JPS62157810A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To improve noise performance and wet performance without impairing controlling safety by specifying the position of a main groove on the outermost part from a tire equation and the form of a block positioned close to a ground contacting end from said main groove. CONSTITUTION:Plural main grooves 1 which extend in the circumferential direction of tire are provided on the tread of a tire. In this tread pattern, the relation between the distance (a) from a center line C-C in the circumferential direction of tire to the outer end part 3 of the main groove 1 provided on the outermost part, and the distance (b) from the center line C-C to a ground contacting end 2, is set as, a/b<0.6. Also, in a single block 4 close to the ground contacting end 2 from the main groove 1 on the outermost part, the relation between the geometrical moment of inertia Ix in the radial direction of tire and the geometrical moment of inertia Iy in the circumferential direction of tire is set as, 0.5<Ix/Iy<2.5. Thereby, noise characteristic and wet performance can be improved without impairing controlling safety.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a pneumatic tire, and more specifically, the present invention relates to a pneumatic tire that improves noise characteristics without impairing steering stability by specifying groove positions and block shapes. Related to pneumatic tires with improved wet performance.

[Prior art]

The noise generated when tires run is largely influenced by the tread pattern and is generally referred to as pattern noise.

Therefore, conventionally, block patterns are often used as trend patterns that emphasize steering stability, and this block pattern has the ability to drain moisture between the tire tread and the road surface to the outside of the tire tread on wet roads. Since it has excellent drainage ability, it has a feature of excellent wet performance, but on the other hand, it also has the disadvantage of a marked tendency to increase pattern noise.

Regarding this point, various improvement studies have been conducted, but these improvements are mainly due to improvements in the minimum unit of repeating patterns on the tire circumference, that is, the shape of the pitch and its construction method. In order to reduce batten noise by improving the arrangement, type of length, and number of pitches on the tire circumference, it is known that it is advantageous to shorten the pitch length (or increase the number of pitches). It is being

However, with this improvement, the current situation is that the pinch becomes smaller and the steering stability deteriorates.

[Purpose of the invention]

The present invention was made to solve these conventional problems, and an object of the present invention is to provide a pneumatic tire with improved noise characteristics and wet performance without impairing steering stability. That is.

[Structure of the invention]

In order to achieve the above object, the pneumatic tire of the present invention has a trend pattern having a main groove extending in the circumferential direction of the tire on the tire tread, the outer end of the main groove being disposed at the outermost side from the tire circumferential center line. Diagram of a block where the distance a from the tire circumferential direction center line to the ground contact edge has a relationship of a / b < 0.6, and the block is located closer to the ground contact edge than the outermost main groove The second moment of inertia Ix in the radial direction of the tire around the center and the second moment of inertia Iy in the tire circumferential direction are 0.5<'I x/
It is characterized by the relationship of Iy<2.5.

Next, the configuration of the pneumatic tire of the present invention will be specifically explained. For pneumatic tires for passenger cars, water drainage in the central area of the tire tread is a very important issue in terms of dynamic performance on wet roads, especially turning performance. Therefore, in order to improve wet performance, the groove area ratio within the contact area must be adjusted. Although drainage performance is improved by increasing
Conversely, in this case, the discontinuity in rigidity between the groove portion and the block portion increases, resulting in worsening of pattern noise.

Therefore, based on these backgrounds, the present invention etc. have developed noise characteristics,
In particular, the position of the main groove and blocks closer to the ground contact edge than the main groove, °
That is, various experiments were conducted focusing on the shape of the shoulder block, and the following was found.

(1) In order to improve drainage in the central area of contact with the ground, it is essential to arrange a plurality of linear main grooves extending in the circumferential direction of the tire.

In other words, the water in the center is removed to the front and back in the direction of travel of the vehicle,
It is necessary to improve drainage performance.

(2) As a result of various experiments regarding the arrangement of the main groove on the tread surface, it is necessary to limit the main groove to a specific range within the ground contact area.

If the number of main grooves is increased and the main grooves are arranged close to the ground contact edge, pattern noise will worsen.

Further, in a turning test on a wet tread with the same number of main grooves, a main groove arrangement in which the outer end of the main groove is located within the above-mentioned range shows good performance.

(3) From the standpoint of noise characteristics and handling stability, when considering the shape of the block closer to the contact edge than the main groove, that is, the shoulder block, in terms of noise characteristics, the second moment of inertia of the cross section in the circumferential direction of the block, zy, should be reduced. It is better to increase the cross-sectional moment of inertia 1-1x in the radial direction of the block in terms of steering stability.

Therefore, the ratio of the second moment of area of the shoulder block in the tire radial direction (tire width direction) and the tire circumferential direction is Ix/
It is necessary to take Iy larger than usual.

However, there is an appropriate value for the ratio I x / I y, and if it is too large, it will adversely affect the steering stability.

As described above, the pneumatic tire of the present invention, in which the position of the outer end of the main groove and the shape of the block outside the main groove are defined within the above range, can be used in turning on a wet road surface without impairing its handling stability. This is an effective means of improving performance and reducing pattern noise at the same time.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 shows a tread pattern of a pneumatic tire according to an embodiment of the present invention, and this tread pattern has a plurality of main grooves 1 extending in the circumferential direction of the tire on the tread surface of the tire.

Next, in FIG. 1, a is the distance from the tire circumferential center line C-C to the outer end 3 of the outermost main groove l, and b is the tire circumferential center line C-C.
The distance from C to the grounding end 2 is shown, and in this embodiment, the relationship is set to be a/b < 0.6.

FIG. 2 is an enlarged view of a single block 4 located closer to the ground contact edge 2 than the outermost main groove 1, and the second moment of inertia in the tire radial direction is Ix, and the second moment of inertia in the tire circumferential direction is is Iy, and the relationship between these Ix and ly is set so that 0.5<I x/I y<2.5.

Therefore, the main groove 1 has a pattern with the same cross-sectional area.
Example 1 of the present invention with / b = 0.52, Ix/Iy = 1.06 and a / b = 0.52, lx/Iy
Example 2 of the present invention where =o, so, and qa/b=0.
78, lx/Iy=0.25 comparison example 1, a/b
= 0.71, Ix/Iy = 0.48 comparison example 2 and a
/b=0.52, lx/Iy=3.25, an experiment was conducted for comparison example 3, and the above a/b, I x, I y
, Tx/Iy, the values of the pattern noise, web)jff one-time performance, and steering stability indices are determined in the table below.

(Left below) In the table above, the larger the number (index), the better the condition.

As shown in the table above, Example 2 of the present invention has a smaller a/b of 52% than Comparative Example 2, so it has excellent wet turning performance, but other characteristics are the same. has a small a/b of 52% compared to Comparative Example 2, and I
Since x/ry is increased to 1.06, wet turning performance and pattern noise are both improved. The results are shown in the relationship diagram between the noise index and Ix/Iy in Figure 3 and the relationship diagram between the wet circle turning index (lateral G) and a/b in Figure 4, where I x / I y is 0. .5 or more, a/b needs to be 0.6 or less.

Note that the higher the above index is, the lower the pattern noise is, and the harder the limit of wet circular turning is.

As mentioned above, generally speaking, the larger I x / I y is, the better the noise characteristics are.
If, for example, the number of pitches is increased in order to increase I y, xy becomes excessively small, and as a result, the total sum of lx decreases due to the increase in groove area, leading to a decrease in the steering stability index. This becomes the steering stability index (
The relationship between CP) and Tx/Iy is shown in the diagram of FIG. 5, and it is necessary that Ix/Ty be 2.5 or less.

(Effects of the Invention) As explained above, in a pneumatic tire consisting of a tread pattern having a main groove in the circumferential direction, the main groove position is located at the outermost part of the tire from the equator, and the shape of the block located closer to the ground contact edge due to the position of the main groove is By specifying this, it is possible to improve noise characteristics and wet performance without impairing steering stability.

[Brief explanation of drawings]

Fig. 1 is a tread pattern diagram of a pneumatic tire according to an embodiment of the present invention, Fig. 2 is an enlarged view of the main part of the block in Fig. 1, Fig. 3 is a diagram showing the noise index, and Fig. 4 is a wet circle. FIG. 5 is a diagram showing turning performance, and FIG. 5 is a diagram showing handling stability. 1...Main groove, 2...Grounding end, 3...Outer end, a.
・・Distance from the center line to the outer end of the main groove, b...
Distance from the center line to the ground contact edge, C-C... Center line in the tire circumferential direction, lx... Moment of inertia of area in the tire radial direction, Iy... Cross section 2 in the tire circumferential direction
°th moment.

Claims (1)

[Claims] In a tread pattern that has a main groove extending in the tire direction on the tire tread, the distance a from the tire circumferential center line to the outermost main groove outer end, and the distance b from the tire circumferential center line to the ground contact edge. is a/b<
0.6, and the cross-sectional moment of inertia Ix in the tire radial direction and the cross-sectional moment of inertia Iy in the tire circumferential direction of the block located closer to the ground contact edge than the outermost main groove
A pneumatic tire with a relationship of 0.5<Ix/Iy<2.5.