JP2001163013A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily vulcanize and mold with ensuring excellent wet performance without causing demolding even by a die of two piece mold. SOLUTION: A tread groove G consisting of a lengthwise main groove 9 or a lug groove 10 inclined at an inclination angle θ of 45 degree or less is provided to an inside region 2C of a tread surface. An outer groove wall surface 21 of the tread groove G consists of an outer groove wall surface base part 21A and a chamfered part 21B. An angle 31 at an intersection point P1 in the chamfered part 21B is 30-60 degree and larger than an angle 82 at an intersection point P2 in the outer groove wall surface base part 21A. A length L3 between the intersection points P1, P2 is set to 0.3-2.0 mm, and a recessed part 23 is formed on the outside of the axial direction of the tire along the tread groove G at an interval L4 of 0.5-2.0 mm from the intersection point P1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire capable of being vulcanized by a two-piece mold while ensuring excellent wet performance.

[0002]

2. Description of the Related Art In order to improve the wet performance of a tire, it is important to discharge a water film on a road surface in a tire circumferential direction and a tire axial direction. As described in, for example, JP-A-6-40215, a vertical main groove extending in the tire circumferential direction and a lug-shaped groove intersecting with the vertical main groove are provided in the vehicle.

[0003] Here, in consideration of drainage on the tire equator side of the ground contact surface, the direction of the groove center line of the lug-like groove is made closer to the tire circumferential direction, so that the water film resistance is reduced and the ground pressure is reduced. The drainage from the high tire equator side to the tire axial side is efficiently performed. Therefore, generally, the lug-shaped groove is formed to have a steeply inclined portion inclined at 45 ° or less with respect to the tire circumferential direction.

[0004] On the other hand, a tire vulcanizing mold includes a two-piece mold having a split surface parallel to the tire equatorial plane, and a split mold having a plurality of segments divided in the tire circumferential direction and movable in the radial direction so as to be able to expand and contract in the radial direction. Among them, the two-piece mold has the advantages that the mold structure and its operation control are simple and the manufacturing cost is very low.

However, in such a two-piece mold, the tire after vulcanization molding is taken out of the mold by being separated outward in the tire axial direction. The so-called demold damage to the tread surface is likely to occur. In particular, this demolding becomes more remarkable on the tire equator side where the direction of the groove is closer to the tire circumferential direction, and further, the outer diameter of the tire is large and the groove forming convex portion is difficult to be extracted from the tread portion.

Accordingly, from the viewpoint of demolding, a tread pattern tire having a lug-like groove including a steeply inclined portion or a vertical main groove on the tire equator side as described above is applied using a two-piece mold. It is very difficult to carry out vulcanization molding, and there has been a problem that vulcanization molding must be performed using a split mold in the past.

The present invention has been devised in view of such a situation, and an object of the present invention is to provide a tire having the lug-like groove or the vertical main groove on the tire equator side with a chamfered portion on an outer groove wall surface. On the other hand, based on the fact that a narrow groove-shaped concave portion is formed along the groove on the tread surface in the vicinity thereof, while ensuring excellent wet performance, demolding is not caused even by a two-piece mold. It is to provide a pneumatic tire that can be easily vulcanized and formed.

[0008]

In order to achieve the above object, the invention of claim 1 of the present application is directed to a tire equator and a contact half width TW / 2 from the tire equator to a tread contact edge of 50%.
%, Or a vertical main groove extending at 0 ° with respect to the tire circumferential direction, or an inclination angle θ within 45 ° with respect to the tire circumferential direction.
A pneumatic tire comprising a tread groove comprising a lug-shaped groove inclined at
The outer groove wall surface of the tread groove in the tire axial direction outside in a cross section perpendicular to the groove center line of the tread groove is formed on an outer groove wall base rising up from the groove bottom and a radial outer edge of the outer groove wall base. A continuous chamfered portion extending to the intersection P1 of the tread surface, and the chamfered portion has an angle δ1 formed by a normal to the tread surface at the intersection P1 with 3
0-60 °, the outer groove wall base forms an outward opening larger than an angle δ2 formed by a normal line on the virtual tread surface at a virtual intersection P2 between the virtual extension line and the virtual tread surface. , From the virtual intersection P2 to the intersection P1
Distance L3 in the cross section up to 0.3 to 2.0 m
m, and a small-width concave portion is formed along the tread groove at a distance L4 of 0.5 to 2.0 mm outward in the tire axial direction from the intersection P1 in the cross section.

In the invention of claim 2, the angle δ2 of the outer groove wall base is 2 to 8 °, and the recess has a width of 0.3 to 3 mm and a depth of 0.3 to 2. 0m
It is characterized by having a curved shape including an arc of m.

According to the third aspect of the present invention, the intersection C1 between the groove bottom of the tread groove and the outer groove wall surface has a radius of curvature r.
1 is an arc of 0.5 to 2.0 mm, and the intersection C2 between the bottom of the front groove and the groove wall surface on the tire equator side of the tread groove.
Is larger than the radius of curvature r2.

Here, the "tread contact edge" is defined as the tread surface contacting the tread surface when the tire is mounted on a regular rim and a regular load is applied in a state where the regular internal pressure is charged. It means a tire circumferential line passing through the outer end. The “regular rim” is a rim defined for each tire in a standard system including the standard on which the tire is based. For example, in JATMA, a standard rim, TRA
"Design Rim" or "ETRTO"
Measuring Rim "." Normal internal pressure "is the air pressure specified in the above standard. For JATMA, the maximum air pressure, and for TRA, the table" TIRE LOAD LIMITS AT VARIOU ".
Maximum value described in "S COLD INFLATION PRESSURES", ETR
If it is TO, it is "INFLATION PRESSURE", but if the tire is for a passenger car, it is 180 (kPa) uniformly. Furthermore, the "regular load" is the load specified in the above-mentioned standard. For JATMA, the maximum load capacity, and for TRA, the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION P
RESSURES ", maximum value for ETRTO," LOAD
CAPACITY ".

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. The pneumatic tire 1 of the present application is a tire which is vulcanized and molded by a two-piece mold 30 as schematically shown in FIG.
As is well known, an upper mold 31U and a lower mold 3 having a split surface 31 in the tire equatorial plane C0 or in the vicinity thereof, and forming the tire forming cavity H by arranging the split surfaces 31 together.
1L. By mounting the upper mold 31U on the ram side of the press and the lower mold 31L on the bed side, the upper mold 31U and the lower mold 31L are moved up and down in the tire axial direction to move the ram up and down. (In the example above and below)
Can move relatively. In this example, the case where the split surface 31 is arranged on the tire equatorial plane C0 is illustrated.

The tire forming cavity H has a contour substantially the same as the contour of the pneumatic tire 1,
A tread forming surface 32 for forming a tread, a side wall forming surface 33 for forming a sidewall, and a bead forming surface 34 for forming a bead are formed. Of the groove-forming convex portion 35 is protruded.

Next, as shown in FIG. 1, the tread surface 2 of the pneumatic tire 1 extends vertically to the inner area 2C of the ground contact surface on the tire equator side at 0 ° with respect to the tire circumferential direction. It has a tread groove G consisting of a main groove or a lug-like groove inclined at an inclination angle θ of 45 ° or less.

The “inner area 2C” is defined as an area between the tire equator C and a position separated from the tire equator C by 50% of a half-width TW / 2 from the tread tread edge Te, Although the tire 1 has a large diameter and is likely to be demolded, it is a part that requires high drainage.

In the present embodiment, the tread groove G has a central vertical main groove 9 passing through the tire equator C in the inner region 2C.
It comprises outer vertical main grooves 3, 3 arranged on both sides thereof, and first and second lug grooves 4, 10 extending inward in the tire axial direction from the outer vertical main grooves 3, and in this example, Of these, the occurrence of demolding due to the central vertical main groove 9 and the second lug-shaped groove 10 is suppressed by means of the present invention.

The occurrence of demolding due to the first lug-shaped groove 4 is suppressed by other means described later. In the present example, the outer vertical main groove 3 is not covered by the present application because the groove wall on the outer side in the tire axial direction is arranged in the outer region 2S outside the inner region 2C in this example. In the case of disposing in 2C, it is necessary to suppress demolding by means of the present invention as in the case of the central vertical main groove 9.

