JP7667407B2 - Tire, tire manufacturing method and vehicle - Google Patents

Description

The present invention relates to a tire, a tire manufacturing method, and a vehicle.

The technology disclosed in Patent Document 1 is known as a technology for reducing the rolling resistance of tires and improving fuel efficiency. In Patent Document 1, the relationship between the tire cross-sectional width and the bead diameter is regulated, and the belt cord angle is regulated to reduce the rolling resistance of the tire.

JP 2015-33984 A

However, the technology disclosed in Patent Document 1 leaves room for improvement in terms of reducing tire rolling resistance and improving fuel efficiency.

The present invention has been made in consideration of the above, and its purpose is to provide a tire, a tire manufacturing method, and a vehicle that can improve fuel efficiency.

In order to solve the above-mentioned problems and achieve the objects, a tire according to one embodiment of the present invention is a tire in which, when mounted on a specified rim and given a specified internal pressure, and in an unloaded state, the relationship between the tire outer diameter OD and total width SW satisfies the following formula (1), and when the length SWD is twice the radial length from the tire rotation axis to the measurement position of the total width SW, the total strength T [kg] of the carcass satisfies the following formula (2) :
OD≦-0.0019×SW ² +1.4×SW+400…(1)
T≧α×[(OD/2) ² - (SWD/2) ² ] …(2)
However, in equation (2), the constant α is 0.224.

It is preferable that the relationship between the tire outer diameter OD and the total width SW satisfies the following formula (3).
OD≦-0.0024×SW ² +1.6×SW+362…(3)

When the total width SW is 150 mm or less, it is preferable that the relationship between the tire outer diameter OD and the total width SW satisfies the following formula (4).
OD≦-0.0060×SW ² +5.9×SW-183…(4)
In another aspect of the present invention, a tire is mounted on a specified rim, a specified internal pressure is applied, and a relationship between a tire outer diameter (OD) and a total width (SW) satisfies the following formula (1) when the tire is in an unloaded state:
When the total width SW is 150 mm or less, the relationship between the tire outer diameter OD and the total width SW satisfies the following formula (4).
OD≦-0.0019×SW ² +1.4×SW+400…(1)
OD≦-0.0060×SW ² +5.9×SW-183…(4)

In the above formula (2), it is preferable that the constant α is 0.448.

It is preferable that the relationship between the tire outer diameter OD and the total width SW satisfies the following formula (5).
OD≧-0.0017×SW ² +0.9×SW+350…(5)

It is preferable that the maximum load capacity W [kgf] satisfies the following formula (6).
W≧β×10 ⁻⁴ ×Sd ^1.39 ×(D−12.7+Sd) …(6)
However, in the formula (6),
The constant β is 7.1,
The value Sd=0.93×SW−0.637×d,
Value d = (0.9 - aspect ratio) x SW - 6.35,
The value D = inner diameter x 25.4.

It is preferable that the maximum load capacity when an internal pressure of 250 kPa is applied is a value that exceeds the load capacity defined by the nominal, aspect ratio, and inner diameter of the JATMA standard for automobile tires.

It is preferable that the maximum load capacity when an internal pressure of 250 kPa is applied be 102% or more and 400% or less of the load capacity defined by the nominal, aspect ratio, and inner diameter of the JATMA standard for automobile tires.

It is preferable that the maximum allowable air pressure be set to a value greater than 180 kPa, the value set by the JATMA standard for automobile tires, and equal to or less than 1200 kPa.

It is preferable that the maximum speed used be 120km/h or less.

It is preferable that the tire outer diameter OD is 480 mm or more.

In order to solve the above-mentioned problems and achieve the object, a manufacturing method of a tire according to an embodiment of the present invention is a manufacturing method of a tire in which, when the tire is mounted on a specified rim and a specified internal pressure is applied, and in a no-load state, the relationship between the tire outer diameter OD and the total width SW satisfies the following formula (1), and when the length SWD is twice the length in the tire radial direction from the tire rotation axis to a measurement position of the total width SW, the total strength T [kg] of the carcass satisfies the following formula (2), the manufacturing method of the tire includes the following steps: a first step of designing a molding die so that the relationship between the tire outer diameter OD and the total width SW satisfies the following formula (1); a second step of determining a carcass to be used for a tire to be molded using the molding die designed in the first step so as to satisfy a total strength T [kg] of the tire; a third step of molding a primary green tire; a fourth step of molding a belt/tread assembly; a fifth step of bonding the primary green tire obtained in the third step and the belt/tread assembly obtained in the fourth step to mold a secondary green tire; and a sixth step of vulcanizing and molding the secondary green tire obtained in the fifth step.
OD≦-0.0019×SW ² +1.4×SW+400…(1)
T≧α×[(OD/2) ² - (SWD/2) ² ] …(2)
However, in equation (2), the constant α is 0.224.

