tire

Abstract

To provide a tire that reduces noise caused by air pumping while maintaining the same wet performance as conventional tires. [Solution] With respect to recesses (16a, 16b) formed in two land portions (14a, 14b) facing each other across the circumferential main groove (12), where the distance between centers D1 measured in the tire width direction is 0 mm ≤ D1 ≤ 10 mm, the length L1 of the first recess and the length L2 of the second recess satisfy 0.75 ≤ L1 / L2 ≤ 1.25, and the average cross-sectional area S1 of the recess in region R1 of the first recess, the average cross-sectional area S2 of the recess in region R2 of the first recess, the average cross-sectional area S3 of the recess in region R3 of the second recess, and the average cross-sectional area S4 of the recess in region R4 of the second recess satisfy S1 > (S2 + S4) / 2 and S3 < (S2 + S4) / 2 or S1 < (S2 + S4) / 2 and S3 > (S2 + S4) / 2.

Description

Technical Field

[0001] The present disclosure relates to tires.

Background Art

[0002] There is disclosed a tire in which lug grooves communicating with the main groove in the tire circumferential direction and extending obliquely with respect to the tire width direction are formed at a predetermined period in the circumferential direction (see FIG. 2 of Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the tire disclosed in Patent Document 1, since lug grooves (grooves having a tire width direction component, which are long portions 41a and short portions 41b in Patent Document 1) are formed so as to communicate with the circumferential groove, there is a possibility that the sound generated due to the presence of the lug grooves excites the air column resonance in the main groove. As a result, there is a possibility of an increase in noise due to an increase in the level of so-called air pumping sound.

[0005] Normally, although the noise can be reduced by reducing the lug groove volume, the drainage performance deteriorates, and thus the wet performance tends to deteriorate. Therefore, even if the lug groove volume is equivalent to that of the conventional one, it has been desired to develop a tire capable of reducing the generated noise.

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to provide a tire that reduces noise caused by air pumping sound while maintaining wet performance equivalent to that of conventional tires.

Means for Solving the Problems

[0007] The tire of the present invention has at least two land areas separated by at least one circumferential main groove, and each of the two land areas facing each other across the circumferential main groove has a recess formed therein, which is composed of at least one of a lug groove or sipe, with one end opening into the circumferential main groove and the other end terminating within the land area, and with respect to the recesses formed in the two facing land areas where the distance between centers D1 measured in the tire width direction satisfies 0 mm ≤ D1 ≤ 10 mm, the length L1 along the extending direction of one first recess and the length L2 along the extending direction of the other second recess are 0.75 ≤ L1 / L2 ≤ 1. The invention satisfies condition 25, and is characterized in that the average cross-sectional area S1 of the recess in 25% of the region R1 located on the side opposite to the main groove along the extension direction of the first recess, the average cross-sectional area S2 of the recess in 75% of the region R2 located on the main groove side along the extension direction of the first recess, the average cross-sectional area S3 of the recess in 25% of the region R3 located on the side opposite to the main groove along the extension direction of the second recess, and the average cross-sectional area S4 of the recess in 75% of the region R4 located on the main groove side along the extension direction of the second recess satisfy the condition S1 > (S2 + S4) / 2 and S3 < (S2 + S4) / 2 or S1 < (S2 + S4) / 2 and S3 > (S2 + S4) / 2. [Effects of the Invention]

[0008] According to the present invention, by forming pairs of recesses on the tread surface that open into the circumferential main grooves and have a predetermined relationship in groove area and position, it is possible to provide a tire that reduces noise caused by air pumping while maintaining the same wet performance as conventional tires. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a plan view showing the main parts of the tire tread pattern of this embodiment. [Figure 2] Figure 2 is a plan view showing modified examples of lug grooves 16a and 16b that open into the circumferential main groove 12 shown in Figure 1. [Figure 3] Figure 3 is a schematic diagram showing the lug grooves 16a and 16b indicated by the circled areas X and Y in Figure 1. [Figure 4] Figure 4 is a plan view of a tire in which one of the pair of lug grooves 16a and 16b that form a recess has one groove, while the other has multiple grooves. [Figure 5] Figure 5 is a plan view of the tire showing the average widths (average recess widths) W1, W2, W3, and W4 in regions R1, R2, R3, and R4, respectively, of the paired lug grooves 16a and 16b. [Figure 6] Figure 6 is a plan view of a tire showing the change in groove depth in the tire width direction of a pair of lug grooves 16a and 16b, using the extreme values ​​of groove depth (specifically, the maximum and minimum values ​​of groove depth). [Figure 7] Figure 7 shows the main parts of the tread pattern. [Figure 8] Figure 8 is a plan view showing the circumferential distance D2 between the end of the lug groove 16a opposite to the circumferential main groove 12 and the end of the lug groove 16b opposite to the circumferential main groove 12 in the main part of the tread pattern shown in Figure 1. [Modes for carrying out the invention]

[0010] <Mode of the present invention> The present invention encompasses the following embodiments. [Form 1] A tire having at least two land areas partitioned by at least one circumferential main groove, and each of the two land areas facing each other across the circumferential main groove having a recess formed therein, which is composed of at least one of a lug groove and a sipe, with one end opening into the circumferential main groove and the other end terminating within the land area, Of the two recesses formed in the opposing land portions, the distance D1 between the centers measured in the tire circumferential direction is 0mm ≤ D1 ≤ 10mm With respect to the recesses that satisfy the condition, the length L1 along the extending direction of one of the first recesses and the length L2 along the extending direction of the other of the second recesses are, 0.75 ≤ L1 / L2 ≤ 1.25 Satisfying that, among the regions along the extending direction of the first concave portion, the average concave cross-sectional area S1 in the 25% region R1 on the opposite side of the main groove, the average concave cross-sectional area S2 in the 75% region R2 on the main groove side among the regions along the extending direction of the first concave portion, the average concave cross-sectional area S3 in the 25% region R3 on the opposite side of the main groove among the regions along the extending direction of the second concave portion, and the average concave cross-sectional area S4 in the 75% region R4 on the main groove side among the regions along the extending direction of the second concave portion, S1 > (S2 + S4) / 2 and S3 < (S2 + S4) / 2 Or S1 < (S2 + S4) / 2 and S3 > (S2 + S4) / 2 A tire characterized by satisfying the above. [Form 2] The average concave widths W1, W2, W3, and W4 in the regions R1, R2, R3, and R4 satisfy 0.75 ≤ W1 / W3 ≤ 1.25 and 0.75 ≤ W2 / W4 ≤ 1.25 The tire according to Form 1, satisfying the above. [Form 3] The average concave cross-sectional areas S2 and S4 satisfy 0.75 ≤ S2 / S4 ≤ 1.25 The tire according to Form 1 or 2, satisfying the above. [Form 4] Among the larger area SL and the smaller area SS of the average concave cross-sectional areas S1 and S3, 1.5 ≤ SL / SS ≤ 2.5 The tire according to Form 1 or 2, satisfying the above, and the difference between the average concave cross-sectional areas S1 and S3 is the difference in groove depth. [Form 5] The first concave portion and the second concave portion have a maximum or minimum value of their groove depth, and the groove depth periodically varies respectively from the opening to the main circumferential groove to the end portion in the land portion, and the phases of the variation between the first concave portion and the second concave portion are opposite. The tire according to Form 1 or 2. [Form 6] There are 4 or more and 7 or less maximum and minimum values. The tire according to Form 5. [Form 7] The two land portions facing each other are two land portions partitioned and formed by the circumferential main groove closest to the tire equatorial plane, the tire according to Form 1 or 2. [Form 8] When the tire is mounted on a standard rim and an internal pressure of 70% of the standard internal pressure is applied and a load of 75% of the maximum load capacity is applied, the number of the paired lug grooves and / or sipes is 15% or more and 80% or less with respect to the number of the lug grooves and / or sipes in the contact surface, the tire according to Form 1 or 2. [Form 9] When the tire is mounted on a standard rim and an internal pressure of 70% of the standard internal pressure is applied and a load of 75% of the maximum load capacity is applied, the contact length CL (mm), the circumferential distance D2 (mm) between the other end of the first recess and the other end of the second recess is 0≦D2<1 / 4×0.082×(CL+30) or 3 / 4×0.082×(CL+30)<D2<5 / 4×0.082×(CL+30) satisfies the requirement, the tire according to Form 1 or 2.

[0011] <Definition> The tire radial direction refers to the direction perpendicular to the tire rotation axis. The tire radial inner side refers to the side facing the tire rotation axis in the tire radial direction, and the tire radial outer side refers to the side away from the tire rotation axis in the tire radial direction. The tire circumferential direction refers to the circumferential direction around the tire rotation axis as the central axis. The tire width direction refers to the direction parallel to the tire rotation axis. The tire width outer side refers to the side away from the tire equatorial plane in the tire width direction, and the tire width inner side refers to the side approaching the tire equatorial plane in the tire width direction. The tire equatorial plane refers to the plane perpendicular to the tire rotation axis and passing through the center of the tire width. The main groove is a groove having a wear indicator indicating the end stage of wear on the groove wall, for example, a circumferential groove, and in this embodiment, has a groove width of 3.0 [mm] or more and a groove depth of 5.0 [mm] or more. A sipe is a recess with an extremely small groove width and groove depth, and in this embodiment, it has a groove width of 1.0 mm or less and a depth of 1.0 mm or more. The groove width is the maximum distance between opposing groove walls at the groove opening on the tread surface when the tire is mounted on a standard rim and filled to the standard internal pressure in an unloaded state (the distance measured in a direction perpendicular to the direction in which the groove extends). If there is a notch or chamfer at the groove opening, the groove width is the value measured with the endpoint being the intersection of the extension line of the tread surface and the extension line of the groove wall in a cross-sectional view parallel to the groove width direction and groove depth direction. The groove depth is the maximum distance from the tread surface to the bottom of the groove (measured in the radial direction of the tire) when the tire is mounted on a standard rim, filled to the standard internal pressure, and under no load. If the groove in question has partial unevenness or sipes at the bottom of the groove, the groove depth shall be the value measured excluding the unevenness or sipes. In this specification, unless otherwise specified, the shape, position, and length (distance) of each component refer to the shape, position, and length in the meridional cross-section of the tire (in an unloaded state with the tire mounted on a standard rim and filled to standard internal pressure). A "regular rim" refers to an "applicable rim" as defined by JATMA, a "Design Rim" as defined by TRA, or a "Measuring Rim" as defined by ETRTO. Standard internal pressure refers to the "maximum air pressure" specified by JATMA, the maximum value listed in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or the "INFLATION PRESSURES" specified by ETRTO. Standard load refers to the "maximum load capacity" specified by JATMA, the maximum value listed in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or the "LOAD CAPACITY" specified by ETRTO. Standards refer to JATMA, TRA, and ETRTO.

[0012] In the examples shown below, although not shown, it is assumed that the tire has a tread pattern in which at least two land areas are partitioned by at least one circumferential main groove, and predetermined recesses (specifically, lug grooves communicating with the circumferential main groove on both sides of the circumferential main groove in the tire width direction) are periodically formed in the circumferential direction of the tire. For the circumferential main groove and the land areas partitioned thereby, for example, the tread pattern shown in Figure 2 of Patent Document 1 applies, but the dimensions in the tire width direction of the lug grooves located on each side of the circumferential main groove in the tire width direction are not particularly limited to the example shown in the figure.

