JP6601182B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire in which foamed rubber is used for a sidewall portion, and more particularly to a pneumatic tire that can reduce tire weight while maintaining cut resistance.

  Conventionally, in the pneumatic tire, from the viewpoint of resource saving and energy saving, the tire weight has been reduced in order to reduce the amount of material used for the tire and to reduce fuel consumption. As a method for reducing the weight of such a tire, for example, it has been proposed to use foamed rubber as the rubber constituting the sidewall portion (see, for example, Patent Document 1).

  However, since foam rubber has lower strength than non-foam rubber, for example, when climbing over a curb stone, between the curb and the rim flange that contacts the outer side in the tire radial direction (tread part side) of the sidewall part. There is a tendency that trauma caused by sandwiching the sidewall portion tends to occur. That is, there is a problem that the cut resistance is lowered. Therefore, in order to reduce the tire weight by adopting a foamed rubber layer in the sidewall portion, there is a demand for measures for preventing a reduction in cut resistance without impairing the effect of weight reduction.

Japanese Patent Application Laid-Open No. 07-102111

  An object of the present invention is to provide a pneumatic tire in which foamed rubber is used for a sidewall portion, and it is possible to reduce the tire weight while maintaining cut resistance. .

In order to achieve the above object, a pneumatic tire according to the present invention includes a tread portion that extends in the tire circumferential direction and has an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and the sidewall portions. A pneumatic tire in which a carcass layer is mounted between the pair of bead portions, and the side wall portion of the carcass layer on the outer side in the tire width direction is provided. The rubber layer is made of foamed rubber, the tire cross-section height is h, and the region included between the tire maximum width position and the position separated by 0.1 times the tire cross-section height h in and out of the tire radial direction. Included between the position of 0.7 times the tire cross-section height h from the rim baseline to the tire rim base line and the position 0.1 times the tire cross-section height h from the rim base line to the inside and outside of the tire radial direction. When a region has an outer region, wherein the specific gravity d _OUT in the outer region of the foamed rubber is greater than the specific gravity d _C in the central region of the foamed rubber.

In the present invention, the rubber layer on the outer side in the tire width direction of the carcass layer in the sidewall portion is made of foamed rubber so that the weight of the foamed rubber is set as described above while achieving weight reduction of the tire. Since the specific gravity d _OUT in the outer region is larger than the specific gravity d _C in the central region, the strength of the outer region of the foamed rubber layer, which tends to come into contact with the curb when moving over the curb, is relatively increased. Thus, it is possible to suppress deformation such that a part of the sidewall portion is sandwiched between the curbstone and the rim flange, and cut resistance can be improved.

In the present invention, it is included between a position that is 0.2 times the tire cross-section height h from the rim base line to the outer side in the tire radial direction and a position that is 0.1 times the tire cross-section height h inside and outside the tire radial direction. When the region is the inner region, the specific gravity d _{IN in} the inner region of the foam rubber is preferably larger than the specific gravity d _C in the central region of the foam rubber. By setting the specific gravity of the foam rubber constituting the sidewall portion in this way, the strength of the inner region of the foam rubber layer contacting the rim flange can be relatively increased, so the sidewall between the curb and the rim flange It is advantageous to suppress deformation that causes a part of the portion to be sandwiched. That is, cut resistance can be improved more effectively. At this time, since the strength of the predetermined portion is compensated by the change in the specific gravity of the foamed rubber, the weight reduction of the tire by the foamed rubber can be sufficiently achieved.

In the present invention, the specific gravity d _{C in} the central region of the foamed rubber is preferably 0.6 to 1.0. Thus, by setting the specific gravity d _C in the central region to an appropriate range, the effect of reducing the weight of the tire and the effect of improving the cut resistance can be made highly compatible with the sidewall portion.

  In the present invention, the bubbles contained in the foamed rubber are preferably closed cells. By using foamed rubber containing closed cells in this way, it is possible to obtain a breaking strength superior to foamed rubber made of open cells having an equivalent specific gravity, and while achieving sufficient weight reduction of the tire, it is excellent It is advantageous to obtain cut resistance.

  At this time, the average cell diameter of the closed cells is preferably 10 μm to 100 μm. By reducing the average cell diameter of closed cells in this way, the distribution density of closed cells in the foamed rubber can be increased, and the crack propagation when a damage occurs in the tire can be dispersed to improve the resistance to damage. it can. In the present invention, the average cell diameter of closed cells is obtained by cutting out a block-shaped sample from foam rubber, photographing the sample cross section with an optical microscope with a magnification of 100 to 400, and measuring the cell diameter of each bubble in the cross section, The average of these bubble diameters was obtained.

