JP4677028B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a tire suitable for use in races such as rally and dirt trials, and more particularly to a pneumatic tire with improved maneuverability during saddle running.

  For tires that run on rough terrain, especially pneumatic tires used in races such as rally and dirt trials, to improve traction on rough terrain, the tread part is connected to the circumferential groove extending in the tire circumferential direction. A block pattern divided into a plurality of blocks by intersecting horizontal grooves is widely adopted.

  On the other hand, in this type of tire, the performance of traveling on a hard flat road surface (sometimes referred to as good road performance) is also important. For this reason, as a tread profile, for example, as shown in FIG. As shown in FIG. 6, the tread ground contact width Tw1 is set to about 80 to 86% of the tire cross-sectional width Tw0, and the camber amount Cb of the tread surface is set to be relatively flat at about 5.0 to 7.0 mm. As a result, when traveling on a flat road surface, a necessary contact width and a uniform contact pressure can be ensured, and high road performance can be exhibited.

  However, when running on rough terrain, the road surface is scraped off due to running (走 行). Therefore, the tread side t2 is in strong contact with the wall surface of the heel in addition to the tread surface t1 being flatly grounded. There are things to do. Therefore, there is a problem that scraping b (indicated by hatching) occurs in the outer portion of the shoulder block a arranged on the outermost side in the tire axial direction, and the running performance is remarkably lowered.

Therefore, the present invention is based on the provision of a protruding portion having a protruding upper wall surface extending from the tread contact edge at a predetermined angle to the tire axial direction on the shoulder block, while maintaining good road traveling performance and traveling during saddle traveling. An object of the present invention is to provide a pneumatic tire that improves performance (hereinafter, sometimes referred to as “driving performance”).
JP 2001-113915 A

In order to achieve the above-mentioned object, the invention of claim 1 of the present application is characterized in that the outer tread portion and the tread shoulder region that is closest to the tread ground contact end in the tire circumferential direction are arranged in the tread shoulder region outside the tire axial direction. By providing an outer lateral groove extending outward in the tire axial direction from the circumferential groove, the tread shoulder region is a pneumatic radial tire having a shoulder block row in which a plurality of shoulder blocks are spaced apart in the tire circumferential direction,
In the meridional section including the tire shaft, the shoulder block protrudes from the tread ground contact end inclining outward in the tire axial direction toward the inner side in the tire radial direction at an angle α of 35 to 45 ° with respect to the tire radial direction. An upper wall,
A protruding portion having a protruding lower side wall surface that is inclined inward in the tire axial direction from the protruding peak that is the outer axial end point of the protruding upper wall surface toward the inner side in the tire radial direction and that continues to the outer surface of the sidewall portion. As well as
The outer lateral groove opens at the protruding lower wall surface ,
The protruding portion is characterized in that an angle β between the protruding upper wall surface and the protruding lower wall surface is 110 to 130 ° .

  In the invention of claim 2, the protruding portion is characterized in that a protruding amount La, which is a distance in the tire axial direction between the tread ground contact end and the protruding apex, is 10 to 15 mm.

According to a third aspect of the present invention, the outer lateral groove comprises a lateral groove main portion extending from the outer circumferential groove to the tread grounding end side, and a lateral groove sub-portion extending from the lateral groove main portion to the protruding lower side wall surface. The groove depth Hy2 from the protruding upper wall surface of the lateral groove sub-portion is 80 to 100% of the groove depth Hy1 from the tread surface of the horizontal groove main portion.

According to a fourth aspect of the invention, the protruding portion is characterized in that a protruding height Lb, which is a height in the tire radial direction between the tread ground contact end and the protruding apex, is 15 to 30 mm.

  The “tread grounding end” means the position of the outermost end in the tire axial direction of the tread grounding surface that comes into contact when a normal load is applied to a normal tire in which a normal rim is assembled and filled with a normal internal pressure. In this specification, unless otherwise specified, the dimensions and the like of each part of the tire are values specified in the normal state.

  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, a standard rim for JATMA, “Design Rim” for TRA, or ETRTO means "Measuring Rim". The “regular internal pressure” is the air pressure defined by the standard for each tire. If JATMA, the maximum air pressure is specified. If TRA, the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES”, ETRTO Means "INFLATION PRESSURE", but in the case of passenger car tires, it is 180 kPa. The “regular load” is a load determined by the standard for each tire. The maximum load capacity in the case of JATMA, the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in the case of TRA, If it is ETRTO, it is "LOAD CAPACITY".

