JP2014151479A - Manufacturing method for tyre - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method for a tyre which enables the suppression in generation of an uneven wear by suppressing a strip transfer during vulcanization molding even when a narrow strip is wound at a small gap ratio to form a circumferential belt reinforcement layer.SOLUTION: A manufacturing method for a tyre, which includes a vulcanization molding process for heating and pressurizing a green tyre in a type molding metal mold, includes a recess forming process in which the green tyre is constituted by sequentially arranging crossing belts, consisting of two or more belt layers, circumferential belt reinforcement layer formed by spirally winding a strip constituted by coating a cord with rubber, outside of a carcass crown part, and unvulcanized tread rubber, with strips adjacent in the tyre width direction separated from each other, and in which the type molding metal mold has a bump which forms a circumferential groove on a tread surface of a tyre, and forms a recess at least in a part of a region to form the circumferential groove, out of the surface of the unvulcanized tread rubber.

Description

  The present invention relates to a tire manufacturing method, and more particularly, to a tire manufacturing method including a circumferential belt reinforcing layer formed by winding a strip (band-like member) formed by covering a cord with rubber in the tire circumferential direction. .

  Conventionally, on the outer circumferential side of the crown portion of the carcass, a cross belt comprising two or more belt layers in which the cords are inclined in different directions with respect to the tire equatorial plane between adjacent belt layers in the tire radial direction, and the cords are covered with rubber A circumferential belt reinforcing layer formed by spirally winding the strip formed in the tire circumferential direction is sequentially disposed, and the reinforcing effect of the cross belt is enhanced by the circumferential belt reinforcing layer, so that the tire at the time of high-speed rotation is improved. There is known a pneumatic tire that suppresses the diameter growth and enhances the high-speed durability of the tire, secures the tire circumferential rigidity of the tread portion, improves the steering stability, and improves the noise performance. (For example, refer to Patent Document 1).

Japanese Patent Laid-Open No. 2007-8250

  Here, in general, a non-stretchable steel cord is used as the cord of the belt layer forming the crossing belt, and a stretchable organic fiber cord is used as the cord of the circumferential belt reinforcing layer. Therefore, in the conventional pneumatic tire having the circumferential belt reinforcing layer in the tread portion that is deformed when the tire contacts the ground, the organic fiber cord of the circumferential belt reinforcing layer may creep and deform to generate a flat spot.

In order to solve such a problem of creep deformation of the organic fiber cord, it is also conceivable to reduce the use amount of the organic fiber cord in the circumferential belt reinforcing layer to suppress the generation of flat spots.
Specifically, it is considered that the strips used for forming the circumferential belt reinforcing layer are wound apart from each other in the tire width direction, thereby reducing the amount of organic fiber cords used and suppressing the occurrence of flat spots. It is done. However, when a large gap is provided between adjacent strips in the tire width direction, the steel cord of the belt layer forming the crossing belt swells (that is, undulates) in the gap portion, and the contact pressure distribution on the tread surface is uneven. Therefore, uneven wear may occur.
On the other hand, the ratio of the gap d between the strips to the winding pitch p of the tire in the tire width direction dimension d (gap ratio d / p) is reduced and the strip is narrowed to suppress the undulation of the steel cord. It is also conceivable to reduce the amount of organic fiber cord used. However, when the strip has a narrow width, when the green tire is vulcanized to form a tire, the strip moves due to the flow of unvulcanized rubber in the tire molding die, and the strip is wound. The turn pitch may deviate from the desired pitch. When the winding pitch of the strip deviates from the desired winding pitch, the ground pressure is locally reduced at the portion where the winding pitch of the strip is increased, and uneven wear may occur. In addition, the movement of the strip at the time of vulcanization molding was particularly likely to occur at a portion where a circumferential groove extending in the tire circumferential direction is formed on the tread surface. A convex part for forming the circumferential groove is provided on the inner peripheral surface of the tire molding die corresponding to the part forming the circumferential groove, and the flow of the unvulcanized rubber is locally caused by the convex part. This is because it becomes larger.

  Therefore, the present invention suppresses the movement of the strip during vulcanization molding of the tire even when a narrow strip is wound with a small porosity to form a circumferential belt reinforcing layer, and uneven wear is prevented. It aims at providing the manufacturing method of the tire which can suppress generation | occurrence | production.

