JPH06179307A - Bias tire for heavy load - Google Patents

Abstract

PURPOSE:To reduce compressive strain occurring on a cord within a carcass ply in the neighborhood of the outermost side of a bead section for restraining the break of the cord. CONSTITUTION:The value of compressive strain acting on a carcass ply 15 at a travel position is proportional to a value S obtained from (1/AN1-1/A2), where A11 is the radius of curvature of the medium line M of a carcass layer 13 before compression, and A2 is the radius of curvature of the line M after compression. Thus, the medium line M of the carcass layer 13 at a bead section 25 under no load is displaced to a position outside a curve Z for a natural equilibrium form, so that the radius of curvature of the line M before compression is preliminarily reduced, and also a variation from A2 to A1 due to compression is reduced. The value of S is thereby made small.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heavy duty pneumatic bias tire in which a breaker layer is arranged outside a carcass layer formed by laminating a large number of carcass plies.

[0002]

2. Description of the Related Art Generally, a pneumatic tire, for example, a heavy load pneumatic bias tire mounted on a large construction vehicle or the like, has a most stable shape, that is, a shape in which a carcass layer medium line is located on a natural equilibrium shape curve. In such pneumatic tires, the medial line of the carcass layer bends in the vicinity of the maximum width position of the tire and the bead portion radially outside the point of separation from the rim (the inner side in the axial direction at the bead portion). It is bent so as to be convex, and is bent so as to be convex outward in the axial direction in the vicinity of the maximum tire width position).

[0003]

When such a tire is mounted on a large construction vehicle and is run under a heavy load, the tire is crushed in the radial direction and the bead outside the rim separation point in the radial direction. Each time the portion reaches the ground contact side, the portion repeatedly falls outward in the axial direction, and the radius of curvature at the bead portion is significantly reduced. Therefore, among the carcass plies of the carcass layer arranged in the bead portion, a large compressive strain is repeatedly applied to the organic fiber cords in the carcass ply located in the outermost vicinity, whereby,
There is a problem that the cord of the portion may be damaged early due to fatigue.

An object of the present invention is to provide a heavy-duty pneumatic bias tire capable of suppressing cord breakage in the carcass ply at the bead portion.

[0005]

Such an object consists of a plurality of pairs of bead rings and a plurality of carcass plies in which a large number of organic fiber cords inclined at a predetermined angle with respect to the equatorial plane of the tire are embedded. A toroidal carcass layer formed by folding back both ends in the width direction of the ply bundle from the inner side in the axial direction to the outer side in the axial direction around the bead ring, a breaker layer arranged on the outer side in the radial direction of the carcass layer, and a breaker layer. In a pneumatic tire for heavy load, which is equipped with a tread arranged radially outside and is mounted on a regular rim in a state of being filled with a regular internal pressure, in a carcass layer mediam line, a carcass section height of 0.9 from the rim line. Let P be a point that is radially outwardly separated by a factor of 2,
When the intersection point of the carcass layer medium line and a straight line that passes through the center of curvature of the rim flange ear and is inclined at an angle of 45 degrees with respect to the straight line parallel to the tire axis is Q,
The length of the medium line of the carcass layer between these points P and Q is set to the points P and Q in the natural equilibrium shape curve where the distance between the maximum width positions passing these points P and Q is 1.21 times the normal rim width. This can be achieved by making the median line of the carcass layer between the point Q and the maximum width position of the natural equilibrium shape curve substantially outside of the natural equilibrium shape curve while being larger than the distance between them. it can.

[0006]

