JPS63199102A - Radial tire - Google Patents

Abstract

PURPOSE:To improve stability of driving and comfortableness to ride, by specifying ratio of height of a carcass in its maximum width position to the overall height of a tire in its condition, filled with air of standard internal pressure, and forming a circular arc part in upper and bottom parts to a predetermined shape in the maximum width position of the carcass further setting the upper circular arc part to a larger radius of curvature. CONSTITUTION:In a flat tread tire, with ratio H/W of tire total height H to tire width W in a value of 1 or less, ratio h/H of height (h) of the carcass maximum width position PM to the tire total height H is specified to 0.4-0.5. While drawing a perpendicular X to a rim base line RB from an end part (b) in a region, where a breaker layer 7A overlaps with 7B, points P1, P2, in which the perpendicular X crosses with a carcass 6, tread part 5 and a bead part 3, are obtained. Circular arcs 20, 21, which pass through the maximum width position PM having their centers on the rim base line RB, are formed so as to pass through both the points P1, P2. Here the circular arm 20 sets its radius of curvature R1 larger than the radius of curvature R2 of the circular arc 21. By this constitution, stability of driving and comfortableness to ride can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a radial tire with improved handling stability and ride comfort.

C. Prior Art] In recent years, radial tires in which carcass ply cords are arranged perpendicularly to the circumferential direction of the tire and a strong breaker layer is provided in the circumferential direction along the tread portion have been increasingly used.

However, in such radial tires, the breaker layer has high rigidity, so although it has a large cornering force and can reduce rolling resistance and improve wear resistance, such a highly rigid breaker layer has a high resistance to the road surface. The cushioning effect of the impact force when riding over unevenness or protrusions, that is, the envelope performance is poor, resulting in poor riding comfort.

On the other hand, in radial tires, the carcass plies are arranged perpendicularly to the circumferential direction and the lateral rigidity is lost, so lateral wobbling is likely to occur.For this reason, so-called flat tires with reduced tire height are used.

However, when flattening a tire, the rigidity in the longitudinal direction also increases, further degrading the above-mentioned en-probe performance, and the impact when riding over uneven road surfaces and protrusions is transmitted to the vehicle through the bead and rim. The vehicle is easily damaged and the riding comfort is affected. In this way, steering stability and ride comfort are contradictory conditions, but this tendency is particularly pronounced with flat tires.

On the other hand, such radial tires have conventionally been vulcanized and molded using a mold that has a bore shape that provides a natural equilibrium shape that does not cause deformation of the carcass even when a standard internal pressure is applied to the molded tire. There is.

Here, the natural equilibrium shape refers to the carcass profile determined by the natural equilibrium shape theory, and the natural equilibrium shape theory is the Hosofaverse (W.

Hofferberth), Kautsch,
Gumii (8-1955, pp. 124-130), and this theory considers the breaker layer to be an open ring body that does not deform when filled with internal pressure, and that this breaker layer and the other do not deform. It is intended that a non-stretchable carcass disposed between the bead core and spanning from the sidewall section to the bead section be pre-formed using a vulcanization mold into a shape that will not be deformed even when filled with the internal pressure.

This Honfaverse theory, which concerns bias tires, was published by Mr. Akasaka in the Journal of the Japan Society for Composite Materials VOL 3.4 (1977), pp. 149-154.
"About the cross-sectional shape of radial tires" has been expanded to be applicable to radial tires as well.

Furthermore, regarding the application of this natural equilibrium shape theory, it is preferable to complement it in at least the following two points.

First, even when the breaker layer is made of metal cord, etc., it is not actually a completely rigid body, and some deformation occurs due to internal pressure.In particular, the smaller the aspect ratio of a flat tire, the more the carcass is pushed up due to internal pressure filling. The breaker layer is prone to deformation due to

Secondly, near the bead, the folded part of the carcass,
The bead apex and other reinforcing layers provide high rigidity, so in the range from the bead core to the inflection point of the carcass profile, usually called the rim point, that is, the equivalent bead position, the natural equilibrium shape theory does not fail. Therefore, the curve based on this theory should be considered starting from the equivalent bead position.

In this way, the natural equilibrium shape theory adopted for conventional tires is based on the theory that, as mentioned above, a tire that has been vulcanized and molded in a vulcanization mold is loaded onto a standard rim and subjected to standard internal pressure. This is a theory to create a curve that produces uniform tension in the carcass without changing the shape of the carcass when it is filled.Also, the clip ring width of the molded tire, that is, the bead, is usually set in the vulcanization mold. The length between the outer surfaces of the bottom is
It is set equal to the width of the rim to be attached.

On the other hand, in order to satisfy the above-mentioned trade-off between handling stability and ride comfort, a proposal to radically deform the carcass profile based on the natural equilibrium shape theory has been made.
For example, this is disclosed in Japanese Patent Publication No. 61-28521.

[Problem that the invention attempts to solve]

As mentioned above, the carcass profile based on the conventional natural equilibrium shape theory cannot satisfy the above-mentioned antinomy conditions, and the tire proposed in Japanese Patent Publication No. 61-28521 (hereinafter referred to as modified tire IA) As shown by the broken line in Fig. 4, the radius of curvature RIA in the upper part of the carcass profile is smaller than that of curve 1B (indicated by a dashed-dotted line) based on the curved natural equilibrium shape theory. Compared to the carcass profile of shape theory, it bulges outward and is formed into an upwardly bulging shape as a whole. The above proposal claims that in order to obtain such a carcass profile, it is essential to use a mold in which the width of the clip ring is larger than the width of the rim.

However, in such a modified tire IA, although the total breaker tension increases when the internal pressure is filled, the tension distribution shows the same tendency as the conventional tire.

The present invention brings the maximum medium KPM of the carcass close to the rim baseline, appropriately sets the curvature radii at the upper and lower parts of the maximum weight position, increases the tension at the shoulder part of the breaker layer, and reduces the total breaker tension. The object of the present invention is to provide a radial tire that can improve riding comfort as well as handling stability by reducing the amount of friction, and that can meet the above requirements.

Means for Solving Problem C] The present invention provides a carcass arranged in a radial direction that passes through a tread portion and a sidewall portion of a tire and is folded at both ends by a bead core of a bead portion, and a main body portion of the carcass and its folded portion. and a bead apex made of a tapered rubber material and extending along the carcass, and a breaker layer made of a low-stretch cord arranged inside the tread portion and outside the carcass, and a regular When installed on the rim and filled with standard internal pressure, the maximum width position PM of the carcass from the rim baseline of the regular rim
The height h in the radial direction from the tire rim baseline to the highest position on the tread surface has a height ratio h/H of 0.4 to 0.5, and the maximum At least two of the breaker layers have respective centers on a line Y that passes through the heavy position PM and is parallel to the rim base line.
The radius of curvature R1 of an arc passing through the first intersection P1 where the vertical #sX extending perpendicularly to the rim baseline from the end of the region where the layers overlap intersects the carcass in the tread portion and the large-medium position PM is This is a radial tire that is larger than the radius of curvature R2 of an arc passing through the second intersection P2 where the line X intersects the carcass at the bead portion and the maximum weight position PM.

An embodiment of the present invention will be described below based on the drawings.

In FIG. 1, which shows a cross section of the right half of the rim R assembled and filled with standard internal pressure, the radial tire l has bead portions 3 on both sides through which bead cores 2 pass, and a radially outward portion from the bead portions 3. Side wall part 4 that extends in the direction
and a tread portion 5 connecting the upper end thereof,
The road portion 3, sidewall portion 4, and tread portion 5 include:
A main body portion of a carcass 6 folded back around the bead core 2 from the inside to the outside is placed over the bead core 2. In addition, a breaker N7 is arranged on the outside of the carcass 6 in the tread part 5, and a bead apex 9 is provided between the main body part of the carcass 6 and its folded part. , and is attached to the rim R by fitting the bead portions 3 together.

The carcass 6 is a so-called radial cord arrangement body in which the cords are arranged at an angle of about 80 to 90 with respect to the tire equatorial plane C, and the cords are made of nylon, polyester, rayon, aromatic polyamide fiber, or steel. be done. For this carcass 6, one to three layers of carcass ply are used.

The breaker layer 7 has a two-layer structure, for example, of a first ply A disposed on the carcass 6 side and a second ply (7B) above it, and the first and second plies 7A and 7B are both i ?2'; In addition, both ends of the first ply 7A extend below the intersection of the sidewall part 4 and the tread part 5.The Yumata bead part 3 has a width that extends from the lower end of the bead core 2 to the carcass 6. An M1 strong layer 8 is provided that extends upward along the folded portion of the bead apex 9 and beyond the upper end of the bead apex 9.The reinforcement jW8 is made of one or more layers of suitable machined fiber cords in addition to metal cords. Consists of the body.

In this embodiment, the radial tire 1 has a distance from the lower end of the bead portion 3, that is, the rim baseline RB, to the maximum height point a of the tire tread surface 12, which is the upper surface of the tread portion 5, when the standard internal pressure is filled. The tire is formed as a flat tire in which the ratio H/W of the total tire height I to the tire width W is smaller than 1, for example, 0.7 or less.

Furthermore, the radial Courier 1 of the present invention has a height ratio h/H of the height in the radial direction from the rim baseline RB of the rim R to the maximum width position PM of the carcass 6 and the total tire height H to 0. It is set in the range of .4 to 0.5. Further, an arc passing through the first intersection point P1 where a perpendicular line X extending perpendicularly to the rim baseline RB intersects with the carcass 6 in the tread portion 5 and the maximum width position PM from the end of the area where the breakers Ff7A and 7B overlap. The radius of curvature R1 of 20 is the second point where the perpendicular line X intersects with the carcass 6 at the bead portion 3.
The radius of curvature R2 of the circular arc 21 passing through the intersection P2 and the maximum medium KPM is set to be larger than the radius of curvature R2. Note that the arc 20.
21 have their centers on a line Y passing through the maximum width position PM and parallel to the rim baseline RB.

Determining the height h5 and the radius of curvature R1 and R2 in this way,
Therefore, compared to the curve based on the natural equilibrium shape theory, the deformed tire IA has an upwardly bulging shape in which the upper part connected to the breaker layer 7 bulges outward, as shown by the broken line in FIG. As shown by the solid line in FIG. 4, the tire 1 of the present invention has a so-called flop shape with a downward bulge that bulges out below the maximum medium IPM. Note that the height ratio h/H is smaller than 0.5 and the radius of curvature R1 is larger than the radius of curvature R2, which means that the carcass profile bulges downward and is not a curve based on the natural equilibrium shape theory. This is a requirement for making the difference, and the height ratio h/H is 0.4
When the following is true, the carcass line in the bead portion 3 is based on the natural equilibrium shape theory (excessively different from the curve IB, causing a sudden curvature change in the bead portion 3,
Stress concentration tends to occur in this part, which tends to impair durability and also makes manufacturing difficult.

Note that the curve IB based on the natural equilibrium shape theory is obtained by the following equation.

Here, as shown in FIG. 3, D: the above-mentioned ' An intersection point where a perpendicular line X (r axis) perpendicular to faY intersects the carcass 6B (corresponding to the first intersection point P1).

C: Maximum position of the carcass (corresponding to the PM).

r: Height in the tire radial direction from the Z axis.

rc: Height in the radial direction from the Z-axis to the point C on the carcass 6B.

rD: Height in the radial direction from the Z axis to the intersection of the carcass 6B.

ΦD=Angle between the normal Yl of the carcass 6B and the Z axis at the intersection.

In (1) 2, the carcass 6B is determined to form an arc at least in the vicinity of the end portion of the belt layer 7. In addition, equation (1) is expressed as r passing through the intersection point.
The intersection point O between the axis and the Z axis is determined as the origin, and in this way, by giving the height r, the horizontal deviation from the r axis, that is, the Z value, can be calculated, It is possible to obtain curves based on natural equilibrium shape theory.

Furthermore, as described above, the bead portion 3 has a relatively large bending property, and therefore has a high rigidity at the upper end of the range, that is, from the equivalent point Fl to the point C.
Natural equilibrium shape theory is applied in the region that passes through and reaches the intersection. In addition, in the vicinity of the equivalent bead position B, the lower part thereof is formed as an inwardly convex arc smoothly connected to the outwardly convex arc found by the natural equilibrium shape theory above the position B, and 1jB forms an inflection point or rim point.

In this manner, in the natural equilibrium shape theory, as is clear from equation T1), when the positions of the heights rC and rD and the angle ΦD are given, the curve is determined. In addition,
When two values of the point C are given in advance, by giving one of the angle ΦD1 and the height rC, the other can be found.

