JP2005088816A - Pneumatic tire and its method of manufacture - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire and its method of manufacture capable of subjecting an integer number of strips constituting a belt layer to butt joining certainly over the whole tire circumference. <P>SOLUTION: The integer number of strips S formed by drawing in alignment a plurality of steel cords and subjecting to rubber coating are spliced together in such a way that their sides are butting to one another while they are inclined with respect to the tire circumferential direction T so as to form one turn of each belt layer B, wherein the cord angle θ<SB>n</SB>should meet the formula θ<SB>n</SB>=sin<SP>-1</SP>(N<SB>n</SB>×A/[L<SB>1</SB>+(n-1)×2Gπ]), where A is the width of the strip, N<SB>n</SB>is the number of strip pieces S constituting the n'th belt layer B<SB>n</SB>(n≥1) reckoned from the innermost one of the belt layers, L<SB>n</SB>is the circumferential length of the n'th belt layer B<SB>n</SB>, θ<SB>n</SB>is the cord angle to the tire circumferential direction of the n'th belt layer B<SB>n</SB>, and G is the thickness of the belt layer B, provided that the number of pieces N<SB>n</SB>is integer. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a pneumatic tire in which a plurality of belt layers are formed from strip pieces and a method for manufacturing the same, and more specifically, to butt-join an integer number of strip pieces constituting the belt layers more securely over the entire circumference of the tire. The present invention relates to a pneumatic tire and a method for manufacturing the same.

  Generally, a belt material for forming a belt layer of a pneumatic tire is formed by bias-cutting a calendered material obtained by aligning a plurality of steel cords and covering them with rubber so that the cut ends become both edges. Obtained by splicing to. On the other hand, a belt layer of a pneumatic tire has a different belt width and cord angle depending on tire specifications. Therefore, it is necessary to prepare in advance various types of belt materials having different dimensions for each tire specification.

  As a result, the conventional tire production facility requires a wide stock space for storing various types of belt materials. In addition, since a belt material processed to a specific tire specification cannot be diverted as a belt material of another tire specification, there is a disadvantage that a surplus of the belt material is generated in the tire production process and the material is wasted. Furthermore, in the case of producing a variety of products in a small quantity, there is a disadvantage that productivity is poor because it is necessary to replace the drum around which the long belt material is wound when changing the tire specifications.

  In contrast, a large number of strip pieces formed by aligning a plurality of steel cords and covering them with rubber are spliced so that both sides abut each other while being inclined with respect to the tire circumferential direction, thereby obtaining a desired dimension. It has been proposed to form a belt layer (see, for example, Patent Document 1 and Patent Document 2). In this case, inconvenience due to the long belt material for each tire specification can be eliminated.

However, when the belt layer of a pneumatic tire is composed of a large number of strip pieces, it is desirable that the width of the strip pieces be constant, and the cord angle of the belt layer is set in advance. It is difficult to butt-join the strip pieces over the entire circumference of the tire. That is, when the strip pieces are arranged in the tire circumferential direction, the strip pieces overlap in a part of the belt layer in the circumferential direction. In addition, even if a butt joint is accidentally formed over the entire circumference of the tire in an arbitrary belt layer, the other belt layers have a different circumferential length compared to the arbitrary belt layer, and therefore, a strip is partially formed in the circumferential direction. Overlap between pieces will occur. And such overlap of strip pieces becomes a factor which worsens the uniformity of a tire.
Japanese Patent Publication No.53-11723 JP-A-11-99564

  An object of the present invention is to provide a pneumatic tire and a method for manufacturing the same that can reliably butt-join an integral number of strip pieces constituting a belt layer over the entire circumference of the tire.

In order to achieve the above object, a pneumatic tire according to the present invention is a pneumatic tire having a plurality of belt layers overlapping each other on the outer peripheral side of a carcass layer in a tread portion. An integral number of strip pieces are tilted with respect to the tire circumferential direction and joined together so that both side portions face each other to form one tire circumference of each belt layer, and the width of the strip pieces is A, Of the belt layers, the number of frames of the strip pieces constituting the nth (n ≧ 1) belt layer counted from the inner circumferential side is N _n , the circumferential length of the _nth belt layer is L _n , and the _nth belt layer When the cord angle of the belt layer with respect to the tire circumferential direction is θ _n and the thickness of each belt layer is G, the cord angle θ _n satisfies the following equation under the condition that the number of frames N _n is an integer: What to do A.

