JPH04365605A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To improve a drive feeling by reducing the road noise and vibration of a pneumatic tire. CONSTITUTION:The road noise is reduced by absorbing the vibration transmitted from a road surface by forming the vibration suppressing rubber members 11 and 9 having the high diving performance on the inner peripheral surface of the tread part T and the head part of a tire 1. Further, the rubber having the less dynamic factor, heat generation and energy loss is used for the topping rubber of the side wall rubber 8 and the carcass 2 of the tire 1, and the intensity of the vibration which is transmitted from the road surface is reduced, and the drive feeling is improved. By using the rubber having the less dynamic factor, the rolling resistance of the tire 1 can be reduced, and fuel consumption is improved.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire that effectively absorbs and reduces vibrations received from the road surface, reduces road noise and vibrations, and improves ride comfort.

0002

[Prior Art] Pneumatic tires for automobiles include a bias tire in which ply cords constituting a carcass are arranged so as to alternately intersect with the circumferential direction of the tire; Radial tires are arranged perpendicularly to the radial tire and are covered with a belt layer on the outside that can support the load in the circumferential direction of the tire. Bias tires provide a soft ride because the crossed ply cords deform into a pantograph shape under the load from the road surface, but on the other hand, due to the deformation, various parts of the tread contact surface move in different directions, which tends to cause wear. There is a problem. On the other hand, radial tires have the advantage of increasing the rigidity of the tread due to the action of the belt layer, providing good handling stability and wear resistance, and have become rapidly popular in recent years instead of the aforementioned bias tires. It shows.

0003

[Problems to be Solved by the Invention] However, the radial tires are inferior to normal bias tires in terms of ride comfort performance due to their structural fate, and improving this ride comfort performance is a major issue for radial tires. ing.

That is, in general, radial tires, and in particular so-called steel radial tires that use steel cord as a belt material, have a steel cord layer that has an extremely high tensile strength compared to the ply cord layer of the carcass, which is parallel or shallow to the circumferential direction of the tire. It is placed at an angle. For this reason, the bending rigidity of the tread portion in the circumferential direction increases, making it difficult to deform due to protrusions of various sizes existing on the road surface, and extremely large impact forces are generated when riding over the protrusions. . Although some of this impact force is absorbed by the sidewalls, the impact force that cannot be absorbed is transmitted to the vehicle body via the bead and wheels, causing vibration and road noise, which significantly impairs comfort. be. However, as mentioned above, radial tires achieve handling stability and wear resistance due to the high rigidity of the tread, so reducing the rigidity of the tread in order to improve ride comfort is not a good idea. This is undesirable as it results in the loss of the desired characteristics.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a pneumatic tire with excellent riding comfort performance.

[0006]

[Means for Solving the Problems] In order to achieve the above-mentioned object, the pneumatic tire of the present invention has a structure in which the inner peripheral part of the tire corresponding to the tread part or the peripheral part of the bead wire is larger than other rubber members of the tire. The first feature is that a damping rubber member having a loss tangent is provided.

Furthermore, the pneumatic tire of the present invention has a damping rubber member having a loss tangent larger than other rubber members of the tire arranged at the inner circumference of the tire corresponding to the tread portion and around the bead wire. is the second feature.

In addition to the first or second feature described above, the third feature of the present invention is that a material having a dynamic magnification of 1.10 or less is used for the sidewall rubber or the topping rubber of the carcass.

In addition to the above-mentioned first or second feature, the present invention has a fourth feature in that a material having a dynamic magnification of 1.10 or less is used for the sidewall rubber and the topping rubber of the carcass.

0010

Embodiments Hereinafter, embodiments of the present invention will be explained based on the drawings.

FIG. 1 is a sectional view of a radial tire according to a first embodiment of the present invention. As shown in the figure, the tire 1 includes a tread portion T located on its outer periphery and forming a ground contact surface, a sidewall portion S extending on both left and right sides of the tread portion T and forming tire side walls, and the sidewall portion. S
It consists of a bead part B provided on the inner periphery of the wheel and connected to the wheel.

The carcass 2, which constitutes a strength member for maintaining the air pressure filled inside the tire 1, is made of a ply cord made of rayon, nylon, polyester, etc., in a direction perpendicular to the circumferential direction of the tire 1. The surface is covered with topping rubber. Both ends of the carcass 2 are wound around a ring-shaped bead wire 3 embedded in the bead portion B and folded back in order to resist the air pressure. A hard apex rubber 4 is disposed in a wedge-shaped space formed between the double-folded carcass 2 at the bead portion B.
This increases the lateral rigidity of the tire 1 in order to maintain its cornering performance.

The carcass 2 has a ply cord connected to the tire 1.
Since the carcass 2 is disposed perpendicularly to the circumferential direction and cannot support the load in the circumferential direction, two layers of steel belts 5 are laminated on the outside of the carcass 2 in the tread portion T and a belt reinforcing ply 6 is provided. Fixed. Said steel belt 5
The steel cord is arranged parallel to the circumferential direction of the tire 1 or at a shallow angle, and its high tensile strength increases the rigidity of the tread portion T in order to improve handling stability and wear resistance.

A tread pattern 7 is provided on the outer side of the belt reinforcing ply 6 in the tread portion T of the tire 1.
Thick tread rubber 7 having a contact surface formed with a is laminated. The tread rubber 7 is a member that transmits various forces acting in the vertical direction, traveling direction, and lateral direction between the tire 1 and the road surface, and is made of a material that satisfies conditions such as wear resistance, cut resistance, and skid resistance. Ru. The outer surface of the sidewall portion S of the tire 1 is covered with a sidewall rubber 8 having bending resistance to protect the carcass 2. Further, the peripheries of the bead wire 3 and the apex rubber 4 are covered with a damping rubber member 9, and the outside thereof is further covered with a rim strip rubber 12 and an inner liner layer 10. Thus, the outer shape of the tire 1 is formed by the tread rubber 7, sidewall rubber 8, and rim strip rubber 12.

The inner surface of the tire 1 corresponding to the tread portion T and the sidewall portion S is coated with an inner liner layer 10 made of a material with low air permeability in order to maintain airtightness without using a tire tube. And tread part T
The inner surface of the inner liner layer 10 corresponding to the above is covered with a vibration damping rubber member 11 made of the same material as the vibration damping rubber member 9.

Next, the damping rubber members 9 and 11 will be explained. The properties of rubber having viscoelasticity are represented by a damper component and a spring component as a mechanical model, and the damping rubber members 9 and 11 have a relatively large damper component, that is, a rubber member with damping performance that absorbs vibrations. Rubber members with high resistance are used. Rubber members with such a large damper component have the property of converting deformation into thermal energy, and therefore generate heat when used in areas where the amount of deformation is large, such as the tread rubber 7, sidewall rubber 8, carcass 2, and inner liner layer 10 of the tire 1. However, when used in areas with a small amount of deformation, such as the inner surface of the inner liner layer 10 corresponding to the tread portion T or the bead portion B, it does not generate much heat. It can effectively absorb vibration.

The loss tangent tan δ, that is, the ratio of the loss modulus to the storage modulus (tan δ = loss modulus/storage modulus) is used as an index representing the magnitude of the damping performance of the damping rubber members 9 and 11. , the larger the value of the loss tangent tan δ, the greater the damping performance. Loss tangent tan δ of vibration damping rubber members 9 and 11 in the present invention
is preferably 0.3 or more, for example, and the value is set to be larger than the loss tangent tan δ of other rubber members such as the tread rubber 7, sidewall rubber 8, carcass 2, and inner liner layer 10 of the tire 1. It is determined. Note that the relative magnitude of the loss tangent tan δ of the vibration damping rubber member 9 and the vibration damping rubber member 11 has no direct effect on performance.

Examples of the composition of the vibration damping rubber members 9 and 11 are shown below.

Out of 100 parts by weight of polymer, 5 to 100 parts by weight of polynorbornene rubber, preferably 2
0 to 60 parts by weight ■ Elastomer NR (natural rubber) SBR (styrene butadiene rubber) BR (butadiene rubber), etc. In addition to the above polymers, reinforcing materials and/or fillers such as carbon black can be used. A combination of ingredients is added.

