JP2008162433A - Tire for motorcycle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance turning performance by mitigating a resisting effect at a tread end and/or a side wall to easily give a large camber angle when a motorcycle makes a turn. <P>SOLUTION: This tire 1 for the motorcycle has a tread part 2, a side wall 3 and a bead 4. In a tire meridian section including the axis of the rotation of the tire in a normal state that the tire is rim-assembled to a normal rim J, normal internal pressure is filled in the tire, and no load is applied to the tire, a contour line 1L of the tire outer surface comprises a tread side contour line TL composed of an arc-shaped curve extending between tire maximum width positions P1, P1 and projecting outwardly in the tire radial direction, and a side contour line SL composed of an arc-shaped curve extending from the tire maximum width position P1 to a separation point P2 from the rim J and projecting outwardly in the tire axial direction. In addition, these contour lines TL and SL are smoothly connected to each other without forming any angle. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a motorcycle tire capable of improving turning performance.

  For example, as shown in FIG. 5, in the conventional motorcycle tire a <b> 1, the outer surface outline of the tread portion b is formed from an arcuate curve that protrudes outward in the tire radial direction, and the tread portion b and the sidewall portion are formed. A clear corner (edge) is formed at the intersection d with c (see Patent Document 1 below).

  However, such a motorcycle tire a1 is difficult to deform because the intersection portion d has high rigidity. For this reason, as shown in FIG. 6, when the camber angle α is given to the tire a during turning, the angle of the intersection d stretches against the road surface g so as to prevent the tire a from falling down. There is a problem that it is difficult to provide a sufficient camber angle α. For this reason, the camber thrust (centripetal force for balancing with the centrifugal force at the time of turning) that is generated substantially in proportion to the camber angle α is reduced, and there is room for further improvement in turning performance.

  Further, in Patent Document 2 below, as shown in FIG. 7, in order to prevent heat generation at the end portion of the tread portion b, an intersection d of the tread portion b and the sidewall portion c is formed with an arc surface. A motorcycle tire a2 is described. However, the sidewall portion c of the motorcycle tire a2 has a tendency that it is difficult to bend because its outer surface contour line is formed in a substantially straight line. Therefore, as shown in FIG. 6, when the camber angle α is given, the side wall portion c is stretched so as to prevent the tire from falling down, and similarly to the above, it is difficult to give the tire a large camber angle α. was there.

JP-A-10-109507 JP 2002-331809 A

  The present invention has been devised in view of the above circumstances, and the tread-side contour formed of an arcuate curve that extends between the tire maximum width position and protrudes outward in the tire radial direction as a contour line of the tire outer surface. And a side-side contour line consisting of an arc-shaped curve extending from the tire maximum width position to the separation point from the rim and projecting outward in the tire axial direction, and further comprising a tread-side contour line and a side-side contour line. Based on the smooth connection without corners, it is possible to alleviate the tension action at the tread edge and / or the side wall during turning and thus easily give a large camber angle to improve the turning performance. The object is to provide a tire for a motorcycle.

  The invention according to claim 1 of the present invention includes a tread portion, a sidewall portion extending inward in the tire radial direction from both ends of the tread portion, and a bead portion provided at an inner end of the sidewall portion. A motorcycle tire having a tire rim assembled in a regular rim, filled with a regular internal pressure and loaded with a regular internal pressure and including a normal tire rotation axis, wherein the contour line on the outer surface of the tire is a tire maximum width position. A tread-side contour line formed of an arcuate curve that protrudes outward in the tire radial direction, and an arcuate curve that protrudes from the tire maximum width position to the separation point from the rim and protrudes outward in the tire axial direction. The tread side contour line and the side side contour line are smoothly connected without having a corner.

  The invention according to claim 2 is the motorcycle tire according to claim 1, wherein both ends of the tread side contour line are small arcs having a curvature radius Re of 5 to 25 mm.

  According to a third aspect of the present invention, in the motorcycle tire according to the first or second aspect, the side-side contour line comprises a single circular arc, and the radius of curvature Rw thereof is 15 to 40 mm.

