JPH11310013A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic radial tire for a car capable of effectively improving in on-ice performance including braking, accelerating and turning performance on ice. SOLUTION: A pneumatic radial tire has peripheral grooves and cross grooves extending thereacross on a tread and block patterns defined by these grooves. The blocks 3a, 3b, 3c in a center area, a mediate area and a shoulder area, respectively, includes plurality of wavy sipes 4a, 4b, 4c extending in the cross direction of the tire are formed in the respective blocks to be gradually larger in wavy amplitude and larger in sipe space, the amplitude A of the wavy sipe in the center area with respect to the sipe space (X) being set A=0.3X to 0.7X and the amplitude B, C of the respective wavy sipes in the mediate area and the shoulder area with respect to the amplitude (A) being set B=1.4A to 2.0A, C=2.4A to 3.0A.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tire for a passenger car, and more particularly to a pneumatic radial tire having improved on-ice performance such as braking, acceleration and turning.

[0002]

2. Description of the Related Art A plurality of vertical grooves such as a plurality of main grooves and sub-grooves in the circumferential direction of a tire, a large number of horizontal grooves intersecting the vertical grooves, and a large number of blocks defined by these grooves. There is known a so-called block pattern tire having the following.

In the tire having this pattern, a large number of sipes are arranged in blocks of a center portion, a shoulder portion, and a mediate portion therebetween in order to improve the performance on a snowy road surface as a studless tire. And the shape of the sipe is often corrugated.

As shown in FIG. 4, the arrangement and shape of the waveform sipe are, as shown in FIG. 4, a block (3a) of each part of a center part, a mediate part and a shoulder part.
(3b) In many cases, the waveform sipe (4) in (3c) has the same shape (waveform amplitude and the like) and arrangement (interval and density) all.

However, when the sipe shape of each block is the same as described above, the edge effect can be similarly obtained at the sipe of each section, but the braking and acceleration performances are mainly the same as those of the center section. Since the block of the eight portion contributes greatly, the sipe extending from the center portion to the mediate portion in the direction of 90 ° with respect to the vehicle traveling direction (front-back direction) (a sipe exhibiting an edge effect in the front-back direction) is required. . Also, when the amplitude of the waveform sipe becomes large, the sipe component exhibiting the lateral edge effect increases, and the sipe component in the front-rear direction decreases.Therefore, in order to secure braking and acceleration performance, the smaller the amplitude is, the better. good.

On the other hand, regarding the turning performance, since the shoulder portion mainly contributes to the block, the shoulder portion needs to have a sipe having a larger sipe component exhibiting a lateral edge effect than the center portion. is there. In this case, the amplitude of the sipe should be large.

[0007] From the above, it is considered inefficient to make the shape of the waveform sipe the same from the center to the shoulder.

Further, there is a case where the shape and arrangement of the waveform sipe of each part are irregular, but also in this case, efficiency is poor due to lack of regularity.

The present invention has been made in view of the above, and the braking, acceleration, and the like are achieved by gradually changing the shape of a sipe disposed in a block of a center portion, a mediate portion, and a shoulder portion for each block of each portion. And a pneumatic radial tire capable of effectively improving on-ice performance such as turning.

[0010]

According to the present invention, a plurality of vertical grooves extending in the circumferential direction of the tire, a large number of horizontal grooves intersecting the vertical grooves, and a large number of blocks defined by these grooves are provided on a tread tread portion. In the pneumatic radial tire having a plurality of waveform sipes extending in the tire width direction in the block, from the center part to the mediate part and the shoulder part, the amplitude of the waveform and the sipe interval gradually increase for each block of each part. The amplitude (A) of the waveform sipe at the center portion is A = 0.3X to 0.7X with respect to the sipe interval (X), and the amplitude of each waveform sipe at the mediate portion and the shoulder portion is (B) and (C) are respectively set to B = 1.4A to 2.0A C = 2.4A to 3.0A with respect to the amplitude (A) of the waveform sipe at the center portion. It is characterized by comprising.

Thus, the waveform sipe of the center portion, the mediate portion, and the shoulder portion can satisfactorily reduce the sipe component exerting the front-back edge effect and the sipe component exerting the lateral edge effect required for each portion. Holding, it is possible to effectively improve the performance on ice such as braking, acceleration and turning.

Further, according to the present invention, each sipe interval (X) of the center portion, the mediate portion and the shoulder portion is provided.
It is preferable that (X1) and (X2) be set in the range of 3 to 7 mm. As a result, the amplitude and the sipe density can be kept in good ranges.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a partially developed view schematically showing a basic pattern of the radial tire of the present invention, and FIGS. 2 (a) and 2 (b).
(C) is an enlarged plan view of each of the center block, the mediate block, and the shoulder block.

