JP2005014898A - Pneumatic radial tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic radial tire capable of increasing the durability of a belt by effectively preventing separation between belt layers and increasing cornering performance by increasing the rigidity of the belt. <P>SOLUTION: This tire 1 comprises, on the outer periphery of the crown part 3 of a carcass 2, the belt 7 having three layers of belt layers 4, 5, and 6. The belt 7 comprises a first belt layer 4 and a second belt layer 5 stacked adjacent to each other in an arrangement relation in which reinforcement elements 8a and 8b extend aslant in the same direction relative to a tire equatorial plane E and a third belt layer 6 stacked adjacent to the second belt layer 5 in an arrangement relation in which a reinforcement element 8c crosses the reinforcement element 8b on both sides of the tire equatorial plane E. The second belt layer 5 is disposed with its center aligned with the tire equatorial plane E, and a width W<SB>2</SB>is narrower than the width W<SB>3</SB>of the third belt layer. Each of an angle θ<SB>1</SB>formed by the reinforcement element 8a and the tire equatorial plane E and an angle θ<SB>2</SB>formed by the reinforcement element 8b and the tire equatorial plane E is smaller than an angle θ<SB>3</SB>formed by the reinforcement element 8c and the tire equatorial plane E. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to pneumatic radial tires, and more particularly to heavy duty tires used for large vehicles such as large trucks and buses in addition to small trucks, and in particular, improvement in both durability and rigidity of the belts of such tires. Plan.

  In addition to small trucks, heavy duty pneumatic tires used for large vehicles such as large trucks and buses are used under the action of high internal pressure and heavy load. In order to enhance the reinforcing effect, such belt layers are generally laminated in order so that the reinforcing elements cross each other to form a cross belt. However, between the belt layers constituting such a cross belt, the reinforcing elements are arranged so as to intersect across the tire equatorial plane, so that when the tire rolls, a large shearing force acts between the belt layers, In particular, there is a problem in that separation is likely to occur between the reinforcing element and the rubber covering it at both ends of the belt layer where stress tends to concentrate.

  As pneumatic tires that prevent the occurrence of such separation, Patent Documents 1 and 2 disclose, as shown in FIG. 6A, adjacent belts that constitute a cross belt 101 in which reinforcing elements intersect each other across the tire equatorial plane. The wedge rubber 103 having a wedge-shaped cross section is disposed between both end portions of the layers 102a and 102b, and the tire radial direction reinforcing element interval between the adjacent belt layers 102a and 102b is widened at the end portions, thereby fatigue around the belt end portions. It describes what prevents crack damage and prevents the occurrence of separation. However, in such a tire, the distance between the reinforcing elements in the tire radial direction of the adjacent belt layers 102a and 102b at the position of the inner end 104 in the tire width direction of the wedge rubber 103 is narrower than that at other positions. As a result, separation may occur between the adjacent belt layers 102a and 102b.

  As a means for avoiding the concentration of the interlaminar shear force, Patent Document 3 discloses a tire radial direction reinforcing element interval between adjacent belt layers 102a and 102b constituting the cross belt 101 as shown in FIG. In this method, not only both ends of the cross belt 101 but also a method of uniformly widening the entire width direction is described. However, in this method, the thickness of the entire belt increases, and the weight of the tire increases. There is a problem that the cornering property is insufficient as a result of the fact that the reinforcing effect due to the crossing of the reinforcing elements of the constituting belt cannot be sufficiently obtained and the belt rigidity is lowered.

  In order to solve these problems, Patent Document 4 discloses a two-layer, preferably wide belt layer, in which the metal cords are inclined in directions opposite to each other and at a small angle of 5 to 40 ° with respect to the tire equatorial plane. In the meantime, there is described a heavy duty radial tire comprising a belt in which a metal cord is inclined at a large angle of 40 to 85 ° with respect to the tire equatorial plane, and preferably a narrow belt layer. According to this description, a belt having a so-called triangle structure can be formed by each metal cord of the belt layer, and the tread portion of the tire can be effectively reinforced, and the cut end of the metal cord can be prevented from being sharp. Thus, separation from the belt end can be suppressed. However, in such a tire, since the metal cord angle of the narrow belt layer is large, the circumferential rigidity tends to be insufficient, and there is still a problem that sufficient belt rigidity cannot be obtained.

JP-A-9-263108 Japanese Patent Laid-Open No. 11-32224 JP-A-11-235904 JP-A-8-40012

  Accordingly, an object of the present invention is to optimize the width of the belt layer constituting the belt and the extending direction of the reinforcing element, thereby effectively preventing the separation between the belt layers and improving the durability of the belt. Another object of the present invention is to provide a pneumatic radial tire having improved cornering by increasing the rigidity of the belt.

  In order to achieve the above object, the present invention provides a belt comprising at least three belt layers in which a reinforcing element is covered with rubber on the outer periphery of a crown portion of a carcass extending in a toroidal shape between a pair of bead portions. In the pneumatic radial tire, the belt includes a first belt layer and a second belt layer that are laminated adjacent to each other in the tire radial direction so that the reinforcing elements extend in the same direction with respect to the tire equatorial plane. And the reinforcing element constituting the second belt layer and the third belt layer laminated adjacent to each other in the tire radial direction in an arrangement relationship in which the reinforcing element intersects the tire equatorial plane. The second belt layer is disposed around the tire equator plane, the width thereof is narrower than the width of the third belt layer, and the reinforcing element constituting the first belt layer and the tire equator are measured from an acute angle side. The angle formed by the surface A pneumatic radial tire characterized in that each angle formed by the reinforcing element constituting the second belt layer and the tire equatorial plane is smaller than the angle formed by the reinforcing element constituting the third belt layer and the tire equatorial plane. is there.

  As used herein, “disposed around the tire equator plane” means that the both ends of the belt layer are disposed on the left and right sides of the tire equator plane in the tire width direction cross section, The present invention is not limited to the case where the center position in the width direction of the belt layer coincides with the tire equator plane, and includes the case where the center position in the width direction is arranged to be shifted from the tire equator plane.

  In order to positively suppress the diameter growth during traveling, it is preferable that the first belt layer is located on the outer side in the tire radial direction of the second belt layer.

  Furthermore, when improving the damage resistance, the first belt layer is preferably located on the inner side in the tire radial direction of the second belt layer.

  Furthermore, the width of the second belt layer is preferably 70% or less of the width of the first belt layer, particularly 30 to 60% of the width of the first belt layer.

  In addition, the widths of the first belt layer and the third belt layer are preferably narrower at the outer side in the tire radial direction.

  In addition, it is preferable that the reinforcing element constituting the first belt layer and the reinforcing element constituting the second belt layer extend while being inclined at substantially the same angle with respect to the tire equatorial plane. Here, “substantially the same angle” means that the difference in angle is within ± 2 °.

  In addition, it is preferable that the spacing between the reinforcing elements measured in the tire radial direction is substantially constant over the entire width of the narrower belt layer of the first belt layer and the third belt layer. More preferably, a rubber sheet having a substantially uniform thickness is disposed between the first belt layer and the third belt layer on the outer side in the tire width direction of the second belt layer. Here, “the spacing between the reinforcing elements is substantially constant” means that the difference between the maximum value and the minimum value of the reinforcing element spacing is within 1 mm.

  According to the present invention, by optimizing the width of the belt layer constituting the belt and the extending direction of the reinforcing element, the separation between the belt layers is effectively prevented and the durability of the belt is improved. Further, it is possible to provide a pneumatic radial tire in which the rigidity of the belt is increased and the cornering property is improved.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of an essential part of a typical pneumatic radial tire (hereinafter referred to as “tire”) according to the present invention, and FIG. 2 is a partially broken plan view of a belt constituting the tire shown in FIG. is there.

  A tire 1 shown in FIG. 1 has at least three belt layers formed by rubber-covering a reinforcing element on the outer periphery of a crown portion 3 of a carcass 2 extending in a toroidal shape between a pair of bead portions (not shown). It comprises a belt 7 consisting of belt layers 4, 5, 6 of layers.

The main feature of the structure of the present invention is that the belt 7 has a reinforcing element 8a, 8b extending in the same direction with respect to the tire equatorial plane E. For example, in FIG. When the angle between the tire equatorial plane E and the reinforcing elements 8a and 8b is θ ₁ and θ _{2 as} measured, θ ₁ and θ ₂ are located on the same side with respect to the tire equatorial plane E, and on the right side in FIG. The first belt layer 4 and the second belt layer 5 stacked adjacent to each other in the tire radial direction, the reinforcing element 8c and the reinforcing element 8b constituting the second belt layer 5 and the tire equator. The second belt layer 5 includes a third belt layer 6 that is disposed adjacent to each other across the surface E and that is laminated adjacent to the tire radial direction. The width W ₂ of the third belt layer 6 is arranged around E. _The angle θ ₁ formed between the reinforcing element 8a constituting the first belt layer 4 and the tire equatorial plane E, and the reinforcing element 8b constituting the second belt layer 5 and the tire equatorial plane E, which are narrower than ₃ and measured from the acute angle side. each angle theta ₂ of is to be smaller than the angle theta ₃ reinforcement elements 8c and the tire equatorial plane E which constitute the third belt layer 6.

Hereinafter, how the present invention has adopted the above configuration will be described together with the operation.
As described above, in a tire provided with a cross belt, when the tire rolls, a shearing force acts between adjacent belt layers, and particularly at both ends of the belt layer where stress tends to concentrate, the reinforcing element and the There was a problem that separation was easily generated between the rubber to be coated. In order to solve this, it is known that a wedge rubber is disposed between the cross belts. In this case, the separation at the belt end is suppressed by the provision of the wedge rubber. There is a possibility that stress concentrates at a position where the distance between the reinforcing elements in the tire radial direction is small, resulting in a new separation between belts. In order to avoid this stress concentration, the distance between the belt layers constituting the cross belt may be widened not only at both ends but also in the entire width direction of the tire. As a result of the fact that the reinforcing effect due to the crossing of the two members cannot be obtained and the belt rigidity is lowered, the cornering property may be insufficient.

  Therefore, when the inventor studied to achieve both durability and cornering properties, the reinforcement element is located between the first belt layer and the third belt layer in a disposition relationship in which the reinforcing elements intersect with each other across the tire equatorial plane E. Further, if a second belt layer that is narrower than these two belt layers and the reinforcing element intersects with the reinforcing element of the third belt layer across the tire equatorial plane is disposed, the first belt layer and the first belt layer Since the reinforcing element interval can be widened at the end position with respect to the three belt layers, the separation at the end position of the belt can be effectively suppressed, and the reinforcing element of the second belt layer is provided at the center position of the width of the belt. It has been found that a cross belt having a high reinforcing effect can be constituted by the second belt layer and the third belt layer by extending in the same direction as the reinforcing element of the belt layer. However, if the angles formed by the reinforcing elements of the first and second belt layers and the third belt layer are the same across the tire equatorial plane, the reinforcing elements at the end positions of the first and third belt layers However, it was not possible to reinforce the portion where the rigidity was lowered by widening the interval. Therefore, the inventor further studied, and if the extending direction of the reinforcing elements of the first belt layer and the second belt layer is made smaller than that of the third belt layer, that is, closer to the tire equator plane, It has been found that the belt tightening effect by the first belt layer and the second belt layer is enhanced, and as a result of the increase in the tire circumferential rigidity, the belt rigidity can be improved more than the belt end position, and the present invention is completed. It came to.

  3A to 3D are diagrams schematically showing the arrangement state of the belt layer 7. In order to suppress the diameter growth during traveling, it is preferable that the first belt layer 4 is located on the outer side in the tire radial direction of the second belt layer 5 as shown in FIG. This is because the entire tread portion can be protected.

  Alternatively, in order to improve the damage resistance, it is preferable that the first belt layer 4 is located on the inner side in the tire radial direction of the second belt layer 5 as shown in FIG.

The width W ₂ of the second belt layer 5 is preferably 70% or less of the width W ₁ of the first belt layer 4. Since the second belt layer 5 is not disposed between the first belt layer 4 and the third belt layer 6, a region where the reinforcing element interval between the first belt layer 4 and the third belt layer 6 is wide can be sufficiently secured. This is because the separation generated at both ends of the belt layer 7 can be more effectively suppressed. In this case, the width W ₂ of the second belt layer 5 is more preferably 30 to 60% of the width W ₁ of the first belt layer 4. It is because the width W ₂ of the second belt layer 5 in the case of less than 30% of the width W1 of the first belt layer 4 may become impossible to secure a sufficient circumferential rigidity, the weight in the case of more than 60% This is because there is a possibility that an increase in the number of times becomes a problem.

Furthermore, as shown in FIGS. 3C and 3D, the widths W ₁ and W ₃ of the first belt layer 4 and the third belt layer 6 are preferably narrower on the outer side in the tire radial direction. . This is because, by narrowing the width of the belt layer located on the outer side in the tire radial direction, it is possible to prevent air from being mixed during tire manufacture.

