JP2006192962A - Safety tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a safety tire capable of making continuous stable and safe running in the period from a drop of the internal pressure of a tire air chamber caused by flat tire etc. to the recovery of the internal air pressure established on the basis of a volume increase of hollow particles. <P>SOLUTION: The tire 1 equipped with a rim guard 10 and having a flatness ranging between 30-50% is set on a rim 2, and a number of hollow particles 13 consisting of a continuous phase made of resin and independent bubbles surrounded thereby and able to make thermal expansion are encapsulated by pressure in a tire air chamber 3 bounded by the rim 2 and the tire 1. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  In the present invention, the tire and the applied rim can be punctured due to trauma or the like, and the internal pressure of the tire is leaked. The present invention relates to a safety tire in which hollow particles capable of thermal expansion are enclosed under pressure into a tire chamber to be partitioned.

  A large number of bubble-containing particles consisting of a continuous phase made of resin and closed cells held at a pressure higher than atmospheric pressure are enclosed in a space defined by the tire and the rim under the mounting posture of the tire on the rim. The safety tire formed is described in, for example, Patent Document 1 related to the applicant's previous proposal.

In this safety tire, when the tire is damaged and the internal pressure begins to decrease, the bubble-containing particles seal the damaged portion and suppress a rapid decrease in the internal pressure, while the amount of deflection of the tire increases with a decrease in the tire internal pressure. By increasing the tire internal volume and reducing the internal volume of the tire, the bubble-containing particles themselves will bear the load directly, and will maintain the minimum tire internal pressure necessary for the subsequent driving. The pressure inside the closed cells of the bubble-containing particles that existed under the tire internal pressure remains the same as the above-mentioned tire pressure even after the damage, in other words, maintains the total volume of the bubble-containing particles before the damage. Therefore, when the tire rolls further, the bubble-containing particles themselves bear a load while the bubble-containing particles cause friction and self-heat. As a result, when the temperature of the bubble-containing particles in the tire rises rapidly, and the temperature exceeds the softening temperature of the resin forming the continuous phase of the bubble-containing particles, the bubble internal pressure in the closed cells of the bubble-containing particles causes the tire before being damaged. In addition to the pressure according to the internal pressure, the bubble internal pressure further increases due to the rapid increase in the temperature of the bubble-containing particles, so that the bubble-containing particles expand at once, and the tire internal pressure is restored to a pressure close to that before the injury. Suppose that
JP 2003-118312 A

  However, in such a conventional technology, comparison is made between the start of the decrease in the tire internal pressure and the time when the bubble-containing particles increase in volume due to thermal expansion based on frictional heat generation and the tire internal pressure is restored. In this case, in particular, after the internal pressure of the tire decreases so that the bubble-containing particles are in frictional contact with each other, until the bubble-containing particles start thermal expansion, Since the internal pressure becomes extremely low and the amount of deformation of the safety tire increases, there is a risk that stable continuous running under tire puncture may not be possible, which means that the leak speed of the tire internal pressure is low. Thus, the mutual friction time until the bubble-containing particles reached thermal expansion, and thus the time until they increase in volume, was particularly serious.

  The object of the present invention is to solve such problems of the prior art, and the object of the present invention is to reduce the pressure in the tire chamber due to tire punctures, etc. Based on the increase in the volume of the hollow particles including the bubble-containing particles that are filled, the tires, and directly the tire side part, are inadvertently deformed until the tire air pressure is restored. It is to provide a safety tire that can be stably and safely continued by restraining.

  The safety tire according to the present invention is provided with a tire having a rim guard and a flatness ratio in the range of 30 to 50% on an applied rim, and is made of resin in a tire chamber partitioned by the applied rim and the tire. A large number of thermally expandable hollow particles composed of a continuous phase including one or a plurality of small chambers and one or a plurality of closed cells surrounded by the continuous phase are sealed under pressure.

  Here, the rim guard means a side convex portion or ridge formed on the side portion of the tire and functioning to protect the rim and the tire itself from curbstones and the like, and the applicable rim depends on the tire size. The rim specified in the following standards.

  This standard is determined by an industrial standard effective in the region where tires are produced or used. For example, “THE TIRE AND RIM ASSOCIAITION INC. YEAR BOOK” in the United States, and “THE” in Europe. The “STANDAS MANUAL” of the European Tire and Rim Technical Organization, and the “JATMA YEAR BOOK” of the Japan Automobile Association in Japan.

  Here, “under pressure” means that the tire is in the applied state of the internal pressure of the tire, and the internal pressure of the tire is the pressure in the tire chamber (for each mounting position specified by the vehicle manufacturer for each vehicle) Gauge pressure).

In such a safety tire, the tire cross-sectional height is preferably set to 100 mm or less.
The tire cross-section height here means a dimension that is 1/2 of the difference between the outer diameter of the tire and the rim diameter, and the above-mentioned outer diameter means that the tire is mounted on the applicable rim and has a prescribed air pressure. The tire outer diameter in a no-load state.

Furthermore, the “specified air pressure” means the air pressure defined in accordance with the maximum load capacity in the above-mentioned standard, and in this case, the maximum load capacity is permitted to be applied to the tire according to the above-mentioned regulations. The maximum mass that can be measured.
Of course, the air here can be replaced with an inert gas such as nitrogen gas.

  And preferably, the cross-sectional shape forms a crescent shape at least on the inner surface of the side portion of the tire. A reinforcing rubber having a maximum thickness in the range of 2 to 7 mm is disposed.

  Here, more preferably, the filling rate of the hollow particles into the tire chamber according to the following formula (I) is 5 Vol% or more and 80 Vol% or less, preferably 10 Vol% or more, and the inside of the hollow part pressure of the hollow particles is The internal pressure of the tire is set to 70% or more, and the expansion start temperature (Ts2) of the hollow particles is set to 90 to 200 ° C, more preferably 110 to 200 ° C.

Filling ratio of hollow particles = (particle volume value / tire chamber volume value) × 100 (I)
here,
Particle volume value: The total amount of the total volume of all hollow particles arranged in the tire chamber under atmospheric pressure and the void volume between the particles (cm ³ )
Tire chamber volume value: After filling the tire and rim assembly with only air and adjusting it to the internal pressure (kPa), the amount of air discharged when the internal air is discharged until the internal pressure reaches atmospheric pressure ( cm ³ ), the value obtained from the following formula (II) (cm ³ )
Tire chamber volume value = (filled air discharge) / (internal pressure / atmospheric pressure) (II)
In the formula (II), the internal pressure used is a gauge pressure value (kPa), and the atmospheric pressure value is an absolute value (kPa) obtained by a barometer.
Here, the “hollow part” refers to the inside of one or a plurality of closed cells of a hollow particle.

  More preferably, the water vapor content of the filling gas into the tire chamber under an atmospheric pressure of 30 ° C. is adjusted to 70% or less.

  In the safety tire according to the present invention, the flatness of the tire is in the range of 30 to 50%, and the ratio of the cross-sectional height to the cross-sectional width of the tire is reduced, so that the steady-state tire itself has a high road surface grip force. High responsiveness. Excellent interlocking performance such as braking performance can be exhibited.

  Moreover, since the hollow particles filled in the tire chamber function to greatly reduce the cavity resonance sound in the tire chamber, especially during steady running on a road surface with large road noise, The quietness of this will be further improved.

That is, assuming that it is an open air column tube, the tire has a natural frequency expressed by the following formula, and in this case, the wavelength λ is expressed by (D−R) π / 2. ,

f = V / λ = 2V / (D−R) π
f: Tire chamber natural frequency [Hz]
V: Sound velocity [m / s]
λ: Wavelength [m]
D: Tire outer diameter [m]
R: Rim diameter [m]

The tire has a specific resonance sound (cavity resonance sound) in the vicinity of its natural frequency f≈250 Hz, and when traveling on a road noise road with rough road surface, the cavity resonance sound is excited by vibration from the road surface and has a peak feeling. This impairs silence.
However, in tires encapsulating hollow particles, the amount of air itself can be reduced by enclosing the hollow particles, and the wavelength is dispersed and the frequency is dispersed by the hollow particles. That is, the cavity resonance sound is drastically reduced.

On the other hand, when the tire is punctured due to an injury such as a cut wound, first, hollow particles in the tire chamber enter the wound, block the wound, and the air chamber pressure rapidly decreases. Suppress.
Thereafter, the hollow particles rub against each other and self-heat under the increase in the amount of deformation of the tire as the pressure inside the air chamber decreases. Based on this, the softening of the resin continuous phase and the increase in the pressure of the hollow part cause the hollow particles to self-heat. Volume expansion causes the tire air chamber pressure to be restored to at least the tire air chamber pressure at which the side portion of the tire does not touch the ground. For this reason, a vehicle equipped with this safety tire can continue to travel sufficiently safely over the required distance.

  Moreover, in such a tire, the tire flatness is set to 30 to 50%, the height of the tire side portion is suppressed, the rigidity of the side portion is increased, and the rim guard formed on the side portion is brought into contact with the flange portion of the rim. By allowing the rim guard to function as a reinforcing rib that suppresses the deformation of the side portion, the tire air pressure is reduced to near atmospheric pressure, for example. It is possible to effectively suppress the crushing deformation of the safety tire until the air pressure is restored based on the increase in the volume of the hollow particles. For this reason, the tire air pressure is the lowest value. Even if the value is close to the time when it is fully restored, it is possible to sufficiently ensure the stable and safe continuous running of the safety tire.

  That is, when the tire flatness ratio is 55% or more, the tire has a high cross-sectional height, and the side portion, and thus the tire itself is easily crushed and deformed against the leakage of the pressure in the tire chamber. This is because a tire having a rate of 25% or less has a cross-sectional height that is too low to be practically difficult to manufacture.

The running stability of the safety tire after the tire puncture until the tire air pressure is restored is determined by the tire cross-sectional height, for example, 215/45 R17, 215/45 R18, 245 / It can be made more reliable by further increasing the rigidity of the tire side portion with respect to the bending deformation by setting it to 100 mm or less like tires of sizes such as 40R 18 and 245/35 R19.
On the other hand, when the tire cross-section height exceeds 100 mm, crushing deformation tends to occur easily due to low-speed leakage of the tire chamber pressure.

  By the way, instead of or in addition to the above-described driving stability of the safety tire, a reinforcing rubber having a maximum thickness of 2 to 7 mm and a crescent cross-sectional shape is arranged on the inner surface of the tire side portion. Thus, when the load is applied to the reinforcing rubber, it can be further improved. In this case, even if the tire internal pressure leaks at a low speed, regardless of whether the tire internal pressure decreases or not, It will be possible to guarantee stable continuous driving at all times.

  Here, when the maximum thickness of the reinforcing rubber is less than 2 mm, the tire side portions cannot be easily crushed. On the other hand, when the thickness exceeds 7 mm, the upper and lower sides of the tire under the steady state of the tire There are disadvantages that the rigidity becomes too high and the riding comfort deteriorates, and that the tire mass increases and the rolling resistance increases.

  In such a tire, when the filling rate of the hollow particles into the tire chamber is 5 vol% or more and 80 vol% or less, the damaged portion is more appropriately closed by the hollow particles, and the function of restoring the internal pressure at the time of puncture is expected. It can be demonstrated as you did.

  Further, here, when the pressure of the hollow part of the hollow particle is set to 70% or more of the use internal pressure of the tire, the pressure in the tire chamber is reduced to the atmospheric pressure due to the puncture, and the hollow particle has the above-described pressure. Under the function of restoring the internal pressure, the tire air pressure can be increased more than the side portion of the tire does not touch the ground.

  Furthermore, when the water vapor content at 30 ° C. under atmospheric pressure, such as air, nitrogen gas, or other inert gas, into the tire chamber is 70% or less, hollow tires The smooth fluidity in the air chamber is ensured, and the hollow particle can exhibit the function of restoring the internal pressure as expected.

  FIG. 1 is a cross-sectional view illustrating a tire / rim assembly that is an object of the present invention. This illustrated assembly is divided into a tire 1 and a rim 2 by assembling the tire 1 to an application rim 2. The tire air chamber 3 is filled with a specified internal pressure.

  The tire 1 here includes a carcass 6 composed of at least one carcass ply extending in a toroidal shape between a pair of bead portions 5 on which bead cores 4 are disposed, and is disposed on the outer peripheral side of the crown region of the carcass 6. The belt 7 is composed of at least one belt layer, and the tread 8 is disposed on the outer peripheral side of the belt 7 to form a tread. Each side portion of the carcass 6 is provided around the bead core 4. It is fixed by rolling back from the inside in the tire radial direction to the outside.

Also here, the flatness of the tire, which can be defined as the ratio of the cross-sectional height SH to the cross-sectional width W of the tire, for example, the sizes 225/45 R17, 235/45 R17, 255/40 R17 and 245/35 Like tires such as R19, the range is 30 to 50%, and at least one of the side walls 9 in the figure protects the tire itself and the rim 2 from curbstones and the like in the vicinity of the maximum tire width. For example, a rim guard 10 constituted by a single annular protrusion having a triangular mountain shape in cross section is provided.
More preferably, the tire cross-section height SH is set to a height of 100 mm or less.

Further preferably, the tire is reinforced at least on the inner surface of the sidewall 9, for example, between the inner liner and the carcass 6 and having a crescent cross-sectional shape and a maximum thickness in the range of 2 to 7 mm. The rubber 11 is also arranged in an annular shape.
In FIG. 1, reference numeral 12 denotes a supply / exhaust valve attached to the valve mounting port of the applicable rim 2.

As described above, the safety tire according to the present invention using such a tire / rim assembly includes a continuous phase made of resin and closed cells in the tire chamber 3, as shown in a cross-sectional view in the width direction in FIG. A large number of hollow particles 13 that can be thermally expanded are filled and arranged under pressure.
In the figure, reference numeral 14 denotes a void existing between the hollow particles 13.

  This hollow particle 13 has closed cells surrounded by a continuous phase of a substantially spherical resin, for example, a hollow body having a particle size distribution in the range of about 10 μm to 500 μm, or a small chamber of closed cells. It consists of a spongy structure containing many. That is, the hollow particles 13 are particles that enclose closed closed cells that do not communicate with the outside, and the number of closed cells may be singular or plural. In this specification, the inside of one or a plurality of closed cells of a hollow particle is expressed as a “hollow part”.

  The hollow particles 13 having closed cells indicate that the particles have a “resin shell” for enclosing the closed cells in a sealed state. Further, the continuous phase of the resin is the “resin”. It refers to the “continuous phase on the composition of the components that make up the shell”. The composition of the resin shell will be described later.

  The hollow particle group, which is a large number of the hollow particles 13, is filled and arranged inside the tire chamber 3 together with the high-pressure gas, so that it partially bears the internal pressure of the tire under normal use conditions, and the tire 1 is damaged. Sometimes, it becomes a source for expressing the function of restoring the pressure lost in the tire chamber 3. This “internal pressure restoration function” will be described later.

  Now, the tire 1 of the tire / rim assembly as described above has a small flatness ratio of 30 to 50% and runs with the tire chamber pressure lowered to atmospheric pressure even though it has a rim guard. Then, the tire 1 may be greatly bent by the load, and the side wall 9 may be in contact with the road surface. Therefore, the carcass forming a skeleton by heat generated due to friction with the road surface of the side wall 9 and repeated bending deformation. 6 is fatigued, and the frictional scratches on the sidewall 9 eventually penetrate into the tire chamber, leading to destruction.

  Therefore, when the gas in the tire chamber 3 leaks due to an external injury, the safety tire according to the present invention closes the wound, recovers the lost pressure, and is the minimum necessary for the subsequent traveling. The main purpose is to prevent the failure destruction of the tire 1 as described above by properly applying the tire chamber pressure.

