JP3378789B2 - 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 suitable for running on rough roads, which can improve hydroplaning performance and mud performance without impairing noise performance.

[0002]

2. Description of the Related Art A pneumatic tire for mud and snow mounted on a four-wheel drive vehicle running on a rough road is used to improve hydro performance and mud performance. It is necessary to form a large groove area ratio on the tread surface, including circumferential grooves and lateral grooves.

However, an increase in the groove area ratio on the tread surface causes deterioration of the noise performance of the tire. Therefore, for example, Japanese Patent Laid-Open No. 3-125609 discloses
We propose to improve the wet performance and noise performance in a well-balanced manner by optimizing the ratio of the groove area ratio on the tread surface.

The present inventors pay attention to individual noise generation mechanisms that deteriorate the noise performance of tires, that is, air column resonance sounds due to circumferential grooves, air pumping sounds due to lateral grooves, and impact sounds when blocks hit the road surface. However, it has been found that the hydroplaning performance and the mud performance can be improved while suppressing the noise performance by improving the circumferential groove and the lateral groove.

As described above, an object of the present invention is to provide a pneumatic tire capable of improving hydroplaning performance and mud performance while suppressing noise performance.

[0006]

According to a first aspect of the present invention, the tread surface is provided between the crown rib extending in the tire circumferential direction including the tire equator C and the outer edge of the ground contact surface in the axial direction of the tire. Four or more circumferential grooves that divide the shoulder rib and the middle rib between the crown rib and the shoulder rib are provided, and the inner circumferential groove extends linearly.
In both cases , the outer circumferential groove extends in a zigzag shape , and the rib width Wm of each middle rib is set to 20 to 30% of the ground contact width, and the middle rib extends in the tire circumferential direction and has a longitudinal width of 1 to 2 mm. By providing the narrow groove, the middle rib is formed on the outer side between the outer circumferential groove on the tire axial direction outer side and the vertical narrow groove, and between the inner circumferential direction groove on the tire axial direction inner side and the vertical narrow groove. A lateral groove is formed on the inside and outside, connecting the circumferential grooves and the vertical narrow grooves and inclined at an inclination angle α of 30 to 70 ° with respect to the tire circumferential direction. By dividing the middle rib into blocks surrounded by each circumferential groove, vertical narrow groove, and horizontal groove, and each open end of the horizontal groove of the outer groove and the inner groove of the inner groove is a tire. Pneumatic tie characterized by being displaced in the circumferential direction It is.

According to a second aspect of the present invention, the block of the middle rib is a block in which the circumferential groove and the vertical narrow groove form an inclination angle β from each circumferential groove and the vertical narrow groove with respect to the tire circumferential direction. It is characterized by having a substantially Z-shaped sipe consisting of sipe on both sides extending inward and a tie sipe which joins the inner ends of the sipe on both sides and is inclined at an inclination angle γ smaller than the inclination angle β. The pneumatic tire according to claim 1.

According to a third aspect of the present invention, the syping
Divide the block into a substantially triangular shape.
I am trying.

Further, in the present specification, the term "ground contact width" means a tire between outer contact ends which is grounded on a flat surface by assembling a tire on a regular rim, filling a regular internal pressure and applying a regular load at a camber angle of 0 °. Axial distance.

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, it becomes "Measuring Rim".

The "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. In the case of JATMA, the maximum air pressure, and in the case of TRA, the table " TIRE LOAD LIMITS AT VARIOU
Maximum value stated in "S COLD INFLATION PRESSURES", ETR
If it is TO, it is "INFLATION PRESSURE", but if the tire is for passenger cars, it is 180KPa.