  The tire manufacturing method of the present invention is a tire manufacturing method including a vulcanization molding process in which a green tire is heated and pressed in a tire molding die to form a tire, and the green tire includes a carcass crown. An outer belt in the tire radial direction of the belt, a cross belt comprising two or more belt layers in which the cord is inclined in different directions with respect to the tire equatorial plane between the belt layers adjacent in the tire radial direction, and the cord is covered with rubber A circumferential belt reinforcing layer formed by spirally winding a strip formed in the tire circumferential direction and an unvulcanized tread rubber are sequentially disposed, and in the tire width direction cross-sectional view of the green tire, the tire width direction The strips adjacent to each other are spaced apart from each other, and the tire molding die has a convex portion that forms a circumferential groove extending in the tire circumferential direction on the tread portion tread surface of the tire. Has a mold inner peripheral surface, wherein one of the unvulcanized tread rubber surface, characterized in that it comprises a recess forming step of forming a recess in at least part of the region to be the fact that the circumferential groove is formed. In this way, if a recess is formed in at least a part of a region where a circumferential groove is to be formed in the unvulcanized tread rubber, a green tire is not added in the vulcanization molding step. The concave portion formed in the sulfurized tread rubber and the convex portion provided on the inner peripheral surface of the tire molding die are in contact with each other. Therefore, even when a circumferential strip belt reinforcement layer is formed by winding a narrow strip with a small porosity, the green tire is vulcanized compared to the case where no recess is formed in the unvulcanized tread rubber. In doing so, it is possible to prevent the flow of the unvulcanized tread rubber from locally increasing due to the convex portion. As a result, it is possible to suppress the movement of the strip due to the flow of the unvulcanized tread rubber in the tire molding die, thereby suppressing the occurrence of uneven wear due to the disturbance of the winding pitch of the strip. it can.

  According to the tire manufacturing method of the present invention, even when a circumferential belt reinforcing layer is formed by winding a narrow strip with a small porosity, an unvulcanized tread rubber in a tire molding die is formed. It is possible to suppress the occurrence of uneven wear by suppressing the movement of the strip due to the flow of.

It is a tire width direction sectional view of a pneumatic tire manufactured using a typical tire manufacturing method according to the present invention. It is a figure which expands and shows the vicinity of a tread part about the tire width direction cross section of the green tire used for manufacture of the pneumatic tire shown in FIG. (A), (b) is explanatory drawing which expands and shows a part of green tire and the mold for tire shaping | molding about the vulcanization molding process at the time of manufacturing the pneumatic tire shown in FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Here, an example of the manufacturing method of the tire of the present invention is used when manufacturing a tire including a circumferential belt reinforcing layer formed by winding a strip formed by covering a cord with rubber in the tire circumferential direction. Specifically, an example of the tire manufacturing method of the present invention can be used, for example, for manufacturing a pneumatic tire 10 whose cross section in the tire width direction is shown in FIG.

  A pneumatic tire 10 shown in FIG. 1 is connected to a tread portion 1, a pair of sidewall portions 2 extending inward in the tire radial direction from a side portion of the tread portion 1, and a tire radial direction inward of the sidewall portion 2. A pair of bead portions 3 is provided. A pneumatic tire 10 shown in FIG. 1 includes a radial carcass 5 made of one ply extending between a pair of bead portions 3. Here, the radial carcass 5 extends in a toroidal shape from the tread portion 1 to the pair of bead portions 3 via the pair of sidewall portions 2, and is folded back around a bead core 4 having a rectangular cross section embedded in the bead portion 3. It becomes. Further, in this pneumatic tire 10, the cross belt 6 composed of two belt layers 61 and 62 and a cord are rubber-coated on the outer side in the radial direction of the crown portion of the radial carcass 5 (outside of the crown portion). A circumferential belt reinforcing layer 7 formed by spirally winding the strip 71 in the tire circumferential direction is sequentially arranged from the inner side in the tire radial direction to the outer side in the tire radial direction.

Here, the belt layers 61 and 62 constituting the crossing belt 6 are configured by using a ply formed by rubber coating a plurality of cords (not shown) arranged in parallel to each other, and the inclined belt layer 61. , 62 are arranged at a predetermined inclination angle with respect to the tire circumferential direction. The cord of the belt layer 61 located on the inner side in the tire radial direction and the cord of the belt layer 62 located on the outer side in the tire radial direction intersect with each other across the tire equatorial plane EP. In addition, as a cord of the belt layers 61 and 62, a non-extensible cord, for example, a steel cord can be used.
The circumferential belt reinforcing layer 7 formed by winding the strip 71 in the tire circumferential direction is disposed on the outer side in the tire radial direction of the crown portion of the radial carcass 5, more specifically on the outer side in the tire radial direction of the cross belt 6. ing. As the cord of the strip 71, an extensible cord such as an organic fiber cord can be used. Examples of the organic fiber cord include nylon cord, polyethylene terephthalate (PET) cord, polyethylene naphthalate (PEN) cord, aramid cord, and aramid and nylon hybrid cord. As the fiber cord, it is preferable to use a cord that hardly undergoes creep deformation, such as a PET cord, a PEN cord, an aramid cord, and an aramid and nylon hybrid cord.

