Tire

Abstract

Provided is a tire which enables improving low noise performance while ensuring excellent snow performance. The tire has shoulder blocks 12 partitioned by shoulder lug grooves 11 in a shoulder region of a tread part 1. The tire is provided with a plurality of auxiliary grooves 13 on the upper surface of each shoulder block 12. On a tread surface: each shoulder block 12 has a plurality of edge components 11e, 13e extending linearly along the shoulder lug grooves 11 and the auxiliary grooves 13; the plurality of edge components 11e, 13e form two or more sets of parallel edge groups comprising four or more edge components 11e, 13e that are parallel to each other; and each parallel edge group includes at least one edge component 13e running along the auxiliary grooves 13 and at least one edge component 11e running along the shoulder lug grooves 11.

Description

tire

[0001] The present invention relates to a tire intended for running on unpaved roads and the like, and more particularly to a tire that enables improved low noise performance while ensuring excellent snow performance.

[0002] Tires (e.g., all-terrain tires, all-terrain tires, etc.) designed for driving on unpaved roads (uneven terrain, muddy terrain, sandy terrain, rocky areas, etc.) in addition to paved roads are required to have excellent driving performance on various road surfaces, and in particular, excellent snow performance (driving performance on snow-covered roads). For example, in Europe, tires that have been recognized as being capable of being used on roads under severe snowy conditions are marked with the so-called "Three Peak Mountain Snowflake Mark (Severe Snow Mark)," and there is a trend toward placing importance on snow performance. In such tires, for example, multiple auxiliary grooves (grooves shallower than lug grooves) are provided on the surface of the shoulder blocks to increase the edge component, thereby improving snow performance (see, for example, Patent Document 1). On the other hand, providing multiple auxiliary grooves increases the groove component (increasing the groove area ratio), which tends to worsen pass-by noise outside the vehicle. Therefore, there is a need to improve snow performance without worsening pass-by noise, thereby achieving a high level of both performance.

[0003] Japanese Patent Application Publication No. 2023-119951

[0004] An object of the present invention is to provide a tire that allows for improved low noise performance while ensuring excellent snow performance.

[0005] The tire of the present invention for achieving the above object has a tread portion extending in the tire circumferential direction and forming an annular shape, the tire having a pair of main grooves on the surface of the tread portion extending along the tire circumferential direction on both sides of the tire equator, and a plurality of shoulder lug grooves extending from the main grooves toward the outer side in the tire width direction and spaced apart in the tire circumferential direction in shoulder regions located on the outer side in the tire width direction of the main grooves, and a plurality of shoulder blocks partitioned by the main grooves and the shoulder lug grooves and arranged in the tire circumferential direction, and a plurality of auxiliary grooves having a groove depth smaller than that of the shoulder lug grooves are provided on the surface of each shoulder block, and each auxiliary groove has a groove depth smaller than that of the shoulder lug grooves, and The grooves extend from the tread surface of each shoulder block across the ground contact edge toward the side of each shoulder block, and on the tread surface, each shoulder block has a plurality of edge components extending linearly along the shoulder lug groove and the auxiliary groove, the contour lines of the shoulder lug groove and the auxiliary groove each have a curved shape made up of a combination of the plurality of edge components, and the plurality of edge components form two or more sets of parallel edge groups made up of four or more edge components parallel to each other, and each parallel edge group includes at least one edge component along the auxiliary groove and at least one edge component along the shoulder lug groove.

[0006] The tire of the present invention uses auxiliary grooves with a smaller groove depth than the shoulder lug grooves as an element for increasing groove components in the shoulder blocks to improve snow performance, thereby preventing deterioration of noise performance due to an increase in groove components. Furthermore, the shoulder lug grooves and auxiliary grooves each have a curved shape, which prevents noise caused by the tread pattern from radiating outside the vehicle through the grooves. Meanwhile, the tire has two or more sets of parallel edge groups, each containing at least one edge component along the auxiliary groove and at least one edge component along the shoulder lug groove. The parallel edge components contained in the parallel edge groups synergistically ensure an excellent edge effect, effectively improving snow performance. These combined effects enable a high level of both snow performance and low noise performance.