[0013] <Basic tire configurations> One embodiment of the present invention will be described below with reference to the drawings. Figure 1 is a plan view showing the main part of the tread pattern of the tire of this embodiment. As shown in Figure 1, the tire 10 of this embodiment has land portions 14 (14a, 14b) divided by circumferential main grooves 12. Each of these land portions 14 has recesses (in the figure, both are lug grooves 16a, 16b) which consist of at least one of lug grooves and sipes.

[0014] [Characteristics of the basic form of a tire] (Recesses 16a and 16b formed in the land portions 14a and 14b, respectively) As shown in Figure 1, the lug grooves 16a and 16b open at one end into the circumferential main groove 12 and terminate at the other end within the land portions 14a and 14b, respectively, and extend in a direction inclined with respect to the tire width direction. Although not shown, these lug grooves 16a and 16b are formed at a predetermined period in the circumferential direction.

[0015] In the tire 10 of this embodiment, the lug grooves 16a and 16b formed in two land portions 14a and 14b facing each other across the circumferential main groove 12, respectively, are the subject of the invention, and the center-to-center distance D1 measured in the circumferential direction of the tire that satisfies 0 mm ≤ D1 ≤ 10 mm is the subject of the invention. Here, the center-to-center distance D1 refers to the circumferential distance of the tire between the midpoint of the opening edge of one lug groove 16a to the circumferential main groove 12 and the midpoint of the opening edge of the other lug groove 16b to the circumferential main groove 12. The opening edge is a point where a step usually occurs in the radial direction of the tire in the communication region between grooves (in the case shown in the figure, the circumferential main groove 12 and the lug grooves 16a and 16b), and the midpoint of the opening edge refers to the circumferential midpoint of the tire between the foot-in side end and the kick-out side end of the opening edge in a plan view of the tire.

[0016] Based on the above, the tire 10 of this embodiment has a length L1 along the extending direction of one lug groove 16a and a length L2 along the extending direction of the other lug groove 16b, 0.75 ≤ L1 / L2 ≤ 1.25 It satisfies the condition.

[0017] Figure 2 is a plan view showing modified examples of lug grooves 16a and 16b that open into the circumferential main groove 12 shown in Figure 1. The example shown in Figure 2(A) is one in which the lug grooves 16a and 16b extend to opposite sides in the tire circumferential direction as they move away from the circumferential main groove 12, while the example shown in Figure 2(B) is one in which the lug grooves 16a and 16b extend to the same side in the tire circumferential direction as they move away from the circumferential main groove 12. Here, the length L1 in the extending direction of one of the lug grooves 16a is the average value of the lengths L11 and L12 along the profile line of the lug groove 16a from the end position P1 along the profile line to the respective opening positions P2 and P3 in the circumferential main groove 12, for both Figures 2(A) and (B). Similarly, the length L2 in the extending direction of the other lug groove 16b is the average of the lengths L21 and L22 along the profile line of the lug groove 16b from the end position P4 along the profile line to the opening positions P5 and P6 in the circumferential main groove 12, for both Figures 2(A) and (B). Here, the end position is the outermost point in the tire width direction of the lug groove, and the opening position is the foot-in side end or kick-out side end of the opening edge. If there are multiple outermost points in the tire width direction of the lug groove that can be considered as end positions, these outermost points in the tire width direction of the lug groove are determined such that the lengths L11, L12, L21, and L22 are all the shortest.

[0018] Figure 3 is a schematic diagram showing the lug grooves 16a and 16b indicated by the circled areas X and Y in Figure 1. Here, R1 is defined as the 25% region of the lug groove 16a that lies on the opposite side of the main groove 12 in the tire width direction from the extension direction, R2 is defined as the 75% region of the lug groove 16a that lies on the main groove 12 side in the tire width direction from the extension direction, R3 is defined as the 25% region of the lug groove 16b that lies on the opposite side of the main groove 12 in the tire width direction from the extension direction, and R4 is defined as the 75% region of the lug groove 16b that lies on the main groove 12 side in the tire width direction from the extension direction.

[0019] Under these premises, the tire 10 of this embodiment has an average cross-sectional area of ​​recesses in regions R1, R2, R3, and R4 (in the figure, the cross-sectional area of ​​lug grooves 16a and 16b) S1, S2, S3, and S4, S1 > (S2 + S4) / 2 and S3 < (S2 + S4) / 2, or S1 < (S2 + S4) / 2 and S3 > (S2 + S4) / 2 It satisfies the condition.

[0020] Here, the recess cross-sectional area refers to the size of the surface having a normal perpendicular to both the groove width and groove depth of the recess (in this example, lug grooves 16a and 16b). The average recess cross-sectional area is the average value of the above cross-sectional areas measured every 1 mm in the extension direction of the recess.

[0021] Note that in Figure 3, the average cross-sectional areas of the recesses S1, S2, S3, and S4 are depicted as cross-sections at specific extension direction locations. This is merely a convenient indication to show that the average cross-sectional areas of the recesses S1, S2, S3, and S4 are indeed cross-sectional areas. As stated above, the average cross-sectional areas of the recesses S1, S2, S3, and S4 are not cross-sectional areas at specific locations, but rather the average cross-sectional areas of the lug grooves 16a (lug grooves 16b) in regions R1, R2, R3, and R4, calculated based on the above definition. The same applies when the average cross-sectional areas of the recesses S1, S2, S3, and S4 are shown in drawings other than Figure 3.

[0022] In the tire 10 of this embodiment, the two recesses 16, 16 (lug grooves 16a, 16b) that satisfy the above relationship are referred to as "paired recesses (paired lug grooves)". Note that the paired recesses may also be sipes, and the paired recesses may also be a combination of lug grooves and sipes.

[0023] Figure 4 is a plan view of a tire in which one of the pair of recesses, lug grooves 16a and 16b, consists of one lug groove, while the other consists of multiple lug grooves. As shown in Figure 4(A), for each pair of recesses 16, 16, there may be multiple corresponding lug grooves 16b1 and 16b2 for each lug groove 16a. Similarly, as shown in Figure 4(B), there may be multiple corresponding lug grooves 16a1 and 16a2 for each lug groove 16b.

