JPH03136908A - Pneumatic tire with reduced noise characteristics - Google Patents

Abstract

PURPOSE:To reduce a pattern noise in a tire forming different pitch block patterns with widthwise grooves by constituting a tread with a central area having parallel widthwise grooves and a tread shoulder area having widthwise grooves of the smaller peripheral inclination angles with the longer pitch. CONSTITUTION:A tread part T is divided into a central area C and a shoulder area S with peripheral grooves 1A and 1C, and the width ratio thereof is set to about 70:30 to 30:70. Also, the widthwise grooves 2A of the central area C are inclined at angles of alpha1 to alpha2 with a peripheral direction, and so formed as to be parallel to each other. In addition, the tread part T forms a land part 3A and a pitch variation different from pitches P1 to P3 from widthwise grooves. When a relationship between the inclination angles beta1 to beta2 of respective widthwise grooves with a peripheral direction and the length l1 to l3 of pitches P1 to P3 is established as l1<l2<l3, the inclination angles are determined as beta1>beta2>beta3. According to the aforesaid construction, a pattern noise can be reduced.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to an improvement of a pneumatic tire, and more particularly to a pneumatic tire having a block pattern of pitch variations that reduces pattern noise. It is.

(Prior Art) Generally, a unique block pattern is formed in the tread of a tire by a plurality of circumferential grooves extending endlessly in the circumferential direction and lateral grooves arranged at regular intervals in the circumferential direction. This block pattern is intended to improve various properties such as high-speed durability and drainage performance.

However, for tires having such a block pattern, a so-called pitch variation method is generally adopted for the purpose of reducing noise generated from the pattern during running.

This pitch variation method eliminates the sound pressure protrusion (peak) at a specific frequency of the sound generated from the tread contact surface while driving, and disperses the sound pressure over a wide frequency band to create white noise. Blocks having different circumferential lengths are arranged randomly or with a certain regularity on each circumferential land row.

Specifically, on the circumferential land row that constitutes the tread, one block and the horizontal groove adjacent to one of the blocks in the circumferential direction are the constituent elements, and the length in the circumferential direction (pitch length)
Two to seven types of components with different values are arranged on the circumference of the tread in random or regular combinations. Taking a passenger car tire as an example, on the circumference of the tread for each land row The total number of components (pitch) is usually 40
~80.

The lateral grooves dividing the constituent elements in each land row are arranged parallel to each other over the entire tread, or
Alternatively, the inclination angle over the entire tread is changed depending on the pitch length of each component.

(Problem to be Solved by the Invention) By the way, in the case of a tire whose cross-sectional aspect ratio is 75% or less, the tread has a substantially flat shape and is wide in the radial direction.
Both end portions have a relatively circular shape, and the ground contact shape of such a tire during running takes approximately the shape shown in FIG. 4 depending on the running conditions and the state of the road surface.

In Fig. 4, the load due to load fluctuations during driving is divided into three tire contact contours: large, medium, and small.Especially in the shoulder part of the tire, each contact contour is greatly curved. The degree of inclination of the ground contact contour changes due to load fluctuations.

Therefore, if the rotation direction of the tire is the direction of the arrow, both the stepping side and the kicking side of the tire produce a ground contact contour in a direction (axial direction) approximately perpendicular to the center line of the tire.
In the tire shoulder area immediately after stepping in and just before kicking off, each contact contour is curved as described above, so the lateral groove intersects with the contact contour at various angles depending on load fluctuations, and under a certain load There is a tendency for sound to be generated easily.

However, in the conventional block pattern tires with pitch variations mentioned above, little consideration is given to the relationship between the lateral grooves and the contact profile, so if the lateral grooves are arranged at a constant angle over the entire tread, This has the problem that peak noise tends to occur in the tire shoulder area when the load fluctuates, and that the generated peak noise is directed toward the side surface of the tire along the direction of the lateral grooves.

In addition, if the lateral grooves are arranged to vary the inclination angle over the entire tread depending on the circumferential pitch length of each pitch, in the central area of the tread, pitches that deviate from the optimal angle that does not generate noise will occur. As a result, there is a problem in that noise is likely to be generated from the center area of the tire.

