JPH0123323B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tire with reduced rolling resistance.

The rolling resistance of tires has been attracting a lot of attention in recent years because it has a direct effect on the fuel consumption of automobiles.

Measures that have been taken in the past to reduce the rolling resistance of tires have been based on the fact that the main cause of rolling resistance is the internal loss of rubber due to deflection or deformation during tire rotation. The quantity is also particularly large,
By using rubber with low energy loss and by lowering the flange height of the rim used, when the tire is assembled with a rim, the deformation area of the tire sidewall is expanded, giving flexibility, and the height is increased accordingly. It has previously been proposed to further reduce the load on the tire rubber itself by applying internal pressure.

However, regarding the former, there is a nearly positive correlation between the energy loss characteristics of rubber and the coefficient of friction, so if a rubber with low energy loss is used for the tread, the skid resistance of the tire, especially the wet skid resistance, will both decrease. This poses a safety problem. In the latter case, not only is there the disadvantage of requiring a rim with a special shape for the rim flange part, but also the ride quality tends to be impaired due to poor vibration damping due to the high filling internal pressure. It was hot.

According to the inventors' research, in addition to the internal loss in the rubber substance such as the tread, the internal loss due to the repeated bending deformation of the belt centered on the tire's equator, which occurs every time the tire tread makes contact with the ground, is the cause of tire damage. The influence on the rolling resistance of belts is significant, and the above internal losses can be significantly reduced by creating a specific relationship between the shape of the belt and the shape of the tread.
We have found that this is highly effective in reducing tire rolling resistance.

In this invention, the sidewalls extending from both ends of the crown located in the center are connected in a toroidal manner,
The inner end of the sidewall in the radial direction is reinforced with a carcass between one of the reinforced beads through the crown and the other side of the bead, and the equator of the tire is disposed between the tread occupying the road surface-engaging part of the crown and the carcass. A belt consisting of a plurality of cord layers arranged at a small angle of 10° to 25° to the plane and stacked one on top of the other in a direction in which the cords intersect is placed across the tread, and the tread and the belt are arranged on the cross section of the tire. In a tire having an outwardly convex curved profile under normal internal pressure, the ratio of the crown R defining the cross-sectional profile of the tread to the tire radius is in the range of 0.5 to 4.0, and the surface of the tread on the equatorial plane and the center of the belt's thickness are points A and B, respectively, and the surface of the tread and the center of the belt's thickness on the plane ee passing through the grounding end of the tread and parallel to the equator plane are points C and D, respectively.
As, the shortest distance k of the above point D with respect to a line parallel to the tire rotation axis passing through the above point B is 0.2≦k with respect to the shortest distance l of the above point C with respect to a line parallel to the tire rotation axis passing through the above point A This is a pneumatic tire with reduced rolling resistance characterized by a belt arrangement with a relative shape of /l≦0.8.

Before explaining the specific development of the present invention, the shape of the tread and belt in a conventional tire will be reviewed with reference to FIG.

Fig. 1 is a cross-sectional view hypothetically showing the internal pressure filling of the left half of a conventional tire.In the tire 1, sidewalls 3 extend radially inward from both ends of a crown 2 located in the center and are connected in a toroidal manner. . The radially inner end of this sidewall 3 is reinforced with a carcass 5 from one side of the reinforced bead 4 to the other side of the bead 4 through the crown 2,
The structure is such that a belt 7 is arranged across the entire width of the tread 2 between the tread 6 and the carcass 5 which occupy the road surface engaging part of the crown 2 for reinforcement.

In the figure, point C indicates the tread contact side end, which is the side end at which the tread 6 contacts the road surface and limits the road surface engagement area during normal, ie, straight-line running under normal internal pressure and normal load. The buttress section extending from this point C to the groove edge of the shoulder groove 8 functions as an auxiliary tread 9 that contacts the ground when a lateral force is applied to the tire, such as when the tire runs on a curve, but in the following explanation, the tread is not a point. In particular, it refers to a section between a pair of planes ee (one of the planes is omitted) parallel to the tire's equatorial plane oo passing through C.

In the case of conventional tires, the tread gauge (thickness of the tread rubber) is uniform throughout the tire, or
- Since the belt is slightly increased from the o position toward the plane ee, the belt 7 should be placed parallel to the cross-sectional contour 10 of the tread 6, or the belt 7 should be stronger than the curvature of the contour 10. It was arranged with a hint of darkness. Here, the cross-sectional profile 10 of the tread 6 is determined by a so-called crown R, and the ratio of this crown R to the tire radius is usually in the range of 0.5 to 4.0.

In the case of a tire in which the tread 6 has a shape that bulges outward in a convex manner and the belt 7 is arranged parallel to the cross-sectional contour 10 of the tread 6 as shown in FIG. 1, when a ground reaction force is applied while traveling straight, The entire area of the tread 6 moves to a flat position where it coincides with the road surface. In other words, due to the deformation of the tire due to the load, the parallel line GG to the tire rotation axis passing through point A on the tread surface position on the equatorial plane moves to a position passing through point C, and at that time, a line GG is generated at tread 6. The displacement is between point C and line G
- G is given by the shortest distance l. In this case, regarding the belt 7, it passes through a point D, the center of the thickness of the belt 7 on the plane ee corresponding to the point C, and a point B, the center of the thickness of the belt 7 on the equatorial plane oo. Parallel line I-I to the tire rotation axis
move until they match, and the belt 7 also becomes flat. However, the displacement k represented by the shortest distance between the point D and the line II is considered to be equal to the displacement l at the point C position. Note that point D here indicates a so-called fold structure in which, for example, the cord layer 7 ₁ constituting the belt 7 is folded back toward the crown center at both side edges, or further wraps the cord layer 7 ₂ , or other folding structures. When the belt 7 includes an auxiliary cord similar to the above, it is defined as the center of thickness of the main belt excluding it.
Now, Figure 2 shows the ratio of distance k to distance l above for 185/65SR14 size passenger car tires k/l.
1 is a graph showing the relationship between the value of the ratio and the rolling resistance of the tire by making trial tires with various values of .

The specific structure of this tire is to use a carcass 5 made of two overlapping rubberized plies of 1500d/2 polyester cord in a radial arrangement, and for the belt 7, a steel cord with a twisted structure of 1 x 5 x 0.25 is used. Two rubberized layers are arranged at an angle of 18.5 degrees with respect to the equatorial plane of the tire, and are stacked one on top of the other so that the cords intersect with each other between the layers.

In measuring the rolling resistance, the tire internal pressure and load were set to 1.7 Kg/cm ² and 385 Kg, respectively, and the measurement was carried out on a steel drum with a diameter of 1.7 m and a smooth surface.

For convenience, the graph shown in Figure 2 is a normal speed of 50.
The reciprocal of the rolling resistance measured at Km/h is k/l.
The tire performance value at =0.5 is expressed as an index of 100. Therefore, the larger the index of rolling resistance shown on the vertical axis, the better.

FIGS. 3a, b, and c are cross-sectional views schematically showing how the belt 7 moves depending on the value of k/l, corresponding to the graph of FIG. 2.

In the case of Fig. 3-a, the belt 7 shows its shape at a position where it is not affected by load deformation during internal pressure filling or driving, and when the tire is subjected to load deformation (especially directly under the load), the belt 7 shows its shape at a position corresponding to the tread end. It is considered that point D, which is the center of the thickness of belt 7, moves to point D', and at this time, belt 7 deforms as shown by a broken line 7'. A plane parallel to the tire's equatorial plane e-
The distance between points D and D' on e is the tread end C
is equal to the transition distance l (Fig. 1), but in the example shown in Fig. 3-a, the shortest distance between point D and the parallel line II to the rotation axis passing through point B at the center of the belt thickness on the equatorial plane The distance, that is, the distance k ₁ between the two on the plane ee is the distance l
In contrast, this corresponds to the case where k/l is less than 0.5 on the curve in FIG. 2, which is smaller than the distance between line II and point D'.

Next, Fig. 3-b shows the state of the belt 7 when k2/l is 0.5, and it can be seen that in this case, the belt 7 undergoes symmetrical deformation about the line II when the tire runs.

Also, Figure 3-c is a diagram showing the situation when the belt 7 is provided so as to be deformed in an area opposite to that shown in Figure 3-a, and the belt arrangement of a conventional tire (Figure 1) is an example of this. corresponds to As shown in Figure 2, the rolling resistance of the tire exhibits a tendency to increase with distance from k/l = 0.5 to both sides, indicating that the range of k/l = 0.2 to 0.8 is good, and It is shown that it is even better in the range of 0.35 to 0.65. It is also shown that the conventional product (FIG. 1) where k/l=1 is the worst.

FIG. 4 shows an example in which an actual tire has the belt shape shown in FIG. 3-b in which k/l=0.5 in the left half sectional view of the tire according to the present invention. Here, the ratio of the crown R to the tire radius, which defines the cross-sectional profile 10 of the tread 6, is 0.5 to 4.0.
It is necessary to keep it within the range of 0.6 to 3.0.

In this example, the belt 7 consists of two cord layers 7-1 and 7-2 in which metal cords are arranged at an angle of 10° to 25° with respect to the equatorial plane, and these cords intersect with each other between the layers. In addition to the example shown in this figure, it is also possible to use a wider cord layer as the cord layer 7-1, or to fold an even wider one by wrapping both ends of the cord layer 7-2, or vice versa. In this case, the cord layer 7-2 is made wider and its both ends are folded back toward the tread 10, and the cord layers 7-1 and 7-2 are made of a combination of a metal cord layer and an aromatic polyamide fiber cord layer. Use especially code layer 7-1 or 7
Even when the latter is used for one of the above-mentioned belts, any other known belt lamination structure can be applied to the present invention, including folding or folding back as described above.

In addition, it is of course possible for the width of the belt 7 to extend beyond the plane ee at the end to the vicinity of the shoulder groove 8. What is noteworthy here is that the width of the belt 7 can be expanded beyond the plane ee to the vicinity of the shoulder groove 8. Height H/
In tires with a small W, the belt width is widened, so the loss due to the deformation of the belt layer accounts for a large proportion of the rolling resistance.Therefore, it is particularly important to apply this invention to flat tires with a H/W of 0.3 to 0.8. Effective.

The carcass 5 may have one (example shown in FIG. 4) or two or more fiber cord layers arranged in a radial arrangement in other known structures.

As described above, according to the present invention, it is possible to advantageously reduce the rolling resistance of a pneumatic tire by cleverly avoiding the internal energy loss resulting from its deformation behavior simply by proper belt arrangement. Can be done.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a conventional radial tire, Figure 2 is a graph showing the dependence of rolling resistance on belt arrangement, and Figures 3 a, b, and c are the behavior of bending deformation that occurs in the belt contact area with the tire. FIG. 4 is a sectional view of a radial tire according to the present invention. 1...tire, 2...crown, 3...sidewall, 4...bead, 5...carcass, 6...tread,
7...Belt, 10...Tread cross-sectional contour.

Claims (1)

[Scope of Claims] 1 Sidewalls extending from both ends of the crown located in the center are connected in a toroidal manner, and the inner end of the sidewall in the radial direction is reinforced from one side of the bead through the crown to the other side of the bead. A plurality of cord layers are reinforced with the carcass and arranged at a small angle of 10° to 25° with respect to the tire's equatorial plane between the tread and the carcass, which occupy the road surface-engaging portion of the crown, with the cords intersecting each other. In a tire in which overlapping belts are arranged across the tread, and the tread and the belt have an outwardly convex curved profile on their cross section, the ratio of the crown R defining the cross-sectional profile of the tread to the tire radius is 0.5. ~4.0, the surface of the tread on the equatorial plane and the center of the thickness of the belt are points A and B, respectively, and the surface of the tread and the center of the thickness of the belt on the equatorial plane are taken as points A and B, respectively, and the surface of the tread and the center of the thickness of the belt on the equatorial plane are taken as points A and B, respectively, and the surface of the tread and the center of the thickness of the belt on the equatorial plane are taken as points A and B, respectively. Center of belt thickness at point C
and D, the shortest distance k of the above point D with respect to a line parallel to the tire rotation axis passing through the above point B is 0.2 with respect to the shortest distance l of the above point C with respect to a line parallel to the tire rotation axis passing through the above point A. A pneumatic tire with reduced rolling resistance characterized by a belt arrangement with a relative shape of ≦k/l≦0.8. 2. A tire according to claim 1, wherein the carcass is at least one rubberized layer with a radial arrangement of fiber cords. 3. The tire according to claim 1 or 2, wherein the belt includes one rubberized layer in which metal cords are arranged obliquely with respect to the equatorial plane of the tire. 4. The tire according to claim 3, wherein the belt consists of two metal cord rubberized layers. 5. The tire according to claim 3, wherein the belt includes, in addition to the metal cord rubberized layer, an aromatic polyamide fiber cord rubberized layer whose both ends are folded toward the equatorial plane of the tire. 6 The ratio of distance k to distance l is 0.35≦k/l≦
Claims 1 and 2 falling within the range of 0.65
The tire according to any one of Items 3, 4, and 5.