JP2015024715A - Radial tire for aircraft - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radial tire for an aircraft.SOLUTION: In a tire-width directional cross-section upon the standard state, intersections of a straight line M which passes through a center A of a bead core 1a and is vertical to a tire-width direction and a tire inner surface are put as P and Q. In the tire-width directional cross-section upon the triple load state, a point located on the outermost side is put as R. A tire is provided with a belt 4 and, when the tire is divided into a center part and a shoulder part on the basis of a straight line L which passes through a point B of the tip of a bead toe 8 and is vertical to the tire width direction, the belt is configured such that the number of layers on the shoulder part is smaller than the number of layers on the center part, and a radially innermost side position D1 of a belt layer on the radially innermost side on the shoulder part is located on the radially inner side than a radially innermost side position D2 of a belt layer 4a on the radially innermost side of the center part. Upon the triple load state, the P is located on the tire radially outer side than the straight line QP made by connecting the point Q on the tire inner surface on tire equatorial surface and the point R.

Description

  The present invention relates to an aircraft radial tire.

  In recent years, radial tires excellent in characteristics such as wear resistance have become mainstream in aircraft tires (see, for example, Patent Document 1). By the way, in such a radial tire for an aircraft, it is found in an excessively high load (overload) test assuming an emergency stop or the like, and it may be difficult to maintain an internal pressure particularly in a tire for a front wheel. It was.

Japanese Patent Laid-Open No. 5-220211

  An object of the present invention is to provide a radial tire for an aircraft that can maintain the internal pressure even during an emergency stop or the like.

  The inventor has intensively studied to solve the above problems. As a result, the inventors have found that the following phenomenon that occurs during an emergency stop or the like is the main cause that makes it difficult to maintain the internal pressure. That is, during an emergency stop or the like, an overload may be applied particularly to the front wheels due to rapid deceleration, and the tire continues to roll at that time, but the deflection of the tire increases due to the overload, and as a result, FIG. As shown in FIG. 2, so-called bottoming occurs, in which the bead portion 91 and the crown portion 92 are in contact with each other on the tire inner surface 90, which makes it difficult to maintain the internal pressure of the tire. In particular, in the case of radial tires for aircraft, the tires for the front wheels often have a small diameter that is limited by the volume of the hangar. In such tires, the distance between the bead portion and the crown portion is shortened, so that the above bottoming occurs. It turns out that it is easy to do. Furthermore, the inventor has obtained the knowledge that even if it is an overload, there is actually a certain limit.

  This invention is made | formed based on said knowledge, The summary structure is as follows. A radial tire for aircraft according to the present invention includes a pair of bead cores, a carcass straddling the pair of bead cores, and a tread. The tire is mounted on an applied rim, filled with a specified internal pressure, and is in an unloaded state. In the tire width direction cross section in the reference state, on the tire inner surface which is the intersection point on the outer side in the tire radial direction among the two intersection points of the straight line M passing through the center A of the bead core and perpendicular to the tire width direction and the tire inner surface. The point on the tire inner surface at the tire equatorial plane is Q, the tire is mounted on the applicable rim, filled with the specified internal pressure, and loaded with a load three times the specified load. In the tire width direction cross section, the point on the tire surface which is the outermost side in the tire width direction is R, and the tire includes a belt composed of one or more belt layers, and the tire width direction in the reference state In the plane, with reference to a straight line L passing through the point B at the tip of the bead toe and perpendicular to the tire width direction, the tire width direction range from the tire equatorial plane to the straight line L is a center portion, and the tire width direction from the straight line L When the outer side is a shoulder portion, the belt has the number of belt layers in the shoulder portion smaller than the number of belt layers in the center portion, and the innermost radial layer of the belt layer in the tire radial direction in the shoulder portion. The position D1 is located on the inner side in the tire radial direction from the innermost position D2 in the tire radial direction of the belt layer on the innermost side in the tire radial direction in the center portion. In the triple load state, the point P is the tire on the tire equatorial plane. It is characterized by being located on the outer side in the tire radial direction from a straight line QR connecting the point Q on the inner surface and the point R. This is because the thickness of the tread portion can be reduced by this configuration, and the occurrence of bottoming due to contact with the inside of the tire when a load is applied can be suppressed. Here, the “center of the bead core” means the center of gravity of the bead core. “Applicable rim” is an industrial standard effective in the area where tires are produced and used. In Japan, JATMA (Japan Automobile Tire Association) YEAR BOOK is used. In Europe, ETRTO (European Tire and Rim Technical Organization) is used. Standard MANUAL, in the United States, refers to a standard rim defined in TRA (THE TIRE and RIM ASSOCATION INC.) YEAR BOOK, etc. In addition, the “specified load” is the maximum load (maximum load capacity) of a single wheel at the applicable size described in the predetermined industrial standard, and the “specified internal pressure” is the maximum load. Corresponding air pressure. In addition, regarding the “number of belt layers”, when a belt protective layer is provided on the outer side in the tire radial direction of the belt, the belt protective layer is also included.