The present invention aims to solve the problems of the conventional pneumatic tires mentioned above.

Therefore, an object of the present invention is to provide a pneumatic tire having a block pattern with pitch variations and reduced pattern noise.

[Structure of the Invention] (Means for Solving the Problems) That is, the pneumatic tire of the present invention includes a pair of annular sidewalls, and a tread portion that extends in a toroidal manner on the radially outer side of both sidewalls, and the tread portion The tread includes a large number of lateral grooves that extend continuously or intermittently at an angle to the circumferential direction from approximately the center of the tread to both ends of the tread, and land areas separated by these lateral grooves, and each land area has a In a tire in which a plurality of circumferential tread components have a combination of different pitch lengths, with one lateral groove adjacent to these tread components,
The tread includes a tread central region in which the lateral grooves are circumferentially arranged in a substantially parallel relationship with each other, and a circumferential direction of the lateral grooves included in the tread component having a longer pitch length depending on the pitch length. It is characterized by comprising tread shoulder areas disposed circumferentially with a small inclination angle relative to the tread shoulder area.

(Function) In the pneumatic tire of the present invention, in the block pattern of the pitch variation, the lateral grooves in the central area of the tread are arranged parallel to each other, and the constituent elements (pitch ) The lateral grooves included in the tire are arranged with a small inclination angle relative to the circumferential direction, so the optimal angle is maintained in the tire center area to avoid generating noise, while in the tire shoulder area, each lateral groove is arranged with a small angle of inclination to the circumferential direction. It therefore intersects with the ground contour, so that the generation of noise is likewise suppressed.

(Example) Hereinafter, examples of the pneumatic tire of the present invention will be described in detail according to the drawings.

Fig. 1 is a developed view of a tire tread section showing a first embodiment of the pneumatic tire of the present invention, Fig. 2 is a developed view of a tire tread section showing a second embodiment of the same, and Fig. 3 is a developed view of a tire tread section showing a third embodiment of the same. FIG. 2 is a developed view of a tire tread portion showing an example.

In the drawings, parts other than the tread part are not shown, but the parts other than the shown parts, such as the crown part, sidewalls, carcass, and belt layer, have a well-known structure.

That is, a pair of sidewalls extending radially inward from both ends of the cylindrical crown part are connected in a toroidal manner, and the sidewalls and the crown part are reinforced with a carcass,
The radially outer side is occupied by a tread portion that engages with the road surface.

Further, when the carcass has a so-called radial structure, a non-stretchable belt layer is provided between the tread portion and the carcass.

First, in the first embodiment shown in FIG. 1, the tread portion T of the tire has three circumferential grooves IA, IB extending parallel to the equatorial plane O at positions that approximately equally divide the distance between both ends of the tread.
and ICs are arranged linearly and endlessly at predetermined intervals in the radial direction. Although these circumferential grooves are not necessarily essential in the present invention, usually about 1 to 8 circumferential grooves are provided for purposes such as improving drainage performance.

Note that the width ratio of the center area C and the shoulder area S in the tread portion T of the tire is usually 70:30 to 30:
Although selected from a range of 70, in the first embodiment,
A center area C and a shoulder area S are defined with the circumferential grooves IA and IC on both sides as boundaries, and the tread width TS is 100.
Then, the width of the central area C is 50, and the width of each shoulder area S on both sides is 25.25.

On the other hand, a large number of lateral grooves 2 extend from the central circumferential groove IB to both ends of the tread T, each obliquely with respect to the circumferential groove direction.
A and 2B are provided, and radial land portions 3A, 3B, 3C, . . . are divided by these lateral grooves.

Here, the lateral groove 2A in the central area C of the tread T
is inclined at an angle α with respect to the circumferential direction, and the shoulder area S
The lateral grooves 2B are inclined at an angle of β with respect to the circumferential direction, and in the opposite direction to the lateral grooves 2A.

Note that the inclination angle of the horizontal groove 2A in the central area C is usually 40
~80 degrees, and the inclination angle of the transverse grooves 2B in the shoulder area S is usually selected from the range of 50 to 90 degrees.

The tread portion T incorporates a so-called pitch variation method.

That is, the tread component (pitch) PI is the land portion 3
Consisting of A and one horizontal groove adjacent to it, with a pitch of 2
Similarly, P is the land portion 3A and one horizontal groove adjacent to this,
Similarly, the pitches 3C each consist of a land portion 3C and one lateral groove adjacent to the land portion 3C.

Circumferential pitch length L of each pitch P1, P2, and P3
SL and L3 have a relationship of L1, L2, and L3, respectively, and in this first embodiment, the relationship is 7:9:11, respectively.
The ratio is

In this case, the circumferential length of each land portion and the circumferential length (or distance) of the lateral grooves can also be changed according to the pitch ratio.

In the present invention, the inclination angle α of the lateral groove 2A in the central area C of the tread T with respect to the circumferential direction is
α − α2 common to the three pitches P1, P2 and P3
-α3, and the lateral grooves 2A are parallel to each other, but the inclination angles β1, β and β3 of the lateral grooves 2B in the shoulder area S with respect to the circumferential direction are the same as the three pitches P1, P2 and P3. Contrary to the pitch length relationship, it is important that the inclination angle has a change such that β1>β>β3.

In this way, the lateral grooves in the tread center area C are arranged parallel to each other, and the inclination angle of the lateral grooves in the shoulder area S with respect to the circumferential direction is changed such that the longer the pitch length is, the smaller the lateral groove is. As a result, the pattern noise in the central area C and both side shoulder areas S of the tread T is effectively reduced, and an excellent noise improvement effect can be obtained.

Next, in the second embodiment shown in FIG. 2, one center circumferential groove IB is formed on the equatorial plane O of the tread T;
Relatively wide side circumferential grooves IA and IC are provided in the center between the center circumferential groove IB and both side circumferential grooves IA and IC, respectively, and lateral grooves 2A are provided from intermediate positions between the center circumferential groove IB and both side circumferential grooves IA and IC to both tread ends. , 2B and 2C are arranged in a herringbone shape, which is different from the first embodiment described above.

A component (pitch) consisting of each land portion 3A, 3B, and 3C and the adjacent lateral grooves 2A, 2B, and 2C, respectively.
PI, P2 and P3 are the respective pitch lengths LSL
and L are respectively L kuL2ku1 2 3
1L3, and the inclination angles α11α and α3 of the lateral grooves 2A in the central area C of the tread T with respect to the circumferential direction are all the same, whereas the inclination angles α11α and α3 of the lateral grooves 2B in the shoulder area S in the circumferential direction are the same. The inclination angles β, β, and β3 are opposite to the pitch length relationship of the three pitches, β1>β2>β
There is a relationship of 3.

Furthermore, the third embodiment shown in FIG. Two circumferential grooves IB.

ICs are provided at regular intervals, and the central area C of the tread T is
A zigzag and parallel S or 2-shaped lateral groove 2A is provided in the shoulder area S, and a 7-shaped lateral groove 2B is provided in the shoulder area S, and linear cuts (sipes) 4A, S are provided between each groove.
Alternatively, this embodiment is different from the first and second embodiments described above in that a large number of two-character-shaped sipes 4B and a large number of polygonal line-shaped sipes 4C are provided.

Also in the third embodiment, the constituent elements (pitch) Pl, P2 and P3 consisting of the land portions 3A, 3B and 3C and the adjacent lateral grooves 2A12B and 2C have their respective pitch lengths L SL and 2 L are in the relationship L1 × L2 < L8, respectively, and Tolerado T
The inclination angles α, α, and α3 with respect to the circumferential direction of the lateral grooves 2A interposed in the central region C of 2 are all the same.
The inclination angles β , β2 and β with respect to the circumferential direction are β
By establishing the relationship 〉β2〉β3, pattern noise is reduced.

Next, the structure and effects of the pneumatic tire of the present invention will be explained in more detail using test examples.

(Test example) Tire size 195/60R14, rim used: 5-Shi JX
14. Air pressure: 1. 9kg/cd, load 400k
The block pattern shown in FIG. 1 described above was formed on the tread portion of the passenger car radial tire No. g, and this tire was evaluated.

Note that other structures such as the radial carcass and belt layer of the tire and manufacturing conditions were similar to those of conventional tires, so details will be omitted.

