JP5168804B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire that improves the problem of baldness and cracks while ensuring the effect of preventing splashing of water splashes.

  When the vehicle travels on a wet road surface in rainy weather or the like, the vehicle splashes water droplets, which deteriorates the visibility of the vehicle traveling behind and adversely affects traveling safety. In particular, when heavy-duty vehicles such as trucks and buses travel on wet roads, water splashes greatly, affecting vehicles traveling behind. Thus, in recent years, a pneumatic tire has been proposed in which an annular protrusion for preventing splashing of water droplets is provided on the outer surface of the sidewall portion on the tread portion side (see, for example, Patent Document 1).

However, pneumatic tires used in heavy-duty vehicles such as trucks and buses often run on stepped portions such as curbs, and at that time, a strong tensile stress is applied to the contact portion of the annular protrusion that contacts the stepped portion. Because of the action, there is a problem that the contact portion is easily broken (severed). In addition, since the annular protrusion is repeatedly compressed and pulled even during normal tire rolling, cracks are likely to occur at the boundary between the annular protrusion and the surface of the sidewall part due to deterioration of the rubber of the sidewall part due to deterioration over time. There is also a problem of becoming.
JP 2000-318410 A

  An object of the present invention is to provide a pneumatic tire capable of improving the problem of baldness and cracks while ensuring the effect of preventing splashing of water splashes.

The pneumatic tire of the present invention that achieves the above object is a pneumatic tire provided with a protrusion on the tread portion side of the outer surface of the sidewall portion that prevents splashing of water droplets when traveling on a wet road. A plurality of projecting pieces extending in the tire circumferential direction, the plurality of projecting pieces being arranged in an annular manner in the tire circumferential direction in two rows in a staggered manner, and the projecting pieces when viewed from the tire radial direction And arranging the plurality of protruding pieces in a staggered manner so as to close the cut portion by,
In projecting piece arranged in staggered the two rows, projecting towards the second column of the projecting piece away from the tread portion side of the first column of the projecting piece close to the tread portion outward in the tire axial direction,
In the tire meridian cross section when the tire is in contact with the road surface, with respect to a virtual straight line passing through the grounding end of the tread surface and the protruding end of the first row of protruding pieces, the protruding piece of the second row has a protruding end. It is located on the virtual straight line or protrudes outward in the tire axial direction beyond the virtual straight line .

  According to the present invention described above, the protrusion that prevents the splashing of water when traveling on a wet road is composed of a plurality of protrusions, so that the rigidity of the protrusion (protrusion) is lower than that of the conventional annular protrusion. Can do. Therefore, even if the protruding piece comes into contact with a stepped portion such as a curbstone, the protruding piece can bend and the stress acting on the contacting portion can be relieved, so that the contacting portion of the protruding piece becomes difficult to break, and the burr resistance is improved. It becomes possible to do.

  In addition, even if compression and tension repeatedly act on the protruding piece during rolling of a normal tire, the protruding piece easily bends, so that it is difficult for cracks to occur at the boundary between the protruding piece and the sidewall surface. it can.

  Furthermore, since a plurality of protruding pieces are arranged in a zigzag and annular manner in the tire circumferential direction so as to block off the cut portions, the water splashes are applied to the protruding pieces regardless of the position of the vehicle tire. Therefore, it is possible to prevent the splash of water from being scattered.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows an essential part of a heavy-duty pneumatic tire used for buses, trucks and the like, which is an embodiment of the pneumatic tire of the present invention, where 1 is a tread portion and 2 is a sidewall portion. A carcass layer 3 extends between a pair of left and right bead portions (not shown), and both ends of the carcass layer 3 are folded back from the inside to the outside of a bead core (not shown) embedded in the bead portion. A plurality of belt layers 4 are provided on the outer peripheral side of the carcass layer 3 of the tread portion 1. A plurality of main grooves 5 extending in the tire circumferential direction are formed on the tread surface 1A.

  Protrusion for preventing splashing of water when traveling on wet roads on the outer surface 2a of the sidewall portion 2 located on the tread portion 1 side from the maximum tire width position (cross-sectional width position defined by JATMA) S Part 6 is provided. As shown in FIG. 2, the projection 6 is composed of a plurality of projection pieces 7 made of rubber extending in the tire circumferential direction TC, and the plurality of projection pieces 7 are arranged in two rows in a zigzag manner in the tire circumferential direction. It is configured to be arranged in an annular manner intermittently in TC. When viewed from the tire radial direction TR, the second row of projecting pieces 7B apart from the tread portion 1 side is connected to the discontinuity 8 between the first row of intermittently arranged projecting pieces 7A close to the tread portion 1 side. A plurality of projecting pieces 7 are arranged in a staggered manner so as to be closed.

