JP4406455B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire that is improved in stability and drainage during turning without lowering various performances during straight running.

  Conventionally, in a pneumatic tire having a tread pattern that is asymmetrical to the vehicle, the land ratio of the area outside the vehicle from the tire equator is higher than the inner land ratio to improve turning performance. (See, for example, Patent Document 1 below). However, such a tire has a drawback in that the drainage performance during turning decreases in exchange for the improvement in turning performance. In particular, in the case of an RV vehicle with a high center of gravity of the vehicle, the ground contact area of the tread portion at the time of turning moves more outward than a general passenger car, so that the drainage performance at the time of turning tends to be significantly reduced. It was.

JP 2004-155416 A JP 2006-176079 A

  The present invention has been devised in view of the above situation, and contrary to the conventional idea, the land ratio of the outer region of the tread portion when the vehicle is mounted is made smaller than the land ratio of the inner region, Based on the arrangement of ribs on both sides of the two wide main grooves provided on the outside of the vehicle, it is a pneumatic that can achieve both stability and drainage while turning without compromising running performance when traveling straight ahead. The main purpose is to provide tires.

  The invention according to claim 1 of the present invention is a pneumatic tire having a left-right asymmetric tread pattern in which the direction of mounting on the vehicle is specified, and the tread located on the outer side of the tire equator when the vehicle is mounted. The land ratio of the outer region of the tire part is smaller than the land ratio of the inner region of the tread part located on the vehicle inner side than the tire equator, and the tread part has a plurality of tires extending continuously in the tire circumferential direction. A wide main groove is provided, and the wide main groove includes an outer wide main groove provided in the outer region and an inner wide main groove provided in the inner region, and the outer wide main groove is a tire. A first outer wide main groove on the tire equator side having a groove centerline at a distance of 5 to 15% of the tread contact width from the equator, and a distance of 15 to 28% of the tread contact width from the tire equator. Position And a second outer wide main groove on the tread ground end side having a groove center line, and the first outer wide main groove and the second outer wide main groove on both sides in the tire axial direction are separated by lateral grooves. And a rib extending continuously in the circumferential direction of the tire.

  According to a second aspect of the present invention, in the outer region and the inner region, a groove or a shoulder lateral groove including a groove and a sipe extending across the tread contact end inward and outward in the tire axial direction is provided in the tire circumferential direction. 2. The pneumatic tire according to claim 1, wherein a total groove width of all the shoulder lateral grooves at the tread ground end in the outer region is larger than a total groove width of all the shoulder lateral grooves at the tread ground end of the inner region. .

  According to a third aspect of the present invention, in the outer region and the inner region, a groove or a shoulder lateral groove including a groove and a sipe extending across the tread ground end inward and outward in the tire axial direction is provided in the tire circumferential direction. The total number of shoulder lateral grooves in the inner region is greater than the total number of shoulder lateral grooves in the outer region.

  According to a fourth aspect of the present invention, in the outer region and the inner region, a groove or a shoulder lateral groove including a groove and a sipe extending across the tread grounding end in the tire axial direction is provided in the tire circumferential direction. 4. The pneumatic tire according to claim 1, wherein the shoulder lateral groove in the outer region includes a widened shoulder lateral groove whose groove width increases toward the outer side in the tire axial direction.

  The invention according to claim 5 is the pneumatic tire according to any one of claims 1 to 4, wherein a chamfered portion is provided on a groove wall surface on the inner side in the tire axial direction of the second outer wide main groove.

  The invention according to claim 6 is the pneumatic tire according to claim 5, wherein the chamfered portion is recessed in a concave arc shape.

  Further, in the invention according to claim 7, the inner wide main groove is composed of a first inner wide main groove extending on the tire equator side and a second inner wide main groove extending on the tread grounding end side. In the inner region, inner middle lateral grooves that connect between the first inner wide main groove and the second inner wide main groove are provided in the tire circumferential direction, and the total number of the inner middle lateral grooves Is a pneumatic tire according to any one of claims 2 to 4, wherein the number is smaller than the total number of shoulder lateral grooves in the outer region.

  The invention according to claim 8 is characterized in that a center block divided by a center lateral groove is arranged in the tire circumferential direction between the first inner wide main groove and the first outer wide main groove and on the tire equator. The pneumatic tire according to claim 7, wherein a block row is formed, and a total number of the inner middle lateral grooves is larger than a total number of the center lateral grooves.

  In the pneumatic tire of the present invention, the land ratio of the outer region of the tread portion located outside the tire equator when the vehicle is mounted is smaller than the land ratio of the inner region of the tread portion located inside the vehicle than the tire equator. Composed. Accordingly, the drainage performance in the outer region that mainly contacts the road surface during turning is greatly improved. Further, since the wide main groove includes an outer wide main groove provided in the outer region and an inner wide main groove provided in the inner region that is located on the inner side of the tire equator, drainage is performed in both the inner region and the outer region. It becomes possible to ensure the sex. Further, the outer wide main groove includes a first outer wide main groove on the tire equator side and a second outer wide main groove on the tread grounding end side that are separated from the tire equator by a predetermined distance. Ribs extending continuously in the tire circumferential direction are formed on both sides of the outer wide main groove and the second outer wide main groove in the tire axial direction without being divided by the lateral grooves. For this reason, even if the land ratio in the outer region is small, the rigidity can be prevented from being lowered, and as a result, the stability during turning is ensured.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a developed view of a tread portion of a pneumatic tire (not shown) of the present embodiment, and FIG.