In order to solve the above problems and achieve the above object, a vehicle according to one aspect of the present invention is a vehicle that includes any one of the above tires and has at least one motor as a power source. It is also preferable that the vehicle includes five or more of any one of the above tires.

The tire, tire manufacturing method, and vehicle of the present invention can improve fuel efficiency.

FIG. 1 is a meridian cross-sectional view showing an example of a tire according to the present embodiment. FIG. 2 is an enlarged view of a portion of FIG. FIG. 3 is a flowchart showing a method for manufacturing a tire according to this embodiment. FIG. 4 is a diagram showing an example of a shaping process. FIG. 5 is a diagram showing an example of tire arrangement on a vehicle. FIG. 6 is a diagram showing an example of tire arrangement on a vehicle. FIG. 7 is a diagram showing an example of tire arrangement on a vehicle. FIG. 8 is a diagram showing an example of tire arrangement on a vehicle. FIG. 9 is a diagram showing an example of tire arrangement on a vehicle. FIG. 10 is a diagram showing an example of tire arrangement on a vehicle. FIG. 11 is a diagram showing an example of tire arrangement on a vehicle. FIG. 12 is a diagram showing an example of tire arrangement on a vehicle.

The following describes in detail an embodiment of the present invention with reference to the drawings. In the following description of each embodiment, components that are the same as or equivalent to those in other embodiments are given the same reference numerals, and their description is simplified or omitted. The present invention is not limited to each embodiment. Furthermore, the components of each embodiment include those that are replaceable and easy for a person skilled in the art, or those that are substantially the same. The configurations described below can be combined as appropriate. Furthermore, the configurations can be omitted, replaced, or modified without departing from the spirit of the invention.

(tire)
FIG. 1 is a meridian cross-sectional view showing an example of a tire 1 according to the present embodiment. FIG. 2 is an enlarged view of a portion of FIG. 1. In the following description, the meridian cross-section of the tire refers to a cross-section of the tire cut by a plane including the rotation axis AX of the tire. The tire radial direction refers to a direction perpendicular to the rotation axis AX of the tire 1, the tire radial inner side refers to a side toward the rotation axis AX in the tire radial direction, and the tire radial outer side refers to a side away from the rotation axis AX in the tire radial direction. The tire circumferential direction refers to a direction around the rotation axis AX as a central axis. The tire width direction refers to a direction parallel to the rotation axis AX, the tire width inner side refers to a side toward the tire equatorial plane (tire equator line) CL in the tire width direction, and the tire width outer side refers to a side away from the tire equatorial plane CL in the tire width direction. The tire equatorial plane CL is a plane perpendicular to the rotation axis AX of the tire 1 and passing through the center of the tire width of the tire 1. The tire width is the width in the tire width direction between the portions located on the outer sides in the tire width direction, that is, the distance between the portions farthest from the tire equatorial plane CL in the tire width direction. The tire equatorial line refers to a line that is on the tire equatorial plane CL and extends along the tire circumferential direction of the tire 1. In this embodiment, the tire equatorial line is given the same symbol "CL" as the tire equatorial plane.

The tire 1 according to this embodiment is preferably a pneumatic tire. The gas to be filled into the tire 1 may be normal air or air with an adjusted oxygen partial pressure, or an inert gas such as nitrogen, argon, or helium.

The tire 1 according to this embodiment has an annular structure centered on the rotation axis AX and is rotatable about the rotation axis AX. The tire 1 has a tread portion 2, shoulder portions 3 on both sides of the tread portion 2, and sidewall portions 4 and bead portions 5 successively continuing from each shoulder portion 3. The tire 1 also has a carcass layer 6, a belt layer 7, a belt reinforcing layer 8, and an inner liner 9.

When viewed in a tire meridian section, the tread portion 2 is formed in an annular shape extending in the tire circumferential direction at the outermost part in the tire radial direction, and is exposed at the outermost part in the tire radial direction of the tire 1, and its outer peripheral surface forms the contour of the tire 1. The outer peripheral surface of the tread portion 2 is formed as a contact surface 10, which is a surface that may come into contact with the road surface mainly during running, and the contact surface 10 has multiple grooves formed therein, such as circumferential grooves 16 extending in the tire circumferential direction and lug grooves (not shown) extending in the tire width direction. The tread portion 2 also has tread rubber 18, which is a rubber composition. The tread rubber 18 may be formed by layering multiple rubber compositions with different physical properties in the tire radial direction.

