JP2002127711A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire which retains the desired shape at an aspect ratio of 70% or lower, improves the safety by heightening the predictability of cornering traveling, and exhibits better durability than existing tires. SOLUTION: In a pneumatic tire with an aspect ratio of 70% or lower provided with a carcass layer 5 of two or more plies reinforcing between a pair of beads 1a and with a reinforcing layer 6 in the circumferential direction installed at the lower side of a tread part on the outside circumference face of the carcass layer, the cords of the carcass layer 5 are arranged approximately in the radial direction RD of the tire from the beads 1a to positions near to the maximum width of the tire, from the positions of which to ground-touching edges PT the angles of the cords to the circumferential direction are gradually changed and are arranged at 20-60 degrees in the vicinity of the ground-touching edges PT and at 20-50 degrees at the tread part Tr, and furthermore the carcass layer 5 is laminated nearly symmetrically to the tire equator line CL and the tensile modulus per width of the reinforcing layer 6 is equal to or higher than 1.2 times that of the carcass layer 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carcass layer which reinforces a space between a pair of annular beads and changes the inclination angle of a cord for each tire portion, and the cords provided on the outer peripheral surface thereof are arranged in the tire circumferential direction. The present invention relates to a pneumatic tire including a reinforcing layer.

[0002]

2. Description of the Related Art At present, radial tires, which are the mainstream of pneumatic tires, reinforce a space between a pair of annular beads.
A carcass layer in which a plurality of cords are arranged in the tire radial direction (meridian direction), and a plurality of belt layers in which the carcass layer located below the tread is reinforced by a tag effect and the cords are inclined with respect to the tire circumferential direction. The structure is common. The carcass layer has high rigidity in the tire radial direction but low rigidity in the circumferential direction. Conversely, the belt layer has high rigidity in the tire circumferential direction but low rigidity in the radial direction.

For this reason, local stress concentration is likely to occur at the belt edge near the boundary between the carcass layer and the belt layer,
This has reduced the durability of the tire. It is also generally known that in cornering traveling, when the vehicle reaches a slip limit, the reaction force is suddenly lost, and the vehicle may become unable to steer.

[0004] On the other hand, bias tires that exist before radial tires have insufficient stiffness of the tread portion and do not have sufficient cornering reaction force, so their exercise ability is inferior. It is known that the crossing causes shear strain between the layers and easily causes fatigue fracture.

In order to compensate for the above-mentioned drawbacks of both tires, Japanese Unexamined Patent Publication (Kokai) No. 61-263805 discloses that the cord of the carcass layer located below the tread is greatly inclined from the meridian direction and is located on the tire side. There has been proposed a pneumatic tire in which carcass layers in which cords are arranged in the radial direction are laminated in two layers so that inclined cords cross each other, and a reinforcing layer in which the cords are arranged in the tire circumferential direction is provided on the outer peripheral surface thereof. I have. Further, as a method of manufacturing a ply for forming such a carcass layer, a ply in which a plurality of cords are linearly arranged is attached to a forming drum having a plurality of cylindrical drums on the same axis, and then the cylinder is formed. A method is disclosed in which the cord angle of the plies is partially changed by providing a predetermined declination between the drums. The cylindrical ply obtained in this way, after driving the bead,
After the tubular airbag is inserted and shaped into a donut shape by the internal pressure, the circumferential reinforcing layer is attached.

[0006]

However, since the above-mentioned tire is manufactured by the above-described manufacturing method, the radius of curvature of the bent portion where the cord angle changes is likely to be small, and as described in the above-mentioned publication, vulcanization molding Sometimes, even when the tension is moderated by applying tension, if the flatness is reduced to some extent, the angle change from the side to the tread is abrupt,
It was difficult to make the curvature of the bent portion gentle. If the radius of curvature of the bent portion is small, a large shear force is generated between the lower bent portion and the upper bent portion when tension is generated in the cord during traveling, so that fatigue failure is likely to occur from the vicinity of the bent portion. There is. Further, since the cord angle changes discontinuously at the bent portion, there is a problem that the predictability of the slip limit at the time of cornering traveling is low and the effect of improving safety is small as in the case of the radial tire.

On the other hand, the present applicant has newly developed a method for producing a carcass ply for forming a carcass layer in which the inclination angle of the cord changes for each part of the tire (unknown at the time of filing the present application), and Although the carcass layer can be formed with a gradual change in the cord angle even if is small to some extent, the following new problem arises. That is, when the flatness becomes smaller, the width of the tread portion becomes relatively wide, and therefore, unless the rigidity of the circumferential reinforcing layer provided on the outer periphery of the carcass layer is increased, the desired shape can be maintained at the tread portion of the tire. It becomes difficult and hinders driving performance.

