Pneumatic tires

Abstract

The present invention provides a pneumatic tire capable of reducing Cfmax when a vehicle with a large steering angle turns. The pneumatic tire (1) is provided with a groove (505) extending in a predetermined direction within a predetermined range outside ground contact ends (501, 502) on a tread portion, the ground contact ends (501, 502) being the ends of the tread surface in the tire width direction when the tire (1) is loaded with 70% of the maximum load of the load index at a tire internal pressure of 230 kPa, the predetermined range (T) being the range of the portion outside the ground contact ends in the width direction of the tire (1), and being the range of the distance from the ground contact ends being not less than 8% and not more than 15% of the width from one ground contact end (501) to the other ground contact end (502) in the width direction of the tire (1), and the predetermined direction being the direction forming an angle of not less than 0 degrees and not more than 35 degrees with respect to the circumferential direction of the tire (1).

Description

Technical Field

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

[0002] In the past, it is well known that a tire has a groove formed in the tread portion. For example, Patent Document 1 discloses a tire as follows: a groove is formed in the tread portion along the tire circumferential direction, and a groove is formed that extends at a predetermined angle relative to the tire circumferential direction.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2006-069435 Summary of the invention

[0006] In recent years, there has been a growing demand in the tire market for improved braking performance (μ), and Cfmax (maximum lateral force / friction coefficient) is increased by increasing μ. However, when a vehicle with a large steering angle turns, if Cfmax is too high, the tires will grip the ground too much, causing the vehicle to tilt significantly. Especially in the case of vehicles with a high center of gravity such as small trucks, it is conceivable that the center of gravity of the vehicle is located further outboard than the outer wheels of the vehicle, which will greatly disrupt the balance.

[0007] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a pneumatic tire capable of reducing Cfmax when a vehicle with a large steering angle turns.

[0008] The pneumatic tire of the present invention comprises: a tread portion having a tread surface that contacts a road surface, characterized in that the tread portion is provided with: a groove extending along a prescribed direction within a prescribed range outside a ground contact end, the ground contact end being: the end of the tread surface in the width direction of the tire when the tire internal pressure is set to 230 kPa and a load of 70% of the maximum load of the load index is applied to the tire, the prescribed range is: the range of the portion outside the ground contact end in the width direction of the tire, and the distance from the ground contact end is a range of not less than 8% and not more than 15% of the width from the ground contact end on one side to the ground contact end on the other side in the width direction of the tire, and the prescribed direction is: a direction that forms an angle of not less than 0 degrees and not more than 35 degrees relative to the circumferential direction of the tire.

[0009] According to the present invention, it is possible to provide a pneumatic tire capable of reducing Cfmax when a vehicle having a large steering angle turns. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1It is a cross-sectional view in the tire width direction of the tire according to the first embodiment.

[0011] Figure 2 When the vehicle is moving straight as viewed from the direction of arrow II Figure 1 A forward view of the tire.

[0012] Figure 3 When the vehicle is turning left as viewed from the direction of arrow II Figure 1 A forward view of the tire.

[0013] Figure 4 It is from Figure 1 The tire of the second embodiment is viewed in the same direction as arrow II when the vehicle is traveling straight.

[0014] Figure 5 It is from Figure 1 The tire of the second embodiment is viewed in the same direction as arrow II when the vehicle turns left.

[0015] Description of Reference Numerals

[0016] 1, 1A…tire; 4, 4A…tread; 501, 501A, 502, 502A…ground contact; 505, 505A…groove; T, TA…specified range. DETAILED DESCRIPTION

[0017] Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. Figure 1 It is a cross-sectional view of the tire 1 in the tire width direction. Figure 2 When the vehicle is moving straight as viewed from the direction of arrow II Figure 1 A forward view of the tire. Figure 3 When the vehicle is turning, it is viewed from the direction of arrow II. Figure 1 . In the figure, the symbol S1 represents the tire equatorial plane. The tire equatorial plane S1 is a plane that is orthogonal to the tire rotation axis (tire meridian) and is located at the center of the tire width direction.

[0018] Here, the tire width direction refers to the direction parallel to the tire rotation axis. Figure 1 The left-right direction of the paper in the cross-sectional view. Figure 1 The figure shows the tire width direction W. Moreover, the so-called inner side in the tire width direction refers to the direction approaching the tire equatorial plane S1. The so-called outer side in the tire width direction refers to the direction away from the tire equatorial plane S1. In addition, for the convenience of explanation, Figure 1 The left side is defined as the inner side in the width direction of the vehicle when the tire is mounted on the vehicle. Figure 1 The right side is defined as the outer side in the width direction of the vehicle when the tire is mounted on the vehicle.

