JPH02306803A - Pneumatic tire for heavy load - Google Patents

Abstract

PURPOSE:To reduce rim frictional trouble in a bead part by specifying the position of the contact top between a tire outline and a rim flange and the height of curvature radial center of a tire mode in a position corresponding to the rim flange in a subjected tire for constructing vehicle. CONSTITUTION:The tire width directional length A from the contact top P between a tire outline 3 and a rim flange 4 to the extension line of the standing part 10 of a rim 1 is set 0.5-0.8 time the width B of the rim flange 4. The height (h) from the surface of the rim 1 in a position corresponding to the rim diameter to the center point (m) of curvature radial R2 of a tire mode in a position corresponding to the rim flange 4 is set in such a manner as to satisfy the relational scheme of rim flange height G and curvature radial R2, h=(0.8-0.9)G-R2. According to this constitution, rim frictional trouble in a bead part can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heavy-load pneumatic tire that reduces rim rubbing failures at the bead portion.

(Prior art) Conventionally, in the design method of the outer contour shape on the mold of the tire bead portion in contact with the rim, as shown in Fig. 2, only the tightness t of the bead base portion 2 with respect to the rim 1 is Taking this into account, the shape of other parts was generally designed to match the inner contour of the rim.When a tire designed in this way is assembled with a rim and inflated, the shape of the bead part changes to the shape of the rim. As shown in FIG. 3, the tire outline 3 was integrated with the rim 1 at the bead portion 5 along the shape of the rim l.

Note that 3 represents the tire outline, R2 represents the radius of curvature of the tire mold at a location corresponding to the rim flange 4, and 6 represents the bead wire.

However, in heavy-duty pneumatic tires used for construction vehicles, etc. that run on rough ground or muddy ground under high-load conditions, when the bead section is designed in this way, under high loads, as shown in Figure 4, As shown by the dotted line, the sidewall portion 7 is significantly deformed so as to protrude outward in the width direction, compared to the no-load state shown by the solid line. As a result, the rim cushion part of the bead part 5 in contact with the rim flange 4, indicated by the symbol M, undergoes repeated large deformations during driving, and foreign objects such as stones and sand enter between the tire and the rim flange 4. There was a problem in that the rim cushion portion of the bead portion 5 suffered from rim rubbing failure. In particular, in loader tires, the longitudinal strain exceeds 25% due to high loads, resulting in large deformation at the rim cushion, and foreign objects such as stones and sand can get between the tire and the rim flange 4 due to driving on rough roads. Since it is easy to enter, the result is that the rim rubbing failure of the rim cushion portion is exacerbated.

[Problem to be solved by the invention]

The present invention is a pneumatic pump for heavy loads that reduces rim rubbing failures at the bead area by suppressing large deformation of the rim cushion part under high loads and reducing the amount of foreign matter that gets between the tire and the rim flange. The purpose is to provide tires.

[Means to solve the problem]

In the heavy-duty pneumatic tire of the present invention, when the tire is assembled into a rim and the inside is filled with standard air pressure, the cross section of the bead in the meridian direction of the tire extends from the contact apex P between the tire outline and the rim flange to the rising part of the rim. The width direction length A to the extension line is A to the rim flange width B, =
B h for the radius of curvature R2
-(0,8-0.9)G-R.

It is characterized by being closed.

This means will be explained in detail below with reference to the drawings.

FIG. 1 shows a cross section of a bead portion in the meridian direction of the tire when the pneumatic tire for heavy loads of the present invention is assembled into a rim and the inside is filled with standard air pressure specified by JIS.

(11 In the present invention, in FIG.
The length A from the apex P of contact with the rim flange 4 to the extension line of the rising portion 10 of the rim in the width direction parallel to the tire axial direction is A=BX0.5 for the rim flange 5 width.
~0.8.

The rim flange width B is a specific dimension defined by JIS.

If A is smaller than BXo, 5, the gap between the tire and the rim flange will be too wide, making it easy for foreign matter to get into the gap. On the other hand, A is BXo.

If it is larger than 8, the tire will overlap the rim flange, making it difficult to insert the detachment lever between the tire and the rim when attaching the tire to the rim, making attachment and detachment difficult. 'Also, the angle C between the tangent 11 of the rim flange 4 passing through the contact apex P and the tangent 12 of the tire outline 3 passing through the contact apex P is 40° or more, more preferably 406 to 60°.
' is better. If the angle C is less than 40'', the gap between the tire and the rim flange will be narrow, making it difficult to insert the lever for detaching and attaching the tire.

