JPS6137122B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a radial tire for heavy vehicles such as trucks and buses, and particularly to a radial tire useful for steering wheels. The purpose is to advantageously suppress the

In general, radial tires are becoming more popular because they have significantly superior characteristics in terms of handling stability, wear resistance, and many other aspects compared to conventional bias tires. Vehicle compatibility with the road surface is important as long, long journeys are becoming more and more commonplace.

However, due to frequent and severe use under the above conditions, ruts are formed on the road surface with a width corresponding to the traversal of vehicles, and at the end of the road surface repair and renovation cycle, deep gouges often reach 2 cm, and sometimes even 3 cm. This growth is not uncommon even on motorways, which are representative of well-paved roads, and is mainly due to repeated subsidence and wear of the road surface due to the weight of heavily loaded vehicles, and due to congested traffic conditions. Since it is difficult to shorten the repair cycle under such conditions, the weaknesses of radial tires, which were originally developed primarily for use on well-paved roads, have been exposed.

This is because while driving along such ruts, sometimes when the tire rides on the edge of the rut, or when changing lanes to escape from the rut, the tire is hit from the road side. Disturbances can cause overly sensitive reactions that place a significant burden on the steering and steering operations of large vehicles, especially trucks and buses, causing a phenomenon called wandering, which is commonly referred to as the steering wheel being taken away. be.

In contrast, this did not pose a particular problem for radial tires for passenger cars due to their relatively low internal pressure, and for bias tires for heavy vehicles due to their carcass characteristics. Wandering, which can be called a peculiar phenomenon that appears especially in radial tires for heavy vehicles, which have a tread reinforced by a belt layer with extremely high rigidity and is used under particularly high internal pressure, is a phenomenon that can be called a wandering phenomenon. Combined with the fact that the above behavior is almost unrecognizable, it not only creates a vague sense of anxiety for truck and bus drivers, but also causes the operation of these types of vehicles to take long, long hours as mentioned earlier. Because of this, it actually becomes a factor that increases fatigue and cannot be ignored.

That is, the inventors found that this problem did not arise with heavy vehicle tires equipped with conventional bias structure carcass. Regarding the above-mentioned wandering phenomenon peculiar to heavy vehicle tires with radial carcass-belt reinforcement, we conducted a study comparing both types of tires, and after much trial and error, we found that tires with carcass structure or tread reinforcement structure We have reached the knowledge that camber thrust has a direct effect on wandering.

Regarding this camber thrust, the normal internal pressure of the tire tread (7.25Kg/cm ² ) and the normal load (2425
As a result of conducting a detailed study of the shape of the ground contact (so-called foot print) under 11.00 kg, it was revealed that the shape of the footprint (so-called foot print) occurs in completely opposite directions between the two types of tires.

Also, the more this camber thrust acts in the direction of the bias tire, that is, in the direction of the camber angle when the tire is given a camber angle, the more effective it is in suppressing wandering. It became clear.

Here, there are two causes of camber thrust: a structural factor due to the breaker or belt layer, and a pattern factor on the tread, and the camber thrust acts in opposite directions between the radial structure and bias structure mentioned above. This is thought to be caused by the difference in the overall effects of structural factors and pattern factors between the radial structure and the bias structure. Therefore, in order to cause camber thrust to act in the direction of the bias tire in a radial structure, it is only necessary to consider the pattern factor among the aforementioned camber thrust generation factors.

Therefore, the inventor focused on the above-mentioned pattern factors and utilized them to control camber thrust.
We repeatedly investigated and experimented with specific means to generate camber thrust in the same direction that occurs in bias tires.

Here, the area that can be treated as the above pattern factor is the area that is hardly affected by the tread reinforcement by the belt layer and is exclusively subjected to inward shearing force based on the squeezing action of the rubber itself (hereinafter referred to as crushing), In other words, for normal square shoulder radial tires,
Approximately the tread width from the shoulder to the center of the tread
25%, especially within the 15% range.

Now, Fig. 1 and Fig. 2 show the contact status of tires with and without camber angle, but Fig. 3 shows the crushing of the same part of the tire toward the perpendicular bisector of the tread side area. If the net changes α and β obtained by calculating the difference between α and β are made larger with respect to the former α, it is possible to generate an outward shearing force as a pattern factor, and in this way, it is possible to generate an outward shearing force that is It is possible to generate camber thrust in the same direction as .

Here, as shown in Fig. 4, at least one sub-groove 1 is provided which is inclined at an angle θ with respect to a perpendicular line V drawn to the axis of rotation of the tire and opens obliquely toward the center of the tread. It was discovered that the above expected results of crushing inverse emphasis could be obtained. The arrows in the figure indicate the direction of the shearing force based on the above-mentioned crushing, 2 is a main groove, at least one of which is disposed in the main tread region 3, and 4 indicates the tread side region. The main groove 2 may be formed in accordance with the usual practice, and should be at least 3% or more of the tread width, preferably about 3 to 6%.

The width of the minor groove 1 is much narrower than the width of the main groove 2, and may be about 50% or less, but it should be at least 5%, and preferably 20 to 40%. be. It has also been confirmed that the above requirements are met when the groove depth is equal to or less than that of the main groove 2 and 20% or more as measured in the direction of the perpendicular line V.

Incidentally, if the sub-grooves 1' as shown in FIG. 5 are provided aligned in the direction of the perpendicular line V, the crushing that occurs facing the perpendicular bisector of the rib divided by the sub-grooves 1' cancels each other out.

