JP7052319B2 - 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 improve steering stability on a dry road surface.

Japanese Unexamined Patent Publication No. 2016-13820

However, in recent years, as the performance of vehicles has improved, not only steering stability on dry road surfaces but also wet performance has been required to be improved. As a result of various experiments, the inventors have found that by improving the crown pavement arranged on the land part of the crown, it is possible to improve the steering stability and the wet performance on a dry road surface in a well-balanced manner.

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 improving steering stability and wet performance on a dry road surface.

The present invention is a tire having a tread portion whose mounting direction on a vehicle is specified, and the tread portion includes an outer shoulder main groove and an inner shoulder main groove continuously extending in the tire circumferential direction, and the outer shoulder. A crown main groove that continuously extends between the main groove and the inner shoulder main groove in the tire circumferential direction, an inner crown land portion divided by the crown main groove and the inner shoulder main groove, and the crown main groove. Including the outer crown land portion separated from the outer shoulder main groove, the inner crown land portion extends from the inner shoulder main groove to the side of the crown main groove with a width of 1.5 mm or more and the inner side. A plurality of crown lug grooves having an inner end in the land portion of the crown, a first inner crown sipe having a width extending from the inner end of each of the crown lug grooves to the crown main groove of less than 1.5 mm, and the inner shoulder main. A plurality of second inner crown sipes extending from the groove to the side of the crown main groove and having an inner end in the land portion of the inner crown and having a width of less than 1.5 mm, and from the crown main groove to the side of the inner shoulder main groove. A plurality of third inner crown sipes extending and having an outer end in the inner crown land portion and having a width of less than 1.5 mm are provided, and the outer crown land portion is provided with the outer shoulder main from the crown main groove. A first outer crown sipe extending to the groove and a second outer crown sipe extending from the crown main groove to the side of the outer shoulder main groove and having an outer end in the land portion of the outer crown are provided, and the third outer crown sipe is provided. Each of the inner crown sipes is provided at a position smoothly continuous with the second outer crown sipes via the crown main groove.

In the tire of the present invention, it is desirable that both the inner edge of the inner crown land portion on the side of the crown main groove and the outer edge on the side of the inner shoulder main groove are chamfered.

In the tire of the present invention, it is desirable that both the inner edge on the side of the crown main groove and the outer edge on the side of the outer shoulder main groove of the outer crown land portion are chamfered.

In the tire of the present invention, it is desirable that the groove width of the crown main groove is larger than the groove width of each of the inner shoulder main groove and the outer shoulder main groove.

In the tire of the present invention, it is desirable that the groove width of the inner shoulder main groove is larger than the groove width of the outer shoulder main groove.

In the tire of the present invention, it is desirable that the first outer crown sipe includes a fine sipe portion and a thick sipe portion having a width larger than that of the fine sipe portion.

In the tire of the present invention, it is desirable that the thick sipe portion communicates with the outer shoulder main groove.

In the tire of the present invention, it is desirable that the thick sipe portion has a length in the tire axial direction smaller than that of the crown lug groove.

The present invention is a tire having a tread portion whose mounting direction on a vehicle is specified. The tread portion of the tire of the present invention is a crown main groove that continuously extends in the tire circumferential direction between the outer shoulder main groove and the inner shoulder main groove that extend continuously in the tire circumferential direction and the outer shoulder main groove and the inner shoulder main groove. It includes a groove, an inner crown land portion divided by a crown main groove and an inner shoulder main groove, and an outer crown land portion divided by a crown main groove and an outer shoulder main groove. Since such tires tend to exert a relatively large contact pressure on the inner crown land portion and the outer crown land portion when traveling straight and turning, the grooves and sipes arranged in these land portions are not included. It greatly contributes to steering stability and wet performance on dry roads.

The inner crown land portion of the tire of the present invention has a plurality of crown lug grooves extending from the inner shoulder main groove to the side of the crown main groove and having an inner end in the inner crown land portion having a width of 1.5 mm or more, and a crown lug. The width of the first inner crown sipe that extends from each inner end of the groove to the crown main groove is less than 1.5 mm, and the width that extends from the inner shoulder main groove to the side of the crown main groove and has an inner end in the inner crown land portion. Multiple second inner crown sipes less than 1.5 mm and multiple third inner crown sipes less than 1.5 mm wide extending from the crown main groove to the side of the inner shoulder main groove and having an outer end in the inner crown land area. And are provided.

The crown lug groove, the first inner crown sipe, the second inner crown sipe and the third inner crown sipe help maintain the rigidity of the inner crown land. In addition, the crown lug groove cooperates with the inner shoulder main groove to improve drainage near the inner crown land area. The first inner crown sipe, the second inner crown sipe and the third inner crown sipe provide frictional force on a wet road surface by their respective edges. As described above, since a relatively large ground pressure acts on the land portion of the inner crown, the action of these grooves and sipes enhances steering stability and wet performance on a dry road surface.

The outer crown land portion of the tire of the present invention has a first outer crown sipe extending from the crown main groove to the outer shoulder main groove, and an outer end extending from the crown main groove toward the outer shoulder main groove to the outer crown land portion. A second outer crown sipe to have is provided. The first outer crown sipe and the second outer crown sipe provide frictional forces on wet road surfaces by their respective edges.

The second outer crown sipe, together with the first outer crown sipe, further relaxes the stiffness of the outer crown land portion on the side of the crown main groove. Therefore, for example, the outer crown land portion can easily follow the road surface even in the initial turning state where the ground pressure is not sufficiently increased, and thus excellent initial responsiveness can be obtained. On the other hand, since the second outer crown sipe is terminated within the outer crown land portion, the outer crown land portion has high rigidity on the side of the outer shoulder main groove. Therefore, the outer crown land portion can exert a large cornering force, for example, in the middle stage of turning when a sufficient ground contact load is applied to the tire, and can improve the steering stability on a dry road surface.

Moreover, in the present invention, since each of the third inner crown sipes is provided at a position smoothly continuous with the second outer crown sipes via the crown main groove, the third inner crown sipes and the second outer crown sipes are provided. The sipes are easier to open and each edge can provide greater friction during wet driving.

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 and the inner crown land part of FIG. It is an enlarged view of the 2nd outer crown sipe and the 3rd inner crown sipe of FIG. (A) is a cross-sectional view taken along the line HH of FIG. 3, (b) is a cross-sectional view taken along the line I-I of FIG. 3, and (c) is a cross-sectional view taken along the line JJ 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 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 an enlarged view of the outer crown land part and the inner crown land part of the comparative example.

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. 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 has an outer shoulder main groove 3A provided between the first tread end Te1 and the tire equator C, and an inner side provided between the second tread end Te2 and the tire equator C. Includes 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, and in this embodiment, for example, it is provided on 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 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.

FIG. 3 shows an enlarged view of the outer crown land portion 8A and the inner crown land portion 8B. As shown in FIG. 3, 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. In addition, in this specification, a "sipe" is a notch having a width of less than 1.5 mm.

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 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.

The crown lug groove 34, the first inner crown sipe 36, the second inner crown sipe 37 and the third inner crown sipe 38 help maintain the rigidity of the inner crown land portion 8B. Further, the crown lug groove 34 cooperates with the inner shoulder main groove 3B to improve the drainage property in the vicinity of the inner crown land portion 8B. The first inner crown sipe 36, the second inner crown sipe 37 and the third inner crown sipe 38 provide frictional force on the wet road surface by their respective edges. Since a relatively large contact pressure acts on the inner crown land portion 8B, the action of these grooves and sipes enhances steering stability and wet performance on a dry road surface.

The outer crown land portion 8A is provided with a first outer crown sipe 26 and a second outer crown sipe 27. The first outer crown sipe 26 extends from the crown main groove 4 to the outer shoulder main groove 3A. The second outer crown sipe 27 extends from the crown main groove 4 toward the outer shoulder main groove 3A and has an outer end within the outer crown land portion 8A. The first outer crown sipe 26 and the second outer crown sipe 27 provide frictional forces on wet road surfaces by their respective edges.

The second outer crown sipe 27, together with the first outer crown sipe 26, further relaxes the rigidity of the outer crown land portion 8A on the side of the crown main groove 4. Therefore, for example, the outer crown land portion 8A can easily follow the road surface even in the initial state of turning where the ground pressure is not sufficiently increased, and thus excellent initial responsiveness can be obtained. On the other hand, since the second outer crown sipe 27 is terminated in the outer crown land portion 8A, the outer crown land portion 8A has high rigidity on the side of the outer shoulder main groove 3A. Therefore, the outer crown land portion 8A can exert a large cornering force, for example, in the middle of turning when a sufficient ground contact load is applied to the tire, and can improve the steering stability on a dry road surface.

FIG. 4 shows an enlarged view of the third inner crown sipe 38 and the second outer crown sipe 27. As shown in FIG. 4, each of the third inner crown sipes 38 is provided at a position smoothly continuous with the second outer crown sipes 27 via the crown main groove 4. It should be noted that "provided at a position where the sipes are smoothly continuous" is at least the shortest in the tire circumferential direction between the first region 32a in which one sipes is virtually extended and the second region 32b in which the other sipes are virtually extended. Includes an embodiment in which the separation distance is less than 1.0 mm. In the present embodiment, the first region 32a and the second region 32b intersect at least at a part (that is, the shortest separation distance = 0). In a more preferred embodiment, the first region 32a intersects the end of the other sipe and the second region 32b intersects the end of the other sipe.

In the present invention, the arrangement of the sipes described above facilitates the opening of the third inner crown sipe 38 and the second outer crown sipe 27, and the respective edges can provide a larger frictional force during wet running.

As shown in FIG. 3, the tire axial length L12 of the crown lug groove 34 is configured to be larger than the tire axial length L13 of the second inner crown sipe 37. 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. 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. In the present embodiment, the chamfered portion 40 of the first inner crown sipe 36 is provided on the opposite side of the chamfered portion 39 provided on the groove wall of the crown lug groove 34 in the tire circumferential direction.

FIG. 5A 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. 5A, 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. 3, 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 tire axial length L13 of the second inner crown sipe 37 and the tire axial length L16 of the third inner crown sipe 38 of the present embodiment are the widths of the inner crown land portion 8B in the tire axial direction, respectively. It is desirable that it is 0.30 to 0.50 times W8.

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. 5B shows a cross-sectional view taken along the line II orthogonal to the second inner crown sipe 37 of FIG. As shown in FIG. 5B, 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. The third inner crown sipe 38 has, for example, the same cross-sectional shape as the second inner crown sipe 37 described above.

FIG. 5 (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. 5 (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. 3, it is desirable that the first outer crown sipe 26 includes, for example, 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, for example, 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 the steering stability.

FIG. 6A shows a sectional view taken along line BB of the thick sipe portion 23 of FIG. FIG. 6B shows a sectional view taken along line CC of the fine sipe portion 22. As shown in FIGS. 6 (a) and 6 (b), 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 of 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 6A, 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. In a preferred embodiment, the chamfered portion 25 of the narrow groove portion 24 is arranged on the same side of the chamfered portion 40 of the first inner crown sipe 36 and the tire circumferential direction.

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. Further, it is desirable that the length L9 of the thick sipe portion 23 is smaller than, for example, the length L12 of the crown lug groove 34. As a result, the rigidity of the outer crown land portion 8A is relatively increased, and the steering stability during turning is enhanced.

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 side opposite to the chamfered portion 25 provided on the groove wall of the narrow groove portion 24 (lower side in FIG. 3). 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. 7A shows a sectional view taken along line EE of the first outer crown sipe 26 of FIG. As shown in FIG. 7A, the first outer 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. There is. 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 outer 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, 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 pavement to follow the road surface, and the initial responsiveness is enhanced.

The tire axial length L11 of the second outer 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. It is 48 times. Further, it is desirable that the interrupted end 29 of the second outer 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 outer crown sipe 26 on the crown main groove 4 side. Such a second outer crown sipe 27 can suppress an excessive decrease in rigidity of the outer crown land portion 8A and provide a large cornering force.

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 pavement to follow the road surface, and the initial responsiveness is enhanced.

FIG. 7B shows a sectional view taken along line FF orthogonal to the second outer crown sipe 27 of FIG. As shown in FIG. 7B, it is desirable that the second outer 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 outer crown sipe 27 in the tire circumferential direction. In the second outer crown sipe 27, for example, the sipe walls 31 on both sides may be inclined. Further, the second outer crown sipe 27 may be provided at the bottom of the above-mentioned narrow groove portion, for example.

As shown in FIG. 3, in the present embodiment, the inclined sipe wall 31 of the second outer crown sipe 27 is arranged on one side in the tire circumferential direction, and the inclined sipe wall 42 of the second inner crown sipe 37 is provided. , It is desirable that it is arranged on the other side in the tire circumferential direction.

