JPH0463704A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To restrain the lopsided wear of a land portion during both straight run and turning by forming thin ribs, which are extended in a peripheral direc tion between pairs of peripheral grooves, so that the respective lateral variations show specified values when lateral force is applied thereto under different speci fied conditions. CONSTITUTION:A pneumatic radial tire l has pairs of peripheral grooves 11, 12, 13, 14 formed outside of shoulder ribs 7a, 7b, respectively, in a cross direction and thin ribs 17, 20 partitioned between the peripheral grooves 11, 12 and be tween the peripheral grooves 13, 14, respectively. The width W of a land portion, located on at least one side of the thin ribs 17, 20, defined to be 10mm or great er, the lateral variation of the thin ribs 17, 20, when lateral force at a value that the thin rib width L per peripheral distance 1cm is multiplied by two is applied to the radial outside edges of the thin ribs 17. 20, defined to be A and the lateral variation of the smaller land portion, when lateral force at a value that the land portion width M per peripheral distance 1cm is multiplied by two is applied to the radial outside edge of the land portion of width 10mm or more located on the sides of the thin ribs 17, 20, defined to be B, the lateral variation A is set within 1.2-7.9 times as large as the lateral variation B.

Description

DETAILED DESCRIPTION OF THE INVENTION The above invention relates to a pneumatic tire in which a circumferential groove and narrow ribs are formed in the tread portion.

BACKGROUND ART Conventional pneumatic tires such as those shown below are known, for example. This tire has a stepped area on the land part of the pneumatic tire that is stepped down from the cross-sectional contour of the tread, bisects the land part by a pair of narrow grooves or sipes continuous around the tread, and has a step area that is independent from the two. The surface of this step area is provided with an uneven wear victim part that makes full contact with the road surface within the tread surface area that supports the load acting on the tire. In this case, when the pneumatic tire runs straight, the surface of the step area slides into contact with the road surface within the tread surface area, so an extremely large shearing force in the braking direction is generated in the step area. The shearing force on the land portions on both sides is shifted up toward the driving side, and as a result, the shearing force in the driving direction is applied to the surrounding land portions.

Here, the wear rate of the tread surface receiving shear force in the driving direction is significantly slower than the wear rate of the tread surface receiving shear force in the braking direction, so only the step area receiving shear force in the braking direction is sacrificed and wears out. Therefore, uneven wear on the land portion is suppressed.

Here, pneumatic tires purchased by users are used in various ways, with the main driving being straight-line or turning, but pneumatic tires with a step area as mentioned above Although it can reliably suppress the uneven wear of the land part when traveling straight, it has no effect on uneven wear of the land part when running in a straight line, and as a result, it is only partially effective in suppressing uneven wear. There was only a certain effect. .

An object of the present invention is to provide a pneumatic tire that can reliably suppress uneven wear on the land portion either when traveling straight or when turning.

This purpose is to form at least one pair of circumferential grooves that extend continuously in the circumferential direction in the tread portion, and to form thin ribs that extend in the circumferential direction between the pairs of circumferential grooves. In the pneumatic tire, the width of the land portion located on at least one side of the thin rib is 10 mm or more, and the width of the land portion located on at least one side of the thin rib is 1 cm or more in the circumferential direction at the outer end in the radial direction of the thin rib.
The lateral force (kg) is the width (cm) of the narrow rib multiplied by 2.
) is applied to the thin rib, and the amount of lateral deformation of the thin rib is A, and the land portion is I! When a lateral force (kg) of a value obtained by multiplying (cm) by 2 is applied, and B is the smaller lateral deformation amount of the land section, the lateral deformation amount A is 1.2 of the lateral deformation amount B. from double
This can be achieved by keeping it within the range of 7.9 times.

Function: Let us now assume that a pneumatic tire whose land portion and thin ribs are at approximately the same height is traveling straight. Here, since the amount of lateral deformation of the thin ribs of the pneumatic tire is larger than that of the lateral land portions as described above, the compression rigidity in the radial direction is also lower than that of the lateral land portions. For this reason, when the thin ribs are subjected to compressive force due to contact with the ground, the rubber escapes in the width direction and the ribs become depressed from the side land portions. When the narrow rib is recessed from the side land portion in this manner, the surface of the narrow rib slides into contact with the road surface, and an extremely large shearing force in the braking direction is generated in the narrow rib. As a result, the shearing force in any land portion of the narrow rib is shifted up toward the drive side, and as a result, a shearing force in the driving direction is applied to the land portion.

