JP3365744B2 - Pneumatic tire - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire capable of satisfying both traveling performance on muddy ground and wandering performance on paved roads.

[0002]

2. Description of the Related Art Pneumatic tires intended for running on mud have to improve their ability to escape from muddy ruts. Generally, when traveling on a muddy ground, the tire sneaks into the mud relatively deeply. Therefore, it is effective to obtain the traction force not only from the normal tread portion but also from the buttress portion connected to the tread portion.

Therefore, in a pneumatic tire for traveling on a muddy ground, a block b formed in a tread shoulder portion as shown in FIG. 6, as represented by, for example, an agricultural tire.
Is extended to the buttress portion c, and this portion is projected outward in the tire axial direction.

However, in recent years, even with this type of tire, the opportunity to run on a paved road has increased, and particularly when a rut is formed on the paved road, the above-mentioned protruding portion of the buttress portion c, particularly the protruding portion thereof, is protruded. The tread edge d or the like is caught on an inclined surface of a rut or the like, and a force for changing the direction of the tire is generated, so that a wandering phenomenon that causes the vehicle to stagger is likely to occur.

The present invention has been devised in view of the above problems, and it is an object of the present invention to provide a pneumatic tire which can achieve both traveling performance on a mud and the like and wandering performance on a paved road. Has an aim.

[0006]

The invention according to claim 1 of the present invention is a pneumatic tire suitable for traveling on mud, which extends from the tread shoulder portion to the buttress portion and alternates in the tire circumferential direction. In the contour line of the tire outer surface in the tire meridian section in the normal state in which the rim is assembled to the regular rim and the regular internal pressure is filled, the first block part and the second block part Has a first buttress surface extending inward in the tire radial direction from the tread edge of the first block portion, and the first buttress surface extends in the tire radial direction passing through the tread edge of the first block portion. The angle of intersection θ1 with the line extends from 0 ° to 20 ° outwardly in the tire axial direction and extends inward in the radial direction of the tire, and the second block portion has a tread edge of the second block portion. Building to Luo radially inner second
And a tread edge of the second block portion is formed further inward in the tire axial direction than the tread edge of the first block portion, and the contour line of the second buttress surface is , A concave portion that passes inside the tire from the contour line of the first block portion in which the tire rotation axes are aligned,
It is characterized in that it includes a projecting portion that is continuous with the inner end of the recessed portion in the radial direction of the tire and that extends beyond the contour line of the first block portion to the outside of the tire.

The "regular rim" used in this specification
Is a rim that is defined for each tire in the standard system including the standard on which the tire is based.
Standard rim for ATMA, "Design R for TRA
In the case of im "or ETRTO, it is" Measuring Rim "In addition," regular internal pressure "is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. For JATMA, the maximum air pressure, for TRA, see the table "TIRE LOAD LIMITS ATVARIOUS C
Maximum value stated in "OLD INFLATION PRESSURES", ETRT
If it is O, it is "INFLATION PRESSURE", but if the tire is for passenger cars, it is 180 kPa.

The tread edges of the first and second block portions are the intersections of the tread surface and the buttress surface of each block portion. If this portion is rounded with an arc, Apply a regular load to the tire in the regular state,
This is the tire circumferential direction line that passes through the outermost edge of the ground contact in the tire axial direction of each block when it is grounded on a plane. At this time, the “regular load” is a load defined by each standard in the standard system including the standard on which the tire is based. For example, in the case of JATMA, the maximum load capacity, T
If it's RA, please see "TIRE LOAD LIMITS AT VARIOUS COLD I
The maximum value stated in "NFLATION PRESSURES" is "LOAD CAPACITY" for ETRTO, but 85% of the corresponding load with an internal pressure of 180 kPa when the tire is for passenger cars.

Further, "the first ones arranged alternately in the tire circumferential direction
"The block portion and the second block portion of" are provided at least at one place in the tread shoulder portion, in addition to the case where these blocks are provided alternately and continuously on the tire circumference. It suffices to include those that are arranged alternately. Therefore, for example, a mode in which the plurality of first block portions are arranged continuously and then the plurality of second block portions are arranged is also included in the present invention.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a partial cross-sectional view of the pneumatic tire 1 of the present embodiment in the tire meridian direction (a normal state in which the tire is assembled to the regular rim J and the regular internal pressure is filled).
Further, FIG. 2 shows a partial perspective view in which the tread shoulder portion is enlarged. In the drawings, the pneumatic tire of the present embodiment is a pneumatic tire suitable for traveling on a muddy ground, a snowy road, or the like, and may be configured as a pneumatic tire for mud and snow, for example.

