JPH11291718A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reconcile reduction in car outside noise and an improvement in running-through performance by circumferentially separately arranging extending blocks extending up to the sidewall part by going over the buttress part from the shoulder part, and specifying a tire radial directional inside end position of the respective extending blocks and a protrusion quantity in a prescribed position. SOLUTION: Among plural blocks B1 to B3 arranged on the tread surface 2a of a tire, extending blocks 9 extending up to the sidewall part 3 by going over the buttress part 12 from the shoulder part S of the tread part 2 is circumferentially separately arranged in the third block B3 to form the recessed part 10 between these. The radial directional inside end (a) of the extending blocks 9 is arranged in an area separating by a height not more than 0.3 to 0.5 times from a tread equatorial point to a tire cross-sectional height H. A protrusion quantity D from the recessed part 10 of the extending blocks 9 in a prescribed position (b) is set not less than 2.0 mm. An angle α of the extending blocks 9 to a tire radial line is set to 25 deg. to 45 deg..

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 improving running performance on muddy roads or the like without impairing noise outside the vehicle, and more particularly to a pneumatic tire for mud and snow suitable for a four-wheel drive vehicle.

[0002]

2. Description of the Related Art A so-called mud-and-snow tire mounted on a four-wheel drive vehicle or the like has a tread surface having a pattern in which a large number of blocks with siping are provided, and a tread surface. The driving performance on muddy land (hereinafter, such performance is referred to as "mud performance") is enhanced by setting the groove volume ratio occupying a large area.

[0003] However, when a tire having such a large groove volume ratio is mounted on a vehicle and travels on, for example, a dry asphalt road surface, a large amount of air is repeatedly compressed and released in the groove on the ground contact surface. There is a problem that a loud noise (external noise) is generated. In other words, mud performance and tire noise performance outside the vehicle are two trade-offs.

[0004] The present inventors have conducted various studies to improve the mud performance without impairing the noise outside the vehicle.
When driving on muddy ground, we noticed that the buttress part of the tire sunk into the muddy ground. Then, the inventors basically provided an extension block extending from the shoulder portion of the tread portion to the sidewall portion beyond the buttress portion in the circumferential direction, without substantially changing the groove volume ratio of the tread surface. The inventors have found that the mud performance can be improved, and have completed the present invention.

As described above, an object of the present invention is to improve the mud performance without impairing the noise outside the vehicle, which is a trade-off.

[0006]

The present invention according to claim 1 of the present invention is a pneumatic tire suitable for traveling on snowy roads and muddy terrain, from a shoulder portion to a sidewall portion over a buttress portion. By extending the extending extension block in the circumferential direction, a concave portion is formed between the extension blocks,
And, the radial inner end a of the extension block is located in a region separating the height of 0.3 to 0.5 times the tire cross-section height H from the tread equator point, and The protruding amount D of the extension block from the concave portion at a position b which is 1/3 of the radial height L from the end a to the tread equatorial point in the radial direction outward from the inner end a is 2.0 mm or more. And the inclination angle β of the side edge of the extension block with respect to the tire radial direction is 45 ° or less,
In addition, in the cross section of the tire meridian, the angle α of the buttress surface of the extension block with respect to the tire radius line is 25 ° to 4 °.
It is characterized by 5 °.

Further, according to the present invention, the angle α
The pneumatic tire according to claim 1, wherein the angle is greater than 30 ° and equal to or less than 40 °.

According to a third aspect of the present invention, the groove area ratio (Sg / St), which is the ratio of the groove area Sg to the tread contact area St in the tread surface, is 25 to 35%. Item 3. The pneumatic tire according to item 1 or 2.

In this specification, the dimensions of each part of the pneumatic tire defined in claims 1 and 2 are measured in a no-load state in which the tire is mounted on a regular rim defined by a standard and filled with a regular internal pressure. It shall be measured. 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 for ATMA, "Design R for TRA
im "or" Measuring Rim "for ETRTO.

[0010] The "normal internal pressure" is the air pressure defined for each tire in the standard system including the standard on which the tire is based. TIRE LOAD LIMITS AT VARIOU
Maximum value described in "S COLD INFLATION PRESSURES", ETR
If it is TO, it is "INFLATION PRESSURE", but if the tire is for a passenger car, it is 180 KPa.