[0007] In the present invention, it is preferable that at least two of the edge components located at the inner ends of the auxiliary grooves in the tire width direction are parallel to each other, which further improves the edge effect and is advantageous for improving snow performance.

[0008] In the present invention, the groove width of the auxiliary groove is preferably 10% to 50% of the minimum groove width of the shoulder lug groove, which optimizes the groove width of the auxiliary groove, thereby achieving a good balance between ensuring edge components and suppressing noise.

[0009] In the present invention, the groove depth of the auxiliary groove is preferably 3% to 30% of the minimum groove depth of the shoulder lug grooves, which optimizes the groove depth of the auxiliary groove, thereby achieving a good balance between ensuring edge components and suppressing noise.

[0010] In the present invention, it is preferable that all edge components are inclined to one side with respect to the tire width direction, which can further improve the edge effect and is advantageous for improving snow performance.

[0011] In the present invention, it is preferable that the auxiliary grooves are provided closer to the tread edge than the center of the shoulder block in the tire width direction, which allows the auxiliary grooves to be located in areas that are likely to come into contact with snow on the road surface when traveling on unpaved roads (e.g., snowy roads), further improving the edge effect and advantageously improving snow performance.

[0012] In the present invention, the total area of ​​the auxiliary grooves is preferably 1% to 10% of the area of ​​the tread surface of the shoulder block, which optimizes the proportion of the auxiliary grooves in each shoulder block, achieving a good balance between ensuring edge components and suppressing noise.

[0013] In the present invention, the term "ground contact edge" refers to both ends in the axial direction of the tire of the ground contact area formed when the tire is mounted on a standard rim, inflated to the standard internal pressure, placed vertically on a flat surface, and subjected to a standard load. The term "standard rim" refers to the rim determined for each tire by the standard system that includes the standard on which the tire is based, and is, for example, the standard rim in the case of JATMA, the "Design Rim" in the case of TRA, or the "Measuring Rim" in the case of ETRTO. "Normal internal pressure" refers to the air pressure determined for each tire by the respective standards, including the standards on which the tire is based, and is the maximum air pressure in the case of JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the case of TRA, and the "INFLATION PRESSURE" in the case of ETRTO, but is set to 180 kPa when the tire is for a passenger car. The "normal load" is the load determined for each tire by each standard in the standard system including the standard on which the tire is based, and is the maximum load capacity in the case of JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the case of TRA, and the "LOAD CAPACITY" in the case of ETRTO.

[0014] The tire of the present invention is preferably a pneumatic tire, but may also be a non-pneumatic tire. In the case of a pneumatic tire, the interior thereof can be filled with air, an inert gas such as nitrogen, or other gases.

[0015] Fig. 1 is a meridian half cross-sectional view of a tire according to an embodiment of the present invention, Fig. 2 is a perspective view showing a shoulder block according to an embodiment of the present invention, and Fig. 3 is a schematic diagram illustrating a group of parallel edges according to the present invention.

[0016] The configuration of the present invention will be described in detail below with reference to the accompanying drawings.

[0017] When the tire of the present invention is a pneumatic tire as shown in Figure 1, it comprises a tread portion 1 that contacts the road surface, a pair of sidewall portions 2 arranged on both sides of the tread portion 1, and a pair of bead portions 3 arranged radially inward of the sidewall portions 2. In Figure 1, the symbol CL indicates the tire equator, and the symbol E indicates the contact edge. Although not depicted in Figure 1 because it is a meridian half cross section, the tread portion 1, sidewall portions 2, and bead portions 3 each extend in the tire circumferential direction and form an annular shape, thereby constituting the basic toroidal structure of a pneumatic tire. The following explanation using Figure 1 will be basically based on the meridian cross section shown, but each tire constituent member also extends in the tire circumferential direction and forms an annular shape.

