Patent Application
20220063339
The present invention relates to an aircraft pneumatic tire.
In recent years, due to increasing environment consciousness, a reduction in fuel consumption of aircrafts has keenly been demanded. For the reduction in fuel consumption of the aircraft, a reduction in weight of the tires is very effective. A belt layer provided in a circumferential direction of a tread section for reinforcing the tread section of an aircraft tire is produced by stacking multiple belts including organic fibers, and a reduction in the number of the stacked belt layers is very effective for a reduction in the weight of the tire.
As a conventional aircraft pneumatic tire aimed at a reduction in weight, there has been known one in which the number of stacked belt layers is gradually decreased in going from a tire central region toward tire side part regions in the width direction of the tire (see Patent Document 1).
However, a decrease in the number of stacked belt layers leads to lowering in rigidity of the belt but an increase in tensile/compressive strain generated in the belt cord. Repeated taking off and landing of an aircraft would lead to accumulation of fatigue caused by tensile/compressive strain in the belt cord, resulting in lowered strength of the belt cord. Particularly, high compressive/tensile strain is generated in end portions in the width direction of the belt at the tire side part regions, leading to large lowering in the strength of the belt cord and causing influence on durability of the tire.
The side part regions of the tire are shorter in circumferential length of belt as compared to the central region of the tire, but, in the region to be grounded, the belt is extended such as to be approximately equal in diameter to the tire central region, and a large tensile strain is generated there. As a reaction to this, the belt is compressed before and after grounding. In addition, during high-speed running of the tires at the times of taking off and landing of an aircraft, a high centrifugal force is exerted on a side wall section, and the centrifugal force on the side wall section is received by the tire side part regions of the belt, so that high tensile input is generated in the tire side part regions of the belt.
As described above, there is a challenge of satisfying both a reduction in weight of the tire and enhancement of durability of the tire through enhancement of fatigue resistance performance of the belt cord, particularly enhancement of fatigue resistance performance at width directional end portions of the belt.
[Patent Document]
It is an object of the present invention to realize both a reduction in weight of an aircraft pneumatic tire and enhancement of durability of the tire through enhancement of fatigue resistance performance of a belt.
In order to achieve the above object, the present invention is an aircraft pneumatic tire including
a pair of bead cores,
a radial carcass including at least one carcass ply extending toroidally between both the bead cores, and
a belt layer that is disposed on an outer circumferential side of a crown region of the radial carcass and reinforces the radial carcass,
in which the belt layer includes
the first belt cord of the spirally wound belt layer extends at an angle of equal to or less than 5° relative to a tire equatorial plane,
the second belt cord of the zigzag belt layer extends at an inclination of an angle of 2° to 45° relative to the tire equatorial plane, to folding back points where the second belt cord is folded back at each width directional end edge of the zigzag belt layer, and
a relation of
N
95
>N
50
is satisfied,
where N50 is the number of stacked belt layers of the spirally wound belt layer at a distance of 50% of half the length of a maximum belt width of the belt layers from the tire equatorial plane, and
N95 is the number of stacked belt layers of the spirally wound belt layer at a distance of 95% of half the length of the maximum belt width from the tire equatorial plane.
The present invention is configured as described above, and the relation of N95>N50 is satisfied, where N50 is the number of stacked belt layers of the spirally wound belt layers at a distance of 50% of half the length of the maximum belt width of the belt layers from the tire equatorial plane and N95 is the number of stacked belt layers of the spirally wound belt layers at a distance of 95% of half the length of the maximum belt width from the tire equatorial plane.
Since the number of stacked belt layers is larger in the tire side part regions farther from the tire equatorial plane at the distance of 95% of half the length of the maximum belt width Wb from the tire equatorial plane than in the tire central region nearer to the tire equatorial plane at the distance of 50% of half the length of the maximum belt width Wb of the belt layers from the tire equatorial plane. Thus, by reducing the number of stacked layers of the belt layers in the tire central region, a reduction in weight of the tire as a whole can be realized. In addition, by increasing the number of stacked layers of the belt layers in the tire side part regions, tensile/compressive strain in the tire side part regions of the belt can be restrained, fatigue of the belt cord can be reduced, the fatigue resistance performance of the belt can be enhanced, and durability of the tire as a whole can be enhanced.
In the abovementioned configuration, N95 and N50 may be set such that the relation of
N
95
=N
50+1
is satisfied.
