JP2966488B2 - Pneumatic radial tire - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a pneumatic radial tire capable of improving running on sand and improving high-speed running on a pavement.

[Conventional technology]

In recent years, four-wheel drive vehicles that enable off-road travel, and even high-floor four-wheel drive vehicles, are becoming widespread.

Such a four-wheel drive vehicle not only runs on a sandy surface such as a desert, but also needs to run at high speed even on a paved road. In particular, vehicles used in the Middle East require high-speed running performance of 160 km / H or more on paved roads in addition to sandy road running performance.

Conventionally, as a tire for running on sand, as shown in FIG. 5, a tire having a flatness of about 95% and a constant radius of curvature r on the tire meridional surface of the tread surface has been used. However, when running at high speeds with such a tire, high-speed durability such as poor steering stability and riding comfort, cracks in the tread, peeling of the belt layer edge, and uneven wear occur. Inferior.

The present inventors have paid attention to the fact that the tread surface shares functions in the central region, the intermediate region, and the outer region in the cross section in the meridian direction, and regulate the cross-sectional shape in each region. He completed the invention.

The invention according to claim 1 is based on the fact that the tire surface is virtually divided into three regions and the radius of curvature of each region is regulated, so that the running performance on sand is improved and the running stability at high speed running on a pavement road is improved. In addition to the above, the invention according to claim 2 provides a pneumatic radial that can solve the above-mentioned problems by, for example, exhibiting sufficient durability while increasing buoyancy by setting the tire to a low internal pressure when running on sand. It aims to provide tires.

[Means for solving the problem]

The present invention relates to a carcass comprising at least one carcass ply that turns around a bead core of a bead portion from a tread portion through a sidewall portion, and at least one belt ply disposed inside the tread portion and outside the carcass. Flatness ratio (H1 / WA), which is the ratio of the tire section height (H1) to the tire maximum width (WA).
Is a pneumatic radial tire of not less than 0.55 and not more than 0.70, and the tire surface extending from the tread portion to the sidewall portion in a standard state mounted on a standard rim and filled with a standard internal pressure has a tread width (WT). 0.17
A first section (P) separating the tire equator on both sides by a distance of 5 times, a central area (SC) between the (P) and 0.4 times the first section (P) and the tread width (WT). Intermediate region (SM) between the second segment (Q) separating the distance from the tire equator
And 0.6 of the second section point (Q) and the tread width (WT).
The radius of curvature (RC) of the meridian plane of the tire in the central area (SC) virtually divided into the outer area (SO) between the outer end point (O) and the outer end point (O) separated from the tire equator by twice the tread width (WT)
3.1 times or more and 3.4 times or less, and the radius of curvature (RM) of the tire meridian in the middle area (SM) should be 2.2 times or more and 2.5 times or less the tread width (WT), and to improve running on sand. A pneumatic radial tire characterized in that the radius of curvature (RO) of the tire meridional surface in the outer region (SO) is formed to be 0.22 times or more and 0.28 times or less the tread width (WT).

The belt layer is preferably covered on both sides of the belt ply with a band layer composed of at least one band ply in which organic fiber cords are juxtaposed.

[Action]

By setting the radius of curvature RC of the central region SC to be in a range of 3.1 to 3.4 times the tread width WT, the contact surface in the region SC increases, wear resistance on pavement roads is increased, and steering stability is improved.

In addition to the configuration of the central region SC, the radius of curvature RC of the intermediate region SM is set to a range of 2.2 to 2.5 times the tread width WT, so that the conventional tread shown in FIG. 5 is formed with a single radius of curvature. As compared with the structure, the contact area increases in the circumferential direction of the tire, and the contact pressure decreases, so that the durability in high-speed running on a pavement can be enhanced.

In the middle area SM, the difference in circumference between the center area SC and the center area SC is small, which reduces slippage during high-speed running, reduces rolling resistance, and prevents heat generation, thereby improving durability. Can improve.