  As described above, the protruding portion provided in the shoulder block has a protruding upper wall surface that inclines inwardly in the tire axial direction from the tread contact end toward the inner side in the tire radial direction. Therefore, when running on a flat road surface, the protruding portion does not come into contact with the road surface, and adverse effects on good road running performance can be prevented.

  On the other hand, the protruding upper wall surface is inclined at an angle α of 35 to 45 ° with respect to the tire radial direction. This angle α is close to the shaving angle of the shoulder block caused by rubbing with the saddle wall surface during saddle running. Therefore, when the protruding upper wall surface is inclined at the angle α, the protruding portion can smoothly come into contact with the wall surface with a wide contact area when the vehicle is traveling. In addition, the protruding lower wall surface of the protruding portion is inclined inward in the tire axial direction from the protruding peak toward the inner side in the tire radial direction, and an outer lateral groove extends and opens to the protruding lower wall surface. . Therefore, the rigidity of the protruding portion can be appropriately reduced, and the followability to the wall surface can be ensured. And by these interactions, the shaving of the shoulder block can be suppressed, and the traction property can be enhanced such that a high traction force can be secured from the saddle wall surface, so that the saddle running performance can be improved.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of a pneumatic tire according to the present invention in a normal state, and FIG. 2 is a plan view of a tread portion showing a tread pattern thereof.

  A pneumatic tire 1 according to this embodiment is a rough terrain tire used in races such as rally and dirt trials, and includes a carcass 6 extending from the tread portion 2 to the bead core 5 of the bead portion 4 through the sidewall portion 3. And a belt layer 7 disposed outside the carcass 6 in the tire radial direction and inside the tread portion 2.

  The carcass 6 is composed of one or more carcass plies 6A in which carcass cords are arranged at an angle of, for example, 75 ° to 90 ° with respect to the tire equator C, and in this example, two carcass plies 6A. As the carcass cord, a polyester cord is used in this example, but other than this, an organic fiber cord such as nylon, rayon, aramid, or a steel cord may be used as necessary. The carcass 6 includes folded portions 6b that are folded and locked from the inner side to the outer side in the tire axial direction around the bead core 5 at both ends of the toroidal main body portion 6a straddling the bead cores 5 and 5. A bead apex 8 made of hard rubber having a triangular cross section extending from the bead core 5 to the outside in the tire radial direction is disposed between the main body portion 6a and the folded portion 6b, and is reinforced from the bead portion 4 to the sidewall portion 3. ing.

  The belt layer 7 is formed of at least two belt plies 7A and 7B in this example in which strong belt cords are arranged at an angle of, for example, 10 to 45 ° with respect to the tire equator C. The belt layer 7 has a belt cord crossing with each other between the plies to enhance belt rigidity, and substantially reinforces almost the entire width of the tread portion 2. As the belt cord, a steel cord is employed in this example, but a highly elastic organic fiber cord such as aramid or rayon may be used as necessary.

  Further, in this example, the pneumatic tire 1 has a tread grounding width Tw1 which is a width in the tire axial direction between the tread grounding ends E and E, 80 to 86% of the tire cross-sectional width Tw0, and a camber amount Cb of the tread surface 2S. It is set to 5.0 to 7.0 mm. As a result, when traveling on a hard flat road surface, a necessary contact width and uniform contact pressure can be ensured, and high road performance can be exhibited.

  Next, in the tread portion 2, the tire extends from the outer circumferential groove 9 o to the tread shoulder region Ys on the outer side in the tire axial direction with respect to the outer circumferential groove 9 o that extends closest to the tread grounding end E in the tire circumferential direction. An outer lateral groove 10o extending outward in the axial direction is provided, whereby the tread shoulder region Ys is formed in a shoulder block row 11oR in which a plurality of shoulder blocks 11o are spaced apart in the tire circumferential direction.

