JP4377862B2 - Heavy duty pneumatic tire - Google Patents

Description

  The present invention relates to a heavy-duty pneumatic tire improved in both low noise performance and on-snow performance, and more particularly to a tread pattern of an all-season heavy-duty pneumatic tire.

  In heavy-duty pneumatic tires used for heavy vehicles such as trucks and buses, there is a great demand for all-season tires having on-snow performance capable of running even on remaining snow road surfaces. In this heavy-duty all-season tire, a block pattern is adopted to improve performance on snow. In addition, with the improvement in vehicle performance, particularly with increased horsepower, further improvement in snow performance is desired.

It is known that the performance on snow tends to be improved by increasing the number of horizontal grooves, vertical grooves, and groove volume. On the other hand, all-season tires also run on dry road surfaces in many cases along with snow-melting road surfaces and wet road surfaces, so low noise performance is also required, but the number of horizontal grooves, vertical grooves, and groove volume described above are required. The increase also increases the air column resonance noise in the groove, impairing the low noise performance of the tire. As described above, the running performance on snow and the low noise performance were recognized as contradictory performance.

  In addition, in order to improve driving / braking performance on icy and snowy roads, there has also been proposed a sipe provided on the block (see, for example, Patent Document 1), but this sipe is formed in a U-shape, and is lacking. Although it is useful for preventing cracks, it does not contribute to noise reduction.

There has also been a proposal intended to improve tire uniformity to reduce pitch noise and suppress unpleasant tire noise (see, for example, Patent Document 2), which is mainly based on the idea of pitch variation. It is only intended to be noise.

Furthermore, there is a proposal of Patent Document 3 regarding a tread pattern. However, this is intended to avoid uneven wear and improve running performance on wet road surfaces.

JP 2000-255220 A JP-A-10-166816 JP 2004-142549 A

Thus, no proposal has been made that can sufficiently satisfy the performance required in recent years for a heavy-duty pneumatic tire capable of improving the contradictory performance of low noise performance and on-snow performance.

  Accordingly, the present invention has been devised in view of such problems, and adopts a block pattern as a tread pattern and optimizes the block pattern to improve performance on snow, and a specific wall groove on the vertical groove wall surface. It is an object of the present invention to provide a heavy-duty pneumatic tire in which air column resonance is reduced to improve low noise performance. The tread pattern is useful for maintaining uneven wear resistance and tire life, and the wall groove can also contribute to improving the running performance on snow.

The invention according to claim 1 includes a central vertical groove 2C intersecting the tire equator Q and extending zigzag on the tread surface T, an outer vertical groove 2S on the outer side in the tire axial direction, and an intermediate vertical groove passing therebetween. At least five longitudinal grooves (2) extending in the circumferential direction of the tire with 2M, as well as a central lateral groove 3C connecting between the central longitudinal groove 2C and the intermediate longitudinal groove 2M, an intermediate longitudinal groove 2M and the outer longitudinal groove By arranging an intermediate lateral groove 3M connecting between the groove 2S and an outer lateral groove 3S extending from the outer longitudinal groove 2S to the tread end E,
A central block 4C delimited by a central vertical groove 2C, an intermediate vertical groove 2M and a central horizontal groove 3C, and an intermediate block 4M delimited by an intermediate vertical groove 2M, an outer vertical groove 2S and an intermediate horizontal groove 3M And a block pattern using at least three types of blocks (4) consisting of an outer block 4S divided by the outer vertical groove 2S and the outer horizontal groove 3S, and
The vertical length L4C of the central block, the vertical length L4M of the intermediate block, the vertical length of the outer block, which is the distance in the tire circumferential direction between the most protruding end points on both sides in the tire circumferential direction of each central, intermediate and outer block (4) L4S, and the central block lateral length W4C, which is the distance in the tire axial direction between the most protruding end points on both sides in the tire axial direction of each central, intermediate and outer block (4), the lateral length W4M of the intermediate block, For the horizontal length W4S of the block, the vertical ratio of each block (in the central block 4C (L4C / W4C), in the intermediate block 4M (L4M / W4M), in the outer block (L4S / W4S)),
(L4S / W4S) <(L4M / W4M) <(L4C / W4C)
1.60 <L4C / W4C < 1.70
1.40 <L4M / W4M < 1.55
0.95 <L4S / W4S < 1.05
As well as
The sealand ratio Ss / Sl between the total sea area Ss which is the area of the entire groove on the ground contact surface and the total land area S1 which is the total land area formed by the upper surface of each block 4 on the ground contact surface is 0.20-0. .80,
Moreover, in the central vertical groove 2C, the intermediate vertical groove 2M, and the outer vertical groove 2S, the groove width W2 perpendicular to the groove center line between the groove edges on the tread surface is the widest or the next widest. The vertical groove is a grooved vertical groove 2g provided with a wall groove (5) extending in the depth direction on the groove wall on one side or both sides facing the vertical groove,
The ratio W5 / W2ga between the length W5 of the wall groove (5) in the tire axial direction and the groove width W2ga in the tire axial direction of the grooved vertical groove 2g provided with the wall groove (5) is less than 0.08. Large and smaller than 0.28 ,
The ratio D5 / D2g between the groove depth D5 from the tread surface of the wall groove (5) and the groove depth D2g of the grooved vertical groove 2g provided with the wall groove (5) is greater than 0.4 and 0. .9, and the radius of curvature R5 between the wall groove (5) and the back end surface of the wall groove (5) is greater than 0.8 mm and less than 2.0 mm. Tire.