In addition, the reinforcing element 8a constituting the first belt layer 4 and the reinforcing element 8b constituting the second belt layer 5 extend with an inclination at substantially the same angle with respect to the tire equatorial plane E, that is, θ _1. = Θ ₂ ± 2 ° is preferable. When the extending directions of the reinforcing elements 8a and 8b of the first belt layer 4 and the second belt layer 5 are substantially different, the difference in tension between the first belt layer 4 and the second belt layer 5 increases, and these belt layers This is because there is a possibility that sufficient belt rigidity cannot be ensured as a result of the generation of a shearing force between the two. Further, the angle θ ₂ formed by the reinforcing element 8b constituting the second belt layer 5 and the tire equatorial plane E is 5 ° than the angle θ ₃ formed by the reinforcing element 8c constituting the third belt layer 6 and the tire equatorial plane E. It is preferable to make it smaller. This is because the circumferential rigidity of the belt can be improved by making the angles of the first and second belt layers closer to the equator plane E. In particular, the angles θ ₁ and θ ₂ are preferably in the range of 10 to 20 °, and the angle θ ₃ is preferably in the range of 20 to 40 °.

Reference is now made to FIG. Of the first belt layer 4 and the third belt layer 6, the narrower belt layer, in FIG. 4, the spacing between the reinforcing elements measured in the tire radial direction over the entire width direction of the third belt layer 6 is substantially constant. That is, it is preferable that the difference Δd between the maximum value d _max and the minimum value d _min of the reinforcing element interval is within 1 mm. By making the spacing between the reinforcing elements substantially constant in this way, it is possible to prevent the occurrence of a location where the interlaminar shear force is concentrated between the first belt layer 4 and the third belt layer 6. is there. In this case, as shown in FIG. 5, a rubber having a substantially uniform thickness between the first belt layer 4 and the third belt layer 6 on the outer side in the tire width direction of the second belt layer 5. More preferably, the sheet 9 is provided. This is because the arrangement of the rubber sheet 9 makes it possible to easily make the reinforcing element interval between the first belt layer 4 and the third belt layer 6 constant. Further, from the viewpoint of enhancing the effect of reducing / reducing the interlayer shear force, the value of the 100% elongation modulus of the rubber sheet 9 is 50 as the value of the 100% elongation modulus of the covering rubber of the first belt layer 4 and the third belt layer 6. It is preferable to be in the range of ˜150%.

  In addition, the place mentioned above only showed a part of embodiment of this invention, and can add a various change in a claim.

  Next, a pneumatic radial tire according to the present invention was prototyped and performance evaluation was performed, which will be described below.

The tires of Examples 1 to 4 are radial tires for trucks and buses having a tire size of 11 / 70R22.5, and the carcass has a steel cord (3 + 9 + 15 + 0.165, cord diameter of 1.00 mm) driven in at 30/50 mm. 3 is a belt layer formed of a single ply coated with a rubber and having a belt coated with a steel cord (1 + 6 × 0.34, cord diameter 1.06 mm) with a number of 24/50 mm. (D) Three layers are stacked as shown in (Examples 1 and 2), FIG. 3 (c) (Example 3) or FIG. 8 (Example 4), and the tires of Examples 1 to 3 are not shown. However, on the outer side in the tire width direction of the second belt layer, a rubber sheet having a substantially uniform thickness is disposed between the first belt layer and the third belt layer. , First belt layer and third belt as shown It will be disposed a wedge rubber between the coat layer, having specifications shown in Table 1. In the column of Table 1 theta ₁ through? _3, "R" and "L", the inclination angle of the reinforcing element constituting the belt layer with respect to the tire equatorial plane, each means upper right and left upward as viewed in FIG. 2 To do.

  For comparison, the tire size and carcass are the same as those of the tires of Examples 1 to 4, have the specifications shown in Table 1, and the same belt layer as that of Examples 1 to 4 is shown in FIG. The tire (Comparative Example 1) in which the wedge rubber is arranged between the second belt layer and the third belt layer, and the same belt layer as in Examples 1 to 4 are arranged as shown in FIG. Although not shown in the drawings, a tire (Comparative Example 2) in which a rubber sheet having substantially the same width as the third belt layer is disposed between the second belt layer and the third belt layer, the same belt layer as in Examples 1 to 4. Are arranged as shown in FIG. 3D and are not shown, but the thickness is substantially uniform between the first belt layer and the third belt layer outside the second belt layer in the tire width direction. However, the relationship between the extension angles of the reinforcing elements of the second belt layer and the third belt layer is outside the scope of the present invention. The prototype also together for ya (Comparative Example 3).

(Belt durability)
Belt durability is determined by attaching each test tire to a rim of size 8.25 × 22.5 to form a tire wheel, applying an air pressure of 800 kPa (relative pressure) to the tire wheel, speed 60 km / h, tire load load After running for 48 hours on a drum test machine under a constant load of 15 kN with a side force of 27 kN, disassemble the tire and measure the tire circumferential length of the separation generated at the belt end. The average value was evaluated.

(Cornering)
The cornering property is that each test tire is attached to a rim of size 8.25 × 22.5 to form a tire wheel, and an air pressure of 800 kPa (relative pressure) is applied to the tire wheel, and a tire load is measured using a flat belt type testing machine. The lateral force applied to the tire was measured and evaluated under the conditions where the load was 27 kN, the speed was 60 km / h, and the deviation between the traveling direction of the tire and the rotating surface of the testing machine was 1 degree.

  In addition, all the evaluation results in Table 1 are shown as index ratios when the evaluation result of Comparative Example 1 is set to 100, and the lower the numerical value, the better the belt durability, and no separation occurs. Is represented by zero (0), and the cornering property is better as the value is larger.

  From the results shown in Table 1, it can be seen that the tires of Examples 1 to 4 are excellent in belt durability while having the same or better cornering performance as compared with the tire of Comparative Example 1. In addition, the tires of Examples 1 to 3 are all excellent in cornering properties while having the same belt durability as the tires of Comparative Examples 2 and 3, and the tire of Example 4 is Comparative Example 2. As compared with the tires No. 3 and No. 3, the belt durability is slightly inferior, but the cornering performance is excellent and it can be seen that the tire is excellent overall.

  According to the present invention, by optimizing the width of the belt layer constituting the belt and the extending direction of the reinforcing element, separation between the belt layers is effectively prevented, and the durability of the belt is improved. It has become possible to provide a pneumatic radial tire with improved cornering by improving the rigidity of the tire.

1 is a cross-sectional view of a main part of a typical pneumatic radial tire according to the present invention. It is a partially broken top view of the belt which comprises the tire shown in FIG. (A)-(d) is a figure which shows typically the arrangement | positioning state of the belt layer of the various tires according to this invention. 1 is a partial cross-sectional view of a belt constituting a tire according to the present invention. 1 is a partial cross-sectional view of a belt constituting a tire according to the present invention. It is principal part sectional drawing of the conventional tire. (A) And (b) is a figure which shows typically the arrangement | positioning state of the belt layer of the tire of the prior art examples 1 and 2, respectively. It is a figure which shows typically the arrangement | positioning state of the belt layer of the tire of Example 4. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tire 2 Carcass 3 Crown part 4 1st belt layer 5 2nd belt layer 6 3rd belt layer 7 Belt 8a, 8b, 8c Reinforcing element 9 Rubber sheet

Claims (9)

In a pneumatic radial tire including a belt composed of at least three belt layers formed by rubber-covering a reinforcing element on the outer periphery of a crown portion of a carcass extending in a toroidal shape between a pair of bead portions,
The belt has a disposition relationship in which the reinforcing element extends in the same direction with respect to the tire equator plane,
The first and second belt layers stacked adjacent to each other in the tire radial direction, and the second belt in a disposition relationship in which the reinforcing elements intersect with each other across the tire equatorial plane and the reinforcing elements constituting the second belt layer. A layer and a third belt layer laminated adjacent to each other in the tire radial direction,
The second belt layer is disposed around the tire equatorial plane, and its width is narrower than the width of the third belt layer,
Measured from the acute angle side, the angle formed between the reinforcing element constituting the first belt layer and the tire equatorial plane and the angle formed between the reinforcing element constituting the second belt layer and the tire equatorial plane constitute the third belt layer. A pneumatic radial tire characterized in that the pneumatic radial tire is smaller than an angle formed by the reinforcing element and the tire equatorial plane.   The pneumatic radial tire according to claim 1, wherein the first belt layer is located on the outer side in the tire radial direction of the second belt layer.   The pneumatic radial tire according to claim 1, wherein the first belt layer is located on the inner side in the tire radial direction of the second belt layer.   The pneumatic radial tire according to claim 2 or 3, wherein the width of the second belt layer is 70% or less of the width of the first belt layer.   The pneumatic radial tire according to claim 4, wherein the width of the second belt layer is 30 to 60% of the width of the first belt layer.   The pneumatic radial tire according to any one of claims 1 to 5, wherein the widths of the first belt layer and the third belt layer are narrower on the outer side in the tire radial direction.   The reinforcing element that constitutes the first belt layer and the reinforcing element that constitutes the second belt layer extend with an inclination at substantially the same angle with respect to the tire equatorial plane. Pneumatic radial tire.   The reinforcing element interval measured in the tire radial direction over the entire width of the narrower belt layer of the first belt layer and the third belt layer is substantially constant. Pneumatic radial tires.   The pneumatic radial tire according to claim 8, wherein a rubber sheet having a substantially uniform thickness is disposed between the first belt layer and the third belt layer on the outer side in the tire width direction of the second belt layer.

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