JP2000185524A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve wandering performance while regulating asymmetric wear or the like. SOLUTION: A shoulder groove 10 disposed on the outermost side of a tire in the axial direction and which extends in the tire circumferential tire direction is provided on a tread surface 2. The tread surface axially outside of a groove edge P on the outside of the shoulder groove 10 includes a first inclined surface 11 inclined by an angle α between 5 and 10 degrees in the radially inward direction of the tire with respect to a tangent N of an tread arc CT at the groove edge P, and a second inclined surface 12 which extends from this first inclined surface 11 in the radially outward direction of the tire and inclined by an angle β between 5 and 10 degrees in the radially inward direction of the tire with respect to the first inclined surface 11, continuing onto a buttress surface. A tire axial length Y of the first inclined surface 11 is made greater than or equal to 0.5 times and less than or equal to 0.8 times a tire axial direction distance L of a groove edge P and an imaginary tread end Q.

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 Pneumatic tires, especially pneumatic tires for light trucks used for 1.5 to 3.5 tons of light trucks, have a greater size than passenger car tires. Due to the high rigidity of the tread portion, when the tread edge comes into contact with the rut slope during the rut traveling on the road surface, a reaction force acts on the handle, and the handle is easily taken off. In addition, this kind of tire has a disadvantage that the rut escape performance that gets out of a large rut formed by a large vehicle is low. Therefore, there is a strong demand for small truck tires to have improved stability performance during such rutted traveling, that is, improved wandering performance.

Conventionally, in order to improve such wandering performance, the axial edge region of the tread surface is formed by, for example, a small arc b having a small radius of curvature Ra as shown in FIG. As shown in FIG. 3 (b), the tapered slope c
In addition, it has been proposed to provide a narrow groove in the shoulder portion in the circumferential direction of the tire (for example, JP-A-1-95911).

In general, in order to improve the wandering performance, the rigidity of the edge portion of the tread portion is reduced, so that the reaction force to the handle is eliminated, and a large lateral force is required to climb a rut on the tire. It is effective to generate force (camber thrust). As a result, the tire climbs the rut without difficulty, and at this time, the driver of the vehicle hardly gets the steering wheel.

However, since a large load acts on the shoulder portion of the tread surface of the pneumatic tire during turning or the like, depending on the method of reducing the rigidity, not only the steering stability is deteriorated but also the edge portion of the tread surface. However, there is a problem that uneven wear occurs, which wears earlier than other parts.

The present invention has been devised in view of such a problem, and is based on the fact that a shoulder portion includes a first slope and a second slope, while suppressing the occurrence of uneven wear. It is another object of the present invention to provide a pneumatic tire which can suitably soften the rigidity of a tread shoulder portion and greatly improve wandering performance, particularly a pneumatic tire most suitable for a small truck.

[0007]

According to the present invention, a shoulder groove extending in the tire circumferential direction and disposed on the outermost side in the tire axial direction is provided on the tread surface, and the shoulder groove extends in the tire axial direction from the tire equatorial plane. The tread surface up to the outer groove edge P of the tire is substantially formed by a single tread arc, and the shoulder groove is formed in a tire meridian section in a normal state under no load where the rim is assembled to a normal rim and filled with a normal internal pressure. A virtual tread end Q at which an extension of the tread arc and a buttress contour line S forming the buttress surface intersects from the tire equatorial plane C to the outside in the tire axial direction,
A groove center is located at a distance X that is 0.2 to 0.3 times the tread width TW between Q, and a tread surface on the outer side in the tire axial direction of the outer groove edge P is formed of the shoulder groove. The groove edge P
A first slope that extends outward in the tire axial direction and inclines at an angle α of 5 ° or more and 10 ° or less inward in the tire radial direction with respect to a tangent line of the tread arc at the groove edge P;
The first slope extends outward in the tire axial direction and the first
5 ° or more inward in the tire radial direction with respect to the slope of
゜ a second slope inclined at the following angle β and continuing to the buttress surface, and the length Y of the first slope in the tire axial direction is set to the groove edge P and the outside in the tire axial direction. The tire axial distance L from the virtual tread end Q is 0.
This is a pneumatic tire that is at least 5 times and at most 0.8 times.

