JPH03136905A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To prevent the wavy wear of a tread surface in a pneumatic radial tire having a trochoidal carcass layer and a belt layer by constituting the belt layer with inner plies having wavy reinforcement elements laid in the same phase, and outer plies having a plurality of reinforcement cords so laid as to intersect one wavelength of the reinforcement elements. CONSTITUTION:A belt layer 26 is constituted with an inner ply 31 and an outer ply 35. The inner ply 31 is formed with many wavy and peripherally extended reinforcement elements 33 embedded in the same phase. The outer ply 35 is formed with non-extensible reinforcement cords 38 comprising a steel or the like embedded while inclined at about 15 to 45 degrees with a tire equator surface 37. In addition, two or more reinforcement cords 38 are made to intersect one wavelength of the reinforcement elements 33. According to the aforesaid construction, the wavy wear of a tread surface is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pneumatic radial tire in which a belt layer and a tread are arranged radially outside a toroidal carcass layer.

Traditionally, vulcanization molding can be easily performed, and
As a pneumatic radial tire capable of exhibiting a strong hoop effect, one example, as shown in Fig. 4.5.6, is known.

This thing consists of a toroidal carcass layer 2 in which a large number of cords l extending in the radial direction are embedded, a belt layer 3 arranged radially outside the carcass layer 2, and a belt layer 3 arranged radially outside the belt layer 3. and a tread 4,
The belt layer 3 is.

It has a belt ply B in the circumferential direction while being bent in a wavy or zigzag shape, and this belt ply 8 and the carcass layer 2
An inclined ply 8 in which a large number of reinforcing cords 8 which are inclined with respect to the tire equatorial plane 7 are buried is interposed between the tire and the tire.

However, such pneumatic radial tires
There is a problem in that the tread 4 deforms in a wave-like manner along the circumferential direction, resulting in wave-like wear (uneven wear) on the tread surface.

The reason is that generally when vulcanizing green tires,
Since the inner circumference of the vulcanization mold is larger than the outer circumference of the green tire, when vulcanizing fluid is injected into the green tire,
The green tire expands until its outer circumference becomes the same length as the inner circumference of the vulcanization mold. At this time, a reinforcing element 5 having a wavy or zigzag shape is embedded in the belt ply 8 of the green tire. , these reinforcing elements 5 are also stretched while being elastically deformed due to the expansion of the green tire, and as the wavelength becomes longer, the amplitude becomes smaller.
When vulcanization is completed and the vulcanizing fluid is discharged from the vulcanized tire, the stretching force acting on the reinforcing elements 5 disappears, so each reinforcing element 5 contracts due to the elastic force and the wavelength becomes shorter. And the amplitude tends to increase. Here, when the cord 1 embedded in the carcass layer 2 is made of a heat-shrinkable material, the above-mentioned situation becomes even more remarkable as the cord 1 contracts after vulcanization is completed.

The deforming force of the reinforcing element 5 acts on the tread 4 that is in direct contact with the belt layer 3, causing the tread 4 to move in the opposite direction every half wavelength of the reinforcing element 5 as shown by the imaginary line. At the same time, a shearing force A based on the wave-like deformation is generated inside the tread 4. Note that the deformation of the tread 4 as described above occurs at a position close to the belt layer 3.

That is, it is large at the groove bottoms of the main grooves, lateral grooves 10, etc. formed in the tread 4, and conversely becomes small at positions distant from the belt layer 3, that is, on the tread surface. By the way, when a pneumatic radial tire as described above is transferred while being subjected to a load, the tread 4 in the ground contact area is crushed and deformed by the load, and as a result, tread shear is created inside the tread in the axial direction. Force B is generated. Therefore, in the region C where the shear force A and the tread shear force B are in the same direction, the shear forces A and B are added together and the shear force acting on the tread 4 becomes large; In a region where the tread surface shear force B is in the opposite direction, these shear forces A and B cancel each other out, and the shear force acting on the tread 4 becomes small. Therefore, wear progresses rapidly in area C, while wear progresses slowly in area C, resulting in a state in which areas with large amounts of wear and areas with small amounts of wear occur alternately in the circumferential direction on the tread surface. This results in wavy wear.

This invention provides a pneumatic radial tire that can prevent undulating wear on the tread surface even when a ply in which a large number of reinforcing elements bent in a wavy or zigzag manner and having the same phase is embedded in the belt layer is used. The purpose is to provide

Therefore, this purpose consists of a toroidal carcass layer in which a large number of cords extending in the radial direction are embedded, a belt layer placed radially outside the carcass layer, and a toroidal carcass layer placed radially outside the belt layer. A pneumatic radial tire comprising: a tread; the belt layer; , at least one outer ply in which a large number of reinforcing cords are embedded, superimposed on the radially outer side of the inner ply and inclined with respect to the tire equatorial plane, and two or more reinforcing cords are provided in the one-wavelength reinforcing element. This can be achieved by crossing the reinforcing cords.

