JPH02171306A - Radial tire - Google Patents

Abstract

PURPOSE:To increase uniformity by equalizing a groove cross-sectional ratio in circumferential cross-section of a tire between blocks for which unit pitch lengths are different with each other and equalizing the circumferential radius on the block surface of the tire with the reference outside diameter of the tire, in the titled tire with a tread pattern for which the unit pitches of the blocks are varied with each other. CONSTITUTION:A groove cross-sectional area ratio ((groove cross-sectional area A) X 100 / (unit pitch length P) X (tread thickness D)) in circumferential cross-section of a tire is substantially equalized between blocks 1S for which unit pitch lengths are different with each other. Also, the circumferential radius Rp on the block surface of the tire is equalized with the reference outside diameter Rreg of the tire. By this, a distance (under-groove gauge) from the bottom of the grooves forming blocks to a belt layer 5 is equalized to increase uniformity. Thus, vibration during running is reduced to increase comfortability during driving and anti-wear property.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a tire with excellent uniformity in the circumferential direction, low vibration during high-speed running, excellent ride comfort, and excellent uneven wear resistance. Regarding radial tires.

[Conventional technology]

Conventionally, as shown in FIG. 2, a pneumatic tire having a block-based pattern in which blocks 1 divided by vertical grooves 2 and lateral grooves 3 are arranged in the tire circumferential direction has a tendency to generate noise due to the pattern. In order to reduce this, generally the pitch length in the tire circumferential direction is made random, and the tire width direction grooves are arranged at random intervals in the tire circumferential direction. Changes in pitch length in the circumferential direction of a tire are determined by how grooves extending in the width direction are arranged in the circumferential direction of the tire. formed at the same depth. Therefore, in a tire having a block pattern with random unit pitch length in the tire circumferential direction, the groove cross-sectional area ratio of the block in the circumferential cross section of the tire (the groove area ratio to the trend rubber cross-sectional area) corresponds to the change in the unit pitch length. percentage) will change.

That is, as shown in FIG. 3, which is a cross-sectional view taken along line A-A' in FIG. Groove bottom gauge Gs corresponding to the distance from the groove bottom to belt N5
is small, but in the area where the pitch length is small, the groove bottom gauge G
L increases, and the groove gauge in the circumferential direction of the tire fluctuates. This is because during tire vulcanization, the forming bones of the mold dig into the tread rubber while excluding rubber, forming grooves, and the rubber is removed due to the density and density of the widthwise grooves arranged in the circumferential direction of the tire. This is due to the difference in the amount of When such a tire is filled with the specified amount of air, the uniformity in the circumferential direction of the tire decreases in response to fluctuations in the groove gauge, causing the vehicle to vibrate while driving, worsening ride comfort, and reducing wear resistance. Decreases sex.

Particularly in tires where the groove bottom gauge (distance between the groove bottom and the belt) is 4 ms or less, such gauge fluctuations have become a fatal defect in tire performance.

On the other hand, tires with varying groove widths in the width direction have been proposed for various purposes, and it is possible to adjust the amount of rubber flow during vulcanization by changing the groove width. However, changing the groove width according to the pitch length was not sufficient to eliminate fluctuations in the groove bottom gauge in the tire circumferential direction.

In order to obtain a tire with no fluctuation in the groove bottom gauge, the inventor determined that the proportion of tread rubber removed by molding bones of a mold for forming tread grooves during tire vulcanization, regardless of the pitch length. In order to keep it constant, we focused on the "ratio of the groove area to the tread rubber cross-sectional area" in the tire circumferential cross-section, and called this the "groove cross-sectional area ratio". They succeeded in making the material substantially uniform and completed the present invention.

[Problem to be solved by the invention]

An object of the present invention is to improve uniformity of a tire having a block-based pattern in which the unit pitch length in the tire circumferential direction is changed by reducing fluctuations in groove gauge in the circumferential direction, and to provide excellent ride comfort and durability. An object of the present invention is to provide a radial tire with less reduction in wear properties.

