JPH1178424A - Pneumatic tire and mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain dispersion of a tread gauge caused by a large difference of a block and to improve steering stability. SOLUTION: The capacity of a large land part 24L of a large pitch part is relatively increased by making an angle θ1 against the tire radial direction of a wall surface of a peripheral directional groove 14 of the large pitch part larger than an angle θ3 against the tire radial direction of the wall surface of the peripheral directional groove 14 of a small pitch part. It comes to be possible to absorb a part of rubber flowing in a recessed part of a mold for formation of a land part by capacity increase of the land part at the time of molding with the mold and to restrain recession of a belt, that is, increase of a tread gauge G1 of the large land part 24L of the large pitch part against a tread gauge G3 of a small land part 24S of the small pitch part. As dispersion of the tread gauges is restrained, steering stability is improved.

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 more particularly to a pneumatic tire which suppresses variations in a tread gauge due to a change in the size of a block during one rotation of the tire, thereby improving steering stability. The present invention relates to a mold for molding the pneumatic tire.

[0002]

2. Description of the Related Art In general, in a pneumatic tire, in order to reduce various noises generated from a tire pattern, a plurality of types of pitches having different pitch lengths are arranged in an appropriate combination on a circumference to form a tread pattern. Is formed.

Conventionally, each lateral groove included in each pitch and having an extending component in the tread width direction has a constant depth while maintaining a constant groove wall angle with respect to the tire radial direction. Is selected so that the ratio of the opening widths is equal to the pitch ratio.
The circumferential groove has a constant groove width, and the groove wall angle with respect to the tire radial direction is set to be constant regardless of the pitch.

[0004]

However, in this prior art, there is a problem that the tread gauge varies as the size of the block around the tire changes.
The reason why the tread gauge varies depending on the size of the tread is known from JP-A-6-239106.

[0005] A mold for vulcanizing a tire has a concave portion forming a block, a projection forming a lateral groove, and the like. When a green tread having a constant thickness (gauge) of the green tire is pressed against the mold, the lateral groove forming projections provided on the mold push away the rubber, and the pushed rubber flows toward the block forming recess.

Here, if the pitch is large or small, the amount of rubber flowing per unit volume of the concave portion is relatively large in the concave portion of the large pitch portion than in the small pitch portion. As a result, the tread gauge of the large block increases with respect to the tread gauge of the small block.

[0007] If the variation of the tread gauge becomes large, the steering stability is reduced. Therefore, it is desired to suppress the variation of the tread gauge.

In view of the above facts, the present invention provides a pneumatic tire capable of suppressing variations in tread gauge caused by a difference in block size and improving steering stability, and a mold for molding the pneumatic tire. The purpose is to do.

[0009]

According to the first aspect of the present invention, a tread pattern is formed by forming a circumferential groove and a lateral groove in a tread tread portion and combining at least two kinds of different pitches in the tread circumferential direction. The pneumatic tire is characterized in that the angle of the circumferential groove wall surface of the large pitch portion with respect to the tire radial direction is larger than the angle of the circumferential groove wall surface of the small pitch portion with respect to the tire radial direction.

Next, the operation of the pneumatic tire according to the first aspect will be described. Since the angle of the circumferential groove wall surface of the large pitch portion with respect to the tire radial direction is larger than the angle of the circumferential groove wall surface of the small pitch portion with respect to the tire radial direction,
The land volume of the large pitch portion relatively increases. Therefore, at the time of molding with the mold, a part of the rubber flowing into the concave portion of the land portion forming mold can be absorbed by an increase in the capacity of the land portion, and the belt is dented, that is, the small pitch portion of the land portion is formed. As compared with the tread gauge, the increase of the tread gauge on the land portion of the large pitch portion is suppressed.

Since the dispersion of the tread gauge is suppressed, the steering stability is improved. According to a second aspect of the invention, in the pneumatic tire according to the first aspect, the angle of the circumferential groove wall surface at the maximum pitch portion is larger than the angle of the circumferential groove wall surface at the minimum pitch portion by 3 ° or more. Features.

[0012] In the pneumatic tire according to the second aspect, the angle of the circumferential groove wall surface at the maximum pitch portion is larger than the angle of the circumferential groove wall surface at the minimum pitch portion by 3 ° or more.
The difference between the tread gauge at the land portion of the small pitch portion and the tread gauge at the land portion of the large pitch portion can be reliably reduced.