Here, "tire for mud and snow"
Is designed to improve starting, acceleration, and driving performance on snowy roads and on mud.
It is defined by A (Rubber Manufacturers Association). In such a tire for mud and snow, the letters "M" and "S" (that is, MS, M + S, M / S, M & S, etc.) may be stamped on the sidewall portion.

In this example, the pneumatic tire 1 has a carcass 6 extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and a carcass 6 radially outside the carcass 6 and inside the tread portion 2. A radial structure having a belt layer 7 arranged is illustrated.

The carcass 6 is composed of one or more carcass plies 6A and 6B, in this example, two carcass plies 6A and 6B.
Both ends are folded back around the bead core 5 and locked. The carcass plies 6A and 6B are at the tire equator C.
The carcass cord is arranged at an angle of 75 to 90 degrees with respect to. As a carcass cord, nylon,
Organic fiber cords such as rayon, polyester and aromatic polyamide are suitable.

In this embodiment, the belt layer 7 is composed of two belt plies 7A and 7B which are overlapped with each other inside and outside in the radial direction of the tire.
In each of the belt plies 7A and 7B, steel belt cords arranged at a small angle of 10 to 45 degrees with respect to the tire equator C are arranged in different directions so that the plies cross each other. If necessary, a reinforcing layer made of an organic fiber cord may be appropriately provided on the outer side of the belt layer 7 in the tire radial direction. The structure of the tire may be of any type such as bias or belted bias.

As shown in FIGS. 1 and 2, the tread portion 2 in this embodiment has a longitudinal groove G1 extending in the tire circumferential direction.
And a lateral groove G2 extending in a direction intersecting with this is formed. Further, the pneumatic tire 1 has a first block portion B1 and a second block portion that extend from the shoulder portion Sh, which is an outer region in the tire axial direction of the tread portion 2, to the buttress portion Bu and are arranged alternately in the tire circumferential direction. B2 and. As shown in FIG. 2, each of these block portions B1 and B2 is exemplified in the present embodiment as being formed separately through the lateral groove G2 in the tire circumferential direction. In addition, the "Butless part"
Is a portion of the sidewall portion 3 on the outer side in the tire radial direction, and is an area that does not contact the ground during general straight running on a flat paved road.

3 and 4 show contour lines of the tire outer surface in the tire meridional section in the normal state for each block portion. FIG. 3 shows the first block portion B1. The first block portion B1 has a first buttress surface 9 extending inward in the tire radial direction from the tread edge e1 of the first block portion.

The first buttress surface 9 is a tire radial direction line N1 passing through the tread edge e1 of the first block portion.
The angle .theta.1 of intersection with .theta. Is 0 to 20.degree. Therefore, the first buttress surface 9 of the present example extends to the sidewall portion 3 with a relatively steep inclination. As a result, the buttress surface 9 is less likely to be caught by a rut on the pavement, which helps improve the wandering performance. When the intersecting angle θ1 exceeds 20 °, the first angle
The protrusion of the buttress surface 9 on the outer side in the tire axial direction becomes large, and the rut slope on the paved road is likely to be caught.

Further, the first buttress surface 9 includes a first outer buttress surface 9a on the outer side in the tire radial direction and a first inner buttress surface 9b on the inner side thereof in this example. Of these, the buttress surfaces 9a and 9b on the outside intersect at an intersection P1. The intersection P1 is shown as a point where the shortest distance h1 from the groove bottom of the lateral groove G2 is set to, for example, about 2 to 10 mm.

Further, the first outer buttress surface 9a is formed as a concave surface which is concave toward the inner side of the tire in this example. More specifically, it is substantially formed by an arc having a radius of curvature Rb1 centered outside the tire. This radius of curvature Rb1 is preferably in the range of 50 to 500 mm, for example. The first inner buttress surface 9b is formed by smoothly connecting the intersection P1 to the outer surface of the sidewall portion 3. The first inner buttress surface 9b may be concave, convex or flat.

The first buttress surface 9 of the present example is shown to intersect with the tread surface 2a of the first block portion with a clear edge (corner), which is shown by a chain line in FIG. As described above, these may be connected via a small arc. In this case, since the vicinity of the tread edge e1 becomes softer than that formed by the edge, the impact at the time of being caught with the rutted slope can be further alleviated, and the wandering performance on the paved road can be further improved. Be useful. The small arc preferably has a radius of curvature of 5 to 100 mm.

