JP2007245886A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of making ease of rim assembling compatible with fitting after the rim assembling. <P>SOLUTION: A bead core 20 is formed by a steel filament 28 having the optimum amplitude A and pitch P. When it is assembled to the rim 30, since the bead core 20 is elongated within an elasticity limit and easily overrides a hump 36 when a bead part 18 overrides the hump 36, the rim assembling workability is sufficient. Further, after it overrides the hump, since the bead core 20 is returned to an original state, compression deformation of a rubber just below the bead core can be properly retained and it can ensure the fitting property with the rim 30. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire that can achieve both ease of rim assembly and fit after rim assembly.

  In a vehicle wheel, the fitting between the pneumatic tire and the rim is very important. Naturally, the air sealability of the tire is impaired by the state of fitting with the rim, and the response at the minute steering angle, the performance at the limit, and the generation of relatively low-order (primary and secondary) vibration modes It is known that the ride performance associated with the vehicle will be affected, and the tire and automobile industries are struggling to devise how to obtain a uniform fit.

  The fitting of the pneumatic tire to the rim is performed by the bead portion tightening the rim. The ideal fit is to have sufficient concentricity with the rim and deformation of the member below the bead core (inward in the radial direction). The inner circumference of the bead portion is set to be smaller than the outer circumference of the rim, and when the tire is fitted, the tire expands as the air is filled, and the slope of the bottom of the rim slides up to the rim flange side while the bead portion is crushed. The air seal and the tire positioning are performed.

Therefore, first, the bead core is required to have sufficient rigidity so as not to bend the inner circumference accuracy. Further, in the fitting, the rim flange and the back of the bead are in close contact with each other without any gap, and vibration and force must be accurately transmitted between the tire, the rim, the shock absorber of the vehicle, and the handle.
There is a considerable frequency in which a gap is formed between the rim flange and the back of the bead when the tire is fitted to the rim. There are various causes: (1) The lubricant at the time of assembling the rim is partially caught, and (2) there is a problem in the inner circumference setting of the bead, and the rim flange has not been slid up.
The examples of (1) and (2) are examples in which there is a defect and as a result, the fitting is poor, but there is a case where there is a problem in fitting even if an appropriate tire is secured with an appropriate tire. .

In a normal rim assembly, the part corresponding to the half circumference of the tire is set on the rim flange, and the remaining half circumference is over the rim hump. When the hump is passed over, deformation on the stretch side of the rubber, carcass ply, and bead core occurs directly under the bead core, or the stretch deformation from both sides concentrates on the last part over the hump. One turn, compression side deformation will occur. Compression deformation displaces the bead portion in three directions as a possibility. The three directions are (1) lifting the bead upward, (2) bending the bead to the inside of the tire, and (3) bending the bead to the outside of the tire.
Of these, (3) is generated as a force, but is less likely to occur due to the ease of bending from the bead core shape (cross section) and the presence of a rim flange in the bent direction. 1) + (2) deformation occurs.

Usually, a bead core is formed by covering a straight piano wire (steel filament) with a tensile strength of about 1400-3500 N / mm ² with rubber and bundling it into a circle. When getting over rim hump, it is necessary to apply great force. In addition, there is a limit to increasing the bead diameter from the viewpoint of air sealability after assembling the rim and occurrence of slip between the tire and the rim, and the current situation is that the optimum point is set among the contradicting characteristics .

  Normally, the bead core is stretched when the bead core gets over the hump. Regarding the elongation, the rubber directly under the bead is first deformed, and then the steel filament is elongated. Conventionally, the bead core is such that the steel filament itself is stretched and partially extends to the plastic region. In the bead core extended to the plastic region, the portion where the bead portion fits the bead sheet becomes excessive (= not returned to the original length), and the above-mentioned poor fitting is caused.

As a conventional technique, there is a method of increasing a rubber gauge directly under a bead core that is deformed first. According to this technology, the fit will certainly improve, but due to the nature of the material rubber, there are problems such as deterioration of fit due to deterioration over time and peeling off the rubber with a lever when repairing a tire. Only employed (see Patent Document 1)
JP 2004-359196 A

  In view of the above fact, an object of the present invention is to provide a pneumatic tire capable of achieving both ease of rim assembly and fit after rim assembly.

  The invention according to claim 1 is a pneumatic tire including a bead core formed by winding a steel filament a plurality of times, wherein the steel filament has an amplitude.

