JP2009202706A - Pneumatic radial tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic radial tire capable of enhancing wear-resistant characteristic of a center land part row of a tread part and a shoulder land part row. <P>SOLUTION: In the pneumatic radial tire 1, a circumferential groove 5a extending in a tire circumferential direction is formed on a tread step surface 2a of the tread part 2. In the state that a predetermined internal pressure is filled, a profile of the tread surface 2a of the tread part 2 includes a curved line L1 having a radius of curvature R1 in a vehicle width direction of 500 mm or longer, and when the tread surface 2a of the tread part 2 is contacted with ground, profiles of a ground-contact shape of the land part rows 6a, 7a include a component in an approximately vehicle width direction respectively. Ground-contact length of a central land part row 6a is made longer than ground-contact length of the shoulder land part row 7a, and respective edge parts extending in a longitudinal direction of the ground-contact shape of the central land part row 6a and the shoulder land part row 7a are formed to a substantially linear shape with no ground-contact variation. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pneumatic radial tire.

  FIG. 4 is a cross-sectional view of a main part of this type of conventional pneumatic radial tire, and FIG. 5 is a diagram showing the ground contact shape of the tread portion. A pneumatic radial tire (hereinafter referred to as a tire) 101 shown in FIG. 4 and FIG. 5 has a tread portion 102 disposed on the outer side in the tire radial direction of a pair of bead portions (not shown). A carcass layer (not shown) continuously extending over each of these portions is provided inside each tread portion 102, and the tread portion 102 is reinforced by a belt layer (not shown). A center land portion row 104a and a pair of left and right shoulder land portion rows 104b are formed on the surface (tread surface) of the tread portion 102 by a plurality of main grooves 103 extending in the tire circumferential direction. 104 b is partitioned into a plurality of shoulder land portions 106 by lug grooves 105.

FIG. 6 is a diagram illustrating a ground contact shape of a tread portion of a pneumatic tire disclosed in Patent Document 1. In the pneumatic tire 111 shown in FIG. 6, by specifying the relationship between the contact length L21 of the center land portion row 112a and the contact length L22 of the outer edge portion of the shoulder land portion row 112b at the time of tread surface contact, The ground contact shape is optimized for shoulder uneven wear in which the row 112b is worn significantly. Further, by specifying the relationship between the contact length L22 of the outer edge of the shoulder land portion row 112b and the contact length L23 of the inner edge portion, one edge portion of the land portion row, in particular, the inner edge of the shoulder land portion row 112b. Optimize the ground contact shape against uneven wear of the railway where wear progresses along the part. Thereby, the partial wear of the shoulder land part row | line | column 112b can be suppressed.
JP 2005-138609 A

  However, in the conventional tire 101 shown in FIG. 4 and FIG. 5 described above, the width of the belt layer is narrower than the ground contact width of the tread portion 102 due to manufacturing and wear resistance characteristics. The center portion (the portion near the tire centerline CL) is mainly reinforced, but the shoulder land portion row 104b located on the vehicle width direction end portion A side of the tread portion 102 cannot be sufficiently restrained by the belt layer. . As a result, when running with the tire 101 mounted on the vehicle and filled with a predetermined internal pressure, the shoulder land portion row 104b bulges in the radial direction from the center land portion row 104a due to the tire internal pressure and the centrifugal force during tire rotation. Since the ground contact lengths L12 and L13 of the shoulder land portion row 104b are longer than the ground contact length L11 of the center land portion row 104a, shoulder uneven wear occurs in which the shoulder land portion row 104b is significantly worn compared to the center land portion row 104a. . An example of this uneven shoulder wear is shoulder drop wear, which is a phenomenon in which the vehicle width direction end portion A of the tread portion 102, that is, the outer edge of the shoulder land portion row 104b is significantly worn.

  Further, in a state where the tire 101 is filled with a predetermined internal pressure, the radius of curvature R in the vehicle width direction of the tread surface of the tread portion 102 is relatively small, and the tread surface contour of the tread portion 102 is considerably curved, that is, rounded. Therefore, when the tread surface of the tread portion 102 is grounded, the outer edge portion extending in the longitudinal direction of the ground shape of the shoulder land portion row 104b is formed in an arc shape. As a result, the distribution of the shear force acting on the shoulder land portion 106 becomes non-uniform in the vehicle width direction, and the stress concentration of the shear force tends to occur inside the shoulder land portion row 104b in the vehicle width direction. As a result, railway uneven wear in which wear progresses along the inner edge of the shoulder land portion row 104b occurs. In particular, when traveling in a heavy load state, it tends to cause the uneven wear of the shoulder land portion row 104b, which is not preferable.

  In the conventional pneumatic tire 111 shown in FIG. 6, the relationship between the contact length L21 of the center land portion row 112a and the contact length L22 of the outer edge portion of the shoulder land portion row 112b is specified, and the shoulder land portion By specifying the relationship between the contact length L22 of the outer edge portion of the row 112b and the contact length L23 of the inner edge portion, uneven wear of the shoulder land portion row 112b can be suppressed. There is a need to further improve the wear characteristics. Furthermore, the subject about the abrasion resistance characteristic of the center land part row | line | column 104a is also left.

  Therefore, the present invention has been made to solve the above-described problems, and provides a pneumatic radial tire that can improve the wear resistance characteristics of the center land portion row and the shoulder land portion row of the tread portion. Objective.

  In the pneumatic radial tire in which the circumferential groove extending in the tire circumferential direction is formed on the tread surface of the tread portion, the contour of the tread surface in a state filled with a predetermined internal pressure is a vehicle. It is characterized in that it is constituted by a discontinuous curve in which arcs each having a curvature radius in the width direction of 500 mm or more are connected at the position of the circumferential groove.

  According to a second aspect of the present invention, in the first aspect of the invention, at least two circumferential grooves are formed on the tread surface, and the radius of curvature of the arc constituting the discontinuous curve is composed of two or more types. It is characterized by that.

  The invention of claim 3 is characterized in that, in the invention of claim 2, the circumferential groove is disposed at a position of 30% to 60% of the tire ground contact width.

  According to the first aspect of the present invention, the contour of the tread surface of the tread portion is a discontinuous curve in which arcs each having a curvature radius in the vehicle width direction of 500 mm or more are connected at the position of the circumferential groove while being filled with a predetermined internal pressure. This makes the tread tread surface curve more gradual, and when the tread tread surface of the tread comes in contact with the ground, the contact profile is made closer to the vehicle width direction component and the distribution of shear force is made uniform. be able to. Thereby, the wear resistance characteristics of the center land portion row and the shoulder land portion row of the tread portion can be further improved.

  In addition, by connecting multiple arcs that form the tread tread contour at the circumferential groove position, it is possible to prevent the tread tread from forming a step that tends to damage the wear resistance due to stress concentration when the tread is touched. it can.

  According to the invention of claim 2, by forming at least two circumferential grooves on the tread surface, the center land portion row on the tire width direction center side and the shoulder land portion row on the shoulder side are formed on the tread portion. Since the contours of the ground contact shapes of the center land portion row and the shoulder land portion row each include a component in the vehicle width direction, the distribution of shearing force applied to the center land portion row and the shoulder land portion row is the vehicle width. It becomes substantially uniform in the direction component, and stress concentration of shearing force can be avoided in the center land portion row and the shoulder land portion row. Thereby, the abrasion resistance characteristic of the center land part row | line | column and shoulder land part row | line | column of a tread part can be improved.

  According to the invention of claim 3, since the circumferential groove is disposed at a position of 30% to 60% of the tire ground contact width, the center land portion row and the shoulder land portion row defined by the circumferential groove are arranged. The width dimension can be sufficiently secured, and the deterioration of the wear resistance due to insufficient rigidity of the center land portion row and the shoulder land portion row can be prevented.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 to 3 show an embodiment of the present invention, FIG. 1 is a cross-sectional view of a main part of a pneumatic radial tire, FIG. 2 is a diagram schematically showing a contact shape of a tread portion, and FIG. 3 is an actual state of the tread portion. It is a figure which shows the earthing | grounding shape.

