JPS63188505A - Low noise pneumatic tire - Google Patents

Abstract

PURPOSE:To lower the rigidity of a pattern without cut-in parts being visualized, by forming put-in parts in the wall surface of each tire radial groove of the pattern only on the forward side in the tire rotating direction so that the wall surface is vertically divided. CONSTITUTION:A plurality of main grooves 1 directed in the tire circumferential direction E-E and grooves 2 directed in the tire radial direction are obliquely crossed with each other so as to form a plurality of blocks 3. Of the forward and rear wall surfaces, in the tire rotating direction R, which define each tire radial groove 2, the forward one is formed therein with a suitable number of cut-in parts 4 which vertically divide the wall surface. With this arrangement, the presence of the cut-in parts 4 is not externally visualized but the rigidity of the forward end, in the rotating direction, of each block, rug or the like of the tread pattern may be lowered. Accordingly, it is possible to attain the reduction of tire noise without the control stability of the tire and the like being deteriorated.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a pneumatic tire that is improved to have low noise characteristics by having grooves on the tread surface extending at least in the tire radial direction, such as a block pattern or a lug pattern. It is related to.

[Prior art]

The noise generated when tires run is largely influenced by the tread pattern and is generally referred to as pattern noise. Conventionally, as a measure to reduce this pattern noise, changing the pitch length, pitch number, etc. of the minimum unit (pitch) of a repeating pattern on the tire circumference has been carried out, and this has been somewhat effective.

Incidentally, among trend patterns, a block pattern formed by grooves extending in the tire circumferential direction and grooves extending in the tire radial direction has a feature of excellent maneuverability on a wet road surface (wet performance). However, in such tires, in order to prevent noise as mentioned above, if the groove depth is made shallower, the groove length is shortened, or the groove width in the tire radial direction is narrowed, etc. There has been a problem in that performance (wet performance, etc.) is degraded, and in extreme cases, the image of the block pattern is also changed, resulting in a decrease in steering stability and ride comfort.

Additionally, the lug pattern formed from grooves in the tire's radial direction has an advantage in that it has excellent traction characteristics on uneven terrain.

However, even in the case of this lug pattern, if the groove depth is made shallower, the groove length is shortened, or the groove width in the tire radial direction is narrowed, the original good condition can be improved in order to prevent noise on smooth road surfaces. This had the disadvantage that the traction characteristics on rough terrain deteriorated.

[Object of the Invention] The object of the present invention is to improve the width and length of the radial groove necessary for the original tire performance in a tire having grooves extending in the tire radial direction on the tread surface, such as a block pattern or a lug pattern. Without changing the groove angle etc.
The object of the present invention is to provide a pneumatic tire that has low noise characteristics particularly in the normal speed range (40 to 60 km/hr).

[Structure of the invention]

A pneumatic tire of the present invention that achieves the above object has a pattern having grooves extending in the tire radial direction at least on the tread surface, and among the front and rear facing wall surfaces forming the tire radial grooves, the wall surface on the front side in the tire rotation direction It is characterized by having a notch that separates the wall surface into upper and lower parts.

In the present invention, as the pattern having grooves extending at least in the tire radial direction, preferably a block pattern, a lug pattern, or a pattern in which these patterns are mainly combined with other patterns such as a rib pattern is applied.

Vibration noise, friction noise, air pumping, etc. are cited as causes of tire noise, but in the case of the block pattern, lug pattern, etc. applied to the present invention, vibration noise is the main cause. . That is, in these block patterns and lug patterns, when the tire rotates and is pressed against the road surface, impact vibrations are applied to the ends of the blocks and lugs in the tire circumferential direction, generating noise.

The present invention is designed to vertically separate only the wall surface on the front side in the tire rotational direction among the front and rear wall surfaces of the tire radial groove adjacent to the block end and lug end that generate such impact vibrations. In this way, a notch is provided for the purpose. By providing this notch, the rigidity of the end of the block and the end of the lug is reduced, thereby reducing the above-mentioned vibration impact force when stepping on the pedal, and reducing the generated vibration energy, making it possible to achieve the desired noise reduction. It can be done. Moreover, such a reduction in vibration impact force can immediately be accompanied by an improvement in riding comfort.

FIG. 1 shows an example of a tread when the present invention is applied to a tire with a block pattern, and the direction indicated by arrow R is the tire rotation direction. 1. -11 is a plurality of leads toward the tire circumferential direction E-E'; 2. −
．． 2 is a groove provided in the tire radial direction so as to diagonally cross these plurality of main grooves l, -91, and the grooves provided on the left and right with respect to the center of the tread surface have different inclination directions.