(2) In addition, in the present invention, the height h in the trend direction from the rim surface at a position corresponding to the rim diameter to the center point m of the radius of curvature R2 of the tire mold at a location corresponding to the rim flange is defined as the rim flange height. G and the radius of curvature R2
It is set so that h = (0°8 to 0.9) G - RZ.

The rim flange height G is a specific dimension defined by JIS. Further, the radius of curvature R2 of the tire mold is equal to the radius of curvature R2 of the rim flange, and is a specific dimension defined by JIS.

When h is smaller than the value of (0,80-R2), h becomes smaller and the tire profile line 13 descends, causing the surface pressure (contact pressure) between the tire and the rim to become abnormally high. rim rubbing failures will be exacerbated. On the other hand, when h is larger than the value of (0,9G-R2), h becomes thicker (and the tire profile line 13 rises, so the contact pressure between the tire and the rim decreases, and the tire and rim flange 4 The gap between the two becomes wider.

Therefore, the deformation of the rim cushion portion in contact with the rim flange 4 becomes large under high loads, and it becomes easy for foreign matter to enter this gap.

In contrast to the tire of the present invention as described above, h is constant in conventional tires. Therefore, the difference between the center point n of the radius of curvature R2 of the rim flange and the center point m of the radius of curvature R2 of the tire mold is equal to the tightness of the bead base portion 2 (t=t'). However, in the present invention, h is (0,
8 to 0.9) By setting it within the range of G Rz, there is a tit' relationship, and by setting such a difference, the contact pressure between the tire and the rim is optimized,
This prevents large deformation of the rim cushion portion and the intrusion of foreign matter, and also reduces rim rubbing failures.

Examples are shown below.

Example tire size 45/65-45-38PR, B=73,
For heavy-duty pneumatic tires with A-B Xo, 712 = 52, and C = 50', the presence or absence of rim rubbing failure at the bead portion was evaluated by varying h by the following method. The results are shown in Table 1 below.

In this case, G=114 and Rz=63.5 (B, G, and R2 are specific dimensions defined by JIS).

L method for rim aging: Install the tire in an indoor rotation testing machine, fill it with the air pressure specified by JIS, apply the load specified by JIS, and run for a certain period of time. The evaluation was conducted by investigating the presence or absence of

As is clear from Table 1, h is (0,8~0°9)G
It can be seen that no rim rubbing failure occurs within the range of -R1.

〔Effect of the invention〕

As explained above, according to the present invention, in a pneumatic tire for heavy loads, A=BX is set to 0.5 to 0.8, and h
= (0,8 to 0.9)G-R, it is possible to suppress large deformation of the rim cushion part under high loads and to reduce the amount of foreign matter that gets between the tire and the rim flange. This makes it possible to sufficiently reduce rim rubbing failures at the bead portion.

[Brief explanation of drawings]

Figure 1 is an explanatory cross-sectional view of the bead section in the meridian direction of the tire when the heavy-duty pneumatic tire of the present invention is assembled into a rim and the inside is filled with standard air pressure, and Figure 2 is a cross-sectional view of the tire bead section in contact with the rim. An explanatory diagram showing an example of the design method for the outer contour shape, Fig. 3 is an explanatory diagram showing the shape of the bead part of a tire obtained by this design method when the rim is assembled and inflated, and Fig. 4 is an explanatory diagram showing the shape of the bead part when the tire is assembled and inflated using this design method. FIG. 3 is an explanatory diagram showing changes in shape under load and under high load. l... Rim, 2... Bead base portion, 3... Tire external line, 4... Rim flange, 5... Bead portion,
6... Bead wire, 7... Side wall part, 1
0... Rising part of the rim.

Claims (1)

[Claims] In the cross section of the bead section in the meridian direction of the tire when the tire is assembled into the rim and the inside is filled with standard air pressure, the width direction length A from the contact apex P between the tire outline and the rim flange to the extension line of the rising part of the rim is , A = B x 0.5 to 0.8 for the rim flange width B, and from the rim surface at a position corresponding to the rim diameter to the center point m of the radius of curvature R_2 of the tire mold at a location corresponding to the rim flange. , the height h of the rim flange height G and the radius of curvature R
Heavy-duty pneumatic tire with h=(0.8-0.9)G-R_2 for _2.