JP7634953B2 - Pneumatic tires - Google Patents

Description

This disclosure relates to pneumatic tires.

Pneumatic tires used on trucks and buses are known that have three or more belt plies around the outer periphery of the carcass in the tread. For example, Patent Document 1 discloses a pneumatic tire with four belt plies.

The shoulder portion of the tread is the thickest part of the tire and the part where the most heat is generated. 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.

JP 2019-99077 A

The objective of this disclosure is to provide a pneumatic tire that can suppress separation at the ends of the belt plies.

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 outboard of ends of the first and second belt plies in the tire width direction, and is located between the ends of the first and second belt plies and a maximum width position of the tire in the tire radial direction.

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 one embodiment; FIG. 2 is an enlarged view of region II of the pneumatic tire shown in FIG. FIG. 3 is an enlarged view of region III of the pneumatic tire shown in FIG.

One embodiment of a pneumatic tire will be described below 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.

In each figure, 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 the 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.

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 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.

The tire equatorial plane S1 is a plane perpendicular to the tire rotation axis and located at the center of 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 equator line is a line where the outer surface of the tire 1 in the tire radial direction D2 (the tread surface 3a described later) and the tire equatorial plane S1 intersect.

As shown in FIG. 1, the 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 the tire radial direction D2, and a tread 3 connected to the 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.

The tire 1 also includes a carcass 4 that is stretched between a pair of bead cores, and an inner liner 5 that is disposed inside the carcass 4 and has excellent gas permeability prevention properties to maintain air pressure. The carcass 4 and the inner liner 5 are disposed along the inner circumference of the tire, spanning the beads, sidewalls 2, and tread 3.

The tread 3 comprises 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 the 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 vertically on a flat road surface, and a standard load is applied.

A genuine rim is a rim that is determined for each tire 1 by the standard system that includes the standard on which the tire 1 is based. For example, in the case of JATMA, it is a standard rim, and in the cases of TRA and ETRTO, it is a "Measuring Rim."

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 "INFLATION PRESSURE". If tire 1 is for passenger cars, it is 180 kPa, but if tire 1 is a tire that is listed as Extra Load or Reinforced, it is 220 kPa.

The normal load is the load that each standard specifies for each tire 1 in the standard system that includes the standard on which tire 1 is based. For JATMA, it is the maximum load capacity, for TRA, it is the maximum value listed 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.

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.

The main grooves 31a, 31b may have a shallow portion, known as a tread wear indicator (not shown), that becomes exposed as the tire wears, allowing the degree of wear to be known. Also, for example, the main grooves 31a, 31b may have a groove width of 5 mm or more.

The pair of main grooves 31a located on the outermost sides in the tire width direction D1 are called shoulder main grooves 31a, and the main groove 31b located 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 in this embodiment, there are four.

The tread rubber 30 has multiple main grooves 31a, 31b and multiple lands 3c to 3e defined by a pair of ground contact edges 3b. The number of lands 3c to 3e is not particularly limited, but in this embodiment, there are five.

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 also called the quarter land (also called the "mediate land") 3d, and the land 3e defined by the pair of center main grooves 31b is also called the center land 3e.

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 comprises four belt plies 61-64 that are layered in order from the inside to the outside in the tire radial direction D2. All four belt plies 61-64 are arranged consecutively on both sides of the tire equatorial plane S1 in the tire width direction D1. In addition, 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.

Each of the four belt plies 61 to 64 includes multiple cords arranged in parallel like a blind and are rubber-coated. The cords are preferably steel cords.

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 degrees relative to the tire circumferential direction.

Of 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 third belt ply 63, which is the third, cross at an inclination in the opposite direction to each other with respect to the tire circumferential direction. The cords of the second belt ply 62 and the third belt ply 63 are also collectively referred to as the working belt. The cords of the second belt ply 62 and the third belt ply 63 extend at an inclination of 10 to 30 degrees with respect to the tire circumferential direction. The cords of the second belt ply 62 are slanted in the same direction with respect to the tire circumferential direction as the cords of the first belt ply 61.

In addition, of the four belt plies 61 to 64, the cords of the fourth belt ply 64, which is the fourth from the carcass 4 toward the outer periphery, extend at an angle of 10 to 30 degrees with respect to the tire circumferential direction. In addition, the cords of the fourth belt ply 64 are inclined in the same direction with respect to the tire circumferential direction as the cords of the third belt ply 63.

