JPH0930214A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniform ground pressure of a tire by offsetting the main groove side edge on the flat portion of the tire so that it may be more to the outer diameter side of the tire than the circular arc extension line forming the flat portion of the tread central area and forming the cross section of the flat portion surface with a line segment made gradually to the inner diameter side of the tire from the main groove side edge to the tire ground plane. SOLUTION: A meridional cross section on a tire tread forms a flat portion Ly on a tread central area in an uniform circular arc C shape having a specific radius Ry. In comparison thereof, a main groove side edge Lx1 on the flat portion Lx of the shoulder area is offsetted so that it may be more to the outer diameter side of a tire than the extension line C' of the circular arc C forming the flat portion Ly on the tread central area and the cross section of the flat portion Lx surface is formed by a line segment Z gradually continuing to the inner diameter side of the tire from the main groove side edge Lx1 to the tire ground end P. The tire ground and P is more to the inner diameter side than an extension line C' of the circular arc C forming the flat portion Ly on the tread central area.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire in which the ground contact pressure in the land area in the shoulder area of the tread surface is made more uniform.

[0002]

2. Description of the Related Art Conventionally, a tire meridian sectional shape on a tread surface has been formed by one arc having a constant radius (a so-called one-step radius structure). Such a pneumatic tire has a ground contact pressure of a land portion in a shoulder region from a tire outermost main groove to a tire contact end,
The inside of the tire is low and the outside is high. Therefore, in the shoulder region, there is a problem in that the outside of the tire having a high ground contact pressure is rapidly worn, and uneven wear occurs in the land portion.

Therefore, as a solution to the above problem, the tire meridian sectional shape on the tread surface is not formed with a uniform arc, but the land portion in the shoulder area is formed as a continuous line segment with an arc smaller than the arc forming the tread central area. There is a proposal of a so-called two-step radius or three-step radius structure to be formed. As a result, the tire ground contact end side is lowered to the tire inner diameter side compared to the conventional one, and the contact pressure of the shoulder region land portion is made uniform, but the effect is insufficient, and in particular, the load factor is In a high-priced vehicle, the outer side of the tire in the land area of the shoulder region is quickly worn out, which tends to cause uneven wear, and improvement thereof has been strongly desired.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a pneumatic tire capable of making the contact pressure of the land portion in the shoulder region of the tread surface more uniform and suppressing uneven wear in the land portion. Especially.

[0005]

According to the present invention, which achieves the above object, a plurality of main grooves extending in the tire circumferential direction are provided on a tread surface formed in an arc shape having a tire meridian cross-section having a predetermined radius. , A pneumatic tire having a shoulder region from the outermost main groove of the tire to the ground contact edge of the tire, and a land portion formed in the tread central region between the outermost main grooves of the tire, in the main groove side edge of the land portion of the shoulder region Is offset so as to be on the tire outer diameter side with respect to the extension line of the arc forming the land portion of the tread central region, the cross-sectional shape of the surface of the shoulder region land portion from the main groove side edge to the tire ground contact end It is characterized in that it is formed by a continuous line segment gradually extending toward the inner diameter side of the tire.

As described above, according to the present invention, the edge on the main groove side of the land portion of the shoulder region is not arranged on the line segment continuous to the arc forming the tread central region as in the conventional case, but is offset to the tire outer diameter side. In the protruding state, since the tire inner portion having a low ground contact pressure in the shoulder area land portion is configured to positively increase the ground contact pressure, it is possible to increase the tire inner ground contact pressure in the shoulder area land portion. Since the total amount of energy when the tire touches the ground does not change, it is possible to decrease the tire outside ground pressure of the shoulder area land portion according to the increase of the inside pressure of the tire, thereby,
The contact pressure on the land portion of the shoulder region is made more uniform than before, and uneven wear occurring on the land portion can be suppressed.

[0007]

DETAILED DESCRIPTION OF THE INVENTION The configuration of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 shows an example of a tread pattern of the pneumatic tire of the present invention. The tread surface 1 is provided with a plurality of (three in the figure) straight main grooves 2 extending along the tire circumferential direction T, and between the main grooves 2, a large number of lateral grooves extending in the tire width direction are provided. 3 are formed, and the main groove 2 and the lateral groove 3 divide and form a large number of blocks 4 on the tread surface 1.

