JPS61143204A - Pneumatic radial tire for heavy load - Google Patents

Abstract

PURPOSE:To improve the straight running property by specifying the cord arranging angles of a belt reinforcing layer and belt tension resisting layers, and using a specific steel cord stranded in bundle in the belt tension resisting layers, and specifying the relationship between a cord stranding direction and a layer structure. CONSTITUTION:The cord arranging angle of a belt reinforcing layer 4r is set to 45 deg.-75 deg. against a circumference direction EE' of a tire, and the cord arranging angles of belt tension resisting layers 4d, 4u are set to 15 deg.-30 deg. in the same manner. And a type of steel cord stranded in bundle is used in the cords of the belt tension resisting layers 4d, 4u, in which steel cord each wire is stranded with the same pitch and the same stranding direction. If the stranding direction of the steel cord is a Z-strand, the belt tension resisting layers 4d, 4u are made to an S laminating structure, and if the stranding direction of the steel cord is an S-strand, the belt tension resisting layers are made to a Z laminating structure. By this constitution, it is possible to improve the tire uniformity and the rigidity of tire in a circumference direction to relieve the plies tear and to improve the straight running property.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a heavy-duty pneumatic radial tire that reduces plysteer and improves straight running performance.

[Prior art]

Conventionally, in pneumatic radial tires for heavy loads such as trucks and buses or small trucks, the cord angle between the tread and the carcass layer and adjacent to the carcass layer is 40 degrees with respect to the tire circumferential direction. The belt reinforcing layer has an angle of 15° to 75° and the cords laminated on the upper surface of the belt reinforcing layer have an angle of 15° to 30° with respect to the tire circumferential direction.
0.

It is constructed by a stacked arrangement of belt reinforcement layers consisting of at least 2N belt tension-resistant layers intersecting each other at ~165°. The carcass layer in this case consists of one layer or two layers, and the carcass cord forms an angle of approximately 90° (substantially in the radial direction) with respect to the circumferential direction of the tire.

Compared to bias tires, this type of radial tire has superior braking performance, fuel efficiency, wear resistance, etc. due to the effect of the belt reinforcement layer described in 1. As a result, there is a problem that straight running performance is poor. In other words, when a radial tire rotates, a lateral force is generated in either the left or right direction with respect to the direction of travel, even if the slip angle is zero, and this lateral force causes the vehicle to move in a direction different from the direction intended by the driver. There are cases where this progresses.

Generally, the lateral force at a slip angle of zero consists of force components generated by two different mechanisms, one of which is called conicity (CT) and the other is called plysteer (PS). It is classified as part of the tire's uniformity characteristics. On the other hand, the uniformity test method for automobile tires (JASOC60
According to 7), when the average value of the lateral force when the tire rotates once is LFD, LFDw measured on the surface of the tire, LFDs measured with the tire replaced with the backside, and ``2''. The connected conicity CT and plysteer PS have a relationship expressed by the following equation from the definition.

LFDw=PS+CT H-...(llLF
Ds = PS-CT ・---・(2) Above (1
), PS, , CT are calculated from equation (2) as follows.

The relationships (1, 1, (2), (3), and (4)) above can be represented in a diagram as shown in FIG.

By the way, among the above-mentioned conicity and plystea,
Conicity is considered to be the geometric asymmetrical shape of a tire with respect to its circumferential center, that is, the force generated when a truncated conical tire shifts.

Since this cause is mainly affected by the position of the belt reinforcing layer inserted into the tire tread, this can be reduced by improving the manufacturing process.

On the other hand, plysteer is an inherent force caused by the structure of the belt reinforcing layer, and it is virtually impossible to reduce it significantly unless the structure of the belt reinforcing layer itself is changed.
It was said to be #.

Now, if we take out the belt reinforcing layer and consider it, we can see that it is shown in Figure 8 (A
) as shown in the belt tension-resistant layer 4u.

4d and a belt reinforcing layer 4r. With respect to this three-layer laminate 4, the tire circumferential direction EE
When a tensile force is applied to ゛, the three-layer laminate 4 deforms not only within the two-dimensional plane where the tension acts, but also three-dimensionally out of the plane, as shown in Figure 8 (B). It is well known that this can cause severe torsional deformation. As mentioned above 5
) Plysteer occurs due to such torsional deformation of the belt reinforcing layer.

Conventionally, various studies have been made to reduce this plysteer by adding a new belt reinforcing layer to the belt reinforcing layer, but adding a new belt reinforcing layer in this way is This could not be said to be very desirable as it would impair characteristics such as fuel efficiency.

[Purpose of the invention]

An object of the present invention is to provide a heavy-duty pneumatic radial tire that reduces plysteer and improves straight running performance by specifying the belt structure of the tire.

