JPH06227212A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To provide the maneuvering stability and the comfortableness in a car cabin compatibly by forming siping in ribs in the tread central area, setting the circumferential direction pattern rigidity of the area in a specific range, and also setting the siping width and inclination angle to specified ranges. CONSTITUTION:A pneumatic tire is provided with a plurality of main grooves G stretching in the circumferential direction on the tread surface TS, which is therewith divided into a plurality of ribs R. The tire is installed on a regular rim and filled with the regular internal pressure, and the regular load is applied. Therein a siping S is formed on the ribs R1, R2 in the central area K1 as the regions apart a distance L 0.2-0.35 times as large as the width W of the tire grounding region to each side of the equator CO. Thereby the circumferential direction pattern rigidity of the central area K1 is set to 0.1-0.3 times as large as the circumference direction pattern rigidity of the grounding area. The siping S is given a width 0.1-2.0mm and inclined at an angle 50-60 deg. to the equator CO.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire having improved riding comfort while maintaining steering stability.

[0002]

2. Description of the Related Art In recent years, with the improvement of road networks and the improvement in performance of vehicles, high steering stability and high-speed drivability are required even for heavy-duty tires used in, for example, trucks and buses. Therefore, in this type of tire, a rib pattern having excellent rolling properties is adopted for the tread surface, the tread portion is reinforced with a strong belt layer, and the flatness of the tire is promoted by the hoop effect. This is because the lateral rigidity of the tire can be greatly increased by the flattening, the straight running property and the turning property can be improved, and the rolling resistance can be reduced and the ground contact width can be increased.

[0003]

However, in such a tire, since the flexible region of the sidewall portion is greatly reduced, the tire vertical rigidity is remarkably increased, and the tread portion itself is reinforced by the belt layer, so that the envelope portion is not reinforced. There is a problem in that the effect is poor and, as a result, the riding comfort is greatly reduced.

Conventionally, in order to improve the riding comfort, the cord angle of the belt layer is increased, the tread rubber hardness is reduced, and the overall pattern rigidity is relaxed. However, the reduction of the overall tread rigidity causes a decrease in steering stability, and the appearance of a material that can achieve both the steering stability and the steering stability has not been achieved.

The present invention is based on the fact that the pattern rigidity a in the circumferential direction in the central area of the tread is reduced to 0.1 to 0.3 times the total pattern rigidity in the circumferential direction of the ground contact area by forming the siping, and the steering stability is basically reduced. It is an object of the present invention to provide a pneumatic tire capable of improving ride comfort while maintaining the above.

[0006]

In order to achieve the above object, the pneumatic tire of the present invention is provided with a plurality of ribs on the tread surface by providing at least two main grooves extending in the tire circumferential direction on the tread surface. A rib pattern tire that divides into a regular rim, which has a regular rim, is filled with a regular internal pressure, and is loaded with a regular load. By providing sipes on the ribs in the tread central region, which is a region that separates the distance L of 35 times from the tire equator on both sides, the circumferential pattern rigidity a of the tread central region is made equal to the total pattern rigidity A of the ground contact region in the circumferential direction. 0.1 to 0.3 times,
Moreover, the siping has a siping width of 0.1 to 2.0.
mm and inclined at 50 to 60 degrees with respect to the tire equator.

[0007]

As described above, according to the present invention, siping is frequently used in the tread central area on the tire equator side of the ground contact area, and the overall pattern rigidity in the circumferential direction of the ground contact area is small in the tread central area and outside the tread. In the shoulder region, they are largely distributed and distributed. That is, since the pattern rigidity in the circumferential direction of the tread central region where the ground pressure is large is reduced,
Shocks such as road protrusions can be effectively mitigated and riding comfort can be improved. On the contrary, since the pattern rigidity in the circumferential direction of the tread shoulder region is increased, the cornering force is increased and the steering stability can be maintained. Further, these effects are obtained by the concentrated formation of the siping in the central region of the tread, so that the construction is easy, and the formation of the siping also contributes to the improvement of the wet grip performance.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a meridional section of a tire having a regular rim assembled to a regular rim and filled with a regular internal pressure. The pneumatic tire 1 has bead portions 3 on both sides through which a bead core 2 passes,
3, sidewall portions 4 extending outward from each bead portion 3 in the tire radial direction, and a tread portion 5 connecting between upper ends thereof.
In this example, the tire is formed as a heavy duty radial tire. A tread portion 5 is provided between the bead portions 3 and 3.
From the carcass 6 passing through the side wall portion 4 and folding back around the bead core 2
A tough belt layer 7 is wound on the outer side in the radial direction and on the inner side of the tread portion 5.