  According to a fourth aspect of the present invention, the side-side contour line includes a first arc on the outer side in the tire radial direction and a second arc connected to the inner side in the tire radial direction, and the first arc has a radius of curvature. 3. The motorcycle tire according to claim 1, wherein Rw1 is 15 to 40 mm, and the second arc has a radius of curvature Rw2 larger than 40 mm.

  In the outer tire contour line of the motorcycle tire of the present invention, the tread-side contour line and the side-side contour line that are continuous with the tire maximum width position as a boundary are smoothly connected without having a corner. For this reason, during turning, the tension action which tends to occur at the end of the tread portion and / or the sidewall portion is alleviated, and as a result, a large camber angle can be easily given to the tire. Therefore, since the motorcycle tire of the present invention can generate a large camber thrust, the turning performance is improved.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a tire meridian cross-sectional view including a tire rotation axis of an assembly in which a motorcycle tire 1 of this embodiment is mounted on a regular rim J.

  Here, FIG. 1 shows the normal state of the unloaded tire in which the motorcycle tire 1 is assembled to the normal rim J and filled with the normal internal pressure. In addition, the “regular rim” is a rim determined for each tire in a standard system including a standard on which a tire is based, for example, a standard rim for JATMA, “Design Rim” for TRA, For ETRTO, use “Measuring Rim”. The “regular internal pressure” is the air pressure defined by each standard for each tire in the standard system including the standard on which the tire is based. The maximum air pressure is JATMA, and the table “TIRE LOAD” is TRA. Maximum value described in “LIMITS AT VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” for ETRTO.

  The motorcycle tire 1 of the present embodiment is suitably used for a rear wheel that receives driving force, and includes a tread portion 2 and a pair of sidewalls extending inward in the tire radial direction from both ends thereof. Parts 3 and 3, and bead parts 4 located at the inner ends of the respective side wall parts 3 and having bead cores 5 embedded therein. The pneumatic tire 1 includes a carcass 6 including at least one carcass ply 6A extending across the bead cores 5 and 5, and a belt layer 7 disposed on the outer side in the tire radial direction of the carcass 6 and inside the tread portion. And are provided.

  The tread portion 2 is smoothly curved and formed in an arc shape so as to protrude outward in the tire radial direction. Although not shown, the tread portion 2 may be appropriately provided with a draining groove.

  The carcass 6 is composed of at least one carcass ply in which carcass cords are arranged at an angle of 60 to 90 ° with respect to the tire equator C, for example. The carcass 6 of the present embodiment is composed of one carcass ply 6A that is inclined at 90 degrees with respect to the tire equator C. As the carcass cord, an organic fiber cord such as nylon, polyester, or rayon is preferably employed in order to reduce the weight of the tire and improve the riding comfort.

  In addition, the carcass ply 6A includes a main body portion 6a that extends from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and a turn-up portion that is turned around the bead core 5 from the inner side to the outer side in the tire axial direction. 6b and a so-called winding ply. A bead apex 8 made of hard rubber is provided between the main body portion 6a and the folded portion 6b. The bead portion 4 and the sidewall portion 3 are formed by a hard rubber extending in a radially outward direction from the bead core 5. Is effectively reinforced.

  The belt layer 7 is composed of at least one belt ply 7A and 7B using a belt cord, in this embodiment. The belt ply 7A may be, for example, a cut ply, or a belt-like ply covered with a belt cord is wound around the carcass 6 in the spiral direction at an angle of 5 ° or less with respect to the tire radial direction and the tire circumferential direction. Any of the so-called jointless plies formed by may be used. As the belt cord, an organic fiber cord such as nylon, polyester, rayon or aromatic polyamide, or a steel cord is employed.

