tire

Abstract

The tread pattern of this tire comprises: a pair of first circumferential main grooves provided in a first half-tread region on one tire-width-direction side; a pair of second circumferential main grooves provided in a second half-tread region; a plurality of first sipes that are provided in a first region between the first circumferential main grooves, the first spies communicating with one of the first circumferential main grooves, extending in the tire width direction, and being blocked within the first region; a circumferential microgroove that is narrower than the groove width of the first circumferential main grooves and extends in the tire width direction within the first region; and a plurality of second sipes that are provided in a second region between the second circumferential main grooves, the second sipes communicating with one or the other of the second circumferential main grooves, extending in the tire width direction, and being blocked within the first region. The number of intervals at which the second sipes are adjacent is greater than the number of intervals at which the first sipes are adjacent.

Description

[Technical field]

[0001] The present invention relates to a tire having a tread pattern in a tread portion. [Background technology]

[0002] In order to improve the wet performance of tires, it is known to provide lug grooves extending in the tire width direction in addition to the main grooves extending in the tire circumferential direction on the tread surface of the tire to ensure drainage. However, if the groove volume of the lug groove is large, the pumping noise generated at the time of kicking out becomes louder, and there is a problem that the performance of reducing tire noise (hereinafter referred to as noise performance) deteriorates.

[0003] 2. Description of the Related Art Conventionally, there is known a tire in which no grooves having a width of 2 mm or more are provided in the crown land portion and middle land portion of the tread portion (Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-226369 A Summary of the Invention [Problem to be solved by the invention]

[0005] If grooves 2 mm or wider are omitted from the crown and middle land areas of the tread surface, which have main grooves and lug grooves, in order to avoid deteriorating noise performance, the noise performance will improve as the groove volume is reduced. However, the reduced groove volume makes it difficult to ensure drainage, resulting in reduced wet performance.

[0006] An object of the present invention is to provide a tire which improves noise performance while suppressing deterioration of wet performance. [Means for solving the problem]

[0007] One aspect of the present invention is a tire having a tread pattern in a tread portion. The tread pattern is A pair of first circumferential main grooves are provided in a first half tread region on one side in the tire width direction with respect to a tire center line, extend in the tire circumferential direction, and are spaced apart from each other in the tire width direction; a pair of second circumferential main grooves provided in a second half tread region on the other side in the tire width direction, extending in the tire circumferential direction, and spaced apart from each other in the tire width direction; A plurality of first sipes are provided in a first region between the first circumferential main grooves, communicate with one of the first circumferential main grooves, extend in the tire width direction, and are closed within the first region; A circumferential narrow groove that is narrower than the groove width of the first circumferential main groove and extends in the tire circumferential direction within the first region; a plurality of second sipes provided in a second region between the second circumferential main grooves, communicating with one or the other of the second circumferential main grooves, extending in the tire width direction and closing within the first region; The tire is characterized in that the number of intervals between adjacent second sipes in the tire circumferential direction is greater than the number of intervals between adjacent first sipes in the tire circumferential direction.

[0008] It is preferable that the tread pattern does not include a lug groove provided in the first region, communicating with the first circumferential main groove and extending in the tire width direction, and a lug groove provided in the second region, communicating with the second circumferential main groove and extending in the tire width direction.

[0009] The second sipe is a second sipe A communicating with one of the second circumferential main grooves; It is preferable that the second sipe B communicates with the other of the second circumferential main grooves at a circumferential position of the tire different from a circumferential position of the tire where the second sipe A communicates with the circumferential main groove.

[0010] The second sipes A and the second sipes B are each provided at intervals in the tire circumferential direction, It is preferable that each of the second sipes B is disposed between two of the second sipes A adjacent to each other in the tire circumferential direction.

[0011] It is preferable that a direction connecting both ends of the second sipe A in the extension direction and a direction connecting both ends of the second sipe B in the extension direction are inclined toward the same side in the tire circumferential direction with respect to the tire width direction.

[0012] It is preferable that the length of the interval between the second sipes be different between adjacent intervals in the tire circumferential direction.

[0013] It is preferable that the first sipe communicates with the circumferential narrow groove.

[0014] A sipe depth of the narrow groove side connection portion of the first sipe connected to the circumferential narrow groove is shallower than a groove depth of the circumferential narrow groove, It is preferable that a sipe depth of an intermediate portion of the first sipe located between the first circumferential main groove to which the first sipe is connected and the narrow groove side connection portion is deeper than a groove depth of the circumferential narrow groove.

[0015] It is preferable that a sipe depth of a main groove side communicating portion of the first sipe communicating with the first circumferential main groove is shallower than a groove depth of the circumferential narrow groove.

[0016] The first sipe preferably extends in a curved shape so as to bulge roundly on one side in the tire circumferential direction on the tread surface.

[0017] It is preferable that the length of the first sipes in the extending direction is longer than the length of the second sipes in the extending direction.

[0018] It is preferable that the second sipes extend linearly, and that the inclination angles of the direction connecting both ends of the extension direction of the second sipes with respect to the tire width direction differ between the second sipes adjacent in the tire circumferential direction.

[0019] the tread pattern includes a third region between a first circumferential main groove that is closest to a tire centerline among the first circumferential main grooves and a second circumferential main groove that is closest to the tire centerline among the second circumferential main grooves, the third sipes communicate with one of the first circumferential main groove and the second circumferential main groove, extend in the tire width direction, and are closed within the third region; It is preferable that the number of intervals between the second sipes is greater than the number of intervals between adjacent third sipes in the tire circumferential direction.

[0020] The length of the second sipe in the tire width direction is half or less of the length of the second region in the tire width direction, The length of the third sipe in the tire width direction is preferably equal to or less than half the length of the third region in the tire width direction.

[0021] The tread pattern is preferably oriented on a vehicle such that the second half tread region is disposed on an outer side of the vehicle relative to the first half tread region. Effect of the Invention

[0022] According to the tire of the above aspect, it is possible to improve noise performance while suppressing deterioration of wet performance. [Brief description of the drawings]

[0023] [Figure 1] FIG. 2 is a diagram showing an example of a profile cross section of the pneumatic tire of the present embodiment. [Diagram 2] FIG. 2 is a diagram showing an example of a tread pattern of the tire shown in FIG. [Diagram 3] 11 is a diagram showing a cross section of a portion of the first middle region. FIG. [Figure 4] FIG. 4 is a perspective view showing a shape of a chamfered portion. [Diagram 5] FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] (Overall tire description) The tire of this embodiment will be described below. The tire of the present invention is preferably a pneumatic tire, and the tire of this embodiment is a pneumatic tire. A pneumatic tire is a tire in which air is filled into a hollow area surrounded by the tire and the rim. Note that the tire of this embodiment may be a tire in which an inert gas such as nitrogen or other gas is filled instead of air into the hollow area surrounded by the tire and the rim. This embodiment includes various embodiments described later.

[0025] FIG. 1 is a tire cross-sectional view showing an example of a profile cross-section of a pneumatic tire (hereinafter simply referred to as tire) 10. As shown in FIG. The tire 10 is, for example, a tire for a passenger car. A tire for a passenger car is a tire defined in Chapter A of the JATMA YEAR BOOK 2012 (Japan Automobile Tire Manufacturers Association standard). In addition, the tire 10 can be applied to a tire for a small truck defined in Chapter B and a tire for a truck and a bus defined in Chapter C.

[0026] The tire width direction is the direction parallel to the tire's rotation axis. The outer side in the tire width direction is the side away from the tire center line CL (tire equator line) representing the tire equatorial plane in the tire width direction. The inner side in the tire width direction is the side closer to the tire center line CL in the tire width direction. The tire circumferential direction is the direction in which the tire rotates around the tire's rotation axis. The tire radial direction is the direction perpendicular to the tire's rotation axis. The outer side in the tire radial direction is the side away from the rotation axis. The inner side in the tire radial direction is the side closer to the rotation axis.

[0027] (Tire structure) The tire 10 includes a tread portion 10T having a tread pattern, a pair of bead portions 10B, and a pair of side portions 10S provided on both sides of the tread portion 10T and connected to the pair of bead portions 10B and the tread portion 10T. The tire 10 has a carcass ply 12, a belt 14, and a bead core 16 as framework materials, and mainly has a tread rubber member 18, a side rubber member 20, a bead filler rubber member 22, a rim cushion rubber member 24, and an inner liner rubber member 26 around these framework materials.

[0028] The carcass ply 12 is made of a carcass ply material made of organic fibers covered with rubber, wound around a pair of annular bead cores 16 to form a toroidal shape. The carcass ply 12 is wound around the bead cores 16 and extends radially outward of the tire. A belt 14 made of two belt materials 14a, 14b is provided on the radially outward side of the carcass ply 12. The belt 14 is made of a member made of a rubber-covered steel cord arranged at a predetermined angle, for example, 20 to 30 degrees, with respect to the tire circumferential direction, and the belt material 14a of the inner layer is wider in the tire width direction than the belt material 14b of the outer layer. The inclination directions of the steel cords of the two layers of belt materials 14a, 14b are opposite to each other. Therefore, the belt materials 14a, 14b are intersecting layers, which suppress the expansion of the carcass ply 12 due to the air pressure filled in the tire.

[0029] A tread rubber member 18 is provided on the outer side of the belt 14 in the tire radial direction, and a side rubber member 20 is connected to both ends of the tread rubber member 18 to form a side portion 10S. A rim cushion rubber member 24 is provided on the inner end of the side rubber member 20 in the tire radial direction, which contacts the rim on which the tire 10 is mounted. A bead filler rubber member 22 is provided on the outer side of the bead core 16 in the tire radial direction so as to be sandwiched between a portion of the carcass ply 12 before being wound around the bead core 16 and a portion of the carcass ply 12 wound around the bead core 16. An inner liner rubber member 26 is provided on the inner surface of the tire 10 facing the tire cavity region filled with air surrounded by the tire 10 and the rim. In addition, a two-layer belt cover 30 made of organic fiber coated with rubber is provided between the belt material 14b and the tread rubber member 18, covering the belt 14 from the outer side of the belt 14 in the tire radial direction.

[0030] (Tread pattern) FIG. 2 is a diagram showing a part of an example of a tread pattern of the tire 10 in FIG. 1 developed on a plane.

[0031] The tread pattern of the example shown in FIG. 2 includes a first outer main groove 21, a first inner main groove 23, a second inner main groove 25, and a second outer main groove 27 as circumferential main grooves extending in the tire circumferential direction. The first outer main groove 21 and the first inner main groove 23 are provided in a first half tread region on one side in the tire width direction (the left side in Figure 2) of the tire center line CL, and are arranged at intervals from each other in the tire width direction. The second inner main groove 25 and the second outer main groove 27 are provided in a second half tread region on the other side in the tire width direction (the right side in FIG. 2), and are spaced apart from each other in the tire width direction.

[0032] In this specification, the main groove means a groove having a groove depth of, for example, 6.5 to 9.0 mm and a groove width of, for example, 5.0 to 15.0 mm. The number of main grooves provided in the tread pattern is four in the example shown in Fig. 2, but may be three, five, etc. In the case of three main grooves, one circumferential main groove passing through the tire centerline CL is provided instead of the first inner main groove 23 and the second inner main groove 25 in the example shown in Fig. 2.

[0033] The tread pattern of the example shown in Fig. 2 further includes narrow grooves 31 and 33 as two circumferential narrow grooves extending in the tire circumferential direction. The narrow grooves 31 and 33 have a narrower groove width than the main grooves 21, 23, 25 and 27. It is preferable that the narrow grooves 31 and 33 have a shallower groove depth than the main grooves 21, 23, 25 and 27. The groove depth of the narrow grooves 31 and 33 is, for example, 1.0 to 5.0 mm, and the groove width of the narrow grooves 31 and 33 is, for example, 0.8 to 3.0 mm. The narrow groove 31 is provided in a shoulder region 77 of the tread pattern on the outer side of the first outer main groove 21 in the tire width direction. The narrow groove 33 is provided in a first middle region (first region) 71 between the first outer main groove 21 and the first inner main groove 23. The narrow groove 33 is located in the first middle region 71 on the first inner main groove 23 side relative to the center of the first middle region 71 in the tire width direction. According to one embodiment, it is preferable that the circumferential narrow groove is not provided in a second middle region 75 and a center region 73, which will be described later. In the tread pattern of the example shown in Fig. 2, the circumferential narrow groove is not provided in a shoulder region 79, which will be described later.

[0034] The tread pattern of the example shown in Fig. 2 further includes a first sipe 51, second sipes 55, 57, and a third sipe 53. The first sipe 51, the second sipes 55, 57, and the third sipe 53 ensure edge components extending in the tire width direction, thereby improving the edge effect against forces in the front-rear direction (directions in the contact surface parallel to the tire circumferential direction). In this specification, the sipe refers to a sipe having a sipe depth of, for example, 2.0 to 7.5 mm and a sipe width of, for example, 0.3 to 1.0 mm.

[0035] The first sipes 51 are provided in the first middle region 71 at intervals in the tire circumferential direction, communicate with the first outer main groove 21, extend in the tire width direction, and are closed within the first middle region 71. According to one embodiment, the first sipes 51 may communicate with the first inner main groove 23 instead of communicating with the first outer main groove 21.

[0036] The second sipes 55 (second sipes A) are provided in multiple locations spaced apart in the circumferential direction of the tire in a second middle region 75 between the second inner main groove 25 and the second outer main groove 27, are connected to the second inner main groove 25, extend in the tire width direction and are closed within the second middle region 75.

[0037] The second sipes 57 (second sipes B) are provided in multiple spaces spaced apart in the tire circumferential direction in the second middle region 75, communicate with the second outer main groove 27, and extend through the second middle region 75 in the tire width direction without reaching the second inner main groove 25, but are closed within the second middle region 75.

[0038] According to one embodiment, the second middle region 75 may be provided with only one of the second sipes 55 and the second sipes 57 .

[0039] The third sipes 53 are provided in a plurality of positions spaced apart in the tire circumferential direction in a center region (third region) 73 between the first inner main groove 23 and the second inner main groove 25, communicate with the first inner main groove 23, extend in the tire width direction, and are closed within the center region 73. According to one embodiment, the third sipes 53 may communicate with the second inner main groove 25 instead of communicating with the first inner main groove 23.

[0040] In this embodiment, the number of intervals G2 between the second sipes 55, 57 adjacent to each other in the tire circumferential direction (hereinafter, referred to as the interval G2 between the second sipes 55, 57) is greater than the number of intervals G1 between the first sipes 51 adjacent to each other in the tire circumferential direction (hereinafter, referred to as the interval G1 between the first sipes 51). The interval between adjacent sipes in the tire circumferential direction refers to the interval between adjacent positions in the tire circumferential direction at positions where a line extending from the sipe along the shape of the sipe extending on the tread surface intersects with the groove wall of the main groove to which the sipe is connected (hereinafter, also referred to as the connecting position). Two adjacent connecting positions may be located in the same main groove or may be located in different main grooves. Therefore, the interval between second middle sipes having connecting positions at the same circumferential position in the region is not included in the "interval between adjacent sipes in the tire circumferential direction".

[0041] In this embodiment, the sipes 51, 55, 57 are provided in the first middle region 71 and the second middle region 75, so that the groove volume is smaller and the noise performance is improved compared to the case where lug grooves are provided instead of the sipes 51, 55, 57. On the other hand, the fine grooves 33 are provided in the first middle region 71, so that the decrease in drainage caused by providing the sipes 51 instead of the lug grooves is compensated for, and the decrease in steering stability performance (wet performance) on wet road surfaces is suppressed. In addition, as described above, in the second middle region 75, the number of intervals G2 of the second sipes 55, 57 is greater than the number of intervals G1 of the first sipes 51, so that the rigidity of the land portion of the second middle region 75 is reduced and the land portion is easily deformed, and the followability to the road surface is high. Therefore, in the second middle region 75, the adhesion friction with the road surface is large, and the above-mentioned effect of suppressing the decrease in wet performance is enhanced. That is, in this embodiment, noise performance is improved while wet performance deterioration is suppressed compared to the case where lug grooves are provided instead of the sipes 51, 55, 57. In this embodiment, the two middle regions 71, 75 have different shapes, and as described above, exert different functions with respect to wet performance, thereby obtaining an effect of suppressing the deterioration of wet performance. Thus, in this embodiment, the tread pattern is asymmetric with respect to the tire center line CL.

[0042] Here, if the number of the intervals G2 of the second sipes 55, 57 is equal to or less than the number of the intervals G1 of the first sipes 51, the rigidity of the second middle region 75 is too high, the land portion is difficult to deform, and the followability to the road surface is not high. Therefore, the force to grip the road surface due to the change in the force received from the road surface becomes insufficient. According to one embodiment, the number of the intervals G2 of the second sipes 55, 57 is preferably 1.5 to 2.5 times, more preferably 1.8 to 2.2 times, the number of the intervals G1 of the first sipes 51. Also, according to one embodiment, the average of the intervals G2 of the second sipes 55, 57 in the second middle region 75 is preferably smaller than the average of the intervals G1 of the first sipes 51 in the first middle region 71.

[0043] The example tread pattern shown in FIG. 2 further includes shoulder lug grooves 58, 59. The shoulder lug grooves 58 are provided in multiple spaces spaced apart in the tire circumferential direction in a shoulder region 77 on the tire width direction outer side of the first outer main groove 21, and extend in the tire width direction from the tire width direction outer side toward the first outer main groove 21 within an outer region 77A of the shoulder region 77 on the tire width direction outer side of the narrow groove 31, intersect with the narrow groove 31, and are closed in an inner region 77B between the narrow groove 31 and the main groove 21 without reaching the first outer main groove 21. The shoulder lug grooves 59 are provided in a plurality of positions spaced apart in the tire circumferential direction in a shoulder region 79 on the tire widthwise outer side of the second outer main groove 27, and extend in the tire width direction within the shoulder region 79 from the tire widthwise outer side toward the main groove 27, but are closed within the region 79 without reaching the main groove 27.

[0044] The tire width direction ground contact edge E is located within the regions 77B and 79. The ground contact edges are both ends in the tire width direction of the contact surface when the tire 10 is mounted on a standard rim, inflated to the standard internal pressure, and placed on a horizontal surface under a load of 88% of the standard load. The standard rim refers to the "measurement rim" specified by JATMA, the "design rim" specified by TRA, or the "measuring rim" specified by ETRTO. The standard internal pressure refers to the "maximum air pressure" specified by JATMA, the maximum value of the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or the "INFLATION PRESSURES" specified by ETRTO. Normal load refers to the "maximum load capacity" specified by JATMA, the maximum value of the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or the "LOAD CAPACITY" specified by ETRTO.

[0045] The shoulder lug grooves 58, 59 include closed ends 58a, 59a of the shoulder lug grooves 58, 59, and main groove side portions 58b, 59b located on the outer main groove 21, 27 side of the ground contact edge E extend at an angle with respect to the tire width direction.

[0046] According to one embodiment, the tread pattern preferably does not include a lug groove provided in the first middle region 71, communicating with at least one of the first outer main groove 21 and the first inner main groove 23, and extending in the tire width direction, and a lug groove provided in the second middle region 75, communicating with at least one of the second outer main groove 27 and the second inner main groove 25, and extending in the tire width direction. This reduces the groove volume and improves tire noise performance. Furthermore, according to one embodiment, it is preferable that the tread pattern does not include a lug groove provided in the center region 73, communicating with at least one of the first inner main groove 23 and the second inner main groove 25, and extending in the tire width direction. The lug groove is a groove having a component extending in the tire width direction and having a groove width of 1.5 mm or more.

[0047] According to one embodiment, the second sipes preferably include a second sipe 55 (second sipe A) communicating with the second inner main groove 25, and a second sipe 57 (second sipe B) having a communicating position with the second outer main groove 27 at a tire circumferential position different from the communicating position of the second sipe 55 with the second inner main groove 25, as shown in the example of FIG. 2. In this way, the second middle region 75 includes a mixture of sipes communicating with the second inner main groove 25 and sipes communicating with the second outer main groove 27, so that the balance of rigidity in the tire width direction of the land portion of the second middle region 75 is improved, and the land portion easily follows various changes in the force received from the road surface. The ratio of the number of the second sipes 55 and the number of the second sipes 57 to the total number of the second sipes is preferably 20 to 80%, and more preferably 30 to 70%.

[0048] In this embodiment, and according to one further embodiment, it is preferable that the second sipes 57 are disposed one by one between the second sipes 55 adjacent in the tire circumferential direction. This provides a particularly good balance of rigidity in the tire width direction of the land portion of the second middle region 75. The above-mentioned ratio is preferably 50% each.

[0049] According to one embodiment, when the length along the tire circumferential direction between two communication positions where two circumferentially adjacent second sipes 55 communicate with the second inner main groove 25 is L1, as shown in FIG. 2, the communication position of the second sipe 57 with the second outer main groove 27 is preferably within a range of 50 to 97% of the length L1 from the communication position of one of the two communication positions (the first side in FIG. 2), and more preferably within a range of 70 to 95%. This increases the effect of reducing tire noise. Note that the one communication position refers to the communication position of the second sipe 55 with the second inner main groove 25 that has a closed end within the tire circumferential range between the two communication positions.

[0050] In these embodiments, according to one embodiment, the direction connecting both ends of the second sipe 55 in the extension direction and the direction connecting both ends of the second sipe 57 in the extension direction are preferably inclined toward the same side in the tire circumferential direction with respect to the tire width direction in the direction from one end to the other end in the tire width direction. This makes it possible to suppress concentration of the land portion in the second middle region 75 where the rigidity is reduced. In the example shown in FIG. 2, these two directions are inclined toward the first side in the tire circumferential direction (upper side in FIG. 2) with respect to the tire width direction. According to one embodiment, it is preferable that the first sipe 51 and the second sipes 55, 57 have the above-mentioned relationship of inclination toward the same side, and it is more preferable that the first sipe 51, the third sipe 53, and the second sipes 55, 57 have the above-mentioned relationship of inclination toward the same side.

[0051] According to one embodiment, the length of the interval G2 between the second sipes 55, 57 is preferably different between adjacent intervals in the tire circumferential direction. Figure 2 shows a plurality of intervals G2 having different lengths. This provides the effect of dispersing the frequency of pattern noise, contributing to improved noise performance.

[0052] According to one embodiment, the first sipes 51 are preferably connected to the narrow grooves 33. This increases the drainage in the first middle region 71.

[0053] In this embodiment, according to another embodiment, as shown in FIG. 3, the sipe depth D51c of the narrow groove side connecting portion 51c of the first sipe 51 connected to the narrow groove 33 is shallower than the groove depth D33 of the narrow groove 33, and the sipe depth D51b of the middle portion 51b of the first sipe 51 located between the first outer main groove 21 and the narrow groove side connecting portion 51c to which the first sipe 51 is connected is deeper than the groove depth D33 of the narrow groove 33. In this way, since the narrow groove side connecting portion 51c has a bottom portion with a raised bottom, it is possible to suppress a decrease in rigidity at the connecting position of the first sipe 51 with the narrow groove 33. In addition, since the middle portion 51b of the first sipe 51 is deeper than the narrow groove 33, the water absorption of the first sipe 51 is improved, which contributes to improving wet performance. FIG. 3 is a diagram showing a cross section of a part of the region in the tire width direction of the first middle region 71 along the extension direction of the first sipe 51. In FIG. 3, a third chamfered surface, which will be described later, is omitted from the illustration.

[0054] In these two embodiments, and further according to one embodiment, the sipe depth D51a of the main groove side communicating portion 51a of the first sipe 51 communicating with the first outer main groove 21 is preferably shallower than the groove depth D33 of the narrow groove 33. In this manner, the main groove side communicating portion 51a has a raised bottom portion, so that a decrease in rigidity at the communicating position of the first sipe 51 with the first outer main groove 21 can be suppressed. According to one embodiment, the sipe depth D51c of the narrow groove side connecting portion 51c and the sipe depth D51a of the main groove side communicating portion 51a are preferably 20 to 50%, and more preferably 30 to 40%, of the sipe depth D51b of the intermediate portion 51b.

[0055] According to one embodiment, it is preferable that the groove depth D21 of the first outer main groove 21, the sip depth D51b of the intermediate portion 51b, the sip depths D51c and D51a of the fine groove side connection portion 51c and the main groove side communication portion 51a, and the groove depth D33 of the fine groove 33 decrease in this order. That is, it is preferable that D21 < D51b < D33 < D51c, D51a. D51c and D51a may be different from each other, but are preferably equal.

[0056] According to one embodiment, the first sip 51 preferably extends in a curved shape so as to bulge roundly toward one side in the tire circumferential direction on the tread surface. Thereby, when a lateral force is received, in the first middle region 71, the movement of the portions on both sides in the tire circumferential direction of the first sip 51 being displaced from each other in the tire width direction is suppressed, which contributes to the improvement of wet performance. In the example shown in FIG. 2, the first sip 51 extends so as to form an arc shape that bulges toward the first side in the tire circumferential direction on the tread surface. The radius of curvature of the arc shape of the first sip 51 is preferably 50 to 150 mm. On the other hand, according to one embodiment, the second sips 55, 57 and the third sip 53 preferably extend linearly on the tread surface.

[0057] In this case, according to a further embodiment, it is preferable that the length in the extending direction of the first sip 51 is longer than the lengths in the extending direction of the second sips 55, 57. Since the number of the first sips 51 is smaller than the total number of the second sips 55, 57, such a form contributes to improving the balance of the rigidity between the first middle region 71 and the second middle region 75. Further, this makes it easier to adjust the magnitude of the rigidity of the first middle region 71 to a magnitude between the magnitude of the rigidity of the second middle region 75 and the magnitude of the rigidity of the center region 73. Incidentally, according to one embodiment, the length in the extending direction of the first sip 51 is preferably longer than the length in the extending direction of the third sip 53 (for example, 115 to 125% of the length in the extending direction of the third sip 53).

[0058] According to one embodiment, the second sipes 55, 57 extend in a straight line, and it is preferable that the inclination angle with respect to the tire width direction in the direction connecting both ends of the extension direction of the second sipes 55, 57 is different between adjacent second sipes 55, 57 in the tire circumferential direction.

[0059] According to one embodiment, the number of intervals G2 between the second sipes 55, 57 is preferably greater than the number of intervals G3 between adjacent third sipes 53 in the tire circumferential direction (hereinafter, referred to as intervals G3 between the third sipes 53). That is, the number of intervals G3 between the third sipes 53 is preferably less than the number of intervals G2 between the second sipes 55, 57. Since the center region 73 has the longest contact length in the tire circumferential direction in the tread portion, it is preferable to ensure a contact area with the road surface by the above-mentioned embodiment. According to one embodiment, the number of intervals G2 between the second sipes 55, 57 is preferably 1.5 to 2.5 times the number of intervals G3 between the third sipes 53, and more preferably 1.8 to 2.2 times.

[0060] In this case, according to one embodiment, the second sipes 55, 57 in the tire width direction of The length is preferably 20 to 50% of the length of the second middle region 75 in the tire width direction, and more preferably 30 to 40% of the length of the third sipe 53 in the tire width direction. of The length is preferably 20 to 50%, and more preferably 30 to 40%, of the length in the tire width direction of the center region 73. This makes it possible to prevent the rigidity in the second middle region 75 and the center region 73 from decreasing too much.

[0061] According to one embodiment, the tread pattern is preferably oriented such that the second half tread region is located on the vehicle outer side (the "OUT" side shown in FIG. 2) relative to the first half tread region. The second half tread region has a smaller groove area ratio than the first half tread region, and being located on the vehicle outer side improves noise performance.

[0062] (Beveled surface) According to one embodiment, the tread pattern preferably has one of a first chamfered surface 81, a second chamfered surface 85, 87, and a third chamfered surface 83 corresponding to the first sipe 51, the second sipes 55, 57, and the third sipe 53.

[0063] The first chamfered surface 81 is a surface where one of the tread surfaces of a land portion adjacent in the tire circumferential direction to the tire width direction end of the first sipe 51 communicating with the first outer main groove 21 is inclined toward the first outer main groove 21. A plurality of first chamfered surfaces 81 are provided in the tire circumferential direction, and the first sipes 51 are open without reaching the groove wall of the first outer main groove 21.

[0064] The second chamfered surface 85 is a surface where one of the tread surfaces of a land portion adjacent in the tire circumferential direction to the tire width direction end of the second sipe 55 communicating with the second inner main groove 25 is inclined toward the second inner main groove 25. A plurality of second chamfered surfaces 85 are provided in the tire circumferential direction, and the second sipes 55 are open without reaching the groove wall of the second inner main groove 25.

[0065] The second chamfered surface 87 is a surface where one of the tread surfaces of a land portion adjacent in the tire circumferential direction to the tire width direction end of the second sipe 57 communicating with the second outer main groove 27 is inclined toward the second outer main groove 27. A plurality of second chamfered surfaces 87 are provided in the tire circumferential direction, and the second sipes 57 are open without reaching the groove wall of the second outer main groove 27.

[0066] The third chamfered surface 83 is a surface where one of the tread surfaces of a land portion adjacent in the tire circumferential direction to the tire width direction end of the third sipe 53 communicating with the first inner main groove 23 is inclined toward the first inner main groove 23. A plurality of third chamfered surfaces 83 are provided in the tire circumferential direction, and the third sipes 53 are open without reaching the groove wall of the first inner main groove 23.

[0067] According to one embodiment, the circumferential length of the chamfered surfaces 81, 83, 85, 87 is preferably longer than the widthwise length of the tire. In this embodiment, the sipes 51, 53, 55, 57 are provided in the first middle region 71, the center region 73, and the second middle region 75, so that the groove volume is smaller and the noise performance is superior compared to the case where lug grooves are provided instead of the sipes 51, 53, 55, 57. On the other hand, the chamfered surfaces 81, 83, 85, 87 are provided in the first middle region 71, the center region 73, and the second middle region 75, so that the edge components that come into contact with the road surface are larger and a larger edge effect is obtained compared to the case where the chamfered surface is not provided. Therefore, the deterioration of wet performance due to the deterioration of drainage caused by the provision of the sipes 51, 53, 55, 57 instead of the lug grooves is suppressed. In addition, as described above, the sipes 51, 53, 55, 57 provide an edge component that is effective against forces in the front-rear direction (tire circumferential direction), so that the tire circumferential length of the chamfered surfaces 81, 83, 85, 87 is made longer than the tire width direction length to provide an edge component that is effective against forces in the front-rear direction while also providing an edge component that is effective against lateral forces, thereby improving wet performance against forces in various directions received from the road surface. Therefore, the above-mentioned effect of suppressing the deterioration of wet performance is enhanced. That is, in this embodiment, noise performance is improved while the deterioration of wet performance is suppressed compared to the case where lug grooves are provided instead of the sipes 51, 53, 55, 57. In this embodiment, the groove volume increases by providing at least one of the chamfered surfaces 81, 83, 85, and 87 in the first middle region 71, the center region 73, and the second middle region 75 compared to when the chamfered surface is not provided; however, the increase is smaller than when, for example, a notch (a lateral groove with a relatively short length in the extension direction) is provided, and the effect on noise performance is small.

[0068] According to one embodiment, the circumferential length of the chamfered surfaces 81, 83, 85, 87 is preferably 5 to 50% of the circumferential interval between adjacent sipes 51, 53, 55, 57 that open to the chamfered surfaces 81, 83, 85, 87. If the circumferential length of the chamfered surfaces 81, 83, 85, 87 is longer than this ratio, the noise performance is likely to deteriorate due to an increase in groove volume, and the rigidity of the land portion is reduced, which may adversely affect wet performance. In addition, if the circumferential length of the chamfered surfaces 81, 83, 85, 87 is shorter than this ratio, the effect of improving wet performance is reduced.

[0069] According to one embodiment, the ratio of the length in the tire circumferential direction to the length in the tire width direction of the chamfered surfaces 81, 83, 85, 87 is preferably greater than 1 and less than or equal to 10, and more preferably greater than or equal to 1.5 and less than or equal to 8.

[0070] According to one embodiment, the first chamfered surface 81 and the third chamfered surface 83 preferably have different tire circumferential lengths. Also, according to one embodiment, the second chamfered surfaces 87, 85 preferably have different tire circumferential lengths. In these embodiments, the chamfered surfaces 81, 87 having a longer tire circumferential length can improve wet performance by providing edge components that are effective against lateral forces, and the chamfered surfaces 83, 85 having a shorter tire circumferential length can improve noise performance by reducing groove volume. Among the chamfered surfaces having different tire circumferential lengths, the tire circumferential length of the chamfered surface having the longest tire circumferential length is preferably 1.2 to 3 times, and more preferably 1.5 to 2 times, the tire circumferential length of the chamfered surface having the shortest tire circumferential length.

[0071] According to one embodiment, the tire circumferential length of the chamfered surface 81 farther from the tire centerline CL among the first chamfered surface 81 and the third chamfered surface 83 is preferably longer than the tire circumferential length of the chamfered surface 83 closer to the tire centerline CL. Also, according to one embodiment, the tire circumferential length of the chamfered surface 87 farther from the tire centerline CL among the second chamfered surfaces 87, 85 is preferably longer than the tire circumferential length of the chamfered surface 87 closer to the tire centerline CL. In these embodiments, the effect of improving wet performance is large in the region far from the tire centerline CL, and the effect of improving noise performance is large in the region near the tire centerline CL, so that the above effect of improving noise performance while suppressing deterioration of wet performance can be effectively obtained.

[0072] According to one embodiment, it is preferable that the ranges in the tire circumferential direction in which the first chamfered surface 81 and the third chamfered surface 83 are located do not overlap with each other. Also, according to one embodiment, it is preferable that the ranges in the tire circumferential direction in which the second chamfered surfaces 85 and 87 are located do not overlap with each other. Furthermore, according to one embodiment, it is preferable that the ranges in the tire circumferential direction in which the chamfered surfaces 81, 83, 85 and 87 are located do not overlap with each other. By disposing the chamfered surfaces 81, 83, 85 and 87 in a dispersed manner in the tire circumferential direction in this way, it is possible to disperse the influence of each of the chamfered surfaces 81, 83, 85 and 87 on noise performance.

[0073] According to one embodiment, the maximum depth of the chamfered surface 81, 83, 85, 87 is preferably greater than the depth (maximum depth) of the sipe 51, 53, 55, 57 that opens onto the chamfered surface 81, 83, 85, 87. The chamfered surface 81, 83, 85, 87 is inclined toward the main groove 21, 23, 25, 27, so that the depth is maximum at the groove wall of the main groove 21, 23, 25, 27. The maximum depth D81 of the chamfered surface 81 is shown in FIG. 3. FIG. 3 shows a cross section of the area between the first outer main groove 21 and the narrow groove 33. In this way, the maximum depth of the chamfered surfaces 81, 83, 85, 87 is deeper than the depth of the sipes 51, 53, 55, 57, so that the sipes 51, 53, 55, 57 do not reach the groove wall of the main grooves 21, 23, 25, 27, but open to the chamfered surfaces 81, 83, 85, 87 and are closed within the chamfered surfaces 81, 83, 85, 87, as shown in Fig. 4. That is, the sipes 51, 53, 55, 57 are not connected (directly open) to the main grooves 21, 23, 25, 27, but are connected to the main grooves 21, 23, 25, 27 by opening to the chamfered surfaces 81, 83, 85, 87 as described above. Fig. 4 shows the shape of the chamfered surfaces 81, 83 as a representative of the chamfered surfaces 81, 83, 85, 87. In this way, since the sipes 51, 53, 55, 57 are not connected to the main grooves 21, 23, 25, 27, the rigidity of the land portions is reduced and excessive deformation of the land portions is suppressed, and appropriate rigidity is obtained, compared to when the sipes are connected to the main grooves 21, 23, 25, 27. Such a configuration contributes to improving wet performance.

[0074] According to one embodiment, the maximum depths of the chamfers 81, 83, 85, 87 are preferably equal to each other.

[0075] According to one embodiment, the tire circumferential side on which the first chamfered surface 81 is positioned relative to the first sipe 51 (the second side in FIG. 2) is preferably the same side in the tire circumferential direction as the tire circumferential side on which the third chamfered surface 83 is positioned relative to the third sipe 53 (the second side in FIG. 2). Also, according to one embodiment, the tire circumferential side on which the second chamfered surface 85 is positioned relative to the second sipe 55 (the second side in FIG. 2) is preferably opposite to the tire circumferential side on which the second chamfered surface 87 is positioned relative to the second sipe 57 (the first side in FIG. 2).

[0076] According to one embodiment, the chamfered surfaces 81, 83, 85, and 87 are preferably substantially triangular surfaces whose tire widthwise length decreases from one side to the other side in the tire circumferential direction, as shown in Fig. 4. This makes it possible to minimize the effect of the chamfered surfaces 81, 83, 85, and 87 on noise performance. The apexes of the substantially triangular shapes are located within the groove wall of the main groove, within the ground contact surface of the land portion in contact with the groove wall, and at the boundary between the ground contact surface and the groove wall.

[0077] According to one embodiment, the sipes 51, 53, 55, 57 are preferably open at the portion of the chamfered surface 81, 83, 85, 87 where the length in the tire width direction is maximum (a portion forming one apex of a substantially triangular shape in FIG. 4).

[0078] According to one embodiment, the sipes 51, 53, 55, 57 preferably have bottom-up portions (main groove side communicating portions) shallower than the maximum depth of the sipes 51, 53, 55, 57 at the opening ends of the sipes 51, 53, 55, 57 that open to the chamfered surfaces 81, 83, 85, 87. This enhances the above-mentioned effect of obtaining appropriate rigidity of the land portions by not connecting the sipes 51, 53, 55, 57 to the main grooves 21, 23, 25, 27.

[0079] According to one embodiment, the tread pattern has a wall surface of the land portion of the first middle region 71, the center region 73, and the second middle region 75 adjacent to the chamfered surface 81, 83, 85, 87, as shown in FIG. 4, which extends continuously from the wall surface of the sipe 51, 53, 55, 57 from the opening end of the sipe 51, 53, 55, 57 that opens to the chamfered surface 81, 83, 85, 87 to the groove wall of the main groove 21, 23, 25, 27 toward which the chamfered surface 81, 83, 85, 87 is inclined. FIG. 4 shows the wall surfaces 82, 84 as representative examples. It is preferable that the wall surface extends without inclining with respect to the tire radial direction. This reduces the groove volume compared to the case where the wall surface is inclined with respect to the tire radial direction, contributing to improvement of noise performance. Furthermore, compared to a case in which the wall surface is inclined relative to the tire radial direction, the effect of cutting through the water film is improved, which contributes to improved wet performance.

[0080] According to one embodiment, the wall surface preferably extends along the extension direction of the sipes 51, 53, 55, 57 that open to the chamfered surfaces 81, 83, 85, 87. If the wall surface extends away from the chamfered surfaces 81, 83, 85, 87 (so that the inclination angle with respect to the tire width direction becomes large) with respect to the extension direction of the sipes 51, 53, 55, 57, the edge component that is effective against lateral forces is reduced, and the effect of suppressing deterioration of wet performance may be reduced.

[0081] According to one embodiment, the inclination angle of the sipes 51, 53, 55, 57 with respect to the tire width direction is preferably 45 degrees or less. Since the edge components that are effective against lateral forces are secured by the chamfered surfaces 81, 83, 85, 87, the edge effect against forces in the front-rear direction can be increased by reducing the inclination angle of the sipes 51, 53, 55, 57. The inclination angle is preferably 10 to 35 degrees.

[0082] According to one embodiment, it is preferable that the tread pattern further includes a chamfered surface 89 inclined toward the narrow groove 33 at an end in the tire width direction of the region 71A, in which the first sipe 51 is arranged, on the narrow groove 33 side, among the regions divided in the tire width direction in the first middle region 71 by the narrow groove 33. A plurality of chamfered surfaces 89 are provided in the tire circumferential direction, and are surfaces connected to sipe wall surfaces at connection ends of the first sipes 51 and the narrow groove 33. According to one embodiment, it is preferable that the maximum depth of the chamfered surface 89 is shallower than the depth of the first sipes 51.

[0083] According to one embodiment, the length of the chamfered surface 89 in the tire circumferential direction is preferably shorter than the length of the chamfered surfaces 81, 83, 85, 87 in the tire circumferential direction.

[0084] According to one embodiment, the chamfered surface 81 and the chamfered surface 89 are preferably located on opposite sides in the tire circumferential direction with the first sipe 51 as a boundary (the second side and the first side in FIG. 2).

[0085] (extension line) According to one embodiment, as in the example shown in Fig. 5, the second sipes 55 preferably overlap each of the multiple extension lines S. The second sipes 57 extend in a direction along the extension lines S between two of the multiple extension lines S that are adjacent in the tire circumferential direction. Fig. 5 is a diagram for explaining the extension lines S, and two representative extension lines S are shown by dashed lines. The extension line S is an imaginary line extending smoothly from the closed end 59a of each of the shoulder lug grooves 59 along the inclination direction of the main groove side portion 59b toward each of the closed ends 53a of the third sipes 53. The main groove side portion 59b is a portion of the shoulder lug groove 59 on the side of the main groove 27 including the closed end 59a. The extension line S is a straight line. "Smoothly extending" means that at the closed end 59a of the shoulder lug groove 59, the smaller angle between the inclination direction of the shoulder lug groove 59 with respect to the tire width direction and the extension direction of the extension line S is 10 degrees or less, preferably 5 degrees or less. At the closed end 53a of the third sipe 53, the smaller angle between the inclination direction of the third sipe 53 and the inclination direction of the extension line S is preferably 10 degrees or less, more preferably 5 degrees or less, and more preferably these two directions are the same. The second sipe 55 overlapping with the extension line S includes a state in which the second sipe 55 is in contact with or intersects with the extension line S, as well as a state in which the second sipe 55 is in contact with or intersects with a region that is twice (preferably the same) the groove width of the main groove side portion 59b of the shoulder lug groove 59 from the extension line S in a direction perpendicular to the extension line S. In addition, the second sipe 57 extending in a direction along the extension line S means that the inclination angle of the extension direction of the second sipe 57 with respect to the extension line S is within 10 degrees, preferably 5 degrees or less, and more preferably 0 degree.

[0086] By positioning the shoulder lug grooves 59, the second sipes 55, and the third sipes 53 so that they overlap with the extension line S that is inclined relative to the tire width direction, the shoulder lug grooves 59, the second chamfered surfaces 87, and the second chamfered surfaces 85 are easily arranged in a dispersed manner in the tire circumferential direction, contributing to improved noise performance. On the other hand, the second sipes 57 are disposed closer to the shoulder lug grooves 59 than the third sipes 53 and the second sipes 55. For this reason, the second sipes 57 are disposed so as to extend along the extension lines S between two extension lines S adjacent to each other in the tire circumferential direction, thereby preventing the second sipes 57 from overlapping with the extension lines S. This is because the shoulder lug grooves 59 have a large groove volume and generate a loud pumping noise, so it is desirable for the second sipes 57 and the shoulder lug grooves 59 to be separated in the tire circumferential direction.

[0087] According to one embodiment, it is preferable that all of the shoulder lug grooves 59 and the third sipes 53 form ends in the extension direction of any of the extension lines S, all of the second sipes 55 overlap with any of the extension lines S, and all of the second sipes 57 extend between any of two extension lines S adjacent in the tire circumferential direction. This provides the effect of distributing the second chamfered surfaces 85, 87, and the shoulder lug grooves 59 at different positions in the tire circumferential direction all around the tire, thereby enhancing the effect of improving noise performance.

[0088] According to one embodiment, it is preferable that the range of the second chamfered surface 85 along the tire circumferential direction does not overlap with the range of the shoulder lug groove 59 along the tire circumferential direction. In this way, the second chamfered surface 85 and the shoulder lug groove 59 are disposed at different positions in the tire circumferential direction, which contributes to improving noise performance.

[0089] According to one embodiment, it is preferable that the tire circumferential ranges of adjacent extension lines S in the tire circumferential direction do not overlap. If the ranges of two extension lines S along the tire circumferential direction overlap, it is difficult to obtain the effect of distributing the second chamfered surface 85, the second chamfered surface 87, and the shoulder lug grooves 59 in the tire circumferential direction. For this reason, it is preferable that the inclination angle of the extension lines S with respect to the tire width direction is 10 to 30 degrees.

[0090] According to one embodiment, the inclination angles of the third sipes 53, the second sipes 55, and the second sipes 57 with respect to the tire width direction are preferably substantially equal to each other. “Substantially equal” means that the difference in the inclination angles between the lug grooves is within a maximum of 10 degrees, preferably within a maximum of 5 degrees.

[0091] According to one embodiment, the first sipe 51 preferably overlaps with an imaginary straight line (second extension line) extending from a connection position of the third sipe 53 with the first inner main groove 23 toward the outer side in the tire width direction (the inner side mounted on the vehicle in FIG. 2) along the inclination direction of the third sipe 53 with respect to the tire width direction. The first sipe 51 overlapping with the second extension line includes a form in which the first sipe 51 is in contact with or intersects with the second extension line, as well as a form in which the first sipe 51 is in contact with or intersects with a region that is twice (preferably the same) the groove width of the main groove side portion 58b of the shoulder lug groove 58 in a direction perpendicular to the second extension line.

[0092] In the tread pattern of the example shown in FIG. 2, in the region 71B between the narrow groove 33 and the first inner main groove 23, no lug grooves or sipes communicating or connected to the narrow groove 33 or the first inner main groove 23 are provided, and a rib continuous in the tire circumferential direction is formed. In the region 77B, no lug grooves or sipes connected to the narrow groove 31 or the main groove 21 are provided, and a rib continuous in the tire circumferential direction is formed. In this way, in the region of the tread pattern arranged on the vehicle inner side, many edge components extending in the tire circumferential direction are created by the two narrow grooves 31, 33, and the rigidity of the two ribs is ensured, thereby increasing the steering stability by the inner wheel during cornering. Preferably, the tire width direction length (width) of the region 77B is wider than the width of the region 71B. It is preferable that the narrow groove 31 has a groove width wider than the narrow groove 33.

[0093] The tread pattern of this embodiment is not limited to the example tread pattern shown in FIG.

[0094] (Comparative Examples and Examples) In order to investigate the effect of the tire of this embodiment, the tire tread pattern was changed in various ways, and wet performance and noise performance were investigated. The prototype tire had a size of 225 / 65R17, and except for the specifications shown in Table 1 and below, the tire was based on the tread pattern shown in Figure 2 and the cross-sectional profile shown in Figures 1 and 3, and the chamfered surface and wall surface were based on the form shown in Figure 4.

[0095] Table 1 shows the tread pattern of each tire and its evaluation results. In Table 1, with regard to the "number of sipe spacings in regions 71 and 75," "71=75" means that the number of spacings G1 in the first middle region 71 is equal to the number of spacings G2 in the second middle region 75, and "71<75" means that the number of spacings G2 is greater than the number of spacings G1. Regarding the "arrangement configuration of the second sipes 55, 57," "55 only" means that the second sipes 57 are not arranged in the second middle region 75, and only the second sipes 55 are arranged, and "alternate" means that the second sipes 55 and the second sipes 57 are arranged alternately in the circumferential direction of the tire. The "amount of deviation of the second sipe 57 from the second sipe 55" indicates what percentage of the spacing L1 between the adjacent second sipes 55 is located at the connection position of the second sipe 57 with the second outer main groove from the second sipe 55 adjacent to the second sipe 57 on the first side in the circumferential direction of the tire to the second side. "The vertical and horizontal lengths of the chamfered surfaces 81, 83, 85, and 87" represent the relationship in size between the tire circumferential (vertical) length and tire width (horizontal) length of each of the chamfered surfaces 81, 83, 85, and 87. "Overlap between the second sipe 55 and the extension line" indicates whether the second sipe 55 overlaps with the extension line S and the second sipe 57 passes between the extension line S, where "overlap" means that this is the case and "non-overlap" means that this is not the case.

[0096] In examples including Example 5 where the "overlap between the second sipes 55 and the extension line" is "non-overlapping," in Example 6, in FIG. 2, the second middle region was shifted in the tire circumferential direction relative to the center region and shoulder region so that the second sipes 55 do not overlap the extension line S and the second sipes 57 overlap the extension line S. In Example 5, the tire circumferential length of the chamfered surfaces 81, 83, 85, 87 in Example 4 is three times the tire width direction length. In Examples including Example 4 in which the "vertical and horizontal lengths of the chamfered surfaces 81, 83, 85, 87" are "vertical = horizontal", the tire circumferential length and tire width direction length of the chamfered surfaces 81, 83, 85, 87 are both 5% of the interval between adjacent sipes 51, 53, 55, 57 opening on the chamfered surfaces 81, 83, 85, 87 in the tire circumferential direction. In the Comparative Example and Examples, the maximum depth of the chamfered surfaces 81, 83, 85, 87 is deeper than the maximum depth of the sipes 51, 53, 55, 57 opening on the chamfered surfaces 81, 83, 85, 87. In Comparative Example 2 and Examples 1 to 3, the extension direction length of the first sipes 51 was set to 80% of the width direction length of the region 71A. In Example 1, the second sipes 57 in Example 2 were omitted, and the same number of second sipes 55 as the omitted second sipes 57 were added. In Comparative Example 2, the number of second sipes 55 was halved compared to Example 1. In Examples 1 to 6, the number of intervals G2 was twice the number of intervals G1. In Comparative Example 1, the sipes 51, 53, and 55 in Comparative Example 2 were replaced with lug grooves. In the comparative example and the example, the inclination angle of the lug grooves and sipes in the first middle region 71, the center region 73, and the second middle region 75 with respect to the tire width direction was set to 20 to 30 degrees. Also, the inclination angle of the extension line S with respect to the tire width direction was set to 20 to 30 degrees.

[0097] These test tires were mounted on a vehicle so that the second half tread region was located on the outer side of the vehicle relative to the first half tread region, and the noise performance and wet performance were evaluated as described below, with the results shown in Tables 1 and 2. Each evaluation was performed under the conditions that the test tires were mounted on wheels with a rim size of 17x7J and mounted on a front-wheel drive vehicle with an engine displacement of 2400cc, with an air pressure of 230kPa.

[0098] Noise Performance For each test tire, the pass-by noise outside the vehicle was measured in accordance with the European noise regulation (ECE R117). The evaluation results were expressed as an index using the reciprocal of the measured value, with Comparative Example 1 being set at 100. The higher the index, the better the noise performance.

[0099] Wet Performance The test course was covered with water less than 1mm deep on an asphalt surface, and the test driver ran the test at a speed of 40 to 100 km / h, and performed a sensory evaluation of the steering when changing lanes and cornering, as well as the stability when going straight. The wet performance was expressed as an index, with Comparative Example 1, which is likened to a conventional tire, being set at 100, and the higher the index, the better the wet performance.

[0100] The acceptable range for tires of size 225 / 65R17 is a noise performance index of 103 or more and a wet performance index of 97 or more, and if these are met, it is evaluated as having improved noise performance while suppressing deterioration of wet performance.

[0101] [Table 1]

[0102] A comparison between Comparative Example 1 and Example 1 shows that by providing first sipes and second sipes and by making the spacing between the second sipes greater than the spacing between the first sipes, noise performance can be improved while suppressing deterioration of wet performance. A comparison between Comparative Example 2 and Example 1 shows that wet performance is improved by making the spacing number of the second sipes larger than the spacing number of the first sipes.

