JPH11278014A - Radial tire containing air for heavy load - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve belt-end-separation resistance and abrasion resistance performances, by respectively specifying cord angles and cross section widths of a reinforcement belt layer and a cross belt layer constituting a belt. SOLUTION: A belt, which covers substantially non-expanding metal cord at a circumferentially relatively small cord angel, is constituted of a reinforcement belt layer 2 whose cross section width is 25-60% of a tread width, and a cross belt layer 3 which is layered so that cords extend mutually in parallel in a layer, the cords cross each other between adjacent layers, and circumferential cord angle is 10 or 40 degrees and is larger than the cord angle of the reinforcement belt layer 2, and has a cross section width wider than that of the reinforcement belt layer 2. Assuming that a hypothetical falling distance of a hypothetical extension line of crown radius R forming the outer periphery inside of the tire axis direction at the end of a tread 4 is H, and an actual falling distance of the outer periphery outside of the tire axis direction is h, the relationship 0.1 H<h<H is established.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire, and more particularly, to a bead core provided on a pair of right and left bead portions and extending from one bead portion to the other bead portion. A carcass ply composed of a radial cord layer wound around the bead portion and a belt and a tread arranged radially outside the crown portion of the carcass ply, and mainly used for traveling on rough terrain. The present invention relates to a pneumatic radial tire for heavy loads.

[0002]

2. Description of the Related Art In general, heavy-duty pneumatic tires such as pneumatic tires for construction vehicles are often used on rough roads or rough terrain where rocks and crushed stones are scattered. Failure easily occurs. In order to suppress or prevent the separation failure at the end of the belt, a narrow belt layer having a small cord angle with respect to the circumferential direction is disposed inside the conventional belt, that is, between the belt and the carcass, and the internal pressure is applied to the tire. It has been proposed to increase the cord angle with respect to the circumferential direction of the conventional belt by maintaining the cross-section of the tire in a desired shape by suppressing the tension when the tire is filled, suppressing the radial growth.

[0003]

However, when a narrow belt layer in which the cord arrangement angle with respect to the circumferential direction is reduced as described above is arranged between the belt and the carcass,
The rigidity of the central portion of the tire is significantly increased, the rigidity of both shoulder regions is relatively reduced, and the deformation of the shoulder portion at the time of load rotation increases, and the contact shape becomes uneven. In other words, since the contact length and contact pressure of both shoulder regions increase, the wear resistance of the tire decreases, and
Heat generation in both shoulder regions is increased, and a heat separation failure of the belt is likely to occur.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned disadvantages of the conventional tire, and to provide a heavy load pneumatic radial tire for traveling on rough terrain, which is excellent in belt end separation performance and wear resistance. It is to provide.

[0005]

In order to achieve the above object, a tire according to the present invention comprises a bead core provided on a pair of left and right bead portions, and a tire extending from one bead portion to the other bead portion. Pneumatically provided with a carcass ply composed of a radial cord layer wound around the bead core and moored at a bead portion, and a belt and a tread disposed radially outside a crown portion of the carcass ply in a radial direction. In a radial tire, when the tire is mounted on a regular rim and filled with a regular internal pressure, (1) the belt forms a substantially inextensible metal cord at a relatively small cord angle α with respect to the circumferential direction. At least one reinforcing belt layer having a cross-sectional width of 25 to 60% of the tread width and embedded in the covering rubber, and a substantially non-stretchable metal cord, wherein the cords are alternated within the layer. And the cords are laminated so that the cord angle β with respect to the circumferential direction is 10 to 40 degrees and larger than the cord angle α of the reinforcing belt layer so that the cords intersect each other between adjacent layers. Comprises at least two crossed belt layers wider than the reinforcing belt layer, and (2) passing the carcass belt through an end of the reinforcing belt layer.
Assuming that a point at which a perpendicular line formed on the ply intersects with the outer contour of the tread is P, an outer contour in the tire axial direction outside of the intersection P forms an outer contour in a tire axial direction inner side of the intersection P. (3) A virtual drop from the tire center height of a virtual extension line of a crown radius R forming an outer contour in the tire axial direction at the end of the tread, which is located radially inward from the virtual extension line. The height is defined as H, and the virtual fall height H of the actual outer contour on the outer side in the tire axial direction.
A heavy-duty pneumatic radial tire mainly used for running on rough terrain, where h is the height of fall from the tire.

