JP2012171423A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic radial tire capable of reducing pass-by noise particularly when traveling by accelerating, while maintaining lightness in weight and fuel consumption-saving.SOLUTION: This pneumatic radial tire has belts and a tread in order on the outside in the radial direction of a crown part of a carcass constituted of at least one layer of ply formed by covering a plurality of cords extending along a tire equatorial plane with rubber, the carcass straddling between paired bead parts in a toroidal form. The belts includes: a main oblique belt layer of one layer formed by covering a plurality of steel cords extending obliquely by 40 to 60 degrees relative to the tire equatorial plane with the rubber; a sub oblique belt layer of one layer formed by covering a plurality of steel cords extending, in a central region in a tread width direction of the oblique belt layer, obliquely by 8 to 20 degrees relative to the tire equatorial plane with the rubber; and divided circumferential-direction belt layers each of at least one layer each formed by covering a plurality of cords extending along the tire equatorial plane in both side regions in the tread width direction of the main oblique belt layer with the rubber. The sub oblique belt layer and divided circumferential-direction belt layers, are arranged radially outside the main oblique belt layer.

Description

  The present invention relates to a pneumatic radial tire that can reduce the passage noise particularly during acceleration while maintaining light weight and fuel saving.

  Conventionally, as a tread structure for a tire for a passenger car, a carcass is formed by one piece of a carcass ply in which a large number of cords extending at an angle of substantially 90 ° with respect to the tire circumferential direction are covered with rubber. Arranged on the outer periphery of the crown portion are two layers of inclined belt layers made of ply covered with rubber on a number of metal cords extending at a relatively small inclination angle with respect to the tire circumferential direction so that the cords cross each other An additional reinforcement having a width slightly wider than the belt full width, for example, comprising a ply covered with an organic fiber cord extending substantially in the tire circumferential direction with rubber on the further outer peripheral side of the belt. Layers, so-called caps are additionally arranged.

  On the other hand, since the structure is simple, it is easy to manufacture, and as a light weight and low rolling resistance tire, it is located on one inclined belt layer made of steel cord and this inclined belt layer, in the tire circumferential direction. On the other hand, a pneumatic radial tire including at least one circumferential belt layer in which a plurality of cords are arranged substantially in parallel has been proposed (see Patent Documents 1 to 5).

Japanese Patent Laid-Open No. 2002-19414 Japanese Patent No. 3071808 Japanese Patent Laid-Open No. 2001-206010 Japanese Patent No. 4054072 JP 2007-161026

  However, the tire in which the circumferential belt layer is disposed on the outer periphery of the single inclined belt layer described above has a problem that the passing noise during acceleration traveling is particularly large. Here, the passing noise is noise caused by sound generated toward the outside of the vehicle when the vehicle travels. That is, since the inclined belt layer is a single layer, the out-of-plane bending rigidity in the tread width direction is low, and the vibration characteristics in the higher-order vibration mode in the tire width direction cross section deteriorate. In addition, since the circumferential rigidity of the tread portion is high, the fact that the input to the tread easily propagates in the tire circumferential direction also contributes to increase the passing noise.

  Therefore, the present invention provides a pneumatic radial tire that can reduce the passage noise especially during acceleration while maintaining light weight and fuel saving.

Now, the inventors diligently investigated the problem of the tire with a simplified structure in which the circumferential belt layer is disposed on the outer periphery of the above-described single inclined belt layer and the solution thereof, and obtained the following knowledge. The present invention has been completed.
That is, when a conventional tire, that is, a tire having a belt in which two inclined belt layers are laminated in a direction in which the cords cross each other is compared with a tire having the simplified structure, the tire having the simplified structure has an inclined belt layer. Due to one layer, the widthwise bending rigidity (out-of-plane bending rigidity) of the tread portion is low. Therefore, the tread tends to vibrate in the cross section in the tire width direction.

Here, when the tire rolls on the road surface, the tread portion is deformed according to the unevenness of the road surface or the unevenness of the tread surface itself, and vibration is generated in the tread portion due to the deformation. And this vibration forms a vibration mode that propagates in the tire width direction by creating a standing wave between the two bead portions as the fixed end, similar to the vibration of the string with both ends fixed. It is a cause of noise generated by tires.
For such noise, it is effective to increase the rigidity in the width direction of the central region of the tread, which becomes an antinode of vibration in the vibration mode, and suppress the amplitude of the region. That is, by disposing the inclined belt layer in the central region in the tread (belt) width direction, the rigidity in the belt width direction in the central region of the tread is increased, so that noise can be reduced. Furthermore, in addition to the change from the circumferential belt layer to the inclined belt layer, as the angle of the inclined belt layer cord with respect to the tire circumferential direction is increased, the circumferential rigidity of the belt decreases and the lateral rigidity improves. become.

