Patent ID: 12227033

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be described below with reference to the drawings.FIG.1is a half sectional view along a tire meridian and schematically showing an example of a pneumatic tire according to the invention.FIG.1corresponds to a section along line A-A inFIG.2.FIG.2is a developed view schematically showing a shoulder area and a buttress area of the pneumatic tire. InFIG.2, a left-right direction corresponds to a tire circumferential direction, a downward direction corresponds to an outward direction in a tire width direction, and an upward direction corresponds to an inward direction in the tire width direction.FIGS.3A to3Dare schematic views of sections along lines A-A, B-B, C-C, and D-D inFIG.2, respectively.

The pneumatic tire T is an off-road pneumatic radial tire intended for traveling on a punishing road such as a muddy ground and a rocky stretch. As shown inFIG.1, the pneumatic tire T includes a pair of bead portions1, a pair of sidewall portions2extending outward in a tire diametrical direction X from each of the pair of bead portions1, and a tread portion3connected to an outer end of each of the pair of sidewall portions2in the tire diametrical direction. Each of the bead portions1is provided with an annular bead core1aformed by covering a bundle of steel wires or the like with rubber and a bead filler1bdisposed on an outer side of the bead core1ain the tire diametrical direction.

The pneumatic tire T further includes a carcass4provided between the pair of bead portions1, a belt5provided on an outer peripheral side of the carcass4in the tread portion3, and an inner liner6provided on an inner peripheral side of the carcass4in order to maintain air pressure. The carcass4is in a toroidal shape as a whole and has end portions each of which is rolled up to wrap the bead core1aand the bead filler1b. The belt5includes two belt plies layered on inner and outer sides. A tread rubber30is provided on an outer peripheral side of the belt5. The inner liner6faces an inner space of the tire T that is filled with air. In the sidewall portion2, the inner liner6is directly attached to an inner peripheral side of the carcass4and no other member is provided between the inner liner6and the carcass4. As shown inFIG.1, the tread portion3is provided with an edge3aat an outer end of the tire width direction Y of the tread portion3.

As shown inFIGS.1and2, a plurality of main grooves7extending along the tire circumferential direction Z and a plurality of lug grooves8extending in directions intersecting the tire circumferential direction are formed in a surface of the tread rubber30. The plurality of lug grooves8is arranged at intervals in the tire circumferential direction. The pneumatic tire T has the plurality of lug grooves8extending outward in the tire width direction Y from the shoulder area3S of the tread portion3to reach the buttress area2B of the sidewall portion2and blocks defined by the plurality of lug grooves8. The blocks defined by the lug grooves8include shoulder blocks31provided in the shoulder area3S and buttress blocks21provided in the buttress area2B. The plurality of shoulder blocks31and the plurality of buttress blocks21are respectively arranged at intervals in the tire circumferential direction.

The shoulder area3S is an area on outer sides of the shoulder main grooves71in the tire width direction in the tread portion3. The shoulder main groove71is positioned on the outermost side in the tire width direction among the plurality of main grooves7. The shoulder blocks31are provided on the outer sides in the tire width direction of the shoulder main groove71. In the present embodiment, what is called staggered shoulder is employed. In the staggered shoulder, the shoulder blocks31ahaving edges on relatively outer sides in the tire width direction and the shoulder blocks31bhaving edges on relatively inner sides in the tire width direction are arranged alternately in the tire circumferential direction. With this structure, traction is generated by shearing resistance of the shoulder blocks31ahaving the edges protruding farther outward than the shoulder blocks31b, which improves punishing road run-through performance.

The buttress area2B is an outer area of the sidewall portion2in the tire diametrical direction. More specifically, the buttress area2B is an area on the outer side in the tire diametrical direction of tire largest width position10and is a portion that does not come in contact with a ground during normal traveling on a flat paved road. On a soft road such as the muddy ground and sandy soil, each of the tires sinks under a weight of a vehicle and the buttress area2B comes in virtual contact with the ground. The tire largest width position10is a position where profile line of the tire T is farthest from a tire equator TE in the tire width direction. The profile line of the tire T is an outline of an outer surface of the sidewall portion2excluding protrusions such as a rim protector11and normally has a sectional shape along the meridian defined by smoothly connecting a plurality of arcs.

As shown inFIGS.2and3A to3D, the buttress blocks21are arranged on the outer side in the tire width direction of the shoulder blocks31and extend along the tire diametrical direction. A lower end (an inner end in the tire diametrical direction) of the buttress block21is arranged closer to an outer side in the tire diametrical direction than the tire maximum width position10is. The buttress blocks21are upraised from the outer surface2aof the sidewall portion2along the profile line of the tire T.