Next, the operation of the pneumatic tire according to claim 1 will be described.
In the pneumatic tire according to claim 1, since the bead core has an amplitude, that is, is formed of a plurality of bent steel filaments, it is necessary to increase the bead core elongation in a region where stress is not large and to get over the hump. Elongation (within the elastic limit) can be ensured, the elongation of the bead core can be prevented from reaching the plastic region, and the compression deformation of the rubber immediately below the bead core after overcoming the hump can be optimally ensured. In other words, a bead core formed of a steel filament having an amplitude has an elongation (within the elastic limit) compared to a straight steel filament by an amount corresponding to the amplitude and pitch, and when the elongation passes over the hump of the rim. Works in the direction to return to the original, can secure the fit with the rim.

  According to a second aspect of the present invention, in the pneumatic tire according to the first aspect, an amplitude direction of the steel filament is a tire axial direction.

Next, the operation of the pneumatic tire according to claim 2 will be described.
By making the amplitude direction of the steel filament the tire axial direction, the bead core can be easily manufactured.

  The invention according to claim 3 is the pneumatic tire according to claim 1 or 2, wherein the steel filament has an amplitude in a range of 0.3 to 3.0 mm and a pitch of 5 to 200 times the amplitude. It is in the range of.

Next, the operation of the pneumatic tire according to claim 3 will be described.
By setting the amplitude of the steel filament within the range of 0.3 to 3.0 mm and the pitch within the range of 5 to 200 times the amplitude, it is possible to give the optimum elastic range to the bead core and fit after assembling the rim. Can also be secured.

If the amplitude of the steel filament is less than 0.3 mm, the amplitude is too small to ensure a necessary elastic region (elongation necessary for the rim assembly). On the other hand, when the amplitude of the steel filament exceeds 3.0 mm, the amplitude is too large, the tensile rigidity of the bead core is too low, and the fit property is lowered.
On the other hand, if the pitch of the steel filament is less than 5 times the amplitude, the pitch is too fine, the tensile rigidity of the bead core is too low, and the fit is reduced. On the other hand, when the pitch of the steel filament exceeds 200 times the amplitude, the pitch is too large to secure a necessary elastic region (elongation necessary for the rim assembly).

  According to a fourth aspect of the present invention, in the pneumatic tire according to any one of the first to third aspects, the steel filament is covered with rubber at the periphery.

Next, the operation of the pneumatic tire according to claim 4 will be described.
Since the periphery of the steel filament is covered with rubber, the unevenness of the amplitude of the steel filament is gently filled with the rubber, and it becomes easy to ensure adhesion to the ply. Moreover, like a general tire, the rust of the steel filament is prevented, and the steel filament is resistant to rubbing.

  According to a fifth aspect of the present invention, in the pneumatic tire according to any one of the first to fourth aspects, the bead core has a circular shape when viewed from the axial direction.

Next, the operation of the pneumatic tire according to claim 5 will be described.
Since the shape of the bead core when viewed from the axial direction is circular, the roundness of the inner circumference can be secured, and the tire that has a small absolute volume of the material constituting the bead core (to make the bead shape by filling the amplitude) However, the accuracy on the inner circumference side is relatively easy to obtain. Even if the elongation can be secured, it is impossible to achieve an overall advantage compared to conventional products unless the roundness is absolutely obtained.

  A sixth aspect of the present invention is the pneumatic tire according to any one of the first to fourth aspects, wherein the bead core has a polygonal shape when viewed from the axial direction. .

Next, the operation of the pneumatic tire according to claim 6 will be described.
Since the shape of the bead core viewed from the axial direction is a polygon, the bead core is elastically deformed until the linear side of the polygon becomes an arc, and the bead core is easily stretched when the diameter of the bead core is increased.

  A seventh aspect of the present invention is the pneumatic tire according to any one of the first to sixth aspects, wherein the pneumatic tire is for a motorcycle.

  A two-wheeled vehicle has few objects interposed between the rider and the tire, and the behavior of the tire is easily transmitted directly to the rider. In particular, since there are no cushioning parts in the steering angle direction of the steering wheel, force fluctuations due to poor fitting are directly transmitted. Therefore, it is effective to apply the present invention to a pneumatic tire for a motorcycle.

  As described above, according to the pneumatic tire of the present invention, there is an excellent effect that both ease of rim assembly and fit after rim assembly can be achieved.

Next, an embodiment of the present invention will be described with reference to FIGS.
As shown in FIG. 1, the pneumatic tire 10 of the present embodiment is for a two-wheeled vehicle, and a first carcass ply 12 and a second carcass ply in which cords extending in a direction intersecting the tire equatorial plane CL are embedded. A carcass 16 composed of 14 is provided. In FIG. 1, reference numeral 30 denotes a rim for mounting the pneumatic tire 10 of the present embodiment, reference numeral 32 denotes a bead seat, reference numeral 34 denotes a rim flange, reference numeral 36 denotes a hump, and reference numeral 38 denotes a well portion.

