JPH03271003A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To improve a wet property and a partial abrasion resistant property by forming a stepped land part whose surface is recessed from a main groove in a peripheral direction main groove at a tread end part on the inside of mounting, and forming a plurality of lateral grooves between main grooves at the tread end part on the outside of mounting, in a pneumatic tire for a heavy load vehicle. CONSTITUTION:Peripheral direction main grooves 14, 15 and 16, 17 are respectively provided in tread parts at respective tread end parts on the outside of mounting and on the inside of mounting so as to form land parts 18-20. A plurality of lateral grooves 22 are provided at intervals therebetween in the peripheral direction across the land parts 18-20. Each lateral groove 22 is formed to cross the rotation direction between the main grooves 14 and 17. In the main groove 17 at the tread end on the inside of mounting, a stepped land part 28 is formed, whose surface is located more inside in the radial direction than an outline shape of the tread part. According to this constitution, a wet property and a partial abrasion resistant property are improved.

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention relates to a pneumatic tire that has improved wet performance and uneven wear resistance without compromising steering stability on 1'-lie road surfaces. be.

(Prior art) Conventionally, tires used for heavy-duty vehicles such as trunks and lotuses have a plurality of circumferential main grooves that are continuous in the circumferential direction of the tire because they have low rolling resistance and excellent handling stability. The so-called rib pattern, which has ribs separated by main grooves, has been used favorably, but with the increasing performance of vehicles and the spread of expressway networks, cars that travel long distances at high speed have become more popular. For trucks, lotuses, etc., which are increasingly used, improving uneven wear resistance and wet performance has become an important issue.

Normally, uneven wear such as radius drop and one-sided wear often occurs at the edge of the trend section on the outer side of the tire. As the ground contact area moves relative to the road surface, it undergoes shear deformation in the tangential direction, but the distribution of the shear force differs in the tire width direction, with the tread edge having a larger force in the braking direction than the tread center. A large shear force acts,
This is due to the tread end being dragged against the road surface.

In order to suppress such uneven wear, the radius of the tread part on the outer side of the tire is set smaller than the radius of the tread part on the inner side of the tire, and when the normal internal pressure is applied, the contour shape of the tire tread part is asymmetrical with respect to the tire's equatorial plane. The ground pressure of the outer tread part is higher than the ground pressure of the inner tread part, reducing the shear force in the braking direction that acts on the outer part of the tread, suppressing the movement of the tread edge relative to the road surface, and reducing drag. tires have been proposed.

(Problem to be Solved by the Invention) However, since the sum of shear forces in the driving and braking directions per unit area acting on the ground contact area of the tread portion is considered to be approximately constant, such conventional When it comes to tires, the ground contact pressure of the tread part on the inner side of the tire is lower, so when the tire is transferred, the trend part of the inner side of the tire gets dragged on the road surface, causing damage to the tire.
A new problem arises in that uneven wear occurs in the positive trend portion.

On the other hand, tires with a rib pattern can
When the vehicle is running straight in a so-called wet condition, drainage is carried out along the circumferential main grooves, and good wet performance can be achieved. However, when the vehicle turns, there is a There was also the problem that desired drainage performance could not be expected because there were no extending grooves.

The present invention was made in view of such problems, and
The purpose of the present invention is to provide a heavy-duty pneumatic tire with improved uneven wear resistance and wet performance without impairing handling stability.

(Means for Achieving the Object) In order to achieve this object, in the present invention, the radius of the trend portion between the maximum outer diameter position of the tread portion and the tread end on the outer side of the tread portion is The tire has a tread portion with an asymmetric contour shape, which is smaller than the radius of the tread portion between the position and the tread end on the inner side of the tire, and the maximum outer diameter position of the tread portion of the tire is shifted from the tire equatorial plane to the outer side of the tire. In a pneumatic tire, at least one circumferential main groove is disposed in each tread portion and extends in the circumferential direction of the tire, and the circumferential main groove is disposed in the circumferential main groove located on the tread end side on the inner side of the tire. , a stepped land portion having a surface located inward in the tire radial direction from the contour shape of the tread portion, a circumferential main groove having the stepped land portion, and a circumferential main groove located on the tread end side on the outer side of the tire. It includes a plurality of lateral grooves that extend across the rotational direction and intersperse with each other in the tire circumferential direction.