θ _n = sin ⁻¹ (N _n × A / [L ₁ + (n−1) × 2Gπ])
On the other hand, a pneumatic tire manufacturing method of the present invention for achieving the above object is a method for manufacturing a pneumatic tire having a plurality of belt layers overlapping each other on the outer peripheral side of the carcass layer in the tread portion. Forming an integral number of strip pieces formed by aligning steel cords of rubber and covering them with rubber so as to incline with respect to the tire circumferential direction so that both sides abut each other to form one circumference of each belt layer The width of the strip piece is A, the number of frames of the strip pieces constituting the n-th (n ≧ 1) belt layer counted from the inner circumference side of the belt layer is N _n , and the n-th belt The circumferential length of the layer is L _n , the cord angle of the n-th belt layer with respect to the tire circumferential direction is θ _n , the basic design value of the cord angle of the n-th belt layer with respect to the tire circumferential direction is α _n , and each bell When the thickness of the strip layer is G, when the belt layer is formed, the inclination angle of the strip piece is basically set so that the cord angle θ _n satisfies the following formula under the condition that the number of frames N _n is an integer. It is characterized by fine adjustment with respect to the design value α _n .
θ _n = sin ⁻¹ (N _n × A / [L ₁ + (n−1) × 2Gπ])

In the pneumatic tire according to the present invention, the belt layer cord angle θ _n satisfies the above equation under the condition that the number of frames N _n is an integer. Therefore, an integer number of strip pieces constituting the belt layer are surely provided over the entire circumference of the tire. It becomes possible to join the butt.

In the method for manufacturing a pneumatic tire according to the present invention, when the belt layer is formed, the inclination angle of the strip piece is a basic design value so that the cord angle θ _n satisfies the above equation under the condition that the number of frames N _n is an integer. Since fine adjustment is made with respect to α _n , it is possible to reliably butt-join the whole number of strip pieces constituting the belt layer over the entire circumference of the tire.

  According to the present invention, the advantage in the case where the belt layer is formed of strip pieces can be utilized. In other words, when the tire size is changed, it is possible to form various belt layers by using strip pieces of the same width corresponding to various sizes by changing the inclination angle, length, and number of frames of the strip pieces. It becomes possible. Therefore, the stock space for each tire specification is eliminated, no end material is generated, and a large-scale setup change operation is not required, so that high-mix low-volume production can be performed efficiently.

  In the present invention, the number of belt layers is not particularly limited, and can be, for example, 2 to 4 layers. The above relationship may be set for at least two belt layers overlapping each other, and it is not always necessary to set the above relationship for all belt layers. Of course, if the above relationship is set for all the belt layers, the effect of improving uniformity can be maximized.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows a pneumatic tire according to an embodiment of the present invention, and FIGS. 2 and 3 show an extracted belt layer. In FIG. 1, 1 is a tread portion, 2 is a sidewall portion, and 3 is a bead portion.

  As shown in FIG. 1, a carcass layer 4 is mounted between the pair of left and right bead portions 3 and 3. The carcass layer 4 is wound up around the bead core 5 embedded in each bead portion 3 from the tire inner side to the outer side. On the other hand, on the outer peripheral side of the carcass layer 4 in the tread portion 1, two belt layers B formed by arranging a plurality of steel cords and covering them with rubber are embedded so as to overlap each other.

  As shown in FIG. 2, each belt layer B has both sides facing each other while inclining an integer number of strip pieces S formed by aligning a plurality of steel cords C and covering them with rubber, with respect to the tire circumferential direction. Thus, one tire is formed by joining together. These belt layers B are arranged such that the steel cords C intersect with each other.

Here, the width of the strip piece S is A, the number of frames of the strip piece S constituting the _nth (n ≧ 1) belt layer Bn counted from the inner circumference side of the belt layer B is _Nn , and the nth When the circumferential length of the belt layer B _n is L _n , the cord angle of the n-th belt layer B _n with respect to the tire circumferential direction is θ _n , and the thickness of each belt layer B is G, the cord angle θ _n is the number of frames N _The following formula is satisfied under the condition that _n is an integer.
θ _n = sin ⁻¹ (N _n × A / [L ₁ + (n−1) × 2Gπ])

  Next, the process for forming the belt layer of the pneumatic tire will be described. FIG. 4 shows the process of forming the first belt layer, and FIG. 5 shows the process of forming the nth belt layer.

