JPS6045402A - Pneumatic tyre for agricultural vehicle - Google Patents

Abstract

PURPOSE:In a pneumatic tyre having an outer peripheral portion constituted by a number of vane lug parts and small lug parts arranged between the vane lug parts, to reduce vibration of the tyre by specifying lug pitches between the vane lug parts and spacings between the small lug parts. CONSTITUTION:In a pneumatic tyre 3 for agriculture to be mounted on a wheel 2, an outer peripheral portion 19 constituted by a tread surface 17 and outer side surfaces 18 of right and left side wall portions 15 is provided with a number of lugs 20 arranged at pitches R in the peripheral direction and integral with a tyre body 10. The lugs 20 comprise vane lug parts 21 disposed at vane pitches L in the peripheral direction and small lug parts 22 arranged at lug spacings S between the vane lug parts 21, where at least one of lug pitches R between the vane lug parts 21 is established at a value different from another so that the ratio of the maximum pitch/the minimum pitch ranges from 1.2-1.8. Further, the spacing S4 between each vane lug part 21 and the small lug part 22 arranged on the rear row side thereof is set up more widely than another spacing S.

Description

[Detailed description of the invention] This invention relates to agricultural pneumatic tires used for agricultural purposes.

In order to travel through wet fields, wheels for wet fields are equipped with a plurality of blades on the outer periphery of the wheel to provide traction and buoyancy, and between the blade lugs. A large number of small lugs of various shapes are formed to assist in traction and to alleviate vibrations during running.

Conventional wheels include pipe-coated wheels in which rubber is baked on the annular pipe rim.This wheel has approximately the same wall thickness on the vane lug and small lug on the rim, so the rubber does not burn under load. is approximately the same all around the circumference, and vibration during running does not cause problems when the lug pitch interval is the same and the running surface is smooth such as concrete, but it is very large on steady roads or in fields, making the ride uncomfortable. are doing.

Therefore, pneumatic tire wheels have been considered as wheels for driving on rough terrain such as on steady roads and in fields.

This tire wheel has a series of small lugs and no vane lugs.

Therefore, the amount of tire deflection under load is approximately the same in all parts 4, and vibration is reduced compared to a wheel with a pipe seizure.
However, in the field, tires with only small lugs had the disadvantage of weak traction and a high slip rate.

The present invention is designed to provide a blade lug A3 in order to improve performance in the field, and also to reduce vibration. The vane lug part extends to the sidewall part of the tire and has greater rigidity than the small lug part, so there is a large difference in the amount of deflection under a constant load between the vane lug part with a 1st lug pitch and the small lug part. However, it is difficult to effectively reduce vibrations, and good riding comfort has not yet been achieved.

Such tire wheel vibrations are caused not only by the presence of the blade lugs but also by various factors, as shown in Figure 7 (
As shown in 1), a large shock is generated at a constant period during rotation.

By the way, before considering this mechanical vibration, if we consider the vibration of sound, when sound is a pure tone with a single frequency, it can be aggregated into unpleasant noise that can be clearly heard. It is known that by frequency modulating this, the noise is dispersed into many frequencies at a low level V, some of which are mixed with surrounding sounds, and the noise is perceptually reduced.

Such frequency modulation theory of noise (FM Richo) has been applied to the tread pattern of automobile tires and has been demonstrated in Japanese Patent Publication No. 58-22364.

This frequency modulation theory can be applied not only to sound vibrations but also to mechanical vibrations. However, the technical idea of an automobile tire with a constant lug height and rotating at high speed is applied to a tire with vane lugs and It is difficult to apply it directly to tires for wet fields that rotate at extremely low speeds.

Therefore, the present invention is based on such frequency modulation theory,
As a result of repeated experiments taking into consideration the specificity of the application, the product was successfully developed.The aim is to create an agricultural air system that can significantly reduce the maximum impact by creating a required pitch difference in the lug pitch. The main feature of this tire is that a large number of lugs are formed on the outer periphery at intervals in the circumferential direction, and these lugs are connected to a large number of vane lug parts and a predetermined space between each vane lug part. In an agricultural pneumatic tire formed of individually arranged small lug parts, one or more of the lug pitches between the blade lug parts is different from the others, and the maximum pitch is about 1.2 to 5 pitches. 1.8 times, and the gap between each blade lug and the small lug on the trailing side is set wider than the other lug gaps.

Examples of the present invention will be described in detail below.

