JPH0386603A - Radial tire for construction vehicle - Google Patents

Abstract

PURPOSE:To prevent the belt separation and improve abrasion resistance by forming a tread pattern from the grooves in the circumferential direction and sectional surface direction and equally dividing the part from the equator to the tread edge into four parts and setting the negative ratio in each region on the equator side, tread edge side, and between the both so as to satisfy a prescribed relation. CONSTITUTION:A tread pattern is constituted of the grooves in the circumferential direction and the grooves in the sectional surface direction on a tread part 22. The width direction of a tire 10 is equally divided into eight parts, and the dividing points are set at CL point, 1/8 point, 1/4 point, 3/8 point, and SH point from the center in the tire width direction to both edge shoulder parts, and when the part between the CL point and the 1/8 point is set as X region, and the part between 1/8 point and 3/8 point is set as Y region, and the part between 3/8 point and SH point is set as Z region, each negative ratio NX, NY, NZ is set so that relating to NY>NZ>NX, and NX/NY is set larger than 0.1 and smaller than 0.3. With this constitution, belt separation can be prevented, and the abrasion life can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a radial tire for construction vehicles that prevents belt separation and improves wear life of a heavy-duty pneumatic radial tire that runs on rough terrain.

[Prior art]

Traditionally, tires for dump trucks and other vehicles used on rough, unpaved roads have mainly had lateral groove lug patterns, but in recent years, there has been an increase in the number of sites where tires are driven under heavy loads and at high speeds in order to improve construction efficiency. It's coming. Along with this, separation of belt ends due to heat has frequently occurred. To deal with this, in order to reduce the amount of rubber near the ends of the belt and increase the heat dissipation effect, patterns in which circumferential grooves were arranged in the lug pattern came to be used (for example, Japanese Patent Publication No. 53-11726). (see publication).

Here, increasing the volume of tread rubber that contributes to wear was thought to worsen heat separation durability, so it can be obtained by analyzing the drum durability (heat separation durability) results of conventional belts. It is said that it is preferable for the temperature distribution at the crown portion to be flat, and the tread pattern of the tire described in the above-mentioned publication was also set so as to have this temperature distribution (see FIG. 9).

[Problem to be solved by the invention]

However, although such a temperature distribution improves Behito separation durability compared to tires with only a rub pattern, there is a problem in that sufficient wear resistance and cut resistance cannot be obtained. There is a contradictory relationship.

In addition, by increasing the efficiency of the current construction work, high-speed operation will enable
The durability of heat separation that was conventionally allowed is incomplete, and in reality, the permissible durability is about 20% higher than the conventional durability rate.

The present invention takes the above facts into account, and aims to obtain a radial tire for construction vehicles that can maintain heat separation durability that meets current construction efficiency, as well as improve wear resistance and cut resistance. It is.

[Means to solve the problem]

The invention described in claim (1) provides a carcass ply consisting of a radially arranged steel cord extending in a toroidal manner between a pair of beads, and a rubber coating of the steel cord surrounding the outer periphery of the crown portion of the carcass ply. In a pneumatic radial tire, the pneumatic radial tire includes a belt made of a plurality of laminated layers, and a tread provided on the outer periphery of the belt. The tread is divided into one central portion and two both side portions in the circumferential direction of the tread by the directional groove,
Divide the area from the equator to the tread edge, which corresponds to 172 of the full arc width of the tread, into four equal parts, and divide 1/1 pitch from the equator side into four equal parts.
When the 4 areas are the X area, the 1/4 area on the tread edge side is the Z area, the 2/4 area between the X area and the Z area is the Y area, and the negative ratios of each are NX, Nv, Nz, It is characterized by having the relationship Ny>Nz>NX.

The invention according to claim (2) provides that the negative ratio NX
When the relationship between and NY is NX /Ny = n, it is characterized by having the following relationship: 0.1 < n < 0.3.

[Effect]

The operation of the invention according to claim (1) will be explained. Generally, the ends of the main belt are often located around the 1/4 point to 3/8 point. Therefore, increasing the negative ratio of this portion to enhance the heat dissipation effect is effective for separating the belt ends.

