Pneumatic tire

Abstract

A pneumatic tire includes: a carcass; at least one layer of a belt; and a tread, the belt including an endless belt layer having provided therein treats, each of the treats being formed by covering a cord with rubber and extending in zigzag fashion in the tire circumferential direction, in which in the endless belt layer, a front surface a and a rear surface of each of the treats are reversed at both tire widthwise ends, and on at least one tire widthwise end of the treats, a treat reversal position is, at least partially in the tire circumferential direction, displaced in the tire width direction from another treat reversal position adjacent in tire circumferential direction.

Claims

1. A pneumatic tire comprising: a carcass extending toroidally between a pair of bead portions; a belt formed by at least one belt layer disposed outward of the carcass in a tire radial direction; and a tread disposed outward of the belt in the tire radial direction, the belt layer comprising an endless belt layer having provided therein treats, each of the treats being formed by covering a cord with rubber and directed so as to change direction at both tire widthwise ends toward a tire width direction inner side such that the treat extends in zigzag fashion in the tire circumferential direction, wherein in the endless belt layer, a front surface and a rear surface of each of the treats are reversed at both tire widthwise ends, on at least one tire widthwise end of the treats, a treat reversal position at which front and rear surfaces of each of the treats are reversed is, at least partially in the tire circumferential direction, displaced in the tire width direction from another treat reversal position adjacent in the tire circumferential direction, and the treat reversal positions are alternatively displaced between a widthwise end position and a widthwise inner side position in the tire width direction for each tire circumferential round.

2. The pneumatic tire according to claim 1, wherein an inclination angle of each of the treats with respect to the tire circumferential direction is more than 45° and less than 90°.

3. The pneumatic tire according to claim 1, wherein a displacement width between the treat reversal positions of the treats at each of the tire widthwise ends of the treats is not wider than a width of each of the treats.

4. The pneumatic tire according to claim 1, further comprising a belt protective layer disposed between the belt and the tread in the tire radial direction, wherein the belt includes a spiral belt layer disposed inward of the endless belt layer in the tire radial direction.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the accompanying drawings:

(2) FIG. 1 is a cross-sectional view of a tire half portion of a pneumatic tire according to one of the disclosed embodiments of the present disclosure, taken along a cross section in the tire width direction;

(3) FIG. 2 is an explanatory diagram conceptually illustrating a zigzag arrangement of an endless belt layer in the pneumatic tire of FIG. 1;

(4) FIG. 3 is an explanatory development view illustrating how the endless belt layer is wound in the pneumatic tire of FIG. 1;

(5) FIG. 4A is an explanatory diagram illustrating the movement of a head portion of the endless belt layer during right-up inclined movement in an example of the forming process for production of the pneumatic tire illustrated in FIG. 1;

(6) FIG. 4B is an explanatory diagram illustrating the movement of the head portion of the endless belt layer during clockwise rotation in an example of the forming process for production of the pneumatic tire illustrated in FIG. 1;

(7) FIG. 4C is an explanatory diagram illustrating the movement of the head portion of the endless belt layer during left-up inclined movement in an example of the forming process for production of the pneumatic tire illustrated in FIG. 1;

(8) FIG. 4D is an explanatory diagram illustrating the movement of the head portion of the endless belt layer during counterclockwise rotation in an example of the forming process for production of the pneumatic tire illustrated in FIG. 1;

(9) FIG. 5A is a front view illustrating the head portion used for production of the pneumatic tire illustrated in FIG. 1;

(10) FIG. 5B is a plan view illustrating the head portion used for production of the pneumatic tire illustrated in FIG. 1; and

(11) FIG. 5C is a side view illustrating the head portion used for production of the pneumatic tire illustrated in FIG. 1.

DETAILED DESCRIPTION

(12) Hereinafter, an embodiment for carrying out the present disclosure will be described with reference to the drawings.

