JP6443376B2 - Heavy duty pneumatic tire - Google Patents

Description

  The present invention relates to a heavy duty pneumatic tire with a tread pattern.

  Heavy duty tires mounted on large vehicles such as dump trucks are frequently braked and driven, and have a high frequency of sharp curves. Prone to uneven wear. For this reason, high uneven wear resistance is required for heavy duty tires. On the other hand, heavy-duty tires with multiple blocks on the tread surface tend to generate heat due to repeated deformation of the block during running, especially during long-distance running off-road, due to the heat generated by the block, the tread rubber and tread It is easy to cause peeling called heat separation with the belt layer inside the part. For this reason, high heat resistance is required for heavy duty tires.

As a conventional heavy duty tire in which a plurality of blocks are formed on the tread surface, for example, there is a tire described in Patent Document 1. Specifically, the heavy load tire of Patent Document 1 is a center block row defined by a circumferential narrow groove formed along the tire circumferential direction and a wide narrow groove formed along the tire width direction; A shoulder block row defined by the circumferential narrow groove and the main lug groove, the tread gauge in the tread center region is 95 mm or more, the depth of the main lug groove is 70 to 80% of the tread gauge, The negative rate in the contact width is 15-30%, the number of center blocks or shoulder blocks is 32-44, and the center block has a length of 100-180% of the circumferential length of the center block. One or more grooves are provided.
According to such a heavy-duty tire, heat resistance is improved, so that it can be suitably used as a heavy-duty tire for construction vehicles. Moreover, according to such a heavy duty tire, the cooling effect of the crown portion is enhanced by providing one or more sub-grooves having a length of 100 to 180% of the circumferential length of the center block, and the cut separation resistance. It can be improved.

Japanese Patent No. 4676959

However, the tire of Patent Document 1 cannot achieve both heat resistance and uneven wear resistance.
The present invention provides a heavy duty pneumatic tire capable of achieving both heat resistance and uneven wear resistance.

One aspect of the present invention is a heavy duty pneumatic tire with a tread pattern,
A plurality of tire circumferential directions are provided at intervals in the tire circumferential direction, and the tire width direction and the tire are arranged in a half tread region on the first side and the second side in the tire width direction with respect to the tire equator line so as to cross the tire equator line. A linear center lug groove extending in a direction inclined with respect to the circumferential direction and having both ends;
In each of the half tread regions, a plurality of shoulder lug grooves that are provided at intervals in the tire circumferential direction, extend outward in the tire width direction, and open to the ground contact ends on both sides in the tire width direction. The position in the tire width direction of the end in the tire width direction of the shoulder lug groove is outside the position in the tire width direction of the end of the center lug groove, and in the tire circumferential direction, the center Shoulder lug grooves provided one by one between adjacent center lug grooves adjacent in the tire circumferential direction among the lug grooves;
A first curve that is provided in each of the half tread regions and is curved or bent outward in the tire width direction so as to alternately connect the end of the center lug groove and the inner end of the shoulder lug groove in the tire width direction. A pair of circumferential main grooves formed in a wave shape over the tire circumferential direction, wherein the groove curved portion and the second groove curved portion curved or bent inside the tire width direction are disposed;
Center blocks defined by the adjacent center lug grooves and the pair of circumferential main grooves and formed in a row in the tire circumferential direction;
Extending the area of the center block and having an opening end that opens to each of the adjacent center lug grooves at a position in the tire width direction excluding on the tire equator line, the groove width is narrower than the groove width of the shoulder lug groove, and has a linear shape Not a center narrow groove,
The tread pattern including
The groove width of the center lug groove and the circumferential main groove is narrower than that of the shoulder lug groove,
The center narrow groove, wherein one of the half tread region of the semi-tread region one open end is positioned within the open end, the open end of said one tire width direction inner side and the tire equatorial line and parallel to the direction It has a portion that extends to the outside in the tire width direction without extending in any way, and the portion has the one opening end .

  It is preferable that the maximum groove depth of the circumferential main groove is shallower than the maximum groove depth of the center lug groove, and the maximum groove depth of the center lug groove is shallower than the maximum groove depth of the shoulder lug groove.

  When the maximum groove depth of the center narrow groove is D1 and the maximum groove depth of the circumferential main groove is D2, the ratio D1 / D2 is preferably 0.05 or more and 0.2 or less.

  When the length of the center narrow groove is L1, and the length of the center block in the tire circumferential direction is L2, the ratio L1 / L2 is preferably more than 1.8 and not more than 2.2.

  Each of the pair of circumferential main grooves preferably includes a bottom-up portion in which the groove depth is partially shallow.

  The ratio D3 / T is preferably 0.01 or more and 0.05 or less, where D3 is the shallowest groove depth in the raised portion and T is the tread width in the tire width direction of the tread portion.

  It is preferable that the center narrow groove has one convex bending portion extending so as to protrude outward in the tire width direction with respect to the tire equator line in each of the half tread regions.

  The length of the center narrow groove extending from the opening end to the top of the convex bent portion is La, and the length of the center narrow groove extending between the tops of the convex bent portion is Lb. In this case, Lb may be longer than La.

The tread pattern further includes
In each of the half tread regions, a tire circumferential direction defined by a pair of adjacent shoulder lug grooves adjacent to each other in the tire circumferential direction, the circumferential main grooves, and the tread portion in the tire width direction among the shoulder lug grooves. A plurality of shoulder blocks formed in a row,
Preferably, the shoulder block includes a shoulder narrow groove extending in the shoulder block region and opening in each of the adjacent shoulder lug grooves and having a groove width narrower than the groove width of the shoulder lug groove.

The length of the shoulder narrow groove in the shoulder block and L3, when the tire circumferential direction of the minimum length of the shoulder block and L4, it is preferable the ratio L3 / L4 is 1.0 to 1.4 .

  The tread pattern is preferably point-symmetric with respect to a center point on the tread surface of the center block.

  The widths of the circumferential main groove and the center lug groove are preferably 7 mm or more and 20 mm or less, respectively.

  The heavy-duty pneumatic tire is suitable for mounting on a construction vehicle or an industrial vehicle.

