JP2966517B2 - Pneumatic tire - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a pneumatic tire capable of improving one-way flow of a vehicle and improving straight-running performance by reducing residual CF in addition to improving conicity.

[Conventional technology]

With the recent improvement in vehicle performance and the improvement of the road network, tires have not only improved their basic performance such as durability, driving stability, and riding comfort, but also have a certain distance with the steering wheel released. It is desired to further improve the driving comfort by reducing the so-called one-sided flow of the vehicle in which a lateral flow occurs while traveling, and improving the straight running stability.

Conventionally, this one-sided flow of the vehicle has been attributed to the so-called conicity in which the circumferential length of the belt layer is particularly different in the left and right directions in the tire axial direction of the tread portion, so that the uniformity of the left and right directions in the tire axial direction is improved. In order to increase the height, as shown in FIG. 11, an inclined surface f, which becomes deeper toward the tread edge e, is formed on the tread surface a on the upstream side in the direction of action of the conicity force c by buffing.

[Problems to be solved by the invention]

However, as described above, the inclined surface f
It has been found that even when the conicity is improved, the one-sided flow of the vehicle may increase. The inventors repeated experiments to investigate the cause,
It has been found that the conicity may be improved by providing an inclined surface on the tread surface on the downstream side in the direction of action of the conicity force c, that is, the conventional technical idea.

As a result, it has been found that simply removing the cone shape in the tread portion as in the related art cannot sufficiently prevent one-sided flow of the vehicle.

On the other hand, due to recent advances in tire measurement technology, as shown schematically in FIG. 3, when a small slip angle α is applied to the tire traveling direction X, the cornering force generated in the tire lateral direction Y, that is, the lateral force F and the self-aligning torque SAT rotating in the direction of the slip angle α about the vertical axis Z passing through the center of the tire can be measured with high accuracy.

Such a measurement result is obtained by setting the camber angle β to 0.
For example, as shown in FIG. 4, the horizontal axis represents the self-aligning torque SAT, and the vertical axis represents the lateral force F using a straight line K. On the straight line K, the slip angle α is 0 degree, −0.
The cases of 2 degrees and +0.4 degrees are indicated by black circles.

As described above, in the radial tire, the lateral force F and the self-aligning torque SAT are generally generated even in the running state at the slip angle α = 0 °. The lateral force F when both the slip angle α and the camber angle β are 0 is referred to as LFD (lateral force deviation).

In such a relationship between the self-aligning torque SAT and the lateral force F, the lateral force F at the intersection k1 where the straight line K intersects the vertical axis, that is, the lateral force F when the self-aligning torque SAT does not occur is defined as the residual CF. Name it. It has been found that this residual CF affects the one-way flow of the vehicle. In other words, when the residual CF is in the plus direction, it means that the vehicle flows in the right direction, so that the direction and size of the residual CF can be used to evaluate the vehicle's one-sidedness. It is necessary to reduce this residual CF.

The lateral force F and the self-aligning torque SAT
Are displayed for the slip angle α, respectively.
CF and residual self-aligning torque SAT are shown as in FIG.

In addition, in a tire having a so-called conicity in which a difference in radius occurs on the left and right with respect to the tire equator, when assembling the tire, the residual CF and the self-aligning torque SAT change right or left on the large diameter side. In the case of so-called front and back facing, as shown in FIG. 6, the straight line K is two parallel straight lines as indicated by a straight line K1 of the front facing and a straight line K2 of the back facing. Also, as shown in FIG.
In both cases, the average value of the lateral force when the slip angle α is 0 and the camber angle β is 0 is called ply steer, and the deviation from each average value is defined as the conicity at the lateral force F.

Further, in the relationship between the one-sided flow of the vehicle, the residual CF, and the residual self-aligning torque SAT, when the vehicle is driven away from the steering wheel, the total self-aligning torque SA
Since T becomes 0, the tires at this time have a residual CF
Will occur. Normally, a force based on conicity acts on this, and a lateral force based on the resultant force of the residual CF and the conicity is generated in the vehicle with respect to the tire.

