JPH02225106A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To improve vibratory comfortableness of riding without deteriorating abrasion property resistance or the like, by forming a tread rubber covering the circumference of a belt with base rubber consisting of foaming rubber and cap rubber consisting of non-foaming rubber arranged on the outer side, in the radial direction, of the base rubber. CONSTITUTION:A tire 1 has a toroidal carcass 3 whose both end part in its axial direction is folded back along the circumference of a bead 2, a belt 4 arranged on the outer side in the radial direction of the carcass 3 and tread rubber 5 covering the circumference of the belt 4. And, at least two rubber coated code layers 6 are laminated to form the belt 4. In this occasion, the tread rubber 5 is formed with base rubber 8 consisting of foaming rubber which is located on the inner side in the radial direction and provided with a plurality of independent bubbles inside thereof, and cap rubber 9 located on the outer side in the radial direction and consisting of non-foaming rubber. Thereby, it is possible to improve vibratory comfortableness of riding without deteriorating abrasion property resistance or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pneumatic tire with an improved tread structure.

BACKGROUND ART Hitherto, a pneumatic tire with an improved tread structure has been known, such as the one described in Japanese Patent Application Laid-open No. 83-93804. This product has a pneumatic tire tread with an outer tread part made of a single type of rubber located on the outside in the tire's radial direction, and an outer tread part made of multiple types of rubber located radially inward from the surface of the tread's wear indicator. Consisting of an inner tread portion located radially inward, the inner tread portion is divided into at least three areas in the axial direction of the tire, namely, a central area spanning the tire equator and side end areas continuous to both ends of the central area. are doing. The hardness of the tread rubber in the center area of the inner tread portion is made smaller than the hardness of the tread rubber in the side edge areas and the outer tread area, and the hardness of the tread rubber in the inner tread area is placed closer to the side edge area than the center area. The hardness of the tread rubber in the area is set to be as high as the hardness of the tread rubber in the area, and the hardness of the tread rubber in the area disposed on the outermost side in the axial direction of the tire in the inner tread part is set to be less than or equal to the hardness of the tread rubber in the outer tread part. In this way, by decreasing the rubber hardness of the tread toward the inside in the radial direction and toward the inside in the axial direction, it is possible to improve the vibration ride quality without impairing wear resistance.

However, in the above-mentioned vehicle, the tread rubber, that is, the rubber of the inner and outer tread parts, are all made of non-foamed rubber.
Such non-foamed rubber hardly compresses its volume even when compressive force is applied to it, so even if the rubber hardness of a part of the tread, that is, the inner tread part, is reduced as mentioned above, the compression modulus of the entire tread will actually be There was almost no decline, and as a result,
This only improves the vibration ride comfort performance to a certain extent, and the effect in actual use is not sufficient. As for the tensile modulus of ordinary non-foamed rubber, if the rubber hardness is reduced as described above, the tensile modulus of the rubber will decrease correspondingly.

An object of the present invention is to provide a pneumatic tire that can significantly improve vibration riding comfort without impairing wear resistance or the like.

Such an object comprises a pneumatic carcass having a toroidal shape, a belt consisting of at least two layers of rubberized cord arranged radially outwardly of the carcass, and a tread rubber surrounding the belt. This can be achieved by providing a tire in which the tread rubber is composed of a base rubber made of foamed rubber and a cap rubber made of non-foamed rubber and disposed on the outside of the base rubber in the radial direction.

Here, it is preferable to arrange the cap rubber on both sides of the base rubber in the width direction by making the widthwise center of the base rubber approximately coincide with the tire equatorial plane and making the width of the base rubber narrower than the width of the belt. In addition, the foaming rate A of the base rubber is within the range of 10% to 50%, and the ratio b/W between the width of the base rubber and the tread contact width W is 0.15.
Furthermore, the ratio of the maximum thickness T of the tread rubber to the maximum thickness t of the base rubber, t/T, is within the range of 0.85 from 0.85.
It is preferable to set it within the range of 0.05 to 0.50.

January The tread rubber of the pneumatic tire of this invention has a base rubber made of foamed rubber, but when compressive force is applied to such foamed rubber, the air bubbles inside are soaked and the volume is compressed. The compression modulus is smaller than that of non-foamed rubber, and as a result, the compression modulus of the tread rubber is
The rigidity of the tread rubber is lower than that when the entire tread rubber is made of non-foamed rubber. When such a pneumatic tire is run, compressive stress is applied to the tread rubber in the contact area due to the load, and vibrations due to unevenness are input from the road surface. The vibration is damped by the base rubber which effectively compresses the volume, and the ride comfort performance is greatly improved. On the other hand, since the cap rubber placed radially outward of the base rubber is made of non-foamed rubber, the wear resistance performance etc. will not deteriorate.In this way, the present invention improves the wear resistance performance. Vibration ride comfort performance can be significantly improved without any loss.