The central vertical main groove 9 extends substantially linearly in the tire circumferential direction similarly to the outer vertical main groove 3, and cooperates with the outer vertical main groove 3 to form a water film on a road surface. Discharges backward in the tire running direction. Especially, the central vertical main groove 9 is arranged on the tire equator C where the contact pressure is high and the contact length is the longest,
A more efficient drainage effect can be obtained.

As shown in FIG. 2, in the central vertical main groove 9, in a cross section perpendicular to the groove center line, the outer groove wall surface 21 on the outer side in the tire axial direction is inclined from the groove bottom 22. 21A, and an intersection P of the tread surface 2 continuing to the radial outer edge of the outer groove wall base 21A.
1 and a chamfered portion 21B. In this example, since the vertical main groove 9 is arranged on the tire equator C,
The groove wall surfaces on both sides are formed as the outer groove wall surfaces 21.

The chamfered portion 21B is formed at an angle δ between the intersection P1 and a normal N to the tread surface 2.
1 is in the range of 30 to 60 degrees, and the outer groove wall base 2
1A is a virtual intersection P between the virtual extension line and the virtual tread surface.
2 is formed so as to form an outward divergence larger than an angle δ2 formed between the virtual tread surface and the normal line N.

Note that the angle δ2 is the angle δ1
Although it is not particularly limited as long as it is smaller, it is preferable to set the angle to 2 to 8 degrees, which is substantially the same as the groove wall of the conventional vertical main groove, from the viewpoint of securing the groove volume and appearance. Further, it is preferable that the intersection C1 between the groove bottom 22 and the outer groove wall surface 21 has an arc shape with a curvature radius r1 of 0.5 to 2.0 mm and is smoothly connected.

The chamfered portion 21B has a distance L3 in the cross section from the virtual intersection P2 to the intersection P1.
Is formed at a relatively small slope of 0.3 to 2.0 mm, and a small width is provided at a distance L4 of 0.5 to 2.0 mm outward in the tire axial direction from the intersection P1 in the cross section. A groove-shaped recess 23 is formed along the vertical main groove 9.

The recess 23 has a width W4 in the cross section.
0.3-3.0 mm, depth D4 0.3-2.0 mm
The bottom surface is formed in a curved shape including an arc, in this example, a semicircular shape.

As described above, the chamfered portion 21B and the recess 2
By combining with 3, the edge portion of the vertical main groove 9 on the outer side in the tire axial direction is provided with flexibility, and demolding is effectively suppressed, for example, the mold is easily removed from the vertical main groove 9.

In the case where only the chamfered portion 21B or only the concave portion 23 is formed, the size of the chamfered portion 21B or the concave portion 23 (distance L3, width W4, depth D4) must be set extremely large, and as a result, various problems such as a decrease in steering stability, a decrease in appearance, and a decrease in wear resistance due to a decrease in the contact area are caused. On the other hand, when the chamfered portion 21B and the concave portion 23 are combined, a sufficient demold suppressing effect can be exhibited even with the small size as described above.

The angle δ1 is less than 30 degrees or 60
Degree, the distance L3 is less than 0.3 mm, the distance L
4 is greater than 2.0 mm, the width W4 is less than 0.3 mm,
In addition, when the depth D4 is less than 0.3 mm, the demold suppressing effect becomes insufficient. Conversely, the distance L3 is larger than 2.0 mm, and the width W4 is 3.0 m.
When it is larger than m, the reduction of the contact area and the deterioration of appearance are remarkable. If the distance L4 is less than 0.5 mm and the depth D4 is greater than 2.0 mm, crack damage such as chipping of rubber is likely to occur between the chamfered portion 21B and the concave portion 23.

Next, the second lug-shaped groove 10 has an inclination angle θ of 30 to 60 ° with respect to the tire circumferential direction at the intersection J2 with the vertical main groove 3, and the inclination angle θ from the intersection J2. It is smoothly curved in a substantially arc shape inward in the tire axial direction while gradually decreasing θ. The second lug-shaped groove 10 includes a steeply inclined region 10A in which the inclination angle θ is 45 ° or less in all or a part of the second lug-shaped groove 10. In this example, at least the steeply inclined region 10A is provided. , Vertical main groove 9
The same demold suppression means as described above is applied.

That is, similarly, the second lug-shaped groove 10
As shown in FIG. 3, in a cross section perpendicular to the groove center line,
The outer groove wall surface 21 includes an outer groove wall base 21A rising from the groove bottom 22 and a chamfered portion 21B connected to the outer groove wall base 21A and extending to the intersection P1 of the tread surface 2.

The chamfered portion 21B has an angle δ1 at the intersection P1 in the range of 30 to 60 degrees and an angle δ2 formed by the outer groove wall base 21A at the virtual intersection P2.
And greater than. The angle δ2 is preferably 2 to 8 °. The intersection C1 between the groove bottom 22 and the outer groove wall surface 21 has an arc shape with a curvature radius r1 of 0.5 to 2.0 mm, and the curvature at the intersection C2 between the groove bottom 22 and the inner groove wall surface 24. It is preferable that the radius be larger than the radius r2 from the viewpoint of securing the groove volume. The chamfered portion 21B is located at the virtual intersection P
The distance L3 between 2 and the intersection P1 is 0.3 to 2.0 mm.

On the outside of the intersection P1 in the tire axial direction, for example, a width W4 of 0.3 to 3.0 mm and a depth D4 of 0.5 to 2.0 mm apart from the intersection P1.
Are formed along the lug-shaped groove 10 with a small-width, shallow-bottom concave portion 23 of 0.3 to 2.0 mm.

Next, demolding of the first lug-shaped groove 4 is suppressed by the following means. That is, when viewed from the shape of the groove center line, the first lug-shaped groove 4 includes a curved portion 4A and a linear portion 4B as shown in an enlarged manner in FIG.

The curved portion 4A has an inclination angle θ1 with respect to the tire circumferential direction at the intersection J1 with the vertical main groove 3 of 30.
The inclination angle θ1 is gradually reduced, and in this example, the curved portion smoothly curves in a substantially arc shape from the intersection J1 toward the inside in the tire axial direction until the angle becomes substantially 0 ° in this example.
The linear portion 4B smoothly continues to the curved portion 4A, and extends linearly outside the tire equator C in the tire axial direction along the tire circumferential direction.

At this time, the distance L1 of the groove center line of the linear portion 4B from the tire equator C is 3/3 of the ground contact half width TW / 2.
This linear portion 4B is formed at a position of 0% or less and a higher ground pressure. The tire circumferential length L2 of the curved portion 4A is equal to the tire circumferential length L0 of the entire first lug groove 4.
50% or more, thereby suppressing a sudden change in the flow direction of the water film and a decrease in drainage.

When viewed from the groove width w of the first lug-shaped groove 4, the connecting position K between the curved portion 4A and the linear portion 4B is defined as the maximum groove width position Q, and the curved portions 4A and It has widened portions 6 extending on both sides of the linear portion 4B. In addition,
The “sequence position K” means a position where the groove center line of the curved portion 4A and the groove center line of the linear portion 4B are connected,
The figure illustrates the most preferred case of inscribing.

In this embodiment, the widened portion 6 has a maximum width region 6A in which the maximum groove width position Q is continuous, and a gradually decreasing width region 6 extending from both sides of the maximum width region 6A and gradually reducing the groove width.
B, 6C. In addition, one of the gradually decreasing width regions 6B
Is smoothly connected to a constant width region R extending from the intersection J1 with a substantially constant groove width, and the other gradually decreasing width region 6C extends to the end of the linear portion 4B.

Accordingly, in the present embodiment, the curved portion 4A has the constant width region R, the gradually decreasing width region 6B, and the maximum width region 6A.
And the linear portion 4B is formed by the gradually decreasing width region 6C and the region portion 6A2 of the maximum width region 6A up to the continuous position K. Have been.

As the widened portion 6, for example, the maximum groove width is peaked, so that the maximum groove width position Q is not continuous, that is, without having the maximum width region 6A, Width position Q and gradually decreasing width area 6B, 6C
And can also be formed.

