JP2009279953A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire effectively reducing rolling resistance without impairing uneven wear resistance. <P>SOLUTION: This pneumatic tire is provided with a tread part 1, a pair of sidewall parts 2, a pair of bead parts 3, a carcass 5 and an inclined belt layer 6. A ratio BD/BW of a diametrical difference BD between a width direction center part and a width direction end part of the outermost layer inclined belt layer to a width BW of the outermost layer of the inclined belt layer 6 in tire meridian cross section in an assembled state to an applicable rim is in the range of 0.10 to 0.13. A shoulder side region 13 has a smaller negative ratio of a lug groove than that of a center side region 14 by making 1/2 of the half width of a tread surface 8 provided with a groove part as a boundary. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire with reduced rolling resistance without impairing uneven wear resistance.

  In recent years, development in consideration of environmental problems such as global warming has been actively carried out, and one example is the reduction in fuel consumption of automobiles. One means for achieving this is to reduce the rolling resistance of the tire, and various technical developments have been made conventionally.

It is known that tire rolling resistance is often generated in the tread rubber. For example, changing the tread rubber used for the tread portion to one having a small loss tangent reduces the rolling resistance. It is said that it is effective. However, it is also known that this method sacrifices other performances such as uneven wear resistance of the tire.
In order to reduce rolling resistance, a method of reducing the thickness of the tread rubber can be considered, but in this case, there is a possibility that sufficient uneven wear resistance of the tire cannot be ensured.

  Accordingly, the present invention provides a pneumatic tire in which rolling resistance is effectively reduced without impairing uneven wear resistance.

  The inventor has found that the shear resistance in the tire circumferential direction has a great influence on the rolling resistance of the tire, and the shear distortion in the tire width direction has a great influence on the shoulder area. In particular, the present inventors have found that by reducing the shear strain in the tire width direction in the shoulder region, energy loss accompanying shear deformation can be reduced, and as a result, rolling resistance can be reduced.

  For this reason, in particular, the negative rate of the lug groove in the shoulder region can be reduced, the shear rigidity in the tire width direction of the contact portion of the shoulder region of the tread rubber can be increased, and the shear strain in the tire width direction can be reduced.

  Therefore, in the pneumatic tire of the present invention, a tread portion, a pair of sidewall portions, a pair of bead portions, and a carcass made of at least one carcass ply extending in a toroid shape between bead cores in each bead portion. , Comprising two or more inclined belt layers made of cords extending in a direction inclined with respect to the tire equatorial plane, disposed on the outer peripheral side of the crown region of the carcass, and assembled to an applicable rim The ratio BD / BW of the diameter difference BD between the widthwise central portion and the widthwise end portion of the outermost inclined belt layer with respect to the outermost layer width BW of the inclined belt layer in the tire meridian cross section in the bent state is 0. The shoulder side region has a negative ratio of the lug groove smaller than that of the center side region, with a range of 10 to 0.13 and a half of the half width of the tread surface provided with the groove as a boundary. Than is.

Here, the “applicable rim” means a rim defined by an industrial standard effective in an area where a tire is produced and used. For example, in Japan, JATMA (Japan Automobile Tire Association) YEAR BOOK, in Europe, ETRTO (European Tire and Rim Technical Organization) STANDARD MANUAL, in the United States, TRA (THE TIRE and RIM ASSOCIATION INC.) YEAR BOOK.
“Assembled to the applicable rim” means that the tire is assembled to the applicable rim specified in JATMA, etc., and the internal pressure is not applied, or an extremely low internal pressure of up to about 30 kPa is given to give the tire a standard property. It shall mean the added state.
Here, the “negative ratio of the lug grooves” refers to the ratio of the sum of the area of the lug grooves to the total area of the tread surface assuming that no grooves or the like are arranged.

In such a tire, more preferably, in the carcass pass line from the position corresponding to the widthwise end of the outermost inclined belt layer to the bead core, the portion showing the minimum radius of curvature, the center of curvature being located inside the tire However, it is located inward in the tire radial direction from the half point of the cross-sectional height SH of the tire.
The “carcass pass line” refers to the center line of the thickness of the main body of the carcass, and does not consider the folded portion of the carcass with respect to the bead core.

  Preferably, the ratio SWh / SH of the radial distance SWh from the rim diameter line to the maximum width position of the tire with respect to the tire cross-section height SH is set to 0.55 or less.

  More preferably, the ratio GB / GA of the tread rubber thickness GA located at the center in the belt width direction of the outermost inclined belt layer and the tread rubber thickness GB located at the end in the belt width direction is 0.75 or more. .

