Pneumatic tire

Abstract

Provided is a pneumatic tire which is suitable as a tire for driving on an unpaved road and which has improved driving performance and cut resistance on the unpaved road. A pair of sidewall blocks (21) facing each other across sidewall grooves (22) extending in the width direction of the tire are provided in a sidewall region located on the outside of a shoulder region of a tread portion (1) in the width direction of the tire, and repeating elements (20) comprising the sidewall grooves (22) and the pair of sidewall blocks (21) are arranged at intervals in the circumferential direction of the tire. The tread surface of each sidewall block (21) has a concave-convex shape formed by a reference surface (21a) located on the sidewall groove (22) side and a step portion (21b) located on the opposite side of the sidewall groove (22) and protruding from the reference surface (21a), and the sidewall groove (22) is provided with a bottom raised portion (22a) protruding from the bottom of the sidewall groove (22) and connecting the pair of sidewall blocks (21).

Description

[0001] This application is a divisional application of Chinese patent application filed on July 25, 2018, with application number 201880047405.7 and invention title: "Pneumatic Tire". Technical Field

[0002] This invention relates to a pneumatic tire suitable for use as a tire for unpaved roads, and more specifically, to a tire that improves driving performance and cut resistance on unpaved roads. ( ) pneumatic tires. Background Technology

[0003] Pneumatic tires used on unpaved roads such as uneven ground, muddy ground, snow tracks, sandy ground, and rocky ground generally employ lateral grooves with a higher proportion of edge components (Japanese: The tire features a tread pattern with blocks as the main body and a large groove area. In such a tire, traction is achieved by gripping mud, snow, sand, stones, rocks, etc. (hereinafter collectively referred to as "mud, etc.") on the road surface, and the traction is improved by preventing mud, etc. from clogging the grooves. In particular, in tires intended for driving on rocky terrain, by also setting blocks in the sidewall area on the outer sidewall in the tire width direction compared to the shoulder area (contact end), the driving performance on rocky terrain (lock performance) is improved (for example, see Patent Document 1).

[0004] However, in such tires, blocks are formed in the shoulder and sidewall areas. On the other hand, because the groove area in these areas is also larger, stones, rocks, and foreign objects on the road can easily enter the grooves in the shoulder and sidewall areas, causing damage to the bottom of the grooves (poor cut resistance). Therefore, a solution has been sought that can effectively bite into mud and other debris into the grooves without deteriorating cut resistance, thereby improving driving performance on unpaved roads (especially rocky terrain), and achieving a good balance between these performance characteristics.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2010-047251 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] The purpose of this invention is to provide a pneumatic tire suitable for use as a tire on unpaved roads, which improves driving performance and cut resistance on unpaved roads.

[0010] Technical solutions for solving the problem

[0011] The pneumatic tire of the present invention for achieving the above-mentioned objectives comprises a tread portion extending in an annular shape along the tire circumference, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed on the radially inner side of these sidewall portions. The pneumatic tire is characterized in that a pair of sidewall blocks facing each other are provided in the sidewall region located on the outer side of the tire width direction of the shoulder region of the tread portion, separated by sidewall grooves extending in the tire width direction. The repetitive elements formed by these sidewall grooves and the pair of sidewall blocks are arranged at intervals in the tire circumference direction. The tread surface of each sidewall block has a concave-convex shape formed by a reference surface located on the sidewall groove side and a stepped portion located on the opposite side of the sidewall groove and raised from the reference surface. The sidewall groove has a raised bottom portion that raises from the bottom of the groove and connects the pair of sidewall blocks.

[0012] The effects of the invention

[0013] In this invention, because the sidewall blocks are provided with complex concave-convex shapes as described above, the edge component of the sidewall blocks is increased, enabling excellent edge effects and improving driving performance (especially locking performance) on unpaved roads. On the other hand, the presence of a raised section within the sidewall groove improves cut resistance. Furthermore, the raised section connects a pair of sidewall blocks adjacent to the sidewall groove, thereby increasing the rigidity of the pair of sidewall blocks and the raised section as a series of protrusions, which is beneficial for improving locking performance.

