JP7006183B2 - tire - Google Patents

Description

The present invention relates to a tire having a crown sipe.

The following Patent Document 1 proposes to provide a shoulder sipe extending in the tire axial direction on the shoulder land portion in order to suppress uneven wear of the shoulder land portion of the pneumatic tire.

Japanese Unexamined Patent Publication No. 2016-13820

However, in recent years, as the performance of vehicles has improved, not only the wear resistance performance but also the steering stability has been required to be further improved. As a result of various experiments, the inventors have found that by improving the crown sipes arranged on the land part of the crown, the steering stability can be improved while maintaining the wear resistance of the land part of the crown.

The present invention has been devised in view of the above circumstances, and an object of the present invention is to provide a tire capable of exhibiting excellent steering stability while suppressing uneven wear of the land portion of the crown.

The present invention is a tire having a tread portion, wherein the tread portion includes a first tread end, a shoulder main groove continuously extending between the first tread end and the tire equatorial line in the tire circumferential direction, and the said. A crown main groove adjacent to the shoulder main groove and continuously extending in the tire circumferential direction, and a crown land portion divided between the shoulder main groove and the crown main groove are included, and the crown land portion includes. A crown sipe extending in the tire axial direction with a width of less than 1.5 mm is provided, the crown sipe includes a first crown sipe that traverses the land portion of the crown, and the first crown sipe is a fine sipe portion. A thick tread portion having a width larger than that of the fine tread portion is included, and the thick tread portion communicates with the shoulder main groove.

In the tire of the present invention, it is desirable that the fine sipe portion communicates with the crown main groove.

In the tire of the present invention, it is desirable that the length of the fine sipe portion in the tire axial direction is larger than the length of the thick sipe portion in the tire axial direction.

In the tire of the present invention, it is desirable that the crown sipe includes a second crown sipe extending from the crown main groove toward the shoulder main groove and having a break in the land portion of the crown.

In the tire of the present invention, it is desirable that the break end is located closer to the crown main groove than the end of the thick sipe portion of the first crown sipe on the crown main groove side.

In the tire of the present invention, the crown land portion is provided with a fine groove portion having a groove width of 1.5 mm or more and a groove depth of 2.0 mm or less, and the thick sipe portion is a groove bottom of the fine groove portion. It is desirable that the tire extends inward in the radial direction from the tire.

In the tire of the present invention, the narrow groove portion is chamfered between at least one groove wall and the tread ground contact surface so that the groove width gradually increases toward the shoulder main groove in the communication portion with the shoulder main groove. It is desirable that it is done.

In the tire of the present invention, the tread portion includes a shoulder land portion divided between the first tread end and the shoulder main groove, and the shoulder land portion includes a tire shaft having a width of less than 1.5 mm. It is desirable that a shoulder sipe extending in the direction and communicating with the shoulder main groove is provided, and the shoulder sipe is arranged so as to be continuous with the first crown sipe via the shoulder main groove.

In the tire of the present invention, it is desirable that the shoulder sipe has a portion linearly continuous with the first crown sipe via the shoulder main groove.

The land portion of the crown of the tire of the present invention is provided with a crown sipe extending in the tire axial direction with a width of less than 1.5 mm. The crown sipe includes a first crown sipe that traverses the land of the crown. The first crown sipe alleviates the distortion of the land portion of the crown when it touches the ground and suppresses its uneven wear.

The first crown sipe includes a fine sipe portion and a thick sipe portion having a width larger than that of the fine sipe portion. The thick sipe part communicates with the shoulder main groove. The thick sipe portion can further relax the rigidity of the land portion around the thick sipe portion as compared with the thin sipe portion. On the other hand, in the land portion of the crown, the fluctuation of the ground contact load during traveling is larger on the shoulder main groove side than on the crown main groove side, and uneven wear tends to occur due to minute slippage of the ground contact surface. In the present invention, by providing the thick sipe portion in this region, the land portion around the thick sipe portion can easily follow the road surface, the minute slip can be suppressed, and the uneven wear of the crown land portion can be further suppressed. ..

Further, in the land portion of the crown, the land portion around the thick sipe portion can easily follow the road surface even in the initial state of turning where the ground contact load is not sufficiently increased, so that the initial responsiveness can be improved.

Further, in the land part of the crown, the land part around the fine sipe part is arranged on the crown main groove side rather than the fine sipe part, and provides higher rigidity than the land part around the thick sipe part, so that a large cornering force is obtained. And, by extension, the steering stability can be improved.

It is a development view of the tread part of the tire of one Embodiment of this invention. FIG. 3 is a cross-sectional view taken along the line AA of FIG. It is an enlarged view of the outer crown land part of FIG. (A) is a sectional view taken along line BB of FIG. 3, and (b) is a sectional view taken along line CC of FIG. (A) is a sectional view taken along line EE of FIG. 3, (b) is a sectional view taken along line FF of FIG. 3, and (c) is a sectional view taken along line GG of FIG. .. It is an enlarged view of the land part of the inner crown of FIG. (A) is a cross-sectional view taken along the line HH of FIG. 6, (b) is a cross-sectional view taken along the line I-I of FIG. 6, and (c) is a cross-sectional view taken along the line JJ of FIG. .. It is an enlarged view of the outer shoulder land part of FIG. It is an enlarged view of the land part of the inner shoulder of FIG. 9 is a cross-sectional view taken along the line DD of FIG. It is a development view of the tread part of the tire of another embodiment of this invention. It is an enlarged view of the outer crown land part of the comparative example 1. FIG. It is an enlarged view of the outer crown land part of the comparative example 2.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a developed 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, for example, a pneumatic tire for a passenger car.