The carcass 6 is a radial direction array body using at least one carcass ply in which the carcass cords are arrayed at an angle of 75 to 90 degrees with respect to the tire equator CO, and other carcass cords include steel cords. Fiber cords such as nylon, polyester, and rayon are used.

Further, the belt layer 7 has at least one belt ply 7A in which the belt cords are arranged at an angle of 10 to 70 degrees with respect to the tire equator CO, and in this example, four belt plies 7A (first, second, from the carcass side, Second and fourth belt plies 7A1, 7
A2, 7A3, 7A4), the belt cords of the first and second belt plies 7A1, 7A2 are in the same direction, and the belt cords of the third and fourth belt plies 7A3, 7A4 are in the same direction. Moreover, it intersects with the first and second belt cords. Further, as the belt cord of this example, a metal fiber cord such as steel is used, but other organic fiber cords such as nylon, polyester and rayon can also be used. In this example, the second belt ply 7A2 is the largest ply cord. Has a width.

The tread surface TS, which is the outer surface of the tread portion 5, is a convex arc having a radius of curvature TR1 centered on the tire equatorial surface in this example, and moreover, the tread surface TS.
Comprises a so-called square shoulder that intersects the buttress surface BS extending from the sidewall portion 4 with a concave arc and has an edge at the tread edge Te.

Further, as shown in FIG. 2, a rib pattern formed by providing at least two main grooves G extending in the tire circumferential direction is formed on the tread surface TS. In the present example, the main groove G has a straight groove shape having a groove width of 6 to 16 mm and extends linearly, and is arranged on the tire equator C in the inner main groove G1 and on the outer side in the tire axial direction. And a pair of outer main grooves G3 arranged outside the main groove G2. Therefore, the main groove G is the main groove G
An inner rib R1 is formed between 1 and G2, an inner rib R2 is formed between the main grooves G2 and G3, and an outer rib R3 is formed between the main groove G3 and the tread edge Te.

In the present invention, in the ground contact area K where the tread surface TS is in contact with the road surface when a normal load defined by JIS or the like is applied to the tire in the normal internal pressure state, the ground contact area K is defined as the tread central area K1 on the tire equator side. And a tread shoulder area K2 outside thereof, and
By providing sipes S on the ribs included in the tread central region K1, the pattern rigidity a in the circumferential direction of the tread central region K1 is 0.1 to 0.3 times the total pattern rigidity A in the circumferential direction of the ground contact region K. The range has been reduced.

Here, in the tread central area K1, the tire equator C is located at a distance L which is 0.2 to 0.35 times the width W of the ground contact area.
Since the tread surface TS is formed by a convex arc on the equatorial plane of the tire, the ground pressure of the tread central area K1 causes the tread shoulder area K2 outside the tread surface area K2 to be defined as an area in a range separated from O on both sides. It is set higher than the ground pressure of. As shown in FIG. 3, in order to more positively make the difference between the ground pressure in the tread central area K1 and the ground pressure in the tread shoulder area K2, for example, the tread shoulder area K2
Is inscribed in the tread central area K1 and has the radius of curvature TR
It may be formed by an arc having a curvature radius TR2 smaller than 1. Further, in this example, as described above, the width W of the ground contact area matches the tread width TW because the tread portion 5 forms a square shoulder.

Further, in this example, the main grooves G1 and G2 pass through the inside of the tread central region K1, so that the inner rib R1 is formed.
And the inner portion R2a of the inner rib R2 in the tire axial direction is included in the tread central region K1, and the siping S is formed on the inner rib R1 and the inner portion R2a of the inner rib R2, respectively.

In the present application, the siping S is a slit-like narrow groove having a siping width of 0.1 to 2.0 mm in the normal internal pressure state, and the inner rib R1 has ribs R1 at both ends. Open at both edges, that is, the rib R1
A siping S1 is formed that traverses the. In this example, the siping S1 includes a narrow first siping S1A having an equal width over the entire length and a second siping S1B having a wide portion a and a narrow portion b.

The siping S2 disposed on the inner portion R2a of the rib R2 in the middle is, for example, a narrow end-shaped strip having one end opened at the inner edge of the middle rib R2 and the other end interrupted in the rib R2. A wide fourth siping S2B that is continuous with the third siping S2A and the siping SO that has one end opening at the inner edge and the other end traversing the outer portion R2b of the rib R2.
Including and

While the sipings S1 and S2 are inclined at an angle θ of 50 to 60 degrees with respect to the tire equator CO, the sipings S1 and S2 are densely arranged in the tire circumferential direction at unequal pitches such as an equal pitch or a variable pitch. It is formed. As a result, the pattern rigidity a in the circumferential direction of the tread central region K1
Is being reduced. On the other hand, in order to suppress an excessive decrease in the overall pattern rigidity A in the circumferential direction of the entire ground area K, formation of siping or the like in the tread shoulder area K2 is eliminated, or the number and formation length of siping are formed. And the ratio a / A is set to 0.1 to 0.3.

