Pneumatic tire

Abstract

To provide a tire that establishes compatibility between side-cut performance and air resistance reduction.SOLUTION: A pneumatic tire 1 according to one embodiment comprises a tread, a side wall and a bead. The side wall has a side block. The height of the side block based on a profile surface of the side wall is in the range of 1-15 mm. A lower end of the side block has a vertical plane.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a pneumatic tire.

Background Art

[0002] In recent years, from the viewpoint of improving fuel efficiency such as that of an L, reduction of air resistance has been demanded also for tires. Conventionally, in order to improve side cut performance and the like during off-road driving, a pneumatic tire having side blocks formed on a sidewall has been widely known (see, for example, Patent Document 1). However, when side blocks are present, it becomes more difficult to reduce air resistance. That is, the side blocks increase the air resistance of the tire.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Conventional tires cannot be said to have been sufficiently considered in terms of reducing air resistance, and there is a great deal of room for improvement. An object of the present invention is to provide a tire that achieves both side cut performance and air resistance reduction.

Means for Solving the Problems

[0005] A pneumatic tire according to one aspect of the present invention includes a tread, a sidewall, and a bead. The sidewall has side blocks, the height of the side blocks based on the profile surface of the sidewall is 1 mm or more and 15 mm or less, and the lower end of the side blocks has a vertical surface.

Effects of the Invention

[0006] According to one aspect of the present invention, in a pneumatic tire with improved side cut performance by side blocks, air resistance can be effectively reduced.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0008] Hereinafter, with reference to the drawings, an example of an embodiment of a pneumatic tire according to the present invention will be described in detail. The embodiments described below are merely examples, and the present invention is not limited to the following embodiments. In addition, forms formed by selectively combining the constituent elements of the following plurality of embodiments and modified examples are included in the present invention.

[0009] FIG. 1 is a perspective view of a pneumatic tire 1 which is an example of an embodiment. As shown in FIG. 1, the pneumatic tire 1 includes a tread 2 which is a portion in contact with the road surface, a sidewall 3 which forms the tire side surface, and a bead 4 which is a portion fixed to the rim of the wheel. The tread 2 has a tread pattern including a plurality of blocks such as shoulder blocks 2a and 2b. Further, a plurality of grooves 2c and 2d for partitioning the blocks are formed in the tread 2. The tread 2, the sidewall 3, and the bead 4 are formed in an annular shape along the tire circumferential direction.

[0010] The sidewall 3 extends radially inward from both axial ends of the tread 2 in the tire axial direction and, together with the bead 4, forms the left and right side surfaces of the pneumatic tire 1. Although details will be described later, the sidewall 3 has side blocks 3b. The side blocks 3b protrude outward in the tire axial direction from the profile surface 3a of the sidewall 3. As will be described later, by arranging a vertical surface at the lower end of the side block 3b while setting the height of the side block 3b within a predetermined range, air resistance can be suppressed. In this specification, the lower end of the side block 3b means the radially inner end of the side block 3b, and the upper end of the side block 3b means the radially outer end of the side block 3b. Also, the upper end and the lower end may be referred to in the same sense for vertical surfaces and the like included in the side block 3b.

[0011] The side blocks 3b improve the traction performance and side cut performance during off-road driving. When the side blocks 3b are present, it becomes more difficult to reduce air resistance, but the function of the vertical surface greatly reduces air resistance. The pneumatic tire 1 is suitable for, for example, tires for light trucks. Light trucks include pickup trucks, sports utility vehicles (SUVs), etc. An example of the size of the pneumatic tire 1 is LT275 / 60R20.

[0012] In the pneumatic tire 1, side ribs 5 are formed in the vicinity of the tread 2 on the tire side surface. The side ribs 5 are convex portions protruding outward in the tire axial direction and are formed annularly along the tire circumferential direction. In the present embodiment, the portion from the axially outer end of the surface of the shoulder blocks 2a, 2b facing radially outward of the tire to the side ribs 5 is defined as the buttress region, and the portion from the bead 4 to the side ribs 5 is defined as the sidewall 3. Note that the shape of the axially outer side surfaces 6a, 6b of the shoulder blocks 2a, 2b affects the shape of the buttress region.