That is, in Fig. 1, the tread width TS: 150 mm
, Width of central area C near 0+II+s, Width of both shoulder areas S: 40m1% Depth of each circumferential groove: 81111%
Same width, 7mm, Depth of lateral groove 2A: 6.5 order, Same groove width: 5mm, Depth of lateral groove 2B near + a + *, Same groove width near 1■, Circumferential length of pitch P1 L: 23mm, ■ Circumferential length of pitch P2 L: 30vua, Circumferential length of pitch P3 L: 37, L: L: L3
1 2 3 -7:9:11, Inclination angles α, α and α of lateral groove 2A with respect to the circumferential direction: 60 degrees, lateral groove 1 2
Tire 3 of the present invention was obtained by setting the inclination angle of -3 2B to the circumferential direction β: 67 degrees, β 2: 60 degrees, and β: 52 degrees.

On the other hand, for comparison, a conventional tire A was obtained in the same manner as above except that the inclination angles of each lateral groove were all fixed at 60 degrees.

Furthermore, depending on each pitch length, the noise feeling when driving at 60 km/h on a road with the entire tread is reduced to 10%.
Score evaluation using point system.

Table 1 β: Conventional tire B was obtained in the same manner as above except that the angle was 52 degrees.

The following table shows the results of evaluating the pattern noise generation status of these three types of tires under the following conditions.

(Evaluation method) A vehicle equipped with bench noise test tires is run at a speed of 60 km/h on a steel drum with a smooth surface of 3 m in diameter, and the sound pressure peak in the 173 octave band of the noise generated at that time is measured. 1111 constant.

Dry asphalt Note) 5 points: The noise is a concern when the tires are installed on a front-wheel drive passenger car.

8 points: It's noticeable if you pay attention, but it's not a big deal.

As is clear from the results shown in the table above, the pattern noise of the tire B1 of the present invention is effectively improved compared to the conventional tires A and B.

[Effects of the Invention] As described in detail above, in the pneumatic tire of the present invention, in the pitch variation block pattern, the lateral grooves in the central area of the tread are arranged parallel to each other, and the lateral grooves in the shoulder area of the tread are arranged parallel to each other. The lateral grooves included in the long pitch components (pitch) are arranged with a small inclination angle to the circumferential direction, so the optimum angle that does not generate noise is maintained in the center area of the tire, and at the shoulder area of the tire. Each lateral groove intersects the ground contact profile at an angle, eliminating angles that tend to generate noise.

Therefore, according to the pneumatic tire of the present invention, the occurrence of pattern noise is reduced throughout the radial direction of the tire, and excellent low noise performance is obtained, resulting in an excellent running feeling as a high-speed tire. It is possible.

[Brief explanation of the drawing]

Fig. 1 is a developed view of a tire tread section showing a first embodiment of the pneumatic tire of the present invention, Fig. 2 is a developed view of a tire tread section showing a second embodiment of the same, and Fig. 3 is a developed view of a tire tread section showing a third embodiment of the same. FIG. 4, which is a developed view of a tire tread portion showing an example, is a conceptual diagram illustrating load fluctuations and a contact contour of a tire contact surface. T...Tread section TS...Tread width C...Tread center area S...
...Tread shoulder areas IA to ID...Circumferential grooves 2A to 2C...Lateral grooves 3A to 3C...Land portions 4A to 4C...Notches (sipes) P1 to P3...Configuration Element (pitch)

Claims (1)

[Claims] A pair of annular sidewalls and a tread portion are connected in a toroidal manner on the radially outer side of both sidewalls, and the tread portion extends continuously or intermittently at an angle with respect to the circumferential direction from approximately the center thereof to both ends of the tread. A plurality of circumferential tread components including a large number of lateral grooves and a land section separated by these lateral grooves, and one of each land section and one lateral groove adjacent to these as a tread component. In a tire configured with a combination of different pitch lengths, the tread has a central tread region in which the transverse grooves are disposed circumferentially in a substantially parallel relationship with each other, and the pitch length is 1. A pneumatic tire with reduced noise, characterized in that the pneumatic tire comprises a tread shoulder area disposed on the circumference with a lateral groove included in a long tread component having a small inclination angle with respect to the circumferential direction.