JPH0515564B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to an ultra-low pressure pneumatic tire and is used for buggies and the like that travel on rough terrain. (Prior Art) Buggy tires have been known as ultra-low pressure pneumatic tires for driving on rough terrain. Buggy vehicles are mainly used on muddy ground, grassland, snow, etc.
Vehicles of this type run on sandy areas, and are used for sports, leisure, or competition. Buggy vehicles may be three- or four-wheeled vehicles, and use ultra-low-pressure pneumatic tires with an internal pressure of around 0.15 kg/ ^cm2 . This ultra-low pressure pneumatic tire has USP Design Patent No. 277373, and Figures 11 and 1
This is illustrated in Figure 2. That is, in FIGS. 11 and 12,
This conventional tire 1 includes, on the outer surface of a tread 4 including both shoulders 3 between left and right sidewalls 2, a block 5 whose length in the tire axial direction is longer than the circumferential length of the tire, which protrudes in the tire radial direction. The blocks 5 are regularly arranged in a plurality of rows in the axial direction of the tire with intervals in the circumferential direction of the tire. (Problems to be Solved by the Invention) However, in the ultra-low pressure pneumatic tire 1 according to the prior art, when the tire is mounted on a vehicle and runs, the rigidity of the block 5 is too strong and it is difficult to elastically deform. Because the snow and sand road surface was scraped too much and the circumferential spacing (block pitch) of the blocks 5 was relatively narrow, the tires 1 sank in, making it impossible to drive. This is because if the block 5 is highly rigid and the block pitch is narrow, the block 5 will dig into the road surface, making it difficult to expect the flotation effect (the effect of vertically supporting the vehicle body) of the tire 1. There is. This problem in the prior art arises because the conventional tire 1 aims to be able to run on steady roads to a certain extent, and has a long block life when running on steady roads. The present invention divides the block into a first wall portion and a second wall portion by forming grooves in the block, and allows elastic deformation of the first wall portion when traveling on snow, sand, or mud. The amount of scraping on the road surface is extremely small, the contact area of the tire tread is widened, and the flotation effect on uneven ground is maximized. The purpose of this is to secure the rigidity of the block by abutting it against the second wall portion and closing the groove, thereby suppressing early wear and not impairing durability. (Means for Solving the Problems) The present invention includes a block 16 protruding in the tire radial direction on the outer surface of the tread 13 between the left and right sidewalls 11, the block 16 having a length in the tire axial direction longer than the tire circumferential length, In an ultra-low pressure pneumatic tire in which the blocks 16 are arranged in a plurality of rows in the axial direction of the tire with intervals in the circumferential direction of the tire, the following technical measures have been taken to achieve the above-mentioned object. That is, in the present invention, the block 16 has a groove 21 which is opened with a width that approximately divides the circumferential length of the tire circumferential direction of the ground contact surface 20 at the tire radial direction projecting end into thirds, and extends in the groove longitudinal direction in the tire axial direction. the block 16 is formed in the first wall portion 16A and the second wall portion 16B through the open edge of the groove 21;
The groove 21 has a groove bottom at a position that is more than half of the protruding height of the block 16, and the opening width of the groove 21 is set to allow elastic deformation when the first wall portion 16A hits the road surface, and to accommodate the elastically deformed first wall portion 16A. It is characterized in that the first wall portion 16A has a length such that it comes into contact with the second wall portion 16B and closes the opening. (Function) When the tire 10 rolls on a road surface such as snow or sand,
The block 16 is connected to the first wall portion 16A by a groove 21.
and the second wall portion 16B, so the first
Since the wall portion 16A is easily elastically deformed, that is, it is flexible, the amount of road surface scraping by the block 16 is reduced, and the flotation effect of the tire 10 on snow, sand, and mud is increased. On the other hand, when driving on a steady road, as shown in FIG.
When the width of the opening is elastically deformed and comes into contact with the second wall portion 16B to close the groove 21, it becomes almost the same as one without the groove 21, although the groove 21 is formed here. Since the block 16 is elastically deformed as a whole and the amount of this deformation is suppressed,
