JP4571664B2 - Pneumatic tire and manufacturing method thereof - Google Patents

Description

  The present invention relates to a pneumatic tire capable of discharging static electricity of a vehicle to a road surface and a manufacturing method thereof.

  In recent years, many silicas have been blended into 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 may 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 a vehicle, for example, a tread rubber a as shown in FIG. 13A has been proposed. The tread rubber a has a two-layer structure including a base portion b on the inner side in the tire radial direction and a cap portion c on the outer side in the tire radial direction. The base portion b and the cap portion c are made of non-conductive rubber having a silica-rich composition in order to improve the tire performance and the like. Moreover, the base part b and the cap part c are each divided | segmented into right and left, and the conduction | electrical_connection part d which consists of conductive rubber which carried out carbon rich compounding, for example is provided between them.

  The conduction part d extends continuously in the tire circumferential direction, for example, and the outer surface in the tire radial direction constitutes a part of the ground contact surface g. Further, the inner surface in the tire radial direction of the conduction portion d is connected to a tread reinforcing cord layer f etc. that is electrically connected to a rim (not shown) via a carcass or the like when the rim is assembled. Such a tread rubber a can discharge static electricity accumulated in the vehicle to the road surface via the rim, the carcass, the tread reinforcing cord layer f, and the conduction part d.

  Related technologies include the following.

JP 9-71112 A JP 2000-94542 A

  By the way, the rubber constituting the conduction part d tends to be inferior in movement performance such as rolling resistance and wet grip performance as compared with the rubber of the cap part c. For this reason, in order to improve the exercise performance of the tire, it is desirable that the width w of the conductive portion d appearing on the ground contact surface g is as small as possible.

  However. When the width w of the conductive portion d is reduced, as shown in an enlarged view in FIG. 13 (b), the surface of the conductive portion d is covered with the rubber of the plasticized cap portion c during vulcanization molding. In some cases, the conductive portion cannot be exposed at the ground plane g. In such a tire, there is a possibility that the above-described energization effect may be significantly reduced.

  The present invention has been devised in view of the above problems, such as a spew sucked up into a vent hole of a mold at the time of vulcanization molding or a raised object such as a burr sucked up on a dividing surface of the mold. The main object of the present invention is to provide a pneumatic tire and a method for manufacturing the same that can surely exert a current-carrying effect while miniaturizing the conductive portion on the basis that at least a part is constituted by the conductive portion.

The invention according to claim 1 of the present invention is the air having a raised object including any one of a spew having an outer diameter of 0.6 to 2.0 mm and a spew excision mark obtained by excising the spew on the grounding surface of the tread rubber. The tread rubber comprises a cap portion made of non-conductive rubber and a conductive rubber, one end of which is exposed to the ground surface and the other end. Includes a conductive portion connected to a conductive path that is electrically conductive with the rim when the rim is assembled, and the cap portion includes a first cap portion divided into left and right in the tire axial direction, and a second cap portion. The first cap portion and the second cap portion each have a tapered portion whose thickness gradually decreases toward the inner end in the tire axial direction, and the first cap portion is the tire at the inner end. Radially outward The second cap portion includes a tapered inner surface facing the tapered outer surface on the inner side in the tire radial direction of the inner end, and a radial direction of the tire between the tapered outer surface and the tapered inner surface. The conducting portion extending obliquely toward the inside is disposed, and the one end of the conducting portion has a width in the tire axial direction and is continuously exposed in the tire circumferential direction, and is exposed to the ground contact surface. The one end of the portion has a width in the tire axial direction and is continuously exposed in the tire circumferential direction, and is exposed to the ground contact surface. Further, it is characterized in that the conductive portion constitutes at least a part of at least one raised object .

Further, the invention according to claim 2 is that when a normal load is applied to a tire in a normal state in which a rim is assembled to a normal rim and a normal internal pressure is filled, and the tire is grounded and rolled on a plane with a camber angle of 0 degrees, The pneumatic tire according to claim 1, wherein two or more of the raised objects are always included in the ground contact area.

The invention according to claim 3 is a method for producing a pneumatic tire having a tread rubber, comprising: a tread rubber molding step for molding the tread rubber; and a raw tire including the tread rubber in a tread portion. A vulcanization step of vulcanization molding using a mold having a vent hole, and the tread rubber constitutes a main portion of the ground surface and is made of a non-conductive rubber, and a conductive rubber. And one end of which has a width in the tire axial direction, is exposed to the ground contact surface and is continuous in the tire circumferential direction, and the other end is arranged at a position connected to a conductive path electrically connected to the rim when the rim is assembled. And the vulcanizing step vulcanizes the vulcanization step by facing and vulcanizing at least a part of the conductive part that appears on the grounding surface to the vent hole of the mold. Characterized in that sucks up the vent hole.

