JP2007253848A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of reducing the rolling resistance. <P>SOLUTION: In the pneumatic tire, a belt layer is laminated on an outer circumference of a carcass 11, and a tread part consisting of a tread rubber is arranged on an outer circumference of the belt layer. The belt layer is constituted of three layers of steel belts having a steel cord. A first belt 21 forming an inner circumferential layer and a second belt 22 forming an intermediate layer are arranged so that the direction a steel cord 21A of the first belt 21 and the direction of a steel cord 22A of the second belt 22 are across each other, and inclined with respect to the tire width direction W, and a third belt 23 forming an outer circumferential layer is arranged so that the direction of a steel cord 23A of the third belt 23 is along the tire width direction W. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pneumatic tire used by being mounted on a vehicle or the like.

  In general, as a pneumatic tire used for an automobile or the like, a tire in which a belt layer for reinforcing the carcass is arranged on the outer periphery of the carcass serving as a skeleton is provided. (See Patent Document 1). Usually, the belt layer is composed of a two-layer steel belt with a steel cord and a belt auxiliary layer, these two-layer steel belts are arranged so that the steel cords cross each other, on which, for example, A belt auxiliary layer having a width of about 10% to 15% of the width of the belt layer is disposed in the vicinity of both ends of the belt layer, and a belt auxiliary layer is disposed over the entire width of the belt layer. ing.

In recent years, as a part of environmental measures, reduction of exhaust gas has been demanded by reducing the fuel consumption of automobiles, and in pneumatic tires, reduction of rolling resistance of tires is regarded as important.
It is known that the rolling resistance of the tire when the vehicle travels is greatly contributed by the tread portion disposed in the outermost layer of the tire and in direct contact with the road surface and the belt layer that is a reinforcing member of the tire.
JP 2004-90826 A

  By the way, as a method for reducing the rolling resistance, the thickness of the tread rubber constituting the tread portion (hereinafter referred to as a tread rubber gauge) is reduced to reduce the amount of tread rubber, and the heat generation amount of the tread rubber is reduced. Although it is conceivable to reduce the energy loss, there is a problem that the tire life is shortened because the tread rubber is made thin.

  FIG. 4 shows how the shape changes when a load is applied to the pneumatic tire. The pneumatic tire has a double curvature in the circumferential direction and the width direction, and when the pneumatic tire is deformed by being loaded with a load, as shown in FIG. And a large shear force SF is generated at the shoulder portions which are both end portions of the tread portion. In the tire in which the steel cords of the conventional two-layer steel belt are arranged so as to cross each other, the shear force SF generated in the shoulder portion cannot be received by these steel cords, and the tread rubber is subjected to shear deformation. There is a problem that the rolling resistance increases due to the strain energy.

  This invention is made | formed in view of such a situation, Comprising: It aims at providing the pneumatic tire which can reduce rolling resistance.

  In order to solve the above-described problems and achieve such an object, the present invention provides a pneumatic structure in which a belt layer is laminated on the outer periphery of the carcass and a tread portion made of tread rubber is disposed on the outer periphery of the belt layer. In the tire, the belt layer is configured by laminating three steel belts each having a steel cord, and the first belt serving as an inner circumferential layer and the second belt serving as an intermediate layer include the first belt. The direction of the steel cord of one belt and the direction of the steel cord of the second belt are arranged so as to intersect with each other and incline with respect to the tire width direction, and the third belt serving as an outer circumferential layer, The steel cord of the third belt is arranged so that the direction of the steel cord is along the tire width direction.

  In the present invention, the third belt is arranged on the first belt and the second belt arranged so as to cross each other's steel cord so that the direction of the steel cord is along the width direction of the tire. The cord of the third belt receives the shearing force generated in the shoulder portion of the tire ground contact surface, so that distortion deformation of the shoulder portion can be suppressed, and rolling resistance of the pneumatic tire can be reduced.