Here, there is little wear during steady road driving, and durability remains intact. (Example) An example of the present invention will be described in detail with reference to the drawings. 1 and 2 show a tire 10 according to the present invention, which has a pair of sidewalls 11 and a tread 13 connected in a toroidal manner between the sidewalls 11 via a shoulder 12. There is. This tire 10 is made of rubber or other elastic material, and has a bead core in the bead portion 14, and each bead core is wound with a single-layer or multi-layer carcass ply 5 (see FIGS. 7 and 9). A rim (not shown) is fitted to the bead portion 14, and the internal pressure is kept at an ultra-low pressure of 0.15 to 0.5 kg/cm ² by means of a valve. Blocks 16 whose length in the tire axial direction is longer than the tire length are provided in a radially protruding shape, and the blocks 16 are arranged in plural rows in the tire axial direction with intervals in the tire circumferential direction on the tire tread surface 17 of the tread 13 including the shoulder 12. It is located in The block 16 is connected to the tire tread 1 as shown in FIG.
The front and rear rising surfaces 18 and 19 projecting from 7 have a trapezoidal cross section, and this projecting end surface has a circumferential width C.
It has a top surface 20 of 10 to 25 mm. Here, the total ground surface area (area of the top surface 20) of the block 16 is less than 10% of the entire area of the tread 13, and as shown in FIG. Arranged in multiple rows. The height H of the block 16 is 10 to 23 mm, preferably 12 to 18 mm, and the rising surface 18 on the leading side (front) in the rotation direction has an inclination angle α of the tread 13 with respect to the tire tread surface 17, as shown in FIG. but
The angle of inclination θ of the rising surface 19 on the trailing side (rear) in the rotational direction with respect to the tire tread surface 17 of the tread 13 is approximately 90° as shown in FIG.
The bases, or bases, of the rising surfaces 18 and 19 are both connected to the surface of the tread 13 via curved surfaces 18A and 19A, and the base width F of the block 16 is wider than the width C of the top surface (ground plane) 20. It is said to be wide. In the top surface 20 of the block 16, a groove 21 is formed in the center portion in the width direction thereof and has a groove width D corresponding to approximately 1/3 of the top surface width C, and extends in the longitudinal direction of the groove in the tire axial direction. By forming this groove 21, the block 16 substantially forms the first wall portion 16A.
and a second wall portion 16B. The groove 21 has a groove bottom at a position where the groove depth is the same depth (100%) as the height H of the block 16, as shown in FIG. Also, the groove depth is determined by the block 16 as shown in FIG.
The bottom of the groove is at least half of the height H of the first wall portion 16.
Easily elastically deform A. 7 and 8 show a second embodiment of the tire of the present invention, and FIGS. 9 and 10 similarly show a third embodiment, which is similar to the first embodiment except that the shape of the block 16 described above is different. , 2, etc., and common parts are indicated by common symbols. The block 16 of the second embodiment has a long length in the tire axial direction, and in the third embodiment, the block 16 having a long tire axial length is bent into a so-called lightning shape. In the second and third embodiments, the tread 13
The width of the crown part 1 is as shown in Figs. 7 and 9.
3A and both shoulder parts 13B, the tread 1
The width of the crown portion 13A in 3 is the width of the entire tread 1
This is the part that mainly makes contact with the road surface to obtain driving force, and both shoulder portions 13B mainly make contact with the road surface during cornering. Therefore, the groove 21 is basically formed in all of the blocks 16 arranged in a row corresponding to the crown portion 13A and both shoulder portions 13B. However, the groove 21 may not be formed in the block 16 corresponding to both shoulder portions 13B. Here, it is recommended that the shape of the block 16, the shape of the groove 21, and their numerical values be set as follows, and the reason for this will also be explained. The width C of the block 16 is 10 to 25 mm. This is because if it is less than 10 mm, the block 16 will be extremely elastically deformed when driving on a steady road, resulting in poor durability. On the other hand, if it is more than 25 mm, the rigidity of the block 16 will be too strong when driving on snow, and the shear force ( This is because it is difficult to obtain traction (traction force). The groove width D is basically 1/3 of the lug width C, that is, 3
If it is not more than mm, the lug rigidity will be strong when the lug width C is 10 mm, and it will be difficult to obtain shearing force on the snow. Also, even if it is less than 12%, the lug rigidity will be strong and it will be difficult to obtain shearing force on snow, and the lug width C will be 36%.
% or more, the lugs are too flexible and are subject to severe wear during steady road driving, resulting in inferior durability. The depth of the groove 21 is approximately half or more of the lug height H.
It is said to be 100%, but this means that if the groove depth is shallow, groove 21
There is no point in lowering the block rigidity by forming
This is because block rigidity increases, making it difficult to obtain shearing force on snow, and if it exceeds 100%, dents will essentially be formed on the surface of the tread 13, causing cracks and tire punctures. . Next, experimental data of the tire 10 according to the first embodiment of the present invention shown in FIGS. 1 and 2 and the conventional tire 1 shown in FIGS. 11 and 12 are as follows. It is. The internal pressures and block dimensions of both tires 1 and 10 are as shown in FIG. 13 (invention) and FIG. 14 (prior art), and their specifications are as follows. Note that the numerical units in FIGS. 13 and 14 are mm, except for degrees.