The invention according to claim 4 is a method for producing a pneumatic tire having a tread rubber, comprising: a tread rubber molding step for molding the tread rubber; and a raw tire including the tread rubber in a tread portion. A vulcanization step of vulcanization molding using a mold having a split surface, and the tread rubber constitutes a main portion of the ground surface and is made of a non-conductive rubber, and a conductive rubber And one end of which has a width in the tire axial direction, is exposed to the ground contact surface and is continuous in the tire circumferential direction, and the other end is arranged at a position connected to a conductive path electrically connected to the rim when the rim is assembled. And the vulcanization step vulcanizes the vulcanizing step by facing and vulcanizing at least a part of the conductive part that appears on the ground plane to the divided surface. Gap Characterized in that the siphon.

In the present specification, “conductive” means a property that a substance substantially conducts electricity. Specifically, a material having a volume specific electric resistance value of less than 1.0 × 10 ⁸ (Ω · cm) is used. It is assumed to have the properties shown. On the other hand, “non-conductive” means that a substance does not substantially conduct electricity. Specifically, a material having a volume specific electrical resistance value of 1.0 × 10 ⁸ (Ω · cm) or more is used. It is assumed to have the properties shown. Further, the volume specific electrical resistance value of rubber is measured with an electrical resistance measuring instrument under conditions of an applied voltage of 500 V, an air temperature of 25 ° C., and a humidity of 50% with respect to a rubber sample of 15 cm square and 2 mm thick.

  In the pneumatic tire according to claim 1, a part of the conductive portion made of conductive rubber constitutes at least a part of a raised object including any of a spew, a spew excision mark obtained by excising the spew, and a burr. . These ridges are all formed by being sucked up outward in the tire radial direction from the regular ground contact surface by a vent hole or a split surface of the mold during vulcanization molding. Therefore, by constituting a part of such a raised object with a conductive portion, for example, a conductive rubber can be reliably exposed to the ground plane even with a narrow conductive portion. Therefore, the pneumatic tire of the present invention can exhibit a high electrostatic discharge effect.

Moreover, in the manufacturing method of the pneumatic tire of this invention described in Claim 3 or 4 , the above-mentioned pneumatic tire can be manufactured efficiently.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a cross-sectional view of a pneumatic tire 1 of the present embodiment. The pneumatic tire 1 includes a toroidal carcass 6 that extends from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and the carcass 6 on the outer side in the tire radial direction and inside the tread portion 2. Tread reinforcing cord layer 7 is provided.

  The carcass 6 is formed of one carcass ply 6A having a radial structure, for example. The carcass ply 6A includes a carcass cord of, for example, an organic fiber cord. In the present embodiment, the toroid-like main body portion 6a straddling the bead cores 5 and 5 and the bead cores 5 are connected to both sides of the carcass ply 6A from the inner side to the outer side in the tire axial direction. And a pair of folded-back portions 6b folded back. 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.

  The tread reinforcing cord layer 7 is formed by stacking two or more belt plies 7A and 7B in this example, in which metal cords are arranged at an angle of, for example, 15 to 40 degrees with respect to the tire circumferential direction. If necessary, the tread reinforcing cord layer 7 can include a band ply (not shown) including organic fiber cords arranged substantially parallel to the tire circumferential direction outside the belt ply 7B in the tire radial direction. .

Each of the carcass plies 6A and the belt plies 7A and 7B is composed of a tire ply made of a cord and a topping rubber covering the cord. The topping rubber contains abundant carbon black as a filler. For this reason, each topping rubber has electrical conductivity whose volume specific electrical resistance value is less than 1.0 × 10 ⁸ (Ω · cm).

Further, outside the carcass 6, a sidewall rubber 3 </ b> G that forms a tire skin in the sidewall region is disposed. The outer end of the sidewall rubber 3G in the tire radial direction extends between the carcass 6 and the tread reinforcing cord layer 7 and terminates. A clinch rubber 4G that can come into contact with the rim J when mounted on a metal (conductive) rim J is disposed outside the carcass 6 and in the bead region. The clinch rubber 4G is connected to the sidewall rubber 3G. Since the side wall rubber 3G and the clinch rubber 4G contain abundant carbon black as a filler, the side wall rubber 3G and the clinch rubber 4G have conductivity having a volume specific electric resistance value of less than 1.0 × 10 ⁸ (Ω · cm). An inner liner rubber 12 having excellent air impermeability is disposed inside the carcass 6.

  A tread rubber 2G is disposed outside the tread reinforcing cord layer 7 in the tire radial direction. The tread rubber 2G of the present embodiment includes a base portion 9 made of non-conductive rubber that is disposed on the inner side in the tire radial direction, and a main portion of the ground contact surface 2a that is disposed on the outer side in the tire radial direction of the base portion 9. And a conducting portion 11 having one end exposed to the ground plane 2a and the other end connected to a conducting path that is electrically conducted to the rim J when the rim is assembled. Consists of including. In this embodiment, the conductive path is constituted by the sidewall rubber 3G and the clinch rubber 4G. However, the conductive path passes through another conductive material (such as the topping rubber of the carcass 6 or the topping rubber of the tread reinforcing cord layer 7). Needless to say, it may be a passage.

  The contact surface 2a of the tread portion 2 is a flat surface of the tread portion 2 with a camber angle of 0 degree by applying a normal load to the tire in a normal state in which the tire 1 is assembled to a normal rim and filled with a normal internal pressure. It is a surface that contacts the plane when it is grounded. The positions on the outermost side in the tire axial direction of the contact surface are tread ends e1 and e2.

  Here, the regular rim is a rim determined for each tire in the standard system including the standard on which the tire is based. For example, the standard rim is “standard rim” for JATMA, and “Design Rim” for TRA. For ETRTO, use "Measuring Rim". The normal internal pressure is an air pressure determined by each standard for each tire in the standard system including the standard on which the tire is based. The maximum air pressure is JATMA, and the table "TIRE LOAD LIMITS AT" is TRA. Maximum value described in “VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” for ETRTO, but 180 kPa for tires for passenger cars. Further, the normal load is a load determined by each standard for each tire in a standard system including a standard on which the tire is based. “JATMA” indicates “maximum load capacity”, and TRA indicates “TIRE”. The maximum value described in “LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” is “LOAD CAPACITY” in the case of ETRTO.

  In the present embodiment, the base portion 9 and the cap portion 10 are made of silica-rich compound rubber containing a large amount of silica. Such a silica-rich compounded rubber can exhibit excellent actual vehicle running performance such as improving wet grip performance and wear resistance in the cap portion 10 and reducing heat generation and rolling resistance in the base portion 9. On the other hand, when the silica is blended in a large amount, the base portion 9 and the cap portion 10 both show non-conductivity.

  Examples of the rubber polymer constituting the base portion 9 and the cap portion 10 include natural rubber (NR), butadiene rubber (BR), styrene butadiene rubber (SBR), polyisoprene rubber (IR), nitrile rubber (NBR), or chloroprene rubber. (CR) etc. can be mentioned, These 1 type (s) or 2 or more types can be blended and used.

Further, the silica to be blended in the base portion 9 and the cap portion 10 is not particularly limited. However, in order to enhance the reinforcing effect on rubber and rubber processability, the nitrogen adsorption specific surface area (BET) is 150 to 250 m ² /. Those having colloidal characteristics in the range of g and dibutyl phthalate (DBP) oil absorption of 180 ml / 100 g or more are desirable.

  As the silane coupling agent, bis (triethoxysilylpropyl) tetrasulfide and α-mercaptopropyltrimethoxysilane are suitable. In order to achieve both low rolling resistance and wet grip performance at a higher level, the blending amount of silica in the base portion 9 and the cap portion 10 is preferably 30 parts by mass with respect to 100 parts by mass of the rubber polymer. As described above, more preferably 40 parts by mass or more, and 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.

  Needless to say, the base portion 9 and the cap portion 10 may be supplemented with carbon black as well as silica. This is useful for adjusting other rubber physical properties such as rubber elasticity and rubber hardness. In this case, the compounding amount of carbon black is less than the compounding amount of silica, and is particularly preferably 15 parts by mass or less, more preferably 10 parts by mass or less with respect to 100 parts by mass of the rubber polymer. If the blending amount of the carbon black exceeds 15 parts by mass, the low rolling resistance due to silica is impaired, and the rubber tends to be excessively hard, which is not preferable.

  In the present embodiment, the base portion 9 is disposed so as to overlap the tread reinforcing cord layer 7 and continuously extends from one tread end e1 side to the other tread end e2 side without interruption. The base portion 9 of the present embodiment has a tire axial width larger than that so as to completely cover the tread reinforcing cord layer 7. Accordingly, the outer ends 9 a and 9 b of the base portion 9 in the tire axial direction are both on the outer side in the tire axial direction than the ends of the tread reinforcing cord layer 7. Each outer end 9a, 9b of the base portion 9 has a tapered shape, and is connected to, for example, the sidewall rubber 3G.

  In the present embodiment, the cap portion 10 includes a first cap portion 10A and a second cap portion 10B that are divided into left and right in the tire axial direction. In the present embodiment, the first cap portion 10A is arranged on one tread end e1 side (right side in FIG. 1) from the tire equator C, and the second cap portion 10B is on the other tread than the tire equator C. It is arranged on the end e2 side (left side in FIG. 1). Further, the outer ends 10Ao and 10Bo of the cap portions 10A and 10B in the tire axial direction are on the outer side in the tire axial direction with respect to the tread ends e1 or e2 on the respective sides, particularly on the outer side of the outer ends 9a or 9b of the base portion 9. Provided. That is, except for the conducting portion 11, the ground contact surface 2a is formed by the outer surfaces in the tire radial direction of the first cap portion 10A and the second cap portion 10B. Thereby, wet grip performance and abrasion resistance can be improved.

  Further, as shown in an enlarged view in FIG. 2, each cap portion 10A and 10B includes a tapered portion T whose thickness gradually decreases toward the inner end 10Ai or 10Bi in the tire axial direction. The first cap portion 10A includes a tapered outer surface Ta that is inclined outward in the tire radial direction. On the other hand, the second cap portion 10B includes a tapered inner surface Tb facing the tapered outer surface Ta on the inner side in the tire radial direction. And the said conduction | electrical_connection part 11 is distribute | arranged between these taper outer surface Ta and taper inner surface Tb.

  The conduction part 11 is made of conductive rubber. As such a rubber composition, for example, a carbon-rich rubber composition is suitable. For example, a conductive powder (for example, metal powder) may be blended in place of carbon or together with carbon.

  Further, one end 11a located on the outer side in the tire radial direction of the conduction portion 11 is provided exposed to the ground contact surface 2a. In this embodiment, the said one end 11a of the conduction | electrical_connection part 11 is exposed to the contact surface 2a continuously in a tire circumferential direction, as FIG. 6 (a) and (b) show. Therefore, the conduction | electrical_connection part 11 can be grounded continuously with the road surface at the time of driving | running | working of a tire. In addition, since the conducting portion 11 of the present embodiment is provided substantially in the vicinity of the tire equator C, it can be grounded not only when traveling straight but also when turning.

  Further, the conducting portion 11 of the present embodiment is between the first cap portion 10A and the second cap portion 10B from the one end 11a exposed at the ground surface 2a, that is, between the tapered outer surface Ta and the tapered inner surface Tb. Extends diagonally inward in the tire radial direction, and extends between the second cap portion 10B and the base portion 9 in the tire axial direction outside along the inclination. And as FIG. 1 shows, the other end 11b of the conduction | electrical_connection part 11 is connected to the sidewall rubber | gum 3G beyond the other outer end 9b of the base part 9, and terminates. Therefore, when the pneumatic tire 1 of the present embodiment is assembled to the rim J, the rim J and the conductive portion 11 are electrically connected to each other through a conductive path made of the sidewall rubber 3G and the clinch rubber 4G. To do. The other end 11b of the conducting part 11 is covered with the second cap part 10B.

  Further, in the pneumatic tire 1 of the present embodiment, the conducting portion 11 is formed by the spew 13a as shown in FIGS. 1 and 2, the spew excision mark 13b obtained by excising the spew 13a as shown in FIG. 3, and FIG. It constitutes at least a part of the raised object 13 including any of the burr 13c as shown in b).

  As partly shown in FIG. 5 (a), air remaining between the tread rubber 2G is released on the tread molding surface Mt of the mold M for molding the pneumatic tire 1 of the present embodiment. A plurality of vent holes V each having a small hole are provided. As shown in FIG. 5 (b), this vent hole V is usually evacuated from the outside and / or because of pressure to press the tread rubber 2G by a bladder against the mold. A part of the resin enters the vent hole V and hardens. This remains on the surface of the vulcanized tread rubber 2G to form the spew 13a. The spew 13a is provided at a position other than the tread groove provided in the tread rubber 2G.

  Then, by configuring at least a part of the spew 13a with the conducting portion 11, for example, even the conducting portion 11 having a small width R in the tire axial direction (shown in FIG. 2) is covered with the rubber of the cap portion 10. Without being exposed to the ground surface 2a. Therefore, the pneumatic tire 1 of the present embodiment can exhibit an excellent electrostatic discharge effect.

For reasons of appearance, a part of the spew 13a may be cut out by a trimming process. Even in such a case, as shown in FIG. 3 , the spout excision mark 13b is slightly outward in the tire radial direction from the regular ground surface 2a (the portion formed by the tread molding surface Mt of the mold M). Since it protrudes, the conduction | electrical_connection part 11 can be reliably earth | grounded with the road surface by this spew excision mark 13b, and by extension, a reliable discharge effect can be exhibited.

  Furthermore, as shown in FIG. 4B, the mold M is usually composed of a plurality of segments, and a minute gap is formed on the dividing surface K on which the segments face each other. Then, a part of the tread rubber 2G enters and cures in the gap between the divided surfaces K, thereby forming a burr 13c as shown in FIG. Therefore, the same effect as in the case of the spew 13a can be exhibited also by configuring a part of the burr 13c with the conductive portion 11.

The spew 13a is most preferable as the raised object 13. However, if the outer diameter D of the spew 13a is too small, the effect of sucking the conductive rubber may be insufficient. May be seriously damaged. From such a viewpoint, the outer diameter D of the spew 13a is preferably 0.6 mm or more, more preferably 0.8 mm or more, and 2.0 mm or less, more preferably 1.5 mm or less.

Moreover, as shown in FIG.2 and FIG.6 (a), all of the spew 13a as the protruding object 13 may be comprised by the conduction | electrical_connection part 11, and as FIG.6 (b) shows, Only a part of the spew 13 a may be configured by the conductive portion 11. In the latter case, it is desirable to arrange so as to satisfy the following formula (1), more preferably the following formula (2), in order to exhibit the discharge effect by the spew 13a more reliably.
x ≦ | R / 2 + D | (1)
x <| R / 2 + D | (2)
Here, x is the tire axial distance from the center line CL of the conducting portion 11 to the outermost position of the spew 13a, R is the width of the conducting portion 11 in the tire axial direction, and D is the maximum outer diameter of the spew 13a. And In addition, when providing the spew 13a offset from the center of the conduction | electrical_connection part 11, since the conduction | electrical_connection part 11 inclines inside a tire in this embodiment, the spew 13a is offset to this inclination side (left side in a figure). It is desirable. This is desirable in that more conductive rubber can be sucked up.

  Further, when the raised object 13 at least partly formed by the conductive portion 11 is the spew 13a or the spew excision mark 13b, a normal load is applied to the tire in the normal state, the camber angle is 0 degrees, and the flat surface is grounded. When moved, it is desirable to always include two or more, more preferably three or more of the raised objects 13 in the ground contact area. As a result, the static electricity of the vehicle can be discharged to the road surface more reliably.

  In the pneumatic tire as described above, the static electricity accumulated in the vehicle is reliably discharged to the road surface via the rim J, the clinch rubber 4G, the sidewall rubber 3G, and the conduction portion 11. Thus, problems such as radio noise are improved.

  Further, in order to sufficiently exhibit the above-described discharge effect, as shown in FIG. 2, in the tire meridian cross section including the tire rotation axis, the thickness te perpendicular to the longitudinal direction of the conducting portion 11 is preferably 0.3 mm. More preferably, 0.5 mm or more is desirable. Similarly, the width R of the conductive portion 11 exposed on the ground plane 2a is preferably 0.5 mm or more, more preferably 0.7 mm or more. On the other hand, when the thickness te or the width R of the conductive portion 11 is increased, the actual vehicle performance such as the wet performance and the rolling resistance of the tread rubber 2G may be deteriorated. From such a viewpoint, the thickness te of the conductive portion 11 is preferably 5 mm or less, more preferably 3 mm or less. Similarly, the width R of the conductive portion 11 is preferably 5 mm or less, more preferably 3 mm or less, and particularly 2 mm or less. In particular, when the above formula (2) is satisfied, even if the width R is small, a sufficient effect cannot be exhibited (see Example 9, etc. described later).

  Moreover, since the said conduction | electrical_connection part 11 has few compounding quantities of a silica compared with the 1st and 2nd cap parts 10A and 10B, there exists a tendency for abrasion resistance to be inferior. Therefore, preferably, the orientation of the pneumatic tire 1 to be mounted on the vehicle is specified, and the one end 11a of the conducting portion 11 exposed to the ground contact surface 2a is connected to the tire equator C as shown by the phantom line in FIG. It is desirable to be provided closer to the inside of the vehicle. Thereby, the conduction part 11 can be kept away as much as possible from a large lateral force generated on the tread grounding surface outside the vehicle during turning, and early wear of the conduction part 11 can be suppressed.

  Moreover, it is desirable that the conducting portion 11 extends from the one end 11a to the inside of the vehicle in the tire radial direction. Thereby, the position of the one end 11a of the conduction | electrical_connection part 11 exposed to a ground-contact surface can be moved to the vehicle inner side further with wear. The direction of mounting on the vehicle is specified by, for example, displaying one side wall portion 3 indicating that the vehicle is inside (for example, “INSIDE”) and the other side wall portion 3 on the outside of the vehicle. Is displayed (for example, “OUTSIDE”).

  Further, as shown in FIG. 7, it is preferable that the conductive portion 11 is formed of a strip laminated body in which a ribbon-shaped rubber strip 15 having a small width and a small thickness is wound spirally. Thereby, the conduction part 11 having a small width R can be efficiently formed.

  In a preferred embodiment, all members constituting the tread rubber 2G, that is, the base portion 9, the cap portion 10, and the conducting portion 11 are formed by spirally winding the unvulcanized rubber strip 15 shown in FIG. Is done. The “unvulcanized” refers to the state of rubber that has not been completely vulcanized. Therefore, rubber that has only been pre-vulcanized is included in unvulcanized rubber.

  The rubber strip 15 is formed in a ribbon shape having a rectangular cross section having a width W larger than the thickness t. The width W and the thickness t of the rubber strip are not particularly limited, but the width W is preferably 5 to 50 mm and the thickness t is preferably about 0.5 to 3 mm. When the width W of the rubber strip is less than 5 mm or the thickness t is less than 0.5 mm, the rubber strip is liable to be broken when it is wound in a spiral shape, and the number of windings may be remarkably increased and productivity may be lowered. Conversely, when the width W of the rubber strip exceeds 50 mm or when the thickness t exceeds 3 mm, it tends to be difficult to form an accurate cross-sectional shape by spirally winding.

  8 and 9 show an example of a tread rubber molding process for molding the tread rubber 2G in time series.

  In the tread rubber molding step, first, as shown in FIG. 8 (a), a rubber strip that exhibits non-conductivity by silica-rich compounding on the outside of a cylindrical molding former F around which a tread reinforcing cord layer 7 is wound in advance. The base portion 9 is formed by winding 15A in a spiral shape. Specifically, first, on one tread end e1 side, the winding start end 15As of the rubber strip 15A is fixed on the molding former at a position outside the tread reinforcing cord layer 7 in the tire axial direction, and then the molding former F is fixed. The rubber strip 15 is rotated and moved to the other tread end e2 side at a predetermined speed, whereby the rubber strip 15A is spirally wound on the molding former F. At this time, it is desirable that the side edges of the rubber strip 15 </ b> A overlap each other. Thereafter, the molding former F is stopped, and the winding end 15Ae of the rubber strip 15A is fixed on the molding former F at a position beyond the tread reinforcing cord layer 7 outward in the tire axial direction. Thereby, the base portion 9 is formed with a width that completely covers the tread reinforcing cord layer 7. Note that the thickness and / or the cross-sectional shape of the base portion 9 can be freely set by adjusting the number of rolls of the rubber strip 15.

  Next, as shown in FIG. 8B, the first cap portion 10A is formed on the outer side in the tire radial direction of the base portion 9 and on the one tread end e1 side. At this stage, the winding start end 15Bs of the rubber strip 15B that exhibits non-conductivity due to the silica-rich compound is fixed on the base portion 9 and approximately in the middle between the outer end 10Ao and the inner end 10Ai of the first cap portion 10A. . The rubber strip 15B is spirally wound toward the outer side in the tire axial direction, and is wound around the inner side in the tire axial direction by changing the direction at the outer end 10Ao. Then, the winding is finished by changing the winding direction to the outer side in the tire axial direction again at the inner end 10Ai beyond the winding start end 15Bs toward the inner side in the tire axial direction. It should be noted that the winding end 15Be of the rubber strip 15B is fastened approximately in the middle between the outer end 10Ao and the inner end 10Ai. During this time, the rubber strip 15B is continuous. In such a first cap portion 10A, the winding start end 15Bs and the winding end end 15Be of the rubber strip 15B do not appear at both ends, so that it is prevented from becoming the starting point of peeling or the like. However, it goes without saying that the winding mode of the rubber strip 15B is not limited to such a mode and can be variously changed.

  Next, as shown in FIG. 9A, a rubber strip 15C made of conductive rubber is wound around the outer surface of the taper outer surface Ta of the base portion 9 and the first cap portion 10 in a spiral manner, thereby making the conduction. Forming the part 11 is performed. At this stage, for example, the winding start end 15Cs of the rubber strip 15C is fixed to the outermost side of the tapered outer surface Ta of the first cap portion 10A, and the rubber strip 15C is spirally wound around the other tread end e2 side. The winding end 15Ce is fixed on the former F beyond the base portion 9 to the outside. When winding the rubber strip 15C, it is preferable to wind the rubber strip 15C without any gap so that the side edges of the rubber strip 15C overlap each other as in the present embodiment. Thereby, a more reliable conductive path can be formed.

  Thereafter, as shown in FIG. 9B, a step of forming the second cap portion 10 </ b> B outside the conduction portion 11 in the tire radial direction is performed. At this stage, first, the winding start end 15Ds of the rubber strip 15D that exhibits non-conductivity by silica-rich compounding (the same compounding as the rubber strip 15B of the first cap part 10A may be used) is formed on the base part 9. And it adheres to the middle of the outer end 10Bo and the inner end 10Bi. The rubber strip 15B is spirally wound outward in the tire axial direction and is wound inward in the tire axial direction by changing the direction at the outer end 10Bo. Then, the winding is finished by changing the winding direction to the outer side in the tire axial direction again at the inner end 10Bi beyond the winding start end 15Ds toward the inner side in the tire axial direction. The winding end 15De of the rubber strip 15D is fastened to approximately the middle between the outer end 10Bo and the inner end 10Bi.

  By the tread rubber molding process as described above, the tread rubber 2G formed integrally with the tread reinforcing cord layer 7 is formed. Then, in accordance with customary practice, the raw tire is molded by extrapolating the tread rubber 2G into the tread region of the carcass 6 shaped in a toroid shape. And the vulcanization | cure process which vulcanizes-molds this raw tire using the metal mold | die M which has the vent hole V is performed.

In the vulcanization step, as shown in FIG. 5 (a), by positioning and vulcanizing at least a part of the conductive portion 11 appearing on the ground surface 2a to the vent hole V of the mold M, At least a part of the rubber of the conductive portion 11 is sucked up so as to constitute the spew 13a. Note that such positioning, as possible out be easily performed by determining the position of the conductive portion 11 of the green tire based on the position of the vent hole V of the mold M is known in advance. Further, as shown in FIG. 4 (a), as the vulcanization step, by positioning and vulcanizing at least a part of the conductive portion 11 appearing on the ground contact surface 2a on the split surface K of the mold M so as to face each other. Then, at least a part of the rubber of the conducting portion 11 is sucked up so as to constitute the burr 13c. Since the position of the dividing surface K of the mold M is also known, the rubber of the conducting portion 11 can be sucked into the gap of the dividing surface K by arranging the dividing surface K so as to face the conducting portion 11 .

  FIG. 10 shows another embodiment of the method for manufacturing a pneumatic tire. In the present embodiment, the conductive portion 11 is formed by winding at least one round of the rubber sheet 17 continuous in the width direction from the other end 11b to the one end 11a and splicing both ends in the tire circumferential direction. Show. However, it goes without saying that a rubber strip is preferably used for the conductive portion 11 in order to increase the uniformity of the tire. After this, a second cap portion is disposed outside the conductive portion 11 (not shown).

  FIG. 11 further shows another embodiment of the tread rubber 2G. In this embodiment, the base part 9 and the cap part 10 show what was formed by splicing the extruded rubber 19 extruded by the rubber extruder. In this embodiment, after the extruded rubber 19 of the base portion 9 and the first cap portion 10A is wound around the outer side of the tread reinforcing cord layer 7, a rubber strip 15C made of conductive rubber having a ribbon shape is further formed on the outer side thereof. Is spirally wound to form the conductive portion 11. Thereafter, the extruded rubber 19 constituting the second cap portion 10B is wound around the outside of the conducting portion 11 and spliced.

  In each of the above-described embodiments, since the base portion 9 is formed without being divided into left and right in the tire axial direction, it is useful for suppressing deterioration in uniformity of the finished tire.

  As mentioned above, although the pneumatic tire of this invention and its manufacturing method were demonstrated in detail, it cannot be overemphasized that this invention can be deform | transformed and implemented in a various aspect, without being limited to said specific embodiment. For example, in the present embodiment, the tread rubber 2G has a two-layer structure of the base portion 9 and the cap portion 10, but may be composed of one layer or may be composed of three or more layers.

A pneumatic tire (size: 215 / 45R17) having the basic structure shown in Table 1 was prototyped, and the electrical resistance of each tire was measured . In each example, non-conductive rubber was used for the cap part and the base part, and conductive rubber was used for the conduction part (through terminal part). The formulation is the same for each example. In addition, the parameters other than those shown in Table 1 are the same for each tire, and as the tread rubber, as shown in FIG.
The test method is as follows.

<Occurrence rate of poorly powered tires>
As shown in FIG. 12, the insulating plate 20 (electric resistance 10 ¹² Omega higher) plate metal installation surface is polished on a 21 (electric resistance 10Ω or less), tire rim assembly The electrical resistance value of the assembly of the test tire and the rim J was measured in accordance with JATMA regulations using a measuring device including a conductive tire mounting shaft 22 that holds the tire and an electrical resistance measuring device 23. Each test tire 1 was a tire in which the surface release agent and dirt were sufficiently removed in advance and were sufficiently dried. Other conditions are as follows.
Rim material: Aluminum alloy Rim size: 17 × 7J
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 1 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 allowed to stand in the test room for 2 hours and then attached to the tire mounting shaft 22.
(3) The tire / rim assembly is loaded with the load for 0.5 minutes, and further for 0.5 minutes after being released and for 2 minutes after being released.
(4) When the test voltage is applied and 5 minutes have passed, the electrical resistance value between the tire mounting shaft 22 and the metal plate 21 is measured by the electrical resistance measuring instrument 23. 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.

200 test tires were manufactured according to the specifications shown in Table 1, and their electrical resistance values were measured in a new state based on the test method. Then, for each example, the number of tires having an electric resistance value of 1 × 10 ⁸ Ω or more was examined, and the ratio was shown. The smaller the value, the better.
Table 1 shows the test results.

  As a result of the test, it was confirmed that the tire of the example can obtain a tire having a sufficiently small electric resistance value even if the width of the conductive portion is set small.

It is sectional drawing of the pneumatic tire of this embodiment. It is the elements on larger scale of the tread part. It is the elements on larger scale of the tread part explaining a spew excision mark. (A) And (b) is the elements on larger scale of the tread part explaining a burr | flash. (A) And (b) is sectional drawing explaining the effect | action by a spew. (A) And (b) is a partial top view of a tread part. It is a perspective view which shows an example of a rubber strip. (A) And (b) is sectional drawing for demonstrating a tread rubber molding process. (A) And (b) is sectional drawing for demonstrating a tread rubber molding process. It is sectional drawing for demonstrating other embodiment of the shaping | molding process of a conduction | electrical_connection part. It is sectional drawing for demonstrating other embodiment of a tread rubber shaping | molding process. 1 is a schematic cross-sectional view conceptually showing a tire electrical resistance measuring device. (A) is sectional drawing of the conventional tread rubber, (b) is the elements on larger scale.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 2a Grounding surface 2G Tread rubber 3 Side wall part 3G Side wall rubber 4 Bead part 4G Clinch rubber 5 Bead core 6 Carcass 7 Tread reinforcement cord layer 9 Base part 10 Cap part 10A 1st cap part 10B 2nd Cap part 11 Conducting part 13 Raised part 13a Spew 13b Spew excision mark 13c Burr

Claims (8)

