JP2007320523A - Pneumatic radial tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic radial tire, improved in steering stability at a cornering travel time and high speed durability, to be mounted on a vehicle imparted with a negative camber angle. <P>SOLUTION: This pneumatic radial tire 1 has at least two belt layers 4 having belt cords S intersecting with each other between the layers 4. Rigidity of the belt layers 4 are made different from each other on right and left sides of the tire width direction. When the tire 1 is mounted on the vehicle set with the negative camber, the higher rigidity sides of the belt layers 4 are located at the outside of the vehicle. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pneumatic radial tire. More specifically, the present invention relates to a pneumatic radial tire mounted on a vehicle provided with a negative camber, which improves steering stability during cornering and at the same time improves high-speed durability. About.

  In order to ensure the handling stability of a high-speed vehicle, it is required that the limit running performance is high when cornering as a pneumatic tire. In the case of a pneumatic radial tire, in order to improve the limit running performance, it is common to increase the rigidity of the belt layer of the tread portion (for example, Patent Document 1).

On the other hand, in high-speed vehicles, the wheels are attached as negative cambers to ensure running stability during high-speed running. However, when a pneumatic radial tire with a high belt layer rigidity is attached to a vehicle with such a negative camber, stress concentrates on the end of the belt layer located inside the vehicle, inducing belt separation. There was a problem that the high-speed durability deteriorated.
JP-A-6-336102

  An object of the present invention is to solve such a conventional problem, and is mounted on a vehicle provided with a negative camber, which is improved in steering stability during cornering traveling and at the same time improved in high-speed durability. The object is to provide a pneumatic radial tire.

  In order to achieve the above object, a pneumatic radial tire according to the present invention is a pneumatic radial tire having at least two belt layers in which belt cords intersect each other between layers, and the rigidity of the belt layer is determined at the left and right ends in the tire width direction. The gist of the invention is that the belt layer is mounted so that the side on which the rigidity of the belt layer is high is located on the outside of the vehicle.

  Further, at least one belt layer among the above-described belt layers may be configured as described in any one of (1) to (4) below.

(1) The number of belt cords driven at one end A of the belt layer is made smaller than the number of belt cords driven at the center C of the belt width and the other end B. In this case, the width of one end A and the other end B of the belt layer may be 2 to 25% of the width W of the belt layer. Further, the number of belt cords driven at one end A of the belt layer may be 0.50 to 0.85 times the number of belt cords driven at the belt width central portion C.

(2) The number of belt cords driven at one end D of the belt layer is made smaller than the number of belt cords driven at the belt width central portion F and the other end E, and the belt layer is centered on the tire equator line. The width W2 from the tire equator line to the end of the end E side where the number of belt cords is driven is offset from the end E side where the number of belt cords is driven, and the end D side where the number of belt cords is driven from the tire equator line The ratio W2 / W1 with the width W1 to the terminal is set to 1.0 to 1.2. In this case, the width of one end D and the other end E of the belt layer may be 2 to 25% of the width W of the belt layer. Furthermore, the number of belt cords driven at one end D of the belt layer may be 0.50 to 0.85 times the number of belt cords driven at the belt width central portion F.

(3) The cord angle on the acute angle side with respect to the tire circumferential direction of the belt cord in the belt layer is larger than the belt width central portion I at one end portion G of the belt layer, and the belt width central portion at the other end portion H. Same or smaller than I. In this case, the width of one end G and the other end H of the belt layer may be 10 to 45% of the width W of the belt layer. Further, the cord angle α at the belt width central portion I is 15 to 24 °, the cord angle γ at the one end G is 20 to 28 °, and the cord angle β at the other end H is 13 to 22 °. Good.

(4) The belt cord twist pitch in the belt layer is smaller than the belt width central portion L at one end J of the belt layer and larger than the belt width central portion L at the other end K. In this case, the width of one end J and the other end K of the belt layer may be 10 to 40% of the width W of the belt layer. Furthermore, the twist pitch length at the one end J may be 10 to 80% of the twist pitch length at the other end K. Furthermore, the twist pitch of the belt cord may be gradually changed from one end of the belt layer to the other end.

  According to the present invention, when the rigidity of the belt layer is made different at both the left and right ends in the tire width direction and the belt layer is mounted on a vehicle having a negative camber, the end side where the belt layer is highly rigid is mounted on the outside of the vehicle. Since the rigidity of the belt layer in the tread part is low inside the vehicle where the vehicle load is the largest, the stress on the belt layer is efficiently distributed and the high-speed durability is improved. Can do. In addition, since the rigidity of the belt layer is high outside the vehicle, a high level of cornering limit performance can be obtained, and steering stability during cornering traveling can be improved.

Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a cross-sectional view showing an example of a pneumatic radial tire according to an embodiment of the present invention. In FIG. 1, a pneumatic radial tire 1 has belt layers 4 and 4 of at least two layers (two layers in the figure) in which belt cords cross each other on the outer periphery of a carcass layer 3 in a tread portion 2. The belt cord is made of steel cord or aramid cord, and the inclination angle of the cord on the acute angle side with respect to the tire circumferential direction is set to 15 to 30 °.

  The rigidity of the belt layers 4 and 4 at the left and right ends in the tire width direction is different from each other, and the belt layers 4 and 4 are mounted so that the end portions on which the rigidity of the belt layers 4 and 4 is high are located outside the vehicle on which the negative camber is set.

  Thereby, since the rigidity of the belt layers 4 and 4 in the tread portion 2 is low inside the vehicle where the load of the vehicle is the largest, the stress on the belt layers 4 and 4 is efficiently dispersed, and high speed durability is achieved. Can be improved. In addition, since the rigidity of the belt layers 4 and 4 is high on the outside of the vehicle, a high level of cornering limit performance can be obtained, and the steering stability during cornering traveling can be improved.

  In the present invention, at least one of the belt layers 4 and 4 is configured such that the rigidity at the left and right ends is different from each other. FIG. 2 is a plan view showing an embodiment of the belt layer 4 in which the left and right stiffnesses are different. In this embodiment, the number of driven belt cords S at one end A of the belt layer 4 is represented by the center C of the belt width. And the number of driven belt cords S at the other end B is smaller.

  Thereby, the left and right rigidity of the belt layer 4 sandwiching the tire equator line CL is low on the end A side and high on the end B side. The embodiment shown in FIG. 2 shows a case where the number of cords driven at the end A is half the number of cords driven at the center C, and the number of cords driven at the end B is equal to the number of cords driven at the center C. However, the number of cords driven in the end portion B can be made smaller than the number of cords driven in the central portion C. In addition, the ends of the belt cords S can be uneven in the width direction of the belt layer 4 at both ends A and B, respectively.

  In the present embodiment, the widths of both end portions A and B may be set to 2 to 25%, preferably 15 to 20% of the width W of the belt layer 4, respectively. Thereby, the right and left rigidity in the belt layers 4 and 4 can be efficiently varied without impairing various performances of the tire.

  In the embodiment described above, the number of cords to be driven at the end A on the side where the number of cords to be corded is small may be set to 0.50 to 0.85 times the number of cords to be corded at the center C. As a result, the left and right rigidity of the belt layers 4 and 4 can be made to differ more efficiently.

  In order to manufacture the belt layer 4 in which the number of cords driven at both ends A and B is smaller than the number of cords driven at the central portion C, as shown in FIG. When the sides of the belt-like body T are connected to each other, it is preferable that the strips T, T adjacent to each other be bonded together so as to be offset in the tire width direction.

  FIG. 4 is a plan view showing another embodiment of the belt layer 4 with different left and right rigidity. In this embodiment, the number of cords driven at both ends D and E of the belt layer 4 is different from each other. The number of cords to be driven is made smaller than the number of cords to be driven in the central portion F, and the center line G of the belt layer 4 is offset from the tire equator line CL to the end E side where the number of cords to be driven is large. The ratio W2 / W1 of the width W2 from the end E side end 4b on the side where the number of driving is large to the width W1 from the tire equator line CL to the end 4a end 4a on the side where the number of driving cords is small is 1 It is adjusted to be 0 to 1.2.