  Further, in the radial tire for aircraft according to the present invention, when the point on the tire inner surface that is the intersection of the extended line of the perpendicular drawn from the tread end TE to the carcass and the tire inner surface is D, the tread thickness It is preferable that the height gradually decreases from the point P to the point D toward the outer side in the tire width direction. This is because by gradually reducing the thickness of the tread portion, it is possible to suppress the occurrence of bottoming due to contact with the inside of the tire when a load is applied. Here, the “perpendicular to the carcass” means that when the carcass is composed of a plurality of carcass plies, the perpendicular is lowered with respect to the innermost carcass ply in the tire radial direction. Further, the “tread end” refers to a ground contact end (both ends in the tire width direction of the ground contact surface) when the tire is mounted on the applied rim, filled with a specified internal pressure, and a specified load is applied.

  Furthermore, in the radial tire for aircraft according to the present invention, the distance from one point on the inner surface of the tire to the intersection of the extended line of the perpendicular extending from the one point to the carcass and the tread surface is determined by the distance from the one point. The tread thickness at the point Q is defined as d1, the tread thickness at the point Q is a point on the tire inner surface which is the intersection of the straight line L passing through the point B at the tip of the bead toe and perpendicular to the tire width direction and the tire inner surface. When the tread thickness at C is d2, and the tread thickness at the point P is d3, the ratio d2 / d1 is preferably smaller than the ratio d3 / d2. Thereby, the change in the tread thickness from the shoulder portion to the tread end portion is larger than the change in the tread thickness from the center portion to the shoulder portion of the tread portion, and the tread thickness can be greatly reduced in this region. Therefore, even when an overload is applied to the tire, bottoming can be suppressed and the internal pressure can be maintained.

  Further, in the radial tire for aircraft according to the present invention, in the tire width direction cross section in the reference state, a distance h1 in the tire radial direction between the point P and the center A of the bead core is the point Q, It is preferably 90% or more and 100% or less with respect to a distance h2 from a straight line passing through the center A of the bead core and parallel to the tire width direction. By setting it as the said range, an internal pressure can be hold | maintained on more severe conditions.

  Furthermore, in the radial tire for aircraft according to the present invention, in the tire width direction cross section in the reference state, between the point P and the point T on the tire inner surface which is two intersections of the straight line M and the tire inner surface. The distance h3 in the tire radial direction is preferably 76% or more and 90% or less with respect to the distance h2 between the point Q and a straight line passing through the center A of the bead core and parallel to the tire width direction. By setting it as the said range, an internal pressure can be hold | maintained on more severe conditions.

  Here, in the radial tire for aircraft according to the present invention, in the cross section in the tire width direction in the triple load state, the point P is located on the outer side in the tire radial direction from a straight line passing through the point Q and parallel to the tire width direction. It is preferable to do. As a result, the internal pressure can be maintained even under more severe conditions.

  ADVANTAGE OF THE INVENTION According to this invention, the radial tire for aircraft which can hold | maintain an internal pressure also at the time of an emergency stop etc. can be provided.

It is a figure for demonstrating bottoming. It is a tire width direction sectional view of the tire concerning one embodiment of the present invention. It is a tire width direction sectional view of the tire concerning one embodiment of the present invention. It is a tire width direction sectional view in the 3 times load state of the tire concerning one embodiment of the present invention. It is a tire width direction sectional view in the 3 times load state of the tire concerning one embodiment of the present invention. It is a tire width direction partial sectional view of a tire concerning one embodiment of the present invention. It is a tire width direction sectional view of the tire concerning one embodiment of the present invention. It is a tire width direction sectional view of the tire concerning one embodiment of the present invention.