Accordingly, an object of the present invention is to provide a tire having an aspect ratio of 70% or less, to maintain a desired shape, to improve the predictability of cornering running and to improve safety, and to have a more excellent durability than conventional tires. It is to provide a pneumatic tire.

[0009]

The above object can be achieved by the present invention as described below.

That is, the pneumatic tire according to the present invention has a reinforcing layer in which two or more carcass layers for reinforcing a space between a pair of annular beads and a cord arranged on the outer peripheral surface of the carcass layer below the tread portion in the tire circumferential direction. A pneumatic tire having a flattening rate of 70% or less, comprising: a cord forming the carcass layer is disposed substantially in a tire radial direction from the bead to a position near a tire maximum width; The angle with respect to the tire circumferential direction is gradually changed, and is arranged at an angle of 20 to 60 ° with respect to the tire circumferential direction near the ground contact end, and at an angle of 20 to 50 ° with the tread portion, and with respect to the tire equator line. The carcass layers are stacked so that the cords are arranged at substantially symmetrical angles, and the tensile modulus per width of the reinforcing layer is at least 1.2 times the carcass layer. Here, the tread portion refers to a range inside the grounded ends on both sides of the tire. Also, the tensile modulus per width of the reinforcing layer is based on the entire width of the reinforcing layer, the tensile modulus per width of the carcass layer is based on the tread portion,
According to the initial tensile resistance of the JIS L-1017 synthetic fiber tire cord test method, the apparent Young's modulus of the cord was measured, and the value obtained by multiplying the number of cords per width, the cord cross-sectional area and the number of layers was defined as the tensile modulus. The number of shots is based on the tire after vulcanization, but the number of shots in the material preparation stage can be set from the inflation rate during molding.

In the above, the reinforcing layer is disposed at a central position below the tread portion in a range of 45 to 80% of the entire width of the tread portion, and has a lower tensile modulus per width than the central portion. It is preferred to have both sides.
Here, the tensile modulus per width of each part of the reinforcing layer is:
Based on the full width of each part.

Further, it is preferable that the tensile modulus per width of the central portion is 1.2 times or more as large as the tensile modulus per width of the side portion.

According to the pneumatic tire of the present invention, since the cord angle with respect to the tire circumferential direction is gradually changed from the vicinity of the maximum width of the tire to the ground contact end, the reinforcing effect is continuous. Is highly predictable and safety is improved. In addition, since there is no bent portion where the cord angle changes discontinuously, and the cords are arranged in the tire radial direction from the bead to the vicinity of the tire maximum width, peeling between two layers and the like hardly occur and stress concentration hardly occurs. . Further, not only the tread portion but also the outer shoulder portion crosses the cord at a small angle to increase the rigidity in the circumferential direction, so that the kinematic ability of cornering traveling is also improved. On the other hand, the tensile modulus per width of the reinforcing layer is 1.2 times that of the carcass layer.
Since it is twice or more, a desired shape can be obtained in the tread portion even if the flatness is small. Further, not only the rigidity in the circumferential direction is improved by the reinforcing layer, but also the rigidity in the lateral direction is improved in combination with the carcass layer where the cords cross each other, so that it is possible to achieve both exercise performance and safety in cornering traveling. As a result, it is possible to provide a pneumatic tire that can maintain a desired shape in a tire having a flattening rate of 70% or less, improve the predictability of cornering running and improve safety, and have more excellent durability than conventional tires. it can.

The reinforcing layer is provided at a central position below the tread portion in a range of 45 to 80% of the entire width of the tread portion, and on both sides having a lower tensile modulus per width than the center portion. In the case of having a portion, since the tensile modulus of the central portion of the reinforcing layer is higher than that of the side portion, a more desired shape can be maintained by reinforcing the central portion of the swelling tread surface with high rigidity.

[0015] The tensile modulus per width of the central portion is 1: 1 with respect to the tensile modulus per width of the side portion.
If it is twice or more, it becomes easier to hold the desired shape more reliably.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a partial cross-sectional view showing an example of the pneumatic tire of the present invention, and FIG.
Is a front view of a partially broken pneumatic tire, and FIG. 2B is a plan view thereof.

As shown in FIG. 1, the pneumatic tire of the present invention has two or more carcass layers 5 for reinforcing between a pair of annular beads 1a, and is provided below the tread portion Tr on the outer peripheral surface of the carcass layer 5. Provided reinforcement layer 6. In the present embodiment, an example in which the carcass layer 5 is composed of two layers will be described.

In the present invention, the flatness, which is the percentage obtained by dividing the tire section height H by the tire maximum width W, is 70%.
The present invention having the above-described functions and effects becomes more useful as the flattening rate becomes 65% or less and 60% or less. In other words, cornering performance and the like can be improved by flattening the tires while improving the predictability of cornering traveling and improving safety.

