JP2713735B2 - Pneumatic radial tires for high internal pressure and heavy loads - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement in bead portion durability of a pneumatic radial tire used at a high internal pressure and a heavy load, for example, an aircraft radial tire.

(Prior Art) Generally, in the case of a radial tire, a structure in which a ply of a carcass is wrapped from the inside to the outside around a bead core is widely used. In particular, in a tire used at a high internal pressure such as an aircraft tire, A plurality of plies, especially at least one layer, an inner carcass folded back from the inside of the tire to the outside around the bead core, and at least one outer carcass wrapped around the inner carcass including its winding back and wound at least immediately below the bead core; An up-down structure is used, which means that when used at a high internal pressure for a long period of time, the pulling-out force acts on the tire at the ply rewinding portion of the carcass, that is, the carcass and the bead core The external carcass can reduce the excessive shear force generated between This is because the occurrence of separation in the part can be advantageously suppressed.

However, in the case of radial tires for heavy loads, especially pneumatic radial tires for large aircraft, the load applied is extremely high and the deflection is large, so that the contact pressure at the contact portion under the load on the flange of the rim is high. In the case of a tire having a carcass with an up-down structure, the bead lower portion is surrounded by an inner carcass and an outer carcass, so that the bead rigidity is increased, and in addition, a gap between the outer carcass and the rim flange is increased. Since the above deformation concentrates on the rubber part of the rubber part, separation between this rubber part and the outer carcass, and rubber cracks at the position of contact with the rim flange are likely to occur, and the durability of the bead part is sufficient. I couldn't say.

Therefore, an object of the present invention is to provide a bead structure having excellent durability which can advantageously solve the above-mentioned problem.

(Means for Solving the Problems) The present invention has a carcass comprising a plurality of plies of organic fiber cords arranged at a cord angle of 70 ° to 90 ° with respect to the tire equatorial plane, and the carcass is used as a body reinforcement. At least one inner carcass in the form of a toroid wound around the pair of bead cores 2 from the inside to the outside of the tire.
3a, and at least one outer carcass 3b, which wraps the inner carcass including its rewind and wraps it at least immediately below the bead core, in a tire loaded with a standard load under a standard internal pressure The standard internal pressure filling posture of the tire excluding the above-mentioned load from a point e ′ on the outer cross-sectional contour of the bead portion body outer skin 4 corresponding to a separation point e of contact between the bead portion body outer skin 4 and the flange 5 of the rim 1 immediately below. Normal n drawn on the pass line connecting the thickness center of all the plies of the inner carcass 3a
Of the bead portion body skin 4 on a reference line m passing through the center of gravity of the cross-sectional figure of the bead core 2 and parallel to the tire rotation axis with respect to the distance A from the tire outer cross-sectional profile to the above-mentioned pass line of the inner carcass 3a. A pneumatic radial tire for high internal pressure and heavy load, wherein a ratio B / A of a distance B from an outer cross-sectional contour to a path line of the inner carcass 3a is 1.8 or more.

Here, the value of the ratio B / A is set to 2.0 or more,
Furthermore, an outer cross-sectional profile of the bead portion body outer cover 4 corresponding to a separation point e of contact between the bead portion body outer cover 4 and the flange 5 of the rim 1 immediately below the load of the tire loaded with the standard load under the standard internal pressure. The inner carcass 3a in the standard internal pressure filling position of the tire excluding the above load from the point e 'above
On the normal line n drawn on the above-mentioned pass line, the distance C from the outer cross-sectional contour of the tire to the pass line connecting the thickness center of all the plies of the outer carcass 3b and the center of gravity of the cross-sectional figure of the bead core 2 and the tire rotation On a reference line m parallel to the axis, the ratio of the distance D from the outer cross-sectional profile of the bead body 4 to the pass line of the outer carcass 3b, and the value of C / D
2.3 or less, more preferably 2.0 or less. In addition, the separation point of contact between the bead portion body skin 4 and the flange 5 of the rim 1 immediately below the load of the tire loaded with the standard load under the standard internal pressure a point e ′ on the outer cross-sectional contour of the bead body outer skin 4 corresponding to the point e, a point of separation of contact between the bead body outer skin 4 and the flange 5 of the rim 1 in the standard internal pressure filling posture of the tire after removing the above-mentioned load. h, the outer cross-sectional profile of the body skin 4 in the standard internal pressure filling posture of the tire excluding the load is a curve, and the tire excluding the load from the points e ′ and h is The above-mentioned pass line of the inner carcass 3a in a region surrounded by the normal line n, n 'drawn on the above-mentioned pass line of the inner carcass 3a in the standard internal pressure filling posture forms a curve, and both of these curves It is more advantageous that the outer profile has a smaller curvature than the curvature of the pass line.