  In the present invention, the modulus at 100% elongation of the foamed rubber is preferably 0.9 MPa or more. By using the foam rubber having such characteristics, it is possible to reduce the amount of curb stones and rim flanges that bite into the sidewall portion when overcoming the curb stones and the like, which is advantageous for improving the cut resistance. In addition, in this invention, the modulus at the time of 100% expansion | extension of foamed rubber is the value measured on each conditions of tensile speed 500mm / min and temperature 23 degreeC using 3 type | mold dumbbell test piece based on JISK6251. It is.

  In the present invention, it is preferable that the minimum thickness of the rubber layer on the outer side in the tire width direction of the carcass layer in the sidewall portion is 1.0 mm to 2.5 mm. By setting the thickness of the rubber layer in this way, it is advantageous to achieve both weight reduction of the tire and improvement of cut resistance.

  In the present invention, the “specific gravity” of the foamed rubber is an apparent specific gravity of the whole foamed rubber including bubbles, and varies depending on the size and distribution density of the bubbles in the foamed rubber. As the numerical value, a value measured according to JIS K6268 is used.

  Further, in the present invention, the “tire maximum width position” means the tire diameter at the point where the carcass layer protrudes most outward in the tire width direction in a no-load state in which the tire is assembled on a regular rim and filled with a regular internal pressure. The “rim base line” is a reference line indicating a rim diameter position of a normal rim on which a pneumatic tire is mounted. 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 it is “Measuring Rim” in the case of ETRTO, and “normal internal pressure” is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. TRA is the maximum value described in the table “TIRE ROAD LIMITS AT VARIOUS COLD INFRATION PRESURES”, and ETRTO is “INFLATION PRESSURE”, but 180 kPa when the tire is a passenger car.

It is a meridian half section view of the pneumatic tire which consists of an embodiment of the present invention. It is a meridian half section view of the pneumatic tire which consists of another embodiment of the present invention.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.

  As shown in FIG. 1, the pneumatic tire of the present invention includes a tread portion 1 that extends in the tire circumferential direction and has an annular shape, a pair of sidewall portions 2 that are disposed on both sides of the tread portion 1, And a pair of bead portions 3 disposed inside the wall portion 2 in the tire radial direction. In FIG. 1, only one side of the tire equator CL is shown, but the other side of the tire equator CL has a similar structure.

  A carcass layer 4 is mounted between the pair of left and right bead portions 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction, and is folded back around the bead core 5 disposed in each bead portion 3 from the vehicle inner side to the outer side. A bead filler 6 is disposed on the outer periphery of the bead core 5, and the bead filler 6 is wrapped by the main body portion and the folded portion of the carcass layer 4. On the other hand, a plurality of layers (two layers in FIG. 1) of belt layers 7 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. Each belt layer 7 includes a plurality of reinforcing cords that are inclined with respect to the tire circumferential direction, and is disposed so that the reinforcing cords cross each other between the layers. In these belt layers 7, the inclination angle of the reinforcing cord with respect to the tire circumferential direction is set in a range of, for example, 10 ° to 40 °. Further, a belt reinforcing layer 8 is provided on the outer peripheral side of the belt layer 7. The belt reinforcing layer 8 includes an organic fiber cord oriented in the tire circumferential direction. In the belt reinforcing layer 8, the organic fiber cord has an angle with respect to the tire circumferential direction set to, for example, 0 ° to 5 °.

  Since the present invention defines the structure of the side rubber layer G (shaded portion in the figure) located on the outer side in the tire width direction of the carcass layer 4 in the sidewall portion 2 as will be described later, its cross-sectional structure is the above-mentioned basic structure. The structure is not limited.

  In the present invention, the side rubber layer G is made of foamed rubber. The foamed rubber is a rubber composition containing open cells or closed cells obtained by adding a foaming agent during molding and generating bubbles during vulcanization, for example. Such foamed rubber has a smaller specific gravity than ordinary non-foamed rubber, and therefore, by adopting the side rubber layer G, the tire can be reduced in weight.

