JP2813125B2 - Pneumatic tire with lug - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire for cultivated land, for example, a pneumatic tire with lugs which is mounted on an agricultural tractor or the like and is used for paddy field work and field work.

[0002]

2. Description of the Related Art Conventionally, a pneumatic tire for agricultural land has a lug-shaped pattern in which a large number of lugs are arranged in a U-shape on a tread surface in order to ensure running performance when traveling on muddy or soft ground. Is used. Especially for agricultural products, high rug patterns with high rug heights were the mainstream in Japan because paddy field work was the center. However, in recent years, the shift from paddy field cultivation to field cultivation has increased due to a change in agricultural policy, and cases that are used for both paddy field work and field work have become mainstream.

[0003]

By the way, the conventional pneumatic tire with lugs of the high lag pattern is manufactured mainly in consideration of paddy field work, and can exhibit excellent traction in muddy places and the like. However, there is a drawback that soil is dug not only in the paddy field but also in the field work, the cultivation is deepened, and the field is exposed.

In the field work, when a tractor or the like travels along a ridge, the tractor travels along the ridge using the width of the sidewall of the tire as a guide. As shown in FIG. 10, the tire has a disadvantage that the ridge 21 is broken by the lug portion 5a exceeding the sidewall width W1 because the tread width W2 is set to be wider than the tire sidewall width W1 which is a guide. there were. An object of the present invention is to solve the above-mentioned drawbacks and to perform paddy work while maintaining traction on muddy or soft lands, which is an excellent advantage of the conventional high lag pattern, and to improve the depth of soil in a field. It is an object of the present invention to provide a pneumatic tire with lugs that suppresses digging. A further object of the present invention is to provide a pneumatic tire with lugs that can be used for paddy field cultivation and field cultivation that prevent ridge collapse in field work.

[0005]

In order to achieve the above-mentioned object, the present invention provides a pair of left and right sidewalls and a crown portion extending from the central portion to the two sidewalls. A lug extending obliquely with respect to the circumferential direction toward the shoulder portion side and protruding in the shape of a letter C, and a tread arranged in the circumferential direction, and the tip portion of the lug at the center side of the crown portion is grounded first. In the case of a pneumatic tire with a lug in which the rotation direction of the tire is specified such that the rear end of the crown shoulder side comes in contact with the ground with a delay, the lug is depressed in the lug cross-sectional shape on a cross section parallel to the equatorial plane of the tire. The side wall has an angle of 30 ° or more with a straight line connecting the tip edge of the side wall and the tire rotation axis, and the width of the tread does not exceed the width of the tire sidewall. In the side wall of the depression side of the lug,
It is formed by connecting linearly from the tip edge of the side wall to the base of the side wall on the kick-out side of the lug adjacent in the circumferential direction.

[0006]

[0007]

The traction performance of a pneumatic tire with lugs is greatly affected by the lug projected area in the tire radial cross section. That is, the larger the projected area is, the more the traction is improved, and the more easily the vehicle travels on a soft ground. However, there is a limitation due to the conditions of use of the tire, durability and size of the tire, and the projection area of the lug is limited.
Further, for example, the projection area is also limited when the tread width is set not to exceed the tire sidewall width in order to satisfy the use conditions of both paddy field cultivation and field cultivation.

[0008] Then, when the running locus of the rug in the soil is examined, when viewed in the horizontal direction, there are a portion where the rug acts as traction to the soil and a portion which acts as running resistance. It was found that when the tires received from the soil, there were parts where the buoyancy (upward) and the sinking (downward) were applied. The operation of the pneumatic tire with lugs of the present invention will be described with reference to FIGS. In FIG. 6, the tire 1 rotates in the direction indicated by the arrow D about its rotation axis m, and the vehicle advances in the direction of the arrow AD. Reference numeral 5 denotes a large number of lugs provided on the tire 1. The lug 5 has a side wall 6 on the stepping side (in the direction of the arrow D indicating the tire rotation direction) and a kick-out side (tire rotation direction D).
(In the opposite direction). The leading edge of the side wall 6 on the stepping side is indicated by A, and the field surface is indicated by Q.

As shown in FIG. 6, when the tire cross section is viewed from the tire rotation axis direction, attention is paid to one lug cross section of the tire.
FIG. 7 shows the position of the side wall 6 on the lug stepping side and the position of the leading edge A at a rolling angle of 5 ° when the tire 1 is rolled at a slip ratio of 10%. 7, the side wall 6 of the lug depression side when the tire is rolling code from the code T ₁ T
_The rolling trajectory progresses in the order of ₁₆ , indicating that the lag is in trochoidal motion. Next, a region where the side wall 6 on the lug stepping side in FIG. 7 acts in the soil is shown as U in FIG.
FIG. 9 shows the area U divided according to the operation contents. In FIG. 9, a region where traction, buoyancy and soil compaction are generated is indicated by T, and a region where settlement force and soil lifting is generated is indicated by S. It is an object of the present invention to make the region S as small as possible and the region T as large as possible.

