JP4571282B2 - Pneumatic tire - Google Patents

Description

[0001]
[Technical field to which the invention belongs]
The present invention relates to a pneumatic tire with improved steering stability performance.
[0002]
[Prior art]
Conventionally, the block height is usually constant in a pneumatic tire.
[0003]
The block 100 formed in this way is deformed as shown in FIG. 14B when traveling, and the ground pressure on the tread 102 becomes non-uniform (high at the end) (see FIG. 14A). It becomes difficult to transmit the braking force / driving force to the road surface 104 over the entire tread 102.
[0004]
In addition, uneven wear in which a part of the block 100 is worn early due to such variations in ground pressure is likely to occur, and only the vicinity of the grounding end on the input side when shearing input is caused by local concentration of ground pressure. Grounding is performed locally at a high pressure, and the tread 102 is turned up (see FIG. 15), which adversely affects steering stability.
[0005]
[Problems to be solved by the invention]
In order to improve the ground contact characteristics of tires, tread patterns have been improved in the past, but the current situation is that there is a limit in terms of drainage and other performance.
[0006]
In addition, although inventions have been made in which the block height is convex in the tire circumferential direction or the cross-section in the width direction, it is difficult to obtain a tread shape considering compatibility with various performances only by such a method, and the shape Decisions usually involve trial and error and are difficult. The reason is the following two points.
[0007]
First of all, the distribution of the contact pressure depends on the pattern shape and is difficult to predict because it is affected by the deformation of the input.
[0008]
Secondly, there are various inputs received by the tire, and it is very difficult to uniquely determine an appropriate improvement direction that satisfies all of them.
[0009]
Accordingly, an object of the present invention is to define a shape that optimizes the block height in each block existing in the tread pattern, thereby eliminating unevenness in contact pressure and improving steering stability performance and uneven wear resistance performance. It is to provide a pneumatic tire.
[0010]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention according to claim 1 is an air in which a tread is provided with a number of blocks defined by a circumferential groove extending in the circumferential direction of a tire and a groove intersecting the circumferential groove. In a tire, a chamfered portion is formed on at least one side of the tread surface of the block, and a number of blocks divided by a circumferential groove extending in the circumferential direction of the tire and a groove intersecting the circumferential groove are treaded. In the pneumatic tire provided in the above, a chamfered portion is formed on at least one side of the tread surface side of the block, and a chamfering depth H of the chamfered portion is at least at both ends in the longitudinal direction of the one side of the tread surface side. On the extension line of the chamfered portion that is gradually increased from the longitudinal center side of one side of the tread surface side toward the longitudinal end side and projected onto the extension line of the center portion surface of the block When the length is L, the length L extends from the longitudinal center side of the one side of the tread side to the longitudinal end side of the one side of the tread side at least at both ends in the longitudinal direction of the one side of the tread surface. It is characterized by gradually increasing toward the end.
[0011]
Next, the operation of the pneumatic tire according to claim 1 will be described.
[0012]
As shown in FIG. 14 (A), the contact pressure distribution of the block without chamfer formed on the tread gradually increases from the central portion toward the end portion and locally increases at the end portion.
[0013]
From this fact, if the chamfered portion is provided at the end portion on the tread surface side of the block, the contact pressure at the end portion can be reduced, and the contact pressure on the block tread surface can be made uniform. As a result, steering stability is improved.
In addition, the ground contact pressure of the block has a distribution when the end portion on the tread side is viewed in the circumferential direction of the block. For example, in the case of a rectangular block, when one side on the tread side is viewed, one side on the tread side There is a tendency that the ground contact pressure is larger in the vicinity of both sides in the longitudinal direction than on the longitudinal center side of. Accordingly, by increasing the chamfering depth near the longitudinal end of one side of the tread side, the amount of decrease in the contact pressure near the longitudinal end is increased, and the tread side 1 is increased. The contact pressure can be made uniform over the entire side.
[0014]
[0015]
[0016]
[0017]
[0018]
The invention according to claim 2 is characterized in that, in the pneumatic tire according to claim 1, the cross-sectional shape of the chamfered portion is formed by a convex curve that smoothly connects to the block ground surface. .
[0019]
Next, the operation of the pneumatic tire according to claim 2 will be described .
[0020]
If the cross-sectional shape of the chamfered part is an inclined surface with a certain angle, the grounding pressure changes extremely near the connection part between the block grounding surface (treading surface) and the chamfered part, and may not correspond to the actual change in grounding pressure. Arise.
[0021]
For this reason, it is preferable to form the cross-sectional shape of the chamfered portion with a convex curve that smoothly connects to the block ground surface.
[0022]
According to a third aspect of the present invention, in the pneumatic tire according to the first or second aspect, the cross-sectional shape of the chamfered portion has a center of curvature inside the block and is smoothly connected to the block ground surface. It is characterized by being formed by a circular arc.
[0023]
Next, the operation of the pneumatic tire according to claim 3 will be described .
[0024]
In the pneumatic tire according to claim 3, since the center of curvature is formed in an arc having the center of curvature in the block and smoothly connected to the block ground surface, the processing of the mold for forming the chamfered portion is facilitated. .
[0025]
[0026]
[0027]
[0028]
[0029]
[0030]
[0031]
[0032]
[0033]
[0034]
[0035]
[0036]
[0037]
[0038]
[0039]
[0040]
[0041]
[0042]
[0043]
[0044]
[0045]
[0046]
[0047]
[0048]
[0049]
DETAILED DESCRIPTION OF THE INVENTION
[ First Reference Example ]
First, before describing an embodiment of the invention, a pneumatic tire according to a first reference example will be described in detail. Hereinafter, the present embodiment will be described with reference to FIGS. 1 and 2.
[0050]
As shown in FIG. 2, the pneumatic tire 10 includes a cylindrical tread 12 that straddles a pair of left and right sidewalls (not shown).
[0051]
A plurality of main grooves 14 formed along the tire circumferential direction (arrow P direction) and a plurality of lug grooves 16 formed along the tire width direction (arrow W direction) are formed on the tread 12. Yes.
[0052]
A plurality of blocks 18 are partitioned by the main groove 14 and the lug groove 16.
[0053]
These blocks 18 are formed in a rectangular parallelepiped shape in which the length in the tire width direction of the tread surface 20 is equal to the length in the tire circumferential direction.
[0054]
All of the end portions of the tread surface 20 of the block 18 are chamfered (hereinafter, the chamfered portion is referred to as a chamfered portion 24).
[0055]
FIG. 1 shows a cross-sectional shape (only in the vicinity of the end portion) in a direction (hereinafter referred to as a cross-sectional direction) from the groove wall surface 22 in contact with the chamfered portion 24 of the block 18 toward the other side surface perpendicular to the wall surface.
[0056]
The cross-sectional shape (cross-section perpendicular to the groove wall surface) of the chamfered portion 24 of the present reference example is smooth in the block center portion 21 (the portion of the tread surface 20 of the block 18 that is not chamfered in the center) in the vicinity of the end portion of the block 18. It is an arc shape with a curvature radius R to be connected.
[0057]
In this reference example , the block 18 has a tire width direction dimension of 30 mm, a tire circumferential direction dimension of 30 mm, and a height of 10 mm.
[0058]
Further, in the chamfered portion 24 of this reference example , H is 0.5 mm, L is 5.0 mm, and R is about 6.7 mm. These dimensions are constant over the entire circumference of the block.
(Function)
Forming the pneumatic tire 10 in this way has the following effects.
[0059]
That is, since the chamfered portion 24 is formed at all the end portions of the tread surface 20 where the ground pressure increases remarkably, the ground pressure on the tread surface 20 of the block 18 can be made uniform.
[0060]
Here, in order to confirm the effect of this reference example , the test was done.
[0061]
The test tire is a radial tire having the tread pattern described in this reference example of size 205 / 55R16.
[0062]
In the test, tires were mounted on the actual vehicle, and test drivers drove in various modes on the test course.
[0063]
The evaluation is a feeling evaluation by a test driver, and the rating is 100 for the conventional tire. In addition, it represents that it is excellent in performance, so that a numerical value is large.
[0064]
In addition, when there is a difference of 10 or more in the score, it is a level where a general driver can clearly see the difference.
[0065]
[Table 1]
[ Second Reference Example ]
A second reference example will be described with reference to FIGS. In addition, the same code | symbol is attached | subjected to the same structure as a 1st reference example, and the description is abbreviate | omitted.
[0066]
In this reference example , the dimension H and length L of the chamfered portion 24 are changed on the circumference of the block 18.