  The protrusions 7B in the second row protrude outward in the tire axial direction from the protrusions 7A in the first row, and block the splashing of water droplets passing through the cut portions 8 between the protrusions 7A. Further, as shown in FIG. 3, the tire circumferential direction length L2 (mm) on the sidewall portion outer surface 2a of the second row of projection pieces 7B is equal to that of the sidewall portion outer surface 2a of the first row of projection pieces 7A. It is shorter than the tire circumferential length L1 (mm). Since the second row of protruding pieces 7B protrude from the first row of protruding pieces 7A, the amount of rubber used is greater than that of the first row of protruding pieces 7A. Therefore, the amount of rubber used for the second row of projecting pieces 7B is reduced by reducing the tire circumferential length L2 of the second row of projecting pieces 7B to be shorter than that of the first row of projecting pieces 7A. I try to suppress the increase.

  As described above, according to the present invention, the protrusion 6 that prevents the splash of water from splashing when traveling on a wet road is composed of the plurality of protrusions 7, so that the rigidity of the protrusion 6 (protrusion piece 7) can be improved. Since the projection piece 7 is bent and the tensile stress acting on the contact portion is relieved even if the projection piece 7 comes into contact with a stepped portion such as a curbstone, the contact portion is less likely to break and the resistance to peeling. Can increase the sex.

  Further, even when compression and tension repeatedly act on the protruding piece 7 during rolling of the tire, the protruding piece 7 is easily bent, so that a crack is hardly generated at the boundary between the protruding piece 7 and the sidewall outer surface 2a. .

  In addition, since the plurality of protruding pieces 7 are arranged in a zigzag and annular manner in the tire circumferential direction TC so as to block the cut portions 8, the water splashes can be generated even if the vehicle tire scatters the water splashes at any position. Since it becomes possible to prevent splashing by hitting the protruding pieces 7, it is possible to ensure the effect of preventing splashing of water splashes.

  In the present invention, the tire circumferential direction length L (mm) (see FIGS. 2 and 3) on the sidewall portion outer surface 2a of the protrusion piece 7 is the maximum tire contact length at the time of tire contact when the tire is grounded on the road surface R. It is preferable to set it to 0.6 W or less with respect to W (mm). If the circumferential length L of the protruding piece 7 exceeds 0.6 W, the circumferential length of the protruding piece 7 becomes too long, so that the effect of reducing the rigidity of the protruding piece 7 is reduced and the contact portion is easily broken. The lower limit of the circumferential length L of the protrusion piece 7 is preferably 0.1 W or more from the viewpoint of manufacturing.

  As shown in FIG. 4, the protrusion piece 7 has a tire circumferential length that decreases as it goes to the protruding end of the protrusion piece 7 in order to improve the scuff resistance. The ratio L ′ / L between the tire circumferential direction length L ′ (mm) at the protruding end of the protruding piece 7 and the tire circumferential direction length L on the sidewall portion outer surface 2a of the protruding piece 7 is 0.8 or less. In order to effectively improve the bald resistance of the protruding piece 7, it is sufficient. The lower limit value of the ratio L ′ / L is preferably 0.5 or more from the viewpoint of weight increase and the effect of preventing scattering.

  Further, as shown in FIG. 5, in the tire meridian cross section when the tire is in contact with the road surface R, a virtual straight line passing through the contact end A of the tread surface 1A and the protrusion b of the first row of projecting pieces 7A is obtained. Assuming M, the protrusions 7B in the second row have their protrusions c positioned on the straight line M or projecting outward in the tire axial direction beyond the virtual straight line M. It is good for improving the scattering prevention effect by the protruding piece 7B. The angle θ of the virtual straight line M with respect to the road surface R is preferably 45 ° or more. Note that the protruding ends b and c of the protruding pieces 7A and 7B are the positions of the contacts when the virtual straight line M is drawn so as to contact the protruding end surface when the protruding end is not sharp as shown in FIG. .

  Further, when viewed from the direction in which the virtual straight line M extends, the overlap length D (mm) of the projecting pieces 7A and 7B (the tire circumferential direction length of the shortest portion of the overlapping portions) is set to 0 or more. In addition, when the distance between the protrusions b and c in the direction orthogonal to the tire axis is H (mm), it is ensured that the ratio H / D satisfies 0 <H / D ≦ 3. Preferred above.

  As shown in FIG. 1, the protrusion piece 7 is provided in the region of the outer surface 2a of the tread portion facing the edge 4e of the belt layer 4, and the protrusion amount of the protrusion piece 7 is kept low while ensuring the scattering prevention effect. This is preferable because the amount of rubber used can be reduced. More preferably, the projecting end portion of the projecting piece 7 should be located on the inner side in the tire radial direction from the groove bottom 5a of the main groove 5 when the tire contacts the ground, so that the projecting piece 7 is used until the main groove 5 reaches the wear life. A scattering prevention effect can be obtained.

Projecting pieces 7, as shown in the embodiment described above, it is preferable to place the two rows staggered, it is also possible to arrange three or more rows of staggered, least be two rows staggered Thus, it may be arranged in an annular manner intermittently in the tire circumferential direction TC.

