Motorcycle tire for driving on uneven ground

Abstract

The present invention provides a motorcycle tire for traveling on an uneven ground with excellent steering performance. The tire has tread blocks (30). The tread block (30) has a land (36b), a transverse groove (48b), a longitudinal groove (50b), and a side surface (38b). The land (36b) is flat. The transverse groove (48b) is recessed from the land (36b). The transverse groove (48b) has an axially inner end (52) and an axially outer end (54). The transverse groove (48b) opens to the side surface (38b) at the inner end (52). The transverse groove (48b) does not open to the side surface (38b) at the outer end (54). The transverse groove (48b) is present biased axially inward.

Description

Technical Field

[0001] The present invention relates to a motorcycle tire for traveling on an uneven ground. More specifically, the present invention relates to an improvement in the tread of the tire. Background Art

[0002] A motorcycle tire for traveling on an uneven ground has a tread with a block pattern. The block pattern includes grooves and a plurality of tread blocks. Each tread block stands up from the groove. On a soft road surface, the tread block penetrates into the road surface. By the edge effect of the tread block, the tire exhibits excellent traction performance on the soft road surface.

[0003] In Japanese Unexamined Patent Application Publication No. 2014-34334 (Japanese Patent No. 5629293), a motorcycle tire in which a tread block has a groove is disclosed. The groove opens on the side surface of the tread block. The rigidity of the tread block having the groove is not too large. The tread block contributes to the grip performance on a hard road surface.

[0004] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2014-34334

[0005] In a motorcycle tire in which a tread block has a groove, the groove may generate an inappropriate torque in the yaw direction. This torque impairs the steering performance. Summary of the Invention

[0006] An object of the present invention is to provide a motorcycle tire for traveling on an uneven ground with excellent steering performance.

[0007] The motorcycle tire for traveling on an uneven ground according to the present invention has a tread with a block pattern. The block pattern has grooves and a plurality of tread blocks that stand up from the grooves respectively. These tread blocks include a plurality of tread blocks with transverse grooves. Each tread block with a transverse groove has a land, a transverse groove recessed from the land, and a side surface facing the groove from the land. The transverse groove has an axially inner end opening to the side surface and an axially outer end not opening to the side surface.

[0008] Preferably, the transverse groove has a width that is large at the axially inner end and small at the axially outer end. Preferably, the transverse groove has a width that gradually decreases as it goes from the axially inner end to the axially outer end. Preferably, the ratio Wi / Wo of the width Wi of the axially inner end of the transverse groove to the width Wo of the axially outer end exceeds 1.0 and is 4.0 or less.

[0009] Preferably, the transverse groove has a depth that is large at the axially inner end and small at the axially outer end. Preferably, the transverse groove has a depth that gradually decreases as it goes from the axially inner end to the axially outer end. Preferably, the ratio Di / Do of the depth Di of the axially inner end of the transverse groove to the depth Do of the axially outer end exceeds 1.0 and is 4.0 or less.

[0010] The block with transverse grooves may also have longitudinal grooves recessed from the land. The longitudinal grooves may be continuous with the transverse grooves. Preferably, the longitudinal grooves have rear landing side ends that open laterally.

[0011] The tread may have a crown region located axially in the center, a pair of intermediate regions respectively located at axially outer positions of the crown region, and a pair of shoulder regions respectively located at axially outer positions of the intermediate regions. Preferably, the ratio Ng / Nb of the number Ng of blocks with transverse grooves in each intermediate region to the total number Nb of blocks is 0.50 or more.

[0012] Preferably, the land ratio of the block pattern is 13% or more and 60% or less.

[0013] Preferably, the JIS-A hardness of the block with transverse grooves is 45 or more and 88 or less.

[0014] The block with transverse grooves of the motorcycle tire for traveling on uneven ground according to the present invention generates an appropriate moment in the deflection direction. In this tire, a positive rotational force acts on the steering device during turning. This tire has excellent steering performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a developed view showing a part of a motorcycle tire for traveling on uneven ground according to an embodiment of the present invention.

[0016] Figure 2 is showing Figure 1 a cross-sectional view of a part of the tire.

[0017] Figure 3 is showing Figure 1 a perspective view of the first block of the tire.

[0018] Figure 4 is showing Figure 1 a perspective view of the second block of the tire.

[0019] Figure 5 is showing Figure 4 a top view of the second block.

[0020] Figure 6 is showing Figure 5 an enlarged top view of the second block.

[0021] Figure 7 is showing Figure 5 a cross-sectional view of the second block.

