JP5164730B2 - Precure tread and retreaded tire using the same - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a precure tread used for retreading a tire, and more particularly to a precure tread that enables reduction of air column resonance caused by a circumferential groove formed on a tread contact surface and a retread tire using the precure tread. Is.

  With the recent quietness of vehicles, the proportion of tire noise in automobile noise has become relatively large, so reducing tire noise has become a major issue. Among these, tire noise around 1000 Hz is a major factor of noise outside the vehicle, and an immediate countermeasure is desired for this noise from the viewpoint of environmental problems.

By the way, in general trucks and buses, tire noise belonging to a frequency band of 500 to 2000 Hz is caused by resonance of air columns defined by circumferential grooves and road surfaces formed in the tread within the tire contact surface. It is known to occur by so-called air column resonance.
In other words, when a tire having a circumferential groove is in contact with the ground, a tube having the same length as the contact length is formed between the groove wall of the circumferential groove and the contact surface. Noise called sound is generated. The frequency f ₀ of the air column resonance sound is defined as L, where the speed of sound is c, the length of the tube, that is, the length of the circumferential groove and the opening end correction amount is added.
f ₀ = c / 2L
It is a constant frequency represented by The opening end correction amount is normally obtained by experiment, and when the tube is cylindrical, it is obtained by multiplying the radius inside the tube by a constant.

  This air column resonance sound has a high peak and a wide frequency band, and is one of the main factors that cause a direct sound due to tires among noises. In addition, human hearing is sensitive in a frequency band around 1000 Hz, as indicated by a frequency correction characteristic called A characteristic that reflects human auditory sensitivity characteristics, and this reduction in air column resonance is quiet in the passenger compartment. It is very effective for improving the performance and reducing the noise near the road.

で表されることが分かっている。 In order to suppress such air column resonance, Patent Documents 1 and 2 provide a circumferential groove extending continuously in the circumferential direction on the tread ground surface, and on the land surface at a position away from the circumferential groove. There has been proposed a tire provided with a branch groove that is a so-called Helmholtz resonator, which is composed of an open air chamber portion and a branch groove that communicates the air chamber portion with the circumferential groove.
As schematically shown in FIG. 1, the Helmholtz resonator has a sound velocity of c, a length of the tubular portion 1 corresponding to the branch groove, l, a cross-sectional area of the tubular portion 1, S, a radius of the tubular portion 1 r, Assuming that the volume of the air chamber 2 is V, the frequency f to be reduced is

It is known that

  Further, Patent Documents 3 and 4 propose a tire including a circumferential groove continuously extending in the circumferential direction on the tread contact surface and a Helmholtz resonator embedded in the tread in communication with the circumferential groove. ing.

By the way, in recent years, in order to consider environmental problems, the demand for recycling tires has increased. Recycled tires are widely known as retreaded tires. A retread tire is a tire obtained by removing a tread or a tread and a part of a belt layer from a used tire to form a base tire, and a new material is attached to the base tire as a tread portion. The retreaded tire manufacturing method includes a method in which an unvulcanized tread rubber is laminated to a base tire and vulcanized in a mold, and the tread rubber is previously patterned and vulcanized with a long mold, and a pre-cured tread is obtained. And vulcanizing and bonding the precure tread to the base tire at a relatively low temperature and a low pressure state on the bonding surface (see, for example, Patent Document 5).
Japanese Patent Laid-Open No. 5-338411 JP 2007-269144 A JP 2000-118207 A Japanese Patent Laid-Open No. 2001-239809 JP-A-10-119054

Here, in the retreaded tire, as in the example described above, noise reduction has been required, but an example in which noise has been sufficiently reduced without impairing steering stability and wear performance has been proposed. Absent.
SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for reducing air column resonance caused by a circumferential groove in a precure tread used for tire retreading, and further to provide this precure tread and a retread tire using the precure tread. There is to do.