In order to achieve the above object, in the tire according to the present invention, the cord angle α of the reinforcing belt layer with respect to the circumferential direction is greater than 0 ° and 10 ° or less, and the reinforcing belt layer is formed of the carcass ply. And the reinforcing belt layer comprises at least two layers in which the cords extend parallel to each other within the layers and the cords intersect each other between adjacent layers. It is preferable to be formed from a rubber-coated cord layer.

In order to achieve the above object, in the tire according to the present invention, the cord of the reinforcing belt layer is not a normal tire cord extending linearly in the longitudinal direction of the cord, but is wavy in the longitudinal direction of the cord. The reinforcing belt layer may be formed by extending a corrugated cord and covering the rubber so that the cord angle α with respect to the circumferential direction becomes substantially 0 degrees. As used herein, the term "corrugated cord" refers to a cord having a small amplitude in the longitudinal direction of the cord and extending in a sawtooth, zigzag, or sine curve shape, and is a normal tire extending linearly in the longitudinal direction of the cord.・ Used in comparison with a code.

[0008] Pneumatic tires are available in JATMA (Japan), TRA (US) and ET, depending on their size.
It is used by being mounted on a standard rim specified in a standard issued by RTO (Europe) or the like, and this standard rim is usually called a regular rim. In this specification, the "regular rim" refers to a standard rim in an application size specified in the 1997 edition of YEAR BOOK issued by the United States Tire and Rim Association TRA. Similarly, "regular load" refers to the 1999 tire and rim association TRA issued by the TRA.
Applicable size specified in the 7-year version of YEAR BOOK
The "normal internal pressure" refers to the maximum load at the ply rating and the air pressure corresponding to the maximum load at the applicable size ply rating specified in the 1997 edition of YEAR BOOK issued by the American Tire and Rim Association TRA. In the present specification, the “contact width” or “tread contact width” refers to a tread contact width when the tire is mounted on a regular rim, filled with a regular internal pressure, and statically loaded with a regular load. As used herein, "substantially non-extensible metal cord" refers to a metal cord having an elongation at break (Eb) of 1 to 3%, preferably a steel cord, and "a substantially extensible metal cord". The "cord" refers to a metal cord, preferably a steel cord, having an elongation at break (Eb) of 4 to 7%, and the "cross-sectional width of the belt layer" refers to the width of the belt layer in a cross section including the rotation axis of the tire. Point to.

As described above, in the case of a heavy-duty pneumatic radial tire mainly for traveling on rough terrain, in order to suppress or prevent separation failure at the belt end, the inside of a conventional cross belt, that is, the space between the belt and the carcass is used. In addition, a narrow reinforcing belt layer having a small cord angle with respect to the circumferential direction is disposed, and the tension when the tire is filled with the internal pressure is borne by the reinforcing belt layer to maintain the cross section of the tire in a desired shape to maintain a desired diameter. It has been proposed to suppress the growth and increase the cord angle with respect to the circumferential direction of the conventional cross belt. However, when the narrow belt layer in which the arrangement angle of the cords with respect to the circumferential direction is reduced as described above is disposed between the belt and the carcass, the rigidity of the central portion of the tire is significantly increased, and the relative positions of the two shoulder regions are relatively increased. The rigidity is reduced, the deformation of the shoulder portion during load rotation is increased, and the contact shape is not uniform. In other words, since the contact length and contact pressure of both shoulder regions increase, the abrasion resistance of the tire decreases, and furthermore, the heat generation of both shoulder regions increases, which tends to cause a heat separation failure of the belt. there were. The tire of the present invention is configured as described above. In particular, (1) the belt has a substantially inextensible metal cord embedded in the covering rubber at a relatively small cord angle α with respect to the circumferential direction. At least one reinforcing belt layer having a cross-sectional width of 25 to 60% of the tread width, and a substantially inextensible metal cord, wherein the cords extend parallel to one another in the layers and between adjacent layers. Are so laminated that the cord angle β with respect to the circumferential direction is 10 to 40 degrees and the cord angle α of the reinforcing belt layer is larger than the cord angle α of the reinforcing belt layer, and the sectional width is at least wider than the reinforcing belt layer. (2) passing the carcass through the reinforcing belt layer end.
Assuming that a point at which a perpendicular line formed on the ply intersects with the outer contour of the tread is P, an outer contour in the tire axial direction outside of the intersection P forms an outer contour in a tire axial direction inner side of the intersection P. (3) A virtual drop from the tire center height of a virtual extension line of a crown radius R forming an outer contour in the tire axial direction at the end of the tread, which is located radially inward from the virtual extension line. The height is defined as H, and the virtual fall height H of the actual outer contour on the outer side in the tire axial direction.
Assuming that the falling height from the height is h, since 0.1H <h <H, a uniform contact shape can be obtained. With this arrangement, the narrow reinforcing belt layer having a small cord angle with respect to the circumferential direction is arranged, and the tension when the tire is filled with the internal pressure is applied to the reinforcing belt layer, and the cross section of the tire is maintained in a desired shape. The disadvantages of tires with reduced diameter growth, such as reduced wear resistance of the tires, and increased heat generation in both shoulder regions, which easily causes a heat separation failure of the belt, are eliminated. It became so.