(Function) Since the radius of the tread portion located on the outer side of the tire is smaller than the radius of the tread portion located on the inner side, the ground pressure of the tread portion located on the outer side of the tire is higher, and therefore, Since there is almost no sliding contact with the road surface, there is no uneven wear on the tread portion.

On the other hand, since the ground pressure acting on the tread part located on the inner side of the tire is low, it is more likely to be dragged against the road surface as the tire rotates. The stepped land portion provided within the circumferential main groove also comes into contact with the road surface. The surface of this stepped land area is
Since it is located inward in the tire radial direction from the contour shape of the tread portion, a large shearing force acts on the surface of the stepped land portion in the tire braking direction.

However, since the sum of the shear forces in the driving direction and the braking direction that act on the unit area of the tread contact area is considered to be approximately constant, if the shear force in the braking direction that acts on the stepped land area increases, This is equivalent to a substantial reduction in the shear force in the braking direction that acts on the ground contact area adjacent to the step land area, and considering that uneven wear on tires occurs in the area where the braking direction is applied, The land portion functions as an uneven wear victim part and suppresses occurrence of uneven wear on adjacent ribs.

Moreover, when driving straight on a wet road surface, water is mainly drained along the circumferential main groove that extends in the circumferential direction of the tire, and when turning, the water is drained at each tread end side. Since water is drained along the lateral grooves that extend between the circumferential main grooves and intersect with the tire rotation direction, sufficient drainage performance can be ensured regardless of whether the vehicle is moving straight or turning.

(Embodiments) Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1(a) is a view of the tread pattern of the heavy-duty pneumatic tire 10 according to the present invention, seen from the front in the tire rotation direction indicated by the symbol R, and its internal structure has a general radial structure. Therefore, the explanation is omitted here.

As clearly shown in FIG. 1B, the tire 10 has a radius of the contour of the tread portion 12a located between the maximum outer diameter position M of the tread portion 12 and the outer tread end of the tire 10.
and when the radius of the outline of the tread portion 12b located between the maximum outer diameter position M and the inner tread end is R1, it is set to satisfy R,<R,
As a result, when the tire IO is filled with the normal internal pressure, the tire IO has an asymmetrical tread contour shape in which the maximum outer diameter position of the tread portion 12 is shifted toward the outside of the tire with respect to the equatorial plane S of the tire.

Then, the distance H8 in the tire height direction between the maximum outer diameter position M and the tread end on the outside of the installation is made smaller than the distance H8 in the tire height direction between the maximum outside diameter position M and the tread end on the inside of the installation, The ground pressure acting on the tread portion 12a on the outside of the installation is made higher than the ground pressure acting on the tread portion 12b on the inside of the installation. Note that although the deviation amount varies depending on the tire specifications, it is 0.07 to 0.0 of the tread width W.
The selection shall be made within the range of 13XW. This is because when the deviation amount becomes smaller than 7% of the tread width W, the difference between the ground contact pressure of the outer tread portion 12a and the ground pressure of the inner tread portion 12b decreases, and It is less effective in suppressing uneven wear in
Moreover, if the deviation i1L becomes larger than 13% of the tread width W, the ground contact pressure of the tread portion 12a on the outer side of the mounting becomes too high, causing premature wear of the tread portion.

In addition, the tread portions 12a and 12b each have at least one circumferential main groove 14 in consideration of the drainage performance of the tire, and in this embodiment, two circumferential main grooves 14 each in order to further improve the drainage performance. .15 and H x 6.17 were formed continuously in the tire circumferential direction, but the total groove width of these circumferential main grooves was 20 to 25% of the width W of the tread portion.
By selecting from the range, good drainage properties can be ensured.

A plurality of lateral grooves 22 extending between the ridges 18 to 20 between the circumferential main grooves are provided spaced apart from each other in the tire circumferential direction, and a block row in which a plurality of blocks are aligned in the tire circumferential direction. 24-26
form.

The lateral grooves 22 may extend across the tire rotation direction between the circumferential main grooves 14 and 17 located on the respective tread end sides, and in this embodiment, the lateral grooves 22
2 partitions the ribs 18 and 19 located on the mounting outer side from the maximum outer diameter position M of the tread portion to form block rows 24 and 2.
5 and the rib 20 located on the inside of the mounting
The tire is provided with lateral groove portions that partition the tire to form block rows 2o, and these lateral groove portions are shaped like the letter ``■'' when viewed from the front in the tire rotational direction, but as in the other embodiment shown in FIG. Extending diagonally backward in one direction in the rotational direction from the circumferential main groove 17 on the inner side of the mounting to the circumferential main groove 14 on the outer side of the mounting, and making the lateral groove 22 substantially orthogonal to the circumferential main grooves. The angle between the lateral grooves 22 and the tire equatorial plane can be arbitrarily selected within the range of 0° to 89°. Furthermore, by gradually decreasing the angles θ1 to θ3 that the groove portions of the lateral grooves 22 make with respect to the line segment perpendicular to the tire equatorial plane toward the tread end, drainage along the lateral grooves is improved. You can also do that.

Therefore, the lateral grooves 22 that are spaced apart from each other in the tire circumferential direction are
During cornering to the left and right, circumferential grooves 14 to 17
In cooperation with this, the drainage performance of the tread portion 12 is further improved.

In addition, in a tire having a row of blocks like this, a large shearing force acts in the braking direction on the kick-out portion of each block, which tends to cause uneven wear called heel and toe. In this case, as shown in FIG. 3, the cross-sectional shapes of the lateral grooves 22 are made to be different on the stepping side and the kicking side of the block. That is, horizontal groove 2
2, the angle α between the groove wall on the stepping-in side and a line segment perpendicular to the surface of the tread portion 12 is the angle β between the groove wall on the kick-out side and a line segment perpendicular to the surface. for,
It is assumed that the selection is made so as to satisfy the relationship α<β.

This increases the rigidity of the kick-off side of each block and increases the ground pressure at that part, suppressing the movement of the block rubber on the kick-off side, effectively preventing heel-and-toe, and This is because the blocks can be worn uniformly.

Furthermore, in the tire of the present invention, the contour shape of the tread portion 12 is asymmetrical so that the ground contact pressure of the outer tread portion is higher than that of the inner tread portion.
Since the tread portion 12b on the inner side of the mounting is dragged on the road surface, uneven wear is likely to occur on the tread portion on the inner side of the mounting.
A stepped land portion 28 is provided that extends in the tire circumferential direction along the circumferential main groove and has a surface that is located radially inward of the tire radial direction from the contour shape of the tread portion 12.

The surface of this step land portion 28 can come into contact with the road surface when a regular load is applied to the tire, and the height d from the groove bottom of the circumferential main groove is equal to the groove depth of 17 of the circumferential main groove. Saho
The width e is 45 to 80%, preferably 60 to 70% of the groove width of the circumferential main groove 17.

Since this surface is located inward in the tire radial direction from the surface of the tread portion 12, when the tire 10 is transferred, it will cause damage to other adjacent ribs 20 and the circumferential main groove 14.1.
7 and each shoulder rib 30.32 partitioned by each trend end, the stepped land portion 28 undergoes a large deformation, so a large shearing force acts in the tire braking direction.

On the other hand, since the sum of the shear forces acting in the driving direction and the braking direction acting on the unit contact area of the tread portion is considered to be approximately constant, the rib 2 adjacent to the stepped land portion 28
0 and the shear force acting on the shoulder ribs 30 and 32 is substantially shifted in the driving direction.

Therefore, uneven wear along the ribs 20, 30 and 32, particularly along the edges of the ribs, can be suppressed. In addition, in this embodiment, since the contour shape of the tread portion 12 is asymmetrical with respect to the tire equatorial plane, the shoulder rib 32 located on the inner side of the tire is dragged against the road surface, causing uneven wear there. Since the stepped land portion 28 is easily disposed, the stepped land portion 28 is shifted toward the tread end side. However, for the purpose of suppressing uneven wear on both the ribs 20 and the shoulder ribs 32 that are adjacent to the stepped land portion 28, The stepped land portion may be formed approximately in the center of the circumferential main groove 17, and furthermore, it may be provided close to the rib 20 mainly for the purpose of suppressing uneven wear on the rib 20. .

In order to examine the handling performance, wet performance, and uneven wear resistance performance of such tires, a comparative test was conducted using the tire of the present invention and a conventionally constructed tire, and the results are shown in the following table. The size of the tires used in the comparison test was 1.
1R22.5.