As shown in FIG. 1, the tire 1 of the present embodiment has, for example, a tread portion 2 having a designated orientation for mounting on a vehicle. However, the present invention is not limited to such an aspect. The tread portion 2 has, for example, a first tread end Te1 located on the outside of the vehicle when the tire 1 is mounted on the vehicle, and a second tread end Te2 located on the inside of the vehicle when the tire 1 is mounted on the vehicle. The direction of mounting on the vehicle is indicated by characters or symbols on the sidewall portion (not shown), for example.

In the case of a pneumatic tire, the tread ends Te1 and Te2 are the most outer contact positions in the tire axial direction when a normal load is applied to the tire 1 in a normal state and the tire 1 touches a flat surface at a camber angle of 0 °. The normal state is a state in which the tire is rim-assembled on the normal rim, the normal internal pressure is filled, and there is no load. In the present specification, unless otherwise specified, the dimensions and the like of each part of the tire are values measured in the 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 there is, 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 JATTA, "maximum air pressure", for TRA, the table "TIRE LOAD LIMITS AT" The maximum value described in "VARIOUS COLD INFLATION PRESSURES", or "INFLATION PRESSURE" for ETRTO.

"Regular load" is the load defined for each tire in the standard system including the standard on which the tire is based. "Maximum load capacity" for JATTA and "TIRE LOAD LIMITS" for TRA. The maximum value described in "AT VARIOUS COLD INFLATION PRESSURES", or "LOAD CAPACITY" for ETRTO.

The tread portion 2 of the present embodiment is provided with, for example, a main groove continuously extending in the tire circumferential direction. The main groove is adjacent to, for example, a shoulder main groove 3 provided between the first tread end Te1 and the tire equator C, or between the second tread end Te2 and the tire equator C, and the shoulder main groove 3. Includes the crown main groove 4.

The shoulder main groove 3 of the present embodiment is provided, for example, between the outer shoulder main groove 3A provided between the first tread end Te1 and the tire equator C, and between the second tread end Te2 and the tire equator C. Including the inner shoulder main groove 3B.

For the shoulder main groove 3, for example, it is desirable that the distance L1 from the tire equator C to the groove center line is 0.20 to 0.30 times the tread width TW. The tread width TW is the distance in the tire axial direction from the first tread end Te1 to the second tread end Te2 in the normal state.

One crown main groove 4 is provided between the two shoulder main grooves 3, for example, and is provided on the tire equator C in the present embodiment. However, the present invention is not limited to such an aspect, and for example, two crown main grooves 4 may be provided so as to sandwich the tire equator C.

It is desirable that the groove width W1a of the crown main groove 4 is larger than, for example, the groove width W1b of the outer shoulder main groove 3A and the groove width W1c of the inner shoulder main groove 3B. Specifically, it is desirable that the groove width W1a of the crown main groove 4 is 1.25 to 1.35 times the groove width W1b of the outer shoulder main groove 3A. As a result, excellent wet performance can be obtained.

It is desirable that the groove width W1c of the inner shoulder main groove 3B is larger than the groove width W1b of the outer shoulder main groove 3A, for example. Specifically, it is desirable that the groove width W1c of the inner shoulder main groove 3B is 1.20 to 1.28 times the groove width W1b of the outer shoulder main groove 3A.

In order to improve steering stability and wet performance on a dry road surface in a well-balanced manner, the groove width W1a of the crown main groove 4, the groove width W1b of the outer shoulder main groove 3A, and the groove width W1c of the inner shoulder main groove 3B are, for example, The tread width TW is preferably 4.0% to 7.0%. In addition, when the dimension of the groove is shown in this specification, the dimension which does not include chamfer is shown.

FIG. 2 shows a cross-sectional view taken along the line AA of FIG. As shown in FIG. 2, the groove depth D1a of the crown main groove 4, the groove depth D1b of the outer shoulder main groove 3A, and the groove depth D1c of the inner shoulder main groove 3B are, for example, 6.0 to 12.0 mm. Is desirable.

As shown in FIG. 1, the tread portion 2 of the present embodiment is divided into a shoulder land portion 7 and a crown land portion 8 by the above-mentioned main groove. The shoulder land portion 7 is divided between the tread end and the shoulder main groove 3. The shoulder land portion 7 of the present embodiment includes, for example, an outer shoulder land portion 7A and an inner shoulder land portion 7B. The outer shoulder land portion 7A is divided between the first tread end Te1 and the outer shoulder main groove 3A. The inner shoulder land portion 7B is divided between the second tread end Te2 and the inner shoulder main groove 3B.

The crown land portion 8 is divided between the two shoulder main grooves 3A and 3B. The crown land portion 8 includes, for example, an outer crown land portion 8A and an inner crown land portion 8B. The outer crown land portion 8A is divided between the outer shoulder main groove 3A and the crown main groove 4. The inner crown land portion 8B is divided between the inner shoulder main groove 3B and the crown main groove 4. However, the present invention is not limited to such an aspect, and for example, three crown land portions 8 may be divided between the two shoulder main grooves 3.

FIG. 3 is an enlarged view of the outer crown land portion 8A as a diagram showing an example of the crown land portion 8. As shown in FIG. 3, the outer crown land portion 8A is provided with, for example, a crown sipe 21 extending in the tire axial direction with a width of less than 1.5 mm. In addition, in this specification, a "sipe" is a notch having a width of less than 1.5 mm. In the present specification, the crown sipe 21 provided on the outer crown land portion 8A may be referred to as an outer crown sipe.

The crown sipe 21 includes a first crown sipe 26 that traverses the outer crown land portion 8A. The first crown sipe 26 alleviates the distortion of the outer crown land portion 8A at the time of touchdown and suppresses uneven wear thereof. The first crown sipe 26 may be referred to as a first outer crown sipe.

