CN113752752B

CN113752752B - Low rolling resistance type load-carrying all-steel tire

Info

Publication number: CN113752752B
Application number: CN202110976117.3A
Authority: CN
Inventors: 孙丽娟; 黄春莲; 黄耀华; 黄学海
Original assignee: Anhui Giti Radial Tire Co Ltd
Current assignee: Anhui Giti Radial Tire Co Ltd
Priority date: 2021-08-24
Filing date: 2021-08-24
Publication date: 2023-01-10
Anticipated expiration: 2041-08-24
Also published as: CN113752752A

Abstract

The invention discloses a low rolling resistance type load-carrying all-steel tire, which relates to the field of tires and has a simple structure, wherein the tread can be uniformly deformed in the width direction of the tire by adjusting the trend of a crown tire body and a running surface, so that the grounding performance is improved, and the partial abrasion of the tire is effectively prevented; by limiting the relationship between the maximum section width and the rim engagement width, the shoulder growth of the tire can be inhibited when the tire is inflated, and the crown energy loss is reduced, so that the rolling resistance is further reduced; meanwhile, through limiting the position relation between the tire shoulder cushion rubber and the upper tire side, the bending deformation of the tire side can be controlled in a reasonable range, the rigidity of the lower tire side is increased, the deformation area of the tire side is concentrated in the upper tire side area with less rubber, the bending deformation of the tire bead area with more rubber is reduced, and compared with the tire in the prior art, the tire provided by the invention can effectively reduce the heat generation of the tire, reduce the rolling resistance of the tire and improve the overall performance of the tire.

Description

Low rolling resistance type load-carrying all-steel tire

Technical Field

The invention relates to the field of tires, in particular to a low rolling resistance type load-carrying all-steel tire.

Background

Three main deformations occur when the tire is in contact with the ground: tread, sidewall, and bead bending, tread compression, and tread to sidewall shear. The deformation generates energy dissipation resulting in fuel consumption. The direct contact component of the tire and the ground is a tread, and the energy dissipation of the tread part has the influence on the rolling resistance of the tire, which accounts for about 60-70%. Meanwhile, the stress and deformation of the tread are important factors influencing the grounding performance and the durability of the tire.

The interaction between the various service properties of a tire affects the parameters that affect the rolling resistance properties as well as the wear and durability properties of the tire. In the prior art, the rubber compound formula is adjusted to reduce the depth of the pattern groove and the width of the running surface of the tire to reduce rolling resistance, the cutting resistance of the tire can be reduced while the formula is adjusted, and the effective abrasion volume is reduced to reduce the abrasion service life of the tire due to the reduction of the depth of the pattern groove and the width of the running surface. Some techniques also adopt adjustment of profile (such as tire flattening ratio) and structure (such as shape position of bead apex, height of turn-up of carcass, etc.) to reduce rolling resistance, but also cause reduction of tire durability and uneven wear resistance.

Disclosure of Invention

The invention aims to provide a low rolling resistance type heavy-load all-steel tire, which solves the problems in the background technology by adjusting the relative sizes of structures in the tire matched with each other.

In order to achieve the purpose, the invention provides the following technical scheme:

the low rolling resistance type load-bearing all-steel tire comprises a tire tread, a tire body and a tire shoulder cushion rubber, wherein the distance between the end point of the axial cross section of the tire tread and the maximum outer diameter point of the center of the tire tread is h1 in the radial direction of the tire, the distance between the end point of the axial cross section of the tire tread and the vertical foot of the inner surface of the tire body and the highest point of the axial cross section of the tire body is h2 in the radial direction of the tire, h2/h1 is more than or equal to 0.96 and less than or equal to 1.8, the maximum cross section width in the width direction of the tire is Cw, the rim engagement width is Bw, and Cw/Bw is more than or equal to 1.1 and less than or equal to 1.4.

As a further scheme of the invention: the maximum cross-sectional width Cw is 1.25 times the rim engagement width Bw.

As a further scheme of the invention: the distance between the end point of the tire shoulder wedge on the radial inner side of the tire and the maximum diameter of the axial cross section of the tire body is H1, the distance between the highest point of the tire body on the radial outer side of the tire and the maximum diameter of the axial cross section of the tire body is H2, and H1/H2 is more than or equal to 0.35 and less than or equal to 0.6.

As a further scheme of the invention: the distance between the maximum section width of the carcass and the rim contact position is 1/2, forming a point N, the distance between the point N and the outer end point of the maximum section width of the carcass closest to the point N along the axial direction of the tire is Cw2, and the relationship between the Cw2 and the maximum section width Cw of the carcass is as follows: cw2/Cw is more than or equal to 0.04.

As a further scheme of the invention: the relationship between Cw2 and the maximum section width Cw of the tire body is that Cw2/Cw is more than or equal to 0.04 and less than or equal to 0.06.

As a further scheme of the invention: the tire comprises a plurality of grooves distributed along the circumferential direction of the tire tread, the grooves being composed of groove wide portions extending in a wave shape on the tread and groove narrow portions forming a funnel shape having an outer width and an inner width in the axial cross section of the tire.

As a further scheme of the invention: the widths d1 and d2 of the groove narrow portion and the groove wide portion in the tire axial direction satisfy: d1 is more than or equal to 1mm and less than or equal to 4mm, d2 is more than or equal to 3mm and less than or equal to 9mm, and d2-d1 is more than or equal to 2mm and less than or equal to 5mm.

Compared with the prior art, the invention has the beneficial effects that: the invention has novel structure, can ensure that the running surface deforms uniformly in the width direction of the tire by adjusting the trend of the crown tire body and the running surface (tire tread), and improves the grounding performance to effectively prevent the partial abrasion of the tire; by limiting the relation between the maximum section width and the rim engaging width, the growth of the shoulder part of the tire can be inhibited when the tire is inflated, and the energy loss of the crown part is reduced, so that the rolling resistance is further reduced; meanwhile, through limiting the position relation between the tire shoulder cushion rubber and the upper tire side, the bending deformation of the tire side can be controlled within a reasonable range, the rigidity of the lower tire side is increased, the deformation area of the tire side is concentrated in the upper tire side area with less rubber, the bending deformation of the tire bead area with more rubber is reduced, and compared with the tire in the prior art, the tire provided by the invention can effectively reduce the heat generation of the tire, reduce the rolling resistance of the tire and improve the overall performance of the tire.

Drawings

FIG. 1 is a schematic view of a tire axial cross section of a low rolling resistance truck all steel tire;

FIG. 2 is a schematic view of a first footprint of a low rolling resistance truck all-steel tire;

FIG. 3 is a schematic view of a second footprint of a low rolling resistance truck all steel tire;

FIG. 4 is a third footprint schematic of a low rolling resistance truck all steel tire;

FIG. 5 is a schematic view of a partial groove structure of a low rolling resistance truck all-steel tire;

FIG. 6 is a schematic representation of a groove of a low rolling resistance truck all steel tire in a tire axial cross section;

FIG. 7 is a prior art stress grid schematic in a tire with no groove self-contact;

FIG. 8 is a schematic view of a stress grid with grooves in self-contact state in a low rolling resistance type truck all-steel tire;

in the figure: 1-tread, 2-sidewall, 3-bead, 4-carcass, 5-belt, 6-groove, 7-shoulder wedge, 8-groove wide, 9-groove narrow.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the embodiment of the invention, the low rolling resistance type load-carrying all-steel tire comprises a tire tread 1, wherein the distance between the end point of the axial cross section of the tire tread and the maximum outer diameter point of the center of the tire tread in the radial direction of the tire is h1, the distance between the end point of the axial cross section of the tire tread and the inner surface of a tire body and the highest point of the axial cross section of the tire body is h2, and the relation between h1 and h2 is that h2/h1 is more than or equal to 0.96 and less than or equal to 1.8.

The ratio of h2/h1 is in the range, so that the running surface and the crown carcass are kept approximately consistent in trend, according to the natural balance profile theory of the tire, when the tire is inflated, the shape of the crown carcass does not excessively deviate from the natural balance shape, the outer diameter of the tire is uniformly changed in growth, the tire tread is uniformly deformed in the width direction of the tire in the running process of the tire, the grounding performance is improved, and the tire is prevented from generating eccentric wear. The outer diameter growth here means that the tread changes in the radial direction of the tire from 10% to 100% of the inflation pressure.

As shown in fig. 2, is the tire footprint at which the ratio of h1 to h2 exceeds the lower limit of the above range; as shown in fig. 3, is the tire footprint at which the ratio of h1 to h2 exceeds the upper end of the above range; as shown in FIG. 4, for a tire footprint with a ratio of h1 to h2 within the above-described ranges, the non-uniform tire footprint variation shown in FIGS. 2 and 3 causes the shoulder to grow too little or too much, and the more uniform tire footprint variation shown in FIG. 4 reflects, to some extent: when the ratio of h1 to h2 is in the above range, the shoulder can grow in a normal range, and the grounding performance of the tire can be effectively improved to prevent the tire from partial abrasion.

In the width direction of the tire, the maximum section width Cw is 1.1-1.4 times of the rim bonding width Bw, namely: cw/Bw is more than or equal to 1.1 and less than or equal to 1.4, and the maximum section width Cw can be but is not limited to be 1.1, 1.25 and 1.4 times of the rim landing width Bw. When the tyre is mounted on a corresponding rim and inflated, the bead part at the joint of the rim can expand and deform until the tyre stops meeting a rigid rim flange, and the deformation also extends to the tyre side and the tyre shoulder. By limiting the range, on one hand, the growth of the tire shoulder can be inhibited, so that the shear deformation of the belt end part of the crown part is reduced, and the rolling resistance is reduced; on the other hand, the rubber amount of the tread can be reduced, the heat generation of the rubber is reduced, and the hysteresis loss is reduced. It should be noted that too small a ratio is detrimental to the ground contact performance, and too large a ratio may cause the sidewalls to be too soft and reduce the response of the tire during running.

In order to verify the theory that the performance of the tire can be improved after the ratio range of h1 to h2 and the ratio range of Cw to Bw are limited, the following experimental verification is made: (the experimental tire size is 385/65R22.5)

	Comparative example 1	Example 1	Example 2	Example 3	Comparative example 2
						h2/h1	0.8	0.96	1.38	1.8	2.0
Cw/Bw	1.0	1.1	1.25	1.4	1.5
						Rolling resistance index	100	101	102	103	103.5
Durability index	100	101	102	103	104
						Index of ground performance	100	102	102	102	100

TABLE 1

The analysis of the experimental data in table 1 can result in:

1. compared with the experimental results of the comparative examples 1-2 and the examples 1-3, the specificity of the range limitation of h2/h1 and Cw/Bw can be proved, and within the range limitation, the rolling resistance index and the durability index of the tire can be effectively improved, and meanwhile, the grounding performance of the tire can be correspondingly improved to a certain degree. (the larger the index the better the performance)

2. Comparing the experimental results of comparative examples 1-2 and examples 1-3, it can be concluded that: the influence effect on the rolling resistance performance is in a decreasing trend along with the increase of the ratio of h2/h1 to Cw/Bw. Beyond the above-defined range, the tire has a marked drop in the ground contact performance index, thus inversely demonstrating the particularity of the above-defined range.

In summary, the examples have stable grounding performance (the larger the grounding performance index is, the better) compared with the comparative examples, the rolling resistance is reduced, the durability is improved, and when the parameters defined by the tire are out of the range, the tire is subjected to partial abrasion.

A low rolling resistance type heavy-duty all-steel tire comprises a tire shoulder wedge 7 and a tire body 4 which are positioned on a tire side portion, wherein the distance between the end point of the tire shoulder wedge 7 on the inner side of the tire in the radial direction and the maximum diameter of the axial cross section of the tire body is H1, the distance between the maximum point of the tire body on the outer side of the tire in the radial direction and the maximum diameter of the axial cross section of the tire body is H2, the relation between H1 and H2 is 0.35-H1/H2-0.6, and through limiting the range of the ratio of H1 to H2, the bending deformation of an upper tire side can be increased in the running process of the tire, the shearing deformation between belt layers, between a belt layer and a rubber material and the expansion amplitude of the belt layer in the radial direction of the tire are reduced, so that the strain energy loss of a crown portion and the crown portion rubber material is reduced. This is because the heat generation and crown compound strain energy loss due to belt shear deformation and radial expansion is large, while the heat generation and strain energy loss of the sidewall compound due to bending deformation of the sidewall are small, and the amount of crown rubber is more than the amount of sidewall rubber.

The ratio of H1 to H2 defines the positional relationship of the shoulder wedge to the upper sidewall. When the lower end point of the shoulder wedge moves upwards, namely H1 is increased, the curvature radius of the tire body corresponding to the position is reduced, so that the rigidity of the tire side is weakened, and the bending deformation is increased; when the lower end point of the shoulder wedge moves downwards, namely H1 is reduced, the curvature radius of the tire body corresponding to the lower end point is increased, the rigidity of the tire side is enhanced, and the bending deformation is reduced. The ratio of the undersize of H1 and H2 is too large, the energy consumption of the brought bending deformation cannot offset the energy consumption of the shearing deformation, the rolling resistance is not facilitated, and the ratio of the undersize can increase the rubber amount of the upper tire side to a certain extent, and the rolling resistance is also not facilitated. The ratio of H1 to H2 is defined, so that the bending deformation of the tire side can be in a more reasonable range, and the rolling resistance is further reduced.

The distance between the maximum cross-sectional width of the tire and the rim closing position is LH, a virtual intersection point N is transversely arranged at the position of 1/2LH, the distance between the virtual intersection point N and the outer end point of the maximum cross-sectional width of the tire body along the axial direction of the tire is Cw2, and the relationship between the Cw2 and the maximum cross-sectional width Cw of the tire body is as follows: cw2/Cw is more than or equal to 0.04. When Cw2 is increased, the tire body profile moves towards the inner side of the tire axial direction, the corresponding curvature radius is increased, the rigidity of the lower tire side is increased, the flexing area of the tire side part moves towards the upper tire side with small curvature radius after the tire is loaded, and because the upper tire side is thin (less rubber material) and the lower tire side is thick (more rubber material), the strain energy loss of the rubber material of the upper tire side is smaller than that of the lower tire side. Therefore, by limiting the range of the ratio of Cw to Cw2, the sidewall deformation region can be concentrated in the upper sidewall region with a small rubber amount, and the bending deformation of the bead region with a large rubber amount can be reduced, thereby reducing the heat generation of the tire as a whole and the rolling resistance of the tire. If the ratio of Cw2 to Cw is too small, the sidewall flexing region may be moved downward, which is disadvantageous in terms of reduction of rolling resistance.

In order to verify the principle of the technical effect, the following experimental verification is made: (the experimental tire size is 385/65R22.5)

	Conventional example	Example 1	Example 2	Example 3	Example 4	Example 5	Comparative example 1
								H1/H2	0.3	0.35	0.41	0.47	0.52	0.6	0.65
Cw2/Cw	0.03	0.04	0.05	0.06	0.07	0.08	0.09
								Rolling resistance index	100	101	102	102.5	102	101	100

TABLE 2

As can be seen from the results of the experimental data in table 2: from example 1 to example 5, the tire rolling resistance index was gradually higher than that of the conventional example and comparative example 1, and it could be confirmed that the present invention could effectively reduce the tire rolling resistance to some extent.

As seen from examples 1-3: as the ratio of H1/H2, cw2/Cw increases, the rolling resistance index of the tire gradually increases because the upward shift of the flex zone relieves the belt end shear somewhat and the sidewall deformation is concentrated in the upper sidewall region where there is less compound. However, as seen from examples 4 and 5 and comparative example 1, as H1/H2, cw2/Cw increase, the rolling resistance index tends to decrease again, because an increase in Cw2/Cw results in a certain increase in the amount of bead filler (increase in the amount of filler energy consumption), an excessive increase in H1/H2 results in a large amount of energy consumption for bending deformation, and when the increased strain energy loss exceeds the reduced belt shear strain, expansion amplitude strain energy loss, the rolling resistance increases.

The invention focuses on the combination implementation of the upper tire side and the lower tire side to bring about more obvious rolling resistance change, the traditional tire profile design lacks of the integral combination consideration of the upper tire side and the lower tire side, and the change of a single factor has little influence on the rolling resistance.

The tire bead bending deformation limiting device is novel in structure and stable in operation, when the tire bead bending deformation limiting device is used, bending deformation of the tire side can be controlled within a reasonable range through limiting the position relation between the tire shoulder cushion rubber and the upper tire side, meanwhile, the tire contour size is limited, the rigidity of the lower tire side can be increased, meanwhile, the deformation area of the tire side is concentrated in the upper tire side area with less rubber, the bending deformation of the tire bead area with more rubber is reduced, compared with the change of the contour size of a single factor of the upper tire side and the lower tire side in the prior art, the tire bead bending deformation limiting device changes two factors in a combined mode, and the heat generation of the tire and the rolling resistance of the tire can be effectively reduced.

As shown in FIG. 1, the low rolling resistance type heavy-duty all-steel tire further comprises a plurality of circumferential grooves distributed along the tread of the tire, wherein the grooves divide the tread into strip-shaped blocks extending along the circumferential direction of the tire; as shown in FIG. 5, the groove is composed of a groove wide portion extending in a wave shape on the tread and a groove narrow portion located at one side of the groove and asymmetrically distributed with respect to the groove in the direction of the tire wide portion, and the groove is set in a wave shape along the tire circumferential direction and forms an asymmetric funnel shape on the tire axial cross section, so that the loss of braking and wet skid performance due to a shallow groove can be compensated, rolling resistance is ensured, and the grip force of the tire is increased to a certain extent.

The groove narrow portions are circularly distributed at the edges of the groove wide portions instead of the middle of the groove from left to right in turn along the circumferential direction of the tire, so that the groove forms an asymmetric funnel shape on the axial section of the tire.

The widths d1 and d2 of the groove narrow portion and the groove wide portion in the tire axial direction satisfy: d1 is more than or equal to 1mm and less than or equal to 4mm, d2 is more than or equal to 3mm and less than or equal to 9mm, and d2-d1 is more than or equal to 2mm and less than or equal to 5mm. When d1 is less than or equal to 4mm and d2 is less than or equal to 9mm, the two pattern blocks can be in self-contact, the deformation of the pattern blocks in the running process of the tire is reduced, the rigidity of the pattern blocks is improved, and therefore the rolling resistance can be effectively reduced, but when d1 is too small, the self-contact fit formed between the two pattern blocks is tighter, the significance of the pattern grooves is lost, and the braking and ground-gripping performance of the tire is not facilitated. When d1 > 4mm, the two blocks cannot form self-contact.

The reason why d2-d1 is defined is that if the difference is too small, the braking and wet skid performance is reduced, and if the difference is too large, the block edge tends to generate stress concentration from top to bottom, resulting in that the groove edge tends to tear. The reason is that local stress increases in a region where the shape of the object changes rapidly, fatigue cracks occur in the object due to stress concentration, and the rubber tire tears.

In order to verify the reasonability and the authenticity of the technical effect which can be achieved after the widths of d1 and d2 and the difference range of d1-d2 are limited, the following experimental verification is made: (the experimental tire size is 385/65R22.5)

TABLE 3

The comparative examples 1 and 2 in table 3 define groove widths such that the blocks in comparative examples 1 and 2 are free from self-contact, whereas the grooves of examples 1-4 are capable of forming self-contact. Analysis of the experimental results in the above table can yield:

1. from comparative example 1, comparative example 2 and example 1, it can be seen that: the rise in the rolling resistance index of the tire from comparative example 2 to example 1 was very significant, whereas the change in the rolling resistance index was smaller in comparative example 1 and comparative example 2.

2. From comparative example 1, comparative example 2 and examples 1 to 4, it can be concluded that: the tire rolling resistance indexes in examples 1 to 4 were all significantly increased compared to the tire rolling resistance in the comparative example, and the rolling resistance change between examples was small.

3. According to examples 1 to 4 and comparative example 3, when d1 is less than 1mm, the deep steel piece of the thickness on the mold is liable to be broken and is disadvantageous in tire grip.

4. As can be seen from the description accompanying FIGS. 7 and 8: the pattern block grid without self-contact is changed greatly, the pattern block grid with self-contact is changed slightly, the deformation of the pattern block with self-contact is small, the pattern block with self-contact is proved on the side surface, the rigidity of the pattern block can be effectively improved, and the rolling resistance of the tire is reduced.

The invention has novel structure and stable running, and when in use, through improving the axial cross section shape and the corresponding width dimension of the tire of the middle groove, the tread pattern blocks formed by separating the tread of the tire by the tread pattern grooves can be in self-contact in the driving process, the deformation of the tread pattern blocks can be effectively reduced, the rigidity of the tread pattern blocks is improved, the rolling resistance of the tire is reduced, and the tire grip force is guaranteed to a certain extent.

When the improved sizes are simultaneously acted, the deformation of the driving surface in the width direction of the tire can be uniformly realized, the bending of the sidewall is controlled within a resultant force range, the deformation of the tread pattern block is reduced, and under the simultaneous limiting action of the sizes of multiple parts of the tire, the heat generation of the tire and the rolling resistance of the tire can be better reduced.