In the above description, “standard internal pressure” and “standard load” are referred to as The Tire and Rim Association Standard (The Tire and Rim Association
Standards) means the no-load internal pressure and the maximum load.

The carcass pass line refers to a curve connecting all the plus thickness centers constituting the inner and outer carcass in a cross section including the rotation axis of the tire.

1 to 5 show a specific example of a pneumatic radial tire for an aircraft having an up-down structure carcass as a body reinforcement according to the present invention in a cross section of a main part, in which 1 is a rim, 2 is a bead core, 3a is an inner carcass, 3b is an outer carcass, 4 is a bead portion body skin, 5 is a flange of the rim 1, and a standard internal pressure filling posture is indicated by a solid line, especially in FIG. 1 by applying a standard load. The deformed state of the bead portion is compared with a virtual line.

Due to the application of the standard load, the separation point h of the contact of the bead portion body outer skin 4 with the flange 5 of the rim 1 when there is no load causes the bead portion to deform while moving to the point e in FIG. From the point e ′ on the outer cross-sectional contour of the bead body outer skin 4 corresponding to the separation point e just below the load under the load, the tire is lowered onto the pass line of the inner carcass 3a in the standard internal pressure filling posture of the tire excluding the standard load. The bead core parallel to the axis of rotation of the tire from the position where the body skin 4 contacts the flange 5 of the rim 1 with respect to the vertical distance A from the outer cross-sectional profile of the tire to the pass line of the inner carcass 3a on the normal n Distance B to the pass line of the inner carcass 3a measured along the standard line m passing through the center of gravity of the cross-sectional figure 2
The value of the ratio B / A must be at least 1.8, and likewise,
The distance C from the point e 'on the normal line n to the pass line of the outer carcass 3b and the outer carcass along the reference line m
The ratio C / to the distance D where the pass line 3b is separated from the flange 5
It is desirable that the value of D is 2.3 or less.

In the examples of FIGS. 1 to 3, the value of the ratio B / A is 2.2, the value of the ratio C / D is 1.5, 2.0, 2.2 in order, and in FIG. 4, the value of the ratio B / A is 1.9.
The value of the ratio C / D is 2.2, whereas in the comparative examples of FIGS. 6 and 7, the values of the ratio B / A are 1.6 and 1.4, respectively, and the value of the ratio C / D is 2.9, respectively.

Next, from the point e ′ on the outer cross-sectional contour of the bead portion body outer skin 4 to the separation point h of the contact between the bead portion body outer skin 4 and the flange 5 of the rim 1 in the standard internal pressure filling posture of the tire excluding the standard load. The outer cross-sectional profile of the body outer skin 4 in the standard internal pressure filling posture of the tire excluding the above-mentioned load in a region up to and including the load is curved. Also, from the points e 'and h, the inner carcass 3a in a region surrounded by the normal line n and the normal line n' drawn on the pass line of the inner carcass 3a in the standard internal pressure filling posture of the tire excluding the load, respectively. Path line also forms a curve.

Next, the curve of the pass line of the inner carcass 3a between the normal n and the normal n 'usually has a center of curvature inside the tire and therefore the inner carcass 3a between this normal n and the normal n'
Is convex toward the outside of the tire. Therefore, the curvature of the curve of the outer cross-sectional contour between the point e 'and the point h of the body cover 4 is smaller than the curvature of the curve of the path line of the inner carcass 3a between the normal line n and the normal line n'. This means that the curve of the outer profile is
As in the pass line 3a, this includes not only having the inside of the tire and projecting toward the outside of the tire, but also having the center of curvature outside the tire by reversing the direction of curvature as shown in FIGS. This naturally includes a case in which the tire is concave outward, in other words, a convex is formed inward of the tire.

(Operation) As described above, in the case of a radial tire for heavy loads, for example, a radial tire for aircraft, the deflection is large and the contact pressure at the contact portion with the rim flange is high, and the failure of the bead portion is concentrated in this region. .

In order to reduce the contact pressure, as a result of various investigations, the carcass structure inside the tire and the shape of the gap from the separation point h of the contact between the flange 5 of the rim 1 and the outer shell 4 of the tire to the outer edge of the flange 5 are changed. It was found to have a significant effect.