In order to increase the traction, as in the present invention, in the lug cross-sectional shape on a cross section parallel to the equatorial plane of the tire, the side wall 6 on the stepping side of the lug has its leading edge A
Β with respect to a straight line n connecting the tire rotation axis m and the tire rotation axis m
Is set to 30 ° or more, and the inclination angle β of the side wall 6 is set to be large, so that the side wall 6 on the step side of the rug compacts the soil more downward while acting on the soil, and the rug kicks the solidified soil. Greater traction occurs. Also,
By increasing the inclination angle β so that the cultivator is not deepened, the area T that brings buoyancy and compaction of the soil can be obtained.
Is increased, and the region S that brings the settlement force and the soil lifting action can be minimized.

In the present invention, since the tread width is made smaller than the tire sidewall width, the rug does not exceed the tire width, so that the ridge does not break the ridge. And here, the side wall on the step side of the lug is
Since it is formed so as to be linearly connected to the base of the side wall on the kick side of the adjacent lug, the area of the side wall on the step side can be maximized, and the action of this side wall as described above is promoted. .

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. As shown in FIGS. 1 and 2, a pneumatic tire 1 with lugs according to the present invention has a pair of left and right sidewalls 2 (FIG. 2).
And only one of them is shown in the figure), and a lug 5 extending from the central portion toward the shoulder portion side and extending in the circumferential direction from the center portion thereof to the crown portion 3 extending across the sidewalls 2 and extending over the sidewalls. And a tread 4 protruding in the shape of a letter and arranged in the circumferential direction. Each lug 5 is such that when the tire rotates, the tip of the lug at the center of the crown portion contacts the ground first,
The lug is formed such that the rear end of the lug on the shoulder side of the crown comes into contact with the ground with a delay.

As shown in FIGS. 1 to 3, the lug 5 has a side wall 6 on the stepping side (the direction in the tire rotation direction D) and a side wall 7 on the kicking side (the direction opposite to the rotation direction D). In the lug cross-sectional shape in a cross section parallel to the equatorial plane of the tire (FIG. 3), the inclination angle formed by the side wall 6 on the stepping side of the lug 5 with respect to the straight line n connecting the tip edge A and the tire rotation axis m. β is increased to 38 °. The width W2 in the tire axial direction of the tread 4 provided with a large number of lugs 5 is set to a range not exceeding the tire sidewall width W1. The side wall 6 may be formed in a straight line as shown in FIGS. 3 and 4, but is not limited to this, and may be connected in a concave or convex shape with a large radius curve from the leading edge A to the base.

In the pneumatic tire with lugs according to the embodiment shown in FIG. 4, the side wall 6 on the stepping side of the lug 5 has a leading edge A
And is formed linearly at the base B of the side wall 7 on the kick-out side of the adjacent lug 5 to increase the area of the step-side wall 6. OD is the tire outer diameter, P is the lug pitch number, LH is the lug height, and α is the angle formed by the straight line connecting the tip edge A and the axis m and the straight line connecting the base B and the axis m. Taking the XY coordinates as shown in FIG. 4, the inclination angle β _max of the stepping side wall 6 of this embodiment can be obtained by the following equation.

(Equation 1)

In the pneumatic tire with lugs shown in FIGS. 1 to 3, the inclination angle β of the linear side wall 6 on the stepping side of the lug 5 was set to 38 ° and the inclination angle β was set to 15 °. The lug cross-section locus was analyzed for Comparative Example 1. FIG. 5A is a trajectory diagram of a lug cross section of Comparative Example 1 (β = 15 °).
b is a lag section locus diagram of Example 1 (β = 38 °).
It was found that the tire S of Example 1 had a smaller area S that encouraged the settlement of the tire and the effect of excavating the soil as compared with the tire of Comparative Example 1. Wet field running performance was tested to confirm the effect. Table 1 shows the results.

The method of measuring net traction is as follows. Two tractors are connected via a load cell. A test tire is mounted on the rear wheel of the front tractor, and the traveling speed of the rear tractor is reduced with respect to the front tractor, and the traction generated by the front tractor is measured. The force measured by the load cell is defined as net traction. The rear wheel of the front tractor is equipped with a torque meter that can measure axle torque.