Blocks 4 are respectively formed in both shoulder regions X from the outermost main grooves 2A, 2B of the tire to the tire ground contact ends P and the tread central region Y between the outermost main grooves 2A, 2B of the tire. It has a structure with a land portion formed. In the land portions of both shoulder regions X, one narrow groove 5 extending along the tire circumferential direction T is provided, and a lateral groove 3 is also provided for the narrow groove 5 to form a block 4. I am trying to do it.

According to the present invention, in the pneumatic tire having the above-described structure, the tire meridian cross-sectional shape on the tread surface 1 has a predetermined radius R _y for the land portion L _y in the tread central region Y as shown in FIG. Is formed in a uniform circular arc c shape having, while the main groove side edge L _X1 of the land portion L _X of the shoulder region X is an extension line of the circular arc c forming the land portion L _y of the tread central region Y. Offset from c ′ toward the tire outer diameter side, and the cross-sectional shape of the surface of the land portion L _X is formed by a continuous line segment z gradually extending from the main groove side edge L _X1 to the tire ground contact end P toward the tire inner diameter side. ing. The tire ground contact end P is an arc c forming the land portion L _y of the tread central region Y.
Is on the inner diameter side of the tire with respect to the extension line c ′.

As described above, the main groove side edge L _X1 of the shoulder region land portion L _X is not arranged on the line segment continuous to the arc c forming the tread central region as in the conventional case, but is arranged on the tire outer diameter side. Since the tire inner side of the shoulder region land portion L _X where the ground contact pressure is low is positively increased, the inner side tire contact pressure of the land portion L _X can be increased. it can be one, because the tire does not change the total amount of energy when the ground, it is possible to correspond to the ground pressure increases in the tire inner land portion L _X, reducing the tire outer ground contact pressure of the land portion L _X. Therefore, more uniform than the conventional ground pressure of the land portion L _X in the shoulder area X of the tread surface 1, it is possible to suppress uneven wear of the land portion L _X.

Also, the tire ground contact end on the tread surface 1
P is the land portion L of the tread central area Y _yArc c forming
It should be structured such that it is lowered toward the tire inner diameter side from the extension line c'of
By the above, the above effect is further enhanced, and the entire tread surface 1 is
The ground pressure can be made uniform. Main groove side d
Judge L_X1The offset amount s of 0. is preferably 0.
It is recommended that the range is 1 to 1.0 mm. Offset amount s
If it is less than 0.1 mm, the shoulder area land portion L_XInside the tire
It is difficult to increase the side ground pressure sufficiently.
On the contrary, when it exceeds, the shoulder area L_XInscribed on the tire
Ground pressure becomes too high and it is difficult to obtain the above-mentioned effects.
Become.

Further, the lowering amount t to be lowered toward the tire inner diameter side from the extension line c'of the arc c of the tire ground contact end P is preferably 0.1 to 1.0 mm, like the offset amount s. . The line segment z that forms the cross-sectional shape of the surface of the shoulder region land portion L _X can be a curve (an arc having a center on the tire inner diameter side) or a straight line, or a line segment that combines a curved line and a straight line.

Further, the land portion L _X of the shoulder region X is preferably chamfered at its main groove side edge L _X1 . For example, the land portion L _X can be chamfered so as to have a curved or straight cross section. The main groove 2 in the present invention means a groove having a groove width exceeding 3 mm, and a groove extending in the tire circumferential direction of 3 mm or less is defined as a fine groove 5.

Further, in the present invention, the case where the block pattern is formed on the tread surface 1 in the above-described embodiment has been described, but a rib pattern in which land portions made of ribs are provided on both sides of the main groove, The present invention can be preferably used.

[0015]

Example: Tire size is 205 / 65R15 94
A tire of the present invention in which the main groove side edge of the shoulder area land portion shown in FIG. 2 is offset, and the tread surface is formed of one arc, and the one-step radius structure is formed by using one arc. The conventional tire 1 and the conventional tire 2 having a two-step radius structure were manufactured.

The cross-sectional shape of the tread surface in the central region of the tread of each test tire is composed of an arc having a radius of 600 mm, and the width of the land portion in the shoulder region from the outermost main groove (width 8 mm) to the tire ground contact end is It is 35 mm. In the tire of the present invention, both the offset amount s and the lowered amount t are 0.5 mm, and the line segment of the shoulder area land portion has a radius of 600 mm.
It consists of mm arcs. The shoulder area land portion of the conventional tire 2 is composed of an arc having a radius of 300 mm, and the lowered amount t is 1.5 mm.