  That is, even if the tire chamber pressure is reduced to atmospheric pressure, it is important to prevent the tire 1 from being destroyed as described above by causing the hollow particles 13 to exhibit the above-described function early. For this purpose, by appropriately filling the hollow particles 13 and causing them to function as expected, the pressure in the tire chamber 3 can be reduced to “at least the pressure at which the tire sidewall 9 does not contact the ground or the inner liner surfaces. It is important to restore the pressure until it stops touching.

  In this case, it is preferable that the hollow particles 14 disposed in the tire chamber 3 have a filling rate according to the following formula (I) of 5 Vol% or more and 80 Vol% or less.

Filling ratio of hollow particles = (particle volume value / tire chamber volume value) × 100 (I)
Here, the particle volume value is the total amount (cm ³ ) of the total volume of all the hollow particles arranged in the tire chamber 3 under the atmospheric pressure and the void volume between the particles.
Further, the tire chamber volume value is obtained when the assembly of the tire 1 and the rim 2 is filled with only air and adjusted to the working internal pressure (kPa), and then the filled air is discharged until the internal pressure becomes atmospheric pressure. It is a value (cm ³ ) obtained from the following formula (II) using the charged air discharge amount (cm ³ ).
Tire chamber volume value = (filled air discharge) / (internal pressure / atmospheric pressure) (II)

In the formula (II), the internal pressure used is a gauge pressure value (kPa), and the atmospheric pressure value is an absolute value (kPa) obtained by a barometer. That is, the atmospheric pressure is represented by 0 [kPa] as a gauge pressure, but since the atmospheric pressure itself fluctuates every day, the absolute value observed from the barometer at that time is used.
Therefore, for example, when the atmospheric pressure at a certain time is 1013 hPa, 101.3 kPa is used as the absolute value of atmospheric pressure in the formula (II). Here, “in-use pressure” refers to “a tire chamber pressure value (gauge pressure value) for each mounting position specified by an automobile manufacturer for each vehicle” as described above.

  Furthermore, by setting the pressure in the hollow portion of the hollow particles 13 to at least 70% of the pressure in the tire chamber (usually the use internal pressure), the particle shape is maintained in a substantially spherical shape and the durability of the particles is guaranteed. It is preferable that the pressure inside the hollow part of the hollow particles is 70% or more of the working internal pressure.

Thus, by disposing the hollow particles having a pressure in the hollow portion of the hollow particles 13 of 70% or more with respect to the pressure in the desired tire chamber in the tire chamber 3 at a predetermined filling rate, for example, When traveling in a state where the internal pressure of the tire chamber 3 is atmospheric pressure (that is, a puncture state), at least the tire chamber pressure until the tire sidewall 9 does not come into contact with each other, or the inner liner surfaces do not come into contact with each other, The pressure in the tire chamber 3 can be recovered.
Below, the restoration | recovery function of the tire air chamber pressure is demonstrated.

That is, in the safety tire formed by the assembly of the tire 1 and the rim 2 in which the above-described hollow particle group is arranged in the tire chamber, when the tire 1 is damaged, the tire air that exists in the gap 14 between the hollow particles is present. The high-pressure gas in the room leaks to the outside of the tire, whereby a large number of hollow particles 13 that are accompanied by the outflow of the high-pressure gas block the damaged part, and suppress a rapid drop in the pressure in the air chamber.
In other words, the wound of the damaged part becomes a flow path through which the gas in the tire chamber 3 leaks, but the hollow particles 13 enter the flow path in a “consolidated” state and clog the flow path with a large number of particles 13. be able to.

  Further, when the pressure in the tire chamber 3 is increased from, for example, atmospheric pressure by an internal pressure restoration function described later, the tension is applied to the carcass 6 as the tire skeleton so that the inner diameter of the wound is narrowed. Therefore, a compressive force acts on the hollow particle group that has entered the wound in a compacted state so as to be squeezed from the tire side due to the pressure increase in the tire chamber 3.

In this case, since the hollow particle 13 has a high hollow part pressure, a reaction force based on the hollow part pressure can be generated against the compressive force to increase the degree of consolidation, and even at a wound with a larger inner diameter, The wound can be closed to such an extent that the gas in the tire chamber 3 hardly leaks.
Therefore, the wound that caused the puncture is instantly and reliably blocked by the hollow particles 13.

  On the other hand, as the air chamber pressure decreases, the amount of crushing deformation of the tire 1, in other words, the amount of flexural deformation of the tire side portion including the sidewall 9 increases, and the tire air chamber volume decreases. Due to the large deflection, the hollow particles 13 arranged in the tire chamber receive compression and shear inputs while being sandwiched between the tire inner surface and the rim inner surface in relation to the filling rate. become. According to this, since the hollow particles rub against each other and self-heat, the temperature of the hollow particles 13 in the tire chamber 3 rises rapidly, and this temperature forms a continuous phase that is the shell of the hollow particles 13. When the thermal expansion start temperature Ts2 of the resin (corresponding to the glass transition temperature of the resin) is exceeded, the shell of the particles starts to soften.

  At this time, in addition to the pressure inside the hollow particles 13 being a high pressure corresponding to the working internal pressure, the hollow portion 13 is further expanded in volume at a stroke because the pressure inside the hollow portion further increases due to a sudden rise in the temperature of the hollow particles. By compressing the void gas around the particles, the pressure of the tire chamber 3 can be recovered to at least the tire chamber pressure at which the tire sidewall 9 is not grounded. As a result, the safety tire, As a result, a vehicle equipped with the vehicle can continuously travel safely over a required distance.

