Pneumatic tires

Abstract

To provide a pneumatic tire capable of restraining separation at the edge part of a belt ply.SOLUTION: A pneumatic tire 1 has a carcass 4, and the first, second and third belt plies 61, 62, 63 laminated by turns to the outer periphery of the carcass 4 in tread 3 from inside in a tire radial direction toward outside. The edge part 63a of the third belt ply is located outside the edge parts 61a and 62a of the first and second belt plies in a tire width direction and located between the edge parts 61a and 62a, and a tire maximum width position.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to pneumatic tires. [Background technology]

[0002] As a pneumatic tire used for trucks and buses, a tire in which three or more belt plies are provided on the outer periphery of a carcass in a tread is known. For example, Patent Document 1 discloses a pneumatic tire provided with four belt plies.

[0003] The shoulder portion of the tread is the thickest part of the tire and generates the most heat. Therefore, if the end of the belt ply, where distortion is likely to concentrate, is located near the shoulder portion, separation is likely to occur at the end of the belt ply. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-99077 A Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present disclosure is to provide a pneumatic tire that can suppress separation at the ends of the belt ply. [Means for solving the problem]

[0006] A pneumatic tire according to the present disclosure includes a carcass, and first, second, and third belt plies that are laminated in order from an inner side to an outer side in a tire radial direction on an outer periphery of the carcass in a tread, An end portion of the third belt ply is located outward in the tire width direction from ends of the first and second belt plies, and is located between the ends of the first and second belt plies and the maximum width position of the tire in the tire radial direction. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a half cross-sectional view showing one side of a cross section in a tire meridian plane of a pneumatic tire according to an embodiment; [Diagram 2] Enlarged view of area II of the pneumatic tire shown in Figure 1 [Diagram 3] Enlarged view of region III of the pneumatic tire shown in Figure 2 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, one embodiment of a pneumatic tire will be described with reference to Figures 1 to 3. Note that in each figure, the dimensional ratios in the drawing do not necessarily match the actual dimensional ratios, and the dimensional ratios between the drawings do not necessarily match either.

[0009] In each drawing, the first direction D1 is the tire width direction D1 that is parallel to the tire rotation axis that is the center of rotation of a pneumatic tire (hereinafter also simply referred to as "tire") 1, and the second direction D2 is the tire radial direction D2 that is the diameter direction of the tire 1. The tire circumferential direction (not shown) is the direction around the tire rotation axis.

[0010] In the tire width direction D1, the inner side is the side closer to the tire equatorial plane S1, and the outer side is the side farther from the tire equatorial plane S1. In addition, in the tire radial direction D2, the inner side is the side closer to the tire rotation axis, and the outer side is the side farther from the tire rotation axis.

[0011] The tire equatorial plane S1 is a plane perpendicular to the tire rotation axis and located at the center in the tire width direction D1 of the tire 1, and the tire meridian plane is a plane that includes the tire rotation axis and is perpendicular to the tire equatorial plane S1. The tire equatorial line is a line where the outer surface of the tire 1 in the tire radial direction D2 (a tread surface 3a described later) and the tire equatorial plane S1 intersect.

[0012] 1, a tire 1 according to this embodiment includes a pair of beads (not shown) each having a bead core (not shown), a sidewall 2 extending outward from each bead in a tire radial direction D2, and a tread 3 connected to outer ends of the pair of sidewalls 2 in the tire radial direction D2, the outer surface of which in the tire radial direction D2 comes into contact with the road surface. In this embodiment, the tire 1 is a pneumatic tire 1 in which air is put, and is mounted on a rim.

[0013] The tire 1 also includes a carcass 4 that is bridged between a pair of bead cores, and an inner liner 5 that is disposed inside the carcass 4 and has an excellent function of preventing gas permeation in order to maintain air pressure. The carcass 4 and the inner liner 5 are disposed along the inner circumference of the tire, spanning the beads, the sidewall 2, and the tread 3.

[0014] The tread 3 includes a tread rubber 30 having a tread surface 3a that comes into contact with the road surface, and a belt 6 disposed between the tread rubber 30 and the carcass 4. The tread surface 3a has a contact surface that actually comes into contact with the road surface, and the outer end of the contact surface in the tire width direction D1 is called a contact edge 3b. The contact surface refers to the tread surface 3a that comes into contact with the road surface when the tire 1 is mounted on a standard rim, inflated to the standard internal pressure, placed perpendicularly on a flat road surface, and a standard load is applied.

[0015] The regular rim is a rim that is defined for each tire 1 by a standard system including the standard on which the tire 1 is based, for example, a standard rim in the case of JATMA, and a "Measuring Rim" in the cases of TRA and ETRTO.

[0016] The normal internal pressure is the air pressure set for each tire 1 by each standard in the standard system including the standard on which tire 1 is based. For JATMA, it is the maximum air pressure, for TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and for ETRTO, it is the "INFLATION PRESSURE". If tire 1 is for passenger cars, it is 180 kPa, but if tire 1 is labeled as Extra Load or Reinforced, it is 220 kPa.

[0017] The normal load is the load determined for each tire 1 by each standard in the standard system including the standard on which tire 1 is based. For JATMA, it is the maximum load capacity, for TRA, it is the maximum value shown in the table above, and for ETRTO, it is the "LOAD CAPACITY." However, if tire 1 is for passenger cars, it is 85% of the corresponding load at an internal pressure of 180 kPa.

[0018] The tread rubber 30 has a cap rubber 31 having a tread surface 3a, and a base rubber 32 provided on the inner side of the cap rubber 31 in the tire radial direction D2. The cap rubber 31 has a plurality of main grooves 31a, 31b extending in the tire circumferential direction. The main grooves 31a, 31b extend continuously in the tire circumferential direction.

[0019] The main grooves 31a, 31b may have a shallow portion, a so-called tread wear indicator (not shown), which becomes exposed as the grooves wear, so that the degree of wear can be known. Also, for example, the main grooves 31a, 31b may have a groove width of 5 mm or more.

[0020] The pair of main grooves 31a arranged on the outermost sides in the tire width direction D1 are called shoulder main grooves 31a, and the main groove 31b arranged between the pair of shoulder main grooves 31a is called center main groove 31b. The number of main grooves 31a, 31b is not particularly limited, but is set to four in this embodiment.

[0021] The tread rubber 30 includes a plurality of lands 3c to 3e defined by a plurality of main grooves 31a, 31b and a pair of ground contact edges 3b. The number of the lands 3c to 3e is not particularly limited, but is set to five in this embodiment.

[0022] The land 3c defined by the shoulder main groove 31a and the ground contact edge 3b is called the shoulder land 3c, and the land 3d, 3e defined by the pair of adjacent main grooves 31a, 31b are called the middle land 3d, 3e. The land 3d defined by the shoulder main groove 31a and the center main groove 31b is called the quarter land (also called the "mediate land") 3d, and the land 3e defined by the pair of center main grooves 31b is called the center land 3e.

[0023] A belt 6 for reinforcing the carcass 4 is provided on the outer periphery of the carcass 4 in the tread 3. The belt 6 includes four belt plies 61-64 laminated in order from the inside to the outside in the tire radial direction D2. The four belt plies 61-64 are all disposed consecutively on both sides in the tire width direction D1 with the tire equatorial plane S1 in between. The four belt plies 61-64 are in contact with adjacent belt plies, and no other members such as the tread rubber 30 are sandwiched between the adjacent belt plies.

[0024] Each of the four belt plies 61 to 64 includes a plurality of cords arranged in parallel in a blind shape, and is formed by covering the cords with rubber. The cords are preferably steel cords.

[0025] Of the four belt plies 61 to 64, the cords of the first belt ply 61, which is the first from the carcass 4 toward the outer periphery, extend at an angle of 40 to 65° with respect to the tire circumferential direction.

[0026] Among the four belt plies 61 to 64, the cords of the second belt ply 62, which is the second from the carcass 4 toward the outer periphery, and the cords of the third belt ply 63, which is the third, are inclined in opposite directions to each other with respect to the tire circumferential direction and cross each other. The cords of the second belt ply 62 and the third belt ply 63 are inclined at the same angle with respect to the tire circumferential direction. The second belt ply 62 and the third belt ply 63 are also collectively referred to as a working belt. The cords of the second belt ply 62 and the third belt ply 63 extend inclined at an angle of 10 to 30° with respect to the tire circumferential direction. The cords of the second belt ply 62 are inclined in the same direction as the cords of the first belt ply 61 with respect to the tire circumferential direction.

[0027] Among the four belt plies 61-64, the cords of a fourth belt ply 64, which is the fourth from the carcass 4 toward the outer periphery, extend inclined at an angle of 10 to 30° with respect to the tire circumferential direction. The cords of the fourth belt ply 64 are inclined in the same direction as the cords of the third belt ply 63 with respect to the tire circumferential direction.

[0028] An end 62a of the second belt ply 62 is located outside in the tire width direction D1 of an end 61a of the first belt ply 61. An end 63a of the third belt ply 63 is located outside in the tire width direction D1 of an end 62a of the second belt ply 62. An end 64a of the fourth belt ply 64 is located inside in the tire width direction D1 of the end 61a of the first belt ply 61. Thus, the first to fourth belt plies 61 to 64 have increasing widths in the tire width direction D1 in the order of the fourth belt ply 64, the first belt ply 61, the second belt ply 62, and the third belt ply 63.

[0029] An end 61a of the first belt ply 61 and an end 62a of the second belt ply 62 are located at the center of the shoulder land 3c in the tire width direction D1 and on the inner side in the tire radial direction D2. An end 63a of the third belt ply 63 is located on the outer side in the tire width direction D1 of the ground contact edge 3b of the tread 3. An end 64a of the fourth belt ply 64 is located on the quarter land 3d near the center main groove 31b in the tire width direction D1 and on the inner side in the tire radial direction D2.

[0030] 2, a distance L3 between an end 63a of the third belt ply 63 and an end 62a of the second belt ply 62 is greater than a distance L2 between an end 62a of the second belt ply 62 and an end 61a of the first belt ply 61. The distance L3 is preferably at least twice the distance L2, and more preferably at least three times the distance L2. Note that the distance L3 is the distance along the third belt ply 63, and the distance L2 is the distance along the second belt ply 62.

[0031] Incidentally, the shoulder portion of the tread 3 is the part of the tire 1 that is thickest and generates the most heat. Therefore, if the ends of the belt plies 61-64, where distortion is likely to concentrate, are located in the shoulder portion, separation is likely to occur at the ends of the belt plies 61-64. The shoulder portion of the tread 3 is a portion located on the outer side in the tire width direction D1 than the shoulder main groove 31a.

[0032] Furthermore, the third belt ply 63 is an outer belt ply in the tire radial direction D2 among the working belts, and strain is likely to concentrate at the end portion 63a of the third belt ply 63. Therefore, from the viewpoint of preventing separation at the end portion 63a of the third belt ply 63, it is not desirable to dispose the end portion 63a of the third belt ply 63 in the shoulder portion of the tread 3.

[0033] In this embodiment, the end 63a of the third belt ply 63 is located outside the end 61a of the first belt ply 61 and the end 62a of the second belt ply 62 in the tire width direction D1, and is located between the end 61a of the first belt ply 61 and the end 62a of the second belt ply 62 and the tire maximum width position 1a in the tire radial direction D2. According to this configuration, the end 63a of the third belt ply 63 is located in a so-called buttress portion that is inside the shoulder portion in the tire radial direction D2, so that separation at the end 63a of the third belt ply 63 can be suppressed. The tire maximum width position 1a is the position where the profile line of the outer surface of the tire 1 in the sidewall 2 is farthest from the tire equatorial plane S1 in the tire width direction D1. This profile line is the contour of the outer surface of the sidewall body excluding protrusions such as rim protectors, and usually has a tire meridian cross-sectional shape defined by smoothly connecting multiple arcs.

[0034] 3, a distance W1 in the tire width direction D1 between an end 63a of the third belt ply 63 and an end 61a of the first belt ply 61 is greater than a distance R1 in the tire radial direction D2. On the other hand, a distance R2 in the tire radial direction D2 between an end 63a of the third belt ply 63 and an end 62a of the second belt ply 62 is greater than a distance W2 in the tire width direction D1.

[0035] 1, a shoulder pad rubber 7 is disposed between the first to third belt plies 61 to 63 and the carcass 4. An inner end 7a of the shoulder pad rubber 7 in the tire radial direction D2 is located inside in the tire radial direction D2 and outside in the tire width direction D1 of an end 63a of the third belt ply 63.

[0036] Also, an inner end 32a of the base rubber 32 in the tire radial direction D2 is located inside in the tire radial direction D2 and outside in the tire width direction D1 of an end 63a of the third belt ply 63. Therefore, the end 63a of the third belt ply 63 is sandwiched between the base rubber 32 arranged on the outer periphery of the third belt ply 63 and the shoulder pad rubber 7 arranged on the inner periphery of the third belt ply 63.

[0037] The base rubber 32 and the shoulder pad rubber 7 have a smaller loss tangent tanδ than the sidewall rubber 21 disposed on the outer surface of the sidewall 2. That is, the base rubber 32 and the shoulder pad rubber 7 have a lower heat generation property than the sidewall rubber 21. This makes it possible to suppress heat generation at the end 63a of the third belt ply 63, and to suppress separation. The loss tangent tanδ of the present invention is measured by using a rheospectrometer E4000 manufactured by USM under the conditions of a frequency of 50 Hz, a static strain of 10%, a dynamic strain of 2%, and a temperature of 0°C. In this embodiment, for example, the loss tangent tanδ of the base rubber 32 is 0.03 to 0.10, the loss tangent tanδ of the shoulder pad rubber 7 is 0.05 to 0.12, and the loss tangent tanδ of the sidewall rubber 21 is 0.14 to 0.20.

[0038] The end 63a of the third belt ply 63 is located at a height that is 0.5 to 0.9 times the height H of the end 61a of the first belt ply 61, based on the tire maximum width position 1a. That is, the height h63 of the end 63a satisfies the relationship 0.5H≦h63≦0.9H.

[0039] As described above, the pneumatic tire 1 according to this embodiment has the carcass 4, and the first, second, and third belt plies 61, 62, and 63 laminated in order from the inner side to the outer side in the tire radial direction D2 on the outer periphery of the carcass 4 in the tread 3, The end 63a of the third belt ply 63 is located outside the ends 61a, 62a of the first and second belt plies 61, 62 in the tire width direction D1, and is located between the ends 61a, 62a of the first and second belt plies 61, 62 and the tire maximum width position 1a in the tire radial direction D2.

[0040] According to this configuration, the end portion 63a of the third belt ply 63 is disposed on the inner side in the tire radial direction D2 than the shoulder portion, so that separation at the end portion 63a of the third belt ply 63 can be suppressed.

[0041] In addition, in the pneumatic tire 1 according to this embodiment, the end 62a of the second belt ply 62 is located outward in the tire width direction D1 from the end 61a of the first belt ply 61, and the distance L3 between the end 63a of the third belt ply 63 and the end 62a of the second belt ply 62 is greater than the distance L2 between the end 62a of the second belt ply 62 and the end 61a of the first belt ply 61.

[0042] According to this configuration, the end portion 63a of the third belt ply 63 is reliably disposed on the inner side in the tire radial direction D2 than the shoulder portion.

[0043] In the pneumatic tire 1 according to this embodiment, the end portion 63a of the third belt ply 63 is positioned outward of the ground contact end 3b of the tread 3 in the tire width direction D1.

[0044] According to this configuration, the end portion 63a of the third belt ply 63 is reliably disposed further inward in the tire radial direction D2 than the shoulder portion.

[0045] Moreover, the pneumatic tire 1 according to this embodiment includes a base rubber 32 arranged on the outer periphery of the third belt ply 63, a shoulder pad rubber 7 arranged on the inner periphery of the third belt ply 63, and a sidewall rubber 21 forming the outer surface of the sidewall 2, and an end portion 63a of the third belt ply 63 is sandwiched between the base rubber 32 and the shoulder pad rubber 7, and the base rubber 32 and the shoulder pad rubber 7 have a smaller loss tangent tan δ than the sidewall rubber 21.

[0046] According to this configuration, heat generation at the end portion 63a of the third belt ply 63 can be suppressed, and separation can be suppressed.

[0047] The pneumatic tire 1 is not limited to the configurations of the above-described embodiments, and is not limited to the above-described effects. Of course, the pneumatic tire 1 can be modified in various ways without departing from the spirit of the present invention. For example, the configurations and methods of the above-described embodiments may be arbitrarily adopted and combined, and one or more of the configurations and methods of the various modified examples described below may be arbitrarily selected and adopted in the configurations and methods of the above-described embodiments.