A pneumatic tire having a protuberance including any one of a spew having an outer diameter of 0.6 to 2.0 mm and a spew excision mark obtained by excising the spew on the ground surface of the tread rubber,
The tread rubber constitutes a main part of the grounding surface and a cap part made of non-conductive rubber;
A conductive portion made of conductive rubber and having one end exposed to the grounding surface and the other end connected to a conductive path that is electrically conductive with the rim when the rim is assembled;
The cap portion is composed of a first cap portion and a second cap portion that are divided into left and right in the tire axial direction, and the first cap portion and the second cap portion are respectively in the tire axial direction. It has a taper that gradually decreases in thickness toward the inner edge,
The first cap portion includes a tapered outer surface that is inclined outward in the tire radial direction of the inner end, while the second cap portion includes a tapered inner surface that faces the tapered outer surface on the inner side in the tire radial direction of the inner end. In addition, between the tapered outer surface and the tapered inner surface, the conductive portion extending obliquely toward the inside in the tire radial direction is arranged,
The one end of the conducting portion has a width in the tire axial direction and is exposed to the ground contact surface continuously in the tire circumferential direction,
The one end of the conducting portion has a width in the tire axial direction and is exposed to the ground contact surface continuously in the tire circumferential direction,
The raised object is provided in a portion other than the tread groove so as to extend outward in the tire radial direction from the ground contact surface, and the conductive portion constitutes at least a part of at least one raised object. tire.   When a normal load is loaded on a normal tire that is assembled with a normal rim and filled with a normal internal pressure, the raised object is always in the ground contact area when it is grounded and rolled on a flat surface with a camber angle of 0 degrees. The pneumatic tire according to claim 1, wherein two or more are included. A method for producing a pneumatic tire having tread rubber,
A tread rubber molding step for molding the tread rubber;
A vulcanization step of vulcanizing a raw tire having the tread rubber in a tread portion using a mold having a vent hole, and the tread rubber constitutes a main part of the ground surface and is non-conductive A cap portion made of a conductive rubber, one end having a width in the tire axial direction, exposed to the ground contact surface and continuous in the tire circumferential direction, and the other end electrically connected to the rim when the rim is assembled. Including a conductive portion disposed at a position connected to a conductive path that is conductive to
The cap portion is composed of a first cap portion and a second cap portion that are divided into left and right in the tire axial direction, and the first cap portion and the second cap portion are respectively in the tire axial direction. It has a taper that gradually decreases in thickness toward the inner edge,
The first cap portion includes a tapered outer surface that is inclined outward in the tire radial direction of the inner end, while the second cap portion includes a tapered inner surface that faces the tapered outer surface on the inner side in the tire radial direction of the inner end. In addition, between the tapered outer surface and the tapered inner surface, the conductive portion extending obliquely inwardly in the tire radial direction is disposed, and the vulcanization step is performed on the ground contact surface in the vent hole of the mold. A method for producing a pneumatic tire, comprising sucking a part of the conductive part into the vent hole by facing and vulcanizing at least a part of the conductive part appearing in FIG. A method for producing a pneumatic tire having tread rubber,
A tread rubber molding step for molding the tread rubber;
A vulcanization step of vulcanizing a raw tire having the tread rubber in a tread portion using a mold having a split surface, and the tread rubber constitutes a main part of the ground surface and is non-conductive A cap portion made of a conductive rubber, one end having a width in the tire axial direction, exposed to the ground contact surface and continuous in the tire circumferential direction, and the other end electrically connected to the rim when the rim is assembled. Including a conductive portion disposed at a position connected to a conductive path that is conductive to
The cap portion is composed of a first cap portion and a second cap portion that are divided into left and right in the tire axial direction, and the first cap portion and the second cap portion are respectively in the tire axial direction. It has a taper that gradually decreases in thickness toward the inner edge,
The first cap portion includes a tapered outer surface that is inclined outward in the tire radial direction of the inner end, while the second cap portion includes a tapered inner surface that faces the tapered outer surface on the inner side in the tire radial direction of the inner end. The conductive portion extending obliquely inward in the tire radial direction is disposed between the tapered outer surface and the tapered inner surface, and the vulcanization step is conducted on the divided surface on the ground contact surface. A method for manufacturing a pneumatic tire, comprising sucking a part of the conducting part into the gap between the divided surfaces by facing and vulcanizing at least a part of the part. 2. The pneumatic tire according to claim 1, wherein the raised object includes at least one spew that is offset from a center of a width of the conductive portion toward the inclined side of the conductive portion . The pneumatic installation according to claim 1, 2, or 5, wherein a direction of mounting on the vehicle is displayed on a sidewall portion, and the conductive portion is inclined toward the vehicle inner side from the one end toward the inner side in the tire radial direction. tire. The pneumatic tire according to any one of claims 1, 2, 5, and 6 , wherein the conductive portion is formed of a strip laminated body in which a ribbon-shaped rubber strip having a small width and a small thickness is spirally wound . 5. The pneumatic tire according to claim 3, wherein the tread rubber molding step includes a step of forming the conductive portion by a strip laminated body in which a ribbon-shaped rubber strip having a small width and a small thickness is spirally wound. Manufacturing method.

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