JP6911636B2 - tire - Google Patents

Description

The present invention relates to a tire having well-balanced noise performance and wet performance.

Generally, the tread portion of a tire is provided with a main groove that extends continuously in the tire circumferential direction in order to smoothly discharge water on the road surface to the rear in the tire rotation direction. However, during traveling on a dry road surface, a standing wave is generated in the air flowing through the main groove, so that an air column resonance sound is generated. This air column resonance is known to be a major source of noise generated by tires. In order to improve the noise performance of the tire, a main groove having a small groove volume has been proposed.

However, when the groove volume of the main groove is reduced, there is a problem that the drainage property is lowered and the wet performance is deteriorated. As described above, the noise performance and the wet performance have a reciprocal relationship, and it is difficult to improve both of these performances in a well-balanced manner.

JP-A-2015-157600

The present invention has been devised in view of the above problems, and provides a tire having effectively improved noise performance while maintaining wet performance, based on improving the shoulder main groove of the tread portion. The main purpose is to do.

In the present invention, the tread portion has a crown main groove that extends continuously in a zigzag shape in the tire circumferential direction and a shoulder main groove that extends continuously in a zigzag shape outside the crown main groove in the tire axial direction in the tire circumferential direction. The tire is characterized in that the number of zigzag pitches of the crown main groove is 0.21 to 0.32 times the number of zigzag pitches of the shoulder main groove.

In the tire according to the present invention, the crown main groove includes a plurality of crown inclined portions inclined with respect to the tire axial direction, and the shoulder main groove includes a plurality of shoulder inclined portions inclined with respect to the tire axial direction. It is desirable that the maximum value of the angle of each crown inclined portion with respect to the tire axial direction is smaller than the maximum value of the angle of each shoulder inclined portion with respect to the tire axial direction.

In the tire according to the present invention, the maximum value of the angle of each crown inclined portion with respect to the tire axial direction is 55 to 70 degrees, and the maximum value of the angle of each shoulder inclined portion with respect to the tire axial direction is 60 to 75 degrees. Is desirable.

In the tire according to the present invention, it is desirable that the minimum value of the angle of each crown inclined portion with respect to the tire axial direction is larger than the minimum value of the angle of each shoulder inclined portion with respect to the tire axial direction.

In the tire according to the present invention, the minimum value of the angle of each crown inclined portion with respect to the tire axial direction is 50 to 65 degrees, and the minimum value of the angle of each shoulder inclined portion with respect to the tire axial direction is 35 to 60 degrees. Is desirable.

In the tire according to the present invention, it is desirable that the crown main groove and the shoulder main groove have a groove wall, and the angle of the groove wall with respect to the tread normal is 4 to 15 degrees.

In the tire according to the present invention, the shoulder main groove is the first inner top portion on the innermost side in the tire axial direction of the groove edge on the outer side in the tire axial direction, and the second outer side on the outermost side in the tire axial direction on the inner groove edge in the tire axial direction. It has a top, and the length in the tire axial direction between the first inner top and the second outer top is preferably 3% to 5% of the tread width.

In the tire according to the present invention, it is desirable that the groove width of the shoulder main groove is larger than the groove width of the crown main groove.

The tire of the present invention has a crown main groove that extends continuously in the tire circumferential direction in a zigzag shape on the tread portion, and a shoulder main groove that extends continuously in a zigzag shape on the outside of the crown main groove in the tire axial direction in the tire circumferential direction. It has a groove. Since the crown main groove and the shoulder main groove extending in a zigzag shape disturb the vibration of the air passing through each main groove, the air column resonance sound can be effectively suppressed. Further, since the crown main groove and the shoulder main groove have drainage properties, high wet performance is maintained.

The number of zigzag pitches in the crown main groove is 0.21 to 0.32 times the number of zigzag pitches in the shoulder main groove. As a result, the air column resonance sounds generated from the crown main groove and the shoulder main groove have different frequencies and become white noise, so that the noise performance is further improved. Further, the water film on the tread portion on the equator side of the tire is less likely to be discharged than the water film on the tread portion on the tread end side. Since the crown main groove arranged on the equator side of the tire has a smaller number of pitches than the shoulder main groove, the water in the main groove flows relatively smoothly. Therefore, the wet performance is maintained higher.