Further, "regular load" is a load defined by each standard in the standard system including the standard on which the tire is based. In the case of JATMA, it is the maximum load capacity, and in the case of TRA, it is the table. TIRE LOAD LIMITS AT VARIOU
Maximum value stated in "S COLD INFLATION PRESSURES", ETR
If it is TO, it is "LOAD CAPACITY", but if the tire is for passenger cars, it is 88% of the maximum load capacity.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. In the present embodiment, a mud & tire mounted as a pneumatic tire on a four-wheel drive vehicle traveling on a rough road
A snow tire is exemplified, and as shown in FIG. 1, a shoulder rib 6 between a tread surface 2 extending in the tire circumferential direction including a tire equator C and a tire axial direction outer edge E of the ground contact surface. And four or more circumferential grooves 3 that are divided into the crown rib 4 and the middle rib 5 between the shoulder ribs 6.

In the present embodiment, the circumferential groove 3 is an inner circumferential groove 3 which is symmetrically arranged on both sides of the tire equator C.
a, 3a and outer circumferential grooves 3b, 3b, which are respectively arranged on the outer sides of the outer peripheral grooves 3a and 3a, are illustrated as a total of four.

These circumferential grooves 3 have, for example, a groove width of 2 to 6%, more preferably 2.5 to 4% of the ground contact width TW. In this embodiment, the inner circumferential groove 3a has the ground contact width TW. Of 3
%, The outer circumferential groove 3b is set to 4% of the ground contact width TW. The groove depth is, for example, 5 mm or more,
More preferably, it is desired to be 7 mm or more.

The rib width Wc of the crown rib 4 divided by the inner circumferential grooves 3a, 3a is set to about 8 to 11% of the ground contact width TW in this example. In the above,
The rib width Wm of each middle rib 5 divided into the outer circumferential grooves 3a and 3b is 20 to 30% of the ground contact width TW. This rib width is specified by the actual rib width as shown in FIG.

As described above, by setting the rib width Wm of the middle rib 5 to be relatively large at 20 to 30% of the ground contact width TW, the outer circumferential groove 3b can be moved away from the tire equator C in the axially outward direction. it can. When the circumferential groove 3b on the outer side in the tire axial direction of the four circumferential grooves 3 is arranged outward from the tire equator C in this way, the effect of reducing the passing noise due to the outer circumferential groove 3b is obtained. It has been confirmed.

If the rib width Wm of the middle rib 5 is less than 20% of the ground contact width TW, the passing noise suppressing effect is reduced. Conversely, if the rib width Wm of the middle rib 5 exceeds 30% of the ground contact width TW, There is a problem that the rib width Ws of the shoulder rib 6 becomes too small and uneven wear occurs. Preferably, the rib width Wm of the middle rib 5 is 20 times the ground contact width TW.
-25%.

Further, in this embodiment, a vertical fine groove 7 extending linearly and having a groove width of 1 to 2 mm is provided substantially in the middle of the middle rib 5 in the tire circumferential direction. With such a vertical narrow groove 7, the middle rib 5 is provided with the outer circumferential groove 3
It is divided into an outer portion 5o between b and the vertical narrow groove 7, and an inner portion 5i between the inner circumferential groove 3a and the vertical narrow groove 7.

The vertical fine grooves 7 moderately reduce the pattern rigidity of the middle rib 5 having a comparatively wide width, thereby mitigating the impact sound generated when the middle rib 5 hits the road surface while the tire is running. Exert the effect of. Further, since the vertical narrow groove 7 forms an edge component in the radial direction, it is possible to further improve running performance, that is, snow performance, especially on a snowy road. The vertical fine groove 7 has a groove depth of 40 to 60 of the circumferential groove 3 in order to exert the above effect more effectively.
% Is particularly preferable.

Further, the inner groove 5i and the outer groove 5o connect the circumferential groove 3a or 3b with the vertical narrow groove 7, and the lateral groove 9i is inclined at an inclination angle α of 30 to 70 ° with respect to the tire circumferential direction. , 9o to form the middle rib 5 in the circumferential groove 3a or 3b, the vertical narrow groove 7, the lateral groove 9i or 9o.
Are divided into blocks B1, B1 ...

By forming a large number of blocks B1 on the middle rib 5 in this manner, it is possible to maintain a high driving force in a mud and to improve the running performance in the mud. In the present embodiment, the lateral grooves 9i and 9o are inclined in the same direction with respect to the tire circumferential direction by the respective middle ribs 5 and 5 and the range of the inclination angle α is limited to improve drainage performance and hydro performance. sell. Note that such lateral grooves 9i, 9o
If the groove width in the direction orthogonal to the extending direction of the groove is too large, a resonance sound with this lateral groove as an air column tube is likely to be generated, and conversely, if it is too small, the hydro performance tends to be deteriorated. It is particularly preferable to set the groove width of No. 3 to 50 to 80%.

Further, the lateral groove 9o of the outer portion 5o and the inner portion 5 are
open ends 11o of the vertical narrow groove 7 with the lateral groove 9i of i, 1
1i is displaced in the tire circumferential direction. As a result, since the lateral grooves 9i and 9o are not continuously aligned in the tilt direction, it is possible to suppress the generation of resonance sound having the lateral grooves 9i and 9o as an air column tube and improve noise performance.

The positional deviation amount L of the opening ends 11i and 11o in the tire circumferential direction is 0.5 times or more the groove width of the lateral groove 9i or 9o and 0.25 of the tire circumferential length BL of the block B1. It is desirable that the number be less than twice.

If the amount L of displacement is less than 0.5 times the groove width of the lateral groove, the effect of the positional displacement of the opening ends 11i, 11o is reduced, and the effect of suppressing the air column resonance sound generated in the lateral groove is reduced. Less. On the contrary, when the positional deviation amount L exceeds 0.25 times the tire circumferential direction length BL of the block B1, the pitch noise tends to increase this time.

Further, in this embodiment, the block B1 of the middle rib 5 has a substantially Z-shaped sipe S formed therein. As shown in FIG. 2, this substantially Z-shaped sipe S is the same as the circumferential groove 3 and the vertical narrow groove 7 in the present embodiment, in the circumferential groove 3 and the vertical narrow groove 7 in the tire circumferential direction. Sipe 13 and 13 on both sides that extend in a straight line inwardly of the block with a direction and an inclination angle β, and sipe 13 and 13 on both sides.
The inner end 14 of each of the above is joined to a straight sipe 15 that is inclined in the same direction at an inclination angle γ smaller than the inclination angle β.

The inclination angle β is, for example, 55 to 80 °,
It is more preferably 60 to 70 °, and the inclination angle γ is 0 to 30 °, and more preferably 0 to 10 °.
It is preferable that the angle is °.

By forming such a substantially Z-shaped sipe S on the block B1 of the middle rib 5, the substantially Z-shaped sipe S does not come out of the ground contact surface at the same time due to the presence of the splicing sipe 15, so it is difficult to open the sipe. However, it is possible to reduce the noise due to the opening of the sipe that occurs during acceleration traveling, and it is possible to effectively reduce the pattern rigidity of the block B1 while improving the noise performance. In addition, the substantially Z-shaped sipe S is formed by the lateral grooves 9i, 9
The blocks B1 are divided into substantially triangular shapes by being arranged in the inclination direction and direction of o.

The depth of the substantially Z-shaped sipe S is 50 to 100% of the groove depth of the circumferential groove 3, and more preferably 50.
It is desirable to set it to -80%.

Further, in this embodiment, the inner circumferential groove 3 is formed.
“A” exemplifies a linear extension. As a result, the road surface water film on both sides of the crown rib 4 having a high ground pressure is effectively drained from the inner circumferential groove 3a to further improve the hydro performance.

The outer circumferential groove 3b has a zigzag shape. The air discharged from the lateral groove 9o is often discharged to the outer circumferential groove 3b. Therefore, the outer circumferential groove 3b is formed into a zigzag shape so that the outer circumferential groove 3b is formed into an air column. The resonance of the tube can be suppressed, and the noise performance can be further improved. Note that the lateral grooves 9o are shown so as to be separated so as to intersect with each other at a bent portion on one side (in this example, the inner side in the axial direction) of the zigzag in the tire axial direction.