[0014] In this invention, it is preferable that the sidewall blocks included in the repetitive elements each have a shape in which the block width converges towards the sidewall groove as it approaches the radial inner side of the tire. Thus, the groove portions formed between adjacent repetitive elements in the tire circumferential direction widen radially inward relative to the sidewall grooves extending at approximately a certain width. These grooves are alternately arranged in the tire circumferential direction, thereby enabling an edge effect on rocks of various sizes, and improving the discharge performance of mud, etc., thus enhancing driving performance on unpaved roads.

[0015] In this invention, it is preferable that the ratio A / SH of the vertical distance A measured radially from the contact patch end of the tread towards the radially inner end of the sidewall block to the tire section height SH is 0.15 to 0.50. This results in a better sidewall block configuration, which is beneficial for improving driving performance (especially locking performance) on unpaved roads.

[0016] In this invention, it is preferred that the reference surface of the sidewall block protrudes from the bottom of the sidewall groove by 8mm to 13mm. By setting this protrusion, the size of the sidewall block is optimized, which is beneficial to improving driving performance (especially locking performance) on unpaved roads.

[0017] In this invention, preferably, the protrusion of the stepped portion of the sidewall block from the bottom of the sidewall groove is 110% to 130% of the protrusion of the reference surface of the sidewall block from the bottom of the sidewall groove. By setting the protrusion in this way, the concave-convex shape of the sidewall block becomes better, which is beneficial to improving driving performance (especially locking performance) on unpaved roads.

[0018] In this invention, it is preferable that the area of ​​the top surface of the step portion of the sidewall block when viewed from the tread side of the sidewall block is 40% to 60% of the total area of ​​the tread side of the sidewall block. By setting the area ratio of the step portion to the total tread side of the sidewall block in this way, the uneven shape of the sidewall block becomes better, which is beneficial to improving driving performance (especially locking performance) on unpaved roads.

[0019] In this invention, it is preferable that the ratio of the vertical distance B from the contact patch end of the tread towards the radially inner end of the bottom riser, measured radially towards the tire, to the tire section height SH, is B / SH, which is 0.20 to 0.40. This results in a favorable configuration of the bottom riser, which is beneficial for balancing cut resistance and driving performance (especially locking performance) on unpaved roads.

[0020] In this invention, it is preferable that the protrusion of the underbody riser from the bottom of the sidewall groove is 3mm to 5mm. By setting the protrusion amount in this way, the size of the underbody riser is optimized, which is beneficial to both cut resistance and driving performance on unpaved roads (especially locking performance).

[0021] In this invention, unless otherwise specified, all dimensions refer to the dimensions of the tread surface. The "tread surface" of each piece refers to the dimensions within the tread area when the tire rim is assembled onto a standard rim (Japanese: ). ) and filled with normal internal pressure (Japanese: It was placed vertically on a plane and subjected to a normal load in the state of (Japanese: ) When the tire is in contact with the surface of the plane on which it rests, the term "grounding end" refers to the surface portions of each piece that actually make contact with the plane on which the tire is placed, excluding non-contact portions such as chamfered areas. Additionally, "grounding end" refers to the two ends of the tire's axial direction in this state. "Standard rim" refers to the rim defined for each tire within a standard system that includes the standard on which the tire is based; for example, if it is JATMA, it is defined as a standard rim (Japanese: ). If it is TRA, it is set to "Design Rim"; if it is ETRTO, it is set to "Measuring Rim". "Regular Inflation Pressure" refers to the air pressure specified for each tire in the standard system that includes the standard on which the tire is based. If it is JATMA, it is the maximum air pressure; if it is TRA, it is the maximum value recorded in the table "TIRE ROAD LIMITS AT VARIOUS COLD INFLATIONPRESSURES"; if it is ETRTO, it is "INFLATION PRESSURE", but it is set to 180 kPa if the tire is for passenger cars. "Regular load" refers to the load defined for each tire within a standard system that includes the standard on which the tire is based. For JATMA, it is the maximum load capacity; for TRA, it is the maximum value recorded in the table "TIRE ROAD LIMITS AT VARIOUS COLDINFLATION PRESSURES"; and for ETRTO, it is "LOAD CAPACITY". However, when the tire is for passenger cars, it is set to a load equivalent to 88% of the stated load. Attached Figure Description

[0022] Figure 1 This is a radial cross-sectional view of an inflatable tire formed according to an embodiment of the present invention.

