JP2008013000A - Pneumatic tire and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of easing accumulation of static electricity to a vehicle. <P>SOLUTION: The pneumatic tire has a rubber member composed of a rubber strip winding body formed by winding up the rubber strip in a spiral shape. The rubber strip is composed of a first rubber part 15a and a rubber having a volume specific electric resistance value smaller than the first rubber 15a, and includes a compound rubber strip 15 composed of a second rubber part 15b forming a part of the surface F1 of one side of the rubber strip or the surface F2 of the other side. The compound rubber strip 15 sets a strip width Ws to be within 5 to 50 mm and a strip thickness Ts to be 0.5 to 3.0 mm, and the second rubber part 15b sets the width Wb to be smaller than the strip width Ws and the thickness is set to be smaller than the strip thickness Ts. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pneumatic tire that can alleviate accumulation of static electricity in a vehicle, and a manufacturing method thereof.

  In recent years, many silicas are blended in various rubber members including tread rubber of pneumatic tires. Silica provides the advantages of reducing tire rolling resistance and increasing wet grip. On the other hand, since silica is inferior in conductivity, it increases the electrical resistance of the tire. Tires with high electrical resistance tend to accumulate static electricity in the vehicle and cause radio interference such as radio noise.

  Conventionally, in order to prevent the accumulation of static electricity in such a vehicle, for example, a tread rubber a1 as shown in FIG. 17A has been proposed. The tread rubber a1 is composed of a base rubber layer b made of a rubber having a carbon rich composition containing carbon black and having conductivity, and a non-silica rich composition arranged on the outside of the base rubber layer b and containing a lot of silica. And a cap rubber layer c made of conductive rubber. The base rubber layer b includes a base portion b1 located inside the cap rubber layer c, and a through terminal portion b2 protruding outward from the base portion b1 in the tire radial direction and penetrating through the cap rubber layer c and exposed to the ground plane ( For example, see Patent Document 1). Such a tread rubber a1 can discharge the static electricity of the vehicle from the rim to the road surface via the base b1 and the through terminal part b2 of the base rubber part b.

  In recent years, as shown in a simplified manner in FIG. 17B, a ribbon-like and unvulcanized rubber strip g continuously supplied from an extruder or the like is replaced with a cylindrical article to be wound d. There has been proposed a tread rubber a2 composed of a strip wound body formed by spirally winding around a central axis (see, for example, Patent Document 2). Such a rubber member forming method is also called a so-called strip wind method. The tread rubber a2 has no splice portion compared to the conventional integral extrusion type shown in FIG. 17 (A), and also reduces the intermediate stock of rubber extruded products, thereby saving space in factories and the like. Brings the benefits. However, in such a tread rubber a2, since the rubber strip g is continuously wound, it is difficult to provide the above-described discharge through terminal portion.

JP 9-71112 A JP 2000-94542 A

  The present invention has been devised in view of the above problems, and as a rubber strip for forming a rubber member for a tire, a first rubber portion made of a first rubber and a volume larger than that of the first rubber. A strip wind system based on using a composite rubber strip made of a second rubber having a small specific electric resistance value and comprising a second rubber portion that forms part of the surface on one side or the other side of the rubber strip. It is an object of the present invention to provide a pneumatic tire capable of achieving both real vehicle performance and conductivity of a rubber member, and a method for manufacturing the same.

The invention according to claim 1 of the present invention is a pneumatic tire having a rubber member formed of a rubber strip wound body formed by spirally rolling rubber strips,
The rubber strip is composed of a first rubber portion made of a first rubber and a second rubber having a volume specific electrical resistance value smaller than that of the first rubber, and one surface of the rubber strip or the other surface. Including a composite rubber strip comprising a second rubber part forming part,
The composite rubber strip has a strip width Ws of 5 to 50 mm and a strip thickness Ts of 0.5 to 3.0 mm, and the second rubber portion has a width Wb on the surface that is greater than the strip width Ws. And the thickness Tb is smaller than the strip thickness Ts.

  In the invention of claim 2, the second rubber portion is characterized in that the width Wb is 25 to 75% of the strip width Ws.

  According to a third aspect of the invention, the rubber member is characterized in that the composite rubber strip has a reversing portion in which the surface on one side and the surface on the other side are reversed and turned over.

In the invention of claim 4, the rubber member is a tread rubber that is disposed in the tread portion and has an outer peripheral surface that contacts the road surface.
The inner peripheral surface of the tread rubber is in contact with a conductive tread conductive portion that is arranged on the inner side and is electrically connected to the rim.
The second rubber portion is characterized in that a conductive path capable of electrical conduction is formed between the outer peripheral surface and the inner peripheral surface of the tread rubber.

