JPH11180115A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease pattern noise from when the tire is new to when the tire is worm without losing the uneven wear characteristics in a pneumatic tire having blocks in the tread. SOLUTION: A vertical cut-out 26 is made vertically in the block wall 24A in the interim in the direction of tire rotation (the side of the direction of Arrow R) in a second block 24 that joins on the inside of the shoulder block. The compression rigidity of the treading end of the second block 24 diminishes because of the cut-out 26. This generates heal and toe wear of the shoulder block. Noise during treading even with a heavy load on the treading end of the second block is controlled and the worsening of pattern noise is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire having a block in a tread, and more particularly to a new pneumatic tire having a tread pattern having a block having sharp corners without impairing uneven wear of a pneumatic tire. The present invention relates to a pneumatic tire with improved pattern noise during time to wear.

[0002]

2. Description of the Related Art In general, a pneumatic tire having a block pattern tends to cause uneven wear called so-called heel-and-toe wear in which a step is formed between a stepped side and a kicked-out side of a block. However, the appearance and noise are deteriorated with this, and it is strongly demanded to improve them.

The heel-and-toe wear is a phenomenon in which the toe side, which is a kick-out side, is worn earlier than the heel side, which is a step-in side, so that a step is generated. , Shoulder blocks.).

Conventionally, a method of reducing pattern noise when a product is new and a method of reducing heel-and-toe wear have been studied. For example, a method of reducing pattern noise is disclosed in Japanese Patent Application Laid-Open No. 63-188505. In addition, a device has been proposed in which a sipe is provided on the side wall of the stepped end of the block to reduce the compression rigidity.

[0005]

However, reducing the compression stiffness on the stepping side of the shoulder block for the purpose of reducing the pattern noise at the time of new article causes deterioration of heel and toe wear, and On the contrary, there is a problem that the noise is also deteriorated. In addition, it is naturally not preferable from the appearance.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems of the prior art as described above, and an object of the present invention is to provide a new product having a high wear resistance without losing uneven wear. It is an object of the present invention to provide a pneumatic tire capable of improving pattern noise at the time.

[0007]

SUMMARY OF THE INVENTION When heel and toe wear occurs in a tire having a block pattern,
In order to investigate why the pattern noise deteriorates, the inventors have observed in detail the change in tread behavior of a new article and a worn article, and as a result, the following has been found.

That is, when the distribution of the increase in the contact pressure, which is a measure indicating the magnitude of the impact with the tread of the pattern, was examined, the circumferential shape was greatly reduced due to the occurrence of heel and toe wear. A second block whose circumferential shape has hardly changed at the same level as the changing shoulder block (the second block that is adjacent to the shoulder block and counted from the outside in the tire width direction to the tire equatorial plane side)
However, it was found that the increase in the contact pressure doubled.

[0009] This is because, in the shoulder block, an area where a load cannot be applied (a heel portion of heel-and-toe wear) is generated, and the area must be supported by the area, so that the stepping angle may increase. found.

From the above results, it was found that deterioration of the pattern noise can be prevented by lowering the compression rigidity at the stepping end of the second block so that the contact pressure does not suddenly increase even if the stepping angle increases.

The invention described in claim 1 has been made in view of the above fact, and has an acute corner portion formed by a plurality of circumferential grooves and a plurality of lateral grooves extending substantially along the tire circumferential direction. A pneumatic tire provided with a directional tread pattern formed on the tread, the block having the following structure, wherein the end of the second block counted from the shoulder side to the tire equatorial plane side first contacts the ground when the tire rotates forward. A concave portion is formed on the side wall surface of the block on the part side.

Next, the operation of the pneumatic tire according to the first aspect will be described. In the pneumatic tire having the directional tread pattern according to claim 1, the end side of the second block counted from the shoulder side to the tire equatorial plane side, which comes in contact with the tire first when the tire rotates forward. Since the concave portion is formed on the side wall surface of the second block, the compression rigidity of the stepped end of the second block is reduced. Therefore, even if heel-and-toe wear occurs in the block of the shoulder portion, the degree of increase in the contact pressure applied to the stepped end of the second block at the time of stepping can be reduced, and deterioration of the hitting sound, that is, pattern noise can be prevented. . According to the present invention, it is possible to prevent the pattern noise from aggravating at the time of abrasion only by forming a concave portion on the block side wall surface of the second block, so that it is not necessary to perform special work on the shoulder block.

If a concave portion is formed at the stepped end of the block of the shoulder portion, the wear at the stepped end is reduced, and as a result, the difference in the amount of wear between the stepped end and the kick-out end is increased. Furthermore, providing a concave portion at an unnecessary place causes a decrease in block rigidity, resulting in a decrease in steering stability.

Next, in the case of a block pattern having no directionality (non-directionality (point symmetry)), both ends of the block in the tire circumferential direction can be both stepping ends because the mounting direction of the tire does not matter.

Here, as a result of examining where the influence of the area in which the load generated on the shoulder block cannot be borne due to the occurrence of heel-and-toe wear is exerted, it is found that the second block is closer to the shoulder on the stepping side. It has been found that the influence is large when stepping on a certain sharp corner, but is small on the sharp corner near the equatorial plane of the tire (that is, a portion far from the shoulder block).

From the above results, in the case of a block pattern having no directionality, in order to prevent the ground pressure from increasing sharply, one side of the sharp corner near the shoulder is set in the block side wall of the second block. It has been found that pattern noise can be prevented from deteriorating by reducing the compression rigidity of the block end corresponding to the formed horizontal groove.

The invention according to claim 2 has been made in view of the above fact, and has an acute corner portion formed by a plurality of circumferential grooves and a plurality of lateral grooves extending substantially along the tire circumferential direction. Is a pneumatic tire provided with a non-directional tread pattern formed on a tread, the block being a shoulder portion of the acute angle corners of the second block counting from the shoulder side to the tire equatorial plane side. A concave portion is formed on the block side wall surface corresponding to the lateral groove forming one side of the acute-angled corner portion adjacent to.

Next, the operation of the pneumatic tire according to claim 2 will be described. In this pneumatic tire, a lateral groove forming one side of an acute angle corner adjacent to the shoulder block among the acute angle corners of a second block, a so-called second block, counted from the shoulder side to the tire equatorial plane side. Since the concave portion is formed on the block side wall surface corresponding to the above, the compression rigidity of the block end portion at the portion where the concave portion is formed is reduced.

When the acute angle near the shoulder of the second block and the acute angle near the equatorial plane of the tire are compared,
The sharp corner near the shoulder has a large effect when stepping on the area where the load generated on the shoulder cannot be loaded, while the sharp corner near the tire equatorial plane has the effect of the area where the load generated on the shoulder cannot be loaded. Is small.

In the second block, the sharp corner adjacent to the shoulder block first comes into contact with the ground, so that the concave portion is formed as described above.
The compressive stiffness of the end of the block that forms the sharp corner side that first contacts the second block is reduced.

Therefore, when heel-and-toe wear occurs on the shoulder block, the degree of increase in the contact pressure applied to the end of the block that first contacts the second block can be reduced, and the hitting sound, that is, the pattern noise can be reduced. Can be prevented.

According to a third aspect of the present invention, in the pneumatic tire according to the first or second aspect, when the cross section of the block is perpendicular to the block groove wall surface, the cross-sectional area of the concave portion is one. The cross-sectional area of the lateral groove per block is 1 to 30%.