Further, as shown in FIG. 4, the second block portion B2 has a second buttress surface 10 extending inward in the tire radial direction from the tread edge e2 of the second block portion. In the present example, the second buttress surface 10 is similar to the first buttress surface 9 in that
Outer buttress surface 10a and a second inner buttress surface 10b inside thereof. Of these, the buttress surfaces 10a and 10b on the outside intersect at an intersection P2. The intersection P2 is shown to be outside the intersection P1 in both the tire radial direction and the tire axial direction.

Further, the second outer buttress surface 10a is formed as a concave surface which is concave toward the tire cavity side in this example. More specifically, it is substantially formed by an arc having a radius of curvature Rb2 centered on the outside of the tire. This radius of curvature Rb2 is preferably in the range of 30 to 300 mm, for example.

The second outer buttress surface 10a has a second
The intersection angle θ2 with the tire radial direction line N2 passing through the tread edge e2 of the block is set larger than the intersection angle θ1 and is set to, for example, about 10 to 45 °, and the tire is inclined outward in the tire axial direction. It is formed so as to extend inward in the radial direction. Therefore, the second buttress surface 1 of the present example
0 extends to the side wall portion 3 at a gentler inclination than the first buttress surface 9. As a result, the second block portion B2 can utilize the protruding portion of the buttress portion to improve the rutability of the rut in mud and the like.

The second inner buttress surface 10b is formed by smoothly connecting the intersection P1 to the outer surface of the sidewall portion 3. This second inner buttress surface 10b
May be a concave surface, a convex surface, or a flat surface, and is linear in this example.

By the way, in order to improve the rut escape property in a muddy area, it is effective to overhang the buttress portion Bu as described above. However, such a structure is effective for wandering on a paved road. As described above, the ring performance tends to be deteriorated. In the present invention, in order to make these contradictory performances compatible with each other, the second block portion B2 has the tread edge e2 of the second block portion inside the tread edge e1 of the first block portion in the tire axial direction. Is formed. Thereby, the tread edge e2 of the second block portion
Effectively prevents it from getting caught on the rutted slope on the paved road.

The distance X in the tire axial direction between the tread edge e1 of the first block portion and the tread edge e2 of the second block portion is, for example, the tread edge e of the first block portion.
2 to 10% of the first tread width TW1 (shown in FIG. 1), which is the tire axial distance between 1 and e1, more preferably 5
It is desirable to set it to 10%. This makes it possible to more effectively prevent the rut slope from being caught. The first tread width TW1 is set to be approximately 70 to 95% of the tire sectional width SW (shown in FIG. 1).

Further, as shown in FIG. 4, the contour line L2 of the second buttress surface 10 is a recessed portion 1 which passes inside the tire more than the contour line L1 of the first block portion in which the tire rotation axes are aligned.
1 and an overhanging portion 12 that is continuous with the inner end of the recessed portion 11 in the tire radial direction and that extends outward of the tire beyond the contour line L1 of the first block portion. As described above, the buttress surface 10 of the second block portion B2 includes the projecting portion 12 that projects from the contour line L1 of the first block portion to the outside of the tire through the recessed portion that is once recessed. It is difficult for the overhanging portion 12 to collide with the slope of the rut formed on the paved road, and the rutability in the mud can be improved without impairing the wandering performance on the paved road.

Here, the recessed portion 11 extends inward from the tread edge e2 of the second block portion in the tire radial direction, and in this embodiment, the tire radial length Z1 is
It is set to 10 mm or more, and more preferably set to 12 to 30 mm. As a result, it is possible to more reliably prevent the protruding portion 12 of the second buttress surface 10 from being caught by a general rutted surface that is formed on a paved road.

The projecting portion 12 is included in a wide range from the inner end of the recessed portion 11 to the second inner buttress surface 10b. The length Z2 of the overhanging portion 12 in the tire radial direction is 20 mm or more in this example, and more preferably 25 to 70 mm. When the tire sinks in the mud, the mud is once compacted in the lateral groove G2, but the second buttress surface 1
0 indicates an overhanging portion 12 over a wide range in the tire radial direction.
Since the mud is formed, the mud compacted at the overhanging portion 12 can be sheared to exert a large traction and the rutability in the mud can be further improved.