Therefore, the tire of the present invention exhibits excellent noise performance while maintaining wet performance.

It is a development view of the tread part of the tire of one Embodiment of this invention. It is an enlarged view of the crown main groove of FIG. It is an enlarged view of the shoulder main groove of FIG. It is an enlarged view of the crown main groove of FIG. It is an enlarged view of the shoulder main groove of FIG. (A) is a cross-sectional view taken along the line AA of FIG. 1, and (b) is a cross-sectional view taken along the line BB of FIG. It is an enlarged view of the tread part on the left side of FIG. FIG. 5 is a cross-sectional view taken along the line CC of FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a development view of a tread portion 2 of a tire 1 showing an embodiment of the present invention. The tire 1 of the present embodiment can be used for various tires such as pneumatic tires for passenger cars and heavy loads, and non-pneumatic tires in which pressurized air is not filled inside the tires. The tire 1 of the present embodiment is suitably used as a pneumatic tire for a passenger car.

As shown in FIG. 1, the tire 1 of the present embodiment has a crown main groove 3 extending continuously in a zigzag shape in the tire circumferential direction on the tread portion 2, and a tire on the outside of the crown main groove 3 in the tire axial direction. It is equipped with a shoulder main groove 4 that extends continuously in the circumferential direction in a zigzag shape. Since the crown main groove 3 and the shoulder main groove 4 extending in a zigzag shape disturb the vibration of the air passing through the main grooves 3 and 4, the air column resonance sound can be effectively suppressed. Further, since the crown main groove 3 and the shoulder main groove 4 have drainage properties, they exhibit wet performance.

In this embodiment, the crown main grooves 3 are arranged on both sides of the tire equator C. The pair of crown main grooves 3 and 3 of the present embodiment have zigzag phases aligned. In the present embodiment, the shoulder main groove 4 is provided between each crown main groove 3 and the tread end Te adjacent to the crown main groove 3.

The "tread end" Te is when a tire 1 in a normal state, which is rim-assembled on a regular rim and is filled with a regular internal pressure and is in a normal state, is grounded on a flat surface at a camber angle of 0 degrees by applying a regular load. It is defined as the ground contact position on the outermost side in the tire axial direction. In the normal state, the distance between the tread ends Te on both sides in the tire axial direction and the Te in the tire axial direction is defined as the tread width TW. Unless otherwise specified, the dimensions and the like of each part of the tire are values measured in a normal state.

A "regular rim" is a rim defined for each tire in the standard system including the standard on which the tire is based. For example, "standard rim" for JATMA, "Design Rim" for TRA, and ETRTO. If so, it is "Measuring Rim".

"Regular internal pressure" is the air pressure defined for each tire in the standard system including the standard on which the tire is based. For JATMA, "maximum air pressure", for TRA, the table "TIRE LOAD LIMITS" The maximum value described in "AT VARIOUS COLD INFLATION PRESSURES", or "INFLATION PRESSURE" for ETRTO. If the tires are for passenger cars, the regular internal pressure is 180 kPa. Also, when there is no applicable standard such as racing tires, the rim and air pressure recommended by the manufacturer are applied to the regular rim and regular internal pressure.

"Regular load" is the load defined for each tire in the standard system including the standard on which the tire is based. For JATMA, "maximum load capacity", for TRA, the table "TIRE LOAD" The maximum value described in "LIMITS AT VARIOUS COLD INFLATION PRESSURES", or "LOAD CAPACITY" for ETRTO. When the tire is for a passenger car, the normal load is a load corresponding to 88% of the load.

