JPH02204104A - Pneumatic tire for heavy load use - Google Patents

Abstract

PURPOSE:To enhance the durability in bead parts while preventing the separation at the ends of a belt by forming a carcass shape curve so as to pass through specific three points and to have a specific maximum distance and an axial direction distance, and also to include a curved part and a straight part. CONSTITUTION:A carcass shape curve C passes through a point I at a specific distance from the equator surface M of a tire on a curve F, a point E at a specific distance from a rim diameter line L on a natural balance shape curve S, and a point D at a specific distance from the sectional height H of the carcass layer respectively, and also forms a curve which is positioned at the outside of respective curves S, F between the points I and E, and which is positioned at the inside of the curve S between the points E and D. And the maximum distance t and the axial directional distance u with respect to the carcass shape curve C are set at specific ratios to the rim width J respectively. Further, the carcass shape curve C is formed in a smoothly changing curve between the specific points I and X, and also is formed nearly in a straight line between another specific points X and D.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heavy-duty pneumatic tire with improved bead durability by improving the carcass line.

Generally speaking, pneumatic tires for heavy loads are often used under harsh conditions such as running continuously for long periods of time under heavy loads.
Large circumferential shearing deformations are repeatedly applied to the bead near the ground contact area, and as a result, separation occurs in the rubber at one end of the chafer, or cracks occur in the chafer in contact with the rim, which reduces the durability of the bead. had to be low.

In particular, a heavy-duty pneumatic tire whose carcass line has a natural equilibrium shape curve as shown by the broken line in FIG.
The carcass line is filled with an internal pressure of 5% of the normal internal pressure. 0.9 of the cross-sectional height H from the rim diameter line L on a straight line P parallel to the tire equatorial plane M and 0.5 times the rim width J away from the tire equatorial plane M toward the outside in the axial direction.
Pass through both the point G that is 1 times the distance and the point that is 0.15 to 0.25 times the cross-sectional height H, and at the maximum width position (height R1 from the rim diameter line L, that is, the cross-sectional height H). The natural equilibrium shape curve mT that passes through the maximum width point N, which is 0.70 to 0.72 times the rim width J, from the tire equatorial plane M on the tire equatorial plane M, which is 0.58 to 0.60 times away. In the case of heavy-duty pneumatic tires, the bead portion is damaged early due to the above-mentioned reasons, and as a result, the tire has to be replaced once in a while. Here, the natural equilibrium shape curve as described above is created by first selecting the tire outer diameter, maximum width, tread radius, etc. from the tire specifications, and then determining the reference point and bead at the shoulder part from these main dimensions of the tire. Determine the reference point at U, It is obtained by performing a convergence calculation using Z as a variable. Here, φ is the angle between the tangent of one curve and a straight line parallel to the rotation axis at a distance K from the tire rotation axis, U is the distance from the point where one curve takes the maximum distance in the axial direction to the rotation axis, and Z is the distance from the point where the tangent to the extension of the above curve is parallel to the rotation axis to the rotation axis.

In order to solve the problems mentioned above, conventionally,
The carcass line is, for example, the point G mentioned above.

Passing through both D and at the maximum width position, the tire equatorial plane M
A natural equilibrium shape curve S, as shown by the temporary g line in Figure 4, passing through the maximum width point A, which is 0.73 to 0.75 times the rim width J, is created, thereby increasing the tire maximum width. Heavy-duty pneumatic tires have been proposed. As mentioned above, this tire increases the carcass length in the meridian cross section by increasing the maximum width of the tire, which promotes deformation absorption in the sidewall area and, as a result, suppresses deformation in the bead area. For example, in the former tire, the shear strain in the rubber at one end of the chafer during filling with internal pressure was 100 in terms of index, but in the latter tire, it was reduced to 82.

However, such heavy-duty pneumatic tires,
Although the effect of suppressing deformation of the bead portion to some extent can be expected, it is still not sufficient, and therefore, tires have to be replaced frequently due to failure of the bead portion. Moreover, simply widening the maximum width of the tire increases the belt tension, which increases the diameter growth of the shoulder part during internal pressure filling, and as a result, the belt located in the shoulder part increases. A large shear strain occurs at the ends of 0
For example, in the former tire, the shear strain at the end of the belt during internal pressure filling was 100 on an index scale, but in the latter tire, it had worsened to 135. For this reason,
In such tires, there is a problem in that separation may occur at the end of the belt in some cases.

An object of the present invention is to provide a heavy-duty pneumatic tire that can significantly improve the durability of the bead portion without preventing separation at the belt end.

