JP6693146B2 - tire - Google Patents

Description

  The present invention relates to a tire capable of improving rolling resistance performance, wear resistance performance, and wet performance in a well-balanced manner.

  In recent years, in order to save energy, it is required to reduce rolling resistance of tires and improve fuel efficiency of vehicles. Generally, about half of the rolling resistance of a tire is energy loss due to the deformation of the tread portion of the tire. Therefore, for example, by reducing the sipes provided on the tread portion, the rigidity of the tread portion is increased, and the deformation of the tread portion during traveling is suppressed, whereby a tire having improved rolling resistance performance has been proposed. .. Further, such a tire having increased rigidity has excellent wear resistance performance.

  However, such a tire with reduced sipes reduces the effect of removing the water film on the wet road surface by utilizing the scratching force of the sipes, and particularly the braking performance on wet roads (hereinafter, simply referred to as "wet performance"). There is a problem that it decreases.

JP, 2013-193463, A

  The present invention has been devised in view of the above situation, and is based on improving the shape of the sipe provided in the crown land portion and the middle land portion, the rolling resistance performance and wear resistance performance, and wet. The main purpose is to provide a tire that can improve the performance in a well-balanced manner.

  The present invention is a tire having a tread portion whose rotational direction is designated, wherein the tread portion has a pair of crown main grooves continuously extending on both outer sides of the tire equator in the tire circumferential direction, and the crown main groove. By providing a pair of shoulder main grooves extending continuously in the tire circumferential direction on the outer side in the tire axial direction, a crown land portion divided by the pair of crown main grooves, and the crown main groove and the shoulder main groove. A pair of middle land portions divided by is formed, the crown land portion, a plurality of crown sipes that communicate between the crown main grooves, are provided in the tire circumferential direction, the middle land portion, the A plurality of middle sipes that connect the crown main groove and the shoulder main groove are provided in the tire circumferential direction, and the crown sipes rotate from the top on the center side toward both ends. The middle sipe has a substantially V-shape that inclines toward a rearward side, and the middle sipe has an inner side portion that inclines toward a rearward side in the rotational direction from the crown main groove toward the shoulder main groove side, and the tire axial direction of the inner side portion. An intermediate portion that is inclined from the outer end toward the shoulder main groove side toward the rearward side in the rotation direction at a larger angle than the inner portion, and a tire axial direction outer end of the intermediate portion toward the shoulder main groove side. It is a substantially hook shape including an outer side portion inclined to the rearward side in the rotation direction at an angle smaller than the intermediate portion, and the inner side portion of the middle sipe is substantially continuous with the crown sipe via the crown main groove. Is characterized by.

  In the tire according to the present invention, it is preferable that the crown sipe and the middle sipe are respectively inclined inward in the tire radial direction toward a rearward side in the rotation direction in a cross section orthogonal to the longitudinal direction thereof. ..

  In the tire according to the present invention, the crown sipe has an angle of 5 to 15 ° with respect to a tire normal in a cross section orthogonal to its longitudinal direction, and the middle sipe has a tire in a cross section orthogonal to its longitudinal direction. The angle with respect to the normal is preferably 5 to 15 °.

  In the tire according to the present invention, it is desirable that the middle sipe and the crown sipe overlap in the tire circumferential direction.

  In the tire according to the present invention, it is preferable that only the substantially V-shaped crown sipes are provided on the crown land portion.

  In the tire according to the present invention, it is preferable that only the substantially hook-shaped middle sipes are provided on the middle land portion.

  In the tire according to the present invention, the angle of the middle portion of the middle sipe with respect to the tire axial direction is preferably 35 to 50 °.

  In the tire according to the present invention, it is preferable that an angle of the outer side portion, the inner side portion of the middle sipe, and the crown sipe with respect to the tire axial direction is 5 to 15 °.

  In the tire according to the present invention, the tread portion is further formed with a shoulder land portion divided by the shoulder main groove and a tread end, and the shoulder land portion has the shoulder main groove and a tread end. It is desirable that a plurality of communicating shoulder sipes be provided in the tire circumferential direction, and that the shoulder sipes linearly extend from the shoulder main groove toward the tread end side toward the rearward side in the rotational direction.

  In the tire according to the present invention, it is preferable that the shoulder sipe is substantially continuous with the outer side portion of the middle sipe via the shoulder main groove.

  In the tire of the present invention, the crown land portion is provided with a substantially V-shaped crown sipe that communicates between the crown main grooves and inclines toward the rearward side in the rotation direction from the top portion on the center side toward both end sides. Since such a crown sipe has an edge component in the tire circumferential direction, by utilizing the rolling of the tire, the water film between the tread surface of the crown land portion and the road surface is effectively discharged into the crown main grooves on both sides. You can. This improves wet performance.