[Means to solve the problem]

The tire of the present invention has a tire having a block-based tread pattern in which the unit pitch length of the blocks arranged in the tire circumferential direction changes, and the groove cross-sectional area ratio in the tire circumferential cross section between the blocks having different unit pitch lengths. By making them substantially the same, the groove bottom gauge, which is the distance from the bottom of the grooves constituting these blocks to the belt layer, is made substantially the same, and at least part of the radius in the tire circumferential direction on the surface of each block is made substantially the same. is made part of the standard outer diameter of the tire to improve uniformity in the circumferential direction of the tire.

In the present invention, the groove cross-sectional area ratio of the block in the tire circumferential cross section is a value defined by the following formula.

(Margins below this page) Groove cross-sectional area ratio - The groove cross-sectional area ratio is the unit pitch length P (the distance between the center lines dividing the groove width into two), as shown in the enlarged cross-sectional view of the groove part in Figure 5. ) refers to the ratio of the groove cross-sectional area between the tire reference outer diameter line Q, which is the outermost road surface of the tire tread, and the belt layer 5, and in particular, the groove cross-sectional area A refers to the area of the shaded part in the figure. say.

In order to make the groove bottom gauges of tires having block patterns with different unit pitch lengths, which is a feature of the present invention, substantially the same, it is necessary to The purpose is to minimize the difference in the groove cross-sectional area ratios and to make the groove cross-sectional area ratios substantially the same.

In order to make the groove cross-sectional area ratio between the blocks substantially the same, the volume of the block with a large unit pitch length in the tire circumferential direction is reduced, and the 'lfG cross-sectional area ratio in the circumferential cross section is increased. Alternatively, this can be achieved by increasing the volume of a block with a small unit pitch length and decreasing the groove cross-sectional area ratio in its circumferential cross section, or by a combination of these.

In the present invention, for example, as shown in FIG. 1, the surface of the block 13 in the region S having a large unit pitch length P in the tire circumferential direction is made convex or spherical (as shown in FIG. shape) and expand the groove cross-sectional area ratio so that it becomes substantially the same as the groove cross-sectional area ratio of the block IL in the area where the unit pitch length P is small in the tire circumferential direction. The gauge G is made to be substantially the same.

That is, the tire of the present invention shown in FIG. 1 is used as a tire molding mold by reducing the volume of the block molding portion of the mold corresponding to the block IS in the region S where the unit pitch length P is large and the groove cross-sectional area ratio is small. Specifically, by making the block forming part between the groove forming bones concave and reducing the volume of the block, the volume of the block IL in the area where the unit pitch length is small and the groove cross-sectional area ratio is large. This can be obtained by using a mold in which the volume difference between the two blocks is reduced and the volumes of these blocks are made substantially the same. 6 and 7 show the circumferential cross-sectional shape of a block in which the volume of the block with the large unit pitch length P is reduced and the back cross-sectional area ratio is enlarged, which is another embodiment of the tire of the present invention. .

On the other hand, as a method of increasing the volume of a small block with a unit pitch length P, there is a method of narrowing the groove width or shallowing the groove depth of the widthwise groove forming this block. Even if only these methods are adopted, it is actually difficult to make the gage under the grooves uniform, so it is preferable to use these methods in combination with the above embodiments.

In order to make the groove cross-sectional area ratios in the tire circumferential sections of blocks with different unit pitch lengths substantially the same, as shown in FIG. 1, FIG. 6, or FIG. Although it is common to make the surface of the block uneven or flat depending on the size of the block, it is preferable to make the block surface curved (convex or spherical) as shown in FIG.

However, even if the groove cross-sectional area ratio in the tire circumferential cross section is made substantially the same and the groove bottom gauge is made to be substantially the same, the above-mentioned difference when the tire is filled with the normal internal pressure is At least a portion of the surface of each block needs to have a tire circumferential radius Rp that matches the tire reference outer diameter Rreg, thereby ensuring uniformity. That is, in FIG. 1, which shows a state in which the tire of the present invention is filled with the normal internal pressure, the block IL in the region with a small unit pitch length has a circumferential radius RL that matches the reference outer diameter Rrag on the entire surface thereof. , the block IS in the region S with a large unit pitch length has a circumferential radius Rp (maximum radius portion) only at the center of its surface that matches the reference outer diameter Rreg of the tire, and from this center surface to the left and right. As the position shifts, the circumferential radius Rs gradually becomes smaller. In addition, in the case of FIGS. 6 and 7, the circumferential radius RL of the block IL in the region with a small unit pitch length matches the reference outer diameter Rreg over the entire surface, but the surface is concave or flat. In the block IS of the region S with a large unit pitch length, the circumferential radius Rp (maximum radius portion) matches the reference outer diameter Rreg only at the peripheral edge, and the circumferential radius Rs at the center portion changes. There is.

