JPH11170814A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the electric conductivity, the low rolling resistance, the wet performance, and the wear resistance by forming a through part and a wing part of a specific electric conductive rubber, forming a cap part of a specific insulation rubber, setting the loss tangent of the rubber to be a specific value, and specifying the width of an exposed surface of the through part. SOLUTION: A tread rubber 10 is provided with a through part 11 having an exposed surface on a ground-contact part, a wing part 12 and a main part 13. The main part 13 comprises a base part consisting of a low heat generation rubber in which the loss tangent (tanδ) of the rubber to which emphasis is given to the low rolling resistance is <=0.10, and a cap part 16 in which the volumetric specific electric resistance shows the high insulation of >=10<8> Ω. The through part 11 and the wing part 12 are formed of an electric conductive rubber in which emphasis is placed on the electric conductivity and the volumetric specific electric resistance is below 10<8> Ωcm, and the excellent electric conductivity and wear resistance are provided. The width of the exposed surface of the through part in the axial direction of a tire is 1.0-15.0 mm. The excellent wear resistance, the wet performance and the low rolling resistance are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tire using silica or the like as a reinforcing agent for a tread rubber, which exhibits excellent low rolling resistance performance and wet performance while effectively discharging static electricity generated on a vehicle to a road surface. The present invention relates to a pneumatic tire capable of discharging and stably exhibiting these characteristics from the initial use to the final use.

[0002]

2. Description of the Related Art In recent years, tires using silica or the like as a main reinforcing agent for tread rubber have been proposed in order to improve the fuel efficiency of automobiles. This product exhibits excellent wet performance because the hysteresis loss on the low temperature side is maintained high, while exhibiting low rolling resistance due to low hysteresis loss on the high temperature side, and achieves both low rolling resistance performance and wet performance. There is an advantage that it can be improved.

[0003] However, silica has a high electrical insulating property, and therefore, when a tread rubber containing silica is used, the electrical resistance of the tire is increased, and static electricity is accumulated in a vehicle to cause radio interference such as radio noise. This causes many electrical malfunctions.

In order to improve the electric resistance of a tire, for example, JP-A-8-244409 discloses a method in which a conductive thin film containing carbon black is attached to the surface of tread rubber containing silica. 9-71
No. 112 discloses that a tread rubber is formed by a cap rubber layer (containing silica) on the tread surface side and a conductive base rubber layer on the belt layer side, and a part of the base rubber layer is raised to form a tread. One that is exposed on the surface has been proposed.

[0005]

However, in the former, since the entire surface of the tread rubber containing silica is exposed due to the abrasion of the outer conductive thin film, the electric resistance and other tires before and after this exposure are different. It is difficult to exhibit stable performance from the initial stage of wear (when a new tire is used) to the end of wear, for example, causing a significant change in performance.

In the latter case, it is necessary to mix carbon black at a high ratio in order to impart conductivity to the inner base rubber layer. Therefore, the hysteresis loss on the base rubber layer side is increased, and the effect of improving the low rolling resistance performance by the cap rubber layer (containing silica) cannot be sufficiently obtained.

[0007] Accordingly, the present invention provides a tread rubber main part,
For example, it is formed by a cap portion made of silica or the like and a base portion made of a low heat-generating rubber material, and imparts conductivity to the belt layer, while a penetrating portion made of a conductive rubber material stands directly from the belt layer to the tread surface. Raising, and on the basis of providing a wing portion of a conductive rubber material on both sides of the main portion, the tire can reduce the tire electrical resistance while achieving excellent low rolling resistance performance and wet performance by the cap portion, and An object of the present invention is to provide a pneumatic tire that can exhibit these characteristics stably from the initial use to the final use.

[0008]

In order to achieve the above-mentioned object, a pneumatic tire according to the present invention comprises a tread disposed radially outside a conductive belt layer and forming a tread surface and buttress surfaces on both sides thereof. The rubber extends from the belt layer and has an exposed surface that is exposed at a ground contact portion of the tread surface and a through portion that is continuous in a tire circumferential direction, a wing portion that forms the buttress surface, and the through portion between the wing portions. And the main portion is filled with the exposed surface remaining, and the main portion is composed of a base portion on the belt layer side and a cap portion on the tread surface side, and the side portion in the tire axial direction of the main portion is the aforementioned. While being covered by the wing portion, the penetration portion and each wing portion are made of a conductive rubber material having a volume specific electrical resistance value of less than 10 ⁸ Ωcm, and the cap portion is
It is made of an insulating rubber material having a volume specific electric resistance of 10 ⁸ Ωcm or more, and the base portion has a loss tangent t of the rubber.
It is formed of a low heat-generating rubber material having an δ of 0.10 or less, and the width of the exposed surface of the through portion in the tire axial direction is 1.0 to 15.0 mm.

It is preferable to form the penetrating portion and each wing portion with a conductive rubber material having the same composition from the viewpoint of improving the productivity, whereby the tread rubber can be formed by using a conventional triple head tread extruder. And can be integrally extruded.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, a pneumatic tire 1 (hereinafter referred to as a tire 1) is, in this example, a pneumatic tire for a passenger car, and includes a tread portion 2 and a pair of sidewall portions extending inward in the tire radial direction from both ends thereof. 3
And a bead portion 4 located at a radially inner end of each side wall portion 3 in the tire radial direction. The tire 1 is reinforced by a carcass 6 bridged between the beads 4 and a tough belt layer 7 wound radially outside the carcass 6 and inward of the tread portion 2. Tire rigidity is provided.

In the carcass 6, the carcass cords are arranged at an angle of 75 to 90 degrees with respect to the tire equator C.
Or more, in this example, two inner and outer carcass plies,
The bead portion 4 is folded around the bead core 5 from the tread rubber portion 2 to the side wall portion 3 and locked.

The belt layer 7 is composed of two or more belt plies 7A and 7B in which the belt cords are arranged at an angle of 30 degrees or less with respect to the tire equator C, for example, 24 degrees in this example. The truss structure is formed by intersecting each other, and the tread portion 2 is reinforced with a tag effect.

In this embodiment, the belt cord is used as a steel cord.
Cord is used as the topping rubber for the ply.
Volume specific electrical resistance
10 ⁸Use a conventional conductive rubber material of less than Ωcm
Thereby, conductivity is imparted to the belt layer 7. The belt
Metal cord, carbon fiber cord as cord
Other conductive cords can be used upon request.

The tread portion 2 is disposed outside the belt layer 7 and has an outer surface tread contact edge Te,
Tread surface S1 between Te and buttress surfaces S on both sides
2 is formed from the tread rubber 10.

The tread rubber 10 is provided on the belt layer 7.
A penetrating portion 11 extending from the tread surface S1 and having an exposed surface 11S exposed at a ground contact portion of the tread surface S1;
2 and the wings 12, 12
And a main portion 13 to be filled while leaving the exposed surface 11S therebetween. The ground contact portion of the tread surface S1 is a portion that is actually in contact with the road surface, and means a land portion other than the pattern groove G on the tread surface S1.

The main portion 13 is formed of a base portion 15 on the belt layer side and a cap portion 16 on the tread surface side.

The cap portion 16 has a volume specific electric resistance value of 10 ^8, which is set in consideration of wear resistance, low rolling resistance, and wet performance, which are characteristics other than conductivity.
Ωcm or more high-performance rubber, in 100 parts by weight of the rubber base material, in this example, 30 to 100 parts by weight, preferably 40 to 70 parts by weight, more preferably 40 to 60 parts by weight with silica as a main reinforcing agent. An insulating rubber material which is blended and contains carbon black in an amount of 30 parts by weight or less, preferably 10 parts by weight or less, and more preferably substantially no carbon black is employed. As the rubber substrate, for example, one or a combination of a plurality of diene rubbers such as natural rubber (NR), styrene-butadiene rubber (SBR), butadiene rubber (BR), and isoplane rubber (IR) is used. It can be used, and if necessary, known additives such as sulfur, a vulcanization accelerator and an antioxidant are added.

The base portion 15 is made of a low-heat-generating rubber material having a low loss tangent (tan δ) of 0.10 or less for rubber with an emphasis on low rolling resistance, and has a sheet shape having a substantially constant thickness of about 1 to 3 mm. Formed. This loss tangent (tan δ) is
It is smaller than the loss tangent (tan δ) of the cap portion 16.
The 0.10 low values to be achieved by such means as the use of a coarse soft carbon subtracting the content and the particles of carbon black, volume electrical resistivity of 10 ⁸
Ωcm or higher, usually 10 ¹⁰ Ωcm or higher. The value of the loss tangent (tan δ) was measured using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho at a frequency of 10 H
z, a static strain of 10.0%, a dynamic strain of 2.0% and a temperature of 60 ° C.

In the present embodiment, as shown in an enlarged manner in FIG. 2, the through portion 11 extends from the lower end in contact with the belt layer 7 to the upper end having the exposed surface 11S with a substantially constant width.
For example, it is formed in a single annular shape extending continuously in the circumferential direction on the center of the tread where the contact pressure is high, in this example, on the equatorial plane of the tire. In this example, the lower end of the base 17 is
A wide root portion 18 that smoothly contacts with the belt layer 7 by a curved line such as a circular arc is connected, thereby alleviating stress concentration, increasing the contact area with the belt layer 7, and smoothing the flow of static electricity. Is done. At this time, the height H2 of the root portion 18 is two times the height H1 of the entire penetrating portion 11.
0% or less is preferable.

The vertical groove Gm in the circumferential direction of the pattern groove G is provided at a position avoiding the penetrating portion 11, but when the horizontal groove Gy crosses the penetrating portion 11, the exposed surface 11S on the tread surface S1 is formed. May be discontinuous.

The exposed surface 11S has a width W1 in the axial direction of the tire in a range from 1.0 mm to 15.0 mm.

Further, the penetrating portion 11 has a tapered or tapered shape in which the width of the base 17 rises toward the tread surface S1 while gradually decreasing or increasing toward the tread surface S1, as shown in FIGS. 3 (A) and 3 (B). In addition to the tapered shape, as shown in FIG.
A constricted portion 17A or a bulged portion 17B may be formed at the center. When the width changes in this way, the tread surface S1
The maximum width W1a and the minimum width W1b of the base 17 in the wear region Y extending from the position A to the maximum depth position of the pattern groove G are both in the range of 1.0 to 15.0 mm.

When the width of the base 17 is constant, the total width W1 of the exposed surface 11S is 15 mm or less when the width of the base 17 is constant, and when the width of the base 17 changes, the total width at each height position is 15 mm or less. In this case, two or more lines may be formed.

Here, the penetrating portion 11 is made of a conductive rubber material having a volume specific electric resistance of less than 10 ⁸ Ωcm with emphasis on conductivity. In the present embodiment, 100 parts by weight of the diene rubber base material is used. By combining 40 parts by weight or more, preferably 45 to 70 parts by weight of carbon black, excellent conductivity and abrasion resistance are imparted. In order to obtain conductivity, a conductive agent such as an antistatic agent, a conductive plasticizer, or a metal salt may be used in combination as needed.

The wing portions 12 are disposed at both ends of the main portion 13 so as to form a triangular cross-section covering the side portion in the tire axial direction of the main portion 13, and the outer surface thereof constitutes the buttress surface S2. I do. In this example, the wing portion 12
Is the side wall rubber 20 which forms the side wall portion 3
And rises in a tapered shape radially outward from the upper end portion 20A, and is formed apart from the belt layer 7. The sidewall rubber 20 is made of a conductive rubber material containing carbon black, like the conventional tire, extends along the carcass 6, and its upper end portion 20A enters below the belt layer 7 and is cut off.

The wing portion 12, like the through portion 11, is formed of a conductive rubber material having a volume specific electric resistance of less than 10 ⁸ Ωcm. In particular, in this example, the wing portion 12 and the penetrating portion 11 are formed of a conductive rubber material having the same composition, whereby the integral extrusion molding of the tread rubber 10 using a conventional so-called triple head tread extruder is performed. And productivity can be greatly improved.

As described above, the tread portion 2 of the tire 1 of this embodiment has the base portion 15 made of a low heat-generating rubber material inside the cap portion 16 made of, for example, silica. 16 can greatly improve the low rolling resistance while maintaining the excellent wear resistance and wet performance.

Further, since the penetrating portion 11 and the wing portion 12 made of a conductive rubber material are exposed at the tread center region and the tread grounding edges Te at both ends, static electricity can be grounded over a wide range in a well-balanced manner. The electric resistance of the entire tire can be effectively reduced.

The width W1 of the exposed surface 11S is 1.0 m.
When it is less than m, the effect of reducing the electric resistance cannot be sufficiently and reliably achieved, and when it exceeds 15.0 mm, low rolling resistance and abrasion resistance decrease.

Also, since the rubber properties of the main portion 13 and the through portion 11 are different, the contact property of the through portion 11 tends to decrease as the wear progresses. However, since the wing portion 12 has a triangular cross section and the exposed area increases as the wear progresses, excellent low electrical resistance can be stably exhibited from the initial stage of wear (when the tire is new) to the final stage of wear.

The loss tangent (tan) of the base portion 15
When δ) is greater than 0.10, the effect of reducing the rolling resistance by the base portion 15 is not achieved. The lower limit of the loss tangent (tan δ) is set to 0.03.
It is preferable in terms of durability.

[0032]

EXAMPLES A tire having a tire size of 195 / 65R15 and having a structure shown in FIG. 1 was prototyped based on the specifications shown in Table 1, and the electrical resistance, low rolling resistance, wet performance, and wear resistance of each sample tire were tested. While measuring
Table 1 shows the results. Table 2 shows the rubber composition of the rubber material used for each part of the tread rubber.

1. Tire electric resistance:
With the rim assembled on a standard rim at an air pressure of 200 kpa, the measurement was carried out according to the “Measurement procedure of tire electric resistance under load” specified by Blatt 3, WDK, Germany. That is,
As shown in FIG. 4, the rim-assembled tire 1 is placed on a steel plate 31 which is attached to the base plate 30 in an insulated state, with a load of 450 k.
Then, the electrical resistance between the central portion of the standard rim R and the steel plate 31 is measured using a resistance measuring device 32 having an applied voltage of 1000 volts. The temperature at the time of measurement was 25 ° C. and the humidity was 50%.

2. Low rolling resistance: Using a rolling resistance tester, the rim-assembled tire was subjected to a speed of 80 km / h and a load of 3
Rolling resistance was measured by running at 45 kg, and Comparative Example 1 was evaluated as 1
It was indicated by an index of 00. The larger the index, the smaller the rolling resistance and the better.

3. Wet performance: After mounting the rim-assembled tire on all the wheels of a passenger vehicle and spraying water on a test course with tiles of low friction coefficient spread, measure the maximum speed when slipping in a circular turn, It is indicated by a 10-point evaluation. The larger the index, the better.

4. Abrasion resistance: The balance of the tread groove was measured at the time when the passenger vehicle equipped with the test tires was used and the expressway and the general road were mixed and traveled a total of 30,000 km, and displayed by a five-point evaluation. . The larger the index, the better.

The specific volume resistivity value of each rubber composition was determined by preparing a 15 cm square, 2 mm thick sample piece using each rubber composition and measuring the volume specific resistance value using an ADVANTESTR8340A electric resistance measuring instrument. did. The applied voltage was 1000 V, the temperature was 25 ° C., and the humidity was 50%. The results are shown in Tables 1 and 2.

[0038]

[Table 1]

[0039]

[Table 2]

As shown in Tables 1 and 2, Examples 1 to 3 of the present invention were used.
It can be confirmed that the tire No. 3 can exhibit excellent low rolling resistance, wet performance, and abrasion resistance while maintaining conductivity. When the width W1 of the exposed surface is 15.0 mm,
The wear resistance and low rolling resistance are at the lower limit of the allowable level. When the diameter is 1.0 mm, a portion where the tire electric resistance exceeds 10 ⁸ Ωcm is partially generated during one round of the tire. Therefore, the width W1 of the exposed surface is 3.0 to 12.0 mm
Is preferable.

[0041]

Since the present invention is configured as described above,
Excellent low rolling resistance while maintaining the required conductivity,
It can exhibit wet performance and wear resistance.

[Brief description of the drawings]

FIG. 1 is a sectional view of a tire showing one embodiment of the present invention.

FIG. 2 is an enlarged sectional view showing a penetrating portion.

FIGS. 3A, 3B, and 3C are cross-sectional views showing other examples of the penetrating portion.

FIG. 4 is a diagram illustrating a method for measuring tire electrical resistance.

[Explanation of symbols]

 Reference Signs List 7 belt layer 10 tread rubber 11 penetration part 11S exposed surface of penetration part 12 wing part 13 main part 15 base part 16 cap part S1 tread surface S2 buttress surface

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08K 3/36 C08K 3/36 C08L 21/00 C08L 21/00

Claims (2)

[Claims] 1. An exposed surface extending from the belt layer and exposed at a ground portion of the tread surface, the tread rubber being disposed radially outside the conductive belt layer and forming a tread surface and buttress surfaces on both sides thereof. And a wing portion forming the buttress surface, and a main portion filled between the wing portions leaving an exposed surface of the through portion, and the main portion is formed. Is composed of a base portion on the belt layer side and a cap portion on the tread surface side, and the side portion in the tire axial direction of the main portion is covered with the wing portion. resistance is from a small conductive rubber material than 10 ⁸ [Omega] cm, and the cap portion is made of insulating rubber material having a volume electrical resistivity and 10 ⁸ [Omega] cm or higher, and the base portion, Beam loss tangent tanδ of the formed by the low heat generation rubber material was 0.10 or less, yet pneumatic tire as 1.0~15.0mm the tire axial direction of the width of the exposed surface of the penetrating portion of the. 2. The piercing portion and each wing portion are made of a conductive rubber material having the same composition, and each of the wing portions has a triangular cross section that tapers outward in the radial direction, and wear progresses. The pneumatic tire according to claim 1, wherein the exposed area is increased.