JP3759826B2 - Pneumatic tire and mold - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic tire and relates to a pneumatic tire that suppresses variations in tread gauge associated with a change in the size of a block during one rotation of the tire and improves steering stability, and the pneumatic tire is molded. It relates to a mold.
[0002]
[Prior art]
In general, in a pneumatic tire, in order to reduce various noises generated from a tire pattern, a tread pattern is formed by arranging a plurality of types of pitches having different pitch lengths in an appropriate combination on the circumference. .
[0003]
Conventionally, each lateral groove included in each pitch and having an extending component in the tread width direction has a constant groove wall angle with respect to the tire radial direction, and has a constant depth. Is selected so as to be equal to the pitch ratio. Further, 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]
[Problems to be solved by the invention]
However, this conventional technique has a problem in that the tread gauge varies as the size of the block around one 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 recess for forming a block, a protrusion for forming a lateral groove, and the like. When a raw tread having a certain thickness (gauge) of the raw tire is pressed against the mold, the lateral groove forming projection provided on the mold pushes the rubber away, and the pushed rubber flows toward the concave portion for forming the block.
[0006]
Here, if the pitch is large or small, the amount of rubber flowing in per unit volume of the concave portion is larger in the concave portion in the large pitch portion than in the concave portion in the small pitch portion. The tread gauge of the part increases relative to the tread gauge of the small block part.
[0007]
When the variation in the tread gauge increases, it leads to a decrease in the handling stability. Therefore, it is desired to suppress the variation in the tread gauge.
[0008]
In view of the above facts, the present invention provides a pneumatic tire capable of suppressing tread gauge variations caused by differences in block sizes and improving steering stability, and a mold for molding the pneumatic tire. Is the purpose.
[0009]
[Means for Solving the Problems]
The invention according to claim 1 is a pneumatic tire in which a tread pattern portion is formed with a circumferential groove and a transverse groove, and a tread pattern is formed by combining at least two different pitches in the tread circumferential direction. The angle of the circumferential groove wall surface of the portion with respect to the tire radial direction is characterized by being larger than the angle of the circumferential groove wall surface of the small pitch portion with respect to the tire radial direction.
[0010]
Next, the operation of the pneumatic tire according to claim 1 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 volume of the land portion 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 forming mold can be absorbed by the increase in the capacity of the land portion, and the belt is recessed, that is, the land portion of the small pitch portion. An increase in the tread gauge in the land portion of the large pitch portion is suppressed compared to the tread gauge.
[0011]
Steering stability is improved because variations in the tread gauge are suppressed.
The invention according to claim 2 is the pneumatic tire according to claim 1, wherein the angle of the circumferential groove wall surface of the maximum pitch portion is 3 ° or more larger than the angle of the circumferential groove wall surface of the minimum pitch portion. It is a feature.
[0012]
In the pneumatic tire according to claim 2, the angle of the circumferential groove wall surface of the maximum pitch portion is set to be 3 ° or more larger than the angle of the circumferential groove wall surface of the minimum pitch portion. The difference between the gauge and the land tread gauge in the large pitch portion can be reliably reduced.
[0013]
If it is less than 3 °, the effect of reducing the difference in the tread gauge 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 pitch types, the angle of the circumferential groove wall surface increases as the pitch increases. It is characterized by that.
[0014]
In the pneumatic tire according to claim 3, when there are three or more types of pitches, the angle of the circumferential groove wall surface increases as the pitch increases. It is possible to reliably reduce the variation of.
[0015]
For example, in the case where large pitch, medium pitch, and small pitch are mixed, the angle of the circumferential groove wall surface with respect to the large pitch tire radial direction> the angle of the circumferential groove wall surface with respect to the medium pitch tire radial direction> small pitch tire The angle of the circumferential groove wall surface with respect to the radial direction.
[0016]
The invention according to claim 4 is a mold for molding a pneumatic tire in which a tread pattern portion is formed with a circumferential groove and a lateral groove, and a tread pattern is formed by combining at least two different pitches in the tread circumferential direction. The angle of the protrusion forming the circumferential wall surface is set 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. It is characterized by having been decided.
[0017]
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 is determined so that the angle of the protrusion forming the circumferential wall surface is larger than the angle of the circumferential groove wall surface of the small pitch portion with respect to the tire radial direction. The volume of the land portion of the large pitch portion is relatively increased. Accordingly, at the time of molding, a part of the rubber flowing into the concave portion (with respect to the projection) of the land forming mold can be absorbed by the increase in the capacity of the land portion, and the belt is recessed, that is, the small pitch portion. An increase in the tread gauge in the land portion of the large pitch portion is suppressed as compared with the tread gauge in the land portion, and a pneumatic tire in which variations in the tread gauge are suppressed can be molded.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
1A to 1C 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 that of a normal radial tire, and a description thereof will be omitted.
[0019]
As shown in FIGS. 1A to 1C, the tread 12 disposed on the belt 11 of the pneumatic tire 10 has a tire equatorial plane CL on both sides in the tire width direction (arrow W direction). Directional grooves 14 are provided, and circumferential grooves 16 are formed on the outer sides of the circumferential grooves 14 in the tire width direction. Further, the tread 12 has a lateral groove 18 between the circumferential groove 14 and the circumferential groove 14, and a lateral groove 20 between the circumferential groove 14 and the circumferential groove 16. A lateral groove 22 is formed in the upper surface.
[0020]
The land portion sandwiched between the circumferential groove 14 and the circumferential groove 14 is partitioned into a plurality of first land portions 24 (L, M, S) having different sizes in the tire circumferential direction (arrow S direction) by the lateral grooves 18. The land portion sandwiched between the circumferential groove 14 and the circumferential groove 16 is divided into a plurality of second land portions 26 (L, M, S) having different sizes in the tire circumferential direction by the lateral grooves 20. The land portion outside the directional groove 16 in the tire width direction is substantially divided into a plurality of third land portions 28 (L, M, S) having different sizes in the tire circumferential direction by the lateral grooves 22.
[0021]
In the present embodiment, the circumferential pitches of the lateral grooves 18, 20, and 22 are large, as shown in FIG. 1A, and small as shown in FIG. The first land portion 24 is divided into three types of continental portions 24L, inland portions 24M, and small land portions 24S having different circumferential dimensions, and the second land portion 26 is divided into three types of continental portions 26L having different circumferential dimensions. The third land portion 28 is divided into three types of continental portions 28L, inland portions 28M, and small land portions 28S having different circumferential dimensions.
[0022]
As shown in FIGS. 1 (A) to 1 (C) and FIGS. 2 (A) to 2 (C), in this pneumatic tire 10, a large pitch P1, a medium pitch P2, and a small pitch P3 which are different from each other are well-known methods ( In the present embodiment, the pattern noise is prevented from deteriorating by combining in the tire circumferential direction with a 3-pitch 3-crest arrangement).
[0023]
These lateral grooves 18, 20, and 22 are adjacent to land portions having a longer groove width and adjacent to land portions having a shorter circumferential dimension so that the negative ratio is uniform in the tire circumferential direction. The width of the groove is set narrower (the circumferential length of the continental portion 24L: the circumferential length of the inland portion 24M: the circumferential length of the small land portion 24S = the circumference of the transverse groove 18 defining the continental portion 26L) Directional length: circumferential length of the lateral groove 18 that defines the inland portion 24M: the circumferential length of the lateral groove 18 that defines the small land portion 24S, and the other land portions are also the same).
[0024]
In this embodiment, the tire circumferential dimension L1 of the continental parts 24L, 26L, 28L is 33 mm, the tire circumferential dimension L2 of the inland parts 24M, 26M, 28M is 27 mm, and the tire circumferential direction of the small land parts 24S, 26S, 28S. The dimension L3 is set to 21 mm.
[0025]
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.
[0026]
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.
[0027]
The circumferential grooves 14 and 16 have a depth d of 7.7 mm and a groove width W4 of 10 mm.
[0028]
As shown in FIGS. 2A to 2C, the groove wall angle of the circumferential groove 14 with respect to the tire radial direction (value measured in a cross section perpendicular to the circumferential groove wall) is the portion of the large pitch P1. Is set so that .theta.1>.theta.2> .theta.3 where .theta.1 at the middle pitch P2 and .theta.2 at the middle pitch P2 and .theta.3 at the small pitch P3. The groove wall angle of the circumferential groove 16 is set in the same manner.
[0029]
The difference between the maximum groove wall angle θ3 and the minimum groove wall angle θ1 is preferably 3 ° or more. In this embodiment, θ1 is set to 21 °, θ2 is set to 11 °, and θ3 is set to 5 °.
[0030]
Moreover, the angle with respect to the tire radial direction of the horizontal groove wall of the horizontal groove 18, the horizontal groove 20, and the horizontal groove 22 is 3 degrees.
[0031]
As shown in FIG. 2 (A), 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 an uneven shape opposite to the uneven shape of the tread 12. ing.
[0032]
Next, the effect | action of the pneumatic tire 10 of this embodiment is demonstrated.
In the pneumatic tire 10 of this embodiment, 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. It is possible to suppress the phenomenon that the tread gauge increases more than the tread gauge of the land portion having a smaller pitch.
[0033]
Accordingly, the tread gauge G1 (the dimension from the outermost belt to the tread surface) of the continental parts 24L, 26L, and 28L, the tread gauge G2 of the inland parts 24M, 26M, and 28M, and the tread gauges of the small land parts 24S, 26S, and 28S. The difference in G3 is reduced, and the level fluctuation of the ground contact characteristic during tire rolling can be suppressed. As a result, the handling stability of the pneumatic tire 10 is improved.
[0034]
Moreover, since the groove cross-sectional area of the circumferential grooves 14 and 16 changes in the tire circumferential direction, the sound pressure level of air column resonance of the circumferential grooves 14 and 16 can be reduced.
[0035]
In this embodiment, θ1 is set to 21 °, θ2 is set to 11 °, and θ3 is set to 5 °. However, the present invention is not limited to this angle.
[0036]
In addition, it is more effective if the difference between the minimum and maximum angles of the circumferential groove wall surface is large. However, if the difference is too large, the maximum angle becomes too large and the circumferential groove wall surfaces facing each other interfere with each other. There is an effect that the groove depth becomes shallow and the drainage performance decreases.
(Test example)
In order to confirm the effect of the present invention, a tire of a conventional example and a tire of an example to which the present invention is applied are prepared, measurement of a tread gauge at each pitch, measurement of a tertiary component of RFV (radial force variation). A steering stability test and a noise test were conducted.
[0037]
The tires of the examples used in the tests are the tires of the above-described embodiment, and the tires of the conventional examples are set to 11 ° in the groove wall angles of the circumferential grooves (all other specifications are the same as the tires of the embodiments). ) Tire. In each tire, the tread has 15 large pitches, 24 medium pitches, and 24 small pitches in the circumferential direction, and 8 small pitches, 4 medium pitches, and 5 large pitches in the circumferential direction. One set is arranged in the order of 4 pieces and medium pitch, and 3 sets are arranged in the circumferential direction.
[0038]
Since a three-times repeated arrangement with three types of large, medium and small pitches was applied, the third order component of RFV was measured with a drum tester. As a result, in the tire of the example, the tertiary component of RFV was reduced by 40% as compared with the tire of the conventional example.
[0039]
In addition, as a result of measuring the tread gauge, in the conventional tire, the difference in the tread gauge between the continental part and the small land part was 0.2 mm on the average, but in the tire of the example, the difference in the tread gauge was 0 on the average. It became .02mm.
[0040]
Steering stability test: An actual vehicle equipped with tires was run on a test course (dry road and wet road). According to a 10-point scale evaluation by a test driver, the conventional tire was 6 points, but the example tire was 6.5 points.
[0041]
Noise test (air column resonance): Measured according to JASO C 606 (drum method). The test device is composed of a rotating drum and a tire support device that are surface-treated as a substitute road surface in a sound-treated room. The drum has a diameter of 3.0 m in JASO and has a coarse grain surface attached to the surface. In this case, the measurement was performed at 50 km / h.
[0042]
As a result of the test, the noise of the tire of the example was 1 dB lower than that of the conventional tire at 1000 Hz.
[0043]
In addition, as a result of filling the circumferential groove with urethane and filling the groove to eliminate the air column resonance component and measuring the sound, there was no difference between the two tires.
[0044]
【The invention's effect】
As described above, since the pneumatic tire according to claim 1 has the above-described configuration, it is possible to suppress variations in the tread gauge due to a change in the size of the block during one rotation of the tire, and to control the tire. It has an excellent effect that stability can be improved.
[0045]
Since the pneumatic tire according to claim 2 has the above-described configuration, it has an excellent effect that variation in the tread gauge can be surely suppressed.
[0046]
Since the pneumatic tire according to claim 3 has the above-described configuration, it has an excellent effect that the variation of the tread gauge can be surely suppressed even when the pitches of various sizes are mixed.
[0047]
Since the mold according to claim 4 has the above-described configuration, it has an excellent effect that it is possible to mold a pneumatic tire in which variations in the tread gauge are suppressed.
[Brief description of the drawings]
FIG. 1A is a plan view of a tread of a large pitch portion, FIG. 1B is a plan view of a tread of a middle pitch portion, and FIG. 1C is a plan view of a tread of a small pitch portion.
2A is a cross-sectional view in the width direction of a tread of a large pitch portion (cross-sectional view taken along line 2 (A) -2 (A) in FIG. 1A), and FIG. 2B is a tread of a middle pitch portion. FIG. 2C is a cross-sectional view in the width direction (cross-sectional view taken along line 2 (B) -2 (B) in FIG. 1B), and FIG. (C) -2 (C) sectional view).
[Explanation of symbols]
10 Pneumatic tire 12 Tread 14 Circumferential groove 16 Circumferential groove 32 Projection P1 Large pitch P2 Medium pitch P3 Small pitch

Claims (4)

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

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