Operation: It is assumed that the heavy duty pneumatic bias tire is running while receiving a heavy load. At this time, since the tire is crushed by a heavy load, the bead portion radially outside of the rim separation point repeatedly falls outward in the axial direction every time it reaches the ground contact side, and the radius of curvature thereof becomes small. Among the carcass plies of the carcass layer arranged in, the large compressive strain repeatedly acts on the organic fiber cords in the carcass ply located in the outermost vicinity.
Here, the value of such compressive strain is the radius of curvature of the mediam line of the carcass layer in the bead portion after the collapse.
It is well known that when A1 is set and the radius of curvature of the median line before collapse is A2, it is proportional to the value S obtained by 1 / A1-1 / A2. As a result, the compression strain is To make it smaller, the value S should be made smaller. Therefore, in the present invention, the length of the medium line of the carcass layer between the points P and Q is made larger (extended) than the length between the points P and Q in the natural equilibrium shape curve, and the extended amount is set to the point Q. And the median line of the carcass layer in the vicinity of the bead portion is located outside the natural equilibrium shape curve by being concentrated between the position and the maximum width position of the natural equilibrium shape curve. In this way, the mediam line of the carcass layer at the bead portion under no load (inner pressure filling) is displaced to the outside of the natural equilibrium shape curve, and the radius of curvature of the mediam line before collapse is reduced in advance, When the amount of radial crushing of the tire based on heavy load is the same, the amount of change from the radius of curvature A2 to A1 based on the collapse is small, and thus the value S is also small, and the carcass located near the outermost side is small. Fatigue of the organic fiber cord in the ply,
Damage is suppressed.

According to the second and third aspects, fatigue and breakage of the organic fiber cord can be effectively suppressed. Further, if configured as in claim 4,
Since the radius of curvature before deformation in the vicinity of the tire maximum width position also becomes small in advance, of the carcass plies of the carcass layer arranged in the region, the compressive strain acting on the organic fiber cord in the carcass ply located in the vicinity of the innermost side. As a result, fatigue and breakage of the cord at the portion are also suppressed.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 11 is a heavy-duty pneumatic bias tire mounted on a large construction vehicle or the like, and this tire 11 has a toroidal carcass layer 13 composed of a plurality, here three, of ply bundles 12. 14 are a plurality of pairs, here three pairs of bead rings. These bead rings
Both ends in the width direction of the ply bundle 12 are folded and moored in the axial direction from the inner side in the axial direction to the outer side in the axial direction. Although each ply bundle 12 is formed by superposing two or more carcass plies 15 on each other, each ply bundle 12 may have a different number of constituent carcass plies 15.
In each carcass ply 15, a large number of cords (not shown) made of organic fiber such as nylon and inclined at a predetermined angle with respect to the tire equatorial plane E are embedded. Adjacent carcass plies 15 have opposite directions, so that the cords in these carcass plies 15 intersect each other in each layer. A breaker layer 16 is provided outside the carcass layer 13 in the radial direction.
Is arranged, and a tread 17 is arranged on the outer side in the radial direction of the breaker layer 16. Reference numeral 21 is a regular rim on which the tire 11 is mounted, and the regular rim 21 has rim flanges 22 at both ends in the axial direction. And such a regular rim 21
After the tire 11 is mounted on the tire 11, when the internal pressure of the tire 11 is filled with the regular internal pressure, the medium portion of the carcass layer 13 in the vicinity of the bead portion 25 and the tire maximum width position radially outside the point T of separation from the regular rim 21. M is bent (bead portion 25
Bends so as to be convex inward in the axial direction, and is bent outwardly in the axial direction in the vicinity of the maximum tire width position). Here, the medium line M of the carcass layer 13 means the tire 11
Is a curve connecting the centers in the thickness direction of the carcass layer 13 in a meridional section obtained by cutting the tire along a plane including the tire rotation axis.

When the tire 11 thus mounted on the regular rim 21 and filled with the regular internal pressure is mounted on a large construction vehicle and is run under a heavy load, the tire 11 is crushed in the radial direction and the regular tire is crushed. Each time the bead portion 25 (bent so as to be convex inward in the axial direction even when no load is applied as described above) radially outside the point of separation T from the rim 21 reaches the ground side, the bead portion 25 is repeatedly axially outside. Fell greatly into the bead part
The radius of curvature of the medium line M of the carcass layer 13 at 25 is significantly reduced. Therefore, of the carcass plies 15 of the carcass layer 13 arranged in the bead portion 25, a large compressive strain is repeatedly applied to the cord in the carcass ply 15 located near the outermost side.

Here, the value of the compressive strain acting on the cord in the carcass ply 15 located in the outermost vicinity is as follows.
When the radius of curvature of the mediam line M of the carcass layer 13 in the bead portion 25 after the collapse is A1 and the radius of curvature of the mediam line M before the collapse is A2, 1 / A1-1 /
It is well known that the value S is proportional to the value S obtained by A2, and as a result, the value S can be reduced in order to reduce the compression strain described above.