  In the figure, the pneumatic tire of the present embodiment has an asymmetric tread pattern that is asymmetrical with respect to the tire equator C, and the mounting direction of the pneumatic tire is determined. That is, the pneumatic tire shown in FIG. 1 is mounted such that the region on the right side of the tire equator C is located outside the vehicle and the left side is located inside the vehicle when the vehicle is mounted. In addition, the direction of mounting on the vehicle (for example, “INSIDE” and / or “OUTSIDE”) is clearly indicated by letters or the like (not shown) on the sidewall portion of the tire. Note that the pneumatic tire of the present embodiment is configured as a radial tire for passenger cars.

  In the pneumatic tire of the present embodiment, the land ratio Lo of the outer region Ao of the tread portion 2 positioned on the vehicle outer side than the tire equator C when the vehicle is mounted is the inner region of the tread portion positioned on the vehicle inner side of the tire equator C. It is configured to be smaller than the land ratio Li of Ai. When the vehicle is turning, the contact ratio of the outer region Ao is higher than that of the inner region Ai on the contact surface. Therefore, by forming the land ratio of the outer region Ao relatively small and increasing the groove ratio, the drainage performance at the time of turning can be improved. Further, by making the land ratio Li of the inner region Ai relatively large, the riding comfort and the straight running stability are improved. In particular, in a minivan vehicle that has a larger vehicle weight and a higher center of gravity than a normal passenger car, the load movement during braking (front turning) pushes down the tire in the C-shaped direction, and the inner area Ai of the tread portion 2 is more likely to contact the ground. . Therefore, by mounting the tire according to the present embodiment on a minivan (minivan tire), the ride comfort and straight running stability can be more effectively enhanced.

  Here, the land ratio Lo of the outer area Ao is the total contact area S2 of land portions (blocks, ribs, etc.) that can contact the road surface in the section from the tire equator C of the tread portion 2 to the tread contact end 2e outside the vehicle. And the ratio S2 / S1 to the surface area S1 of the section of the tread portion 2 in the slick state, assuming that all the grooves are filled. Further, the land ratio of the inner region Ai is obtained in the same manner as described above in the section from the tire equator C of the tread portion 2 to the tread ground contact edge 2e on the vehicle inner side.

  The tread grounding end 2e is the most tire when a normal load is applied to a tire in a normal state in which a rim is assembled to a normal rim and a normal internal pressure is filled, and the tread portion 2 is grounded to a flat surface with a camber angle of 0 degrees. It is defined as the ground contact position on the outside in the axial direction.

  The regular rim is a rim determined for each tire in the standard system including the standard on which the tire is based. For example, “Standard Rim” for JATMA, “Design Rim” for TRA, For ETRTO, use “Measuring Rim”. Further, the normal internal pressure is an air pressure determined by each standard for each tire in a standard system including a standard on which the tire is based. “JATMA” indicates “maximum air pressure”, and TRA indicates “TIRE LOAD”. The maximum value described in LIMITS AT VARIOUS COLD INFLATION PRESSURES is "INFLATION PRESSURE" if it is ETRTO, but it is uniformly 180 kPa if the tire is for passenger cars. The normal load is a load determined by each standard for each tire in the standard system including the standard on which the tire is based, and is “maximum load capacity” for JATMA and “TIRE” for TRA. The maximum value described in “LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” is “LOAD CAPACITY” if it is ETRTO.

  The specific value of the land ratio Lo of the outer area Ao can be variously set in view of the vehicle to be mounted, etc., but if the value becomes extremely small, the stability at the time of turning may be impaired. If it is too large, the drainage performance during turning may not be sufficiently improved. From such a viewpoint, the land ratio Lo of the outer region Ao is preferably 0.65 or more, more preferably 0.66 or more, further preferably 0.67 or more, and preferably 0.70 or less. Preferably it is 0.69 or less, more preferably 0.68 or less. Similarly, the land ratio Li of the inner region Ai is preferably 0.70 or more, more preferably 0.71 or more, still more preferably 0.72 or more, and preferably 0.76 or less, more preferably 0. .75 or less, more preferably 0.74 or less.

  In addition, if the difference between the land ratio Lo of the outer area Ao and the land ratio Li of the inner area Ai is small, the drainage improvement effect during turning may not be sufficient, or the stability during straight running may decrease, If the difference in the land ratio becomes large, uneven wear may occur in the tread portion 2. From such a viewpoint, the ratio (Lo / Li) of the land ratio Lo of the outer area Ao and the land ratio Li of the inner area Ai is preferably 0.90 or more, more preferably 0.91 or more, Preferably it is 0.95 or less, more preferably 0.93 or less.

  The total land ratio of the tread portion 2 (land ratio between the tread grounding ends 2e and 2e) is preferably 0.67 or more, more preferably 0.68 or more, and preferably 0.71 or less. More preferably, 0.70 or less is desirable. In the present embodiment, the tread portion 2 is provided with various grooves, but the above-mentioned land ratio can be easily adjusted by adjusting the width and / or the number of the grooves.

  In order to obtain basic drainage, the tread portion 2 is provided with a plurality of wide main grooves 3 extending continuously in the tire circumferential direction. As the wide main groove 3, as shown in FIG. 1, a linear groove along the tire circumferential direction that can minimize drainage resistance is most preferable. However, the wide main groove 3 can be formed in various shapes such as a zigzag shape and a wave shape as long as it extends continuously in the tire circumferential direction.