Now, vibrations received from the road surface when the vehicle is running are transmitted from the tread portion T of the tire 1 to the steel belt 5.
, is transmitted to the vehicle body via the sidewall portion S, bead portion B, wheels, and suspension. At this time, since the rigidity of the steel belt 5 is extremely high, the tread portion T
The vibrations entering from the side wall portion S are transmitted to the sidewall portion S with almost no attenuation. However, by providing the damping rubber member 11 on the inner circumference of the inner liner layer 10 corresponding to the tread portion T, the vibration of the steel belt 5 can be effectively absorbed, and the vibration transmitted to the sidewall portion S. can be reduced. Furthermore, vibrations transmitted to the sidewall portion S without being completely absorbed by the vibration damping rubber member 11 are
The vibration is effectively absorbed by the damping rubber member 9 installed around the bead wire 3, and the transmission to the wheel can be made very small.

As mentioned above, if a rubber member with high damping performance is applied to the tread part T, which tends to rise in temperature due to friction with the road surface, and the sidewall part S, which is deformed due to loads and tends to rise in temperature, the heat generation effect of the rubber member increases. There is a risk that the temperature of the tire 1 will rise excessively and the performance will deteriorate. However, by applying a rubber member with high damping performance to the inner peripheral part of the inner liner layer 10 corresponding to the tread part T that does not come into direct contact with the road surface and to the bead part B, which has a small amount of deformation due to load, the temperature rise of the tire 1 can be reduced. It is possible to effectively prevent road noise by blocking vibrations from the road surface while avoiding vibrations. For these reasons, even when the damping rubber member 11 is used at the inner circumferential portion of the inner liner layer 10, it is preferably used only at the portion corresponding to the tread portion T where the amount of deformation due to load is particularly small.

FIG. 2 shows the loss tangent tan of the tread rubber 7.
δ is 0.29, loss tangent tan δ of carcass 2 is 0.1
1. Loss tangent tanδ of sidewall part S is 0.16
, the loss tangent tan δ of the inner liner layer 10 is 0.3
0, and the loss tangent tan of the vibration damping rubber members 9 and 11
Vehicles equipped with the original tire with δ of 0.399 (shown by broken lines) and general tires (shown by solid lines) that do not use vibration damping rubber members 9 and 11 were driven for 60 km on a rough road at a temperature of 25°C. This is a graph comparing the sound pressure level inside the vehicle when the vehicle is traveling at a constant speed at h. The above loss tangent ta
nδ was measured using a viscoelasticity measuring device manufactured by Iwamoto Seisakusho.
A test piece of x5 x 40 mm was tested under conditions of initial strain of 10%, dynamic strain of 0.2%, air temperature of 25°C, and frequency of 10Hz. As is clear from this graph, the sound pressure level has clearly decreased except in some low frequency areas and some high frequency areas, indicating that road noise reduction has been achieved through the use of high damping rubber. is understood.

FIG. 3 shows a second embodiment of the present invention.
In this embodiment, rubber members with a small dynamic magnification are used for the topping rubber of the carcass 2 of the tire 1 and the sidewall rubber 8 to reduce the intensity of vibration, thereby improving ride comfort and reducing rolling resistance. .

The dynamic magnification of rubber is defined as the quotient of the storage elastic modulus when high frequency vibrations are input divided by the storage elastic modulus when low frequency vibrations are input. Rubber with a small dynamic magnification has a small damper component and a large spring component, so even when high-frequency vibrations are input, the spring does not become stiff, and has the property of having small energy loss, which reduces displacement. Even when used in large areas, the vibration intensity can be reduced without generating heat. Furthermore, the amount of rolling resistance of the tire 1 largely depends on the distortion of the contact area with the road surface.
Sidewall rubber that is highly deformed due to contact with the road surface 8
If a rubber having a large damper component is used as the topping rubber of the carcass 2 or the carcass 2, the thermal energy generated due to its deformation is lost as an increase in rolling resistance. However, by using rubber with a small damper component, that is, a rubber with a small dynamic magnification, for the sidewall rubber 8 and the topping rubber of the carcass 2, the heat generation can be prevented and the rolling resistance can be reduced.

A rubber having such a low dynamic ratio can be obtained, for example, by blending NR and BR with a small vinyl content as polymers in a ratio of 6:4 and further reducing the amount of carbon black.