Further, in the outer region SO, the radius of curvature RO is set to the tread width.
Since it is 0.22 to 0.28 times the WT, the radius of curvature RO in the outer region is significantly smaller than that of the conventional tire formed with a single radius of curvature shown in FIG. 5, and therefore, when traveling on sand,
Sand can be efficiently discharged from the outer region, and traveling performance on sand can be improved.

Further, in the outer region SO, when traveling on a pavement road, there are few regions where the tire comes into contact with the ground, the deformation of the tire near the tread edge can be suppressed, the separation of the belt layer can be prevented, and the durability of the tread portion can be improved.

As described above, in the present invention, the respective regions are integrated, and the high-speed traveling performance and the durability on the pavement road can be improved without lowering the traveling performance on sand. Also, when both sides of the belt layer are covered with the band layer, even when the tire air pressure is set to a low internal pressure in order to improve the levitation force for off-road traveling, the side of the belt layer due to the deformation of the tread portion. The peeling can be prevented, and the durability can be further improved in any case of running on a pavement road at high speed.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

In the figure, a pneumatic radial tire 1 includes a carcass 6 that passes from a tread portion 2 through a side wall portion 3 and turns around a bead core 5 of a bead portion 4, and a belt disposed inside the tread portion 2 and outside the carcass 6. And a layer 7.

The pneumatic radial tire 1 has an aspect ratio (H1 / WA) of 0.5, which is the ratio of the tire section height H1 to the tire maximum width WA.
It is formed as a flat tire having a value of 5 or more and 0.70 or less. Here, the tire section height H1 refers to a distance from the bead bottom surface of the bead portion 4 to the outermost end of the tread portion 2 in the tire radial direction.

Further, the pneumatic radial tire 1 virtually divides the tire surface A extending from the tread portion 2 to the sidewall portion 3 into a central region SC, an intermediate region SM, and an outer region SO. The radius of curvature of the tire meridian is regulated within a certain range.

In this embodiment, both sides of the belt layer 7 are
Covered by

The carcass 6 has one or more radially arranged carcass cords inclined at an angle of 85 to 90 degrees with respect to the tire equator C, and in the present embodiment, two inner and outer carcass plies 6A,
6B, and the carcass plies 6A and 6B extend from the tread section 2 through the side wall section 3 to the bead section 4.
6a and a winding portion 6b connected to the main body 6a and winding up the bead core 5 from the inside to the outside in the tire axial direction. In this embodiment, the height H2 from the bead bottom surface 12 at the tip of the winding portion is set to 0.6 times or less the tire cross-sectional height H1,
The ride is improved.

As the carcass cord, an organic fiber cord such as polyester, nylon, rayon, or aromatic polyamide, and in this embodiment, a polyester cord obtained by twisting two strands having a denier of 1500d are used.

The belt layer 7 is composed of at least one belt ply 7A, 7B in the present embodiment, and each of the belt plies 7A, 7B has a belt cord made of steel arranged in a direction to intersect at an angle of 16 to 24 degrees. Therefore, this belt cord exhibits a hammering effect with the carcass cord, increases the rigidity of the tread portion 2 in tandem with the use of the steel cord, and aims to improve wear resistance and steering stability. . As the belt cord, other than steel, an organic fiber cord having a large initial elastic modulus such as an aromatic polyamide can be used.

The band layer 10 includes one or more, in this embodiment, two band plies 10A, 10B that cover both side portions F, F of the belt layer 7 from outside in the tire radial direction.

The band plies 10A and 10B consist of a sheet body in which two 840 denier nylon strands are twisted together and band cords are juxtaposed and embedded in topping rubber.
10 is the width WB of the belt layer 7 in the vicinity of both sides F and F of the belt layer 7.
It is desirable to cover at least 0.2 times of. The band layer 10 is
The belt layer 7 may be entirely covered from the outside in the radial direction.