[0048] (1) In the pneumatic tire 1 according to the above embodiment, the end 62a of the second belt ply 62 is located outside the end 61a of the first belt ply 61 in the tire width direction D1, and the distance L3 between the end 63a of the third belt ply 63 and the end 62a of the second belt ply 62 is greater than the distance L2 between the end 62a of the second belt ply 62 and the end 61a of the first belt ply 61. However, the pneumatic tire 1 is not limited to this configuration. For example, the end 61a of the first belt ply 61 may be located outside the end 62a of the second belt ply 62 in the tire width direction D1.

[0049] (2) In the pneumatic tire 1 according to the above embodiment, the end 63a of the third belt ply 63 is located on the outer side in the tire width direction D1 than the ground contact end 3b of the tread 3. However, the pneumatic tire 1 is not limited to such a configuration. For example, the end 63a of the third belt ply 63 may be located on the inner side in the tire width direction D1 than the ground contact end 3b of the tread 3. However, in order to separate the end 63a of the third belt ply 63 from the shoulder portion, it is preferable to dispose the end 63a of the third belt ply 63 on the outer side in the tire width direction D1 than the ground contact end 3b of the tread 3.

[0050] (3) In addition, the pneumatic tire 1 according to the above embodiment includes the base rubber 32 arranged on the outer periphery of the third belt ply 63, the shoulder pad rubber 7 arranged on the inner periphery of the third belt ply 63, and the sidewall rubber 21 constituting the outer surface of the sidewall 2, and the end portion 63a of the third belt ply 63 is sandwiched between the base rubber 32 and the shoulder pad rubber 7, and the base rubber 32 and the shoulder pad rubber 7 have a smaller loss tangent tan δ than the sidewall rubber 21. However, the pneumatic tire 1 is not limited to such a configuration. For example, only one of the base rubber 32 and the shoulder pad rubber 7 may have a smaller loss tangent tan δ than the sidewall rubber 21. In addition, the base rubber 32 and the shoulder pad rubber 7 may be formed of the same rubber. [Explanation of symbols]

[0051] Reference Signs List 1...pneumatic tire, 1a...maximum tire width position, 2...sidewall, 3...tread, 3c to 3e...land, 4...carcass, 5...inner liner, 6...belt, 7...shoulder pad rubber, 21...sidewall rubber, 30...tread rubber, 31...cap rubber, 31a, 31b...main groove, 32...base rubber, 61...first belt ply, 61a...end of first belt ply, 62...second belt ply, 62a...end of second belt ply, 63...third belt ply, 63a...end of third belt ply, 64...fourth belt ply, 64a...end of fourth belt ply, D1...tire width direction, D2...tire radial direction, S1...tire equatorial plane

Claims

1. A tire has a carcass, and first, second, and third belt plies that are laminated in order from the inner side to the outer side in the tire radial direction on an outer periphery of the carcass in a tread, an end portion of the third belt ply is located outward in the tire width direction from ends of the first and second belt plies, and is located between the ends of the first and second belt plies and a maximum tire width position in the tire radial direction, An end portion of the second belt ply is located on the outer side in the tire width direction than an end portion of the first belt ply, a distance in a tire width direction between the end of the third belt ply and the end of the first belt ply is larger than a distance in a tire radial direction between the end of the third belt ply and the end of the first belt ply, and a distance in a tire radial direction between the end of the third belt ply and the end of the second belt ply is larger than a distance in a tire width direction between the end of the third belt ply and the end of the second belt ply.

2. An end portion of the second belt ply is located on the outer side in the tire width direction than an end portion of the first belt ply, The pneumatic tire according to claim 1 , wherein a distance between an end of the third belt ply and an end of the second belt ply is greater than a distance between an end of the second belt ply and an end of the first belt ply.

3. The pneumatic tire according to claim 1 or 2, wherein an end portion of the third belt ply is located outboard of a ground contact end of the tread in a tire width direction.

4. A base rubber is disposed on an outer periphery of the third belt ply, a shoulder pad rubber is disposed on an inner periphery of the third belt ply, and a sidewall rubber forms an outer surface of a sidewall, The pneumatic tire according to any one of claims 1 to 3, wherein an end portion of the third belt ply is sandwiched between the base rubber and the shoulder pad rubber, and the base rubber and the shoulder pad rubber have a loss tangent tan δ smaller than that of the sidewall rubber.

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