First, based on Figures 1 to 6, the pneumatic tire (3) of the present invention
Explain the structure of

The pneumatic tire (3) is a tubeless type, and is attached to the wheel (2) to constitute an agricultural wheel (1), and rotates forward in the direction of the arrow in FIG.

The wheel (2) has a disk (4) and a pair of support members (6) that are removably attached to both sides of the outer circumference with bolts and nuts (5), and each support member (6) has a disk (4). ) A rim (7) is formed to protrude in a tapered shape in the radially outward direction and in the off-axis direction from the outer periphery of the rim (7).

Pneumatic tire (3) is attached to the bead part (1) of the tire body QO.
1) is received by the left and right rims (7), and the bead core Oa
Fixed by

In the tire body 0 (l), left and right sidewall portions αF9 extend radially inward from the crown portion 03 via the left and right shoulder portions 0Φ, and the radially inner side of the left and right sidewall portions 0υ is a bead portion αυ. From the tread surface αη, which is the outer peripheral surface of the crown part α3, to the outer surface (to) of the left and right sidewall parts aF9, the outer peripheral part O9 of the tire body αQ
is formed, and a lug pitch (
A large number of lug ridges are provided protruding from n), and these lugs (a) are integrally molded with the tire body QO from an elastic material such as rubber.

The blade lug portions 6 are arranged at a blade pitch (L) in the circumferential direction! and a small lug portion (a) arranged with a lug gap (8) between the blade lug portions (b).

The blade lug section (c) is for obtaining buoyancy and traction force, and extends from the tread surface αη to the sidewall section α.
It is formed to approximately the middle of the outer surface (to) of θ, and the height is the same as that of the small arm.For example, the height is half the width of the tire body OQ, and the width is 2.5 times the width of the tire body αQ. The angle of inclination (θ) with respect to the tire radial center line is set to 50°.

(on the small lug portion) is for obtaining traction force,
It is mainly formed on the tread surface a'i), and is formed in the shape of a substantially hexagonal pyramidal trapezoidal block. Since this small lug portion (A) has a substantially hexagonal truncated pyramid shape, the space (α) formed by the tread surface aη, the small lug portion (A), and the blade lug portion Qη is radially outward from the tread surface αη. It has a wide angle (flaring toward the end) in both directions and outward from the left and right axis from the tread center.

A pointed end (C) is formed approximately in the widthwise center of the leading side of the small lug part in the rotational direction, and serves to cut through the mud when the small lug part (A) is pulled out of the mud. Small lug part (a)
By forming a pointed end (C) on the leading side of the surface, the traction force is slightly reduced as it holds less mud than if it were a flat surface, but it also lifts less mud and sticks to it (C). Even if it sticks, when the mud is pressed during the next rotation, the tip (
c) Separation to the left and right from the space (α)t- filling the space (α)t- is prevented from increasing.

The apex angle ψ) of the pointed end (c) is preferably in the range of 80 to 170°, and the optimum angle obtained by experiment is 110 to 1
If the apex angle ψ) is larger than 170°, it will be difficult to remove the adhered mud, and if it is as small as 80°, a loss in traction force will occur.

In the crown portion α1 of the tire body OQ, a raised portion (C) that is pointed in the radially outward direction is formed in the tread center and is continuous with the pointed portion. This ridge (c)
has a mountain-shaped cross section, and is formed in the area between the small arm part (a) and the small lug part (a) and the blade lug part, and is lower than them.

That is, the height of the raised part (c) is 10~8ON (optimal value about 15~50%)% of the top angle (γ
) is 10 to 100° (optimal value about 20 to 50°),
The top part acts as a watershed, so the tread surface αη
Even if mud adheres to the area, it is pressed down by the mud and the wetland base each time it rotates, so the adhered soil separates from the raised area (c) to the left and right and does not pile up and increase in size. α) can be prevented from being filled with mud.

If this raised part (e) has a high height (h) and a large angle (r), the traction force and buoyancy of the lug will decrease, which will have a negative effect on wet field performance. .

The sludge removal performance of the raised part (c) is reduced, and if the height (h) is high and the angle (γ) is small, the strength of the raised part (c) is low and it becomes easy to break. was gotten.

Approximately center position (P) between the blade lug parts θυ of the tire body αQ
A thick-walled member that protrudes inward is formed on the inner side of the blade lug portion 6!, increasing the rigidity of the tire body at that position compared to other positions. The rigidity is made as equal as possible to that of the main position.

