Heavy load pneumatic tire

Abstract

To provide a heavy load pneumatic tire 2 which is excellent in abrasion resistance of a tread and suppresses chipping in a center land part from occurring and uneven wear in a shoulder land part from occurring.SOLUTION: A tire 2 comprises: a tread 4; and a reinforcement layer 20. Two circumferential main grooves 28 are formed in the tread 4 so that shoulder land parts 30s and a center land part 30c are provided. The center land part 30c is a land part including an equator of the tire 2 and at least one circumferential narrow groove 48 is formed in the center land part 30c. The reinforcement layer 20 includes: a belt 38; and a pair of edge bands 60. The belt includes a plurality of belt plies arrayed in a radial direction, an end of at least one belt ply is positioned on an inner side of the shoulder land part in the radial direction, and an edge band 60 is positioned only on the inner side of the shoulder land part 30s in the radial direction. Rubber hardness of the shoulder land part 30s is harder than that of the center land part 30c.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a pneumatic tire for heavy loads.

Background Art

[0002] In an electric vehicle (hereinafter also referred to as an EV vehicle), a battery is mounted on the vehicle. Therefore, the total weight becomes heavier compared to a gasoline vehicle. In particular, in an EV vehicle of a heavy vehicle such as a truck or a bus, since the battery itself becomes larger, the weight difference from a gasoline vehicle is likely to become large. In a pneumatic tire for heavy loads mounted on an EV vehicle of a heavy vehicle, the center portion with high ground pressure is likely to wear. Further, for example, in an EV bus, there is a type in which a battery is mounted on the upper part of the vehicle body. The pneumatic tire for heavy loads mounted on this type of EV bus is likely to cause uneven wear due to a load being applied to the shoulder portion during turning.

[0003] Patent Document 1 proposes a pneumatic tire for heavy loads that ensures uneven wear resistance, comprising a belt composed of a plurality of layers located on the radially inner side of the tread, and a pair of edge bands including metal band cords wound in a spiral shape and located between the tread and the belt in the radial direction. In the radial direction, the edge bands are laminated on the ends of the belt and overlap with the shoulder circumferential grooves.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] An object of the present invention is to provide a pneumatic tire for heavy loads in which the wear resistance of the center portion and the shoulder portion of the tread is good and the shoulder portion is less likely to undergo uneven wear.

Means for Solving the Problem

[0006] The pneumatic tire for heavy loads according to the present invention includes a tread that contacts the road surface and a reinforcing layer located inside the tread in the radial direction, by forming two circumferential main grooves in the tread, three land portions arranged in parallel in the axial direction are formed. The land portion located outside the circumferential main groove in the axial direction is the shoulder land portion, and the land portion sandwiched between the two land portions in the axial direction is the center land portion. The center land portion is the land portion including the equator of the tire. At least one circumferential narrow groove having a groove width narrower than that of the circumferential main groove is formed in the center land portion. The reinforcing layer includes a belt including a large number of belt cords arranged in parallel and a pair of edge bands including spiral band cords. The belt includes a plurality of belt plies arranged in the radial direction, and the end of at least one of the belt plies is located inside the shoulder land portion in the radial direction. The edge band is located only inside the shoulder land portion in the radial direction. The rubber hardness of the shoulder land portion is harder than the rubber hardness of the center land portion.

Advantages of the Invention

[0007] According to the present invention, it is possible to provide a pneumatic tire for heavy loads with good wear resistance of the tread, and suppression of the occurrence of chipping in the center land portion and uneven wear in the shoulder land portion. The above pneumatic tire for heavy loads is particularly effective when used for an EV vehicle of a heavy truck with a high load on the tire and a high center of gravity.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

BEST MODE FOR CARRYING OUT THE INVENTION

[0009] The pneumatic heavy-load tire of the present invention (hereinafter, also simply referred to as a tire) is assembled to a rim. Air is filled inside the tire, and the internal pressure of the tire is adjusted. The tire assembled to the rim is also called a tire-rim assembly. The tire-rim assembly includes a rim and a tire assembled to this rim.

[0010] In the present invention, a state in which the tire is assembled to a standard rim, the internal pressure of the tire is adjusted to a standard internal pressure, and no load is applied to this tire is called a standard state.

[0011] In the present invention, unless otherwise specified, the dimensions and angles of each part of the tire are measured in the standard state. The dimensions and angles of each part in the meridian cross-section of the tire that cannot be measured in the state where the tire is assembled to the standard rim are measured on the cut surface of the tire obtained by cutting the tire along a plane including the rotation axis. In this measurement, the tire is set so that the distance between the left and right beads matches the distance between the beads in the tire assembled to the standard rim. Note that the configuration of the tire that cannot be confirmed in the state where the tire is assembled to the standard rim is confirmed on the aforementioned cut surface.

[0012] The standard rim means a rim defined in the standard to which the tire conforms. The "Standard Rim" in the JATMA standard, the "Design Rim" in the TRA standard, and the "Measuring Rim" in the ETRTO standard are standard rims.

[0013] The normal internal pressure means the internal pressure defined in the standard on which the tire depends. The "maximum air pressure" in the JATMA standard, the "maximum value" published in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "INFLATION PRESSURE" in the ETRTO standard are the normal internal pressures.

[0014] The normal load means the load defined in the standard on which the tire depends. The "maximum load capacity" in the JATMA standard, the "maximum value" published in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "LOAD CAPACITY" in the ETRTO standard are the normal loads.

[0015] In the present invention, among the elements constituting the tire, the tensile strength and the elongation at break of the element made of crosslinked rubber are measured at a temperature of 23°C in an atmosphere using a tensile tester in accordance with the provisions of JIS K6251. In this measurement, strip pieces (length 150 mm × width 25 mm × thickness 2 mm) are sampled from the tire, and No. 3 dumbbell test pieces are prepared using these strip pieces. The length direction of the strip pieces is made to coincide with the circumferential direction of the tire.

[0016] When test pieces cannot be sampled from the tire, test pieces are sampled from a sheet-like crosslinked rubber (hereinafter also referred to as a rubber sheet) obtained by pressurizing and heating the rubber composition used for forming the element to be measured at a temperature of 170°C for 12 minutes. In the present invention, the fracture energy is represented by a value that is half of the product of the tensile strength and the elongation at break. The unit of the fracture energy is MPa·%.

[0017] In the present invention, among the elements constituting the tire, the rubber hardness of the element made of crosslinked rubber is the durometer A hardness measured at a temperature of 23°C using a type A durometer in accordance with the provisions of JIS K6253-3. In this measurement, a test piece of a predetermined size is sampled from the tire, and the measurement is performed using this test piece. When a test piece cannot be sampled from the tire, a test piece is prepared from the rubber sheet described above.

[0018] [Findings on which the present invention is based] As already described, EV vehicles for heavy vehicles such as trucks and buses have a heavy total weight, and pneumatic tires for heavy loads mounted on such vehicles are prone to wear. In particular, the ground contact pressure in the center region of the tread becomes high, and this center region is prone to wear. As a countermeasure, it is possible to consider increasing the rigidity of the center region of the tread. On the other hand, when the rigidity of the center region of the tread is increased, the ground contact pressure in the center region of the tread increases, and as a result, chipping is likely to occur in the center region of the tread. In addition, there is a type of EV vehicle that stacks batteries on the upper part of the vehicle body. This type of EV vehicle has a larger load on the shoulder region of the tread during turning compared to conventional gasoline vehicles, and the shoulder region of the tread wears more significantly than the center region, and uneven wear in the shoulder region is likely to occur.

[0019] The present invention has been made in view of such circumstances. The present inventor has studied means for suppressing the occurrence of chipping in the center land portion of the tire and the occurrence of uneven wear in the shoulder land portion while improving the wear resistance of the tread of the tire, and has completed the invention described below.

[0020] [Details of Embodiments of the Present Invention] Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings.

[0021] FIG. 1 shows a part of a pneumatic heavy-duty tire 2 (hereinafter also simply referred to as "tire 2") according to an embodiment of the present invention. This tire 2 is mounted on vehicles such as trucks and buses. This tire 2 is preferably mounted on electric vehicles (EVs) such as trucks and buses, and is particularly preferably mounted on an EV bus with a battery stacked on the upper part of the vehicle body. Such an EV bus has a heavy total weight due to the battery mounted on the upper part of the vehicle body, and the lateral force applied to the tire during turning becomes large. However, the tire 2 according to the embodiment of the present invention has the following configuration. Therefore, this tire 2 has good wear resistance in each of the center land portion and the shoulder land portion, and uneven wear of the shoulder land portion is less likely to occur. In this specification, an EV vehicle that is a truck is also referred to as an EV truck, and an EV vehicle that is a bus is also referred to as an EV bus.

[0022] FIG. 2 shows a part of a cross section (hereinafter, a meridian cross section) of this tire 2 along a plane including the rotation axis of the tire 2. In FIG. 1, the left-right direction is the axial direction of the tire 2, and the up-down direction is the radial direction of the tire 2. The direction perpendicular to the paper surface of FIG. 1 is the circumferential direction of the tire 2. The dashed-dotted line CL represents the equatorial plane of the tire 2.

[0023] FIG. 2 shows a part of the meridian cross section of the tire 2. FIG. 2 also shows another part in the same cross section as the cross section of the tire 2 shown in FIG. 1. This FIG. 2 mainly shows the tread of this tire 2. In FIG. 2, the left-right direction is the axial direction of the tire 2, and the up-down direction is the radial direction of the tire 2. The direction perpendicular to the paper surface of FIG. 2 is the circumferential direction of the tire 2.

[0024] The tire 2 is assembled to a rim (not shown). The rim is a standard rim. The inside of the tire 2 is filled with air, and the internal pressure of the tire 2 is adjusted. The tire 2 assembled to the rim is also referred to as a tire-rim assembly. The tire-rim assembly includes a rim and the tire 2 assembled to this rim.

[0025] This tire 2 includes a tread 4, a pair of sidewalls 6, a pair of beads 8, a pair of chafers 10, a carcass 12, a pair of cushion layers 14, an inner liner 16, a pair of steel fillers 18, and a reinforcing layer 20.

[0026] The tread 4 contacts the road surface on its outer surface. This outer surface is the tread surface 22. In FIG. 1, the symbol PC is the intersection of the tread surface 22 and the equatorial plane. This intersection PC is the equator of the tire 2.

[0027] In FIGS. 1 and 2, the symbol PE is the end of the tread surface 22. The double-headed arrow WT shown in FIG. 2 is the width of the tread surface 22. The width WT of this tread surface 22 is represented by the axial distance from one end PE of the tread surface 22 to the other end PE of the tread surface 22.

[0028] The tread 4 includes a base portion 24 and a cap portion 26 located radially outside of this base portion. In this case, both the base portion 24 and the cap portion 26 are made of crosslinked rubber. The base portion 24 is made of a crosslinked rubber with low heat generation. The cap portion 26 is made of a crosslinked rubber considering wear resistance, low temperature characteristics, and grip performance.

[0029] In this tire 2, two circumferential main grooves 28 are engraved in the tread 4. The two circumferential main grooves 28 are arranged in parallel in the axial direction and extend continuously in the circumferential direction. The two circumferential main grooves 28 engraved in the tread 4 form three land portions 30 in this tread 4. These land portions 30 are arranged in parallel in the axial direction and extend continuously in the circumferential direction.

[0030] Among the three land portions 30 formed in the tread 4, the middle land portion is the center land portion 30c. In the axial direction, each land portion 30 located on both outer sides of the center land portion is a shoulder land portion 30s. Since the land part of this tire 2 is composed of three land parts, it is easy to increase the width of the center land part 30c and is suitable for ensuring the rigidity of the center land part 30c. In other words, it is suitable for increasing the rigidity of the center region of the tread compared to a tire having four or more land parts.

[0031] In this tire 2, the center land part 30c is the land part including the equator PC of the tire. The tire 2 provided with such a center land part 30c has an increased rigidity in the center region of the tread 4. The shoulder land part 30s is located outside the circumferential main groove 28 in the axial direction. The shoulder land part 30s includes the edge PE of the tread surface 22 of the tire 2. In the tire 2 shown in FIGS. 1 and 2, the land part 30 is composed of a center land part 30c and a pair of shoulder land parts 30s.

[0032] In the tire 2, transverse grooves crossing the land part 30 may be engraved on each land part 30. The land part with such transverse grooves will be composed of a plurality of blocks arranged in the circumferential direction. In the tire 2, when transverse grooves are engraved on the land part 30, these transverse grooves may be engraved only on the center land part 30c, or only on the shoulder land part 30s, or on both the center land part 30c and the shoulder land part 30s.

[0033] In this tire 2, the rubber hardness of the shoulder land part 30s is harder than that of the center land part 30c. In this case, the tread 4 has a center region that is softer than the shoulder region, and the contact pressure in the center region of the tread 4 is easily dispersed. Therefore, the contact pressure of the entire tread 4 is averaged, the wear resistance of the tread 4 is improved, and uneven wear of the shoulder land part 30 is less likely to occur. Moreover, chipping in the center land part 30c, which is likely to occur due to an increase in the rubber hardness of the center land part 30c, can also be suppressed.

[0034] In tire 2, the preferred rubber hardness (durometer A hardness) of the shoulder land portion 30s is 65 or more and 75 or less, and the preferred rubber hardness (durometer A hardness) of the center land portion 30c is 63 or more and 73 or less. If the rubber hardness of the shoulder land portion 30s is less than 65, uneven wear of the shoulder land portion 30s may not be sufficiently suppressed. If the rubber hardness of the center land portion 30c exceeds 73, chipping in the center land portion 30c may not be sufficiently suppressed.

[0035] When tire 2 includes a base portion 24 and a cap portion 26 like the tread 4, the rubber hardness of the cap portion 26s that constitutes the shoulder land portion 30s may be harder than the rubber hardness of the cap portion 26c that constitutes the center land portion 30c. In this case, the rubber hardness of the base portion that constitutes the shoulder land portion 30s may be harder than the rubber hardness of the base portion that constitutes the center land portion 30c, or may be the same as the rubber hardness of the base portion that constitutes the center land portion 30c.

[0036] In tire 2, the preferred fracture energy of the shoulder land portion 30s is 6500 MPa·% or more and 8500 MPa·% or less, and the preferred fracture energy of the center land portion 30c is 6000 MPa·% or more and 8000 MPa·% or less. If the fracture energy of the shoulder land portion 30s is less than 6500 MPa·%, chipping is likely to occur in the shoulder portion. On the other hand, if the fracture energy of the center land portion 30c is less than 6000 MPa·%, chipping is likely to occur in the center portion.

[0037] When tire 2 includes a base portion 24 and a cap portion 26 like the tread 4, it is preferable that the fracture energy of the rubber of the cap portion 26s that constitutes the shoulder land portion 30s and the fracture energy of the rubber of the cap portion 26c that constitutes the center land portion 30c are respectively within the aforementioned ranges.

[0038] In tire 2, circumferential grooves 48 are engraved in the center land portion 30c. In this tire 2, the circumferential grooves 48 are engraved at a position overlapping the equator PC of the tire 2. When such circumferential grooves 48 are engraved, it is suitable for improving the WET performance of the tire 2 while ensuring the rigidity of the center region of the tread 4 as compared with the case where circumferential main grooves are engraved at a position overlapping the equator PC of the tire 2.

[0039] In this specification, for the center land portion 30c in which the circumferential grooves 48 are engraved, the portion on one axial side (the right side in FIG. 2) with respect to the circumferential grooves 48 is referred to as the first region 30c1, and the portion on the other axial side (the left side in FIG. 2) is referred to as the second region 30c2. In this case, in the axial direction, the circumferential grooves 48 are sandwiched between the first region 30c1 and the second region 30c2.

[0040] In the embodiments of the present invention, the circumferential main groove refers to a circumferential groove having a dimension such that a pair of wall surfaces do not contact each other even when the tire contacts the road surface. Further, the circumferential fine groove refers to a circumferential groove having a dimension such that a pair of wall surfaces can contact each other when the tire contacts the road surface.

[0041] FIG. 3 is a cross-sectional view of the circumferential groove 48. FIG. 3 shows the cross-sectional shape of the circumferential groove 48 in a cross-section (meridian cross-section) perpendicular to the circumferential direction of the tire 2. The circumferential groove 48 of this tire 2 includes a tapered portion 50, a body portion 52, and an enlarged portion 54. The cross-sectional shape of the circumferential groove 48 is a shape like the cross-section of a flask. The circumferential groove 48 having a cross-sectional shape including the body portion 52 and the enlarged portion 54 located radially inside the body portion 52 is suitable as a circumferential groove for improving the WET performance of the tire 2.

[0042] The tapered portion 50 includes the groove opening 48M of the circumferential groove 48. The tapered portion 50 tapers inward from the groove opening 48M. In the tapered portion 50 shown in FIG. 3, the contour of the wall surface 48W is represented by a straight line. This contour may be represented by a curve. The body portion 52 is located radially inward of the tapered portion 50. The body portion 52 is continuous with the tapered portion 50. The body portion 52 extends straight. In FIG. 3, the contour of the wall surface 48W of the body portion 52 is represented by a straight line. The enlarged width portion 54 is located radially inward of the body portion 52. The enlarged width portion 54 is continuous with the body portion 52. The enlarged width portion 54 has a groove width wider than the groove width of the body portion 52. The enlarged width portion 54 includes the groove bottom 48T of the circumferential fine groove 48.

[0043] In FIG. 3, the position indicated by the reference sign PU is the boundary between the tapered portion 50 and the body portion 52. The boundary PU is represented by the intersection of the wall surface contour line of the tapered portion 50 and the wall surface contour line of the body portion 52. As shown in FIG. 3, when the boundary portion between the tapered portion 50 and the body portion 52 is rounded, the boundary PU is represented by the intersection of the extension line of the wall surface contour line of the tapered portion 50 and the extension line of the wall surface contour line of the body portion 52.

[0044] In FIG. 3, the position indicated by the reference sign PS is the boundary between the body portion 52 and the enlarged width portion 54. In FIG. 3, the length indicated by the double arrow WD is the groove width of the body portion 52. In the groove width from the body portion 52 to the enlarged width portion 54, the position showing a groove width 1.1 times the groove width WD of the body portion 52 is represented as the boundary PS between the body portion 52 and the enlarged width portion 54.

[0045] In FIG. 3, the length indicated by the double arrow WH is the maximum width of the enlarged width portion 54. The position indicated by the reference sign PH is the position where the enlarged width portion 54 shows the maximum width WH. The enlarged width portion 54 tapers outward from the portion showing the maximum width WH. In the portion from the maximum width position PH to the boundary PS, the enlarged width portion 54 curves so as to be recessed inward from its outer side. The enlarged width portion 54 tapers inward from the portion showing the maximum width WH. In the portion from the maximum width position PH to the groove bottom 48T, the enlarged width portion 54 has a rounded contour. In this portion, the enlarged width portion 54 curves so as to bulge outward from its inner side. In the enlarged-width portion 54, the boundary between the portion that curves inwardly so as to be recessed from the outside and the portion that curves outwardly so as to bulge from the inside is located radially outside the maximum-width position PM.

[0046] The tread portion 52 of the circumferential groove 48 of this tire 2 has a groove width WD that is narrower than the groove width WG at the groove opening of the shoulder circumferential groove 28s. In this circumferential groove 48, when the tire 2 comes into contact with the road surface, in this tread portion 52, a pair of wall surfaces 48W come into contact with each other. As a result, the first region 30c1 of the center land portion 30c adjacent to the circumferential groove 48 across the circumferential groove 48 and the second region 30c2 of the center land portion 30c support each other. By the first region 30c1 and the second region 30c2 supporting each other, the rigidity of the entire center land portion 30c is increased. This tire 2 can effectively suppress the occurrence of wear in the center land portion 30c.

[0047] In the circumferential groove 48, the tapered portion 50 includes the groove opening 48M of the circumferential groove 48 and tapers inward from the groove opening 48M. The tread portion 52 is continuous with this tapered portion 50. The tapered portion 50 increases the groove volume of the circumferential groove 48. The tapered portion 50 improves drainage performance. The tapered portion 50 suppresses the concentration of distortion at the groove opening 48M of the circumferential groove 48. The tapered portion 50 can contribute to the improvement of WET performance and resistance to uneven wear. From these viewpoints, as shown in FIG. 3, it is preferable that the circumferential groove 48 has a tapered portion 50 that includes the groove opening 48M and tapers inward in the radial direction.

[0048] From this viewpoint, the ratio (WD / WG) of the groove width WD of the tread portion 52 of the circumferential groove 48 to the groove width WG at the groove opening of the circumferential groove 48 is preferably 0.35 or less, and more preferably 0.20 or less. From the viewpoint that the circumferential groove 48 can contribute to drainage and the tire 2 can maintain good WET performance, the ratio (WD / WG) is preferably 0.01 or more, and more preferably 0.05 or more.

[0049] In the circumferential fine groove 48, the maximum width WH of the widened portion 54 is preferably at least twice the groove width WD of the carcass portion 52, more preferably at least three times the groove width WD of the carcass portion 52, from the viewpoint of ensuring good WET performance. On the other hand, from the viewpoint of suppressing the influence on the rigidity of the center land portion 30c, the maximum width WH of the widened portion 54 is preferably at most eight times the groove width WD of the carcass portion 52, more preferably at most seven times the groove width WD of the carcass portion 52.

[0050] In FIG. 3, the length indicated by the double arrow DC is the groove depth of the circumferential fine groove 48. This groove depth DC is, for example, 10 mm or more and 25 mm or less. The length indicated by the double arrow DD is the groove depth of the portion composed of the tapered portion 50 and the carcass portion 52 (hereinafter also referred to as the fine groove main body 48m). The groove depth DD of the fine groove main body 48m is represented by the radial distance from the groove opening 48M to the boundary PS between the carcass portion 52 and the widened portion 54. This groove depth DD is, for example, shallower than the groove depth DC and 5 mm or more and 15 mm or less. The length indicated by the double arrow DU is the groove depth of the tapered portion 50. The groove depth DU of the tapered portion 50 is represented by the radial distance from the groove opening 48M to the boundary PU between the tapered portion 50 and the carcass portion 52. This groove depth DU is, for example, shallower than the groove depth DC and 1 mm or more and 5 mm or less.

[0051] In the tire 2 shown in FIGS. 1 and 2, one circumferential fine groove 48 is engraved. However, in the tire 2, the number of circumferential fine grooves 48 engraved in the center land portion may be two or more. The number of circumferential fine grooves 48 engraved in the center land portion is preferably one or three, more preferably one, from the viewpoint of easily ensuring the rigidity of the center land portion. When one circumferential fine groove 48 is engraved in the tire 2, this circumferential fine groove 48 is preferably engraved at a position overlapping the equator of the tire. In this case, it is suitable for suppressing uneven wear of the center land portion 30c and ensuring good WET performance. When an odd number of circumferential fine grooves 48 are engraved in the tire 2, one circumferential fine groove 48 is preferably engraved at a position overlapping the equator of the tire.

[0052] As described above, two circumferential main grooves 28 are engraved on the tire 2. In the tire 2, the ratio of the circumferential main grooves 28 on the surface 22 of the tread 4 is 5% or more and 25% or less. In this case, the volume of the rubber provided in the tread 4 of the tire 2 can be increased, and the rigidity of the tire 2 can be improved. On the other hand, if the ratio of the circumferential main grooves 28 on the surface 22 of the tread 4 is less than 5%, the rigidity of the tread 4 of the tire 2 becomes excessively high, and chipping is likely to occur in the tread 4. Further, if the ratio of the circumferential main grooves 28 exceeds 25%, it is difficult to ensure the rigidity of the tire 2, and it becomes difficult to use the tire 2 for heavy vehicles such as EV trucks and EV buses.

[0053] The ratio of the circumferential main grooves 28 on the tread surface 22 described above is the ratio (%) of the total area of the groove openings of the circumferential main grooves 28 to the area of the tread surface 22 when it is assumed that no grooves are formed in the tread 4. Here, the area of the tread surface 22 is the area of the outer surface of the tread 4 sandwiched between the end PE of one tread surface and the end PE of the other tread surface.

[0054] In FIG. 2, the double-headed arrow DG is the depth of the circumferential main groove 28. In this tire 2, the depth DG of the circumferential main groove 28 is, for example, 10 mm or more and 25 mm or less. The depth of the circumferential main groove 28 is represented by the distance from the tread surface 22 to the bottom of the circumferential main groove 28.

[0055] In FIG. 2, the double-headed arrow WC is the width of the center land portion 30c. The double-headed arrow WS is the width of the shoulder land portion 30s. The width of the land portion 30 is represented by the axial width of the top surface of the land portion 30 that forms part of the tread surface 22. Accordingly, the width WC of the center land portion 30c is represented by the axial distance from one end to the other end of the top surface of the center land portion 30c (the axial distance between the inner edges of the circumferential main grooves 28). The axial width WS of the shoulder land portion 30s is represented by the axial distance from the inner end of the top surface of the shoulder land portion 30s (the outer edge of the circumferential main groove 28s) to the outer end of this top surface (the end PE of the tread surface 22 in the tire 2).

