JP2001301425A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire remarkably enhancing partial wear resistance by remarkably reducing the local wear of a shoulder part (a shoulder rib) in turning and in straight traveling. SOLUTION: In the section of an assembly of the tire in the maximum pneumatic state and an applicable rim, (1) the shoulder rib formed with a circumferential direction groove has a complex contour of a projecting curve having a center of curvature on the inside of the tire on the circumferential groove side and a recessed curve connected to the projecting curve through an inflection point of the projecting curve and having a center of curvature on the tire outside on a ground width end side, and (2) in a grade in the tire shaft direction, the grade K2 of a tangent of the recessed curve passing the ground width end is smaller than a grade K1 of a straight line connecting the circumferential direction groove edge of the shoulder rib and the tire ground width end.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire, and more particularly to a radial ply tire for use in heavy vehicles such as trucks and buses, and more particularly to an uneven wear resistance at shoulder ribs on both sides of a tread portion. It relates to a greatly improved pneumatic tire.

[0002]

2. Description of the Prior Art Pneumatic tires of the type mentioned at the beginning are:
When viewed from the cross section, the crown (tread surface) contour of the tread portion is formed by one or more arcs projecting outward in the tire radial direction. That is, a radius difference is provided between the radius of the tire equatorial plane or its vicinity and the radius of the shoulder part, regardless of the degree, so that when the vehicle turns, of the lateral force inevitably acting on the tire, This is based on the intention that the lateral force borne by the shoulder portion, in other words, the shear force in the width direction of the tread portion is set to an appropriate value so that no inconvenience occurs in the shoulder portion.

However, on the other hand, when the vehicle travels straight, a difference in rolling speed occurs due to the difference in radius. In particular, the difference in rolling speed between the tire equatorial plane or a position near the tire and the shoulder portion is remarkable. As a result, a braking force is generated in the shoulder portion, and the braking force promotes abrasion of the tread rubber in the shoulder portion, causes local wear, and causes so-called uneven wear. Such uneven wear is remarkable in the case of shoulder ribs defined by circumferential grooves provided on both side regions of the tread portion.

[0004]

To summarize the above, the local wear of the shoulder portion during turning and straight running of the vehicle has a trade-off relationship, and therefore, the crown contour of the cross section of the tread portion. It is difficult to improve both at the same time no matter how one or more arcs are adjusted.

Accordingly, an object of the present invention described in claims 1 to 5 of the present invention is to completely solve the above two trade-off problems, and more specifically, a shoulder portion between when the vehicle is turning and when traveling straight ahead. An object of the present invention is to provide a pneumatic tire in which local wear, particularly local wear of shoulder ribs, that is, uneven wear, is remarkably reduced to greatly improve uneven wear resistance.

[0006]

According to a first aspect of the present invention, there is provided a tread portion having a pair of sidewall portions and a pair of bead portions connected to both sides of the tread portion. A radial ply carcass that reinforces each of these portions between bead cores embedded in the bead portion, and a belt that strengthens the tread portion around the carcass outer periphery, and the tread portion is formed by circumferential grooves provided in both shoulder portions. In a pneumatic tire having a shoulder rib, the tire is mounted on a rim to which the tire is applied, and a cross section of an assembly of the tire and the rim filled with the maximum air pressure of the tire is: (1) The shoulder rib has a circumferential groove side. A convex curve having a center of curvature inside the tire, and a concave having a center of curvature outside the tire at the tire contact width end side, connected to the convex curve via an inflection point. Has a contour consisting of a composite curve with the curve, (2) per gradient with respect to the tire axial direction, the slope K ₂ tangent of the concave curve passing through the tire contact width end, the circumferential groove edge and the tire contact width end of the shoulder ribs a pneumatic tire characterized by having a smaller value than the than the gradient K ₁ of a straight line connecting and.

Here, the applicable rim and the maximum air pressure according to the first aspect are determined according to JATMA YEAR BOOK 1999, TRA 1999 YEAR
BOOK (THE TIRE and RIM ASSOCIATION INC.), ETRTO ST
Follow the contents described in standards such as ANDARD MANUAL 1999.
For example, in JATMA YEAR BOOK 1999, the applicable rims are the rims described in the table for each tire type and size, and the maximum air pressure is described in the air pressure-load capacity correspondence table for each tire type and size. Is the air pressure corresponding to the maximum load capacity. In ETRTO STANDARD MANUAL 1999, in the same table, applicable rims are described in APPPROVED RIM CONTOURS,
The maximum load capacity is described in LOAD CAPACITY PER AKLE, and the maximum air pressure is the INFLATION PRESSURE corresponding to the maximum load capacity.
It has been described in. The tire contact width ends described in claim 1 refer to both ends of the maximum axial distance in the tire axial direction based on the definition of “contact width” described in the general information section of the standard. However, the maximum air pressure is applied to “specified air pressure” in the definition, and the load corresponding to the maximum load capacity is applied to “specified mass”.

