JPH05193312A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To sufficiently improve proofing of a tire against slipping off of a rim and/or smoothness against a rim without making the tire and rim assembly work difficult. CONSTITUTION:A shape, which is similar to a circular arc shaped protrusion made when a bead portion 23 is pressed outward with a uniform pressure, is turned reversely and a recessed groove 38 is formed on a bead base part 36. Thus, when the bead base part 36 is so deformed as to overlap on one circular cone surface (outside surface of a rim) by virtue of equipping it to a rim, the contact pressure between the bead base part 36 and the outside surface of the rim becomes so uniform that sliding of the tire 21 in the shaft direction or in the circumference direction may be strongly restrained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire in which the shape of a bead base is improved to improve rim detachment resistance and rim slip resistance.

[0002]

2. Description of the Related Art In general, it is well known that the friction resistance between the bead base portion of the tire and the outer surface of the rim may be increased in order to improve the rim detachment resistance and the rim slipperiness of the tire. However, such a frictional resistance force is obtained by multiplying the vertical force applied from the tire to the rim by the friction coefficient between the tire and the rim. Then, in order to accurately obtain such a frictional resistance force, while dividing the contact area between the bead base portion and the outer surface of the rim into a large number of unit areas,
After obtaining the vertical force and friction coefficient in each unit area, multiply these friction forces by the friction coefficient to obtain the friction resistance force in each unit area, and integrate the friction resistance force in each unit area over the entire contact area. Good. Here, assuming that the total of the vertical forces applied from the tire to the rim is constant, when the vertical forces in each unit area are different from each other (when the contact pressure is nonuniform in the bead base portion), When the normal force in the area is the same (when the contact pressure is uniform in the bead base portion), which is the larger frictional resistance force is the normal pressure between the rubber and the solid surface and the friction coefficient. Since the relationship is as in the Mayer's experimental result (shown by a curve similar to the inverse proportional curve), the frictional resistance becomes larger when the contact pressure is uniform.

For this reason, conventionally, in order to equalize the contact pressure in the bead base portion, a pneumatic tire in which the bead base portion has two conical surfaces has been proposed. As shown in FIG. 6, this product has a groove 74 extending in the circumferential direction in a bead base portion 71, and the groove 74 intersects at the central portion in the axial direction.
By comprising the individual conical surfaces 72, 73, the cross section (cross section having a plane including the rotation axis of the tire as a cut surface) has a triangular shape. And like this, the groove 74
When the tire 75 formed on the bead base 71 is assembled on the rim, the deformable bead heel 76 and the bead toe 77 are easily deformed.
The rubber in the vicinity is pressed by the outer surface 78 of the rim and largely deforms (expands) outward in the radial direction, and the reaction force of the large compression force generated thereby acts on the rim surface 78 as a contact pressure. On the other hand, the rubber on the inner side of the bead 79 in the radial direction is constrained by the non-stretchable bead 79 and is difficult to be deformed.
When it is pressed by and deformed (expanded) even slightly, a large compressive force is generated inside, but the bead heel 76, bead toe
Since the concave groove 74 is crushed to the middle of the vicinity of 77 and does not contact the outer surface 78 of the rim but contacts the outer surface 78 of the rim from the middle, the compressive force generated inside is in the vicinity of the bead heel 76 and the bead toe 77. It is close to the compressive force generated in rubber. As a result, the contact pressure is made uniform in the entire area of the bead base portion 71, and the rim detachment resistance and slipperiness of the tire 75 are improved.

[0004]

However, in such a conventional pneumatic tire, the rim detachment resistance,
Although the rim slip resistance can be improved to some extent, the improvement effect was not sufficient.

[0005]

For this reason, when the groove 74 has a triangular cross section as described above, the reason why the effect of improving the rim detachment resistance and the rim slip resistance is not sufficient is sought and investigated. As a result, it was found that when the groove 74 had a triangular cross section, the contact pressure in the entire area of the bead base portion 71 at the time of filling with internal pressure could not be made sufficiently uniform, and the contact pressure varied considerably depending on the location.

As a result, the inventor of the present invention has conducted various studies to find out how to make the contact pressure surely uniform, and in the examination, he found out the following. That is, as shown in FIG. 7, the bead 82 is attached to the metal ring 90 whose shape contacting the inner surface of the bead 82 is similar to the flange of the rim.
While inserting the, insert the bladder 83 filled with the pressure fluid inside the bead portion 82 of the tire 81 in the radial direction, after that,
A pressure fluid is further injected into the bladder 83, and a constant pressure (target contact pressure) is applied to the bead base portion 84 having a single conical surface by the bladder 83 to spread it outward in the radial direction. At this time,
The rubber in the vicinity of the bead heel 85 and the bead toe 86 is easily deformed, so it is largely deformed radially outward, but the bead 87
The rubber on the inner side in the radial direction is difficult to deform because the bead 87 is hard to stretch, and the axial center portion of the bead base portion 84 rises in a substantially arcuate cross section. The contact pressure between the bead base portion 84 and the bladder 83 at this time is completely the same (uniform) at any position according to the principle of Pascal. Therefore, the same shape as the bulging portion 89 having a substantially arcuate cross-section located radially inward of the conical surface 88 connecting the bead heel 85 and the bead toe 86 at this point has a bead base with the conical surface 88 as a symmetrical surface. If it is formed as a groove in the portion 84, the bead base portion having such a groove rides on the outer surface of the rim by the rim assembly, whereby the bead base portion is pushed outward in the radial direction and the entire bead base portion is formed. When overlapping with one conical surface (rim outer surface), that is, when the entire bead base is in close contact with the outer surface of the rim, the contact pressure between the bead base and the rim outer surface is a completely uniform target contact. It should be pressure. When the entire bead base is brought into close contact with the outer surface of the rim in this way, the rubber near the bead heel and bead toe is deformed from the beginning, so the amount of deformation is large and the contact pressure is large, but Even if the rubber is deformed by a small amount from the middle, the deformation is limited by the bead that is difficult to stretch, so that the contact pressure becomes large, so that the contact pressure becomes uniform over the entire bead base portion.

The present invention has been made on the basis of the above-mentioned findings, and a pair of bead portions to be seated on the rim, a pair of sidewall portions extending outward from the bead portions in a substantially radial direction, and these side portions. In a pneumatic tire including a substantially cylindrical tread portion that connects between wall portions, a bead base portion surface from a bead toe to a bead heel of the bead portion extends in the circumferential direction and has a substantially arc-shaped cross section. It is a pneumatic tire in which a concave groove is formed, and a deepest portion of the concave groove and a bead embedded in a bead portion are radially overlapped with each other.

[0008]

First, the pneumatic tire described above is mounted on the rim. At this time, since the inner diameter of the bead base portion is the same as the inner diameter of the bead base portion of a general pneumatic tire, it becomes difficult to assemble the rim. There is no. Next, when the pneumatic tire is filled with the internal pressure, each bead portion moves outward in the axial direction while slidingly contacting the outer surface of the rim. At this time, since the outer surface of the rim is a conical surface whose diameter gradually increases toward the outer side in the axial direction, the rubber near the bead heel and the bead toe that is easily deformed by the outer surface of the rim is directed toward the outer side in the radial direction. And greatly deform (expand). On the other hand, the rubber on the inner side in the radial direction of the bead does not contact the outer surface of the rim due to the crushing of the groove until the vicinity of the bead heel and the toe of the bead is deformed, but contacts the outer surface of the rim from the middle and goes outward. It is deformed (expanded). Here, the above-mentioned concave groove has a substantially arcuate transverse cross section, and since the deepest part thereof is a position where it overlaps with the bead in the radial direction, its shape and forming position are the same as those of the aforementioned bulging part. Is approximated to an imaginary groove formed in the bead base with the conical surface as the symmetrical surface. Therefore, when the rubber of the bead portion is deformed as described above and the entire bead base portion overlaps with one conical surface (rim outer surface), that is, when the entire bead base portion is in close contact with the rim outer surface, the bead The contact pressure between the base portion and the outer surface of the rim becomes sufficiently uniform, and the frictional resistance force between them becomes almost maximum. As a result, axial slippage and circumferential slippage of the tire are strongly suppressed, and rim detachment resistance and slipperiness are reliably improved. When the entire bead base is brought into close contact with the outer surface of the rim in this way, the rubber near the bead heel and bead toe is deformed from the beginning, so the amount of deformation is large and the contact pressure is large, but Even if the rubber is deformed by a small amount from the middle, the deformation is limited to the bead that is difficult to stretch, so the contact pressure becomes large, and as a result, the contact pressure is sufficient in the entire bead base. It becomes uniform.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 21 denotes a pneumatic tire. The tire 21 includes a pair of bead portions 23 each having a bead 22 buried therein, and a sidewall portion 24 extending from the bead portions 23 toward the outer side in the substantially radial direction. And a substantially cylindrical tread portion 25 that connects the outer ends of the sidewall portions 24 in the radial direction. Further, the tire 21 is reinforced by a toroidal carcass layer 26 extending from one bead portion 23 to the other bead portion,
Both ends in the width direction of the carcass layer 26 are folded back around the beads 22 from the inner side in the axial direction toward the outer side in the axial direction. A belt layer 27 is arranged on the outer side in the radial direction of the carcass layer 26, and a tread rubber 30 having a large number of grooves 28 formed on the outer surface thereof is arranged on the outer side in the radial direction of these belt layers 27.