  Further, since the shear deformation of the shoulder portion can be suppressed, the shoulder portion can be prevented from coming into strong contact with the road surface, and uneven wear of the tread rubber at the shoulder portion can be suppressed. In addition, since the binding force at the center portion in the tire width direction is increased by arranging the third belt, the amount of change in the radial direction at the center portion in the tire width direction and the change in the radial direction at the shoulder portion when air is injected into the tire. The difference with the amount is reduced, drag wear due to the diameter difference at the time of tire contact can be suppressed, and the life of the pneumatic tire can be improved.

  In addition, since the wear of the tread rubber can be suppressed in this way, even if the tread rubber gauge is thinned, the same life as that of the conventional one can be achieved. Therefore, by reducing the thickness of the tread rubber gauge, it is possible to reduce the amount of heat generated by the tread rubber and further reduce the rolling resistance.

  Here, by making the angle formed by the direction of the steel cord of the third belt and the tire width direction within a range of 0 to 2 °, distortion of the shoulder portion at the time of tire contact by the third belt described above The inhibitory effect can be reliably achieved.

  Further, the angle α formed by the direction of the steel cord of the first belt and the tire width direction and the angle β formed by the direction of the steel cord of the second belt and the tire width direction are in the range of 60 ° to 75 °. By setting it inside, the directionality with respect to the bending of the tire ground contact surface is reduced, and the bending rigidity of the pneumatic tire can be improved.

  Further, by setting the width L1 of the first belt, the width L2 of the second belt, and the width L3 of the third belt to L2 <L1 <L3, the third belt serving as the outer circumferential layer is changed to the first belt. It can arrange | position so that a belt and a 2nd belt may be covered, and a pneumatic tire can be reinforced reliably. Moreover, since the width | variety of a 2nd belt is made the smallest, a 3rd belt can be arrange | positioned along the shape of a shoulder part in a tire both ends.

  Further, by setting the tread rubber thickness in the shoulder side portion of the tread portion to 90% or less of the tread rubber thickness in the tire width center portion of the tread portion, it is possible to uniformly generate wear in the tire width direction. It is possible to further reduce the rolling resistance by further reducing the amount of tread rubber.

  Further, by laminating a belt auxiliary layer made of organic fibers on the outer periphery of the third belt, it is possible to suppress the distortion at the belt end and improve the durability of the pneumatic tire.

  Note that the above-described effects can be obtained even if the steel cord of the first belt and the steel cord of the second belt have a wave shape obtained by bending a monofilament or a single wire.

  Further, by making the steel cord of the third belt a stranded wire in which two or more steel single wires are twisted, a large compressive force acts due to tire deformation at the time of tire contact or when a lateral force acts on the tire. The rigidity of the third belt can be improved.

  Furthermore, the number of steel cords driven per 50 mm width in the third belt is insufficient when the number of driven steel cords is less than 15 and the effect of improving the wear resistance of the tire is reduced. Even if the number is increased, the wear resistance of the tire is not greatly improved.

  According to the present invention, the belt layer has a three-layer structure, and the direction of the steel cord of the third belt serving as the outer peripheral layer of the belt layer is arranged along the tire width direction. It is possible to provide a pneumatic tire that can suppress distortion deformation of the portion and can reduce rolling resistance of the tire.

Hereinafter, a pneumatic tire according to an embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a partial cross-sectional view of a pneumatic tire 10 according to the present embodiment. The pneumatic tire 10 includes a carcass 11 serving as a skeleton, and a tread portion 12 that is disposed on the outermost layer of the tire 10 and contacts a road surface. And a belt layer 20 disposed between the carcass 11 and the tread portion 12 for reinforcing the carcass 11.

  FIG. 2 shows a stacked state of the carcass 11 and the belt layer 20 constituting the tire 10 on a plane. As shown in FIG. 2, the carcass 11 is configured by arranging the polyester cord 11 </ b> A along the radial direction of the tire 10 and along the width direction W of the tire 10. The tire 10 has a so-called radial structure.

