JP2000255218A - Pneumatic tire, blade for tire vulcanizing mold, and manufacture of pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire in which a performance change from the time of a new product until the last stage of wear can be suppressed. SOLUTION: A sipe 20 formed in a block 18 is inclined at both ends in the longitudinal direction and terminated in the block 18, and formed such that a length of the bottom side is longer than a length of the tread side. When the pneumatic tire is a new product, a length of the sipe 20 appearing on the tread is short and lowering of block rigidity is suppressed. Though the rigidity of the block 18 is increased with progress of wear, an increase in the block rigidity is suppressed because the length of the sipe 20 becomes longer, and a change in the block rigidity is thereby suppressed from the time of a new product until the last stage of wear. Moreover, a volume of a main groove is decreased by wear of the tread to cause deterioration in wet performance, however, the length of the sipe 20 for absorbing water between the tread and a road surface becomes longer and deterioration in wet performance can be thereby suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire provided with a sipe on a tread, and more particularly to a pneumatic tire capable of suppressing a change in performance from a new time to a wear time.

[0002]

2. Description of the Related Art Conventionally, tread patterns have been used to improve the performance in rainy weather, that is, when running on a wet road surface. The arrangement and design of the grooves in the tire circumferential or width direction of the tread portion improve the performance in rainy weather.

[0003] The major aim is drainage from the tire contact surface, and it is known that the volume of the groove should be increased.

However, an increase in the volume of the groove leads to a decrease in the ground contact area, which lowers the steering stability performance in fine weather.

[0005] Improvements in sipes (narrow grooves) have also been made for the purpose of minimizing the decrease in ground contact area and ensuring drainage.

[0006] The sipes ensure the contact with the road surface by draining water from the block ground surface.

[0007] Therefore, it is considered that drainage is improved by arranging more sipes in the block.

[0008]

By the way, when many sipes are arranged in a block, the rigidity of the block is greatly reduced, causing uneven wear of the block and deteriorating the steering stability performance.

In order to reduce a change in steering stability and the like, it is desirable that the tread rigidity be constant from the time of new product to the end of wear. Conventionally, a sipe was sometimes provided to adjust the rigidity of the tread.However, since the conventional sipe had a constant length from the tread to the bottom, the rigidity of the tread was suppressed from increasing as it was worn. I couldn't do that.

An object of the present invention is to further improve a sipe formed in a block so that a change in performance from a new article to the end of wear can be suppressed, and a tire for forming a pneumatic tire. An object of the present invention is to provide a tire vulcanization mold blade used for a vulcanization mold and a method for manufacturing a tire.

[0011]

According to a first aspect of the present invention, in a pneumatic tire having a sipe formed on a tread, the sipe is longer on a bottom side than on a tread side.

If a large number of sipes are formed on a tread made of thick rubber, the tread rigidity is reduced.

[0013] Further, when comparing the thick tread when new and the worn tread, the apparent stiffness of the tread is that the tread surface after the abrasion when the tread surface is close to a highly rigid belt or the like. The tread is higher.

In the pneumatic tire according to the first aspect, since the sipe is longer on the bottom side than on the tread side, the sipe density when new is low, and a decrease in tread rigidity can be suppressed.

Here, as the tread wears, the tread rigidity increases. On the contrary, the sipe density increases, so that the increase in the tread rigidity is suppressed.

Therefore, it is possible to suppress a change in tread rigidity from the time of new article to the time of wear.

Since the sipe length increases as the tread wears, the water absorbing power between the tread and the road surface increases, and the edge effect also increases.

According to a second aspect of the present invention, in the pneumatic tire according to the first aspect, the sipe is formed in a block formed by a plurality of main grooves crossing each other.

In the pneumatic tire according to the second aspect, since the block has a sipe longer on the bottom side than on the tread side, a decrease in block rigidity when new is suppressed and an increase in block rigidity after wear is suppressed. It is possible to suppress a change in block rigidity from the time of new article to the time of wear.

Further, the volume of the main groove is reduced due to the wear of the tread, and the wet performance is reduced. However, since the length of the sipe is increased, the reduction in the wet performance can be suppressed.

According to a third aspect of the present invention, in the pneumatic tire according to the second aspect, the sipes are such that at least an inner end of the block is open to the main groove.

If the end of the sipe is not open in the main groove, the water cannot be absorbed any more when the sipe is filled with water (that is, the water absorption capacity becomes saturated). In the pneumatic tire according to the third aspect, at least the inner end of the sipe is open to the main groove, and the water absorbed by the sipe can be sequentially discharged to the main groove outside the block. Therefore, the water absorption capacity of the sipe does not saturate, the contact between the tread and the road surface is enhanced, and high wet performance can be maintained.

