JP2544553B2 - Radial tire - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radial tire capable of relieving push-up to a vehicle when riding over a protrusion.

[0002]

2. Description of the Related Art As the road network is improved and the performance of vehicles is improved, tires are required to have high steering stability and high-speed driving performance. In recent years, a strong belt layer has been used on the outside of a radial array carcass. Tightened flat radial tires are often used.

By flattening the tire, the tire lateral rigidity as well as the tread in-plane rigidity can be greatly increased, the straight running performance and the turning performance can be improved, and the rolling resistance can be reduced and the ground contact width can be expanded. It depends.

However, in such a flat radial tire, while the running performance is improved, the height of the tire cross section is reduced due to the flatness, which causes the inner surface of the tread and the rim sheet to come close to each other.

As a result, when an excessive load f impacts the tread surface, such as when riding over a large projection on the road surface, the tire t is largely deflected, and the tread portion a as shown in FIG. The so-called rim touch in which the swelling adheres to the bead portion b is likely to occur. This rim touch is
Since the load is directly transmitted to the rim r, a large push-up force acts on the vehicle, and as a result, the durability of the vehicle is significantly impaired, resulting in serious adverse effects.

Therefore, in order to suppress the occurrence of such a rim touch, conventionally, for example, the carcass case is strengthened, or the gauge thickness from the bead portion to the sidewall portion is increased to increase the vertical spring constant of the tire. Deformation is being reduced.

[0007]

However, such reinforcing means by increasing the volume not only lowers the riding comfort, but also reduces the flexing margin leading to a rim touch, thereby achieving a sufficiently satisfactory effect. It's hard to do.

A part of a double structure type in which an inner tire is further provided in the tire inner cavity has been proposed, but this structure causes a large increase in tire weight and impairs fuel efficiency. In addition, durability will be reduced.

Therefore, in view of such a situation, the present inventor has considered
Sincere research has been conducted on the suppression of rim touch.

As a result, as shown in the relationship between the flexure amount K of the tire and the load f in FIG. 7, the tire increases the flexure amount K as the load f increases, the flexure amount reaches KO, and a rim touch occurs. Up to the load-deflection curve and the area surrounded by the x-axis (shown by diagonal lines), the load energy S is accumulated in the tire. Therefore, the greater the load energy S leading up to the rim touch, the more the impact force can be absorbed, and the more effective suppression of the occurrence of the rim touch and the alleviation of the thrust force to the vehicle when the rim touch occurs. . It has been found that, for that purpose, it is necessary to increase both the flexure amount KO up to the rim touch and the proof stress against the load f.

That is, the present invention can increase the load energy leading to the rim touch without impairing the durability, riding comfort, steering stability, etc. by specifying the cross-sectional shape of the tire skin, and solve the above problems. The purpose is to provide a possible radial tire.

[0012]

In order to achieve the above object, a radial tire of the present invention has a carcass folded around a bead core of a bead portion from a tread portion to a sidewall portion, and a radius of the carcass. A radial tire comprising a belt layer arranged on the outside in the direction and on the inside of the tread portion, the rim of the regular rim being mounted on the regular rim and having a regular internal pressure filled with a regular internal pressure in a meridional section of the tire. The reference line X in the tire radial direction passing through the bead heel point PO where the flange inner surface and the rim seat surface intersect is the thickness of the bead portion in the normal direction of the bead inner surface point P1 at the bead inner surface point P1 that intersects the inner surface of the bead portion. The distance h in the tire radial direction from the upper end of the rim flange to the tire equatorial point C where the outer surface of the tread portion intersects with the tire equatorial surface for a certain bead thickness F. A ratio F / h is 0.092 or less, and a normal line of the tread inner surface point P2 at a middle point Q1 of the bead thickness F and a tread inner surface point P2 where the reference line X intersects the inner surface of the tread portion. The radius of curvature R of the arc L passing through the thickness midpoint Q2 of the tread thickness H, which is the thickness of the tread portion in the direction, and the thickness midpoint Q3 of the thickness of the sidewall portion at the tire maximum width position, Ratio of the distance h R / h
Is set to 0.77 or more.