When the negative ratio is divided into three X, Y, and Z regions in the cross-sectional direction, for the above reasons, it is optimal to set the part with the largest negative ratio as the Y region, which is the best way to achieve heat separation in line with current construction efficiency. Experiments have shown that it can maintain durability.

Further, in order to make the temperature of the center portion a predetermined temperature higher (for example, 15±5° C.) than the temperature of the end portions of the belt, the negative ratio NX in the X region is made the smallest.

Therefore, the negative ratio Nz in the Z area is intermediate between the negative ratio NY in the Y area and the negative ratio NX in the X area.

In this way, the present invention improves wear resistance and cut resistance over the entire tire area by dividing the arc half width of the tread into three regions (left and right) and correlating the negative ratios of each region. I can do it.

Furthermore, in order to obtain a temperature distribution in which the temperature of the center portion is higher than the predetermined temperature with respect to the belt end, as described in claim (2), the ratio (N
X/Ny) must be 0.1 to 0.3. That is, when NX/NY is less than 0.1, the temperature difference between the belt ends and the center portion becomes larger than a predetermined temperature, causing thermal deterioration of the belt in the center portion and causing heat separation.

Furthermore, when NX/NY exceeds 0.3, the temperature difference between the belt ends and the center portion becomes smaller than a predetermined temperature, and the heat separation performance at the belt ends deteriorates.

Therefore, the ratio of negative ratio NX and NY (
By setting NX/Nv), the durability of the heat separation at both the belt end and the center portion is improved.

[First embodiment] Figure 1 shows ○RR (OFF T) 18 according to this embodiment.
A ROAD RADIAL tire 10 is shown. The size of the tire 10 is 18.00 R33** deep groove type. Note that ``**'' is referred to as Two 5tar, and may also be written as ``☆☆''.
A pressure vessel is formed. The carcass 12 is constructed by arranging a plurality of steel cords in a horseshoe shape and covering the cords with a rubber layer.

The cord applied to the carcass 12 of the tire 1 (l) applied to this embodiment has an axial direction along the width direction of the tire 10 (approximately 90° with respect to the tire circumferential direction), and has a radial structure. .

The surface of the carcass 12 is covered with a rubber layer 14. This rubber layer 14 covers the tire 10 shown in FIG.
The side part of the carcass 12 is called the side wall 16.
0 has the role of protecting the outside of both side walls.

Both ends of the carcass 12 are held by being wrapped around a ring-shaped bead 18 around the rotational axis of the tire. This bead 18 is also covered with the rubber layer 14 and constitutes a bead portion 20 as a whole. This bead part 2
0 defines the dimensions of the inner circumference of the tire 10 and ensures fitting with the rim 21.

The upper part of the rubber layer 14 in FIG. 1 is continuous with the tread portion 22. The tread portion 22 is the portion that actually contacts the ground, and is thick enough to withstand wear and damage.

Belts 26 are arranged in layers between the carcass 12 and the tread portion 22 so as to intersect with each other. In this embodiment, the belt 26 has four layers and uses steel cord (7×7+1). Also, along the outermost layer of the belt, add a high elongation cord (3 x 7,
Breaking strength 140 kg/piece, number of shots 19 pieces 75cm)
27 are buried. This belt 26, code 27
Therefore, the rigidity of the tire 10 is maintained.

Further, as shown in FIG. 2, a predetermined tread pattern is provided on the ground surface of the tread portion 22. The length dimension WT of the arc of the tread surface provided with the tread pattern is 445 mm. In addition to being a design element, the tread pattern also serves to prevent slippage between the tire and the road surface and to dissipate heat generated in the tread. Moreover, this tread pattern has a predetermined pitch in the circumferential direction (in this example, the pitch dimension P=325
The same shape is repeated every 2 mm).

As shown in FIG. 2, the tread pattern applied to the tire 10 of this embodiment has both cross-sectional grooves and circumferential grooves. The circumferential groove is wavy along the circumferential direction, and provides a certain degree of traction to the block at the center of the tire. Additionally, a plurality of narrow grooves 29 parallel to each other are provided between the circumferential grooves, further improving traction performance. here,
The width dimension Wl of the cross-sectional groove is 37 mm, and the width dimension of the circumferential groove is two different width dimensions W2 and W3 at the bent part, W, = 28111111, W3 = 22 m.
It is said to be ffI. Moreover, the width dimension W4 of the groove 29 is lQ
It is said to be mm.