[0103] From a comparison between Example 1 and Example 2, it can be seen that the wet performance is improved by arranging the second sipes 55 and the second sipes 57 alternately in the tire circumferential direction. A comparison between Example 2 and Example 3 shows that noise performance is improved by setting the "amount of deviation of second sipes 57 relative to second sipes 55" to a value other than 50% and by setting the spacing between the second sipes to multiple lengths. From a comparison between Example 3 and Example 4, it can be seen that by connecting the first sipes to the fine grooves 33, the wet performance is improved. A comparison between Example 4 and Example 5 shows that wet performance is improved by making the tire circumferential length of the chamfered surfaces 81, 83, 85, and 87 longer than the tire width direction length. From a comparison between Example 5 and Example 6, it can be seen that the second sipes 55 overlap with the extension lines S and the second sipes 57 pass between the extension lines S, thereby improving the noise performance.

[0104] Although the tire of the present invention has been described in detail above, the tire of the present invention is not limited to the above-mentioned embodiment or examples, and it goes without saying that various improvements and modifications may be made without departing from the spirit and scope of the present invention. [Explanation of symbols]

[0105] 10 Tires 10T tread section 10S Side section 10B Bead section 12 Carcass ply 14 Belt 16 Bead core 18 Tread rubber material 20 Side rubber material 22 Bead filler rubber material 24 Rim cushion rubber material 26 Inner liner rubber material 21 First outer main groove (first circumferential main groove) 23 First inner main groove (first circumferential main groove) 25 Second inner main groove (second circumferential main groove) 27 Second outer main groove (second circumferential main groove) 31,33 narrow groove 51 First sipe 51a Main groove side communication part 51b Middle part 51c Narrow groove side connection part 53 3rd sipe 55 Second sipe (Second sipe A) 57 Second sipe (Second sipe B) 58,59 Shoulder lug groove 58a,59a Closed end 58b,59b Main groove side part 51a Closed end 71 First Middle Zone (First Zone) 71A, 71B Area in the first middle area 73 Center Area (Third Area) 75 Second Middle Zone (Second Zone) 77,79 Shoulder area 77A Outer area 77B Inner area 81,83,85,87,89 Chamfered surface 82,84 Wall

Claims

1. A tire having a tread pattern on the surface of the tread portion that comes into contact with the road surface, The tread pattern is a pair of first circumferential main grooves provided in a first half tread region on one side in the tire width direction with respect to a tire center line, extending in the tire circumferential direction, and spaced apart from each other in the tire width direction; a pair of second circumferential main grooves provided in a second half tread region on the other side in the tire width direction, extending in the tire circumferential direction, and spaced apart from each other in the tire width direction; a plurality of first sipes provided in a first region between the first circumferential main grooves, communicating with one of the first circumferential main grooves, extending in the tire width direction, and closing within the first region; a circumferential narrow groove that is narrower than the groove width of the first circumferential main groove and extends in the tire circumferential direction within the first region; a plurality of second sipes provided in a second region between the second circumferential main grooves, communicating with one or the other of the second circumferential main grooves, extending in the tire width direction and closing within the second region; The number of intervals between adjacent second sipes in the tire circumferential direction is greater than the number of intervals between adjacent first sipes in the tire circumferential direction, The tire according to claim 1, wherein the first sipe is in communication with the circumferential narrow groove.

2. 2. The tire according to claim 1, wherein the tread pattern does not include a lug groove provided in the first region, communicating with the first circumferential main groove, and extending in the tire width direction, and a lug groove provided in the second region, communicating with the second circumferential main groove, and extending in the tire width direction.

3. The second sipe is a second sipe A communicating with one of the second circumferential main grooves; 3. The tire according to claim 1, further comprising: a second sipe B communicating with the other of the second circumferential main grooves at a tire circumferential position different from a tire circumferential position at which the second sipe A communicates with the circumferential main groove.

4. The second sipes A and the second sipes B are each provided in a plurality of positions spaced apart from each other in the tire circumferential direction, The tire according to claim 3 , wherein the second sipes B are arranged one each between the second sipes A adjacent to each other in the tire circumferential direction.

5. The tire according to claim 3 or 4, wherein a direction connecting both ends of the second sipe A in the extension direction and a direction connecting both ends of the second sipe B in the extension direction are inclined toward the same side in the tire circumferential direction with respect to the tire width direction.

6. The tire according to claim 1 , wherein a length of the interval between the second sipes is different between adjacent intervals in the tire circumferential direction.

7. A sipe depth of a narrow groove side connection portion of the first sipe connected to the circumferential narrow groove is shallower than a groove depth of the circumferential narrow groove, 7. The tire according to claim 1, wherein a sipe depth of an intermediate portion of the first sipe located between the first circumferential main groove to which the first sipe is connected and the narrow groove side connection portion is deeper than a groove depth of the circumferential narrow groove.

8. The tire according to claim 1 , wherein a sipe depth of a main groove side communicating portion of the first sipe communicating with the first circumferential main groove is shallower than a groove depth of the circumferential narrow groove.

9. The tire according to claim 1 , wherein the first sipe extends in a curved shape so as to bulge roundly on one side in the tire circumferential direction on the tread surface.

10. The tire according to claim 9 , wherein a length in the extension direction of the first sipe is longer than a length in the extension direction of the second sipe.

11. 11. The tire according to claim 1, wherein the second sipes extend linearly, and an inclination angle of a direction connecting both ends of the extension direction of the second sipes with respect to the tire width direction is different between the second sipes adjacent in the tire circumferential direction.

12. the tread pattern includes a plurality of third sipes provided in a third region between a first circumferential main groove that is closest to a tire center line among the first circumferential main grooves and a second circumferential main groove that is closest to the tire center line among the second circumferential main grooves, communicating with one of the first circumferential main groove and the second circumferential main groove, extending in the tire width direction, and closing within the third region; The tire according to claim 1 , wherein the number of the intervals between the second sipes is greater than the number of intervals between adjacent third sipes in the tire circumferential direction.

13. The length of the second sipe in the tire width direction is half or less of the length of the second region in the tire width direction, The tire according to claim 12 , wherein a length of the third sipe in the tire width direction is equal to or less than half a length of the third region in the tire width direction.

14. A tire having a tread pattern on the surface of the tread portion that comes into contact with the road surface, The tread pattern is a pair of first circumferential main grooves provided in a first half tread region on one side in the tire width direction with respect to a tire center line, extending in the tire circumferential direction, and spaced apart from each other in the tire width direction; a pair of second circumferential main grooves provided in a second half tread region on the other side in the tire width direction, extending in the tire circumferential direction, and spaced apart from each other in the tire width direction; a plurality of first sipes provided in a first region between the first circumferential main grooves, communicating with one of the first circumferential main grooves, extending in the tire width direction, and closing within the first region; a circumferential narrow groove that is narrower than the groove width of the first circumferential main groove and extends in the tire circumferential direction within the first region; a plurality of second sipes provided in a second region between the second circumferential main grooves, communicating with one or the other of the second circumferential main grooves, extending in the tire width direction and closing within the second region; The number of intervals between adjacent second sipes in the tire circumferential direction is greater than the number of intervals between adjacent first sipes in the tire circumferential direction, The tire according to claim 1, wherein the tread pattern is oriented on a vehicle such that the second half tread region is disposed on an outer side of the vehicle relative to the first half tread region.

Images