JPS6378805A - Pneumatic radial type - Google Patents

Abstract

PURPOSE:To reduce the generation of pattern noise, by a method wherein, in an automobile tyre for high speed running, a design rib at a central section is divided into auxiliary design ribs by means of an auxiliary groove, and a transverse groove is circumferentially displaced in a position of intersection between main and auxiliary grooves. CONSTITUTION:A tyre tread 12 is partitioned into a central section 17, end sections 18 on both sides by means of a main groove 13, design ribs 20a-20c are formed at the central section 17, and design ribs 21d and 21e are formed at the end sections 18 on both sides. Further, each of the design ribs 20a-20c, 21d, and 21e is divided into two parts by means of an auxiliary groove 23 extending in parallel to the main groove 13 to form auxiliary design ribs 20a1, a2-c1, c2, 21d1, d2, e1, and e2. An S-shaped transverse groove 15 is circumferentially displaced by distances Pa-Pe being 0.5-5 times as long as transverse widths W15a-W15c in positions 23a-23e intersecting the design ribs 20a-20c, 21d, and 21e, respectively. This constitution enables reduction of the generation of pattern noise.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to improvement of so-called pattern noise generated by the tread pattern of pneumatic radial tires, such as tires for high-speed automobiles.

(Prior Art) In general, steering stability performance, vibration riding comfort performance, etc. are very important functions in tires for automobiles that run at high speeds.

In particular, when driving performance on wet road surfaces (wet performance) is important, the tread has multiple circumferential main grooves on the surface of the tread, and transverse grooves that continuously cross the circumferential main grooves (ribs) between the circumferential main grooves. A so-called block pattern is used, which is divided by both grooves.

An example of a conventional tire of this type is shown in FIG. 2. FIG. 2 is a developed plan view of the tread 2 of the conventional pneumatic radial tire 1. FIG. The tread 2 includes a plurality of wide circumferential main grooves 3, a transverse main groove 5 that crosses the circumferential main groove 3 in the tire cross-sectional direction from one end 2a to the other end 2b of the tread 2, and these circumferential main grooves 3. It has a block-shaped ridge 6 formed by the groove 3 and the transverse main groove 5. The so-called block pattern tread 2 having these block-shaped ridges 6 has good wet performance by cutting off a water film on the road surface with the edge 6a of the ridges 6 when running on a wet road surface. There is a problem in that noise caused by the many ridges 6 hitting the road surface, so-called pattern noise, is generated.

In addition, when traveling under load, the edges 6b and 6c of the ridge 6 in the cross-sectional direction of the tire hit the road surface at the same time on the stepping side, which causes the problem that the tire rotation lacks smoothness and vibration ride quality is poor. be.

Therefore, the present invention has been developed to reduce tire pattern noise (
The purpose of the present invention is to provide a pneumatic radial tire with significantly reduced noise.

(Means for Solving the Problems) The present inventors have conducted various studies on the arrangement of tread grooves and ridges, the drainage effect of these on the road surface, the function of each ridge, and the generation mechanism of pattern noise.

As a result, in the tread that is in contact with the wet road surface, water drainage is mainly performed by the wide circumferential main grooves that extend linearly in the tire circumferential direction. In addition, the cutting action of the water film on the road surface is mainly performed by the edge of the transverse groove, and even if the transverse groove is disposed offset in the circumferential direction of the tire, the cutting action of the water film is
If the lengths of the edges of the ridges in the cross-sectional direction of the tire are approximately equal,
It has been found that the water film cutting action is almost the same as in the case where there is no deviation in the circumferential direction.

In addition, the noise caused by such a block pattern tread is caused by the axial direction of the transverse grooves in the central area of the tread, where the ground pressure of the tread is high and air envelopment is large, and the impact force of the ridges on the road surface is large. It has been found that by providing the tread closer to each other in the circumferential direction so that the contact shapes on both sides of the tire equator E of the tread do not become similar during load rolling, it is possible to significantly reduce the amount.

Based on these results, the present inventors further conducted various studies and arrived at the present invention.