By intersecting these grooves, a plurality of blocks 3. -..., 3 are formed.

In the present invention, the main groove 1 is formed to be oriented in the tire circumferential direction, and /#2 is formed to be oriented in the tire radial direction, but this tire circumferential direction or tire radial direction does not necessarily mean the complete tire circumferential direction. Alternatively, it does not mean that it is only parallel to the tire radial direction, but it may be oriented in the tire circumferential direction or in the tire radial direction as a whole. Therefore, there is no problem even if it has a zigzag shape or a meandering shape with mixed diagonal parts. Due to such deformation grooves, the shape of the block 3 is not limited to the parallelogram shown in the above embodiment, but may be a deformed shape as shown in FIG. 8.

Furthermore, the pattern formed on the tread by the main groove in the circumferential direction of the tire and the groove in the tire radial direction does not necessarily have to be symmetrical with respect to the center of the tread as in the above embodiment.
It may be asymmetrical as shown in Figure 3.

Of the front and rear wall surfaces forming the groove 2 in the tire radial direction,
One or more (two in the illustrated embodiment) notches 4 are provided on the front wall surface in the tire rotation direction R to separate the wall surface into upper and lower sections. When two or more of these cuts 4 are provided per wall surface, they may be provided with different depths as shown in FIG. 3, or may be provided with the same depth as shown in FIG. 5. Further, the cross-sectional shape of the cut is not particularly limited, and may be a special shape such as a wave-shaped cross-section or a saw-like shape as shown in FIGS. 6 and 7.

Further, the cut 4 does not necessarily have to be parallel to the block surface, but may be made at an angle to the block surface for manufacturing reasons such as vulcanization. Also, the cut 4 does not have to be straight parallel to the tread as shown in Figure 2;
It may also be curved as shown in FIG. Furthermore, the depth of the cut 4 does not need to be the same throughout its length, and may vary as shown in FIGS. 8, 9, and 10, respectively.

However, regardless of the form, the notch 4 provided in the present invention must be cut into the wall surface of the block 3 (that is, the wall surface of the example in the rotation direction R) so as to separate the wall surface vertically. be. By providing such a cut, the presence of the cut 4 cannot be seen from the outside of the tread. In other words, while it looks the same as a conventional block, the rigidity of the block end on the front side in the tire rotation direction R is reduced, and by reducing the rigidity, the impact force applied to the block end by stepping on the tire when rotating is suppressed, reducing noise. It will be possible to reduce the

This noise reduction effect is possible only when the wall surface having the notch is at the front end in the tire rotation direction. In addition, this noise reduction effect is particularly noticeable in 4
This is noticeable in the normal speed range of 0 to 60 km/hr.

Further, in the present invention, in order to make the noise reduction by the above-mentioned cuts more effective, it is desirable that the cut depth D is at least 2ffII11 or more at the deepest part. This is clear from the following experiment.

That is, in order to investigate the substitute characteristics of the block rigidity, a large number of rubber pieces 13 of 20 mm x 15 mm x 8 mm as shown in FIG. make. These test pieces were sheared and deformed by pulling each other in directions F and F as shown in FIG. 11B, respectively.
At that time, the rate of decrease in resistance force (rate of decrease in rigidity) is measured.

The results of this measurement are shown in the graph of FIG.

In FIG. 12, the change in shear rigidity decrease in the tensile direction F (incision direction) is shown by a curved line, and the change in shear rigidity decrease in the direction orthogonal to this is shown by a curve M. From this figure, it can be seen that when the depth D of the cut I4 is set to 2ffIII+ or more, the rigidity in the direction of the cut can be sharply reduced.

Furthermore, in the present invention, if the notches are provided as described above to reduce the rigidity of the block on the front side in the tire rotational direction, the effect of reducing noise can be obtained. As shown by curve M, the block rigidity in the direction perpendicular to the tire rotation direction also decreases, and as a result, the road surface gripping force decreases, resulting in deterioration of steering stability. In order to maintain such steering stability, in the present invention, it is desirable that the area of the notch projected onto the tread does not exceed 1/4 of the total ground contact area of the tread.

