JPS61108004A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To effectively prevent railway wear without reduction in wet skid performance, by inverting at least one of convex ridge lines of a rib adjacent to a main groove with an amplitude smaller than that of the main groove. CONSTITUTION:A main groove 10 has a zigzag shape such that at least one of convex ridge lines R1 of a rib R adjacent to the main groove 10 are inverted with an amplitude Wt smaller than an amplitude W of the main groove 10 and with a depth of 50-70% of the main groove from a tread surface T. The amplitude Wt of an inverted portion 20 is set to the range of 1/5-1/2 of the amplitude W of the main groove 10. With this structure, it is possible to effectively prevent railway wear without reduction in wet skid performance over initial to terminal period in wear life.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention can prevent uneven wear, which is a particular problem in the early stages of running, without affecting wet skid performance.
This is a pneumatic radial tire that can prevent stones from getting stuck in the grooves, and is mainly used as tires for heavy vehicles such as trunks and buses.

[Conventional technology]

A pneumatic radial tire that has a tread pattern consisting of at least one zigzag-shaped main groove that continues in the circumferential direction of the tire on its tread surface, and is particularly used as a tire for heavy vehicles such as trucks and buses. The tires are number 5
As in the conventional example shown in the figure, the amplitude W of the main groove is pitch 1,000 P.
If it is larger than the main groove, it is easy to bite stones at the zigzag corners of the groove, sometimes causing trend cuts, and furthermore, when this type of tire is used under high load conditions or low air pressure conditions, it may become stuck in the main groove. Partial early wear that occurs at the side protrusions of the ribs gradually grows toward the inside of the ribs, often resulting in step-like uneven wear along the edges of the ribs.

Generally, this uneven wear phenomenon is called railway wear, and the main cause is that lateral stress is easily applied to the protruding end of the rib during running.

As a conventional measure to prevent this, as shown in FIG. Measures are taken to reduce the amount of protrusion of the side projecting ends and to disperse the stress applied to the projecting ends.

However, although this method is effective in preventing stone build-up and railway wear, it also reduces traction performance and braking performance on water-soaked roads (hereinafter referred to as wet skid performance). Currently, the deterioration of wet skid performance cannot be ignored, especially under high load conditions and when the cruelty is less than 30% as shown in FIG.

[Purpose of the invention]

The present invention was achieved as a result of experiments and studies aimed at solving the above-mentioned problems.

Therefore, an object of the present invention is to reduce uneven wear, which is a particular problem in the early stages of running, by making it possible to change the pinch and amplitude of the main groove formed in a zigzag shape between when the tire is new and when it is worn out. To provide an excellent pneumatic radial tire which can prevent skids without impairing skidding performance and can also prevent stones from getting into grooves.

[Structure of the invention]

That is, the present invention provides a pneumatic radial tire having a trend pattern in which at least one zigzag-shaped main groove continuous in the tire circumferential direction is arranged on the tread surface of the tire, in which the zigzag shape of the main groove is At least one of the convex side ridgelines of the ribs connected to the main groove is inverted with an amplitude (2) smaller than the amplitude W of the main groove in a range of 50 to 70% from the tread in the groove depth direction. The gist of this is a pneumatic radial tire.

Hereinafter, the present invention will be specifically described by way of examples with reference to the drawings.

Figures 1 to 4 show a pneumatic radial tire according to an embodiment of the present invention, Figure 1 is a plan view explanatory diagram showing a part of the tread when new, and Figure 2 shows a shallow groove of 30% as above. FIG. 3 is an enlarged plan view explanatory view showing the main parts of the present invention, FIG. (bl is Figure 3 B-B
FIG. 5 is an explanatory cross-sectional view, and FIGS. 5 to 8 show each side of a conventional pneumatic radial tire, and FIG. 5 is a plan view showing a part of the tread of the first conventional tire when new. Figure 6 is a plan view explanatory view showing a case where the tread has worn down to the point where the shallow grooves are 30% of the above, and Fig. 7 is a plan view explanatory view showing a part of the tread when the second conventional tire is new. , and FIG. 8 is an explanatory plan view showing a case where the tread has worn down to 30% of the shallow grooves.

