Pneumatic tires

Abstract

To provide a pneumatic tire that can avoid deterioration of rolling resistance and occurrence of a manufacturing failure, while attaining high-withstand load capacity and space-saving.SOLUTION: An outer diameter of a pneumatic tire (10) is 350 mm or more and 600 mm or less. When a rim width of a rim wheel (100) assembled into the pneumatic tire (10) is defined as RW and a tire width of the pneumatic tire (10) is defined as SW, a relational expression of 0.78≤RW / SW≤0.99 is satisfied. A carcass has carcass cords arranged along a tire width direction. The carcass cord is formed of filaments of steel. An outer diameter of the carcass cord is 0.7 mm or less, and an interval between the adjacent carcass cords is 4.0 mm or less.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a small diameter pneumatic tire having an increased load-bearing capacity. [Background technology]

[0002] Conventionally, pneumatic tires that have a small diameter while increasing the load-bearing capacity (maximum load capacity) are known (see Patent Document 1). It is said that such pneumatic tires can save space, particularly in small vehicles, and ensure a large passenger space.

[0003] Moreover, in the pneumatic tire, a carcass cord made of an organic fiber is used. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-138435 A Summary of the Invention

[0005] In recent years, new small shuttle buses have been proposed that focus on transporting people and goods within cities. These small shuttle buses are expected to be about 5m long and 2m wide, with a total vehicle weight exceeding 3t. There is also a demand for pneumatic tires to be space-saving while still having the necessary load-bearing capacity.

[0006] When such a high load-bearing capacity is required, it may be considered to use steel for the carcass cord, but this would increase the weight of the pneumatic tire and worsen the rolling resistance compared to when an organic fiber carcass cord is used.

[0007] In addition, when steel is used for the carcass cords, the bending rigidity of the carcass increases, and therefore, particularly in the case of small tire sizes, the folded-back portion of the carcass that is folded back through the bead cores is not close to the bead cores, which is likely to cause manufacturing defects.

[0008] Therefore, the present invention has been made in consideration of such circumstances, and has an object to provide a pneumatic tire that can achieve high load-bearing capacity and space saving while avoiding deterioration of rolling resistance and the occurrence of manufacturing defects.

[0009] One aspect of the present invention is a pneumatic tire (pneumatic tire 10) having an annular carcass (carcass 40) that forms a tire skeleton and is fitted to a vehicle (vehicle 1), the outer diameter of the pneumatic tire is 350 mm or more and 600 mm or less, and when the rim width of a rim wheel that is mounted to the pneumatic tire is RW and the tire width of the pneumatic tire is SW, the relationship satisfies 0.78≦RW / SW≦0.99, the carcass has a carcass cord arranged along the tire width direction, the carcass cord is formed from steel filaments (filaments FL1, FL2), the outer diameter of the carcass cord is 0.7 mm or less, and the distance between adjacent carcass cords is 4.0 mm or less. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic overall side view of a vehicle 1 on which a pneumatic tire 10 is mounted. [Diagram 2] FIG. 2 is a cross-sectional view of the pneumatic tire 10 and the rim wheel 100. [Diagram 3] FIG. 3 is a cross-sectional view of the pneumatic tire 10 alone. [Figure 4] FIG. 4 is a partial perspective view of the carcass 40. As shown in FIG. [Diagram 5] FIG. 5 is a diagram illustrating a cross-sectional shape of the carcass cord 40a. [Figure 6A] FIG. 6A is a perspective view of the belt layer 50 during its manufacture. [Figure 6B] FIG. 6B is a perspective view of the belt layer 50 after manufacture. [Figure 7] FIG. 7 is a diagram showing the positioning of typical tire sizes based on the combination of the tire shape (tire outer diameter OD and tire width SW) and the rim / wheel shape (rim diameter RD and rim width RW). [Figure 8] FIG. 8 is a diagram illustrating a cross-sectional shape of a carcass cord 42a according to a modified example. [Figure 9] FIG. 9 is a diagram illustrating a cross-sectional shape of a carcass cord 43a according to another modified example. [Figure 10] FIG. 10 is a cross-sectional view of a pneumatic tire 10A according to a modified example. [Figure 11] FIG. 11 is a cross-sectional view of a pneumatic tire 10B according to another modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment will be described with reference to the drawings. Note that the same or similar reference numerals are used to designate the same functions or configurations, and the description thereof will be omitted as appropriate.

