspective view of a sidewall portion of a tire of a comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a cross-sectional view including the tire rotation axis of a pneumatic tire 1 (hereinafter sometimes simply referred to as "tire") of this embodiment in a normal state. Fig. 1 is a diagram showing a tire cross section on one side in the tire axial direction of the tire equator C when the tire 1 extending in an annular shape is cut by a virtual plane perpendicular to the tire circumferential direction. The tire 1 of this embodiment is suitably used, for example, for RVs or SUVs compatible with off-road driving.

[0025] In the case of a pneumatic tire for which various standards are established, the normal state refers to a state in which the tire is mounted on a normal rim, inflated to a normal internal pressure, and no load is applied. In the case of a tire for which various standards are not established, the normal state refers to a standard use state according to the intended use of the tire, and a state in which no load is applied. In this specification, unless otherwise specified, the dimensions of each part of the tire are values ​​measured in the normal state. Note that each configuration described in this specification is assumed to allow for normal errors contained in rubber molded products.

[0026] A "genuine rim" is a rim that is defined for each tire by the standard system that includes the standard on which the tire is based. For example, in the case of JATMA, it is called a "standard rim," in the case of TRA, it is called a "Design Rim," and in the case of ETRTO, it is called a "Measuring Rim."

[0027] "Normal internal pressure" is the air pressure set for each tire by each standard in the standard system on which the tire is based. In the case of JATMA, it is the "maximum air pressure." In the case of TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES." In the case of ETRTO, it is the "INFLATION PRESSURE."

[0028] As shown in Fig. 1, a tire 1 of this embodiment includes a tread portion 2, a pair of sidewall portions 3, a pair of bead portions 4, and a carcass 6. A bead core 5 is embedded in the bead portion 4. The carcass 6 straddles the pair of bead portions 4 in a toroidal shape. Note that half of the tread portion 2, one of the pair of sidewall portions 3, and one of the pair of bead portions 4 are omitted in Fig. 1.

[0029] The carcass 6 includes a carcass ply 6A having a carcass cord extending from one bead portion 4 through the tread portion 2 to the other bead portion (not shown). It goes without saying that the carcass cord passes through the sidewall portion 3.

[0030] The carcass ply 6A in this embodiment is formed by, for example, covering parallel carcass cords with a topping rubber. The carcass 6 in this embodiment is formed of one carcass ply 6A, but may be formed of a plurality of carcass plies 6A.

[0031] The carcass ply 6A includes, for example, a main body portion 6a and a turned-up portion 6b. The main body portion 6a extends, for example, between two bead portions 4. As a result, the main body portion 6a extends from at least the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4. The turned-up portion 6b is, for example, continuous with the main body portion 6a and turned up around the bead core 5 from the inner side in the axial direction of the tire to the outer side. A bead apex 8 extending from the bead core 5 to the outer side in the radial direction of the tire is disposed between the main body portion 6a and the turned-up portion 6b, and the bead portion 4 is appropriately reinforced.

[0032] The carcass cords are made of organic fibers such as aramid, rayon, etc. The carcass cords are desirably arranged at an angle of 70 to 90° with respect to the tire equator C.

[0033] As a preferred embodiment, a belt layer 7 is provided on the radially outer side of the carcass 6 of the present embodiment. The belt layer 7 is, for example, composed of two belt plies 7A and 7B overlapped in the radial direction of the tire. Each of the belt plies 7A and 7B is composed of a belt cord covered with a topping rubber, and is overlapped on the inner and outer sides in the radial direction of the tire so that the belt cords cross each other.

[0034] Fig. 2 shows an enlarged perspective view of the sidewall portion 3. As shown in Fig. 2, an outer surface in the tire axial direction of at least one of the pair of sidewall portions 3 includes a base surface 10, at least one first protruding portion 11, and a recessed portion 13. The first protruding portion 11 protrudes outward in the tire axial direction beyond the base surface 10. The recessed portion extends on the base surface 10 so as to separate the first protruding portion 11 from the base surface 10. In this embodiment, a plurality of first protruding portions 11 are provided in the tire circumferential direction.

