JP5022003B2 - Heavy duty tire - Google Patents

Description

  The present invention relates to a heavy load tire, and more particularly to a heavy load tire capable of reducing rolling resistance without impairing durability by improving sidewall rubber.

  In recent years, in connection with global environmental problems and the like, it has been desired to reduce the fuel consumption of vehicles, and various attempts have been made to reduce the rolling resistance of tires. In particular, for heavy duty tires used in heavy vehicles such as trucks and buses that consume large amounts of fuel, it is an urgent task to reduce rolling resistance. Conventionally, in order to reduce the rolling resistance of a heavy-duty tire, for example, a rubber material having a small energy loss is used for tread rubber and / or a strain at the time of load deformation of the tire is reduced.

  However, in the former method, the steering stability and the wear resistance may be deteriorated. Further, the latter method tends to cause a decrease in ride comfort. Therefore, all the conventional methods have room for improvement.

  Patent Document 1 below teaches that the sidewall rubber disposed in the sidewall portion is divided into an inner rubber portion inside the tire axial direction and an outer rubber portion outside the tire. However, this teaches nothing about reducing rolling resistance.

JP 2002-127718 A

  The present invention has been devised in view of the above situation, and the sidewall rubber is composed of an inner rubber portion on the carcass side and an outer rubber portion that is arranged outside and forms the outer surface of the tire. In addition, the main object is to provide a heavy duty tire capable of reducing rolling resistance without impairing the durability of the sidewall portion, based on defining the loss tangent tan δ and the complex elastic modulus in association with each other. .

The invention according to claim 1 of the present invention is a carcass having a carcass cord extending from a tread portion through a sidewall portion to a bead core of the bead portion, and a belt disposed outside the carcass in the tire radial direction and inside the tread portion. In the heavy-duty tire having a layer, in the sidewall portion, the sidewall rubber that extends outside in the tire axial direction of the carcass in the tire radial direction is arranged on the inner rubber portion on the carcass side and on the outside thereof. And the outer rubber portion forming the outer surface of the tire, and the inner rubber portion has a smaller loss tangent tan δ than the outer rubber portion, and the difference is 0.010 to 0.035, and inner rubber portion has a smaller modulus of elasticity than the outer rubber portion and its difference is 0.5 to 1.4 (MPa), moreover, before The thickness of the inner rubber portion is the rubber thickness from the carcass cord to the tire outer surface at an intermediate position (M) of the tire radial distance (X) from the outer end of the belt layer to the outer surface of the bead core in the tire radial direction. It is 0.5 to 0.8 times the height .

  In the present specification, the loss tangent tan δ and the complex elastic modulus are both a strip sample having a width of 4 mm × 30 mm length × 1.5 mm and a viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd. And a value measured under conditions of a temperature of 70 ° C., a frequency of 10 Hz, an initial strain of 10%, and a dynamic strain of ± 2%.

In the invention according to claim 2, the outer end of the inner rubber portion in the tire radial direction is at least 0.25 times the tire radial distance (X) from the intermediate position (M) at the outer side in the tire radial direction. and position (PU) separating the a heavy duty tire according to claim 1 wherein located between the outer end of the belt layer.

According to a third aspect of the present invention, the bead portion is provided with a reinforcing cord layer extending in a substantially U-shaped cross section so as to wrap the bead core, and the inner end of the inner rubber portion is at least at the intermediate position ( M) is located between a position (PD) separating a distance of 0.25 times the tire radial distance (X) inward in the tire radial direction and an outer end of the reinforcing cord layer on the outermost side in the tire radial direction. A heavy-duty tire according to claim 1 or 2 .

According to a fourth aspect of the present invention, a bead apex rubber extending in a tapered shape from the bead core to the tire radial direction is disposed on the bead portion, and an outer end portion of the bead apex rubber is formed on the sidewall rubber. The heavy duty tire according to any one of claims 1 to 3 , wherein the tire extends between the inner rubber portion and the outer rubber portion.