[0013] The tread 2 and the sidewall 3 are generally composed of different types of rubber. The buttress area may be composed of the same rubber as the tread 2 or different rubbers. The bead 4 has, for example, a bead core and a bead filler. The bead core is a ring-shaped member obtained by covering a bundled steel wire (bead wire) with rubber. The bead filler is composed of a rubber harder than the tread rubber and the sidewall rubber and has a function of enhancing the rigidity of the bead 4.

[0014] The pneumatic tire 1 includes, for example, a carcass, a belt, and an inner liner. The carcass is a cord layer covered with rubber and forms the framework of the pneumatic tire 1 that withstands loads, impacts, air pressure, etc. The belt is a reinforcing band disposed between the rubber constituting the tread 2 and the carcass. The belt strongly tightens the carcass to enhance the rigidity of the pneumatic tire 1. The inner liner is a rubber layer provided on the inner peripheral surface of the carcass and holds the air pressure of the pneumatic tire 1.

[0015] FIG. 1 shows the side block 3b on the left side surface of the pneumatic tire 1. The pneumatic tire 1 preferably has side blocks 3b on the left and right sidewalls 3. And it is preferable that vertical surfaces are formed on both the left and right side blocks 3b. However, the left and right side blocks 3b are not limited to blocks of the same shape and may have completely different shapes. The side block 3b on the right side surface has, for example, a shape obtained by rotating the side block 3b on the left side surface 180° with respect to the center line passing through the tire equator and perpendicular to the tire rotation axis. The pneumatic tire 1 may be a tire without a specified mounting direction.

[0016] Hereinafter, with further reference to FIG. 2, the sidewall 3 and the battless region of the pneumatic tire 1 will be described in detail. FIG. 2 is a left side view of the pneumatic tire 1, showing an enlarged view of the sidewall 3 and the battless region. Hereinafter, the first direction in the tire circumferential direction may be referred to as the "X1 direction", and the second direction may be referred to as the "X2 direction". Also, the direction facing the outer side in the tire radial direction may be referred to as the "Y1 direction", and the direction facing the inner side in the radial direction may be referred to as the "Y2 direction".

[0017] As shown in FIGS. 1 and 2, the pneumatic tire 1 has a plurality of side blocks 3b formed in the sidewall 3. The plurality of side blocks 3b are arranged at a predetermined interval in the tire circumferential direction. The predetermined interval may be constant, or may be a variable pitch in which the interval between the blocks is slightly changed in units of a predetermined number. Also, the side block 3b includes a first side block 10 and a second side block 20. A step is formed at the boundary 15 between the first side block 10 and the second side block 20, and the first side block 10 protrudes more than the second side block 20.

[0018] In the present embodiment, side blocks 3b having substantially the same shape and the same size are arranged in the tire circumferential direction, but two or more types of blocks having different shapes from each other may be arranged alternately or in a predetermined pattern in the tire circumferential direction. The number of side blocks 3b arranged in the tire circumferential direction is not particularly limited, but as an example, it is 20 or more and 30 or less.

[0019] The side block 3b is preferably formed between the side rib 5 and the tire maximum width position P. In this case, it becomes easy to reduce air resistance while ensuring good side traction performance and side cut (protection) performance. In this specification, the "tire maximum width position P" means the position where the tire axial length is maximum on the profile surface 3a of the sidewall 3. Also, the "profile surface 3a" of the sidewall 3 means the surface facing the outside in the tire axial direction of the sidewall 3 when the side block 3b is not formed. For the virtual surface along the surface of the sidewall 3 and the surface hidden by the side block 3b, it is distinguished from the exposed surface and referred to as the "profile surface 3x".

[0020] The side block 3b is a block in which one first side block 10 and one second side block 20 are connected and integrated. The portion located between the side blocks 3b is at the same height as the profile surface 3a of the sidewall 3. For this reason, irregularities are formed in the circumferential direction of the tire in the portion located between the side rib 5 and the tire maximum width position P of the sidewall 3. These irregularities improve the side traction performance on muddy ground, sandy ground, or snowy roads. From the viewpoint of improving the side cut performance, it is preferable that the length of the side block 3b along the circumferential direction of the tire is longer than the interval between the side blocks 3b.

[0021] The side block 3b and the shoulder blocks 2a, 2b of the tread 2 are preferably arranged in a regular pattern related to each other. In this case, a regular pattern is formed integrally in the sidewall 3 and the buttress region. For example, the side traction performance is stabilized and the effect of reducing air resistance is also improved. In the present embodiment, the first side block 10 is formed so as to be aligned with the shoulder block 2a in the tire radial direction, and the second side block 20 is formed so as to be aligned with the shoulder block 2b in the tire radial direction.

[0022] The shoulder blocks 2a, 2b are blocks formed in the outer portion of the tread 2 in the tire axial direction, and are alternately arranged in the tire circumferential direction. The shoulder blocks 2a, 2b have, for example, similar sizes to each other, but are different in shape in that the side surface 6b of the shoulder block 2b is recessed more than the side surface 6a of the shoulder block 2a. The side surface 6b of the shoulder block 2b has a step formed over the entire circumferential length of the side surface 6b, and the block surface side is recessed more than the side rib 5 side.

[0023] The shoulder blocks 2a, 2b are divided by grooves 2c, 2d extending in the tire axial direction. The groove 2c is formed with substantially the same width from between each block to the side rib 5, while the groove 2d widens in the vicinity of the side rib 5. The side surfaces 6a, 6b of the shoulder blocks 2a, 2b and the grooves 2c, 2d form irregularities in the circumferential direction in the buttress region of the pneumatic tire 1. These irregularities improve the side traction performance on muddy ground, sandy ground, or snowy roads, similar to the side block 3b.

[0024] The side blocks 3b are formed in a range overlapping the shoulder blocks 2a, 2b and the groove 2c in the tire radial direction, and are not formed in the portion overlapping the groove 2d in the tire radial direction. That is, the side blocks 3b are formed at the same pitch as the pair of shoulder blocks 2a, 2b in the tire circumferential direction. The interval between the side blocks 3b is wider on the tire maximum width position P side than on the side rib 5 side. In this case, for example, the mud evacuation property is improved on muddy ground, and the side traction performance is improved.

[0025] The first side block 10 that constitutes the side block 3b is sandwiched between two second side blocks 20, but is continuous with one of the second side blocks 20 and not connected to the other second side block 20. The first side block 10 is formed in a range that overlaps with the shoulder block 2a in the tire radial direction, and the second side block 20 is formed in a range that overlaps with the shoulder block 2b and the groove 2c in the tire radial direction. The second side block 20 is larger than the first side block 10, and a part of it extends to a position that overlaps with the shoulder block 2a in the tire radial direction.

[0026] As described above, the first side block 10 and the second side block 20 have different heights from each other, and the first side block 10 is formed higher. The height of the side block 3b means the length along the normal direction of the profile surface 3x from the profile surface 3x of the sidewall 3 to the surface of the side block 3b. Due to the height difference between the two blocks that constitute the side block 3b and the height difference between the side block 3b and its gap, irregularities are formed on the sidewall 3, and these irregularities improve the side traction performance on muddy ground, sandy ground, or snow roads.

[0027] The first side block 10 has substantially the same height, for example, except at the block ends. On the other hand, the second side block 20 has three regions (the first region 21, the second region 22, and the third region 23) with different heights along the tire radial direction. The height of the second side block 20 is substantially constant in the first region 21 adjacent to the side rib 5, and is the lowest at the boundary between the second region 22 and the third region 23.

[0028] The first side block 10 has a shape in which the portion located on the inner side in the tire radial direction is convex in the X1 direction. This convex portion 11 is formed, for example, in a length range of 30% or more and 70% or less of the tire radial length of the first side block 10 from the inner end in the tire radial direction (the end in the Y2 direction). In other words, the portion of the first side block 10 located on the outer side in the tire radial direction (the Y1 direction side) close to the side rib 5 has a shape that is recessed in the X2 direction. Such unevenness of the first side block 10 contributes to the improvement of the side traction performance. Note that the X1 direction end of the convex portion 11 is formed in a substantially straight line shape in side view along the tire radial direction.

[0029] The block end of the side block 3b may be formed perpendicular to the profile surface 3a, or may be inclined so that the height of the block gradually decreases. At the end of the convex portion 11 of the first side block 10, a slope 12 with a gentler inclination than other block ends is formed. The slope 12 is located at the block end facing the Y1 direction. By forming the gentle slope 12 at the Y1 direction end of the convex portion 11, an air flow along the surface of the sidewall 3 is likely to occur, and an increase in air resistance can be suppressed. The inclination angle of the slope 12 with respect to the profile surface 3x is, for example, 40° or more and 75° or less.