2 and 3, the bead portion 23 has a bead base portion 36 extending from a bead toe 34 to a bead heel 35 at an inner end in the radial direction. These bead base portions 36 have an inner diameter from the inner side in the axial direction to the outer side in the axial direction. The diameter gradually becomes larger as it goes to, and as a result, its surface is a substantially conical surface.
Recessed grooves 38 extending continuously in the circumferential direction are formed on the surface of the central portion of the bead base portion 36 in the axial direction. The recessed grooves 38 extend radially outward (the beads 22) from the surface of the bead base portion 36. It is dented. Each groove 38 has a substantially arc-shaped cross section (a section including a plane including the rotation axis of the tire 21 as a cut surface), and its surface is formed by combining one or more arc-shaped curved surfaces. In this embodiment, a bead is formed. Base part 36
It is composed of one arcuate curved surface whose center of curvature is located on the inner side in the radial direction of the surface. Therefore, the depth of the groove 38 in this embodiment changes gently in the axial direction, that is, the inclination of the tangent to the surface changes continuously. Moreover, the deepest part 39 of the groove 38 overlaps the bead 22 in the radial direction, that is, the axially inner end 41 and the axially outer end of the bead 22.
The deepest portion 39 of the groove 38 is located in the area between and 42.

Such a tire 21 is mounted on the rim 47. At this time, since the inner diameter of the bead base portion 36 is the same as the inner diameter of the bead base portion of a general tire, it is difficult to assemble the rim. Has not changed. Next, the tire 21
When the inside pressure is filled, the bead portion 23 seated on the bead seat portion 48 of the rim 47 moves axially outward while slidingly contacting the outer surface of the bead seat portion 48. Since the surface is a general conical surface whose diameter gradually increases toward the outside in the axial direction, the rubber near the bead heel 35 and the bead toe 34, which is easily deformed by being pressed by the outer surface of the bead seat 48, has a radius. Largely deformed (diameter expansion) toward the outside in the direction. On the other hand, the rubber on the radially inner side of the bead 22 does not come into contact with the outer surface of the bead seat portion 48 by collapsing the groove 38 until the bead heel 35 and the vicinity of the bead toe 34 are deformed, but from the middle. The bead seat portion 48 comes into contact with the outer surface thereof, and from this time, the bead seat portion 48 is pushed by the outer surface of the bead seat portion 48 to be deformed (diameter expansion) outward in the radial direction. Here, the above-mentioned concave groove 38 has a substantially arcuate cross-section, and since the deepest portion 39 thereof is a position overlapping the bead 22 in the radial direction, the shape and forming position of each concave groove 38 are the same as those described above. The same shape as that of the bulging portion is approximated to a virtual concave groove formed in the bead base portion 36 with the conical surface as the symmetrical surface. Therefore, when the rubber of the bead portion 23 is deformed as described above and the entire bead base portion 36 overlaps with one conical surface (the outer surface of the bead seat portion 48), that is, on the outer surface of the bead seat portion 48. When the entire bead base portion 36 comes into close contact, the contact pressure between the bead base portion 36 and the bead seat portion 48 becomes sufficiently uniform, and the frictional resistance force between them becomes almost the maximum value. As a result, axial slippage and circumferential slippage of the tire 21 are strongly suppressed, and rim detachment resistance and rim slip resistance are reliably improved. When the entire bead base portion 36 comes into close contact with the outer surface of the bead seat portion 48 in this way, the rubber in the vicinity of the bead heel 35 and the bead toe 34 is deformed from the beginning, so the deformation amount is large and the contact pressure is also large. However, even if a small amount of deformation of the rubber in the groove 38 is limited from the middle, the deformation is limited to the bead 22 that is difficult to stretch, so that the contact pressure becomes large, and thus the contact pressure is the same as described above. Thus, the entire bead base portion 36 becomes sufficiently uniform.

The width H of the groove 38 is in the range of 0.4 to 1.5 times the width L of the bead 22, and the maximum depth D of the groove 38 from the surface of the bead base 36 is the same as that of the bead 22. A range of 0.1 to 0.5 times the shortest distance M (here, the distance from the bead 22 to the axially outer end of the concave groove 38) to the virtual conical surface indicated by the virtual line is preferable. The reason is that if the maximum depth D and the width H of the concave groove 38 are within the above ranges, the contact pressure at the bead base portion 36 can be made substantially the same at any position, as will be described later, and the rim slip resistance can be improved. This is because it is possible to reliably improve the sex and the like.

Next, the first test example will be described. In this test, the bead base portion 71 has two conical surfaces 72, 73 as shown in FIG. 6 (the inclination angle J of the conical surface 72 is 10 degrees, the conical surface 73
The angle of inclination K is 20 degrees)
The conventional tire with the same shape as the conventional tire, the same groove as the conventional tire is formed in the bead base, and the inner diameter of the bead base is 2 mm smaller than that of the conventional tire. The inner diameter of the bead base 36 is the same as that of the conventional tire. However, the bead base portion 36 is provided with a concave groove 38 (width H is equal to width L) as shown in FIG.
A test tire 1 having 1.0 times the maximum depth D and 0.3 times the shortest distance M) was prepared. Here, the size of each tire was 185/70 R14. Next, attach each of these tires to the regular rim, and add 1.0kgf to these tires.
After filling the inner pressure of / cm ² , the steel block was axially pressed against the sidewall portion of each tire, and the pressing force when the bead portion was removed from the rim was measured. The results were 500 kgf for the conventional tire and 600 kgf for the comparative tire, but 630 kgf for the test tire 1, which was higher than the conventional and comparative tires in rim detachment resistance. Moreover, the pressing force when each tire was filled with an internal pressure of 1.9 kgf / cm ² was also measured. The results were 1000 kgf for the conventional tire and 1200 kgf for the comparative tire, while the test tire 1
In this case, it was 1250 kgf, and in this case as well, the rim detachment resistance was improved compared with the comparative tire. In addition, each tire (internal pressure
1.9kgf / cm ² ) was attached to a 3000cc class domestic passenger car, and then while running on a dry paved road at 50km / h, sudden braking was applied to measure the amount of circumferential slip of each tire with respect to the rim. The result was 30 mm for the conventional tire and 20 mm for the comparative tire, but 10 mm for the sample tire 1,
The rim slip resistance was improved over any of the comparative tires. The conventional tire and the test tire 1 have one rim set.
Although it could be easily performed by a person, it was difficult to perform the rim assembly by one person for the comparative tire, and two persons were needed.

Next, a second test example will be described. In this test, the bead base 36 has a width H as shown in FIG.
Tire 2 with a groove 38 having a width 0.3 times the width L
And a test tire 3 which is the same as the test tire 2 except that the width H of the groove 38 is 0.4 times the width L, and the width H of the groove 38 is
Test tire 4 identical to test tire 2 except for 1.0 times
And a test tire 5 which is the same as the test tire 2 except that the width H of the groove 38 is 1.5 times the width L, and the width H of the groove 38 is
Test tire 6 which is the same as test tire 2 except that it is 1.6 times
And prepared. Here, the size of each tire is 185/70
R14, the maximum depth D of the groove 38 was 0.3 times the shortest distance M. Next, each tire like this is mounted on a regular rim attached to a 3000cc class domestic passenger car, and after filling these tires with an internal pressure of 1.9kgf / cm ² , 50
While traveling on a dry paved road surface at km / h, sudden braking was applied to measure the amount of circumferential slip of each tire with respect to the rim. The results are 18 mm for each of the tested tires 2 and 6,
Although the rim slip resistance was improved to some extent compared with the conventional tire of 18 mm, the test tires 3, 4, 5 (width H has width L
In the range of 0.4 times to 1.5 times) 12mm, 10mm, 12m respectively
m and rim slip resistance were significantly improved. The pressing force described in Test Example 1 was measured for each of these tires. The results show that the test tires 2 and 6 have improved rim detachment resistance to 1210 kgf and 1210 kgf, respectively. However, each of the tested tires 3, 4, and 5 is 1240 kg.
F, 1250kgf, 1240kgf and rim detachment resistance were also greatly improved.

