JPS6361604A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To improve the operational safety and the high-speed durability by specifying a ratio and groove depth of a tread ground part, and arranging between a carcass layer and belt with a specified auxiliary layer, and outside the belt layer with a specified rubber seat in tires for rally etc. CONSTITUTION:A ratio of a ground part is made to be 55-30%, and a groove depth 10mm or more at the center of the ground part in a tread 3. And a carcass auxiliary layer 7 composed of cords having a cord angle of 0 deg. to the tire circumferential direction EE' is interposed between a carcass layer 4 and the inmost layer 5d of a belt layer. Furthermore, a rubber sheet 8 having a tensile product of 3X10<4>%.kg/cm<2> or more, a loss tangent of 0.2 or more, and a thickness of 0.5-3mm is arranged with a larger width than that of a belt layer 5 on the outmost layer 5u of the belt layer. This constitution enables the better operational safety and high-speed durability.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention provides a pneumatic tire with improved handling stability and high-speed durability useful as a mud & snow tire or a rally tire that runs on unpaved or rough roads. Regarding tires.

[Prior art]

Conventionally, in order to obtain radial tires with excellent high-speed performance,
As shown in FIGS. 7 and 8, a pair of left and right bead portions 1
.
A plurality of belt layers 5 intersecting each other at cord angles of 10 DEG to 30 DEG with respect to E' are disposed, and a cover layer 6 is disposed on the outermost NSu of the belt layers 5. Note that 6a represents a cord constituting the cover layer 6, 5a a cord constituting the belt layer 5, and 5d the innermost layer of the belt layer 5.

Here, in the conventional tire, since the carcass layer 4 and the belt layer 5d are adhered adjacent to each other, when the tire is molded and cured, the carcass layer 4 disposed in the cross-sectional direction of the tire is 15° to 30° from the tire circumferential direction. A pantograph effect (compensated by angle change during tire molding and vulcanization) is caused by the belt layer 5d disposed in the tire, so that in the tire after molding and vulcanization, the carcass layer 4 is substantially aligned with the tire cross-sectional direction near a part of the tire shoulder. It was molded and vulcanized with a deviation of 2° to 3°. This non-uniform cord arrangement in the carcass layer 4 improves tire uniformity, especially L F V (Lateral Fo
rce Variation).

Further, the cover layer 6 has the function of reinforcing the belt layer 5, preventing the belt layer 5 from rising during high-speed running, and further improving the rigidity of the tire in the circumferential direction in combination with the belt layer 5. The cord 6a of the cover layer 6 is generally a textile cord made of a heat-shrinkable material such as a nylon cord or a polyester cord, and the cord 6a is arranged at approximately 0° with respect to the tire circumferential direction EE'. There is.

By the way, in the manufacturing process of the tire provided with the cover layer 6, after the belt layer 5 is arranged, the tire shown in FIG. 9(a),
As shown in (b), on the outermost layer of this belt layer 5,
A cover layer 6 in which the cord 6a is arranged at approximately 0° with respect to the tire circumferential direction is disposed, and the end portions 62 and 63 thereof are overlapped to form a splice portion 61. At this time,
The length of the splice portion 61 of the cover layer 6 in the tire circumferential direction! , (see FIG. 9(a)). Next, tire constituent members such as the trend section 3 are placed, and then this unvulcanized tire is heated under pressure in a vulcanization mold (not shown) to be vulcanized to form a product tire. The situation after this vulcanization is shown in FIG. 9(b).

The outer circumference of the tire before vulcanization is smaller than the inner circumference of the vulcanization mold, and the unvulcanized tire is pressurized from the inside of the tire in the vulcanization mold to grow the tire. It is brought into close contact with the inner peripheral surface of the vulcanization mold. This is generally referred to as applying a lift.

When the carcass layer 4 and the belt layer 5 are lifted in this way, the outer circumferential length can grow due to their structure, but the cover layer 6 has its cords extending in the tire circumferential direction as described above. It cannot grow because it is located almost at Oo.

