JP2000168313A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of reducing a out-of-car noise at the time of acceleration on level ground without impairing traction capability on off-road place. SOLUTION: A main groove 2 extending in tire circumferential direction is provided in a tread surface 1, and ribs extending in tire circumferential direction is formed dividedly in the main groove 2. Also, lug grooves extending in tire lateral direction from the main groove 2 to both outer sides of a tire beyond tire ground-contact end are disposed at a specified pitch in tire circumferential direction. A tread radius(r) at the time of inflation is set at 25 to 45% of a tire outside diameter X, the lug groove is formed of a shallow groove part 4a on the inside of the tire and a deep groove part 4b extending to the outside of the tire, a groove depth da of the shallow groove part 4a and a groove depth db of the deep groove part 4b are set at 10 to 25% of a groove depth D of the main groove 2 and 60 to 120% of a groove depth D of the main groove 2, respectively, and then a boundary position P of the shallow groove part 4a continuing to the deep groove part side is positioned in the range of 20 to 40% of a tire ground-contact width in the direction from a tire equator line CL to a tire outer side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire having a rib lug pattern formed on a tread surface, while ensuring good traction on uneven terrain while maintaining good traction on uneven terrain. The present invention relates to a pneumatic tire configured to reduce external noise during acceleration.

[0002]

2. Description of the Related Art In general, a pneumatic tire having a rib lug pattern formed on a tread surface is used for a vehicle, such as a dump truck, which travels on both leveled and uneven terrain.
The lug grooves arranged on the shoulder side ensure traction when running on uneven terrain, while the ribs provided on the center side provide steering stability when running on terrain such as paved roads. .

In recent years, there has been a strong demand for reduction of vehicle noise, and a pneumatic tire having a rib lug pattern as described above is no exception. Pneumatic tires provided with lug grooves for ensuring traction on such uneven terrain have a problem that the noise generated outside the vehicle, particularly when accelerating on level terrain, is increased due to the lug grooves. Was.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to reduce external noise during acceleration on level ground, without impairing traction on uneven ground, in a pneumatic tire having a rib lug pattern on a tread pattern. It is to provide a pneumatic tire which can be used.

[0005]

In order to achieve the above object, the present invention provides a main groove extending in a tire circumferential direction on a tread surface,
While the ribs extending in the circumferential direction of the tire are separately formed by the main grooves, lug grooves extending in the width direction of the tire beyond the tire grounding end on both outer sides of the tire from the main grooves are formed at a predetermined pitch in the circumferential direction of the tire. In the arranged pneumatic tire, the tread radius at the time of inflation is set to 25 to 45% of the outer diameter of the tire, and the lug groove is extended to the outside of the tire from the shallow groove portion in which the groove depth inside the tire is reduced. The shallow groove portion has a depth of 10 to 25% of the groove depth of the main groove, and the groove depth of the deep groove portion has a groove depth of the main groove. And the boundary position of the shallow groove portion following the deep groove portion is located in the range of 20 to 40% of the tire contact width from the tire equator line to the outside of the tire.

As described above, in order to reduce the tread radius at the time of inflation to 45% or less of the tire outer diameter, which is much larger than the conventional tread radius generally used, the shoulder portion side with respect to the center side of the tread surface. Can be located on the tire inner diameter side than before. for that reason,
Since the ground pressure on the shoulder portion side of the tread surface where the lug grooves are disposed is lower than in the related art, noise generated by the lug grooves can be reduced.

On the other hand, since the lug groove located on the inner side of the tire is formed in a shallow groove portion having a groove depth shallower than that of the conventional one by making the portion of the lug groove less than 25% of the groove depth of the main groove, the volume of the lug groove is reduced. Accordingly, noise of the lug groove can be reduced. Therefore, it is possible to effectively reduce the noise outside the vehicle at the time of acceleration generated due to the lag groove during the acceleration traveling on the leveling.

[0008] Further, the tread radius at the time of inflation is set to 25% or more of the tire outer diameter, and the contact pressure difference between the center side and the shoulder side of the tread surface is not made extremely large. By securing 10% or more of the groove depth of the main groove and 60% or more of the groove depth of the main groove at the depth of the main groove, it is possible to secure good traction on irregular terrain due to the lug groove. Can be.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be specifically described below with reference to the embodiment shown in the drawings. FIG. 1 shows an example of a pneumatic tire according to the present invention. A tread surface 1 is provided with three zigzag main grooves 2 extending along a tire circumferential direction T. These three main grooves 2 are arranged on the center portion side of the tread surface 1, one extends along the tire equator line CL, and one each is arranged symmetrically on both sides thereof. The main groove 2 is provided on the toret surface 1.
The ribs 3 extending in the tire circumferential direction are formed separately.

A lug groove 4 extending in the tire width direction beyond the tire grounding end E is provided along the tire circumferential direction T on both shoulder portions on both outer sides of the tire from the main grooves 2A arranged on both sides. The pitch is provided. The groove width of the lug groove 4 is configured to be wider than the groove width of the main groove 2.

A single cut-out sipe 5 is arranged on each of the projections 3a formed at predetermined intervals along both sides of the rib 3A formed between the main grooves 2. Only one end of the sipe 5 communicates with the main groove 2 and is a short sipe extending along the tire width direction from the apex of the protrusion 3a in the protrusion 3a.

In the present invention, in the pneumatic tire provided with the rib lug pattern on the tread surface 1 as described above, the tread radius r at the time of inflation is 25 to the outer diameter X of the tire.
45% length.

As shown in FIG. 2, the lug groove 4 includes a shallow groove portion 4a located inside the tire and having a reduced depth, and a deep groove portion extending from the shallow groove portion 4a to the outside of the tire. 4b. Groove depth d _a of the shallow groove portion 4a is formed in a 10% to 25% of the groove depth D of the main groove 2, 60 of the groove depth d _b is the groove depth D of the main groove 2 of the deep groove portion 4b
It is set to ~ 120%. The left and right lug grooves 4 are arranged such that the boundary position P of the shallow groove portion 4a continuing to the deep groove portion 4b side has a tire contact width W of 20 from the tire equator line CL to the tire outside.
It is designed to be located in the range of ４０40%.

As described above, the tread radius r at the time of inflation is set to 0.45X or less, which is much smaller than the tread radius generally used, so that the tread surface 1 on which the lug grooves 4 are arranged is located on the shoulder portion side. In this case, the contact pressure at the tire is made lower than before to reduce the noise generated by the lug groove 4, and the portion of the lug groove 4 located inside the tire is set to a range of 0.25D or less, so that the groove depth becomes lower than before. Is formed in the shallow groove portion 4a having a reduced depth, the noise of the lug groove 4 can be reduced even by reducing the groove volume. As a result, the external noise generated due to the lug groove 4 during acceleration running on level ground is reduced. It can be reduced effectively.

The tread radius r is set to 0.25X or more so that the contact pressure difference between the center portion and the shoulder portion of the tread surface 1 is not made extremely large.
The groove depth d of _a is 0.1D or more, and the groove depth d of the deep groove portion 4b is d.
_{Since b} is secured to 0.6D or more, traction on uneven terrain due to the lug grooves 4 is not impaired.

[0016] The tread radius r is 25 of the tire outer diameter X.
Be less than%, the groove depth d _a of the shallow groove portion 4a is even less than 10% of the groove depth D of the main groove 2, insufficient traction is rough terrain. Conversely, the tread radius r is greater than 45% of the outer diameter of the tire X, even if the groove depth d _a of the shallow groove portion 4a exceeds 25% of the groove depth D of the main groove 2, good low noise effect Is difficult to obtain.

[0017] When the groove depth d _b of the deep groove portion 4b is smaller than 60% of the groove depth D of the main groove 2 also, the traction of the rough terrain is impaired. Conversely, the groove depth D of the main groove 2 is 12
If it is larger than 0%, it is necessary to increase the thickness of the tread gauge in the shoulder portion, so that it is difficult to achieve the tread radius r described above.

When the boundary position P of the shallow groove portion 4a is located on the inner side of the tire from the tire equator line CL to 20% of the tire contact width W, the length of the deep groove portion increases by that amount, so that the groove volume is reduced. However, when the tire is located outside the tire by more than 40% of the tire contact width W, the length of the shallow groove increases by that amount, so that the traction on uneven terrain is increased. This results in a lack of sex.

