JPH075003B2 - Low internal pressure pneumatic tire for rough terrain - Google Patents

Description

TECHNICAL FIELD The present invention relates to a low internal pressure pneumatic tire for rough terrain.

Low internal pressure pneumatic tires for rough terrain are commonly used in, for example, Buggy vehicles under significantly low internal pressure applications.
The buggy car is mainly used for running over grasslands, muddy grounds, or areas such as snow and sand, and its purpose is for sports, leisure or competition.

Buggy vehicles include three-wheeled and four-wheeled vehicles, but generally the low internal pressure pneumatic tires used for this have an internal pressure of 0.15 Kg / c.
Ultra low pressures such as around m ² are applied.

For this reason, the tire structure is divided into, for example, when there is substantially no rubber without reinforcement, when the cord layer is applied only in the tread area, and in addition to the carcass in which cords are arranged in the radial direction across the 1-ply bead, A so-called deformed radial structure, which does not use a belt layer which is usually applied to a carcass crown portion in a structure of this kind, is also used for the tread portion.

(Prior Art) A tread of a tire of this type is provided with projecting row-shaped blocks or lugs parallel to the rotation axis of the tire, that is, along the width direction of the tread, and these blocks or lugs are provided along the circumference of the tread. For example, it is assumed that they are regularly arranged at a predetermined interval.

(Problems to be solved by the invention) However, such a conventional tread pattern has almost no problem with respect to the driving force or the braking force acting during straight running, but when steering or turning, the width direction of the tread, that is, the lateral direction of the tread. Since the blocks or lugs are arranged side by side, there is a problem that the ground gripping force is insufficient with respect to the lateral action (lateral force), resulting in poor steering performance.

Further, in order to ensure running stability especially on rough terrain, it is necessary for mud in the groove of the tread to have excellent (removal) resistance, whereas conventional tires have had problems in this respect as well.

The present invention solves such a problem, can advantageously avoid a decrease in maneuverability even under the action of lateral force, and has a low internal pressure pneumatic tire for rough terrain that is also excellent in mud drainage property. Is to provide.

(Means for Solving the Problems) The present invention is that the treads that are connected to both the left and right sidewalls and the toroidal are in multiple rows along the circumference of the tread, and descend from the width center of the tread toward both end edges. Forming a multi-tiered, with a large number of blocks, the part of the groove portion that vertically and horizontally separates these blocks from each other is relatively wide, and has an area within the range of 65 to 85% with respect to the total area of the tread, In a low internal pressure pneumatic tire for uneven terrain with a sparsely distributed land area, each block has a length A of 0.3 along the circumference of the tread between adjacent rows of blocks in the width direction of the tread. ~ 0.7 times the offset amount x on the circumference of the tread, which forms a tilted array on both sides of the tread at an angle of 10 ° to 35 ° with respect to the width direction of the tread. A low internal pressure pneumatic tire for rough terrain, characterized in that it has a large number of directional chevron grooves that are open diagonally between the arrangements on both sides of the tread widely.

It goes without saying that the total area of the tread here follows the convention of being expressed by the product of the peripheral width and the peripheral length of the tread, and the directional chevron groove means that the tire rotates in the forward direction of the vehicle, It refers to an obliquely arranged groove in which the earth and sand trapped in the chevron groove can be removed to both sides of the tread by the advanced ground contact in the chevron groove in the direction of generating a driving force with respect to the ground.

The low internal pressure pneumatic tire for uneven terrain according to the present invention can have the following basic structure.

(1) Carcass (a) In the case of total rubber in which the cord reinforcing layer across the beads cannot be seen, (b) It has a one-ply or at most two-ply carcass in which the fiber cords are arranged in the radial direction between the beads.
If the belt that is normally applied to this type of tire is not visible on the carcass crown, (c) A layer (breaker) in which the fiber cords are arranged only in the crown portion of the tread, for example, in the direction intersecting the tread circumference. ) Is used at most once. However, there is no particular limitation as long as the structure is suitable for use at ultra-low internal pressure.

(2) Cross-sectional shape of tire The ratio of the cross-sectional height to the maximum width of the tire 1 for uneven terrain at the time of internal pressure filling (no load) that has passed through the rim assembly is 0.6 to 0.9, and 0.7 to
The range of 0.8 is more preferable.

(3) Tread pattern (a) As shown in FIGS. 1 and 2, a large number of blocks B are provided on the circumference of the tread 2 of the tire 1 for rough terrain. The shape of the block B may be any shape, but it is preferable that the contour is a block B having a linear shape, for example, a rectangular basic tone as shown in FIG. 1, rather than a curved line.

FIG. 1 exemplifies a block type tread pattern of a pneumatic tire for rough terrain with a rotation index (not shown) directed from the bottom of this figure to the top of the drawing and going up, and FIG. 2 is FIG. A part of the tread 2 of the tire 1 of FIG.

As shown in the figure, it is desirable to provide the rectangular depressions 3 (two in the example shown) on the surface of the block B because the ridgelines of the block B increase.

When projecting the block B on the tread 2, make sure that the groove portion is within 65 to 85% of the total area of the tread (the sum of the block surface area and the opening area of the groove that limits this). Determine the block array.

(B) In the example of the tire 1 for uneven terrain shown in FIG. 1, the block B projecting from the tread 2 is first spread laterally in the form of a geese-like spread, that is, it is slanted to both sides and is bent by the lateral groove 4, In addition, B ₁ , B ₂ , and B ₃ form a staggered multi-row from the central block B ₀ through the longitudinal groove 5.

