JP2866633B2 - 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 improving driving / braking performance on ice and preventing occurrence of cracks and chips due to siping provided on a block.

[0002]

2. Description of the Related Art Since the use of spiked tires has been banned to prevent road damage and dust pollution, pneumatic tires called so-called studless tires have been widely used in snowy areas and the like. In recent years, such pneumatic tires have adopted a block pattern in which a large number of blocks are formed on a tread surface, in addition to the development of a tread rubber material or the like which can maintain flexibility even in a low-temperature environment, and a large number of blocks are used. The performance on snow is greatly improved by the provision of siping.

[0003] However, pneumatic tires without spikes are still inferior to spiked tires in terms of running performance on slippery icy roads. Therefore, this type of pneumatic tire has been conventionally improved in performance on ice. There have been many suggestions for doing so.

For example, Japanese Unexamined Patent Publication (Kokai) No. 59-199306 discloses that a large number of blocks are formed on a tread surface, and each block has a wavy shape substantially in the tire axial direction as shown in FIG. It is proposed to improve the on-ice performance by increasing the edge component of the sipe by forming a sipe b extending.

[0005]

However, FIG.
In the siping b shown in FIG. 3A, satisfactory performance on ice cannot be obtained due to a decrease in block rigidity and a decrease in ground contact area. As shown in (B), when the block a receives the shearing force F in the tire circumferential direction, the siping b is easily opened, the deformation becomes large, and the block is chipped.
Cracks and other damage are likely to occur.

SUMMARY OF THE INVENTION The present invention has been devised to solve the above-mentioned problems, and suppresses the opening of siping while improving the running performance on icy roads by increasing the edge component of siping. Accordingly, an object of the present invention is to provide a pneumatic tire that can prevent the occurrence of chipping and cracking of blocks.

[0007]

Means for Solving the Problems In the present invention, claim 1 is provided.
The described invention is to provide a tread groove comprising a vertical groove extending in the tire circumferential direction and a horizontal groove extending in a direction intersecting the vertical groove on a tread surface between the tread edges E. Alternatively, a block surrounded by a side wall formed by the tread edge is formed, and the block extends from a first opening A opened on one side wall and a second opening B opened on another side wall. The siping includes a block with a siping in which a book siping is formed, and the siping is one of two block areas divided by a base line AB connecting the first opening A to the first and second openings A and B. The first extending to the first inner end point C in the area
And a second siping piece extending from the second opening B to a second inner end point D in the other block area;
The first and second siping pieces consist of a central siping piece that connects between the inner end points C and D, and the first inner end point C is the second
Distance in the tire axial direction to the opening B of the second inner end point D
Since it is smaller than the distance in the tire axial direction to the second opening B, the direction of the inclination of the line segment CD with respect to the base line AB is the same as the direction of the line segments CA and BD, and The second sipe piece and the central sipe piece are connected via a small arc, and the sipe is a first sipe.
Piece or second siping piece bent in zigzag or wavy form
It wants is a pneumatic tire, characterized in that.

The invention according to claim 2 is characterized in that the baseline AB between the first and second inner end points C and D of the siping.
The length W1 of the parallel component parallel to the first and second inner end points C and D is 0.1 to 0.6 times the length W of the base line AB.
A length W2 of a right angle component perpendicular to the base line AB is 0.2 to 1.0 times the length W of the base line AB.

[0009]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 illustrates a tread pattern when the pneumatic tire of the present invention is employed as a heavy-duty tire suitably used for trucks, buses, and the like. FIG. 2 shows a partial internal structure of the carcass 1 of a radial ply made of steel cord.
4 and a belt layer 15 made up of a plurality of, for example, four plies, which give the carcass a hoop effect and tighten it.

In FIG. 1, the pneumatic tire has a tread groove comprising a longitudinal groove 3 extending in the tire circumferential direction and a lateral groove 4 extending in a direction intersecting the longitudinal groove 3 on a tread surface 2 between tread edges E. By providing the TG, a block 7 surrounded by the groove wall 5 of the tread groove TG or the side wall 6 formed by the tread edge E is formed. In this example, the ratio of the total block surface area to the total tread surface area is set to 50 to 75% to form a winter tire.

In the present embodiment, the longitudinal grooves 3 include a main longitudinal groove 3A, which extends in a wavy shape, a narrow groove 3B narrow between the main longitudinal grooves 3A and 3A, and an ultrafine groove 3C closest to the tread edge E. Including
One or more, for example three, two on the tread surface 2
Two books are provided.

