JPH0717218A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To improve an anti-cut property without lowering operation stability and riding comfortableness by providing at each side wall portion a protector which rises from its outer wall surface and extends peripherally and at the same time makes an outer peripheral contour line at a tire meridian section wavelike. CONSTITUTION:In the case of each side wall portion 3 whose outer wall surface 3A is formed of side wall rubber stuck on the tire axial outside of a carcass 7, a protector 12 that rises in a tire axial direction and extends in a tire peripheral direction is provided on the outer wall surface 3A. This protector 12 is provided by being extended from the tire maximum width point B on the outer wall surface 3A at the tire maximum width MW to the radial inside and outside, and its outer peripheral contour line 12A at the section shape of a tire meridian section is formed into corrugation whose projecting portions and recessed portions continue alternately and smoothly in the radial direction. Also, this protector 12 is formed of a rubber composition in which short fiber of 10-50PHR is mixed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire capable of improving the cut resistance of a sidewall portion without deteriorating steering stability and riding comfort.

[0002]

2. Description of the Related Art Recently, due to environmental problems and energy problems,
The demand for low fuel consumption performance of vehicles is increasing. This also applies to tires, which have less rolling resistance,
It is desired to be lightweight. In particular, the reduction of the tire weight can improve both the rolling resistance of the tire and the fuel economy of the vehicle.

On the other hand, in order to extend the life of the tire, it is effective to improve the cut resistance of the side wall portion. Therefore, as shown in FIG. 2, the protector b protruding from the outer wall surface of the side wall portion a is effective. A pneumatic tire t provided with is conventionally used in many cases.

[0004]

However, in the conventional case in which the protector b as shown in FIG. 2 is formed in the sidewall portion a, the cut resistance is improved, but a large increase in tire weight is avoided. This is one of the reasons that the bending of the sidewall portion is not uniform and the steering stability and riding comfort are deteriorated.

The present invention is based on the fact that the sidewall portion is provided with a protector having a wavy outer peripheral contour line and using short fiber mixed rubber, which suppresses an increase in tire weight and improves steering stability and riding comfort. An object of the present invention is to provide a pneumatic tire capable of improving the cut resistance without lowering.

[0006]

SUMMARY OF THE INVENTION The present invention is a pneumatic tire having a carcass which passes from a tread portion to a sidewall portion and folds around a bead core of a bead portion, wherein the sidewall portion has an outer wall surface thereof. Provided is a protector which is raised from the base and extends in the circumferential direction, has a wavy outer peripheral contour line in the meridional section of the tire, and uses short fiber mixed rubber.

The short fibers are preferably oriented in the tire radial direction along the outer wall surface.

[0008]

[Function] The sidewall portion is provided with a protector that is raised from the outer wall surface and extends in the circumferential direction and that uses short fiber mixed rubber. Therefore, when the sidewall portion of the tire comes into contact with, for example, the road shoulder during traveling, this protector collides with the road shoulder, prevents damage to the sidewall portion, improves cut resistance, and improves the rubber forming the protector. Since short fibers are mixed in the composition,
The thickness of this protector can be reduced without lowering the cut resistance of the protector, and an increase in tire weight can be suppressed.

Further, when a protector is provided on the sidewall portion, generally the rigidity in that portion, that is, the so-called vertical spring constant locally increases, and the deflection of the sidewall portion becomes uneven, so that the steering stability and the riding comfort are improved. Although it tends to decrease, since the protector of the present invention has a wavy outer peripheral contour line in the tire meridional cross section, it is possible to make the thickness of the protector thin as described above, and a local increase in the vertical spring constant. It is possible to suppress the deterioration of driving stability and riding comfort.

When the short fibers are oriented in the tire radial direction, the cut resistance in the radial direction can be greatly improved.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, a pneumatic tire 1 of the present invention includes a pair of bead portions 2 and 2, sidewall portions 3 and 3 extending outward from the bead portions 2 and 2 in the tire radial direction, respectively.
A troid-shaped tire base body 5 including a tread portion 4 connecting the outer ends of the sidewall portions 3 and 3 is provided.

