JPS6350205B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pneumatic tire for automobiles, and in particular, the arrangement of minor grooves in a pneumatic tire in which the main groove in the tire tread design is arranged at approximately 0° with respect to the circumferential direction of the tire. The present invention relates to a pneumatic tire for automobiles that is capable of effectively improving driving performance by improving slip resistance on wet road surfaces without deteriorating the wear characteristics of the tire.

In pneumatic automobile tires, the design placed on the surface of the tire tread not only shapes the image of the tire as a product, but also influences the tire's driving performance, wear characteristics, and noise generated from the design (hereinafter referred to as pattern noise). It has a great influence on the basic characteristics, and among these characteristics, dynamic performance is especially important for ensuring safe driving of the automobile.

In recent years, with the development of expressway networks, opportunities for ordinary drivers to drive at high speeds have increased, and the decline in driving performance has a strong possibility of leading to serious accidents. Under such conditions, the frictional force between the tires and the road decreases, and in addition, a so-called hydroplaning phenomenon occurs in which a water film is formed between the tire contact surface and the road surface, resulting in a significant decrease in maneuverability and the difficulty of high-speed driving. In some cases, the possibility of an accident becomes even stronger.

As mentioned above, the maneuverability on a wet road surface, that is, the anti-slip performance, is greatly influenced by the ability of the tire to drain water from the road surface to the rear of the tire and to the sides of the tire in the area where the tire is in contact with the road surface. The effect depends on the arrangement of the main grooves circumferentially arranged on the tire tread surface, the sub-grooves connecting the main grooves, and the sub-grooves opening at the tire contact edge.

In the first place, in order to efficiently discharge water that enters from the front of the tire to the rear of the tire when driving on a wet road surface, it is better to have the main grooves arranged circumferentially on the tire tread surface in a zigzag shape. Straight grooves with no angles are more advantageous, and in order to guide the water that has gotten under the tread block to the main groove and discharge it to the sides of the tire, the structure of the minor grooves is better than a bent groove. too,
A straight shape is more advantageous.

As mentioned above, in order to efficiently discharge water that has entered from the front of the tire to the rear of the tire and to the sides of the tire, it is necessary to ensure that the tread block, which is separated by the main groove and the minor groove, does not obstruct the flow of water at the contact area. , the main groove, and the sub-groove are desirably constituted by substantially continuous straight lines.

Accordingly, when investigating tires on the market, as shown in Figs. 1 and 2, main grooves 1 having no angle in the circumferential direction, that is, straight main grooves 1, are arranged on the tread surface of the tire, and each of the main grooves is 1, and between the outermost main groove 1 and the shoulder edge, ribs 3, 4, and 5 are formed, respectively, and both edges of the ribs are connected by linear minor grooves 2. There are also tires.

However, in this type of tire, as shown in FIG. 1, the minor grooves 2 are arranged in parallel, and as shown in FIG. The absolute angle in the tire circumferential direction of each linear sub-groove 2 connecting the edges of the ribs 3, 4, and 5 formed between the main grooves and between the outermost main groove and the shoulder edge is the same. However, the absolute angle that each sub groove 2 makes with respect to the main groove 1 is in the range of 50° to 60°.As a result of the experiments described below, these tire tread designs All of the conventional tires having the above-mentioned abrasion characteristics are observed to have the above-mentioned effect of improving the wear characteristics, but the important effect of improving the anti-slip characteristics on a wet road surface is not observed.

The present invention was made in view of the above-mentioned current situation, and in particular, by improving the arrangement of the minor grooves of a pneumatic tire in which the main groove in the tire tread design is arranged at approximately 0 degrees with respect to the tire circumferential direction. It is an object of the present invention to provide a pneumatic tire for automobiles that can significantly improve maneuverability by improving slip resistance on wet road surfaces without deteriorating the wear characteristics of the tire.