  In the simplified structure tire described above, since the inclined belt layer is a single layer, the “tag” effect imposed on the inclined belt layer of the belt is weak, so in order to ensure durability at high speed and durability against filling air pressure, It was necessary to use a highly rigid circumferential belt layer (cap) compared to a conventional tire having two inclined belt layers. When this cap is used, the input applied to one point on the tread is easily propagated in the tread circumferential direction, so that noise is likely to deteriorate. Further, since the tread portion is fastened by the highly rigid circumferential belt layer (cap), the circumferential tension of the belt is made uniform in the width direction, and the difference in belt tension between the center portion of the tread and both side portions thereof is reduced. Therefore, when the tire rolls, the tread central portion and both side portions simultaneously release large energy, and noise is likely to deteriorate.

  As described above, in order to ensure high-speed durability, a “tag” effect in the belt (inclined belt layer + circumferential belt layer) is necessary. In particular, since tire diameter growth increases at both ends (shoulder portions) of the tread at high speeds, it is important to suppress diameter growth at both ends of the belt. Here, the circumferential belt layer is usually formed by spirally winding a belt-shaped belt member in the tire circumferential direction. Therefore, if circumferential belts are provided on both sides of the tread, deformation at both ends of the belt is suppressed, and as a result, durability by the circumferential belt layer described above, particularly high-speed durability, can be ensured.

The present invention has been made based on the above knowledge, and the gist of the present invention is as follows.
(1) A belt and a tread are disposed radially outside a crown portion of a carcass formed of at least one layer of a ply in which a plurality of cords extending along a tire equatorial plane and covered with a rubber are straddled between a pair of bead portions. In order,
The belt
On the outside in the radial direction of one main inclined belt layer in which a plurality of steel cords extending at an angle of 40 to 60 ° with respect to the tire equator are coated with rubber,
A sub-inclined belt layer in which a plurality of steel cords extending with an inclination of 8 to 20 ° with respect to the tire equatorial plane is coated with rubber in a central region in the tread width direction of the inclined belt layer;
At least one divided circumferential belt layer in which a plurality of cords extending along the tire equatorial plane are covered with rubber in each of the two sides in the tread width direction of the main inclined belt layer is placed in the pneumatic. Radial tire.

(2) The pneumatic radial tire according to (1), wherein both end portions in the width direction of the sub-inclined belt layer and end portions on the tire equatorial plane side of the divided circumferential belt layer are disposed so as to overlap each other. .

(3) The pneumatic radial tire according to (1) or (2), wherein the width of the main inclined belt layer: W1 and the width of the auxiliary inclined belt layer: W2 satisfy the following formula.
Record
0.25 ≦ W2 / W1 ≦ 0.6

(4) (1), (2) or (3), wherein the divided circumferential belt layer is disposed below the overlapping width: 5 to 15 mm on the radially outer side of the sub-inclined belt layer. Pneumatic radial tire described in 2.

  ADVANTAGE OF THE INVENTION According to this invention, the pneumatic radial tire which can reduce noise, especially the passage noise at the time of acceleration driving | running | working can be provided, maintaining lightweight and fuel-saving property.

1 is a cross-sectional view in the width direction of a pneumatic tire according to the present invention. FIG. 2 is a development view of the belt of the pneumatic tire shown in FIG. 1. It is an expanded view of the belt of another structure. It is an expanded view of the belt used as a comparison. It is an expanded view of the belt used as a comparison. It is an expanded view of the belt used as a comparison.

Hereinafter, the pneumatic tire of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a cross-sectional view in the width direction of the pneumatic tire of the present invention, and FIG. 2 is a development view of the belt of the pneumatic tire of the present invention. The pneumatic tire 10 of the present invention has a carcass 2 straddling a toroidal shape between a pair of bead portions in which a bead core 1 is embedded, and a belt 3 and a tread 4 are disposed outside the crown portion of the carcass 2 in the tire radial direction. Do it.

  As shown in FIG. 2, the belt 3 includes a main inclined belt layer 3a in which a plurality of steel cords extending with an inclination of 40 to 60 ° with respect to the tire equatorial plane CL are covered with rubber, and the main inclination. On the radially outer side of the belt layer 3a, a plurality of steel cords extending at an angle of 8 to 20 ° with respect to the tire equatorial plane CL and straddling the central region in the tread width direction of the main inclined belt layer 3a are covered with rubber. A sub-slope of at least one layer in which a plurality of cords extending along the tire equatorial plane CL are coated with rubber and provided on each of the two side regions in the tread width direction of the main inclined belt layer 3a. Direction belt layer 3c.

