JPS623B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a pneumatic radial tire for automobiles, and in particular, the carcass layer is arranged so that its cross-sectional shape has an equilibrium cross-sectional shape from the area where the tire and rim make the strongest contact to the sidewall portion and the crown portion, and The present invention relates to a pneumatic radial tire for automobiles in which steering stability performance and vibration riding comfort performance can be significantly improved by improving the locking structure around the bead of the carcass layer. In the first place, the cross-sectional shape of the carcass layer is determined by the cross-sectional shape ( (hereinafter referred to as the equilibrium cross-sectional shape). However, from near the top of the rim flange to the bead where the carcass layer is rolled up, the equilibrium cross-sectional shape enters at a very small angle with respect to the rotational axis of the tire, so in reality, the equilibrium cross-sectional shape is It was impossible to extend it directly to the bead, so we had no choice but to connect it with another curve different from the equilibrium cross-sectional shape. This has conventionally been considered to be one of the reasons why the carcass cross-sectional shape and the equilibrium cross-sectional shape of an actual tire are significantly different, especially around the bead portion. Moreover, since there is a filler above the bead with a large volume, in tires with one carcass there is a part where the carcass is rolled up from the bead, and in tires with two or more carcass there is a part where the carcass is rolled up or down from the bead. had no choice but to take a different shape from the equilibrium cross-sectional shape. Particularly in a two-carcass radial tire, the means for winding up the two carcass layers onto a bead includes means for rolling up two carcass layers from the inside of the bead to the outside, and a means for winding up the first carcass layer from the inside of the bead to the outside. Similarly, roll the bead from the inside to the outside,
It is broadly divided into a means for rolling up the second carcass layer from the outside of the bead to the inside. In conventional radial tires with the latter structure, from the sidewall to the bead, there is a first carcass layer, a second carcass layer, and the end of the first carcass layer after wrapping the bead. The carcass layers are essentially composed of two different cross-sectional shapes with the bead filler as a boundary, and in particular, the part where the second carcass layer is rolled down to the bead, which bears a large load, has a significantly different cross-sectional shape from the equilibrium cross-sectional shape. Since they are configured with different cross-sectional shapes, it was not possible to obtain a stable balanced cross-sectional shape. As shown above, in a radial tire with a carcass layer, the equilibrium cross-sectional shape cannot extend to the bead, which is the anchoring point of the carcass layer, and the carcass layer does not meet the bead at this most unstable part. The fact that different cross-sectional shapes are formed in the locking portions is the reason why the equilibrium cross-sectional shape and the actual tire carcass cross-sectional shape differ around the bead portion. Now, in conventional tires that have a cross-sectional shape that differs from the equilibrium cross-sectional shape, there is a tendency for local deformation of the carcass cross-sectional shape to be large because the tire tries to approach a stable shape by filling with internal pressure. Ta. In such tires,
Various forcing forces are applied to tires during actual driving, such as torsional force applied when turning the steering wheel, lateral force due to load fluctuations, circumferential force applied when accelerating or decelerating, seams on the road, unevenness, etc. As a result, in terms of steering stability, not only is the operation feeling poor and unstable performance is obtained, but the vibration and riding comfort are also poor. , especially for tires with a part where the carcass is rolled down, for example, the first tire is rolled up from the inside of the bead,
The second problem was noticeable in tires with a carcass rolled down on the outside of the bead. Conventionally, as a means to improve the instability of the cross-sectional shape, the use of highly rigid rubber as a filler, or the insertion of a reinforcing layer other than the carcass layer in the bead portion have been used, and these methods have achieved some results. I was able to give it to you. However, although such improvements have some effect on steering stability, they have no effect on vibration ride comfort, and may even change the properties of radial tires, which are said to have poor vibration ride comfort. It wasn't something. Furthermore, as a means to further improve steering stability and vibration riding comfort, as seen in Japanese Patent Publication No. 53-8403, a rim with a flange shape different from that generally used in the past is used, and a balanced cross-sectional shape is used. A method was also proposed in which the wheel was extended to the bead, and it became possible to have improved performance in terms of steering stability and vibration ride comfort. However, since this method cannot be used in common with conventional rims, there is a natural limit to its widespread use, and the cross-sectional shape of the carcass layer, including the winding up and down winding near the bead, is substantially different from the equilibrium cross-section. However, the drawbacks of the conventional method of forming a The present invention has been made in view of the above-mentioned current situation, and it is an object of the present invention to provide a pneumatic radial tire for automobiles that is configured to eliminate the above-mentioned drawbacks all at once. The feature is that in pneumatic radial tires for automobiles, the cross-sectional shape of the carcass layer has an equilibrium cross-sectional shape from the area where the tire and rim make the strongest contact to the sidewall and crown parts. so as to conform substantially to the equilibrium cross-sectional shape up to the bead, and at least extend the rolled up portion of the carcass layer wound around the bead and/or other reinforcing layers from the area of strongest contact between said tire and rim to the crown. By arranging the carcass layer along the carcass layer, which is arranged in an equilibrium cross-sectional shape on the side, a stable tire shape is maintained against the internal filling pressure and various external forces applied to the tire during running, improving handling stability and vibration resistance. In addition to significantly improving comfort performance,
Even if a filler with high hardness and a large volume, which was conventionally thought to be necessary, is replaced with a filler with a low hardness and a small volume, the above-mentioned good steering stability performance and vibration riding comfort performance can be maintained. The present invention will be explained below by way of examples with reference to the drawings. In this embodiment, as shown in FIGS. 3 to 5, there are two carcass. The present invention will be explained using a radial tire as an example. As shown in the figure, the present invention has two carcass layers 6 and 8 made of fiber cord layers typified by rayon, nylon, polyester, etc., arranged at approximately 70 to 90 degrees with respect to the equatorial plane of the tire. Both ends of the carcass layers 6, 8 are wrapped around a pair of beads 2, and in an area corresponding to the tire ground contact area, a gap is formed between the cap tread T and the carcass layers 6, 8 in a direction of approximately 10 to 30 degrees with respect to the equatorial plane. In a pneumatic radial tire for automobiles, the carcass layer 6 has a belt layer 9 made of a metal cord layer or a non-stretch fiber cord layer typified by rayon, polyester, aromatic polyamide fibers, etc., arranged in the carcass layer 6,
8 is shown in FIG. 1, the angle θ from the inner carcass proximal end Q of the bead 2 to the rotational axis of the tire is
Straight line S ₂ within the range of 30~55°, tire and rim 1
The intersection point M where the perpendicular line S 1 made from the position 1b where the rim flange 1a makes the strongest contact with the inner surface of the rim flange _1a intersects with the straight line S ₃ parallel to the tire equatorial plane at a distance of rim width x _R and the intersection point N including the intersection point N with the straight line _S2 within the range of 30 to 55 degrees, so that the equilibrium cross-sectional shape L is reached until it reaches the sidewall part E and the crown part F. The rolled-up part 6a of the first carcass layer 6 rolled up around the bead 2 and the rolled-up part of the second carcass layer 8 rolled down around the bead 2 Lowering part 8
A is arranged along the carcass layers 6 and 8 which are arranged in an equilibrium cross-sectional shape L on the tread side from between M and N including the M point and the N point, respectively. In this example, an example in which two carcass layers are arranged as described above is explained.
It goes without saying that one or more of these may be arranged as needed. In addition, the angle θ that the straight line S ₂ makes with the rotational axis of the tire from the inner carcass proximal end Q of the bead 2
If the angle is less than 30 degrees, the tire may shift from the rim during running, and if it is greater than 55 degrees, it may lose its integrity with the tire rim, which is not preferable.
Preferably, the angle θ is in the range of 40 to 50 degrees. There are various formulas that indicate the above-mentioned equilibrium cross-sectional shape depending on the concept etc., and which formula is used to determine the equilibrium cross-sectional shape L.
For example, the shape is expressed by the following equation. That is, in the range that includes the belt layer and the carcass layer, the radius of curvature R is R = (y _D ² - y _C ² ) + η (y _A ² - y _D ² )/2η
y...(1), and the radius of curvature R in the range that includes only the carcass layer from the end of the belt layer to the above-mentioned end point is R=y _D ² - y _C ² + η (y _A ² - y _D ² )/2y …(2
). Here, y _A is the distance from the rotation axis of the carcass line apex. y _D is the distance from the rotation axis of the belt end. y _C is the distance from the rotation axis of the maximum width of the carcass line. y is an arbitrary distance from the rotation axis. η is a coefficient for considering that the internal pressure filled in the tire is shared between the belt layer and the carcass layer, and is the ratio that the carcass layer is responsible for. In addition, the above dimensions such as y _A , y _D , y _C , y, etc.
The distance to the center of the carcass layer. (See FIG. 2) FIG. 1 is an explanatory diagram of the vicinity of the bead portion, illustrating the starting point of the balanced cross-sectional shape in the present invention. In the figure, 1 is the rim, 2 is the bead, x _R is the width of the rim seen from the tire equatorial plane, L is a curve showing the equilibrium cross-sectional shape, and G is the pressure distribution when the tire and rim flange 1a contact each other. The balanced cross-sectional shape L is a straight line S ₂ from the inner carcass proximal end Q of the bead 2 to the tire rotation axis at an angle θ of 30 to 55 degrees.
and the perpendicular line _S1 drawn from the position 1b where the tire and rim 1 make the strongest contact on the rim flange portion 1a to the inner surface of the rim flange 1a intersect with the tire equatorial plane at a distance of rim width x _R. parallel straight line S ₃
It passes through a point P between the intersection point M and the intersection point N including the intersection point N with the straight line _S2 within the range of 30 to 55 degrees, and reaches the sidewall portion E and the crown portion F. Also, the angle θ that the straight line S ₂ makes with the tire rotation axis from the inner carcass proximal end Q of the bead 2
If the angle is less than 30 degrees, the tire may shift from the rim during running, and if it is greater than 55 degrees, it may lose its integrity with the tire rim, which is not preferable.
Preferably, the angle θ is in the range of 40 to 50 degrees. Figure 8 is a diagram showing the relationship between the maximum ground pressure at the position 1b where the rim flange makes the strongest contact and the angle θ. Pressure-sensitive paper is placed on the tire contact area of the rim flange, and the ground pressure is judged by the shade of color. The results are shown below.
In FIG. 8, the larger the index, the higher the maximum ground pressure, which is not preferable. As can be seen from Figure 8, the angle θ is
When the angle is 30° or less, the maximum ground pressure is 100 (practical level) or more. Moreover, FIG. 9 is an explanatory diagram showing the relationship between the carcass line and the angle θ. In Fig. 9, θ of carcass line A is 55°, θ of carcass line B is 60°, and θ of carcass line C is 63°.
It is ゜. When θ exceeds 55°, the degree of inflection connecting the carcass layer and the straight line _S2 is large near the intersection point N between the straight line _S3 and the carcass layer, making it difficult to maintain an equilibrium cross-sectional shape up to the vicinity of the bead. Become. FIG. 2 shows an example of an equilibrium cross-sectional shape L according to the invention. Point A is within the equatorial plane, point D indicates the end of belt layer 9, and point C indicates the maximum width of carcass layers 6, 8. y _A , y _D , and y _C each indicate the distance from the tire rotation axis to the above point. M and N are points determined from FIG. 1 as described above. In this figure, the shape L ₁ between A and D is determined by equation (1), and the shape L ₂ between D, C, and P is determined by equation (2). O
-Y and O-X are coordinate axes whose origin is the intersection O between the tire equatorial plane and the rotation axis, and the coordinates of each point are shown in Table 1 for an example of tire size 205/60R15.

[Table] Figure 3 shows an embodiment of the present invention, where 1 is a rim, 2
is a bead, 3 and 4 are bead fillers, 5 is a reinforcing layer that wraps the bead filler 3, 6 is the first carcass layer, 6a is the first carcass layer folded back by the bead, 8 is the second carcass layer It is. In FIG. 3, the starting point of the equilibrium cross-sectional shape L extends to point P, and the fiber layers shown at 5, 6, and 8 are
Everything above the point is configured to follow the equilibrium cross-sectional shape. The filler 3 is inserted so as to fill the gap between the fiber layers from the top of the bead 2 to the point P. Although a very small filler 4 is also shown in this embodiment, due to the nature of the present invention,
Filler 4 can be omitted. The filler 4 is arranged from the flange part of the rim 1 to the sidewall part E along the outer carcass layer 8 arranged in the equilibrium cross-sectional shape L. Further, the reinforcing fiber layer, which is not shown in this figure, is characterized in that it is inserted along the equilibrium cross-sectional shape L above point P. FIG. 4 is an enlarged view of FIG. 3, showing the arrangement of the carcass layer and the like in the vicinity of the bead, excluding the filler 4. FIG. 5 shows an embodiment in which a reinforcing layer 10 is inserted, and this layer is also arranged along the equilibrium cross-sectional shape L. To further explain the embodiment of the present invention, as described above, the present invention provides the carcass layers 6 and 8 in the range where the integrity of the tire and the rim is strongest, that is, the M point and the N point including the M point and the N point. The arrangement is such that an equilibrium cross-sectional shape L is formed from a point P between the two to the sidewall portion E and the crown portion F. In other words, the first carcass layer 6 is extended along the equilibrium cross-sectional shape L to the target point P, and the bead 2 is rolled up from the inside to the outside. At this time, the rolled up part 6
a has the same equilibrium cross-sectional shape L as the first carcass layer 6 from the starting point P to the crown side.
