JP2001199205A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance camber thrust, and improve wandering performance. SOLUTION: The land ratio S/S0 in a central area Zc in a tread part 2 is set not more than 0.8, and a pattern shape factor K in the central area Zc determined by an expression (1) (x: A distance turning outside in the tire axis direction with a tire equatorial point as the origin. y: The sum total (y=f(x)) of the circumferential directional length of a land part included in tire one round in a position (x). S: The land part area in a tread surface in the central area. w: A distance up to a contact point J from the tire equatorial point. L: The tire circumferential length.) is set not less than 0.8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a pneumatic tire capable of improving wandering performance.

[0002]

2. Description of the Related Art A pneumatic tire, particularly a pneumatic tire for a light truck, has a higher tread rigidity than a tire for a passenger car. Handle is easy to remove. Therefore, there is a strong demand for small truck tires to have improved stability performance during such rutted traveling, that is, improved wandering performance.

[0003] Conventionally, in order to improve the wandering performance, techniques such as reducing the radius of curvature in the meridional section of the tread surface and reducing the tread width have been used. For example, there is a problem that the running performance of the tire is deteriorated.

In recent years, as shown in FIG. 9, the camber thrust CT, which is a lateral force generated when a tire is rolled by giving it a camber angle θ, is increased to the plus side, and the camber thrust CT is moved in a direction of riding on a rut. It has been proposed to improve wandering performance by acting. In general, the camber thrust CT is expressed as plus (+) when it works on the inclined side and as minus (-) when it works on the side opposite to the slope.

Here, it is assumed that the camber thrust CT is generated by the following mechanism. That is, as shown in FIG. 8, when the rolling tire is contacted with the camber angle θ, the tread point Pt on the tread surface before the contact is changed to the tread point on the road surface due to the deformation of the tire after the contact. Move to Pt '. The belt point P on the outer surface of the belt layer B corresponding to the tread point Pt
b moves to the belt point Pb 'after the touchdown.

At this time, since the belt layer B is a non-extensible body made of a belt cord, the belt point is changed from Pb to Pb ′.
The tread point moves from Pt to Pt 'substantially in parallel with the tire equatorial plane because the tread rubber is stretchable. Accordingly, a lateral displacement D 'occurs between the points Pt' and Pb ', and a lateral force F proportional to the displacement D' is generated.

In the lateral force F, the tread point Pt 'is equal to the belt point Pb' in the outer region of the tread on the inclined side (the left side in the figure).
In the tread central area on the opposite side (right side in the figure), the tread point Pt 'is displaced more toward the opposite side than the belt point Pb', so that it is negative. appear. Then, a camber thrust CT is generated as a resultant force of each lateral force F over the entire contact surface A.

Therefore, in order to increase the camber thrust CT to the positive side (hereinafter, there may be a case where the camber thrust CT is improved), the shape of the ground contact surface is improved,
Either the proportion of the central area surface portion Ac where the lateral force F on the minus side of the ground contact surface A is occupied is reduced, or the value of the displacement D 'itself is reduced in the tread central area, or the lateral force caused by this displacement D' It is necessary to reduce the value of the force F in the central region of the tread.

When the camber angle θ is 0 °, the point P
A lateral force is generated due to a displacement D (shown in FIG. 8) between t and Pb. However, since the displacement, the lateral force, and the shape of the ground contact surface are substantially symmetrical about the tire equator, the camber thrust itself is It becomes 0 (zero).

Therefore, the present invention is based on the fact that the tread pattern in the central region is indexed using a new pattern shape factor K, and the lateral rigidity of the tread pattern in the central region is reduced. The same can be said, the lateral force F resulting from this displacement D 'can be further reduced in the central region, the camber thrust is relatively improved, and the wandering performance is improved without changing the tread radius or tread width. The aim is to provide pneumatic tires.

[0011]

In order to achieve the above object, according to the present invention, there is provided a carcass extending from a tread portion to a sidewall portion to a bead core of a bead portion,
A pneumatic tire comprising a belt layer disposed inside the tread portion and radially outside the carcass, and having a land portion where the tread portion is divided by a groove portion,
In the cross section of the tire meridian, there is a contact point J in the tread plane where a line segment in which the tread edge side inclines inward in the radial direction at 6 ° to the tire equator line is in contact with the tread surface, and between the contact point J and the tire equatorial point. The area S0 of the tread surface in the central area of
The land ratio S / S0 with respect to the land area S on the tread surface in the central region is 0.8 or less, and the pattern shape factor K obtained by the following formula (1) in the central region is 0.8 or more. It is characterized by.

(Equation 1) Here, x: the distance from the tire equator point to the origin in the axial direction of the tire, y: the sum of the circumferential lengths of the land portions included in one round of the tire at the position x, (y = f (x)) S : Land area on the tread surface in the central region, w: Distance from tire equatorial point to contact point J L: Tire circumference

As a result, the lateral rigidity of the tread pattern in the central region can be kept low, and even when the same displacement D 'occurs during camber, the lateral force F generated from this displacement D' in the central region is small. It becomes smaller and the camber thrust can be relatively improved.

[0013] In the invention of claim 2, the central area is
It is characterized by having a groove extending substantially continuously in the tire circumferential direction, whereby it is possible to set the lateral rigidity low while maintaining the circumferential rigidity high in the central region.

In the invention according to claim 3, the contact point J is
The contact point J is located on a tread surface between a 1/3 point separating a half of the tread half width WT / 2 from the tire equatorial point and a 2/3 point separating a 2/3 time. It is characterized in that a circumferential groove extending in the tire circumferential direction is formed. Thereby, the displacement D 'itself can be largely changed in an outer region that is outside the circumferential groove in the tire axial direction, and the camber thrust can be further improved.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a pneumatic tire 1 according to the present invention, which is formed as a light truck tire, is mounted on a regular rim, and is filled with an internal pressure of 50 kPa.
The meridional section in a 0 kPa internal pressure state is shown.

The "regular rim" is a rim defined for each tire in a standard system including the standard on which the tire is based. For example, a standard rim for JATMA and a "Design Rim" for TRA Or ETRTO
Then it means "Measuring Rim". Also 50 kPa
The tire in the internal pressure state is a state where the internal distortion is small and the deformation is the smallest, and approximates the tire shape in a state where the tire is vulcanized and molded in a mold.

In the figure, a pneumatic tire 1 has a tread portion 2, a pair of sidewall portions 3 extending inward in the tire radial direction from both ends thereof, and a bead portion 4 located at an inner end of each sidewall portion 3. And A carcass 6 is bridged between the bead portions 4, and a tough belt layer 7 is wound inside the tread portion 2 and outside the carcass 6.

The carcass 6 is formed of one or more carcass cords arranged at an angle of 75 ° to 90 ° with respect to the tire circumferential direction, and in this example, two carcass plies 6A and 6B. ing. As the carcass cord, an organic fiber cord such as nylon, polyester, rayon, or aromatic polyamide is preferably employed, but a steel cord may be employed according to the size and category of the tire or required characteristics.

The carcass 6 is locked on both sides of the main body 6a extending from the tread portion 2 to the bead core 5 of the bead portion 4 through the sidewall portion 3 by being turned from the inside to the outside around the bead core 5. It has a folded portion 6b. A bead apex rubber 8 extending from the bead core 5 to the outside in the tire radial direction in a tapered shape is disposed between the main body 6a and the folded portion 6b.

In this embodiment, the folded portion 6b has a so-called high turn-up structure in which the height of the outer end in the radial direction from the bead base line BL is larger than the height of the outer end in the radial direction of the bead apex rubber 8. None, the bead portion 4 is reinforced in cooperation with the bead apex rubber 8 and the tire lateral rigidity is increased. When the carcass 6 is formed of a plurality of plies as in this example, it is preferable that at least one carcass ply has a high turn-up structure.

The belt layer 7 includes two or more belt plies 7A and 7 in which high elastic belt cords are arranged at an angle of 10 ° to 35 ° with respect to the tire circumferential direction.
The case where it is formed from B will be exemplified. Each belt ply 7
A and 7B are arranged in different directions so that the belt cords cross each other between the plies, thereby increasing the belt rigidity by the triangle structure of the cords, and reinforcing substantially the entire width of the tread portion 2 with a tag effect. I do. As the belt cord, a steel cord or a highly elastic fiber cord having a strength close to that of steel, such as an aromatic polyamide fiber or an aromatic polyester fiber, is preferably used.

In this embodiment, the inner belt ply 7A is formed to be slightly wider than the outer belt ply 7B, so that stress concentration acting on the outer end of the belt is reduced.