The direction of the steel cord constituting the sub-inclined belt layer 3b is an arrangement in which the directions of the steel cord intersect with the main inclined belt layer 3a.
For the divided circumferential belt layer 3c, it is preferable to use a cord composed of a steel cord or an aramid fiber, or a composite cord composed of an aramid fiber and a nylon fiber. The divided circumferential belt layer 3c may be at least one layer,
In order to sufficiently obtain the “tag” effect of tightening in the circumferential direction while suppressing an increase in weight, one or two layers are preferable. On the other hand, one layer is sufficient for the main and sub inclined belt layers 3a and 3b.

In addition to the main inclined belt layer 3a, the auxiliary inclined belt layer 3b is arranged only in the central region in the tread width direction, so that a circumferential belt layer is additionally arranged over the entire region of the main inclined belt layer 3a. As a result, the circumferential rigidity of the tread central region decreases, while the width rigidity increases. As a result, noise can be reduced as described above.
The sub-inclined belt layer 3b in the central region in the tread width direction has a lower circumferential rigidity and an increased width direction rigidity as the cord angle (the inclination angle of the cord shaft with respect to the tire equatorial plane) increases. If this cord angle is made too large, the circumferential rigidity (tag effect) in the central area is lowered and the high-speed durability is lowered. On the other hand, if the cord angle is too small, the difference between the central region and both end regions becomes small and the noise reduction effect is lost.

  Next, the reason why the cord angle of the main inclined belt layer 3a is 40 to 60 ° is as follows. That is, when the cord angle of the main inclined belt layer 3a is less than 40 °, the rolling resistance increases and the fuel saving effect cannot be obtained. On the other hand, when the cord angle exceeds 60 °, the circumferential rigidity of the tire decreases, and the high-speed durability significantly decreases.

  The divisional circumferential belt layer 3c is provided to be divided into both sides in the tread width direction in order to ensure high-speed durability as described above.

  In addition, said tread width direction center area | region refers to the area | region of 20 to 50% of tread surface width centering on tire equator surface CL, and areas other than this center area become both tread width direction both sides area.

  Further, as shown in FIG. 2, it is preferable that the end portion on the tire equatorial plane side and the end portion in the width direction of the auxiliary inclined belt layer 3b partially overlap each other in the divided circumferential belt layer 3c. It is important that there is no space in the width direction between the end portion on the tire equatorial plane side of the layer 3c and the width direction end of the sub-inclined belt layer 3b. If there is a gap here, the belt rigidity at the gap will be low, and the high-speed durability of the tire will be reduced.

  Here, in the example shown in FIGS. 1 and 2, the main inclined belt layer 3a, the auxiliary inclined belt layer 3b, and the divided circumferential belt layer 3c are arranged in this order from the carcass 2 side to the radially outer side. As shown in FIG. 3, the divided circumferential belt layer 3c and then the sub-inclined belt layer 3b may be arranged in this order on the radially outer side of the main inclined belt layer 3a.

  By the way, regarding the stacking order of the above-mentioned divided circumferential belt layer and sub-inclined belt layer, it is possible to arrange the inclined belt layer in the tread central region on the inner side in the tire radial direction and the circumferential belt layers on both sides of the tread on the outer side. It is preferable in production. That is, when a ply of an inclined belt layer is wound around the central area after the ply of the circumferential belt layer is wound around the both sides of the tread, air may enter the central portion, which may cause a product defect.

  The sub-inclined belt layer 3b and the circumferential belt layer 3c preferably overlap with an overlap width L (see FIG. 2) of about 5 to 15 mm. That is, when the overlap width L between the belt layers is less than 5 mm, the effect of the overlap is reduced, and a failure tends to occur from that portion during high-speed running. On the other hand, if the overlap width L exceeds 15 mm, the tire becomes heavy, which is not preferable.

Further, as shown in FIG. 2, the width of the main inclined belt layer 3a: W1 and the width of the auxiliary inclined belt layer 3b: W2 satisfy the following expression, that is, the width W2 of the auxiliary inclined belt layer 3b is the main inclined belt layer 3a. The width W1 is preferably 0.25 to 0.6 times.
Record
0.25 ≦ W2 / W1 ≦ 0.6
This is because if the width W2 of the sub-inclined belt exceeds 0.6W1, the circumferential rigidity (tagged effect) in the central area of the tread decreases, and the high-speed durability tends to decrease. On the other hand, when the width W2 of the sub-inclined belt is less than 0.25W1, the difference in rigidity in the width direction between the tread central area and both end areas becomes small, and the noise reduction effect becomes small. More preferably, it is W2: 0.3W1-0.4W1.