[0035] In this embodiment, the region between the maximum width position of the tire 1 and the tread end Te is included in the outer surface of the sidewall portion 3. The base surface 10 constitutes a major portion of the outer surface of the sidewall portion 3, and smoothly connects to the outer surface of the tread portion 2 and the outer surface of the bead portion 4. The tread end Te is the axially outermost contact point when the tire 1 in the normal state is loaded with a normal load and contacts a flat surface with a camber angle of 0°.

[0036] In the case of a pneumatic tire for which various standards are established, the "normal load" is the load that each standard specifies for each tire in the standard system including the standard on which the tire is based, and is the "maximum load capacity" for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "LOAD CAPACITY" for ETRTO. In addition, in the case of a tire for which various standards are not established, the "normal load" refers to the load acting on one tire in the standard use condition of the tire. The "standard use condition" refers to a state in which the tire is mounted on a standard vehicle corresponding to the intended use of the tire, and the vehicle is stationary on a flat road surface in a drivable state.

[0037] Fig. 3 shows an end view taken along line AA in Fig. 2. As shown in Fig. 3, the first protruding portion 11 includes a first surface 16 having a first protruding amount h1 relative to the base surface 10, and a second surface 17 having a second protruding amount h2 different from the first protruding amount h1 relative to the base surface 10, which are connected to form a step 18. The tire 1 of the present invention employs the above-mentioned configuration, thereby improving traction on soft roads. The following mechanism is believed to be the reason for this.

[0038] Generally, when a tire runs on soft roads such as snowy roads or sandy ground, not only the tread portion 2 but also the outer surface of the sidewall portion 3 comes into contact with the road surface. Therefore, on soft roads, the first protrusions 11 provide a reaction force in the circumferential direction of the tire as the tire rotates, thereby improving traction performance.

[0039] In the present invention, the first protruding portion 11 is easily deformed in the tire circumferential direction from its base portion due to the recess 13. Therefore, the first protruding portion 11 can deform appropriately and exhibit great traction even on a soft road.

[0040] Furthermore, the step 18 in the first protruding portion 11 increases the surface area of ​​the top face 15. This increases the contact area between the top face 15 and the road surface, further improving traction performance on soft roads. It is presumed that this mechanism allows the tire 1 of the present invention to improve traction on soft roads.

[0041] A more detailed configuration of this embodiment will be described below. The configuration described below shows a specific embodiment of this embodiment. Therefore, it goes without saying that the present invention can achieve the above-mentioned effects even if it does not have the configuration described below. In addition, even if any one of the configurations described below is applied alone to the tire of the present invention having the above-mentioned characteristics, an improvement in performance according to each configuration can be expected. Furthermore, when some of the configurations described below are applied in combination, a composite improvement in performance according to each configuration can be expected.

[0042] 1, the first protruding portion 11 is preferably provided at a position that comes into contact with the road surface when the tire 1 runs on a soft road. For this reason, the first protruding portion 11 is provided in the sidewall portion 3, radially outward of the maximum width position of the tire 1. In a more preferable embodiment, the distance in the tire radial direction from the tread edge Te to the radially outer end of the first protruding portion 11 is set to 50 mm or less.

[0043] 2, the top surface 15 of the first protrusion 11 is, for example, rectangular in plan view, preferably rectangular in shape elongated in the tire radial direction. However, the top surface 15 is not limited to this shape, and various shapes such as a polygonal shape and an elliptical shape may be adopted.

[0044] The step 18 extends, for example, in the tire circumferential direction on the top surface 15 of the first protruding portion 11. The step in this embodiment extends parallel to the tire circumferential direction and completely traverses the top surface 15.

[0045] As shown in Fig. 3, in the first protruding portion 11, the first surface 16 and the second surface 17 are aligned in the tire radial direction. The second protruding amount h2 is smaller than the first protruding amount h1, and the second surface 17 is located outside the first surface 16 in the tire radial direction. Since a large load acts on the first protruding portion 11 in the region on the outer side in the tire radial direction, the load acting on the first protruding portion 11 can be dispersed by relatively reducing the protruding amount of this region. Therefore, with the above-mentioned configuration, excessive deformation of the first protruding portion 11 when the first protruding portion 11 comes into contact with a soft road can be suppressed, and the reaction force in the tire circumferential direction can be increased.