Next, as shown in FIG. 4, the tread portion 2 has land portions 21 divided by grooves 20, for example, a rib type, a rib lug type, a rib block type, or a block type. The tread pattern is formed. The groove portion 20 includes a circumferential groove 22 extending in the tire circumferential direction and / or a transverse groove 23 intersecting with the circumferential groove 22. Further, the groove portion 20 may include a thin groove-shaped siping 24 having a groove width of 1.5 mm or less. .

FIG. 4 illustrates a rib-type tread pattern in which inner and outer circumferential grooves 22A and 22B are arranged on both sides of the tire equator C, respectively. , 22A, and circumferential grooves 22A, 2A,
One or more (three in this example) circumferential sipes 24Ac and a horizontal siping 24Bc in a direction intersecting with the circumferential sipes 24Ac are provided between 2B. An outer circumferential groove 22B;
Between the tread edge TE, for example, is divided by one circumferential siping 24Ao, and between the siping 24Ao and the outer circumferential groove 22B, and / or between the siping 24Ao and the tread edge TE. The horizontal groove 23 and / or the horizontal siping 24Bo are arranged with a smaller pitch interval than the horizontal siping 24Bc.

In the present application, as shown in FIG. 1, when the tread surface 2S is divided into a central region Zc on the tire equator C side and an outer region Zo outside the tread surface 2S in the meridional section of the tire, The land ratio S / S0 is set to 0.8 or less, and the pattern shape coefficient K obtained by the following equation (1) is set to 0.8 or more in the central area Zc.

(Equation 1) In the equation (1), x: distance toward the outside in the tire axial direction with the tire equator point C1 as the origin O, y: sum of circumferential lengths of the land portions 21 included in one round of the tire at the position x, S: center Land area on tread surface 2S in area Zc, w: distance from tire equatorial point C1 to contact point J L: tire circumference

Here, the "center area Zc" refers to the tread edge T at an angle α of 6 ° with respect to the tire equator line CN.
Assuming that a point (contact point) at which a line segment N in which the E side is inclined inward in the radial direction contacts the tread surface 2S is J, it means an area between the contact point J and the tire equator point C1. The outer region Zo means a region between the contact point J and the tread edge TE. The tire equator line CN means a tire axial line passing through a point (tire equatorial point) C1 on the tread surface 2S on the tire equator C.

The "land ratio S / S0" is defined as the area S0 of the tread surface 2S in the central area Zc and the area S0 in the central area Zc.
The ratio S / S to the land area S on the tread surface 2S at c.
Means 0.

Next, the pattern shape coefficient K will be described. FIG. 5A is a drawing in which a tread pattern (for one round of the tire) in the central region Zc in FIG. 4 is modeled and developed in the circumferential direction. In this development, the distance from the tire equatorial point C1 to the origin O with respect to the tire equatorial point C1 is x, and the sum Σyi of the circumferential length yi of the land portion 21 included in one circumference of the tire at each position x is y. At this time, as shown in FIG. 5B, y can be expressed as a function f (x) of x.

In the equation, S / w is a value obtained by dividing the land area S in the central area Zc by the width w of the central area Zc, that is, the circumference when the land area S is equalized over the entire width w. Mean average length in direction.

Therefore, the value of the numerator in the equation (1) is calculated as shown in FIG.
It corresponds to the area of the shaded portion in (B), and indicates the degree of displacement of y = f (x) with respect to y = S / w. Here, when the tread pattern in the central region Zc is a lug pattern (shown in FIG. 6A) uniformly formed only by the lateral groove 23, the value of the numerator of the expression (1) is 0 and the minimum value is obtained. Make On the other hand, as shown in FIG. 6B, when the tread pattern in the central area Zc is a rib pattern formed only by the circumferential groove 22, the formula (1) is used.
The value of the numerator is the same as the denominator and forms the maximum.

That is, the pattern shape coefficient K is an index indicating how close the tread pattern in the central area Zc is to the rib pattern. It shows a rib pattern, and when K = 0, it shows a uniform lug pattern in the tire axial direction.

As is well known, at the same land ratio S / S0, the rib pattern is a pattern having a large circumferential rigidity and a small lateral rigidity.
A pattern with low circumferential stiffness and large lateral stiffness
The pattern shape coefficient K also functions as an index indicating the ratio of the lateral rigidity to the pattern rigidity.