The first crown sipe 26 includes a fine sipe portion 22 and a thick sipe portion 23 having a width larger than that of the fine sipe portion 22. The thick sipe portion 23 communicates with the outer shoulder main groove 3A. The fine sipe portion 22 has a width of, for example, 0.4 to 0.8 mm. The width of the thick sipe portion 23 is, for example, preferably 1.50 to 1.80 times, more preferably 1.60 to 1.70 times the width of the thin sipe portion 22, and specifically, 0.8. It is desirable to have a width of ~ 1.2 mm.

The thick sipe portion 23 can further relax the rigidity of the land portion around the thick sipe portion 23 as compared with the thin sipe portion 22. On the other hand, in the crown land portion 8A, the fluctuation of the ground contact load during traveling is larger on the shoulder main groove 3A side than on the crown main groove 4 side, and uneven wear tends to occur due to minute slippage of the ground contact surface. In the present embodiment, by providing the thick sipe portion 23 in this region, the land portion around the thick sipe portion 23 can easily follow the road surface and suppress the minute slip, and further suppress the uneven wear of the crown land portion 8A. be able to.

Further, in the outer crown land portion 8A, the land portion around the thick sipe portion 23 can easily follow the road surface even in the initial state of turning where the ground contact load is not sufficiently increased, so that the initial responsiveness is also improved. Can be done.

Further, in the outer crown land portion 8A, the land portion around the fine sipe portion 22 is arranged closer to the crown main groove 4 than the fine sipe portion 22, and provides higher rigidity than the land portion around the thick sipe portion 23. Therefore, it is possible to exert a large cornering force and, by extension, improve steering stability.

FIG. 4A shows a sectional view taken along line BB of the thick sipe portion 23 of FIG. FIG. 4B shows a sectional view taken along line CC of the fine sipe portion 22. As shown in FIGS. 4A and 4B, it is desirable that the depth d1 of the thick sipe portion 23 is larger than the depth d2 of the thin sipe portion 22. Specifically, the depth d1 of the thick sipe portion 23 is preferably 1.03 times or more, more preferably 1.06 times or more, and preferably 1.15 times or less the depth d2 of the thin sipe portion 22. , More preferably 1.12 times or less. The depths d1 and d2 correspond to, for example, the distance along the depth direction of the sipe from the tread of the land portion to the bottom of the sipe.

As shown in FIGS. 3 and 4A, the crown land portion 8A is provided with a narrow groove portion 24 having a groove width of 1.5 mm or more and a groove depth of 2.0 mm or less, and is provided with a thick sipe portion. It is desirable that 23 extends inward in the radial direction of the tire from the groove bottom of the narrow groove portion 24. The depth d3 of the fine groove portion 24 is, for example, 1.0 to 2.0 mm. Such a narrow groove portion 24 and a thick sipe portion 23 can further enhance the uneven wear resistance.

As shown in FIG. 3, the narrow groove portion 24 is tread-contacted with at least one groove wall so that the groove width gradually increases toward the outer shoulder main groove 3A, for example, in the communication portion with the outer shoulder main groove 3A. It is desirable that the space between the ground and the ground is chamfered. The narrow groove portion 24 provided in the outer crown land portion 8A has a chamfered portion 25 on one of the groove walls.

It is desirable that the length L9 of the thick sipe portion 23 in the tire axial direction is, for example, 0.30 to 0.40 times the width W7 of the outer crown land portion 8A.

The fine sipe portion 22 communicates with, for example, the crown main groove 4. It is desirable that the length L10 of the fine sipe portion 22 in the tire axial direction is larger than the length L9 of the thick sipe portion 23 in the tire axial direction. The length L10 of the fine sipe portion 22 is, for example, 1.60 to 1.80 times the length L9 of the thick sipe portion 23. With such a thick sipe portion 23 and a thin sipe portion 22, a large cornering force can be obtained while exhibiting excellent initial responsiveness.

The fine sipe portion 22 is chamfered between at least one sipe wall and the tread ground contact surface so that the width gradually increases toward the crown main groove 4, for example, in the communication portion with the crown main groove. desirable. In the present embodiment, the chamfered portion 28 is provided on the sipe wall on the opposite side (lower side in FIG. 3) of the chamfered portion 25 provided on the groove wall of the narrow groove portion 24. Such a chamfered portion 28 can reduce the air column resonance sound of the crown main groove 4, and thus can improve the noise performance.

FIG. 5A shows a sectional view taken along line EE of the first crown sipe 26 of FIG. As shown in FIG. 5A, the first crown sipe 26 includes, for example, a first sipe portion 26a on the outer shoulder main groove 3A side and a second sipe portion 26b on the crown main groove 4 side. .. The second sipe portion 26b has a depth smaller than, for example, the first sipe portion 26a. The depth d5 of the second sipe portion 26b is, for example, 0.45 to 0.55 times the depth d4 of the first sipe portion 26a. Such a first crown sipe 26 can maintain the rigidity of the outer crown land portion 8A on the side of the tire equator C while enhancing the initial responsiveness, and can exhibit further excellent steering stability.

As shown in FIG. 3, the crown sipe 21 provided on the outer crown land portion 8A includes a second crown sipe 27. The second crown sipe 27 extends from the crown main groove 4 to the side of the outer shoulder main groove 3A and has a break 29 in the outer crown land portion 8A, for example. The second crown sipe 27 may be referred to as a second outer crown sipe.

The tire axial length L11 of the second crown sipe 27 is, for example, 0.35 to 0.55 times the tire axial width W7 of the outer crown land portion 8A, preferably 0.42 to 0.48. It is double. Further, it is desirable that the interrupted end 29 of the second crown sipe 27 is located closer to the crown main groove 4 than the end portion of the thick sipe portion 23 of the first crown sipe 26 on the crown main groove 4 side. Such a second crown sipe 27 can suppress an excessive decrease in rigidity of the outer crown land portion 8A and provide a large cornering force.