Here, the wear rate of the land part receiving shear force in the driving direction is significantly slower than the wear rate of the land part (thin rib) receiving shear force in the braking direction, so the thin rib receiving shear force in the braking direction This causes sacrificial wear, and uneven wear of the land portions on the sides of the thin ribs is suppressed. Note that if the narrow ribs are recessed from the land portion from the beginning, the above-mentioned suppressing effect will be exhibited from the start of straight travel.

When a pneumatic tire in which the land portion and the thin rib are approximately at the same height is driven around, the thin rib and the land portion receive lateral force, but at this time, the thin rib has a larger amount of lateral deformation than the land portion. Because it is large (low shear stiffness in the width direction) and easily deforms laterally, the burden of lateral force is smaller than on land, and the amount of wear is also reduced.
The lateral land portions wear out before the narrow ribs, resulting in the narrow ribs protruding from the lateral land portions. And when the thin ribs come to protrude from the side land parts like this,
The amount of lateral deformation of the thin ribs is considerably larger than that of the land portions on the sides, and as a result, the ground pressure on the land portions in the direction of lateral force action (inside in the width direction) becomes uniform, preventing the occurrence of local wear. is,
This suppresses uneven wear of the land portion on the widthwise inner side of the narrow rib. Note that if the thin ribs protrude from the land portion from the beginning, the above-mentioned suppressing effect is exhibited from the start of travel.

In this way, uneven wear on the land part is suppressed both when traveling straight and when turning, and even when the driving style changes, the tapered tabs are recessed or protruded depending on the driving style, so that the land part wears smoothly. Uneven wear is suppressed.

Point] L Example A first embodiment of the present invention will be described below based on the drawings.

In Fig. 1.2, 1 is a pneumatic radial tire, and on the surface of the tread portion 2 of this tire 1, there are a plurality of (three in this embodiment) linear treads extending continuously in the circumferential direction. A main groove 3 is formed. Although the main grooves 3 extend linearly, they may also extend in a zigzag pattern. Here, the main grooves 3 are such that when the tire 1 is rolling under load, the groove walls contact each other in the ground contact area. The groove is wide enough to avoid any damage. By forming a plurality of main grooves 3 in the tread portion 2 in this way, the tread portion 2 has a land portion, specifically, these three main grooves, the outermost main groove 3 in the axial direction, the tread end 4, 5, two center ribs 6a, 6b and two shoulder ribs 7a, 7b extending in the circumferential direction are defined, respectively.

A pair of linear circumferential grooves 11112 and 13.14 that extend continuously in the circumferential direction are formed at both ends of the tread portion 2 in the width direction, that is, on the outer sides of the shoulder ribs 7a and 7b in the width direction, respectively. Circumferential groove 11.12.1
3.14 is a narrow groove with a narrow width that closes when it touches the ground.

As a result, the shoulder rib 7a has these circumferential grooves 11.12.
It is divided into two parts, an outer land part 15 and an inner land part 16, and narrow ribs 17 extending in the circumferential direction are defined between these circumferential grooves 1.1.12. It is divided into an outer land portion 18 and an inner land portion 19 by the grooves 13 and 14, and these circumferential grooves 13.
A narrow rib 20 extending in the circumferential direction is defined between the ribs 14. Note that the circumferential grooves 11, 12, 13, and 14 do not need to extend in the circumferential direction in a strict sense, but only need to extend approximately in the circumferential direction, and may also be bent in a zigzag shape. Here, the thin rib 17.20 and the outer and inner land portions 15.18.16.
Same height as 19 (flush), details: thin rib 17.20
The outer end surface in the radial direction is an outer land portion 15.18 and an inner land portion]6
．． It is located on the extension line of the outer contour line of No. 19.