Further, in the present embodiment, the shoulder rib 6 is provided on the block B2 by disposing the shoulder lateral groove 15 extending axially outward from the outer circumferential groove 3b to the tire axial outer edge E of the ground contact surface. The divided ones are illustrated.

In the present embodiment, the shoulder lateral groove 15 exemplifies an example in which the shoulder lateral groove 15 makes an inclination angle δ of 50 to 60 ° with respect to the tire circumferential direction and extends in the same direction as the lateral grooves 9i and 9o. Further, the shoulder lateral grooves 15 are shown so as to be separated so as to intersect with each other at the bent portion of the other zigzag of the outer circumferential groove 3B in the axial direction of the tire (the axially outer side in this example). Thereby, the lateral groove 9o and the shoulder lateral groove 1
5 is not aligned in the axial direction, which is preferable in that the generation of resonance noise can be further prevented.

Further, in the present embodiment, the shoulder lateral groove 15 has a groove width increasing portion in which the groove width increases between the axially inner base portion 15a and the base portion 15a and the tire axially outer edge E of the ground contact surface. 15b, and in this example, the groove width increase ratio M, which is the ratio of the groove width at the tire axial outer edge E of the contact surface to the groove width at the outer circumferential groove 3b, is 2.0 to 2.5.
The doubled one is illustrated.

As a result, while reducing pumping noise and the like on the circumferential groove 3b side outside the shoulder lateral groove 15, widening the groove width on the tire axial direction outer edge E side of the ground contact surface, mud,
It can improve the discharge performance of dirt and the like, and especially improve the mud performance.

Further, in the present embodiment, the auxiliary groove 1 extending in the tire axial direction outside the tire axial outer edge E of the ground contact surface.
7 is formed. Such an auxiliary groove 1
For example, 7 may contact the road surface at a portion outside the tire axial direction outer edge E of the ground contact surface which is not normally grounded in a swamp, so that in such a case, the turning performance and the soil discharging performance can be improved.

As described in detail above, the present invention can be preferably applied to a tire having a radial structure including a carcass having a radial structure and a belt layer for tightening the carcass.

[0038]

[Examples] A mud and snow pneumatic tire having a tire size of 265 / 70R16 and having the specifications shown in Fig. 1 and Table 1 was experimentally manufactured (Examples 1 to 13 and Comparative Examples 1 to 1).
2. Conventional example), mud performance, hydro performance, and noise performance were tested. The tire's common specifications and test conditions are as follows.

<Tire common specifications>   Circumferential groove Number: 4 Groove width: 6.5 mm Groove depth: 9.0 mm   Vertical groove Groove width: 1.5 mm Groove depth: 4.5 mm (50% depth of circumferential groove)

<Passing noise test> The test tire was assembled on a rim of 7JJ and 3,000 cc at an internal pressure of 2.0 kgf / cm ² .
It was mounted on a domestic four-wheel drive vehicle and coasted on a smooth asphalt road surface at a passing speed of 57 km / h, and the passing noise was specified based on the JASO standard and the performance was compared. The results are expressed as an index with the conventional example being 100, and the larger the index, the smaller the passing noise and the better.

<Hydro performance (lateral hydro)>
Using the above vehicle, on a course with a puddle with a water depth of 10 mm and a length of 20 m on an asphalt road surface with a radius of 100 m, the vehicle is advanced while gradually increasing the speed, and the lateral acceleration (lateral G) is applied. The measurement was performed and the average lateral G of the front wheels at a speed of 50 to 80 km / h was calculated. The results are expressed as an index with the conventional example being 100, and the larger the value, the better.

<Mud performance> A mud road surface test course consisting mainly of mud and soil was fully accelerated in the D range of the transmission from speed 0 using the above vehicle to obtain a straight line 3
The passing time at 0 m was measured. The results are expressed as an index with the conventional example being 100, and the larger the value, the better. Table 1 shows the test results and the like.

[0043]

[Table 1]

As a result of the test, it was confirmed that the tires of the examples have improved mud performance and hydro performance without impairing noise performance.

[0045]

As described above, in the invention according to claim 1, the rib width Wm of the middle rib is 20 to 3 of the ground contact width TW.
By setting a relatively large value of 0%, the outer circumferential groove can be arranged outward from the tire equator C to reduce passing noise. In addition, the lateral grooves arranged on the middle rib are arranged such that the open ends of the vertical narrow grooves that divide the middle rib into the inside and the outside are displaced in the tire circumferential direction, so that the lateral grooves are continuously aligned in the inclination direction. Therefore, it is possible to suppress the generation of resonance sound having the lateral groove as an air column tube. Due to these synergistic effects, the pneumatic tire of the present invention can improve mud performance and hydro performance without impairing noise performance.

Further, in the invention according to claim 1,
The circumferential groove extends in a straight line, so the ground contact pressure is high.
The drainage film on both sides of the rib is effectively drained from the inner circumferential groove.
Water to further improve hydro performance. Also the outer circumferential groove
Is formed in a zigzag shape so that the outer circumferential groove is formed.
The resonance of the air column can be suppressed and the noise performance is further improved.
You can.

According to the second aspect of the invention, the middle rib is provided.
Forming a substantially Z-shaped sipe in the block dividing
Effectively reduces the pattern rigidity of the block,
It is possible to achieve the effect of reducing the pact sound, and it has a substantially Z shape.
The sipe did not come out of the ground plane at once by doing
Therefore, it is difficult to open the sipe, and the sipe that occurs when accelerating
It is possible to reduce the sound caused by opening.

[Brief description of drawings]

FIG. 1 is a development view showing a tread pattern of a pneumatic tire showing an embodiment of the present invention.

FIG. 2 is an enlarged view of a block formed on a middle rib.

[Explanation of symbols]

2 tread surface 3 circumferential groove Circumferential groove in 3a 3b Outer circumferential groove 4 crown ribs 5 Middle rib 6 shoulder ribs 7 vertical grooves 9i, 9o lateral groove S Almost Z-shaped sipe

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) B60C 11/00-19/12

Claims (3)

(57) [Claims] 1. A tread surface is provided with a crown rib extending in the tire circumferential direction including the tire equator C, a shoulder rib between the outer peripheral edge of the ground contact surface in the tire axial direction, and a middle rib between the crown rib and the shoulder rib. There are four or more circumferential grooves to be divided, and the inner circumferential groove extends linearly and the outer circumferential direction
The facing groove extends in a zigzag shape , and the rib width Wm of each middle rib is 20 to 30% of the ground contact width.
In addition, the middle rib extends in the tire circumferential direction and has a groove width of 1 to
By providing a vertical fine groove of 2 mm, the middle rib is provided with an outer portion between the outer circumferential groove on the tire axial direction outer side and the vertical fine groove, and the inner circumferential groove on the tire axial direction inner side with the vertical fine groove. It is divided into an inner part between the groove and the inner part, the outer part is connected to each circumferential groove and the vertical narrow groove, and is inclined at an inclination angle α of 30 to 70 ° with respect to the tire circumferential direction. By forming a lateral groove, the middle rib is divided into circumferential grooves, vertical narrow grooves, and blocks surrounded by the lateral grooves, and each open end of the lateral groove of the outer portion and the lateral groove of the inner portion in the vertical narrow groove. Is a pneumatic tire characterized by being displaced in the tire circumferential direction. 2. The middle rib block includes a sipe on both sides extending inwardly of the circumferential groove and the vertical narrow groove, forming an inclination angle β from the circumferential groove and the vertical narrow groove with respect to the tire circumferential direction. The substantially Z-shaped sipe comprising: a sipe and a joint sipe that joins the inner ends of the sipe on both sides and inclines at an inclination angle γ that is smaller than the inclination angle β. tire. 3. The siping has a substantially triangular shape in the block.
The pneumatic tire according to claim 2, wherein the pneumatic tire is divided into shapes .