JP3517366B2 - Automotive pneumatic tires with ABS - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automobile having an anti-lock brake system (hereinafter referred to as ABS).
The present invention relates to a pneumatic tire for an ABS vehicle capable of exhibiting excellent braking performance in (in this specification, sometimes referred to as an ABS vehicle) . [0002] In recent years, various automobiles (ABS vehicles) provided with ABS as braking means have been proposed. This AB
In S, the slip ratio generated in the tire during braking is maintained in the range of about 5 to 15% by the brake control, and the controllability of the vehicle by operating the steering wheel is maintained by maintaining the rotation of the tire during braking. In general, the friction coefficient μ between a tire and a road surface is
For example, as shown in FIG. 5, the relationship between the slip ratio S and the slip ratio S can be specified by a μ-S curve in which the vertical axis represents the friction coefficient μ and the horizontal axis represents the slip ratio S. As shown in FIG. 5, this μ-S curve indicates that the slip ratio S is 5% or less in a normal asphalt drying path.
Increases, the friction coefficient μ increases substantially linearly. Then, the slip ratio S reaches a maximum value near 10%, and in a region where the slip ratio S is even higher, the slip ratio S
Shows a characteristic in which the friction coefficient μ gradually decreases as the value increases. [0004] Therefore, in ABS braking, the tire is controlled in the range of the slip ratio S at which the friction coefficient μ becomes high within the range of 5 to 15%. [0005] However, ABS
In braking, the difference between the braking distance on a dry road surface and the braking distance on a wet road surface tends to be large due to the influence of a water film on the road surface.Therefore, it is strongly required to reduce the braking distance particularly on a wet road surface. It has been demanded. In view of such a situation, the inventor pays attention to the lateral edge component length L of the tread groove included in the ground contact surface of the tire and the circumferential rigidity of the tread pattern. The relationship between the coefficient of friction and the friction coefficient μ was studied. Among them, based on the block pattern as shown in FIG. 6 (A), for example, tires having various patterns in which, for example, the edge component length L in the lateral direction and the rigidity in the circumferential direction were respectively changed by changing the block size were manufactured. [0007] Then, the μ-S curve of each trial tire on a wet road (water film thickness of about 1-2 mm) was measured, and the average friction coefficient μ0 in the range of the slip ratio S of 5 to 15% was measured.
Were compared. FIG. 7 shows the lateral edge component length L and the circumferential stiffness by using an index with the friction coefficient μ0 of the tire of a rib pattern (shown in FIG. 6B) having no lateral edge component length L as 100. And the coefficient of friction μ
The relationship with 0 is shown. As a result, the friction coefficient μ0 on a wet road when the slip ratio S is in the range of 5 to 15% increases as the length L of the edge component in the lateral direction and the rigidity in the circumferential direction increase. In order to secure a friction coefficient μ0 of an index 105 or more at which the effect of shortening the tire is remarkable, the tire circumferential rigidity Cx, which is the circumferential rigidity per tread unit area (1 cm ² ), is 10.0 N / mm or more, and It has been found that the lateral edge component length L of the tread groove per unit length (10 cm) in the circumferential direction needs to be 600 mm or more. It has also been confirmed that this regulation is effective in various tread patterns other than the block type. That is, in the present invention, the slip ratio S is 5 to 1
It is an object of the present invention to provide a pneumatic tire that can significantly increase the friction coefficient μ0 on a wet road in the range of 5%, and can exhibit excellent braking performance on a wet road, particularly in an automobile equipped with an ABS braking mechanism. The purpose is. [0010] In order to achieve the above object, an invention according to claim 1 is a pneumatic tie for an ABS vehicle.
A tread unit area (1 cm) of a tread pattern formed by providing a tread groove including a vertical groove in a tire circumferential direction and a horizontal groove in a direction intersecting with the tire in a tread surface.
² ) The tire circumferential rigidity Cx, which is the circumferential rigidity per unit, is 10.0 N / mm or more and the circumferential unit length (10c
lateral edge components of the tread groove of m) per a length L and 600mm or more and 1500mm less Tei
You . An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, a pneumatic tire for an ABS vehicle (hereinafter sometimes simply referred to as a pneumatic tire).