FIG. 5B shows a sectional view taken along line FF orthogonal to the second crown sipe 27 of FIG. As shown in FIG. 5B, it is desirable that the second crown sipe 27 has, for example, an opening 30 that widens toward the outside in the radial direction of the tire. In the present embodiment, the opening 30 is formed by inclining the sipe wall 31 on one side of the second crown sipe 27 in the tire circumferential direction. In the second crown sipe 27, for example, the sipe walls 31 on both sides may be inclined. Further, the second crown sipe 27 may be provided at the bottom of the above-mentioned narrow groove portion, for example.

FIG. 5 (c) shows a cross-sectional view taken along the line GG along the second crown sipe 27 of FIG. As shown in FIG. 5C, it is desirable that the second crown sipe 27 includes a first sipe portion 27a on the interrupted end 29 side and a second sipe portion 27b on the crown main groove 4 side. The second sipe portion 27b has a depth smaller than, for example, the first sipe portion 27a. It is desirable that the depth d7 of the second sipe portion 27b is, for example, 0.45 to 0.55 times the depth d6 of the first sipe portion 27a. Such a second crown sipe 27 can suppress the side of the crown main groove 4 from being excessively opened, and can improve uneven wear resistance and steering stability.

FIG. 6 shows an enlarged view of the inner crown land portion 8B of the present embodiment as a diagram showing another example of the crown land portion 8. As shown in FIG. 6, the inner crown land portion 8B is provided with a plurality of crown lug grooves 34 having a width of 1.5 mm or more and a plurality of inner crown sipes 35 having a width of less than 1.5 mm. ing.

The crown lug groove 34 extends from the inner shoulder main groove 3B toward the crown main groove 4 and has an inner end in the inner crown land portion 8B. The crown lug groove 34 cooperates with, for example, the inner shoulder main groove 3B to improve drainage in the vicinity of the inner crown land portion 8B.

The inner crown sipe 35 includes, for example, a first inner crown sipe 36, a second inner crown sipe 37 and a third inner crown sipe 38. The first inner crown sipe 36 extends from each inner end of the crown lug groove 34 to the crown main groove 4. The second inner crown sipe 37 extends from the inner shoulder main groove 3B toward the crown main groove 4 and has an inner end in the inner crown land portion 8B. The third inner crown sipe 38 extends from the crown main groove 4 toward the inner shoulder main groove 3B and has an outer end in the inner crown land portion 8B. These sipes provide frictional forces on wet road surfaces by their respective edges. Further, since a relatively large ground pressure acts on the inner crown land portion 8B, the wet performance is remarkably enhanced by the action of these grooves and sipes.

Since the width of the first inner crown sipe 36, the second inner crown sipe 37, and the third inner crown sipe 38 is less than 1.5 mm, pumping noise is hardly generated at the time of touchdown. Further, the first inner crown sipe 36, the second inner crown sipe 37, and the third inner crown sipe 38 can moderately relax the rigidity of the inner crown land portion 8B, so that the striking sound when the land portion touches the ground can be reduced. Therefore, excellent noise performance can be obtained.

It is desirable that the length L12 of the crown lug groove 34 in the tire axial direction is larger than, for example, the length L13 of the second inner crown sipe 37 in the tire axial direction. As a result, the frequency band between the hitting sound when the edge of the crown lug groove 34 touches the ground and the hitting sound when the edge of the second inner crown sipe 37 touches the ground is dispersed, and the noise performance is improved. Further, the crown lug groove 34, which has a large length with respect to the sipes, can be expected to have high drainage.

In order to further enhance the above-mentioned effect, the length L12 of the crown lug groove 34 is preferably 105% or more, more preferably 108% or more of the length L13 in the tire axial direction of the second inner crown sipe 37. It is preferably 120% or less, more preferably 114% or less.

The crown lug groove 34 is inclined with respect to the tire axial direction, for example. For the crown lug groove 34, for example, it is desirable that the groove width gradually decreases toward the crown main groove 4 side.

The crown lug groove 34 is chamfered between at least one groove wall and the tread ground contact surface so that the groove width gradually increases toward the inner shoulder main groove 3B, for example, at the communication portion with the inner shoulder main groove 3B. It is desirable to have. In the present embodiment, the chamfered portion 39 is provided on one groove wall of the crown lug groove 34. In a preferred embodiment, a chamfered portion 39 of the crown lug groove 34 is provided on the same side as the chamfered portion 28 (shown in FIG. 3) provided in the fine sipe portion 22 of the first outer crown sipe 26 in the tire circumferential direction. Such a crown lug groove 34 can suppress the generation of a standing wave in the inner shoulder main groove 3B while enhancing the uneven wear resistance, and can reduce the air column resonance sound.

It is desirable that the length L14 of the chamfered portion 39 of the crown lug groove 34 in the tire circumferential direction is, for example, 0.15 to 0.30 times the one-pitch length P1 of the crown lug groove 34. As a result, the wet performance and the noise performance are improved in a well-balanced manner.

The first inner crown sipe 36 is inclined in the same direction as the crown lug groove 34, for example. In this embodiment, one edge of the first inner crown sipe 36 extends so as to be smoothly continuous with the edge of the crown lug groove 34.

The first inner crown sipe 36 is chamfered between at least one sipe wall and the tread ground plane so that the width gradually increases toward the crown main groove 4, for example, in the communication portion with the crown main groove 4. It is desirable to have it. It is desirable that the first inner crown sipe 36 has, for example, a chamfered portion 40 on the side opposite to the chamfered portion 39 of the crown lug groove 34 in the tire circumferential direction. As a result, the frequency band between the hitting sound when one edge of the first inner crown sipe 36 and the crown lug groove 34 comes into contact with the road surface and the hitting sound when the other edge touches the road surface is easily dispersed. , Noise performance is improved.

