JPH0741766B2 - Tires for running on rough terrain - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is for traveling on rough terrain that can satisfy ride comfort, shock absorption, slidability, and figure stability in a well-balanced manner and can enhance durability. Regarding tires.

[Conventional technology]

Regarding tires for running on rough terrain, in order to maintain controllability, shock absorption and slidability even when driving on rough roads with many irregularities, tires with low internal pressure of 0.1 to 0.5 kg / cm ² and cords are used. The carcass ply, which was inclined at a high angle of 60 ° or more with respect to the equator, was formed by a carcass in which two layers were stacked. However, such a carcass structure has a problem that the posture stability and riding comfort of the vehicle are deteriorated.

On the other hand, there are cordless tires that do not use cords in the carcass ply, but the cordless tires are improved in riding comfort but inferior in controllability, shock absorption, and slidability.

Further, by adopting a beltless monoply radial structure for the tire, riding comfort is improved, but controllability and shock absorption are poor.

Here, by comparing the performances of the carcass structure and the tire, the evaluations shown in Table 1 are obtained. In addition, the evaluation in the table is based on the driver's feeling with the actual tire equipped on the actual vehicle.
Shown by stages.

As described above, none of the conventional tires can satisfy all the tire characteristics for traveling on rough terrain.

[Problems to be Solved by the Invention]

However, with the spread of all-terrain vehicles, demands for tires capable of satisfying the above-mentioned various characteristics in a balanced manner are increasing.

As a result of earnest research to meet the demand, the inventor has balanced the tire characteristics by controlling the rubber thickness at each position in the tire cross section in addition to the configuration of the carcass and the configuration of the belt layer. We have found that it is very satisfying.

INDUSTRIAL APPLICABILITY The present invention can regulate the rubber thickness of a tire in addition to the constitution of a carcass and a belt layer, and can improve ride comfort, shock absorption, slidability, and controllability uniformly and can improve durability on uneven terrain. The purpose is to provide running tires.

[Issues for solving problems]

In order to solve the above problems, in the tire for running on uneven terrain of the present invention, the tread portion is passed through the sidewall portion to fold back around the bead core of the bead portion and at an angle of 70 ° to 90 ° with respect to the tire equator. Carcass cord tilts in the range 1
A carcass provided with two layers of carcass plies and a belt layer composed of two layers of belt plies in which the belt cord is inclined in the range of 20 ° to 50 ° with respect to the tire equator (A), and the tread surface While bulging the block on the tire, the rubber thickness of the groove bottom between the outward surface of the carcass, the groove bottom line, and the sidewall surface is set to the tire equator (A).
Equatorial groove bottom rubber thickness (TA) and tire equator (A)
To the tire axially outer end point (C) of the tire contact surface from the tire equator (A) at half the distance (S) from the tire equator (A). (TB / TA), which is the ratio (TB / TA) of 1.0 or more and 1.3 or less, and the outer end groove bottom rubber thickness (TC) at the outer end point (C) and the quadrant groove bottom rubber thickness (TB). The ratio (TC / TB) is 1.0 or more and 2.5 or less, and 90% of the maximum tire width (WS) is 90% of the maximum width (WS) of the sidewall.
The ratio (TD / TC) of the rubber thickness (TC) to the outer edge groove bottom rubber (TC) is 1.2 or more and 3.5 or less, and the rubber thickness (TE) is 95% of the tire maximum width (WS) in the sidewall portion. And the ratio (TE / TC) of the outer edge groove bottom rubber thickness (TC) is 0.5 or more and 0.8
The ratio (TF / TE) between the maximum width rubber thickness (TF) at the tire maximum width (WS) point and the 95% width rubber thickness (TE) is 0.8 or more and 1.5 or less.

[Action]

By tilting the carcass cord of the carcass by 70 ° to 90 ° in a so-called radial arrangement, controllability, shock absorption, and slidability can be enhanced.

Further, the belt layer is formed by two layers of belt plies, and the rubber thickness at the tread portion is set to the equatorial groove bottom rubber thickness T.
A: The rubber rubber thickness TB at the quadrant is thicker in the order of the rubber thickness TB and the rubber thickness TC at the outer end groove. Therefore, the rigidity of the tread is reduced to reduce the riding comfort because the outer side is gradually increased in the tire axial direction. Can be increased without

Further, by making the 90% rubber thickness TD thicker than the outer end groove bottom rubber thickness TC, the bending rigidity of the sidewall portion is increased and the durability is improved.

