JPH04362406A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To prevent increasing heat and rolling resistance of a bead, inhibiting separation in the vicinity of the radial outside end of an outside ply which is arranged axially outside of the bead and restrain ozone crack to the recess of a tire side and the irregularity of a side wall. CONSTITUTION:The first recess 36 is formed on the outside surface 34 of a tire between the radial outside end 32 of the turn section 20 of a carcass ply 16 in a pneumatic radial tire 10 and the maximum width position M of the tire. The second recess 40 shallower than the first recess 36 is formed outside of the first recess 36, and constructed of an annular groove which is continuously extended in a peripheral direction.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire with improved bead durability.

0002

[Prior Art] Generally, when a pneumatic radial tire is loaded with a load, the sidewall portion on the ground contact side is deflected by the reaction force of the load from the road surface, which causes the folded portion of the carcass ply to bend outward in the radial direction. Large compressive strain occurs at the edges. Here, since the cut end of the cord buried in the carcass ply is exposed at the radial outer end of the folded part, compressive strain is generated at the radial outer end of the folded part as described above. Repeated action may cause cracks in the rubber near the radially outer ends of the folds, eventually leading to separation.

Conventionally, in order to prevent such folded end separation, the rubber height of the bead feeler is increased, or a reinforcing ply is placed outside the folded part in the axial direction along the folded part, and the bending at the bead part is prevented. It has been proposed to suppress the

However, in such conventional pneumatic radial tires, the bending rigidity of the bead portion is high and the weight is also large, so the bead portion generates heat during running and the rolling resistance of the tire increases. There is a problem with storing it away. In addition, in the latter case, there is also a problem that separation occurs at the folded portion of the reinforcing ply and in the vicinity of the outer end in the radial direction of the reinforcing ply.

[0005] As shown in FIG. 8(A), a pneumatic tire that improves this problem is constructed by combining outer ends 50A and 52A of the carcass 50 or the bead reinforcing layer 52 with an end 52A located on the outer side in the radial direction; A pneumatic tire is known in which a recess 54 is formed along the tire circumferential direction on the outer surface of the tire between the maximum axial width position of the tire.

[0006]

[Problems to be Solved by the Invention] However, in this pneumatic tire, a convex part is provided in the vulcanization mold to form a concave part, and it is necessary to form a deep concave part to improve bead durability. In this case, it is necessary to enlarge the convex part of the vulcanization mold. However, when the convex part of the vulcanization mold is made larger, the carcass ply near the convex part becomes smaller inside the vulcanization mold.
It is easily deformed into a concave shape by being pressed by the convex portion.

[0007] Therefore, after being removed from the vulcanization mold,
Even before the internal pressure is filled, the carcass line is deformed into a concave shape at a position corresponding to the concave portion on the outer surface of the tire. Therefore, when internal pressure is filled in this state, the air pressure causes the carcass ply to approach its natural equilibrium shape, thereby correcting the concave portion of the carcass line. That is, a local curvature change occurs that becomes convex toward the tire side. Due to this local curvature change, tensile strain occurs on the rubber near the concave part of the carcass line, that is, on the rubber surface of the concave part of the tire side part, causing wrinkle-like cracks and
So-called ozone cracks are likely to occur, and when deep recesses are provided intermittently in the circumferential direction, there are problems in that unevenness occurs in the sidewall portion depending on the presence or absence of the deep recesses.

[0008] In consideration of the above facts, the present invention prevents heat generation and an increase in rolling resistance in the bead portion, while preventing an increase in the heat generation and rolling resistance in the bead portion, while improving the outer ply arranged on the axially outer side of the bead, for example, the folded portion of the carcass ply, and the radial direction of the reinforcing ply. Separation near the outer end can be prevented, and
An object of the present invention is to provide a pneumatic radial tire capable of suppressing ozone cracks in concave portions of tire side portions and unevenness of sidewall portions.

[0009]

In the present invention as set forth in claim 1, at least one of the layers in which metal cords are arranged in a radial direction is provided.
A toroidal carcass consisting of a toroidal carcass, a pair of bead cores embedded in the radially inner end of the carcass, and the carcass layer is wound up from the axially inner side to the outer side around both bead cores, and the tip portion remains at a relatively low position. a winding part of the carcass, at least one bead cord reinforcing layer disposed close to the winding part and at least along the axially outer side of the winding part, the radially outer end of which remains at a relatively low position similar to the carcass winding end; The outer surface of the tire, including the outer rubber covering around the carcass and bead reinforcing layer, between the outer end of the carcass or bead reinforcing layer that is more radially outward and the maximum axial width position of the tire. A pneumatic radial tire in which a first recess is formed continuously or intermittently along the circumferential direction of the tire, wherein at least a part of the first recess is overlapped with the first recess and It is characterized by having a shallow second recess.