Therefore, in this embodiment, the length V of the medium line M of the carcass layer 13 between the reference points P and Q is set to the natural equilibrium shape curve Z passing through these reference points P and Q.
The length is made larger than the length W between the reference points P and Q of, that is, extended. Here, the reference point P refers to a point on the mediam line M of the carcass layer 13 which is radially outward from the rim line N by 0.9 times the carcass section height D, and the reference point Q is the carcass layer 13 Of the medium line M and a straight line C that passes through the center Y of curvature of the ears 24 of the rim flange 22 and is inclined at an angle of 45 degrees with respect to a straight line B parallel to the tire axis. Providing the reference points P and Q at such positions is considered that the carcass layer 13 radially outside (axially inside) of the reference point P is strongly constrained by the breaker layer 16 and maintains a constant shape. On the contrary, it is considered that the carcass layer 13 on the inner side in the radial direction of the reference point Q is strongly constrained by the regular rim 21 and maintains a constant shape. In addition, the natural equilibrium shape curve Z means that the tire equatorial plane E passes through the reference points P and Q as described above.
Is in contact with a straight line parallel to the tire equatorial plane E, which is 0.605 times the regular rim width F outward from the axis (the distance between the maximum width positions G is 1.21 times the regular rim width F), and the following formula cosφ = a ^{(R 2 -Re 2) / (} Rs 2 -Re 2) shape that satisfies a curve obtained by convergent calculation the Re, the Rs for variables. Here, φ is an angle formed by a tangent of the curve and a straight line parallel to the rotation axis with a distance R from the tire rotation axis, Re is a distance from the point where the curve has the maximum axial distance to the rotation axis, and Rs is It is the distance from the point where the tangent of the extended line of the curve becomes parallel to the rotation axis to the rotation axis. Here, the reason why the distance between the maximum width positions G of the natural equilibrium shape curve Z is set to 1.21 times the regular rim width F is that the conventional maximum width position G of the pneumatic bias tire 11 for heavy load is required due to rim workability. This is because the maximum distance is 1.21 times the regular rim width F. Then, as described above, the reference point P
Of the carcass layer 13 between the reference point Q and the reference point Q
The length V is set larger than the length W between the reference points P and Q of the natural equilibrium shape curve Z, and is longer than that of the conventional tire. Further, in this embodiment, the above-mentioned stretched portion is concentrated between the reference point Q and the maximum width position G of the natural equilibrium shape curve Z, so that the reference point Q and the maximum width position G are substantially set. Only the mediam line M of the carcass layer 13 between them is located axially outside the natural equilibrium shape curve Z (in some cases, a part of the mediam line M of the carcass layer 13 between the reference point P and the maximum width position G). May be located outside the natural equilibrium shape curve Z in the axial direction). In this way, the mediam line M of the carcass layer 13 in the bead portion 25 between the reference point Q and the maximum width position G under no load (filling with internal pressure), is displaced to the outside of the natural equilibrium shape curve Z, If the radius of curvature of the media line M before collapse is reduced in advance, when the radial collapse amount of the tire 11 due to the heavy load is the same, the curvature radius A2 changes from A2 due to the collapse of the bead portion 25. The amount becomes small, and thereby the value S also becomes small, and the fatigue of the cord in the carcass ply 15 located near the outermost side of the bead portion 25,
Damage is suppressed. Here, the length V is preferably in the range of 1.02 times to 1.10 times the length W.
The reason is that when the length V is less than 1.02 times the length W, the compressive strain acting on the cord of the carcass ply 15 near the outermost portion of the bead portion 25 is reduced as shown in FIG. This is because it is impossible to sufficiently suppress fatigue and breakage of the cord. Here, FIG. 2 shows the results obtained as follows. That is, a tire whose length V is from 1.00 times to 1.10 times the length W (the tire size is 45 / 65-45
38PR) is prepared, and the normal internal pressure (2.1kgf / c) is applied to each tire.
m ² ) and 140% of the normal load (5270
The compressive strain acting on the outermost carcass ply 15 of the bead portion 25 when 0 kgf) is applied is obtained by the finite element method, and the compressive strain of the tire whose length V is 1.00 times the length W is
The index is displayed as 100. Further, when the length V of the median line M of the carcass layer 13 between the reference points P and Q exceeds 1.10 times the length W between the reference points P and Q of the natural equilibrium shape curve Z, the reference points P and Q The maximum displacement from the natural equilibrium shape curve Z of the mediam line M between is the carcass section height D.
0.06 times more than 0.06 times, the local collapse becomes large, and it becomes difficult to maintain the shape under load. Therefore, as described above, the length V is preferably 1.10 times or less the length W. And when doing in this way, the height L from the rim line N of the tire maximum width position J in the medium line M of the carcass layer 13 is set to the height U of the maximum width position G of the natural equilibrium shape curve Z.
It is preferable to set it in the range of 0.65 times to 0.90 times from the viewpoint of effectively suppressing fatigue and damage of the cord.

