JP2000071721A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire with a rim protector that facilitates controllability during turning without deteriorating riding comfort. SOLUTION: In a pneumatic tire, a bead portion 4 is provided with an annular rim protector 9 projecting outwards in the axial direction of the tire and continuously formed along the periphery thereof. The rim protector 9 is provided with a circumferential groove 12 continuously formed in the peripheral direction. The circumferential groove 12 forms a wedge shape having the meridional section with its groove width gradually reduced from outside of the axial direction of tire to the inside thereof. The groove bottom 12B as the inner end of the circumferential groove 12 in the axial direction of tire is apart from the carcass 6 by the distance D equal to or greater than 2 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a pneumatic tire provided with a rim protector for protecting a rim flange.

[0002]

2. Description of the Related Art In recent years, flattening of tires has been advanced in order to improve lateral stiffness of the tires and improve athletic performance.
Various tires with a percentage of less than 10% have also appeared. As the flattening of the tire progresses, the cross-sectional height of the tire becomes relatively small, so that the rim flange of the rim and the like pass relatively close to the road surface. Therefore, for example, if the vehicle is brought too close to the road shoulder, the rim flange may come into contact with the curb and damage it.

[0005] In order to prevent such damage to the rim flange, for example, as shown in FIG. 5, a bead portion b is formed so as to protrude outward in the tire axial direction so as to cover the rim flange jf and to be continuous in the tire circumferential direction. It has been proposed to provide a rim protector d. As a result, the rim protector d abuts on the curbstone of the road shoulder before the rim flange jf, thereby preventing the rim flange jf from being damaged.

By the way, such a rim protector d
Is generally formed by increasing the rubber gauge, so that the bending region such as the sidewall portion is reduced, and the longitudinal spring of the tire tends to be increased, thereby deteriorating the riding comfort and increasing the load burden on the bead portion b. The durability may be reduced.

In general, during normal running, such a rim protector d has a certain gap between an inward surface i facing inward in the tire radial direction and a rim flange jf. However, during turning, as shown by the dashed line in the figure, the inward surface i of the rim protector contacts a wide area so as to rest on the rim flange jf and sharply increases the tire rigidity. There is a problem that it is very difficult to control the vehicle at the time of the limit.

The present invention has been devised in view of the above-mentioned problems, and is based on forming a circumferential groove having a substantially wedge-shaped cross section in the rim protector. It is an object of the present invention to provide a pneumatic tire with a rim protector that can easily control the vehicle at the time.

[0007]

The invention according to claim 1 of the present invention is a pneumatic tire having a carcass extending from a tread portion to a bead core of a bead portion through a sidewall portion. An annular rim protector that projects outward in the tire axial direction and is continuous in the tire circumferential direction, and a circumferential groove that is continuous in the circumferential direction is formed on the rim protector, and the circumferential groove extends along the tire axis. In the tire meridian cross-section, the groove width is gradually reduced from the outer side in the tire axial direction toward the inner side in the tire axial direction, and has a substantially wedge-shaped cross-section. Distance D of 2mm or more from carcass
It is characterized by being separated.

[0008] In the invention described in claim 2, the circumferential groove divides the rim protector into an inner peripheral portion on the tire radial inner side and an outer peripheral portion on the tire radial outer side.
2. The pneumatic tire according to claim 1, wherein a groove wall in which the inner peripheral portion faces the circumferential groove has an arc shape that protrudes into the circumferential groove in a tire meridian section. 3.

[0009]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 illustrates an assembly of a pneumatic tire in a standard state and a normal rim which is assembled to a regular rim J, filled with a regular internal pressure, and has no load. Appears symmetrically with half.

[0010] The "regular rim" is a rim defined for each tire in the standard system including the standard on which the tire is based.
"Standard rim", "Measuring Rim" for TRA, or "Measuring Rim" for ETRTO.

[0011] The "normal internal pressure" is the air pressure that is defined for each tire in the standard system including the standard on which the tire is based. Table "TIRE LOAD LIMITS AT
VARIOUS COLD INFLATION PRESSURES "
EINFTO means "INFLATION PRESSURE",
When the tire is for a passenger car, the pressure is 300 kPa.

Further, the "regular load" is a load defined by each standard in each standard in a standard system including a standard on which the tire is based. Ba Table "TIRE LOAD LIMITS A
The maximum value described in "T VARIOUS COLD INFLATION PRESSURES", or "LOAD CAPACITY" for ETRTO.

In FIG. 1, a pneumatic tire according to the present embodiment includes a carcass 6 extending from a tread portion 2 to a bead core 5 of a bead portion 4 through a sidewall portion 3, and a tire radius inside the tread portion 2 and the carcass 6. A flat tire having a belt layer 7 disposed on the outer side in the direction and having a flatness of 50% or less, and a flattening ratio of 45% in this example, is illustrated as an example.

The carcass 6 is composed of, for example, one or more carcass plies 6A having a radial structure in which carcass cords are arranged at an angle of 75 ° to 90 ° with respect to the tire equator C, in this embodiment. The carcass ply 6A
In this example, a toroidal main body 6a extending from the tread portion 2 to the bead core 5 of the bead portion 4 via the sidewall portion 3 is connected to the main body portion 6a and inward in the tire axial direction around the bead core 5. And a folded portion 6b that is folded outward from the outside. As the carcass cord, an organic fiber cord such as polyester, nylon, rayon or the like is preferably adopted, but a steel cord may be adopted depending on the tire.

The main body 6a of the carcass ply 6A
A bead apex 8 that extends from the bead core 5 in the tire radial direction and is made of hard rubber is disposed between the bead portion 5 and the folded portion 6b to reinforce the bead portion 4.

The belt layer 7 is formed by forming a high elastic cord such as a metal cord by 10 to 40 ° with respect to the tire equator.
At least two, in this example, inner and outer belt plies 7A and 7B, which are arranged at a small angle, are superposed in a direction in which the cords cross each other. Although not shown, a so-called band layer or the like in which a low elasticity organic fiber cord is substantially arranged in the tire circumferential direction may be appropriately arranged on the outer side of the belt layer 7 in the tire radial direction.

Further, the pneumatic tire includes the bead portion 4.
Further, an annular rim protector 9 protruding outward in the tire axial direction and continuing in the tire circumferential direction is formed. Such a bead protector 9 has a larger tire profile than a standard tire bead profile N that smoothly joins the sidewall portion 3 and a separation point P at which the bead portion 4 is separated from the rim J, as shown in an enlarged view in FIG. It protrudes axially outward. The rim protector 9 extends so as to cover a radially outer portion of the flange arc portion JF1 which is an arc-shaped portion of the rim flange JF and with a small gap therebetween, and extends the rim flange JF from a curb on a road shoulder. Protect.

In the present embodiment, the surface of the rim protector 9 has a convex top 9a, which is the portion most protruding outward in the tire axial direction from the bead profile N of the standard tire.
And hem portions 14 and 15 smoothly extending inward and outward in the tire radial direction from both ends of the top portion 9a and smoothly continuing to the bead profile N of the standard tire. The raised one is illustrated.

The skirt portion 14 on the inner side in the radial direction of the tire.
Indicates that, in the standard state, the flange arc portion JF2 of the rim flange JF is separated from the tire outermost point M in the tire radial direction. In addition, such a rim protector 9
Is preferably formed from a rubber having excellent wear resistance and trauma resistance using, for example, a hard clinch rubber which is in contact with the vertical portion JF1 of the rim flange.

In the present embodiment, the rim protector 9 is formed on the top 9a of the rim protector 9 in a circumferential direction that divides the rim protector 9 into an inner peripheral portion 10 on the inner side in the tire radial direction and an outer peripheral portion 11 on the outer side in the tire radial direction. One circumferential groove 12
Is formed, and the circumferential groove 12 has a substantially wedge-shaped cross section in which the groove width gradually decreases from the outer side in the tire axial direction to the inner side in the tire axial direction in the tire meridian cross section including the tire axis. One.

Such a circumferential groove 12 having a substantially wedge-shaped cross section.
As a result, the deformation of the rim protector 9 can be promoted by reducing the width of the circumferential groove 12 when a vertical load is applied to the tire, and as a result, the shock absorbing effect is exhibited and the riding comfort is deteriorated. Can be suitably prevented.

