JP3342912B2 - Aircraft radial tires - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radial tire for an aircraft having a belt ply having a cord embedded therein, which extends in a substantially circumferential direction while zigzag by bending at both ply ends.

[0002]

2. Description of the Related Art Conventionally, as a radial tire, for example, one described in Japanese Utility Model Laid-Open No. 48-96259 has been known. This has a belt ply in which cords extending substantially in the circumferential direction while being zigzag by being bent at both ends of the ply are almost uniformly buried in all regions.

[0003] In the radial tire having such a belt ply, since the cut ends of the cords are not exposed at both belt ends, the inclination angle of the cords with respect to the tire equatorial plane is reduced to improve the total strength of the belt. Even when the belt end is used, the interlayer shear strain at the belt end is small and the belt end separation hardly occurs. As a result,
The weight can be reduced by reducing the total number of belt plies while maintaining the specified safety factor. Since the reduction in the weight of the belt layer can suppress the occurrence of a standing wave during high-speed running such as takeoff on the runway, the tire having the above-described belt ply is extremely suitable as an aircraft tire.

[0004]

When a belt having high in-plane bending (bending in the direction along the surface) rigidity such as a zigzag belt is used for a tire, when a slip angle is given to the tire, the rotation axis of the tire is reduced. The side force generated in the direction decreases in the large slip angle region.

Further, when the tire is rolled with a large slip angle added, the belt is bent in the plane (see FIG. 16), the tread rubber is sheared, and the sidewall is deformed (see FIG. 17).
However, when the in-plane bending of the belt is suppressed, the deformation of the side wall tends to be promoted. As shown in FIG. 18, this deformation of the sidewall deforms the contact region between the tire and the road surface (from a region surrounded by a solid line to a region surrounded by a two-dot chain line).

In particular, when the slip angle is increased, the side of the side force is slightly lifted up, the contact area is reduced, the tire is liable to slip, and the side force is reduced by increasing the slip of the tire.

As a result of various experiments and studies, the inventors have found that
It has been found that the cross-sectional shape of the tire outer surface near the ground contact edge is a factor affecting this tendency. In particular, experiments by the inventors have confirmed that the presence of an acute angle near the grounding end promotes a reduction in the area of the contact region.

[0008] Such a decrease in side force in the large slip angle region causes instability in the steering stability of the aircraft when cornering at high speed. Therefore, the above-mentioned technology for improving the side force characteristics without impairing the merits of the zigzag belt (reducing tire weight and improving tire durability during high-speed driving) is not suitable for practical use when applying the zigzag belt to radial tires for aircraft. Is required.

In view of the above, it is an object of the present invention to provide a radial tire for an aircraft capable of improving the side force characteristics while maintaining the advantages of the zigzag belt and maintaining good steering stability during cornering. It is.

[0010]

The radial tire for an aircraft according to claim 1, wherein the carcass layer has a toroidal shape in which a number of cords substantially perpendicular to the tire equatorial plane are embedded. A tread rubber disposed radially outside the layer, and a zigzag, which is disposed between the carcass layer and the tread rubber, intersects the tire equatorial plane at a small angle and bends at both ends of the belt ply with a curvature. A belt layer having at least one belt ply in which cords extending along the circumferential direction of the tire are buried almost uniformly in the entire area, and having a gentle round shoulder shape in the cross-sectional shape of the tire outer surface near the ground contact end. At the same time , any point on the inner surface of the tire in the cross section along the tire axis near the ground contact end is denoted by A,
In the cross section, the point measured along the tire inner surface from the point A is a point on the tire inner surface near the ground contact end separated by 5 mm or more.
As B , the distance from the tire inner surface to the tire outer surface measured on the normal line of the tire inner surface passing through the point A is G _A , and the distance from the tire inner surface to the tire outer surface measured on the normal line of the tire inner surface passing through the point B is G G _B, the distance from point a as measured along the tire inner surface to the point B when the x (x ≧ 5mm), thickness distribution gradient _{(| G a -G B |)} / x is 0.9 or less It is characterized by:

The radial tire for aircraft according to claim 2 is characterized in that, in the radial tire for aircraft according to claim 1, the thickness distribution gradient from the ground contact end to the outside in the rotation axis direction does not fall below 0.6. I have.