FIG. 2 is an enlarged view of the crown main groove 3 on the left side of the tread portion 2 of FIG. 1, and FIG. 3 is an enlarged view of the shoulder main groove 4 on the left side of the tread portion 2 of FIG. As shown in FIG. 2 or 3, the zigzag pitch number P1 of the crown main groove 3 is 0.21 to 0.32 times the zigzag pitch number P2 of the shoulder main groove 4. As a result, the air column resonance sounds generated from the crown main groove 3 and the shoulder main groove 4 have different frequencies and become white noise, so that the noise performance is further improved. Further, the water film on the tread portion 2 on the tire equator C side is less likely to be discharged than the water film on the tread portion 2 on the tread end Te side. Since the crown main groove 3 arranged on the equator C side of the tire has a smaller number of pitches than the shoulder main groove 4, the water in the main groove 3 flows relatively smoothly. Therefore, the wet performance is maintained high. In order to exert such an action more effectively, the zigzag pitch number P1 of the crown main groove 3 is 0.25 times (1/4 times) the zigzag pitch number P2 of the shoulder main groove 4. desirable. The number of zigzag pitches is specified by the crown inclined portion 5 and the shoulder inclined portion 6 as described later.

The crown main groove 3 includes a plurality of crown inclined portions 5 that are inclined with respect to the tire axial direction. The crown inclined portion 5 has a first crown inclined portion 5A that is inclined to one side (lower left side in the figure) with respect to the tire axial direction, and the first crown inclined portion 5A is in opposite directions (lower right side in the figure). ) Includes a second crown tilted portion 5B. The second crown inclined portion 5B of the present embodiment is arranged between the pair of inclined portions 5a and 5a and the pair of inclined portions 5a and 5a that are inclined to the other side with respect to the tire axial direction, and is arranged with the inclined portion 5a. Is formed of a small inclined portion 5b which is in the opposite direction and has a small length Lb in the tire circumferential direction.

The shoulder main groove 4 includes a plurality of shoulder inclined portions 6 that are inclined with respect to the tire axial direction. The shoulder inclined portion 6 has a first shoulder inclined portion 6A inclined to the other side (lower right side in the figure) with respect to the tire axial direction, and the first shoulder inclined portion 6A is in opposite directions (lower left side in the figure). ) Is included with the second shoulder inclined portion 6B. The second shoulder inclined portion 6B is formed to have a shorter length in the tire circumferential direction and a smaller angle with respect to the tire axial direction than the first shoulder inclined portion 6A. The first shoulder inclined portion 6A and the second shoulder inclined portion 6B are provided alternately in the tire circumferential direction.

It is desirable that the maximum value of the angle α1 (shown in FIG. 4) of each crown inclined portion 5 with respect to the tire axial direction is smaller than the maximum value of the angle α2 (shown in FIG. 5) of each shoulder inclined portion 6 with respect to the tire axial direction. .. As a result, the relative decrease in the water flow in the shoulder main groove 4 due to the pitch number P1 being 0.21 to 0.32 times the pitch number P2 is suppressed, and the deterioration of the wet performance is reduced. Will be done. Further, the relative decrease in the disturbance effect of the air column resonance sound in the crown main groove 3 due to the pitch number P1 being 0.21 to 0.32 times the pitch number P2 is suppressed, and the noise performance is maintained. Will be done.

When the maximum value of the angle α1 of the crown inclined portion 5 and the maximum value of the angle α2 of the shoulder inclined portion 6 are large, the air column resonance sound generated in each of the main grooves 3 and 4 cannot be effectively disturbed, and the noise performance. May worsen. When the maximum value of the angle α1 of the crown inclined portion 5 and the maximum value of the angle α2 of the shoulder inclined portion 6 are small, the water in each of the main grooves 3 and 4 does not flow smoothly, so that the wet performance may deteriorate. From this point of view, it is desirable that the maximum value of the angle α1 of each crown inclined portion 5 with respect to the tire axial direction is 55 to 70 degrees. Further, it is desirable that the maximum value of the angle α2 of each shoulder inclined portion 6 with respect to the tire axial direction is 60 to 75 degrees.

