JPS60121103A - Low noise pneumatic tire - Google Patents

Abstract

PURPOSE:To improve running stability and avoid generation of cracks in the connection portion between a weir plate and a groove bottom by specifying projected length of the upper area of the weir plate and average thickness of the weir plate, in a low-noise tire in which the weir plate is arranged in a longitudinal groove, and constructing a lower area in such a way that it dents toward the groove wall side. CONSTITUTION:A weir plate 4 comprises an upper area 4a which is in form of a straight line and in which a projected length b at an optional point in the depth direction of a longitudinal groove 3 is 20-48% of the groove depth B at the position and a lower area 4b whose tip end is bent curvedly from the tip end of the upper area 4a to the groove wall 3a side. And an average thickness of the weir plate 4 is set to 20-80% of a projected length b0 of the weir plate on the tire surface. Further, height d of the upper area 4a is made as 30-80% of the depth D of the groove. Thereby, running stability can be improved without deteriorating low noise performance, and generation of cracks in the connection portion between the weir plate and a groove bottom can be prevented.

Description

[Detailed description of the invention] TECHNICAL FIELD This invention relates to a low-noise bolt-inflating tire.

In a pneumatic tire for automobiles having at least two vertical grooves continuous in the circumferential direction on the tread surface of the tire, the above If & By installing multiple weir plates protruding in the groove width direction on the groove walls of the groove, the speed of the airflow due to the pumping action when touching the ground is reduced, while the frequency of the air column resonance tube formed by the above-mentioned vertical grooves is dispersed. It is known to lower the V sensitivity level (see Japanese Utility Model Application Publication No. 58-22801v).

However, in the above-mentioned known low-noise pneumatic tire, the protruding length of the weir plate is large, the tip of which extends beyond the center line of the longitudinal groove, and the part that touches the vicinity of the groove bottom has the same protruding length as the upper part. Because of this, when driving on a wet road, drainage of the vertical groove is obstructed and running stability is reduced, and stress is applied to the connection between the weir plate and the groove bottom when touching the ground. There is a drawback that cracks are generated in a concentrated manner in this connection, and these cracks grow, shortening the tire life tt.

This invention provides a low-noise pneumatic tire in which a weir plate is provided in the longitudinal groove, while keeping the wavy pattern noise to the same level as the known low-noise pneumatic tire, and moreover, This improves the durability of the tire and makes it difficult for cracks to occur at the connection between the weir plate and the vicinity of the groove bottom, thereby extending the life of the tire.

That is, the present invention provides a low-noise pneumatic tire having at least two longitudinal grooves continuous in the circumferential direction of the tire and having a plurality of weir plates protruding from the groove walls of the longitudinal grooves in the groove width direction. The weir plate consists of a lower region close to the groove bottom and an upper region excluding the lower region, and the protrusion length of the upper region at any position in the groove depth direction is equal to the groove width at any position. The tip of the lower region is recessed from the tip of the upper region toward the groove wall, and is formed in a curved shape that touches the vicinity of the groove bottom, and the average thickness of the weir plate is equal to the protruding length of the weir plate on the tire surface. It is a low-noise pneumatic tire characterized by a pitch of 20 to 80 strokes.

Embodiments of the present invention will be described below with reference to the drawings. In FIG.
2 is a tire shoulder, 8 is a longitudinal groove, and P is an equator, and a weir plate 4 is provided to protrude from the groove wall 8a of the longitudinal groove 8. As shown in FIG. 2, this weir plate 4 consists of an upper region 4 & whose tip is formed in a straight line, and a lower region 4b whose tip is formed in a curved shape. Area 4&
It is recessed from the tip toward the groove wall 8 & side and is inscribed in the groove bottom 8b.

Generally, when a tire rotates under load, each part of the tread 1 repeatedly contacts the ground every rotation, and a large shear strain is generated near the bottom 8b of the vertical groove 8 each time the tire contacts the ground, and when the tire is separated from the ground. When a large tensile strain occurs, and when there is a protrusion like a conventional weir plate in this area, stress may be concentrated at the base of the protrusion and cracks may easily occur, or the weir in the above example may The plate 4 has a protruding length in the upper region 4.
Since the lower region 4b is provided, which is shorter than a, the concentration of stress is reduced, the occurrence of cracks is reduced, and the life of the tire is extended. Since the lower region 4b exists, even when the tread 1 is in contact with the ground and the groove m of the longitudinal groove 8 is reduced and the upper region 4- of the weir plate 4 closes most of the longitudinal groove 8, the groove bottom 8b remains. Adjacent parts are open without being blocked, making drainage easy when driving on wet roads, and driving stability is ensured.