  According to the heavy duty pneumatic tire of the present invention, both heat resistance and uneven wear resistance can be achieved.

It is sectional drawing which shows a part of heavy-duty pneumatic tire of one Embodiment of this invention. It is the figure which planarly viewed the tread pattern of the heavy duty pneumatic tire. (A) is a figure which shows the tread pattern of the heavy load pneumatic tire in the early stage of wear, (b) is a figure which shows the tread pattern of the heavy load pneumatic tire in which wear advanced further. It is the figure which planarly viewed the tread pattern of the heavy duty pneumatic tire. It is sectional drawing which shows the bottom raising part of the circumferential direction main groove. It is a figure which shows the modification of the tread pattern of FIG. It is a figure which shows the other modification of the tread pattern of FIG.

Hereinafter, the heavy duty pneumatic tire of the present invention will be described in detail.
FIG. 1 includes a tire rotation shaft of a heavy-duty pneumatic tire (hereinafter also referred to as a tire) 1 according to the present embodiment, and is a plane including a tire radial direction through line II in FIG. The profile of the tire 1 when the tire 1 is cut is shown.
The heavy-duty pneumatic tire referred to in this specification is one type (dump truck, scraper) described in Chapter D in addition to the tire described in Chapter C of JATMA (Japan Automobile Tire Association Standard) YEAR BOOK 2014. Tires, 2 types (Grada) tires, 3 types (excavator loader) tires, 4 types (tire roller) tires, mobile crane (truck crane, wheel crane) tires, or SECTION 4 of TRA 2013 YEAR BOOK Or the vehicle tire described in SECTION 6.
The tire 1 includes a carcass ply 3, a belt portion 4, and a pair of bead cores 5 as skeleton materials. A tread portion 6, a side portion 7, a bead filler 8, and an inner liner 9 are provided around these skeleton materials. Etc. each rubber layer.

  The belt portion 4 is disposed between the pair of first cross belt layers 31, the pair of second cross belt layers 33, the pair of third cross belt layers 35, and the belt layers of the second cross belt layers 33. Sheet-like rubber 37. The first cross belt layer 31, the second cross belt layer 33, and the third cross belt layer 35 are each a pair of belt layers in which the direction of the belt cord is inclined in the opposite direction with respect to the tire circumferential direction, The tires are arranged in this order from the inside to the outside in the tire radial direction.

  The tread portion 6 includes a tread pattern 10 shown in FIG. FIG. 2 is a plan view of the tread pattern of the tire 1. In FIG. 2, the vertical direction is the tire circumferential direction, and the horizontal direction is the tire width direction. Here, the tire circumferential direction is the rotation direction of the rotation surface of the tread surface that is formed when the tire 1 is rotated about the tire rotation center axis. The tire width direction is the rotation center axis direction of the tire 1. The tire radial direction is a direction orthogonal to the tire circumferential direction and the tire width direction. The direction of rotation of the tire of the tread pattern and the direction of the tire width direction when the vehicle is mounted are not particularly specified.

  The tread pattern 10 includes a center lug groove 11, a shoulder lug groove 13, a pair of circumferential main grooves 15, a center block 23, and a shoulder block 27.

  A plurality of center lug grooves 11 are provided at intervals in the tire circumferential direction. The center lug groove 11 extends in the tire width direction on the half tread regions Ta and Tb on both sides (first side and second side) in the tire width direction with respect to the tire equator line CL so as to cross the tire equator line CL. And it has the both ends 11a and 11a extended in the direction inclined with respect to the tire circumferential direction. The center lug groove 11 connects second groove bent portions 15b described later of the pair of circumferential main grooves 15 to each other. As will be described later, since the pair of circumferential main grooves 15 have different phases and extend in a wave shape, the center lug groove 11 extends while being inclined with respect to the tire width direction. The center lug groove 11 is a linear groove. For this reason, compared with the case where the center lug groove 11 is not a linear shape, the block rigidity of the center block 23 is made uniform, and uneven wear can be suppressed. The groove width of the center lug groove 11 is narrower than that of the shoulder lug groove 13. For this reason, the contact pressure of the center block 23 during traveling is relaxed, and the wear life of the tire 1 is extended.

A plurality of shoulder lug grooves 13 are provided at intervals in the tire circumferential direction in each of the half tread regions Ta and Tb. The shoulder lug groove 13 extends outward in the tire width direction in each of the half tread regions Ta and Tb, and opens to the adjacent grounding end of the grounding ends 10a and 10b on both sides in the tire width direction.
Here, the grounding terminals 10a and 10b are determined as follows. The ground contact ends 10a and 10b are tire width direction ends of the ground contact surface when the tire 1 is assembled to a regular rim, filled with a regular internal pressure, and grounded on a horizontal plane under the condition that the load is 100% of the regular load. . The regular rim referred to here means “measurement rim” defined in JATMA, “Design Rim” defined in TRA, or “Measuring Rim” defined in ETRTO. In addition, the normal internal pressure means “maximum air pressure” defined by JATMA, the maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “INFLATION PRESSURES” defined by ETRTO. The normal load means “maximum load capacity” defined in JATMA, the maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined in TRA, or “LOAD CAPACITY” defined in ETRTO. The tire width direction positions of the ground contact ends 10a and 10b coincide with the tire width direction positions of both ends of the tread width described later.

In the shoulder lug grooves 13 located on both sides in the tire width direction, the position in the tire circumferential direction of one shoulder lug groove 13 arranged in one half-tread region is adjacent to the two adjacent half-tread regions. The two shoulder lug grooves 13 are located between the positions in the tire circumferential direction.
Further, the shoulder lug groove 13 has a tire width direction position of an end 13a on the inner side in the tire width direction of the shoulder lug groove 13 in each of the half tread regions Ta and Tb. The shoulder lug groove 13 is located on the outer side in the tire width direction with respect to the position in the width direction, and the shoulder lug groove 13 is located between adjacent center lug grooves 11 adjacent to each other in the tire circumferential direction in the center lug groove 11 in the tire circumferential direction. One is provided in each area. Thereby, the circumferential main groove 15 to be described later is formed by alternately connecting the end 11a of the center lug groove 11 and the inner end 13a of the shoulder lug groove 13 in the tire width direction in each of the half tread regions Ta and Tb. Form the shape. The shoulder lug groove 13 has a groove width that changes in the direction in which the groove extends in FIG. 2, but may be constant.

  The circumferential main groove 15 is provided in each of the half tread regions Ta and Tb on both sides in the tire width direction with respect to the tire equator line CL as a pair. The circumferential main grooves 15 are arranged in the tire width direction so as to alternately connect the ends 11a of the center lug grooves 11 and the inner ends 13a of the shoulder lug grooves 13 in the half tread regions Ta and Tb. A first groove bent portion 15a that is curved or bent outward and a second groove bent portion 15b that is bent or bent inside in the tire width direction are disposed and formed in a wave shape over the entire circumference in the tire circumferential direction. As a result, the circumferential main groove 15 is connected to the shoulder lug groove 13 at the first groove bent portion 15a that is curved to protrude outward in the tire width direction, and is bent to be convex inward in the tire width direction. It connects with the center lug groove 11 by the 2 groove bending part 15b. The groove having a wave shape means a shape in which the groove meanders. The circumferential main groove 15 has a plurality of first groove bent portions 15a and second groove bent portions 15b on the tire circumference, and extends in the tire circumferential direction while meandering so as to form a wave shape by alternately connecting them. Since the circumferential main groove 15 has a wave shape, the surface area of the groove wall is increased, and heat dissipation is improved. For this reason, the heat resistance is improved.

  The first groove bent portion 15a and the second groove bent portion 15b may have a bent shape, a rounded curved shape, or a combination of a bent shape and a curved shape. The curved shape also includes a shape obtained by rounding the top of the bent shape, for example, by defining a curvature radius. The combination of the bent shape and the curved shape means a shape in which one side extends linearly from the top of the groove bent portion and the other side curves and extends from the top. Of the bent shape, the curved shape, and combinations thereof, the groove bent portion may have the same shape, or may have different types of shapes. Further, portions other than the groove bent portion of the circumferential main groove 15 may be linear or curved. When both the groove bent portion and the portion other than the groove bent portion are curved, the two curved shapes may be curved with the same radius of curvature.

In FIG. 2, the circumferential main groove 15 extends in a wave shape with the same period and with a phase shifted in the tire circumferential direction. Specifically, the position in the tire circumferential direction of the second groove bent portion 15b is displaced in the tire circumferential direction with respect to the second groove bent portion 15b in the opposite half tread region. The circumferential main grooves 15 may extend in a wave shape with the same period and the same phase, or may extend in a wave shape with different periods.
The groove width of the circumferential main groove 15 is narrower than the shoulder lug groove 13. For this reason, the contact pressure of the center block 23 during traveling is relaxed, and the wear life of the tire 1 is extended.

  The center block 23 is defined by the center lug groove 11 and the circumferential main groove 15 and formed in a plurality in a row in the tire circumferential direction, and the tire equator line CL passes through. The center block 23 is inclined with respect to the tire width direction by the center lug groove 11 being inclined with respect to the tire width direction.

  The shoulder block 27 includes a pair of adjacent shoulder lug grooves 13 adjacent to each other in the tire circumferential direction, the circumferential main groove 15 and the tire width direction of the tread portion 6 in each of the half tread regions Ta and Tb. Are formed by a plurality of lines in the circumferential direction of the tire. In the example shown in FIG. 2, the shoulder block 27 is inclined to a side different from the side where the center block 23 is inclined with respect to the tire equator line CL.

  The tread pattern 10 of the present embodiment is characterized by further comprising a center narrow groove 17 in addition to the above basic form.

The center narrow groove 17 extends in the area of the center block 23. For this reason, the center block 23 is divided into two regions 21 and 22 that sandwich the center narrow groove 17. The center narrow groove 17 has opening ends 17a and 17b that open to the adjacent center lug grooves 11 at positions in the tire width direction except on the tire equator line CL. Since both ends of the center narrow groove 17 are opened in the center lug groove 11 in this way, air flow in the center region (region sandwiched between the pair of circumferential main grooves 15) is improved, and heat resistance is improved. improves. Further, since the opening ends 17a and 17b are located at positions in the tire width direction except on the tire equator line CL, and the center narrow groove 17 is not linear, it is easy to secure the groove volume of the center narrow groove 17, and the center block 23 can be sufficiently cooled. In the example shown in FIG. 2, the opening end 17a and the opening end 17b are located in different half-tread regions, and the center narrow groove 17 intersects the tire equator line CL, but is located in the same half-tread region. May be. In this case, in order to ensure a sufficient groove volume, it is preferable that the center narrow groove 17 intersects the tire equator line CL.
When the opening end 17a and the opening end 17b are located in different half-tread regions, the opening end 17a and the opening end 17b are disposed on the same side as the tire width direction side where the center block 23 is inclined with respect to the tire equator line CL. It is preferable that the opening end 17a and the opening end 17b are positioned so that a virtual straight line connecting the two is inclined with respect to the tire equator line CL. Specifically, the opening end 17a is located in the half-tread region Ta as in the example shown in FIG. 2 rather than the form in which the opening end 17a is located in the half-tread region Tb and the opening end 17b is located in the half-tread region Ta. The opening end 17b is preferably located in the half-tread region Tb. Thereby, the groove volume of the center narrow groove 17 can be sufficiently secured, and the heat resistance can be improved.
The center narrow groove 17 is narrower than the shoulder lug groove 13.

  The center narrow groove 17 has a portion 17c extending outward in the tire width direction from the opening end 17a in the half tread region Ta where the opening end 17a is located, and a tire 17 extending from the opening end 17b in the half tread region Tb where the opening end 17b is located. A portion 17d extending outward in the width direction is included. Since the center narrow groove 17 has such portions 17c and 17d, it becomes difficult for the ground pressure to become constant when the tire 1 rotates, so that stress is concentrated at a specific position in the center block 23. Can be avoided. More specifically, when the same position in the tire width direction does not always contact when the tire 1 rotates, that is, when the position that does not contact always remains the same in the tire width direction, stress concentrates at that position, and early Although wear tends to occur, the portions 17c and 17d extend outward in the tire width direction, so that the position where the tire does not come into contact with the tire during rotation can be varied in the tire circumferential direction, and the stress concentrated positions can be dispersed. it can. In particular, since the portions 17c and 17d extend outward in the tire width direction so as to move away from the tire equator line CL, the position at which no contact is made during tire rotation can be varied over a wider range in the tire width direction.

  The tread pattern 10 further includes one or a plurality of second center narrow grooves different from the first center narrow groove in the region of the center block 23 when the center narrow groove 17 is referred to as a first center narrow groove. May be. The groove width of the second center narrow groove is narrower than the groove width of the shoulder lug groove 13, and is equal to, for example, the groove width of the first center narrow groove. The second center narrow groove may have both ends opened to the adjacent center lug groove 11, one end opened to the center lug groove 11, and the other end closed, Both ends may be closed in the area of the center block 23. Instead of opening in the center lug groove 11, the second center narrow groove may open in the circumferential main groove 15. The second center narrow groove may be connected to the first center narrow groove or may not be connected to the first center narrow groove. The second center narrow groove may intersect with the first center narrow groove when connecting to the first center narrow groove. The second center narrow groove may be formed so as to continuously extend with the first center narrow groove of the adjacent center block 23 or the second center narrow groove and the center lug groove 11 interposed therebetween. The maximum groove depth of the second center narrow groove is preferably shallower than the maximum groove depth of the circumferential main groove 15, and is equal to, for example, the maximum groove depth of the first center narrow groove.

  In the tire 1 of the present embodiment, the maximum groove depth of the circumferential main groove 15 is shallower than the maximum groove depth of the center lug groove 11, and the maximum groove depth of the center lug groove 11 is the maximum groove of the shoulder lug groove 13. It is preferably shallower than the depth. Due to the order of the groove depths, as the tire 1 wears, the circumferential main groove 15 and the center lug groove 11 disappear in this order from the tread surface, and the shoulder lug groove 13 remains at the end. In the tread portion 6, the center region has a high ground pressure, and the center block 23 is easily deformed by repeatedly deforming. Therefore, in order to improve the heat resistance, it is preferable that the maximum groove depth of the center lug groove 11 is greater than or equal to the maximum groove depth of the circumferential main groove 15. Further, if the maximum groove depth of the circumferential main groove 15 is too large, sufficient rigidity of the tread portion 6 cannot be secured, and it becomes difficult to extend the wear life. Therefore, the maximum groove depth of the circumferential main groove 15 is The lug groove 11 is preferably shallower than the maximum groove depth. Note that the maximum groove depth refers to the maximum groove depth when the groove depth is not constant in the direction in which the groove extends, and refers to the groove depth when the groove depth is constant. For example, when the circumferential main groove 15 includes a bottom raised portion 15c described later, the maximum groove depth is a groove depth of a portion of the circumferential main groove 15 that is not raised.

In the tire 1 of the present embodiment, the maximum groove depth of the center narrow groove 17 is preferably shallower than the maximum groove depth of the circumferential main groove 15. When the tire 1 is worn because the maximum groove depth is shallower than the maximum groove depth of the circumferential main groove 15, the center narrow groove 17 is more than the circumferential main groove 15 as shown in FIG. Disappears quickly. FIG. 3B is a diagram showing a tread pattern of the tire 1 in which wear has progressed from the early stage of wear. FIG. 3A is a diagram showing a tread pattern of the tire 1 in the initial stage of wear. The initial stage of wear refers to the wear stage of the tire 1 where the groove with the shallowest groove depth has not yet disappeared, and includes when the tire 1 is new.
In particular, in the tire 1 of the present embodiment, when the maximum groove depth of the center narrow groove 17 is D1 and the maximum groove depth of the circumferential main groove 15 is D2, the ratio D1 / D2 is 0.05 or more and 0.00. More preferably, it is 2 or less. When the ratio D1 / D2 exceeds 0.2, the rigidity of the center block 23 is lowered and uneven wear is likely to occur, and the rubber amount of the center block 23 is insufficient and the wear resistance may be lowered. On the other hand, if the ratio D1 / D2 is less than 0.05, the center narrow groove 17 does not sufficiently function as an air passage in the early stage of wear, and the heat resistance is hardly improved. The ratio D1 / D2 is more preferably 0.1 or more and 0.2 or less. In addition, regarding each groove included in the tread pattern 10, when the groove depth is simply referred to, it indicates the maximum groove depth. In the cross section taken along the line II, the circumferential main groove 15 has a portion where a bottom raised portion 15c, which will be described later, is located. For convenience of explanation, the groove depth of the bottom raised portion 15c is shown in FIG. The groove depth D2 of the circumferential main groove 15 is shown instead of D3 (described later).

  In the tire 1 of the present embodiment, as shown in FIG. 4, when the groove length of the center narrow groove 17 is L1 and the length in the tire circumferential direction of the center block 23 is L2, the ratio L1 / L2 is 1. It is preferably more than 8 and less than 2.2. FIG. 4 shows the same tread pattern as in FIG. In the example shown in FIG. 4, L2 is constant in the same tire width direction region as the tire width direction region in which the center lug groove 11 is located. For example, when the adjacent center lug grooves 11 are not parallel to each other, Its maximum length. When the ratio L1 / L2 exceeds 1.8, the groove volume in the region of the center block 23 is sufficiently secured, and the heat resistance can be improved. On the other hand, even if the ratio L1 / L2 exceeds 1.8, if the maximum groove depth of the center narrow groove 17 is shallower than the maximum groove depth of the circumferential main groove 15, the center narrow groove 17 is caused by wear as described above. Disappears relatively early, so that a decrease in the rigidity of the center block 23 can be suppressed. That is, when the ratio L1 / L2 exceeds 1.8, the heat resistance in the initial stage of wear with a large amount of rubber is improved, and the maximum groove depth of the center narrow groove 17 is larger than the maximum groove depth of the circumferential main groove 15. If it is shallow, the wear life can be extended. When the ratio L1 / L2 is 1.8 or less, the center narrow groove 17 does not sufficiently function as an air passage. Moreover, generation | occurrence | production of the partial wear by the rigidity fall of the center block 23 can be suppressed because ratio L1 / L2 is 2.2 or less. If the ratio L1 / L2 exceeds 2.2, the rigidity of the center block 23 may be reduced and uneven wear may occur. The ratio L1 / L2 is more preferably 1.9 or more and 2.1 or less.

