Tire

Abstract

To provide a tire capable of reducing air resistance during tire rotation and improving fuel consumption performance.SOLUTION: In a tire including a tread portion 1 and a pair of sidewall portions 2, a plurality of recessed portions 10 are formed on outer surfaces of the sidewall portions 2, the plurality of recessed portions 10 have first elements 11 and second elements 12 which are arranged in a tire circumferential direction and connected to each other, width w1 of the first elements 11 in the tire radial direction are wider than width w2 of the second elements 12 in the tire radial direction, and surface shapes of the recessed portions 10 have longitudinal directions in the tire circumferential direction.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a tire having a plurality of recesses formed on the outer surface of a tire sidewall portion.

Background Art

[0002] In recent years, in order to reduce the air resistance of a vehicle by changing the air flow near the tire and thereby improve the fuel consumption performance, a large number of recesses (so-called "dimples") have been provided on the outer surface of the sidewall portion (see, for example, Patent Document 1). Such recesses are intended to improve the fuel consumption performance by generating turbulent flow during tire rotation to suppress an increase in air resistance and reducing rolling resistance. However, in the case of recesses (dimples) having a conventional shape (circular, elliptical, polygonal, etc.), the effect of generating turbulent flow is not always sufficient, and further improvement in reducing air resistance and improving fuel consumption performance by the recesses (dimples) is required.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present invention is to provide a tire capable of reducing air resistance during tire rotation and improving fuel consumption performance.

Means for Solving the Problems

[0005] In order to achieve the above object, a tire of the present invention includes a tread portion that extends in the tire circumferential direction and forms an annular shape, and a pair of sidewall portions disposed on both sides of the tread portion. In the tire, a plurality of recesses are formed on the outer surface of the sidewall portion. The plurality of recesses each have a first element and a second element that are arranged in the tire circumferential direction and connected to each other. The width of the first element in the tire radial direction is wider than the width of the second element in the tire radial direction, and the surface shape of the recess has a longitudinal direction in the tire circumferential direction.

Advantages of the Invention

[0006] As a result of intensive research on a tire having a large number of recesses (dimples) on the outer surface of the sidewall portion, the inventor of the present invention found that the tire has a first element and a second element that are arranged in the tire circumferential direction and connected to each other. The width of the first element in the tire radial direction is wider than the width of the second element in the tire radial direction, and the recess having a surface shape (the whole composed of the first element and the second element) with a longitudinal direction in the tire circumferential direction is effective in generating turbulent flow when the tire rotates. That is, in the recess of this shape, since each recess includes a portion with a large width (the first element) and a portion with a small width (the second element), it can exhibit a turbulent flow generation effect at different vehicle speeds as two types of recesses with different sizes. Further, since the length (the length along the vehicle traveling direction) of the recess of this shape with respect to the air flow direction changes depending on the position on the tire circumference, it also functions as recesses with different sizes in this respect, and can exhibit a turbulent flow generation effect at different vehicle speeds. The present invention is based on the above findings. Since the plurality of recesses formed on the outer surface of the sidewall portion each have a shape composed of the aforementioned first element and second element, turbulent flow can be effectively generated when the tire rotates, suppressing an increase in air resistance, reducing rolling resistance, and improving fuel consumption performance.

[0007] In the tire of the present invention, it is preferable that the width w2 in the tire radial direction of the second element is less than 50% of the width w1 in the tire radial direction of the first element. This improves the balance of the sizes (widths in the tire radial direction) of the first element and the second element, effectively generates turbulent flow to suppress air resistance, and is advantageous for improving fuel consumption performance.

[0008] In the tire of the present invention, it is preferable that the depth d1 of the first element is greater than the depth d2 of the second element. This improves the balance of the sizes (volumes) of the first element and the second element, effectively generates turbulent flow to suppress air resistance, and is advantageous for improving fuel consumption performance.

[0009] In the tire of the present invention, it is preferable that a plurality of recesses are arranged on the tread portion side rather than at the tire maximum width position. Since this position is a site where the influence of the air flow is large, arranging recesses at this site enables efficient generation of turbulent flow, suppresses air resistance, and is advantageous for improving fuel consumption performance.

[0010] In the tire of the present invention, it is preferable that a plurality of recesses are arranged in the tire circumferential direction and the tire radial direction, and a second element of another recess is arranged between the first elements of a pair of adjacent recesses in the tire radial direction. With such an arrangement, a larger number of recesses can be arranged densely, effectively generating turbulent flow to suppress air resistance, and being advantageous for improving fuel consumption performance.