As shown in FIG. 1, each of the first outer crown sipes 26 provided on the outer crown land portion 8A is provided at a position smoothly continuous with the first inner crown sipes 36 via the crown main groove 4. It is desirable to have. This makes it easier for the land portion around the sipe to follow the road surface, and the initial responsiveness is enhanced.

FIG. 7A shows a sectional view taken along line OH of the crown lug groove 34 and the first inner crown sipe 36 of FIG. As shown in FIG. 7A, the first inner crown sipe 36 includes a first sipe portion 36a on the crown main groove 4 side and a second sipe portion 36b on the crown lug groove 34 side. desirable.

The first sipe portion 36a has, for example, the same depth d8 as the depth d14 of the crown lug groove 34. It is desirable that the second sipe portion 36b has, for example, a depth d9 smaller than that of the first sipe portion 36a. The depth d9 of the second sipe portion 36b is, for example, 0.40 to 0.60 times the depth d8 of the first sipe portion 36a. Such a first inner crown sipe 36 makes it easy to appropriately deform the side of the crown main groove 4 of the inner crown land portion 8B, and can suppress the generation of a standing wave in the crown main groove 4, so that the crown main The air column resonance sound of the groove 4 can be reduced.

As shown in FIG. 6, the second inner crown sipe 37 and the third inner crown sipe 38 are interrupted without straddling the center position of the inner crown land portion 8B in the tire axial direction, respectively. The second inner crown sipe 37 and the third inner crown sipe 38 of the present embodiment have a tire axial length smaller than, for example, the first inner crown sipe 36. The tire axial length L13 of the second inner crown sipe 37 and the tire axial length L16 of the third inner crown sipe 38 are the tire axial lengths L15 of the first inner crown sipe 36, respectively. It is desirable that it is 0.60 to 0.75 times.

It is desirable that the second inner crown sipe 37 and the third inner crown sipe 38 are inclined in the same direction as the first inner crown sipe 36 with respect to the tire axial direction, for example. The angle θ1 of the second inner crown sipe 37 with respect to the tire axial direction is preferably, for example, 0 to 20 °. The angle θ2 of the third inner crown sipe 38 with respect to the tire axial direction is preferably larger than the angle θ1, and is, for example, 20 to 40 °. Such a second inner crown sipe 37 and a third inner crown sipe 38 are useful for making the hitting sound when the respective edges come into contact with the road surface into white noise.

FIG. 7B shows a cross-sectional view taken along the line II orthogonal to the second inner crown sipe 37 of FIG. As shown in FIG. 7B, it is desirable that the second inner crown sipe 37 has, for example, an opening 41 that widens toward the outside in the radial direction of the tire. In the present embodiment, the opening 41 is formed by inclining the sipe wall 42 on one side of the second inner crown sipe 37 in the tire circumferential direction. In the second inner crown sipe 37, for example, the sipe walls 42 on both sides may be inclined. Further, the second inner crown sipe 37 may be provided at the bottom of the above-mentioned narrow groove portion, for example. The third inner crown sipe 38 has, for example, the same cross-sectional shape as the second inner crown sipe 37 described above.

As shown in FIG. 1, in the present embodiment, the inclined sipe wall 31 of the second outer crown sipe 27 is arranged on one side (lower side in FIG. 1) in the tire circumferential direction, and the second inner crown sipe 37 is arranged. It is desirable that the inclined sipe wall 42 of the tire is arranged on the other side (upper side in FIG. 1) in the tire circumferential direction.

FIG. 7 (c) shows a sectional view taken along line JJ of the second inner crown sipe 37 and the third inner crown sipe 38 of FIG. As shown in FIG. 7 (c), the second inner crown sipe 37 extends at a constant depth and gradually decreases in depth near the inner end. The third inner crown sipe 38 includes a first sipe portion 38a on the side of the second inner crown sipe 37 and a second sipe portion 38b on the side of the crown main groove 4. The first sipe portion 38a has, for example, the same depth d10 as the depth d15 of the second inner crown sipe 37. The second sipe portion 38b has, for example, a depth d11 smaller than that of the first sipe portion 38a. It is desirable that the depth d11 of the second sipe portion 38b is, for example, 0.45 to 0.55 times the depth d10 of the first sipe portion 38a. Such a second inner crown sipe 37 and a third inner crown sipe 38 can enhance wet performance and noise performance in a well-balanced manner in combination with the above-mentioned first inner crown sipe 36.

As shown in FIG. 1, it is desirable that each of the second outer crown sipes 27 is provided at a position smoothly continuous with the third inner crown sipes 38 via the crown main groove 4. This makes it easier for the land portion around the sipe to follow the road surface, and the initial responsiveness is enhanced.

As shown in FIG. 2, it is desirable that both the inner edge 43a on the side of the crown main groove 4 and the outer edge 43b on the side of the inner shoulder main groove 3B of the inner crown land portion 8B are chamfered. Similarly, it is desirable that both the inner edge 43a on the side of the crown main groove 4 and the outer edge 43b on the side of the outer shoulder main groove 3A of the outer crown land portion 8A are chamfered. Each such land portion can mitigate the tapping sound when the edge comes into contact with the road surface.

It is desirable that the radius of curvature R1 of the tread ground contact surface of each of the inner crown land portion 8B and the outer crown land portion 8A is 560 mm or less. Specifically, it is desirable that the radius of curvature R1 is 400 to 500 mm. As a result, the contact pressure acting on the inner crown land portion 8B and the outer crown land portion 8A is increased, while the contact pressure acting on the outer shoulder land portion 7A and the inner shoulder land portion 7B is relaxed, and each shoulder land portion 7A, The sound when the 7B rolls can be reduced.