FIG. 7 shows an example of the residual CF and the vehicle flow. The one-sided flow amount of this vehicle is a lateral displacement amount generated when the steering wheel is driven at 100 km / h at 50 km / h with the steering wheel released.
The figure is measured using tires of size 215SR15. Thus, it can be seen that there is a correlation between the residual CF and the vehicle flow, and it is better to reduce the residual CF in order to prevent the vehicle flow, and by setting the residual CF to +4 kg to -4 kg, the amount of one-sided flow is reduced. It was found that the vehicle flow was almost satisfactory, less than 0.5m.

The inventors prototyped a plurality of types of tires having different tread patterns and belt layer structures for tires of a tire size of 225 / 50R16, and measured the relationship between the conicity and the residual CF of each tire. FIG. 8 shows the measurement results. In the figure The marks and ◎ indicate the relationship between the values of the conicity force c and the residual CFk immediately after molding of each tire, respectively.

Further, the test tires were divided into two groups in order to reduce the conicity. In FIG. 8, the marks ◎ and the marks in FIG. Make corrections, As shown in FIG. 1, the tread surface on the downstream side where the conicity force acts was buff-finished to correct the tread surface as shown in FIG.

As a result of the correction by the buffing, the arrow indicates the direction of change in the conicity and residual CF of each tire. The marks indicate the values of conicity and residual CF after buffing. According to FIG. 8, while the residual CF is reduced or increased by performing the conventional buffing shown in FIG. 11, the buffing is performed in a direction opposite to the conventional direction as shown in FIG. As a result, it has been found that the residual CF can be reduced with conicity in some cases.

In this way, when conventional buffing is performed, the conicity is reduced by removing the taper of the tread surface, but the residual CF may increase on the contrary, so the conventional correction expects one-way flow of the vehicle Turned out to be worse.

On the other hand, even when buffing is performed at a position opposite to the conventional position as shown in FIG. 1, there are cases where the residual CF decreases and cases where the residual CF increases.
It has been found that it is appropriate to use a combination of buffing at the conventional position and buffing at the opposite position in order to make both the values close to 0.

As a result of the test, it was found that the residual CF changes depending on the tread pattern of the tire and the structure of the belt layer.

Here, the effect of the tread pattern on the residual CF means that, as shown in FIG. 9, especially when a block is divided by an oblique horizontal groove, the difference in radius between the tire equator CO and the tread edge causes the block to have a different shape. Based on the generated traction FT and braking force FB, it is considered to be caused by the rotational moment M acting on the tread surface of this block.

The lateral groove rises left at the crown with respect to the traveling direction of the tire, and the residual CF is positive in the pattern of the upper right in the shoulder, and the residual CF is negative in the pattern of the upper right of the crown and the upper left in the shoulder. It turned out to be in the direction of.

On the other hand, the residual CF exerted by the belt layer structure is caused by the expansion and contraction of the belt in the ground contact portion, and the belt of the radial tire arranged in the cross ply is subjected to in-plane shearing such that the cord moves in parallel due to the expansion and contraction. It is considered that the tread rubber undergoes the deformation, which causes the in-plane shear deformation together with the deformation of the outermost layer of the belt ply, thereby generating residual CF.

It has also been found that the structure of the belt layer can greatly contribute to reducing its rigidity, particularly to increasing the inclination angle of the belt cord with respect to the tire equator.

According to the above-described tests, the inventors have found that: a) As in the conventional case, simply removing the large diameter side of the cone of the tread portion may deteriorate the one-sided flow of the vehicle in the tire configuration. thing.

Conversely, by buffing the small diameter side of the cone, one-sided flow may be improved.

b) The one-sided flow of the vehicle is due to the residual CF
Needs to be close to zero.

Was found.

Changing the tread pattern and belt layer to reduce residual CF is not preferable because it has a significant effect on steering stability, ride comfort, and grip performance.Constancy and residual CF are reduced to 0 while maintaining these various performances. There must be.

An object of the present invention is to provide a pneumatic tire capable of reducing one-sided flow of a vehicle without changing the configuration of the tire.