When forming the _first belt layer B ₁ , as shown in FIG. 4, an integral number of strip pieces S are joined together so that both side portions face each other while being inclined with respect to the tire circumferential direction T. Minutes. At this time, assuming that the length component in the tire circumferential direction of each strip piece S is a ₁ , a relationship of a ₁ = A / sin θ ₁ is established. Further, since the number of frames of the strip piece S is N ₁ , L ₁ = N ₁ × a ₁ . By arranging these relationships, the following equation (1) is obtained.
θ ₁ = sin ⁻¹ (N ₁ × A / L ₁ ) (1)

That is, in order to butt-join the integer number of strip pieces S over the entire circumference of the tire, the cord angle θ ₁ of the belt layer B ₁ needs to satisfy the relationship of the above expression (1). Here, when the basic design value α ₁ of the cord angle with respect to the tire circumferential direction T of the belt layer B ₁ is inconsistent with the cord angle θ ₁ required for butt joining, the strip piece S with respect to the tire circumferential direction T is determined. It is necessary to finely adjust the inclination angle from the basic design value α ₁ to achieve the relationship (1).

On the other hand, when forming the n-th belt layer B _n , as shown in FIG. 5, an integer number of strip pieces S are spliced with respect to the tire circumferential direction T and joined together so that both sides face each other. One lap. At this time, the tire circumferential length component of each strip pieces S When a _n, holds the relationship a _n = A / sinθ _n. Further, the frame number of the strip pieces S is because it is N _n, the _{L n = N n × a n} . Here, since the circumference of the _first belt layer B ₁ is L ₁ and the thickness of each belt layer B is G, L _n = L ₁ + (n−1) × 2Gπ. By arranging these relationships, the following equation (2) is obtained.
θ _n = sin ⁻¹ (N ₁ × A / [L ₁ + (n−1) × 2Gπ]) (2)

That is, in order to butt-join the integer number of strip pieces S over the entire circumference of the tire, the cord angle θ _n of the belt layer B _n needs to satisfy the relationship of the above expression (2). Here, when the basic design value α _n of the cord angle with respect to the tire circumferential direction T of the belt layer B _n does not match the cord angle θ _n required for butt joining, the strip piece S with respect to the tire circumferential direction T It is necessary to finely adjust the inclination angle from the basic design value α _n to achieve the relationship (2).

In the pneumatic tire, the circumferential lengths of the plurality of belt layers B are different from each other due to the thickness G. In the present invention, the cord angle θ _{n of the nth} belt layer B _n is finely adjusted according to the thickness G. . As a result, even when a common strip piece S having the same width A is used, it is possible to reliably butt-join an integral number of strip pieces S over the entire circumference of the tire in all belt layers B. .

In the present invention, the difference between the basic design value α _n and the cord angle θ _n is preferably 0.5 ° or less. If this difference exceeds 0.5 °, the performance of a predesigned pneumatic tire will be affected. In FIG. 4, the difference between the basic design value α ₁ and the chord angle θ ₁ is significant. In FIG. 5, the difference between the basic design value α _n and the chord angle θ _n is significant. In order to make it easy to understand the relationship with the basic design value, the angle difference is drawn excessively.

  In the present invention, the belt forming machine includes a strip supply device that continuously supplies a strip material in which a plurality of steel cords are aligned and rubber-coated, and the strip material to a predetermined length at a predetermined cutting angle. A cutting device for cutting, a conveying device for moving strip pieces cut from the strip material in the belt circumferential direction, and a splicing device for joining adjacent strip pieces can be used. Since a pneumatic tire generally has a plurality of belt layers having different inclination directions of steel cords, two belt forming machines are prepared, and these belt forming machines are arranged so that the inclination directions of the strip materials are different from each other. It is possible to form all kinds of belt layers by installing in.

  Next, a calculation procedure when actually manufacturing a pneumatic tire will be described.

Example 1
In a passenger car pneumatic tire (175 / 65R14), the width A of the common strip piece is 2π mm, the thickness G of each belt layer is 2 mm, the circumferential length L ₁ of the first belt layer is 2π × 268 mm, and the first belt layer The basic design value α ₁ of the cord angle is 20 °, and the basic design value α ₂ of the cord angle of the second belt layer is 20 °.