The radial tire for an aircraft according to the third aspect is the radial tire for an aircraft according to any one of the first to second aspects, wherein the thickness distribution gradient at the outer side in the rotational axis direction from the ground contact end is zero. .8 is not exceeded.

According to a fourth aspect of the present invention, there is provided the radial tire for an aircraft according to any one of the first, second, and third aspects, wherein the belt layer comprises a plurality of cords. Is coated with a rubber, and the elongated body has a straight portion parallel to the tire equatorial plane when bent at the belt end.

[0014]

In the radial tire for an aircraft according to the first aspect, the cord is formed in a zigzag shape and there is no cut cord end at the end of the belt ply. Even if the angle of the cord is increased to cause an increase in interlaminar shear strain or the amount of rubber between cords is reduced, delamination does not occur. Therefore, it is possible to reduce the weight by reducing the amount of rubber without changing the cord total strength, that is, the tire internal pressure safety factor.

Further, since the cord constituting the belt ply is bent at the ply end with a curvature, the cord is oriented in the circumferential direction at the end of the belt, and at the ply end there is a portion where the cord overlaps three or more times. Overlapping portions occur continuously in the tire circumferential direction. For this reason, the circumferential rigidity of the belt end is increased, and the generation of a standing wave is suppressed.

In the radial tire for an aircraft of the present invention, since the outer surface of the tire near the ground contact end has a gentle round shoulder shape, when a slip angle is given, the curvature of the round shoulder is reduced due to the deformation of the tire. It comes into contact with the road surface sequentially, and the side opposite to the side force direction (outside when turning the vehicle)
The contact area to the side wall side is enlarged, and the decrease in the contact area on the opposite side (side force direction side) is offset, whereby the decrease in the contact area is prevented and the occurrence of early tire slip is suppressed. Here, in the present invention, since the thickness distribution gradient in the vicinity of the ground contact end is optimized, the decrease in the ground contact area during cornering can be effectively prevented, and early tire slip can be suppressed.

In the radial tire for an aircraft according to the second aspect, since the thickness distribution gradient is not less than 0.6, the cross-sectional shape of the ground contact end does not become an unnecessarily large round shape. The reduction in the contact area can be prevented while suppressing uneven wear based on the difference in the radial length between the width direction center portion and the contact end portion from the tire axis.

In the radial tire for an aircraft according to the third aspect, the thickness distribution gradient does not exceed 0.8, so that the side force reduction rate can be further reduced.

Further, in the radial tire for an aircraft according to the fourth aspect, the belt layer is constituted by an elongated body in which a plurality of cords are covered with rubber, and when the elongated body is bent at the belt end, it is parallel to the tire equatorial plane. It has a straight portion (see FIG. 7). When this linear portion is provided, the total number of cords at the end of the belt increases as compared with the case where there is no linear portion, and thus the circumferential rigidity of the end of the belt increases,
Since the increase in the outer diameter of the contact edge at the time of high-speed running is suppressed, the heat generation due to the increase in the contact pressure at the contact edge is suppressed, and the durability is improved.

The function of the linear portion is particularly effective for improving the durability of the belt end portion of the radial tire under the conditions of high load and high speed use such as takeoff of an aircraft tire. As the length of the straight portion increases, the rigidity of the belt end increases, and the effect of suppressing the increase in the outer diameter of the contact end during high-speed running increases. However, the increase in the number of laminations of the elongated bodies at the belt end caused by the increase in the length of the linear portion tends to increase self-heating generated by bending deformation of the elongated bodies themselves during rolling.
That is, the entire belt is deformed so that the circumferential curvature of the belt is close to 0 in the ground contact area during the rolling of the tire, that is, becomes flat, and outside the ground contact area, the belt returns to the circumferential curvature at the time of internal pressure charging. The belt undergoes bending deformation. At this time, if the belt has a large thickness (the number of laminations of the elongated body), the amplitude of the circumferential compression and tensile strain generated by out-of-plane bending increases, and the self-heating also increases.

