JPH05278408A - Pneumatic flat tire - Google Patents

Abstract

PURPOSE:To effectively restrict hydroplaning during cornering operation, in the case of a flat tire having an annular recession formed by wholly recessing the cross directional center part of a crown part inward in the radial direction. CONSTITUTION:If an annular recession 35 is displaced in a waveform in the cross direction of a crown part 15, the annular recession 35 is partly placed in the rotational outside from the cross directional center part (the tread area is increased during the cornering operation), and drain is performed at this part. Moreover, it becomes hard that water enters the tread because a place where the dynamic water pressure becomes highest during cornering operation is continuously fluctuated in the cross direction.

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 an aspect ratio of 50 or less.

[0002]

2. Description of the Related Art Conventional pneumatic flat tires are known, for example, those described in Japanese Utility Model Publication No. 50-21203. This one comprises 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, and the width direction of the crown portion. The carcass layer, the breaker layer, and the tread in the central portion are entirely recessed inward in the radial direction to form an annular recess in the central portion in the width direction of the crown portion. Then, by using such an annular recess as a passage for drainage, the drainage performance is improved, but such an annular recess is a tire whose drainage performance is deteriorated due to its wide width, particularly the flatness ratio. It is recommended to install it on a pneumatic tire having a value of 50 or less.

[0003]

In such a conventional pneumatic tire, since the annular recess extends straight in the vicinity of the center in the width direction of the tire, that is, extends in the circumferential direction, it is possible to drive straight ahead. The effect of suppressing hydroplaning in Example 1 is sufficient, but the effect of suppressing hydroplaning during cornering is still insufficient. The reason is that during cornering, the contact area on the outside of the turning increases from the center of the tire in the width direction, while the contact area on the inside of the turning decreases from the center in the width direction, and the overall contact shape becomes a substantially triangular shape. Because the annular recess that performs drainage is located only near the center of the tire in the width direction,
This is because it is not possible to perform drainage on the outside of the turning in which the ground contact area, which has a large influence on the hydroplaning suppression performance, is increased. Moreover, if the annular recess extends straight, the water pressure in a part of the annular recess becomes considerably high during running on cornering, so that water easily enters the ground contact surface from the part, that is, the tire and the road surface. This is because water will infiltrate during the period.

It is an object of the present invention to provide a pneumatic flat tire capable of effectively suppressing hydroplaning both during straight running and cornering.

[0005]

The object of the present invention is to provide a toroidal carcass layer, a belt layer formed of two or more belt plies radially outward of the crown portion of the carcass layer, and a belt layer. And a tread arranged radially outside, and by denting the carcass layer, the belt layer and the tread in the central portion in the width direction of the crown portion inward in the radial direction as a whole, the crown portion at the time of normal internal pressure filling is formed. The flatness ratio is 50, which forms an annular recess with a distance of 10 to 15 mm from the straight line connecting the outer surfaces of the maximum diameter parts located on both sides in the width direction to the deepest part.
In the following pneumatic flat tire, the pneumatic flat tire is mounted on a regular rim and filled with regular internal pressure,
Further, assuming that the ground contact width of the tread when a load of 80% of the normal load is applied is S, the annular recess is displaced in the width direction of the crown portion to a waveform whose amplitude P is 0.35 times or less than the ground contact width S. In addition, it can be achieved by setting the number of times of waviness of the annular recess to 7 or less.

[0006]