[Problems to be Solved by the Invention] The present invention is directed to a tread surface 2 in which a tread pattern 3 including ribs 4 or blocks 5 arranged in a circumferential direction is formed on a tread surface 2 and conicity force is increased from one side 6 in a tire axial direction. Side 7
A pneumatic tire acting toward the outer peripheral surface 9 of the rib 4 or the block 5 located on the other side 7 side,
The rib 4 or the block 5 is an edge on the tire tread end E side.
This is a pneumatic tire in which a slope 10 that becomes shallower toward E1 is formed by buffing.

In addition, as shown in FIG. 1, the inclined surface 10 is the edge on the tire equator side except the outer peripheral surface 9 of the edge F1 on the tire tread end side.
The rib may be formed only on the F2 side, or the rib may be formed with an inclined surface substantially over the entire outer peripheral surface of the block. Further, when a plurality of ribs or blocks are provided on the other side, all of the ribs or blocks may be provided with inclined surfaces, or some of the ribs or blocks may be provided with inclined surfaces.

[Action]

By providing the above configuration, depending on the shape of the tread pattern and the configuration of the belt layer, it is possible to reduce both the conicity and the residual CF to 0 even for a tire having a large residual CF, thereby reducing the one-way flow of the vehicle. Can be done.

Further, since the inclined surface is formed by buffing, it is easy to form the inclined surface with a small inclination angle and high accuracy, and it is possible to accurately reduce the one-sided flow of the vehicle.

 Hereinafter, the reason will be described with reference to the graph of FIG.

In the figure The A group indicated by the mark and the B group indicated by the ◎ mark are ascending leftward in the tire rotation direction R between the vertical grooves G, G at the crown portion TS on the tread surface 2 as shown in FIG. 10 (a). 10B, a shoulder groove SH is provided on the shoulder portion SH as shown in FIG. 10 (b), and a transverse groove SR is provided in the tire rotation direction R. As shown in FIG. 10 (c), a vertical groove is provided. Including horizontal transverse grooves provided between the belt cords D and the belt cord D of the belt layer inclining to the upper right with respect to the tire rotation direction R, and a combination of the above-mentioned FIGS. 10 (a) to 10 (c). I have.

As shown in FIG. 1, the rib 4 or the outer peripheral surface 9 of the block 5 located on the downstream side in the direction of action of the conicity C, that is, on the other side of the group A, is shallow toward the edge F1 on the tread end E side. By forming the inclined surface 10, the conicity C moves in the negative direction, and the residual CF also moves in the negative direction. That is, despite the increase in the taper of the tread surface, the one-sided flow of the vehicle is reduced, so that the straight running performance is improved.

This fact indicates that bringing both the conicity C and the residual CF close to 0 means a decrease in one-sided flow.

On the other hand, in the group B, the tread portion has the same configuration as that of the group A, but the inclined surface is formed on one side of the upstream side where the conicity C acts as shown in FIG. 11, that is, on the large diameter side of the taper. Because of the conventional configuration provided, in those belonging to the group B, while the conicity C decreases, the residual CF increases and the one-sided flow increases.

In the case of pneumatic tires, the tread pattern, particularly the position and inclination of the lateral groove and the inclination angle of the belt cord of the belt layer are mutually related, so the configuration of the present application should be adopted in a limited manner. By using the configuration of the present application together with the conventional configuration shown in FIG. 11, one-sided flow of the vehicle can be reliably reduced.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

1 and 2, a pneumatic tire 1 has a tread portion 12 having a tread surface 2 on an outer peripheral surface, and a sidewall portion 1 extending inward in a tire radial direction at both ends of the tread portion 12.
The pneumatic tire 1 includes a bead portion 13 extending from the tread portion 12 through the sidewall portion 13 and a bead portion 14 located radially inward of the sidewall portion 13 in the tire radial direction.
A carcass 17 that turns around the 14 bead cores 15, and a belt layer 19 is provided radially outside the carcass 17 and inside the tread portion 12. In this example, the belt layer 19 includes two inner and outer belt plies 19A and 19B. The inner and outer belt plies 17A and 17B are opposite to each other at an inclination angle of 30 degrees or less with respect to the tire equator CO. Equipped with belt cords that are arranged side by side. The belt cord is steel cord, nylon,
Organic fiber cords such as polyester and aromatic polyamide are used.

