JPS61226305A - Pneumatic radial-ply tire - Google Patents

Abstract

PURPOSE:To make improvements in traction performance, sideway grip capacity and abrasion resistance, by specifying a correlation ratio in the sum total of projected length in both tire circumferential and widthwise directions of each side of each block in a tread pattern and a ratio to tire outer circumferential length, in case of a tire for non-pavement use. CONSTITUTION:The sum total of tire circumferential projected length ai in each side of each block constituting a tread pattern, that is, a summed value of the total of a1-a16 on illustration as to all blocks is set down to CG. Likewise, another summed value of the total of tire widthwise projected length b1-b16 of each block side as to all blocks is set down to LG. And, LG/CG is set down to 0.9-1.2. In addition, the sum total CG is set to be larger than 8.0 times of tire outer circumferential length CL while the sum total LG to be smaller than 14.0 times of the tier outer circumferential length CL, respectively. With this constitution, traction performance, sideway grip capacity and abrasion resistance are all improvable.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a pneumatic tire particularly useful as a tire for unpaved roads, which balances traction performance and lateral grip performance during cornering and has improved wear resistance. Regarding radial tires.

[Prior art]

Much of the performance of tires, especially tires for unpaved roads, is determined by
It is determined by the tread pattern formed on the tire's contact surface. Therefore, the tread pattern can be said to be the most important factor in determining tire characteristics.

Conventionally, tread patterns have often been determined based on vision and sensation. For this reason, the tread pattern is determined by trial and error, which is inefficient and wasteful. Additionally, because the correlation between the elements of a tread pattern and traction performance and lateral grip performance (cornering limit speed) was not clear, it was difficult to determine a tread pattern that would exhibit sufficiently satisfactory tire characteristics. there were.

[Purpose of the invention]

An object of the present invention is to provide a pneumatic radial tire with improved tire properties such as traction performance, lateral grip performance, and wear resistance by forming a specific tread pattern on the tire contact surface.

[Structure of the invention]

Therefore, the present invention provides a pneumatic radial tire with a groove area ratio of 45 to 65% in a tread pattern formed on the tire contact surface, the total projected length in the tire circumferential direction of each side of each block constituting the tread pattern. CG
The ratio LG/CG of the total projected length in the tire width direction LG is set to 0.9 to 1.2, and furthermore, these CG, LG
8 for each tire outer circumference length CL. OXCL<C
The gist of this invention is a pneumatic radial tire characterized by G, LG <14.0XCL.

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

FIG. 1 is an explanatory diagram of a meridional cross section of an example of the pneumatic radial tire of the present invention. In Figure 1, l is the tread;
2 is a carcass layer mounted between a pair of left and right bead portions 4° 4, and in the tread l, an upper belt layer 3u and a lower belt layer 3d are arranged so as to surround the outer periphery of this carcass layer 2. . Reference numerals 5 and 5 designate a pair of left and right sidewall portions connected to a pair of left and right bead portions 4, 4.

A tread pattern as shown in FIG. 2 is formed on the outer surface of the tread 1, that is, on the tire contact surface.

This trend pattern is applicable to radial tires with a groove area ratio of 45 to 65%. The groove area ratio of the embodiment shown in FIG. 2 is 56%. This tread pattern is in the form of an aggregate in which a plurality of blocks 10, 11, 12, and 13 each have a basic shape.

EE' represents the tire circumferential direction.

FIG. 3 shows an outline of the tread pattern in FIG. 2. In FIG. 3, a is the projected length of one side of the block constituting the tread pattern in the tire circumferential direction, and b is the projected length of one side of this block in the tire width direction.

In the present invention, in the tire tread pattern shown in FIGS. 1 to 3, the total projected length CG in the tire circumferential direction and the total projected length LG in the tire width direction of each block are
The ratio LG/CG is set to 0.9 to 1.2. in this case,
The sum CG of tire circumferential projected lengths is the sum of the tire circumferential projected lengths a of each side of all blocks constituting the tread pattern over the entire circumference of the tire. Further, the total projected length in the tire width direction LG is the sum of the projected lengths b in the tire width direction of each side of all the blocks constituting the tread pattern for the entire circumference of the tire. That is,
As shown in FIG. 4 as an enlarged view of block 11 in FIG.
The blocks constituting the tread pattern are polygonal (hexagonal in FIG. 4), and each side of the block is divided into a circumferential component a and an axial component. The projected length A of the block in the tire circumferential direction is al +a2+...+a76
The projected length B in the tire width direction is b1+b2+...
+b76. Therefore, when all blocks are similarly measured over the entire circumference of the tire, CG=Σ(a, +a2 +-+an) LG=Σ(bI +b2 +. . +bn).

Furthermore, in the present invention, these CG and LG are each 8. O×CL<CG.

LG<14. Ox ct, and further 8. OX
Preferably, CL<CG and LG<12.0XCL.

The reason for this definition in the present invention is as follows.

(1) FIG. 5 shows the relationship between LG/CG and Traxisin performance. In Fig. 5, traction performance is shown as an index, and when LG/CGIJ<1.0, 100
It is said that According to this Figure 5, as LG/CG increases, traction performance increases, and LG/CG increases.
The increase becomes rapid when G exceeds 0.9, and L
It reaches its maximum near G/CG=1.25.

Further, FIG. 6 shows the relationship between LG/CG and lateral grip performance (cornering limit speed). In FIG. 6, the lateral grip performance is shown as an index, where LG/CG is 1.
When it is 0, it is set as 100.

According to FIG. 6, as LG/CG increases, lateral grip performance decreases, and LG/CG = 1°2.
It decreases rapidly when it exceeds .

From the results shown in FIGS. 5 and 6, the traction performance and lateral grip performance are LG/CG=0.9 to 1.
．． It can be seen that the condition is good within the range of 2.

(2) Next, in Figure 7, LG,! : Indicates the relationship with CG.

In FIG. 7, the area marked ■ is an area where both LG and CG are 8 to 14 times the tire outer circumference length CL (for example, the outer circumference length CL of a 165SR13 size tire = 1879 mm), and the traction performance and lateral grip are Both performances are good. In the area of ■, both traction performance and lateral grip performance decrease, and in the area of ■, both traction performance and lateral grip performance are good, but
Abrasion resistance decreases significantly, and in the region of ■, lateral grip performance is high but traction performance is insufficient, and conversely, ■
Traction performance is good in this region, but lateral grip performance is significantly reduced.

From the above, in the present invention, LG/CG=0.9 to 1
．． 2, LG, CG=8. OXCL~14.0XCL
That's what I did.

Moreover, in the present invention, FIG. 8(A) is further provided.

For blocks 10.11.12.13 of the basic shape shown in (B), (C), and (D),
).

As shown in blocks 10', 11', 12°, and 13'' shown in (B"), (C'), and CD'), two or more zigzags are arranged on at least two sides, and the basic shape of the block is The side length BL and the side length BL' of the zigzag block corresponding to that side are 1.05 x BL
It is preferable that the relationship is <Bl,'<1.15XBL. Figure 9 shows the relationship between anus/BL and traction performance. In Figure 9, traction performance is expressed as an index, and when BL'/BL is 1.0, it is 1.
It is set to 00.

According to FIG. 9, the traction performance becomes better as BL'/BL increases.

Furthermore, if the length of the zigzag in the zigzag block is 5~b, it is not effective as the edge part of that side will lose its 41 property, and conversely, if it exceeds 10mm, the block will not be able to maintain its basic shape. It is.

〔Effect of the invention〕

As explained above, the present invention focuses on the fact that the tread pattern of a tire greatly affects traction performance and lateral grip performance, and defines blocks of the tread pattern as described above. The grip performance in the lateral direction can be maintained in a well-balanced manner, and the wear resistance can also be improved. Therefore, the tire of the present invention is particularly useful as a tire for unpaved roads.

The effects of the present invention will be specifically explained below using experimental examples.

Experimental Example Traction performance, lateral grip performance, and wear resistance were measured for tires A (tire of the present invention) and B (conventional tire) shown in Table 1 below. Each tire has a tire size of 165SR13, a groove area ratio in the trend pattern of 56%, and a tire outer circumference length CL of 1.
879+*m, rim; 51 /2 J x13, air pressure; 2. kg/cd.

Table 1 Scrap soil ■Z plate ■ Separate A 1.12 18940mn+ 169
12mmB 0.502 10894+wm
The methods for measuring 21700 mm traction performance, lateral grip performance, and abrasion resistance are as follows.

Kamidanriku'Ei 1' [Grade 5-6°, dirt road, distance 1i1t500m, accelerate from initial speed 20ko+/h and measure time and slip rate.

Timed distance running time.

Slip rate: Tire rotation distance/actual distance.

Slip rate per unit time: Measured at n=10.

Sideways 1-KannoX and TL-Tane: Circular turns on dirt roads. Calculated based on the limit lateral acceleration at a radius of 30m.

■Star ■Characteristics: The vehicle was run continuously for 4.2km on a designated dirt road course, and the amount of wear measured up to 10, 15, 20, and 40 laps.

These results are shown in Table 2 below. Note that the numerical values in the table are expressed as an index (when B tire is taken as lOO).

Table 2 L mountain Kuniroe traction performance 123 100 Lateral grip performance 97 100 Abrasion resistance
112 100 As is clear from Table 2 above, the tire A of the present invention has better balance in both traction performance and lateral grip performance than the conventional tire B, and is also superior in wear resistance. . Therefore, the tire A of the present invention is particularly useful as a tire for use on unpaved roads that are rich in unevenness.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a meridional cross section of an example of a pneumatic radial tire of the present invention, FIG. 2 is an explanatory diagram showing a tread pattern formed on the contact surface of the tire of FIG. 1, and FIG. FIG. 4 is a plan view explanatory diagram showing an example of the shape of blocks constituting the tread pattern in the present invention; FIG. 5 is a diagram showing the relationship between LG/CG and traction performance; FIG. The figure is a relationship diagram between LG/CG and lateral grip performance, Figure 7 is a relationship diagram between LG and CG, and Figures 8 (A), (B), and (C). (D) is an explanatory diagram showing the basic shape blocks, and Fig. 8 (A
'), (B'), (C"), and (D') are explanatory diagrams showing the cases where zigzags are provided on the sides of these basic-shaped blocks, and Figure 9 shows the length of the sides of the basic-shaped blocks. BL
and the length of the side of the zigzag block corresponding to that side BL'
FIG. 2 is a diagram showing the relationship between the ratio BL'/BL and traction performance. DESCRIPTION OF SYMBOLS 1... Tread, 2... Carcass layer, 31... Upper belt layer, 3d... Lower belt layer, 4... Bead part, 5... Side wall part, 11.12.13 .1
4...Blocks with basic shapes.

Claims (1)

[Claims] In a pneumatic radial tire with a groove area ratio of 45 to 65% in the tread pattern formed on the tire contact surface, the sum CG of the projected length in the tire circumferential direction of each side of each block constituting the tread pattern and the projected length in the tire width direction The ratio LG/CG to the total length LG is set to 0.9 to 1.2, and furthermore, these CG and LG are each determined as the tire outer circumference length C.
8.0×CL<CG, LG<14.0×CL for L
A pneumatic radial tire characterized by: