JP4763902B2 - Pneumatic tire - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic tire, particularly a heavy duty radial tire used for construction vehicles and industrial vehicles, and improves the durability of the bead portion of the tire.
[0002]
[Prior art]
The pneumatic tire is mounted on the vehicle as a tire wheel assembled to the applicable rim.
The separation point from the rim flange of the tire when viewed as a tire wheel moves to the flange edge side as the load applied to the tire increases, and in particular, a heavy duty radial tire used for construction vehicles, industrial vehicles, etc. In this case, the phenomenon that the tire rides on the flange edge is likely to occur, and as a result, a large shear strain is generated on the outer surface of the bead portion of the tire between the rim flange, and defects such as cracks are likely to occur. There was a problem that sufficient bead durability could not be obtained.
[0003]
For this reason, conventionally, the rubber gauge constituting the outer surface portion of the bead portion of the tire is increased, or a reinforcing member such as a nylon chafer or a wire chafer is disposed on the outer surface portion of the bead portion in contact with the rim. The method was taken.
[0004]
However, it is not preferable to increase the thickness of the rubber gauge or to provide the reinforcing member because such problems as an increase in cost due to an increase in tire weight, an increase in rolling resistance, and a deterioration in fuel consumption occur.
[0005]
For this reason, it has been necessary to improve the bead portion durability without causing problems such as an increase in tire weight.
[0006]
[Problems to be solved by the invention]
An object of the present invention is to form a tire contour shape so that a distance between a predetermined position on the rim flange upper portion and a tire outer surface position corresponding to the predetermined position is appropriate in relation to a flange radius of the rim. Pneumatic tires, particularly heavy duty radial tires used in construction vehicles and industrial vehicles, which effectively suppresses shear strain generated on the outer surface of the bead portion of the tire between the rim flange and significantly improves the durability of the bead portion. Is to provide.
[0007]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the present invention applies a maximum air pressure to a pneumatic tyre with a flatness ratio of 90% or more that is attached to a standard rim having a bead seat angle of 5 ° or less and the tire is attached to the standard rim. As seen in the cross section in the width direction of the unloaded tire wheel, the position of the intersection of the straight line extending in the tire radial direction through the center of curvature of the flange of the standard rim and the outer surface of the flange, and the outer surface of the tire from this intersection the separation between the normal position and is h, the flange radius of a standard rim is R, the distance is Ri range near the 28 to 45% of said flange radius, the normal position (a) in measured tire outer surface radius of curvature (r) is 4 to 8 times the standard rim flange radius (R), a tire outer contour in the normal position (a) is Ru Totsudea outward in the tire width direction Air characterized by Ri is a tire.
The “standard rim” and “maximum air pressure” here mean the standard rim and the maximum air pressure defined in JATMA YEAR BOOK (2001).
[0008]
The tire includes a bead core embedded in a pair of bead portions, a cord rubberized layer, a ply main body portion extending from the crown portion to both bead portions via both sidewall portions, and an end portion of the ply main body portion. From a tire outer surface position measured on a straight line passing through the center of curvature of the flange of the standard rim and extending along the tire rotation axis direction. The distance to the thickness center position of the ply folding portion is D1, and the shortest distance between the separation point from the tire rim and the thickness center position of the ply folding portion when the maximum air pressure and maximum load capacity are applied is D2. In this case, it is preferable that the shortest distance D2 satisfies the range represented by the following expression (1) as a percentage with respect to the distance D1.
The "maximum load capacity" here means the maximum load capacity defined in JATMA YEAR BOOK (2001).
[0009]
Record
130% ≦ D2 / D1 ≦ 230% ---- (1)
[0010]
Further, when the tire outer surface position located on a straight line extending along the tire width direction passing through the bisector of the distance measured along the tire radial direction between the separation point and the tire total width position is defined as S When the edge position of the ply turn-up part is outside the tire outer surface position in the tire radial direction, the shortest distance between the tire outer face position and the thickness center position of the ply turn-up part is set to D3. For example, it is preferable that the shortest distance D3 satisfies a range in which the percentage with respect to the distance D1 is expressed by the following equation (2). In the case of being radially inward, if the shortest distance between the tire outer surface position and the thickness center position of the ply main body is D4, the shortest distance D4 has the following percentage (3) with respect to the distance D1. In the formula It is preferable to satisfy the range shown.
The “total tire width position” here means a tire surface position for measuring the total tire width defined in JATMA YEAR BOOK (2001).
[0011]
Record
100% ≤D3 / D1≤170% ---- (2)
180% ≦ D4 / D1 ≦ 280% ---- (3)
[0013]
In addition, it is preferable that the pneumatic tire of the said structure is a heavy duty tire used for a construction vehicle or an industrial vehicle.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 1 shows a typical cross-section in the width direction of a main part including one bead portion of a pneumatic tire according to the present invention in a state where it is assembled to a standard rim. Is a bead core, 3 is a bead core, 4 is a carcass, 5 is a side wall, 6 is a ply body, 7 is a ply turn-up portion, 8 is a standard rim, and 9 is a flange of a standard rim.
[0015]
A tire 1 shown in FIG. 1 includes a bead core 3 embedded in a pair of bead portions 2 and a carcass 4 made of a cord rubber pulling ply. A reinforcing belt made of a cord rubberized layer and a tread are disposed.
[0016]
The carcass 4 includes a ply body 6 extending in a toroidal shape from the crown (not shown) through the sidewall 5 to the bead 2, and extending from both ends of the ply body 6 around the bead core 3 in the tire width direction. It is comprised by the ply folding | turning part 7 folded back toward the outer side.
[0017]
In the tire having the above-described configuration, the phenomenon that the tire runs on the flange edge and the occurrence of defects such as cracks on the outer surface of the bead portion of the tire is particularly noticeable. A tire having an aspect ratio of 90% or more, particularly construction vehicles and industries Since this is a case where a heavy duty tire used in a vehicle is assembled to a standard rim having a bead seat angle of 5 ° or less, in the present invention, a tire having a flatness ratio of 90% or more is set to a bead seat angle of 5 ° or less. Only when assembled on a standard rim with
[0018]
The main feature of the present invention is that the distance between the predetermined position of the rim flange upper portion and the tire outer surface position corresponding to the predetermined position is appropriate in relation to the flange radius of the rim. More specifically, the tire 1 is mounted on the standard rim 8, and the unloaded tire wheel to which the highest air pressure is applied is viewed in the cross-section in the width direction, and the flange of the standard rim 8 is formed. 9 is the intersection position Q of the straight line x passing through the center of curvature O of the tire 9 in the tire radial direction and the flange outer surface 9a, and the normal position established from the intersection position Q to the outer surface of the tire 1, more precisely, the outer surface of the bead portion 2. When the separation distance from a is h and the flange radius of the standard rim 8 is R, the separation distance h is set within a range of 28 to 45% of the flange radius R. By adopting the rim Results shear strain occurring in the outer surface of the bead portion 2 of the tire 1 with the flange outer surface 9a is effectively suppressed, it is possible to greatly improve the bead portion durability.
[0019]
When the separation distance h is less than 28% of the flange radius R, the outer surface of the tire bead portion 2 easily rides on the rim flange edge when a heavy load is applied, and shear strain acting on the outer surface of the bead portion 2 is sufficiently suppressed. In addition, when the separation distance h exceeds 45% of the flange radius R, the separation point between the standard rim 8 and the tire 1 comes to be located below the rim flange, and the tire bead This is because a sufficient area for the outer surface of the portion 2 to contact the rim 8 cannot be secured, and rim displacement is likely to occur.
[0020]
Further, when it is necessary to further suppress the shear strain generated on the outer surface of the bead portion 2 with the rim flange 8, the separation point of the tire 1 from the rim 8 when the maximum air pressure and the maximum load capacity are applied. From the tire outer surface position c, the shortest distance D2 between b and the thickness center position e of the ply turn-up portion 7 is measured on a straight line m passing through the center of curvature O of the flange 9 of the standard rim 8 and extending in the tire rotation axis direction. The percentage with respect to the distance D1 to the thickness center position d of the ply turn-up portion 7 is preferably in the range of 130 to 230%.
[0021]
This is because if the percentage is less than 130%, the effect of suppressing shear strain generated on the outer surface of the bead part 2 is small, and if the percentage exceeds 230%, the rubber part of the bead part 2 that contacts the rim 8 This is because the gauge of the rubber chafer 10 is too thick and causes an increase in tire weight.
[0022]
Furthermore, when it is necessary to further suppress the shear strain generated on the outer surface of the bead portion 2 with the rim flange 9, it is preferable to employ the following configuration.