Here, the inclination θ of the minor groove 1 is 5° to 60° depending on the type and size of the tire, especially normally,
A range of 15° to 45° is advantageously suitable.

Although it is desirable that the sub-groove 1 be continuous in the circumferential direction of the tire, it is acceptable even if it is discontinuous if the discontinuity is very small, or even if it is divided by a lateral groove, which is sometimes required. , and at least one of these sub-grooves 1 extends straight along the circumferential direction of the tire, including when two or more sub-grooves are provided as shown in Fig. 4, or has an appropriate constant or variable pitch. It may extend in a zigzag pattern.

Now, FIG. 6 shows an embodiment of the tire according to the present invention in a cross section of the main part on the left half, FIG. 7 shows the development plane of the part, and FIG. A cross section of the part and a development plane of the part are shown in FIG. 9, respectively.

Regarding the numbers in the figure, the parts that are the same as those already mentioned in Figure 4 have been written in a uniform manner.

In each figure, 5 is a carcass made of radially arranged cords, and 6 is a strong material. direction, the same hereafter), 70°, upper left 70°, and upper left 70°
The belt layer 6 is a rigid annular belt layer superimposed at a cord angle of .degree., and the main tread region 3 is rigidly reinforced.

These test tires are 10.00R20 size,
The camber thrust was compared at a normal internal pressure of 7.25Kg/cm ² and a normal load of 2425Kg, and the results shown in Figure 10 were obtained.

In addition, in the embodiment of the present invention shown in FIG.
The dimensions are a groove width of 3 mm and a groove depth of 14 mm measured diagonally, and a groove width of 11 mm located at the end of the tread main area 3.
Two grooves are provided, one separated by 10 mm from the edge of the main groove 2 with a depth of 14 mm, and one in which the edge of the diagonal opening is located 20 mm away from the edge of the opening toward the shoulder side. Ta.

Now, in Figure 10, the horizontal axis is the camber angle, and the vertical axis is the camber thrust.
The changes in camber thrust associated with increases and decreases in camber angle are shown for both of the test tires above, but in contrast to the control tire shown by the solid line, which has an upward slope characteristic extending from the origin to the first and third quadrants. The tire of the present invention exhibits a rightward downward characteristic extending between the second and fourth quadrants, as shown by the dotted line, and this rightward downward characteristic is similar to the characteristic of a conventional bias carcass heavy vehicle tire.

Incidentally, in the case where the upright sub-groove 1' is provided as shown in Fig. 5, the above-mentioned upward slope characteristic as shown in Fig. 11 simply reduces the slope while maintaining the same tendency. Therefore, the effects of this invention cannot be expected at all.

Next, when we conducted an actual vehicle test on each test tire, we found that the comparison tire shown in Figure 5 only had an index of 90, where the control tire's steering force was 100, whereas the tire of this invention 68, and there was a noticeable improvement in terms of feel.

In this way, according to the present invention, it has been possible to particularly advantageously solve the problem of wandering, which is a problem unique to radial tires for heavy vehicles and which has hindered the further expansion of their uses. be.

[Brief explanation of the drawing]

Fig. 1 and Fig. 2 are explanatory diagrams of the ground contact situation of square shoulder tires, Fig. 3 is an explanatory diagram of crushing, Fig. 4 is an explanatory diagram of the configuration of this invention, and Fig. 5 is an explanatory diagram of a comparative tire. 6 and 7 are a cutaway end view and a developed plan view of a main part of an embodiment of the present invention, and FIGS. 8 and 9 are a similar cutaway end view and a developed plan view of the control. FIG. 10 is a comparison graph of camber thrust, and FIG. 11 is a graph showing a slight camber thrust reduction effect for the comparative tires. 1...Minor groove, 2...Main groove, 3...Tread main area, 4...Tread side area, 5...Carcass, 6...
...belt layer.

Claims (1)

[Scope of Claims] 1. A tread that is rigidly reinforced by a rigid annular belt layer in which at least two layers of cords made of a rigid material are aligned and arranged and overlapped with each other at a slight intersecting angle of the cords; In a radial tire having at least one main groove with a relatively wide width, at least one of the tread side areas extending from the tread edge to about 25% of the tread width toward the center of the tread, lowered to the axis of rotation of the tire. It has at least one minor groove that is inclined with respect to the perpendicular line and opens obliquely toward the center of the tread, and this minor groove has a groove width of about 50% or less of the main groove, and extends in the direction of the perpendicular line. A radial tire for heavy vehicles characterized by a groove depth that is equal to or less than the same when measured. 2. The radial tire for a heavy vehicle according to claim 1, wherein the sub-groove extends linearly along the circumferential direction of the tire. 3. The radial tire for a heavy vehicle according to claim 1, wherein the minor groove extends in a zigzag shape along the circumferential direction of the tire. 4. The radial tire for a heavy vehicle as claimed in claim 1, 2 or 3, wherein the sub-groove has an inclination of 5 to 60 degrees, particularly 15 to 45 degrees, with respect to a perpendicular to the rotational axis of the tire. 5 The groove width of the above-mentioned minor groove is 5 to 50 mm of the groove width of the above-mentioned main groove.
%, especially from 20 to 40%,
The radial tire for heavy vehicles described in 2 or 3. 6 The depth of the above-mentioned minor groove is 20 to 100 times the depth of the above-mentioned main groove.
%. 7. The radial tire for a heavy vehicle as claimed in claim 1, wherein at least a portion of the minor groove passes through a position spaced apart from the tread edge by 15% of the tread width.