At this time, the specific gravity of the foamed rubber is not constant throughout the side rubber layer G, is set to be large at the tread portion 1 side from the maximum width position P _C tires. Specifically, the tire section height and h, the central region A _C a region comprised between a position away by 0.1 times the tire section height h from the maximum width position P _C tires in the tire radial direction inside and outside Included between the position P _OUT of 0.7 times the tire cross-section height h from the rim base line BL to the outer side in the tire radial direction and the position distant from the rim base line BL by 0.1 times the tire cross-section height h in and out of the tire radial direction. when the region is the outer region a _OUT which specific gravity d _OUT at the outer region a _OUT of the foamed rubber than the specific gravity d _C of the central region a _C of the foamed rubber is large. Since the specific gravity of the foamed rubber is set in this way, the strength of the outer region A _OUT that comes into contact with the curb or the like when climbing over the curb is relatively increased, and the side wall portion 2 is between the curb and the rim flange. It is possible to suppress deformation such that a portion is sandwiched, and to improve cut resistance.

At this time, the central region A when the difference between the specific gravity d _OUT of specific gravity d _C and an outer region A _OUT of the foamed rubber in _C is extremely large, the tire maximum width position P _C near (central region under a load of the foamed rubber Since the deformation of A _C ) becomes too large and the cut resistance may be lowered, the specific gravity ratio d _OUT / d _C is preferably set to 1.4 or less.

Further, in the present invention, the specific gravity of the foamed rubber is preferably set to be larger in the bead part 3 side than the maximum width position P _C tires. Specifically, the rim base from line BL of a position away from the 0.2 times the position P _IN of the tire section height h on the outer side in the tire radial direction in the tire radial direction and out by 0.1 times the tire section height h when the area included between the inner region a _iN, it is preferable specific gravity of the inside region a _iN of the foamed rubber than the specific gravity of the central region a _C of the foamed rubber is large. By setting the specific gravity of the thus foam rubber, because it can relatively increase the strength of the inner region A _IN that contacts the rim flange, part of the side wall portion is sandwiched between the curb and the rim flange It is advantageous to suppress such deformation. That is, cut resistance can be improved more effectively.

At this time, the central region A when the difference between the specific gravity d _IN of specific gravity d _C and inner region A _IN of the foamed rubber in _C is extremely large, the tire maximum width position P _C near (central region under a load of the foamed rubber Since the deformation of A _C ) becomes too large and the cut resistance may decrease, the specific gravity ratio d _IN / d _C is preferably set to 1.4 or less.

Accordingly, in the present invention, looking at the entire side rubber layer G, and a specific gravity d _C of the central region A _C, a specific gravity d _OUT and the bead part 3 side of the inner area A in the outer region A _OUT of the tread portion 1 side it is preferable that each of the specific gravity d _iN at _iN is large. Thus when changing the specific gravity of the foamed rubber, for example may be the specifications gravity gradually increases toward the tire maximum width position P _C to the tread portion 1 side or bead part 3 side. Alternatively, as shown in FIG. 2, the side rubber layer G can be configured by combining foam rubbers having different specific gravities in the tire radial direction so that the specific gravity can be changed stepwise. In the example of FIG. 2, two different types of foam rubber is used in specific gravity, low foamed rubber having relatively specific gravity is arranged in a portion including a central region A _C, another foamed rubber having a large relative density outer By being arranged in each of the part including the area A _OUT and the part including the inner area A _IN , the specific gravity d _OUT in the outer area A _OUT and the specific gravity d _OUT in the inner area A _IN are higher than the specific gravity d _C in the central area A _C. Specific gravity _dIN is increased. Thus, when changing specific gravity in steps, it is preferable that the boundary of the foam rubber from which specific gravity differs is inclined with respect to the tire width direction, as shown in FIG. The specification of the change in specific gravity toward the tread portion 1 side (outer region A _OUT ) from the tire maximum width position P _C (center region A _C ) and the change in specific gravity toward the bead portion 3 side (inner region A _IN ). The specifications may be the same or different.

For example, in the example of FIG. 2, the foam rubber having the same specific gravity as the foam rubber (the foam having a relatively higher specific gravity than the foam rubber disposed in the part including the central region A _{C) is used} for the site including the outer region A _OUT and the site including the inner region A _IN. the rubber) is disposed, but is the same and the density d _iN of specific gravity d _OUT and an inner region a _iN at the outer region a _OUT, a specific gravity d _OUT inner area a in the outer region a _OUT it may be larger than the specific gravity d _iN in _iN. That is, it is preferable that these specific gravity d _OUT and d _IN have a relationship of d _OUT ≧ d _IN . More preferably, the ratio d _OUT / d _{IN of} these specific gravities is 1.0 ≦ d _OUT / d _IN <1.2. In this way, by reliably increasing the specific gravity in the outer region A _OUT , these tire constituent members are not included as compared with the inner region A _{IN including} the folded portion of the carcass layer 4 and the bead filler 6, so that the structural fracture characteristics. it is difficult to obtain the outer region a _OUT external damage resistance can be reliably enhanced, and the overall external damage of the sidewall portions 2 can be increased with good balance. Also in the case of specifications specific gravity of the foamed rubber is gradually increased toward the tread portion 1 side or bead part 3 side from the maximum width position P _C tires, the specific gravity of the specific gravity d _OUT and an inner region A _IN at the outer region A _OUT relationship between d _iN is preferably set as described above.