Of the spirally wound belt layers, the number of stacked belt layers is greater by one in the tire side part region farther from the tire equatorial plane at the distance of 95% of half the length of the belt maximum width from the tire equatorial plane than in the tire central region nearer to the tire equatorial plane at the distance of 50% of half the length of the belt maximum width from the tire equatorial plane. Thus, by decreasing the number of stacked layers of the belt layers in the tire central region, a reduction in weight of the tire as a whole can be realized. In addition, by increasing the number of stacked layers of the belt layers in the tire side part regions, tensile/compressive strain in the tire side part regions of the belt layer can be restrained, fatigue of the belt cord can be reduced, fatigue resistance performance thereof can be enhanced, and durability of the tire as a whole can be enhanced. Further, since the number of stacked layers of the belt layers is set greater by one in the tire side part regions than in the tire central region, it becomes easy to continuously wind the first strip material spirally.
In the abovementioned configuration, an innermost side layer located on the most inner side in the tire radial direction, of the plurality of spirally wound belt layers, may be disposed on one side of the tire equatorial plane in the tire width direction, the inner end portion on an inner side in the tire width direction, of end portions of the innermost side layer in the tire width direction, may be located with a predetermined spacing Ws1 from the tire equatorial plane, the outer end portion on an outer side in the tire width direction, of the end portions of the innermost side layer, may be located on a tire width directionally outer side than the inner end portion of the innermost side layer, an outermost side layer located on the most outer side in the tire radial direction, of the plurality of spirally wound belt layers, may be disposed on one side or the other side relative to the tire equatorial plane in the tire width direction, the inner end portion on an inner side in the tire width direction, of the end portions of the outermost side layer in the tire width direction, may be located with a predetermined spacing Ws2 from the tire equatorial plane, and the outer end portion on an outer side in the tire width direction, of the end portions of the outermost side layer, may be located on a tire width directionally outer side than the inner end portion of the outermost side layer.
According to this configuration, by decreasing the number of layers of the belt layers in the tire central region of the spirally wound belt layers, a reduction in weight of the tire is realized. In addition, by increasing the number of belt layers in the tire side regions of the spirally wound belt layers as compared to that in the tire central region, fatigue of the belt cord can be reduced, fatigue resistance performance of the belt can be enhanced, and durability of the tire as a whole can be enhanced.
The maximum belt width Wb of the belt layers, Ws1 and Ws2 may be set such that the relations of
0.7≤Ws1/(Wb/2)≤0.9, and
0.7≤Ws2/(Wb/2)≤0.9
are satisfied.
According to the abovementioned configuration, by decreasing the number of stacked layers of the spirally wound layers in a wide range in the tire width direction of the tire central region within 70% to 90% of the half of the maximum belt width Wb of the belt layer from the tire equatorial plane, a reduction in weight of the tire can be realized. In addition, by increasing the number of stacked layers of the spirally wound belt layers in the region on the outside of 70% to 90% of the half of the maximum belt width Wb of the belt layers from the tire equatorial plane as compared to that in the tire central region, tensile/compressive strain in the tire side part regions of the spirally wound belt layers can be restrained sufficiently, fatigue of the belt cord can be reduced, and durability of the tire as a whole can be enhanced.
The aircraft pneumatic of the present invention makes it possible to realize a reduction in weight of the tire, to reduce fatigue of the belt cord, to realize enhancement of fatigue resistance performance of the belt, and to enhance durability of the tire as a whole.
A first embodiment of an aircraft pneumatic tire according to the present invention will be described based on
In the figure, symbol CL corresponds to the center in the tire width direction, and indicates a tire equatorial plane which is a plane orthogonal to the tire rotational axis. The tire width direction is a direction parallel to the tire rotational axis, and the tire radial direction is a direction approaching or spacing away from the tire rotational axis, orthogonally to the tire rotational axis.
The tire 1 includes bead sections 5 in which a pair of left and right ring-shaped bead cores 6 are embedded, a radial carcass 7 arranged to extend toroidally between the pair of bead cores 6, belt layers 10 in circumferential contact with the radial direction outside of the radial carcass 7, a tread section 3 having a tread rubber 38 in circumferential contact with an outer circumferential surface of the belt layers 10, and side wall sections 4 covering side parts of the tire 1.
The radial carcass 7 has one or more carcass plies 7a stacked on one another; for example, four to seven carcass plies 7a are stacked, and both end portions thereof are fixed to the periphery of the bead cores 6 by being wound up from the inner side to the outer side of the radial direction. In the tire 1 of the present embodiment, seven carcass plies 7a including nylon cords are stacked.
On the tire radial directional outer side of a crown region 7b of the radial carcass 7, the belt layers 10 are provided. The belt layers 10 include spirally wound belt layers 20 wound around an outer circumferential surface of the radial carcass 7, zigzag belt layers 30 laid on an outer circumference of the spirally wound belt layers 20, and a protective belt layer 37 wound around an outer circumference of the zigzag belt layer. A tread rubber 38 is attached to an outer circumferential surface of the protective belt layer 37, to form a tread section 3. The maximum belt width in the width direction of the belt layers 10 is defined as Wb, and both edges of the belt layers 10 in the width direction are defined as width directional end edges 10a.
As depicted in
As the organic fiber-made belt cords 26a and 36a used for the spiral winding strips 26 and zigzag winding strips 36, in the present embodiment, organic fiber cords of an aromatic polyamide such as aramid are used. Alternatively, hybrid fiber cords produced by combining an aromatic polyamide such as aramid and an aliphatic polyamide such as nylon can also be used.
The hybrid cord of the aliphatic polyamide fiber and the aromatic polyamide fiber may be a twined combination of yarn of an aliphatic polyamide fiber and yarn of an aromatic polyamide fiber or may be twined yarn obtained by twining preliminarily hybridized yarn of an aliphatic polyamide fiber and an aromatic polyamide fiber.
As depicted in
When the spiral winding strip 26 starts to be wound in the crown region 7b of the radial carcass 7, the winding is not started from the position of the width directional end edge 10a of the belt layers 10 in the tire width direction, but, as depicted in
As depicted in
As depicted in
Ws1 and Ws2 are set longer than at least 50% of half the length of the maximum belt width Wb of the belt layers 10. In other words, as depicted in
More preferably, Ws1 and Ws2 are 70% to 90% of half the length of the maximum belt width Wb, and satisfy the relation of
0.7≤Ws1/(Wb/2)≤0.9, and
0.7≤Ws2/(Wb/2)≤0.9.
In other words, the spiral winding strip 26 is wound, to provide the spirally wound belt layers 20, such that an inner end portion 21a of the first layer 21 and an inner end portion 25a of the fifth layer 25 are located at a position spaced by 70% to 90% of half the length of the maximum belt width Wb from the tire equatorial plane CL.
Since the spirally wound belt layers 20 are produced by winding the spiral winding strip 26 as described above, as depicted in
With such a configuration, the relation of
N
95
>N
50
is satisfied, where N50 is the number of stacked belt layers of the spirally wound belt layers 20 at a distance of 50% of half the length of the maximum belt width Wb of the belt layers 10 from the tire equatorial plane CL, and N95 is the number of stacked belt layers of the spirally wound belt layers 20 at a distance of 95% of half the length of the maximum belt width Wb from the tire equatorial plane CL.
Further, the spirally wound belt layers 20 in the present embodiment satisfy the relation of
N
95
=N
50+1.
The zigzag belt layers 30 are configured by winding, by a predetermined method, a ribbon-shaped zigzag winding strip 36 with a predetermined width that is formed by arranging or aligning one or a plurality of organic fiber-made belt cords 36a and covering them with rubber, as depicted in
After the raw tire is produced in such a state that the spirally wound belt layers 20, the zigzag belt layers 30, and the protective belt layer 37 are wound on the circumferential directionally outer side of the crown region 7b of the radial carcass 7 and the tread rubber 38 is wound around the outer circumferential surface thereof in this way, the raw tire is subjected to vulcanization molding, whereby the tire 1 of the present embodiment is obtained.
Since the spirally wound belt layers 20 in the tire 1 of the present embodiment are configured as described above, the number of stacked layers of the spirally wound belt layers 20 can be reduced in a tire central region, to thereby realize a reduction in weight of the tire, and the number of stacked layers of the spirally wound belt layers 20 can be increased in the tire side part regions, to thereby enhance the fatigue resistance performance of the belt cords 26a and to enhance durability of the tire 1.
Further, since N95 and N50 are set such as to satisfy the relation of N95=N50+1, the spiral winding strip 26 can easily be wound continuously.
In addition, Ws1 and Ws2 are set such as to satisfy the relation of
0.7≤Ws1/(Wb/2)≤0.9, and
0.7≤Ws2/(Wb/2)≤0.9.
In other words, Ws1 and Ws2 are set to be between 70% and 90% of half the length of the maximum belt width Wb. Since the inner end portion 21a of the first layer 21 and the inner end portion 25a of the fifth layer 25 are located on the outer side of the position of 70% of the half of the maximum belt width Wb from the tire equatorial plane CL, the spirally wound belt layers 20 can be more reduced in weight, and a sufficient reduction in weight of the tire as a whole can be realized. In addition, since the inner end portion 21a of the first layer 21 and the inner end portion 25a of the fifth layer 25 are located on the inner side of the position of 90% of the half of the maximum belt width Wb from the tire equatorial plane CL, the region in which the number of stacked layers of the belt layers 10 is great can be secured sufficiently, a tensile/compressive strain of the tire side part regions of the spirally wound belt layers 20 can be sufficiently restrained, fatigue of the belt cords 26a can be reduced, and durability of the tire 1 as a whole can be enhanced.
For each of tires having the abovementioned configuration and a size of 52×21.OR22, of Prior Art Examples 1 and 2 and Examples 1 to 5 of which the specifications are set forth in Table 1 and those of Prior Art Examples 3 and 4 and Examples 6 to 10 of which the specifications are set forth in Table 3, tire mass and belt cord strength after drum traveling are obtained, and the results are set forth in terms of indices in Tables 2 and 4.
The tires set forth in Tables 1 and 3 all include the radial carcass 7 in which seven layers of carcass plies 7a including nylon cord are stacked and the belt layers 10 having the spirally wound belt layers 20 and the zigzag belt layers 30. In the tires set forth in Table 1, aramid is used as a belt cord material of the spiral winding strip 26 and the zigzag winding strip 36. In the tires set forth in Table 3, a hybrid cord of aramid and nylon is used as the belt cord material of the spiral winding strip 26 and the zigzag winding strip 36.
The number of layers of the spirally wound belt layers 20 is measured at a position of 50% of the half of the maximum belt width Wb of the belt layers 10 from the tire equatorial plane CL and at a position of 95% of the half of the maximum belt width Wb of the belt layers 10 from the tire equatorial plane CL.
The ribbon winding start position is indicated by a proportion obtained by dividing the distance Ws1 from the tire equatorial plane CL to the inner end portion 21a of the first layer 21 of the spirally wound belt layers 20 by half the length of the maximum belt width Wb of the belt layers 10 from the tire equatorial plane CL.
The manner of winding the spiral winding strip 26 of the spirally wound belt layers 20 in each of various tires is selectively indicated by any of the first, second, third, and fourth manners. The first to fourth manners of winding are schematically depicted respectively in
As depicted in
As for tire mass, a test of producing, on a trial basis, ten tires for each kind of tires, measuring the mass of each tire, and determining an average of the masses of the ten tires is conducted. The test results for Prior Art Example 2 and Examples 1 to 5 are represented in terms of index with the mass of the tire of Prior Art Example 1 as 100, and are compared. The test results for Prior Art Example 4 and Examples 6 to 10 are represented in terms of index with the mass of the tire of Prior Art Example 3 as 100, and are compared. A lower index means a lighter tire mass, and indicates that the tire is higher in performance. A higher index means an increase in mass, and a lower index means a decrease in mass and indicates realization of a reduction in weight of the tire.
The belt cord strength after drum traveling is measured as follows. Each tire is attached to a prescribed rim, is filled with air to a prescribed internal pressure, and is subjected to a drum test. After drum traveling for a predetermined distance under a load and a speed in simulation of a market, the tire is dissected, the belt cord of the spirally wound belt layer is taken out and subjected to measurement of strength, and the strength is evaluated. The test results for Prior Art Example 2 and Examples 1 to 5 are represented in terms of index with the strength of the cord taken out from the tire of Prior Art Example 1 as 100, and are compared. The test results for Prior Art Example 4 and Examples 6 to 10 are represented in terms of index with the strength of the cord taken out from the tire of Prior Art Example 3 as 100, and are compared. A higher index means small fatigue and good fatigue resistance performance of the belt cord, and indicates that the tire is higher in durability.
While the manner of winding the spiral winding strip 26 of the spirally wound belt layers 20 in Examples 1 to 5 of the present invention is the third manner of winding as depicted in
While the embodiment of the present invention has been described above, it is natural that the modes of the present invention are not limited to the abovementioned embodiment, and include the modes carried out in various forms within the scope of the gist of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2018-239331 | Dec 2018 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2019/049071 | 12/14/2019 | WO | 00 |