The tire base 5 has a main body portion 7A extending from the tread portion 4 to the bead portion 2 through the sidewall portion 3.
A carcass 7 provided with a turnback portion 7B formed by folding back around the bead core 6 from the inner side in the tire axial direction, and the carcass 7 inside the tread portion 4 and the carcass 7
Of the belt layer 9 disposed radially outward of the carcass 7, the body portion 7A of the carcass 7 and the folded portion 7B.
And a bead apex 10 having a triangular cross section that rises from the bead core 6 toward the outside in the radial direction.

The carcass 7 is made of nylon, rayon,
In this embodiment, a carcass cord made of an organic fiber such as an aromatic polyamide is arranged at an angle of 70 to 90 ° with respect to the tire equator C to form one or more layers of a carcass ply of radial or semi-radial arrangement, and in this example, one layer. is doing.

The belt layer 9 is composed of one or a plurality of belt cords made of organic fiber cords such as nylon, rayon and aromatic polyamide or steel cords arranged parallel to the tire equator C or inclined at a small angle. In the example, it is formed by two belt plies.

An outer wall surface 3A of the side wall portion 3 is formed of a side wall rubber attached to the outer side of the carcass 7 in the tire axial direction. The side wall rubber is softer than the tread rubber forming the tread surface 4A.

A protector 12 is provided on the outer wall surface 3A of the sidewall portion 3 so as to protrude from the outer wall surface 3A in the tire axial direction and extend in the tire circumferential direction.

The protector 12 extends inward and outward in the radial direction from the tire maximum width point B on the outer wall surface 3A in the tire maximum width MW, and also surrounds the outer wall surface 3A in an endless manner.
The tire meridional section has a substantially rectangular cross section, and the outer peripheral contour line 12A has a wavy shape in which convex portions and concave portions are alternately and smoothly arranged in the radial direction.

The protector 12 is made of a rubber composition which is slightly harder than the side wall rubber. In this embodiment, short fibers of 10 to 50 PHR are mixed in the rubber composition, and the short fibers are mixed. The outer wall surface 3A
Are arranged in the tire radial direction. That is, the short fibers are oriented in the tire radial direction, but from 0 ° (tire radial direction) to 90 ° with respect to the tire radial direction.
It can be oriented in various directions up to ° (tire circumferential direction).

As the short fiber material, nylon, rayon, polyester, aromatic polyamide, cellulose resin, crystalline polybutadiene, organic fiber such as cotton thread, carbon fiber, metal fiber, boron and glass fiber can be used. As such a short fiber material, an organic fiber, especially nylon can be preferably used.

If the amount of the short fibers mixed is less than 10 PHR, the effect of rigidity of the protector 12 is poor and sufficient cut resistance cannot be obtained. On the other hand, if it exceeds 50 PHR, adhesion failure between the rubber and the fiber may occur, and the rigidity of the protector 12 may become excessively large, resulting in uneven bending of the sidewall portion 3 and improving steering stability and riding comfort. Lower.

The short fibers preferably have a diameter of 1 μmm to 0.1 mm and a length of 20 μmm to 2 mm. If the thickness and the length are smaller than the above values, the cut resistance is inferior, while if it exceeds the above values, the fatigue resistance of the rubber layer may be deteriorated.

When the short fibers are oriented substantially in the tire radial direction with the inclination thereof being in the range of 0 ° to 10 °, the cut resistance in the radial direction is greatly improved. You can.

Since short fibers are mixed in the protector 12, the thickness of the protector 12 can be reduced while maintaining the cut resistance, the increase in tire weight can be suppressed, and the outer peripheral contour line 12A is wavy. It is possible to reduce rigidity, unevenness of bending, and dispersion in the sidewall portion 3, and prevent deterioration of steering stability and riding comfort.
Further, by providing the protector 12, the thickness of the sidewall rubber can be reduced, and the weight of the tire can be reduced.

