JP2588064B2 - Pneumatic flat tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic flat tire having an annular recess formed in a crown portion and having a flatness of 50 or less.

[0002]

2. Description of the Related Art As a conventional pneumatic flat tire, for example, a tire described in Japanese Utility Model Publication No. 50-21203 is known. This includes a toroidal carcass layer, a breaker layer arranged radially outside the crown portion of the carcass layer, and a tread arranged radially outside the breaker layer. The carcass layer, the breaker layer, and the tread in the central portion are entirely depressed inward in the radial direction, so that an annular depression is formed in the central portion in the width direction of the crown portion. And by making such an annular dent a passage for drainage, the drainage performance is improved. However, such an annular dent is used for tires whose drainage performance is reduced due to their wide width, especially for flatness. Is preferably provided for a pneumatic tire having a diameter of 50 or less.

[0003]

However, in such a conventional pneumatic tire, the radius near the deepest portion of the annular recess is smaller than the maximum diameter portions located on both sides in the width direction of the annular recess. At the time of grounding, a large tensile stress acts in the equatorial direction in the grounding surface, and as a result, a large strain is generated near the deepest portion of the annular dent, so that there is a problem that separation occurs between the belt plies at the site.

An object of the present invention is to provide a pneumatic flat tire that can effectively suppress separation between belt plies near the deepest portion of an annular recess.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a carcass layer having a toroidal shape, a belt layer which is disposed radially outside a crown portion of the carcass layer, and is composed of two or more belt plies; A tread arranged radially outward, and the carcass layer, the belt layer, and the tread substantially at the center in the width direction of the crown are entirely depressed radially inward, so that the crown portion at the time of normal internal pressure filling is formed. The flatness is 50 mm to form an annular dent whose distance from the straight line connecting the outer surfaces of the largest diameter parts located on both sides in the width direction to the deepest part is 10 mm to 15 mm.
The following pneumatic flat tire, wherein the rubber gauge between the belt plies at the deepest part of the annular recess is 1.5 to 2.0 times the rubber gauge between the belt plies at a position spaced inward in the width direction by 1/4 of the belt width from the belt end. This can be achieved by making the range twice as large.

[0006]

Suppose now that the tire is running at high speed after filling the tire with internal pressure. At this time, if the tire is a wide flat tire having a flattening ratio of 50% or less, drainage at the center in the width direction is deteriorated. By indenting the carcass layer, belt layer and tread entirely inward in the radial direction, from the straight line connecting the outer surfaces of the largest diameter portions located on both sides in the width direction of the crown portion at the time of normal internal pressure filling to the deepest portion If the annular recess is formed with a distance of 10 mm to 15 mm, the annular recess serves as a drainage passage during traveling, and the drainage property increases to a practical value. Also, at this time, since the radius near the deepest portion of the annular dent is smaller than the maximum diameter portion located on both sides in the width direction of the annular dent, a large tensile stress acts in the equator direction in the ground contact surface at the time of contact with the ground. Large distortion occurs near the deepest part of the annular dent. For this reason, in the present invention, the rubber gauge between the belt plies at the deepest part of the annular recess is in a range of 1.5 to 2.0 times the rubber gauge between the belt plies at a position away from the belt end by 1/4 of the belt width inward in the width direction. This makes it possible to disperse the distortion between the belt plies at the deepest part of the annular dent and suppress the occurrence of separation at the part without lowering the turning performance in the dry state.

[0007]

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 11 denotes a pneumatic flat tire. The tire 11 includes a pair of bead portions 13 in which beads 12 are respectively buried, and a pair of sidewall portions 14 extending substantially radially outward from the bead portions 13. And a substantially cylindrical crown portion 15 connecting the radially outer ends of the sidewall portions 14 to each other. And the tire
11 is reinforced by a toroidal carcass layer 21 extending from one bead portion 13 to the other bead portion 13, and this carcass layer 21 is composed of at least one carcass ply 22 in this embodiment. . Both ends in the width direction of the carcass ply 22 are folded around the bead 12 from the inside in the axial direction to the outside in the axial direction.
A belt layer 29 composed of at least two belt plies 28 is disposed radially outside the carcass layer 21 in the crown portion 15, and the cords embedded in these belt plies 28 improve the belt breaking durability. Therefore, at least one belt ply 28 is made of organic fibers. A tread 33 in which a groove 32 such as a main groove or a lateral groove is formed is disposed radially outside the belt layer 29. The thickness of the tread 33, that is, the tread gauge is 7 mm.
Range from to 10mm.

The tire 11 has a flatness factor, that is, a value obtained by dividing the tire height T by the tire width W and then multiplying by 100.
The flat tire has a width of not more than 50, and as a result, the contact width is wide, and the drainage property is considerably poor at the center in the width direction of the crown portion 15. Therefore, in this embodiment, the tire 11
Layer at the approximate center of the crown 15 in the width direction
21, the belt layer 29 and the tread 33 are entirely recessed inward in the radial direction, and an annular recess 35 extending continuously in the circumferential direction is formed at the portion, and the annular recess 35 is used as a drainage passage during traveling. This improves drainage to a practical value.
Here, in order to dent radially inward like this,
An annular projection complementary to the annular recess 35 is provided at a portion of the vulcanization mold for vulcanizing the tire 11 that contacts the center of the crown portion 15 in the width direction. The central portion in the width direction of the crown portion 15 may be pushed inward in the radial direction. In addition, in this embodiment, in order to reliably maintain such an annular recess 35 even when the internal pressure is charged and during high-speed running, a belt layer is formed at the center of the crown portion 15 in the width direction.
A narrow reinforcing layer 36 is arranged radially outward of 29. Here, a large number of organic fiber cords, for example, nylon cords extending in the circumferential direction are buried inside the reinforcing layer 36.
In this way, an annular recess is formed at the approximate center of the crown 15 in the width direction.
When 35 is formed, the maximum diameter portions 37, 38 of the tire 11 are provided on both sides in the width direction of the crown portion 15 located on both sides of the annular groove 35.
The distance D between the straight line L connecting the outer surfaces of the largest diameter portions 37 and 38 and the deepest portion 39 of the annular recess 35 is equal to the normal internal pressure of the tire 11. Is between 10 mm and 15 mm when is filled. The reason is that if the distance D is less than 10 mm, the sectional area of the annular recess 35 is too small to improve the drainage performance described above to a practical value, and if it exceeds 15 mm, This is because the amount of bending of the belt layer 29 becomes too large, and the shear strain between layers of the belt becomes large, which may cause separation between belts. Here, the carcass layer 21,
When the belt layer 29 is depressed as described above, its shape changes gradually, so that the distance D is from 10 mm as described above.
If it is 15 mm, the width direction distance F between the maximum diameter portions 37 and 38 is usually 15% to 50% of the tread width J. Further, in this embodiment, the deepest portion 39 of the annular recess 35 is located at the center in the width direction of the crown portion 15, that is, on the tire equatorial plane, but the deepest portion 39 is located at the tread width from the center of the crown portion 15 in the width direction. J of 20
Only% may be shifted inward and outward in the width direction.

In such a tire 11,
Since the annular dent 35 serves as a drainage passage during traveling, drainage is improved, but near the deepest portion 39 of the annular dent 35,
Since its radius is smaller than the radius of the maximum diameter parts 37 and 38, a large tensile stress works in the equator direction in the ground contact surface at the time of ground contact,
As a result, large distortion occurs near the deepest portion 39 of the annular recess 35. For this reason, in this embodiment, the rubber gauge G between the belt plies 28 at the deepest portion 39 of the annular recess 35 is changed from the belt end 41 to the belt ply 28 at a position 42 which is separated by 1/4 of the belt width B inward in the width direction. Rubber gauge H
It is 1.5 to 2.0 times thicker. Here, if the G / H value is less than 1.5, separation occurs between the belt plies 28 when the vehicle runs for a long time. On the other hand, when the G / H value exceeds 2.0, the in-plane This is because, since the belt rigidity is reduced, the side force is reduced, and as a result, the turning performance when traveling on a dry road surface is reduced to a practical value or less. Thus, the value of G / H
If it is in the range of 1.5 to 2.0, the distortion between the belt plies 28 at the deepest portion 39 of the annular recess 35 can be dispersed without lowering the turning performance at the time of dry, and the separation at this portion is effectively suppressed. You can do it. In this case, the rubber gauge is
Means the distance between the centers in the thickness direction.

Next, test examples will be described. In this test, a comparative tire 1 having the G / H value of 1.0,
Comparative tire 2 having a G / H value of 1.3, and a G / H value of 1.3.
Test tire 1 having a G / H value of 1.6, test tire 2 having a G / H value of 1.6, and test tire 3 having a G / H value of 2.0
And a comparative tire 3 having a G / H value of 2.1 and a comparative tire 4 having a G / H value of 2.2. here,
The size of each tire was 335/35 R17, and the distance D in the annular recess formed at the center in the width direction of the crown portion was 14 mm when each tire was filled with the normal internal pressure. Then, after filling the inner pressure of 2.5 kg / cm ² in each of these tires, while a load of 430kg on the drum at 90 km / h
We ran 17,000 km. During this run, the tires were given a slip angle so that the side force was 300 kg for only 30 seconds, and then straight ahead for the next 30 seconds. After running the above distance, each tire was dissected to examine the state between the belt plies near the deepest part of the annular dent. As a result, the separation between the belt plies occurred in the comparative tires 1 and 2, but the separation between the belt plies occurred in the test tires 1, 2, and 3 and the comparative tires 3 and 4. There was no. next,
Each tire was run on a safety walk at a speed of 50 km / h while giving a load of 645 kg and a slip angle of 0 to 10 degrees, and the side force at this time was measured. The results are shown in exponential notation.
00, 95 for Comparative Tire 2, 94 for Tire 1, 92 for Tire 2, and 92 for Tire 3, but practical values for Comparative Tires 3 and 4, ie, 90 or less. It dropped to 88 and 88 respectively. Where the index 1
00 was actually 666kgf.

In the above embodiment, the tread
The thickness of the tread 33 is substantially equal in the entire width of the crown portion 15 in the present invention.
The thickness of 33 is thinner than the thickness of other parts.
It may be made thinner as it approaches.

[0012]

As described above, according to the present invention, separation between belt plies near the deepest portion of the annular recess can be effectively suppressed.

[Brief description of the drawings]

FIG. 1 is a meridian sectional view of an embodiment of the present invention.

[Explanation of symbols]

 11 ... pneumatic flat tire 15 ... crown 21 ... carcass layer 28 ... belt ply 29 ... belt layer 33 ... tread 35 ... annular recess 37, 38 ... maximum diameter part 39 ... deepest part 41 ... belt end 42 ... position L ... straight line D: distance G: rubber gauge B: belt width H: rubber gauge

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-49-61803 (JP, A) JP-A-63-34204 (JP, A) JP-A-61-60304 (JP, A) 48806 (JP, U) Japanese Utility Model Showa 50-52602 (JP, U) JP-B 35-6053 (JP, B1)

Claims (1)

(57) [Claims] 1. A toroidal carcass layer, a belt layer comprising two or more belt plies disposed radially outside a crown portion of the carcass layer, and a tread disposed radially outside the belt layer. By having the carcass layer, belt layer and tread in the center in the width direction of the crown part generally radially inward,
At the time of normal internal pressure filling, the flattening rate is such that the distance from the straight line connecting the outer surfaces of the largest diameter parts located on both sides in the width direction of the crown part to the deepest part is an annular dent whose depth is 10 mm to 15 mm is 50 mm. The following pneumatic flat tires,
The rubber gauge between the belt plies at the deepest part of the annular recess is 1.5 to 2.0 times the rubber gauge between the belt plies at a position spaced inward in the width direction by 1/4 of the belt width from the belt end.
A pneumatic flat tire characterized by having a range twice as large.