As shown in FIG. 5, the tire 1 of the present embodiment preferably includes a bottom raised portion 15 c in which the groove is partially shallow in each of the circumferential main grooves 15. FIG. 5 shows a partial profile of the tread portion when the tire 1 is cut along a plane including the tire radial direction through the VV line in FIG. 2. The bottom of the raised portion 15c is raised at the bottom corresponding to the position where the first groove bent portion 15a and the second groove bent portion 15b are disposed. In this way, the circumferential main groove 15 includes the bottom raised portion 15c at a position where it is connected to the center lug groove 11 and the shoulder lug groove 13, so that the adjacent center block 23 and shoulder block 27 are supported and the block collapses. Is suppressed, the block rigidity becomes an appropriate size. Thereby, early wear due to uneven wear can be suppressed. In the intermediate region of the circumferential main grooves 15 extending between adjacent bottom raised portions 15c, the groove volume is ensured due to the deep groove depth, and the heat resistance is improved.
The bottom raised portion 15c may have a constant groove depth D3 as illustrated, or the groove depth may not be constant. The groove depth D3 refers to the shallowest groove depth in the bottom raised portion 15c, and is the minimum groove depth of the circumferential main groove 15. In the example shown in FIG. 5, the bottom raised portion 15c is formed at a position corresponding to the first groove bent portion 15a and the second groove bent portion 15b, but may be formed in the intermediate region.

  Further, regarding the shallowest groove depth D3 in the bottom raised portion 15c and the tread width T in the tire width direction of the tread portion 6, the ratio D3 / T is preferably 0.01 or more and 0.05 or less. The tread width T is a peripheral length along the outer shape between both ends (grounding ends 10a, 10b) of the tread portion 6 in the tire width direction. When the ratio D3 / T is 0.05 or less, the center block 23 and the shoulder block 27 support each other, so that the rigidity of the block becomes more appropriate and early wear due to uneven wear can be suppressed. Further, when the ratio D3 / T is equal to or greater than 0.01, it is possible to avoid deterioration of air passage in the groove. The ratio D3 / T is more preferably 0.02 or more and 0.04 or less.

In the tire 1 of the present embodiment, the center narrow groove 17 has one convex bent portion 18a or 18b extending in the tire width direction outer side with respect to the tire equator line CL in each of the half tread regions Ta and Tb. It is preferable to have. The convex bent portions 18a and 18b are portions of the center narrow groove 17 that are bent by changing the direction of the groove on the tread surface. Specifically, the bent portions 18a and 18b may be bent or rounded. Alternatively, a combination of a bent shape and a curved shape may be used. As the curved shape, the convex curved portions 18a and 18b are rounded by setting the radius of curvature, and the bent top portions 17e and 17f (see FIG. 2) are, for example, curved radii as shown in FIG. Also included are rounded shapes. The combination of the bent shape and the curved shape means a shape in which one side of the top portions 17e and 17f of the convex bent portions 18a and 18b extends linearly and the other side curves and extends from the top portions 17e and 17f. Of the bent shape, the curved shape, and combinations thereof, the convex bent portions 18a and 18b may have the same shape, or may have different types of shapes. Moreover, portions other than the convex bent portions 18a and 18b in the center narrow groove 17 may be linear or curved. In the example shown in FIG. 2, the portions other than the convex bent portions 18a and 18b have a linear shape. When the portions other than the convex bent portions 18a and 18b and the convex bent portions 18a and 18b are curved, the two curved shapes may be curved with the same radius of curvature.
In addition, the convex bending part 18a and the convex bending part 18b are connected through the part 17g extended linearly so that the tire equator line CL may be crossed in the example shown by FIG.
Since the center narrow groove 17 has the convex bent portions 18a and 18b, the block rigidity of the regions 21 and 22 divided by the center narrow groove 17 is appropriate, and the occurrence of uneven wear is suppressed. The Further, a sufficient groove volume is secured in the area of the center block 23, and the heat resistance is improved. When only one convex bent portion is disposed in the center narrow groove 17, or when only one convex bending portion is disposed in one half tread region, uneven block rigidity is generated, and uneven wear tends to occur.

  In the tire 1 of the present embodiment, the length of the portion of the center narrow groove 17 extending from the open ends 17a and 17b to the top portions 17e and 17f of the convex bent portions 18a and 18b is La, and between the top portions of the convex bent portions. When the length of the extending center narrow groove is Lb, Lb is preferably longer than La. The top portions 17e and 17f of the convex bent portions 18a and 18b are bending points when the convex bent portions 18a and 18b have a bent shape, and include a shape in which the convex bent portions 18a and 18b are rounded with a curvature radius determined. In this case, it is the midpoints (midpoints on the arc) 17e and 17f of the groove length of the portion having a rounded shape. Since Lb is longer than La, the convex bent portion 18a and the convex bent portion 18b are sufficiently separated from each other, and the block rigidity tends to be more appropriate in each of the regions 21 and 22 divided by the center narrow groove 17. The occurrence of wear is further suppressed.

In the tire 1 of the present embodiment, the tread pattern 10 extends in the region of the shoulder block 27 in each of the half-tread regions Ta and Tb and opens in each of the adjacent shoulder lug grooves 13 as shown in FIG. It is preferable to include a shoulder narrow groove 19 having a groove width narrower than that of the shoulder lug groove 13. The shoulder narrow groove 19 having both ends opened to the shoulder lug groove 13 in the region of the shoulder block 27 increases the surface area of the tread portion 6 and improves the passage of air, thereby preventing heat generation. Improves. Further, the width of the shoulder narrow groove 19 is narrower than the width of the shoulder lug groove 13. The shoulder block 27 includes two regions 25 and 26 divided by the shoulder narrow groove 19.
In the example shown in FIG. 2, the shoulder narrow groove 19 has a linear shape, but may not have a linear shape. For example, the shoulder narrow groove 19 has a groove bent portion similar to the groove bent portions 15 a and 15 b of the circumferential main groove 15. You may do it. In the example shown in FIG. 2, the shoulder narrow groove 19 extends in the tire circumferential direction, but may extend in an inclined manner with respect to the tire circumferential direction. As shown in FIG. 2, the adjacent shoulder narrow grooves 19 adjacent to each other in the tire circumferential direction may be connected to the shoulder lug grooves 13 at the same tire width direction position, or may be connected at different tire width direction positions. May be.