According to the present invention, in the above embodiment, the main groove 2
Although the case where this is provided has been described, the present invention is not limited thereto.
A tire having a rib-lag pattern in which at least one main groove is provided on the center portion side of the tread surface 1 and lug grooves 4 are arranged on both shoulder portions at a predetermined pitch in the tire circumferential direction. The main groove 2 is formed in a zigzag shape, but may be a straight main groove instead.

The present invention can be particularly suitably applied to a heavy-duty pneumatic tire used for a heavy-duty vehicle which is heavier than a light truck. In the above embodiment, the tread radius r and the tire contact width W at the time of inflation are values when a maximum load and a maximum air pressure are applied when a single wheel is used according to the JATMA standard.

[0021]

EXAMPLE The tire of the present invention and the comparative tire having the structure shown in FIG. 1 in which the tire size was made common to 195 / 85R16 and the tread radius, the groove depth of the shallow groove portion, and the groove depth of the deep groove portion were changed as shown in Table 1. In FIGS. 1 to 5 and FIG. 1, conventional tires having a large tread radius and a lug groove having no shallow groove portion as shown in Table 1 were produced.

In each test tire, the tire outer diameter is 73
The common groove is 8 mm and the depth of the main groove is 10 mm. In the tire of the present invention and the comparative tire, the boundary position P between the two shallow groove portions is located at 35% of the tire contact width from the tire equator line, respectively.

Each of these test tires was rim size 15 × 5
・ Attach to 1 / 2K rim and set air pressure to 600kPa.
Attachment was carried out on a light truck (dump truck), and an evaluation test of traction performance and external noise during acceleration was performed under the following measurement conditions. The results shown in Table 1 were obtained. Traction On an unpaved road, the tractive force of an empty vehicle is measured using a torque meter.
The index value was evaluated. The larger the value, the better the traction. Noise outside the vehicle at the time of acceleration JIS D1024 The test was carried out in accordance with the method for testing the noise outside the vehicle at the time of acceleration of a vehicle, and the result was evaluated by ± using the conventional tire as a reference (0). The larger the value of-, the more the noise outside the vehicle during acceleration is improved.

[0024]

[Table 1] As is clear from Table 1, the tire of the present invention can effectively reduce the external noise during acceleration to -1 dB (A) or less while securing the same level of traction as the conventional tire having good traction. It can be seen that it can be improved.

[0025]

As described above, the present invention relates to a pneumatic tire provided with a rib lug pattern on a tread surface, a tread radius at the time of inflation, a groove depth of a shallow groove portion of a lug groove, and a groove depth of a deep groove portion. By setting the boundary positions of the shallow grooves as described above, it is possible to reduce external noise during acceleration on level ground without impairing traction on uneven ground.

[Brief description of the drawings]

FIG. 1 is a development view of an essential part showing an example of a tread surface of a pneumatic tire of the present invention.

FIG. 2 is a sectional view of a main part of the pneumatic tire of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Tread surface 2 Main groove 3, 3A rib 3a convex part 4 Lug groove 4a Shallow groove part 4b Deep groove part 5 Sipe CL Tire equator line D Depth of main groove E Tire ground end P Boundary position of shallow groove part T Tire circumferential direction X Tire Outer diameter W Tire contact width d _a Groove depth of shallow groove d _b Groove depth of deep groove r Tread radius

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) B60C 11/08 A

Claims (4)

[Claims] 1. A main groove extending in the tire circumferential direction is provided on a tread surface, and a rib extending in the tire circumferential direction is formed by the main groove. In a pneumatic tire in which lug grooves extending in the tire width direction are arranged at a predetermined pitch in the tire circumferential direction, the tread radius at the time of inflation is set to 25 to 4 of the tire outer diameter.
On the other hand, the lug groove is configured to have a shallow groove portion having a shallower groove depth inside the tire and a deeper groove portion extending to the outside of the tire from the shallow groove portion. The depth is set to 10 to 25% of the groove depth of the main groove, the depth of the deep groove is set to 60 to 120% of the groove depth of the main groove, and the boundary of the shallow groove following the deep groove is set. A pneumatic tire whose position is located outside the tire from the tire equator line within a range of 20 to 40% of the tire contact width. 2. The pneumatic tire according to claim 1, wherein the main groove is formed in a zigzag shape. 3. The pneumatic tire according to claim 2, wherein three main grooves are arranged. 4. The pneumatic tire according to claim 3, wherein one sipe extending in the tire width direction is arranged on both sides of the rib formed between the main grooves.