  As shown in FIG. 1 and FIG. 2 in which the contour line is enlarged, the motorcycle tire 1 of the present invention has a tire meridian cross section in a normal state, and the contour line 1L of the tire outer surface is the tire maximum width position P1, P1. Between the tire tread side contour line TL, which is an arcuate curve that protrudes outward in the tire radial direction, and from the tire maximum width position P1 to the separation point P2 from the rim J, and protrudes outward in the tire axial direction. The tread side contour line TL and the side side contour line SL are smoothly connected without having a corner.

  In such a motorcycle tire 1, as shown in FIG. 6, when the tire is given a camber angle α, the intersection of the tread portion 2 and the sidewall portion 3 is rounded by an arc. In this portion, the tensioning action that has been apt to occur in the past is greatly relieved. In addition, since the sidewall portion 3 also has an outer surface contour shape that protrudes outward in the tire axial direction, this portion can be effectively deflected when a load is applied, which can contribute to providing a large camber angle, and when overcoming protrusions and steps Is effectively absorbed. Thus, the motorcycle tire 1 of the present invention can easily give a large camber angle corresponding to the turning speed and turning radius and generate a large camber thrust. Accordingly, the turning performance is greatly improved.

  Here, when the tread portion 2 is provided with grooves, sipes, spews, and the like, the tread side contour line TL is determined on the assumption that these are not present.

  Similarly, when the side wall portion 3 is provided with a raised object for representing a tire size, a trademark, other decorative patterns, etc., the side outline SL excludes these raised objects ( (Assuming there is no).

  In addition, the tire maximum width position P1 is a position that protrudes most outward in the tire axial direction on the contour line 1L, and when the position is specified, a protruding object for representing characters, symbols, and the like is excluded (not present) (Assuming that)

  The separation point P2 is a point on the outermost side in the tire radial direction where the bead portion 4 of the tire 1 and the rim J are in contact.

  In the present embodiment, the tread side contour line TL is formed from a plurality of arcs, for example, a crown arc portion Ac extending in the center portion of the tread and having a radius of curvature Rc, and smoothly connecting to both outer sides thereof and the crown arc A pair of shoulder arc portions As having a radius of curvature Rs larger than the portion Ac, and a small arc Ae smoothly connected to both outer sides thereof and having a smaller radius of curvature Re than the crown arc portion Ac.

  When the small arc Ae is provided at both ends of the tread side contour line TL, the tire maximum width position P1 can be easily positioned inward in the tire radial direction. The motorcycle tire 1 in which the tire maximum width position P1 is provided inwardly in the tire radial direction can increase the so-called design camber angle β, and can easily give the tire a large camber angle even during actual running. it can. Here, as shown in FIG. 1, the design camber angle β is a tire axis of a straight line N drawn from the tire maximum width position P1 to a tire equator point CP which is an intersection of the tread side contour line TL and the tire equator C. The angle with respect to the direction is preferably 30 degrees or more, more preferably 31 degrees or more, and still more preferably 34 degrees or more. If the design camber angle β is too large, the straight running stability may be deteriorated. Therefore, it is preferably 40 degrees or less, more preferably 36 degrees or less.

  The small arc Ae may be a single arc or one whose curvature radius changes continuously. In any case, the radius of curvature Re of the small arc Ae is preferably 5 to 25 mm.

  When the radius of curvature Re of the small arc Ae is less than 5 mm, the shape of the end portion of the tread side contour line TL approaches a sharp corner, and as a result, the end portion of the tread side contour line TL tends to stick to the road surface during turning. Become. From this point of view, the radius of curvature Re of the small arc Ae is more preferably 10 mm or more, and more preferably 15 mm or more. On the other hand, when the radius of curvature Re of the small arc Ae exceeds 25 mm, the end portion of the tread outline is flattened and it is difficult to smoothly connect with the side outline SL. From such a viewpoint, the radius of curvature Re of the small arc Ae is preferably 20 mm or less.

