JP3357458B2 - Pneumatic radial 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 radial tire, and more particularly to an improvement in pattern noise and an improvement in wet road running performance.

[0002]

2. Description of the Related Art Generally, pattern noise is caused by repetition of a so-called "pattern", which is a circumferential repetitive pattern engraved on a tread surface. It is caused by striking the road surface sequentially. Therefore, the pattern noise is mainly composed of the vibration noise because the vibration of the frequency determined by the pitch number and the rotation speed of the tire causes the tire to vibrate.

Therefore, in the conventional noise reduction method, as a generally used means in a rib pattern, as shown in FIG. There is provided a tire in which a groove component perpendicular to the tire rotation direction, which is a cause of the occurrence, is reduced. In FIG. 7, reference numeral 3 denotes a rib-shaped land portion divided by the vertical groove 1.

In a pattern having blocks, FIG.
As shown in the figure, the width of the lateral groove 2 is reduced and the depth thereof is reduced.
In order to reduce the impact force by increasing the time required for ground contact by changing the angle in the direction along the circumferential direction, or to reduce the impact energy by softening the rubber of the tread portion.

In addition, for example, Japanese Patent Application Laid-Open No.
As disclosed in Japanese Patent No. 9, there is a tire in which the direction (angle) of the lateral groove is specified to have a unidirectional property to reduce the tire. Tires with randomized pattern pitch lengths are also provided.

[0006]

However, in the case of a rib type tire having a small longitudinal groove and a straight tone, it is effective for reducing pattern noise and improving uneven wear, but has poor braking performance on wet roads, There are disadvantages that lack security. In addition, in the case of a block type tire having a narrow width and a small width of the lateral groove, a water film is easily formed between the tire and the road surface to make the drainage performance inferior, and a coefficient of friction with the road surface is reduced,
The braking performance on wet roads decreases. Also, when the block type lateral grooves are arranged at different angles in the direction along the tire circumferential direction, part of the block formed at the intersection of the lateral groove and the vertical groove becomes an acute angle, and the rigidity changes extremely at this part. This tends to cause uneven wear.

[0007] In a tire in which the rubber is softened to reduce the impact force at the time of contact with the ground, deformation of the tread surface due to bending and, consequently, slippage are increased, so that uneven wear is promoted. In the case of a block pattern having a unidirectional shape, both the pattern and the uneven wear vary greatly depending on the rotation direction, and in order to maintain good results, the rotation direction of the tire must be always constant. This is extremely complicated for the vehicle manager in terms of maintenance.

The method of randomizing the pitch length of the pattern requires at least 1: 1.5 or more in order for the length ratio to be effective for noise reduction. In this case, the difference in pitch size, That is, since the difference in rigidity immediately becomes the difference in slip on the tread surface, there is a problem that it appears as uneven wear.

An object of the present invention is to provide a pneumatic radial tire capable of reducing pattern noise without impairing traction and braking on wet roads.

[0010]

As described above, the main factor of the pattern noise is that the pattern formed on the surface of the tread has a problem in the circumferential direction of the tire due to the component in the tread width direction (horizontal groove component) particularly of the horizontal groove or the vertical groove. The impact force generated when the continuous land portion comes into discontinuous contact with the road surface is the vibration sound caused by exciting the tire. This is particularly apparent as the width of the lateral groove becomes wider and deeper and longer.

The generation of vibration noise can be compared to rolling a spur gear on a hard plane. In other words, the circle forming the outer circumference of the tire is divided by the lateral groove, the distance between the tire rotation center axis and the road surface of the divided part is smaller than that of the part other than the divided part, the rotation center of the tire changes at the time of ground contact at every pitch, and the tire This is caused by Therefore, the effect is stronger as the groove width is wider. Further, in addition to the effect of the groove width, as shown in FIG. 9, the groove opening end 5 in the tread portion T of the land portion 3 is more restrained by the belt layer B which is the tire reinforcing layer than the inner side of the land portion 3. In the vulcanization process, which is the final stage of tire production, after vulcanization at high temperature and high pressure in the mold, shrinkage occurs when cooling from high temperature to room temperature. The shape opening of the groove opening end 5 causes a discontinuity of the circumference of the tire, thereby increasing the excitation force. In addition, in the figure, the chain line shows the position shape of the tire molding die M.

Accordingly, the present invention is intended to reduce the width effect of the lateral groove and the effect of the bounce of the groove opening end to suppress vibration noise, and to provide a plurality of longitudinal grooves extending in the tire circumferential direction and the longitudinal grooves. In a pneumatic tire in which a large number of block-shaped land portions are formed in a tread portion by a lateral groove that opens to a land portion side wall surface that defines a boundary between the land portion and the lateral groove, a land portion side wall surface facing each other is formed. In the meantime, a plurality of reinforcing elements whose cross-sectional area gradually increases from the tread portion opening end of the lateral groove toward the groove bottom side are in a zigzag state, that is, in a so-called fork-like state, that is, they alternately enter and overlap each other in a cross-sectional shape. A configuration in which the projection is formed in a state is adopted.

[0013] That is, the opening end and the bottom of the lateral groove are connected by the reinforcing element to give the land part a restraining property, thereby preventing the land part at the tread surface opening end of the lateral groove from bouncing up.

This is because the larger the length of the reinforcing element toward the groove bottom, that is, the larger the degree of increase in the cross-sectional area from the tread opening end of the lateral groove of the reinforcing element toward the groove bottom, the so-called. The reinforcing effect as a rib is large, leading to a reduction in vibration noise. In order to obtain the desired effect on the reduction of vibration noise, in the cross-sectional shape of the reinforcing element, the reinforcement from the point a at the bottom of the lateral groove lowered vertically from the tread opening end to the center of the tire to the end point b of the reinforcing element The element length L must be at least 30% of the lateral groove depth H. 30 of horizontal groove depth H
If it is less than%, it is not necessarily sufficient in terms of the restraint of the land portion, and it is difficult to reduce vibration noise in preventing the land portion from rising. The upper limit of the length L of the reinforcing element is naturally limited due to a problem in a tire production process and a problem in molding, and also an increase in uneven wear due to a decrease in rigidity of a land portion.

In order to reduce the vibration noise, it is also important to reduce the width effect of the lateral groove. However, the expansion of the reinforcing element toward the groove bottom depends on the length of the reinforcing element according to the wear of the tire. Appears large and protrudes in a fork form from the end of the land, and overlaps with the reinforcing element from the opposite land, so that the load on the reinforcing element reduces the change in distance from the center of rotation of the tire, which leads to the width effect of the lateral groove. The vibration noise is reduced by reducing the excitation force.

In this respect, in order to further reduce the width effect of the lateral groove, the width of the lateral groove is increased from the tread opening end to the groove bottom side.
Progressively expanding direction Te, and configure inclined obliquely the land portion side wall facing each other, the reinforcing elements, so as to extend from the tread opening ends of the lateral grooves, to the groove bottom side end portion of the land portion side opposing wall surfaces Is appropriate.

The shape of the reinforcing element is not particularly limited.
For example, a triangular or short reinforcing element can be exemplified. Also,
The land portion of the present invention may be a “block-shaped” land portion, and may be not only a so-called block pattern but also a rib pattern. This is because the distinction between the block pattern and the rib pattern is only a type roughly determined according to the depth of the lateral groove.

It is preferable that the width of the lateral groove has a width that does not easily block when the tire is in contact with the ground. Specifically, it is desirable that the dimension between the open ends of the treads of the lateral grooves is at least 2 mm or more.

[0019]

According to the present invention, there is provided a pneumatic tire in which a large number of block-shaped land portions are formed in a tread portion by a plurality of vertical grooves extending in a tire circumferential direction and a horizontal groove opening in the vertical grooves.
The lateral groove has a width that does not block when the tire is in contact with the ground, and the lateral side wall surface defining the boundary between the land portion and the lateral groove has a step between the opposing land side wall surfaces. A plurality of reinforcing elements whose cross-sectional areas gradually increase from the surface opening end toward the groove bottom are pneumatic radial tires that are formed so as to protrude in a zigzag shape with respect to each other. At the time of cooling from a high temperature after vulcanization of the tire by connecting the end and the bottom of the lateral groove to provide a restraining property to the land, the shape of the land at the opening end of the tread opening of the lateral groove is prevented from rising, The continuity of the tire circumference can be improved. In addition, the expansion of the reinforcing element toward the groove bottom increases the length of the reinforcing element according to the wear of the tire, protrudes in a fork shape from the end of the land portion, and overlaps with the reinforcing element from the opposite land portion. And reduces the change in the distance from the center of rotation of the tire to the road surface, which is linked to the width effect of the lateral groove, and reduces vibration noise by reducing the excitation force.

Further, the vertical grooves are not made smaller and straighter as in the prior art, and the width of the horizontal grooves is made smaller and the depth is not made smaller. On the other hand, the presence of the reinforcing element increases the block rigidity in the circumferential direction. Even if it is applied, the drainage can be ensured without blocking the lateral groove, so that the pattern noise can be reduced without impairing the traction and braking on wet roads.