Further, in this pneumatic tire 10, a bead filler 8 having a substantially triangular cross section is disposed on the outer side of the bead core 4 of the bead portion 3 in the tire radial direction along the radial carcass 5 and gradually decreases in thickness toward the outer side of the tire radial direction. It is installed.
Further, in this pneumatic tire 10, tread rubber is disposed on the outer side in the tire radial direction of the circumferential belt reinforcing layer 7, and, for example, three circumferential directions extending in the tire circumferential direction are formed on the surface of the tread rubber. Grooves 91, 92, and 93 are formed. The circumferential grooves 91, 92, and 93 are disposed so as to be plane-symmetric with respect to the tire equatorial plane EP. Incidentally, the width of the circumferential grooves 91, 92, 93 can be 8 to 18 mm, for example, and the depth of the circumferential grooves 91, 92, 93 can be 6 to 10 mm, for example.

And this pneumatic tire 10 can be manufactured as follows, for example using an example of the manufacturing method of the tire of this invention.
<Green tire formation process>
First, in a green tire formation process, a green tire is produced according to a conventional method. Here, as shown in FIG. 2 which is a sectional view in the tire width direction in the vicinity of the tread portion of the green tire 10A, the green tire 10A has two belt layers 61, on the outer side in the tire radial direction of the crown portion of the radial carcass 5. The crossing belt 6 made of 62, the circumferential belt reinforcing layer 7, and the unvulcanized tread rubber 1A are sequentially disposed.

  Here, the belt layers 61 and 62 are made of a ply formed by rubber coating a plurality of cords (not shown) arranged parallel to each other, and the cords are tires between the belt layers 61 and 62 adjacent in the tire radial direction. It can be formed by being sequentially attached to the outer peripheral surface side of the radial carcass 5 so as to be inclined in different directions with respect to the equator plane EP.

  The circumferential belt reinforcing layer 7 is formed by spirally winding a strip 71 formed by covering a cord with unvulcanized rubber on the outer circumferential surface side of the belt layer 62 in the tire circumferential direction. As shown in FIG. 2 in which a part of the circumferential belt reinforcing layer 7 is enlarged, the strip 71 has a width w and is wound at a winding pitch p. In the cross-sectional view in the tire width direction, the strips 71 adjacent in the tire width direction are separated from each other, and the dimension in the tire width direction of the gap between the adjacent strips 71 is d.

A total of three recesses 91A, 92A, 93A extending in the tire circumferential direction are formed on the surface of the unvulcanized tread rubber 1A. Specifically, among the surfaces of the unvulcanized tread rubber 1A, when the green tire 10A is heated and pressurized in a tire molding die to form the pneumatic tire 10 shown in FIG. Recesses 91A, 92A, and 93A are formed in the regions where 92 and 93 are to be formed. Here, the formation of the recesses 91A, 92A, 93A (recess formation step) may be performed by adjusting the shape of the die when the unvulcanized rubber is extruded from the extruder to form the unvulcanized tread rubber 10A. Alternatively, it may be performed by excavating the surface after extruding the band-like unvulcanized rubber from the extruder.
In the green tire 10A of the above example, the recesses 91A, 92A, 93A are formed in all the regions where the circumferential grooves 91, 92, 93 are formed. However, in the tire manufacturing method of the present invention, the recesses 91A, 92A, 93A are formed. May be formed in at least a part of a region where a circumferential groove is to be formed on the surface of the unvulcanized tread rubber.
Incidentally, in the present invention, “unvulcanized” refers to a state in which the vulcanization reaction is not completely completed, and “unvulcanized” includes a state in which a part is vulcanized.