In the present embodiment, the lateral groove 4 is provided with the narrow groove 3B,
The blocks 7, 7 adjacent to each other in the tire axial direction via the ultrafine grooves 3C are formed so as to be arranged in a zigzag manner in the tire circumferential direction.

The vertical grooves 3 and the horizontal grooves 4 can be formed in any shape other than those shown in the drawings, such as those bent straight or zigzag, and when the tire is filled with the normal internal pressure, the groove width measured on the tread surface is reduced. The main vertical groove 3A and the horizontal groove 4 preferably have a diameter of 10 to 20 mm, the fine groove 3B has a diameter of 4 to 8 mm, and the ultra-fine groove 3C has a diameter of 2 to 5 mm. The groove depth is, for example, 7 to 20 mm according to the conventional example. Is preferred.

The block 7 has one side wall 6.
The first opening A that opens at the other side wall and the second opening A that opens at the other side wall 6
In this example, all the blocks 7 are used as the siping-containing blocks.

The siping 11 has a groove width of 0.3 mm to 2.0 mm for tires for heavy loads and passenger cars.
mm can be preferably adopted. Especially siping 11
However, when vulcanization molding in a mold, it is good to be 0.5mm ~ 2.0mm in consideration of the thickness of the knife blade of the mold,
Further, the groove width of the siping is set to 0.5 mm to 1.5 mm, more preferably 0.1 mm so as not to lower the block rigidity.
It is good to be 5 mm to 1.0 mm.

As shown in FIG. 3, the siping 11 has two block areas 7 divided by a base line AB which is a line connecting the first opening A to the first and second openings A and B.
A, a first inner end point C in one block area 7A of 7B
A first siping piece 11A extending from the second opening B to a second inner end point D in the other block area 7B, and inner end points of the first and second siping pieces. It consists of a central siping piece 11C connecting C and D.

In the present embodiment, the first siping piece 11A extends from the first opening A to the other block area 7B.
Bulge in an arc (the center is one block area 7A)
Side) and the end curved portion 20 extending in the one block region 7A beyond the base line AB, and smoothly connecting to the end curved portion 20 via an inflection point and extending linearly in the one block region 7A. It comprises a linear portion 21 and an inner curved portion 22 that smoothly connects to the linear portion 21 via an inflection point and curves in an arc shape (the center is on the other block region 7B side).

In the present embodiment, the second siping piece 11B is provided point-symmetrically with the first siping piece 11A about the intersection of the central siping piece 11C and the base line AB.

The first inner end point C is equal to the second inner end point D.
Since it is closer to the second opening B, the inclination direction of the line segment CD with respect to the base line AB is the same as the direction of the line segments CA and BD. Here, the first inner end point C is the second inner end point.
The fact that it is closer to the second opening B than the point D is clearly shown in FIG.
Close to the tire axial direction, that is, the first inner end
Point C is the distance in the tire axial direction from the second opening B to the second opening B.
From the distance in the tire axial direction from the inner end point D to the second opening B
Is also small.

In the present embodiment, the center siping piece 11C comprises a straight portion 24 overlapping the line segment CD, and the first and second siping pieces 11A and 11B and the center siping piece 11C are Inner curved part 22 and straight part 2
4 and smoothly connected to 0.5mm or more and 1.0mm
They are connected via a small arc 9 having the following radius R.

Accordingly, the first and second inner end points C and D
Is defined as the intersection of the virtual extension line of the first and second siping pieces 11A and 11B and the virtual extension line of the central siping piece 11C.

By providing such a siping 11, the edge component of the siping 11, particularly the edge component in the tire axial direction, can be substantially increased, and the driving / braking performance on an icy road can be improved.

Further, even if a shearing force in a direction perpendicular to the siping 11 acts on the block 7, the siping 11 forms a substantially Z-shape, so that the one and the other block area 7A divided by the siping 11 are formed. , 7B are engaged with each other to suppress the opening of the siping 11 as shown in FIG. 4, prevent the block rigidity and the ground contact area from decreasing, and also cause damage such as chipping of the block and cracks at the bottom of the siping 11. And even if a shear force, for example, a lateral force, substantially parallel to the siping 11 acts on the block 7, the amount of deformation of the block 7 can be greatly reduced by the siping 11, and cracks and chipping can be prevented.