[0012] (1) General configuration of a vehicle on which pneumatic tires are installed Fig. 1 is a schematic overall side view of a vehicle 1 on which a pneumatic tire 10 according to this embodiment is mounted. As shown in Fig. 1, in this embodiment, the vehicle 1 is a four-wheeled automobile. Note that the vehicle 1 is not limited to having four wheels, and may have six or eight wheels, for example.

[0013] A predetermined number of pneumatic tires 10 are mounted on the vehicle 1 according to the wheel configuration. Specifically, the pneumatic tires 10 assembled to rim wheels 100 are mounted on the vehicle 1 at predetermined positions.

[0014] Vehicle 1 belongs to a new type of small shuttle bus that is primarily intended for transporting people and goods within cities. In this embodiment, the new small shuttle bus is assumed to be a vehicle with an overall length of 4 m to 7 m, an overall width of about 2 m, and a total vehicle weight of about 3 tons. However, the size and total vehicle weight are not necessarily limited to these ranges, and may deviate from these ranges to some extent.

[0015] Furthermore, the small shuttle bus is not necessarily limited to being used for transporting people, but may also be used for transporting goods, as a mobile store, a mobile office, etc.

[0016] Furthermore, since small shuttle buses are primarily intended for transporting people and goods within cities, they are expected to operate at a relatively low speed range (maximum speed of 70 km / h or less, average speed of around 50 km / h). For this reason, measures against hydroplaning do not need to be given much importance.

[0017] In this embodiment, the vehicle 1 is assumed to be an electric vehicle equipped with an autonomous driving function (assuming level 4 or higher), but the autonomous driving function is not essential, and the vehicle does not have to be an electric vehicle.

[0018] When the vehicle 1 is an electric vehicle, it is preferable to use an in-wheel motor (not shown) as the power unit. The in-wheel motor may be provided as a whole unit in the inner space of the rim wheel 100, or a part of the unit may be provided in the inner space of the rim wheel 100.

[0019] Furthermore, when using in-wheel motors, it is preferable that the vehicle 1 has an independent steering function that allows each wheel to be steered independently. This allows the vehicle 1 to turn around on the spot and move laterally, and also eliminates the need for a power transmission mechanism, improving the space efficiency of the vehicle 1.

[0020] Thus, high space efficiency is required in the vehicle 1. For this reason, it is preferable that the pneumatic tire 10 has as small a diameter as possible.

[0021] On the other hand, since it is to be mounted on the vehicle 1 having an appropriate gross vehicle weight according to the vehicle size and usage, a high load-bearing capacity (maximum load capacity) is required.

[0022] The pneumatic tire 10 has a load-bearing capacity corresponding to the gross vehicle weight of the vehicle 1 while reducing the tire outer diameter OD (not shown in FIG. 1, see FIG. 2) in order to meet such requirements.

[0023] Further, when the vehicle 1 is equipped with an in-wheel motor and an independent steering function, from the viewpoint of improving responsiveness, it is preferable that the aspect ratio of the pneumatic tire 10 is low, and considering the accommodation space for the in-wheel motor and the like, the rim diameter RD (not shown in FIG. 1, see FIG. 2) of the pneumatic tire 10 is preferably large.

[0024] (2) Structure of pneumatic tire FIG. 2 is a cross-sectional view of the pneumatic tire 10 and the rim wheel 100. Specifically, FIG. 2 is a cross-sectional view along the tire width direction and the tire diameter direction of the pneumatic tire 10 assembled to the rim wheel 100. In FIG. 2, the hatching display of the cross-section is omitted (the same applies to FIG. 3 and subsequent figures).