【table】

【table】

[Table] As is clear from the above experimental data, on snow,
It is recognized that the running performance on sand and mud is significantly improved compared to the conventional example. The design dimensions of the buggy tire to which the present invention is applied are a tire cross-sectional width of 154 mm to 304 mm, and a tire outer diameter of 381 mm to 610 mm. (Effects of the Invention) The present invention is as described above, and the first wall portion 16A
Since the block is deformed within the width of the groove 21, the block is extremely flexible, reduces the amount of scratching on the road surface, and maximizes the flotation effect of the tire tread, particularly improving running performance and traction on snow and sand. This greatly improves the vehicle's performance and prevents the vehicle from sinking and becoming unable to drive. Further, as shown in FIG. 5, when the tire 10 is rotated in the direction of the arrow and runs on the ground surface G, the first wall portion 16A of the block 16 is
The first wall portion 16A is elastically deformed against the rigidity (small) of itself until it comes into contact with the groove B, but when both wall portions 16A and 16B come into contact, in other words, the groove 2
1 is closed, both wall portions 16A, 16B
are integrated, and here, sufficient rigidity is secured to suppress elastic deformation, and the flow capacity G1 of the soil thrown up by block 16 is reduced, so that there is less wear and extreme deformation is suppressed, and wear is suppressed. significantly improves durability.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of a tire according to a first embodiment of the present invention, Fig. 2 is a developed plan view showing the lug pattern on the tread surface, Fig. 3 is an enlarged view of a block, and Fig. 4 is Fig. 3 X sectional view, FIG. 5 is an operation explanatory diagram, FIG. 6 is a sectional view showing a modification of FIG. 4, and FIG.
The figure is a sectional view of the second embodiment, FIG. 8 is a developed plan view thereof, FIG. 9 is a sectional view of the third embodiment, FIG. 10 is a developed plan view thereof, and FIG. 11 is a perspective view of a conventional tire.
FIG. 12 is a plan view of the same, FIG. 13 is a developed plan view showing the tire of the present invention that was subjected to a running test, and FIG. 14 is a developed plan view of the conventional tire. 10... Tire, 11... Sidewall, 1
3...Trend, 16...Block, 16A...
First wall portion, 16B...Second wall portion, 21...
groove.

Claims (1)

[Scope of Claims] 1. A block 16 whose length in the axial direction of the tire is longer than the length in the circumferential direction of the tire is provided on the outer surface of the tread 13 between the left and right sidewalls 11 in a protruding shape in the tire radial direction. In an ultra-low pressure pneumatic tire that is arranged in multiple rows in the tire axial direction with intervals in the tire direction, the blocks 16 divide the tire circumferential length of the ground contact surface 20 at the tire radial projecting end into approximately three equal parts. The block 16 is provided with a groove 21 which is open in width and extends in the longitudinal direction of the groove in the axial direction of the tire, and the block 16 is connected to the first wall portion 16A and the second wall portion 16A through the open edge of the groove 21.
The groove 21 is formed in the wall portion 16B, and the groove 21 has a groove bottom at a position of more than half of the protruding height of the block 16;
The opening width of the groove 21 is set to a length that allows elastic deformation when the first wall portion 16A hits the road surface and closes the opening when the elastically deformed first wall portion 16A comes into contact with the second wall portion 16B. An ultra-low pressure pneumatic tire characterized by: