JPH05155204A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To reconcile the traveling performances on a general road, and a field, etc., by specifying the respective negative ratio and groove volume ratio of the whole, the side, and the center of a tread face, and also, selecting a tread pattern. CONSTITUTION:Plural pieces of lug grooves opened to tread ends are arranged, at nearly regular intervals in circumferential direction of a tire, at both side divisions 2 of a tread face 1. And, the ratio of the total groove area to the apparent total area of the tread face is made 50-80%, and also the ratio of the total groove volume to the apparent total volume of the tread part is made 3-60%. Moreover, the respective indexes in the tread center division when the ratios of the total groove area and the total groove volume in either of both side divisions 2 of the tread face are 1 in index are specified as 0.3-1.0. The respective lugs extending in the side divisions are separated at the center part 3 by a sub groove 6. This divided lugs 5 are extended obliquely upward toward the tread ends from the center, and are arranged alternately in circumferential direction, differentiating the phase by the amount of a half pitch.

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 a light truck, which is capable of sufficiently traveling from a general road to a soft land such as a field, a mud, a sandy land, and the like. Relates to the structure of the tread portion.

[0002]

2. Description of the Related Art In the field of agricultural work, for example, when transporting harvested products, a normal small truck or other transport vehicle is used, and it is run on a general road at a normal speed.
While parked on soft ground such as in the field, in mud, sand, etc. and waiting, in the field, harvest the harvest using a tractor equipped with agricultural tires called high lag tires. For example, transport the harvested cargo loaded on a tractor to a small truck, transfer it to a small truck, and then drive the harvested truck to the market, warehouse, etc. It has been widely and generally carried in conventionally.

In other words, tires for light trucks running on general roads are required to have high-speed running property, wear resistance performance, vibration riding comfort, etc., while tires for tractors working in the field. Tires are required to have traction performance on soft ground and the like, and accompanying mud-repellency and flotation performance, so that some small trucks equipped with tires for running on general roads cannot drive in the field. On the other hand, some tractors equipped with agricultural tires cannot drive on ordinary roads and provide excellent wear resistance, vibration ride comfort, etc.
For crops and other items, the above-mentioned reshipment was essential.

[0004]

However, in recent years, due to labor shortages, the aging of agricultural workers, etc., various types of work have become light labor, and in particular, crops and other small-sized tractors are used. There has been a strong demand for eliminating the need for reloading work on trucks and vice versa, which requires tires to have both running performance on ordinary roads and running performance in the field. It is necessary to give sufficient performance.

Therefore, the present invention provides a pneumatic tire, particularly a pneumatic tire, capable of sufficiently exhibiting traction performance and the like in a field while ensuring performance such as abrasion resistance and vibration riding comfort when traveling on a general road. Providing radial tires.

[0006]

Means for Solving the Problems The inventor has conducted a detailed investigation of the work site as described above, and as a result of repeated research and development from various aspects, in order to make the traveling performance compatible with both the general road and the field. First, the groove ratio occupying the entire tread surface, in other words, the negative ratio should be set to a completely different range from that of the conventional tire. Secondly, each side area and central area in the tread width direction. Selecting a negative rate and a groove volume rate, and a third
Has found that choosing a tread pattern is important.

The pneumatic tire of the present invention is a combination of the above-mentioned points most appropriately, and more specifically, a lug groove opening at the tread end is provided in at least both sides of the tread tread. In the tire circumferential direction, for example, when a plurality of tires are arranged at substantially equal intervals, the ratio of the total groove area to the apparent total area of the tread is 50 to 80%, and the apparent total area of the tread portion is When the ratio of the total groove volume to the volume is set to 30 to 60% and the ratio of the total groove area in any one of the side areas of the tread tread is set to an index 1, the index in the tread central area is given. 0.3 to 1.0, and the index in the tread central area is 0.3 to 1 when the ratio of the total groove volume in any one of the side areas is set to 1.
It is assumed to be 0.

Here, the tread tread means a ground contact portion including a groove portion when a tire is mounted on a specified rim to be filled with a specified internal pressure and a static load is applied when a specified load (100%) is applied. , Tread width, the ground contact width under the same conditions, and the apparent total area of the tread tread means the tread tread's total tread surface area including the groove, respectively. The side section and the central section, when referring to the area, in the cross section in the tread width direction, the outer side of the tread tread surface is divided into three parts in the tread width direction. When referring to the volume, it means each part divided by the normal line set up on the outer contour line of the tread at each of these trisecting positions.

Further, the apparent total volume of the tread portion means the outer surface of the outermost belt layer and its extension in the tread widthwise cross section under the condition that the tire is mounted on the specified rim and filled with the specified internal pressure. It means the volume including the tread rubber and the lug groove portion located on the outer peripheral side of the line.

By the way, more preferably, in this tire, each lug defined by the lug groove extends obliquely upward from the tread center side toward the tread end in a front view of the tire, so-called directionality. The lugs are arranged in a pattern and are arranged alternately in the tire circumferential direction with a phase difference of, for example, a half pitch, between the lugs located apart from the tread center.

Further preferably, each lug extending to each side area is extended to a central portion of the tread and is separated by a sub-groove shallower and narrower than the lug groove, and the lug has a central portion of the tread. By arranging the side edge at a position that does not exceed the tread center, the end portion of the tread center side of each lug,
Avoid overlapping in the tread width direction. More preferably, the auxiliary groove is formed continuously in a zigzag shape in the tire circumferential direction.

Preferably, each lug is provided with an auxiliary groove that is shallower and narrower than the lug groove, and more preferably each auxiliary groove extends substantially parallel to the tread center. Here, the width of each of the auxiliary groove and the auxiliary groove is set to 3 to 15% of the tread width, and the depth thereof is set to 20 of the lug groove depth near the quadrant of the tread width from the tread center.
It is preferably set to 80%. The depth of the lug groove in the vicinity of the quarter position of the tread width from the tread center is preferably 10 to 20 mm. More preferably, the crossing angle of the tread side wall of each lug with respect to the normal line standing on the tread surface is gradually increased from the tread end side toward the tread central portion side.

[0013]

[Function] In this pneumatic tire, the ratio of the total groove area to the apparent total area of the tread surface is 50 to 80%, preferably 60 to 70%, and the total groove volume to the apparent total volume of the tread portion is also set. 30 ~ 60%, preferably 35 ~ 55
By setting it as%, both the running performance on the general road and the traction performance on the field are achieved.

That is, when the ratio of each of these is set to a value less than the lower limit value, the traction performance in the field, especially in the mud, cannot be effectively exerted, and the mud discharge performance is improved. On the other hand, if the value exceeds the upper limit of each ratio, wear resistance performance on a general road, vibration riding comfort, etc. cannot be secured, and especially, the rigidity of the land portion in the central area of the tread If it becomes too low, the steering stability on ordinary roads will be significantly reduced.

Further, here, when the ratio of the total groove area in any one of the side regions of the tread is set to an index of 1, the index in the central region of the tread is 0.3 to 1.0,
Preferably, it is in the range of 0.5 to 0.9, and the ratio of the total groove volume in either one of the side regions is an index of 1.
The index in the central area of the tread is 0.3 to 1.0
, Preferably in the range of 0.5 to 0.9,
This further improves the running performance on the general road and the traction performance on the field.

In other words, when each index is less than the lower limit value, the running performance in the field, that is, the traction performance is not sufficient, and when the value exceeds the upper limit value,
The running performance on a general road is deteriorated, and particularly, the rigidity of the central area of the tread is lowered, so that the wear resistance performance and the vibration riding comfort cannot be effectively improved.

By the way, in this tire, each lug extending at least in each side area is extended obliquely upward from the tread central portion side toward the tread end in a front view of the tire to form a tread center. On the other hand, when the directional pattern has a V-shaped tendency, the drainage performance and the mud discharge performance can be improved, and the discontinuity on the circumference is eliminated to improve vibration and riding comfort. It is possible to improve the steering stability.

Further, when the lugs which are separated from each other by the tread center are alternately arranged in the circumferential direction of the tire, vibration and riding comfort can be particularly improved (a circumferential discontinuous portion during rotation). Form) together with
Noise can be reduced, and this is particularly remarkable when the phase difference between the lugs in each side area is half the pitch of the lugs.

When each lug extending to each side area is extended to the central part of the tread and separated by a sub-groove shallower and narrower than the lug groove, it is effective for drainage, mud drainage, etc. In addition to the above, it is possible to improve straightness, and in this case, when the end edge of each lug on the center side of the tread is positioned so as not to exceed the tread center, obtain the optimum lug rigidity. It is possible to improve wear resistance and steering stability when traveling on a general road.

Further, when each lug is formed with an auxiliary groove shallower than the lug groove and narrower in width, which extends in the tire circumferential direction, particularly drainage and traction performance,
Furthermore, the straight running performance can be improved. Here, when each auxiliary groove extends substantially parallel to the tread center, it is possible to further improve the straight running performance.

Further, the crossing angle of the side wall of the tread side of each lug with respect to the normal line standing on the tread tread surface is gradually increased from the tread end side toward the tread central portion side, so that the rigidity of each rib is increased. By gradually increasing it toward the section side, wear resistance performance on a general road and vibration riding comfort are secured, and at the same time, under the small intersection angle on the tread end side, drainage performance and traction performance in the field are improved. secure.

Here, the width of each of the sub-groove and the auxiliary groove is set to 3 to 15% of the tread width, and the depth of the sub-groove and the auxiliary groove is set to the lug groove depth near the quarter position of the tread width from the tread center. When it is set to 20 to 80%, it is possible to achieve both traction performance in the field, wear resistance on general roads, and maneuverability.

When the depth of the lug groove from the tread center to the quarter position of the tread width is set to 10 to 20 mm, the traction performance on muddy ground and the steerability on general roads, especially vibration and riding It is possible to achieve both comfort and the like.

Further, when the auxiliary groove extending to the central portion of the tread is formed continuously in a zigzag shape in the tire circumferential direction, the traction performance on muddy ground and the straight running performance on muddy ground and general roads are improved. It is possible to strike a balance.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on illustrated examples. FIG. 1 is a schematic diagram of a tread tread showing a tire front view of an embodiment of the present invention. A radial tire of this example has a size of 155 R12, a specified rim of 4.50 B and a specified internal pressure of 3.5 kg. / Cm ² .

Here, the tread tread 1 having a width W of 128 mm
A plurality of lug grooves 4 opening at respective tread ends ee from each side area 2 to central area 3 of the
Are formed at substantially equal intervals in the tire circumferential direction, so that the respective lugs 5 are formed between the lug grooves.
Partitioning each of the lugs 5 of each side area 2
In a front view of the tire, gradually extending obliquely upward from the tread center portion side toward the tread end ee, and each of the lugs 5 located at the tread center oo is separated in the tire circumferential direction. 1 / the pitch of the lug 5
Position them alternately with a phase difference of 2.

Further, here, the respective lugs 5 extending in the respective side areas are extended to the tread central portion so as to be shallower than the lug groove 4 and narrower in the auxiliary groove 6, in the figure,
Separated in the tread width direction by the sub-grooves 6 that overlap the tread center o-o and extend substantially continuously in a zigzag shape in the tire circumferential direction, and the end edges of each of the lugs 5 on the tread center portion side, Position the tread center oo substantially not to exceed it. Of course, it does not matter if it exceeds some extent.

Further, each lug 5 is provided with an auxiliary groove 7 shallower and narrower than the lug groove 4 so as to extend in the tire circumferential direction, more preferably, the tread center o.
-O is formed so as to extend substantially parallel to each other, and the crossing angle of the side wall on the stepping side of each lug 5 with respect to the normal line set up on the tread is defined by aa line, bb line and As is clear from FIG. 2 exemplifying each cross section of the line cc, the width is gradually increased from the tread end side toward the tread central portion side.

With this structure, the tire also has a ratio of the total groove area to the apparent total area of the tread tread 1 of 65%, and as shown in FIG. 3, the outermost belt layer 8 is formed. Of the outer groove surface and the extension of the outer surface shown by the broken line in the figure, the ratio of the total groove volume to the apparent total volume of the tread portion 9 located on the outer peripheral side is 45%, and in addition, When the ratio of the total groove area in one of the side areas 2 is 68%, the index in the tread central area 3 is 0.88 (60%), and On the other hand, when the ratio of the total groove volume is 48% and the index is 1, the index in the tread central area is 0.77 (37%).
The ratio of the total groove area for the entire tread tread, its ratio in each area, and the ratio of the total groove volume for the entire tread portion, and its ratio in each area are optimized, and as described above, on a general road. Both traveling performance and traveling performance in a field are compatible at a high level.

