JP2003127618A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of preventing degradation in pattern stiffness while improving a coefficient of friction on a low μ road surface. SOLUTION: On a tread surface 2, an annular siping 3 orbiting around the tread surface 2 is provided.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a pneumatic tire capable of increasing a friction coefficient on a low μ road surface while maintaining pattern rigidity of a tread portion.

[0002]

2. Description of the Related Art Conventionally, the problems to be solved by the invention
In a pneumatic tire, in order to improve the friction coefficient on low μ road surface (μ is friction coefficient) such as ice road and wet road,
Forming sipings on the tread surface is performed. In many cases, the siping has a notch shape with a thickness of 1 mm or less, and is mainly formed in a straight line extending in the tire axial direction. Then, such siping exerts an edge effect of scraping the road surface at its edge (corner) portion, a wiping effect of removing a water film, and the like, and functions to increase a friction coefficient with the road surface.

However, with linear siping,
Since the edge effect is not exerted on the force parallel to the siping, in order to increase the friction coefficient with the low μ road surface, it is necessary to provide a large number of linear sipings in various directions. The pattern rigidity tends to decrease. Therefore, there is a problem that steering stability is deteriorated on a road surface having a large μ, such as a dry asphalt road surface.

The present invention has been devised in view of the above-mentioned problems. Basically, the tread surface is provided with an annular siping that surrounds the tread surface. It is an object of the present invention to provide a pneumatic tire capable of suppressing a decrease in pattern rigidity while increasing it.

[0005]

The invention according to claim 1 of the present invention is a pneumatic tire characterized in that an annular siping is provided on the tread surface so as to circulate around the tread surface.

It is desirable that the annular siping has, for example, a circular shape including an ellipse and an ellipse, and is formed in a central area of the tread surface which is an area of 50% of the tread ground contact width centered on the tire equator.

Further, it is preferable that the annular siping is a continuous body which does not communicate with the other grooves and the siping on the tread surface and has no discontinuity.

Further, the annular siping has a maximum diameter of 3 to 10 mm, a siping thickness of 1 mm or less, and a siping depth of 2 mm or more smaller than the depth of the vertical main groove formed on the tread surface. It is suitable.

Further, the tread surface is formed with at least one rib continuously extending in the tire circumferential direction in the tread surface central area which is an area of 50% of the tread ground width centering on the tire equator. It is desirable to provide the rib with the annular siping. Here, the “tread ground contact width” is the distance in the tire axial direction between the tread ground contact ends when the tire is assembled on a regular rim and filled with a regular internal pressure, and a regular load is applied to make contact with a flat surface. .

The "regular rim" is a rim that is defined for each tire in the standard system including the standard on which the tire is based. For example, the standard rim for JATMA and the "Design Rim" for TRA. , Or ETRTO
If so, use "Measuring Rim". Also, "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.
Maximum air pressure for TMA, and table "TIRE L for TRA.
Maximum value described in OAD LIMITS AT VARIOUS COLD INFLATION PRESSURES, or "INFLATION PRESSU for ETRTO
RE ", but 180 if the tire is for passenger cars
KPa. Furthermore, the "regular load" is the load that each standard defines for each tire in the standard system including the standard on which the tire is based. In the case of JATMA, it is 70% of the maximum load capacity, and in the case of TRA it is the table. TIRE LOAD LIMITS
70% of the maximum value described in "AT VARIOUS COLD INFLATION PRESSURES", 7 for "LOAD CAPACITY" for ETRTO
The load is 0%.

Further, in a state where the regular rim is assembled to the rim, the regular internal pressure is filled, and the regular load is applied to be grounded on a flat surface, it is preferable that the tread grounding surface includes 20 to 70 of the annular sipings. .

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. 1 is a development view showing a tread portion of a pneumatic tire showing an embodiment of the present invention in an expanded manner, FIG.
Shows a partially enlarged view thereof, and FIG. 3 shows the same perspective view. In the figure, the tread surface 2 that is in contact with the road surface is the tread surface 2
An annular siping 3 that goes around is provided. “To go around” means that the siping having a small thickness and a predetermined depth goes around the normal line N of the tread surface 2 as shown in FIG.

In this example, the annular siping 3 appears in a substantially circular shape on the tread surface 2 and extends to the inside of the tread surface 2 at a predetermined depth. Also ring-shaped siping 3
In the present example, is made of a continuous body having no discontinuity that does not communicate with other grooves formed on the tread surface 2 and other sipings. It is preferably formed in a substantially circular shape shown in FIGS. However, the annular siping 3 may have a polygonal shape as well as a circular shape including, for example, an oval or an ellipse, as long as it surrounds the tread surface 2. In particular, a shape having no acute-angled bent portion is preferable, and the circular shape is particularly preferable.

Unlike the conventional linear siping, the annular siping 3 can exert an edge effect in multiple directions such as the tire circumferential direction, the tire axial direction, and even the oblique direction. Particularly, in the case of a perfect circle and a continuous body as in this example, the edge effect can be exhibited in all directions. Therefore, the friction coefficient on the low μ road surface can be increased not only during braking and driving but also during turning with various slip angles.

Further, as shown in FIG. 4 (A), in the case of the straight-line siping S, when a shearing force in the direction perpendicular to the siping S is applied as shown in FIG. 4 (B), the land portion (for example, block b). Is more likely to fall, resulting in a decrease in the effective ground contact area and a decrease in rigidity, which tends to deteriorate the steering stability. on the other hand,
In this example, the ring-shaped siping 3 defines a cylindrical land portion 4 therein, and the land portion 4 is surrounded by other land portions via the ring-shaped siping 3. For this reason,
Even if a large shearing force is generated between the road surface and the road surface, the collapse of the land portion 4 is limited to be small in all directions, and the reduction of the ground contact area and the reduction of rigidity are prevented.

Further, in the case where the annular siping 3 does not communicate with other grooves as in this example, when an external force is applied,
Substantially only the land portion 4 surrounded by the siping 3 is deformed. Therefore, the deformation at the time of contact with the ground can be more effectively suppressed, and the pattern rigidity can be prevented from being significantly reduced. Thus, the annular siping 3 can effectively prevent the pattern rigidity from decreasing while increasing μ.

The annular siping 3 is not particularly limited, but as shown in FIG. 2, the siping thickness t is preferably 1 mm or less, more preferably 0.8 mm or less. When the siping thickness t is larger than 1 mm,
Since the columnar land portion 4 surrounded by the annular siping 3 tends to deform or move largely due to the amount of collapse, it is likely to be disadvantageous in terms of steering stability, wear resistance, and edge effect. The lower limit of the siping thickness t is not particularly limited as long as it can be carved by hand or can be formed by a cylindrical knife blade provided in a vulcanization mold.

The annular siping 3 is not particularly limited, but it is desirable that the maximum diameter D on the tread surface 2 be about 3 to 10 mm as shown in FIG.
The maximum diameter D is measured on the outer peripheral edge side of the siping 3 on the tread surface 2 as shown in FIG. If the maximum diameter D is less than 3 mm, the edge effect tends to be reduced, and conversely, if it exceeds 10 mm, the pattern rigidity may be deteriorated. For example, in the case of tires for passenger cars, in order to maintain the edge effect and the pattern effect in the best balance, it is desirable that the maximum diameter is about 4 to 8 mm.

Further, as shown in FIG. 3, the annular siping 3 preferably has a siping depth d which is smaller than the depth Gd of the deepest vertical groove formed on the tread surface 2 by 2 mm or more. is there. That is, it is preferable to satisfy the requirement of Gd−d ≧ 2 (mm). When (Gd-d) is less than 2 mm,
The siping depth d becomes large, and the pattern rigidity tends to decrease. If the siping depth d is too small, the annular siping 3 tends to disappear early due to wear or the like.
It is desirable to set it to mm or more.

Further, such an annular siping 3 is
As shown in FIG. 1, the central region Cr of the tread surface, which is the region of 50% of the tread contact width centered on the tire equator C,
It is effective to form it. Tread surface center area Cr
Has a high ground pressure and can greatly affect the rigidity of the entire pattern. Therefore, by providing the annular siping 3 in the tread surface central region Cr, the effect of increasing μ and preventing the decrease in pattern rigidity is maximized. It can be demonstrated.