Further, in the first lug-shaped groove 4,
As shown in FIGS. 5A to 5C, which are cross sections taken along lines II, II-II, and III-III in FIG. Outer groove wall 4o
Is the angle of inclination α formed at the intersection of the outer groove wall surface 4o and the tread surface 2 with respect to the normal N erected on the tread surface 2.
At the maximum groove width position Q so as to have a maximum inclination angle αmax of 15 to 45 degrees. The widening portion 6 has a maximum inclination angle α at both end regions thereof.
Angle gradually decreasing ranges YB and YC that gradually decrease from max are provided. It is preferable that the angle gradually decreasing ranges YB and YC are formed so as to substantially coincide with the gradually decreasing width regions 6B and 6C, but they do not have to coincide with each other.

As shown in the figure, the inner wall surface 4i on the inner side in the tire axial direction in the groove cross section has a normal line N set on the tread surface 2 at the intersection of the inner wall surface 4i and the tread surface 2. Is substantially constant in the length direction of the lug-shaped groove 4 in the range of 0 to 6 degrees.

As described above, since the first lug-shaped groove 4 includes the linear portion 4B and the curved portion 4A which are smoothly connected to each other, the water film in the inner region 2C is formed from the tire equator side where the contact pressure is high. The gas is smoothly guided to the outside in the tire axial direction through the straight portion 4B and the curved portion 4A, and is effectively discharged out of the ground contact surface through the vertical main groove 3.

At this time, the widened portion 6 having the maximum groove width is provided at the continuous position K between the linear portion 4B and the curved portion 4A, while the inclination angle α of the outer groove wall surface 4o in the lug-shaped groove 4 is reduced. The outer groove wall surface 4o is formed with a gentle gradient so that the maximum inclination angle αmax is obtained at the maximum groove width position Q. As a result, the flow of the water film from the linear portion 4B to the curved portion 4A is further smoothed, and it is possible to drain more quickly and with low resistance.

On the other hand, the demold caused by the two-piece mold 30 has an inclination angle θ1 with respect to the tire circumferential direction.
Are frequently generated in the vicinity of the connecting position K in the curved portion 4A and in the linear portion 4B, but the outer groove wall surface 4o in this portion is formed with a gentle slope at which the maximum inclination angle αmax becomes 15 to 45 degrees. ing. Therefore, when the upper mold 31U is moved in parallel in the tire axial direction and the tire 1 is taken out after vulcanization molding, the groove forming convex portion 35 for forming the lug-shaped groove 4 is easily removed from the tire tread, and demolding occurs. Is effectively suppressed.

Further, since the decrease in the groove volume due to the gentle inclination of the outer groove wall surface 4o is compensated for by the formation of the widened portion 6, excellent drainage is ensured. In this example, since the inner groove wall surface 4i has a steep gradient of 0 to 6 degrees, a sufficient groove volume can be ensured, and the smooth water flow can be achieved by the gentle gradient outer groove wall surface 4o. Therefore, drainage to the outside in the tire axial direction becomes easier.
In addition, an edge effect can be expected on the groove wall surface 4i, which is useful for improving grip on a dry road surface.

If the inclination angle θ of the lug-shaped groove 4 at the intersection J1 exceeds 60 degrees, the water film resistance in the curved portion 4A and the resistance at the time of merging with the vertical main groove 3 become excessive, so This leads to a decrease in sex. If the angle is less than 30 degrees, a sufficient effect of suppressing the demolding cannot be obtained, for example, the possibility of demolding occurring over the entire lug-shaped groove 4.
Therefore, the inclination angle θ1 at the intersection J1 is preferably 40 to 50 degrees, and is about 45 degrees in this example.

The maximum inclination angle αma of the outer groove wall surface 4o.
If x is less than 15, the above-mentioned effect of improving drainage and suppression of demolding will not be sufficiently achieved. Conversely, if it exceeds 45 degrees, the appearance of the tire will be significantly deteriorated.
Therefore, the maximum inclination angle αmax is preferably in the range of 15 to 25 degrees.

In order to further suppress demolding, as shown in FIGS. 5A to 5C, a radius of curvature r of 1.0 mm or more is provided between the outer groove wall surface 4o and the groove bottom 4b. It is preferable to interpose the circular arc portion 4c because the groove forming convex portion 35 can easily come off the tire tread. If the radius of curvature r exceeds 3.0 mm, the appearance may be deteriorated.

