JP5671298B2 - Heavy duty tire - Google Patents

Description

  The present invention relates to a heavy duty tire in which occurrence of cracks in a sidewall portion is reduced.

  Tires used in heavy-duty vehicles such as trucks and buses have a large load deformation, so the amount of tire deformation during driving is large.Therefore, the surface distortion at the sidewalls is larger than that for passenger car tires. Repeatedly occurs. As shown in FIG. 3, this surface distortion is caused by the radial height position Z1 of the tire maximum width position Qm and the radial height of the carcass maximum height point Qc that is a point on the outer surface of the carcass a on the tire equator C. It has a peak point Pε in a region Y between the position Z2.

  On the other hand, in heavy-duty tires, for the purpose of improving design properties, for the purpose of reducing the feeling of bending of the tire, or for the purpose of protecting the carcass, etc., the side wall is raised from its outer surface, and the tire circumference is increased. In some cases, an annular rib b (indicated by a one-dot chain line) extending in the direction is formed (see, for example, Patent Documents 1 and 2).

  However, when the annular rib b is formed, the rubber thickness between the outer surface of the sidewall portion and the carcass greatly changes at the radially inner end and the outer end of the annular rib b. Therefore, when the radially inner end or outer end of the annular rib b is formed close to the position of the surface strain peak point Pε, the amount of surface strain distortion is amplified, and the inner end or There is a problem that cracks are likely to occur on the outer surface of the sidewall portion at the position of the outer end. In particular, in a tire having a large ratio TW / W0 of the tread width TW and the tire maximum width W0 of, for example, 0.89 to 0.99, the contour of the outer surface of the sidewall portion is nearly vertical, and the surface distortion becomes local. Therefore, the cracks are more likely to occur.

  In view of such a situation, as a result of research conducted by the present inventor, in a tire in which the annular rib b is not formed, the peak point Pε of the surface strain is approximately 15 to 20 of the carcass height Hc from the tire maximum width position Qm. %, And the formation of the annular rib b so that the central portion of the annular rib b comes to this position can be prevented from generating cracks due to surface distortion. I was able to find out.

JP 2003-025813 A JP 2000-025424 A

  Therefore, the present invention is based on the fact that the radial distance from the tire maximum width position to the center portion of the annular rib is in the range of 15 to 20% of the carcass height Hc, and the width of the annular rib is regulated. An object of the present invention is to provide a heavy duty tire that can suppress an increase in the peak value of the tire and suppress the occurrence of cracks on the outer surface of the sidewall portion.

In order to solve the above-mentioned problem, the invention of claim 1 of the present application includes a carcass that extends from a tread portion to a bead core of a bead portion through a sidewall portion, and a belt disposed radially outside the carcass and inside the tread portion. A heavy duty tire comprising a layer,
Said sidewall portion, the sidewall region extending to the tread end from the tire maximum width position, comprises a raised and annular rib extending in the tire circumferential direction from the outer surface of the side wall portion,
Wherein in the state where the annular rib is not formed, the peak point Pε the surface strain of the sidewall portion, the radial height from the tire maximum width position, from the bead base line to a point on the outer surface of the carcass in the tire equator The distance of 15 to 20% of the carcass height Hc is radially outwardly separated,
The annular rib has, in a tire meridional section including a tire shaft, an inner and outer side surface that rises from a radially inner and outer raised point on the outer surface of the sidewall portion, and a central surface portion that connects between the tips of the inner and outer side surface portions. A trapezoidal cross section,
In a normal internal pressure state in which the tire is assembled to a normal rim and filled with a normal internal pressure, the radial distance L1 from the tire maximum width position to the radial middle point of the central surface portion is 15 to 20 of the carcass height Hc. % and is, moreover radial width W of the central surface is characterized in that in the range of 15 to 25 mm.

  According to a second aspect of the present invention, the annular rib has heights Ho and Hi raised from the virtual surface of the outer surface of the sidewall portion at the front end of the inner side surface portion and the front end of the outer side surface portion of 0. 0, respectively. The height is in the range of 5 to 1.5 mm, and at least one of the raised heights Ho and Hi is the maximum height of the raised height of the annular rib.

  The invention of claim 3 is characterized in that the difference | Ho−Hi | between the raised heights Ho and Hi is 0.5 mm or less.

  The invention of claim 4 is characterized in that the ratio TW / W0 between the tread width TW and the tire maximum width W0 is in the range of 0.89 to 0.99.

  The invention according to claim 5 is characterized in that a flatness ratio, which is a ratio T0 / W0 between a tire cross-sectional height T0 and a tire maximum width W0, is in a range of 0.5 to 0.7.