  Thus, if the pressure in the hollow part of the hollow particles 13 is set to a pressure higher than the atmospheric pressure, the function of restoring the internal pressure can be exhibited, but the pressure in the tire chamber 3 can be increased to the tire internal pressure at which the sidewall 9 does not contact the ground. In order to restore the above, it is preferable that the hollow particles 13 in which the pressure in the hollow portion is 70% or more of the use internal pressure be arranged in the tire chamber under a filling rate of 5 Vol% or more and 80 Vol% or less. is there.

  That is, if the filling rate of the hollow particles 13 is less than 5 Vol%, the wounded portion can be closed without any problem, but the absolute amount of the hollow particles 13 is insufficient and the side walls 9 are not grounded or the inner liner surfaces are It may be difficult to obtain a sufficient resurrection pressure up to the pressure level at which it does not touch. On the other hand, if the filling rate exceeds 80 Vol%, the hollow particles 13 will expand beyond the expansion start temperature Ts2 before the tire is punctured due to heat generated by particle friction during high-speed running during normal use. There is a fear that the function of restoring the internal pressure when the tire 1 is punctured may be lost.

  By the way, in order to reliably develop such an internal pressure restoration function, it is necessary to reliably close the wounded part before the function is manifested. That is, if the wounded part is not completely closed, the pressure that should have been restored leaks from the wounded part, and the pressure obtained by the internal pressure restoration function can only temporarily contribute to safe driving thereafter. The driving performance after injury will not be guaranteed.

  Since the hollow particles 13 are particles having a low specific gravity and high elasticity due to the hollow structure, when the tire is damaged and void gas around the hollow particles starts to leak from the damaged portion, the flow is caused by leakage of the void gas. It gets on the wounded area immediately after riding, and the wound of the wounded area is instantly closed. Therefore, the function of closing the damaged part by the hollow particles 13 is an essential function that supports the function of restoring the internal pressure of the safety tire.

  As described above, the safety tire filled with the hollow particles 13 causes the friction between the hollow particles 13 by causing friction between the hollow particles due to a decrease in the tire chamber volume and an increase in the amount of tire deflection due to a decrease in the internal pressure after puncture. Along with rapid temperature rise, the internal pressure is restored by expansion of the hollow particles, and safe driving after puncture can be realized.

  Here, in order to dispose the hollow particles whose hollow part internal pressure of the hollow particles 13 is 70% or more with respect to a desired tire air pressure, in the tire air chamber at a predetermined filling rate, It is effective to fill the tire air chamber with the hollow particles and the high-pressure gas from a pressure-resistant container containing a large number of the hollow particles 13 in the high-pressure gas.

In this case, the different meanings of accommodating the hollow particles 13 and the high-pressure gas in the pressure vessel are as follows.
The hollow particles 13 are accommodated together with the high-pressure gas in the pressure-resistant container. When initially accommodated with the high-pressure gas in the pressure-resistant container, the pressure in the hollow portion of the hollow particles 13 (pressure in the closed cell) is atmospheric pressure. And the volume of the particles is reduced because it is less than the pressure in the container. The shape of the hollow particles 13 at this time is not a substantially spherical shape, but is a flattened shape distorted from a spherical shape.

  When the hollow particles 13 are filled in the tire chamber in a state where the particle shape is flattened and distorted, the pressure in the hollow portion (pressure in the closed cell) is almost equal to the atmospheric pressure, so that the tire 1 It is limited to the small size of the wound that is formed by the wound and is blocked by the hollow particles 13 entering, and the hollow particles 13 are not ejected to the outside of the tire. However, since the hollow particles 13 are flattened and distorted, a lot of micro passages are generated, and thus the gas in the tire chamber may leak.

In addition, the hollow particles 13 are more likely to break due to collision between the particles and collision with the tire and the inner surface of the rim, as compared with the case of the spherical shape.
That is, when the hollow particles 13 are flattened and distorted, the input due to the collision cannot be uniformly dispersed, resulting in a great disadvantage in terms of durability.

On the other hand, the flattened and distorted hollow particles 13 are initially exposed to the internal pressure of the pressure vessel or the like for a certain period of time, although they are initially in a reduced volume due to the difference between the pressure in the hollow portion and the pressure in the vessel. By this, the pressure in the hollow part of the hollow particle 13, in other words, the pressure in the closed cell in the particle can be increased to the pressure of the pressure vessel.
That is, a force to return to the original substantially spherical shape acts on the shell portion of the flattened hollow particle 13, and the pressure in the hollow portion of the flattened hollow particle 13 tends to be lower than the pressure in the pressure vessel. Therefore, in order to eliminate the pressure difference, gas molecules in the pressure vessel pass through the shell of the continuous phase made of resin and permeate into the hollow portion of the particle.

  Moreover, since the hollow part of the hollow particle 13 is a closed cell and the gas in it is filled with the gas resulting from a foaming agent, it may differ from the gas in a pressure-resistant container (interparticle space | gap part), In this case, not only the simple pressure difference as described above but also the high-pressure gas in the pressure-resistant container permeates into the particle hollow portion until the partial pressure difference is eliminated while following the partial pressure difference of the gas.

As described above, the high-pressure gas in the pressure vessel penetrates into the hollow portion of the hollow particle 13 with the passage of time, so that the pressure in the pressure vessel decreases by the amount permeated into the hollow particle.
Therefore, in order to compensate for the amount of the hollow particles 13 that have permeated into the hollow portion, a hollow particle in which the internal pressure of the hollow portion is adjusted to a required pressure can be easily obtained by replenishing the high pressure gas and then applying a desired pressure. Can do.

