Tire

Abstract

The tire has a plurality of circumferential main grooves (2) on a tread surface (1). The tire is characterized in that, when a pair of circumferential main grooves arranged closest to the tire width direction both sides of the tread end are called shoulder main grooves (21a) and (21b) from among the plurality of circumferential main grooves (2), at least one of the shoulder main grooves is a normal main groove configured so that, in the groove depth direction, a maximum groove width position is only at a tread surface position, and at least one circumferential main groove other than the at least one shoulder main groove is a widened main groove configured so that at least one maximum groove width position is located at a position on the groove bottom side from the tread surface position in the groove depth direction.

Description

Technical Field

[0001] This disclosure relates to a tire. Background Technology

[0002] Regarding noise generated by a moving vehicle, as vehicles become quieter, the proportion of noise caused by the rolling load of the tires increases, thus requiring a reduction in this proportion. Among these, noise caused by air column resonance is a major source of external noise generated by the tires. Air column resonance is noise generated by the resonance of air within the circumferential grooves continuously extending circumferentially on the tire tread surface and the ducts surrounded by the road surface.

[0003] For example, a tire designed to reduce air column resonance noise has a Helmholtz-type resonator disposed in a land section divided by a plurality of circumferential main grooves. The Helmholtz-type resonator includes a chamber substantially sealed within the land section and terminating at both ends in the longitudinal direction within the land section, a connecting hole connecting the chamber and the circumferential main grooves, and a cutter groove (Patent Document 1).

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2019-116195 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] However, simpler construction methods are needed to reduce air column resonance noise.

[0009] Therefore, the purpose of this disclosure is to provide a tire that can reduce air column resonance noise during vehicle operation.

[0010] Solution for solving the problem

[0011] The main points of this disclosure are as follows.

[0012] A tire includes a plurality of circumferential main grooves on its tread surface, the circumferential main grooves extending circumferentially and having a groove width that prevents two sidewalls from contacting each other when the tire touches the ground, wherein...

[0013] When the pair of circumferential main grooves positioned closest to the tread ends in the tire width direction are referred to as the shoulder main grooves,

[0014] At least one of the shoulder main grooves is a normal main groove, which is configured such that the maximum groove width in the groove depth direction is located only at the tread surface, and

[0015] In addition to the at least one shoulder main groove, at least one circumferential main groove is a widened main groove, which is configured such that at least one maximum groove width position in the groove depth direction is located on the bottom side of the groove than the tread surface position.

[0016] The effects of the invention

[0017] According to this disclosure, it is possible to provide a tire that can reduce air column resonance noise when a vehicle is in motion. Attached Figure Description

[0018] In the attached diagram:

[0019] [ Figure 1 ] Figure 1 This is a partial unfolded view of a tire according to the first embodiment of the present disclosure, which schematically illustrates the tread surface;

[0020] [ Figure 2 ] Figure 2 This is a cross-sectional view of the tire in the width direction, which illustrates... Figure 1 The tires in the middle are along Figure 1 The portion of the cross section of line AA in the middle;

[0021] [ Figure 3A ] Figure 3A This is a partial cross-sectional view along the width of the tire, which schematically illustrates... Figure 2 The enlarged section of the tire in the image;

[0022] [ Figure 3B ] Figure 3B This is a partial cross-sectional view along the width of the tire, which schematically illustrates... Figure 2 The enlarged section of the tire in the image;

[0023] [ Figure 4 ] Figure 4 It is a diagram used to illustrate the frequencies of air column resonance sound;

[0024] [ Figure 5 ] Figure 5 Another example of a widened main slot is illustrated;

[0025] [ Figure 6 ] Figure 6 This is a partial unfolded view of a tire according to the second embodiment of the present disclosure, which schematically illustrates the tread surface;

[0026] [ Figure 7 ] Figure 7 It is a diagram used to illustrate the frequencies of air column resonance sound;

[0027] [ Figure 8 ] Figure 8 It is a schematic diagram. Figure 6A partially unfolded view of the enlarged portion of the tire tread surface; and

[0028] [ Figure 9 ] Figure 9 This illustrates another example of a width-oriented slot. Detailed Implementation

[0029] The tires disclosed herein can be used for any type of tire. However, they are suitable for use in passenger car tires.

[0030] In the following description, embodiments of the tire according to the present disclosure will be illustrated by way of example with reference to the accompanying drawings. Common components in each figure are given the same reference numerals.