  In the tire 1 of the present embodiment, when the length of the shoulder narrow groove 19 is L3 and the minimum length of the shoulder block in the tire circumferential direction is L4, the ratio L3 / L4 is 1.0 or more and 1.4 or less. It is preferable. When the ratio L3 / L4 is 1.0 or more, the shoulder narrow groove 19 opens in both the adjacent shoulder lug grooves 13 at a position where at least L4 is minimum. Further, when the ratio L3 / L4 is 1.4 or less, uneven wear due to a decrease in the block rigidity of the shoulder block 27 can be suppressed. The length in the tire circumferential direction of the shoulder block 27 may be constant in the tire width direction, or may not be constant as in the example shown in FIG. In the example shown in FIG. 2, L4 is a tire circumferential direction length at a position in the tire width direction at which the tire circumferential direction length is minimum in the shoulder block 27.

  In the tire 1 of the present embodiment, the tread pattern 10 is preferably point-symmetric with respect to the center point P (see FIG. 2) on the tread surface of the center block 23. When the tread pattern 10 has such a form, rigidity is uniform on both sides in the tire width direction, and uneven wear can be suppressed. If it is not point-symmetric, rigidity will be uneven and uneven wear tends to occur. In the tread pattern 10, the center blocks 23 have the same form in the center block row.

  In the tire 1 of the present embodiment, it is preferable that the groove widths of the circumferential main groove 15 and the center lug groove 11 are 7 mm or more and 20 mm or less, respectively. The width of the circumferential main groove 15 and the center lug groove 11 is, for example, 18 mm. In addition, it is suitable when the tire 1 is used as an off-road tire that the groove width of the circumferential main groove 15 and the center lug groove 11 is in the above range. In this case, it is preferable that the groove widths of the center narrow groove 17 and the shoulder narrow groove 19 are 7 mm or more and 20 mm or less, respectively.

  The tire 1 of the present embodiment is suitable for mounting on a construction vehicle or an industrial vehicle. Construction vehicles or industrial vehicles are, for example, dump trucks, scrapers, graders, excavator loaders, tire rollers, wheel cranes, truck cranes described in JATMA, or `` COMPACTOR '', `` EARTHMOVING '' as defined in TRA, Includes vehicles such as “GREADER” and “LOADER AND DOZER”.

As a modification, the tire 1 of the present embodiment may have the tread pattern 10 shown in FIG. 6 or 7 instead of the example shown in FIG. FIG. 6 and FIG. 7 are diagrams showing modifications of the tread pattern of FIG. 6 and 7, the same reference numerals as those used in FIG. 2 are used for elements corresponding to the elements included in the tread pattern 10 shown in FIG.
In FIG. 6, the convex bent portions 18a and 18b have a shape rounded with a radius of curvature as a whole, and the midpoints on the arc are apexes 17e and 17f. Further, in FIG. 7, the convex bent portions 18a and 18b have two bent portions with a linearly extending portion 17g interposed therebetween, and one of these is located on the outer side in the tire width direction. The bent portions are the top portions 17e and 17f. In the modification shown in FIGS. 6 and 7, the length Lb of the portion 17g extending between the two top portions 17e and 17f is equal to the portion 17c extending from the open end 17a to the apex 17e (the portion extending from the open end 17b to the apex 17f). It is longer than the length La of 17d).

  According to the heavy load pneumatic tire 1 of the present embodiment, the center lug groove 11 has a linear shape, so that the block rigidity of the center block 23 adjacent in the tire circumferential direction is made uniform, and uneven wear is suppressed. it can. Moreover, by having the center narrow groove 17 opened to the adjacent center lug groove 11, the air flow in the center region is improved, and the heat resistance is improved. Further, since the center narrow groove 17 has portions 17c and 17d extending from the opening ends 17a and 17b to the outer side in the tire width direction, the position where the center does not come into contact with the tire in the tire width direction in the center region. By changing, it is possible to avoid stress concentration at the same position in the tire width direction and to suppress the occurrence of early wear.

  When the maximum groove depth of the circumferential main groove 15 is shallower than the maximum groove depth of the center lug groove 11 and the maximum groove depth of the center lug groove 11 is shallower than the maximum groove depth of the shoulder lug groove 13, The heat generation can be improved, the rigidity of the tread portion 6 can be sufficiently secured, and the wear life can be extended.

  When the ratio D1 / D2 is 0.2 or less, the lowering of rigidity of the center block 23 can be suppressed and the occurrence of uneven wear can be suppressed, and the rubber amount of the center block 23 can be secured to suppress the deterioration of wear resistance. Can do. Further, when the ratio D1 / D2 is 0.05 or more, the center narrow groove 17 functions sufficiently as an air passage in the early stage of wear, and heat resistance can be improved.

  When the ratio L1 / L2 exceeds 1.8, the groove volume in the region of the center block 23 is sufficiently secured, and the heat resistance can be improved. On the other hand, even if the ratio L1 / L2 exceeds 1.8, if the maximum groove depth of the center narrow groove 17 is shallower than the maximum groove depth of the circumferential main groove 15, the center narrow groove 17 is caused by wear as described above. Disappears relatively early, so that a decrease in the rigidity of the center block 23 can be suppressed. That is, when the ratio L1 / L2 exceeds 1.8, the heat resistance in the initial stage of wear with a large amount of rubber is improved, and the maximum groove depth of the center narrow groove 17 is larger than the maximum groove depth of the circumferential main groove 15. If it is shallow, the wear life can be extended. When the ratio L1 / L2 is 1.8 or less, the center narrow groove 17 does not sufficiently function as an air passage. Moreover, generation | occurrence | production of the partial wear by the rigidity fall of the center block 23 can be suppressed because ratio L1 / L2 is 2.2 or less.