Both ends of the first carcass ply 12 and the second carcass ply 14 are wound around the bead core 20 embedded in the bead portion 18 from the tire inner side toward the outer side.
A belt layer 22 is provided outside the carcass 16 in the tire radial direction. The cord of the belt layer 22 is, for example, an organic fiber cord or a steel cord. A tread 26 made of thick rubber is disposed outside the belt layer 22 in the tire radial direction.

As shown in FIGS. 2 (A) and 2 (B), the bead core 20 is formed by corrugated steel filaments 28 covered with rubber 32 in a longitudinal (tire radial direction) and lateral (tire axial direction). In addition, it is wound a plurality of times so as to form a row, and is formed in a circular shape when viewed from the axial direction. The wave shape may be a zigzag shape as shown in FIG. 2A or another shape such as a sine wave shape. Moreover, conventionally well-known shapes, such as circular and a polygon, can be used for the cross-sectional shape of the bead core 20. FIG.
In the bead core 20 of the present embodiment, the steel filament 28 has an amplitude in the tire axial direction over the entire circumference. The steel filament 28 has an amplitude A set within a range of 0.3 to 3.0 mm, and a pitch (in the case of a corrugated shape, a distance from a mountain to a valley; see FIG. 2A). It is preferable to set within a range of up to 200 times. The steel filament 28 of this embodiment uses a diameter φ1.00 mm. The bead core 20 of this embodiment is different from the conventional one only in the shape of the steel filament 28, and the manufacturing method is the same as the conventional one.

(Function)
In the pneumatic tire 10 of the present embodiment, since the bead core 20 is formed of the steel filament 28 having the optimal amplitude A and pitch P, when the bead portion 18 gets over the hump 36 when assembled to the rim 30. Since the bead core 20 extends within the elastic limit and easily gets over the hump 36, the rim assembly workability is good. That is, the bead core 20 has an elastic region until the amplitude A of the corrugated steel filament 28 becomes zero. In addition, since the bead core 20 returns to the original state after overcoming the hump, the compression deformation of the rubber directly under the bead core can be appropriately maintained, and the fit with the rim 30 can be secured.

  Since the two-wheeled vehicle has few objects interposed between the rider and the pneumatic tire 10 and the behavior of the pneumatic tire 10 is easily transmitted directly to the rider, the pneumatic tire 10 of the present embodiment having good fit to the rim 30 is provided. It is preferable to wear.

  In this embodiment, since the amplitude A of the steel filament 28 is the tire axial direction, the bead core 20 can be easily manufactured.

  Since the circumference of the steel filament 28 is covered with the rubber 32, the rubber 32 gently fills the unevenness of the amplitude A of the steel filament 28, and it becomes easy to ensure adhesion to the carcass ply. Further, like the general tire, the rust of the steel filaments 28 is prevented, the steel filaments 28 are resistant to rubbing, and the durability is excellent.

  Since the shape of the bead core 20 when viewed from the axial direction is circular, the roundness of the inner circumference can be ensured, and the accuracy on the inner circumference side is relatively easy even if the rubber 32 constituting the bead core 20 is small. Even if the elongation can be ensured, it cannot be advantageous in comparison with the conventional products unless the roundness is absolutely obtained.

  By setting the amplitude A of the steel filament 28 within a range of 0.3 to 3.0 mm and the pitch P within a range of 5 to 200 times the amplitude A, an optimum elastic range can be given to the bead core 20, and Fit after rim assembly can be secured.

  If the amplitude A of the steel filament 28 is less than 0.3 mm, the amplitude A is too small to secure a necessary elastic region (elongation required for the rim assembly). On the other hand, when the amplitude A of the steel filament 28 exceeds 3.0 mm, the amplitude A is too large, the tensile rigidity of the bead core 20 is excessively decreased, and the fit property is deteriorated. If the pitch P of the steel filament 28 is less than 5 times the amplitude A, the pitch P is too fine, the tensile rigidity of the bead core 20 is too low, and the fit property is low. On the other hand, if the pitch P of the steel filament 28 exceeds 200 times the amplitude A, the pitch P is too large to secure a necessary elastic region (elongation necessary for the rim assembly).

