JPH11170815A - Pneumatic tire with lug - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tire with lug having performance with concurrent use possible in a paddy field and a field, and in a pavement road, without causing a change of running distance by a slip. SOLUTION: In a pneumatic tire provided with a tread arranging many lugs 4 tilt extended relating to a tire equator in a crown part continued astride between a pair of side wall parts toward an outer side from a width direction central part thereof in both sides of the tire equator alternately and with a space part in a peripheral direction of the tire to designate a tire rotational direction to a successively grounded direction of each lug 4 in an outer side from the center of a tread width direction, in a section in parallel to a tire equator surface, an angle (thereinafter, shown singly tilt angle) dA formed relating to a line segment L connecting a tip end edge E of a side wall 5 in a tread-in side of the lug 4 and a tire rotary axis R is set to 15 deg. or less. Similarly, a tilt angle dB of the lug 4 in an end part region in the tread width direction is set to 30 deg. or more. Further, a tilt angle of the side wall 5 in this tread-in side is gradually increased from the center of the tread width direction, that is, equator O of the tire to the outside.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire with a lug, which is mounted on an agricultural tractor or the like and is used for traveling in fields, suitable for agricultural machine tires.

[0002]

2. Description of the Related Art Agricultural machinery tires generally have a lug pattern in which a large number of lugs are arranged at intervals in a circumferential direction of the tire tread in order to ensure running performance on muddy or soft ground. It is. In Japan, in particular, since the agricultural work is mainly performed in paddy fields, tires having a so-called high lag pattern, which generate strong traction in soft mud and have a high rug height, are mainly used.

[0003] With the recent shift in agricultural policy, there has been an increase in the number of farmers who have shifted from cultivation in paddy fields to cultivation in fields, and there is an opportunity to work in paddy fields and fields in parallel. Is increasing. However, tires with a high rug pattern designed for agricultural work in paddy fields show excellent characteristics in paddy fields, but in field work, high rugs excavate the soil and destroy the field, especially breaking ridges Therefore, it was difficult to use the agricultural machinery used in the paddy field for the field work.

Japanese Unexamined Patent Publication (Kokai) No. 6-156018 discloses a tire which can be used for both paddy and field work.
It has been proposed that the side wall on the kick-out side of the lug has an average angle substantially parallel to the tire radial direction while the taper is inclined at an average angle of. Similarly, JP-A-7-23251
No. 6 discloses that the angle formed by the side wall on the step side of the lug with respect to a straight line connecting the tip end thereof and the rotation axis of the tire is 30 degrees.
° or more is disclosed.

[0005] In accordance with these proposals, by setting the inclination angle of the side wall on the step side of the lug to 30 ° or more, even when the tread width is narrowed to avoid raising the soil or breaking down the ridges in the field work, the mud is muddy. It is now possible to provide tires with excellent traction on the ground.

[0006]

However, when traveling from a paddy field to another paddy field or a field, mainly on a paved road, when each lug shifts from stepping to kicking out during rolling of a tire, a so-called so-called "kick-out" is performed. Since the wiping phenomenon occurs and the lug moves in the opposite direction to the traveling direction and slips, the actual running distance when the tire makes one revolution becomes smaller than the circumference of the tire, which has been a problem. .

[0007] In particular, when the vehicle is driven by four wheels, if this slip occurs, the traveling distance between the front wheel and the rear wheel deviates from the design of each agricultural machine, and usually the front wheel having a smaller diameter than the rear wheel pulls the rear wheel. In other words, the large-diameter rear wheel acts as a brake, and the front wheel is pulled so as to drag the rear wheel. As a result, premature wear of the front wheel tire is caused.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a rugged tire having a performance that can be used for paddy fields and fields, and that does not cause a change in running distance due to slippage on a pavement road. .

[0009]

That is, the present invention provides:
A plurality of lugs extending inclining from the center in the width direction to the outer side with respect to the equator of the tire are alternately provided on both sides of the equator of the tire, and the tire is provided on the crown portion extending continuously between the pair of sidewall portions. A pneumatic tire having a tread, which is arranged at intervals in the circumferential direction of the tire, and in which the direction of rotation of the tire is specified such that each lug sequentially contacts the outside from the center in the tread width direction, and the equatorial plane of the tire In the cross section parallel to the tread, the angle formed by the side wall on the stepping side of the lug with respect to a line segment connecting the tip edge thereof and the tire rotation axis gradually increases from the center in the tread width direction to the outside, and in the tread width direction. 15 ° or less in the central area and 30 ° in the same end area
A pneumatic tire with a lug characterized by the above.

[0010] Further, the side wall on the step side of the lug in an intermediate area between the center area and the same end area in the tread width direction,
It is preferable that the angle formed with respect to a line segment connecting the tip edge and the tire rotation axis is 20 ° or more.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a tire with lugs according to the present invention. In FIG. 1, reference numeral 1 denotes a crown portion extending across a pair of sidewall portions 2, and the crown portion 1 includes a tread 3 having a pattern shown in FIG. 2. That is, the tread 3 has a large number of lugs 4 extending from the center in the width direction to the outside with respect to the equator O of the tire at an angle of, for example, about 30 to 50 °, alternately on both sides of the equator O of the tire. The rotation direction D of the tire is specified such that each lug 4 sequentially contacts the center from the center in the tread width direction to the outside in the tread width direction.

The lug 4 is composed of a side wall 5 on the stepping side in the tire rotation direction D and a side wall 6 on the kicking side facing the side wall 5, and it is particularly important to limit the inclination of the side wall 5 on the stepping side. It is.

That is, FIG. 3A shows a lug portion in the central region C in the tread width direction in FIG. 2 as a cross section parallel to the equatorial plane of the tire, that is, a cross section along the line AA in FIG. In addition, the tip edge E of the side wall 5 on the stepping side of the lug 4
And an angle formed with respect to the line segment L connecting the tire rotation axis R (hereinafter, simply referred to as tilt angle) of alpha _A and 15 ° or less. Similarly, as shown in FIG. 3B, the lug portion in the end region S in the tread width direction is a cross section along the line BB in FIG. 2, and the inclination angle α _B of the lug 4 here is 30 °. Above. Further, the inclination angle of the side wall 5 on the stepping side is gradually increased outward from the center in the tread width direction, that is, from the equator O of the tire.

Here, as shown in JP-A-6-156018 or JP-A-7-232516, when a tire with a rug is used on muddy ground, the inclination angle of the side wall on the side where the rug is depressed is set to 30 °. In this way, until the rug enters and exits the soil, in other words, in the process of stepping and kicking out, the amount of the rug pushing away or excavating the soil is reduced and the running resistance is reduced, as a result, compared to the conventional structure Traction on mud is greatly improved. However, when the inclination angle of the side wall is large, when the rugged tire is driven on a pavement road, the actual traveling distance when the tire makes one revolution due to the slip backward due to the wiping phenomenon is reduced by the tire circumference. Is more likely to be smaller than. In other words, setting the inclination angle of the side wall of the rug stepping side to 30 ° or more is effective for improving traction on muddy ground, but more induces rug slip on a pavement road. .

Therefore, in the present invention, the role sharing of the lugs was studied in order to improve both of the characteristics that are in conflict with each other. In other words, traction on muddy ground depends on running resistance caused by the movement of rugs in the soil,
Generally, in a lug tire in which the lug height gradually increases from the tread width center to the outside, the running resistance on the lug on the tread end side becomes larger than that near the tread width center.
In other words, most of the running resistance of the rugged tire is the running resistance of the lugs in the region from the middle to the outside of the tread width. Therefore, by reducing the running resistance of the lug in this region, the running resistance of the tire is greatly reduced, so that the inclination angle of the side wall on the step side of the lug is set to 30 °.
The region to be described above was limited to the tread edge region.

On the other hand, the upper limit of the inclination angle is preferably set to 50 °. Because, the inclination angle of the lug side wall of this kind of tire is 30 ° in total on the stepping side and the kicking side.
It is customary to design the angle to be up to 40 °. If the angle on the stepping side is increased, the kicking side becomes relatively small, but if the angle on the kicking side becomes −10 ° or less, the angle on the stepping side becomes smaller. As in the case of 30 ° or less, the amount of excavation of the soil by the lugs increases and the traction performance deteriorates, so the side wall angle on the kicking side is -10 ° or more, that is, the side wall angle on the stepping side is 50 ° or less. It is desirable to do.

Next, the amount of slip of the lug on the pavement is strongly affected by the contact pressure on the tread at the tip of the lug. That is, the slip amount tends to increase in a portion where the contact pressure is high. On the other hand, the contact pressure of a lug tire is generally higher on the width center side than on the tread edge. Therefore, the inclination angle of the side wall on the stepping side at the center of the tread width of the lug having a high contact pressure is limited to 15 ° or less. This is because the amount of slip varies depending on the side wall angle, but is substantially equal to a straight line bisecting an angle formed by an extension line of each wall on the stepping side and the kicking side, and a straight line connecting the leading edge of the side wall and the tire rotation center. The slip amount is determined by the angle formed by the slip angle. That is, if this angle (hereinafter referred to as ω) is a positive kick-out angle and the angle is + 10 ° or less, the slip tends to occur in a direction opposite to the traveling direction and the traveling distance tends to be short. Further, as the angle becomes smaller, the traveling distance also becomes shorter. However, when the angle ω exceeds + 10 °, the traveling distance becomes longer because the slip is in the same direction as the traveling direction when the angle ω exceeds + 10 °. Therefore, when the inclination angle on the stepping side is 15 °, the kicking side is 15 ° ~
25 °, and the angle ω is about + 10 °, so that a reduction in the traveling distance due to slip does not occur.

Here, if the angle on the stepping side is set to 15 ° or less as described above, it is possible to prevent the traveling distance from being shortened. However, the longer the traveling distance is, the better it is, and there is an optimum value for each vehicle. If the angle of inclination is set to 5 ° or less, the angle ω increases and the traveling distance becomes too large, so that the rear wheels tend to drag to drag the front wheels during traveling, which is not preferable. Therefore, the lower limit is preferably set to 5 °.

Further, at an intermediate point in the tread width direction,
FIG. 3 is a cross-sectional view taken along the line CC of FIG.
As shown in (c), the inclination of the side wall 5 on the stepping side here is shown.
Oblique angle α _CIs preferably 20 ° or more. sand
In other words, the side wall angle on the lug stepping side is gradually
It keeps growing, but keeps the rate of change constant
And the side wall angle at the midpoint is usually around 25 °.
You. The side wall angle at the midpoint depends on traction and mileage.
I'm both involved, but the bigger the traction the better
On the other hand, the mileage has an optimal value,
At the midpoint, traction is prioritized. This traction
The lower the side wall angle, the better the better.
As a result, the lower limit angle was set to 20 °.

On the other hand, when the side wall angle changes at a constant rate, the angle is about 25 °. When the side wall angle deviates greatly from this value, the change rate of the side wall angle is between the central part and the intermediate point and between the intermediate point and the end part. Will change greatly. When the tire rotates, the lug is in contact with the ground sequentially from the center to the end, but if the side wall angle changes significantly, the amount of lag slip on the ground contact surface will change drastically, adding singular input and causing uneven wear etc. Is not preferred. As described above, the larger the side wall angle at the intermediate point is, the larger the traction becomes. However, for the above reason, it is not preferable to largely deviate from 25 ° when the side wall angle changes at a fixed rate, so the upper limit is set to 30 °. Is preferred.

