JP3101555B2 - 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 suppressing a decrease in wet performance (drainage performance) and ice plate running performance due to progress of tire wear.

[0002]

2. Description of the Related Art Conventionally, in order to suppress hydroplaning, which is likely to occur when driving at high speed on a wet road surface in rainy weather or the like, and to improve wet performance, a tire circle is provided on a tread surface. A vertical groove for drainage that is continuous in the circumferential direction is provided, and in order to further improve the wet performance, improvements are made in the position of forming the vertical groove, the groove width, the groove volume, and the like.

However, as shown in FIG. 9, the vertical groove g generally has a V-shaped cross-sectional shape in which the groove width is reduced toward the groove bottom, so that the opening width gradually decreases with the progress of wear as the wear progresses. There is a problem that the wet performance is deteriorated.

Japanese Patent Application Laid-Open No. 7-112603 discloses a tire in consideration of a decrease in wet performance due to wear.
JP-A-6-115318 and JP-A-5-338
No. 412 is known.

Among them, Japanese Patent Application Laid-Open No. Hei 7-112603 discloses that, as shown in FIG. 10A, the groove width of an intermediate portion b is smaller than the groove width of an upper portion a and the groove width of a lower portion c. Disclosed the horizontal groove y, and the excessive fall of the block at the time of ground contact,
The groove width of the upper part a and the lower part c is set to be larger than the groove width of the normal lateral groove while suppressing the heel and toe wear by preventing the abutment between the wall surfaces in the intermediate part b. Has improved drainage performance. However, in this case, in order to prevent the block from falling down, it is necessary to reduce the groove width bw to 1 to 4 mm in the middle portion b over a length bh of about 4 mm. It is difficult to set the groove width larger than the groove width of the upper part a. Therefore, such a groove shape,
When adopted in a vertical groove that requires higher drainage performance,
The effect of improving drainage in the latter part of wear becomes insufficient, and especially in the middle part of wear when the intermediate part b is exposed, there is a state where the drainage is significantly reduced for a long period of time, which hinders safe driving in rainy weather. I do.

Japanese Patent Application Laid-Open No. 6-115318 discloses that
As shown in FIG. 10 (B), a heavy duty tire is disclosed in which an oblique projection d protruding from an intermediate height position is provided on a groove side wall of a vertical groove g. This is a step e for preventing stone biting which is conventionally formed from an intermediate height position to a groove bottom.
Since the protrusion d is provided instead of (shown by a dashed line), the groove width below the protrusion d is increased as a result. However, since the width of the groove at the bottom of the groove is still smaller than the width of the groove at the top of the groove, a decrease in drainage due to the progress of wear cannot be suppressed.

Japanese Unexamined Patent Publication No. Hei 5-338412 has a groove wall surface gs which extends in a direction in which the groove width decreases from the groove bottom of a single arc toward the tread surface, as shown in FIG. 10 (C). Disclosed is a vertical groove g, which reduces crack damage at the bottom of the groove and maintains drainage during progress of wear. However, with such a groove shape, there is a problem that the contact area at the end of wear is insufficient, so that wear is abrupt and durability is impaired.

As a result of repeated studies to solve the above problems, the inventor has found that a part or all of a plurality of circumferentially extending main grooves are formed by a bifurcated main groove branched at a groove bottom. In the late stage of tire wear , the number of the main grooves is doubled, so that the edge effect by the groove edge is increased, and it is possible to maintain wet performance (drainage performance) and ice plate running performance, and completed the present invention. It is.

SUMMARY OF THE INVENTION An object of the present invention is to provide a pneumatic tire capable of suppressing a decrease in wet performance and ice running performance due to progress of tire wear.

[0010]

According to the first aspect of the present invention, a main groove group including a main groove extending in a tire circumferential direction is formed on a tread surface, and the main groove group includes a cross section including a tire shaft. And a bifurcated main groove having a maximum groove width W1 at the bottom of the opening below the opening width W3 on the tread surface and having a protrusion protruding at a distance from both groove walls at the bottom of the groove. The opening groove width W3 of the forked main groove is:
A pneumatic tire having a tread width TW of 0.04 to 0.12 times.

Further, in the invention of claim 1, the structure
In addition to the protrusion, the protrusion is located at the top of the protrusion in the tire axial direction.
The width W2 is 0.1 to 0.3 times the maximum groove width W1.
You.

According to the second aspect of the present invention, there is provided the first aspect.
In addition to the above configuration, the protrusion is formed in a two-groove main groove from the tread surface.
A height H of 0.5 to 0.7 times the groove depth H1 to the deepest groove bottom
It is 2.

According to a third aspect of the present invention, in addition to the configuration of the first aspect, the forked main groove has a groove width in a cross section in the tire axial direction between the opening and the top of the projection. The groove width is continuous with the groove width W3, and the groove width is gradually increased from the top to the deepest groove bottom.

The gap between the groove wall and the projection is substantially constant in the depth direction in the cross section including the tire axis, and the width w in the tire axis direction is 0.3 to 1.0 times the opening groove width W3. It is preferred that

By forming a part or the entirety of the main groove as the two-groove main groove, the protrusion comes into contact with the ground at the end of wear of the tread surface, and the number of the main grooves in the tread surface increases. This allows the tire to increase the grip in the axial direction when traveling on wet roads, compensate for the decrease in grip due to excessive pattern rigidity due to the decrease in the depth of the main groove, and maintain the hydroplaning resistance when traveling in rainy weather, In addition, it is possible to maintain the ice floe running property.

Japanese Patent Application Laid-Open Nos. 5-85110, 5-338417 and 6-1 disclose tires that disclose branching of a groove formed on a tread surface.
No. 91230 is known.

Japanese Unexamined Patent Publication No. 5-85110 discloses a technique for preventing a stone from being caught in a small auxiliary groove.
Further, the present invention does not satisfy the main requirement of the present invention that the width of the groove bottom is larger than the opening width and the projection is provided on the groove bottom.

Further, Japanese Patent Publication No. 5-338417 has an object to balance the tread surface's groundability and abrasion resistance, and discloses the provision of a small notch in a groove wall. However, there is no disclosure in the present invention of a configuration in which the width of the main groove is increased toward the groove bottom and a projection is provided on the groove bottom.

Further, JP-A-6-191230 discloses that
The object of the present invention is to prevent stones from being caught in a narrow groove provided in a shoulder rib, and does not disclose a configuration for a main groove having a wide groove width.

As described above, each of the publications described above has a different problem from the invention of the present application, and does not disclose the configuration of the present invention. Therefore, the inventions described in the respective publications solve the problems of the present invention. It is not possible.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1 to 3, a pneumatic tire 1 is a tread of a rib type, a rib lug type, a block type, and a rib block type in which a main groove group 3 including a plurality of main grooves 4 extending in a tire circumferential direction is formed on a tread surface 2. As shown in FIG. 2, in the present embodiment, a block type is formed by providing a plurality of horizontal grooves 15 arranged in a direction intersecting with the main grooves 4 in addition to the main grooves 4 having the above-described configuration.

In the present embodiment, the main grooves 4 are straight grooves extending linearly in the tire circumferential direction.
Is a central main groove 4A arranged on the tire equator C and a pair of main grooves 4A arranged respectively on the outer side in the tire axial direction.
B, 4B.

Each of the main grooves 4 has a maximum groove width W1 at a groove bottom 7 below the opening 6 larger than an opening groove width W3 at the tread surface 2 in a cross section including the tire shaft.

Here, the groove bottom 7 means a range which is 1/2 of the groove depth H1 which is the depth from the tread surface 2 to the deepest groove bottom 9 of the main groove 4 located on the groove bottom side.

In this embodiment of the main groove group 3, all of the central main groove 4A and the side main grooves 4B, 4B protrude from the groove bottom 7 with the gap G from both side groove walls 10, 10. It is formed as a forked main groove 5 having a projection 11. Note that the forked main groove 5 is limited to a part of the main grooves in the main groove group 3 and, for example, only the main grooves 4B and 4B on the side arranged at a position effective for preventing side slip as shown in FIG. May be implemented.

The forked main groove 5 has an opening groove width W3 of 0.04 times or more and 0.12 times or less of the tread width TW, which is the distance between the tread edges E and E in the tire axial direction, and at least 5 mm. That is all.

When the width W3 of the opening groove is less than 0.04 times or less than 5 mm of the tread width, drainage during wet running is inferior and hydroplaning is liable to occur, and when it exceeds 0.12 times, the contact area of the tread surface 2 is reduced. This is because, in some cases, the wear resistance during running of the drum is reduced.

The projections 11 may be formed continuously in the groove direction, or may be formed intermittently with a break in the circumferential direction.

The height H2 from the bottom 9 of the deepest groove to the top 12 of the protrusion 11 is defined by the depth H1 of the groove.
Is formed as 0.5 to 0.7 times. If the height H2 is less than 0.5 times the groove depth H1, the number of grooves does not increase until the end of wear, and the recovery of wet performance and ice plate running performance is delayed in the latter part of wear, and the running unstable state is prolonged,
Projection wall 1 that forms the wall surface of projection 11 when 0.7 times larger
When the rigidity of No. 6 decreases, uneven wear is likely to occur.

Further, the protrusion 11 has a width W2 of the top 12 of the protrusion 11 in the tire axial direction set to 0.1 to 0.3 times the maximum groove width W1.
The width w of the gap G between the groove and the groove wall 10 is substantially constant in the depth direction in a cross section including the tire axis. By keeping the width w of the gap constant, drainage performance can be stabilized in the later stage of wear of the tread surface 2. The width w of the gap G in the tire axial direction is 0.3 to 1.0 times the opening groove width W3 and 3
It is preferably set to be at least mm.

If the width W2 at the top of the projection 11 exceeds 0.3 times the maximum groove width W1 , the drainage in the latter stage of wear is inferior, and the wet and ice plate running performance deteriorates.
On the other hand, if the width W2 is less than 0.1 times , the contact area of the tire will be insufficient in the latter stage of wear, resulting in poor wear resistance.

In forming the forked main groove 5, FIG.
As shown in (A), the inclination angle θ of the side wall 10 is the tread surface 2
0 ° to 30 ° from the opening 6 to the upper end of the groove bottom 7 with respect to the vertical line N, and the inclination angle γ of the projection wall 16 facing the side wall 10 of the projection 11 is 5 degrees with respect to the vertical line N. ° ~
Preferably, it is 30 °.

In the two-groove main groove 5, the intersection between the groove bottom 9 and the side wall 10 and the intersection between the groove bottom 9 and the projection wall 16 are connected by an arc to prevent a groove bottom crack. I have. Furthermore, it is more preferable to connect the three parts of the groove bottom 9, the side wall 10, and the projection wall 16 with a large arc that is in contact with the three.

The lateral groove 15 is formed in a normal groove shape having a U-shaped or V-shaped cross section in this embodiment. However, in order to maintain grip performance at the time of starting or braking when traveling on ice or snow at the end of wear, the lateral grooves 15 are required.
Also, the grooves may be formed as bifurcated grooves having the above-described configuration at all or at equal pitch intervals.

Further, the pneumatic tire 1 in this embodiment is
A carcass 26 which is turned from the tread portion 12 forming the tread surface 2 to the bead portion 25 of the bead portion 24 from the inner side in the tire axial direction to the outer side through the sidewall portion 13, and a tread portion outside the carcass 26. And a belt layer 27 disposed inside.

In this embodiment, a bead apex 28 made of hard rubber extends radially outward from the bead core 5 between the main body portion and the folded portion of the carcass 6.

The carcass 26 comprises one or more carcass plies, in this example one carcass ply.
In the present embodiment, the carcass cords made of organic fibers such as nylon, polyester, rayon, and aromatic polyamide have a radial arrangement or a semi-radial arrangement inclined at 70 to 90 degrees with respect to the tire equator C.

The belt layer 27 is made of the carcass 2 in this embodiment.
6 and a first belt ply 27A disposed radially outside the belt ply 27A therein.
And two belt plies 27B.

The inner and outer belt plies 27A, 27B
The belt cord 12 made of an organic fiber such as nylon, polyester, rayon, or aromatic polyamide fiber or a steel cord, is arranged side by side at an angle of 10 to 40 °, preferably 16 to 30 ° with respect to the tire equator C, and These cords are formed as a sheet body covered with topping rubber.

Further, as shown in FIG. 3A, the width of the two-groove main groove 5 may be gradually increased uniformly from the opening 6 to the deepest groove bottom 9, or as shown in FIG. Opening 6 as shown in FIG.
From the top 12 to the top 12 of the protrusion 11 may be continuous with the opening groove width W3, and the groove width may be gradually increased from the top 12 to the deepest groove bottom.

FIGS. 4A, 4B, 4C, and 4D show an embodiment of the groove bottom 7. FIG. (A), the maximum groove width W1 is located at the deepest groove bottom 9 and the width w of the gap G between the side wall 10 and the projection 11 in the tire axial direction is constant over the entire area of the groove bottom 7. 4B, the maximum groove width W1 is located at the deepest groove bottom 9, and the width w is gradually increased toward the deepest groove bottom 9. Further, in (C), the maximum groove width W1
Is located at the middle position in the height direction of the groove bottom 7,
The gap G is formed to be maximum at the position of the maximum groove width W1.

Further, as shown in FIG. 3 (D), in the groove bottom 7, the side wall 10, the projection wall 16 and the deepest groove bottom 9 may be formed by a curve enveloping both. As described above, the groove bottom 7 can be modified into various forms.