[0025] The pneumatic tire 10 has a relatively small diameter while being wide. Specifically, the rim diameter RD which is the diameter of the rim wheel 100 is preferably 12 inches or more and 17.5 inches or less. However, the rim diameter RD may be 10 inches or more and 22 inches or less as long as it satisfies other numerical ranges.

[0026] As shown in FIG. 2, the rim diameter RD is the outer diameter of the rim body portion of the rim wheel 100 and does not include the rim flange 110 portion.

[0027] Also, the tire width SW of the pneumatic tire 10 is preferably 125 mm or more and 255 mm or less. As shown in FIG. 2, the tire width SW means the cross-sectional width of the pneumatic tire 10, and when the pneumatic tire 10 is provided with a rim guard (not shown), the rim guard portion is not included.

[0028] Furthermore, it is preferable that the aspect ratio of the pneumatic tire 10 is 35% or more and 75% or less.

[0029] Aspect ratio (%) = tire section height H / tire width SW (section width) x 100 ... (Formula 1) The tire outer diameter OD of the pneumatic tire 10 is 350 mm or more and 600 mm or less. The tire outer diameter OD is preferably 500 mm or less.

[0030] When the tire outer diameter OD is of this size and the rim width of the rim wheel 100 mounted on the pneumatic tire 10 is taken as the rim width RW, the pneumatic tire 10 satisfies the relationships of (Equation 2) and (Equation 3).

[0031] 0.78≦RW / SW≦0.99…(Formula 2) 0.56≦RD / OD≦0.75…(Formula 3) The pneumatic tire 10 preferably satisfies 0.78≦RW / SW≦0.98, and more preferably satisfies 0.78≦RW / SW≦0.95. The pneumatic tire 10 preferably satisfies 0.56≦RD / OD≦0.72, and more preferably satisfies 0.56≦RD / OD≦0.71.

[0032] The pneumatic tire 10 that satisfies such a relationship can ensure the air volume necessary to support the total weight of the vehicle 1, even though it has a small diameter. Specifically, the air volume is 20,000 cm3, taking into account the load support performance. 3 In addition, if space saving is taken into consideration, 80,000 cm is required. 3 The following is required:

[0033] As long as the above relationship is satisfied, the rim width RW is not particularly limited, but from the viewpoint of ensuring air volume, it is preferable that the rim width is as wide as possible. For example, the rim width may be 3.8 to 7.8J.

[0034] Similarly, from the viewpoint of ensuring air volume, it is preferable that the ratio of the rim diameter RD to the tire outer diameter OD is small, that is, the aspect ratio is high. However, as described above, from the viewpoint of responsiveness, a low aspect ratio is preferable, and considering the accommodation space for an in-wheel motor, etc., a large rim diameter RD is preferable, so the aspect ratio and the rim diameter RD are in a trade-off relationship between the air volume, and the responsiveness and the accommodation space for an in-wheel motor, etc.

[0035] An example of a suitable size for the pneumatic tire 10 is 205 / 40R15. The suitable rim width is about 7.5J. Another example of a suitable size is 215 / 45R12. In this case, the suitable rim width is about 7.0J.

[0036] Furthermore, although not particularly limited, the set internal pressure (normal internal pressure) of the pneumatic tire 10 is assumed to be 400 to 1,100 kPa, and more realistically, 500 to 900 kPa. Note that the normal internal pressure is, for example, the air pressure that corresponds to the maximum load capacity in the YearBook of the Japan Automobile Tire Manufacturers Association (JATMA) in Japan, the ETRTO in Europe, the TRA in the United States, and tire standards of other countries.

[0037] The load borne by the pneumatic tire 10 is assumed to be 500 to 1,500 kgf, and realistically, approximately 900 kgf.

[0038] Fig. 3 is a cross-sectional view of the pneumatic tire 10. Specifically, Fig. 3 is a cross-sectional view of the pneumatic tire 10 taken along the tire width direction and the tire radial direction.

[0039] As shown in FIG. 3, the pneumatic tire 10 includes a tread 20, a tire side portion 30, a carcass 40, a belt layer 50, and a bead portion 60.