Further, when turning, a lateral force acts on the tire, so that the tire is deformed as shown in FIGS. 3A to 3B, and the rim protector 9 comes into contact with the flange arc JF2. However, even thereafter, as shown in FIG. 3 (C), when further lateral force acts, the groove width of the circumferential groove 12 can be narrowed to allow further deformation of the rim protector 9. For this reason, a sudden change in tire stiffness can be prevented even at the time of turning, and controllability of the vehicle at the time of limit running can be facilitated. Further, the wedge-shaped circumferential groove 12 enhances the heat radiation effect of the rim protector 9 that easily accumulates heat due to the large rubber gauge, and helps to improve the durability of the bead portion 4.

The circumferential groove 12 must have a groove bottom 12B, which is the inner end in the tire axial direction, separated from the carcass 6 by a distance D of at least 2 mm, preferably more than 2 mm. If the distance D is less than 2 mm, cracks that reach the carcass from the groove bottom 12B of the circumferential groove 12 as a starting point easily occur due to stress concentration or the like, and tire durability is reduced. Preferably, the distance D is 2.0 to
It is desirable to set it to 5.0 mm.

In this embodiment, as shown in FIG. 2, the circumferential groove 12 is formed by forming a groove wall 12i in which the inner peripheral portion 10 of the rim protector 9 faces the circumferential groove 12 in a tire meridian section. An example is shown in which a circular arc is formed so as to project into the circumferential groove 12, and the other outer groove wall 12o is formed in a substantially linear shape. Thus, when each groove wall is formed, the contact area of the facing groove walls 12i and 12o can be gradually increased as the load applied to the tire increases. For this reason, the rigidity of the tire gradually increases as the load increases, so that the driving feeling during turning and the controllability of the vehicle can be further improved. In the present embodiment, the inner groove wall is exemplified by an arc having a curvature radius R of 10 mm.

As an example in which the groove width of the circumferential groove 12 gradually decreases, the inner groove wall 12i is formed into an arc shape which is convex into the groove and the outer groove wall 12o is formed into a linear shape as in this embodiment. 4A, the inner and outer groove walls 12 are formed as shown in FIG.
Both i and 12o are linear, or as shown in FIG. 4B, the outer groove wall 12o is formed into an arc shape that protrudes into the groove, and the inner groove wall 12i is formed linear. FIG.
As shown in (C), various configurations can be employed, such as a configuration in which each of the inner and outer groove walls 12i and 12o is formed in an arc shape that projects into the groove.

In the groove bottom 12b of the circumferential groove 12, for example, the radius of curvature is 0.5 to less to prevent stress concentration.
Provision of a small arc portion of 1.0 mm may be preferably implemented. Further, the groove depth of the circumferential groove 12 may be determined in consideration of the reason for limiting the groove bottom position.
It can be set to about 10 to 10 mm, and in this example, it is set to 7 mm.

Further, the groove width of the circumferential groove 12 on the surface of the rim protector 9 can be variously determined according to the size of the tire and the like, but is preferably 2 to 5 mm, more preferably 2 to 4 m.
m, and 3 mm in this example. Since it is desired that such a groove width is closed at the time of a critical turning, for example, the tire is assembled to a regular rim to fill a regular internal pressure, and is pressed against a road surface with a regular load and a lateral force of 1.8 G is applied. It is also preferable to set a width in which the circumferential groove 12 closes on the surface of the rim protector 9 at this time.

In this embodiment, the circumferential groove 12 extends in a direction perpendicular to the bead profile N of the standard tire, but may extend in the tire axial direction. Further, the pneumatic tire of the present invention may be modified in various forms and implemented, for example, two or more circumferential grooves 12 may be formed.

[0029]

EXAMPLE A pneumatic tire having a tire size of 215 / 45R17, having the basic structure shown in FIG. 1 and having the specifications shown in Table 1 was prototyped (Examples 1 and 2), riding comfort and steering stability. , Bead durability, tire weight and the like were measured and evaluated. As shown in FIG. 4 (D), a test was also performed on a conventional example having a siping circumferential groove, and the performance was compared. The test method is as follows.