As a tread pattern of the tire, a plurality of (four in the figure) main grooves (1 in the figure) are provided in the tread tread portion as vertical grooves in the tire circumferential direction and intersect with the main grooves (1). Lateral grooves (2) extending in the lateral direction are provided, and a large number of blocks (3a) (3b) (3c) are arranged in the tire circumferential direction as land portions defined by these grooves. Is formed.

The center block (3a), the mediate block (3b) and the shoulder block (3c) include a waveform sipe (4a) crossing the block as shown in FIG. A plurality of (4b) and (4c) are formed respectively. Sipe is usually
The groove width is 0.2 to 1.5 mm, preferably 0.5 to 1.0
In mm, a narrow groove having a depth of 20 to 90% of the main groove is referred to, and a wavy sipe refers to a narrow groove having a wavy shape.

The waveform sipe (4a) (4b) (4c)
From the center part to the mediate part and shoulder part, for each block (3a) (3b) (3c) of each part,
It is formed by gradually increasing the amplitudes (A), (B) and (C) of the waveform and gradually increasing the sipe intervals (X) (X1) (X2).

Specifically, the waveform sipe (4
The amplitude (A) of a) is set to A = 0.3X to 0.7X with respect to the sipe interval (X) at the center portion, and the waveform sipe (4
b) amplitude (B) and the waveform sipe (4
The amplitude (C) of c is determined by the waveform sipe (4
For the amplitude (A) of a), set B = 1.4A to 2.0A C = 2.4A to 3.0A.

That is, the waveform sipe (4a) of each part
(4b) When the amplitudes (A), (B), and (C) of (4c) are smaller than the above ranges, the sipe component exhibiting the edge effect in the front-back direction increases, but the sipe density decreases, and the overall edge in the horizontal direction decreases. The sipe component that exerts its effect is reduced,
Turning performance will be reduced. The amplitude (A)
When (B) and (C) are larger than the above range, the sipe component exerting the edge effect in the lateral direction increases, but the sipe component exerting the edge effect in the front-rear direction decreases, and the braking and acceleration performance decreases. Therefore, it is preferable to set the above range. Among them, the amplitude of the sipe of each part is 0.5 mm.
The one set in the range of 6.5 mm is particularly preferable from the viewpoint of the effect.

Further, the waveform sipe (4a) (4
b) The sipe interval (X) (X1) (X2) of (4c) is
Within the range of 3 to 7 mm, the difference between the sipe intervals of each part is 0.1
It is better to set it gradually larger in the range of mm to 2.0 mm.

That is, the sipe interval (X) (X1
If (X2) is smaller than 3 mm, the rigidity of each block (3a) (3b) (3c) decreases, and the amplitudes (A) (B) of the waveform sipes (4a) (4b) (4c). (C) It is necessary to reduce (C), and the effect of the waveform is reduced. When it exceeds 7 mm, the sipe density is reduced and the effect of the sipe is reduced.

The waveform sipe (4a) (4
b) The pitch of the waveform of (4c) is preferably changed so as to increase toward the shoulder according to the change in the amplitude of each portion, but it is preferable in practice, but the amplitude is changed while maintaining the same pitch. It is also possible to change the pitch, and it is not always necessary to change the pitch. The pitch of the waveform sipe is preferably in the range of 0.5 to 4.5 mm from the viewpoint of the edge effect and the like.

FIG. 1 shows a waveform sipe of the present invention.
As shown in FIG. 2A and FIG. 2B, a one-sided open type having only one end opened as shown in FIG. A double-sided closed type with both ends closed as shown in FIG. Further, each waveform sipe may extend in a wave shape in a direction substantially perpendicular to the tire circumferential direction as shown in the figure, or may be formed in an oblique direction or partially refracted according to the block shape.

The radial tire of the present invention described above has a waveform sipe (4) having blocks (3a), (3b), and (3c) from the center to the mediate and shoulder portions.
a) Since (4b) and (4c) are set to gradually increase the amplitude of the waveform and the sipe interval for each block of each portion, the waveform sipe from the center portion to the mediate portion, which greatly contributes to braking and acceleration performance, is set. The interval and the amplitude are smaller than those of the shoulders in the outer region, and more sipes are arranged in a direction crossing the vehicle traveling direction (front-back direction). For example, as shown in FIG. 1, the number of waveform sipes in the center portion is one more than in the mediate portion. Therefore, the effect of the sipe component that exerts the edge effect in the front-rear direction becomes larger toward the center, and the performance (braking and acceleration performance) in the front-rear direction is improved.