[Structure of the invention]

For this reason, the present invention has a carcass layer with a carcass cord arranged substantially in the radial direction,
In a pneumatic radial tire in which a belt reinforcing layer is provided outside the carcass layer and at least two belt tension-resistant layers are laminated on a bias outside the belt reinforcing layer, (]) cord arrangement angle of the belt reinforcing layer; is 45° to 75° with respect to the tire circumferential direction, (2) the cord arrangement angle of the belt tension-resistant layer is 15° to 30° with respect to the tire circumferential direction, and (3) the belt As the cord for the tensile strength layer, we used a bundle of 1-heat type steel cord in which each strand was fitted at the same pitch and in the same twisting direction.
When the direction of the steel cord is Zl, the belt tension-resistant layer has an S-layer structure, and when the steel cord is twisted in the S-twist direction, the belt tension-resistant layer has a Z-layer structure. The gist of this invention is a heavy-duty pneumatic radial tire characterized by a laminated structure.

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

FIG. 1 is a partially cutaway radial cross-sectional perspective view of an example of a heavy-duty pneumatic radial tire of the present invention. In this FIG. 1, 1 is a tread, 2 is a sidewall part provided so as to extend on both sides of the tread 1,
3 is attached to the lower end of this sidewall portion 2 in the tire circumferential direction E.
This is a bead wire buried along E.

A carcass layer 5 that wraps around the bead wires 3 at both ends and extends along the inner surface of the sidewall portion 2 and the tread 1 so that the cord angle with respect to the tire circumferential direction EE' is approximately 90° (substantially in the radial direction).
A belt reinforcing layer made of steel cord is interposed between the carcass layer 5 and the tread 1. At least one carcass layer 5 is provided. Further, the belt reinforcing layer includes belt reinforcing IW4. provided on the outside of the carcass layer 5. r, the lower belt tension-resistant layer 4d provided on the outside of this belt reinforcement jt44r, and the upper belt tension-resistant layer M4. It is composed of at least three layers with u. FIG. 2 shows an enlarged view of the structure of this belt reinforcing layer.

In addition, in order to protect against the impact load from the tread 1, a belt protection layer 6 is provided on the outside of the two-side belt with a tensile strength of 1i4u.
may be placed.

In the present invention, the following requirements are defined for the tire shown in FIG. 1 above.

(1) The cord arrangement angle of the belt reinforcing layer 4r is set to 45° to 75" with respect to the tire circumferential direction EE'.

The cord arrangement angle of the belt reinforcing layer 4r adjacent to the carcass layer 5 is set at a high angle (4
5° to 75°), the bending rigidity of the tread 1 in the tire meridional cross-section direction is increased and straight-line stability is improved.

This cord arrangement angle is preferably around 55°. This is because by setting the angle to around 55°, the arrangement angle of the carcass cords of the carcass layer 5 adjacent to the belt reinforcing layer 4r can be made substantially in the radial direction, thereby making it possible to particularly improve tire uniformity. It is.

(2) The cord arrangement angle of the belt tension strength IW4d and 4u was set at 15° to 30° with respect to the tire circumferential direction EE'.

This is because it becomes possible to maintain sufficient rigidity in the tire circumferential direction EE'.

(3) When using a bundled type steel cord in which each strand is twisted at the same pitch and in the same direction as a cord with belt tensile strength FW4d, 4u, and the lp direction of this steel cord is 71p, The belt tension-resistant layer has an S laminated structure, and the twist direction of the steel cord is 5tff.
In the case of I, the belt tension-resistant layer has a Z-layered structure.

Here, sl, zl? ! ! "Twisting" refers to the way the cord is twisted in a certain twisting direction, and is generally known.

That is, in the S twist, as shown in FIG. 3(A), the twisting direction a of the cord is from the upper left to the lower right, and the cord is twisted as if drawing a figure eight. In addition, in the Z twist, as shown in FIG. 3(B), the direction of the cord is from the upper right to the lower left, and it is twisted as if drawing a letter 7.

S laminated structure and Z laminated structure are belt tension-resistant layers 4d, 4
Refers to the laminated structure defined by the difference in the inclination direction of the cords of each layer when u is viewed from the outside of the tire (or may be viewed from within the tire (!1.+1)).