FIG. 8 shows an enlarged view of the outer shoulder land portion 7A as a diagram showing an example of the shoulder land portion 7. As shown in FIG. 8, the shoulder land portion 7A is provided with a shoulder sipe 10 extending in the tire axial direction. Further, in the present specification, the shoulder sipe provided on the outer shoulder land portion 7A may be referred to as an outer shoulder sipe. The shoulder sipe 10 alleviates the distortion of the shoulder land portion 7A at the time of contact with the ground and suppresses uneven wear thereof.

The shoulder sipe 10 of the present embodiment extends from the shoulder main groove 3A to the first tread end Te1. However, the shoulder sipe 10 is not limited to such an aspect, and one end or both ends of the shoulder sipe 10 may be interrupted within the shoulder land portion 7A.

The shoulder sipe 10 includes a fine sipe portion 11 and a thick sipe portion 12 having a width larger than that of the fine sipe portion 11. The dimensions of the fine sipe portion 22 and the thick sipe portion 23 of the outer crown sipe 21 described above can be applied to the thin sipe portion 11 and the thick sipe portion 12 of the shoulder sipe 10.

The thick sipe portion 12 can further relax the rigidity of the land portion around the thick sipe portion 12 as compared with the thin sipe portion 11. Therefore, the land portion around the thick sipe portion 12 can easily follow the road surface even in the initial state of turning where the ground contact load is not sufficiently increased, and excellent initial responsiveness can be obtained.

The thick sipe portion 12 of the present invention is arranged on the side of the shoulder main groove 3A. The shoulder main groove 3A side of the shoulder land portion 7A tends to have a larger ground contact load than the tread end Te1 side at the initial stage of turning. Therefore, by providing the thick sipe portion 12 in this region, the initial responsiveness is remarkably improved.

Further, the land portion around the fine sipe portion 11 is arranged closer to the tread end Te1 side than the thick sipe portion 12, and provides higher rigidity than the land portion around the thick sipe portion 12, so that it is sufficient for a tire, for example. In the middle of turning when a heavy ground load is applied, a large cornering force can be exerted, which in turn can improve steering stability.

It is desirable that the thick sipe portion 12 communicates with, for example, the shoulder main groove 3A. It is desirable that the length L2 of the thick sipe portion 12 in the tire axial direction is, for example, 0.15 to 0.30 times the width W2 of the shoulder land portion 7A. Such a thick sipe portion 12 can improve uneven wear resistance and steering stability in a well-balanced manner.

It is desirable that the fine sipe portion 11 communicates with, for example, the first tread end Te1. Further, it is desirable that the length L3 of the fine sipe portion 11 in the tire axial direction is larger than the length L2 of the thick sipe portion 12 in the tire axial direction. Specifically, it is desirable that the length L3 of the fine sipe portion 11 is, for example, 3.0 to 4.5 times the length L2 of the thick sipe portion 12.

The shoulder land portion 7A is provided with, for example, a fine groove portion 13 similar to the fine groove portion 24 (shown in FIG. 3) provided in the outer crown land portion 8A, and the thick sipe portion 12 is a groove of the fine groove portion 13. It is desirable that it extends inward in the radial direction of the tire from the bottom. Such a narrow groove portion 13 and a thick sipe portion 12 can further enhance the uneven wear resistance.

The narrow groove portion 13 extends from the shoulder main groove 3A to the outside in the tire axial direction, and is terminated between the outer end of the thick sipe portion 12 in the tire axial direction and the first tread end Te1. desirable. It is desirable that the length L4 of the narrow groove portion 13 in the tire axial direction is, for example, 1.5 to 2.5 times the length L2 of the thick sipe portion 12 in the tire axial direction.

Between the outer end of the thick sipe portion 12 and the outer end of the fine groove portion 13, it is desirable that the fine sipe portion 11 extends inward in the tire radial direction from the groove bottom of the fine groove portion 13. Further, in the region between the outer end of the narrow groove portion 13 and the first tread end Te1, it is desirable that the fine sipe portion 11 extends from the bottom to the tread with a constant width.

It is desirable that the narrow groove portion 13 is chamfered between at least one groove wall and the tread ground contact surface so that the groove width gradually increases toward the shoulder main groove 3A in the communication portion with the shoulder main groove 3A. .. In the fine groove portion 13 of the present embodiment, for example, only one groove wall (lower groove wall in FIG. 8) has a chamfered portion 14. Such a narrow groove portion 13 can reduce the air column resonance sound in the outer shoulder main groove 3A while increasing the uneven wear resistance.

In the present embodiment, as shown in FIG. 1, the narrow groove portion 13 provided in the outer shoulder land portion 7A has a chamfered portion 14 on the groove wall on one side (lower side in FIG. 1) in the tire circumferential direction. The narrow groove portion 24 provided in the outer crown land portion 8A has a chamfered portion 25 on the groove wall on the other side (upper side in FIG. 1) in the tire circumferential direction. The chamfered portion 25 provided on the outer crown land portion 8A has a larger chamfered length in the tire circumferential direction than the chamfered portion 14 provided on the outer shoulder land portion 7A. Such an arrangement of the narrow groove portion 24 can enhance the uneven wear resistance, suppress the generation of a standing wave in the outer shoulder main groove 3A, and can reduce the air column resonance sound.

Further, it is desirable that the first crown sipe 26 has a displacement of 1.0 mm or less from the outer shoulder sipe 10 in the outer shoulder main groove 3A in the tire circumferential direction. In the present embodiment, the outer shoulder sipe 10 is arranged so as to be continuous with the first crown sipe 26 via the outer shoulder main groove 3A, and in a preferred embodiment, the outer shoulder sipe 10 is arranged via the shoulder main groove 3A. A portion that is linearly continuous with the first crown sipe 26 is included. Such an arrangement of the pavement makes it easier for the surrounding land portion to follow the road surface, and can further enhance the initial responsiveness.