  Specifically, in this example, the tread portion 2 is provided with a plurality of circumferential grooves 9 extending continuously in the tire circumferential direction and a plurality of lateral grooves 10 intersecting with the circumferential grooves 9. A block pattern including a plurality of block rows 11R in which the blocks 11 are spaced in the circumferential direction is formed on the tread portion 2.

  More specifically, in this example, as shown in FIG. 2, as the circumferential groove 9, a central circumferential groove 9i disposed on the tire equator C and an intermediate circumferential groove 9m disposed on the outer side thereof. And five outer circumferential grooves 9o disposed on the outer side thereof. Further, as the lateral groove 10, the lateral groove 10i that traverses between the circumferential grooves 9i and 9m, the lateral groove 10m that traverses between the circumferential grooves 9m and 9o, and the circumferential groove 9o extends outward in the tire axial direction. An outer lateral groove 10o is formed. Thereby, an area between the circumferential grooves 9i and 9m is formed as an inner block row 11iR in which an inner block 11i is spaced in the tire circumferential direction, and an area between the circumferential grooves 9m and 9o is The block 11m is formed as a block row 11mR that is spaced apart in the tire circumferential direction, and the tread shoulder region Ys, which is the region outside the outer circumferential groove 9o, is used as the outer block, the shoulder block 11o being the outer block. It is formed in a shoulder block row 11oR spaced in the circumferential direction.

  In this example, the circumferential groove 9 is formed in a zigzag shape, particularly a rectangular wave shape, and the edge component in the tire axial direction is increased to ensure higher traction. In addition, the groove depth Hg of the circumferential groove 9 and the groove depth Hy of the lateral groove 10 are not particularly limited, and a normal tire for traveling on rough terrain can be suitably employed. For example, the groove depth Hg is 6.0 to 12.5 mm, and the groove depth Hy is 6.0 to 12.5 mm. From the viewpoint of traction, the groove depth Hy is substantially equal to the groove depth Hg. preferable. In addition, the code | symbol 12 in a figure is a tie bar which protrudes from a groove bottom, and improves block rigidity by connecting between the blocks adjacent in the circumferential direction and / or the blocks adjacent in the tire axial direction.

  Next, as shown in an enlarged view in FIG. 4, the shoulder block 11o is formed with a protruding portion 15 that protrudes outward in the tire axial direction as compared with the conventional contour shape J (indicated by a two-dot chain line). The Specifically, the protruding portion 15 extends from the tread ground contact edge E so as to incline outward in the tire axial direction toward the inner side in the tire radial direction at an angle α of 35 to 45 ° with respect to the radial direction of the tire. A wall surface SU and a protrusion vertex Ps which is an outer end point in the tire axial direction of the upper wall surface SU of the protruding upper wall are inclined inward in the tire axial direction toward the inner side in the tire radial direction and are extended to the outer surface 3S of the sidewall portion 3. A lower wall surface SL.

  It is preferable that the protruding upper wall surface SU is substantially linear. The “substantially straight line shape” includes, in addition to a straight line, a convex arc shape or a concave arc shape curve having a curvature radius as large as 500 mm or more and close to a straight line. In the case of the curve, the radius of curvature is more preferably 1000 mm or more, and particularly preferably, the radius of curvature is ∞, that is, substantially a straight line. In the case of a curve, the angle α is defined as an angle formed by an imaginary straight line passing through the tread ground contact E and the protruding vertex Ps with the tire radial direction.

  Here, the angle α in the range of 35 to 45 ° is approximate to the angle of the shoulder block shaving caused by rubbing against the saddle wall surface during saddle running. Accordingly, the protruding upper wall surface SU is inclined at the angle α within the above range, so that the protruding portion 15 can smoothly come into contact with the wall surface with a wide contact area during the saddle traveling. The protruding portion 15 has a protruding lower wall surface SL inclined inward in the tire axial direction from the protruding vertex Ps toward the inner side in the tire radial direction, and the outer lateral groove 10o extends to the protruding lower wall surface SL. It extends and is open. Therefore, the rigidity of the protruding portion 15 can be appropriately reduced, and the followability of the protruding portion 15 to the wall surface can be ensured.

  And, by these interactions, a high traction force can be secured from the saddle wall surface, and the traction performance can be improved to improve the saddle running performance. In addition, since the ground can be smoothly grounded with a wide contact area with the saddle wall surface, the shoulder block can be prevented from being scraped, and the improved saddle running performance can be maintained over a long period of time. If the angle α is out of the range of 35 to 45 °, the contact with the heel wall becomes localized, the traction force obtained from the heel wall becomes insufficient, and the shoulder block is scraped to reduce durability. Let When the protruding lower wall surface SL extends radially inward from the protruding apex Ps in the tire radial direction or tilts outward in the tire axial direction, the rigidity of the protruding portion 15 becomes excessive and the protruding portion 15追 従 Followability to the wall surface is significantly reduced. As a result, the traction force obtained from the heel wall becomes insufficient and the shoulder block is scraped. FIG. 5 is a schematic cross-sectional view showing a state when the pneumatic tire of the present invention travels on a saddle.

  Next, in order to improve the saddle running performance, in the protruding portion 15, a protruding amount La that is a distance in the tire axial direction between the tread ground contact end E and the protruding vertex Ps is 10 to 15 mm. preferable. When the protruding amount La is less than 10 mm, the protruding portion 15 itself becomes excessively small, and the effect by the protruding portion 15 is not sufficiently exhibited. On the contrary, even when the protruding amount La exceeds 15 mm, the shoulder block 11o is easily deformed at the base portion, and the rigidity of the block is reduced. Not fully achieved. Further, there is a risk that the shoulder block 11o may be damaged such as a chipped block.

  In the protruding portion 15, it is also preferable that a protruding height Lb, which is a height in the tire radial direction between the tread ground contact E and the protruding apex Ps, is 15 to 30 mm. This is because the range in which the traction force can be obtained from the wall surface is approximately the range of 15 to 30 mm when assuming the shape of the basket. Therefore, if the protruding height Lb is less than 15 mm, the contact area with the wall surface becomes small and the traction force becomes insufficient. Conversely, even if the protruding height Lb exceeds 30 mm, an increase in traction force is not expected and an unnecessary increase in tire mass is caused.

Further, in order to optimize the rigidity of the protruding portion 15, the angle β between the protruding upper wall surface SU and the protruding lower wall surface SL is set to 110 to 130 ° . If the angle β exceeds 130 °, the rigidity of the protruding portion 15 becomes excessive, leading to a deterioration in followability to the heel wall surface and insufficient traction force from the heel wall surface. On the other hand, when the angle β is less than 110 °, the rigidity of the protruding portion 15 becomes too small, so that the traction force from the wall surface is lowered although the followability is increased. In addition, it is preferable that the protruding lower side wall surface SL is substantially linear, like the protruding upper wall surface SU. The protruding vertex Ps preferably has a substantially edge shape so that the edge effect can be exerted when traveling on rough terrain. The “substantially edge shape” includes a small arc close to an edge having a curvature radius of 0.5 mm or less in addition to the edge.

  Further, the outer lateral groove 10o has an outer end opened at the protruding lower side wall surface SL. That is, the outer lateral groove 10o is formed by a lateral groove main portion 10o1 extending from the outer circumferential groove to the tread grounding end E side, and a lateral groove sub-portion 10o2 extending from the lateral groove main portion 10o1 to the protruding lower side wall surface SL. The At this time, it is preferable that the groove depth Hy2 from the protruding upper wall surface SU of the horizontal groove sub-portion 10o2 is 80 to 100% of the groove depth Hy1 from the tread surface of the horizontal groove main portion. When the outer lateral groove 10o is not opened in the protruding lower side wall surface SL, and when the groove depth Hy2 is less than 80% of the groove depth Hy1, the flexibility of the protruding portion 15 is insufficient. As a result, the followability to the heel wall is deteriorated and the scratching effect on the heel wall is reduced, so that the traction force is not sufficiently exhibited. Further, when the groove depth Hy2 exceeds 100% of the groove depth Hy1, the rigidity of the shoulder block 11o is lowered, and the effect of improving the traction force is peaked, and there is a possibility of causing damage such as block chipping. From such a viewpoint, the lower limit of the groove depth Hy2 is preferably 90% or more of the groove depth Hy1. The lateral groove sub-portion 10o2 preferably has a constant groove depth Hy2. However, the groove depth Hy2 can be gradually increased or decreased toward the outer side in the tire axial direction. The average value of the maximum value and the minimum value of the depth Hy2 is 80 to 100% of the groove depth Hy1, and more preferably, the maximum value and the minimum value of the groove depth Hy2 are the groove depth Hy1. It is desirable that it is 80 to 100%.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

  The tire size shown in FIG. 1 and the tread pattern shown in FIG. 2 is a 205 / 65R15 pneumatic tire for a rally based on the specifications shown in Table 1, and the traction performance of each sample tire. The turning performance, grip feeling, and wear resistance were tested. Each tire has substantially the same specifications except for the protruding portion.

(1) Traction performance, turning performance, grip feeling:
The test tire is mounted on all wheels of a rally racing four-wheel drive vehicle with a rim (7J x 15) and internal pressure (210 kPa) with a displacement of 2000 cc. A dry, hard dirt test course (one lap, approximately 2.5 km) ) Was evaluated for the traction performance, turning performance, and grip feeling by a 10-point method with Comparative Example 1 as 5 points. The larger the value, the better.

(2) Wear resistance performance:
Using the vehicle, the state of wear (scraping) when traveling on the dirt course for 300 km was visually examined and indexed into a 10-point method with Comparative Example 1 as 5 points. The larger the value, the better.

表１に示すように、実施例のタイヤは、ダート路面におけるトラクション性を向上し、かつショルダーブロック外側での削れを抑止しうるのが確認できる。

As shown in Table 1, it can be confirmed that the tires of the examples can improve the traction on the dirt road surface and suppress the shaving on the outer side of the shoulder block.

It is sectional drawing which shows one Example of the pneumatic tire of this invention. It is a top view of the tread part which shows the tread pattern. It is a fragmentary perspective view which shows a shoulder block with a protrusion part. It is a fragmentary sectional view which expands and shows a protrusion part. It is a schematic sectional view showing a state when the pneumatic tire of the present invention travels on a saddle. It is sectional drawing which shows the conventional pneumatic tire.

Explanation of symbols

2 Outer circumferential groove 10o Outer circumferential groove 10o Outer lateral groove 10o1 Lateral groove main part 10o2 Lateral groove sub-part 11o Shoulder block 11oR Shoulder block row 15 Projection part E Tread grounding end Ps Projection vertex SU Projection upper wall surface SL Projection lower side wall surface Ys Tread shoulder region

Claims (4)

An outer lateral groove extending from the outer circumferential groove to the outer side in the tire axial direction is provided in the tread shoulder region on the outer side in the tire axial direction from the outer circumferential groove extending in the tire circumferential direction at the tread portion and closest to the tread grounding end. The pneumatic tire is a pneumatic radial tire in which the tread shoulder region is a shoulder block row in which a plurality of shoulder blocks are spaced apart in the tire circumferential direction,
In the meridional section including the tire shaft, the shoulder block protrudes from the tread ground contact end inclining outward in the tire axial direction toward the inner side in the tire radial direction at an angle α of 35 to 45 ° with respect to the tire radial direction. An upper wall,
A protruding portion having a protruding lower side wall surface that is inclined inward in the tire axial direction from the protruding peak that is the outer axial end point of the protruding upper wall surface toward the inner side in the tire radial direction and that continues to the outer surface of the sidewall portion. As well as
The outer lateral groove opens at the protruding lower wall surface ,
The pneumatic tire is characterized in that the protruding portion has an angle β between the protruding upper wall surface and the protruding lower wall surface of 110 to 130 ° .   2. The pneumatic tire according to claim 1, wherein the protruding portion has a protruding amount La of 10 to 15 mm, which is a distance in the tire axial direction between the tread ground contact end and the protruding apex. The outer lateral groove includes a lateral groove main portion extending from the outer circumferential groove to the tread grounding end side, and a lateral groove subportion extending from the lateral groove main portion to the protruding lower side wall surface, and the lateral groove subportion overhang groove depth Hy2 from the upper wall, the groove depth Hy1 from the tread surface of the lateral groove main portion, the pneumatic tire according to claim 1 or 2, characterized in that 80 to 100%. The protruding portion has a protruding height Lb, which is a height in the tire radial direction between the tread ground contact end and the protruding peak, of 15 to 30 mm , according to any one of claims 1 to 3. Pneumatic tire.

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