Further, the outer land portion 15, the inner land portion 16, the outer land portion 18, and the inner land portion 1 located on both sides of the narrow rib 17.20 in the axial direction.
At least one of 9 must have a width W of 10 m+a or more. The reason is that if the width W of the land portions located on both sides is less than 10 mm, the narrow rib 17.2
Even if 0 has the relationship as described later with the outer land portion 15.18 and the inner land portion 16.19, the width direction shear rigidity of these thin ribs 17.20 becomes too low and the uneven wear suppressing effect is lost. It is. In this embodiment, the inner land portion 16.
19 both have a width W of 10 mm or more, here both are 1
9mm, but the outer land portion 15.18 is both IiW
is 10 mm or less, here 6 mm.

Further, when a lateral force (kg) of a value obtained by multiplying the width L (cm) of the narrow rib by 2 per 1 cm of circumferential distance is applied to the outer end of the narrow rib 17.20 in the radial direction, the narrow rib 17.20
The amount of lateral deformation of
6.19) The amount of lateral deformation of these land parts when a lateral force (kg) of a value equal to the width M (cm) of the land part multiplied by 2 per 1 cm of circumferential distance is applied to the outer end in the radial direction of The one with the smaller value (in this embodiment, only the width W of the inner land portions 16.19 is 10+am or more, so the inner land portions 16.
The amount of lateral deformation A is within the range of 1.2 times to 7.9 times the amount of lateral deformation B.

Then, when the amount of lateral deformation A is within the above-mentioned range with respect to the amount of lateral deformation, it functions as follows.

That is, when the tire l as described above travels straight, the thin ribs 17.20, which have low compression rigidity in the radial direction, receive compressive force due to contact with the ground, and their rubber escapes in the width direction, causing the inner land portions 16.19
It becomes more concave, and like this the thin rib 17.2
0 is recessed from the land portion 16.19, the surface of the narrow rib 17.20 slides into contact with the road surface, and an extremely large shearing force in the braking direction is generated on the narrow rib 17.20. The shear forces on the land portions 16.19 on the sides of the .

Here, the wear rate of the land portion receiving shear force in the driving direction, that is, the inner land portion 16.19, is significantly slower than the wear rate of the land portion receiving shear force in the braking direction, that is, the narrow rib 17.20. The thin ribs 17.20, which are subjected to the shearing force in the braking direction, wear out at the cost, and uneven wear of the inner land portions 16.19 on the sides of the narrow ribs 17.20 is suppressed. In this way, these thin ribs 17 and 20 are sacrificed and worn out, so if you go straight for a certain distance, the side land portions 16
．． Although it is recessed from 19, when it is recessed in this way, it functions in the same manner as described above, and uneven wear is subsequently suppressed. On the other hand, when the tire 1 as described above is turned, the thin ribs 17.20
, the inner land portions 16.19 are subjected to lateral force, but at this time, the thin ribs 17.20 have a larger amount of lateral deformation than the side land portions 16.19, that is, they have low shear rigidity in the width direction and are easily lateral deformed. ,
The burden of lateral force is smaller than that of the land part, and the amount of wear is also reduced, and as a result, the lateral land part 16.19 becomes thin rib 17.20.
As a result, the narrow ribs 17.20 protrude from the land portions 16.19 on both sides. When the thin ribs 17.20 protrude from the side land portions 16.19 in this way, the amount of lateral deformation of the thin ribs 17.20 is considerably larger than the amount of lateral deformation of the land portions 16.19 on both sides. As a result, when the lateral force Y is acting from the direction of action of the lateral force (inner side in the width direction), for example from the right side in FIG. The ground pressure becomes uniform and local wear is prevented. In this way, uneven wear of the inner land portion 16.19 located on the widthwise inner side of the narrow rib 17.20 is suppressed. In this way, in the tire 1 of this embodiment, uneven wear on the land portion is suppressed both when traveling straight and when turning, and even when the running mode changes, the thin ribs 1
7.20 is recessed or protruded, and uneven wear on the land portion is suppressed. On the other hand, the amount of lateral deformation A is the amount of lateral deformation B
If it is less than 1.2 times the amount of lateral deformation, as described later, the thin rib will wear by the same amount as the surrounding land area, and uneven wear will not be suppressed at all. If it exceeds 7.9 times, the thin ribs bear almost no lateral force as described later, so
Since it protrudes when traveling both straight and when turning, and uneven wear is not suppressed at all, the value of the amount of lateral deformation A relative to the amount of lateral deformation B must be within the above-mentioned range. Furthermore, the value of the lateral deformation amount A relative to the lateral deformation amount B is 1.4 to 4.
．． A range of 0 is preferred. The reason is that within this range, as shown in the test results described later, the depth of uneven wear during mainly straight-line driving can be significantly reduced. In order to suppress uneven wear from the beginning of running, it is preferable to make the thin rib 17.20 and the land portions 15.16.18.19 on both sides almost the same height as in this embodiment. .