When the tire receives the resistance in the state of sinking in the soil and receives the resistance as the soil running resistance, and the tangential force in the horizontal direction of the tire is defined as gross traction, the relationship between the three is: net traction = gross traction−soil running resistance. It is represented by the following equation. In addition, gross structuring has a relation of gross structuring = axle torque / tire turning radius. The tire slip rate was tested at two levels of 15% and 25%. The net traction and running resistance are indicated by indices when the comparative example is set to 100. The higher the net traction and the lower the running resistance, the higher the wetland performance. Also, with regard to the field workability, it was recognized that the tire of Example 1 did not cause the ridge collapse that the conventional tire of FIG. 10 caused.

[0018]

[Table 1]

[0019]

By increasing the angle of inclination of the side wall on the stepping side of the lug, buoyancy and compaction of the soil can be promoted, and the settlement force and the lifting action of the soil can be minimized, so that traction can be improved. It is useful for paddy cultivation and upland cultivation because it does not cause excessive excavation of soil. Further, the action of the side wall is promoted without breaking the ridge and further maximizing the area of the side wall on the step side of the lug.

[Brief description of the drawings]

FIG. 1 is a plan view of a pneumatic tire with lugs according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a pneumatic tire with lugs according to one embodiment of the present invention.

FIG. 3 is a partially cutaway cross-sectional view showing a lug cross-sectional shape on a cross-section parallel to the tire equatorial plane of the lug pneumatic tire according to one embodiment of the present invention.

FIG. 4 is a partially cutaway cross-sectional view showing a lug cross-sectional shape on a cross-section parallel to the equatorial plane of the tire, showing another lug shape of the present invention.

FIG. 5A is an explanatory diagram showing a trajectory of a lug cross section when the inclination angle β of the step side wall of the lug is 15 ° (comparative example).

FIG. 5B is an explanatory view showing a trajectory of a lug cross section when the inclination angle β of the step side wall of the lug is 38 ° (Example).

FIG. 6 is a cross-sectional view of a pneumatic tire with lugs as viewed from the tire rotation axis direction.

FIG. 7 is an explanatory diagram showing the position of the side wall on the stepping side of the lug when the pneumatic tire with lug is rolled at a slip ratio of 10%.

FIG. 8 is an explanatory view showing a region (U) where the side wall on the step side of the lug acts in soil in FIG. 7;

FIG. 9 is an explanatory diagram showing an area U of FIG. 8 divided according to operation contents.

FIG. 10 is a sectional view showing a conventional pneumatic tire with lugs.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Pneumatic tire with lug 2 Side wall part 3 Crown part 4 Tread 5 Lug 6 Side wall on step side 7 Side wall on kick side β Inclination angle of side wall on step side A Tip edge of side wall on step side B Kick out adjacent lug Root of side wall m Tire rotation axis D Tire rotation direction W1 Axial width of tire sidewall W2 Axial width of tread T Buoyancy, traction generation area S Subsidence force, soil excavation generation area

Continuation of the front page (56) References JP-A-59-73301 (JP, A) JP-B4-78482 (JP, B2) JP-B-46-23161 (JP, B1) JP-B-55-13924 (JP) , B2) JP-B 52-23121 (JP, B2) JP-B 55-242 (JP, B2) JP-B 61-59921 (JP, B2) JP-B 57-32893 (JP, Y2) 50-18245 (JP, Y1) (58) Fields investigated (Int. Cl. ⁶ , DB name) B60C 11/08

Claims (1)

(57) [Claims] 1. A pair of left and right sidewalls, and a lug extending from the central portion toward the shoulder portion of the crown portion extending from the sidewalls and extending over the sidewalls so as to be inclined with respect to the circumferential direction. And a tread protruding in the shape of a letter C and arranged in the circumferential direction, such that the center end of the lug on the center side of the lug contacts the ground first, and the rear end of the crown shoulder side contacts the ground with a delay. A pneumatic tire with a lug in which the rotation direction of the tire is specified, wherein in the lug cross-sectional shape on a cross section parallel to the equatorial plane of the tire, the side wall on the stepping side of the lug and the tip edge of the side wall and the tire rotation axis. The angle formed with respect to the straight line connecting the center is 30 ° or more, the width of the tread does not exceed the width of the tire sidewall, and the side wall on the stepping side of the lug is formed in a circumferential direction from the leading edge of the side wall. adjacent A pneumatic tire with lugs, characterized in that it is formed tied linearly in the base portion of the kick out side wall of the lug that.