  In the invention according to claim 2, the ratio W2C / WT of the groove width W2C and the grounding width WT in the direction perpendicular to the groove center line of the central vertical groove 2C is 0.020 to 0.040, and the intermediate vertical groove 2C The ratio W2C / WT of the groove width W2M in the direction perpendicular to the groove center line of the groove 2M and the grounding width WT is 0.020 to 0.040, and the groove width in the direction perpendicular to the groove center line of the outer vertical groove 2S. The ratio W2C / WT between W2S and grounding width WT is 0.040 to 0.060, and W2C <W2M <W2S.

Further, in the invention according to claim 3, the grooved vertical groove 2g is an intermediate vertical groove 2M and an outer vertical groove 2S, and the intermediate wall surface of the central block 4C facing the intermediate vertical groove 2M is intermediate to the wall of the block a 4M, into a groove wall of the wall and an intermediate block 4M outer block 4S outer longitudinal grooves 2S faces, characterized in that the wall troughs (5) are formed. In the invention according to claim 4, the tread surface T is provided with five vertical grooves, the central vertical groove 2C, the outer vertical groove 2S, and the intermediate vertical groove 2M. It is characterized by the zigzag shape of the grooved piece being repeated in the circumferential direction. The invention according to claim 5 is characterized in that a width LG of the wall groove is 1.0 to 2.5 mm.

The invention according to claim 1 has at least five vertical grooves, and has a tread pattern configuration having the vertical grooves and the horizontal grooves as described above, thereby improving snow gripping force and suppressing skidding to run on snow. To increase. Furthermore, when the sealand ratio Ss / Sl is 0.20 to 0.80, and the value is selected to be a relatively large value compared with a normal tire, the snow-engagement capacity is increased, and on the snow. It can improve traction and braking performance and improve performance on snow (you can select the normal tire sealand ratio). In addition, because the length ratio of the block is set to a predetermined value, the vertical and horizontal rigidity of the tread can be optimized along with the above-mentioned performance on snow, and the block can be prevented from being chipped with the wet grip performance of the block. It also helps to improve performance and steering stability.
Furthermore, the wall groove formed in the vertical groove meshes with the snow column in the vertical groove formed immediately after the ground contact, improves the shearing force in the traveling direction, can improve the running performance on snow including traction, and the wall groove. By setting to a predetermined value, it is beneficial to improve the shearing force. This wall groove can also disperse and disperse the air column resonance, which is a noise inherent to the tire, based on the vibration having a constant frequency of air generated in the process of propagating along the longitudinal groove, and the low noise of the entire tire. Can be realized.

  In the invention according to claim 2, by increasing the groove width of the vertical groove from the tire equator side to the tread edge side of the central vertical groove, the intermediate vertical groove, and the outer vertical groove, the snow column on the tread edge side Shear force can be improved, slip resistance on the outer tread edge side can be improved during turning, etc., running performance on snow can be improved, and steering stability can be improved.