[0023] Figure 2 This shows the tread surface of a pneumatic tire formed according to an embodiment of the present invention (Japanese: The main view of ().

[0024] Figure 3 This is an explanatory diagram showing a combination of a front view (viewed from the side of the tire) and a side view (viewed from the radially inner side of the tire) of the repeating elements of the present invention.

[0025] Figure 4 This is an explanatory diagram showing the area of ​​the stepped portion of the tire sidewall block.

[0026] Figure 5 This is an illustrative diagram showing another example of a different sidewall block of the present invention. Detailed Implementation

[0027] The structure of the present invention will now be described in detail with reference to the accompanying drawings.

[0028] like Figure 1As shown, the pneumatic tire of the present invention includes a tread portion 1 extending in an annular shape along the tire circumference, a pair of sidewall portions 2 disposed on both sides of the tread portion 1, and a pair of bead portions 3 disposed radially inside the sidewall portions 2. Furthermore, in Figure 1 In the attached diagram, CL represents the tire equator, and E represents the grounding terminal.

[0029] A carcass layer 4 is provided between a pair of left and right bead portions 3. This carcass layer 4 includes multiple reinforcing cords extending radially along the tire and folding back from the inside of the vehicle to the outside around the bead core 5 disposed in each bead portion 3. Additionally, a bead filler 6 is disposed on the outer periphery of the bead core 5, which is enclosed by the main body and folded-back portion of the carcass layer 4. Furthermore, multiple layers (in...) are embedded on the outer periphery of the carcass layer 4 at the tread portion 1. Figure 1 The belt layer 7 consists of two layers. Each belt layer 7 contains multiple reinforcing cords inclined relative to the tire circumference, and the reinforcing cords are arranged in a manner that the reinforcing cords intersect each other between layers. In these belt layers 7, the inclination angle of the reinforcing cords relative to the tire circumference is set, for example, in the range of 10° to 40°. Furthermore, a belt reinforcement layer 8 is provided on the outer periphery of the belt layer 7. The belt reinforcement layer 8 contains organic fiber cords oriented in the tire circumference direction. In the belt reinforcement layer 8, the angle of the organic fiber cords relative to the tire circumference is set, for example, in the range of 0° to 5°.

[0030] This invention applies to general pneumatic tires, but their cross-sectional structure is not limited to the basic construction described above. Furthermore, this invention targets tires intended for use on rocky terrain and which have sidewall blocks (described later) in the sidewall region located outward in the tire width direction from the contact patch end E. The shape of this sidewall region (sidewall block) is defined, therefore, the shape (i.e., tread pattern) located inward in the tire width direction from the contact patch end E is not particularly limited. For example, in... Figure 2 In its morphology, the tread pattern has the following structure. Furthermore, Figure 2 The tread pattern, in conjunction with the construction of the sidewall area described later, enables excellent driving performance on unpaved roads.

[0031] exist Figure 2 In the example, multiple longitudinal grooves 11 extending along the tire circumference, multiple transverse grooves 12 extending along the tire width, and multiple blocks 13 divided by these longitudinal grooves 11 and transverse grooves 12 are formed. In particular, in Figure 2In this configuration, within the tire width direction of the outermost block 13 (hereinafter referred to as the outermost block 13o), a plurality of blocks 13 (hereinafter referred to as inner blocks 13i) are arranged side-by-side relative to the outermost block 13o along the tire width direction. Furthermore, a block group 14 consisting of the outermost block 13o and the plurality of inner blocks 13i (i.e., at least three blocks 13 adjacent in the tire width direction, including the outermost block 13o) is repeatedly arranged in the tire circumferential direction across the transverse groove 12. In the illustrated example, the outermost block 13o and two inner blocks 13i constitute a block group 14 consisting of three blocks 13.

[0032] Each block group 14 exists on a platform 15 that rises from the bottom of the transverse groove 12 and has a flat top surface on which blocks 13 and longitudinal grooves 11 can be arranged. At this time, the longitudinal grooves 11 located between the blocks 13 constituting each block group 14 also exist on the platform 15, and the bottom of the longitudinal grooves 11 is consistent with the top surface of the platform 15, or located on the tread side closer to the top surface of the platform 15. When viewed from the tread side, each platform 15 has a shape that protrudes to both sides of the tire circumferential direction relative to at least three blocks 13 constituting each platform 15, and the outline of each platform 15 bends along the outline of at least three blocks 13 constituting each platform 15.