[0022] Figure 8 is showing Figure 1 a perspective view of the third block of the tire.

[0023] Figure 9 It is an exploded view showing a part of a motorcycle tire for traveling on an uneven ground according to another embodiment of the present invention.

[0024] Figure 10 It shows Figure 9 a perspective view of the third tread block of the tire.

[0025] Explanation of reference numerals

[0026] 2, 60... Motorcycle tire for traveling on an uneven ground; 4, 62... Tread; 26, 64... Groove; 28, 66... First tread block; 30, 68... Second tread block; 32, 70... Third tread block; 34, 72... Fourth tread block; 36a, 36b, 36c, 36d, 36e... Land; 38a, 38b, 38c, 38d, 38e... Side; 40a, 40b, 40c, 40e... Inner edge; 42a, 42b, 42c, 42e... Outer edge; 48b, 48c, 48e... Transverse groove; 50b, 50c... Longitudinal groove; 52, 80... Axial inner end; 54, 82... Axial outer end; 74... Fifth tread block; 76... Sixth tread block; 78... Seventh tread block. Detailed description of the preferred embodiment

[0027] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings based on the preferred embodiments.

[0028] In Figure 1 and 2, a motorcycle tire 2 is shown. The tire 2 is suitable for traveling on uneven ground such as in mountains and wilderness. The tire 2 includes a tread 4, a sidewall 6, a bead 8, a carcass 10, a belt 12, a chafing strip 14, and a liner 16. In Figure 1 and 2, the reference numeral X represents the axial direction, the reference numeral Y represents the circumferential direction, and the reference numeral Z represents the radial direction. However, in Figure 1 the exploded view, the surface (curved surface) of the tire 2 is planarized. Figure 2 The dash-dot line Eq in

[0029] represents the equatorial plane of the tire 2. The tire 2 has an almost mirror-symmetric shape centered on the equatorial plane Eq. In the present embodiment, the tire 2 is mounted on the front wheel rim of a motorcycle. The tire 2 according to the present invention may also be mounted on the rear wheel rim of a motorcycle.

[0030] The sidewall 6 extends radially inwardly substantially from the end of the tread 4. The sidewall 6 is made of crosslinked rubber. The sidewall 6 absorbs impacts from the road surface by flexing. Also, the sidewall 6 prevents external injuries to the carcass 10. In the present embodiment, the material of the sidewall 6 is the same as that of the base portion 18. The sidewall 6 and the base portion 18 are integrally formed.

[0031] The bead 8 is located at a position radially inwardly substantially from the sidewall 6. The bead 8 includes a core portion 22 and a chafer 24 extending radially outwardly from the core portion 22. The core portion 22 is annular. In the core portion 22, non-stretchable cords are wound multiple times. A typical material of the non-stretchable cords is steel. The chafer 24 tapers radially outwardly. The chafer 24 is made of crosslinked rubber with high hardness.

[0032] The carcass 10 is stretched between the beads 8 on both sides and extends along the inside of the tread 4 and the sidewall 6. The carcass 10 is laminated on the inner liner 16. The carcass 10 is folded back around the core portion 22 from the inner side in the axial direction toward the outer side. The carcass 10 is made of a single ply. The number of plies of the carcass 10 may also be two or more.

[0033] Although not shown, the carcass 10 includes a plurality of parallel cords and skim coats. Each cord intersects obliquely with respect to the equatorial plane Eq. The cords may also be substantially orthogonal to the equatorial plane Eq. Typical cords are made of organic fibers. As preferred organic fibers, polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers are exemplified.

[0034] The belt 12 is located radially outside the carcass 10. The belt 12 is laminated with the carcass 10. The belt 12 reinforces the carcass 10. The belt 12 is made of a single layer. The number of layers of the belt 12 may also be two or more. Although not shown, the belt 12 includes a plurality of parallel cords and skim coats. Each cord is inclined with respect to the equatorial plane Eq. The absolute value of the inclination angle is 10° or more and 35° or less. Typical cords are made of organic fibers. The material of the cords may also be steel.

[0035] In Figure 1 a part of the tread pattern is shown. In the entire tire 2, Figure 1 the pattern repeats in the circumferential direction. In the present embodiment, the tread pattern is mirror-symmetric with respect to the equatorial plane Eq. The tread pattern may also be asymmetric with respect to the equatorial plane Eq.

[0036] Figure 1The arrow Wp in [the figure] indicates the periphery length of the tread 4. The tread 4 can be divided into a crown region Zc, a pair of intermediate regions Zm, and a pair of shoulder regions Zs. The periphery length of the crown region Zc is 1 / 3 of the periphery length Wp of the tread 4. The periphery length of each intermediate region Zm is 1 / 6 of the periphery length Wp of the tread 4. The total periphery length of the two intermediate regions Zm is 1 / 3 of the periphery length Wp of the tread 4. The periphery length of each shoulder region Zs is 1 / 6 of the periphery length Wp of the tread 4. The total periphery length of the two shoulder regions Zs is 1 / 3 of the periphery length Wp of the tread 4.

[0037] The tread pattern has grooves 26, a plurality of first tread blocks 28, a plurality of second tread blocks 30, a plurality of third tread blocks 32, and a plurality of fourth tread blocks 34. Each tread block stands up from the groove 26. This tread pattern is called a block pattern.

[0038] As can be clearly seen according to Figure 1 There are a first tread block 28 and a second tread block 30 in the crown region Zc. There are a first tread block 28, a second tread block 30, and a third tread block 32 in the intermediate region Zm. There is a fourth tread block 34 in the shoulder region Zs. In the present invention, for the belonging of the tread blocks existing across the dividing line of the region, it is determined based on the area centroid of the contour shape of the land (described in detail later). The region to which the area centroid belongs is the region to which the tread block belongs. On the basis of assuming that there is no groove (described in detail later) recessed from the land, the contour shape of the land is determined.

[0039] Figure 3 is a perspective view showing Figure 1 the first tread block 28 of the tire 2. This first tread block 28 is located at a position on the right side of the equatorial plane Eq in Figure 1 . The first tread block 28 located at a position on the left side of the equatorial plane Eq has Figure 3 a shape in which the shape of the first tread block 28 is reversed. This first tread block 28 has a land 36a and a side surface 38a. The land 36a is flat. The land 36a has an inner edge 40a, an outer edge 42a, a first contact side edge 44a, and a second contact side edge 46a. The outer edge 42a is located on the outer side in the axial direction compared to the inner edge 40a. When the tire 2 rotates forward, after the first contact side edge 44a touches the ground, the second contact side edge 46a touches the ground. The side surface 38a extends from the land 36a toward the groove 26 (refer to Figure 1 ). In Figure 1 , the illustration of the side surface 38 is omitted.

[0040] Figure 4 is a perspective view showing Figure 1 the second tread block 30 of the tire 2,Figure 5 is its top view. The second tread block 30 is located Figure 1 in a position to the right of the equatorial plane Eq. The second tread block 308 located in a position to the left of the equatorial plane Eq has Figure 4 and a shape in which the shape of the second tread block 30 of 5 is reversed. The second tread block 30 has a land 36b, a transverse groove 48b, a longitudinal groove 50b, and a side surface 38b. The land 36b is flat. The land 36b has an inner edge 40b, an outer edge 42b, a leading contact edge 44b, and a trailing contact edge 46b. The outer edge 42b is axially located outside the inner edge 40b. When the tire 2 rotates forward, after the leading contact edge 44b contacts the ground, the trailing contact edge 46b contacts the ground. The side surface 38b extends from the land 36b toward the groove 26 (see Figure 1 ). In Figure 1 and 5, the illustration of the side surface 38b is omitted.

[0041] In the present invention, a tread block having a transverse groove 48b is called a "transverse groove tread block". The second tread block 30 is a transverse groove tread block. The above-mentioned first tread block 28 is not a transverse groove tread block.

[0042] The transverse groove 48b is recessed from the land 36b. The transverse groove 48b has an axially inner end 52 and an axially outer end 54. The transverse groove 48b opens to the side surface 38b at the inner end 52. The transverse groove 48b does not open to the side surface 38b at the outer end 54.

[0043] The longitudinal groove 50b is recessed from the land 36b. The longitudinal groove 50b has a leading contact end 56 and a trailing contact end 58. The longitudinal groove 50b opens to the side surface 38b at the trailing contact end 58. The longitudinal groove 50b does not open to the side surface 38b at the leading contact end 56. The tire 2 may also have a transverse groove tread block that does not have the longitudinal groove 50b.

[0044] The longitudinal groove 50b is continuous with the transverse groove 48b. The leading contact end 56 of the longitudinal groove 50b substantially coincides with the outer end 54 of the transverse groove 48b. The longitudinal groove 50b helps to discharge mud, water, etc. that invade the transverse groove 48b.

[0045] Figure 5 The dotted line CL in Figure 5In the figure, reference numeral θ represents the angle between the extending direction of the groove and the circumferential direction (Y direction). The minimum value of the angle θ is 0°, and its maximum value is 180°. In the present invention, the groove with the angle θ of 45° or more and 135° or less is referred to as the transverse groove 48b. The groove with the angle θ of 0° or more and less than 45°, and the groove with the angle θ exceeding 135° and 180° or less are referred to as the longitudinal groove 50b.

[0046] Since the second tread block 30 has the transverse groove 48b (or the longitudinal groove 50b), the rigidity of the second tread block 30 is not too large. The second tread block 30 can contribute to the grip performance of the tire 2 when traveling on a hard road surface.

[0047] As described above, the transverse groove 48b opens to the side surface 38b at the inner end 52. The transverse groove 48b does not open to the side surface 38b at the outer end 54. In other words, the transverse groove 48b exists biased toward the axial inner side. Therefore, in the second tread block 30, the rigidity near the inner edge 40b is low, and the rigidity near the outer edge 42b is high. When the motorcycle turns, a load is applied to the second tread block 30. In the second tread block 30 subjected to this load, the deformation amount near the inner edge 40b is large, and the deformation amount near the outer edge 42b is small. Due to this difference in deformation amount, a moment in the deflection direction is generated. The direction of this moment is the direction assisting steering. In the tire 2, a positive rotational force acts on the steering device during turning. The second tread block 30 can contribute to the steering performance of the tire 2.

[0048] During turning, a large load is applied to the tire 2. When turning the steering device under this load, the rider requires a large force. In the tire 2 according to the present invention, the second tread block 30 reduces the burden on the rider.

[0049] From the viewpoint of an appropriate moment during turning, the angle θ is preferably 50° or more and 130° or less, more preferably 55° or more and 125° or less, and particularly preferably 60° or more and 120° or less. From the viewpoint of the drainage performance based on the transverse groove 48b, the angle θ is preferably 85° or more, more preferably 90° or more, and particularly preferably 95° or more.

[0050] Figure 6 is a magnified top view showing Figure 5 the second tread block 30. As Figure 1 shown in and 6, the width of the transverse groove 48b is large at the inner end 52 and small at the outer end 54. Therefore, in the second tread block 30, the rigidity near the inner end 52 is low, and the rigidity near the outer end 54 is high. The second tread block 30 can generate an appropriate moment during motorcycle turning.

[0051] In Figure 6In this case, reference numeral Wi denotes the width of the inner end 52, and reference numeral Wo denotes the width of the outer end 54. The ratio Wi / Wo of the width Wi to the width Wo preferably exceeds 1.0 and is 4.0 or less. The transverse groove 48b with the ratio Wi / Wo within this range can generate an appropriate moment during turning. From the viewpoint of the moment, the ratio Wi / Wo is more preferably 1.5 or more, and particularly preferably 1.8 or more. From the viewpoint of the moment, the ratio Wi / Wo is more preferably 3.5 or less, and particularly preferably 3.0 or less. The width Wi and the width Wo are measured in the circumferential direction.

[0052] As can be clearly seen from Figure 6 the width of the transverse groove 48b gradually decreases from the inner end 52 toward the outer end 54. In this second tread block 30, the rigidity does not change abruptly. In this second tread block 30, it is difficult to cause tipping.

[0053] In Figure 6 reference numeral Wb is the width of the second tread block 30. The width Wb is measured in the circumferential direction. From the viewpoint of an appropriate moment during turning, the ratio Wi / Wb of the width Wi to the width Wb is preferably 0.10 or more, more preferably 0.15 or more, and particularly preferably 0.18 or more. From the viewpoint of the grip performance on a soft road surface, this ratio Wi / Wb is preferably 0.40 or less, more preferably 0.35 or less, and particularly preferably 0.30 or less.

[0054] In Figure 6 reference numeral Lg is the length of the transverse groove 48b, and reference numeral Lb is the length of the second tread block 30. The length Lg and the length Lb are measured in the axial direction. From the viewpoint of an appropriate moment during turning, the ratio Lg / Lb of the length Lg to the length Lb is preferably 0.30 or more, more preferably 0.35 or more, and particularly preferably 0.40 or more. From the viewpoint of the grip performance on a soft road surface, this ratio Lg / Lb is preferably 0.70 or less, more preferably 0.60 or less, and particularly preferably 0.55 or less.

[0055] Figure 7 is a cross-sectional view of the second tread block 30 showing Figure 5 In Figure 7 a cross-section taken along a plane including the Figure 5 center line CL is shown. As Figure 7 shown, the depth of the transverse groove 48b is large at the inner end 52 and small at the outer end 54. Therefore, in this second tread block 30, the rigidity near the inner end 52 is low, and the rigidity near the outer end 54 is high. This second tread block 30 can generate an appropriate moment.

[0056] In Figure 7In this case, the reference numeral Di indicates the depth of the inner end 52, and the reference numeral Do indicates the depth of the outer end 54. The ratio Di / Do of the depth Di to the depth Do is preferably more than 1.0 and 4.0 or less. The transverse groove 48b with the ratio Di / Do within this range can generate an appropriate torque. From the viewpoint of torque, the ratio Di / Do is more preferably 1.2 or more, particularly preferably 1.3 or more. From the viewpoint of torque, the ratio Di / Do is more preferably 3.0 or less, particularly preferably 2.5 or less.

[0057] As can be clearly seen from Figure 7 the depth of the transverse groove 48b gradually decreases as it goes from the inner end 52 toward the outer end 54. In this second tread block 30, the rigidity does not change abruptly. In this second tread block 30, it is difficult to cause tipping.

[0058] In Figure 7 the reference numeral Hb is the height of the second tread block 30. From the viewpoint of an appropriate torque during turning, the ratio Di / Hb of the depth Di to the height Hb is preferably 0.10 or more, more preferably 0.15 or more, particularly preferably 0.20 or more. From the viewpoint of the grip performance on a soft road surface, this ratio Di / Hb is preferably 0.50 or less, more preferably 0.40 or less, particularly preferably 0.35 or less.

[0059] Figure 8 is a perspective view of the third tread block 32 of the tire 2 showing Figure 1 This third tread block 32 is located at a position to the right of the equatorial plane Eq in Figure 1 The third tread block 32 located at a position to the left of the equatorial plane Eq has a shape in which the shape of Figure 8 the third tread block 32 is reversed. This third tread block 32 has a land 36c, a transverse groove 48c, a longitudinal groove 50c, and a side surface 38c. The land 36c is flat. The land 36c has an inner edge 40c, an outer edge 42c, a first contact edge 44c, and a second contact edge 46c. The outer edge 42c is located axially outside the inner edge 40c. When the tire 2 rotates forward, after the first contact edge 44c contacts the ground, the second contact edge 46c contacts the ground. The side surface 38c extends from the land 36c toward the groove 26 (see Figure 1 ). In Figure 1 the illustration of the side surface 38c is omitted. This third tread block 32 is a "transverse-grooved tread block".

[0060] The specifications of the transverse groove 48c in the third tread block 32 are substantially the same as those of the transverse groove 48b in the second tread block 30. The third tread block 32 having the transverse groove 48c can contribute to the steering performance of the tire 2. Moreover, this third tread block 32 can contribute to the grip performance of the tire 2 when traveling on a hard road surface.

[0061] As can be clearly seen from Figure 1 the fourth tread block 34 exists only in the shoulder region Zs. Although detailed illustrations are omitted, the fourth tread block 34 also has a land 36d and a side 38d. The land 36d is flat. The side 38d extends from the land 36d toward the groove 26. The fourth tread block 34 does not have a transverse groove 48. The fourth tread block 34 is not a "transverse-grooved tread block".

[0062] During motorcycle turning, any one of the intermediate regions Zm is mainly in contact with the ground. As described above, in the intermediate region Zm, there are a first tread block 28, a second tread block 30, and a third tread block 32. The first tread block 28 is not a transverse-grooved tread block. The second tread block 30 is a transverse-grooved tread block. The third tread block 32 is a transverse-grooved tread block. In the intermediate region Zm, transverse-grooved tread blocks and other tread blocks are mixed and present.

[0063] The ratio Ng / Nb of the number Ng of transverse-grooved tread blocks present in the intermediate region Zm to the number Nb of all tread blocks present in the intermediate region Zm is preferably 0.50 or more. In the tire 2 where the ratio Ng / Nb is 0.50 or more, an appropriate torque can be generated during turning. From this viewpoint, the ratio Ng / Nb is more preferably 0.60 or more, and particularly preferably 0.70 or more. The ratio Ng / Nb can also be 1.00.