<Vulcanization process>
Next, in the vulcanization molding step, the pneumatic tire 10 is formed by heating and pressurizing the green tire 10A produced in the green tire formation step in a tire molding die. Specifically, in the vulcanization molding step, an unvulcanized green tire 10A is loaded into a tire molding die, and then a high-temperature and high-pressure fluid is introduced into the bladder installed on the inner peripheral surface side of the green tire 10A. The pneumatic tire 10 is formed by supplying and inflating the bladder and pressing the inner peripheral surface of the green tire 10A with the outer peripheral surface of the bladder to press the green tire 10A against the inner peripheral surface of the mold.

  Here, the mold for tire molding used in the vulcanization molding step is a tread portion molding surface for molding the tread portion 1 of the pneumatic tire 10 and a sidewall portion molding for molding the sidewall portion 2 of the pneumatic tire 10. And a bead portion molding surface for molding the bead portion 3 of the pneumatic tire 10. 3A and 3B, the inner peripheral surface of the mold of the tire molding die 100, more specifically, as shown in a part of the mold width direction cross section of the tire molding die 100. The tread portion molding surface is formed with a convex portion for forming a circumferential groove extending in the tire circumferential direction on the tread portion tread surface of the pneumatic tire 10 (in FIG. 3A and FIG. 3B, the circumferential groove). Only the convex portion 113 for forming 93 is shown).

  In the vulcanization molding step, the concave portions 91A, 92A, 93A formed in the unvulcanized tread rubber 1A of the green tire 10A and the convex portions formed on the tread portion molding surface of the tire molding die 100 are illustrated. As shown in FIG. 3 (a), the green tire 10A is loaded into a tire molding die in a state of facing the tire radial direction (or the mold radial direction), and the green tire as shown in FIG. 3 (b). 10A is pressed against the inner peripheral surface of the mold and vulcanization molding is performed.

  Here, according to the tire manufacturing method of this example, in the vulcanization molding step, the concave portion formed in the unvulcanized tread rubber 1A of the green tire 10A and the inner peripheral surface of the tire molding die 100 are provided. The convex part comes into contact. Therefore, according to the tire manufacturing method of this example, as compared with the case where the concave portion is not formed on the unvulcanized tread rubber 1A, the inside of the tire molding die generated by the contact between the unvulcanized tread rubber 1A and the convex portion is produced. The flow of the unvulcanized tread rubber 1A can be reduced. Therefore, the strip 71 is wound so that the strip 71 having a narrow width is used, and the ratio (gap ratio d / p) of the tire width direction dimension d of the gap between the strips 71 to the winding pitch p of the strip 71 is reduced. Even when the circumferential belt reinforcing layer 7 is formed by turning, it is possible to suppress the movement of the strip 71 due to the flow of the unvulcanized tread rubber 1A in the tire molding die. As a result, it is possible to suppress the occurrence of disturbance in the winding pitch of the strip 71 and to prevent the occurrence of uneven wear due to the disturbance in the winding pitch.

  When the green tire 10A is pressed against the inner peripheral surface of the mold using a bladder, the unvulcanized tread rubber 1A is moved from the center side in the tire width direction toward the outer side in the tire width direction in the tire molding die. To flow. Accordingly, the flow of the unvulcanized tread rubber 1 </ b> A tends to be particularly large in the region where the circumferential grooves 92 and 93 located on the outermost side in the tire width direction of the pneumatic tire 10 are formed. However, in the green tire 10A, a recess is formed in a region where the circumferential grooves 92 and 93 are formed, that is, a region located on the outermost side in the tire width direction among the regions where the circumferential grooves are formed. Since 92A and 93A are formed, according to the tire manufacturing method of this example, it is possible to suppress an increase in rubber flow in a region where the circumferential grooves 92 and 93 are formed. Accordingly, the movement of the strip 71 can be efficiently suppressed in the outer region in the tire width direction, and the occurrence of uneven wear due to the disturbance of the winding pitch can be suppressed.

Here, the circumferential belt reinforcing layer 7 of the green tire 10A is preferably formed by winding the strip 71 so that the porosity d / p is 0.2 or more and 0.7 or less. If the porosity d / p is 0.2 or more, the amount of cord used in the circumferential belt reinforcing layer 7 can be reduced, so that the flat spot caused by the creep deformation of the cord in the circumferential belt reinforcing layer 7 can be reduced. It is because generation | occurrence | production can fully be suppressed. Further, if the gap ratio d / p is 0.7 or less, the gap between the strips 71 is prevented from becoming too large, and the effect of reinforcing the cross belt 6 by the circumferential belt reinforcing layer 7 is sufficiently ensured. Because you can. Further, if the porosity d / p is 0.7 or less, it is possible to sufficiently suppress the cords of the belt layers 61 and 62 forming the crossing belt 6 from undulating (waving) in the gap portion between the strips 71. Because.
In the present invention, the “porosity d / p” means the gap in the circumferential belt layer when the winding pitch p and the tire width direction dimension d of the gap are changed in the circumferential belt reinforcing layer. Refers to the average rate.