Furthermore, the ride comfort can be improved by making the 95% rubber thickness TE thinner than the outer end groove bottom rubber thickness TC. As described above, according to the present invention, the above-described configurations are organically integrated, and riding comfort, shock absorption, slidability, and controllability can be uniformly improved and durability can be enhanced.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

The tire for running on uneven terrain of the present invention comprises bead portions 3 and 3 on both sides through which the bead core 2 passes, a sidewall portion 4 extending outward from the bead portion 3 in the radial direction of the tire, and a tread portion 5 joining the upper end thereof. The carcass 6 has a carcass 6 which is folded from the tread portion 5 through the sidewall portion 4 and around the bead core 2 of the bead portion 3, and a belt layer 10 is provided radially outside the carcass 6 inwardly of the tread portion 5. It is located and arranged. In the bead portion 3, a bead apex 8 is erected from the bead core 2 toward the outer side in the radial direction. A block 12 is raised on the tread surface 14 of the tread portion 5.

The carcass 6 is a single-layer carcass ply 7 in this embodiment.
The carcass ply 7 consists of steel or nylon,
A radial direction array is formed by arranging cords made of organic fibers such as polyester at an angle of 70 ° to 90 °. If the inclination of the carcass cord is less than 70 °, riding comfort will be reduced.
The carcass 6 can also be formed by stacking two carcass plies with the carcass cords arranged in mutually opposite directions and superposed in two layers.

The belt layer 9 covers the tread surface from the outside of the carcass 6.
Inner belt ply B1 toward 14, outer belt ply B0
It consists of two layers of belt plies 11, 11 arranged in this order,
These belt plies 11, 11 are made of steel or organic fiber cords having a high elastic modulus at 20 ° to the tire equator A.
The belt cords of the belt plies 11 and 11 are arranged in the range of 50 ° in reverse.

By reversing the direction of the cords in this way, a triangular truss structure is formed between the belt cords of both belt plies, and the restraining force between the belt plies can be increased.
If the inclination of the belt cord is 20 ° or less, riding comfort is deteriorated, while if it is 50 ° or more, slidability and posture stability are poor.

The tread portion 5 has a plurality of blocks 12 raised from the tread surface 10. In this embodiment, the block 12 is L-shaped as shown in FIG. 2, and the block 12 is an S-shaped central block group centered on the tire equator A and shoulder portions arranged on both sides thereof. And a side block group having a U-shaped array extending to the side. Further, the surface of the block 12 has a notch groove having a groove depth shallower than the block height.
21 is provided. In this embodiment, the total surface area of the blocks 12 is smaller than the area of the tread surface, that is, the land area is smaller than the sea area.

Further, in the present application, the groove bottom rubber thickness in the tire axial section is defined with reference to the groove bottom rubber thickness at the tire equator A. The groove bottom rubber thickness means a groove bottom line or a side wall surface 15 that is a line connecting the outward facing surface 13 of the carcass and the groove bottom.
The thickness of the rubber between and.

Here, in order to regulate the rubber thickness in the tread portion 5, the reference point is set as follows. The outer end in the tire axial direction of the ground contact surface 16 of the tire formed by the surface of the block 12 is defined as the outer end point C, and 1/2 of the distance S from the tire equator A to the outer end point C is separated from the tire equator A. The position is set to the 4-minute point B.

The ratio TB / TA between the equatorial groove bottom rubber thickness TA at the tire equator A and the four-minute point groove bottom rubber thickness TB at the four-minute point B is set to 1.0 or more and 1.3 or less, and the rubber thickness at the four-minute point. The ratio TC / TB of the groove bottom rubber thickness TC at the outer end point C is 1.0 or more and
Set it to 2.5 or less.

Therefore, the groove bottom rubber thickness in the tread portion 5 is formed such that the rubber thickness gradually increases from the tire equator A toward the outer end portion C of the tire ground contact surface. While the riding comfort is reduced by gradually reducing the rubber thickness from the tire equator A toward the outer end portion C, when the rubber thickness of the outer end portion C is suddenly increased beyond the above range, the tread portion 5 The deformation in the vicinity of the tire equator A becomes large and the posture stability deteriorates.

Further, a reference point of the rubber thickness is determined both on the sidewall portion 4 and on the sidewall surface 15. 90% of the maximum tire width WS is distributed to both sides around the tire equator A, and the position is 90% width point D on the sidewall surface 15 at both ends and 95% width point E of the tire maximum width WS dimension. At the same time, the position of the maximum tire width W on the tire outward surface is defined as the maximum width point F.

The ratio TD / TC of the outer end rubber thickness TC at the outer end point C and the 90% width rubber thickness TD at the 90% width point D is 1.2 or more and 3.5 or more.
On the other hand, the ratio TE / TC between the outer end rubber thickness TC and the 95% width rubber thickness TE at the 95% width point E is 0.5 or more and 0.8 or less.

In this way, 90% width rubber thickness TD is Larger and 95% wider rubber thickness TE than outer TC
By making it smaller than the above, rigidity distribution of the sidewall portion becomes appropriate, and the tire characteristics are improved.

Furthermore, by setting the ratio TF / TE of the maximum width rubber thickness TF of the maximum width point F to the above 95% width rubber thickness TE to be 0.8 or more and 1.5 or less, that is, both rubber thicknesses TE and TF are set close to each other. , Keeps the elasticity of the tire and enhances ride comfort.

〔Concrete example〕

Tires having a tire size of 24 × 13-9 were manufactured as prototypes having the specifications shown in Examples 1 to 4 of Table 2, and the tires were mounted on a standard rim and run in an actual vehicle under an internal pressure of 0.2 kgf / cm ^2. I did a test. For comparison, tires having conventional specifications (Comparative Examples 1 to 8) were also prototyped and tested.

The test results are shown in Table 2.

It was found that all of the examples had good balance of ride comfort, shock absorption, slidability, and posture stability, and were superior in durability to the comparative examples.

〔The invention's effect〕

As described above, the tire for running on rough terrain of the present invention comprises the above-mentioned carcass and play belt layer, and the rubber thickness of the tire axial section is regulated at a plurality of positions, so that the riding comfort, shock absorption, and slidability are improved. As a result, various characteristics of posture stability can be improved in a well-balanced manner, and durability can be improved, so that it can be suitably used for running on rough terrain.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, and FIG. 2 is a developed plan view illustrating a block of a tread portion surface. 2 ... bead core, 3 ... bead part, 4 ... sidewall part, 5 ... tread part, 6 ... carcass, 7 ... carcass ply, 9 ... belt layer, 12 ... block, 13 ... carcass Outward surface, 14 ... Groove bottom line, 15 ... Sidewall surface, 16 ... Tire contact surface, A ... Tire equator, B ... 4-minute point, C ... Outer end point, S ... Distance, TA: Equatorial groove bottom rubber thickness, TB: Quadrant groove bottom rubber thickness, TC: Outer end groove bottom rubber thickness, TD: 90% width rubber thickness TE: 95% width rubber thickness TF: maximum width rubber thickness, WS: maximum tire width.

Claims (1)

[Claims] 1. The carcass cord is folded back from the tread portion to the sidewall portion around the bead core of the bead portion, and the carcass cord is inclined within a range of 70 ° to 90 ° with respect to the tire equator.
A carcass provided with two layers of carcass plies and a belt layer composed of two layers of belt plies in which the belt cord is inclined in the range of 20 ° to 50 ° with respect to the tire equator (A), and the tread surface is provided. While raising the block,
The rubber thickness between the outward surface of the carcass, the groove bottom line, and the sidewall surface can be calculated by measuring the rubber thickness (TA) at the equator of the tire equator (A) from the tire equator (A) to the tire contact surface. Ratio with the quadrant groove bottom rubber thickness (TB) at the quadrant (B) that separates 1/2 of the distance (S) from the tire axial direction outer end point (C) from the tire equator (A). (TB / TA) is 1.0 or more and 1.3 or less, and the outer end point (C)
The ratio (TC / TB) of the outer end groove bottom rubber thickness (TC) to the quadrant groove bottom rubber thickness (TB) is 1.0 or more and 2.5 or less, and the tire at the sidewall portion is The ratio (TD / TC) of the 90% width rubber thickness (TD), which is 90% of the maximum width (WS), and the outer end groove bottom rubber thickness (TC) is 1.2 or more and 3.5 or less, The ratio (TE / TC) of the 95% width rubber thickness (TE), which is 95% of the tire maximum width (WS), to the outer edge groove bottom rubber thickness (TC) in the sidewall portion is 0.5 or more and 0.
8 or less, and the ratio (TF / TE) of the maximum width rubber thickness (TF) at the tire maximum width (WS) point to the 95% width rubber thickness (TE) is 0.8 or more and 1.5 or less. Tires for running on rough terrain.