The feature is that a plurality of main grooves are arranged in the tire tread part at approximately 0 degrees with respect to the circumferential direction of the tire, and ribs are provided between the main grooves and between the outermost main groove and the shoulder edge. In the formed pneumatic tire, linear sub-grooves are alternately arranged on the ribs at different absolute angles with respect to the main groove and connecting both edges of the ribs.

Next, the circumstances leading to the present invention will be explained based on the results of experiments and with reference to the drawings.

First, a plurality of main grooves 1 at 0° with respect to the circumferential direction of the tire are arranged in the tire tread, and ribs 3, 4, and 5 are formed between the main grooves and between the outermost main groove and the shoulder edge. When examining the change in anti-slip performance on a wet road surface when the absolute angle of the linear sub-groove 2 connecting both edges of the rib with respect to each main groove 1 is changed in a tire with a wet road surface, the results are as follows. The results shown in Figure 4 were obtained.

In FIG. 4, the vertical axis shows the degree of improvement in anti-slip property (%) on a wet road surface, and the horizontal axis shows the absolute angle of the minor grooves with respect to each main groove. The above-mentioned anti-slip characteristics are based on the anti-slip characteristics on a wet road surface of a tire with a design in which the minor grooves are composed of straight lines in the form of polygonal lines as shown in Fig. 3, and the load is 350 kg and the air pressure is 1.9 kg/cm ² . , running speed 60
This is a value obtained by comparing the average values at Km/h, 80 Km/h, and 100 Km/h with respect to the above reference design. In addition, the ○ mark in the figure indicates the measurement result of a tire having a design in which the minor grooves shown in Fig. 1 are arranged at a single angle θ, and the ● mark indicates the result of tire measurement with a design in which the sub-grooves shown in Fig. 2 are arranged at a single angle θ. - Shows the measurement results of a tire with a design staggered at θ.

When conducting this experiment and other experiments described later, the width of the sub-groove was adjusted so that the ratio of the groove surface to the total ground contact area of the tire was the same, and the carcass layer, belt layer, which forms the frame of the tire, It goes without saying that the bead wire and the rubber material for each part of the tire were all made of the same material to minimize influences other than the tread design.

From FIG. 4, in a tire with a main groove 1 arranged at 0° with respect to the tire circumferential direction, each of the sub-grooves 2 arranged on the ribs is at the same angle as the main groove 1, as shown in FIGS. 1 and 2. An angle that is the same as (absolute angle here)
In the conventional sub-groove arrangement structure in which the sub-grooves 2 are arranged in the ribs, the closer the angle of the sub-grooves 2 to the main groove 1 to the main groove 1 is in the circumferential direction, the more the anti-slip performance on a wet road improves. The slip resistance does not become minimum even if the direction is perpendicular to the circumferential direction (that is, 90 degrees), but rather around 60 degrees, which is often used in the conventional tires with this type of design,
It has become clear that there is an angular range in which the anti-slip performance on wet roads is minimal.

However, as mentioned above, tread design should not be determined solely by the superiority or inferiority of a single performance, but should also consider other performances at the same time. For example, the experimental results shown in Fig. 4 show that as mentioned above, the closer the sub-groove arrangement angle is to 30° in the circumferential direction, the better the anti-slip performance is.
Due to the shape of the tread block surrounded by Therefore, a structure in which the arrangement angle of the sub-grooves is made small as described above cannot be put to practical use.

After all, from the above experiment, if each sub-groove 2 is arranged at the same angle (absolute angle in this case) with respect to the main groove 1, each sub-groove 2 as shown in FIG.
Even if the sub-grooves 2 are arranged parallel to each other, or even if the sub-grooves 2 are arranged in an alternating manner as shown in Fig. 2, the anti-slip performance on wet road surfaces can be improved without deteriorating the wear characteristics of the tire. It turned out that it was not possible.

Therefore, the present inventors further extended the above-mentioned experiment, and in the process of carrying out the experiment, they came to discover the following fact.

