Patent Application
20180141379
This disclosure relates to a tire that can be used without being filled with pressurized air.
For pneumatic tires that need to be filled with pressurized air and always kept at constant internal air pressure during use, various measures have conventionally been taken to prevent a puncture which leads to such a state where the internal air pressure cannot be kept constant. However, the structure of pneumatic tires makes a puncture unavoidable.
In view of this, “non-air pressure tires” have been proposed in recent years as tires that need not be filled with pressurized air. For example, a “non-air pressure tire” includes: a support structure for supporting a load from the vehicle; a belt layer (omissible) provided on the outer circumferential side of the support structure; and a tread layer provided on the outer side (outer circumferential side) of the belt layer (see Patent Literature (PTL) 1). This support structure is a structure provided with an inner cylindrical member, an outer cylindrical member disposed in a concentric circular shape on a side outer than the inner cylindrical member, and a plurality of connecting members connecting the inner cylindrical member and the outer cylindrical member.
PTL1: JP2011-219009A
Such non-pneumatic tire as described in PTL1 is supported by a load from the vehicle via the support structure, and thus does not need to be filled with pressurized air, which prevents puncture thereof. However, since the load is carried by the connecting members connecting the inner cylindrical member and the outer cylindrical member of the support structure, a portion on a tread rubber with a comparatively larger ground contact pressure to a road surface (a tread rubber portion (tread rubber junction) located on a tire radial outer side of a junction joined to the outer cylindrical member of the connecting members) is generated. As a result, the ground contact pressure of the tread rubber to the road surface becomes uneven, which generates a vibration in the tire, and thus a ride comfort of the tire is casually insufficient.
Then, this disclosure aims to provide a tire capable of improving the ride comfort.
The tire of this disclosure is a tire comprising: a case portion comprising: an inner cylindrical member; an outer cylindrical member surrounding the inner cylindrical member from a tire radial outer side; and a plurality of connecting members arranged between the inner cylindrical member and the outer cylindrical member and connecting the two cylindrical members; and a tread portion having a tread rubber disposed on a tire radial outer side of the outer cylindrical member, wherein: when a portion of the tread rubber located on a tire radial outer side of a junction of the connecting members joined to the outer cylindrical member is defined as a tread rubber junction, a JIS hardness of a first portion of the tread rubber inclusive of the tread rubber junction is smaller than a JIS hardness of a second portion of the tread rubber other than the first portion.
According to the tire of this disclosure, it is possible to improve the ride comfort.
Note that in this disclosure, the “JIS hardness” is a hardness measured according to JIS K6253 via a Durometer hardness test by using a type A tester.
In this disclosure, “a boundary extends in a tire circumferential direction” means that the boundary extends linearly or curvedly in parallel to the tire circumferential direction, or inclined at an angle of 45° or less with respect to the tire circumferential direction.
In this disclosure, “a boundary extends in a tire width direction” means that the boundary extends linearly or curvedly in parallel to the tire width direction, or inclined at an angle of less than 45° with respect to the tire width direction.
According to this disclosure, it is possible to provide a tire capable of improving the ride comfort.
Hereinafter, embodiments of the disclosure will be described with reference to the drawings.
As illustrated in
Here, the attachment body 4, the inner cylindrical member 22, the outer cylindrical member 23 and the tread portion 3 are arranged respectively coaxially with an axis in common, and their tire widthwise central portions are in accordance with each other.
From the viewpoint of uniformity of the tire 1. the inner cylindrical member 22 and the outer cylindrical member 23 of the case portion 2 are respectively cylindrical with constant thickness and width. An inner circumferential surface of the inner cylindrical member 22 may be provided with protrusions and recesses, etc. for fitting with the attachment body 4 attached to the axle. Note that although the tire 1 has the attachment body 4 in the illustrated example, but the tire 1 may have, e.g., protrusions and recesses installable to a rim disposed on the inner circumferential surface of the inner cylindrical member 22 instead of the attachment body 4.