[0040] The tread 20 is the portion that comes into contact with the road surface. A pattern (not shown) is formed on the tread 20 according to the environment in which the pneumatic tire 10 is used and the type of vehicle on which the tire is to be mounted.

[0041] The tire side portion 30 is continuous with the tread 20 and is located on the inner side in the tire radial direction of the tread 20. The tire side portion 30 is a region from the outer end of the tread 20 in the tire width direction to the upper end of the bead portion 60. The tire side portion 30 is also called a sidewall or the like.

[0042] The carcass 40 is an annular member that forms the tire skeleton of the pneumatic tire 10. The carcass 40 has a radial structure in which carcass cords 40a (not shown in FIG. 3, see FIG. 4) arranged radially along the tire radial direction are covered with a rubber material.

[0043] The belt layer 50 is provided on the inner side in the tire radial direction of the tread 20. The belt layer 50 is composed of a core belt 51 and a sheath vest 52.

[0044] The core belt 51 is provided across from one shoulder portion 26 of the tread 20 to the other shoulder portion 27 of the tread 20. The shoulder portion 26 is a region that is further outward in the tire width direction than the circumferential main groove 21, and the shoulder portion 27 is a region that is further outward in the tire width direction than the circumferential main groove 22. In other words, the shoulder portion 26 and the shoulder portion 27 are regions that are further outward in the tire width direction than the circumferential main groove that is formed on the outermost side in the tire width direction.

[0045] The core belt 51 is a belt in which a belt cord 51a (not shown in FIG. 3, see FIG. 6A) inclined at a low angle with respect to the tire width direction is rubber-coated. The sheath vest 52 is a tape-like belt including a cord, and is wound around the entire circumference of the core belt 51. The sheath vest 52 provides the same function as the intersecting belt layer. The configuration of the belt layer 50 will be described later.

[0046] The bead portion 60 is continuous with the tire side portion 30, and is located on the inner side in the tire radial direction of the tire side portion 30. The bead portion 60 is engaged with the rim wheel 100, and has an annular bead core 61. The carcass 40 is folded back toward the outside in the tire width direction via the bead cores 61 .

[0047] The bead core 61 is formed by twisting a plurality of bead wires 61a (only a portion of which is shown in FIG. 3). The cross-sectional shape of the bead core 61 formed by the bead wires 61a in this manner may be hexagonal, rectangular, or circular.

[0048] The width of the bead core 61 in the tire width direction is preferably 5 mm or more and 30 mm or less. The height of the bead core 61 in the tire radial direction is preferably 3 mm or more and 15 mm or less. Furthermore, the number of bead wires 61a forming the bead core 61 (the number in a cross section) is preferably 15 or more and 60 or less.

[0049] The folded end 41 of the carcass 40 folded back at the bead portion 60 is provided so as to be wound around the bead core 61. The folded end 41 is in contact with the outer end of the bead core 61 in the tire radial direction. Specifically, at the folded end 41 of the carcass 40, the carcass cord 40a is wound around the outer end of the bead core 61 in the tire radial direction.

[0050] In addition, a bead filler may be provided on the bead portion 60 radially outside of the bead core, and a chafer may be provided to prevent the carcass 40, which is folded over at the bead portion 60, from rubbing against the rim wheel 100 and becoming worn.

[0051] (3) Carcass Structure Next, a description will be given of the configuration of the carcass 40. Fig. 4 is a partial perspective view of the carcass 40. As shown in Fig. 4, the carcass 40 has carcass cords 40a arranged along the tire width direction.

[0052] Specifically, a plurality of carcass cords 40a arranged along the tire width direction are covered with a rubber material.

[0053] The carcass cord 40a is formed by twisting metal filaments. Specifically, the carcass cord 40a is formed by steel filaments.

[0054] Fig. 5 shows a schematic cross-sectional shape of the carcass cord 40a. As shown in Fig. 5, the carcass cord 40a is formed by twisting a plurality of filaments FL1 and a plurality of filaments FL2. Specifically, the carcass cord 40a is formed by two filaments FL1 and six filaments FL2.

