JP4608111B2 - Pneumatic tires for construction vehicles - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire for a construction vehicle having a lug pattern that can enhance the heat dissipation effect of a tread used in a heavy-duty vehicle.
[0002]
[Prior art]
In order to improve the wear resistance of a pneumatic tire (hereinafter abbreviated as “tire” as appropriate), a tread rubber having good wear resistance has been used. Also in the tread, methods such as increasing the tread volume, increasing the thickness of the tread gauge, and reducing the negative rate in the tread have been taken.
[0003]
[Problems to be solved by the invention]
By the way, recently, in order to realize the purpose of improving productivity, the increase in size, flattening, and heavy load of the tire size along with the increase in size of the construction vehicle has been advanced. In addition, the speed of vehicles is increasing. Under such circumstances, there is a concern that the heat generation of the tread portion increases due to the increase in the speed of the vehicle, which may cause a failure such as heat separation of the tread portion.
[0004]
That is, heat generation in the tire tread portion is caused by repeated tread compression regions received in the tire contact region, and bending stress generated in the stepping portion and the kicking-out portion. In particular, in a heavy-duty tire for off-the-road where the thickness of the tread gauge is relatively large, the tread volume at the center portion of the tire is increased, and thus heat storage is increased. As a result, the temperature of the center portion becomes high when the vehicle is traveling, causing a heat separation failure.
[0005]
In view of the above-described facts, an object of the present invention is to provide a pneumatic tire for a construction vehicle capable of suppressing tread wear as much as possible and enhancing the heat dissipation effect.
[0006]
[Means for Solving the Problems]
Pneumatic tire for a construction vehicle according to claim 1, the pneumatic tire for a construction vehicle to form a plurality having lug pattern lug groove extending from a shoulder side in the tread to the tire equatorial plane in the tire circumferential direction, the tire A recess is provided in the center region corresponding to 50% of the maximum ground contact width, the negative rate of the center region excluding the lug groove is 10 to 25% , and the depth of the recess is the maximum depth of the lug groove The maximum depth of the lug groove in the center region corresponding to 50% of the maximum tire ground contact width is 60 mm or more .
[0007]
Next, the operation of the pneumatic tire for construction vehicles according to claim 1 will be described.
[0008]
The basic performance required for pneumatic tires, especially heavy duty tires for off-the-road, is how long they can run until they are completely worn out. The tread portion of the tire generates heat when the vehicle travels, but there is a problem especially in the early stage of travel using a new tire when the tread gauge is relatively thick. As a general usage, a new tire is often mounted on the front, but the side force input is large at the front and is particularly affected by heat.
[0009]
Here, since a concave portion is provided in the center region corresponding to 50% of the maximum tire ground contact width and the negative rate of the center region excluding the lug groove is set to 10 to 25%, the heat generation amount of the tread can be reduced, and the tire The surface area of the tire can be increased, and the heat dissipation of the tire can be improved. At the same time, providing a recess in the center region of the tire reduces the tread volume of the tire and causes wear. However, the negative rate within the above range can suppress this wear as much as possible.
[0010]
Note that if the negative rate is less than 10%, the heat dissipation is reduced, and if it is greater than 25%, the tread is likely to be worn. It is possible to achieve both improvement in performance and reduction in wear.
[0011]
Pneumatic tires are used by being mounted on rims defined by standards issued by JATMA (Japan), TRA (US), ETRTO (Europe), etc., depending on the size. It is called a rim.
[0012]
Similarly, “normal load” and “normal internal pressure” refer to the maximum load and the air pressure with respect to the maximum load in the application size / ply rating defined in the standard.
[0013]
Also, in this specification, “tire maximum contact width” means a tire of a tread when a tire is assembled to a “regular rim” and filled with “regular internal pressure” and a “regular load” is statically applied. The maximum ground contact width in the axial direction.
[0014]
Here, the load is the maximum load (maximum load capacity) of a single wheel at the applicable size described in the following standard, and the internal pressure is the maximum load of a single wheel at the applicable size described in the following standard ( The rim is a standard rim (or “Applied Rim” or “Recommended Rim”) in an applicable size described in the following standard.
[0015]
The standard is determined by an industrial standard effective in the region where the tire is produced or used. For example, “The Tire and Rim Association Inc.'s YEAR BOOK (including design guide)” in the United States, “The European Tire and Rim Technical Standards Manual in Japan, Japan ’s Tire” in Japan “Book”.
[0017]
According to the structure of Claim 1, since the depth of the recessed part was made into 10 to 45% of the maximum depth of a lug groove, the heat dissipation of a tread can be improved and abrasion of a tread can be suppressed.
[0018]
That is, if the depth of the recess is made smaller than 10% of the maximum depth of the lug groove, the recess becomes shallow, and the surface area of the tire cannot be increased. If it is larger than 45% of the maximum depth of the lug groove, the rigidity of the tread will decrease and it will be easy to wear. However, by setting the depth of the recess within the above setting range, both heat dissipation and reduction of wear are achieved. Can be made.
Further , according to the configuration of claim 1 , particularly in a large tire having a tire size of 24.00R49 or more, the maximum depth of the lug groove in the center region corresponding to 50% of the tire ground contact maximum width is set to 60 mm or more. In addition, the heat dissipation of the tire in which the tread volume is increased and the heat generation amount is increased can be effectively improved.
[0019]
The pneumatic tire for a construction vehicle according to claim 2 is characterized in that the concave portion is an auxiliary groove formed continuously in the tire circumferential direction.
[0020]
According to this configuration, the concave portion is an auxiliary groove formed continuously in the tire circumferential direction, whereby the air flow can be improved when the tire rolls. For this reason, the heat dissipation of a tire can be improved more.
[0021]
The pneumatic tire for a construction vehicle according to claim 3 is characterized in that the depth of the lug groove gradually decreases from the shoulder side toward the tire equatorial plane.
[0022]
The conventional tire has a structure in which the depth of the lug groove suddenly increases from about 1/8 point to the shoulder side. For this reason, the rigidity distribution of the tread changed rapidly, which had an adverse effect on the tire wear performance.
[0023]
Here, by gradually decreasing the depth of the lug groove from the shoulder side toward the tire equatorial plane, the rigidity distribution of the tread can be made uniform and the wear of the tread can be reduced.
[0024]
Note that “gradually” means that there is no area (platform) perpendicular to the equator plane between the ¼ point and the tire equator plane, and the slope is 1/5 or more of the tread width. It means about 80 degrees with respect to the equator plane (10 degrees with respect to the tire axial direction). “Abrupt” means a state in which the maximum depth of the lug groove is 0 in the above-mentioned setting region. Usually, a platform having a width of about 10% of the tread width (in the tire axial direction) is near the tire equator plane. Is provided.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
[First embodiment]
Hereinafter, a pneumatic tire according to a first embodiment of the present invention will be described with reference to FIG. 1 with reference to the accompanying drawings.
[0028]
As shown in FIGS. 1A and 1B, the tread 12 of the pneumatic tire 10 of the present embodiment (hereinafter abbreviated as “tire 10” as appropriate) faces the tire equatorial plane CL from the shoulder portion. A plurality of extending lug grooves 14 (main grooves) are formed at intervals in the tire circumferential direction (arrow A direction). In addition, one auxiliary groove 16 (concave portion) continuous to the end portion of the lug groove 14 on the tire equatorial plane CL side is continuously provided in the tire equatorial plane CL in the tire circumferential direction. A land portion 18 is provided between adjacent lug grooves 14.