  Further, in the invention according to claim 3, since W2C <W2M <W2S, and a wall groove is formed in the groove wall facing the intermediate vertical groove and the outer vertical groove having a relatively wide groove width, In a wide groove where a large amount of air column resonance tends to occur, the generation can be effectively suppressed and the noise can be reduced.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a plan view showing a tread pattern of a tread portion obtained by planarly developing a tread portion of a heavy load pneumatic tire (hereinafter sometimes referred to simply as a tire) 1 according to the present invention. The tread surface T between E consists of a single or a plurality of curvature radii in a 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. . Also, the groove width W2 in the direction perpendicular to the groove center line is provided with a wall groove 5 extending in the depth direction on one or both groove walls facing the widest or next widest vertical groove. A vertical groove 2g is used to reduce noise. The tread edge E is the tread surface T, the buttress surface, or when the meridian cross section connecting to the buttress surface forms a straight inclined surface and an edge-shaped ridge line, and the tread surface T and the buttress When intersecting with arcs, it is defined as the intersection line position of the extended surface of the tread surface T 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. As described above, the number of the longitudinal grooves 2 is five or more in the circumferential direction, thereby improving wet grip performance as well as running performance on snow. Thus, in this example, the intermediate longitudinal groove 2M and the outer longitudinal groove 2S are also formed in a zigzag shape together with the central longitudinal groove 2C, and the circumferential grooves in the region adjacent to the circumferential direction pitch of the zigzag in the tire axial direction. Is the same.

  Further, 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.

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

  The central vertical groove 2C has a zigzag shape in which a rectangular groove piece composed of an upper inclined piece 2c1 and a lower inclined piece 2c1 inclined in the opposite direction repeats in the circumferential direction, and is in a tire circumferential line (parallel to the tire equator Q). The inclination angle α2c1 on the acute angle side of the upper oblique piece 2c1 is 15 to 35 °, preferably 20 to 30 °, and the inclination angle α2c2 of the lower oblique piece 2c1 is about 30 to 45 °, preferably about 20 to 35 °. Set, thereby improving grip and improving snow travel.

  On the other hand, the outer vertical groove 2S has an inclination angle α2s on the acute angle side with respect to the circumferential line of the tire within the range of 10 ° between the upper inclined piece 2s1 and the lower inclined piece 2s2 of the zigzag groove piece 2s. 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 20 to 40 °, and the upper inclined piece 2m1 and the lower inclined piece 2m2 of the zigzag groove piece 2m. Is relatively small, and in this embodiment, it is formed at about 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 tire shoulder portion in the tire circumferential direction. Ease discharge and improve wet grip performance.

The central horizontal groove 3C connects the central vertical groove 2C and the intermediate vertical groove 2M at each bent portion, and the intermediate horizontal groove 3M connects the intermediate vertical groove 2M and the outer vertical groove 2S. We succeed at each bend. The outer lateral groove 3S extends to the tread edge E from a bent portion facing the outer side in the tire axial direction of the outer vertical groove 2S.

  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 the present embodiment) forms a horizontal tail, and is inserted with the tire equator C facing each other with a half pitch shift, It is formed in a tying shape. The intermediate block 4M also has a horizontal tail shape, and the outer block 4S has a shogi piece shape in which the outer vertical groove 2S has an apex at the outer side in the tire axial direction.

  Further, the central lateral groove 3C and the intermediate lateral groove 3M are in the same direction and have an acute angle side inclination angle β with respect to the tire axial direction line in the range of 0 to 40 °, preferably in the range of 15 to 25 °. Is set in. Further, the equivalent angle β of the outer lateral groove 3S is set within a range of about ± 10 °, preferably about ± 6 ° with respect to the tire axial line.

  In addition, the angle of the intermediate longitudinal groove 2M with respect to the tire axial direction can be made larger than the angles of the central longitudinal groove 2C and the shoulder longitudinal groove 2S with respect to the tire circumferential direction. This facilitates draining water between the tread surface 1 and the road surface in the tire center and tire shoulder in the tire circumferential direction, improves wet grip performance, and occurs at the middle of the tire equatorial plane C and tread edge E. Block punching that is easy to do is prevented.

  In this way, all the vertical grooves 2 are connected to each other at a plurality of positions in the tire circumferential direction by the horizontal grooves 3 to form a block pattern, and the effect of biting with snow is improved by making the grooves mesh, and running on snow The performance is mainly enhanced with the drainage effect.

  Further, on the side facing the middle vertical groove 2M of the central block 4C and the side facing the middle vertical groove 2M of the middle block 4M, a recess 7 in which each block is cut out at the center of each side, 8 is provided, thereby increasing the meshing force of snow, maintaining the running performance on the snow, and forming a primary water storage portion to improve drainage performance and improve wet grip performance.