  Since each of the circumferential main grooves 15 includes the bottom raised portion 15c in which the grooves are partially shallow, the adjacent center block 23 and the shoulder block 27 support each other, thereby preventing the block from collapsing. Rigidity is moderately sized. Thereby, early wear due to uneven wear can be suppressed.

  When the ratio D3 / T is 0.05 or less, the center block 23 and the shoulder block 27 support each other, so that the rigidity of the block becomes more appropriate and early wear due to uneven wear can be suppressed. Further, when the ratio D3 / T is equal to or greater than 0.01, it is possible to avoid deterioration of air passage in the groove.

  Since the center narrow groove 17 has the convex bent portions 18a and 18b, the block rigidity of the regions 21 and 22 divided by the center narrow groove 17 is appropriate, and the occurrence of uneven wear is suppressed. The Further, a sufficient groove volume is secured in the area of the center block 23, and the heat resistance is improved.

  Regarding the above La and Lb, when Lb is longer than La, the convex bent portion 18a and the convex bent portion 18b are sufficiently separated from each other, and the block rigidity is more appropriate in each of the regions 21 and 22 divided by the center narrow groove 17 And the occurrence of uneven wear is further suppressed.

  When the tread pattern 10 includes the shoulder narrow groove 19, the surface area of the tread portion 6 is increased, and air passage is improved, thereby improving heat resistance.

  Regarding the ratio L3 / L4, when the ratio L3 / L4 is 1.0 or more, the shoulder narrow groove 19 opens in both of the adjacent shoulder lug grooves 13 at least at a position where L4 is minimum. Further, when the ratio L3 / L4 is 1.4 or less, uneven wear due to a decrease in the block rigidity of the shoulder block 27 can be suppressed.

  By being point symmetric with respect to the center point P on the tread surface of the center block 23, rigidity is uniform on both sides in the tire width direction, and uneven wear can be suppressed.

  When the groove widths of the circumferential main groove 15 and the center lug groove 11 are 7 mm or more and 20 mm or less, respectively, it is suitable for use as an off-road tire.

  The tire 1 of the present embodiment is suitable for mounting on a construction vehicle or an industrial vehicle.

(Example)
In order to investigate the effect of the tire of this embodiment, various tires having different tread patterns were produced as shown in Tables 1 to 4 (Examples 1 to 14 and Comparative Examples 1 and 2), and heat resistance in the tread center region was measured. And uneven wear resistance were investigated. In addition, the specification of the tread pattern of FIG. 2 was used for the specifications of the tire other than the specifications shown in Tables 1 to 4.
The sizes of the prototyped tires are 33.00R51. The test piece was mounted on a rim having a size of 51 × 24-5.0, and a heat generation resistance test and a partial wear resistance test were performed using 700 kPa (TRA standard maximum air pressure) as a test condition.

(Heat resistance)
The prototype tire was attached to the indoor drum tester, and it traveled at a speed of 5 km / h under the condition of 110% load load of TRA standard maximum load (38,750 kg), and the speed was increased by 1 km / h every 12 hours. The running time until the tire broke was measured. The result was expressed as an index with Comparative Example 1 as 100. The larger the index, the better the heat resistance.

(Uneven wear resistance)
The degree of uneven wear that occurred when the prototype tire was mounted on an actual vehicle and the mine off-road road surface test was performed under the TRA standard maximum load (38,750 kg) test condition and the vehicle ran for the same time of 3000 hours or more. Was expressed as an index with Comparative Example 1 taken as 100. As uneven wear, the maximum level difference in the tire circumferential direction on the tread surface was observed. The larger the index, the better the uneven wear resistance.
As a result of the above, when the index of heat resistance and uneven wear resistance is both 100 or more and the sum of the indices is 205 or more, both heat resistance and uneven wear resistance can be achieved. It was evaluated.

As shown in Table 1, it has a pair of circumferential main grooves, a straight center lug groove, a center narrow groove that opens to an adjacent center lug groove, and the center narrow groove is In the case of having a portion extending from the opening end to the outer side in the tire width direction (Example 1), both heat resistance and uneven wear resistance were compatible. On the other hand, when the center narrow groove does not have a portion extending outward in the tire width direction from the opening end (Comparative Example 2), the heat resistance and the uneven wear resistance cannot be sufficiently improved. It was. As an aspect in which the center narrow groove does not have a portion extending outward in the tire width direction from the opening end, an aspect in which the center narrow groove extends in the tire circumferential direction from the opening end is adopted.
In addition, as an aspect which does not have the center narrow groove opened to an adjacent center lug groove | channel of the comparative example 1, what the center narrow groove opened only to one side of the adjacent center lug groove | channel was used.

As can be seen from Table 1 and Table 2, when the ratio D1 / D2 is 0.05 or more and 0.2 or less (Examples 2 and 3), D1 / D2 exceeds 0.2 (Example 1). Compared to, improved uneven wear resistance.
Moreover, when ratio L1 / L2 exceeds 1.8 and is 2.2 or less (Examples 4-6), compared with the case where L1 / L2 is less than 1.8 (Example 2), heat resistance is increased. And the uneven wear resistance was improved. Moreover, compared with the case where L1 / L2 exceeds 2.2 (Example 7), the uneven wear resistance was improved and the balance between heat resistance and uneven wear resistance was excellent. In addition, the case where the difference in index between the heat generation resistance and the uneven wear resistance was 7 or less was evaluated as being further excellent in the balance between the heat generation resistance and the uneven wear resistance.

As can be seen from Tables 2 and 3, when the ratio D3 / T is 0.05 or less (Example 8), compared to the above ratio D3 / T exceeding 0.05 (Example 7), uneven wear resistance Greatly improved.
Further, when the center narrow groove has a convex bent portion in each half-tread region (Example 9), the center thin groove does not have a convex bent portion in each half-tread region (Example) Compared to 8), uneven wear resistance was improved. In addition, the aspect which has a convex bending part only in one half-tread area | region was employ | adopted as an aspect which does not have a convex bending part in each half-tread area | region.
Further, when the ratio L3 / L4 is 1.0 or more and 1.4 or less (Examples 11 and 12), compared to the case where the ratio L3 / L4 exceeds 1.4 (Example 13), uneven wear resistance is achieved. And a good balance between heat resistance and uneven wear resistance.