By the way, as described in FIG. 8 showing a contact state in which a camber angle is given, the point P
When the displacement D 'between t' and Pb 'is the same, the lateral force F generated from the displacement D' can be reduced as the lateral rigidity of the pattern is smaller.

Therefore, when the pattern shape coefficient K in the central region Zc is set to 0.8 or more as in the present application, the central region Zc
, The ratio of the lateral rigidity to the pattern rigidity becomes very small. As a result, the camber thrust can be relatively improved, for example, the lateral rigidity is reduced and the negative lateral force F is reduced.

At this time, the land ratio S /
S0 needs to be 0.8 or less, and if it exceeds 0.8, the pattern rigidity itself increases, so that the ratio of the lateral rigidity decreases, but the value is high, and the effect of improving the camber thrust is sufficient. Will not be displayed. But land ratio S
If / S0 is too low, the rigidity in the circumferential direction tends to be insufficient, which may impair the rolling performance and the steering stability.
Preferably, the range is 0.6 to 0.8.

In this embodiment, the outer circumferential groove 22B is
In this case, two circumferential grooves 22A and 22B and a plurality of circumferential sipes 24c are arranged in the central area Zc. Such a circumferential groove, particularly the siping 24c, can set the lateral rigidity only lower while maintaining the circumferential rigidity high in the central region Zc, so that the camber thrust can be further improved.

On the other hand, in the outer zone Zo, it is preferable to increase the lateral rigidity and increase the positive lateral force F.
For this reason, in the outer region Zo, the land ratio S / S0 is 0.
7 to 1.0 is preferable, and a lateral groove 2 is formed in the outer region Zo.
Three and / or lateral sipings 24 may be formed.
In such a case, the pitch interval between the lateral grooves 23 and / or the horizontal sipes 24o in the outer zone Zo is smaller than the pitch interval in the central zone Zc.

Next, in order to improve the camber thrust, it is also preferable to reduce the value of the displacement D 'itself in the central region Zc, as described in FIG. It can be seen that the smaller the thickness, the lower the tendency.

Accordingly, in this embodiment, as shown in FIGS. 1 and 2, the thickness ratio of the average thickness Tc of the tread rubber 2G in the central region Zc to the average thickness To of the tread rubber 2G in the outer region Zo. Tc / To has been reduced to 1.0 or less.

Here, the average thickness Tc is the average of the thickness T between the tread surface 2S and the radially outer surface 7S of the belt layer 7 in the central region Zc, and specifically, the center Tc. The average value (Tmax + Tmin) / 2 of the maximum value Tmax and the minimum value Tmin in the range Zc. Therefore, if the belt layer 7
In the case where a so-called band layer 9 formed by spirally winding an organic fiber cord such as nylon, for example, in the tire circumferential direction is provided on the outside, the thickness T is a value including the thickness of the band layer 9. Similarly, the average thickness To is the thickness T between the tread surface 2S and the radial outer surface 7S of the belt layer 7.
Of the maximum value Tmax and the minimum value Tmin in the outer region Zo (T
max + Tmin) / 2. When the belt layer 7 is interrupted inside the tread edge TE in the tire axial direction, the thickness T is measured using a virtual extension line of the outer surface 7S.

As described above, the thickness ratio Tc / To is set to 1.
By reducing it to 0 or less, the displacement D 'itself in the central region Zc can be relatively reduced, and the camber thrust can be further improved.

At this time, if the tread radius Rt, which is the radius of curvature of the tread surface 2S, is increased, the wandering performance is reduced, and the effect of improving the camber thrust according to the present invention is not effectively exhibited. . Accordingly, while maintaining the tread radius Rt to be substantially the same as that of the conventional tire, that is, 3.8 to 5.1 times the tread half width WT / 2 that is the distance from the tire equator C to the tread edge TE, the belt layer outer surface 7S is maintained. It is necessary to reduce the belt radius Rb which is the radius of curvature of the conventional tire, and set the thickness ratio Tc / To to 1.0 or less.

In order to improve the camber thrust, the thickness ratio Tc / To is preferably less than 1.0, and more preferably 0.9 or less. However, if it is less than 0.75, the cornering force decreases and the steering becomes difficult. It is not preferable because stability is lowered.

Here, the reason why the angle α of the line segment N for defining the contact point J, which is the boundary between the central area Zc and the outer area Zo, is 6 ° is that a tire for a passenger car or a tire for a light truck is used. This is because the camber angle θ at which the rut poses a problem is usually about 6 °. Accordingly, the displacement D ′ is determined in the central area Zc determined by the angle α of 6 °.
, Wandering performance is improved in accordance with actual vehicle driving.