According to a sixth aspect of the present invention, the rubber thickness between the outer surface of the sidewall portion and the carcass gradually increases inward in the radial direction from the position of the inner raised point. In the invention of claim 7, the radial distance between the tip of the inner side surface portion and the inner raised point, and the radial distance between the tip of the outer side surface portion and the outer raised point are: Each is characterized by being in the range of 3.5 to 9.0 mm. In the invention according to claim 8, only one annular rib is provided on the sidewall portion, and the outer protruding point of the annular rib is linear or a concave arc shape having a center on the outer side of the tire. A first surface portion that extends is connected, and a second surface portion that has a center on the inner side of the tire and extends in a convex arc shape is connected to the inner raised point of the annular rib.

  The “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based, for example, a standard rim for JATMA, “Design Rim” for TRA, or ETRTO means "Measuring Rim". The “regular internal pressure” is the air pressure defined by the standard for each tire. If JATMA, the maximum air pressure, if TRA, the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” ETRTO means "INFLATION PRESSURE". In the present specification, unless otherwise specified, the dimensions and the like of each part of the tire are values specified in the normal internal pressure state.

  As described above, the present invention regulates the position of the midpoint of the central surface portion of the annular rib and the width of the central surface portion. Therefore, the inner and outer ends of the annular rib in the radial direction can be moved away from the position of the peak point of the surface distortion of the tire, the increase in the peak value of the distortion amount is suppressed, and the occurrence of cracks on the outer surface of the sidewall portion is suppressed. It becomes possible to do.

It is sectional drawing which shows one implementation of the heavy duty tire of this invention. It is a fragmentary sectional view expanding and showing an annular rib. It is a conceptual diagram explaining the generation | occurrence | production state of the surface distortion in a conventional tire.

  Hereinafter, embodiments of the present invention will be described in detail. FIG. 1 shows a tire meridional section including a tire shaft in an unloaded normal internal pressure state in which a heavy load tire 1 of the present invention is assembled to a normal rim R and filled with a normal internal pressure.

In FIG. 1, a heavy-duty tire 1 is disposed on a carcass 6 that extends from a tread portion 2 through a sidewall portion 3 to a bead core 5 of a bead portion 4, and on the radially outer side of the carcass 6 and inside the tread portion 2. A known radial structure having a belt layer 7 is provided . In this example, the ratio TW / W0 between the tread width TW and the tire maximum width W0 is in the range of 0.89 to 0.99, and the ratio T0 / the ratio between the tire cross-sectional height T0 and the tire maximum width W0. The case where the flatness ratio which is W0 is the range of 0.5-0.7 is illustrated. In such a tire having a large ratio TW / W0, since the contour of the sidewall portion 3 approaches to the vertical, surface distortion at the time of tire deformation is likely to occur locally, so that cracks occur on the outer surface 3S of the sidewall portion 3. It tends to be easy. Further, in a tire having a small flatness ratio of 0.5 to 0.7, the area width of the flexible sidewall portion 3 becomes narrow, so that the surface distortion becomes large and cracks tend to be similarly generated. Therefore, the present invention can be particularly effective for such a tire.

The tread width TW means a distance in the tire axial direction between the tread ends Te and Te, which is an intersection point between the tread surface 2S or its extension line and the outer surface 3S of the sidewall portion 3 or its extension line . The tire maximum width W0 means the distance in the tire axial direction between the tire maximum width positions Qm and Qm where the outer surface 3S of the sidewall portion 3 bulges outward in the tire axial direction. Further, the sectional height T0 of the tire means a radial distance from the bead base line BL to the tread surface 2S on the tire equator C.

  Next, the carcass 6 is formed of at least one carcass ply 6A in this example in which steel carcass cords are arranged at an angle of, for example, 75 to 90 ° with respect to the tire circumferential direction. In this example, the carcass ply 6 </ b> A has ply folding portions 6 b that are folded from the inner side to the outer side in the tire axial direction around the bead core 5 at both ends of the toroidal ply main body portion 6 a that extends between the bead cores 5 and 5. A bead apex rubber 8 having a triangular cross section extending from the bead core 5 to the outer side in the tire radial direction is disposed between the ply main body portion 6a and the ply turn-up portion 6b, and is reinforced from the bead portion 4 to the sidewall portion 3. ing.

  The belt layer 7 includes at least two belt plies 7A to 7C in which steel belt cords are arranged at an angle of, for example, 10 to 70 ° with respect to the tire circumferential direction, usually three to four. Formed from. The belt plies 7A to 7C are provided with one or more locations where the belt cords cross each other between the plies, and are superposed to enhance belt rigidity and reinforce the tread portion 2 with a tagging effect.