The band cord, in combination with the curvature of the outer region described later, enables the pneumatic radial tire to be used at a low internal pressure for off-road driving, and even when the internal pressure is low, the tread portion 2 is deformed. To prevent the side portions F, F of the belt layer 7 from being peeled off and to increase the durability, and also to prevent the tread portion 7 from being damaged even when traveling at high speed on a pavement road, thereby improving the durability at high speed traveling. Can be improved.

The bead portion 4 is fitted into a standard rim J having a bead seat surface on which the bead bottom surface 12 sits.

As described above, the tire surface A is virtually divided into the central area SC, the intermediate area SM, and the outer area SO.

The pneumatic radial tire 1 is mounted on the standard rim J, and the lumen 9 formed between the pneumatic radial tire 1 and the standard rim J
In the standard state where the standard internal pressure is
Is defined as the distance between the first division points P, P which separates the distance 0.175 times the tread width WT from the tire equator C on both sides. Central area SM
Is defined as a distance between the first division point P and the second division point Q that is 0.4 times the tread width WT separated from the tire equator C. Further, the outer region SO is defined by the second division point Q and the tread width WT. WT
Is 0.6 times the distance between the outer end point O and the tire equator C. The tread width WT is the tread edge E,
E means the distance in the tire axial direction.

Here, the radii of curvature RC, RM, and RO on the meridian of the tire in each of the regions SC, SM, and SO are regulated as follows.

In the central region SM, the radius of curvature RC is set to be 3.1 times or more and 3.4 times or less the tread width WT, and in the central region SM, the radius of curvature RM is set to be 2.2 times or more and 2.5 times or less the tread width WT. Further, in the outer region SO, the radius of curvature RO is set to be 0.22 times or more and 0.28 times or less of the tread width WT.

The regulation of the radii of curvature RC and RM in the central area SC and the intermediate area SM is intended to make the shape of the ground contact surface S rectangular or elliptical as shown in FIGS. 2 (a) and 2 (b).
The radius of curvature RC is less than 3.1 times the tread width WT in the central area SC, or the radius of curvature RM is tread width WT in the middle area SM.
When it exceeds 2.5 times, the shape of the ground contact surface S becomes drum-shaped as shown in FIG. 3 (a), and the wear resistance is poor.
If the radius of curvature RC exceeds 3.5 times the tread width WT in the central region SC, or if the radius of curvature RM is less than 2.2 times the tread width WT in the middle region SM, the shape of the contact surface S is as shown in FIG. As shown in the figure, the rhombus has a diamond shape, causing uneven contact with the tire in the vicinity of the equator C, and lacks steering stability.

In the outer region SO, the radius of curvature RO is the tread width.
If the WT is less than 0.22 times, when running on sand, poor sand discharge is likely to occur, resulting in poor sand running performance. Conversely, tread width WT
If it exceeds 0.28 times, the sand discharge efficiency will decrease and the ground surface S
4 swells on both sides as shown in FIG. 4, resulting in imbalance in the contact with the ground, and in particular, durability during high-speed running is reduced.

[Specific Example] Tires (Examples 1 to 6) having a tire size of 275 / 65R15 with the configuration shown in FIG. 1 and the specifications shown in Table 1 were prototyped, and the performance was tested. For comparison, a tire having a conventional structure (Comparative Example 1) and a tire having a structure other than that of the present application (Comparative Example 2)
5) were also manufactured and tested.

The conventional tire of Comparative Example 1 has a tire size of 900
-15, flatness 0.95, carcass This is a bias tire having a loss ply configuration.

 The test was performed under the following conditions.

(1) Abrasion resistance test After a test tire was mounted on an actual vehicle and traveled for a distance of 10.000 km, the amount of wear in the tread portion was measured, and the reciprocal value was indicated by an index with Comparative Example 1 being 100. The higher the numerical value, the better, and more than 120 are acceptable.

(2) Ride comfort and steering stability Equipped on an actual vehicle, judgment was made based on the feeling of the test driver, and the index was set as an index with the comparative example as 100. In each case, the larger the numerical value, the better, and 110 or more is a pass.

(3) Sand traveling performance The time required for traveling on the sand by 50 m while being mounted on an actual vehicle was measured, and the index was set as an index with Comparative Example 1 being 100. The smaller the value, the better, and 90 or less is acceptable.

(4) High-speed durability Using a drum tester, the tire internal pressure was set to 2.6 kg / cm ^{2 and} a load of 1030 kg was applied. After running at 80 km / H for 120 minutes, the speed was increased by 10 km / H every 30 minutes. The traveling speed when the damage occurred and the traveling time at the traveling speed were measured. Those that can run at a speed of 200km / H or more are acceptable.

(5) Low internal pressure durability A tire internal pressure was set to a low internal pressure of 1.0 kg / cm ² , and a durability test was performed using a drum test machine under a load of 1030 kg. The numerical values in the table indicate the total running distance when the tread was damaged.

As a result of the above test, it was found that the example was superior to the comparative example.

〔The invention's effect〕

As described above, the pneumatic radial tire of the present invention divides the tire surface into three regions in the circumferential direction and regulates the radius of curvature on the tire meridian plane in each region. The running stability and durability in running can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, and FIG.
FIGS. 3 (a) to 3 (b), FIGS. 3 (a) to 3 (b) and FIG. 4 are plan views schematically showing the shape of the grounding surface, and FIG. 2 ... tread part, 3 ... side wall part, 4 ... bead part, 5 ... bead core, 6 ... carcass, 6A, 6B ... carcass ply, 7 ... belt layer, 7A, 7B ... belt ply , 10 ... band layer, A ... tire surface, C ... tire equator, H1 ... tire section height, J ... rim, O ... outer end point, P ... first division point, Q ... Second section point, RC, RM, RO: radius of curvature, SC: central area, SM: middle area, SO: outer area, WA: maximum tire width, WT: tread width.

Continuation of the front page (56) References JP-A-2-133201 (JP, A) JP-A-62-91303 (JP, A) JP-A-1-309805 (JP, A) JP-A-63-301107 (JP, A) , A) Japanese Utility Model Showa 61-35004 (JP, U) Japanese Utility Model Utility Model 1-87003 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) B60C 3/04 B B60C 9/08 C B60C 9/18 K B60C 11/01 B

Claims (2)

(57) [Claims] 1. A carcass comprising at least one carcass ply that turns around a bead core of a bead portion from a tread portion through a sidewall portion, and at least one belt disposed inside the tread portion and outside the carcass. Flatness (H1 / WA), which is the ratio of the tire section height (H1) to the tire maximum width (WA), with a belt layer consisting of plies
Is a pneumatic radial tire of not less than 0.55 and not more than 0.70, and the tire surface extending from the tread portion to the sidewall portion in a standard state mounted on a standard rim and filled with a standard internal pressure has a tread width (WT) The first section (P), which is 0.175 times the distance from the tire equator on both sides, the central area (SC) between (P), 0.4 times the first section (P) and the tread width (WT) Area (SM) between the second point (Q) separating the tire distance from the tire equator
And 0.6 of the second section point (Q) and the tread width (WT).
The radius of curvature (RC) of the meridian plane of the tire in the central area (SC) virtually divided into the outer area (SO) between the outer end point (O) and the outer end point (O) separated from the tire equator by twice the tread width (WT)
3.1 times or more and 3.4 times or less, and the radius of curvature (RM) of the tire meridian in the middle area (SM) should be 2.2 times or more and 2.5 times or less the tread width (WT), and to improve running on sand. A pneumatic radial tire characterized in that a radius of curvature (RO) of a meridian plane of the tire in the outer region (SO) is formed to be 0.22 times or more and 0.28 times or less of a tread width (WT). 2. The pneumatic radial tire according to claim 1, wherein the belt layer is formed by covering both side portions of the belt ply with a band layer composed of at least one band ply in which organic fiber cords are juxtaposed.