[0021]

FIG. 1 is a schematic view of a tread pattern showing an embodiment of a pneumatic tire according to the present invention, 2 is a sectional view taken along the line AA, and FIG. 3 is an enlarged schematic perspective view of a main part.

In the figure, reference numeral 1 denotes a plurality of longitudinal grooves extending in the tire circumferential direction in a tire tread portion T;
3 is a block-shaped land portion divided by the vertical groove 1 and the horizontal groove 2, S is a land portion on the shoulder side, and SE is a shoulder end. Reference numeral 4 denotes a land portion side wall surface which forms a boundary between the land portion 3 and the lateral groove 2.

The lateral groove 2 has a width W that does not easily close when the tire is in contact with the ground, and the land side wall surface 4 has a tread surface opening of the lateral groove 2 between the opposing land side wall surfaces 4. A plurality of reinforcing elements 7 having a gradually increasing cross-sectional area from the end 5 toward the groove bottom 6 are formed so as to alternately enter and overlap in cross-sectional shape.

In particular, in this embodiment, the land side wall surfaces 4, 4 facing each other are inclined in a direction in which the width 1W of the lateral groove 2 gradually expands from the tread opening end 5 of the lateral groove 2 toward the groove bottom 6. The reinforcing element 7 extends in a triangular shape from the tread opening end 5 of the lateral groove 2 to the groove bottom side end 8 of the land side wall surface 4 facing the same, and in the cross-sectional shape of the reinforcing element, The length L of the reinforcing element from the point a at the bottom of the lateral groove, which is vertically lowered from the tread surface opening end 5 in the tire center direction, to the end point b of the reinforcing element 7 is 35% of the lateral groove depth H.

Accordingly, the tread surface opening end 5 of the lateral groove 2 in the land portion 3 and the groove bottom 6 can be connected by the reinforcing element 7 so that the land portion 3 can be restrained. Due to the heat shrinkage that occurs when cooling from
The continuity of the circumference of the tire can be improved without the occurrence of a shape jump at the land portion end. In addition, the increase of the reinforcing element toward the groove bottom 6 indicates that the length of the reinforcing element increases as the tire wears, protrudes like a fork from the end of the land portion 3, and overlaps with the reinforcing element 7 from the opposite land portion 3. Therefore, a change in the distance from the center axis of rotation of the tire to the road surface, which is loaded with the reinforcing element 7 and leads to the width effect of the lateral groove 2, is reduced, and the vibration force is reduced by reducing the exciting force.

Therefore, the presence of the reinforcing element 7 increases the rigidity of the block in the circumferential direction, so that even when a load is applied, the lateral groove 2 can be secured without drainage, so that traction and braking on wet roads are impaired. In addition, pattern noise can be reduced. The present invention is not limited to the above embodiment. For example, the land side wall surfaces 4 and 4 facing each other are not inclined in a direction in which the width W of the lateral groove 2 gradually expands from the tread surface opening end 5 of the lateral groove 2 toward the groove bottom 6, and FIGS. As shown in the figure, the shape formed by the land side wall surfaces 4 and 4 and the groove bottom 6 is U-shaped or V-shaped, and accordingly, the reinforcing element 7 is moved from the tread surface opening end 5 of the lateral groove 2 to It can be extended to the groove bottom side end 8 of the land side wall surface 4 that faces the same.

The shape of the reinforcing element is also changed from the tread surface opening end 5 of the lateral groove 2 to the groove bottom side end 8 of the land side wall surface 4 facing the same.
Instead of the configuration extending in a triangular shape, a configuration extending in a rectangular shape as shown in FIG.

Next, a tire size of 10,000 R20 1
A tire having an A pattern and a B pattern corresponding to 4PR in FIGS. 1 and 4, respectively, was prototyped and evaluated for tire noise and braking performance. For comparison, FIGS. 1 and 4
The tires of each of the A pattern and the B pattern corresponding to FIGS. 7 and 8 having no reinforcing element were also evaluated.

For tire noise, a noise test was carried out by a JASO C606 tire base on-body test method. The noise level was an average of the levels at speeds of 20 to 120 km / h. For the wet road braking performance, a test tire was mounted on each of the six wheels of the 2-D vehicle, and an actual running test was performed on a wet test course under the condition of constant load equivalent load.

In each of the tests, the A pattern and the B pattern corresponding to FIGS. 7 and 8 having no reinforcing element were indicated by an index of 100 for each of the example tires having the A pattern and the B pattern. In each case, the smaller the number, the better. The materials of all tires are the same.

FIG. 10 shows the test results of the noise level and wet road braking performance.