[0023]
As shown in FIG. 1, the edge position 11 of the ply turn-up portion 7 of the carcass 4 passes through a bisector g of the distance measured along the tire radial direction between the separation point b and the tire total width position. When the tire outer surface position S is located outside the tire outer surface position S located on the straight line n extending in the tire width direction, the shortest distance D3 between the tire outer surface position S and the thickness center position i of the ply turn-up portion 7 is obtained. The percentage of the distance D1 is preferably in the range of 100 to 170%.
[0024]
This is because if the percentage is less than 100%, it tends to be disadvantageous for external cut input, and other failures tend to occur, and if the percentage exceeds 170%, the ply folding section 7 This is because the gauge of the outer rubber 12 on the outer surface side becomes too thick, resulting in an increase in tire weight.
[0025]
On the other hand, when the edge position 11 of the ply turn-up portion 7 of the carcass 4 is on the inner side in the tire radial direction from the tire outer surface position S, the tire outer surface position S and the thickness center position j of the ply main body portion 6 As for the shortest distance D4 between these, it is preferable that the percentage with respect to the said distance D1 is the range of 180-280%.
[0026]
This is because if the percentage is less than 180%, a space above the ply turn-up end 11 is not secured, and if the percentage exceeds 280%, the gauge of the outer rubber 12 on the outer surface side of the ply turn-up portion 7 is reduced. This is because the tire becomes too thick, resulting in an increase in tire weight.
[0027]
In the present invention, a reinforcing member such as a wire chafer or a nylon chafer can be disposed on the bead portion 2. However, in order to reduce cost, reduce weight, and improve productivity, the reinforcing member is arranged. When not provided, it is preferable that the radius of curvature r of the outer surface of the tire measured at the normal position a is 4 to 8 times the flange radius R of the standard rim 8.
[0028]
When the radius of curvature r is less than 4 times the radius R of the flange, the tire bead portion 2 is greatly deformed by falling, and the rim reaction force is concentrated in the vicinity of the separation point b of the tire 1 so that the bead portion 2 This is because cracks are likely to be generated on the outer surface, and if the gauge of the rubber chafer 10 is increased in order to suppress crack generation, this tends to cause a separation failure. On the other hand, if the radius of curvature r is more than 8 times the flange radius R, the deformation of the tire 1 at the time of load application becomes too large, and a crack failure occurs at the root where the rim flange 9 and the tire 1 are in contact, Because the tension acting on the carcass body 6 becomes extremely large, a separation failure is likely to occur on the carcass body 6 side, and the ply of the bead core 3 and the carcass 4 rubs against each other and the failure is likely to occur. is there.
[0029]
In addition, when the pneumatic tire of this invention is applied to large tires for construction vehicles, industrial vehicles, and the like that are used under high load conditions, the improvement in bead durability is particularly remarkable.
[0030]
The above description is merely an example of the embodiment of the present invention, and various modifications can be made within the scope of the claims.
[0031]
【Example】
Next, a pneumatic tire according to the present invention was prototyped and performance evaluation was performed, which will be described below.
Example 1
The tire of Example 1 is a pneumatic radial tire for construction vehicles having a bead section as shown in FIG. 1, a tire size of ORR 18.00R25, and a flatness ratio of 95%, and the distance h is 15 mm. The percentages of D2, D3, and D4 with respect to D1 were 189%, 167%, and 278%, respectively, and the radius of curvature r at the normal position a was 300 mm.
The standard rim had a size of 13.00 / 2.5 × 25, a bead seat angle of 5 °, a flange radius R of 38 mm, h / R × 100 of 39.5%, and an r / R ratio of 7.9. .
The other tire structures were constructed in substantially the same manner as ordinary pneumatic radial tire doors for construction vehicles.
[0032]
Conventional tire The conventional tire has a distance h of 9 mm, percentages of D2, D3 and D4 with respect to D1 are 250%, 190% and 300%, respectively, and a radius of curvature r at the normal position a is 80 mm. The tire has substantially the same configuration as that of the tire of Example 1 except that h / R × 100 is 23.7% and the r / R ratio is 2.1.
[0033]
(Performance evaluation)
After each of the test tires was attached to a standard rim to form a tire wheel, the tire state and shear strain with respect to the rim were examined when a tire internal pressure of 990 kPa and a tire load mass of 21600 kg were applied.