By the way, in this example, the depth of the lug groove 4 in the vicinity of the quarter position of the tread width W from the tread center oo is set to 15.0 mm, and the center of the tread extends in a zigzag shape in the tire circumferential direction. The example sub-groove is
It has a depth of 7.5 mm, which is much shallower than the lug groove, and has a width of 9.5 mm, which is much narrower than that, and the auxiliary groove 7 formed in each lug 5 is also smaller than the lug groove. It has a much shallower 7.5 mm depth and a much narrower 8.0 mm width.

Further, here, the effect of a so-called directional pattern is ensured by setting the intersection angle α of each lug 5 with respect to the tread end ee to preferably 40 to 80 °. In the illustrated example, the intersection angle α is 65 °.

Further, it is preferable that the angle of intersection of the groove wall of the lug groove 4 and the normal line standing on the tread tread is 10 ° or more from the viewpoint of maintaining mud drainage property and rug rigidity, and the lug thereof. It is preferable that the groove bottom of the groove 4 has a radius of curvature of 10 mm or more in the cross section in the tread width direction, and further, that the tread tread width is 75 to 90% of the maximum tire width, the traction performance and the steering stability. It is preferable from the viewpoint of sex. In this example, the tread width is 82% of the maximum tire width.

Although the embodiments of the present invention have been described with respect to the bilaterally symmetrical pattern, the present invention can be applied to an asymmetrical pattern.

[0034]

[Comparative Example] A comparative test on the running performance of the invention tire, the conventional agricultural tire, and the conventional rally tire having a relatively large total groove area ratio in the field and the general road will be described below. .. Inventive tire Tire described in the examples Agricultural tire Tire having the tread pattern shown in FIG.
Pneumatic tires (size 500-12 with a lug groove depth of 27 mm from the tread center near the quarter of the tread width and a ratio of the total groove area to the total tread tread area of 82%) ). ○ Tire for rally A tire having a tread pattern shown in Fig. 5,
The groove depth is 11.2 mm from the tread center near the quarter of the tread width, and the total groove area ratio is 55.
% Radial tires (size 155 SR12). ○ Test method The running performance on the general road is evaluated by obtaining vibration, riding comfort and steering performance (feeling of the actual vehicle) on the pavement, and the sound is evaluated by measurement and feeling, and running on the field. The performance was evaluated based on the feeling of starting performance, traction, stability, etc. of an actual vehicle in a muddy area. ○ Test results Table 1 shows the results of the above tests.

[0035]

[Table 1]

As is clear from the above test results, according to the present invention, sufficient traction performance can be brought when traveling in the field, and also satisfactory for traveling on general roads. It is possible to exert wear resistance performance, vibration riding comfort, noise, and steering stability to the extent possible.

[Brief description of drawings]

FIG. 1 is a front view of a tread pattern showing an embodiment of the present invention.

FIG. 2 is a sectional view of a lug groove taken along line aa, line bb and line cc of FIG.

3 is a cross-sectional view taken along the line III-III in FIG.

FIG. 4 is a diagram showing a tread pattern of a conventional agricultural tire.

FIG. 5 is a view showing a tread pattern of a conventional rally tire.

[Explanation of symbols]

 1 tread tread 2 side area 3 central area 4 lug groove 5 lug 6 auxiliary groove 7 auxiliary groove 8 outermost belt layer 9 tread e-e tread end o-o tread center

Claims (1)

[Claims] 1. A pneumatic tire having a plurality of lug grooves open at the tread end in the tire circumferential direction in at least both side areas of the tread tread, the total area of the tread tread being apparent. The ratio of the total groove area is 50 to 80%, the ratio of the total groove volume to the apparent total volume of the tread portion is 30 to 60%, and one of the respective side regions of the tread tread, When the ratio of the total groove area is set to 1 and the index in the tread central area is set to 0.3 to 1.0, the ratio of the total groove volume to either side area is set to 1 When, the index in the central area of the tread
0.3 to 1.0, one sub-groove continuously extending in the tire circumferential direction is provided in the center of the tread, and each lug partitioned by the lug groove is viewed from the front of the tire with respect to the sub-groove. Pneumatically characterized in that the lugs are extended in a V-shape, and the respective lugs located apart from the sub-groove are phase-displaced in the tire circumferential direction by a half pitch of the lug arrangement pitch. Included tires.