In the present invention, in setting the magnitude relationship of the specific gravity of the foam rubber as described above, the specific gravity d _C in the central region A _C of the foam rubber is preferably 0.6 to 1.0, more preferably 0.70. To 0.90, more preferably 0.75 to 0.85. By thus setting the specific gravity d _C of the central region A _C of the foamed rubber, it is possible to highly achieve both improvement of weight reduction of the tire and cut resistance. At this time, the specific gravity d _C of the central region A _C of the foamed rubber is less than 0.6, setting the magnitude relationship between the above specific gravity, breaking strength of the entire foam rubber (in particular the central region A _C) is It becomes low and it becomes difficult to obtain sufficient cut resistance. If the specific gravity d _C of the central region A _C of the foamed rubber is greater than 1.0, since the specific gravity of the whole foamed rubber is not sufficiently small, it becomes difficult to obtain a sufficient effect of weight reduction.

  As described above, foamed rubber is a rubber composition containing open cells or closed cells. However, when foamed rubber containing open cells and foamed rubber containing closed cells are compared, both have the same specific gravity. For example, foamed rubber composed of closed cells has higher breaking strength than foamed rubber composed of open cells. Therefore, in the present invention, it is preferable to use a foamed rubber made of closed cells that can obtain a high breaking strength with the same specific gravity. Thereby, it is possible to achieve both high weight reduction of tire and improvement of cut resistance.

  Thus, when using the foamed rubber which consists of closed cells, it is preferable that the average cell diameter of closed cells is 10 micrometers-100 micrometers. Thus, when the average bubble diameter of closed cells is small, the distribution density of closed cells in the foamed rubber increases with the same specific gravity. Therefore, when a trauma occurs in the tire, it is possible to disperse the crack progress starting from the trauma occurrence position, which is advantageous for improving the cut resistance. At this time, if the average bubble diameter of the closed cells is smaller than 10 μm, the bubbles become too small and become substantially the same as the non-foamed rubber, so that it is difficult to obtain a sufficient weight reduction effect. If the average cell diameter of the closed cells is larger than 100 μm, it is difficult to set the specific gravity within an appropriate range, and it becomes difficult to obtain sufficient cut resistance.

  It is preferable that the foamed rubber not only has the above specific gravity but also has a high modulus. Specifically, the modulus at 100% elongation is preferably 0.9 MPa or more, more preferably 1.2 MPa or more. By using the foam rubber having such characteristics, it is possible to reduce the amount of curb stones and rim flanges that bite into the sidewall portion when overcoming the curb stones and the like, which is advantageous for improving the cut resistance.

  In addition to the above-described configuration, it is possible to further reduce the weight of the tire by reducing the thickness of the side rubber layer G, but it is difficult to obtain sufficient cut resistance when the rubber layer G becomes extremely thin. Therefore, the minimum thickness of the rubber layer G is preferably set to 1.0 mm to 2.5 mm, more preferably 1.2 mm to 2.0 mm. At this time, if the minimum thickness of the rubber layer G is smaller than 1.0 mm, it becomes difficult to obtain sufficient cut resistance. If the minimum thickness of the rubber layer G is larger than 2.5 mm, sufficient weight reduction cannot be expected.

In addition, the part where the thickness of the rubber layer G is minimized is a part that contacts the curb stone (that is, the vicinity of the position P _OUT ) or a part that contacts the rim flange (that is, the vicinity of the position P _IN ). It is preferable to avoid. In other words, the rim base tire radial direction inside than 0.7 times the position P _OUT of the tire section from the line BL to the outer side in the tire radial height h, and a rim base from line BL of the tire section height h on the outer side in the tire radial direction It is preferable that a region where the thickness of the rubber layer G is minimum exists in a region on the outer side in the tire radial direction from the 0.2 times position _PIN . More preferably, a rubber layer is formed in a region (a region between the outer region A _OUT and the inner region _IN ) of 0.3 to 0.6 times the tire cross-section height h on the outer side in the tire radial direction from the rim base line BL. There should be a portion where the thickness of G is minimized.