The thick part (E) is formed from the crown part (to) to the middle of the sidewall part αF9, and in the central direction from the central small lug part (A) to the vicinity of the small lug parts (A) before and after it. It is formed. In the illustrated embodiment, the wall thickness (B) is set to half the wall thickness of the crown portion a3, and the circumferential length 9) is set to one quarter of the length between the blade lug portions eη. b) is 30 to 70% (optimal value is 40 to 60%) of the thickness of the crown part α3, and the length box is 60 intervals of the blade lug part (
Although it was found that 10 to 40% of 0 (optimal value is 20 to 30%) is preferable, it differs slightly depending on the shape of the small lug part (a) and the blade lug part Qv. In short, the feather lug part←
By setting the shape of the thick wall part so that the rigidity at the η position and the rigidity at the approximately central position (P) are as small as possible, the amount of deflection at the 1-car position is approximately It becomes mellower, and the difference in the amount of roasting over the entire circumference of the ear (3) is reduced, reducing the vibration of the machine.

Next, the tread pattern will be explained.

The tread pattern of the tire (3) is based on the basic requirement of ensuring the required wet field performance, and taking into account the tire outer diameter and allowable load, the number of blade lugs Qυ is 8 to 10, and the number of blade lugs Qυ is 8 to 10. The number of small lag parts (goods) is set within a range of 1 to 5. In the tire (3) in Fig. 1, the blade lug portion 621) is 9
There are three small lugs (c), making the total number of lugs 36.

In addition, in order to increase the strength when attaching the blade lug part ψυ to the tire body aQ, the rigidity of that part is set higher than that of the small lug part (c). By making the lug gap (84) between the small lug part (A) on the side, that is, the trailing side larger than the other lug gaps (81-81), the load can be reduced compared to the case of the same spacing. The amount of deflection increases and approaches the amount of deflection of the small lug portion (2), reducing the energy of vibration and the maximum value of impact force.

Increasing this lug gap (84) means that the middle l6
11 By using this together with forming a thick wall part (E) on the inside of the central minor arm ridge, the difference in the amount of deflection of the entire tire (3) can be further reduced.

Similarly, since the circumferential length of the ground contact surface of the blade lug Qη is sufficiently shorter than that of the small wing part υ, even if the lug gap (84) is increased, the lug pitch (R4) is smaller than the other lug pitch (
R+ to Rs).

Figures 7 (2) to (7) show the impact force of the modulated wave calculated by the general formula of FM theory, that is, the dispersion state of energy, and the number of blade lags and the number of small lags are used as carrier waves and signal waves. , lug pitch change, blade lug pitch change, and values obtained by converting the rigidity of the blade lug portion into the length of the lug gap (S4), etc. are inserted and calculated. However, in reality, numerical values that include all of these, ie, 36 lag pitches for tire (3), are input into a computer in order in the circumferential direction and calculated.

What is clear from this calculation result is that if the puffer pitches (R) of the lugs (E) are all equal, the vibrations from the blade lug part a°C and the vibrations from the minor blade part are at a constant frequency, and the blade The ratio of the maximum and minimum pitches (Lt to Ls) is Lma
x/Lmin = 1.0, lag pitch (R+ ~R
The maximum and minimum ratio of 4) is Rmax /Rmin =
1.0, and there is only a carrier wave and nothing corresponding to a signal wave, so the FM theory does not hold, and as mentioned above, as shown in Figure 7 (1.
) will result in a large impact force as shown in ().

On the other hand, after keeping the 5-blade pitch (L) constant.

When the maximum-minimum ratio of the lug pitch (Rs to R4) in each blade lug portion (c) was set to Rmaz /Rmin = 1.11, the impact force was dispersed as shown in Figure 7 (2). A small impact force is generated in the place where the large impact force is reduced. This is because the pitch change of the lug pitch (n) becomes a signal wave and modulates the carrier wave of the vibration generated by the single-blade lug portion and the small lug portion.

On the other hand, if we compare the blade pitches (L, , L,) with different minimum-maximum ratios under the condition that the lag pitch (Rs to R4) is set to a constant condition, Figure 7 (6) (7) As shown.

It is clear that changes occur in the magnitude and period of the large impact force and the small impact force, and it is proven that the pitch change in the blade pitch (g) is a signal wave. However, the lag pitch maximum/minimum ratio is Rmaz
/Rmin = 1.92.