[0055] The carcass cord 40a has a smaller outer diameter than a general carcass cord so that it can easily follow the shape of the bead portion 60 of the small-diameter pneumatic tire 10. Specifically, the outer diameter of the carcass cord 40a is 0.7 mm or less. The outer diameter of the carcass cord 40a is more preferably 0.6 mm or less.

[0056] Moreover, the outer diameter of the filaments FL1 and FL2 forming the carcass cord 40a is preferably 0.2 mm or less.

[0057] In this embodiment, the outer diameter of the filament FL1 is 0.15 mm, and the outer diameter of the filament FL2 is 0.175 mm.

[0058] Further, the interval G (see FIG. 4) between adjacent carcass cords 40a is equal to or less than 4.0 mm. Specifically, the interval G is the distance between the outer circumferential surfaces of adjacent carcass cords 40a in the tire circumferential direction.

[0059] The distance G is more preferably 3.5 mm or less, and even more preferably 3.0 mm or less. The distance G is preferably 0.5 mm or more, and even more preferably 1.0 mm or more, and even more preferably 1.5 mm or more. The interval G is the distance between adjacent carcass cords 40a immediately below the tire equator line CL (see FIG. 3).

[0060] (4) Belt layer composition Next, a description will be given of the configuration of the belt layer 50. As described above, the belt layer 50 is configured by the core belt 51 and the sheath vest 52.

[0061] 6A and 6B show the configuration of the belt layer 50. Specifically, Fig. 6A is a perspective view of the belt layer 50 alone during production, and Fig. 6B is a perspective view of the belt layer 50 alone after production.

[0062] 6A, the core belt 51 has belt cords 51a arranged along the tire width direction. The core belt 51 is an annular belt formed by rubber-coating the belt cords 51a.

[0063] It is preferable that the belt cord 51a is slightly inclined with respect to the tire width direction as shown in Fig. 6A. Specifically, it is preferable that the belt cord 51a is inclined in the same direction as the inclination direction of the sheath vest 52 (upward to the left in Fig. 6A).

[0064] The sheath vest 52 is a tape-like belt having a width of about 1 cm, and is wound around the core belt 51 in a spiral shape along the tire circumferential direction. Specifically, the sheath vest 52 is wound around the core belt 51 in a spiral shape along the tire circumferential direction at a predetermined distance that is equal to or greater than the width of the sheath vest 52.

[0065] The sheath vest 52 is wound around the tire circumferential direction multiple times without overlapping with adjacent sheath vests 52, thereby covering the tire radial outer side surface of the core belt 51 and the tire radial inner side surface of the core belt 51.

[0066] Further, the longitudinal ends (not shown) of the tape-shaped sheath vest 52 are wound around the core belt 51 so as not to be positioned in the shoulder regions 26, 27 and the center region (directly below the tire equator).

[0067] As shown in FIG. 6B, the sheath vest 52 is wrapped around the entire circumference of the annular core belt 51.

[0068] In this embodiment, the belt layer 50 is composed only of the core belt 51 and the sheath vest 52. As described above, the belt layer 50 provides the same function as the intersecting belt layer, but in this embodiment, other than the core belt 51 and the sheath vest 52, no additional belt such as a reinforcing belt is provided.

[0069] The end count of the belt cord 51a in the core belt 51 is preferably 15 / 50 mm or more and 30 / 50 mm or less. The end count of the cord in the sheath vest 52 is preferably 10 / 50 mm or more and 25 / 50 mm or less. The end count of the belt cord 51a is preferably greater (i.e., denser) than the end count of the cord in the sheath vest 52.

[0070] The angle that the belt cord 51a forms with the tire width direction is preferably 20 degrees or more and 60 degrees or less. The angle that the cord of the sheath vest 52 forms with the tire width direction is preferably 50 degrees or more and 80 degrees or less. In addition, the angle that the cord of the sheath vest 52 forms with the tire width direction is preferably larger than the angle that the belt cord 51a forms with the tire width direction.