Therefore, such a purpose is to smoothly connect a point V on the tire equatorial plane M that is apart from the rim diameter line L by a cross-sectional height H and the point G, and define a curve that is continuous with the natural equilibrium shape curve S as F, Also, on the natural equilibrium shape curve S, the rim diameter line L
Let E be a point that is 0.76 to 0.80 times the cross-sectional height H, and 0.18 to 0.22 times the rim width J from the tire equatorial plane M on the curve F. When the point is T, the carcass shape curve C of the heavy-duty pneumatic tire passes through the three points I, E, and D, and reaches the point R.

Between points E and D, it is located outside the natural equilibrium shape curve S and curve F, and between points E and D, the natural equilibrium shape curve S
The maximum distance between the natural equilibrium shape curve S and the carcass shape curve C between points X and E, and the maximum distance between the maximum width point A and the carcass shape J at the maximum width position. 0.025 times to 0.05 times, and furthermore, 0.45 times to 0.50 times the cross-sectional height H from the rim diameter line L on the straight line Q parallel to the straight line P passing through the point B. The line segment connecting the distant point Y and the above dot is defined as f, and the point on this line molecule that is 0.38 to 0.45 times the cross-sectional height H from the rim diameter line L is defined as X.
Then, the above point 1. This can be achieved by constructing the carcass shape curve C between points X and D from a smoothly changing curve, while constructing the carcass shape curve C between the points X and D from a substantially straight line.

1" First, in this invention, on the tire equatorial plane M, a point V which is separated from the rim diameter line L by a cross-sectional height H, and the point G
Let F be a curve that smoothly connects and continues to the natural equilibrium shape curve S, and is separated from the rim diameter line L by 0.76 to 0.80 times the cross-sectional height H on the natural equilibrium shape curve S. When the point is E and the point is 0, is or 0°22 times the rim width J from the tire's equatorial plane M on one turn 11F, the condition is when the tire is filled with an internal pressure of 5% of the normal internal pressure. The tire carcass shape curve C in
Passing through the three points I, E, and D, and located outside the natural equilibrium shape curve S and curve F between one point I and E, 1
The curve between points E and D is located inside the natural equilibrium shape curve S, and the maximum distance between the natural equilibrium shape curve S and the carcass shape surface [C between the points E and E, and the maximum width The axial natural pressure 1llu between point A and point B on the carcass shape curve C at the maximum width position is both kept within the range of 0.025 to 0.05 times the rim width J. When such a tire is filled with the normal internal pressure, the carcass shape curve C expands and deforms outward, but at this time, the carcass shape curve C between the 1-point construction and E (near C and Ruder) is in natural equilibrium. Shape curve S
The carcass shape curve C between points E and D (sidewall part) is located inside the natural equilibrium shape curve S. , can grow significantly outward in the axial direction. This suppresses the diameter growth near the shoulder and prevents separation at the belt end. In addition, in this invention, on a straight line Q parallel to a straight line P passing through one point B, a point Y which is separated from the rim diameter line L by 0.45 times the cross-sectional height H to 0,0 times the cross-sectional height H and the above-mentioned point If the connected line segment is f, and the point on the line molecule of and that is 0.38 to 0.45 times the cross-sectional height H from the rim diameter line L is defined as X, then the points X, X@ The carcass-shaped surface Ic is composed of a smoothly changing curve, while the carcass-shaped surface 11C between the points X and D is composed of a substantially straight line.

When the carcass shape curve C at the bead portion is made substantially straight in this way, the tension of the carcass at that portion increases during internal pressure filling, thereby suppressing deformation of the bead portion. As a result, the circumferential shearing force acting on the bead portion near the ground contact portion during running is suppressed, and the occurrence of separation in the rubber at one end of the chafer or cracking in the chafer is prevented, thereby improving the durability of the bead portion.

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

In FIG. 1, 1 is a heavy-duty pneumatic tire used for ultra-large construction vehicles, etc., and this tire 1 has a carcass shape curve C as described below. Since C approximates the natural equilibrium shape curve S described above, it will be explained while comparing it with this.

First, the natural equilibrium shape curve S to be compared passes through both points G and D and the maximum width point A in a state filled with an internal pressure of 5% of the normal internal pressure, and satisfies the above formula (■). It is a curve. Here, point G is 0.5 times the rim width J away from the tire equatorial plane M toward the outside in the axial direction, and is 0.5 times the cross-sectional height H from the rim diameter line L on a straight t&P parallel to the tire equatorial plane M. A point 91 times farther away is the reference point for shoulder part 2. On the other hand, the point is the straight line P
This is a point located at a distance of 0.15 to 0.25 times the cross-sectional height H from the rim diameter line L on the top, and is a reference point at the bead portion 3. Furthermore, the maximum width point A is on the maximum width point M (the radial position where the maximum width point is located apart from the rim diameter line L by a height R1, that is, 0.56 to 0.60 times the cross-sectional height H). This point is 0.73 to 0.75 times the rim width J from the tire equatorial plane M. Here, the distance from the tire equatorial plane M of the maximum width point A is 0.7 of the rim width J.
The reason for setting the range from 3 times to 0.75 times is because if it is less than 0.73 times, the length of the carcass cannot be made too long, so the effect of suppressing deformation in the bead portion 3 will be reduced. On the other hand, if it exceeds 0.75 times,
This is because when used with two wheels, the tires may come into contact with each other depending on the load. Note that between the point G and a point V on the tire equatorial plane M, which is separated from the rim diameter line L by the cross-sectional height H,
Consider a curve F that is connected to the natural equilibrium shape curve S and smoothly connects these two points G and V. If the carcass line of the tire I is approximated to the natural equilibrium shape curve S and the curve F, the carcass length in the meridian section becomes longer, which promotes deformation absorption in the sidewall portion 4, and as a result, the bead Deformation in portion 3 is suppressed.

