JP4577005B2 - Pneumatic tire for light truck - Google Patents

Description

  The present invention relates to a pneumatic tire for a small truck, and more particularly to a pneumatic tire for a small truck that has improved wear resistance.

  In a pneumatic tire for a small truck, an organic fiber cord is used as a reinforcing cord for a carcass layer from the viewpoint of weight reduction and ease of manufacture (for example, see Patent Document 1).

However, a small truck pneumatic tire using an organic fiber cord for the carcass layer in this manner has a higher operating air pressure, higher load, and higher pressure than a pneumatic tire for a passenger car using an organic fiber cord for the carcass layer. Since it is used with a load, creep deformation in which the circumference of the carcass layer gradually increases occurs during the use process. As a result, the contact length at the shoulder increases and the contact shape becomes a drum shape. This increases the contact pressure on the shoulder, causing uneven wear that progresses quickly, reducing wear resistance. There was a problem to do.
JP 2000-142023 A

  An object of the present invention is to provide a pneumatic tire for a small truck that can improve wear resistance in a pneumatic tire for a small truck using an organic fiber cord as a carcass layer.

The present invention that achieves the above object is to extend a carcass layer in which organic fiber cords extending in the tire radial direction are arranged between the left and right bead portions at a predetermined interval in the tire circumferential direction, and the carcass layer outer peripheral side of the tread portion In a pneumatic tire for a small truck, in which a belt layer extending to both shoulder portions of the tread portion is disposed, and a tread rubber layer is disposed on the outer peripheral side of the belt layer, the thickness of the tread rubber layer is set to the tread portion. Both shoulder parts are thinner than the crown part side of the tire, and the thickness of the tread rubber layer on the tire equatorial plane is A (mm). The tire is pulled from both edges of the belt layer located on the outermost circumference side to the tread surface. Assuming that the thickness of the tread rubber layer measured along the normal line is B (mm) and the nominal ratio W , the ratio B / A is in the range of 0.80 to 0.95, and the nominal ratio W is 60. In the range of ~ 85 and biased The ratio of the nominal W the ratio B / A is so as to satisfy the relation of 0.004W + 0.56 ≦ B / A ≦ 0.004W + 0.61, and each edge of the belt layer located on the tire equatorial plane outermost peripheries The thickness of the tread rubber layer in the center region of the crown portion located between the midpoint positions Q between is in the range of ± 2% with respect to the thickness A.

  According to the above-described present invention, by defining the thickness of the tread rubber layer as described above, even if creep deformation occurs in the carcass layer, the grounding shape is changed to a grounding shape that does not increase the grounding length of the shoulder portion. Therefore, the contact pressure on the surface of the tread portion can be made more uniform than before. Therefore, uneven wear at the shoulder is suppressed, and wear resistance can be improved.

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

  FIG. 1 shows an embodiment of a pneumatic tire for a small truck according to the present invention, wherein 1 is a tread portion, 2 is a sidewall portion, 3 is a bead portion, and CL is a tire equatorial plane.

  A bead core 4 is embedded in each of the left and right bead portions 3, and a bead filler 5 having a substantially triangular cross section extending to the sidewall portion 2 is disposed on the outer peripheral side of the bead core 4.

  Inside the tire are two carcass layers 6 and 7 in which organic fiber cords (not shown) such as polyester cords extending in the tire radial direction are arranged at predetermined intervals in the tire circumferential direction. It is extended to. The inner carcass layer 6 is folded back from the tire inner side to the outer side around the bead core 4 so that both end portions 6 a sandwich the bead filler 5. The outer carcass layer 7 has both end portions 7 a extending along the both end portions 6 a of the carcass layer 6 to the outside of the bead core 4.

  On the outer peripheral side of the carcass layer 7 of the tread portion 1, a plurality of belt layers 8, 9, 10 extending to both shoulder portions 1 </ b> X of the tread portion 1 are disposed. A tread rubber layer 11 is disposed on the outer peripheral side of the belt layer 10 located on the outermost peripheral side, and a tread having a plurality of grooves 12 extending in the tire circumferential direction on the tread surface (tread portion surface) 11a as the surface thereof. A pattern is formed. A belt edge cover layer 13 in which an organic fiber cord such as a nylon cord is spirally wound in the tire circumferential direction and covered with rubber is provided on the outer peripheral side of both end portions 10A of the belt layer 10.

  In the figure, reference numeral 14 denotes a side rubber layer disposed on the sidewall portion 2, and 15 denotes an edge cushion rubber layer disposed on the edge portion of the belt layer.

  The tread rubber layer 11 is thinner on both shoulder portions 1X than the crown 1Y side of the tread portion 1, and the thickness of the tread rubber layer 11 on the tire equatorial plane CL is A (mm), and is located on the outermost periphery side. When the thickness of the tread rubber layer 11 measured along the tire normal M drawn from the both edges 10e of the belt layer 10 to the tread surface 11a is B (mm), the ratio B / A is 0.80-0. The range is 95.

  Further, the thickness of the tread rubber layer 11 in the center region y of the crown portion 1Y located between the midpoint positions Q between the tire equatorial plane CL and each edge 10e of the belt layer 10 is made substantially uniform. . Here, the substantially uniform thickness means a thickness within a range of ± 2% with respect to the thickness A, and means an error range of the tread rubber layer 11 to be extruded. The midpoint position Q is the midpoint when measured parallel to the tire axis.

  According to the present invention described above, by specifying the thickness of the tread rubber layer 11 as described above, even if creep deformation occurs in the carcass layers 6 and 7, the ground contact shape of the tread surface 11a is shown in FIG. As shown in a), it is possible to avoid a drum shape in which the contact length at the shoulder portion is increased, and it is possible to obtain a proper contact shape that does not increase the contact length at the shoulder portion as shown in FIG. become. As a result, since the contact pressure on the tread surface 11a can be made more uniform than before, uneven wear on the shoulder portion 1X side can be suppressed, and wear resistance can be improved.

  If the ratio B / A is less than 0.80, the difference in thickness between the crown portion 1Y and the shoulder portion 1X becomes too large, so that the ground contact length of the crown portion 1Y increases and uneven wear occurs on the crown portion 1Y. Is likely to occur. Conversely, if it exceeds 0.95, when creep deformation occurs in the carcass layers 6 and 7, the contact length of the shoulder portion 1X increases, so it becomes difficult to improve the uneven wear of the shoulder portion 1X. If the thickness of the tread rubber layer 11 in the center region y of the crown portion 1Y is not uniform, the contact length at the crown portion 1Y cannot be kept uniform.

In the present invention, the above-described configuration, the polarized Tairahi call is Ru have a hand to light truck pneumatic tire 60 to 85 (aspect ratio 60 to 85%). In a small truck pneumatic tire having an aspect ratio of less than 60, a large effect cannot be expected only by specifying the thickness of the tread rubber layer 11 described above. In a pneumatic tire for a small truck having a flatness ratio larger than 85, even if creep deformation occurs in the carcass layers 6 and 7, the tread rubber has a low tendency to form a drum shape with an increased contact length at the shoulder portion. This is because the thickness of the layer 11 does not have to be defined as described above.

The present invention is called a flat ratio while the 60 to 85, called W and the ratio B / A of the flat ratio, you to satisfy the following relationship.

0.004W + 0.56 ≦ B / A ≦ 0.004W + 0.61
Further, the bead filler 5 in which rubber having a hardness higher than that of the side rubber layer 14 is used, the outer peripheral end 5x is preferably located in a range K from 30% position P1 to 60% position P2 of the tire cross-section height H. As a result, the contact pressure on the tread surface 11a can be made more uniform, and the contact shape of the tread surface 11a can be made more appropriate.

  Although the present invention has been described with respect to the pneumatic tire for small trucks provided with the two carcass layers 6 and 7 in the above embodiment, the compact car having one carcass layer (carcass layer 6) or three carcass layers. It may be a pneumatic tire for trucks.