The protruding length of the upper region 4& of the weir plate 4 is set to the width of the vertical groove 8 -48-. That is, the protrusion length b of the upper region 4 & at an arbitrary position in the groove depth direction is set outside the groove width B at the above-mentioned arbitrary position. If the above-mentioned protrusion length b is less than 20% of the groove width B, it is too small and vibration wave nodes for air column vibration occur and separation occurs.Therefore, no change in the air column vibration frequency occurs, and the effect of reducing noise is obtained. I can't do it.

On the other hand, if it exceeds 48%, most of the vertical grooves 8 are blocked due to the reduction of the groove width B when the tread 1 contacts the ground, increasing drainage resistance when running on a wet road, and resulting in unstable running. When the distance between the weir plates 40 decreases and the distance between the weir plates 40 is short, the air pressure between the weir plates 4 and 4 at the time of grounding is generated and the sheath plates 4 are forced out of the air column pipe.
Since the airflow is suddenly ejected in one direction, front and rear, high-frequency sound is generated and the noise level does not decrease. It should be noted that the weir plate 4 may be provided protruding from either the groove wall 8 on the equator P side or the tire shoulder 2 side, or if it is provided protruding on the equator P side, the vulcanization is completed during tire molding. When the tire is removed from the molding mold, there is less damage to the weir plate 4 and its vicinity, making processing easier. When the weir plate 4 is protruded from the tire shoulder 2 side, fatigue near the groove bottom due to the presence of the weir plate 4 is reduced. few.

Height d of the upper region of the weir plate 4 (length in groove depth direction)
80 to 80% of the depth D, particularly preferably 40 to 70%. If the height d of the upper region 4& is less than 80% of the groove depth D, the effect of providing the weir plate 4 will be lost and the purpose of noise reduction will not be achieved; If it exceeds the limit, drainage performance during no-road driving will deteriorate and cracks will likely occur at the bottom of one groove due to fatigue.

The cross-sectional shape of the weir plate 4 may be any layered shape, such as a rectangular shape with a constant thickness as shown in FIG. 8, or a trapezoidal shape with an uneven thickness as shown in FIG. 4, but the average thickness t is , 2 of the protrusion length bo of the weir plate 4 on the surface of the tread 10 (see @2 figure)
It is set between 0 and 80%.

If the above average thickness t is less than 20%, the rigidity of the weir plate 40 will be low, and the resistance to the airflow pressure in the vertical groove 8 will be insufficient, making it difficult for vibration wave nodes to occur due to air column vibration. On the other hand, if it exceeds 80%, the rigidity of the above-mentioned curve becomes too high, and the drainage resistance when running on a wet road becomes excessive, reducing running stability, and stress concentration occurs at the connection with the groove ff1a&. This makes it easier for cracks to occur. In addition, if the bending rigidity of the weir plates 4 becomes excessive, the resistance to airflow will also increase, and if the weir plates are set at intervals of 40 or shorter than the contact length, the pressure inside the groove will increase when the groove volume is reduced due to contact with the ground. As the noise level increases, some of the air is forced out and expands rapidly outside, generating eddy currents and vibrating the surrounding air, increasing the high frequency components of pattern noise, resulting in a decrease in the noise level. is not obtained. In addition, weir plate 4
Of course, the 0 base is rounded, and this makes the weir plate 4 and the groove a! 81 is reduced, and cranking is prevented.

The distance L in the circumferential direction of the weir plates 40 (see Fig. 1) is such that when the tire touches the ground, there is only one weir plate 4 within the contact length of the tire.
It is preferable to set it so that it is included. That is,
If one weir plate 4 is included in the tire ground contact length,
When the weir plate 4 moves relative to the ground contact length due to tire transfer, one shear plate 4 always remains within the ground contact length.
exists, and the length of the two air columns made up of the weir plate 4, the vertical groove 8, and the road surface always changes continuously.
The frequency of the resonance sound emitted from the air column also changes constantly and is dispersed over a wide range. In other words, the above circumferential spacing is preferably 6 to 35% of the tire outer diameter, and if it is less than 5%, two or more weir plates will be included in the contact length, making it difficult to drive on wet roads. Drainage performance deteriorates, and on the other hand, if it exceeds 35%, an air column with one end closed and one end open may not be formed, making it difficult to obtain the effect of reducing noise.

In the above embodiment, the weir plate 4 is provided protruding from the groove wall 8& on one side of the vertical groove 8, but a pair of weir plates 4.4 are provided at opposite positions of the groove walls 8&, 8& on both sides. (see FIG. 5), the noise can be further reduced. However, the deviation S of the pair of weir plates 4.4 in the direction of the groove center SO is:
It is preferable to set the width smaller than the groove width Bo at the position where the weir plates 4 are provided, and when the above-mentioned deviation S exceeds the groove dIiABo, there is no effect of providing the two weir plates 4.4 as a pair.