[0071] In consideration of ensuring performance and productivity, the number of folds of the sheath vest 52 in the tire circumferential direction is preferably 3 to 6 times.

[0072] (5) Actions and Effects Next, a description will be given of the operation and effect of the above-mentioned pneumatic tire 10. Fig. 7 is a diagram showing the positioning of typical tire sizes based on the combination of the tire shape (tire outer diameter OD and tire width SW) and the rim / wheel shape (rim diameter RD and rim width RW).

[0073] Specifically, the horizontal axis of the graph shown in Fig. 7 indicates the ratio (RW / SW) between the rim width RW and the tire width SW, and the vertical axis indicates the ratio (RD / OD) between the rim diameter RD and the tire outer diameter OD. In Fig. 7, the positions of typical tire sizes are plotted according to the values ​​of RW / SW and RD / OD.

[0074] As shown in Figure 7, the areas of truck and bus tires are lower in both RW / SW and RD / OD. The areas of passenger car or light truck tires are higher than truck and bus tires in both RW / SW and RD / OD.

[0075] The above-mentioned 215 / 45R12, which is an example of a suitable size for the pneumatic tire 10, is included in the region A1. As described above, the region A1 is in the range of 0.78≦RW / SW≦0.99 and 0.56≦RD / OD≦0.75. Such region A1 is positioned as the region for tires for new small shuttle buses that are primarily intended for transporting people and goods within cities, such as the above-mentioned vehicle 1.

[0076] The RD / OD of the new small shuttle bus tire area is not significantly different from the RD / OD of the passenger car or small truck tire area, and there is some overlap, while the RW / SW of the new small shuttle bus tire area is higher than the RW / SW of the passenger car or small truck tire area.

[0077] As described above, the tire outer diameter OD of the pneumatic tire 10 is equal to or greater than 350 mm and equal to or less than 600 mm. Therefore, the tire outer diameter OD is sufficiently small compared to the size of the vehicle 1, and can contribute to space saving of the vehicle 1.

[0078] Furthermore, according to the pneumatic tire 10 of the size included in the region A1, the relationship of 0.78≦RW / SW≦0.99 is satisfied, so the rim width RW is wide relative to the tire width SW, meaning that a wide tire can be constructed, making it easy to ensure the air volume necessary to exhibit a high load-bearing capacity. However, if the rim width RW becomes too wide, the tire width SW also widens, reducing the space efficiency, and the bead portion 60 becomes more likely to come off the rim wheel 100.

[0079] Furthermore, according to the pneumatic tire 10 having a size included in the region A1, the relationship of 0.56≦RD / OD≦0.75 is satisfied, so that the rim diameter RD is large relative to the tire outer diameter OD, and it is easy to secure the space to accommodate an in-wheel motor, etc. However, if the rim diameter RD becomes too small, the diameter size of the disc brake or drum brake becomes small. As a result, the effective contact area of ​​the brake becomes small, making it difficult to secure the required braking performance.

[0080] That is, the pneumatic tire 10 can achieve high space efficiency while having a higher load-bearing capacity when mounted on a new small shuttle bus or the like.

[0081] The rim diameter RD of the pneumatic tire 10 is preferably 12 inches or more and 17.5 inches or less. This makes it possible to secure a necessary and sufficient air volume and a space for accommodating an in-wheel motor, etc., while maintaining a small diameter. In addition, braking performance and driving performance can be secured.

[0082] The tire width SW of the pneumatic tire 10 is preferably 125 mm or more and 255 mm or less. Furthermore, the aspect ratio of the pneumatic tire 10 is preferably 35% or more and 75% or less. This makes it possible to ensure a necessary and sufficient air volume and storage space for an in-wheel motor, etc.

[0083] Furthermore, in this embodiment, as described above, the carcass cord 40a is formed by the steel filaments FL1 and FL2.

[0084] Since the carcass cord 40a is formed from steel filaments in this manner, it is possible to ensure durability while having a high load-bearing capacity.