[0067]
Specifically, assuming that the length of one side of the block 18 on the tread surface 20 side is 100, the dimension H changes as shown in FIG. 3, and the length L changes as shown in FIG. Yes.
[0068]
The same test as in the first reference example was performed. The test results were as shown in Table 2 below.
[0069]
[Table 2]
From the test results, it can be seen that a greater effect than in the first reference example can be obtained by changing the chamfer dimension (H, L) on the block circumference in accordance with the contact pressure.
[ Third and fourth reference examples ]
Third and fourth reference examples will be described with reference to FIGS. In addition, the same code | symbol is attached | subjected to the same structure as a 1st reference example, and the description is abbreviate | omitted.
[0070]
In the third reference example , as shown in FIG. 5, the block 18 is provided with a tapered chamfer 24 having a dimension H of 0.5 mm, a length L of 5.0 mm, and inclined at a constant angle.
[0071]
Further, in the fourth reference example , as shown in FIG. 6, the dimension H is 0.5 mm, the length L is 5.0 mm, and the curved surface is processed so as to have a larger curvature toward the end side. A chamfered portion 24 is formed on the block 18.
[0072]
For the third and fourth reference examples , the same test as in the first reference example was performed. The test results were as shown in Table 3 below.
[0073]
[Table 3]
From the test results, although any reference example has a chamfering effect, in order to satisfy the demand level (obviously, a rating 110 or higher), the chamfered portion 24 has a block center portion 21 for uniform ground pressure. It can be seen that a curved surface connecting smoothly is preferable.
[0074]
Also, the central portion side change of the ground contact pressure is not too large, even more uniform by constituting two curves of different curvature end side change in contact pressure is large, a simple configuration with ground contact pressure Can be achieved.
[ First and Second Embodiments ]
First and second embodiments of the present invention will be described with reference to FIGS. In addition, the same code | symbol is attached | subjected to the same structure as a 1st reference example, and the description is abbreviate | omitted.
[0075]
In the first embodiment , as shown in FIGS. 7 and 8, the chamfered portion 24 is set so that the dimension H and the length L are constant at the center of the side and greatly change near both ends of the side. ing.
[0076]
On the other hand, in the second embodiment , as shown in FIGS. 9 and 10, the chamfered portion 23 has a large drop near both ends of the side with respect to the dimension H and the length L, and the remaining part (the central part of the side). ) Is set to increase slightly toward both sides of the side so that it is smoothly connected.
[0077]
For the first and second embodiments , the same test as in the first reference example was performed. The test results were as shown in Table 4 below.
[0078]
[Table 4]
From the test results, it can be seen that the performances of the first and second embodiments are superior to those of the conventional example, and all the chamfered portions satisfy the demand level.
[0079]
In the first embodiment , the dimension H and the length L of the chamfered portion 24 are set so as to be constant at the center portion of the side and greatly changed near both ends of the side. In the second embodiment , The drop near the both ends of the side is large, and the central part of the side is set to slightly increase toward both sides of the side. However, the present invention is not limited to this, and the chamfered portion 24 is The length L may be set so as to change substantially in the vicinity of both ends of the side, and the length L may be set to increase slightly in the vicinity of both ends of the side. (Combination of FIGS. 7 and 10).
[0080]
Further, the chamfer 24 is set so that the dimension H tends to increase slightly in the central portion of the side and greatly changes in the vicinity of both ends of the side, and the length L is constant in the central portion of the side and is fixed at both ends of the side. You may set so that it may change a lot in the vicinity (combination of FIG. 9 and FIG. 8).
[0081]
By making either one of H or L constant in the central portion of the side, it is easier to process a mold for molding the chamfered portion 24 than when both H and L are changed.
[0082]
That is, it is ideal but complicated to realize a delicate change in curvature as expressed by various functions in a product. Therefore, in order to facilitate the processing of the mold while obtaining high performance, it is effective to keep either H or L constant.
[0083]
Here, the chamfered shape of the first embodiment in which the range of the end portion that changes the dimension of the chamfered portion 24 is variously changed is effective in which region of the side the size of the chamfered portion 24 is increased. Tires were prototyped and evaluated.
[0084]
As shown in FIGS. 11 and 12, the position where the dimension of the chamfered portion starts to change is defined as X (from the end). Evaluation is as shown in Table 5 below.