  Further, it is sufficient that the protruding piece 7 is provided on one side wall portion located outside the vehicle when the tire is mounted, but it may be provided on both side wall portions.

  The present invention can be preferably used for a heavy-duty pneumatic tire particularly used for trucks and buses, but is not limited thereto, and may be a pneumatic tire for passenger cars.

  The term “tire contact” as used in the present invention refers to the time when the tire is grounded by applying the same air pressure as the maximum load capability described in JATMA (JATMA YEAR BOOK 2005) and the same load as the maximum load capability.

1 and 2 in which tire sizes are common to 275 / 80R22.5, projecting pieces are arranged in a zigzag pattern in two rows on the outer surface of the side wall, and each constituent element of the projecting pieces is as shown in Table 1. Examples 1 to 5 of the structure (tire of the present invention) and reference example (reference tire) , a conventional example (conventional tire) in which an annular protrusion is arranged instead of the protrusion piece, and a comparison in which the annular protrusion is interrupted in the conventional tire Each example (comparative tire) was prepared as a test tire.

  Each of these test tires is mounted on a rim having a rim size of 22.5 × 7.50, the air pressure is set to 900 kPa, and it is mounted on a truck having a total weight of 25 tons. When the evaluation test was conducted, the results shown in Table 1 were obtained.

Water splash prevention effect (Water splash prevention effect)
The splash state of water droplets when traveling straight on the wet road test road surface was visually observed by 10 examiners, and the result was shown as an index value with the conventional tire as 100. The larger this value, the higher the effect of preventing splashing of water splashes.

Curing resistance A curb climbing test with a height of 200 mm was repeated 20 times, the number of occurrences of rubber flaking on the projection piece or the annular projection was counted, and the result was shown as an index value where the conventional tire was 100. The larger this value, the better the baldness resistance.

  From Table 1, it can be seen that the tire of the present invention can improve the baldness resistance, but also has an effect of preventing splashing of water splashes of 90 or more, and can ensure the effect of preventing splashing of water splashes.

It is a fragmentary sectional view showing one embodiment of the pneumatic tire of the present invention. It is a partial side view at the time of tire contact. It is explanatory drawing which looked at the projection piece of the 1st row and the 2nd row from the protrusion side. It is a XX arrow line view of FIG. It is principal part cross-sectional explanatory drawing at the time of tire contact. It is sectional explanatory drawing which shows the example which draws the virtual straight line M in another protrusion piece.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 2a Outer surface 6 Protrusion part 7,7A, 7B Protrusion piece 8 Cut part TC Tire circumferential direction

Claims (6)

In a pneumatic tire provided with a protruding portion on the tread portion side of the outer surface of the sidewall portion that prevents splashing of water when traveling on a wet road, the protruding portion is composed of a plurality of protruding pieces extending in the tire circumferential direction. The plurality of protrusions are arranged in a staggered manner in two rows in an annular manner in the tire circumferential direction, and the plurality of protrusions are closed by the protrusions when viewed from the tire radial direction. In a staggered arrangement,
In projecting piece arranged in staggered the two rows, projecting towards the second column of the projecting piece away from the tread portion side of the first column of the projecting piece close to the tread portion outward in the tire axial direction,
In the tire meridian cross section when the tire is in contact with the road surface, with respect to a virtual straight line passing through the grounding end of the tread surface and the protruding end of the first row of protruding pieces, the protruding piece of the second row has a protruding end. A pneumatic tire located on the virtual straight line or protruding outward in the tire axial direction beyond the virtual straight line .   2. The pneumatic tire according to claim 1, wherein a length L in a tire circumferential direction on an outer surface of the sidewall portion of the protruding piece is 0.6 W or less with respect to a tire maximum ground contact length W. 3.   The pneumatic tire according to claim 1, wherein the protruding piece has a tire circumferential direction length that decreases toward a protruding end.   The ratio L ′ / L of the tire circumferential direction length L ′ at the projecting end of the projecting piece and the tire circumferential direction length L on the outer surface of the sidewall portion of the projecting piece is set to 0.8 or less. The described pneumatic tire. In the two rows of staggered protrusions, the second row of protrusions separated from the tread portion side by the tire circumferential direction length L1 on the sidewall outer surface of the first row of protrusion pieces close to the tread portion side. The pneumatic tire according to any one of claims 1 to 4, wherein a length L2 in a tire circumferential direction on an outer surface of one side wall portion is shortened. When viewed from the direction in which the imaginary straight line extends, the tire circumferential direction length D (mm) of the shortest portion in the portion where the first row of protruding pieces and the second row of protruding pieces overlap. The ratio H of the distance H (mm) between the protruding end of the first row of protruding pieces and the protruding end of the second row of protruding pieces measured in a direction perpendicular to the tire axis to the length D is set to 0 or more. The pneumatic tire according to any one of claims 1 to 5, wherein / D satisfies 0 <H / D≤3.

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