Note that when formula (1) of the natural equilibrium shape theory is transformed so as to be expressed by the r value and the radius of curvature R of each part of the carcass profile, the curve based on the natural equilibrium shape theory is expressed as r - R = constant. It can be done.

Therefore, the curve of carcass 6 according to the natural equilibrium shape theory is
The curve becomes a curve in which the radius of curvature R gradually increases as the r value decreases, that is, from the first intersection point P1 to the equivalent bead position RB. In contrast, the deformed tire IA has this tendency significantly, while the radial tire I has a carcass profile that reduces the radius of curvature from the first intersection point P1 to the equivalent bead position B. .

Furthermore, in this example, in the radial tire 1, the first
From the intersection point P1 to the maximum width position PM, a curve approximated to the profile determined by the natural equilibrium shape theory is adopted. Note that the curve based on the natural equilibrium shape theory adopted here means that in equation (1), the height h to the maximum width position PM is 0.4 times or more and smaller than 0.5 times the total tire height H. This refers to a curve defined in advance and determined by the equation (1), which is naturally different from a curve determined based on the natural equilibrium shape theory of the entire carcass profile.

Furthermore, in the range from the maximum width position PM to the second intersection P2, that is, in the lower part, the radius of curvature is larger than the circular arc (indicated by a thin line r in FIG. 2) through which the radius end of the radius of curvature R2 passes.
The radius gradually decreases inwardly toward the inflection point, that is, the equivalent position fiB, and an upwardly convex line portion of the outward bulge reaching the inflection point B is formed, and the upwardly convex line portion is At the inflection point, the center point of the radius of curvature is outside the carcass 6, and the second
In this way, the lower part of the carcass 6 has upper and lower curved parts of the outer and inner bulges. Such a carcass profile has a lower part of the tire 1 than a broken line extending downward from a curve based on the theory of natural equilibrium shape forming an upper part from the first intersection point PL to the maximum width position PM. The tire is significantly dented inward.

Therefore, the radius of curvature R2 of the circular arc 21 in the lower part is smaller than the radius of curvature R1 of the circular arc 20 in the upper part.

In addition, in the radial tire 1, in order to maintain the shape by intentionally deforming the lower part inward compared to the curve IB based on the natural equilibrium shape theory, a bead apex 9 with large bending hardness and dimensions is used. There is.

The bead apex 9 is a tapered rubber body extending from the bead core 2 to a height of 9h beyond the inflection point B,
A hard rubber having a rubber hardness of 85 to 98 degrees, preferably 90 to 95 degrees (Shore A hardness) is used. Further, the thickness 9t in the tire axial direction at the inflection point B is about 0.06 to 0.09 times the height h, and the height 9h is 0.75 to 0.90 times the above height, Its shape is larger than the conventional one.

As described above, the carcass profile according to the natural equilibrium shape theory is a curve in which the shape of the carcass profile does not change even when the internal pressure is filled.

On the other hand, in the radial tire I of the present invention, after the internal pressure is filled, the tire bulges downward compared to the curve 'fJAIB' based on the natural equilibrium shape theory as described above, and the deformed tire IA bulges upward.

On the other hand, as mentioned above, the handling performance and riding comfort performance of a radial tire are contradictory conditions; handling stability performance can be improved by increasing the rigidity of the breaker layer, and riding comfort performance can be improved by decreasing the breaker layer rigidity. can be improved by

On the other hand, the rigidity of the breaker layer is increased by the internal pressure filling, in addition to the rigidity of the breaker layer cord itself.
The tension acting on the breaker layer 7 also acts as resistance when deforming the breaker layer 7, and therefore, this tension also acts on the breaker layer as an apparent stiffness.

On the other hand, even in a tire having a carcass profile based on the natural equilibrium shape theory, as the internal pressure is filled, a tension distribution occurs in which the breaker layer tension is greater in the crown or central portion of the tread surface 12 than in the shoulders.

This is because, as mentioned above, the breaker layer 7 is a completely rigid body, and the carcass 6 actually expands to some extent due to internal pressure filling. As a result, the carcass 6 including the carcass cord layer substantially parallel to the tire axis direction pushes up the lower surface of the breaker layer 7 as it expands, and the breaker layer 7
Increase the radius of

During this diameter increase, the central portion of breaker N7 is most likely to bulge outward, and therefore, the tension in the circumferential direction exhibits a tension distribution that is greatest at the crown portion and gradually decreases toward the shoulder portion (natural equilibrium shape theory). The tension distribution on the curve is shown in Figure 5 with a line of 1 yen per point). Further, the tension distribution of the radial tire 1 of the present invention is shown by a solid line.

Contrary to the tension distribution on curve IB in the natural equilibrium shape theory described above, in the case of the radial tire 1 of the present invention, while the tension increases in the shoulder portion, the tension decreases in the central portion, and furthermore, as a whole, The total tension of is decreasing.

This is because, as described above, the radial tire 1 of the present invention has a carcass profile that deviates from the curve based on the natural equilibrium shape theory. Therefore, when filling the internal pressure, the stress of each part acting on the carcass 6 together with the breaker N7 is deformed so as to be in equilibrium with the internal pressure, and this deformation causes the curve %'i 1 B based on the natural equilibrium shape theory.
Even after this deformation, the shape of the deformed tire IA, radial tire 1, is different from the carcass profile according to the natural equilibrium shape theory, as described above.

As a result, near the end of the breaker]7, the deformed tire I
At A, due to the deformation that approaches the natural equilibrium shape theory, the carcass 6 deforms upward at the end portion, as is clear from FIG. 4, and as a result, it acts to push up the breaker layer 7. By pushing up the end portion of the breaker layer 7, the tension in the shoulder side portion of the breaker layer 7 can be increased, and the apparent rigidity of the shoulder side portion can be improved.

Furthermore, the total breaker l/- force tension, that is, the total circumferential tension that acts throughout the breaker layer 7, is determined by the following equation with reference to FIG.

T=1/2XDr-p (WB-2Rsin θ)-
・------(21, where T is the total breaker tension, Dr is the inner diameter of the breaker layer 7 at the first intersection P1, WB is the width of the breaker layer, and R
is the radius of curvature of the carcass at the first intersection P1, θ is the angle that the tangent at the first intersection P1 makes with a line parallel to the rim baseline RB, and P is the internal pressure.

As can be seen from equation (2), by increasing R1θ, the total tension T acting on the breaker layer 7 decreases.

Therefore, as shown in FIG. 4, in the deformed tire IA where both the radius of curvature R and the angle θ of the upper portion are small, the total tension T is larger than that of the curve IB according to the natural equilibrium shape theory, and the curvature In the radial tire 1 of the present invention in which the radius R is larger and the angle θ is also larger than in the case of the curve IB, the total breaker tension T can also be reduced.

In this way, in the radial tire 1, the tension in the shoulder side portion of the breaker layer 7 is large, and the total breaker tension T is reduced.

Furthermore, increasing the apparent rigidity at the shoulder side can improve steering stability. In the radial tire l, the apparent rigidity of the edge d (shown in FIG. 6(a)) on the ground contact surface is improved by increasing the tension in the shoulder side portion as described above. On the other hand, as shown in FIG. 6(b), the deformation of the breaker layer 7 during cornering of the tire curves as if it bulges laterally within the plane during cornering.
This results in an in-plane bending moment. Therefore, as in the tire 1 of the present invention, by increasing the rigidity at the side edge d, that is, the shoulder side portion of the ground contact surface, the in-plane bending rigidity and the reaction force against the large bending moment at the side edge d can be effectively reduced. It is possible to improve steering stability by improving cornering force.

Furthermore, reducing the total tension of the breaker layer 7 in the radial tire 1 reduces the bending stiffness in the tire radial direction of the breaker layer over the entire breaker N7, that is, the out-of-plane bending stiffness. Therefore, it is possible to effectively buffer the impact when riding over unevenness or protrusions on the road surface, thereby improving riding comfort.

Note-cass profile is a line connecting the thickness centers of the carcass 6, and standard internal pressure refers to the internal pressure filled in the tire under standard usage conditions, or the pressure in a range of 10% above and below the internal pressure.

〔Example〕

A tire shown in FIG. 1 having a tire size of 185/60R14 was manufactured as a prototype according to the specifications shown in Table 1.