  Thereby, the left and right rigidity of the belt layer 4 sandwiching the tire equator line CL is kept low on the terminal 4a side of the belt layer 4 and high on the terminal 4b side of the belt layer 4. Thus, by making the number of cords driven at both ends D and E smaller than the number of cords driven at the central portion F of the belt layer 4, separation at both terminals 4a and 4b of the belt layer 4 can be efficiently suppressed.

  Also in the case of this embodiment, similarly to the embodiment of FIG. 2, the widths of both end portions D and E may be set to 2 to 25%, preferably 15 to 20% of the width W of the belt layer 4, respectively. Furthermore, the number of cords to be driven at the end D may be set to 0.50 to 0.85 times the number of cords to be driven at the central portion F.

  5 (a) and 5 (b) are plan views showing another embodiment of the belt layer 4 with different left and right rigidity, and in the embodiment of FIG. 5 (a), a belt cord constituting the belt layer 4 is shown. The cord angle on the acute angle side with respect to the tire circumferential direction of S is larger than the belt width central portion I at one end G of the belt layer 4 and is equal to or smaller than the belt width central portion I at the other end H. . Accordingly, the left and right rigidity of the belt layers 4 and 4 sandwiching the tire equator line CL is kept low on the end portion G side of the belt layer 4 and high on the end portion H side of the belt layer 4.

  In the present embodiment, the widths of both ends G and H may be set to 10 to 45% of the width W of the belt layer 4, respectively. Further, the cord angle described above is set to α = 15 to 24 °, preferably 20 to 22 ° at the belt width central portion I, and γ = 20 to 28 °, preferably 23 to 25 ° at the end G, and the end H Β = 13 to 22 °, preferably 18 to 20 °. Thereby, the right and left rigidity of the belt layers 4 and 4 can be varied in a well-balanced manner without affecting other performances of the tire.

  In the embodiment of FIG. 5B, the cord angle γ at the end G is gradually increased toward the terminal 4a, and the code angle β at the end H is gradually decreased toward the terminal 4b. The cord angle α in the central portion I is kept constant as shown in the figure, or gradually increases on the end G side and gradually decreases on the end H side with the tire equator line CL as the center. It is good to do so.

  In the embodiment shown in FIGS. 5A and 5B described above, the cord angle of the belt cord S is gradually changed at the boundary between the both end portions G and H and the central portion I without suddenly changing the cord angle. It is good to adjust as follows. Thereby, durability of the belt layer 4 is ensured.

  FIG. 6 is a plan view showing another embodiment of the belt layer 4 with different left and right rigidity. In this embodiment, the twist pitch of the belt cord S in the belt layer 4 is set to one end of the belt layer 4. It is smaller than the central portion L in the belt width direction at J, and larger than the central portion L in the belt width direction at the other end K. Thereby, the left and right rigidity of the belt layers 4 and 4 sandwiching the tire equator line CL is kept low on the end portion J side and high on the end portion K side.

  In the present embodiment, the widths of both ends J and K may be set to 10 to 40%, preferably 20 to 35% of the width W of the belt layer 4, respectively. Furthermore, the twist pitch length of the belt cord S at the end portion J may be set to 10 to 80% of the twist pitch length of the belt cord S at the end portion K. Thereby, the right and left rigidity of the belt layers 4 and 4 can be varied in a well-balanced manner without affecting other performances of the tire.

  In the embodiment of FIG. 6, the twist pitch length of the belt cord S at the end K can be made equal to the twist pitch length of the belt cord S at the central portion L. Furthermore, the twist pitch of the belt cord S may be gradually changed from one terminal 4a or 4b of the belt layer 4 toward the other terminal 4b or 4a.