As a result, in the conventional tire, the bead portion rides on the rim flange edge, whereas in the tires of any of the embodiments, the ride on the flange edge is not allowed, and the tire at the flange edge portion. The shear strain generated on the outer surface of each of the example tires was reduced by about 30% as compared with the conventional example tires.
[0034]
In addition, as a result of investigating the presence or absence of cracks on the outer surface of the bead part after mounting each tire wheel on an actual vehicle and running on the paved road for about 1000 hours, occurrence of cracks was observed in the conventional tire. On the other hand, no cracks were observed in any of the tires of the examples.
[0035]
【The invention's effect】
According to the present invention, it is used in a pneumatic tire, particularly a construction vehicle or an industrial vehicle, in which shear strain generated on the outer surface of the bead portion of the tire is effectively suppressed between the rim flange and the bead portion durability is greatly improved. It is now possible to provide heavy duty radial tires.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a main part of a pneumatic tire according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Bead part 3 Bead core 4 Carcass 5 Side wall part 6 Ply main-body part 7 Ply folding | turning part 8 Standard rim 9 Standard rim flange
10 Rubber chafer
11 Ply folded end
12 outer rubber

Claims (5)

For pneumatic tires with a flatness ratio of 90% or more that are mounted on standard rims with bead seat angles of 5 ° or less.
A straight line (x) extending in the tire radial direction through the center of curvature (O) of the flange of the standard rim when the tire wheel is mounted on the standard rim and the unloaded tire wheel to which the maximum air pressure is applied is viewed in the cross section in the width direction. When the distance between the intersection position (Q) with the outer surface of the flange and the normal position (a) standing on the outer surface of the tire from the intersection position (Q) is h, and the flange radius of the standard rim is R,
The distance (h) is Ri range near the 28 to 45% of the flange radius (R),
The radius of curvature (r) of the tire outer surface measured at the normal line position (a) is 4 to 8 times the flange radius (R) of the standard rim, and the tire outer surface shape at the normal line position (a) is the tire width. a pneumatic tire according to claim Totsudea Rukoto to outward. The tire includes a bead core embedded in a pair of bead portions, a cord rubberized layer, a ply body portion extending from the crown portion to both bead portions through both sidewall portions, and an end portion of the ply body portion. A carcass having a ply turn-up portion that is turned back toward the outside in the tire width direction,
The distance from the tire outer surface position (c) to the thickness center position (d) of the ply turn-up portion measured on a straight line (m) passing through the center of curvature (O) of the flange and extending along the tire rotation axis direction is D1. ,
When the shortest distance between the separation point (b) of the tire from the rim when the maximum air pressure and the maximum load capacity are applied and the thickness center position (e) of the ply turn-up portion is D2, the shortest distance D2 is: The pneumatic tire according to claim 1, wherein the percentage with respect to the distance D1 satisfies a range represented by the following expression (1).
Record
130% ≦ D2 / D1 ≦ 230% ---- (1) Positioned on the straight line (n) extending along the tire width direction through the bisector (g) of the distance measured along the tire radial direction between the separation point (b) and the tire total width position (f) When the outer surface position of the tire to be performed is S,
The ply turn-up portion of the carcass has an edge position on the outer side in the tire radial direction from the tire outer surface position (S),
When the shortest distance between the tire outer surface position (S) and the thickness center position (i) of the ply turn-up portion is D3,
3. The pneumatic tire according to claim 2, wherein the shortest distance D <b> 3 satisfies a range in which a percentage with respect to the distance D <b> 1 is represented by the following expression (2).
Record
100% ≤D3 / D1≤170% ---- (2) A tire outer surface located on a straight line (n) extending along the tire width direction through a bisector (g) of the distance measured along the tire radial direction between the separation point (b) and the tire total width position When the position is S,
The carcass ply turn-up part has an edge position on the inner side in the tire radial direction from the tire outer surface position (S),
When the shortest distance between the tire outer surface position (S) and the thickness center position (j) of the ply main body is D4,
3. The pneumatic tire according to claim 2, wherein the shortest distance D <b> 4 satisfies a range in which a percentage with respect to the distance D <b> 1 is represented by the following expression (3).
Record
180% ≦ D4 / D1 ≦ 280% ---- (3) The pneumatic tire according to any one of claims 1 to 4 , wherein the tire is a heavy-duty tire used for a construction vehicle or an industrial vehicle.

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