FIG. 7 (c) shows a cross-sectional view taken along the line GG along the second outer crown sipe 27 of FIG. As shown in FIG. 7 (c), it is desirable that the second outer 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 outer crown sipe 27 can suppress excessive opening of the side of the crown main groove 4, and can improve uneven wear resistance and steering stability.

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 first outer crown sipe 26 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 11 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, for example, 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 outer 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 outer crown sipe 26 via the outer shoulder main groove 3A, and in a preferred embodiment, the outer shoulder sipe 10 has the shoulder main groove 3A. Includes a portion linearly continuous with the first outer crown sipe 26 through. 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, 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 lug groove 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. There is.

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.

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 a comparative example, as shown in FIG. 11, the second outer crown sipe c provided on the outer crown land portion a and the third inner crown sipe d provided on the inner crown land portion b are smoothly continuous. Instead, a prototype tire was prototyped that was misaligned in the tire circumferential direction. The tread portion of the tire of the comparative example is substantially the same as the tread portion shown in FIG. 1, except for the above points. The steering stability and wet performance of each test tire on dry roads 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 on dry roads>
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.

<Wet performance>
The test vehicle traveled on an asphalt road surface having a depth of 5 mm and a length of 20 m and a radius of 100 m, and the lateral acceleration (lateral G) of the front wheels was measured. The result is an average lateral G of a speed of 50 to 80 km / h, and is shown by an index with the value of Comparative Example 1 as 100. The larger the value, the better the wet performance.
The test results are shown in Table 1.

As a result of the test, it was confirmed that the tire of the example had improved steering stability and wet performance on a dry road surface.

2 Tread part 3A Outer shoulder main groove 3B Inner shoulder main groove 4 Crown main groove 8B Inner crown land part 8A Outer crown land part 34 Crown lug groove 36 1st inner crown sipe 37 2nd inner crown sipe 38 3rd inner crown sipe

Claims (6)

A tire with a tread that is oriented to be mounted on a vehicle.
The tread portion includes an outer shoulder main groove and an inner shoulder main groove that continuously extend in the tire circumferential direction, and a crown main groove that continuously extends in the tire circumferential direction between the outer shoulder main groove and the inner shoulder main groove. , The inner crown land portion divided by the crown main groove and the inner shoulder main groove, and the outer crown land portion divided by the crown main groove and the outer shoulder main groove.
On the land of the inner crown,
A plurality of crown lug grooves extending from the inner shoulder main groove to the side of the crown main groove with a width of 1.5 mm or more and having an inner end in the land portion of the inner crown.
A first inner crown sipe having a width extending from the inner end of each of the crown lug grooves to the crown main groove of less than 1.5 mm.
A plurality of second inner crown sipes extending from the inner shoulder main groove to the side of the crown main groove and having an inner end in the land portion of the inner crown and having a width of less than 1.5 mm.
A plurality of third inner crown sipes extending from the crown main groove toward the inner shoulder main groove and having an outer end in the inner crown land portion and having a width of less than 1.5 mm are provided.
On the land of the outer crown,
A first outer crown sipe extending from the crown main groove to the outer shoulder main groove, and a second outer crown sipe extending from the crown main groove to the side of the outer shoulder main groove and having an outer end in the land portion of the outer crown. Is provided,
Each of the third inner crown sipes is provided at a position smoothly continuous with the second outer crown sipes via the crown main groove .
The first outer crown sipe includes a thin sipe portion and a thick sipe portion which are continuous in the length direction of the first outer crown sipe.
The thick sipe portion is wider than the thin sipe portion.
The thick sipe portion communicates with the outer shoulder main groove.
tire. The tire according to claim 1, wherein both the inner edge on the side of the crown main groove and the outer edge on the side of the inner shoulder main groove of the inner crown land portion are chamfered. The tire according to claim 1 or 2, wherein both the inner edge on the side of the crown main groove and the outer edge on the side of the outer shoulder main groove of the outer crown land portion are chamfered. The tire according to any one of claims 1 to 3, wherein the groove width of the crown main groove is larger than the groove width of each of the inner shoulder main groove and the outer shoulder main groove. The tire according to claim 4, wherein the groove width of the inner shoulder main groove is larger than the groove width of the outer shoulder main groove. The tire according to any one of claims 1 to 5, wherein the thick sipe portion has a length in the tire axial direction smaller than that of the crown lug groove.

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