The gist of the present invention is as follows.
(1) In a precure tread having a surface that is a ground contact surface side of a tire and a back surface that is a side to be attached to a base tire,
It has at least one circumferential groove extending along the tire circumferential direction on the surface, and further includes at least one resonator that communicates with the circumferential groove and is provided on the inner side in the thickness direction of the precure tread,
The resonator includes a tubular portion having one end opened in the circumferential groove, and an air chamber portion connected to the other end of the tubular portion and having a cross-sectional area larger than the cross-sectional area of the tubular portion,
The air chamber portion, the opening on the back, up-les tread that with the progress of the tread portion contact surface wear, characterized in that it is formed by separating the rear groove is exposed to the tread portion a ground plane.

( 2 ) The precure tread as described in (1) above, wherein the tubular portion opens at a groove bottom of the circumferential groove.

( 3 ) The precure tread as described in (1) or (2) above, wherein the tubular portion has a sound absorbing layer.

( 4 ) The precure tread according to any one of the above (1) to ( 3 ), wherein the resonator has a plurality of resonators, and each resonator has a different resonance frequency.

( 5 ) A retread tire characterized in that the precure tread according to any one of (1) to ( 4 ) is adhered to a base tire.

  ADVANTAGE OF THE INVENTION According to this invention, the precure tread which reduced the air column resonance sound resulting from the circumferential groove | channel, and a retreaded tire using the same can be provided.

Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 2A is a perspective view of the precure tread of the present invention, and FIG. 2B is a cross-sectional view of the precure tread of the present invention. The precure tread 10 has a surface 10a that is a tire contact surface side and a back surface 10b that is affixed to a base tire. At least one that extends along the tire circumferential direction on the surface 10a, 4 in the illustrated example. A circumferential groove 11 of the book and at least one resonator 3 that communicates with the circumferential groove 11 and is provided on the inner side in the thickness direction of the precure tread 10 are provided. The resonator 3 includes a tubular portion 1 having one end opened in the circumferential groove 11 and an air chamber portion 2 connected to the other end of the tubular portion 1 and having a cross-sectional area larger than the cross-sectional area of the tubular portion 1. .
As described above, by providing the Helmholtz type resonator 3 in the circumferential groove 11 of the precure tread 10, noise can be reduced in a retread tire using the precure tread 10. Further, since the precure tread 10 has the resonator 3 on the inner side in the thickness direction of the precure tread 10, it is not necessary to change the tread pattern on the surface 10a by the resonator 3. Therefore, when the precure tread 10 of the present invention is bonded to a base tire to obtain a retread tire, the retread tire can maintain good steering stability and wear performance due to the tread pattern.
Although the Helmholtz type resonator 3 has been described in the example of FIG. 2, the resonator 3 may be a side branch type.

  Here, like the other precure tread of the present invention shown in FIG. 3, it is preferable that the air chamber portion 2 opens to the back surface 10b. That is, the air chamber part 2 opened to the back surface 10b can be easily formed by providing a convex part in the mold for vulcanizing the tread rubber in advance. Furthermore, since the tubular portion 1 that communicates the air chamber portion 2 and the circumferential groove 11 can be easily formed, it is advantageous in manufacturing the resonator 3 that communicates with the circumferential groove 11.

として表される。 Further, like the other precure tread of the present invention shown in FIG. 4, it is preferable that the air chamber portion is a back groove that is exposed to the tread portion grounding surface as the tread portion grounding surface wears. is there. With such a configuration, the back groove 12 functions as an air chamber of a Helmholtz resonator for reducing air column resonance caused by the circumferential groove 11 in the initial stage of wear of the tread portion grounding surface. Since it acts as a circumferential groove at the later stage of wear of the partial ground contact surface, it is possible to achieve good wet performance from the early stage to the late stage of wear.
In addition, since the one circumferential groove | channel 11 and the back surface groove | channel 12 which is an air chamber part are connected by the some tubular part 1, if the number of the tubular parts 1 is n, the resonance frequency f to which sound is reduced Using the above equation (1)

Represented as:

  In addition, the air chamber portion is preferably formed by dividing the back groove 12 with, for example, a rubber wall. In this case, since the volume of the air chamber can be adjusted by adjusting the interval that divides the back groove 12 by the rubber wall, the desired resonance frequency can be reduced.

  In the illustrated example described above, the tubular portion 1 opens in the groove wall of the circumferential groove 11, but the tubular portion 1 preferably opens in the groove bottom of the circumferential groove 11. This is because the resonator 3 can function as a resonator even when wear on the tread portion ground contact surface proceeds.

  Further, it is preferable to provide a sound absorbing layer such as a nonwoven fabric, foamed rubber, or foamed urethane on the wall surface of the tubular portion 1. The particle velocity in the resonator 3 is higher at the inlet side of the tubular portion 1 and lower in the air chamber portion 2. By providing the sound absorbing layer in the tubular portion 1 having a high particle velocity, the attenuation characteristics of the resonator 3 can be effectively enhanced, and as a result, the sound pressure level can be attenuated in a wide band.

  Also, a plurality of resonators 3 are provided, and the length l, the cross-sectional area S, the radius r, and the volume V of the air chamber 2 are set so that the resonance frequency of each resonator 3 is different. It is preferable to adjust. This is because when one type of resonator is used, the sound is greatly reduced only at the resonance frequency, and the sound pressure deteriorates at frequencies before and after the resonance frequency, but by using many resonators having different resonance frequencies. This is because there is no worse band and noise can be reduced over the frequency band.

Further, when a plurality of resonators 3 are provided, the resonators 3 do not need to be aligned and are dispersedly arranged as shown in the rear views of the precure tread in FIGS. 5 (a) and 5 (b). Is possible.
Furthermore, the air chamber portion 2 of the resonator 3 is not only in the case of a rectangle as shown in FIG. 6A, but also in a circle as shown in FIG. It can be in any shape as shown.

  The precure tread of the present invention, the precure tread of the conventional example, and the precure tread of the comparative example were prototyped under the specifications described later, and the performance was evaluated.

The precure tread of the conventional example has a tread pattern on the front surface shown in FIG. 7A and a pattern on the back surface shown in FIG. 7B. The precure tread of the conventional example has four circumferential grooves 11a to 11d on the surface 10a, and the two circumferential grooves 11a and 11b and the circumferential grooves 11c and 11d are connected by the lug grooves 13, respectively. . The conventional precure tread has two back grooves 12 on the back surface 10b, and each back surface groove 12 is disposed between the circumferential grooves 11a and 11b and between the circumferential grooves 11c and 11d, respectively. Has been.
The precure tread of the comparative example has a tread pattern on the surface shown in FIG. 8A and a back pattern shown in FIG. The precure tread of the comparative example has four circumferential grooves 11a to 11d on the surface 10a, and has a lug groove 14 communicating with the circumferential groove 11a between the two circumferential grooves 11a and 11b. In addition, a lug groove 14 communicating with the circumferential groove 11d is provided between the two circumferential grooves 11c and 11d. The lug groove 14 constitutes a Helmholtz resonator by being in contact with the road surface. The backside 10b of the precure tread of the comparative example has the same structure as the backside 10b of the precure tread of the conventional example.

The precure treads of Reference Examples and Invention Examples 2 to 5 have tread patterns on the same surface as shown in FIGS. 9 (a) to 11 (a), and FIGS. 9 (b) to 11 (b). Each has a back pattern as shown in FIG.
As shown in FIG. 9B, the precure tread of the reference example has two back surface grooves 12 on the back surface 10b. The back surface groove 12 is a plurality of tubular portions 1 and is formed into circumferential grooves 11b and 11c. It is connected.
As shown in FIG. 10 (b), the precure treads of Invention Examples 2 and 3 have a plurality of air chamber portions by dividing the back groove 12 of the precure tread of the reference example by rubber walls 15, and each air chamber portion. One tubular portion 1 is provided for each, and this tubular portion 1 connects the air chamber portion and the circumferential groove 11b or 11c. In Invention Example 2, the tubular portion 1 communicates with the groove bottoms of the circumferential grooves 11b and 11c, and in Invention Example 3, the tubular portion 1 communicates with the groove walls of the circumferential grooves 11b and 11c.
In the precure tread of Invention Example 4, as shown in FIG. 11B, the back groove 12 is divided by a rubber wall 15 to form air chamber portions having different volumes.
The precure tread of Invention Example 5 has the structure of the precure tread of Invention Example 2, and the tubular portion 1 is provided with a nonwoven fabric.

  Using each prototype precure tread, a worn 11R22.5 tire was rehabilitated in the usual manner. These retreaded tires were assembled on a 7.2 × 22.5J rim to form a tire wheel, the tire internal pressure was adjusted to 900 kPa, and tests for steering stability performance, uneven wear performance, and noise reduction performance were performed. The results are shown in Table 1.

<Steering stability test>
Each retread tire was mounted on the driving wheel of a 2-D / 4-axis large truck, the load was applied as a load, and the driver evaluated the feeling in 10 stages. The larger this value, the better the steering stability performance.

<Uneven wear test>
Each rehabilitated tire is mounted on the driving wheel of a 2-D / 4-axis large truck, and the load is applied as a load. After running 10,000 km, the difference in the tire width direction wear amount between the two ribs in which the lug grooves are arranged Was averaged with the left and right wheels, and the index was evaluated using an index with the conventional example as 100. It means that uneven wear is so small that this figure is small. There is a dominant difference when the numbers differ by 3 or more.

<Noise test>
Each rehabilitated tire is given a load of 0% (empty car), 50%, 75%, and 100% (percentage of maximum load capacity), and an actual vehicle meandering test stipulated in the European Tire Unit Noise Regulation (Detective2001 / 43 / EC) A noise test was conducted under the conditions of the method (C3 condition).
Further, the same test was performed with a load of 75% applied in a state where each retread tire was worn 50%. At the time of this 50% wear, the rear groove is not exposed in any of the retreaded tires.

From Table 1, the precure treads of the reference examples and invention examples 2 to 5 maintain the same steering stability performance and uneven wear performance as compared with the conventional examples, and at all loads including 50% wear. It can be seen that the noise level is reduced.
As described above, it has become possible to provide a precure tread with reduced air column resonance sound caused by the circumferential groove and a retread tire using the same without impairing the steering stability performance and the uneven wear performance.

It is a schematic diagram of a Helmholtz resonator. It is an example of the flops of tread. It is an example of the flops of tread. It is an example of the flops of tread. It is a rear view of the flops of tread. It is a figure which shows the air chamber part of a resonator. It is a figure which shows the precure tread of a prior art example. It is a figure which shows the precure tread of a comparative example. It is a figure which shows the precure tread of a reference example . It is a figure which shows the precure tread of invention example 2,3,5. It is a figure which shows the precure tread of the example 4 of an invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tubular part 2 Air chamber part 3 Resonator 10 Precure tread 11 Circumferential groove 11a, 11b, 11c, 11d Circumferential groove 12 Back surface groove 13, 14 Lug groove 15 Rubber wall

Claims (5)

In a precure tread having a surface that is a ground contact surface side of a tire and a back surface that is a side to be attached to a base tire,
It has at least one circumferential groove extending along the tire circumferential direction on the surface, and further includes at least one resonator that communicates with the circumferential groove and is provided on the inner side in the thickness direction of the precure tread ,
The resonator includes a tubular portion having one end opened in the circumferential groove, and an air chamber portion connected to the other end of the tubular portion and having a cross-sectional area larger than the cross-sectional area of the tubular portion,
Precured tread wherein the air chamber is open to the rear, is formed by separating the rear groove is exposed to the tread portion contact surface with the progress of the tread portion contact surface wear, characterized in Rukoto. The precure tread according to claim 1 , wherein the tubular portion opens at a groove bottom of the circumferential groove. Precured tread according to claim 1 or 2, wherein the tubular portion, and having a sound-absorbing layer. The precure tread according to any one of claims 1 to 3 , wherein the resonator has a plurality of resonators, and each resonator has a different resonance frequency. A retread tire using the precure tread according to any one of claims 1 to 4 adhered to a base tire.

Images