In the present embodiment, buttress blocks21adisposed on the outer side of the shoulder blocks31ain the tire width direction and the buttress blocks21bdisposed on the outer side of the shoulder blocks31bin the tire width direction are arranged alternately in the tire circumferential direction. A lower end of the buttress block21ais positioned closer to an inner side in the tire diametrical direction than a lower end of the buttress block21bis. In a portion not shown in the figures, the two kinds of buttress blocks21aand21bare arranged in the tire circumferential direction and the block arrangements form annular block row20. However, not two but three or more kinds of buttress blocks may form the annular block row20.

Since the tire T in the present embodiment is provided with the plurality of buttress blocks21, the traction effect is exerted by the shearing resistance of the buttress blocks21in traveling on the punishing road such as the muddy ground and the rocky stretch, which enhances the punishing road run-through performance. Moreover, because the buttress blocks21are provided, it is possible to exert protection effect which is keeping an external injury factor such as angular portions of rock surfaces away from the outer surfaces2aof the sidewall portions2to thereby improve external injury resistance. Further, the decoration effect can be achieved by the concavo-convex shape of the buttress block21, and it is possible to improve the design property of the tire side surface.

In the tire T, a buttress area2B is provided with an annular rib22which extends annularly along a tire circumferential direction while cutting across the buttress block21. In the buttress area2B, a plurality of lug grooves8are comparted into an outside lug groove81which is positioned in an outer side of the annular rib22in the tire diametrical direction and which extends in the extension direction81a, and an inside lug groove82which is positioned in an inner side of the annular rib22in the tire diametrical direction and which extends in the extension direction82a. The annular rib22is upraised from the outer surface2aof the sidewall portion2in the same manner as the buttress block21. In the present embodiment, an upraised height of the annular rib22on the basis of the outer surface2ais greater than an upraised height of the buttress block21, and a step is formed thereby. In the light of making the annular rib22hard to be conspicuous, the annular rib22may be formed flush. The buttress block21may include a position which is upraised more greatly than the annular rib22.

The annular rib22is provided with a top surface having a predetermined width W22. The annular rib22has a sectional shape that is a shape of a mountain with a flat top face. To put it more concretely, the sectional shape is a shape of a stratovolcano with a slope gently curved and constricted. However, the sectional shape is not limited to this shape and may be other shapes such as a rectangular or trapezoidal shape with a flat top face and a triangular shape with a tapered top face. An upraised height of the annular rib22from the outer surface2ais 5 mm or larger, for example, and is preferably 8 mm or larger. In the meanwhile, the upraised height of the buttress block21on the basis of the outer surface2ais preferably 5 mm or larger, and more preferably 8 mm or larger, in the light of securing the traction effect and the protection effect. In the case where the upraised heights vary along the tire diametrical direction, the maximum values thereof are preferably in the range mentioned above.

The annular rib22is provided at such a position that a distance Da shown inFIG.1is in a range of 20 mm to 40 mm, for example. The distance Da is obtained as a tire diametrical distance from an outermost diametrical position35of the tire T to an outer edge in the tire diametrical direction of the top face of the annular rib22. The annular rib22is provided at such a position that the distance Db inFIG.1equals to 75% or more of a half width HW of the tire section, for example. The distance Db is obtained as a distance in the tire width direction from the tire equator TE to the outer edge in the tire diametrical direction of the top face of the annular rib22. The half width HW of the tire section is obtained as the distance in tire width direction from the tire equator TE to the tire maximum width position10.

A widened portion23is provided in at least partial lug grooves8A in a plurality of lug grooves8so as to enlarge a width of the annular rib22. As shown inFIG.2, the widened portion23extends in the tire circumferential direction so as to join a pair of buttress blocks21and21(that is, a buttress block21aand a buttress block21b) which are defined by the lug groove8A. Further, as shown inFIG.3B, the widened portion23is upraised from the outer surface2aof the sidewall portion2, and extends from the annular rib22in the tire diametrical direction. According to the structure mentioned above, the rigidity of the annular rib22is enhanced in the lug groove8A in which the widened portion23is provided, and the protection effect of the buttress area2B is improved. Further, on the basis of the provision of the widened portion23as mentioned above, the annular rib22is hard to be conspicuous as the boundary segmentalizing the buttress block21, and the decoration effect of the buttress area2B is improved.

FIG.4shows a comparative example for comparing with the present embodiment, and the same reference numerals are attached to the same portions as the portions described in the present embodiment. The buttress area2B inFIG.4is the same as the buttress area2B inFIG.2except that the widened portion is not provided in the lug groove8A. In this comparative example, since the widened portion23inFIG.2is not provided, the annular rib22is visually conspicuous as the boundary segmentalizing the buttress block21in comparison with the case inFIG.2. As a result, the design of the buttress block21is seen to be segmentalized into upper and lower sections by the annular rib22, and there is the possibility that the buttress block applies a different impression from an intended one to a viewer. On the basis of the view point mentioned above, it can be said that there is room for improvement in relation to the decoration effect of the buttress area2B, in the configuration shown inFIG.4.