The present invention is characterized in that, as shown in FIG. 2, the cords constituting the carcass layer 5 are arranged at different angles depending on the location of the tire. Specifically, the region S from the bead 1a to the position PW near the tire maximum width W
1, the region S2 is disposed substantially in the tire radial direction (for example, θs = 90 °), and extends from the position PW to the ground end PT.
In this case, the angle with respect to the tire circumferential direction (hereinafter, referred to as a cord angle) is gradually changed.
In the tread portion Tr between T, it is arranged at a cord angle of 20 to 50 ° (for example, θt = 35 °). Preferably, the shoulder Sh has a cord angle of 20 to 50 ° and the tread Tr.
Is a cord angle of 20 to 40 °.

When the cord angle at the tread portion Tr exceeds 50 °, the carcass layer 5 at the tread portion Tr becomes in the tire radial direction R.
D becomes easy to stretch, and it becomes difficult to maintain the shape. When the cord angle at the tread portion Tr is less than 20 °, the circumferential rigidity at the tread portion Tr increases, but the rigidity in the width direction decreases, conversely, the cornering performance and the like decrease, and the bead from the ground contact end PT also decreases. It becomes difficult to gradually change the angle toward the part 1.

The lower carcass layer 5a and the upper carcass layer 5b are laminated such that the cords are arranged at substantially symmetrical angles with respect to the tire equator line CL. Carcass layer 5
Are bent outward with a bead 1a, and a bead filler 1b having a high rubber hardness is disposed between the folded portion of the carcass layer 5 and the main body to form a bead portion 1. Note that, outside the carcass layer 5, the sidewall rubber 2a, the inner liner rubber 3,
The tread rubber 4 and the like are arranged, and a predetermined pattern is formed on the outer peripheral surface of the tread rubber 4.

The reinforcing layer 6 is a layer in which cords are arranged in a tire circumferential direction (ie, a direction parallel to the tire equator line CL).
The outermost carcass layer 5b is provided at a position below the tread portion Tr on the outer peripheral surface. However, the width of the reinforcing layer 6 does not need to coincide with the width of the tread portion Tr, and has a width that exceeds the width of the normal tread portion Tr. Specifically, it is preferable that the width of the reinforcing layer 6 is 1.0 to 1.3 times the width of the tread portion Tr.

The tensile modulus per unit width of the reinforcing layer 6 is at least 1.2 times the tensile modulus (sum of each layer) of the carcass layer 5 of the tread portion Tr, preferably 1.5 to 6 times.
It is twice. When the tensile modulus exceeds 6 times, it tends to be disadvantageous in terms of workability and manufacturability. The tensile modulus per width of the reinforcing layer 6 can be adjusted by the number of cords to be driven, the thickness, the material, the structure of the fiber, and the processing conditions of the fiber. The same applies to the carcass layer 5.

The codes constituting the carcass layer 5 include:
Organic fibers such as polyester, polyamide, and polyaramid, and steel and the like are included. In addition, cords constituting the reinforcing layer 6 include organic fibers such as polyester, polyamide, and polyaramid, and steel. In the present invention, it is not necessary to provide a plurality of belt layers as in the conventional radial tire, so that the weight can be reduced. Further, since the reinforcing layer 6 reinforces the biased carcass layer 5, the bending rigidity of that portion also increases. Therefore, both cornering performance and safety can be achieved.

The reinforcing layer 6 is preferably provided at a central position below the tread portion Tr in a range T of 45 to 80% of the entire width of the tread portion Tr.
c has a central portion 6a and side portions 6b on both sides having a lower tensile modulus per width than the central portion 6a. In the present embodiment, the number of shots in the central portion 6a is
An example in which the value is larger than b is shown. The formation of the reinforcing layer 6 is usually performed by spirally winding a ribbon-shaped reinforcing layer composed of one or a small number of cords after shaping in order to eliminate breaks in the cords, but by changing the winding pitch. , The number of shots in the central portion 6a can be increased.

In the present invention, the tensile modulus per width of the central portion 6a is preferably at least 1.2 times the tensile modulus per width of the side portion 6b. More preferably, the tensile modulus per width gradually decreases from the center (the position of the tire equator line CL) to both ends of the reinforcing layer 6, and this can also be achieved by gradually increasing the winding pitch.

The pneumatic tire of the present invention is the same as a normal pneumatic tire except that the carcass plies 8a and 8b in which the cord angle is partially changed according to the position in the width direction as shown in FIG. 3 are used. It can be manufactured by the manufacturing method described above. The two carcass plies 8a and 8b are laminated in a cylindrical shape such that cords are arranged at substantially symmetrical angles with respect to the center line. For example, after disposing a bead, a tubular airbag is inserted, and the internal pressure is applied. After shaping into a donut shape, the reinforcing layer 6 is formed.