First, the frame number N ₁ of the strip piece S constituting the first belt layer is obtained. From α ₁ = sin ⁻¹ (N ₁ × A / L ₁ ), N ₁ = 91.66. Here, in order to satisfy the condition that the frame number N ₁ is an integer, the number is rounded up to N ₁ = 92, for example. When N ₁ = 92 and the above equation (2) is used, θ ₁ ≈20.07 ° from θ ₁ = sin ⁻¹ ([92 × 2π] / [2π × 268]). The code angle θ ₁ is a slight error with respect to the basic design value α ₁ .

Next, the same calculation as described above is performed for the second belt layer. When N ₂ = 92 and the above equation (2) is used, θ ₂ ≈19.92 ° from θ ₂ = sin ⁻¹ ([92 × 2π] / [2π × 268 + 4π]). The code angle θ ₂ is a slight error with respect to the basic design value α ₁ .

When the belt layer is formed using the common strip piece S as described above, the cord angle θ ₁ of the first belt layer is 20.07 °, and the cord angle θ ₂ of the second belt layer is 19.92 °. Thus, the strip pieces can be butt-joined over the entire circumference of the tire in the two belt layers without impairing the pre-designed tire performance.

Example 2
In a pneumatic tire for trucks and buses (1000R20), the width A of the common strip piece is 2π mm, the thickness G of each belt layer is 3 mm, the circumferential length L ₁ of the first belt layer is 2π × 480 mm, and the first belt layer The basic design value α ₁ of the cord angle is 60 °, the basic design value α ₂ of the cord angle of the second belt layer is 20 °, the basic design value α ₃ of the cord angle of the third belt layer is 20 °, and the fourth belt. The basic design value α ₄ of the code angle of the layer is set to 20 °.

First, the frame number N ₁ of the strip piece S constituting the first belt layer is obtained. From α ₁ = sin ⁻¹ (N ₁ × A / L ₁ ), N ₁ = 415.69. Here, in order to satisfy the condition that the frame number N ₁ is an integer, the number is rounded up to N ₁ = 416, for example. When N ₁ = 416 and the above equation (2) is used, θ ₁ ≈60.07 ° from θ ₁ = sin ⁻¹ ([416 × 2π] / [2π × 480]). The code angle θ ₁ is a slight error with respect to the basic design value α ₁ .

Next, the number N ₂ of frames of the strip piece S constituting the second belt layer is obtained. From α ₂ = sin ⁻¹ (N ₂ × A / [L ₁ + 2Gπ]), N ₂ = 165.19. Here, in order to satisfy the condition that the number of frames N ₂ is an integer, it is rounded up to N ₂ = 166, for example. When N ₂ = 166 and the above equation (2) is used, θ ₂ ≈20.10 ° from θ ₂ = sin ⁻¹ ([166 × 2π] / [2π × 480 + 6π]). The code angle θ ₂ is a slight error with respect to the basic design value α ₂ .

Next, the same calculation is performed for the third belt layer. As N ₃ = 166, the use of the above (2), from θ ₃ = sin ^-1 ([166 × 2 [pi] / [2π × 480 + 12π]), and θ ₃ ≒ 19.97 °. The code angle θ ₃ is a slight error with respect to the basic design value α ₃ .

Next, the same calculation is performed for the fourth belt layer. As N ₄ = 166, the use of the above (2), theta than ₄ = sin ^-1 ([166 × 2 [pi] / [2π × 480 + 18π]), and θ ₄ ≒ 19.84 °. The code angle θ ₄ is a slight error with respect to the basic design value α ₄ .

Thus, when forming a belt layer using the common strip piece S, the cord angle θ ₁ of the first belt layer is 60.07 °, the cord angle θ ₂ of the second belt layer is 20.10 °, the third belt layer cord angle theta ₃ was a 19.97 °, by the fourth belt layer cord angle theta ₄ and 19.84 °, without compromising the pre-designed tire performance, the four layer belt The strip pieces can be butt-joined around the tire circumference in the layer.

  The above embodiments are merely examples, and the present invention is not limited to the above embodiments. For example, the width A of the strip piece S can be increased or decreased arbitrarily. However, if the width A of the strip piece S is increased more than necessary, an error with respect to the intended design of the belt layer increases. On the other hand, if the belt layer is formed as designed, the width A of the strip piece S needs to be narrowed, the number of frames increases, and the productivity deteriorates. Therefore, the width A of the strip piece S is preferably 5 mm or more and 100 mm or less.

