JP2003146015A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce rolling resistance and improve hydroplaning performance, ride comfort performance and road noise performance. SOLUTION: A tread part 2 has a grounding swell portion 2A forming a tread grounding surface S whose width is 55 to 70% of an overall tire width SW. A ply width BW of a narrower belt ply 7B out of two belt piles 7A and 7B is larger than the tread grounding width TW, a ratio BW/TW is 1.15 to 1.5, and a difference BW-TW is 10 mm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire capable of reducing rolling resistance and improving hydroplaning performance, riding comfort and road noise performance.

[0002]

2. Description of the Related Art Conventionally, as a method for reducing rolling resistance of a pneumatic tire,
It is known to use a rubber having a small dynamic loss, that is, a low exothermic rubber having a small loss tangent (tan δ) as the tread rubber. However, when such a rubber is used, the rolling resistance is reduced, but the braking performance on the wet road surface (sometimes referred to as wet braking performance) tends to be adversely affected.

By using silica as the rubber reinforcing agent, the deterioration of the wet braking performance can be alleviated, but in such a case, the cost is increased and
In order to ensure the conductivity of the tire, a problem occurs that productivity is impaired, such as a tread rubber having a complicated laminated structure.

Therefore, according to the present invention, the tread portion is provided with a ground contact raised portion so that the tread ground contact width is 55 to 70 of the total tire width SW.
%, And based on the fact that the width of the belt layer is increased within a predetermined range from the tread ground contact width, the rolling resistance can be reduced without using a low heat-generating rubber. It is an object of the present invention to provide a pneumatic tire that can be solved and can also improve the hydroplaning performance, riding comfort, and road noise performance.

[0005]

In order to achieve the above object, the invention according to claim 1 of the present application provides a carcass consisting of a carcass ply extending from a tread portion to a bead core of a bead portion through a sidewall portion and the tread portion. And a belt layer composed of two belt plies that are placed inward and outward in the radial direction on the outside of the carcass, and the tread portion has a tire width of 55 to 70% of the total width SW.
A tread ground contact surface having a width of 1 mm, and a ground contact ridge portion protruding in this region is provided, and the ply width BW of the narrow belt ply of the two belt plies is set to be larger than the tread ground width TW and the ratio BW. / TW 1.15 to 1.
It is characterized in that it is 5 times and the difference BW-TW is 10 mm or more.

Further, in the invention of claim 2, the ply width BW is
Is 0.75 to 0.85 times the total tire width SW, and the tread gauge thickness Tt at the tread ground contact end from the belt layer to the outer surface of the tread portion and the tread at the outer end of the narrow belt ply. The ratio Tb / Tt to the gauge thickness Tb is characterized by being 0.2 to 0.40.

Further, in the invention of claim 3, the tire total width S is
The region from the maximum width point of the tire forming W to the outer end of the narrow belt ply is characterized in that the variation in tire thickness is 5 mm or less.

Further, in the invention of claim 4, the tread portion is provided with two vertical grooves extending in the tire circumferential direction, and lateral grooves which are spaced in the tire circumferential direction in a direction intersecting with the vertical grooves,
Moreover, the groove width of the lateral groove is set to 0.6 to 1.5 mm, and the number N of pitches of the lateral groove in the tire circumferential direction is set to 80 to 14
The feature is that it is zero.

In the present specification, the "tread contact surface" means a tread surface which can be grounded when a normal load is applied to a tire in a normal internal pressure state in which a regular rim is assembled to a rim and filled with a normal internal pressure. The tire axial width of the tread contact surface is referred to as a tread contact width TW.

The "regular rim" is a rim defined by the standard in the standard system including the standard on which the tire is based. For example, in the case of JATMA, the standard rim, T
RA means "Design Rim", and ETRTO means "Measuring Rim". Also, the "regular internal pressure"
Is the air pressure that the standard defines for each tire,
Maximum air pressure for JATMA, table for TRA "TI
RE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURE
If it is the maximum value described in "S" or ETRTO, "INFLATION P"
RESSURE ", but if the tire is for passenger cars, it is set to 180 (kPa) uniformly. The" regular load "is the load defined by the standard for each tire, and
Maximum load capacity for TMA, and table for TRA "TIRE
LOAD LIMITS AT VARIOUSCOLD INFLATION PRESSURES "
If it is the maximum value described in, ETRTO is "LOAD CAPACITY"
The load is 0.8 times each.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below.
This will be described together with the illustrated example. FIG. 1 shows a meridional section when the pneumatic tire of the present invention is a passenger car tire. In FIG. 1, a pneumatic tire 1 has a tread portion 2
The carcass 6 extends from the side wall portion 3 to the bead core 5 of the bead portion 4, and the belt layer 7 disposed inside the tread portion 2 and outside the carcass 6.