In other words, even if a minor groove angle of 60°, which was not effective in improving the anti-slip performance on a wet road surface in the experiment described above, is adopted for one rib, for example, other ribs may have minor grooves at angles other than 60°. If this rib is placed, a significant improvement in slip resistance can be seen, and the slip resistance tends to reach its maximum when the angle is around 90°, and the same tendency is observed no matter which rib is selected. It is.

This fact is shown in FIG. In FIG. 5, the vertical axis shows the degree of improvement (%) in the anti-slip property on a wet road surface, and the horizontal axis shows the angle of the minor grooves with respect to each main groove. The above-mentioned anti-slip properties are based on the values of the anti-slip properties in the case of a minor groove angle of 60° in the above experiment, with a load of 350 kg, an air pressure of 1.9 kg/cm ² , and a running speed of 60 km/h, 80 km/h, and 100 km. /h is the value obtained by comparing the average value with respect to the reference design.

In addition, the ○ mark in the figure shows the slip resistance characteristic value corresponding to each angle when changing the sub-groove angle in the center rib 3, and the ● mark indicates the sub-groove in the second rib 4, that is, the ribs located on both sides of the center rib. The anti-slip characteristic values corresponding to each angle are shown when the angle is changed.
The anti-slip characteristic values corresponding to each angle when the sub-groove angle is changed in the rib formed between the and the shoulder edge and located further outside of the second rib 4 are shown.

The inventors conducted further experiments based on the above experimental results, and found that when a minor groove with an angle of 90° is provided in a certain rib, the closer the minor groove angle in other ribs is to the circumferential direction, the higher the moisture content. It has become clear that the anti-slip performance on road surfaces is improved.

This fact is shown in FIG. In FIG. 6, the degree of improvement (%) in the anti-slip property on a wet road surface is plotted on the vertical axis, and the following conditions are plotted on the horizontal axis.

In addition, the above-mentioned anti-slip properties are shown in Figs. 1 and 2 above.
Based on the values of anti-slip properties when the tread pattern shown in the figure is arranged with a minor groove angle of 60°, the load is 350 kg, the air pressure is 1.9 kg/cm ² , and the running speed is 60 km/cm2.
This is a value obtained by comparing the average values at h, 80 km/h, and 100 km/h with respect to the reference design.

A: When the minor groove is arranged according to the above standard design B: When the minor groove with an angle of 90° is placed on the second rib 4, and the minor groove with an angle of 60° is placed on the other ribs (comparative example) C: When a minor groove with an angle of 90° is placed on the second rib 4, and a minor groove with an angle of 45° is placed on the other ribs (comparative example) D: A minor groove with an angle of 90° and a minor groove with an angle of 45° in the same rib (Embodiment of the present invention) As is clear from FIG. 6, a certain rib has a sub-groove with an angle of 90°, in other words, a sub-groove close to the cross-sectional direction of the tire. When a minor groove with an angle θ ₁ is provided,
If the minor grooves of the other ribs are arranged at a minor groove angle θ ₂ that is closer to the circumferential direction, the closer this minor groove angle θ ₂ is to the circumferential groove, the better the slip resistance on a wet road surface will be.
(Above Comparative Examples) A significant improvement effect can be seen compared to the case where the minor grooves are arranged at a single angle as in the conventional example described above.

However, in the sub-groove arrangement structure (comparative example) as described above, in the rib where the sub-groove is arranged at a sub-groove angle θ ₂ close to the circumferential direction, the sub-groove is arranged at a sub-groove angle θ ₁ close to the cross-sectional direction. This is undesirable because the wear performance is lower than that of other ribs, and the wear performance differs between each rib, causing uneven wear.

Therefore, the present inventors came up with a sub-groove arrangement structure in which sub-grooves having different absolute angles with respect to the main groove are alternately arranged within the same rib, as shown in D above.

If this sub-groove arrangement structure is adopted, as shown in the figure,
Since the anti-slip performance can be improved and the same design blocks can be arranged throughout the tread as shown in FIGS. 8 and 9 (embodiments of the present invention),
There is no difference in wear performance for each rib.

