JPS61125902A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To reduce pattern-noises, to reduce unevenly distributed wear-down, and to enhance riding comfortability by constituting the captioned tire in such a manner that a length-ratio between the maximum pitch and the minimum pitch of the main groove is equal to the predetermined value, while sub-grooves and notches are arranged alternately at different preset angles relative to the circumferential direction of the tire. CONSTITUTION:Ratio alpha between maximum pitch length P1 and minimum pitch length Ps of main grooves 1-4, which are formed in a tire tread part, is set at 1.5 or greater. Subgrooves 5 connecting the main groove 1-4 and notches 6 extending from the main grooves 1-4 are arranged alternately in such a manner that the make different angles theta1 and theta2 relative to the circumferential direction of the tire. At this time, theta1 is set at less than 30 deg. while theta2 60 deg. or greater. With this constitution, pattern noises can be reduced, while unevenly distributed wear-down can be reduced as well. At the same time, riding comfortability can be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a pneumatic tire with low pattern noise and excellent comfort.

[Prior art]

The noise generated when tires run is largely influenced by the tread pattern, and is generally referred to as pattern noise. Looking at this pattern noise in more detail, it is thought that the main cause of its occurrence is changes in the rigidity of the grooves and protrusions that make up the tread pattern.
This noise is mainly in the frequency band of 500 to 1000 Hz.

Conventionally, many research and improvements have been made to reduce pattern noise. For example, such methods include changing the smallest unit (hereinafter referred to as pitch) of a repeating pattern on the tire circumference, changing the type of pitch length,
There are also causes such as changes in the number of pitches on the tire circumference.

However, even if these methods can reduce pattern noise to a certain extent when new, especially in block patterns, they tend to cause uneven wear, cuffing, etc. when worn, and this is a factor in increasing pattern noise. It is difficult to consistently reduce pattern noise from the time of wear to the time of wear.

Further, the noise generated while the tire is running, mainly pattern noise, is caused by the fact that the rigidity of the tread pattern changes along the circumferential direction of the tire as described above. therefore,
In a pattern (block pattern) that has multiple main grooves arranged in the circumferential direction and sub-grooves connecting the main groove and the main groove,
The tread rubber that makes contact with the road surface is broken by the grooves, and as it passes over the road surface, the tread rigidity changes greatly in the tire circumferential direction, generating pattern noise. Against this background, in order to smooth out the discontinuity in rigidity between the block group and the sub-groove, various experiments have shown that by bringing the angle between the sub-groove and the main groove closer to the tire circumferential direction. It is known that it is possible to reduce discontinuities in the stiffness of the entire tire road surface and to reduce pattern noise. However, by bringing the sub-grooves closer in the circumferential direction, the rigidity of each block constituted by the sub-grooves becomes weaker, so although the discontinuity in rigidity is eliminated, problems such as uneven wear and cupping occur. As a way to solve this problem,
The tread shoulders, which are prone to uneven wear and uneven wear, are based on ribs, but this is not sufficient.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a pneumatic tire for military use that does not cause uneven wear even during wear and can consistently reduce pattern noise from when it is new to when it is worn out.

[Structure of the invention]

For this reason, the present invention provides a plurality of main grooves in the tire circumferential direction on the tire contact surface, and arranges sub-grooves and/or notches on the tire contact surface so that the tread shoulders are configured in a rib-based manner, and In a tread pattern in which the main groove is varied with pitches different in length or more, (1
) The ratio (1α) of the length of the main groove 0 maximum and minimum constriction is 1.5 or more, and (2) the sub-grooves and/or notches are arranged alternately at different angles θ1° θ2 with respect to the tire circumferential direction. and 30° θ1. The gist of the present invention is a pneumatic tire for a passenger car characterized by θ2<60°. Note that here, the sub-groove refers to a groove that connects the main groove to the main groove, and the notch refers to a groove that extends from the main groove and does not connect to another main groove or sub-groove.

Hereinafter, the configuration of the present invention will be explained in detail with reference to the drawings.

FIG. 1 is an explanatory plan view partially showing an example of the contact surface of the tire of the present invention. In this Figure 1, EE″
indicates the tire circumferential direction, and T is the tire ground contact width. 1,
2.3.4 are main grooves each provided annularly in the tire circumferential direction EE'. 5 represents a sub-groove connecting the main grooves, and 6 represents a notch extending from the main groove. θ1, θ2
are different angles of the sub-groove 5 or notch 6 with respect to the tire circumferential direction EE'. Pl represents the maximum pitch of the main groove, Pm represents the intermediate pitch of the main groove, and Ps represents the minimum pitch of the main groove. These pitches are the minimum unit of a continuous repeating pattern in the tire circumferential direction EE'', and indicate that the minimum unit on the tire circumference is 31M class.The tread shoulder near the ground contact edge has a rib pattern ( It has a rib base 11).

According to the present invention, the tire shown in FIG. 1 satisfies the following requirements (1) and (2).

(l) The length ratio (α) of the maximum pitch Pg to the minimum pitch Ps of the main groove is 1.5 or more.

This is because by setting α to 1.5 or more, it is possible to disperse the imaging frequencies at which the blocks in the trend pattern occur each other and to reduce the noise level. This is clear from FIG.

FIG. 2 shows experimental results when the pitch ratio α was varied in the tread pattern shown in FIG. In this figure, the vertical axis represents the noise level index, and the horizontal axis represents the pinch ratio. This experimental result is based on tire size 20 as measurement condition.
5 /60 Using RL5 tires, tire internal pressure 1.8
kg/cnl actual vehicle test results.

As can be seen from FIG. 2, the pattern noise decreases as the pinch ratio α increases. When the pitch ratio α is up to 1.5, the rate of change is large, and when it is 1.5 or more, it can be said to be at a stable level.

The index is the pinch ratio α1, which was common in conventional tires.
The case of 3 is shown as 100, and the smaller the value, the better.

(2) The sub-grooves 5 and/or notches 6 are formed at different angles θ1 with respect to the tire circumferential direction. arranged alternately at θ2, and 3
0° θ1. θ2<60".

The sub-grooves 5 and/or notches 6 are formed at different angles θ1 with respect to the tire circumferential direction. The reason why they are arranged alternately at θ2 is that the same effect as simply increasing the pitch variation can be obtained.

Also, 30°〈θ2. The reason for setting θ2<60'' is based on the experimental results shown in FIG.

Preferably, -021≧10'.

FIG. 3 shows the results of an experiment conducted by changing the angle of the sub-grooves 5 in the tread pattern shown in FIG. 1. In this figure, the left vertical axis shows the noise level index, the right vertical axis shows the uneven wear index, and the horizontal axis shows the sub-groove angle. Further, a represents the noise level, and b represents uneven wear. The smaller the index value, the better. Note that the index is set to 100 when the sub-groove angle is 60'', which is often used in conventional tires.

From FIG. 3, it can be seen that as the sub-groove angle becomes smaller, pattern noise decreases, but uneven wear becomes more likely to occur. For this reason, the sub-groove angle is between 30" and 30".
It can be said that the angle is 60°.

The same applies to the notch angle.

〔Effect of the invention〕

As explained above, according to the present invention, since the requirements (1) and (2) are defined in the tire trend pattern shown in FIG. can be kept low, making it possible to significantly improve the comfort during driving.

The effects of the present invention will be specifically explained below with reference to experimental examples.

Experimental Example 1al In the tread pattern (all blocks) shown in Fig. 4, a tire was manufactured with α=Pffi/Ps=1.3, sub-fi5 θ1=60°, and θ2-60'' (Conventional Tire 1) .

For comparison, α=p in the tread pattern shown in FIG. 5 (rib on the back, block in the center)
l/P3=1.3, θ+=60' of sub groove 5, θ2
=60'', θ1-60° of notch 6.

A tire of the same size was similarly produced with θ2=60° (Comparative Tire 1).

Pattern noise was measured for these tires in accordance with JASO-C606-81 tire noise test method.

These results are expressed as an index in Table 1 below. In addition, the index indicates that the smaller the value, the better.

Table 1 Conventional tire l Comparative tire 1 When new 100 95 When worn 120 100 From Table 1, it can be seen that even when worn, Comparative Tire 1 is at the same level as Conventional Tire 1 when new. This is because, as described above, the occurrence of uneven wear is suppressed in the comparative tire 1.

fb) In the tread pattern shown in FIG. 1, α=PIl/Ps=1.55, and θ of the sub-groove 5.

= 35°, θ2 = 45°, θ1 of notch 6 = 35°.

A tire was manufactured with the angle θ2-45° (tire of the present invention).

Also, for comparison, θ+=60' of the sub-groove 5.

A tire was produced in the same manner as in the tire of the present invention, except that θ2=60'' (Comparative Tire 2).

Furthermore, a tire was produced in the same manner as in the tire of the present invention, except that the sub-grooves 5 were θ1 = 35° and θ2 = 35° (Comparative Tire 3).

The noise level and uneven wear of these tires were measured in accordance with the JASO-C5O6-81 tire noise test method. These results are expressed as an index in Table 2 below. In addition, the index indicates that the smaller the value, the better.

(Margin below this page) As can be seen from Table 2, regarding pattern noise, the tire of the present invention has a large angle of 45°, while the comparison tire 3 has a small angle of 35°.
shows a better level. This is because, as described above, in the tire of the present invention, the vibration frequency is dispersed by increasing the pitch variation due to the combination of two types of angles. In addition, regarding uneven wear, although the tire of the present invention is inferior to Comparative Tire 2, it does not change significantly as compared to Comparative Tire 3.

[Brief explanation of drawings]

Fig. 1 is a plan view explanatory diagram partially showing an example of the contact surface of the tire of the present invention, Fig. 2 is a diagram showing the relationship between pitch ratio α and noise level index, and Fig. 3 is a diagram showing the relationship between pitch ratio α and noise level index, and Fig. 3 shows noise level index and uneven wear. FIG. 3 is a relationship diagram between an index and a sub-groove angle. Further, Fig. 4 and Fig. 5 are explanatory diagrams showing examples of tire trend patterns, respectively. 1.2.3.4...Main groove, 5...Sub groove, 6...・
Notch. Agent Patent Attorney Shin Ogawa - Kensho Noguchi Kazuhiko ShimoFigure 1Figure 2Figure 4Figure 3Figure 5

Claims (1)

[Claims] A plurality of main grooves are provided in the tire circumferential direction on the tire contact surface, and sub-grooves and/or notches are arranged on the tire contact surface, so that the tread shoulder is configured in a rib-based manner, and three or more types of different lengths are provided. In a tread pattern in which the main groove is varied in pitch, (1) the ratio (α) of the length of the maximum pitch to the minimum pitch of the main groove is 1.5 or more;
(2) The sub-grooves and/or notches are arranged alternately at different angles θ_1 and θ_2 with respect to the tire circumferential direction, and
A pneumatic tire for a passenger car, characterized in that 0°<θ_1, θ_2<60°.