JPH04266503A - Tire for heavy load - Google Patents

Abstract

PURPOSE:To prevent shoulder wear, wandering and generation of rib-tear by providing striations arranged on both of the outer sides of a central curved surface and extending in the circumferential direction on the edge curved surface consisting of a small circular arc. CONSTITUTION:Edge curved surfaces SS consisting of a small radius circular arc are formed on both of the outer sides of a central curved surface CS formed of a circular arc, and striations S are provided in the circumferential direction by way of positioning their central lines in the neighbourhood of an intersection point of the central curved surface CS and the edge curved surfaces SS. A belt end is ended at a position in the neighbourhood of the striations S by way of setting a distance ratio Wb/Wg from a tire equatorial surface of the striations S and the belt end at 0.97-1.05. Thereafter, the striations S are inclined inward in the tire radius direction and to the equatorial surface side, the depth of striations H is made to be more than 60% of the depth HG of main grooves G, and the width WS of the striations S is made to be more than 0.003 times and less than 0.02 times a tread width TW.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention provides narrow grooves at the tread ends and near the belt ends to separate the movement of the center and end portions of the tread surface during running, improving wandering performance. The present invention relates to a heavy-duty tire that can prevent shoulder drop wear.

0002

[Prior Art] In heavy-duty tires used for large vehicles such as large trucks and buses, the belt layer is made strong using steel cords, etc., and the hoop effect is used to make the belt layer strong.
The overall rigidity of the tread is increased. However, even in the shoulders of the tread, which has a great effect in suppressing lateral vibration, the rigidity is large, reducing the conformability and tracking performance with the road surface. As a result, when the vehicle is traveling on a rutted road surface, a so-called wandering phenomenon occurs in which the steering wheel is taken off by receiving a large external force when escaping from the ruts.

In order to suppress the wandering phenomenon, there is a method of reducing the tread radius tr in order to increase the camber thrust (Fig. 5), and a method of reducing the tread radius tr to increase the camber thrust.
(Fig. 6), and a method of providing a large number of cuts s extending in the axial direction of the tire in the tread side wall w (Fig. 7).
) etc. have been adopted.

Furthermore, according to JP-A-58-194606, narrow, substantially annular circumferential grooves forming side ribs are provided in both shoulder portions of the tread, and the contour of the side ribs in the meridian direction is A shape is proposed that is approximately parallel to and radially inward of the meridional envelope profile of the central portion.

According to Japanese Patent Application Laid-Open No. 143205/1983, at least one continuous shoulder rib has one or more narrow width strips (0.003 of the tread width) extending generally in the circumferential direction.
It has been proposed to provide a sub-groove with a diameter of 0.02 times the width of the shoulder rib at a position shorter than 0.5 times the width of the shoulder rib starting from the tread end.

Furthermore, according to Japanese Patent Application Laid-Open No. 55-44028, it has one or more wide main grooves, has a square shoulder, and has one or more circumferential grooves on at least one side area of the tread, which is approximately 25% of the tread width. A sub-groove extending in the direction is provided,
This sub-groove is located 55 degrees outward in the axial direction of the tire with respect to the tread normal.
It has been proposed to tilt at an angle of ~60°.

[0007] Furthermore, the tire proposed in JP-A-63-106112 has a plurality of circumferential main grooves arranged substantially parallel to the circumferential direction of the tire, and a shoulder rib on at least one side has a plurality of circumferential main grooves arranged substantially parallel to the circumferential direction of the tire. In addition to arranging an auxiliary groove extending in the direction, a large number of sipes facing in the axial direction of the tire are arranged at intervals in the circumferential direction on the land portion outside the auxiliary groove so as to cross this land portion, and The auxiliary groove is narrow enough that both side walls of the groove do not come into contact with each other when the tire is rolling, and the angle of inclination of the auxiliary groove with respect to the normal line of the tread is 10° to 6.
0°, and the auxiliary groove is placed at a distance of 20 to 80% of the shoulder rib width, measured from the tread edge.Compared to conventional tires, the camber thrust,
Wandering is prevented by increasing both camber torques.

[0008]

[Problems to be Solved by the Invention] However, although wandering resistance is improved by reducing the tread radius tr, at the center and shoulder portions of the tread surface,
This results in a difference in length in the circumferential direction, and the shoulders are likely to be dragged, resulting in shoulder drop wear. This tendency is particularly noticeable in the case of steel radial tires. In addition, in the case of a so-called round shoulder in which the shoulders of the tread portion are formed with small arcs r, deformation of the shoulders becomes somewhat easier, but this does not prevent shoulder drop wear. Furthermore, there are many cuts in the axial direction of the tire.
Even when such tires are provided, there is a problem that uneven wear such as so-called heel-and-toe wear occurs on the shoulders, reducing the tire life.

[0009] Furthermore, the proposal in Japanese Patent Application Laid-Open No. 194606/1983 has a shape in which the contour of the side ribs in the meridian direction is radially inward from the contour of the central portion, which is effective against wandering, but causes shoulder drop wear. There is a problem that this is likely to occur.

Furthermore, the proposal in Japanese Patent Application Laid-open No. 143205/1983 is aimed at preventing uneven wear, but it has a square shoulder and is not very effective against wandering.

[0011] JP-A-55-44028 also has a similar problem. The radial tire disclosed in JP-A-63-106112 is effective against wandering in the ruts of expressways and general roads, but when driving on unpaved roads and other rough roads, the radial tire is If a large external force is applied to the tread side edge by rubbing or riding on the tread,
There is a problem in that rib tears from the groove bottom of the auxiliary groove are likely to occur in the land portion located outside of the auxiliary groove.

[0012] The present invention advantageously prevents shoulder drop wear and wandering by providing narrow grooves extending in the circumferential direction on the end curved surfaces formed by small arcs and arranged on both outside sides of the central curved surface. The present invention also aims to provide a heavy-duty tire that can sufficiently prevent the occurrence of rib tears.

[0013]

[Means for Solving the Problems] The present invention provides a carcass that passes from a tread portion through a sidewall portion and folds around a bead core of a bead portion, and a carcass that is arranged inside the tread portion and outside the carcass in the tire radial direction. comprising a belt layer;
In the meridian plane that includes the tire axis, the tread surface is a medium curved surface (CS) that has a circular arc with a radius of curvature (CR) centered on the tire equatorial plane as a reference curved surface and has a main groove (G) extending in the circumferential direction. 3 to 1 of the tread width (TW), which is the length between the tread ends, and forms the tread edges located on both outer sides of this medium curved surface (CS) and extending to the tread width.
It includes an end curved surface (SS) whose reference curved surface is an arc with a radius of curvature (SR) of 0%, and the center line is located near the intersection where the medium curved surface (CS) and the end curved surface (SS) intersect. In addition, narrow grooves (S) are provided in the circumferential direction that are inclined at an angle (β) of 0 to 5 degrees toward the tire equatorial plane with respect to the normal line (n) on the tread surface, and the depth of the narrow grooves (S) is H) to main groove (G)
60% or more of the depth (HG) of the tire, and the distance (wg) in the tire axial direction from the tire equatorial plane to the narrow groove (S).
The distance ratio wb/wg, which is the ratio of the distance (wb) in the tire axial direction from the tire equatorial plane to the outer end of the belt layer, is 0.
．． This is a heavy-duty tire with a rating of 97 or more and 1.05 or less.

[0014] Further, it is preferable that the width (WS) of the narrow groove S is 0.003 times or more and 0.02 times or less the tread width (TW).

[0015]

[Operation] The present invention provides a medium curved surface CS formed by a circular arc.
Since curved end surfaces SS consisting of small radius arcs are formed on both outer sides of the vehicle, the medium curved surface CS is the main contact with the ground during driving, and the camber thrust increases against ruts on the road due to the action of the curved end surfaces SS. , the wandering resistance is improved.

Further, the narrow groove S is provided in the circumferential direction with the center line located near the intersection of the medium curved surface CS and the end curved surface SS. Moreover, the distance ratio W between the narrow groove S and the belt end from the tire equatorial plane
b/Wg is set to 0.97 to 1.05, that is, the belt end is terminated near the narrow groove S, so the tread surface rigidity can be clearly and step-wise controlled inside and outside the narrow groove S. Can be partitioned. Therefore, the outer end curved surface SS is not dragged by the movement of the inner medium curved surface CS, thereby suppressing the occurrence of shoulder drop wear.

Further, the narrow groove S is inclined inward in the tire's radial direction and toward the tire's equatorial plane, and its groove depth H is equal to that of the main groove G.
Because the depth of the tread is 60% or more of HG, the tread edge maintains the necessary strength and prevents rib tear, while effectively preventing the propagation of lateral forces from medium curved surfaces and further reducing the occurrence of shoulder drop wear. It can be suppressed. Furthermore, since the narrow groove is provided near the intersection of the medium curved surface and the end curved surface, the rib lines of the medium curved surface work effectively to improve camber thrust and effectively prevent wandering.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings. In the figure, heavy load tire 1 of the present invention
has a bead portion 3 through which the bead core 2 passes, a sidewall portion 4 that is continuous with the bead portion 3 and extends outward in the tire radial direction, and a tread portion 5 that connects the upper end of the sidewall portion 4. A carcass 6 passing through the section 4 and folded back around the bead core 2 of the bead section 3, and a belt layer 7 inside the tread section 5 and outside the carcass 6 in the radial direction.

The belt layer 7 includes at least one belt ply, in this example, first, second, third, and fourth belt plies 7a arranged in order from the carcass 6 toward the tread surface 10. , 7b, 7c, and 7d. Further, the second belt ply 7b has a ply width in the tire axial direction that is equal to that of the other belt plies 7a, 7c, and 7d.
The belt width BW of the belt layer 7 which is formed to be larger than each ply width and has the maximum width, that is, the ply width of the second belt ply 7b in this example, is set to be 0.8 times or more the tread width TW. As a result, the tread portion 5 is strongly reinforced with a hoop effect.

In this example, each of the belt plies 7a to 7d is made of a strong steel belt cord having an initial elastic modulus of, for example, 15×10 5 kg/cm or more, at an angle of 10 to 70 degrees with respect to the tire equatorial plane. This is an array of code arrays. In addition, in this example, the ply width of the fourth belt ply 7d is set to the third ply width.
The ply width is smaller than that of the belt ply 7c, and a protective rubber sheet 8 is provided at the end of each ply to cover the end.
By regulating the distance between belt cords between adjacent plies to 1/4 or more and 4 times or less of the belt cord diameter at the end, concentration of shear stress at the belt end is alleviated and separation between the plies is suppressed. are doing.

The tread surface 10 of the tread portion 5 in which such a belt layer 7 is embedded has a medium curved surface CS and an end curved surface SS that forms tread edge portions E, E located on both outer sides of the medium curved surface CS and extending to the tread ends. including.

The medium curved surface CS consists of an arc with a radius of curvature CR having its center on the tire equatorial plane including the tire equator C, and as shown in FIG. , Gi and outer main grooves Go, four main grooves G are formed. In addition, in this embodiment, each main groove G,
G between the main grooves G, a plurality of lateral grooves F1 connecting between G, F1, F
2 is provided.

In this embodiment, the depth HG of each main groove G is
Both are formed at approximately the same depth. The end curved surface SS is an arc that smoothly connects the end of the medium curved surface CS and the tire side wall surface 11 extending inward in the tire radial direction from the tread end.