Furthermore, a tire having a carcass profile IB based on the natural equilibrium shape theory as shown in FIG. 4 was manufactured as a comparative example. All of these tires differ only in carcass profile, and their structure is the same as that shown in FIG. 1. These tires are 5・1/2JJX1
The rim is assembled to the regular rim of No. 4, and the standard internal pressure is 2.0 kg/
The internal pressure of cnl was filled and the dimensions of each part were measured. The results are shown in Table 1.

Furthermore, the cornering force and the reaction force acting on the tire shaft when going over a bump were measured using an indoor drum testing machine.
Comparative Example 1 is also listed in Table 1 in an index format using lOO. The higher the number, the better the result.
It can be seen that the actual product is superior to the comparative product in terms of cornering force and overcoming bumps. Additionally 1.31 FF
We conducted an evaluation of the feeling of the actual vehicle. The results are shown in Table 1 using similar index representations. The specific model has excellent handling stability and ride comfort.

[Effect of clarity]

In this way, the radial tire of the present invention is a radial tire that can satisfy both handling stability and ride comfort by appropriately selecting the radii of curvature at the maximum 111 position and the upper and lower parts of the maximum width position of the carcass. can be provided.

Chapter 1 Table

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing one embodiment of the present invention, Fig. 2 is a line diagram explaining the carcass profile, Fig. 3 is a line diagram explaining the theory of the natural child (ET shape T'), and Fig. 4 is a line diagram explaining the carcass profile. 5 is a diagram showing an exaggerated force profile of the radial tire of the present invention, the tire according to the natural equilibrium shape theory, and the deformed tire. FIG. 5 is a diagram showing the tension distribution acting on the breaker layer. FIG. 6(a) is a diagram 3 showing the tension distribution on the ground contact surface.FIG. 6(b) is a diagram illustrating the cornering force, and FIG. 7 is a diagram illustrating the formula for calculating the total tension. 2-bead core, 3-bead section, 4-side wall section, 5-tread section, 6-
carcass, 7-breaker layer, 8-reinforcement layer,
9-.Bead apex, 20.21.--Circular arc. Patent Applicant Sumitomo Rubber Industries Co., Ltd. Agent Patent Attorney Nae Mura Shodo b Figure 2

Claims (4)

[Claims] (1) A carcass arranged in a radial direction that passes through the tread portion and sidewall portion of the tire and is folded at both ends by the bead core of the bead portion, and is disposed between the main body portion of the carcass and the folded portion and along the carcass. The bead apex is tapered and made of a rubber material, and the breaker layer is made of a low-stretch cord and is arranged inside the tread part and outside the carcass. , the height ratio h between the height in the radial direction from the rim baseline of the regular rim to the maximum width position PM of the carcass and the height H in the radial direction from the rim baseline of the tire to the highest position on the tread surface.
/H is 0.4 to 0.5, and the maximum width position P
In the tread portion, a perpendicular line X extends perpendicularly to the rim baseline from an end of a region where at least two of the breaker layers overlap and has a center on a line Y that passes through M and is parallel to the rim baseline. The radius of curvature R1 of the circular arc that passes through the first intersection point P1 where the carcass intersects and the maximum width position PM is the radius of curvature R1 of the circular arc that passes through the second intersection point P2 where the perpendicular line X intersects with the carcass at the bead portion and the maximum width position PM. A radial tire with a radius of curvature larger than R2. (2) The carcass has an upper curved part of the outer bulge near the maximum width position PM between the maximum width position PM and the bead core, and an inflection point B between the upper curved part and the upper curved part near the bead core.
and a lower curved portion of the inner bulge that continues smoothly through the inner bulge, and the radius of curvature of this upper curved portion gradually decreases from the maximum width position PM toward the inflection point B.
Radial tires listed in section. (3) The bead apex extends beyond the inflection point from the bead core, and the height 9h from the bead bottom to the tip of the bead apex is 0.75 to 0.75 of the height h.
0.90 times, and the thickness 9t in the tire axial direction at the position of the inflection point B is 0.07 to 0.09 times the height h. The radial tire described in item 2. (4) The bead apex has a Shore A hardness of 85
The radial tire according to claim 1, 2 or 3, characterized in that it is made of hard rubber with an angle of ~98°.