  The pressure in the hollow part of the hollow particle 13 approaches the pressure in the pressure vessel (interparticle void part) as described above, whereby the hollow particle 13 recovers the once reduced particle volume, The flattened and distorted particle shape is restored to the original substantially spherical shape. In this shape recovery process, the hollow part internal pressure of the hollow particles 13 is increased to 70% or more with respect to the internal pressure of the pressure vessel, so that the particle shape can sufficiently recover from a flattened state to a substantially spherical shape, Thereby, the durability of the hollow particles 13 described above can be ensured.

  Accordingly, the hollow particles 13 are placed in a pressure vessel separate from the tire 1, and the void pressure between the particles is maintained at a level higher than the desired working pressure in the tire chamber, and the pressure is kept applied while the pressure is kept applied. By storing the hollow particles 13 in a state where the pressure in the hollow portion has increased in the pressure chamber and supplying the hollow particles 13 together with the surrounding atmosphere into the tire chamber, the hollow particles 13 recover the particle volume, Since the particle shape has been restored to a substantially spherical shape, fatigue and breakage applied to the particles due to repeated deformation during rolling of the tire after filling the hollow particles can be greatly reduced, and the durability of the hollow particles is impaired. There is nothing.

  The preferred range in which the durability of the hollow particles 13 is not impaired is that the pressure in the hollow portion of the hollow particles 13 is desired in the high pressure environment in which the pressure in the tire chamber 3 is desired, such as the vehicle designated internal pressure to be mounted. It is particularly recommended that the pressure is at least 70%, more preferably 80% or more, further 90% or more, and 100% or more.

  Here, the appropriate holding time of the hollow particles 13 in the pressure vessel is determined by the permeability of the void gas to the shell portion of the hollow particles, that is, the continuous phase of the particles, and the separation between the gas in the particle hollow portion and the void gas. It can be set in consideration of the pressure difference.

  In accordance with the change process of the particle shape and volume as described above, the type and pressure of the gas filled in the pressure vessel (the void around the particle) are appropriately selected and adjusted, so that the hollow particles The pressure in the hollow portion can be set to a desired range.

  When the hollow particles 13 thus adjusted in the pressure vessel are supplied into the tire chamber 3, the pressure in the hollow portion (the pressure in the bubbles in the closed cells) is increased in the tire chamber 3. While maintaining a high pressure in accordance with the working internal pressure, in other words, it is present in the tire chamber while maintaining the particle volume and the hollow portion pressure, the above-mentioned internal pressure restoration function required for the safety tire is sufficiently obtained. Can be demonstrated.

  The means for obtaining such a safety tire having the function of restoring the internal pressure is not limited to the above method, and the tire air chamber of the tire / rim assembly is replaced with the pressure vessel without using the pressure vessel. A similar safety tire can also be obtained.

Furthermore, in obtaining the safety tire as described above, it is preferable that the high-pressure gas filled in the tire chamber is adjusted to have a water vapor content of 70% or less under an atmospheric pressure of 30 ° C.
During rolling of the safety tire filled with the hollow particles 13, the hollow particles 13 in the tire form a layer on the inner surface side of the tire crown due to the centrifugal force accompanying the rolling. And in this hollow particle group layer, the hollow particle temperature rises due to frictional heat generation between the hollow particles, on the other hand, due to the active movement of the hollow particles 13 and the cooling effect of the gas present in the rim inner surface side gap, As a result of maintaining the heat balance, the temperature of the hollow particles 13 is stabilized within the range of the expansion start temperature Ts2 or less.

However, when the temperature of the atmospheric gas is high in the tire chamber in which the hollow particle group exists, the excellent fluidity that is a characteristic of the hollow particle 13 is lowered, and the hollow particle 13 may be aggregated.
Then, during tire rolling in steady running, the mutual movement of the hollow particles 13 is hindered. As a result, frictional heat generation between the hollow particles occurs in a limited region, and in addition, the movement of the hollow particles 13 Since the cooling capacity decreases with the suppression, a partial heat storage region is generated in the layer of the hollow particle group. In this partial heat storage region, particles that expand beyond the expansion start temperature Ts2 of the hollow particles 13 are scattered, leading to an increase in the total volume of the hollow particles 13. This means that the void volume is reduced, and the mutual movement of the hollow particles 13 is further restricted to accelerate the decrease in cooling capacity. In the worst case, the tire is in the initial stage where the heat storage region is generated. As a result of the hollow particle temperature in the air chamber rising all at once and the total hollow particles exceeding the expansion start temperature Ts2, the function of restoring the internal pressure after the tire has reached the puncture state may be lost.

  In order to avoid such a situation, the tire chamber temperature during steady running is about 30 ° C. to 70 ° C., so the water vapor content at 30 ° C., which is the temperature range, is adjusted to 70% or less. It is important to.

By the way, the hollow particles 13 are obtained by heating and expanding the “expandable resin particles” as a raw material, that is, particles encapsulated in a resin using a gas component as a liquid foaming agent. There is a temperature Ts1.
When the hollow particles 13 obtained by such heat expansion are heated again from room temperature, the hollow particles 13 start to expand further, and the expansion start temperature Ts2 of the hollow particles is present here. As a result of producing hollow particles from many expandable resin particles and studying them, the inventors have used Ts1 as an index of expansion characteristics. However, Ts2 is appropriate as an index of expansion characteristics of hollow particles. I came to find out.