In FIG. 10, L / H = 0 is a comparative example tire of each of the A pattern and the B pattern corresponding to FIGS. 7 and 8 having no reinforcing element, and the plot of L / H ≠ 0 indicates the reinforcing element. It is an example tire having.

From FIG. 10, it can be understood that the larger the L / H, the better the pattern noise of the tire according to the present invention as compared with the comparative tire. In particular, when the L / H exceeds 20%, the noise level index sharply decreases, and when the L / H is 30% or more, the pattern noise and running performance on wet roads are remarkably good. Is recognized.

On the other hand, the braking performance on a wet road hardly changes and does not deteriorate regardless of the presence or absence of the reinforcing element.

[0035]

According to the present invention, the lateral groove has a width which does not close when the tire is in contact with the ground, and the land side wall surface which forms the boundary between the land portion and the lateral groove has a land side wall surface facing the land portion. A plurality of reinforcing elements whose cross-sectional area gradually increases from the tread opening opening end of the lateral groove toward the groove bottom are pneumatic tires formed so as to protrude in a zigzag shape with each other. As a result, the reinforcing element connects the open end of the land portion and the bottom of the lateral groove to provide the land portion with the restraining property, and as a result, the shape of the land portion generated at the open end of the tread portion of the lateral groove during thermal contraction during tire molding. It is possible to prevent the target bounce and enhance the continuity of the tire circumference to reduce the pattern noise.

Further, the expansion of the reinforcing element toward the groove bottom causes the length of the reinforcing element to be large as the tire wears, protruding in a fork shape from the land portion end, and overlapping with the reinforcing element from the opposite land portion. In addition, a change in the distance from the rotation center axis of the tire, which is loaded by the reinforcing element and leads to the width effect of the lateral groove, is reduced, and the vibration noise is reduced even in a process in which the wear progresses due to the reduction in the excitation force.

Further, since the presence of the reinforcing element increases the block rigidity in the circumferential direction, even if a load is applied, the drainage can be secured without closing the lateral groove, so that the traction and braking performance on wet roads are not impaired. Pattern noise can be reduced.

In particular, in the cross-sectional shape of the reinforcing element, the length L of the reinforcing element from the point a of the bottom of the lateral groove, which is lowered vertically from the opening end of the tread portion to the center of the tire, to the extreme point b of the reinforcing element is the lateral groove depth. When L / H is 30% or more in relation to H, pattern noise and running on wet roads are remarkably good.

[Brief description of the drawings]

FIG. 1 is a schematic view of a tread pattern showing one embodiment of a pneumatic tire according to the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is an enlarged schematic perspective view of a main part.

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

FIG. 5 is a sectional view taken along line BB in FIG.

FIG. 6 is an enlarged schematic perspective view of a main part showing a rectangular reinforcing element.

FIG. 7 is a schematic view showing a pattern of a conventional tire.

FIG. 8 is a schematic view showing a conventional tire having a block pattern.

FIG. 9 is an enlarged cross-sectional view of a main part showing a state in which a groove opening end of a land portion is raised when a tire is molded.

FIG. 10 shows a noise level index and a damping index, and L / H.
6 is a graph showing a relationship with the graph.

[Explanation of symbols]

 Reference Signs List 1 vertical groove 2 horizontal groove 3 land portion 4 land portion side wall surface 5 tread opening end 6 groove bottom 7 reinforcing element 8 groove bottom side end T tread part L reinforcing element length H horizontal groove depth W horizontal groove width

Claims (3)

(57) [Claims] 1. A pneumatic tire in which a plurality of block-shaped land portions are formed in a tread portion by a plurality of vertical grooves extending in a tire circumferential direction and a horizontal groove opening in the vertical grooves. On the land side wall surface forming the boundary, between the land side wall surfaces facing each other, a plurality of reinforcing elements whose cross-sectional area gradually increases from the tread surface opening end of the lateral groove toward the groove bottom side,
A pneumatic radial tire characterized by being formed so as to alternately enter and overlap one another. 2. The width of the lateral groove is from the tread opening end to the groove bottom side.
The land side walls opposing each other are inclined in the direction in which the side walls gradually incline, and the reinforcing element is provided at the groove bottom side end of the land side wall opposite to the tread surface opening end of the lateral groove. The pneumatic radial tire according to claim 1, which extends to: 3. The cross-sectional shape of the reinforcing element, a point a at the bottom of the lateral groove which is lowered vertically from the tread opening end to the center of the tire.
The length L of the reinforcing element from the end point b of the reinforcing element to
The pneumatic radial tire according to claim 1 or 2, wherein the depth is at least 30% of the transverse groove depth H.