[0046] A length L1 in the tire radial direction of the first surface 16 is smaller than a length L2 in the tire radial direction of the second surface 17. Specifically, the length L1 of the first surface 16 is 40% to 60% of the length L2 of the second surface 17. Such first surface 16 and second surface 17 can improve traction performance while maintaining the durability of the first protrusion 11.

[0047] The first protrusion amount h1 from the base surface 10 is, for example, 2 to 6 mm, and preferably 3 to 5 mm. The second protrusion amount h2 from the base surface 10 is, for example, 1 to 5 mm, and preferably 2 to 4 mm. The size h3 of the step 18 is, for example, 1 to 4 mm, and preferably 2 to 3 mm.

[0048] It is desirable that the area of ​​the cross section of the first protrusion 11 along the base surface 10 increases toward the bottom side of the recess 13. The area of ​​the top surface 15 of the first protrusion 11 in a plan view (the sum of the areas of the first surface 16 and the second surface 17) is 65% to 95% of the area of ​​the cross section of the first protrusion 11 at the bottom of the recess 13. This increases the rigidity of the base portion of the first protrusion 11, improving traction performance. In addition, such a first protrusion 11 can also prevent snow or sand from being retained in the recess 13.

[0049] 2, the recess 13 is desirably, for example, in a loop shape surrounding the first protruding portion 11. This ensures a large area of ​​the side surface of the first protruding portion 11 facing the tire circumferential direction, and further improves traction performance.

[0050] 3, the opening width L3 of the recess 13 along the base surface 10 is, for example, 0.5 to 3.0 mm. The depth d1 of the recess 13 is, for example, 1.0 to 4.0 mm. However, the recess 13 of the present invention is not limited to this embodiment.

[0051] Hereinafter, other embodiments of the present invention will be described. In the drawings showing the other embodiments, the elements already described are given the same reference numerals as those described above, and the above-described configurations can be applied.

[0052] 4 shows an enlarged perspective view of a sidewall portion 3 according to another embodiment of the present invention. The sidewall portion 3 according to this embodiment includes a plurality of first protruding portions 11, and second protruding portions 12 that protrude axially outward from the base surface 10 are disposed between the first protruding portions 11. In this embodiment, the first protruding portions 11 and the second protruding portions 12 are expected to further improve traction performance.

[0053] The second protruding portion 12 is configured to have a different shape from the first protruding portion 11. Therefore, the first protruding portion 11 and the second protruding portion 12 are deformed in different manners, and snow and mud on the sidewall portion 3 can be prevented from adhering and being retained.

[0054] The second protruding portion 12 protrudes, for example, directly outward in the tire axial direction from the base surface 10. In other words, the side surface of the second protruding portion 12 is continuous with the base surface 10. Such a second protruding portion 12 has high rigidity and is useful for improving traction not only on soft roads but also on rocky roads covered with relatively large stones.

[0055] In this embodiment, the maximum length of the second protrusion 12 in the tire radial direction is smaller than the maximum length of the first protrusion 11 in the tire radial direction. Also, the maximum length of the second protrusion 12 in the tire circumferential direction is smaller than the maximum length of the first protrusion 11 in the tire circumferential direction. Furthermore, the maximum protrusion amount of the second protrusion 12 from the base surface 10 is smaller than the maximum protrusion amount of the first protrusion 11 from the base surface 10. This makes it possible to prevent mud or snow from adhering and being held between the first protrusion 11 and the second protrusion 12.

[0056] Fig. 5 shows an end view taken along line BB in Fig. 4. As shown in Fig. 5, the top surface 20 of the second protruding portion 12 has no step. The top surface 20 of the second protruding portion 12 is formed, for example, of a surface that is curved convexly toward the outside of the tire. This improves the durability of the second protruding portion 12.

[0057] The amount of protrusion of the second protrusion 12 from the base surface 10 decreases toward the inside in the tire radial direction (to the right in FIG. 5). As a result, the angle θ1 of the top surface 20 of the second protrusion 12 with respect to the base surface 10 is, for example, 10 to 45°, and preferably 15 to 25°. Such a second protrusion 12 guides snow and sand to the part of the first protrusion 11 with high rigidity. Therefore, the second protrusion 12 in combination with the above-mentioned first protrusion 11 can further improve traction performance.