If both ends of the sipe are opened in the main groove, drainage to the main groove is further improved.

According to a fourth aspect of the present invention, in the pneumatic tire according to the third aspect, the sipe does not open to the main groove on the tread side.

In the pneumatic tire according to the fourth aspect, the sipe does not open to the main groove on the tread side. That is, on the tread side, since the one side region and the other side region are connected with the sipe therebetween, high block rigidity can be maintained from the time of new product to the early stage of wear.

The invention according to claim 5 is a tire vulcanization mold blade used for a tire vulcanization mold and forming a sipe on a land portion of a tire, the blade being fixed to the tire vulcanization mold. It has a main part, and at least one subpart provided in the main part and movable inside and outside of the main part.

[0027] In the tire vulcanizing mold blade according to claim 5, the main body is fixed to the tire vulcanizing mold,
The main body has sub-portions movably inside and outside the main body.

Therefore, the green case is loaded into the tire vulcanization mold with the sub-portion protruding outward from the main body, vulcanization molding is performed, and when the vulcanized tire is taken out, the inside of the main body is removed. If the sub-portion is moved in the direction, the tire can be easily taken out without being caught by the sub-portion.

As a result, a sipe whose bottom side is longer than the tread side can be formed in the tread of the tire.

Further, since the tire is not caught on the sub-portion, the tire is not damaged when the tire is taken out.

According to a sixth aspect of the present invention, in the tire vulcanizing mold blade according to the fifth aspect, when the vulcanized tire is pulled out of the tire vulcanizing mold, the vulcanized tire is removed. The tire is pushed by the tire by the pulling-out operation of the tire and moves inward of the main body.

[0032] In the tire vulcanizing mold blade according to the sixth aspect, the auxiliary portion protruding from the main body is pushed by the tire by a pulling-out operation of pulling out the vulcanized tire from the tire vulcanizing mold, and is moved inward of the main body. Move automatically.
Therefore, it is not necessary to move the sub part inward of the main body when removing the tire.

According to a seventh aspect of the present invention, in the tire vulcanizing mold blade according to the fifth or sixth aspect, the sub-portion is a projection plane in which the main body is projected in the moving direction of the sub-portion. It is characterized by moving with.

The sub-part moves within a projection plane (a plane perpendicular to the direction of movement) in which the main body is projected in the direction of movement of the sub-part.
That is, the projection area does not change even if the sub-portion is moved.

That is, even if the sub-portion is moved, the shadow of the sub-portion is not reflected on the projection surface, that is, there is no protrusion, so that the tire does not catch on the sub-portion when the tire is taken out.

[0036] In the method for manufacturing a pneumatic tire according to claim 8, a main body fixed to a tread forming portion of a tire vulcanizing mold, and provided on the main body and movable inward and outward of the main body. Loading the green case into a tire vulcanizing mold having a tire vulcanizing mold blade having at least one sub-part, and expanding the green case to contact the tire vulcanizing mold. And vice versa, before the rubber member of the green case is vulcanized, arranging the sub-portion outside the main body, heating and vulcanizing the green case, After the end, removing the vulcanized tire from the tire vulcanization mold and moving the sub-portion inward of the main body.

In the method for manufacturing a pneumatic tire according to the eighth aspect, first, the sub-portion of the tire vulcanization mold blade is disposed outside the main body portion.

Next, a green case is loaded into a tire vulcanizing mold.

Next, the green case is expanded, and the green case is brought into contact with the tire vulcanization mold.

Next, the green case is heated to perform vulcanization.

After the vulcanization molding is completed, the vulcanized tire is released from the tire vulcanization mold after or while moving the sub part into the main body part.

Thus, a pneumatic tire having a sipe formed on the bottom side longer than the tread side can be obtained.

[0043]

[First Embodiment] A first embodiment of a pneumatic tire according to the present invention will be described with reference to FIGS.

As shown in FIG. 1, the tread 12 of the pneumatic tire 10 of the present embodiment has a tire circumferential direction (arrow S).
), And a plurality of blocks 18 defined by a plurality of lateral grooves 16 extending along the tire width direction (arrow W direction).

In each block 18, a sipe 20 is formed in a straight line along a diagonal line of the block 18.

As shown in FIG. 2, the sipe 2
The reference numeral 0 indicates that both ends in the longitudinal direction are inclined and end in the block 18, and the length (Lb) on the bottom side is longer than the length (La) on the tread side.

As shown in FIG. 1, the tire equatorial plane C
The block 18 on one side and the block 1 on the other side across L
8, the sipe 20 is formed in the opposite direction. (Operation) Next, the operation of the pneumatic tire 10 of the present embodiment will be described.