[0031] The tire in each embodiment described herein may have any internal configuration. For example, the tire in each embodiment may include a pair of bead cores (not shown) disposed in a pair of bead portions, a pair of bead fillers (not shown) located radially outside the bead cores, and a tire carcass 70 ( Figure 2 ), belt section 60 ( Figure 2 ), tread rubber 80 ( Figure 2 The carcass 70 extends annularly between a pair of bead cores. The carcass 70 includes at least one carcass ply (one in the illustrated example). The carcass ply of the carcass 70 may be made of, for example, rubber-coated steel cords or organic fiber cords. The carcass 70 may include, for example, a body portion extending annularly between a pair of bead cores and a pair of folded-back portions folded back from the innermost radial end of the body portion around the bead cores toward the outer side in the tire width direction on each side of the tire equatorial plane CL. A belt portion 60 is arranged radially outward in the tread portion 90 in the crown region of the carcass 70. Figure 2 The belt portion 60 consists of at least one belt layer (two layers in the illustrated example). The belt layer may be made of, for example, rubber-coated steel cord or organic fiber cord. The tread rubber 80 is disposed on the radially outer side of the belt portion 60.

[0032] As used herein, the term “tread surface (1)” means the outer peripheral surface of the tire that is in contact with the road surface when the tire is mounted on a rim, filled with a specified internal pressure and rolling under maximum load.

[0033] As used in this article, the term "tread end" means the outer end of the tread surface in the tire width direction.

[0034] Furthermore, as used herein, the term “grounding length” means the length of the tire’s contact patch along the tire’s circumference, and the term “grounding patch” means the outer surface of the tire that contacts the road surface when the tire is mounted on a rim, inflated to a specified internal pressure, and grounded under maximum load.

[0035] Here, the term "rim" refers to a standard rim of applicable size as recorded or potentially to be recorded in an industry standard effective in the region where the tire is produced and used (measured rims in the ETRTO Standards Manual and designed rims in the TRA Yearbook), such as the JATMA Yearbook of Japan's JATMA (Japan Automobile Tire Manufacturers Association), the standards manual of ETRTO (European Tire and Rim Technology Organization) in Europe, and the yearbook of TRA (Tire and Rim Association) in the United States (i.e., "rim" includes current sizes as well as future sizes to be listed in the aforementioned industry standards. An example of "future sizes" could be sizes listed as "FUTURE DEVELOPMENTS" in the 2013 edition of the ETRTO Standards Manual). For sizes not listed in the aforementioned industry standards, the term "rim" refers to a rim whose width corresponds to the width of the tire's bead.

[0036] Furthermore, "specified internal pressure" refers to the air pressure (maximum air pressure) corresponding to the maximum load capacity of a single wheel for the applicable size and ply rating as described in the aforementioned JATMA Yearbook and other industry standards. In the case of sizes not listed in the aforementioned industry standards, "specified internal pressure" refers to the air pressure (maximum air pressure) corresponding to the maximum load capacity specified for each vehicle with the tires mounted.

[0037] The term "maximum load" should mean the load corresponding to the maximum load capacity mentioned above.

[0038] Note that the term "air" as used in this article may be replaced by inert gases such as nitrogen or other inert gases.

[0039] In this document, unless otherwise specified, dimensions such as the dimensions of the various elements of the trench and land section, the ground width (TW), etc., shall be measured under the “reference conditions” described below.

[0040] In this document, "baseline condition" refers to the condition in which the tire is mounted on the rim, filled with the specified internal pressure as described above, and is unloaded.

[0041] Furthermore, in this document, "groove width of the circumferential main groove" should mean the length in the direction perpendicular to the extension direction of the circumferential main groove when measured under the aforementioned reference conditions. Similarly, "groove width of the width direction groove" should mean the length in the direction perpendicular to the extension direction of the width direction groove when measured under the reference conditions.

[0042] [First Implementation Method]

[0043] Reference Figure 1 , Figure 2 , Figure 3A and Figure 3B The tire according to the first embodiment of this disclosure is described below.