[0085] In addition, since the filaments FL1 and FL2 are thinner than tires of a similar size (for example, small diameter size 225 / 80R17.5 for truck and bus tires), even when a steel filament is used, the carcass cord 40a can easily follow the shape of the small diameter bead portion 60. In particular, even when the radius of curvature of the folded-back portion of the carcass 40 at the bead core 61 is small, the carcass 40 can easily be folded back to the outside in the tire width direction via the bead core 61, which is effective in preventing manufacturing defects.

[0086] Furthermore, while using such thin steel filaments, the spacing G between adjacent carcass cords 40a is set to 4.0 mm or less, so that even when the pneumatic tire 10 mounted on the rim wheel 100 is filled with air (gas), the carcass cords 40a can be prevented from protruding from the outer surface of the bead portion 60 (side unevenness).

[0087] In addition, since a constant interval G is ensured, an increase in the weight of the carcass 40 can be suppressed even when steel filaments are used, and therefore a deterioration in rolling resistance can also be suppressed.

[0088] That is, the pneumatic tire 10 can achieve high load-bearing capacity and space-saving, while avoiding deterioration of rolling resistance and the occurrence of manufacturing defects.

[0089] In this embodiment, the outer diameter of the filaments FL1 and FL2 is 0.2 mm or less. This allows the carcass 40 to more easily conform to the shape of the small-diameter bead portion 60, and also prevents weight increase. This makes it possible to more reliably avoid deterioration of rolling resistance and the occurrence of manufacturing defects.

[0090] In the present embodiment, at the folded end 41 of the carcass 40, the carcass 40, specifically, the carcass cord 40a is wound around the tire radial direction outer end of the bead core 61. This can more reliably prevent the carcass cord 40a from protruding from the outer surface of the bead portion 60 (side unevenness). Also, the progress of cracks at the end of the carcass cord 40a can be suppressed.

[0091] (6) Other embodiments The present invention has been described above with reference to the embodiments. However, the present invention is not limited to these embodiments, and it will be obvious to those skilled in the art that various modifications and improvements are possible.

[0092] For example, in the above-described embodiment, the carcass cord 40a is formed by twisting the filaments FL1 and FL2 (see FIG. 5), but the carcass cord 40a may be formed as follows.

[0093] Fig. 8 is a diagram showing a cross-sectional shape of a carcass cord 42a according to a modified example, and Fig. 9 is a diagram showing a cross-sectional shape of a carcass cord 43a according to another modified example.

[0094] As shown in Fig. 8, the carcass cord 42a is formed of only one type of filament FL1, and as shown in Fig. 9, the carcass cord 43a is formed of three types of filaments, specifically, filaments FL1, FL2, and FL3.

[0095] That is, the carcass cord may be formed of a single (type) of filament, or may be formed of a plurality of filaments.

[0096] As in the above-described embodiment, the outer diameter of the filaments FL1, FL2, and FL3 is preferably 0.2 mm or less, more preferably 0.175 mm or less, and further preferably 0.150 mm or less.

[0097] In addition, in the above-described embodiment, the pneumatic tire 10 satisfies the relationship 0.56≦RD / OD≦0.75, but this relationship does not necessarily have to be satisfied.

[0098] In the above-described embodiment, the carcass cord 40a is wound around the outer end of the bead core 61 in the tire radial direction, but such a configuration is not necessarily required.

[0099] Furthermore, in the above-described embodiment, the belt layer 50 constituted by the core belt 51 and the sheath vest 52 is used, but the belt layer 50 may have the following shape.

[0100] Fig. 10 is a cross-sectional view of a pneumatic tire 10A according to a modified example. As shown in Fig. 10, a belt layer 50A provided in the pneumatic tire 10A includes a pair of intersecting belts in which cords intersect. The configuration of the belt layer 50 is generally similar to the configuration of the belt layer of a typical truck or bus tire.

[0101] Fig. 11 is a cross-sectional view of a pneumatic tire 10B according to another modified example. As shown in Fig. 11, a belt layer 50B included in the pneumatic tire 10B is a spiral belt formed by winding a resin-coated cord coated with a resin material in the tire circumferential direction.