  Hereinafter, an aircraft radial tire (hereinafter also simply referred to as a tire) according to an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 2 is a cross-sectional view in the tire width direction showing a tire according to one embodiment of the present invention. Since the tire shown in FIG. 2 has a symmetrical structure with the tire equatorial plane CL as a boundary, only one half of the tire width direction is shown, and the other half of the tire width direction is not shown. FIG. 2 shows a cross section in the tire width direction in a reference state in which a tire is incorporated into an applied rim, filled with a specified internal pressure, and in a no-load state.

  As shown in FIG. 2, the tire according to the present embodiment includes a bead core 1 a embedded in a pair of bead portions 1, a carcass 2 straddling in a toroidal shape between the pair of left and right bead cores 1 a, and a tread 3. . Here, the carcass 2 is composed of at least one carcass ply. In the illustrated example, the carcass 2 is composed of two carcass plies 2a and 2b. In the illustrated example, on the outer side in the tire radial direction of the carcass 2, a belt 4 including a main belt including main belt layers 4 a and 4 b and a sub belt including sub belt layers 4 c and 4 d is provided. In the illustrated example, the main belt layers 4a and 4b are formed by spirally winding a rubber-coated cord along the tire circumferential direction, and in the illustrated example, the auxiliary belt layers 4c and 4d are rubbers that intersect each other between the layers. It consists of a coated cord. Further, in the illustrated example, a belt protective layer 5 is provided on the outer side in the tire radial direction of the belt 4. In the illustrated example, the belt protective layer 5 is composed of a rubberized layer of cords arranged substantially parallel to the tire circumferential direction. In the present invention, the belt structure is not particularly limited, and the number of belt layers and the like can be appropriately changed. Further, the belt protective layer may or may not have.

  Here, as shown in FIG. 2, on the tire inner surface, which is the intersection point on the outer side in the tire radial direction among the two intersection points of the straight line M passing through the center A of the bead core 1 a and perpendicular to the tire width direction and the tire inner surface 6. Is a point on the tire inner surface 6 at the tire equatorial plane CL.

  FIG. 3 is a cross-sectional view in the tire width direction showing the tire according to one embodiment of the present invention. Like FIG. 2, the tire equator plane CL is a symmetric structure with the tire equator plane CL as a boundary. Only one half is shown. FIG. 3 shows a cross section in the tire width direction in the reference state.

  As shown in FIG. 3, the tire includes a belt 4 including one or more layers, and four belt layers 4 a to 4 d in the illustrated example. Here, as shown in FIG. 3, the tire width direction range from the tire equatorial plane CL to the straight line L is defined as the center portion with reference to a straight line L passing through the point B at the tip of the bead toe 8 and perpendicular to the tire width direction. The outer side in the tire width direction from the straight line L is defined as a shoulder portion. As shown in FIG. 3, in the tire, the number of belt layers in the shoulder portion is two, and the number of belt layers in the center portion is four. Further, as shown in FIG. 3, the tire radial innermost position D1 of the tire radial direction innermost belt layer 4a in the shoulder portion is the tire radial innermost position of the tire radial innermost belt layer 4a in the center portion. It is located on the inner side in the tire radial direction from D2. As described above, in the tire according to the present embodiment, the belt 4 has the number of belt layers in the shoulder portion smaller than the number of belt layers in the center portion, and the belt layer on the innermost side in the tire radial direction in the shoulder portion. The innermost position D1 in the tire radial direction is located on the inner side in the tire radial direction from the innermost position D2 in the tire radial direction of the belt layer on the innermost side in the tire radial direction at the center portion.

  FIG. 4 shows a cross section in the tire width direction in a triple load state in which the tire according to the present embodiment is incorporated in an applied rim, filled with a specified internal pressure, and loaded with a load three times the specified load. In FIG. 4, as in FIGS. 2 and 3, only one half in the tire width direction with the tire equator plane CL as a boundary is shown, and the other half in the tire width direction is omitted. Moreover, illustration is abbreviate | omitted about tire structural members (carcass, a belt, a belt protective layer) other than the bead core 1a.