  In the invention of claim 5, the tread conductive portion is a tread reinforcing cord layer including a belt or a base rubber portion.

The invention of claim 6 is a pneumatic tire manufacturing method for manufacturing a pneumatic tire using a rubber member comprising a rubber strip wound body in which rubber strips are spirally wound.
The wound body has a first rubber portion made of the first rubber and a second rubber having a volume specific electrical resistance value smaller than that of the first rubber and the surface of one side or the other side of the rubber strip. A strip supplying step for supplying a composite rubber strip comprising a second rubber part forming a part;
A winding step of winding the supplied composite rubber strip around the wound body to form the rubber member;
In addition, by this winding, the second rubber portion forms a conductive path that can be conducted between the inner peripheral surface in contact with the member to be wound of the rubber member and the outer peripheral surface that is the opposite surface. It is said.

  According to a seventh aspect of the present invention, the winding step includes a reversing step in which the surface on one side and the surface on the other side of the composite rubber strip are reversed and turned over during winding.

  According to an eighth aspect of the present invention, the composite rubber strip is formed of a laminated body in which a first strip piece obtained by extruding a first rubber and a second strip piece obtained by extruding a second rubber are bonded together. It is characterized by becoming.

  According to a ninth aspect of the present invention, the composite rubber strip is formed of an extruded product obtained by integrally extruding a first rubber and a second rubber by a two-layer extruder.

  The invention according to claim 10 is characterized in that the bonded body or the extruded molded body is narrowed between the calender rolls.

  The pneumatic tire of the present invention has a rubber member made of a rubber strip wound body formed by winding a rubber strip spirally. The rubber strip includes a first rubber portion made of a first rubber and a second rubber having a volume specific electrical resistance smaller than that of the first rubber, and one surface or the other surface of the rubber strip. A composite rubber strip made up of a second rubber part that forms a part of is used. In such a composite rubber strip, a conductive path can be formed by the second rubber portion appearing on the surface, so that the discharge performance can be improved in a rubber member made by a strip wind method.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a cross-sectional view of the pneumatic tire of the present embodiment. The pneumatic tire 1 includes a tread portion 2, a pair of sidewall portions 3 extending inward in the tire radial direction from both ends thereof, and a bead portion 4 provided at an inner end of each sidewall portion 3. In this example, a tire for a passenger car is shown. The pneumatic tire 1 includes, for example, a carcass 6 extending between the bead cores 5 and 5 of each bead portion 4 in a toroidal shape, and a tread reinforcement disposed on the outer side in the tire radial direction of the carcass 6 and inside the tread portion 2. The code layer 7 is included.

  The carcass 6 is formed of one carcass ply 6A having a radial structure, for example. The carcass ply 6A includes, for example, a toroid-shaped main body portion 6a straddling between the bead cores 5 and 5, and a pair of folded portions 6b which are connected to both sides and folded around the bead core 5 from the inner side toward the outer side in the tire axial direction. Have. A bead apex rubber 8 extending radially outward from the bead core 5 is disposed between the main body portion 6a and the folded portion 6b of the carcass ply 6A.

  Further, the tread reinforcing cord layer 7 includes two or more belt plies 9A and 9B in which metal cords are arranged at an angle of, for example, 15 to 40 degrees with respect to the tire circumferential direction. The belt 9 is configured to be overlapped, and a band 10 made of a band ply 10A having a cord extending in the tire circumferential direction and arranged on the outer side in the tire radial direction. The band 10 can be omitted as necessary.

Each of the carcass plies 6A, belt plies 9A and 9B, and band ply 10A is composed of a cord and a topping rubber that covers them. This topping rubber includes a conductive material such as carbon black as a filler. For this reason, the topping rubber has a volume specific electrical resistance value after vulcanization of, for example, less than 1.0 × 10 ⁸ (Ω · cm), and exhibits good conductivity.

  In this specification, the volume specific electric resistance value of rubber is an electric resistance measuring instrument (in this example, in the case of an applied voltage of 500 V, an air temperature of 25 ° C., and a humidity of 50% for a rubber sample of 15 cm square and 2 mm thick. Displayed with the value measured using ADVANTESTER 8340A).

  Further, on the outside of the carcass 6, a sidewall rubber 3G that forms a tire skin is disposed in the sidewall region, and a clinch rubber 4G is disposed in the bead region. Here, the outer end in the tire radial direction of the clinch rubber 4G is connected to the sidewall rubber 3G, and the inner end in the tire radial direction can contact the metal rim R.

The side wall rubber 3G and the clinch rubber 4G contain carbon black as a filler as in the conventional general tire. For this reason, the volume specific electric resistance value after vulcanization of both these rubbers 3G and 4G is less than 1.0 × 10 ⁸ (Ω · cm), and shows good conductivity.

  In the present embodiment, in the pneumatic tire 1, the tread rubber 2 </ b> G is disposed on the outer side in the tire radial direction of the tread reinforcing cord layer 7 via the base rubber portion 12.

The base rubber portion 12 is made of a conductive rubber having a volume specific electrical resistance value of less than 1.0 × 10 ⁸ (Ω · cm) after vulcanization. Further, both side edges in the tire axial direction of the base rubber portion 12 are connected to the sidewall rubber 3G. Therefore, when assembling the rim, the base rubber portion 12 constitutes a tread conductive portion 14 that can be electrically connected to the rim R through the sidewall rubber 3G, the clinch rubber 4G, and the like. Needless to say, the base rubber portion 12 may be omitted and the tread reinforcing cord layer 7 may be used as the tread conductive portion 14.

  The tread rubber 2G of the present embodiment is made of a rubber strip wound body GS formed by winding a composite rubber strip 15 in a spiral shape. In FIG. 1, for easy understanding, the boundary between adjacent composite rubber strips 15 is indicated by a broken line.

  FIG. 2A shows a cross-sectional view of one composite rubber strip 15. In the present embodiment, the composite rubber strip 15 has a flat rectangular cross section. One of the composite rubber strips 15 includes a first rubber portion 15a made of the first rubber ga and a volume specific to the first rubber ga. A second rubber portion 15b made of the second rubber gb having a small electric resistance value is integrally included.

  The composite rubber strip 15 has a strip width Ws of 5 to 50 mm, a strip thickness Ts of 0.5 to 3.0 mm, and a strip width Ws of less than 5 mm or a thickness Ts of 0.5 mm. In the case where the rubber member is wound spirally, the number of windings of the composite rubber strip 15 is remarkably increased and the productivity tends to be lowered. Conversely, when the width Ws exceeds 50 mm or the thickness Ts When the thickness exceeds 3.0 mm, it tends to be difficult to make a fine cross-sectional shape. From such a viewpoint, the lower limit of the strip width Ws is preferably 10 mm or more, more preferably 15 mm or more, and the upper limit is preferably 40 mm or less, more preferably 30 mm or less.

  In the present embodiment, the first rubber ga is a silica-rich rubber containing a large amount of silica. The silica-rich first rubber ga exhibits excellent wet performance because it maintains a high hysteresis loss on the low temperature side, while rolling resistance is reduced because the hysteresis loss on the high temperature side is low. That is, excellent actual vehicle running performance can be obtained.

  In the first rubber ga, the blending amount of silica is not particularly limited, but if the blending amount is small, the above-described improvement in actual vehicle performance tends not to be sufficiently expected. From such a viewpoint, the compounding amount of silica in the first rubber ga is preferably 30 parts by mass or more, more preferably 40 parts by mass or more with respect to 100 parts by mass of the rubber polymer. In addition, the upper limit of the amount of silica is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, and still more preferably 60 parts by mass or less, from the viewpoint of cost and peaking of the expression effect. Thereby, both low rolling resistance and wet grip properties can be achieved at a higher level.

The silica to be blended is not particularly limited, but exhibits colloidal characteristics in which the nitrogen adsorption specific surface area (BET) is in the range of 150 to 250 m ² / g and the dibutyl phthalate (DBP) oil absorption is 180 ml / 100 g or more. A thing is preferable at points, such as a reinforcement effect to rubber | gum and rubber processability. As the silane coupling agent, bis (triethoxysilylpropyl) tetrasulfide and α-mercaptopropyltrimethoxysilane are suitable.

  Further, the rubber polymer of the first rubber ga is not particularly limited. For example, natural rubber (NR), butadiene rubber (BR) which is a polymer of butadiene, so-called emulsion polymerization styrene butadiene rubber (E- SBR), solution-polymerized styrene-butadiene rubber (S-SBR), synthetic polyisoprene rubber (IR) which is a polymer of isoprene, nitrile rubber (NBR) which is a copolymer of butadiene and acrylonitrile, or a polymer of chloroprene. A certain chloroprene rubber (CR) etc. can be mentioned, These 1 type (s) or 2 or more types can be blended and used.

  The first rubber ga can be supplemented with not only silica but also carbon black. This is useful for appropriately controlling other rubber physical properties such as rubber elasticity and rubber hardness. However, an increase in the amount of carbon black is not preferable because the low rolling resistance due to silica is impaired and the rubber tends to be excessively hard. From such a viewpoint, in the first rubber ga, the amount of carbon black is desirably 10% or less of the mass of the total filler in mass ratio. As other fillers, aluminum hydroxide, calcium carbonate and the like can be used.

Such a first rubber ga has a volume specific electrical resistance value of 1.0 × 10 ⁸ (Ω · cm) or more due to silica-rich compounding, and exhibits substantial non-conductivity that is difficult to conduct electricity.

In the present embodiment, the second rubber gb is a rubber composition containing a large amount of carbon black as a filler. Thereby, the second rubber gb has a volume specific electrical resistance value smaller than that of the first rubber ga, specifically, the value after vulcanization is less than 1.0 × 10 ⁸ (Ω · cm), more preferably Those having good conductivity of 1.0 × 10 ⁷ (Ω · cm) or less are desirable.

  In the second rubber gb, the blending amount of carbon black is not particularly limited, but if it is too small, good conductivity tends not to be obtained. From such a viewpoint, the blending amount of carbon black in the second rubber gb is preferably 10 parts by mass or more, more preferably 20 parts by mass or more with respect to 100 parts by mass of the rubber polymer. Further, from the viewpoints of cost and peak effect, etc., the upper limit of the amount of carbon black is preferably 100 parts by mass or less, more preferably 80 parts by mass or less.

  Moreover, you may mix | blend other fillers, such as a silica, also in the 2nd rubber | gum gb. However, in order to prevent an increase in electrical resistance, it is desirable that the amount of carbon black in the second rubber gb is 30% or more of the mass of the total filler in the mass ratio.

  Next, the second rubber portion 15b made of the second rubber gb is a surface layer that does not penetrate the composite rubber strip 15 in the thickness direction, and the surface F1 on one side of the composite rubber strip 15 or the second rubber portion 15b on the other side. A part of the surface F2 (in this example, a part of the surface F1) is formed. At this time, the width Wb of the second rubber portion 15b on the surface is smaller than the strip width Ws, and the thickness Tb is smaller than the strip thickness Ts. Here, the strip width Ws is a width between the side edges es and es of the composite rubber strip 15, and the surfaces F1 and F2 are surfaces in the width direction between the side edges es and es. The strip thickness Ts means the maximum thickness when the thickness of the composite rubber strip 15 changes, and the thickness Tb also changes when the thickness of the second rubber portion 15b changes. Means the maximum thickness.

  In this example, the case where both side edges e2 of the second rubber portion 15b are arranged at a distance in the width direction from the both side edges es of the composite rubber strip 15 is illustrated as an example in FIG. As shown, the side edge e2 and the side edge es can be aligned on one side edge side.

  3 and 4 show a process of making the tread rubber 2G using such a composite rubber strip 15. FIG. In FIG. 3, the tread reinforcing cord layer 7 and the base rubber portion 12 are arranged on the molding surface U of the molding drum D in advance. The molding surface U of the present embodiment is provided with a recess Ua equal to the width and thickness of the tread reinforcing cord layer 7. The concave portion Ua absorbs the thickness of the tread reinforcing cord layer 7 and makes the winding surface of the base rubber portion 12 arranged on the outside thereof a substantially flat outer peripheral surface. This is useful for improving the finishing accuracy of the base rubber portion 12.

The base rubber portion 12 of the present embodiment has a width of one rubber strip 16 made of one kind of rubber having a good electrical conductivity with a volume specific electrical resistance value of less than 1.0 × 10 ⁸ (Ω · cm). What is formed in an annular shape by continuously winding in a spiral shape with an overlap allowance from one end S1 to the other end S2 in the direction is shown. The winding of the rubber strip 16 is performed by, for example, fixing one end of the rubber strip 16 continuously supplied from the extruder to a predetermined position in the width direction of the molding drum D and rotating the molding drum D. This is done by moving the rubber strip 16 laterally in the width direction.

  Next, as shown in FIG. 4, a tread rubber 2 </ b> G is formed on the outside of the base rubber portion 12 using a composite rubber strip 15. In this step, the base rubber portion 12 that forms the tread conductive portion 14 wound around the molding drum D in advance is used as a body to be wound, and the composite rubber strip from the composite rubber strip forming apparatus 40 is conceptually shown in FIG. The strip supplying step for supplying 15 to the body to be wound, and the composite rubber strip 15 to be fed are continuously wound around the body to be wound using the strip winding device 50 having the delivery roller 50A. Winding step to form 2G. However, for example, a raw cover base composed of a carcass 6 expanded in a toroidal shape and a tread conductive portion 14 arranged on the outside thereof is used as a body to be wound, and the composite rubber strip 15 is directly attached to the toroidal expanded portion. It can also be wound. In this example, the strip winding device 50 is also used to form the base rubber portion 12.

  The tread rubber 2G of the present embodiment is wound around the rubber strip by winding the composite rubber strip 15 in a spiral shape with an overlap margin from one end S1 to the other end S2 of the base rubber portion 12. Formed as body GS. The thickness of the rubber strip wound body GS can be changed, for example, by changing the winding pitch of the composite rubber strip 15 in the width direction. In this example, the composite rubber strip 15 is moved from one end S1 to the other end S2 to finish winding. For example, the composite rubber strip 15 is turned around at the other end S2 and wound in two layers to form a tread rubber 2G. You can also

  FIG. 6 shows a partially enlarged view of the tread rubber 2G produced by the winding step. In the tread rubber 2G, the composite rubber strip 15 has a predetermined winding pitch P and is sequentially displaced in the width direction. Therefore, by spirally winding the composite rubber strip 15 with the second rubber portion 15b facing outward in the radial direction (that is, with the surface F1 facing outward in the radial direction), the displacement in the width direction causes The second rubber portion 15b can be exposed at the radially outer peripheral surface 11o of the tread rubber 2G. The exposed portion 15b1 of the second rubber portion 15b is exposed on the outer peripheral surface 11o even after vulcanization molding, so that it can be grounded to the road surface for electrical conduction. In order to form the exposed portion 15b1, in the outer edge es of the composite rubber strip 15 that is radially outward when wound, the width in the width direction between the outer edge es and the side edge e2 of the second rubber portion 15b is increased. The distance L is preferably 20% or less, more preferably 10% or less of the strip width Ws (shown in FIG. 2). The lower limit value of the distance L is 0% as shown in FIG.

  On the other hand, the second rubber portion 15b of the composite rubber strip 15 is also required to have an exposed portion 15b2 exposed at the radially inner peripheral surface 11i of the tread rubber 2G and conducting with the tread conductive portion 14. Therefore, in this example, as shown in FIG. 7, at the beginning of winding of the composite rubber strip 15, the second rubber portion 15b is directed radially inward (that is, the surface F1 is directed radially inward). Thus, the second rubber portion 15b and the tread conductive portion 14 are electrically connected. Further, the composite rubber strip 15 has a reversing portion Q in which the surface F1 and the surface F2 are reversed and turned over in the course of winding, thereby enabling conduction with the road surface.

  In this example, the case where the inversion part Q is formed by folding the composite rubber strip 15 into a U shape in the length direction is shown. This inversion part Q is performed by the inversion step in the winding step. In this reversal step, as shown in FIG. 8, the direction of rotation of the forming drum D is reversed in the normal / reverse direction during winding. As shown in FIG. 9, the reversing part Q can be formed by twisting the composite rubber strip 15 in the width direction. The reversing part Q has the feeding roller 50 </ b> A connected to the length of the composite rubber strip 15. It can be formed by a reversing step for reversing up and down around the axial axis. The inversion portion Q is preferably formed at least radially inward from the height position at which the wear indicator is exposed. Particularly, from the viewpoint of minimizing winding disturbance, within one round of the start of winding of the composite rubber strip 15 It is preferable to form it. As described above, by providing the reversing portion Q, the second rubber portion 15b continuously extends between the exposed portions 15b1 and 15b2, and thereby the outer peripheral surface 11o and the inner peripheral surface 11i of the tread rubber 2G. A spiral conductive path 17 that can conduct between the two can be formed.

  Next, the tread rubber 2G made in this way is removed from the molding drum D together with the tread reinforcing cord layer 7 and the base rubber portion 12. Then, as shown in FIG. 10, these are extrapolated to the carcass ply 6A, the side wall rubber 3G, and the clinch rubber 4G wound around the molding former FM in a cylindrical shape, and carcass ply 6A ( (Indicated by phantom lines). Thereby, the raw cover 1a is formed. The raw cover 1a is vulcanized by a vulcanization mold to produce a pneumatic tire.

  In the pneumatic tire 1 obtained by vulcanizing the raw cover 1a, the conductive path 17 extending continuously from the inner peripheral surface 11i to the outer peripheral surface 11o of the tread rubber 2G is formed even after vulcanization. Such a pneumatic tire 1 can exhibit good wet performance and low rolling resistance performance when the tread rubber 2G includes the first rubber portion 15a of silica-rich composition. The conductive path 17 can be electrically connected to the rim R through the tread conductive portion 14 (base rubber portion 12), the sidewall rubber 3G, and the clinch rubber 4G, and efficiently discharges static electricity accumulated in the vehicle to the ground. sell.

  Therefore, according to the present invention, it is possible to provide the pneumatic tire 1 that can achieve both the actual vehicle performance and the static electricity discharge performance while adopting the strip wind method. Moreover, since the second rubber portion 15b can be exposed on the outer peripheral surface 11o at any stage of wear, the electrostatic discharge performance can be maintained for a long time. Furthermore, since the conductive path 17 is formed by the second rubber portion 15b that forms part of the surface F1, F2 on one side or the other side, the amount of the second rubber gb used can be greatly reduced, and the necessary static electricity While maintaining the release performance, the wet performance and the low rolling resistance performance by the first rubber ga can be exhibited more highly.

  Here, as conceptually shown in FIG. 11 (A), as the width Wb of the second rubber portion 15b increases, the electrostatic discharge performance increases and radio interference is suppressed, whereas the first rubber portion. The improvement effect of wet grip property by 15a will decrease, and it will become the tendency to reduce steering stability. From such a viewpoint, the lower limit value of the width Wb of the second rubber portion 15b is preferably 25% or more, more preferably 30% or more of the strip width Ws, and the upper limit is preferably 75% or less, more preferably 70% or less. Similarly, as conceptually shown in FIG. 11B, as the thickness Tb of the second rubber portion 15b increases, the radio wave interference is suppressed, but the steering stability tends to decrease. . From such a viewpoint, the lower limit value of the thickness Tb of the second rubber portion 15b is preferably 10% or more, more preferably 20% or more of the strip thickness Ts, and the upper limit value is 50% or less, further 40% or less. preferable.

  Next, the composite rubber strip 15 can be formed by a composite rubber strip forming apparatus 40 (shown in FIG. 5). In this example, a double-layer extruder 41 is used as the composite rubber strip forming apparatus 40, and the composite rubber strip 15 is formed as an extruded product 42 in which the first and second rubbers ga and gb are integrally extruded by the two-layer extruder 41. Are shown.

  As the composite rubber strip forming apparatus 40, as shown in FIG. 12, two independent extruders 45A and 45B can be used. In this case, the first strip piece 46a made of the first rubber ga and the second strip piece 46b made of the second rubber ga are respectively extruded from the extruders 45A and 45B. And the composite rubber strip 15 can also be formed as the bonding body 47 which bonded these strip pieces 46a and 46b together.

  In this case, as shown in FIG. 13A, the second rubber portion 15b is raised with a step 49 from the first rubber portion 15a. However, the winding accuracy and winding of the composite rubber strip 15 are increased. There is no particular problem in workability and the shape and accuracy of the tread rubber 2G. However, as shown in FIGS. 13B and 13C, in order to increase the adhesion between the strip pieces 46a and 46b and to smoothen the surface F1 by reducing or eliminating the step 49, the pasting is performed. The combined body 47 is preferably compressed between the calender rolls 48, 48.

  Also in the extrusion molded body 42, due to the difference in shrinkage between the first rubber ga and the second rubber gb, there is a tendency that a bulging portion or the like is formed on the surface F1, so even in the case of integral extrusion molding, In order to smooth the surface F <b> 1, it is preferable that the extrudate 42 is narrowed between the calender rolls 48, 48.

  In the composite rubber strip 15, it is preferable that the width Wb of the second rubber portion 15b is 3 mm or more and the thickness Tb is 0.2 mm or more from the viewpoint of productivity. If the width Wb is less than 3 mm and the thickness Tb is less than 0.2, the amount of rubber becomes too small when the strip piece 46b is formed or when the second rubber portion 15b is directly formed by integral extrusion. Thus, it becomes difficult to continuously and stably form the strip piece 46b and the second rubber portion 15b. From such a viewpoint, the lower limit of the width Wb is preferably 5 mm or more, more preferably 7 mm or more, and the lower limit of the thickness Tb is preferably 0.2 mm or more, more preferably 0.5 mm or more.

  Next, FIGS. 14 and 15 show another embodiment of the tread rubber 2G. In FIG. 14, the composite rubber strip 15 is wound, for example, from the winding start position S3 on the center side in the width direction toward the other end, folded back at the other end S2, and then wound toward the one end. Turned. Further, after being folded at one end S1, it is terminated at the center. Thus, by forming the tread rubber 2G in a plurality of layers (two layers in this example), the winding pitch P of the composite rubber strip 15 in at least the outermost layer can be set large. As a result, a large exposed area of the second rubber portion 15b can be secured, and the grounding with the road surface can be further ensured. In particular, in this example, since the entire surface F1 is exposed at the winding end position S4, the grounding with the road surface can be further ensured.