Here, 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, JATMA is a standard rim, and TRA is "Design rim". Rim "or ETR
If it is TO, it will be "Measuring Rim". In addition, the "normal internal pressure" is the air pressure that each standard defines for each tire in a standard system including the standard on which the tire is based,
JATMA for maximum air pressure, TRA for table "TI
RE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURE
Maximum value described in "S", or "INFLATION P" for ETRTO
RESSURE "and 180 when the tires are for passenger cars.
(KPa). Further, the “regular load” is a load defined by each standard in the standard system including the standard on which the tire is based. The maximum load capacity is JATMA, and the table “TIRE LOAD” is TRA. LIMITS A
The maximum value described in "T VARIOUS COLD INFLATION PRESSURES" or "LOAD CAPACITY" for ETRTO.

The first slope is connected to the second slope through a small arc having a radius of curvature of 5 mm or more and 20 mm or less, and the second slope has a radius of curvature of 5 mm or more and 20 mm or less. It is desirable to connect to the buttress surface via a small arc.

[0010]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a meridian sectional view including a tire shaft in a normal state in which a pneumatic tire of the present embodiment is rim assembled to a regular rim R and is filled with a normal internal pressure and has no load, and FIG. Is enlarged. In the figure, a pneumatic tire 1 includes a bead core 5 of a bead portion 4 from a tread portion 2 through a sidewall portion 3.
, And a pneumatic radial tire for a small truck, comprising a carcass 6 reaching the inner side of the tread portion 2 and a belt layer 7 disposed outside the carcass 6 in the tire radial direction.

As shown in FIG. 2, the carcass 6 is exemplified by three carcass plies 6A, 6B and 6C, and each of the plies has a carcass cord having a carcass cord with respect to the equator of the tire. It is arranged at an angle of ゜ 90 °. For the carcass cord, for example, an organic fiber cord such as polyester, nylon, and rayon is adopted.
If necessary, a steel cord or the like may be employed. The belt layer 7 includes at least two belt plies 7A and 7B in which steel cords are arranged at a small angle of, for example, 15 to 45 ° with respect to the tire equator in this embodiment, and two inner and outer belt plies 7A and 7B in this embodiment. The cords are configured to overlap each other in a direction crossing each other, and the rigidity of the carcass 6 can be increased by loosely tightening the carcass 6 in the tread portion 2.

The pneumatic tire 1 has a circumferentially continuous crown groove 9 disposed on both sides of the tire equator on the tread surface 2 in this example, and a circumferentially continuous crown groove 9 disposed on both sides thereof. Pair of shoulder grooves 10 which are the outermost in the direction
In this example, land portions of five rows which can be in contact with the road surface are defined by the grooves 9 and 10, respectively. In addition, although these land portions are ribs that are continuous in the tire circumferential direction in this example, they may be provided with appropriate lateral grooves, lug grooves, notches, and the like.

The shoulder groove 10 has a groove width W of, for example, 2.5 to 7%, preferably 3 to 6% of the tread width TW in order to exhibit a good drainage function. The depth is 6mm or more or the tread width TW is 4 ~
It is desirably 9%, preferably 6 to 9%. In the present specification, the “tread width TW” is, as shown in FIG. 2, a virtual tread end Q, Q at which an extension line of the tread arc CT and the buttress contour S forming the buttress surface 13 intersects.
It is defined as the distance between the tires in the axial direction.

Further, in the present embodiment, the tread surface 2A from the tire equatorial plane C to a groove edge P outside the shoulder groove 10 in the tire axial direction is formed by a substantially single tread arc CT. . This tread arc CT is
For example, a relatively large radius of curvature T having a center 0 on the tire equatorial plane C and 1.5 to 3.5 times the tread width TW.
The one formed by R is exemplified.

