JP2015128964A - Pneumatic tire for heavy load - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire for heavy load that can have higher fuel consuming performance and higher chipping-resisting performance.SOLUTION: There is provided a pneumatic tire for heavy load that has a tread part 2 provided with a plurality of peripheral main grooves 3 extending zigzag successively in a tire peripheral direction so as to section off a plurality of land parts 4, and also has each land part 4 provided with a plurality of lateral grooves 5 so as to section off a plurality of block elements 6. The land part 4 includes 40-50 pitches P, and the length of a block element 6 in the tire peripheral direction is 85-95% of a pitch P in the tire peripheral direction. A peripheral main groove 3 includes a crown main groove 3C, a shoulder main groove 3S, and a middle main groove 3M extending between the crown main groove 3C and shoulder main groove 3S, and the middle main groove 3M has a larger zigzag amplitude than the crown main groove 3C and shoulder main groove 3S.

Description

  The present invention relates to a heavy duty pneumatic tire capable of improving fuel efficiency and chipping resistance.

  2. Description of the Related Art Conventionally, a heavy-duty pneumatic tire having excellent drainage properties in which a plurality of block elements are divided by providing a plurality of circumferential main grooves and lateral grooves in the tread portion has been proposed (for example, the following patents) Reference 1).

JP 2006-315579 A

  However, when the tire as described above includes many lateral grooves in the tire circumferential direction, the circumferential rigidity of the tread portion decreases. For this reason, there is a possibility that the energy loss of the tire rubber material increases due to a large deformation of the tread portion at the time of ground contact, and the fuel efficiency is deteriorated.

  In order to improve fuel efficiency, it is conceivable to reduce the number of lateral grooves and increase the circumferential rigidity of the tread portion. However, in such a tire, there is a possibility that chipping such as chipping of rubber occurs in a block element to which a large contact pressure acts.

  The present invention has been made in view of the above circumstances, and has as its main object to provide a heavy duty pneumatic tire that can improve fuel efficiency and chipping resistance.

  The present invention provides the tread portion with a plurality of circumferential main grooves extending in a zigzag shape continuously in the tire circumferential direction so that a plurality of land portions are divided into the tread portion, and each land portion is In addition, a heavy-duty pneumatic tire in which a plurality of horizontal grooves are provided to divide a plurality of block elements, each land portion includes one block element and one horizontal groove adjacent thereto. 40 to 50 pitches are included, and the pitch ranges from 85% to 95% of the maximum length along the tire circumferential direction, and the circumferential main groove extends at least near the tire equator. A crown main groove, a pair of shoulder main grooves extending most on the tread end side, and a middle main groove extending between the crown main groove and the shoulder main groove. It characterized by having a zigzag amplitude greater than the zigzag amplitude of the down main groove and the shoulder main groove.

  In the heavy duty pneumatic tire according to the present invention, the lateral groove includes a plurality of inner middle lateral grooves extending inward in the tire axial direction from an inner top portion of the middle main groove protruding inward in the tire axial direction of the zigzag, and the middle main groove. A plurality of outer middle lateral grooves extending outward in the tire axial direction from the outer top portion of the groove zigzag protruding outward in the tire axial direction, and extending from the groove bottom of the middle main groove to the groove bottom of the inner middle lateral groove A bottom sipe and a second groove bottom sipe extending from the groove bottom of the middle main groove to the groove bottom of the outer middle lateral groove are provided, and the first groove bottom sipe and the second groove bottom sipe communicate with each other. It is desirable that the tires are alternately arranged in the tire circumferential direction.

  In the heavy duty pneumatic tire according to the present invention, the first groove bottom sipe extends at an acute angle intersection where the inner middle lateral groove and the middle main groove intersect at an acute angle, and the second groove bottom sipe is It is desirable that the outer middle lateral groove and the middle main groove extend through an obtuse angle intersection where the obtuse angle intersects.

  In the heavy-duty pneumatic tire according to the present invention, the circumferential main groove includes a pair of crown main grooves extending on both sides of the tire equator, and the lateral groove is formed on the inner side in the tire axial direction of the zigzag of the crown main groove. It is preferable that the crown transverse groove and the inner middle transverse groove are inclined in the tire circumferential direction and the inclination directions are different from each other.

  In the heavy-duty pneumatic tire according to the present invention, in the adjacent land portion, it is desirable that the lateral groove of one land portion is displaced by approximately a half pitch position in the tire circumferential direction with respect to the lateral groove of the other land portion. .

  In the heavy duty pneumatic tire according to the present invention, it is preferable that the middle main groove and the lateral groove have a groove depth smaller than that of the crown main shoulder and the shoulder main groove.

  In the heavy-duty pneumatic tire of the present invention, each land portion includes 40 to 50 pitches composed of one block element and one lateral groove adjacent to the block element. The pitch of a general heavy duty tire is about 60 pieces. Therefore, the tire of the present embodiment has a smaller number of pitches than a general heavy duty tire. Such a tire has high circumferential rigidity of each land portion and excellent fuel efficiency. The pitch is a block element in a range of 85% to 95% of the maximum length along the tire circumferential direction. In such a tire, the tire circumferential length of each block element is sufficiently large, and the circumferential rigidity of the tread portion is enhanced. For this reason, the fuel consumption performance can be further improved by suppressing the deformation of the tread portion at the time of contact and reducing the energy loss of the tire rubber material.

  In the heavy duty pneumatic tire of the present invention, the middle main groove has a zigzag amplitude larger than the zigzag amplitude of the crown main shoulder and the shoulder main groove. In general, a large ground pressure acts on land portions on both sides of the middle main groove, and chipping is likely to occur. However, by making the zigzag amplitude of the middle main groove relatively large, the deformation of the land portion is promoted and the stress is relieved, whereby the chipping resistance can be improved.

It is an expanded view of the tread part of one Embodiment of this invention. It is the elements on larger scale of the AA cross section of FIG. It is the elements on larger scale near the inner middle land part of FIG. It is the elements on larger scale near the outer middle land part of FIG. It is BB sectional drawing of FIG. It is DD sectional drawing of FIG. It is CC sectional drawing of FIG.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a development view of the tread portion 2 of the heavy duty pneumatic tire of the present embodiment (hereinafter sometimes simply referred to as “tire”).

  As shown in FIG. 1, the tread portion 2 is provided with a plurality of circumferential main grooves 3. The circumferential main grooves 3 of the present embodiment are each zigzag-shaped and extend continuously in the tire circumferential direction.

  The circumferential main groove 3 includes at least one crown main groove 3C, a pair of middle main grooves 3M, and a pair of shoulder main grooves 3S. One crown main groove 3C of this embodiment is provided on each side of the tire equator C. The shoulder main groove 3S extends most on the tread end Te side. The middle main groove 3M extends between the crown main groove 3C and the shoulder main groove 3S. Thereby, the some land part 4 is divided. The land portion 4 of the present embodiment includes a crown land portion 4C between the crown main grooves 3C and 3C, an inner middle land portion 4Mi between the crown main groove 3C and the middle main groove 3M, a middle main groove 3M, and a shoulder main groove 3S. The outer middle land portion 4Mo between the shoulder main groove 3S and the shoulder land portion 4S between the tread end Te is included.

  The “tread end” is a position on the outermost side in the tire axial direction of the contact surface when a normal load is loaded on a normal tire and contacted with a flat surface with a camber angle of 0 °. The distance in the tire axial direction between the tread ends Te and Te is the tread width TW.

  The “normal state” is a no-load state in which a tire is assembled on a normal rim (not shown) and filled with a normal internal pressure. In this specification, unless otherwise specified, the dimensions of each part of the tire are values in a normal state.

