JPH0443004B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides wet grip while maintaining
This invention relates to a pneumatic tire that can reduce stone bite.

Pneumatic tires with a rib-type pattern having zigzag longitudinal grooves are often used, and the longitudinal grooves of such tires are as shown in FIGS. 1 to 3.
As shown in the figure, when the cross section is V-shaped, U-shaped, and the bottom is arcuate, stones stuck inside the vertical groove G are pushed inward by the load applied to the tire. It becomes difficult to fall off. This stone-clogged state deteriorates the original function of the groove, and the contact area with the stones becomes a starting point for stress concentration, promoting the occurrence and growth of cracks and shortening the life of the tire.

Therefore, in order to prevent stones from getting stuck, it has been proposed in JP-A-49-120302 to make the cross-sectional shape of the vertical groove G into a step-like shape with two or more steps, as shown in FIG. 4a. There is. However, in this case, when the tread portion wears out to a certain extent, the groove width becomes extremely narrow, and the wet grip properties are significantly reduced. Also, Figure 4b
As shown in Figure 2, it has been proposed that the cross-sectional shape of the groove be V-shaped and the inclination angle a of the side wall be extremely large, but this reduces the effective ground contact area of the tread part when new and reduces the wear resistance. In addition, there is a drawback that stress concentration at the groove bottom tends to occur.

The present invention maintains wet grip properties while
The purpose of this project is to propose a pneumatic tire that reduces stone trapping.

The present invention provides a rib-patterned pneumatic tire having longitudinal grooves extending in a zigzag manner in the circumferential direction of the tire.
is the inclination angle β of the outer wall of the tread edge from 1.2 to
Double the area, and on either the inner wall or the outer wall,
A table-shaped protrusion is formed that rises from the groove bottom and bulges into the vertical groove to prevent stone from building up, and a shelf is formed on the other side wall within the vertical groove so that the top surface is the same as the protrusion and is spaced apart from the groove bottom. A pneumatic tire is provided with a buffer protrusion projecting in the shape of a shape, and the width m of the buffer protrusion in the tire axial direction is 50 to 100% of the longitudinal groove width l on the upper surface of the protrusion.

In this way, since the inclination angle of the inner wall of the longitudinal groove of the tread portion on the side of the tire's equatorial plane is made larger than that of the outer wall, stone entrainment is prevented while preventing deterioration of wear resistance and steering stability. Furthermore, since a protrusion is formed on one side wall and a buffer protrusion of the same height is formed on the other side, stone entrainment is reduced without reducing the effective ground contact area of the tread portion. Furthermore, since the buffer protrusions disappear due to wear, the groove width can be maintained due to wear, and wet grip properties can be maintained.

An embodiment of the present invention will be described below based on the drawings.

In Figures 5 to 7, the pneumatic tire has two longitudinal grooves G1 and G2 each consisting of a zigzag groove extending in a zigzag manner in the tire circumferential direction on both sides of the tire equatorial plane C in the tread part, and Another longitudinal groove passing through the equatorial plane C is provided.

The longitudinal grooves G1, G2 are located on the inner wall A1, which is located on the tire equatorial plane C side in the tire meridian cross section.
The normal to the tread surface of A2, that is, the radius lines L1, L2
The inclination angles α1 and α2 of the outer walls B1 and B2 located on the tread edge side are
It is formed 1.2 to 2 times larger than the

It is preferable to increase the inclination angle of the side wall to reduce stone engraving, but if the inclination angle is increased,
The ground contact area decreases, impairing wear resistance and handling stability, and stone-biting prevention and these performances are at odds with each other.

However, it is wear resistant while preventing stone chewing.
In order to prevent a decline in steering stability, we conducted a study and found that the load acting on the side wall closer to the tire's equatorial plane, that is, the inner wall, is larger than the side wall on the edge of the tread, that is, the outer wall. By increasing the angle of inclination of the stone, stone jamming is prevented.
By reducing the angle of inclination of the outer wall, the ground contact area of the tread portion is ensured, and wear resistance and handling stability are prevented from deteriorating.

Furthermore, the vertical grooves G1 and G2 have the inner walls A1 and
A2, one of the outer walls B1 and B2, in this embodiment, the outer wall B1 of the vertical groove G1 and the inner wall A2 of the vertical groove G2 has a groove that rises from the bottom of the vertical groove G1 and G2 and bulges into the groove. A table-shaped protrusion P for preventing stone entrapment is formed.

As a result, even if a stone gets stuck inside the vertical groove, the protrusion P prevents it from further invading the inside, thereby preventing damage at the bottom of the groove. Although this protrusion is formed continuously in the tire circumferential direction, it may be configured to be partially intermittent.