Now, assume that after the tire is filled with the internal pressure, the tire is run straight at high speed. At this time, if this tire is a wide flat tire having an aspect ratio of 50% or less,
Although the drainage property of the central portion in the width direction is deteriorated, as in the present invention, the carcass layer, the belt layer and the tread in the substantially central portion in the width direction of the crown portion of the tire are dented inward in the radial direction as a whole. When filling with internal pressure,
If a distance from the straight line connecting the outer surfaces of the maximum diameter portions located on both sides in the width direction of the crown portion to the deepest portion is formed to be an annular recess having a diameter of 10 mm to 15 mm, the annular recess has a straight running shape. It becomes a drainage passage, and the hydroplaning suppression performance when going straight up increases to a practical value. next,
When cornering such a tire, the contact area on the outside of the turning increases from the center in the width direction of the tire, while the contact area on the inside of the turning decreases from the center in the width direction, and the overall contact shape becomes a substantially triangular shape. However, since the annular recess that performs the drainage function is displaced in a wavy shape in the width direction of the crown portion as described above, the annular recess is partially located on the outside of the turning that greatly affects the hydroplaning suppression performance. As a result, drainage is also performed in the ground contact surface on the outside of the turn, and hydroplaning during cornering travel is effectively suppressed. Moreover, if the annular recess is undulatingly displaced in the width direction of the crown portion as described above, the position where the hydrodynamic pressure becomes highest during cornering constantly fluctuates in the width direction, so that water intrusion into the ground contact surface occurs. Therefore, hydroplaning during cornering is more effectively suppressed. If the amplitude P of the annular recess exceeds 0.35 times the ground contact width S, or if the number of corrugations of the annular recess exceeds 7, the effect of suppressing hydroplaning is reduced below that of a conventional tire. Its amplitude P is the ground contact width S
Must be less than 0.35 times and less than 7 times.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIGS. 1 and 2, reference numeral 11 denotes a pneumatic flat tire. The tire 11 includes a pair of bead portions 13 in which beads 12 are embedded, and a pair of sidewalls extending outward from the bead portions 13 in a substantially radial direction. Part 14 and
A substantially cylindrical crown portion 15 connecting the outer ends of the sidewall portions 14 in the radial direction is provided. The tire 11 is reinforced by a toroidal carcass layer 21 extending from one bead portion 13 to the other bead portion 13, and at least one carcass layer 21 is formed from one carcass ply 22 in this embodiment. It is configured. Both ends in the width direction of the carcass ply 22 are folded back around the bead 12 from the inner side in the axial direction to the outer side in the axial direction. A belt layer 29 made up of at least two belt plies 28 is arranged on the outer side of the carcass layer 21 in the crown portion 15 in the radial direction, and the cord embedded in these belt plies 28 improves the belt bending durability. Therefore, at least one belt ply 28 is made of organic fibers. Further, a tread 33 having a groove 32 such as a lateral groove is arranged on the outer side in the radial direction of the belt layer 29, and the thickness of the tread 33, that is, the tread gauge is 7 mm.
To 10 mm.

This tire 11 has a flatness, that is, a value obtained by dividing the tire height T by the tire width W and then multiplying by 100.
It is a flat tire with a width of 50 or less, and as a result, the ground contact width is wide, and the drainage performance is considerably poor at the center of the crown portion 15 in the width direction. Therefore, in this embodiment, the tire 11
Carcass layer at approximately the center in the width direction of the crown portion 15 of the
21, the belt layer 29 and the tread 33 are generally recessed inward in the radial direction to form an annular recess 35 continuously extending in the circumferential direction in the region, and the annular recess 35 serves as a drainage passage during traveling. This improves the hydroplaning suppression performance when driving straight ahead to a practical value. Here, in order to make the depression inward in the radial direction as described above, a portion of the vulcanization mold for vulcanizing the tire 11 that comes into contact with the center portion in the width direction of the crown portion 15 has an annular shape complementary to the annular depression 35. It suffices to provide a protrusion and press the center portion in the width direction of the crown portion 15 of the tire 11 at the time of vulcanization inward in the radial direction by such an annular protrusion. Thus, when the annular recess 35 is formed substantially in the center of the crown portion 15 in the width direction, the maximum diameter portion 3 of the tire 11 is formed on both sides in the width direction of the crown portion 15 located on both sides of the annular groove 35.
7 and 38 are formed respectively, the distance D between the straight line L connecting the outer surfaces of the maximum diameter portions 37 and 38 and the deepest portion 39 of the annular recess 35 is equal to the tire 11 When is filled with normal internal pressure, it is in the range of 10mm to 15mm.
The reason is that if the distance D is less than 10 mm, the annular recess
This is because the cross-sectional area of 35 is too small to improve the above-described hydroplaning suppression performance when going straight to a practical value, and when it exceeds 15 mm, the amount of bending of the belt layer 29 becomes too large. This is because the belt-to-belt shear strain becomes large and separation between belts may occur. Here, the carcass layer 21 and the belt layer 29
When the distance D is 10 mm to 15 mm as described above, the width direction distance F between the maximum diameter portions 37 and 38 is normally the tread width J because the shape changes gently when it is dented as described above. 15% to 50%.

Here, when the above-mentioned annular recess 35 extends straight, that is, extends in the circumferential direction, drainage on the outside of the turning which has a great influence on the hydroplaning performance during cornering as described above. However, hydrodynamic planing is likely to occur because the dynamic water pressure in a part of the annular recess 35 is so high that water easily enters the ground contact surface. For this reason, in this embodiment, the annular recess 35 that performs the drainage action is displaced in a waveform in the width direction of the crown portion 15. As a result, the annular recess 35 is partially located on the outside of the turning surface of the contact surface that has a great influence on the hydroplaning performance, and drainage is also performed inside the contact surface on the outside of the turning surface, and hydroplaning is effective. It will be suppressed. Moreover, the annular recess 35 has the crown portion 15 as described above.
If the water is displaced in the width direction, the position where the hydrodynamic pressure is highest during cornering constantly changes in the width direction, making it difficult for water to enter the ground contact surface and making hydroplaning more effective. It is suppressed by. Here, the annular recess 35 is largely displaced in the width direction, and its amplitude P, that is, the center C in the width direction of the annular recess 35 is most displaced to one side in the width direction and is most displaced to the other side in the width direction. If the distance in the width direction between the position C2 and the position C2 exceeds 0.35 times the ground contact width S, the effect of suppressing hydroplaning is less than the effect of suppressing a straight annular recess, as will be described later. Must be less than 0.35 times the width S. Here, the ground contact width S means the ground contact width of the tread 33 when the tire 11 is mounted on the regular rim of JATMA standard, the regular internal pressure is filled, and 80% of the regular load is applied. In addition, the number of corrugations of the annular recess 35 (from the position where the center C in the width direction of the annular recess 35 is most displaced to one side in the width direction to the position where it is most displaced to one side in the next width direction
Counted as 1 time, 1 time in this example), when it exceeds 7 times, the suppressing effect of hydroplaning becomes equal to or less than the suppressing effect of a straight annular recess as will be described later. Must be 7 or less.

Next, the first test example will be described. In this test, a conventional tire having an amplitude P of 0.00 times the ground contact width S (straight), a test tire 1 having an amplitude P of 0.10 times the ground contact width S, and an amplitude P of 0.20 times the ground contact width S Test tire 2 having an amplitude P of 0.30 times the ground contact width S, and test tire 4 having an amplitude P of 0.35 times the ground contact width S
And a comparative tire 1 having an amplitude P of 0.40 times the ground contact width S,
A comparative tire 2 having an amplitude P of 0.50 times the ground contact width S was prepared. Here, the size of each tire was 225 / 50ZR16, the distance D in the annular recess formed in the center of the crown in the width direction was 14 mm, the ground contact width S was 180 mm, and the number of corrugations was once. .. Then for each of these tires 2.0
After filling the internal pressure of kg / cm ² , a cornering was carried out with a radius of 100 m on a puddle with a depth of 10 mm while applying a load of 320 kg, and the minimum speed at which hydroplaning occurred was determined. Expressing the result as an index of 100 for the conventional tire, 102 for test tire 1 and 1 for test tire 2
04, 102 for test tire 3, 101 for test tire 4, 98 for comparative tire 1 and 85 for comparative tire 2. Here, the index 100 is actually 77km / h. Further, each of these tires was run straight under the same conditions as described above, and the minimum speed at which hydroplaning occurred at this time was also obtained. Expressing the result with the conventional tire as an index of 100, 101 for test tire 1, 102 for test tire 2, 101 for test tire 3, 100 for test tire 4 and 98 for comparative tire 1,
In comparison Taya 2, it was 95. Here, the index 100 is actually 125 km / h.

Next, Test Example 2 will be described. In this test, a conventional tire without waviness (straight),
Test tire 5 with one waving, Test tire 6 with five waving, and Test tire 7 with seven waving
And a comparative tire 3 having 8 times of waving were prepared.
Here, the specifications of each tire are the same as in Test Example 1 above, except that the amplitude P is 0.30 times the ground contact width S. Next, in the same manner as in Test Example 1 of such a tire, the minimum speed of hydroplaning generation during cornering was determined.
The results are shown by indexing the conventional tire with an index of 100: 102 for test tire 5, 104 for test tire 6, and 104 for test tire 7.
101 and 99 for Comparative Tire 3. Where index 100
Is actually 77 km / h.

[0012]

As described above, according to the present invention, hydroplaning can be effectively suppressed in both straight traveling and cornering traveling.

[Brief description of drawings]

FIG. 1 is a development view of a tread showing an embodiment of the present invention.

FIG. 2 is a sectional view taken along the line II of FIG.

[Explanation of symbols]

 11 ... Pneumatic flat tire 15 ... Crown 21 ... Carcass layer 28 ... Belt ply 29 ... Belt layer 33 ... Tread 35 ... Annular recess P ... Amplitude S ... Grounding width

Claims (1)

[Claims] 1. A toroidal carcass layer, a belt layer composed of two or more belt plies arranged radially outside a crown portion of the carcass layer, and a tread arranged radially outside the belt layer. By denting the carcass layer, the belt layer, and the tread in the substantially central portion in the width direction of the crown portion inward in the radial direction as a whole,
At the time of normal internal pressure filling, the flatness ratio of 50 to form an annular recess whose distance from the straight line connecting the outer surfaces of the maximum diameter portions located on both sides in the width direction of the crown portion to the deepest portion is 10 mm to 15 mm is 50. In the following pneumatic flat tires,
When the flat width of the pneumatic tire is mounted on a regular rim, the regular internal pressure is filled, and the ground contact width of the tread when a load of 80% of the regular load is applied is S, the annular recess is formed in the width direction of the crown portion. In addition, the pneumatic flat tire is characterized in that its amplitude P is displaced to a waveform of 0.35 times or less of the ground contact width S and the number of corrugations of the annular recess is set to 7 or less.