In order to improve the scratch resistance and durability of the sidewall portion S, in the embodiment shown in FIG.
Rubber 71 with a large amount of carbon black on the surface (for example, there are NR/BR type or NR/SBR/BR type rubbers with a carbon black amount of 30 PHR or more.
is expressed in parts by weight based on 100 parts by weight of rubber. ) for protection. Here, the rubber 71 is particularly affected by the sidewall part S due to foreign matter on the road.
This is a member for effectively preventing damage to the sidewall portion S, and is provided on the outer surface of the sidewall portion S and closer to the tread portion T than the most protruding portion of the sidewall portion S. The rubber 71 with a large amount of carbon black is integrally molded as a part of the tread rubber 7. That is, a nozzle that discharges the material for the main body of the tread rubber 7 and two or more nozzles that discharge the material of the rubber 71 with a large amount of carbon black are placed side by side on both sides of the tread rubber 7, and two types of materials are disposed. It is integrally molded by passing it through a die at the same time. Thereby, the tire of the present invention can be manufactured without increasing the number of steps compared to conventional tires.

Next, a test example of the tire according to the second embodiment will be shown.

Table 1 compares the characteristics of Tire 1 (■ to ■) of the second embodiment and general tires (■ to ■), and the dynamic magnification of the sidewall rubber 8 and the topping rubber of the carcass 2 is the same as that of the present invention. The elastic modulus of the tread rubber 7 is set to be small (1.05), and large (1.15 or 1.25) for ordinary ones.
35×10-7 dyn/cm2). Note that the tire 1 of this test example did not include the vibration damping rubber members 9 and 11 of the first embodiment.

The dynamic magnification and elastic modulus were measured using a viscoelasticity measuring device manufactured by Iwamoto Seisakusho.
The test was conducted at frequencies of 10 Hz and 100 Hz. here,
Dynamic magnification=storage modulus at 100 Hz vibration/storage modulus at 10 Hz vibration Elastic modulus=storage modulus at 10 Hz vibration, and ride comfort is a sensory evaluation. In addition, the rolling resistance index is shown in Figure 4.
As shown in the figure, the diameter 1708 rotates at a circumferential speed of 80 km/h.
The tangential resistance f1 that the rotating shaft S of the tire T receives when the tire T is pressed against the drum D of mm with a load of 300 kgf
was determined based on the resistance f1.

[0030]

[Table 1]

As is clear from Table 1, the tire of the present invention ■
It is understood that tires 1 to 2 are superior to general tires 1 to 2 in terms of ride comfort, that is, reduction in harshness and shock feeling, and reduction in rolling resistance. From the above test examples, it is desirable that the dynamic magnification of the sidewall rubber 8 and the topping rubber of the carcass 2 be 1.10 or less.

Next, another test example of the tire according to the second embodiment will be shown.

The tire 1 of this test example has the damping rubber members 9 and 11 of the first embodiment (loss tangent tan δ = 0.399).
In this tire, a rubber member with a small dynamic magnification is further applied to the sidewall rubber 8 and the topping rubber of the carcass 2. As shown in Table 2, the materials of the sidewall rubber 8 and the topping rubber of the carcass 2 are as follows:
NR and BR with a small vinyl content are used as the polymer, and the amount of carbon black is reduced to increase the dynamic magnification to 1.
It has been lowered to 05.

[0034]

[Table 2]

Furthermore, in order to improve grip properties, the following compositions of tread rubber are selected, and in order to improve steering response with high-rigidity rubber, the topping rubber of the steel belt 5 and the apex rubber 4 are selected. The following formulations are selected: ■ Tread rubber S-SBR=100 Carbon black ISAF 1
00PHR oil aromatic 75PHR plasticizer
DOS10
PHR■ Steel belt topping rubber NR/B
R=80/20 carbon black HAF
50PHR sulfur
5PHR■
Apex rubber NR/BR=80/20 carbon black HAF
75PHR modified alkylphenol resin
10PHR sulfur

5PHR Fig. 5 shows a test device that measures the vertical load f2 acting on the rotating shaft S of a tire T mounted on a plate P that vibrates vertically with a constant acceleration a, and the load f2 is expressed as the acceleration a. The graph of FIG. 7 shows the relative intensity divided by dB relative to a constant reference value. As is clear from the graph of FIG. 7, it is understood that the vibration level of the tire according to the invention (shown by a broken line) is lower than that of the conventional tire (shown by a solid line).

FIG. 6 shows a test device in which the protrusion D1 of the drum D of the test device shown in FIG.
(enveloping power) is measured. Figure 8 is Figure 6
This is a graph showing the enveloping power measured by the test device shown in FIG. 1, in which the enveloping power of the tire according to the present invention (shown by a broken line) is smaller than that of a general tire (shown by a solid line).