In the pneumatic tire according to the third aspect, the cross-sectional area of the concave portion when the block is formed to be perpendicular to the block groove wall surface is 1 to 30% of the cross-sectional area of the lateral groove per block. Therefore, the compression rigidity of the block end can be reduced to a level sufficient to reduce the hitting sound. If the cross-sectional area of the concave portion is less than 1% of the cross-sectional area of the lateral groove per block, the compressive rigidity of the block end is hardly reduced, and it is not possible to prevent the hitting sound from deteriorating. On the other hand, if the cross-sectional area of the concave portion exceeds 30% of the cross-sectional area of the lateral groove per block, the compression rigidity at the end of the block is reduced. As a result, the steering stability decreases.

The height of the lateral groove is H, and the lateral groove is
The height of the top of the recess measured from the bottom is h _maxAnd h
_max/ H is preferably 0.8 or less. h_max/
When H exceeds 0.8, the concave portion for reducing the hitting sound
There is a problem that it decreases early due to wear of the lock.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] A first embodiment of a pneumatic tire according to the present invention will be described below with reference to FIGS.

As shown in FIG. 1, the tread 12 of the pneumatic tire 10 of the present embodiment has a tire circumferential direction (arrow R).
Direction and direction opposite to the direction of arrow R: The pneumatic tire 10 of the present embodiment has a designated rotation direction, and the direction of arrow R is the tire rotation direction. ) Are formed along the tire circumferential direction along the tire circumferential direction, and four circumferential main grooves 14 are formed extending from the center in the tire width direction (arrow W direction) to the outside in the tire width direction. Are formed.

A rib 18 is formed at the center of the tread 12 in the tire width direction, and a narrow groove 20 is formed on the rib 18 on the tire equatorial plane CL.

The inclined groove 16 extends from the end of the rib 18 in the direction opposite to the arrow R with respect to the width direction of the tire, and extends in the direction of the arrow R near the shoulder portion.

A shoulder block 22 defined by a circumferential main groove 14 and an inclined groove 16 is arranged on the shoulder side (both sides in the width direction) of the tread 12 along the tire circumferential direction. A second block 24 also defined by the circumferential main groove 14 and the inclined groove 16 is disposed along the tire circumferential direction.

As shown in FIGS. 2 and 3, a recess 26 having a substantially triangular cross section is formed at a middle position in the height direction on the block wall surface 24A on the tire rotation direction side (the direction of the arrow R) of the second block 24. Is formed.

Next, the operation of the pneumatic tire of this embodiment will be described. The pneumatic tire 10 of the present embodiment is mounted on a vehicle so as to rotate in the direction of arrow R when the vehicle advances.

As the heel-and-toe wear of the shoulder block 22 occurs, an area where the load cannot be applied to the shoulder block 22 is generated, and the load applied to the stepped end of the second block 24 is increased.

However, since the compression rigidity at the stepped end of the second block 24 is reduced by the recess 26, even when the load on the stepped end becomes large, the tapping sound at the time of stepping is suppressed, and the deterioration of pattern noise is prevented. Is done.

In this embodiment, the block wall surface 24
The cross-sectional shape of the undercut 26 formed in A is substantially triangular, but the cross-sectional shape of the undercut 26 may be substantially semicircular as shown in FIG. 4, and as shown in FIG. The cross section may be substantially triangular in shape so as to be continuous with the bottom of the hole, and the cross section of the hole is not limited thereto.

The number of the recesses 26 formed on the block wall surface 24A may be plural. Here, the cross-sectional area of the bore 26 when formed in a cross section perpendicular to the block groove wall surface is:
It is preferable to set the cross-sectional area of the inclined groove 16 per block to 1 to 30%.

Further, the height of the inclined groove 16 is H,
The height of the upper end of the hole 26 measured from the groove bottom of No. 6 is h _max
Hmax / H is preferably 0.8 or less.

In the case of a general pneumatic tire for a passenger car, the height of the second block 24 is about 8 mm. In this case, in order to reduce the hitting sound when stepping on, the second block 24 is actually attached to the block wall surface 24A. It is preferable that the cross-sectional area of the bore 26 when it is formed in a cross section at a right angle is 1.0 to 6.0 mm ² per block. Second Embodiment A pneumatic tire according to a second embodiment of the present invention will be described below with reference to FIGS.