  In the heavy duty tire of the present invention, the sidewall rubber disposed in the sidewall portion includes an inner rubber portion on the carcass side and an outer rubber portion disposed on the outer side and forming the outer surface of the tire. Moreover, the inner rubber portion has a smaller loss tangent tan δ than the outer rubber portion, and the difference is defined within a certain range. Furthermore, the inner rubber portion has a smaller complex elastic modulus than the outer rubber portion, and the difference is also defined within a certain range. Such heavy-duty tires have a low loss tangent and a low complex elastic modulus rubber disposed on the inner part of the side wall part that is bent at the time of running, thereby reducing the energy loss in the side wall part and thus rolling resistance. Is reduced. Moreover, since the rubber | gum whose loss tangent and complex elastic modulus are larger than an inner rubber part is used for an outer rubber part, the fall of durability of a side wall part can be prevented.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a right half sectional view of a normal state of a heavy load tire 1 according to the present embodiment, and FIG. Here, the “normal state” means that the tire is assembled to the normal rim J and is in an unloaded state in which the normal internal pressure is filled, and unless otherwise specified, the dimensions and the like of each part of the tire are in the normal state. The value of

  In addition, the “regular rim” is a rim determined for each tire in a standard system including a standard on which a tire is based, for example, a standard rim for JATMA, “Design Rim” for TRA, Or, for ETRTO, “Measuring Rim”. Furthermore, the “regular internal pressure” is the air pressure specified by the standard for each tire. The maximum air pressure described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” is the maximum air pressure for JATMA and TRA for TRA. In case of ETRTO, “INFLATION PRESSURE”.

  The heavy load tire 1 is disposed in a toroidal carcass 6 extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and on the outer side in the tire radial direction of the carcass 6 and inside the tread portion 2. And a belt layer 7.

  The carcass 6 is composed of one or more carcass plies 6A, in this example, one carcass ply 6A in which carcass cords made of steel cords are arranged at an angle of, for example, 80 to 90 degrees with respect to the tire equator C. The carcass ply 6A is formed by covering both side surfaces of the carcass cord 6C with a topping rubber 6T as shown in an enlarged manner in FIG. Further, the carcass ply 6A has a main body portion 6a straddling the bead cores 5 and 5 in a toroidal shape, and a folded portion 6b that is continuous on both sides and folded around the bead core 5 from the inner side to the outer side in the tire axial direction. . Further, a bead apex rubber 8 extending in a taper shape outward from the bead core 5 in the tire radial direction is disposed between the main body portion 6a and the folded portion 6b.

  The belt layer 7 is formed of at least three belt plies using a steel cord, in this example, four belt plies. That is, the belt layer 7 includes a first belt ply 7A in which the belt cord is arranged at an angle of, for example, 60 ± 15 ° with respect to the tire equator C and is arranged on the innermost side in the tire radial direction, and the belt cord is connected to the tire equator. 2nd to 4th belt plies 7B, 7C and 7D arranged at a small angle of 10 to 35 ° with respect to C, for example. The second to fourth belt plies 7B, 7C and 7D are overlapped so that the belt cords cross each other.

  As is apparent from FIG. 1, in order to fill the difference in curvature between the belt layer 7 and the main body portion 6a of the carcass ply 6A, a substantially triangular cross section is formed between both ends of the belt layer 7 and the carcass 6. Cushion rubber Cg is arranged.

  Further, the bead portion 4 is provided with a reinforcing cord layer 9 having a steel cord extending in a substantially U-shaped cross section so as to wrap the bead core 5. That is, the reinforcing cord layer 9 includes an inner piece 9i extending along the tire axial direction inner side of the main body portion 6a of the carcass ply 6A, an outer piece 9o extending along the tire axial direction outer side of the folded portion 6b, and these And an intermediate piece 9c extending inward in the tire radial direction of the bead core.

  For example, the reinforcing cord layer 9 is configured such that the outer end 9it of the inner piece 9i is positioned more outward in the tire radial direction than the outer end of the folded portion 6b and the outer end 9ot of the outer piece 9o in the tire radial direction. Is positioned inward in the tire radial direction with respect to the outer end of the turned-up portion 6b, thereby reducing strain acting on the outer end of the turned-up portion 6b during load traveling, and thus improving the durability of the bead portion 4.

  Sidewall rubber 3g extending outside the carcass 6 inward and outward in the tire radial direction is disposed on the sidewall 3. The sidewall rubber 3g is composed of two layers of an inner rubber portion 10 disposed on the carcass 6 side and an outer rubber portion 11 disposed on the outer side and forming the tire outer surface. In the heavy load tire 1 of the present invention, the inner rubber portion 10 has a loss tangent tan δ smaller than that of the outer rubber portion 11 and the difference is set to 0.010 to 0.035. The part 10 has a smaller complex elastic modulus than the outer rubber part 11, and the difference is set to 0.5 to 1.4 MPa.

  When the tire is loaded, a large bending strain is repeatedly generated in the sidewall portion 3. For this reason, rolling resistance can be reduced by using the rubber | gum mixing | blending with small loss tangent tan-delta which is hard to generate | occur | produce for the side wall rubber 3g. Further, in order to follow the large bending strain and prevent peeling from the carcass cord, the side wall rubber 3g needs to be soft rubber that can be flexibly deformed. On the other hand, the sidewall rubber 3g is required to have an appropriate rigidity and sufficient cut resistance to protect the carcass 6 even when it comes into contact with foreign matter.