  The groove width and groove depth of the wide main groove 3 can be appropriately determined according to the tire size and the like. However, if they are too large, the rigidity of the tread portion 2 tends to be reduced. There is a tendency to deteriorate. In order to prevent a significant decrease in the tread rigidity while ensuring sufficient drainage, the width of the wide main groove 3 of the tread portion 2 is preferably 3% or more, more preferably 4% of the tread grounding width TW. The above is desirable, and it is preferably 7% or less, more preferably 6% or less. Similarly, the groove depth of the wide main groove 3 is preferably 6 mm or more, more preferably 7 mm or more, and preferably 10 mm or less, more preferably 9 mm or less.

  In addition, the dimensions of each part of the tire such as the groove width and groove depth are values measured in the normal state unless otherwise specified, and the groove width is measured in a direction perpendicular to the longitudinal direction of the groove in principle. . The tread contact width is a distance in the tire axial direction between the tread contact ends 2e and 2e in the normal state.

  In the present embodiment, the wide main groove 3 is composed of two outer wide main grooves 4 provided in the outer region Ao and two inner wide main grooves 5 provided in the inner region Ai. That is, in the present embodiment, two wide main grooves 3 are provided in each of the outer region Ao and the inner region Ai. As a result, five main land portions divided by the four wide main grooves 3 are formed in the tread portion 2.

  As shown in an enlarged view in FIG. 3, the outer wide main groove 4 is formed on the tire equator side of the tire equator side having a groove center line at a distance d1 of 5 to 15% of the tread ground contact width TW from the tire equator C. A first outer wide main groove 4a, and a second outer wide main groove 4b on the tread grounding end 2e side having a groove center line at a distance d2 of 15 to 28% of the tread grounding width TW from the tire equator C; Consists of. The “tire equator side” and the “tread grounding end side” merely specify the relative positional relationship between the two grooves 4a and 4b (d1 <d2), for example, the second outer wide main groove. It does not mean that 4b is provided closer to the tread ground contact end 2e than the tire equator C. Each groove center line is a center line of the width of the opening groove on the outer surface of the tread.

  By providing the first outer wide main groove 4a and the second outer wide main groove 4b at such a position, the balance between the land portion rigidity and the drainage of the outer region Ao is improved. That is, when the first outer wide main groove 4a and / or the second outer wide main groove 4b is provided on the tire equator C side than the respective positions, the rigidity of the outer region Ao on the tire equator side is reduced, There is a possibility that the drainage at the tread grounding end 2e side is deteriorated. Conversely, when the first outer wide main groove 4a and / or the second outer wide main groove 4b is provided at the tread ground contact end 2e with respect to the respective positions, the drainage property on the tire equator side of the outer region Ao is improved. There is a possibility that the lowering or the rigidity lowering on the tread grounding end 2e side may occur. In particular, the distance d1 is preferably 7% or more, more preferably 8% or more, and preferably 13% or less, more preferably 12% or less of the tread ground contact width TW. Similarly, the distance d2 is desirably 18% or more of the tread ground contact width TW, more desirably 20% or more, and desirably 26% or less, and more desirably 24% or less.

  On the other hand, the inner wide main groove 5 provided in the inner region Ai has a groove center at a position separated from the tire equator C by a distance d3 of 11 to 16% of the tread ground contact width TW, as shown in an enlarged view in FIG. A first inner wide main groove 5a on the tire equator side provided with a line, and a tread grounding end provided with a groove centerline at a distance d4 of 27 to 34% of the tread grounding width TW from the tire equator C The second inner wide main groove 5b on the 2e side.

  By providing the first inner wide main groove 5a and the second inner wide main groove 5b at such a position, the inner region Ai is desirable in that the balance between the land portion rigidity and drainage is improved. . That is, when the first inner wide main groove 5a and / or the second inner wide main groove 5b is provided on the tire equator C side than the respective positions, the rigidity reduction on the tire equator side of the inner region Ai, A drop in drainage on the tread grounding end 2e side tends to occur. On the contrary, when the first inner wide main groove 5a and / or the second inner wide main groove 5b are provided at the tread ground contact end 2e from the respective positions, the drainage property on the tire equator side of the inner region Ai is improved. Decrease and rigidity decrease on the tread grounding end 2e side are likely to occur.

  As described above, in the pneumatic tire according to the present embodiment, two wide main grooves 3 are provided in each of the outer region Ao and the inner region Ai, and the arrangement positions thereof are restricted. The rigidity and drainage can be improved in a well-balanced manner.

  Further, in the outer region Ao, one outer fine groove 6 extending linearly and continuously in the tire circumferential direction is provided outside the second outer wide main groove 4b in the tire axial direction. The outer narrow groove 6 extends linearly in the tire circumferential direction, and no lateral groove or the like extending in the tire axial direction is provided between the outer narrow groove 6 and the second outer wide main groove 4b. . As a result, a first straight rib 7 extending linearly in the tire circumferential direction is formed between the outer narrow groove 6 and the second outer wide main groove 4b.