  The belt layer 20 for reinforcing the carcass 11 includes three layers including a first belt 21 that is an inner peripheral layer, a second belt 22 that is an intermediate layer, and a third belt 23 that is an outer peripheral layer. The first belt 21, the second belt 22, and the third belt 23 are steel belts provided with a steel cord.

  Here, the first belt 21 and the second belt 22 are inclined with respect to the tire width direction W while the direction of the steel cord 21A of the first belt 21 and the direction of the steel cord 22A of the second belt 22 intersect each other. Are arranged to be. Specifically, as shown in FIG. 2, the angle α formed by the direction of the steel cord 21A of the first belt 21 and the tire width direction W is in the range of 60 ° to 75 °, and the steel of the second belt 22 The angle β formed by the direction of the cord 22A and the tire width direction W is also in the range of 60 ° to 75 °. The crossing angle between the steel cord 21A of the first belt 21 and the steel cord 22A of the second belt 22 Is arranged in the range of 30 ° to 60 °.

As shown in FIG. 2, the third belt 23 that is the outer peripheral layer of the belt layer 20 is more specifically configured so that the direction of the steel cord 23A is along the tire width direction W. And the tire width direction W are arranged so that the angle is in the range of 0 to 2 °.
The steel cord 23A of the third belt 23 is a stranded wire obtained by twisting two or more steel single wires, and the number of driven steel cords 23A per 50 mm is 15 or more and 20 or less.

The width L1 of the first belt 21, the width L2 of the second belt 22, and the width L3 of the third belt 23 are configured such that L2 <L1 <L3 as shown in FIG.
In addition, a belt auxiliary layer 24 made of an organic fiber such as an aramid fiber is laminated on the outside of the third belt 23.

As described above, the tread portion 12 made of tread rubber and actually in contact with the road surface is disposed outside the belt layer 20 including the three-layer belt and the belt auxiliary layer 24. As shown in FIG. 1, a plurality of blocks 14 defined by drainage grooves 13 are formed in the tread portion 12.
In this embodiment, the tread rubber gauge, which is the thickness of the tread rubber, is T1 at the center portion of the tread portion 12, T2 at the shoulder portions (both end portions) of the tread portion 12, and T2 / T1 = 0.9 or less. It is comprised so that it may become.

  According to the pneumatic tire 10 according to the present embodiment configured as described above, the belt layer 20 has a three-layer structure, and the third belt 23 is provided outside the first belt 21 and the second belt 22. The direction of the steel cord 23A is along the tire width direction W, specifically, the angle formed by the direction of the steel cord 23A and the tire width direction W is within a range of 0 to 2 °. Therefore, the shearing force generated in the shoulder portion of the tire ground contact surface is received by the steel cord 23A of the third belt 23, and distortion deformation of the shoulder portion can be suppressed. Rolling resistance can be reduced.

  In addition, since deformation of the shoulder portion is suppressed, it is possible to suppress uneven wear of the shoulder portion. Moreover, since the 3rd belt 23 is arrange | positioned as mentioned above, the restraint force in the tire width direction W center part becomes high. Then, the amount of change in the radial direction when air is injected into the tire 10 is not greatly different between the central portion of the tire width direction W and the shoulder portion, and drag wear due to the difference in diameter at the time of tire contact can be suppressed. 10 lifespan can be improved.

  The angle formed by the direction of the steel cord 21A of the first belt 21 and the tire width direction W and the angle formed by the direction of the steel cord 22A of the second belt 22 and the tire width direction W are 60 ° to 75 °. Since the crossing angle between the steel cord 21A of the belt 21 and the steel cord 22A of the second belt 22 is within a range of 30 ° to 60 °, the directionality of the tire contact surface with respect to bending is reduced. The bending rigidity of the pneumatic tire 10 can be improved.

  Further, since the width L1 of the first belt 21, the width L2 of the second belt 22, and the width L3 of the third belt 23 are configured to satisfy L2 <L1 <L3, the first outer circumferential layer is formed. The three belts 23 can be arranged so as to cover the first belt 21 and the second belt 22, and the rigidity of the pneumatic tire 10 can be improved. In addition, since the width L2 of the second belt 22 located inside the third belt 23 is the smallest, the third belt 23 is disposed at both ends of the tire 10 so as to deform along the shape of the shoulder portion. be able to.