[0013]

In the radial tire of the present invention thus constructed, the ratio F / h between the distance h in the tire radial direction from the upper end of the rim flange to the tire equator point C and the bead thickness F at the bead inner surface point P1 is calculated. It is set to 0.092 or less, which is smaller than that of conventional tires. The conventional tire has a ratio F / h of about 0.110 or more. By reducing the ratio F / h in this way, it becomes possible to increase the bending margin of the tire leading to the rim touch. In addition, the radius of curvature R of the arc L passing through the thickness midpoint Q1 of the bead thickness F, the thickness midpoint Q2 of the tread thickness H, and the thickness midpoint Q3 of the sidewall portion at the maximum tire width position. The distance h is 0.77 times or more, which is higher than that of the conventional tire.
As a result, the degree of curvature of the sidewall portion can be reduced, and the amount of protrusion of the sidewall portion from the reference line X to the outside in the tire axial direction can be reduced. As a result, in the lower region portion below the tire maximum width position, the component force of the tire radial component of the axial force of the lower region portion increases,
It is possible to effectively increase the vertical spring constant of the tire without increasing the gauge thickness of the outer cover of the tire, that is, reducing the bending margin. As a result of these synergistic effects, the load energy of the tire can be greatly improved, as shown by the chain line in FIG. 7, without compromising durability, riding comfort, steering stability, etc. It can enhance sex.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a meridian cross section of a tire mounted on a regular rim Ra and filled with a regular internal pressure in a regular internal pressure state.

In the figure, a radial tire 1 includes a tread portion 2, sidewall portions 3 extending inward in the tire radial direction from both ends thereof, a tire radial inner end of each sidewall portion 3 and reinforcement by a bead core 5. And the bead portion 4 formed.

A tread portion 2 is provided between the bead portions 4 and 4.
The carcass 6 is folded around the bead core 5 from the inside of the tire to the outside through the sidewall part 3 and the belt layer 9 is provided outside the carcass 6 in the tire radial direction and inside the tread part 2. It is wound in the circumferential direction.

In this example, the carcass 6 includes two carcass plies 6a, an inner and outer carcass ply, in which carcass cords are arranged at an angle of 75 degrees or more and 90 degrees or less with respect to the tire equatorial plane CO.
6b, the folded end of the inner carcass ply 6a covers the folded end of the outer carcass ply 6b and is interrupted near the tire maximum width position. Also, the main body portion 6A of the carcass 6
A hard bead apex rubber 8 that extends in a tapered shape from the bead core 5 toward the outer side in the tire radial direction is arranged between the and the folded portion 6B.

As the carcass cord, organic fiber cords such as nylon, polyester and rayon are preferably used, and the carcass cords are arranged so that the plies cross each other. A metal fiber cord such as steel may be used as the carcass cord depending on the required tire performance.

The belt layer 9 is composed of two inner and outer belt plies 9a and 9b, and the ply width of the inner belt ply 9a in the tire axial direction is set to be larger than that of the outer belt ply 9b.

Further, the belt layer 9 has a maximum ply width, that is, a belt width which is the ply width of the inner belt ply 9a in this example, is 0.8 times or more the tread width TW, whereby almost all of the tread portion 2 is formed. The entire width is reinforced by the hoop effect and, in this example, the tire is restrained with a high flatness of 0.7 or less. The flatness ratio is indicated by the ratio H / W of the tire cross-section height H to the tire width W.

The belt plies 9a and 9b have belt cords arranged at an angle of 0 to 30 degrees with respect to the tire equatorial plane CO. The belt cords include steel cords and aromatic polyamide cords. Highly elastic material is used.

Further, in the present invention, the cross-sectional shape of the tire outer cover in the normal internal pressure state is specified.

That is, as shown in FIG.
When a vertical reference line X passing through the bead heel point PO in the tire radial direction is provided, the bead inner surface point P1 at the bead inner surface point P1 where the reference line X intersects with the inner surface of the bead portion 4 is provided.
A bead thickness F which is the thickness of the bead portion 4 in the normal direction of
The ratio F / h to the distance h in the tire radial direction from the upper end of the rim flange Ra1 to the tire equator point C is 0.092 or less. Moreover, in this example, the reference line X is the tread portion 2
Of the tread thickness H which is the thickness of the tread portion 2 in the normal direction of the tread inner surface point P2 intersecting the inner surface of the tread and the bead thickness F and the distance h to the thickness F + H The ratio (F + H) / h is 0.21 or less.

The bead heel point PO means the intersection where the inner surface of the rim Ra1 of the rim Ra and the upper surface of the rim seat Ra2 intersect, and the tire equator point C is on the tire equator line where the outer surface of the tread portion 2 intersects the tire equator surface CO. Is the point.

Here, in the tire 1, as shown schematically in FIG. 2, when an impact load f acts on the tread portion 2, both the bead portion 4 and the side wall portion 3 are deformed, and the tread on the rim flange Ra1. A rim touch occurs when the inner surface point P2 collides with the bead inner surface point P1. Therefore, the upper end of the rim flange Ra1 means a reference height position when a rim touch occurs, and the ratio of the bead thickness F to the distance h which is the tire height from the upper end of the rim flange Ra1, that is, the ratio F / h is smaller than the conventional 0.
By setting it to 092 or less, the amount of deflection in tires of the same size can be increased.

The tire size shown in FIG. 3 is 185/60.
The relationship between the ratio F / h and the load energy at R14 is shown, and the load energy of the tire of the present invention is 5
The load energy of the conventional tire is as low as 44.3 kgfm or less as compared with 1.6 kgfm or more, and it can be seen that the rim touch occurs relatively early in the conventional tire.

However, even if the ratio F / h is reduced, the load energy cannot be sufficiently increased when the tread thickness H increases, and therefore the effect of the ratio F / h is obtained in this example. Ratio (F + H)
/ H is 0.21 or less. In the conventional tire, the ratio (F + H) / h is about 0.24 or more.

In the present invention, the midpoint Q1 of the bead thickness F and the midpoint Q of the tread thickness H are further added.
2 and the ratio R / h of the distance h to the radius of curvature R of the arc L passing through the thickness middle point Q3 of the thickness of the sidewall portion 3 at the tire maximum width position M is 0.77 or more.

By setting the ratio R / h to 0.77 or more, the degree of curvature of the sidewall portion 3 can be reduced and the amount of the sidewall portion 3 overhanging from the reference line X can be reduced. As a result, as shown in FIG. 5, the component force Gx of the tire radial component of the axial force G of the lower region portion RT below the maximum tire width position M is increased, and the vertical spring of the tire is increased. The constant can be increased and the proof stress against the impact load f can be improved.

In FIG. 4, the tire size is 185 / 60R.
The relationship between the ratio R / h and the load energy at the time of 14 is shown. In the tire of the present invention, the longitudinal spring constant index increases, while in the conventional tire the load energy is 45 kgfm, whereas in the present invention, 50 kgfm. The above load energy index can be obtained.

As described above, according to the present invention, the improvement of the proof stress and the increase of the deflection amount can be independently achieved by specifying the tire cross-sectional shape. Therefore, as shown by the one-dot chain line in FIG. 7, the tire accumulates and absorbs. The load energy that can be applied can be greatly increased, and the rim touch resistance and the effect of alleviating the thrust force to the vehicle when a rim touch occurs can be improved.

The ratio F / h and the ratio (F + H) / h
Are preferably 0.080 or more and 0.18 or more, respectively, and the ratio F / h and the ratio (F + H) / h are respectively 0.
When it is less than 080 and 0.18, the bead thickness F and the tread thickness H become too small, which makes it difficult to maintain the tire rigidity, impairing the tire durability and, conversely, inducing a rim touch.

The ratio R / h is preferably 0.79 or less. When the ratio R / h is more than 0.79, the riding comfort is impaired, the tire lateral rigidity is reduced, and the steering stability is reduced. To do.