As mentioned above, if a large number of wavy or zigzag reinforcing elements of the same phase are embedded in the ply that makes up the belt layer, these reinforcing elements will be stretched during vulcanization, but once vulcanization is complete, Since the stretching force acting on the reinforcing elements disappears, each reinforcing element contracts due to the elastic force, and the wavelength becomes shorter and the amplitude becomes larger. However, in the present invention, on the radially outer side of the inner ply in which the reinforcing element is embedded, at least one outer ply in which a large number of reinforcing cords inclined with respect to the tire equatorial plane are embedded is superimposed, The outer ply is interposed between the inner ply and the tread, and two or more reinforcing cords are made to cross the one-wavelength reinforcing element. As a result, the non-stretchable reinforcing cord embedded in the outer ply blocks the deformation force generated in the reinforcing element from being transmitted to the supporting tread. This prevents the tread from being subjected to wave-like deformation in the opposite direction every half wavelength of the reinforcing element, and also prevents shearing forces from occurring inside the tread due to this wave-like deformation.

This prevents undulating wear on the tread surface.

1 presentation 1 Hereinafter, one embodiment of the present invention will be described based on the drawings.

In Fig. 1.2, 21 is a pneumatic radial tire, and this tire 21 has a toroidal-shaped carcass layer 22, in which a large number of cords 23 extending in the radial direction are embedded. at least 1
It is composed of two carcass plies 24. A belt layer 2e is arranged on the radially outer side of the carcass layer 22, and a tread 28 in which a plurality of main grooves 27, etc. are formed is arranged on the radial outer side of this belt layer 26. The belt layer 2B has at least one (one in this embodiment) inner ply 31 arranged radially inward. A large number of reinforcing elements 33 extending in the circumferential direction are embedded within the inner ply 31, and these reinforcing elements 33 are composed of cords (twisted wires) or single wire filaments. In addition, these reinforcing elements 33 are made of steel, Kevlar (
It is made of a non-extensible material such as (aromatic polyaramid) and has a wavy or zigzag shape in a plane parallel to the front and back surfaces of the inner ply 31.

For example, they are bent in the shape of a square wave, triangular wave, or sine wave, and are arranged in the same phase. When a large number of reinforcing elements 33 having the same phase and having a wavy or zigzag shape are buried in the inner ply 31 in this way, these reinforcing elements 33 are stretched during vulcanization, but when vulcanization is completed, the reinforcing elements 33 Since the stretching force that had been acting disappears, each reinforcing element 33 contracts due to the elastic force, and the wavelength tends to become shorter and the amplitude becomes larger. Therefore, in this embodiment, at least one (in this embodiment, one) outer ply 35 is superimposed on the radially outer side of the inner ply 31, and the inner ply 31 is
The outer ply 35 is interposed between the tire 1 and the tread 28. Inside this outer ply 35 are a number of reinforcing cords 3 made of non-stretchable steel, for example, which are inclined at an angle of 15 degrees to 45 degrees with respect to the tire equatorial plane 37.
B is buried. As a result, the deformation force generated in the reinforcing element 33 is prevented from being transmitted to the supporting tread 28 by the non-stretchable reinforcing cord 38 embedded in the outer ply 35. As a result, the tread 28 has the reinforcing element 33
This prevents wave-like deformation from occurring in opposite directions every half wavelength of the tread, and no shearing force based on this wave-like deformation is generated internally, thereby preventing wave-like wear on the tread surface. In addition, when there are two or more outer plies 35, these outer plies 35 are preferably arranged so that the reinforcing cords 38 intersect with each other, and the width W of the outer ply 35 is equal to the width of the inner ply 31. Therefore, it is preferable that the outer ply 35 covers the entire width of the inner ply 31 from the outside.The reason is that when the width W of the outer ply 35 is less than the width of the inner ply 31, This is because an area where the inner ply 31 and the tread 28 are in direct contact occurs at the tread end where conditions are particularly severe, and there is a risk that wave-like wear may occur in this area. Further, in this embodiment, as shown in FIG. 3, two or more reinforcing cords 38 are crossed with respect to the reinforcing element 33 of one wavelength G. Here, if the number of crossings is two, the reinforcing cords 38 will be crossed at the peaks T and valleys V of the reinforcing element 33, respectively.
Transmission of deforming force from the reinforcing element 33 to the tread 28 can be prevented. However, in reality, it is difficult to cross the reinforcing element 33 and the reinforcing cord 38 at the above-mentioned position due to variations in the insertion positions of the reinforcing element 33 and the reinforcing cord 38.
It is preferable that four or more reinforcing cords 38 cross each reinforcing element 33.