  As described above, in the pneumatic radial tire of the present invention, the rigidity of the belt layer is different at the left and right ends in the tire width direction, and when this is mounted on a vehicle in which a negative camber is set, the rigidity of the belt layer is high. By attaching the end side to the outside of the vehicle, the steering stability during cornering running is improved and at the same time the high-speed durability is improved. Especially, the FF vehicle for competitions that repeatedly performs cornering running It is preferably applied to.

  A conventional tire in which the tire size is 235 / 45R17 94W, the tire structure is the same as in FIG. 1, and the number of steel cords driven in the two belt layers 4 and 4 is equal throughout the entire tire width direction, and the outer belt layer 4 The tires of the present invention in which only the number of steel cords to be struck was made different at the left and right ends as shown in FIG. In each tire, the width W of the outer belt layer 4 is 210 mm, the width of the end A in the tire of the present invention is 40 mm, the number of steel cords driven is 0.75 times the end A, the end B and the center C In the same way.

  These two types of tires were filled with an air pressure of 200 kPa, and steering stability, turning limit, turning braking stability, and high-speed durability were evaluated by the following test methods. The results are shown in Table 1. The steering stability, turning limit, and turning braking stability were evaluated by attaching each tire to a vehicle (3000 cc, FR vehicle, negative camber angle 2 °) according to the following procedure. For the evaluation of high-speed durability, an indoor test was conducted, and the results of the indoor test were displayed as a conventional example (conventional tire) and an example (invention tire), respectively, in the same manner as the test result using the actual vehicle described above.

[Vehicle installation instructions]
Conventional example: Conventional tires were mounted on the front and rear wheels of the vehicle as they were.
Example: The tire of the present invention was mounted on the front and rear wheels of a vehicle such that the side with high belt rigidity (the end B side in FIG. 2) was on the outside of the vehicle.
Comparative Example 1: Conventional tires were mounted on the front wheels of the vehicle, and tires of the present invention were mounted on the rear wheels such that the side with high belt rigidity was on the outside of the vehicle.
Comparative Example 2: The tire of the present invention was mounted on the front wheel so that the side with high belt rigidity was on the outside of the vehicle, and the conventional tire was mounted on the rear wheel of the vehicle.

[Maneuvering stability]
A test course consisting of an asphalt road surface was run straight and lane-changed at 60 to 120 km / h, and was evaluated by sensory performance by a test driver. The results are shown in Table 1 using an index with the conventional example being 100. The larger the value, the better. When these values have a difference of 5 or more, a difference in steering stability is recognized.

[Turning limit]
Evaluation was made by measuring the limit speed that can be traced on a circular turning test course (R = 60 m) comprising an asphalt road surface. The results are shown in Table 1 using an index with the conventional example being 100. The larger the value, the better. In addition, when these values have a difference of 5 or more, a difference is recognized in the turning limit.

(Swivel braking stability)
In a circular turning test course (R = 250 m) composed of an asphalt road surface, an initial speed was set to 150 km / h, a maximum braking speed until the turning radius was increased or decreased was generated, and the maximum braking speed was measured. The results are shown in Table 1 using an index with the conventional example being 100. The larger the value, the better. In addition, when these numerical values have a difference of 5 or more, a difference is recognized in turning braking stability.

[High-speed durability]
The load corresponding to 88% of the maximum load specified by JATMA is applied, and the drum rotation speed is accelerated by 10 km / h every 10 minutes by the indoor endurance test (drum diameter: 1707 mm, camber angle 3 °). The travel distance until separation occurred in the part was measured. The results are shown in Table 1 using an index with the conventional example (conventional tire) as 100. The larger the value, the better. In addition, when these numerical values have a difference of 5 or more, a difference is recognized in high-speed durability.