By the way, the width W3 in each of the both sides of the divided circumferential belt layer 3c in the tread width direction is determined to be a width obtained by removing W2 and L from W1 if the width of the belt layer is determined as W1 and W2. And in relation to W1 and W2 and the overlap width L described above, the following formula W3 × 2 + W2-2L: 0.9 to 1.1W1
Is preferably satisfied.
That is, it is preferable that the main inclined belt layer 3a is substantially covered with the circumferential belt layer 3c and the auxiliary inclined belt layer 3b. This is because the rigidity increases when belt layers having different cord angles are laminated, and therefore it is preferable to dispose the sub-inclined belt layer and the circumferential belt layer so as to substantially cover the entire width of the main inclined belt layer. However, if the width end positions of the main inclined belt layer 3a and the divided circumferential belt layer 3c coincide with each other, strain may concentrate and the durability may decrease, so the width end in the range of 0.9 to 1.1W1. It is advantageous to shift the position.

  In addition, the carcass structure of the example of illustration is an example, and this invention is not limited to this. For example, in the illustrated example, the carcass 2 is composed of a single radial carcass ply. However, the carcass ply may be composed of a plurality of radial carcass plies. On the other hand, you may incline to about 85 degrees.

  According to the conditions shown in FIGS. 1 and 2, a tire having a size of 205 / 55R16 was manufactured in accordance with the specifications shown in Tables 1 and 2. Each of the obtained prototype tires was incorporated into a rim of size 6.5J, an internal pressure of 230 kPa was applied, and subjected to various tests, and rolling resistance, noise characteristics, and high-speed durability were evaluated as follows. 4 to 6 referring to the belt structure shown in Tables 1 and 2, reference numerals 30, 30a, and 30b are inclined belt layers, and reference numeral 40 is a circumferential belt layer.

<Rolling resistance>
Each test tire was mounted on a steel drum tester with a 1707mm diameter surface and the rolling resistance when running at a speed of 80km / h under load condition: 4.OkN was measured by the ellipse method. . The measurement results are shown as an index when the rolling resistance of the tire of Comparative Example 1 shown in Table 1 is set to “100”. It shows that rolling resistance is so small that this figure is small.

<Noise characteristics>
Noise characteristics were measured by an actual vehicle acceleration noise test specified in ISO362. In other words, an actual vehicle equipped with a test tire is run at a constant speed of 50 km / h from the front of the noise measurement section on a solid test course, and the vehicle rear end reaches the measurement section when the vehicle front end reaches the measurement section. Until the vehicle exits, run the accelerator pedal fully, and at a midpoint of the course, use a stationary microphone installed at a position 7.5m above the running center line and 1.2mm above the test road surface. Accelerated running noise was measured.

<High speed durability>
The test tire is mounted on a testing machine with a drum diameter of 1707 mm, subjected to a high-speed durability test specified in JIS-D4230, and further accelerated at 10 km / h every 30 minutes until the tire breaks. Was measured. The measurement result was expressed as an index when the running distance of the test tire of Comparative Example 1 was set to 100. The larger this value, the higher the durability and the better.

1 bead core 2 carcass 3a main inclined belt layer 3b sub inclined belt layer 3c divided circumferential belt layer 4 tread 10 pneumatic tire

Claims (4)

A belt and a tread are arranged in this order on the radially outer side of the crown portion of the carcass composed of at least one layer of a ply covering a toroidal shape between a pair of bead portions and extending along the tire equatorial plane with a rubber-coated ply. ,
The belt
On the outside in the radial direction of one main inclined belt layer in which a plurality of steel cords extending at an angle of 40 to 60 ° with respect to the tire equator are coated with rubber,
A sub-inclined belt layer in which a plurality of steel cords extending with an inclination of 8 to 20 ° with respect to the tire equatorial plane is coated with rubber in a central region in the tread width direction of the inclined belt layer;
At least one divided circumferential belt layer in which a plurality of cords extending along the tire equatorial plane are coated with rubber in each of the tread width direction both sides of the main inclined belt layer;
This is a pneumatic radial tire.   The pneumatic radial tire according to claim 1, wherein both end portions in the width direction of the sub-inclined belt layer and end portions on the tire equatorial plane side of the divided circumferential belt layer are overlapped with each other. The pneumatic radial tire according to claim 1 or 2, wherein the width of the main inclined belt layer: W1 and the width of the auxiliary inclined belt layer: W2 satisfy the following formula.
Record
0.25 ≦ W2 / W1 ≦ 0.6 4. The pneumatic radial tire according to claim 1, wherein the divided circumferential belt layer is disposed below the overlapping width: 5 to 15 mm on a radially outer side of the sub-inclined belt layer.

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