Therefore, the growth of the cover layer 6 can only be achieved by stretching the cords 6a constituting it or by mutually shifting the end portions 62, 63 at the splice portion 61 thereof.

However, since the adhesive strength of the splice portion 61 is small compared to the tensile strength of the cord 6a, most of the growth is due to the displacement of the splice portion 61. As a result, the length e2 of the splice portion becomes shorter than l before vulcanization.

As a result, most of the growth of the belt layer 5 and the trend portion 3 occurs in the portion adjacent to the splice portion 61 described above.

As a result, non-uniform portions occur on the circumference of the tire, and this non-uniformity contributes to vehicle vibration when the automobile travels at high speed, and also leads to deterioration of the high-speed durability of the tire.

As a countermeasure for this, Japanese Patent Application Laid-open No. 60-50003 states:
Tires with orthogonal construction have been proposed.

That is, it consists of a pair of left and right bead parts, a pair of left and right sidewall parts connected to the bead parts, and a tread part located between the sidewall parts. is actually 90
In a pneumatic tire in which a carcass layer is mounted, and a plurality of belt layers intersecting each other at a cord angle of 10° to 30° with respect to the tire circumferential direction are arranged on the carcass layer in the tread part, A carcass auxiliary layer made of cords having a cord angle of approximately 0° with respect to the tire circumferential direction is interposed between the carcass layer and the innermost layer of the belt layer, and the carcass auxiliary layer and the carcass layer form an orthogonal structure. It's a tire.

By adopting such a structure, the uniformity and high-speed durability of the general tire were greatly improved. However, in passenger car tires (so-called snow tires, rally tires) whose tread groove depth exceeds 10.5 mm, separation between the tread rubber and the belt layer occurs due to the heat storage effect caused by the thick gauge of trend rubber. separation),
No improvement in high-speed durability is seen.

Furthermore, when the coat rubber of the carcass layer and the coat rubber of the carcass auxiliary layer are different types, there is also the problem that separation is likely to occur between the carcass layer and the carcass auxiliary layer.

[Purpose of the invention]

When the present invention is used as a tire with a thick tire throat gauge such as a mud & snow tire or a rally tire that runs on unpaved roads or rough roads, it reduces internal heat generation during high-speed running and prevents the occurrence of separation. It is an object of the present invention to provide a pneumatic tire that has high-speed durability such that it is possible to avoid the above problems, and also has excellent handling stability.

[Structure of the invention]

Therefore, the present invention provides a tire in which a plurality of belt layers are arranged on a carcass layer in a tread portion.
) Increase the ratio of the contact area of the tire tread to 55-30%,
The depth of the groove should be 1011Iffi or more at the center of contact with the ground (
2) between the carcass layer and the innermost layer of the belt layer,
(3) interposing a carcass auxiliary layer consisting of cords having a cord angle of approximately 0° with respect to the tire circumferential direction to form an orthogonal structure between the carcass auxiliary layer and the carcass layer; (3) covering the cords of the carcass auxiliary layer; The rubber used in the carcass layer is the same as the coat rubber of the carcass layer, and a rubber with a tensile product of 3 x 104% kg/cm is added on the outermost belt layer.
2 or more, loss tangent 0.2 or less, thickness 0.5-3mm
The gist of the tire is a pneumatic tire characterized by having rubber sheets arranged with a width larger than that of the belt layer.

Hereinafter, the configuration of the present invention will be explained in detail with reference to the drawings.

(1) In the present invention, in a tire in which multiple belt layers are arranged on the carcass layer in the trend part, the ratio of the ground contact area on the tire tread surface (tread surface) is 55 to 55.
30%, and the depth of the groove shall be 10 mm or more at the center of contact with the ground.

Here, the ratio of the ground contact portion refers to the ground contact portion/ground contact groove portion.