[0029]
In other words, in the tread 12, the area corresponding to 50% (440 mm in the present embodiment) of the tire ground contact width W (880 mm in the present embodiment) on both sides of the tire equatorial plane CL is defined as the center area 20 and the areas on both sides thereof. When the two side regions 22 are formed, the lug grooves 14 are formed so as to gradually decrease in depth from both side regions to the center region 20, and in particular, the maximum depth in the center region 20 is 60 mm or more ( In the present embodiment, the depth D at the ¼ point (distance of W / 4 from the tire equatorial plane CL) is set to 85 mm. Moreover, the negative rate (the lag groove 14 is a negative part) in the center area | region 20 is set within the range of 15-25%.
[0030]
On the other hand, the auxiliary groove 16 is formed in the center region 20, and the negative rate (the auxiliary groove 16 is a negative portion) in the center region 20 excluding the lug groove 14 is set to 10 to 25% by the formation of the auxiliary groove 16. ing. The depth d of the auxiliary groove 16 is set to 10 to 45% of the maximum depth of the lug groove 14. In the present embodiment, the depth d is 12 mm, and the width H of the auxiliary groove 16 is set to 50 mm.
[0031]
Note that the number of auxiliary grooves 16 is not limited to one, and may be any number as long as the above setting is satisfied.
[0032]
The physical properties of the tread rubber used in the tread 12 are as follows: tan δ at room temperature (25 ° C.) is 0.05 to 0.4, and Young's modulus (E ′) is 3 × 10 6 to 20 × 10 6 (Pa ) Is preferred.
[0033]
Next, the operation and effect of the pneumatic tire 10 will be described with reference to FIGS. 4 and 5.
[0034]
First, FIG. 4 and FIG. 5 will be described.
[0035]
FIG. 4A is a graph showing the relationship between the wear index (vertical axis) and the negative rate (horizontal axis) of the center region 20 excluding the lug groove 14, and (B) is the temperature reduction effect (vertical axis). And a negative rate (horizontal axis) of the center region 20 excluding the lug groove 14.
[0036]
FIG. 5A is a graph showing the relationship between the wear index (vertical axis) and the ratio of the depth of the auxiliary groove 16 to the maximum depth of the lug groove 14 (horizontal axis), and (B) shows the temperature reduction effect. 5 is a graph showing the relationship between the (vertical axis) and the ratio of the depth of the auxiliary groove 16 to the maximum depth of the lug groove 14 (horizontal axis).
[0037]
In FIG. 4, the depth of the auxiliary groove 16 is 15% (constant) with respect to the maximum depth of the lug groove 14. In FIG. 5, the negative rate of the center region 20 excluding the lug groove 14 is It is a value at 12.5% (constant).
[0038]
Also, the solid lines in FIGS. 4 (A) and 5 (A) are curves in the case where the lug groove 14 formed gradually shallower from the 1/4 point to the tire equatorial plane CL is set, and the dotted line is the 1/8 point. It is a curve at the time of setting the lug groove 14 which becomes deep rapidly from (distance of W / 8 from the tire equatorial plane CL).
[0039]
Further, the “wear index” in the figure is a value expressing the time until the belt disposed inside the tire 10 is exposed in the center region 20 (between ¼ points) (hereinafter referred to as “belt out”). “Temperature” is the average temperature in the center region 20 (between ¼ points).
[0040]
When the tire 10 rolls and the tread 12 repeatedly bends and deforms, the tread 12 generates heat. However, in the tire 10 of the present embodiment, the auxiliary groove 16 is formed in the center region 20 of the tread 12, so the center region 20 That is, the tread volume in the vicinity of the tire equatorial plane CL is reduced, and the compressive stress in the center region 20 is alleviated, so that the heat generation near the tire equatorial plane CL is reduced and the surface area of the tire 10 is increased. And the temperature rise near the tire equatorial plane CL during rolling can be suppressed.
[0041]
Further, as shown in FIG. 4, by forming the auxiliary groove 16, the negative rate in the center region 20 excluding the lug groove 14 is set to 10 to 25%, so the reduction in tread volume can be suppressed as much as possible. The wear of the tread 12 can be suppressed as much as possible. As a result, it is possible to achieve both the temperature reduction effect of the tread 12 and the reduction of wear.
[0042]
In addition, as shown in FIG. 5, by setting the depth of the auxiliary groove 16 to 10 to 45% of the maximum depth of the lug groove 14, it is possible to suppress a decrease in rigidity of the tread 12 as much as possible. The effect of reducing the temperature and reducing wear can be realized.
[0043]
In addition, since the depth of the lug groove 14 is formed gradually shallower from the shoulder side toward the tire equatorial plane CL, the rigidity distribution of the tread 12 becomes constant and may adversely affect the wear performance of the tire 10. Absent.
[Second Embodiment]
Next, a pneumatic tire 30 according to a second embodiment of the present invention will be described.
[0044]
In the present embodiment, the configuration overlapping with the pneumatic tire 10 of the first embodiment will be omitted as appropriate, and the overlapping configuration will be described with the same reference numeral.
[0045]
As shown in FIGS. 2 (A) and 2 (B), the pneumatic tire 30 of the present embodiment has a tire circumferential direction at a position approximately 1/8 of the land portion 18 located between the adjacent lug grooves 14. A plurality of auxiliary grooves 32 extending in the direction of arrow A are formed. The auxiliary groove 32 is formed in a rectangular shape, and an end portion in the tire circumferential direction extends to the adjacent lug groove 14.
[0046]
In the present embodiment, the auxiliary groove 16 formed in the tire equatorial plane CL has a width H of 50 mm and a depth d of 35 mm. The auxiliary groove 32 formed at the 1/8 point has a width S of 25 mm and a depth t of 35 mm.
[0047]
Further, the pneumatic tire 30 of the present embodiment has a maximum tire ground contact width W of 1200 mm (one side of 600 mm), a distance from the tire equatorial plane CL to 1/4 point of 300 mm, and the lug groove 14 at 1/4 point. The depth D is 89 mm.
[0048]
Also in the pneumatic tire 30 of this embodiment, the effect similar to the effect which the pneumatic tire 10 of 1st Embodiment show | plays can be show | played, and the improvement of a thermal radiation effect and suppression of abrasion can be aimed at.
[Third embodiment]
Next, a pneumatic tire 40 according to a third embodiment of the present invention will be described.
[0049]
In the present embodiment, the configuration overlapping with the pneumatic tire 10 of the first embodiment will be omitted as appropriate, and the overlapping configuration will be described with the same reference numeral.
[0050]
As shown in FIGS. 3 (A) and 3 (B), the pneumatic tire 40 of the present embodiment has a circular auxiliary groove at the position of approximately 1/8 point of the land portion 18 located between the adjacent lug grooves 14. A plurality of 42 are formed.
[0051]
In the present embodiment, the width H of the auxiliary groove 16 formed on the tire equatorial plane CL is 50 mm and the depth d is 35 mm. The auxiliary groove 42 has a diameter R of 70 mm and a depth l of 20 mm.
[0052]
Further, the pneumatic tire 40 of the present embodiment has a tire grounding maximum width W of 1200 mm (600 mm on one side), a distance from the tire equatorial plane CL to 1/4 point of 300 mm, and the lug groove 14 at 1/4 point. The depth D is 89 mm.
[0053]
Also in the pneumatic tire 40 of this embodiment, the effect similar to the effect which the pneumatic tire 10 of 1st Embodiment show | plays can be shown, and coexistence with the improvement of a thermal radiation effect and suppression of abrasion can be aimed at.
[0054]
Other than the circular auxiliary groove 42, a tangible self-closing groove such as an ellipse may be used.
[Test example]
Next, the test results of the pneumatic tires 10, 30, and 40 of the above embodiments will be described.