  In view of such circumstances, in the present invention, a rubber compound having a small loss tangent tan δ and a complex elastic modulus is used for the inner rubber portion 10 disposed on the side of the carcass 6 of the sidewall rubber 3g, and heat generation and energy in this portion are used. Loss can be reduced. Thereby, the rolling resistance accompanying the bending distortion of the side wall part 3 is reduced. Further, since the inner rubber portion 10 has a complex elastic modulus that can be flexibly deformed following the carcass cord 6C, peeling from the cord is suppressed, and as a result, durability of the sidewall portion is improved. Further, the outer rubber portion 11 of the side wall rubber 3g uses a rubber compound having a large loss tangent tan δ and complex elastic modulus, thereby maintaining durability, particularly cut resistance. Therefore, the heavy load tire 1 of the present invention can reduce rolling resistance without impairing the durability of the sidewall portion 3.

  Here, the value of the loss tangent tan δ of the inner rubber portion 10 is not particularly limited, but if it is too large, the heat generation and the energy loss cannot be sufficiently reduced, and the effect of the present invention tends to be relatively lowered. From such a viewpoint, the loss tangent tan δ of the inner rubber portion 10 is preferably 0.075 or less, more preferably 0.060 or less, and still more preferably 0.050 or less. In addition, when the loss tangent tan δ of the inner rubber portion 10 is too small, there is a tendency that the inner rubber portion 10 is vulnerable to an external impact. From such a viewpoint, the loss tangent tan δ of the inner rubber portion 10 is preferably 0.030 or more, more preferably 0.040 or more.

  In addition, when the difference between the loss tangent tan δ of the outer rubber portion 11 and the loss tangent tan δ of the inner rubber portion 10 is less than 0.010, the loss tangent tan δ of both approaches, so the cut resistance of the outer rubber portion 11 is improved. There exists a possibility that it may fall or the improvement effect of the rolling resistance of the inner side rubber part 10 may fall. On the other hand, if the difference between the loss tangent tan δ exceeds 0.035, the strain tends to concentrate on the interface between the rubber parts 10 and 11, and as a result, the durability of the side wall rubber 3g may be lowered, for example, causing peeling. is there. From such a viewpoint, the difference in loss tangent tan δ between the outer rubber portion 11 and the inner rubber portion 10 is preferably 0.015 or more, more preferably 0.020 or more, and preferably 0.030 or less. Preferably it is 0.025 or less.

  Further, the value of the complex elastic modulus of the inner rubber portion 10 is not particularly limited, but if it is too large, the inner rubber portion 10 cannot be flexibly deformed flexibly following the sidewall portion 3 at the time of running on load, and thus peels off from the cord, etc. Such damage is likely to occur. Moreover, there is a possibility that the shock absorbing performance is lowered and the ride comfort is deteriorated. From such a viewpoint, the complex elastic modulus of the inner rubber portion 10 is preferably 3.5 MPa or less, more preferably 3.0 MPa or less. Further, if the complex elastic modulus of the inner rubber part 10 is too small, the rigidity of the sidewall part 3 may be remarkably lowered and the steering stability may be deteriorated. Therefore, it is preferably 2.0 MPa or more, more preferably 2.5 MPa. The above is desirable.

  Further, when the difference between the complex elastic modulus of the outer rubber part 11 and the complex elastic modulus of the inner rubber part 10 is less than 0.5 MPa, the complex elastic modulus of both approaches, so the cut resistance of the outer rubber part 11 is improved. There is a possibility that it will decrease, or the flexible deformation followability of the inner rubber part 10 will decrease, and as a result, peeling from the cord or the like will occur. On the other hand, when the difference in the complex elastic modulus exceeds 1.4 MPa, strain tends to concentrate on the interface between the rubber parts 10 and 11, and the durability of the sidewall rubber 3g may be reduced. From such a viewpoint, the difference in complex elastic modulus between the outer rubber portion 11 and the inner rubber portion 10 is preferably 0.7 MPa or more, more preferably 1.0 MPa or more, and preferably 1.3 MPa or less. Preferably it is 1.2 MPa or less.