[0058] The maximum protrusion amount h4 of the second protrusion 12 from the base surface 10 is smaller than the first protrusion amount h1 (shown in FIG. 3) of the first protrusion 11 from the base surface 10. The maximum protrusion amount h4 of the second protrusion 12 is, for example, 30% to 60% of the first protrusion amount h1 of the first protrusion 11. Such a second protrusion 12 can improve traction performance while maintaining durability.

[0059] In this embodiment, the second protruding portion 12 has a maximum protruding amount h4 at the outer end portion in the tire radial direction of the second protruding portion 12. The second protruding portion 12 has a minimum protruding amount h5 at the inner end portion in the tire radial direction of the second protruding portion 12. The minimum protruding amount h5 is 10% to 30% of the maximum protruding amount h4. This makes it easier for snow and sand pushed aside by the second protruding portion 12 to be guided further toward the first surface 16 of the first protruding portion 11, further improving traction performance.

[0060] Fig. 6 shows an enlarged perspective view of a sidewall portion 3 provided with a second protruding portion 12 having a shape different from that shown in Fig. 4. As shown in Fig. 6, a recessed groove 21 is provided on a top surface 20 of the second protruding portion 12 of this embodiment. This allows the second protruding portion 12 to deform appropriately in the tire circumferential direction, and further improves traction performance on soft roads.

[0061] In order to ensure the above-mentioned effects, the groove 21 extends, for example, in the tire radial direction on the top surface 20 of the second protruding portion 12. The groove 21 extends, for example, with a constant width in parallel to the tire radial direction. It is preferable that the groove 21 crosses the top surface 20 in the tire radial direction. It is also preferable that the groove 21 is provided above the center position of the top surface 20 of the second protruding portion 12 in the tire circumferential direction. The second protruding portion 12 having such a groove 21 can exhibit excellent traction performance on various road surfaces in combination with the above-mentioned first protruding portion 11.

[0062] 7 shows an end view of line CC in FIG. 6. As shown in FIG. 7, in this embodiment, the second surface 17 of the first protruding portion 11 protrudes from the top surface 20 of the second protruding portion 12. The difference h6 in the protruding amount between the second surface 17 of the first protruding portion 11 and the top surface 20 of the second protruding portion 12 is preferably 1.0 mm or more, more preferably 1.5 mm or more, and is preferably 3.0 mm or less, more preferably 2.5 mm or less. This allows the first protruding portion 11 and the second protruding portion 12 to work together to exhibit excellent traction performance.

[0063] The width W1 of the groove 21 in the tire circumferential direction is, for example, 50% or less of the length L4 in the tire circumferential direction of the top surface 20 of the second protrusion 12, and preferably 20 to 45%. The maximum depth d2 of the groove 21 is preferably smaller than the maximum depth d1 of the recess 13 adjacent to the first protrusion 11. Specifically, the depth d2 of the groove 21 is 0.5 to 2.0 mm, and preferably 1.0 to 1.5 mm. Such a groove 21 is useful for improving traction performance while maintaining the durability of the second protrusion 12.

[0064] Fig. 8 shows an enlarged perspective view of a sidewall portion 3 of still another embodiment. As shown in Fig. 8, in this embodiment, a rib 23 is provided between the first protruding portions 11 arranged in the tire circumferential direction, connecting the first protruding portions 11 and extending in the tire circumferential direction. Such a rib 23 deforms in conjunction with the first protruding portions 11, and can prevent mud and earth from being trapped around the first protruding portions 11 when traveling on soft roads.

[0065] The top surface of the rib 23 is connected to, for example, the second surface 17 of the first protruding portion 11 without any step. As a result, the protruding amount of the rib 23 from the base surface 10 is the same as the second protruding amount h2 of the second surface 17. However, this embodiment is not limited to this aspect.

[0066] The rib 23 extends, for example, parallel to the tire circumferential direction. The rib 23 crosses the recess 13 and is connected to the first protruding portion 11. As a result, the recess 13 is divided into one side and the other side in the tire radial direction by the rib 23. Such a rib 23 can reliably prevent mud or earth from being retained around the first protruding portion 11.