FIG. 9 shows rolling resistance values measured using the above-mentioned test apparatus shown in FIG. 4, and the rolling resistance value of the tire of the present invention is lower than that of a general tire.

FIG. 10 shows a modification of the second embodiment, in which rubber 8 with a large amount of carbon black is used to improve the scratch resistance and durability of the sidewall portion S.
1 is integrally molded as a part of the sidewall rubber 8. Further, FIG. 11 shows another modification of the second embodiment, in which a rubber 81 containing a large amount of carbon black is integrally molded to cover the entire outer surface of the sidewall rubber 8. In this case, the thickness of the main body of the inner sidewall rubber 8 needs to be greater than the thickness of the outer rubber 81 having a large amount of carbon black. Comparing the above three types with different arrangements of rubber 81 with a large amount of carbon black, the ones in FIGS. 3 and 10 are superior in terms of ride comfort.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-mentioned embodiments, and various small design changes can be made without departing from the scope of the invention described in the claims. It is possible to do this.

For example, in the first embodiment, the tread portion T
The inner surface of the inner liner layer 10 and the bead portion B corresponding to
Although damping rubber members 9 and 11 with high damping performance are used at two locations near the damping member, a sufficient effect can be obtained by using them at just one location. Further, in the second embodiment, rubber members with a small dynamic magnification are used in two places, the topping rubber of the carcass 2 and the sidewall rubber 8, but sufficient effects can be obtained even if they are used in only one place. Can be done. Further, when using the rubber member with a small dynamic magnification, it is not necessarily necessary to use it in combination with the vibration damping rubber members 9, 11 having high damping performance, and the effect can be exhibited even when used alone. Although the present invention exhibits particularly excellent effects when applied to radial tires as described above, it is clear that it can also be applied to bias tires.

[0041]

As described above, according to the first or second feature of the present invention, the vibration damping rubber member having high damping performance deforms due to vibrations from the road surface, thereby absorbing the kinetic energy of the vibrations. This reduces road noise transmitted to the vehicle body, improving ride comfort.

According to the third or fourth feature of the present invention, the vibration damping rubber member with high damping performance and the rubber member with low dynamic magnification reduce the intensity of vibrations transmitted from the road surface to the vehicle body and road noise. and ride comfort performance is improved. Moreover, since the rolling resistance of the tires is reduced, the amount of fuel consumed by the engine can be reduced.

[Brief explanation of drawings]

FIG. 1: Cross-sectional view of a tire according to a first embodiment of the present invention.

[Figure 2]
Graph showing road noise reduction characteristics of the tire of the first example

FIG. 3 is a sectional view of a tire according to a second embodiment of the present invention.

[Figure 4]
Diagram showing how to measure rolling resistance value

[Figure 5] Diagram showing how to measure vibration level

[Figure 6] Diagram showing how to measure enveloping power

[Fig. 7] Graph showing the vibration level of the tire of the second example

[Fig. 8] Graph showing the enveloping power of the tire of the second example.

[Figure 9] Graph showing the rolling resistance of the tire of the second example

FIG. 10 is a sectional view of a tire according to a modification of the second embodiment.

[
FIG. 11: Cross-sectional view of a tire according to another modification of the second embodiment

[Explanation of symbols]

2...Carcass 3...Bead wire 8...Side wall rubber 9...Rubber member for vibration damping 11...Rubber member for vibration damping T...Tread section

Claims (4)

[Claims] Claim 1: A damping rubber member (9, 11) having a loss tangent larger than other rubber members of the tire is provided at the inner circumference of the tire corresponding to the tread portion (T) or at the periphery of the bead wire (3). A pneumatic tire characterized by the arrangement of. 2. Vibration damping rubber members (9, 11) having a loss tangent larger than other rubber members of the tire are provided in the inner circumference of the tire corresponding to the tread portion (T) and in the periphery of the bead wire (3). A pneumatic tire characterized by the arrangement of. 3. The pneumatic tire according to claim 1, wherein the sidewall rubber (8) or the topping rubber of the carcass (2) is made of a material having a dynamic magnification of 1.10 or less. 4. The pneumatic tire according to claim 1, wherein a material having a dynamic magnification of 1.10 or less is used for the sidewall rubber (8) and the topping rubber of the carcass (2).