Further, since the amplitude and the interval of the waveform sipe of the shoulder portion which greatly contributes to the turning performance are larger than the mediate portion and the center portion inside the shoulder portion,
The more sipe components that exert an edge effect in the horizontal direction increase (for example, the number of waveform sipe becomes one less than the mediate portion), the horizontal edge effect increases,
This improves the turning performance.

In order to confirm the above effects, the tires having the basic pattern shown in FIG. 1 and having the sipe intervals and the waveforms set as shown in Table 1 below, and Comparative Examples 2 and 3 And the tire of Comparative Example 1 having a pattern in which the waveform sipe (4) having the same amplitude and the same interval is arranged in each part (center part, mediate part and shoulder part) shown in FIG. In the same way, comparative tests of braking, acceleration and turning performance on ice were performed. Note that the tires of Comparative Example 1 were all the same as the tires except for the amplitude and interval of the waveform sipe.

The tire subjected to the test has a tire size of 1
85 / 70R14, tire pressure: 2.0 kg / cm ²
And the test vehicle was Bluebird 1800 (F
As F), one passenger performs an actual vehicle driving test on ice,
The test was performed by the following method.

Braking on ice: Full-lock braking distance from a speed of 40 km / h was measured. Acceleration performance on ice: The running time from stop to 30 m was measured. Turning performance on ice: The lap time on the lemniscate curve (figure 8) was measured. The evaluation of each test was represented by an index with the case of Comparative Example 1 being 100. The larger the numerical value, the better the evaluation.

[0029]

[Table 1]

[Table 2] As a result, in the case of the tire of Comparative Example 2, although the amplitude and the interval gradually changed from the center portion to the shoulder portion, since the amplitude was small, the lateral edge effect was inferior and the turning performance was poor. It becomes worse than 1. In the case of the tire of Comparative Example 3, the amplitude is large and the sipe interval is also large, so that the sipe density is reduced, the turning performance due to the lateral edge effect is deteriorated, and the braking and acceleration are performed due to the decrease in the number of sipe. On the contrary, the performance deteriorated.

On the other hand, in the case of the tire according to the embodiment of the present invention, the on-ice performances such as braking and acceleration and turning performance were improved as compared with Comparative Example 1.

[0031]

As described above, according to the pneumatic radial tire of the present invention, the waveform sipe in which the amplitude of the waveform and the sipe interval are increased for each block from the center to the mediate and shoulder portions. , The performance on ice such as braking and acceleration and turning performance can be effectively improved.

[Brief description of the drawings]

FIG. 1 is a partially developed view schematically showing a basic pattern in which a waveform sipe of a tire according to the present invention is arranged.

FIG. 2 is a plan view of a block (a) of a center portion, a block (b) of a mediate portion, and a block (c) of a shoulder portion for explaining a waveform sipe of the above.

FIG. 3 is a schematic plan view of one block showing another example of each of the waveform sipes (a) to (c).

FIG. 4 is a partial development view illustrating a basic pattern in which a waveform sipe of a conventional tire is arranged.

[Explanation of symbols]

 (1) Vertical groove (2) Lateral groove (3a) Center block (3b) Mediate block (3c) Shoulder block (4a) Center waveform sipe (4b) Mediate waveform sipe (4c) ) Waveform sipe at shoulder (X) Sipe interval at center (X1) Sipe interval at mediate (X2) Sipe interval at shoulder (A) (B) (C) Amplitude of waveform sipe at each part

Claims (2)

[Claims] 1. A pneumatic radial tire having a plurality of vertical grooves extending in a tire circumferential direction, a number of transverse grooves intersecting the longitudinal grooves, and a number of blocks defined by these grooves on a tread tread portion. In the block, a plurality of waveform sipes extending in the tire width direction are formed from the center part to the mediate part and the shoulder part by gradually increasing the amplitude of the waveform and the sipe interval for each block of each part. The amplitude (A) of the waveform sipe with respect to the sipe interval (X) is A = 0.3X to 0.7X, and the amplitudes (B) and (C) of the waveform sipe of the mediate portion and the shoulder portion are B = 1.4A to 2.0A C = 2.4A to 3.0A with respect to the amplitude (A) of the waveform sipe of the center portion, respectively. Pneumatic radial tire. 2. The sipe intervals (X) (X1) (X2) of the center portion, the mediate portion and the shoulder portion are 3 to 3
The pneumatic radial tire according to claim 1, which is set in a range of 7 mm.