On the other hand, the carcass shape curve uAC of the tire 1 is not the same as the natural equilibrium shape surface MS and the curve F, but passes through points E and D on the natural equilibrium shape curve S and the points on the curve F.

Here, point E is a point on the natural equilibrium shape curve S that is away from the rim diameter line L by 0.76 times the cross-sectional height H or O,SO times, while one-point construction is on the one curve F. This is a point that is away from the tire equatorial plane M by 0.18 to 0822 times the rim width J. For this reason, the size of the tire l.

The router part 2 is placed between the said dot and point E, while
The sidewall portion 4 including the maximum width point A is arranged between the point E and the dot. In this embodiment, the carcass shape curve C between points I and E is located outside the natural equilibrium shape curve S and curve F, and the point E
, D, the carcass shape curve C is located inside the natural equilibrium shape curve S. Here, when the tire 1 is filled with the normal internal pressure, the carcass shape curve C expands and deforms outward, but at this time, the carcass shape curve C at the point of construction and between 8 (shoulder part 2) has a natural equilibrium shape. Since it is located outside the curves S and F, the carcass shape curve C between points E and D (sidewall section 4 including the maximum width point A) is in natural equilibrium. Because it is located inside the shape curve S, it can grow thickly outward in the axial direction.This suppresses the diameter growth near the shoulder part 2 as shown in Figure 2, and the Separation is prevented. At this time, the maximum distance between the natural equilibrium shape curve S and curve F and the carcass shape curve C between points I and 8 is t, and the distance between the maximum width point A and the carcass shape curve C at the maximum width position is t. Let U be the axial distance between point B and point B, then these distances $1t and u are both approximately equal, and their values are in the range from 0.025 times the rim width J to 0.05 times. Within. Here, if the values of the distances t and u are less than 0.025 times the rim width J, the above-mentioned function will hardly be exhibited. This is because it becomes too large, and on the other hand, if it exceeds 0.05 times, 1 point E, D
The axial growth in the belt (sidewall portion 4) is too large, resulting in a small tread radius, and as a result, the shear strain at the belt end increases when a load is applied, offsetting the effect of reducing shear strain when filling with internal pressure. This is because it will be put away.

Note that the index 100 in FIG. 3 is based on the value of a tire with a wide maximum width among conventional tires.

Further, in this embodiment, the carcass shape curve C is formed from a smooth curve between points I and X, while it is formed from a substantially straight line between points X and D. here,
Point X is 0.45 to 0.5 times the cross-sectional height H from the rim diameter line L on the straight line Q parallel to the straight line P passing through the point B.
Assuming that a point Y is 0 times distant, and the line segment connecting this point Y and the above-mentioned dot is f, then on this line molecule, from rim diameter line L to 0.38 times the cross-sectional height H It is a point 0.45 times farther away. When the carcass shape curve C in the bead portion 3 is made substantially straight in this manner, the tension of the carcass at this portion increases during internal pressure filling, thereby suppressing circumferential shear deformation of the bead portion 3.

As a result, during load transfer, separation in the rubber at one end of the chafer near the ground contact area or cracking in the chafer is prevented, and the durability of the bead part is improved. The shear strain of the rubber at one end of the CHIEFER was 100 on an index scale, but in the tire of this example, the strain decreased to 85 due to the longer carcass length mentioned above. Here, the point Y is a point on the straight line Q that is more than 0.45 times the cross-sectional height H from the rim diameter line L, and the point
The reason for setting the point on the line molecule at least 0.38 times the cross-sectional height H from the rim diameter line L is because if it is less than these values, the tension in the bead portion 3 described above will not increase, and the load will be reduced. This is because the shear deformation of the bead portion 3 at the time of transfer becomes large.On the other hand, the point Y is set to be a point on the straight line Q that is less than 0.50 times the cross-sectional height H from the rim diameter line L, and 1
Point X is located on the line molecule from rim diameter line L to 0.
The reason why the points were chosen to be 45 times or less apart is because, if these values are exceeded, the carcass length becomes shorter and the effect of increasing the maximum width is reduced.