(1) Ride Comfort Four test tires were mounted on a test vehicle, and the tires felt rugged on a dry asphalt road surface of a tire test course.
The sensory evaluation of the driver regarding the thrust-up and the damping was performed, and the result was indicated by an index with the conventional example being 100. The higher the value, the better.

(2) Steering stability On the dry asphalt road surface of the tire test course,
The vehicle was turned at the limit of the turn, and the controllability of the vehicle was emphasized. The higher the value, the better.

(3) Bead durability The test tire was mounted on a regular rim (17 × 7.0JJ), filled with an internal pressure of 300 kPa, run on a drum at a load of 10.07 kN and at a speed of 60 km / h, and was placed on a bead portion. When the damage that can be confirmed visually is generated, the driving ends.
The running time was measured and evaluated by an index using the conventional example as 100. The higher the value, the better.

(4) Tire weight The weight per tire is measured and is indicated by an index with the conventional example being 100. The smaller the index, the better.
Table 1 shows the test results.

[0034]

[Table 1]

As a result of the test, it is found that the tires of the examples have excellent ride comfort and vehicle controllability.

[0036]

As described above, according to the first aspect of the present invention, the circumferential groove having a substantially wedge-shaped cross section is formed in the rim protector, so that the circumferential groove is formed when a vertical load is applied to the tire. By reducing the width, the deformation of the rim protector can be promoted, so that it is possible to suitably prevent the ride comfort from deteriorating due to the effect of absorbing shock.

During turning, the tire is deformed by the lateral force, and the rim protector comes into contact with the rim flange so as to rest on the rim flange. Even in such a case, the width of the circumferential groove is increased or decreased to further increase the rim protector. Can be tolerated. For this reason, a sudden change in tire stiffness can be prevented even at the time of turning, and controllability of the vehicle at the time of limit running can be facilitated. Further, such wedge-shaped circumferential grooves enhance the heat radiation effect of the rim protector that easily accumulates heat due to the large rubber gauge, and serve to improve the durability of the bead portion.

According to the second aspect of the present invention, the circumferential groove has a groove wall i formed in a circular arc shape that protrudes into the circumferential groove in the tire meridian section, so that the load applied to the tire increases. Accordingly, it is possible to gradually increase the contact area between the facing groove walls. Therefore, since the rigidity of the tire gradually increases as the load increases, the driving feeling during turning and the controllability of the vehicle can be further improved.

[Brief description of the drawings]

FIG. 1 is a right half sectional view of a pneumatic tire showing one embodiment of the present invention.

FIG. 2 is an enlarged sectional view showing a bead portion.

FIGS. 3A to 3C are schematic diagrams showing deformed states of a bead portion.

FIGS. 4A to 4D are contour views showing another example of the rim protection.

FIG. 5 is a sectional view of a bead portion showing a conventional rim protector.

[Explanation of symbols]

 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 6A Carcass ply 6a Carcass ply main body 6b Carcass ply turnback part 9 Rim protector 10 Inner peripheral part 11 Outer peripheral part 12 Circumferential groove 12i

Claims (2)

[Claims] 1. A pneumatic tire having a carcass extending from a tread portion to a bead core of a bead portion through a sidewall portion, wherein the bead portion has an annular shape projecting outward in the tire axial direction and continuous in the tire circumferential direction. In addition to the rim protector, the rim protector is formed with a circumferential groove continuous in the circumferential direction, and the circumferential groove extends from the tire axial direction outside to the tire axial direction inside in the tire meridian section including the tire axis. The groove width is gradually reduced toward the cross-section. The groove width is gradually reduced, and the groove bottom, which is the inner end of the circumferential groove in the tire axial direction, is separated from the carcass by a distance D of 2 mm or more. tire. 2. The circumferential groove divides the rim protector into an inner peripheral portion on the tire radial inner side and an outer peripheral portion on the tire radial outer side, and the inner peripheral portion faces the circumferential groove. 2. The pneumatic tire according to claim 1, wherein the groove wall has an arc shape that protrudes into the circumferential groove in a tire meridian section.