[0033] In addition, a raised portion 16 is provided at the bottom of the longitudinal groove 11 adjacent to the outermost block 13o. The raised portion 16 connects the outermost block 13o and the inner block 13i adjacent to the outermost block 13o.

[0034] The following is for reference Figure 2 , Figure 3 The shape of the sidewall region of the pneumatic tire of the present invention will be described.

[0035] A plurality of sidewall blocks 21 are formed in the sidewall region of the pneumatic tire of the present invention. As shown, the sidewall blocks 21 are arranged in pairs facing each other with a sidewall groove 22 extending along the tire width direction, and these pairs of sidewall blocks 21 and sidewall grooves 22 constitute a repeating element 20. The repeating element 20 is arranged at intervals in the tire circumferential direction.

[0036] The tread surface of each sidewall block 21 is not flat, but has an uneven shape formed by a reference surface 21a located on the sidewall groove 22 side and a stepped portion 21b located on the opposite side of the sidewall groove 22 and raised from the reference surface 21a. On the other hand, a bottom rise portion 22a is formed at the bottom of the sidewall groove 22, which rises from the bottom of the groove and connects the pair of sidewall blocks 21. In particular, in the illustrated example, the bottom rise portion 22a is formed from the outermost radial direction of the sidewall groove 22 to the middle part of the sidewall groove 22.

[0037] Thus, by providing sidewall blocks 21 and sidewall grooves 22 with complex concave-convex shapes in the sidewall area, their excellent edge effect can improve driving performance (especially locking performance) on unpaved roads. On the other hand, since a bottom riser 22a is provided in the sidewall groove 22, cut resistance can be improved. In addition, since a pair of sidewall blocks 21 adjacent to the sidewall groove 22 are connected by the bottom riser 22a, the pair of sidewall blocks and the bottom riser are rigidly increased as a series of protrusions, which is beneficial to improving the durability of the sidewall blocks 21 and improving locking performance.

[0038] At this point, it is preferable that the sidewall blocks 21 included in the repeating element 20 each have a shape (approximately triangular shape) in which the block width converges towards the sidewall groove 22 the closer to the radial inner side of the tire. By setting such a shape, the groove portions 23 formed between adjacent repeating elements 20 in the tire circumferential direction widen towards the radial inner side of the tire relative to the sidewall groove 22 which extends with approximately a certain width. Such sidewall grooves 22 and groove portions 23 are alternately arranged in the tire circumferential direction, thus enabling the edge effect to be exerted on rocks of various sizes. In addition, the discharge performance of mud and the like in the groove portions 23 is also improved, thus benefiting the improvement of driving performance on unpaved roads.

[0039] The step portion 21b of the sidewall block 21 protrudes from the reference surface 21a as described above, but it is also preferable to form a V-shaped notch 21c on the side of the step portion 21b on the reference surface 21a side as shown in the figure. By providing such a notch 21c, the edge component of the step portion 21b is increased, which is beneficial to improving the driving performance on unpaved roads.

[0040] Furthermore, the inner edge of the tire radial side of the underbody lift 22a can be inclined relative to the width direction (tire circumferential direction) of the sidewall groove 22 as shown in the figure, and a V-shaped notch 22b can also be formed on this edge. By setting it in this shape, the edge component can also be increased through the underbody lift 22a, which is beneficial to improving driving performance on unpaved roads.

[0041] The protrusion H1 of the reference surface 21a of the sidewall block 21 from the bottom of the sidewall groove 22 is preferably 8mm to 13mm, for example. Furthermore, the protrusion H2 of the stepped portion 21b of the sidewall block 21 from the bottom of the sidewall groove 22 is preferably 110% to 130% of the protrusion H1. By setting the protrusions H1 and H2 of each part in this way, the concave-convex shape of the sidewall block 21 becomes favorable, which is beneficial to improving driving performance (especially locking performance) on unpaved roads. At this time, if the protrusion H1 is less than 8mm, the sidewall block 21 is too small, and therefore it is difficult to fully obtain the effect brought by setting the sidewall block 21. If the protrusion H1 is greater than 13mm, the amount of rubber (weight) of the sidewall portion 2 increases, the traction performance decreases, and the performance on unpaved roads (especially rocky terrain) may be affected. The protrusion H2 has an impact. If the protrusion H2 is less than 110% of the protrusion H1, the top surface of the sidewall block 21 becomes essentially flat, and the effect of improving locking performance is limited. If the protrusion H2 is greater than 130% of the protrusion H1, only the step portion 21b protrudes extremely, and the durability of the sidewall block 21 (step portion 21b) decreases.