  As shown in FIG. 4, R is a point on the tire surface 7 that is the outermost side in the tire width direction. At this time, as shown in FIG. 4, in the tire of the present embodiment, the point P is located on the outer side in the tire radial direction from the straight line QR connecting the point Q and the point R.

  According to the tire of the present embodiment, the number of belt layers in the shoulder portion is less than the number of belt layers in the center portion, and the innermost position in the tire radial direction of the innermost belt layer in the tire radial direction in the shoulder portion. Since D1 is located on the inner side in the tire radial direction from the innermost position D2 in the tire radial direction of the belt layer on the innermost side in the tire radial direction in the center portion, the tread thickness in the shoulder portion is made thinner than the center portion. Can do. For this reason, even when an overload is applied, the distance between the bead portion and the crown portion can be ensured to prevent bottoming. Specifically, since the point P is on the outer side in the tire radial direction from the straight line connecting the point Q and the point R, the vicinity of the crown portion and the vicinity of the bead portion do not contact with each other on the tire inner surface, thereby suppressing bottoming. can do. Accordingly, the internal pressure of the tire can be maintained even when an excessive load is applied to the tire, such as during an emergency stop of the vehicle.

  FIG. 5 is a cross-sectional view in the tire width direction showing an example of the tire of the present invention. Like FIGS. 2 to 4, the tire equator plane CL is a symmetric structure with the tire equator plane CL as a boundary. Only one half is shown. Moreover, illustration is abbreviate | omitted about tire structural members (carcass, a belt, a belt protective layer) other than the bead core 1a. FIG. 5 shows a cross section in the tire width direction in the triple load state.

  As shown in FIG. 5, in the present invention, in the triple load state, the point P is preferably located on the outer side in the tire radial direction from the straight line passing through the point Q and parallel to the tire width direction. This is because bottoming can be suppressed and the internal pressure can be maintained even under more severe conditions.

  FIG. 6 is a partial cross-sectional view in the tire width direction showing a tire according to another embodiment of the present invention with the belt 4 and the belt protective layer 5 removed. Similar to FIGS. 2 to 5, since the structure is symmetric with respect to the tire equatorial plane CL, only a part of one half portion with the tire equatorial plane CL as a boundary is illustrated. FIG. 6 shows a cross section in the tire width direction in the reference state.

  Here, let D be a point on the tire inner surface 6 that is an intersection of an extended line of a perpendicular line extending from the tread end TE to the carcass 2 and the tire inner surface 6. At this time, it is preferable that the tread thickness gradually decreases from the point P to the point D toward the outer side in the tire width direction. At the time of loading, the center part first contacts the ground, the contact area gradually widens outward in the width direction, and the tire crown part deforms.Therefore, the tread thickness gradually decreases as it goes outward in the width direction. This is because it is possible to avoid the occurrence of bottoming while maintaining a distance from the above.

  FIG. 7 is a cross-sectional view in the tire width direction showing a tire according to an embodiment of the present invention. Since the tire equatorial plane CL is symmetric with respect to the tire equatorial plane CL as in FIGS. Only one half of the boundary is shown. FIG. 7 shows a cross section in the tire width direction in the reference state.

  Here, the distance from one point on the tire inner surface 6 to the intersection of the perpendicular extending from the one point to the carcass 2 and the tread surface 3a is defined as the tread thickness at the one point. As shown in FIG. 7, the tread thickness at the point Q is d1, and the straight line L passing through the point B at the tip of the bead tow 8 (the innermost side in the tire width direction) and the tire inner surface 6 is perpendicular to the tire width direction. The tread thickness at the intersection C is d2. The tread thickness at the point P is d3. At this time, in the tire of the present embodiment, the ratio d2 / d1 is preferably smaller than the ratio d3 / d2. Since the ratio d2 / d1 is smaller than the ratio d3 / d2, the change in the tread thickness from the bead toe tip position to the tread edge rather than the tread thickness change from the tire equatorial plane CL to the bead toe tip position in the tread portion. Because the tread thickness can be greatly reduced in this region, the crown portion and the bead portion can be used even when the tire is loaded with a load that is three times the specified load, which is a reference for the overload limit. Can keep the distance.