(13) As illustrated in FIG. 1, a pneumatic tire 10 according to this embodiment comprises: a carcass 12 toroidally extending between a pair of bead portions 11; a belt 13 formed by at least one belt layer disposed outward in the tire radial direction of the carcass 12; and a tread 14 disposed outward in the tire radial direction of the belt 13. In FIG. 1, only one half of the tire in the tire width direction on one side of a tire equatorial plane CL is illustrated, and the other half, which has a line-symmetric inverted shape about the tire equatorial plane CL, is not illustrated.

(14) The pneumatic tire 10 is, for example, an aircraft pneumatic tire (aircraft pneumatic radial tire or aircraft pneumatic bias tire). In this embodiment, each bead portion 11 is embedded with a cable bead-shaped bead core 11a covered with rubber in which a wire is spirally wound around an annular core, the belt 13 comprises a spiral belt layer 15 and an endless belt layer 16 disposed outward in the tire radial direction thereof, and the tread 14 is stacked on the belt 13 via a belt protective layer 17 which covers the belt 13 and is formed by, for example, a single layer of aramid fibers, and has provided therein only a plurality of circumferential grooves 14a along the tire circumferential direction.

(15) The endless belt layer 16 according to this embodiment is configured such that a treat 18 formed by covering an organic fiber cord with rubber, for example, is directed so as to change its direction at both tire widthwise ends toward a tire width direction inner side such that it extends in zigzags fashion in the tire circumferential direction.

(16) As used herein, the term “endless” for the endless belt layer 16 means that there is no cut surface in the organic fiber cord at any of the tire widthwise ends.

(17) The spiral belt layer 15 according to this embodiment is formed by being spirally wound around the tire axial direction on the tire circumferential surface. For example, six to eight such spiral belt layers 15 are provided.

(18) In the endless belt layer 16 according to this embodiment, a front surface a and a rear surface b of each treat 18 are reversed, and on at least one tire widthwise end of the treats 18, a treat reversal position at which the front surface a and the rear surface b of each treat 18 are reversed is, at least partially in the tire circumferential direction, displaced in the tire width direction from another treat reversal position adjacent in the tire circumferential direction. For example, two such endless belt layers 16 are provided.

(19) As illustrated in FIG. 2, each of the treats 18 according to this embodiment forming the corresponding endless belt layer 16 is formed by right-up inclined portions 18a extending in a right-rising manner in the tire width direction and left-up inclined portions 18b extending in a left-rising manner in the tire width direction that are alternately repeated in a continuous manner on a plane on which the tire circumferential surface is formed. Assuming that one of the outer surfaces of each treat 18 is defined as a front surface a and the other as a rear surface b, the front surface a and the rear surface b of each treat 18 are reversed at both tire widthwise ends, and on at least one tire widthwise end of the treats 18, a treat reversal position at which the front surface a and the rear surface b of each treat are reversed is, at least partially in the tire circumferential direction, displaced in the tire width direction from another treat reversal position adjacent in tire circumferential direction.

(20) In this embodiment, the right-up inclined portions 18a and the left-up inclined portions b are arranged such that as each right-up inclined portion 18a extends from one end side in the tire width direction of the corresponding treat 18 (in this example, the left end side in FIG. 2) toward the other end side in the tire width direction (in this example, the right end side in FIG. 2), it extends toward one side in the tire circumferential direction (in this example, the upper side in FIG. 2), while as each left-up inclined portion 18b extends from the other end side in the tire width direction (in this example, the right end side in FIG. 2) toward the one end side (in this example, the left end side in FIG. 2), it extends toward one side in the tire circumferential direction (in this example, the upper side in FIG. 2).

(21) As illustrated in FIG. 3, in this embodiment, assuming a series of one right-up inclined portion 18a and one left-up inclined portion 18b of a treat 18 as one turn, this turn is repeated continuously in the tire circumferential direction such that treats 18 are disposed over the spiral belt layer 15 so as to be affixed to the entire formation surface on which the corresponding endless belt layer 16 is to be formed.