The shoulder portions 3 are the portions of the tread portion 2 on both outer sides in the tire width direction. The sidewall portions 4 are located on the inner side of the shoulder portions 3 in the tire radial direction, with a pair disposed on both sides in the tire width direction. That is, the pair of sidewall portions 4 are disposed on both sides of the tread portion 2 in the tire width direction, or in other words, the sidewall portions 4 are disposed at two locations on both sides of the tire 1 in the tire width direction. The sidewall portions 4 thus formed are curved in a direction that convexly extends outward in the tire width direction when viewed in a tire meridian cross section, and are the portions of the tire 1 that are exposed most outward in the tire width direction.

The bead portions 5 are disposed on the radially inner side of each of the pair of sidewall portions 4, and like the sidewall portions 4, a pair are disposed on both sides of the tire equatorial plane CL in the tire width direction. Each bead portion 5 has a bead core 11 and a bead filler 12. The bead core 11 is formed by winding a bead wire, which is a steel wire, into a ring shape. The bead filler 12 is a rubber material disposed in a space formed by folding back the tire width direction end of the carcass layer 6 at the position of the bead core 11.

The sidewall portion 4 and the bead portion 5 are included in the tire side portion 20 located on both sides in the tire width direction. In this embodiment, the tire side portion 20 refers to the area between the tire radially inner position of the tread rubber 18 and the bead heel 14, which is the end of the inner circumferential surface of the bead portion 5 on the outer side in the tire width direction.

The total width SW of the tire 1 refers to the straight-line distance between the sides of the tire 1 when the tire 1 is mounted on a specified rim, inflated to a specified air pressure, and in an unloaded state, including any patterns or letters on the side of the tire 1. In other words, the total width of the tire 1 refers to the distance in the tire width direction between the outermost part of the structure constituting the tire 1 located on one side of the tire equatorial plane CL and the outermost part of the structure constituting the tire 1 located on the other side. Note that the distance SWD is twice the distance from the axis of rotation AX to the measurement position of the total width SW.

The specified rim here is the "standard rim" specified by JATMA, the "design rim" specified by TRA, or the "measuring rim" specified by ETRTO. The specified internal pressure is the "maximum air pressure" specified by JATMA, the maximum value listed in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or the "INFLATION PRESSURES" specified by ETRTO. For example, the specified internal pressure is 250 kPa.

The carcass layer 6 has a single-layer structure consisting of one carcass ply or a multi-layer structure consisting of multiple carcass plies stacked together. The carcass layer 6 is toroidally stretched between the left and right bead cores 11, 11 to form the framework of the tire 1. In addition, both ends of the carcass layer 6 are wrapped around and secured to the outside in the tire width direction so as to envelop the bead cores 11 and the bead fillers 12. In addition, the carcass ply of the carcass layer 6 is formed by coating multiple carcass cords made of steel or organic fiber material with coating rubber and rolling them, and has a cord angle of 80 degrees or more and 100 degrees or less. The cord angle is defined as the inclination angle of the carcass cords in the longitudinal direction with respect to the tire circumferential direction.

The belt layer 7 has a multi-layer structure in which at least two layers of belts 7a and 7b are laminated. The belt layer 7 is arranged on the outer periphery of the carcass layer 6 in the tread portion 2, i.e., on the radially outer side of the tire. The belt layer 7 covers the carcass layer 6 in the tire circumferential direction. The belts 7a and 7b have multiple cords (not shown) arranged in parallel at a predetermined angle (e.g., 20° to 30°) to the tire circumferential direction. The cords are covered with a coating rubber. The cords are made of, for example, steel or organic fibers such as polyester, rayon, or nylon. The overlapping belts 7a and 7b are arranged so that the cords cross each other.

The belt reinforcement layer 8 is disposed on the outer side of the belt layer 7 in the tire radial direction, and covers the belt layer 7 in the tire circumferential direction. The belt reinforcement layer 8 is formed by covering a plurality of cords (not shown) arranged in parallel in the tire circumferential direction and in the tire width direction with a coating rubber. The cords are made of, for example, steel or organic fibers such as polyester, rayon, or nylon, and the angle of the cords is within the range of ±5° with respect to the tire circumferential direction. In this embodiment, the belt reinforcement layer 8 is formed by laminating two layers: a belt cover 8a arranged to cover the entire belt layer 7 in the tire width direction, and an edge cover 8b arranged only near the tire width direction end of the belt layer 7 on the tire radial outer side of the belt cover 8a. The belt reinforcement layer 8 may have a configuration other than this, and may be composed of only the belt cover 8a arranged to cover the entire belt layer 7, or only the edge cover 8b arranged to cover the tire width direction end of the belt layer 7. The belt reinforcement layer 8 may be arranged to overlap at least the tire width direction end of the belt layer 7. The belt reinforcing layer 8 configured as above is arranged by wrapping a strip of material, for example, about 10 mm wide, around the tire circumferential direction.

The inner liner 9 is disposed along the carcass layer 6 on the inner surface of the tire 1. The inner liner 9 is an air permeation prevention layer that covers the carcass layer 6. The inner liner 9 suppresses oxidation due to exposure of the carcass layer 6, and also prevents leakage of the air filled in the tire 1. The inner liner 9 is composed of, for example, a rubber composition mainly composed of butyl rubber, a thermoplastic resin, or a thermoplastic elastomer composition in which an elastomer component is blended into a thermoplastic resin.

The above-mentioned internal structure of tire 1 shows a typical example of tire 1, and the internal structure is not limited to this.

(Relationship between tire outer diameter and total width, total strength of carcass layer)
When the tire 1 of the present embodiment is mounted on a specified rim, given a specified internal pressure, and in an unloaded state, it is preferable that the relationship between the tire outer diameter OD and the total width SW satisfies the following formula (1).
OD≦-0.0019×SW ² +1.4×SW+400…(1)

A tire 1 that satisfies the relationship of formula (1) can reduce rotational inertia and weight, improving fuel economy. Here, it is also possible to narrow the tire and increase its outer diameter in order to improve fuel economy. However, such a tire can reduce rolling resistance, but the rotational inertia force is large. For this reason, it may not be possible to improve fuel economy. On the other hand, a tire 1 with a small outer diameter has a small rotational inertia force and a small tire mass, improving fuel economy.

Furthermore, since the tire 1 that satisfies the relationship of formula (1) has a small outer diameter, the vehicle on which the tire 1 is mounted can have a low floor, and space inside the vehicle can be secured. Here, the space inside the vehicle refers to the living space and luggage carrying space inside the vehicle.

Furthermore, in the tire 1 of the present embodiment, when the length SWD is twice the radial length from the rotation axis AX to the measurement position of the total width SW, it is preferable that the total strength T [kg] of the carcass layer 6 satisfies the following formula (2):
T≧α×[(OD/2) ² - (SWD/2) ² ] …(2)
However, in equation (2), the constant α is 0.224.

By satisfying formula (2), the total strength of the carcass layer 6, which is the tire skeleton, can be increased, and the load capacity of the tire 1 can be ensured even when the load increases. In other words, by reducing the outer diameter of the tire 1 while setting the total strength T of the carcass layer 6 to a predetermined value or more, it is possible to achieve both a smaller diameter and improved load capacity.

The carcass ply of the carcass layer 6 can be selected arbitrarily as long as the total strength meets the specified value. In addition to rayon and polyester, high-strength steel, nylon, aramid, hybrids, etc. can be selected. By using high-strength cords, weight can be reduced, which is more effective. By increasing the strength of the carcass layer 6, it can be used at high internal pressures such as 500 kPa and 900 kPa, and the load capacity can be further increased. The total strength T is calculated by multiplying the strength per cord by the number of cords. The tire outer diameter OD, total width SW, and length SWD mentioned above are values measured when the tire 1 is mounted on a specified rim, the specified internal pressure is applied, and no load is applied.

In addition, in the tire 1 of the present embodiment, when the total width SW is 150 mm or less, it is preferable that the relationship between the tire outer diameter OD and the total width SW satisfies the following formula (3).
OD≦-0.0024×SW ² +1.6×SW+362…(3)

A tire 1 that satisfies formula (3) can have a smaller outer diameter. This can further improve fuel efficiency, lower the floor of the vehicle on which it is mounted, and ensure a large space inside the vehicle.

Furthermore, in the tire 1 of the present embodiment, when the total width SW is 150 mm or less, it is preferable that the relationship between the tire outer diameter OD and the total width SW satisfies the following formula (4).
OD≦-0.0060×SW ² +5.9×SW-183…(4)

When the total width SW is 150 mm or less, the outer diameter grows larger during inflation, and the contact length becomes longer, resulting in increased rolling resistance. By making the diameter smaller, rolling resistance decreases and rolling resistance performance improves.

In addition, in the above formula (2), it is more preferable that the constant α is 0.448. This allows the load capacity to be increased and the fuel efficiency of the vehicle equipped with the tire 1 to be improved. It is more preferable that the constant α is 0.672, and even more preferable that it is 0.896.

It is preferable that the tire outer diameter OD is 480 mm or more. If the tire outer diameter OD is too small, the load capacity described below may be insufficient. By making the tire outer diameter OD larger than 480 mm, a large space can be secured inside the vehicle and a high load capacity can be achieved.

Furthermore, it is preferable that the relationship between the tire outer diameter OD and the total width SW satisfies the following formula (5): When the tire outer diameter OD and the total width SW have such a relationship, fuel efficiency performance can be improved.
OD≧-0.0017×SW ² +0.9×SW+350…(5)

(Maximum load capacity)
It is preferable that the maximum load capacity W [kgf] of the tire 1 satisfies the following formula (6).
W≧β×10 ⁻⁴ ×Sd ^1.39 ×(D−12.7+Sd) …(6)

In formula (6), the constant β is 7.1, the value Sd = 0.93 x SW - 0.637 x d [mm], the value d = (0.9 - aspect ratio) x SW - 6.35 [mm], and the value D = inner diameter x 25.4 [mm]. Note that the maximum load capacity W [kgf] is the load index defined by JATMA.

By increasing the total strength T of the carcass layer 6, the maximum load capacity W can be set in a high range as shown in the above formula (5). The constant β is 9.1, more preferably 10.1, and even more preferably 12.8. By setting the constant β in this way, the effect of reducing transportation costs is further increased.

Here, the maximum load capacity W when an internal pressure of 250 kPa is applied to the tire 1 may be a value that exceeds the load capacity defined by the nominal, aspect ratio, and inner diameter of automobile tire standards (e.g., JATMA). Since the total strength T of the carcass layer 6 is large, the tire 1 can be used in a high load capacity range.

It is also preferable that the value of the maximum load capacity W when the tire 1 is subjected to an internal pressure of 250 kPa is in the range of 102% to 400% of the load capacity defined by the nominal, aspect ratio, and inner diameter of the standard for automobile tires (e.g., JATMA). Since the total strength T of the carcass layer 6 is large, the load capacity can be used at a high value. If the value of the maximum load capacity W is smaller than the above range, the effect of reducing transportation costs is small, which is not preferable. If the value of the maximum load capacity W is larger than the above range, the deformation of the tire 1 is significantly large, which is not preferable, as the effect of reducing transportation costs is small. It is more preferable that the value of the maximum load capacity W when the tire 1 is subjected to an internal pressure of 250 kPa is in the range of 114% to 330% of the load capacity defined by the nominal, aspect ratio, and inner diameter of the standard for automobile tires (e.g., JATMA).

(Maximum operating pressure)
It is preferable that the maximum usable air pressure of the tire 1 is greater than the stipulated value of 180 [kPa] in the standard for automobile tires (for example, JATMA) and is equal to or less than 1200 [kPa]. Since the total strength T of the carcass layer 6 is increased, the air pressure applied to the tire 1 can be set in a high range. By increasing the air pressure, the load capacity can be increased, and the effect of reducing transportation costs can be further increased. If the air pressure is set above the range, a risk arises in the internal pressure filling operation, which is not preferable. It is more preferable that the maximum usable air pressure of the tire 1 is equal to or less than 1000 [kPa].

(Maximum speed)
The maximum speed at which the tire 1 is used is preferably 120 km/h or less. The maximum speed at which the tire 1 is used is preferably 100 km/h or less, more preferably 80 km/h or less, and even more preferably 60 km/h or less. The tire 1 can have a larger load capacity when used at low speeds.

(Tire manufacturing method)
Fig. 3 is a flowchart showing a method for manufacturing a tire according to this embodiment. Fig. 3 shows a method for manufacturing the tire 1 shown in Figs. 1 and 2. In the flowchart shown in Fig. 3, first, a molding die is designed (step ST11) so that the relationship between the tire outer diameter OD and the total width SW satisfies the formula (1). Designing the molding die is the first step in the method for manufacturing the tire 1. The designed molding die is manufactured and set in a vulcanizer (not shown).

Next, the carcass to be used for the tire to be molded using the molding die designed in step ST11 is determined (step ST12). Determining the carcass is the second step in the manufacturing method of tire 1. At this time, the carcass is determined so that the total strength T of the carcass layer 6 satisfies formula (2). The material of the carcass used for the carcass layer 6 is a material suitable for the small tire outer diameter OD and total width SW. For example, a steel carcass is used.

Next, the primary green tire is molded (step ST13). Molding the primary green tire is the third step in the manufacturing method of tire 1. When molding the primary green tire, materials for forming each part of the bead member, carcass layer 6, sidewall portion 4, and inner liner 9 are set on a molding drum that can expand and contract in the axial direction. The bead member includes a pair of bead cores 11, a pair of bead fillers 12, and rim cushion rubber. Then, the left and right carcass layers are rolled up to mold a cylindrical primary green tire (step ST13). In other words, the primary green tire does not include the belt layer 7, and is the part that is radially inward of the belt layer 7.