In the tire meridian section of the pneumatic tire in the normal state, the shoulder groove 10 is
A groove center is located at a position spaced apart from the tire equatorial plane C by a distance X of 0.2 to 0.3 times the tread width TW outward in the tire axial direction. In this way, by restricting the position of the shoulder groove 10 in the tire axial direction, a land portion Sh of the shoulder having a specific width can be formed on both sides of the groove edge P outside the shoulder groove in the tire axial direction. If the distance X is less than 0.2 times the tread width TW, the width of the land portion Sh of the shoulder in the tire axial direction is too large, and the first and second slopes 1 to be described later.
When 1, 12 are formed, the contact property of the tread surface is deteriorated. On the contrary, when it exceeds 0.3 times, the rigidity of the land portion Sh of the shoulder is excessively reduced, and the steering stability tends to be reduced.

The groove edge P of the shoulder groove 10
One of the features is that the tread surface of the land portion Sh of the shoulder forming the outer side in the tire axial direction includes a first slope 11 and a second slope 12.

The first slope 11 extends from a groove edge P outside the shoulder groove 10 outward in the tire axial direction and radially inward in the tire radial direction with respect to a tangent N of the tread arc CT at the groove edge P. It is formed as being inclined at an angle α of not less than か つ and not more than 10 °. The second slope 12 is
The buttress surface 13 extends outward from the first slope 11 in the tire axial direction and is inclined inward in the tire radial direction at an angle β of 5 ° or more and 10 ° or less with respect to the first slope 11.
Continue to.

With such two slopes 11, 12,
The land portion Sh of the shoulder can soften its rigidity, can appropriately absorb the impact at the time of collision with the inclined surface of the rut, and can reduce the acting force on the steering wheel. Further, the first slope 11 is 5 to 1 with respect to the tangent N of the tread arc of the outer groove edge P.
Since it is inclined at a small angle of 0 °, it is possible to effectively prevent the contact pressure of this portion from being significantly reduced as compared with the central portion of the tread surface. Therefore, the first slope 11 effectively suppresses, for example, drag between the first slope 11 and the road surface, and helps to suppress uneven wear over a long period of time.

The second slope 12 has a first slope 11.
The angle of inclination is 5 to 10 ° with respect to the first slope 11, so that a sudden change in rigidity between the first slope 11 and the first slope 11 can be prevented. Further, an equatorial point CP where the tread surface 2A and the tire equatorial surface C intersect, the second slope 12 and the buttress surface 13
And the camber amount, which is the distance in the tire radial direction between the slope end Z and the intersection of the shoulders Z, can be increased without a large change in rigidity of the land portion Sh of the shoulder. This helps to smoothly increase the camber-thrust value in accordance with an increase in the camber angle (corresponding to the slope angle of the rut), and in particular, makes it easier to escape the rut and improves the wandering performance.

When the angles α and β of the first slope 11 and the second slope 12 are both less than 5 °,
An effective increase in camber thrust value cannot be expected, and no improvement in wandering performance can be expected. Conversely, when the angles α and β of the first slope 11 and the second slope 12 both exceed 10 °, an increase in the camber thrust value can be expected, but the ground pressure on the shoulder side significantly decreases. In addition, uneven wear, in which the shoulder portion is worn early, is liable to occur due to, for example, a decrease in ground contact with the road surface. The angles α and β may be any of α> β, α = β or α <β.

Here, the length Y of the first slope 11 in the axial direction of the tire is defined as a groove edge P outside the shoulder groove 10,
It is necessary to be 0.5 times or more and 0.8 times or less of the distance L in the tire axial direction with respect to the virtual tread end Q on the outer side in the tire axial direction, and more preferably 0.65 times or more and 0. Eight times is particularly desirable.

The inventors conducted experiments by changing the length Y of the first slope 11 in the tire axial direction.
It was found that by regulating the content within the above range, both the wear resistance performance and the wandering performance can be more effectively achieved. On the other hand, the length Y in the tire axial direction of the first slope 11
Is less than 0.5 times the tire axial distance L,
The proportion occupied by the second slope 11 becomes too large, and the slope end Z is deviated inward in the tire radial direction, causing uneven wear and lowering of steering stability. Conversely, if the ratio exceeds 0.8, the proportion of the second slope 12 occupied becomes small, so that the camber thrust value cannot be increased and the effect of suppressing uneven wear decreases.

