JPH02234805A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To prevent separation of a transportation layer by forming a crown reinforce layer of a belt, which is arranged between a carcass and belt transportion layer, through orientation of specific cords, etc., in a certain direction, and by specifying the distance of the equator surface from the outer end in the width direction. CONSTITUTION:A pneumatic tire has transposition layers 1, 2 of belt reinforced by a number of cords or filaments intersecting with the equator pinched at an inclination angle of 10 deg.-40 deg. to the tire equator. A crown reinforce layer 3 is provided on the inside of these transposition layers 1, 2. In this crown reinforce layer 3, corrugated or zigzagged cords or filaments as reinforcing elements are oriented substantially in parallel with the equator. The distance of the equator surface from the width direction outer end of this crown reinforce layer 3 shall be set within the range 25-47.5% of the actual cord transposition area max. width in the transposition layers 1, 2.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The object of the present invention is to propose an effective improvement in crown reinforcement, particularly for pneumatic tires.

(Prior Art) Crown reinforcement of pneumatic tires has generally relied solely on belts, but it has not been possible to overcome the problem of separation.

JP-A-54-126306 and JP-A-55-132
Patent No. 307 specifically states that by sharing the circumferential tension with a cord layer laminate called a limiter block or limiter assembly, the circumferential tension acting on the belt can be reduced and the separation can be prevented. The purpose is stated. However, in reality, it is a good thing that separation occurs between limiter blocks, because in order to obtain high rigidity along the circumference, it is necessary to stack the cord layers by intersecting the cords at an extremely shallow angle of inclination. This is because it is necessary.

However, in this case, by placing a strip with a cord angle of 0° in place of the limiter block, the separation can be avoided since the cut-off end will not appear. In green tires, belt expansion within the vulcanizer is suppressed, which poses significant difficulties in tire manufacturing. It is not impossible to create a structure in which the cords used for the reinforcing elements of the strip are twisted so that they stretch only in the initial stage of vulcanization and that the desired rigidity is obtained after vulcanization, but such cords Not only is the twisting pitch shortened, which is disadvantageous in terms of productivity, but also the cord strength decreases due to twisting, and the tire has to be driven more due to the fear of so-called cut burst, which increases the weight of the tire. disadvantages, and the use of monofilament is not possible.

Note that as a technology for reinforcing tires using a protective layer consisting of a corrugated cord layer, Japanese Patent Laid-Open No. 57-209403 discloses, in addition to a breaker with two or more layers, a corrugated strength carrier made of fiber or metal with extremely low elongation. It is disclosed that the protective layer is constituted by. However, depending on the arrangement of the protective layer shown here, its characteristics as a crown reinforcing layer cannot be fully brought out.

(Problem to be Solved by the Invention) Separation in the intersecting layers of a belt useful for reinforcing the crown of a pneumatic tire and in particular in the crown reinforcing layer is advantageously prevented by using ordinary cords or filaments,
It is an object of the present invention to provide a pneumatic tire equipped with crown reinforcing means that is easy to manufacture and does not increase weight.

(Means for Solving the Problems) The present invention includes at least one toroid-shaped radial carcass extending from one bead portion to the other bead portion, and a belt reinforcing the tread on the radial carcass, This belt is 10' from the tire's equatorial plane.
at least two interlacing layers with reinforcing elements consisting of a number of cords or filaments intersecting each other across the equator at an inclination angle of ~40°, and at least one crown reinforcement layer located between the carcass and the interlacing layer. The crown reinforcing layer is formed by arranging corrugated or zigzag-shaped cords or filaments as reinforcing elements in an orientation substantially parallel to the equator, and the crown reinforcing layer has a width direction of the crown reinforcing layer. The pneumatic tire is characterized in that the distance from the outer edge to the equatorial plane is 25 to 47.5% of the maximum width of the actual cord crossing area in the crossing layer.

The key point of this invention is to use strips of corrugated or zigzag cords or filaments oriented along the equator for the reinforcing elements of the crown reinforcing layer, which facilitates elongation during vulcanization. There is no need to control the elongation by twisting or twisting, which saves manufacturing time, so low-cost filaments can be used, and the strength of the cord does not decrease due to twisting, so cordburst No worries,
The weight of the tire does not increase either.

Now, Figures 1 (a) and 1 (b) illustrate the cross section of a pneumatic tire according to the present invention, and in the figure, 1.2 is an inclination angle of 10'' to 40'' with respect to the tire's equatorial plane, and the equator is sandwiched between each other. The intersecting layers of the belt each having a number of intersecting cords or filaments as reinforcing elements are shown by solid lines, and 3 is a crown reinforcing layer arranged inside the intersecting layer 1.2 of the belt as shown by the broken line in the figure, and as its reinforcing element. The corrugated or zigzag shaped cords or filaments are arranged with their orientation substantially parallel to the equator. In the figure, C is a carcass, and T is a tread.

The crown reinforcing layer 3 may have a hollow structure as shown in FIG. 1(a), or may have a series of layers in the width direction as shown in FIG. Needless to say, it is possible to have two or more layers.

In manufacturing such tires, the various parts of the tire are assembled to form a green tire, and then the tire is vulcanized in a vulcanization mold.
The tire diameter will be increased by 2-6%. The reinforcing elements constituting the crown reinforcing layer 3 must be arranged substantially parallel to the equator from the viewpoint of durability. It needs to be expanded.

If the reinforcing elements do not stretch, the cross-sectional shape of the completed tire will be distorted and cannot withstand use. For this purpose, the reinforcing elements of the crown reinforcing layer must have a cutting elongation that exceeds the above expansion rate due to vulcanization, and steel cords or filaments that are originally suitable as this type of reinforcing element have extremely low elongation. , it is necessary to pre-shape it into a wavy or zigzag shape.

(Function) Regarding the protective layer using a wavy cord, the above-mentioned Japanese Patent Application Laid-Open No. 57
- According to Publication No. 209403. allows the protective layer to be provided on the radially outer side of the belt, in the layer of the belt, or even on the radially inner side, but it is intended to be used as a crown reinforcing layer. Considering the displacement of each layer along the circumference of the belt as a whole on the tire equator with reference to FIGS. 2(a) and (b), it is as follows. This figure 2 (a) (b
) is a cross-section taken parallel to the tire's equatorial plane through the area where the reinforcing layer of the tire exists, and the left half shows the state of ground contact deformation under load transfer, and the right half shows the free state.

First, when the protective layer 3' is arranged radially outward of the intersecting layer 1.2 as shown in FIG. 2(a), the intersecting layer 1.2.
The circumference of #2 is shorter than the circumference of #I3', and
Since the circumferential length of the protective layer 3' hardly changes due to the grounding deformation, the entire intersecting layers 1, 2, and the protective layer 3' are subjected to the bending force P shown by the arrow due to the grounding, and as shown in F in the figure. When deformed flat, the intersection 1.2 is stretched by the protective layer 3'.

On the other hand, as shown in FIG. 2(b), when the crown reinforcing layer 3 is placed inside the radially outermost layer 1 of the intersecting layers 1 and 2, here particularly between the inner layer 2 and the carcass C. When the intersecting layers 1 and 2 and the crown reinforcing layer 3 of the belt are similarly deformed flat due to the bending force P due to ground contact, the intersecting layers 1 and 2 outside the crown reinforcing layer 3 are crown reinforced, contrary to the above. It is compressed by layer 3.

In this way, the crown reinforcing layer 3 is attached to the intersecting layers 1 and 2 of the belt.
By disposing it between the carcass C on the radially inner side of the crown reinforcing layer, the cross layer 1.2 on the radially outer side of the crown reinforcing layer is also influenced by the compressive force at its widthwise side ends,
Shear forces at the belt ends are further suppressed.

Since the crown reinforcement N3 uses a corrugated or zigzag shaped cord or filament as a reinforcing element, there is no possibility of separation from the side edges. Because the ends of the cord (breaks) as at the ends of the belt interlacing layers
This is because there is no distortion at all, and so-called distortion concentration does not occur there.

Furthermore, it is important to keep the distance from the equatorial plane of the outer end of the crown reinforcing layer 3 in the width direction within a range of 25 to 47.5% of the maximum width of the intersecting layer of the belt where the cords actually intersect.

Figure 3 shows the results of measuring the shear strain along the tire circumference at the end of the intersecting layer 1.2 of the belt.This shear strain causes the problem of separation from the intersecting layer end as described above. be.