[0067] The width of the rib 23 in a direction perpendicular to the length direction is, for example, smaller than the length in the tire radial direction of the second surface 17. Also, the width of the rib 23 is, for example, smaller than the length in the tire radial direction of the first surface 16. Specifically, the width of the rib 23 is 0.5 to 2.0 mm.

[0068] FIG. 9 shows an enlarged plan view of the top surface 15 of the first protrusion 11 and the opening surface of the recess 13. In FIG. 9, the opening surface of the recess 13 is colored. FIG. 10 shows an end view taken along the line DD in FIG. 9. As shown in FIG. 9 and FIG. 10, a groove 25 is provided on the bottom surface of the recess 13, extending along the opening shape of the recess 13. The opening width W2 of the groove 25 is 5% to 15% of the opening width L3 of the recess 13, and preferably 7% to 12%. The depth d3 of the groove 25 is 5% to 20% of the depth d1 of the recess 13 (the depth excluding the groove 25). The recess 13 provided with such a groove 25 is easy to open, and can take in a lot of snow and sand therein.

[0069] The recess 13 in this embodiment is divided by the rib 23, for example, and includes an outer portion 31 that is radially outward of the rib 23 and an inner portion 32 that is radially inward of the rib 23. The inner portion 32 includes one circumferential portion 33 extending in the tire circumferential direction and two radial portions 34 that are continuous with both sides of the circumferential portion 33 and extend in the tire radial direction. In this embodiment, the radial portion 34 of the recess 13 is provided with a groove portion 25. On the other hand, the entire outer portion 31 and the circumferential portion 33 of the inner portion 32 are not provided with a groove portion 25. Such an arrangement of the groove portions 25 can achieve the above-mentioned effect while maintaining the durability of the first protruding portion 11.

[0070] As shown in Fig. 8, the sidewall portion 3 of this embodiment is provided with a circumferential groove 40 extending in the circumferential direction of the tire on the radially outer side of the first protruding portion 11. When traveling on a soft road, such a circumferential groove 40 works together with the first protruding portion 11 to compact mud or earth, providing a reaction force in the circumferential direction of the tire, thereby improving traction performance. In particular, in this embodiment, the combination of the circumferential groove 40 and the recessed portion 13 provided with the groove portion 25 provides excellent traction performance on muddy ground.

[0071] The opening width W3 of the circumferential groove 40 is, for example, smaller than the length of the second surface 17 of the first protrusion 11 in the tire radial direction. Also, the opening width W3 of the circumferential groove 40 is, for example, larger than the width of the rib 23. The opening width W3 of the circumferential groove 40 is, for example, 1.5 to 3.0 mm. The depth of the circumferential groove 40 is, for example, 0.5 to 2.5 mm.

[0072] FIG. 11 shows an end view of the line EE in FIG. 8. As shown in FIG. 11, the circumferential groove 40 has, for example, a semicircular cross-sectional shape. In this embodiment, the circumferential groove 40 includes an edge 41 continuing to the base surface 10 and a bottom 42 that is the deepest position from the base surface 10. In a cross section of the circumferential groove 40, an angle θ2 of a normal line 42a passing through the bottom 42 with respect to the tire axial direction is smaller than an angle θ3 of a normal line 41a passing through the edge 41 with respect to the tire axial direction. The angle θ2 is, for example, 5 to 30°, and preferably 10 to 25°. Such a circumferential groove 40 makes it easier to compact mud toward the first protruding portion 11 side, and further improves traction performance.

[0073] Although the tire according to one embodiment of the present invention has been described in detail above, the present invention is not limited to the above specific embodiment and can be modified and carried out in various aspects. EXAMPLES

[0074] A pneumatic tire having a size of 35×12.50R20LT was prototyped, which had the basic structure of FIG. 1 and a sidewall portion shown in any one of FIG. 2 to FIG. 11. As a comparative example, a tire having a sidewall portion a shown in FIG. 12 was prototyped. As shown in FIG. 12, the sidewall portion a of the comparative example has a plurality of protrusions b that are not surrounded by recesses. Moreover, the protrusions b of the comparative example have flat top surfaces and do not have steps like the first protrusions of the present invention. The comparative example tire has substantially the same configuration as the tire of the example, except for the configuration of the protrusions. The traction performance and durability of the protrusions of each test tire were tested. The common specifications and test methods of each test tire are as follows. Rim: 10.0JJ x 20 Tire pressure: 450kPa Test vehicle: 4700cc displacement, four-wheel drive Test tire mounting position: All wheels

