JP3315169B2 - 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 lug shape of a pneumatic tire for a vehicle running on soil, for example, a lug for use in an agricultural tractor or the like.

[0002]

2. Description of the Related Art Conventionally, a so-called lug pattern in which lugs are arranged in a U-shape on a tread surface has been used for a pneumatic tire for traveling on a soil in order to ensure the traveling performance of a vehicle for a muddy land. Especially for agricultural products, high lag patterns with high rug heights were the mainstream in Japan because paddy field work was the center. However, this high lag pattern was of a type that provided great traction on mud, especially on soft soil, but was unsuitable for field work.

[0003]

In Japan, the shift from paddy cultivation to field cultivation has recently increased due to a change in agricultural policy, and cases in which paddy field work and field work are performed simultaneously in parallel have become mainstream. On the other hand, the high rug pattern in the tread pattern of rug tires is manufactured mainly considering paddy field work, and exhibits excellent traction in wet fields, but digs up soil in field work. There are drawbacks such as roughening the field and breaking the ridge because the tread width is larger than the tire width. The present invention has been made in order to solve the above-mentioned drawbacks, and it is possible to perform paddy work while maintaining traction in muddy land, which is an excellent advantage of the conventional high lag pattern, and to dig soil in a field. It is an object of the present invention to provide a pneumatic tire with a lug having a lug suitable for field work, which can prevent ridges and ridge breaks.

[0004]

In order to achieve the above object, in a pneumatic tire with lugs according to the present invention, a pair of left and right sidewalls and a crown portion extending between both sidewalls are connected in a toroidal shape. A lug is provided on the crown portion so as to protrude in a C-shape from the center portion of the crown portion toward both sides in the circumferential direction, and is arranged in the circumferential direction. The tire has a specified rotation direction such that the other end of the lug contacts the ground with a delay, and the stepped side wall of the lug on a cross section parallel to the equatorial plane of the tire is at 35 ° to the radial direction of the tire. What is provided is a taper that is tapered at an average angle of ~ 55 [deg.] While the kickout side wall of the lug forms an average angle substantially parallel to the radial direction of the tire.

[0005]

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 better the traveling performance on the soft ground. However, under the conditions of use of the tire, constraints such as durability and size of the tire, there is a limit on the rug projection area, for example, in order to satisfy the use conditions of both fields, paddy fields, tread width ≤ tire width In this case, the projection area is limited. Then, when the running locus of the rug in the soil was examined, it was found that there were a portion where the rug acted as traction to the soil and a portion which acted as running resistance.

This will be described in detail with reference to FIGS. Here, in order to organize the effect of the tire on the soil, the input to the soil of the tire is Gross Traction, the resistance received from the soil is the running resistance,
Net traction (Net Tractio)
n) In order to improve the traction of so-called rugged tires, it is necessary to improve gross traction and reduce running resistance.

FIG. 4 shows a trajectory of the lug (slip rate 10%) of the conventional pneumatic tire with a lug. In FIG. 1, the lug L is treaded in the circumferential section of the lug on the tread surface T in FIG. the leading side lug side S _f, when considered separately in the trailing side lug side S _k, the mean for the radial direction on the circumferential section of the tire of the trailing side lug side S _k a depression surface as shown in Fig. 2 If the angle is 15 °,
The kicking side and the tread act on the running resistance (a negative force acts on the vehicle traveling), and the stepping side also acts as a resistance to lift the soil when moving away from above. That is, in FIG. 4, the portion of the cross section a ₁ accompanies a ₁ ,
a _2, ... a a _n As you move the portion kicking side lug side resistor R _1, also a portion where part of the R ₂ acts as a tread running resistance, the portion of R ₃ is leading side lug side surface soil It is the part that acts as the lifting resistance, which is the part that serves as the overall resistance, so that it is sufficient to eliminate that part.

Therefore, in the present invention, in order to minimize such running resistance, the average angle with respect to the radial direction on the circumferential cross section of the tire on the kick-out side is -5 ° to + 5 °, preferably 0 °. By setting the angle to -5 ° or more, the running resistance on the side surface of the kick-out lug can be substantially eliminated as shown in FIG. When the angle is set to 5 ° or more, the effect of reducing the running resistance is small, and when the angle is smaller than −5 °, cracks are easily generated at the root of the lug L. Of course it is possible to further reduce the running resistance by minimizing the lug width L _B, on the other hand, when considering the inherent abrasion resistance tires, some lag width L _B of the ground plane constant width above is required, 0.040 × S _.7 ≦ lug width L _B ≦ 0.
085 × _S.7 is preferable. However, 70% width of the maximum width of the tire according to the US FRA standard _S.7 = S _W × _1/13
^{5.6 {180 ° -Sin -1 (R} W / S W)} S W: tire section width, if narrower than R _W = rim width 0.035 S _.7, wear resistance, such as reduction tire lug stiffness durability sex on not preferable, it is difficult to obtain the effect of reducing the running resistance as compared with the conventional high lug tire if wider than 0.085 S _.7.

As described above, the running resistance of the lug can be reduced efficiently by setting the lug kick-out side wall in the range of -5 ° to 5 ° at an average angle substantially parallel to the radial direction of the tire. is there. In addition, the average angle of the side wall on the lug tread side with respect to the radial direction on the circumferential section of the tire is 35 ° to 5 °.
By setting the angle to 5 °, the working volume of the traction based on the shearing force on the soil is increased, the soil can be compacted and run, and the gross traction (Gross Traction) can be improved and the lifting resistance of the soil can be eliminated. In addition, it is possible to reduce the phenomenon of damaging the field. If the average angle of the side wall on the step side of the rug is smaller than 35 °, there is no effect on the lifting of the soil, the field is easily roughened, and
When the angle exceeds °, a phenomenon that the lug L enters the soil first from the root may occur, which is not preferable because it causes running resistance. As described above, the average angle theta ₁ of the inclination of the sidewalls of the depression-side and the kicking-side with respect to the radial direction on the tire circumferential direction cross section of the lug, theta _2, all the lug width L _B by the range described above Tire gross
The traction (Gross Traction) can be improved and the soil running resistance can be reduced efficiently, and the traction performance of the vehicle can be improved.

[0010]

Embodiments will be described below with reference to the drawings. In the pneumatic tire with lugs according to the present invention, the tire body B is formed by a pair of left and right sidewalls S and a crown portion (without reference numeral) extending between both sidewalls S connected in a toroidal shape. The lugs L are inclined in the circumferential direction from the center to both sides from the center thereof, and are arranged so as to protrude in a C-shape deviated by half a pitch on the left and right sides of the equatorial plane C, and the tread surface T of FIG. It is formed as follows. And when rotating the tire in the direction of the arrow, S _f lag L is the leading side sidewall (surface), S _k is the trailing sidewall (surface). Fig. 2 shows the pneumatic tire with lugs.
The average angle of the leading side sidewall S _f lag L in the equatorial plane c parallel to the cross section of the tire as shown in (b) is inclined with respect to radial direction of the tire (hereinafter, referred to as depression Ragutepa.) At 35 ° to 55 ° is inclined tapered, the average angle of inclination kicking side wall S _k is relative radial tire (hereinafter, referred to as the kicking Ragutepa.) - 5 ° be inclined in the range of to 5 °, and the tread surface T Are connected by a smooth curve as shown in FIG. The dotted line in FIG. 2B indicates the lug of the conventional example in FIG. 2A, so that the difference between the two can be clearly understood. FIG. 3 shows a cross section of the pneumatic tire with lugs, and it can be seen that the lugs L are buried in the soil. The 70 of maximum width of the tire as the lug width L _B of the lug L as described in the section of the working
The value of% is specified by _S.7 . The above is the structure of the pneumatic tire with lugs of the present invention.
A pneumatic tire with lugs was applied to AGS11.2-24 4PR, and an actual vehicle test was performed. The following results were obtained.

I. Test method Using a 25-horsepower 4-wheel drive tractor, measure net traction with a load cell, and measure gross traction with a torque meter.
Traction) was measured, and the slip ratio was measured from the running distance and the tire rotation speed.

(1) Specifications of the test tire

(2) Test Conditions The load was a vehicle load, the internal pressure of the pneumatic tire with lugs was 1.2 kg / cm ² , and the test was performed by four-wheel drive running. (3) Field conditions A paddy field having a tillage depth of 10 cm and a slip ratio of 20
%.

II. Test results The index of the net traction, gross traction and soil running resistance of Conventional Example 1 was set to 100, and the values of Conventional Example 2, Examples 1 to 3, and Comparative Examples 1 and 2 were represented by evaluation indexes.

[0015]

From the above results, the lug pneumatic tires of Examples 1 to 3 of the present invention have much less gross traction than that of Conventional Example 1 and a slight decrease in net traction is seen. Despite the reduction in the rug projection area, it was found that the soil running resistance was greatly reduced and the traction was improved, making it suitable for both field and paddy fields.

[0017]

As described in detail above, since the present invention is constituted, excavation of soil while maintaining traction on a muddy ground with a conventional pneumatic tire with a rug having a high lag pattern is performed. In addition, it is possible to provide a lubricated pneumatic tire suitable for field work and paddy field work without causing ridge collapse or the like.

[Brief description of the drawings]

FIG. 1 is a view showing a tread pattern of a pneumatic tire with lugs of the present invention.

FIG. 2A is a side view showing a lug shape of a conventional pneumatic tire with lugs. (B) is a side view showing the shape of the lug of the pneumatic tire with lug of the present invention.

FIG. 3 is a cross-sectional view of the pneumatic tire with lugs of the present invention in a state where lugs are buried in soil.

FIG. 4 is a view showing a cross section of the movement of the rug from stepping into the soil to kicking of the rug during rotation of the conventional pneumatic tire with rug.

FIG. 5 is a view showing a cross section of the movement of the lug from the stepping into the soil to the kicking of the lug during rotation of the pneumatic tire with lugs according to the present invention.

[Explanation of symbols]

B tire body T tread surface S side wall L lag L _B lug width theta ₁ depression Ragutepa theta ₂ kicking Ragutepa

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B60C 11/11-11/117 B60B 15/00-15/02 A01C 11/02

Claims (1)

(57) [Claims] 1. A pair of left and right sidewalls and a crown portion extending between the sidewalls are connected in a toroidal shape,
A lug is provided on the crown portion so as to protrude in a C-shape from the center portion toward both sides in the circumferential direction from the center portion thereof and is arranged in the circumferential direction. The tire has a rotation direction specified such that the other end of the lug is in contact with the ground with a delay, and the stepped side wall of the lug on a cross section parallel to the equatorial plane of the tire is 35 ° to the radial direction of the tire. A pneumatic tire with lugs, characterized in that, while being tapered at an average angle of 55 °, the lug kick-out side wall forms an average angle substantially parallel to the radial direction of the tire.