  The “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based. For example, “Standard Rim” for JATMA, “Design Rim” for TRA, For ETRTO, "Measuring Rim".

  “Regular internal pressure” is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. For example, “maximum air pressure” for JATMA, “TIRE” for TRA The maximum value described in “LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” in the case of ETRTO.

  “Regular load” is a load determined by each standard for each tire in the standard system including the standard on which the tire is based. For example, “maximum load capacity” for JATMA, “table for TRA” The maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES”, or “LOAD CAPACITY” in the case of ETRTO.

  FIG. 2 shows a partially enlarged view of the AA cross section of FIG. As shown in FIG. 2, the groove widths CW2 and SW2 of the crown main groove 3C and the shoulder main groove 3S are, for example, 2% to 4% of the tread width TW to ensure the rigidity and drainage of the tread portion 2. A range is desirable. From the same viewpoint, the groove width MW2 of the middle main groove 3M is preferably in the range of 1% to 3% of the tread width TW, for example.

  From the same viewpoint as the groove widths CW2 and SW2, the depths CD1 and SD1 of the crown main groove 3C and the shoulder main groove 3S are preferably 10.0 mm or more, more preferably 12.0 mm or more, preferably 22. It is 0 mm or less, more preferably 20.0 mm or less.

  Each land portion 4 is provided with a plurality of lateral grooves 5. The lateral groove 5 of the present embodiment includes a crown lateral groove 5C, an inner middle lateral groove 5Mi, an outer middle lateral groove 5Mo, and a shoulder lateral groove 5S.

  As shown in FIG. 3, the crown lateral groove 5C is provided in the crown land portion 4C. The crown lateral groove 5C of this embodiment extends so as to connect between the zigzag inner top portions 3Ci and 3Ci of the pair of crown main grooves 3C and 3C. Thereby, the crown land portion 4C is divided into a plurality of crown block elements 6C.

  The crown lateral grooves 5C are preferably inclined at an angle of, for example, 55 to 75 degrees with respect to the tire circumferential direction. Such a crown lateral groove 5C exhibits an edge effect in the tire circumferential direction and the tire axial direction, and can smoothly guide the water film between the road surface and the road surface outward in the tire axial direction along the inclination thereof. Helps improve performance and wet performance.

  FIG. 5 is a sectional view taken along line BB in FIG. As shown in FIG. 5, in the cross section perpendicular to the longitudinal direction of the crown transverse groove 5C, the groove depth CD2 of the crown transverse groove 5C is, for example, in the range of 50% to 60% of the groove depth CD1 of the crown main groove 3C. It is desirable. Such a crown lateral groove 5C can increase the circumferential rigidity of the crown land portion 4C, reduce the energy loss of the tire rubber member, and further improve the fuel efficiency.

  The crown transverse groove 5C of the present embodiment is provided with a crown groove bottom sipe 7C extending along the groove center of the crown transverse groove 5C. The crown groove bottom sipe 7C can suppress the circumferential rigidity of the crown land portion 4C from being excessively increased. For this reason, the crown groove bottom sipe 7C can further improve the chipping resistance performance by accelerating the deformation of the crown land portion 4C and relieving the stress.

  The depth CD3 of the crown groove bottom sipe 7C is preferably in the range of 40% to 50% of the groove depth CD1 of the crown main groove 3C, for example. If the depth CD3 is less than 40%, the effect of improving chipping resistance may not be exhibited. On the other hand, when the depth CD3 is larger than 50%, the fuel efficiency may be lowered.

  As shown in FIG. 4, the shoulder lateral groove 5S is provided in the shoulder land portion 4S. The shoulder lateral groove 5S of the present embodiment extends from the shoulder main groove 3S to the tread end Te. Thereby, the shoulder land portion 4S is divided into a plurality of shoulder block elements 6S.