The protector 12 has a complex elastic modulus E * of 50 to 45 measured by the viscoelasticity spectrum meter.
0 kg / cm ^2, are set preferably to 80~400kg / cm ^2. This is because even if the value is higher or lower than the above value, sufficient cut resistance and fatigue resistance, which are maintained in harmony with the sidewall rubber, cannot be obtained.

The protector 12 is kneaded using a Banbury or calender roll, and a rubber body formed by calender roll molding or extrusion is attached to the outer surface of the sidewall rubber in the tire molding step prior to vulcanization. Further, it is formed on the sidewall portion 3 by being integrally fixed to the sidewall rubber by vulcanization.

[0026]

SPECIFIC EXAMPLES Tires (Examples 1 to 3) each having a tire size of 185 / 60R14 and having the configuration shown in FIG. 1 were prototyped and their performances were tested.
It should be noted that a tire having a conventional structure in which the protector 12 is not provided (Comparative Example 1), a tire having a structure shown in FIG. 2 in which the protector is formed but the outer peripheral contour line in the tire meridional section is not wavy (Comparative Example 2), and the protector A tire (Comparative Example 3) having a wavy outer peripheral contour line but no short fibers mixed therein was also tested and the performance was compared. The tires of Examples 1 to 3 were made thinner by reducing the thickness of the sidewall rubber than the tires of Comparative Example. The test specifications are as follows.

A) Cut resistance A so-called pendulum type sidewall impact test is conducted. As shown in FIG. 3, the weight 16 is provided with a wedge-shaped blade 15 attached to the lower end of the pendulum 17, and the sidewall of the tire T is impacted by the free fall method.
It is a test for obtaining and evaluating the breaking energy of the tire sidewall from 6 and the drop height H. The blade 15
As shown in FIGS. 4 (a) and 4 (b), the blade edge 15A is formed of a flat body having a tapered cross section with an arcuate tip. The longitudinal direction of the cutting edge 15A was evaluated parallel to the tire radial direction and parallel to the tire circumferential direction, and each index was shown as 100 in Comparative Example 1.
The larger the value, the better the cut resistance of the sidewall portion.

(B) Steering stability and riding comfort The judgment was made based on the driver's feeling in the actual vehicle running, and it was displayed as an index with Comparative Example 1 as 100. The larger the value, the better. The test results are shown in Table 1.

[0029]

[Table 1]

As a result of the test, the tire of the example has a reduced tire weight as compared with the tire of the comparative example, but has improved cut resistance without lowering steering stability and riding comfort. Was confirmed.

[0031]

As described above, the pneumatic tire of the present invention is
Since a protector made of short fiber mixed rubber that extends in the circumferential direction and has a wavy outer peripheral contour is provided on the outer wall surface of the sidewall portion, it suppresses an increase in tire weight and reduces steering stability and riding comfort. The cut resistance can be improved without

[Brief description of drawings]

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

FIG. 2 is a cross-sectional view illustrating a conventional technique.

FIG. 3 is a diagram showing a method for testing cut resistance.

FIG. 4 shows the shape of a blade used in the test method,
(A) is a plan view and (b) is a side view.

[Explanation of symbols]

 2 bead part 3 side wall part 3A outer wall surface 4 tread part 6 bead core 7 carcass 12 protector 12A outer peripheral contour line

Claims (2)

[Claims] 1. A pneumatic tire having a carcass which passes from a tread portion to a sidewall portion and folds around a bead core of a bead portion, wherein the sidewall portion is raised from its outer wall surface and extends in the circumferential direction. A pneumatic tire having a wavy outer peripheral contour line in a meridional section of the tire and provided with a protector made of short fiber mixed rubber. 2. The pneumatic tire according to claim 1, wherein the short fibers are oriented in the tire radial direction along the outer wall surface.