In the pneumatic radial tire according to the present invention, as described above, the height of the virtual center of the crown radius R forming the outer contour in the tire axial direction at the end of the tread is the height of the tire center portion. The virtual fall height from
When the drop height of the actual outer contour outside the tire axial direction from the virtual drop height H is h, 0.1H <h <H, but the drop height h is 10% of the virtual drop height H. In the following cases, a uniform grounding shape cannot be obtained, and the effects of the present invention as described above cannot be obtained. On the other hand, when the drop height h is 100% or more of the hypothetical drop height H, the contact pressure in the tread center area increases, causing center wear, and further, the shoulder portion is greatly extended in the circumferential direction at the time of load, and crossing occurs. A disadvantage occurs that separation failure is likely to occur at both ends of the belt layer.

In the tire according to the present invention, the cord angle α of the reinforcing belt layer with respect to the circumferential direction is greater than 0 ° and not more than 10 °, so that the tension when the tire is filled with the internal pressure is applied to the reinforcing belt layer. This is effective for maintaining the cross section of the tire in a desired shape and suppressing the radial growth. In addition, it is effective that the reinforcing belt layer is disposed between the carcass ply and the cross belt layer in order to effectively prevent the occurrence of separation failure. When the reinforcing belt layer is formed of at least two rubber-coated cord layers, in which the cords extend parallel to each other in the layers and the cords intersect each other between adjacent layers, the cross section of the tire is desired. It is effective to maintain the shape of and suppress the diameter growth. In the tire according to the present invention, the cord of the reinforcing belt layer is formed of a wavy cord that extends in a wavy manner at a small pitch in the longitudinal direction of the cord, instead of a normal tire cord that extends linearly in the longitudinal direction of the cord. The reinforcing belt layer may be formed by coating the rubber so that the cord angle α becomes substantially 0 degrees. In the tire according to the present invention, a protective belt layer substantially composed of an extensible metal cord is disposed radially outside the belt composed of the reinforcing belt layer and the cross belt layer, so that the reinforcing belt layer and the cross belt layer are cut. It is preferable to effectively suppress or prevent separation failure. In this case, it is preferable that the protective belt layer disposed radially outward has a cross-sectional width larger than the cross-sectional width of the inner belt layer so as to cover both ends of the inner belt layer.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, pneumatic radial tires for construction vehicles according to Examples 1 to 4 according to the present invention and pneumatic radial tires for construction vehicles according to comparative examples will be described below.
The tire will be described. All tire sizes are 40.00R57.