  A central block 4C of the block 4 is shown in FIG. 2, an intermediate block 4M is shown in FIG. 3, and an outer block 4S located at the shoulder is shown in FIG. In each block 4, the distance between two tire axial direction lines yc1, yc2, ym1, ym2, and ys1, ys2 extending in the tire axial direction through the uppermost and lowermost projecting ends in the tire circumferential direction, that is, each The distances in the tire circumferential direction of the center, middle, and outer blocks 4 are defined as a center block vertical length L4C, a middle block vertical length L4M, and an outer block vertical length L4S.

  On the other hand, tire shafts between the tire circumferential direction lines xc1 and xc2, between xm1 and xm2, and between xs1 and xs2 that pass through the most projecting end points on both sides in the tire axial direction of each center, middle, and outer block 4 The central block horizontal length W4C, the intermediate block horizontal length W4M, and the outer block horizontal length W4S, which are directional distances.

At this time, the following expression is satisfied in the longitudinal ratio of each block ((L4C / W4C) in the central block 4C, (L4M / W4M) in the intermediate block 4M, (L4S / W4S) in the outer block). .
(L4S / W4S) <(L4M / W4M) <(L4C / W4C)

  In this way, the vertical length ratio L4 / W4 of the block 4 is made smaller as it goes from the central block 4C to the outer block 4S, and the degree of the vertical length of the block is reduced to approach a square shape. The vertical length L of each block 4 corresponds to a length obtained by subtracting the groove width W3 of the horizontal groove 3 above and below the block 4 from the pitch p of the pattern constituent unit d, and accordingly, the vertical length ratio of the block (L4S / W4S). , (L4M / W4M) and (L4C / W4C) mainly correlate with the length of the lateral groove 4 in the tire axial direction, and the length ratio L / W increases as the length decreases.

  By the way, in general, in a heavy duty pneumatic tire, the center portion of the tire, that is, the crown portion is grounded first, and then the intermediate portion or the shoulder portion is grounded. Therefore, on a wet road surface, water between the tread surface T and the road surface flows from the center portion of the tread to both sides in the tire axial direction. At this time, drainage is better when the length of the central lateral groove 3C in the tire axial direction is shorter.

  Further, the force applied to the central block 4C is greater in the tire circumferential direction than in the tire axial direction. Therefore, when the tire circumferential direction is viewed vertically and the tire axial direction is viewed horizontally as shown in FIG. 1, the central block 4 </ b> C has a vertically long shape to enhance the traction performance and the effect of suppressing uneven wear of the block.

  On the other hand, since the tread surface T of the tire inevitably has a curvature, the amount of slip is generally larger than that of the tire center. For this reason, the outer lateral groove 3S has a high so-called wiping effect for sweeping out a water film formed on the road surface. For this reason, as compared with the central lateral groove 3C, a longer one in the tire axial direction is advantageous in improving the engagement with snow and the wet grip performance. Further, the lateral force applied to the outer block 4S is larger than the lateral force applied to the central block 4C. This is particularly noticeable when turning, and the lateral rigidity of the outer block 4S greatly affects the steering stability performance. Accordingly, when the tire circumferential direction is viewed vertically and the tire axial direction is viewed horizontally as shown in FIG. 1, the vertically long shape is preferable in terms of wet grip performance and steering stability performance. The intermediate block 4M is required to have intermediate characteristics between the central block 4C and the outer block 4S, and therefore, the shape characteristics need to be intermediate.

The length ratio of each block (center block 4C: (L4C / W4C), middle block 4M: (L4M / W4M), outer block: (L4S / W4S)) is set as follows. Is good.
1.60 <L4C / W4C < 1.70
1.40 <L4M / W4M < 1.55
0.95 <L4S / W4S < 1.05
It was proved that the above-mentioned effects were excellent by setting the above range.

  In this example, the block protrusion part which exists in the tire circumferential direction center part of each block and protrudes in a tire axial direction has circular arc shape with fixed curvature radius R4 (R4C, R4M, R4S). This is to prevent chipping of this part and uneven wear starting from this part.