As shown in FIG. 6, the tread 34 of the pneumatic tire 32 of this embodiment has a non-directional pattern.

The tread 34 is formed with four circumferential main grooves 36 extending along the tire circumferential direction.

In the outer portion in the tire width direction of the circumferential main groove 14 formed on both sides in the tire width direction (arrow W direction) of the tread 34, a plurality of circumferential main grooves 36 and a plurality of extending in the tire width direction are provided. A plurality of shoulder blocks 40 defined by the lateral grooves 38 are arranged along the tire circumferential direction.

The tread 34 has a shoulder block 4
A plurality of substantially parallelogram-shaped second blocks 44 defined by inclined grooves 42 serving as lateral grooves inclined upward to the right with respect to the tire width direction are arranged inside the tire 0 along the tire circumferential direction. A sipe 46 parallel to the inclined groove 42 is provided at an intermediate portion of the second block 44 in the tire circumferential direction.
Are formed.

The tread 34 has a tire equatorial plane C
A rib 48 extending along the circumferential direction of the tire is arranged on L.

As shown in FIG. 7, in the present embodiment, in the second block 44 disposed on the right side (in the direction of the arrow B) of the tire equatorial plane CL, the hollow 26 is formed on the block wall surface 44A in the direction of the arrow R. In the second block 44 which is formed and is disposed on the left side of the tire equatorial plane CL (in the direction of arrow A), the hole 26 is formed in the block wall surface 44B on the side opposite to the direction of arrow R.

When heel-and-toe wear occurs on the shoulder block 40, the load on the second block 44 near the acute angle near the shoulder block 40 increases, but one side of the acute angle is formed. Since the compression stiffness of the block ends corresponding to the block wall surfaces 44A and 44B is reduced by the recesses 26, the tapping sound at the time of stepping on does not increase, and deterioration of pattern noise is prevented.

[0045] Regardless of the direction in which the pneumatic tire 32 rotates, deterioration of pattern noise is prevented.

The hole 26 in the above-described embodiment is
Although it has a continuous groove shape, it may be formed intermittently. [Test Example] In order to confirm the effect of the present invention, using the directional pattern of FIG.
Kind, one kind of conventional example tire, and two kinds of comparative example tires (each having a tire size of 225 / 50R16) were prepared, and the wear level, the noise level, and the cornering power were compared by the following method.

The details of the test tire will be described below. Example tire 1: The tire (see FIGS. 1 to 3) described in the first embodiment.

Example Tire 2: The pattern is the same as that of Example Tire 1, and a substantially triangular cross section continuous with the bottom of the inclined groove 16 is formed in the second block 2 as shown in FIG.
4 is a tire formed on the stepping side.

Example tire 3: The pattern is the same as that of Example tire 1, and as shown in FIG. 10, a tire in which a recess 26 is formed on both the stepping side and the kicking side wall surface of the second block 24. .

Conventional tire 1: The pattern is the same as that of the tire 1 of the embodiment, and a tire in which the shoulder block and the second block are not formed with a gouge.

Comparative Example Tire 1: The pattern is the same as that of Example Tire 1, and as shown in FIG. 8, a tire in which a recess 26 is formed on the block wall on the stepping side of the shoulder block.

Comparative Example Tire 2: The pattern is the same as that of the Example Tire 1, and a small bore 26 is formed on the block wall surface 24A on the stepping side of the second block 24 as shown in FIG.

Table 1 shows the dimensions of the grooves and the dimensions of the holes (see FIGS. 3, 5, 8 to 10) of the test tire. (Test method) Test method for the amount of abrasion: The test tire was mounted on an 8J x 16-inch rim, filled with an internal pressure of 2.2 kgf / cm ^2, and tested using a flat belt abrasion tester. The test conditions are as follows.