In the present embodiment, regarding the inner cylindrical member 22 and the outer cylindrical member 23, the cylindrical members may be respectively divided in the tire width direction (divided at a tire widthwise center in the illustrated example), and may include, e.g., a one-side divided inner cylindrical member and a one-side divided outer cylindrical member located on one side in the tire width direction, and an other-side divided inner cylindrical member and an other-side divided outer cylindrical member located on the other side in the tire width direction. Note that the inner cylindrical member 22 and the outer cylindrical member 23 may be ones without being divided in the tire width direction as well.
The connecting members 21 of the case portion 2 are not limited as long as they connect the inner cylindrical member 22 and the outer cylindrical member 23 to each other, but in the present embodiment, they include the first connecting plates 21a and the second connecting plates 21b with respectively different arranging positions in the tire width direction. A plurality of the first connecting plates 21a are arranged along the tire circumferential direction at one tire widthwise position with respect to the tire widthwise center, and a plurality of the second connecting plates 21b are arranged along the tire circumferential direction at another tire widthwise position different from the one tire widthwise position with respect to the tire widthwise center. In the present embodiment, the first connecting plates 21a connect the one-side divided inner cylindrical member and the one-side divided outer cylindrical member, and the second connecting plates 21b connect the other-side divided inner cylindrical member and the other-side divided outer cylindrical member. In total, 60 first connecting plates 21a and second connecting plates 21b are disposed.
The number of the connecting members 21 in total of the first connecting plates 21a and the second connecting plates 21b may be adjusted appropriately. For example, the number is 60 here, but may also be, e.g., 30, 40, 72, 80, and 144.
As illustrated in
Moreover, in the illustrated example, the first connecting plates 21a and the second connecting plates 21b are formed not linearly, but in a manner curved in the tire circumferential direction.
A plurality of the first connecting plates 21a are arranged along the tire circumferential direction respectively at an identical position in the tire width direction, and a plurality of the second connecting plates 21b are arranged along the tire circumferential direction respectively at an identical position in the tire width direction, which is a position spaced from the first connecting plates 21a in the tire width direction.
Note that the plurality of the connecting members 21 may be each arranged at positions symmetrical to each other with respect to an axis O between the inner cylindrical member 22 and the outer cylindrical member 23. Moreover, all connecting members 21 are of the same shape and size, and a width of the connecting members 21 may be smaller than a tire widthwise width of the outer cylindrical member 23. Furthermore, in order to support the load from the vehicle with the case portion 2 and to simultaneously absorb compact from the road surface, the connecting members 21 may be an elastic body.
As illustrated in a group of the first connecting plate 21a and the second connecting plate 21b drawn with solid lines with emphasis in
Note that in the present embodiment, the first connecting plates 21a and the second connecting plates 21b are used as the connecting members 21, and the first connecting plates 21a and the second connecting plates 21b extend in a manner inclined with respect to the tire radial direction, but the connecting members 21, including the first connecting plates 21a and the second connecting plates 21b, may have any shape and inclination direction with respect to the tire radial direction. Specifically, the connecting members 21 may, for example, have only one of the first connecting plates 21a and the second connecting plates 21b, or, be of a plate-like or columnar (cylindrical or prismatic) shape extending in parallel to the tire radial direction (from the inner cylindrical member 22 to the tire radial outer side).
In the present embodiment, all of the inner cylindrical member 22, the outer cylindrical member 23 and the plurality of the connecting members 21 of the case portion 2 may be, for example, formed integrally with a synthetic resin material. More specifically, in the present embodiment, the inner cylindrical member 22 and the outer cylindrical member 23 are respectively divided in the tire width direction, but there is no problem to integrally form the one-side divided inner cylindrical member, the one-side divided outer cylindrical member and the first connecting plates 21a located on the one side in the tire width direction (a one-side case portion), and to integrally form the other-side divided inner cylindrical member, the other-side outer cylindrical member and the second connecting plates 21b located on the other side in the tire width direction (an other-side case portion). Moreover, all of the inner cylindrical member 22, the outer cylindrical member 23 and the plurality of the connecting members 21 may be formed integrally without being divided in the tire width direction.
