JP7494637B2 - Airless tires - Google Patents

Description

The present invention relates to an airless tire that can support a load using its own structure without using high-pressure air.

Various airless tires have been known in the past in which the tread ring and hub are connected by spokes. For example, the following Patent Document 1 proposes an airless tire in which the compression stiffness of the outer ends of the spokes is greater than the compression stiffness of the inner ends of the spokes.

JP 2017-081199 A

The airless tire in Patent Document 1 attempts to improve durability by increasing the thickness of the spokes in the circumferential direction of the tire, but there is a problem in that increasing the thickness of the spokes reduces ride comfort, and there has been a demand for further improvement in terms of achieving both ride comfort and durability.

The present invention was devised in consideration of the above-mentioned circumstances, and its main objective is to provide an airless tire that can achieve both high levels of ride comfort and durability.

The present invention is an airless tire comprising a tread ring having a contact surface, a hub disposed radially inside the tread ring and fixed to an axle, and spokes for connecting the tread ring and the hub, the spokes including a plurality of plate-shaped spoke plate portions whose width in the tire axial direction is greater than the tire circumferential thickness, each of the spoke plate portions having a first edge portion that is an edge on the hub side, a second edge portion that is an edge on the tread ring side, and a third edge portion and a fourth edge portion that are a pair of edges connecting the first edge portion and the second edge portion, when viewed in the spoke thickness direction, the first edge portion extends at an obtuse angle to the third edge portion and an acute angle to the fourth edge portion, and the thickness of the first edge portion gradually decreases from the fourth edge portion to the third edge portion.

In the airless tire of the present invention, it is preferable that the second edge portion extends at an acute angle to the third edge portion and at an obtuse angle to the fourth edge portion, and that the thickness of the second edge portion gradually decreases from the third edge portion to the fourth edge portion.

In the airless tire of the present invention, it is preferable that the thickness of the third edge portion gradually decreases from the second edge portion to the first edge portion.

In the airless tire of the present invention, it is preferable that the thickness of the fourth edge portion gradually decreases from the first edge portion to the second edge portion.

In the airless tire of the present invention, it is desirable that the thickness of the first edge portion on the third edge portion side is 1.5 mm or more.

In the airless tire of the present invention, it is desirable that the thickness of the first edge portion on the fourth edge portion side is two to three times the thickness of the first edge portion on the third edge portion side.

In the airless tire of the present invention, it is desirable that the thickness of the second edge portion on the fourth edge portion side is equal to the thickness of the first edge portion on the third edge portion side.

In the airless tire of the present invention, each of the spoke plate portions includes, when viewed in the spoke width direction, a first curved portion that curves to protrude in one direction in the tire circumferential direction on the first edge portion side, and a second curved portion that curves to protrude in the other direction in the tire circumferential direction on the second edge portion side, and it is preferable that the first curved portion and the second curved portion are each formed from the third edge portion to the fourth edge portion.

In the airless tire of the present invention, it is desirable that each of the spoke plate portions includes a connection portion that connects the first curved portion and the second curved portion, and that the distance in the tire radial direction from the first edge portion to the connection portion is equal to the distance in the tire radial direction from the second edge portion to the connection portion.

In the airless tire of the present invention, the spoke includes a plurality of plate-shaped spoke plate portions whose axial width is greater than their circumferential thickness, and each of the spoke plate portions has, as viewed in the spoke thickness direction, a first edge portion that is the edge on the hub side, a second edge portion that is the edge on the tread ring side, and a third edge portion and a fourth edge portion that are a pair of edges connecting the first edge portion and the second edge portion. Such spoke plate portions can absorb impacts when touching the ground while also providing high rigidity, thereby achieving both ride comfort and durability performance of the airless tire.

In the airless tire of the present invention, the first edge portion extends at an obtuse angle to the third edge portion and at an acute angle to the fourth edge portion, and the thickness of the first edge portion gradually decreases from the fourth edge portion to the third edge portion.

This type of spoke plate portion has a small thickness on the third edge side, which is the center in the tire axial direction where stress at the first edge tends to concentrate, and is therefore easily deformed, thereby alleviating distortion at the center in the tire axial direction of the first edge portion and improving the durability of the airless tire. In addition, because the thickness of the first edge portion of this spoke plate portion is gradually reduced, local changes in stress can be suppressed and the ride comfort of the airless tire can be improved. For this reason, the airless tire of the present invention can achieve both ride comfort and durability at a high level.