[0044] Figure 1 This is a partial unfolded view of a tire 10 according to the first embodiment of the present disclosure, which schematically illustrates the tread surface 1. Figure 2 This is a cross-sectional view of the tire in the width direction, which illustrates... Figure 1 Tire 10 in the middle along Figure 1 The portion of the cross section of line AA in the middle. Figure 3A This is a partial cross-sectional view along the width of the tire, which schematically illustrates... Figure 2 The enlarged portion of the tire in the image, and Figure 3B This is a partial cross-sectional view along the width of the tire, which schematically illustrates... Figure 2 An enlarged view of the tires in the image.

[0045] like Figure 1 As shown, the tire 10 of the first embodiment includes a plurality of circumferential main grooves 2 on the tread surface 1. Each circumferential main groove 2 extends along the tire circumference. Each circumferential main groove 2 can extend in a straight line along the circumference, such as... Figure 1 As shown, they can extend circumferentially in a zigzag or wavy pattern. Among the multiple circumferential main grooves 2, the pair of circumferential main grooves located at the tread ends TE closest to each side in the tire width direction are referred to as a pair of shoulder main grooves 21a and 21b. In addition, one or more circumferential main grooves located inside the pair of shoulder main grooves in the tire width direction are referred to as one or more central main grooves 22.

[0046] From the point of view of drainage performance, the number of circumferential main channels 2 should be more than three (three in this embodiment), but two can also be used.

[0047] Each circumferential main groove 2 has a groove width that prevents the two sidewalls from contacting each other when the tire touches the ground. That is, the circumferential main groove is constructed such that when the tire is mounted on the rim, filled with a specified internal pressure and loaded with the maximum load, a pair of opposing groove walls located directly below the load do not contact each other.

[0048] Furthermore, the tread surface 1 of the tire 10 in the first embodiment has four land portions 31a, 31b, 32a, and 32b defined by shoulder main grooves 21a and 21b, a central main groove 22, and a tread end TE. The tread end TE and the shoulder main grooves 21a and 21b define the shoulder land portions 31a and 31b located on the outer side in the tire width direction, and the central main groove 22 and the shoulder main grooves 21a and 22b define the central land portions 32a and 32b located on the inner side in the tire width direction of the land portions 31a and 31a.

[0049] like Figure 2 and Figure 3AAs shown, at least one shoulder main groove (both of the pair of shoulder main grooves 21a and 21b in the first embodiment) is a normal main groove, which is configured such that the maximum groove width in the groove depth direction is located only at the tread surface position. That is, for shoulder main grooves 21a and 21b, in the reference state, the groove width w1 at the position of the tread surface 1 is the maximum groove width, and the groove width is less than the groove width w1 at any position on the radially inner side of the tread surface 1, i.e., the groove bottom side. In the tire 10 of this embodiment, the groove width gradually decreases from the tread surface 1 side with groove width w1 toward the radially inner side of the tire, and the groove width w2 at the groove bottom is the minimum groove width. Note that the "normal main groove" only needs to have the maximum groove width at the tread surface position, while the minimum groove width can be at a position other than the groove bottom.

[0050] Here, "gradually decreasing" means that the slot width is constantly decreasing.

[0051] In addition, such as Figure 2 and Figure 3B As shown, at least one circumferential main groove (central main groove 22 in this embodiment), in addition to the at least one shoulder main groove, is a widened main groove. The widened main groove is configured such that at least one maximum groove width position in the groove depth direction is located closer to the bottom of the groove than the tread surface position. In this example, for the central main groove 22, in the baseline state, the groove width w4 at the groove bottom is the maximum groove width, and the groove width is less than w4 at any position radially outward from the groove bottom, i.e., on the tread surface 1 side. In this embodiment, the groove width gradually decreases from the groove bottom side with groove width w4 towards the radially outward side of the tire, and the groove width w3 at the tread surface 1 is the minimum groove width. Note that a "widened main groove" only needs to have at least one maximum groove width position in the groove depth direction at a position closer to the bottom of the groove than the tread surface position. Therefore, the term "widened main groove" should include configurations with multiple maximum groove width positions in the groove depth direction and configurations with a constant groove width in the groove depth direction. However, from the viewpoint of more effectively reducing air column resonance noise, etc., it is preferred, as described below, that the "widened main groove" does not have a constant groove width in the groove depth direction, and that all maximum groove width positions in the groove depth direction are closer to the bottom side of the groove than the tread surface.

[0052] In the following text, reference will be made to Figure 4 The effects of the tire structure of the first embodiment are explained.

[0053] Figure 4 This is a diagram used to illustrate the frequency of the air column resonance sound in the circumferential main groove. Figure 4 The relationship between sound pressure and frequency of the air column resonance sound in the normal main slot and the widened main slot is provided.

