JPS58167208A - Low noise lug tyre - Google Patents

Abstract

PURPOSE:To reduce the noise without decreasing the characteristics and the performance of a lug tyre by arranging main lug grooves and short lug grooves alternately or one main lug groove subsequent to every 2 or 3 short lug grooves. CONSTITUTION:A lug groove 4 has a currently applied dimension, in particular, has a specified lateral length l with its inner end wall 4' sufficiently approaching a tread center 3, or a length from a shoulder 2 to the inner end wall 4' of the lug groove 4. A lug groove 4a has a lateral length which is measured from the shoulder 2 to an inner end wall 4a' thereof and shorter than that of the lug groove 4, that is, has a lateral length with its inner end wall 4a' inconsiderably apart from the tread center 3 so that the length is shorter by a certain extent than the specified lateral length of the lug groove 4. The lug groove 4 and lug groove 4a are arranged alternately.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a lug type pneumatic tire that is mounted on trucks, buses (all including medium-sized and small-sized vehicles), and industrial vehicles and used for running on general roads, expressways, etc. This is related to the improvement of.

This type of conventional lug type pneumatic tire (hereinafter referred to as lug tire) has particularly superior lug tire characteristics such as wear resistance and braking resistance due to its unique tread pattern compared to so-called rib tires. However, on the other hand, the drawback is that the noise associated with rolling is high.

In recent years, strict regulations regarding automobile noise have been strengthened.
Since this vehicle noise includes tire noise to a considerable extent, there is a strong need to reduce lug tire noise.

By the way, the first cause of the noise generated by tire rolling is that the tread groove wall deforms due to contact with the ground, and the air in the groove is compressed and then expanded, resulting in linear density. Second, the thickness and shape of the tread rubber suddenly change due to the dents in the tread groove, which causes periodic impacts with the ground when the tire rotates, causing the tread and case to vibrate. It is said that

From this point of view, it is well known that improving the tread radius, tread groove shape, lug lateral groove position, pitch number, pitch variation, etc. contributes to reducing noise levels. For example, reducing the tread radius can reduce noise, but increases the disadvantage of deteriorating the wear life of the tire. On the other hand, it has been found that when the tread radius is maintained large and the distance between the inner end wall of the lug groove and the tread center is increased, the noise can be reduced. In order to maintain the best characteristic performance, that is, wear resistance performance or braking performance, it is necessary to make the distance between the inner end wall of the lug groove and the tread center as close as possible. It is essential to form the groove so that it narrows towards the back, or at least to form a shape that extends flat from the bottom without widening towards the back. Even in a lug groove that has a bend or bend, the degree of bend or bend is within an extremely narrow range that does not exceed the above-mentioned shape that virtually extends flat without expanding toward the back from the shoulder. must be limited to.

The present invention has been made in view of the above points, and the tread radius, that is, the radius of curvature CR of the crown outer contour, is 250 to 45.
Currently, lug grooves are used in tires with a lug-type tread pattern that maintains a large tread pattern within the range of 0.11 m, and at the same time, the lug grooves slope out of the containing plane and are bent or curved toward the back from the tire. A lug groove based on the lug lateral groove length, and a short lug groove with the lug lateral groove length cut at an appropriate pitch interval from this basic lug groove, alternately or every 2 or 3 lug grooves. The object of the present invention is to provide a low-noise lug tire that can reduce noise without impairing the characteristics of the lug tire.

An example of implementing the present invention will be described below with reference to the drawings.

Figure 1 shows a cross-section of the tire, where ] is the tread, 2 is the shoulder on both sides of the tread, 3 is the tread center, 4 is the lug groove, and shoulder 2 is the outer contour formed by the crown radius CR of the tread 1. , is defined by the intersection with the so-called sidewall outer surface contour, or the intersection on the extension line thereof.

