JP2899654B2 - 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 in which the influence of a residual cornering force caused by a tread pattern is suppressed and steering stability is improved.

[0002]

2. Description of the Related Art To improve drainage of general road surfaces,
Since the center is high and has a slope (kant) that decreases as it goes to the shoulder, when the vehicle travels straight on a straight road, the vehicle receives force in a direction down the cant from the road surface, so that direction Vehicles tend to flow. But,
Due to factors such as the structure and shape of the tire, the tire itself can generate a lateral force. This lateral force is called residual cornering force. If the residual cornering force and the lateral force by the cant are balanced, the flow of the vehicle described above does not occur. Usually, the residual cornering force is
The direction of the belt buried in the tread, particularly the belt cord radially outward, is greatly affected, and the sticking direction of the belt cord is determined by the cant of the road surface. For example, when traveling on the left side, the road surface is provided with a cant that descends to the left, so the outermost layer belt cord is attached in an upward right direction when viewed from the outside of the tire (FIG. 6). Therefore, the flow of the vehicle can be prevented by affixing the outermost layer belt cord in an upwardly leftward direction as viewed from the outside of the tire (FIG. 7).

[0003]

However, some of the residual cornering forces are caused by a tread pattern provided on the tread, and it is difficult to obtain a proper generation of the residual cornering force only by attaching the belt cord. there were. Here, the mechanism of generation of the residual cornering force will be described.Since the rotation radius of the crown portion of the tire tread is larger than the rotation radius of the shoulder portion, a traction force acts on the block provided on the crown portion, and the block is provided on the shoulder portion. A braking force acts on the block. For this reason, the block is twisted in a direction determined by the direction of inclination of the block side with respect to the flow direction of the tread pattern, that is, the width direction of the tread, and a torque is generated, thereby generating a residual cornering force.
In a conventional tire, for example, as shown in FIG. 4A, a block Bcr provided on a crown portion is inclined rearward in a tire rotation direction toward an outer side in a tread width direction, and a block Bsh provided on a shoulder portion. Is inclined forward in the tire rotation direction toward the outer side in the tread width direction, and the traction force Ft acts on the inner end of the block Bcr, and the braking force Fb acts on the outer end of the block Bsh. Torque T which is twisted outward and is clockwise on the right (counterclockwise on the left) from the center of the tread shown.
_R occurs, and the self-aligning torque (Self Alignin
gTorque) The SAT increases to increase the residual cornering force as a whole (see FIG. 5A). 4B, the block Bcr provided on the crown portion is inclined forward in the tire rotation direction toward the outside in the tread width direction, and the block Bsh provided on the shoulder portion is provided on the outside in the tread width direction. As the traction force Ft acts on the outer end of the block Bcr and the braking force Fb acts on the inner end of the block Bsh, the two blocks Bcr and Bsh are twisted inward. A torque _{TL in a} counterclockwise direction (clockwise on the left side) is generated on the right side of the illustrated tread center, and the self-aligning torque SAT is reduced to reduce the residual cornering force as a whole (see FIG. 5B). ). As described above, the residual cornering force as a whole varies depending on the flow direction of the tread pattern, and depending on the tread pattern, a large force is generated in a direction opposite to the residual cornering force based on the belt cord sticking direction to slide down the cant. There was a problem of fear.

An object of the present invention is to provide a pneumatic tire which suppresses the influence of a tread pattern on a residual cornering force, has a high steering stability, and is suitable for right-hand running on a road surface having a downward-sloping cant. is there.

[0005]

In order to achieve the above object, a pneumatic tire according to the present invention is provided symmetrically with respect to a tire equatorial plane and has two main grooves extending in a tire circumferential direction in a tread, The tread is divided into a central portion formed between the main grooves and a shoulder portion formed outside the main groove in the tire width direction, and a plurality of lateral grooves extending in the tire width direction are provided in the central portion and the shoulder portion. The outermost layer belt cord is arranged upwardly to the left when viewed from the tire radial outside when mounted on the vehicle, and the groove direction of the central lateral groove is upwardly to the left when viewed from the tire radially outside. The groove direction of the lateral groove of the shoulder portion is disposed upward to the right as viewed from the tire radial direction outside, all the groove walls of the central lateral groove are inclined in the same direction with respect to the tire radial direction line, and the shoulder portion It is obtained by inclined groove wall and the opposite direction of the lateral groove in the central portion with respect to all the groove walls of the groove the tire radial direction line.