  Further, as shown in an enlarged view in FIG. 2, the small arc Ae is connected to the shoulder arc portion As at a small length extending from the tire maximum width position P1 to the inside in the tire axial direction at a connection point P3. If the thickness is excessively small, it is difficult to obtain the above-described effect. Conversely, if the length of the small arc Ae is too large, the tread width TW may be reduced, or the design camber angle β may be excessively increased. From such a viewpoint, the length of the small arc Ae is preferably 10 mm or more, more preferably 15 mm or more, and preferably 25 mm or less, more preferably 20 mm or less. In the present embodiment, the tread width TW is a tire axial direction distance between the tire maximum width positions P1 and P1, and the width TW is formed to be larger than the rim width.

  The radius of curvature Rc of the crown arc portion Ac is set to a preferable range that sufficiently secures the contact area of the tread portion 2 during straight traveling and improves stability. That is, when the radius of curvature Rc of the crown arc portion Ac becomes excessively small, the contact area of the tread portion 2 during straight traveling decreases and stability tends to deteriorate. On the other hand, when the curvature radius Rc becomes excessively large, the central region of the tread portion 2 becomes excessively flat, and there is a concern that the operability at the time of transition from straight traveling to turning, for example, may deteriorate.

  From such a viewpoint, the radius of curvature Rc of the crown arc portion Ac is preferably 10% or more, more preferably 15% or more, preferably 25% or less, more preferably 20% or less of the tread width TW. desirable. Further, such a crown arc portion Ac preferably occupies a region Cr of about 15 to 25% of the tread width TW.

  The shoulder arc portion As is preferably formed with a radius of curvature Rs larger than that of the crown arc portion Ac in order to sufficiently secure a ground contact area at the time of turning given a camber angle. Although not particularly limited, the ratio of the radii of curvature (Rs / Rc) is preferably 0.9 or more. On the other hand, if the ratio (Rs / Rc) is too large, uneven wear tends to occur at the boundary portion, or uncomfortable feeling tends to occur at the time of maneuvering when the ground contact area shifts from the crown arc portion Ac to the shoulder arc portion As. . From such a viewpoint, the ratio (Rs / Rc) is preferably 4 or less, more preferably 3 or less.

  In the present embodiment, the side contour line SL is formed by a single arc Aw having a curvature radius Rw. That is, the side contour line SL is continuously formed from the tire maximum width position P1 to the separation point P2 by the arc Aw.

  The curvature radius Rw of the side contour line SL is not particularly limited, but is preferably larger than the curvature radius Re of the small arc Ae of the tread side contour line TL. That is, when the curvature radius Rw of the side contour line SL is smaller than the curvature radius Re of the small arc Ae at the end of the tread profile line TL, the vicinity of the tire maximum width position P1 has a sharp angle as in the prior art. There is a risk of approaching. From such a viewpoint, the curvature radius Rw is preferably 15 mm or more, and more preferably 20 mm or more.

  On the other hand, if the curvature radius Rw is too large, the outer surface of the sidewall portion 3 approaches a straight line, and it is difficult to obtain a large camber angle when turning, making it difficult to obtain a large camber angle. From such a viewpoint, the curvature radius Rw is preferably 40 mm or less.

  FIG. 3 shows another embodiment of the side contour line SL. In this embodiment, the side contour line SL is composed of a first arc Aw1 on the outer side in the tire radial direction and a second arc Aw2 on the inner side in the tire radial direction. These are smoothly connected at the connection point P4. The first arc Aw1 is formed with a radius of curvature Rw1 of 15 to 40 mm, while the radius of curvature Rw2 of the second arc Aw2 is formed to be larger than 40 mm. In such an embodiment, since the bending rigidity on the inner side in the tire radial direction of the sidewall portion 3 is higher than that in the embodiment of FIG. 2, the shock absorption capacity is slightly inferior, but the stability during straight running is improved. It can be improved.

  Although the embodiment of the present invention has been described in detail above, it is needless to say that the present invention can be implemented by being modified into various modes without being limited to the illustrated embodiment.