Next, a second embodiment of the present invention will be described with reference to FIG. Since the second embodiment is substantially the same as the first embodiment described above, the same parts are designated by the same reference numerals in FIG. 3 and their detailed description is omitted. Only different parts will be described. In this embodiment, the length V of the medium line M of the carcass layer 13 between the reference points P and Q is set to the reference point of the natural equilibrium shape curve Z passing through these reference points P and Q in the same manner as described above. The length W between P and Q is made larger (stretched), and this stretched portion is distributed almost evenly between the reference points P and Q, so that the reference point Q and the maximum width position G are Carcass layer not only in the space but also between the maximum width position G and the reference point P
The 13 medium lines M are also positioned axially outside the natural equilibrium shape curve Z. As a result, the mediam line of the carcass layer 13 between the reference point P and the reference point Q when there is no load, that is, the bead portion 25 and the sidewall portion 26, particularly near the tire maximum width position where the radius of curvature is small even when there is no load. M is displaced to the outside of the natural equilibrium shape curve Z, and the radius of curvature of the bead portion 25 and the mediam line M near the tire maximum width position J before the collapse is reduced in advance. It is possible to suppress both fatigue and breakage of the carcass ply 15 located and the cord in the carcass ply 15 located near the innermost side in the vicinity of the tire maximum width position J. Then, as described above, if the expanded portion is distributed substantially evenly between the reference point P and the reference point Q, the median line M has a shape in which the natural equilibrium shape curve Z is swollen in the axial direction. The tire maximum width position J of the medium line M is not displaced in the radial direction, and is located near the maximum width position G of the natural equilibrium shape curve Z, that is, at substantially the same height. And this second
In the embodiment, the length V is 1.03 times the length W to 1.
It is preferably within the range of 15 times. The reason is that when the length V is less than 1.03 times the length W, the compression strain acting on the cord of the carcass ply 15 near the outermost portion of the bead portion 25 and the maximum tire width as shown in FIG. This is because the compressive strain acting on the cord of the carcass ply 15 near the innermost position at the position J does not decrease so much, and fatigue and breakage of the cord cannot be sufficiently suppressed. Here, FIG. 4 shows the results obtained as follows. That is, the length V
Of tires whose tire length is 1.00 to 1.20 times (tire size is 45 / 65-45 38PR) are prepared, and each tire is filled with normal internal pressure (2.1kgf / cm ² ) and the normal load is 140
%, The compressive strain acting on the outermost carcass ply 15 of the bead portion 25 and the compressive strain acting on the innermost carcass ply 15 at the tire maximum width position J when a load (52700 kgf) was applied were obtained by the finite element method. The tires whose length V is 1.00 times the length W are indexed with 100 as the compressive strain of each tire. If the length V exceeds 1.15 times the length W, the maximum tire width may deviate from the tire standard. Therefore, the length V is preferably 1.15 times or less the length W.