The carcass 6 is formed by one or more carcass plies 6A in which carcass cords are arranged at an angle of 75 ° to 90 ° with respect to the tire circumferential direction, and in this example, one carcass ply 6A. The carcass ply 6A includes the bead core 5,
The bead core 5 is provided on both sides of the ply body 6a extending across
Has a folded-back portion 6b that is folded back from inside to outside,
A bead apex rubber 8 rising in a tapered shape from the bead core 5 is provided between the ply body 6a and the folded-back portion 6b.
Are arranged. In the present example, the folded-back portion 6b has a so-called high turn-up structure in which the sidewall portion 3 extends to the vicinity of the maximum tire width point P that the sidewall portion 3 extends most outward in the tire axial direction, and cooperates with the bead apex rubber 8. Thus, the bead portion 4 is reinforced and the tire lateral rigidity is increased.

The belt layer 7 is formed of two belt plies 7A and 7B which are placed inside and outside in the radial direction.
The inner and outer belt plies 7A and 7B have high-elasticity belt cords that are inclined and arranged at an angle of 10 ° to 35 ° with respect to the tire circumferential direction so that the belt cords cross each other. It is arranged with different inclination directions.

In this example, the outer belt ply 7B is
It is slightly narrower than the inner belt ply 7A, and relaxes the stress concentration acting on the outer end portion of the belt. The narrow belt ply 7B may have a ply width BW in a range of 0.75 to 0.85 times the tire total width SW which is the axial distance between the tire maximum width points P and P. Preferably, this allows the tire to be firmly restrained with a predetermined flatness. The ply width BW is an effective width of the belt on which the two belt plies 7A and 7B are superposed.

In the present embodiment, the tread portion 2
A ground contact ridge 2A that forms a tread ground contact surface S by being bulged at the center thereof, whereby the tread ground contact width TW is in the range of 55 to 70% of the total tire width W and the conventional tire ( (Shown in FIG. 4) is very narrow. The tread contact width TW is more preferably 55 to 65% of the total tire width W.

Here, the ground contact raised portion 2A is raised relative to the non-protruded portion 2B located on the outer side in the tire axial direction. Therefore, by setting the tread gauge thickness T of the ground contact raised portion 2A to a value substantially equal to the tread gauge thickness of a conventional tire, for example, about 12.0 mm, while ensuring a conventional level of wear life, The non-raised portion 2B becomes thin, and the weight of the tire can be reduced.

As described above, the tread ground contact width TW is significantly reduced, the tread deformation in the ground / non-ground contact is suppressed, and the rolling resistance can be effectively reduced by reducing the weight of the tire. It becomes.

Further, in the present embodiment, the tread ground contact width T
By reducing W, conversely, the circumferential length of the tread contact surface S (tread contact length) increases, and the hydroplaning performance and riding comfort can be improved. Regarding the hydroplaning performance, the tread contact width TW
It is presumed that the decrease in the water content improves the drainage performance in the axial direction of the tire and increases the tread ground contact length to ensure the required ground contact area. Regarding riding comfort,
It is speculated that the vertical spring constant of the tire decreases as the tread contact length increases.

Further, in the above structure, the belt layer 7 may be extended below the non-raised portion 2B in order to suppress the deformation of the non-raised portion 2B and sufficiently secure the tread rigidity and durability. Required, especially narrow belt ply 7
It is important to set the ratio BW / TW of the ply width BW of B to the tread ground contact width TW in the range of 1.15 to 1.5 times and to secure the difference BW-TW of 10 mm or more.

If the ratio BW / TW is less than 1.15 times and the difference BW-TW is less than 10 mm, the deformation in the non-raised portion 2B cannot be suppressed, and the tread rigidity becomes insufficient, so that the maneuverability is reduced. It has a negative impact on stability. Further, the outer end 7e of the narrow belt ply 7B comes too close to the tread ground contact end E, and the outer end 7e becomes a starting point of damage, resulting in deterioration of durability. Further, increasing the ply width BW by more than 1.50 is wasteful, is disadvantageous in cost and weight reduction, and makes tire manufacturing difficult. Therefore, the ratio B
W / TW is preferably in the range of 1.2 to 1.4 times.