Then, as shown in #c7 diagrams (3) to (5), the lag pitch maximum/minimum ratio is set to Rmax/Rmin = 1.2
Set the blade pitch maximum to minimum ratio to 0 to 1.80.
If /Lmin z is set to 1.06 to 1.20, the impact force will be further dispersed and made uniform. The total sum of this impact force is always approximately constant, and although the energy does not decrease, changes in magnitude are reduced and evened out.

The dispersion of impact force due to such pitch variations is at least one of the pitches of one blade (1).

This occurs when at least one of the lug pitches (b) between the blade lug portions (c) is made different from the other pitches, and when all of the blade pitches (L) and lug pitches (R) are made different. Although it is possible to change the pitch, it is difficult to manufacture, and since it combines two types of pitch changes: blade pitch (1) and lag pitch (transport), it is not necessary, and each pitch (L
) (R) It is sufficient to make two to three types of changes for both.

In the table below, the results of the actual vehicle feeling test are evaluated on a 5-point, 14-point scale, where 1 means that all puffer pitches (R) are equal, and 5 is the best. The test was conducted at a speed of 7.9 km/h on a commercially available m6-row Ueda Alt-concrete flat road.

Tire vibrations are not only generated by the tire itself, but are also compounded by various conditions such as road surface irregularities, engine vibrations, and phase differences between the left and right wheels. The results also show that approximately the above-mentioned theoretical vibration mitigation is observed, and the lag pitch ratio is 1.2 to 1.2.
It is clear that by setting the 1.81 blade pitch ratio to 1.06 to 1.2, vibrations can be alleviated to an extent that does not make the human body feel uncomfortable. The lag pitch ratio is 1.8~2.
Even if the blade pitch ratio is set to about 1.20, it is possible to increase the hendolphy'):/I''fr direction A15.

According to the present invention described in detail above, one or more of the lug pitches (b) between the respective blade lug portions Qυ is different from the others, such as the maximum pitch "/
4- (Rmax) is the minimum pitch 4- (Rmin
), the tire vibration generates a signal wave in addition to the carrier wave, and this signal wave modulates the frequency of the carrier wave, thereby dispersing the impact force. Therefore, large impact forces are reduced, all impact forces are evened out, and vibrations that make the human body feel uncomfortable are reduced.

In addition, each blade lug part Qη and the small lug part (a) on the succeeding side
The gap between the small lug (S4) and the other lug gaps (8) is set wider than the other lug gaps (8) to increase the amount of challenge of the highly rigid blade lug (B), so the small lug (A) As the difference in the amount of deflection is reduced, vibration can be further reduced.

[Brief explanation of drawings]

1 to 6 show examples of the present invention, in which FIG. 1 is an overall front view of the tire, FIG. 2 is a partially enlarged view of the tire, and FIG. 3 is a partially enlarged view of the tire.
The figure is a plan view of the blade lug, FIG. 4 is a sectional view of the wheel corresponding to the ff-W line in FIG. 2, and FIG. 5 is a plan view of the small lug.
FIG. 6 #'i The line ■--■ in FIG. 2 is a sectional view of the corresponding element and the wheel, and FIGS. 7 (1) to (7) are graphs showing the theoretical vibrations of seven examples of tread patterns. 111... Agricultural heavy wheels, (3)... Pneumatic tires,
αQ...Tire body, Q91-...Outer periphery, Leopard...Lug, (21)...Blade lug...Small lug part, (to)
... Protuberance, QfQ stomach thickness, (L) ... Blade pitch, (R) ... Lug pitch, (S) ... Lug gap. Patent applicant: Otsu Tire Juuni Company Il Ryoi JP-A-Sho GO-45402 (7)

Claims (1)

[Claims] 1. A large number of lugs (E) are formed at intervals in the circumferential direction on the outer circumferential portion OI, and a predetermined number of lugs are arranged between the lugs, a large number of vane lug parts QD, and each vane lug part (C). In agricultural pneumatic tires formed with a small ridge,
The lug pitch between each of the blade lug parts (c) (one or more of the lug parts is different from the others, the maximum pitch (Rmax') is set to about 1.2 to 1.8 times the minimum pitch (Rmin), and , an agricultural pneumatic tire characterized in that a gap (84) between each blade lug portion Qp and a small lug portion (support) on the trailing side thereof is set wider than other lug gaps (8).