[0030] The boundary 15 between the two blocks constituting the side block 3b extends along the tire radial direction from the side rib 5 and bends in the X1 direction at the center in the tire radial direction of the block. For this reason, the portion of the first side block 10 located on the Y2 direction side gradually decreases in tire circumferential length toward the Y2 direction. Note that since the first side block 10 and the second side block 20 have different heights, a step is formed along the boundary 15.

[0031] As described above, the height of the second side block 20 varies in the tire radial direction, and the first region 21 adjacent to the side rib 5 is the highest. The second region 22 adjacent to the first region 21 in the Y2 direction slopes so that the height gradually decreases in the Y2 direction, and the third region 23 adjacent to the second region 22 in the Y2 direction slopes so that the height gradually increases in the Y2 direction. By providing a gentle slope on the surface of the second side block 20, an air flow along the surface of the second side block 20 is likely to occur, and an increase in air resistance can be suppressed.

[0032] The second side block 20 is inclined with respect to the tire radial direction such that the block end facing the X2 direction is gradually positioned in the X1 direction in the Y2 direction. The second side block 20 has a tapered shape in which the circumferential length of the tire is slightly shorter at the Y2 direction end than at the Y1 direction end.

[0033] In a plan view of the side surface of the pneumatic tire 1, the area of the side block 3b is preferably 20% to 60% of the area of the region from the ground contact end E to the tire maximum width position P. Thereby, the effect of suppressing air resistance becomes more remarkable. In this specification, the "ground contact end E" means the tire axial end of the region that contacts the flat road surface when a load of 85% of the normal load (maximum load capacity) at the normal internal pressure is applied in a state where the unused pneumatic tire 1 is mounted on a normal rim and filled with air to reach the normal internal pressure.

[0034] Hereinafter, with reference to FIGS. 2 to 3, the vertical surface formed at the lower end of the side block 3b will be described in more detail. FIG. 3 is a view showing a part of the cross section taken along line AA in FIG. 2.

[0035] The height of the side block 3b based on the profile surface 3x of the sidewall 3 is 1 mm or more and 15 mm or less. In FIG. 3, H represents the maximum height of the first side block 10 and satisfies 1 mm ≤ H ≤ 15 mm. Since the first side block 10 is higher than the second side block 20, H represents the maximum height of the side block 3b. When the height of H is less than 1 mm, the side cut performance deteriorates. On the other hand, when the height of H exceeds 15 mm, the drag (resistance) increases.

[0036] In the example shown in FIGS. 2 to 3, the sidewall 3 has a vertical surface 30 at the lower end of the first side block 10 that constitutes the side block 3b. Thereby, convection and vortices generated in the vicinity of the lower end of the side block 3b are suppressed, and an air flow along the surface of the sidewall 3 is created, effectively reducing the air resistance of the tire. Since the first side block is higher than the second side block 20, forming the vertical surface 30 at the lower end of the first side block 10 has a great effect on reducing the air resistance of the tire. Note that a vertical surface 30 may be formed at the lower end of the second side block 20.

[0037] The vertical surface 30 means a surface that is substantially perpendicular to the ground surface when the pneumatic tire 1 is grounded on a horizontal surface. As shown in FIG. 3, when looking from the outside to the inside in the tire radial direction, with the direction in which the surface inclines inward in the tire width direction being -, and the direction in which the surface inclines outward in the tire radial direction being +, the angle of the vertical surface 30 with respect to the perpendicular line of the ground surface is, for example, an angle of -2° or more and 10° or less.

[0038] It is preferable that the upper end and the lower end of the vertical surface 30 are chamfered. Thereby, the generation of convection and vortices can be more significantly suppressed. The chamfering is, for example, R chamfering. Note that only the lower end of the vertical surface 30 may be chamfered, or only the upper end of the vertical surface may be chamfered, but it is more preferable that both the upper end and the lower end of the vertical surface are chamfered.

[0039] The length L1 from the upper end to the lower end of the vertical surface 30 and the length L2 from the grounding end E to the tire maximum width position P preferably satisfy the relationship of 0.05 ≦ L1 / L2 ≦ 0.3.

[0040] The ratio L1 / H of L1 to H preferably satisfies 0.05 ≦ L1 / H ≦ 50, more preferably satisfies 0.05 ≦ L1 / H ≦ 20, and even more preferably satisfies 0.05 ≦ L1 / H ≦ 10.