The first and second siping pieces 11
A, 11B and the central siping piece 11C are connected via the small circular arc 9, so that stress can be dispersed as compared with an acutely formed one, and cracks at the bottom of this portion can be effectively prevented.

If the radius R of the small circular arc 9 is smaller than 0.5 mm, it is difficult to obtain a sufficient crack prevention effect.
7 mm or more is more preferable. Conversely, when the radius R is larger than 1.0 mm, the siping 11 is easily opened, and therefore, it is more preferably 0.9 mm or less.

The length W1 of the parallel component parallel to the base line AB between the first and second inner end points C and D of the siping 11 is at least 0.1 times the length W of the base line AB. And 0.
The length W2 of a right angle component perpendicular to the base line AB between the first and second inner end points C and D is 0.2 times or more and 1.0 times the length W of the base line AB. It is desirable that:

The length W1 is equal to the length W of the base line AB.
If the ratio is less than one, the opening of the siping 11 cannot be sufficiently suppressed, and cracks are likely to occur at the bottom of the siping 11. Therefore, the length W1 is more preferably 0.15 times or more the length W, and even more preferably 0.2 times or more.

If the length W1 is larger than 0.6 times the length W of the base line AB, the rigidity of the block due to the siping 11 is remarkably reduced, and the chip is likely to be chipped. Therefore, the length W1 is more preferably not more than 0.5 times the length W, and even more preferably not more than 0.3 times.

When the length W2 is less than 0.2 times the length W of the base line AB, the opening of the siping 11 cannot be sufficiently suppressed, and cracks are easily generated at the bottom of the siping 11. Therefore, the length W2 is more preferably 0.3 times or more the length W, and even more preferably 0.35 times or more.

Conversely, the length W2 is the length W of the base line AB.
If it is larger than 1.0 times, the rigidity of the block due to the siping 11 is significantly reduced, and the chip is likely to be chipped, and the performance on ice is also reduced. Accordingly, the length W2 is more preferably equal to or less than 0.6 times the length W, and still more preferably equal to or less than 0.5 times the length W.

Here, the present inventors, in order to confirm that the opening of the siping 11 is suppressed, FIG.
As shown in the figure, the falling angle δ of the block was measured. This inclination angle δ is provided at 14 measurement positions at equal intervals in the circumferential length of the block, and the inclination angle of each position with respect to the normal direction is measured. The magnitude of the lateral force is 60 (kgf), and one siping is provided in the middle of the circumferential length of the block.

FIG. 5 (B) shows the results, where ● represents the result of the siping of the present example, and ○ represents the result of the conventional siping consisting of a single straight line extending in the tire axial direction. In the case where the siping of this example is provided, the average falling angle of the first arrival side is 23.36 ° from the siping, and that of the second arrival side is 21.36 °.
78 °, and the difference between them is 1.58 °. However,
In the conventional siping, the average falling angle of the first arrival side is 24.
It is 64 °, that of the rear arrival side is 21.42 °, and the difference between the two is extremely large at 3.22 °.

As described above, the siping 11 of the present invention is
Falling angle δ at each of the first and last positions of the block
Is smaller than that of the conventional siping, and it can be confirmed that they fall almost uniformly. Therefore, the opening amount of the siping 11 is naturally smaller than the conventional one.

In this connection, the siping 11 of the present invention
Can make the ground pressure of the block uniform because the block falls down substantially uniformly as a whole. Therefore,
In a tire having a block pattern, uneven wear such as heel and toe wear caused by uneven contact pressure can be suppressed, and wear resistance can be improved.

When the vehicle turns, a slip angle is given to the tire. When the slip angle is given in a direction intersecting with the central siping piece 11C, especially when the blocks are integrated. As a result, the rigidity of the block is increased, so that the sliding of the block is suppressed, and the steering stability performance can be greatly improved.

From such a viewpoint, the intersection angles α1, α2 at the first and second inner end points C, D of the first and second siping pieces 11A, 11B and the central siping piece 11C are determined as follows. , Preferably at least 16 °, more preferably at least 24 °, even more preferably at 36 ° to 70 °, and still more preferably at 36 ° to 56 °, at the positions near the first and second inner end points C and D. It is desirable to prevent the occurrence of.

In this embodiment, the central siping piece 11
The example in which C is provided at an intermediate position of the siping 11 is illustrated. This case is preferable in that the effect of preventing the opening of the siping 11 is higher and the appearance of the siping 11 as a design is improved.