  Further, since the belt auxiliary layer 24 made of an organic fiber such as an aramid fiber is laminated on the outer periphery of the third belt 23, the distortion at both ends of the belt layer 20 can be suppressed, and the durability of the pneumatic tire 10 is improved. Can be improved.

Further, since the steel cord 23A of the third belt 23 is a stranded wire in which two or more steel single wires are twisted, a large compressive force is exerted due to deformation when a lateral force acts on the tire 10 or when the tire 10 touches the tire 10. The rigidity of the three belts 23 can be improved.
Further, since the number of driven steel cords 23A of the third belt 23 per 50 mm is 15 or more and 20 or less, the effect of improving the wearability of the pneumatic tire 10 can be reliably achieved.

  Further, since the top rubber gauge T2 on the shoulder side of the tread portion 12 and the top rubber gauge T1 at the center portion of the tread portion 12 are configured to be T2 / T1 = 0.9 or less, the tire width direction In W, wear of the tread portion 12 can be uniformly generated. Therefore, the amount of heat generated by the tread rubber can be suppressed by reducing the amount of the tread rubber, and the rolling resistance can be further reduced.

As mentioned above, although the pneumatic tire which is embodiment of this invention was demonstrated, this invention is not limited to this, In the range which does not deviate from the technical idea of the invention, it can change suitably.
For example, the first belt and the second belt have been described as having a single wire steel cord. However, the present invention is not limited to this, and the steel cord is a monofilament or a wave shape obtained by bending a single wire. Also good.

Similarly, the third belt has been described as having a stranded steel cord, but the invention is not limited to this. For example, as shown in FIG. Also good. In this case, it is only necessary that the direction in which the wave-shaped steel cord extends is arranged along the tire width direction.
Moreover, although the belt auxiliary layer made of organic fibers is disposed outside the third belt, the belt auxiliary layer is not limited to this and may not be provided.

An evaluation test was conducted to confirm the effect of the present invention. The results of the evaluation test will be described below.
The tire size was 205 / 55R16, the tire was attached to a rim with a 7J × 16 rim, the load was 4.90 kN, and the tire air pressure was set to 210 kPa.
The vehicle equipped with this tire was run 3000 km on the test course, and then the groove depth of the tire drainage groove was measured to confirm the wear state of the tread rubber.
In addition, as a rolling resistance test, rolling resistance values were measured at four levels of speeds of 40, 60, 80, and 100 km / h using a vehicle equipped with the tires with an indoor drum tester.

The comparative test results are shown in Table 1. In addition, about wear performance, the groove depth in the shoulder side part and center part by a prior art example was set to 100, and index evaluation was carried out. The larger the index, the deeper the groove depth after running and the better the wear performance.
In addition, the rolling resistance value was also index-evaluated by setting the value according to the conventional example to 100. It shows that rolling resistance is so small that this index | exponent is large.

In Table 1, the tread rubber gauge and the amount of tread rubber are shown as an index with the conventional example being 100.
Compared with the conventional example which does not have a 3rd belt, in this invention example 1 which reduced the amount of tread rubber and has arrange | positioned the 3rd belt, wear performance improved and rolling resistance reduced.

On the other hand, in Example 2 of the present invention in which the amount of tread rubber was greatly reduced, it was confirmed that although the improvement in wear performance was not recognized, the rolling resistance was greatly reduced. Further, it was confirmed that in Invention Example 3 in which the amount of tread rubber was the same as that of the conventional example, the wear performance could be greatly improved although the effect of reducing rolling resistance was small.
As described above, since the wear characteristics and the rolling resistance vary in a contradictory manner depending on the amount of tread rubber, it is preferable to appropriately set the amount of tread rubber according to the purpose of use of the pneumatic tire.