[0011] In the region where a plurality of recesses are provided in the tire of the present invention, it is preferable that the ratio of the areas of the plurality of recesses included in a unit area of 1 cm square is 60% to 95%. This enables the recesses to be arranged densely enough, effectively generates turbulent flow to suppress air resistance, and is advantageous for improving fuel consumption performance.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Mode for Carrying Out the Invention

[0013] Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.

[0014] As shown in FIG. 1, the pneumatic tire of the present invention includes a tread portion 1 that contacts the road surface, a pair of sidewall portions 2 disposed on both sides of the tread portion 1, and a pair of bead portions 3 disposed on the inner side in the tire radial direction of the sidewall portion 2. In FIG. 1, the symbol CL indicates the tire equator. Although not depicted because FIG. 1 is a meridian half-sectional view, the tread portion 1, the sidewall portion 2, and the bead portion 3 each extend in the tire circumferential direction to form an annular shape, thereby constituting the toroidal basic structure of the pneumatic tire. Hereinafter, the description using FIG. 1 is basically based on the illustrated meridian cross-sectional shape, but each tire component member extends in the tire circumferential direction to form an annular shape.

[0015] A carcass layer 4 is mounted between a 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 from the inner side to the outer side in the tire width direction around a bead core 5 disposed in each bead portion 3. Further, a bead filler 6 is disposed on the outer periphery of the bead core 5, and this bead filler 6 is wrapped by the main body portion and the folded-back portion of the carcass layer 4. On the other hand, a plurality 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 inclined with respect to the tire circumferential direction, and the reinforcing cords are arranged so as to cross each other between the layers. In these belt layers 7, the inclination angle of the reinforcing cords with respect to the tire circumferential direction is set in the range of, for example, 10° to 40°. Further, at least one belt reinforcing layer 8 is provided on the outer peripheral side of the belt layer 7. The belt reinforcing layer 8 includes organic fiber cords oriented in the tire circumferential direction. In the belt reinforcing layer 8, the angle of the organic fiber cords with respect to the tire circumferential direction is set in the range of, for example, 0° to 5°.

[0016] Since the present invention relates to a recess 10 (dimple) provided in the sidewall portion 2 described later, the basic structure (cross-sectional structure) of the tire in other portions is not limited to the above-described general structure. It should be noted that the tire of the present invention is preferably a pneumatic tire as described above, but may be a non-pneumatic tire as long as it has a side surface (a portion where the recess 10 described later can be formed) corresponding to the sidewall portion 2. In the case of a pneumatic tire, it can be filled with air, an inert gas such as nitrogen, or other gases inside.

[0017] In the present invention, as shown in FIG. 2, a plurality of recesses 10 are provided on the outer surface of the sidewall portion 2. As enlarged and shown in FIG. 3(a), each of the plurality of recesses 10 has a first element 11 and a second element 12 that are arranged side by side in the tire circumferential direction and connected to each other. In each recess 10, the width w1 in the tire radial direction of the first element 11 is configured to be wider than the width w2 in the tire radial direction of the second element 12. Further, the surface shape of the recess 10 (the overall shape composed of the first element 11 and the second element 12) has a longitudinal direction in the tire circumferential direction. For example, the recess 10 in FIG. 3(a) is composed of a first element 11 having a substantially rectangular shape (a shape in which the vertices of the rectangle are chamfered in an arc shape) and a second element 12 having a rectangular shape with a smaller width in the tire radial direction than the first element 11, thus satisfying all of the above-described conditions.

[0018] Compared with conventional circular dimples, such recesses 10 are excellent in the effect of generating turbulent flow when the tire rotates, can suppress an increase in air resistance around the tire during running, reduce rolling resistance, and improve fuel consumption performance. Specifically, since each recess 10 includes a portion with a large width (the first element 11) and a portion with a small width (the second element 12), it can exhibit a turbulent flow generation effect at different vehicle speeds as two types of recesses 10 with different sizes. Further, since the length (the length along the vehicle traveling direction) of the recess 10 in this shape with respect to the air flow direction changes depending on the position on the tire circumference, it also functions as recesses 10 with different sizes in this respect, and can exhibit a turbulent flow generation effect at different vehicle speeds. As a result, it is possible to effectively generate turbulent flow when the tire rotates, suppress an increase in air resistance, reduce rolling resistance, and improve fuel consumption performance.