That is, the pneumatic radial tire according to the present invention has at least three circumferential main grooves extending substantially parallel to the circumferential direction of the tire on the surface of the tread, and a circumferential main groove extending substantially parallel to the tire circumferential direction on the surface of the tread, and a circumferential main groove extending from one end of the tread to the other end of the tread across the circumferential main groove. A central region having a plurality of transverse grooves extending in an S-shape to the end and arranged at approximately equal intervals in the circumferential direction of the tire, and at least two design ribs partitioned by the circumferential main groove; and a design rib in the central area is arranged substantially parallel to the circumferential main groove and is divided into sub design ribs by a circumferential sub groove having groove wall surfaces that come into contact with each other during load rolling. , the transverse groove has a circumferential deviation of 0.5 to 5 times the circumferential width of the transverse groove at the intersection position with the circumferential groove and the circumferential sub-groove.

Here, the design ribs refer to circumferential ridges including transverse grooves, narrow grooves, sipes (cuts), etc., provided between the circumferential main grooves.

Further, the deviation caused in the circumferential direction at the intersection of the transverse groove with the circumferential sub-groove is desirably 0.5 to 5 times, and preferably 1 to 3 times, the circumferential width of the transverse groove. Here, the reason why the tread pattern is set to 0.5 to 5 times is because if it is less than 0.5 times, the tread pattern becomes almost the same as a conventional tread pattern, and there is no noise reduction effect. Moreover, if it exceeds 5 times, transverse grooves will be scattered within the design rib of the tread, which is not preferable.

The width of the design rib in the cross-sectional direction of the tire is preferably 5 to 20% of the tread width, preferably 10 to 15%.
It is.

Further, the width of the circumferential minor groove is desirably 0.5 to 3 fl, preferably 1 to 21 fl. Here, the reason why the value is 0.5 to 311 is because if it is less than 0.5 va, the entire groove wall surface will come into close contact with the entire surface during load rolling, blocking air circulation and not functioning as a groove through which air can flow. If three or more cuts are made, the pattern will be the same as the conventional pattern, and the design rib will be divided in the cross-sectional direction of the tire, making the present invention ineffective.

In addition, the transverse groove of the tread crosses the circumferential main groove and extends in an S-shape from one end of the tread to the other end, and the acute groove angle θ between the tangent to the axis of the transverse groove and the cross-sectional direction of the tire is ,
It is provided so that it gradually increases from both side end areas toward the center area. The groove angle θ is 45 to 45 at both end areas.
80 degrees and 50-60 degrees in the central area. The reason why the transverse groove is S-shaped is that the ground contact pressure is high in the contact area of the tread from both end areas toward the center area, and the ridges of the tread receive a large impact input from the road surface. It's easy. Therefore, by increasing the groove angle θ of the transverse groove, the shape of the ridge portion becomes elongated in the circumferential direction of the tire, which lengthens the time during ground contact and reduces the impact input from the road surface.

(Function) In the tread of the present invention, the design rib in the central area is divided into two sub-design ribs by the circumferential sub-groove, and the length of one ridge in the sub-design in the tire cross-sectional direction is the same as that of the conventional tread pattern. Since the length is approximately half that of the ridge, the frequency at which the crest vibrates due to the impact input from the road surface when it touches the ground during load rolling is approximately doubled, resulting in an extremely high frequency range that is difficult for human ears to hear. .

In addition, since the transverse groove has a deviation of 0.5 to 5 times the circumferential width of the transverse groove in the tire circumferential direction at the intersection position with the circumferential sub-groove, the inside of the transverse groove is The flowing air does not flow all at once, and the flow velocity is significantly suppressed. Therefore, the noise generated by this air flow is significantly suppressed and reduced. In addition, the air whose flow is suppressed within the transverse groove is
It passes through the circumferential main groove and the circumferential sub-groove and is discharged without being wrapped up in the ground contact part of the tread.

(Example) Next, a first embodiment of the present invention will be described based on the drawings.

FIG. 1 is a diagram showing a first embodiment of a pneumatic radial tire according to the present invention.

First, the configuration will be explained. In Fig. 1, 12 is a pneumatic radial tire 11 (tire size 205/
60R15) tread, and the structure other than tread 12 is the same as that of a normal pneumatic radial tire. The tread 12 has a contact area 14 (contact width W, 4) where the pneumatic radial tire 11 contacts the road surface when rolling under load, and a padless area 14a (buttress width W + 4-) on both sides thereof.
It has The surface of the tread 12 has four wide circumferential main grooves 13 extending linearly and substantially parallel to the tire circumferential direction and extending substantially symmetrically with respect to the tire equator E.

15 is a transverse groove, and the transverse groove 15 crosses the circumferential main groove 13, opens into the circumferential main groove 13, and extends in an S-shape from one end 12a of the tread 12 to the other end 12b of the tread 12. As a result, block-shaped ridges (indicated by diagonal lines in the figure) 16 are formed and are arranged at approximately equal intervals in the tire circumferential direction. The tread 12 has a central region 17 defined by a circumferential main groove 13 and both end regions 18 located outside the central region 17.
It is equipped with The central area 17 has three design ribs 20a (rib width Wzo-21m), 20b (rib width Wzo-21m), which include a part of the transverse groove 15 and a sub-groove to be described later between the circumferential grooves 13.
Rib width W2゜b 15mm), 20c (rib width W
zo c21 m). Side edge area 18
are two design ribs 21d and 21e similar to the design ribs 20a-c (rib width W!IdsWzI-25m
(approximately equal to the width of the side end area 18).

23 is a circumferential minor groove, and the circumferential minor groove 23 is arranged approximately parallel to the circumferential major groove 13 at approximately the center of each of the design ribs 20a''-c, 21d, and e.
0c, 21d, and e are further added to two sub-design ribs 20a.
+, az~cI+02%21dl.

dZ, el+”Z. As a result, the rib part 16
The circumferential minor groove 23 further provides two minor ridges 16 (shown with diagonal lines in the figure) having two approximately half equal areas.
It is divided into A and 16B. The circumferential direction minor groove 23 has a minor groove width of 1
fi and groove wall surfaces 23a that come into contact with each other during load rolling.

In each design rib 20a''c, 21d, e, the groove width W153-8 in the circumferential direction of the transverse groove 15 is 5 squares at the center in the cross-sectional direction of each sub-design rib 20a+, b+, C+, 21d+, er. 15 is each design rib 20a.

At approximately the center of b, cs 21 d, e, at the intersection position 23a-e with the circumferential minor groove 23, the right transverse groove of the circumferential minor groove 23 crosses the left side lateral angle when viewed from the outside of the tread 12. They each have deviation lengths P a - e that are deviated upward in the tire circumferential direction from the grooves. Displacement length Pd, Pe
is 0.5 times the groove width WISd+Ise, and the deviation length P a -c is 1.0 times the groove width WISm""lsc.

In each sub-design rib 20al-62, the transverse grooves 15a1-e2 that cross the sub-design rib are connected to the circumferential main groove 15a1-e2.
The angles θa, ~θe2 between the tangents I, a, xez of the transverse groove 15a+""ex and the tire cross-sectional direction at the intersection position where they intersect with the circumferential minor groove 23 are θdl, and θe2 is 2.
0 degrees, θd2, θe are 30 degrees, θal+θc2 is 35
degree, θa2, θC1 is 45 degrees, θb1. θb2 is 55 degrees, and gradually increases from one end 12a and the other end 12b of the tread toward the center of the tire (equator).

Next, the effect will be explained.

The tread 12 of the present invention has a design rib 2 in the central region 17.
0a-c is divided into sub-design ribs 20al to 21C2, and the sub-design ribs 16A and 16B have a length W in the cross-sectional direction of the tire.
Z. , xi/2) is the conventional tread pattern, that is,
Since the length is approximately half of the width of the ridge 16 of only the circumferential main groove 13 (width Wzo- of the design rib), one of the auxiliary ridges 16A of the auxiliary design ribs 20a to 21e2 during load rolling.
The weight is approximately half that of the conventional one.

For this reason, the frequency of vibrations due to the impact input from the road surface is approximately doubled, reaching an extremely high frequency range, making it difficult for human ears to hear.

Further, the crossing position 23a where the transverse groove 15 intersects with the circumferential sub-groove 23
-wQ, the deviation length pa-e(0
, 5 times and 1.0 times), the tread 1
In the grounding portion of No. 2, the air flowing in the transverse groove 15 is not enveloped in the grounding portion or its flow is suppressed, and gradually passes through the circumferential main groove 13 and the circumferential minor groove 23 through which air can flow. outside air flows out.

Therefore, noise is significantly reduced.

Further, since the length of the transverse groove 15 from one end of the tread 12 to the other end is longer than that of the conventional one, the action of cutting the water film by the edge of the ridge 16 is the same.

Also, cross section: $15 is the circumferential main groove 13 and the circumferential side:
a23, the groove angle θ increases from 20 degrees to 45 degrees as it goes from one end 12a and the other end 12b of the tread 12 toward the tire central red groove, and the groove angle θ increases from 20 degrees to 45 degrees in the central region 17 where the ground contact pressure of the tread 12 is high. Since the secondary ridges 16A and 16B have a long shape in the tire circumferential direction from the tip 16a, the surface area increases as it goes downward in the figure. The contact start times of the edge edges 16a and 16b are shifted, and as a result, the impact input to the secondary ridges 16m is alleviated, and the contact time of the secondary ridges 16A and 16B is different from that of the conventional transverse grooves that cross approximately in the cross-sectional direction of the tire. It will be longer than if you do it. Therefore, the impact input from the road surface is further alleviated, and the generation of noise is significantly reduced.

These results show that the pneumatic radial tire 11 does not degrade wet performance and significantly reduces noise generation.

Next, test tires (tire size 205/60R15
) were prepared (first example, second example, and comparative example) and the effects of the present invention were confirmed, which will be explained below.

The first embodiment (tire of the invention) is the same as the one shown in FIG. 1 and described above. In the second embodiment, in the first embodiment,
The circumferential minor groove 23 in the central area is not provided. The comparative example is the same as that shown in FIG. 2, and has the same configuration except for the shape of the tread grooves.

The test focused on wet performance, especially drainage performance and water film cutting performance. Drainage performance was measured by driving on a road surface with a water depth of 5 cm and measuring the speed at which the hydroplaning phenomenon occurred, and expressed as an index.

The cutting performance of the water film was evaluated by driving on a test road with continuous curves having a small radius of curvature at a water depth of 1 to 2 nm, and by a test driver's sensory test, and the results were expressed as an index. Noise performance is J
The overall value dB(A) when measured under the standard bench test conditions indicated in IS was measured and expressed as an index.

The test results are shown in the following table as an index with the comparative example set as 100.

The larger the number, the better.

(This page, hereafter in the margin) As shown in the previous table, both the first example and the second example are compared to the comparative example, and the noise performance of the tire is significantly improved while maintaining the wet performance.

(Effects) As described above, according to the present invention, tire pattern noise (noise) can be significantly reduced and noise performance can be significantly improved without reducing wet performance when driving on a wet road surface.

[Brief explanation of the drawing]

FIG. 1 is a developed plan view of a tread showing a first embodiment of a pneumatic radial tire according to the present invention. FIG. 2 is a developed plan view of the tread of a conventional pneumatic radial tire. 11...Pneumatic radial tire, 12...
... Tread, 13 ... Circumferential main groove, 14 ... Ground contact area, 15 ... Crossing groove, 16 ... Ridge section, 16A, 16B・・・・・・Sub-clinic part, 17・・・Central area, 18・・・Side edge area, 20a, 20b, 20c, 21d, 21e-・-・・-
Design rib, 23... Circumferential minor groove.

Claims (1)

[Claims] At least three circumferential main grooves extending substantially parallel to the tire circumferential direction on the surface of the tread, and an S-shaped groove extending across the circumferential main grooves from one end of the tread to the other end of the tread in the tire circumferential direction. a plurality of transverse grooves arranged at approximately equal intervals;
A central region having at least two design ribs defined by a circumferential main groove, and both end regions located outside the central region, the design ribs of the central region being arranged substantially parallel to the circumferential main groove. It is divided into sub-design ribs by a circumferential sub-groove having groove wall surfaces that come into contact with each other during load rolling, and the transverse groove extends in the circumferential direction at the intersection position of the circumferential main groove and the circumferential sub-groove. 0.5 to 5 of direction width
A pneumatic radial tire characterized by having a double deviation.