[0041] Regarding the pneumatic tire 1 having the above configuration, the maximum height H of the side block 3b (the first side block 10), the length L1 from the upper end to the lower end of the vertical surface 30, the length L2 from the grounding end E to the tire maximum width position P, and the inclination angle of the vertical surface were changed, and the air resistance, side cut performance, and riding comfort were evaluated by the following method. The evaluation results are shown in Table 1. In the plan view of the tire side surface, the area of the side block 3b was 40% with respect to the area of the region from the grounding end E to the tire maximum width position P.

[0042] [Evaluation of air resistance] For each test tire, by using a simulation with FEM that analyzes the air flow around the rotating tire, the drag force (the force acting on the tire placed in the air flow and having the same direction in the direction parallel to the flow) was measured, and the drag coefficient Cd was calculated from the following formula. The drag force was obtained from the pressure difference before and after the tire by simulation. Cd = D / (1 / 2ρU2S) In the formula, D is the generated drag force. ρ is the air density, and it was set to 1.18415 [kg / m 3 . U is the representative speed of the relative speed between the tire and the air, and it was set to 36.1 [m / s]. S is the representative area (frontal projected area) of the tire. The evaluation results shown in Table 1 are relative values when the value of the No. 1 tire is set to 100, and the larger the numerical value, the smaller the air resistance.

[0043] [Evaluation of side cut performance and riding comfort performance] Based on the single-wheel traction test "ASTM F1805" used in snow traction evaluation, the side cut performance and ride comfort performance of each test tire were evaluated on muddy ground. This evaluation was conducted by sensory evaluation. Regarding the side cut performance, the damage that occurred in the bald area after the above test drive was observed, and an index evaluation was performed with the conventional example used as an index set to 100. Regarding the ride comfort performance, the driver evaluated the ride comfort during the above test drive. The evaluation results shown in Table 1 are relative values when the value of tire No. 5 is set to 100, and the larger the numerical value, the better the ride comfort performance.

[0044] This test is performed by mounting each test tire and the reference tire on one test wheel of the test vehicle and driving on the test course. Also, the evaluation is conducted based on the following standards. ASTM F1805 ASTM F377 ASTM D2487 ASTM D4318

[0045] The load and air pressure of the tire shall be the values applicable to light truck tires. Specifically, the test load shall be 425 kgf and the air pressure shall be 240 kPa.

[0046]

Table 1

[0047] Tires No. 2 to No. 5 are provided with side blocks 3b having the shapes shown in FIGS. 1 to 3, and since the maximum height H of the side block 3b (the first side block 10) is in the range of 1 mm to 15 mm, both side cut performance and air resistance reduction can be achieved. In particular, tire No. 2 is also excellent in ride comfort performance.

[0048] From the above results, it can be seen that according to the pneumatic tire 1 having a side block with a vertical surface at the lower end at a predetermined height, both side cut performance and air resistance reduction can be achieved. Furthermore, by setting L1 / H within a predetermined range, the riding comfort performance can also be improved.

[0049] Note that the above embodiment can be appropriately modified in design without impairing the object of the present invention. For example, Side ribs may be formed on the sidewall instead of the side blocks.

Explanation of Signs

[0050] 1 Pneumatic tire, 2 Tread, 2a, 2b Shoulder blocks, 2c, 2d Grooves, 3 Sidewall, 3a, 3x Profile surfaces, 3b Side block, 4 Bead, 5 Side rib, 6a, 6b Side surfaces, 10 First side block, 11 Convex portion, 12 Inclined surface, 15 Boundary, 20 Second side block, 21 First region, 22 Second region, 23 Third region, 30 Vertical surface, P Tire maximum width position

Claims

1. A pneumatic tire comprising a tread, a sidewall, and a bead, wherein the sidewall has side blocks, the height of the side blocks based on the profile surface of the sidewall is 1 mm or more and 15 mm or less, the pneumatic tire having a vertical surface at the lower end of the side blocks.

2. The pneumatic tire according to claim 1, wherein the length L1 between the upper end and the lower end of the vertical surface and the length L2 between the grounding end and the tire maximum width position satisfy the relationship of 0.05 ≦ L1 / L2 ≦ 0.

3.

3. The pneumatic tire according to claim 1, wherein the upper end and the lower end of the vertical surface are chamfered.

4. The pneumatic tire according to any one of claims 1 to 3, wherein, in a plan view of the side surface, the area of the side blocks is 20% to 60% of the area of the region between the grounding end and the tire maximum width position.

Images