[0006]

The groove direction of the lateral groove in the center and the groove direction of the lateral groove in the shoulder are inclined in opposite directions with respect to the tire axial direction, and the groove walls of the central groove are all in the tire radial direction line. In the same direction, and all the groove walls of the lateral grooves of the shoulder are inclined in the opposite direction to the groove walls of the central lateral grooves with respect to the tire radial direction line, so that the traction force Ft of the crown block located in the central part is increased. And the braking force Fb of the shoulder block located at the shoulder portion is reduced, the generated torque is reduced to suppress the change in the self-aligning torque SAT, and the rigidity of the crown block and the shoulder block in the front-rear direction in the tire traveling direction is reduced. To reduce the tractive force Ft and the braking force Fb, and the tread pattern exerts on the residual cornering force. It is possible to suppress the sound. The outermost layer belt cord and the central lateral groove are arranged at the upper left as viewed from the tire radial outside when the outermost layer belt cord is mounted on the vehicle, and the central lateral groove groove direction is viewed from the tire radial outside when mounted on the vehicle. By arranging it upward to the left and inclining it in the same direction, it is possible to secure a residual cornering force in the left direction based on the belt cord attaching direction.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG.
In FIG. 1, a tread 1 of a pneumatic tire for right-hand running is obtained by attaching an outermost layer belt cord in an upwardly-leftward direction (see FIG. 7) when the vehicle is mounted on the tire in a radially outward direction. The pattern includes a central sub-groove 2 provided at the center of the tread and extending in the tire circumferential direction, a pair of main grooves 3 symmetrically provided on both sides of the central sub-groove 2 and extending in the tire circumferential direction, and a center. A pair of first sub-grooves 4 provided between the sub-groove 2 and the main groove 3 and extending in the tire circumferential direction.
A pair of second sub-grooves 5 provided on the outer side in the tread width direction of the main groove 3 and extending in the tire circumferential direction; and a pair of second sub-grooves 5 provided on both sides of the central sub-groove 2 and having one end closed near the central sub-groove 2. And
A central lateral groove 6 having the other end communicating with the main groove 3 and extending in the tread width direction; a shoulder lateral groove 7 extending in the tread width direction having one end communicating with the main groove 3 and having the other end reaching the tread end 1a. And Here, a crown portion, that is, a center portion Cr, is formed between the main grooves 3 and 3, the main groove 3 and the tread end 1a.
Is defined as a shoulder Sh, and the width CW of the central portion Cr is set to 40 to 60%, preferably 50% of the tread width TW.

The central sub-groove 2, the first sub-groove 4, and the central lateral groove 6 form a pair of central crown blocks 8 disposed on both sides of the central sub-groove 2 in the tire circumferential direction. An outer crown block 9 is formed by the sub-groove 4 and the central lateral groove 6, and an inner shoulder block 10 is formed by the main groove 3, the second sub-groove 5 and the shoulder lateral groove 7,
The outer shoulder block 11 is formed by the sub-groove 5 and the shoulder lateral groove 7.

The direction of the central lateral grooves 6, 6 rises to the left when the vehicle is mounted on the vehicle from the outside in the radial direction of the tire (left in FIG. 1).
When the vehicle is mounted on the vehicle, the groove direction of the shoulder lateral grooves 7, 7 rises to the right as viewed from the outside in the tire radial direction (to the right in FIG. 1), that is, in the direction opposite to the groove direction of the central lateral groove 6 with respect to the tire axial direction. The center horizontal groove direction angle θc which is formed, that is, the groove center line connecting the centers of the groove widths of the central horizontal grooves 6, 6 is an acute angle formed with respect to the tire axial direction, and the shoulder horizontal grooves 7,
The shoulder center groove direction angle θs, which is an acute angle formed by the groove center line connecting the centers of the groove widths 7 with respect to the tire axial direction, is formed in a direction opposite to the tire axial direction. As described above, the groove directions of the central lateral grooves 6, 6 are formed in the same direction as the outermost layer belt cord (upward in the figure). The rotation direction of the tire is indicated by an arrow R.