The tread contact area S described in claim 3
t "is the area of the land portion included in the ground contact area of the tread surface and the groove portion (non-ground contact) when the tire is assembled on the regular rim, filled with the regular internal pressure, pressed with a regular load, and pressed against a flat plate. It refers to the total area. The “groove area Sg in the tread surface” refers to the groove area in the ground range. The "normal load" is a load defined for each tire in the standard system including the standard on which the tire is based. For JATMA, the maximum load capacity, and for TRA, the table "TIRE LOAD LIMITS" AT VARIOUS
Maximum value described in "COLD INFLATION PRESSURES", ETRT
If it is O, it is "LOAD CAPACITY", but when the tire is for a passenger car, the corresponding load of the internal pressure of 180 KPa is 85.
%.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. As shown in FIGS. 1 and 2, the pneumatic tire of the present embodiment is a mud-and-snow pneumatic tire that can be suitably mounted on a four-wheel drive passenger car. Here, mud and snow tires are designed to improve starting, acceleration and running performance on snowy roads and muddy grounds.
er Manufacturers Association). Such tires have the letters "M" and "S" (ie, MS, M) on at least one side of the sidewall.
+ S, M / S or M & S).

The pneumatic tire is a tread portion 2 in this embodiment.
And a carcass 6 whose both ends are locked by being turned around the bead core 5 of the bead portion 4 from the inner side to the outer side in the tire axial direction through the side wall portion 3 and the outer side of the carcass 6 in the radial direction and the tread. A radial structure having a belt layer 7 disposed inside the portion 2 is illustrated.

The carcass 6 includes two or more carcass plies 6A and 6B in this embodiment. The carcass plies 6A and 6B have carcass cords arranged at an angle of 75 to 90 degrees with respect to the tire equator C. In addition, as carcass cord, nylon,
Organic fiber cords such as rayon, polyester and aromatic polyamide are preferably used.

The carcass plies 6A and 6B are folded back so as to enclose a bead apex rubber 8 made of hard rubber and having a substantially triangular cross section rising from the bead core 5 to the outside in the radial direction. Is appropriately reinforced.

The belt layer 7 is composed of two belt plies 7A and 7B that overlap each other in the radial direction of the tire. Each of the belt plies 7A and 7B has a small angle of 10 to 45 degrees with respect to the tire equator C. The steel belt cords are arranged in different directions so as to cross each other between plies. A reinforcing layer made of an organic fiber cord or the like can be appropriately disposed outside the belt layer 7 in the tire radial direction as necessary.

As shown in FIGS. 1 and 2, the tread surface 2a of the tread portion 2 has a center rib L extending substantially on the tire equator C in the tire circumferential direction in the present embodiment.
c, and first, second and third blocks B1, B2, B3 which are sequentially arranged toward both sides in the tire axial direction on the outside thereof, and these blocks B1, B2, B3 or rib L
A vertical groove G1 extending in the tire circumferential direction and a horizontal groove G2 extending in a direction intersecting with the vertical groove G1 are formed between c.

In the present embodiment, the third block B3 includes an extension block 9 extending from the shoulder portion S of the tread portion 2 to the sidewall portion 3 beyond the buttress portion 12, and the third block B3 extends around the extension block 9. In this example, the recesses 10 extending from the buttress surface 12a between the extension blocks 9 and 9 to the side wall surface 3a are shown. "Butless part"
The term “part of the sidewall part 3 on the outside in the tire radial direction” refers to a region that does not touch the ground during normal running on a flat pavement.

The concave portion 10 formed between the extension blocks 9 and 9 can once compact the mud in the concave portion 10 when the tire sinks into muddy ground, and shears the compacted mud. This is very effective in exerting traction and improving mud performance.

In the present invention, the inner end a in the radial direction of the extension block 9 has a tire sectional height H from the tread equator point CP.
The height L which is 0.3 times or more and 0.5 times or less of the above is located in a region separated inward in the tire radial direction. The tread equatorial point CP refers to the intersection of the tire equatorial plane and the tread contour in the tire meridian section, and when there is a groove on the tire equatorial plane, the tread contour is a virtual contour filled with the groove. Shall be used.

Here, the inner end a in the radial direction of the extension block 9 is set at 0. 0 of the tire section height H from the tire equator point CP.
If the gap is less than three times the height, the effect of improving the mud performance using the concave portion 10 cannot be sufficiently exhibited. In consideration of the general sinking amount of the tire on muddy ground, the radial inner end a of the extension block 9 is separated from the tire equator point CP by more than 0.5 times the tire section height H. Unnecessarily increasing the size of the extension block 9 unnecessarily increases the weight of the tire.