In addition, by arranging cap rubber not only on the outside in the radial direction of the base rubber but also on both sides in the width direction, the rigidity of both sides and part of the tire and the bending rigidity of the tread rubber of the pneumatic tire can be maintained at the same values as before. This prevents deterioration of steering stability performance, and protects foamed rubber, ie, base rubber, which wears out quickly, from wear. Furthermore, if the foaming ratio A, ratio b/W, and gauge ratio t/T are kept within the ranges mentioned above, both vibration riding comfort performance and steering stability performance can be improved compared to conventional tires. It is also possible to prevent a decline in the generous lifespan.

Difference 1 A first embodiment of the present invention will be described below based on the drawings.

In Fig. 1, 1 is a pneumatic tire, and this tire 1 has a toroidal shape, and has a carcass 3 whose axial ends are folded back around a bead 2, and a belt disposed on the outside of the carcass 3 in the radial direction. 4 and this belt 4
tread rubber 5 surrounding the periphery of the tread rubber. The belt 4 is constructed by laminating at least two rubberized cord layers 6. The tread rubber 5 is composed of a base rubber 8 located on the inside in the radial direction and made of foamed rubber having a large number of closed cells inside, and a cap rubber 8 located on the outside in the radial direction and made of non-foamed rubber. has been done. Here, when compressive force is applied to the foamed rubber constituting the base rubber 8, the internal closed cells collapse and the volume is compressed. Moreover, the base rubber 8 is arranged so that its center in the width direction substantially coincides with the tire equatorial plane 10, and
The width ll@b is narrower than the width of the belt 4, so that the gap rubber 8 made of non-foamed rubber is arranged on the outside of the base rubber 8 in the radial direction and on both sides in the width direction. As a result, the cap rubber 8 surrounds the base rubber 8 from the outside and both sides, and as a result, the rigidity of both cylinder parts 11 of the tire l and the bending rigidity of the tread rubber 5 completely eliminate the tread rubber. The value is maintained at approximately the same value as in the case of foamed rubber, thereby preventing a decrease in steering stability, and the foamed rubber, that is, the base rubber 8, which wears quickly, is protected from wear. Then, the ratio b/W of @b of this base rubber 8 to the tread contact width W when the tire 1 is mounted on a standard rim, filled with the normal internal pressure, and a standard load is applied, is from 0.15. 0.
It is preferable that the ratio is within the range of 65, because the ratio b
This is because if /W is less than 0.15, the vibration riding comfort performance will be lower than that of conventional tires, as will be described later.
．． This is because if it exceeds 85, the steering stability performance will similarly be lower than that of conventional tires. Further, the foaming ratio A of the base rubber 8 is preferably within the range of 10% to 50%.The reason is that when the foaming ratio A is less than 10%, as will be described later, the vibration riding comfort performance is lower than that of a conventional tire. On the other hand, if it exceeds 50%, the steering stability performance will be lower than that of conventional tires and the generous life will be sharply reduced. Here, the foaming rate is 1 from the value obtained by dividing the specific gravity of only the rubber in the foam rubber by the specific gravity of the entire foam rubber including bubbles.
It is the value obtained by subtracting , and multiplying the result by 100. Further, the gauge ratio t/T between the maximum thickness T of the tread rubber 5 and the maximum thickness t of the base rubber 8 is 0.05 to 0.50.
The reason is that if the gauge ratio t/T is less than 0.05, the vibration riding comfort performance will be lower than that of conventional tires, as will be described later. This is because, if the tire exceeds this value, the base rubber 8, which wears out at a high rate, will be exposed on the tire surface at the end of wear, resulting in a sharp reduction in the generous service life, and at the same time, the handling stability performance will be lower than that of conventional tires. In addition, the tread surface of tire 1! If a deep main groove 17 is formed in the main shaft 17, the base rubber 8 may be exposed at the groove bottom of the main shaft 17, but such a base rubber 8 made of foamed rubber is weaker than non-foamed rubber and breaks easily. Therefore, the base rubber 8 should not be exposed at the bottom of the main groove 17.
The outer surface is recessed radially inward.

Then, after installing such a tire l on a vehicle, the tire ! When you rotate the vehicle and run the vehicle.