The outline of the method of manufacturing the carcass plies 8a and 8b shown in FIG. 3 is as follows. Using a device as shown in FIG. 4, the cord material 10 is taken up by the roller group 13, so that the cord material 10 is fed from the bobbin 11 while passing through the base 12 a of the extruder 12 for uncured rubber. The rubber-coated cord covered with rubber is sent between the buffer rollers 14a of the buffer unit 14 and becomes loose. The tip of the rubber-coated cord is attached by a sticking roller 16c provided on a driving unit 16b of the driving mechanism 16.
It is attached to the tray 17 along a desired route, and the length of the cord corresponding to the amount of attachment is
Will be taken over. The control of the pasting path is performed on tray 1
7, the position control of the movement in the longitudinal direction (Y direction), and the driving unit 16 that reciprocates (X direction) the support 16a of the driving mechanism 16.
This can be performed by controlling the position of the movement of b. It is convenient to perform the pasting without cutting the cord. In this case, the two pasting rollers 16 having the same axis and the same height are used.
c is used.

In the formation of the reinforcing layer 6, it is preferable that one or a small number of cords are spirally wound around the shaped article, but the shaped article is formed by using a rubber-coated cord in the same manner as described above. By moving the guide of the cord in the width direction while rotating, the cord can be spirally wound. By changing the moving speed of the guide at that time, the number of hits can be changed at a position in the width direction.

In order to obtain a desired tire shape and a desired cord angle at each part, it is preferable to appropriately adjust the cord angle when producing the carcass plies 8a and 8b. In the bias tire, the relationship between the cord angle in the ply state and the cord angle after tire molding can be calculated by the following well-known relational expression (approximate expression). In the present invention, the relational expression can be similarly applied, and Can be determined by determining R of the corresponding part using the variable as a variable.

Rd cosA = R cosAd where:
Rd is the radius of the drum, Ad is the cord angle with respect to the circumferential direction on the drum, R is the radius corresponding to the position of the cord after tire molding, and A is the cord angle with respect to the circumferential direction after tire molding.

[Other Embodiments] Hereinafter, other embodiments of the present invention will be described.

(1) In the above-described embodiment, an example in which two carcass layers are provided is shown, but an even number layer such as four layers may be used.
Even in that case, the pair of carcass layers are stacked such that the cords are arranged at substantially symmetrical angles with respect to the tire equator line, and the cords of the carcass layers stacked in the same direction are in the same direction at each part. Preferably, they are arranged.

(2) In the above-described embodiment, one reinforcing layer in the circumferential direction is provided, and the number of shots is changed at the center, whereby
Although an example in which the tensile modulus per width is increased has been described, the tensile modulus per width may be increased by using two reinforcing layers at the center. Further, the entire reinforcing layer may be two or more layers.

[Brief description of the drawings]

FIG. 1 is a partial sectional view showing an example of a pneumatic tire of the present invention.

FIG. 2 is a view showing a main part of a pneumatic tire of the present invention, wherein (a) is a front view of a partially broken pneumatic tire,
(B) is the plan view

FIG. 3 is a view showing an example of a carcass ply used in the present invention, wherein (a) is a plan view of a ply for a lower layer,
(B) is a plan view of a ply for the upper layer.

FIG. 4 is a schematic perspective view of an apparatus used for manufacturing a carcass ply.

[Explanation of symbols]

 1a Bead 5 Carcass layer 5a Lower carcass layer 5b Upper carcass layer 6 Reinforcement layer 8a Lower carcass ply 8b Upper carcass ply Tr Tread surface portion W Tire maximum width PT Ground end CL Tire equator line RD Tire radial direction

Claims (3)

[Claims] 1. An aspect ratio of 70% or less comprising: two or more carcass layers for reinforcing between a pair of annular beads; and a reinforcing layer in which cords are arranged in a tire circumferential direction on an outer peripheral surface of the carcass layer below a tread portion. In the pneumatic tire, the cord constituting the carcass layer is disposed in a substantially radial direction from the bead to a position near the tire maximum width, gradually from the position to the ground contact end with respect to the tire circumferential direction. At an angle of 20 to 60 ° with respect to the tire circumferential direction near the ground contact end, and 20 to 50 ° at the tread portion.
And the carcass layers are stacked so that the cords are arranged at an angle substantially symmetrical with respect to the tire equator, and the tensile modulus per width of the reinforcing layer is 1.2% of the carcass layer. Pneumatic tires that are more than double. 2. The reinforcing layer has a central portion disposed at a central position below the tread portion in a range of 45 to 80% of the entire width of the tread portion, and both sides having a lower tensile modulus per width than the central portion. The pneumatic tire according to claim 1, comprising: 3. The tensile modulus per width of the central portion is equal to 1.10 with respect to the tensile modulus per width of the side portion.
The pneumatic tire according to claim 2, which is at least twice as large.