JP2011005946A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire which suppresses dimension variation in a radial direction of a tire by centrifugal force at traveling of a vehicle and enhancing operation property (especially linear advancement traveling property) of the vehicle.SOLUTION: In the pneumatic tire 1, at least part of an outer surface contour CR in a tread width direction in a tread 5 is set to a predetermined radius R of curvature making a tire center point O as a center and a belt layer 4 extending in a tread width direction is provided inside the tire radial direction of the tread 5. When an angle formed by a linear line LO connecting a predetermined part L of an outer surface 5a of the tread 5 and the tire center point O and a tire equator line CL is θ, the tread thickness outside the tire radial direction further than the outermost belt layer 8 positioned on the outermost side in the tire radial direction of the belt layer 4 is T, and the tread thickness on the outer side in the tire radial direction further than the outermost belt layer 8 on the tire equator line CL is T0, it satisfies a relationship of T=To-R(1-cosθ)±5%.

Description

  The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire with high straight running performance of a vehicle.

  Conventionally, a pneumatic tire is known in which a belt layer including a plurality of belts is provided in a tread portion. In these belt layers, wandering is performed by gradually reducing the thickness of the tread disposed on the outer side of the tire diameter from the belt layer located on the outermost side in the tire radial direction from the center in the tread width direction to the outer side in the tread width direction. The improvement of property and rolling resistance are improved (for example, refer patent document 1).

Japanese Patent Laid-Open No. 5-221205

  However, the conventional pneumatic tire described above has a problem that the rigidity of the shoulder portion is lowered and steering stability is lowered because the belt is curved when the tire rolls and contacts the road surface.

  An object of the present invention is to provide a pneumatic tire that can suppress dimensional fluctuations in the radial direction of the tire due to centrifugal force during traveling of the vehicle and that improves the maneuverability of the vehicle (particularly straight traveling performance).

  In the pneumatic tire 1 according to the first aspect of the present invention, at least a part of the outer surface contour (outer surface contour CR) in the tread width direction (tread portion 5) in the tread width direction cross section in the tread width direction cross section is tire rotation. A plurality of belt layers (belts) that are set to a predetermined radius of curvature (curvature radius R) around a tire center point (tire center point O) located on the axis and extend in the tread width direction inside the tread portion in the tire radial direction. A pneumatic tire (pneumatic tire 1) provided with a layer 4), the tire center point from a predetermined portion (predetermined portion L) of the outer surface (outer surface 5a) of the tread portion in the cross section in the tread width direction The angle between the straight line (straight line LO) connecting to the tire and the tire equator line (tire equator line CL) is θ, and the outermost belt located on the outermost side in the tire radial direction among the plurality of belt layers When the thickness of the tread on the outer side in the tire radial direction from the (outermost belt layer 8) is T, and the tread thickness on the outer side in the tire radial direction from the outermost belt layer on the tire equator line is To, T = The gist is to satisfy the relationship of To-R (1-cosθ) ± 5%.

  Thereby, since it is possible to suppress the bending of the belt layer when it is pressed against the mold by the prider during tire vulcanization, a flat belt shape can be obtained. When the belt is flat, the contact pressure at the time of rolling the tire becomes uniform, and the change in the crossing angle of the belt layer cords can be suppressed by the contact pressure in the vertical direction of the tire rolling. Therefore, changes in the cross-sectional shape are reduced at the center portion in the tread width direction and the outer side in the tread width direction during travel, and steering stability (particularly straight running stability) is improved. Moreover, since the rigidity of a tread part improves, the change of the diameter dimension of a shoulder part can be suppressed.

  In another feature, in the cross section in the tread width direction, the distance W2 along the tread width direction between the predetermined portions on both the left and right sides with respect to the tire equator line is equal to the tread ground contact width TW where the tread portion contacts the road surface. On the other hand, it is set to 50% to 80%.

  In another feature, the predetermined portion L of the outer surface (outer surface 5a) of the tread portion (tread portion 5) is disposed at a position of a dimension W along the tread width direction from the tire equator line (tire equator line CL). The reduction amount of the tread thickness T with respect to the tread thickness T0 satisfies the relationship T0-R (1-cos θ).

  According to the pneumatic tire according to the present invention, it is possible to suppress the dimensional variation in the tire radial direction due to the centrifugal force when the vehicle travels, and to improve the maneuverability of the vehicle (particularly straight travelability).

It is a tread width direction sectional view of a pneumatic tire by an embodiment of the present invention. 1 is a schematic view of an entire pneumatic tire according to an embodiment of the present invention. It is the schematic of the pneumatic tire cross section at the time of comparing the radial direction outermost belt by embodiment of this invention with a prior art example.

  Hereinafter, details of a pneumatic tire according to an embodiment of the present invention will be described with reference to the drawings. However, it should be noted that the drawings are schematic, and the thicknesses and ratios of the material layers are different from actual ones. Therefore, specific thicknesses and dimensions should be determined in consideration of the following description. Moreover, the part from which the relationship and ratio of a mutual dimension differ also in between drawings is contained.

  FIG. 1 is a cross-sectional view in the tread width direction of a pneumatic tire according to an embodiment of the present invention, and FIG. 2 is a schematic view of the entire pneumatic tire according to an embodiment of the present invention.

  The pneumatic tire 1 includes a pair of annular bead cores 2 and 2 that are spaced apart from each other in the tread width direction, a carcass 3 that connects these bead cores 2 and 2 in a toroidal shape and serves as a tire skeleton, On the crown portion 3a at the center in the tread width direction of the carcass 3, a three-layer belt layer 4 extending in the tread width direction is provided. The outermost belt layer 8 is disposed on the outermost side in the tire radial direction of the belt layer 4.

  Further, a crown portion 3a of the carcass 3, a belt layer 4, and a tread portion 5 made of a tread rubber covering these are formed in the center portion of the pneumatic tire 1 in the tread width direction. Side wall portions 6 and 6 are provided on the left and right sides of the tread portion 5. A bead portion 7 is formed in the vicinity of the bead core 2 on the inner diameter side of the sidewall portion 6.

  In the cross section in the tread width direction, the outer surface 5a of the tread portion 5 on the center side in the tread width direction has a radius of curvature around the tire center point O (see FIG. 2) located on the tire rotation axis S (see FIG. 2). Is set to the arc-shaped outer surface contour CR set to R. That is, the outer surface 5a of the tread portion 5 and the outer surface contour CR coincide with each other on the inner side in the tread width direction, but the outer surface 5a of the tread portion 5 with respect to the outer surface contour CR on the outer side in the tread width direction. Is arranged on the inner side in the tire radial direction.

  Further, a straight line LO connecting the predetermined portion L of the width dimension W and the tire center point O from the tire equator line CL toward the outer side in the tread width direction on the outer surface 5a of the tread portion 5 is the tire equator line CL. Cross at an inclination angle θ. The tread contact width at which the tread portion 5 of the pneumatic tire 1 contacts the road surface is set to TW, and the distance along the tread width direction between the predetermined portion L and the tire equator line CL is set to W. Yes.

  In the cross section in the tread width direction, the distance W2 (W × 2) along the tread width direction between the predetermined portions L on the left and right sides with respect to the tire equator line CL is a position of 50% to 80% with respect to the tread ground contact width TW. Is arranged.

  Here, T is the tread thickness outside the outermost belt layer 8 in the predetermined portion L in the tire radial direction, and T0 is the tread thickness outside the outermost belt layer 8 on the tire equator line CL. In this case, the relationship T = To-R (1-cos θ) ± 5% is satisfied. Further, the reduction amount of the tread thickness T with respect to T0 satisfies the relationship T0-R (1-cos θ).

  FIG. 3 is a schematic view of a cross section of a pneumatic tire when a radially outermost belt according to an embodiment of the present invention is compared with a conventional example.

  In FIG. 3, the solid line indicates the outermost belt layer 8 according to the embodiment of the present invention, and the broken line indicates the outermost belt layer 108 according to the conventional example. In the cross section in the tread width direction, the outermost belt layer 8 is arranged substantially linearly along the tread width direction. The outermost belt layer 108 extends while curving gradually inward in the tire radial direction toward the outer side in the tread width direction. A plurality of cords are embedded in the belt layer 4 along the tire circumferential direction, and the extending directions of the plurality of cords extend so as to cross each other. The crossing direction of the cords in the inner portion 8a of the outermost belt layer 8 in the tread width direction is 60 ° in the present embodiment, and the crossing direction of the cords in the outer portion 8b in the tread width direction is also 60 ° in the present embodiment. Is set. Thus, in the present invention, the outermost belt layer 8 extends substantially linearly in the tread width direction, and the crossing direction of the cords can be set to be substantially the same on the inner side and the outer side in the tread width direction. it can.

  On the other hand, in the outermost belt layer 108 according to the conventional example, the cord crossing direction of the portion 108a inside the tread width direction is set to 60 °, and the cord crossing direction of the portion 108b outside the tread width direction is set to 55 °. Yes. When the tire rolls, the crossing direction of the cords of the portion 108b outside the tread width direction varies from 55 ° to 60 °.

  Below, the effect by embodiment of this invention is demonstrated.

<Operation effect>
(1) In the pneumatic tire 1 according to the present embodiment, at least a part of the outer surface contour CR in the tread width direction in the tread portion 5 is set to a predetermined curvature radius R around the tire center point O, and the tread portion 5 is a pneumatic tire 1 provided with a belt layer 4 extending in the tread width direction, and an angle formed by a straight line LO connecting a predetermined portion L of the outer surface 5a of the tread portion 5 and the tire center point O and a tire equator line CL. , T is the tread thickness on the outer side in the tire radial direction of the outermost belt layer 8 located on the outermost side in the tire radial direction of the belt layer 4, and the radial direction of the tire is on the tire equator line CL relative to the outermost belt layer 8 When the outer tread thickness is T0, the relationship of T = To−R (1−cos θ) ± 5% is satisfied.

  Thereby, since it is possible to suppress the curvature of the belt layer 4 when pressed against the mold by the ladder during tire vulcanization, a flat belt shape can be obtained. When the belt is flat, the contact pressure at the time of rolling the tire becomes uniform, and the change in the crossing angle of the cords of the belt layer 4 can be suppressed by the contact pressure in the vertical direction of the tire rolling. Therefore, a change in cross-sectional shape is reduced between the center side in the tread width direction and the outer side in the tread width direction during traveling, and steering stability (particularly, straight running stability) is improved. Moreover, since the rigidity of the tread part 5 improves, the change of the diameter dimension of a shoulder part can be suppressed.

  (2) In the cross section in the tread width direction, the distance W2 along the tread width direction between the predetermined portions L on the left and right sides of the tire equator line CL is set to 50% to 80% with respect to the tread ground contact width TW. Has been.

  Accordingly, the curvature of the belt layer 4 can be further suppressed when the tire is vulcanized and pressed against the mold by the prider, so that a further flat (flat) belt shape can be obtained.

  (3) The predetermined portion L of the outer surface 5a of the tread portion 5 is disposed at a position of the dimension W along the tread width direction from the tire equator line CL, and is the outermost portion from the tire equator line CL to the predetermined portion L. A reduction amount of the tread thickness T on the outer side in the tire radial direction from the belt layer 8 with respect to the tread thickness T0 satisfies T0-R (1-cos θ).

  As a result, the belt shape can be further flattened, and steering stability (particularly, straight running stability) is further improved.

  It should not be understood that the description and the drawings, which form part of the disclosure of the above-described embodiments, limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  For example, in the above-described embodiment, the belt layer 4 is composed of three belts, and the belt positioned on the outermost side in the tire radial direction is the outermost belt layer 8, but the number of belts is set to two or less or four or more. May be.

  Next, the present invention will be described more specifically through examples.