Next, the belt/tread assembly is molded (step ST14). Molding the belt/tread assembly is the fourth step in the manufacturing method of the tire 1. The belt/tread assembly includes the belt layer 7, material corresponding to the belt reinforcing layer 8, and tread rubber corresponding to the tread portion 2. In other words, the belt/tread assembly includes the belt layer 7 and is the portion radially outward from the belt layer 7 in the tire.

Then, shaping is performed (step ST15). Shaping is the fifth step in the manufacturing method of tire 1. Shaping is a process in which the primary green tire obtained in step ST13 and the belt/tread assembly obtained in step ST14 are bonded together to form a secondary green tire.

Figure 4 is a diagram showing an example of the shaping process. In the shaping process of step ST15, a bladder 26 for crimping is used when bonding the primary green tire and the belt-tread assembly. In the shaping process, the primary green tire X and the belt-tread assembly Y are crimped to form a green tire Z having a toroidal shape. More specifically, as shown in FIG. 4A, the primary green tire X is held on the left and right beadlock drums 25, 25, and the belt-tread assembly Y is held from the circumferential outside by a transfer (not shown). Then, as shown in FIG. 4B, while the interval between the left and right beadlock drums 25, 25 is narrowed, the primary green tire X is expanded in diameter by the bladder 26 for crimping and pressed against the belt-tread assembly Y. At this time, the internal pressure of the bladder 26 is set higher to apply pressure, and the spacing between the beads is narrowed to give the tire a vertically elongated shape, thereby achieving both a smaller diameter and improved load capacity. In this way, the primary green tire X and the belt/tread assembly Y are pressed together to form the secondary green tire Z.

Then, in step ST11, the secondary green tire Z is placed in a molding die set in a vulcanizer and vulcanized (step ST16). Vulcanization is the sixth step in the manufacturing method of tire 1. During vulcanization, a bladder for vulcanization (not shown) separate from the bladder 26 for pressing is used.

(vehicle)
Here, a vehicle on which the tire 1 is mounted will be described. Figs. 5 to 12 are diagrams showing examples of the arrangement of the tires 1 on a vehicle. The vehicle on which the tire 1 is mounted preferably includes five or more tires 1. The vehicle on which the tire 1 is mounted may have, for example, three axles and include five tires 1. The vehicle on which the tire 1 is mounted may also have, for example, three axles and include six tires 1. In addition, since the tire 1 has a small outer diameter, increasing the number of wheels has little effect on the space inside the vehicle. By employing the tire 1, the load capacity can be improved, which greatly reduces transportation costs.

The number of wheels of the vehicle on which the tire 1 is mounted, i.e., the number of tires 1, is preferably in the range of 6 to 12. Fewer than 5 wheels is not preferred because the load capacity is insufficient. More than 12 wheels is not preferred because the space inside the vehicle becomes narrow.

Fig. 5 is a side view of a vehicle 100A on which a tire 1 is mounted. Fig. 6 is a tire arrangement diagram of the vehicle 100A shown in Fig. 5. As shown in Figs. 5 and 6, the vehicle 100A has four axles J1 to J4 and eight tires ₁₁ to _18. Tires ₁₁ and ₁₂ are connected to the axle J1. Tires ₁₃ and ₁₄ are connected to the axle J2. Tires ₁₅ and ₁₆ are connected to the axle J3. Tires ₁₇ and ₁₈ are connected to the axle J4.

The vehicle 100A also has a power unit 101. The power unit 101 provides power to at least one of the axles J1 to J4. The power unit 101 is, for example, an internal combustion engine or a motor that operates using electrical energy. In other words, it is preferable that the vehicle 100A on which the tire 1 is mounted has at least a motor as one of its power sources. When a motor is the power source, reducing the rotational inertia has a significant effect of reducing fuel consumption (power consumption), and also leads to an increase in the life of the motor itself. When the motor output of the tire 1 is reduced, for example with an in-wheel motor, the effect of reducing fuel consumption (power consumption) is very large.

Fig. 7 is a side view of a vehicle 100B on which the tire 1 is mounted. Fig. 8 is a tire arrangement diagram of the vehicle 100B shown in Fig. 7. As shown in Fig. 7 and Fig. 8, the vehicle 100B has three axles J1 to J3 and six tires _1-1 to _1-6 . Tires _1-1 and _1-2 are connected to the axle J1. Tires _1-3 and _1-4 are connected to the axle J2. Tires _1-5 and _1-6 are connected to the axle J3.