  From Table 1, in the example in which the tire of the present invention is properly mounted, compared to the conventional example in which the conventional tire is mounted as it is and the comparative examples 1 and 2 in which the tire of the present invention and the conventional tire are divided into front and rear wheels, It can be seen that the steering stability, turning limit and turning braking stability are well balanced. Furthermore, it can be seen that the tires of the present invention (Examples) have drastically improved high-speed durability compared to conventional tires (Conventional Examples).

It is sectional drawing which shows an example of the pneumatic radial tire by embodiment of this invention. FIG. 2 is a plan view showing an embodiment of a belt layer in which the rigidity of both left and right ends of the pneumatic radial tire of FIG. 1 is different. It is explanatory drawing which shows the manufacturing process of the belt layer of FIG. FIG. 9 is a plan view corresponding to FIG. 2 showing another embodiment of a belt layer in which the rigidity of the left and right ends is different. (A) And (b) is a top view equivalent to FIG. 2 which shows other embodiment of the belt layer which varied the rigidity of both right-and-left both ends, respectively. FIG. 9 is a plan view corresponding to FIG. 2 showing another embodiment of a belt layer in which the rigidity of the left and right ends is different.

Explanation of symbols

l Pneumatic radial tire 2 Tread part 3 Carcass layer 4 Belt layer S Belt cord G Belt center line CL Tire equator line

Claims (13)

In a pneumatic radial tire having at least two belt layers in which belt cords cross each other between layers,
Air for mounting the belt layer so that the rigidity of the belt layer is different between the left and right ends in the tire width direction, and the side where the rigidity of the belt layer is higher is positioned outside the vehicle with respect to a vehicle having a negative camber angle. Entering radial tire.   In at least one belt layer of the belt layers, the number of belt cords driven at one end of the belt layer is less than the number of belt cords driven at the belt width central portion and the other end. The described pneumatic radial tire.   The pneumatic radial tire according to claim 2, wherein the width of one end and the other end of the belt layer is 2 to 25% of the width of the belt layer.   The pneumatic radial tire according to claim 2 or 3, wherein the number of belt cords driven at one end of the belt layer is 0.50 to 0.85 times the number of belt cords driven at a belt width center portion.   The belt layer is offset from the tire equator line toward the end side where the number of belt cords driven is large, and the width W2 from the tire equator line to the terminal on the end side where the number of belt cords is driven and belt cords from the tire equator line The pneumatic radial tire according to claim 2, 3 or 4, wherein a ratio W2 / W1 to a width W1 to a terminal on an end side where the number of driving is small is 1.0 to 1.2.   The belt layer is formed such that a plurality of belt cords arranged in parallel are connected to each other on the sides of the belt-like body, and the end portions of the belt-like members adjacent to each other are offset in the tire width direction. The pneumatic radial tire according to 2, 3, 4 or 5.   In at least one of the belt layers, the cord angle on the acute angle side with respect to the tire circumferential direction of the belt cord in the belt layer is larger at one end of the belt layer than the central portion of the belt width, The pneumatic radial tire according to claim 1, wherein the end portion is equal to or smaller than the belt width central portion.   The pneumatic radial tire according to claim 7, wherein the width of one end and the other end of the belt layer is 10 to 45% of the width of the belt layer.   The cord angle α at the central portion of the belt width is 15 to 24 °, the cord angle γ at the one end is 20 to 28 °, and the cord angle β at the other end is 13 to 22 °. 8. A pneumatic radial tire according to 8.   In at least one belt layer of the belt layers, the belt cord twist pitch in the belt layer is smaller than the belt width center at one end of the belt layer, and the belt width center at the other end. The pneumatic radial tire according to claim 1, wherein the pneumatic radial tire is larger than a portion.   The pneumatic radial tire according to claim 10, wherein the width of one end and the other end of the belt layer is 10 to 40% of the width of the belt layer.   The pneumatic radial tire according to claim 10 or 11, wherein a twist pitch length at the one end portion is 10 to 80% of a twist pitch length at the other end portion.   The pneumatic radial tire according to claim 10, 11 or 12, wherein a twist pitch of the belt cord gradually changes from one end of the belt layer toward the other end.

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