1 is a perspective view showing an embodiment of an airless tire of the present invention. FIG. FIG. 2 is a side view of the airless tire of FIG. 1 . FIG. 4 is an end view of the spoke plate portion as viewed from the thickness direction of the spoke. FIG. FIG. 4 is an end view of the spoke plate portion as viewed from a direction A in FIG. 3 . FIG. 4 is an end view of the spoke plate portion as viewed from the direction B in FIG. 3 . 3 is a cross-sectional view taken along line CC of FIG. 2.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
Fig. 1 is a perspective view showing an airless tire 1 of this embodiment, and Fig. 2 is a side view of the airless tire 1. As shown in Fig. 1 and Fig. 2, the airless tire 1 of this embodiment includes a tread ring 2 having a ground contact surface 2a, a hub 3 disposed on the inner side of the tread ring 2 in the tire radial direction, and spokes 4 for connecting the tread ring 2 and the hub 3.

The hub 3 preferably includes a fixing portion 3a that is fixed to the vehicle axle (not shown). Such an airless tire 1 can support the load acting on the tread ring 2 by the hub 3 and spokes 4 without using high-pressure air. Therefore, the airless tire 1 of this embodiment is unlikely to get punctured.

The spokes 4 of this embodiment include plate-shaped spoke plate portions 5 whose axial width is greater than their circumferential thickness. When a load acts on the tread ring 2, such spokes 4 are able to support the load by applying a tensile force to the spoke plate portions 5 located above the hub 3 and a compressive force to the spoke plate portions 5 located below the hub 3.

Figure 3 is an end view of the spoke plate portion 5 as viewed from the spoke thickness direction. As shown in Figure 3, each of the spoke plate portions 5 of this embodiment includes a first edge portion 6, which is the edge on the hub 3 side, and a second edge portion 7, which is the edge on the tread ring 2 side, as viewed from the spoke thickness direction. It is preferable that the spoke plate portion 5 further includes a third edge portion 8 and a fourth edge portion 9, which are a pair of edges connecting the first edge portion 6 and the second edge portion 7. Such a spoke plate portion 5 is suitable for achieving both shock absorption properties and high rigidity when touching the ground, and can achieve both ride comfort performance and durability performance of the airless tire 1.

In this embodiment, the first edge 6 extends at an obtuse angle with respect to the third edge 8 and at an acute angle with respect to the fourth edge 9. That is, the first edge 6 is an edge that has an obtuse angle θ1 with respect to the third edge 8 and an acute angle θ2 with respect to the fourth edge 9.

Figure 4 is a perspective view of the spoke plate portion 5. As shown in Figures 3 and 4, the thickness t1 of the first edge portion 6 in this embodiment gradually decreases from the fourth edge portion 9 to the third edge portion 8. In such a spoke plate portion 5, the thickness t2 on the third edge portion 8 side, which is the center side in the tire axial direction where stress of the first edge portion 6 is likely to concentrate, is small and easily deformed, so that the distortion on the center side in the tire axial direction of the first edge portion 6 can be alleviated, and the durability performance of the airless tire 1 can be improved.

In addition, since the thickness t1 of the first edge portion 6 of the spoke plate portion 5 is gradually reduced, local changes in stress can be suppressed and the ride comfort performance of the airless tire 1 can be improved. Therefore, the airless tire 1 of this embodiment can achieve both ride comfort performance and durability performance at a high level.

The thickness t2 of the first edge 6 on the third edge 8 side is preferably 1.5 mm or more. By having the thickness t2 of 1.5 mm or more, the necessary rigidity of the spoke 4 can be maintained and premature breakage can be suppressed. From this perspective, the thickness t2 of the first edge 6 on the third edge 8 side is more preferably 2.0 mm or more, and even more preferably 2.5 mm or more.

The thickness t2 of the first edge 6 on the third edge 8 side is preferably 4.0 mm or less. By having the thickness t2 of 4.0 mm or less, the distortion of the first edge 6 on the center side in the tire axial direction can be alleviated, and the durability performance of the airless tire 1 can be improved. From this perspective, the thickness t2 of the first edge 6 on the third edge 8 side is more preferably 3.5 mm or less, and even more preferably 3.0 mm or less.

The thickness t3 of the first edge 6 on the fourth edge 9 side is preferably 2 to 3 times the thickness t2 of the first edge 6 on the third edge 8 side. By making the thickness t3 at least twice the thickness t2, the strain at the center and end sides in the axial direction of the tire can be distributed in a balanced manner. By making the thickness t3 no more than three times the thickness t2, the occurrence of excessive strain at the end sides in the axial direction of the tire can be suppressed.