That is, when a load is applied to the tire, the bead portion bends along the flange 5 starting from a point h at which the flange 5 of the rim 1 and the outer shell 4 of the tire are separated from each other in an unloaded state (filled with a standard internal pressure). At this time, as the pass line of the inner carcass 3a is further inward of the tire, the bend point having a large change in the curvature of the bead portion under load is moved more radially outward, so that the flange of the rim 1 The contact pressure at the time of load decreases as the gap between the flange 5 of the rim 1 and the outer shell 4 of the tire in a no-load state (filled with a standard internal pressure) increases. That is what was found.

Therefore, in order to insert the pass line of the inner carcass 3a in the bead portion as inside as possible and to increase the void area, the tire outer cross-sectional contour on a reference line m which passes through the center of gravity of the cross-sectional figure of the bead core 2 and is parallel to the tire rotation axis. From the distance B to the pass line of the inner carcass 3a and a point e 'in a no-load state, which corresponds to a separation point e between the body outer skin 4 of the bead portion and the flange 5 of the rim 1 immediately below the load under load,
By increasing the ratio of the distance A to the pass line of the inner carcass 3a to the pass line of the inner carcass 3a on the pass line of the inner carcass 3a and the value of B / A to 1.8 or more, more preferably 2.0 or more, the load Tire body outer skin 4 and rim 1 flange 5
As shown in FIG. 5 for an example of the actual measurement results, the contact pressure with the rubber can be greatly reduced, and thus, the rubber crack which easily occurs in the portion and the separation at the rubber interface between the outer carcass 3b and the rubber can be advantageously prevented. It becomes possible.

In the area where the outer shell 4 of the tire and the flange 5 of the rim 1 are in contact with each other when the load is applied, if the thickness of the rubber occupying the outside of the outer carcass 3b is too large, the heat generation becomes high even with the same contact pressure, which is disadvantageous in terms of durability. Therefore, it is better not to be too thick, and in order to obtain 1.8 or more for the value of the ratio B / A described above, the tire on the reference line m passing through the center of gravity of the sectional shape of the bead core 2 and being parallel to the tire rotation axis. The inner carcass 3a extends from a point in a no-load state corresponding to a separation point between the bead portion body outer skin 4 and the flange 5 of the rim 1 under a load when the load is applied, with respect to a distance D from the outer cross-sectional contour to the pass line of the outer carcass 3b. Normal n lowered to the pass line
The ratio C / of the distance C to the pass line of the outer carcass 3b above
It is even more desirable that the value of D is 2.3 or less, preferably 2.0 or less.

Further, in a region where the outer shell 4 of the tire and the flange 5 of the rim 1 are in contact with each other at the time of loading, if the outer cross-sectional profile of the tire is outwardly convex and has an excessively large curvature, the shape of the flange 5 of the rim 1 Therefore, the contact pressure may be non-uniform, and a locally high contact pressure may be generated to deteriorate the durability of the bead portion. In addition, the bead portion deformation of the up-down carcass structure is such that when the bead portion is bent under a load, tensile strain occurs in the inner carcass 3a and compressive strain occurs in the outer carcass 3b. Since the elastic coefficient is low, the tension side inner carcass 3a is closer to the neutral axis of the bending deformation, and the entire lower part of the bead is bent along the deformation of the inner carcass 3a.

Then, from the separation point h between the bead portion body skin 4 and the flange 5 of the rim 1 in a state where the internal pressure is filled and no load is applied, from the separation point e between the body skin 4 and the flange 5 of the rim 1 immediately below the load under load. In the case where the outer cross-sectional profile of the body outer skin 4 in the region between the points e ′ in the corresponding no-load state has a curvature convex toward the outside of the tire as shown in FIGS. 3 and 4, From the points h and e ′, the normal internal pressure is applied to the inner carcass 3a in a no-load state. In order to equalize the contact pressure with the rim flange under load, it is preferable to have a smaller curvature, and more preferably to have a concave curvature toward the outside of the tire as shown in FIG. 1 and FIG. Conformity, bead part durability In more desirable.

(Example) FIG. 1 shows a pneumatic radial tire for high internal pressure and heavy load according to the present invention in a cross section of a main part.

The tire size in this example is H46 × 18.0 R20 (for aircraft), and the inner carcass 3a and outer carcass 3b are nylon 66
(1890 D / 3) Using a ply consisting of cords, all arranged at a cord angle of approximately 90 ° with respect to the equatorial plane of the tire,
In this case, a three-layer inner carcass 3a and a two-layer outer carcass 3b
And up and down structure.

2 to 4 show other embodiments having the same size.
6 and 7 show two types of comparative examples, and the symbols in each figure are the same as those in FIG. FIG. 5 already referred to shows the flange 5 of the rim 1 for each of the above embodiments and comparative examples.
Shows the relationship between the contact pressure of the bead portion with the body skin 4 and the value of the ratio B / A, where the contact pressure is a point e to a point e when a load of 44200 Lbs is applied at an internal pressure of 14.1 kgf / cm ^2. It shows the maximum value of the contact pressure in the region h, that is, the amount of change in the contact pressure from a no-load state to a loaded state.