[0075] <Traction performance> The test vehicle was driven around a circuit consisting of soft roads including snow and sand, and the average time was measured. The results are expressed as an index with the reciprocal of the time of the comparative example being set at 100, and the larger the index, the shorter the time and the better the traction performance on soft roads.

[0076] <Durability of protruding parts> After driving a certain distance on a rocky road surface paved with relatively large stones, the number of cracks that occurred in the first protrusion was counted. The results are the reciprocal of the number of cracks that occurred, and are expressed as an index with the comparative example being 100. The larger the value, the more unlikely it is that cracks will occur in the protrusion and the better the crack durability.

[0077] In each table shown below, the sum of the index indicating the traction performance and the index indicating the durability of the protrusions may be treated as a score indicating the overall performance of the tire.

[0078] Tires were produced as prototypes, each having the protrusion shown in Fig. 2 and varying the size of the step h3 and the depth d1 of the recess. The above-mentioned tests were also carried out on these tires. The test results are shown in Table 1.

[0079] [Table 1]

[0080] As shown in Table 1, it was confirmed that the embodiment shown in Fig. 2 exhibits excellent traction performance on soft roads. In addition, it was also confirmed that the protruding portions of the example tires shown in Table 1 have appropriate flexibility compared to the protruding portions of the comparative example tires, making them less susceptible to cracking and exhibiting excellent durability.

[0081] Tires were prototyped that had the protrusion shown in Fig. 2 and changed the area Sa of the top surface of the first protrusion in a plan view relative to the area Sb of the cross section along the base surface at the bottom of the recess of the first protrusion. The above-mentioned tests were also carried out on these tires. The results of the tests are shown in Table 2.

[0082] [Table 2]

[0083] As shown in Table 2, it was confirmed that the area of ​​the top surface of the first protrusion correlates with the traction performance. It was also confirmed that the examples shown in Table 2 had excellent durability of the protrusion.

[0084] Tires were produced as prototypes, each having the protrusion shown in Fig. 4 and varying the angle θ1 of the top surface of the second protrusion. The above-mentioned tests were also carried out on these tires. The results of the tests are shown in Table 3.

[0085] [Table 3]

[0086] As shown in Table 3, it was confirmed that the embodiment shown in Fig. 4 exhibits excellent traction performance. It was also confirmed that the angle θ1 of the top surface of the second protrusion is correlated with the traction performance.

[0087] Tires were prototyped that had the protruding portion shown in Fig. 6, and in which the difference in protruding amount h6 between the first protruding portion and the second protruding portion and the depth d2 of the recessed groove were changed. The above-mentioned tests were also carried out on these tires. The results of the tests are shown in Table 4.

[0088] [Table 4]

[0089] As shown in Table 4, it was confirmed that the embodiment shown in Fig. 6 exhibits excellent traction performance. It was also confirmed that the difference in protrusion amount h6 and the depth d2 of the recessed groove are correlated with the traction performance.

[0090] Tires were produced as prototypes, each having a protrusion as shown in Fig. 8 and varying the dimensions of the groove provided in the recess. The above-mentioned tests were also carried out on these tires. The results of the tests are shown in Table 5.

[0091] [Table 5]

[0092] As shown in Table 5, it was confirmed that the embodiment shown in Fig. 8 exhibits excellent traction performance. It was also confirmed that the grooves provided in the recesses are correlated with the traction performance.

[0093] Tires were prototyped that had the protrusions shown in Fig. 8 and had different angles θ2 of the normal line passing through the bottom of the circumferential groove. The above-mentioned tests were also carried out on these tires. Note that the angle θ3 of the normal line passing through the edge of the circumferential groove of these test tires was standardized to 35°. The results of the tests are shown in Table 6.