Also, the depth D of the upper surface of the protrusion P from the tread surface
1 is in the range of 30 to 70% of the vertical groove depth D2. 30%
If it is shallower, the groove width will be reduced early due to the progression of wear on the tread portion, resulting in a decrease in drainage performance, while if it is deeper than 70%, the prevention effect of stone encroachment will not be sufficient.

Further, in the vertical grooves G1 and G2, the other side wall, in this embodiment, the inner wall A1 of the vertical groove G1 and the outer wall B2 of the vertical groove G2 have the same upper surface as the protruding part P, and are located inside the vertical groove. In addition, buffer protrusions 4 and 5 are formed that protrude in a shelf-like manner at a height that separates a distance from the groove bottom.

The width m of the buffer protrusions 4 and 5 in the tire axial direction is
The range is 50 to 100% of the longitudinal groove width l in the tire axial direction of the longitudinal groove on the upper surface of the protrusion P.

When a stone enters the vertical groove, the buffer protrusions 4 and 5 together with the protrusion prevent the stone from entering toward the groove bottom, and at the same time, reduce the amount of decrease in the effective volume of the vertical groove. maintains wet grip properties.

Note that the buffer projections 4 and 5 can be formed continuously in the tire circumferential direction, but as shown in FIG.
From the viewpoint of drainage, it is preferable to form the pipe intermittently with discontinuous parts. In this case, the circumferential length n of the buffer protrusions 4, 5 is at least 5 mm;
The length W in the circumferential direction of the discontinuous portion in between is set to be three times or less the length n in the circumferential direction of the buffer protrusion.

As described above, in the pneumatic tire of the present invention, the inclination angle of the side wall of the longitudinal groove of the tread portion is made larger on the inner wall than on the outer wall, a protrusion is formed on one side wall, and the protrusion is formed on the other side. Since the buffer protrusions are formed on the side walls at the same height as the top surface, it is possible to reduce stone entrapment and maintain wet grip without significantly reducing the effective ground contact area of the tread portion.

Example Example product of the present invention (Example 1), which is a tire with a tire size of 7.50R16.14PR and has the vertical grooves shown in FIGS. 5, 6, and 7, and the vertical groove G shown in FIG.
1, G2 is replaced with the vertical groove shape shown in Fig. 8 (Comparative Example 1), and as a conventional example, the vertical groove G shown in Fig. 5 is used.
1. A prototype with the vertical groove shape shown in Figure 1 instead of G2 (Comparative Example 2) was manufactured according to the specifications shown in Table 1.
The device was attached to a 4-ton vehicle with an internal pressure of 7.0 kg/cm ² and the stone chewing test and wet grip performance were evaluated by driving the vehicle.

The stone chewing test was performed by calculating the number of stones remaining inside the vertical groove after driving at a speed of 59 km/h over a total distance of 10 km, including 4 km on gravel road and 6 km on paved road.

On the other hand, wet grip performance was measured by using tires with 50% tread wear, spraying water on a slippery road surface, and measuring the speed at which sideslip occurred when driving on the slippery road surface with a turning radius of 40 m. These results are shown in Table 1. From Table 1, it can be seen that all of the examples of the present invention are excellent in stone-biting prevention and wet grip properties.

[Brief explanation of drawings]

1 to 4 a and b are sectional views illustrating conventional vertical grooves, FIG. 5 is a partial plan view illustrating an embodiment of the present invention, FIG. 6 is a sectional view thereof, and FIG. 6 is an enlarged sectional view of the longitudinal groove G1, and FIG. 8 is Comparative Example 1.
FIG. 4...Buffer protrusion, A1, A2...Inner wall, B
1, B2... Outer wall, C... Tire equatorial plane, G
1, G2... vertical groove, L1, L2, L3, L4...
Radius line, P... protrusion, α1, α2... inclination angle of inner wall, β1, β2... inclination angle of outer wall.

【table】

Claims (1)

[Scope of Claims] 1. In a pneumatic tire with a rib pattern that includes longitudinal grooves extending in a zigzag manner in the circumferential direction of the tire, an inclination in a tire meridian cross section that an inner wall of the longitudinal groove on the tire equatorial plane side makes with respect to a radial line. Angle α
is the inclination angle β of the outer wall of the tread edge from 1.2 to
Double the area, and on either the inner wall or the outer wall,
A table-shaped protrusion is formed that rises from the groove bottom and bulges into the vertical groove to prevent stone encroachment, and a shelf is formed in the vertical groove on the other side wall, the top surface of which is the same as the protrusion, and spaced apart from the groove bottom. 1. A pneumatic tire comprising: a buffer protrusion projecting in the shape of a shape; the width m of the buffer protrusion in the tire axial direction is 50 to 100% of the longitudinal groove width l on the upper surface of the protrusion.