For example, as shown in FIG. 3, the measurement of the amount of lateral deformation is performed using
Attaching one end of the easily bendable sheet 33 to 2,
The other end of the sheet 33 is hung around a rotatable roller 34, and a weight 35 of a predetermined weight is attached to the other end, so that a circumferential distance of 1 cm is applied to the outer end of the thin rib 31 in the radial direction.
A lateral force (kg) of a value obtained by multiplying the width (cm) of the thin rib 31 by 2 is applied to the thin rib 31, and in this state, the amount of deformation at the outer end in the radial direction of the thin rib 31 is measured.

On the other hand, the amount of deformation in the land portion having a width of 10 mm or more located on the side of the thin rib 31 is also measured in the same manner as described above.

FIG. 4 is a diagram showing a second embodiment of the invention. In this embodiment, at least one of the pair of circumferential grooves 40 and 41, here the side wall of the circumferential groove 40, is provided with unevenness. In this way, the radial compressive rigidity of the thin ribs 42 can be improved while maintaining the shear stiffness in the width direction of the thin ribs 42, thereby allowing the thin ribs 42 to protrude at an early stage when turning. . Also,
In this embodiment, the remaining circumferential groove 41 has a wide width, that is, a width that does not close even when the vehicle touches the ground.

FIG. 5 is a diagram showing a third embodiment of the present invention. In this embodiment, one of the pair of circumferential grooves 45 and 46 is a sipe.

FIG. 6 is a diagram showing a fourth embodiment of the invention. In this embodiment, the narrow ribs 51 are inclined so as to approach the tread ends 4 and 5 as they go radially inward.

! @Figure 7 is a diagram showing a fifth embodiment of the present invention. In this embodiment, one of the circumferential grooves, here the circumferential groove 55, is deeper than the remaining circumferential groove 56.

FIG. 8 is a diagram showing a sixth embodiment of the present invention. In this embodiment, the thin ribs 58 are formed on the land portions 59 on both sides from the beginning.
．． It is made to protrude from 60. If the thin ribs 58 are made to protrude from the beginning in this way, it is advantageous when the vehicle mainly runs in turns since the above-mentioned suppressing effect is exhibited from the start of travel, but when the vehicle mainly travels straight ahead, the narrow ribs 58 are advantageous. There is a drawback in that the rib 58 cannot be expected to have a suppressing effect until the land portions 59 and 60 on both sides wear out to approximately the same height.

FIG. 9 is a diagram showing a seventh embodiment of the present invention. In this embodiment, the thin ribs 62 are connected to the land portions 63 on both sides from the beginning.
．． It is recessed from 64. If the thin ribs 62 are recessed from the beginning in this way, it is advantageous when the vehicle mainly travels in a straight line because the above-mentioned suppressing effect is exhibited from the start of travel, but when the vehicle primarily travels in turns, the narrow ribs 62 are recessed from the beginning. There is a drawback that a suppressing effect cannot be expected until the rib 62 protrudes.

FIG. 10 is a diagram showing an eighth embodiment of the present invention. In this embodiment, a horizontal groove 68 is formed in the axially inner land portion 67 to define a plurality of blocks 69, and the width of the thin rib 70 is adjusted from the kicking end 71 of each block 69 to the stepping end 72. It is changed periodically so that it becomes narrower according to the following.

FIG. 11 is a diagram showing a ninth embodiment of the present invention. In this embodiment, a thin rib 77 is formed by continuously arranging columnar projections 76 in a circumferential direction with their outer peripheral surfaces in contact with each other. In this way, the circumferential rigidity of the narrow ribs 77 is reduced, so that even if the narrow ribs 77 are wide, they protrude early during turning.

Next, a test example will be explained. For this test, 1.
The width of the inner land area is 1 with the tread pattern shown in Figure 2.
Seven types of tires were prepared in which the width of the outer land portion was constant at 9 mm and the width of the outer land portion was 6 mm, and the width of the thin rib was varied to vary the value of the amount of lateral deformation B relative to the amount of lateral deformation A. That is,
A comparative tire 1 in which the lateral deformation amount A is 1.0 times the lateral deformation amount B, a comparative tire 2 in which the lateral deformation amount A is 8.1 times the lateral deformation amount B, and a comparative tire 2 in which the lateral deformation amount A is 8.1 times the lateral deformation amount B. 1°2 of lateral deformation amount B
The test tire 1 is twice as large as the lateral deformation amount A, and the lateral deformation amount B is
test tire 2, in which the lateral deformation amount A is 2.0 times the lateral deformation amount B, and test tire 3, in which the lateral deformation amount A is 4.0 times the lateral deformation amount B. A test tire 4 has a lateral deformation amount A of 7.9 times the lateral deformation amount B, and a test tire 5 has a lateral deformation amount A that is 7.9 times the lateral deformation amount B. The amount of lateral deformation (smaller amount of lateral deformation) B of the inner land portion of the test tire 1 is actually 0.9 m.
+a, and on the other hand, the amount of lateral deformation A of the thin rib is actually 1
．． It was 1 mm. Here, each of these tires had a primary size of 6.5OR16gPR, and each of these tires was filled with an internal pressure of 4.25kg/crrf, and a load of 870kg was applied to each tire. I attached it to the front wheel of the vehicle and was able to drive it for 60,000 +a constant driving hours. Here, 80% of driving is mainly straight-ahead driving on expressways.
, the vehicle is driven on a road with 20% of the road being a general road, while when driving mainly by turning, the vehicle is driven on a road where 70% is a mountain board and 20% is a general road.
, 10% of the roads were highways. After traveling the above distance, measure the width and depth of the worn part of the land located on one side of the tire's equatorial plane, and for the width, the total value is the uneven wear width, while for the depth, the average was taken as the uneven wear depth. The results and the condition of the thin ribs are shown in the attached table.As can be understood from this attached table, the amount of lateral deformation A
is within the range of 1.2 to 7.9 times the amount of lateral deformation B, regardless of whether the vehicle is traveling mainly straight or mainly turning.
Uneven wear is significantly suppressed.

1. As explained above, according to the present invention, it is possible to reliably suppress the uneven wear of the land portion whether the vehicle is traveling straight or turning.

[Brief explanation of drawings]

FIG. 1 is a developed view of a tread portion showing a first embodiment of the present invention, FIG. 2 is a meridian sectional view thereof, and FIG. 3 is a perspective view illustrating a state in which the amount of lateral deformation of a thin rib is measured. FIG. 4 is a meridional sectional view showing the main parts of the second embodiment of the invention, FIG. 5 is a meridian sectional view showing the main parts of the third embodiment of the invention, and FIG. 6 is the fourth embodiment of the invention. 7 is a meridian sectional view showing the main parts of the fifth embodiment of the present invention; FIG. 8 is a meridian sectional view showing the main parts of the sixth embodiment of the invention; FIG. 9 is a meridian sectional view showing the main parts of the seventh embodiment of the invention, FIG. 10 is a developed tread view showing the main parts of the eighth embodiment of the invention, and FIG. 11 is a ninth embodiment of the invention. FIG. 3 is a developed tread diagram showing main parts of an example. 2... Tread part 11.12.13.14... Circumferential groove 15.16.17.18... Land part 17.20... Thin rib

Claims (1)

[Claims] A pneumatic tire in which at least one pair of circumferential grooves extending continuously in the circumferential direction is formed in the tread portion, and thin ribs extending in the circumferential direction are formed between the pairs of circumferential grooves, wherein the thin ribs The width of the land portion located on at least one side of the thin rib is 10 mm or more, and the width of the thin rib (
Let A be the amount of lateral deformation of the thin rib when a lateral force (kg) with a value of cm) multiplied by 2 is applied, and the radius of the land portion with a width of 10 mm or more located on the side of the thin rib. When a lateral force (kg) of a value obtained by multiplying the width (cm) of the land part by 2 per 1 cm of circumferential distance is applied to the outer end of the direction, the amount of lateral deformation of the smaller land part is defined as B, Said lateral deformation amount A
A pneumatic tire characterized in that the amount of lateral deformation B is within a range of 1.2 to 7.9 times.