Compressive stress acts on the tread rubber 5 in the contact area due to the load, and vibrations due to unevenness are input from the road surface. Here, since the base rubber 8 of the tire 1 is made of foamed rubber whose compression modulus is reduced to about 2 for each layer of non-foamed rubber, the input vibration effectively compresses the volume under compressive stress. The base rubber 8 significantly absorbs and damps vibrations, greatly improving the ride quality of the vehicle. - On the other hand, since the cap rubber 9 disposed radially outward of the base rubber 8 is made of non-foamed rubber with a slow wear rate, the wear resistance does not deteriorate.

Next, the first test example will be explained. For this test, Comparative Tire 1 whose tread rubber was entirely made of non-foamed rubber and Test Tires 1 to 7 to which the present invention was applied were prepared. Here, the specifications of each tire are as shown in Attached Table 1, and the size of each tire is 185/70S R14.Next, each such tire was installed on a passenger car, and its vibration ride comfort performance was evaluated. The evaluation was based on the driver's feeling.

The results are shown in index form in Attached Table 1, and as is clear from Attached Table 1, the vibration riding comfort performance of the test tires has improved. As shown in FIGS. 2 and 3, this vibration riding comfort improves as the value of the foaming ratio A increases and as the value of the gauge ratio L/T increases. In addition, in this test, the tire was run for a long period of time to measure its generous lifespan. Here, the generous service life refers to the mileage l1l (10,000 km) when the remaining groove of the main groove becomes 1.0 cm or less in at least one place, and the main groove is the deepest part on the tread. 6 The results are shown in Attached Table 1 and Section 4.5.
As shown in the figure, it can be understood from the results that the higher the value of the foaming ratio A and the larger the value of the gauge ratio t/T, the lower the generous life. When the foaming ratio A exceeds 50%, the gauge ratio t/T also becomes 0.
．． If it exceeds 50, the generous lifespan will decrease rapidly, so it is preferable that the foaming ratio A is 50% or less and the gauge ratio t/T is also 0.50 or less.

Next, a second test example will be explained. In this test, comparative tires 2 and 3 whose tread rubber was entirely made of non-foamed rubber, test tires 8 to 14 to which the present invention was applied,
? Got ready. Here, Comparative Tire 2 is a tire that achieves both conflicting vibration ride comfort performance and handling stability performance by selecting the type of non-foamed rubber, and has a vibration ride comfort performance and handling stability performance that are sufficient for practical use. have. Also, the tire size used in this test was 185/70S R14.
And, the tread contact width W of each tire is 121
1, and the specifications of each tire are as shown in Attached Table 2.Next, after each tire is installed on a passenger car, it is driven on a test course, and the vibration ride comfort performance and steering stability performance are evaluated by the driver. The evaluation was based on the feeling. The results are shown in the attached table and Figures 6 to 11. From this test, the vibration riding comfort performance is shown in attached table 2. As can be understood from Figures 6 and 7.8, the larger the ratio b/W, the larger the gauge ratio t.
The larger /T and the higher the foaming rate A, the better. However, when the ratio b/W is less than 0.15, when the gauge ratio t/T is less than 0.05, and when the 1 foaming ratio A is less than 10%, the vibration riding comfort performance is lower than that of the comparative tire mentioned above. Since the ratio b/
W is preferably 0115 or more, gauge ratio t/T is 0.55 or more, and foaming ratio A is preferably 10% or more.
On the other hand, the handling stability performance is shown in Appendix 2. As is clear from FIG. 9.10.11, the larger the ratio b/W, the larger the gauge ratio t/T, and the larger the foaming ratio A, the lower the ratio. When the ratio b/W exceeds 0.65, and when the gauge ratio t/T exceeds 0.50.

Furthermore, if the foaming ratio A exceeds 50%, the steering stability performance will be lower than that of Comparative Tire 2, so the ratio b/W is 0.
．． 65 or less, the gauge ratio t/T is preferably 0.50 or less, and the foaming ratio A is preferably 50% or less.
In Attached Table 2, 10% compression modulus means that static compressive force is applied uniformly from above and below to a rubber flat plate of 40 mm in length and width and 10 cm in thickness, and this rubber flat plate is 10% in the thickness direction.
It is the value obtained by dividing the compressive stress value when compressed by 0% by the compressive strain.

FIG. 12 is a diagram showing a second embodiment of the invention. In this embodiment, the center of the base rubber 21 in the width direction is separated from the tire equatorial plane lO, and here the entire base rubber 21 is disposed on one side of the tire equatorial plane 10. In this way, in the pneumatic tire whose mounting position is determined, it is possible to achieve both wear resistance performance and vibration riding comfort performance. Note that the other configurations and functions are the same as those of the first embodiment.