(22) One turn may correspond to, for example, a full round of the circumference of the tire circumferential surface (0° to 360°) or a half round (0° to 180°). The circumference of the tire circumferential surface is formed of one turn in the former case, and two turns in the latter case. However, it is not particularly limited how many rounds of the circumference of the tire circumferential surface one turn forms.

(23) In this embodiment, the direction of extension of each treat 18 in the tire width direction is reversed at each tire widthwise end of the treat, and at each point where the direction of extension is reversed, the treat 18 is folded back so as to be symmetrical about the tire width direction (tire widthwise line) along each tire widthwise end (or, each line parallel to the tire widthwise end) as a crease, whereby the front surface a and the rear surface b of the treat 18 are reversed (turned over) (see FIGS. 2 and 3).

(24) Further, in the endless belt layer 16 according to this embodiment, the front surface a and the rear surface b of each treat 18 are reversed at both tire widthwise ends, and on at least one tire widthwise end of the treats 18, a treat reversal position at which the front surface a and the rear surface b of each treat 18 are reversed is, at least partially in the tire circumferential direction, displaced in the tire width direction from another treat reversal position adjacent in the tire circumferential direction.

(25) That is, as illustrated in FIG. 3, in this embodiment, assuming one turn corresponding to a full round of the circumference of the tire circumferential surface, a treat reversal position 19 at which the front and rear surfaces of each treat 18 are reversed is displaced from another treat reversal position, for example, in the following way: in the first tire circumferential round, the tire widthwise position of a treat 18 is located at each tire widthwise end (indicated as 19a in the figure), in the second tire circumferential round, another treat 18 is located inward in the tire width direction of each tire widthwise end, i.e., on each tire widthwise end inner side (indicated as 19b in the figure), in the third tire circumferential round, another treat 18 is located at each tire widthwise end (indicated as 19a in the figure), in the fourth tire circumferential round, another treat 18 is located on each tire widthwise end inner side (indicated as 19b in the figure), and so on. That is, the tire widthwise positions of the treats 18 are shifted (offset) in the tire circumferential direction between adjacent ones (see the broken line in the figure) such that in the odd-numbered tire circumferential rounds, the tire widthwise positions of the treats 18 are located at each tire widthwise end (indicated as 19a in the figure), and in the even-numbered tire circumferential rounds, the tire widthwise positions of the treats 18 are located on each tire widthwise end inner side (indicated as 19b in the figure).

(26) In this way, each treat 18 is folded back along a tire circumferential line as a crease, the front surface a and the back surface b of the treat 18 are reversed, and the treat reversal position 19 of the treat 18 is displaced in the tire width direction from another one for each tire circumferential round. Thus, it is possible to eliminate the occurrence of wide overlapping portions where redundant parts of treats 18 forming the endless belt layer 16 overlap one another. That is, since each treat 18 has no linear portion at any of the tire widthwise ends, even with long linear portions, there will be no wide overlapping portions where redundant parts of the treats 18 overlap one another at the linear portions. In addition, reversed parts of each treat 18 prevent bent portions that respectively continue from linear portions to inclined portions from being lifted or turned up.

(27) In this embodiment, the treats 18 are folded such that the treat reversal positions 19 are displaced in the tire width direction from one another for each tire circumferential round, that is, the tire widthwise positions of the treat reversal positions 19 are shifted (offset), rather than matched, in the tire circumferential direction between adjacent treat reversal positions 19. The position to be shifted (offset) in the tire circumferential direction and the amount to be shifted (offset) in the tire width direction are not limited to constant intervals or the same amount, and may be adjusted as necessary, for example, every turn, depending on the arrangement of the treats 18, such as the degree of overlap between adjacent treats 18.

(28) For example, as illustrated in FIG. 3, if treats 18 are disposed so as to eliminate the overlap between right-up inclined portions 18a and between left-up inclined portions 18b adjacent to one another in the tire circumferential direction, respectively, it is possible to completely eliminate overlapping portions where redundant parts of the treats 18 overlap one another.