Figure 2 shows a partially developed view of the tire tread pattern.
The lug groove 4 has a specified length of the lug lateral groove located with the back end wall 4' of the lug groove 4 sufficiently close to the tread center 3, that is, from the 7th direction 2 to the back end wall 4' of the lug groove 4. The lug lateral groove length is currently used. Does the lug groove 4a have a lug lateral groove length in which the length from the handle 2 to the back end wall 4a' of the lug groove 4a is shorter than the lug groove 4? 7/ That is, the rear end wall 4 for the lug lateral groove length of the specified length of the lug groove 4
a/ is positioned slightly apart from the tread center 3 and shortened by a predetermined dimension. The lug grooves 4 and the lug grooves 4a are arranged alternately.

Therefore, the tread pattern shown in FIG.
An experiment was conducted using a tread pattern in which the lug lateral groove length of the lug groove 4 was
A reduction in tire noise was confirmed when the ratio of lug lateral groove length to ' was 1:9°5.

The table below shows the ratio of the lug lateral groove lengths 1' and 1' for tires with the tread pattern shown in the second figure, in which the lug lateral groove lengths 1 and 1' are arranged alternately. = 1'=H1:9, tire size: 10.00-20-14 PR air pressure: 6.75 kgf4□2 load These are the results obtained under the test conditions of constant loading.

Table A (when installed on a vehicle) From Tables A and B above, it is clear that the invented tire significantly reduces noise compared to the current tire.

Further, as shown in the second diagram, in a tread pattern in which the lug grooves 4 and 4a are arranged alternately, the ratio of the lug lateral groove lengths is slightly over 10:8, that is, the lug grooves 4 and 4a are arranged alternately. "" Hl +
From 7.8 onwards, a phenomenon was observed in which the wear resistance and braking performance, which are characteristic performances of lug tires, decreased.

In the tread pattern shown in the second figure, the lug grooves 4 and 4a are inclined out of the concentric cross section, and the lateral groove walls 4" and 4" and 4a and 4a of the lug grooves 4 and 4a face each other, respectively.
"" is formed asymmetrically with respect to the joint axis cross section.The reduction phenomenon in tire noise obtained with such a shape of the lug groove 4゜4a/ can be adopted in the tire pattern shown in Fig. 3 and below. It is clear that a more significant noise reduction effect can be obtained.

Furthermore, the lug grooves 4 and 4a are not necessarily limited to the tire pattern shown in FIG. 2, and may be arranged at intervals of every two or three lug grooves.

Therefore, the present invention can reduce the noise level without impairing the wear resistance performance, braking performance, etc., which are the characteristic performances of lug type tires. Noise and level can be easily reduced by cutting the lug groove length to an appropriate pitch interval, such as every second or every second lug groove.
Therefore, there are advantages such as the ability to obtain a desired lug type pattern only by improving the mold currently in use.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a lug type tire, FIG. 2 is a partially developed view of a tread pattern, and FIG. 3 is a partially developed view of different patterns.

Claims (4)

[Claims] (1) In a pneumatic tire that has a lug type tread pattern and has a crown outer contour radius of curvature CR of 250 to 450 m, the length of the lug lateral groove from the shoulder of the lug groove to the tip wall is such that the length of the lug lateral groove extends from the back end wall to the tread center. a lug groove having a lug lateral groove length of a prescribed length that is positioned sufficiently close to the tread center; and a predetermined dimension that positions the rear end wall slightly away from the tread center with respect to the lug lateral groove length of the prescribed length of the lug groove. A low-noise lug tire constructed by alternately arranging lug grooves having short lug lateral groove lengths. (2) The low-noise lug tire according to claim 1, wherein the lug groove has a shape that is bent or curved from the shoulder toward the rear end and inclined away from the axial cross section. (3) A low-noise lug tire according to claim 1, wherein the lateral groove walls of the lug grooves facing each other are asymmetrical. (4) The lug lateral groove length of each lug groove has a prescribed length that positions the far end wall sufficiently close to the tread center, and the lug lateral groove length that positions the far end wall slightly away from the tread center. What is the ratio to 1'? The low noise lug tire according to claim 1, wherein =1'=10=9 to 10:8.