The thickness of the inner rubber portion 10 is not particularly limited. However, if the thickness is too small, the effect of reducing the rolling resistance described above may not be obtained sufficiently. There is a possibility that the cut resistance of the sidewall portion 3 is lowered due to a relative decrease. From such a viewpoint, the thickness ti (shown in FIG. 2) of the inner rubber portion 10 is an intermediate position of the tire radial direction distance X from the outer end 7e of the belt layer 7 to the outer surface of the bead core 5 in the tire radial direction. In M, it is desirable that the rubber thickness T from the carcass cord 6C to the tire outer surface is 0.5 to 0.8 times the rubber thickness T (this thickness T includes one topping rubber 6T). The inner rubber portion 10 of the present embodiment extends inward and outward in the tire radial direction while substantially maintaining the thickness ti at the intermediate position M.

  The outer end 7e of the belt layer 7 is positioned at the outermost side in the tire axial direction of the belt layer 7 and at the radially inner side.

  The outer end 10o of the inner rubber portion 10 in the tire radial direction is a position PU that separates a distance (0.25X) of the tire radial direction distance X from the intermediate position M to the outer side in the tire radial direction, and It is desirable to locate between the belt layer 7 and the outer end 7e. Here, “between” includes both ends of the section. That is, the outer end 10 o of the inner rubber portion 10 may be at each position of the position PU or the outer end 7 e of the belt layer 7.

  If the outer end 10o of the inner rubber portion 10 is located inward in the tire radial direction from the position PU, sufficient rolling resistance is provided in the buttress region from the position PU to the outer end 7e of the belt layer 7. It cannot be reduced. Further, even if the outer end 10o of the inner rubber portion 10 is provided at a position beyond the outer end 7e of the belt layer 7 in the tire radial direction, the effect of reducing the rolling resistance is hardly obtained and the steering stability is lowered. Rather, it is not preferable. From such a viewpoint, the outer end 10o of the inner rubber portion 10 of the present embodiment is provided at substantially the same position as the outer end 7e of the belt layer 7 in the tire axial direction, and on the buttress portion side of the sidewall portion 3. The rolling resistance is reduced in a wider range.

  Further, an inner end 10i in the tire radial direction of the inner rubber portion 10 has a position PD that separates a distance (0.25X) of the tire radial direction distance X from the intermediate position M to the inner side in the tire radial direction, and It is desirable that the reinforcing cord layer 9 is located between the outermost end in the tire radial direction (in this example, the outer end 9it of the inner piece 9i). Here, “between” includes both ends of the section. That is, the inner end 10 i of the inner rubber portion 10 may be at each position of the position PD or the outer end 9 it of the reinforcing cord layer 9.

  If the inner end 10i of the inner rubber portion 10 is positioned outward in the tire radial direction from the position PD, it is sufficient in the bead inner region from the position PD to the outer end 9it of the reinforcing cord layer 9. The rolling resistance cannot be reduced. Even if the inner end 10i of the inner rubber portion 10 is provided at a position beyond the outer end 9it of the reinforcing cord layer 9 inward in the tire radial direction, the effect of reducing the rolling resistance reaches a peak. From such a viewpoint, the outer end 10o of the inner rubber portion 10 of the present embodiment is provided at substantially the same position as the outer end 9it of the inner piece 9i of the reinforcing cord layer 9, and the bead portion side of the sidewall portion 3 , Rolling resistance is reduced in a wider range.

  Further, the outer end 10o and the inner end 10i of the inner rubber portion 10 both have a taper shape in which the thickness is smoothly reduced toward the tip. As a result, the rigidity step with the surrounding rubber part is relaxed, stress concentration and the like are avoided at each of the end parts 10o and 10i, and the starting point of damage is prevented.

  As a particularly preferred embodiment, the outer end portion 8t of the bead apex rubber 8 is desirably extended between the inner rubber portion 10 and the outer rubber portion 11 of the side wall rubber 3g. The inner rubber portion 10 of the present embodiment has a complex elastic modulus smaller than that of the bead apex rubber 8. Therefore, by interposing the inner rubber portion 10 between the main body portion 6a of the carcass ply 6A and the bead apex rubber 8, the inner rubber portion 10 follows the large bending strain of the carcass cord 6C at the bead portion 4, As a result, the distortion in this portion can be effectively reduced. Therefore, the durability of the bead portion 4 can be further improved.

  In the present embodiment, the outer rubber portion 11 has a larger tire radial direction length than the inner rubber portion 10. Thereby, the outer rubber part 11 can be coated without exposing the inner rubber part 10 to the outside. Therefore, the outer surface of the sidewall portion 3 is formed by the outer rubber portion 11 having a high cutting property throughout the entire area.

  The outer end 11o of the outer rubber portion 11 in the tire radial direction extends in a tapered shape in the present embodiment, covers the side end surface 2ge in the tire axial direction of the tread rubber 2g, and reaches the tread grounding end E before reaching it. Terminate with Such an outer rubber part 11 can enhance cut resistance in a wide range up to the tread part 2. Further, the outer rubber portion 11 can be prevented from coming into contact with the road surface, and thus can be prevented from being rubbed and worn.