[0055]
The pneumatic tires 10, 30, and 40 of the above embodiments were mounted on regular rims, and wear performance evaluation and heat generation performance evaluation were performed. The test results are shown in the table shown in FIG. Here, the “wear index” in the table is an index obtained by indexing the running time until the belt comes out between ¼ points in actual practice. Therefore, it means that it is easy to wear, so that a value is small. “Temperature” is an average temperature between ¼ points after running on a drum for 24 hours under normal internal pressure and normal load.
[0056]
According to this table, the average temperature of the pneumatic tire 10 of the first embodiment (tire size ORR 37.00 R57) can be reduced by 4 ° C. compared to the conventional pneumatic tire in which the auxiliary groove 16 is not formed. It was. In addition, the wear index could be reduced to 2 points.
[0057]
About the pneumatic tire 30 (tire size ORR 55 / 80R63) of the said 2nd Embodiment, the average temperature could be reduced 6 degreeC with respect to the conventional pneumatic tire. Also, the wear index could be kept at a 4 point drop.
[0058]
About the pneumatic tire 40 (tire size ORR 55 / 80R63) of the said 3rd Embodiment, the average temperature could be reduced 7 degreeC with respect to the conventional pneumatic tire. Also, the wear index could be kept at a 4 point drop.
[0059]
From the above test results, in any of the pneumatic tires 10, 30, and 40 of the respective embodiments, the temperature is decreased by 3 ° C. or more without lowering the wear index by 5 points or more as compared with the conventional pneumatic tire. It was found that both temperature reduction and wear suppression can be achieved.
[0060]
【The invention's effect】
According to the pneumatic tire of the present invention, it is possible to suppress the tread wear as much as possible and enhance the heat dissipation effect.
[Brief description of the drawings]
FIG. 1A is a plan view of a tread of a pneumatic tire according to a first embodiment of the present invention, and FIG. 1B is a tread 1 (B) -1 (B) line shown in FIG. It is sectional drawing.
2A is a plan view of a tread of a pneumatic tire according to a second embodiment of the present invention, and FIG. 2B is a tread 2 (B) -2 (B) line shown in FIG. 2A. It is sectional drawing.
3A is a plan view of a tread of a pneumatic tire according to a third embodiment of the present invention, and FIG. 3B is a tread 3 (B) -3 (B) line shown in FIG. 3A. It is sectional drawing.
FIG. 4 shows the relationship between the wear index (vertical axis) and the negative rate of the center region excluding the lug groove (horizontal axis), and the temperature reduction effect (vertical axis) and the negative rate of the center region excluding the lug groove (horizontal axis). It is the graph which showed the relationship with an axis | shaft.
FIG. 5 shows the relationship between the wear index (vertical axis) and the ratio of the depth of the auxiliary groove to the maximum depth of the lug groove (horizontal axis); It is the graph which showed the relationship with the ratio (horizontal axis) of the depth of a groove | channel.
FIG. 6 is a table showing test results in the pneumatic tire of each embodiment of the present invention.
[Explanation of symbols]
10, 30, 40 Pneumatic tire 14 Lug grooves 16, 32, 42 Auxiliary grooves (recesses)
18 Land

Claims (3)

In a pneumatic tire for construction vehicles having a plurality of lug grooves extending from the shoulder side toward the tire equatorial plane in the tread in the tire circumferential direction, and forming a lug pattern,
A center region corresponding to 50% of the tire ground contact maximum width is provided with a recess, and the negative rate of the center region excluding the lug groove is 10 to 25% ,
The depth of the recess is 10 to 45% of the maximum depth of the lug groove,
A pneumatic tire for construction vehicles, wherein the maximum depth of the lug groove in the center region corresponding to 50% of the maximum tire ground contact width is 60 mm or more . The pneumatic tire for a construction vehicle according to claim 1, wherein the concave portion is an auxiliary groove formed continuously in the tire circumferential direction. The pneumatic tire for a construction vehicle according to claim 1 or 2, wherein the depth of the lug groove gradually decreases from the shoulder side toward the tire equatorial plane.

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