(29) Further, in this embodiment, the inclination angle of each treat 18 with respect to the tire circumferential direction, that is, the inclination angle θ of each right-up inclined portion 18a and each left-up inclined portion 18b (see FIG. 2) is preferably more than 10° and less than 90° (10°<θ<90°), and more preferably more than 45° and less than 90° (45°<θ<90°). If the inclination angle exceeds 10°, the circumferential rigidity can be secured more preferentially than the lateral rigidity, if it exceeds 45°, the wear rate can be reduced by increased lateral rigidity, and if it is less than 90°, the wear rate can be further reduced by further increased lateral rigidity.

(30) Next, an example of a method for manufacturing the pneumatic tire 10 (for example, an aircraft tire) according to this embodiment described above will be described.

(31) This method comprises the step of forming the endless belt layer 16 used for the belt 13 (a forming process). In the forming step, as illustrated in FIGS. 4A, 4B, 4C, and 4D, the endless belt layer 16 in this example is formed by continuously winding a treat 18 formed by covering a cord with rubber in zigzag fashion on a forming rotator (drum) 20. When the treat 18 is wound, a head portion 21 of the belt forming device is rotated at each end of the reciprocating traverse in the tire width direction (see FIGS. 4B and 4D) to change the winding direction of the treat 18 such that the front surface a and the rear surface b of the treat 18 are reversed.

(32) As illustrated in FIGS. 5A, 5B, and 5C, for example, the head portion 21 in this example is formed in a disk-like shape having an opening 21a penetrating substantially the center of the disk surface, has two rollers, a first roller 22a and a second roller 22b (see FIG. 5B), for guiding treats 18 individually, and is provided with a rotation mechanism (not illustrated) that enables rotation of the forming rotator 20 on the winding surface. One of the surfaces of the heat portions 21 is disposed to face the outer surface of the forming rotator 20. In FIGS. 4A, 4B, 4C, and 4D, the facing surface 21b of the head portion 21 that faces the outer surface of the forming rotator 20 is illustrated as a surface for reference (in a plan view). In fact, when forming the endless belt layer 16, the illustrated facing surface 21b is directed to face the outer surface of the forming rotator 20.

(33) In this example, the first roller 22a and the second roller 22b have substantially the same shape made of, for example, a cylindrical rotator (see FIGS. 5A and 5B). The first roller 22a and the second roller 22b are spaced above from the facing surface 21b of the head portion 21 and disposed in substantially parallel spaced relation with each other (see FIGS. 5B and 5C), and are pivotally supported so as to be pivotable about the axis. In this example, the head portion 21 rotates approximately 90° to the left and right on the facing surface 21b about the center of the disk-like surface as a rotation axis, such that the first roller 22a and the second roller 22b can also be rotated approximately 90° to the left and right on the facing surface 21b.

(34) In this example, the endless belt layer 16 is formed through the following forming process using the above-described forming rotator 20 and head portion 21 (see FIGS. 4A, 4B, 4C, and 4D).

(35) As will be described later, the following forming process (see FIGS. 4A, 4B, 4C, and 4D) focuses on three points: (i) two rollers (in this example, the first roller 22a and the second roller 22b) are provided; (ii) a rotation mechanism for rotating the two rollers is provided; and (iii) the head portion 21 of the belt forming device is rotated at each end of the reciprocating traverse in the tire width direction such that the rotation direction is reversed at the right and left ends to prevent the treat 18 from twisting while changing the winding direction.

(36) First, the treat 18 is positioned on the facing surface 21b side of the head portion 21 through the opening 21a and guided by the first roller 22a, and in this state the treat 18 is affixed to the outer surface of the forming rotator 20 while moving the head portion 21 on the outer surface of the rotating forming rotator 20 in a right-up inclined direction from the widthwise left end side toward the widthwise right end side (see the arrow in FIG. 4A). As a result, a right-up inclined portion 18a is formed with the front surface a side of the treat 18 facing upward (see FIG. 3).

