JPH1178423A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain a change of a grounding characteristic in accordance with a change of a size of a block during one rotation of a tire and to improve steering stability and partial wear resistance. SOLUTION: It is possible to restrain level variation of a grounding characteristic during rolling of a tire and to improve steering stability and uneven abrasion resistance as a difference between rigidity of a small land part 24S of a small pitch P3 part and rigidity of a large land part 24L of a large pitch P1 part becomes small by making an angle θ3 against the tire radial direction of a translot wall surface of the small pitch P3 part larger than an angle θ1 against the tire radial direction of a translot wall surface of the large pitch P1 part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire, which suppresses a change in grounding characteristics due to a change in the size of a block during one rotation of the tire, thereby improving steering stability and uneven wear resistance. Related to pneumatic tires.

[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.

[0004]

However, in this prior art, there is a problem that the level of the grounding characteristics (RFV, etc.) during the rolling of the tire does not become the same due to the difference in the size of the block.

When the level variation of the grounding characteristic increases,
It is desired that the level of the ground contact characteristics during the rolling of the tires be the same, since this leads to a decrease in steering stability and resistance to uneven wear.

An object of the present invention is to provide a pneumatic tire that can suppress the level fluctuation of the ground contact characteristic during rolling of a tire in consideration of the above fact.

[0007]

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 lateral wall surface of the small pitch portion with respect to the tire radial direction is larger than the angle of the lateral wall surface of the large pitch portion with respect to the tire radial direction.

In the pneumatic tire according to the first aspect, the angle of the small pitch portion with respect to the tire radial direction of the lateral groove wall surface is made larger than the angle of the large pitch portion with the lateral groove wall surface with respect to the tire radial direction. The difference between the rigidity of the land part (for example, block) and the rigidity of the land part of the large pitch part becomes small, and the level fluctuation of the ground contact characteristic during rolling of the tire can be suppressed, and the steering stability and uneven wear resistance can be improved. Can be improved.

According to a second aspect of the present invention, in the pneumatic tire according to the first aspect, the angle of the lateral groove wall surface at the minimum pitch portion is 3 ° more than the angle of the lateral groove wall surface at the maximum pitch portion.
The feature is that it is large.

[0010] In the pneumatic tire according to the second aspect, the angle of the horizontal groove wall surface at the minimum pitch portion is set to be larger than the angle of the horizontal groove wall surface at the maximum pitch portion by 3 ° or more. Fluctuations can be reliably suppressed.

If the angle is less than 3 °, the effect of suppressing the level fluctuation of the ground contact characteristic during rolling of the tire is small.

According to a third aspect of the present 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 lateral groove wall surface increases as the pitch decreases. It is characterized by becoming.

In the pneumatic tire according to the third aspect, when there are three or more kinds of pitches, the angle of the lateral groove wall surface becomes larger as the pitch becomes smaller. It is possible to suppress the level fluctuation of the grounding characteristic during rolling.

For example, when a large pitch, a medium pitch, and a small pitch are mixed, the angle of the lateral groove wall surface with respect to the tire radial direction of the small pitch> the angle of the lateral groove wall surface with respect to the tire radial direction of the medium pitch> the tire radius of the large pitch Angle of the lateral groove wall with respect to the direction.

[0015]

1 (A) to 1 (C) show a tread pattern 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 disposed 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. In the present embodiment,
The groove width of the circumferential groove 14 and the groove width of the circumferential groove 16 are each 10
mm.

Further, the tread 12 has a circumferential groove 14.
A lateral groove 18 is formed between the circumferential groove 14 and the circumferential groove 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 lateral grooves 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 the present 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 central land 26M, and the small land 26S are divided, and the third land 28 is divided into three types of the continent 28L, the central land 28M, and the small 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 well-known method (in this embodiment, three repetitions with three pitches) to prevent the pattern noise from deteriorating.

The lateral grooves 18, 20, 22 have a wider groove width and a land portion having a shorter circumferential dimension, so that the negative ratio becomes uniform in the tire circumferential direction, so that the adjacent groove sections have a larger circumferential width. The groove width is set to be narrower as the position is closer to.

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 d1 of the lateral groove 18 and the lateral groove 20
And the groove depth d3 of the lateral groove 22 is 7.7 mm.

As shown in FIGS. 2A to 2C,
The groove wall angle of the lateral groove 18 with respect to the tire radial direction (value measured at a section perpendicular to the lateral groove wall) is θ1 at the large pitch P1, θ2 at the medium pitch P2, and small P3 at the medium pitch P2.
Are set so that θ3>θ2> θ1 when θ3 is set in the portion. Here, the difference between the maximum groove wall angle θ3 and the minimum groove wall angle θ1 is preferably 3 ° or more. In the present embodiment, θ3 is set to 10 °, θ2 is set to 3 °, and θ1 is set to 0 °.

The groove wall angle of the lateral groove 20 and the groove wall angle of the lateral groove 22 are set in the same manner as the groove wall angle of the lateral groove 18.