  Further, the tread rubber 2g has an end portion on the outer side in the tire axial direction and on the inner side in the tire radial direction, and ends between the inner rubber portion 10 and the outer rubber portion 11 in a tapered shape. Thereby, the tread rubber 2g is connected to the cushion rubber Cg via the inner rubber portion 10. In such embodiment, it is preferable at the point which is excellent in durability.

  Further, the outer rubber portion 11 extends inward in the tire radial direction through the outer surface in the tire axial direction of the bead apex rubber 8. The inner end 11 i of the outer rubber portion 11 in the tire radial direction extends in a tapered shape and terminates at substantially the same height as the outer surface of the bead core 5. Therefore, the outer rubber portion 11 can improve cut resistance in a wide range even on the bead portion 4 side of the sidewall portion 3.

  Although various embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and can be implemented in various modes.

Heavy duty radial tires of size 11R22.5 14PR having the basic structure of FIG. 1 were prototyped based on the specifications in Table 1 and tested for their rolling resistance and durability. All specifications were the same except for the specifications shown in Table 1.
The test method is as follows.

<Rolling resistance>
Using a rolling resistance tester, rolling resistance when each tire was run under the following conditions was measured. The results were expressed as an index with the value of Comparative Example 1 as 100. The smaller the value, the smaller the rolling resistance and the better.
Rims: 7.50 x 22.5
Internal pressure: 700 kPa
Speed: 80km / H
Load: 24.52kN

<Durability>
One cut flaw was formed in advance at the intermediate position M of the sidewall portion, and a drum durability test was performed under the following conditions. Then, the degree of growth of the cut wound was observed with the naked eye. The results were displayed as an index with the length after growth of the cut flaw of Comparative Example 1 being 100. The smaller the value, the higher the durability and the better.
Rims: 7.50 x 22.5
Internal pressure: 850 kPa
Speed: 50km / H
Load: 39.8kN
Traveling time: 450 hours In addition, the specifications of the cut flaw are as follows.
Length 5mm
Depth 3mm
Table 1 shows the test results.

  As a result of the test, it was confirmed that the heavy load tire of the example significantly improved the rolling resistance without impairing the durability.

It is sectional drawing of the tire for heavy loads of this embodiment. It is the principal part enlarged view.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 3 Side wall part 3g Side wall rubber 4 Bead part 5 Bead core 6 Carcass 7 Belt layer 8 Bead apex rubber 9 Reinforcement cord layer 10 Inner rubber part 11 Outer rubber part

Claims (4)

A heavy duty tire having a carcass having a carcass cord extending from a tread portion through a sidewall portion to a bead core of the bead portion, and a belt layer disposed on the outer side in the tire radial direction of the carcass and inside the tread portion,
In the sidewall portion, the sidewall rubber that extends outside in the tire axial direction of the carcass in the tire radial direction is an inner rubber portion on the carcass side, and an outer rubber portion that is arranged outside and forms the tire outer surface. And the inner rubber portion has a smaller loss tangent tan δ than the outer rubber portion, and the difference is between 0.010 and 0.035 , and
The inner rubber part has a smaller complex elastic modulus than the outer rubber part and the difference is 0.5 to 1.4 (MPa),
In addition, the thickness of the inner rubber portion is from the carcass cord to the tire outer surface at an intermediate position (M) of the tire radial distance (X) from the outer end of the belt layer to the outer surface of the bead core in the tire radial direction. A heavy-duty tire characterized by being 0.5 to 0.8 times the rubber thickness . The outer end of the inner rubber portion in the tire radial direction has a position (PU) that separates at least 0.25 times the tire radial direction distance (X) from the intermediate position (M) to the outer side in the tire radial direction, and The heavy duty tire according to claim 1, which is located between the outer end of the belt layer . The bead portion is provided with a reinforcing cord layer extending in a substantially U-shaped cross section so as to wrap the bead core,
The inner end of the inner rubber portion has at least a position (PD) separating the distance in the tire radial direction from the intermediate position (M) by 0.25 times the tire radial distance (X), and the reinforcing cord layer. The heavy-duty tire according to claim 1 or 2, which is located between the outer end in the tire radial direction . The bead portion is provided with a bead apex rubber extending in a tapered shape from the bead core to the outer side in the tire radial direction,
The heavy duty tire according to any one of claims 1 to 3 , wherein an outer end portion of the bead apex rubber extends between an inner rubber portion and an outer rubber portion of the sidewall rubber .

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