  Test tires (size 180 / 55ZR17) based on the specifications in Table 1 were prototyped, and their turning performance and shock absorption were tested. A carcass ply made of nylon cord was used for the carcass, and a jointless belt in which aramid cords were spirally wound at an angle of 5 degrees or less with respect to the tire circumferential direction was used for the belt layer.

Further, as Comparative Example 1, as shown in FIG. 5, the tread-side contour line and the side-side contour line are connected with a corner and the side-side contour line is formed as a straight line, Comparative Example 2 As shown in FIG. 7, the tread-side contour line and the side-side contour line are connected without a corner (R = 20 mm and chamfered), but the side-side contour line is a straight line. A similar test was conducted. Note that, as common specifications, the radius of curvature of the crown arc Rc = 100 mm and the radius of curvature of the shoulder arc Rs = 200 mm, the length of each arc is appropriately set so that the tread outline TL is smooth and the tread width TW does not change. Adjusted.
The test method is as follows.

<Swivel performance>
Using a steering performance tester, the camber thrust was measured when a camber angle of 45 degrees was given to the test tire under the following conditions. The larger the value, the better. The result is an index with Comparative Example 1 as 100, and the larger the value, the better.
Rims: 17 x MT5.00
Internal pressure: 300 kPa
Load: 1.3kN
Speed: 60km / H

<Shock absorbing performance during turning>
When each test tire is mounted on the rear wheel of a motorcycle under the following conditions, a turning circle course with a radius of curvature of 40 m with a ridge is run at a speed of 60 km / H, and over the ridge by the feeling of a professional driver The shock absorption performance of was evaluated. A result is a score which sets the comparative example 1 to 100, and it is so favorable that a numerical value is large. As shown in FIG. 4, the protrusion j has a square cross section with a height of 10 mm and a width of 10 mm and is provided so as to extend in a direction perpendicular to the traveling direction F.
Rims: 17 x MT3.50
Internal pressure: 300 kPa
Test vehicle: displacement 1000cc
Table 1 shows the test results.

  As a result of the test, it was confirmed that the tires of the examples had superior turning performance and shock absorption performance as compared with the comparative examples.

1 is a cross-sectional view of a motorcycle tire showing an embodiment of the present invention. It is the elements on larger scale of the tire outer surface outline. It is the elements on larger scale of the tire outer surface outline which shows other embodiments. It is a perspective view of the protrusion used in order to evaluate shock absorption performance. FIG. 6 is a cross-sectional view of a conventional motorcycle tire. It is sectional drawing of the state which gave the load and the camber angle to it. FIG. 6 is a cross-sectional view of another conventional motorcycle tire.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Motorcycle tire 1L Outer surface outline 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass TL Tread side outline SL Side side outline P1 Tire maximum width position P2 Separation point

Claims (4)

A motorcycle tire having a tread portion, a sidewall portion extending inward in the tire radial direction from both ends of the tread portion, and a bead portion provided at an inner end of the sidewall portion,
In the tire meridian cross section including the tire rotation shaft in the normal state in which the rim is assembled to the normal rim and the normal internal pressure is filled and no load is applied,
The contour line of the tire outer surface is a tread side contour line consisting of an arc-shaped curve extending between the tire maximum width position and protruding outward in the tire radial direction,
It consists of a side contour line consisting of an arc-shaped curve extending from the tire maximum width position to a separation point with the rim and protruding outward in the tire axial direction,
Moreover, the tread side contour line and the side side contour line are smoothly connected without having corners.   The tire for a motorcycle according to claim 1, wherein both ends of the tread side contour line are small arcs having a curvature radius Re of 5 to 25 mm.   3. The motorcycle tire according to claim 1, wherein the side-side contour line is formed of a single arc and has a curvature radius Rw of 15 to 40 mm. The side contour line includes a first arc on the outer side in the tire radial direction and a second arc connected to the inner side in the tire radial direction,
The tire for a motorcycle according to claim 1 or 2, wherein the first arc has a radius of curvature Rw1 of 15 to 40 mm, and the second arc has a radius of curvature Rw2 larger than 40 mm.

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