Next, the wear performance and ride comfort when the number of driven third belts (per 50 mm) was changed were compared and evaluated.
The tire size was 205 / 55R16, the tire was attached to a rim with a 7J × 16 rim, the load was 4.90 kN, and the tire air pressure was set to 210 kPa.
Riding comfort at a speed of 40 to 100 km / h was evaluated by a sensory feeling evaluation test using a vehicle equipped with the tire. The wear performance was evaluated in the same manner as in Example 2.

  The comparative test results are shown in Table 2.

  In Invention Example 4 in which the number of steel cords to be driven in the third belt is 36 and in Example 8 in which the number of driven steel cords is 25, the wear performance is improved as compared with the conventional example. Is greatly reduced. In addition, it was confirmed that in the invention example 5 in which the number of implantations was 10, the wear performance was not greatly improved from the conventional example.

On the other hand, in Invention Example 6 in which the number of driving is 15 and Invention Example 7 in which the number of driving is 20, the wear characteristics are excellent, and the ride comfort is set to a certain level or more. It was confirmed that
As described above, the wear characteristics and the riding comfort vary in a contradictory manner depending on the number of driven steel cords, and therefore it is preferable to appropriately set the number of driven steel cords according to the intended use of the pneumatic tire.

1 is a partial cross-sectional view of a pneumatic tire according to an embodiment of the present invention. It is explanatory drawing which showed planarly the lamination | stacking state of the carcass and belt layer of the pneumatic tire which concerns on embodiment of this invention. It is explanatory drawing which showed the lamination | stacking state of the carcass and belt layer of the pneumatic tire which concerns on other embodiment of this invention planarly. In a pneumatic tire, it is explanatory drawing which shows the deformation | transformation state of the tread part at the time of no load and load loading.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Pneumatic tire 11 Carcass 12 Tread part 20 Belt layer 21 1st belt 22 2nd belt 23 3rd belt 24 Belt auxiliary layer

Claims (9)

In a pneumatic tire in which a belt layer is laminated on the outer periphery of the carcass and a tread portion made of tread rubber is arranged on the outer periphery of the belt layer,
The belt layer is formed by laminating three layers of steel belts equipped with steel cords,
The first belt that is the inner circumferential layer and the second belt that is the intermediate layer are configured such that the direction of the steel cord of the first belt and the direction of the steel cord of the second belt intersect with each other and the tire width. Arranged to be inclined with respect to the direction,
The pneumatic tire according to claim 1, wherein the third belt as an outer circumferential layer is disposed such that a direction of the steel cord of the third belt is along the tire width direction.   2. The pneumatic tire according to claim 1, wherein an angle formed by the direction of the steel cord of the third belt and the tire width direction is within a range of 0 to 2 °.   The angle α formed between the direction of the steel cord of the first belt and the tire width direction and the angle β formed between the direction of the steel cord of the second belt and the tire width direction are 60 ° to 75 °, respectively. The pneumatic tire according to claim 1 or 2, wherein the pneumatic tire falls within a range.   The width L1 of the first belt, the width L2 of the second belt, and the width L3 of the third belt satisfy L2 <L1 <L3. The pneumatic tire according to any one of the above.   5. The tread rubber thickness in the shoulder side portion of the tread portion is 90% or less of the tread rubber thickness in the tire width center portion of the tread portion. Pneumatic tire described in 2.   The pneumatic tire according to any one of claims 1 to 5, wherein a belt auxiliary layer made of an organic fiber is laminated on an outer periphery of the third belt.   The air according to any one of claims 1 to 6, wherein the steel cord of the first belt and the steel cord of the second belt are formed into a wave shape obtained by bending a monofilament or a single wire. Enter tire.   The pneumatic tire according to any one of claims 1 to 7, wherein the steel cord of the third belt is a stranded wire obtained by twisting two or more steel single wires.   9. The pneumatic tire according to claim 8, wherein the number of driven steel cords per 50 mm width in the third belt is 15 or more and 20 or less.

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