When the end position of the crown reinforcing layer 3 coincides with the outer edge position of the intersecting area (50% position in the figure), the strain at the end of the intersecting layer becomes large, whereas when the end position of the crown reinforcing layer 3 is moved inward in the width direction The strain at the end of the intersecting layer once reaches a minimum value and then tends to gradually increase.

In addition to separation being caused by the large shear strain at the ends of such intersections N1 and N2, it is also necessary to consider heat generation by the crown reinforcing layer 3.

In other words, since the crown reinforcing layer 3 is almost non-extensible along the equator, when multiple crown reinforcing layers 3, intersecting layers, and crown reinforcing layers are used, the solid ground deformation shown in FIG. Shear strain along the circumference occurs at the stepping-in position and kick-out position as shown in FIG.

Therefore, it is necessary to consider the heat generation in the corrugated crown reinforcement layer due to this distortion, and the wider the width of the crown reinforcement N3, the greater the heat generation, which is also disadvantageous in terms of separation at the ends of the intersecting layers 1 and 2. The narrower the width of the crown reinforcing layer, the less heat generated, which is preferable in terms of durability. Note that the ends of the crown reinforcement layer 3 are crossed bells}1.2N
If the crown reinforcing layer 3 is located inside and away from the end of the interlaced belt 1.2, the effect of heat generated by the crown reinforcing layer 3 on the end of the intersecting belt 1.2 will be reduced, and separation will be less likely to occur at the layer end of the intersecting belt 1.2. Therefore, in order to comprehensively evaluate the above-mentioned effects, tires were made in which the end position of the crown reinforcing layer 3 was changed in various ways, and a drum test was conducted. The results are shown in FIG.

The horizontal axis represents the distance from the outer edge of the crown reinforcement layer 3 in the width direction to the equatorial plane, and the vertical axis represents the distance traveled in the indoor drum test for comparison. This relationship is the result of considering not only the magnitude of strain at the ends of the intersecting layers 1 and 2 as shown in Figure 3, but also the heat generation. It can be seen that the position from the plane is 25 to 47.5% of the maximum width where the intersecting layers 1 and 2 actually intersect.

In addition, as an embodiment, it is of course possible to use a plurality of crown reinforcing layers 3 instead of just one.

The test tires with spot size 11/70 R22.5 are shown in Table 1 below.
A prototype was made according to the following.

Table 2 shows a comparison of the drum durability mileage index with respect to Tire F for each of the above trial tires.

Table 2 The drum test was performed at an air pressure of 8.0 kg/cm2, a speed of 60 kg/h, and a load of 24 kg from an initial load of 2500 kg.
The test was carried out under the condition that the weight was increased by 500 kg every hour, and the number of kilometers traveled until separation occurred between the intersecting layers was compared.

(Effects of the Invention) According to the present invention, crown portion reinforcement effective for preventing separation in the intersecting layers of the belt is appropriately achieved by optimally arranging the corrugated reinforcing elements.

[Brief explanation of the drawing]

Figures 1 (a) and (b) are cross-sectional views of the tire according to the present invention; Figure 2 is a cross-sectional view parallel to the equatorial plane of the tire showing the deformation behavior of the tread; and Figure 3 is a cross-sectional view of the position of the edge of the crown reinforcing layer. Graph showing the influence of laminar shear strain at belt crossing edges on changes. Figure 4 is a distribution diagram of interlaminar shear strain due to deformation due to tread loading, Figure 5 is a diagram of the relationship between the position of the crown reinforcement layer edge and drum travel distance, and Figure 6 is a comparison diagram of tire crown cross sections. It is. 1.2... Cross layer 3... Crown reinforcement layer C
...Carcass Patent Applicant Bridgestone Corporation Figure 1<a) (b} Figure 3 Figure 5 Figure 6 (a)

Claims (1)

[Claims] 1. At least one radial carcass in a toroidal shape extending from one bead part to the other bead part, and a belt reinforcing the tread on this radial carcass, and this belt is used for a tire. 10° to 40° to the equatorial plane of
at least two interlaced layers having reinforcing elements consisting of a number of cords or filaments intersecting each other across the equator at an inclination angle of °, and at least one crown reinforcing layer located between the carcass and the intersecting layers; The crown reinforcing layer is formed by arranging corrugated or zigzag-shaped cords or filaments as reinforcing elements in an orientation substantially parallel to the equator; The distance from the outer edge to the equatorial plane is 25 to 47.
A pneumatic tire characterized by 5%.