[0019] In addition, the tire radial direction refers to the direction perpendicular to the tire rotation axis. Figure 1 The up and down direction on paper. Figure 1 The figure in the middle shows the tire radial direction R. The outer side in the tire radial direction refers to the direction away from the tire rotation axis. Figure 1 The inner side of the tire radial direction refers to the direction close to the tire rotation axis. Figure 1 The middle is the lower side of the paper.

[0020] in addition, Figure 1 The cross-sectional view is a cross-sectional view in the width direction of the tire (including a cross-sectional view of the tire meridian) in an unloaded state when the tire is mounted on a specified rim and filled with a specified internal pressure. In addition, the so-called specified rim refers to a standard rim corresponding to the tire size and specified by JATMA. In addition, in the case of a tire for a passenger car, for example, the specified internal pressure is 180 kPa.

[0021] The tire 1 of this embodiment includes: a pair of bead portions 2, which are provided on both sides in the tire width direction; a sidewall portion 3, which extends radially outward from each bead portion 2; and an annular tread portion 4, which is connected to the radially outer side of each sidewall portion 3, has a tread surface that contacts the road surface, and extends along the circumferential direction of the tire 1. A shoulder portion 50 is formed on the outer side of the tread portion 4 in the tire width direction.

[0022] The tire bead portion 2 is configured to include: a bead core 21 formed into a ring shape by winding a rubber-coated metal bead wire multiple times, and a rubber bead outer rubber 22 in which the bead core 21 is implanted. The bead core 21 is a component for fixing the tire 1 filled with air to a wheel rim (rim flange) not shown. The bead outer rubber 22 is a component for improving the rigidity of the bead portion and ensuring high maneuverability and stability.

[0023] Inside the tire 1, carcass plies (23, 27) serving as the frame of the tire 1 are implanted. Although the carcass plies (23, 27) are formed by overlapping a first carcass ply 23 and a second carcass ply 27 to form a double-layer carcass ply, the carcass ply (23, 27) may be a single layer or may be three or more layers.

[0024] like Figure 1 as well as Figure 2As shown, the tread portion 4 includes: a belt layer 26 implanted on the radially outer side of the carcass cord (23, 27); and a tread rubber 28 implanted with the belt layer 26 and arranged to be closer to the radially outer side of the tire than the belt layer 26, and the outer surface of which serves as the tread surface. The tread rubber 28 includes: a plurality of main grooves 41, 42, 43 extending continuously along the tire circumferential direction and surrounding the tire 1. The main grooves 41, 42, 43 extend continuously along the tire circumferential direction.

[0025] Among the plurality of main grooves 41, 42, 43, a pair of main grooves 41, 42 arranged at the outermost sides in the tire width direction constitute shoulder main grooves 41, 42. In further detail, the shoulder main groove 41 on the inner side of the vehicle constitutes an inner shoulder main groove 41 as an inner main groove, and the shoulder main groove 42 on the outer side of the vehicle constitutes an outer shoulder main groove 42 as an outer main groove. The main groove 43 arranged between the pair of shoulder main grooves 41, 42 constitutes a center main groove 43.

[0026] The tread portion 4 includes an inner shoulder land portion 51 , an outer shoulder land portion 52 , an inner center land portion 53 , and an outer center land portion 54 .

[0027] The inner shoulder land portion 51 is formed by the land portion divided by the shoulder main groove 41 and the contact edge 501. The outer shoulder land portion 52 is formed by the land portion divided by the shoulder main groove 42 and the contact edge 502. Figure 2 As shown, grooves 46 and 47 and sipes 48 and 49 are formed in the inner shoulder land portion 51 and the outer shoulder land portion 52, respectively.

[0028] Here, the ground contact ends 501 and 502 refer to the ends of the tread surface in the width direction of the tire when the tire internal pressure is set to 230 kPa and a load of 70% of the maximum load of the load index is applied to the tire when the tire is running straight. Figure 3 As shown, when the vehicle equipped with the tire 1 turns left and the tire 1 is turned, the ground contact end 502 is closer to the outer side in the tire width direction ( Figure 3 In the figure, a portion of the range shown by T which is further to the right than the ground terminal 502 is also grounded.

[0029] The inner center land portion 53 is formed by the land portion divided by the adjacent main grooves 41 and 43. The outer center land portion 54 is formed by the land portion divided by the adjacent main grooves 42 and 43. Figure 2 As shown, slits 551 , 552 , and 553 are formed in the inner center land portion 53 and the outer center land portion 54 , respectively.

[0030] In addition, if Figure 2As shown in the portion surrounded by the dotted line in FIG. 1 , the tread portion 4 is provided with a groove 505 extending in a predetermined direction within a predetermined range T outside the ground contact ends 501 and 502. Specifically, as shown in FIG. Figure 2 As shown in the above, the so-called prescribed range T is: Figure 2 As shown in FIG. 1 , a vehicle equipped with tire 1 has a range of a portion not in contact with the ground when traveling straight, and Figure 3 As shown, the vehicle equipped with the tire 1 is turned to the left at an angle of about 10 degrees, and the tire 1 is in the range of the portion where the tire 1 contacts the ground.

[0031] More specifically, the predetermined range T refers to the outer side of the ground contact edges 501 and 502 of the tire 1 in the width direction ( Figure 2 The distance between the ground contact ends 501 and 502 in the width direction of the tire 1 is within a range T of 8% or more and 15% or less of the width from the ground contact end 501 on one side to the ground contact end 502 on the other side in the width direction of the tire 1. This is because, when the distance between the ground contact ends 501 and 502 is less than 8%, Cfmax (maximum lateral force / friction coefficient) is reduced to a limit. In addition, this is because, when the distance between the ground contact ends 501 and 502 exceeds 15%, the effect of reducing Cfmax when the vehicle turns cannot be obtained.

[0032] In addition, the prescribed direction refers to a direction in which the angle formed with respect to the circumferential direction of the tire 1 is greater than 0 degrees and less than 35 degrees. That is, although the circumferential direction of the tire 1 includes a circumferential direction on one side (clockwise direction) and a circumferential direction on the other side opposite to the circumferential direction on the one side (counterclockwise direction), any direction in which the angle formed with respect to the circumferential direction on either side is greater than 0 degrees and less than 35 degrees will suffice. This is because: once the angle formed with respect to the circumferential direction exceeds 35 degrees, the pressure from the road surface relative to the edge of the opening of the groove 505 will not increase and it is difficult to reduce the braking performance (μ). A further preferred direction is: a direction in which the angle formed with respect to the circumferential direction on either side is greater than 0 degrees and less than 15 degrees. This is because: as long as it is less than 15 degrees, the braking performance (μ) can be sufficiently reduced.

[0033] like Figure 2 As shown in the figure, the groove 505 extends continuously along the circumferential direction of the tire 1. In this case, the aforementioned predetermined direction is: the angle formed with respect to the circumferential direction of the tire 1 is 0 degrees. The depth of the groove 505 can be 0.5 mm or more, and in this embodiment, it is 1.5 mm. The width of the groove 505 can be 0.5 mm or more, and in this embodiment, it is 4.0 mm. This is because: when the width of the groove 505 is less than 0.5 mm, the contact area with the road surface during cornering cannot be sufficiently reduced.

[0034] Next, a second embodiment of the present invention will be described with reference to the drawings. Figure 4 It is from Figure 1 The tire 1A is viewed in the same direction as arrow II. Figure 5 It is from Figure 1 A forward view of tire 1A when the vehicle is turning, viewed in the same direction as arrow II.

[0035] In the second embodiment, the configuration of the groove 505A is mainly different from the groove 505 of the first embodiment. In addition, the configurations of the other grooves 46A, sipes 48A, 49A, 55A, etc. are also different from the configurations of the grooves 46, 47, sipes 48, 49, etc. of the first embodiment. Since the configurations other than these are the same as those of the first embodiment, the same reference numerals are given to indicate them, and the description thereof is omitted. Specifically, Figure 4 As shown, a plurality of sipes 55A are formed in the inner center land portion 53A and the outer center land portion 54A. The inner shoulder land portion 51A and the outer shoulder land portion 52A are formed with sipes 48A and 49A extending in the width direction of the tire 1A, and grooves 505A extending in a manner that straddles the ends of the sipes 48A and the ends of the sipes 49A on the outer sides in the width direction of the tire 1A. In addition, between the grooves 505A and the grooves 505A adjacent to each other in the circumferential direction of the tire 1A, sipes 48A extending in the width direction of the tire 1A and grooves 46A further extending from the ends of the sipes 48A are formed. The grooves 505A extend in a direction that forms an angle of 35 degrees with respect to the circumferential direction of the tire 1A. The depth of the grooves 505A is 0.5 mm, and the width of the grooves 505A is 2.0 mm.