In this embodiment, the center of the arc forming the medium curved surface CS is on the tire equator C, and the radius of curvature CR is at least twice and not more than 5 times the tread width TW, which is the length between the tread ends. while the radius of curvature SR of the end curved surface SS is 0.03 times or more the tread width TW and 0.10
The range is less than twice that.

[0025] The narrow groove S is an endless groove that has a center line on the end curved surface SS and near the intersection point P where the medium curved surface CS and the curved surface SS intersect, and that goes around the tread surface 10 in the circumferential direction. The radial center line L of the groove is inclined toward the tire equatorial plane at an inclination angle β in the range of 0 to 5 degrees with respect to the normal n on the tread surface.

By thus providing the opening center of the narrow groove S on the end curved surface SS of the tread surface 10 and in the vicinity of the intersection point P, the tire's contact surface is limited to the medium curved surface CS during running, and the end curved surface The ground pressure applied to the SS is significantly reduced.

Further, as described above, the narrow grooves S are inclined toward the equatorial plane within the inclination angle β range, thereby increasing the thickness from the tire side wall surface 11 at the groove bottom and maintaining the strength at the tread edge E.

Further, in the present invention, in order to make the movement of the rubber on the end curved surface SS independent of the movement of the rubber on the middle curved surface CS, and to suppress shoulder drop wear of the tread surface 10, The distance ratio Wb/Wg between the distance Wg in the tire axial direction to the groove S and the distance Wb from the tire equatorial plane to the outer end of the belt layer 7 is set to be 0.97 or more and 1.05 or less. In addition, the distance Wg is, more specifically, the length between the inner opening edge of the narrow groove S on the tire equatorial plane side and the tire equatorial plane, and the distance Wb is 1 of the belt width BW.
/2 value.

Further, the distance ratio Wb/Wg is set to 0.97 to 1.
05, the central region of the tread having the medium curved surface CS can be made to coincide with the restraint region where the movement of the rubber is restrained by the belt layer 7 present at the bottom, and the tread edge having the end curved surface SS can be The lower region can correspond to an unconstrained region where the movement of the rubber is not constrained by the belt layer 7. Moreover, since the restricted area and the non-restricted area are separated by a narrow groove, it is possible to make the rubber movement in each area independent, and it is possible to effectively suppress shoulder drop wear caused by dragging or the like.

Further, the depth H of the narrow groove S is 0.6 times or more the depth HG of the main groove G. If the groove depth H is less than 0.6 times, the movement of the rubber on the surface of the end curved surface SS will be insufficient, resulting in shoulder drop wear, and an increase in camber thrust and camber torque cannot be expected, so wandering performance cannot be achieved sufficiently. It cannot be improved.

In this embodiment, the width WS is set to be at least 0.003 times and at most 0.02 times the tread width TW. Note that if the width WS is larger than 0.02TW, the bending strength of the end curved surface SS is insufficient, so that cracks occur at the tread edge E, which reduces durability and tends to cause stone encrustation.

Further, when the width WS is less than 0.003 TW, the groove walls of the narrow groove S come into pressure contact due to the load during ground contact, and independence of the movement of the rubber is not achieved.

[0033] In this embodiment, the tire side wall portion 1
1, as shown in FIG. 4, shallow pattern grooves 13 are continuously provided in the circumferential direction, and by providing the pattern grooves 13, the heat dissipation effect of the tread edge is enhanced and the wandering performance is also improved.

[Comparative example] Tire size 10.00R20
Regarding the 14PR tire, the results of a comparative test of the tire of the present invention, a conventional tire, and a comparative tire will be explained regarding the effect of preventing shoulder drop wear and the effect of suppressing wandering. The test tires had the specifications shown below.