As shown in FIG. 4(A), in the S laminated structure, the cords 4dc of the lower belt tension-resistant layer 4d are inclined from the upper right to the lower left with respect to the tire circumferential direction EE', and the upper belt tension-resistant layer 4d is inclined from the upper right to the lower left. The cord 4uc of the layer 4u is inclined from the upper left to the lower right with respect to the tire circumferential direction EE'', and the cord 4dc and the cord 4uc form a figure 8. As shown in Figure 4 (B), the code 4dc of the lower belt tension resistance i4d is inclined from the upper left to the lower right with respect to the tire circumferential direction EE'', and the code 4uc of the upper belt tension resistance N4u is inclined in the tire circumferential direction EE''. These cords 4dc are inclined from upper right to lower left with respect to the direction EE.
The code 4uc has a structure that looks like 7 characters.

Conventionally, the steel cord of the belt tension-resistant layers 4d and 4u has a layer-twisted type of 3 (0, 20) + 6 (0
,38) ,3 + 9 +15 (0,22) 1
w etc. were used. This is because the l-direction of the inner layer and the lp-direction of the outer layer are opposite to each other, which prevents the cord from rotating due to untwisting when tension is applied to the cord, and improves the structure of the belt reinforcing layer. It is suppressing the inherent power that is caused by this. In contrast, in the present invention, a bundle-type steel cord in which each strand is twisted in the same twisting direction with the same pinch is used as a cord with a belt tension resistance of 1 m4d and 4U. For example, if there are 12 to 37 strands,
A bundled type steel cord in which all the wires are twisted in the same direction with the same pinch (e.g. 1 x 12
(0,32), 1 x27 (0,22), etc.). In the case of Tonenki type steel cord,
As shown in Figure 5, when tension is applied to the cord, the rotation of the cord due to its return is greater than that of the conventional steel cord mentioned above. This is intended to reduce the inherent force caused by the belt reinforcing layer.

That is, in the present invention, the belt tension-resistant layer 4d.

When the t-direction of the 4u steel cord is zt2, the belt tensile strength Ft4d, 4u has an S-laminated structure, and when the steel cord has an S-twist direction, the belt tensile strength Ft4d The tensions N4d and 4u are set to the Z laminated structure. This is because when a tensile force is applied in the tire circumferential direction BE', in the case of S lamination, torsional deformation occurs in the belt reinforcing layer as shown in FIG. 8(B), which is attached to the belt reinforcing layer. On the other hand, considering a single cord, when a tensile force is applied to it, in the case of slippage, Fig. 9 (A)
A torsional deformation occurs from the state shown in FIG. 9(B). This combination of the two results in further twisting of the belt reinforcing layer, which is undesirable. In the combination of SMH and Z twist, the torsion caused by the Z twist of the cord acts to cancel out the torsional deformation caused by the S lamination, resulting in a reduction in PS. Therefore, in the present invention, the S-laminated structure is combined with the Z-twist, or the Z-laminated structure is combined with the S-twist, so that the torsional deformations are mutually canceled out, thereby reducing plysteer.

〔Effect of the invention〕

As explained above, according to the present invention, the above (1) to (3)
), it is possible to reduce plysteer and sufficiently improve straight-line running performance.

The effects of the present invention will be specifically explained below using experimental examples.

EXPERIMENTAL EXAMPLE Trial tires of the following inventive tire, comparative tire, and conventional tire were manufactured with a tire size of IIR22,514PR, and plysteer (PS) was evaluated.

(81 Tire of the present invention.

It has the structure of the belt reinforcing layer and carcass layer shown in Fig. 1, and the carcass layer uses conventionally used steel cord 3 + 9 + 15 (0,175) 1W.

In each layer of the belt reinforcing layer, IX12 (0,32> The belt reinforcement layer 4r has an inner layer of steel cord of the same type as layer 1, with a pitch of 10 mm.

Outer layer is S-twist, single pinch 18mm, breaking strength 180
kg of 3 (0,20) +6 (0,38), and the belt protective layer 6 uses double-strand type high elongation steel cord 4 x 4 (0,22), respectively.

The arrangement angle of the steel cords of the 2N bias laminated parts 4d and 4u is 18° from the acute angle side with respect to the tire circumferential direction,
The number of inserted cords was 22.5 and 150 mm. Tire A had an S-laminated structure with the cords twisted in the 71st direction, and Tire B had the Z-laminated structure with the cords twisted in the S direction.

The cord arrangement angle of the belt reinforcing layer 4r and the belt protective layer 6 is 6 from the acute angle side with respect to the tire circumferential direction.
2° and 18°, and the cord arrangement direction of each layer at this time was the same direction as that of the adjacent two-layer bias laminated portions 4d and 4u, respectively. Further, the number of steel cords inserted is 22 for belt reinforcement N4r and 150 mm, and 19.5150 mm for belt protective layer 6.

(bl Comparative tire.

A tire C having an S laminated structure at 81 heat and a tire D having a Z laminated structure at z+ heat were made as prototypes, which had the same structure as the tire of the present invention except that the cord twist direction and the laminated structure were different.