As shown inFIG.2, among a plurality of lug grooves8, the widened portion23is not provided in the other lug groove8B,181,182than the lug groove8A in which the widened portion23is provided. In the present embodiment, one lug groove8A in which the widened portion23is provided, and one lug groove8B in which the widened portion23is not provided, are alternately arranged in the tire circumferential direction. As a result, the lug groove8A and the lug groove8B are appropriately mixed, the annular rib22serving as the boundary segmentalizing the buttress block21is hard to be conspicuous, and the decoration effect is well improved. In order to obtain the effect of improvement mentioned above, it is preferable to arrange alternately in the tire circumferential direction one lug groove8A or two lug grooves8A in which the widened portion23is provided, and one lug groove8B or two lug grooves8B in which the widened portion23is not provided.

In the present embodiment, the widened portion23is provided in both of the outer side and the inner side of the annular rib22in the tire diametrical direction. The lug groove8A is provided with the widened portion23which extends outward in the tire diametrical direction from the annular rib22, and the widened portion23which extends inward in the tire diametrical direction from the annular rib22. As a result, it is possible to well enhance the protection effect of the buttress area2B. Further, since the design sense of unity can be easily applied to the outer side of the annular rib22in the tire diametrical direction and the inner side of the annular rib22in the tire diametrical direction by the widened portion23, the decoration effect of the buttress area2B is improved.

In the present embodiment, in the lug groove8A in which the widened portion23is provided, an extending direction of the outside lug groove81to the inner side in the tire diametrical direction and an extending direction of the inside lug groove82to the outer side in the tire diametrical direction are out of alignment each other. According to the structure mentioned above, in the lug groove8A, it is possible to make the annular rib22appear as though the annular rib22does not extend in the tire circumferential direction, by reducing the design continuity between the outside lug groove81and the inside lug groove82. As a result, the annular rib22serving as the boundary segmentalizing the buttress block21is hard to be conspicuous, and the decoration effect is well improved. Here, the extending direction of the outside lug groove81corresponds to an extending direction of a center line which passes through the center of a groove width of the outside lug groove81, and the extending direction of the inside lug groove82is also based thereon (refer to chain lines BL1and BL2inFIG.2).

In the lug groove8A in which the widened portion23is provided, at least one of the extending direction of the outside lug groove81to the inner side in the tire diametrical direction, and the extending direction of the inside lug groove82to the outer side in the tire diametrical direction is preferably inclined to the tire circumferential direction. In the present embodiment, both the extending directions are inclined to the tire circumferential direction. More specifically, the extending direction of the outside lug groove81to the inner side in the tire diametrical direction is inclined to one side (a right side inFIG.2) in the tire circumferential direction toward the inner side in the tire diametrical direction, and the extending direction of the inside lug groove82to the outer side in the tire diametrical direction is inclined to the other side (a left side inFIG.2) in the tire circumferential direction toward the outer side in the tire diametrical direction. Therefore, these extending directions have a positional relationship that the extending directions do not intersect each other. As a result, the annular rib22serving as the boundary segmentalizing the buttress block21is hard to be more conspicuous, and the decoration effect is well improved.

In the lug groove8A in which the widened portion23is provided, a termination of at least one of the outside lug groove81and the inside lug groove82is preferably inclined to the tire circumferential direction. As a result, in the lug groove8A, it is possible to make the annular rib22appear as though the annular rib22does not extend in the tire circumferential direction, the annular rib22serving as the boundary segmentalizing the buttress block21is hard to be conspicuous, and the decoration effect is well improved. In the present embodiment, there is shown an example in which the termination of the inside lug groove82(the outer end in the tire diametrical direction) is inclined to the tire circumferential direction. In place of this, or in addition to this, the termination of the outside lug groove81(the inner end in the tire diametrical direction) may be inclined to the tire circumferential direction. InFIG.2, there is shown an angle of gradient0of the termination of the inside lug groove82in relation to the tire circumferential direction. The first continuous groove wall81-6includes the first groove wall portion81-1, the second groove wall portion81-2, the third groove wall portion81-3, the fourth groove wall portion81-4and the fifth groove wall portion81-5in this order. The second groove wall portion81-2is opposed to the fourth groove wall portion81-4to form a first portion81b. The first groove wall portion81-1is opposed to the fifth groove wall portion81-5to form a second portion81c. A first hypothetical line81-1A extends along the first groove wall portion81-1. A fifth hypothetical line81-5A extends along the fifth groove wall portion81-5. A second hypothetical line81-2A extends along the second groove wall portion81-2. A fourth hypothetical line81-4A extended along the fourth groove wall portion81-4. The first inside lug groove82includes a second continuous groove wall82-4including a sixth groove wall portion82-1, a seventh groove wall portion82-2, and an eighth groove wall portion82-3in this order. The sixth groove wall portion82-1is opposed to the eighth groove wall portion82-3to form a third portion82b. A sixth hypothetical line82-1A extends along the sixth groove wall portion82-1. A seventh hypothetical line82-2A extends along the seventh groove wall portion82-2.

