JPH04103406A - Pneumatic radial tire for heavy load - Google Patents

Abstract

PURPOSE:To provide a large block edge effect by adopting double-projection tread face wherein a circular arc with the outline of small radius passing a tread center point and a tread side edge is the contour in section, and forming a groove contiguous in the circumferential direction at the substantially central position of each outlined circular arc. CONSTITUTION:A reference circular arc 16 is so assumed that it has its center on the equatorial plane 10 of tire and passes both tread side edges. The radius of the reference circular arc 16 is set 2-3 times the maximum width W in section of tire. The crossing point between the reference circular arc 16 and the tire equatorial plane 10 is assumed to be the tread center point 18. In this case, the sectional contour of tread face is formed in a double projection shape of one outlined circular arc 20 passing one tread side edge 12 and the tread center point 18 and the other outlined circular arc 22 passing the other tread side edge 14 and the tread center point 18. At the tread face, three zigzaged main grooves 31, 32, 33 contiguous to each other in the circumferential direction of tire and auxiliary grooves crossing them, and the main grooves 31, 32, 33 on both sides are respectively positioned at the central part of the circular arcs 20, 22 substantially.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heavy-duty pneumatic radial tire for trucks, buses, etc.

[Prior Art] Conventionally, in the field of heavy-duty tires, so-called spike tires, in which bottles are driven into the tire tread, have been common for winter use. However, since spiked tires scrape the road surface and cause dust pollution, the development of studless tires is desired.

This type of studless tire is known to have a tread with a block pattern in which many grooves are formed in the tire circumferential direction, and each block is provided with a large number of sipes that intersect in the tire circumferential direction. was a single item whose radius r was more than twice and less than three times the maximum cross-sectional width W of the tire, and whose cross-sectional outline was an arc centered on the tire's equatorial plane. However, in this specification, the radius of the tread surface refers to the value when the tire is mounted on a standard rim and filled with standard pressure air.

In this tire, each edge of the block rubber formed by providing grooves in the circumferential direction of the tire scratches the frozen road surface when skidding, so the skidding resistance is improved by the so-called edge effect. The reason why the radius r of the arc was set in the range 7 above is because when r/W is less than 2, the difference in ground pressure between a part of the tread center and a part of the tread shoulder becomes large, causing blocks to form. This is because uneven wear is likely to occur, and conversely, when r/W becomes larger than 3, heat generation in a portion of the tread shoulder becomes high and belt durability is significantly reduced.

[Problems to be Solved by the Invention] Required performances on frozen roads include braking, starting, indexing, skidding resistance, etc., but performance to prevent skidding is particularly important.

This is because, unlike other performances, it is difficult for drivers to compensate for this with driving techniques. Insufficient anti-skid performance may cause a so-called jack-knife phenomenon, for example, when a trailer is running, resulting in a serious accident.

However, it has been difficult to obtain sufficient anti-skid performance with the conventional tires. Because the tre-sod surface had a single convex cross-sectional shape with a cross-sectional outline of an arc centered on the tire equatorial plane, the ground contact pressure at a location away from a part of the tre-sod center was low, and the tire circumferential direction was This is because even if grooves are provided, a sufficient edge effect cannot be obtained. Especially when the load is low, such as when the vehicle is empty, the ground contact pressure on the tread surface other than a portion of the tread center becomes extremely low, making it impossible to exhibit the edge effect. Furthermore, as the number of grooves increases, the area occupied by the grooves on the tread surface increases, resulting in a problem in which the tread rigidity decreases and the grip of the tire becomes weaker.

An object of the present invention is to provide a heavy-duty pneumatic radial tire that improves anti-skid performance on frozen roads by changing the cross-sectional profile of the tread portion and combining it with a groove device without sacrificing other required performances. purpose.

[Means for Solving the Problems] A heavy-duty pneumatic radial tire according to the present invention has a block pattern tread surface.

Furthermore, assuming a reference arc that has its center on the tire equatorial plane and passes through both side edges of the tread, the reference arc when the radius r of this reference arc is set to be more than twice and less than three times the maximum cross-sectional width W of the tire. When the intersection with the tire equatorial plane is taken as the tread center point, the radius R of the tread surface is the radius r of the reference arc.
It has a biconvex cross-sectional shape whose cross-sectional shape is a contour arc that passes through the tread side edge and the tread center point, and is 0°5 times or more and 0.8 times or less of the tread center point. Each groove is formed in a row in the circumferential direction.

[Function] In the heavy-duty pneumatic radial tire according to the present invention, since the radius R of the contour arc is smaller than the radius r of the reference arc, unlike the conventional case, the center of the contour arc moves from the tire equatorial plane to the tread side edge side. The tread surface is biconvex. Therefore, the ground contact pressure at approximately the center position of each contour arc is increased, and a large frictional force is obtained at this position.

Since grooves are provided in this position that extend in the tire circumferential direction, the edges of the block rubber formed by providing these grooves efficiently scratch the frozen road surface during skidding. By realizing this large edge effect, the anti-skid performance is greatly improved.

If the radius R of the contour arc is less than 0.5 times the radius r of the reference arc, the deviation of the ground pressure distribution will become too large and uneven wear will occur in the block. If R/r exceeds 0.8, the desired biconvex ground pressure distribution cannot be obtained, and a sufficient edge effect cannot be expected.

[Example 1] Fig. 1 is a schematic cross-sectional view of the tread portion of a heavy-duty pneumatic radial tire according to an embodiment of the present invention, and Fig. 2 is a partially enlarged developed view showing the tread pattern of this radial tire.

As shown in FIG. 1, a reference arc 1B is assumed to have its center on the tire equatorial plane 10 and pass through both side edges 12 and 14 of the tread. The radius r of this reference arc 16, that is, the reference crown radius, is more than twice and less than three times the maximum cross-sectional width W of the tire, as in the conventional tread cross-sectional profile. The intersection of the reference arc 1B and the tire equatorial plane 10 is defined as a tread center point 18. The cross-sectional profile of the tread surface consists of one contour arc 20 passing through one tread side edge 12 and the tread center point 18, and another contour arc 22 passing through the other tread side edge 14 and the tread center point 18. It is biconvex. However, the radius R of the two contour arcs 20.22, that is, the contour crown radius, is both 0.5 of r.
It is 0.8 times or more and 0.8 times or less.

As shown in Fig. 2, the tread surface of this tire has three main grooves 31, 32, 3 that are continuous in a zigzag shape in the tire circumferential direction.
3 and sub-grooves 41 to 48 intersecting these, the main grooves 31.33 on both sides are formed at approximately the center of the contour arc 20.22. Each block 51, 52, 53, 54 has a plurality of sipes 61, 82, 61, 82, 61, 52, 53, 52, 53, 53, 53, 53, 52, 61, 52, 61, 61, 61, 61, 82, 61, 82, 61, 82, 61, 61, 61, 61, 61, 61, 61, 61, 82, 61, 61, 61, 61, 61, 82, sipes, respectively, which intersect with each other in the tire circumferential direction. H,84 is provided.

FIG. 3 is a graph showing the relationship between the distance from the tire equatorial plane 10 and the ground contact pressure in the tread portion of the radial tire of size 10.0OR2014PR, together with a conventional example.

As can be seen from the figure, in conventional tires, the tread surface of which had a semi-convex cross-sectional shape with a cross-sectional outline of one arc centered on the tire's equatorial plane, the ground contact pressure at a position away from a part of the tread center was low. Even if a groove in the tire circumferential direction is provided at this position, a sufficient edge effect cannot be obtained. On the other hand, in the tire according to this embodiment, the ground contact pressure at approximately the center position of each contour arc 20, 22 is increased, and a large frictional force is obtained at this position. Since the main grooves 31 and 33 are provided in this position, which are continuous in the tire circumferential direction, the block edges 71, 72, 73 formed by providing these grooves are
．． 74 (see Figure 2) efficiently scratches the frozen road surface when skidding.