In the pneumatic tire 10 of the present embodiment, the sipe 20 having the bottom portion longer than the tread side is connected to the block 18.
Because it was formed in, to suppress the decrease in block rigidity when new,
An increase in block rigidity after wear can be suppressed, and a change in block rigidity from new to wear can be suppressed.

Further, the wear of the tread 12 reduces the volume of the circumferential groove 14 and the lateral groove 16 and deteriorates the wet performance, but the length of the sipe 20 for absorbing water between the tread and the road surface becomes longer. A decrease in wet performance can be suppressed. Second Embodiment A second embodiment of the pneumatic tire according to the present invention will be described with reference to FIG. Note that the same components as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

As shown in FIG. 3, the sipe 22 formed in the block 18 of the pneumatic tire 10 according to the present embodiment includes:
A drain 22A is formed along the tire width direction (the direction of the arrow W) and extends to the circumferential groove 14 (not shown in FIG. 3) at the bottom of one end in the longitudinal direction and opens.

In the sipe 22 of the present embodiment, the absorbed water can be sequentially discharged to the circumferential groove 14 outside the block 18, so that the water absorbing capacity of the sipe 22 does not become saturated, and the tread 12 and the road surface are not saturated. The contact property of the metal is increased, and high wet performance can be maintained.

Further, the sipe 22 does not open to the circumferential groove 14 on the tread side, that is, the one side region and the other side region are connected to each other across the sipe 22 on the tread side. A high block rigidity can be maintained from the time of a new article to the beginning of wear.

Further, as shown in FIG. 4, drainage portions 22A may be provided on both sides of the sipe 22, so that drainage properties can be further improved. Third Embodiment A third embodiment of the pneumatic tire according to the present invention will be described with reference to FIG. Note that the same components as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

As shown in FIG. 5, the sipe 24 formed in the block 18 of the pneumatic tire 10 according to the present embodiment includes:
A drain portion 24A is formed along the tire width direction (the direction of the arrow W) and extends in a direction perpendicular to the longitudinal direction of the sipe 24 at the bottom of the intermediate portion in the longitudinal direction. The drainage portion 24A of the present embodiment is open in the lateral groove 16 (not shown in FIG. 5).

In the sipe 24 of the present embodiment, the absorbed water can be sequentially discharged to the lateral groove 16 outside the block 18, so that the water absorbing capacity of the sipe 24 does not become saturated,
The contact between the tread 12 and the road surface is enhanced, and high wet performance can be maintained.

Although not shown, drainage portions 24A may be provided on both sides of the sipe 24. Thereby, drainage can be further improved.

Also in this embodiment, the sipe 24 is not open to the circumferential groove 14 on the tread side, so
High block rigidity can be maintained in the early stage of wear. [Fourth Embodiment] A fourth embodiment of the pneumatic tire according to the present invention will be described with reference to FIGS. Note that the same components as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

As shown in FIG. 6, the sipe 26 formed in the block 18 of the pneumatic tire 10 according to the present embodiment includes:
At both ends in the longitudinal direction, there are provided drainage portions 26A which open to the circumferential grooves 14 (not shown in FIG. 6).

In the sipe 26 of this embodiment, the absorbed water can be sequentially discharged to the circumferential groove 14 outside the block 18, so that the water absorption capacity of the sipe 26 is not saturated, and the tread 12 and the road surface The contact property of the metal is increased, and high wet performance can be maintained.

Also in this embodiment, since the sipe 26 is not opened in the circumferential groove 14 on the tread side, the sipe 26 is not new.
High block rigidity can be maintained in the early stage of wear.

Next, an example of a method for forming the sipe 26 of this embodiment will be described below.

As shown in FIGS. 7 and 8A and 8B, a blade 30 for forming the aforementioned sipe 26 is formed.
Is the concave portion 34 (block 18) of the tire vulcanizing mold 32.
Forming part. ) Of the main body 3 fixed to the bottom 34A
6 and a pair of sub-portions 38 movably supported by the main body 36.

As shown in FIG. 7, the main body 36 is formed by bending a rectangular thin metal plate into a U-shape to form a pair of flat portions 36.
A gap is provided between A.

A pair of substantially fan-shaped sub-parts 38 made of a thin metal plate are arranged between the pair of plane parts 36A, and a pin provided near the corner at the end opposite to the bending side is provided. 40
Supports an end portion 38A of the sub-portion 38.