Further, in this example, the groove width W2 in a direction orthogonal to the groove center line of the vertical groove 2 and the groove center of the horizontal groove 3 that is located outward in the tire axial direction of the vertical groove 2 and opens to the vertical groove 2 The ratio W3 / W2 to the opening width W3 in the direction orthogonal to the line is set to be larger than 0.9 and smaller than 1.10. That is, the following formulas are satisfied in the central vertical groove 2C, the intermediate vertical groove 2M, and the outer vertical groove 2S.
0.8 <W3C / W2C <1.10
0.8 <W3M / W2M <1.10
0.9 <W3S / W2S <1.10

  This is because the inventors found that the width of the vertical groove and the horizontal groove connected to the groove are almost the same, which is good for water flow promotion and uneven wear resistance performance in straight contact and turning, and on snow performance. As a result, it was found that the range of the difference is an allowable limit of less than ± 10%. Preferably, it is set in the range of 0.85 or more and 1.05 or less.

Further, the groove width W2 (W2C, W2M, W2S) of each vertical groove is set larger as the vertical groove is closer to the tread end as described below.
W2C <W2M <W2S

In general, when the vehicle is traveling straight ahead and stopped, the ground contact pressure of the tire is maximized at the equator plane and becomes smaller toward the tread end. Therefore, on the dry road surface, the grip performance is higher and the wear resistance performance is better as the actual ground contact area at the center is larger. On the wet road surface, the wet grip performance increases as the width of the longitudinal groove increases, but if the width of the longitudinal groove in the central portion is increased, the above performance tends to be adversely affected. In order to improve both of the conflicting performances, the groove width W2 is set to the above relationship. Preferably, the following range is set with respect to the ground contact width WT in the standard state under the above relationship.
0.020 ≦ (W2C / WT) ≦ 0.040
0.025 ≦ (W2M / WT) ≦ 0.045
0.040 ≦ (W2S / WT) ≦ 0.060
Furthermore, for the same reason, the groove width W3 of the lateral groove is also set as follows.
W3C <W3M <W3S

Preferably, the following range is set with respect to the ground contact width WT in the standard state under the above relationship.
0.015 ≦ (W3C / WT) ≦ 0.035
0.030 ≦ (W3M / WT) ≦ 0.050
0.035 ≦ (W3S / WT) ≦ 0.055

  By setting the groove width W3 of the lateral groove to be larger as it is closer to the tread end, it is possible to promote the water flow in which the water in the ground plane flows from the equator plane toward the tread end and improve the wet grip performance. Here, the “ground contact width in the standard state” in the present invention means the maximum width of the contact surface when a normal load is applied in a state where it is incorporated in a normal rim and filled with a normal internal pressure.

  By adopting such a tread pattern of the groove arrangement, the total sea area Ss which is the area of the entire groove on the ground contact surface and the total land area S1 which is the total land area formed by the upper surface of each block 4 on the ground contact surface. The land ratio Ss / Sl is set to 0.20 to 0.80, which can be made larger than the conventionally used sealand ratio. By increasing the sealand ratio, it is possible to increase the groove capacity, improve the snow biting performance, and improve the running performance on snow. However, excessively taking into consideration the dry season runnability is not suitable for reducing wear resistance and reducing noise. A range of about 0.25 to 0.60 can be preferably selected.

  By adopting such a configuration, the central block close to the tire equator where the force applied in the tire circumferential direction is large has little H / T wear even if the width variation rate is relatively large in the tire circumferential direction, and has a traction property. Can be increased. Also, the block close to the tread end E where the force in the tire axial direction is large is rectangular, thereby ensuring the tire driving force and steering stability. 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, It is possible to suppress uneven wear energy, which is the cause of H / T wear of other blocks, and this also helps improve the performance on snow.

  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 defined by JATMA, the maximum value described in the TRA table “TIRE LOADIMIWT AT VARIOUS COLD INFRATIONPRESSURES”, or “INFLATION PRESSURE” defined by ETRTO. “Normal load” means the maximum load corresponding to the normal internal pressure in each standard.

  As described above, the wall groove 5 has a direction perpendicular to the groove center line between the groove edges on the tread surface in the central vertical groove 2C, the intermediate vertical groove 2M, and the outer vertical groove 2S. The groove width W2 is the groove groove on one side or both sides facing the widest or the next widest vertical groove, and wall grooves 5 extending in the depth direction are provided to form a grooved vertical groove 2g to reduce noise. ing. The “widest or next widest vertical groove” includes the case where only the widest vertical groove or only the widest vertical groove and the next widest vertical groove are the grooved vertical grooves 2g. Or the case where the wall grooves 5 are provided on one side or both sides.