[0054] In a normal main groove, the maximum groove width is located only at the tread surface, so the groove opening in contact with the road surface and air is open. In contrast, in a widened main groove, the maximum groove width is located closer to the bottom of the groove than at the tread surface, so the groove opening in contact with the road surface and air is closed compared to a normal main groove. Here, the widened main groove, due to the modified opening end, appears as a relatively "longer" tube than a normal main groove with the same cross-sectional area. Therefore, when the tube is relatively longer, the frequency of the air column resonance sound generated in the circumferential main groove during vehicle movement is relatively low. Consequently, compared to a normal main groove, the peak sound pressure level in a widened main groove can shift to a lower frequency side.

[0055] In this way, by shifting the peak frequency of the air column resonance sound generated in the circumferential main groove when the vehicle is running between the normal main groove and the widened main groove, the peak value of the sum of these sound pressures can be reduced, thereby reducing the air column resonance sound and softening (making it less harsh) the overall tire noise.

[0056] Furthermore, according to the tire of this embodiment, since the central main groove 22 is configured such that the maximum groove width of the central main groove 22 is located closer to the bottom of the groove than the tread surface, as tire wear progresses, the portion with a larger groove width is exposed on the tread surface 1. Compared to the case where the maximum groove width of the central main groove 22 is located at the tread surface, this improves the drainage performance as tire wear progresses and suppresses the decline in drainage performance even as tire wear progresses. Since the central main groove 22 is located inside the shoulder main grooves 21a and 21b in the tire width direction, the ground contact pressure in the tire width direction tends to be higher relative to the shoulder main groove side when the tire is traveling in a straight line. This is particularly effective in ensuring sufficient drainage performance when the tire is traveling in a straight line as tire wear progresses.

[0057] In the following text, preferred constructions and variations of the tire according to the first embodiment will be described.

[0058] In the tire 10 of the first embodiment, the number of normal main grooves and widened main grooves is not limited, as long as there is one or more of both normal main grooves and widened main grooves. However, it is preferred that the circumferential main groove 2 includes a pair of shoulder main grooves 21a and 2b and at least one central main groove 22, and the pair of shoulder main grooves 21a and 21b are normal main grooves and the central main groove 22 is a widened main groove.

[0059] Here, typically, the tire's contact patch length is longer on the equatorial plane (CL) side than on the tread side (TE). Therefore, the contact patch length of the circumferential main groove is also typically longer on the equatorial plane (CL) side than on the tread side (TE). On the other hand, when comparing circumferential main grooves with the same cross-sectional shape and size, the peak sound pressure frequency of the air column resonance is lower in the circumferential main groove with the longer contact patch length than in the circumferential main groove with the shorter contact patch length. Therefore, the circumferential main groove on the equatorial plane (CL) side typically has a lower peak sound pressure frequency of the air column resonance than the circumferential main groove on the tread side (TE). Therefore, by making the circumferential main groove on the tread side (TE) side a normal main groove and the circumferential main groove on the equatorial plane (CL) side a widened main groove (whose peak sound pressure frequency is lower than that of the normal main groove), as described above, the difference in peak sound pressure frequency between the circumferential main groove on the tread side (TE) side and the circumferential main groove on the equatorial plane (CL) side can be further increased, while the peak value of the sum of these sound pressures can be further reduced.

[0060] In other words, the above configuration can balance and distribute the frequency of air column resonance noise when the vehicle is running, so as to more effectively reduce air column resonance noise and soften (make it less harsh) the overall tire noise.

[0061] In the tire 10 of the first embodiment, since the number of the central main groove 22, which is a widened main groove, is 1, and the number of the shoulder main grooves 21a and 21b, which are normal main grooves, is 2, the ratio of the number of widened main grooves to the number of normal main grooves (number of widened main grooves / number of normal main grooves) is 1 / 2. However, the ratio of the number of widened main grooves to the number of normal main grooves is not particularly limited.

[0062] In the tire 10 of the first embodiment, the ratio of the number of widened main grooves to the number of normal main grooves is preferably 1 / 1 to 3 / 2. This configuration can balance and distribute the frequency of air column resonance sound during vehicle operation, so as to more effectively reduce air column resonance sound and soften (make it less harsh) the overall tire noise.