Place it along the On the other hand, the second carcass layer 8 extends from the area common to the belt layer 9 to the tire side E and the starting point of the equilibrium cross-sectional shape L.
It is arranged along the second carcass 6, that is, along the equilibrium cross-sectional shape L, and its unrolling portion 8a is wound from the outside of the bead 2 inward. Now, in this arrangement of the carcass layers, the two carcass layers 6 and 8 form substantially one equilibrium cross-sectional shape L from the apex of the carcass line to the target starting point.
This solves the problem of the two carcass layers 6 and 8 having different cross-sectional shapes from the sidewall E to the bead part 2, as seen in conventional tires. The day came. As described above, in the present invention, in order to make the equilibrium cross-sectional shape L described above possible, one or more carcass layers can all be arranged on this curve. Furthermore, reinforcing layers other than the carcass layer, that is, a reinforcing layer 5 of plain weave or blind weave fabric that protects the beads 2 and bead filler 3, and a reinforcing layer 10 of blind weave fabric or metal inserted from the outside of the carcass layer, etc. Arranging along the equilibrium cross-sectional shape L from the above-mentioned starting point upward does not cause any inconvenience. Further, in this embodiment, as shown in FIGS. 3 to 5, the two carcass layers are not in close contact below the starting point of the equilibrium cross-sectional shape L. In order to eliminate this gap, a small filler 3 whose height does not exceed the starting point of the equilibrium cross-sectional shape L is inserted from above the bead 2.
This filler 3 is not for reinforcing the bead part 2, but is for eliminating gaps, and there is no need for hard rubber with a JIS hardness of 70 or higher, as in the past.
The following soft rubber is sufficient. Further, from the outside side of the bead to the side part, another filler 4 is added from the outside of the carcass layer 8 and the reinforcing layer 10.
Insert. (Second Filler) Like the first filler 3, rubber with a JIS hardness of 70 or less is sufficient for this filler 4. In other words, in conventional radial tires, the filler 3 must have a large volume with a JIS hardness of 70 or higher in order to function as a bead reinforcing material that compensates for the instability of the carcass cross-sectional shape around the bead. Ta. However, in the present invention, the effect as a bead reinforcing material is no longer necessary as described above, and as described above, the hardness is low and the volume is reduced, so there is no problem. Furthermore, it goes without saying that no inconvenience will occur even if the second filler 4 is removed and rim rubber or side rubber is used instead. Next, the cornering power of a tire according to an embodiment of the present invention and a conventional tire will be compared through an experiment. FIG. 6 shows a tire according to an embodiment of the present invention, that is, 1) the carcass cross-sectional shape has the shape according to the embodiment of the present invention, 2) the carcass layer has the structure according to the embodiment of the present invention, and 3) the bead filler hardness is the same as that of the embodiment of the present invention. The tire (in the figure) is within the range of the invention example (JIS hardness 65), 1) the carcass shape has the shape according to the invention example, 2) the carcass layer has a conventional arrangement structure, so the bead area is A tire that has essentially two cross-sectional shapes, and 3) has a filler between these two carcass layers with a JIS hardness of 75 (as shown in the figure)
1) The carcass shape has a conventional shape not according to the embodiment of the present invention, 2) The carcass arrangement structure has the same conventional arrangement structure, and 3) The filler has a conventional arrangement structure.