[0024] For example, in the example shown in Figure 4(A), the following three relationships exist with respect to the lug groove 16a: 0mm ≤ D1 ≤ 10mm 0.75 ≤ L1 / L2 ≤ 1.25 • S1 > (S2 + S4) / 2 and S3 < (S2 + S4) / 2 or S1 < (S2 + S4) / 2 and S3 > (S2 + S4) / 2 If all of the above conditions are met, both lug grooves 16b1 and 16b2 are recognized as elements of the pair.

[0025] Similarly, in the example shown in Figure 4(B), if all three relationships described above are satisfied in relation to the lug groove 16b, then both lug grooves 16a1 and 16a2 are recognized as a pair of elements.

[0026] [Technical knowledge regarding the basic form of tires, as well as their function and effects] In conventional tires (for example, Figure 2 of Patent Document 1), when recesses (at least one of lug grooves and sipes) are formed in the circumferential main grooves to improve drainage performance, the air pumping noise caused by the presence of these recesses can excite air column resonance in the circumferential main grooves, potentially causing external noise. While the air pumping noise can be reduced by decreasing the groove volume of the recesses, drainage performance is reduced. Therefore, there has been room for improvement in the form (shape and dimensions, etc.) of these recesses in conventional tires, and there has been a demand to reduce noise while maintaining drainage performance (and thus wet performance).

[0027] Therefore, the inventors have found that even with a groove volume equivalent to that of conventional designs, improving the shape of the recesses can efficiently suppress the excitation of air column resonance in the circumferential main grooves, thereby reducing external vehicle noise.

[0028] More specifically, the inventors diligently studied a pair of recesses that face the circumferential main groove and have a predetermined relationship. As a result, the inventors found that by effectively designing the shape of each recess such that the phase of the pressure fluctuation of the air pumping sound in one recess is opposite to the phase of the pressure fluctuation of the air pumping sound in the other recess, the two air pumping sounds interfere with and cancel each other out. Consequently, even with a groove volume equivalent to that of conventional designs, the air pumping sound based on the recesses can be reduced, the excitation of air column resonance in the circumferential main groove can be suppressed, and ultimately, external vehicle noise can be reduced. With this finding, the inventors completed the present invention.

[0029] In other words, in the tire 10 of this embodiment shown in Figure 1, with respect to the lug grooves 16a and 16b, the cross-sectional area of ​​the recess (in the case shown in the figure, the cross-sectional area of ​​the lug groove) from one end opening into the circumferential main groove 12 to the other end terminating in the land area fluctuates symmetrically between the lug grooves 16a and 16b. As a result, the phase of the pressure fluctuation of the air pumping sound from the lug groove 16a to the circumferential main groove 12 is opposite to the phase of the pressure fluctuation of the air pumping sound from the lug groove 16b to the circumferential main groove 12. These air pumping sounds interfere with and cancel each other out, suppressing the excitation of air column resonance in the circumferential main groove 12, and consequently reducing external noise.

[0030] As described above, the tire 10 of this embodiment can reduce noise caused by air pumping while maintaining the same drainage performance as conventional tires.

[0031] Furthermore, it is preferable to make the paired recesses (lug grooves and / or sipes) account for 20% or more of the recesses within the tire contact surface (more specifically, 20% or more of the total recess area) because this efficiently achieves the above-mentioned external noise reduction effect. Here, the recess area refers to the area of ​​all lug grooves and sipes at their outermost radial positions in the tire (the area that can be determined by viewing the tire from above).

[0032] <Preferred tire configuration> The following shows suitable configurations for the basic form of a tire. Figure 5 is a plan view of a tire showing the average widths (average recess widths) W1, W2, W3, and W4 of the paired lug grooves 16a and 16b in regions R1, R2, R3, and R4, respectively. The average widths W1, W2, W3, and W4 of the lug grooves 16a and 16b in Figure 5 are the average values ​​of the groove widths measured every 1 mm in the extending direction of the lug groove in regions R1, R2, R3, and R4, respectively.

[0033] Under these premises, in the tire 10 of this embodiment, it is preferable that the average widths W1, W2, W3, and W4 of the lug grooves 16a and 16b satisfy 0.75 ≤ W1 / W3 ≤ 1.25 and 0.75 ≤ W2 / W4 ≤ 1.25.

[0034] By setting 0.75≦W1 / W3≦1.25 and 0.75≦W2 / W4≦1.25, the widths of the regions of the paired lug grooves 16a and 16b corresponding to their distance from the circumferential main groove 12 (regions R1 and R3, and regions R2 and R4) are not excessively different. By making the overall frequency of the sound generated from each of the lug grooves 16a and 16b equivalent, the cancellation of air pumping noise based on the phase difference of the pressure fluctuations described above can be performed more efficiently, further reducing external vehicle noise.

[0035] Furthermore, the relationship regarding the average width of the recesses shown above is more preferably 0.82 ≤ W1 / W3 ≤ 1.18, and more preferably 0.90 ≤ W1 / W3 ≤ 1.10. Similarly, it is more preferably 0.82 ≤ W2 / W4 ≤ 1.18, and more preferably 0.90 ≤ W2 / W4 ≤ 1.10.

[0036] In the tire 10 of this embodiment, it is preferable that the average cross-sectional area S2 of the recess in the 75% region R2 that is located on the main groove 12 side in the tire width direction along the extending direction of the lug groove 16a shown in Figure 1, and the average cross-sectional area S4 of the recess in the 75% region R4 that is located on the main groove 12 side in the tire width direction along the extending direction of the lug groove 16b satisfy the condition 0.75 ≤ S2 / S4 ≤ 1.25.

[0037] By setting 0.75 ≤ S2 / S4 ≤ 1.25, the volume of region R2, which occupies most of the lug groove 16a side, and the volume of region R4, which occupies most of the lug groove 16b side, can be made to be equal in magnitude to the air pumping sound generated in region R2 and the air pumping sound generated in region R4. As a result, the air pumping sounds originating from region R2, which occupies most of the lug groove 16a, and the air pumping sounds originating from region R4, which occupies most of the lug groove 16b, interfere with each other and cancel each other out. Even when comparing the entire lug groove 16a and the entire lug groove 16b, the air pumping sounds from both lug grooves interfere with each other and almost cancel each other out, thereby further reducing external vehicle noise.

[0038] Furthermore, it is even more preferable that 0.82 ≤ S2 / S4 ≤ 1.18, and it is extremely preferable that 0.90 ≤ S2 / S4 ≤ 1.10.

[0039] In the tire 10 of this embodiment, it is preferable that the larger area SL and the smaller area SS of the average recess cross-sectional areas S1 and S3 shown in Figure 3 satisfy 1.5 ≤ SL / SS ≤ 2.5, and that the difference between the average recess cross-sectional areas S1 and S3 is the difference in groove depth. In the example shown in Figure 3, when comparing the average recess cross-sectional areas S1 and S3, the average recess cross-sectional area S3 is larger, so the average recess cross-sectional area S3 becomes area SL and the average recess cross-sectional area S1 becomes SS.

[0040] Under these conditions, by ensuring that areas SL and SS satisfy 1.5 ≤ SL / SS, a certain degree of phase difference in pressure fluctuations can be effectively generated between regions R1 and R3, which are relatively small regions far from the circumferential main groove 12. This allows for even more effective cancellation of sound based on this phase difference, further reducing the level of external noise.

[0041] In contrast, by ensuring that the area SL and area SS satisfy SL / SS ≤ 2.5, sufficient cross-sectional area can be secured even in the region R1 having the smaller area SS (S1 in the figure), thereby further improving drainage performance and, consequently, wet performance.

[0042] In the tire 10 of this embodiment, it is preferable that the difference between the average cross-sectional area S1 and the average cross-sectional area S3 of the recess shown in Figure 3 is the difference in groove depth. As shown in Figure 3, by having the difference between the average cross-sectional area S1 and the average cross-sectional area S3 of the recess be the difference in groove depth, the groove widths in regions R1 and R3 can be made equal, and consequently, the frequencies of the air pumping sound generated when the tire vibrates in contact with the road surface during driving can be made equal. This makes it possible to more efficiently cancel out the air pumping sound between the pair of lug grooves 16a and 16b separated by the circumferential main groove 12. In addition, by making the frequencies of the air pumping sound generated by making the groove widths in regions R1 and R3 equal can be made equal, it is possible to suppress the air pumping sound itself, which has excessively different frequency components, from becoming a cause of external noise, and external noise can be further reduced.

[0043] Furthermore, it is more preferable that the larger of the average cross-sectional areas of the recesses S1 and S3, SL and SS, satisfy 1.6 ≤ SL / SS ≤ 2.4, and it is extremely preferable that they satisfy 1.8 ≤ SL / SS ≤ 2.3.

[0044] Figure 6 is a plan view of a tire showing the change in groove depth in the tire width direction of a pair of lug grooves 16a and 16b, using the extreme values ​​of groove depth (specifically, the maximum and minimum values ​​of groove depth). In this figure, the groove depths of the lug grooves 16a and 16b are schematically shown with dashed lines, with the maximum value shown on the right side of the figure and the minimum value shown on the left side, relative to the average depth of the recess.

[0045] Here, the groove depth of the lug grooves 16a and 16b shall be measured at the midpoint of the lug grooves 16a and 16b in the tire circumferential direction, at intervals of 1 mm in the extending direction of the lug grooves 16a and 16b, from the opening of the lug grooves 16a and 16b to the circumferential main groove 12 to the end portion within the land area. Furthermore, the position where the groove depth reaches its extreme value is defined as the position in the tire width direction, between the opening and the end portion within the land area, where the groove depth changes from increasing to decreasing (the position where the groove depth changes from decreasing to increasing), and where the groove depth changes by 5% of the maximum groove depth between this position and the adjacent extreme value position. Among such positions, the position where the groove depth changes from increasing to decreasing is called the position where the groove depth reaches its maximum value, and the position where the groove depth changes from decreasing to increasing is called the position where the groove depth reaches its minimum value.

[0046] For example, in the case of the lug groove 16a shown in Figure 6, at measurement points P7 (opening), P8, P9, P10, P11, P12, and P13 (end), if the difference in groove depth at measurement point P8 and P9 is 5% or more of the maximum groove depth (for example, 5%), then the groove depth at measurement point P7 and P8 will be a local maximum, and the groove depth at measurement point P9 and P10 will be a local minimum. Similarly, if the difference in groove depth at measurement point P10 and P11 is 5% or more of the maximum groove depth, then the groove depth at measurement point P11 and P12 will be a local maximum.

[0047] In contrast, in the case of the lug groove 16b shown in Figure 6, at measurement points P14 (opening), P15, P16, P17, P18, P19, and P20 (end), if the difference in groove depth at measurement point P15 and P16 is less than 5% (e.g., 3%) of the maximum groove depth, the groove depth at measurement point P14 and P15 will not be a minimum. Similarly, if the difference in groove depth at measurement point P18 and P19 is less than 5% of the maximum groove depth, the groove depth at measurement points P16, P17, and P18 will not be a maximum, and the groove depth at measurement point P19 and P20 will not be a minimum.

[0048] Thus, in the tire 10 of this embodiment, the first recess (lug groove 16a in Figure 6) and the second recess (lug groove 16b in the same figure) have a maximum or minimum value of groove depth, and it is preferable that the groove depths of these grooves fluctuate periodically from the opening to the circumferential main groove to the end portion within the land area, and that the phase of fluctuations is opposite for lug groove 16a and lug groove 16b.