[0063] In the tire 10 of the first embodiment, the central main groove 22, which is a widened main groove, preferably has a portion where the groove width gradually increases from the tread surface 1 side to the groove bottom side. This structure can suppress the decrease in drainage performance as tire wear progresses over a long period of time. More preferably, the groove width gradually increases from the tread surface 1 to the groove bottom. This structure can more effectively suppress the deterioration of drainage performance as tire wear progresses over a long period of time.

[0064] In the tire of the first embodiment, each circumferential main groove 2 needs to have a groove width that prevents the sidewalls from contacting each other when the tire touches the ground, but the minimum groove width ( Figure 3A and Figure 3BIn the example, the groove widths (w2 and w3) are preferably 1.5 mm or more. This construction can reliably reduce air column resonance noise during vehicle operation and ensure adequate water drainage performance both when the tire is new and as tire wear progresses.

[0065] The depth of each circumferential main groove 2 ( Figure 3A and Figure 3B In the example, the groove depths d1 and d2 are preferably 3.0 mm or more. This ensures adequate drainage performance. From the viewpoint of the rigidity of the tire 10, the groove depth of each circumferential main groove 2 ( Figure 3A and Figure 3B In the example, the groove depths d1 and d2 are preferably 20 mm or less. More preferably, in order to ensure adequate drainage performance, the groove depth of each circumferential main groove 2 is 3.0 mm or more, and in terms of the rigidity of the tire 10, the groove depth of each circumferential main groove 2 is 15 mm or less.

[0066] In the tire of the first embodiment 1, the inclination angles θ1 and θ2 of the sidewalls 211 and 222 constituting the shoulder main grooves 21a and 21b, which are normal main grooves, are preferably 91° or more from the perspective of ensuring rigidity. Moreover, from the viewpoint of ensuring sufficient drainage performance, the inclination angles θ1 and θ2 are preferably 150° or less. More preferably, the inclination angles θ1 and θ2 are 100° or more in terms of ensuring rigidity and 130° or less in terms of ensuring sufficient drainage performance.

[0067] Here, "the inclination angle of the sidewalls 211 and 222 that constitute the shoulder main grooves 21a and 21b as normal main grooves" refers to the angle formed by the tread surface 1 and the sidewall 211, and the tread surface 1 and the sidewall 222 at the respective opening ends of the shoulder main grooves 21a and 2b in the tire width direction cross-sectional view.

[0068] In the tire of the first embodiment, the inclination angles θ3 and θ4 of the sidewalls 221 and 222 constituting the central main groove 22, which is a widened main groove, are preferably 30° or more to prevent the open end from bending at the tread surface 1 when the tire touches the ground. Meanwhile, the inclination angles θ3 and θ4 are preferably 89° or less to suppress the decrease in drainage performance as tire wear progresses over a long period. More preferably, from the viewpoint of effectively preventing the open end of the tread surface 1 from bending when touching the ground, the inclination angles θ3 and θ4 are 50° or more; from the viewpoint of more effectively suppressing the deterioration of drainage performance as tire wear progresses over a long period, the inclination angles θ3 and θ4 are 85° or less.

[0069] Here, "the inclination angles of the sidewalls 221 and 222 constituting the central main groove 22 as a widened main groove" refers to the angles formed by the tread surface 1 and the sidewall 221, and the tread surface 1 and the sidewall 222 at the opening end of the central main groove 22, respectively.

[0070] Furthermore, in the tire 10 of the first embodiment, in Figure 3B In the example shown, the sidewalls 221 and bottom 223 of the central main channel 22, which constitutes the widened main channel, are straight in a cross-section perpendicular to the extension direction of the channel. However, as Figure 5 As shown, the boundary between sidewall 221 and bottom 223, and the boundary between sidewall 222 and bottom 223, can be constructed as arc-shaped sidewalls and bottoms with radii of curvature R1 and R2.

[0071] This construction can increase the durability of the central main slot 22, which serves as a widened main slot.

[0072] In the tire 10 of the first embodiment, the values ​​of the radii of curvature R1 and R2 are not limited, but the radii of curvature R1 and R2 are preferably 0.5 mm or more. This structure effectively prevents cracking at the boundary between the sidewall 221 or sidewall 222 and the groove bottom 223, thereby making the central main groove 22 more durable. From the viewpoint of drainage performance, the radii of curvature R1 and R2 are preferably 5.0 mm or less. More preferably, in terms of greater durability of the central main groove 22, the radii of curvature R1 and R2 are 1 mm or more, and in terms of drainage performance, the radii of curvature R1 and R2 are 3.0 mm or less.