  In the tire 1 of the present embodiment, the annular rib that protrudes from the outer surface 3S of the sidewall portion 3 and continuously extends in the tire circumferential direction in the sidewall upper region YU extending from the tire maximum width position Qm to the tread end Te. 10 is provided. In the present example, the annular rib 10 is formed for the purpose of giving the tire an apparent strength and enhancing the design, but besides this, for various purposes such as preventing the carcass from being damaged. Can be formed.

  The outer surface 3S of the sidewall portion 3 is the sidewall portion 3 that extends smoothly from the tread edge Te except for a local unevenness including a raised mark such as a mark or an uneven pattern in the normal internal pressure state with no load. Of the reference curved surface XS. Further, in this example, the reference curved surface XS in the sidewall upper region YU includes a first surface portion XS1 extending from the tread end Te in a straight line shape or a concave arc shape having a center on the tire outer side, and the tire maximum width position Qm. The second surface portion XS2 extends in the shape of a convex arc having a center on the inner side of the tire and smoothly communicates with the first surface portion XS1.

  Next, as shown in an enlarged view in FIG. 2, the annular rib 10 includes inner and outer side surface portions 11 and 12 rising from the radially inner and outer raised points 11 a and 12 a on the outer surface 3 </ b> S of the sidewall portion 3. It forms a trapezoidal cross section having a central surface portion 13 that connects between the tips 11b, 12b of the inner and outer side surface portions 11, 12.

  The inner and outer side surface portions 11 and 12 are preferably formed as concave arcuate curved surfaces that are smoothly connected to the outer surface 3S at the inner and outer raised points 11a and 12a, but intersect the outer surface 3S as required. It can also be formed on a slope. The central surface portion 13 is preferably formed in a straight line from the viewpoint of appearance, and the straight line includes, in addition to a straight line, a concave or convex arc surface close to a straight line having a curvature radius of 800 mm or more. It is.

  In the annular rib 10, the radial distance L1 from the tire maximum width position Qm to the radial middle point 13m of the central surface portion 13 is a point on the outer surface of the carcass 6 from the bead base line BL to the tire equator C. The radial height W is 15 to 20% of the radial height Hc to the carcass maximum height point Pc, and the radial width W of the central surface portion 13 is in the range of 15 to 25 mm.

  With this configuration, the inner and outer raised points 11a and 12a of the annular rib 10 can be kept away from the peak point Pε (shown in FIG. 3) of the surface distortion when the annular rib 10 is not provided, An increase in the peak value of the amount can be suppressed, and the occurrence of cracks at the raised points 11a or 12a can be suppressed.

When the radial distance L1 exceeds the range of 15 to 20% of the height Hc, the position of the intermediate point 13m is displaced from the peak point Pε of the surface strain, and thus the raised points 11a and 12a are peaked. In order to move away from the point Pε, the width W needs to be set large. For this reason, there is a problem that the designability is deteriorated and the degree of freedom of the design is impaired, for example, the display space for the mark, which is a character or symbol representing the manufacturer name, product name, size, etc., of the tire is reduced. If the width W is less than 15 mm, the raised points 11a and 12a cannot be sufficiently separated from the peak point Pε even when the position of the intermediate point 13m becomes the peak point Pε. On the other hand, when the width W exceeds 25 mm, appearance and display space are reduced.

Further, in this example, the annular rib 10 is formed such that the protruding heights Ho and Hi from the virtual surface X of the outer surface 3S of the sidewall portion 3 of the distal end 11b of the inner side surface portion 11 and the distal end 12b of the outer side surface portion 12 are as follows. Are preferably in the range of 0.5 to 1.5 mm, and at least one of the raised heights Ho and Hi is preferably the maximum raised height of the annular rib 10. The virtual surface X is the outer surface 3S of the sidewall portion 3 when there is no annular rib 10, and corresponds to the reference curved surface XS . When the raised heights Ho and Hi are each 0.5 mm or less, the annular rib 10 cannot be made sufficiently conspicuous, and the design purpose such as improvement in design is not sufficiently achieved. On the other hand, if it exceeds 1.5 mm, it is advantageous for the design and the like, but the difference in the rubber thickness from the carcass 6 becomes large inside and outside the annular rib 10, so that the increase in strain increases and cracks occur. It is disadvantageous to occurrence. Note that the difference | Ho−Hi | between the raised heights Ho and Hi is preferably 0.5 mm or less.

  The radial distance L11 between the tip 11b of the inner side surface portion 11 and the inner raised point 11a and the radial distance L12 between the tip 11b of the outer side surface portion 12 and the outer raised point 11a are: The range of 3.5 to 9.0 mm is preferable. If the thickness is less than 3.5 mm, the change in the rubber thickness becomes abrupt and disadvantageous for the generation of cracks. Conversely, if the thickness exceeds 9.0 mm, the annular rib 10 becomes inconspicuous, resulting in a disadvantage in design.