  That is, when the expansion behavior in the case where the expandable resin particles are overheated is observed, the expandable resin is in a stage before expansion, and therefore the particle size is extremely small compared to the state of the hollow particles 13 and is made of resin. Since the thickness of the shell portion is extremely thick, the rigidity as a microcapsule is high. Therefore, even if the continuous phase of the resin shell exceeds the glass transition point in the process of thermal expansion, the expansion force of the internal gas must overcome the rigidity of the shell until the shell is softened to some extent by further heating. I can't. Therefore, Ts1 shows a value higher than the glass transition point of the actual shell.

  On the other hand, when the hollow particles 13 are heated and expanded, the thickness of the shell of the hollow particles 13 is thin, and the rigidity of the hollow body is low. Therefore, in the process of heating and expanding the hollow particles 13, since the continuous phase of the shell part exceeds the glass transition point and starts to expand, Ts2 is positioned lower than Ts1.

  Therefore, in this safety tire, the further expansion characteristic of the hollow particles 13 obtained by once expanding the expandable resin particle diameter is utilized.

Therefore, in this safety tire, further expansion characteristics of the hollow particles 13 obtained by once expanding the expandable resin particles are utilized.
In this case, Ts2 of the hollow particles 13 is preferably 90 ° C. or higher and 200 ° C. or lower, particularly 110 ° C. or higher and 200 ° C. or lower, particularly 130 ° C. or higher and 200 ° C. or lower.
That is, if Ts2 of the hollow particles 13 is less than 90 ° C., there is a risk of expansion in the temperature environment of the tire chamber during steady running, whereas if it exceeds 200 ° C., in the run flat running after puncture damage. Even if the temperature rises due to frictional heat generation of the hollow particles 13, Ts2 may not be reached, and the intended “internal pressure restoration function” may not be fully developed. is there.

Next, the gas constituting the hollow portion (closed cell) of the hollow particle 13 includes nitrogen, air, linear and branched aliphatic hydrocarbons having 2 to 8 carbon atoms, fluorinated products thereof, and carbon numbers. 2 to 8 alicyclic hydrocarbons and fluorinated products thereof, and the following general formula (III)

R ¹ —O—R ² (III)

(Wherein R ¹ and R ² are each independently a monovalent hydrocarbon group having 1 to 5 carbon atoms, and part of the hydrogen atoms of the hydrocarbon group may be replaced by fluorine atoms) And at least one selected from the group consisting of ether compounds.

  By the way, the gas filled in the tire chamber 3 may be air, but when the gas in the particles is not a fluorinated product, a gas not containing oxygen, such as nitrogen or an inert gas, is preferable from the viewpoint of safety. .

The method for obtaining the hollow particles 13 having closed cells is not particularly limited, but a general method is to produce “expandable resin particles” using a foaming agent and to overheat them.
Examples of the foaming agent include a method utilizing vapor pressure such as high-pressure compressed gas and liquefied gas, and a method utilizing a thermally decomposable foaming agent that generates gas by thermal decomposition.

  Many of the latter thermally decomposable foaming agents are characterized by generating nitrogen, and the particles obtained by appropriately suppressing the reaction of the expandable resin particles obtained by foaming by these have mainly nitrogen in the bubbles. It will be a thing. Although it does not specifically limit as this thermally decomposable foaming agent, Dinitroso pentamethylene tetramine, azodicarbonamide, para-toluene sulfonyl hydrazine and its derivative (s), and oxybisbenzene sulfonyl hydrazine can be mentioned suitably.

Next, a technique for obtaining “expandable resin particles” that become hollow particles by utilizing the vapor pressure of the former high-pressure compressed gas and liquefied gas will be described.
When polymerizing a continuous phase of the resin forming the hollow particles, linear and branched aliphatic hydrocarbons having 2 to 8 carbon atoms and fluorinated products thereof, alicyclic hydrocarbons having 2 to 8 carbon atoms And its fluorinated compounds, and the following general formula (IV)

R ¹ —O—R ² (IV)

(Wherein R ¹ and R ² are each independently a monovalent hydrocarbon group having 1 to 5 carbon atoms, and part of the hydrogen atoms of the hydrocarbon group may be replaced by fluorine atoms) In this method, at least one selected from the group consisting of ether compounds represented by the following formula is liquefied under high pressure as a blowing agent and dispersed in a reaction solvent, followed by emulsion polymerization. As a result, it is possible to obtain “expandable resin particles” in which the gas components shown above are contained in the above-mentioned resin continuous phase as a foaming agent in a liquid state, and by heating and expanding the particles, desired hollow particles 13 are obtained. I can get it.

  In addition, the surface of the “expandable resin particles” is coated with an anti-blocking agent such as silica particles, carbon black derivative, antistatic agent, sea surface active agent, and the like to obtain the desired hollow particles by overheating. You can also.

  Here, in order to apply the necessary minimum internal pressure by the hollow particles 13 in a state where the tire chamber force is reduced due to the damage, the gas sealed in the hollow part of the hollow particles 13 at a predetermined pressure In other words, it is important that the continuous phase of the resin corresponding to the shell portion of the hollow particle 13 has a property that gas is difficult to permeate.

