JPH02147411A - Pneumatic tire and vulcanizing metal mold thereof - Google Patents

Abstract

PURPOSE:To improve performance on ice by forming a zone of a defined range having a specific surface roughness of tread on the tread of a new tire. CONSTITUTION:The zone A of an area approx. 80% the area of a surface S obtained by multiplying the distance L between both end edges (a), (a) of a tread portion 2 in a condition of assembling a new tire to a regular rim R and charging a regular inner pressure, is formed into a rough surface between 30mum and 200mum in the ten-point means roughness. By this structure, the braking property on ice of a new product can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pneumatic tire with improved on-ice performance in the initial stage of running, and a vulcanization mold for a pneumatic tire for molding and vulcanizing the tire.

[Conventional technology]

Traditionally, winter tires used when driving on snow and ice include spiked tires, studless tires, etc. The spiked tires have excellent grip performance especially on icy roads, but in recent years, they have been used for driving on paved roads. In addition to the severe damage caused to the road surface, the dust pollution caused by this has become a social problem, and its use has been regulated. In addition, studless tires are intended to improve the low-temperature properties of the tread rubber and provide the same performance on ice as spiked tires, but they are slightly inferior to spiked tires in terms of grip performance on icy roads, and they also have long-term durability. If stored for a long time, the hardness will increase and the wear life will decrease.

On the other hand, in addition to such spiked tires and studless tires, even in ordinary pneumatic tires that run on non-icy roads, when new, the braking performance on icy roads is lower than that after a 200km break-in. It was confirmed that it was inferior.

[Problem to be solved by the invention]

This is because when molded using a vulcanization mold, the surface roughness of the contact surface of the tread is conventionally 10 to 30μ on a ten-point average roughness.
It turns out that this is due to the fact that fine irregularities occur due to contact with the road surface after driving on the road surface.

Therefore, an object of the present invention is to provide a pneumatic tire and a vulcanization mold thereof, which can provide the same braking performance on ice as after driving by providing a region of a predetermined roughness on the ground contact surface even when new. There is.

(Means for Solving the Problems) The present invention is a pneumatic tire having a tread surface having a surface roughness of 30 μl or more and 200 μl or less in ten-point average roughness before running.

The present invention also provides a vulcanized pneumatic tire, which has a surface roughness of 30μ or more and 200μ or less in ten-point average roughness provided by etching or sandblasting on the inner surface that forms the contact surface of the tire. It is a mold.

[Effect]

When the tires were new before running, the surface roughness of the ground contact surface was 30μ on a 10-point average roughness, almost the same as after about 2001 runs.
By setting the thickness to be at least m and not more than 200 μm, it is possible to maintain the same braking performance even when new as after running in. This is due to the edge effect due to the roughness of the contact surface, where the edges of the concave and convex portions come into contact with the frozen road surface and a large stress is applied to that area.The apparent hardness of the tread surface decreases due to the unevenness, causing the tread to cool This is thought to be due to the softening effect, which improves the characteristics as a result, and the drainage effect, which removes water formed by melting ice due to the pressure applied to the frozen road surface.

The area of the tread surface having the above-mentioned surface roughness is preferably wide enough not to cause any problems in manufacturing, and is usually set to 80% or more of the area.

Furthermore, the pneumatic tire can be easily produced by providing a rough area in advance on the inner surface of the vulcanization mold by etching or sandblasting.

〔Example〕

An embodiment of the present invention will be described below based on the drawings.

In FIG. 1, a pneumatic tire 1 includes a tread portion 2,
A carcass 5 which passes through the sidewall part 3 and is rolled up from inside to outside around the bead cores of a pair of bead parts 4 and is locked, and a breaker 6 placed on the outside in the radial direction.
and has. The carcass 5 and the breaker 6 can be made of various kinds of cords such as organic fiber cords made of aliphatic polyamide, polyester, aromatic polyamide, etc. or steel cords, and the carcass 5 can have a bias structure or a radial structure. The tire 1, which may not have the breaker 6, can be formed into various tires such as tires for passenger cars, tires for trucks and buses, tires for motorcycles, tires for aircraft, and tires for races and rallies.