  Preferably, the shoulder lateral groove 5S extends between the zigzag outer top 3So of the shoulder main groove 3S and the tread end Te. For example, the shoulder lateral groove 5S desirably extends substantially along the tire axial direction.

  FIG. 6 is a sectional view taken along the line DD of FIG. As shown in FIG. 4 or 6, the shoulder lateral groove 5S of the present embodiment includes, for example, a shallow bottom portion 9i on the tire axial direction inner side with a small groove depth SD2 and a groove on the outer side in the tire axial direction with a large groove depth SD3. And bottom 9o.

  The depth SD2 of the shallow bottom portion 9i is preferably in the range of, for example, 15% to 70% of the groove depth CD1 of the crown main groove 3C in the cross section perpendicular to the longitudinal direction of the shoulder lateral groove 5S. The depth SD3 of the groove bottom portion 9o is preferably about the same as the groove depth CD1 of the crown main groove 3C, for example. Such a shoulder lateral groove 5S increases the circumferential rigidity of the shoulder land portion 4S by the shallow bottom portion 9i, and is useful for improving fuel efficiency. Further, when running on a wet road surface, for example, water flowing in from the shoulder main groove 3S is accelerated at the shallow bottom portion 9i, and water accelerated through the groove bottom portion 9o can be drained to the outside in the tire axial direction. Performance can be improved.

  For example, the shoulder lateral groove 5S of the present embodiment does not have a groove bottom sipe at the groove bottom. For this reason, the circumferential rigidity of the shoulder land portion 4S can be maintained at a higher level, and the steering stability performance can be improved in addition to the fuel efficiency performance.

  As shown in FIG. 3, the inner middle lateral groove 5Mi is provided in the inner middle land portion 4Mi. The inner middle lateral groove 5Mi of the present embodiment extends from the inner top portion 3Mi of the middle main groove 3M toward the outer top portion 3Co of the crown main groove 3C, and terminates in the inner middle land portion 4Mi without communicating with the crown main groove 3C. doing. Thereby, the inner middle land portion 4Mi is divided into a plurality of inner middle block elements 6Mi. The crown main groove 3C side of each inner middle block element 6Mi is connected in the tire circumferential direction. In such an embodiment, the inner middle land portion 4Mi having a high contact pressure is preferable in that the circumferential rigidity of the land portion is increased.

  The inner middle lateral groove 5Mi of the present embodiment is inclined at an angle of, for example, 55 to 75 degrees with respect to the tire circumferential direction. The inner middle lateral groove 5Mi is preferably different in inclination direction from the crown lateral groove 5C, for example. Such an inner middle lateral groove 5Mi differs from the crown lateral groove 5C in the direction in which the edge effect is exhibited. For this reason, in the tire of this embodiment, for example, when turning right and turning left, the edge effect can be effectively exhibited by the crown lateral groove 5C and the inner middle lateral groove 5Mi.

  FIG. 7 shows a cross-sectional view taken along the line CC of FIG. As shown in FIG. 3 or FIG. 7, in the cross section perpendicular to the longitudinal direction of the inner middle lateral groove 5Mi, the groove depth MD2 of the inner middle lateral groove 5Mi is approximately the same as the groove depth CD2 of the crown lateral groove 5C. desirable. Such an inner middle lateral groove 5Mi can increase the circumferential rigidity of the inner middle land portion 4Mi, reduce the energy loss of the tire rubber member, and further improve fuel efficiency.

  The outer middle lateral groove 5Mo is provided in the outer middle land portion 4Mo. The outer middle lateral groove 5Mo of the present embodiment extends outward in the tire axial direction from the outer middle main groove 3M. Preferably, the outer middle lateral groove 5Mo extends between the zigzag outer top 3Mo of the middle main groove 3M and the zigzag inner top 3Si of the shoulder lateral groove 3S. Thereby, the outer middle land portion 4Mo is divided into a plurality of outer middle block elements 6Mo. The outer middle lateral groove 5Mo is preferably inclined at an angle of, for example, 55 to 75 degrees with respect to the tire circumferential direction.

  The groove depth (not shown) of the outer middle horizontal groove 5Mo of the present embodiment is, for example, approximately the same as the groove depth MD2 of the inner middle horizontal groove 5Mi. Such outer middle lateral grooves 5Mo can increase the circumferential rigidity of the outer middle land portion 4Mo, reduce the energy loss of the tire rubber member, and further improve the fuel efficiency.

  The tread portion 2 configured as described above preferably has a land ratio in the range of 70% to 80% in order to achieve a good balance between fuel efficiency and wet performance. “Land ratio” is the ratio of the total surface area of the tread portion 2 measured under the assumption that all grooves provided in the tread portion 2 are filled to the total surface area of the land portion 4 that actually contacts the road surface. is there.

  As a more preferable aspect, in the present embodiment, in the adjacent land portions 4, the lateral groove 5 of one land portion 4 is displaced by approximately a half pitch position in the tire circumferential direction with respect to the lateral groove 5 of the other land portion 4. . For example, it is desirable that the inner middle lateral groove 5Mi is displaced from the crown lateral groove 5C by approximately a half pitch position in the tire circumferential direction. Further, the outer middle lateral groove 5Mo is displaced from the inner middle lateral groove 5Mi by approximately a half pitch position in the tire circumferential direction. Further, the shoulder lateral groove 5S is displaced from the outer middle lateral groove 5Mo by approximately a half pitch position in the tire circumferential direction. In such a tread portion 2, a position where the axial width of the land portion 4 is maximized and a position where the axial width of the land portion 4 is minimized are alternately arranged in the tire axial direction. For this reason, the land parts 4 and 4 adjacent to each other in the tire axial direction are connected to each other in a well-balanced manner, and deformation of the land part 4 is suppressed to be small, and fuel efficiency can be further improved.

  Here, the “pitch” is a pattern unit including one block element 6 and one horizontal groove 5 adjacent to the block element 6. The “substantially half pitch” includes at least a length of about 40 to 60% of one pitch P.

  As a more preferable aspect, each land portion 4 of the present embodiment includes, for example, 40 to 50 pitches P. The pitch P of a general heavy load tire is about 60 pieces. Therefore, the tire of the present embodiment has a smaller number of pitches P than that of a general heavy duty tire. Such a tire has high circumferential rigidity of each land portion 4 and is excellent in fuel efficiency.

  As a more preferable aspect, it is desirable that each pitch P is occupied by the block element 6 in the range of, for example, 85% to 95% of the maximum length along the tire circumferential direction. When the block element 6 is less than 85%, the rigidity of the land portion 4 is reduced, and the fuel efficiency may be lowered. On the contrary, when the block element 6 is larger than 95%, the drainage property is deteriorated and the wet performance may be deteriorated.

  As shown in FIG. 1, FIG. 3, or FIG. 4, the middle main groove 3M has a zigzag amplitude MW1 larger than the zigzag amplitude CW1 of the crown main groove 3C and the zigzag amplitude SW1 of the shoulder main groove 3S. Generally, a large ground pressure acts on the inner middle land portion 4Mi and the outer middle land portion 4Mo on both sides of the middle main groove 3M both during straight travel and during turning, and chipping is likely to occur. In the present invention, by increasing the zigzag amplitude MW1 of the middle main groove 3M relatively, the deformation of the inner middle land portion 4Mi and the outer middle land portion 4Mo is promoted, and the stress is relieved, thereby achieving high chipping resistance. May be provided.

  The zigzag amplitude CW1 of the crown main groove 3C is preferably determined in the range of 1% to 3% of the tread width TW, for example, from the viewpoint of drainage and traction performance. From the same viewpoint, the zigzag amplitude SW1 of the shoulder main groove 3S is preferably in the range of 1% to 3% of the tread width TW, for example.

  The zigzag amplitude MW1 of the middle main groove 3M is preferably in the range of 3% to 5% of the tread width TW, for example. When the zigzag amplitude MW1 of the middle main groove 3M is less than 3% of the tread width TW, the effect of improving the chipping resistance may not be sufficiently exhibited. Conversely, when the zigzag amplitude MW1 of the middle main groove 3M is larger than 5% of the tread width TW, the axial rigidity of the block element 6 may be excessively lowered.

  As shown in FIG. 2, the groove depth MD1 of the middle main groove 3M is preferably smaller than the groove depth CD1 of the crown main groove 3C and the groove depth SD1 of the shoulder main groove 3S. Such a middle main groove 3M enhances the connection between the inner middle land portion 4Mi and the outer middle land portion 4Mo, and integrally deforms both the land portions 4Mi, 4Mo, and helps to further improve the chipping performance. . The groove depth MD1 is preferably 4.0 mm or more, more preferably 6.0 mm or more, preferably 13.0 mm or less, more preferably 11.0 mm or less.

  In order to further improve chipping resistance, as shown in FIG. 1 or FIG. 3, a middle groove bottom sipe 7M is provided at the groove bottom of the middle main groove 3M, the inner middle lateral groove 5Mi, and the outer middle lateral groove 5Mo. desirable.

  The middle groove bottom sipe 7M includes, for example, a first groove bottom sipe 7Mi and a second groove bottom sipe 7Mo.

  For example, the first groove bottom sipe 7Mi extends from the middle main groove 3M to the inner middle lateral groove 3Mi. In a more specific aspect, the first groove bottom sipe 7Mi extends so as to be bent at the inner top portion 3Mi where the inner middle lateral groove 5Mi and the middle main groove 3M intersect at an acute angle, and has an acute angle intersection 8i. .

  The second groove bottom sipe 7Mo extends from the middle main groove 3M to the outer middle lateral groove 5Mo. In a more specific aspect, the second groove bottom sipe 7Mo has, for example, an obtuse angle intersection 8o such that the outer middle lateral groove 5Mo and the middle main groove 3M bend at an outer top 3Mo where the obtuse angle intersects. .

  The first groove bottom sipe 7Mi and the second groove bottom sipe 7Mo prevent the rigidity of the inner middle land portion 4Mi and the outer middle land portion 4Mo from being excessively increased. For this reason, chipping resistance is further improved by accelerating the relative deformation of the middle block elements 6Mi and 6Mo and relieving the stress. In addition, a larger ground pressure acts on the inner middle land portion 4Mi than on the outer middle land portion 4Mo. The first groove bottom sipe 7Mi of the present embodiment relatively decreases the axial rigidity of the inner middle land portion 4Mi by the acute angle crossing portion 8i. For this reason, the deformation of the inner middle block element 6Mi can be further promoted, and the chipping resistance can be further improved by relaxing the stress.

  It is desirable that the first groove bottom sipes 7Mi and the second groove bottom sipes 7Mo are alternately arranged in the tire circumferential direction, for example. Since the first groove bottom sipe 7Mi and the second groove bottom sipe 7Mo are not in communication with each other, the circumferential rigidity of the inner middle land portion 4Mi and the outer middle land portion 4Mo is suppressed from excessively decreasing. This is useful for maintaining or improving fuel economy performance.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to these embodiment, It can deform | transform and implement in a various aspect.

Tires (size: 275 / 80R22.5) having the basic pattern shown in FIG. 1 and based on the specifications of Table 1 were prototyped and their performance was tested. The crown main groove of each sample tire has a groove depth of 20.0 mm.
The test method is as follows.

