JP2003054216A - Pneumatic tire and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the fluctuation of a tire axle force caused by a lateral channel component in a tire pattern by increasing the rigidity of an edge part of a lateral channel in a pneumatic tire. SOLUTION: In the pneumatic tire 10 constituted by forming a plurality of block rows B1, B2, B3, B4 and B5 by channels 12 in the peripheral direction extending in the peripheral direction of the tire and lateral channels 16 extending in the direction of tire width in a step face part T of a tread part 11, a lateral channel wall 16a face of the tread part 11 is reinforced by a rubber layer 20 containing short fibers, and a road surface reaction force generated in the vicinity of the lateral channel wall 16a face is increased to reduce the fluctuation of an axle force by a tire tread.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire and a method for manufacturing the pneumatic tire, and more particularly to a pneumatic tire and a method for manufacturing the pneumatic tire, which reduce noise in a passenger compartment due to grooves extending in a tire width direction.

[0002]

2. Description of the Related Art In a pneumatic tire such as a radial tire mounted on a vehicle such as a general automobile, a tread portion contacting the road surface has a circumferential groove extending in the tire circumferential direction and a lug groove (lateral groove extending in the tire width direction). ), A tire pattern in which a plurality of block rows is formed is provided, and the tire pattern enhances the grip performance with the road surface.

By the way, it is well known that such tire patterns cause noise such as harshness, but in order to improve the pattern noise caused by these tire patterns, patterns, especially circumferential grooves and lug grooves are used. From the idea that the block (land part) surrounded by and will come into contact with the road surface, the method of reducing the rigidity of the edge part of the block, or changing the geometric relationship between the ground contact shape and the groove, etc. The technique is often used.

[0004]

However, one of the phenomena that is a problem among the noises caused by the tire pattern is noise that can be heard in the passenger compartment while the vehicle is running (hereinafter referred to as pattern noise). is there.

This pattern noise phenomenon has a component directly emitted from the tire, but its frequency is 1000 Hz.
From the following, it is considered that the influence of the indirect sound generated by the tire vibrating the axle and the vibration of the vehicle body is large.

In this case, as shown in FIG. 12, the cause of the indirect sound can be understood as a variation in the tire axle force due to the lug groove 2 component of the pattern which becomes a discontinuous component in the circumferential direction of the tire 1. That is, at the moment when the lug groove 2 comes into contact with the road surface 3, the load is greatly reduced because the space S exists.

Therefore, the present invention has been made in view of the above conventional problems, and increases the rigidity of the edge portion of the lateral groove to reduce the fluctuation of the tire axle force due to the lateral groove component of the tire pattern. An object of the present invention is to provide a pneumatic tire and a method for manufacturing the same.

[0008]

In order to achieve the above object, the invention of claim 1 is characterized in that a tread portion of a tread portion is provided with a plurality of circumferential grooves extending in the tire circumferential direction and lateral grooves extending in the tire width direction. A pneumatic tire having a block row is characterized in that the surface of the lateral groove wall of the tread portion is reinforced with a rubber layer containing short fibers.

In this case, since the rigidity of the lateral groove wall surface is increased by the rubber layer containing the short fibers, the road surface reaction force generated near the lateral groove wall surface can be increased. Therefore, it is possible to prevent the load from being reduced by the rigidity increasing portion of the lateral groove wall surface at the time when the lateral groove is not present in the ground contact portion of the tire, that is, when the block is present and when the lateral groove is present, that is, at the moment of transition to the void portion. it can. As a result, it is possible to reduce the fluctuation of the axle force due to the tire tread and effectively reduce the pattern noise.

Here, as the short fibers contained in the rubber layer, nylon, polyester, rayon or the like, or fiber-crystalline SPB resin, ABS resin or the like can be used. The diameter (average) of the short fibers is 10 to 200.
Those having a length of μm and a length of 10 to 10,000 times the diameter are used, and the compounding amount thereof is preferably 5 to 60 parts by weight with respect to 100 of rubber.

The invention of claim 2 is the pneumatic tire according to claim 1, characterized in that the tread portion inside the rubber layer does not contain short fibers.

In this case, since the short fibers do not exist in the tread portion inside the rubber layer, it is possible to prevent the block compressive rigidity of the tire from becoming large as a whole.

A third aspect of the present invention is the pneumatic tire according to the first or second aspect, characterized in that the rubber layers are arranged in the shoulder block rows on both sides in the tire width direction.

In this case, in the shoulder portion of the tire, the ground contact shape line and the lateral groove are likely to coincide with each other, and the contribution to the variation of the tire axial force becomes high. Therefore, even when the rubber layer containing the short fibers is arranged only in the shoulder block row, it is possible to effectively reduce the fluctuation of the tire axle force and reduce the installation area of the rubber layer to reduce the cost. Can be achieved.

The invention of claim 4 is characterized in that, in the pneumatic tire according to any one of claims 1 to 3, the thickness of the rubber layer is set between 0.1 and 1.0 mm. .

In this case, the thickness of the rubber layer is 0.1 to 1.0.
Since it is set to mm, only the rigidity near the wall surface of the lateral groove can be increased without increasing the compression rigidity of the entire block. In other words, the thicker the rubber layer containing short fibers, the greater the rigidity of the lug lateral groove and the greater the ground reaction force near the wall surface, but the thicker the rubber layer covering the block surface is. The compression rigidity of the entire block also increases, and other vibration noise performance such as passing noise and road noise deteriorates. Therefore, in order to increase only the rigidity in the vicinity of the wall surface of the lateral groove without significantly changing the rigidity of the entire block, it is preferable to set the thickness of the rubber layer between 0.1 and 1.0 mm, which is preferable. Is preferably about 0.1 to 0.5 mm.

According to a fifth aspect of the present invention, in the pneumatic tire according to any one of the first to fourth aspects, the pneumatic tire has at least one circumferential groove extending in the tire circumferential direction on the tread portion of the tread portion. At least two layers of rubber-coated cords each of which has a plurality of rows of blocks formed between the ends of each tread tread surface and which intersect each other at a relatively small angle with respect to the tire circumferential direction. Of the belt layer, and the rubber-coated cord is provided in the tire radial direction of the belt layer with respect to the tire circumferential direction.
The carcass layer includes at least one carcass layer inclined at an angle of 90 degrees to 90 degrees, and the other end of each carcass layer, which is opposite to the lower end of the belt layer, extends to at least a substantially radial inner end region of each bead portion. It is characterized by that.

In this case, the pneumatic tire is configured as a radial tire, and by adopting the configurations of claims 1 to 4, the pattern noise of the radial tire can be effectively reduced.

In the pneumatic tire manufacturing method according to the sixth aspect of the present invention, a thin rubber layer in which short fibers are oriented in one direction is provided on the surface of the green tire so that the direction of the short fibers coincides with the circumferential direction of the tire. And a vulcanization step of vulcanizing the green tire on which the rubber layer is arranged using a vulcanization mold having a mesh pattern corresponding to the circumferential grooves and the lateral grooves on the inner surface. It is characterized by having.

In this case, the rubber layer arranged on the surface of the green tire in the step of attaching the short fiber sheet has a rubber layer of the rubber layer when the circumferential groove and the lateral groove are formed in the mesh pattern of the vulcanizing mold in the vulcanizing step. The short fibers will be oriented in the block thickness direction of the groove wall portion of the block. However, since the short fibers are oriented in the tire circumferential direction, the short fibers are discontinuous in the block thickness direction on the circumferential groove wall surface along the tire circumferential direction, while the direction perpendicular to the tire circumferential direction, that is, The wall surface of the lateral groove along the tire width direction is continuous in the block thickness direction.

Therefore, it is possible to increase only the compression rigidity of the lateral groove wall surface along the tire width direction and the vicinity thereof, and it is possible to increase the road surface reaction force generated at that portion. On the other hand, as described above, since the compression rigidity is kept small on the circumferential groove wall surface in which the short fibers are discontinuous in the block thickness direction, it is possible to prevent the impact component of the block from increasing. Of course, even in this case, the rubber layer may be arranged over the entire tire width,
Further, it may be arranged only in the shoulder block rows on both sides in the tire width direction.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Here, FIG. 1 shows a sectional view of a pneumatic tire 10 to which the present invention is applied, and the pneumatic tire 10 is configured as a radial tire. The tread portion T of the tread portion 11 is provided with at least one circumferential groove 12 extending in the tire circumferential direction, and a plurality of block rows B1, B are provided between the ends of the tread tread portions T.
2, B3, B4, B5 are formed. The tread portion 1
1, a belt layer 13 of at least two layers of rubber-coated cords intersecting each other at a relatively small angle with respect to the tire circumferential direction is arranged substantially over the width of the tread portion 11.

The belt reinforcing layer 13a is provided with at least one carcass layer 14 which is in direct contact with the rubber reinforcing cord and is inclined at an angle of 70 to 90 degrees with respect to the tire circumferential direction. The other end of each carcass layer, which is opposite to the lower end of the layer 13, is configured to extend to at least a substantially radial inner end region of each bead portion 15.

Further, in this embodiment, one of the plurality of belt layers 13 in contact with the carcass layer 14 is the belt reinforcing layer 13a.

(First Embodiment) FIGS. 2 to 6 show a first embodiment of a pneumatic tire according to the present invention, and FIG. 2 shows a state in which a rubber layer containing short fibers is arranged on the surface of a green tire. 3 is a perspective view of a main part of a tire pattern formed by setting a green tire in a vulcanizing mold, FIG. 4 is an enlarged cross-sectional view taken along the line AA in FIG. 3, and FIG. FIG. 3 is an enlarged cross-sectional view taken along the line BB in FIG. 3, and FIG. 6 is a graph showing the relationship between the compression rigidity with respect to the short fiber sheet in the vicinity of the wall surface and the entire block.

The pneumatic radial tire of this embodiment is
As shown in FIG. 2, at the stage of molding the tire, a thin rubber layer 20 (hereinafter referred to as a short fiber sheet) containing the short fibers F oriented in one direction is arranged (short) on the surface of the green tire 10a. After the fiber sheet is attached, the green tire 10a on which the rubber layer 20 is arranged is set in a vulcanization die (not shown) for vulcanization (vulcanization step).

The green tire 10a is formed through a first molding process such as carcass ply and side wall rubber bonding and a second molding process such as belt and tread rubber bonding. The green tire is set in the vulcanizing mold. As a result, a tire pattern is formed on the tread portion 11 (see FIG. 1). That is, as shown in FIG. 3, the inner surface of the vulcanization mold has a tire circumferential direction (vertical direction in the figure).
A mesh-like pattern (not shown) corresponding to the circumferential groove 12 extending in the direction and the lug groove 16 as a lateral groove extending in the tire width direction (the lateral direction in the drawing) is formed.

Therefore, in the vulcanizing step, the short fiber sheet 20 is integrated at the same time when the circumferential groove 12 and the lug groove 16 are formed. At this time, when the short fiber sheet 20 is arranged in the short fiber sheet attaching step, the short fiber F direction oriented in one direction on the short fiber sheet 20 is arranged so as to coincide with the tire circumferential direction.

Here, the short fibers F mean an average length of 10 mm.
The following organic short fibers or inorganic short fibers are referred to. As organic short fibers, aliphatic polyamide short fibers such as nylon, aromatic polyamide / aramid short fibers such as Kevlar, cellulose short fibers such as rayon, polyethylene terephthalate. Polyester short fibers such as polybutylene terephthalate and aromatic polyester, polyvinyl alcohol short fibers such as vinylon, syndiotactic 1,2 polybutadiene short fibers, polyolefin short fibers such as polyethylene and polypropylene, short polyether fibers, short polyurea Examples include fibers, polyurethane short fibers, polyethylene sulfide short fibers and the like.

In this case, preferred aliphatic polyamides include nylon 6, nylon 66, nylon 6-nylon 66 copolymer, nylon 610, nylon 612, nylon 46, nylon 11, nylon 12, nylon MX.
Examples include D6, a polymer of an aliphatic diamine and an aromatic dicarboxylic acid, and the like. Further, the polyvinyl alcohol-based short fibers are preferably fibrillated.

Examples of the inorganic short fibers include glass fibers, carbon fibers, steel fibers and the like.

In this embodiment, as a particularly preferable material,
Nylon, polyester, rayon or the like, or fiber crystalline SPB resin, ABS resin or the like is used. Also,
The diameter (average) of the short fibers is 10 to 200 μm, and the length thereof is about 10 to 10,000 times the diameter, and the compounding amount thereof is suitably 5 to 60 parts by weight with respect to 100 of rubber.

The short fiber F may be mixed and kneaded with other compounding chemicals, but from the viewpoint of productivity, it may be previously kneaded with a small amount of a rubber component to prepare a rubber-short fiber masterbatch. An example of such a masterbatch is a fiber-reinforced thermoplastic polyolefin-elastomer composition (a thermoplastic polyamide is dispersed in a fine fiber state in a matrix composed of a polyolefin and an elastomer). .

The tire pattern shown in FIG. 3 has a circumferential groove 1
2 and the lug groove 16 divide into a large number of blocks 17, and these blocks 17 are regularly arranged in the tire circumferential direction, and a plurality of block rows B1, B2, B3, B4, B5.
And, in particular, the block rows B4 and B on both sides in the tire width direction.
5 is a shoulder block row and is arranged in the shoulder portion 18. In FIG. 3, K is a ground contact shape line of the tread surface portion T, and in the tread surface portion T surrounded by the ground contact shape line K, the plurality of block rows B1, B2, B3 are arranged, and A part of the block rows B4, B5 is arranged.

The block 17 divided by the circumferential groove 12 and the lug groove 16 has a circumferential groove wall 12a extending in the tire circumferential direction and a lug groove wall 16 extending in the tire width direction.
and a are formed in the thickness direction of the block 17.

Here, the thickness t (see FIG. 4) of the short fiber sheet 20 containing the short fibers F is determined for the following reason. That is, as the thickness t of the short fiber sheet 20 increases, the rigidity of the lug groove wall 16a increases, and thus the ground reaction force in the vicinity of the lug groove wall 16a can be increased, but in this case, the block 17 Since the thickness of the short fiber sheet 20 covering the surface of the block 17 also increases, the compression rigidity of the entire block 17 also increases, and other vibration noise performance such as passing noise and road noise deteriorates.

That is, the thickness t of the short fiber sheet 20 is shown in FIG.
Shows the relationship between (horizontal axis) and the magnitude of compression rigidity (vertical axis),
The plotted rhombus points indicate the compression rigidity near the lug groove wall 16a,
The square points are the compression rigidity of the entire block 17. As is clear from the figure, the thickness t of the short fiber sheet 20 is 0.0 to
Up to 1.0 mm, the compression rigidity of the lug groove wall 16a is approximately equal to or greater than the compression rigidity of the entire block 17, but t
Is more than 1.0 mm, the compression rigidity of the entire block 17 is superior.

Therefore, in order to increase only the lug groove wall 16a without changing the rigidity of the block 17 as a whole, the thickness t of the short fiber sheet 20 is set to 0.1 to 1.
It may be set in the range of 0 mm, and in particular, 0.1 to 0.5
It is preferable to set in the range of mm.

The tread portion 11 shown in FIG. 3 thus formed has the short fiber sheet 2 over the entire block portion 17.
0 is bonded by vulcanization and integrated. At this time, the short fibers F
Since the orientation direction of is the same as the circumferential direction of the tire 10, the short fibers F are continuous on the wall surface of the lug groove wall 16a in the thickness direction of the block 17, as shown in FIG. on the other hand,
On the wall surface of the circumferential groove wall 12a, the short fibers F are discontinuous in the thickness direction of the block 17, as shown in FIG.
Therefore, it is possible to increase only the compressive rigidity of the surface of the lug groove wall 16a along the tire width direction and the vicinity thereof, which in turn can increase the road surface reaction force generated at that portion, and also to increase the circumferential groove wall. Since it is possible to prevent the compression rigidity of 12a from greatly increasing, it is possible to prevent the impact component of the block 17 from increasing.

The inner tread portion 11 to which the short fiber sheet 20 is vulcanized and bonded does not contain the short fibers F in order to prevent the rigidity of the entire block 17 from being excessively increased.

Therefore, in the pneumatic radial tire 10 of this embodiment, when the vehicle is running, there is no lug groove 16 in the ground contact portion of the tire, that is, the state where the block 17 exists to the lug groove 16 exists. In other words, it is possible to prevent the load from decreasing due to the increased rigidity portion of the surface of the lug groove wall 16a at the moment of transition to the void portion. As a result, it is possible to reduce the fluctuation of the axle force due to the tire tread and effectively reduce the pattern noise.

(Second Embodiment) FIGS. 7 to 11 show a second embodiment, in which the same components as those in the first embodiment are designated by the same reference numerals and a duplicate description will be omitted. FIG. 7 is a perspective view of a main part showing a state in which a rubber layer containing short fibers is arranged on the surface of a green tire, and FIG. 8 is a plan view of a main part of a tire pattern formed by setting the green tire in a vulcanization mold. 9, FIG. 9 is an enlarged sectional view taken along the line AA in FIG. 8, FIG. 10 is an enlarged sectional view taken along the line BB in FIG. 8, and FIG. 11 is an explanatory view showing the lug groove angle of the shoulder portion.

The main difference between this embodiment and the above-described embodiment is that, as shown in FIGS. 7 and 8, the short fiber sheet 20 is divided into two in the tire width direction, and each of them is a shoulder block on both sides in the tire width direction. It is arranged in rows B4 and B5.

Of course, even in this embodiment, the short fiber sheet 20 is arranged so that the orientation direction of the short fibers F coincides with the tire circumferential direction.

That is, in this embodiment, the short fiber sheet 20 is used.
Is arranged only in the shoulder portion 18 in which the shoulder block rows B4 and B5 are arranged.
As shown in, the lug groove 16 angle θ of the shoulder portion 18
Is smaller due to wear resistance and drainage performance,
The ground contact shape line K of the tread surface portion T and the lug groove 16 are likely to coincide with each other, and the shoulder portion 18 is a portion that greatly contributes to the fluctuation of the tire axial force. Therefore, arranging the short fiber sheet 20 only on the shoulder portion 18 does not significantly affect the pattern noise reduction performance.

Therefore, also in this embodiment, as shown in FIG. 9, the short fibers F are continuous on the wall surface of the lug groove wall 16a in the thickness direction of the block 17, and the lug groove wall 1
It is possible to increase only the compression rigidity of the surface 6a and its vicinity. Further, as shown in FIG. 10, the circumferential groove wall 12a
The short fibers F are discontinuous in the wall thickness direction of the block 17 in the thickness direction of the block 17, and it is possible to prevent the compressive rigidity of the circumferential groove wall 12a from greatly increasing. At this time, since the short fiber sheet 20 is arranged only on the block rows B4, B5 side and is not provided on the block rows B1, B3 side, the wall surface of the circumferential groove wall 12a is in the central block row B1, B2, B3. Since it is possible to prevent the increase of the compression rigidity in the block 17, it is possible to further reduce the increase of the impact component of the block 17.

(Third Embodiment) Although not shown in this embodiment, a rubber layer containing a non-woven fabric instead of the short fibers F contained in the short fiber sheet 20 shown in the first and second embodiments. And the rubber layer containing the non-woven fabric is formed into a short fiber sheet 2
0 is placed on the surface of the green tire (step of attaching short fiber sheet), and then the green tire having this rubber layer is set in a vulcanization mold (not shown) for vulcanization (vulcanization step)
It is something that is done.

Here, the non-woven fabric is different from the interwoven weave of the fiber cord for tires and is composed of a large number of fibers (filaments).
A large number of fibers are directly clothed without twisting or weaving a bundle, and carding method, papermaking method, air-laying method, melt blow,
The web is manufactured using the spunbond method.

As a fiber bonding method for webs other than melt blown and spunbonding methods, a heat fusion method, a binder method, a water entanglement method in which fibers are entangled by water flow or the force of a needle,
A nonwoven fabric using a needle punch method or the like can be preferably used. Above all, a non-woven fabric made by a hydroentangling method in which fibers are entangled by a water current or a needle, a needle punching method, a melt blow, and a spunbond method are preferably used.

In this embodiment, the non-woven fabric has a structure in which every corner of the fiber is impregnated with rubber, and has a structure in which the fiber and the rubber layer can be continuous layers over a relatively long distance and a wide range. It is a fundamentally important requirement that the fibers be arranged in a very random arrangement with respect to the rubber matrix, particularly in the thickness direction of the composite.

The filament applied to the non-woven fabric has a diameter or maximum diameter within the range of about 0.1 to about 50 μ, and has a disk-shaped cross section or a cross section different from the disk. Can be suitably used including those having a hollow portion. Further, the filament is preferably a long fiber having a length of 3 cm or more.

As the material of the non-woven fabric, in addition to fibers such as cotton, rayon, cellulose acetate, nylon, polyester, vinylon and aramid, one or more kinds selected from carbon fiber, glass fiber, steel wire and the like are mixed. It is preferably used, and rayon, nylon and polyester are particularly preferable.