The gradients K ₁ , K ₂ are the inclination angles θ ₁ , θ _{2 of} the tangents having the straight line parallel to the tire axis on the plane including the tire axis as the original line (the angles θ ₁ , θ ₂ will be described later). ), Tan θ ₁ and tan θ ₂ , and the gradient K ₁ is tan
theta ₁ values, the gradient K ₂ is the value of tan .theta _2. The same applies hereinafter.

According to the invention described in claim 1, claim 2 is provided.
As described above, the inflection point is located in a region between the width center of the shoulder rib and the vicinity of both sides thereof.

According to the first and second aspects of the present invention, as in the third aspect of the invention, with respect to the tire axis extending outward from the tire, the gradient K ₂ of the tangent passing through the contact width end is changed from a downward gradient to an upward gradient. When the linear gradient K ₁ has only a downward gradient and the downward gradient is a positive value and the upward gradient is a negative value, the ratio K ₂ of the gradient K _{2 to} the gradient K ₁ . the value of ₂ / K ₁ is 1 -0.5 or more.
It is in the range less than 0.

According to the invention set forth in claims 1 to 3, as in the invention set forth in claim 4, in a cross section of a tire having an inner rib adjacent to a shoulder rib with the circumferential groove interposed therebetween, Projection length L _{1 of the} rib on the tire axis
The value A of the ratio H ₁ / L ₁ of the radius difference H ₁ obtained by subtracting the outer edge radius from the inner edge radius of the inner rib, and the inner edge of the shoulder rib relative to the projected length L ₂ of the shoulder rib on the tire axis. The value of the ratio B / A of the value B to the value A satisfies the relationship of less than 2.0 between the radius difference H ₂ and the value B of the ratio H ₂ / L ₂ obtained by subtracting the tire contact width end radius from the radius. .

According to the invention described in the first to fourth aspects, as in the invention described in the fifth aspect, on the contour of each of the shoulder ribs and the inner ribs, the radius is farther from the radius closer to the tire equatorial plane. The sign of the difference between the radii obtained by subtracting the radius of the position is given a positive or negative sign.
₁ has only a positive value, the radius difference H ₂ has a value ranging from positive to negative, and the value of the ratio B / A is −1.0.
Exists in the range of １．５1.5.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a right half sectional view of the pneumatic tire of the present invention, and FIG. 2 is an enlarged sectional view of a main part of the tire shown in FIG. In FIG. 1, a pneumatic tire (hereinafter referred to as a tire) 1 has a tread portion 2, a pair of sidewall portions 3 (only one side is shown) connected to both sides thereof, and a pair of bead portions 4. Also, tire 1
Is provided with a radial ply carcass 6 extending between the bead cores 5 embedded in the bead portion 4, and a belt 7 on the outer periphery of the carcass 6.

The carcass 6 is made of a rubber-coated ply having a radially arranged cord, and reinforces each part 2 to 4 of the tire 1. As the ply cord of the carcass 6, a high modulus and high strength cord such as a steel cord is preferably applied. Further, the belt 7 has two or more layers, in the illustrated example, four rubber-coated steel cord layers, and at least two adjacent layers form a cord crossing layer to strengthen the tread portion 2.

The tread portion 2 has circumferential grooves 8 on both shoulder portions thereof, and has a shoulder rib 9 defined by the circumferential grooves 8. Here, FIG. 1 shows a cross section of an assembly of the tire 1 and the rim 10 in which the tire 1 is assembled on an applicable rim 10 showing only a cross-sectional contour and the tire 1 is filled with the maximum air pressure. 1 and 2 show an example in which the tread portion 2 is provided with a separate circumferential groove 12 forming an inner rib 11 adjacent to the shoulder rib 9 with the circumferential groove 8 interposed therebetween. Can be omitted. The inner rib 11 at that time forms an integral rib between the two circumferential grooves 8.