As shown in FIG. 8, a plurality of shoulder sipes 10 are arranged at intervals in the tire circumferential direction on the shoulder land portion 7A of the present embodiment, and are located between the shoulder sipes 10 adjacent to the tire circumferential direction. The shoulder lug groove 15 is arranged. In the present specification, the shoulder lug groove 15 provided in the outer shoulder land portion 7A may be referred to as an outer shoulder lug groove.

The shoulder lug groove 15 extends inward in the tire axial direction from, for example, the first tread end Te1 and terminates without communicating with the shoulder main groove 3A. Such a shoulder lug groove 15 can improve wet performance while maintaining the rigidity of the shoulder land portion 7A.

It is desirable that the inner end 15a of the shoulder lug groove 15 in the tire axial direction is located outside the tire axial direction of the outer end 12a of the thick sipe portion 12 in the tire axial direction. The length L5 of the shoulder lug groove 15 in the tire axial direction is, for example, preferably 0.45 times or more, more preferably 0.52 times or more, and preferably 0, the width W2 of the shoulder land portion 7A in the tire axial direction. It is preferably .65 times or less, more preferably 0.58 times or less.

In order to exhibit sufficient drainage, it is desirable that the groove width W3 of the shoulder lug groove 15 is, for example, 1.5 to 2.5 times the groove width W4 of the narrow groove portion 13.

FIG. 9 shows an enlarged view of the inner shoulder land portion 7B as a diagram showing another example of the shoulder land portion 7. As shown in FIG. 9, the inner shoulder land portion 7B is provided with, for example, a plurality of inner shoulder lug grooves 16. The inner shoulder lug groove 16 extends inward in the tire axial direction from, for example, the second tread end Te2 and terminates without communicating with the inner shoulder main groove 3B.

The length L6 of the inner shoulder lug groove 16 in the tire axial direction is, for example, preferably 0.60 times or more, more preferably 0.65 times or more, and preferably 0.65 times or more the width W5 of the inner shoulder land portion 7B in the tire axial direction. Is 0.76 times or less, more preferably 0.71 times or less. Such an inner shoulder lug groove 16 can improve steering stability and wet performance in a well-balanced manner.

The distance L7 in the tire axial direction from the inner end of the inner shoulder lug groove 16 to the inner shoulder main groove 3B is, for example, the distance L8 from the inner end of the outer shoulder lug groove 15 to the outer shoulder main groove 3A (shown in FIG. 8). It is desirable that it is smaller than.

The inner shoulder lug groove 16 has, for example, a groove width W6 larger than 2 mm. It is desirable that the groove width W6 of the inner shoulder lug groove 16 is, for example, 0.40 to 0.60 times the groove width W1c (shown in FIG. 1) of the inner shoulder main groove 3B.

The inner shoulder land portion 7B is provided with an inner shoulder sipe 18 between the connecting sipe 17 extending from the inner shoulder lug groove 16 to the inner shoulder main groove 3B and the inner shoulder lug groove 16 adjacent to the tire circumferential direction. ..

The connecting sipe 17 extends inward in the tire radial direction from the groove bottom of the narrow groove portion 19 having a groove width of 1.5 mm or more and a groove depth of 2.0 mm or less, for example. The connecting sipes 17 have a width of, for example, 0.4 to 0.8 mm. As the dimensions of the fine groove portion 19, for example, the dimensions of the fine groove portion 13 arranged on the outer shoulder land portion 7A can be applied.

FIG. 10 shows a cross-sectional view taken along the line DD of the connecting sipe 17 of FIG. As shown in FIG. 10, the connecting sipe 17 includes, for example, a first sipe portion 17a on the inner shoulder lug groove 16 side and a second sipe portion 17b on the inner shoulder main groove 3B side. The second sipe portion 17b has a depth smaller than, for example, the first sipe portion 17a. It is desirable that the depth d13 of the second sipe portion 17b is 0.35 to 0.55 times the depth d12 of the first sipe portion 17a. Such a connection sipe 17 can improve the initial responsiveness, suppress the side of the inner shoulder main groove 3B from opening excessively, and improve the uneven wear resistance.

As shown in FIG. 9, the inner shoulder sipe 18 extends, for example, along the inner shoulder lug groove 16. Both ends of the inner shoulder sipe 18 are interrupted in the inner shoulder land portion 7B, for example. Such an inner shoulder sipe 18 can easily make the land portion follow the road surface while suppressing an excessive decrease in rigidity of the land portion, and can exhibit excellent steering stability and initial responsiveness.

The inner shoulder sipe 18 extends inward in the radial direction of the tire from the groove bottom of the narrow groove portion, for example, like the connection sipe 17 described above.

As shown in FIG. 1, the land ratio Lr1 in the region between the tire equator C and the first tread end Te1 is based on the land ratio Lr2 in the region between the tire equator C and the second tread end Te2. Is also desirable. Specifically, it is desirable that the land ratio Lr1 is 1.05 to 1.10 times the land ratio Lr2. As a result, the response during steering can be made linear, and excellent steering stability can be exhibited. As used herein, the "land ratio" is the ratio Sb / Sa of the actual total ground contact area Sb to the total area Sa of the virtual ground contact patch in which each groove and sipes are completely filled.

FIG. 11 shows a developed view of the tread portion 2 of the tire 1 according to another embodiment of the present invention. As shown in FIG. 11, in this embodiment, the outer crown main groove 4A and the inner crown main groove 4B are provided on both sides of the tire equator C. The outer crown main groove 4A is provided between the tire equator C and the outer shoulder main groove 3A. The inner crown main groove 4B is provided between the tire equator C and the inner shoulder main groove 3B.

In this embodiment, it is desirable that the shoulder main groove 3 has, for example, a distance L1a from the tire equator C to the groove center line 0.20 to 0.30 times the tread width TW. For the crown main groove 4, for example, it is desirable that the distance L1b from the tire equator C to the groove center line is 0.05 to 0.15 times the tread width TW.