  That is, the resin constituting the continuous phase is made of a material having a high gas barrier property, specifically, it may be composed of at least one of an acrylonitrile polymer, an acrylic copolymer, and a vinylidene chloride copolymer. preferable. These materials are particularly effective when applied to safety tires because they have flexibility as hollow particles with respect to input due to tire deformation.

  In particular, it is preferable to apply any one of an acrylonitrile polymer, an acrylic polymer, and a vinylidene chloride polymer to the continuous phase of the hollow particles 13. More specifically, the polymer constituting the polymer is a polymer selected from acrylonitrile, methacrylonitrile, methyl methacrylate, methacrylic acid, and vinylidene chloride, preferably an acrylonitrile / methacrylonitrile / methyl methacrylate terpolymer, Each of at least one selected from acrylonitrile / methacrylonitrile / methacrylic acid terpolymer is advantageously suitable. Since these materials all have a small gas permeability coefficient and are difficult for gas to permeate, the gas in the hollow portion of the hollow particle 13 is difficult to leak to the outside, and the pressure in the hollow portion can be appropriately maintained.

Further, the continuous phase of the hollow particles 13 has a gas permeability coefficient at 30 ° C. of 300 × 10 ⁻¹² (cc · cm / cm ² · s · cmHg) or less, preferably a gas permeability coefficient at 30 ° C. of 20 × 10 ^−12. (Cc · cm / cm ² · s · cmHg) or less, more preferably a gas permeability coefficient at 30 ° C. of 2 × 10 ⁻¹² (cc · cm / cm ² · s · cmHg) or less is recommended.
That is, the gas permeability coefficient of the inner liner layer in a normal pneumatic tire is a level of 300 × 10 ⁻¹² (cc · cm / cm ² · s · cmHg) or less and has a sufficient internal pressure holding function. In view of the above, the gas permeation coefficient at 30 ° C. of the continuous phase of the particles was set to 300 × 10 ⁻¹² (cc · cm / cm ² · s · cmHg) or less. However, at this gas permeation coefficient level, internal pressure replenishment of about once every 3 to 6 months is necessary. From the standpoint of maintainability, 20 × 10 ⁻¹² (cc · cm / cm ² · s · cmHg) or less, more preferably 2 × 10 ⁻¹² (cc · cm / cm ² · s · cmHg) or less is recommended.

  The tire pressure and the tire cross-section height were used as parameters, and the low pressure of the tire air pressure was measured for each of the example tire and the conventional tire in which the hollow particles were filled in the tire air chamber and the filling rate was changed. The initial maneuverability at the time of leakage and the run-flat mileage under puncture conditions were determined based on actual vehicle travel, along with riding comfort and quietness during steady travel, and the results shown in Table 1 were obtained.

表１に示すところによれば、実施例タイヤはいずれも、従来タイヤに比し、乗心地の低下なしに、各種の性能を有利に向上させることができ、なかでも、中空粒子の充填率が高いほど静粛性、ランフラット走行性を高め得ることが解かる。

According to the results shown in Table 1, all of the example tires can advantageously improve various performances without a decrease in riding comfort as compared with the conventional tires. It can be seen that the higher the value, the higher the quietness and the run-flat driving performance.

1 is a cross-sectional view in the width direction illustrating a tire / rim assembly as an object of the present invention in a state of being filled with internal pressure. 1 is a cross-sectional view in the width direction illustrating a safety tire according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tire 2 Applicable rim 3 Tire air chamber 4 Bead core 5 Bead part 6 Carcass 7 Belt 8 Tread 9 Side wall 10 Rim guard 11 Reinforcement rubber 12 Supply / exhaust valve 13 Hollow particle 14 Cavity

Claims (5)

  A tire having a rim guard with a flatness ratio in the range of 30 to 50% is mounted on the applied rim, and a continuous phase made of resin is provided in the tire chamber partitioned by the applied rim and the tire, and the independent is surrounded by it. A safety tire in which a large number of thermally expandable hollow particles composed of bubbles are sealed under pressure.   The safety tire according to claim 1, wherein the tire cross-sectional height is 100 mm or less.   The safety tire according to claim 1 or 2, wherein a reinforcing rubber having a crescent cross-sectional shape and a maximum thickness of 2 to 7 mm is disposed on at least an inner surface of a side portion of the tire. The filling rate of the hollow particles into the tire chamber according to the following formula (I) is set to 5 Vol% or more and 80 Vol% or less, and the hollow portion pressure inside the hollow particles is set to 70% or more of the use internal pressure of the tire. The safety tire according to any one of claims 1 to 3, which has an expansion start temperature (Ts2) of 90 to 200 ° C.
Filling ratio of hollow particles = (particle volume value / tire chamber volume value) × 100 (I)
here,
Particle volume value: The total amount of the total volume of all hollow particles arranged in the tire chamber under atmospheric pressure and the void volume between the particles (cm ³ )
Tire chamber volume value: After filling the tire and rim assembly with only air and adjusting it to the internal pressure (kPa), the amount of air discharged when the internal air is discharged until the internal pressure reaches atmospheric pressure ( cm ³ ), the value obtained from the following formula (II) (cm ³ )
Tire chamber volume value = (filled air discharge) / (internal pressure / atmospheric pressure) (II)
In the formula (II), the internal pressure used is a gauge pressure value (kPa), and the atmospheric pressure value is an absolute value (kPa) obtained by a barometer.   The safety tire according to any one of claims 1 to 4, wherein the gas content in the tire chamber is adjusted to a water vapor content of 70% or less under an atmospheric pressure of 30 ° C.

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