In the figure, E denotes a pneumatic radial tire according to an embodiment of the present invention, which is constructed by arranging at least one zigzag-shaped main groove 10 continuous in the tire circumferential direction on the tread T. In the invention, in particular,
The zigzag shape of the main groove 10 is such that at least one of the convex side edges IJ'lR1 of the rib R connected to the main groove 10 is formed in a range of 50 to 70% from the tread surface T in the groove depth direction. The signal is inverted at an amplitude smaller than the amplitude W of 10.

To explain further, the reason why the above-mentioned inverted portion 20 is formed within the range of 50 to 70% from the tread surface T in the groove depth direction is that if this is less than 50%, the rigidity of the protruding end of the rib will decrease. Since the height of the tip is high and the lateral stress applied to this tip is easily received, there is a risk of railway wear.
This is because if it exceeds %, the discharge function against stone buildup in the grooves will deteriorate, which is not preferable.

Therefore, considering that railway wear is particularly likely to occur in the early stages of running as described above, and that wet skid performance deteriorates rapidly when the amount of brutality is 30% or less, the reversing section 20 is 50-70% in groove depth direction
It is preferable to form it within the range of .

Furthermore, on the groove bottom side of the main groove 10, as shown in FIG. It is formed in the same shape as the groove.

It goes without saying that the pitch P and amplitude W of the above zigzag shape a10 are set so as to ensure the necessary wet skid performance.

It is preferable that the amplitude tVt of the above-mentioned inversion section 20 is set within a range of 115 to 1/2 of the amplitude W of the main groove IO.

This is because if the amplitude deviation is less than 115 of the amplitude W of the main groove IO, the amount of protrusion of the protruding end of the rib on the convex side is large, and the lateral stress applied to the protruding end is not sufficiently dispersed, causing railway wear. This is because even if an amplitude Wt exceeding 1/2 is provided, it is not expected to have much of a railway wear reduction effect, and rather it is undesirable because it leads to a decrease in wear resistance due to a decrease in the amount of rubber on the tread surface. .

Furthermore, the pitch pt of this reversing portion 20 is
It is preferable to set it within the range of 115 to 1/2 of the pitch P of .

This is because if the pitch pt is less than 115 of the pitch P of the main groove 10, the amount of protrusion of the tip is large, so the lateral stress applied to the tip is insufficiently distributed, and 1/
This is because even if a pitch pt of more than 2 is provided, the railway wear reduction effect cannot be expected to be so great, and on the contrary, it is undesirable because it leads to a decrease in wear resistance due to a decrease in the amount of rubber in the tread portion.

Therefore, as mentioned above, the deflection of the reversing section 20 is reduced by the main groove 10.
is set within the range of 115 to 1/2 of the amplitude W of
Setting the pitch pt within the range of 115 to 1/2 of the pitch P of the main groove 10 is expected to have the same effect as setting the pitch P and amplitude W of the main groove 10 to a substantially smaller range. This makes it possible to effectively prevent railway wear that tends to occur in the early stages of travel.・ To explain more specifically, FIGS. 1 and 2 show tire size 295/75 R22,50-Drainage G (
14PR), in which Fig. 1 is a plan view explanatory diagram showing a part of the tread when new, and Fig. 2 shows the case where the tread has worn down to the point where the shallow grooves are reduced to 30%. An explanatory plan view is shown.

In this embodiment, four main grooves 10 having a zigzag shape are arranged on the tread T, the pitch P of the zigzag portion of the main groove IO is set to 40+n, and the width W of Ji is set to 9mm, in particular, to ensure sufficient wet skid performance. It was assumed that it could be secured. Furthermore, the convex side ridgeline portion R1 of the rib R for preventing railway wear
The amount of inversion is such that the pitch pt of the inversion section 20 is 10u+, and the amplitude Wt of the inversion section 20 is 3fi.

In addition, as shown in FIG. 4, the reversing portion 20 has an area up to 60% from the tread surface T in the groove depth direction, and a 40% area on the groove bottom side.
The range is such that the convex side ridgeline R1 of the rib R is not folded back, the pitch P of the zigzag portion of the main groove 10 described above is 40 mm, and the width of the j layer is 91.