Furthermore, in the present invention, it is not necessary to provide notches in all blocks on the tire tread, but at least 5 incisions.
It is sufficient if it is provided in 0% or more blocks. As a block without such a notch, it is preferable to use a block that is part of the shoulder, as shown in the embodiment of FIG. 13, for example.

In the above-mentioned embodiments, the case of a block pattern was explained, but the present invention can be similarly applied to a lug pattern as well as to grooves in the tire radial direction. The present invention can be similarly applied to a pattern that is a combination of rib patterns.

〔Example〕

Both tire sizes are 195/60R14,
Tire A of the present invention has a tread pattern as shown in FIG. 1, and has grooves in the radial direction of the tire with cuts in the rotational direction R of the tire radial grooves on the wall surface of the previous example, and a tread as shown in FIG. 13. Tire B of the present invention, in which grooves in the tire radial direction are cut in the rotational direction R of the tire radial grooves on all the other blocks except for the left and right Tsuyorda blocks, as shown in FIG. 14. It has a tread pattern that is 1/1/1 of the block contact area on the rear wall surface in the rotation direction R of the groove in the tire radial direction for all blocks.
A comparative tire with 2 notches and a conventional tire with no notches having a tread pattern as shown in FIG. 15 were manufactured.

Each of these tires has an internal pressure of 2゜0kg/c.
o! The indoor noise generated during normal rotation was measured while varying the speed under the condition of a load of 350 kg.

The results are as shown in the graph in Figure 16, and it can be seen that the tires A and B of the present invention have a noise reduction of 1 to 2 dB compared to the conventional tires, especially in the normal speed range of 40 to 60 km/hr, by 2 to 4 dB. It can be seen that there is a significant reduction in noise. In contrast, the noise level of the comparative tires was almost the same as that of the conventional tires.

Furthermore, each of the four types of tires mentioned above was mounted on a domestically produced small car and the vehicle was run on a slalom course, and the time required was measured.

As a result, when the time required for conventional tires is expressed as an index of 100, the tire A of the present invention is 102, and the tire B of the present invention is 1.
00, and there is almost no change in steering stability in either case, whereas the comparison tire has a rating of 109, which shows that the steering stability is lower than that of the conventional tire.

〔Effect of the invention〕

As described above, the pneumatic tire of the present invention has a notch that separates the wall surface vertically from the front wall surface in the tire rotation direction among the front and rear wall surfaces of the tire radial groove. The rigidity of the front ends of blocks, lugs, etc. in the rotational direction of the tread pattern is reduced while making the presence of the cuts invisible. Therefore, according to the tire of the present invention, tire noise can be reduced without causing an extreme change in pattern image or deterioration of steering stability as described above.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing a main part of the tread of a pneumatic tire according to an embodiment of the present invention, FIG. 2 is a perspective view showing blocks on the tread of the same tire, and FIG. 3 is an I-I [ 4 is a perspective view of another embodiment corresponding to FIG. 2, FIG. 5.6.7 is a sectional view of another embodiment corresponding to FIG. 3, and FIG. 9.10 is a plan view of a block according to another embodiment, FIG. 11A is a side view of a test piece for measuring a proxy value of block stiffness,
Figure 11B is an explanatory diagram when testing the same test piece;
FIG. 13 is a plan view of the main part of the tread of a tire according to another embodiment of the present invention, FIG. 14 is a plan view of the main part of the tread of a comparative tire, and FIG. 15 is a conventional tire. FIG. 16 is a graph showing the results of an indoor noise test. ■...Leading (in the tire circumferential direction), 2...VN (in the tire radial direction), 3...Block, 4...
- Cut, R... Tire rotation direction.

Claims (5)

[Claims] (1) A pattern having at least grooves extending in the tire radial direction is provided on the tread surface, and of the front and rear facing wall surfaces forming the tire radial grooves, a cut is made only on the front wall surface in the tire rotational direction to separate the wall surface vertically. A low-noise pneumatic tire characterized by the following: (2) The low-noise pneumatic tire according to claim 1, wherein the pattern is either a block pattern, a lug pattern, or a combination of these as main patterns and other patterns. (3) The low-noise pneumatic tire according to claim 1, wherein the depth of the deepest part of the cut is at least 2 mm or more. (4) The low-noise pneumatic tire according to claim 1, wherein the projected area of the cut on the tread surface is within 1/4 of the total ground contact area of the tread surface. (5) The low-noise pneumatic tire according to claim 1, wherein the number of blocks having notches is 50% or more of the total number of blocks of the tire.