JPH04334605A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To unify ground pressure on respective parts of ribs 16 or blocks 26 and improve dry running performance. CONSTITUTION:Ground pressure at respective parts are unified, by setting the distance in the radial direction from the outer surface of ribs 16 and blocks 26 to the groove bottoms 20, 32 of main grooves 13, 24 at crossing parts 18 and angle parts 30 which are easily deformed and pressed by low ground pressure due to small crossing angles of two edges 17, 28, 29, larger than the above- mentioned distance in the radial direction at crossing parts 19 and angle parts 31 which are hardly deformed and pressed by high ground pressure due to large crossing angles of two edges 17, 28, 29.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire having a plurality of ribs or a plurality of blocks defined by grooves formed on the outer surface of a red portion.

0002

[Prior Art] Conventionally, the tread pattern of a pneumatic tire is such that, for example, a plurality of main grooves extending in the circumferential direction and bent in a zigzag shape are formed on the outer surface of a tread portion. A so-called rib type, in which a plurality of ribs are defined between the main groove and the edge of the main groove, and an edge is formed at the boundary between the outer surface of these ribs and the side wall of the main groove, or By forming a plurality of main grooves extending in the circumferential direction and a plurality of lateral grooves extending approximately in the axial direction and intersecting the main grooves on the outer surface of the section, a large number of polygonal blocks are defined, and these A so-called block type is known in which an edge is formed at the boundary between the outer surface of the block and the side walls of the main groove and the lateral groove.

0003

[Problem to be Solved by the Invention] However, such conventional pneumatic tires have the problem that the maximum cornering force decreases significantly in a large steering angle region, and the dry running performance of the tire deteriorates. .

0004

[Means for Solving the Problem] Therefore, the inventor of the present invention has conducted intensive research to clarify the cause of the decrease in maximum cornering force in such a large steering angle range, and has obtained the following findings. . In other words, rubber is generally incompressible (when pressure is applied to rubber, it deforms but its volume does not change).
Therefore, when a rib or block made of rubber is placed on the ground, the rib, etc. collapses in the radial direction under the load and tries to escape (bulge) parallel to the ground surface, but at this time, the two edges Near intersections (corners) where the intersection angle is small, the occupation ratio of ribs, etc. is low, and there is a large space for rubber to escape, so the ground pressure of ribs, etc. near the intersections (corners) is low; , the occupation ratio of ribs, etc. is high near the intersection (corner) where two edges intersect at a large angle,
Since the space through which the rubber can escape is narrow, the ground pressure of the ribs and the like near the intersection (corner) increases. If the ground pressure is uneven in each part of the rib or block in this way, as the steering angle increases, side force will be concentrated in areas with high ground pressure, resulting in a decrease in maximum cornering force.

The present invention has been made based on the above-mentioned knowledge, and by forming a plurality of main grooves extending in the circumferential direction and bending in a zigzag shape on the outer surface of the tread portion, there is a gap between the main grooves and between the main grooves. In a pneumatic tire in which a plurality of ribs are defined between the red end and an edge is formed at the boundary between the outer surface of these ribs and the side wall of the main groove, two The radial distance from the outer surface of the rib near the intersection where the edges intersect with each other to the groove bottom of the main groove is increased as the intersection angle between the edges becomes smaller. By forming a plurality of main grooves extending in the circumferential direction and a plurality of lateral grooves extending substantially in the axial direction and intersecting the main grooves on the outer surface, a large number of polygonal blocks are defined, and
In these pneumatic tires in which edges are formed at the boundaries between the outer surface of the block and the side walls of the main groove and lateral groove, from the outer surface of the block near the corner where the two edges intersect due to the intersection of the main groove and lateral groove. The radial distance of the main groove to the groove bottom is increased as the intersection angle becomes smaller.

[0006]

[Effect] When running on a road surface, the ground pressure of ribs and blocks is low near intersections (corners) where the intersection angle is small, and on the other hand, at intersections (corners) where the intersection angle is large.
It becomes higher in the vicinity. Therefore, in this invention, the radial distance from the outer surface of the rib or block near the intersection to the groove bottom of the main groove is made larger as the intersection angle between the edges becomes smaller, thereby increasing the intersection angle. The amount of rubber near intersections (corners) with small intersections is increased to increase the ground pressure near the intersections, while the amount of rubber near intersections (corners) with large intersection angles is decreased to increase the ground pressure near the intersections. This reduces the ground pressure near the ribs and blocks, thereby making the ground pressure uniform at each part of the rib and block. As a result, even if the steering angle increases, the concentration of side force on areas with high ground contact pressure is alleviated, and as a result, a decrease in maximum cornering force is prevented. Further, since both the widthwise center portion of the rib and the center portion of the face of the block are entirely surrounded by rubber, there is no place for the rubber to escape upon contact with the ground, and as a result, the ground contact pressure is maximized. Therefore, in claims 2 and 4, the radial distance of these parts is made smaller than the minimum value of the radial distance in the vicinity of the intersection (corner) to further equalize the ground pressure across the ribs and the block. ing.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 11 denotes a pneumatic tire, and a plurality of, in this case four, main grooves 13 are formed on the outer surface of the red portion 12 of the tire 11, extending in the circumferential direction. These main grooves 13 are bent in a zigzag shape at the same pitch and with the same amplitude, and are arranged in the same phase in the circumferential direction. Among these main grooves 13, between two adjacent main grooves 13 and between the tread end 14 and the outermost main groove 13, there are a plurality of grooves, five in this case, extending in the circumferential direction and bent in a zigzag shape. Ribs 16 are each defined. 17 is the outer circumference of each rib 16 and the main groove 1
3 with the side wall 15, that is, the outer surface of the rib 16 and the main groove 1
These edges 17 extend in a zigzag shape along the main groove 13.
As a result, two linear edges 17 adjacent in the circumferential direction
They intersect with each other either at an intersection angle a less than 180 degrees or an intersection angle b greater than 180 degrees. When such a tire 11 is run under a load, since rubber is incompressible, the ribs 16 will collapse in the radial direction and escape parallel to the ground contact surface (bulge into the main groove 13).
However, at this time, in the vicinity of a small intersection (protruding end) 18 where the intersection angle a between the edges 17 is less than 180 degrees,
Since the occupation ratio of the surrounding space of the rib 16 is low and the space in which the rubber can escape is wide, the contact strength of the rib 16 in the vicinity of the intersection 18 is low, and on the other hand, the edge 1
A large intersection where the intersection angle b between 7s exceeds 180 degrees (
In the vicinity of the concave end) 19, the occupation ratio of the rib 16 is high;
Since the space through which the rubber can escape is narrow, the ground pressure of the ribs 16 near the intersection 19 increases. In addition, since the widthwise central portion of each rib 16 is entirely surrounded by rubber, there is no place for the rubber to escape when it touches the ground, and as a result, the rib 16
The ground pressure at the center in the width direction is higher than the ground pressure near the intersection 19 and reaches a maximum. If the ground pressure is uneven in each part of the rib 16 in this way, as the steering angle increases, the side force will concentrate on the area where the ground pressure is high, and as a result, the maximum cornering force will decrease.

Therefore, in this embodiment, FIGS.
, 5, the radial distance H from the outer surface of the rib 16 to the groove bottom 20 of the main groove 13 near the intersection 18 where the text difference angle a is small is the same as that near the intersection 19 where the intersection angle b is large. The radial distance J from the outer surface of the rib 16 to the groove bottom 20 of the main groove 13 is set to be larger than the radial distance J from the outer surface of the rib 16 to the groove bottom 20 of the main groove 13. On the other hand, the vicinity of the intersection 19 is recessed inward in the radial direction from the cross-sectional contour of the tread portion 12, and each rib 16
The radial distance K from the outer surface of the main groove 13 to the groove bottom 20 of the main groove 13 at the center in the width direction is set to be the minimum value of the radial distance near the intersection, which is smaller than the radial distance J in this case. The outer surfaces of each part of the rib 16 are connected by smooth curved surfaces. Here, the groove bottom 2 of the main groove 18
0 means a pair of main grooves 1 arranged on both sides of the rib 16.
It means a curve (shown by an imaginary line) connecting the groove bottoms of No. 3 and parallel to the cross-sectional contour of the red portion 12. As a result, the amount of rubber near the intersection 18 where the intersection angle a is small is increased, and the intersection 1
On the other hand, the amount of rubber near the intersection 19 where the intersection angle b is large is decreased, and the ground pressure near the intersection 19 is reduced. The amount of rubber decreases the most, and the ground pressure at the center in the width direction decreases the most. This equalizes the ground pressure at each part of the rib 16. As a result, even if the steering angle increases when the vehicle is running on the tires 11, the concentration of side force on areas with high ground contact pressure is alleviated, and as a result, a decrease in maximum cornering force is prevented. Here, the difference (mm) between the radial distance H and the radial distance J is equal to the difference (degrees) between the intersection angle a and the intersection angle b by 0.
The range is preferably from 0.005 times to 0.015 times. The reason is that if it is less than 0.005 times, the ground pressure will not be uniform enough;
If it exceeds five times, the ground pressure near the intersection 18 will increase too much, and the ground pressure near the intersection 19 will decrease too much, resulting in uneven ground pressure. Further, the difference (mm) between the radial distance K and the minimum value of the radial distance near the intersection, here the radial distance J, is:
A range of 0.3 to 0.8 is preferred.

[0009] In the above-mentioned embodiment, there are two types of intersection angles, large and small, at the intersection, but there may be three or more types of intersection angles. In this case, the smaller the intersection angle, the larger the radial distance from the outer surface of the rib to the bottom of the main groove in the vicinity of the intersection.

FIG. 6 is a diagram showing a second embodiment of the invention. In this embodiment, the outer surface of the red portion 22 includes a plurality of main grooves 24 extending linearly and a plurality of lateral grooves 25 extending substantially in the axial direction and intersecting the main grooves 24.
The main grooves 24 and the lateral grooves 25 define a large number of blocks 26 in the tread portion 22 in the shape of a polygon, here a parallelogram. In these blocks 26 as well, the outer surface of each block 26 and the side wall 23 of the main groove 24
and the boundary between the horizontal groove 25 and the side wall 27, that is, the block 26
Edges 28 and 29 are formed at intersections between the outer surface of the main groove 24 and the side walls 23 and 27 of the lateral groove 25. The two edges 2 are formed by the intersection of the main groove 24 and the lateral groove 25.
Each block 26 has a corner 30 where the edges 8 and 29 intersect with each other at a small intersection angle c of less than 90 degrees, and a corner 31 where the two edges 28 and 29 intersect with each other at a large intersection angle d exceeding 90 degrees. is formed. Here, corner 3 with a small intersection angle c
The ground contact pressure is low near 0 as described above, whereas the ground pressure is high near the corner 31 with a large intersection angle d, so the ground contact pressure becomes uneven and the maximum cornering force decreases. Therefore, in this embodiment, as shown in FIGS. 7, 8, and 9, the radial distance L from the outer surface of the block 26 to the groove bottom 32 of the main groove 24 near the corner 30 of the small intersection angle c is ,
The distance in the radial direction from the outer surface of the block 26 to the groove bottom 32 of the main groove 24 in the vicinity of the corner 31 with a large intersection angle d is greater than the radial distance M; It protrudes outward in the radial direction, and on the other hand, the vicinity of the corner 31 is recessed inward in the radial direction from the cross-sectional contour of the red part 22 shown by the imaginary line. In addition, since the center part of the outer surface of each block 26 is also surrounded by rubber and has the highest ground pressure, the distance from the outer surface to the groove bottom 32 of the main groove 24 at the center part of each block 26 is The radial distance N is the minimum value of the radial distance near the corner, which is smaller than the radial distance M here. The outer surfaces of each part of the block 26 are connected by smooth curved surfaces. As a result, the ground pressure near the corner 30 increases, while the ground pressure near the corner 31 decreases, furthermore, the ground pressure at the center of the face of each block 26 decreases the most, and the ground pressure at each part of the block 26 decreases. The pressure becomes even. This results in
Even when the steering angle increases, the concentration of side force on areas with high ground contact pressure is alleviated, and as a result, a decrease in maximum cornering force is prevented. Here, the difference (mm) between the radial distance L and the radial distance M may be in the range of 0.01 to 0.025 times the difference (degrees) between the intersection angle c and the intersection angle d. preferable. The reason for this is that if it is less than 0.01 times, the ground pressure will not be uniform enough, whereas if it exceeds 0.025 times, the ground pressure near the corner 30 will increase too much, and This is because if the ground pressure near the corner 31 is reduced too much, the ground pressure becomes uneven. Further, the difference (mm) between the radial distance N and the minimum value of the radial distance near the intersection, here the radial distance M, is preferably in the range of 0.3 to 0.8.

[0011] In the above-described embodiment, there are two types of intersection angles, large and small, at the corners, but there may be three or more types of intersection angles. In this case, the smaller the crossing angle, the larger the radial distance from the outer surface of the block to the bottom of the main groove in the vicinity of the crossing. Further, in the embodiment described above, the outer surface of the block 26 has a convex polygonal shape, but the outer surface of this block may have a concave polygonal shape, for example, a T-shape.

Next, a test example will be explained. In this test, a red pattern as shown in FIG. Comparative tire 1 having the same directional distances and a red pattern as shown in FIG. A test tire 1 having a tread pattern as shown in FIG. , corner 30
, 31 and at the center of the surface of the block 26, the comparison tire 2 has the same radial distance from the outer surface of the block 26 to the groove bottom 32 of the main groove 24, and a red pattern as shown in FIG. radial distance L near the corner 30 and radial distance M near the corner 31
A test tire 2 was prepared in which the difference between the radial distance N at the center of the surface of the block 26 and the radial distance M at the corner 31 was 0.5 mm. Here, the intersecting angle a of the ribs 16 in the comparison test tire 1 is 120 degrees and the intersecting angle b is 240 degrees, while the intersecting angle c of the blocks 26 in the comparative test tire 2 is 60 degrees. d was 120 degrees. Moreover, the size of each tire was 205/60R15. next,
Each of these tires was filled with an internal pressure of 2 kgf/cm2 and was run on a drum at 30 km/h while applying a load of 360 kgf, and the maximum cornering force was measured while varying the slip angle. The results are shown in Table 1 and FIGS. 10 and 11 below.

[Table 1] As is clear from Figures 10 and 11, for the comparison tires, the maximum cornering force decreases significantly as the slip angle increases (in the large steering angle range), but for the test tires There is no decrease in maximum cornering force; on the contrary, there is a slight increase in maximum cornering force.

[0013] Furthermore, after installing the same comparison tires 1 and 2 and test tires 1 and 2 as described above on a domestic passenger car, the car was driven on a winding road, and the driving feeling of the driver on board was quantified. We looked for the dry performance of the tires. The results are shown in Table 1 above. From this test result, it is understood that the test tire has better dry performance than the comparative tire.

[0014]

As described above, according to the present invention, the dry running performance of the tire can be improved by preventing the maximum cornering force from decreasing in the large steering angle range.

[Brief explanation of drawings]

FIG. 1 is a developed view of a red portion showing a first embodiment of the present invention.

FIG. 2 is a sectional view taken along the line II in FIG. 1;

FIG. 3 is a sectional view taken along the line II-II in FIG. 1;

FIG. 4 is a sectional view taken along the line III-III in FIG. 1;

FIG. 5 is a sectional view taken along the line IV-IV in FIG. 1;

FIG. 6 is a developed view of a red portion showing a second embodiment of the present invention.

FIG. 7 is a sectional view taken along the line V-V in FIG. 2;

FIG. 8 is a sectional view taken along the line VI-VI in FIG. 2;

9 is a sectional view taken along the line VII-VII in FIG. 2. FIG.

FIG. 10 is a graph showing the value of maximum cornering force versus slip angle.

FIG. 11 is a graph showing the value of maximum cornering force versus slip angle.

[Explanation of symbols]

11...Pneumatic tire 12...Red part 13...Main groove 1
4...Red end 15...Side wall
16...Rib 17...Edge
18, 19...Intersection 20...Groove bottom
H, J, K...Radial distance a, b...Intersection angle

Claims (4)

[Claims] [Claim 1] A plurality of main grooves extending in the circumferential direction and bent in a zigzag shape are formed on the outer surface of the tread portion, so that a plurality of ribs are formed between the main grooves and between the main groove and the edge of the tread. In a pneumatic tire in which edges are formed at the boundary between the outer surface of these ribs and the side wall of the main groove, the rib near the intersection where the two edge directions intersect due to the bending of the main groove. A pneumatic tire characterized in that the radial distance from the outer surface of the main groove to the groove bottom of the main groove is increased as the intersection angle between the edges becomes smaller. 2. The pneumatic tire according to claim 1, wherein the radial distance at the widthwise central portion of the rib is smaller than the minimum value of the radial distance near the intersection. 3. A large number of polygonal blocks are formed by forming a plurality of circumferentially extending main grooves and a plurality of lateral grooves substantially axially extending and intersecting the main grooves on the outer surface of the tread portion. In addition, in a pneumatic tire in which edges are formed at the boundaries between the outer surface of these blocks and the side walls of the main groove and the lateral groove, the area near the corner where the two edges intersect due to the intersection of the main groove and the lateral groove. A pneumatic tire characterized in that the radial distance from the outer surface of the block to the bottom of the main groove is increased as the intersection angle becomes smaller. 4. The pneumatic tire according to claim 3, wherein the radial distance at the center of the face of the block is smaller than the minimum value of the radial distance near the corners.