As shown in FIG. 1, in a more preferred embodiment, the tread ring 2 is formed in a cylindrical shape from an elastic body such as rubber. It is desirable that the tread ring 2 has a contact surface 2a formed thereon, which contacts the road surface during running. The contact surface 2a is not limited to this embodiment, and may be, for example, block-shaped, or may have a number of recesses formed therein.

As shown in Figs. 1 and 2, the hub 3 is formed of a non-elastic material such as metal. The hub 3 preferably has a disk-shaped fixing portion 3a that is fixed to the axle, and a cylindrical portion 3b that is connected to the spokes 4. The fixing portion 3a of the hub 3 has, for example, a plurality of fixing holes formed therein. The fixing portion 3a of the hub 3 is not limited to this form, and may be, for example, one that can be attached to a dedicated axle with a single touch.

The spokes 4 are formed of an elastic resin such as a thermosetting resin. In this embodiment, the spokes 4 include a plurality of spoke plate portions 5, an inner cylindrical portion 11 connected to the hub 3, and an outer cylindrical portion 12 connected to the tread ring 2. Such spokes 4 can be firmly connected to the hub 3 and the tread ring 2, and the durability of the airless tire 1 can be improved. Note that the spokes 4 may be configured such that, for example, the inner cylindrical portion 11 and the outer cylindrical portion 12 are omitted, and the spoke plate portions 5 are directly connected to the tread ring 2 and the hub 3.

As shown in Figs. 1 and 3, the spoke plate portion 5 is formed integrally with the inner cylindrical portion 11 and the outer cylindrical portion 12 via the curved surface portion 5a, for example. If the inner cylindrical portion 11 and the outer cylindrical portion 12 are omitted, it is preferable that the spoke plate portion 5 is connected to the tread ring 2 and the hub 3 via the curved surface portion 5a. Such a curved surface portion 5a can reduce stress concentration and further improve the durability performance of the airless tire 1.

The spoke plate portions 5 are arranged, for example, at an incline with respect to the tire axial direction. The inclination angle of the spoke plate portions 5 with respect to the tire axial direction is preferably 2 to 10°. An inclination angle of 2° or more can improve the rigidity in the tire circumferential direction and improve the durability performance of the airless tire 1. An inclination angle of 10° or less can prevent the rigidity in the tire circumferential direction from becoming excessive and can improve the ride comfort performance of the airless tire 1.

As shown in FIG. 3, the second edge 7 of this embodiment extends at an acute angle relative to the third edge 8 and at an obtuse angle relative to the fourth edge 9. That is, the second edge 7 is an edge that has an acute angle θ3 relative to the third edge 8 and an obtuse angle θ4 relative to the first edge 6. Such a spoke plate portion 5 is suitable for achieving both shock absorption at the time of contact with the ground and high rigidity, and can achieve both ride comfort and durability performance of the airless tire 1.

The angle θ3 between the second edge 7 and the third edge 8 is preferably equal to the angle θ2 between the first edge 6 and the fourth edge 9. The angle θ4 between the second edge 7 and the fourth edge 9 is preferably equal to the angle θ1 between the first edge 6 and the third edge 8. Therefore, the spoke plate portion 5 has a substantially parallelogram shape when viewed from the spoke thickness direction.

As shown in FIG. 4, the thickness t4 of the second edge 7 in this embodiment gradually decreases from the third edge 8 to the fourth edge 9. In such a spoke plate portion 5, the thickness t5 on the fourth edge 9 side, which is the center side in the tire axial direction where stress of the second edge 7 is likely to concentrate, is small and easily deformed, so that the distortion on the center side in the tire axial direction of the second edge 7 can be alleviated, and the durability performance of the airless tire 1 can be improved.

In addition, since the thickness t4 of the first edge portion 6 of the spoke plate portion 5 is gradually reduced, local changes in stress can be suppressed and the ride comfort performance of the airless tire 1 can be improved. Therefore, the airless tire 1 of this embodiment can achieve both ride comfort performance and durability performance at a high level.

The thickness t5 of the second edge 7 on the fourth edge 9 side is preferably 1.5 mm or more. By having the thickness t5 of 1.5 mm or more, the necessary rigidity of the spoke 4 can be maintained and premature breakage can be suppressed. From this perspective, the thickness t5 of the second edge 7 on the fourth edge 9 side is more preferably 2.0 mm or more, and even more preferably 2.5 mm or more.

The thickness t5 of the second edge portion 7 on the fourth edge portion 9 side is preferably 4.0 mm or less. By making the thickness t5 4.0 mm or less, the distortion of the second edge portion 7 on the center side in the tire axial direction can be alleviated, and the durability performance of the airless tire 1 can be improved. From this perspective, the thickness t5 of the second edge portion 7 on the fourth edge portion 9 side is more preferably 3.5 mm or less, and even more preferably 3.0 mm or less.