Next, a first test example will be explained. In this test, as shown in Attached Table 1, inclined plies with embedded steel inclined cords were used as the radially inner first and second belt plies, and as the radially outer third and fourth belt plies. Comparative tire 1 using a wavy ply in which a wavy reinforcing element made of steel is embedded, and @1 on the radially inner side. Second
Test tire 1.2 using an inner ply in which a wavy reinforcing element made of steel is embedded as a belt ply, and an outer ply in which a sloped steel cord is embedded as a radially outer third and fourth belt ply. .3.4 were prepared. Here, the size of each tire is T B R1
1/70R22.5, and other specifications are as shown in Attached Table 1. 8th order, each of these tires was investigated for the presence or absence of wave-like deformation in the tread before rim assembly. Each of these tires was mounted on a truck and driven for 20,000 km, and the presence or absence of wave-like wear on the tread at the end of the journey was investigated. The results of the investigation on the wave-like deformation and wave-like wear are shown in Attached Table 1. Compared to Comparative Tire 1, each test tire had improved both wave-like deformation and wave-like wear. In addition, among the test tires, test tire 3, in which the number of intersecting layers is 4 or more and the width W of the outer ply is greater than or equal to the width of the inner ply, is different from the test tire 1, in which the number of intersecting layers is less than 4.
, 2, the wave-like deformation and wave-like wear are further improved compared to the test tire 4 in which the cap W of the outer ply is less than the radius of the outer ply.

Next, a second test example will be explained. In this test, as shown in Attachment 2, plies with embedded steel inclined cords were used as the radially inner first and second belt plies, and 1,500 plies were used as the radially outer third belt ply.
Comparative tire 2 using a wavy ply in which a wavy reinforcing element made of d/2 Kevlar is embedded, and a first tire on the radially inner side. A test using an inner ply in which a wavy reinforcing element made of 1500 d/2 Kevlar was embedded as the second belt ply, and an outer ply in which a steel sloped cord was embedded as the radially outer third belt ply. With the tire 5, an inner ply in which a wavy reinforcing element made of steel is embedded is used as a radially inner first belt ply, and an outer ply in which a steel inclined cord is embedded as a radially outer second belt ply. Test tires 6.7.8 were prepared. Here, the comparative tire 2 and the test tire 5 are those in which the reinforcing element located near the tire equatorial plane is fully extended and the amplitude becomes zero due to a large expansion rate during vulcanization. . Also, the size of each tire is P S R185/705 R1
4, and other specifications are as shown in Attached Table 2. Next, we investigated the presence or absence of wave-like deformation in the tread of each tire before assembling the rim. 20,000km with tires installed on a domestic passenger car
The vehicle was run, and the presence or absence of wave-like wear on the tread at the end of the run was investigated. The results of the investigation on the wave-like deformation and wave-like wear are shown in Attached Table 2. Compared to Comparative Tire 2, each test tire had improved both wave-like deformation and wave-like wear. Also, among the test tires, test tire 5 has four or more intersecting layers and the width W of the outer ply is greater than or equal to the width of the inner ply.
．． No. 7 has further improved wave-like deformation and wave-like wear than test tire 6 in which the number of intersecting layers is less than four, and test tire 8 in which the width W of the outer ply is less than the width of the inner ply.

As explained above, according to the present invention, the belt layer has
Even when a ply in which a large number of reinforcing elements having the same phase and bending in a wavy or zigzag manner is embedded, it is possible to prevent wavy wear that occurs on the tread surface.

[Brief explanation of the drawing]

@Ill is a meridian cross-sectional view showing an embodiment of the present invention, FIG. 2 is a partially broken developed view, FIG. 3 is an explanatory view illustrating the intersecting state of the reinforcing element and the reinforcing cord, and FIG. The figure shows a partially cutaway exploded view of a conventional pneumatic tire.
FIG. 6 is a cross-sectional view taken along the line I--I in the figure, and FIG. 6 is a cross-sectional view taken along the line ■--■ in FIG. 22...Carcass layer 23...Code 26...
・Belt layer 31...Inner ply 35...Outer ply 38...Reinforcement cord

Claims (1)

[Claims] A toroidal carcass layer in which a large number of cords extending in the radial direction are embedded, a belt layer arranged radially outside the carcass layer, and a tread arranged radially outside the belt layer. radial tire, the belt layer having at least one inner ply embedded therein with a plurality of reinforcing elements of the same phase extending in the circumferential direction while being bent in a wavy or zigzag shape; and a radially outer side of the inner ply. at least one outer ply in which a large number of reinforcing cords are buried, superimposed on each other and inclined with respect to the tire equatorial plane, and two or more reinforcing cords are crossed over the one-wavelength reinforcing element. A pneumatic radial tire characterized by: