JP4355276B2 - Heavy duty pneumatic tire - Google Patents

Description

  The present invention relates to a heavy duty pneumatic tire having improved uneven wear resistance performance by improving a tread pattern.

  For heavy-duty pneumatic tires used in heavy vehicles such as trucks and buses, all-season tires are desired, and all-season heavy-duty pneumatic tires can safely run on various road conditions. Therefore, it is necessary to maintain high wet grip performance and steering stability performance. For this reason, in many cases, a block pattern is adopted as a tread pattern.

  On the other hand, in the case of block pattern tires, particularly in the case of pneumatic tires for heavy loads, a large shearing force acts on the first arrival side and the rear arrival side in the rotational direction during driving and braking, and sliding friction occurs between the road surface and the road surface. For this reason, so-called heel and toe wear (referred to as H / T wear) is likely to occur, where the first and second wear sides of the block are worn locally.

  As a countermeasure for preventing this H / T wear, a technique in which a tie bar is provided between blocks is known (see, for example, Patent Document 1 and Patent Document 2). Moreover, by increasing the land / sea ratio, the tread surface is prevented by increasing its rigidity, for example, a shoulder block formed on the shoulder portion is divided inward and outward in the tire axial direction, and the intermediate portion is curved outwardly. A heavy duty pneumatic tire provided with siping has been proposed (see, for example, cited document 3).

JP 2004-106747 A JP 2004-203268 A JP 2000-177326 A

However, a simple tie bar is effective to some extent, but it alone reduces the circumferential deflection of the block, reduces the edge component, and reduces the groove volume. It is easy to lose, and the performance on the snow tends to decrease for all season use.

  A tread pattern with a high land / sea ratio also has a large tread surface rigidity, and a large land / sea ratio is usually configured such that some grooves disappear with wear and become rib-like. At this time, the wet grip performance and the running performance on snow may be deteriorated, and the all-season property may be impaired. In addition, siping and adding a narrow groove tend to promote chipping of the block.

  The present invention provides a heavy-duty pneumatic tire that has a block pattern and improves uneven wear resistance without sacrificing wet grip performance, running performance on snow, etc. as much as possible, and can be suitably used particularly for all seasons. The purpose is to provide.

In order to achieve the above object, the invention according to claim 1 of the present application is directed to a tread surface T, a longitudinal groove 2C in the center crossing the tire equator Q and extending in a zigzag manner, and a longitudinal groove 2S on the outer side in the tire axial direction. And at least five longitudinal grooves (2) extending in the tire circumferential direction with an intermediate longitudinal groove 2M passing therebetween, and a central lateral groove 3C connecting between the central longitudinal groove 2C and the intermediate longitudinal groove 2M, By arranging an intermediate horizontal groove 3M connecting between the intermediate vertical groove 2M and the outer vertical groove 2S, and an outer horizontal groove 3S extending from the outer vertical groove 2S to the tread end E,
A central block 4C sandwiched between the central vertical groove 2C and the intermediate vertical groove 2M and separated by the central horizontal groove 3C, and sandwiched between the intermediate vertical groove 2M and the outer vertical groove 2S and partitioned by the intermediate horizontal groove 3M. Heavy load air having a block pattern using at least three types of blocks 4 consisting of an intermediate block 4M and an outer block 4S sandwiched between an outer longitudinal groove 2S and a tread edge E and separated by an outer lateral groove 3S A tire containing
The central vertical groove 2C, the intermediate vertical groove 2M, and the outer vertical groove 2S have the same pitch and are inclined at the first vertex that protrudes in one direction in the tire axial direction and the second vertex that protrudes in the other direction. Zigzag repeating zigzag groove pieces composed of first and second slant pieces with different orientations,
The central lateral groove 3C on one side in the tire axial direction joins the first vertex of the central longitudinal groove 2C and the first vertex of the adjacent intermediate longitudinal groove 2M,
The central lateral groove 3C on the other side joins the second vertex of the central longitudinal groove 2C and the second vertex of the intermediate longitudinal groove 2M adjacent thereto, and
The intermediate lateral groove 3M on one side in the tire axial direction connects the second vertex of the intermediate longitudinal groove 2M and the second vertex of the adjacent outer longitudinal groove 2S, and the intermediate lateral groove 3M on the other side. Is connected to the first intermediate vertex and the first vertex of the adjacent outer longitudinal groove 2S,
The outer lateral groove 3S on one side in the tire axial direction is a tread from the first vertex of the outer longitudinal groove 2S, and the outer lateral groove 3S on the other side is a tread from the second vertex of the outer longitudinal groove 2S. Extending to the edge,
The central longitudinal groove 2C has a ratio (L2c1 / L2c2) of a tire circumferential direction length L2c1 of the first oblique piece and a tire circumferential direction length L2c2 of the second oblique piece of 1.2 to 1.2. The central block which is 1.7 and is the maximum measured in the tire axial direction at each position in the tire circumferential direction in the region sandwiched between the central vertical groove 2C and the intermediate vertical groove 2M in the central block 4C Measured in the tire axial direction at each position in the tire circumferential direction in the area sandwiched between the intermediate vertical groove 2M and the outer vertical groove 2S in the intermediate block 4M, the maximum width W4Cmax, the minimum central block minimum width W4Cmin The maximum intermediate block width W4Mmax, the minimum intermediate block minimum width W4Mmin, and the tire circumference in the region sandwiched between the outer vertical groove 2S and the tread edge E in the outer block 4S. Outer block maximum width W4Smax that maximizes measure the tire axial direction at each position of the direction, the smallest outer block minimum width W4Smin,
(W4Smax / W4Smin) <(W4Mmax / W4Mmin) <(W4Cmax / W4Cmin)
And 1.00 ≦ W4Smax / W4Smin ≦ 1.20
1.15 ≦ W4Mmax / W4Mmin ≦ 1.40
1.40 ≦ W4Cmax / W4Cmin ≦ 1.70
It is characterized by having the relationship.

In the invention according to claim 2, the intermediate lateral groove 3M has a tie bar (5) that protrudes from the groove bottom and joins the groove wall of the intermediate lateral groove 3M.
The tire axial distance W5 of this tie bar is 20% or more and 65% or less of the tire axial direction length W3M of the intermediate lateral groove 3M.
The tie bar depth D5, which is the distance in the tire radial direction from the tread surface T to the tie bar surface, is 25% or more and 70% or less of the average groove depth D3M of the intermediate lateral groove 3M.
The siping depth D6 from the surface of the tie bar of the siping (6) formed on the tie bar (5) is determined by the difference (D3M-D5) between the average groove depth D3M of the intermediate lateral groove 3M and the tie bar depth D5. It is characterized by being 50% or more and 100% or less.

In the invention according to claim 3 , the central block 4C on one side in the tire axial direction has a horizontal tail shape having a protrusion formed by the second apex of the central longitudinal groove 2C, and the other in the tire axial direction. The central block 4C on the side has a horizontal tail shape having a protrusion formed by the first vertex of the central longitudinal groove 2C,
The intermediate block 4M on one side in the tire axial direction has a horizontal tail shape having a protrusion formed by the first vertex of the outer longitudinal groove 2S, and the intermediate block 4M on the other side in the tire axial direction is , Forming a horizontal tail shape having a protrusion formed by the second vertex of the outer longitudinal groove 2C,
The outer block 4S on one side in the tire axial direction has a shogi piece shape having a protrusion formed by the second vertex of the outer longitudinal groove 2S, and the outer block 4S on the other side in the tire axial direction is In addition, it is characterized by forming a shogi piece shape having a protrusion formed by the first vertex of the outer vertical groove 2S.

  In the invention according to claim 1, wet grip performance is improved by providing at least five longitudinal grooves. On the other hand, in the case of H / T wear, when the wear energy on the rear side of the block receiving the braking force increases and the heel side wears, on the other hand, the drive force acts on the tire mounted on the drive shaft. In some cases, the wear energy on the block first arrival side increases due to the occurrence of uneven wear on the toe side. In the present invention, on the other hand, in the central block maximum width W4Cmax, the central block minimum width W4Cmin, the intermediate block maximum width W4Mmax, the intermediate block minimum width W4Mmin, the outer block maximum width W4Smax, and the outer block minimum width W4Smin, The range of the described mathematical formula is selected.

According to the above formula, each block has a large force applied in the tire circumferential direction, and the central block near the tire equator has little H / T wear even if the width variation rate is relatively large in the tire circumferential direction, and has a traction property. While increasing, the outer block close to the tread end E where the force in the tire axial direction is large has a rectangular shape, thereby ensuring the driving force and steering stability of the tire. As described above, in general, in the case of normal straight traveling, the center block is first grounded in the block, the residence time on the ground surface is long, and the ground pressure is high. The wiping effect that breaks and sweeps the water film can be greatly achieved by increasing the ratio between the large and minimum widths. In addition, in the shoulder portion where the slip amount in the tire circumferential direction is large, the ratio of the maximum width and the minimum width of the block is made small to suppress the occurrence of H / T wear, and by optimizing the block width fluctuation ratio, In particular, in the outer side block on the shoulder side where H / T wear tends to occur, the difference in wear energy distribution on the first side and rear side can be reduced by reducing the block width variation ratio, and together with the outer block, Non-uniform wear energy, which is the cause of H / T wear in other blocks, is suppressed.