[0094] [Table 6]

[0095] As shown in Table 5, it was confirmed that the embodiment shown in Fig. 8 exhibits excellent traction performance. It was also confirmed that the angle θ2 is correlated with the traction performance. [Explanation of symbols]

[0096] 3 Sidewall 10 Base surface 11 First protrusion 13 Recess 16 Front page 17 Side 2 h1 1st protrusion amount h2 2nd protrusion amount

Claims

1. A pneumatic tire having a pair of sidewall portions, The axially outer surface of at least one of the pair of sidewall portions is A base surface; At least one first protruding portion protruding outward in the tire axial direction from the base surface; a recess extending through the base surface to space the first protrusion from the base surface; the first protruding portion includes a first surface having a first protruding amount with respect to the base surface and a second surface having a second protruding amount with respect to the base surface different from the first protruding amount, and these surfaces are connected to each other to form a step; the at least one sidewall portion includes a plurality of the first protrusions, a second protruding portion protruding axially outward from the base surface is disposed between the first protruding portions, The second protruding portion has a protruding amount from the base surface that becomes smaller toward the inside in the tire radial direction. Pneumatic tires.

2. A pneumatic tire having a pair of sidewall portions, The axially outer surface of at least one of the pair of sidewall portions is A base surface; At least one first protruding portion protruding outward in the tire axial direction from the base surface; a recess extending through the base surface to space the first protrusion from the base surface; the first protruding portion includes a first surface having a first protruding amount with respect to the base surface and a second surface having a second protruding amount with respect to the base surface different from the first protruding amount, and these surfaces are connected to each other to form a step; the at least one sidewall portion includes a plurality of the first protrusions, a second protruding portion protruding axially outward from the base surface is disposed between the first protruding portions, a maximum length of the second protrusion in the tire circumferential direction is smaller than a maximum length of the first protrusion in the tire circumferential direction, The second protruding portion includes a top surface facing axially outward of the tire, The top surface is provided with a recessed groove extending parallel to the tire radial direction. Pneumatic tires.

3. The pneumatic tire according to claim 1 , wherein a maximum amount of protrusion of the second protrusion from the base surface is smaller than a maximum amount of protrusion of the first protrusion from the base surface.

4. The pneumatic tire according to claim 1 , wherein a maximum length in the tire radial direction of the second protrusion is smaller than a maximum length in the tire radial direction of the first protrusion.

5. A pneumatic tire having a pair of sidewall portions, The axially outer surface of at least one of the pair of sidewall portions is A base surface; At least one first protruding portion protruding outward in the tire axial direction from the base surface; a recess extending through the base surface to space the first protrusion from the base surface; the first protruding portion includes a first surface having a first protruding amount with respect to the base surface and a second surface having a second protruding amount with respect to the base surface different from the first protruding amount, and these surfaces are connected to each other to form a step; A groove portion is provided on a bottom surface of the recess portion so as to extend along the opening shape of the recess portion. Pneumatic tires.

6. A pneumatic tire having a pair of sidewall portions, The axially outer surface of at least one of the pair of sidewall portions is A base surface; At least one first protruding portion protruding outward in the tire axial direction from the base surface; a recess extending through the base surface to space the first protrusion from the base surface; the first protruding portion includes a first surface having a first protruding amount with respect to the base surface and a second surface having a second protruding amount with respect to the base surface different from the first protruding amount, and these surfaces are connected to each other to form a step; a circumferential groove extending in a tire circumferential direction is provided on the at least one sidewall portion on an outer side in a tire radial direction of the first protruding portion, The circumferential groove includes an edge that is continuous with the base surface and a bottom that is a deepest position from the base surface, In a cross section of the circumferential groove, an angle of a normal line passing through the bottom with respect to the tire axial direction is smaller than an angle of a normal line passing through the edge with respect to the tire axial direction. Pneumatic tires.

7. The pneumatic tire according to claim 1 , wherein the first surface and the second surface of the first protrusion are aligned in a radial direction of the tire.

8. The second protrusion amount is smaller than the first protrusion amount, The pneumatic tire according to claim 7 , wherein the second surface is located outside the first surface in the tire radial direction.

9. The pneumatic tire according to claim 1 , wherein a cross-sectional area of ​​the first protrusion along the base surface increases toward a bottom side of the recess.

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