Here, in the cross section shown in FIGS. 1 and 2, first, the shoulder rib 9 has at least two curves,
The illustrated example has a contour composed of a composite curve of two curves S ₁ and S ₂ . The curve S ₁ is a convex curve having a center of curvature C ₁ inside the tire 1 on the circumferential groove 8 side, and the curve S ₂ has a center of curvature C ₂ outside the tire 1 on the contact width end M side. It is a concave curve. At this time, the concave curve S ₂ becomes the convex curve S ₁
And smoothly via the inflection point Pi.

Next, as shown in FIG. 2, the inclination of the tire 1 with respect to the axial direction will be described with reference to the axis of the tire 1 (not shown).
Parallel to the said axis on the plane including the straight line T ₁ 2 present the following in the case of an original line of the straight line L passing through the contact width end M, the slope K _1, K ₂ tangent T ₂ is always the following relational Shall be satisfied. That is, the tangent T of the concave curve S ₂ passing through the contact width end M
₂ means that the slope K ₂ has a smaller value than the slope K ₁ of the straight line T ₁ connecting the inner edge N of the shoulder rib 9 and the contact width end M.

Incidentally, the gradient K ₁ is a tangent of the inclination angle θ ₁ of the straight line T ₁ with respect to the straight line L, that is, tan θ
_The slope K ₂ is a tangent of the inclination angle θ ₂ of the tangent T _{2 to} the straight line L, that is, a value of tan θ ₂ .

The shoulder rib 9 having the structure described above
Has the following effects. That is, one of the effects is that the contact start timing of the shoulder rib of the conventional tire is in the order from the inside of the tire to the outside of the tire on the contact stepping side of the tire 1 rolling under a load, whereas In the shoulder rib 9, at least in the region from the inflection point Pi to the contact width end M, the contact start timing of the shoulder rib 9 can be changed in the order from the outside of the tire to the inside of the tire. Timing is earlier than conventional tires.

When the tread portion 2 comes into contact with the ground, the tread portion 2 having a convex cross section as a whole is subjected to the action of forced bending deformation toward the tire equatorial surface E in conformity with a flat road surface. At this time, if the contact start timing of the contact width end M is advanced,
The deformation of the shoulder rib 9 toward the tire equatorial plane E at the time of contact with the ground is suppressed. On the other hand, since the contact width end M is located outside the tire 1 from the maximum width end of the belt 7, as a second effect, a cross-sectional view of FIG. As shown in (1), a shear force fw outward in the width direction of the tread portion 2 is generated in the shoulder rib 9 in the contact area.

FIG. 3 shows the shoulder rib 9 when the vehicle turns left.
Indicates the direction of the lateral force SF acting on the shoulder rib 9, that is, the outward shear force fw generated from the shoulder rib 9 in the contact area reduces the inward shear force SF. As a result, the inward shearing force acting on the shoulder rib 9 during turning of the vehicle is greatly reduced.

When the vehicle turns, the inward shearing force applied to the shoulder ribs 9 is greatly reduced, so that the acceleration of the wear of the shoulder ribs 9 due to the turning movement of the tire 1 is reduced. As a third effect of this reduction, the cross-sectional profile of the tread portion 2 can be optimized with respect to the wear of the shoulder rib 9 during straight running of the vehicle independently of the wear of the shoulder rib 9 during the turning motion, independently of the wear. After all, according to the first to third effects, it becomes possible to remarkably improve the uneven wear resistance associated with the edge wear of the shoulder rib 9.

An outward shear force f in the width direction of the tread portion 2
To increase to made the w, point Pi, it is effective to position near both sides in the areas which sandwich the width L ₂ central shoulder ribs 9.

As shown in FIG. 2, with respect to the axis extending toward the outside of the tire 1, more practically, of the straight line L, the straight line L extending from the contact width end M toward the outside of the tire 1.
The gradient K ₂ = tan θ ₂ of the tangent passing through the contact width end M has a gradient ranging from a downward gradient shown to an upward gradient not shown. The slope K ₁ = tan θ ₁ of the straight line T ₁ is only a down slope. The downward slope in a positive value, when representing the upward gradient in a negative value, the value of the ratio K ₂ / K ₁ for the gradient K ₁ gradient K ₂ is present in the range of less than 1.0 -0.5 or more I do.

When the value of the ratio K ₂ / K ₁ is less than −0.5, that is, when the absolute value of the negative value is more than 0.5, the amount of jump of the contact width end M becomes too large, and The vicinity including M is subject to forced wear, so that edge wear is likely to occur.

As shown in FIGS. 1 and 2, in the case of the tire 1 having the inner rib 11 adjacent to the shoulder rib 9 with the circumferential groove 8 interposed therebetween, the inner rib 1
Projected length L ₁ of the first tire axis, i.e. with respect to the distance L ₁ between the outer edge Q and the inner edge R of the inner rib 11, as measured parallel to the straight line L, the inner edge of the inner rib 11 R Ratio H ₁ / L of radius difference H ₁ obtained by subtracting the radius of the outer edge Q from the radius of
The value A of _{1 and} the length L _{2 of} the shoulder rib 9 projected on the tire axis, that is, the shoulder rib 9 measured in parallel with the straight line L
The relative distance L ₂ between the contact width edge M and the inner edge N, the value of the radius from the radius difference H ₂ obtained by subtracting the radius of the contact width edge M of the inner edge N ratio H of ₂ / L ₂ shoulder ribs B It is suitable that the ratio of the value B to the value A satisfy the relationship B / A of less than 2.0, and more preferably that the value of the ratio B / A is less than 1.5. .

[0027] In the case of the tire 1 without a separate circumferential groove 12, the projection length L ₁ is the distance between the outer edge Q and the tire equatorial plane E of the inner ribs 11, the difference between the radii H ₁
Adopts a value obtained by subtracting the radius of the outer edge Q from the radius of the inner rib 11 at the position of the tire equatorial plane E.

On the contours of the shoulder ribs 9 and the inner ribs 11, positive and negative signs are given to a radius difference obtained by subtracting a radius at a position farther from a radius at a position closer to the tire equatorial plane E, Radius difference H ₁ has only positive values, and radius difference H ₂ has values ranging from positive to negative. At this time, it is suitable that the value of the ratio B / A exists in the range of -1.0 to 1.5. This is because if the absolute value of the negative value of the ratio B / A exceeds 1, as in the case described above, the vicinity including the contact width end M is subjected to forced wear and edge wear is likely to occur.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A radial ply tire for trucks and buses, having a size of 315 / 80R22.5, has a structure according to FIGS. Tires 1 of Examples 1 to 6 are JATMA YE
In AR BOOK 1999, standard rim among applicable rims, ETRTO ST
In ANDARD MANUAL 1999, it is assembled to the rim 9.00x22.5 described in the MEASURING RIM WIDTH CODE,
O STANDARD MANUAL Filled with an internal pressure of 850 kP specified by 1999.

The tires of Examples 1 and 2 have a ratio K_Two / K₁ of
With respect to the values, the tires of Examples 3 to 6 have the values of the ratio B / A.
And Conventional tires 1 and 2 and Comparative tire 1 respectively.
Comparative evaluation was carried out with No. 2. Tires of Examples 1 and 2
Is K₁ = Tanθ₁ , K_Two = Tanθ_Two , And the ratio K_Two 
/ K₁ Table 1 shows the radius difference H of the tires of Examples 3 to 6.
₁ (Mm), H_Two (Mm), projection length L₁ (Mm), L
_Two Table 2 shows the values of (mm) and the ratio B / A.
The description includes tires 1 and 2 and comparative tires 1 and 2.

[0031]

[Table 1]

[0032]

[Table 2]

Each of the example tires, the prior art tires 1 and 2 and the comparative example tires 1 and 2 were used as test tires, and these tires were of a 2-D4 type (one front shaft, two rear wheels, D is a drive shaft, and numerical values are 1
Attached to the front wheels of a truck with a loading capacity of 98 kN with the number of mounted tires per axle). After running 10,000 km, the average wear amount of the shoulder rib 9 was measured. The measurement results are represented by an index with the value of the conventional tires 1 and 2 being 100, and the smaller the value, the better. The results are shown in Tables 1 and 2, respectively.

From the results shown in Table 1, the gradient K ₂ is equal to the gradient K ₁
The tires of Examples 1 and ₂ having a smaller value than that of the tire of Example 1 and the value of the ratio K ₂ / K _{1 in} the range of −0.5 or more and less than 1.0 are smaller than the tires of Conventional Example 1 by 9%. It can be seen that the wear amount of the shoulder rib 9 is significantly increased in the tire of Comparative Example 1 in which the abrasion amount of the shoulder rib 9 is significantly increased as compared with the conventional tire. From these facts, the tires of Examples 1 to 6 can further improve the wear resistance of the shoulder rib 9 during straight running as compared with the conventional tires 1 and 2.