[Other Embodiments]
In the above embodiment, the amplitude A of the steel filament 28 is the tire axial direction, but the present invention is not limited to this, and the amplitude A may be a direction different from the tire axial direction, such as the tire radial direction.
In the said embodiment, although the example which applied this invention to the pneumatic tire for two-wheeled vehicles was shown, it is needless to say that it is applicable to the pneumatic tire of other uses, such as for four wheels.

  In the above embodiment, the shape of the bead core 20 as viewed from the axial direction is circular, but may be polygonal as shown in FIG. The bead core 20 having a polygonal shape when viewed from the axial direction is such that the shape of the inner steel filament 28 is also a polygon, and the elastic deformation region of the bead core 20 until the polygonal linear side becomes an arc. Thus, like the above-described embodiment, the bead core 20 is easily stretched when the diameter is increased. Such a polygonal bead core 20 can be manufactured by forming the bead core 20 in a circular shape as usual and then brazing it into the polygon.

(Test example)
In order to confirm the effect of the present invention, a pneumatic tire having a conventional structure and a pneumatic tire to which the present invention was applied were prepared and subjected to various evaluations.
The structure of the test tire will be described below.
・ Conventional pneumatic tire: Bead core steel filament is straight.
-Example 1 structure (refer FIG. 2): The amplitude A of a steel filament is a tire radial direction. The amplitude A is 0.48 mm, the pitch P is 140 mm, and the bead inner diameter is 1370 mm. The bead core has a circular cross-sectional shape.
Example 2 structure (see FIG. 3): The amplitude A of the steel filament is the tire radial direction. The amplitude A is 0.48 mm, the pitch P is 105 mm, and the bead inner diameter is 1366 mm. The bead core has a circular cross-sectional shape.
Example 3 Structure: The shape of the bead core (steel filament) viewed from the axial direction is a polygon. The amplitude A is 1.0 mm, the pitch P is 120 mm, and the bead inner diameter is 1370 mm.

Next, a test method and an evaluation method will be described.
・ Rim flange clearance measurement: Rim assembly is performed as usual, and then the clearance between the back of the bead and the rim flange is measured. The measured value shows the maximum value.
・ Tire runout: Rotate the tires assembled on the rim and measure the runout around the tire. The evaluation is represented by an index with the reciprocal of the measured value of the conventional example being 100, and the larger the index, the smaller the fluctuation.
・ Uniformity: RFV is measured with a uniformity machine. The index is displayed with the reciprocal of the measured value of the conventional example as 100, and the larger the index, the better the uniformity.
-Riding comfort: Sensory evaluation of test riders when running with tires mounted on a real vehicle (1000cc road motorcycle). The evaluation is an index display with the conventional example being 100, and the larger the index, the better the riding comfort.
-Maneuverability: Sensory evaluation of specialized riders when driving with tires attached to the actual vehicle. The evaluation is an index display with the conventional example being 100, and the larger the index, the better the maneuverability.
The evaluation results are as shown in Tables 1 and 2 below.

試験の結果、実施例の構造を用いたタイヤは、全ての項目について従来構造のタイヤよりも優れていることが分かった。

As a result of the test, it was found that the tire using the structure of the example is superior to the tire of the conventional structure in all items.

It is sectional drawing of a pneumatic tire and a rim. (A) is the side view which looked at the bead core from the tire radial direction, (B) is a sectional view (only an outline is shown) of the bead core. (A) is the side view which looked at the bead core of Example 2 structure from the tire radial direction, and (B) is a sectional view (only an outline is shown) of a bead core. (A) is the side view which looked at the bead core of Example 3 structure from the tire radial direction, and (B) is a sectional view (only an outline is shown) of a bead core.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Pneumatic tire 12 1st carcass ply 14 2nd carcass ply 18 Bead part 20 Bead core 28 Steel filament 32 Rubber

Claims (7)

A pneumatic tire having a bead core formed by winding a steel filament multiple times,
A pneumatic tire characterized in that the steel filament has an amplitude.   The pneumatic tire according to claim 1, wherein an amplitude direction of the steel filament is a tire axial direction.   The pneumatic tire according to claim 1 or 2, wherein the steel filament has an amplitude in a range of 0.3 to 3.0 mm and a pitch in a range of 5 to 200 times the amplitude. .   The pneumatic tire according to any one of claims 1 to 3, wherein the steel filament is covered with rubber at a periphery thereof.   The pneumatic tire according to any one of claims 1 to 4, wherein the bead core has a circular shape when viewed from the axial direction.   The pneumatic tire according to any one of claims 1 to 4, wherein the bead core has a polygonal shape when viewed from the axial direction.   The pneumatic tire according to any one of claims 1 to 6, wherein the pneumatic tire is used for a motorcycle.

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