Here, regarding the groove width w of the lug-shaped groove 4 in the groove cross section, the groove width w is 25 to 6 of the groove width W0 of the vertical main groove 3 at the intersection J1.
In the range of 0% and the connecting position K, the groove width W
A range of 60 to 100% of 0 is preferred. If the groove width w
At the intersection J1 and the connecting position K, respectively.
If it is less than 5% or less than 60%, a sufficient groove volume cannot be secured, and if it exceeds 60% or 100%, the tread rigidity is reduced and uneven wear is liable to occur. In the present application, the groove width is a value measured on the tread surface.

Preferably, the groove width W0 of the vertical main groove 3 is preferably set to the ground half width TW in order to more reliably improve drainage.
/ 2 is preferably 5.0% or more, more preferably 6.0% or more. The upper limit of the groove width W0 is appropriately determined depending on the balance of tread rigidity and the like.

Regarding the groove depth d of the lug-shaped groove 4,
As shown in FIG. 6 which shows a groove cross section along the groove center line, in order to secure a groove volume, the lug groove depth d at the intersection J1 is set.
Is preferably substantially equal to the groove depth D0 of the vertical main groove 3. In the linear portion 4B, the lug groove depth d is set to the groove depth D0 of the vertical main groove 3 from the viewpoint of demolding and noise.
Is preferably 80% or less.

For this purpose, in this embodiment, the lug groove depth d is
At the intersection J1, the intersection is substantially equal to the groove depth D0, and at the linear portion 4B, not more than 80% of the groove depth D0, and the intersection is made for smoothing the water flow or reducing the change in rigidity. The lug groove depth d is gradually reduced between the portion J1 and the linear portion 4B. In the curved portion 4A and the linear portion 4B, a constant depth portion having a substantially constant lug groove depth d and a gradually decreasing depth portion in which the lug groove depth d gradually decreases can be mixed.

In this embodiment, the joint width between the linear portions 4B and 4B of the lug-like groove 4 adjacent in the tire circumferential direction is 0.5 to 3 mm.
2 illustrates an example in which the connection is made by a circumferential joint groove 7 having a depth of 2 to 5 mm. Thereby, each linear portion 4
As a result of being able to form a circumferentially continuous vertical groove body in cooperation with B, it is preferable in that drainage properties are further improved and wet performance is further improved. Further, by restricting the joint width and the depth of the joint groove 7 within the above ranges, the occurrence of demolding due to the joint groove 7 is prevented, and the tread rigidity is maintained.

Next, in the outer region 2S, in this example,
A wide first outer lug-like groove 26 gradually increasing in groove width from the outer vertical main groove 3 toward the tread contact edge Te.
And a narrow second outer lug-like groove 27 whose width gradually decreases toward the tread contact edge Te, and these are alternately arranged in the tire circumferential direction. In this example, the first outer lug-shaped groove 26 is connected to the first lug-shaped groove 4, and the second outer lug-shaped groove 27 is connected to the second lug-shaped groove 10. The case where it arrange | positions is illustrated.

Generally, when turning, the tread contact edge T
Although a large load acts on the e-side, the rigidity near the tread contact edge Te is reduced by including the second outer lug groove 27 that gradually reduces the groove width toward the tread contact edge Te as in this example. Can be prevented, and the wear resistance at this portion can be improved.

Note that such outer lug-like grooves 26, 27
Is arbitrary, and the outer region 2S may be formed in a rib shape.

In the embodiment of the present invention, the illustrated pattern is formed as a point-symmetric pattern, but may be formed as a left-right symmetric pattern centered on the tire equator C. In this case, the present invention can be preferably implemented as a pneumatic tire having a directional pattern in which the direction of rotation is determined such that the lug-shaped grooves 4 and 10 come into contact with the inner end side thereof. In this symmetric pattern, a pattern shift in which each side of the tire equator is shifted in the tire circumferential direction can be adopted, and the present invention can be modified into various modes. Further, in the present application, the second lug-shaped grooves 10 may be spaced at small pitch intervals in the tire circumferential direction without using the first lug-shaped grooves 4.