  In addition, the second straight rib 8 extending continuously in the tire circumferential direction without being divided by the lateral groove is also formed in the entire region between the second outer wide main groove 4b and the first outer wide main groove 4a. The

  Furthermore, one intermediate narrow groove 9 extending continuously in the tire circumferential direction is provided between the first outer wide main groove 4a and the first inner wide main groove 5a and in the present embodiment in the outer region Ao. . The intermediate narrow groove 9 extends linearly in the tire circumferential direction, and a lateral groove extending in the tire axial direction is not provided between the intermediate narrow groove 9 and the first outer wide main groove 4a. Absent. As a result, the third straight rib 10 extending linearly in the tire circumferential direction is also formed between the intermediate narrow groove 9 and the first outer wide main groove 4a.

  In the pneumatic tire of the present embodiment, the land ratio Lo of the outer area Ao is set smaller than that of the inner area Ai in order to improve drainage performance during turning. Such an idea is opposite to the conventional one, and until now, there has been a concern about the stability at the time of turning contrary to the drainage. However, as described above, the tire circumferential rigidity that extends continuously in the tire circumferential direction without being divided by the lateral grooves on both sides in the tire axial direction of the first outer wide main groove 4a and the second outer wide main groove 4b. By forming the high ribs 7, 8, and 10, the pattern rigidity of the outer region Ao is effectively increased, so that the stability at the time of turning can be maintained.

  The widths W1, W2, and W3 of the first to third straight ribs 7, 8, and 10 in the tire axial direction are not particularly limited. However, if the width is reduced, stability during turning may be impaired. On the contrary, if it becomes larger, drainage may be deteriorated. From such a point of view, the widths W1, W2 and W3 are preferably 3% or more, more preferably 4% or more, and preferably 10% or less, more preferably 9% or less of the tread grounding width TW. Is desirable.

  Further, as a result of various experiments by the inventors, when the outer wide main grooves 4a and 4b are provided at the above-described positions, the second lateral rib 8 located in the middle of the three straight ribs has the largest lateral width. It was found that force is easy to act. In view of such a fact, the width W2 of the second straight rib 8 is desirably formed larger than the widths W1 and W2 of the first and third straight ribs 7 and 10. Specifically, the width W2 of the second straight rib 8 is desirably about 7 to 9% of the tread grounding width TW, and the widths W1 and W2 of the other ribs 7 and 10 are 4 to 6 of the tread grounding width TW. % Is desirable. Thereby, stability at the time of turning, especially wobbling at the time of turning can be suppressed.

  Further, in order to further increase the lateral rigidity of the second straight rib 8 and increase the groove volume of the second outer wide main groove 4b without reducing the rigidity of the outer region Ao, it is enlarged to FIG. As shown, it is desirable to provide the chamfered portion b on the groove wall surface 4bw on the inner side in the tire axial direction of the second outer wide main groove 4b. That is, the groove wall surface 4bw is composed of a gentle slope portion a extending from the groove bottom c outward in the tire radial direction at a small height, and a chamfer portion b cut out between the gentle slope portion a and the tread ground contact surface 2a. Composed.

  The chamfered portion b can adopt various shapes such as a flat surface or a curved surface as long as the groove volume is increased by forming a gentle slope than the gentle slope portion a. The chamfered portion b of the present embodiment is formed by a curved surface that is recessed in a concave arc shape with a radius of curvature R having a center outside the tire. Such a chamfered portion b efficiently increases the volume of the groove and further enhances the drainage performance of the second outer wide main groove 4b, increases the lateral rigidity of the second straight rib 8, and consequently, stability during turning. Can be further improved.

  The height hm of the chamfered portion b in the tire radial direction is preferably 80 to 84% of the groove depth Gd of the second outer wide main groove 4b. When the height hm of the chamfered portion is less than 80% of the depth Gd of the second outer wide main groove 4b, it is difficult to obtain a sufficient effect of increasing the groove volume. There is a possibility that b becomes large and the pattern rigidity is lowered. Further, the curvature radius R of the chamfered portion b is preferably about 5 to 15 mm.

  Further, as shown in FIG. 2, in the outer region Ao, a shoulder lateral groove Yo extending outward from the outer narrow groove 6 in the tire axial direction and crossing the tread grounding end 2e to the outer side in the tire axial direction is formed in the tire circumference. It is separated in the direction. The shoulder lateral groove Yo is a concept including all the recessed objects extending in and out of the tire axial direction across the outer tread ground contact edge 2e. Specifically, the shoulder lateral groove Yo is a so-called “groove” having a groove width of 1 mm or more. In addition, a "sipe" having a groove width of 1 mm or less may be included, and further, these may be connected. In the present embodiment, only the outer shoulder lateral grooves 11 spaced in the tire circumferential direction are provided in the outer region Ao, and sipes are not included. Thus, an outer shoulder block row 13 in which the outer shoulder blocks 12 divided by the outer shoulder lateral grooves 11 are arranged in the tire circumferential direction is formed on the outer side in the tire axial direction of the outer narrow groove 6. In order to increase the lateral rigidity of the outer shoulder block 12 and to ensure stability during turning, the angle θ1 of the outer shoulder lateral groove 11 with respect to the tire circumferential direction is preferably 70 degrees or more, and more preferably 75 degrees or more. On the other hand, if the angle θ1 is too large, the noise performance may be deteriorated, and is preferably 85 degrees or less, more preferably 80 degrees or less. The groove angle is a straight line connecting both ends of the groove center line.