(37) Then, when the head portion 21 reaches a widthwise right end point P on the outer surface of the forming rotator 20, the rotation of the forming rotator 20 is stopped, and while the treat 18 being positioned on the facing surface 21b side of the head portion 21 through the opening 21a, the head portion 21 is rotated approximately 90° clockwise (see the arrow in FIG. 4B) such that the treat 18 is guided by the second roller 22b (see FIG. 4B). The rotation of the head portion 21 causes the treat 18 to be folded back at a tire widthwise end along a tire circumferential line as a crease such that the front surface a and the rear surface b of the treat 18 are reversed, with the rear surface b side facing upward, and the treat 18 is folded back (see FIG. 4B) at a treat reversal position 19 as a tire widthwise end 19a (see FIG. 3).

(38) Then, while the treat 18 being positioned on the facing surface 21b side of the head portion 21 through the opening 21a and being guided by the second roller 22b, the treat 18 is affixed to the outer surface of the forming rotator 20 while moving the head portion 21 on the outer surface of the rotating forming rotator 20 in a left-up inclined direction from the widthwise right end side toward the widthwise left end side (see the arrow in FIG. 4C). As a result, a left-up inclined portion 18b is formed with the rear surface b side of the treat 18 facing upward (see FIG. 3).

(39) Then, when the head portion 21 reaches a widthwise left end point P on the outer surface of the forming rotator 20, the rotation of the forming rotator 20 is stopped, and while the treat 18 being positioned on the facing surface 21b side of the head portion 21 through the opening 21a, the head portion 21 is rotated approximately 90° counterclockwise (see the arrow in FIG. 4D) such that the treat 18 is guided by the first roller 22a (see FIG. 4D). The rotation of the head portion 21 causes the treat 18 to be folded back at a tire widthwise end along a tire circumferential line as a crease such that the rear surface b and the front surface a of the treat 18 are reversed, with the front surface a side facing upward, and the treat 18 is folded back (see FIG. 4D) at a treat reversal position 19 as a tire widthwise end inner side 19b (see FIG. 3).

(40) Through the above process, the treat 18 is folded back along each tire widthwise end 19a as a crease such that the front surface a and the rear surface b of the treat 18 are reversed to provide one right-up inclined portion 18a and one left-up inclined portion 18b, a combination of which is taken as one turn, and this one turn forms the first tire circumferential round of the treat 18 (see FIG. 3).

(41) Subsequently, the movement of the head portion 21 in the right-up inclined direction (see FIG. 4A), the rotation of the head portion 21 in the clockwise direction (see FIG. 4B), the movement of the head portion 21 in the left-up inclined direction (see FIG. 4C), and the rotation of the head portion 21 in the counterclockwise direction (see FIG. 4D) are repeated in the stated order to form the second tire circumferential round of the treat 18. In the second round, during the clockwise rotation of the heat portion 21 (see FIG. 4B), the rotation position of the head portion 21 (i.e., the position on the forming rotator 20 at which the head portion 21 is rotated) is set at, for example, a position retracted inward from the widthwise right end, not at the widthwise right end in the first round, on the outer surface of the forming rotator 20. Similarly, when the head portion 21 is rotated counterclockwise (see FIG. 4D), the rotation position of the head portion 21 is set at, for example, a position retracted inward from the widthwise left end, not at the widthwise left end in the first round, on the outer surface of the forming rotator 20.

(42) Thus, in this example, by setting the rotation position of the head portion 21 in the second tire circumferential round of a treat 18 at, for example, a position retracted inward from each widthwise end, not at each widthwise end, on the outer surface of the forming rotator 20, treat reversal positions 19 adjacent in the tire circumferential direction at which treats 18 are folded back in the first and second tire circumferential rounds of the treats 18 can be shifted (offset), rather than matched, in the tire width direction between the treats 18 adjacent to each other in the tire circumferential direction (see FIG. 3).