The vehicle 100B also has a power unit 101. The power unit 101 provides power to at least one of the axles J1 to J3. The power unit 101 is, for example, an internal combustion engine or a motor that operates using electrical energy.

Fig. 9 is a side view of a vehicle 100C on which a tire 1 is mounted. Fig. 10 is a tire arrangement diagram of the vehicle 100C shown in Fig. 9. As shown in Figs. 9 and 10, the vehicle 100C has three axles J1, J2 and JC and five tires _1-1 to _1-5 . Tires _1-1 and _1-2 are connected to the axle J1. Tires _1-3 and _1-4 are connected to the axle J2. Tire _1-5 is connected to the axle JC.

The vehicle 100C also has a power unit 101. The power unit 101 provides power to at least one of the axles J1, J2, and JC. The power unit 101 is, for example, an internal combustion engine or a motor that operates using electrical energy.

Fig. 11 is a side view of a vehicle 100D on which a tire 1 is mounted. Fig. 12 is a tire arrangement diagram of the vehicle 100D shown in Fig. 11. As shown in Figs. 11 and 12, the vehicle 100D has six axles J1 to J6 and twelve tires _1-1 to _1-12 . Tires _1-1 and _1-2 are connected to the axle J1. Tires _1-3 and _1-4 are connected to the axle J2. Tires _1-5 and _1-6 are connected to the axle J3. Tires _1-7 and _1-8 are connected to the axle J4. Tires _1-9 and _1-10 are connected to the axle J5. Tires _1-11 and _1-12 are connected to the axle J6.

The vehicle 100D also has a power unit 101. The power unit 101 provides power to at least one of the axles J1 to J6. The power unit 101 is, for example, an internal combustion engine or a motor that operates using electrical energy.

The tires 1 on the vehicle may be arranged in a manner other than that shown in Figures 5 to 12. For example, a double tire arrangement in which four tires are mounted on one axle may be used.

Each of the vehicles 100A to 100D described with reference to Figures 5 to 12 may be an autonomous vehicle. An autonomous vehicle is a vehicle that can run autonomously without human driving operations.

(Example)
Tables 1 and 2 show the results of performance tests of tire 1 according to the present invention. In these performance tests, different tires were evaluated for fuel economy and maximum load support capacity. In these performance tests, tires of sizes such as 145/80R12 were mounted on rims of 12×4.00B. The above-mentioned "145/80R12" is an example, and evaluation was performed on tires with different outer diameters and total widths as shown in Tables 1 and 2. In addition, the air pressures shown in Tables 1 and 2 were applied.

For fuel economy, an evaluation vehicle fitted with test tires was driven 50 times around a 2-km test course at 100 km/h, and the fuel consumption (km/l) during the test run was measured. Fuel economy was expressed as an index calculated by taking the reciprocal of the measured fuel consumption and setting the conventional example described below as the standard (100). The higher the figure, the lower the fuel consumption and the better the fuel economy.

Maximum load-bearing capacity is calculated by multiplying the load capacity by the number of wheels fitted. It is shown as an index with the conventional example described below as the standard (100). The higher the index, the higher the load capacity. The total strength of the carcass layer is calculated by multiplying the strength of one cord by the number of cords. The strength of one cord was determined by removing the carcass cord from the sidewall and measuring the breaking strength of the carcass cord in accordance with JIS L1017, and then calculating the strength of the carcass layer from the breaking strength. The breaking strength was calculated as the average value of a total of 30 carcass cords, 10 cords taken from each of three tires.

In Tables 1 and 2, "O" indicates that the condition is met, and "X" indicates that the condition is not met.

In Table 1, the conventional tire has an outer diameter OD of 559 mm, a total width SW of 139 mm, a length SWD of 421 mm, a value Sd of 124 mm, an aspect ratio of 80, an inner diameter of 12 inches, a value D of 305 mm, and a value d of 8 mm.

As shown in Tables 1 and 2, the tires of Examples 1 to 12 showed better results in terms of fuel economy performance than the conventional tires. Also, as shown in Tables 1 and 2, the tires of Examples 1 to 12 showed better results in terms of maximum load support capacity than the conventional tires.