As shown in FIG.
It is an abbreviation for id Depth, and in this example it is 60.9m.
m) is preferably 88% to 110%, and in this example, 9
It is said to be 0%. Also, the depth dimension B of the circumferential groove is NS
D is preferably 70% to 90%, and in this example, it is 80%. Further, the groove depth C of the groove 29 extending from the circumferential groove to the center of the tire is preferably 65% to 85% of the NSD, and is set to 75% in this embodiment.

In this embodiment, the width direction of the tire 10 is equally divided into 8 parts, and the dividing points are CL point, 178 point, 1/4 point,
3/8 point, SH point (see Figure 1), C in the center of the tire
The area from point L to point 178 is the area X, and from point 178 to point 3
The area up to the 78th point is defined as the Y area, and the area from the 3/8 point to the SH point is defined as the Z area (see Figure 2). Note that the circumferential groove is always provided within the Y area. Here, the distance α from the bending part on the tire center side of the circumferential groove to the 178th point is preferably in the range of 0 to 50% of the arc length D from the CL point to the 1/8 point, and in this example, the distance α is 25%. %.In addition, the distance β from the tire shoulder side bending part of the circumferential groove to the 378th point is the arc length E from the SH point to the 3/8 point.
It is preferably 45% to 95%, and in this example it is 70%. As shown in FIG.
Temperature difference (Tct Tl/4) with 78 points is 15℃±
It is set to be 5t.

Negative ratio of each area (Nll SNy N N Z
) is set so that the negative ratio NY in the Y area is the largest. Furthermore, the negative ratio NX of the X region is the negative ratio of the other two regions (NY, NZ
) is set to be smaller than Note that in the first embodiment, NX = 6.3%, Nr = 32.9%
, Nz = 23.1%, and N/NY = 0.19.

In this way, by setting the negative ratio of each region, temperature measurement points TCL, TI/II shown in FIG.
The temperature distribution measured at Tl/4, T3/8, and T'sa can have the characteristics shown in FIG.

Here, as shown in the temperature distribution in Fig. 3, the tire IO
The temperature at the center of the belt (T CL point) and the temperature at the end of the belt (T
1/4 point) so that the temperature difference is approximately 15℃±5℃
Area negative ratio NX and Y area negative ratio Nv
The ratio (NY/NY) is set to 0.1 to 0.3. This is set in order to maintain the temperature difference (TCL Tl/4) between the CL point and the 3/8 point at 15° C.±5° C., as shown in FIG. In addition, if the temperature difference between the CL point and the 378 point (TCL T1/4) is out of the above range, the belt at the center will be susceptible to thermal deterioration, which may cause heat separation (if the temperature difference exceeds 20°C) ), the heat separation performance at the belt end may deteriorate (if the temperature difference is less than 10℃)
.

The operation of the first embodiment will be explained below.

First, the results of a heat generation temperature test using a drum of tire 1 (1) according to the present example will be explained.

The test conditions were an internal pressure of 7.0 kg/c++! , 100%
Load (12,200kg load), speed 16km/h
(constant speed). The test method was to run the tire 10 under the above test conditions until it reached the saturation temperature, and immediately after that, the temperature of the outermost layer of the tread portion 22 above the cord 27 (temperature measurement points TCL, T, 78 shown in FIG. 1) was measured. , Tl/4s
This temperature measurement point is approximately 2 mm above the belt.

As shown in Figure 3, the test results showed that the TCL point was 94℃,
The T378 point is 80℃ (left and right average), and the temperature difference is 14
℃, indicating an almost optimal temperature distribution. here,
As a comparative example, the temperature distribution of a conventional tire is shown by the broken line in FIG. In this temperature distribution, the temperature difference is about 2°C.

Next, the heat generating belt durability test results will be explained.

The test conditions were a drum with an external dimension of 5 m, and an internal pressure of 7.
0 kg/cd, running at a speed of 16 km/h (constant speed),
Initially 3 at 80% load of normal load (12,200kg)
0 minutes, 100% load for the next 30 minutes, and then adding 10% load every 30 minutes to calculate the running time (distance) until belt end failure (judging from the appearance of the bulge). The index was obtained as This can be cleared up. In addition, as shown in FIG.
/Ny belt durability index can also be improved.

Next, the actual wear test will be explained.

In this test, the tire 10 according to this example was mounted on a 32-ton rear dump truck at a crushed stone shipping site, and the tire was run, and its wear resistance was compared with that of a conventional tire.

The index is a value when the engine hour (cumulative engine starting time) required for 1mm of wear is set as 100 for the conventional tire.As a result, the tire of this example has a value of 117, which is a 20% increase as required. can be reached.

[Second example] A second embodiment of the present invention will be described below.

In the second embodiment, as shown in FIG.
Since the structure of the tire 10 is the same as that of the first embodiment except that the tread pattern is slightly different, a description of the structure will be omitted. Further, the negative ratio of each region also ensures a predetermined condition.

Below, the negative ratios of each region of the second embodiment are shown, and the negative ratios of the tire according to the first embodiment and the conventional tire are also shown.

In the second embodiment, the grooves 29 between adjacent circumferential grooves are set so as to widen toward each other, and as a result, the pitch dimension P' in the circumferential direction is larger than the pitch dimension P in the first embodiment. It's getting longer.

The tire 10 according to the second example was subjected to the same tests as the tire according to the first example, and the results are shown below. In addition, the test results of the first example and the conventional tire are also shown.

As described above, in this example, by making the negative ratio of the Y area higher than that of other areas, the heat separation durability at the belt end is improved, and the temperature distribution of the tire is adjusted so that the temperature at the tire center area is adjusted to 378 points. 15℃ higher than the temperature of
By setting the temperature to be higher by ±5°C, wear resistance and cut resistance can be improved. Therefore, it is possible to achieve a performance that is 20% higher than the conventional one, which is in line with current construction efficiency.

〔Effect of the invention〕

As explained above, the radial tire for construction vehicles according to the present invention has the excellent effect of being able to maintain heat separation durability in line with current construction efficiency and improving wear resistance and cut resistance. has.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the tire according to the present embodiment, and FIG. 2 is a developed road surface diagram showing the tread pattern according to the first embodiment.
Figure 3 is a characteristic diagram showing the temperature distribution in the tread width direction;
The figure is a characteristic diagram showing the belt separation durability index with respect to the temperature difference between the CL point and the 3/8 point. Figure 5 is the characteristic diagram showing the temperature difference between the CL point and the 378 point according to the ratio of the negative ratio NX and NY. Figure 6 shows the negative ratio NX and NY
FIG. 7 is a developed view of the tread surface showing the tread pattern according to the second embodiment, and FIG. 8 is a characteristic diagram showing the relationship between circumferential groove position and temperature difference. , FIG. 9 is a developed view of the tread showing the tread pattern of a conventional tire. 10...Tire, 12...Carcass, 22...Tread portion, 26...Belt.

Claims (1)

[Claims] (1) A carcass ply consisting of a radially arranged steel cord spanning a pair of beads in a toroidal manner;
In a pneumatic radial tire, the pneumatic radial tire includes a belt in which multiple layers are laminated to surround the outer periphery of the crown portion of the carcass ply and serve as the rubber coating of the steel cord, and a tread provided on the outer periphery of the belt. A cross-sectional groove is formed, and the tread surface is divided by two circumferential grooves into one central portion and two side portions in the circumferential direction of the tread, and one part of the entire arc width of the tread portion.
Divide the area from the equator to the edge of the tread corresponding to /2 into four equal parts,
For one pitch, the 1/4 area on the equator side is the X area, the 1/4 area on the tread edge side is the Z area, and the 2/4 area between the X area and the Z area is the Y area, and the negative ratio of each is N_X. , N_Y, N_Z, a radial tire for a construction vehicle is characterized by having a relationship of N_Y>N_Z>N_X. (2) The relationship between the negative ratio N_X and N_Y is N
The radial tire for a construction vehicle according to claim 1, wherein the radial tire for a construction vehicle has a relationship of 0.1<n<0.3, where _X/N_Y=n.