[0049] As shown in Figure 6, the lug grooves 16a and 16b have a maximum or minimum value in their groove depth, which effectively creates out-of-phase pressure fluctuations in the air pumping sound generated in the lug grooves 16a and 16b. This allows for more efficient cancellation of the air pumping sounds generated in the lug grooves 16a and 16b through interaction, ultimately further reducing external vehicle noise.

[0050] Here, with respect to the air pumping sound, the statement that the pressure fluctuations are in opposite phase means that, for each lug groove 16a and 16b, when the groove depth is sequentially measured in the same manner every 1 mm in the extending direction from the opening to the end part in the land portion, in sections where the distance from the opening (measured in the extending direction of each lug groove 16a and 16b) is the same, and the sections are sandwiched between two extreme values ​​that fluctuate by 5% or more of the maximum groove depth, as the distance from the opening increases, for example, the groove depth of one lug groove 16a decreases while the groove depth of the other lug groove 16b increases.

[0051] Figure 7 shows the main parts of the tread pattern, with Figure 7(A) showing a conventional tire and Figure 7(B) showing the tire of this embodiment. In both Figure 7(A) and Figure 7(B), the circumferential main grooves 120 and 12 are depicted in plan view, while the lug grooves 160 (160a, 160b) and 16 (16a, 16b) are depicted in perspective view.

[0052] In both the conventional tire 100 shown in Figure 7(A) and the tire 10 of this embodiment shown in Figure 7(B), the land portions 140 (140a, 140b) and 14 (14a, 14b), respectively, are divided by common circumferential main grooves 120 and 12. In addition, both figures also share the fact that the lug grooves 160a, 160b, 16a, and 16b are formed on either side of the circumferential main grooves 120 and 12, respectively.

[0053] However, in the conventional tire 100 shown in Figure 7(A), the groove depth of the lug groove 160 (160a, 160b) is constant from the opening to the end, whereas in the tire 10 of this embodiment shown in Figure 7(B), the groove depth of the lug groove 16 (16a, 16b) fluctuates periodically from the opening to the end, and the groove depth of the lug groove 16a fluctuates in opposite phases.

[0054] In particular, in the tire 10 of this embodiment, the groove depth of the lug grooves 16 (16a, 16b) fluctuates periodically from the opening to the circumferential main groove 12 to the end portion within the land portion 14, and there may be extreme values ​​for the groove depth. It is preferable that there are 4 to 7 such extreme values.

[0055] The presence of 4 to 7 extreme values ​​allows for more efficient pressure fluctuations in response to the air pumping noise generated in the lug grooves 16a and 16b, enabling a higher level of cancellation through the interaction of these air pumping noises, and ultimately further reducing external vehicle noise.

[0056] More specifically, by setting the aforementioned extreme values ​​to four or more points, it is possible to ensure that there are areas where the air pumping sound generated in the lug grooves 16a and 16b experiences pressure fluctuations, thereby reliably reducing external noise caused by the cancellation of the air pumping sound.

[0057] In contrast, by limiting the number of extreme values ​​to seven or fewer, it is possible to ensure a sufficiently large absolute value for each extreme value, thereby reliably reducing the external noise caused by the cancellation of the air pumping sounds.

[0058] Furthermore, it is extremely preferable that the aforementioned extreme values ​​include 5 to 6 points.

[0059] In the tire 10 of this embodiment, it is preferable that the two opposing land portions 14a and 14b shown in Figure 1 are two land portions that are separated by the circumferential main groove closest to the tire's equatorial plane.

[0060] Typically, the circumferential main groove closest to the tire's equator is most likely to be adjacent to other circumferential main grooves, and furthermore, such a groove has a higher contact pressure compared to other circumferential main grooves. By adopting this configuration, the circumferential main groove closest to the tire's equator, where the air pumping noise level is assumed to be highest, will experience the cancellation effect of the air pumping noise, thereby reducing external noise to an even higher level.

[0061] This configuration applies not only when an odd number of circumferential main grooves are formed (i.e., when the centerlines of the circumferential main grooves usually coincide with the tire's equatorial plane), but also when an even number of circumferential main grooves are formed (i.e., when two circumferential main grooves are usually formed symmetrically on both sides of the tire's equatorial plane in the tire's width direction).

[0062] Furthermore, it is even more preferable that the two opposing land areas 14a and 14b shown in Figure 1 are two land areas demarcated by the circumferential main groove closest to the tire's equatorial plane, and two land areas demarcated by the circumferential main groove second closest to the tire's equatorial plane.

[0063] In the tire 10 of this embodiment, when mounted on a regular rim and subjected to an internal pressure of 70% of the regular internal pressure and a load of 75% of the maximum load capacity, it is preferable that the number of paired lug grooves and / or sipes is 15% or more and 80% or less of the total number of lug grooves and / or sipes within the contact surface.

[0064] Here, the paired lug grooves and / or sipes are separated by a specific circumferential main groove, When the lug grooves are paired, • When sipes form pairs, and • When the lug grooves and sipes are in communication and these combinations form pairs. It includes.

[0065] When mounted on a standard rim and subjected to an internal pressure of 70% of the standard internal pressure and a load of 75% of the maximum load capacity, by setting the number of paired lug grooves and / or sipes (hereinafter sometimes referred to as the "percentage of paired recesses") to 15% or more and 80% or less relative to the number of lug grooves and / or sipes within the contact surface, it is possible to achieve an even higher level of reduction in external noise caused by the cancellation of air pumping sounds generated in the aforementioned lug grooves 16a and 16b (including cases where sipes are used or where lug grooves and sipes are used in combination).

[0066] More specifically, by ensuring that the proportion of paired recesses within the contact surface is 15% or more, the excitation suppression effect of the circumferential main grooves on air column resonance can be fully utilized, thereby achieving a more efficient reduction of external noise.

[0067] In contrast, by setting the ratio of paired recesses within the contact surface to 80% or less, it is possible to suppress the excitation of air column resonance in the circumferential main grooves while suppressing the generation of pattern vibrations caused by rigidity imbalance due to irregularities within the lug grooves, thereby further reducing external noise.

[0068] Furthermore, within the contact surface, the proportion of pairs of recesses is more preferably 20% to 75%, and most preferably 25% to 70%.

[0069] Figure 8 is a plan view showing the circumferential distance D2 between the end of the lug groove 16a opposite to the circumferential main groove 12 and the end of the lug groove 16b opposite to the circumferential main groove 12 in the main part of the tread pattern shown in Figure 1.

[0070] In the tire 10 of this embodiment, when the tire is mounted on a regular rim and subjected to an internal pressure of 70% of the regular internal pressure and a load of 75% of the maximum load capacity, the contact length CL (mm) and the circumferential distance D2 (mm) between the end of the lug groove 16a opposite to the circumferential main groove and the end of the lug groove 16b opposite to the circumferential main groove are, 0 ≤ D2 < 1 / 4 × 0.082 × (CL + 30) or 3 / 4 × 0.082 × (CL + 30) <D2<5 / 4×0.082×(CL+30) It is preferable that the following conditions be met.

[0071] Here, contact length CL (mm) refers to the circumferential dimension of the tire at the contact surface. More specifically, contact length CL (mm) refers to the dimension of any line segment on the contact surface that extends in the circumferential direction of the tire, passing through a point on the land portion adjacent to the circumferential main groove closest to the tire's equator, and located at a distance of more than 0 mm but no more than 5 mm in the tire width direction from the said circumferential main groove.

[0072] By satisfying either of the two inequalities above, the opening and closing timings of the paired recesses will be synchronized during vehicle operation, allowing for more efficient cancellation of the air pumping sounds generated from the paired recesses. As a result, the excitation of air column resonance in the circumferential main grooves can be further suppressed, and consequently, external noise can be reduced to an extremely high level.

[0073] In addition, in the tire 10 of this embodiment, The circumferential distance D2 (mm) is, 1 / 20×0.082×(CL+30)≦D2<1 / 5×0.082×(CL+30) or 4 / 5 × 0.082 × (CL + 30) <D2<6 / 5×0.082×(CL+30) It is even more preferable that the following conditions be met: 1 / 10×0.082×(CL+30)≦D2<3 / 20×0.082×(CL+30) or 17 / 20 × 0.082 × (CL + 30) <D2<23 / 20×0.082×(CL+30) It is highly desirable that these conditions be met.

[0074] The tire of this embodiment, as shown above, has a meridional cross-sectional shape similar to that of a conventional tire, although it is not shown in the illustration. Here, the meridional cross-sectional shape of a tire refers to the cross-sectional shape of the tire as it appears on a plane perpendicular to the tire's equatorial plane. In a meridional cross-sectional view of the tire, the tire of this embodiment has a bead portion, a sidewall portion, a shoulder portion, and a tread portion, extending from the inside to the outside in the radial direction of the tire. The tire, for example, in a meridional cross-sectional view of the tire, comprises a carcass extending from the tread portion to the bead portions on both sides and wound around a pair of bead cores, a belt layer and a belt reinforcing layer sequentially formed on the radially outer side of the carcass, and further comprising a predetermined tread rubber on the radially outer side of the tire.

[0075] <Tire manufacturing method> The tire of this embodiment is obtained through the usual manufacturing processes, namely the mixing process of the tire material, the processing process of the tire material, the molding process of the green tire, the vulcanization process, and the inspection process after vulcanization. When manufacturing the tire of this embodiment, protrusions corresponding to the circumferential main grooves and lug grooves that are formed as the main parts of the tread pattern shown in Figure 1 are formed on the inner wall of the vulcanization mold, and vulcanization is performed using this mold. [Examples]

[0076] Each of the test tires shown below was manufactured, and its performance in terms of external noise (PBN performance) and wet handling stability (wet performance) was evaluated.

[0077] (Preparation of test tires) A tire with a tire size of 205 / 55R16 91V, in which four land areas are divided by three circumferential main grooves, and lug grooves are formed in each of the two land areas facing each other across the circumferential main grooves, with one end opening into the circumferential main groove and the other end terminating within the land area, and test tires for the conventional example, each comparative example, and each inventive example were manufactured, having the essential parts of the tread pattern shown in Figure 1 (however, the specifications of the lug grooves 16a and 16b shown in Figure 1 are as shown in Table 1). In each test tire, the lug grooves 16a and 16b have the regions R1 to R4 described above.

[0078] Next, each test tire prepared in this manner was mounted on a 16×6.5J rim and a front-engine, front-wheel-drive (FF) vehicle (2000cc engine displacement). With the air pressure set to 250kPa in all four tires, the performance of each tire was evaluated according to the following procedure.

[0079] Note that the terms in Table 1 are equivalent to those explained in this specification, and their descriptions have been partially simplified.

[0080] (Evaluation of PBN performance) The test vehicle was driven on a dry road surface, the transmission was put in neutral at 50 km / h, and the engine was stopped. The level of pass-by noise (PBN) [dB] was measured in accordance with European noise regulations (ECE R117). The measurement results are shown as the difference [dB] from the reference value (0) of the measured value in the previous example (PBN reference difference [dB]). A decrease in PBN is indicated by a negative value, and a larger negative PBN reference difference indicates a lower external noise level.

[0081] (Evaluation of wet performance) The test vehicle was driven three laps on a closed course sprayed with 1 mm of water. The lap time for each lap was measured, and the average lap time was calculated. Based on the average lap time, an index evaluation was performed, with the conventional tire set as the baseline (100). A smaller value indicates better wet performance. The results of these two performance evaluations are shown together in Table 1.

[0082] [Table 1-1] [Table 1-2]

[0083] As shown in Table 1, the technical scope of the present invention is: When two opposing lug grooves 16a and 16b (see Figure 1) are formed on the land portion, and the distance between the centers D1 measured in the circumferential direction of the tire is 0 mm ≤ D1 ≤ 10 mm, the length L1 of one of the lug grooves 16a along the extending direction and the length L2 of the other lug groove 16b along the extending direction satisfy 0.75 ≤ L1 / L2 ≤ 1.25, and the average cross-sectional area S of the recess in the 25% region R1 of the area along the extending direction of the lug groove 16a that is on the opposite side of the circumferential main groove 12 1, the average cross-sectional area S2 of the recess in the 75% region R2 located on the circumferential main groove side of the region along the extending direction of the lug groove 16b, the average cross-sectional area S3 of the recess in the 25% region R3 located on the opposite side of the circumferential main groove of the region along the extending direction of the lug groove 16b, and the average cross-sectional area S4 of the recess in the 75% region R4 located on the circumferential main groove side of the region along the extending direction of the lug groove 16b are such that S1 > (S2 + S4) / 2 and S3 < (S2 + S4) / 2 or S1 < (S2 + S4) / 2 and S3 > (S2 + S4) / 2 It can be seen that, for each example of the invention that satisfies the above technical scope of the present invention, the tires are able to reduce external noise while maintaining wet performance, compared to the conventional examples and comparative examples of tires that do not satisfy the above technical scope of the present invention. [Explanation of Symbols]

[0084] 10,100 tires 12, 120 Circumferential main groove 14, 14a, 14b, 140, 140a, 140b Land 16, 16a, 16b, 16a1, 16a2, 16b1, 16b2, 160, 160a, 160b lug grooves D1 Center distance D2 Circumferential distance L1, L2 Length along the extension direction of the lug groove L11, L12, L21, L22 Length along the profile line of the lug groove End positions of lug grooves P1 and P4 P2, P3, P5, P6 Lug groove opening positions P7, P8, P9, P10, P11, P12, P13, P14, P15, P16, P17, P18, P19, P20 Groove depth measurement points R1, R2, R3, R4 area S1, S2, S3, S4 cross section W1, W2, W3, W4 groove width

Claims

1. A tire having at least two land areas partitioned by at least one circumferential main groove, and each of the two land areas facing each other across the circumferential main groove having a recess formed therein, which is composed of at least one of a lug groove and a sipe, with one end opening into the circumferential main groove and the other end terminating within the land area, Of the two recesses formed in the opposing land portions, the distance D1 between the centers measured in the tire circumferential direction is 0 mm ≤ D1 ≤ 10 mm With respect to the recesses that satisfy the condition, the length L1 along the extending direction of one of the first recesses and the length L2 along the extending direction of the other of the second recesses are, 0.75 ≤ L1 / L2 ≤ 1.25 The above conditions are met, and the average cross-sectional area S1 of the recess in the 25% region R1 of the region along the extending direction of the first recess that is on the side opposite to the main groove, the average cross-sectional area S2 of the recess in the 75% region R2 of the region along the extending direction of the first recess that is on the side of the main groove, the average cross-sectional area S3 of the recess in the 25% region R3 of the region along the extending direction of the second recess that is on the side opposite to the main groove, and the average cross-sectional area S4 of the recess in the 75% region R4 of the region along the extending direction of the second recess that is on the side of the main groove, S1 > (S2 + S4) / 2 and S3 < (S2 + S4) / 2 or S1 < (S2 + S4) / 2 and S3 > (S2 + S4) / 2 A tire characterized by satisfying the following conditions.

2. The average widths of the recesses W1, W2, W3, and W4 in the regions R1, R2, R3, and R4 are, 0.75 ≤ W1 / W3 ≤ 1.25 and 0.75 ≤ W2 / W4 ≤ 1.25 A tire according to claim 1, satisfying the requirements.

3. The average cross-sectional areas of the recesses S2 and S4 are, 0.75 ≤ S² / S⁴ ≤ 1.25 A tire according to claim 1 or 2, satisfying the requirements.

4. The larger of the average cross-sectional areas S1 and S3 of the recesses, SL and the smaller of the two, SS, 1.5 ≤ SL / SS ≤ 2.5 The tire according to claim 1 or 2, wherein the difference between the average cross-sectional areas S1 and S3 of the recesses is the difference in groove depth.

5. The tire according to claim 1 or 2, wherein the first recess and the second recess have a maximum or minimum value of groove depth, the groove depth fluctuates periodically from the opening to the circumferential main groove to the end portion within the land portion, and the phase of the fluctuations is opposite in the first recess and the second recess.

6. The tire according to claim 5, wherein the aforementioned maximum value and the aforementioned minimum value exist at 4 to 7 points.

7. The tire according to claim 1 or 2, wherein the two opposing land portions are two land portions separated by the circumferential main groove closest to the tire's equatorial plane.

8. The tire according to claim 1 or 2, wherein when mounted on a regular rim and subjected to an internal pressure of 70% of the regular internal pressure and subjected to a load of 75% of the maximum load capacity, the number of pairs of lug grooves and / or sipes is 15% or more and 80% or less of the number of lug grooves and / or sipes in the contact surface.

9. When the tire is mounted on a regular rim and subjected to an internal pressure of 70% of the regular internal pressure and a load of 75% of the maximum load capacity, the contact length CL (mm) and the circumferential distance D2 (mm) between the other end of the first recess and the other end of the second recess are, 0≦D2<1 / 4×0.082×(CL+30) or 3 / 4×0.082×(CL+30)<D2<5 / 4×0.082×(CL+30) A tire according to claim 1 or 2, satisfying the requirements.

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