FIG. 1 is a schematic cross-sectional view of an upper left half of a pneumatic radial tire for a construction vehicle according to a first embodiment of the present invention. The tire according to the first embodiment shown in FIG. 1 has a bead core (not shown) provided on a pair of right and left beads, extends from one bead to the other bead, and is wound around the bead core. Pneumatically provided for a construction vehicle, comprising a carcass ply 1 made of a radial cord layer and moored to a bead portion, and belts 2 and 3 and a tread 4 arranged radially outside a crown portion of the carcass ply. It is a radial tire. Belt is reinforced belt layer 2
And a cross belt layer 3, and a reinforcing belt layer 2 is disposed between the carcass ply 1 and the cross belt layer 3. A protective belt layer 5 is further disposed radially outside the cross belt layer 3. The reinforced belt layer 2 comprises substantially inextensible metal cords having an elongation at break (Eb) of 2%, such that the cords run parallel to each other within the layers and intersect each other between adjacent layers. The cord angle α1 with respect to the circumferential direction of the inner reinforcing belt layer 21 is stacked at an angle of 8 degrees to the right, and the cord angle α2 with respect to the circumferential direction of the outer reinforcing belt layer 22 is stacked at an angle of 7 degrees to the left. Since the cross-sectional widths of the reinforcing belt layers 21 and 22 are 440 mm and 400 mm, and the tread width TW is 930 mm, they are 47% and 43% of the tread width TW, respectively. The crossed belt layer 3 comprises substantially inextensible metal cords having an elongation at break (Eb) of 2%, such that the cords run parallel to one another in the layers and intersect each other between adjacent layers.
Cord angle β1 with respect to the circumferential direction of the inner cross belt layer 31
Are stacked at an angle of 30 degrees rising to the left and a cord angle β2 with respect to the circumferential direction of the outer cross belt layer 32 of 20 degrees rising to the right. The cord angles β (β1, β
2) is a value larger than the code angle α (α1, α2). The protective belt layer 5 is formed as a single layer in which a substantially extensible metal cord having an elongation at break (Eb) of 6% is embedded in a covering rubber. Tire the regular rim (29.0
0 / 6.0) and filled with a normal internal pressure (700 kPa), the point at which a perpendicular line passing through the end of the reinforcing belt layer 2 and standing on the carcass ply 1 intersects the outer contour of the tread 4 is denoted by P. Then, the outer contour in the tire axial direction outside the intersection P is located radially inward from the virtual extension line of the crown radius R forming the outer contour in the tire axial direction from the intersection P, and the tire shaft at the end of the tread 4 The virtual fall height from the center of the tire center of the virtual extension line of the crown radius R forming the outer contour in the direction is defined as H, and the actual outer contour in the tire axial direction outside falls from the virtual fall height H. Assuming that the height is h, H = 55 mm and h = 39 mm, and the drop height h is 71% of the virtual drop height H.

The pneumatic radial for construction vehicles of the second embodiment
In the tire, the reinforcing belt layer 2 is formed of a single metal cord layer having a cord angle α with respect to the circumferential direction of 9 degrees, which rises to the left,
Its cross-sectional width is 400 mm, and the tread width TW is 43 mm.
%, The reinforcing belt layer 2 is arranged radially outside the cross belt layer 3, and the drop height h
Is 22 mm, which is almost the same as the tire of Example 1 except that it is 40% of the virtual fall height H.

The pneumatic radial for construction vehicles of the third embodiment
In the tire, the reinforcing belt layer 2 is formed of a single metal cord layer having a cord angle α with respect to the circumferential direction of 7 degrees, which rises to the right,
Its cross-sectional width is 420 mm, and the tread width TW is 45 mm.
%, And the drop height h is 22 mm, which is almost the same as the tire of Example 1 except that it is 40% of the virtual drop height H.

The pneumatic radial for construction vehicles of the fourth embodiment
In the tire, the reinforcing belt layer 2 is formed of a corrugated cord having a cord angle α with respect to the circumferential direction of substantially 0 °, the cross-sectional widths of the reinforcing belt layers 21 and 22 are 500 mm and 560 mm, and the tread width TW 54% and 6
Except that it is 0%, the drop height h is 34 mm, and is 62% of the virtual drop height H, which is almost the same as the tire of the first embodiment.

In the conventional pneumatic radial tire for construction vehicles, the reinforcing belt layer 2 has a cord angle α 1 with respect to the circumferential direction of the inner reinforcing belt layer 21 of 7 ° which rises to the right and the circumferential direction of the outer reinforcing belt layer 22. The cord angle α2 with respect to the upper left is 6 degrees, and the reinforcing belt layer 2
1, 22 have a cross-sectional width of 270 mm and 240 mm, and 29% and 26% of the tread width TW,
And the outer contour in the tire axial direction outside the intersection P is located at the same level as the (virtual) extension of the crown radius R forming the outer contour in the tire axial direction from the intersection P, and therefore, at the end of the tread 4, The virtual fall height H from the tire center portion height of the virtual extension line of the crown radius R forming the outer contour in the tire axial direction is the same as the fall height of the actual outer contour in the tire axial direction outside, H = 55m
It is almost the same as the tire of Example 1 except that m and h = 0 mm.