FIG. 2 shows a cross section of the central lateral groove 6 and the shoulder lateral groove 7, that is, a cross section perpendicular to the groove center line and the tread surface. FIG. 2 (A) shows AA ', JJ' in FIG.
(B) is a sectional view taken along the line BB 'and II', and (c) is a sectional view taken along the line CC 'and HH'.
(D) is a sectional view taken along the line DD ′ and GG ′, and (e) is a sectional view taken along the line EE ′ and FF ′. The direction from left to right in the figure is the tire rotation direction. R. In the central portion Cr, as shown in FIGS. 2D and 2E, the groove walls 6a and 6b of the central lateral groove 6 are moved from the groove bottom toward the opening side.
It is inclined in the tire rotation direction R with reference to the tire radial direction line (that is, the line perpendicular to the tread surface) SL, and the front end side groove wall 6a of the crown block, that is, the center crown block 8 and the outer crown block 9 in the tire rotation direction R, is inclined. The front end groove wall angle α (α = + 5 ° in this embodiment) and the rear end groove wall 6
b is different from the rear end groove wall angle β (β = + 10 ° in this embodiment) (α ≠ β).

In the shoulder Sh, FIG.
As shown in (a), (b), and (c), the groove walls 7a and 7b of the shoulder lateral groove 7 are opposite to the tire rotation direction R based on the tire radial direction line SL from the groove bottom toward the opening side. Direction, that is, in the direction opposite to the groove walls 6a and 6b of the central lateral groove 6, and the front end groove wall angle γ of the front end side groove wall 7a of the shoulder block, ie, the inner shoulder block 10 and the outer shoulder block 11, in the tire rotation direction R. In this embodiment, γ
= −10 °) and the rear end groove wall angle δ (δ = −5 ° in the present embodiment) and the rear end groove wall angle 7b (γ ≠ δ). The crown block and the shoulder block have different groove wall angles at the front and rear ends in the tire rotation direction R. That is, α ≠ γ, β ≠ γ, α ≠ δ, β ≠ δ.

With this configuration, the stiffness of the crown block provided at the center portion Cr, ie, the center crown block 8 and the outer crown block 9 in the tire rotation direction R is reduced to reduce the traction force Ft, and the shoulder block, ie, the inner shoulder block. The rigidity of the outer shoulder block 10 and the outer shoulder block 11 in the tire rotation direction R can be reduced to reduce the braking force Fb, and the generated torque can be reduced to suppress the change in the self-aligning torque SAT, resulting from the tread pattern. Reduce residual cornering force.

The operation of this embodiment will be described in detail. In the attaching direction and the tread pattern of the outermost layer belt cord of the belt, the outermost layer belt cord of the belt is located in a left-upward direction when viewed from the tire radial outside when mounted on the vehicle. Since the belt is stuck, the direction in which the residual cornering force generated by the belt acts is the left direction. On the other hand, the central lateral grooves 6 and 6 rise to the left, and the shoulder lateral grooves 7 and
7, the direction in which the residual cornering force due to the tread pattern acts is opposite to the direction of the residual cornering force due to the belt, that is, rightward. And the shoulder block groove walls are inclined in the opposite direction with respect to the tire radial line SL,
By changing the groove wall angles at the front and rear ends in the tire rotation direction of both blocks, the residual cornering force caused by the tread pattern is reduced, and the influence thereof is suppressed.

Next, the results of an evaluation test performed using an example tire manufactured by applying the present invention and a comparative example tire having a conventional structure will be described with reference to Table 1 (FIG. 3). Table 1 is a right-hand running tire having a tire size of 185 / 60R14, using Examples 1 and 2 and Comparative Examples 1 to 4 having the tread pattern shown in FIG. 1 and having the same tread pattern dimensions. 4 shows the result of measuring the residual cornering force by using the above method.