Road surface: Safety walk Room temperature: 30 ° C. Slip angle: 0.5 ° Load: 450 Kgf Braking force: 45 Kgf Speed: 50 km / h Travel distance: 300 Km The difference in wear between the stepped end and the kicked-out end is indicated by an index, with the conventional tire set as 100. The numerical values indicate that the larger the value is for convenience, the smaller the difference in abrasion and the better. The results are as shown in Table 1 below. Noise level test method: A drum noise tester was used under the same conditions as above. The noise level meter was installed at a distance of 50 cm in front of the tire from the side where the tire was stepped on, and comparison was made with the noise level of the primary component of the pitch at 40 km / h. The evaluation was shown by an index by comparing and evaluating the noise level of the worn tire of the conventional tire. The larger the value, the lower the noise level and the better the noise level. The results are as shown in Table 1 below. Cornering power test method: Test tire 8J
A cornering power was measured by a drum tester under a condition of a load of 450 kgf, with an internal pressure of 2.2 kgf / cm ² and a 16-inch rim. The cornering power is a cornering force per slip angle of 1 °. In this test, the average value up to a slip angle of 7 ° is indicated as an index with the value of the conventional tire being 100. The numerical value indicates that the larger the value is for convenience, the larger the cornering power and the higher the steering stability.

[0055]

[Table 1]

As a result of the test, it can be seen that the tires 1 to 3 to which the present invention is applied have a reduced noise level at the time of wear without impairing uneven wear.

[0057]

As described above, the pneumatic tires according to the first and second aspects have the above-described structure.
This has an excellent effect that pattern noise from new to worn can be improved without impairing uneven wear.

Further, the pneumatic tire according to the third aspect has the above-described configuration, and thus has an excellent effect that pattern noise can be reliably prevented from being deteriorated when worn.

[Brief description of the drawings]

FIG. 1 is a plan view of a tread of a pneumatic tire according to a first embodiment of the present invention.

FIG. 2 is an enlarged plan view of a second block shown in FIG.

FIG. 3 is a sectional view taken along line 3-3 of FIG. 2;

FIG. 4 is a sectional view of a tread of a pneumatic tire according to another embodiment of the present invention.

FIG. 5 is a cross-sectional view of a block of a pneumatic tire (Example tire 2 used in a test) according to still another embodiment of the present invention.

FIG. 6 is a plan view of a tread of a pneumatic tire according to a second embodiment of the present invention.

FIG. 7 is an enlarged view of the tread shown in FIG. 6;

FIG. 8 is a cross-sectional view of a block of the comparative example tire 1.

FIG. 9 is a sectional view of a block of the comparative example tire 2;

FIG. 10 is a sectional view of a block of a comparative example tire 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Pneumatic tire 12 Tread 14 Circumferential main groove 16 Inclined groove (lateral groove) 24 Second block 26 Gobo (recess) 44 Second block 42 Inclined groove (lateral groove)

Claims (3)

[Claims] An air having a directional tread pattern in which a block having an acute corner is formed on a tread by a plurality of circumferential grooves and a plurality of lateral grooves extending substantially along a tire circumferential direction. A pneumatic tire, comprising: a recess formed in a side wall surface of an end side of a second block counted from a shoulder side to a tire equatorial plane side, which is first contacted with the ground when the tire rotates forward. tire. 2. Air having a non-directional tread pattern in which a block having an acute corner is formed on a tread by a plurality of circumferential grooves and a plurality of lateral grooves extending substantially along a tire circumferential direction. A block corresponding to a lateral groove forming one side of an acute corner adjacent to the shoulder block among the acute corners of the second block counted from the shoulder side to the tire equatorial plane side A pneumatic tire having a recess formed on a side wall surface. 3. The cross-sectional area of the concave portion when the block is formed in a cross section perpendicular to the block groove wall surface is 1 to 30% of the cross-sectional area of the lateral groove per block. The pneumatic tire according to claim 1 or 2.