It is desirable that the minimum value of the angle α1 of each crown inclined portion 5 with respect to the tire axial direction is larger than the minimum value of the angle α2 of each shoulder inclined portion 6 with respect to the tire axial direction. As a result, the relative deterioration of the water flow in the crown main groove 3 due to making the maximum value of the angle α1 of the crown inclined portion 5 smaller than the maximum value of the angle α2 of the shoulder inclined portion 6 is reduced. Therefore, wet performance is maintained. Further, in the shoulder main groove 4, the relative disturbance effect of the shoulder main groove 4 due to making the maximum value of the angle α1 of the crown inclined portion 5 smaller than the maximum value of the angle α2 of the shoulder inclined portion 6 is relative. Since the reduction is suppressed, the noise performance is maintained. Therefore, it is desirable that the minimum value of the angle α1 of each crown inclined portion 5 with respect to the tire axial direction is 50 to 65 degrees. Further, it is desirable that the minimum value of the angle α2 of each shoulder inclined portion 6 with respect to the tire axial direction is 35 to 60 degrees.

As described above, in the present embodiment, the difference between the maximum value and the minimum value of the angle α2 of the shoulder inclined portion 6 is formed larger than the difference between the maximum value and the minimum value of the angle α1 of the crown inclined portion 5. ing.

The angle α1 of the crown inclined portion 5 is defined as follows. As shown in FIG. 4, the crown main groove 3 has a groove edge 3a on the outer side in the tire axial direction and a groove edge 3b on the inner side in the tire axial direction. The groove edge 3a on the outer side in the tire axial direction has a first inner top portion 7a arranged on the innermost side in the tire axial direction and a first outer top portion 7b arranged on the outermost side in the tire axial direction. The groove edge 3b on the inner side in the tire axial direction has a second inner top portion 7c arranged on the innermost side in the tire axial direction and a second outer top portion 7d arranged on the outermost side in the tire axial direction. The virtual groove center line 5c connecting the midpoint 14a of the virtual straight line connecting the first inner top 7a and the second inner top 7c and the midpoint 14b of the virtual straight line connecting the first outer top 7b and the second outer top 7d. The angle with respect to the tire axial direction is the angle α1 of the crown inclined portion 5. Similarly, the angle α2 of the shoulder inclined portion 6 is defined as follows. As shown in FIG. 5, the shoulder main groove 4 has a groove edge 4a on the outer side in the tire axial direction and a groove edge 4b on the inner side in the tire axial direction. The groove edge 4a on the outer side in the tire axial direction has a first inner top portion 8a arranged on the innermost side in the tire axial direction and a first outer top portion 8b arranged on the outermost side in the tire axial direction. The groove edge 4b on the inner side in the tire axial direction has a second inner top portion 8c arranged on the innermost side in the tire axial direction and a second outer top portion 8d arranged on the outermost side in the tire axial direction. The virtual groove center line 6c connecting the midpoint 14c of the virtual straight line connecting the first inner top 8a and the second inner top 8c and the midpoint 14d of the virtual straight line connecting the first outer top 8b and the second outer top 8d. The angle with respect to the tire axial direction is the angle α2 of the shoulder inclined portion 6.

As shown in FIG. 3, the length W in the tire axial direction between the first inner top 8a and the second outer top 8d of the shoulder main groove 4 is 3% to 5% of the tread width TW. desirable. The length W in the tire axial direction between the first inner top portion 8a and the second outer top portion 8d can form a region 4R through which water can pass without contacting the groove edges 4a and 4b in the shoulder main groove 4. .. If the length W is less than 3% of the tread width TW, the drainage property may be significantly reduced. When the length W exceeds 5% of the tread width TW, the effect of disturbing the vibration of the air flowing in the shoulder main groove 4 is reduced, and the noise performance may be deteriorated.

It is desirable that the groove width w2 of the shoulder main groove 4 is larger than the groove width w1 of the crown main groove 3. As a result, wet performance is ensured even in the shoulder main groove 4 having a large zigzag pitch number P2.

In order to improve the noise performance and the wet performance in a more balanced manner, the groove width w1 of the crown main groove 3 is preferably 1.5% to 4% of the tread width TW. From the same viewpoint, the groove width w2 of the shoulder main groove 4 is preferably 5% to 7% of the tread width TW.

As shown in FIGS. 6A and 6B, the crown main groove 3 has a groove wall 9 extending from the groove bottom 3s. The angle θ1 of the groove wall 9 with respect to the tread normal n is preferably 4 to 15 degrees. If the angle θ1 of the groove wall 9 is less than 4 degrees, the groove volume becomes large and the noise performance may deteriorate. If the angle θ1 of the groove wall 9 exceeds 15 degrees, the groove volume may become small and the wet performance may deteriorate. From the same viewpoint, it is desirable that the angle θ2 of the groove wall 10 of the shoulder main groove 4 with respect to the tread normal line n is 6 to 15 degrees.

The groove wall 9 of the crown main groove 3 includes an inner groove wall 9a arranged inside the groove bottom 3s in the tire axial direction and an outer groove wall 9b arranged outside the groove bottom 3s in the tire axial direction. There is. It is desirable that the angle θ1a of the inner groove wall 9a with respect to the tread normal line n and the angle θ1b of the outer groove wall 9b with respect to the tread normal line n are different. As a result, the rigidity of the inner groove wall 9a and the outer groove wall 9b are different, and the deformations of the two groove walls 9a and 9b when the tire touches the ground are different, so that white noise of the air column resonance sound can be promoted. From this point of view, the groove wall 10 of the shoulder main groove 4 also has an angle θ2a with respect to the tread normal line n of the inner groove wall 10a and a tread of the outer groove wall 10b arranged outside the inner groove wall 10a in the tire axial direction. It is desirable that the angle θ2b with respect to the normal n is different.

It is desirable that the angle θ1a of the inner groove wall 9a of the crown main groove 3 is smaller than the angle θ1b of the outer groove wall 9b of the crown main groove 3. As a result, the deformation of the outer groove wall 9b on which a large lateral force acts during turning travel is effectively increased, and the air column resonance sound can be further reduced. In order to effectively exert the above-mentioned action, the difference in angle (θ1a−θ1b) between the inner groove wall 9a of the crown main groove 3 and the outer groove wall 9b of the crown main groove 3 is preferably 4 to 8 degrees. From the same viewpoint, the difference in angle (θ2a−θ2b) between the inner groove wall 10a and the outer groove wall 10b of the shoulder main groove 4 is preferably 4 to 8 degrees.

As shown in FIG. 1, such a crown main groove 3 and a shoulder main groove 4 allow the tread portion 2 to have a crown land portion 11, a pair of middle land portions 12, 12, and a pair of shoulder land portions 13. 13 is formed.

The crown land portion 11 is provided with a crown lateral groove 15 that connects between the crown main grooves 3 and 3, and a crown lug groove 16 that extends from the crown main groove 3 toward the tire equator C and terminates within the crown land portion 11. ing.

In the present embodiment, the crown lateral groove 15 communicates with the first crown inclined portions 5A and 5A adjacent to each other in the tire axial direction. Such a crown gutter 15 can further enhance the wet performance and promote local deformation of the inner groove wall 9a to disturb the air column resonance.

The crown lateral groove 15 is inclined in the direction opposite to that of the first crown inclined portion 5A. Since the groove wall of such a crown lateral groove 15 acts as a resistance to the vibration of the air in the crown main groove 3, the air column resonance sound is effectively reduced. In order to effectively exert such an action, it is desirable that the crossing angle α3 at which the crown lateral groove 15 and the first crown inclined portion 5A intersect is 75 to 105 degrees. The intersection angle α3 is specified by the groove center line of the crown lateral groove 15 and the virtual groove center line 5c of the crown inclined portion 5.

The groove width w3 of the crown lateral groove 15 is preferably 30% to 45% of the groove width w1 of the crown main groove 3 in order to improve the wet performance and the noise performance in a well-balanced manner.

As shown in FIG. 7, the crown lug groove 16 is provided at the intersection position 5x between the first crown inclined portion 5A and the second crown inclined portion 5B. For example, the groove edge 5h on the inner side of the first crown inclined portion 5A in the tire axial direction and the groove edge 16a of the crown lug groove 16 form a smooth line, in the present embodiment, an arc shape. As a result, the vibration of the air in the crown main groove 3 is effectively disturbed in the crown lug groove 16, so that the noise performance is further improved.

The middle land portion 12 is provided with a middle lateral groove 17 connecting the crown main groove 3 and the shoulder main groove 4. Such a middle lateral groove 17 also improves wet performance.

The middle lateral groove 17 communicates with the second crown inclined portion 5B and the second shoulder inclined portion 6B. As described above, in the present embodiment, since the crown lateral groove 15 communicates with the first crown inclined portion 5A and the middle lateral groove 17 communicates with the second crown inclined portion 5B, the crown main groove 3 and the shoulder main groove 4 are communicated with each other. The water inside can flow in each of the main grooves 3 and 4 in a well-balanced manner.

The middle lateral groove 17 includes a first portion 17A and a second portion 17B. The first portion 17A connects the end portion 5e (upper side in the figure) on one side in the tire circumferential direction of the second crown inclined portion 5B and the second shoulder inclined portion 6B. The second portion 17B connects the other end portion 5i (lower side in the figure) of the second crown inclined portion 5B in the tire circumferential direction and the second shoulder inclined portion 6B. As a result, the water in the shoulder main groove 4 and the crown main groove 3 can smoothly move to each other, so that the wet performance is further improved.

The middle lateral groove 17 is inclined in the opposite direction to the second crown inclined portion 5B. Since such a middle lateral groove 17 acts as a resistance to vibration of air from the second crown inclined portion 5B, the air column resonance sound is effectively reduced. In order to effectively exert such an action, it is desirable that the crossing angle α4 at which the middle lateral groove 17 and the second crown inclined portion 5B intersect is 75 to 105 degrees.

The middle lateral groove 17 and the second shoulder inclined portion 6B form one smooth groove-shaped portion 18. As a result, the water in the shoulder main groove 4 and the crown main groove 3 can move to each other more smoothly. "Forming one smooth groove-shaped portion 18" means that the groove edge (not shown) on the inner side in the tire axial direction of the second shoulder inclined portion 6B through which the middle lateral groove 17 communicates is not formed on the tread surface of the tread portion 2. Aspect.

As shown in FIG. 8, in the present embodiment, the middle lateral groove 17 includes a shallow groove portion 20 in which the groove bottom is raised inside in the tire axial direction, and a deep groove portion 21 in which the groove bottom is not raised. As a result, the rigidity of the middle land portion 12 adjacent to the portion provided with the shallow groove portion 20 and the portion provided with the deep groove portion 21 is different, so that the deformation of the groove wall of the middle lateral groove 17 when the tire touches the ground is different. Therefore, the white noise of the air column resonance is further promoted, and the noise performance is improved.

In the present embodiment, the shallow groove portion 20 is provided with a groove bottom sipe 22. Since the groove bottom sipe 22 opens the middle lateral groove 17 greatly when the middle land portion 12 touches the ground, the wet performance is effectively improved.

As shown in FIG. 7, it is desirable that the groove width w4 of the middle lateral groove 17 is larger than the groove width w3 of the crown lateral groove 15 (shown in FIG. 1). As a result, the water film on the tread surface of the tread portion 2 can be smoothly discharged from the tire equator C side through the shoulder lateral groove 19 described later. From this point of view, the groove width w4 of the middle lateral groove 17 is preferably about 110% to 150% of the groove width w3 of the crown lateral groove 15. Further, the crown lateral groove 15 having a small groove width maintains a high effect of suppressing the air column resonance sound.

The shoulder land portion 13 is provided with a shoulder lateral groove 19 connecting the shoulder main groove 4 and the tread end Te, and a shoulder sipe 23 extending from the shoulder main groove 4 to the tread end Te side. The shoulder lateral groove 19 further improves wet performance.

The shoulder lateral groove 19 communicates with the first shoulder inclined portion 6A. As described above, in the present embodiment, the middle lateral groove 17 communicates with the second shoulder inclined portion 6B, and the shoulder lateral groove 19 communicates with the first shoulder inclined portion 6A. Therefore, the water in the shoulder main groove 4 can be drained to the tread end Te and the crown main groove 3 in a well-balanced manner, so that the wet performance is improved. In the present embodiment, the shoulder lateral grooves 19 and the middle lateral grooves 17 are alternately provided in the tire circumferential direction.

In the present embodiment, the shoulder lateral groove 19 includes a shallow groove portion 24 in which the groove bottom is raised inside in the tire axial direction, and a deep groove portion 25 in which the groove bottom is not raised. As a result, the rigidity of the shoulder land portion 13 adjacent to the portion provided with the shallow groove portion 24 and the portion provided with the deep groove portion 25 is different, so that the deformation of the groove wall of the shoulder lateral groove 19 when the tire touches the ground is different. Therefore, the white noise of the air column resonance is further promoted, and the noise performance is improved.

In the present embodiment, the shallow groove portion 24 is provided with a groove bottom sipe 26. Since the groove bottom sipe 26 opens the shoulder lateral groove 19 greatly when the shoulder land portion 13 touches the ground, the wet performance is effectively improved.

As shown in FIG. 1, the shoulder sipe 23 is provided at a position facing the middle lateral groove 17 in the present embodiment. In such a shoulder sipe 23, the rigidity of the shoulder land portion 13 is effectively reduced, and the vibration of the air flowing from the middle lateral groove 17 to the shoulder main groove 4 is disturbed by the groove wall of the shoulder main groove 4, and the air is generated. Reduce column resonance. The "position facing the middle lateral groove 17" means a mode in which the virtual extension line 23c in which the shoulder sipe 23 is smoothly extended inward in the tire axial direction intersects the opening end 17e on the shoulder main groove 4 side of the middle lateral groove 17. ..

In the present embodiment, the shoulder sipe 23 communicates with the outer end 4e of the outer groove edge 4a (shown in FIG. 3) of the shoulder main groove 4 extending in a zigzag shape in the tire axial direction. As a result, the rigidity of the shoulder land portion 13 is effectively reduced, and the groove wall of the shoulder main groove 4 becomes a large resistance to vibration, so that the effect of disturbing the vibration of air is further enhanced.

The shoulder land portion 13 is provided with a plurality of shoulder blocks 13B classified by shoulder lateral grooves 19 arranged side by side in the tire circumferential direction. Further, the shoulder block 13B is provided with a pair of shoulder block pieces 13a and 13b that are divided in the tire circumferential direction by the shoulder sipe 23.

As shown in FIG. 7, the opening position 20a of the shoulder lateral groove 19 to the shoulder main groove 4 is displaced from the opening position 20b of the middle lateral groove 17 to the shoulder main groove 4 in the tire circumferential direction. As a result, the superposition of pitch noise is suppressed, and the noise performance is further improved. From this point of view, in the present embodiment, it is desirable that the pitch P4 of the shoulder lateral groove 19 in the tire circumferential direction is deviated by a half pitch from the pitch P3 of the middle lateral groove 17 in the tire circumferential direction.

As shown in FIG. 1, the crown land portion 11 and the middle land portion 12 are each provided with sipes S for increasing the scratching force on the road surface. This improves wet performance.

Although the tire of the present invention has been described in detail above, it goes without saying that the present invention can be implemented by changing to various aspects without being limited to the above-mentioned specific embodiment.

A 275 / 55R20 size pneumatic tire with the basic pattern of FIG. 1 was prototyped. Each test tire was tested for wet and noise performance. The test method and common specifications are as follows.
Mounting rim: 20 x 9.0J
Test internal pressure: 250 kPa
Test vehicle: Four-wheel drive vehicle with a displacement of 3700 cc Number of pitches in the crown main groove P1: The same test method is used for both the comparative example and the embodiment.

<Wet performance>
A test driver runs a test vehicle equipped with each test tire on a test course on a wet asphalt road surface with a water depth of 10 mm, and the running characteristics related to traction performance and braking performance at this time are evaluated by the test driver's sensuality. rice field. The result is displayed with a score of 100 in Comparative Example 1. The larger the value, the better.

<Noise performance (outside noise test)>
A test driver traveled on a dry asphalt road surface at a speed of 70 km / h using the above vehicle, and the noise outside the vehicle was measured at this time. The result is displayed as an index with the value of Comparative Example 1 as 100 using the reciprocal of the measured value, and the larger the value, the smaller the noise outside the vehicle and the better.
The test results are shown in Table 1.

As a result of the test, it can be confirmed that the tire of the example is effectively improved in noise performance while maintaining the wet performance as compared with the tire of the comparative example. We also tested tire sizes different from the above and showed the same tendency.

1 Tire 2 Tread part 3 Crown main groove 4 Shoulder main groove P1 Number of zigzag pitches of crown main groove P2 Number of zigzag pitches of shoulder main groove

Claims (8)

A tire having a tread portion having a crown main groove that extends continuously in a zigzag shape in the tire circumferential direction and a shoulder main groove that extends continuously in a zigzag shape outside the tire axial direction from the crown main groove in the tire circumferential direction. And
Number of pitches of the zigzag of the crown main groove, Ri 0.21 to 0.32 Baidea the number of pitches of the zigzag of the shoulder main grooves,
The crown main groove includes a plurality of crown inclined portions inclined with respect to the tire axial direction.
The shoulder main groove includes a plurality of shoulder inclined portions inclined with respect to the tire axial direction.
A tire characterized in that the maximum value of the angle of each crown inclined portion with respect to the tire axial direction is smaller than the maximum value of the angle of each shoulder inclined portion with respect to the tire axial direction . The maximum value of the angle of each crown inclined portion with respect to the tire axial direction is 55 to 70 degrees.
The tire according to claim 1 , wherein the maximum value of the angle of each shoulder inclined portion with respect to the tire axial direction is 60 to 75 degrees. A tire having a tread portion having a crown main groove that extends continuously in a zigzag shape in the tire circumferential direction and a shoulder main groove that extends continuously in a zigzag shape outside the tire axial direction from the crown main groove in the tire circumferential direction. And
The number of zigzag pitches of the crown main groove is 0.21 to 0.32 times the number of zigzag pitches of the shoulder main groove.
The crown main groove includes a plurality of crown inclined portions inclined with respect to the tire axial direction.
The shoulder main groove includes a plurality of shoulder inclined portions inclined with respect to the tire axial direction.
A tire characterized in that the minimum value of the angle of each crown inclined portion with respect to the tire axial direction is larger than the minimum value of the angle of each shoulder inclined portion with respect to the tire axial direction . The minimum value of the angle of each crown inclined portion with respect to the tire axial direction is 50 to 65 degrees.
The tire according to claim 3, wherein the minimum value of the angle of each shoulder inclined portion with respect to the tire axial direction is 35 to 60 degrees. A tire having a tread portion having a crown main groove that extends continuously in a zigzag shape in the tire circumferential direction and a shoulder main groove that extends continuously in a zigzag shape outside the tire axial direction from the crown main groove in the tire circumferential direction. And
Number of pitches of zigzag of the crown main groove, Ri Oh at 0.21 to 0.32 times the number of pitches of zigzag of the shoulder main groove,
A tire characterized in that the groove width of the shoulder main groove is larger than the groove width of the crown main groove. A tire having a tread portion having a crown main groove that extends continuously in a zigzag shape in the tire circumferential direction and a shoulder main groove that extends continuously in a zigzag shape outside the tire axial direction from the crown main groove in the tire circumferential direction. And
A tire characterized in that the number of zigzag pitches of the crown main groove is 0.21 to 0.25 times the number of zigzag pitches of the shoulder main groove. The crown main groove and the shoulder main groove have a groove wall and have a groove wall.
The tire according to any one of claims 1 to 6, wherein the angle of the groove wall with respect to the tread normal is 4 to 15 degrees. The shoulder main groove has a first inner apex on the innermost side in the tire axial direction of the groove edge on the outer side in the tire axial direction, and a second outer apex on the outermost side in the tire axial direction on the inner groove edge in the tire axial direction.
The tire according to any one of claims 1 to 7, wherein the length in the tire axial direction between the first inner top portion and the second outer top portion is 3% to 5% of the tread width.

Images