Furthermore, the groove angle θ of the main a10 with respect to the tread T and the inversion gI
The groove angle θL of S2o is the same angle, and the reversal part 20
The convex portion of the rib R at the position changing from the groove bottom side to the bottom side of the groove is formed in a step-like manner to improve the ability to discharge stones when biting stones.

[Experiment example]

The specifications of the tires used in this experimental example are as follows.

(Tire of the Invention) The structure is as shown in FIGS. 1 to 4, and the specifications are as described above.

(First Conventional Tire) The structure is as shown in FIGS. 5 and 6, and the specifications are Pifty P40m and amplitude W9 Tsuru.

(Second Conventional Tire) The structure is as shown in FIGS. 7 and 8, and the specifications are a pitch of 20 m and an amplitude of W 3 m.

The specifications of each tire, tread rubber compound, and reinforcement structure are the same.

As a result of evaluating the wet skid performance, railway abrasion resistance, and stone removal performance of each of the above-mentioned tires when new and when remaining A was 30%, the experimental results shown in Table 1 were obtained.

The experimental method was as follows.

(11. Wet skid performance test. Under 100% load and regular internal pressure conditions, the tire was run at a speed of 40.60.80 km/h on a special test track with a water depth of 15. The I]J friction coefficient (μ) was measured and expressed as an index, with the performance of Conventional Example Tire 1 set as 100.

(2) Railway wear performance test A road test was carried out under the conditions of 80% load and 90% filled air pressure of the normal internal pressure, and the amount of railway wear generated at the time of running 70,000 km was calculated by the amount of step and uneven wear width. The performance of the conventional tire I was measured and expressed as an index, with the performance of the conventional tire I set as 100.

(3) Stone removal performance test After running on a riverbed test road with a length of 0.8 km under the conditions of 80% load and 90% full air pressure of the normal internal pressure, lengths 1 and 2 km
The number of stones caught in the grooves was measured by driving on a paved road of m.

(Left below) Table 1 From the experimental results shown in Table 1, it is clear that the tire of the present invention effectively prevents railway wear from when new to the end of its wear life without deteriorating wet skid performance. It can be seen that not only this is possible, but also the discharge function against stone encroachment can be greatly improved.

〔Effect of the invention〕

As described above, the present invention provides a pneumatic radial tire having a trend pattern in which at least one main groove in a zigzag shape continuous in the circumferential direction of the tire is arranged on the tread surface of the tire. shape,
Since at least one of the convex side ridgelines of the ribs connected to the main groove is inverted with an amplitude smaller than the amplitude of the main groove in a range of 50 to 70% from the tread in the groove depth direction, the wear life is shortened even when new. Toward the final stage, not only can railway wear be effectively prevented without deterioration of wet skid performance, but also the discharge function against stone encrustation can be greatly improved.

[Brief explanation of the drawing]

Figures 1 to 4 show a pneumatic radial tire according to an embodiment of the present invention, Figure 1 is a plan view explanatory diagram showing a part of the tread when new, and Figure 2 shows a shallow groove of 30% as above. Fig. 3 is an enlarged plan view explanatory view showing the main parts of the present invention, Fig. 4 fat is an explanatory cross-sectional view taken along the line A-A in Fig. (bl is Figure 3 B-B
FIG. 5 is a cross-sectional explanatory diagram, and FIGS. 5 to 8 show each side of a conventional pneumatic radial tire, and FIG. 5 is a plan view explanation showing a part of the tread of the first conventional tire when new. Figure 6 is a plan view explanatory view showing a case where the tread has worn down to the point where the shallow grooves are 30% of the above, and Fig. 7 is a plan view explanatory view showing a part of the tread when the second conventional tire is new. , and FIG. 8 is an explanatory plan view showing a case where the tread has worn down to 30% of the shallow grooves. T...Tread, 10...Zigzag shaped main groove, R
...Rib, R1... Rib convex side ridgeline, 20...
Inversion part.

Claims (1)

[Claims] A pneumatic radial tire having a tread pattern in which at least one zigzag-shaped main groove continuous in the tire circumferential direction is arranged on the tread surface of the tire,
The zigzag shape of the main groove is 50 mm in the groove depth direction from the tread surface.
A pneumatic radial tire characterized in that at least one of the ridge lines on the convex side of the rib connected to the main groove is reversed by an amplitude Wt smaller than an amplitude W of the main groove within a range of 70%.