  In addition, a substantially hook-shaped middle sipe that connects the crown main groove and the shoulder main groove is provided in the middle land portion. The middle sipe includes an inner portion, a middle portion, and an outer portion. The inner part is inclined from the crown main groove toward the shoulder main groove toward the rear side in the rotational direction. The intermediate portion is inclined toward the rearward side in the rotational direction from the outer end of the inner portion in the tire axial direction toward the shoulder main groove side at an angle larger than that of the inner portion. The outer side portion is inclined toward the rearward side in the rotational direction at an angle smaller than that of the middle portion from the outer end in the tire axial direction of the middle portion toward the shoulder main groove side. Since such a middle sipe also has an edge component in the tire circumferential direction, the water film between the tread surface of the middle land portion and the road surface can be discharged to the shoulder main groove by utilizing the rolling of the tire. Further, since the intermediate portion that is inclined at a larger angle than the inner portion has a large edge component in the tire circumferential direction, the water film can be effectively discharged into the shoulder main groove. Therefore, the water film can be smoothly discharged even in the middle land portion where a ground pressure smaller than that in the crown land portion acts. Further, since such an intermediate portion is provided in the central portion in the tire axial direction where the rigidity of the land portion is high, deformation of the middle land portion is suppressed, and wear resistance performance and rolling resistance performance are improved. Since the inner portion and the outer portion have a smaller angle in the tire axial direction than the middle portion, the inner portion of the middle land portion where the inner portion and the crown main groove intersect, and the middle portion where the shoulder main groove and the outer portion intersect. The rigidity of the outer part of the land is kept high. Therefore, excellent wear resistance performance and rolling resistance performance are exhibited.

  The inner side portion of the middle sipe is substantially continuous with the crown sipe through the crown main groove. That is, the crown sipe and the middle sipe form one virtual sipe that greatly extends in the tire axial direction. Since such a virtual sipe exerts a large scratching force, it is possible to more effectively discharge the water film on the treads of the crown land portion and the middle land portion.

  Therefore, the tire of the present invention has a well-balanced improvement in wet performance, rolling resistance performance, and wear resistance performance.

It is a development view of a tread part showing one embodiment of the present invention. It is an enlarged view of the crown land portion of FIG. (A) is sectional drawing of a crown sipe, (b) is sectional drawing of a middle sipe. (A) is sectional drawing which shows the grounding state of the crown sipe of this embodiment, (b) is sectional drawing which shows the grounding state of the crown sipe of other embodiment. It is an enlarged view of the middle land part of FIG. It is a development view of a tread portion of a comparative example.

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

  The tread portion 2 of this embodiment has a predetermined rotation direction R. In this specification, the direction of the arrow indicates the first-arrival side of the ground contact by rotation. The rotation direction R is displayed, for example, in characters on the sidewall portion (not shown).

  The tread portion 2 has a pair of crown main grooves 3, 3 that continuously extend on both outer sides of the tire equator C in the tire circumferential direction, and a pair that continuously extends axially outer sides of the crown main groove 3 in the tire circumferential direction. Shoulder main grooves 4 and 4 are provided.

  In the present embodiment, the crown main groove 3 and the shoulder main groove 4 extend in a zigzag shape in the tire circumferential direction. Such main grooves 3 and 4 can effectively collect a water film between the road surface and the land surface of the land near the crown main groove 3 and the shoulder main groove 4 when traveling on a wet road surface. Therefore, improve the wet performance.

  The crown main groove 3 is, for example, a first portion 3A that is inclined to one side with respect to the tire circumferential direction, and a second portion that has the same tire circumferential length as the first portion 3A and that is opposite to the first portion 3A. It is composed of a portion 3B. In such a crown main groove 3, the water in the crown main groove 3 smoothly flows to the trailing side of the rotation direction R, so that high wet performance is maintained. Also in the shoulder main groove 4 of the present embodiment, the first portion 4A inclined to one side with respect to the tire circumferential direction and the first portion 4A have the same tire circumferential length and are inclined to the opposite side to the first portion 4A. It is composed of the second portion 4B.

  The angle α1 of the crown main groove 3 with respect to the tire circumferential direction is preferably 5 to 20 degrees. That is, if the angle α1 of the crown main groove 3 is less than 5 degrees, there is a possibility that the water film between the tread surface and the road surface of the land portion near both sides of the crown main groove 3 cannot be effectively collected. When the angle α1 of the crown main groove 3 exceeds 20 degrees, the rigidity in the tire circumferential direction of the land portion near the crown main groove 3 decreases, and thus the rolling resistance performance may deteriorate. From the same viewpoint, the angle α2 of the shoulder main groove 4 with respect to the tire circumferential direction is also preferably 5 to 20 degrees. The angles α1 and α2 are angles at the groove center lines of the main grooves 3 and 4, respectively.

  The groove width W1 of the crown main groove 3 is preferably smaller than the groove width W2 of the shoulder main groove 4. When the groove width W1 of the crown main groove 3 is larger than the groove width W2 of the shoulder main groove 4, the rigidity of the crown land portion 5 having a high ground contact pressure may be insufficient and the rolling resistance performance may be deteriorated. From this point of view, the groove width W1 of the crown main groove 3 is preferably 30% to 70% of the groove width W2 of the shoulder main groove 4. From the viewpoint of improving the wet performance, the groove width W2 of the shoulder main groove 4 is preferably 2% to 6% of the tread width TW. The groove depth (not shown) of the crown main groove 3 and the shoulder main groove 4 is preferably 15 to 20 mm.

  The “tread width” TW is defined as the distance between the tread ends Te, Te in the tire axial direction. The tread end Te is the most tire axis when the tire 1 in a normal state in which the rim is assembled to the regular rim and filled with the regular internal pressure is in an unloaded state and the regular load is applied and the tire 1 is grounded on a plane at a camber angle of 0 degree. It is the grounding position on the outside in the direction. Unless otherwise specified, the dimensions and the like of each part of the tire are values measured in a normal state.

  The "regular rim" is a rim that is 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, ETRTO. If so, it is "Measuring Rim".

  "Regular internal pressure" is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. For JATMA, "maximum air pressure", and for TRA, the table "TIRE LOAD LIMITS" The maximum value described in "AT VARIOUS COLD INFLATION PRESSURES" is "INFLATION PRESSURE" for ETRTO. When the tire is for passenger cars, the normal internal pressure is 180 kPa.

  "Regular load" is the load that each standard defines for each tire in the standard system including the standard on which the tire is based. For JATMA, "maximum load capacity", and for TRA, the table "TIRE LOAD The maximum value stated in "LIMITS AT VARIOUS COLD INFLATION PRESSURES" is "LOAD CAPACITY" for ETRTO. When the tire is for a passenger car, the regular load is a load equivalent to 88% of the above load.

  In the tread portion 2 of the present embodiment, the crown land portion 5, the pair of middle land portions 6, and the pair of shoulder land portions 7 are divided by the crown main groove 3 and the shoulder main groove 4 as described above. There is. The crown land portion 5 is provided between the pair of crown main grooves 3, 3. The middle land portion 6 is provided between the crown main groove 3 and the shoulder main groove 4. The shoulder land portion 7 is provided outside the shoulder main groove 4.

  The crown land portion 5 is provided with a plurality of crown sipes 12 that communicate between the crown main grooves 3 and 3 in the tire circumferential direction.

  FIG. 2 is an enlarged view of the crown land portion 5 of FIG. As shown in FIG. 2, the crown sipe 12 has a substantially V-shape that inclines toward the rear-end side of the rotation direction R from both ends (outer ends) 12e, 12e in the tire axial direction from the central top 12c. Is. Since such a crown sipe 12 has an edge component in the tire circumferential direction, the rolling of the tire 1 is utilized to form a water film between the tread surface of the crown land portion 5 and the road surface on both sides of the crown main groove 3, 3 can be effectively discharged. Therefore, the wet performance is improved. In the present embodiment, the top portion 12c is provided on the tire equator C, and extends linearly from the top portion 12c to both ends 12e, 12e.

  The crown sipe 12 preferably has an angle α3 with respect to the tire axial direction of 5 to 15 °. If the angle α3 of the crown sipe 12 is less than 5 °, the edge component in the tire circumferential direction becomes small, and the water film may not be smoothly discharged into the crown main grooves 3, 3. If the angle α3 of the crown sipe 12 exceeds 15 °, the rigidity of both side portions of the crown land portion 5 in the tire axial direction may decrease, and the rolling resistance performance may deteriorate.

  FIG. 3A is a cross-sectional view orthogonal to the longitudinal direction of the crown sipe 12. As shown in FIG. 3 (a), the crown sipe 12 includes a first wall surface 12 a that is disposed on the first-arrival side in the rotation direction R and extends in the tire radial direction, and a first wall surface 12 a that faces the first wall surface 12 a and a rear-arrival side of the rotation direction R. And a second wall surface 12b arranged in the direction of the tire and extending in the tire radial direction. Each wall surface 12a, 12b of the crown sipe 12 extends linearly in the present embodiment.

  In the present embodiment, the crown sipe 12 is inclined inward in the tire radial direction toward the rear side of the rotation direction R in the present embodiment. As a result, as shown in FIG. 4 (a), when the tire 1 is braked, the second wall surface 12 b and the first wall surface 12 a of the crown sipe 12 closely contact and support each other, so that the rigidity of the crown land portion 5 is high. Secured. Moreover, such a crown sipe 12 can remove a water film by the edge e of the 2nd wall surface 12b of the crown sipe 12 at the time of braking of the tire 1. Therefore, wet performance and wear resistance performance are improved.

  In order to effectively exhibit the above-mentioned effect, the angle S1 of the crown sipe 12 with respect to the tire normal line N is preferably 5 to 15 °. That is, when the angle θ1 of the crown sipe 12 is less than 5 °, the first wall surface 12a and the second wall surface 12b are separated from each other when the tire 1 is braked, as shown in FIG. 4B. Large slippage occurs in the crown land portion 5 near the wall surface 12a. Therefore, there is a possibility that the wet performance and the wear resistance performance may not be improved. If the angle θ1 of the crown sipe 12 exceeds 15 °, the rigidity of the crown land portion 5 in the vicinity of the crown sipe 12 may be excessively reduced, and the rolling resistance performance and the wear resistance performance may be deteriorated. The tire normal line N is a tire radial direction line passing through the tire rotation axis.

  The width W3 (shown in FIG. 2) of the crown sipe 12 is preferably 0.3 to 1.0 mm. The depth D1 (shown in FIG. 3A) of the crown sipe 12 in the tire radial direction is preferably 65% to 100% of the groove depth of the crown main groove 3. In such a crown sipe 12, both wall surfaces 12a and 12b effectively support each other and exhibit an excellent scratching force.

  The crown land portion 5 is provided with only the substantially V-shaped crown sipes 12. That is, the crown land portion 5 of this embodiment is not provided with other sipes or grooves. Such a crown land portion 5 maintains a large land rigidity, and exhibits excellent rolling resistance performance and wear resistance performance.

  The maximum width Lc in the tire axial direction of the crown land portion 5 is preferably set to, for example, 18 to 22% of the tread width TW. As a result, the rigidity of the crown land portion 5 on which a large ground pressure acts can be secured to be large, so that the rolling resistance performance can be maintained high.

  FIG. 5 is an enlarged view of the middle land portion 6 of FIG. As shown in FIG. 5, the middle land portion 6 has an inner land portion edge 6x and an outer land portion edge 6y which are edges of the tread surface of the middle land portion 6. The inner land portion edge 6x extends in the tire circumferential direction from the inner end of the middle land portion 6 in the tire axial direction. The outer land edge 6y extends in the tire circumferential direction at the outer end of the middle land portion 6 in the tire axial direction.

  The inner land portion edge 6x and the outer land portion edge 6y of the present embodiment are formed in a zigzag shape. As a result, the middle land portion 6 has an inner projecting corner point 6a where the inner land portion edge 6x is convex inward in the tire axial direction and an inner entering corner point 6b where the inner land portion edge 6x is projecting outward in the tire axial direction. Are provided alternately in the tire circumferential direction. Further, the middle land portion 6 has an outer projecting corner point 6c in which the outer land portion edge 6y is convex outward in the tire axial direction and an outer entering corner point 6d in which the outer land portion edge 6y is convex inward in the tire axial direction. They are provided alternately in the tire circumferential direction.

  The middle land portion 6 is provided with a plurality of middle sipes 13 that communicate the crown main groove 3 and the shoulder main groove 4 in the tire circumferential direction. In the present embodiment, the middle sipe 13 includes an inner portion 16, an intermediate portion 17, and an outer portion 18.

  The inner portion 16 is continuously inclined from the crown main groove 3 toward the shoulder main groove 4 toward the rearward side in the rotational direction. The intermediate portion 17 continuously inclines toward the rear side in the rotational direction at an angle larger than that of the inner portion 16 from the outer end 16e of the inner portion 16 in the tire axial direction toward the shoulder main groove 4 side. The outer side portion 18 communicates with the shoulder main groove 4 by continuously inclining toward the shoulder main groove 4 side from the tire axial direction outer end 17e of the middle portion 17 at a smaller angle than the middle portion 17 toward the rear side in the rotational direction. is doing. In this way, the middle sipe 13 is formed in a substantially hook shape.

  Since the middle sipe 13 has an edge component in the tire circumferential direction, the rolling of the tire 1 can be used to discharge the water film between the tread surface of the middle land portion 6 and the road surface to the shoulder main groove 4. Further, since the intermediate portion 17 that is inclined at a larger angle than the inner portion 16 has a large edge component in the tire circumferential direction, the water film can be effectively discharged into the shoulder main groove 4. Therefore, the water film is smoothly discharged even in the middle land portion 6 where a ground pressure smaller than that in the crown land portion 5 acts. Further, since such an intermediate portion 17 is provided in the central portion in the tire axial direction where the rigidity of the land portion is high, the deformation of the middle land portion 6 is suppressed, and the rolling resistance performance is maintained high. Since the inner portion 16 and the outer portion 18 have a smaller angle in the tire axial direction than the intermediate portion 17, the inner portion 6i of the middle land portion 6 where the inner portion 16 and the crown main groove 3 intersect, and the shoulder main groove 4 The rigidity of the outer part 6s of the middle land part 6 where the outer part 18 and the outer part 18 intersect is maintained high. Therefore, the rolling resistance performance is further improved.

  In the present embodiment, the middle sipe 13 includes a first middle sipe 13A that joins the inner projecting corner point 6a and the outer projecting corner point 6c, and a second middle sipe 13B that joins the inner working corner point 6b and the outer working corner point 6d. .. That is, since the first middle sipe 13A is provided at the maximum width position of the middle land portion 6, it has a large edge component, so that the wet performance is improved. Further, the second middle sipe 13B is provided at the minimum width position of the middle land portion 6, but since the second middle sipe 13B has a substantially hook shape, excessive deformation of this portion is suppressed, so that the rolling resistance performance is improved. Is greatly suppressed.

  The inner side portion 16 of the middle sipe 13 is substantially connected to the crown sipe 12 via the crown main groove 3. As a result, the crown sipes 12 and the middle sipes 13 are grounded almost at the same time. Therefore, the crown sipe 12 and the middle sipe 13 form one virtual sipe that greatly extends in the tire axial direction. Since such a virtual sipe exerts a large scratching force, the water film on the treads of the crown land portion 5 and the middle land portion 6 can be more effectively discharged. In particular, since the crown sipes 12 and the middle sipes 13 are continuously inclined in the same direction on both sides of the tire equator C, the above-described action is effectively exhibited.

  The phrase “substantially connected” includes the case where the crown sipes 12 are provided on the virtual line 13k obtained by smoothly extending the center line 13c of the middle sipes 13. Further, “substantially continuous” means that the tire circumferential direction distance L1 between the tire axial outer end 12e of the crown sipe 12 and the imaginary line 13k of the middle sipe 13 is 80 which is the groove width W1 of the crown main groove 3. Including the case of% or less.

  In order to further enhance the above-mentioned action, it is desirable that the imaginary line 13k of the middle sipe 13 is provided on the tire axial direction outer end 12e position of the crown sipe 12 on the rotational direction R side of the outer end 12e. Since the middle sipe 13 of this embodiment has the overlapping portion 13t that overlaps the crown sipe 12 in the tire circumferential direction, the wet performance and the rolling resistance performance are improved in a well-balanced manner.

  The angle α5 of the intermediate portion 17 of the middle sipe 13 with respect to the tire axial direction is preferably 35 to 50 °. When the angle α5 of the intermediate portion 17 is less than 35 °, the edge component in the tire circumferential direction becomes small, so that the shoulder main groove 4 side can be smoothly smoothed especially in the tire axial direction central portion of the middle land portion 6 where it is difficult to discharge the water film. The water film may not be discharged. When the angle α5 of the intermediate portion 17 exceeds 50 °, the rigidity in the vicinity of the intermediate portion 17 of the middle land portion 6 is reduced, and thus the rolling resistance performance may be deteriorated.

  It is desirable that the angle α4 of the inner portion 16 with respect to the tire axial direction and the angle α6 of the outer portion 18 with respect to the tire axial direction be 5 to 15 °. When the angle α6 of the outer side portion 18 and the angle α4 of the inner side portion 16 are less than 5 °, the edge component in the tire circumferential direction of the inner side portion 16 and the outer side portion 18 becomes small, and the water film is smoothly discharged to the shoulder main groove 4 side. It may not be possible. When the angle α6 of the outer side portion 18 and the angle α4 of the inner side portion 16 exceed 15 °, the rigidity of the inner portion 6i of the middle land portion 6 and the outer portion 6s of the middle land portion 6 which have low rigidity decreases. The rolling resistance performance may deteriorate.

  FIG. 3B is a transverse sectional view orthogonal to the longitudinal direction of the middle sipe 13. As shown in FIG. 3B, the middle sipe 13 is arranged on the first-arrival side in the rotation direction R and extends in the tire radial direction, and the first wall surface 13a is arranged on the last-arrival side in the rotation direction R and extends in the tire radial direction. It has the 2nd wall surface 13b. The wall surfaces 13a and 13b of the middle sipe 13 extend linearly in the present embodiment.

  In the present embodiment, the middle sipe 13 is inclined inward in the tire radial direction toward the rear side of the rotation direction R in the cross section. Like the crown sipe 12, the middle sipe 13 as described above maintains the rigidity of the middle land portion 6 at a high level because the second wall surface 13b and the first wall surface 13a closely support each other during braking of the tire 1. Since the water film is effectively removed by the edge of the second wall surface 13b, the wet performance and wear resistance performance are greatly improved.

  As described above, in the present embodiment, the substantially V-shaped crown sipe 12 and the substantially hook-shaped middle sipe 13 are inclined inward in the tire radial direction toward the trailing side of the rotation direction R in the cross section. .. As a result, in the crown land portion 5 and the middle land portion 6 where the scratching force is effectively exerted, the wet performance is enhanced, and particularly, a large braking force acts, the crown land portion 5 and the middle land portion 6 at the time of grounding. Keeps high rigidity and enhances wear resistance and wet performance.

  Further, for example, when manufacturing a tire using a tire mold, each sipe 12, 13 is formed by a knife blade (not shown) having the same shape as each sipe 12, 13 provided on the tire mold. That is, the crown sipe 12 is formed by a substantially V-shaped knife blade in plan view, and the middle sipe 13 is formed by a substantially hook-shaped knife blade. Then, when the knife blade is inserted into the rubber material for tire molding and the rubber is vulcanized, a large compressive load acts on the knife blade. Further, when pulling out the tire mold after rubber vulcanization, a large tensile load acts on the knife blade. However, since the substantially V-shaped knife blade and the substantially hook-shaped knife blade have large rigidity due to bending, bending deformation due to compressive load or tensile load is suppressed.

As with the crown sipe 12, the middle sipe 13 preferably has an angle θ2 with respect to the tire normal line N of 5 to 15 °. If the angle θ2 of the middle sipe 13 is less than 5 °, wet performance and abrasion resistance may not be improved. If the angle θ2 of the middle sipe 13 exceeds 15 °, the rigidity of the middle land portion 6 in the vicinity of the middle sipe 13 may be excessively reduced, and the rolling resistance performance and the wear resistance performance may be deteriorated.

  In order to further improve the wet performance while maintaining the rolling resistance performance, it is desirable that the middle sipes 13 and the crown sipes 12 be provided at the same pitch. The number of crown sipes 12 and middle sipes 13 provided on each land portion 5, 6 is preferably 35 to 55.

  In the present embodiment, only the middle hook-shaped middle sipes 13 are provided on the middle land portion 6. That is, the middle land portion 6 is not provided with a groove-shaped body including sipes other than the substantially hook shape. Accordingly, the rigidity of the middle land portion 6 is maintained high, and the water film on the tread surface of the middle land portion 6 is effectively discharged by the substantially hook-shaped middle sipes 13. The maximum width Lm in the tire axial direction of the middle land portion 6 is preferably set to, for example, 18% to 22% of the tread width TW.

  The width W4 (shown in FIG. 2) of the middle sipe 13 is preferably 0.3 to 1.0 mm. The depth D2 (shown in FIG. 3B) of the middle sipe 13 in the tire radial direction is preferably 65% to 100% of the groove depth of the crown main groove 3. In such a middle sipe 13, both wall surfaces 13a and 13b effectively support each other and exhibit an excellent scratching force.

  As shown in FIG. 1, the shoulder land portion 7 is provided with shoulder sipes 14 and shoulder lateral grooves 15 alternately in the tire circumferential direction. The shoulder lateral groove 15 connects the shoulder main groove 4 and the tread end Te. As a result, the shoulder land portion 7 is formed as a block row in which a plurality of shoulder blocks 7A that are divided by the shoulder main groove 4, the tread end Te, and the shoulder lateral groove 15 are provided in the tire circumferential direction.

  The shoulder sipe 14 connects the shoulder main groove 4 and the tread end Te. The shoulder sipe 14 extends linearly from the shoulder main groove 4 toward the tread end Te side toward the rear side in the rotational direction. Since the shoulder sipe 14 has an edge component in the tire circumferential direction, the water film between the tread surface of the shoulder land portion 7 and the road surface is effectively discharged to the outside of the tread end Te, so that it is wet. Improve performance.

  As shown in FIG. 5, the shoulder sipe 14 is substantially connected to the outer side portion 18 of the middle sipe 13 via the shoulder main groove 4. As a result, the shoulder sipe 14 and the middle sipe 13 form one virtual sipe that greatly extends in the tire axial direction. Since this virtual sipe exerts a large scratching force, the water film on the treads of the shoulder land portion 7 and the middle land portion 6 can be discharged more effectively. In particular, since the shoulder sipes 14 and the middle sipes 13 are continuously inclined in the same direction, the above-mentioned action is effectively exhibited.

  The term “substantially connected” includes the case where the shoulder sipes 14 are provided on the virtual line 13k obtained by smoothly extending the centerline 13c of the middle sipe 13. Also, when the tire circumferential direction distance L2 between the tire axial inner end 14i of the shoulder sipe 14 and the imaginary line 13k of the middle sipe 13 is 70% or less of the groove width W2 of the shoulder main groove 4, "substantially continuous. Included. In the present embodiment, the crown sipe 12, the middle sipe 13, and the shoulder sipe 14 are substantially continuous, so the wet performance is further improved.

  The tire axially inner end 14i of the shoulder sipe 14 is preferably provided on the rotational direction R side of the middle sipe 13 at the virtual axial line 13k at the tire axial position. As a result, the wet performance is improved more effectively.

  As shown in FIG. 1, the shoulder lateral groove 15 extends linearly from the shoulder main groove 4 toward the trailing side of the rotation direction R toward the tread end Te side. Such shoulder lateral grooves 15 smoothly discharge the water in the grooves to the outside of the tread end Te by utilizing the rolling of the tire 1.

  The shoulder lateral groove 15 overlaps the outer end 18e of the outer side portion 18 of the middle sipe 13 in the tire axial direction via the shoulder main groove 4 in the tire circumferential direction. As a result, the water film on the tread surface of the middle land portion 6 discharged into the shoulder main groove 4 by the middle sipe 13 is also discharged through the shoulder lateral groove 15. From such a viewpoint, it is desirable that the opening end 15e of the shoulder lateral groove 15 in the shoulder main groove 4 and the outer end 18e of the outer portion 18 overlap in the tire circumferential direction.

  The angle α7 of the shoulder sipe 14 with respect to the tire axial direction is preferably 5 to 15 °. The angle α8 of the shoulder lateral groove 15 with respect to the tire axial direction is preferably 5 to 15 °. When the angle α7 of the shoulder sipe 14 and the angle α8 of the shoulder lateral groove 15 are less than 5 °, the water film or water in the groove may not be smoothly discharged to the outside of the tread end Te. When the angle α7 of the shoulder sipe 14 and the angle α8 of the shoulder lateral groove 15 exceed 15 °, the deformation of the shoulder land portion 7 is not suppressed, and the rolling resistance performance may deteriorate. From the viewpoint of maintaining high rigidity of the shoulder land portion 7, it is desirable that the angle α7 of the shoulder sipe 14 and the angle α8 of the shoulder lateral groove 15 be the same.

  The width W5 of the shoulder sipe 14 is preferably 10% to 30% of the groove width W2 of the shoulder main groove 4, for example. The width W6 of the shoulder lateral groove 15 is preferably 40% to 80% of the groove width W2 of the shoulder main groove 4, for example. The depth of the shoulder sipe 14 and the groove depth (not shown) of the shoulder lateral groove 15 are preferably 15% to 35% of the groove depth of the shoulder main groove 4. It is desirable that the depth of the shoulder sipe 14 and the groove depth of the shoulder lateral groove 15 are the same.

  The maximum width Ls in the tire axial direction of the shoulder land portion 7 where the shoulder sipes 14 and the shoulder lateral grooves 15 are provided is preferably set to, for example, 16 to 19% of the tread width TW. That is, the maximum width Ls of the shoulder land portion 7 is preferably smaller than the maximum width Lm of the middle land portion 6 and the maximum width Lc of the crown land portion 5. As a result, since the rigidity of the crown land portion 5 and the middle land portion 6 on which a relatively large ground pressure acts is maintained high, the rolling resistance performance is effectively reduced even when the sipes 12 and 13 are provided. Suppressed.

  In order to make the pattern rigidity of the tread portion 2 and the drainage property compatible with each other at a high level, the land ratio of the tire 1 of the present embodiment is set to 75 to 85%. The land ratio is represented by a ratio Sb / Sa of a total ground contact surface area Sa of the tread part 2 obtained by filling all grooves and sipes of the tread part 2 and a total ground contact surface area Sb of all land parts of the tread part 2. It When the land ratio Sb / Sa is less than 75%, the rigidity of the tread portion 2 is reduced, rolling resistance is increased, and steering stability is reduced. On the contrary, when the land ratio Sb / Sa is larger than 85%, the groove volume becomes small and the wet performance deteriorates. The "ground contact surface area" is measured as the ground contact surface area when the tire 1 in the normal state is loaded with the normal load and rolled on a plane at a camber angle of 0 degree.

  Although the embodiments of the present invention have been described in detail above, it is needless to say that the present invention is not limited to the illustrated embodiments and can be modified into various modes for implementation.

A heavy-duty pneumatic tire having a size of 315 / 80R22.5 forming the basic pattern of FIG. 1 was prototyped based on the specifications of Table 1, and the rolling resistance performance and the wet performance of each test tire were tested. The test method is as follows. The "-" sign of the "tire circumferential distance L1 / W1" in the example indicates that the outer end of the crown sipe is on the rotation direction R side with respect to the imaginary line of the middle sipe. In addition, the “−” signs of the “crown sipe angle θ1” and the “middle sipe angle θ2” in the example are, in a cross section, the crown sipe or the middle sipe toward the inner side in the tire radial direction toward the first arrival side in the rotation direction. It shows that it is inclined.
Groove depth of crown main groove and shoulder main groove: 17.2 mm
Crown sipe and middle sipe depths D1 and D2: 14.2 mm

<Rolling resistance performance>
The rolling resistance of each test tire was measured by a rolling resistance tester. The measurement conditions are shown below. The result is an index in which the reciprocal of the rolling resistance value of Comparative Example 1 is 100, and the larger the value is, the better the rolling resistance performance is.
Mounting rim: 7.50 x 22.5
Internal pressure: 800 kPa
Vertical load: 29.42kN
Speed 80km / h

<Wet performance>
A test vehicle equipped with all the test tires on all wheels was run on a wet asphalt road surface. When the speed of the test vehicle was 65 km / h, the brake was actuated, and the braking time from deceleration from 60 km / h to 20 km / h was measured. The result is an index in which the reciprocal of the braking time of Comparative Example 1 is 100, and the larger the value, the shorter the braking time and the better.
Mounting rim: 7.50 x 22.5
Internal pressure: 800 kPa
Test vehicle: 2-D vehicle (load capacity 10t)
Depth of road surface: 2.0 mm

<Abrasion resistance>
Using the above test vehicle, a test course on a dry road surface was run for 20,000 km. Then, the wear amount (height in the radial direction of the tire) of each main groove and lateral groove of all the wheels was measured. The measurement was carried out at eight locations on the tire circumference in each main groove and each sipe, and the average value of all was obtained. The result is an index with the reciprocal of the average wear amount of Comparative Example 1 being 100, and the larger the value, the better.
Average speed 80km / h
The test results are shown in Table 1.

  As is clear from Table 1, it can be confirmed that the pneumatic tires of Examples have significantly improved wet performance, rolling resistance performance, and wear resistance performance as compared with Comparative Examples.

1 Tire 3 Crown Main Groove 4 Shoulder Main Groove 5 Crown Land 6 Middle Land 12 Crown Sipe 13 Middle Sipe 16 Inner Part 16e Inner Part Outer End 17 Middle Part 17e Middle Part Outer End 18 Outer Part R Rotation Direction

Claims (9)

A tire having a tread portion whose rotation direction is designated,
The tread portion, a pair of crown main grooves that continuously extend on both sides of the tire equator in the tire circumferential direction, and a pair of shoulder main grooves that continuously extend on the tire axial direction outer side of the crown main groove in the tire circumferential direction. Is provided,
A crown land portion divided by the pair of crown main grooves, and a pair of middle land portions divided by the crown main groove and the shoulder main groove are formed,
In the crown land portion, a plurality of crown sipes communicating between the crown main grooves are provided in the tire circumferential direction,
In the middle land portion, a plurality of middle sipes that connect the crown main groove and the shoulder main groove are provided in the tire circumferential direction,
The crown sipe has a substantially V-shape that inclines toward the rear side in the rotational direction from the top on the center side toward both ends.
The middle sipe includes an inner portion that is inclined from the crown main groove toward the shoulder main groove side toward the rear side in the rotational direction, and an inner portion that is located from the tire axial outer end of the inner portion toward the shoulder main groove side. An intermediate portion that inclines toward the rearward side in the rotational direction at a larger angle, and an inclination toward the rearward side in the rotational direction at an angle that is smaller than the intermediate portion from the tire axial direction outer end of the intermediate portion toward the shoulder main groove side. It has a substantially hook shape including an outer side portion,
It said inner portion of said Midorusaipu is Ri substantially communication with the crown sipes through the crown main grooves,
The crown sipes and the Midorusaipu are each tire in cross-section perpendicular to the longitudinal direction, characterized that you have inclined called side after the rotating direction towards the inside in the tire radial direction. A tire having a tread portion whose rotation direction is designated,
The tread portion, a pair of crown main grooves extending continuously on both outer sides of the tire equator in the tire circumferential direction, and a pair of shoulder main grooves extending continuously on the tire axial direction outer side of the crown main groove in the tire circumferential direction. Is provided,
A crown land portion divided by the pair of crown main grooves, and a pair of middle land portions divided by the crown main groove and the shoulder main groove are formed,
In the crown land portion, a plurality of crown sipes communicating between the crown main grooves are provided in the tire circumferential direction,
In the middle land portion, a plurality of middle sipes that connect the crown main groove and the shoulder main groove are provided in the tire circumferential direction,
The crown sipe has a substantially V-shape that inclines toward the rear side in the rotational direction from the top on the center side toward both ends.
The middle sipe includes an inner portion that is inclined from the crown main groove toward the shoulder main groove side toward the rear side in the rotational direction, and an inner portion that is from the tire axial outer end of the inner portion toward the shoulder main groove side. An intermediate portion that inclines toward the rearward side in the rotational direction at a larger angle, and an inclination toward the rearward side in the rotational direction at an angle that is smaller than the intermediate portion from the tire axial direction outer end of the intermediate portion toward the shoulder main groove side. It has a substantially hook shape including an outer side portion,
The inner portion of the middle sipe is substantially continuous with the crown sipe via the crown main groove,
The cross section of the crown sipe orthogonal to the longitudinal direction has an angle of 5 to 15 ° with respect to the tire normal line,
A tire characterized in that the middle sipe has an angle of 5 to 15 ° with respect to a tire normal in a cross section orthogonal to the longitudinal direction thereof. A tire having a tread portion whose rotation direction is designated,
The tread portion, a pair of crown main grooves extending continuously on both outer sides of the tire equator in the tire circumferential direction, and a pair of shoulder main grooves extending continuously on the tire axial direction outer side of the crown main groove in the tire circumferential direction. Is provided,
A crown land portion divided by the pair of crown main grooves, and a pair of middle land portions divided by the crown main groove and the shoulder main groove are formed,
In the crown land portion, a plurality of crown sipes communicating between the crown main grooves are provided in the tire circumferential direction,
In the middle land portion, a plurality of middle sipes that connect the crown main groove and the shoulder main groove are provided in the tire circumferential direction,
The crown sipe has a substantially V shape that inclines toward the rear side in the rotational direction from the top on the center side toward both ends,
The middle sipe includes an inner portion that is inclined from the crown main groove toward the shoulder main groove side toward the rear side in the rotational direction, and an inner portion that is located from the tire axial outer end of the inner portion toward the shoulder main groove side. An intermediate portion that inclines toward the rearward side in the rotational direction at a larger angle, and an inclination toward the rearward side in the rotational direction at an angle that is smaller than the intermediate portion from the tire axial direction outer end of the intermediate portion toward the shoulder main groove side. It has a substantially hook shape including an outer side portion,
The inner portion of the middle sipe is substantially continuous with the crown sipe via the crown main groove,
A tire characterized in that only the substantially V-shaped crown sipes are provided on the crown land portion. A tire having a tread portion whose rotation direction is designated,
The tread portion, a pair of crown main grooves extending continuously on both outer sides of the tire equator in the tire circumferential direction, and a pair of shoulder main grooves extending continuously on the tire axial direction outer side of the crown main groove in the tire circumferential direction. Is provided,
A crown land portion divided by the pair of crown main grooves, and a pair of middle land portions divided by the crown main groove and the shoulder main groove are formed,
In the crown land portion, a plurality of crown sipes communicating between the crown main grooves are provided in the tire circumferential direction,
In the middle land portion, a plurality of middle sipes that connect the crown main groove and the shoulder main groove are provided in the tire circumferential direction,
The crown sipe has a substantially V shape that inclines toward the rear side in the rotational direction from the top on the center side toward both ends,
The middle sipe includes an inner portion that is inclined from the crown main groove toward the shoulder main groove side toward the rear side in the rotational direction, and an inner portion that is from the tire axial outer end of the inner portion toward the shoulder main groove side. An intermediate portion that inclines toward the rearward side in the rotational direction at a larger angle, and an inclination toward the rearward side in the rotational direction at an angle that is smaller than the intermediate portion from the tire axial direction outer end of the intermediate portion toward the shoulder main groove side. It has a substantially hook shape including an outer side portion,
The inner portion of the middle sipe is substantially continuous with the crown sipe via the crown main groove,
The tire, wherein the middle land portion is provided with only the substantially hook-shaped middle sipes. The tire according to claim 1 , wherein the middle sipe overlaps with the crown sipe in a tire circumferential direction . The tire according to any one of claims 1 to 5, wherein the angle of the middle portion of the middle sipe with respect to the tire axial direction is 35 to 50 ° . The tire according to claim 1 , wherein an angle of the outer side portion, the inner side portion of the middle sipe, and the crown sipe with respect to the tire axial direction is 5 to 15 ° . The tread portion is further formed with a shoulder land portion divided by the shoulder main groove and a tread end,
In the shoulder land portion, a plurality of shoulder sipes communicating the shoulder main groove and the tread end are provided in the tire circumferential direction,
The tire according to any one of claims 1 to 7, wherein the shoulder sipe extends linearly from the shoulder main groove toward the tread end side toward the trailing side in the rotational direction . The tire according to claim 8, wherein the shoulder sipe is substantially continuous with the outer side portion of the middle sipe via the shoulder main groove .

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