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. The end 63a of the third belt ply 63 is located outside the end 62a of the second belt ply 62 in the tire width direction D1. The end 64a of the fourth belt ply 64 is located inside the end 61a of the first belt ply 61 in the tire width direction D1. Therefore, the first to fourth belt plies 61 to 64 have the following widths in the tire width direction D1: fourth belt ply 64, first belt ply 61, second belt ply 62, third belt ply 63.

The end 61a of the first belt ply 61 and the end 62a of the second belt ply 62 are located in the center of the shoulder land 3c in the tire width direction D1 and on the inside in the tire radial direction D2. The end 63a of the third belt ply 63 is located on the outside in the tire width direction D1 of the ground contact end 3b of the tread 3. The 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 inside in the tire radial direction D2.

As shown in FIG. 2, 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. 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.

The shoulder portion of the tread 3 is the thickest part of the tire 1 and is also the part that generates the most heat. Therefore, if the ends of the belt plies 61 to 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 to 64. The shoulder portion of the tread 3 is located outside the shoulder main groove 31a in the tire width direction D1.

The third belt ply 63 is the outer belt ply in the tire radial direction D2 of the working belt, and distortion is likely to concentrate at the end 63a of the third belt ply 63. Therefore, from the viewpoint of preventing separation at the end 63a of the third belt ply 63, it is not desirable to place the end 63a of the third belt ply 63 in the shoulder portion of the tread 3.

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 the so-called buttress part, which is inside the shoulder part 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.

As shown in FIG. 3, the distance W1 in the tire width direction D1 between the end 63a of the third belt ply 63 and the end 61a of the first belt ply 61 is greater than the distance R1 in the tire radial direction D2. On the other hand, the distance R2 in the tire radial direction D2 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 W2 in the tire width direction D1.

As shown in FIG. 1, a shoulder pad rubber 7 is disposed between the first to third belt plies 61 to 63 and the carcass 4. The 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 the end 63a of the third belt ply 63.

The inner end 32a of the base rubber 32 in the tire radial direction D2 is located inside the end 63a of the third belt ply 63 in the tire radial direction D2 and outside the tire width direction D1. 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.

The base rubber 32 and the shoulder pad rubber 7 have a smaller loss tangent tanδ than the sidewall rubber 21 arranged on the outer surface of the sidewall 2. In other words, the base rubber 32 and the shoulder pad rubber 7 have a lower heat generation 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 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.

The end 63a of the third belt ply 63 is located at a height 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. In other words, the height h63 of the end 63a satisfies the relationship 0.5H≦h63≦0.9H.

As described above, the pneumatic tire 1 according to the present embodiment includes the carcass 4, and the first, second, and third belt plies 61, 62, and 63 that are 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 outboard of 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.

With this configuration, the end 63a of the third belt ply 63 is positioned further inward in the tire radial direction D2 than the shoulder portion, thereby suppressing separation at the end 63a of the third belt ply 63.

In addition, in the pneumatic tire 1 according to this 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.

This configuration ensures that the end 63a of the third belt ply 63 is positioned further inward in the tire radial direction D2 than the shoulder portion.

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

This configuration ensures that the end 63a of the third belt ply 63 is positioned more inward in the tire radial direction D2 than the shoulder portion.

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 that constitutes the outer surface of the sidewall 2. The end 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.

This configuration reduces heat generation at the end 63a of the third belt ply 63, thereby suppressing separation.

The pneumatic tire 1 is not limited to the configuration of the above-mentioned embodiment, nor is it limited to the above-mentioned effects. Furthermore, the pneumatic tire 1 can of course be modified in various ways without departing from the spirit of the present invention. For example, the configurations and methods of the above-mentioned embodiments may be arbitrarily adopted and combined, and further, 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-mentioned embodiment.

(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.

(2) In addition, in the pneumatic tire 1 according to the above embodiment, the end 63a of the third belt ply 63 is located outside the ground contact end 3b of the tread 3 in the tire width direction D1. 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 inside the ground contact end 3b of the tread 3 in the tire width direction D1. However, in order to separate the end 63a of the third belt ply 63 from the shoulder portion, it is preferable to position the end 63a of the third belt ply 63 outside the ground contact end 3b of the tread 3 in the tire width direction D1.

(3) In addition, the pneumatic tire 1 according to the above 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. The end 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. The base rubber 32 and the shoulder pad rubber 7 may be made of the same rubber.

1...pneumatic tire, 1a...maximum tire width position, 2...sidewall, 3...tread, 3c-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 (4)

A tire has a carcass, and first, second, and third belt plies 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 . 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. The pneumatic tire according to claim 1 or 2, wherein the end of the third belt ply is located outside the ground contact end of the tread in the tire width direction. 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.