The pneumatic radial tires for construction vehicles of Examples 1 to 4 and the pneumatic radial tires for construction vehicles of the above-described conventional examples were subjected to a comparison test of separation resistance and abrasion resistance at the belt end. In the comparative test, each of the test tires was rim 29.00.
/6.0 with a regular internal pressure of 700 kPa and a load of 72
The test is started at the same time, and when any of the test tires fails, the running of the drum is stopped all at once and the belt of the test tires is loaded. The length of the separation at the end and the amount of wear of the tread rubber are measured and evaluated.

According to the results of the above comparative test, the separation resistance at the belt end was 1
Assuming 00, the tires of Examples 1 to 4 were 250, 190, 200 and 220, respectively. In addition, as a result of the comparative test of the abrasion resistance characteristics, assuming that the tire of the comparative example is 100, the tires of Examples 1 to 4 were 110, 105, 107, and 111, respectively.

Tables 1 and 2 show the outline of the test tire and the results of the comparative test.

[0021]

[Table 1]

[0022]

[Table 2]

[0023]

From the results of the above comparative tests, it is understood that the present invention can provide a heavy-duty pneumatic radial tire having excellent separation resistance and abrasion resistance at the belt end.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an arrangement of a belt layer of a tire according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Carcass 2 Reinforcement belt 3 Crossing belt 4 Tread 5 Protective belt H Virtual fall height h Fall height from virtual fall height P Point where perpendicular line intersects outer contour of tread TW tread width

Claims (5)

[Claims] 1. A bead core provided on a pair of left and right bead portions, and a radial cord extending from one bead portion to the other bead portion, wound around the bead core and moored to the bead portion. Carcass ply consisting of layers,
In a pneumatic radial tire including a belt and a tread arranged radially outward of a crown portion of the carcass ply, when the tire is mounted on a regular rim and filled with a regular internal pressure, (1) the belt is: At least one reinforced belt having a substantially inextensible metal cord embedded in a covering rubber at a relatively small cord angle α with respect to a circumferential direction and having a cross-sectional width of 25 to 60% of a tread width. The layer and the substantially inextensible metal cord are arranged at a cord angle β of 10 to 40 degrees with respect to the circumferential direction so that the cords extend parallel to each other in the layer and intersect each other between adjacent layers. The reinforcing belt layer is laminated so as to be larger than the cord angle α, and has a cross-sectional width wider than the reinforcing belt layer, including at least two crossed belt layers,
(2) Assuming that a point at which a perpendicular line passing through the end of the reinforcing belt layer and standing on the carcass ply intersects the outer contour of the tread is P, the outer contour in the tire axial direction outside the intersection P is the tire from the intersection P. It is located radially inward from an imaginary extension of the crown radius R that forms the outer contour in the axial direction,
(3) The virtual fall height from the tire center portion height of the virtual extension line of the crown radius R that forms the outer contour in the tire axial direction at the end of the tread is defined as H, and the actual value of the virtual outer portion in the tire axial direction is defined as H. A heavy-duty pneumatic radial tire mainly used for traveling on rough terrain, wherein h is a fall height from the virtual fall height H of the outer contour of the tire. 2. The pneumatic tire according to claim 1, wherein a cord angle α of the reinforcing belt layer with respect to a circumferential direction is larger than 0 degree and 10 degrees or less. 3. The pneumatic tire according to claim 1, wherein the reinforcing belt layer is disposed between the carcass ply and the cross belt layer. 4. The reinforcing belt layer is formed of at least two rubber-coated cord layers laminated so that cords extend parallel to each other within the layer and cords intersect each other between adjacent layers. Claims 1 to 3
The pneumatic tire as described. 5. The pneumatic tire according to claim 1, wherein the reinforcing belt layer is formed of a corrugated cord having a cord angle α with respect to a circumferential direction of substantially 0 °.