In the present embodiment, as described above, the width W2 (W2C, W2M, W2S) of each vertical groove is larger as the vertical groove is closer to the tread end, and W2C <W2M <W2S. Therefore, the groove width is the widest. The wall grooves 5 are formed in the outer wide vertical groove 2S and the intermediate vertical groove 2M, and the vertical grooves 2C and 2M are formed as grooved vertical grooves 2g. In this embodiment, the wall groove 5 extends parallel to the tire axial direction.

  The wall groove 5 can constantly disperse and disperse the flowing air by changing the volume of the vertical groove 2 due to the load while the vertical groove 2 in the ground contact surface of the tire is rotating. As a result, it is possible to suppress the generation of resonance sound having a wavelength approximately twice the ground contact length of the longitudinal groove 2 where the ground contact length is substantially constant. Moreover, the wall groove | channel 5 meshes with the compressed snow pushed in in a groove | channel, and can increase the traction force at the time of running on snow, and can improve snow performance.

5 is a cross-sectional view taken along line AA ′ shown in FIG. A wall groove 5So is formed on the outer wall surface in the tire axial direction of the outer vertical groove 2S, a wall groove 5Si is formed on the inner wall surface in the tire axial direction, and a wall groove 5Mo is formed on the outer wall surface in the tire axial direction of the intermediate vertical groove 2M. The wall groove 5Mi is disposed on the inner wall surface in the tire axial direction. o and i are suffixes respectively indicating the outward and inward directions in the tire axial direction (the same applies hereinafter). The length W5 (W5Mo, W5Mi, W5So, W5Si) in the tire axial direction of each intermediate vertical groove 2M and the outer vertical groove 2S on the tread surface of the wall groove 5 is the vertical groove 2 (groove vertical) in which it is arranged. For the groove width W2ga measured in the tire axial direction of the groove 2g) (the groove width in the tire axial direction of the longitudinal grooves that face each other),
0.08 <(W5 / W2ga) <0.28
Is set in the range. If it is 0.08 or less, the air column resonance suppressing effect is not exerted, and if it is 0.28 or more, chipping due to heavy load tends to occur.
Further, the depth D5 of the wall groove 5, that is, the depth (D5Mo, D5Mi, D5So, D5Si) at the groove wall of each intermediate vertical groove 2M and the outer vertical groove 2S facing each other is the vertical groove in which it is arranged. For depth D2g (groove width in the tire axial direction of the vertical grooves facing each other) of 2 (grooved vertical groove 2g) measured in the tire axial direction,
0.4 <(D5 / D2g) < 0.9
Is set in the range. Similarly to the above, when 0.4 or less, the effect of suppressing air column resonance is not exhibited, and when 0.9 or more, chipping due to heavy load tends to occur.

  The wall grooves 5 are preferably formed with a circumferential pitch P5 of 3 to 15 mm, preferably 4 to 8 mm.

Also, as shown in FIG. 6, in order to prevent cracks starting from the end of the wall groove 5, it intersects with the tread surface in a circular shape at the back end of the wall groove 5, and its radius of curvature R5 is
0.8mm <R5 <2.0mm
Is set in the range.

The wall groove 5 may be a siping that completely closes under no load, but preferably the wall groove 5 has a width LG of 1.0 mm or more so that it can be recognized as a groove unlike siping. Thus, air column resonance can be further suppressed and the performance on snow can be improved. In this case, the width LG of the wall groove 5 is set to 2.5 mm or less. This is because it tends to be the starting point of chipping and uneven wear.

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 Tables 1 and 2.
Various test conditions shown in Table 2 are as follows.
(1) Noise test location: Sumitomo Rubber Industries, Ltd. Okayama Test Course rim size: 7.50 x 22.5
Internal pressure: 700 kPa
Vehicle: Domestic 10ton truck 2-D car (constant load)
Microphone position: 7.5m lateral from vehicle center Speed: 70km / h
Measurement method: JASO C606 compliant (2) Performance evaluation on snow Location: Asahikawa test course (our company)
Rim size: 7.50 x 22.5
Internal pressure: 700 kPa
Vehicle: Domestic 10ton truck 2-D car (constant load)
Method: Measure the time to pass from 0 km / h through an uphill road 20 m with a snowfall of 3.0 cm and an inclination angle of 5 °. The reciprocal of the reference time was expressed as an index with Comparative Example 1 as 100. At that time, the presence or absence of a block defect was also evaluated.