The tread portion 2 of this embodiment has the outer shoulder land portion 7A, the inner shoulder land portion 7B, the outer crown land portion 8A, the inner crown land portion 8B, and the central crown by arranging the above-mentioned main groove. Includes tread 8C. The above configuration may be applied to the outer shoulder land portion 7A, the inner shoulder land portion 7B, the outer crown land portion 8A and the inner crown land portion 8B.

The central crown land portion 8C is divided between the outer crown main groove 4A and the inner crown main groove 4B. The central crown land portion 8C of the present embodiment is provided with, for example, a first central crown sipe 45 and a second central crown sipe 46. The first central crown sipe 45 crosses, for example, the central crown land portion 8C. The second central crown sipe 46 extends from the inner crown main groove 4B toward the tire equator C side, and is interrupted in front of the tire equator C, for example.

Although the tire of one embodiment of the present invention has been described in detail above, the present invention is not limited to the specific embodiment described above, and may be modified into various embodiments.

A tire of size 195 / 65R15 having the basic pattern of FIG. 1 was prototyped based on the specifications in Table 1. As Comparative Example 1, as shown in FIG. 12, a tire having an outer crown land portion a on which a first outer crown sipe b extending with a constant width is arranged was prototyped. As Comparative Example 2, as shown in FIG. 13, a tire in which the thick sipe portion is arranged on the side of the crown main groove was prototyped. The first outer crown sipe b of Comparative Example 1 extends with the same width as the fine sipe portion of the first outer crown sipe of the embodiment shown in FIG. The thick sipe portion and the thin sipe portion of Comparative Example 2 each have the same width as that of the embodiment shown in FIG. The tread portion of the tires of Comparative Examples 1 and 2 is substantially the same as the tread portion shown in FIG. 1, except for the configuration of the first outer crown sipe. The steering stability of each test tire and the uneven wear resistance of the land part of the crown were tested. The common specifications and test methods for each test tire are as follows.
Mounting rim: 15 x 6.5J
Tire internal pressure: front wheels 250kPa, rear wheels 240kPa
Test vehicle: Front-wheel drive vehicle, displacement 1800cc
Tire mounting position: All-wheel test method is as follows.

<Maneuvering stability>
The steering stability including the initial responsiveness when traveling on a dry road surface with the above test vehicle was evaluated by the driver's sensuality. The result is a score with a comparative example of 100, and the larger the value, the better the steering stability.

<Uneven wear resistance>
A wear energy measuring device was used to measure the wear energy of the outer crown land. The result is an index with the wear energy of the comparative example as 100, and the smaller the value, the smaller the wear energy and the better the uneven wear resistance.
The test results are shown in Table 1.

As a result of the test, it was confirmed that the tire of the example had excellent steering stability and the uneven wear resistance of the land part of the crown was enhanced.

2 Tread part 3A Shoulder main groove 4 Crown main groove 8A Crown land part 21 Crown sipe 22 Fine sipe part 23 Thick sipe part 26 1st crown sipe Te1 1st tread end C Tire equator

Claims (9)

A tire with a tread
The tread portion has a shoulder main groove continuously extending in the tire circumferential direction between the first tread end, the first tread end and the tire equatorial line, and a shoulder main groove adjacent to the shoulder main groove and continuous in the tire circumferential direction. Includes a crown tread extending along the road and a tread section of the crown divided between the shoulder tread and the crown tread.
A crown sipe extending in the tire axial direction with a width of less than 1.5 mm is provided on the land portion of the crown.
The crown sipe includes a first crown sipe that traverses the land of the crown and a second crown sipe that extends from the main groove of the crown to the side of the main groove of the shoulder and has a break in the land of the crown .
The first crown sipe includes a fine sipe portion and a thick sipe portion having a width larger than that of the fine sipe portion.
The thick sipe portion communicates with the shoulder main groove, and the thick sipe portion communicates with the shoulder main groove .
The break end of the second crown sipe is located closer to the crown main groove than the end of the thick sipe portion of the first crown sipe on the crown main groove side.
tire.
The tire according to claim 1, wherein the fine sipe portion communicates with the crown main groove. The tire according to claim 1 or 2, wherein the length of the fine sipe portion in the tire axial direction is larger than the length of the thick sipe portion in the tire axial direction. The first crown sipe includes a first sipe portion including the thick sipe portion and extending at a constant depth, and a second sipe portion on the crown main groove side.
The tire according to any one of claims 1 to 3, wherein the second sipe portion has a depth smaller than that of the first sipe portion.
The second crown sipe includes a first sipe portion on the interrupted end side and a second sipe portion on the crown main groove side.
The tire according to any one of claims 1 to 4, wherein the second sipe portion of the second crown sipe has a depth smaller than that of the first sipe portion of the second crown sipe. The land portion of the crown is provided with a fine groove portion having a groove width of 1.5 mm or more and a groove depth of 2.0 mm or less, and the thick sipe portion is inward in the tire radial direction from the groove bottom of the fine groove portion. The tire according to any one of claims 1 to 5, which extends to. The narrow groove portion is chamfered between at least one groove wall and a tread ground contact surface so that the groove width gradually increases toward the shoulder main groove in a communication portion with the shoulder main groove. The tire described in 6. The tread portion includes a shoulder land portion divided between the first tread end and the shoulder main groove.
The shoulder land portion is provided with a shoulder sipe extending in the tire axial direction with a width of less than 1.5 mm and communicating with the shoulder main groove.
The tire according to any one of claims 1 to 7, wherein the shoulder sipe is arranged so as to be continuous with the first crown sipe via the shoulder main groove. The tire according to claim 8, wherein the shoulder sipe has a portion linearly continuous with the first crown sipe via the shoulder main groove.

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