  Further, in the invention according to claim 2, by forming a predetermined siping on the tie bar, in combination with the requirement of claim 1, the effect of the tie bar for improving the circumferential rigidity of the intermediate block 4M is reduced. In addition, the effect of shattering the water film is improved by the slight opening and closing of siping within the ground plane. Furthermore, it is possible to suppress a decrease in wet grip performance when wear progresses and a tie bar appears on the tread surface and the intermediate block 4M is connected.

By adopting the configuration of the invention according to claim 3 , the driving stability of the tire can be ensured and the wiping effect when traveling on a wet road surface can be increased while reducing the H / T wear. it can.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a developed plan view showing a tread pattern of a tread portion obtained by developing a tread portion of a heavy load pneumatic tire (hereinafter sometimes referred to simply as a tire) 1 of the present invention. , E consists of a single or a plurality of curvature radii in the cross section including the tire axis. Further, the tread surface T is divided into blocks 4 by providing a plurality of vertical grooves 2 extending in the tire circumferential direction and a plurality of horizontal grooves 3 extending in the direction intersecting with the vertical grooves 2. . The tread edge E refers to the ridge line when the tread surface T forms an edge-shaped ridge line with the inclined surface continuous with the buttress surface or the buttress surface, and when the tread surface T and the buttress intersect with an arc, the tread surface T It is defined as the position of the line of intersection between the extended surface and the extended surface from the buttress surface.

  The longitudinal groove 2 intersects the tire equator Q and extends in the tire circumferential direction in a zigzag manner in the center, and the outer longitudinal groove 2S extends in the tire circumferential direction in a zigzag manner in the present embodiment outside the tire axial direction. And at least five intermediate longitudinal grooves 2M extending in a zigzag shape with a moderate angle in the tire circumferential direction between the central longitudinal groove 2C and the outer longitudinal groove 2S. Thus, wet grip performance is improved by making the longitudinal groove 2 into five or more in the circumferential direction.

  The horizontal groove 3 includes a central horizontal groove 3C that connects between the central vertical groove 2C and the intermediate vertical groove 2M, an intermediate horizontal groove 3M that connects between the intermediate vertical groove 2M and the outer vertical groove 2S, and an outer side. The outer lateral groove 3S extending from the longitudinal groove 2S to the tread end E is included.

  Accordingly, the block 4 is sandwiched between the central vertical groove 2M and the intermediate vertical groove 2M and is divided by the central horizontal groove 3C, and is divided between the intermediate vertical groove 2M and the outer vertical groove 2S. The tread includes an intermediate block 4M divided by a lateral groove 3M, and at least three types of blocks 4 consisting of an outer block 4S sandwiched between an outer longitudinal groove 2S and a tread edge E and separated by an outer lateral groove 3S. The surface T is formed as a block pattern.

  This block pattern is a repeating pattern of the pattern constituent unit d. For example, the upper and lower pitch lines y1 that are located immediately above (in the drawing) the lateral grooves 3S and 3S on the left end of FIG. 1 and extend in the tire axial direction. , Y2 is assumed as a repeating pattern constituent unit d. The length of the pattern constituent unit d in the tire circumferential direction is referred to as a pitch p. In this embodiment, a plurality of different types of pattern constituent units d are arranged in a length range of about 1.0 to 1.3 times the pitch p. The vibration and noise frequencies due to running are dispersed by using a block pattern using the so-called variable pitch method.

  The central vertical groove 2C, the intermediate vertical groove 2M, and the outer vertical groove 2S have the same pitch p in each pattern constituent unit d, and are convex in one of the tire axial directions (the left side in the figure in the present embodiment). A zigzag pattern is formed by repeating zigzag groove pieces 2c, 2m, and 2s having different inclination directions for each vertex c1, m1, and s1 and second vertex c2, m2, and s2 that are convex on the other side (right side). In this specification, the position or angle in each groove such as the vertexes c1, m1, s1, c2, m2, and s2 refers to the position at the groove center line and the angle of the groove center line.

In this example, the central longitudinal groove 2C has a circumferential length L2c that is twice as long as the zigzag groove piece 2c and the first slant piece 2c1 as compared with the second slant piece 2c2. Note that the ratio (L2c1 / L2c2) of the tire circumferential direction length L2c1 of the first diagonal piece 2c1 and the tire circumferential direction length L2c2 of the second diagonal piece 2c2 is set to 1.2 to 1.7. Can do. By providing the difference in length in this way, the horizontal grooves 3C and the middle 3M in the left and right horizontal grooves 3 in the drawing can be made to have the same direction, and the tire can be used more easily and uneven wear can be achieved. This makes it possible to obtain a tire with excellent left and right running characteristics while exhibiting its characteristics on the left and right sides of the vehicle while preventing the above.

On the other hand, the intermediate longitudinal grooves 2M on both sides of the tire equator Q are both zigzag groove pieces 2m having a vertex m1 (first vertex) protruding left and a vertex m2 (second vertex) protruding right. It is a circumferentially repeated body, and the pitch line y1 passes through the vicinity of the center point cm1 of the length of the upper slope 2m1 of the zigzag groove piece 2m. In this example, the first slant piece 2m1 and the second slant piece 2m2 have the same length, and the middle vertical grooves 2M on both sides (left and right) are formed in the same phase in the circumferential direction.

The outer vertical groove 2S has a first vertex s1 projecting to the left and a second vertex s2 projecting to the right in FIG. 1, like the central and intermediate vertical grooves 2C and 2M. the first oblique piece 2s1, a circumferential repeating body zigzag Mizohen 2s having a second oblique piece 2s2, tire equator Q both sides of the outer longitudinal grooves 2S, the 2S, for example, longitudinal grooves 2S on the left side of FIG. The position of the first vertex s1 is shifted to the tire circumferential direction by about 0.05 to 0.30 times the pitch p as compared with the first vertex s1 on the right side. The horizontal grooves 3C and the intermediate 3M horizontal grooves 3M can be set in the same direction.

  The first vertices c1, m1, s1, and the second vertices c2, m2, and s2 of the longitudinal grooves 2C, 2M, and 2S are juxtaposed in the tire circumferential direction at the same position in the tire axial direction. Is set so as not to vary for each longitudinal groove 2. It can be changed for each pattern constituent unit m.

In addition, an inclination angle α2s1 on the acute angle side formed by the first inclined piece 2c1 of the central longitudinal groove 2C with respect to the tire circumferential line (parallel to the tire equator Q) is 15 to 35 °, preferably 20 to 30 ° . The inclination angle α2s2 of the second inclined piece 2c1 is set to about 30 to 45 °, preferably about 20 to 35 °, thereby improving grip performance and improving running performance on snow.

On the other hand, the outer side longitudinal groove 2S has the same inclination angle α2s on the acute side with respect to the tire circumferential direction line in the first oblique piece 2s1 and the second oblique piece 2s2 of the zigzag groove piece 2s. Further, the inclination angle α2m on the acute angle side with respect to the tire circumferential direction line of the intermediate longitudinal groove 2M is about the first inclined piece 2m1 of the zigzag groove piece 2m1 and the second inclined angle. The piece 2m2 is relatively small. In this embodiment, the piece 2m2 is formed at 1 to 15 °, preferably about 2 to 8 °, so that water between the tread surface 1 and the road surface at the tire central portion and the tire shoulder portion is removed from the tire circumference. Easily drain in the direction to improve wet grip performance.

  Further, the central lateral groove 3C has a first vertex c1 of the central longitudinal groove 2C and a first vertex m1 of the intermediate longitudinal groove 2M on the left side (one side in the tire axial direction) of the tire equator Q in FIG. And the intermediate lateral groove 2M connects the second vertex m2 of the intermediate longitudinal groove 2M and the second vertex s2 of the outer longitudinal groove 2S. The outer lateral groove 3S extends from the first vertex s1 of the outer vertical groove 2S to the tread edge E. On the right side (the other side in the tire axial direction), the central lateral groove 3C joins the second vertex c2 of the central longitudinal groove 2C and the second vertex m2 of the intermediate longitudinal groove 2M, and the intermediate lateral groove 2M. Joins the first vertex m1 of the intermediate longitudinal groove 2M and the first vertex s1 of the outer longitudinal groove 2S. The outer lateral groove 3S extends from the second vertex s2 of the outer vertical groove 2S to the tread edge E.

  As a result, the central block 4C on one side in the tire axial direction (the left side of the tire equator Q in the figure in this embodiment) has a horizontal tail shape having a protrusion formed by the second vertex c2 of the central longitudinal groove 2C. None and the central block 4C on the other side has a horizontal tail shape having a protrusion formed by the first apex c1 of the central longitudinal groove 2C, and the protrusions are inserted into each other with a half-pitch shifted from each other. It is formed in a shape.

  The intermediate block 4M on one side has a horizontal tail shape having a protrusion formed by the first vertex s1 of the outer vertical groove 2S, and the intermediate block 4M on the other side has an outer vertical groove. It has a horizontal tail shape having a protrusion formed by the second vertex s2 of 2S.

  Further, the outer block 4S on one side in the tire axial direction has a shogi piece shape having a protrusion formed by the second vertex s1 of the outer longitudinal groove 2S, and the outer block 4S on the other side is , A shogi piece shape having a protrusion formed by the first vertex s1 of the outer longitudinal groove 2S.

The block pattern is preferably configured to be point-symmetric about the central point cc2 of the second oblique piece 2c2 of the central longitudinal groove 2C for each of the pattern constituent units d. It improves drainage and wet grip, and also improves steering stability by eliminating left and right variation. The center point cc1 of the first slant piece 2c1 passes through the pitch line y1.

  Further, the central lateral groove 3C and the intermediate lateral groove 3M are inclined in the same direction, for example, the left side is upward, and the inclination angles β3c and β3m on the acute angle side with respect to the tire circumferential direction line are Are the same and are set in the range of 50 ° to less than 90 °, preferably in the range of 65 to 85 °. Further, the equivalent angle β3s of the outer lateral groove 3S is set within a range of ± 10 °, preferably about ± 6 ° with respect to the tire axial direction or the tire axial direction line.

  The side facing the longitudinal groove 2M in the middle of the central block 4C and the side facing the longitudinal groove 2M in the middle block 4M have recesses 7 in which the blocks are cut out at the center of each side. 8 is provided. Thereby, the primary storage part of water is formed, drainage performance is improved, and traction property is enhanced.

  Next, in the tire block direction at each position in the tire circumferential direction in the region sandwiched in the tire axial direction by the central vertical groove 2C and the intermediate vertical groove 2M in the central block 4C shown in FIGS. The maximum central block width W4Cmax which is the maximum measured, the minimum central block minimum width W4Cmin which is the minimum, and each of the tire circumferential direction in the region sandwiched between the intermediate vertical groove 2M and the outer vertical groove 2S in the intermediate block 4M The maximum intermediate block width W4Mmax measured in the tire axial direction at the position, the minimum intermediate block minimum width W4Mmin, and the area between the outer vertical groove 2S and the tread edge E in the outer block 4S. The maximum outer block width W4Smax and the minimum outer block minimum width W4Smin that are the maximum measured in the tire axial direction at each position in the tire circumferential direction are as follows. It is made to satisfy the equation. The maximum block width and the minimum block width are measured on the side facing the intermediate vertical groove 4M on the basis of the extension line of each groove wall 4Mw facing the intermediate vertical groove 4M. Shall be ignored.

    (W4Smax / W4Smin) <(W4Mmax / W4Mmin) <(W4Cmax / W4Cmin)

The ( W4Smax / W4Smin), (W4Mmax / W4Mmin), and (W4Cmax / W4Cmin) mean the variation rate of the width in the tire axial direction in each block 4, and although the force acting in the tire circumferential direction is large, the drag is generated. The central block 4C that is small and has a relatively small H / T wear and close to the tire equator Q has a larger fluctuation rate than other blocks, that is, the zigzag degree of the central longitudinal groove 2C is increased. For example, the longitudinal and lateral rigidity of the central portion in the tire circumferential direction is increased to improve grip performance and steering stability. Also, increasing the rate of variation contributes to improving traction. On the other hand, in the outer block 4S close to the tread end E where the force in the tire axial direction is large, the ratio (W4Smax / W4Smin) is made small, approaching a rectangular shape, and the wear energy is made uniform in the tire circumferential direction, thereby causing H / T wear. In addition to reducing the driving force and steering stability of the tire.

  That is, generally, in normal straight traveling, the central block 4C is grounded first in each block, and the time that exists in the grounding surface is the longest and the grounding pressure is high. In such a block, when traveling on a wet road surface, the larger the ratio between the maximum width and the minimum width, the greater the wiping effect that breaks and sweeps away the water film and improves wet grip performance. On the other hand, since the amount of slip in the tire circumferential direction is large in the shoulder portion, heel and toe wear tends to occur if the ratio of the maximum width and the minimum width of the block is large. In addition, it becomes easy to prevent generation | occurrence | production of H / T abrasion that the block maximum width arrange | positions in the tire circumferential direction center position vicinity of each block. In addition, the width of the middle block 4M in the tire axial direction is uniform in the tire circumferential direction, for example, by setting the ratio of the maximum value to the minimum value as described above, the rigidity on the first arrival side and the rear arrival side is made uniform, and the heel Intended to reduce andtoe wear.

further,
1.00 ≦ W4Smax / W4Smin ≦ 1.20
1.15 ≦ W4Mmax / W4Mmin ≦ 1.40
1.40 ≦ W4Cmax / W4Cmin ≦ 1.70
It is said.

  When W4Smax / W4Smin> 1.20, H / T wear of the outer block 4S cannot be prevented. In addition, when 1.15> W4Mmax / W4Mmin or 1.40> W4Mmax / W4Mmin, the wet grip performance is insufficient, and when W4Cmax / W4Cmin <1.40 or W4Cmax / W4Cmin> 1.70, the intermediate block 4M, the center Even in the block 4C, H / T wear tends to occur.

Preferably,
1.05 ≦ W4Smax / W4Smin ≦ 1.10.
1.20 ≦ W4Mmax / W4Mmin ≦ 1.30
1.50 ≦ W4Cmax / W4Cmin ≦ 1.60
And

In this embodiment, the maximum width W4Smax, W4Mmax / W4Mmin, and W4Cmax of each block are set to the ground contact width WT in the standard state.
0.16 ≦ W4Smax / WT ≦ 0.20
0.12 ≦ W4Mmax / WT ≦ 0.16
0.11 ≦ W4Cmax / WT ≦ 0.15
The range is as follows.

  In addition, 0.16 ≦ W4Smax / WT ≦ 0.20, 0.12 ≦ W4Mmax / WT ≦ 0.16, 0.11 ≦ W4Cmax / WT ≦ 0.15, W4Smax / WT is 0.20 When it exceeds, H / T deteriorates, and when it is less than 0.16, it becomes SH shoulder wear. When W4Mmax / WT exceeds 0.16, H / T deteriorates, and when it is smaller than 0.12, 2nd punching wear occurs. When W4Cmax / WT exceeds 0.15, H / T deteriorates, and when it is less than 0.11, punching wear occurs.

  Here, the “contact width in the standard state” means the maximum width of the contact surface when a normal load is applied in a state where the normal rim is installed and the normal internal pressure is filled. In this specification, “regular rim” is defined in accordance with either a standard rim defined by JATMA, “Design Rim” defined by TRA, or “Measuring Rim” defined by ETRTO. , The maximum air pressure specified by JATMA, the maximum value described in the TRA table “TIRE LOADILIMITS AT VARIOUS COLD INFLATIONPRESSURES”, or “INFLATION PRESSURE” specified by ETRTO. “Normal load” means the maximum load corresponding to the normal internal pressure in each standard. In this example, it means the length between the tread edges E and E in the ground contact state.

By adopting the above-described configuration, it is possible to suppress uneven wear due to slip in the tire circumferential direction while suppressing other performance degradation, but rib punching that causes early wear is likely to occur in the intermediate block 4M. It is preferable to further suppress this uneven wear.

For this reason, in this embodiment, the tie bar 5 is provided in the intermediate lateral groove 3M between the intermediate blocks 4M and 4M. FIG. 5 is a partially enlarged view of the intermediate blocks 4M and 4M and the intermediate lateral groove 3M between them, FIG. 6 (a) shows the AA cross section of FIG. 5, and FIG. 6 (b) shows the BB cross section. In addition, the tie bar 5 protrudes from the groove bottom substantially at the center in the tire axial direction of the intermediate lateral groove 3M and joins the groove walls of the intermediate blocks 4M and 4M. The tie bar 5 suppresses the movement of the intermediate block 4M in the tire circumferential direction and reduces the wear energy, thereby suppressing the occurrence of the above-described uneven wear.

  The tire axial distance W5 of the tie bar 5 is set to 20% to 65% of the tire axial direction length W3M of the intermediate lateral groove 3M. If it is less than 20%, the effect of the tie bar is insufficient, and if it exceeds 65%, the wet grip performance tends to be adversely affected. The tie bar depth D5 represented by the distance in the tire radial direction from the tread surface T to the surface of the tie bar 5 is 25% or more and 70% or less of the average groove depth D3M of the intermediate lateral groove 3M. If it is less than 25%, the effect of the tie bar is not exhibited. If it exceeds 70%, the wet grip performance tends to be adversely affected.

  Further, the tie bar 5 has a siping 6. The siping 6 may be a notch with a width w6 of 1 mm or less and substantially zero, thereby preventing the effect of the tie bar that improves the circumferential rigidity of the intermediate block 4M from being reduced. In addition, the effect of shattering the water film is improved by minute opening and closing within the ground plane. If the width exceeds 1 mm, the effect of the tie bar will be reduced. Furthermore, the wear grip performance can be suppressed when wear progresses and the tie bar appears on the tread surface and the intermediate block 4M is connected. The siping depth D6 is 50% or more and 100% or less of the difference (D3M-D5) between the average groove depth of the intermediate transverse groove 3M and the tie bar depth. If it is less than 50%, the effect of siping cannot be exhibited. If it exceeds 100%, that is, if the end of siping is located inward in the tire radial direction from the bottom of the intermediate lateral groove 3M, the tire circumference of the intermediate block 4M This reduces the effect of the tie bar to increase the directional rigidity.