The thickness of the non-woven fabric is preferably in the range of 0.1 to 3.0 mm, and the basis weight (weight per square meter) is preferably in the range of 10 to 500 gr. It is necessary to allow some variation in the basis weight depending on the type of fiber used, but if the basis weight is too large, a sufficient amount of rubber will not penetrate into the voids inside the nonwoven fabric when compounding with the rubber described below, and the tire It is not preferable because it is disadvantageous in peeling resistance as a member.

Since the above-mentioned non-woven fabric is used as a composite member, it is possible to apply an unvulcanized rubber composition to the non-woven fabric in advance at the stage of the non-vulcanized member to integrally form a composite.
In this compounding, if the adhesiveness to the rubber after vulcanization is sufficient without subjecting the nonwoven fabric to adhesion treatment in advance, to the untreated nonwoven fabric, and if this adhesion is insufficient, to the tire fiber cord and rubber As in the case of increasing the adhesive strength with the sheet, the sheet-shaped unvulcanized rubber composition is pressed from the upper and lower surfaces of the nonwoven fabric that has been subjected to the dipping / heat-setting treatment by pressing or rolling, and the air inside the nonwoven fabric is removed. It is also possible to sufficiently replace the unvulcanized rubber composition. It is one of the preferred embodiments that a green tire is molded by applying the unvulcanized sheet composite member thus obtained, and vulcanization molding is performed on the green tire to obtain a composite member.

(Performance Test) Of the first, second, and third embodiments, the rubber layer 20 containing the short fibers F used in the first and second embodiments is arranged on the wall surface of the block 17 to form the tire. The simplex axial force was measured. The condition in this case is tire size 19
At 5 / 65R14, internal pressure 200kPa, load 4kN, speed 50km / h,
At a band value of 400 to 600 Hz including the primary pitch frequency of the pattern, an improvement of 4 dB in comparison with the conventional tire was confirmed.

(Vehicle Interior Noise Evaluation Test of Each Embodiment) Next, in a 2000 cc class passenger car, the pneumatic tire 10 of each of the first, second, and third embodiments was used. Interior noise of tires (400-600Hz band value including the primary pitch frequency of the pattern)
Was measured individually and the results are shown in the following table. In this case, the vehicle interior noise is measured based on the sound around the driver's ears, and the sensory evaluation of the driver is also described. In addition, the traveling condition of the passenger car is such that two passengers are traveling on a smooth concrete road at a vehicle speed of 50 km / h.

[0057]

[Table 1]

[0058]

According to the pneumatic tire of the first aspect of the present invention, since the surface of the lateral groove wall of the tread portion is reinforced by the rubber layer containing short fibers, the road surface reaction force generated near the lateral groove wall surface is obtained. Can be increased to reduce the fluctuation of the axle force due to the tire tread, and the pattern noise can be effectively reduced.

According to the pneumatic tire of the second aspect of the invention, in addition to the effect of the first aspect of the invention, the tread portion inside the rubber layer does not contain short fibers. It is possible to prevent the block compression rigidity from becoming large as a whole.

According to the pneumatic tire of the third aspect of the invention, in addition to the effects of the first and second aspects of the invention, the rubber layers are arranged on the shoulder block rows on both sides in the tire width direction. Accordingly, it is possible to reduce the cost by reducing the installation area of the rubber layer while reducing the fluctuation of the tire axle force.

According to the pneumatic tire of the fourth aspect of the invention, in addition to the effects of the first to third aspects of the invention, the thickness of the rubber layer is set between 0.1 and 1.0 mm. So
Only the rigidity near the wall surface of the lateral groove can be increased without increasing the compression rigidity of the entire block.

According to the pneumatic tire of the fifth aspect of the invention, in addition to the effects of the first to fourth aspects of the invention, the pneumatic tire is a radial tire.
The pattern noise of the radial tire can be effectively reduced.