In the present embodiment, a sipe24is formed on a surface of a buttress block21which is defined by a lug groove8A where a widened portion23is provided, as shown inFIG.2. The sipe24is formed into an incision shape, and a groove width of the sipe24is smaller than a groove width of a lug groove8. An edge component of the buttress block21is somewhat reduced by the provision of the widened portion23, however, the edge component can be increased by forming the sipe24mentioned above in the buttress block21. As a result, the sipe is of help to maintain and improve the traction effect. The sipe24extends along a tire diametrical direction, and is arranged in both of an outer side and an inner side of the annular rib22in the tire diametrical direction.

In the light of increase of the edge component by the sipe24, a front end of the sipe24(or tip24a) is preferably closer to the annular rib22than the outside lug groove81and the inside lug groove82. In the present embodiment, the front end of the sipe24formed in the outer side of the annular rib22in the tire diametrical direction comes closer to the annular rib22than the outside lug groove81, and the front end of the sipe24formed in the inner side of the annular rib22in the tire diametrical direction comes closer to the annular rib22than the inside lug groove82. On the surface of the buttress area2B, a distance from the front end of the sipe24in the outer side of the annular rib22in the tire diametrical direction to the annular rib22is smaller than a distance (corresponding to a distance D1 inFIG.5) from the termination of the outside lug groove81to the annular rib22. In the same manner, a distance from the front end of the sipe24in the inner side of the annular rib22in the tire diametrical direction to the annular rib22is smaller than a distance (corresponding to a distance D2 inFIG.5) from the inside lug groove82to the annular rib22.

The above-described respective dimensions are measured in a normal condition in which the tire is mounted to a normal rim and filled with air to normal internal pressure under no load. The “normal rim” refers to a rim specified for each tire by standards in a standard system including the standards according to which tires are provided, and is “Standard Rim” in JATMA, “Design Rim” in TRA, or “Measuring Rim” in ETRTO, for example. Moreover, the “normal internal pressure” refers to an air pressure specified for each tire by the standards in the standard system including the standards according to which tires are provided, and is “Maximum Air Pressure” in JATMA, a maximum value shown in Table, “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in TRA, or “INFLATION PRESSURE” in ETRTO.

It is essential only that the annular block row20be formed on at least one of the sidewall portions2. However, from a viewpoint of further satisfactory improvement of the protection effect and decoration effect of the buttress areas, it is preferable to form the annular block rows20on the sidewall portions2on both sides.

In a modified example inFIG.5, the distance D1 in the tire diametrical direction from the termination of the outside lug groove81to the annular rib22, and the distance D2 in the tire diametrical direction from the termination of the inside lug groove82to the annular rib22are made larger than the embodiment inFIG.2. In this embodiment, since the length of the widened portion23in the tire diametrical direction is great, it is possible to comparatively greatly improve the protection effect by the widened portion23. In the light of well enhancing the protection effect by the widened portion23as mentioned above, each of the distances D1 and D2 is preferably 1 mm or larger, more preferably 3 mm or larger, and further preferably 5 mm or larger. Further, the distances D1 and D2 are, for example, equal to or less than 10 mm.

In a modified example inFIG.6, the lug groove8A shown inFIG.2(the left lug groove8A) and the lug groove8A shown inFIG.5(the right lug groove8A) are mixed as the lug groove8A in which the widened portion23is provided. In the left lug groove8A, a greater amount of edge components are provided in the buttress block21in comparison with the right lug groove8A, and an excellent traction effect can be therefore obtained. Further, in the right lug groove8A, a more excellent protection effect can be obtained as mentioned above than that in the left lug groove8A. As a result, the left lug groove8A and the right lug groove8A are alternately arranged in the tire circumferential direction, for example, while holding the lug groove8B therebetween with the left lug groove8A and the right lug groove8A mixed, and it is possible to improve the traction effect and the protection effect in a balanced manner.

The pneumatic tire according to the invention can be formed in the same way as that of a normal pneumatic tire except that the buttress area of the sidewall portion is formed in the above-described manners. Therefore, any of conventionally known materials, shapes, configurations, and manufacturing methods can be employed in the invention.

The present invention is not limited to the embodiment mentioned above, but can be improved and modified variously within the scope of the present invention.