[0035] Invention tire: A tire having the configuration shown in Figs. 1 to 4, the basic dimensions of which are the depth H of the main groove as shown below.
G = 157mm Depth of narrow groove H = 157mm Thin groove width WS = 2mm Slope angle β = 2° Radius of curvature of medium curved surface CS CR = 575mm Radius of curvature of end curved surface SS SR = 15mm Tread width TW = 208mm ○ Conventional tire: The curved end surface SS of the invention tire was eliminated, the entire tread width TW was formed with one radius of curvature CR, and the shoulders were made square. Furthermore, the slope of the narrow groove S was tilted toward the tread end in the opposite direction to that of the invention tire. ○Comparison tire: A tire with the narrow groove S omitted from the invention tire.

Test method 1) Wandering performance A 2-D-D type truck with a camber angle of 6 degrees, an internal pressure of 7.25 kg/cm2, and a load of 2750 kg was run at high speed and evaluated by the driver's feeling of the actual vehicle. 2) Uneven shoulder drop wear The actual test vehicle described in item 1) was driven for 60,000 km, and then the occurrence of shoulder drop wear was checked. The above test results are shown in Table 1, and it can be seen that the tires of the present invention are superior to conventional tires for comparison.

[0037]

[Table 1]

[0038]

[Effects of the Invention] As mentioned above, the heavy-duty tire of the present invention has
The tread surface is formed by a medium curved surface with a circular arc as a reference, and end curved surfaces consisting of circular arcs with a radius of curvature smaller than that of the medium curved surface on both sides, and the center line is located near the intersection of both curved surfaces in the circumferential direction. While the belt has a narrow groove extending across the belt, the end of the belt terminates near the narrow groove, which makes it possible to separate the movement of the center and edge of the tread surface during running, which prevents shoulder drop wear. Wandering can be effectively prevented by the effects of the thin grooves in the circumferential direction and their positions.

[Brief explanation of the drawing]

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

FIG. 2 is a cross-sectional view showing an enlarged outline of the surface of the tread portion.

FIG. 3 is a developed plan view showing the tread pattern.

FIG. 4 is a partial side view showing a part of the side wall surface.

FIG. 5 is a diagram illustrating the prior art.

FIG. 6 is a diagram illustrating the prior art.

FIG. 7 is a diagram showing the prior art.

[Explanation of symbols]

2 Bead core 3 Bead part 4 Sidewall part 5 Tread section 6 Carcass 7 Belt layer 10 Tread surface C Tire equator CR　Curvature radius CS Medium curved surface E Tread edge G Main groove H Depth of narrow groove HG Depth L Center line P intersection point S narrow groove SR　Curvature radius SS　End curved surface TW Tread width WS narrow groove width

Claims (2)

[Claims] 1. A tire shaft comprising: a carcass that passes from a tread portion through a sidewall portion and folds around a bead core of a bead portion; and a belt layer disposed inside the tread portion and outside the carcass in the tire radial direction. In the meridian plane including the tread surface, the tread surface has a medium curved surface (CS) having a circular arc having a radius of curvature (CR) having a center on the tire equatorial plane as a reference curved surface and having a main groove (G) extending in the circumferential direction; The tread edges are located on both outer sides of this medium curved surface (CS) and reach the tread ends, and the radius of curvature (
The center line is located near the intersection of the intermediate curved surface (CS) and the end curved surface (SS), and the normal to the tread surface (n ) to the tire equatorial plane at an angle of 0 to 5 degrees (β
) is provided in the circumferential direction, and the depth (H) of the narrow groove (S) is set to 60% of the depth (HG) of the main groove (G).
% or more, and the ratio of the axial distance (Wg) from the tire equator plane to the narrow groove (S) to the axial distance (Wb) from the tire equator plane to the outer edge of the belt layer. A certain distance ratio Wb/Wg is 0.97 or more and 1.0
Heavy load tires with a rating of 5 or less. 2. The heavy-duty tire according to claim 1, wherein the narrow groove S has a groove width (WS) of 0.003 times or more and 0.02 times or less of the tread width (TW). .