Next, a test example will be explained. In this test, the cross-sectional height H was 788.7 m (the maximum width W was 933.7 mm,
Height R is 41113.1mm, rim width J is 880.4m
m, the cross-sectional height H is 788.7 mm,
Maximum width W is 948.9gg, height R is 483.1mm,
Rim width J is 860.4mm, distance fit and u are both 20.
0mm, the axial distance from the tire equatorial plane M to point ■ is 132.1mm, and the height of point E from the rim diameter line L is 6
14.9m mouth, height of rim diameter line L at point Y is 37
0.7mm, the height of point X from rim diameter line L is 331
．． A test tire to which the present invention was applied having a diameter of 2 mm was prepared. Here, the size of each tire is ORR38,00R
It was 51.

Next, after filling each such tire with an internal pressure of 7.00 Kg/Crn', 90 tons (J ATMA standard 20
It was pressed against a drum with a diameter of 5 m while applying a load of 0%) and rotated at a speed of 8 KII. In the conventional tire, separation occurred at the end of the wire chafer after traveling for 3E100 km, which led to cracks on the outer surface of the wire chafer, resulting in bead failure. At this time,
Cracks had occurred on the outer surface of many other parts, and separation had occurred at the y-end of the wire chafe. On the other hand, for the test tire, the test was terminated after running 4000+, at which time diagonal cracks were observed on the outer surface of the rubber chafer, but there was no separation on one end of the wire chafer. was not seen. Furthermore, no separation occurred at the belt ends. As described above, in the test tire to which the present invention is applied, it is possible to suppress shear deformation of the bead portion during internal pressure filling and load transfer, and therefore the durability of the bead portion can be significantly improved. It was also possible to reliably prevent separation at the end of the belt.

As explained above, according to the present invention, it is possible to significantly improve the durability of the bead portion without preventing separation at the end of the belt.

[Brief explanation of the drawing]

FIG. 1 is a meridional cross-sectional view mainly showing a carcass line showing an embodiment of the present invention, FIG. 2 is a graph showing the relationship between the axial position of the tire and the radial growth, and FIG. 3 is the distance t, u. FIG. 4 is a graph showing the relationship between shear strain generated at the belt end and FIG. 4 is a meridian cross-sectional view mainly showing the shape of the carcass line of a conventional tire. H... Section height W... Maximum width L... Rim diameter line A... Maximum width point F... Curve
V...Point R...Height J...Rim width M...Tire equatorial plane P...Straight line G...Point D
...Point S...Natural equilibrium shape curve E...Point I...Point C...Carcass shape curve t...Maximum distance B...Point U...Distance Q...Straight line Y... point
f...Line segment

Claims (1)

[Claims] The cross-sectional height of the carcass layer is H, the maximum width of the carcass layer is W,
In a heavy-duty pneumatic tire where the height from the rim diameter line L to the maximum width position is R and the rim width is J, the tire equatorial plane M when filled with an internal pressure of 5% of the regular internal pressure.
A point G that is 0.5 times the rim width J axially outward from the rim and 0.91 times the cross-sectional height H from the rim diameter line L on a straight line P parallel to the tire equatorial plane M, and the cross-sectional height It passes through both points D, which are 0.15 to 0.25 times apart from H, and the tire equatorial plane M at the maximum width position.
Let S be the natural equilibrium shape curve that passes through the maximum width point A, which is 0.73 to 0.75 times the rim width J, and is separated from the rim diameter line L by a cross-sectional height H on the tire equatorial plane M. Let F be a curve that smoothly connects the point V and the point G and continues to the natural equilibrium shape curve S, and further, on this natural equilibrium shape curve S, 0.7 of the cross-sectional height H from the rim diameter line L.
Let E be a point 8 to 0.80 times away, and I be a point 0.18 to 0.22 times the rim width J from the tire equatorial plane M on curve F. The shape curve C passes through the three points I, E, and D, and the point I
, E is located outside the natural equilibrium shape curve and curve F, and between points E and D, the natural equilibrium shape curve S
The maximum distance between the natural equilibrium shape curve S and the carcass shape curve C between points I and E, and the maximum width point A and the carcass shape curve C at the maximum width position. The axial distance u from point B is within the range of 0.025 to 0.05 times the rim width J, and the rim diameter is Let f be a line segment connecting the point Y and the point D, which is 0.45 to 0.50 times the cross-sectional height H from the line L, and the cross-sectional height from the rim diameter line L on this line segment f. When X is a point separated by 0.38 to 0.45 times H, the carcass shape curve C between the points I and X is composed of a smoothly changing curve, while the curve between the points X and D A pneumatic tire for heavy loads, characterized in that a carcass shape curve C is formed from a substantially straight line.