Since the pattern rigidity a in the central region K1 of the tread where the ground pressure is large is reduced in this way, shocks such as road protrusions can be alleviated and riding comfort can be improved. On the other hand, while suppressing the decrease in the pattern rigidity A of the entire ground contact area K, the pattern rigidity in the tread shoulder area is increased, so that the cornering force is increased and the steering stability can be maintained.

4 (a) and 4 (b), the ratio a / A of the circumferential pattern rigidity derived by the inventor of the present invention in the actual vehicle running test, the relationship between the riding comfort and the steering stability, and the ratio of the area width. 2 shows the relationship between 2L / W and riding comfort and steering stability. As can be seen from the figure, when the distance L is smaller than 0.2 W and the rigidity a is larger than 0.3 A, the riding comfort cannot be improved, and conversely, the distance L is smaller than 0.35 W. When it is large and the rigidity a is smaller than 0.1 A, the steering stability cannot be maintained.

Here, the pattern rigidity a in the circumferential direction of the tread central region K1 can be obtained as follows. That is, as shown in FIG. 5 (a), the road surface plate that can move back and forth has the same width W1 (= 2 × L) as the tread central region K1 in the tread portion 5 of the tire 1 whose rim is fixed so as not to rotate. Formula is obtained by press-contacting B1 and measuring the longitudinal force F1 (kg) and the amount of movement x1 (mm) when the road surface plate B1 is moved in the front-rear direction without causing slippage with the tread portion 5. It can be obtained by a = F1 / x1. The pressure contact force T
1 is set to a pressure at which the contact length m of the tire 1 with the road surface plate B1 is equal to the contact length M of the contact area K.

Similarly, as for the overall pattern rigidity A in the circumferential direction of the ground contact area K, as shown in FIG. 5 (b), the road surface plate B2 having the width W2 and the width W2 of the ground contact area is provided in the tread portion 5 of the tire 1. Pressure contact, longitudinal force F2 (kg) and movement amount x2 (m
m) is measured to obtain the following formula A = F2 / x2. The pressure contact force T2 is set to a pressure at which the contact length m is equal to the contact length M of the contact area K, that is, equal to the normal load.

The sipings S1 and S2 are formed as follows.
The pattern rigidity a in the circumferential direction of the central region K1 of the tread can be reduced, the drainage can be improved, and the wet grip property can be enhanced. However, the inclination angle θ of the sipings S1 and S2 is 50
When it is less than 100 degrees, the wet grip property is reduced, and moreover, uneven wear such as heel and toe wear is promoted before and after the circumferential direction of the siping. Further, when the inclination angle θ is larger than 60 degrees, the wear resistance is similarly reduced and the riding comfort is deteriorated.

[0024]

Since the pneumatic tire of the present invention is constructed as described above, it is possible to improve riding comfort while maintaining steering stability, and also to improve wet grip performance.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a tire showing an embodiment of the present invention.

FIG. 2 is a plan view showing the tread pattern.

FIG. 3 is a diagram showing another example of the profile of the tread surface.

FIG. 4 (a) is a diagram showing the relationship between the ratio a / A of pattern rigidity in the circumferential direction and the riding comfort / maneuvering stability, and FIG. 4 (b) is a region width ratio 2L / w and riding comfort. It is a diagram which shows the relationship with steering stability.

5A and 5B are schematic diagrams for explaining pattern rigidity in the circumferential direction.

[Explanation of symbols]

 G, G1, G2, G3 main groove, K regular K1 tread central area R, R1, R2, R3 rib S, S1, S2 siping TS tread surface

Claims (1)

[Claims] 1. A tire having a rib pattern in which the tread surface is divided into a plurality of ribs by providing at least two main grooves extending in the tire circumferential direction, and the tire is assembled on a regular rim. In addition, in the ground contact area when the normal internal pressure is filled and the normal load is applied, a distance L of 0.2 to 0.35 times the width W of the ground contact area is separated from the tire equator on both sides of the tread central area. By providing sipings on the ribs, the pattern rigidity a in the circumferential direction of the tread central region is made 0.1 to 0.3 times the total pattern rigidity A in the circumferential direction of the ground contact region, and the siping has a siping width of 0. A pneumatic tire characterized by being inclined at 1 to 2.0 mm and at an angle of 50 to 60 degrees with respect to the tire equator.