The tire size is 205 / 55R16, has the basic structure shown in FIG. 1, and the side rubber layer G is composed of a material (foamed rubber or non-foamed rubber), and the type of bubbles when made of foamed rubber (closed cells or continuous cells). specific gravity d _iN), modulus at 100% elongation, the minimum thickness of the specific gravity d _C, a specific gravity d _OUT at the outer region a _OUT, inner area a _iN of bubbles), average cell diameter, the specific gravity (center region a _C 17 types of pneumatic tires of Conventional Example 1, Comparative Examples 1 and 2, and Examples 1 to 14 were set as shown in Tables 1 and 2, respectively.

In these examples, parts the thickness of the side rubber layer G is minimized, both are present in the central region A _C.

  About the column of "Material" of Tables 1-2, when the material which comprises the side rubber layer G is a foamed rubber, it showed as "foaming", and when it was a non-foamed rubber, it showed as "non-foaming." In the column of “Bubble type” in Tables 1 and 2, “independent” is shown for closed cells, and “continuous” is shown for open cells.

  About these 17 types of pneumatic tires, the tire weight and cut resistance were evaluated by the following evaluation methods, and the results are also shown in Tables 1 and 2.

Tire Weight The weight of each test tire was measured. The evaluation results are shown as an index with the reciprocal of the measured value of Conventional Example 1 being 100. A larger index value means a smaller tire weight.

Cut resistance Each test tire is mounted on a wheel with a rim size of 16 x 6.5 JJ, mounted on a test vehicle with an air pressure of 230 kPa and a displacement of 1600 cc. I got on. The degree of damage of the sidewall portion after this riding was repeated 5 times was evaluated. The evaluation results are shown as an index with Conventional Example 1 as 100. A larger index value means better cut resistance.

  As is clear from Tables 1 and 2, all of Examples 1 to 14 improved the cut resistance while reducing the tire weight with respect to Conventional Example 1. On the other hand, in Comparative Example 1, since the side rubber layer G is made of non-foamed rubber, the cut resistance is excellent, but the tire weight is greatly deteriorated. In Comparative Example 2, the entire side rubber layer G was made of foamed rubber having a constant specific gravity (low specific gravity), so that the tire weight could be greatly reduced, but the cut resistance was greatly deteriorated.

1 tread portion 2 sidewall portion 3 bead portion 4 carcass layer 5 bead core 6 bead filler 7 belt layer 8 belt reinforcing layer G side rubber layer P _C maximum tire width position A _C central region A _OUT outer region A _IN inner region CL tire equator

Claims (7)

An annular tread portion extending in the tire circumferential direction, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed on the inner side in the tire radial direction of the sidewall portions. A pneumatic tire having a carcass layer mounted between the pair of beads,
A rubber layer on the outer side in the tire width direction of the carcass layer in the sidewall portion is made of foamed rubber, where the tire cross-section height is h, and the tire cross-section height h is 0 from the tire maximum width position to the inside and outside in the tire radial direction. The region included between the positions separated by a factor of 1 is defined as the central region, and the tire cross-section height h from the position 0.7 times the tire cross-section height h outward from the rim base line in the tire radial direction. When the region included between the positions separated by 0.1 times each is the outer region, the specific gravity d _OUT of the foamed rubber in the outer region is larger than the specific gravity d _C of the foamed rubber in the central region. A pneumatic tire characterized by that. A region included between a position that is 0.2 times the tire cross-section height h from the rim base line and a position that is 0.1 times the tire cross-section height h inside and outside the tire in the tire radial direction. 2. The pneumatic tire according to claim 1, wherein a specific gravity d _IN in the inner region of the foam rubber is larger than a specific gravity d _C in the central region of the foam rubber when the region is a region. 3. The pneumatic tire according to claim 1, wherein a specific gravity d _C in the central region of the foamed rubber is 0.6 to 1.0.   The pneumatic tire according to claim 1, wherein the bubbles contained in the foamed rubber are closed cells.   The pneumatic tire according to claim 4, wherein an average cell diameter of the closed cells is 10 μm to 100 μm.   The pneumatic tire according to any one of claims 1 to 5, wherein a modulus at 100% elongation of the foamed rubber is 0.9 MPa or more.   The pneumatic tire according to any one of claims 1 to 6, wherein a minimum thickness of a rubber layer on an outer side in the tire width direction of the carcass layer in the sidewall portion is 1.0 mm to 2.5 mm.

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