The length of the straight portion of the elongated body has an optimum range from the viewpoint of the above two effects, and the range is further determined by the width of the elongated body and the inclination angle of the elongated body measured from the tire equatorial plane. Is done. When this is expressed as a formula, the number of laminations of the elongated body at the belt end (n) is represented by the width of the elongated body (W), the slant angle (A °) of the elongated body measured from the tire equatorial plane, and the elongated at the belt end. According to the linear length (L) of the body, n = L / (W
/ SinA). In the radial tire for an aircraft according to the fourth aspect, L in the above equation is represented by L = 4.5 W to 12.
When it is set to 5 W, the durability of the ground contact end at high speed and high load is improved.

[0022]

An embodiment of the present invention will be described below with reference to the drawings.

1 and 2, reference numeral 21 denotes a radial tire mounted on an aircraft. Such a tire 21 includes a pair of bead portions 23 each having a bead 22 embedded therein.
Each of the sidewall portions 24 includes a sidewall portion 24 extending substantially radially outward from the bead portion 23, and a substantially cylindrical tread portion 25 connecting the radially outer ends of the sidewall portions 24.

The tire 21 has one bead portion 2
The carcass layer 31 is reinforced by a toroidal carcass layer 31 extending from 3 to the other bead portion. The carcass layer 31 is composed of one or more carcass plies 32 overlapped with each other, in this embodiment, six layers. ing. Of these carcass plies 32, the inner four layers are turn-up plies whose both ends in the width direction are turned around the bead 22 from the inner side in the axial direction to the outer side in the axial direction. The two layers are down plies extending to the bead 22 along the outside of the folded portion of the carcass ply 32 on the inner layer side.

The inside of each carcass ply 32 is substantially perpendicular to the tire equatorial plane E (extends in the radial direction).
A number of nylons, for example, cords 33 made of 66 nylon are embedded. A tread rubber 36 is disposed radially outside the carcass layer 31.

The tread rubber 36 has a plurality (six in this embodiment) of grooves 54 extending in the circumferential direction.

A belt layer 40 is provided between the carcass layer 31 and the tread rubber 36.
Are a number of inner belt plies 41 located on the side close to the carcass layer 31, here six inner belt plies 41 and the tread rubber 3
6, and two outer belt plies 42 in this case.

Here, for each inner belt ply 41, as shown in FIGS. 3 and 4, an elongated body 43 composed of one or more, usually one or several cords covered with rubber is prepared.
Each time the elongate body 43 makes one round, the ply ends 44 and 45
It is formed by winding in the circumferential direction while reciprocating the space only once, and performing such winding many times by shifting the width of the elongated body 43 almost so that no gap is formed between the elongated bodies 43.

As a result, in each inner belt ply 41, the cords 4 extending substantially in the circumferential direction while zigzag by changing the bending direction at both ply ends 44 and 45.
6 are buried almost uniformly in the entire area of the inner belt ply 41.

If the inner belt ply 41 is formed by the above-described method, the cords 46 are doubled. Two belt plies 41 at a time are
Will be molded crossing each other.

The cord 46 is made of synthetic resin fiber such as nylon or Kevlar (polyamide fiber) or steel.

Here, the cord 46 made of the polyamide fiber is a polyamide fiber after being treated with an adhesive using a resorcinol-formaldehyde / rubber latex (hereinafter referred to as RFL) adhesive solution, embedded in rubber, and vulcanized. Cord is preferable, and the cord strength in the vulcanized rubber is 8.0 g / d or more, preferably 8.5 g / d or more, more preferably 9.0 g / d or more, and the single-fiber fineness is 1.5 to 10 The denier is preferably 3 to 8 denier, and the expansion degree X of the RFL adhesive impregnated in the cord in dimethyl sulfoxide (hereinafter referred to as DMSO) is preferably 122% ≦ X ≦ 340%.