  Further, the outer shoulder lateral groove 11 of the present embodiment has two types, an equal width shoulder lateral groove 11a extending with a substantially constant groove width Gs, and a widened shoulder lateral groove 11b with the groove width increasing toward the outer side in the tire axial direction. Including. Such a widened shoulder lateral groove 11b is useful for improving the drainage of the outer region Ao.

  The widened shoulder lateral groove 11b includes an inner portion 11b1 in the tire axial direction having a groove width Gs1 and an outer portion 11b2 in the tire axial direction in which the groove width gradually changes from Gs1 to Gs2. However, the widened shoulder lateral groove 11b may have a groove width that gradually increases toward the outer side in the tire axial direction. In the widened shoulder lateral groove 11b, the ratio of the groove width (Gs2 / Gs1) is preferably about 1.5 to 2.5, for example. In this embodiment, the ratio (Gs1 / Gs) between the groove width Gs of the equal width shoulder lateral groove 11a and the groove width Gs1 on the inner side in the tire axial direction of the wide width shoulder lateral groove 11b is about 0.8 to 1.0. Yes, they are set to be substantially the same.

  In the present embodiment, the equal width shoulder lateral grooves 11a and the wide width shoulder lateral grooves 11b are provided at a ratio of 2: 1. However, when the land ratio Lo of the outer region Ao is desired to be smaller, the wide width is increased. It is desirable to further increase the arrangement ratio of the shoulder lateral grooves 11b.

  In addition, the groove widths Gs1, Gs2, and Gs of the outer shoulder lateral groove 11 are formed to be smaller than the groove width of the wide main groove 3, and preferably about 1.5 to 3.5% of the tread grounding width TW. The groove depth is preferably about 1.9 to 3.0 mm.

  Further, between the intermediate narrow groove 9 and the first inner wide main groove 5a, there is a center lateral groove 15 that completely crosses between the middle narrow groove 9 and the tire lateral direction, and between the center lateral grooves 15, 15 And a center sub-groove 16 extending inward in the tire axial direction from the first inner wide main groove 5a and terminating without communicating with the intermediate narrow groove 9. As a result, a center block row 18 is formed between the intermediate narrow groove 9 and the first inner wide main groove 5a in which the center blocks 17 divided by the center lateral grooves 15 are arranged in the tire circumferential direction. The center block 17 is formed so as to straddle the tire equator C.

  In the present embodiment, the center lateral groove 15 is inclined in a direction opposite to the outer shoulder lateral groove 11 and extends substantially linearly. Thereby, the center block 17 is formed in a substantially rhombus shape. As shown in FIG. 4, the angle θ <b> 2 of the center lateral groove 15 with respect to the tire circumferential direction is not particularly limited, but if it is too small, the lateral rigidity of the center block 17 may be reduced, and conversely if it is too large. The drainage near the tire equator may deteriorate. From such a viewpoint, the angle θ2 is preferably 20 degrees or more, more preferably 25 degrees or more, and preferably 35 degrees or less, more preferably 30 degrees or less. As shown in FIG. 2A, the center lateral groove 15 of the present embodiment shows a preferred mode in which the groove depth gradually increases toward the first inner wide main groove 5a. This is useful for improving the drainability in the inner region Ai while increasing the rigidity of the center block 17 near the tire equator of the high ground pressure.

  The center sub-groove 16 is provided at a substantially intermediate position between the center lateral grooves 15 and 15 adjacent in the tire circumferential direction and extends substantially parallel to the center lateral groove 15. Such a center sub-groove 16 is useful for relaxing the rigidity of the center block 17 without excessively reducing it and improving its wear resistance. From such a viewpoint, it is preferable that the groove width and the groove depth of the center sub-groove 16 are formed smaller than the center lateral groove 15. In order to sufficiently secure the rigidity of the center block 17, it is desirable that the inner end of the center auxiliary groove 16 in the tire axial direction is terminated without reaching the tire equator C.

  The center lateral groove 15 and the center sub-groove 16 are formed to have a groove width smaller than that of the wide main groove 3, and preferably about 0.8 to 2.0% of the tread grounding width TW. The groove depth is preferably about 0.9 to 1.8 mm.

  Moreover, between the 1st inner side wide main groove 5a and the 2nd inner side wide main groove 5b, the inner side middle lateral groove 20 which connects between these is spaced apart by the tire circumferential direction. Accordingly, a middle block row 22 in which the middle blocks 21 are arranged in the tire circumferential direction is formed between the first inner wide main groove 5a and the second inner wide main groove 5b. The middle block 21 is provided with a small sipe 23 for strain relief that extends from the second inner wide main groove 5b in the opposite direction to the inner middle lateral groove 20 and terminates inside the block.

  In the present embodiment, the inner middle lateral groove 20 is inclined in the same direction as the center lateral groove 15 and extends substantially linearly. Thereby, the middle block 21 is also formed in a substantially rhombus shape. The angle θ3 of the inner middle lateral groove 20 with respect to the tire circumferential direction is not particularly limited, but if it is too small, the lateral rigidity of the middle block 21 may be reduced, and conversely if too large, drainage in the inner region Ai. May deteriorate. From such a viewpoint, the angle θ3 is preferably 30 degrees or more, more preferably 34 degrees or more, and preferably 45 degrees or less, more preferably 40 degrees or less.