  In this example, the rubber thickness T between the outer surface 3S of the sidewall portion 3 and the carcass 6 gradually increases inward in the radial direction from the position of the inner raised point 11a. As a result, an abrupt change in surface distortion is suppressed on the inner side in the radial direction from the raised point 11a, which is advantageous for suppressing the occurrence of cracks.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

  A heavy-duty tire having the structure shown in FIG. 1 and having a tire size of 215 / 70R17.5 was manufactured based on the specifications shown in Table 1, and the peak value of the surface distortion and the appearance of each sample tire were tested and compared. . Each tire is different only in the formation position and size of the annular rib, and the other specifications are substantially the same.

(1) Peak value of surface strain:
Radius generated in the sidewall when a tire is deformed by applying a longitudinal load (15.2 kPa) to a tire assembled with the rim (6.00 × 17.5) and internal pressure (800 kPa). The surface strain ε (%) on the tensile side in the direction was measured and compared with the peak value. A lower peak value is preferable because cracks are less likely to occur.

(2) Appearance:
As a result of visual inspection, sensory evaluation was performed by a five-point method in which Comparative Example 1 was set to 1 by five inspectors with respect to the strength (design effect) given to the tire by the annular rib, and the average values were compared. The larger the value, the greater the strength and the better the design effect.

As shown in the table, it can be confirmed that the tires of the examples can suppress the increase in the peak value of the strain amount and suppress the occurrence of cracks on the outer surface of the sidewall portion.

DESCRIPTION OF SYMBOLS 1 Heavy load tire 2 Tread part 3S Outer surface 3 of side wall part 4 Side wall part 4 Bead part 5 Bead core 6 Carcass 7 Belt layer 10 Annular rib 11 Side face part 11a Raised point 11b Tip 12 Side face part 12a Raised point 12b Tip 13 Central surface part 13m Radial midpoint BL Bead baseline C Tire equator Pc Maximum carcass height point Qm Maximum tire width position Te Tread end YU Side wall area

Claims (8)

A heavy duty tire comprising a carcass extending from a tread portion through a sidewall portion to a bead core of a bead portion, and a belt layer disposed radially outside the carcass and inside the tread portion,
Said sidewall portion, the sidewall region extending to the tread end from the tire maximum width position, comprises a raised and annular rib extending in the tire circumferential direction from the outer surface of the side wall portion,
Wherein in the state where the annular rib is not formed, the peak point Pε the surface strain of the sidewall portion, the radial height from the tire maximum width position, from the bead base line to a point on the outer surface of the carcass in the tire equator The distance of 15 to 20% of the carcass height Hc is radially outwardly separated,
In the tire meridional section including the tire shaft, the annular rib includes an inner and outer side surface that rises from a radially inner and outer raised point on the outer surface of the sidewall portion, and a central surface portion that connects between the distal ends of the inner and outer side surfaces. Having a cross-sectional trapezoidal shape,
In a normal internal pressure state in which the tire is assembled to a normal rim and filled with a normal internal pressure, the radial distance L1 from the tire maximum width position to the radial middle point of the central surface portion is 15 to 20 of the carcass height Hc. % , And the width W in the radial direction of the central surface portion is in the range of 15 to 25 mm. Said annular rib, the distal end of the tip and the outer side surface portion of the side portion in said raised height Ho from the virtual plane of the outer surface of the sidewall portion, Hi is the range of each 0.5~1.5mm The heavy load tire according to claim 1, wherein at least one of the raised heights Ho and Hi forms a maximum raised height of the annular rib.   The heavy load tire according to claim 2, wherein the difference | Ho-Hi | between the raised heights Ho and Hi is 0.5 mm or less.   The heavy duty tire according to any one of claims 1 to 3, wherein a ratio TW / W0 of the tread width TW and the tire maximum width W0 is in a range of 0.89 to 0.99.   The flatness which is the ratio T0 / W0 of the tire cross-sectional height T0 and the tire maximum width W0 is in the range of 0.5 to 0.7, according to any one of claims 1 to 4. Heavy duty tire. The rubber thickness between the outer surface of the sidewall portion and the carcass, according to claim 1, characterized in that gradually increases radially inwardly from the position of the ridge point in the Heavy duty tires.   The radial distance between the tip of the inner side surface portion and the inner raised point, and the radial distance between the tip of the outer side surface portion and the outer raised point are 3.5 to 9.0 mm, respectively. The heavy-duty tire according to any one of claims 1 to 6, characterized in that Only one annular rib is provided on the sidewall portion,
  The outer surface of the annular rib is connected to the first surface portion extending in a straight line shape or a concave arc shape having a center on the tire outer side,
  The heavy duty tire according to any one of claims 1 to 7, wherein a second surface portion having a center on the inner side of the tire and extending in a convex arc shape is connected to the inner raised point of the annular rib.

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