  Moreover, it is preferable that the width | variety w of the strip 71 which forms the circumferential belt reinforcement layer 7 of 10 A of green tires is 7 mm or less. When the strip 71 is wound at the same gap ratio d / p, if the width w of the strip 71 is 7 mm or less, the belt layer that forms the crossing belt 6 as compared with the case where a strip having a width w of more than 7 mm is used. This is because the cords 61 and 62 can be reliably restrained from undulating (waving).

Furthermore, the tire width direction cross-sectional area B of the concave portion formed in the unvulcanized tread rubber 1A of the green tire 10A is the mold width direction cut-off of the convex portion formed on the inner peripheral surface of the mold for tire molding 100. The area A is preferably 0.3 to 0.9 times (0.3 ≦ B / A ≦ 0.9). If the ratio B / A is 0.3 or more, it is possible to sufficiently suppress the local increase in the flow of the unvulcanized tread rubber 1A due to the convex portion when the green tire 10A is vulcanized. It is. Further, if the ratio B / A is 0.9 or less, it is possible to suppress non-uniform shrinkage of the unvulcanized tread rubber 1A between the portion where the recess is formed and the portion where the recess is not formed. Because it can be done. Further, if the ratio B / A is set to 0.9 or less, it is possible to prevent the unvulcanized tread rubber 1A from being easily bent at the portion where the concave portion is formed, and to suppress a decrease in tire manufacturing efficiency. Because it can.
In addition, the tire width direction cross-sectional area B of a recessed part is an area of the area | region enclosed by the virtual line l, the virtual line m, and the virtual line n shown to Fig.3 (a). Incidentally, the virtual line 1 is a line extending in the tire radial direction (or the mold radial direction) through one base P1 of the convex portion of the tire molding die, and the virtual line m is a tire molding die. This is a line extending in the tire radial direction (or mold radial direction) through the other base portion Q1 of the convex portion. The virtual line n passes through a position twice the distance from the width center line of the convex portion to each virtual line l, m and extends in the tire radial direction (or mold radial direction). 'And a line connecting the intersections P2 and Q2 with the surface of the unvulcanized tread rubber 1A.

Normally, the greater the gap ratio d / p (that is, the greater the gap between the strips 71), the more easily the winding pitch p of the strips 71 is disturbed. Therefore, from the viewpoint of sufficiently suppressing the occurrence of the disturbance of the winding pitch p of the strip 71, the porosity d / p is large so that the porosity d / p and the ratio B / A satisfy the following relationship. It is preferable to vary the ratio B / A in accordance with the thickness.
0.5 ≦ (porosity d / p) / (ratio B / A) ≦ 1.5

  As mentioned above, although the manufacturing method of the tire of this invention was demonstrated with reference to drawings, the manufacturing method of the tire of this invention is not limited to the said example, It changes suitably in the manufacturing method of the tire of this invention. Can be added.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to the following Example at all.

(Examples 1-3)
Using a green tire having a concave portion formed on the surface of an unvulcanized tread rubber, a pneumatic tire having the configuration shown in FIG. 1 and having a size of 205 / 55R16 was produced according to the specifications shown in Table 1.
And the performance was evaluated with the following method about the produced pneumatic tire. The results are shown in Table 1.
(Comparative Examples 1-5)
Using a green tire in which a concave portion is not formed on the surface of the unvulcanized tread rubber, a pneumatic tire having the configuration shown in FIG. 1 and having a size of 205 / 55R16 was manufactured according to the specifications shown in Table 1.
And the performance was evaluated with the following method about the produced pneumatic tire. The results are shown in Table 1.

