JP2588065B2 - 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 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 substantially central portion are entirely recessed radially inward to form an annular recess extending continuously in the circumferential direction substantially in the center in the width direction of the crown portion, and the annular recess is formed. A pair of land portions between the tread ends and a pair of land portions, each having one main groove extending in the circumferential direction and bent in a zigzag shape and a plurality of lateral grooves branching from the apex of the main groove and extending in the width direction. It is. The drainage performance is improved by using such an annular dent and the main groove as a passage for drainage. However, such an annular dent is formed in a central portion in the width direction of the crown portion for widening. It is good to install it on tires with reduced drainage performance, especially pneumatic tires with an aspect ratio of 50 or less.

[0003]

However, in such a conventional pneumatic tire, when traveling on a wet road surface, a part of the water that is going to enter between the land portions and the road surface is not covered by the water. Because it is discharged just before both lands through the main ditch,
The amount of water immediately before the contact area increases, and as a result, water penetrates deeply between the land portion and the road surface, so that the contact area of the tire decreases and the wet performance deteriorates.

[0004] It is an object of the present invention to provide a pneumatic flat tire that can improve wet performance by suppressing intrusion of water between a tire land portion and a road surface when traveling on a wet road surface.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a carcass layer having a toroidal shape, a belt layer disposed radially outside a crown portion of the carcass layer, and a belt layer disposed radially outside the belt layer. And a tread, and a carcass layer, a belt layer, and a tread at a substantially central portion in the width direction of the crown portion are entirely recessed inward in the radial direction. In a pneumatic flat tire having an aspect ratio of not more than 50, which forms an annular recess extending in a pair, a pair of land portions between the annular recess and the tread end are respectively arranged from the front in the rotation direction to the rear in the rotation direction. This can be achieved by forming a plurality of inclined grooves that are inclined so as to approach both ends in the width direction from the center in the width direction of the land portion.

[0006]

Now, it is assumed that the vehicle is running on a wet road surface with a tire filled with internal pressure. At this time, this tire
If the width of the tire is 50% or less, the drainage property at the center in the width direction is deteriorated. However, as in the present invention, the carcass layer, the belt layer, and the tread at the substantially center in the width direction of the crown portion of the tire are removed. If the whole is radially inwardly recessed and an annular recess extending continuously in the circumferential direction is formed substantially at the center of the crown in the width direction, the annular recess becomes a passage and becomes the center of the crown in the width direction. Water that tends to enter between the part and the road surface is discharged, and wet performance is improved.
At this time, water also tries to enter between a pair of land portions defined between the annular recess and the tread edge and the road surface, but this water is generated by a plurality of inclined portions formed on these land portions. Exhausted through the groove. Here, since these inclined grooves are inclined so as to approach both ends in the width direction from the center in the width direction of each land portion from the front in the rotation direction of the tire to the rear in the rotation direction, water is fan-shaped in front of each land portion. In other words, a part of the water outside the land portion in the width direction is diagonally outside the land portion, and a part of the water inside the land portion in the width direction is diagonally inside (the annular concave portion). Immediately before). As a result, the amount of water immediately before the contact area (land portion) of the tire decreases, the amount of water entering between the land portion and the road surface decreases, and wet performance improves.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings. 1 and 2, reference numeral 11 denotes a pneumatic flat tire. The tire 11 has a pair of bead portions 13 in which beads 12 are respectively buried, and a pair of sidewalls extending radially outward from the bead portions 13. Part 14
And a substantially cylindrical crown portion 15 connecting the radially outer ends of the sidewall portions 14 to each other. The tire 11 is reinforced by a carcass layer 21 having a toroidal shape extending from one bead portion 13 to the other bead portion 13. The carcass layer 21 is formed of at least one carcass ply 22 in this embodiment. It is configured. 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 is disposed radially outside of the belt layer 29, and the thickness of the tread 33, that is, the tread gauge is in the range of 7 mm to 10 mm.

