JPS60255506A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To quicken damping of a vibration due to a surge of a vehicle and improve housing property by forming the average pitch of a kerf, covering the whole circumference of a tire, smaller than the average length of a projection of the kerf in the direction of the tire crossing. CONSTITUTION:Four grooves 2, 2' continuing in the circumferential direction of a tire are carved in a grounding area A of a tread, while five ribs 1, 1' are formed between each groove 2, 2' and, outside the grooves 2' on both outer sides. The rib 1 interposed between grooves 2 and 2' is provided, through carving, with the plural number of kerfs 3, which cross the grooves on both sides and crosscut the rib 1, while the plural number of kerfs 3' are carved on the ribs 1'. Further, angles theta of the kerfs 3 and 3' with respect to the direction of tire crossing are below 45 deg., while the average pitch of the kerfs 3, 3' covering the whole circumference of the tire are formed smaller than the average length L of a projection in the direction of tire crossing of the kerfs 3, 3'.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire that eliminates vehicle surge.

[Prior art]

Tread patterns for passenger car tires can be broadly classified into two types: ribbed pattern and block pattern. Conventionally, ribbed pattern is considered to be more advantageous in terms of noise than block pattern, and has been mainly used in tires with emphasis on comfort. .

On the other hand, low-frequency longitudinal vibrations that occur when a vehicle suddenly accelerates from deceleration, so-called vehicle surge, are also a factor in livability, but compared to block patterns, rib patterns are had the disadvantage of slow decay time.

[Purpose of the invention]

An object of the present invention is to provide a pneumatic tire that has a rib pattern on the tread surface that quickly damps vibrations in the longitudinal direction of the vehicle due to vehicle surge, and has improved comfort.

[Structure of the invention]

That is, the present invention provides a pneumatic radial tire having grooves continuously carved in the tire circumferential direction and ribs formed apart from the grooves on the tread surface, in which the ribs are arranged at an angle of 45° or less with respect to the tire transverse direction. The element is formed by carving a plurality of kerfs cut at an angle of , and the average pitch P of each kerf over the entire circumference of the tire is smaller than the average projected length of the kerf in the tire transverse direction. Its gist is pneumatic tires.

Hereinafter, the configuration of the present invention will be explained in detail.

The main cause of vehicle surge is fluctuations in driving torque due to irregular combustion in the engine, but the degree of vehicle surge is greatly influenced by tires.

Generally, the quality of vehicle surge can be expressed by the magnitude of the damping ratio of longitudinal vibration, and the larger the damping ratio, the better the vehicle surge.

Figure 5 is a graph showing how the longitudinal vibration attenuates over time. At this time, the damping ratio ζ is ζ-1/n Jn (XI
/X2).

Next, regarding the relationship between the damping ratio and the tire, it was found through experiments that the damping ratio is related to the tire's longitudinal slip rigidity.

FIG. 6 shows the relationship between slip stiffness and damping ratio. As can be seen from Fig. 6, there is a negative correlation between the damping ratio and the slip stiffness, and when the damping ratio is plotted on the Y axis and the slip stiffness is plotted on the X axis, Y = -2,81x 10-' X + 0. 204
In this case, the correlation coefficient γ is r = -0,858
It becomes 9.

Slip rigidity is the slope of the slip ratio and tire shaft torque curve at the origin obtained by measuring the torque acting on the tire shaft when the slip rate is varied while keeping the tire speed constant.

FIG. 7 is a graph showing the relationship between the slip speed νS and the tire shaft torque T. The slope b of this curve a at the origin is the slip stiffness dT/dVs. If this slope is small, the slip rigidity is low, and if the slip rigidity is low, the damping ratio of vehicle longitudinal vibration becomes large (see FIG. 6), so that vehicle surge is improved.

In order to reduce slip rigidity, it is effective to generate slip between the tires and the road surface by changing the trend in response to the longitudinal force that acts between the tires and the road surface when a vehicle surge occurs.

On the other hand, trend deformation is a combination of shear deformation and bending deformation, and increasing the bending deformation is effective in reducing slip rigidity.

FIG. 8 shows how the tread deforms.

The trend B at the depth D of contact with the road surface is deformed as shown by the broken line due to the tangential force f.

The reason why bending deformation is effective in reducing slip rigidity is thought to be that the ground contact area of the tread is reduced, as seen in FIG.

The deformation δ due to bending can be expressed by the following formula.

δ=D3/, (3E I) ・f (f: tangential force (back and forth direction), D: element thickness, E
Young's modulus of Nidred rubber, ■Second moment of area with respect to the axis perpendicular to the longitudinal tangential force f applied to the Nidred element and passing through the centroid of the flat section of the element) In other words, factors regarding the pattern that affect the deformation of the tread is D and 1, and increasing D or decreasing I increases the deformation of the tread, which in turn improves vehicle surge.

However, the problem here is the deformation of the tread portion in the tire transverse direction, and if the deformation in the tire transverse direction is large, the steering stability will be impaired. Therefore, in order to improve vehicle surge while ensuring straight-line stability, the deformation of the tread must be large in the tire circumferential direction and small in the transverse direction.

Diagrams of the rib pattern and elements are shown in FIGS. 9-11. In the figure, 1 is a rib, 2 is a groove continuous in the circumferential direction,
3 is a kerf, and 4 is a rib element cut by the kerfs 3, 3'.

Here, consider one element 4 of a rectangular rib in which the pinch of each kerf 3 is Pi and the width of the rib I is Li.

In order to make it easier for this element 4 to deform in the circumferential direction, it is effective to increase D3/I, that is, increase D/Pi, from the above equation. Furthermore, in order to make the deformation in the circumferential direction smaller than the deformation in the transverse direction, it is necessary to make Li larger than Pi. ``To summarize these things, it is important to increase (DxLi)/Pi2. In addition, as the element 4 changes direction from the circumferential direction to the transverse direction, the deformation in the circumferential direction becomes smaller, so the direction of the carfee perpendicular to the circumferential direction (tire transverse direction) is most effective, and preferably 4 for the direction
The angle is 5° or less. If the angle θ of the kerf with respect to the tire transverse direction exceeds 45°, the tire will deform in the circumferential direction.
<, Vehicle surge is not improved.

Furthermore, considering the entire contact area of the element 4, the width Li of a rib is the width Li of one rib multiplied by the number n of ribs.

Vehicle surge can be improved by reducing the synergistic effect of the above, that is, Pi''/(nXLiXDXcos θ).

In the end, in order to quickly attenuate vibrations in the longitudinal direction of the vehicle caused by vehicle surges and to obtain a pneumatic tire with improved comfort, multiple kerfs are required in which the ribs are cut at an angle of 45 degrees or less with respect to the cross direction of the tire. It is necessary to form elements by engraving, and furthermore, it is necessary to make the average pitch P of each of the kerfs over the entire circumference of the tire smaller than the average projected length of the kerfs in the tire transverse direction.

It is preferable that elements satisfying the following formula account for 35% or more of the elements in the entire tire.

0,05≦Pi2/ (nXLiXDXcos θ)≦
0.40 However, Pi: pitch of the kerf in the tire circumferential direction.

Li...Curf ρ projected length in the tire transverse direction.

θ...Angle of the kerf in the tire transverse direction.

n...Number of ribs.

D...Depth of kerf.

Furthermore, it is desirable that all elements of the tire fall within the ranges described above.

[Experiment example]

In order to confirm the effects of the present invention, the following experiment was conducted.

A tire with a tire size of 185/70SR14 having the pattern shown in Figure 1 and the shape shown in the table below was made,
The damping ratio was measured.

(The following is a blank space) The relationship between Pi2/ (nxLixDXcosθ) and the damping ratio is shown in FIG. 12.

From the results in Figure 12, Pi2/ (n XLiX D Xcosθ) is 0.4
Below, it can be seen that the damping ratio is 0.05 or less, and the effect of improving vehicle surge is large.

However, Pi2/ (n XLi X D Xcos
If the value of θ) exceeds 0.05, the elements divided by the kerf will become too small, leading to a decrease in steering stability, which is undesirable. Also, if the width of the kerf exceeds 211, each element will become too small, similar to the block pattern. Since the elements are completely independent and generate noise, the kerf width is preferably 2fi or less.

Furthermore, in order to reduce noise levels, Tire Trend Bakoon divides the length of each element in the circumferential direction into several types so that the ratio of the maximum element length to the minimum element length is 1.7 or less. Generally speaking, 35 out of all the elements in tires and road surfaces
It is sufficient if the element has a size within the above range.

More preferably, all elements of the tire fall within the ranges described above.

The present invention will be specifically described below with reference to Examples.

〔Example〕

FIG. 1 shows a tread pattern of a radial tire according to a first embodiment of the present invention, and FIG. 2 is a partially enlarged view thereof.

The contact area A of the tread surface has grooves 2 that are continuous in the tire circumferential direction.
are carved, and five ribs 1 and 1° are formed between each port 2 and on the outside of the grooves 2° on both outer sides. Groove 2 on both sides
．． A plurality of kerfs 3 are carved into the rib 1 sandwiched between the grooves 2" on both sides to cut the rib 1. Also, the rib 1 at both ends has the groove 2" on only one side. Mo groove 2
An element 4 is formed by cutting a plurality of kerfs 3' which cross the tread contact area B and cut the rib 1°.

The angle θ of the kerfs 3 and 3' with respect to the tire transverse direction is 45 degrees or less, and the average pitch P over the entire tire circumference of each of the kerfs 3 and 3' is set to The average projection length in the direction is smaller than that in the direction.

In this embodiment, the angle θ of the kerfs 3 and 3' with respect to the tire transverse direction is θ1. θ
2 are different from each other.

Therefore, the angle θ has a value of (θ1+02)/2 of 45°.
It is as below.

Furthermore, the pitch of each of the kerfs 3 and 3' over the entire circumference of the tire is also determined by the pitch of each element 4 as shown in FIGS.
Bi-nochi is Pl, P2. ...Pi...Pm. Therefore, the average pitch P over the entire circumference of the tire is (P
Let P be the value of l+P2 +·+Pi+···+pm)/m.

Note that the pinch Pi of the element 4 at an arbitrary position is Pi=(Pa+Pb)/2 since the left and right intervals are different in this embodiment as shown in FIG.

Furthermore, the average projected length of each kerf in the tire transverse direction is also determined by each rib, as shown in Figure 1.
i...Ln. Therefore, the average projected length of each kerf in the tire transverse direction is (L1+L2+・+Li+・
・+Ln)/n is set to L.

In addition, the projected length Li of the rib in the tire transverse direction at an arbitrary position
In this embodiment, as shown in FIG. 2, Li=(La+Lb)/2.

Moreover, in this embodiment, among the elements 4, 0.05≦
Pi2/ (n XLiX D Xcos θ)≦0.
It goes without saying that elements satisfying the relationship of 40 account for 35% or more of the elements in the entire tire.

FIG. 3 shows a tread pattern showing another embodiment, in which the kerf 3 is not a straight line but a broken line.

FIG. 4 shows a tread pattern showing yet another embodiment, in which the width of the grooves 2 is not constant (it has branch grooves 5), and the kerf 3 is also bent at two places.

〔Effect of the invention〕

The present invention exhibits the following effects.

fal The vibrations caused by vehicle surges are quickly damped, providing excellent comfort.

(Since it is a bl rep pattern, it generates less noise.

[Brief explanation of drawings]

FIG. 1 is a tread pattern diagram showing the first embodiment of the present invention, FIG. 2 is a partially enlarged view of FIG. 1, FIG. 3 is a trend pattern diagram showing the second embodiment, and FIG. 4 is a tread pattern diagram showing the second embodiment. FIG. 5 is a graph showing the damping state of longitudinal vibration, FIG. 6 is a graph showing the relationship between slip rigidity and damping ratio, FIG. 7 is a graph showing slip rigidity, and FIG. 8 is a graph showing the relationship between slip rigidity and damping ratio.
The figure is an explanatory diagram showing the deformation state of the trend rubber, Fig. 9 is an explanatory diagram of the tread pattern, Fig. 10 is an explanatory diagram of the element, Fig. 11 is an explanatory diagram showing the kerf angle, and Fig. 12 is an explanatory diagram of the trend pattern and damping. It is a graph showing the relationship between ratios. ■...rib, 2...groove, 3...calf, 4...
Eleme Agent Patent Attorney Shin Ogawa - Patent Attorney Ken Noguchi Teru Patent Attorney Kazuhiko Saishita Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 81A

Claims (1)

[Claims] 1. In a pneumatic radial tire having grooves continuously carved in the circumferential direction of the tire and ribs formed by extending the grooves on the trend surface, the ribs are formed in the tire transverse direction. A plurality of kerfs are cut at an angle of 45° or less to form an element, and the average pitch P of each kerf over the entire circumference of the tire is smaller than the average projected length of the kerf in the tire transverse direction. A pneumatic tire characterized by: 2. The pneumatic tire according to claim 1, wherein the elements satisfying the following formula account for 35% or more of the elements of the entire tire. 0.05≦Pi2/ (n XLiX D Xcos
θ)≦0.40 However, Pi: Pitch of the kerf in the tire circumferential direction. Li...Projected length of the kerf in the tire transverse direction. θ...Angle of the kerf in the tire transverse direction. n...Number of ribs. D...Depth of kerf.