However, even when the displacement D 'in the central region Zc is reduced, the effect of improving the camber thrust is reduced if the area of the central region Zc is large. Therefore, in order to secure the minimum area of the central zone Zc, as shown in FIG. 2, the contact point J is connected to the tire equator point C1 by a 1/3 point separated by 1/3 of the tread half width WT / 2. It is preferable to be located between J1 and a 2/3 point J2 separated by 2/3 times.

At this time, it is preferable to form a circumferential groove 22B at the position of the contact point J on the tread surface 2S as in this embodiment. The circumferential groove 22B reduces the tread rigidity and separates the blocks in the central area and the outer area, so that the displacement D 'in the outer area Zo can be relatively increased. In such a case, as shown in FIG. 3, the angle β1 with respect to the normal to the tread surface of the groove wall surface W1 on the central region Zc side of the circumferential groove 22B is set to 0 to 10 degrees, and the outer region Zo is formed.
Β2 with respect to the normal to the tread surface of the side groove wall surface W2
It is better to make it smaller. The angle β2 is 20 to 3
A range of 0 degrees is good.

Next, in the tread rubber 2G, in order to prevent the thickness T from suddenly changing between the central region Zc and the outer region Zo, and to prevent the grounding property and uneven wear resistance from being deteriorated, It is preferable to have a gradually increasing region V in which the thickness gradually increases outward in the tire axial direction. This gradually increasing region V is, as in this example,
It is preferable to form at least the central area Zc.

In this embodiment, the tread rubber 2G is
A case where the base rubber layer Gb on the side of the belt layer 7 and the cap rubber layer Gk on the tread surface 2S side having a rubber hardness Hsk smaller than the rubber hardness Hsb of the base rubber layer Gb has a two-layer structure. For example. This base rubber layer G
b, the rubber hardness Hsb is 64 to 70 degrees, and the cap rubber layer G
It is preferable that the rubber hardness Hsk of k is 62 to 68 degrees, and the difference in rubber hardness (Hsb-Hsk) is 2 degrees or more. Thereby, while excellent grounding properties and grip properties are ensured by the soft cap rubber layer Gk, excellent steering stability and rolling performance can be exhibited by the hard base rubber layer Gb.

At this time, the ratio M of the rubber thickness Mb of the base rubber layer Gb to the rubber thickness Mk of the cap rubber layer Gk is obtained.
In this example, k / Mb is an average value (M
k / Mb) c is 70/30 or more, and the average value (Mk / Mb) o in the outer region Zo is less than 70/30.

Thus, the rigidity of the tread rubber 2G in the central area Zc is reduced as compared with the outer area Zo. As a result, even if the value of the displacement D 'is the same, the lateral force generated from the central region Zc can be made smaller, and the lateral force generated from the outer region Zo can be made larger, and the camber thrust can be further improved. Becomes possible. Therefore, the average value (Mk / Mb) c is more preferably in the range of 65/35 to 55/45, and the average value (Mk / Mb) o is more preferably in the range of 72/25 to 90/10.

Further, in this embodiment, the tread portion 2 has a thickness in the range of the tread portion 2 centered on the tire equator C and between the carcass 6 and the belt layer 7 in the tire axial direction outward. A buffer layer 11 made of cushion rubber 11G for reducing t1 is provided. This cushion rubber 1
1G is smaller than the rubber hardness Hst of the tread rubber 2G,
When the tread rubber 2G has a two-layer structure as in this example, it is formed of a soft rubber smaller than the base rubber layer Gb, preferably smaller than the cap rubber layer Gk. At this time, the difference between the rubber hardness Hsc of the cushion rubber 11G and the rubber hardness Hst or Hsb or Hsk is preferably 5 degrees or more.

In the present application, the rubber hardness is JIS-K6
253 is defined as a durometer type A hardness.

This buffer layer 11 (cushion rubber 11G)
Reduces the rigidity below the belt layer 7 in the central region Zc. Therefore, the belt layer 7 itself easily moves in the lateral direction, particularly in the central region Zc. As a result, the central zone Z
The displacement D 'at c is relatively reduced, and the camber thrust can be further improved.