Preferably, the radially inner end a of the extension block 9 has a tire sectional height H from the tread equator point CP.
It is preferable to separate a height L of 0.35 times or more and 0.5 times or less, more preferably 0.4 times or more and 0.5 times or less, inward in the tire radial direction.

The extension block 9 is provided with the recess 1.
In order to effectively use 0, it is necessary to regulate the amount of protrusion of the extension block 9 from the recess 10. As a result of various experiments by the inventors, tires that have sunk into mud when driving on mud have a particularly important role in mud performance.
It can be seen that the amount of protrusion D at a position b that is approximately one-third the radial height L from the inner end a of the extension block 9 to the tread equator point CP is radially outward from the inner end a. Was.

Therefore, in the present invention, a position b which is 1/3 times the height L in the radial direction from the inner end a of the extension block 9 to the tread equator point CP is radially outwardly separated from the inner end a.
, The amount of protrusion D of the extension block 9 from the recess 10 is limited to 2.0 mm or more. The amount of protrusion D is 2.
If it is less than 0 mm, the side edge (edge) of the extension block 9
The shearing ability of the mud using the water is reduced, and the mud performance cannot be sufficiently improved. Preferably, the protrusion amount D is 2.5 mm or more, more preferably 3.0 mm or more and 5.
It is desirable to set it to 0 mm or less.

In this embodiment, as shown in FIG. 1, the protruding amount D of the extension block 9 is relatively large at the buttress portion 12 of the extension block 9 and gradually decreases toward the sidewall portion 3. Is formed, but the present invention is not limited to this.

In this embodiment, the extension block 9 has an extension groove 13 extending from the shoulder S of the tread surface 2a and terminating inside the extension block 9, and recesses 14 formed on both sides of the extension groove 13. Is formed. By providing such extension grooves 13 and depressions 14, the extension blocks 9 of the tire submerged in mud are provided.
Helps increase the ability to shear mud and generate more traction to further improve mud performance. It is particularly preferable that each of the extension groove 13 and the depression 14 includes a portion having a depth of 2 mm or more.

Furthermore, in such an extension block 9, the inclination angle β (shown in FIG. 2) of the side edge 9e with respect to the tire radial line M is important for mud performance, and if the inclination angle β is too large. The edge effect of scraping mud is reduced by the concave portion 10 between the extension blocks 9. From such a viewpoint, the inclination angle β is desirably 45 ° or less, more desirably 35 ° or less, and further desirably 0 to 25 °.

Further, as a result of various experiments conducted by the inventors, an angle α (shown in FIG. 1) of the buttress surface 12b of the extension block 9 with respect to the tire radius line N in a tire meridian section including the tire axis shown in FIG. 25 to 45
°, preferably greater than 25 ° and less than or equal to 40 °, more preferably greater than 30 ° and less than or equal to 40 °.

In the conventional M + S tire, the angle α of the buttress surface with respect to the tire radial line N in the tire meridian section including the tire axis is smaller than that of the present embodiment.
Although the improvement of the mud performance using this portion could not be expected much, by setting the angle α to be large as in the present embodiment, a larger mud performance can be secured in muddy ground.

As described above, according to the present invention, in the pneumatic tire suitable for traveling on snowy roads and muddy lands, the buttress portion 12 can be moved from the shoulder portion S to the tread portion 12 without depending on the increase in the groove volume ratio of the tread surface 2a. The extension block 9 extending to the side wall portion 3 is basically spaced apart in the circumferential direction, and the mud performance can be improved by limiting the inner end of the extension block 9 in the tire radial direction and the amount of protrusion D.
The buttress portion 1 formed between the extension blocks 9, 9
2. Since the concave portion 10 of the sidewall portion 3 does not contact the road surface when traveling on a dry asphalt road surface, it is possible to prevent noise outside the vehicle from increasing.

Therefore, for example, while keeping the groove area ratio (Sg / St), which is the ratio of the groove area Sg in the tread surface 2a to the tread contact area St, at about 25 to 35% as in the prior art, the noise outside the vehicle is maintained. The mud performance can be improved as compared with the conventional M + S tire without increasing the tire size.