The measurement conditions shown below for each of these test tires
The ground pressure and uneven wear resistance were evaluated by
The results shown in FIG. 3 and Table 1 were obtained. In addition, in FIG.
The solid line indicates the tire of the present invention, the one-dot chain line indicates the conventional tire 1, the dotted line
Indicates a conventional tire 2.Ground pressure Attach each test tire to the rim of rim size 15 × 6JJ
And air pressure 2.0kgf / cm ^Two As a static earth pressure tester
And the land between the main groove in the center of the tire and the outermost groove.
A), the land portion between the outermost main groove and the narrow groove (block)
H) b, and the land (block) outside the tire than the narrow groove
The contact pressure at c was measured and the result was used for each test tire.
Both were evaluated by an index value with the ground contact pressure of the land a as 100.
The larger this value, the higher the ground pressure, and the smaller this value, the lower the ground pressure.
Indicates thatUneven wear resistance Attach each test tire to the rim of rim size 15 × 6JJ
And air pressure 2.0kgf / cm ^Two As a 2000cc vehicle
Running on a dry test road consisting of a pavement and 10,000 km
After traveling, the land area between the main groove in the center of the tire and the outermost groove
(Block) a, land between the outermost main groove and the narrow groove
Land (block) b and land outside the narrow groove
Measure the amount of wear in (block) c and calculate the average value.
The amount of wear (mm) is shown in Table 1.

[0018]

[Table 1]

As is clear from FIG. 3 and Table 1, in the tire of the present invention, the ground contact pressure of the shoulder region land portion outside the tire outermost main groove is equalized without being different between the tire inner side and the tire outer side. It can be seen that uneven wear on the land portion can be suppressed. Further, it can be seen that the ground contact pressures of the shoulder area land portions b and c and the land portion c in the tread central area are equal, and the contact pressure can be made uniform over the entire tread surface.

[0020]

As described above, according to the present invention, a plurality of main grooves extending in the tire circumferential direction are provided on a tread surface formed in an arc shape having a tire meridian cross section having a predetermined radius, and the tire outermost portion is provided. Shoulder area from the main groove to the tire ground contact edge,
And a pneumatic tire in which a land portion is formed in the tread central region between the outermost main grooves of the tire, the main groove side edge of the land portion of the shoulder region is an extension line of an arc forming the land portion of the tread central region. Since it is offset to be on the tire outer diameter side, and the cross-sectional shape of the surface of the shoulder region land portion is formed by a continuous line segment that gradually becomes the tire inner diameter side from the main groove side edge to the tire ground contact end, the tread It is possible to make the ground contact pressure in the land portion in the shoulder region of the surface more uniform and suppress uneven wear in the land portion.

[Brief description of drawings]

FIG. 1 is a plan view of relevant parts showing an example of a tread surface of a pneumatic tire of the present invention.

FIG. 2 is a sectional view of a main part of FIG.

FIG. 3 is a graph showing a measurement result of ground pressure.

[Explanation of symbols]

1 tread surface 2 main groove 2A, 2B outermost main groove 3 lateral groove 4 block 5 narrow groove L _x, L _y land portion L _x1 main groove side edge P tire contact end T tire circumferential direction X shoulder area Y tread central area c circular arc c'extended line of arc s offset amount z line segment

Claims (5)

[Claims] 1. A plurality of main grooves extending in the tire circumferential direction are provided on a tread surface formed in an arc shape with a tire meridian cross-section having a predetermined radius, and a main groove from the outermost side of the tire to a tire ground contact end. In a pneumatic tire in which a land portion is formed in a shoulder region and a tread central region between outermost main grooves of the tire, a main groove side edge of the land portion of the shoulder region is an arc forming a land portion of the tread central region. Offset from the extension line of the tire outer diameter side, the cross-sectional shape of the surface of the shoulder region land portion is formed by a continuous line segment gradually toward the tire inner diameter side from the main groove side edge to the tire ground contact end Pneumatic tires. 2. The pneumatic tire according to claim 1, wherein the tire ground contact end is located on a tire inner diameter side with respect to an extension line of an arc forming a land portion of the tread central region. 3. The offset amount of the main groove side edge is set to 0.
The pneumatic tire according to claim 1, which has a diameter of 1 to 1.0 mm. 4. The line segment of the cross-sectional shape is formed by a curved line, a straight line, or a combination of a curved line and a straight line.
The pneumatic tire according to any one of 1 to 3. 5. The main groove side edge is chamfered.
The pneumatic tire according to any one of items 1 to 4.