In addition, when the above-mentioned weir plates 4.4 are provided oppositely, the protrusion length of one may be set short and the protrusion length of the other may be set long (
(See Figure 6), especially when the tie and shoulder 2 side are set short and the equator P side is set long, when removing the tire from the mold after vulcanization during tire manufacturing, the weir plate 4 and its vicinity Less damage.

Next, the effect will be explained in more detail using an experimental example0 Experimental Example 1 1st! It has an i4 tread pattern and a size 10.
For 00-2014 PR pneumatic tires, the thickness of the weir plate 4 was fixed at 3CI% of the groove width, and the protruding length was adjusted in various ways and installed on the J-engine S standard rim, and the J
Apply the maximum load to the machine S. 1. A bench test was conducted at a speed of 20 to 100 kJn/h based on TASO-0606, the average noise level was measured, and the graph of No. 7 [i4] was obtained.

This graph shows the ratio of the above protrusion length to the groove width B (support)
is taken on the horizontal axis, and the noise level index (b/B = addition %
The vertical axis is taken as the noise level at the time of 100), and the curved person has the weir plate 4 on one side, and the curved person has the weir plate 4 on both sides. In addition, the fatigue durability (total number of tire rotations until a crank occurs at the base of the weir plate 40) was measured for one side of the weir plate 4, and b/B
= Index of fatigue durability at 100% (song MX
). As is clear from FIG. 7, when the protrusion length b of the weir plate 4 becomes smaller than the addition percentage of the groove width B, the noise level rises rapidly. On the other hand, when the protrusion length b increases from the above 20%, the noise level reaches its lowest when the protrusion length b is 5% to 1% of the groove width B, and then gradually increases. This is thought to be because the resistance of the weir plate 4 to the airflow increases as described above. Moreover, if the above-mentioned protrusion length exceeds z4B%, the fatigue durability index decreases drastically.

Experimental Example 2 In the tire of Experimental Example 1, the thickness of the sheath plate 4 was varied in R.
, t, the noise level index and braking distance on a wet road were compared, and the results are shown in Table 1. However, the ratio between the protruding length 1 of the weir plate 4 and the groove width B, the ratio between the weir plate 40 interval and the tire outer diameter, and the ratio between the height d of the upper region of the weir plate 4 and the groove depth p. were standardized to 7% and 60%, respectively. Note that the noise level and braking distance on a wet road are expressed as an index based on the numerical value of Example 1 as 100, and the smaller the value of both the noise level and braking distance, the better. In addition, the braking distance on a wet road is 40% on a smooth road surface (test course) with a water film of a certain depth on the surface of a vehicle with the same tires on all axles.
It represents the distance from the time the vehicle locks to when the vehicle slides on the road surface and finally comes to a halt when the vehicle is traveling at 1 b/h and the tires are suddenly put into a p-tuck state.

Table 1 As is clear from Table 1, in Comparative Example 11, Comparative Example 8, in which the thickness of the weir plate 4 is set to be small, and Comparative Example 5, in which the weir plate 4 is not provided, the noise level is high, and the above thickness is Comparative Examples 2 and 4, in which the noise level is set to a large value, tend to have a high noise level and a long braking distance on a wet road. In addition, in Examples 1, 2, and 8, in which the above-mentioned thickness was set within a predetermined range, both the noise level and the braking performance on a wet road were excellent.

[Brief explanation of drawings]

Fig. 1 is a surface view of a tread according to an embodiment of the present invention, Fig. 2 is a sectional view of company-grade grooves, Fig. 8 and Fig. 4 are sectional views of a weir plate, Fig. 6 is a surface view of a modified example, Figure 6 is a surface view of another modified example, and Figure 7 is a graph of the relationship between the protrusion length of the weir plate and the noise level in Experimental Example 1.
Groove wall, 8); 11I bottom, 4; weir plate, 4 &; upper region,
4b: Lower region, F: Equator, b+protrusion length, B: Groove width at any position in the groove depth direction. Patent applicant Toyo Rubber Industries Co., Ltd. Agent Patent attorney Takeshi Sakano Fuyoshi 1) Tsukasa Ryo

Claims (1)

[Scope of Claims] [1] A low-noise pneumatic tire having at least two longitudinal grooves continuous in the circumferential direction of the tire, and a plurality of weir plates protruding from the groove walls of the longitudinal grooves in the groove width direction. The weir plate is composed of a lower region close to the groove bottom and an upper region excluding the lower region, and the protrusion length of the upper region at any position in the groove depth direction is The groove width is increased by ~48%, and it is formed in a curved shape that is recessed from the tip of the lower region or the tip of the upper region to the groove wall side and touches the vicinity of the groove bottom, and the average thickness of the weir plate is the same as that of the weir plate on the tire surface. A low-noise pneumatic tire characterized in that the protrusion length is 20 to 80% of the protrusion length of the tire. [2] A low-noise pneumatic tire according to claim 1, wherein the weir plates or both groove walls are provided in pairs protruding from opposing positions f.