[0035]

According to the first to fifth aspects of the present invention, in particular, edge wear, which is local wear of a shoulder rib inherent to a tire used as a steering wheel of a heavy vehicle, is remarkably reduced, and resistance to the tire is greatly reduced. The present invention provides a pneumatic tire that can significantly improve uneven wear, thereby completely solving a trade-off problem relating to local wear of shoulder ribs when the vehicle is turning and traveling straight. be able to.

[Brief description of the drawings]

FIG. 1 is a right half sectional view of a pneumatic tire of the present invention.

FIG. 2 is an enlarged sectional view of a main part of the tire shown in FIG.

FIG. 3 is an operation explanatory view of the tire of the present invention.

[Explanation of symbols]

Reference Signs List 1 tire 2 tread portion 3 sidewall portion 4 bead portion 5 bead core 6 carcass 7 belt 8 circumferential groove 9 shoulder rib 10 rim 11 inner rib 12 separate circumferential groove S ₁ convex curve S ₂ concave curve Pi inflection point M Contact width end N Shoulder rib inner edge Q Inner rib outer edge R Inner rib inner edge L Straight line parallel to axis passing through contact width end T ₁ Straight line connecting shoulder rib inner edge to contact width end T ₂ Tangent line K ₁ , radius difference H ₂ shoulder rib between K ₂ gradient theta ₁ linear T ₁ of the inclination angle theta ₂ tangents T ₂ of the inclination angle L ₁ inward rib projected length L ₂ the shoulder rib edges of the projection length H ₁ inward rib Radius difference between both edges of

Claims (5)

[Claims] 1. A radial ply carcass having a tread portion, a pair of side wall portions and a pair of bead portions connected to both sides thereof, and reinforcing these portions between bead cores embedded in the bead portion, and a carcass outer periphery. A belt that strengthens the tread portion with a tread portion.The tread portion is a pneumatic tire having a shoulder rib defined by circumferential grooves provided in both shoulder portions. In the cross section of the assembly of the tire and the rim filled with the maximum air pressure, (1) the shoulder rib has a convex curve having a center of curvature inside the tire on the circumferential groove side, and a convex curve and an inflection point. And (2) a gradient with respect to the tire axial direction having a composite curve with a concave curve having a center of curvature outside the tire at the end of the tire contact width. The slope (K ₂ ) of the tangent of the concave curve passing through the end of the tire contact width has a smaller value than the slope (K ₁ ) of the straight line connecting the circumferential groove edge of the shoulder rib and the end of the tire contact width. A pneumatic tire, characterized in that: 2. The tire according to claim 1, wherein the inflection point is located in a region near both sides sandwiching the width center of the shoulder rib. 3. With respect to a tire axis directed toward the outside of the tire,
The slope of the tangent (K ₂ ) passing through the contact width end has a slope ranging from a down slope to an up slope, and the slope of the straight line (K ₂ )
₁ ) has only a descending gradient, and when the descending gradient is represented by a positive value and the ascending gradient is represented by a negative value, the gradient (K ₂ ) of the gradient (K ₂ )
The value of the ratio (K ₂ / K ₁₎ for _1), a tire according to claim 1 or 2 present in the range of less than 1.0 at -0.5 or more. 4. Adjacent to a shoulder rib with the circumferential groove interposed therebetween.
In the cross section of the tire with the inner rib,
Projection length on the tire axis (L₁ Inner rib for)
Radius difference obtained by subtracting the outer edge radius from the inner edge radius (H
₁ ) Ratio (H₁ / L ₁ ) And the shoulder rib
Projection length on the tire axis (L_Two ) Against the shoulder
The tire contact width end radius is subtracted from the inner edge radius of the rib
Radius difference (H_Two) Ratio (H_Two / L_Two ) Value (B)
And the value of the ratio (B / A) of the value (B) to the value (A) is
4. The method according to claim 1, wherein the relation of less than 2.0 is satisfied.
The tire according to any one of the preceding claims. 5. A radius difference obtained by subtracting a radius at a position farther from a radius closer to the tire equatorial plane from a radius at a position closer to the tire equatorial plane on each contour of the shoulder rib and the inner rib, and a sign of the radius difference is provided. (H ₁ ) has only a positive value, the radius difference (H ₂ ) has a value ranging from positive to negative, and the value of the ratio (B / A) is −1.0 to 1 The tire according to any one of claims 1 to 4, which is within a range of 0.5.