The sub part 38 is swingable about a pin 40. The sub-portion 38 includes an arc portion 38B having the pin 40 as a center of curvature, a straight portion 38C and a straight portion 38D extending substantially in the radial direction from the vicinity of the center of curvature, and further has a straight portion 38D and an arc portion. 38B, a linear contact portion 38E is provided.

As shown in FIG. 8B, when the sub-part 38 swings out of the main body part 36, the contact part 38E
8 is in contact with the side surface 34B of FIG.
As shown in FIG. 3A, the entire body is completely accommodated in the main body 36 when the main body 36 is swung inward.

The tire vulcanization mold 32 is provided with a slit 46 penetrating inside and outside.
, A thin metal plate 48 is inserted.

The metal plate 48 can enter and exit between a pair of flat portions 36 A of the main body 36.

An air cylinder 50 is mounted on the outer surface of the tire vulcanization mold 32, and a metal plate 48 is fixed to a piston 52 of the air cylinder 50.

In this embodiment, the metal plate 48 is moved in and out of the air cylinder 50 as shown in FIG.
It can be moved between the position shown in FIG. 8A and the position shown in FIG. In this embodiment, the movement of the metal plate 48 is performed by the air cylinder 50. However, the movement of the metal plate 48 may be performed by an actuator or the like that performs a linear motion.

An example of the dimensions of the blade 30 will be described below.

The blade 30 shown in FIG. 7 is for a block having a length of 35 mm, the main body 36 is formed of a 0.5 mm steel plate, the length L1 of the main body 36 is 25 mm, and the main body 3 has a length L1 of 25 mm.
6, the height L2 is 14 mm, and the gap between the flat portions 36A is about 0.5 mm.

The position of the pin 40 is such that the dimension L3 from the end in the longitudinal direction is 2 mm and the dimension L4 from the end opposite to the bending side is 2 mm.

The sub part 38 is formed of a 0.5 mm steel plate, the radius of curvature R of the arc part 38B is 10 mm, and the length L5 of the contact part 38E is 2 mm.

When the sub-portion 38 projects and the contact portion 38E comes into contact with the side surface 34B of the concave portion 34 of the tire vulcanizing mold 32, the protrusion dimension L6 of the sub-portion 38 becomes 5 mm.

Next, a process of forming the sipe 26 using the tire vulcanization mold 32 will be described. (1) First, air is supplied into the air cylinder 50 using an air compressor or the like, and the metal plate 48 is inserted into the main body 36 of the blade 30. Thereby, the blade 30
Of the contact portion 38E swings outward of the main body portion 36.
Abuts against the side surface 34B of the concave portion 34 of the tire vulcanization mold 32 (see FIG. 8B). (2) A green case (raw tire) is loaded into the tire vulcanizing mold 32. (3) The bladder (not shown) of the tire vulcanizing mold 32 is expanded to expand the green case, and the green case is brought into contact with the tire vulcanizing mold 32. As a result, the rubber (unvulcanized) 42 of the green case enters the concave portion 34 and comes into close contact therewith. (4) Vulcanize by heating the green case. (5) After completion of the vulcanization molding, the tire vulcanization mold 32 is opened, the air in the air cylinder 50 is evacuated by a vacuum pump or the like, and the metal plate 48 is removed from the main body 36 of the blade 30 as shown in FIG. Then, the vulcanized tire 44 is taken out as shown in FIG. 9 (B).

The movement of the tire 44 (in the direction of arrow A)
Since the rubber 42 of the block 18 pushes the linear portion 38D of the sub-portion 38 in the direction of the main body 36 (the direction of arrow B), the sub-portion 38 is automatically stored inside the main body 36, and the block 18 is drained. A sipe 26 having a portion 26A is formed, and
The tire 44 can be easily taken out as before. (Test Example 1) In order to confirm the effect of the present invention, a conventional tire and a tire of the embodiment to which the present invention was applied were prepared, and a wet road surface running test was performed in a state where the tire was worn by 20% from the time of new. .

Example tire: A tire provided with the sipe-equipped block described in the first embodiment. When the block is new, the tire circumferential dimension (W1) is 20mm
× tire width direction dimension (W2) 20 mm × height (H) 8 mm. The size of the sipe is 15m in length on the tread (La)
m, length (Lb) at bottom is 25 mm, thickness (t) is 1 m
m, depth (d) is 7 mm.

Conventional tire: It has a block of the same size as the tire of the embodiment, except that the sipe has a fixed length of 15 mm from the tread to the bottom.

All tire sizes are 185 / 60R14
It is.

Wet road surface running test: On the test course, water was sprayed on the road surface to an average water depth of 1 mm. The handling test was mainly performed, and the feeling was expressed by the score of the test driver. The scores are shown in Table 1 below.

[0082]

[Table 1]

As a result of the test, it was found that the tire of the example to which the present invention was applied had improved wet performance as compared with the conventional tire. (Test Example 2) In order to confirm the effect of the present invention, a conventional tire and a tire of an example to which the present invention was applied were prepared, and a wet road running test was performed in the same manner as in Test Example 1.

Example tire: A tire provided with a block with a sipe shown in FIG. The dimensions of the block are the same as those of the tire of Test Example 1. The dimensions of the sipes are tread length (La) of 12 mm and bottom length (Lb) of 20 m
m, depth (d) is 7 mm, thickness (t) is 0.8 mm, and height (h) of the drain portion is 1 mm.

Conventional tire: It has a block of the same size as the tire of the embodiment. The difference from the embodiment is that the sipe has no drainage portion and has a fixed length of 1 from the tread to the bottom.
2 mm and a depth of 7 mm.

All tire sizes are 185 / 60R14
It is.

[0087]

[Table 2]

As a result of the test, it was found that the tire according to the example to which the present invention was applied had significantly improved wet performance as compared with the conventional tire.

[0089]

As described above, since the pneumatic tire of the present invention has the above-described structure, it has an excellent effect that a change in performance from the time of new product to the end of wear can be suppressed.

The tire vulcanizing mold blade of the present invention has an excellent effect that a sipe capable of suppressing a change in performance from the time when a tread is new to the end of wear can be formed.

Further, the pneumatic tire manufacturing method of the present invention has an excellent effect that a pneumatic tire capable of suppressing a change in performance from a new time to the end of wear can be efficiently manufactured.

[Brief description of the drawings]

FIG. 1 is a plan view of a tread of a pneumatic tire according to a first embodiment of the present invention.

FIG. 2 is a perspective view of a block of the pneumatic tire according to the first embodiment.

FIG. 3 is a perspective view of a block of a pneumatic tire according to a second embodiment.

FIG. 4 is a perspective view of a block of a pneumatic tire according to another embodiment.

FIG. 5 is a perspective view of a block of a pneumatic tire according to a third embodiment.

FIG. 6 is a perspective view of a block of a pneumatic tire according to a fourth embodiment.

FIG. 7 is a perspective view of a blade forming a sipe.

8A is a cross-sectional view of a main part of a mold showing a blade before a metal plate is inserted, and FIG. 8B is a cross-sectional view of a main part of the mold showing a blade after a metal plate is inserted.

FIG. 9A is a cross-sectional view of a main part of a mold showing a state where rubber is filled and closely adhered, and FIG. 9B is a cross-sectional view of a main part of the mold showing a middle of pulling out a tire after vulcanization. .

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Pneumatic tire 12 Tread 14 Circumferential groove (main groove) 16 Lateral groove (main groove) 18 Block 20 Sipe 22 Sipe 24 Sipe 26 Sipe 30 Blade for tire vulcanization mold 32 Mold for tire vulcanization 36 Main part 38 Sub part

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) B29D 30/68 B29D 30/68 B60C 11/11 B60C 11/11 C // B29K 21:00 B29L 30:00

Claims (8)

[Claims] 1. A pneumatic tire having a sipe formed on a tread, wherein the sipe is longer on a bottom side than on a tread side. 2. The pneumatic tire according to claim 1, wherein the sipe is formed in a block formed by a plurality of main grooves crossing each other. 3. The pneumatic tire according to claim 2, wherein the sipe is open at least at an inner end of the block in the main groove. 4. The pneumatic tire according to claim 3, wherein the sipe does not open to the main groove on the tread side. 5. A tire vulcanization mold blade used for a tire vulcanization mold and forming a sipe on a land portion of a tire, wherein the main body is fixed to the tire vulcanization mold; And at least one sub-portion that is movable inward and outward of the main body portion. 6. When the vulcanized tire is pulled out from a tire vulcanization mold, the sub-portion is pushed by the tire by the pulling-out operation of the vulcanized tire and moves inward of the main body. The tire vulcanization mold blade according to claim 5, wherein 7. The tire vulcanizing mold blade according to claim 5, wherein the sub-portion moves within a projection plane that projects the main body in a moving direction of the sub-portion. 8. A main body fixed to a tread forming portion of a tire vulcanizing mold, and at least one sub-portion provided on the main body and movable inward and outward of the main body. Loading a green case into a tire vulcanization mold having a tire vulcanization mold blade; expanding the green case to contact the tire vulcanization mold; and vulcanizing the rubber member of the green case. And vulcanizing the green case by heating the green case, and vulcanizing the vulcanized tire after vulcanization. Removing the mold from the mold and moving the sub-portion inward of the body portion.