[0010] Further, in the present invention as set forth in claim 2, a toroidal carcass comprising at least one layer in which metal cords are arranged in a radial direction, and a pair of bead cores embedded in the radially inner end of the carcass are provided. The winding part of the carcass layer is rolled up from the inside in the axial direction to the outside around the carcass layer, and the tip part stays at a relatively low position, and the outer covering rubber that covers the circumference of the carcass, and the outer part in the radial direction of the carcass. A pneumatic radial tire in which a first recess is formed continuously or intermittently along the circumferential direction of the tire on the outer surface of the tire between the end and the maximum axial width position of the tire, wherein the first recess is formed continuously or intermittently along the circumferential direction of the tire. The invention is characterized in that it includes a second recess that is shallower than the first recess and that is provided at least partially overlapping the recess.

[0011] Further, in the present invention as set forth in claim 3, the depth of the first recess is equal to the distance from the imaginary line on the outer surface of the tire to the main body of the carcass at that position without the first recess. It is characterized by more than one third.

[0012] In the present invention as set forth in claim 4, the depth of the second recess is equal to the distance from the imaginary line on the outer surface of the tire to the main body of the carcass at that position without the second recess. If the number exceeds one-third, a third recess is provided that at least partially overlaps the second recess and is shallower than the second recess.

[0013]

[Operation] When there is a convex part in the vulcanization mold to form the first concave part on the outer surface of the tire, by vulcanization molding,
The causes of the formation of concave portions in the carcass line are as follows.

That is, when providing the first recess in the tire bead, a convex part is provided in the vulcanization mold, and the convex part pushes away the rubber in the bead of the green tire within the vulcanization mold. The rubber is made to flow to form the recesses. Therefore, the first
If the depth of the concave portion is deep, the amount of rubber that must escape locally increases due to the convex portion of the vulcanization mold. Therefore, some of the rubber pushes the ply cord into the inside of the tire. As a result, a carcass line recess is formed near the first recess.

Therefore, in the present invention, by providing the second recess shallower than the first recess so that at least a portion thereof overlaps with the first recess, for example, the second recess is provided outside the first recess. The relatively shallow second recess may be formed in a step shape, or the second recess and a relatively deep first recess having a width exceeding the radial width of the second recess may be formed circumferentially. By forming them continuously, changes in the depth of the recesses that occur in the tire are alleviated. As a result, in the vulcanization mold,
The convex portion of the vulcanization mold reduces the local amount of rubber that is displaced. That is, in the present invention, by providing the second recess shallower than the first recess so that at least a portion thereof overlaps with the first recess, localized rubber that pushes the ply cord into the inside of the tire during vulcanization molding is provided. The flow of the carcass line becomes smaller, causing depressions in the carcass line. Therefore, the tensile strain on the rubber surface of the first concave portion of the tire side portion during load rolling due to the concave portion of the carcass line is reduced, and ozone cracks in the first concave portion of the tire side portion can be suppressed. can. Further, when the first recesses are provided intermittently in the circumferential direction, unevenness of the sidewall portion can be suppressed.

[0016] The first concave portion also prevents heat generation and an increase in rolling resistance at the bead portion, while also preventing an increase in heat generation and rolling resistance at the bead portion, while also preventing an increase in heat generation and rolling resistance at the bead portion. Separation near the edges can be prevented.

[0017] If the depth of the first recess exceeds one-third of the distance from the imaginary line on the outer surface of the tire to the main body of the carcass without the first recess at that position, the carcass Since the tensile strain on the rubber surface of the first recess caused by the line recess becomes relatively large, it is necessary to provide the second recess. In addition, if the depth of the second recess exceeds one-third of the distance from the virtual line on the outer surface of the tire to the main body of the carcass without the second recess at that position, the recess on the carcass line Since the tensile strain on the rubber surfaces of the first and second recesses caused by this becomes relatively large, it is necessary to further form a third recess.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS. 1 to 3.

As shown in FIG. 1, the pneumatic radial tire 10 has a pair of beads 12 and a toroidal carcass layer 14, which extends in the radial direction (meridian direction). It is composed of at least one carcass ply 16 in which a large number of cords are embedded.