[0056] In the tire 2, the ratio WC / WS of the width WC of the center land portion 30c to the width WS of the shoulder land portion 30s preferably satisfies 2.0 ≦ WC / WS ≦ 2.5. By having WC / WS satisfy the above range, the width WC of the center land portion 30c is sufficiently ensured to secure the rigidity of the center land portion 30c, and without making the width WS of the shoulder land portion 30s too narrow, the rigidity of the shoulder land portion 30s is also ensured. That is, by satisfying the above range, the rigidity of the center land portion 30c and the rigidity of the shoulder land portion 30s can be ensured in a well-balanced manner. Therefore, it is easy to improve the wear resistance of both the center land portion 30c and the shoulder land portion 30s. Also, when WC / WS satisfies the above range, even if the rubber hardness of the center land portion 30c is low, it is easy to secure the rigidity of the center land portion 30c, and it is suitable for suppressing the occurrence of chipping in the center land portion 30c.

[0057] The width WC of the center land portion 30c is preferably 42% or more and 55% or less of the width WT of the tread surface 22. If the width WC of the center land portion 30c is less than 42% of the width WT of the tread surface 22, it is difficult to secure the rigidity of the center land portion 30c. On the other hand, if the width WC of the center land portion 30c exceeds 55% of the width WT of the tread surface 22, it becomes difficult to secure the rigidity of the shoulder land portion 30s. A more preferable width WC of the center land portion 30c is 46% or more and 50% or less of the width WT of the tread surface 22.

[0058] The width WS of the shoulder land portion 30s is preferably 16% or more and 27% or less of the width WT of the tread surface 22. If the width WS of the shoulder land portion 30s is less than 16% of the width WT of the tread surface 22, it is difficult to ensure the rigidity of the shoulder land portion 30s, and the shoulder land portion 30s is likely to experience uneven wear. On the other hand, if the width WS of the shoulder land portion 30s exceeds 27% of the width WT of the tread surface 22, it becomes difficult to ensure the rigidity of the center land portion 30c. A more preferable width WS of the shoulder land portion 30s is 18% or more and 25% or less of the width WT of the tread surface 22.

[0059] Each sidewall 6 is continuous with the end of the tread 4. The sidewall 6 extends radially inward from the end of the tread 4. The sidewall 6 is made of crosslinked rubber.

[0060] Each bead 8 is located radially inside the sidewall 6. The bead 8 includes a core 32 and an apex 34.

[0061] The core 32 extends in the circumferential direction. The core 32 includes a wound steel wire. The core 32 has a substantially hexagonal cross-sectional shape.

[0062] The apex 34 is located radially outside the core 32. The apex 34 includes an inner apex 34u and an outer apex 34s. The inner apex 34u extends radially outward from the core 32. The outer apex 34s is located radially outside the inner apex 34u. The inner apex 34u is made of hard crosslinked rubber. The outer apex 34s is made of crosslinked rubber that is softer than the inner apex 34u. The outer apex 34s is softer than the inner apex 34u.

[0063] Each chafer 10 is located axially outside the bead 8. The chafer 10 is located radially inside the sidewall 6. The chafer 10 contacts a rim (not shown). The chafer 10 is made of crosslinked rubber with wear resistance taken into consideration.

[0064] The carcass 12 is located inside the tread 4, the sidewall 6, and the chafer 10. The carcass 12 includes at least one carcass ply 36. The carcass 12 of this tire 2 consists of one carcass ply 36. The carcass ply 36 is folded from the axially inner side to the outer side around each core 32.

[0065] Although not shown, the carcass ply 36 includes a number of carcass cords arranged in parallel. These carcass cords are covered with topping rubber. Each carcass cord intersects the equatorial plane. In this tire 2, the angle formed by the carcass cord with respect to the equatorial plane is 70° or more and 90° or less. This carcass 12 has a radial structure. In this tire 2, steel cords are used as the carcass cords.

[0066] Each cushion layer 14 is located between the reinforcement layer 20 and the carcass 12 at the end of the reinforcement layer 20. The cushion layer 14 is made of a soft cross-linked rubber.

[0067] The inner liner 16 is located inside the carcass 12. The inner liner 16 constitutes the inner surface of the tire 2. The inner liner 16 is made of a cross-linked rubber with excellent air barrier properties. The inner liner 16 retains the internal pressure of the tire 2.

[0068] Each steel filler 18 is located at the bead 8 portion. The steel filler 18 is folded from the axially inner side to the outer side along the carcass ply 36 around the core 32.

[0069] Although not shown, the steel filler 18 includes a number of filler cords arranged in parallel. In the steel filler 18, the filler cords are covered with topping rubber. In this tire 2, steel cords are used as the filler cords.

[0070] As shown in FIGS. 1 and 2, the reinforcing layer 20 is located inside the tread 4 in the radial direction. The reinforcing layer 20 is located between the carcass 12 and the tread 4. The reinforcing layer 20 includes a belt 38 and a pair of edge bands 60.

[0071] The belt 38 includes a plurality of belt plies 42 arranged in the radial direction. Each belt ply 42 is arranged such that both ends are opposite to each other across the equatorial plane. The belt 38 of this tire 2 includes four belt plies 42. The four belt plies 42 include a first belt ply 42A located inside in the radial direction, a second belt ply 42B located outside the first belt ply 42A, a third belt ply 42C located outside the second belt ply 42B, and a fourth belt ply 42D located outside the third belt ply 42C. The number of belt plies 42 provided in the tire 2 may be two or more.

[0072] In this tire 2, the second belt ply 42B has the widest axial width, and the fourth belt ply 42D has the narrowest axial width. The first belt ply 42A and the third belt ply 42C have the same axial width or the axial width of the first belt ply 42A is narrower than the axial width of the third belt ply 42C.

[0073] The end 38e of the belt 38 of this tire 2 is represented by the end of the belt ply 42 having the widest axial width among the plurality of belt plies 42 constituting the belt 38. In this tire 2, as described above, among the four belt plies 42 constituting the belt 38, the second belt ply 42B has the widest axial width. The end 38e of the belt 38 of this tire 2 is represented by the end 42Be of the second belt ply 42B having the widest axial width.

[0074] As shown in FIG. 2, in the tire 2, the respective ends 42e of the first belt ply 42A to the third belt ply 42C are located outside the circumferential main groove 28 in the axial direction. In other words, the respective ends 42e of the first belt ply 42A to the third belt ply 42C are located inside the shoulder land portion 30s in the radial direction. In this way, by providing the first belt ply 42A to the third belt ply 42C, not only the center land portion 30c but also the shoulder land portion 30s can be restrained by the belt 38. The rigidity of each land portion 30 can be increased.

[0075] On the other hand, the end 42e of the fourth belt ply 42D is located inside the circumferential main groove 28 in the axial direction. In other words, the fourth belt ply 42D is located only inside the center land portion 30c in the radial direction. Providing such a fourth belt ply 42D is suitable for increasing the rigidity of the center land portion 30c. For the plurality of belt plies 42 provided in the tire 2, it is sufficient that the end 42e of at least one belt ply 42 is located inside the shoulder land portion 30s in the radial direction.

[0076] In this tire 2, from the viewpoint of ensuring the rigidity of the tread 4 portion, it is preferable that the ratio of the axial width of the belt ply 42 to the width WT of the tread surface 22 is within the following range. The ratio of the axial width of the first belt ply 42A to the width WT of the tread surface 22 is preferably 0.70 or more and preferably 0.90 or less. The ratio of the axial width of the second belt ply 42B to the width WT of the tread surface 22 is preferably 0.85 or more and preferably 0.95 or less. The ratio of the axial width W3 of the third belt ply 42C to the width WT of the tread surface 22 is preferably 0.75 or more and preferably 0.90 or less. The ratio of the axial width W4 of the fourth belt ply 42D to the width WT of the tread surface 22 is preferably 0.25 or more and preferably 0.40 or less. The width of each belt ply 42 is represented by the axial distance from one end 42e to the other end 42e of the belt ply 42.

[0077] FIG. 4 shows the configuration of the reinforcing layer 20. In FIG. 4, the left - right direction is the axial direction of the tire 2, the up - down direction is the circumferential direction of the tire 2, and the direction perpendicular to the paper surface is the radial direction of the tire 2. The front side of the paper surface is the outer side in the radial direction, and the back side is the inner side in the radial direction.

[0078] As shown in FIG. 4, in this tire 2, each belt ply 42 constituting the belt 38 includes a large number of belt cords 44 arranged in parallel. In FIG. 4, for the sake of convenience of explanation, the belt cords 44 are represented by solid lines, but the belt cords 44 are covered with topping rubber 46. The belt cords 44 of this tire 2 are steel cords.

[0079] In this tire 2, the density of the belt cords 44 (the number of cord cross - sections per unit width) in each belt ply 42 is preferably 15 ends / 5 cm or more and 30 ends / 5 cm or less.

[0080] In each belt ply 42, the belt cords 44 are inclined with respect to the circumferential direction. The direction of inclination of the belt cords 44 in the first belt ply 42A with respect to the circumferential direction (hereinafter, the inclination direction of the first belt ply 42A) is the same as the direction of inclination of the belt cords 44 in the second belt ply 42B with respect to the circumferential direction (hereinafter, the inclination direction of the second belt ply 42B). The inclination direction of the second belt ply 42B is opposite to the direction of inclination of the belt cords 44 in the third belt ply 42C with respect to the circumferential direction (hereinafter, the inclination direction of the third belt ply 42C). The inclination direction of the third belt ply 42C is the same as the direction of inclination of the belt cords 44 in the fourth belt ply 42D with respect to the circumferential direction (hereinafter, the inclination direction of the fourth belt ply 42D). Note that the inclination direction of the first belt ply 42A may be opposite to that of the second belt ply 42B, and the inclination direction of the fourth belt ply 42D may be opposite to that of the third belt ply 42C. From the viewpoint of ensuring a stable grounding shape, the inclination direction of the second belt ply 42B is preferably opposite to that of the third belt ply 42C.

[0081] In FIG. 4, the angle θ1 is the inclination angle formed by the belt cord 44 included in the first belt ply 42A with respect to the equatorial plane (hereinafter referred to as the first inclination angle θ1). The angle θ2 is the inclination angle formed by the belt cord 44 included in the second belt ply 42B with respect to the equatorial plane (hereinafter referred to as the second inclination angle θ2). The angle θ3 is the inclination angle formed by the belt cord 44 included in the third belt ply 42C with respect to the equatorial plane (hereinafter referred to as the third inclination angle θ3). The angle θ4 is the inclination angle formed by the belt cord 44 included in the fourth belt ply 42D with respect to the equatorial plane (hereinafter referred to as the fourth inclination angle θ4).

[0082] In this tire 2, the first inclination angle θ1, the second inclination angle θ2, the third inclination angle θ3, and the fourth inclination angle θ4 are preferably 10° or more and preferably 60° or less. From the viewpoint of effectively restraining the movement of the tire 2 and ensuring a stable grounding shape, the first inclination angle θ1 is preferably 40° or more and preferably 60° or less. The second inclination angle θ2 is preferably 10° or more and preferably 20° or less. The third inclination angle θ3 is preferably 10° or more and preferably 20° or less. The fourth inclination angle θ4 is preferably 10° or more and preferably 60° or less. Furthermore, both the third inclination angle θ2 and the fourth inclination angle θ4 are more preferably 12° or more and more preferably 18° or less.

[0083] The reinforcing layer 20 includes a pair of edge bands 60. As shown in FIGS. 1 and 2, the pair of edge bands 60 are arranged axially spaced apart with the equatorial plane interposed therebetween. In this tire 2, the fourth belt ply 42D is positioned spaced apart from the edge bands 60 between the left and right edge bands 60.

[0084] Each edge band 60 is positioned between the tread 4 and the third belt ply 42C. The edge band 60 is positioned only inside the shoulder land portion 30s in the radial direction. By providing the edge band 60 in such a position, the shoulder land portion 30s can be constrained without impairing the constraining force of the shoulder land portion 30s by the belt 38. Therefore, the rigidity of the shoulder land portion 30s can be improved.

[0085] As shown in FIG. 4, a pair of edge bands 60 includes a band cord 62 wound in a spiral shape. In FIG. 4, the band cord 62 is represented by a solid line for convenience of explanation, but the band cord 62 is covered with topping rubber 64.

[0086] In this tire 2, the band cord 62 is a steel cord or a cord made of organic fiber (hereinafter referred to as an organic fiber cord). When an organic fiber cord is used as the band cord 62, examples of such organic fiber include nylon fiber, polyester fiber, rayon fiber, and aramid fiber. The band cord 62 is preferably a steel cord from the viewpoint of rigidity.

[0087] As described above, the edge band 60 includes a band cord 62 wound in a spiral shape. The edge band 60 has a jointless structure. In the edge band 60, the angle formed by the band cord 62 with respect to the circumferential direction (hereinafter referred to as the inclination angle of the band cord) is preferably 5° or less, more preferably 2° or less. By setting the inclination angle of the band cord to 5° or less, the shoulder land portion 30s can be effectively constrained, and the rigidity of the shoulder land portion 30s can be further improved. As a result, the shoulder land portion 30s becomes more difficult to deform. The band cord 62 of the edge band 60 extends substantially in the circumferential direction. When the band cord 62 is inclined with respect to the circumferential direction, the inclination direction of the band cord 62 in one edge band 60 and the inclination direction of the band cord 62 in the other edge band 60 may be the same direction or different directions.

[0088] In the edge band 60, the density of the preferred band cord 62 is 20 ends / 5 cm or more and 35 ends / 5 cm or less. The density of the band cord 62 of the edge band 60 is represented by the number of cross-sections of the band cord 62 included per 5 cm width of the edge band 60 in the cross-section of the edge band 60 along a plane perpendicular to the extending direction of the band cord 62.

[0089] In this tire 2, the end 42Be of the second belt ply 42B and the end 42Ce of the third belt ply 42C are each covered with a rubber layer 56. In FIG. 2, 42Ae is the end of the first belt ply 42A, and 42De is the end of the fourth belt ply 42D.

[0090] In FIG. 2, the double-headed arrow WE is the width of the edge band 60. The width of the edge band 60 is represented by the axial distance from the inner end 60ue to the other end 60se of the edge band 60. In this tire 2, the width WE of the edge band 60 is preferably 30% or more and 60% or less of the width WS of the shoulder land portion 30s. In this case, the rigidity of the shoulder land portion 30s is improved, thereby suppressing uneven wear of the shoulder land portion 30s.

[0091] In this tire 2, the deformation of the shoulder land portion 30s is suppressed by the edge band 60. Therefore, the occurrence of uneven wear of the shoulder land portion 30s in the tire 2 is effectively suppressed. In particular, it is suitable for suppressing the occurrence of uneven wear of the shoulder land portion 30s when mounted on an EV truck or an EV bus.

[0092] In this tire 2, while setting the ratio WC / WS of the width WC of the center land portion 30c and the width WS of the shoulder land portion 30s within the aforementioned preferable range of 2.0 ≦ WC / WS ≦ 2.5, it is preferable that the width WE of the edge band 60 be 30% or more and 60% or less of the width WS of the shoulder land portion 30s. In this case, sufficient rigidity is ensured in each of the center land portion 30c and the shoulder land portion 30s, and the rigidities of both are ensured in a well-balanced manner. Therefore, it is more suitable for suppressing the occurrence of chipping in the center land portion 30c and suppressing the uneven wear of the shoulder land portion 30s.

[0093] In FIG. 2, the double-headed arrow WF is the axial distance from the outer edge of the circumferential main groove 28, specifically, from the outer edge of the circumferential main groove 28 to the inner end 60ue of the edge band 60. In this tire 2, the axial distance WF from the circumferential main groove 28 to the inner end 60ue of the edge band 60 is preferably 10% or more of the axial width WS of the shoulder land portion 30s. In this case, the inner end 60ue of the edge band 60 is arranged at an appropriate interval from the bottom of the circumferential main groove 28. In this tire 2, the occurrence of damage starting from the bottom of the circumferential main groove 28 is suppressed. The distance WF is more preferably 25% or more of the width WS. The distance WF is preferably 50% or less of the width WS, and more preferably 40% or less.

[0094] In the tire 2 according to the embodiment of the present invention, the cross-sectional shape of the circumferential fine groove is not limited to the shape shown in FIG. 3. FIGS. 5 and 6 are cross-sectional views showing modified examples of the circumferential fine groove, respectively. The circumferential fine groove provided in the tire 2 may be composed of only the tread portion 152, like the circumferential fine groove 148 shown in FIG. 5. Also, like the circumferential fine groove 248 shown in FIG. 6, it may be composed of the tread portion 252 and the widened portion 254 without providing a tapered portion. Even when the circumferential fine grooves 148 and 248 having such shapes are provided in the center land portion 30c of the tire 2, the WET performance of the tire 2 can be ensured without impairing the rigidity of the center land portion 30c.

[0095] In the circumferential groove 148 shown in FIG. 5, the barrel portion 152 extends straight. In FIG. 5, the contour of the wall surface 148W of the barrel portion 152 is represented by a straight line. The bottom (the bottom of the circumferential groove 148) 148T of the barrel portion 152 has a rounded contour.

[0096] In the circumferential groove 248 shown in FIG. 6, the barrel portion 152 extends straight. In FIG. 6, the contour of the wall surface 148W of the barrel portion 152 is represented by a straight line. In the circumferential groove 248, the enlarged portion 154 is located radially inside the barrel portion 152. The enlarged portion 154 is continuous with the barrel portion 152. The enlarged portion 154 has a groove width wider than the groove width of the barrel portion 152. The enlarged portion 154 includes the groove bottom 148T of the circumferential groove 148. The cross-sectional shape of the circumferential groove 248 shown in FIG. 6 is the same as the cross-sectional shape of the circumferential groove 48 shown in FIG. 3, except that there is no tapered portion. [Industrial Applicability]

[0097] The technology described above for improving the wear resistance of the tread and suppressing the occurrence of chipping in the center land portion and the occurrence of uneven wear in the shoulder land portion can be applied to various heavy-duty tires. This technology can be particularly preferably applied to tires for EV buses and EV trucks.

[0098] [Appendix] The present invention includes the following aspects.

[0099] [1] A tread that contacts the road surface and a reinforcing layer located inside the tread in the radial direction. By forming two circumferential main grooves in the tread, three land portions arranged in parallel in the axial direction are formed. The land portion located outside the circumferential main groove in the axial direction is the shoulder land portion, and the land portion sandwiched between the two land portions in the axial direction is the center land portion. The center land portion is the land portion including the equator of the tire. At least one circumferential groove narrower in groove width than the circumferential main groove is formed in the center land portion. The reinforcing layer includes a belt including a large number of belt cords arranged in parallel and a pair of edge bands including band cords wound in a spiral shape. The belt includes a plurality of belt plies arranged in the radial direction, and ends of at least one of the belt plies are located inside the shoulder land portion in the radial direction. The edge band is located only inside the shoulder land portion in the radial direction. The rubber hardness of the shoulder land portion is harder than the rubber hardness of the center land portion. Pneumatic heavy-duty tire.

[0100] [2] For the pneumatic heavy-duty tire according to [1] above, the ratio WC / WS of the width WC of the center land portion to the width WS of the shoulder land portion is 2.0 ≤ WC / WS ≤ 2.5.

[0101] [3] For the pneumatic heavy-duty tire according to [1] or [2] above, the circumferential fine grooves are engraved at a position overlapping the equator of the tire.

[0102] [4] For the pneumatic heavy-duty tire according to any one of [1] to [3] above, the proportion of the circumferential main grooves on the surface of the tread is 5% or more and 25% or less.

[0103] [5] For the pneumatic heavy-duty tire according to any one of [1] to [4] above, the inclination of the band cord with respect to the tire circumferential direction is 5° or less.

[0104] [6] For the pneumatic heavy-duty tire according to any one of [1] to [5] above, the pair of edge bands are arranged outside the belt in the radial direction.

[0105] [7] For the pneumatic heavy-duty tire according to any one of [1] to [6] above, the shape of the cross section perpendicular to the tire circumferential direction of the circumferential fine grooves is a shape including a carcass portion and an enlarged portion located radially inside the carcass portion.

[0106] [8] The rubber hardness of the shoulder land portion is 65 or more and 75 or less, and the rubber hardness of the center land portion is 63 or more and 73 or less. The pneumatic tire for heavy loads according to any one of [1] to [7] above.

[0107] [9] The fracture energy of the shoulder land portion is 6500 MPa·% or more and 8500 MPa·% or less, and the fracture energy of the center land portion is 6000 MPa·% or more and 8000 MPa·% or less. The pneumatic tire for heavy loads according to any one of [1] to [8] above.

[0108]

[10] The width of each of the edge bands is 30% or more and 60% or less of the width WS of the shoulder land portion. The pneumatic tire for heavy loads according to any one of [1] to [9] above.

[0109]

[11] The axial distance from the outer edge of the circumferential main groove to the inner end of the edge band 60 is 10% or more and 50% or less of the width of the shoulder land portion. The pneumatic tire for heavy loads according to any one of [1] to

[10] above.

[0110]

[12] The pneumatic tire for heavy loads according to any one of [1] to

[11] above, which is mounted on an EV bus having a battery mounted on the upper part of the vehicle body.

Explanation of symbols

[0111] 2 ··· Tire 4 ··· Tread 20 ··· Reinforcing layer 22 ··· Tread surface 24 ··· Base portion 26, 26s, 26c ··· Cap portion 28 ··· Circumferential main groove 30, 30s, 30c ··· Land portion 38 ··· Belt 42 ··· Belt ply 44 ··· Belt cord 48, 148, 248 ··· Circumferential fine grooves 60 ··· Edge band 60se ··· Outer end of the edge band 60 60ue ··· Inner end of the edge band 60 62 ··· Band code

Claims

1. A tire having a tread that contacts the road surface and a reinforcing layer located inside the tread in the radial direction, By forming two circumferential main grooves in the tread, three land portions arranged in parallel in the axial direction are formed. The land portion located outside the circumferential main groove in the axial direction is a shoulder land portion, and the land portion sandwiched between the two land portions in the axial direction is a center land portion. The center land portion is the land portion including the equator of the tire. At least one circumferential fine groove having a groove width narrower than that of the circumferential main groove is formed in the center land portion. The reinforcing layer includes a belt including a large number of belt cords arranged in parallel and a pair of edge bands including band cords wound in a spiral shape. The belt includes a plurality of belt plies arranged in the radial direction, and the end of at least one of the belt plies is located inside the shoulder land portion in the radial direction. The edge band is located only inside the shoulder land portion in the radial direction. The rubber hardness of the shoulder land portion is harder than the rubber hardness of the center land portion. A pneumatic tire for heavy loads.

2. The ratio WC / WS of the width WC of the center land portion to the width WS of the shoulder land portion is 2.0 ≤ WC / WS ≤ 2.

5. The pneumatic tire for heavy loads according to Claim 1.

3. The circumferential fine groove is formed at a position overlapping the equator of the tire. The pneumatic tire for heavy loads according to Claim 1 or 2.

4. The proportion of the circumferential main groove on the surface of the tread is 5% or more and 25% or less. The pneumatic tire for heavy loads according to Claim 1 or 2.

5. The inclination of the band cord with respect to the tire circumferential direction is 5° or less. The pneumatic tire for heavy loads according to Claim 1 or 2.

6. The pair of edge bands are arranged outside the belt in the radial direction. The pneumatic tire for heavy loads according to Claim 1 or 2.

7. The shape of the cross section perpendicular to the tire circumferential direction of the circumferential fine groove is a shape including a barrel portion and an enlarged portion located radially inside the barrel portion. The pneumatic tire for heavy loads according to Claim 1 or 2.

8. The rubber hardness of the shoulder land portion is 65 or more and 75 or less, and the rubber hardness of the center land portion is 63 or more and 73 or less. The pneumatic tire for heavy loads according to Claim 1 or 2.

9. The fracture energy of the shoulder tread portion is 6500 MPa·% or more and 8500 MPa·% or less, and the fracture energy of the center tread portion is 6000 MPa·% or more and 8000 MPa·% or less. The pneumatic tire for heavy loads according to claim 1 or 2.

10. The width of each of the edge bands is 30% or more and 60% or less of the width WS of the shoulder tread portion. The pneumatic tire for heavy loads according to claim 1 or 2.

11. The axial distance from the outer edge of the circumferential main groove to the inner end of the edge band 60 is 10% or more and 50% or less of the width of the shoulder tread portion. The pneumatic tire for heavy loads according to claim 1 or 2.

12. Mounted on an EV bus with a battery mounted on the upper part of the vehicle body. The pneumatic tire for heavy loads according to claim 1 or 2.

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