<Fuel efficiency (rolling resistance)>
Each sample tire was run on the drum of a rolling resistance tester under the following conditions, and the rolling resistance was measured. The result is the reciprocal of the rolling resistance, and is indicated by an index with the value of Example 1 being 100. The larger the value, the better the fuel efficiency.
Rims: 22.5 x 7.50
Internal pressure: 900 kPa
Load: 33.83kN
Speed: 80km / h

<Chip resistance>
The sample tire is mounted on one of the rear wheels of the truck, and the tire of Example 1 is mounted on the other of the rear wheels of the truck. The depth of the crown main groove of any tire is 1.6 mm. The chipping was evaluated visually. In

<Wet performance>
The above sample tire with 80% progress of wear is mounted on all wheels of a semi-loaded truck loaded with luggage only on the front side, and on a wet road surface with a 5 mm water film, the clutch is engaged at a speed of 2 to 1500 rpm. From the moment they were connected, the time required to travel 10m was measured. The result is the reciprocal of the running time and is an index with the value of Example 1 as 100. The larger the value, the better.

  As shown in Table 1, it was confirmed that the tires of each example were improved in fuel efficiency and chipping resistance.

2 Tread part 3 Circumferential main groove 3C Crown main groove 3M Middle main groove 3S Shoulder main groove 4 Land part 5 Horizontal groove 6 Block element P Pitch C Tire equator

Claims (6)

The tread portion is provided with a plurality of circumferential main grooves extending in a zigzag shape continuously in the tire circumferential direction, so that a plurality of land portions are divided in the tread portion, and a plurality of land portions are provided in each land portion. A pneumatic tire for heavy loads in which a plurality of block elements are divided by providing lateral grooves of
Each land portion includes 40 to 50 pitches composed of one block element and one lateral groove adjacent to the block element,
The block element has a range of 85% to 95% of the maximum length along the tire circumferential direction,
The circumferential main groove includes at least one crown main groove extending in the vicinity of the tire equator, a pair of shoulder main grooves extending most on the tread end side, and a middle extending between the crown main groove and the shoulder main groove. Including a main groove,
The heavy tire is characterized in that the middle main groove has a zigzag amplitude larger than the zigzag amplitude of the crown main groove and the shoulder main groove. The lateral groove includes a plurality of inner middle lateral grooves extending inward in the tire axial direction from an inner top portion protruding in the tire axial direction of the zigzag of the middle main groove, and an outer side protruding outward in the tire axial direction of the zigzag of the middle main groove. Including a plurality of outer middle lateral grooves extending outward from the top in the axial direction of the tire,
A first groove bottom sipe extending from the groove bottom of the middle main groove to the groove bottom of the inner middle horizontal groove and a second groove bottom sipe extending from the groove bottom of the middle main groove to the groove bottom of the outer middle horizontal groove are provided. ,
2. The heavy duty pneumatic tire according to claim 1, wherein the first groove bottom sipes and the second groove bottom sipes are alternately arranged in the tire circumferential direction without communicating with each other. The first groove bottom sipe extends an acute angle intersection where the inner middle lateral groove and the middle main groove intersect at an acute angle,
3. The heavy duty pneumatic tire according to claim 2, wherein the second groove bottom sipe extends an obtuse angle intersection where the outer middle lateral groove and the middle main groove intersect at an obtuse angle. The circumferential main groove includes a pair of crown main grooves extending on both sides of the tire equator,
The lateral groove includes a plurality of crown lateral grooves that connect inner top portions that protrude inward in the tire axial direction of the zigzag of the crown main groove,
4. The heavy duty pneumatic tire according to claim 2, wherein the crown lateral groove and the inner middle lateral groove are inclined in the tire circumferential direction and have different inclination directions.   5. The heavy-duty pneumatic system according to claim 1, wherein in the adjacent land portion, the lateral groove of one land portion is displaced by a substantially half pitch position in the tire circumferential direction with respect to the lateral groove of the other land portion. tire.   6. The heavy duty pneumatic tire according to claim 1, wherein the middle main groove and the lateral groove have a groove depth smaller than that of the crown main groove and the shoulder main groove.

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