Further, in the third test example, the maximum depth D of the bead base portion 36 as shown in FIG.
The test tire 7 having the 05-fold concave groove 38, and the test tire 8 which is the same as the test tire 7 except that the maximum depth D of the concave groove 38 is 0.1 times the shortest distance M, and the concave groove The same test tire 9 as the test tire 7 except that the maximum depth D of 38 was 0.3 times the shortest distance M, and the maximum depth D of the concave groove 38 was 0.5 of the shortest distance M.
Test tire 10 identical to test tire 7 except doubled
And a test tire 11 which is the same as the test tire 7 except that the maximum depth D of the groove 38 is set to 0.6 times the shortest distance M. Here, the size of each tire is 185/70 R14,
The width H of the groove 38 was 1.0 times the width L. Next, the same test as in Test Example 2 was performed on each of these tires, and the amount of circumferential slip of each tire with respect to the rim was measured. As a result, the test tires 7 and 11 were 24 mm and 22 mm, respectively, and the rim slip resistance was improved to some extent as compared with the conventional tire, but the test tires 8, 9 and 10 (the maximum depth D was the shortest distance) M
In the range of 0.1 to 0.5 times) of 12 mm, 10 mm,
The rim slip resistance of 12 mm was significantly improved. The pressing force described in Test Example 1 was measured for each of these tires. The results show that the test tires 7 and 11 have improved rim detachment resistance to 1100 kgf and 1150 kgf to some extent. , 1 for test tires 8, 9 and 10
The rim removal resistance was also markedly improved at 240kgf, 1250kgf, and 1240kgf.

FIG. 4 is a diagram showing a second embodiment of the present invention. In this embodiment, the surface of the concave groove 60 formed in the bead base portion 36 is provided with two or more conical surfaces, here two conical surfaces 61, 62 and one or more arc-shaped curved surfaces, here one. It is configured by combining with an arcuate curved surface 63. As a result, the groove 60 has a substantially arc-shaped cross section.

FIG. 5 is a diagram showing a third embodiment of the present invention. In this embodiment, the surface of the concave groove 65 formed in the bead base portion 36 is formed by combining three or more conical surfaces, here four conical surfaces 66, 67, 68, 69. As a result, the concave groove 65 has a substantially arcuate cross-section that is similar to an arcuate shape.

In the above embodiment, the bead 22 is used.
The cross section of the bead was substantially square, but if the cross section of the bead was circular, that is, if the radially inner surface of the bead was convex inward in the radial direction, the top and It is advisable to overlap the deepest part of the groove in the radial direction.

[0019]

As described above, according to the present invention, the rim removal resistance and the rim slip resistance can be sufficiently improved without making the rim assembly work difficult.

[Brief description of drawings]

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

FIG. 2 is an enlarged cross-sectional view of a bead portion.

FIG. 3 is a cross-sectional view of a bead portion showing a state of being mounted on a rim.

FIG. 4 is an enlarged cross-sectional view of the vicinity of a bead portion showing a second embodiment of the present invention.

FIG. 5 is an enlarged sectional view of the vicinity of a bead portion showing a third embodiment of the present invention.

FIG. 6 is a sectional view of a bead portion showing an example of a conventional pneumatic tire.

FIG. 7 is an enlarged sectional view illustrating a deformed state of a bead portion.

[Explanation of symbols]

 21 ... Pneumatic tire 22 ... Bead 23 ... Bead part 24 ... Sidewall part 25 ... Tread part 34 ... Bead toe 35 ... Bead heel 36 ... Bead base part 38 ... Concave groove 39 ... Deepest part 47 ... Rim

Claims (4)

[Claims] 1. A pair of bead portions to be seated on a rim, a pair of sidewall portions extending outward from the bead portions in a substantially radial direction, and a substantially cylindrical tread portion connecting the sidewall portions. In a pneumatic tire including, in the bead base portion surface from the bead toe to the bead heel of the bead portion, a groove extending in the circumferential direction and having a substantially arc-shaped cross section is formed, and the deepest portion of the groove is formed. A pneumatic tire characterized in that a bead embedded in a bead portion is overlapped in a radial direction. 2. The pneumatic tire according to claim 1, wherein the groove surface is formed by combining one or more arc-shaped curved surfaces. 3. The pneumatic tire according to claim 1, wherein the groove surface is formed by combining two or more conical surfaces and one or more arc-shaped curved surfaces. 4. The pneumatic tire according to claim 1, wherein the groove surface is formed by combining three or more conical surfaces.