For this purpose, it is preferable to ensure that the thickness t1max of the buffer layer 11 at the tire equator is 2.0 mm or more. However, when the thickness t1max is excessively large, the amount of movement of the belt layer 7 is increased and steering stability and rolling performance are reduced. Therefore, the upper limit of the thickness t1max is preferably set to 5.0 mm.

In this example, the average thickness Tc of the tread rubber 2G in the central region Zc is relatively reduced, so that the envelope effect and the riding comfort tend to decrease in the central region Zc. Relaxation of rigidity by the buffer layer 11 can compensate for and improve this. Therefore, it is preferable that the buffer layer 11 has substantially the same width as the gradually increasing region V and is formed to oppose the gradually increasing region V.

Although the preferred embodiment of the present invention has been described in detail, the present invention is not limited to the illustrated embodiment, but can be implemented in various modes such as a tire for a passenger car.

[0057]

EXAMPLE A small truck tire having a tire size of 205 / 70R16 and having the structure shown in FIG. 1 was prototyped based on the specifications shown in Table 1, and the camber thrust CT and uneven wear resistance of each sample tire were tested. did.

(1) Using a camber thrust CT maneuverability tester (flat belt tester), a rim (51/2), internal pressure (600 kPa), load (10.6 k)
Under the condition of N), the camber thrust at a camber angle of 6 ° was measured.

(2) Uneven wear resistance The test tires were mounted on all the wheels of a small truck, and the tires were run on a general road and a highway for a total of 3000 km.
Was measured for the difference in the amount of wear between the inside and outside in the tire axial direction.

[0060]

[Table 1]

[0061]

Since the present invention is configured as described above,
The lateral stiffness of the tread pattern in the central area can be reduced, and the generation of negative lateral force can be relatively reduced.The camber thrust can be relatively improved, and wander can be achieved without changing the tread radius or tread width. Ring performance can be enhanced.

[Brief description of the drawings]

FIG. 1 is a sectional view of a tire according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view showing the tread portion.

FIG. 3 is a sectional view showing a circumferential groove.

FIG. 4 is a diagram showing an example of a tread pattern suitable for the present application.

FIGS. 5A and 5B are diagrams illustrating a pattern shape coefficient K. FIGS. FIG. 4 is a diagram illustrating a mechanism of generating camber thrust.

FIGS. 6A and 6B are diagrams illustrating a state in which a pattern shape coefficient K is 1 and 0. FIG.

FIGS. 7A to 7D are diagrams illustrating tread patterns used in Table 1. FIG.

FIG. 8 is a diagram illustrating a mechanism of generating camber thrust.

FIG. 9 is a diagram illustrating a conventional technique.

[Explanation of symbols]

 Reference Signs List 2 tread portion 2S tread surface 3 side wall portion 4 bead portion 5 bead core 6 carcass 7 belt layer 20 groove portion 21 land portion 22 circumferential groove CN tire equator line J1 1/3 point J2 2/3 point N line segment TE tread edge Zc Central area

Claims (3)

[Claims] 1. A carcass extending from a tread portion to a bead core of a bead portion through a sidewall portion, and a belt layer disposed inside the tread portion and radially outside the carcass, and the tread portion is provided. A pneumatic tire having a land portion divided by a groove portion, wherein a tread surface contacts a contact J at a tire meridian section and a line segment in which the tread edge side inclines radially inward at 6 ° with respect to the tire equator line. And a tread surface area S0 in a central region between the contact point J and the tire equator point,
The land ratio S / S0 to the land area S on the tread surface in the central region is 0.8 or less, and the pattern shape factor K obtained by the following equation (1) in the central region is 0.8 or more. A pneumatic tire characterized by the following. (Equation 1) Here, x: the distance from the tire equator point to the origin in the axial direction of the tire, y: the sum of the circumferential lengths of the land portions included in one round of the tire at the position x, (y = f (x)) S : Land area on the tread surface in the central region, w: Distance from tire equatorial point to contact point J L: Tire circumference 2. The pneumatic tire according to claim 1, wherein the central region has a groove extending substantially continuously in a tire circumferential direction. 3. The contact point J has a 1/3 point which is separated from the equatorial point of the tire by 1/3 of a half tread half width WT / 2;
The air according to claim 1 or 2, wherein a circumferential groove is formed on the tread surface between two-thirds points separated by three times and extends in the tire circumferential direction through the position of the contact point (J). Containing tires.