It is an expanded view of the tread surface which shows the tread pattern of this embodiment. It is a top view which shows a center block. It is a top view which shows an intermediate | middle block. It is a top view which shows an outer side block. It is AA 'line sectional drawing. It is a top view which expands and shows a wall groove.

Explanation of symbols

1 Tread surface 2 Vertical groove 3 Horizontal groove 4 Block 5 Wall groove E Tread edge

Claims (5)

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 delimited by a central vertical groove 2C, an intermediate vertical groove 2M and a central horizontal groove 3C, and an intermediate block 4M delimited by an intermediate vertical groove 2M, an outer vertical groove 2S and an intermediate horizontal groove 3M And a block pattern using at least three types of blocks (4) consisting of an outer block 4S divided by the outer vertical groove 2S and the outer horizontal groove 3S, and
The vertical length L4C of the central block, the vertical length L4M of the intermediate block, the vertical length of the outer block, which is the distance in the tire circumferential direction between the most protruding end points on both sides in the tire circumferential direction of each central, intermediate and outer block (4) L4S, and the central block lateral length W4C, which is the distance in the tire axial direction between the most protruding end points on both sides in the tire axial direction of each central, intermediate and outer block (4), the lateral length W4M of the intermediate block, For the horizontal length W4S of the block, the vertical ratio of each block (in the central block 4C (L4C / W4C), in the intermediate block 4M (L4M / W4M), in the outer block (L4S / W4S)),
(L4S / W4S) <(L4M / W4M) <(L4C / W4C)
1.60 <L4C / W4C < 1.70
1.40 <L4M / W4M < 1.55
0.95 <L4S / W4S < 1.05
As well as
The sealand ratio Ss / Sl between the total sea area Ss which is the area of the entire groove on the ground contact surface and the total land area S1 which is the total land area formed by the upper surface of each block 4 on the ground contact surface is 0.20-0. .80,
Moreover, in the central vertical groove 2C, the intermediate vertical groove 2M, and the outer vertical groove 2S, the groove width W2 perpendicular to the groove center line between the groove edges on the tread surface is the widest or the next widest. The vertical groove is a grooved vertical groove 2g provided with a wall groove (5) extending in the depth direction on the groove wall on one side or both sides facing the vertical groove,
The ratio W5 / W2ga between the length W5 of the wall groove (5) in the tire axial direction and the groove width W2ga in the tire axial direction of the grooved vertical groove 2g provided with the wall groove (5) is less than 0.08. Large and smaller than 0.28 ,
The ratio D5 / D2g between the groove depth D5 from the tread surface of the wall groove (5) and the groove depth D2g of the grooved vertical groove 2g provided with the wall groove (5) is greater than 0.4 and 0. .. and a radius of curvature R5 formed by the rear end surface of the wall groove (5) being a tread surface is larger than 0.8 mm and smaller than 2.0 mm, and is a heavy duty pneumatic tire. . The ratio W2C / WT of the groove width W2C and the ground contact width WT in the direction perpendicular to the center line of the central vertical groove 2C is 0.020 to 0.040,
The ratio W2C / WT of the groove width W2M in the direction perpendicular to the groove center line of the intermediate vertical groove 2M and the ground contact width WT is 0.020 to 0.040,
The ratio W2C / WT of the groove width W2S in the direction perpendicular to the groove center line of the outer vertical groove 2S and the grounding width WT is 0.040 to 0.060, and W2C <W2M <W2S. The heavy-duty pneumatic tire according to claim 1 . The grooved vertical groove 2g is formed on the outer vertical groove 2S on the wall surface of the central block 4C and the wall surface of the intermediate block 4M facing the intermediate vertical groove 2M and the intermediate vertical groove 2M. The heavy load pneumatic tire according to claim 2, wherein the wall groove (5) is formed in a wall surface of the outer block 4S facing the groove and a groove wall of the intermediate block 4M. The tread surface T is provided with five vertical grooves, the central vertical groove 2C, the outer vertical groove 2S, and the intermediate vertical groove 2M.
  4. The heavy duty pneumatic tire according to claim 1, wherein each longitudinal groove has a zigzag shape in which a rectangular groove piece is repeated in the circumferential direction. 5. 5. The heavy duty pneumatic tire according to claim 1, wherein a width LG of the wall groove is 1.0 to 2.5 mm.

Images