In the minor groove arrangement structure of the present invention, one minor groove angle θ ₁ is
According to the experimental results shown in Fig. 5, it is desirable to set the angle between 70° and 110° with respect to the main groove, and the other minor groove angle θ ₂ is set within the range of 70° to 110° with respect to the main groove, as shown in the experimental results shown in Fig. 4. It is desirable to set it to 60° or less.

Furthermore, in the sub-groove arrangement structure of the present invention, if the deformation resistance of the tread block surrounded by the main groove and the sub-groove includes large and small parts, it will affect the friction characteristics, so θ ₁ and θ ₂ are ( θ ₁ + θ ₂ )/2
It is desirable to set it within the range of ≧60°.

FIG. 7 is a diagram showing that the value of (θ ₁ +θ ₂ )/2 at the minor groove angles θ ₁ and θ ₂ arranged alternately within the same rib as described above is related to the quality of wear resistance. The wear level (%) is scaled on the vertical axis, and this scale is an index value with the value at (θ ₁ + θ ₂ )/2 = 90° as 100, and the wear value is the value of the four wheels. It is an average value.

As is clear from FIG. 7, (θ ₁ +
A range in which the value of θ ₂ )/2 is greater than 60° is an acceptable range for wear resistance, and when this value falls below 60°, the wear resistance deteriorates rapidly.

FIG. 8 shows a first embodiment of the present invention. In this embodiment, the angle θ 1 of one of the sub-grooves, that is, the angle θ ₁ of the sub-groove near the cross-sectional direction of the tire, is set at 75° with respect to the main groove 1. and the angle of the other minor groove, that is, the angle θ ₂ of the minor groove closer to the circumferential direction of the tire, with respect to the main groove 1.
This is an example in which the angle is 50°, and the second embodiment shown in FIG. 9 is an example in which θ ₁ =100° and θ ₂ =50°. In the figure, 3 indicates the center rib, 4 indicates the second rib, and 5 indicates the third rib.

As described above, the present invention provides a pneumatic tire in which a plurality of main grooves are arranged in the tire tread portion at approximately 0 degrees with respect to the circumferential direction of the tire. Since the grooves are arranged alternately, the anti-slip performance on wet road surfaces can be improved without deteriorating the wear characteristics of the tire, and the driving performance can be effectively improved.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a conventional tire tread design in which a pneumatic tire has a plurality of main grooves arranged at 0° with respect to the circumferential direction of the tire in the tire tread portion, and sub-grooves are arranged at a single angle; Fig. 2 is an explanatory diagram showing a conventional tire tread design in which sub-grooves are alternately arranged at a single angle in the pneumatic tire, and Fig. 3 is an explanatory diagram showing a conventional tire tread design in which sub-grooves are arranged in straight lines in the form of polygonal lines in the pneumatic tire. FIG. 4 is an explanatory diagram showing the conventional tire tread design arranged; FIG. 4 is a diagram showing the anti-slip characteristics on a wet road surface when the minor groove angle of the pattern of each of the above-mentioned conventional minor groove arrangement structures is changed; Figure 5 shows the effect on slip resistance on a wet road surface when the minor groove arrangement angle is changed for a specific rib, and Figure 6 shows the influence on the slip resistance performance on a wet road surface when the minor groove angle is fixed at 90° for the second rib. , a diagram showing the influence on the anti _- slip performance on a wet road surface when changing the _minor groove arrangement angle with other ribs _.
A diagram showing the relationship between θ ₂ )/2 and wear resistance properties, and FIGS. 8 and 9 are explanatory diagrams showing examples of the present invention, respectively. 1...Main groove, 2...Minor groove.

Claims (1)

[Claims] 1. A pneumatic tire in which a plurality of main grooves at approximately 0° with respect to the circumferential direction of the tire are arranged in the tire tread, and ribs are formed between the main grooves and between the outermost main groove and the shoulder edge, The ribs have different absolute angles with respect to the main groove,
A pneumatic tire for automobiles in which linear sub-grooves connecting both edges of the rib are arranged alternately.