Further, the inclination angle of the side wall 6 of the trailing side of the lugs, Fig. 3 15-25 ° angle of inclination beta _A in the central region C of the tread width direction (a), the FIG. 3 (b) As shown in the figure, the inclination angle β _B in the same end region S is almost 0 °.
In addition, as shown in FIG. 3C, it is preferable that the inclination angle β _C at the intermediate point M be 10 ° or less and gradually decrease from the equator O toward the outside of the tire. That is, as described above, since the total of the side wall angles of the stepping side and the kicking side is set to a constant value, since the stepping side angle is determined as described above, the kicking side angle is also determined. is there.

Incidentally, in the present invention, the central area C in the tread width direction is defined from the center line O in FIG.
The end area S is obtained by taking a width of 2/5 from O to B inside B, and a point of 1/2 of the width from O to B. Is an intermediate point M.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In accordance with the structure shown in FIGS.
The agricultural tire of 1.2-24-4PR (AG) is shown in FIG.
The inclination angle α _A of the side wall on the stepping side in each part of the lug shown in (a): 8 ° (center area of the tread), and α _B : 35 °
(Tread edge area) and α _c : 22 ° (tread middle area), and similarly, inclination angle β _A of the side wall on the kicking side: 27 °
(Tread central region), the beta _B: 0 ° (the tread edge region)
And β _C : 14 ° (tread middle region).

For comparison, a conventional tire and a comparative tire were manufactured with the same tire size and the inclination angle of the side wall of the lug shown in FIGS. That is, in the conventional tire shown in FIG. 4 with a lug, the inclination angle of the side wall on the stepping side is fixed at 12 °, the inclination angle of the side wall on the kicking side is 25 ° in the center region of the tread, 25 ° in the middle region of the tread, and the tread. The angle was 29 ° in the end area. On the other hand, FIG.
The inclination angle of the side wall on the stepping side was constant at 40 ° and the inclination angle of the side wall on the kicking side was constant at −3 °.

For each of the tires thus obtained, 25
The tractor was mounted on the rear wheel of a horsepower rear-wheel drive tractor, and the traction when traveling on wetlands was measured with a torque meter. Furthermore, the traveling distance of one rotation of the rear wheel tire when traveling on a paved road with a tractor was measured, and the evaluation was made using an index when the measured value of the conventional tire was set to 100. Table 1 shows the evaluation results.

[0026]

[Table 1]

[0027]

According to the present invention, the necessary traction can be secured in muddy terrain, and rug slippage can be avoided, especially on paved roads. An agricultural tire suitable for traveling on a pavement can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view of a tire with lugs.

FIG. 2 is a development view showing a lag pattern.

FIG. 3 is a diagram showing an inclination angle of a side wall of a lug according to the present invention.

FIG. 4 is a view showing an inclination angle of a side wall of a lug of a conventional tire.

FIG. 5 is a diagram showing an inclination angle of a side wall of a lug of a comparative tire.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Crown part 2 Side wall part 3 Tread 4 Lug 5 Side wall 6 Side wall

Claims (2)

[Claims] 1. A plurality of lugs, which extend from the center in the width direction to the outside and incline with respect to the equator of the tire, are provided on a crown portion extending across a pair of sidewall portions on both sides of the equator of the tire. A pneumatic tire having a tread, which is arranged alternately and at intervals in the circumferential direction of the tire, and in which the rotation direction of the tire is specified such that each lug sequentially contacts the outside from the center in the tread width direction to the outside. In the cross section parallel to the equatorial plane of the tire, the angle formed by the side wall on the stepping side of the lug with respect to the line connecting the tip edge and the tire rotation axis gradually increases from the center in the tread width direction to the outside. A pneumatic tire with lugs, characterized in that the angle is 15 ° or less in a central region in the tread width direction and 30 ° or more in the same end region. 2. The vehicle according to claim 1, wherein the side wall on the step side of the lug forms an angle with respect to a line connecting the front end edge and the tire rotation axis with the center area and the same end area in the tread width direction. A pneumatic tire with lugs, wherein the angle is set to 20 ° or more in an intermediate region between the two.