The distance S between the intersection point P1 of the outer buttress surfaces 9a and 9b of the first buttress surface 9 and the intersection point P2 of the outer buttress surfaces 10a and 10b of the second buttress surface 10. Is preferably 10 to 50 mm, for example. If the distance S is less than 10 mm, the running performance in the mud tends to be relatively lowered, and conversely 5
If it exceeds 0 mm, the amount of overhang tends to increase and the weight of the tire tends to unnecessarily increase.

FIG. 5 shows another embodiment of the present invention. In the present embodiment, the first block portion B1 is formed integrally with the second block portion B2 without the lateral groove G2. Even with such a configuration, the same operational effects as those of the above embodiment can be exhibited.

Although the embodiment of the present invention has been described in detail above, one or both of the first and second block portions B1 and B2 may further extend to the sidewall portion 3. In this case, when the tire travels at a low internal pressure, the first and second blocks can effectively enlarge the ground contact end. In addition, since tires of this type are often formed with a high groove ratio in the tread shoulder portion, tire noise, particularly large passing noise, is likely to occur. Therefore,
At least these first and second block parts B1 and B2
In addition, it is also preferable to reduce the pattern noise by using a soft compounded rubber material having a lower JIS A hardness than the rubber material of the inner tread crown portion.

[0033]

EXAMPLE A tire having a tire size of 265 / 70R16 and having the configuration shown in FIGS. 1 and 2 was prototyped based on the specifications shown in Table 1, and the trial tire was tested for wandering performance and mud running performance. . The test method is as follows.

1) Wandering performance Each sample tire was assembled on a rim (8JJ) and the internal pressure was 1
The vehicle was mounted on a vehicle under 80 kPa, traveled in the rut of a paved road at a speed of 80 km / h, and the degree of vehicle wandering was evaluated by a 10-point method by the sensory function of the driver. The larger the value, the smaller the fluctuation and the better the wandering performance.

2) Running performance on mud ground A four-wheel drive vehicle equipped with all the test tires runs on a muddy, rough road having a mud layer with a depth of about 200 mm. Evaluation was made by a 10-point method with a score of 6. The test results are shown in Table 1.

[0036]

[Table 1]

As a result of the test, it can be confirmed that the embodiment has both the wandering performance and the mud running performance as compared with the conventional example.

[0038]

As described above, the pneumatic tire of the present invention can achieve both traveling performance on muddy ground and wandering performance on paved roads.

[Brief description of drawings]

FIG. 1 is a meridian sectional view of a tire showing an embodiment of the present invention.

FIG. 2 is a partial perspective view showing enlarged first and second block portions.

FIG. 3 is a cross-sectional view illustrating a contour line of a first block portion.

FIG. 4 is a cross-sectional view illustrating a contour line of a second block portion.

FIG. 5 is a cross-sectional view of a first block portion showing another embodiment.

FIG. 6 is a perspective view showing a block of a conventional pneumatic tire.

[Explanation of symbols]

2 tread section 3 Side wall part 4 bead section 5 bead core 6 carcass 7 Belt layer 9 First buttress surface 10 Second Buttress Surface 11 Recessed portion of second buttress surface 12 Overhanging portion of the second buttress surface B1 First block part B2 Second block part e1 Tread edge of the first block e2 tread edge of second block

Claims (3)

(57) [Claims] 1. A pneumatic tire suitable for running on mud, comprising a first block portion and a second block portion extending from a tread shoulder portion to a buttress portion and arranged alternately in the tire circumferential direction. In the contour line of the tire outer surface in the tire meridian cross section in the normal state in which the regular rim is assembled to the rim and filled with the regular internal pressure, the first block portion is the inner side in the tire radial direction from the tread edge of the first block portion. A first buttress surface that extends, and the first buttress surface intersects with a tire radial direction line passing through a tread edge of the first block portion at an angle θ1.
Is 0 to 20 ° and extends outward in the tire axial direction, and extends inward in the tire radial direction, and the second block portion extends inward in the tire radial direction from the tread edge of the second block portion. And a tread edge of the second block portion is formed on the inner side in the tire axial direction with respect to the tread edge of the first block portion, and the contour line of the second buttress surface is a tire. A concave portion that passes inside the tire with respect to the contour line of the first block portion with the rotation axes aligned, and a tire radial direction inner end of the concave portion that is continuous with the concave portion and protrudes outward of the tire from the contour line of the first block portion. A pneumatic tire including an overhanging portion. 2. The pneumatic tire according to claim 1, wherein the first block portion is formed separately from the second block portion by way of a lateral groove. 3. The pneumatic tire according to claim 1, wherein the first block portion is integrally formed with the second block portion without a lateral groove.