[0102] As in the pneumatic tires 10A and 10B, the configuration of the belt layers and the shape of the folded end portion 41 of the carcass 40 may be changed as appropriate depending on the characteristics of the vehicle 1 and the like.

[0103] As described above, the embodiment of the present invention has been described, but the description and drawings forming a part of this disclosure should not be understood as limiting this invention. Various alternative embodiments, examples and operating techniques will become apparent to those skilled in the art from this disclosure. [Explanation of symbols]

[0104] 1 vehicle 10, 10A, 10B Pneumatic tires 20 Tread 21, 22 Circumferential main groove 26, 27 Shoulder section 30 Tire side 40 Carcass 40a, 42a, 43a carcass cord 41 Folded end 50, 50A, 50B belt layer 51 Core Belt 51a Belt cord 52 Sheath Vest 60 Bead section 61 Bead core 61a Bead Wire 100 Rim Wheel 110 Rim flange FL1, FL2, FL3 filaments

Claims

1. A pneumatic tire to be mounted on a vehicle includes an annular carcass that forms a tire framework, and a bead portion that is fixed to a rim wheel and has an annular bead core, The outer diameter of the pneumatic tire is 350 mm or more and 600 mm or less, The rim width of the rim wheel to be mounted on the pneumatic tire is RW, If the tire width of the pneumatic tire is SW, The relationship 0.78≦RW / SW≦0.99 is satisfied. The carcass has a carcass cord arranged along the tire width direction, The carcass cord is formed of steel filaments, The outer diameter of the filament is 0.2 mm or less, The carcass is folded back toward the outside in the tire width direction via the bead core, At a folded end portion of the carcass, the carcass cord is wound around an outer end of the bead core in a radial direction of the tire, The set internal pressure of the pneumatic tire is 400 to 1,100 kPa.

2. A pneumatic tire to be mounted on a vehicle includes an annular carcass that forms a tire framework, and a bead portion that is fixed to a rim wheel and has an annular bead core, The outer diameter of the pneumatic tire is 350 mm or more and 600 mm or less, The rim width of the rim wheel to be mounted on the pneumatic tire is RW, If the tire width of the pneumatic tire is SW, The relationship 0.78≦RW / SW≦0.99 is satisfied. The carcass has a carcass cord arranged along the tire width direction, The carcass cord is formed of steel filaments, The interval between adjacent carcass cords is 4.0 mm or less, The carcass is folded back toward the outside in the tire width direction via the bead core, At a folded end portion of the carcass, the carcass cord is wound around an outer end of the bead core in a radial direction of the tire, The set internal pressure of the pneumatic tire is 400 to 1,100 kPa.

3. A pneumatic tire to be mounted on a vehicle includes an annular carcass that forms a tire framework, and a bead portion that is fixed to a rim wheel and has an annular bead core, The outer diameter of the pneumatic tire is 350 mm or more and 600 mm or less, The rim width of the rim wheel to be mounted on the pneumatic tire is RW, If the tire width of the pneumatic tire is SW, The relationship 0.78≦RW / SW≦0.99 is satisfied. The carcass has a carcass cord arranged along the tire width direction, The carcass cord is formed of steel filaments, The width of the bead core along the tire width direction is 5 mm or more and 30 mm or less, The height of the bead core along the tire radial direction is 3 mm or more and 15 mm or less, The number of bead wires forming the bead core in a cross section of the bead core is 15 or more and 60 or less, The carcass is folded back toward the outside in the tire width direction via the bead core, At a folded end portion of the carcass, the carcass cord is wound around an outer end of the bead core in a radial direction of the tire, The set internal pressure of the pneumatic tire is 400 to 1,100 kPa.

4. A pneumatic tire described in any one of claims 1 to 3, wherein the load borne by the pneumatic tire is 500 to 1,500 kgf.

5. A pneumatic tire as described in any one of claims 1 to 3, wherein the air volume of the pneumatic tire is 20,000 cm 3 or more and 80,000 cm 3 or less.

6. The pneumatic tire described in any one of claims 1 to 3, which is a tire for trucks and buses.

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