[0043]

EXAMPLE A tire having a tire size of 175 / 70R13 and having a block pattern shown in FIG. 2 on a tread surface 2 having a groove sectional shape shown in FIGS. 4) and a test of its performance. In addition, a test was also performed on a tire having a conventional configuration (conventional example) and a tire configured with a main groove having a shape other than the configuration of the present application (comparative example), and performance was compared.

The test was performed as follows. 1) Ice driving test Each test tire was mounted on all the wheels of a passenger car, and the time required for lapping was measured by running the vehicle on a test road having a radius of 50 m and freezing the road surface.
It was indicated by an index of 0. The smaller the value, the better. At the time of the test, judgment based on the driver's feeling was also performed, and the evaluation was made according to a five-step method.

The test was performed when the test tire was new and when the main groove was worn by 50% in the depth direction. The higher the evaluation at 50% wear, and the smaller the difference between 50% wear and the new product, the better.

2) Wet road surface running test On a running road composed of a smooth concrete road surface with a radius of 40 m, a water pool having a depth of 3 mm was formed over the entire area, and a running test was performed in the same manner as the ice floe test. The evaluation determination method is based on the ice floe running test.

Table 1 shows the groove shapes, dimensions, and dimensional ratios of the respective examples, the conventional example, and the comparative example, and Table 2 shows the results of the ice floe test and FIGS. 6A, 6B, and 6C. Table 3 and the results of the wet road running test are shown in Table 3 and FIGS.
(C) shows each.

[0048]

[Table 1]

[0049]

[Table 2]

[0050]

[Table 3]

As a result of the test, it was confirmed that the example can maintain stable running performance even at the time of 50% wear as compared with the comparative example.

[0052]

As described above, the pneumatic tire of the present invention has the following features.
Since the main groove extending in the circumferential direction includes the bifurcated main groove having the structure described in claim 1, deterioration of the wedge performance and ice plate running performance due to the progress of tire wear can be suppressed, and the tire life can be reduced. Running stability can be maintained over the entire period.

By regulating the height of the projections, the running stability can be maintained over the entire period of wear, and the occurrence of uneven wear can be prevented.

Further, by regulating the width of the top of the projection as described in claim 3, the wettability and the ice-board running property can be further improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of an embodiment of the present invention.

FIG. 2 is a plan view showing the tread pattern.

FIGS. 3A, 3B, 3C, and 3D are partial cross-sectional views showing the forked main groove.

FIGS. 4A, 4B, 4C, and 4D are partial cross-sectional views showing other embodiments of the forked main groove.

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

6A, 6B, and 6C are graphs each showing a relationship between a dimensional ratio of a forked main groove and a turning time (index) in a wet road surface running test.

FIGS. 7A, 7B, and 7C are graphs each showing a relationship between a dimensional ratio of a forked main groove and a turning time (index) in an ice floe running test.

FIG. 8 is a cross-sectional view illustrating a shape of a main groove in a comparative example.

FIG. 9 is a sectional view showing the shape of a conventional main groove.

FIGS. 10A, 10B, and 10C are cross-sectional views each showing the shape of a conventional main groove.

[Explanation of symbols]

 2 Tread surface 3 Main groove group 4 Main groove 5 Two-groove main groove 6 Opening 7 Groove bottom 9 Deepest groove bottom 10 Projection 11 Projection 12 Top G Gap H1 Groove depth H2 Height of protrusion TW Tread width W1 Maximum groove width W2 The width of the top of the projection W3 The width of the opening groove

Claims (3)

(57) [Claims] 1. A main groove group comprising a main groove extending in a tire circumferential direction is formed on a tread surface, and the main groove group has an opening lower than an opening groove width W3 on a tread surface in a cross section including a tire shaft. The groove width of the groove bottom has a maximum groove width W1 and the groove bottom has a bifurcated main groove having a protrusion protruding with a gap from both groove walls, and the opening groove width W3 of the bifurcated main groove is a tread. Width TW
0.04 to 0.12 times , and the protrusion is
The width W2 in the tire axial direction at the top of the rise is the maximum groove width W1.
A pneumatic tire characterized by being 0.1 to 0.3 times . 2. The projection has a height H2 0.5 to 0.7 times the groove depth H1 from the tread surface to the deepest groove bottom of the forked main groove.
The pneumatic tire according to claim 1, comprising: 3. The bifurcated main groove is formed in a cross section in the tire axial direction.
Groove width is from the opening to the top of the protrusion,
Continuous with the opening groove width W3, and from the top to the deepest groove bottom
2. The pneumatic tire according to claim 1, wherein the groove width gradually increases up to.