On the surface S of the tread portion 2, a region A having a ten-point average roughness of 30 μm or more and 200 μm or less is formed. The surface S is the product of the distance between both edges 3 of the tread portion 2 and the circumference of the tire when the tire l is assembled on the regular rim R and filled with the regular internal pressure, and is the area A. is an area portion that accounts for 80% or more of the total area of the surface S, and this region A preferably extends on both sides of the tire equator. Preferably, it is placed over the entire contact area of the surface that the tire comes into contact with when a regular load is applied.

In order to enhance the design effect, the regions A may be distributed in various shapes such as a staggered shape and a ladder shape.

Here, the above-mentioned ten-point average roughness refers to the JIS standard BO6 roughness obtained by touching the tire tread surface with a sharp needle in the width direction or circumferential direction of the tire, and then measuring the waveform recorded as shown in Figure 2.
01, the ten-point average roughness (RZ) is a value determined by the following formula.

RZ-((R1+R3+R5+R7+R9)-(R2+
R4+R6+R8+R10))15 As mentioned above, the ten-point average roughness is required to be 30 to 200 μm. 30μ
If it is less than 20, the desired on-ice performance cannot be achieved and the
If the value exceeds 0μ, the ground contact area is substantially reduced and the grip performance on icy roads and ordinary paved roads deteriorates.

Further, during tire vulcanization, air remains in the concave bones on the tread surface, which tends to cause poor rubber flow and poor appearance, so it is preferably set to 50 to 100 μm.

As shown in FIG. 3, the vulcanization mold 11 for manufacturing tires has an inner surface 12 forming the surface S of the tread 2 of the tire, and has a surface roughness of 30 to 200 μm in ten-point average roughness.
A region AT is provided.

Such inner surface 12 can be processed by etching or sandblasting. Note that in order to improve the accuracy of the ten-point average roughness, it is desirable to finish by etching.

Therefore, the tire 1 can be efficiently produced using this mold 10, and in such a tire 1, the unevenness formed on the tread surface S has the following effect on an icy road surface.

■ Edge effect The edges of the uneven parts come into contact with the icy road surface, applying large stress to that area, and the so-called edge effect improves grip performance.

■ Softening effect The roughness reduces the apparent hardness of the tread surface, improving the tread's low-temperature properties and improving grip performance.

■ Drainage effect Melt water due to pressure applied to frozen roads forms a water belly between the tread and the road surface, reducing grip, but the unevenness of the tread surface removes this water and improves grip performance. This effect is particularly noticeable on icy roads near the freezing point, e.g.
It is noticeable under conditions of about 5 to θ°C.

The tire of the present invention can be combined with various tires having various tread patterns, studless tires with rubber treads with improved low-temperature characteristics, and even spiked tires to further improve performance on ice during the initial stage of driving. It is also possible.

〔Example〕

A so-called plain tire without grooves with a tire size of 175/70R13 was prototyped and installed on a passenger car with a displacement of 1600 cc, and the surface temperature was -2 to 0°C. Measure the braking distance with the lock brake and use the result to determine the friction coefficient μ.
was calculated. The numerical values are shown in Table 1 as an index with Comparative Example 2 set as 100, and the larger the numerical value, the better the result.

The tire of the present invention showed high performance on ice.

〔Effect of the invention〕

In this way, even before driving, it is possible to exhibit the same grip performance on an icy road surface as after driving. Also, vulcanization molds can easily produce such tires.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing one embodiment of the present invention, FIG. 2 is a line diagram illustrating ten-point average roughness, and FIG. 3 is a sectional view showing one embodiment of a vulcanization mold. 2...Tread part, 3-...Side wall part,
4.--bead core, 5.-carcass, 11-.-
- Tire vulcanization mold, 12--inner surface, A... area, S-... surface. Patent Applicant Sumitomo Rubber Industries Co., Ltd. Agent Patent Attorney Tadashi Naemura Figure 1

Claims (1)

[Scope of Claims] 1. A pneumatic tire having a tread surface having a surface roughness of 30 mμ or more and 200 μm or less in ten-point average roughness before running. 2 The area is an area that accounts for 80% or more of the surface area, and the surface roughness of the area is 50 μm as a ten-point average roughness.
The pneumatic tire according to claim 1, wherein the pneumatic tire has a diameter of at least 100 μm. 3. A vulcanization mold for a pneumatic tire, which has a surface roughness of 30 μm or more and 200 μm or less in ten-point average roughness provided by etching or sandblasting on the inner surface that forms the contact surface of the tire.