In the tire of the present invention, in order to more effectively improve the uniformity of the tire, the groove bottom gauge G should be 41
It is desirable to set it to I+IIl or less.

Hereinafter, the present invention will be specifically explained using examples and conventional examples.

The vibration characteristics and wear resistance of the tires were evaluated by the following method.

Vibration characteristics that indicate ride comfort: Three testers evaluated the feeling by driving the vehicle (out of 10).

Wear resistance: The test tires were mounted on a large vehicle and run on a course with high frequency of driving and braking. The difference (average) in the amount of wear in the block before and after running for OOOKm was measured and evaluated.

EXAMPLE, CONVENTIONAL EXAMPLE By changing only the tread forming surface of the tire mold, the following tires of the present invention and conventional tires (tire size: 19
5/70R1490S) was prepared and its performance was evaluated. That is, it has a tread pattern shown in FIG.
A tire of the present invention having a circumferential cross-section shown in FIG. 1 with substantially the same groove cross-sectional area ratio in the tire circumferential cross-section, and a tire having a tread pattern shown in FIG. The vibration characteristics and wear resistance of conventional tires having the circumferential cross section shown in FIG. 3 with varying ratios were evaluated, and the results shown in Table 1 were obtained.

(Blank below next summer) Table 1 From Table 1, compared to the conventional tire, the tires of the present invention have reduced fluctuations in the groove gauge in the tire circumferential direction, which improves the uniformity in the tire circumferential direction, which is shown in the vibration characteristics. It can be seen that ride comfort has been improved and wear resistance has also been improved.

Next, as shown in Table 2, for the tires of the present invention and conventional tires, only the groove gauge was changed, and the vibration characteristics were evaluated for the tires in which the groove gauge exceeded 411 Ill, as shown in Table 2. The following results were obtained.

Table 2 From Table 2, for tires with a groove gauge of 4 mm or more,
It was confirmed that fluctuations in the groove gauge had little effect on the vibration characteristics of the tire.

[Effects of the Invention] According to the present invention, in a radial tire having a block-based pattern in which the block length in the tire circumferential direction is changed, the groove cross-sectional area ratio in the tire circumferential cross section is made substantially the same, and the tire circumferential direction By making the bottom groove gauges of the tires substantially the same, the uniformity of the tire is improved, which reduces vibrations during running of radial tires with a block pattern, improves ride comfort, and improves wear resistance. It can be improved.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view along the tire circumferential direction showing an example of the tire of the present invention, FIG. 2 is a partial plan view showing an example of a block-based tread pattern, and FIG. 3 is a partial cross-sectional view of a conventional tire along the tire circumferential direction. (corresponding to the section taken along line A-A' in Figure 2), Figure 4A is a perspective view showing an example of a block whose mouth has the curved surface of Figure 1, and Figure 5 shows a groove. A partially enlarged cross-sectional view of a block on the tire circumference 11 analysis surface for explaining the cross-sectional area ratio, and FIGS. 6 and 7 are partial cross-sections along the tire circumferential direction showing other aspects of the tire of the present invention. It is a diagram. 1...Flock, 2...Vertical groove, 3...Horizontal 21st, 5...Belt layer, G...Groove lower gauge, A...Bone 1
4 area, P... pinch length, D... trend thickness,
RL, Rs -, Rp...Circumferential radius of the block surface, Rreg...Reference outer diameter of the tire, Q...Reference outer diameter line of the tire. Agent Patent Attorney Nobuo Ogawa −

Claims (1)

[Claims] In a tire having a block-based tread pattern in which blocks are arranged with varying unit pitch lengths in the tire circumferential direction, groove cross-sectional area ratios in the tire circumferential cross section between blocks having different unit pitch lengths are substantially the same. , and a radius in the tire circumferential direction of at least a portion of the surface of each block is made to match a reference outer diameter of the tire.