[0056]

[Example] The tire size is 185 / 70R14,
A pneumatic tire for a passenger car having the basic pattern shown in FIG. 1 was prototyped by vulcanization molding using a two-piece mold based on the specifications in Tables 1 to 3, and the occurrence of demolding and appearance were evaluated. Tested. The test method is as follows. Specifications other than Tables 1 to 3 are summarized in Table 4.

(1) Occurrence of demolding: The presence or absence of demolding at the time of vulcanization molding was visually confirmed. A mark that appeared as a scratch was rated as X, a mark with rubbing was rated as △, and a mark without scratches was rated as ○. (2) Appearance: Sensory evaluation of appearance was performed visually. Poor ×, slightly poor △, good ○.

[0058]

[Table 1]

[0059]

[Table 2]

[0060]

[Table 3]

[0061]

[Table 4]

[0062]

Since the present invention is configured as described above,
While ensuring excellent wet performance, vulcanization molding can be easily performed with a two-piece mold without demolding.

[Brief description of the drawings]

FIG. 1 is a plan view showing a tread pattern of a tire according to an embodiment of the present invention.

FIG. 2 is a line cross section perpendicular to a groove center line of a central vertical main groove.

FIG. 3 is a line cross section of the second lug-shaped groove perpendicular to the groove center line.

FIG. 4 is an enlarged sectional view showing a lug-shaped groove.

5 (A) to 5 (C) are cross sections taken along lines II, II-II and III-III in FIG. 4 in a direction perpendicular to the groove center line of the lug-shaped groove.

FIG. 6 is a sectional view taken along a groove center line of the lug-shaped groove.

FIG. 7 is a schematic sectional view showing a two-piece mold for vulcanizing the tire of the present invention.

[Explanation of symbols]

 Reference Signs List 2 Tread surface 2C Inner region 9 Vertical main groove 10 Lug-shaped groove 21 Outer groove wall surface 21A Outer groove wall base 21B Chamfered portion 22 Groove bottom 23 Concave portion 24 Groove wall surface 30 Two-piece mold C Tire equator Te Tread grounding edge

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // B29K 21:00 B29L 30:00 105: 24 B60C 11/04 H B29L 30:00 C

Claims (3)

[Claims] 1. A vertical main groove extending at 0 ° to the tire circumferential direction in an inner region between a tire equator and a position separated by 50% of a contact half width TW / 2 from the tire equator to a tread contact edge. Or a tread groove having a lug-shaped groove inclined at an inclination angle θ of 45 ° or less, and formed by a two-piece mold, wherein the tread has a cross section perpendicular to a groove center line of the tread groove. The outer groove wall surface on the outer side in the tire axial direction of the groove includes an outer groove wall base that rises inclining from the groove bottom, and a chamfer that extends to the radially outer edge of the outer groove wall base and extends to the intersection P1 of the tread surface, The chamfered portion has an angle δ1 between 30 ° and 60 ° with respect to a normal line formed on the tread surface at the intersection P1, and the outer groove wall base has a virtual intersection between the virtual extension line and the virtual tread surface. 2 and an angle δ2 larger than an angle δ2 formed with a normal line on the virtual tread surface, and a distance L3 in the cross section from the virtual intersection P2 to the intersection P1 is 0.3 to 2.0 mm, and 0.5 to 2.0 mm outward in the tire axial direction from the intersection P1 in the cross section
A pneumatic tire, wherein a small width recess is formed along the tread groove at an interval L4. 2. The angle δ2 of the outer groove wall base is 2-8.
゜, and the recess has a width of 0.3 to 3 m in the cross section.
The pneumatic tire according to claim 1, wherein the pneumatic tire has a curved surface including an arc having a depth m of 0.3 to 2.0 mm. 3. An intersection C1 between the groove bottom of the tread groove and the outer groove wall surface has an arc shape having a radius of curvature r1 of 0.5 to 2.0 mm, and the front groove bottom and the tread groove have a tire equator side. 3. The pneumatic tire according to claim 1, wherein the radius of curvature r2 of the intersection C2 with the groove wall surface is larger than r2.