Next, a test example will be described. In this test, the conventional tire in which the mediam line of the carcass layer between the reference points P and Q is located on the natural equilibrium shape curve, and the rim line in which the length V is 1.04 times the length W and the tire has the maximum width position in the mediam line And the test tire 1 described in Example 1 whose height is 0.8 times the maximum width position height of the natural equilibrium shape curve, and the length V is 1.11 times the length W and the tire maximum width position at the median line is Was prepared near the maximum width position of the natural equilibrium shape curve, and the test tire 2 described in Example 2 was prepared. Here, the size of each tire was 45 / 65-4538PR. Next, 2.
After being filled with a normal internal pressure of 1 kgf / cm ² , it was run on the drum at a speed of 15 km for a maximum of 500 hours while applying a load of 52700 kgf (140% of the normal load). As a result, in the conventional tire, the bead part after running for 265 hours,
Although the cord was damaged at both of the maximum width positions and it became impossible to run, the test tire 1 did not have cord breakage at the bead portion at the time of completion, and the test tire 2 had the bead portion at the time of completion and maximum width. There was no code destruction near the position. Further, the compressive strain acting on the outermost carcass ply of the bead portion of each tire under the action of the load was obtained by the finite element method. The result is shown by index 100 for the conventional tire. And was 66 for the test tire 2. Further, the compressive strain acting on the innermost carcass ply at the tire maximum width position of each tire was obtained by the finite element method,
When the result is displayed with the index of 100 for the conventional tire, it is 48 for the test tire 2.

[0014]

As described above, according to the present invention, it is possible to suppress the breakage of the cord in the carcass ply at the bead portion.

[Brief description of drawings]

FIG. 1 is a meridian sectional view of a tire showing a first embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the compressive strain in the bead portion and the value of V / W.

FIG. 3 is a meridian sectional view of a tire showing a second embodiment of the present invention.

FIG. 4 is a graph showing a relationship between a compressive strain and a V / W value at a bead portion and a tire maximum width position.

[Explanation of symbols]

 11 ... Tire 12 ... Ply bundle 13 ... Carcass layer 14 ... Bead ring 15 ... Carcass ply 16 ... Breaker layer 17 ... Tread 21 ... Regular rim 22 ... Rim flange 24 ... Ear E ... Tire equator M ... Medium line N ... Rim line D ... Carcass cross section height Y ... Center of curvature B ... Straight line C ... Straight line G ... Maximum width position F ... Regular rim width Z ... Natural equilibrium shape curve J ... Tire maximum width position L ... Height U ... Maximum width position height

Claims (4)

[Claims] 1. A bead ring having a plurality of pairs of bead rings and a widthwise end portion of a ply bundle composed of a plurality of carcass plies in which a large number of organic fiber cords inclined at a predetermined angle with respect to a tire equatorial plane are embedded. A toroidal carcass layer formed by folding back from the inner side in the axial direction to the outer side in the axial direction, a breaker layer arranged on the outer side in the radial direction of the carcass layer, and a tread arranged on the outer side in the radial direction of the breaker layer. In a heavy duty pneumatic bias tire equipped with a regular internal pressure and equipped with a regular rim, a point on the carcass layer mediam line that is radially outwardly separated from the rim line by 0.9 times the carcass section height. P is 45 with respect to the carcass layer medium line and the straight line that passes through the center of curvature of the rim flange ear and is parallel to the tire axis. When the point of intersection with a straight line inclined at an angle of is defined as Q, the length of the mediam line of the carcass layer between these points P and Q is defined as the maximum width position distance through these points P and Q. It is larger than the length between points P and Q on the natural equilibrium shape curve which is 1.21 times the width, and
A pneumatic bias tire for heavy loads, wherein substantially only the mediam line of the carcass layer between the point Q and the maximum width position of the natural equilibrium shape curve is positioned outside the natural equilibrium shape curve. 2. The length between points P and Q on the medium line of the carcass layer is set within a range of 1.02 to 1.10 times the length between points P and Q on the natural equilibrium shape curve. Pneumatic bias tire for heavy loads. 3. The heavy duty pneumatic tire according to claim 1, wherein the height of the tire maximum width position on the mediam line from the rim line is within a range of 0.65 to 0.90 times the maximum width position height of the natural equilibrium shape curve. Bias tire. 4. The length between points P and Q on the medial line of the carcass layer is set within a range of 1.03 to 1.15 times the length between points P and Q on the natural equilibrium shape curve, Not only between the point Q and the maximum width position of the natural equilibrium shape curve, the mediam line of the carcass layer between the point P and the maximum width position of the natural equilibrium shape curve is also positioned outside the natural equilibrium shape curve, The pneumatic bias tire for heavy load according to claim 1, wherein the tire maximum width position in the medium line is located near the maximum width position of the natural equilibrium shape curve.