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 medium pitch P2 is larger than the groove wall angle θ1 at the large pitch P1.
Since the groove wall angle θ2 at
The rubber volumes at both ends in the tire circumferential direction of 6M and 28M increase, and the rigidity (especially in the tire circumferential direction) of the inland portions 24M, 26M and 28M increases.

Since the groove wall angle θ3 at the small pitch P3 is larger than the groove wall angle θ2 at the medium pitch P2, the rubber volume at both ends in the tire circumferential direction of the small land portions 24S, 26S, 28S increases. , Shores 24S, 26S, 28S
(Particularly in the tire circumferential direction) increases.

Thus, the continents 24L, 26L, 28
The rigidity of L, the rigidity of the land portions 24M, 26M, and 28M and the rigidity of the land portions 24S, 26S, and 28S approach uniformity, and it is possible to suppress the level variation of the grounding characteristics during rolling of the tire. As a result, the steering stability and uneven wear resistance of the pneumatic tire 10 are improved.

In this embodiment, θ3 is 10 °, θ2
Is set to 3 ° and θ1 is set to 0 °, 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 lateral groove wall surface is large. However, if the difference is too large, the maximum angle becomes too large, and the opposing lateral groove wall surfaces interfere with each other and cause the groove to have a large difference. The effect is that the depth becomes shallow and the drainage performance decreases. In a normal passenger car tire, the difference between the minimum angle and the maximum angle of the lateral groove wall is up to about 12 °. (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.
RFV (radial force variation), LFV
(Lateral force variation) and TFV (tangential force variation) were measured, and an uneven wear test, a steering stability and a straight running stability test were performed.

The tires of the examples used in the test are the tires of the above-described embodiment, and the tires of the conventional example have all the groove wall angles of the lateral grooves set to 3 ° (all other specifications are the same as those of the tire of the embodiment). The same). 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.

RFV, LFV and TFV were measured by a drum tester. The results show that the tire of the example has an RFV of 15%, an LFV of 10%, and a TF of
V improved by 20%. By the way, the position on the circumference of the tire and R
The relationship between the FV and the pattern component is as shown in FIG.
As shown in FIG. 3, since a three-time repetition arrangement with three types of large, medium, and small pitches is applied, the position on the tire circumference and the RFV
FIG. 4 shows the result of detailing the relationship with the third order component.

Uneven wear test: The difference in height (mm) between the continental part and the continent part at the time of 50% wear of each tire was measured. The tire of the example had a difference size 15% smaller than the tire of the conventional example.

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.

Straight running stability test: An actual vehicle equipped with tires was run on a test course. 1 by test driver
On a scale of 0 to 0, the conventional tire scored 6 points, while the example tire scored 6.5.

Also, the rigidity ratio of the lateral rigidity of the continental part to the lateral rigidity of the small land part (rigidity of the small land part / rigidity of the continent part)
As a result of examining the relationship between the force input direction and the force input direction (see FIG. 5A), as shown in FIG. 5B, in the conventional tire, the rigidity ratio increases when the force input direction changes. However, the rigidity ratio hardly fluctuated even when the force input direction changed in the tire of the example.

[0038]

As described above, the pneumatic tire according to the first aspect has the above-described structure, so that it is possible to suppress the level fluctuation of the contact characteristics during the rolling of the tire, thereby improving the steering stability and It has an excellent effect that uneven wear can be improved.

Since the pneumatic tire according to the second aspect has the above-described configuration, it has an excellent effect that the level variation of the ground contact characteristics during the rolling of the tire can be reliably suppressed.

Further, since the pneumatic tire according to the third aspect has the above-described configuration, even when various pitches of various sizes are mixed, it is possible to reliably suppress the level fluctuation of the ground contact characteristic during the rolling of the tire. It has an excellent effect of being able to.

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

FIG. 3 is a graph showing a relationship between a position on a circumference of a tire and a pattern component of RFV.

FIG. 4 is a graph showing a relationship between a position on the circumference of a tire and an RFV tertiary component.

FIG. 5A is an explanatory diagram showing a force input direction to a land portion, and FIG. 5B is a graph showing a relationship between a rigidity ratio and a rigidity evaluation direction (force input direction).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Pneumatic tire 12 Tread 14 Circumferential groove 16 Circumferential groove 18 Lateral groove 20 Lateral groove 22 Lateral groove P1 Large pitch P2 Medium pitch P3 Small pitch

Claims (3)

[Claims] A pneumatic tire 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 circumferential direction of the tread, wherein a lateral groove wall surface of a small pitch portion is provided. Wherein the angle of the large pitch portion with respect to the tire radial direction is greater than the angle of the large pitch portion wall surface with respect to the tire radial direction. 2. The pneumatic tire according to claim 1, wherein the angle of the horizontal groove wall surface at the minimum pitch portion is larger than the angle of the horizontal groove wall surface at the maximum pitch portion by 3 ° or more. 3. The pneumatic tire according to claim 1, wherein when there are three or more types of pitches, the angle of the lateral groove wall surface increases as the pitch decreases.