  Furthermore, in this embodiment, the groove depth is about 15 to 20 mm in the central vertical groove 2C and the horizontal groove 3C, and the groove depths of the outer vertical groove 2S and the horizontal groove 3S are the groove depths of the central vertical groove 2C and the horizontal groove 3S. The tread pattern of the vertical groove 2 and the horizontal groove 3 is set to a full depth depth that clearly remains except for the tie bar 5 even at the end of wear (at least 50% depth wear). ing. The groove width w2C of the central vertical groove 2C on the tread surface T is 4.0 mm, the groove width w2M of the intermediate vertical groove 2M is 8.0 mm, and the groove width w2M of the outer vertical groove 2S is about 10.0 mm. The groove width w3C of the central lateral groove 3C is 5.0 mm, the groove width w3M of the intermediate lateral groove 3M is 8.0 mm, and the groove width w3S of the outer lateral groove 3S is about 10.0 mm. The groove width of each groove bottom is set to about 50 to 90% of the groove width on the tread surface. With this setting, wet grip performance and steering stability (particularly straight running stability) can be solved by securing the edge component at the end and improving the block rigidity of the crown portion. The groove width is measured in a direction perpendicular to the groove center line.

  Further, with respect to the intermediate block 4M, the angle γ of the intersection j between the side facing the outer vertical groove 2S and the side facing the intermediate horizontal groove 3M is maintained at an obtuse angle at the top and bottom of the figure to prevent the concern of punching wear.

  The heavy-duty pneumatic tire of the present invention can be variously modified within the scope of the claims without stopping at the above-described configuration.

A heavy-duty pneumatic tire of size 11R22.5 having the tread pattern of FIG. 1 was prototyped and evaluated for each performance. The results are shown in Table 1. Although this is a reference value, the tire axial distance W5 of the tie bar is 45% of the width W4Mmin of the intermediate block (this is substantially equal to the tire axial direction length of the intermediate lateral groove 3M). The various test conditions shown in Table 1 are as follows. The rim size is 7.50 × 22.5, the internal pressure is 800 kPa, and the test vehicle is a domestic 10-ton truck 2-D4 vehicle (half-loading and loaded in front of the loading platform).

(1) WET grip performance Place: Sumitomo Rubber Industries, Ltd. Okayama Test Course Method: The lap time when making a round of a 30 m radius course in a wet state is represented by the reciprocal of the ratio with Comparative Example 1. The comparative example 1 is set to 100, and a larger value indicates a better result.
(2) Uneven wear resistance Traveling distance: 40000km
Evaluation method: A fixed volume (10t) load was loaded on a 2-D4 type box-type truck and traveled for 40,000 km. The wear resistance performance index is calculated from the remaining groove after running and compared.
Wear resistance performance index: The value of (new product depth-depth after wear) / (new groove depth) of the test tire is compared with that of the control tire.

It is an expanded view of the tread surface which shows the tread pattern of this embodiment. It is a top view showing the detail of a center block. It is a top view showing the detail of an intermediate | middle block. It is a top view showing the detail of a shoulder block. It is a top view showing an intermediate block, an intermediate horizontal groove, and a tie bar / It is sectional drawing of an intermediate horizontal groove, Comprising: (a) is the sectional view on the AA line of FIG. 5, (b) is BB sectional drawing.

Explanation of symbols

2 Vertical groove 3 Vertical groove 4 Block E Tread edge Q Tire equator T Tread surface

Claims (3)