In the tire of the present invention, the groove depth is often set in a range of about 10 m+a to about 12 mm in order to obtain good grip on uneven road surfaces. This means that if the groove is less than 10 mm, the groove is too shallow to back dirt and snow into the groove and generate shear resistance between the groove and the road surface below to obtain grip. This is because if the thickness exceeds 12 mm, the tread rubber gauge becomes too thick for passenger cars, resulting in an increase in tie weight. Further, the ratio of the ground contact portion is also set in the range of 55 to 30% for the same reason.

(2) While scratching, increase the ratio of the ground contact part to 55
~30%, and tires with groove depth of 10mm or more at the center of contact with the ground are general tires (groove depth of about 5mm to about 9mm).
, the ratio of the ground-contact area is about 55% or more), the movement of the tread rubber is large and it is easy to generate heat, resulting in a decrease in high-speed durability. Therefore, in the present invention, a carcass auxiliary layer made of cords having a cord angle of approximately 0° with respect to the tire circumferential direction is interposed between the carcass layer and the innermost layer of the belt layer, so that the carcass auxiliary layer and the carcass layer are perpendicular to each other. It forms a structure.

This allows the adjacent adhesive relationship between the carcass layer and the belt layer (
In addition to eliminating the pantograph effect), it is also possible to reduce local deformation of the splice part of the cover layer.
Speed durability can be improved.

FIG. 1 is an explanatory half-sectional view in the meridian direction of a pneumatic tire having a carcass auxiliary layer, and FIG. 2 is a developed plan view thereof.

In these figures, the carcass auxiliary layer 7 is made of cords with a cord angle of approximately 0° with respect to the tire circumferential direction EE'.
is interposed between the carcass layer 4 and the innermost layer 5d of the belt layer 5.

As the cord of the carcass layer 4, chemical fibers such as nylon and polyester are generally used. In addition, the belt layer 5
As the cord, a steel cord is mainly used, but an aromatic polyamide fiber cord called aramid may also be used.

Further, as the cord constituting the carcass auxiliary layer 7, it is sufficient to use cords normally used for tires, preferably cords made of nylon or polyester, and cords made of steel, aramid, rayon, etc. can be used. . These materials can be selected depending on the lift rate and circumferential rigidity of the tire during tire molding and vulcanization. It is preferable to use textile cords such as nylon cords, especially nylon cords, and steel cords and aramid cords can be used when increasing the circumferential rigidity of the tire in the cefsilanal mode.

The cover layer 7 is formed using a material made of rubberized tire blind cords in which such cords are arranged in parallel, or a material in which one cord is wound and arranged in parallel (a so-called single-wound cord 71). Ru. The width of this cover layer 7 is
The width is preferably larger than the width of the adjacent belt layer 5.

When this cover layer 7 is interposed between the carcass layer 4 and the belt layer 5, the cord angle of the cover layer 7 with respect to the tire circumferential direction is approximately O'', and the cord angle of the carcass layer 4 with respect to the tire circumferential direction is substantially O''. 90'', the cord 7a of the cover layer 7 as shown in FIGS. 3 and 4.
and the cord 4a of the carcass layer 4 are orthogonal to each other, thereby forming an orthogonal structure between the cover layer 7 and the carcass M4.

In this orthogonal structure, the carcass 1i4 and the carcass auxiliary layer 7
The directions of the principal axes of elasticity correspond to the cross-sectional direction of the tire and the circumferential direction of the tire, respectively, and are perpendicular to each other. Therefore, during tire molding and vulcanization, unlike conventional tires, the cord angle of the carcass cord does not change due to the pantograph effect, so the carcass cord is essentially arranged in the cross-sectional direction of the tire, improving tire uniformity and improving high-speed durability. Sexuality also improves.

Further, the carcass auxiliary layer 7 is the belt layer 5d and the carcass layer 4.
Because it is inserted between the splice and the splice, local deformation of the splice part is less likely to occur, which contributes to high-speed durability.

However, in snow tires and rally tires with deep grooves, separation between the carcass auxiliary layer 7 and the carcass layer 4, and separation between the trend rubber and the belt layer 5 is required due to the heat storage effect due to the thick gauge of the tread rubber. may occur. In particular, the occurrence of separation between the tread rubber and the belt layer 5 poses a major safety problem.