<Strip winding pitch disorder>
For all the strips located on the inner side in the tire radial direction of the circumferential groove, the tire width direction dimension of the gap between the strips was measured. Then, for the plurality of measured gaps, the minimum dimension was divided by the maximum dimension to obtain the gap dimension ratio. The closer the gap size ratio is to 1.0, the more preferable the winding pitch is not disturbed.
<Wavy belt layer>
Cut out five cut samples from the prepared tire, and for the crossing belt composed of two belt layers, the distance in the tire radial direction (belt undulation) between the outermost cord in the tire radial direction and the innermost cord. Amount) was measured. And the average value of the amount of belt waviness was calculated | required. The smaller the value of the belt undulation amount, the smaller the undulation of the cord of the belt layer, which is preferable.
<Flat spot resistance>
The produced tire was assembled on a rim having a size of 6.5 J × 16 and filled with an internal pressure of 230 kPa. And the flat spot test was done in the following procedures.
(1) The tire's RFV (Radial Force Variation) is measured.
(2) After performing a drum running test at 96 km / h for 1 hour, RFV is measured, and the waveform obtained from the relationship between the obtained RFV and the rotation angle of the tire is Fourier transformed to obtain the coefficient of the primary component. The RFV primary bottom (the position where the RFV value is the smallest in the primary wave of the RFV subjected to Fourier transform) is searched for. Subsequently, a static load of 5.88 kN is applied to the tire at the position of the obtained RFV primary bottom, and it is continuously pressed against the drum for 16 hours. Thereafter, the drum running test is performed again at 96 km / h, a graph is drawn with the running time on the horizontal axis and the RFV primary bottom value on the vertical axis, and the difference from the RFV primary bottom value measured in the test procedure (1) is 1 The area obtained by integrating in the range of ˜30 minutes is calculated as a flat spot value.
The index was evaluated with the flat spot value of the tire of Comparative Example 1 as 100. The index of the flat spot value shown in Table 1 indicates that the flat spot is reduced as the value is smaller.

  From Table 1, in the tires of Examples 1 to 3, the occurrence of flat spots and cord undulation was suppressed, and the movement of the strip due to the flow of unvulcanized tread rubber in the tire molding die was suppressed. It can be seen that the disturbance of the winding pitch can be suppressed. Note that the tire of Comparative Example 1 has low flat spot resistance. Moreover, the tires of Comparative Examples 2 to 4 have a large winding pitch disturbance. Further, the tire of Comparative Example 5 has a large amount of belt layer waviness.

  According to the tire manufacturing method of the present invention, even when a circumferential belt reinforcing layer is formed by winding a narrow strip with a small porosity, an unvulcanized tread rubber in a tire molding die is formed. It is possible to suppress the occurrence of uneven wear by suppressing the movement of the strip due to the flow of.

1 tread part, 2 side wall part, 3 bead part, 4 bead core, 5 radial carcass, 6 cross belt, 7 circumferential belt reinforcing layer, 8 bead filler, 91, 92, 93 circumferential groove, 10 pneumatic tire, 61 , 62 Belt layer, 71 strip, 1A unvulcanized tread rubber, 10A green tire, 91A, 92A, 93A recess, 100 tire mold, 113 protrusion

Claims (5)

A tire manufacturing method comprising a vulcanization molding step of forming a tire by heating and pressing a green tire in a tire molding die,
The green tire is a cross belt comprising two or more belt layers in which the cords are inclined in different directions with respect to the tire equatorial plane between belt layers adjacent to each other in the tire radial direction on the outer side in the tire radial direction of the crown portion of the carcass. And a circumferential belt reinforcement layer formed by spirally winding a strip formed by covering a cord with a rubber in the tire circumferential direction, and an unvulcanized tread rubber,
In the tire width direction cross-sectional view of the green tire, the strips adjacent in the tire width direction are separated from each other,
The tire molding die has a convex portion on the inner peripheral surface of the mold that forms a circumferential groove extending in the tire circumferential direction on the tread portion tread surface of the tire,
A tire manufacturing method comprising a recess forming step of forming a recess in at least a part of a region where a circumferential groove is to be formed in the surface of the unvulcanized tread rubber.   2. The tire manufacturing method according to claim 1, wherein, in the recess forming step, the recess is formed in a region where a circumferential groove located on the outermost side in the tire width direction of the tire is to be formed. The winding pitch p of the strip and a tire width direction dimension d of a gap between adjacent strips in the tire width direction satisfy the following relational expression (1). Tire manufacturing method.
0.2 ≦ d / p ≦ 0.7 (1)   The tire manufacturing method according to any one of claims 1 to 3, wherein the strip has a width of 7 mm or less. The mold width direction cross-sectional area A of the said convex part and the tire width direction cross-sectional area B of the said recessed part satisfy | fill the following relational expression (2), The one in any one of Claims 1-4 characterized by the above-mentioned. Tire manufacturing method.
0.3 ≦ B / A ≦ 0.9 (2)

Images