The thickness t6 of the second edge 7 on the third edge 8 side is preferably 2 to 3 times the thickness t5 of the second edge 7 on the fourth edge 9 side. By making the thickness t6 at least twice the thickness t5, the strain at the center and end sides in the axial direction of the tire can be distributed in a balanced manner. By making the thickness t6 no more than three times the thickness t5, the occurrence of excessive strain at the end sides in the axial direction of the tire can be suppressed.

The thickness t5 of the second edge 7 on the fourth edge 9 side is equal to, for example, the thickness t2 of the first edge 6 on the third edge 8 side. The thickness t6 of the second edge 7 on the third edge 8 side is equal to, for example, the thickness t3 of the first edge 6 on the fourth edge 9 side. Such spoke plate portions 5 have good balance in the tire radial direction, and can improve the ride comfort performance of the airless tire 1.

Figure 5 is an end view of the spoke plate portion 5 as viewed from the direction A in Figure 3. As shown in Figures 4 and 5, the thickness t7 of the third edge portion 8 in this embodiment gradually decreases from the second edge portion 7 to the first edge portion 6. In such a spoke plate portion 5, the thickness t7 of the third edge portion 8 gradually decreases, thereby suppressing local changes in stress and improving the ride comfort performance of the airless tire 1.

Figure 6 is an end view of the spoke plate portion 5 as viewed from direction B in Figure 3. As shown in Figures 4 and 6, the thickness t8 of the fourth edge portion 9 in this embodiment gradually decreases from the first edge portion 6 to the second edge portion 7. In such a spoke plate portion 5, the thickness t8 of the fourth edge portion 9 gradually decreases, thereby suppressing local changes in stress and improving the ride comfort performance of the airless tire 1.

As shown in Figures 3 to 6, each of the spoke plate portions 5 of this embodiment includes a first curved portion 13 that is curved to protrude in one direction in the tire circumferential direction when viewed in the spoke width direction, and a second curved portion 14 that is curved to protrude in the other direction in the tire circumferential direction.

The first curved portion 13 is disposed, for example, on the first edge portion 6 side. The second curved portion 14 is disposed, for example, on the second edge portion 7 side. In this embodiment, the first curved portion 13 and the second curved portion 14 are each formed from the third edge portion 8 to the fourth edge portion 9. Such a spoke plate portion 5 can improve the ride comfort performance of the airless tire 1 by deforming the first curved portion 13 and the second curved portion 14.

In this embodiment, the first curved portion 13 and the second curved portion 14 each have approximately the same amplitude from the third edge portion 8 to the fourth edge portion 9. The amplitude of each of the first curved portion 13 and the second curved portion 14 is preferably 2 to 12 mm.

By making the amplitude of the first curved portion 13 and the second curved portion 14 2 mm or more, shocks at the time of contact with the ground can be reliably absorbed, and the ride comfort performance of the airless tire 1 can be improved. From this perspective, the amplitude of the first curved portion 13 and the second curved portion 14 is more preferably 3 mm or more, and even more preferably 5 mm or more.

By setting the amplitude of the first curved portion 13 and the second curved portion 14 to 12 mm or less, it is possible to suppress a decrease in rigidity and improve the durability performance of the airless tire 1. From this perspective, the amplitude of the first curved portion 13 and the second curved portion 14 is more preferably 10 mm or less, and even more preferably 8 mm or less.

Each of the spoke plate portions 5 in this embodiment includes a connection portion 15 that connects the first curved portion 13 and the second curved portion 14. The connection portion 15 extends linearly in the spoke width direction, for example, from the third edge portion 8 to the fourth edge portion 9. Such a connection portion 15 helps to reduce distortion between the first curved portion 13 and the second curved portion 14, and achieve both ride comfort and durability performance of the airless tire 1.

It is desirable that the distance L1 in the tire radial direction from the first edge portion 6 to the connection portion 15 be equal to the distance L2 in the tire radial direction from the second edge portion 7 to the connection portion 15. Such a spoke plate portion 5 has a good balance in the tire radial direction, and can improve the ride comfort performance of the airless tire 1. Note that the distance L1 and the distance L2 may be different from each other, for example.

Figure 7 is a cross-sectional view taken along line CC in Figure 2. As shown in Figures 1 and 7, the spoke plate portion 5 of this embodiment includes a first spoke plate portion 5A that is inclined to one side in the tire axial direction, and a second spoke plate portion 5B that is inclined to the opposite side to the first spoke plate portion 5A. Such a spoke plate portion 5 has a good rigidity balance in the tire axial direction, and can achieve both ride comfort and durability performance for the airless tire 1.

The first spoke plate portions 5A and the second spoke plate portions 5B are desirably arranged alternately in the tire circumferential direction. When the first spoke plate portion 5A and the second spoke plate portion 5B form one pair, preferably 20 to 30 pairs of spoke plate portions 5 are arranged in the tire circumferential direction. Such spoke plate portions 5 have a good balance of rigidity in the tire circumferential direction, and can achieve both ride comfort and durability performance of the airless tire 1.

The above describes in detail a particularly preferred embodiment of the present invention, but the present invention is not limited to the above-described embodiment and can be modified in various ways.

An airless tire with the basic structure shown in Figure 1 was prototyped based on the specifications in Table 1, and its ride comfort and durability were tested. The main common specifications and test methods are as follows:

<Common specifications>
Tread ring width: 145mm
Tread ring outer diameter: 588mm
Tread ring inner diameter: 537mm
Hub outer diameter: 14 inches Number of spokes: 24 pairs Spoke plate inclination angle: 4°
Amplitude of the first curved portion and the second curved portion: 6 mm

<Ride comfort performance>
As a representative index showing the ride comfort performance, the vertical spring constant was measured at a load of 3.0 kN. The results are expressed as an index with Comparative Example 1 being 100, and the smaller the value, the better the ride comfort performance.

<Durability>
Using a drum tester, the running distance until damage occurred to the airless tires was measured under conditions of a load of 3.0 kN and a speed of 60 km/h. The results are expressed as an index with Comparative Example 1 being 100, and the larger the value, the more excellent the durability.

The results of the tests are shown in Table 1.

The test results confirmed that the airless tire of the embodiment had improved ride comfort and durability performance compared to the comparative example, achieving a high level of both ride comfort and durability.

Reference Signs List 1 Airless tire 2 Tread ring 2a Ground contact surface 3 Hub 4 Spoke 5 Spoke plate portion 6 First edge portion 7 Second edge portion 8 Third edge portion 9 Fourth edge portion

Claims (9)

An airless tire,
The tire comprises a tread ring having a ground contact surface, a hub disposed radially inward of the tread ring and fixed to an axle, and spokes for connecting the tread ring and the hub,
The spokes include a plurality of plate-shaped spoke plate portions each having a width in an axial direction of the tire that is greater than a thickness in a circumferential direction of the tire,
Each of the spoke plate portions has, when viewed in a spoke thickness direction, a first edge portion which is an edge on the hub side, a second edge portion which is an edge on the tread ring side, and a third edge portion and a fourth edge portion which are a pair of edges connecting the first edge portion and the second edge portion,
the first edge extends at an obtuse angle relative to the third edge and at an acute angle relative to the fourth edge;
The thickness of the first edge portion gradually decreases from the fourth edge portion to the third edge portion.
Airless tires. the second edge extends at an acute angle relative to the third edge and at an obtuse angle relative to the fourth edge;
2. The airless tire of claim 1, wherein the thickness of the second edge portion gradually decreases from the third edge portion to the fourth edge portion. The airless tire according to claim 1 or 2, wherein the thickness of the third edge portion gradually decreases from the second edge portion to the first edge portion. The airless tire according to any one of claims 1 to 3, wherein the thickness of the fourth edge portion gradually decreases from the first edge portion to the second edge portion. The airless tire according to any one of claims 1 to 4, wherein the thickness of the first edge portion on the third edge portion side is 1.5 mm or more. The airless tire according to any one of claims 1 to 5, wherein the thickness of the first edge portion on the fourth edge side is 2 to 3 times the thickness of the first edge portion on the third edge side. The airless tire according to any one of claims 1 to 6, wherein the thickness of the second edge portion on the fourth edge side is equal to the thickness of the first edge portion on the third edge side. Each of the spoke plate portions includes, when viewed in the spoke width direction, a first curved portion that is curved at the first edge portion side so as to protrude in one direction in the tire circumferential direction, and a second curved portion that is curved at the second edge portion side so as to protrude in the other direction in the tire circumferential direction,
The airless tire according to claim 1 , wherein the first curved portion and the second curved portion are each formed from the third edge portion to the fourth edge portion. Each of the spoke plate portions includes a connection portion that connects the first curved portion and the second curved portion,
The airless tire according to claim 8 , wherein a distance in the tire radial direction from the first edge portion to the connecting portion is equal to a distance in the tire radial direction from the second edge portion to the connecting portion.

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