Table 1 shows the evaluation results of the bead durability of the tires of the example and the comparative example by a drum test.

In this drum test, under the following conditions, each tire is repeatedly run on the circumference of the drum at a running distance of 3500 ft each time, and the number of repetitions until the separation occurs in the bead portion is indicated by an index of 100 for Comparative Example 1, Bead durability.

Test conditions Internal pressure: 14.1 kgf / cm ² load: 53040 Lbs (24,058 kg) Speed: 40 MPH (64.374 km / h) (Effects of the Invention) The tire of the present invention can reduce the contact pressure generated between the rim 1 and the flange 5 at the time of load, and the bead portion durability is greatly improved.

[Brief description of the drawings]

1 to 4 are sectional views of a bead portion of the pneumatic radial tire according to the present invention, and FIG. 5 is a relationship between a contact pressure between a rim flange and a bead portion body skin under a load and a value of a ratio B / A. 6 and 7 are cross-sectional views of a bead portion of a comparative tire for a comparative test. 1 rim 2 bead core 3a inner carcass 3b outer carcass 4 bead body skin 5 flange

Claims (3)

(57) [Claims] 1. A carcass comprising a plurality of plies of organic fiber cords arranged at a cord angle of 70 ° to 90 ° with respect to the tire equatorial plane, said carcass being a pair of bead cores (2) for body reinforcement. At least one inner carcass (3a) having a toroidal shape wound around from the inside to the outside of the tire, and at least one outer carcass (3b) wound around at least immediately below the bead core by wrapping the inner carcass including the winding back. ), The separation point (e) of the contact between the bead portion body outer skin (4) and the flange (5) of the rim (1) immediately below the load of the tire to which the standard load is applied under the standard internal pressure. ), The inner force in the standard internal pressure filling position of the tire excluding the above load from the point (e ′) on the outer cross-sectional contour of the bead portion body outer skin (4). Bead core for the distance (A) from the outer contour of the tire to the above-mentioned pass line of the inner carcass (3a) on the normal line (n) drawn on the pass line connecting the thickness centers of all the plies of the carcass (3a) The distance from the outer cross-sectional profile of the bead body outer skin (4) to the above-mentioned pass line of the inner carcass (3a) on a reference line (m) passing through the center of gravity of the cross-sectional figure of (2) and parallel to the tire rotation axis ( B) ratio (B) /
A pneumatic radial tire for high internal pressure and heavy load, wherein the value of (A) is 1.8 or more. 2. A separation point (e) of contact between the bead portion body outer skin (4) and the flange (5) of the rim (1) immediately below the load of the tire loaded with the standard load under the standard internal pressure. The normal (n) drawn on the pass line of the inner carcass (3a) in the standard internal pressure filling position of the tire excluding the load from the point (e ') on the outer cross-sectional profile of the bead portion body outer skin (4) The distance (C) from the outer cross-sectional contour of the tire to the pass line connecting the thickness center of all the plies of the outer carcass (3b) and the reference parallel to the tire rotation axis passing through the center of gravity of the cross-sectional figure of the bead core (2) On the line (m), the ratio of the distance (D) from the outer cross-sectional profile of the bead portion body outer skin (4) to the above-mentioned pass line of the outer carcass (3b), and the value of (C) / (D) is 2.3. Claim 1 is characterized in that: The pneumatic radial tire for high internal pressure heavy load according to the description. 3. A separation point (e) at which a contact between the bead portion body skin (4) and the flange (5) of the rim (1) immediately below the load of the tire loaded with the standard load under the standard internal pressure. From the point (e ') on the outer cross-sectional contour of the bead portion body outer skin (4), the bead portion body outer skin (4) and the rim (1) in the standard internal pressure filling posture of the tire excluding the above load.
The outer cross-sectional profile of the body outer skin (4) in the standard internal pressure filling posture of the tire excluding the above load in a region up to the point of separation (h) of contact with the flange (5) is curved, From point (e ') and point (h),
The inner carcass (3a) in the standard internal pressure filling posture of the tire excluding the load is surrounded by a normal (n, n ') drawn on the pass line.
3. The method according to claim 1, wherein the pass line of a) forms a curve, and for each of the curvatures of these curves, the outer cross-sectional profile has a smaller curvature than the curvature of the pass line. A pneumatic radial tire for high internal pressure and heavy load according to the above item.