Cornering power of three types of JIS85 tires (in the figure) (cornering force required to create a slip angle of 1°)
This is a comparison and shows the effect of improving steering stability. The tire size is 205/60R15. As shown in this figure, conventional tires either have low cornering power in the entire load range, or have high cornering power in the low load range, but the cornering power is saturated in the high load range. , does not increase with load. Normally, in a steering stability test using an actual vehicle, the steering wheel is operated to the extent that a lateral acceleration of approximately 0.7 to 1.0G is generated in the driver's seat. If you do this, a load of approximately 600 kg or more will be applied. Therefore, a tire whose cornering power changes with respect to load as shown in the figure has a poorer operating feel than the tire shown in the figure. From the above, it is clear that the tires according to the examples of the present invention have excellent handling stability. Next, the vibration riding comfort of the tire according to the present invention and a conventional tire will be compared through experiments. Figure 7 shows the vibration riding comfort of the three types of tires ^mentioned above.
This figure shows the change in axial force in the front-rear direction that occurs on the tire shaft. Tire size is 205/60R for all three tires.
It is 15. Ride comfort varies depending on how well the tires absorb the impact force caused by uneven road surfaces. As is clear from the figure, the tire according to the embodiment of the present invention has superior vibration ride comfort performance compared to the conventional tire. As described above, the present invention maintains the carcass layer in equilibrium from the range where the integrity of the tire and rim is strongest, that is, from the point between the M point and the N point including the M point and the N point, to the sidewall part and the crown part. Since the carcass layer is arranged to have a cross-sectional shape, the equilibrium cross-sectional shape of the carcass layer can be extended substantially to the vicinity of the bead even if a rim having a flange shape, which has been commonly used in the past, is used. Further, as described above, the present invention provides that the rolled-up portion of the carcass layer rolled up around the bead and/or other reinforcing layers have an equilibrium cross-sectional shape on the crown portion side from the point between M and N including the points M and N. Since it was arranged along the arranged carcass layer,
It is possible to maintain a stable tire shape against the internal filling pressure and various external forces applied to the tire while running, and because there is no unnecessary reinforcement at the bead, it is possible to significantly improve handling stability and vibration ride comfort. Rather, even if the high hardness, large volume filler that was conventionally thought to be necessary is replaced with a less hard and smaller volume filler, the above-mentioned good steering stability performance and vibration ride comfort performance can be maintained.

[Brief explanation of the drawing]

The drawings show embodiments of the present invention; FIG. 1 is an explanatory diagram of the vicinity of the bead, FIG. 2 is an explanatory diagram for explaining the balanced cross-sectional shape, and FIG. 3 is a first embodiment of the tire of the present invention. FIG. 4 is an enlarged sectional view of the vicinity of the bead in FIG. 3 excluding the filler 4, FIG. 5 is an enlarged sectional view of the vicinity of the bead of the second embodiment, and FIG. A diagram showing the experimental results of
Figure 7 is a diagram showing the experimental results of ride comfort, Figure 8 is a diagram of the relationship between the maximum ground pressure at the position of the tire that makes the strongest contact at the rim flange and the angle θ, and Figure 9 is the relationship between the carcass line and the angle θ. It is an explanatory diagram showing the relationship. 1... Rim, 1a... Flange part, 1b... Strongest contact position in the flange part, 2... Bead, 6... Carcass layer, 6a... Rolling part, Q
...Inside upper part of the bead, S ₁ ...perpendicular line, S ₂ ...straight line passing through points Q, M and N, S ₃ ...straight line parallel to the tire equatorial plane at the rim width, x _R ...rim width , E...side wall part, F...crown part.

Claims (1)

[Claims] 1 The cross-sectional shape of the carcass layer is 30 mm from the near end of the carcass inside the bead to the axis of rotation of the tire.
The intersection point M between a straight line within the range of ~55° and a perpendicular line drawn from the point where the tire and rim make the strongest contact at the rim flange to the inner surface of the rim flange, and the tire equator at a distance of rim width. Intersection point N between a straight line parallel to the surface and a straight line within the range of 30 to 55 degrees
The carcass layer is arranged so as to have an equilibrium cross-sectional shape through the space between the bead and the sidewall part and the crown part, and at least the rolled up part of the carcass layer rolled up around the bead is connected to the points M and N including the points M and N. A pneumatic radial tire for an automobile, characterized in that the pneumatic radial tire is arranged along the carcass layer which is arranged in an equilibrium cross-sectional shape on the crown side from the center.