In the present embodiment, the one-side case portion and the other-side case portion may be joined to each other via welding, melting or adhesion. Note that the one-side case portion and the other-side case portion may be formed with either different materials or an identical material, such as metal materials and rigid resin materials, but from the viewpoint of weight reduction and uniformity, it is preferable to form them with an identical synthetic resin material, particularly a thermoplastic resin material.
The attachment body 4 usable in the present embodiment includes: a holding cylindrical portion 41 in which an end of the axle is held; an outer ring portion 42 surrounding the holding cylindrical portion 41 from the tire radial outer side; and a plurality of ribs 43 connecting the holding cylindrical portion 41 and the outer ring portion 42 (see
The holding cylindrical portion 41, the outer ring portion 42, and the ribs 43 may be integrally formed of a metal material such as an aluminum alloy. The holding cylindrical portion 41 and the outer ring portion 42 are each shaped like a cylinder, and disposed coaxially with the axis O. The plurality of ribs 43 are arranged at a constant spacing in the circumferential direction.
The tread portion 3 has on its surface a vulcanized tread rubber 31, which becomes a tread surface. Moreover, the tread portion 3 is disposed on the tire radial outer side of the outer cylindrical member 23 by, e.g., adhering with an adhesive, etc. Note that if necessary, a belt including a rubber-coated cord layer, etc. may be disposed inside the tread portion 3 or between the tread portion 3 and the outer cylindrical member 23.
In the present embodiment, as illustrated in
Here, in the tread rubber 31, the part located on the tire radial outer side of the junction (one end of the connecting members 21) 21c of the connecting members 21 joined to the outer cylindrical member 23 is referred to as the tread rubber junction 31a. More specifically, the tread rubber junction 31a is a part of the tread rubber 31 in which the junction 21c of the connecting members 21 is projected on the tire radial outer side in accordance with the tread rubber 31.
In the present embodiment, as illustrated in
Moreover, in the present embodiment, in the first portion 31b, a boundary BL of the first portion 31b and the second portion 31c, which have different JIS hardness from each other, extends in the tire width direction and the tire circumferential direction. In other words, the second portion 31c is disposed between first portions 31b adjacent in the tire circumferential direction, and the second portion 31c is disposed between first portions 31b spaced from each other in the tire width direction and between the first portions 31b and the tread edges.
Here, the function and effect of the tire 1 according to the embodiment of this disclosure is described.
In a conventional tire including: a case portion including an inner cylindrical member, an outer cylindrical member and connecting members; and a tread portion, since the connecting members carry the load, a part with a comparatively large ground contact pressure is generated on the tread rubber, and therefore, vibration is generated in the tire, and the ride comfort is casually insufficient.
Then, in the tire 1 of the present embodiment, since the JIS hardness of the first portion 31b of the tread rubber 31 inclusive of the tread rubber junction 31a is smaller than the JIS hardness of the second portion 31c, the first portion 31b inclusive of the tread rubber junction 31a buffers the large ground contact pressure, and when the tread rubber junction 31a is in contact with the road surface, the first portion 31b is deformed due to the ground contact pressure, while the second portion 31c with a comparatively high ground contact pressure shares the ground contact pressure as well. Therefore, the ground contact pressure can be equalized.
Therefore, according to the tire 1 of this disclosure, it is possible to suppress generation of vibration in the tire 1, and to improve the ride comfort.
The method for adjusting the JIS hardness of the first portion 31b and the second portion 31c is not specifically limited, and may be a well-known method. Examples of a method for reducing the JIS hardness include: reducing a particle size of a carbon black contained in the tread rubber (i.e., a rubber composition for forming the tread rubber) of the part of which the JIS hardness is to be reduced; reducing an amount of the carbon black contained in the tread rubber (i.e., the rubber composition for forming the tread rubber); reducing an amount of a vulcanizing agent contained in the rubber composition such as sulfur; and a combination thereof. By reducing the amount of the vulcanizing agent contained in the rubber composition, a formed vulcanization mesh is reduced, and the JIS hardness of the part constituted by the rubber composition is reduced.
In the present embodiment, preferably, the JIS hardness of the first portion 31b of the tread rubber 31 is preferably 0.9 times or less, more preferably 0.5 to 0.9 times of the JIS hardness of the second portion 31c of the tread rubber 31.
By setting the JIS hardness of the first portion 31b to 0.9 times or less of the JIS hardness of the second portion 31c, the first portion 31b sufficiently buffers the large ground contact pressure, and it is possible to sufficiently equalize the ground contact pressure. Furthermore, by setting the JIS hardness of the first portion 31b to 0.5 times or more of the JIS hardness of the second portion 31c, it is possible to avoid an excessively large difference of the JIS hardness of the first portion 31b and the second portion 31c, and to suppress generation of uneven wear.
In the tire 1 of the present embodiment, as illustrated in
Moreover, in the tire 1 of the present embodiment, as illustrated in
Note that in the present embodiment, if the first portion 31b is inclusive of the tread rubber junction 31a, it may have an area of any value within the tread pattern, but the first portion 31b preferably has an area of 1 to 10 times, more preferably 1 to 2 times, further more preferably 1 to 1.5 times of an area of the tread rubber junction 31a. This is because that it is possible to uniformly control the wear resistance of the tread rubber 31.
In the present embodiment, although not illustrated in
In the present embodiment, as illustrated in
Therefore, in the varied example of the embodiment as illustrated in
In the present embodiment, as illustrated in
Therefore, in the varied example of the embodiment as illustrated in
Moreover,
The method for forming the first portion 31b as illustrated in
In
As illustrated in
As mentioned above, the connecting members may be either of only one type as exemplified in
The foregoing explains embodiments of the disclosure with reference to the drawings. However, the tire described herein is not particularly limited to the aforementioned examples, and appropriate changes may be made.
The disclosure will be described further in detail by Examples hereinafter without being restricted thereto by any means.
In order to ensure the effect of the tire of this disclosure, tires of the examples and the comparative examples as described below were manufactured and evaluated.
Upon manufacture of the tires of the examples and the comparative examples, in each sample tire. Rubber Members 1 to 4 having the formulation as indicated in the following Table 1 were used in the tread rubber.
Note that the “NS” in the table refers to a vulcanization accelerator NS (N-t-butyl-2-benzothiazylsulfenamide). and the “CZ” refers to a vulcanization accelerator (“Nocceler CZ”, manufactured by Ouchi Shinko Chemical Industrial Co., Ltd.).
Note that the “JIS hardness” is a hardness measured according to JIS K6253 via a Durometer hardness test by using a type A tester.
The tire of Example 1 has the tread rubber structure as illustrated in
The tires of Examples 2 to 4 are similar as the tire of Example 1 except that the tread rubber structure and the rubber member of the tread rubber are changed as indicated in Table 2.
Moreover, the tires of Examples 5 to 8 are similar as the tire of Example 1 except that they have undivided case portions and their tread rubber structure and rubber member of tread rubber are changed as indicated in Table 2.
The tires of Comparative Examples 1 to 4 are similar as the tire of Example 1 except that the tread rubber structure and the rubber member of the tread rubber are changed as indicated in Table 2.
Moreover, the tires of Comparative Examples 5 to 8 are similar as the tire of Example 1 except that they have undivided case portions and their tread rubber structure and rubber member of tread rubber are changed as indicated in Table 2.
Note that the reference signs 13, 13a, 13b, 131, 131a, 131b in
The aforementioned tires of Examples 1 to 8 and Comparative Examples 1 to 8 were subjected to evaluation of the ride comfort as described below.
The aforementioned sample tires were mounted to an actual vehicle. Then, the ride comfort was evaluated via feeling of a driver when running at a speed of hour of 60 km/h. The evaluation was performed in 10 stages, where 10 is a maximum value. A larger value indicates excellent ride comfort. The result is as indicated in Table 2.
As indicated in Table 2, it is understood that since the tires of Examples 1 to 8 have a JIS hardness of the first portion inclusive of the tread rubber junction smaller than the JIS hardness of the second portion, they have improved ride comfort as compared to the tires of Comparative Examples 1 to 8, which have only the first portion without the second portion.
According to this disclosure, it is possible to provide a tire capable of improving the ride comfort.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015-134564 | Jul 2015 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2016/003161 | 7/1/2016 | WO | 00 |