  By finely adjusting the cord angle of the belt layer as described above, the end material can be eliminated even when the belt layer is formed using the common strip piece S having the same width A. Therefore, the material can be directly supplied from the belt layer cutting device to the belt layer forming device (forming drum). Of course, the cord angle of the belt layer can be selected from a wide range as in the prior art.

  Further, even when a pneumatic tire is molded with the same mold, when the speed standard is changed from SR to HR, or from HR to VR or ZR, a reinforcement made of an organic fiber cord called a belt cover layer is used. The layer is added to the outer peripheral side of the belt layer. In this case, it is necessary to shorten the circumferential length of the belt layer by several millimeters. Even in this case, the strip piece S can be butt-joined over the entire circumference of the tire by finely adjusting the cord angle.

  In addition, when the circumference of the belt layer largely changes due to the difference in size, it can be dealt with by changing the number of frames of the strip piece S, and further, the circumference difference between a plurality of belt layers can be dealt with by adjusting the angle of the strip piece S. It ’s fine.

  As described above, according to the present invention, in a pneumatic tire having a plurality of belt layers overlapping each other on the outer peripheral side of the carcass layer in the tread portion, an integer formed by aligning a plurality of steel cords and covering them with rubber The strip pieces are slanted with respect to the tire circumferential direction and joined together so that both side portions face each other to form one tire circumference of each belt layer, and the cord angle in consideration of the thickness of these belt layers Therefore, it is possible to reliably butt-join an integral number of strip pieces constituting the belt layer over the entire circumference of the tire. Accordingly, various belt layers can be formed by using strip pieces having the same width, and high-mix low-volume production can be performed efficiently.

It is meridian sectional drawing which shows the pneumatic tire which consists of embodiment of this invention. It is a top view which extracts and shows the belt layer of the pneumatic tire which consists of an embodiment of the present invention. It is sectional drawing which extracts and shows the belt layer of the pneumatic tire which consists of embodiment of this invention. It is a top view which shows the formation process of the 1st belt layer in this invention. It is a top view which shows the formation process of the nth belt layer in this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 5 Bead core B Belt layer B ₁ 1st belt layer B ₂ 2nd belt layer C Steel cord S Strip piece

Claims (2)

In a pneumatic tire having a plurality of belt layers overlapping each other on the outer peripheral side of the carcass layer in the tread portion, an integer number of strip pieces formed by aligning a plurality of steel cords and covering them with rubber are arranged in the tire circumferential direction. The belt layers are joined together so that both side portions face each other while being inclined, and each belt layer constitutes one round of the tire. The width of the strip piece is A, and the nth (n ≧ 1) The number of strip pieces constituting the belt layer is N _n , the circumferential length of the n-th belt layer is L _n , the cord angle of the n-th belt layer with respect to the tire circumferential direction is θ _n , and each belt A pneumatic tire that satisfies the following formula under the condition that the cord angle θ _n is an integer of the number of frames N _n when the layer thickness is G.
θ _n = sin ⁻¹ (N _n × A / [L ₁ + (n−1) × 2Gπ]) In a method of manufacturing a pneumatic tire having a plurality of belt layers overlapping each other on the outer periphery side of a carcass layer in a tread portion, an integer number of strip pieces formed by aligning a plurality of steel cords and covering them with rubber A step of forming the circumference of the tire of each belt layer by joining together so that both side portions face each other while being inclined with respect to the direction, and the width of the strip piece is A, the inner circumference side of the belt layer n th the number of frames of the strip pieces composing the belt layer _(n ≧ 1) n n, encoding the circumference of the n-th belt layer L _n, with respect to the tire circumferential direction of the n-th belt layer counted from When the angle is θ _n , the basic design value of the cord angle with respect to the tire circumferential direction of the n-th belt layer is α _n , and the thickness of each belt layer is G, the cord angle is formed when the belt layer is formed. A manufacturing method of a pneumatic tire, wherein the inclination angle of the strip piece is finely adjusted with respect to the basic design value α _n so that θ _n satisfies the following expression under the condition that the number of frames N _n is an integer.
θ _n = sin ⁻¹ (N _n × A / [L ₁ + (n−1) × 2Gπ])

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