  FIG. 8 is a cross-sectional view in the tire width direction showing a tire according to another embodiment of the present invention. Like FIG. 2 to FIG. 7, the tire equatorial plane is a symmetrical structure with the tire equatorial plane CL as a boundary. Only one half with CL as the boundary is shown. FIG. 8 shows a cross section in the tire width direction in the reference state.

  As shown in FIG. 8, the distance in the tire radial direction between the point P and the center A of the bead core 1a is h1, and the tire width direction passes through the point Q on the tire inner surface 6 on the tire equatorial plane CL and the center A of the bead core 1a. (Ie, the intersection of the straight line passing through the center A of the bead core 1a and parallel to the tire width direction and the tire equatorial plane CL is S in the tire radial direction between the point Q and the point S). Let the distance be h2. At this time, in the present invention, the ratio h1 / h2 is preferably 90% or more and 100% or less. By setting the ratio h1 / h2 to 90% or more, the tire inner surface distance in the tire radial direction between the vicinity of the crown portion and the vicinity of the bead portion is ensured, and is a standard that serves as a reference for the limit of the overload. Even when a load three times the load is applied, the point P is located on the outer side in the tire radial direction from the straight line QR connecting the point Q and the point R, and the vicinity of the crown portion and the vicinity of the bead portion are tires. This is because it is possible to prevent contact with the inner surface, and on the other hand, by setting the ratio h1 / h2 to 100% or less, the tension load of the carcass ply can be appropriately maintained. In particular, the ratio h1 / h2 is preferably 92% or more. Even when the tire inner surface further secures the distance in the tire radial direction between the vicinity of the crown portion at the shoulder portion and the vicinity of the bead portion, and when a load that is three times the specified load as a reference for the limit of the overload is applied. The point P is located on the outer side in the tire radial direction from the line passing through the point Q and parallel to the tire width direction so that the vicinity of the crown portion and the vicinity of the bead portion do not contact with each other on the tire inner surface even under more severe conditions. Because it can.

  Further, as shown in FIG. 8, the tire diameter between the point P on the tire inner surface 6 and the point T between two points of the straight line M passing through the center A of the bead core 1 a and perpendicular to the tire width direction and the tire inner surface 6. Let the distance in the direction be h3. At this time, the ratio h3 / h2 is preferably 76% or more and 90% or less. By setting the ratio h3 / h2 to be 76% or more, a tire radial distance between the vicinity of the crown portion and the vicinity of the bead portion on the inner surface of the tire is secured, and a standard that serves as a reference for the limit of the overload. Even when a load three times the load is applied, the point P is located on the outer side in the tire radial direction from the straight line QR connecting the point Q and the point R, and the vicinity of the crown portion and the vicinity of the bead portion are tires. This is because it is possible to prevent contact with the inner surface, and on the other hand, by setting the ratio h3 / h2 to 90% or less, the tension load of the carcass ply can be properly maintained. In particular, the ratio h3 / h2 is preferably 80% or more. Even when the tire inner surface further secures the distance in the tire radial direction between the vicinity of the crown portion at the shoulder portion and the vicinity of the bead portion, and when a load that is three times the specified load as a reference for the limit of the overload is applied. The point P is located on the outer side in the tire radial direction from the line passing through the point Q and parallel to the tire width direction so that the vicinity of the crown portion and the vicinity of the bead portion do not contact with each other on the tire inner surface even under more severe conditions. Because it can.

  In order to confirm the effects of the present invention, tires according to Invention Examples 1 to 7 and tires according to Comparative Examples were made on a trial basis. Each of these tires was mounted on an applicable rim, filled with a specified internal pressure, and a bottoming test was conducted. In the bottoming test, the presence or absence of bottoming when a load three times the specified load was applied was confirmed using a bottoming tester described in JP-A-9-11716. The specifications and evaluation results of each tire are shown in Table 1. Here, in Table 1, “the position of the point P” is “outside in the radial direction from the straight line QR” means “the point P is the point Q and the point R in the cross section in the tire width direction under a triple load state”. Is located on the outer side in the tire radial direction than the straight line QR connecting the Further, “the position of the point P” is “outside in the radial direction from the point Q” means that “the point P passes through the point Q and is parallel to the tire width direction in the cross section in the tire width direction in the triple load state”. It means “located outside in the tire radial direction”. Further, the positional relationship between the points D1 and D2 means the positional relationship in the reference state.