[0019] The specific shape of the recess 10 is not particularly limited as long as it is composed of the aforementioned first element 11 and second element 12. That is, as the shapes of the first element 11 and the second element 12, any shapes such as circular, elliptical, polygonal, etc. can be adopted respectively. For example, the shape in Fig. 3(a) is composed of the first element 11 having a substantially rectangular shape (a shape in which the vertices of the rectangle are chamfered in an arc shape) as described above, and the second element 12 having a rectangular shape with a smaller width in the tire diameter direction than the first element 11, but it is not limited to this shape and various modes described later can be adopted. In addition, in the present invention, the surface shape of the recess 10 is important and the cross-sectional shape of the recess 10 is not particularly limited. The cross-sectional shape of the recess 10 (especially the first element 11) may be, for example, semi-circular as shown in Fig. 3(b) or rectangular as shown in Fig. 3(c) regardless of its surface shape (Figs. 3(b) to 3(c) are cross-sectional views taken along the X-X arrow in Fig. 3(a)).

[0020] In addition to the example of FIG. 3(a), for example, as shown in FIG. 4, examples include a mode in which an elliptical second element 12 is connected to a circular first element 11 (FIG. 4(a)), a mode in which a triangular second element 12 is connected to a circular first element 11 (FIG. 4(b)), and a mode in which a rectangular second element 12 is connected to a circular first element 11 (FIGS. 4(c) to (d)). Further, examples include a mode in which a circular second element 12 is connected to an elliptical first element 11 (FIG. 5(a)), a mode in which a triangular second element 12 is connected to an elliptical first element 11 (FIG. 5(b)), and a mode in which a rectangular second element 12 is connected to an elliptical first element 11 (FIGS. 5(c) to (d)). Alternatively, examples include a mode in which a circular second element 12 is connected to a rectangular first element 11 (FIG. 6(a)), a mode in which an elliptical second element 12 is connected to a rectangular first element 11 (FIG. 6(b)), a mode in which a triangular second element 12 is connected to a rectangular first element 11 (FIG. 6(c)), and a mode in which a rectangular second element 12 (a rhombus shape) is connected to a rectangular first element 11 in a direction different from the example of FIG. 3(a) (FIG. 6(d)). In any of these various modes, the recess 10 has a first element 11 and a second element 12 that are arranged side by side in the tire circumferential direction and connected to each other. The width of the first element 11 in the tire radial direction is wider than the width of the second element 12 in the tire radial direction, and the surface shape of the recess 10 has a longitudinal direction in the tire circumferential direction. Therefore, the effects of the present invention described above can be exhibited.

[0021] As described above, the tire radial width w1 of the first element 11 is configured to be wider than the tire radial width w2 of the second element 12. At this time, the tire radial width w2 of the second element 12 is preferably less than 50%, more preferably less than 35%, and still more preferably 25% or more and less than 35% of the tire radial width w1 of the first element 11. This improves the balance of the sizes (tire radial widths) of the first element 11 and the second element 12, effectively generates turbulent flow to suppress air resistance, and is advantageous for improving fuel consumption performance. That is, according to the findings of the inventor of the present invention, in the case of a conventional circular dimple, the larger the width (diameter) of the dimple, the more effective it is in generating turbulent flow during high-speed driving, and the smaller the width (diameter) of the dimple, the more effective it is in generating turbulent flow during low-speed driving. Therefore, in the case of the recess 10 of the present invention as well, by providing an appropriate difference in the sizes of the first element 11 and the second element 12, the first region 11 with a larger width can exhibit its effect in the high-speed range, and the second region 12 with a smaller width can exhibit its effect in the low-speed range. Thus, by their cooperation, it is possible to effectively generate turbulent flow in various speed ranges and obtain the effect of suppressing air resistance. At this time, if the tire radial width w2 of the second element is 50% or more of the tire radial width w1 of the first element, a sufficient difference in the sizes of the first element 11 and the second element 12 will not occur, and thus the above-described effects cannot be fully expected.

[0022] In addition to the relationship between the widths w1 and w2 described above, as shown in FIGS. 3(b) to 3(c), it is preferable that the depth d1 of the first element 11 is greater than the depth d2 of the second element 12. This improves the balance of the sizes (volumes) of the first element 11 and the second element 12, effectively generates turbulent flow to suppress air resistance, and is advantageous for improving fuel consumption performance. That is, similar to the case of the widths w1 and w2 described above, by providing an appropriate difference in the sizes (depths d1 and d2) of the first element 11 and the second element 12, the effect in the high-speed range can be exerted in the first region 11 with a large amount of depression (i.e., volume), and the effect in the low-speed range can be expected in the second region 12 with a small amount of depression (volume). Therefore, by the cooperation of these, the effect of effectively generating turbulent flow in various speed ranges to suppress air resistance can be obtained. In increasing the depth d1 of the first element 11 to be greater than the depth d2 of the second element 12, the depth d2 of the second element 12 is preferably less than 80% of the depth d1 of the first element 11, more preferably 60% to 70%.

[0023] As described above, the surface shape of the recess 10 has a longitudinal direction in the tire circumferential direction. At this time, the length L of the recess 10 along the tire circumferential direction is preferably 2 mm to 20 mm, more preferably 3 mm to 10 mm. By having the recess 10 with an appropriate length in this way, it becomes possible to effectively generate turbulent flow. When the length L of the recess 10 along the tire circumferential direction is less than 2 mm, each recess 10 is too small, so the effect of generating turbulent flow is limited. When the length L of the recess 10 along the tire circumferential direction exceeds 20 mm, the unevenness of the surface of the sidewall portion 2 at the position where the recess 10 is provided becomes prominent, and the appearance of the tire deteriorates.

[0024] In addition, the individual values of the widths w1 and w2 and the depths d1 and d2 are not particularly limited, but the width w1 of the first element 11 in the tire radial direction can be set to, for example, 2 mm to 10 mm, and the width w2 of the second element 12 in the tire radial direction can be set to, for example, 0.5 mm to 5 mm. Also, the depth d1 of the first element 11 can be set to, for example, 0.5 mm to 5 mm, and the depth d2 of the second element 12 can be set to, for example, 0.3 mm to 4 mm.

[0025] The plurality of recesses 10 can be provided at any position of the sidewall portion 2. However, considering that the recesses 10 are elements for generating turbulent flow, it is preferable to concentrate and provide the plurality of recesses 10 at a site where the influence of the air flow is large in the sidewall portion 2. That is, the plurality of recesses 10 are preferably arranged on the tread portion 1 side rather than the tire maximum width position P. Thereby, it becomes possible to generate turbulent flow more efficiently, which is advantageous for suppressing air resistance and improving fuel consumption performance.

[0026] The plurality of recesses 10 are preferably arranged in the tire circumferential direction and the tire radial direction. Thereby, since a large number of recesses 10 are concentrated and arranged in a specific region of the sidewall portion 2, it becomes possible to effectively generate turbulent flow. In particular, as shown in FIG. 2, it is preferable to arrange the second element 12 of another recess 10 between the first elements 11 of a pair of adjacent recesses 10 in the tire radial direction. In such an arrangement, since a larger number of recesses 10 can be densely arranged, it is advantageous for effectively generating turbulent flow, suppressing air resistance, and improving fuel consumption performance.

[0027] If the plurality of recesses 10 are spaced apart from each other and sparsely arranged, there is a possibility that the effect of generating turbulent flow cannot be sufficiently obtained. Therefore, the plurality of recesses 10 are preferably provided in a moderately concentrated manner. Specifically, as shown in FIG. 7, in the region where the plurality of recesses 10 are provided, an arbitrary unit area of 1 cm square (the hatched area in the figure) is assumed, and the ratio of the surface area of the plurality of recesses 10 included in this unit area (area: 1 cm 2 ) is preferably set to 60% to 95%, more preferably 75% to 90%. Thereby, the recesses 10 can be arranged sufficiently densely, which is advantageous for effectively generating turbulent flow, suppressing air resistance, and improving fuel consumption performance. If the ratio of the surface area of the plurality of recesses 10 included in the unit area is less than 60%, the arrangement of the plurality of recesses 10 becomes sparse, so that the effect of generating turbulent flow is limited. If the ratio of the surface area of the plurality of recesses 10 included in the unit area exceeds 95%, the portion other than the recesses 10 is too small to function as a desired concavo-convex shape, and the effect of generating turbulent flow is limited.

[0028] Hereinafter, the present invention will be further described by way of examples, but the scope of the present invention is not limited to these examples.

Example

[0029] The tire size is 235 / 60R18, and it has the basic structure (cross-sectional structure) illustrated in FIG. 1. Regarding the shape of the recess provided in the sidewall portion, the shape of the first element, the shape of the second element, the general shape (drawing number) of the recess, the ratio of the width w2 in the tire radial direction of the second element to the width w1 in the tire radial direction of the first element (w2 / w1×100%), the magnitude relationship between the depth d1 of the first element and the depth d2 of the second element (depth magnitude relationship), the location of the recess with respect to the maximum width position, and the ratio of the area of the recess shown in the unit area were set as shown in Table 1, and pneumatic tires of Comparative Example 1, Comparative Example 1, and Examples 1 to 6 were created.

[0030] In the "General shape of the recess (drawing number)" in Table 1, the drawing number indicating which of the recess shapes illustrated in FIG. 8 was shown. In the column of "Location of the recess with respect to the maximum width position" in Table 1, when the recess was provided on the bead side rather than the maximum width position, it was indicated as "inside", and when the recess was provided on the tread side rather than the maximum width position, it was indicated as "outside".

[0031] Note that Comparative Example 1 is an example in which only a plurality of recesses (circular dimples) separated from each other are provided as in Conventional Example 1, but it includes two types of dimples with different diameters as shown in FIG. 8(b), and these two types of dimples are alternately arranged in the tire circumferential direction. For the sake of convenience, the dimple with the larger diameter was regarded as the first element and the dimple with the smaller diameter was regarded as the second element, and reference values were shown in the columns of "Shape of the second element", "w2 / w1×100%", and "Depth magnitude relationship" in Table 1.

[0032] For these pneumatic tires (test tires), the fuel consumption performance was evaluated by the following evaluation method, and the results are also shown in Table 1.

[0033] Fuel consumption performance Each test tire was assembled onto a wheel (rim size: 18×7.0J) and mounted on a test vehicle (front-wheel drive SUV with a displacement of 2000 cc). The tire was filled with air pressure of 230 kPa, and the fuel consumption rate was measured when the test course with a total length of 2 km was traveled 500 laps at a speed of 100 km / h. Note that the fuel consumption rate is the distance traveled per liter of gasoline. The evaluation results were shown as an index with the fuel consumption rate of Comparative Example 1 being 100. The larger this index value is, the better the fuel consumption performance.

[0034]

Table 1

[0035] As is clear from Table 1, the pneumatic tires of Examples 1 to 6 improved the fuel consumption performance compared with Comparative Example 1. On the other hand, Comparative Example 1 provided with two types of dimples having different sizes could not sufficiently improve the fuel consumption performance.

[0036] This disclosure includes the following inventions. Invention [1] In a tire having a tread portion extending in the tire circumferential direction and forming an annular shape, and a pair of sidewall portions disposed on both sides of the tread portion, a plurality of recesses are formed on the outer surface of the sidewall portion, the plurality of recesses each have a first element and a second element arranged side by side in the tire circumferential direction and connected to each other, the width of the first element in the tire radial direction is wider than the width of the second element in the tire radial direction, and the surface shape of the recess has a longitudinal direction in the tire circumferential direction. Invention [2] The tire according to Invention [1], wherein the width w2 of the second element in the tire radial direction is less than 50% of the width w1 of the first element in the tire radial direction. Invention [3] The tire according to Invention [1] or [2], wherein the depth d1 of the first element is greater than the depth d2 of the second element. Invention [4] The tire according to any one of Inventions [1] to [3], wherein the plurality of recesses are disposed on the tread portion side rather than at the tire maximum width position. Invention [5] The tire according to any one of Inventions [1] to [4], characterized in that the plurality of recesses are arranged in the tire circumferential direction and the tire radial direction, and a second element of another recess is arranged between first elements of a pair of adjacent recesses in the tire radial direction. Invention [6] The tire according to any one of Inventions [1] to [5], characterized in that in the region where the plurality of recesses are provided, the ratio of the surface area of the plurality of recesses included in a unit area of 1 cm square is 60% to 95%.

Explanation of reference numerals

[0037] 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 10 Recess 11 First element 12 Second element CL Tire equator P Tire maximum width position

Claims

1. In a tire having a tread portion extending in the tire circumferential direction and forming an annular shape, and a pair of sidewall portions disposed on both sides of the tread portion, a plurality of recesses are formed on the outer surface of the sidewall portion, the plurality of recesses each have a first element and a second element arranged side by side in the tire circumferential direction and connected to each other, a width in the tire radial direction of the first element is wider than a width in the tire radial direction of the second element, and a surface shape of the recess has a longitudinal direction in the tire circumferential direction. A tire characterized by this.

2. The tire according to claim 1, wherein a width w2 in the tire radial direction of the second element is less than 50% of a width w1 in the tire radial direction of the first element.

3. The tire according to claim 1 or 2, wherein a depth d1 of the first element is greater than a depth d2 of the second element.

4. The tire according to claim 1 or 2, wherein the plurality of recesses are disposed closer to the tread portion side than the tire maximum width position.

5. The tire according to claim 1 or 2, wherein the plurality of recesses are arranged in the tire circumferential direction and the tire radial direction, and a second element of another recess is disposed between first elements of a pair of adjacent recesses in the tire radial direction.

6. The tire according to claim 1 or 2, wherein in a region where the plurality of recesses are provided, a ratio of a surface area of the plurality of recesses included in a unit area of 1 cm square is 60% to 95%.

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