Here, the RFL adhesive liquid is resorcinol /
The molar ratio R / F of the total amount of formaldehyde is 1 / 2.3 ≦ R
/F≦1/1.1 (molar ratio), the ratio RF / L of the total amount of resorcinol and formaldehyde to the total amount of solid rubber latex is 1/10 ≦ RF / L ≦ 1/4 (weight ratio of solid content) And the weight% S of the alkali metal hydroxide based on the total solid content of the RFL adhesive solution is 0.05 ≦ S ≦ 0.8.
(Weight%), of NH ₄ OH-based aqueous NH ₃ to total solids content of RFL adhesive solution wt% A is 0 ≦ A
≦ 0.5 (% by weight), weight% S + A is 0.05 ≦ S + A
≦ 0.8 (% by weight), the total solids content% C of the RFL adhesive solution satisfies all of 10 ≦ C ≦ 24 (% by weight) at the same time, and constitutes the latex component in this solution. Vinyl pyridine (VP) latex, styrene butadiene rubber (SBR) latex, natural rubber (NR) and / or
Or the weight ratio% of each solid content weight of isoprene rubber (IR) latex to the total latex solid content weight
Where a, b and c are respectively VP latex: 10 ≦ a ≦ 80 (% by weight) SBR latex: 0 ≦ b ≦ 70 (% by weight) IR and / or NR latex: 20 ≦ c ≦ 60
(% By weight) at the same time.

As an example of the polyamide fiber used for the polyamide fiber cord, 66 nylon can be used.

In this embodiment, the widths of the inner belt plies 41 become narrower toward the outside in the radial direction, that is, closer to the tread rubber 36. Also, as described above, a plurality of cords 46 arranged in parallel are provided.
When the inner belt ply 41 is formed by winding a strip-like elongated body 43 formed by rubber coating, the molding time can be shortened and the cord alignment can be improved.
Since the slender body 43 is bent at the ply ends 44 and 45 with a small radius of curvature R as shown in FIG. 5, a large compressive strain is generated in the innermost curvature of the cord 46 and remains in the cord 46 as residual strain.

When the cord 46 is made of nylon, if the compression strain exceeds 25%, cord fatigue may be accelerated. However, as shown in FIG. With the above, the compression distortion generated in the code 46 can be suppressed to 25% or less. FIG. 6 is a graph of the result of the desk calculation.

For this reason, when the inner belt ply 41 is formed from the elongated body 43 formed by coating a plurality of nylon cords 46 with rubber, the value of R / W is set to 2.0.
It is preferable to make the above. Here, R is the radius of curvature (mm) at the ply ends 44 and 45 of the elongated body 43, and W is the width (mm) of the elongated body 43.

As described above, when the elongated body 43 is wound at the ply ends 44 and 45 while being bent at a predetermined radius of curvature R, these bent portions, that is, both ply ends 44 and 45 are formed.
In the vicinity of 45, the half widths of the three elongated bodies 43 as shown in FIG. 8 overlap vertically (normally, as described above, the two elongated bodies 43 are overlapped by one molding, As shown in FIG. 5, the elongated body 43, that is, a substantially triangular area 47 in which the cords 46 are overlapped three times, is repeatedly generated in the circumferential direction. Is a laminated portion 48 having a narrow width (the width varies depending on the position in the circumferential direction) successively in the circumferential direction.
Is configured.

As shown in FIG. 8, these laminated portions 48 are located on the radially outer side as shown in FIG. 8 because the width of the inner belt ply 41 is narrower toward the outer side in the radial direction as described above. Those that are located are located axially inward. In the bent portion, the widthwise outer end of the intermediate elongated body 43c sandwiched between the upper and lower elongated bodies 43a and 43b is located in a region 47 located radially inward of the intermediate elongated body 43c. It overlaps four times.
When the inner belt ply 41 as described above is provided on the belt layer 40, the total number of belt plies can be reduced while maintaining the total strength, and the weight can be reduced. The generation of standing waves can be prevented.