1 ) The tread surface 2 is provided with a tread groove 3 including a vertical groove 3a extending in the tire circumferential direction and a horizontal groove 3b extending in a direction intersecting with the tread surface 2, thereby forming a tread pattern 4 including a land portion 2A and a sea portion 2B. Is done. The tread groove 3 includes a vertical groove 3a and a lateral groove 3b having a substantially groove width for drainage, a siping 3c having substantially no groove width such as closing an opening when grounding, and a notch. Slot (not shown) and the like. The vertical groove 3a and the horizontal groove 3b can be formed in various shapes such as zigzag, arc-shaped, and the like, in addition to the linear shape as illustrated, and the tread pattern 4 is also a block pattern as illustrated. In addition, various pattern shapes such as a rib / block pattern and a rib / rug pattern can be adopted. The tread surface 2 refers to a surface area of the tread surface that comes into contact with a road surface. More specifically, the tire is mounted on a regular rim, filled with a regular internal pressure, and loaded with a regular load. On the grounding surface 5 (shown in FIG. 2) when grounded on a flat surface, it is defined as a region sandwiched between circumferential lines 5e, 5e passing through the grounding end in the tire axial direction. The pneumatic tire 1 of the present invention has a circumferential rigidity per tread unit area (1 cm ² ) of the tread pattern 4, that is, a tire circumferential rigidity Cx of 10.
0 N / mm or more, and the tire circumferential unit length (10
cm) per inch in the lateral direction edge component length L of the tread groove 3 is set to 600 mm or more. Here, the tire circumferential rigidity Cx is the land rigidity that is the circumferential rigidity of each land 2A for all the land 2A between the circumferential lines 5e and 5e in the tread surface 2. The sum ΣCi of circumferential stiffness Ci (N / mm) is obtained,
The total sum ΣCi can be obtained by dividing the total area S0 (unit: 1 cm ² ) of the tread surface 2 including the land 2A and the sea 2B. That is, “Cx = ΣCi / S
0 ". The land portion circumferential rigidity Ci (N) of each land portion 2A
/ Mm) is defined by the following equation (1) (when the land 2A has the siping 3c, the equation is modified from the equation (2)). [Equation 1] (Equation 2) Where F: tangential force at the time of touchdown y: displacement of land portion h: height of land portion E: Young's modulus of tread rubber G: shear rigidity of tread rubber (= E / 3) I: cross section of land portion Moment A: Cross-sectional area of land portion W: Width of land portion LO: Component length of siping in the tire axial direction hs: Depth of siping n: Number of sipings The above equation (1) indicates that the land portion 2A, for example, FIG.
In the block 6 shown in (A), the model can be simulated as a cantilever supported on the inner end side in the tire radial direction. The land circumferential rigidity Ci is specified not by actual measurement but by approximate calculation. However, as shown in FIG.
When the sipe 3c is formed on A, the circumferential rigidity of the land portion 2A is reduced. Therefore, the land portion 2A on which the sipe 3c is formed is obtained from empirical rules such as experiments in consideration of the influence of the sipe 3c. The corrected equation (2) is used. In addition, since the actual land portion 2A includes various things such as those having a complicated shape, when calculating the rigidity in the circumferential direction of each land portion 2A, it is calculated using a quadrature method or coordinate transformation. You can also. When the land portion 2A is a rib 7 continuous in the tire circumferential direction as shown in FIG. 6 (B), experience has shown that the rib 7 may be connected to the periphery of the grounding surface 5 which is currently grounded. The rigidity in the circumferential direction is determined by setting the height h of the land portion 2A to half of the groove depth with the block having the discontinuous length. In this embodiment, to determine the circumferential rigidity, the land portion 2A between the circumferential lines 5e and 5e shown in FIG. Therefore, the outermost block 6a
(Shoulder block), the width of the block is W3
Instead, the circumferential rigidity is calculated as W2. The land portion circumferential rigidity Ci of each land portion 2A
(N / mm) to the total area S of the tread surface 2
The tire circumferential rigidity Cx, which is a value divided by 0 (1 cm ² ), is set to 10.0 (N / mm) or more. Further, a lateral edge component length L per circumferential unit length (10 cm) of the tread groove 3 of the pneumatic tire 1 is set to 600 mm or more. The length L of the lateral edge component is obtained by calculating the sum ΣLi of the lengths Li of the edge components in the tire axis direction (lateral direction) of each edge formed by the tread groove 3 and calculating the sum ΣLi by the circumferential unit length (10 cm). In addition, the edge component is the circumferential line 5
e, all the elements forming an edge by the edges thereof, such as the tread grooves 3 arranged between the e and 5e, that is, the vertical grooves 3a, the horizontal grooves 3b, the sipes 3c, and the slots. For example, as shown in FIG. 4, when the tread groove 3 is composed of two zigzag grooves 3A having a zigzag pitch number n having a groove width (the number of repetitions n per tire circumference), each groove 3
The edges 3e and 3e of both groove edges are the length L of the edge component.