In the pneumatic tire manufacturing method according to the sixth aspect of the present invention, the short fiber direction of the thin rubber layer in which the short fibers are oriented in one direction is the tire circumferential direction in the short fiber sheet attaching step. The green tires are placed on the surface of the green tire so as to be coincident with each other, and the vulcanization process is used to vulcanize the green tire on which the rubber layer is placed by using a vulcanization mold having a mesh pattern corresponding to circumferential grooves and lateral grooves on the inner surface. As a result, when the short fibers of the rubber layer are oriented in the block thickness direction of the groove wall portion of the block, the short fibers become discontinuous in the circumferential groove wall surface in the block thickness direction, while the short groove wall surface becomes discontinuous. Can be continuous in the block thickness direction. Therefore, while increasing only the compression rigidity of the lateral groove wall surface and its vicinity to increase the road surface reaction force generated at that portion,
It is possible to keep the compression rigidity small at the circumferential groove wall surface and prevent the impact component of the block from increasing.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a pneumatic tire showing an embodiment of the present invention.

FIG. 2 is a perspective view of a main part of a state in which a rubber layer containing short fibers is arranged on the surface of the green tire showing the first embodiment of the present invention.

FIG. 3 is a plan view of a main part of a tire pattern showing the first embodiment of the present invention.

FIG. 4 is an enlarged sectional view taken along the line AA in FIG. 3 showing the first embodiment of the present invention.

FIG. 5 is an enlarged cross-sectional view taken along line BB in FIG. 3 showing the first embodiment of the present invention.

FIG. 6 is a graph showing the relationship between the compression rigidity with respect to the short fiber sheet in the vicinity of the wall surface and the entire block, showing the first embodiment of the present invention.

FIG. 7 is a perspective view of an essential part of a state in which a rubber layer containing short fibers is arranged on the surface of a green tire showing a second embodiment of the present invention.

FIG. 8 is a plan view of a main part of a tire pattern showing a second embodiment of the present invention.

FIG. 9 is an enlarged cross-sectional view taken along the line AA in FIG. 8 showing the second embodiment of the present invention.

FIG. 10 is an enlarged sectional view taken along line BB in FIG. 8 showing the second embodiment of the present invention.

FIG. 11 is an explanatory diagram of a lug groove angle of a shoulder portion showing a second embodiment of the present invention.

FIG. 12 is a side view of an essential part showing an enlarged ground contact portion of a conventional pneumatic tire.

[Explanation of symbols]

10 radial tires (pneumatic tires) 10a green tire 11 tread section 12 circumferential groove 12a circumferential groove wall 13 Belt layer 13a Belt reinforcement layer 14 carcass layer 15 bead 16 lug groove (lateral groove) 16a rug groove wall 17 blocks 18 Shoulder 20 Short fiber sheet (rubber layer) F short fiber T tread K grounding shape line B1, B2, B3 block row B4, B5 Shoulder block row

Claims (6)

[Claims] 1. A pneumatic tire having a plurality of block rows formed on a tread portion of a tread portion by a circumferential groove extending in the tire circumferential direction and a lateral groove extending in the tire width direction, wherein the lateral groove wall surface of the tread portion is A pneumatic tire characterized by being reinforced with a rubber layer containing short fibers. 2. The pneumatic tire according to claim 1, wherein the tread portion inside the rubber layer does not contain short fibers. 3. The rubber layer is arranged in the shoulder block rows on both sides in the tire width direction.
Or the pneumatic tire according to 2. 4. The rubber layer has a thickness of 0.1 to 1.0 mm.
The pneumatic tire according to any one of claims 1 to 3, wherein the pneumatic tire is set between 1 and 2. 5. A pneumatic tire is provided with at least one circumferential groove extending in a tire circumferential direction on a tread surface of a tread portion, and a plurality of block rows are formed between ends of the tread tread surface portions. In the tread portion, at least two belt layers of rubber-coated cords intersecting each other at a relatively small angle with respect to the tire circumferential direction are arranged, and the rubber clothing is provided on the inner side of the belt layer in the tire radial direction. The cord is provided with at least one carcass layer that is inclined at an angle of 70 to 90 degrees with respect to the tire circumferential direction, and the other end of each carcass layer that contradicts the belt layer lower end has at least one bead portion. The pneumatic tire according to any one of claims 1 to 4, wherein the pneumatic tire extends to a substantially radial inner end region. 6. A short fiber sheet attaching step of arranging a thin rubber layer in which short fibers are oriented in one direction on the surface of a green tire so that the short fiber direction coincides with the tire circumferential direction, and a rubber layer is provided. A vulcanizing step of vulcanizing the arranged green tire using a vulcanizing mold having a mesh pattern corresponding to the circumferential grooves and the lateral grooves on the inner surface, and a method for manufacturing a pneumatic tire, comprising: .