JPH01136802A - Low pressure pneumatic tyre - Google Patents

Abstract

PURPOSE:To improve running, by a method wherein, in a tyre for running on a soft ground for a rice reaping machine, rags extending from the central part of a tread to both sides in an axial direction are situated in a manner to be displaced from each other by a given amount in a circumferential direction, and a ratio of the height of the rag to the outer size of a tyre is specified. CONSTITUTION:Rags 15 and 15 are formed in a range of from a central part 12b of a tread 12 to both sides 12A and 12B in an axial direction. The two rags 15 and 15 are situated in a manner to be circumferentially displaced from each other by a half (1/2P) a rag pitch P. A height H of the rag to an outer size D of a tyre is set so that H/(D-2H) is equal to or smaller than 0.04. This constitution enables improvement of running on a soft ground.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a low-pressure pneumatic tire, for example, a low-pressure pneumatic tire for use on soft terrain, which is installed on rice harvesters, transport vehicles, lawn mowers, leisure vehicles, etc. Regarding low pressure pneumatic tires.

(Conventional technology and its problems) Conventional low-pressure pneumatic tires for soft terrain (hereinafter simply referred to as tires) have, for example, a V-shaped tread on the surface of the tread in order to obtain the driving force necessary for running. The height of the lug is designed to be as high as possible, usually at least 6% of the diameter under the lug (excluding the progeny of the lug from the outer diameter of the tire), and the shear resistance of the soil due to the lug is utilized as much as possible. There are some that have achieved good traction. Such a tire has high traction performance on -C soft ground, so its running performance is extremely good. However, in the case of extremely soft soil, the viscosity of the soil in the surface layer is too low, and as shown in Figure 5, the tire 1 sinks within ±2 due to the wheel load, and the amount of settlement S is The soil resistance T increases.

When the subsidence 1 s is large, when a driving force acts on the tire 1 having lugs with high traction performance, the tire does not run but rotates at that location and digs up the soil around the tire. In this case, the settling 1s of the tire 1 increases more and more, and the resistance T of the soil further increases. There is a problem in that such a vicious cycle occurs, and eventually the vehicle becomes unable to travel.

This tendency is especially noticeable in tires with the same tire width, which have high tread lugs and which make use of the shear resistance of the soil to a large extent, causing them to dig above the soil layer.

Further, the outer diameter of the tire is determined and limited so that there is a certain gap between the tire and the vehicle on which the tire is mounted.

For this reason, the larger the height of the lugs of the tire tread, the smaller the diameter of the tire under the lugs, which reduces the contact area of the tire on soft ground and increases the amount of subsidence S described above.

There is also another conventional tire 5 shown in Fig. 7.8. In FIG. 7, the lug 7 is continuous between both ends 6a of the trend 6 in the axial direction of the tire 5. In this way, when the lugs 7 are continuous in the axial direction of the tire, when the tire 5 sinks on soft ground, as shown in FIG. 7, soil is trapped 8 just before the tire touches the ground. There is a problem that the resistance T further increases.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a low-pressure pneumatic tire that eliminates digging caused by the lugs and increases the buoyancy of the tire, and reduces mud retention by the lugs, thereby making it possible to run on soft ground.

(Means for Solving the Problems) A low-pressure pneumatic tire according to the present invention has a tire that extends approximately axially from the center of the tread to one side and the other side in the circumferential direction from the center of the tread on the surface of the tread. A low-pressure pneumatic tire having a plurality of lugs arranged discontinuously at substantially constant pitch intervals, wherein the lugs on one side in the axial direction of the trend and the lugs on the other side in the axial direction are substantially halved in the circumferential direction. The lug heights H and the tire outer diameter have a relationship expressed by the following formula: %.

Here, the lug height H and tire outer diameter are expressed by the following formula ηη-H/
(D-2H) ≦0.04, that is, the height of the lug is 0.04 or less in accordance with the outer diameter of the tire. This is because if H exceeds 4%, the tire will not be able to obtain sufficient buoyancy when running on soft ground, and the effect of the lugs digging into the soil will increase. Here, when the tire width is the same and the lug height 11 is 2.5% in the previous formula η,
We made four types of prototypes of 4.0%, 5.0% and 7.5%, ran them on soft ground, and tested them for buoyancy and traction.

As a result, 2.5% and 4.0% were good, and 5%
．． 0% was slightly poor, and 7.5% was undrivable.