As shown in FIG. 1, the tread surface 2 of the present embodiment has a total of three vertical main grooves 5 extending continuously in the tire circumferential direction, and between the vertical main grooves 5 and 5, and in the vertical direction. A total of four vertical narrow grooves 6 extending continuously in the tire circumferential direction between the main groove 5 and the tread ground contact end e are formed. The vertical main groove 5
In this example, is composed of a central vertical main groove 5a extending continuously on the tire equator C, and vertical main grooves 5b and 5b on both sides of the central vertical main groove 5a. The groove depth is the deepest in the vertical grooves, for example, 5 mm or more, and the groove width is greater than 3 mm. Further, the vertical narrow groove 6 is the central vertical main groove 5a.
And vertical narrow grooves 6a, 6a extending between the vertical main groove 5b on the side
And outer vertical fine grooves 6b and 6b extending between the vertical main groove 5a on the side and the tread ground contact end e. In the present example, the vertical fine grooves 6 are each formed with a groove width of about 1 to 2 mm and a groove depth smaller than that of the vertical main groove 5.

A first rib L1 is provided between the central vertical main groove 5a and the inner vertical narrow groove 6a, and the inner vertical narrow groove 6a is also provided.
Second ribs L2 are respectively formed between the vertical main groove 5b on the side of and. These ribs L1 and L2 both extend continuously in the tire circumferential direction without interruption, and
It is formed in the central region Cr of the tread surface. Also,
Block rows L3 and L4 are formed on the outer side of the second rib L2, in which blocks partitioned by the lateral groove 7 in the tire circumferential direction are arranged. In this example, the annular siping 3 is formed on the first and second ribs L1 and L2.

In such a tread pattern, since the rib is formed in the central region Cr of the tread surface where the ground pressure is high, the pattern rigidity can be made larger than that of the block pattern. Moreover, the ring-shaped siping 3 is provided with such a rib L.
Since it is provided in No. 1 and L2, it is possible to maximize the friction coefficient while minimizing the decrease in pattern rigidity.
Particularly preferably, in a state where the tire is assembled on a regular rim, is filled with a regular internal pressure, and is applied with a regular load to be grounded on a flat surface, 20 to 70, more preferably 20 to 70, of the annular sipings are provided in the tread grounding surface. It is desirable to set it so that 30 to 60 pieces are preferably included. When the number of the annular sipings 3 appearing in the ground contact surface is regulated in this way, the edge effect and the pattern rigidity can be more effectively balanced in a good balance.

In the above-described embodiment, the annular siping 3 may have an elliptical shape as shown in FIG. 5 (A) or an elliptical shape as shown in FIG. 5 (B), as described above. It is also possible to provide a mixture of two or more of the above. Further, those having different maximum diameters D and depths d may be mixed. Further, in the above-described embodiment, the rib provided with the annular siping 3 has been described, but the rib is not limited to this and may be formed in a block, for example. Further, it may be provided in a mixed manner with the conventional linear siping. When the annular siping 3 has a discontinuity 9 as shown in FIG. 6, the distance K between the ends is preferably 3 mm or less.

[0025]

EXAMPLE A size 175 / with the basic pattern of FIG.
A 65R14 pneumatic radial tire for passenger cars was prototyped based on the specifications in Table 1, and various tests were performed to compare the performances. The depth of the vertical main groove was 7.5 mm. The test method is as follows.

<Friction Coefficient Test on Wet Road> The test tire was assembled on a rim (14 × 5.5 JJ), filled with an internal pressure of 200 kPa, and mounted on a self-propelled traction test vehicle to a depth of about 1 mm on the asphalt road. The maximum friction coefficient when running at a speed of 64 km / h (load of 4.0 kN) was measured on the course sprinkled with water, and the index was evaluated with the index of Comparative Example 1 being 100. The larger the value, the larger the friction coefficient on the wet road surface and the better.

<Stiffness Test> A flat belt type bench cornering tester was used to measure the rising slope (stiffness) of μ when braking was applied from a speed of 80 km / h, and the index was set to 100 as Comparative Example 1. evaluated. The larger the value, the greater the stiffness and the better. The rim, internal pressure, and load were the same as in the above test.

<Unbalanced Wear Test> A test tire was mounted on an actual vehicle, and a rapid wear test was performed on the actual vehicle by a 300 km test running in a mode in which turning, braking and driving were combined, and the appearance was visually observed and evaluated. Table 1 shows the test results and the like.

[0029]

[Table 1]

[0030]

As described above, according to the first aspect of the present invention, since the tread surface is provided with the annular siping that circulates around the tread surface, the friction coefficient on the low μ road surface is increased and the pattern rigidity is improved. It can prevent the deterioration.

When the annular siping has a circular shape including an ellipse and an ellipse as in the second aspect of the invention, unlike the linear siping, the tire circumferential direction, the tire axial direction, and the diagonal direction are different. The edge effect can be exhibited in all directions. Therefore, the friction coefficient on the low μ road surface can be increased not only during braking and driving but also during turning with various slip angles. Moreover, when the annular siping is formed in the central area of the tread surface, which is the area of 50% of the tread contact width centered on the tire equator, where the contact pressure is high and has a large effect on the rigidity of the entire pattern, an increase in μ and pattern rigidity It is possible to maximize the effect of preventing the deterioration of

When the annular siping is formed as a continuous body which does not communicate with other grooves and the siping of the tread surface and has no continuous portion, it is substantially deformed. Is limited to the land portion surrounded by siping, so that the reduction in pattern rigidity can be further suppressed.

Further, as in the invention described in claims 4 to 5, the maximum diameter, the siping thickness, and the siping depth of the annular siping are limited to a certain range, and the ribs provided in the central region of the tread surface are provided. When the annular siping is formed, it is possible to more effectively increase the friction coefficient on the low μ road surface and prevent the pattern rigidity from decreasing.

According to the sixth aspect of the invention, in a state in which the rim is assembled to the regular rim, the regular internal pressure is filled, and the regular load is applied to be grounded on the flat surface, the annular shape is formed in the tread grounding surface. When 20 to 70 sipings are included, it is possible to more effectively increase the friction coefficient on the low μ road surface and prevent the pattern rigidity from decreasing.

[Brief description of drawings]

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

FIG. 2 is a partially enlarged view thereof.

FIG. 3 is a partial perspective view thereof.

4A is a perspective view of a block provided with linear sipings, and FIG. 4B is a side view showing an example of a braking state thereof.

5A to 5B are plan views showing another embodiment of the annular siping.

FIG. 6 is a plan view showing another embodiment of the annular siping.

[Explanation of symbols]

2 tread surface 3 annular siping 4 land 5 vertical main groove 6 vertical grooves 7 lateral groove L1 first rib L2 second rib

Claims (6)

[Claims] 1. A pneumatic tire having a tread surface provided with an annular siping that surrounds the tread surface. 2. The annular siping has a circular shape including an ellipse and an ellipse, and is formed in a central area of a tread surface which is an area of 50% of a tread contact width centered on the tire equator. The pneumatic tire according to claim 1. 3. The pneumatic tire according to claim 1 or 2, wherein the annular siping is a continuous body having no discontinuity that does not communicate with other grooves on the tread surface and the siping. . 4. The maximum diameter of the annular siping is 3
10. The sipe thickness is 1 mm or less, and the sipe depth is 2 mm or more smaller than the depth of the vertical main groove formed on the tread surface.
The pneumatic tire according to any one of 1. 5. The tread surface is formed with at least one rib extending continuously in the tire circumferential direction in a tread surface central area which is an area of 50% of the tread ground contact width centering on the tire equator. The pneumatic tire according to any one of claims 1 to 4, wherein the rib is provided with the annular siping. 6. The ring-shaped siping is provided in the tread contact surface in a state where the regular rim is assembled to the rim, the regular internal pressure is filled, and the regular load is applied to be grounded on a flat surface.
The pneumatic tire according to any one of claims 1 to 5, wherein the pneumatic tire contains 70 to 70 pieces.