Further, by forming the belt layer 7 wider than the tread contact surface S as described above, the vibration damping effect against the disturbance received from the road surface is significantly enhanced, and as a result, the road noise performance is also improved. At the same time, there is a new merit that it can be improved.

Further, in this example, in order to make the tire as light as possible and to exert the rolling resistance reducing effect more effectively, the tread gauge thickness Tb at the outer end 7e of the narrow belt ply 7B is set to the tread ground contact end E. The thickness of the tread gauge Tt is 0.2 to 0.40 times, preferably 0.2 to 0.35 times. If it exceeds 0.40 times, the rolling resistance reducing effect becomes insufficient,
If it is less than 0.2 times, the coating thickness of the belt layer 7 becomes too small, and damage such as cracks tends to occur. The tread gauge thickness Tb is 2.0 for passenger car tires.
It can be set to a range of up to 3.0 mm.

Further, in this example, in order to further improve the durability, in the region Y from the tire maximum width point P to the outer end 7e of the narrow belt ply 7B, the variation of the tire thickness t is 5 mm or less. , And more preferably 4 mm or less. This is because if there is a change in the rigidity of the region Y, stress and strain may be concentrated at the position of the outer end 7e to cause damage, and by suppressing the variation in the tire thickness t. The stress can be evenly distributed over a wide range, which is advantageous for durability.

The tire thickness t means the total thickness from the inner surface of the tire to the outer surface of the tire, and the tread gauge thickness T means the thickness from the outer surface of the belt layer 7 to the outer surface of the tire. Means Therefore, when a conventional band layer (not shown) is arranged on the outer side of the belt layer 7,
The tread gauge thickness T is a thickness including the band layer.

Further, in the present specification, the tread ground contact width T
Dimensions such as W, the total tire width W, and the ply width BW are values measured in the tire with the normal internal pressure.

Next, in the tire of the present embodiment, the ground contact shape (so-called footprint) becomes longer than that of the conventional one, such as the tread ground contact length increasing. Therefore, it is preferable to adopt a tread pattern having high lateral rigidity in order to sufficiently secure the lateral force generated from the ground contact surface and to exhibit excellent steering stability.

Therefore, in this example, as the tread pattern, as shown in FIG. 3, two vertical grooves 20 extending in the tire circumferential direction and the tire circumferential direction spaced in the direction intersecting with the vertical grooves 20 are provided. The block type is composed of the horizontal groove 21 and the horizontal groove 21.

At this time, as the lateral groove 21, an extremely fine groove having a groove width Wy of 0.6 to 1.5 mm is used.
The number N of pitches of the lateral grooves 21 in the tire circumferential direction is 80 to 14
The number is 0.

As described above, since the ultra-fine lateral groove 21 is used and the pitch number N thereof is increased to about twice that of the conventional tire, only the circumferential rigidity of the block is reduced while maintaining the land ratio high. It is possible to reduce the power of hitting the road surface and reduce the pattern noise. On the other hand, since the vertical groove 20 is two and the land ratio is maintained high, the lateral rigidity of the block is ensured to be high, and as a result, the tire of the present embodiment is optimally matched, The steering stability can be improved.

Here, the groove width Wg of the vertical groove 20 is preferably in the range of 5 to 7% of the tread ground contact width TW from the viewpoint of drainage. Further, the number N of pitches is more preferably 100 to 140 in order to reduce pattern noise. In this example, the lateral groove 21 is formed on one tread ground contact end E.
From the first to the other tread ground contact end E, for example, a continuous S-shaped one is shown as an example, but it may be a straight groove and is arranged between the vertical groove 20 and the tread ground end E. The pitch number N of the lateral grooves 21 may be different from the pitch number N of the lateral grooves 21 arranged between the vertical grooves 20, 20.

Although a particularly preferred embodiment of the present invention has been described above in detail, the present invention is not limited to the illustrated embodiment and can be modified into various modes.

[0032]

EXAMPLE A tire having a tire size of 195 / 65R15 and having a configuration shown in FIG. 1 was prototyped according to the specifications shown in Table 1, and rolling resistance, cornering power (CP), longitudinal spring constant, and hydro of the sample tire were tested. The planing performance, steering stability, riding comfort, and road noise performance were tested, and the results are shown in Table 1.