  Further, as shown in FIG. 4, the inner middle lateral groove 20 has a wide portion 20a having a large width provided on the tire equator side, and a second inner wide main groove that is connected to the wide portion 20a with a step. The narrow portion 20b extends up to 5b. However, the inner middle lateral groove 20 is not limited to such a mode.

  As a preferred embodiment, the total number Nim of the inner middle lateral grooves 20 is preferably smaller than the total number of shoulder lateral grooves Yo (the total number of outer shoulder lateral grooves 11 in this example) Nos in the outer region. The groove area per inner middle lateral groove 20 is formed smaller than the groove area per outer shoulder lateral groove 11. For this reason, when the number of grooves is regulated in the above-described relationship, it is useful to efficiently make the land ratio Lo of the outer area Ao smaller than the land ratio Li of the inner area Ai. In addition, by setting Nim <Nos, the tire block length in the tire circumferential direction of the middle block 21 having a high contribution ratio to the ride comfort is increased, and the effect of improving the ride comfort is further enhanced, and the contribution ratio to the stability during turning is also increased. The length in the tire axial direction of the high outer shoulder block 12 can be made relatively large, and the effect of improving the stability during turning can be further enhanced. From such a viewpoint, the ratio (Nim / No) of the total number Nim of the inner middle lateral grooves 20 and the total number Nos of the outer shoulder lateral grooves 11 is preferably about 0.6 to 0.8, for example.

  Further, it is desirable that the total number Nim of the inner middle lateral grooves 20 is larger than the total number of the center lateral grooves 15 (thus, the center subgroove 16 is not included) Nc. Thus, the ride comfort can be improved while maintaining the stability during straight traveling by making the length of the center block 17 in the tire circumferential direction larger than the middle block 21 with the highest ground pressure. From such a viewpoint, the ratio (Nim / Nc) of the total number Nim of the inner middle lateral grooves 20 and the total number Nc of the center lateral grooves 15 is preferably about 1.5 to 2.5, for example. By making the total number of such grooves different in each part, noise is dispersed and the quietness during running can be improved.

  Further, on the outer side in the tire axial direction of the second inner wide main groove 5b, the inner narrow groove 24 extending continuously in the tire circumferential direction and the tread grounding end 2e in the inner region Ai cross in and out of the tire axial direction. Shoulder lateral grooves Yi spaced apart in the tire circumferential direction are provided. Thereby, a fourth straight rib 26 extending continuously in the tire circumferential direction without being divided by the lateral groove is formed between the inner narrow groove 24 and the second inner wide main groove 5b. Thus, by providing the straight ribs 26 having high rigidity along the wide main groove 5b also in the inner area Ai, the pattern rigidity of the inner area Ai is improved, which is particularly desirable from the viewpoint of improving the stability during straight traveling. .

  The width W4 of the fourth straight rib 26 is not particularly limited, but if it becomes extremely small, the stability during straight travel may be impaired, and conversely, if it becomes significantly large, the drainage property may deteriorate. . From such a viewpoint, the width W4 is preferably 3.0% or more, more preferably 4.0% or more of the tread grounding width TW, and preferably 6.0% or less, more preferably 5. 0% or less is desirable.

  The groove width of each narrow groove (outer narrow groove 6 and intermediate narrow groove 9) including the inner narrow groove 24 is preferably about 1.5 to 3.0 mm, and the groove depth is preferably About 5.0 to 6.0 mm is desirable.

  In addition, the shoulder lateral groove Yi is a concept including all recessed objects extending in and out of the tire axial direction across the inner tread grounding end 2e, as in the case of the shoulder lateral groove Yo. It is a waste. In the shoulder lateral groove Yo of the present embodiment, inner shoulder lateral grooves 25 having a groove width of 1 mm or more and shoulder sipes 31 having a groove width of less than 1 mm are alternately provided in the tire circumferential direction.

  The inner shoulder lateral groove 25 extends from the portion having a groove width of 1 mm or more to the main portion 25a on the outer side in the tire axial direction and the inner end 25i of the main portion 25a to the inner narrow groove 24 and has a groove width of less than 1 mm. Part 25b. An inner end 25 i of the main portion 25 a is provided between the tread grounding end 2 e and the intermediate narrow groove 24. Thus, the inner shoulder ribs 30 that are partially divided by the main portion 25a of the inner shoulder lateral groove 25 are provided on the outer side in the tire axial direction of the inner narrow groove 24. The main portion 25a of the inner shoulder lateral groove 25 of the present embodiment has a groove width Gsi at the tread grounding end 2e, and the groove width gradually decreases from the inner end 25i.

  The inner shoulder lateral groove 25 is useful for increasing the land ratio of the inner region Ai while ensuring drainage at the tread ground contact end 2e by the main portion. In addition, in a passenger car with a negative camber, the inner region Ai mainly touches down when traveling straight, so the inner shoulder rib 30 having a continuous portion in the tire circumferential direction generates noise such as impact noise and vibration during straight traveling. It also helps to reduce and increase ride comfort. Moreover, the sipe part 25b is useful for relieving distortion during traveling of the inner shoulder rib 30 and improving wear resistance.

  The inner shoulder lateral grooves 25 are preferably inclined at a relatively large angle θ4 in the same direction as the outer shoulder lateral grooves 11 and, for example, 70 to 80 degrees, more preferably 73 to 77 degrees with respect to the tire circumferential direction. This increases the lateral rigidity of the inner shoulder rib 30 and helps to ensure stability during straight traveling.