(C1 conventional tire.

The 2-layer bias WI layer portions 4d and 4u are made of layer-twisted steel cord with an inner layer tS rib width of 10Illm.
+ 3 (0, 20) + 6 (0, 38) with an outer layer twist pinch of 18 mm and a breaking strength of 180 kg, and the number of cords inserted was 2 to make the strength equivalent to the tire of the present invention.
Nine cords were 150 mm long, and the cord arrangement angle was 18 degrees from the acute angle side with respect to the tire circumferential direction.

Tire A' with S laminated structure where the cord twist direction is Zl
, Tire B', which is made of Si and has a Z-laminated structure, Tire C', which is made of Si and has a Z-laminated structure, and Tire D, which is made of Si and has a Z-laminated structure, were prototyped.

The angle of cord arrangement, the direction of cord arrangement, the cords used, and the number of cords inserted between the belt reinforcing layer 4r and the belt protection layer 6 are the same as those of the present invention tire and the comparison tire.

About Flysteer' (PS): According to the uniformity test method for automobile tires (JASOC607), rim 8.25 x 22.5, air pressure 7.0 kg
ps was measured at /cJ and a load of 2450 kg. This result is the 6th page! Shown in U. In addition, in FIG. 6, ◯ indicates a bundle twist type, and . indicates an N twist type.

As is clear from FIG. 6, the two-layer piezo laminated portion 4d,
The tire of the present invention uses a bundled type steel cord for 4u, and has an S-laminated structure when the cord is twisted in Z-twist, and a Z-laminated structure when it is StS, has less plysteer than conventional tires. It turns out that it is. Therefore, the tire of the present invention can improve straight running performance.

On the other hand, a comparison tire with a two-layer bias bias part with bundle-stranded steel cords having an 81 S-laminate structure and a Z-twisted Z-laminate structure has a thicker plysteer than the conventional tire. .

In addition, in this experimental example, the cord arrangement direction of the belt protective layer 6 was made to be the same inclination direction with respect to the adjacent layer side of the 2N bias laminated parts 4d and 4u and the tire equator line, but in the present invention, the cord arrangement direction was There is no restriction, and they may be arranged in an intersecting manner. Further, in principle, the cords of the belt reinforcement layer 4r and the cords of the two-layer bias laminated portions 4d and 4u adjacent thereto are arranged in the same inclination direction with respect to the tire equator line, due to the nature of the belt reinforcement layer.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway radial cross-sectional perspective view of an example of a heavy-duty pneumatic radial tire of the present invention, FIG. 2 is an enlarged view of the belt reinforcing layer in FIG. 1, FIG. Figure (B) is an explanatory diagram showing the twisting direction of the cords in the belt reinforcing layer, Figure 4 (A) and Figure 4 (
B) is an explanatory diagram showing the bond layer structure of the belt reinforcing layer, FIG. 5 is a diagram showing the relationship between the straight return angle of the cord and the cord tensile force, and FIG. 6 is an explanatory diagram showing the structure of the belt reinforcing layer and plysteer. This is a relationship diagram. Figure 7 is a relationship diagram between tire running distance and lateral force, Figure 8 (A>, (B) is a model diagram showing the state of deformation of the belt reinforcing layer, and Figure 9 (A). (P,) is It is an explanatory diagram showing a state in which twisting deformation occurs in the cord. 1... Tread, 2... Sidewall portion, 3...
...Bead wire, 4r...Belt reinforcement layer, 4d...
- Lower belt tension-resistant layer, 4u... Upper belt tension-resistant layer, 5... Carcass layer, 6... Belt protective layer. Y-Gil 4/4 figure 4 Figure 9 (A) Valve Figure 9 (B) (Ts-23=

Claims (1)

[Claims] at least one carcass layer having carcass cords arranged substantially in the radial direction, a belt reinforcement layer provided outside the carcass layer, and at least two belt tension resistant layers biased outside the belt reinforcement layer; (1) The cord arrangement angle of the belt reinforcement layer is 45° with respect to the tire circumferential direction.
75 degrees, (2) the cord arrangement angle of the belt tension-resistant layer is 15 degrees to 30 degrees with respect to the tire circumferential direction, and (3) each strand is used as the cord of the belt tension-resistant layer. If a bundle-type steel cord is used, in which the steel cords are twisted at the same pitch and in the same direction, and the direction of the steel cord is Z-twist, the belt tension-resistant layer is
1. A pneumatic radial tire for heavy loads, characterized in that it has a laminated structure, and when the twisting direction of the steel cord is an S twist, the belt tension-resistant layer has a Z laminated structure.