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 to form an annular recess 35 continuously extending in the circumferential direction at the portion, and the annular recess 35 is used as a drainage passage when traveling on a wet road surface. By doing so, the wet performance is improved.
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 the 35 is formed, the maximum diameter portions 37 and 38 of the tire 11 are formed on both sides of the annular groove 35, respectively, and a straight line L connecting the outer surfaces of the maximum diameter portions 37 and 38 is formed. And the deepest portion 39 of the annular recess 35 is the distance D
When is filled with the normal internal pressure, it is preferably in the range of 10 mm to 15 mm. The reason is that the distance D is 10 mm
If it is less than 15 mm, the cross-sectional area of the annular recess 35 is too small to sufficiently improve the above-mentioned wet performance, and if it exceeds 15 mm, the amount of bending of the belt layer 29 becomes too large and the belt This is because interlayer shear strain increases and separation between belts may occur. Even when the tire 11 is filled with the normal internal pressure and travels at high speed, most of the annular recess 35 remains as a recess. Here, when the carcass layer 21 and the belt layer 29 are depressed as described above, their shapes gradually change. Therefore, when the distance D is 10 mm to 15 mm as described above, the distance between the maximum diameter portions 37 and 38 is reduced. Is 15% of the normal tread width J
From 50%.

As described above, when the annular recess 35 is formed substantially at the center of the crown portion 15 in the width direction, the crown portion 15 between the annular recess 35 and the tread ends 41 and 42 is continuous in the circumferential direction. And a pair of land portions 43 and 44 having a rib shape extending in a vertical direction are defined. Here, when the tire 11 travels on a wet road surface, water also invades between the pair of land portions 43 and 44 and the road surface and the wet performance is reduced. , 44, a plurality of inclined grooves 45, 46, 47, 48 extending linearly and equidistant in the circumferential direction are formed on the outer surface, and these inclined grooves 45, 46, 47, 48 are rotated in the rotation direction (arrows). Direction) Each land 4
In order to approach both ends in the width direction from the center in the width direction of 3 and 44, in detail, regarding the inclined grooves 45 and 48, the outer ends in the width direction from the center in the width direction of the land portions 43 and 44 (sides close to the tread ends 41 and 42) , While the inclined grooves 46 and 47 extend from the widthwise center of the land portions 43 and 44 to the widthwise inner ends (annular recesses 35 and 44).
(Closer to the side). As a result, the water that tries to enter between the land 43, 44 and the road surface,
Land part by the inclined grooves 45, 46, 47, 48 inclined as described above
Dispersed in a fan shape in front of 43, 44, that is, part of the water outside the width direction of each land portion 43, 44 is landed 43, 44 by the inclined grooves 45, 48.
Part of the water inside the land portions 43 and 44 in the width direction is discharged diagonally inside (immediately before the annular recess 35) by the inclined grooves 46 and 47. As a result, the amount of water immediately before the contact area (land portions 43 and 44) of the tire 11 decreases, and the land portion 43 and
The amount of water that tries to penetrate between the 44 and the road surface is reduced, improving wet performance. In this embodiment, the inclined grooves 45 and 46 and 47 and 48 are out of phase in the circumferential direction by 1/2 pitch, and the inclined angle A of the inclined grooves 45 and 47 with respect to the tire equatorial plane Q is: The inclined grooves 46 and 48 are smaller than the inclined angle B with respect to the tire equatorial plane Q.

Next, test examples will be described. In this test, a conventional tire having a linear main groove extending in the circumferential direction in both land portions and a test tire having an inclined groove formed in both land portions as shown in FIG. 1 were prepared. Here, the size of each tire was 335/35 R17. Then, after filling the inner pressure of 2.5 kg / cm ² in each of these tires, and measuring the peak μ while traveling wet road surface at 50 km / h and mounted on the trailer to be towed, wet μ index and the average value Was converted to
The result was that the index was 100 for the conventional tire, but the wet performance was improved to 108 for the test tire. Here, the wet μ index of 100 is the peak μ
The average value of the index was 0.83.

FIG. 3 is a diagram showing a second embodiment of the present invention. In this embodiment, the annular recess 35 is
Is shifted from the tire equatorial plane Q to the tread edge 42 side. In addition, this shift amount is the tread width J.
There is no problem if it is within 20%. In this embodiment, the inclination angles of the inclined grooves 51 and 52 formed on the land portion 50 with respect to the tire equatorial plane Q are both the same.
The inclination angle of the tire with respect to the equatorial plane Q of 4, 55 is made smaller. Here, the tire 11 having such an inclination angle is
In order to improve the drainage performance and improve the turning performance of the land 53, it is preferable to mount the land 53 so that the land 53 comes to the outside of the mounting that receives a large lateral force during turning.

FIG. 4 is a diagram showing a third embodiment of the present invention. In this embodiment, an inclined groove formed in the land 57
The widthwise inner ends of 58 and 59 and the widthwise inner ends of the inclined grooves 61 and 62 formed in the land portion 60 intersect and are continuous. In this embodiment, the inclined grooves 58, 59, 61, 62
Are the same with respect to the tire equatorial plane Q.

In the above embodiment, the inclined groove 4
Although the case where 5, 46, 47, and 48 extend linearly has been described, in the present invention, these inclined grooves are inclined with respect to the tire equatorial plane Q from the center in the width direction of the land portion toward both ends in the width direction. May be curved so as to increase. Further, in the above-described invention, the thickness of the tread 33 is set to be substantially equal in the entire width of the crown portion 15, but in the present invention, the thickness of the tread 33 at the portion of the annular recess 35 is changed to the thickness of the other portions. You may make it thinner, for example, as it approaches the deepest part 39. Further, in the present invention, the inclination angle of the inclined groove formed outside in the width direction of each land portion with respect to the tire equatorial plane Q is smaller than the inclination angle of the inclined groove formed inside in the width direction with respect to the tire equatorial plane Q. Conversely, the inclination angle of the inclined groove formed on the inner side in the width direction of each land portion with respect to the tire equatorial plane Q may be smaller than the inclination angle of the inclined groove formed on the outer side in the width direction with respect to the tire equatorial plane Q. Good.

[0014]

As described above, according to the present invention, it is possible to suppress the intrusion of water between the tire land portion and the road surface when the vehicle is running on a wet road surface and improve the wet performance.

[Brief description of the drawings]

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

FIG. 2 is a meridian sectional view of the tire showing the first embodiment of the present invention.

FIG. 3 is a development view of a tread showing a second embodiment of the present invention.

FIG. 4 is a development view of a tread showing a third embodiment of the present invention.

[Explanation of symbols]

 11 ... pneumatic flat tire 15 ... crown 21 ... carcass layer 29 ... belt layer 33 ... tread 35 ... annular recess 41, 42 ... tread end 43, 44 ... land 45, 46, 47, 48 ... inclined groove

Continuation of the front page (72) Inventor Isao Akimoto 1-4-1 Chuo, Wako-shi, Saitama Prefecture Honda R & D Co., Ltd. (56) References JP-A-59-81203 (JP, A) Jpn. (JP, U) Japanese Utility Model Showa 51-29504 (JP, U) Japanese Utility Model Showa 46-1041 (JP, Y1)

Claims (1)

(57) [Claims] 1. A carcass layer having a toroidal shape, a belt layer disposed radially outside a crown portion of the carcass layer, and a tread disposed radially outside the belt layer.
An annular ring extending substantially circumferentially at the center in the width direction of the crown by substantially recessing the carcass layer, the belt layer, and the tread at the substantially center in the width direction of the crown inward in the radial direction. In a pneumatic flat tire having a flattening rate of not more than 50 in which a dent is formed, a pair of land portions between the annular dent and the tread end, respectively, as each goes from the front in the rotation direction to the rear in the rotation direction. A pneumatic flat tire characterized by forming a plurality of inclined grooves that are inclined so as to approach both ends in the width direction from the center in the width direction.