(1) Rolling resistance: Using a rolling resistance tester, the tire was rim (6JJ × 15) and internal pressure (250 kP).
The rolling resistance was measured at a), an hourly speed (80 km / h), and a load (4 kN), and the rolling resistance was displayed as an index with Comparative Example 1 as 100.
The smaller the value, the better.

(2) Cornering power: The lateral force (cornering power) at a slip angle of 1 ° in the rim-assembled tire was measured using an indoor tester.
The index was set to 0. The larger the value, the greater the lateral force.

(3) Longitudinal spring constant: For the rim set tire,
The reciprocal of the difference in the amount of vertical deflection when the load was changed ± (0.5 kN) around the load state of the load (4.00 kN) was displayed as an index with Comparative Example 1 as 100. The larger the value, the less tire deformation.

(4) Hydroplaning performance: Tires were mounted on all wheels of a domestic 2000cc class FF vehicle with a rim (6JJ × 15) and an internal pressure (230kPa), and a radius of 100.
A maximum turning width G was measured by making a circular turn on a course provided with a puddle having a depth of 5 mm and a length of 20 m on an asphalt road surface of m, and the index was expressed as an index with Comparative Example 1 being 100. The larger the value, the better.

(5) Driving stability, riding comfort, and road noise performance: Driving stability, riding comfort, and road noise performance of the driver on the tire test course of dry asphalt using the above-mentioned vehicle for sensory evaluation of the driver. Therefore, Comparative Example 1 is indicated by an index of 5. The larger the index, the better.

[0038]

[Table 1]

[0039]

As described above, in the pneumatic tire of the present invention, the tread portion is provided with the ground contact raised portion to reduce the tread ground contact width to 55 to 65% of the total tire width, and the belt layer width to the tread ground contact. It is higher than the width within a predetermined range. Therefore, the rolling resistance can be reduced without using a low heat-generating rubber, and the above problems caused by the low heat-generating rubber can be solved, and also with respect to hydroplaning performance, riding comfort, and road noise performance. Each performance can be improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a pneumatic tire of the present invention.

FIG. 2 is a cross-sectional view showing an enlarged ground contact ridge.

FIG. 3 is a development view showing an example of a tread pattern adopted in the present invention.

FIG. 4 is a cross-sectional view of a tire of Comparative Example 1 shown in Table 1.

5 is a tread pattern diagram of the tire of Comparative Example 1 shown in Table 1. FIG.

[Explanation of symbols]

2 tread section 2A Ground protrusion 3 Side wall part 4 bead section 5 bead core 6 carcass 6A carcass ply 7 Belt layer 7A, 7B Belt ply 20 vertical grooves 21 lateral groove S tread contact surface

Claims (4)

[Claims] 1. A carcass comprising a carcass ply extending from a tread portion to a side wall portion to a bead core of a bead portion, and two belt plies that are placed inwardly and outwardly in the radial direction inside the tread portion and outside the carcass. A pneumatic tire comprising a belt layer made of, wherein the tread portion is provided with a tread contact surface having a width of 55 to 70% of the total tire width SW and a ground contact raised portion protruding in this region, The ply width BW of the narrower one of the two belt plies is set larger than the tread ground contact width TW and the ratio B is
W / TW is 1.15 to 1.5 times and difference BW-TW is 10
A pneumatic tire characterized by having a diameter of at least mm. 2. The tire ply width BW is the tire total width SW.
Ratio of the tread gauge thickness Tt at the tread grounding end from the belt layer to the outer surface of the tread portion and the tread gauge thickness Tb at the outer end of the narrow belt ply. Tb / Tt is 0.2 ~
It is 0.40, The pneumatic tire of Claim 1 characterized by the above-mentioned. 3. The tire thickness variation in the region from the maximum tire width point forming the total tire width SW to the outer end of the narrow belt ply is 5 mm or less. 2. The pneumatic tire described in 2. 4. The tread portion is provided with two vertical grooves extending in the tire circumferential direction and lateral grooves spaced in the tire circumferential direction in a direction intersecting with the vertical grooves, and a groove width of the lateral groove is set. 0.
The pneumatic tire according to any one of claims 1 to 3, wherein the lateral groove has a pitch number N in the tire circumferential direction of 80 to 140 while being 6 to 1.5 mm.