  In the pneumatic tire of the present invention, particularly in the tire meridian section in a state assembled to the applicable rim, with respect to the width BW of the outermost layer of the inclined belt layer, the widthwise central portion and the width direction of the outermost inclined belt layer The ratio BD / BW of the diameter difference BD with the end portion is set to 0.10 to 0.13, the diameter difference in the tire width direction of the inclined belt layer is increased, and the crown region of the tread portion is rounded. Reduce the ground contact width of the shoulder area. As a result, the range in the width direction of the tread rubber that is deformed in the shoulder region, and hence the tread rubber volume, is reduced, so that the energy loss in the shoulder region can be effectively reduced.

  That is, when BD / BW is less than 0.10, the ground contact width of the shoulder region is not narrowed as expected, and it is difficult to reduce energy loss due to shear deformation, while when it exceeds 0.13, The contact width of the shoulder region becomes too narrow, and the tread central region tends to wear early.

  And by setting the shoulder side region to have a negative rate of lug groove smaller than the center side region, the shear rigidity in the tire width direction is increased with the half width of the tread tread provided with the groove as a boundary, and the tire width The shear strain in the direction can be reduced, while the shear rigidity in the tire circumferential direction is reduced, but the contribution to the rolling resistance is small in the shoulder region. As a result, rolling resistance can be reduced when viewed as a whole tire.

Hereinafter, the pneumatic tire of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a meridian cross-sectional view of a half portion of a tire and a partial development view of a tread pattern, showing an embodiment of a pneumatic tire according to the present invention in a state assembled to an applied rim.

  In the figure, 1 is a tread portion, 2 is a pair of sidewall portions extending radially inward continuously to the respective side portions of the tread portion 1, and 3 is a radially inward direction of the sidewall portion 2. The continuous bead portions are shown in FIG.

  Here, for example, around the pair of bead cores 4 embedded in the bead part 3, each side part is wound up and moored, for example, on the outer peripheral side of the crown region of the carcass 5 made of one carcass ply, Two or more rubber-coated belt layers, in the drawing, two inclined belt layers 6 are provided, extending in a direction inclined at 15 to 30 ° with respect to the tire equatorial plane. In the radially outward direction, a number of cords extending along the equatorial plane of the tire are covered with rubber. In the figure, two circumferential belt layers 7 and a tread rubber 9 forming a tread tread surface 8 are provided. Arrange.

Further, the tread tread surface 8 includes, for example, a plurality of circumferential grooves 10 extending in the circumferential direction of the tread, two circumferential grooves 10 in the figure, and a plurality of lateral grooves extending in the tread width direction across the circumferential grooves 10. 11 are provided with four lateral grooves 11 extending at predetermined intervals in the tread circumferential direction, and three block rows 12 are defined between these grooves 10 and 11 and the tread side edge. To do.
Here, the circumferential grooves 10 are provided so as to extend linearly in the tread circumferential direction. For example, the circumferential grooves 10 can have a width of 5 to 10 mm and a depth of 3 to 8 mm. For example, the width of the lateral groove 11 intersecting with can be set to 1 to 7 mm in width and 3 to 8 mm in depth.

Furthermore, in this tire, the ratio BD / BW of the diameter difference BD between the width direction central portion and the width direction end portion of the outermost layer inclined belt layer with respect to the width BW of the outermost layer of the inclined belt layer 6 is 0.10 to 0. .13, with the half of the half width of the tread tread 8 as a boundary, the shoulder side region 13 makes the negative rate of the lug groove smaller than the center side region 14.
Thereby, rolling resistance can be reduced without impairing the uneven wear resistance of the tread tread surface 8.

In this case, preferably, the negative rate of the lug groove of the shoulder side region 13 with respect to the negative rate of the center side region 14 is set to 0.4 to 0.9.
If it is less than 0.4, the rubber volume of the shoulder side region 13 becomes large, and the effect of reducing the bending resistance cannot be obtained. On the other hand, if it exceeds 0.9, the desired effect tends not to be obtained. is there.

  In such a pneumatic tire, preferably, in the carcass pass line extending from the position corresponding to the widthwise end of the outermost inclined belt layer to the radially inner side portion of the bead core 4, the center of curvature is the tire's center. A portion indicating the minimum radius of curvature located on the inner side is positioned inward in the tire radial direction from a half point of the cross-sectional height SH of the tire.

  With this configuration, the minimum radius of curvature position of the carcass line is set on the bead portion 3 side, and the carcass 5 can be reduced in the vertical rigidity of the tire on the bead portion 3 side. Shear deformation can be suppressed and strain energy loss can be reduced.

  Preferably, the ratio SWh / SH of the radial distance SWh from the rim diameter line to the maximum width position of the tire with respect to the tire cross-section height SH is 0.55 or less.

That is, when SWh / SH is set to 0.55 or less, the carcass 5 is a line that hangs from the belt width direction end portion to the bead portion 3 side with a small radius of curvature, so the belt tension near the belt width direction end portion decreases. On the other hand, the belt tension at the center in the belt width direction increases, and the circumferential shear strain that occurs between the stepped-in portion and the kick-out portion in the contact surface is suppressed, resulting in a reduction in strain energy loss. Can do.
SWh / SH is preferably 0.4 or more. This is because if the SWh / SH is less than 0.4, the belt tension in the shoulder side region 13 is too low, and the uneven wear resistance of the shoulder side region 13 is reduced.