Referring again to FIGS. 1 and 2, in each outer belt ply 42, a cord 51 having a crossing angle B larger than the angle A with respect to the tire equatorial plane E is buried almost uniformly in the entire area. Here, the cord 51 in each outer belt ply 42 is inclined at the same angle B in the same direction with respect to the tire equatorial plane E and is exposed by the cut ends located at both ply ends 52 as shown in the figure. Alternatively, it may extend substantially in the circumferential direction while zigzag by bending at both ply ends 52 similarly to the cord 46 in the inner belt ply 41. In the former case, at least two of the outer bell plies 42 (the two outer belt plies 42 in this embodiment) are arranged such that the cords 51 intersect each other between layers, that is, in the opposite direction. It is arranged to be inclined.

Here, among the above-mentioned inner belt plies 41, the cords 46 in the outermost inner belt plies 41 have an angle A degrees with respect to the tire equatorial plane E, as shown in FIG. There are two types, one inclined and the other inclined at an angle A in the opposite direction.
There are two regions where the intersection angle between the cord 51 in the inside and the cord 46 in the outermost inner belt ply 41 is smaller than A degree and a region larger than A degree, but in the two directions. The area occupied by the inclined cords 46 is also substantially equal, so that the innermost outer belt plies 42 can be arranged outside the inner belt plies 41 without taking the orientation of the cords 51 into account.

On the other hand, as shown in FIG.
Has a round shoulder shape having a center of curvature inside the tire.

As shown in FIG. 10, an arbitrary point on the inner surface of the tire in the cross section along the tire axis is A near the contact edge 25A, and the distance measured along the inner surface of the tire from the point A is 5 mm or more. On the inner surface of the tire near the ground contact
Point as B, from the inner surface of the tire measured on the normal line of the tire inner surface through the point A of the distance to the external surface of the tire G _A, from the tire inner surface was measured on the normal line of the tire inner surface through the point B to the tire outer surface distance G _B, the distance from point a as measured along the tire inner surface to the point B when the x (x ≧ 5mm), thickness distribution gradient _{(| G a -G B |)} / x is 0.
It is preferably 9 or less, more preferably 0.8 or less. Further, it is preferable that this thickness distribution gradient does not fall below 0.6. In the tire 21 of the present embodiment,
The thickness distribution gradient near the ground end 25A is 0.42.

[Test Examples] Five types of test tires according to the present invention (first to fifth examples) and two types of test tires according to comparative examples (comparative examples 1 and 2) were prepared. Then, the side force reduction rate of each test tire was measured.

The tire size of each test tire is H
46 × 18.0R20, and each test tire has a different thickness distribution gradient as described in Table 1 below. 12 shows the tire of the second embodiment, FIG. 13 shows the tire of the fifth embodiment, FIG. 14 shows the tire of Comparative Example 1, and FIG. 15 shows the tire of Comparative Example 2 (the third and fourth examples). Illustration of the example tire is omitted).

The side force was measured with a tire testing machine in the room, the test tire was mounted on a regular rim, and the internal pressure (20
5 psi), the load was 44200 LBS, and the speed was 5 MPH. The slip angle was changed in 2 ° steps from 0 ° to 20 °, and the side force at that time was measured. The side force reduction rate was calculated by the following equation (1). Calculated.

Side force reduction rate = (1-F ₁ /
F ₀ ) × 100 (%) (1) Here, F ₀ is the maximum value of the side force, and F ₁ is the minimum value after the maximum value of the side force (see FIG. 11).

The thickness gradient of the groove 54 closest to the side wall 24 among the grooves 54
From the outside (sidewall side) of the tire height H
/ 2 (the range indicated by the arrow L in FIG. 1).

[0049]

[Table 1] From the test results in Table 1 above, it is clear that the radial tire for aircraft to which the present invention is applied has a small side force reduction rate and has excellent side force characteristics. For this reason, in the radial tire for aircraft to which the present invention is applied, the occurrence of early tire slippage during high-speed cornering is suppressed, and the steering stability is favorably maintained.

[0050]

As described above, the radial tire for an aircraft according to the first aspect has the above-described structure, so that at the time of cornering, a decrease in the contact area is prevented and the occurrence of early tire slip is suppressed, so that steering stability is improved. It has an excellent effect of being kept well.