  The shoulder sipe 31 also extends in and out of the tire axial direction across the inner tread grounding end 2 e, and the inner end in the tire axial direction is connected to the inner narrow groove 24. Further, the shoulder sipe 31 is inclined in the same direction as the inner shoulder lateral groove 25 and, for example, 70 to 80 degrees, more preferably 73 to 77 degrees, more preferably substantially the same angle θ5 with respect to the tire circumferential direction. preferable.

  The width W5 of the inner shoulder rib 30 in the tire axial direction is preferably 10% or more of the tread contact width TW, more preferably 12% or more, and preferably 20% or less, more preferably 17% or less. . In particular, the outer shoulder block 12 is desirably smaller than the width W7 in the tire axial direction. This makes it possible to achieve both higher levels of stability during turning and ride comfort when going straight. Further, in order to enhance the ride comfort, the width W6 of the inner shoulder rib 30 that is continuous in the tire circumferential direction (ignoring sipes having no substantial width) is more preferably 50% or more of the rib width W5. 60 to 80% is desirable.

  Moreover, as a preferable aspect, for example, the total groove width Gao for one tire circumference of all the shoulder lateral grooves Yo (that is, the outer shoulder lateral grooves 11) at the tread ground end 2e in the outer region Ao is set to the tread ground end 2e in the inner region Ai. It is desirable to make it larger than the total groove width Gai of all the shoulder lateral grooves Yi in (i.e., the inner shoulder lateral grooves 25 and the shoulder sipes 31) (Gao> Gai). In addition, the groove width said here shall be measured in the tire circumferential direction in the position of the tread grounding end 2e. This helps to adjust the land ratio between the outer area Ao and the inner area Ai of the tread portion 2, and can greatly improve the drainage performance during turning. As an example, the total groove width ratio (Gao / Gai) is preferably 1.05 or more, more preferably 1.1 or more. However, if the ratio (Gao> Gai) becomes excessively large, the difference in rigidity between the inner and outer grounding ends 2e may increase and wear resistance may deteriorate. Preferably 1.2 or less is desirable.

  Similarly, the total number of shoulder lateral grooves Yi in the inner region Ai (that is, the total number of inner shoulder lateral grooves 25 and shoulder sipes 31) Nis is the total number of the shoulder lateral grooves Yo in the outer region Ao (that is, the total number of outer shoulder lateral grooves 11). The number is preferably more than Nos. By defining the total number of the shoulder lateral grooves Yi and Yo in the relationship as described above, the envelope performance in the inner area Ai is enhanced and the riding comfort is enhanced, and the pattern rigidity is relatively increased in the outer area Ao, and the turning Stability is improved. In order to exhibit such an action more effectively, the ratio of the total number (Nos / Nis) is preferably 0.6 or more, more preferably 0.7 or more, and preferably 0.9. Below, more preferably 0.8 or less.

As described above, the total number of lateral grooves has a great influence on the envelope performance and the stability at the time of turning.
Nc <Nim <Nos <Nis
The total number of grooves is preferably set so as to satisfy the above relationship. As a result, in addition to the above action, the center block 17 is more rigid than the middle block 21 in the center portion of the tread, which is the main ground contact area during straight travel, and the straight travel stability can be further improved.

  Although the embodiment of the present invention has been described above, it is needless to say that the present invention is not limited to the above-described embodiment and can be implemented by being modified into various modes.

Radial tires for passenger cars of size 215 / 60R16 were prototyped based on the basic pattern in FIG. 1 and the specifications in Table 1, and various performances were tested. The common specifications are as follows, and the land ratio is adjusted by adjusting the number of grooves other than the wide main groove.
Tread contact width: 167mm
Groove width of the first outer wide main groove: 12.1 mm, groove depth: 8.1 mm
Groove width of the second outer wide main groove: 8.4 mm, groove depth: 8.1 mm
First inner wide main groove groove width: 9.2 mm, groove depth: 8.1 mm
Second inner wide main groove groove width: 9.0 mm, groove depth: 8.1 mm
Outer shoulder lateral groove angle θ1: 79.2 degrees Groove width of outer shoulder lateral groove Gs: 4.0 mm
Gs1: 3.5mm
Gs2: 5.6 mm
Outer shoulder lateral groove depth: 5.0mm
Center transverse groove angle θ2: 27.2 degrees Center transverse groove width: 2.1-3.3 mm, groove depth 5.1-7.0 mm
Inner middle horizontal groove angle θ3: 36.4 degrees Groove width of inner middle horizontal groove: wide part 1.0 mm, narrow part 4.0 mm
Inner shoulder transverse groove angle θ4: 75.5 degrees Groove width of inner shoulder transverse groove Main part: 5.2 mm
Sipe part: 0.6mm
Inner shoulder lateral groove depth: 5.6mm
Shoulder sipe angle θ5: 76.8 degrees Shoulder sipe width: 0.6 mm
Groove width of outer and inner narrow grooves: 5.0 mm, groove depth: 5.0 mm
Intermediate narrow groove width: 5.9 mm, groove depth: 5.0 mm
The test method is as follows.