  By satisfying both 0.10 ≦ BD / HBW ≦ 0.13 and SWh / SH ≦ 0.55, the ground contact width of the shoulder side region 13 can be narrowed, and the belt tension in that region can be increased. The shear strain in the tire width direction can be greatly reduced and strain energy loss can be suppressed.

Further, the ratio GB / GA between the thickness of the tread rubber (GA) located at the center in the belt width direction of the outermost inclined belt layer and the thickness of the tread rubber (GB) located at the end in the belt width direction is 0.75 or more. It is preferable that
With this configuration, the thickness of the tread rubber in the shoulder side region 13 is reduced, so that strain energy loss generated in the shoulder side region 13 can be reduced and uneven wear resistance can be improved.

  That is, when GB / GA is less than 0.75, the rubber thickness of the tread rubber 9 in the shoulder side region 13 becomes thin, and uneven wear resistance deteriorates. There is a tendency that the improvement of rolling resistance and reduction of rolling resistance cannot be sufficiently achieved.

Next, a tire having a structure as shown in FIGS. 1 and 2 and having a size of PSR 225 / 45R17 is prototyped, and two carcass plies and the inclined belt layer are inclined at 24 ° with respect to the tire equatorial plane. The steel cord arranged in (2) is made of two layers crossing each other, and a ribbon-like strip coated with a rubberized nylon cord is provided on it and a circumferential belt layer formed into a spiral winding structure is provided in Table 1. As shown, rolling resistance was measured for each of Example tires and Comparative Example tires 1 to 5 in which the respective specifications were changed.
In addition, since the comparative example tire does not require modification about structures other than the tread portion, it was assumed to be in conformity with the example tire.
FIG. 2 shows an embodiment of a pneumatic tire in which a circumferential groove is provided in the shoulder region of the tread tread and at least part of the loss tangent of the cap rubber in the range is assembled to an applied rim. It is meridian sectional drawing about a half part.

For each of the example tires and comparative tires 1 to 5, the tire is assembled on a 7.5 × 17 rim in accordance with ISO 18164, the internal pressure is 230 kPa, the load load is 4.3 kN, and the speed is 80 km / h. The tire was rolled, and the rolling resistance of the axle was measured and evaluated using a drum testing machine having a steel plate surface having a diameter of 1.7 m. The results are shown in Table 2 as an index.
In addition, the index value in a table | surface is calculated | required using the value of the comparative example tire 2 as control, and shows that rolling resistance is excellent, so that an index | exponent is small.

  From the results in Table 2, the tires 1 and 2 were able to reduce rolling resistance compared to the comparative tires 1 to 4.

FIG. 2 is a meridian cross-sectional view of a half portion of the tire and a partial development view of a tread pattern in a state where one embodiment of the pneumatic tire of the present invention is assembled to an application rim. It is meridian sectional drawing about the half part of a tire in the state assembled | attached to the application rim, with the embodiment of the conventional pneumatic tire.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Bead core 5 Carcass 6 Inclined belt layer 7 Circumferential belt layer 8 Tread tread 9 Tread rubber 10 Circumferential groove 11 Horizontal groove 12 Block row 13 Shoulder side area 14 Center side area

Claims (4)

A tread portion, a pair of sidewall portions, a pair of bead portions, a carcass made of at least one carcass ply extending in a toroid shape between bead cores in each bead portion, and an outer peripheral side of the crown region of the carcass In a pneumatic tire comprising two or more inclined belt layers made of a cord extending in a direction inclined with respect to the tire equator plane,
The ratio BD of the diameter difference BD between the center portion in the width direction and the end portion in the width direction of the outermost layer inclined belt layer with respect to the width BW of the outermost layer of the inclined belt layer in the tire meridian section assembled in the applied rim. / BW is in the range of 0.10 to 0.13,
A pneumatic tire characterized in that the negative rate of the lug groove is smaller in the shoulder side region than in the center side region, with a half of the half width of the tread surface provided with the groove as a boundary.   In the carcass pass line extending from the position corresponding to the widthwise end of the outermost layer inclined belt layer to the bead core, the portion showing the minimum radius of curvature where the center of curvature is located inside the tire is the cross-sectional height SH of the tire. The pneumatic tire according to claim 1, which is located inward in the tire radial direction from the half point.   The pneumatic tire according to claim 1 or 2, wherein a ratio SWh / SH of a radial distance SWh from the rim diameter line to the maximum width position of the tire with respect to the tire cross-section height SH is 0.55 or less.   The ratio GB / GA of the tread rubber thickness GA located at the center in the belt width direction of the outermost inclined belt layer and the tread rubber thickness GB located at the end in the belt width direction is 0.75 or more. 4. The pneumatic tire according to any one of 3.

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