In Examples 1 and 2 and Comparative Example 1, the direction of the outermost belt cord is upwardly leftward, and the angle of the outermost belt cord is
In Comparative Examples 2 and 3, the direction of the outermost layer belt cord rises to the right, and the angle of the outermost layer belt cord is 22 °. The dimensions of the tread pattern in Examples 1 and 2 and Comparative Examples 1, 2 and 3 were as follows: tread width TW = 152 mm, width CW of central portion Cr = 62 mm, width SW of shoulder portion Sh =
36 mm, groove width GW of main groove 3 = 9 mm, groove width MW of central sub groove 2
= 7.5 mm, the groove width LW1 of the first sub-groove 4 = 3.0 mm, the groove width LW2 of the second sub-groove 5 = 2.5 mm, the groove direction of the central lateral groove 6 rises to the right, and the groove direction angle θc of the central lateral groove 6 is 20. 5050 °, the groove direction of the shoulder lateral groove 7 is raised to the left, the groove direction angle θs of the shoulder lateral groove 7 is 30 to 35 °, and the groove depth of each groove is 8 mm. In addition, the expressions of "upward to the right" and "upward to the left" indicating the direction of the outermost layer belt cord and the groove direction of the lateral groove are as follows when the tire is mounted on the vehicle and viewed from the tire equatorial plane from the tire radial outside. It shows the status.

In the first embodiment, the front end groove wall angle α = + 5 ° and the rear end groove wall angle β = + 10 ° of the central lateral groove 6 at the central portion Cr.
(See DD ', EE', FF ', GG' cross section)
And the front end groove wall angle γ = −10 ° and the rear end groove wall angle δ = −5 ° of the shoulder lateral groove 7 in the shoulder Sh.
-A ', BB', CC ', HH', II ', J
(Refer to -J 'cross section) (Here, the positive and negative angles are positive (+) in the tire rotation direction and negative (-) in the reverse direction). In the second embodiment, the front end groove wall angle α of the central transverse groove 6 is
+ 5 °, rear end groove wall angle β = + 5 ° (α = β), the front end groove wall angle γ = −10 °, and the rear end groove wall angle δ = −5 ° of the shoulder lateral groove 7 are the same as in the first embodiment. is there.

Comparative Example 1 is a tire having a conventional structure having a symmetrical transverse groove cross-sectional shape. The front end groove wall angle α = −5 °, the rear end groove wall angle β = + 5 °, and the shoulder lateral groove 7 of the central transverse groove 6. Front end groove wall angle γ = −5 °, rear end groove wall angle δ = + 5
It is. Comparative Example 2 has the same horizontal groove cross-sectional shape as that of Example 1, Comparative Example 3 has the same horizontal groove cross-sectional shape as that of Example 2, and Comparative Example 4 has the same horizontal groove cross-sectional shape of Comparative Example 1. The residual cornering force is a value when the self-aligning torque SAT = 0 kgf · m measured under a standard condition with a cornering force measuring device on the indoor stand, and a positive (+) value acts on the right side in the traveling direction. Indicates force, and negative (-) values indicate the force acting on the left side.

As is clear from the results in Table 1, Example 1
And in Example 2, the residual cornering force was negative (-).
The force acts on the left side with respect to the traveling direction, and when traveling on the right side, the force acts in the direction opposite to the lateral force due to the cant, so that the flow of the vehicle due to the cant can be suppressed.
On the other hand, in the comparative example 1 of the conventional structure, the force acting on the right side caused by the tread pattern is larger than the force acting on the left side in the traveling direction due to the outermost layer belt cord being stuck to the upper left, and the residual force acting on the right side as a whole. A cornering force is generated, and in the right side traveling, a force in the same direction as the lateral force exerted by the cant acts to promote the flow of the vehicle due to the cant.

In Comparative Examples 2, 3, and 4, a force acting on the right side in the traveling direction is generated by attaching the outermost layer belt cord upward to the right, and the force acting on the right side caused by the tread pattern and the lateral force caused by the cant. The force in the same direction as the force acts more, and further promotes the flow of the vehicle by the cant. As a result, in the example tire, it is clear that the residual cornering force caused by the tread pattern is reduced, and the influence on the residual cornering force generated by the belt is suppressed.

[0020]

Since the present invention is configured as described above, the following effects can be obtained. The groove direction of the lateral groove in the central portion and the groove direction of the lateral groove in the shoulder portion are inclined in opposite directions with respect to the tire axial direction, and the groove walls of the central groove are all in the same direction with respect to the tire radial direction line. And all the groove walls of the lateral grooves of the shoulder are inclined in the direction opposite to the groove walls of the central lateral groove with respect to the tire radial direction line, so that the traction force Ft of the crown block located at the central part and the shoulder part In addition to reducing the braking force Fb in the shoulder block located at the lower position, reducing the generated torque to suppress the change in the self-aligning torque SAT, and changing the rigidity of the crown block and the shoulder block in the front-rear direction in the tire traveling direction. Reduces the traction force Ft and the braking force Fb to reduce the effect of the tread pattern on the residual cornering force. Rukoto can. The outermost layer belt cord and the central lateral groove are arranged at the upper left as viewed from the tire radial outside when the outermost layer belt cord is mounted on the vehicle, and the central lateral groove groove direction is viewed from the tire radial outside when mounted on the vehicle. By arranging it upward to the left and inclining it in the same direction, it is possible to secure a residual cornering force in the left direction based on the belt cord attaching direction.

[Brief description of the drawings]

FIG. 1 is a tread pattern developed view showing an example of a pneumatic tire for traveling on the right side to which the present invention is applied.

2A is a cross-sectional view taken along line AA ′ (JJJ ′) of FIG. 1, FIG. 2B is a cross-sectional view taken along line BB ′ (II ′) of FIG.
(C) is a sectional view taken along the line CC ′ (HH ′).
Is a sectional view taken along the line DD ′ (GG ′), and FIG. 4E is a sectional view taken along the line EE ′ (FF ′).

FIG. 3 is a table 1 showing measurement results of a residual cornering force of an example of the present invention and a comparative example.

FIG. 4 is an explanatory diagram showing a flow direction of a crown block and a shoulder block.

FIG. 5 is a characteristic diagram of a cornering force and a self-aligning torque showing a change of a residual cornering force caused by the tread pattern shown in FIG. 7;

FIG. 6 is a plan view of a belt layer provided with a belt cord direction that rises to the right when viewed from the outside of the tire.

FIG. 7 is a plan view of a belt layer provided with a belt cord direction which rises to the left as viewed from the outside of the tire.

[Explanation of symbols]

Cr central part, Sh shoulder part 1 tread, 2 central sub-grooves, 3 main grooves (intermediate vertical grooves),
4 First sub-groove 5 Second sub-groove, 6 Central lateral groove, 7 Shoulder lateral groove 8 Central crown block, 9 Outer crown block 10 Inner shoulder block, 11 Outer shoulder block

Continuation of front page (56) References JP-A-5-178026 (JP, A) JP-A-5-77612 (JP, A) JP-A-5-270214 (JP, A) JP-A-1-22602 (JP) JP-A-3-32906 (JP, A) JP-A-4-100706 (JP, A) JP-A-1-309806 (JP, A) JP-A-63-222905 (JP, A) JP-A-3-273903 (JP, A) JP-A-4-193607 (JP, A) JP-A-2-147415 (JP, A) JP-A-3-143708 (JP, A) A) US Patent 5200008 (US, A) European Patent Application Publication 605849 (EP, A1) (58) Fields investigated (Int. Cl. ⁶ , DB name) B60C 11/04-11/11 B60C 9/18

Claims (1)

(57) [Claims] 1. The tire is provided symmetrically with respect to the equatorial plane of the tire,
The tread is provided with two main grooves extending in the tire circumferential direction, and the tread is divided into a central portion formed between the main grooves and a shoulder portion formed outside the main groove in the tire width direction. A pneumatic tire provided with a plurality of lateral grooves extending in a tire width direction in a shoulder portion, wherein an outermost layer belt cord is disposed at an upper left as viewed from the tire radial outside when the vehicle is mounted, and a central lateral groove is provided. The groove direction of the shoulder is arranged upward to the left when viewed from the tire radial outside, the groove direction of the lateral groove of the shoulder portion is disposed to the right as viewed from the tire radial outside, and all the groove walls of the central lateral groove are tires. The pneumatic tire is characterized by being inclined in the same direction with respect to the radial direction line, and all the groove walls of the lateral grooves in the shoulder portion being inclined in the opposite direction to the groove wall of the central groove in the tire radial direction line. .