  As can be seen from Tables 3 and 4, when the tread pattern is point-symmetric (Example 14), both heat resistance and uneven wear resistance are improved compared to the case where the tread pattern is not point-symmetric (Example 11). . As an aspect in which the tread pattern is not point-symmetric, an aspect in which the patterns in both half-tread areas are different from each other was adopted.

  As mentioned above, although the heavy duty pneumatic tire of this invention was demonstrated in detail, this invention is not limited to the said embodiment, In the range which does not deviate from the main point of this invention, what may be variously improved and changed. Of course.

1 Pneumatic tire for heavy load 4 Belt portion 6 Tread portion 10 Tread pattern 11 Center lug groove 13 Shoulder lug groove 15 Circumferential main groove 15a First groove bent portion 15b Second groove bent portion 15c Bottom raised portion 17 Center narrow grooves 17c, 17d Center narrow groove portions 18a and 18b extending outward from the opening end in the tire width direction Convex bent portion 19 Shoulder narrow groove 23 Center block 27 Shoulder block

Claims (13)

A heavy duty pneumatic tire with a tread pattern,
A plurality of tire circumferential directions are provided at intervals in the tire circumferential direction, and the tire width direction and the tire are arranged in a half tread region on the first side and the second side in the tire width direction with respect to the tire equator line so as to cross the tire equator line. A linear center lug groove extending in a direction inclined with respect to the circumferential direction and having both ends;
In each of the half tread regions, a plurality of shoulder lug grooves that are provided at intervals in the tire circumferential direction, extend outward in the tire width direction, and open to the ground contact ends on both sides in the tire width direction. The position in the tire width direction of the end in the tire width direction of the shoulder lug groove is outside the position in the tire width direction of the end of the center lug groove, and in the tire circumferential direction, the center Shoulder lug grooves provided one by one between adjacent center lug grooves adjacent in the tire circumferential direction among the lug grooves;
A first curve that is provided in each of the half tread regions and is curved or bent outward in the tire width direction so as to alternately connect the end of the center lug groove and the inner end of the shoulder lug groove in the tire width direction. A pair of circumferential main grooves formed in a wave shape over the tire circumferential direction, wherein the groove curved portion and the second groove curved portion curved or bent inside the tire width direction are disposed;
Center blocks defined by the adjacent center lug grooves and the pair of circumferential main grooves and formed in a row in the tire circumferential direction;
Extending the area of the center block and having an opening end that opens to each of the adjacent center lug grooves at a position in the tire width direction excluding on the tire equator line, the groove width is narrower than the groove width of the shoulder lug groove, and has a linear shape Not a center narrow groove,
The tread pattern including
The groove width of the center lug groove and the circumferential main groove is narrower than that of the shoulder lug groove,
The center narrow groove, wherein one of the half tread region of the semi-tread region one open end is positioned within the open end, the open end of said one tire width direction inner side and the tire equatorial line and parallel to the direction A heavy-duty pneumatic tire characterized by having a portion extending outward in the tire width direction without extending to any of the portions, and the portion having the one open end .   The maximum groove depth of the circumferential main groove is shallower than the maximum groove depth of the center lug groove, and the maximum groove depth of the center lug groove is shallower than the maximum groove depth of the shoulder lug groove. Heavy duty pneumatic tire as described in 1.   The ratio D1 / D2 is 0.05 or more and 0.2 or less, where D1 is the maximum groove depth of the center narrow groove and D2 is the maximum groove depth of the circumferential main groove. Heavy duty pneumatic tire as described in 1.   The ratio L1 / L2 is more than 1.8 and not more than 2.2 when the groove length of the center narrow groove is L1 and the tire circumferential length of the center block is L2. The heavy duty pneumatic tire according to any one of the preceding claims.   The heavy-duty pneumatic tire according to any one of claims 1 to 4, further comprising a bottom raised portion in which a groove depth is partially shallow in each of the pair of circumferential main grooves.   The ratio D3 / T is 0.01 or more and 0.05 or less, where D3 is the shallowest groove depth in the raised portion and T is the tread width in the tire width direction of the tread portion. Heavy duty pneumatic tires.   The center narrow groove has one convex bending portion extending so as to protrude outward in the tire width direction with respect to the tire equator line in each of the half tread regions. The heavy-duty pneumatic tire described in the item.   The length of the center narrow groove extending from the opening end to the top of the convex bent portion is La, and the length of the center narrow groove extending between the tops of the convex bent portion is Lb. The heavy duty pneumatic tire according to claim 7, wherein Lb is longer than La. The tread pattern further includes
In each of the half tread regions, a tire circumferential direction defined by a pair of adjacent shoulder lug grooves adjacent to each other in the tire circumferential direction of the shoulder lug grooves, the circumferential main grooves, and ends of the tread portion in the tire width direction. A plurality of shoulder blocks formed in a row,
9. A shoulder narrow groove extending in a region of the shoulder block and opening in each of the adjacent shoulder lug grooves, and having a groove width narrower than a groove width of the shoulder lug groove, 9. Heavy duty pneumatic tire as described in 1. Wherein the length of the shoulder narrow groove in the shoulder block and L3, when the tire circumferential direction of the minimum length of the shoulder block and L4, the ratio L3 / L4 is 1.0 to 1.4, claims 9. A heavy-duty pneumatic tire according to 9.   The heavy tire for a heavy load according to any one of claims 1 to 10, wherein the tread pattern is point-symmetric with respect to a center point on a tread surface of the center block.   The heavy duty pneumatic tire according to any one of claims 1 to 11, wherein groove widths of the circumferential main groove and the center lug groove are 7 mm or more and 20 mm or less, respectively.   The heavy-duty pneumatic tire according to any one of claims 1 to 12, which is mounted on a construction vehicle or an industrial vehicle.

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