If the angle is less than 3 °, the effect of reducing the difference in tread gauge is small. According to a third aspect of the invention, in the pneumatic tire according to the first or second aspect, when there are three or more types of pitches, the angle of the circumferential groove wall surface increases as the pitch increases. It is characterized by:

In the pneumatic tire according to the third aspect, when there are three or more types of pitches, the angle of the circumferential groove wall surface increases as the pitch increases, so that various sizes of pitches are mixed. Also, the variation of the tread gauge can be reliably reduced.

For example, when a large pitch, a middle pitch, and a small pitch are mixed, the angle of the circumferential groove wall surface with respect to the tire radial direction of the large pitch> the angle of the circumferential groove wall surface with respect to the tire radial direction of the medium pitch> small. The pitch is the angle of the circumferential groove wall surface with respect to the tire radial direction.

According to a fourth aspect of the present invention, a pneumatic tire having a tread pattern formed by forming a circumferential groove and a lateral groove in a tread tread portion and combining at least two kinds of different pitches in the tread circumferential direction. A protrusion that forms a circumferential wall surface so that the angle of the circumferential groove wall surface of the large pitch portion with respect to the tire radial direction is larger than the angle of the circumferential groove wall surface of the small pitch portion with respect to the tire radial direction. Is determined.

Next, the operation of the mold according to claim 4 will be described. Since the angle of the circumferential groove wall surface of the large pitch portion with respect to the tire radial direction, the angle of the projection forming the circumferential wall surface was determined so as to be larger than the angle of the circumferential groove wall surface of the small pitch portion with respect to the tire radial direction, The land volume of the large pitch portion relatively increases. Therefore, at the time of molding, a part of the rubber flowing into the concave portion (relative to the projection) of the land portion forming mold can be absorbed by the increased capacity of the land portion, and the belt is dented, that is, the small pitch portion is formed. An increase in the tread gauge at the land portion of the large pitch portion relative to the tread gauge at the land portion is suppressed, and a pneumatic tire with reduced variation in the tread gauge can be molded.

[0018]

1 (A) to 1 (C) show tread patterns of a pneumatic tire 10 (tire size 195 / 65R14) according to an embodiment of the present invention. Note that the internal structure of the pneumatic tire 10 is the same as the structure of a normal radial tire, and a description thereof will be omitted.

As shown in FIGS. 1A to 1C, a tread 12 arranged on a belt 11 of a pneumatic tire 10 is provided.
In the tire width direction (arrow W
Direction) is provided with a circumferential groove 14 on each side,
A circumferential groove 16 is formed outside each of the circumferential grooves 14 in the tire width direction. Further, the tread 12 has a lateral groove 18 between the circumferential grooves 14,
A lateral groove 20 is formed between the circumferential groove 14 and the circumferential groove 16, and a lateral groove 22 is formed outside the circumferential groove 16 in the tire width direction.

A land portion sandwiched between the circumferential grooves 14 is formed by a lateral groove 18 in the tire circumferential direction (arrow S).
A plurality of first land portions 24 (L,
M, S), and a land portion sandwiched between the circumferential groove 14 and the circumferential groove 16 has a plurality of second land portions 26 (L, M, S) having different sizes in the tire circumferential direction by the lateral groove 20. )
The land portion on the outer side in the tire width direction of the circumferential groove 16 is substantially partitioned by the lateral groove 22 into a plurality of third land portions 28 (L, M, S) having different sizes in the tire circumferential direction.

In this embodiment, there are three types of circumferential pitches of the lateral grooves 18, 20, and 22: a large pitch shown in FIG. 1A, a small pitch shown in FIG. Thereby, the first land portion 24 is divided into three types of continent portions 24L, central land portions 24M, and small land portions 24S having different circumferential dimensions, and the second land portion 26 has three types of different circumferential sizes. The continent 26L, the land 26M, and the land 26S are divided, and the third land 28 is divided into three types of continents 28L, land 28M, and land 28S having different circumferential dimensions. .

FIGS. 1A to 1C and FIGS.
As shown in FIG. 1C, in the pneumatic tire 10, the large pitch P1, the medium pitch P2, and the small pitch P3 differ from each other.
Are combined in the tire circumferential direction by a known method (in this embodiment, three pitches and three peaks arrangement) to prevent the pattern noise from deteriorating.

The lateral grooves 18, 20, and 22 have a greater groove width and a land portion with a shorter circumferential dimension so that the negative ratio is uniform in the tire circumferential direction, so that the adjacent grooves are longer in the circumferential direction. (The circumferential length of the continent portion 24L: the circumferential length of the central land portion 24M: the circumferential length of the small land portion 24S = the continental portion 26L).
The circumferential length of the lateral groove 18 that defines the land portion 24M is the circumferential length of the lateral groove 18 that defines the land portion 24M, and the circumferential length of the lateral groove 18 that defines the small land portion 24S.

In this embodiment, the continents 24L, 26L,
28L tire circumferential dimension L1 is 33mm,
M, 26M, 28M tire circumferential dimension L2 is 27mm,
Tire circumferential dimension L3 of continents 24S, 26S, 28S
Is set to 21 mm.

The width W1 of the first land portion 24 is 25 mm, the width W2 of the second land portion 26 is 25 mm, and the width W3 of the third land portion 28 is 25 mm.

Further, the groove depth of the lateral groove 18, the groove depth of the lateral groove 20, and the groove depth of the lateral groove 22 are each 7.7 mm.

The circumferential groove 14 and the circumferential groove 16 are
The depth d is 7.7 mm and the groove width W4 is 10 mm.

As shown in FIGS. 2A to 2C, the groove wall angle of the circumferential groove 14 with respect to the tire radial direction (a value measured at a cross section perpendicular to the circumferential groove wall) is large pitch. P1
In the area of θ1, medium pitch P2 in the area of θ2, small pitch P
The setting is such that when θ3 is set in part 3, θ1>θ2> θ3. In addition, the groove wall angle of the circumferential groove 16 is set similarly.

The maximum groove wall angle θ3 and the minimum groove wall angle θ1
Is preferably 3 ° or more, and in the present embodiment, θ1 is 2 °.
1 °, θ2 are set to 11 °, and θ3 is set to 5 °.

The angle of the lateral groove walls of the lateral grooves 18, 20 and 22 with respect to the tire radial direction is 3 °.

As shown in FIG. 2A, a projection 32 for forming a circumferential groove is formed on the inner surface of a mold 30 for molding the pneumatic tire 10, and has a shape opposite to the unevenness of the tread 12. It is uneven.

Next, the operation of the pneumatic tire 10 of the present embodiment will be described. In the pneumatic tire 10 of the present embodiment, since the groove wall angle θ1 at the large pitch P1> the groove wall angle θ2 at the medium pitch P2> the groove wall angle θ3 at the small pitch P3, the land portion having the larger pitch Can be suppressed from increasing more than the tread gauge of the land portion having the smaller pitch.

Thus, the continents 24L, 26L, 28
The difference between the tread gauge G1 of L (the dimension from the outermost belt to the tread surface), the tread gauge G2 of the inland portions 24M, 26M, and 28M and the tread gauge G3 of the land portions 24S, 26S, and 28S is reduced, and the tire rolling The level variation of the grounding characteristic during operation can be suppressed. As a result, the steering stability of the pneumatic tire 10 is improved.

Further, since the groove cross-sectional area of the circumferential grooves 14 and 16 changes in the tire circumferential direction, the sound pressure level of columnar resonance of the circumferential grooves 14 and 16 can be reduced.

In this embodiment, θ1 is 21 °, θ2
Is set to 11 ° and θ3 is set to 5 °, but the present invention is not limited to this angle.

It is more effective that the difference between the minimum angle and the maximum angle of the circumferential groove wall surface is large. However, if the difference is too large, the maximum angle becomes too large, and the opposing circumferential groove wall surfaces may be separated from each other. The interference causes the groove depth to be shallow, and the drainage performance to be reduced. (Test Example) In order to confirm the effects of the present invention, a conventional tire and a tire according to an embodiment to which the present invention is applied are prepared.
A tread gauge measurement at each pitch, a tertiary component of RFV (radial force variation), a steering stability test, and a noise test were performed.

The tire of the example used in the test is the tire of the above-described embodiment, and the tire of the conventional example has the groove wall angles of the circumferential grooves set to 11 ° (all other specifications are the same as those of the embodiment). (Same as tire). For each tire, the tread has 15 large pitches in the circumferential direction, 24 medium pitches, and 24 small pitches, and 8 small pitches, 4 medium pitches, and 5 large pitches in the circumferential direction. And a set of four medium pitches are arranged as one set, and three sets are arranged in the circumferential direction.

Since a three-time repeating arrangement with three types of large, medium and small pitches was applied, the tertiary component of RFV was measured by a drum tester. As a result, the tertiary component of RFV was reduced by 40% in the tire of the example as compared with the tire of the conventional example.

As a result of the measurement of the tread gauge, the difference between the tread gauges of the continent portion and the small land portion was 0.2 mm on average in the conventional tire, but the difference in the tread gauge was not large in the tire of the embodiment. The average was 0.02 mm.

Driving stability test: An actual vehicle equipped with tires was run on a test course (dry road and wet road).
In a 10-point evaluation by the test driver, the score of the conventional tire was 6 points, but that of the example tire was 6.5 points.

Noise test (air column resonance): JASO C
The measurement was performed according to 606 (drum method). The test device is composed of a rotating drum and a tire support device whose surface has been processed as a substitute road surface in a room subjected to acoustic processing. The drum is J
ASO has a diameter of 3.0 m and a coarse-grained surface attached to the surface. In this case, the measurement was performed at 50 km / h.

As a result of the test, the noise of the example tire was 1 dB smaller than that of the conventional tire at 1000 Hz.

It should be noted that the circumferential groove was filled with urethane, and the groove was filled to eliminate the columnar resonance component and the sound was measured.
There was no difference between the two tires.

[0044]

As described above, the pneumatic tire according to the first aspect has the above-described structure, so that variations in the tread gauge due to a change in the size of the block during one rotation of the tire are suppressed. And has an excellent effect that steering stability can be improved.

Since the pneumatic tire according to the second aspect has the above-described configuration, it has an excellent effect that variation in the tread gauge can be reliably suppressed.

Since the pneumatic tire according to the third aspect has the above-described configuration, it has an excellent effect that the variation in the tread gauge can be suppressed reliably even when various pitches are mixed. .

Since the mold according to the fourth aspect has the above-described configuration, it has an excellent effect that a pneumatic tire with a small variation in tread gauge can be molded.

[Brief description of the drawings]

1 (A) is a plan view of a tread of a large pitch portion, FIG. 1 (B) is a plan view of a tread of a middle pitch portion, and FIG. 1 (C) is a plan view of a tread of a small pitch portion.

FIG. 2A is a cross-sectional view in the width direction of a tread of a large pitch portion (a cross-sectional view taken along line 2 (A) -2 (A) of FIG. 1A), and FIG. FIG. 2 is a cross-sectional view (cross-sectional view taken along line 2 (B) -2 (B) in FIG.
(C) is a cross-sectional view in the width direction of the tread of the small pitch portion (FIG. 1)
(C) is a sectional view taken along line 2 (C) -2 (C).

[Explanation of symbols]

 Reference Signs List 10 Pneumatic tire 12 Tread 14 Circumferential groove 16 Circumferential groove 32 Projection P1 Large pitch P2 Medium pitch P3 Small pitch

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI B60C 11/04 B60C 11/04 H 11/13

Claims (4)

[Claims] 1. A pneumatic tire having a tread pattern in which a circumferential groove and a lateral groove are formed in a tread tread portion, and a tread pattern is formed by combining at least two different pitches in a tread circumferential direction. A pneumatic tire, wherein an angle of the groove wall surface with respect to the tire radial direction is larger than an angle of the circumferential groove wall surface of the small pitch portion with respect to the tire radial direction. 2. The pneumatic tire according to claim 1, wherein the angle of the circumferential groove wall surface at the maximum pitch portion is larger than the angle of the circumferential groove wall surface at the minimum pitch portion by 3 ° or more. 3. The pneumatic tire according to claim 1, wherein when there are three or more kinds of pitches, the angle of the circumferential groove wall surface increases as the pitch increases. 4. A mold for molding a pneumatic tire having a tread pattern formed by forming a circumferential groove and a lateral groove in a tread tread portion and combining at least two kinds of different pitches in the tread circumferential direction. The angle of the projection forming the circumferential wall is determined so that the angle of the circumferential groove wall of the portion with respect to the tire radial direction is larger than the angle of the circumferential groove wall of the small pitch portion with respect to the tire radial direction. Characteristic mold.