A part of the tread 2 is expanded and shown in FIG. 2, and a straight line K- connecting the centers (hereinafter abbreviated as centroids) G of the graphic of each block B
K is inclined to the left in a direction parallel to the rotation axis of the tire, that is, a line J-J indicating the width direction of the tread 2, and the inclination angle θ is 10 ° to 35 °, preferably 15 ° to 25 °. , Each block B ′ ₁ , which similarly forms a block array through the next lateral groove 4,
In the case of B ′ ₂ and B ′ _3, the angle θ is the same as above with respect to the width direction J′-J ′.

(C) The inclination angle of the block array with respect to the straight line JJ has been described with reference to FIG. 2 on the left side with respect to the equator OO, but the right side block row symmetrical with respect to the equator OO is also inclined to the right downward in the above angle range. It is an array.

(D) the slope of the block row, will be described as an example block B _'1 and B' ₂ adjacent the left side of the equatorial O-O, through the centroid G of these blocks respectively, of the tread 2 widthwise J- Straight lines L-L and M-M parallel to J are circumferentially displaced by a length x. That is, the offset x is provided. This offset x corresponds to 0.3 to 0.7 times the circumferential length A of the tread of the block B.

(E) In the concrete examples shown in FIGS. 1 and 2, the blocks in each row are provided with an offset y also in the width direction of the tread, so that the vertical groove 5 between the adjacent block rows can be made horizontal. It is blocked by a block that has shifted to. This will be explained using blocks B ₀ and B ′ _0. Lines P-P and Q-Q passing through the centroid G of each block B and parallel to the equator O-O are provided with offsets of a length y. Block B'to a position to close the vertical groove 5 interposed between the block B ₀ and the right side B _1.
0 is provided.

The value of y may be zero, and it is not necessary to make it constant between the upper and lower blocks.

(F) In the example shown in the figure, the blocks have the same shape symmetrically with respect to the equator OO, but it is not necessary that all the blocks have the same shape and the same size. Further, the line connecting the centroids of the blocks B ₀ , B ₁ , B ₂ , B ₃ is a straight line and forms an inclination angle θ with respect to the width direction of the tread 2, but it is not always necessary to incline the block row in a straight line, and the zigzag It may be sloped or curved. In this case, the tilt angle is
It may be expressed by the average inclination angle of the block row.

One of the features of the present invention is that the blocks extending from the center of the tread to the edge of the tread to the edge of the tread form a row of blocks at an average inclination angle of 10 ° to 35 °, preferably 15 ° to 25 ° with respect to the tire rotation axis direction. Although it is expressed as eggplant, like the case shown in the figure,
When the line connecting the centroids is a straight line, the inclination angle and the average inclination angle are equal.

The effect of the present invention is that tire size 20 × 7.00-8 for front wheels, 22 × 11.00-8 for rear wheels, carcass (90 with respect to the equatorial plane of the tire).
°, that is, radial direction: nylon cord; 1 ply) is reinforced, and the tread 2 is provided with a block (angle θ = 20 °, offset ratio x / A = 0.5) of the shape shown in FIG. Per three-wheel buggy with tires protruding so that the area of the vehicle is 75% and a three-wheel buggy with conventional tires of block (angle θ = 0 °, offset ratio x / A = 0) for comparison , Each mud land, 0
The vehicle was run at a speed of 60 kg / hr to evaluate straightness and turning performance. The results obtained are shown in Table 1 below.

In the conventional tire, the lateral groove 4 is provided in parallel with the width direction of the tread, and the carcass is composed of the cord layer in the radial direction. Therefore, after the tire is vulcanized, the number of cords to be driven corresponds to the groove portion. However, in the tires of the examples, the block row has an angle (in this case, 20 degrees) with respect to the rotation axis direction.
), The degree of coarseness and denseness of the code layer was remarkably reduced.

(Effects of the Invention) The tire of the present invention has a significantly improved running performance as shown in Table 1 by specifying the arrangement of the blocks protruding on the tread, and also has a low tread rigidity. That is, the lateral grooves interposed between each block row effectively function as directional chevron grooves to provide excellent mud-repelling properties required on rough terrain such as muddy ground, and to enter the contact area while the tire is running. And the extremely large circumferential bending deformation of the tread that occurs when coming out of the contact area is not concentrated in the lateral grooves unlike the conventional structure, but is dispersed in the block row part, so cracks that may occur along the lateral grooves Occurrence of can be advantageously suppressed.

[Brief description of drawings]

FIG. 1 is a side view of an example tire of the present invention, and FIG. 2 is an enlarged view of a part of the tread of the tire shown in FIG. 1 ... Tire 2 ... Tread 3 ... Dimple 4 ... Horizontal groove 5 ... Vertical groove B ... Block D ... Direction of driving force

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-55-140604 (JP, A) JP-B 53-3521 (JP, B2) JP-B 53-42921 (JP, B2) JP-B 54- 7082 (JP, B2)

Claims (1)

[Claims] 1. Treads connected to both left and right sidewalls and a toroidal are arranged in multiple rows along the circumference of the tread, and in a multi-tiered manner from the width center of the tread to both edges. The area of the groove part which is provided between the blocks and which vertically and horizontally separates these blocks from each other is relatively wide, and has an area within the range of 65 to 85% with respect to the total area of the tread. In a low internal pressure pneumatic tire for leveling, each block is on the tread circumference that is 0.3 to 0.7 times the length A along the tread circumference of the block between the rows of blocks that are adjacent to each other in the width direction of the tread. Due to the step of the offset amount x, a tilted array is formed on both sides of the tread at an angle of 10 ° to 35 ° with respect to the width direction of the tread, and the treads are widely slanted between the multi-staged arrays of the blocks. Low pressure pneumatic tire for rough terrain, characterized by having a large number of directional chevron grooves opened on both sides of.