On the tread surface T, at least five tires including a central longitudinal groove 2C that intersects the tire equator Q and extends in a zigzag shape, an outer longitudinal groove 2S on the outer side in the tire axial direction, and an intermediate longitudinal groove 2M that passes between them. A longitudinal groove (2) extending in the circumferential direction, a central transverse groove 3C connecting between the central longitudinal groove 2C and the intermediate longitudinal groove 2M, and an intermediate joining between the intermediate longitudinal groove 2M and the outer longitudinal groove 2S By arranging the lateral groove 3M of the outer side and the outer lateral groove 3S extending from the outer longitudinal groove 2S to the tread end E,
A central block 4C sandwiched between the central vertical groove 2C and the intermediate vertical groove 2M and separated by the central horizontal groove 3C, and sandwiched between the intermediate vertical groove 2M and the outer vertical groove 2S and partitioned by the intermediate horizontal groove 3M. Heavy load air having a block pattern using at least three types of blocks 4 consisting of an intermediate block 4M and an outer block 4S sandwiched between an outer longitudinal groove 2S and a tread edge E and separated by an outer lateral groove 3S A tire containing
The central vertical groove 2C, the intermediate vertical groove 2M, and the outer vertical groove 2S have the same pitch and are inclined at the first vertex that protrudes in one direction in the tire axial direction and the second vertex that protrudes in the other direction. Zigzag repeating zigzag groove pieces composed of first and second slant pieces with different orientations,
The central lateral groove 3C on one side in the tire axial direction joins the first vertex of the central longitudinal groove 2C and the first vertex of the adjacent intermediate longitudinal groove 2M,
The central lateral groove 3C on the other side joins the second vertex of the central longitudinal groove 2C and the second vertex of the intermediate longitudinal groove 2M adjacent thereto, and
The intermediate lateral groove 3M on one side in the tire axial direction connects the second vertex of the intermediate longitudinal groove 2M and the second vertex of the adjacent outer longitudinal groove 2S, and the intermediate lateral groove 3M on the other side. Is connected to the first intermediate vertex and the first vertex of the adjacent outer longitudinal groove 2S,
The outer lateral groove 3S on one side in the tire axial direction is a tread from the first vertex of the outer longitudinal groove 2S, and the outer lateral groove 3S on the other side is a tread from the second vertex of the outer longitudinal groove 2S. Extending to the edge,
The central longitudinal groove 2C has a ratio (L2c1 / L2c2) between a tire circumferential direction length L2c1 of the first slant piece and a tire circumferential direction length L2c2 of the second slant piece from 1.2 to 1.2. The central block which is 1.7 and is the maximum measured in the tire axial direction at each position in the tire circumferential direction in the region sandwiched between the central vertical groove 2C and the intermediate vertical groove 2M in the central block 4C Measured in the tire axial direction at each position in the tire circumferential direction in the region sandwiched between the intermediate vertical groove 2M and the outer vertical groove 2S in the intermediate block 4M, the maximum width W4Cmax, the minimum central block minimum width W4Cmin The maximum intermediate block width W4Mmax, the minimum intermediate block minimum width W4Mmin, and the tire circumference in the region sandwiched between the outer vertical groove 2S and the tread edge E in the outer block 4S. Outer block maximum width W4Smax that maximizes measure the tire axial direction at each position of the direction, the smallest outer block minimum width W4Smin,
(W4Smax / W4Smin) <(W4Mmax / W4Mmin) <(W4Cmax / W4Cmin)
And 1.00 ≦ W4Smax / W4Smin ≦ 1.20
1.15 ≦ W4Mmax / W4Mmin ≦ 1.40
1.40 ≦ W4Cmax / W4Cmin ≦ 1.70
A heavy-duty pneumatic tire characterized by the following relationship: The intermediate lateral groove 3M has a tie bar (5) that protrudes from the groove bottom and joins the groove wall of the intermediate lateral groove 3M.
The tire axial distance W5 of this tie bar is 20% or more and 65% or less of the tire axial direction length W3M of the intermediate lateral groove 3M.
The tie bar depth D5, which is the distance in the tire radial direction from the tread surface T to the surface of the tie bar, is 25% or more and 70% or less of the average groove depth D3M of the intermediate lateral groove 3M.
The siping depth D6 from the surface of the tie bar of the siping (6) formed on the tie bar (5) is determined by the difference (D3M-D5) between the average groove depth D3M of the intermediate lateral groove 3M and the tie bar depth D5. The heavy-duty pneumatic tire according to claim 1, wherein the pneumatic tire is 50% or more and 100% or less. The central block 4C on one side in the tire axial direction has a horizontal tail shape having a protrusion formed by the second apex of the central longitudinal groove 2C, and the central block 4C on the other side in the tire axial direction is A horizontal tail having a protrusion formed by the first vertex of the central longitudinal groove 2C,
The intermediate block 4M on one side in the tire axial direction has a horizontal tail shape having a protrusion formed by the first vertex of the outer longitudinal groove 2S, and the intermediate block 4M on the other side in the tire axial direction is , Forming a horizontal tail shape having a protrusion formed by the second vertex of the outer longitudinal groove 2C,
The outer block 4S on one side in the tire axial direction has a shogi piece shape having a protrusion formed by the second vertex of the outer longitudinal groove 2S, and the outer block 4S on the other side in the tire axial direction is The heavy duty pneumatic tire according to claim 2, wherein the pneumatic tire is a shogi piece having a protrusion formed by a first vertex of the outer longitudinal groove 2 </ b > S.

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