(43) Subsequently, the movement of the head portion 21 in the right-up inclined direction (see FIG. 4A), the rotation of the head portion 21 in the clockwise direction (see FIG. 4B), the movement of the head portion 21 in the left-up inclined direction (see FIG. 4C), and the rotation of the head portion 21 in the counterclockwise direction (see FIG. 4D) are repeated in the stated order with the treat reversal positions 19 at which treats 18 are folded back being displaced in the tire width direction between odd-numbered and even-numbered tire circumferential rounds (see FIG. 3), and the treats 18 are affixed to the entire formation surface on which the endless belt layer 16 is to be formed.

(44) When the treat reversal positions 19 at which treats 18 are folded back are displaced in the tire width direction (see FIG. 3), in addition to merely rotating the head portion 21 in which the first roller 22a and the second roller 22b are arranged side by side approximately 90° to the left and right on the facing surface 21b, it is also possible to finely adjust the rotation angle of the head portion 21 as necessary to eliminate the occurrence of wide overlapping portions where redundant parts of folded treats 18 overlap one another. By finely adjusting the rotation angle of the head portion 21, the treat 18 that is folded back while being guided by the first roller 22a or the second roller 22b can take a trajectory to prevent the occurrence of wide overlapping portions where redundant parts of the treat 18 on the forming rotator 20 overlap one another.

(45) Further, in the above example, when the treat 18 is affixed to the outer surface of the forming rotator 20, the head portion 21 is moved in the right-up or left-up inclined direction while the forming rotator 20 is caused to rotate. However, the head portion 21 may be simply moved to the left and right while the forming rotator 20 is caused to rotate.

(46) In this way, by forming the endless belt layer 16 through the above-described steps using the forming rotator 20 and the head portion 21 in this example, it is possible to set the folding angle freely for folding back each treat 18, while making adjustments such that redundant parts where treats 18 overlap one another would not be formed widely or not at all. This setup can relax the rigidity in the tire circumferential direction, reduce the incidence of uneven shoulder wear, and eliminate the possibility of contact between cords inside the belt during vulcanization, avoiding the occurrence of a starting point of separation between belts.

(47) Further, in this example, two rollers (the first roller 22a and the second roller 22b) are arranged in parallel, and a treat 18 is wound around the forming rotator 20 via the head portion 21 that can be rotated to the left and right on the facing surface 21b. With this setup, at the time of winding a treat 18, the treat 18 can be folded back easily and the inclination angle of the treat 18 can be finely adjusted with ease.

(48) Further, the head portion 21 in this example contains the first roller 22a and the second roller 22b arranged side by side, and can be rotated to the left and right on the facing surface 21b. Since this rotation is accomplished in the same plane facing the outer surface of the forming rotator 20, it is easy to finely adjust the rotation angle of the head portion 21, i.e., the first roller 22a and the second roller 22b (for example, by 1° or 2°), and the rotation angle can be controlled simply by adjusting the amount of rotation.

(49) Further, in this example, although the affixing of the wound treat 18 is performed while the first roller 22a and the second roller 22b are always kept in tension, it is easy to make adjustments to keep the tension constantly applied to the rollers since the first roller 22a and the second roller 22b are arranged in parallel side by side in the same plane facing the outer surface of the forming rotator 20.

(50) Furthermore, in the forming process of the endless belt layer 16 in this example, when treats 18 are folded back, the direction of the treats 18 can be changed at each tire widthwise end with a slight shift or in a curved manner. With this configuration, it is ensured that the treats 18 do not overlap when folded back.

REFERENCE SIGNS LIST

(51) 10: pneumatic tire 11: bead portion 11a: bead core 12: carcass 13: belt 14: tread 14a: circumferential groove 15: spiral belt layer (belt layer) 16: endless belt layer (belt layer) 17: belt protective layer 18: treat 18a: right-up inclined portion 18b: left-up inclined portion 19: treat reversal position 19a: tire widthwise end 19b: tire widthwise end inner side 20: forming rotator 21: head portion 21a: opening 21b: facing surface 22a: first roller 22b: second roller CL: tire equatorial plane P: end point a: front surface b: rear surface θ: inclination angle