[0042] Furthermore, the protrusion H3 of the underside riser 22a from the bottom of the sidewall groove 22 is preferably, for example, 3mm to 5mm. By setting the protrusion of the underside riser 22a within an appropriate range, the size of the underside riser is optimized, which is beneficial for balancing cut resistance and driving performance (especially locking performance) on unpaved roads. At this time, if the protrusion H3 is less than 3mm, the bottom of the sidewall groove 22 is not substantially raised, and it is not possible to connect the sidewall blocks 21 to sufficiently improve rigidity. If the protrusion H1 is greater than 5mm, the groove volume of the sidewall groove 22 is reduced, which may affect the discharge performance of mud, etc.

[0043] Sidewall blocks 21 are formed in the sidewall area, but are particularly preferably located in the area that comes into contact with mud, etc., when driving on unpaved roads (especially in the area that comes into contact with rock when driving on rocky ground). Specifically, as Figure 1 As shown, the ratio A / SH of the vertical distance A measured radially from the contact point E towards the radially inner end of the sidewall block 21 to the tire section height SH is preferably, for example, 0.15 to 0.50. This results in a better sidewall block configuration, which is beneficial for improving driving performance (especially locking performance) on unpaved roads. If the ratio A / SH is less than 0.15, the radial length of the sidewall block 21 becomes shorter, and the sidewall block 21 itself becomes smaller, thus limiting the effect brought by the sidewall block 21. If the ratio A / SH is greater than 0.50, the amount of rubber (weight) in the sidewall portion 2 increases, traction performance decreases, and it may affect the performance on unpaved roads (especially rocky terrain).

[0044] Furthermore, since the underbody elevation 22a is formed within the sidewall groove 22 between the sidewall blocks 21, it is formed at least within the aforementioned A / SH ratio range. However, if a large portion of the sidewall groove 22 is underbody raised, the groove volume of the sidewall groove is reduced, which may affect driving performance on unpaved roads. Therefore, if... Figure 1As shown, the ratio B / SH of the vertical distance B measured radially from the ground contact point E towards the radially inner end of the bottom riser 22a to the tire section height SH is preferably set to, for example, 0.20 to 0.40. This results in a better configuration of the bottom riser 22a, which is beneficial for balancing cut resistance and driving performance (especially locking performance) on unpaved roads. If the ratio B / SH is less than 0.20, the radial length of the bottom riser 22a becomes shorter, and the bottom riser 22a itself becomes smaller, thus limiting the effect brought by the bottom riser 22a. If the ratio B / SH is greater than 0.40, the proportion of the bottom riser 22a in the sidewall groove 22 becomes larger, and the groove volume of the sidewall groove 22 decreases, which may affect the mud removal performance. More preferably, considering the balance between the size of the sidewall block 21 and the bottom riser 22a, the ratio B / A of the vertical distance A to the vertical distance B can be set to, for example, a range of 0.65 to 0.90.

[0045] To improve driving performance (especially locking performance) on unpaved roads through the aforementioned uneven shape of the sidewall block 21, it is preferable that the reference surface 21a of the sidewall block 21 and the step portion 21b are well balanced. Specifically, as Figure 4 As shown, the area of ​​the top surface of the step portion 21b when viewed from the tread side of each sidewall block 21 ( Figure 4 (a) The oblique portion is preferably the area of ​​the entire tread surface of the sidewall block 21. Figure 4 The area of ​​the stepped portion 21b in the tread surface of the sidewall block 21 is set to a ratio of 40% to 60%. By setting the area ratio of the stepped portion 21b in the tread surface of the sidewall block 21 in this way, the uneven shape of the sidewall block 21 becomes better, which is beneficial to improving the driving performance (especially the locking performance) on unpaved roads. At this time, if the area of ​​the top surface of the stepped portion 21b is less than 40% of the area of ​​the tread surface of the sidewall block 21, the stepped portion 21b becomes smaller, so the effect brought by the stepped portion 21b is limited. If the area of ​​the top surface of the stepped portion 21b is greater than 60% of the area of ​​the tread surface of the sidewall block 21, the proportion of the stepped portion 21 in the sidewall block 21 becomes larger, which is essentially the same as the case where the protrusion height of the tread surface of the sidewall block 21 becomes larger, so the effect of adding edge components as a step is limited. In addition, the rubber amount (weight) of the sidewall portion 2 increases, the traction performance decreases, and it may affect the performance on unpaved roads (especially rocky terrain).

[0046] In this invention, such as Figure 2As shown, it can also be configured as follows: all the repeating elements 20 exist on a platform 30 that protrudes 8mm to 17mm from the outer surface of the sidewall portion 2, has a flat top surface, and has a contour line with arbitrary amplitude and a serrated bend. This allows for the edge effect brought about by the platform 30 and improves the overall rigidity of the repeating elements 20 formed on the tire circumference, enhancing its durability and improving driving performance (especially locking performance) on unpaved roads.

[0047] like Figure 5 As shown, a protrusion 24 extending along the periphery can also be provided on the tread of the sidewall block 21 of the present invention. By providing such a protrusion 24, the sidewall block 21 can easily get caught in mud or the like when driving on unpaved roads, which is beneficial to improving driving performance on unpaved roads. In addition, tires with sidewall blocks 21 in the sidewall area as in the present invention may have reduced exhaust performance during vulcanization due to the sidewall blocks 21, but with the protrusion 24 as described above, a groove for forming the aforementioned protrusion 24 is provided in the mold, through which air can be discharged from the mold, thus improving the manufacturability of tires with complex sidewall blocks 21 as in the present invention. In this case, by connecting the groove for forming the protrusion 24 to a vent hole, particularly excellent exhaust performance can be achieved.

[0048] In the Figure 2 In the case of the tread pattern combination of the sidewall block 21 of the present invention, as shown in the figure, the sidewall groove 22 can be arranged on the extension line of the transverse groove 12, and the sidewall block 21 can be arranged adjacent to the outermost sidewall block 13o in the tire width direction. Furthermore, as shown in the figure, it is preferable that the groove width of the sidewall groove 22 is equal to the groove width of the transverse groove 12 at the ground contact end E, and the block width of the outermost sidewall block 21 in the tire radial direction is equal to the block width of the outermost block 13o at the ground contact end E.

[0049] Example

[0050] The following 23 types of pneumatic tires were manufactured: Previous Example 1, Comparative Examples 1-2, and Examples 1-20: The tire size was 35×12.50R17 and had… Figure 1 The basic construction shown is based on Figure 2The tread pattern is the base color, and regarding the construction of the sidewall area, the following parameters are set as shown in Tables 1-3: presence or absence of the sidewall block step portion, presence or absence of the bottom rise portion in the sidewall groove, ratio of the vertical distance A from the contact end of the tread towards the radial direction to the radially inner end of the sidewall block to the tire section height SH (A / SH), the amount of the sidewall block reference surface protruding from the bottom of the sidewall groove (H1), the ratio of the amount of the sidewall block step portion protruding from the bottom of the sidewall groove (H2) to the amount of protrusion (H1) (ratio H2 / H1×100%), the ratio of the area of ​​the top surface of the sidewall block step portion to the area of ​​the entire sidewall block tread surface, the ratio of the vertical distance B from the contact end of the tread towards the radial direction to the radially inner end of the bottom rise portion to the tire section height SH (B / SH), and the amount of the bottom rise portion protruding from the bottom of the tread groove (H3).

[0051] For these pneumatic tires, the locking performance and cut resistance were evaluated using the following evaluation methods, and the results are shown in Tables 1-3.

[0052] Lock performance

[0053] Each test tire was assembled onto a 17×10.0J rim, with the tire pressure set to 240 kPa, and mounted on a test vehicle (four-wheel drive). Traction and starting performance were evaluated based on the test driver's sensory feedback on a rocky surface. The evaluation results are expressed as an index with the value of Example 1 set to 100. A higher index value indicates better locking performance.

[0054] Cut resistance

[0055] Following the evaluation of the locking performance described above, the length of the cut edge of the damage caused in the sidewall and shoulder areas was measured. The evaluation results were expressed as an exponent with the reciprocal of the value in Example 1 set to 100. The larger the exponent value, the shorter the cut edge length and the better the cut resistance.

[0056] [Table 1]

[0057]

[0058] [Table 2]

[0059]

[0060] [Table 3]

[0061]

[0062] As shown in Tables 1-3, compared with the previous Example 1, Examples 1-20 all improved locking performance and cut resistance, and achieved a good balance of these properties. Furthermore, while locking performance on rocky surfaces was evaluated, even when driving on other unpaved roads (muddy roads, snow tracks, sand, etc.), the tires of this invention functioned similarly to those on rocky surfaces, thus demonstrating excellent driving performance on unpaved roads.

[0063] On the other hand, although Comparative Example 1 has a stepped portion, it does not have a raised bottom portion, thus failing to improve cut resistance. Although Comparative Example 2 has a raised bottom portion, it does not have a stepped portion, thus failing to improve locking performance.

[0064] Explanation of reference numerals in the attached figures

[0065] 1. Fetal face

[0066] 2. Side of the tire

[0067] 3. Bead area

[0068] 4. Fetal body layers

[0069] 5. Bead core

[0070] 6. Bead filling

[0071] 7. Belt layer

[0072] 8. Belt reinforcement layer

[0073] 20 Recurring Elements

[0074] 21 Sidewall block

[0075] 21a Reference Surface

[0076] 21b Step section

[0077] 21c gap

[0078] 22 Sidewall groove

[0079] 22a Bottom rise section

[0080] 22b Gap

[0081] CL Tire Equator

[0082] E Grounding terminal

Claims

1. A pneumatic tire comprising a tread portion extending in an annular shape along the tire circumference, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed radially inside the sidewall portions, characterized in that, A pair of sidewall blocks facing each other are provided in the sidewall region located on the outer side of the tire shoulder area in the tire width direction, separated by sidewall grooves extending in the tire width direction. The repetitive elements formed by these sidewall grooves and the pair of sidewall blocks are arranged at intervals in the tire circumferential direction. Each sidewall block has a tread surface with a concave-convex shape consisting of a reference surface located on the sidewall groove side and a stepped portion located on the opposite side of the sidewall groove and raised from the reference surface. The side surface of the stepped portion on the reference surface side has a V-shaped notch. The sidewall groove has a raised portion that rises from the bottom of the groove and connects the pair of sidewall blocks.

2. The pneumatic tire according to claim 1, characterized in that, The sidewall blocks included in the repetitive elements each have a shape in which the block width converges towards the sidewall groove the further inward it is from the radial side of the tire.

3. The pneumatic tire according to claim 1 or 2, characterized in that, The ratio of the vertical distance A from the contact point of the tread portion toward the radially inner end of the sidewall block to the tire section height SH is 0.15 to 0.

50.

4. The pneumatic tire according to claim 1 or 2, characterized in that, The reference surface of the sidewall block protrudes from the bottom of the sidewall groove by an amount of 8mm to 13mm.

5. The pneumatic tire according to claim 1 or 2, characterized in that, The amount by which the stepped portion of the sidewall block protrudes from the bottom of the sidewall groove is 110% to 130% of the amount by which the reference surface of the sidewall block protrudes from the bottom of the sidewall groove.

6. The pneumatic tire according to claim 1 or 2, characterized in that, When viewed from the tread side of the sidewall block, the area of ​​the top surface of the step portion of the sidewall block is 40% to 60% of the total area of ​​the tread of the sidewall block.

7. The pneumatic tire according to claim 1 or 2, characterized in that, The ratio of the vertical distance B from the contact point of the tread portion toward the radially inner end of the tire to the tire section height SH is 0.20 to 0.

40.

8. The pneumatic tire according to claim 1 or 2, characterized in that, The protrusion of the raised portion from the bottom of the sidewall groove is 3mm to 5mm.

9. The pneumatic tire according to claim 1 or 2, characterized in that, The tread of the sidewall block has a protrusion extending along the periphery.

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