Further, in this example, the bead portion 4 is provided with a bead filler 10 made of steel cords arranged in a direction intersecting with the carcass cord at an angle of 20 to 70 degrees. In this example, the bead filler 10 has a base piece 10A extending along the outer surface of the folded portion 6B of the carcass 6, and the bottom end 10A has a bottom piece 10B at the lower end thereof.
An inner piece 10C extending along the main body 6A is provided.
Further, the upper end of the base piece 10A extends outward in the radial direction of the tire beyond the normal line at the bead inner surface point P1, thereby reinforcing the bead portion 4 and increasing the vertical spring constant.

(Specific Example) A tire having a tire structure of 185 / 60R14 having the tire structure shown in FIG. 1 was prototyped based on the specifications shown in Table 1, and the load energy leading to the rim touch of the tire, steering stability, and riding comfort were obtained. And the rolling resistance was compared with the conventional product and the comparative example product.

[0036]

[Table 1]

The load energy is 14 × 5 1/2 in size.
The value when mounted on the JJ rim R and filled with an internal pressure of 2.0 kc is represented by an index with the conventional tire as 100.
The rolling resistance is an index of rolling resistance when a load of 350 kg is applied to the tire and the tire is rolled at a constant speed of 80 km / h, with the conventional tire being 100, and the steering stability is also stable. And ride comfort are evaluated based on the driver's feeling when the vehicle actually travels.

[0038]

Since the radial tire of the present invention is constructed as described above, the rim touch resistance of the tire can be greatly improved without impairing riding comfort, steering stability and the like.

[Brief description of drawings]

FIG. 1 is a meridional sectional view of a tire showing an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing a flexed state of a tire.

FIG. 3 is a diagram showing a relationship between a ratio F / h and load energy.

FIG. 4 is a diagram showing a relationship between a ratio R / h and load energy.

FIG. 5 is a schematic diagram illustrating the action of the ratio R / h.

FIG. 6 is a schematic cross-sectional view of a tire for explaining a rim touch.

FIG. 7 is a diagram showing a load-deflection curve of a tire before a rim touch.

[Explanation of symbols]

 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 9 Belt layer Ra Regular rim Ra1 Rim flange Ra2 Rim sheet

Continuation of the front page (56) Reference JP-A-3-169709 (JP, A) JP-A-63-199102 (JP, A) JP-A-56-60701 (JP, A) JP-A-54-40406 (JP , A) JP 59-48204 (JP, A) JP 58-161603 (JP, A) JP 64-9007 (JP, A) JP 1-309805 (JP, A) JP 60-8102 (JP, A) JP-A-3-79404 (JP, A) JP-A-1-114501 (JP, A) JP-A-63-154402 (JP, A) JP-A-1-202502 (JP, A) A) JP-A-57-47203 (JP, A)

Claims (1)

(57) [Claims] 1. A radial tire comprising a carcass folded back from a tread portion to a sidewall portion around a bead core of a bead portion, and a belt layer arranged radially outside the carcass and inside the tread portion. Then, in a tire meridional section of a normal internal pressure state where the tire is attached to the normal rim and filled with a normal value of internal pressure, a tire radial reference line passing through a bead heel point PO at which the rim flange inner surface of the normal rim and the rim seat surface intersect. The outer surface of the tread portion from the upper end of the rim flange is the tire equatorial plane with respect to the bead thickness F which is the thickness of the bead portion in the normal direction of the bead inner surface point P1 at the bead inner surface point P1 where X intersects the inner surface of the bead portion. The ratio F / h of the distance h in the tire radial direction to the tire equator point C that intersects with 0.09 or less, and the thickness midpoint Q1 of the bead thickness F, The tread inner surface point P2 in serial reference line X is the tread portion tread inner surface point P2 intersecting the inner surface of the
Radius of curvature of an arc L passing through a thickness midpoint Q2 of the tread thickness H which is the thickness of the tread portion in the normal line direction and a thickness midpoint Q3 of the thickness of the sidewall portion at the tire maximum width position. A radial tire in which the ratio R / h of the distance h to R is 0.77 or more.