By realizing this large edge effect, the anti-skid performance is greatly improved.

FIG. 4 shows the results of an actual vehicle test conducted to determine the ratio of the contour crown radius to the reference crown radius, that is, the appropriate value of R/r.

The wear deviation on the vertical axis is the block wear amount at approximately the center of the contour arc 20.22 minus the block wear amount at the tread center point 18. As can be seen from the figure, R/r is 0. If it is less than 5, the wear deviation will exceed 3 mm, resulting in unacceptable uneven wear.

Table 1 shows the skidding resistance of two types of tires with biconvex tread surfaces with different r/W and R/r (Example 1 and 2) and the conventional tire with the semi-convex tread surface. Shows the results of performance tests. However, each tire has a maximum cross-sectional width W of 270 mrn and a tread width TW of 206 mm. The skidding resistance performance index in the same table is obtained based on the lap time measurement results per lap on the frozen circular turning test course, with the conventional example set as 100, and the larger the index value, the higher the index value. Indicates good anti-skid performance.

From the results shown in the same table and Figure 4, r/W = 2~
3. It can be seen that when the conditions of R/r-0.5 to 0.8 are satisfied, the anti-skid performance on frozen roads can be improved without deteriorating the anti-uniform wear performance.

(Left below) [Effects of the Invention] The heavy-duty pneumatic radial tire according to the present invention has a tread center point assuming a reference arc having a radius r that is at least twice and not more than three times the maximum cross-sectional width W of the tire. By determining the tread center point and the tread side edge and adopting a biconvex tread surface whose cross-sectional outline is a contour arc with a small radius R, the ground contact pressure at approximately the center of each contour arc is increased. Since grooves that extend in the tire circumferential direction are formed at these positions, a large block edge effect can be obtained. Moreover, since R/r is limited to a range of 0.5 to 0.8, uneven wear of the block can be prevented. Therefore, according to the present invention, it is possible to significantly improve skidding resistance on frozen roads without sacrificing uneven wear resistance.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view of the tread portion of a heavy-duty pneumatic radial tire according to an embodiment of the present invention, FIG. 2 is a partially enlarged developed view showing the tread pattern of the previous radial tire, and FIG. FIG. 2 is a graph showing the relationship between the distance from the tire equatorial plane and the ground contact pressure in the tread portion of the tire, together with a conventional example. FIG. 4 is a graph showing the relationship between R/r and block wear deviation. Explanation of symbols 10: Tire equatorial plane, 12.14: Tread side edge, 1): Reference arc, 18: Tread center point, 20.2: Contour arc, 31, 32 .33...
・Main groove, 41-48... Minor groove, 51.52.58.5
4...Block, B1.62, 63.84...Sipe, 71.72.73.74...Block edge,
r...Reference crown radius, R...contour crown radius, TW, tread width, W...maximum tire cross-sectional width. Awn copy 1 1 relaxation is 1 尰↓Jj1η Fig. 1 - Iku ψ Fig. 3

Claims (1)

[Claims] 1. Assuming a heavy-duty pneumatic radial tire with a block pattern tread surface, the reference arc is centered on the tire equatorial plane and passes through both side edges of the tread.
When the radius (r) of this reference arc is set to be more than twice and less than 3 times the maximum cross-sectional width (W) of the tire, and the intersection of the reference arc and the tire equatorial plane is taken as the tread center point, the tread surface has a radius of (R) is 0.5 times or more and 0.8 times or less the radius (r) of the reference arc, and the cross-sectional outline is a contour arc that passes through the tread side edge and the tread center point. A pneumatic radial tire for heavy loads, characterized in that grooves extending in the tire circumferential direction are formed on the tread surface at approximately the center of the contour arc.