JPH06156018A - Pneumatic tire with lug - Google Patents

Abstract

PURPOSE:To provide a pneumatic tire with a lug which can work on a paddy field maintaining traction on a muddy ground, that is an advantage of conventional high-lug pattern, and is suitable for field work which can prevent digging up or furrow breaking of a soil in the cultivated field. CONSTITUTION:A pair of right of left side walls and a crown part between both the side walls continue in the toroidal state, and a tread T in which a lug L is provided in the diverging state is inclined against the circumferential direction from the central part to both sides in the crown part. The rotation direction is specified so that the central part end of the crown part of the lug L lands the first and then, the other end of the lug L lands, and a side wall Sf of the stepping side of the lug L in the cross section in parallel with the equatorial face of a tire is inclined in the tapered state by an average angle theta1 of 35 to 55 degrees against the radial direction of the tire, and a side wall Sk on the kicking out side of the lug L makes an average angle of theta2 in almost parallel with the radial direction of the tire.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rug shape of a pneumatic tire for a vehicle running on soil, for example, a pneumatic tire with a lug used for an agricultural tractor or the like.

[0002]

2. Description of the Related Art Conventionally, a so-called rug pattern in which lugs are arranged in a V shape on a tread surface is used in a pneumatic tire for traveling on soil in order to secure the traveling performance of a vehicle for mud ground. Especially for agricultural products, high rug patterns with high rugs were the mainstream, because paddy field work was the main activity in Japan. However, this high rug pattern was of a type that was not suitable for work in fields, although a large traction force could be obtained especially in soft soil of mud.

[0003]

In Japan, due to the shift of agricultural policy, the shift from cultivation of paddy fields to upland cultivation has recently been increasing, and the case where paddy field work and field work are simultaneously performed is becoming mainstream. On the other hand, the high rug pattern in the tread pattern of rug tires is produced mainly considering paddy field work, and exhibits excellent traction in wet fields, but in field work, dug up soil. There were drawbacks such as roughening the field and breaking the ridges because the tread width was larger than the tire width. The present invention was devised in order to eliminate the above-mentioned drawbacks, and can perform paddy work while maintaining traction on mud, which is an excellent advantage of conventional high rug patterns, and excavation of soil in a field. An object of the present invention is to provide a pneumatic tire with a lug that has a rug suitable for field work that can prevent rising and ridges.

[0004]

In order to achieve the above object, in a pneumatic tire with a lug 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. The crown portion is provided with a tread in which lugs extending from the central portion toward both sides inclining to the circumferential direction in a protruding manner in a V shape are arranged and arranged in the circumferential direction, and the crown portion central side end of the lug is first. In the tire whose rotation direction is specified so that the lug comes into contact with the ground and the other end of the lug comes into contact with the ground later, the side wall of the lug on the stepping side on the cross section parallel to the equatorial plane of the tire is 35 ° with respect to the radial direction of the tire. Provided is that the taper side wall of the lug makes an average angle approximately parallel to the radial direction of the tire while tapering at an average angle of ~ 55 °.

[0005]

The traction performance of the pneumatic tire with lugs is greatly affected by the projected area of the lug in the tire radial cross section. That is, the larger the projected area is, the more the traction is improved, and the traveling performance on the soft ground is also improved. However, under the conditions of use of the tire, the durability and size of the tire, there is a limit to the projected area of the lug, and for example, tread width ≤ tire width to meet the use conditions of both fields and paddy fields. , Which limits the projected area in this case. Then, when the running locus of the rug in the soil was examined, it was found that the rug had a part acting as traction and a part acting as running resistance against the soil.

This will be described in detail with reference to FIGS. 4 and 5. Here, in order to sort out 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,
The output from the vehicle is changed to Net Tractio
n) Therefore, in order to improve the traction of so-called lugged tires, it is necessary to improve the gross traction and reduce the running resistance at the same time.

FIG. 4 shows the running locus (slip ratio 10%) of the conventional pneumatic tire with lugs (slip ratio 10%). 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 surface act on the running resistance (a negative force is applied to the progress of the vehicle), and the tread side surface also acts as a resistance to lift the soil when trying to separate from the top. That is, with the rotating part of the cross-section a ₁ is the wheel in FIG. 4, a _1,
When moving with a ₂ , ... a _n , the R ₁ part acts as the kick-side lug side surface resistance, the R ₂ part acts as the tread running resistance, and the R ₃ part acts as the tread side lug side surface soil. It is a part that acts as a lifting resistance, and since it is a part that acts as a total resistance, it suffices to eliminate that part.

Therefore, in the present invention, in order to suppress such running resistance to a minimum, the average angle with respect to the radial direction is -5 ° to + 5 °, preferably 0 ° on the circumferential cross section of the tire on the kicking side. By setting the angle to be −5 ° or more, it is possible to substantially eliminate the running resistance on the side surface of the kick-side lug as shown in FIG. If the angle is 5 ° or more, the effect of reducing the running resistance is small, and if it is less than -5 °, cracks are likely to occur at the root of the lug L. Further, it is natural that the running resistance can be reduced by making the lug width L _B as small as possible. On the other hand, when the wear resistance inherent to the tire is taken into consideration, the lug width L _B on the ground contact plane is present. A certain width or more is required, and 0.040 x S _0.7 ≤ lug width L _B ≤ 0.
It is preferably 085 × S _0.7 . However, 70% of the maximum width of the tire according to the US FRA standard width S _0.7 = 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 If it is wider than 0.085 S _.7 , it is difficult to obtain the effect of reducing the running resistance as compared with the conventional high lug tire.

As described above, the running resistance of the lug can be effectively reduced by setting the kicking side wall of the lug within the range of −5 ° to 5 ° at the average angle substantially parallel to the radial direction of the tire. is there. Further, the average angle of the side wall of the lug on the step side with respect to the radial direction on the tire circumferential section is 35 ° to 5 °.
By making it 5 °, the working volume of the traction based on the shearing force on the soil becomes large, the soil can be compacted and run, the 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 of the lug on the stepping side is smaller than 35 °, there is no effect on lifting the soil and the field is easily roughened.
If it exceeds 0, a phenomenon may occur in which the root of the lug L first enters the soil, which causes running resistance, which is not preferable. As described above, by setting the average angles θ ₁ and θ ₂ and the lug width L _B of the inclinations of the sidewalls on the stepping side and the kicking side with respect to the radial direction of the lug on the tire circumferential direction cross section to all within the above ranges. Tire gloss
It is possible to efficiently improve the traction (Gross Traction) and reduce the soil running resistance, and improve the traction performance of the vehicle.

[0010]

EXAMPLES Examples will be described below with reference to the drawings. In the pneumatic tire with lugs of the present invention, the tire body B has a pair of left and right sidewalls S, and a crown portion (no reference numeral) extending between both sidewalls S is connected in a toroidal shape, and the crown thereof is formed. 1, the lugs L are inclined from the central portion toward both sides toward the circumferential direction so as to project in the shape of a V with a half pitch shift on the left and right sides of the equatorial plane C, and the tread surface T of FIG. Is formed. When the tire is rotated in the direction of the arrow, S _{f of} the lug L is the step-side wall (face) and S _k is the kick-side side wall (face). When the pneumatic tire with lugs is viewed from the side,
As shown in (b), the step side wall S _f of the lug L on a cross section parallel to the equatorial plane c of the tire has an average angle of inclination with respect to the tire radial direction (hereinafter referred to as step lug taper) of 35 ° to 55 °. The tapered side wall S _k is inclined in the range of −5 ° to 5 ° of the average angle of inclination of the side wall S _k with respect to the radial direction of the tire (hereinafter, referred to as “raised taper lug taper”) to the tread surface T. Are connected by a smooth curve as shown in FIG. The dotted line in FIG. 2B shows the lag of the conventional example of FIG. 2A, and the difference between the two can be clearly seen. Furthermore, the cross section of this pneumatic tire with lugs is shown in FIG. 3, and it can be seen that the lug L is buried in the soil. The lug width L _B of the lug L is 70% of the maximum width of the tire as described in the section of the action.
The value of% _S.7 is specified. The above is the structure of the pneumatic tire with lugs of the present invention.
When applied to AGS11.2-24 4PR, a pneumatic tire with lugs was manufactured and tested in an actual vehicle, the following results were obtained.

I. Test method A four-wheel drive tractor with 25 horsepower was used to measure the net traction with a load cell, while a torque meter was used to measure the gross traction.
Traction) was also measured, and the slip ratio was also measured from the traveling distance and the tire rotation speed.

(1) Specifications of test tire

(2) Test conditions The load was the vehicle load, the internal pressure of the pneumatic tire with lugs was 1.2 kg / cm ² , and the test was carried out by four-wheel drive. (3) Field conditions It is a paddy field, the platter depth is 10 cm, and the slip ratio is 20.
%.

II. Test Results The index of 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 to 2 were expressed by evaluation indexes.

[0015]

From the above results, Examples 1 to 3, which are pneumatic tires with lugs according to the present invention, show substantially the same gross traction as those of Conventional Example 1, and although a slight decrease is seen in net traction, It was found that the running resistance of the soil was significantly reduced and the traction was improved despite the decrease in the projected area of the rug, which was suitable for both field and paddy use conditions.

[0017]

Since the present invention is configured as described in detail above, it is possible to excavate soil while maintaining traction in a mud with a pneumatic tire with a lug having a conventional high lug pattern. It is possible to provide a pneumatic tire with lugs that is suitable for field work and paddy field work, and that does not cause ridge collapse and the like.

[Brief description of drawings]

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

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

FIG. 3 is a cross-sectional view showing a state in which a lug of the pneumatic tire with a lug of the present invention is buried in soil.

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

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

[Explanation of symbols]

B Tire body T Tread surface S Sidewall L Lug L _B Lug width θ ₁ Stepped lug taper θ ₂ Raised lug taper

Claims (1)

[Claims] 1. A pair of left and right sidewalls and a crown portion extending between both sidewalls are connected in a toroidal shape,
The crown portion is provided with a tread that is provided in the shape of a letter V and extends inclining toward the circumferential direction from both sides of the central portion toward both sides, and the treads are arranged in the circumferential direction. A tire whose rotation direction is specified so that the tire comes into contact with the ground and the other end of the lug lags behind, and the step 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 it slopes taper at an average angle of 55 °, while the side wall of the lug on the kicking side makes an average angle substantially parallel to the radial direction of the tire.