  INDUSTRIAL APPLICABILITY The present invention can be preferably used for a pneumatic tire for a small truck that is used at a high operating air pressure corresponding to the maximum load capacity specified in JATMA (2004 YEAR BOOK), which is in the range of 350 to 650 kPa. .

  The tire 1 of the present invention having the configuration shown in FIG. 1 in which the tire size is common to 205, the flatness ratio is called, the ratio B / A, and the thickness of the tread rubber layer in the center region of the crown portion are as shown in Table 1. -4, comparative tires 1-3, and conventional tires were produced.

  In each test tire, the position of the outer peripheral edge of the bead filler is common at a position of 45% of the tire cross-section height H.

Each of these test tires is mounted on a rim having a rim size of 17.5 × 5.25, mounted on a small truck with a load capacity of 2 t with an air pressure of 600 kPa, and an abrasion resistance evaluation test is performed by the following test method. As a result, the results shown in Table 1 were obtained.
Abrasion resistance After running 30000 km on a general road, the amount of wear on the tread surface was measured, and the result was shown as an index value with the conventional tire as 100. The higher this value, the better the wear resistance.

  Table 1 shows that the tire of the present invention can improve the wear resistance.

  Tires 5 to 10 of the present invention having the configuration shown in FIG. 1 were prepared in which the tire size was the same for 205 / 60R17.5 and the position of the outer peripheral edge of the bead filler was as shown in Table 2.

  In each test tire, the ratio B / A is 0.80, and the thickness of the tread rubber layer in the center region of the crown portion is substantially uniform.

  When each of these test tires was subjected to an abrasion resistance evaluation test in the same manner as in Example 1, the results shown in Table 2 were obtained.

  From Table 2, it can be seen that the wear resistance can be further improved by setting the position of the outer peripheral edge of the bead filler to a range of 30 to 60% of the tire cross-section height H.

It is a tire meridian half section view showing one embodiment of a pneumatic tire for small trucks of the present invention. The grounding shape of the tread surface is shown, (a) is the grounding shape before improvement, and (b) is the grounding shape after improvement.

Explanation of symbols

1 Tread
1X Shoulder part 1Y Crown part 2 Side wall part 3 Bead part 4 Bead core 5 Bead filler 6, 7 Carcass layer
6a, 7a End 8, 9, 10 Belt layer 10e Edge 11 Tread rubber layer 11a Tread surface (tread surface)
CL tire equatorial plane M tire normal y center area

Claims (3)

A carcass layer in which organic fiber cords extending in the tire radial direction are arranged between the left and right bead portions at predetermined intervals in the tire circumferential direction is extended to both shoulder portions of the tread portion on the outer circumferential side of the tread portion. In a pneumatic tire for a small truck in which an extended belt layer is disposed and a tread rubber layer is disposed on the outer peripheral side of the belt layer,
The thickness of the tread rubber layer is made thinner on both shoulder sides than the crown side of the tread portion, and the thickness of the tread rubber layer on the tire equator surface is A (mm). If the thickness of the tread rubber layer measured along the tire normal drawn from both edges to the tread surface is B (mm) and the flatness ratio is W , the ratio B / A is 0.80 to 0.95. The nominal ratio W is in the range of 60 to 85, and the nominal ratio W and the ratio B / A satisfy the relationship of 0.004W + 0.56 ≦ B / A ≦ 0.004W + 0.61. West,
The thickness of the tread rubber layer in the center region of the crown located between the midpoints Q between the tire equator plane and each edge of the belt layer located on the outermost peripheral side is ± Pneumatic tire for light trucks in the range of 2% . The bead filler is disposed on the outer peripheral side of the bead core embedded in the bead portions of the left and right, for small trucks according to claim 1, the outer peripheral end was positioned in the range of 30% to 60% of the tire section height H of the bead filler Pneumatic tire. The pneumatic tire for a small truck according to claim 1 or 2 , wherein an air pressure corresponding to a maximum load capacity defined by JATMA falls within a range of 350 to 650 kPa.

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