A tread pattern 3 is formed on the tread surface 2.
In this embodiment, the tread pattern is as shown in FIG.
First longitudinal grooves G1, G1 on both sides of the tire equator CO, and the longitudinal grooves
On the outer side in the tire axial direction of G1, second longitudinal grooves G2 and G2,
On the outer side in the axial direction of the second vertical groove G2, vertical grooves G each including a third vertical groove G3 are provided.

In this example, the two second longitudinal grooves G sandwiching the tire equator CO
The portion between G2 and G2 is defined as a crown portion TC, and the portion between the second vertical groove G2 and the tread edge E is defined as a shoulder portion TS.

In this embodiment, in FIGS. 1 and 2, the right side has higher conicity than the left side, so that the conicity force C acts from one side 6 located on the right side to the other side 7 located on the left side. The rotation direction R of the tire is set to rotate from bottom to top in FIG.

In FIG. 2, between the first and second longitudinal grooves G1 and G2, there is a left-upward horizontal groove SL in which the other side 7 is at a higher position than one side, and is located on one side of the tread surface. The same inclination angle is arranged on the side 6 side and the other side 7 side, and therefore, between the first and second vertical grooves G1 and G2, the vertical grooves G1 and G2 and the left-upward horizontal groove S
A block row composed of blocks 5 separated by L and SL is formed.

In this example, between the two first vertical grooves G1, G1, and between the second vertical grooves G1, G1,
No ribs are provided between the third vertical grooves G2 and G3, and the ribs 4, 4, 4 are formed. In the block pattern 2 formed in this way, the residual CF is dislocated to the positive side.

In the block pattern 2 having the above configuration, the other side 6,
On the outer peripheral surface 9 of the rib 4 or the block 5.
The rib 4 or the block 5 forms an inclined surface 10 that becomes shallower from the edge F2 on the tire equator CO side toward the edge F1 on the tread end E by buffing.

Due to the buffing, the conicity shifts toward the negative side, and the residual CF also shifts to the negative side, so that both the conicity and the residual CF can be close to 0, reducing the one-way flow of the vehicle and improving the straight running performance. I can do it. It is to be noted that the conicity and the residual CF can be made close to 0 by providing the above-described inclined surface with respect to the tread pattern 2 shown in FIGS. 10 (b) and 10 (c). Becomes

〔The invention's effect〕

As described above, the pneumatic tire of the present invention has the above-described configuration, and in the conventional buffing in which only the conicity is corrected, even if the tire has a tire structure in which the one-sided flow is increased, the residual CF is reduced. It can be made small and reduces the one-sided flow of the vehicle, improving the straight running performance. Furthermore, by selecting the conventional tire and the tire according to the present invention depending on the tire structure, it is possible to reduce the one-sided flow of the vehicle and improve the performance without changing the tire structure, and therefore without reducing the running performance and durability.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, FIG. 2 is a developed plan view showing an example of the tread pattern, FIGS. 3 to 6 are diagrams for explaining the residual CF, and FIG. FIG. 8 is a diagram illustrating a measurement result of residual CF and one-sided flowability, FIG. 8 is a diagram illustrating a change in conicity and residual CF by buffing, FIG.
The figure is a diagram illustrating the relationship of the forces acting on the tread, tenth
Figures (a) to (c) are diagrams illustrating tread patterns,
FIG. 11 is a sectional view showing the prior art. 2 ... tread surface, 3 ... tread pattern, 4 ... rib, 5 ... block, 6 ... one side, 7 ... other side, 9 ... outer peripheral surface, 10 ... inclined surface, C ... … Conicity, CO …… the tire equator, K …… the remaining CF, E …… the tread edge, F1 …… the edge on the tread edge side.

Claims (1)

(57) [Claims] 1. A pneumatic tire in which a tread pattern including ribs or blocks arranged in a circumferential direction is formed on a tread surface and a conicity force acts from one side in a tire axial direction to another side. A pneumatic tire in which a rib or block is formed by buffing an outer peripheral surface of the rib or block located on the other side with an inclined surface which becomes shallower toward an edge on the tire tread end side.