The first slope 11 has a radius of curvature R
A is second through a small arc C1 of 5 mm or more and 20 mm or less.
Similarly, the second slope 12 desirably connects to the buttress surface 13 via a small arc C2 having a radius of curvature RB of 5 mm or more and 20 mm or less. Thereby, the wear resistance is further improved.

The embodiment of the present invention has been described in detail above.
The present invention is not limited to the illustrated form, and various modifications are possible. For example, the rib-shaped portion may be divided in the tire circumferential direction by a lateral groove. Further, the present invention can be suitably applied to a light truck tire, but is not limited to this tire category.

[0025]

EXAMPLES A pneumatic radial tire for a small truck having a tire size of 205 / 70R16 was prototyped, and the camber thrust value, wandering performance and wear resistance of the tire were tested. In addition to the examples belonging to the present invention, for comparison, a round shoulder tire (Comparative Example 2) shown in FIG. 3A (Comparative Example 1) and one tire as shown in FIG. The performance of the tire having a tapered shape and a slope was also compared. The test method is as follows.

<Camber thrust value> 6
A camber thrust value was measured when a camber angle of 4 ° was given in a state where an internal pressure of 00 (kPa) was charged and a load of 9 (kN) was applied.

<Wandering Performance> A test tire was mounted on a small truck, and the vehicle was driven at a speed of 80 km / h in the rut to take the steering wheel of the vehicle. The evaluation was performed by a 10-point method. The higher the value, the better.

<Abrasion resistance> A test tire was mounted on a small truck, and a general road type and a highway type test course were run for a total of 3000 km, and a difference between each average groove depth of the crown groove and the shoulder groove was determined and compared. It is indicated by an index with Example 1 being 100. The closer the numerical value is to 100, the more uniform the abrasion and the higher the abrasion resistance. Table 1 shows the test results and the like.

[0029]

[Table 1]

[0030]

As described above, the pneumatic tire of the present invention can improve the wandering performance by increasing the camber thrust value while suppressing uneven wear.

[Brief description of the drawings]

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

FIG. 2 is a partially enlarged view in which the tread portion is enlarged.

FIGS. 3A and 3B are partial contour views of a tread surface for explaining a conventional technique.

[Explanation of symbols]

 2 Tread portion 2A Tread surface 3 Side wall portion 4 Bead portion 5 Bead core 6 Carcass 10 Shoulder groove 11 First slope 12 Second slope

Claims (3)

[Claims] A shoulder groove extending on the tread surface in the tire circumferential direction and disposed on the outermost side in the tire axial direction, and a groove edge (P) of the shoulder groove from the tire equatorial plane to the outside in the tire axial direction. The tread surface is substantially formed by a single tread arc, and the shoulder groove is formed in a tire meridian section in a normal state of a no-load normal state assembled with a normal rim and filled with a normal internal pressure. 0) of the tread width (TW) between the virtual tread ends (Q) and (Q) at which the extension line of the tread arc and the buttress contour line (S) forming the buttress surface intersects the tire tread axially outward from C). .2
A groove center is located at a distance (X) of about 0.3 times, and a tread surface on an outer side in the tire axial direction of the outer groove edge (P) is the groove edge (P) of the shoulder groove. A first slope extending outwardly in the tire axial direction and inclined at an angle α of 5 ° or more and 10 ° or less inward in the tire radial direction with respect to a tangent of the tread arc at the groove edge (P); From the slope of the tire to the outside in the tire axial direction and the first
5 ° or more inward in the tire radial direction with respect to the slope of
゜ a second slope inclined to the buttress surface at an angle β or less, and the length Y of the first slope in the tire axial direction is defined by the groove edge (P) and the tire axial direction. A pneumatic tire having a distance not less than 0.5 times and not more than 0.8 times an axial distance (L) from the virtual tread end (Q) on the outside. 2. The first slope is connected to the second slope through a small arc having a radius of curvature of 5 mm or more and 20 mm or less, and the second slope has a radius of curvature of 5 mm or more and 20 mm or less. The pneumatic tire according to claim 1, wherein the pneumatic tire is connected to the buttress surface through a small arc. 3. The first slope has a length (Y) in the axial direction of the tire of not less than 0.65 times and not more than 0.8 times the distance (L) in the axial direction of the tire. The pneumatic tire as described.