[0073] In this embodiment, the central main groove 22 is preferably located entirely within the central region C, and the shoulder main grooves 21a and 21b are preferably located entirely within the shoulder regions S, respectively. Here, the central region C refers to the area on the tread surface 1 centered on the tire equatorial plane CL and whose width in the tire width direction is 50% of the ground contact width TW. On the other hand, the shoulder regions S refer to a pair of areas on the tread surface 1 located on the outer side of the tread surface 1 in the tire width direction, compared to the central region C.

[0074] This design can more effectively reduce air column resonance noise and ensure adequate drainage performance.

[0075] Furthermore, in the tire 10 of the first embodiment, the contact length of the tire 10 is appropriately longer on the equatorial plane CL side than on the tread end TE side. Moreover, in the tire 10 of the first embodiment, the contact length of the circumferential main groove 2 is appropriately longer in the central main groove 22 than in the shoulder main grooves 21a and 21b.

[0076] As described above, this configuration reliably shifts the peak frequency of the air column resonance sound generated in the circumferential main groove during vehicle operation between the normal main groove and the widened main groove, thereby reducing the air column resonance sound and softening (making it less harsh) the overall tire noise.

[0077] [Second Implementation]

[0078] Next, we will refer to Figure 6 This describes a tire according to another embodiment (second embodiment) of the present disclosure. Except for including a width-direction groove connected to the normal main groove, the tire 11 of the second embodiment has the same construction as the tire 10 of the first embodiment, and the same components as those in the first embodiment are given the same reference numerals, and their descriptions are omitted.

[0079] Figure 6 This is a partial unfolded view of a tire 11 according to the second embodiment of the present disclosure, which schematically illustrates the tread surface.

[0080] The tire 11 of the second embodiment includes a width direction groove 4, which is connected to the shoulder main grooves 21a and 21b, which are normal main grooves, extends along the tire width direction (in this embodiment, at a predetermined angle of more than 0° relative to the tire width direction) and opens at the tread end TE.

[0081] In the tire 11 of the second embodiment, the width direction groove 4 is arranged on the shoulder land portions 31a and 31b, respectively connected to the shoulder main groove 21a or 21b, extends along the tire width direction, and opens at the tread end TE.

[0082] The width-direction groove 4 can be configured either linearly or point-symmetrically with respect to the tire equatorial plane CL, and does not necessarily need to be configured either linearly or point-symmetrically with respect to the tire equatorial plane CL. Figure 6 In the example, the width direction groove 4 arranged on the shoulder land portion 31a and the width direction groove 4 arranged on the shoulder land portion 31b are configured to be offset along the tire circumferential direction from a state symmetrical with respect to the tire equatorial plane CL point.

[0083] In the following text, reference will be made to Figure 7 The effects of the tire 11 structure in the second embodiment will be explained.

[0084] Figure 7 This is a diagram used to illustrate the frequency of the resonant sound of the air column in the circumferential main groove. Figure 7 The relationship between sound pressure and frequency of air column resonance sound in normal main slot (with width direction slot), normal main slot (without width direction slot), and widened main slot is provided.

[0085] Here, "normal main groove (with width direction groove)" refers to a normal main groove that has a width direction groove that is connected to the normal main groove, extends along the width direction of the tire, and opens at the TE end of the tread. "normal main groove (without width direction groove)" refers to a normal main groove that does not have a width direction groove.

[0086] By adding a width-direction groove to the normal main groove, connecting it to the tread end TE, the air column resonance sound in the normal main groove will have a relatively higher frequency than the air column resonance sound in a normal main groove without a width-direction groove. Therefore, compared to a normal main groove without a width-direction groove, a normal main groove with a width-direction groove can shift the peak sound pressure level to a higher frequency side.

[0087] Furthermore, similar to the widened main groove of the tire 10 in the first embodiment, in the tire 11 of the second embodiment, the peak sound pressure level can be shifted to the lower frequency side in the widened main groove compared to the normal main groove which does not have a width direction groove.

[0088] In this way, the peak frequency of the air column resonance sound generated in the circumferential main slot when the vehicle is moving can be shifted more significantly between the normal main slot with the width direction slot and the widened main slot, and the peak value of the sum of these sound pressures can be lower, thus more effectively reducing air column resonance sound. This allows for more effective reduction of air column resonance sound.