  As shown in FIG. 1, a pneumatic radial tire (hereinafter referred to as a tire) 1A according to the present embodiment includes a pair of left and right bead portions (not shown), and tread treads that are disposed outside the bead portions in the tire radial direction. 2a, and a pair of left and right sidewall portions (not shown) for connecting the vehicle width direction end portion of the tread portion 10 and the tire radial direction outer end of the bead portion. A carcass layer (not shown) is provided in each of the bead portion, sidewall portion, and tread portion 10 so as to extend continuously over these portions. A central portion of the tread portion 10 mainly in the vehicle width direction is reinforced by a belt layer (not shown).

  In the tire 1A of the present embodiment, an outer pattern and an inner pattern are formed on the tread surface 10a of the tread portion 10 with the tire center line (tire equator portion) CL of the tread portion 10 as a boundary, on both sides of the tire center line CL. A pair of left and right circumferential grooves 11a and 11b extending along the tire circumferential direction are disposed. By these circumferential grooves 11a and 11b, the tread tread surface 10a of the tire 1A has a center land portion row 12 extending along the tire center line CL, and a pair of left and right positions positioned outside the center land portion row 12 in the vehicle width direction. It is divided into shoulder land portion rows 13a and 13b. Each shoulder land portion row 13a, 13b is partitioned into a number of shoulder land portions 15 by lug grooves 14 extending in the vehicle width direction.

  A pneumatic radial tire (hereinafter referred to as a tire) 1A according to this embodiment includes a discontinuous curve in which the contour of the tread surface 10a of the tread portion 10 includes two arcs L3 and L4, and the bead portion of the tire 1 is not illustrated. The arcs L3 and L4 are set to have a radius of curvature R3 and R4 in the vehicle width direction of 500 mm or more, for example, 1000 mm, respectively, in a filling state where they are attached to the normal rim of the tire wheel and filled with air of normal internal pressure. Yes. The normal rim and normal internal pressure are the standard rim and maximum internal pressure defined by JATAM.

  In the tire 1A of the present embodiment, the contour of the tread tread surface 10a of the tread portion 10 includes the two arcs L3 and L4, so that the degree of curvature of the tread tread surface 10a is further moderated and the tread tread surface of the tread portion 10 is reduced. When the ground contacts 10a, the contour of the ground shape can be made closer to the component in the vehicle width direction and the distribution of the shearing force can be made uniform. Thereby, the wear resistance characteristics of the center land portion row 12 and the shoulder land portion rows 13a and 13b of the tread portion 10 can be further improved.

  Further, since the two arcs L3 and L4 intersect at the positions Pa and Pb of the circumferential grooves 11a and 11b formed along the tire circumferential direction on the tread tread surface 2a of the tread portion 2, Sometimes, it is possible to prevent a step from being formed on the tread surface 10a. If the above step is formed on the tread surface 10a of the tread portion 10, stress concentration may occur at the step and the wear resistance may be deteriorated. Note that the positions Pa and Pb of the circumferential grooves 11a and 11b indicate regions in and above the circumferential grooves 11a and 11b. Further, the circumferential groove in the present embodiment is formed along the tire circumferential direction on both sides of the tire center line CL, but is not limited to such a shape, and has a relatively wide width and drainage performance of the tread portion. Also included in the circumferential groove are a main groove that bears the main, a secondary groove that is narrower than the main groove and assists drainage performance.

  Further, since the circumferential grooves 11a and 11b are arranged at positions of 30% to 60% of the tire ground contact width W, the center land portion row 12 and the shoulder land portion row defined by the circumferential grooves 11a and 11b. The width dimensions of 13a and 13b can be sufficiently ensured, respectively, and it is possible to prevent a decrease in wear resistance due to insufficient rigidity of the center land portion row 12 and the shoulder land portion rows 13a and 13b. In addition, when the circumferential grooves 11a and 11b are arranged at a position less than 30% of the tire ground contact width W, the rigidity of the center land portion row 12 is insufficient, and the wear resistance characteristics of the center land portion row 12 are reduced. On the other hand, when the circumferential grooves 11a and 11b are disposed at positions exceeding 60% of the tire ground contact width W, the rigidity of the shoulder land portion rows 13a and 13b is insufficient and the wear resistance characteristics of the shoulder land portion rows 13a and 13b. Is unfavorable because of lowering.

  As shown in FIG. 4, when the tire 1 </ b> A is mounted on the vehicle and travels in a state where a predetermined internal pressure is filled, the ground contact lengths of the shoulder land portion rows 13 a and 13 b from the ground contact length a of the center land portion row 12. Since A does not become long, it is possible to suppress the shoulder land portion row 13a, 13b of the tread portion 10 from bulging out from the center land portion row 12 in the tire radial direction by the tire internal pressure or the centrifugal force during rotation. It is possible to prevent uneven shoulder wear such as shoulder drop wear in which the outer edge portions of the partial rows 13a and 13b are significantly worn. Further, the ground contact lengths a, b, and c of the center land portion row 12 are equal, and the contact lengths A, B, and C of the shoulder land portion rows 13a, 13b are equal, and the center land portion row 12 and the shoulder land portion rows 13a, 13b. Each of the edge portions extending in the longitudinal direction has a substantially linear ground contact shape with no ground contact change, and the ground contact widths of the center land portion row 12 and the shoulder land portion rows 13a and 13b are substantially uniform. The land portion row 12 and the shoulder land portion rows 13a and 13b can be brought into contact with the road surface almost simultaneously over the entire length of the ground contact width to express a large frictional force, and shear force is generated on the inner side in the vehicle width direction of the shoulder land portion rows 13a and 13b. Stress concentration can be avoided. Thereby, the railway partial wear which wear progresses along the inner edge part of the shoulder land part row | line | columns 13a and 13b can be suppressed.

  As described above, according to the tire 1A of the present embodiment, the wear resistance characteristics of the center land portion row 12 and the shoulder land portion rows 13a and 13b of the tread portion 10 can be improved.

1 is an essential part cross-sectional view of a pneumatic radial tire according to an embodiment of the present invention. It is a figure which shows one Embodiment of this invention and shows the contact shape of a tread part typically. It is a figure which shows one Embodiment of this invention and shows the actual contact shape of a tread part. It is a principal part sectional drawing of a pneumatic radial tire which shows a prior art example. It is a figure which shows a prior art example and shows the contact shape of the tread part of a pneumatic radial tire. It is a figure which shows another prior art example and shows the contact shape of the tread part of a pneumatic tire.

Explanation of symbols

1,1A Pneumatic radial tire 2 Tread part 2a Tread tread 4 Circumferential groove 5a, 5b Circumferential groove 6a, 6b Center land part row 7a, 7b Shoulder land part row 8 Lug groove 9 Shoulder land part 10 Tread part 10a Tread tread face 11a, 11b Circumferential groove 12 Center land portion row 13a, 13b Shoulder land portion row L1 Curve L3, L4 Arc R1 Curvature radius R3, R4 Curvature radius W Tire contact width

Claims (3)

In a pneumatic radial tire in which a circumferential groove extending in the tire circumferential direction is formed on the tread surface of the tread portion,
The contour of the tread surface in a state filled with a predetermined internal pressure is constituted by a discontinuous curve in which arcs each having a radius of curvature of 500 mm or more in the vehicle width direction are connected at the position of the circumferential groove. Pneumatic radial tire. At least two circumferential grooves are formed on the tread surface;
2. The pneumatic radial tire according to claim 1, wherein a radius of curvature of the arc constituting the discontinuous curve is composed of two or more kinds.   The pneumatic radial tire according to claim 2, wherein the circumferential groove is disposed at a position of 30% to 60% of a tire ground contact width.

Images