[0085]
[Table 5]
As a result of the test, it was found that X is preferably 40 or less in order to satisfy the demand level.
[0086]
It is also inferred that the local contact pressure concentration at the corner should be processed in a relatively local part.
[0087]
Therefore, when considering the durability of the block 18 and the like, as shown in FIG. 13, it may be a good direction to form the block corner portion with a large notch or a curved surface smoothly connected to the groove bottom portion.
[0088]
(Test example)
Here, in order to confirm the optimum range of the dimension H and the length L, the tires of Examples 8 to 13 in which the dimension H of the chamfered portion is constant (same as Example 1) and the lengths L are different from each other. The tires of Examples 14 to 20 with the length L being constant (same as Example 1) and the dimensions H being different from each other were prototyped and subjected to the same test as described above.
[0089]
The results of Examples 8 to 13 are shown in Table 6 below, and the results of Examples 14 to 20 are shown in Table 7 below.
[0090]
[Table 6]
[0091]
[Table 7]
From the test results, it is understood that the length L is preferably 1.0 mm or greater and 10.0 mm or less, and the dimension H is preferably 2.5 mm or less.
[0092]
It can also be seen that when the dimension H is less than 0.15 mm, a great effect cannot be obtained.
[0093]
【The invention's effect】
As described above, the pneumatic tire according to the present invention has an excellent effect that the ground contact pressure on the block tread surface is made uniform and the steering stability performance can be greatly improved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of the vicinity of an end of a block of a pneumatic tire according to a first reference example .
FIG. 2 is a plan view of a tread of a pneumatic tire according to a first reference example .
FIG. 3 is a graph showing a relationship between a position of a side of a chamfered portion and a dimension H in a pneumatic tire according to a second reference example .
FIG. 4 is a graph showing a relationship between a position of a side of a chamfered portion and a length L in a pneumatic tire according to a second reference example .
FIG. 5 is a cross-sectional view of the vicinity of an end of a block of a pneumatic tire according to a third reference example .
FIG. 6 is a cross-sectional view in the vicinity of an end of a block of a pneumatic tire according to a fourth reference example .
FIG. 7 is a graph showing the relationship between the position of the side of the chamfered portion and the dimension H in the pneumatic tire according to the first embodiment of the present invention.
FIG. 8 is a graph showing the relationship between the position of the side of the chamfered portion and the length L in the pneumatic tire according to the first embodiment of the present invention.
FIG. 9 is a graph showing a relationship between a position of a side of a chamfered portion and a dimension H in a pneumatic tire according to a second embodiment of the present invention.
FIG. 10 is a graph showing a relationship between a position of a side of a chamfered portion and a length L in a pneumatic tire according to a second embodiment of the present invention.
11 is a graph for explaining a change start position X with respect to a dimension H. FIG.
12 is a graph for explaining a change start position X with respect to a length L. FIG.
FIG. 13 is a perspective view of the vicinity of a corner of a block of a pneumatic tire according to another embodiment.
14A is a view showing a contact pressure distribution in a conventional pneumatic tire, and FIG. 14B is a block deformation view.
FIG. 15 is a block deformation state diagram of a conventional pneumatic tire.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Pneumatic tire 12 Tread 14 Main groove 16 Lug groove 18 Block 21 Center part 24 Chamfering part

Claims (3)

In a pneumatic tire provided with a tread having a plurality of blocks partitioned by a circumferential groove extending in the circumferential direction of the tire and a groove intersecting the circumferential groove,
A chamfered portion is formed at least on one side of the tread surface side of the block,
The chamfering depth H of the chamfered portion gradually increases from the longitudinal center side of the one side of the tread side toward the longitudinal end side at least at both ends in the longitudinal direction of the one side of the tread surface side.
When the length on the extension line of the chamfered portion projected onto the extension line of the center surface of the block is L, the length L is at least at both ends in the longitudinal direction of one side of the tread surface side. A pneumatic tire characterized by gradually increasing from a longitudinal center side of one side of the tread side toward a longitudinal end side of the one side of the tread side . 2. The pneumatic tire according to claim 1, wherein a cross-sectional shape of the chamfered portion is formed by a convex curve that smoothly connects to a block ground contact surface. The pneumatic structure according to claim 1 or 2, wherein a cross-sectional shape of the chamfered portion is formed by an arc having a center of curvature inward of the block and smoothly connecting to the block ground surface. tire.