(3) In order to solve this problem, in the present invention, the rubber covering the cords of the carcass auxiliary layer 7 is the same as the coat rubber (covering rubber) of the carcass layer 4, and the outermost layer belt On the layer 5u, as shown in FIGS. 5 and 6, a tensile product of 3×104%・kg/c
A rubber sheet 8 having a loss tangent (tan δ) of 0.2 or less and a thickness of 0.5 to 31111 mm is arranged with a width larger than that of the belt layer 5.

By arranging the rubber sheet 8, heat generation near the boundary between the tread rubber and the belt layer 5 is suppressed, and the limit of occurrence of separation is increased.

Furthermore, by using the same rubber that coats the cords of the carcass auxiliary layer 7 as the coating rubber of the carcass layer 4, the adhesion is further improved and the high-speed durability is further improved.

Next, Table 1 below shows the results of high-speed durability tests on the tire of the present invention, a conventional tire, and a tire with only an orthogonal structure. Here, the conventional tire is a tire in which a belt reinforcing layer is arranged on a belt layer.

(Margins below this page) Table 1 Note 2 Tire size 1655R13° Rim used 51/2J X 13° JIS 042
Conducted in accordance with the method prescribed in Article 30.

From Table 1, it can be seen that just using the orthogonal structure improves high-speed durability by 8 to 9% compared to conventional tires, but by adopting the tire structure of the present invention, high-speed durability increases by about 15% compared to the orthogonal structure. It can be seen that the performance improves.

The results of testing for handling stability are shown in Table 2 below.

From Table 2, it can be seen that the tire of the present invention has improved uniformity, so that the steering stability is improved by about 20% compared to the conventional tire.

(Margins below this page) Table 2 note: Index display, the larger the index, the better.

Tire size: 1655R13° Rim used: 51/2J x 13° Air pressure
2.1kg/cm” Vehicle used: Power Roller Levin.

Test course forest road.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to suppress heat generation between the tread rubber and the belt layer, and between the carcass auxiliary layer and the carcass layer, and improve adhesion, thereby improving high-speed durability. , it becomes possible to further improve steering stability.

[Brief explanation of drawings]

Fig. 1 is an explanatory half-sectional view in the meridian direction of a pneumatic tire having a carcass auxiliary layer, Fig. 2 is a developed plan view thereof, Fig. 3 is a developed plan view showing an orthogonal structure, and Fig. 4 is a perspective conceptual view of the same. be. FIG. 5 is an explanatory half-sectional view in the meridian direction of an example of the pneumatic tire of the present invention, and FIG. 6 is a developed plan view thereof. Fig. 7 is an explanatory half-sectional view in the meridian direction of an example of a conventional pneumatic tire, Fig. 8 is its developed plan view, Fig. 9(a),
(b) is an explanatory diagram showing a situation in which the splice portion of the cover layer shifts during the manufacturing process of this type of tire. ■・・・Bead part, 3...Tread part, 4...
Carcass layer, 5...Belt layer, 5U...Outermost layer, 5
d... Innermost layer, 6... Cover layer, 7... Carcass auxiliary layer, 8... Rubber sheet.

Claims (1)

[Scope of Claims] In a tire in which a plurality of belt layers are arranged on a carcass layer in the tread portion, (1) the ratio of the ground contact area on the tire tread is 55 to 30%, and the depth of the groove is set at the center of the ground contact. 10 mm or more, and (2) a carcass auxiliary layer made of cords having a cord angle of approximately 0° with respect to the tire circumferential direction is interposed between the carcass layer and the innermost layer of the belt layer, so that the carcass auxiliary layer and the carcass (3) the rubber covering the cords of the carcass auxiliary layer is the same as the coat rubber of the carcass layer; The air is characterized by a rubber sheet having a thickness of 3×10^4%・kg/cm^2 or more, a loss tangent of 0.2 or less, and a thickness of 0.5 to 3 mm arranged in a width larger than that of the belt layer. Included tires.