JPH01273706A - Tread pattern - Google Patents

Abstract

PURPOSE:To improve durability of a tire by making up small blocks on the surface of the block of a tread pattern, making upper and lower double block construction and making a thin ditch in the lower block along the side face of the upper block. CONSTITUTION:A block which is made up on a tread pattern is of a double construction stacking the upper block 1 on the lower block 2, the area of the upper block 1 is made smaller than that of the lower block 2, the area ratio of the upper face is set to approx. 15-80%. A closed chain shape thin ditch 3 is made on the lower block 2 along the side face of the upper block 1 surrounding the upper block 1. The sum of the depth of this thin ditch 3 and the height of the upper block 1 is made approx. 20-80% of the depth of a main ditch 4. By this constitution, the ground reaction force which concentrates at the ditch bottom is alleviated and cracks of the main ditch and sub ditch are prevented and durability can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a tread pattern that prevents cracks from forming in the major grooves and/or minor grooves on the tread surface.

[Prior art]

On the tread surface of a tire, a plurality of main grooves are formed in the circumferential direction, and a plurality of minor grooves are formed in the width direction. The blocks are divided by these leading grooves and minor grooves to form a tread pattern.

With a tread pattern made of blocks like this, the block surface directly contacts the ground when driving, so
The ground reaction force concentrates on the groove bottom of the main groove and/or the sub groove,
This has caused a problem in that cranks occur in the main groove and/or the sub-groove.

[Purpose of the invention]

An object of the present invention is to provide a tread pattern that reduces the ground reaction force concentrated at the groove bottom, prevents cranks from occurring in the main groove and/or the sub-groove, and thereby improves tire durability. .

[Structure of the invention]

For this reason, the present invention provides a tread pattern consisting of a plurality of blocks formed on the trend surface of a tire, in which small blocks are formed within the surface of the blocks to create a double-structured block consisting of an upper block and a lower block. ,
The gist of the tread pattern is that a narrow groove is provided in the lower block along the side surface of the upper block.

Hereinafter, the configuration of the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a perspective view of an example of a block in the tread pattern of the present invention, FIG. 2 is a plan view thereof, and FIG. 3 is a cross-sectional explanatory view showing the block and the lead.

In these figures, the blocks in the trend pattern of the present invention have a double structure in which the upper block 1 is placed on the lower block 2.3 The area of the upper block l is included in the plan view of Figure 2. The area of the upper surface of the lower block 2 is larger than that of the upper block l. Upper block 1
The area of the top surface is 15% of the area of the top surface of lower block 2
It is good if it is 80%.

A narrow groove 3 is provided in the lower block 2 along the side surface of the upper block 1. The narrow groove 3 is a closed groove surrounding the upper block 1. 4 is initiative.

The height a of the upper block 1 from the lower block 2 is preferably 20% to 80% of the depth C of the main groove 4. Also, the length b, which is the height a of the upper block 1 plus the depth of the narrow groove 3, is also
The depth C of the main groove 4 is preferably 20% to 80% (baa
).

In the tread pattern of the present invention configured in this way,
When touching the ground, only the small block, that is, the upper block 1, touches the ground, and the upper block 1 is compressed and deformed, as shown in Fig. 4 (A).
As shown in the figure, the ground reaction force F is dispersed between the groove bottom B of the main groove and the groove bottom A of the narrow groove 3. Therefore, concentration of the ground reaction force F on the groove bottom B can be avoided. On the other hand, in the conventional tread pattern, the ground reaction force F is concentrated on the groove bottom B of the main groove, as shown in FIG. 4(B).

Examples are shown below.

EXAMPLE A rubber sample shown in FIG. 5(A), which simulates a pair of double-structured blocks separated by closed narrow grooves and having a step and a main groove, was prepared, and the rubber sample shown in FIG. 5(B) was prepared. A striking test was conducted under the following conditions with the convex portion of the impact head H shown in contact with the center of the pair of double-structured blocks.

The results are shown in FIG.

■ Implementation conditions: Ambient temperature 80°C. The weight of the impact head including the weight is 1t17 kg, the impact head falling height is 281゜■ Sample shape: Sample total height H = 35 mm, length of each side of small block t = 20 mm, l = 30 mm and lower side The length of each side of the block is K -30mm, L = 4
0mm [Area of the top surface of the upper block (small block)/Area of the top surface of the lower block] = 50%.

Main groove depth G = 25n + m, groove width w = 15 mm, small block height a = o mm -, 5 mm,, 10 m
m.

Changes from 15 mva to 20 mm. Length b, which is the height a of the small block plus the depth of the closed groove, b = o mm
, 5 mm, 10 nul, 15 mm, 2
Changes to 0 nu++, 25 ra-.

■ Number of hits of the impact head.

The occurrence of cracks at the groove bottom g was investigated after 1 million hits.

FIG. 6 is a diagram showing the relationship between the height a of the upper block and the length b, which is the sum of the height a and the depth of the narrow groove, and the occurrence of cracks in the groove bottom. In Figure 6, rOJ indicates the case where no cracks occur at the groove bottom, "x" indicates the case where cracks occur at the groove bottom, and "△" indicates the case where cracks occur outside the groove bottom (for example, inside the narrow groove). Indicates the case where this occurs.

From Figure 6, the height a of the upper block is 20
% to 80% (a/G), and the length b, which is the height a of the upper block plus the depth of the narrow groove, is 20% to 80% of the depth of the main groove. It turns out that it is good (b/G).

〔Effect of the invention〕

As explained above, according to the present invention, the blocks in the tread pattern have a double structure, and the narrow grooves are provided in the lower block along the side surfaces of the upper block, thereby alleviating the ground reaction force concentrated at the groove bottom. This makes it possible to prevent cracks from forming in the main groove and/or the sub-groove, thereby improving tire durability.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an example of a block in the tread pattern of the present invention, FIG. 2 is a plan view thereof, and FIG. 3 is a cross-sectional explanatory view showing the block and the lead. FIG. 4(A) is an explanatory side view of an example of a block in the tread pattern of the present invention, FIG. 4(B) is an explanatory side view of an example of a block in a conventional tread pattern,
5(A) and 5(B) show an example of a block striking test, with FIG. 5(A) being a perspective explanatory view of the block, and FIG. 5(B) being an impact head. FIG. 6 is a diagram showing the relationship between the height a of the upper block and the length b, which is the sum of the height a and the depth of the narrow groove, and the occurrence of cracks at the groove bottom. l...upper block, 2...lower block, 3...
・Narrow groove, 4...Main groove. Agent Patent Attorney Nobuo Ogawa −

Claims (1)

[Claims] A tread pattern consisting of a plurality of blocks formed on the tread surface of a tire, in which small blocks are formed within the surface of the blocks to form a double-structured block consisting of an upper block and a lower block, A tread pattern characterized by narrow grooves in the lower block along the sides of the upper block.