  In FIG. 15, the tread rubber 2 </ b> G is formed of two types of a composite rubber strip 15 and another rubber strip 20 made of the first rubber ga. The composite rubber strip 15 is wound, for example, on the center side in the width direction, and forms a tread rubber portion 2G1 having, for example, a center having a conductive path 17 (not shown). Further, a shoulder tread rubber portion 2G2 formed of a wound body of the rubber strip 20 is formed on both sides of the center tread rubber portion 2G1. In this case, since the rubber amount of the second rubber gb can be suppressed to a smaller value, the improvement in the actual vehicle performance can be maximized, for example, the wet performance and the low rolling resistance performance can be enhanced. In addition, the formation position of the wound body by the composite rubber strip 15 can be appropriately determined without being limited to the tread center.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect. For example, in the above-described embodiment, the first rubber ga contains a compound containing a large amount of silica. However, other compounds may be adopted according to the performance required for the tire. For example, the first rubber ga can be natural rubber or the like that tends to increase electrical resistance. Further, in order to obtain conductivity, the second rubber gb is blended with a large amount of carbon black, but an ion conductive member using a lithium salt or the like can be used instead of or together with this. .

  A pneumatic tire (size: 225 / 55R16) having the basic structure shown in FIG. 1 and having a tread rubber formed by a strip wind method was prototyped based on the specifications in Table 1. And the rolling resistance and electric resistance of each test tire were measured. The parameters other than those shown in Table 1 are the same for each tire.

In the tires of Examples and Comparative Examples, tread rubber is formed by a strip wind method, and Table 2 shows the composition of the rubber strip. In any example, the slip width Ws of the rubber strip was 20 mm, and the strip thickness Ts was 1 mm.
The test method is as follows.

<Rolling resistance>
Using a rolling resistance tester, rolling resistance was measured under the following conditions. The evaluation was performed using an index with Conventional Example 1 being 100. The smaller the value, the smaller the rolling resistance and the better.
Rim: 16 × 7JJ
Internal pressure: 200 kPa
Load: 4.7kN
Speed: 80km / h

<Electric resistance of tire>
As shown in FIG. 16, the insulating plate 30 and the metal plate 31 is disposed surface is polished on the (electric resistance than 10 ¹² Omega) (electric resistance 10Ω or less), tire rim assembly The electrical resistance value of the tire / rim assembly was measured in accordance with JATMA regulations using a measuring device including a conductive tire mounting shaft 32 for holding the tire and an electrical resistance measuring device 33. Each of the test tires T had a surface release agent and dirt sufficiently removed in advance and sufficiently dried. Other conditions are as follows.
Rim: Aluminum alloy 16 × 7JJ
Internal pressure: 200 kPa
Load: 5.3kN
Test environment temperature (test room temperature): 25 ° C
Humidity: 50%
Measuring range of electric resistance measuring device: 10 3 to 1.6 × 10 ¹⁶ Ω
Test voltage (applied voltage): 1000V

The test procedure is as follows.
(1) A test tire T is mounted on a rim to prepare a tire / rim assembly. At this time, soapy water is used as a lubricant at the contact portion between the two.
(2) The tire / rim assembly is left in the test room for 2 hours and then attached to the tire mounting shaft 32.
(3) The tire / rim assembly is loaded with the load for 0.5 minutes, and after the release, the load is further applied for 0.5 minute, and after the release, the load is further applied for 2 minutes.
(4) When the test voltage is applied and 5 minutes have passed, the electrical resistance value between the tire mounting shaft 32 and the metal plate 31 is measured by the electrical resistance measuring device 33. The measurement is performed at four positions at 90 ° intervals in the tire circumferential direction, and the maximum value among them is taken as the electrical resistance value (measured value) of the tire T.
Table 1 shows the test results and Table 2 shows the rubber composition.

  As a result of the test, even when the tread rubber portion (cap rubber portion) is formed by the strip wind method, the tire of the example can keep the electric resistance of the tire low while maintaining excellent low rolling resistance. Can be confirmed.

It is sectional drawing which shows one Example of the pneumatic tire of this invention. (A), (B) is sectional drawing which shows an example of a composite rubber strip. It is a cross-sectional schematic for demonstrating the manufacturing process of a tread rubber. It is a cross-sectional schematic for demonstrating the manufacturing process of a tread rubber. It is a side view which shows notionally the supply state of a composite rubber strip. It is the elements on larger scale of tread rubber. It is sectional drawing explaining the inversion part of a composite rubber strip. It is a side view explaining an example of the formation method of an inversion part. It is a top view of the composite rubber strip explaining the other example of an inversion part. It is a schematic sectional drawing which shows the manufacturing process of a raw cover. (A) is a graph showing the relationship between the ratio Wb / Ws and electrostatic discharge performance and steering stability, and (B) is a graph showing the relationship between the ratio Tb / Ts and electrostatic discharge performance and steering stability. is there. It is a side view which shows an example of a composite rubber strip formation apparatus. (A)-(C) are sectional drawings which show the other example of a composite rubber strip. It is sectional drawing which shows the other example of a tread rubber. It is sectional drawing which shows the other example of a tread rubber. 1 is a schematic cross-sectional view conceptually showing a tire electrical resistance measuring device. (A) and (B) are schematic sectional views of a tread rubber for explaining the background art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 2G Tread rubber 7 Tread reinforcement cord layer 9 Belt 11i Inner peripheral surface 11o Outer peripheral surface 12 Base rubber part 14 Tread conductive part 15 Composite rubber strip 15a First rubber part 15b Second rubber part 17 Conductivity Road 41 Two-layer extruder 42 Extrusion body 46a First strip piece 46b Second strip piece 47 Laminating body 48 Calendar roll F1, F2 Surface ga First rubber gb Second rubber GS Rubber strip winding body Q Reverse part

Claims (10)

A pneumatic tire having a rubber member made of a rubber strip wound body formed by spirally rolling rubber strips,
The rubber strip is composed of a first rubber portion made of a first rubber and a second rubber having a volume specific electrical resistance value smaller than that of the first rubber, and one surface of the rubber strip or the other surface. Including a composite rubber strip comprising a second rubber part forming part,
The composite rubber strip has a strip width Ws of 5 to 50 mm and a strip thickness Ts of 0.5 to 3.0 mm, and the second rubber portion has a width Wb on the surface that is greater than the strip width Ws. And a thickness Tb smaller than the strip thickness Ts.   2. The pneumatic tire according to claim 1, wherein the second rubber portion has a width Wb of 25 to 75% of the strip width Ws.   3. The pneumatic tire according to claim 1, wherein the rubber member has a reversing portion in which the surface of the one side and the surface of the other side of the composite rubber strip are reversed and turned over. The rubber member is a tread rubber that is disposed in the tread portion and has an outer peripheral surface that contacts the road surface;
The inner peripheral surface of the tread rubber is in contact with a conductive tread conductive portion that is arranged on the inner side and is electrically connected to the rim.
The pneumatic tire according to any one of claims 1 to 3, wherein the second rubber portion forms a conductive path that is electrically conductive between the outer peripheral surface and the inner peripheral surface of the tread rubber. .   The pneumatic tire according to claim 4, wherein the tread conductive portion is a tread reinforcing cord layer including a belt or a base rubber portion. A pneumatic tire manufacturing method for manufacturing a pneumatic tire using a rubber member formed of a rubber strip winding body in which rubber strips are spirally wound,
The wound body has a first rubber portion made of the first rubber and a second rubber having a volume specific electrical resistance value smaller than that of the first rubber and the surface of one side or the other side of the rubber strip. A strip supplying step for supplying a composite rubber strip comprising a second rubber part forming a part;
A winding step of winding the supplied composite rubber strip around the wound body to form the rubber member;
In addition, by this winding, the second rubber portion forms a conductive path that can be conducted between the inner peripheral surface in contact with the member to be wound of the rubber member and the outer peripheral surface that is the opposite surface. A method for manufacturing a pneumatic tire.   The method of manufacturing a pneumatic tire according to claim 6, wherein the winding step includes a reversing step in which the surface on one side and the surface on the other side of the composite rubber strip are reversed and turned over during winding. .   The composite rubber strip is formed of a bonded body in which a first strip piece obtained by extruding a first rubber and a second strip piece obtained by extruding a second rubber are bonded to each other. Item 8. The method for producing a pneumatic tire according to Item 6 or 7.   The method for manufacturing a pneumatic tire according to claim 6 or 7, wherein the composite rubber strip is made of an extruded product obtained by integrally extruding a first rubber and a second rubber by a two-layer extruder.   The method for manufacturing a pneumatic tire according to claim 8 or 9, wherein the bonded body or the extruded molded body is narrowly pressed between calender rolls.

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