Further, the base line AB specifies the extending direction of the sipe 11 by connecting the first opening A and the second opening B of the sipe 11, but the base line AB of the center sipe piece 11C of the sipe 11 is Angle of inclination θ with respect to AB
(Measured on the base line AB) is greater than 0 ° and 83 ° or less, preferably 30 ° or more and 83 ° or less, more preferably 30 ° or more and 76 ° or less, still more preferably 30 ° or more and It is better to be 63 ° or less.

In order to further improve the performance on ice by the siping 11, in this example, the base line AB of the siping 11 is used.
Exemplarily extends in the tire axial direction (within an angle range of ± 5 ° with respect to the tire axial direction). That is, in such a case, when the vehicle is suddenly braked, the siping 1
This is because the effect of the present invention becomes more remarkable because a large shear force acts in the tire circumferential direction to push the tire 1 open.

It should be noted that such an effect is obtained by the siping 11.
The above described baseline AB can extend substantially in the tire axial direction, that is, even when it extends within an angle range of ± 15 ° with respect to the tire axial direction.

Further, the base line AB may be out of an angle range of ± 15 ° with respect to the tire axial direction. This case is preferable in that the opening of the siping can be prevented when the vehicle turns.

In this embodiment, since the blocks 7 are arranged so that the other sipes 11 are not arranged in the tire axial direction of the sipes 11, excessive stress does not concentrate on one siping 11. In addition, the generation of cracks at the bottom of the siping 11 can be effectively prevented, and the pitch between the side of the block 7 and the edge component formed by the siping 11 can be reduced, which also contributes to improvement of performance on ice.

Further, in this embodiment, since the first and second openings A and B are formed at the bending points of the concave or convex portions provided on the side wall of the block 7, the edge effect by the siping 11 is further enhanced. Can improve.

The first and second siping pieces 11
A and 11B may both be straight lines, only one of them may be zigzag, or one or both of them may be wavy, and further modified as appropriate by using a combination of straight, wavy and zigzag. sell.

[0045]

Example 1 The tire size is 11R22.5 and has the configuration shown in FIGS. 1 and 2 and the siping shape (parallel component length W1 / baseline AB length W) (right-angle component length) W
2 / Prototype tires of the present invention (Example products 1 to 8) having variously different base lines AB (length W), and various tests using actual vehicles were performed.

Tires whose siping did not satisfy the requirements of the present invention (comparative products 1 to 3) were also trial manufactured and their performances were compared. Details such as the tire structure are as follows.

Belt layer Belt layer Steel cord (3 + 6) 4-ply, Steel cord angle to tire equator C (from inside radial direction of tire) 50 ° R, 18 ° R, 18 ° L, 18
° L Carcass One ply of steel cord (3 + 7), angle of steel cord with respect to tire equator C: 90 ° Tread width (contact width) TW = 230mm Block size Maximum tire circumferential length 30mm, maximum tire axial direction 20mm width

In the test, the test tires were measured at 7.50 × 22.
5 rims (internal pressure 8.0 kgf / cm ² ), 2/2
Attached to the drive wheels of a -D vehicle (load capacity of 10 tons) and performed as follows.

B) Actual vehicle durability performance The ratio of the number of crack-occurring blocks to the total number of blocks after the completion of a running distance of 20,000 km (breakdown: about 10,000 km on a dry pavement, 5000 km on a wet pavement, and 5000 km on a dirt road) is described. .

B) Braking performance on ice On a slippery ice surface, the braking distance was examined by applying a lock sudden braking at a speed of 30 km / h, and the braking distance was measured.
Is shown as an index with 100 as the index. The larger the value, the shorter the braking distance and the better the braking performance on ice. Table 1 shows the test results.

[0051]

[Table 1]

As a result of the test, the product of the example was improved while maintaining the braking performance on ice compared to the product of the comparative example, or was maintained at the same level.
It was confirmed that the occurrence of cracks was reduced.

[0053]

Embodiment 2 A configuration (shown in FIG. 6) in which the tire size is 11R22.5 and the sipes are arranged in the tire axial direction,
The tires (Examples 9 and 10) of the present invention were prototyped for a configuration (shown in FIG. 7) in which the tires were not aligned in the tire axial direction but staggered in the tire circumferential direction, and various tests using actual vehicles were performed. Was done.