  In the examples, a pneumatic tire having a tire size of 205 / 55R16 was used as a test tire. This test tire is provided with a belt layer composed of two belts, and a belt layer having a plurality of cords crossing each other. In the carcass, 40 bead fillers made of polyester 1500D / 2 are disposed per 50 mm width. These bead fillers extend along the tread width direction (that is, along the direction in which the angle with respect to the tire circumferential direction is substantially 90 °). The bead filler had a JIS hardness of 90 on both the left and right sides. The curvature radius of the outer surface contour was 600 mm. In this pneumatic tire, the flatness in the cross section in the tread width direction of the belt layer was appropriately changed to change the tread thickness of the tread portion, thereby obtaining test tires according to inventive examples 1 to 4 and a conventional example.

  In Example 1 of the present invention, the portion of the outer surface of the tread portion was set at a position that was 80% of the tread width. The angle formed between the straight line connecting the predetermined portion and the tire center point O and the tire equator line is θ, and the tread thickness of the tread portion at the predetermined portion is 600 (1-cos θ) mm.

  In Example 2 of the present invention, the portion of the outer surface of the tread portion was set at a position of 100% of the tread width. The angle formed between the straight line connecting the predetermined portion and the tire center point O and the tire equator line is θ, and the tread thickness of the tread portion at the predetermined portion is 600 (1-cos θ) mm.

  In Example 3 of the present invention, the portion of the outer surface of the tread portion was set to a position of 60% of the tread width. The angle formed between the straight line connecting the predetermined portion and the tire center point O and the tire equator line is θ, and the tread thickness of the tread portion at the predetermined portion is 600 (1-cos θ) mm.

  In Example 4 of the present invention, the portion of the outer surface of the tread portion was set at a position of 30% of the tread width. The angle formed between the straight line connecting the predetermined portion and the tire center point O and the tire equator line is θ, and the tread thickness of the tread portion at the predetermined portion is 600 (1-cos θ) mm.

  In the conventional example, a portion of the outer surface of the tread portion is set to a position of 80% of the tread width. However, the tread thickness of the tread portion at the predetermined portion was set to T0 which is the same as the tread thickness T0 on the tire equator line. That is, the tread thickness was set to the same thickness over the entire tread portion.

  Table 1 shows the dimensions of the test tires and the vehicle running results. Here, the numerical value of the straight running performance is a relative value when the conventional example is set to a reference value of 100.

  Thus, in Examples 1-4 of the present invention, it was found that the straight traveling performance during vehicle traveling is improved as compared with the conventional examples. This is considered to be because the change in the tire radial direction due to the centrifugal force during traveling can be suppressed.

CL tire equator line O tire center point TW tread width L predetermined portion θ angle 4 belt layer 5 tread portion 5a outer surface 8 outermost tort layer

Claims (3)

In the cross section in the tread width direction, at least a part of the outer surface contour in the tread width direction in the tread portion is set to a predetermined radius of curvature R around the tire center point located on the tire rotation axis,
A pneumatic tire provided with a plurality of belt layers extending in the tread width direction on the inner side in the tire radial direction of the tread portion,
An angle formed by a straight line connecting a predetermined portion of the outer surface of the tread portion to the tire center point in the cross section in the tread width direction and the tire equator line is θ, and the outermost position in the tire radial direction among the plurality of belt layers. When the thickness of the tread on the outer side in the tire radial direction from the outer belt layer is T, and the tread thickness on the outer side in the tire radial direction from the outermost belt layer on the tire equator line is To,
A pneumatic tire characterized by satisfying a relationship of T = To-R (1-cos θ) ± 5%.   In the cross section in the tread width direction, the distance W2 along the tread width direction between the predetermined portions on the left and right sides with respect to the tire equator line is 50% to the tread ground contact width TW where the tread portion contacts the road surface. The pneumatic tire according to claim 1, wherein the pneumatic tire is set to 80%. The predetermined portion of the outer surface of the tread portion is disposed at a position of a dimension W along the tread width direction from the tire equator line,
The pneumatic tire according to claim 1 or 2, wherein a decrease amount of the tread thickness T with respect to the tread thickness T0 satisfies a relationship of T0-R (1-cos θ).

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