In the above embodiment, the non-extended block is interposed between the extension blocks 9 adjacent in the tire circumferential direction. However, such a non-extended block may not be interposed. . Further, a sipe or the like can be appropriately applied to the extension block 9 without departing from the operation of the present invention. Furthermore, the extension block 9 of the present embodiment is configured so that
Although e is formed, conversely, it may be formed to be tapered from the inner end a side, or the side edges 9e may be parallel to each other.

[0033]

EXAMPLES A tire having a tire size of 265 / 70R16 and having a configuration shown in FIGS. 1 and 2 was prototyped based on the specifications shown in Table 1 (Examples 1 to 4), and the vehicle exterior noise (passage) of the prototype tire was measured. Noise) and mud performance. For comparison, tests were also performed on conventional mud and snow tires (conventional examples 1 and 2). The test method is as follows.

1) The vehicle exterior noise test was conducted by an actual vehicle coasting test specified in JASO C606. A four-wheel drive vehicle equipped with test tires was set on a linear test course at a passing speed of 53 km / H and a distance of 50 m. At the middle point of the test course, measuring a maximum sound pressure level passing therethrough by a fixed microphone installed at a height of 1.2 m from the test road surface at a distance of 7.5 m laterally from the running center line,
The sound pressure level is represented by the difference of the sound pressure level based on Conventional Example 1. One indication is preferred.

2) Mud performance An actual vehicle is driven on a rough road having a mud layer having a depth of about 200 mm by a four-wheel drive vehicle equipped with test tires on all wheels, and the conventional example is changed to 6 by the driver's feeling. It was evaluated by the point method. Table 1 shows the test results.

[0036]

[Table 1]

As a result of the test, it was confirmed that the example of the present invention improved the mud performance substantially without impairing the noise outside the vehicle as compared with the conventional example 1. In addition, in Conventional Example 2 in which the groove volume ratio is increased, it can be confirmed that the noise outside the vehicle is also deteriorated.

In this embodiment, the rim of the tire is a standard rim of JATMA (8JJ) and the air pressure is 180 kP.
a, The load at the time of measuring the groove area ratio is 800 kgf.

[0039]

As described above, according to the first to third aspects of the present invention, the extension block extending from the shoulder portion to the sidewall portion beyond the buttress portion is circumferentially spaced from each other. By forming a recess and limiting the position of the inner end of the extension block in the tire radial direction and the amount of protrusion at a predetermined position, when the tire sinks into the mud, the extension block removes mud into the recess. Since large traction can be obtained by compacting and shearing the extension block, the mud performance can be greatly improved. In addition, a recess formed between the buttress portion and the sidewall portion formed between the extension blocks,
When traveling on a dry asphalt road surface, the vehicle does not touch the road surface, so that compression and release of air due to the contact with the ground can be prevented, and external noise can be prevented from being impaired. Therefore, both mud performance and external noise can be achieved.

According to the third aspect of the present invention, the absolute value of the noise outside the vehicle can be further restricted by limiting the area ratio between the groove area Sg in the tread surface and the tread contact surface St to a predetermined range. Becomes

[Brief description of the drawings]

FIG. 1 is a meridional section of a tire showing one embodiment of the present invention.

FIG. 2 is an enlarged perspective view showing a tread portion.

[Explanation of symbols]

 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 7 Belt layer 9 Extension block 10 Recess

Claims (3)

[Claims] 1. A pneumatic tire suitable for running on snowy roads and muddy ground, wherein an extension block extending from a shoulder portion to a sidewall portion beyond a buttress portion is circumferentially spaced from each other. Form recesses between extension blocks,
And the radial inner end a of the extension block is located in a region separating the height of 0.3 to 0.5 times the tire cross-section height H from the tread equator point, and the inside of the extension block. The protruding amount D of the extension block from the concave portion at a position b which is 1/3 of the radial height L from the end a to the tread equatorial point in the radial direction outward from the inner end a is 2.0 mm or more. And the inclination angle β of the side edge of the extension block with respect to the tire radial direction is 45 ° or less, and the angle α of the buttress surface of the extension block with respect to the tire radius line in the tire meridian section is 25 ° to 45 °. Features pneumatic tires. 2. The pneumatic tire according to claim 1, wherein the angle α is greater than 30 ° and equal to or less than 40 °. 3. A groove area ratio (Sg / St) which is a ratio of a groove area Sg in the tread surface to a tread contact area St.
The pneumatic tire according to claim 1 or 2, wherein the content is 25 to 35%.