Details such as tire structure and test contents are as follows.
Since this is the same as the first embodiment, the description is omitted, and the results of the test are shown in Table 2.

[0055]

[Table 2]

As a result of the test, it was confirmed that the product of Example 10 had better braking performance on ice than the product of Example 9, and the occurrence of cracks was more effectively reduced.

[0057]

The pneumatic tire of the present invention can improve the driving and braking performance on icy roads by substantially increasing the edge component of siping.

Further, even if a shear force acts on the block, the opening of the siping can be suppressed because the siping has a substantially Z-shape, and a decrease in block rigidity and a decrease in ground contact area can be prevented. In addition to preventing damage such as chipping of the block and cracks at the bottom of the siping, securing the rigidity of the block and the ground contact area also contribute to improving the steering stability on dry pavement roads in addition to the performance on ice.

Further, by providing the siping, the block can fall down substantially uniformly as a whole, the ground pressure of the block can be made uniform, and uneven wear such as heel and toe wear can be suppressed.

[Brief description of the drawings]

FIG. 1 is a development view of a tread pattern showing an embodiment of the present invention.

FIG. 2 is a partial sectional view showing the internal structure of the tire.

FIG. 3 is an enlarged plan view showing details of a block.

FIG. 4 is a schematic diagram showing the behavior of the block when the ground is touched.

FIG. 5A is a side view illustrating a measurement position,
(B) is a graph showing a test result of the present invention.

FIG. 6 is a development view of a tread pattern showing an example product.

FIG. 7 is a development view of a tread pattern showing an example product.

FIG. 8A is a plan view illustrating a conventional siping, and FIG. 8B is a conceptual diagram illustrating its behavior.

[Explanation of symbols]

 2 Tread surface 3 Vertical groove 4 Horizontal groove 5 Groove wall 6 Side wall 7 Block 9 Small arc 11 Siping 11A First siping piece 11B Second siping piece 11C Central siping piece A First opening B Second opening AB Baseline C First inner end point D Second inner end point E Tread edge TG Tread groove

Continuation of the front page (56) References JP-A-1-254406 (JP, A) JP-A-7-1919 (JP, A) JP-A-2-310109 (JP, A) JP-A-4-87806 (JP) JP-A-7-215017 (JP, A) JP-A-62-181904 (JP, A) JP-A-59-199306 (JP, A) JP-A-7-37710 (JP, A) 3-10913 (JP, A) JP-A-4-173407 (JP, A) JP-A-62-50206 (JP, A) JP-A-2-254003 (JP, A) European Patent Application Publication 671288 (EP, A) 1) (58) Field surveyed (Int. Cl. ⁶ , DB name) B60C 11/00-11/24

Claims (2)

(57) [Claims] 1. A tread groove comprising a vertical groove extending in the tire circumferential direction and a horizontal groove extending in a direction intersecting the vertical groove is provided on a tread surface between tread edges E, E, so that a groove wall of the tread groove is provided. Alternatively, a block surrounded by a side wall formed by the tread edge is formed, and the block has a first opening A that is opened by one side wall.
And a siping block formed with a single siping extending continuously from a second opening B that is opened on another side wall, and the siping is a first and a second opening from the first opening A. A first siping piece extending to a first inner end point C in one of the two block areas divided by a base line AB connecting the openings A and B, and a first siping piece extending from the second opening B in the other block area. 2, a second siping piece extending to an inner end point D of the second and a central siping piece joining between the inner end points C and D of the first and second siping pieces, and the first inner end point C is a second siping piece . Tire axial direction up to opening B
Distance of the tire axis from the second inner end point D to the second opening B
Is smaller than the distance in the direction, the inclination direction of the line segment CD with respect to the base line AB is the same as the direction of the line segments CA and BD, and the first and second siping pieces and the central siping piece are: with continuous through the small circular arc, the sipes, the first sipes piece or second rhino
A pneumatic tire, wherein a ping piece is bent in a zigzag or wave shape. 2. The siping has a length W1 of a parallel component parallel to the base line AB between the first and second inner end points C and D.
Is 0.1 to 0.6 times the length W of the base line AB, and the length W2 of a right angle component between the first and second inner end points C and D and perpendicular to the base line AB is the base line AB. 0.2 to 1.0 of the length W
The pneumatic tire according to claim 1, wherein the pneumatic tire is doubled.