[0089] In the following text, refer to Figure 6 and Figure 8 The preferred construction and variations of the width direction groove 4 will be explained. Figure 8 This is a partial unfolded diagram, which schematically illustrates... Figure 6 An enlarged view of the tread surface. However, for illustrative purposes only. Figure 8 With Figure 6 Draw at a slightly different scale.

[0090] Although the width direction grooves 4 are respectively arranged in the shoulder land portions 31a and 31b, as described above, in Figure 6 In the example, the width direction grooves 4 are identical in construction, except that they are configured to be offset circumferentially from a state symmetrical with respect to the tire equatorial plane CL point. Therefore, the width direction grooves 4 arranged in the shoulder land portion 31a will be described below as a typical example.

[0091] The width-direction groove 4 can have a shape with a constant groove width on the tread surface 1 or a shape with a groove width that changes midway in the tire width direction. Compared to the side connected to the shoulder main groove 21a, which serves as a normal main groove, the width-direction groove 4 preferably has a larger groove width at the tread surface 1 on the side opening towards the tread end TE. Figure 8 As shown, the width direction groove 4 includes a first width direction groove portion 4a connected to the main shoulder groove 21a and a second width direction groove portion 4b adjacent to and connected to the tread end TE side of the first width direction groove portion 4a and opening at the tread end TE. The groove width w6 of the second width direction groove portion 4b at the tread surface 1 is greater than the groove width w5 of the first width direction groove portion 4a at the tread surface 1.

[0092] According to this configuration, an airflow is formed from the narrower width-direction groove first portion 4a connected to the main shoulder groove 21a to the wider width-direction groove second portion 4b. This promotes airflow to the outer side in the tire width direction and further reduces air column resonance noise. Furthermore, moisture can easily flow from the narrower width-direction groove first portion 4a to the wider width-direction groove second portion 4b, which facilitates drainage to the tread end TE side and ensures adequate water drainage performance of the tire.

[0093] In the width direction groove 4, the groove width w5 of the first portion 4a of the width direction groove connected to the main shoulder groove 21a is preferably at least 1 mm narrower than the groove width w6 of the second portion 4b of the width direction groove. This configuration allows for more effective reduction of air column resonance noise.

[0094] In the tire 11 of the second embodiment, the groove width w5 of the first portion 4a of the width direction groove at the tread surface 1 is preferably 0.3 mm or more. This configuration allows sufficient air to flow from the main shoulder groove 21a into the first portion 4a of the width direction groove, thereby providing better reduction of air column resonance noise. More preferably, the groove width w5 is 0.4 mm or more.

[0095] In the width direction groove 4, the groove width w6 of the second part 4b of the width direction groove, which opens at the tread end TE, at the tread surface 1 only needs to have a groove width that prevents the two sidewalls from contacting each other when the tire touches the ground, but more preferably has a groove width of 1.5 mm or more. This structure can effectively reduce air column resonance noise and ensure sufficient water drainage performance.

[0096] The groove depth of the first portion 4a of the width-direction groove 4 is preferably approximately the same as the groove depth of the second portion 4b of the width-direction groove. This is because, according to this configuration, drainage performance can be maintained and air column resonance noise can be reduced even after tire wear.

[0097] Furthermore, in the width-direction groove 4, the groove depth of the second portion 4b is preferably the same as the depth of the main shoulder groove 21a. More specifically, the groove depth of the second portion 4b is suitably 3.0 mm or more. This ensures adequate water drainage performance. From the viewpoint of the rigidity of the tire 11, the groove depth of the second portion 4b is suitably 20 mm or less. More preferably, in order to ensure adequate water drainage performance, the groove depth of the second portion 4b is 5.0 mm or more, and in terms of the rigidity of the tire 10, this groove depth is 15 mm or less.

[0098] exist Figure 6 and Figure 8In the example, the width-direction groove 4 has a length L1 along its extension direction of the first portion 4a of the width-direction groove, which is shorter than the length L2 along its extension direction of the second portion 4b of the width-direction groove. However, not limited to this configuration, the length L1 along its extension direction of the first portion 4a of the width-direction groove can be longer than the length L2 along its extension direction of the second portion 4b of the width-direction groove, such as... Figure 9 As shown. However, in terms of providing a volume difference between the first portion 4a and the second portion 4b of the width direction groove to reduce air column resonance sound, it is preferable that the length L1 is shorter than the length L2.

[0099] The width-direction groove 4 preferably has an inclination angle θ5 of 0° to 20° relative to the tire width direction at the tread surface 1. By setting the inclination angle between 0° and 20°, air column resonance noise can be reduced, while preventing uneven wear and other noise generation at the opening end of the width-direction groove 4 leading to the main shoulder groove 21a. From the viewpoint of preventing uneven wear and other noise generation, the inclination angle θ5 is more preferably between 5° and 15°.

[0100] In the second embodiment, the width-direction groove 4 is preferably arranged at both ends of the contact surface of the tire 11 such that the number of grooves in the contact surface is 4 to 10 at both ends of the contact surface. Here, regarding the "number of grooves in the contact surface", if any part of the width-direction groove 4 is located in the contact surface, it is considered that the width-direction groove 4 is located in the contact surface.

[0101] This design can more effectively reduce air column resonance noise and ensure adequate drainage performance.

[0102] More specifically, the width-direction grooves 4 are preferably arranged at intervals of 10 mm to 40 mm along the tire circumference on one side of the tread end TE, bounded by the tire equatorial plane CL. This configuration can more effectively reduce air column resonance noise and ensure adequate water drainage performance. More preferably, the width-direction grooves 4 are arranged at intervals of 20 mm to 30 mm along the tire circumference.

[0103] Industrial availability

[0104] The tires disclosed herein can be used for any type of pneumatic tire, but are suitable for use as pneumatic tires for passenger cars.

[0105] List of reference numerals

[0106] 1. Tread surface

[0107] 2 Circumferential Main Slots

[0108] 4. Width-direction groove

[0109] 4a Width Direction Groove, First Part

[0110] 4b Width Direction Groove Part 2

[0111] Tires 10 and 11

[0112] 21a, 21b Tire shoulder main groove

[0113] 22 Central Main Channel

[0114] 31a, 31b Tire shoulder land

[0115] 32a, 32b Central Land Forces

[0116] 60 Belt section

[0117] 70 fetuses

[0118] 80 Tread Rubber

[0119] 90 Tire Face

[0120] Side walls 211, 212, 221, 222

[0121] 213, 223 trough bottom

[0122] S shoulder area

[0123] C Central Area

[0124] CL tire equatorial plane

[0125] TE tread end

Claims

1. A tire having a plurality of circumferential main grooves on its tread surface, the circumferential main grooves extending circumferentially and having a groove width that prevents two sidewalls from contacting each other when the tire touches the ground, wherein, When the pair of circumferential main grooves positioned closest to the tread ends in the tire width direction are referred to as shoulder main grooves, and the circumferential main grooves other than the shoulder main grooves are referred to as central main grooves, then... All of the main shoulder grooves are normal main grooves, and these normal main grooves are constructed such that the maximum groove width in the groove depth direction is located only at the tread surface, and All of the central main grooves are widened main grooves, and the widened main grooves are constructed such that at least one maximum groove width position in the groove depth direction is located closer to the bottom side of the groove than the tread surface position. The ratio of the number of widened main slots to the number of normal main slots is 1 / 1 to 3 / 2. The widened main groove has a portion where the groove width gradually increases from the surface side of the tread towards the bottom side. The cross-sectional shape of the widened main channel is an uninterrupted trapezoid, which is defined by a continuous channel bottom and a pair of continuous sidewalls.

2. The tire according to claim 1, wherein, When the circumferential main grooves other than the shoulder main grooves are referred to as the central main grooves... The circumferential main groove includes a pair of shoulder main grooves and at least one central main groove, and The pair of said shoulder main grooves are said normal main grooves and the central main groove is said widened main groove.

3. The tire according to claim 1, wherein, The circumferential main groove has a minimum groove width of 1.5 mm or more.

4. The tire according to claim 2, wherein, The circumferential main groove has a minimum groove width of 1.5 mm or more.

5. The tire according to any one of claims 1 to 4, comprising a width-direction groove connected to the shoulder main groove which is the normal main groove, extending in the tire width direction and opening at the tread end.

6. The tire according to claim 5, wherein, Compared to the side connected to the shoulder main groove, which serves as the normal main groove, the width direction groove has a larger groove width on the tread end side.

Images