Further, it is preferable that the lug on one axial side and the lug on the other axial side have a gap spaced apart from each other in the circumferential direction. Here, the void section means that there is no lug in the axial direction. The reason why the lugs on one side and the lugs on the other side are separated in the circumferential direction and have a gap is because this reduces the rigidity of the tire in the circumferential direction, making it easier for the tire to deform on soft ground. This is because it increases buoyancy and is effective in increasing buoyancy. The rate at which the ground contact length increases varies depending on the tire structure and lug rigidity, but it increases by 20 to 50% in this type of low-pressure pneumatic tire. For vehicles that operate on soft soil, rice harvesters, etc., it is necessary to lower the center of gravity of the machine, so the outer diameter of the tires cannot be made too large. Therefore, increasing the contact length with the same tire outer diameter is effective in improving running performance on soft ground. The length of the gap in the circumferential direction is 5 at the center of the tire's equatorial plane.
It is desirable that it is n+ or more, and preferably 10 fl.

Further, it is preferable that the lugs have discontinuous ribs continuous to the lugs in the circumferential direction. Further, it is desirable to provide a substantially circumferential rib having the same height as the lug on the tread center side from a 1/4 point that is 1/4 of the tread width from the trend end of the tread. The reason why the circumferential ribs are provided here is that the lug of the tire of the present invention has a lower height H of the lug and a lower lug between the center line of the lug and the axial direction in order to enhance the effect of the present invention. The mounting angle θ is set to be small, and this has the disadvantage of causing problems in straight running on soft ground and vibrations on general roads, and this is to suppress these problems. The number of circumferential ribs may be one each on one side and the other side of the tread, but preferably there are three in addition to one at the center of the tread. Further, these ribs are preferably located in an area closer to the center of the trend than the 1/4 point of the tire. This is because the ground pressure of the lugs is relatively high in this area, which is effective in improving the straight running performance of the tire and suppressing vibration.

In addition, a belt layer is provided inside the tread, and one to two fiber cord layers are provided at an angle of about 40 degrees or less to the left and right with respect to the tire equatorial plane in the area between the 1/4 points in the center of the tread.
It is desirable to arrange the sheets so that they intersect with each other. This is to make the tread flat.

(Function) The low-pressure pneumatic tire of the present invention has lugs on the surface of the tread that extend substantially axially from the center of the tread to one side and the other side, and are offset from each other by 1/2 pitch in the circumferential direction. Since the height of the lug is low relative to the tire's outer diameter, there is less digging caused by the lug when driving on soft ground, and the outer diameter of the bottom of the lug is larger due to the lower height of the lug. This increases the tire's contact area and increases the tire's buoyancy. In addition, the mud caught by the lugs is pushed left and right in the tire axis direction, and is alternately discharged left and right from between the lugs that are shifted by 1/2 pitch, reducing the amount of mud trapped, reducing the resistance of the soil, and reducing the running speed. Improve your sexuality.

The synergistic effect of these two greatly improves running performance on soft gates.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 1.2 is a diagram showing a first embodiment of a pneumatic tire according to the present invention. First, the configuration will be explained. 1st.
In FIG. 2, 11 is a pneumatic tire, and the tire size is 16×8.0-8 for a rice harvester.

The pneumatic tire 11 has a front part 12a of the tread 12, which extends approximately axially from the central part 12b of the tread 12 to one axial direction 12A and the other 12m, that is, to the left and right when viewed from the outside of the tire, and to the circumferential direction. 1 per side discontinuously arranged at a nearly constant pitch P
It has four lugs 15 each. Center line N of lug 15
Lug installation angle θ1 between Is and the axial direction. is O°~20
° and small.

Lug 15 of axial one-way leg 12A of tread 12. and the lug 153 on the other axial side 12g are provided so as to be offset from each other by 1/2 pitch P in the circumferential direction. pneumatic tire 1
1 has a tire outer diameter of 405 mm and a tread width W of 2.
05 crane, and the height H of the lug 15 is 15 dragon.

The height H of the lug 15 and the tire outer diameter are expressed by the following formula μ, where μ is 0.04, or 4%. A lug 15A of 12 m in the axial direction and the other axial side 12. rug 15
A corridor is a gap in the width direction of the tread 12 where there is no lug 15 (
(shown with diagonal lines in the figure) 17 is provided, and the cavity 1
The circumferential length Ll'l of 7 is Lots. Therefore, the rigidity of the tire decreases, the contact length increases, and the buoyancy of the tire increases. The lug 15 has three circumferentially discontinuous ribs 18 connected to the lug 15 at the same height H1!11 as the lug 15.
511. The rib 18 includes a rib 181 along the tire equatorial plane E and one rib 18A118 between the equatorial plane E and a 1/4 point 19 of the tread width W11.
s is provided. For this reason, the straightness of the tire when traveling on soft ground is increased, and the occurrence of vibrations when traveling on road -a is reduced. Also, on the inside of the tread 12, there is a trend 1
One fiber cord layer 20 between two 1/4 points 19 of 2
A belt layer 21 consisting of the following is provided. fiber cord J
The angle between the direction of the fiber cord of ili20 and the circumferential direction is 60°. For this reason, the tire 11 has an air pressure of 0.1~
When filled with a low pressure of 0.3 kgf/cnl, the flatness of the tread 12 is maintained. The configuration other than the above is the same as that of a normal pneumatic tire.Next, the second and third embodiments of the present invention will be described. 1st
Components that are the same as those in the embodiment are given the same reference numerals.

FIG. 3 is a diagram showing a second embodiment 25 according to the present invention.

In the second embodiment, in the lug 15A on one side and the lug 15a on the other side, the portion 15A and 15□ where the respective center lines Nl5A and Nl5B are inclined with respect to the circumferential direction are long, and the rib 18 is on the equatorial plane. position 18
A and a point near the 1/4 point 19, both of which are provided on one side in the circumferential direction.

Further, FIG. 4 is a diagram showing a third embodiment 27 according to the present invention.

In the third embodiment, the lugs 15 are arranged such that the lugs 15A and 15. In,
This is a case where the lug 15 is bent and the rib 18 is provided only at the equatorial plane E position.

Next, three types of test tires (Example, Comparative Example 1.2) were prepared to confirm the effects of the present invention, which will be described below.

The dimensions and shapes of each part of the test tire are as shown in the table below. (This page, below margins) An example of the test tire is shown in Figure 1.2 above. Comparative example 1 has a lug height of 4.95 in Example 1.
%, and the configurations other than those in the previous table are the same as in Example 1. Comparative Example 2 is a conventional tire in which the lugs are arranged in a V-shape and the lug protrusion is high. The configurations other than those in the previous table are the same as in the embodiment.

In the test, the test tire was assembled on a DT6.5X8 rim, filled with an internal pressure of 0.15 kgf/crA, and then mounted on a 1-row, 2-wheel type rice harvester (binder) with a weight of 90 kg used in clay fields. did. The rice field is 15~
The land has sunk by 16 cm, and there is no water on the surface of the rice field.The water has soaked into the soil and mud has stuck to our feet, making it difficult to walk. A running test was conducted in this rice field to compare the running ability of the rice harvester and the state of subsidence.

As shown at the bottom of the table, the drivability is good.
Bad ones are shown as ×, and those in the middle are shown as Δ.

As shown in the above table, the test results showed that the tires of the Examples had very little sinkage of 5 to 6 cm, and could be run stably by being lightly pushed by hand. In Comparative Example 1, the tire sag was large and tended to sag as the vehicle ran, and could only run after being pushed strongly by hand. Comparative example 2 is
The tire settlement increases as the vehicle runs, and the amount of settlement increases from 12 to 14.
It became impossible to run at cm. As described above, the Example has better running performance on soft ground than Comparative Examples 1 and 2.

In addition, the straight-line performance on soft ground was good, and there was almost no vibration when driving on general roads.

(Effects) As described above, according to the present invention, it is possible to increase the buoyancy of the tire by reducing the digging caused by the lugs, and also to reduce the mud retention caused by the lugs, thereby significantly improving the running performance on soft ground.

[Brief explanation of the drawing]

Fig. 1.2 is a diagram showing a first embodiment of the pneumatic tire according to the present invention, Fig. 1 is a partial plan view thereof, and Fig. 2 is a sectional view taken along the line nn in Fig. 1. be. 3.4 are partial plan views showing 2.3 embodiments of the pneumatic tire according to the present invention, respectively. Figures 5 to 8 are views showing conventional tires, Figures 5.6 and 7.8 are respectively views showing their running conditions and partial plan views thereof. 11.25.27...Pneumatic tires, 12.
...Tread, 12A...One side in the axial direction of the tread, 1211
......Other axial side of the tread, 15.15a
115m...Lug, 17...Gap, 18.18. ．． 18A, 18.・・・・・・Rib, P
······pitch.

Claims (1)

[Claims] On the surface of the tread, there are a plurality of grooves extending substantially axially from the center of the tread to one side and the other side in the axial direction, and discontinuously arranged at substantially constant pitch intervals in the circumferential direction. A low-pressure pneumatic tire having lugs, in which the lugs on one axial side of the tread and the lugs on the other axial side of the tread are provided circumferentially offset from each other by substantially 1/2 pitch, and the lug has a height H.
A low-pressure pneumatic tire characterized in that the tire outer diameter D and the tire outer diameter D have the following relationship: H/(D-2H)≦0.04.