i is the target of calculation. In this example, assuming that the amplitude of the zigzag groove 3A is 5 mm, the length Li of the edge component per one zigzag groove 3A is 5 × n × 2 (mm), and the sum ΣLi is twice that of 20 × n ( mm). Note that only one siping 3c having substantially no groove width is calculated as an edge component. Such an edge component has an effect of enhancing a braking effect on a wet road by an edge effect such as removal of a water film on a road surface. In particular, the lateral edge component length L per unit length in the circumferential direction (10 cm) is at least 600 mm, and the tire circumferential rigidity Cx per unit tread unit area (1 cm ² ) is 10.0 (N / mm) or more, the slip ratio S is 5 to 15% as shown in FIG.
, The friction coefficient μ0 on a wet road can be effectively increased to an index 105 or more at which the effect of shortening the braking distance is remarkable, and the braking performance in ABS braking can be greatly improved. . It should be noted that at least one of the lateral edge component length L and the tire circumferential rigidity Cx is:
When the value falls below the lower limit, it becomes difficult to improve the braking performance. Preferably, the lateral edge component length L is 900 mm or more and the circumferential rigidity Cx is 11
(N / mm) or more. The upper limit of the tire circumferential stiffness Cx is not particularly limited, but is preferably 15 (N / mm) or less from the viewpoint of noise and ride comfort. Although the upper limit of the lateral edge component length L is not particularly limited, the increase in the lateral edge component length L is as follows.
Since the tire circumferential rigidity Cx of the tread pattern 4 is reduced, the tire circumferential rigidity Cx is set to 10.0 (N / mm).
It is necessary to set within the range that can secure the above, and the upper limit is 1500 (mm) or less from the viewpoint of uneven wear. The upper limit of the tire circumferential rigidity Cx is not particularly limited, but is preferably 15 (N / mm) or less from the viewpoint of noise and riding comfort. Although the upper limit of the lateral edge component length L is not particularly limited, the increase in the lateral edge component length L is as follows.
Since the tire circumferential rigidity Cx of the tread pattern 4 is reduced, the tire circumferential rigidity Cx is set to 10.0 (N / mm).
It is necessary to set within the range that can secure the above, and usually the upper limit is preferably 1500 (mm) or less from the viewpoint of uneven wear. In order to increase the tire rigidity Cx in the circumferential direction, it is preferable that the tread rubber forming the tread surface 2 is formed of a hard rubber having a JISA rubber hardness of 59 to 66 degrees, in addition to the pattern shape. The internal structure of the pneumatic tire 1 is as follows:
Although not particularly limited, a radial structure in which a carcass having a radial structure is loosely tightened by a tough belt layer is preferable. The pneumatic tire for an ABS vehicle according to the present invention.
Is configured as described above, so that the slip ratio S is 5 to
The coefficient of friction μ0 on a wet road in the range of 15% can be greatly increased, and an ABS vehicle can exhibit excellent braking performance on a wet road.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a tread pattern of a tire according to one embodiment of the present invention. FIG. 2 is a diagram illustrating a tread surface. FIGS. 3A and 3B are diagrams illustrating a method for calculating a circumferential rigidity of a pattern. FIG. 4 is a diagram illustrating a method of calculating a lateral edge component length in a tread groove. FIG. 5 shows μ-S of a tire on a dry road of asphalt.
It is a diagram showing a curve. 6A and 6B are diagrams showing basic tread patterns in test tires. FIG. 7 is a diagram showing a relationship between a lateral edge component length and a circumferential stiffness and a coefficient of friction obtained on a wet road by a test tire. [Description of Signs] 2 Tread surface 3 Tread groove 3a Vertical groove 3b Horizontal groove 4 Tread pattern

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B60C 11/11 B60C 11/00 B60C 11/12

Claims (1)

(57) [Claims] [Claim 1] A pneumatic tire for automobiles provided with ABS
A tire circumferential direction which is a circumferential rigidity per tread unit area (1 cm ² ) of a tread pattern formed by providing a tread groove including a longitudinal groove in the tire circumferential direction and a transverse groove in a direction intersecting the longitudinal groove on the tread surface. The rigidity Cx is set to 10.0 N /
A pneumatic tire for automobiles provided with an ABS having a lateral edge component length L of the tread groove of not less than 600 mm and not more than 1500 mm per unit length (10 cm) in a circumferential direction.