[0064] During a turn with a small inclination angle, the right half or the left half of the crown region Zc is mainly in contact with the ground. Even when the right half of the crown region Zc is mainly in contact with the ground, the left half of the crown region Zc is also in contact with the ground. Even when the left half of the crown region Zc is mainly in contact with the ground, the right half of the crown region Zc is also in contact with the ground. Therefore, the transverse-grooved tread blocks present in the crown region Zc can generate a negative torque with respect to the turning direction. From the viewpoint of suppressing the negative torque, the ratio of the number of transverse-grooved tread blocks present in the crown region Zc to the number of all tread blocks present in the crown region Zc is preferably 0.40 or less, more preferably 0.30 or less, and particularly preferably 0.20 or less. This ratio can also be zero.

[0065] During a turn under full lean, the shoulder region Zs is mainly in contact with the ground. During a turn under full lean, the rider values steering based on their own will. In other words, the rider does not like the torque generated naturally. From this viewpoint, the ratio of the number of transverse-grooved tread blocks present in the shoulder region Zs to the number of all tread blocks present in the shoulder region Zs is preferably 0.40 or less, more preferably 0.30 or less, and particularly preferably 0.20 or less. This ratio can also be zero.

[0066] The land ratio in the block pattern is preferably 13% or more and 60% or less. In the tire 2 with a land ratio of 13% or more, the ground contact pressure can be dispersed. In this tire 2, damage to the tread blocks can be suppressed. From this perspective, the land ratio is more preferably 14% or more, and particularly preferably 15% or more. When the tire 2 with a land ratio of 60% or less travels on a soft road surface, each tread block sufficiently penetrates the road surface. From this perspective, the land ratio is more preferably 50% or less, and particularly preferably 40% or less.

[0067] The land ratio is the ratio of the total area of all the lands 36 to the area of the imaginary tread surface. The imaginary tread surface means: the tread surface when it is assumed that there are no grooves 26, side surfaces 38, and slots in the tread 4 and it is all land 36.

[0068] The hardness of the tread block with transverse grooves is preferably 45 or more and 88 or less. The tread block with transverse grooves having a hardness within this range can generate an appropriate torque during turning. From the perspective of torque, the hardness is more preferably 55 or more, and particularly preferably 60 or more. From the perspective of torque, the hardness is more preferably 80 or less, and particularly preferably 75 or less. The hardness is measured by pressing a JIS-A type hardness tester against the tread block with transverse grooves. The temperature during measurement is 25 °C.

[0069] In the present invention, the dimensions and angles of each component of the tire 2 are measured in a state where the tire 2 is assembled on a regular rim and air is filled into the tire 2 so as to become the regular internal pressure. During measurement, no load is applied to the tire 2. In this specification, the regular rim means the rim specified in the specifications based on which the tire 2 is designed. The "Standard Rim" in the JATMA specification, the "Design Rim" in the TRA specification, and the "Measuring Rim" in the ETRTO specification are regular rims. In this specification, the regular internal pressure means the internal pressure specified in the specifications based on which the tire 2 is designed. The "Maximum Air Pressure" in the JATMA specification, the "Maximum Value" described in the "TIRE LOAD LIMITSAT VARIOUS COLD INFLATION PRESSURES" in the TRA specification, and the "INFLATION PRESSURE" in the ETRTO specification are regular internal pressures.

[0070] Figure 9 It is a developed view showing a part of the off-road motorcycle tire 60 according to another embodiment of the present invention. In Figure 9 a part of the tread 62 is shown. The tread 62 has a tread pattern. The structure of the components of this tire 60 other than the tread pattern is the same as the corresponding components of the tire 2 shown in Figure 2

[0071] The tread 62 can be divided into a crown region Zc, a pair of intermediate regions Zm, and a pair of shoulder regions Zs. The tread pattern has grooves 64, a plurality of first tread blocks 66, a plurality of second tread blocks 68, a plurality of third tread blocks 70, a plurality of fourth tread blocks 72, a plurality of fifth tread blocks 74, a plurality of sixth tread blocks 76, and a plurality of seventh tread blocks 78. Each tread block stands up from the groove 64. This tread pattern is called a block pattern.

[0072] As can be clearly seen, Figure 9 in the crown region Zc, there are the first tread block 66, the second tread block 68, the third tread block 70, the fourth tread block 72, and the fifth tread block 74. In the intermediate region Zm, there are the third tread block 70 and the fourth tread block 72. In the shoulder region Zs, there are the third tread block 70, the fourth tread block 72, the sixth tread block 76, and the seventh tread block 78.

[0073] Figure 10 is a perspective view of the third tread block 70 of the tire 60 shown Figure 9 . The third tread block 70 has a land 36e, a transverse groove 48e, and a side surface 38e. The land 36e is flat. The land 36e has an inner edge 40e, an outer edge 42e, a leading contact edge 44e, and a trailing contact edge 46e. The outer edge 42e is axially located outside the inner edge 40e. When the tire 60 rotates forward, after the leading contact edge 44e touches the ground, the trailing contact edge 46e touches the ground. The side surface 38e extends from the land 36e toward the groove 64 (see Figure 9 ). In Figure 9 , the illustration of the side surface 38e is omitted. This third tread block 70 is a "transverse groove tread block". The first tread block 66, the second tread block 68, the fourth tread block 72, the fifth tread block 74, the sixth tread block 76, and the seventh tread block 78 are not "transverse groove tread blocks".

[0074] The transverse groove 48e of the third tread block 70 opens to the side surface 38e at the axially inner end 80 and does not open to the side surface 38e at the axially outer end 82. The width of the axially inner end 80 of the transverse groove 48e is large, and the width of the axially outer end 82 is small. The depth of the axially inner end 80 of the transverse groove 48e is large, and the depth of the axially outer end 82 is small. In the third tread block 70 having this transverse groove 48e, the rigidity near the inner edge 40e is small, and the rigidity near the outer edge 42e is large. The third tread block 70 having this transverse groove 48e can contribute to the steering performance of the tire 60. Moreover, this third tread block 70 can contribute to the grip performance of the tire 60 when driving on a hard road surface.

[0075] The ratio Ng / Nb of the number Ng of the transverse groove tread blocks present in the intermediate region Zm to the number Nb of all the tread blocks present in the intermediate region Zm is preferably 0.50 or more. In the tire 60 where the ratio Ng / Nb is 0.50 or more, an appropriate torque can be generated during turning. From this viewpoint, the ratio Ng / Nb is more preferably 0.60 or more, and particularly preferably 0.70 or more. The ratio Ng / Nb can also be 1.00.

[0076]

Example

[0077] Hereinafter, the effects of the present invention will be clarified by examples, but the present invention should not be construed in a limiting manner based on the description of these examples.

[0078] [Example 1]

[0079] A tire having the structure shown in Figure 1 -8 was obtained. The size of this tire is "80 / 100-21". Transverse groove tread blocks are present in the intermediate region of this tire. The ratio (Ng / Nb) of the number of transverse groove tread blocks is 0.75. The ratio Lg / Lb of the length of the transverse grooves of this tread block is 0.5. The detailed content of the specifications of the transverse grooves is shown in Table 1 below.

[0080] [Examples 2-5]

[0081] Tires of Examples 2-5 were obtained in the same manner as in Example 1, except that the ratio Wi / Wo of the width of the transverse grooves in the transverse groove tread blocks was as shown in Table 1 below.

[0082] [Examples 6-8]

[0083] Tires of Examples 6-8 were obtained in the same manner as in Example 1, except that the ratio Di / Do of the depth of the transverse grooves in the transverse groove tread blocks was as shown in Table 2 below.

[0084] [Examples 9-11]

[0085] Tires of Examples 9-11 were obtained in the same manner as in Example 1, except that the ratio Ng / Nb of the number of transverse groove tread blocks in the intermediate region was as shown in Table 3 below.

[0086] [Examples 12 and 13]

[0087] Tires of Examples 12 and 13 were obtained in the same manner as in Example 1, except that the ratio Wi / Wo of the width of the transverse grooves and the ratio Di / Do of the depth of the transverse grooves in the transverse groove tread blocks were as shown in Table 4 below.

[0088] [Comparative Example 1]

[0089] The tire of Comparative Example 1 was obtained in the same manner as in Example 1, except that the block with a transverse groove was not provided in the middle region.

[0090] [Comparative Example 2]

[0091] The tire of Comparative Example 2 was obtained in the same manner as in Example 1, except that the transverse groove which does not open at the axially inner end but opens at the axially outer end was provided in the block with a transverse groove.

[0092] [Comparative Example 3]

[0093] The tire of Comparative Example 3 was obtained in the same manner as in Example 1, except that the transverse groove which does not open at the axially inner end and also does not open at the axially outer end was provided in the block with a transverse groove.

[0094] [Comparative Example 4]

[0095] The tire of Comparative Example 4 was obtained in the same manner as in Example 1, except that the transverse groove which opens at the axially inner end and also opens at the axially outer end was provided in the block with a transverse groove.