The radial tire for an aircraft according to the second aspect has the above-described configuration, and thus has an excellent effect that a reduction in the contact area can be prevented while maintaining the wear resistance of the contact end.

Since the radial tire for an aircraft according to the third aspect has the above-described structure, it has an excellent effect that the side force reduction rate can be reduced.

Further, the radial tire for an aircraft according to the fourth aspect has the above-described configuration, and thus has an excellent effect that the high-speed durability of the grounding end can be improved.

[Brief description of the drawings]

FIG. 1 is a meridian sectional view of an aircraft radial tire according to a first embodiment of the present invention.

FIG. 2 is a partially broken plan view of the aircraft radial tire shown in FIG.

FIG. 3 is a perspective view showing an inner belt ply.

FIG. 4 is a development view showing an inner belt ply.

FIG. 5 is an enlarged development view of an inner belt ply near a ply end.

FIG. 6 is a graph showing a relationship between compression distortion acting on a code and R / W.

FIG. 7 is an enlarged development view of the inner belt ply showing an elongated body having a linear portion parallel to the tire equatorial plane.

FIG. 8 is an enlarged meridian sectional view of a plurality of inner belt plies near a ply end.

FIG. 9 is a development view of the outermost inner belt ply.

FIG. 10 is an enlarged meridian sectional view near a tread edge showing measurement points of a thickness distribution gradient.

FIG. 11 is a graph showing a relationship between a slip angle and a side force.

FIG. 12 is a meridian sectional view of a tire according to a second embodiment of the present invention.

FIG. 13 is a meridian sectional view of a tire according to a fifth embodiment of the present invention.

FIG. 14 is a meridian sectional view of a tire according to Comparative Example 1.

FIG. 15 is a meridian sectional view of a tire according to Comparative Example 2.

FIG. 16 is a perspective view of a tire showing a state where the belt has undergone in-plane bending.

FIG. 17 is a cross-sectional view of the tire showing the tread rubber that has been sheared and the sidewalls that have been deformed.

FIG. 18 is an explanatory diagram showing deformation of a contact area.

[Explanation of symbols]

 Reference Signs List 21 tire (radial tire for aircraft) 31 carcass layer 36 tread rubber 40 belt layer 41 inner belt ply 43 slender body 46 code E tire equatorial plane

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B60C 11 / 00,11 / 01 B60C 9 / 18,9 / 20

Claims (4)

(57) [Claims] 1. A toroidal carcass layer in which a number of cords substantially orthogonal to a tire equatorial plane are embedded, a tread rubber disposed radially outside the carcass layer, and the carcass layer. And disposed between the tread rubber and
A cord extending at a small angle to the tire equatorial plane and extending along the tire circumferential direction while zigzagging by bending at both ends of the belt ply has at least one layer of belt ply buried almost uniformly in the entire area. comprising a belt layer, and with the tire outer surface cross-sectional shape of the ground contact end near a gentle round shoulder shape, the ground near edge, an arbitrary point on the tire inner surface in cross-section along the tire axis a, in the cross-section The distance measured along the inner surface of the tire from point A is 5 mm or more
Assuming that a point on the tire inner surface near the ground contact end is B , the distance from the tire inner surface to the tire outer surface measured on the normal line of the tire inner surface passing through the point A is G _A , and measured on the normal line of the tire inner surface passing the point B. When the distance from the inner surface of the tire to the outer surface of the tire is G _B , and the distance from point A to point B measured along the inner surface of the tire is x (x ≧ 5 mm), the thickness distribution gradient (|
G _A -G _B |) / radial tire for an airplane, characterized in that x is 0.9 or less. 2. The aircraft radial tire according to claim 1, wherein the thickness distribution gradient on the outer side in the rotation axis direction from the ground contact end does not fall below 0.6. 3. The radial tire for an aircraft according to claim 1, wherein the thickness distribution gradient outside the rotation axis direction from the ground contact end does not exceed 0.8. 4. The belt layer is constituted by an elongated body in which a plurality of cords are covered with rubber, and the elongated body has a straight portion parallel to the tire equatorial plane when bent at an end of the belt. 4. The radial tire for an aircraft according to 1, 2, or 3.