Reference Signs List 1, _{1 1} to 1 ₁₂ Tire 2 Tread portion 3 Shoulder portion 4 Sidewall portion 5 Bead portion 6 Carcass layer 7 Belt layer 8 Belt reinforcing layer 9 Inner liner 10 Ground contact surface 11 Bead core 12 Bead filler 14 Bead heel 16 Circumferential groove 18 Tread rubber 20 Tire side portion 100A to 100D Vehicle 101 Power portion AX Rotating axis CL Tire equatorial plane J1 to J6, JC Axle OD Tire outer diameter SW Total width SWD Distance T Total strength X Primary green tire Y Belt/tread assembly Z Secondary green tire Z

Claims (15)

When the tire is mounted on a specified rim and has a specified internal pressure, and is in an unloaded state, the relationship between the tire outer diameter (OD) and the total width (SW) satisfies the following formula (1):
A tire in which the total strength T [kg] of the carcass satisfies the following formula (2), where SWD is twice the radial length from the tire rotation axis to the measurement position of the total width SW .
OD≦-0.0019×SW ² +1.4×SW+400…(1)
T≧α×[(OD/2) ² - (SWD/2) ² ] …(2)
However, in equation (2), the constant α is 0.224. The tire according to claim 1 , wherein the relationship between the tire outer diameter OD and the total width SW satisfies the following formula (3):
OD≦-0.0024×SW ² +1.6×SW+362…(3) 2. The tire according to claim 1 , wherein in said formula (2), the constant α is 0.448. 4. The tire according to claim 1, wherein when the total width SW is 150 mm or less, a relationship between the tire outer diameter OD and the total width SW satisfies the following formula (4):
OD≦-0.0060×SW ² +5.9×SW-183…(4) When the tire is mounted on a specified rim and has a specified internal pressure, and is in an unloaded state, the relationship between the tire outer diameter (OD) and the total width (SW) satisfies the following formula (1):
A tire in which, when the total width SW is 150 mm or less, a relationship between the tire outer diameter OD and the total width SW satisfies the following formula (4):
OD≦-0.0019×SW ² +1.4×SW+400…(1)
OD≦-0.0060×SW ² +5.9×SW-183…(4) The tire according to claim 1 , wherein a relationship between the tire outer diameter OD and the total width SW satisfies the following formula (5):
OD≧-0.0017×SW ² +0.9×SW+350…(5) The tire according to any one of claims 1 to 6, wherein a maximum load capacity W [kgf] satisfies the following formula (6):
W≧β×10 ⁻⁴ ×Sd ^1.39 ×(D−12.7+Sd) …(6)
However, in the formula (6),
The constant β is 7.1,
The value Sd=0.93×SW−0.637×d,
Value d = (0.9 - aspect ratio) x SW - 6.35,
The value D = inner diameter x 25.4. 7. The tire according to claim 1, wherein the maximum load capacity when an internal pressure of 180 kPa is applied is set to a value exceeding the load capacity defined by the nominal size, aspect ratio and inner diameter of the JATMA standard for automobile tires. A tire according to any one of claims 1 to 8, in which the maximum load capacity when an internal pressure of 180 kPa is applied is 102% or more and 400% or less of the load capacity defined by the nominal, aspect ratio and inner diameter of the JATMA standard for automobile tires. A tire according to any one of claims 1 to 9, in which the maximum allowable air pressure is greater than the stipulated value of 180 kPa in the JATMA standard for automobile tires and is equal to or less than 1200 kPa. A tire according to any one of claims 1 to 10, in which the maximum speed used is 120 km/h or less. A tire according to any one of claims 1 to 11, wherein the tire outer diameter OD is 480 mm or more. When the tire is mounted on a specified rim and has a specified internal pressure, and is in an unloaded state, the relationship between the tire outer diameter (OD) and the total width (SW) satisfies the following formula (1), and
A method for manufacturing a tire, in which a total strength T [kg] of a carcass satisfies the following formula (2), when a length SWD is twice the length in the tire radial direction from the tire rotation axis to a measurement position of the total width SW,
A first step of designing a molding die so that a relationship between a tire outer diameter (OD) and a total width (SW) satisfies the following formula (1);
A second step of determining a carcass to be used for a tire to be molded using the molding die designed in the first step so as to satisfy the total strength T [kg] of the following formula (2);
a third step of forming a primary green tire;
a fourth step of forming the belt-tread assembly;
a fifth step of laminating the primary green tire obtained in the third step with the belt-tread assembly obtained in the fourth step to form a secondary green tire;
A sixth step of vulcanizing and molding the secondary green tire obtained by the fifth step;
A method for manufacturing a tire comprising the steps of:
OD≦-0.0019×SW ² +1.4×SW+400…(1)
T≧α×[(OD/2) ² - (SWD/2) ² ] …(2)
However, in equation (2), the constant α is 0.224. A vehicle including a tire according to any one of claims 1 to 12, and having at least one motor as a power source. A vehicle including five or more tires according to any one of claims 1 to 12.

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