To verify the conclusion derived from the above theory, the present invention makes the following experimental verification again: (the experimental tire size is 385/65R22.5)

TABLE 4

From the experimental data in table 4 it can be derived: by limiting the size of each part on the tire, compared with the prior art, the tire provided by the invention can effectively reduce the rolling resistance of the tire and improve the durability of the tire.

In conclusion, the invention has novel structure and stable operation, when in use, the tread of the invention can ensure that the running surface deforms uniformly in the width direction of the tire by adjusting the trend of the crown tire body and the running surface (tread), thereby improving the grounding performance and effectively preventing the partial abrasion of the tire; by limiting the relationship between the maximum section width and the rim engagement width, the shoulder growth of the tire can be inhibited when the tire is inflated, and the crown energy loss is reduced, so that the rolling resistance is further reduced; meanwhile, through limiting the position relation between the tire shoulder cushion rubber and the upper tire side, the bending deformation of the tire side can be controlled in a reasonable range, the rigidity of the lower tire side is increased, the deformation area of the tire side is concentrated in the upper tire side area with less rubber, the bending deformation of the tire bead area with more rubber is reduced, and compared with the tire in the prior art, the tire provided by the invention can effectively reduce the heat generation of the tire, reduce the rolling resistance of the tire and improve the overall performance of the tire; in addition, the invention also adjusts the section shape of the tread groove of the tire tread, can effectively reduce the deformation of the pattern block and improve the rigidity of the pattern block, thereby reducing the rolling resistance of the tire and ensuring the ground gripping capability of the tire to a certain extent.

It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.

Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.

Claims

1. The low rolling resistance type load-bearing all-steel tire comprises a tire tread, a tire body and a tire shoulder cushion rubber, and is characterized in that the distance between the end point of the axial cross section of the tire tread and the maximum outer diameter point of the center of the tire tread is h1 in the radial direction of the tire, the distance between the end point of the axial cross section of the tire tread and the vertical foot of the inner surface of the tire body and the highest point of the axial cross section of the tire body is h2 in the radial direction of the tire, h2/h1 is more than or equal to 0.96 and less than or equal to 1.8, the maximum cross section width of the tire body is Cw, the rim engagement width is Bw, and Cw/Bw is more than or equal to 1.1 and less than or equal to 1.4.

2. The all-steel heavy-duty tire with low rolling resistance as claimed in claim 1, wherein the maximum cross-sectional width Cw is 1.25 times the rim landing width Bw.

3. The low rolling resistance type heavy-duty all steel tire according to claim 1, wherein the distance between the end point of the shoulder wedge at the inner side in the tire radial direction and the maximum diameter of the axial cross section of the tire body is H1, the distance between the highest point of the tire body at the outer side in the tire radial direction and the maximum diameter of the axial cross section of the tire body is H2, and H1/H2 is more than or equal to 0.35 and less than or equal to 0.6.

4. A low rolling resistance type heavy-duty all steel tire according to claim 3, wherein said carcass forms a point N at a distance of 1/2 from its maximum cross-sectional width to the rim engagement position, the distance between the point N and the outer end point of the maximum cross-sectional width of the carcass nearest thereto in the tire axial direction is Cw2, and the relationship between Cw2 and the maximum cross-sectional width of the carcass Cw is: cw2/Cw is more than or equal to 0.04.

5. The all-steel tire of low rolling resistance type load according to claim 4, wherein the relationship between Cw2 and the maximum cross-sectional width Cw of the carcass is 0.04. Ltoreq. Cw 2/Cw. Ltoreq.0.06.

6. A low rolling resistance type heavy load all-steel tire according to claim 1, wherein said tire comprises a plurality of grooves distributed along the circumferential direction of the tire tread, said grooves are composed of groove wide portions extending in a wave shape on the tread and groove narrow portions forming a funnel shape having an outer width and an inner width in the axial cross section of the tire.

7. A low rolling resistance type heavy load all-steel tire according to claim 6, wherein widths d1 and d2 of said groove narrow portion and groove wide portion in the tire axial direction satisfy: d1 is more than or equal to 1mm and less than or equal to 4mm, d2 is more than or equal to 3mm and less than or equal to 9mm, and d2-d1 is more than or equal to 2mm and less than or equal to 5mm.