[0036] Next, the tire 1 of the first embodiment was evaluated as Example 1, the tire 1A of the second embodiment was evaluated as Example 2, and a conventional tire having the same configuration as that of Example 1 except that the grooves 505 extending in the aforementioned prescribed direction were not arranged in the aforementioned prescribed range T outside the contact edges 501 and 502 was prepared as Comparative Example 1. Also, a conventional tire having the same configuration as that of Example 2 was prepared as Comparative Example 2 except that the grooves 505A extending in the aforementioned prescribed direction were not arranged in the aforementioned prescribed range T outside the contact edges 501A and 502A.

[0037] <Rolling resistance evaluation (RRC)>

[0038] A test tire with a tire size of 205 / 60R16 92H was mounted on a standard rim at an air pressure of 230 kPa, and a rolling resistance evaluation test was performed.

[0039] In the rolling resistance test, a uniaxial roller tester for measuring rolling resistance was used to measure the rolling resistance at a load of 400 kg and a speed of 60 km / h. The rolling resistance index of the test tire of Comparative Example 1 was taken as 100 to evaluate the index of the tire of Example 1.

[0040] <Judgment of braking distance>

[0041] The test tire with a tire size of 205 / 60R16 92H was mounted on a standard rim at an air pressure of 230 kPa, and a braking distance evaluation test was conducted. In this evaluation test, the tire was mounted on a test vehicle (a front-wheel drive minivan with a displacement of 2000cc), and the vehicle was driven on a DRY road. The braking force was applied using the ABS (Antilock Brake System) at a speed of 100 km / h, and the braking distance when the vehicle stopped at a speed of 0 km / h was evaluated. The braking distance of the test tire of Comparative Example 1 was taken as an index of 100, and the tire of Example 1 was indexed.

[0042] <Evaluation of Cornering Stiffness (CP)>

[0043] A drum tester with a diameter of 2500 mm was used to measure the cornering force generated by a 205 / 60R16 92H tire 1 with an internal pressure of 230 kPa and a load of 70% of the maximum load of the load index, and the cornering stiffness (cornering power) when the slip angle (slip angle) was 1 degree was solved. Thus, an evaluation test for the cornering stiffness was conducted. The result of Comparative Example 1 was taken as 100, and an index evaluation was performed.

[0044] <Judgment of Maximum Cornering Force (Cfmax)>

[0045] A test tire with a tire size of 205 / 60R16 92H was mounted on a standard rim at an air pressure of 230 kPa, and a load of 70% of the maximum load of the load index was applied to the tire at a running speed of 80 km / h. The maximum value of the cornering force (Cfmax) when the snake angle was gradually increased was measured using a flat belt type cornering tester. The evaluation test was performed on the maximum value of the cornering force. The result of Comparative Example 1 was taken as 100, and the index evaluation was performed.

[0046]

Table 1

[0047] RRC Braking distance CP C fmax Comparative Example 1 100 100 100 100 Example 1 100 100 100 97

[0048]

Table 2

[0049] RRC Braking distance CP C fmax Comparative Example 2 100 100 100 100 Example 2 100 100 100 98

[0050] As shown in Table 1, it can be seen that in Example 1, Cfmax can be a lower value than that of Comparative Example 1 which is a conventional structure, but the same performance as that of Comparative Example 1 can be obtained in any of RCC, braking distance, and CP.

[0051] In addition, as shown in Table 2, it can be seen that: in Example 2, although it is not as good as Example 1, regarding Cfmax, it can be: a lower value than that of Comparative Example 1, which is a conventional structure. Moreover, similarly to Example 1, in any of RCC, braking distance, and CP, it is not inferior to Comparative Example 2 and the same performance as Comparative Example 2 is obtained.

[0052] That is, in Example 1, as described above, the groove 505 extends in a direction that forms an angle of 0 degrees with respect to the circumferential direction of the tire 1, the depth of the groove 505 is 1.5 mm, and the width of the groove 505 is 4.0 mm. In Example 2, as described above, the groove 505A extends in a direction that forms an angle of 35 degrees with respect to the circumferential direction of the tire 1A, the depth of the groove 505A is 0.5 mm, and the width of the groove 505A is 2.0 mm.