FIG. 13 is a diagram showing a third embodiment of the present invention. In this embodiment, narrow base rubbers 22 and 23 are provided on both sides of the tire equatorial plane 10, and the cap rubber 9 is arranged between these base rubbers 22 and 23. Here, the total value of the widths c and d of the base rubber 22 and 23 is equal to the width of the base rubber 8 in the first embodiment, and by doing so, the load bearing within the tread surface becomes uniform. , it is possible to achieve both prevention of uneven wear and improvement of vibration riding comfort. Note that the other configurations and functions are the same as those of the first embodiment.

In the above-mentioned embodiment, the radially outer surface of the base rubber 8 was made substantially flat, but in the present invention, the radially outer surface may be corrugated in the width direction of the base rubber 8. If you do it like this.

It is possible to prevent the exposed area of the base rubber 8 from rapidly increasing in the final stage of wear.

11. As explained above, according to the present invention, the vibration riding comfort performance can be significantly improved without impairing wear resistance and the like.

[Brief explanation of the drawing]

FIG. 1 is a meridian cross-sectional view showing the first embodiment of the present invention, FIG. 2 is a graph showing the results of the first test example, that is, a graph showing changes in vibration comfort performance with respect to foaming ratio, and FIG. The results of the test example, that is, the graph showing the change state of the vibration riding comfort performance with respect to the gauge ratio t/T, FIG. 4 is the result of the first test example,
That is, a graph showing changes in generous lifespan with respect to foaming rate,
Fig. 5 is a graph showing the results of the first test example, that is, changes in generous life with respect to the gauge ratio t/T, and Fig. 6 is a graph showing the results of the second test example, that is, the vibration ride comfort performance with respect to the ratio b/W. 7 is a graph showing the results of the second test example, that is, a graph showing the changes in vibration ride comfort performance with respect to the gauge ratio t/T, and FIG. 8 is a graph showing the results of the second test example, that is, the changes with respect to foaming ratio FIG. 9 is a graph showing the change state of vibration ride comfort performance, the result of the second test example, that is, a graph showing the change state of steering stability performance with respect to the ratio b/W, FIG. 10 is the result of the second test example,
That is, FIG. 11 is a graph showing changes in steering stability performance with respect to gauge ratio t/T, FIG. 11 is a graph showing changes in steering stability performance with respect to foaming ratio, and FIG.
The figure is a meridian sectional view showing a second embodiment of the invention, and FIG. 13 is a meridian sectional view showing a third embodiment of the invention. l...Pneumatic tire 3...Carcass 4...
Belt 5...Tread rubber 6...Rubberized cord layer 8...Base rubber 9...Cap rubber lO...Tire equatorial plane Patent applicant Brideston Co., Ltd. Agent Patent attorney Ta 1) Yuji Toshi Figure 1... Pneumatic tire 4... Belt 6... Rubberized cord layer 9... Cap rubber 3... Carcass 5... Tread rubber 8... Base rubber 10... Tire equator Surface foaming rate (-□ Gekiseven (t/T) - Foaming rate (〃) - Gauge ratio (L/Tl - Ratio (b/W) Gauge ratio (t/Tl) Foaming rate (-□ Ratio (b/Wl) - Diagram gauge ratio (t/T) - Foaming rate (〃) - Diagram

Claims (5)

[Claims] (1) A pneumatic tire comprising a toroidal carcass, a belt made of at least two rubberized cord layers disposed radially outside the carcass, and tread rubber surrounding the belt. A pneumatic tire characterized in that the tread rubber is composed of a base rubber made of foamed rubber and a cap rubber made of non-foamed rubber and arranged radially outward of the base rubber. (2) The foaming rate A of the base rubber is 10% to 50%.
The pneumatic tire according to claim 1, which falls within the range of: (3) By aligning the center of the base rubber in the width direction with the tire equatorial plane and making the width of the base rubber narrower than the width of the belt, cap rubber is arranged on both sides of the base rubber in the width direction. The pneumatic tire according to claim 1. (4) Let W be the tread contact width when the normal internal pressure is filled and a standard load is applied, and b be the width of the base rubber.
Claim 1 wherein b/W is within the range of 0.15 to 0.65.
Pneumatic tires listed. (5) When the maximum thickness of the tread rubber is T and the maximum thickness of the base rubber is t, t/T is 0.05 to 0.
5. A pneumatic tire according to claim 1, wherein the pneumatic tire is within the range of up to 50.