JP2009056908A - Tire filling gas, and tire filled with the gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tire filling gas capable of enhancing operation stability, and a tire filled with it. <P>SOLUTION: The tire filling gas comprises a gas having smaller polytropic exponent than that of air, and in particular, the polytropic exponent is preferably 1.3 or less. In the vibration process (polytropic process of gas) of the tire, volume variation at compression/expansion becomes small, variation of dynamic repulsion, i.e., dynamic spring coefficient is made small. Thereby, the tire with high driveability is obtained. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a tire-filling gas and a tire in which the tire-filling gas is sealed. Specifically, the present invention relates to a tire-filling gas capable of improving driving stability and comfort of an automobile or the like by substantially improving the filling gas. The present invention relates to a gas and a tire enclosing it.

Air and nitrogen are generally used as the tire filling gas, but it has been proposed to fill other gases from the viewpoint of improving tire performance with the tire filling gas.
For example, an inert two-type mixed gas composed of argon gas and nitrogen gas, wherein the volume ratio of the mixed gas is a specific range in which the gas leakage rate is smaller than the leakage rate of nitrogen alone. A gas for filling tires is proposed, and the internal pressure drop (gas leakage) can be remarkably suppressed as compared with the prior art (see, for example, Patent Document 1). Further, in order to reduce road noise, a vehicle tire characterized by injecting 100% helium gas in weight% into the air chamber in the tire body is proposed, and the gas mass is reduced by containing helium, Road noise is suppressed (see, for example, Patent Document 2).
JP 2007-55559 A JP-A-6-156008

  However, with increasing interest in safety in recent years, there is an increasing demand for improvements in driving stability and comfort of automobiles and the like. It was something that stayed like this.

  In order to solve the above-described problems, an object of the present invention is to provide a tire filling gas capable of improving the steering stability and a tire enclosing it.

  As a result of intensive studies to solve the above problems, the present inventor has focused on the fact that the steering stability is a change in resilience at the time of dynamic load of the tire, that is, the resilience of the tire at the time of static load. If the tire is filled with pure air only and its gas polytropic index is 1.4, the tire vibration process (gas polytropic process) will cause compression / Volume change at the time of expansion becomes extremely intense, and dynamic resilience, that is, fluctuation of dynamic spring coefficient becomes large, which adversely affects steering stability. On the other hand, polytropic index of tire is 1.3 or less It is found that if the gas is filled, the dynamic resilience is reduced, the fluctuation of the spring coefficient caused by the dynamic load change during braking and cornering as a tire is suppressed, and the steering stability is improved. Which has led to the completion of the invention.

  That is, the tire filling gas of the present invention is characterized by comprising a gas smaller than the polytropic index of air. Preferably, the filling gas has a polytropic index of 1.3 or less, more preferably 1.0 to 1.2.

The filling gas includes at least one gas selected from carbon dioxide or alternative chlorofluorocarbon having a polytropic index of 1.3 or less.
The tire formed by filling the filling gas preferably has a gas pressure of 1 to 10 kg / cm ³ .

  The tire filling gas of the present invention has a polytropic index n of 1.3 or less, particularly preferably in the range of 1.0 to 1.2. Such a filling gas has a lower polytropic index than air and has a small volume change upon compression / expansion. For this reason, when the resilience of the tire at the time of filling, that is, the fluctuation of the dynamic spring coefficient is small, the value of the so-called dynamic spring coefficient / static spring coefficient (approximately n = 1) is approximately 1.3 or less. In the polytropic process, the volume change during compression / expansion is small, and the dynamic resilience is small. In order to suppress a large variation in the spring coefficient caused by a dynamic load change during braking and cornering as a tire, the balance of the ground contact state of the four tire wheels is stabilized, and steering stability is improved.

Hereinafter, preferred embodiments of the present invention will be described in detail.
The tire filling gas of the present invention comprises a gas smaller than the polytropic index of air. That is, the tire filling gas of the present invention may be mixed with air, but the whole gas is smaller than the polytropic index of air, and preferably 1.3 or less.
In general, the gas equation (1) PV ⁿ = C applied to the sealed gas is applied. Here, n = 0 in the case of a constant pressure change, and n = 1 in the case of a static repulsion in the case of an isothermal change. However, when the actual sealed gas produces dynamic repulsion, a so-called reversible adiabatic change (n = specific heat ratio Cp / Cv) occurs. The index of the reversible adiabatic change of each enclosed gas is the polytropic index n.
Examples of the gas having a low polytropic index include carbon dioxide, chlorofluorocarbon gas, and alternative chlorofluorocarbon gas. Examples thereof include gases other than oxygen and nitrogen shown in Table 1.

The present invention focuses on the fact that when the tire vibrates while traveling, the gas contained in the tire undergoes reversible adiabatic change in compression and expansion.
The tire filling gas according to the present invention has a polytropic index of 1.4 or more, such as conventional air or nitrogen, that is, even if a slight change in compression / expansion is evident from the state equation (1), V The change in dynamic resilience of such a gas-sealed tire or the like is also greatly changed by vibration or the like. For this reason, by using a filling gas having a small polytropic index for the tire, it is possible to improve the driving stability and comfort of an automobile or the like.

(Example)
As a material, styrene butadiene rubber, carbon black, stearic acid, zinc white, anti-aging agent, accelerator and sulfur are blended and kneaded with a Banbury mixer in a tread, to a tire of size 245 / 40R18, The internal pressure was set to 200 kPa, filling gases with different polytropic indexes shown in Table 2 were filled, and the operational stability was measured.
Steering stability: Sensory evaluation test by an evaluation panel. This is a relative evaluation with the conventional product taken as 100, and the larger the value, the better the steering stability.

  From Table 2 above, it can be seen that the steering stability of Example 1 is improved.

  INDUSTRIAL APPLICABILITY The tire filling gas of the present invention has a low index of adiabatic change in compression / expansion in a tire during vibration, a small dynamic rebound resilience, and industrial applicability that can improve the driving stability of an automobile. There is something.

Claims (4)

  A tire filling gas comprising a gas smaller than the polytropic index of air.   The tire filling gas according to claim 1, wherein the polytropic index of the gas is 1.3 or less.   The tire filling gas according to claim 2, wherein the gas contains at least one gas selected from carbon dioxide or alternative chlorofluorocarbon, and has a polytropic index of 1.3 or less.   A tire formed by enclosing the filling gas according to claim 1.