The carcass ply 16 has one bead 12
bead 1 by extending from to the other bead 12.
The main body part 18 is located on the inside in the axial direction of 2, and the bead 12 is folded outward around the bead 12, and along the main body part 18,
That is, it is comprised of a folded part 20 as an outer ply that extends substantially parallel to the main body part 18 and is located on the axially outer side of the bead 12.

A belt layer 24 consisting of at least two belt plies 22 is disposed on the outside of the carcass layer 14 in the radial direction, and within these belt plies 22 are provided a large number of reinforcing cords inclined with respect to the circumferential direction. are buried, and these reinforcing cords cross each other in adjacent belt plies 22.

Furthermore, on the radially outer side of the belt layer 24,
Top tread 28 in which grooves 26 such as main grooves and lateral grooves are formed
However, side treads 30 are further arranged on both axially outer sides of the carcass layer 14, respectively. When such a tire 10 is run while being loaded with a load, the sidewall portion of the tire 10 on the ground contact side bends due to the reaction force from the road surface, and as a result, stress is generated inside the bent portion. , this internal stress is applied to the radially outer end 3 of the folded portion 20.
2 to cause large compressive strain.

For this reason, in this embodiment, a first recess 36 is formed in the tire outer surface 34 between the radially outer end 32 of the folded portion 20 and the tire maximum width position M. This first recess 36 can block the internal stress occurring on the radially outer side of the first recess 36 , thereby reducing the influence of the internal stress on the radially outer end 32 of the folded portion 20 . It is expected to be reduced.

Further, as shown in FIG. 3, in this embodiment, these first recesses 36 are composed of annular grooves extending continuously in the circumferential direction, and the average width of the first recesses 36 is It is preferable that W1 is 1.5 mm or more. The reason for this is that if it is less than 1.5 mm, when the tire 10 is rolling under a load, the first recess 36 will be damaged by a load that is one-half or less of the normal load.
This is because the side walls 38 of the two sides begin to come into contact with each other, and the effect is not fully exhibited.

Here, the region where the internal stress is cut off is the region radially outward from the first recesses 36 and overlapping with the first recesses 36, so in this embodiment, the region shown in FIG. As shown in FIG. The first recess 36 is deep enough to intersect the curve extending parallel to the first recess 36
The deepest part of the curve B is penetrated to a position deeper than that of curve B, thereby expanding the area where internal stress is blocked and increasing the blocking effect.

Further, when the shortest distance from the radially outer end 32 of the folded part 20 to the main body 18 is A, the distance from the radially outer end 32 of the folded part 20 to the radially outer end 32 The distance C on the curve B to the side wall 38 of the recess 36 of No. 1 must be less than or equal to 2.5 times the distance A. The reason for this is that the degree of influence on the compressive strain at the radially outer end 32 is greater as the internal stress of the portion closer to the radially outer end 32 of the folded portion 20 is larger, so that the distance C is 2.5 times the distance A. Internal stress in areas that are separated by a distance of less than Although it can be effectively blocked,
Since the internal stress in a part that is more than 2.5 times away from the radially outer end 32 can hardly affect the radially outer end 32, even if the internal stress in the radially outer part than this part is cut off, the radially outer end 32 This is because the compressive strain in can hardly be reduced.

For this reason, the compressive strain in the vicinity of the radially outer end 32 of the folded portion 20 is effectively reduced.
Separation at this location is prevented. In this embodiment, the bending rigidity of the bead portion does not increase, the tire weight does not increase, and heat generation and rolling resistance at the bead portion do not increase. Note that the distance C may be thin as long as it is a positive value other than 0, that is, as long as the cut surface of the cord located at the radially outer end 32 is covered with rubber.

Furthermore, as shown in FIG. 3, in this embodiment, a second recess 36 having an average width W2 (W2≧1.5W1) and shallower than the first recess 36 is formed outside the first recess 36 of the side tread 30. A recess 40 is formed, and this second recess 4
0 is composed of an annular groove extending continuously in the circumferential direction.

This is because when there is a convex part for forming the first concave part 36 in the vulcanization mold, the first concave part of the tire side part is caused by the concave part of the carcass line caused by this convex part. This is to reduce tensile strain on the rubber surface of the recess 36.

That is, when providing the first recess 36 in the tire bead, a protrusion is provided in the vulcanization mold, and this protrusion pushes away the rubber in the bead of the green tire within the vulcanization mold. , the first recess 36 is formed by causing the rubber to flow. Therefore, when the depth of the first recess 36 is deep, in particular, the depth D1 of the first recess 36 is the distance between the carcass ply 16 and the tire outer surface imaginary line without the first recess 36 at that position. If the distance to the main body portion 18 exceeds one-third of the distance D3, the amount of rubber that must escape locally increases due to the convex portion of the vulcanization mold. Therefore, a portion of the rubber pushes the main body portion 18 of the carcass ply 16 into the inside of the tire. As a result, a carcass line recess 37 (imaginary line in FIG. 2) is generated near the first recess 36 which is deep.

Therefore, in this embodiment, by providing a second recess 40 shallower than the first recess 36 in an annular shape outside the first recess 36, changes in the depth of the recess caused in the tire are alleviated. I'm letting you do it. This reduces the local amount of rubber that is displaced within the vulcanization mold by the convex portion of the vulcanization mold. For this reason, carcass ply 16
The localized rubber flow that pushes the main body 18 into the inside of the tire is also reduced, making it difficult for the recess 37 in the main body 18 of the carcass ply 16 to form. Therefore, the tensile strain on the rubber surface of the first recess 36 caused by the recess 37 of the carcass line is reduced, and ozone cracks in the first recess 36 can be suppressed.

Furthermore, the first recess 36 prevents heat generation and an increase in rolling resistance at the bead, while
Separation in the vicinity of the radially outer end 32 of the folded portion 20 of the carcass ply 16 located on the axially outer side of the bead can be prevented.

Note that as shown in FIG. 2, the second recess 4
0 from the tire outer surface 34 is the first recess 36
0.25 times or more and 0.75 times or less (0.25
D1≦D2≦0.75D1) is preferable.

Next, a second embodiment of the present invention will be explained. Incidentally, the same members as those in the first embodiment are given the same reference numerals and the explanation thereof will be omitted.

As shown in FIG. 4, in this embodiment, the radially outer end 3 of the folded portion 20 of the carcass ply 16
At least one reinforcing ply 48 is arranged on the outside of 2,
The folded portion 20 of the carcass ply 16 is reinforced. The reinforcing ply 48 or the folded portion 20 of the carcass ply 16 may extend to a high position near the tire maximum width position M, but in such a case, the first recess 36 and the second Each of the recesses 40 is formed near the tire maximum width position M.

Note that in the first and second embodiments, the first recess 36 and the second recess 40 are respectively formed of annular grooves, but instead of this, as shown in FIG. The first recess 42 may be formed into a block shape arranged in the circumferential direction at a predetermined interval, and the annular second recess 40 may be formed outside the first recess 42 . In this case, unevenness of the sidewall portion caused by the first recess 42 can be suppressed.

Furthermore, as shown in FIG. 6, the second recess 4
4 may be shaped like blocks lined up in the circumferential direction at predetermined intervals, and a first recess 46 elongated in the radial direction may intersect with the circumferential center of the second recess 44 .

Furthermore, as shown in FIG. 7, the second recess 4
When the depth D2 of 0 becomes one-third or more of the depth D3 of the main body 18 of the carcass ply 16, the second recess 40
However, since the tensile strain on the rubber surface of the concave part of the tire side part caused by the concave part of the carcass line cannot be sufficiently reduced, it is necessary to provide the third concave part 41. Tensile strain on the rubber surface of the concave portion of the tire side portion due to the concave portion is reduced, and ozone cracks in the concave portion of the tire side portion can be suppressed. (Test Example) As shown in FIG. 8(A), Comparative Example 1 tire in which only an annular recess 54 was formed on the outer surface of the tire, and as shown in FIG. 8(B), , Test Example 1 tire in which a shallower annular recess 55 was formed is shown in Table 1.
Specifications (the size of each tire is 11/70R22.5)
Each tire was filled with an internal pressure of 7.5Kg/cm2, a load of 2500Kg was applied, and the speed was 5.
The crack length at the end of the bead ply is measured after traveling 150,000 km with a drum placed outdoors at 0 km/h. In the case of this test example, the carcass ply end 50A is located radially outward from the reinforcing ply end 52A, so the crack length of the carcass ply end 50A was measured, and the state of occurrence of ozone cracks was investigated. are listed in Table 1.

As shown in FIG. 9(A), Comparative Example 2 tire has only block-shaped recesses 56 arranged at intervals in the circumferential direction on the outer surface of the tire, and as shown in FIG. 9(B). , Test Example 2 tire in which recesses 57 shallower than the recess 56 were formed in the circumferential center of the recess 56 in a radially short-hand shape and arranged at intervals in the circumferential direction, and the specifications shown in Table 1 ( The size of each tire was 11/70R22.5), and each tire was filled with an internal pressure of 7.5Kg/cm2, a load of 2500Kg was applied, and the speed was 50Km/H.
After traveling 150,000 km on the drum, the unevenness of the sidewall portion was examined, and the results are listed in Table 1.

[0040]

[Table 1]

From the results shown in Table 1, it is clear that the pneumatic radial tire of the present invention is superior.

[0042]

[Effects of the Invention] Since the present invention has the above structure, heat generation and increase in rolling resistance at the bead portion can be prevented while
Separation can be prevented in the vicinity of the radial outer end of the outer ply arranged on the axially outer side of the bead, such as the folded part of the carcass ply or the radially outer end of the reinforcing ply. It has an excellent effect of suppressing unevenness.

[Brief explanation of drawings]

FIG. 1 is a meridian cross-sectional view showing a pneumatic radial tire according to a first embodiment of the present invention.

FIG. 2 is an enlarged sectional view showing the vicinity of the outer ply of the tire shown in FIG. 1;

FIG. 3 is a side view of the tire shown in FIG. 1.

FIG. 4 is a sectional view similar to FIG. 2 showing a pneumatic radial tire according to a second embodiment of the present invention.

FIG. 5 is a side view similar to FIG. 3 showing a pneumatic radial tire according to another embodiment of the present invention.

FIG. 6 is a side view similar to FIG. 3 showing a pneumatic radial tire according to another embodiment of the present invention.

FIG. 7 is a meridional cross-sectional view showing a pneumatic radial tire according to another embodiment of the present invention.

8A is a meridian cross-sectional view showing a pneumatic radial tire of Comparative Example 1, and FIG. 8B is a meridian cross-sectional view showing a pneumatic radial tire of Test Example 1. FIG.

9A is a side view showing a pneumatic radial tire of Comparative Example 2, and FIG. 9B is a side view showing a pneumatic radial tire of Test Example 2. FIG.

[Explanation of symbols]

10 Pneumatic radial tires 12 Bead 16 Carcass ply 18 Main body 20 Outer ply 32 Radial outer end 34 Tire outer surface 36 First recess 38 Side wall 40 Second recess 41 Third recess 42 First recess 44 Second recess 46 First recess M Tire maximum width position

Claims (4)

[Claims] Claim 1: A toroidal carcass consisting of at least one layer in which metal cords are arranged in a radial direction, and a pair of bead cores embedded in the radially inner end of the carcass, which are arranged around both bead cores from the inside in the axial direction to the outside. a rolled-up part of the carcass layer that is rolled up toward the carcass layer and whose tip remains at a relatively low position; at least one bead cord reinforcing layer that remains at a relatively low position, and an outer rubber covering around the carcass and the bead reinforcing layer, and further radially outward at the outer end of the carcass or bead reinforcing layer. A pneumatic radial tire in which a first recess is formed continuously or intermittently along the tire circumferential direction on the outer surface of the tire between a certain end and the maximum axial width position of the tire, wherein the first recess is formed continuously or intermittently along the tire circumferential direction. A pneumatic radial tire comprising: a second recess that at least partially overlaps the first recess and is shallower than the first recess. 2. A toroidal carcass consisting of at least one layer in which metal cords are arranged in a radial direction, and a pair of bead cores embedded in the radially inner end of the carcass, which are arranged around both bead cores from the inside in the axial direction to the outside. The upper part of the carcass layer that is rolled up towards the carcass and whose tip remains at a relatively low position, and the outer covering rubber that covers the periphery of the carcass, and includes the radially outer end of the carcass and the maximum width in the axial direction of the tire. A pneumatic radial tire in which a first recess is formed continuously or intermittently along the circumferential direction of the tire on the outer surface of the tire between the positions of A pneumatic radial tire comprising: a second recess that is shallower than the first recess. 3. The depth of the first recess exceeds one third of the distance from the imaginary line on the outer surface of the tire to the main body of the carcass without the first recess at that position. The pneumatic radial tire according to claim 1 or claim 2, wherein: 4. When the depth of the second recess exceeds one third of the distance from the imaginary line on the outer surface of the tire to the main body portion of the carcass without the second recess at that position, 3. The pneumatic radial tire according to claim 1, further comprising a third recess that at least partially overlaps the second recess and is shallower than the second recess.