  As shown in Table 1, in the tire according to the comparative example, bottoming occurred when a load three times the specified load was applied, whereas in the tires according to the inventive examples 1 to 7, all of the specified load was 3 Even when a double load was applied, bottoming did not occur, and therefore the internal pressure could be maintained.

1: Bead part, 1a: Bead core, 2: Carcass, 2a, 2b: Carcass ply 3: Tread, 3a: Tread surface, 4: Belt, 4a, 4b: Main belt layer,
4c, 4d: sub belt layer, 5: belt protective layer, 6: tire inner surface, 7: tire surface,
8: Bead toe, 90: Tire inner surface, 91: Bead part, 92: Crown part,
CL: tire equator, TE: tread edge

Claims (6)

In an aircraft radial tire comprising a pair of bead cores, a carcass straddling between the pair of bead cores, and a tread,
A straight line M that passes through the center A of the bead core and is perpendicular to the tire width direction in a cross section in the tire width direction in a reference state in which the tire is mounted on an applicable rim, filled with a specified internal pressure, and in a no-load state Of the two intersections with the tire inner surface, the point on the tire inner surface that is the intersection on the outer side in the tire radial direction is P, and the point on the tire inner surface at the tire equator surface is Q,
The tire is mounted on an applicable rim, filled with a specified internal pressure, and loaded with a load three times the specified load. Let the point be R,
The tire includes a belt composed of one or more belt layers,
In the tire width direction cross-section in the reference state, with reference to a straight line L passing through the point B at the tip of the bead toe and perpendicular to the tire width direction, a range in the tire width direction from the tire equatorial plane to the straight line L is a center portion. When the outer side in the tire width direction from the straight line L is a shoulder portion,
In the belt, the number of belt layers in the shoulder portion is less than the number of belt layers in the center portion,
The innermost radial position D1 of the tire radial direction innermost belt layer in the shoulder portion is located on the inner side in the radial direction of the tire with respect to the innermost radial position D2 of the innermost belt layer in the radial direction of the tire in the center portion.
In the triple load state, the point P is located on the outer side in the tire radial direction with respect to a straight line QR connecting the point Q and the point R on the tire inner surface on the tire equator plane. . When D is a point on the tire inner surface, which is an intersection of an extension of a perpendicular line extending from the tread end TE to the carcass and the tire inner surface,
The radial tire for an aircraft according to claim 1, wherein the tread thickness gradually decreases from the point P to the point D toward the outer side in the tire width direction. The distance from one point on the inner surface of the tire to the intersection of the extended line of the perpendicular extending from the one point to the carcass and the tread surface is defined as the tread thickness at the one point,
The tread thickness at the point Q is d1, the tread thickness at the point C on the tire inner surface, which is the intersection of the straight line L passing through the point B at the tip of the bead toe and perpendicular to the tire width direction, and the tire inner surface is d2. When the tread thickness at point P is d3,
The aircraft radial tire according to claim 1 or 2, wherein the ratio d2 / d1 is smaller than the ratio d3 / d2.   In the tire width direction cross section in the reference state, a distance h1 in the tire radial direction between the point P and the center A of the bead core is a straight line passing through the point Q and the center A of the bead core and parallel to the tire width direction. The radial tire for aircraft according to any one of claims 1 to 3, wherein the radial tire is 90% or more and 100% or less with respect to the distance h2.   In the tire width direction cross section in the reference state, the point P on the tire inner surface which is two intersections of the straight line M and the tire inner surface, and the distance h3 in the tire radial direction between the points T are the point Q and The aircraft according to any one of claims 1 to 4, wherein the aircraft has a distance h2 of 76% or more and 90% or less with respect to a straight line passing through the center A of the bead core and parallel to the tire width direction. For radial tires. In the cross section in the tire width direction in the triple load state,
The radial tire for an aircraft according to any one of claims 1 to 5, wherein the point P is located on the outer side in the tire radial direction from a straight line passing through the point Q and parallel to the tire width direction.

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