◎Test tire: Invention tire: A tire with a tread pattern shown in Figure 1, with a tread radius W of 207 ribs and a deviation measurement of 20111 OI.
, the radius R0 of the tread portion on the outside of the installation is 480 ribs, and the distance MH in the tire height direction between the maximum outer diameter position and the end of the tread on the outside of the installation.

is 7.3 mm, the radius R8 of the inner tread part is 740 mu, the distance in the tire height direction between the maximum outer diameter position and the inner tread edge is 10.4 mm,
The groove width of the circumferential main groove located on the tread end side on the inner side of the installation is 20 mm, the groove depth h is 14 mm, the groove width of the other circumferential main groove is 10111 In, the groove depth is 14 mm, and the stepped land part width e
is 10 mm, and the height d of the circumferential main groove from the groove bottom is 1.
Tires with a diameter of 1mm.

- Test tire: A tire with a tread pattern shown in Figure 4, with a circumferential main groove width of 10 mm and a groove depth of 14 mm.
A flat tire.

◎Test method 1, uneven wear resistance performance: Invented tire and conventional tire loaded with regular load were tested in 2D
- After driving 50,000km111 (of which about 70% on expressways and about 30% on ordinary roads) by attaching it to the front wheels of 4 cars, it was found that the The width of uneven wear (El) at the edge portion of the ridge defined by the groove and the width of uneven wear (E2) at one end of the shoulder are measured, and are expressed as an index with the measurement results of the conventional tire set as 100. Therefore, the larger the value, the better.

2. Wet performance and steering stability performance: Invented tire and conventional tire loaded with regular load at 1Qt
On installed on a large truck (2D-4 vehicle), ・Wet performance: The distance to a stop when the brake is pressed at a vehicle speed of 50 km/h on the wet road of the test course is measured, and the index is set with the conventional tire as 100. Indicated by Therefore, the larger the value, the better.

- Steering and stability performance: The vehicle was driven straight and slalom around the test course at a speed of 80 km/h, and the feel of the vehicle was evaluated on a scale of 10 to 10 for maneuverability and stability.

◎Test results: The test results are shown in the table below.

10 points: Completely satisfied level 9 points: Very satisfied level 8 points Satisfied without any problems 7 points: Very satisfied level 6 points: Barely satisfied level As is clear from this table, conventional In tires with a different structure, wet performance and uneven wear resistance deteriorate if handling performance is to be maintained, whereas the tire of the present invention improves wet performance and uneven wear resistance without impairing handling performance. It can be seen that the performance improves.

(Effects of the Invention) Thus, according to the present invention, it is possible to provide a pneumatic tire that improves wet performance and uneven wear resistance, and does not impair various performances as a tire.

[Brief explanation of drawings]

FIG. 1(a) is a diagram showing the trend pattern of the tire of the present invention, and FIG. 1(b) is a diagram showing the tire line A-A shown in FIG. 1(a).
2 is a diagram showing a tread pattern of another embodiment of the present invention; FIG. 3 is a sectional view taken along line B-B in FIG. 1(a);
This figure shows a tread pattern of a conventional tire, and FIG. 5 is an explanatory diagram showing a measurement site for uneven wear on the shoulder of a tire. 10-Tire 12-Tread portions 14-17
- Circumferential main groove 18 ~ 20 - Rib 22 - Lateral groove
24-26- Block row 28- Step land portion 30.32--Shoulder rib @2 Figure 3 Figure 4

Claims (1)

[Claims] 1. The radius of the tread portion between the maximum outer diameter position of the tread portion and the tread end on the outer side of the tread portion is defined as the radius of the tread portion between the maximum outer diameter position and the tread edge on the inner side of the tread portion. In a pneumatic tire that has a tread portion with an asymmetrical contour shape that is smaller than the tire radius and the maximum outer diameter position of the tire tread portion is shifted from the tire equatorial plane to the outside of the tire, Disposed within at least one circumferential main groove extending in the circumferential direction and within the circumferential main groove located on the tread end side on the inner side of the mounting, and located radially inward of the contour of the tread portion of the tire. extending across the tire rotation direction between a stepped land portion having a surface, a circumferential main groove having the stepped land portion, and a circumferential main groove located on the tread end side on the outer side of the mounting;
A pneumatic radial tire characterized by comprising a plurality of lateral grooves spaced apart from each other in the tire circumferential direction.