[0018] A carcass layer 4 is installed between a pair of left and right bead portions 3. The carcass layer 4 includes multiple reinforcing cords extending in the tire radial direction and folded back from the inner side to the outer side in the tire width direction around bead cores 5 arranged in each bead portion 3. A bead filler 6 is arranged on the outer periphery of each bead core 5, and this bead filler 6 is wrapped by the main portion and folded back portion of the carcass layer 4. Meanwhile, multiple belt layers 7 (two layers in FIG. 1 ) are embedded on the outer periphery of the carcass layer 4 in the tread portion 1. Each belt layer 7 includes multiple reinforcing cords inclined with respect to the tire circumferential direction, and the reinforcing cords are arranged so as to cross each other between the layers. In these belt layers 7, the inclination angle of the reinforcing cords with respect to the tire circumferential direction is set, for example, in the range of 10° to 40°. Furthermore, at least one belt reinforcing layer 8 (two layers in FIG. 1 ) is provided on the outer periphery of the belt layer 7. The belt reinforcing layer 8 includes organic fiber cords oriented in the tire circumferential direction. In the belt reinforcing layer 8, the organic fiber cords are set at an angle of, for example, 0° to 5° with respect to the tire circumferential direction.

[0019] Because the present invention relates to the shoulder region (shoulder blocks) as described below, the basic structure (internal structure) of the tire is not limited to the general structure described above. Furthermore, the detailed shape of the grooves and blocks formed on the surface of the tread portion 1 (tread pattern) is not particularly limited, except for the shoulder region described below. The tread pattern in the portion excluding the shoulder region described below is preferably a block-based pattern suitable for unpaved roads. The present invention can be applied to various types of tires, including non-pneumatic tires, as long as they have regions (regions corresponding to the shoulder region and side region) that may come into contact with mud or the like on the road surface when traveling on unpaved roads.

[0020] As shown in Figures 1 and 2, a pair of main grooves 10 are formed on the surface of the tread portion 1, extending circumferentially around the entire tire on both sides of the tire equator CL. The main grooves 10 preferably have a zigzag shape in which linear sections inclined in one direction relative to the tire circumferential direction and linear sections inclined in the other direction are alternately connected in the tire circumferential direction. The region between the pair of main grooves 10 is the center region (a region in which any tread pattern can be adopted without particular structural limitations in the present invention), and the regions on the outer sides of each main groove 10 in the tire width direction are shoulder regions. The main grooves 10 preferably have a groove width of 3 mm to 30 mm, more preferably 5 mm to 11 mm, and a groove depth of 8 mm to 16 mm, more preferably 10 mm to 15 mm.

[0021] A land portion (shoulder land portion) defined on the outer side of the main groove 10 in the tire width direction is provided with shoulder lug grooves 11 extending outward in the tire width direction from the main groove 10. A plurality of shoulder lug grooves 11 may be provided at intervals around the tire circumferential direction. Each shoulder lug groove 11 has a curved shape at least in the region inward in the tire width direction from the tread edge E. These shoulder lug grooves 11 divide the shoulder land portion into a plurality of blocks (shoulder blocks 12). When the main groove 10 has a zigzag shape, the shoulder lug grooves 11 may be connected to the bending points of each main groove 10 on the outer side in the tire width direction. The groove width of the shoulder lug groove 11 is not particularly limited, but is preferably 70% to 98%, more preferably 80% to 95%, of the groove width of the main groove 10. The groove depth of the shoulder lug groove 11 is not particularly limited, but is preferably 75% to 100%, more preferably 80% to 98% of the groove depth of the main groove 10.

[0022] The surface of each shoulder block 12 is provided with multiple auxiliary grooves 13 (two in the illustrated example), each with a groove depth smaller than that of the shoulder lug grooves 11. Each auxiliary groove 13 extends from the tread of the shoulder block 12 across the ground contact edge E toward the side surface of the shoulder block 12 (the portion more outward in the tire width direction than the ground contact edge E). Like the shoulder lug grooves 11, each auxiliary groove 13 also has a curved shape at least in the region more inward in the tire width direction than the ground contact edge E. Both ends of the auxiliary groove 13 terminate within the shoulder block 12. More specifically, the inner end of the auxiliary groove 13 in the tire width direction terminates at the ground contact surface of the shoulder block 12, and the outer end of the auxiliary groove 13 in the tire width direction terminates at the side surface of the shoulder block 12 (the surface connecting to the sidewall portion 2). There are no particular limitations on the number of auxiliary grooves 13 provided in each shoulder block 12; for example, two to four auxiliary grooves 13 may be provided.

[0023] As described above, the auxiliary grooves 13 have a smaller groove depth than the shoulder lug grooves 11. Specifically, the groove width of the auxiliary grooves 13 is preferably 10% to 50%, more preferably 25% to 45%, of the minimum groove width of the shoulder lug grooves 11. The groove depth of the auxiliary grooves 13 is preferably 3% to 30%, more preferably 4% to 15% of the minimum groove depth of the shoulder lug grooves 11. By setting the dimensions of the auxiliary grooves 13 in this manner, the groove volume of the auxiliary grooves 13 is optimized, thereby achieving a good balance between ensuring the edge components and suppressing noise, as described below. If the groove width or depth of the auxiliary grooves 13 is below the aforementioned range, the groove volume of the auxiliary grooves 13 cannot be sufficiently ensured, limiting the effect of improving snow performance. If the groove width or depth of the auxiliary grooves 13 exceeds the aforementioned range, the groove volume of the auxiliary grooves 13 increases, limiting the effect of suppressing noise.

[0024] When the shoulder lug grooves 11 and auxiliary grooves 13 are viewed from the tread side of the shoulder blocks 12, these grooves have a curved shape as described above, and therefore the contours of these grooves can be regarded as a combination of multiple edge components 11e, 13e extending linearly. In other words, each shoulder block 12 has multiple edge components 11e, 13e extending linearly along the shoulder lug grooves 11 and auxiliary grooves 13. When the edge components 11e, 13e are defined in this manner, in the tire of the present invention, the multiple edge components 11e, 13e form two or more parallel edge groups each consisting of four or more parallel edge components 11e, 13e, and each parallel edge group includes at least one edge component 13e along the auxiliary groove 13 and at least one edge component 11e along the shoulder lug groove 11.

[0025] 3, points are indicated at the points (bending points) where the edge components 11e and 13e connect, and a symbol ">" is added to the line connecting the parallel edge components 11e and 13e to indicate the parallel relationship of the edge components, and three sets of parallel edge groups are formed as shown. More specifically, the edge components 11e along the shoulder lug groove 11 on one side in the tire circumferential direction (the left side in the figure) are defined as a first edge component e1, a second edge component e2, and a third edge component e3 from the outer side in the tire width direction, and the edge components 11e along the shoulder lug groove 11 on the other side in the tire circumferential direction (the right side in the figure) are defined as a first edge component e1, a second edge component e2, and a third edge component e3 from the outer side in the tire width direction. Furthermore, the plurality of edge components 13e along the groove wall on one side in the tire circumferential direction (left side in the drawing) of the auxiliary groove 13 on one side in the tire circumferential direction (left side in the drawing) are defined as a first edge component e1, a second edge component e2, and a third edge component e3 from the outer side in the tire width direction, the plurality of edge components 13e along the groove wall on the other side (right side in the drawing) of the auxiliary groove 13 on one side in the tire circumferential direction (left side in the drawing) are defined as a first edge component e1, a second edge component e2, and a third edge component e3 from the outer side in the tire width direction, and the edge component 13e located at the inner end in the tire width direction of the auxiliary groove 13 on one side in the tire circumferential direction (left side in the drawing) is defined as a terminal edge component e T Similarly, the plurality of edge components 13e along the groove wall on one side in the tire circumferential direction (left side in the drawing) of the auxiliary groove 13 on the other side in the tire circumferential direction (right side in the drawing) are defined as a first edge component e1 and a second edge component e2 from the outer side in the tire width direction, the plurality of edge components 13e along the groove wall on the other side (right side in the drawing) of the auxiliary groove 13 on the other side in the tire circumferential direction (right side in the drawing) are defined as a first edge component e1 and a second edge component e2 from the outer side in the tire width direction, and the edge component 13e located at the inner end in the tire width direction of the auxiliary groove 13 on the other side in the tire circumferential direction (right side in the drawing) is defined as a terminal edge component e TIn this case, in the embodiment of Fig. 3, a group of five parallel edges is formed, consisting of first edge components e1, e1 on both sides in the tire circumferential direction of the auxiliary groove 13 on one side in the tire circumferential direction (left side in the drawing), first edge components e1, e1 on both sides in the tire circumferential direction of the auxiliary groove on the other side in the tire circumferential direction (right side in the drawing), and a first edge component e1 of the shoulder lug groove 11 on the other side in the tire circumferential direction (right side in the drawing). A group of four parallel edges is formed: the second edge components e2, e2 on both sides in the circumferential direction of the tire, and the second edge component e2 of the shoulder lug groove 11 on the other side in the circumferential direction of the tire (right side in the figure); and a group of four parallel edges is formed: the third component e3 of the shoulder lug groove 11 on one side in the circumferential direction of the tire (left side in the figure), the third edge components e3, e3 on both sides in the circumferential direction of the auxiliary groove 13 on one side in the circumferential direction of the tire (left side in the figure), and the third edge component e3 of the shoulder lug groove 11 on the other side in the circumferential direction of the tire (right side in the figure).

[0026] By providing the auxiliary grooves 13 in the shoulder blocks 12 as described above, the groove components are increased, improving snow performance. However, because the auxiliary grooves 13 are smaller in depth than the shoulder lug grooves 11, the deterioration of noise performance associated with the increased groove components is also prevented. Furthermore, because the shoulder lug grooves 11 and the auxiliary grooves 13 each have a curved shape as described above, noise caused by the tread pattern is prevented from radiating outside the vehicle through the grooves. Meanwhile, because two or more sets of parallel edge groups are formed, each containing at least one edge component 13e along the auxiliary groove 13 and at least one edge component 11e along the shoulder lug groove 11, the mutually parallel edge components 11e, 13e included in the parallel edge groups synergistically ensure an excellent edge effect, effectively improving snow performance. This cooperation achieves both high levels of snow performance and low noise performance.

[0027] The edge components 11e, 13e that form the parallel edge group do not need to be completely parallel (their angles with respect to the tire width direction are completely the same), and can be considered parallel as long as the difference in angle between them is less than 10°. In other words, a collection of edge components 11e, 13e that are inclined in the same direction and have an angle difference of preferably less than 10°, more preferably 7° or less, and even more preferably 5° or less is defined as a parallel edge group in the present invention.

[0028] The combination of edge components 11e, 13e that form the parallel edge group is not particularly limited. As described above, any combination can be used as long as it includes at least one edge component 13e along the auxiliary groove 13 and at least one edge component 11e along the shoulder lug groove 11, and is formed of four or more edge components including these. However, it is preferable that the parallel edge components are close to each other in the tire width direction. For example, it is preferable that the first edge components e1, the second edge components e2, and the third edge components e3, as defined above, form the parallel edge group.

[0029] In addition to including the parallel edge group described above, an edge component 13e (the terminal edge component e in the above description) located at the end of the plurality of auxiliary grooves 13 on the inner side in the tire width direction T ) are preferably parallel to each other. This further improves the edge effect, which is advantageous for improving snow performance. In the illustrated example, the terminal edge components e T are parallel to each other, but when three or more auxiliary grooves 13 are provided, at least two of the terminal edge components e T are preferably parallel to each other.

[0030] It is preferable that the edge components 11e, 13e are all inclined to one side with respect to the tire width direction. In other words, using the first to third edge components e1 to e3 in Figure 3, it is preferable that the first to third edge components e1 to e3 in each of the shoulder lug groove 11 and the auxiliary groove 13 are all inclined to one side with respect to the tire width direction. This causes the shoulder lug groove 11 and the auxiliary groove 13 to be inclined to one side with respect to the tire width direction as a whole, which further improves the edge effect and is advantageous for improving snow performance.

[0031] The inclination angle of each edge component 11e, 13e relative to the tire width direction can be preferably set to 0° to 60°, more preferably 40° to 60°. In the present invention, it is important that the curved shape of the shoulder lug grooves 11 and auxiliary grooves 13 and the aforementioned group of parallel edges are formed by combining edge components 11e, 13e with different inclination angles, so the inclination angles of the individual edge components 11e, 13e are not particularly limited. However, if the inclination angles of all edge components 11e, 13e are within the above-mentioned range, the overall shape of the shoulder lug grooves 11 and auxiliary grooves 13 will be good, which is advantageous for further improving the edge effect and improving snow performance.

[0032] As shown in Figure 3, the auxiliary groove 13 is preferably provided closer to the ground contact edge E than the center of the shoulder block 12 in the tire width direction. In particular, the distance A along the tire width direction from the ground contact edge E to the innermost end of the auxiliary groove 13 in the tire width direction is preferably 5% to 45%, and more preferably 15% to 35%, of the length B of the shoulder block 12 in the tire width direction. When a tire runs on an unpaved road (e.g., a snowy road), the shoulder portion of the tire will be buried to a certain extent in snow or the like on the road surface. Therefore, by locating the auxiliary groove in the aforementioned position, the auxiliary groove will act effectively against snow or the like, which is advantageous for improving snow performance.

[0033] When providing auxiliary grooves 13 in each shoulder block 12, the total area of ​​the auxiliary grooves 13 is preferably 1% to 10%, more preferably 2% to 6%, of the tread area of ​​the shoulder block 12. The tread area of ​​the shoulder block 12 refers to the area surrounded by the outer contour of the shoulder block 12, including the auxiliary grooves 13 and sipes 14 formed on the tread surface of the shoulder block 12. This optimizes the proportion of the area of ​​the auxiliary grooves 13 in each shoulder block 12, thereby achieving a good balance between ensuring edge components and suppressing noise. If the ratio of the total area of ​​the auxiliary grooves 13 to the tread area of ​​the shoulder block 12 is less than 1%, the small number of auxiliary grooves 13 limits the effect of enhancing the edge effect. If the ratio of the total area of ​​the auxiliary grooves 13 to the tread area of ​​the shoulder block 12 exceeds 10%, the effect of reducing exterior noise is limited.

[0034] In addition to the auxiliary grooves 13 described above, sipes 14 and notched grooves 15 may be optionally provided on the tread surface of the shoulder block 12, as shown in the example of Figure 3. The shape and number of these sipes 14 and notched grooves 15 are not particularly limited, but it is preferable to provide the same number of sipes 14 as the auxiliary grooves 13 (two in the example shown), and for example, to have a zigzag shape. It is preferable to provide the notched groove 15, for example, at a position adjacent to the shoulder lug groove 11 adjacent to one side of the shoulder block 12.

[0035] The present invention will be further explained below with reference to examples, but the scope of the present invention is not limited to these examples.

[0036] Pneumatic tires of Conventional Example 1, Comparative Example 1, and Examples 1 to 13 were produced, each having a tire size of LT265 / 70R17 115T and the basic structure (cross-sectional structure) illustrated in FIG. 1 , with the number of auxiliary grooves formed in one shoulder block, the number of parallel edge groups, the relationship between the terminal edge components of the auxiliary grooves formed in one shoulder block, the auxiliary groove width, the auxiliary groove depth, the inclination direction of the edge components, the auxiliary groove arrangement, and the auxiliary groove area set as shown in Tables 1 and 2.

[0037] The tread pattern in the center region was common to all examples, with one row of blocks arranged between a pair of main grooves on each side of the tire equator.

[0038] In the "Relationship of Terminal Edge Components" column in Tables 1 and 2, if the terminal edge components of the auxiliary grooves formed in one shoulder block are parallel, it is indicated as "parallel," and if they are not parallel, it is indicated as "non-parallel." "Auxiliary Groove Width" indicates the ratio (unit: %) of the minimum groove width of the shoulder lug groove. "Auxiliary Groove Depth" indicates the ratio (unit: %) of the minimum groove depth of the shoulder lug groove. "Edge Component Inclination Direction" column indicates "unidirectional" if all edge components are inclined in one direction relative to the tire width direction, and "zigzag" if the inclination direction of the edge components is not fixed to one direction and bends in a zigzag pattern. "Auxiliary Groove Arrangement" column indicates the ratio (unit: %) of the distance along the tire width direction from the contact edge to the inner end of the auxiliary groove in the tire width direction to the length of the shoulder block in the tire width direction. "Auxiliary Groove Area" indicates the ratio (unit: %) of the total area of ​​the auxiliary grooves (the sum of the auxiliary grooves formed in one shoulder block) to the area of ​​the shoulder block tread surface.

[0039] These pneumatic tires were evaluated for snow performance and low noise performance by the following evaluation methods, and the results are shown in Tables 1 and 2.

[0040] Snow Performance Each test tire was mounted on a wheel with a rim size of 17x8J, inflated to an air pressure of 340 kPa, and mounted on a test vehicle (a four-wheel drive SUV). A test driver performed a sensory evaluation of traction (starting performance) on a test road consisting of a snowy road surface. The evaluation results were expressed as an index, with the value of Conventional Example 1 being 100. A higher index value indicates better snow performance (snow traction performance).

[0041] The low-noise performance test tire was mounted on a 17x8J rim wheel, inflated to 340 kPa, and mounted on a test vehicle (a four-wheel-drive SUV). External pass-by noise was measured in accordance with the tire noise test method specified in ECE R117-02. Specifically, the test vehicle was run 10 minutes before passing through the noise measurement section, the engine was stopped just before the section, and the vehicle was coasted. The maximum noise value (dB) (noise value in the frequency range of 800 Hz to 1200 Hz) in the noise measurement section was measured at multiple speeds within a ±10 km / h range from the reference speed (50 km / h) divided into eight or more equal intervals. The average value was used as the external pass-by noise. The maximum noise value was measured as sound pressure through an A-weighted frequency weighting circuit using a stationary microphone installed at the midpoint of the noise measurement section, 7.5 m laterally from the centerline of the road and 1.2 m above the road surface. The evaluation results are shown as the amount of change (unit: dB) relative to the measured value of Conventional Example 1. When the outside passing noise decreased, it was shown as a negative value.

[0042]

[0043]

[0044] As is clear from Tables 1 and 2, the pneumatic tires of Examples 1 to 13 had improved snow performance and low noise performance, and achieved a good balance between these performances, compared to Conventional Example 1. On the other hand, Comparative Example 1 did not achieve the effect of improving snow performance and low noise performance because only one set of parallel edges was formed.

[0045] REFERENCE SIGNS LIST 1 tread portion 2 sidewall portion 3 bead portion 4 carcass layer 5 bead core 6 bead filler 7 belt layer 8 belt reinforcing layer 10 main groove 11 shoulder lug groove 12 shoulder block 13 auxiliary groove 11e, 13e edge component 14 sipe 15 notch groove CL tire equator E ground contact edge

Claims

1. A tire having a circumferentially extending annular tread portion, the surface of the tread portion having a pair of main grooves extending circumferentially on both sides of the tire equator, and a shoulder region located on the outer side of the main grooves in the tire width direction, having a plurality of shoulder lug grooves extending from the main grooves toward the outer side in the tire width direction and spaced apart in the tire circumferential direction, and a plurality of shoulder blocks partitioned by the main grooves and the shoulder lug grooves and arranged in the tire circumferential direction, the surface of each shoulder block having a plurality of auxiliary grooves whose groove depth is smaller than that of the shoulder lug grooves, and each auxiliary groove extending from the tread surface of each shoulder block across the ground contact edge toward the side surface of each shoulder block, a tire characterized in that, on the tread surface, each shoulder block has a plurality of edge components extending linearly along the shoulder lug grooves and the auxiliary grooves, the contour lines of the shoulder lug grooves and the auxiliary grooves each have a curved shape formed by a combination of the plurality of edge components, the plurality of edge components form two or more parallel edge groups each consisting of four or more edge components parallel to each other, and each parallel edge group includes at least one edge component along the auxiliary groove and at least one edge component along the shoulder lug groove.

2. The tire according to claim 1, wherein at least two of the edge components located at the inner ends in the tire width direction of the plurality of auxiliary grooves are parallel to each other.

3. The tire according to claim 1 or 2, characterized in that the groove width of the auxiliary groove is 10% to 50% of the minimum groove width of the shoulder lug groove.

4. A tire according to any one of claims 1 to 3, characterized in that the groove depth of the auxiliary groove is 3% to 30% of the minimum groove depth of the shoulder lug groove.

5. A tire according to any one of claims 1 to 4, characterized in that all of the edge components are inclined to one side with respect to the tire width direction.

6. A tire according to any one of claims 1 to 5, characterized in that the auxiliary groove is provided on the side of the shoulder block closer to the ground contact edge than the center in the tire width direction.

7. A tire according to any one of claims 1 to 6, characterized in that the total area of ​​said auxiliary grooves is 1% to 10% of the area of ​​the tread surface of said shoulder block.

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