<Drainage performance>
Each test tire is mounted on four domestically produced 2400cc passenger cars under the following conditions, and the speed is gradually increased to a test course with a water pool of 5mm depth and 20m length on an asphalt road surface with a radius of 100m. The average lateral acceleration of the front wheels at a speed of 50 to 80 km / h was measured. A result is an index | exponent which sets the comparative example 1 to 100, and shows that it is excellent in the drainage property at the time of turning, so that a numerical value is large.
Rims: 16x6.5J
Internal pressure: 220 kPa

<Stability during straight running>
The test vehicle was run straight on a dry dry asphalt road surface, and the presence or absence of wobbling was comprehensively evaluated by the driver's sensuality. All are shown by evaluation points with Comparative Example 1 as 100 points, and the larger the value, the better.

<Steering stability and ride comfort>
The test vehicle was run on a dry dry asphalt road surface, and the steering stability index regarding the response and grip feeling when turning was comprehensively evaluated by the driver's sensuality. Similarly, on the asphalt step road, the Belgian road (cobblestone road surface), the Bitzmann road (road surface covered with pebbles), etc., ride comfort indexes such as ruggedness, push-up and dumping were comprehensively evaluated by the driver's sensuality. All are shown by evaluation points with Comparative Example 1 as 100 points, and the larger the numerical value, the better.

  Table 1 shows the test results. In addition, the code | symbol in Table 1 respond | corresponds with the code | symbol of detailed description and drawing.

  As a result of the test, it was confirmed that the tires of the examples improved drainage performance during turning without losing stability during straight running and exhibited excellent wet grip performance.

It is an expanded view of the tread part of the pneumatic tire of this embodiment. It is the AA sectional view. It is an enlarged view of the outer side area | region of a tread part. It is an enlarged view of the inner side area | region of a tread part.

Explanation of symbols

2 tread portion 2a tread contact surface 2e tread contact end 3 wide main groove 4 outer wide main groove 4a first outer wide main groove 4b second outer wide main groove 5 inner wide main groove 5a first inner wide main groove 5b Second inner wide main groove 6 Outer narrow groove 7 First straight rib 8 Second straight rib 10 Third straight rib 11 Outer shoulder lateral groove 11a Equal width shoulder lateral groove 11b Widened shoulder lateral groove 15 Center lateral groove 17 Center block 18 Center Block row 20 Middle lateral groove 25 Inner shoulder lateral groove 31 Shoulder sipe Ai Inner region Ao Outer region TW Tread contact width Yo Outer region shoulder lateral groove Yi Inner region shoulder lateral groove

Claims (8)

A pneumatic tire having an asymmetric tread pattern in which the direction of mounting on the vehicle is specified;
The land ratio of the outer region of the tread portion located outside the tire equator when the vehicle is mounted is smaller than the land ratio of the inner region of the tread portion located inside the vehicle from the tire equator, and the tread portion Is provided with a plurality of wide main grooves extending continuously in the tire circumferential direction,
The wide main groove includes an outer wide main groove provided in the outer region and an inner wide main groove provided in the inner region, and the outer wide main groove has a tread contact width of 5 from the tire equator. A first outer wide main groove on the tire equator side having a groove centerline at a distance of ~ 15%;
A second outer wide main groove on the tread ground end side having a groove center line at a position spaced 15 to 28% of the tread ground contact width from the tire equator,
A pneumatic tire comprising ribs extending continuously in a tire circumferential direction without being divided by a lateral groove on both sides in the tire axial direction of the first outer wide main groove and the second outer wide main groove. . In the outer region and the inner region, a groove or a shoulder lateral groove including a groove and a sipe extending across the tread contact end in the tire axial direction is provided in the tire circumferential direction.
The pneumatic tire according to claim 1, wherein a total groove width of all shoulder lateral grooves at the tread ground end in the outer region is larger than a total groove width of shoulder lateral grooves at all the tread ground ends in the inner region. In the outer region and the inner region, a groove or a shoulder lateral groove including a groove and a sipe extending across the tread contact end in the tire axial direction is provided in the tire circumferential direction.
The pneumatic tire according to claim 1 or 2, wherein the total number of shoulder lateral grooves in the inner region is larger than the total number of shoulder lateral grooves in the outer region. In the outer region and the inner region, a groove or a shoulder lateral groove including a groove and a sipe extending across the tread contact end in the tire axial direction is provided in the tire circumferential direction.
The pneumatic tire according to any one of claims 1 to 3, wherein the shoulder lateral groove in the outer region includes a widened shoulder lateral groove whose groove width increases toward the outer side in the tire axial direction.   The pneumatic tire according to any one of claims 1 to 4, wherein a chamfered portion is provided on a groove wall surface on the inner side in the tire axial direction of the second outer wide main groove.   The pneumatic tire according to claim 5, wherein the chamfered portion is recessed in a concave arc shape. The inner wide main groove is composed of a first inner wide main groove extending on the tire equator side and a second inner wide main groove extending on the tread ground end side, and the inner region includes the first wide main groove. An inner middle lateral groove that connects between the first inner wide main groove and the second inner wide main groove is spaced apart in the tire circumferential direction;
The pneumatic tire according to any one of claims 2 to 4, wherein the total number of the inner middle lateral grooves is smaller than the total number of shoulder lateral grooves in the outer region. A center block row is formed between the first inner wide main groove and the first outer wide main groove and on the tire equator, and center blocks divided by center lateral grooves are arranged in the tire circumferential direction. The pneumatic tire according to claim 7, wherein the total number of middle lateral grooves is greater than the total number of center lateral grooves.

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