[0096] [Sensory Evaluation]

[0097] Air was filled into the tire, and the internal pressure was set to 80 kPa. This tire was mounted on the front wheel rim (WM1.60) of a commercially available motorcycle for driving on an uneven road surface (engine: four-stroke type, displacement: 450 cc). A commercially available tire was mounted on the rear wheel rim. The motorcycle was driven on a motocross track, and the steering performance during turning was evaluated by the rider. The results are shown in Table 1-4 below in terms of an index. The larger the value, the better the performance.

[0098]

Table 1

[0099] Table 1 Evaluation Results

[0100]

[0101]

Table 2

[0102] Table 2 Evaluation Results

[0103]

[0104]

Table 3

[0105] Table 3 Evaluation Results

[0106]

[0107]

Table 4

[0108] Table 4 Evaluation Results

[0109]

[0110] As shown in Table 1-4, the tire steering performance of each embodiment is excellent. The superiority of the present invention can be clarified from this evaluation result.

[0111] The tire according to the present invention can be mounted on a motorcycle traveling on various road surfaces.

Claims

1. A motorcycle tire for traveling on uneven ground, wherein, it has a tread surface with a shape protruding radially outward and having blocky tread patterns, the above-mentioned blocky tread patterns have grooves and a plurality of tread blocks standing up from the grooves respectively, these tread blocks include a plurality of grooved tread blocks with transverse grooves and a plurality of tread blocks without transverse grooves, each grooved tread block has a land, a transverse groove recessed from the land, and a side surface facing the above-mentioned groove from the land, the above-mentioned transverse groove has an axially inner end opening to the above-mentioned side surface and an axially outer end not opening to the above-mentioned side surface, the above-mentioned grooved tread block has a longitudinal groove recessed from the above-mentioned land, the longitudinal groove is continuous with the above-mentioned transverse groove, and the longitudinal groove has a rear contact side end opening to the above-mentioned side surface, the above-mentioned tread surface has a crown region located at the axial center, a pair of intermediate regions respectively located at positions axially outside the above-mentioned crown region, and a pair of shoulder regions respectively located at positions axially outside the above-mentioned intermediate regions, in the above-mentioned intermediate regions, the above-mentioned grooved tread blocks and the above-mentioned tread blocks without transverse grooves are mixedly present, the area centroids of both the above-mentioned grooved tread blocks and the above-mentioned tread blocks without transverse grooves mixedly present in the above-mentioned intermediate regions are located in the above-mentioned intermediate regions, the above-mentioned grooved tread block has only the above-mentioned transverse groove and the above-mentioned longitudinal groove as grooves on the above-mentioned land.

2. The motorcycle tire for traveling on uneven ground according to claim 1, wherein, the above-mentioned transverse groove has a large width at the axially inner end and a small width at the axially outer end.

3. The motorcycle tire for traveling on uneven ground according to claim 2, wherein, the above-mentioned transverse groove has a width that gradually decreases as it goes from the axially inner end to the axially outer end.

4. The motorcycle tire for traveling on uneven ground according to claim 2 or 3, wherein, the ratio Wi / Wo of the width Wi of the axially inner end of the above-mentioned transverse groove to the width Wo of the axially outer end exceeds 1.0 and is 4.0 or less.

5. The motorcycle tire for traveling on uneven ground according to any one of claims 1 to 3, wherein, the above-mentioned transverse groove has a large depth at the axially inner end and a small depth at the axially outer end.

6. The motorcycle tire for traveling on uneven ground according to claim 5, wherein, the above-mentioned transverse groove has a depth that gradually decreases as it goes from the axially inner end to the axially outer end.

7. The motorcycle tire for traveling on uneven ground according to claim 5, wherein, the ratio Di / Do of the depth Di of the axially inner end of the above-mentioned transverse groove to the depth Do of the axially outer end exceeds 1.0 and is 4.0 or less.

8. The motorcycle tire for traveling on uneven ground according to any one of claims 1 to 3, 6, and 7, wherein, the ratio Ng / Nb of the number Ng of the above-mentioned grooved tread blocks in each intermediate region to the total number Nb of the above-mentioned tread blocks is 0.50 or more.

9. The motorcycle tire for traveling on uneven ground according to any one of claims 1 to 3, 6, and 7, wherein, the land ratio of the above-mentioned blocky tread pattern is 13% or more and 60% or less.

10. The motorcycle tire for traveling on an uneven ground according to any one of claims 1 to 3, 6, and 7, wherein, the JIS-A hardness of the above-mentioned tread block with transverse grooves is 45 or more and 88 or less.

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