[0053] Therefore, it can be seen that good results can be obtained in both the present embodiment 1 and the present embodiment 2 in which the groove depth is greater than 0.5 mm. In addition, it can be seen that good results can be obtained in both the present embodiment 1 and the present embodiment 2 in which the groove width is greater than 1.0 mm and less than 4.0 mm.

[0054] According to the tire 1 of the present embodiment, the following effects can be produced.

[0055] The tread portion of the tire 1 (1A) involved in the present embodiment is configured with: a groove 505 (505A) extending in a predetermined direction within a predetermined range T (TA) outside the ground contact ends 501, 502 (501A, 502A), the ground contact ends 501, 502 (501A, 502A) being: the end of the tread surface of the tire 1 (1A) in the width direction when the internal pressure of the tire 1 (1A) is set to 230 kPa and a load of 70% of the maximum load of the load index is applied to the tire 1 (1A), and the predetermined range T (TA) is: the width of the tire 1 (1A) The range of the outer portion of the ground contact ends 501, 502 (501A, 502A) in the direction, and the distance from the ground contact ends 501, 502 (501A, 502A) is a range of 8% to 15% of the width from the ground contact ends 501, 502 (501A, 502A) on one side to the ground contact ends 501, 502 (501A, 502A) on the other side in the width direction of the tire 1 (1A), that is, the ground contact width of the tire. The specified direction is: the angle formed with respect to the circumferential direction of the tire 1 (1A) is greater than 0 degrees and less than 35 degrees.

[0056] According to this, the contact area between the vehicle and the road surface when turning can be reduced, and the average ground contact pressure of the tread surface can be increased. As a result, the friction coefficient can be reduced. Although Cfmax can be calculated by "lateral friction coefficient × vertical load", as described above, since the friction coefficient can be reduced, Cfmax can be reduced when the vehicle turns at a large steering angle. In addition, since the groove 505 (505A) is arranged in the non-ground contact part at normal times, it is possible to avoid the situation where the mobility / braking performance at normal times is impaired.

[0057] In the tire 1 (1A) according to the present embodiment, the predetermined direction is a direction whose angle with respect to the circumferential direction of the tire 1 (1A) is greater than or equal to 0 degrees and less than or equal to 15 degrees. This can sufficiently reduce the braking performance (μ). This can sufficiently reduce Cfmax.

[0058] In the tire 1 (1A) according to the present embodiment, the groove 505 (505A) is arranged around the circumference of the tire 1 (1A). Therefore, the groove 505 (505A) exists at any position in the circumferential direction of the tire 1 (1A), thereby reducing Cfmax.

[0059] In the tire 1 (1A) according to the present embodiment, the depth of the groove 505 (505A) is 0.5 mm or more. This can sufficiently increase the non-ground contact area when the vehicle turns. As a result, Cfmax can be sufficiently reduced.

[0060] In the tire 1 (1A) according to the present embodiment, the width of the groove 505 (505A) is 1.0 mm or more and 4.0 mm or less. This can sufficiently increase the non-ground contact area when the vehicle turns. As a result, Cfmax can be sufficiently reduced.

[0061] In addition, the present invention is not limited to the above-mentioned embodiment, and any modification or improvement that can achieve the purpose of the present invention is included in the scope of the present invention. For example, in the first embodiment, the groove 505 extends continuously along the circumference of the tire 1, but it is not limited to this configuration. As long as the groove is formed along the circumference of the tire, for example, the groove may be discontinuously formed along the circumference of the tire, or may be formed in a zigzag shape along the circumference of the tire.

Claims

1. A pneumatic tire comprising: a tread portion having a tread surface that contacts a road surface, characterized in that: The tread portion is provided with a groove extending in a predetermined direction within a predetermined range outside the ground contact edge. The predetermined range is a range of 8% or more and 15% or less of the tire's contact patch width. The predetermined direction is a direction whose angle with respect to the circumferential direction of the tire is greater than 0 degrees and less than 15 degrees. The groove goes around the circumference of the tire. The groove is continuous in the circumferential direction of the tire.

2. The pneumatic tire according to claim 1, characterized in that The depth of the groove is 0.5 mm or more.

3. The pneumatic tire according to claim 1, wherein: The width of the groove is not less than 1.0 mm and not more than 4.0 mm.

4. The pneumatic tire according to claim 2, characterized in that: The width of the groove is not less than 1.0 mm and not more than 4.0 mm.

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